Method and gypsum board

Abstract

According to the present invention, there is provided a method of making a gypsum board, the method comprising combining at least one regenerated calcium sulfate material and at least one non-regenerated calcium sulfate material to form a particulate mixture, combining at least the particulate mixture and water to form a solidifiable slurry, and drying the solidifiable slurry to form a gypsum board, wherein the ratio of regenerated calcium sulfate material to non-regenerated calcium sulfate material in the particulate mixture is at least 1: 1, and wherein the method further comprises calcining the particulate mixture prior to combining the particulate mixture with water to form a solidifiable slurry. The invention further provides a gypsum board.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a gypsum board and also relates to a gypsum board and a use of the gypsum board. Background Art

[0002] Gypsum occurs naturally as a raw material in the form of calcium sulfate dihydrate (CaSO4 2(H2O)). Gypsum-containing products, such as gypsum board, are prepared by forming a mixture of calcined or dehydrated gypsum (i.e., calcium sulfate hemihydrate (CaSO4 0.5(H2O))) and water to form a settable slurry that is then cast into a predetermined shape. The calcium sulfate hemihydrate reacts with water and rehydrates into dihydrate crystals that are then cured or dried into a solid state.

[0003] Gypsum products are common in construction due to their versatility, desirable mechanical properties and the possibility of achieving a high level of finish. It is therefore desirable to produce gypsum products that have a reduced environmental impact. Summary of the invention

[0004] According to a first aspect of the present invention, there is provided a method for manufacturing a gypsum board, the method comprising: combining at least one regenerated calcium sulfate material and at least one non-regenerated calcium sulfate material to form a mixture of particles, combining at least the mixture of particles with water to form a settable slurry, and drying the settable slurry to form a gypsum board, wherein the ratio of the regenerated calcium sulfate material to the non-regenerated calcium sulfate material in the mixture of particles is at least 1:1, wherein the method further comprises calcining the mixture of particles before combining the mixture of particles with water to form the settable slurry.

[0005] In this way, a method is provided for manufacturing gypsum board having a reduced environmental impact while maintaining favorable manufacturing and end-product properties.

[0006] Here, for the avoidance of doubt, it should be understood that calcium sulfate material, particularly regenerated calcium sulfate material, may be impure. Therefore, although calcium sulfate material should be understood as primarily comprising calcium sulfate in at least one form of dihydrate, hemihydrate or anhydrite form, it may also include impurities.

[0007] Such impurities may include, but are not limited to, paper, glass fibers, fluidizers, waterproofing agents, and other components that are often introduced into gypsum board during the manufacturing process. It will be appreciated that if these impurities are present in the gypsum board or the like, they will also be incorporated into the regenerated calcium sulfate material. Therefore, when discussing the ratio of regenerated calcium sulfate material to non-regenerated calcium sulfate material, it is correct to compare the relative weights of the two materials (including any impurities).

[0008] Preferably, the method comprises grinding the particle mixture before combining the particle mixture with water to form the settable slurry. In this way, the method can allow the particle size within the particle mixture to be reduced, enabling the overall manufacturing process to be improved and / or accelerated.

[0009] Preferably, the mean average residence time of the particles in the particle mixture in the grinder is less than 75 seconds. More preferably, the mean average residence time of the particles in the particle mixture in the grinder is less than 60 seconds. Most preferably, the mean average residence time of the particles in the particle mixture in the grinder is less than 45 seconds.

[0010] Preferably, the Blaine value for the ground, calcined material is less than 8000 cm 2 More preferably, the Blaine value for the ground and calcined material is less than 7000 cm 2 / g. More preferably, the Blaine value for the ground and calcined material is less than 6000 cm 2 In this way, the particles within the calcined mixture can have a desired hydration characteristic and / or a preferred water demand.

[0011] Preferably, after calcining, the particle mixture comprises less than 20 wt% calcium sulfate anhydrite. More preferably, after calcining, the particle mixture comprises less than 16 wt% calcium sulfate anhydrite. Most preferably, after calcining, the particle mixture comprises less than 10 wt% calcium sulfate anhydrite. Providing such a particle mixture can result in an improved process and / or an improved gypsum board.

[0012] Preferably, at least one non-regenerated calcium sulfate material comprises calcium sulfate hemihydrate. In some embodiments, at least one non-regenerated calcium sulfate material consists of calcium sulfate hemihydrate. Preferably, at least one calcium sulfate material comprises calcium sulfate dihydrate. In some embodiments, at least one non-regenerated calcium sulfate material consists of calcium sulfate dihydrate.

[0013] Preferably, at least one calcium sulfate material of regeneration comprises calcium sulfate hemihydrate. In some embodiments, at least one calcium sulfate material of regeneration consists of calcium sulfate hemihydrate. Preferably, at least one calcium sulfate material of regeneration consists of calcium sulfate dihydrate. In some embodiments, at least one calcium sulfate material of regeneration comprises calcium sulfate dihydrate.

