Use of pre-coated mat for preparing gypsum board
A gypsum board which comprises a set gypsum core sandwiched between and faced with fibrous mats, wherein a free surface of one of said mats is pre-coated with a combination of a mineral pigment, optionally an inorganic adhesive binder and an organic binder, preferably a hydrophobic, UV resistant polymer latex adhesive binder applied to said surface as an aqueous coating composition, said aqueous coating composition upon drying and setting providing a pre-coated mat satisfying certain morphology requirements.
1. A gypsum board comprising:
a gypsum core having a main portion and a second portion, the second portion being more dense than the main portion;
a fiber mat comprising a first side and second side opposite the first side, the second side is bonded to the second portion of the gypsum core such that a tensile strength of the bond is at least 16 pounds per square inch; and
a coating penetrating the fiber mat from the first side into the fiber mat to a depth of about 30 percent to about 50 percent of the thickness of the fiber mat, the coating comprises a mineral pigment and an organic binder.
2. The gypsum board of claim 1 , wherein the second portion is about 18 to 20% more dense than the first portion.
3. The gypsum board of claim 1 , wherein the mineral pigment has a number average particle size of about 40 microns.
4. The gypsum board of claim 1 , wherein the organic binder comprises a hydrophobic, UV resistant polymer latex binder made by copolymerizing a vinyl ester with an acrylate.
5. The gypsum board according to claim 4 , wherein the vinyl ester is vinyl acetate and where the acrylate is butyl acrylate.
6. The gypsum board according to claim 5 , wherein a ratio of the vinyl acetate to the butyl acrylate is 70/30 or smaller.
7. The gypsum board according to claim 1 , wherein the gypsum core in the region of the bond has at least 17 percent combined water.
8. A gypsum board comprising:
a gypsum core having a main portion and a second portion, the second portion being more dense than the main portion;
a first fiber mat comprising a first side and second side opposite the first side, the second side is bonded to the second portion of the gypsum core such that a tensile strength of the bond is at least 16 pounds per square inch;
a first coating penetrating the first fiber mat from the first side into the fiber mat to a depth of about 30 percent to about 50 percent of the thickness of the fiber mat,
a second fiber mat comprising a first side and second side opposite the first side, the second side is bonded to the main portion of the gypsum core;
a second coating penetrating the second fiber mat from the first side into the fiber mat to a depth of about 30 percent to about 50 percent of the thickness of the fiber mat;
wherein both the first fiber mat and the second fiber mat each comprise glass fibers nominally about 10 to 16 microns in diameter and about one-quarter (¼) to about one (1) inch in length, the first fiber mat in the absence of coating has a basis weight of 1 to 3 pounds per 100 square feet.
9. The gypsum board of claim 8 , wherein the first coating and the second coating each comprise an organic binder comprising a hydrophobic, UV resistant polymer latex binder made by copolymerizing a vinyl ester with an acrylate.
10. The gypsum board according to claim 9 , wherein the vinyl ester is vinyl acetate and where the acrylate is butyl acrylate.
11. The gypsum board according to claim 10 , wherein a ratio of the vinyl acetate to the butyl acrylate is 70/30 or smaller.