Foamed gypsum with improved strength

Abstract

The present disclosure relates to gypsum slurries. In one aspect, a surfactant combination containing (i) 20 wt% to 80 wt% of an anionic diaryl oxide surfactant; and (ii) 20 wt% to 80 wt% of a non-ionic glycosyl surfactant can be used as a foaming agent for gypsum slurries used to produce gypsum board. The minimum ratio of anionic surfactant to non-ionic surfactant can vary depending on the lipophilic portion of the anionic surfactant. The resulting board can have a desired combination of weight and physical strength, as evidenced by nail pull resistance.

Description

Technical Field

[0001] This invention relates to the field of gypsum board. Background Technology

[0002] Gypsum primarily consists of calcium sulfate dihydrate (CaSO4 • 2 H2O). Gypsum is the main component of gypsum board, which contains a gypsum-containing core sandwiched between two covering sheets. The covering sheets typically contain paper, but in some cases, other materials may be used in addition to or in place of paper. The gypsum core may contain materials other than gypsum, such as fibers, starch, cellulose pulp, waterproofing additives (such as waxes or bitumen emulsions), foaming agents (such as surfactants), and other additives. Gypsum board is commonly referred to as drywall and is frequently used for constructing interior walls and ceilings.

[0003] The core of gypsum board typically has a foamed structure to reduce the weight of the board, making it easier to transport and use. Different levels of foaming can produce a half-inch (1.26 cm) board weighing approximately 8 kg / m². 2 A standard board or half-inch board weighs approximately 6 kg / m² 2 Lightweight panels.

[0004] Gypsum board is prepared using a multi-step process. See, for example, U.S. Patents 9,181,132 B2 and 9,889,579 B2. First, calcined gypsum is mixed with water, a surfactant, and optionally other core materials and foamed with air to prepare a foamed gypsum slurry. Calcined gypsum typically contains primarily hemihydrated calcium sulfate (CaSO4 • 0.5 H2O), but may also contain other forms of dehydrated gypsum, such as anhydrous gypsum. It may also contain small amounts of other materials, such as rock salt, sulfur, silica, calcium carbonate, and other salts and oxides of silicon and metals (such as potassium, magnesium, and iron). Calcined gypsum is often referred to as stucco or plaster of Paris in technical documents relating to gypsum board.

[0005] Second, a core layer containing foamed gypsum slurry is spread onto the first cover sheet. Third, a second cover sheet is applied to the opposite side of the core layer to form a gypsum board. Fourth, calcined gypsum interacts with water in the foamed gypsum slurry to prepare calcium sulfate dihydrate, which hardens the foamed gypsum slurry and removes excess water with heat. Fifth, the dried gypsum board is cut and milled to the desired dimensions.

[0006] Air bubbles in foamed gypsum mortar become voids in the core of gypsum board. The size and arrangement of these voids affect the physical properties of the gypsum board, such as density and nail pull strength. Surfactants are commonly used as foaming agents in gypsum mortar. Stable surfactants typically produce small, uniformly sized voids. Unstable surfactants allow air bubbles to coalesce, resulting in larger voids with greater size variations. In some cases, mixtures of stable and unstable surfactants are used. See U.S. Patent 5,643,510.

[0007] The aim is to find new combinations of surfactants that can improve the density and strength balance of gypsum boards prepared by this method. Summary of the Invention

[0008] In one embodiment, the present invention relates to a gypsum slurry comprising:

[0009] (a) Aqueous solvents

[0010] (b) Calcined gypsum, in an amount suitable for forming a foamed gypsum slurry in the aqueous solvent;

[0011] (c) A surfactant combination, in an amount suitable for producing foamed gypsum slurry, the surfactant combination containing:

[0012] (i) an anionic diaryl oxide surfactant (“ADO surfactant”) comprising (A) a diaryl oxide moiety, (B) an aliphatic lipophilic moiety having an average of at least 8 carbon atoms bonded to the diaryl oxide moiety, and (C) at least one side-chain sulfonic acid or sulfonate moiety bonded to the diaryl oxide moiety; and

[0013] (ii) Nonionic glycosyl surfactants (“NSB surfactants”),

[0014] The surfactant combination, based solely on the combined weight of the anionic surfactant and the NSB surfactant excluding solvent, comprises (1) 20% to 80% by weight of the ADO surfactant and 80% to 20% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is branched, and (2) greater than 50% to 80% by weight of the ADO surfactant and less than 50% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is linear.

