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.

Abstract: A gypsum wall board is disclosed in which at least one of the paper cover sheets is made with neutral size and a small amount of a cationic polyamide resin is added to the stock used to make the cover sheet. The paper cover sheets provide improved resistance to post-manufacturing problems that involve delamination, such as “Roll-up”.

Abstract: A set gypsum composition and methods for the preparation thereof are disclosed. The set gypsum composition comprises a continuous phase of interlocking set gypsum matrix having an enhanced water voids volume and/or is prepared from a mixture (e.g., slurry) comprising an elevated ratio of water to calcined gypsum. Also disclosed is an article comprising the set gypsum composition.

Abstract: A joint compound composition comprising a filler, a binder and a hydrocarbon substituted sulfate, sulfonate, sulfuric acid or sulfonic acid is disclosed. The composition of the present invention produces a joint compound that shrinks less and is resistant to cracking and cratering.

Abstract: This invention relates to a process for making gypsum board comprising feeding a paper backing sheet and a fiberglass or plastic woven or non-woven scrim material in alignment to a board forming station, separating the paper and the scrim, feeding a high density calcium sulfate hemihydrate slurry into the trough formed between the paper and the scrim, and subsequently compressing the paper and the scrim into contact whereby the high density slurry is forced through the scrim, completely encapsulating the scrim in the high density slurry. As a result of this unique process, excellent bond is developed between the paper, the high density gypsum layer and the foamed gypsum core. The gypsum board has improved through-penetration strength.

Abstract: The invention is directed to a hinged ceiling panel, which is pivotally attached to a suspended ceiling grid structure to provide for a hinged ceiling panel that pivots to allow access to the area above the grid. The hinged ceiling panel includes a hinge located on a first edge and grid-releasable flanges located on the remaining edges of the panel. The hinged ceiling panel is designed so that a single person can easily release the panel from the grid system and pivot it downwards whereby the hinge supports it. The hinged ceiling panel is also designed so that an individual can also reposition the panel within the grid structure without the aid of others.

Abstract: An acoustical ceiling tile having an improved sound absorption value and having a dual layer of acoustical materials. The base mat layer has either no mineral wool or a low mineral wool content. The surface layer has a high mineral wool content which provides improved sound absorption values with or without perforating or fissuring the tile. The dual layer acoustical ceiling tile has a noise reduction coefficient (NRC) value of at least about 0.50.

Abstract: An improved method and apparatus for imparting a smooth surface to a gypsum fiber panels. The method involves imparting energy to the surface of the slurry as the slurry is dewatered just prior to rehydration. The apparatus used to impart the energy is an air lance including an air source such as a blower, a distribution manifold and a plurality of nozzles to direct the flow of air at the surface of the slurry. In operation, the air lance directs a flow of air against the surface of the slurry. The flow disrupts the slurry to a fraction of its total depth, thus dispersing clumps or flocs of crystals in the depth that would give the surface of the finished panel a rough surface if they were allowed to remain.

Abstract: A headbox for use in a water felting process includes a housing and two rotating horizontal distribution rolls. The housing has curved sections shaped to conform to the outer cylindrical surface of the distribution rolls, wherein the curved section is closely spaced to a portion of the outer cylindrical surface of both distribution rolls.

Abstract: An additive for accelerating the setting reaction of gypsum products is disclosed. It comprises a gypsum accelerator combined with a bisulfate salt. The gypsum accelerator is calcium sulfate dihydrate. The accelerator may optionally be ground with a sugar, a starch and/or boric acid. A process utilizing this additive combination is also disclosed. The bisulfate salt is most advantageously prewet with a portion of the calcium sulfate hemihydrate feed before being combined with the gypsum accelerator, water and the remaining portion of the calcium sulfate hemihydrate feed in the main mixer.

