Slurries and methods of making light weight gypsum board

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 is 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 slurry comprising water, stucco, starch, and foaming agent;
 the 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 a set gypsum composition formed from said slurry;   when the slurry is cast and dried as a board comprising said set gypsum composition, 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 and a core hardness of at least about 11 lb, the core hardness determined according to ASTM standard C473.   
     
     
         32 . The slurry of  claim 31 , wherein the foaming agent comprises a blend of the unstable and stable components. 
     
     
         33 . The slurry of  claim 31 , wherein the foaming agent comprises at least about 65% by weight of unstable component. 
     
     
         34 . The slurry of  claim 31 , wherein the foaming agent is in an amount of about 0.1% or less by weight based on the weight of the stucco. 
     
     
         35 . The slurry of  claim 31 , wherein the foaming agent is in an amount from about 0.02% to about 0.03% by weight based on the weight of the stucco. 
     
     
         36 . The slurry of  claim 31 , wherein the slurry is formed from a water to stucco weight ratio from about 0.7 to about 1.2. 
     
     
         37 . The slurry of  claim 31 , wherein when the slurry is cast and dried as a board, the starch is effective to increase the core hardness of the cast and dried board relative to the cast and dried board without the starch. 
     
     
         38 . The slurry of  claim 36 , wherein the starch is in an amount from about 0.5% to about 3% by weight based on the weight of the stucco. 
     
     
         39 . The slurry of  claim 36 , wherein the starch comprises a pregelatinized starch and is in an amount from about 0.5% to about 6% by weight based on the weight of the stucco. 
     
     
         40 . The slurry of  claim 31 , wherein when the slurry is cast and dried as a board, the board has a humidified bond load of at least about 15 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight. 
     
     
         41 . The slurry of  claim 31 , wherein the slurry further comprises dispersant. 
     
     
         42 . The slurry of  claim 31 , wherein the slurry further comprises naphthalenesulfonate dispersant in an amount from about 0.2% to about 3% by weight based on the weight of the stucco. 
     
     
         43 . The slurry of  claim 31 , wherein the slurry further comprises polyphosphate in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco. 
     
     
         44 . The slurry of  claim 31 , wherein when the slurry is cast and dried as a board, (a) the starch is effective to increase the core hardness of the cast and dried board relative to the cast and dried board without the starch, and (b) the board has a humidified bond load of at least about 15 lb after being (i) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (ii) dried to constant weight; and
 at a board thickness of about ¼ inch, the board has a nail pull resistance of at least about 65 lb, as determined according to ASTM standard C473. 
 
     
     
         45 . The slurry of  claim 36 , wherein the foaming agent is in an amount of about 0.1% or less by weight based on the weight of the stucco; and
 when the slurry is cast and dried as a board that is about ½ inch thick, the board has a nail pull resistance of at least about 72 lb, as determined according to ASTM standard C473.   
     
     
         46 . The slurry of  claim 31 , wherein when the slurry is cast and dried as a board, the board has a humidified bond load of at least about 17 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight; and
 when the slurry is cast and dried as a board that is about ½ inch thick, the board has a nail pull resistance of at least about 77 lb, as determined according to ASTM standard C473. 
 
     
     
         47 . The slurry of  claim 36 , wherein when the slurry is cast and dried as a board that is about ½ inch thick, the board has flexural strength of at least about 36 lb in a machine direction and/or about 107 lb in a cross-machine direction, as determined according to ASTM standard C473. 
     
     
         48 . The slurry of  claim 47 , wherein the slurry further comprises dispersant in an amount from about 0.2% to about 3.0% by weight based on the weight of the stucco, and the slurry has water to stucco weight ratio from about 0.7 to about 1.2; and
 wherein, when the slurry is cast and dried as a board the board has a humidified bond load of at least about 17 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight.   
     
     
         49 . The slurry of  claim 48 , wherein the slurry further comprises sodium trimetaphosphate in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco. 
     
     
         50 . A slurry comprising water, stucco, starch, naphthalenesulfonate dispersant, and polyphosphate,
 wherein the stucco is in an amount of at least about 700 lb/MSF;   the 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 polyphosphate is in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco;   when the slurry is cast and dried as a board comprising set gypsum composition, the board has a density from about 24 pcf to about 34 pcf and a core hardness of at least about 11 lb, as determined according to ASTM standard C473; and   the starch is effective to increase the core hardness of the gypsum composition relative to the gypsum composition without the starch;   
     
     
         51 . The slurry of  claim 50 , wherein the stucco is in an amount from about 700 lb/MSF to about 1300 lb/MSF. 
     
