Water-based protective compositions for coating films and preparation processes thereof.

摘要

Disclosed herein are water-based protective composition for coating films. The compositions contain (a) a water-based dispersion of copolymer particles having a number average molecular weight of from 2,000 to 20,000 and a glass transition point of from -10 DEG C to +40 DEG C and obtained by emulsion-polymerizing 100 parts by weight of a monomer mixture consisting substantially of (X) 7-12 parts by weight of an alpha , beta -monoethylenically-unsaturated carboxylic acid and (Y) 88-93 parts by weight of at least one ester selected from the group consisting of C1-4-alkyl acrylates and C1-4-alkyl methacrylates; as well as specific amounts of (b) an ultraviolet absorber, (c) an antioxidant, (d) a thickening agent and (e) a surface active agent. They can form barrier coats having excellent removability, weatherability, waterproofness, heat resistance and coating-film-protecting property. Their preparation processes are also disclosed.