[0015] In one embodiment, the present invention relates to a method for preparing gypsum board, the method comprising the following steps:

[0016] (a) Applying a core layer containing foamed gypsum slurry directly or indirectly to the first cover sheet;

[0017] (b) applying the second cover sheet directly or indirectly to the core layer; and

[0018] (c) Harden and dry the core layer.

[0019] The foamed gypsum slurry contains gypsum slurry from the first aspect of the present invention.

[0020] In one embodiment, the present invention relates to a gypsum board comprising (1) a first cover sheet, (2) a core directly or indirectly adhered to the first cover sheet; and (3) a second cover sheet directly or indirectly adhered to the core opposite to the first cover sheet, wherein the core comprises:

[0021] (a) gypsum; and

[0022] (b) Based on the weight of gypsum, a combination of surfactants comprising 0.004% to 0.5% by weight, the combination of surfactants containing:

[0023] (i) An ADO surfactant comprising (A) a diaryl oxide moiety, (B) an aliphatic lipophilic moiety having an average of at least 8 carbon atoms bonded to the diaryl oxide moiety, and (C) at least one side-chain sulfonic acid or sulfonate moiety bonded to the diaryl oxide moiety; and

[0024] (ii) NSB surfactant,

[0025] The surfactant combination, based solely on the combined weight of the ADO surfactant and the NSB surfactant excluding solvent, comprises (1) 20% to 80% by weight of the ADO surfactant and 80% to 20% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is branched, and (2) greater than 50% to 80% by weight of the ADO surfactant and less than 50% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is linear.

[0026] Compared to gypsum boards foamed using conventional surfactants, gypsum boards prepared using the surfactant combination of the present invention can have lower weight or higher nail pull strength, or both. Detailed Implementation

[0027] One aspect of the invention is a gypsum slurry comprising calcined gypsum, an aqueous solvent, and a combination of surfactants as further described herein. The gypsum slurry is optionally foamed. The gypsum slurry optionally further comprises other additives. A second aspect of the invention is a method using a foamed gypsum slurry to prepare a gypsum board as further described herein. A third aspect of the invention is a gypsum board that can be prepared by the method of the invention as further described herein.

[0028] This invention uses plaster, as described in the background section.

[0029] At the start of this method, when forming the gypsum slurry, the gypsum is calcined gypsum. Calcined gypsum is in powder form miscible with an aqueous solvent. Calcined gypsum is commercially available from many sources known to those skilled in the art. It can also be prepared by heating powdered gypsum according to known methods. Examples of suitable calcined gypsum and methods for its preparation are described in U.S. Patents 8,016,961 and 6,706,128.

[0030] Calcined gypsum is mixed with an aqueous solvent and a surfactant to form a slurry. The aqueous solvent primarily contains water. In some embodiments, the aqueous solvent may contain a small amount of a water-miscible co-solvent, such as an alcohol or glycol. In some embodiments, the amount of the co-solvent does not exceed 10% by weight, or 5% by weight, or 3% by weight, or 1% by weight of the aqueous solvent. In some embodiments, the aqueous solvent is substantially free of the co-solvent (0%).

[0031] The weight ratio of aqueous solvent to calcined gypsum in the slurry is primarily limited by practical considerations. At high water content, more energy and time are required to dry the slurry. At low water content, the slurry may be too viscous to spread easily on the first covering sheet and may harden prematurely. In some embodiments, the weight ratio of aqueous solvent to calcined gypsum is at least 0.5, at least 0.6, or at least 0.7. In some embodiments, the weight ratio is at most 2, at most 1.5, at most 1.4, at most 1.3, at most 1.2, at most 1.1, or at most 1. For example, in some embodiments, the weight ratio of aqueous solvent to calcined gypsum is from 0.70 to 1.

[0032] When calcined gypsum is mixed with water in an aqueous solvent, it reacts, causing the calcined gypsum in the gypsum slurry to transition from a hemihydrate form to a dihydrate form.

