Gypsum wallboard and related methods and slurries
OwnerYijun SANG, Alfred C. LI +1inventors
InventorsYijun SANG, Alfred C. LI, Weixin D. SONG
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Abstract
Disclosed is a gypsum board comprising a set gypsum core disposed between two cover sheets. The set gypsum core is formed from a slurry comprising stucco, water, and at least one pregelatinized starch having a viscosity of from about 20 cP to about 300 cP as measured according to the VMA method described herein. The starch is present in an amount of greater than 10% by weight of the stucco. In preferred embodiments, the board has good strength properties even at lower densities, such as about 31 pcf or less. Also disclosed are a related method of making a gypsum wallboard and a slurry.
Claims20
A gypsum board comprising:
- a set gypsum core disposed between two cover sheets, the core formed from a slurry comprising stucco, water, and at least one pregelatinized starch having a viscosity of from about 20 cP to about 300 cP as measured according to the VMA method, wherein the starch is present in an amount of greater than 10% by weight of the stucco;
- the board having a density of about 31 pcf or less and a core hardness of at least about 11 lbs, as determined according to ASTM C473-10, method B.
A method of making a gypsum board comprising:
- a) mixing at least water, stucco, and at least one pregelatinized starch having a viscosity of from about 20 cP to about 300 cP as measured according to the VMA method, wherein the starch is present in an amount of greater than 10% by weight of the stucco;
- b) disposing the slurry between a first cover sheet and a second cover sheet to form a wet assembly;
- c) cutting the wet assembly into a board;
- and
- d) drying the board;
- the dried board having a density of about 31 pcf or less and a core hardness of at least about 11 lbs, as determined according to ASTM C473-10, method B.
A slurry comprising:
- water, stucco, and pregelatinized starch having a viscosity of from about 20 cP to about 300 cP as measured according to the VMA method, wherein the starch is present in an amount of greater than 10% by weight of the stucco;
- wherein
- when the slurry is cast and dried as board comprising a set gypsum composition, the set gypsum composition comprises a continuous crystalline matrix substantially of calcium sulfate dihydrate, wherein said board has a density of about 31 pcf or less, and at a thickness of one-half inch (about 1.3 cm), the board meets at least one of the following:
- (i) a nail pull resistance of at least about 65 lb (about 29 kg), (ii) an average core hardness of at least about 11 lb (about 5 kg), and (iii) an average flexural strength of at least about 36 lb (about 16 kg) in a machine direction and/or about 107 lb (about 48.5 kg) in a cross-machine direction, the nail pull resistance, the core hardness and the flexural strength determined in accordance with ASTM standard C473-10, method B.
Dependencies are inferred from the claim text.