Composite gypsum board formed from high-salt stucco and related methods

Abstract

A composite gypsum board and a method for making the gypsum board are disclosed. The board contains at least one set gypsum layer sandwiched between a front cover sheet and a back cover sheet. The set gypsum layer is formed from at least stucco and water. Stucco materials typically contain a high salt impurity content, for example, when the stucco is calcined from certain sources of low-quality synthetic gypsum. For example, in some embodiments, the salt is a chloride salt, such as sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl), and / or calcium chloride (CaCl). The board and method improve the bond between the gypsum layer and at least one of the cover sheets (e.g., the back cover sheet). Methods and systems related to drying the gypsum board are also provided.

Description

[Background technology]

[0001] Hardened gypsum is a well-known material used in many products, including panels and other products for building construction and renovation. One such panel (often referred to as gypsum board) is in the form of a hardened gypsum core sandwiched between two cover sheets (e.g., paperboard) and is commonly used in drywall construction for interior walls and ceilings of buildings. One or more dense layers, often referred to as "skim coat," may be included on either side of the core, usually at the paper-core interface.

[0002] Gypsum (calcium sulfate dihydrate) is naturally occurring and can be mined in the form of rock. It can also exist in a synthetic form (referred to as "syngyp" in the art) as a byproduct of industrial processes such as flue gas desulfurization. From either source (natural or synthetic), gypsum can be calcined at high temperatures to form stucco (i.e., calcined gypsum in the form of calcium sulfate hemihydrate and / or calcium sulfate-free), which is then rehydrated to form hardened gypsum in the desired shape (e.g., as board). During the production of the board, the stucco, water, and other components as needed are mixed in a mixer. A slurry is formed and discharged from the mixer onto a moving conveyor that carries a cover sheet to which one of the skim coats (if any) has already been applied (often upstream of the mixer). The slurry is spread onto paper (with the skim coat optionally included on the paper). Another cover sheet, with or without the skim coat, is applied to the slurry and, for example, a forming plate is used to form a sandwich structure of the desired thickness. The mixture is cast and allowed to solidify, forming hardened (i.e., rehydrated) gypsum through the reaction of calcined gypsum with water, creating a matrix of crystalline hydrated gypsum (i.e., calcium sulfate dihydrate). It is the desired hydration of calcined gypsum that enables the formation of an interlocking matrix of hardened gypsum crystals, thereby conferring strength to the gypsum structure in the product. Heat is required (e.g., in a furnace) to remove any remaining free (i.e., unreacted) water to obtain a dry product.

[0003] Gypsum (calcium sulfate dihydrate and any impurities) suitable for use in wall panels can be obtained from both natural and synthetic sources, and is subsequently processed.

[0004] Natural gypsum is sometimes used by calcining its calcium sulfate dihydrate to produce a hemihydrate form. Gypsum from natural resources is a naturally occurring mineral and can be mined in the form of rock. Naturally occurring gypsum is a mineral typically found in ancient salt lake layers, volcanic deposits, and clay layers. When mined, raw gypsum is generally found in the form of a dihydrate. Gypsum is also known as calcium sulfate dihydrate, terra alba, or land plaster. This material is also produced as a byproduct of various industrial processes. For example, synthetic gypsum is a byproduct of flue gas desulfurization processes from power plants. Gypsum contains approximately two molecules of water, each associated with a molecule of calcium sulfate.

[0005] Plaster of Paris is also known as calcined gypsum, stucco, calcium sulfate hemihydrate, calcium sulfate half-hydrate, or calcium sulfate hemihydrate.

[0006] When calcium sulfate dihydrate from any source is heated sufficiently in a process called calcination or gypsum firing, the water of hydration is at least partially expelled, and depending on the temperature and exposure time, either calcium sulfate hemihydrate (CaSO4·1 / 2H2O) (typically provided in materials commonly referred to as "stucco") or anhydrous calcium sulfate gypsum (CaSO4) can be formed. As used herein, the terms "stucco" and "gypsum firing" refer to both forms of calcium sulfate hemihydrate and anhydrous gypsum that may be contained therein. The calcination of gypsum to produce the hemihydrate form is carried out by the following formula: CaSO4·2H2O→CaSO4·0.5H2O+1.5H2O

[0007] Calcined gypsum can react with water to form calcium sulfate dihydrate, which is a rigid product and is referred to herein as "hardened gypsum."

[0008] Gypsum can also be obtained synthetically as a byproduct of industrial processes, such as flue gas desulfurization from power plants (referred to as "syn-gypsum" in the art). Natural or synthetic gypsum can be calcined at high temperatures, typically above 150°C, to form stucco (i.e., calcined gypsum in the form of calcium sulfate hemihydrate and / or anhydrous calcium sulfate gypsum), which may then be rehydrated to form set gypsum in desired shapes, such as boards.

[0009] Synthetic gypsum obtained from power plants is typically suitable for use in gypsum panels for construction projects. Synthetic gypsum is a byproduct of the flue gas desulfurization process from power plants (also known as desulfurized gypsum, desulfogypsum, or DSG). In particular, flue gas containing sulfur dioxide is wet-washed with lime or limestone, which produces calcium sulfite in the following reaction. CaCO3 + SO2 → CaSO3 + CO2 Next, calcium sulfite is converted to calcium sulfate in the following reaction. CaSO3+2H2O+1 / 2O2→CaSO4·2H2O Next, the hemihydrate form may be produced by calcination in a similar manner to that used for natural gypsum.

[0010] However, many conventional coal-fired power plants are being shut down in favor of more environmentally friendly energy sources. The closure of coal-fired power plants is leading to an increasing shortage of synthetic gypsum suitable for the manufacture of gypsum panels. Low-quality synthetic gypsum is available from power plants and other alternative sources, but gypsum from these alternative sources often contains fairly high concentrations of foreign salts, particularly magnesium or sodium salts, especially magnesium chloride and sodium chloride. Small amounts of potassium chloride and calcium chloride may also be present in synthetic gypsum from alternative sources. Foreign salts can be problematic because they tend to reduce the adhesion between the board core and the cover sheet, especially the backing paper cover sheet.

[0011] This description of background art is provided by the inventors to assist the reader and should be noted as not being a prior art reference, nor does it indicate that any of the problems described are recognized in the art in themselves. While the principles described may mitigate problems specific to other systems in some respects and embodiments, it should be understood that the scope of the protected innovation is defined not by the ability of the claimed invention to solve any particular problem described herein, but by the appended claims. [Overview of the project]

[0012] The present invention provides a gypsum board exhibiting improved adhesion between the gypsum layer and the cover sheet of the board, as well as related methods and systems. The present invention is particularly applicable to boards formed from stucco containing high salt impurities. Generally, stucco is formed by calcining gypsum from natural or synthetic sources. In nature, it is a common and abundant mineral that can be mined from the earth. Synthetic forms of gypsum can be derived as a byproduct from flue gas desulfurization (FGD) processes associated with coal-fired power plants that burn high-sulfur coal. At the power plant, sulfur dioxide emissions are removed by a wet washing process. When limestone slurry is injected, synthetic gypsum precipitates after the fly ash has been removed. For example, some forms of synthetic gypsum contain high salt impurities, which then remain in the stucco formed as calcined gypsum. Salt impurities in synthetic gypsum may be due to, for example, high-salt coal. These salt impurities have been found to adversely affect the bonding between the cover sheet (e.g., formed from paper) and the gypsum layer (e.g., the board core) in the board.

[0013] Accordingly, in one embodiment, the present invention provides a gypsum board comprising a hardened gypsum core disposed between a front cover sheet and a back cover sheet. The hardened gypsum core is formed from a first slurry comprising water, stucco, and a high salt impurity content, as well as optional components discussed herein. The board comprises at least one of the following items (1) to (4) (i.e., one, two, three, or four): (1) At least one of the cover sheets, preferably at least the back cover sheet, is perforated. (2) At least one of the cover sheets, preferably at least the back cover sheet, is absorbent paper. (3) Starch is provided between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core. (4) Skim coat starch is provided. The board core prepared from the first slurry is disposed between two cover sheets and has first and second surfaces. The board core may optionally contain board core starch. A back skim coat layer and a front skim coat layer are provided, each defining a first and second skim coat surface. The skim coat is formed from second and third slurries, which may have the same or different compositions. The second and third slurries contain at least water and stucco. At least one of the second and third slurries contains skim coat starch. The back skim coat layer is bonded to the first core surface, and the first surface of the front skim coat layer is bonded to the second surface of the board core. The second surface of the back skim coat layer faces the back cover sheet. The second surface of the front skim coat layer faces the front cover sheet. The skim coat starch enhances the bond between the board core and the skim coat prepared using the skim coat starch, for example, a cover sheet preferably adjacent to at least the back skim coat layer.

[0014] In another embodiment, the present invention provides a method for producing gypsum board. A first slurry is formed by mixing at least water and stucco containing a high salt impurity content. Second and third slurries, which may be the same or different, are formed by mixing at least water and stucco. The second slurry is applied bondably to a front cover sheet to form a skim coat layer, the skim coat layer having a first surface and a second surface, the first surface of the skim coat layer facing the front cover sheet. The first slurry is applied bondably to the skim coat layer to form a board core having a first surface and a second surface, the first surface of the board core facing the second surface of the skim coat layer. A back cover sheet is applied bondably to the second surface of the board core to form a board precursor. A third slurry containing water, stucco, and skim coat starch is applied to the first surface of the back cover sheet to form a second skim coat. When applied on top of a core, a second skim coat is placed between the second cover sheet and the board core. The board precursor is dried in a kiln to form a board. This method further comprises at least one of the following items (i.e., one, two, three, four, or five): (1) At least one of the cover sheets, preferably a back cover sheet, is perforated. (2) At least one of the cover sheets, preferably a back cover sheet, is made of absorbent paper. (3) Starch is applied between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core. (4) Skim coat starch is included in a second and / or third slurry to strengthen the bond between the board core and the front and / or back cover sheets, respectively. (5) The drying process is accompanied by the use of a kiln containing at least one in-kiln high-frequency moisture sensor. Heat can be supplied into the kiln using at least one burner which may have a burner output. The kiln moisture sensor is connected to a controller outside the kiln and generates readings of the kiln's internal moisture content.Drying further includes measuring the moisture content in the board upstream of the kiln using an upstream high-frequency moisture sensor and an upstream sensor (e.g., a microwave sensor) that is less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The upstream sensor communicates with a controller and generates a first upstream moisture reading and a second upstream moisture reading, respectively. The first and second moisture readings from the upstream moisture sensor are correlated. If a delta exists between the first and second moisture readings, the kiln high-frequency moisture sensor is biased to correct any error in the kiln moisture reading (indicated by the delta between the upstream sensor readings). In some embodiments, drying further includes measuring the moisture content in the board downstream of the kiln using a downstream high-frequency moisture sensor and a downstream sensor that is less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The downstream high-frequency sensor and the other sensor less affected by high salt concentrations communicate with a controller and generate a first downstream moisture reading and a second downstream moisture reading, respectively. The downstream moisture readings are correlated. By adjusting the moisture setpoint and / or bias (automatically or manually), the airflow and / or burner output can be altered in relation to any errors generated by the high-frequency sensor, resulting in a properly dried board.

[0015] In another embodiment, the present invention provides a method for producing a gypsum board. This method includes mixing at least water, stucco, and foam to form a first slurry. The first slurry is placed between a front cover sheet and a back cover sheet to form a board precursor. The board precursor is cut into segments. A board in a kiln containing at least one in-kiln high-frequency moisture sensor, which communicates with a controller outside the kiln to generate in-kiln moisture readings. The moisture content in the board upstream of the kiln is evaluated using an upstream high-frequency moisture sensor and an upstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The upstream sensor communicates with the controller and generates a first upstream moisture reading and a second upstream moisture reading, respectively. Moisture readings from the upstream high-frequency moisture sensor and the upstream sensor less affected by high salt concentrations in the slurry are correlated compared to the high-frequency moisture sensor. If a delta exists between the first and second moisture readings, the in-kiln high-frequency moisture sensor is biased to correct any errors in the in-kiln moisture readings. In some embodiments, the method further includes measuring the moisture content in the board downstream of the kiln using a downstream high-frequency moisture sensor and a downstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The downstream high-frequency sensor and the other salt-less sensor communicate with a controller to generate a first downstream moisture reading and a second downstream moisture reading, respectively. The moisture readings from the downstream high-frequency moisture sensor and the downstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor are correlated. The kiln is associated with a burner combustion rate and / or airflow modifier to adjust the heating inside the kiln. The burner combustion rate and / or air extraction device is used to adjust the temperature inside the kiln to reduce heating inside when there is a delta between the moisture readings of the first downstream moisture sensor and the second downstream moisture sensor.

[0016] In another embodiment, the present invention provides a method for drying a board precursor during the manufacture of a board. The method includes providing a board precursor containing a core layer formed from stucco, water, and a high salt impurity content. The board precursor is cut into segments. The segments are dried in a kiln containing at least one kiln-frequency high-frequency moisture sensor. The kiln-frequency moisture sensor communicates with a controller outside the kiln and generates kiln-frequency moisture readings. The moisture content of the board precursor is measured upstream of the kiln using an upstream high-frequency moisture sensor and an upstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The upstream sensor communicates with a controller and generates a first upstream moisture reading and a second upstream moisture reading, respectively. The moisture readings from the upstream high-frequency moisture sensor and the upstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor are correlated. If a delta exists between the first and second moisture readings, the kiln-frequency high-frequency moisture sensor is biased to correct any errors in the kiln-frequency moisture readings. In some embodiments, the method further includes measuring the moisture content in the board downstream of the kiln using a downstream high-frequency moisture sensor and a downstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The downstream high-frequency and high-salt-resistant sensors communicate with a controller to generate a first downstream moisture reading and a second downstream moisture reading, respectively. The moisture readings from the downstream high-frequency moisture sensor and the downstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor are correlated. In some embodiments, a burner output and / or air extraction device associated with the kiln is provided. The burner output and / or air extraction device is used to adjust the temperature inside the kiln to reduce heating inside if there is a discrepancy between the two downstream moisture readings.

[0017] In another embodiment, the present invention provides a system for drying board segments. The system includes a kiln containing at least one heat source and a kiln-internal high-frequency moisture sensor. A controller is provided outside the kiln. An upstream high-frequency moisture sensor and an upstream sensor less affected by high salt concentrations in the slurry compared to a high-frequency moisture sensor are provided. The upstream high-frequency sensor and microwave sensor communicate with the controller and generate a first upstream moisture reading and a second upstream moisture reading, respectively. In some embodiments, the system further includes a burner output and / or air extraction device associated with the kiln. The setpoint and / or air extraction device communicate with the controller. In some embodiments, the system further includes a downstream high-frequency moisture sensor and a downstream sensor less affected by high salt concentrations in the slurry compared to a high-frequency moisture sensor. The downstream sensor communicates with the controller and generates a first downstream moisture reading and a second downstream moisture reading, respectively. The burner output and / or air device can be used to adjust the temperature inside the kiln to reduce heating inside. [Brief explanation of the drawing]

[0018] [Figure 1] The diagram shows a cross-sectional view of the gypsum board of the present invention, in which the board core layer (gypsum core) is sandwiched between the front cover sheet and the back cover sheet, and the back cover sheet contains multiple through-holes. [Figure 2] Figure 1 shows a plan view (axial view) of the gypsum board, which allows a better view of the arrangement of multiple holes in the back cover sheet. [Figure 3] This diagram shows a cross-sectional view of the gypsum board of the present invention, in which a board core (gypsum core) is sandwiched between a front paper cover sheet and a back cover sheet, and at least one of these is coated with a starch layer. [Figure 4] Figure 3 shows a plan view (axial view) of the gypsum board, which allows a better view of the arrangement of multiple holes in the back cover sheet. [Figure 5]This shows a perspective view of the gypsum board of the present invention attached to one side of a metal stud wall suitable for the wall system of the present invention. [Figure 6A] This is a schematic diagram of a cross-section of a wall panel having a skim coat according to an embodiment of the present invention (not drawn to scale). [Figure 6B] This is a schematic diagram of a cross-section of a wall panel having a skim coat according to an embodiment of the present invention (not drawn to scale). [Figure 7] This is a schematic diagram of a line configuration showing the drying process according to the embodiment described herein. [Figure 8] A perspective view of the gypsum board of the present invention, attached to one side of a metal stud wall suitable for use in an exemplary wall system of the present invention, is shown. [Figure 9] The image shows a photograph of a back cover sheet with multiple holes that penetrate it. [Figure 10] The photographs demonstrate the effect of various salts on adhesion to the board core layer in 12-inch x 12-inch x 1 / 2-inch gypsum board, both with and without holes in the back cover sheet. [Figure 11] The photographs demonstrate the effect of various salts on adhesion to the board core layer in 12-inch x 12-inch x 1 / 2-inch gypsum board, both with and without holes in the back cover sheet. [Figure 12] The photographs demonstrate the effect of various salts on adhesion to the board core layer in 12-inch x 12-inch x 1 / 2-inch gypsum board, both with and without holes in the back cover sheet. [Figure 13] To demonstrate the effect of drilling into a 12-inch × 12-inch × 1 / 2-inch gypsum board containing 30 ppm Cl- from NaCl per million parts calcium sulfate hemihydrate, a photograph is shown comparing the board of the present invention having a perforated cover sheet with a board having a non-perforated cover sheet. [Figure 14]The photograph shows the effect of a diluted starch solution containing 1200 ppm Cl- from MgCl2 per million parts calcium sulfate hemihydrate on a 12-inch x 12-inch x 1 / 2-inch gypsum board. [Figure 15] The photograph shows the effect of a diluted starch solution containing 2100 ppm Cl- from MgCl2 per million parts calcium sulfate hemihydrate on a 12-inch x 12-inch x 1 / 2-inch gypsum board. [Figure 16] The image shows the effect of a diluted starch solution and drilling on a 12-inch x 12-inch x 1 / 2-inch gypsum board containing 2000 ppm Cl- from NaCl per million parts calcium sulfate hemihydrate. [Figure 17] The photograph shows the effect of a diluted starch solution containing 30 ppm Cl- from NaCl per million parts calcium sulfate hemihydrate on a 12-inch x 12-inch x 1 / 2-inch gypsum board. [Figure 18] These are photographs of the two boards after the bonding test discussed in Example 3. [Figure 19] These are photographs of the three boards after the bonding test discussed in Example 3. [Figure 20] These are photographs of the three boards after the bonding test discussed in Example 3. [Figure 21] These are photographs of the three boards after the bonding test discussed in Example 3. [Figure 22] These are photographs of the three boards after the bonding test discussed in Example 4. [Figure 23] These are photographs of the three boards after the bonding test discussed in Example 4. [Figure 24A] This is a graph of moisture percentage (x axis) versus actual moisture percentage (y axis), as discussed in Example 5. [Figure 24B] This is a graph of moisture percentage (x axis) versus actual moisture percentage (y axis), as discussed in Example 5. [Modes for carrying out the invention]

[0019] The present invention is at least in part based on strengthening the adhesion between a gypsum layer and a cover sheet (e.g., made of paper). A gypsum board is formed to include a gypsum layer positioned between two cover sheets (a front cover sheet and a back cover sheet). The gypsum layer generally includes a core layer, as well as a skim coat layer between the first main surface of the core and the cover sheet. In some embodiments, there is a second skim coat layer between the second main surface of the core and a second cover sheet facing the first cover sheet, and this arrangement is understood in the art. Embodiments of the present invention are particularly useful for gypsum boards in which the hardened gypsum layer is formed from a stucco slurry containing a considerable amount of foreign salt. For example, in some embodiments, the salt is a chloride salt, such as sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), and / or calcium chloride (CaCl2).