[0033] The gypsum slurry further contains a surfactant combination containing ADO surfactant and NSB surfactant.

[0034] ADO surfactants comprise (A) a diaryl oxide moiety, (B) an aliphatic lipophilic moiety containing at least eight carbon atoms bonded to the diaryl oxide moiety, and (C) at least one side-chain sulfonic acid or sulfonate moiety bonded to the diaryl oxide moiety. The diaryl oxide moiety satisfies Formula 1:

[0035] (1)Ar-O-Ar

[0036] Each Ar group is independently an aryl group, such as a phenyl, tolyl, or isopropylphenyl group. At least one of the aryl groups is bonded to the lipophilic moiety. At least one of the aryl groups has a side-chain sulfonic acid or sulfonate moiety. In some embodiments, each aryl group has a side-chain sulfonic acid or sulfonate moiety.

[0037] In some implementations, the ADO surfactant satisfies the following formula 2:

[0038]

[0039] At least one of A is a sulfonic acid or sulfonate moiety and R 1 and R 2 At least one of them is a lipophilic moiety, as previously described. In some embodiments, A is independently at least one of a sulfonic acid or sulfonate moiety, and when only one A is a sulfonic acid or sulfonate moiety, the other A may be a hydrogen atom. In some embodiments, each A is independently a sulfonic acid or sulfonate moiety. In some embodiments, R 1 and R 2 Only one of them is a lipophilic moiety; in some implementations, R 1 and R 2 Each of these components is independently a lipophilic moiety. In some embodiments, the benzene ring may contain one or more side-chain lower alkyl groups, and in some embodiments, the benzene ring is unsubstituted.

[0040] lipophilic portion (R) 1 and / or R 2 The lipophilic moiety contains an average of at least 8 carbon atoms. In some embodiments, the lipophilic moiety contains an average of at least 10 or at least 12 carbon atoms. In some embodiments, the lipophilic moiety contains an average of up to 20, 18, 16, or 14 carbon atoms. The aliphatic group in the lipophilic moiety can be straight-chain or branched; however (as discussed below), we have found that branched lipophilic moieties allow for a wider range of ADO to NSB surfactant ratios compared to straight-chain lipophilic moieties. The aliphatic group in the lipophilic moiety can be saturated or unsaturated. In some embodiments, the lipophilic moiety is an alkyl group.

[0041] ADO surfactants contain at least one side-chain sulfonic acid group or sulfonate (A) partially bonded to a diaryl oxide. Examples of suitable sulfonates include alkali metal or alkaline earth metal salts and ammonium salts.

[0042] Examples of ADO surfactants are provided by The Dow Chemical Company under DOWFAX. ™ Trademarked commercial sales. Others can be prepared by known methods, such as those described in U.S. Patent 6,743,764 B1. Commercial ADO surfactants containing a diaryl oxide moiety are often sold as solutions containing 30% to 80% water by weight.

[0043] NSB surfactants contain a hydrophilic sugar moiety attached to a lipophilic portion. The lipophilic portion is as described and illustrated above and herein.

[0044] The hydrophilic portion comprises one or more repeating monosaccharide units, such as glucose, fructose, and galactose. In some embodiments, the monosaccharide unit contains glucose, and in some embodiments, the monosaccharide unit consists primarily of glucose. In some embodiments, the hydrophilic portion contains an average of 1 to 8 repeating monosaccharide units, or 1 to 6 repeating monosaccharide units, or 1 to 5 repeating monosaccharide units, or 1 to 4 repeating monosaccharide units, or 1 to 3 repeating monosaccharide units, or 1 to 2 repeating monosaccharide units.

[0045] Common examples of NSB surfactants include:

[0046] • Alkyl polyglucosides: Alkyl polyglucosides are produced by reacting sugars or starches with fatty alcohols at elevated temperatures in the presence of an acid catalyst. They are used in personal care and household cleaning products. Commonly available examples include decyl glucoside and lauryl glucoside.

[0047] • Sucrose esters: Sucrose esters are produced by the reaction of sucrose with fatty acid esters. They are used as emulsifiers and stabilizers in food and cosmetic products.

[0048] • Sorbitol esters: Sorbitol esters are produced by the reaction of sorbitol with fatty acids. They are used as emulsifiers and solubilizers.

