초록 ▼

A composite paper particularly adapted for use as cover sheets in the production of gypsum wallboard, the paper being sufficiently porous to permit better drainage and more rapid drying in the production of the paper, and when applied to the surfaces of a gypsum slurry for forming wallboard, permits

A composite paper particularly adapted for use as cover sheets in the production of gypsum wallboard, the paper being sufficiently porous to permit better drainage and more rapid drying in the production of the paper, and when applied to the surfaces of a gypsum slurry for forming wallboard, permits less heat to be utilized in the wallboard conversion, thereby saving energy in the board production required for drying the board. The paper comprises in weight percent: (A) cellulosic fibers in an amount of from about 65% to about 90% and preferably having a fiber freeness of from about 300 ml to about 550 ml Canadian Standard Freeness, (B) calcium sulfate as a filler in an amount of from about 10% to about 35%, (C) a binder in an amount from about 1% to about 31/2%, (D) a flocculant in an amount of from about 0.1% to about 0.2%, (E) a buffering agent in an amount from about 0.25% to about 10%, (F) a neutral sizing agent in an effective amount to prevent water penetration, (G) an anionic polymer in an amount suitable for retaining said filler in said paper, and (H) a cationic starch when a succinic anhydride is used as the neutral sizing agent. In a preferred embodiment, after the paper is treated with a neutral internal sizing agent during its formation, it is 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 when used to make gypsum wallboard.

대표청구항 ▼

1. A paper suitable for use as cover sheets in the production of gypsum wallboard, said paper comprising: (A) cellulose fibers in an amount of at least about 60% by dry weight, (B) calcium sulfate as a filler in an amount of from about 10% to about 35% in dry weight, (C) a binder in an amount f

1. A paper suitable for use as cover sheets in the production of gypsum wallboard, said paper comprising: (A) cellulose fibers in an amount of at least about 60% by dry weight, (B) calcium sulfate as a filler in an amount of from about 10% to about 35% in dry weight, (C) a binder in an amount from about 1% to about 31/2%, (D) a flocculant in an amount of from about 0.1% to about 0.2%, (E) a neutral sizing agent in an effective amount to prevent water penetration, (F) calcium carbonate as a buffering agent in an amount from about 0.25% to about 10%, and (G) an anionic polyacrylamide as a retention aid in an amount suitable for retaining said filler in said paper. 2. A paper according to claim 1, wherein said filler is calcium sulfate dihydrate. 3. A paper according to claim 1, wherein said neutral sizing agent is a cyclic dicarboxylic acid anhydride applied as an internal sizing agent having the structural formula: ##STR## wherein R is selected from the group consisting of dimethylene and trimethylene radicals, and wherein R' is a hydrophobic group containing more than five carbon atoms selected from the group consisting of alkyl, alkenyl, aralkyl and aralkenyl groups. 4. A paper according to claim 3, wherein said cyclic dicarboxylic acid anhydride is a substituted succinic acid anhydride having a total of 15 to 20 carbon atoms. 5. A paper according to claim 3, wherein said substituted succinic acid anhydride is present in an amount of from about 0.15% to about 0.35% by dry weight. 6. A paper according to claim 3, wherein an emulsifying agent is added to said cyclic dicarboxylic acid anhydride. 7. A paper according to claim 2, wherein said neutral sizing agent has the following structural formula: ##STR## wherein each R has 8-18 carbon atoms. 8. A paper according to claim 7 additionally containing a cationic polymer. 9. A paper according to claim 2, wherein a surface size coating comprising a silicone resin is applied to at least the surface of the bondliner of said paper. 10. A paper according to claim 9, wherein said surface size also includes an acidic agent in an amount suitable for promoting the polymerization of said silicone resin. 11. A paper according to claim 10, wherein said acidic agent is alum. 12. A paper according to claim 11, wherein said silicone resin is present in an amount of from about 0.015% to 0.25%, and said alum is present in an amount of about 21/2 times the dry weight of said silicone resin. 13. A paper according to claim 9, wherein said silicone resin is a dimethyl polysiloxane resin.