[0020] Such salts can be found, for example, in stucco slurries where the stucco is derived from low-quality synthetic gypsum. In this regard, gypsum is typically procured to board manufacturing facilities, and the gypsum is then calcined to form stucco. The stucco is then reacted with water to form a gypsum (i.e., calcium sulfate dihydrate) layer of the desired dimensions. If low-quality synthetic gypsum contains a substantial amount of salt impurities, such salts have been found to remain in the stucco after calcination and therefore be present in the stucco slurry. In some embodiments, the stucco slurry contains high-quality salts, for example, at least about 150 ppm of chloride anions per 1,000,000 parts by weight of the calcium sulfate hemihydrate, for example, about 150 ppm to about 2,000 ppm of chloride anions per 1,000,000 parts by weight of the calcium sulfate hemihydrate. The presence of a substantial amount of salt impurities has been found to hinder adhesion between the gypsum layer and the cover sheet.

[0021] The gypsum layer of the board is prepared by mixing at least stucco, water, and optionally selected additives as needed. The gypsum layer is sandwiched between a front cover sheet and a back cover sheet. One or more gypsum layers can form a main gypsum layer in the form of a board core with two opposing main surfaces. A gypsum layer in the form of a thin skim coat can be placed on either of the main surfaces of the core. The sandwich structure is formed as a continuous ribbon at the wet end of the production line (near the main mixer). The continuous ribbon forms a board precursor, which is transported on a conveyor, cut into segments, and then dried in an oven, at least partially curing by the reaction of water and stucco. The main gypsum layer forms the board core, which is prepared from a first slurry, while the skim coat can be prepared from second and third slurries, which may be the same as or different from each other.

[0022] To enhance the bond between the cover sheet and the gypsum layer, the present invention provides components and techniques for enhancing the bond in the presence of high concentrations of salt impurities in the first slurry (and optionally, the second and / or third slurry). In embodiments of the present invention, at least one, preferably at least two, of the following bond-enhancing items (1) to (5) are employed: (1) At least one of the cover sheets, preferably the back cover sheet, is perforated. (2) At least one of the cover sheets, preferably the back cover sheet, is made of absorbent paper. (3) Starch is applied between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core. (4) Skim coat starch is included in the second and / or third slurry to enhance the bond between the board core and the front and / or back cover sheet, respectively. (5) Drying includes applying heat to a chamber (furnace) and further includes measuring the moisture content in the board upstream of the furrow using an upstream high-frequency moisture sensor and an upstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The furrow contains at least one in-furrow high-frequency moisture sensor, which communicates with a controller outside the furrow and generates an in-furrow moisture reading. An upstream sensor communicates with the controller and generates a first upstream moisture reading and a second upstream moisture reading, respectively. Moisture readings from the upstream high-frequency moisture sensor and the upstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor are correlated. If a delta exists between the first and second moisture readings, the in-furrow high-frequency moisture sensor is biased to correct any errors in the in-furrow moisture reading. In some embodiments, the moisture content in the board downstream of the furrow is measured using a downstream high-frequency moisture sensor and a downstream sensor less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. The downstream sensor communicates with the controller and generates a first downstream moisture reading and a second downstream moisture reading, respectively.A downstream high-frequency moisture sensor is used, and moisture readings from the downstream sensor are correlated with those from the downstream sensor, which is less affected by high salt concentrations in the slurry compared to the high-frequency moisture sensor. If there is a discrepancy between the readings, the burner output and / or air control device are used to adjust the temperature inside the furnace (e.g., to reduce the degree of heating inside). In some embodiments, three of items (1) to (5) are employed. In some embodiments, four of items (1) to (5) are employed. In some embodiments, all five of items (1) to (5) are employed. Related gypsum board products, as well as other methods and systems, are also provided.

[0023] The cover sheets may be fibrous or non-fibrous. In some embodiments, they may be formed from paper, fiber mats, or other types of materials (e.g., foil, plastic, glass mat, nonwoven material, such as a blend of cellulose and inorganic fillers).

[0024] The front and back cover sheets can have any preferred basis weight and thickness. Generally, the thickness of the front and back cover sheets (e.g., made of paper) is determined by the weight of the paper. For example, in some embodiments, the front and back cover sheets can have basis weights such as about 10 lb / msf to about 55 lb / msf, for example, about 20 lb / msf to about 55 lb / msf, about 20 lb / msf to about 50 lb / msf, about 20 lb / msf to about 40 lb / msf, about 30 lb / msf to about 55 lb / msf, about 30 lb / msf to about 50 lb / msf, and about 30 lb / msf to about 40 lb / msf. However, in some embodiments, the presence of an intermediate sheet allows for the use of lighter cover sheets, thereby reducing costs and / or enabling lighter boards. For example, in some embodiments, one or both of the front and back cover sheets have a weight of approximately 15 lb / msf to approximately 35 lb / msf, e.g., approximately 20 lb / msf to approximately 33 lb / msf, approximately 20 lb / msf to approximately 31 lb / msf, approximately 20 lb / msf to approximately 29 lb / msf, approximately 20 lb / msf to approximately 27 lb / msf, and approximately 15 lb / msf to approximately 31 lb / msf. Boards of such weight can have a nominal thickness of approximately 0.005 inches to approximately 0.015 inches, e.g., 0.007 to approximately 0.03 inches (e.g., approximately 0.01 inches).

[0025] In some embodiments, the back cover sheet is perforated, as described in U.S. Patent Application No. 16 / 401,675, incorporated herein by reference. Surprisingly, perforations in the back cover sheet of gypsum board may improve adhesion to the board core layer containing a large amount of foreign salts. The board core layer may be made from an aqueous slurry of stucco containing calcium sulfate hemihydrate and a large amount of foreign salts, particularly chloride salts. One or both of the cover sheets may be paper cover sheets, which may be the same or different paper material. Optionally, the front cover sheet of the gypsum board may be perforated, which may provide similar advantages. Further optionally, various additives may be present in the board core layer, or in the gypsum slurry used to form the board core layer. The board core layer may further include one or more high-density regions (layers) that are in contact with and coated on the inner surfaces of the front or back cover sheet. One or more high-density regions may be in contact with the low-density interior of the board core layer.

[0026] Without being constrained by theory or mechanism, it is thought that the pores in the back cover sheet provide conduits for the outward movement of chloride salts released from the board core layer, otherwise the chloride salts would aggregate unduly at the interface between the board core layer and the cover sheet. Instead, if pores are present, chloride ions and their counterions (e.g., Na) + , K + Mg 2+ and / or Ca 2+ The salt may migrate, at least partially, through the pores and potentially escape from the gypsum board environment. Alternatively, the salt may precipitate inside or just outside the pores on the outer surface of the back cover sheet. Salt precipitation outside the pores reduces the "net salt" between the paper and the core, and therefore reduces the amount of salt present at the interface, resulting in a better bond between the paper and the core. In either case, improved adhesion between the board core layer and the cover sheet may occur.

[0027] If the back cover sheet of a gypsum board is perforated in the manner described herein, the gypsum board may benefit from improved adhesion between the board core layer and the cover sheet compared to the same gypsum board but without perforations in the cover sheet. Accordingly, the present invention provides a gypsum board containing a considerable amount of foreign salts in the board core layer, and a method for producing such a gypsum board using a gypsum source containing a considerable amount of foreign salts. Thus, at least one of the cover sheets of a gypsum board having multiple perforations, particularly the perforations in the back cover sheet, may allow a low-quality gypsum source containing excessive foreign salts, particularly chloride salts, to be used when forming the gypsum board. Otherwise, such a gypsum source may be unsuitable for forming a gypsum board with sufficient adhesion between the board core layer and the cover sheet. Advantageously, the present invention addresses this problem.

[0028] In some embodiments, the back and front cover sheets are made from paper. However, the paper material of each cover sheet may be the same or different. According to embodiments of the present invention, only the back cover sheet of the gypsum board contains multiple through-holes. The back cover sheet is made from perforated paper.

[0029] Various grades of paper can be used for gypsum panels. For example, smooth calendered Manila-grade paper is often used as the facer paper cover sheet, while rougher-finished newsline paper is often used as the backer paper cover sheet. Typically, both paper grades are multilayer, with at least one liner layer and multiple filler layers. However, if necessary, at least one or both paper cover sheets may be made from single-layer paper.

[0030] As described above, the back cover sheet may contain multiple holes in several embodiments. Multiple holes may be arranged in the back cover sheet in any preferred form. Typically, the holes are arranged in a pattern such as a regular grid or array of holes (see, for example, Figure 2). Other patterned arrangements of holes also exist within the scope of this disclosure, and the particular arrangement of holes shown in Figure 2 should not be considered limiting. An exemplary apparatus for perforating one or more cover sheets in gypsum board in a manner consistent with this disclosure is described in U.S. Patent Application Publication 2018 / 0065336, which is incorporated herein by reference in its entirety.

[0031] The holes in the cover sheet are present in a shape, size, and pore density that is suitable for aiding the drying and / or enhanced adhesion of the gypsum board.

[0032] Typically, holes have a substantially circular shape. However, it should be recognized that holes may have alternative geometric shapes such as elliptical, triangular, square, or rectangular. Depending on the requirements of a particular application, any combination of circular and non-circular holes may exist. Any combination of non-circular holes may also exist.

[0033] Each hole in a cover sheet, particularly in a back cover sheet, may define an opening having a size in the range of approximately 0.005 inches to approximately 0.1 inches, preferably approximately 0.01 inches to approximately 0.1 inches, and more preferably approximately 0.01 inches to approximately 0.02 inches in its maximum lateral dimension. The term "maximum lateral dimension" refers to the maximum dimension measured across each hole in the plane of the cover sheet. In the case of a circular hole, the maximum lateral dimension represents the diameter of the circular opening.

[0034] The holes in the back cover sheet are typically the same size and shape. However, the holes may be a mixture of hole sizes and / or shapes. The hole sizes may be the same or different, but within any of the ranges specified above. Furthermore, if at least some of the holes have different shapes, there may be a first set of multiple holes having a first shape and a first size, as well as a second set of multiple holes having different shapes and / or different sizes. For example, the first set of multiple holes and the second set of multiple holes may have different shapes but be substantially the same size.

[0035] Pore ​​coverage density refers to the number of pores per unit area in the back cover sheet. The pores present in the back cover sheet are at a suitable pore coverage density to promote effective adhesion to the board core layer. The pore density in the cover sheet is approximately 5 to 50 pores / in. 2 Preferably about 12 to about 25 holes / in 2 For example, approximately 10 to 15 holes / in 2 , or for example, about 15-20 holes / in 2 This may be the case. Typically, the holes cover about 0.1 to 10% of the surface of the back cover sheet, more typically about 0.5 to 5%.

[0036] In some embodiments, at least one of the cover sheets (e.g., the back cover sheet) is a high-absorbency paper that absorbs more water than conventional paper, as described in U.S. Patent Application No. 62 / 939,264, which is incorporated herein by reference. When using a high-salt stacker, salts move to the surface of the paper cover sheet, between the layers of the paper cover sheet, and the interface between the paper cover sheet and the board core, resulting in reduced adhesion and potential delamination between layers. Without wishing to be bound by a particular theory, the use of high-absorbency paper is thought to increase the amount of salt impurities moving to the outside of the cover paper and correspondingly reduce the amount of salt moving to the interface between the cover sheet and the core. Further, during the drying process in a kiln, as moisture evaporates from the surface of the board, high-absorbency paper tends to absorb and evaporate moisture faster than conventional paper, and as a result, more salts are thought to move to the outside of the paper.

[0037] The high-absorbency paper can have any suitable weight and thickness. Generally, the weight of the paper is determined by the basis weight, which refers to the weight per unit area and can be expressed as pounds per 1000 square feet as the weight of the paper. In some embodiments, the high-absorbency paper has a basis weight of about 30 lb / MSF to about 70 lb / MSF, such as about 42 lb / MSF to about 60 lb / MSF, such as about 45 lb / MSF to about 55 lb / MSF. In some embodiments, the high-absorbency paper has a caliper of about 7 mils to about 20 mils, such as about 10 mils to about 15 mils (e.g., about 12 mils). g / m 2 The water absorption of the surface over 60 seconds, represented by g / m, is measured by the Cobb test. In this test, it is determined how many grams of water are absorbed on the surface of a 100 cm 2 sheet of paper based on the Cobb test. The procedure criteria for the Cobb test are described in TAPPI T 441.

[0038] High-absorbent paper can have any suitable water absorption higher than conventional paper. The binding side bump value refers to the inside of the paper in contact with the gypsum slurry, and the liner side bump value refers to the outside of the paper not in contact with the slurry. These bump values ​​are measured in accordance with the TAPPI criteria described in the TAPPI T 441 test procedure. For example, in some embodiments, high-absorbent paper has at least about 1.8 g / 100 cm 2 For example, approximately 1.8g / 100cm 2 ~About 3g / 100cm 2 For example, approximately 1.8g / 100cm 2 ~Approx. 2.9g / 100cm 2 , about 1.8g / 100cm 2 ~Approx. 2.7g / 100cm 2 , about 1.8g / 100cm 2 ~About 2.5g / 100cm 2 , about 2g / 100cm 2 ~About 3g / 100cm 2 , about 2g / 100cm 2 ~Approx. 2.9g / 100cm 2 , about 2g / 100cm 2 ~Approx. 2.7g / 100cm 2 , about 2g / 100cm 2 ~About 2.5g / 100cm 2 , about 2.1g / 100cm 2 ~About 3g / 100cm 2 , about 2.1g / 100cm 2 ~Approx. 2.9g / 100cm 2 , about 2.1g / 100cm 2 ~Approx. 2.7g / 100cm 2 , about 2.1g / 100cm 2 ~About 2.5g / 100cm 2 , about 2.2g / 100cm 2 ~About 3g / 100cm 2 , about 2g / 100cm 2 ~Approx. 2.9g / 100cm 2 , about 2.2g / 100cm 2 ~Approx. 2.7g / 100cm 2 , or approximately 2.2g / 100cm 2 ~About 2.5g / 100cm 2 , about 2.4g / 100cm2 ~About 3g / 100cm 2 , about 2.4g / 100cm 2 ~Approx. 2.9g / 100cm 2 , about 2.4g / 100cm 2 ~Approx. 2.7g / 100cm 2 It has bond side bump values ​​such as those mentioned above.

[0039] In some embodiments, the absorbent paper has an absorption rate of at least about 0.5 g / 100 cm 2 For example, approximately 0.5g / 100cm 2 ~Approx. 1.5g / 100cm 2 For example, approximately 0.5g / 100cm 2 ~Approx. 1.2g / 100cm 2 , about 0.7g / 100cm 2 ~Approx. 1.5g / 100cm 2 , about 0.7g / 100cm 2 ~Approx. 1.2g / 100cm 2 , about 0.9g / 100cm 2 ~Approx. 1.5g / 100cm 2 , about 0.9g / 100cm 2 ~Approx. 1.2g / 100cm 2 These papers have liner side bump values ​​such as [values ​​omitted]. Examples of high absorbency papers include USG's Newsline Hi-Abs and News SHW HiAbs. Newsline Hi Abs has a basis weight of approximately 45 lb / MSF to 48 lb / MSF. Newsline SHW Hi Abs is an ultra-high absorbency paper with a basis weight of approximately 53 to 63.5 lb / MSF.

[0040] In some embodiments, a starch layer is placed on the inner surface of the cover sheet, as described in U.S. Patent Application No. 16 / 401,719, incorporated herein by reference. Surprisingly, the presence of a starch layer can improve adhesion to a board core made from an aqueous slurry of stucco containing calcium sulfate hemihydrate and a large amount of foreign salt. Preferably, the starch layer is a continuous starch layer placed across the entire inner surface of the back cover sheet. Optionally, another starch layer is also placed across the entire inner surface of the front cover sheet. One or both of the cover sheets may be paper cover sheets, which may be the same or different paper material. Optionally, additional starch and / or other additives may be present in the board core or the aqueous gypsum slurry used to form the board core.

[0041] The board core may include lower-density regions (layers) and may further include one or more higher-density regions (layers) that are in contact with the inner surface of the front paper cover sheet or back paper cover sheet or a starch layer coated thereon.

[0042] Therefore, a starch layer coated on at least one of the cover sheets may allow the use of a low-quality gypsum source containing excessive foreign salts in the formation of gypsum board.