     
         52 . The slurry of  claim 50 , wherein the slurry further comprises a foaming agent having 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 forming a void distribution within a set gypsum composition formed from said slurry. 
     
     
         53 . The slurry of  claim 52 , wherein the foaming agent is in an amount of about 0.1% or less by weight based on the weight of the stucco. 
     
     
         54 . The slurry of  claim 52 , wherein the foaming agent is in an amount from about 0.02% to about 0.03% by weight based on the weight of the stucco. 
     
     
         55 . The slurry of  claim 50 , wherein the slurry further comprises paper fiber and/or glass fiber in an amount from about 0.20% to about 1.30% based on the weight of the dry stucco. 
     
     
         56 . The slurry of  claim 50 , wherein the slurry further comprises accelerator in an amount from about 0.2% to about 0.9% based on the weight of the dry stucco. 
     
     
         57 . The slurry of  claim 50 , wherein the slurry has a water to stucco weight ratio from about 0.7 to about 1.2. 
     
     
         58 . The slurry of  claim 50 , wherein the slurry further comprises foaming agent and accelerator;
 the stucco is in an amount from about 700 lb/MSF to about 1300 lb/MSF;   the starch is in an amount from about 0.5% to about 6% by weight based on the weight of the stucco;   the naphthalenesulfonate dispersant is in an amount from about 0.2% to about 3.0% by weight based on the weight of the stucco;   the foaming agent has 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 a set gypsum composition formed from said slurry, wherein the foaming agent is in an amount of about 0.1% or less by weight based on the weight of the stucco;   when the slurry is cast and dried as a board, the starch and the void distribution are effective to provide a board density of about 24 lb/ft 3  to about 34 lb/ft 3  and, at a board thickness of ½ inch, said core hardness of at least about 11 lb, a nail pull resistance of at least about 65 lb, and a flexural strength of at least about 36 lb in a machine direction and/or about 107 lb in a cross-machine direction, the nail pull resistance and the flexural strength determined according to ASTM standard C473; and   the board has a humidified bond load of at least about 15 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight.   
     
     
         59 . The slurry of  claim 58 , wherein the foaming agent is in an amount from about 0.02% to about 0.03% by weight based on the weight of the stucco. 
     
     
         60 . The slurry of  claim 58 , wherein the slurry further comprises paper fiber and/or glass fiber and the slurry has a water to stucco weight ratio from about 0.7 to about 1.2;
 the starch comprises pregelatinized starch;   the phosphate comprises sodium trimetaphosphate;   the paper fiber and/or glass fiber is present in an amount from about 0.20% to about 1.30% by weight based on the weight of the stucco;   the accelerator comprises heat resistant accelerator and is present in an amount from about 0.2% to about 0.9% by weight based on the weight of the stucco; and   when the board is cast and dried as a board, the board has a humidified bond load of at least about 17 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight.   
     
     
         61 . A method of making a light weight gypsum board, comprising:
 (a) mixing at least water, stucco, starch, and foaming agent to form a slurry, wherein
 the 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 a set gypsum composition formed from said slurry; 
   (b) disposing the slurry between a first cover sheet and a second cover sheet to form a panel;   (c) cutting the panel into a board; and   (d) drying the board; wherein,   when the slurry is cast and dried as a board comprising said set gypsum composition, the board has a density of about 34 pcf or less and an average core hardness of at least about 11 lb as determined according to ASTM standard C473.   
     
     
         62 . The method of  claim 61 , wherein the foaming agent comprises a blend of the unstable and stable components. 
     
     
         63 . The method of  claim 61 , wherein the foaming agent comprises at least about 65% by weight of unstable component. 
     
     
         64 . The method of  claim 61 , wherein the slurry has a water to stucco weight ratio from about 0.7 to about 1.2. 
     
     
         65 . The method of  claim 61 , wherein the starch is effective to increase the core hardness of the gypsum composition relative to the gypsum composition without the starch. 
     
     
         66 . The method of  claim 65 , wherein the starch is in an amount from about 0.5% to about 3% by weight based on the weight of the stucco. 
     
     
         67 . The method of  claim 65 , wherein the starch comprises a pregelatinized starch and is in an amount from about 0.5% to about 6% by weight based on the weight of the stucco. 
     
     
         68 . The method of  claim 61 , wherein the slurry is further formed from dispersant. 
     
     
         69 . The method of  claim 67 , wherein the slurry is further formed from naphthalenesulfonate dispersant in an amount from about 0.2% to about 3% by weight based on the weight of the stucco. 
     
