Abstract: The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1% -3.0% by weight based on the weight of dry stucco. The pregelatinized starch present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

Abstract: The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1%-3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

Abstract: The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1%-3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

Abstract: The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1%-3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

Abstract: The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1%-3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients.

Abstract: The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1%-3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

Abstract: The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1%-3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

Abstract: A process is disclosed for making a blend of alpha- and beta-stucco including a slurry calcination step to produce alpha calcium sulfate hemihydrate followed by a fluidized bed calcination step to produce beta calcium sulfate hemihydrate. The process starts with 50-75% gypsum-containing solids slurry, and then steam calcines the slurry in a first reactor to form partially calcined gypsum slurry which contains calcium sulfate dihydrate and alpha calcium sulfate hemihydrate. The partially calcined slurry is then dewatered. Then the filter cake is fed into a kettle to complete the calcination process by converting the calcium sulfate dihydrate of the filter cake material into beta calcium sulfate hemihydrate.

Abstract: A process is disclosed for making a blend of alpha- and beta-stucco including a slurry calcination step to produce alpha calcium sulfate hemihydrate followed by a fluidized bed calcination step to produce beta calcium sulfate hemihydrate. The process starts with 50-75% gypsum-containing solids slurry, and then steam calcines the slurry in a first reactor to form partially calcined gypsum slurry which contains calcium sulfate dihydrate and alpha calcium sulfate hemihydrate. The partially calcined slurry is then dewatered. Then the filter cake is fed into a kettle to complete the calcination process by converting the calcium sulfate dihydrate of the filter cake material into beta calcium sulfate hemihydrate.

Abstract: A rough-surfaced substrate, such as a fiberboard, is provided with a smoother surface by applying a coating comprising calcium sulfate hemihydrate which has been prevented from hydrating to gypsum by set preventer, and which sets when brought into contact with a set initiator, e.g. aluminum sulfate, preferably present on the surface of the substrate.

Abstract: A rough-surfaced substrate, such as a fiberboard, is provided with a smoother surface by applying a coating comprising calcium sulfate hemihydrate which has been prevented from hydrating to gypsum by set preventer, and which sets when brought into contact with a set initiator, e.g. aluminum sulfate, preferably present on the surface of the substrate.

Abstract: A gypsum/fiber board having improved impact resistance is produced by mixing predetermined amounts of fibers, calcined gypsum and water to form a mixture of wetted, loose fibers; laying out a reinforcing mesh over the upper surface of a forming belt; depositing said mixture on said mesh to form a layer of said mixture, said; and compressing said mesh together with said layer of mixture to embed said mesh in the lower surface of said layer to form a board composed of bonded fibers and gypsum with said mesh embedded in the surface thereof.

Abstract: A gypsum/fiber board having improved impact resistance is produced by mixing predetermined amounts of fibers, calcined gypsum and water to form a mixture of wetted, loose fibers; laying out a reinforcing mesh over the upper surface of a forming belt; depositing said mixture on said mesh to form a layer of said mixture, said; and compressing said mesh together with said layer of mixture to embed said mesh in the lower surface of said layer to form a board composed of bonded fibers and gypsum with said mesh embedded in the surface thereof.

Abstract: A non-combustible gypsum/fiber board comprises two surface layers and at least one core layer, wherein the surface layers comprise a gypsum composition that is reinforced with organic fibers, and the core layer comprises a gypsum composition containing no more than about 3% by weight of organic materials.

Abstract: A gypsum/fiber board having improved impact resistance is produced by mixing predetermined amounts of fibers, calcined gypsum and water to form a mixture of wetted, loose fibers; laying out a reinforcing mesh over the upper surface of a forming belt; depositing said mixture on said mesh to form a layer of said mixture, said; and compressing said mesh together with said layer of mixture to embed said mesh in the lower surface of said layer to form a board composed of bonded fibers and gypsum with said mesh embedded in the surface thereof.