Method For Calcining Gypsum and Making a Gypsum Board

A method for making a gypsum board, the method comprising:

• applying a phosphorus containing compound to a first gypsum composition to provide a phosphorus modified gypsum composition,
• wherein the phosphorus containing compound comprises a phosphite, a phosphate having the formula P(O)n(X)m wherein n is from 0 to 4, m is from 0 to 6, the sum of n and m is from 3 to 6, and X is hydrogen, halogen, sulfur, or selenium, a salt thereof, or a mixture thereof;
• calcining the phosphorus modified gypsum composition to provide a calcined gypsum composition;
• preparing a gypsum slurry by combining water and the calcined gypsum composition;
• depositing the gypsum slurry on a first facing material;
• providing a second facing material on the gypsum slurry;
• and
• allowing the calcined gypsum to convert to calcium sulfate dihydrate.

A method for making a gypsum board, the method comprising:

• applying a phosphorus containing compound to a first gypsum composition to provide a phosphorus modified gypsum composition,
• wherein the first gypsum composition comprises reclaimed gypsum and an organosilicon compound,
• wherein the phosphorus containing compound comprises a phosphite, a phosphate having the formula P(O)n(X)m wherein n is from 0 to 4, m is from 0 to 6, the sum of n and m is from 3 to 6, and X is hydrogen, halogen, sulfur, or selenium, a salt thereof, or a mixture thereof;
• calcining the phosphorus modified gypsum composition to provide a calcined gypsum composition;
• preparing a gypsum slurry by combining water and the calcined gypsum composition;
• depositing the gypsum slurry on a first facing material;
• providing a second facing material on the gypsum slurry;
• and
• allowing the calcined gypsum to convert to calcium sulfate dihydrate.