Abstract: A wet gypsum accelerator comprising particles of calcium sulfate dihydrate, water, and at least one additive selected from the group consisting of (i) an organic phosphonic compound, (ii) a phosphate-containing compound, or (iii) a mixture of (i) and (ii), is disclosed. Also disclosed are a method of preparing a wet gypsum accelerator, a method of hydrating calcined gypsum to form an interlocking matrix of set gypsum, a set gypsum-containing composition, and a set gypsum-containing product.

Abstract: A set gypsum-containing composition is disclosed. In one aspect, the set gypsum-containing composition includes an interlocking matrix of the set gypsum formed from at least calcined gypsum, water, and an enhancing material. The enhancing material can be selected from (i) an organic polyphosphonic compound, or a mixture thereof; (ii) a borate selected from ulexite colemanite, or a mixture thereof; or a mixture of (i) and (ii). In another aspect, the set gypsum-containing composition is treated with an enhancing material which can be selected from (i) an organic phosphonic compound or a mixture thereof; (ii) a borate selected from ulexite, colemanite, or a mixture thereof; (iii) a carboxylic compound or a mixture thereof; or a mixture of (i), (ii) and/or (iii).

Abstract: A paperless gypsum/fiber board with improved surface characteristics has at least one surface comprising a combination of fully hydrated gypsum and reinforcing fiber and has been coated with a primer comprising an aqueous emulsion of a film-forming polymeric material.

Abstract: A composition comprising calcined gypsum, trimetaphosphate ion, and a water-soluble linear polymer formed by the addition reaction of ethylene oxide and/or alkoxy-substituted ethylene oxide with water, having enhanced strength when set and exhibiting high plasticity and workability such that it readily can be applied to a substrate, is disclosed.

Abstract: A plaster composition for making molds for reproduction by casting is disclosed. Calcium sulfate hemihydrate, potassium sulfate and potassium sodium tartrate are mixed together. The potassium sulfate and potassium sodium tartrate are in a ratio of from about 1:1 to about 10:1. Potassium sodium tartrate is present in an amount of from about 1 to about 10 pounds per ton of dry calcium sulfate hemihydrate, and the total of the potassium sulfate and potassium sodium tartrate is from about 2 to about 35 pounds per ton of calcium sulfate hemihydrate. Methods of making and using molds of this composition are also disclosed.

Abstract: A set gypsum composition and methods for the preparation thereof are disclosed. The set gypsum composition comprises a continuous phase of interlocking set gypsum matrix having an enhanced water voids volume and/or is prepared from a mixture (e.g., slurry) comprising an elevated ratio of water to calcined gypsum. Also disclosed is an article comprising the set gypsum composition.

Abstract: A set accelerator for at least one of accelerating the hydration rate and reducing the set time of an aqueous slurry of calcium sulfate hemihydrate is described. The set accelerator consists of a mixture of ground calcium sulfate dihydrate and zinc sulfate material. Aluminum sulfate material is an optional component of the set accelerator. The set accelerator is particularly useful in accelerating the hydration rates of sprayable plasters. A fluid form of the set accelerator may be made by suspending the solids in water. The fluid form is advantageously used in ready mixed setting type joint compounds.

Abstract: A plaster mixture for forming a machinable composition, includes calcium sulfate hemihydrate; an internal lubricating dispersable binder, and an adhesive binder for adhering the plaster mixture to a substrate. In the preferred embodiment, the composition includes calcium sulfate hemihydrate, a poly(ethylene glycol) internal binder, and an ethylene/vinyl acetate copolymer adhesive binder.

Abstract: The invention provides a set gypsum-containing product having increased resistance to permanent deformation and a method for preparing it comprising forming a mixture of a calcium sulfate material, water, and an appropriate amount of one or more enhancing materials chosen from condensed phosphoric acids, each of which comprises 2 or more phosphoric acid units; and salts or ions of condensed phosphates, each of which comprises 2 or more phosphate units. The mixture is then maintained under conditions sufficient for the calcium sulfate material to form a set gypsum material.