Method of making water-resistant gypsum-based article
AssigneeUnited States Gypsum Company
InventorsSrinivas Veeramasuneni, Kathryn Capacasa
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Abstract
A moisture resistant gypsum-based product, e.g., a gypsum board, is made by adding a small amount of a siloxane to the aqueous slurry used to make the gypsum-based product along with a small amount of a dead burned magnesium oxide catalyst to enhance the curing of the siloxane. In the preferred embodiment, the siloxane is formed into an aqueous emulsion in situ with no chemical emulsifier.
Claims14
A method for making a water-resistant gypsum-based board comprising:
- (A) mixing a siloxane emulsion with the gauging water used to prepare said gypsum-based board;
- (B) mixing a small amount of dead-burned magnesium oxide with calcined gypsum, wherein the amount of magnesium oxide is from 0.1 to about 0.5 wt % of the gypsum;
- (C) mixing said siloxane emulsion/gauging water mixture with said calcined gypsum/magnesium oxide mixture to form an aqueous slurry;
- (D) allowing said dead-burned magnesium oxide to catalyze cross-linking of said siloxane;
- and
- (E) shaping said slurry and allowing said shaped slurry to set to form a set gypsum-based, water-resistant board.
A method for making a water-resistant gypsum-based board comprising:
- (A) mixing a quantity of a siloxane fluid with a portion of the gauging water used to prepare said gypsum-based board in a high intensity mixer to form a siloxane/water emulsion in situ;
- (B) mixing a small amount of dead-burned magnesium oxide with calcined gypsum;
- (C) mixing said siloxane/water emulsion with the balance of the gauging water;
- (D) mixing said gypsum/magnesium oxide mixture with the siloxane/water mixture of step (C) to form an aqueous slurry;
- (E) allowing said dead-burned magnesium oxide to catalyze cross-linking of said siloxane;
- and
- (F) shaping said slurry and allowing said shaped slurry to set to form a set gypsum-based, water resistant board.
A method for incorporating siloxane while forming a water-resistant, gypsum-based board, comprising:
- (A) mixing a quantity of siloxane fluid with a portion of the gauging water used to prepare said gypsum-based board in a high intensity mixer to form a siloxane emulsion;
- (B) mixing said siloxane emulsion with balance of the gauging water, calcined gypsum and from about 0.1 to about 0.5 wt % of the gypsum of dead-burned magnesium oxide to form an aqueous slurry;
- (C) allowing said dead-burned magnesium oxide to catalyze cross-linking of said siloxane;
- and
- (D) shaping and allowing said slurry to set to form a set gypsum-based, water-resistant board, said board absorbing less than about 10% of its own weight in water when immersed at 70° F. for two hours in accordance with ASTM Standard 1396 within 24 hours.
Dependencies are inferred from the claim text.