Abstract: A gypsum slurry is described that includes water, a hydraulic component comprising at least 50% calcined gypsum by weight based on the dry weight of the hydraulic component, foam, a defoamer and a polycarboxylate dispersant. In some embodiments of the invention, the defoamer is combined with the dispersant prior to being added to the gypsum slurry. The defoamer and dispersant can be added as a physical mixture, wherein the defoamer is attached onto the dispersant polymer, or a combination thereof. A gypsum building panel is made from the gypsum slurry.

Abstract: A gypsum slurry is described that includes water, a hydraulic component comprising at least 50% calcined gypsum by weight based on the dry weight of the hydraulic component, foam, a defoamer and a polycarboxylate dispersant. In some embodiments of the invention, the defoamer is combined with the dispersant prior to being added to the gypsum slurry. The defoamer and dispersant can be added as a physical mixture, wherein the defoamer is attached onto the dispersant polymer, or a combination thereof. In some embodiments, a gypsum building panel is made from the gypsum slurry.

Abstract: A gypsum slurry is described that includes water, a hydraulic component comprising at least 50% calcined gypsum by weight based on the dry weight of the hydraulic component, foam, a defoamer and a polycarboxylate dispersant. In some embodiments of the invention, the defoamer is combined with the dispersant prior to being added to the gypsum slurry. The defoamer and dispersant can be added as a physical mixture, wherein the defoamer is attached onto the dispersant polymer, or a combination thereof. A gypsum building panel is made from the gypsum slurry.

Abstract: A gypsum slurry is described that includes water, a hydraulic component comprising at least 50% calcined gypsum by weight based on the dry weight of the hydraulic component, foam, a defoamer, a polycarboxylate dispersant having olefinic unsaturated mono-carboxylic acid moieties and (poly)oxyalkylene moieties, a first portion of a retarder and a second portion of a retarder. In some embodiments of the invention, the defoamer is combined with the dispersant prior to being added to the gypsum slurry. The defoamer and dispersant can be added as a physical mixture, wherein the defoamer is attached onto the dispersant polymer, or a combination thereof. In some embodiments, a gypsum building panel is made from the gypsum slurry.

Abstract: A gypsum slurry includes calcium sulfate hemihydrate, a set retarder in amounts of at least 0.15 lb/MSF, a set accelerator, water and aqueous foam. The set accelerator is selected to provide nucleation sites for crystallization of calcium sulfate dihydrate and is present in amounts of at least 5 Ib/MSF. The water to calcium sulfate hemihydrate ratio is at least 0.95. Further, aqueous foam is added in amounts sufficient to create a gypsum board having a dry density of about 29 to about 35 lbs/ft3.

Abstract: A method for providing a smoothly mixed slurry to a web is provided which includes inserting calcined gypsum and water into a mixer (12), agitating the contents of the mixer (12) to form an aqueous dispersion of the calcined gysum, and passing the agitated contents from an outlet (20) of the mixer (12) into a slurry dispensing apparatus (22) including a flexible, resilient conduit (24). Additionally, the method includes the step of creating a back-pressure on the mixture in the slurry dispensing apparatus by constricting the conduit (24). The constricting of the conduit (24) is effected by a constrictor valve (28) located on the conduit (24).

Abstract: An apparatus and method for controlling the flow of a slurry is provided which includes using a constrictor valve on a mixing and dispensing apparatus. The constrictor valve includes a first guide plate and a second guide plate that are spaced a distance apart along the length of the conduit. Extending between the two guide plates, a plurality of elongate members have first and second ends engaged on the first and second guide plates. Upon rotation of at least one of the first and second guide plates, the elongate members are configured to impart pressure on, and constrict the conduit.