[0043] Preferably, the board may include a front skim coat and / or a back skim coat. In preferred embodiments, the skim coat layer is generally denser and much thinner than the hardened gypsum core. In some embodiments, the layer forming the hardened gypsum core contributes most significantly to the cumulative thickness of the gypsum layer and the board as a whole. In some embodiments, the hardened gypsum core constitutes a substantial thickness of the total thickness of all gypsum layers (e.g., at least about 90%, at least about 92%, at least about 95%, or at least about 97%). In some embodiments, the front and / or back skim coat layer has a dry thickness of about 0.125 inches (1 / 8 inch) to about 0.016 inches (1 / 64 inch). In a preferred embodiment, at least one skim coat layer has a thickness of about 0.08 inches to about 0.02 inches, for example, about 0.08 inches to about 0.03 inches, about 0.07 inches to about 0.02 inches, about 0.07 inches to about 0.03 inches, about 0.06 inches to about 0.02 inches, about 0.06 inches to about 0.03 inches, about 0.05 inches to about 0.02 inches, about 0.05 inches to about 0.03 inches, about 0.04 inches to about 0.02 inches, or about 0.04 inches to about 0.03 inches.

[0044] In some embodiments, one or both skim coats can be prepared from a slurry containing skim coat starch, as described in U.S. Patent Application No. 62 / 930,965, filed November 5, 2019, which is incorporated herein by reference. Surprisingly and beyond expectations, it has been found that including skim coat starch in a very thin back skim coat further strengthens the bond between the core and the back cover sheet. While not intended to be found by any particular theory, the presence of skim coat starch in a thin skim coat is thought to be effective in strengthening the bond between the cover sheet and the gypsum core because the starch acts as an adhesive that firmly binds the paper fibers to the gypsum crystals in the core.

[0045] In preferred embodiments, the starch is natural starch and is contained in the skim coat layer between the board core and the backing paper cover sheet. Thus, the present invention enables improved adhesion even when the board core and / or other gypsum layers are formed from stucco derived from low-quality synthetic gypsum that contains undesirable foreign salts, such as chloride salts including NaCl, KCl, MgCl2, and / or CaCl2, which have previously been found to interfere with paper-core bonding.

[0046] Therefore, in some embodiments, the main slurry used to form the gypsum board core may contain core starch, while the back skim coat layer and optionally the front skim coat layer are formed from a slurry containing skim coat starch. In some embodiments, the skim coat starch is provided at a higher relative concentration in the slurry for forming the skim coat layer compared to the amount of core starch in the slurry for forming the board core. As discussed herein, the skim coat starch surprisingly and beyond expectations enhances the adhesion of its corresponding (adjacent) cover sheets, even in the presence of undesirable salt impurities. In some embodiments, core starch is not considered effective in aiding the adhesion of the cover sheets in the presence of salt impurities.

[0047] Core starch is provided to enhance strength, as discussed, for example, in U.S. Patent Nos. 9,540,810, 9,828,441, and 10,399,899, and U.S. Patent Application No. 15 / 934,088. In some embodiments, mobile starch known in the art may be additionally included in the core slurry. Mobile starch typically has a smaller chain length (for example, due to acid or enzymatic denaturation) and migrates to the core-cover sheet interface to further strengthen the bond without significantly affecting the core's strength.

[0048] In preferred embodiments, the core starch is in the form of pregelatinized starch and has a viscosity of about 20 centipoise to about 700 (e.g., about 20 centipoise to about 300 centipoise or about 30 centipoise to about 200 centipoise) when the viscosity is measured while the starch is subjected to VMA conditions. In some embodiments, the core starch is natural starch. In some embodiments, the core starch comprises uncooked starch having a moderate peak viscosity of about 120 to 1000 BU when the viscosity is measured using a Viscograph-E instrument set to 75 rpm and 700 cmg, by (i) a hot water viscosity of about 20 BU to about 300 BU by a hot water viscosity assay (HWVA method), and / or (ii) a moderate peak viscosity of about 120 to 1000 BU when the starch is placed in a slurry containing water with a starch concentration of 15% solids, the starch is heated from 25°C to 95°C at a rate of 3°C / min, the slurry is held at 95°C for 10 minutes, and the starch is cooled to 50°C at a rate of -3°C / min. In some embodiments, the core starch comprises mobile starch having a molecular weight of about 6,000 daltons or less.

[0049] In some embodiments, skim coat starch is included in at least one skim coat layer (and optionally, in some embodiments, both skim coat layers). The starch used to prepare the skim coat layer is effective in strengthening the bond between the core and the adjacent cover sheet compared to boards prepared without starch in the slurry for forming the skim coat layer. In preferred embodiments, the starch is natural starch. In some embodiments, the skim-coated starch contains uncooked starch having a moderate peak viscosity of about 120 to 1000 BU when the viscosity is measured using a Viscograph-E instrument set to 75 rpm and 700 cmg, where (i) the starch has a hot water viscosity of about 20 BU to about 300 BU by hot water viscosity assay (HWVA method), and / or (ii) the starch is placed in a slurry containing water with a starch concentration of 15% solids, the starch is heated from 25°C to 95°C at a rate of 3°C / min, the slurry is held at 95°C for 10 minutes, and the starch is cooled to 50°C at a rate of -3°C / min. Alternatively, if necessary, the skim-coated starch may be in the form of pregelatinized starch, which, for example, has a viscosity of about 20 centipoise to about 700 (e.g., about 20 centipoise to about 300 centipoise or about 30 centipoise to about 200 centipoise) when the viscosity is measured while the starch is subjected to VMA conditions. In some embodiments, the skim-coated starch comprises mobile starch having a molecular weight of about 6,000 daltons or less. The HWVA method is described, for example, in U.S. Patent Publication 2019 / 0023612(A1), while the VMA method is described, for example, in U.S. Patent Publication 2012 / 0113124, and these methodologies are incorporated herein by reference.

[0050] In some embodiments, the skim coat starch is present in at least one of the skim coat layers, preferably at least one skim coat layer adjacent to the backing paper, in the second and / or third slurry in an amount of about 0.3% to about 8.0% by weight of the stucco, for example, about 1.0% to about 4.0% by weight of the stucco. In some embodiments, the skim coat starch is included in the second skim coat layer adjacent to the backing cover sheet, while the slurry for producing the first skim coat layer adjacent to the fronting cover sheet is formed from the same slurry for producing the core, for example, containing core starch. The total amount of skim coat starch used in the second and / or third slurry is greater than the amount of core starch used in the first slurry. In preferred embodiments, the amount of core starch used is about 0.1% to about 1.5% by weight of the stucco, while the amount of skim coat starch used is about 1.5% to about 4.0% by weight of the stucco. In some embodiments, the core starch is pregelatinized starch, the skim coat starch is uncooked starch, and a mobile starch is optionally additionally selected in the core starch and / or skim coat starch.

[0051] Figure 1 shows a cross-sectional embodiment of a wall panel (gypsum board) 10 of the present invention, in which a gypsum core (board core layer) 12 (for example, 0.5 inches thick) is sandwiched between a backer paper cover sheet (back cover sheet) 14 and a facer paper cover sheet (front cover sheet) 18, each of which may be single-layer or multi-layer paper. The backer paper cover sheet (back cover sheet) 14 has holes 20. The inner surface of the backer paper cover sheet 14 forms a bonding surface 24 of the backer paper cover sheet 14 that faces the gypsum core 12. The inner surface of the facer paper cover sheet 18 forms a bonding surface 28 that faces the gypsum core 12. The outer surface of the backer paper cover sheet 14 faces the room's wall framing after the wall panel 10 is installed as an interior wall. The outer surface of the facer paper cover sheet 18 faces the interior of the room after the wall panel 10 is installed as an interior wall.

[0052] The backer paper cover sheet (back cover sheet) 14 contains a plurality of through-holes 20 according to the present invention. Figure 2 shows a plan (axial) view of the wall panel 10, and an exemplary configuration of the holes 20 may be seen within the backer paper cover sheet 14. As shown, the holes 20 are patterned in a regular arrangement of columns and rows. Other patterned arrangements of the holes 20 are also within the scope of the present invention, and it should be recognized that the depicted number, spacing, and covering density of the holes 20 should not be considered limiting.

[0053] The holes 20 in the backer paper cover sheet 14 surprisingly improve the bonding performance between the gypsum core 12 and the backer paper cover sheet 14. This improved bonding performance may be particularly evident when the gypsum used to form the gypsum core 12 has a high salt concentration.

[0054] An optional thin, high-density gypsum layer (low-density region) 22 exists between the gypsum core 12 and the facer paper cover sheet 18, and is in contact with both the gypsum core 12 and the facer paper cover sheet 18. Thus, the thin, high-density gypsum layer 22 is inserted between the gypsum core 12 and the facer paper cover sheet 18. Another optional thin, high-density gypsum layer (not shown) may be inserted between the gypsum core 12 and the backer paper cover sheet 14, and may be in contact with both the gypsum core 12 and the backer paper cover sheet 14. Generally, the gypsum core 12 and the thin, high-density gypsum layer 22 have the same composition and are adjacent to each other. Collectively, the gypsum core 12 and the thin, high-density gypsum layer 22 may define the interior of the gypsum board 10, with the gypsum core 12 being a low-density region or layer and the thin, high-density gypsum layer 22 being a relatively high-density region or layer. Typically, the aqueous gypsum slurry used to form the gypsum core 12 is foamed. Therefore, low-density regions may be formed from foamed gypsum slurry. In contrast, the aqueous gypsum slurry used to form the thin, dense gypsum layer 22 is not foamed. Therefore, high-density regions may be formed from the non-foamed gypsum slurry. Thus, the thin, dense gypsum layer 22 is relatively denser than the rest of the gypsum core 12.

[0055] Therefore, high-density regions may have a lower porosity associated with them than low-density regions. Typically, a thin, high-density gypsum layer 22 is applied to the inner surface of the selected cover sheet. If present, the thin, high-density gypsum layer 22 is inserted between the cover sheet and the low-density region (gypsum core 12).

[0056] Certain amounts of one or more chloride salts may be present in the gypsum core 12 according to this disclosure. If a high-density region (a thin, dense gypsum layer 22) is included, one or more chloride salts may also be present therein. Generally, one or more chloride salts may be selected from the group consisting of NaCl, KCl, MgCl2, CaCl2 and any combination thereof.

[0057] The concentration of chloride anions in the aqueous slurry used to produce the board core 12 and, if present, the high-density region (thin, high-density gypsum layer 22) may range from about 500 ppm to about 3000 ppm per 1,000,000 parts by weight of calcium sulfate hemihydrate, typically from about 500 ppm to about 2000 ppm, and more typically from about 500 ppm to about 1500 ppm per 1,000,000 parts by weight of calcium sulfate hemihydrate.

[0058] As the salt passes through the pores, some of the salt from the original aqueous gypsum slurry may not remain in the core 12 and, if present, in the high-density areas (thin, dense gypsum layer 22), but may be present outside the pores or paper sheet.

[0059] Figure 3 shows a wall panel 110 according to an embodiment of the present invention, in which a gypsum core 112 (for example, about 0.5 inches thick) is sandwiched between a backer paper cover sheet (back cover sheet) 114 and a facer paper cover sheet (front cover sheet) 116, each of which may be single-layer or multi-layer paper. The inner surface of the backer paper cover sheet 114 forms a bonding surface 124 of the backer paper cover sheet 114 that faces the gypsum core. The inner surface of the facer paper cover sheet 116 forms a bonding surface 126 that faces the gypsum core 112. The outer surface of the backer paper cover sheet 114 faces the room wall framing (see Figure 5) after the wall panel 110 is installed as an interior wall. After the wall panel 110 is installed as an interior wall, the outer surface of the facer paper cover sheet 116 faces the interior of the room.

[0060] The starch layer 120 is located on the bonding side 124 of the backer sheet 114. An optional starch layer 120 is located on the bonding side 126 of the facer paper cover sheet 116. An optional thin, dense gypsum layer 122 is located between the gypsum core 112 and the facer paper cover sheet 116 and is in contact with both the gypsum core 112 and the facer paper cover sheet 116. If the thin, dense gypsum layer 122 is present, the starch layer 120 is located between the thin, dense gypsum layer 122 and the facer paper cover sheet 116. Another optional thin, dense gypsum layer (not shown) may be located between the gypsum core 112 and the backer paper cover sheet 114. Generally, the gypsum core 112 and the thin, dense gypsum layer 122 have the same composition and are adjacent to each other. However, the core slurry (aqueous slurry) used to form the gypsum core 112 is foamed, while the aqueous slurry used to form the thin, dense gypsum layer 122 is not foamed. Therefore, the thin, dense gypsum layer slurry is denser than the core slurry.

[0061] Surprisingly, the starch layer 120 improves the bonding performance between the gypsum core 112 and the backer sheet 114. This improved bonding performance is particularly noticeable when the salt concentration of the gypsum is high.

[0062] The starch layer is placed on the backing paper in an amount ranging from approximately 0.5 to 15 lbs / MSF, preferably approximately 0.5 to 5 lbs / MSF, and more preferably approximately 1 to 2 lbs / MSF (MSF = 1000 square feet). The starch is used as a binder and can be natural (uncooked) starch, pregelled starch, or a combination of natural starch and pregelled starch.

[0063] Generally, the relatively low-density internal region (gypsum core 112) and the relatively high-density region (thin, dense gypsum layer 122) have the same composition and are adjacent to each other. However, the low-density internal region may be formed from foamed gypsum slurry, while the high-density region may be formed from unfoamed gypsum slurry so that a higher-density layer is formed. In other words, the high-density region may have a lower porosity associated with it than the low-density internal region. Typically, the thin, dense gypsum layer 122 is applied to the inner surface of the selected cover sheet. If the high-density region is also present on the selected cover sheet, the starch layer 120 is located between the cover sheet and the high-density region (thin, dense gypsum layer 122).

[0064] One or more chloride salts may be present in the board core 112 of this disclosure. If a high-density region (a thin, dense gypsum layer 122) is included, one or more chloride salts may also be present therein. Generally, one or more chloride salts include any chloride salts from stucco or other components used to prepare the aqueous slurry for making the board.

[0065] The concentration of chloride anions in the aqueous slurry used to produce the board core 112 and, if present, the high-density region (thin, high-density gypsum layer 122) may range from about 500 ppm to about 3000 ppm, typically about 1000 ppm to about 3000 ppm, and more typically about 2000 ppm to about 3000 ppm, per 1,000,000 parts by weight of calcium sulfate hemihydrate.

[0066] For illustrative purposes, Figures 6A and 6B schematically illustrate embodiments of the present invention showing a composite gypsum board 210. The board 210 includes a front cover sheet 212 and a back cover sheet 214. The front cover sheet 212 has a first surface 216 and a second surface 218, which is generally the surface visible when the board 210 is installed. The back cover sheet 214 has a first surface 220 and a second surface 222, which is generally the outer surface of the board 210 that faces inward to studs, joists, etc., when installed.

[0067] The back skim coat layer 224 has a first surface 226 and a second surface 228 facing the first surface 220 of the back cover sheet 214. The board core 230 is positioned between the two cover sheets 212 and 214. Generally, the skim coat layer is a relatively denser and thinner gypsum layer than the board core 230. The board core 230 has a first surface 232 and a second surface 234. The first surface 232 of the board core 230 faces the first surface 220 of the back cover sheet 214. The back skim coat layer 224 contains skim coat starch 235 (shown as dots in Figures 6A and 6B) to enhance the adhesion of the core 230 to the cover sheet 214. As shown in Figures 6A and 6B, the front skim coat layer 236 is preferably provided between the front cover sheet 212 and the board core 230.

[0068] If included, the surface skim coat layer 236 has a first surface 238 facing the board core 230 and a second surface 240 facing the surface cover sheet 212, as seen in Figures 6A and 6B. If the surface skim coat layer 236 is present, in some embodiments it is formed from the same slurry used to form the board core, such that it contains core starch but does not contain skim coat starch, as shown in Figure 6A, for example. Alternatively, in some embodiments the surface skim coat layer 236 is formed from a slurry containing skim coat starch 235, as seen in Figure 6B.

[0069] In a wall assembly, boards can be attached to a substrate, typically studs in a framing structure. In a wall assembly, the back side of the board (i.e., the outer surface of the back cover sheet) faces inward toward the studs, whereas the front side of the board (i.e., the outer surface of the front cover sheet) is visible when the board is installed and hanging. Figure 5 is a perspective view of a typical building wall system 530 that may be used in the wall system of the present invention. Figure 5 shows a stud wall "skeleton" 532 including a number of studs 534, an upper track 536, and a lower track 538. Gypsum board 510 may be fastened to one or both sides of the studs 534 in any known way to close the wall and form an interior or surface of the wall or ceiling.

[0070] The stucco slurry used to produce the hardened gypsum layer of the board contains stucco in the form of, for example, calcium sulfate alpha hemihydrate, calcium sulfate beta hemihydrate, and / or calcium sulfate anhydrous. In addition to stucco, water, and core starch, the stucco slurry may contain a generally known optional additive, such as foaming agents, polyphosphates, dispersants, accelerators, retarders, etc. The board core is preferably formed from an agent that contributes to its low density, preferably a foaming agent, but in some embodiments, low-density fillers (e.g., perlite, low-density aggregate, etc.) may be used. Various foaming agent regimes are well known in the art. Foaming agents may be included to form a bubble distribution within the crystalline matrix of the hardened gypsum. In some embodiments, the foaming agent includes an unstable component in the main weight portion and a stable component in the smaller weight portion (e.g., a combination of unstable and stable / unstable blends). The weight ratio of unstable components to stable components is effective in forming a bubble distribution within the hardened gypsum core. See, for example, U.S. Patents 5,643,510, 6,342,284, and 6,632,550. In some embodiments, the foaming agent includes alkyl sulfate surfactants.

[0071] Many commercially known foaming agents are available, such as the HYONIC line of soap products from GEO Specialty Chemicals (Ambler, PA) (e.g., 25AS), and may be used according to embodiments of this disclosure. Other commercially available soaps include Polystep B25 from Stepan Company (Northfield, Illinois). The foaming agents described herein may be used alone or in combination with other foaming agents. Foam may be pre-generated and then added to the stucco slurry. Pre-generation may occur by introducing air into the aqueous foaming agent. Methods and apparatus for generating foam are well known; see, for example, U.S. Patents 4,518,652, 2,080,009, and 2,017,022.

