Abstract: A process for preparing calcined gypsum (stucco) which comprises treating a mass of calcined gypsum by adding, with thorough blending, small portions of an aqueous solution of ligno sulfonate; allowing the treated stucco to heal; and optionally drying the healed stucco and further optionally grinding the healed stucco. If the treated calcined gypsum is not to be used shortly after the healing procedure, it should be dried to provide storage stability. If further strength is desired the treated stucco should be ground to expose fresh crystal faces. The process is particularly useful in gypsum board manufacture and production of bagged building and industrial plasters.

Abstract: This invention relates to a structural laminate having a plastic surface finish coat laminated to a structural base which has exceptional bond strength between the structural base and the plastic layer with which it interfaces. The structural base comprises a glass reinforced gypsum layer. The plastic laminate portion comprises a plastic surface finish coat, preferably a polyester gel coat or an acrylic resin, bonded to a reinforcing layer of curable polyester or epoxy resin reinforced with glass fibers. The reinforcing layer is adhered to a bonding layer which comprises glass fibers protruding from the reinforcing layer and coated with a limited amount of organic resin such as polyester or epoxy resin. The glass reinforced gypsum layer is applied to the protruding fibers of the bonding layer to form an interface having a bond strength of at least about 150 psi as determined by ASTM C297-68.

Abstract: A process and apparatus for producing a healed stucco having lowered water demand without loss of normal strength development potential which comprises, while blending a small amount of water with the calcined gypsum, simultaneously or substantially simultaneously grinding the calcined gypsum so as to increase the surface area of the calcined gypsum particles while incorporating about 1-10% by weight of the calcined gypsum of free water.

Abstract: A mesh electrode for a c.r.t. display device consists of a number of coplanar portions of mesh insulated from each other, and secured to a support plate by means of two layers of refractory compound. The first layer is applied to the support plate and allowed to set before the second layer is applied so as to space the mesh portions from the support plate by at least the thickness of the first layer.

Abstract: Reinforced facings, including reinforcing webs entrained in hydraulic cement via a slurry bath, adhere to a nailable lightweight aggregate cementitious core to form a panel web. The reinforced web is formed on abutting conveyed carrier sheets, and the web is transversely cut, between the sheets, while moving or when stopped, in response to sensing of the sheets. The cut panels, on respective sheets are stacked for curing without damaging the panel edges and in a manner to minimize panel flex. Slurry bath, facing applicators, and cutter and stacking apparatus are included.

Abstract: A process for preparing calcined gypsum (stucco) which comprises treating a mass of calcined gypsum by adding, with thorough blending, small portions of water (about 1-10% by weight) to the calcined gypsum, allowing it to heal, and grinding the healed stucco to recapture the rate of strength development and the ultimate strength which are adversely affected by the water addition. The principal advantage provided by the addition of small portions of water is a reduction in water demand which is retained despite the grinding and optional drying of the healed stucco. If the treated calcined gypsum is not used shortly after the healing procedure, it should be dried to provide storage stability. The reduced water demand is particularly useful in gypsum board manufacture.

Abstract: Plaster board panels wherein at least the top layer of one of the two cardboard sheets contains polyolefin fibrides can be easily dehydrated during their manufacture because of the porosity of the cardboard sheets. The finished panels have a substantially sealed surface of low porosity which is resistant to wet treatment and thus suitable for the application of various painting and coating systems.

Abstract: A composition for accelerating the setting of an aqueous calcined gypsum slurry, the composition comprising finely ground calcium sulfate dihydrate and a lignosulfonate. The composition, when added to an aqueous calcined gypsum slurry, accelerates the setting process and shortens the set time period as determined by the temperature rise set test procedure. The composition is useful for making gypsum wallboard.

Abstract: This invention relates to a novel means of manufacture of gypsum board. The improvement herein comprises the use of sodium and/or ammonium salts of ethoxylated, sulfated alcohols as foaming agents, said alcohols being a mixture of primary, linear alcohols having an average chain length of 9 carbon atoms.

Abstract: A flexible building sheet product is prepared by dry molding a slurry comprising predominantly at least one binder component selected from the group consisting of thermoplastic resin emulsions and aqueous solutions of water-soluble polymers, said solutions containing cross-linking agents for said water-soluble polymers, and a matrix component comprising a calcium sulfate dihydrate powder.

Abstract: A specially prepared paper bond liner, gypsum wallboard, and gypsum wallboard process which bonds the liner to the core by an adhesive confined to the paper-core interface, the adhesive comprising certain starches placed on the bond liner in their raw state.

Abstract: A composition comprising water, finely particulate gypsum and starch is coated on a paper cover sheet in a selective pattern such that the starch composition is disposed only at limited areas of the bond liner surface, and wherein substantial areas of the bond liner surface are free of the coating; the coated paper, either in the wet stage or after drying being used as paper cover sheets to form gypsum wallboard by applying an aqueous slurry of calcined gypsum, which may be free of starch, to the coated surface and setting the gypsum, resulting in a gypsum wallboard having excellent adhesion between the paper cover sheets and the gypsum core.

Abstract: An improved process for producing calcined gypsum which comprises continuously treating a mass of calcined gypsum by adding, with thorough blending agitation, small metered portions of water to result in the incorporation of about 1-8% free water in the mass by weight of the gypsum, allowing the blended mass to heal the calcium sulfate hemihydrate surface fissures and thereafter continuously supplying the treated gypsum mass into gypsum board production.

Abstract: Closed cell foamed polystyrene beads are shredded to form small size, open-celled foam particles. The particles are mixed with a slurry of a granulate and a liquid whereby the slurry enters the open cells to increase the density of the particles. After an even distribution of the particles throughout the slurry is obtained the mixture is dried to form granulate objects, such as boards, having an even distribution of foamed polystyrene particles therein to reduce the density of the object.

Abstract: A specially prepared paper bond liner, gypsum wallboard, and gypsum wallboard process which bonds the liner to the core by an adhesive confined to the paper-core interface, the adhesive comprising certain starches placed on the bond liner in their raw state.

Abstract: A gypsum set accelerator, produced by compression milling a mixture of ground gypsum rock and starch, and the addition thereof to an aqueous slurry of settable calcined gypsum such as in the forming of paper-covered gypsum wallboard.

Abstract: A paper covered gypsum board and a process for its manufacture, with at least one cover of the board comprising a multiply paper sheet containing a major proportion of cellulosic fibers and a minor proportion of short mineral fibers.

Abstract: A specially prepared paper bond liner, gypsum wallboard, and gypsum wallboard process which bonds the liner to the core by an adhesive confined to the paper-core interface, the adhesive comprising certain starches placed on the bond liner in their raw state.

Abstract: A gypsum wallboard or plasterboard having a high mechanical strength, especially high impact strength, and a large bulk density is prepared from a mixture consisting essentially of calcined gypsum, cellulosic fibers, asbestos fibers, a setting retardant for the calcined gypsum and water, by withdrawing solid components of the mixture in layer form. A plurality of the thus-obtained layers is piled to form a preform of the desired thickness and pressure-molding the preform under a molding pressure of from 10 to 400 kg/cm.sup.2 to obtain the board product.