Abstract: A plurality of set stabilizer particles including: a particle core including 50 to 98 wt. %, preferably 70 to 98 wt. % or 70 to 95 wt. %, calcium sulfate dihydrate and 0.05 to 10 wt. %, preferably 0.5 to 5 wt. %, hydrophobic material selected from wax and/or siloxane, and a coating on the particle core, the coating including a dehydration-preventing substance selected from sugars, dextrins, and polyhydroxy alcohols, such as glycerol or polyglycols, at a ratio of about 5 to 25 parts by weight of dehydration-preventing substance per 100 parts by weight of calcium sulfate dihydrate. Methods of making and using the set stabilizer particles are also disclosed.

Abstract: Disclosed are a composite gypsum board and a method of preparing composite gypsum board. The board contains set gypsum layers sandwiched between two cover sheets. The set gypsum layers are formed from at least stucco and water. The set gypsum layers include a board core and one or more skim coat layers. The set gypsum core makes up a substantial thickness (e.g., at least about 90%, at least about 92%, at least about 95%, or at least about 97%) of the total thickness of all the gypsum layers. A first skim coat layer is included on one side of the core, facing a first (face) cover sheet. A second skim coat layer is included on the other side of the core, facing a second (back) cover sheet. At least the second skim layer is formed from a slurry that contains starch. The stucco material generally includes 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 salts are chloride salts, e.g.

Abstract: Disclosed are a composite gypsum board and a method of preparing composite gypsum board. The board contains at least one set gypsum layer sandwiched between two cover sheets. The set gypsum layer is formed from at least stucco and water. The stucco material generally includes 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 salts are chloride salts, e.g., sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), and/or calcium chloride (CaCl2)). At least one of the cover sheets is composed of high absorption paper, which enhances the bond between the set gypsum layer and the cover sheet.

Abstract: A method and apparatus to manufacture gypsum board that directs a first portion of aqueous gypsum slurry to a front cover sheet, directs a second portion of aqueous gypsum slurry to a back cover sheet, passes the back cover sheet over a roller spaced above the front cover sheet so that a majority of the second aqueous gypsum slurry falls off the back cover sheet onto the first portion of aqueous gypsum slurry on the front cover sheet. A gypsum board made by the method or apparatus.

Abstract: An accelerator for accelerating the rate of hydration of calcined gypsum is disclosed. The accelerator comprises calcium sulfate dihydrate particles and a starch. The starch has a cold water solubility of at least about 25% (e.g., at least about 35%) and a viscosity of about 25 Brabender Units (BU) or less when the starch is in a 30% aqueous slurry at 92° C. Also disclosed are a method of preparing an accelerator, method of hydrating stucco to form set gypsum, slurry, and method of making gypsum board.

Abstract: Disclosed are a composite gypsum board and a method of preparing composite gypsum board. The board contains a set gypsum core sandwiched between two cover sheets. The core is formed from a slurry containing stucco, water, and optional ingredients such as foaming agent, accelerator, retarder, polyphosphate, starch, and dispersant, and core intumescent material. The board also contains at least one skim coat and/or hard edges. A face skim coat layer can be included on one side of the core, facing a face cover sheet. A back skim coat layer can be included on the other side of the core, facing a back cover sheet. Hard edges are known in the art and can be formed, e.g., continuously from a stucco slurry for forming the face and/or back skim coats. Preferably, the back skim coat layer and/or the hard edges are formed from a slurry containing stucco, water, skim coat or edge intumescent material (which have the same desired characteristics), and other optional additives as desired.

Abstract: A fire-resistant gypsum panel comprises: a gypsum core layer comprising set gypsum and a high temperature sag-resistant material including mineral wool in an amount between 0.2% and 3.0% by weight of gypsum.

Abstract: Disclosed is a composite gypsum board comprising a set gypsum core disposed between face (e.g., Manila) and back (e.g., Newsline) cover sheets. The set gypsum core is formed from a core slurry comprising stucco, water, and optional additives, such as foaming agent, migrating starch, accelerator, retarder, dispersant, etc. A dense layer formed from a dense layer slurry comprising stucco, water, fiber (e.g., paper fiber), and optionally, strength-enhancing starch, is disposed between the core and the face paper. The dense layer slurry contains a greater concentration of fiber, and optionally, strength-enhancing starch, than the core slurry, but the concentration of one or more other additives (e.g., accelerator, retarder, dispersant, or combinations thereof) is lower or the same in the dense slurry as compared with the core slurry. Also disclosed is a method of making board using one board mixer. In embodiments, paper fiber is added to water to form a suspension.

Abstract: A gypsum wallboard panel comprises: a gypsum core; and a paper cover sheet disposed on the gypsum core, the paper cover sheet comprising pulp fiber and an uncooked starch in an amount of at least 2% by weight of the pulp fiber.

Abstract: Disclosed are a composite gypsum board and a method of preparing composite gypsum board. The board contains a set gypsum core sandwiched between two cover sheets. The core is formed from a slurry containing stucco, water, and optional ingredients such as foaming agent, accelerator, retarder, polyphosphate, starch, and dispersant, and core intumescent material. The board also contains at least one skim coat and/or hard edges. A face skim coat layer can be included on one side of the core, facing a face cover sheet. A back skim coat layer can be included on the other side of the core, facing a back cover sheet. Hard edges are known in the art and can be formed, e.g., continuously from a stucco slurry for forming the face and/or back skim coats. Preferably, the back skim coat layer and/or the hard edges are formed from a slurry containing stucco, water, skim coat or edge intumescent material (which have the same desired characteristics), and other optional additives as desired.