[0072] In some embodiments, the blowing agent comprises, consists of, or is essentially composed of at least one alkyl sulfate, at least one alkyl ether sulfate, or any combination thereof, but is essentially free of olefins (e.g., olefin sulfates) and / or alkynes. Being essentially free of olefins or alkynes means that the blowing agent contains either (i) 0% by weight based on the weight of the stucco, or no olefins and / or alkynes, or (ii) an ineffective amount, or (iii) a negligible amount of olefins and / or alkynes. An example of an ineffective amount is, as those skilled in the art will understand, an amount below the threshold amount required to achieve the intended purpose of using the olefin and / or alkyne blowing agent. A negligible amount may be, as those skilled in the art will understand, based on the weight of the stucco, for example, less than about 0.001% by weight, e.g., less than about 0.0005% by weight, less than about 0.001% by weight, less than about 0.00001% by weight, etc.

[0073] Some types of unstable soaps are alkyl sulfate surfactants having different chain lengths and different cations, according to embodiments of the present disclosure. Preferred chain lengths are, for example, C8-C8. 12 For example, C8~C10 , or C 10 ~C 12 This is possible. Suitable cations include, for example, sodium, ammonium, magnesium, or potassium. Examples of unstable soaps include, for example, sodium dodecyl sulfate, magnesium dodecyl sulfate, sodium decyl sulfate, ammonium dodecyl sulfate, potassium dodecyl sulfate, potassium decyl sulfate, sodium octyl sulfate, magnesium decyl sulfate, ammonium decyl sulfate, blends thereof, and any combination thereof.

[0074] Some types of stable soaps, according to embodiments of this disclosure, are alkoxylated (e.g., ethoxylated) alkyl sulfate surfactants having different (generally longer) chain lengths and different cations. Preferred chain lengths are, for example, C 10 ~C 14 For example, C 12 ~C 14 , or C 10 ~C 12 This may be the case. Suitable cations include, for example, sodium, ammonium, magnesium, or potassium. Examples of stable soaps include, for example, sodium laureth sulfate, potassium laureth sulfate, magnesium laureth sulfate, ammonium laureth sulfate, blends thereof, and any combination thereof. In some embodiments, any combination of stable and unstable soaps from this enumeration may be used.

[0075] Examples of foaming agents and combinations thereof in the preparation of foamed gypsum products are disclosed in U.S. Patent No. 5,643,510, incorporated herein by reference. For example, a first foaming agent that forms stable foam and a second foaming agent that forms unstable foam may be combined. In some embodiments, the first foaming agent is a soap, for example, an alkoxylated alkyl sulfate soap having an alkyl chain length of 8 to 12 carbon atoms and an alkoxy (e.g., ethoxy) group chain length of 1 to 4 units. The second foaming agent is optionally a non-alkoxylated (e.g., non-ethoxylated) alkyl sulfate soap having an alkyl chain length of 6 to 20 carbon atoms, for example, 6 to 18 or 6 to 16 carbon atoms. Adjusting the individual amounts of these two soaps is considered to allow control of the board foam structure until about 100% stable soap or about 100% unstable soap is achieved, according to some embodiments.

[0076] In some embodiments, as described in U.S. Patent Publications 2017 / 0096369(A1), 2017 / 0096366(A1), and 2017 / 0152177(A1), fatty alcohols may optionally be included, together with a foaming agent, for example, in a premix for preparing a foam. This allows for better control of the size and distribution of foam (air) voids by resulting in improved foam stability. The aliphatic alcohol may be any suitable aliphatic fatty alcohol. As defined throughout this specification, “aliphatic” means alkyl, alkenyl, or alkynyl, which may be substituted or unsubstituted, branched or unbranched, and saturated or unsaturated, and in relation to some embodiments, the carbon chain described herein, e.g., C x ~C y It will be understood that this is represented by (where x and y are integers). Thus, the term aliphatic also refers to chains having heteroatom substitutions that maintain the hydrophobicity of the group. Fatty alcohols may be a single compound or a combination of two or more compounds. In some embodiments, the optional fatty alcohol is C6-C6 20Fatty alcohols (e.g., C6 - C 18 、C6 - C 116 、C6 - C 14 、C6 - C 12 、C6 - C 10 、C6 - C8, C8 - C 16 、C8 - C 14 、C8 - C 12 、C8 - C 10 、C 10 - C 16 、C 10 - C 14 、C 10 - C 12 、C 12 - C 16 、C 12 - C 14 、or C 14 - C 16 aliphatic fatty alcohols, etc.). Examples include octanol, nonanol, decanol, undecanol, dodecanol, or any combination thereof.

[0077] In some embodiments, the optional foam stabilizer contains fatty alcohols and is essentially free of fatty acid alkylamides or carboxylic acid taurides. In some embodiments, the optional foam stabilizer is essentially free of glycols, although glycols may be included in some embodiments, for example, to allow for a higher surfactant content. By being essentially free of any of the above components, it means that the foam stabilizer contains (i) 0 wt% based on the weight of any of these components, or (ii) an ineffective amount, or (iii) a trace amount of any of these components. An example of an ineffective amount is an amount less than the threshold amount for achieving the intended purpose for which any of these components are used, as understood by those skilled in the art. A trace amount, as understood by those skilled in the art, may be, for example, less than about 0.0001 wt%, such as less than about 0.00005 wt%, less than about 0.00001 wt%, less than about 0.000001 wt%, etc., based on the weight of the stack.

[0078] A suitable void distribution and wall thickness (independently) have been shown to be particularly effective in increasing strength in lower-density boards (e.g., less than approximately 35 pcf). See, for example, US2007 / 0048490 and US2008 / 0090068. In general, evaporative water voids with a diameter of approximately 5 μm or less also contribute to the total void distribution along with the aforementioned air (bubble) voids. In some embodiments, the volume ratio of voids having a pore diameter greater than approximately 5 microns to voids having a pore diameter of approximately 5 microns or less is approximately 0.5:1 to approximately 9:1, for example, approximately 0.7:1 to approximately 9:1, approximately 0.8:1 to approximately 9:1, approximately 1.4:1 to approximately 9:1, approximately 1.8:1 to approximately 9:1, approximately 2.3:1 to approximately 9:1, approximately 0.7:1 to approximately 6:1, approximately 1.4:1 to approximately 6:1, approximately 1.8:1 to approximately 6:1, approximately 0.7:1 to approximately 4:1, approximately 1.4:1 to approximately 4:1, approximately 1.8:1 to approximately 4:1, approximately 0.5:1 to approximately 2.3:1, approximately 0.7:1 to approximately 2.3:1, approximately 0.8:1 to approximately 2.3:1, approximately 1.4:1 to approximately 2.3:1, approximately 1.8:1 to approximately 2.3:1, etc.

[0079] Where used herein, void size is calculated from the maximum diameter of individual voids within the core. The maximum diameter is the same as the ferret diameter. The maximum diameter of each defined void can be obtained from an image of the sample. The image can be taken using any preferred technique, such as a scanning electron microscope (SEM) that provides two-dimensional images. The pore diameters of a large number of voids can be measured in the SEM image so that the randomness of the void cross-sections (pores) can provide an average diameter. This calculation can be improved by measuring voids in multiple images randomly located throughout the core of the sample. In addition, constructing a three-dimensional model of the core based on several two-dimensional SEM images can also improve the calculation of void size. Another technique is X-ray CT scanning analysis (XMT) which provides three-dimensional images. Another technique is optical microscopy, where optical contrast may be used to assist in determining, for example, the depth of the voids. Voids can be measured either manually or by using image analysis software, such as ImageJ developed by the NIH. Those skilled in the art will understand that the size and distribution of voids from an image can be determined by visual observation of the dimensions of each void. A sample can be obtained by dividing a gypsum board.

[0080] The foaming agent can be included in the stucco slurry in any suitable amount, for example, depending on the desired density. The foaming agent solution is prepared, for example, at about 0.5% (w / w). An appropriate amount of air is mixed with an appropriate amount of foaming agent solution and added to the slurry. Depending on the amount of air required, the concentration of the foaming agent solution can vary from about 0.1% to about 1% (w / w). Since the skim coat layer has a higher density, the slurry for forming the skim coat layer can be made with fewer (or no) bubbles.

[0081] Fatty alcohols, if present, may be present in the stucco slurry in any preferred amount. In some embodiments, fatty alcohols are present in the core slurry in amounts of about 0.0001% to about 0.03% by weight of the stucco, for example, about 0.0001% to about 0.025% by weight of the stucco, about 0.0001% to about 0.02% by weight of the stucco, or about 0.0001% to about 0.01% by weight of the stucco. Since the slurry for the skim coat layer contains little to no foam, fatty alcohols are not required for the skim coat layer, or may be included in smaller amounts, for example, about 0.0001% to about 0.004% by weight of the stucco, for example, about 0.00001% to about 0.003% by weight of the stucco, about 0.00001% to about 0.0015% by weight of the stucco, or about 0.00001% to about 0.001% by weight of the stucco.

[0082] In some embodiments, it has been found that chloride salts can act as accelerators, thus increasing the amount of retarder used. Secondly, when the salt is from a divalent or trivalent chloride salt such as magnesium chloride (MgCl2), calcium chloride (CaCl2), or aluminum chloride (AlCl3), the magnesium, calcium, or aluminum cations are chelated by the retarder, leading to the consumption of the retarder. Therefore, more retarder is required from divalent or trivalent salts than from monovalent salts.

[0083] In some embodiments, the stucco slurry optionally contains boric acid. Surprisingly and unexpectedly, the presence of boric acid can strengthen the bond between the gypsum layer and at least one cover sheet, even when the gypsum layer is made from stucco containing high levels of salt impurities. While we do not wish to be bound by any particular theory, the addition of boric acid is thought to prevent over-firing of the surface gypsum in the kiln. It is also thought to suppress mold formation caused by high salt concentrations on the surface of the board. In some embodiments, boric acid is present in an amount of about 0.01% to about 0.5% by weight of the stucco. In some embodiments, boric acid can be present in an amount of about 0.01% to about 0.3% by weight, or about 0.05% to about 0.3% by weight of the stucco.

[0084] For example, other components known in the art, including accelerators and retarders, may also be included in the board core slurry. Accelerators can take various forms (e.g., wet gypsum accelerators, heat resistance accelerators, and climate stabilization accelerators). See, for example, U.S. Patents 3,573,947 and 6,409,825. In some embodiments including accelerators and / or retarders, the accelerators and / or retarders may each be present in the stucco slurry in solid-based amounts of stucco, for example, about 0% to about 5% by weight (e.g., about 0.1% to about 5%), such as about 0% to about 10% by weight (e.g., about 0.1% to about 10%) of the stucco.

[0085] Furthermore, in some embodiments, the gypsum layer may be further formed from at least one dispersant to enhance fluidity. The dispersant may be present in the stucco slurry in a dry form with other dry components and / or in a liquid form with other liquid components. Examples of dispersants include naphthalene sulfonates such as polynaphthalene sulfonic acid and its salts (polynaphthalene sulfonates) and derivatives, which are condensation products of naphthalene sulfonic acid and formaldehyde; and polycarboxylate dispersants such as polycarboxylic acid ethers, e.g., PCE211, PCE111, 1641, 1641F, or PCE 2641 type dispersants, e.g., MELFLUX 2641F, MELFLUX 2651F, MELFLUX 1641F, MELFLUX 2500L dispersant (BASF), and COATEX Ethacryl M available from Coatex, Inc.; and / or lignosulfonates or sulfonated lignins. Lignosulfonates are water-soluble anionic polymer electrolytes that are byproducts of wood pulp production using sulfite pulping. An example of lignin useful for putting the principles of the embodiments of this disclosure into practice is Marasperse C-21, available from Reed Lignin Inc.

[0086] Low molecular weight dispersants are generally preferred. In the case of naphthalene sulfonate dispersants, in some embodiments they are selected to have a molecular weight of about 3,000 to about 10,000 (e.g., about 8,000 to about 10,000). In some embodiments, naphthalene sulfonates with higher water demands, for example, a molecular weight exceeding 10,000, can be used. As another example, in the case of PCE211 type dispersants, in some embodiments the molecular weight may be about 20,000 to about 60,000, which results in less delay than dispersants with a molecular weight exceeding 60,000.

[0087] An example of naphthalene sulfonate is DILOFLO, available from GEO Specialty Chemicals. DILOFLO is a 45% aqueous solution of naphthalene sulfonate, but other aqueous solutions with a solid content ranging from approximately 35% to 55% by weight are also readily available. Naphthalene sulfonate can be used in dry solid or powder form, such as LOMAR D, available from GEO Specialty Chemicals. Another example of naphthalene sulfonate is DAXAD, available from GEO Specialty Chemicals (Ambler, PA).

[0088] If included, the dispersant may be provided in any preferred amount. In some embodiments, for example, the dispersant may be present in the stucco slurry in amounts such as about 0% to about 0.5% relative to the weight of the stucco, for example, about 0.01% to about 0.7%, for example, about 0.01% to about 0.4%, or about 0.1% to about 0.2%.

[0089] In some embodiments, the gypsum layer may be further formed from at least one phosphate-containing compound as needed to enhance Green strength, dimensional stability, and / or flexure resistance. For example, effective phosphate-containing components in some embodiments include water-soluble components, which may be in the form of ions, salts, or acids, i.e., condensed phosphoric acid, each comprising two or more phosphoric acid units, a salt or ion of a condensed phosphate, each comprising two or more phosphate units, a monobasic salt or monovalent ion of an orthophosphate, and a water-soluble acyclic polyphosphate salt. See, for example, U.S. Patents 6,342,284, 6,632,550, 6,815,049, and 6,822,033.

[0090] When added in some embodiments, the phosphate composition can enhance green strength, resistance to permanent deformation (e.g., deflection), dimensional stability, etc. Green strength refers to the strength of the board that is still wet during manufacturing. Depending on the strictness of the manufacturing process, without sufficient green strength, the board precursor may be damaged on the production line.

[0091] For example, trimetaphosphate compounds including sodium trimetaphosphate, potassium trimetaphosphate, lithium trimetaphosphate, and ammonium trimetaphosphate can be used. Sodium trimetaphosphate (STMP) is preferred, but other phosphates may be suitable, for example, sodium tetrametaphosphate, having about 6 to about 27 repeating phosphate units, with the molecular formula Na n+2 P n O 3n+1 (where n = 6 - 27) sodium hexametaphosphate, tetrapotassium pyrophosphate having the molecular formula K4P2O7, trisodium dipotassium tripolyphosphate having the molecular formula Na3K2P3O 10 having, trisodium tripolyphosphate having the molecular formula Na5P3O 10 having, tetrasodium pyrophosphate having the molecular formula Na4P2O7, aluminum trimetaphosphate having the molecular formula Al(PO3)3, sodium acid pyrophosphate having the molecular formula Na2H2P2O7, having 1,000 - 3,000 repeating phosphate units, with the molecular formula (NH4) n+2 P n O 3n+1 (where n = 1,000 - 3,000) ammonium polyphosphate, or polyphosphoric acid having 2 or more repeating phosphate units, with the molecular formula H n+2 P n O 3n+1 (where n is 2 or more).

[0092] Polyphosphates, if present, may be present in any preferred amount. For illustrative purposes, in some embodiments, polyphosphates may be present in the slurry in amounts of, for example, about 0.1% to about 1% of the stucco, e.g., about 0.2% to about 0.4% by weight, or about 0% to about 0.5% of the stucco, e.g., about 0% to about 0.2% by weight. Thus, the dispersant and polyphosphate may be optionally present in any preferred amount in the stucco slurry.

[0093] If necessary, in some embodiments, components for fire resistance and / or water resistance may be optionally included in the gypsum slurry. Examples include, for example, siloxane (water-resistant), fibers, aluminum trihydrate (ATH), heat sink additives such as magnesium hydroxide, and / or high-expansion particles (e.g., capable of expanding to about 300% or more of the original volume when heated at 1560°F for about 1 hour). Further disclosures relating to such additives can be found in U.S. Patent No. 8,323,785. High-expansion vermiculite may be included, but other fire-resistant materials may be included. Where present, fire-resistant or water-resistant additives may be included in any suitable amount as needed, depending on, for example, the fire grade and similar performance parameters. For example, if included, fire-resistant or water-resistant additives may be present individually in amounts of about 0.5% to about 10% by weight of the stucco, for example, about 1% to about 10% by weight, about 1% to about 8% by weight, about 2% to about 10% by weight, or about 2% to about 8% by weight. If included, siloxane may be introduced, preferably in the form of an emulsion. The slurry can then be molded and dried under conditions that promote the polymerization of siloxane to form a highly crosslinked silicone resin. A catalyst that promotes the polymerization of siloxane to form a highly crosslinked silicone resin may be added to the gypsum slurry. A solvent-free methylhydrogen siloxane fluid can be used as the siloxane. This product is a siloxane fluid that does not contain water or solvents. Based on the weight of the dry raw materials, it is considered that about 0.3% to about 1.0% of siloxane may be used if necessary. For example, if necessary, approximately 0.4% to 0.8% of siloxane may be present in the gypsum slurry based on the dry stucco weight. For fire and / or water resistance, one or more of these components may be absent. For example, siloxane may be absent.

[0094] In such fire-resistant embodiments, it is preferable that clay is included in the stucco slurry. The presence of clay in fire-resistant boards prepared with high levels of chloride is thought to significantly reduce thermal shrinkage during a fire. Any suitable clay, such as kaolin clay, can be used. In some embodiments, the clay is present in an amount of about 1% to about 10% by weight of the stucco. In some embodiments, the clay may be present in an amount of about 1% to about 5% by weight of the stucco.