     
         70 . The method of  claim 61 , wherein the slurry is further formed from polyphosphate in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco. 
     
     
         71 . The method of  claim 61 , wherein the board has a nail pull resistance of at least about 72 lb, as determined according to ASTM standard C473. 
     
     
         72 . The method of  claim 61 , wherein the board has a humidified bond load of at least about 15 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight; and
 at a board thickness of about ½ inch, the board has a nail pull resistance of at least about 65 lb, as determined according to ASTM standard C473. 
 
     
     
         73 . The method of  claim 61 , wherein the board has flexural strength of at least about 36 lb in a machine direction and/or about 107 lb in a cross-machine direction, as determined according to ASTM standard C473. 
     
     
         74 . The method of  claim 61 , wherein the board has a humidified bond load of at least about 17 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight; and
 at a board thickness of about ½ inch the board has a nail pull resistance of at least about 77 lb, as determined according to ASTM standard C473. 
 
     
     
         75 . A method of making a light weight gypsum board, comprising:
 (a) mixing at least water, stucco, starch, naphthalenesulfonate dispersant, and polyphosphate to form a slurry,
 the stucco is in an amount of at least about 700 lb/MSF; 
 the starch is in an amount from about 0.5% to about 10% by weight based on the weight of the stucco; and 
 the starch is effective to increase the core hardness of the gypsum composition relative to the gypsum composition without the starch; 
 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 polyphosphate is in an amount from about 0.12% to about 0.4% by weight based on the weight of the stucco; 
   (b) disposing the slurry between a first cover sheet and a second cover sheet to form a panel;   (c) cutting the panel into a board; and   (d) drying the board;   when the slurry is cast and dried as a board comprising said set gypsum composition, the board has a density from about 24 pcf to about 34 pcf and an average core hardness of at least about 11 lb as determined according to ASTM standard C473.   
     
     
         76 . The method of  claim 75 , wherein the stucco is in an amount from about 700 lb/MSF to about 1300 lb/MSF. 
     
     
         77 . The method of  claim 75 , wherein the slurry comprises foaming agent having 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 forming a void distribution within a set gypsum composition formed from said slurry. 
     
     
         78 . The method of  claim 75 , wherein the slurry is further formed from paper fiber and/or glass fiber in an amount from about 0.20% to about 1.30% based on the weight of the dry stucco. 
     
     
         79 . The method of  claim 75 , wherein the slurry has a water to stucco weight ratio from about 0.7 to about 1.2. 
     
     
         80 . The method of  claim 75 , wherein the slurry is further formed from accelerator in an amount from about 0.2% to about 0.9% based on the weight of the dry stucco. 
     
     
         81 . The method of  claim 75 , wherein the slurry is further formed from foaming agent and accelerator;
 the stucco is in an amount from about 700 lb/MSF to about 1300 lb/MSF;   the starch is in an amount from about 0.5% to about 6% by weight based on the weight of the stucco;   the naphthalenesulfonate dispersant is in an amount from about 0.2% to about 3.0% by weight based on the weight of the stucco;   the foaming agent has 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 a set gypsum composition formed from said slurry;   the starch and the void distribution are effective to provide a board density of about 24 lb/ft 3  to about 34 lb/ft 3  and, at a board thickness of ½ inch, said core hardness of at least about 11 lb, a nail pull resistance of at least about 65 lb, and a flexural strength of at least about 36 lb in a machine direction and/or about 107 lb in a cross-machine direction, the nail pull resistance and the flexural strength determined according to ASTM standard C473; and   the board has a humidified bond load of at least about 15 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight.   
     
     
         82 . The method of  claim 80 , wherein the foaming agent is in an amount from about 0.02% to about 0.03% by weight based on the weight of the stucco. 
     
     
         83 . The method of  claim 80 , wherein the slurry is further from paper fiber and/or glass fiber;
 the slurry has a water to stucco weight ratio from about 0.7 to about 1.2;   the starch comprises pregelatinized starch;   the phosphate comprises sodium trimetaphosphate;   the paper fiber and/or glass fiber is present in an amount from about 0.20% to about 1.30% by weight based on the weight of the stucco;   the accelerator comprises heat resistant accelerator and is present in an amount from about 0.2% to about 0.9% by weight based on the weight of the stucco; and   the board has a humidified bond load of at least about 17 lb after being (a) conditioned for about 6 hours in an environment sufficient to produce conditions of 90% relative humidity and 90° F. temperature, and (b) dried to constant weight.