Gypsum board containing high absorption paper and related methods
AssigneeUnited States Gypsum Company
InventorsQinghua Li, Mark K. Hemphill
Life of this patent
Estimating the term…
Abstract
Disclosed are a composite gypsum board and a method of preparing composite gypsum board. The board contains at least one set gypsum layer sandwiched between two cover sheets. The set gypsum layer is formed from at least stucco and water. The stucco material generally includes a high salt impurity content, for example, when the stucco is calcined from certain sources of low-quality synthetic gypsum. For example, in some embodiments, the salts are chloride salts, e.g., sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), and/or calcium chloride (CaCl2)). At least one of the cover sheets is composed of high absorption paper, which enhances the bond between the set gypsum layer and the cover sheet.
Claims16
A gypsum board comprising a set gypsum core disposed between a face cover sheet and a back cover sheet, the set gypsum core formed from a slurry comprising water, stucco, and a high salt impurity content comprising at least about 150 ppm chloride anion per 1,000,000 parts by weight of stucco, the back cover sheet comprising paper having a bond side Cobb value of at least about 2.1 g/100 cm2 according to the Cobb test, the paper having a basis weight of from about 35 lb/msf to about 65 lb/msf, and the paper having a thickness of about 0.005 inch to about 0.015 inch, wherein the paper allows for a superior bond between the board core and the back cover sheet as compared with the board prepared with the back cover sheet comprising paper having a bond side Cobb value below 2.1 g/100 cm2.
A method of making gypsum board, the method comprising:
- (a) mixing at least water and stucco containing a high salt impurity content, comprising at least about 150 ppm chloride anion per 1,000,000 parts by weight of stucco, to form a first slurry;
- (b) applying the first slurry to form a board core in a bonding relation to a face cover sheet, the board core having a first face and a second face, the first face facing the face cover sheet;
- (c) applying a back cover sheet in bonding relation to the second face of the board core to form a board precursor, the back cover sheet comprising paper having a bond side Cobb value of at least about 2.1 g/100 cm2 according to the Cobb test, the paper having a basis weight of from about 35 lb/msf to about 65 lb/msf, and the paper having a thickness of about 0.005 inch to about 0.015 inch, wherein the paper allows for a superior bond between the board core and the back cover sheet as compared with the board prepared with the back cover sheet comprising paper having a bond side Cobb value below 2.1 g/100 cm2;
- (d) drying the board precursor to form a board.
Dependencies are inferred from the claim text.