Gypsum-containing product having increased resistance to permanent deformation and method and composition for producing it

A gypsum board comprising a core of material sandwiched between cover sheets, wherein the core comprises an interlocking matrix of set gypsum, and the board has been prepared by a method comprising:

• forming or depositing a mixture between the cover sheets, wherein the mixture comprises a calcined gypsum, water, an accelerator, and one or more enhancing materials chosen from the group consisting of:
• condensed phosphoric acids, each of which comprises 2 or more phosphoric acid units;
• and salts or ions of condensed phosphates, each of which comprises 2 or more phosphate units, and
• maintaining the mixture under conditions sufficient for the calcined gypsum to form the interlocking matrix of set gypsum,
• the enhancing material or materials having been included in the mixture in an amount such that the gypsum board has greater sag resistance than it would have if the enhancing material had not been included in the mixture,
• said board having 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 gypsum board has greater strength than it would have if the accelerator had not been included in the mixture.

A method for producing a shaped gypsum board, comprising:

• preparing a uniform aqueous solution comprising water, at least one chloride salt, a wetting agent, and one or more enhancing materials chosen from the group consisting of:
• phosphoric acids, each of which comprises 1 or more phosphoric acid units;
• salts or ions of condensed phosphates, each of which comprises 2 or more phosphate units;
• and monobasic salts or monovalent ions of orthophosphates, and
• applying the uniform aqueous solution to a gypsum board in an amount and manner sufficient to weaken the gypsum board to allow the shape of the gypsum board to be modified,
• modifying the shape of the gypsum board as desired,
• and allowing the gypsum board to dry to produce the shaped gypsum board,
• the chloride salt, the enhancing material or materials, and the wetting agent, having been applied to the gypsum board in an amount and manner such that the modified shape of the shaped gypsum board is achieved in a shorter time and the shaped gypsum board has greater resistance to permanent deformation than if the chloride salt, enhancing material, and wetting agent had not been applied to the gypsum board.

A method for producing a shaped gypsum board comprising:

• applying to the gypsum board a uniform aqueous solution comprising water and a wetting agent,
• applying to the gypsum board a uniform aqueous solution comprising water and at least one chloride salt,
• applying to the gypsum board, prior to allowing the gypsum board to dry, a solution comprising one or more enhancing materials chosen from the group consisting of:
• phosphoric acids, each of which comprises 1 or more phosphoric acid units;
• salts or ions of condensed phosphates, each of which comprises 2 or more phosphate units;
• and monobasic salts or monovalent ions of orthophosphates,
• modifying the shape of the gypsum board as desired,
• and allowing the gypsum board to dry to produce the shaped gypsum board,
• the chloride salt, the enhancing material or materials, and the wetting agent, having been applied to the gypsum board in an amount and manner such that the modified shape of the shaped gypsum board is achieved in a shorter time and the shaped gypsum board has greater resistance to permanent deformation than if the chloride salt, enhancing material, and wetting agent had not been applied to the gypsum board.

A method for producing a set gypsum-containing product comprising:

• forming a mixture of a calcined gypsum water, and one or more enhancing materials chosen from the group consisting of:
• condensed phosphoric acids, each of which comprises 2 or more phosphoric acid units;
• and salts or ions of condensed phosphates, each of which comprises 2 or more phosphate units, and
• maintaining the mixture under conditions sufficient for the calcined gypsum to form a set gypsum material,
• the enhancing material or materials having been included in the mixture in an amount such that the set gypsum formed 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 {fraction (1/2)} 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.

A method for producing a set gypsum-containing product comprising

• forming a mixture of calcined gypsum, water, and one or more enhancing materials chosen from the group consisting of:
• condensed phosphoric acids, each of which comprises 2 or more phosphoric acid units;
• and salts or ions of condensed phosphates, each of which comprises 2 or more phosphate units, and
• maintaining 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 {fraction (1/2)} 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.