To improve the adhesion between a base board paper and a gypsum core and upgrade the economy of a gypsum board by adding a water-soluble polymer, a borax and/or a boric acid to the base board paper and/or the gypsum core.
In a gypsum board made up of a base board paper containing a water-soluble polymer and a gypsum core containing a borax and/or a boric acid, and a gypsum board made up of a base board paper containing a borax and/or a boric acid and a gypsum core containing a water-soluble polymer, a polyvinyl alcohol is especially preferable as the water-soluble polymer, and is preferably of such a nature that the degree of polymerization is about 500-2,200 and the degree of saponification is 80-90 mol% from the viewpoint of, above all, issues such as solubility to water, applicability to the base board paper, coat strength and moisture absorption. The borax and/or the boric acid are preferably used in the form of an aqueous 1-10 wt.% solution, and the boric acid to be used is such as a metaboric acid, an orthoboric acid or a quaternary boric acid, either of which can be used in the form of an aqueous solution of an appropriate concentration.
ABE KOJI
MORIKIYO KOJI
OBUKA NAOTOSHI