[0095] The board core has a desired total composite board density, for example, about 16 pcf (about 260 kg / m³). 3 )~approximately 40pcf, for example, approximately 18pcf~approximately 40pcf, 18pcf~approximately 38pcf, 18pcf~approximately 36pcf, 18pcf~approximately 32pcf, 20pcf~approximately 40pcf, 20pcf~approximately 36pcf, 20pcf~approximately 32pcf, 22pcf~approximately 40pcf, 22pcf~approximately 36pcf, 22pcf~approximately 32pcf, 26pcf~approximately 40pcf, 26pcf~approximately 36pcf, or any preferred density useful for contributing to a core density of 26pcf~approximately 32pcf. In some embodiments, the board core may have an even lower density, for example, approximately 30pcf or less, approximately 29pcf (approximately 460kg / m³). 3 ) or less, approximately 28 pcf or less, approximately 27 pcf (approximately 430 kg / m 3 ) or less, approximately 26 pcf or less. For example, in some embodiments, the core density is approximately 12 pcf (approximately 190 kg / m³). 3 ) ~ approx. 30 pcf, approx. 14 pcf (approx. 220 kg / m 3 ) ~ approx. 30 pcf, 16 pcf ~ approx. 30 pcf, 16 pcf ~ approx. 28 pcf, 16 pcf ~ approx. 26 pcf, 16 pcf ~ approx. 3 These ranges from approximately 18pcf to 30pcf, 18pcf to 28pcf, 18pcf to 26pcf, 18pcf to 24pcf, 20pcf to 30pcf, 20pcf to 28pcf, 20pcf to 26pcf, 20pcf to 24pcf, 22pcf to 28pcf, etc.

[0096] In some embodiments, composite boards manufactured according to this disclosure satisfy the test protocol in accordance with ASTM standard C473-10. For example, in some embodiments, when the board is cast to a thickness of 1 / 2 inch, the dry board is at least about 67 lb, as determined according to ASTM C473-10 (Method B). f (pounds of force), for example, at least about 68 lb f at least about 70 lb f at least about 72 lb f at least about 74 lb f at least about 75 lb f at least about 76 lb f at least about 77 lb f It has nail-pulling resistance such as 67 lb. In various embodiments, the nail-pulling resistance is about 67 lb. f ~approximately 100lb f , about 67lb f ~about 95lb f , about 67lb f ~approximately 90 lb f , about 67lb f ~about 85lb f , about 67lb f ~about 80lb f , about 67lb f ~about 75lb f Approximately 68 lb f ~approximately 100lb f Approximately 68 lb f ~about 95lb f Approximately 68 lb f ~approximately 90 lb f Approximately 68 lb f ~about 85lb f Approximately 68 lb f ~about 80lb f , about 70lb f ~approximately 100lb f , about 70lb f ~about 95lb f , about 70lb f ~approximately 90 lb f , about 70lb f ~about 85lb f , about 70lb f ~about 80lb f , about 72lb f~approximately 100lb f , about 72lb f ~about 95lb f , about 72lb f ~approximately 90 lb f , about 72lb f ~about 85lb f , about 72lb f ~about 80lb f , about 72lb f ~about 77lb f , about 72lb f ~about 75lb f , about 75lb f ~approximately 100lb f , about 75lb f ~about 95lb f , about 75lb f ~approximately 90 lb f , about 75lb f ~about 85lb f , about 75lb f ~about 80lb f , about 75lb f ~about 77lb f , about 77lb f ~approximately 100lb f , about 77lb f ~about 95lb f , about 77lb f ~approximately 90 lb f , about 77lb f ~about 85lb f , or approximately 77 lb f ~about 80lb f It is possible.

[0097] In some embodiments, the composite gypsum board is at least about 11 lb, as determined according to ASTM C473-10, Method B. f For example, at least about 12 lb f at least about 13 lb f at least about 14 lb f at least about 15 lb f at least about 16 lb f at least about 17 lb f at least about 18 lb f at least about 19 lb f at least about 20 lbf at least about 21 lb f , or at least about 22 lb f It can have an average core hardness of approximately 11 lb. In some embodiments, the board may have an average core hardness of approximately 11 lb. f ~about 25lb f For example, about 11 lb f ~about 22lb f Approximately 11 lb f ~about 21lb f Approximately 11 lb f ~about 20lb f Approximately 11 lb f ~about 19lb f Approximately 11 lb f ~approximately 18 lb f Approximately 11 lb f ~about 17lb f Approximately 11 lb f ~about 16lb f Approximately 11 lb f ~approximately 15 lb f Approximately 11 lb f ~about 14lb f Approximately 11 lb f ~about 13lb f Approximately 11 lb f ~about 12lb f , about 12lb f ~about 25lb f , about 12lb f ~about 22lb f , about 12lb f ~about 21lb f , about 12lb f ~about 20lb f , about 12lb f ~about 19lb f , about 12lb f ~approximately 18 lb f , about 12lb f ~about 17lb f , about 12lb f ~about 16lb f , about 12lb f ~approximately 15 lb f , about 12lb f ~about 14lb f , about 12lb f ~about 13lb f , about 13lb f ~about 25lbf Approximately 13 lbs f ~approximately 22 lbs f Approximately 13 lbs f ~approximately 21 lbs f Approximately 13 lbs f ~approximately 20 lbs f Approximately 13 lbs f Approximately 19 lbs f Approximately 13 lbs f ~approximately 18 lbs f Approximately 13 lbs f ~approximately 17 lbs f Approximately 13 lbs f ~approximately 16 lbs f Approximately 13 lbs f ~approximately 15 lbs f Approximately 13 lbs f ~approximately 14 lbs f Approximately 14 lbs f Approximately 25 lbs f Approximately 14 lbs f ~approximately 22 lbs f Approximately 14 lbs f ~approximately 21 lbs f Approximately 14 lbs f ~approximately 20 lbs f Approximately 14 lbs f Approximately 19 lbs f Approximately 14 lbs f ~approximately 18 lbs f Approximately 14 lbs f ~approximately 17 lbs f Approximately 14 lbs f ~approximately 16 lbs f Approximately 14 lbs f ~approximately 15 lbs f Approximately 15 lbs f Approximately 25 lbs f Approximately 15 lbs f ~approximately 22 lbs f Approximately 15 lbs f ~approximately 21 lbs f Approximately 15 lbs f ~approximately 20 lbs f Approximately 15 lbs f Approximately 19 lbs f Approximately 15 lbs f ~approximately 18 lbs f Approximately 15 lbs f ~approximately 17 lbs f Approximately 15 lbs f ~approximately 16 lbs f, about 16lb f ~about 25lb f , about 16lb f ~about 22lb f , about 16lb f ~about 21lb f , about 16lb f ~about 20lb f , about 16lb f ~about 19lb f , about 16lb f ~approximately 18 lb f , about 16lb f ~about 17lb f , about 17lb f ~about 25lb f , about 17lb f ~about 22lb f , about 17lb f ~about 21lb f , about 17lb f ~about 20lb f , about 17lb f ~about 19lb f , about 17lb f ~approximately 18 lb f Approximately 18 lb f ~about 25lb f Approximately 18 lb f ~about 22lb f Approximately 18 lb f ~about 21lb f Approximately 18 lb f ~about 20lb f Approximately 18 lb f ~about 19lb f , about 19lb f ~about 25lb f , about 19lb f ~about 22lb f , about 19lb f ~about 21lb f , about 19lb f ~about 20lb f , about 21lb f ~about 25lb f , about 21lb f ~about 22lb f , or about 22lb f ~about 25lb f It can have a core hardness of [value].

[0098] Regarding bending strength, in some embodiments, when casting to a 1 / 2-inch thick board, the dry board has a bending strength of at least about 36 lb in the machine direction, as determined according to ASTM standard C473-10. f (For example, at least about 38 lb) f at least about 40 lb f (etc.), and / or at least about 107 lb in the width direction. f (For example, at least about 110 lb) f at least approximately 112 lb f It has a bending strength of (etc.). In various embodiments, the board has a bending strength of approximately 36 lb. f ~about 60lb f For example, about 36 lb f ~approximately 55 lb f , about 36lb f ~about 50lb f , about 36lb f ~45lb f , about 36lb f ~40lb f , about 36lb f ~approximately 38 lb f Approximately 38 lb f ~about 60lb f Approximately 38 lb f ~approximately 55 lb f Approximately 38 lb f ~about 50lb f Approximately 38 lb f ~45lb f Approximately 38 lb f ~40lb f Approximately 40 lb f ~about 60lb f Approximately 40 lb f ~approximately 55 lb f Approximately 40 lb f ~about 50lb f , or about 40 lb f ~45lb f It can have a bending strength in the mechanical direction. In various embodiments, the board can have a bending strength of about 107 lb. f ~approximately 130 lb f For example, about 107 lb f ~about 125lb f , about 107lb f~approximately 120 lb f , about 107lb f ~about 115lb f , about 107lb f ~about 112lb f , about 107lb f ~about 110lb f , about 110lb f ~approximately 130 lb f , about 110lb f ~about 125lb f , about 110lb f ~approximately 120 lb f , about 110lb f ~about 115lb f , about 110lb f ~about 112lb f , about 112lb f ~approximately 130 lb f , about 112lb f ~about 125lb f , about 112lb f ~approximately 120 lb f , or approximately 112 lb f ~about 115lb f It can have bending strength in the width direction.

[0099] Advantageously, in the various embodiments of the various board densities described herein, the dry composite gypsum board is at least about 170 psi (1,170 kPa), for example, about 170 psi to about 1,000 psi (6,900 kPa), about 170 psi to about 900 psi (6,200 kPa), about 170 psi to about 800 psi (5,500 kPa), about 170 psi to about 700 psi (4,800 kPa), about 170 psi to about 6 It can have a compressive strength of 00 psi (4,100 kPa), approximately 170 psi to approximately 500 psi (3,450 kPa), approximately 170 psi to approximately 450 psi (3,100 kPa), approximately 170 psi to approximately 400 psi (2,760 kPa), approximately 170 psi to approximately 350 psi (2,410 kPa), approximately 170 psi to approximately 300 psi (2,070 kPa), or approximately 170 psi to approximately 250 psi (1,720 kPa). In some embodiments, the board has a compressive strength of at least about 450 psi (3,100 kPa), at least about 500 psi (3,450 kPa), at least about 550 psi (3,800 kPa), at least about 600 psi (4,100 kPa), at least about 650 psi (4,500 kPa), at least about 700 psi (4,800 kPa), at least about 750 psi (5,200 kPa), at least about 800 psi (5,500 kPa), at least about 850 psi (5,850 kPa), at least about 900 psi (6,200 kPa), at least about 950 psi (6,550 kPa), or at least about 1,000 psi (6,900 kPa). Furthermore, in some embodiments, the compressive strength may be limited by any two of the points described above. For example, compressive strength may range from approximately 450 psi to approximately 1,000 psi (e.g., between approximately 500 psi and approximately 900 psi, between approximately 600 psi and approximately 800 psi, etc.). Where used herein, compressive strength is measured using a material testing system commercially available as the ATS machine model 1610 from Applied Test Systems (Butler, PA). The load is applied continuously at a rate of 1 inch / min without impact.

[0100] A gypsum board according to an embodiment of the present invention can be manufactured on a typical gypsum board manufacturing line. For example, board manufacturing techniques are described, for example, in U.S. Patent No. 7,364,676, U.S. Patent Application Publication No. 2010 / 0247937, and U.S. Patent Application No. 16 / 581,070. Briefly, the process typically involves discharging a cover sheet onto a moving conveyor. Since gypsum boards are usually formed "inside out," this cover sheet is a "front" cover sheet in such embodiments. Front and / or back skim coats, as known in the art, may be included as they may be.

[0101] In some embodiments, one or both skim coat layers have an average dry core hardness at least about 1.5 times greater than the average dry core hardness of the board core, where the average core hardness is measured according to ASTM C-473-07 and is, for example, at least about 2 times greater, 2.5 times greater, 3 times greater, 3.5 times greater, 4 times greater, 4.5 times greater, and so on, and each of these ranges can have any mathematically appropriate upper limit, such as 8, 7, 6, 5, 4, 3, or 2.

[0102] The slurries for forming the board core and the skim coat layer can be formed in any preferred manner. For example, both slurry flows can be developed using a single mixer. The mixer can be, for example, a “pin mixer” or a “pinless mixer” as needed, in which the raw materials are agitated. Alternatively, two or more separate mixers can be used. Multiple mixers can be connected in series or not connected. Examples of mixers are described in European Patent No. 1637302(B1), European Patent No. 2929996(B1), European Patent Application No. 3342571(A1), and U.S. Patent Application No. 2017 / 0008192(A1). Since the amount of slurry that needs to be applied to the skim coat layer is less than the amount of slurry applied to form the board core, as needed for efficiency, the mixer used for the skim coat layer can have a smaller mixing volume in some embodiments. The “main” mixer (i.e., for forming a board core slurry) comprises a body and a discharge conduit (e.g., a gate-canister-boot arrangement known in the art, or an arrangement of modified outlet designs (MODs) described in U.S. Patents No. 6,494,609 and No. 6,874,930). Foaming agents and / or core starches may be added into the discharge conduit of the mixer (e.g., into the gate, as described in U.S. Patents No. 5,683,635 and No. 6,494,609).

[0103] In embodiments where skim coat starch is used, the appropriate amount of starch can be adjusted in each mixer in two mixer systems. When a single mixer is used, any preferred arrangement can be used. For example, the skim coat flow can exit through the ports and outlets of the mixer body, i.e., upstream of the discharge conduit. The skim coat outlet has one or more inlets, allowing for the introduction of any other desired components different from the skim coat starch and the board core slurry exiting the mixer's discharge conduit. If a foaming agent is introduced into the discharge conduit, the amount of foaming agent is reduced or avoided in the skim coat flow because it is removed upstream of where the foaming agent is added, thereby allowing for an increase in the density of the skim coat layer as needed. If a foaming agent is present in the skim coat flow, it can be neutralized by techniques known in the art. In a preferred embodiment, the back skim coat layer is formed from the skim coat flow. If necessary, the front skim coat layer can also be formed from the skim coat flow. However, in some embodiments, the surface skim coat layer can be formed from the slurry flow exiting the discharge conduit, and this flow is also used to form the board core. To increase the density of the surface skim coat layer relative to the board core, any bubbles within it can be neutralized as needed.

[0104] In some embodiments, the discharge conduit may include a slurry distributor having either a single or multiple feed ports, such as those described in U.S. Patent Publication No. 2012 / 0168527(A1) (Application No. 13 / 341,016) and U.S. Patent Publication No. 2012 / 0170403(A1) (Application No. 13 / 341,209). In those embodiments, by using a slurry distributor having multiple feed ports, the discharge conduit may include a suitable flow divider, such as that described in U.S. Patent Publication No. 2012 / 0170403(A1).

[0105] As understood in the art, the board is typically formed in a sandwich structure, simultaneously and continuously. The top cover sheet moves as a continuous ribbon on a moving conveyor. After being discharged from the mixer, the slurry of the top skim coat layer is applied to the (moving) top cover sheet. Also, hard edges known in the art may be formed, if necessary, from the same slurry flow that forms the skim coat layers (e.g., top and / or back skim coat layers), for example, for convenience.

[0106] Next, the board core slurry is applied onto the skim coat layer and covered by a second cover sheet (typically a “back” cover sheet) to form a wet assembly in the form of a sandwich structure, which is a board precursor of the final product. The back (bottom) cover sheet can support the back skim coat layer, which may optionally contain skim coat starch as described herein to enhance the bond between the backing paper and the board core. The back skim coat layer can be formed from the same or a different gypsum slurry as that used for the front skim coat layer. In some embodiments, the skim coat layer is applied to the back side of the board, i.e., to the bottom (back) cover sheet in a bonding relationship, but the skim coat layer is not applied between the core and the top cover sheet.

[0107] The backing sheet (backing paper faceter sheet) may be perforated before it comes into contact with the gypsum slurry. The backing sheet may be procured / obtained from the manufacturer with pre-existing holes, or the holes may be introduced immediately before the backing sheet comes into contact with the gypsum slurry. Therefore, the holes do not extend into the board core layer or gypsum slurry before setting. For example, multiple holes may be introduced using a suitable wall panel perforator, such as that described in U.S. Patent Application Publication 2018 / 0065336. However, it should be noted that any suitable wall panel perforator may be used.

[0108] In some embodiments, the starch layer is present on at least one cover sheet, particularly on the back cover sheet, to increase adhesion thereto. The starch layer may be pre-coated on the inner surface of at least one of the front paper cover sheet and the back cover sheet. In alternative examples, the method may further include applying the starch layer to the inner surface of at least one of the front paper cover sheet and the back cover sheet. The starch may be applied to the inner surface as a continuous starch layer, as defined above. More specifically, the starch may be applied to the inner surface of the front paper cover sheet and / or back paper cover sheet in an amount of about 0.5 to 15 lbs / MSF, preferably about 0.5 to 5 lbs / MSF, more preferably about 1 lbs / MSF to about 2 lbs / MSF. Preferred methods for applying the starch layer to either the back paper cover sheet or the front paper cover sheet may include, for example, spraying, painting, inkjet printing, stenciling, stencil printing, roller coating, dip coating (immersion), etc.

[0109] In some embodiments, the cover (facing down at the wet end of the board machine) can be folded and overlapped at the edge of the board to form a board envelope, so that the edges of the paper align with the backing paper (facing up at the wet end of the board machine), and thus it can be manufactured to be slightly wider than the width of the final board product. For example, for a nominally 48-inch wide board, the cover can be about 50 inches or wider (e.g., about 50 to about 52 inches, e.g., about 50.375 inches). Correspondingly, in some embodiments, the backing paper can be manufactured to be narrower than the width of the board. Thus, for a nominally 48-inch wide board, the backing paper can be less than about 48 inches wide (e.g., about 46.5 to about 47.5 inches, e.g., about 47.125 inches).

[0110] The resulting wet assembly is then transported to a forming station (e.g., via a forming plate) where the product is sized to the desired thickness, and to one or more knife sections where it is cut to the desired length. The wet assembly is then allowed to harden to form an interlocking crystalline matrix of hardened gypsum, and any excess water is removed using a drying process (e.g., by transporting the assembly through a kiln).

[0111] Furthermore, vibration is commonly used in the manufacture of gypsum board to remove large gaps or air pockets from the accumulated slurry. Each of the above steps, as well as the processes and apparatus for carrying out such steps, are known in the art.

[0112] It is known that the presence of high concentrations of salt impurities in the stucco slurry can complicate the drying process. As described herein, after the ribbon of board precursor has hardened considerably, it is cut into segments and dried in an oven. The oven is typically equipped with one or more moisture sensors, which communicate with a programmable logic controller to produce moisture readings (e.g., a percentage of moisture). These moisture values ​​are then used to adjust the degree of heating in the oven, either automatically via the programmable logic controller or manually by a board line operator. However, it is known that high concentrations of salt impurities in the stucco can cause the sensors to produce false moisture readings that are normally higher than the true moisture value. This can lead to overheating of the board (e.g., by excessive time and / or oven temperature).

