초록 ▼

A paper particularly adapted for use as cover sheets in the production of gypsum wallboard, the paper having improved porosity and strength to permit better drainage and more rapid drying in the production of the paper to permit less fiber to be utilized, and to permit less heat to be utilized in dr

A paper particularly adapted for use as cover sheets in the production of gypsum wallboard, the paper having improved porosity and strength to permit better drainage and more rapid drying in the production of the paper to permit less fiber to be utilized, and to permit less heat to be utilized in drying the paper, providing for production of superior gypsum board. The paper comprises in weight percent: (A) fibers having a fiber freeness of from about 350 to 550 ml. Canadian Standard Freeness, (B) a buffering agent in an amount from about 0.25 to about 10%, (C) a neutral sizing agent in an effective amount to prevent water penetration, and (D) a cationic starch. In a preferred embodiment the paper is treated with a neutral internal sizing agent during its formation, and subsequently treated with a surface sizing agent after formation of the paper, in order to provide certain properties including better adhesion to the gypsum core.

대표청구항 ▼

Gyspum wallboard comprising a core of set calcium sulfate dihydrate and a paper cover sheet bonded to each surface thereof, each of said paper cover sheets having been fabricated by first incorporating the ingredients including calcium carbonate into an aqueous slurry and then forming and drying sai

Gyspum wallboard comprising a core of set calcium sulfate dihydrate and a paper cover sheet bonded to each surface thereof, each of said paper cover sheets having been fabricated by first incorporating the ingredients including calcium carbonate into an aqueous slurry and then forming and drying said paper cover sheet, said ingredients comprising: (A) a major proportion of cellulose fibers consisting essentially of waste paper stock providing an acidic furnish, (B) a cyclic dicarboxylic acid anhydride applied as an internal sizing agent having the structural formula: [Figure] wherein R is selected from the group consisting of dimethylene and trimethylene radicals, and wherein R′is a hydrophobic group containing more than 5 carbon atoms selected from the group consisting of alkyl, alkenyl, aralkyl and aralkenyl groups, (C) a cationic agent, and (D) a buffering agent comprising calcium carbonate adapted to maintain the aqueous paper slurry during forming at a pH of at least 7.