Acrylic polymers solutions for use in forming a membrane for curing concrete and the like

An addition polymer is disclosed, the utility being to apply the same as a film to a hydraulic cement-containing article prior to curing, such as concrete, asbestos-cement shingles and the like, for example, to prevent moisture loss during the early hardening period. The polymers are formed of about 10 to 50 percent by weight of an ester of acrylic or methacrylic acid, the alcohol moiety of which has from 12 to about 20 carbon atoms, about 40 to 89.5 percent by weight of a vinyl aromatic monomer, and about 0.5 to 5 percent of a copolymerizable ethylenically unsaturated carboxylic acid, vinyl sulfonic acid, or salts thereof, preferably 15 to 30 percent of the ester, 69 to 84 percent of the vinyl aromatic material, and 1 to 3 percent of the unsaturated acid. In addition to use on concrete, the materials are useful for application to asbestos-cement shingles, prior to curing, and other similar uses. The preferred vinyl aromatic compound is styrene or vinyl toluene, and the preferred acid is itaconic acid, acrylic acid, or methacrylic acid.