[0113] Over-drying the board can lead to board quality problems such as cracking and can further exacerbate poor bonding between the main gypsum layer and one or both cover sheets. Overheating the board can cause some of the hardened gypsum to undesirably sinter, reforming calcium sulfate hemihydrate adjacent to one or both cover sheets, potentially separating the cover sheets from the main gypsum layer. Therefore, achieving good bonding between the cover sheets and the gypsum layer is difficult in the presence of salt impurities, and overheating the board when removing excess water exacerbates this difficulty.

[0114] In some embodiments, additional moisture sensors are provided upstream and / or downstream of the kiln to compensate for and adjust for the presence of salt impurities in the stucco slurry. The sensors communicate with a programmable logic controller (often referred to in the art as a PLC). Moisture values ​​between two upstream sensors and / or between two downstream sensors can be correlated to determine whether there is a delta between any or both sets of readings. If a delta is found, heating inside the kiln can be adjusted manually or automatically by the controller to avoid over-drying. Thus, the drying process according to some embodiments of the present invention makes it possible to determine whether there is a high salt content in the board precursor that interferes with the moisture readings of the kiln sensors, and also allows for adjustment of the drying to correct any errors caused by the salt content.

[0115] For example, Figure 7 schematically illustrates one embodiment of a preferred arrangement. The production line 700 includes a mixer 705 at the wet end of the line. After the stucco slurries of the board core and skim coat layers are placed between cover sheets to form a continuous ribbon of board precursor, the ribbon moves down the line on a conveyor 710 and is cut into segments, for example, with a knife.

[0116] The kiln 715 contains a desired number of drying zones, each equipped with one or more heat sources, such as burners. Two drying zones, 720 and 725, are shown in Figure 7. Alternatively, the kiln 715 may contain one zone, or three or more zones as needed (e.g., up to 24-36 or more zones as needed). Each zone can be individually adjusted to the desired heating environment as needed. The kiln 715 contains two kiln moisture sensors 730 and 735, both located within zone 725. The kiln moisture sensors 730 and 735 are selected to withstand the harsh heating environment within the kiln 715. For example, the kiln moisture sensors 730 and 735 may be in the form of high-frequency sensors that are durable enough to handle the heating environment within the kiln 715 but are susceptible to erroneous moisture readings when high salt concentrations are present in the stucco slurry used to produce the gypsum layer.

[0117] Upstream high-frequency moisture sensors 740 and upstream sensor 745, which are less affected by high salt concentrations (compared to high-frequency sensors), are positioned to measure the moisture content immediately before the cut ribbon enters the kiln 715. Downstream high-frequency moisture sensors 750 and downstream sensor 755, which are less affected by high salt concentrations, are optionally provided and positioned to measure the moisture content of the cut ribbon immediately after it has passed through the kiln 715. Each sensor 730, 735, 740, 745, 750, and 755 communicates with a programmable logic controller 760, which may have known memory hardware as needed. Signals can be transmitted back and forth between the controller 760 and the sensors 730, 735, 740, 745, 750, and 755. The controller 760 is also used to make adjustments using various controls within the kiln, for example, to adjust the heat for the drying process.

[0118] The inventors have found that the kiln-internal high-frequency moisture sensors 730 and 735 may be affected by the salt impurity content associated with the stucco, which may result in inaccurate moisture readings. For example, sensors 730 and 735 may inaccurately identify more moisture than is actually present, leading to over-drying, a decrease in the quality of boards produced during the manufacturing process, and an increased rate of substandard, defective, or unacceptable boards. To correct for erroneous moisture readings from the kiln-internal high-frequency sensors 730 and 735, upstream sensors 740 and 745 and / or downstream sensors 750 and 755 are arranged in conjunction with the controller 760 to adjust the heating within the kiln 715.

[0119] The upstream high-frequency sensor 740 may also be affected by the high salt content associated with the stucco, if present, while other upstream sensors are selected to be less susceptible to salt influence. Thus, the respective moisture readings produced by the upstream sensors 740 and 745 can be correlated, for example, manually or by the controller 760, to determine if there is any delta (difference) between them. If the values ​​correlate without any discrepancies, this indicates that the salt impurity content in the board is negligible and no adjustment is required. In this case, heating in the kiln 715 can proceed using the raw moisture values ​​produced by the kiln sensors 730 and 735.

[0120] However, if there is a delta between the moisture values ​​generated by the upstream sensors 740 and 745, it indicates the presence of salt impurities, which may impair the moisture value generated by the high-frequency sensor 740, and consequently, the in-kiln high-frequency sensors 730 and 735 become inaccurate. To compensate, the controller 760 can be used to bias the moisture values ​​generated by sensors 730 and 735, thereby adjusting the heating control regime communicating with the controller 760 to correct heating parameters and avoiding improper drying (e.g., over-drying).

[0121] Similarly, moisture readings generated by downstream sensors 750 and 755 are also correlated. If there is no discrepancy between the respective temperature readings, no adjustment is required. However, if there is a difference between the moisture readings, thereby indicating a corruption of the moisture value due to a high salt content, the heating regime, which is in communication with controller 760, can be adjusted. In this regard, the kiln 715 has an airflow control device 765 and a burner output 770 which can be modified to adjust the internal temperature of one or more zones of the kiln 715. The burner output 770 uses, for example, a scale from 0 to 100, where 100 is the maximum burner output and 0 indicates off. The output 770 drives the burner to change the fuel and combustion air to increase or decrease the heat.

[0122] For example, if there is a delta in the moisture readings generated by the downstream sensors 750 and 755, the controller 760 or human line operator can extract more hot air from the kiln to lower the drying temperature and / or lower the temperature setpoint to reduce the heat inside the kiln 715. Thus, if present, both downstream sensors 750 and 755 transmit moisture readings to the controller 760, which can calculate whether there is a difference. If necessary, the controller 760 can change the moisture setpoint accordingly. Changing the moisture setpoint can change the temperature inside the kiln 715 by changing either the air extraction or the burner output. These calculations and adjustments can also be performed manually in some embodiments.

[0123] High-frequency moisture sensors can produce dielectric readings. Such sensors can be fabricated to withstand the temperatures inside the kiln 715. Suitable high-frequency sensors are commercially available, for example, from Sensortech Systems, Oxnard, CA. Sensors less susceptible to the effects of high salt content (e.g., associated with stucco) can take the form of microwave or X-ray technology. These types of sensors may not be able to withstand the harsh heating environment inside the kiln. A preferred sensor less susceptible to the effects of salt content is a microwave sensor. While we do not wish to be bound by a specific theory, microwave-based sensors measure the vibration of water molecules and are considered less susceptible to damage in the presence of high levels of salt. Microwave-based sensors are commercially available, for example, from TEWS, Hamburg, Germany.

[0124] The present invention is further illustrated by the following exemplary clauses. However, the present invention is not limited to these clauses.

[0125] Clause 1. A gypsum board, a method for manufacturing a gypsum board, a method for drying a board, or a system for drying a board as described herein.

[0126] Clause 2. A gypsum board comprising a board core layer containing hardened gypsum; a front paper cover sheet having an outer and inner surface, the inner surface of which is in contact with a first surface of the board core layer; and a back paper cover sheet having an outer and inner surface, the inner surface of which is in contact with a second surface of the board core layer, wherein the board core layer is positioned between the front paper cover sheet and the back paper cover sheet, the perforated back paper cover sheet contains a plurality of through-holes, the board core layer is formed from the hardening of an aqueous slurry containing water and stucco between the first cover sheet and the second cover sheet, the stucco contains calcium sulfate hemihydrate, the aqueous slurry contains at least 60 weight percent of said calcium sulfate hemihydrate on a dry basis, about 500 ppm to about 3000 ppm of chloride anions per 1,000,000 parts by weight of said calcium sulfate hemihydrate, and water in a water-to-calcium sulfate hemihydrate weight ratio of 0.2:1 to 1.2:1.

[0127] Clause 3. The gypsum board described in Clause 2, wherein the front cover sheet is a front paper cover sheet and the back cover sheet is a back paper cover sheet.

[0128] Clause 4. A gypsum board as described in Clause 2 or 3, having multiple holes arranged in a pattern.

[0129] Clause 5. A gypsum board according to any one of Clauses 2 to 4, wherein the multiple perforations are substantially circular in shape.

[0130] Clause 6. Gypsum board as described in any one of Clauses 2 to 5, where each hole specifies an opening in the range of approximately 0.005 inches to approximately 0.1 inches in size.

[0131] Clause 7. Gypsum board as described in any one of Clauses 2 to 6, where each hole specifies an opening in the range of approximately 0.01 inches to approximately 0.02 inches in size.

[0132] Clause 8. The back cover sheet has approximately 5 holes / inch 2 ~Approx. 50 holes / in 2The gypsum board according to any one of clauses 2 to 7, having a hole coverage density within the range of.

[0133] Clause 9. The back cover sheet has a hole coverage density in the range of about 12 holes / in 2 to about 25 holes / in 2 The gypsum board according to any one of clauses 2 to 8, having a hole coverage density within the range of.

[0134] Clause 10. The board core layer includes a low-density region and at least one high-density region, and at least one high-density region is inserted as a layer between the low-density region and the front cover sheet or the back cover sheet. The gypsum board according to any one of clauses 2 to 9.

[0135] Clause 11. The low-density region is sandwiched between a first high-density region arranged as a first layer contacting the front cover sheet and a second high-density region arranged as a second layer contacting the back cover sheet. The gypsum board according to clause 10.

[0136] Clause 12. The low-density region is formed from a foamed gypsum slurry and contains a plurality of voids therein. The gypsum board according to clause 10. [[ID=二十一]] [[ID=二十二]]

[0137] [[ID=二十三]] [[ID=二十四]]Clause 13. The hardened gypsum is formed from a synthetic gypsum containing one or more chloride salts, and the chloride salts provide at least a part of the chloride anions. The gypsum board according to any one of clauses 2 to 12. [[ID=二十五]] [[ID=二十六]]

[0138] [[ID=二十七]] [[ID=二十八]]Clause 14. The aqueous slurry has about 1000 ppm to about 3000 ppm of the chloride anions per 1,000,000 parts by weight of the calcium sulfate hemihydrate. The gypsum board according to clause 13. [[ID=二十九]] [[ID=三十]]

[0139] [[ID=三十一]] Clause 15. A gypsum board comprising a board core layer containing hardened gypsum, a front paper cover sheet having an outer surface and an inner surface, the inner surface of which is in contact with a first surface of the board core; and a back paper cover sheet having an outer surface and an inner surface, the inner surface of which is in contact with a second surface of the board core, wherein at least one inner surface of the front paper cover sheet and the back paper cover sheet is coated with a starch layer, and the core layer is between the first cover sheet and the second cover sheet. A gypsum board in which the core layer is formed from the curing of an aqueous slurry containing a mixture of water and stucco between a front paper cover sheet and a back cover sheet, wherein the stucco contains calcium sulfate hemihydrate, and the aqueous slurry contains, on a dry basis, at least 60 weight percent of said calcium sulfate hemihydrate, about 500 ppm to about 3000 ppm of chloride anions per 1,000,000 parts by weight of said calcium sulfate hemihydrate, and said water in a water-to-calcium sulfate hemihydrate weight ratio of 0.2:1 to 1.2:1.

[0140] Clause 16. The gypsum board according to Clause 15, wherein the starch layer is a continuous starch layer on the entire inner surface of at least one of the front paper cover sheet and the back cover sheet.

[0141] Clause 17. Gypsum board as described in Clause 15 or 16, wherein the starch layer contains uncooked starch.

[0142] Clause 18. Gypsum board as described in any one of Clauses 15 to 17, wherein the starch layer comprises a mixture of uncooked starch and cooked starch.

[0143] Clause 19. A gypsum board according to any one of Clauses 15 to 18, wherein the aqueous slurry contains approximately 1,000 ppm to approximately 3,000 ppm of chloride anions per 1,000,000 parts by weight of the calcium sulfate hemihydrate.

[0144] Clause 20. A gypsum board as described in any one of Clauses 15 to 19, wherein a starch layer is coated on the inner surface of the back cover sheet.

[0145] Clause 21. A gypsum board according to any one of Clauses 15 to 20, wherein a starch layer is coated on the inner surface of the front paper cover sheet and the inner surface of the back cover sheet.

[0146] Clause 22. A gypsum board as described in any one of Clauses 15 to 21, wherein the front paper cover sheet is a front paper cover sheet and the back paper cover sheet is a back paper cover sheet.

[0147] Clause 23. A gypsum board according to any one of Clauses 15 to 22, wherein the board core comprises a low-density region and at least one high-density region, the at least one high-density region being inserted as a layer between the low-density region and a front paper cover sheet or a back cover sheet.

[0148] Clause 24. The gypsum board according to Clause 23, wherein a low-density region is sandwiched between a first high-density region, which is arranged as a first layer in contact with a front paper cover sheet or a starch layer coated thereon, and a second high-density region, which is arranged as a second layer in contact with a back paper cover sheet or a starch layer coated thereon.

[0149] Clause 25. The gypsum board according to Clause 23, wherein the low-density region is formed from foamed gypsum slurry and contains a plurality of voids.

[0150] Clause 26. Gypsum board as described in any one of Clauses 15 to 25, with a starch layer coated on the inside in an amount of approximately 0.5 lb / MSF to approximately 15 lbs / MSF.

[0151] Clause 27. A gypsum board according to any one of Clauses 15 to 26, wherein the hardened gypsum is formed from synthetic gypsum containing one or more chloride salts.

[0152] Article 28. (a) A board core comprising cured gypsum formed from a first slurry containing water and a stack having a high salt impurity content, the core defining first and second core surfaces, the board core; (b) A skim coat layer defining first and second skim coat surfaces, the skim coat being formed from a second slurry containing water, stack, and skim coat starch, the skim coat being disposed in a bonding relationship with respect to the first core surface, the skim coat layer; (c) A back cover sheet, wherein the first surface of the skim coat layer faces the back cover sheet, and the second surface of the skim coat layer faces the board core, the back cover sheet, and the skim coat starch strengthens the bond between the board core and the back cover sheet, a composite gypsum board.

[0153] Article 29. The composite gypsum board according to Article 28, further comprising a front cover sheet, wherein the second surface of the board core faces the front cover sheet.

[0154] Article 30. The board is a second skim coat layer defining first and second surfaces, the second skim coat layer being formed from a third slurry containing water, stack, and skim coat starch, the first surface of the second skim coat layer facing the second surface of the board core, and the second surface of the second skim coat layer facing the second cover sheet, further comprising the second skim coat layer, and the skim coat starch strengthens the bond between the board core and the front cover sheet, and the second and third slurries may be the same or different, the composite gypsum board according to Article 29.

[0155] Article 31. The composite gypsum board according to any one of Articles 28 to 30, wherein the first and / or second skim coat layer has a dry thickness of from about 0.125 inches (1 / 8 inch) to about 0.016 inches (1 / 64 inch), for example, from about 0.08 inches (1 / 12 inch) to about 0.03 inches (1 / 32 inch).

[0156] Clause 32. Composite gypsum board according to any one of Clauses 28 to 31, wherein the skim coat starch is present in the second and / or third slurry in an amount of about 0.3% to about 8.0% by weight of the stucco, for example, about 1.0% to about 4.0% by weight of the stucco.

[0157] Clause 33. A composite gypsum board according to any one of Clauses 28 to 32, wherein the high-salt impurities contain at least about 150 ppm of chloride anions per 1,000,000 parts by weight of the calcium sulfate hemihydrate.

[0158] Clause 34. Composite gypsum board as described in any one of Clauses 28 to 33, wherein the salt impurities include chloride salts such as sodium chloride, magnesium chloride, or calcium chloride.

[0159] Clause 35. A composite gypsum board according to any one of Clauses 28 to 34, wherein the first slurry comprises a core starch containing pregelatinized starch and / or mobile starch having a molecular weight of about 6,000 daltons or less.

[0160] Clause 36. Composite gypsum board according to any one of Clauses 28 to 35, comprising uncooked starch, having a moderate peak viscosity of about 120 to 1000 BU when the viscosity is measured using a Viscograph-E instrument set to 75 rpm and 700 cmg, by (i) a hot water viscosity of about 20 to about 300 BU by hot water viscosity assay (HWVA method) and / or (ii) a starch concentration of 15% solids, by placing the starch in a slurry containing water, the starch is heated from 25°C to 95°C at a rate of 3°C / min, the slurry is held at 95°C for 10 minutes, and the starch is cooled to 50°C at a rate of -3°C / min.

[0161] Clause 37. A composite gypsum board according to any one of Clauses 28 to 36, comprising pregelatinized starch, wherein the skim coat starch has a viscosity of about 20 cmpoise to about 700 (e.g., about 20 cmpoise to about 300 cmpoise or about 30 cmpoise to about 200 cmpoise) when the starch is subjected to VMA conditions.

[0162] Clause 38. A gypsum board comprising a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is formed from a slurry containing water, stucco, and a high salt impurity content, and at least one of the cover sheets is a highly absorbent paper.

[0163] Clause 39. The gypsum board as described in Clause 38, further comprising a surface skim coat placed between the surface cover sheet and the hardened gypsum core.

[0164] Clause 40. The gypsum board according to Clause 38 or 39, further comprising a back skim coat placed between the back cover sheet and the hardened gypsum core.

[0165] Clause 41. Gypsum board as described in Clause 39 or 40, wherein the back cover sheet is made of absorbent paper.

[0166] Clause 42. Gypsum board as described in any one of Clauses 39 to 41, wherein the top and / or back skim coat has a dry thickness of approximately 0.125 inches (1 / 8 inch) to approximately 0.016 inches (1 / 64 inch), for example, approximately 0.08 inches (1 / 12 inch) to approximately 0.03 inches (1 / 32 inch).

[0167] Clause 43. A gypsum board according to any one of Clauses 39 to 42, wherein the high-salt impurities contain at least about 150 ppm of chloride anions per 1,000,000 parts by weight of the stucco.

