Lightweight gypsum composition

A composition of matter consisting essentially of:

• (a) gypsum (CaSO4 . 2H2O);
• (b) a latex polymer wherein said polymer is formed by the polymerization of styrene, butyl acrylate and acrylic acid and is present in an amount of between about 0.25 to about 10 parts by weight per 100 parts by weight of gypsum hemihydrate necessary to provide the gypsum;
• and
• (c) a nonionic surfactant comprising an octylphenol ethoxylate present in an amount of between about 0.05 to about 0.3 parts by weight per part by weight of latex polymer;
• wherein wallboard produced form said composition of matter and water satisfies the criteria of ASTM Methods C-36 and C-473 and has a molded density of less than about 0.64g/cm3.

A process for producing lightweight gypsum building materials comprising the steps of:

• (a) providing an amount of stucco (CaSO4 . ½H2O);
• (b) adding water in the amount of 30 to about 90 parts per 100 parts of stucco;
• (c) adding as a binder a naturally occurring or synthetic latex to said stucco and water in the amount of about 0.25 to about 10 parts latex polymer per 100 parts of stucco;
• (d) adding a nonionic surfactant in the amount of about 2 to about 30 parts per 100 parts of naturally occurring or synthetic latex polymer to disperse said naturally occurring or synthetic latex;
• (e) adding a foaming agent;
• and
• (f) mixing said components (a), (b), (c), (d) and (e) to enable said gypsum building material to form and set, producing a building material having a molded density of less than about 0.64g/cm3 and satisfying the criteria of [AST] ASTM in Methods C-36 and C-473.

A composition of matter comprising:

• (a) gypsum (CaSO4 . 2H2O);
• (b) one or more naturally occurring or synthetic latex polymers in an amount of about 0.25 to about 10 parts of latex polymer per 100 parts of gypsum hemihydrate necessary to provide the gypsum;
• and
• (c) in addition to any surfactant employed in polymerization of the latex polymer, one or more nonionic surfactants in an amount of from about 0.05 to about 0.3 parts per part of latex polymer;
• the composition characterized by a density of less than about 0.64 g/cm3 and a compressive strength per unit weight of the composition that is greater than the compressive strength of a similar composition of similar unit weight but not having component (c) present in said similar composition.