Light weight gypsum wallboard

Abstract

The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1% -3.0% by weight based on the weight of dry stucco. The pregelatinized starch present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.

1 - 30 . (canceled) 
     
     
         31 . A light weight gypsum board comprising:
 a set gypsum composition disposed between two cover sheets, the set gypsum composition formed from at least water, stucco, pregelatinized starch, and foaming agent;   the pregelatinized starch is in an amount from about 0.5% to about 10% by weight based on the weight of the stucco;   the foaming agent comprises a major weight portion of unstable component and a minor weight portion of stable component, the amount of foaming agent and the weight ratio of said unstable component to stable component effective to form a void distribution within the set gypsum composition; and   the set gypsum composition comprises a continuous crystalline matrix substantially of calcium sulfate dihydrate, the board having a density of about 34 pcf or less, the pregelatinized starch is effective to increase the core hardness of the board relative to the board without the pregelatinized starch, and the board having a core hardness of at least about 11 lb, the core hardness determined according to ASTM standard C473.   
     
     
         32 . A light weight gypsum board comprising:
 a set gypsum composition disposed between two cover sheets, the set gypsum composition formed from at least water, stucco, pregelatinized starch, and naphthalenesulfonate dispersant,   the stucco is in an amount of at least about 700 lb/MSF;   the pregelatinized starch is in an amount from about 0.5% to about 10% by weight based on the weight of the stucco;   the naphthalenesulfonate dispersant is in an amount from about 0.1% to about 3.0% by weight based on the weight of the stucco; and   the board has a density from about 24 pcf to about 34 pcf, the pregelatinized starch is effective to increase the core hardness of the set gypsum composition relative to the set gypsum composition without the pregelatinized starch, and the board has a core hardness of at least about 11 lb, as determined according to ASTM standard C473.   
     
     
         33 . A light weight gypsum board comprising:
 a set gypsum composition disposed between two cover sheets, the set gypsum composition formed from at least water, stucco, pregelatinized starch, naphthalenesulfonate dispersant, sodium trimetaphosphate, and foaming agent;   the set gypsum composition is formed from a water to stucco weight ratio from about 0.7 to about 1.2;   the pregelatinized starch is in an amount from about 0.5% to about 10% by weight based on the weight of the stucco;   the naphthalenesulfonate dispersant is in an amount from about 0.1% to about 3.0% by weight based on the weight of the stucco;   the sodium trimetaphosphate is in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco;   the foaming agent comprises a major weight portion of unstable component and a minor weight portion of stable component, the amount of foaming agent and the weight ratio of said unstable component to stable component effective to form a void distribution within the set gypsum composition; and   the set gypsum composition comprises a continuous crystalline matrix substantially of calcium sulfate dihydrate, the board having a density of about 34 pcf or less, the pregelatinized starch is effective to increase the core hardness of the board relative to the board without the pregelatinized starch, and the board having a core hardness of at least about 11 lb, the core hardness determined according to ASTM standard C473.