[0014] In some embodiments, the non-regenerated calcium sulfate material and / or the regenerated calcium sulfate material includes both calcium sulfate hemihydrate and calcium sulfate dihydrate.

[0015] Preferably, the regenerated calcium sulfate material comprises paper. More preferably, the regenerated calcium sulfate material comprises 2.2wt.% or less paper, or 2wt.% or less paper. More preferably, the regenerated calcium sulfate material comprises 1.7wt.% or less paper, or 1.6wt.% or less paper, or 1.5wt.% or less paper. Again preferably, the regenerated calcium sulfate material comprises 1.2wt.% or less paper, or 1.0wt.% or less paper. Even more preferably, the regenerated calcium sulfate material comprises 0.84wt.% or less paper, or 0.7wt.% or less paper, or 0.5wt.% or less paper. Most preferably, the regenerated calcium sulfate material comprises 0.4wt.% or less paper, or 0.2wt.% or less paper. In the case where the paper content of the regenerated calcium sulfate material is as described, the regenerated calcium sulfate material may have ideal hydration and / or water consumption characteristics.

[0016] Preferably, the particle mixture comprises 2.2 wt.% or less of paper. More preferably, the particle mixture comprises 2 wt.% or less of paper, or 1.7 wt.% or less of paper, or 1.6 wt.% or less of paper, or 1.5 wt.% or less of paper. Still more preferably, the particle mixture comprises 1.2 wt.% or less of paper. Still more preferably, the particle mixture comprises 1 wt.% or less of paper, or 0.84 wt.% or less of paper. Even more preferably, the particle mixture comprises 0.7 wt.% or less of paper. Still further preferably, the particle mixture comprises 0.5 wt.% or less of paper, or 0.4 wt.% or less of paper. Most preferably, the particle mixture comprises 0.2 wt.% or less of paper. In the case where the paper content of the particle mixture is as described above, the particle mixture may have desired hydration and / or water usage characteristics.

[0017] Preferably, the method produces an equivalent gypsum board at a rate exceeding 80% of the rate of an equivalent process for which the mixture does not include a recycled calcium sulfate material. More preferably, the method produces an equivalent gypsum board at a rate exceeding 90% of the rate of an equivalent process for which the mixture does not include a recycled calcium sulfate material. In this way, the desired properties of the equivalent process are maintained, and the calcium sulfate product (such as gypsum board) has substantially the same properties as an equivalent product produced by the equivalent process.

[0018] Preferably, the calciner throughput rate of the method exceeds 80% of the rate of an equivalent process for which the mixture does not include the regenerated calcium sulfate material, and the gypsum board produced by the method is equivalent to the gypsum board produced by the equivalent process. More preferably, the calciner throughput rate of the method exceeds 90% of the rate of an equivalent process for which the mixture does not include the regenerated calcium sulfate material, and the gypsum board produced by the method is equivalent to the gypsum board produced by the equivalent process. In this way, the desired properties of the equivalent process are maintained.

[0019] Preferably, the method comprises adding a fluidizing agent to the settable slurry. Preferably, the fluidizing agent is added in an amount less than or equal to 1 wt.% of the dry weight of the calcium sulfate material. Preferably, the fluidizing agent is added in an amount greater than or equal to 0.1 wt.% of the dry weight of the calcium sulfate material.

[0020] Preferably, the density of the manufactured gypsum board is 960 kg / m 3 More preferably, the density of the manufactured gypsum board is 760 kg / m 3 Or less. Preferably, the density of the gypsum board is 520kg / m 3 More preferably, the density of the gypsum board is 680 kg / m 3 Preferably, the thickness of the manufactured gypsum board is 12.5 mm or less.

[0021] According to a second aspect of the present invention, there is provided a gypsum board comprising a regenerated calcium sulfate material and a non-regenerated calcium sulfate material, wherein the ratio of the regenerated calcium sulfate material to the non-regenerated calcium sulfate material is at least 1:1.

[0022] Preferably, the density of the gypsum board is 960 kg / m 3 More preferably, the density of the gypsum board is 760 kg / m 3 Preferably, the density of the gypsum board is 520 kg / m 3 More preferably, the density of the gypsum board is 680 kg / m 3 Preferably, the thickness of the gypsum board is 12.5 mm or less.

