Moisture resistance improver for water-based adhesive for inorganic materials, and water-based adhesive for inorganic materials

A moisture resistance improver for a water-based adhesive for inorganic materials, the moisture resistance improver comprising at least one (co)polymer (A) selected from the group consisting of the following (co)polymer (A1) and (co)polymer (A2),

• (co)polymer (A1):
• a (co)polymer comprising an unsaturated (poly)carboxylic acid (anhydride) (a1) having 3 to 30 carbon atoms and a (meth)acrylic acid ester (a2) having a solubility at 25° C. of 10 g or less per 100 g of water as constituent monomers, and having a weight-average molecular weight of 3,000 to 150,000
• (co)polymer (A2):
• a (co)polymer comprising an unsaturated (poly)carboxylic acid (anhydride) (a1) defined above as a constituent monomer with the proviso that no (meth)acrylic acid ester (a2) defined above being contained as a constituent monomer, and having a weight-average molecular weight of 6,000 to 150,000,
• wherein, in the moisture resistance improver, the (co)polymer (A) is either
• (1) a combination of the (co)polymer (A1) defined above and the (co)polymer (A2) defined above;
• or
• (2) the (co)polymer (A1) with the proviso that the (meth)acrylic acid ester (a2) as constituent monomer in the (co)polymer (A1) is a combination of a linear alkyl ester having the linear alkyl of from 2 to 28 carbon atoms and a branched chain alkyl ester having the branched chain alkyl of from 8 to 28 carbon atoms.