[0049] In some implementations, the NSB surfactant comprises an alkyl polyglucan.

[0050] Suitable NSB surfactants can be TRITON ™The trademark was purchased from The Dow Chemical Company. Other NSB surfactants can be prepared using the methods described above. Commercial NSB surfactants are often sold as solutions containing 30% to 80% water by weight.

[0051] The appropriate ratio of ADO surfactant to NSB surfactant in a surfactant blend depends on whether the lipophilic moiety of the ADO surfactant is linear or branched. When the lipophilic moiety of the ADO surfactant is branched:

[0052] • This surfactant blend contains 20% to 80% by weight of ADO surfactant and 80% to 20% by weight of NSB surfactant.

[0053] • In some embodiments, the surfactant combination contains at least 25% by weight or at least 35% by weight or at least 45% by weight or at least 50% by weight or at least 60% by weight or at least 70% by weight of ADO surfactant; and contains at most 75% by weight or at most 65% by weight or at most 55% by weight or at most 50% by weight or at most 40% by weight or at most 30% by weight of NSB surfactant.

[0054] • In some embodiments, the surfactant combination contains up to 78% by weight, up to 76% by weight, or up to 75% by weight of ADO surfactant; and contains at least 22% by weight, at least 24% by weight, or at least 25% by weight of NSB surfactant.

[0055] The ratios mentioned above are based solely on the combined weight of NSB and ADO surfactants and do not include any solvents or other components.

[0056] When the lipophilic portion of an ADO surfactant is linear:

[0057] • This surfactant blend contains more than 50% to 80% by weight of ADO surfactant and less than 50% to 20% by weight of NSB surfactant.

[0058] • In some embodiments, the surfactant combination contains at least 55% by weight, at least 60% by weight, or at least 70% by weight of ADO surfactant; and at most 45% by weight, at most 40% by weight, or at most 30% by weight of NSB surfactant.

[0059] • In some embodiments, the surfactant combination contains up to 78% by weight, up to 76% by weight, or up to 75% by weight of ADO surfactant; and contains at least 22% by weight, at least 24% by weight, or at least 25% by weight of NSB surfactant.

[0060] The ratios mentioned above are based solely on the combined weight of NSB and ADO surfactants and do not include any solvents or other components.

[0061] In some implementations, when the lipophilic portion of the ADO surfactant contains an average of less than 12 carbon atoms, the proportion of the ADO surfactant in the surfactant mix is ​​at the higher end of the range, such as at least 60% by weight, at least 65% by weight, or at least 70% by weight.

[0062] For clarity, the term "surfactant combination" does not mean that NSB surfactants and ADO surfactants must be blended together before they are added to the gypsum slurry. They can be premixed, or they can be added to the aqueous solvent or slurry simultaneously, or they can be added to the aqueous solvent or slurry at different times.

[0063] The ratio of surfactant blend to calcined gypsum in the gypsum slurry is suitable for producing a foamed gypsum slurry. In some embodiments, the weight ratio of surfactant blend to calcined gypsum is at least 0.005% by weight, at least 0.008% by weight, at least 0.01% by weight, at least 0.012% by weight, or at least 0.013% by weight. In some embodiments, the weight ratio of surfactant blend to calcined gypsum is at most 0.5% by weight, at most 0.2% by weight, at most 0.1% by weight, at most 0.05% by weight, at most 0.02% by weight, or at most 0.017% by weight. The above ratios are based solely on the surfactant in the surfactant blend (excluding any solvents) and on the weight of calcined gypsum before addition to the aqueous solvent.

[0064] Plaster slurry may optionally contain additives other than surfactants. Examples of common additives include:

[0065] • Fibers (such as cellulose or glass fiber).

[0066] • Accelerators, such as alum, finely ground calcium sulfate, and potassium sulfate.

[0067] • Retarder used for delayed curing, such as EDTA and other chelating agents,

[0068] •starch,

[0069] Potassium alkali,

[0070] •clay,

[0071] • Boric acid,

[0072] • Dispersants, such as calcium naphthalenesulfonate

[0073] • Refractory additives, such as vermiculite,

[0074] • Anti-mold agent,

[0075] •Thickener,

[0076] • Hydrophobic additives, such as waxes or polysiloxanes, to improve water resistance, and

[0077] • Adhesives, such as ethylene vinyl alcohol.