[0023] Preferably, the gypsum board comprises a core comprising paper in an amount of 2.2 wt.% or less. More preferably, the gypsum board comprises a core comprising paper in an amount of 2 wt.% or less. Still more preferably, the gypsum board comprises a core comprising paper in an amount of 1.7 wt.% or less, or in an amount of 1.6 wt.% or less, or in an amount of 1.5 wt.% or less. Still more preferably, the gypsum board comprises a core comprising paper in an amount of 1.2 wt.% or less. In further preference, the gypsum board comprises a core comprising paper in an amount of 1 wt.% or less, or in an amount of 0.84 wt.% or less. Even more preferably, the gypsum board comprises a core comprising paper in an amount of 0.7 wt.% or less, or in an amount of 0.5 wt.% or less, or in an amount of 0.4 wt.% or less. Most preferably, the gypsum board comprises a core comprising paper in an amount of 0.2 wt.% or less.

[0024] Preferably, the gypsum board comprises a fluidizing agent in an amount of less than 1 wt.% of the dry weight of the calcium sulphate material. Preferably, the gypsum board comprises a fluidizing agent in an amount of greater than 0.1 wt.% of the dry weight of the calcium sulphate material.

[0025] According to a third aspect of the present invention, there is provided the use of a gypsum board as described herein and / or a gypsum board manufactured by a method as described herein. DETAILED DESCRIPTION

[0026] Embodiments of the invention will now be described by way of example only.

[0027] It is well known that changing the particle size of calcium sulfate materials used in gypsum board manufacturing can affect the manufacturing process. Experiments were conducted to investigate the effect of incorporating recycled calcium sulfate raw materials on particle size.

[0028] Here, as the first stage, the mixture of non-regenerated calcium sulfate material and regenerated calcium sulfate material is ground and calcined. The particle size produced by the process is controlled by changing the selector position on the grinding device. The selector position controls the outlet of the mixture from the grinder, and a higher sector position corresponds to a longer residence time and a smaller particle size. The Blaine values ​​of the ground and calcined materials produced in each test were measured and detailed in Table 1 below.

[0029] Table 1

[0030]

[0031] Although the preferred Blaine value for the ground and calcined mixture depends on the overall gypsum board production process, in the present case it is preferably below 8000 cm2 / g value. This preferred Blaine value can be used for pure non-regenerated gypsum (calcium sulfate material 6) and can also be used for a mixture containing conventional levels of recycled materials (calcium sulfate material 5). When the amount of recycled materials and the ratio of non-regenerated materials are increased to 1:1 (such as in calcium sulfate material 4 and calcium sulfate material 4b), the desired Blaine value can be obtained.

[0032] In addition to the Blaine values ​​measured for calcium sulfate mixtures, the composition of the mixtures themselves also affects their suitability for making gypsum board.

[0033] To investigate this, samples of calcium sulfate material 3, calcium sulfate material 4 and calcium sulfate material 4b were used in further experiments. Here, the line speeds achievable during manufacture and the weight percentage of calcium sulfate anhydrite after calcination were measured and compared with existing methods. Here, the percentage of calcium sulfate anhydrite was measured as the weight percentage of the calcined material.

[0034] Table 2 details the results of these experiments.

[0035] Table 2

[0036]

[0037] As can be seen from Table 2, increasing the amount of recycled calcium sulfate material does affect the overall manufacturing process and the composition of the calcined material. First, it is worth noting that as the amount of recycled material increases, the amount of calcium sulfate anhydrite in the calcined mixture increases. Due to the high water usage during the manufacturing process, the presence of calcium sulfate anhydrite is generally undesirable. This high water usage is generally considered to be a reduction in the line speed that can be achieved during the manufacturing process. This effect is also observed in Table 2.

[0038] However, it is noteworthy that despite the increase in the amount of calcium sulfate anhydrite in the mixture, the amount of calcium sulfate anhydrite present after calcination of the non-regenerated calcium sulfate material and the regenerated calcium sulfate material is less than the preferred amount of 20 wt.%, less than the more preferred amount of 16 wt.%, and less than the most preferred amount of 10 wt.%. Therefore, when using a 1:1 ratio of recycled and non-regenerated materials, the line speed of the manufacturing process is not reduced to less than 84% of the equivalent process for the mixture does not include the regenerated calcium sulfate material.

[0039] In addition to the calcium sulfate anhydrite content of the calcined mixture, other ingredients of the mixture introduced from the recycled material also affect the amount of water used in the mixture during the gypsum board manufacturing process. One of the ingredients that has the greatest impact on water consumption is known to be paper. Paper is often present in recycled calcium sulfate materials because paper is often used as a facing layer of gypsum board. Therefore, it is important to keep the paper content in the particle mixture at or below 2.2 wt.%.

[0040] In order to illustrate the effect of paper content on gypsum board production, an experiment was performed as outlined below.

[0041] Here, 200 g samples of calcium sulfate material were prepared, which included 50% non-regenerated calcium sulfate material in the form of calcium sulfate hemihydrate and 50% regenerated calcium sulfate material. The regenerated calcium sulfate material contained 0.4 wt% paper fiber. Therefore, the sample included a baseline level of 0.2 wt% paper fiber. Then different amounts of additional paper fiber were added to the sample, and water was added to the mixture to form a slurry.