Abstract: Disclosed are a composite gypsum board and a method of preparing gypsum board. The board contains at least one set gypsum layer sandwiched between face and back cover sheets. The set gypsum layer is formed from at least stucco and water. The stucco material generally includes 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 salts are chloride salts, e.g., sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), and/or calcium chloride (CaCl2). The board and methods improve the bond between the gypsum layer(s) and at least one of the cover sheets (e.g., the back cover sheet). Also provided are methods and systems relating to drying gypsum board.

Abstract: Disclosed are a composite gypsum board and a method of preparing composite gypsum board. The board contains at least one set gypsum layer sandwiched between two cover sheets. The set gypsum layer is formed from at least stucco and water. The stucco material generally includes 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 salts are chloride salts, e.g., sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), and/or calcium chloride (CaCl2)). At least one of the cover sheets is composed of high absorption paper, which enhances the bond between the set gypsum layer and the cover sheet.

Abstract: Disclosed are a composite gypsum board and a method of preparing composite gypsum board. The board contains set gypsum layers sandwiched between two cover sheets. The set gypsum layers are formed from at least stucco and water. The set gypsum layers include a board core and one or more skim coat layers. The set gypsum core makes up a substantial thickness (e.g., at least about 90%, at least about 92%, at least about 95%, or at least about 97%) of the total thickness of all the gypsum layers. A first skim coat layer is included on one side of the core, facing a first (face) cover sheet. A second skim coat layer is included on the other side of the core, facing a second (back) cover sheet. At least the second skim layer is formed from a slurry that contains starch. The stucco material generally includes 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 salts are chloride salts, e.g.

Abstract: A method of making a gypsum board including: preparing an aqueous slurry including a mixture of: calcium sulfate hemihydrate, water at a weight ratio of water to calcium sulfate hemihydrate of 0.2:1 to 1.2:1, and on a dry basis per 100 parts by weight (pbw) calcium sulfate hemihydrate: 0.2 to 2 pbw siloxane, 0.01 to 2 pbw siloxane polymerization catalyst including magnesium oxide and optionally fly ash, and 0.01 to 0.2 pbw triethanolamine (TEOA); allowing the siloxane to polymerize to polysiloxane; and depositing the slurry on a first cover sheet and covering the slurry with a second cover sheet to shape the slurry, and allowing the shaped slurry to set to form the gypsum board. Also, disclosed is the gypsum board resulting from the method.

Abstract: An accelerator for accelerating the rate of hydration of calcined gypsum is disclosed. The accelerator comprises calcium sulfate dihydrate particles and a starch. The starch has a cold water solubility of at least about 25% (e.g., at least about 35%) and a viscosity of about 25 Brabender Units (BU) or less when the starch is in a 30% aqueous slurry at 92° C. Also disclosed are a method of preparing an accelerator, method of hydrating stucco to form set gypsum, slurry, and method of making gypsum board.

Abstract: Disclosed is gypsum board formed from stucco, water, and at least one migrating starch having a cold-water solubility of at least about 25%. Generally, the starch has a viscosity of less than about 20 centipoise (e.g., from about 1 centipoise to about 20 centipoise), as determined according to the VMA method. Also disclosed are related slurries and methods of preparing gypsum board.

Abstract: An apparatus configured for connection to a mixer for receiving a slurry and altering the flow characteristics of the slurry includes a conduit having a main inlet in slurry receiving communication with the mixer outlet and extending to a spout for discharging the slurry, at least one conduit restrictor associated with the conduit for creating back-pressure between the conduit restrictor and the mixer outlet for keeping the mixer full, and at least one pressure reducer associated with the discharge spout and configured for reducing the pressure of the slurry dispensed from the discharge spout. The apparatus is configured for maintaining a generally laminar flow from the mixer outlet to the discharge spout.

Abstract: An apparatus configured for connection to a mixer for receiving a slurry and altering the flow characteristics of the slurry includes a conduit having a main inlet in slurry receiving communication with the mixer outlet and extending to a spout for discharging the slurry, at least one conduit restrictor associated with the conduit for creating back-pressure between the conduit restrictor and the mixer outlet for keeping the mixer full, and at least one pressure reducer associated with the discharge spout and configured for reducing the pressure of the slurry dispensed from the discharge spout. The apparatus is configured for maintaining a generally laminar flow from the mixer outlet to the discharge spout.

Abstract: An apparatus and method for delivering an additive-enhanced slurry for use in making gypsum wallboard, and configured for connection to a centrifugal mixer with a tangential discharge outlet, includes a conduit having a main inlet in slurry receiving communication with the mixer outlet and extending to a discharge spout for discharging the slurry proximate a wallboard forming area. At least one volume restrictor is associated with the conduit for creating back pressure between the volume restrictor and the outlet for keeping the mixer fill, and at least one pressure reducer associated with the discharge spout and configured for reducing the pressure of the slurry dispensed from the discharge spout. The apparatus is configured for maintaining a generally laminar flow from the mixer outlet to the discharge spout.