[0078] Each of these additives is well-known and commercially available. Those skilled in the art can select the appropriate additive level based on the intended use of the gypsum board.

[0079] In some embodiments, the gypsum slurry contains 0% by weight, or at least 1% by weight, or at least 2% by weight of additives, based on the weight of the calcined gypsum. In some embodiments, the gypsum slurry contains up to 10% by weight, or at most 5% by weight, or at most 3% by weight of additives, based on the weight of the calcined gypsum.

[0080] For use in this invention, the components of a gypsum slurry are mixed together and foamed to prepare a foamed gypsum slurry. Foaming is achieved by mixing at least an aqueous solvent and a surfactant with air under conditions that allow foam formation. Methods for mixing slurry components and foaming them are well known in the gypsum board industry. See, for example, U.S. Patents 2,079,565; 4,057,443 and 4,455,271. Equipment for performing mixing and foaming is commercially available with its instruction manual. Examples of suitable equipment include stirring vessels, static mixers, and needle mixers.

[0081] Foamed gypsum slurry can be formed using any actual sequence of adding components, mixing components, and foaming it. For example:

[0082] • In some implementations, all components of the gypsum slurry are first mixed together, and then the slurry is foamed to prepare foamed gypsum slurry.

[0083] • In some embodiments, the surfactant and optional other liquid components of the slurry are mixed with an aqueous solvent and foamed, and then dried calcined gypsum and any other solid components are added to the foam mixture to prepare a foamed gypsum slurry.

[0084] • In some embodiments, surfactants and optional other additives are mixed with an aqueous solvent and foamed, while calcined gypsum and optional other additives are mixed separately in an aqueous solvent, and then the two mixtures are blended together to prepare a foamed gypsum slurry.

[0085] In some embodiments of gypsum grout, the NSB surfactant is a stable surfactant, meaning it forms stable bubbles that do not coalesce during the time required for the gypsum grout to harden. In some embodiments of gypsum grout, the ADO surfactant is an unstable surfactant, meaning it forms bubbles that coalesce and expand during the time required for the gypsum grout to harden. Combining stable and unstable surfactants provides some control over the void size and size distribution in the resulting gypsum board.

[0086] In some embodiments, the density of the foamed gypsum slurry is at least 60 g / L, at least 65 g / L, at least 70 g / L, at least 75 g / L, or at least 80 g / L. In some embodiments, the density of the foamed gypsum slurry is at most 240 g / L, at most 200 g / L, at most 160 g / L, at most 120 g / L, at most 100 g / L, at most 90 g / L, at most 85 g / L, or at most 80 g / L. In some embodiments, the gas-to-slurry volume ratio in the foamed gypsum slurry is at least 5.0:1, at least 5.5:1, at least 5.8:1, or at least 6.0:1. In some embodiments, the gas-to-slurry volume ratio in the foam is at most 8.0:1, at most 7.5:1, at most 7.0:1, at most 6.5:1, at most 6.2:1, or at most 6.0:1.

[0087] In some embodiments, when measured according to the test method, the 25% water separation time of the foamed gypsum slurry (the time required for 25% of the water in the foam to settle and separate) is at least 200 seconds, at least 225 seconds, or at least 250 seconds. In some embodiments, when measured according to the test method, the 25% water separation time of the foamed gypsum slurry is at most 500 seconds, at most 400 seconds, at most 350 seconds, at most 325 seconds, or at most 300 seconds.

[0088] In the method of this invention, a core layer containing foamed gypsum slurry is applied directly or indirectly to a first cover sheet. The cover sheet may contain many different materials, such as paper, fiberglass, polymers, or metal foil. Most commonly, the cover sheet contains paper, but other materials can provide enhanced strength, toughness, moisture resistance, fire resistance, or radiation protection. In some embodiments, the cover sheet may contain additives or components that improve water resistance, flame retardancy, or mildew resistance. Indirect application means that in some embodiments, an intermediary layer, such as an adhesive layer, a waterproof layer, or a fiber mesh, may be placed between the cover sheet and the foamed gypsum slurry. In some embodiments, the gypsum slurry is applied directly to the cover sheet.

