Accelerator comprising starch, and related board, slurries, and methods
AssigneeUnited States Gypsum Company
InventorsYijun Sang, Mark K. Hemphill, Yongman Kim, James W. Barber
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Abstract
An accelerator for accelerating the rate of hydration of calcined gypsum is disclosed. The accelerator comprises calcium sulfate dihydrate particles and a starch. The starch has a cold water solubility of at least about 25% (e.g., at least about 35%) and a viscosity of about 25 Brabender Units (BU) or less when the starch is in a 30% aqueous slurry at 92° C. Also disclosed are a method of preparing an accelerator, method of hydrating stucco to form set gypsum, slurry, and method of making gypsum board.
Claims12
An accelerator for use in accelerating the rate of hydration of calcined gypsum to set gypsum in gypsum slurries for producing gypsum wallboard panels, said accelerator comprising:
- particles of calcium sulfate dihydrate having an average particle size of from 20 μm to 50 μm, and starch having a cold water solubility of at least about 25% and a viscosity of 25 Brabender Units (BU) or less when the starch is in a 30% solids aqueous slurry at 92° C., wherein the starch is an acid-hydrolyzed starch, and wherein said accelerator has a time to 50% hydration of between 2.42 and 3.83 minutes.
A method of preparing gypsum board comprising:
- (a) providing a first cover sheet;
- (b) mixing a first slurry comprising stucco, water, and an accelerator comprising calcium sulfate dihydrate particles having an average particle size of from 20 μm to 50 μm and starch having a cold water solubility of at least about 25%, and a viscosity of about 25 Brabender Units (BU) or less when the starch is in a 30% solids aqueous starch slurry at 92° C., wherein the starch is an acid-hydrolyzed starch, and wherein said accelerator has a time to 50% hydration of between 2.42 and 3.83 minutes;
- (c) disposing the first μslurry between the first cover sheet and a second cover sheet to form an assembly;
- (d) cutting the assembly into a board;
- and (e) drying the board.
Dependencies are inferred from the claim text.