Gypsum-containing product and method for producing same

  • US 7,964,034 B2
  • Filed: 06/09/2010
  • Issued: 06/21/2011
  • Est. Priority Date: 08/21/1997
  • Status: Expired due to Term
First Claim
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1. A method for producing a set gypsum-containing product comprising forming a mixture of calcined gypsum, water, an accelerator, and one or more enhancing materials chosen from the group consisting of:

  • sodium trimetaphosphate, tetrapotassium pyrophosphate, tetrasodium pyrophosphate, aluminum trimetaphosphate, sodium acid pyrophosphate, ammonium polyphosphate having 1000-3000 repeating phosphate units, and acids, salts, or the anionic portions thereof, andmaintaining the mixture under conditions sufficient for the calcined gypsum to form an interlocking matrix of set gypsum,the enhancing material or materials having been included in the mixture in an amount such that the set gypsum-containing product has greater resistance to permanent deformation than it would have if the enhancing material had not been included in the mixture, such that when the mixture is cast in the form of ½

    inch gypsum board, said board has a sag resistance, as determined according to ASTM C473-95, of less than about 0.1 inch per two foot length of said board,the accelerator having been included in an amount such that the set gypsum-containing product has greater strength than it would have if the accelerator had not been included in the mixture.

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