[0089] A core layer containing foamed gypsum mortar can be applied by pouring and optionally spreading the foamed gypsum mortar using known methods and equipment. See, for example, “Making Gypsum Board” published by the Gypsum Association at https: / / gypsum.org / making-gypsum-board / and “Plasterboard Production” published by Knauf UK GmbH at https: / / www.knauf.co.uk / about-us / knauf-factories / plasterboard-production. In some embodiments, the foamed gypsum mortar layer covers most or all of the cover sheet with a substantially uniform thickness. In some embodiments, the thickness of the foamed gypsum mortar layer is at least ¼ inch (0.6 cm), at least 1 / 3 inch (0.8 cm), or at least ½ inch (1 cm). In some embodiments, the thickness of the foamed gypsum mortar layer is at most 2 inches (5 cm), at most 1 inch (3 cm), or at most ¾ inch (2 cm). Optionally, the core may contain two or more foamed gypsum mortar layers having similar or different compositions. Optionally, in addition to the foamed gypsum slurry layer, the core may further contain one or more layers of another material. Optionally, rollers or scrapers press or flatten the core layer to a uniform thickness.

[0090] A second cover sheet is applied directly or indirectly to the core layer. The second cover sheet may be the same as or different from the first cover sheet. In some embodiments, one cover sheet is a face sheet, which may be optionally selected for the appearance, adhesion, or moisture resistance of the coating. In some embodiments, one cover sheet is a back sheet, which may be optionally selected to provide improved physical or barrier properties. Optionally, after the second cover sheet is applied, rollers press the board to the desired uniform thickness.

[0091] The product of this step is a board consisting of two cover sheets and a core containing foamed gypsum slurry sandwiched between them. Within the foamed gypsum slurry, calcined gypsum interacts with water to form gypsum dihydrate, which hardens the core. The core is then hardened, and the gypsum board is heated to remove excess water and dry the board. Hardening and drying can occur alone or simultaneously.

[0092] In some embodiments, the first and second cover sheets are part of a continuous roll. A second step of the method prepares a continuous gypsum board strip containing two cover sheets and foamed gypsum slurry. In a third step of the method, the continuous gypsum board strip is moved along a belt until it hardens sufficiently to maintain its shape upon cutting. The continuous gypsum board strip is then cut into individual sheets. The individual sheets are placed in an oven to complete the hardening and drying steps.

[0093] After drying, the plasterboard can be optionally finished, such as by trimming the edges.

[0094] The product of this method is a gypsum board, which includes (1) a first cover sheet, (2) a core directly or indirectly adhered to the first cover sheet; and (3) a second cover sheet directly or indirectly adhered to the core opposite to the first cover sheet, wherein the core contains:

[0095] (a) gypsum; and

[0096] (b) Based on the weight of gypsum, a combination of surfactants comprising 0.004% to 0.5% by weight, the combination of surfactants containing:

[0097] (i) the ADO surfactant as previously described; and

[0098] (ii) NSB surfactants as previously described.

[0099] As previously described, the surfactant combination (1) contains 20% to 80% by weight of the ADO surfactant and 80% to 20% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is branched, and (2) contains more than 50% to 80% by weight of the ADO surfactant and less than 50% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is linear.

[0100] The gypsum in the core reflects the calcined gypsum added to the gypsum slurry, except that the gypsum in the core is mainly calcium sulfate dihydrate, while calcined gypsum is usually calcium sulfate hemihydrate. Due to this difference, the gypsum in the core is usually heavier than the calcined gypsum added to the gypsum slurry, for example, by about 15-20%.

[0101] The surfactant combination has the same description and exemplary embodiments as already discussed. The amount of surfactant combination in the core reflects the amount of surfactant combination in the gypsum slurry. However, the weight ratio of surfactant in the core to gypsum may be slightly lower than the weight ratio in the slurry because the gypsum in the core is heavier than the calcined gypsum added to the gypsum slurry. In some embodiments, the weight ratio of surfactant combination in the core to gypsum is at least 0.006 wt%, at least 0.008 wt%, or at least 0.01 wt%. In some embodiments, the weight ratio of surfactant combination in the core to gypsum is at most 0.43 wt%, at most 0.17 wt%, at most 0.1 wt%, at most 0.09 wt%, at most 0.04 wt%, at most 0.02 wt%, or at most 0.015 wt%.

