Fire-resistant gypsum fiberboard
AssigneeGeorgia-Pacific Gypsum LLC
InventorsTurner W. Richards, Hubert C. Francis, George F. Fowler
Life of this patent
Estimating the term…
Abstract
Fiberboards are provided containing at least about 65 wt. % calcium sulfate dihydrate derived from hemihydrate or anhydrous gypsum, and at least about 7 wt. % pulped paper fibers. The boards are capable of being formed into structural members having superior mechanical properties and/or fire resistance, including screw-holding capacities in excess of 650 lbs.
Claims16
A fiberboard comprising (a) set gypsum dihydrate, said gypsum dihydrate derived substantially from a non-fibrous form of calcium sulfate selected from the group consisting of anhydrous gypsum and gypsum hemihydrate, (b) binder polymer, and (c) homogeneously distributed cellulosic fibers, said fiberboard made by pressing and dewatering an aqueous dispersion of solids to form a green casting having homogeneously distributed cellulosic fibers and then drying the green casting to form said fiberboard, wherein said solids in the aqueous dispersion comprise about 53% to about 78% by weight of the non-fibrous form of calcium sulfate, wherein water in said aqueous dispersion is in at least about 25-fold excess of that required to hydrate the non-fibrous form of calcium sulfate, wherein said binder polymer is provided in an amount of about 1% to about 3% of said solids and wherein said fiberboard has a density in the range of about 40 lbs./cu. ft. to about 75 lbs./cu. ft.
A method of preparing a fiberboard comprising (1) forming an aqueous dispersion comprising (a) set gypsum dihydrate, said gypsum dihydrate derived substantially from a non-fibrous form of calcium sulfate selected from the group consisting of anhydrous gypsum and gypsum hemihydrate, (b) binder polymer, and (c) cellulosic fibers, wherein water in said aqueous dispersion is in at least about 25-fold excess of that required to hydrate the calcium sulfate (2) pressing and dewatering said aqueous dispersion to form a green casting having homogeneously distributed cellulosic fibers and (3) drying the green casting to form said fiberboard, wherein the non-fibrous form of calcium sulfate comprises about 53% to about 78% by weight of solids in the aqueous dispersion, wherein said binder polymer is provided in an amount of about 1% to about 3% by weight of said solids and wherein said pressing is sufficient to produce fiberboard having a density in the range of about 40 lbs./cu. ft. to about 75 lbs./cu. ft.
Dependencies are inferred from the claim text.