[0168] Clause 44. Gypsum board as described in any one of Clauses 39 to 43, wherein the salt impurities include chloride salts such as sodium chloride, potassium chloride, magnesium chloride, or calcium chloride.

[0169] Clause 45. The absorbent paper must have an absorption rate of at least approximately 2.1 g / 100 cm² according to the Cobb test. 2 A gypsum board according to any one of clauses 39 to 44, having a joint side bump value.

[0170] Clause 46. High absorbency paper has an absorption rate of approximately 2.1 g / 100 cm² according to the Cobb test. 2 ~Approx. 3.1g / 100cm 2 A gypsum board according to any one of clauses 39 to 45, having a joint side bump value.

[0171] Clause 47. Gypsum board as described in any one of Clauses 39 to 46, wherein the absorbent paper has a basis weight of approximately 35 lb / MSF to approximately 65 lb / MSF, for example, approximately 38 lb / MSF to approximately 60 lb / MSF, for example, approximately 42 lb / MSF to approximately 55 lb / MSF.

[0172] Clause 48. A gypsum board as described in any one of Clauses 39 to 47, wherein the superabsorbent paper has a caliper of approximately 10 mils to approximately 15 mils.

[0173] Clause 49. A gypsum board comprising a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is formed from a slurry containing water, stucco, and high salt impurity content, and the board comprises: (a) at least one of the cover sheets, preferably the back cover sheet, perforated; (b) at least one of the cover sheets, preferably the back cover sheet, in the form of highly absorbent paper; (c) starch contained between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core; and (d)(i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer comprises water, stucco, and skim coat starch. A gypsum board comprising at least one of the following: (i) a back skim coat layer formed from a second slurry containing water, stucco, and optionally skim coat starch, wherein the first surface of the back skim coat layer faces the back cover sheet and the second surface of the back skim coat layer faces the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, wherein the first surface of the front skim coat layer faces the second surface of the board core and the second surface of the front skim coat layer faces the front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different.

[0174] Clause 50. The board according to Clause 49, wherein the high-salt impurities contain at least about 150 ppm of chloride anions per 1,000,000 parts by weight of the stucco.

[0175] Clause 51. The board described in Clause 49 or 50, wherein the salt impurities include chloride salts such as sodium chloride, potassium chloride, magnesium chloride, or calcium chloride.

[0176] Clause 52. A board according to any one of Clauses 49 to 51, wherein at least one of the first slurry, the second slurry, and / or the third slurry contains boric acid.

[0177] Clause 53. The board as described in Clause 52, wherein the amount of boric acid is about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0178] Clause 54. A board according to any one of Clauses 49 to 53, wherein at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, about 1% to about 10% by weight of stucco, or about 1% to about 5% by weight of clay, for example, kaolin clay.

[0179] Clause 55. A board according to any one of Clauses 49 to 54, wherein at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate.

[0180] Clause 56. The board as described in Clause 55, wherein the polyphosphate is sodium trimetaphosphate.

[0181] Clause 57. A board according to any one of Clauses 49 to 56, wherein at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0182] Clause 58. A gypsum board as described in any one of Clauses 49 to 57, wherein the board includes holes in the backing sheet and a backing sheet in the form of absorbent paper.

[0183] Clause 59. A gypsum board according to any one of Clauses 49 to 58, wherein the board comprises holes in the back cover sheet and starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core.

[0184] Clause 60. The board has holes in the back cover sheet; and (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat A gypsum board according to any one of Clauses 49 to 59, comprising a top layer formed from water, stucco, and optionally a third slurry containing skim coat starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different.

[0185] Clause 61. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; and starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core.

[0186] Clause 62. The board comprises a back cover sheet in the form of absorbent paper; and (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from water, stucco, and optionally a third slurry containing skim coat starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different.

[0187] Clause 63. The board contains starch between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, the second surface of the back skim coat facing the first core surface, and (ii) first and A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer defining a second surface, the top skim coat layer being formed from a third slurry comprising water, stucco, and optionally skim coat starch, the first surface of the top skim coat layer facing the second surface of the board core, and the second surface of the top skim coat layer facing the top cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different.

[0188] Clause 64. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; and starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core.

[0189] Clause 65. The board has holes in the back cover sheet; the back cover sheet is in the form of absorbent paper; and (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces. A gypsum board according to any one of the clauses 49 to 59, wherein the surface skim coat layer is formed from water, stucco, and optionally a third slurry containing skim coat starch, the first surface of the surface skim coat layer facing a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different.

[0190] Clause 66. The board includes: holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (i i) A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer defining first and second surfaces, the surface skim coat layer being formed from a third slurry comprising water, stucco, and optionally skim coat starch, the first surface of the surface skim coat layer facing a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different.

[0191] Clause 67. The board comprises: a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer defining first and second surfaces, the surface skim coat layer being formed from a third slurry comprising water, stucco, and optionally skim coat starch, the first surface of the surface skim coat layer facing a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different.

[0192] Clause 68. The board comprises: holes in the back cover sheet; a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces. The gypsum board according to any one of the clauses 49 to 59, wherein the surface skim coat layer is formed from water, stucco, and optionally a third slurry containing skim coat starch, the first surface of the surface skim coat layer facing a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, the skim coat starch strengthens the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; and also contains, for example, about 0.01% to about 0.5% by weight of stucco, for example, about 0.05% to about 0.3% by weight of stucco, in which case it contains boric acid.

[0193] Clause 69. The board includes: holes in the back cover sheet; a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally, skim coat starch. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which the surface skim coat layer faces a second surface of the board core, and the second surface of which the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0194] Clause 70. The board includes: holes in the back cover sheet; a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. - Includes a surface skim coat layer facing the sheet, the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, containing boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry may be, for example The gypsum board according to any one of the clauses 49 to 59, wherein the stucco contains about 1% to about 10% by weight of clay, for example, kaolin clay, in an amount of about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0195] Clause 71. The board includes: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which faces the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0196] Clause 72. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0197] Clause 73. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0198] Clause 74. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0199] Clause 75. The board contains: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and less than one of the first slurry, the second slurry, and / or the third slurry. The gypsum board according to any one of the clauses 49 to 59, wherein one of the slurry contains, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of clay, for example, kaolin clay; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0200] Clause 76. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry, containing a retarder.

[0201] Clause 77. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0202] Clause 78. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0203] Clause 79. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0204] Clause 80. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry, contains polyphosphate.

[0205] Clause 81. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; at least one of the first slurry, the second slurry, and / or the third slurry, containing polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry, containing a retarder.

[0206] Clause 82. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry, containing a retarder.

[0207] Clause 83. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0208] Clause 84. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry containing a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0209] Clause 85. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0210] Clause 86. Boards having holes in a back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally, skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry containing starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and also comprising, for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0211] Clause 87. The board comprises: holes in the back cover sheet; a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0212] Clause 88. The board comprises: holes in the back cover sheet; a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core and the second surface of the front skim coat layer facing the front cover sheet; and skim coat starch The gypsum board according to any one of clauses 49 to 59, wherein the second and third slurries may be the same or different, and further enhance the bond between the core and at least the back cover sheet; for example, the gypsum board contains boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0213] Clause 89. Boards having holes in the back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core and the second surface of the front skim coat layer facing the front cover sheet. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing polyphosphate.

[0214] Clause 90. Boards having holes in the back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0215] Clause 91. Boards having holes in a back cover sheet; back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally, skim coat starch. The gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer, the first surface of which is facing the second surface of the board core, and the second surface of which is facing the top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0216] Clause 92. The board includes: holes in the back cover sheet; a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0217] Clause 93. Boards having holes in the back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the front skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which is a stucco layer facing a second surface of the board core, and the second surface of which is a surface skim coat layer facing a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0218] Clause 94. The board comprises: holes in the back cover sheet; a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which the surface skim coat layer faces a second surface of the board core, and the second surface of which the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, clay, for example, kaolin clay.

[0219] Clause 95. Boards having holes in the back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the second surface of the surface skim coat layer faces the surface cover sheet, the skim coat starch strengthens the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0220] Clause 96. Boards having holes in the back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer facing the surface, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0221] Clause 97. Boards having holes in the back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which faces the surface skim coat layer, the skim coat starch strengthens the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0222] Clause 98. Boards having holes in a back cover sheet; back cover sheet in the form of superabsorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally, skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing skim coat starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0223] Clause 99. Boards having holes in a back cover sheet; back cover sheet in the form of absorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer, the top surface of which is the skim coat layer facing a second surface of the board core, and the top surface of which is the top skim coat layer facing a top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0224] Clause 100. Boards having holes in a back cover sheet; back cover sheet in the form of superabsorbent paper; (i) back skim coat layers defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) front skim coat layers defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing skim coat starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, the skim coat starch enhances the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0225] Clause 101. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the backing sheet; a backing sheet in the form of highly absorbent paper; and boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0226] Clause 102. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the backing sheet; a backing sheet in the form of highly absorbent paper; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0227] Clause 103. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0228] Clause 104. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry, contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0229] Clause 105. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0230] Clause 106. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry containing a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0231] Clause 107. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; a back cover sheet in the form of highly absorbent paper; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0232] Clause 108. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet with holes in it; a backing sheet in the form of absorbent paper; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0233] Clause 109. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet with holes; a backing sheet in the form of absorbent paper; at least one of a first slurry, a second slurry, and / or a third slurry containing, for example, clay in an amount of about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry containing polyphosphate.

[0234] Clause 110. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet with holes; a backing sheet in the form of absorbent paper; at least one of a first slurry, a second slurry, and / or a third slurry containing, for example, clay in an amount of about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, for example, kaolin clay; at least one of the first slurry, the second slurry, and / or the third slurry containing polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0235] Clause 111. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet with holes; a backing sheet in the form of absorbent paper; at least one of a first slurry, a second slurry, and / or a third slurry containing, for example, clay in an amount of about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0236] Clause 112. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes a backing sheet with holes in it; a backing sheet in the form of absorbent paper; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0237] Clause 113. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet with holes; a backing sheet in the form of absorbent paper; at least one of a first slurry, a second slurry, and / or a third slurry containing a polyphosphate; and at least one of the first slurry, a second slurry, and / or a third slurry containing a retarder.

[0238] Clause 114. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet with holes in it; a backing sheet in the form of absorbent paper; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0239] Clause 115. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, the front skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a top layer formed from water, stucco, and optionally a third slurry containing skim coat starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and also comprising, for example, about 0.01% to about 0.5% by weight of stucco, for example, about 0.05% to about 0.3% by weight of stucco, in which case boric acid is present.

[0240] Clause 116. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the front skim A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which is a coat layer facing a second surface of the board core, and the second surface of which is a surface skim coat layer facing a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0241] Clause 117. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0242] Clause 118. The board contains holes in the back cover sheet; starch between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which of the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0243] Clause 119. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which of the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0244] Clause 120. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally, skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry containing starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, containing boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0245] Clause 121. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the front skim The gypsum board according to any one of clauses 49 to 59, comprising a top skim coat layer, the first surface of which is a coat layer facing a second surface of the board core, and the second surface of which is a top skim coat layer facing a top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, containing boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0246] Clause 122. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, the front skim coat layer being made of water, stucco, and optionally skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry containing starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0247] Clause 123. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, the front skim coat layer being made of water, stucco, and optionally, A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry containing skim coat starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; and further comprising, at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, for example, kaolin clay.

[0248] Clause 124. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer, the first surface of which is a skim coat layer facing a second surface of the board core, and the second surface of which is a top skim coat layer facing a top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0249] Clause 125. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the second surface of the surface skim coat layer faces the surface cover sheet, the skim coat starch strengthens the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0250] Clause 126. The board contains holes in the back cover sheet; starch between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which the surface skim coat layer faces a second surface of the board core, and the second surface of which the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0251] Clause 127. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, the front skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from water, stucco, and optionally a third slurry containing skim coat starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, the skim coat starch enhances the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0252] Clause 128. The board has holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally, A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing skim coat starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0253] Clause 129. The board includes: holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from water, stucco, and optionally a third slurry containing skim coat starch, wherein a first surface of the surface skim coat layer faces a second surface of the board core, and the second surface of the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and further comprising at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0254] Clause 130. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0255] Clause 131. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0256] Clause 132. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; starch contained between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0257] Clause 133. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; starch contained between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0258] Clause 134. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0259] Clause 135. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; starch between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0260] Clause 136. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0261] Clause 137. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; starch contained between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0262] Clause 138. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0263] Clause 139. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises: holes in the back cover sheet; starch contained between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, second slurry, and / or third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; at least one of the first slurry, second slurry, and / or third slurry, containing polyphosphate; and at least one of the first slurry, second slurry, and / or third slurry, containing a retarder.

[0264] Clause 140. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; starch contained between the hardened gypsum core and at least one of the cover sheets, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry, contains a retarder.

[0265] Clause 141. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0266] Clause 142. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0267] Clause 143. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises holes in the back cover sheet; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0268] Clause 144. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer containing water, stucco, and optionally, skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; and also comprising, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco, in the amount of boric acid.

[0269] Clause 145. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the front skim coat The gypsum board according to any one of the clauses 49 to 59, comprising a front skim coat layer, the second surface of which of the layers faces the front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0270] Clause 146. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet; The gypsum board according to any one of the clauses 49 to 59, comprising a stucco layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing polyphosphate.

[0271] Clause 147. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. The gypsum board according to any one of the clauses 49 to 59, comprising a skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0272] Clause 148. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer is A gypsum board according to any one of the clauses 49 to 597, comprising a surface skim coat layer facing a second surface of the board core, the surface of which faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0273] Clause 149. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the front skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a front skim coat layer, the second surface of which of the layers faces a front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0274] Clause 50. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the surface of which faces the second surface of the board core, and the surface of which faces the front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0275] Clause 152. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which faces a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, clay, for example, kaolin clay.

[0276] Clause 152. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface, and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the front skim A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which of the coat layers faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0277] Clause 153. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0278] Clause 154. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, The gypsum board according to any one of the clauses 49 to 59, comprising a front skim coat layer, the second surface of which of the skim coat layer faces a front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0279] Clause 155. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally skim coat starch A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing a top skim coat layer, the top surface of which faces a second surface of the board core, and the top surface of which faces a top cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0280] Clause 156. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which faces a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0281] Clause 157. The board has holes in the back cover sheet; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally, skim coat starch A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry containing starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0282] Clause 158. A gypsum board according to any one of Clauses 49 to 59, wherein the board has holes in the back cover sheet; and boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0283] Clause 159. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0284] Clause 160. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0285] Clause 161. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains holes in the back cover sheet; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0286] Clause 162. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco, and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0287] Clause 163. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, or for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0288] Clause 164. A gypsum board according to any one of Clauses 49 to 59, wherein the board contains boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0289] Clause 165. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes holes in the back cover sheet; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, for example, kaolin clay.

[0290] Clause 166. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes holes in the back cover sheet; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0291] Clause 167. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes holes in the back cover sheet; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0292] Clause 168. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes holes in the back cover sheet; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0293] Clause 169. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes holes in the back cover sheet; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0294] Clause 170. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes holes in the back cover sheet; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0295] Clause 171. The board comprises: a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from water, stucco, and optionally a third slurry containing skim coat starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and also comprising, for example, about 0.01% to about 0.5% by weight of stucco, for example, about 0.05% to about 0.3% by weight of stucco, in which case boric acid is present.

[0296] Clause 172. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, with the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which is a stucco layer facing a second surface of the board core, and the second surface of which is a surface skim coat layer facing a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0297] Clause 173. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry comprising water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0298] Clause 174. The board comprises: a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry comprising water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. , comprising a surface skim coat layer, the second surface of which is the surface skim coat layer is facing the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, containing boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate, the gypsum board according to any one of the clauses 49 to 59.

[0299] Clause 175. The board comprises: a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the second surface of the surface skim coat layer faces the surface cover sheet, the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0300] Clause 176. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer contains water, stucco, and optionally, skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry containing starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0301] Clause 177. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, with the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry comprising water, stucco, and optionally, skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which is a stucco layer facing a second surface of the board core, and the second surface of which is a surface skim coat layer facing a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, they contain boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0302] Clause 178. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer contains water, stucco, and optionally, skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer formed from a third slurry containing stucco starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, containing boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0303] Clause 179. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, wherein the front skim coat layer contains water, stucco, and optionally , comprising a top skim coat layer formed from a third slurry containing skim coat starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and the gypsum board according to any one of the first slurry, the second slurry, and / or the third slurry contains, for example, about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of clay, for example, kaolin clay.

[0304] Clause 180. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry comprising water, stucco, and optionally, skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which the surface skim coat layer faces a second surface of the board core, and the second surface of which the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0305] Clause 181. The board comprises: a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, wherein the front skim coat layer is formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which faces the surface skim coat layer, the skim coat starch strengthens the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0306] Clause 182. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry comprising water, stucco, and optionally, skim coat starch. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which the surface skim coat layer faces a second surface of the board core, and the second surface of which the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0307] Clause 183. The board comprises: a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, A gypsum board according to any one of the clauses 49 to 59, comprising a skim coat layer formed from water, stucco, and optionally a third slurry containing skim coat starch, wherein a first surface of the surface skim coat layer faces a second surface of the board core, and a second surface of the surface skim coat layer faces a surface cover sheet, the skim coat starch enhances the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0308] Clause 184. The board comprises: a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, wherein the front skim coat layer contains water, stucco, and optionally, A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing skim coat starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0309] Clause 185. The board comprises: a back cover sheet in the form of absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces. , a gypsum board according to any one of the clauses 49 to 59, wherein the surface skim coat layer is formed from water, stucco, and optionally a third slurry containing skim coat starch, the first surface of the surface skim coat layer facing a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, the skim coat starch strengthens the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0310] Clause 186. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0311] Clause 187. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0312] Clause 188. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0313] Clause 189. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0314] Clause 190. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0315] Clause 191. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0316] Clause 192. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0317] Clause 193. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry, contains polyphosphate.

[0318] Clause 194. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; at least one of the first slurry, the second slurry, and / or the third slurry, containing polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry, containing a retarder.