[0102] The gypsum core may optionally contain other additives as previously discussed for gypsum slurry.

[0103] After the gypsum core dries, it typically contains approximately two water molecules per calcium sulfate molecule, which are incorporated into the gypsum's crystal structure. In some embodiments, it contains only low levels of other free water.

[0104] In some implementations, standard drywall has an average thickness of no more than 8.5 kg / m² per ½ inch (1.27 cm). 2 or not exceeding 8kg / m 2 Or not exceeding 7.8 kg / m 2 The weight. In some implementations, standard drywall has an average thickness of at least 6.5 kg / m² per ½ inch (1.27 cm). 2 Or at least 7.0 kg / m 2 Or at least 7.5 kg / m 2 The weight.

[0105] In some implementations, lightweight gypsum board has an average thickness of no more than 6.5 kg / m² per ½ inch (1.27 cm). 2 Or not exceeding 6.2 kg / m 2 Or not exceeding 6.1 kg / m 2 The weight. In some implementations, lightweight gypsum board has an average thickness of at least 5 kg / m² per ½ inch (1.27 cm). 2 Or at least 5.5 kg / m 2 Or at least 5.7 kg / m 2 Or at least 6.0 kg / m 2 The weight.

[0106] In some embodiments, the core of the gypsum board contains at least 35% by volume, or at least 40% by volume, or at least 45% by volume, or at least 48% by volume of void volume. In some embodiments, the core of the gypsum board contains at most 70% by volume, or at most 65% by volume, or at most 62% by volume, or at most 60% by volume of void volume. In some embodiments, the ratio of the standard deviation to the mean of the void volume is at least 0.5, or at least 0.6, or at least 0.7, or at least 0.8. In some embodiments, the ratio of the standard deviation to the mean of the void volume is at most 2, or at most 1.8, or at most 1.6, or at most 1.4, or at most 1.3.

[0107] In some implementations, when tested according to the test method, the gypsum board has a pull-out nail strength of at least 100 N, at least 110 N, at least 120 N, at least 130 N, at least 140 N, at least 150 N, or at least 160 N. There is no maximum expected pull-out nail strength as long as the board remains sufficiently low in weight, but in some cases, a pull-out nail strength exceeding 200 N or 180 N may be unnecessary.

[0108] The gypsum board of the present invention can be used for common applications of gypsum board, such as walls, ceilings and other interior surfaces of buildings.

[0109] Test methods

[0110] Unless otherwise stated, the measurements listed in this application are performed using the following test methods:

[0111]

[0112] Example

[0113] The following examples illustrate specific implementations of the present invention, but do not limit the widest scope of the invention.

[0114] The surfactants listed in Table 1 are used in the examples:

[0115]

[0116] Preparation of gypsum board

[0117] Mix the surfactant shown in Table 2 with 60g of water and foam to a total volume of 750mL using a paddle in a Hobart mixer at speed 3. Add 200g of calcined gypsum and water (according to Table 2) to a 500mL Waringblender and stir manually for 10s. Select the amount of water based on the amount required to completely wet the calcined gypsum and form a slurry. Add 1g of calcium naphthalenesulfonate dispersant to the mixer and pulse the contents at high speed for 25-30s. Weigh the gypsum-water slurry into a clean Hobart mixing bowl and weigh an appropriate amount of foam into the slurry. Mix the foam and gypsum slurry with a paddle at speed 2 for 25-30s until fully incorporated. The foaming mixture was poured into a 4”×6”×0.5” rectangular mold and placed in an oven at 80°C for 10 min to cure. Once cured, the boards were dried at 60°C for 2–4 h. The density and pull-out strength of each board were measured. The results are listed in Table 2, where “IE#” samples represent embodiments of the invention and “CE#” samples represent comparative examples.

[0118]

[0119] a - Total water, including water added to the surfactant.

[0120] b - weight percentage based on the weight of calcined gypsum.

