Method of making water-resistant gypsum-based article

  • US 7,892,472 B2
  • Filed: 08/12/2004
  • Issued: 02/22/2011
  • Est. Priority Date: 08/12/2004
  • Status: Active Grant
First Claim
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1. 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.

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