Gypsum boards prepared using uncalcined gypsum and slurries and methods related thereto
AssigneeUnited States Gypsum Company
InventorsYijun SANG, Annamaria VILINSKA, Mark Kenneth HEMPHILL
Life of this patent
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Abstract
Disclosed are gypsum boards, slurries, and methods of preparing gypsum board using water, uncalcined gypsum, stucco, and starch binder. The board contains a set gypsum core disposed between two cover sheets. The uncalcined gypsum and starch binder surprisingly and unexpectedly allows for the use of uncalcined gypsum while maintaining desired characteristics in gypsum wallboard, such as low board weight, sufficient strength, score/snap, fire resistance, etc. In embodiments, the presence of the uncalcined gypsum with the starch binder in the core slurry allows for excluding an amount of stucco therein.
Claims20
A gypsum board comprising:
- a set gypsum core disposed between two cover sheets, the core formed from a slurry comprising water, uncalcined gypsum, stucco, and starch binder;
- the starch binder comprising (a) at least one uncooked non-substituted starch having a hot water viscosity of from about 20 Brabender Units to about 300 Brabender Units when the viscosity is measured by the HWVA method, (b) at least one pregelatinized starch, or (c) a combination of (a) and (b).
A method of making gypsum board, the method comprising:
- mixing a slurry comprising water, uncalcined gypsum, a stucco, and a starch binder, the starch binder comprising (a) at least one uncooked non-substituted starch having a hot water viscosity of from about 20 Brabender Units to about 300 Brabender Units when the viscosity is measured by the HWVA method, (b) at least one pregelatinized starch, or (c) a combination of (a) and (b);
- placing the slurry between two cover sheets to form a board precursor;
- allowing the slurry in the precursor to set to form the board;
- and
- cutting the board.
A slurry comprising:
- water, uncalcined gypsum, stucco, and starch binder;
- the starch binder comprising (a) at least one uncooked non-substituted starch having a hot water viscosity of from about 20 Brabender Units to about 300 Brabender Units when the viscosity is measured by the HWVA method, (b) at least one pregelatinized starch, or (c) a combination of (a) and (b);
- wherein the uncalcined gypsum is provided in the slurry in an amount from 25% to 150% by weight of the stucco;
- wherein the starch binder is provided in the slurry in an amount from 2% to 15% by weight of the stucco;
- and
- wherein the slurry has a water/stucco ratio of less than 1.0.
Dependencies are inferred from the claim text.