Claims

1. A gypsum slurry, the gypsum slurry comprising: (a) Aqueous solvents; (b) Calcined gypsum, in an amount suitable for forming a foamed gypsum slurry in the aqueous solvent; and (c) A surfactant combination, in an amount suitable for producing a foamed gypsum slurry, said surfactant combination containing: (i) an anionic diaryl oxide surfactant ("ADO surfactant") comprising (A) a diaryl oxide moiety; (B) an aliphatic lipophilic moiety having an average of at least 8 carbon atoms bonded to said diaryl oxide moiety; and (C) at least one side-chain sulfonic acid or sulfonate moiety bonded to said diaryl oxide moiety; and (ii) Nonionic glycosyl surfactants ("NSB surfactants") The surfactant combination (1) contains 20% to 80% by weight of the ADO surfactant and 80% to 20% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is branched, and (2) contains more than 50% to 80% by weight of the ADO surfactant and less than 50% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is linear.

2. A method for preparing gypsum board, the method comprising the following steps: (a) Applying a core layer containing foamed gypsum slurry directly or indirectly to the first cover sheet; (b) applying the second cover sheet directly or indirectly to the core layer; and (c) Harden and dry the core layer. The foamed gypsum slurry contains the gypsum slurry according to claim 1.

3. A gypsum board, the gypsum board comprising (1) a first cover sheet, (2) a core directly or indirectly adhered to the first cover sheet; and (3) a second cover sheet directly or indirectly adhered to the core opposite to the first cover sheet, wherein the core comprises: (a) gypsum; and (b) Based on the weight of gypsum, a combination of surfactants comprising 0.004% to 0.5% by weight, said surfactants comprising: (i) An anionic diaryl oxide surfactant ("ADO surfactant") comprising (A) a diaryl oxide moiety, (B) an aliphatic lipophilic moiety having an average of at least 8 carbon atoms bonded to said diaryl oxide moiety, and (C) at least one side-chain sulfonic acid or sulfonate moiety bonded to said diaryl oxide moiety; and (ii) Nonionic glycosyl surfactants ("NSB surfactants") The surfactant combination (1) contains 20% to 80% by weight of the ADO surfactant and 80% to 20% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is branched, and (2) contains more than 50% to 80% by weight of the ADO surfactant and less than 50% by weight of the NSB surfactant when the lipophilic portion of the ADO surfactant is linear.

4. The gypsum board according to claim 3, wherein the ADO surfactant satisfies formula 2: At least one of A contains a side-group sulfonic acid or sulfonate moiety and R 1 and R 2 At least one of them is an aliphatic lipophilic moiety containing an average of at least 8 carbon atoms.

5. The gypsum board according to claim 4, wherein the lipophilic portion of the ADO surfactant contains an average of 10 to 18 carbon atoms.

6. The gypsum board of claim 5, wherein the lipophilic portion of the ADO surfactant is linear, and the surfactant combination contains at least 60% by weight of the anionic surfactant and the NSB surfactant, excluding solvents.

7. The gypsum board according to claim 6, wherein the nonionic glycosyl surfactant is an alkyl glucoside surfactant.

8. The gypsum board according to claim 7, wherein the alkyl glucoside surfactant comprises a hydrophilic portion containing 1 to 5 glucose repeating units and a lipophilic portion containing an average of 8 to 16 carbon atoms.

9. The gypsum board according to claim 7, wherein the ratio of the surfactant combination to gypsum is from 0.01% to 0.02% by weight.

10. The gypsum board according to claim 5, wherein the lipophilic portion of the ADO surfactant is branched.

11. The gypsum board according to claim 10, wherein the nonionic glycosyl surfactant is an alkyl glucoside surfactant.

12. The gypsum board of claim 11, wherein the alkyl glucoside surfactant comprises a hydrophilic portion having one to five glucose repeating units and a lipophilic portion having an average of eight to 16 carbon atoms.

13. The gypsum board according to claim 11, wherein the ratio of the surfactant combination to gypsum is 0.01% to 0.02% by weight.

14. The gypsum board according to any one of claims 3 to 13, wherein the gypsum board has an average thickness of 5 kg / m² per ½ inch. 2 Up to 6.2 kg / m 2 The weight.

15. The gypsum board of claim 14, wherein the gypsum board has a nail pull strength of at least 100 N.

Images