[0319] Clause 195. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry, containing, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry, contains a retarder.

[0320] Clause 196. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0321] Clause 197. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0322] Clause 198. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; starch contained between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0323] Clause 199. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally skim coat starch A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing a top skim coat layer, the top surface of which faces a second surface of the board core, and the top surface of which faces a top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and also comprising, for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0324] Clause 200. The board is a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the front skim coat The gypsum board according to any one of the clauses 49 to 59, comprising a front skim coat layer, the second surface of which of the stucco layers faces the front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0325] Clause 201. The board is a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. A gypsum board according to any one of the clauses 49 to 59, comprising a coating layer, wherein skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing polyphosphate.

[0326] Clause 202. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. The gypsum board according to any one of the clauses 49 to 59, comprising a skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry containing a retarder.

[0327] Clause 203. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the surface of which faces a second surface of the board core, and the surface of the surface skim coat layer facing a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0328] Clause 204. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the front skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a front skim coat layer, the second surface of which of the stucco layers faces the front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0329] Clause 205. The board is a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the first surface of which faces a second surface of the board core, and the second surface of the surface skim coat layer facing a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; for example, comprising boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0330] Clause 206. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the front skim coat The gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer, the first surface of which is facing the second surface of the board core, and the second surface of which is facing the top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of clay, for example, kaolin clay.

[0331] Clause 207. The board is a back cover sheet in the form of absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the front skim coat layer A gypsum board according to any one of the clauses 49 to 59, comprising a front skim coat layer, the second surface of which of the skim coat layers faces a front cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0332] Clause 208. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core, and the second surface of the front skim coat layer facing the front cover sheet. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, kaolin clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0333] Clause 209. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer facing the second surface of the board core. The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the second surface of which of the surface skim coat layer faces a surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0334] Clause 210. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0335] Clause 211. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch. A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer, the top surface of which faces a second surface of the board core, and the top surface of which faces a top cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, the second and third slurries may be the same or different; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0336] Clause 212. The board is a back cover sheet in the form of a highly absorbent paper; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being made of water, stucco, and optionally, skim coat A gypsum board according to any one of the clauses 49 to 59, comprising a top skim coat layer formed from a third slurry containing starch, wherein the first surface of the top skim coat layer faces the second surface of the board core, and the second surface of the top skim coat layer faces the top cover sheet, wherein the skim coat starch enhances the bond between the core and at least the back cover sheet, and the second and third slurries may be the same or different; and further comprising a retarder, wherein at least one of the first slurry, the second slurry, and / or the third slurry.

[0337] Clause 213. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet in the form of highly absorbent paper; and boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco.

[0338] Clause 214. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet in the form of highly absorbent paper; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay.

[0339] Clause 215. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet in the form of highly absorbent paper; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0340] Clause 216. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet in the form of highly absorbent paper; boric acid in an amount of, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of, for example, about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0341] Clause 217. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet in the form of highly absorbent paper; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0342] Clause 218. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet in the form of highly absorbent paper; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0343] Clause 219. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a backing sheet in the form of highly absorbent paper; for example, boric acid in an amount of about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0344] Clause 220. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; and at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of stucco, for example, about 1% to about 5% by weight of stucco, for example, kaolin clay.

[0345] Clause 221. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0346] Clause 222. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay, for example, kaolin clay, in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco; at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0347] Clause 223. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; at least one of the first slurry, the second slurry, and / or the third slurry contains, for example, clay in an amount of about 1% to about 10% by weight of the stucco, for example, about 1% to about 5% by weight of the stucco, for example, kaolin clay; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0348] Clause 224. A gypsum board according to any one of Clauses 49 to 59, wherein the board includes a backing sheet in the form of highly absorbent paper; and at least one of the first slurry, the second slurry, and / or the third slurry contains polyphosphate.

[0349] Clause 225. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; at least one of the first slurry, the second slurry, and / or the third slurry contains a polyphosphate; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0350] Clause 226. A gypsum board according to any one of Clauses 49 to 59, wherein the board comprises a back cover sheet in the form of highly absorbent paper; and at least one of the first slurry, the second slurry, and / or the third slurry contains a retarder.

[0351] Clause 227. The board contains starch between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining the first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining the first and second surfaces, the front skim coat layer being water A gypsum board according to any one of the clauses 49 to 59, comprising, stucco, and optionally, a third slurry comprising skim coat starch, wherein the first surface of the surface skim coat layer faces the second surface of the board core, and the second surface of the surface skim coat layer faces the surface cover sheet, the skim coat starch enhances the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; and also comprising, for example, about 0.01% to about 0.5% by weight of the stucco, for example, about 0.05% to about 0.3% by weight of the stucco, in the amount of boric acid.

[0352] Clause 228. The board contains starch between at least one of the hardened gypsum core and the cover sheet, preferably at least between the back cover sheet and the hardened gypsum core; (i) a back skim coat layer defining first and second skim coat surfaces, the back skim coat layer being formed from a second slurry containing water, stucco, and skim coat starch, the first surface of the back skim coat facing the back cover sheet, and the second surface of the back skim coat facing the first core surface; and (ii) a front skim coat layer defining first and second surfaces, the front skim coat layer being formed from a third slurry containing water, stucco, and optionally skim coat starch, the first surface of the front skim coat layer The gypsum board according to any one of the clauses 49 to 59, comprising a surface skim coat layer, the surface of which faces the second surface of the board core, and the second surface of the surface skim coat layer facing the surface cover sheet, wherein the skim coat starch strengthens the bond between the core and at least the surface cover sheet, and the second and third slurries may be the same or different; for example, comprising boric aci...

Claims

1. A gypsum board comprising a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is a first slurry comprising water and stucco containing salt impurities, wherein the salt impurities contain at least 150 ppm of chloride ions (Cl) per stucco. － Formed from a first slurry containing ), the gypsum board is (A) The back cover sheet, which includes a plurality of holes penetrating the back cover sheet, and the hardened gypsum core defining a structure that does not include the holes, (B) At least 2.1 g / 100 cm by Cobb test ２ The back cover sheet includes paper having a joint side bump value, (C) Starch contained between the hardened gypsum core and at least one of the front and back cover sheets, (D) (i) A back skim coat layer defining first and second surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat layer facing the back cover sheet, the second surface of the back skim coat layer facing the first surface of the hardened gypsum core, and the skim coat starch strengthens the bond between the hardened gypsum core and at least the back cover sheet. (ii) a top layer, and a top skim coat layer defining first and second surfaces, wherein the top skim coat layer is formed from water, stucco, and optionally a third slurry containing the skim coat starch, the second and third slurries may be the same or different, the first surface of the top skim coat layer faces the second surface of the hardened gypsum core, and the second surface of the top skim coat layer faces the top cover sheet, It includes at least two of the four types, and one of those two types is either (A) or (B) above. At least two of the four types are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco. Gypsum board.

2. The gypsum board according to claim 1, wherein the salt impurity comprises sodium chloride, potassium chloride, magnesium chloride, calcium chloride, or any combination thereof.

3. A gypsum board comprising a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is a first slurry comprising water and stucco containing salt impurities, wherein the salt impurities contain at least 150 ppm of chloride ions (Cl) per stucco. － Formed from a first slurry containing ), the gypsum board is (A) The back cover sheet, which includes a plurality of holes penetrating the back cover sheet, and the hardened gypsum core defining a structure that does not include the holes, (B) At least 2.1 g / 100 cm by Cobb test ２ The back cover sheet includes paper having a joint side bump value, (C) Starch contained between the hardened gypsum core and at least one of the front and back cover sheets, (D) (i) A back skim coat layer defining first and second surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat layer facing the back cover sheet, the second surface of the back skim coat layer facing the first surface of the hardened gypsum core, and the skim coat starch strengthens the bond between the hardened gypsum core and at least the back cover sheet. (ii) a top layer, and a top skim coat layer defining first and second surfaces, wherein the top skim coat layer is formed from water, stucco, and optionally a third slurry containing the skim coat starch, the second and third slurries may be the same or different, the first surface of the top skim coat layer faces the second surface of the hardened gypsum core, and the second surface of the top skim coat layer faces the top cover sheet, It includes at least two of the four types, At least two of the four types are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco. At least one of the first slurry, the second slurry, and / or the third slurry contains boric acid in an amount of 0.01% to 0.5% by weight of the stucco contained in the slurry. Gypsum board.

4. A gypsum board comprising a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is a first slurry comprising water and stucco containing salt impurities, wherein the salt impurities contain at least 150 ppm of chloride ions (Cl) per stucco. － Formed from a first slurry containing ), the gypsum board is (A) The back cover sheet, which includes a plurality of holes penetrating the back cover sheet, and the hardened gypsum core defining a structure that does not include the holes, (B) At least 2.1 g / 100 cm by Cobb test ２ The back cover sheet includes paper having a joint side bump value, (C) Starch contained between the hardened gypsum core and at least one of the front and back cover sheets, (D) (i) A back skim coat layer defining first and second surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat layer facing the back cover sheet, the second surface of the back skim coat layer facing the first surface of the hardened gypsum core, and the skim coat starch strengthens the bond between the hardened gypsum core and at least the back cover sheet. (ii) a top layer, and a top skim coat layer defining first and second surfaces, wherein the top skim coat layer is formed from water, stucco, and optionally a third slurry containing the skim coat starch, the second and third slurries may be the same or different, the first surface of the top skim coat layer faces the second surface of the hardened gypsum core, and the second surface of the top skim coat layer faces the top cover sheet, It includes at least two of the four types, At least two of the four types are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco. At least one of the first slurry, the second slurry, and / or the third slurry contains clay in an amount of 1% to 10% by weight of the stucco contained in the slurry. Gypsum board.

5. The gypsum board according to claim 1, wherein the gypsum board includes (C).

6. The gypsum board according to claim 1, wherein the gypsum board includes (D).

7. A method for making gypsum board, The gypsum board includes a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is a first slurry comprising water and stucco containing salt impurities, the salt impurities comprising at least 150 ppm of chloride ions (Cl) per stucco. － Formed from a first slurry containing ), the gypsum board is (A) The back cover sheet, which includes a plurality of holes penetrating the back cover sheet, and the hardened gypsum core defining a structure that does not include the holes, (B) At least 2.1 g / 100 cm by Cobb test ２ The back cover sheet includes paper having a joint side bump value, (C) Starch contained between the hardened gypsum core and at least one of the front and back cover sheets, (D) (i) A back skim coat layer defining first and second surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat layer facing the back cover sheet, the second surface of the back skim coat layer facing the first surface of the hardened gypsum core, and the skim coat starch strengthens the bond between the hardened gypsum core and at least the back cover sheet. (ii) a top layer, and a top skim coat layer defining first and second surfaces, wherein the top skim coat layer is formed from water, stucco, and optionally a third slurry containing the skim coat starch, the second and third slurries may be the same or different, the first surface of the top skim coat layer faces the second surface of the hardened gypsum core, and the second surface of the top skim coat layer faces the top cover sheet, It includes at least two of the four types, At least two of the four types are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco. The aforementioned method, (a) Mixing at least water, the stucco, and foam to form the first slurry, (b) Placing the first slurry between the front cover sheet and the back cover sheet to form a board precursor, (c) Cutting the board precursor into boards, (d) Drying the board in a kiln containing at least one kiln-internal high-frequency moisture sensor, which is in communication with a controller outside the kiln, to generate a kiln-internal moisture reading, (e) A first upstream sensor that is a high-frequency moisture sensor, and a second upstream sensor that is less susceptible to the influence of salt impurities containing at least about 150 ppm of chloride ions (Cl － ) per stack in the first slurry, and using the first and second upstream sensors in communication with the controller, measuring the moisture content in the board upstream of the kiln to respectively generate a first upstream moisture reading and a second upstream moisture reading; (f) Correlating the first and second upstream moisture readings from the first upstream sensor and the second upstream sensor, (g) A method comprising biasing the kiln-in-high frequency moisture sensor to correct any errors in the kiln-in-high frequency moisture readings when a delta exists between the first and second upstream moisture readings.

8. The furnace has a burner output and / or related air extraction, and the method, (h) A first downstream sensor which is a high-frequency moisture sensor, and at least about 150 ppm of chloride ions (Cl) per stucco in the first slurry compared to the first downstream sensor. － A second downstream sensor less susceptible to the influence of salt impurities, including the first and second downstream sensors which are in communication with the controller, is used to measure the moisture content in the board downstream of the kiln, generate a first downstream moisture reading, and bias the second downstream moisture reading. (i) Correlating the first and second downstream moisture readings from the first downstream sensor and the second downstream sensor, (j) The method according to claim 7, further comprising adjusting the burner output and / or air device to adjust the temperature inside the furnace and reduce heating inside.

9. The method according to claim 7, further comprising setting point control of the burner output, temperature, and / or airflow within the furnace.

10. The method according to claim 8, wherein at least one of the second upstream sensor and the second downstream sensor is a microwave sensor.

11. The method according to claim 8, wherein the kiln has one zone.

12. The method according to claim 8, wherein the kiln has at least two zones.

13. The method according to claim 8, wherein the kiln includes at least two kiln moisture sensors.

14. The method according to claim 8, wherein the salt impurity includes sodium chloride, potassium chloride, magnesium chloride, calcium chloride, or any combination thereof.

15. A system for drying gypsum board, The gypsum board includes a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is a first slurry comprising water and stucco containing salt impurities, the salt impurities comprising at least 150 ppm of chloride ions (Cl) per stucco. － Formed from a first slurry containing ), the gypsum board is (A) The back cover sheet, which includes a plurality of holes penetrating the back cover sheet, and the hardened gypsum core defining a structure that does not include the holes, (B) At least 2.1 g / 100 cm by Cobb test ２ The back cover sheet includes paper having a joint side bump value, (C) Starch contained between the hardened gypsum core and at least one of the front and back cover sheets, (D) (i) A back skim coat layer defining first and second surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat layer facing the back cover sheet, the second surface of the back skim coat layer facing the first surface of the hardened gypsum core, and the skim coat starch strengthens the bond between the hardened gypsum core and at least the back cover sheet. (ii) a top layer, and a top skim coat layer defining first and second surfaces, wherein the top skim coat layer is formed from water, stucco, and optionally a third slurry containing the skim coat starch, the second and third slurries may be the same or different, the first surface of the top skim coat layer faces the second surface of the hardened gypsum core, and the second surface of the top skim coat layer faces the top cover sheet, It includes at least two of the four types, At least two of the four types are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco. The aforementioned system, (a) A kiln containing at least one heat source and at least one kiln-internal high-frequency moisture sensor, (b) Controller on the outside of the kiln, and (c) A first upstream sensor which is a high-frequency moisture sensor, and a first slurry containing at least about 150 ppm of chloride ions (Cl) per stucco compared to the first upstream sensor. － A system comprising a second upstream sensor less susceptible to the effects of salt impurities including ), communicating with the controller, and the first and second upstream sensors which generate a first upstream moisture reading and a second upstream moisture reading, respectively.

16. The system according to claim 15, further comprising a burner output and / or air extraction device related to the furnace, the burner output and / or air extraction device being in communication with the controller.

17. (d) A first downstream sensor which is a high-frequency moisture sensor, and a first slurry containing at least about 150 ppm of chloride ions (Cl) per stucco compared to the first downstream sensor. － A second downstream sensor less susceptible to the effects of salt impurities including ) and communicating with the controller, further comprising the first and second downstream sensors used to generate a first downstream moisture reading and to bias a second downstream moisture reading, The system according to claim 16, wherein the burner output and / or air device can be used to selectively adjust the temperature inside the furnace to reduce heating inside.

18. The system according to claim 15, wherein the second upstream sensor is a microwave sensor.

19. The system according to claim 15, wherein the kiln includes at least two kiln moisture sensors.

20. The gypsum board includes at least three of the above (A) to (D), The gypsum board according to claim 1, wherein at least three of the above are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco.

21. The gypsum board includes (A), (B), and (C), The gypsum board according to claim 20, wherein (A), (B), and (C) are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco.

22. The gypsum board includes (A), (B), and (D), The gypsum board according to claim 20, wherein (A), (B), and (D) are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco.

23. The gypsum board includes (A) to (D), The gypsum board according to claim 20, wherein (A) to (D) are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco.

24. A gypsum board comprising a hardened gypsum core disposed between a front cover sheet and a back cover sheet, wherein the hardened gypsum core is a first slurry comprising water and stucco containing salt impurities, wherein the salt impurities contain at least 150 ppm of chloride ions (Cl) per stucco. － Formed from a first slurry containing ), the gypsum board is (A) The back cover sheet, which includes a plurality of holes penetrating the back cover sheet, and the hardened gypsum core defining a structure that does not include the holes, (B) At least 2.1 g / 100 cm by Cobb test ２ The back cover sheet includes paper having a joint side bump value, (C) Starch contained between the hardened gypsum core and at least one of the front and back cover sheets, (D) (i) A back skim coat layer defining first and second surfaces, wherein the back skim coat layer is formed from a second slurry comprising water, stucco, and skim coat starch, the first surface of the back skim coat layer facing the back cover sheet, the second surface of the back skim coat layer facing the first surface of the hardened gypsum core, and the skim coat starch strengthens the bond between the hardened gypsum core and at least the back cover sheet. (ii) a top layer, and a top skim coat layer defining first and second surfaces, wherein the top skim coat layer is formed from water, stucco, and optionally a third slurry containing the skim coat starch, the second and third slurries may be the same or different, the first surface of the top skim coat layer faces the second surface of the hardened gypsum core, and the second surface of the top skim coat layer faces the top cover sheet, It includes at least two of the four types, and one of those two types is (A) above. At least two of the four types are effective in strengthening the adhesive strength of the back cover sheet despite the presence of chloride ions in the stucco. The aforementioned back cover sheet has 5 holes / in ２ ~50 holes / in ２ The hardened gypsum core has a pore coverage density in the range of, defining a structure that does not contain pores. Gypsum board.

25. The gypsum board according to claim 1, wherein the gypsum board includes (A) and also includes one or both of (C) and (D).

26. The gypsum board according to claim 1, wherein the gypsum board includes (A) and (B).

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