[0042] Each slurry sample was then mixed in a blender at a constant speed for 10 seconds to ensure that its ingredients were fully mixed. The viscosity of the slurries was measured using a slump testing, where a sample of each slurry was placed in a 60 mm diameter, 50 mm height cylindrical mold on a glass substrate.

[0043] Subsequently, the mold was removed by lifting so that the slurry was not supported. After removing the mold, the spread of the slurry on the substrate was measured after a period of 20 seconds. At the end of this period, the slurry spread was measured three times at different points across the slurry spread, and the average value of these measurements was recorded.

[0044] To measure the effect of paper on the amount of water used in the solid material mixture, the viscosity of samples containing 0.2 wt.% paper fibers was measured. To characterize any increase in the amount of water used, the amount of water added to the samples containing paper fibers was increased until the same slurry spread was observed. In this way, increases in the amount of water used could be characterized. The results of these experiments are listed in Table 3.

[0045]

[0046] Table 3

[0047] Here, the water gauge of the slurry is calculated using the following formula:

[0048]

[0049] As shown in Table 3, increasing the amount of paper fiber in the sample from 0.2 wt.% to 0.7 wt.% had no effect on the slurry viscosity. This is demonstrated by the fact that Example 5 exhibited the same fluidity as Example 4, requiring no additional water to obtain the same measured slump.

[0050] As the paper content increases, additional water is required to maintain the same slurry viscosity seen in Example 4. In Example 6, containing 1.2 wt.% paper, the water gauge increases to 79%. In Example 7, containing 2.2 wt.% paper, the water gauge increases to 83%.

[0051] Thus, while samples containing 2.2 wt.% or less paper showed acceptable water usage for industrial gypsum board manufacturing, 0.7 wt.% or less paper content in the solids mixture used to form the slurry did not result in a significant increase in water usage.

Claims

1. A method for manufacturing a gypsum board, the method comprising: combining at least one regenerated calcium sulfate material and at least one non-regenerated calcium sulfate material to form a particulate mixture, combining at least the particle mixture and water to form a settable slurry, and drying the settable slurry to form a gypsum board, wherein, in the particle mixture, the ratio of the regenerated calcium sulfate material to the non-regenerated calcium sulfate material is at least 1:1, The method further includes calcining the particle mixture before combining the particle mixture with water to form a settable slurry.

2. The method according to claim 1, wherein: The method also includes grinding the particulate mixture before combining the particulate mixture with water to form a settable slurry.

3. The method according to claim 2, wherein: The particles in the particle mixture have an average residence time in the mill of less than 75 seconds.

4. A method according to any one of the preceding claims, wherein: Blaine values ​​for ground and calcined material are less than 8000 cm 2 / g, more preferably less than 7000cm 2 / g.

5. A method according to any one of the preceding claims, wherein: After calcination, the particle mixture comprises less than 20 wt.% calcium sulfate anhydrite, preferably less than 16 wt.% calcium sulfate anhydrite, most preferably less than 10 wt.% calcium sulfate anhydrite.

6. A method according to any one of the preceding claims, wherein: The at least one non-regenerated calcium sulfate material comprises calcium sulfate hemihydrate and / or calcium sulfate dihydrate.

7. A method according to any one of the preceding claims, wherein: The at least one regenerated calcium sulfate material comprises calcium sulfate dihydrate.

8. A method according to any one of the preceding claims, wherein: The at least one regenerated calcium sulfate material comprises calcium sulfate hemihydrate.

9. A method according to any one of the preceding claims, wherein: The particle mixture comprises 2.2 wt.% or less paper, preferably 1.2 wt.% or less paper.

10. A method according to any one of the preceding claims, wherein: The method produces an equivalent gypsum board at a rate exceeding 80%, preferably exceeding 90% of the rate of an equivalent process where the particle mixture does not include regenerated calcium sulfate material.

11. A gypsum board comprising a regenerated calcium sulfate material and a non-regenerated calcium sulfate material, wherein: The ratio of the regenerated calcium sulfate material to the non-regenerated calcium sulfate material is at least 1:

1.

12. The gypsum board according to claim 11, wherein The gypsum board comprises a core comprising paper in an amount of 2.2 wt.% or less, preferably 1.2 wt.% or less.

13. A gypsum board according to claim 11 or claim 12, wherein The gypsum board includes a fluidizing agent in an amount less than or equal to 1 wt. % of the dry weight of the calcium sulfate material.

14. The gypsum board according to any one of claims 11 to 12, wherein The density of the gypsum board is between 680kg / m 3 and 760kg / m 3 between.

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