| 摘要 |
PROBLEM TO BE SOLVED: To obtain a resin composition excellent in resistances to corrosion and scratch by incorporating, into the same, a water-soluble copolymer which is formed from styrene, a methacrylic ester, and a carboxylated monomer in a specified wt. ratio of styrene to the methacrylic ester and has a specified acid value. SOLUTION: This composition contains a water-soluble copolymer which is formed from styrene, a methacrylic ester having a glass transition temperature of 0 deg.C or higher, and a carboxylated monomer (e.g. acrylic acid) in a wt. ratio of styrene to the methacrylic ester of (1/0.005)-(1/0.3) and has an acid value of 50-200 mgKOH/g. The composition is further compounded with a heavy metal ion source (e.g. zinc sulfate), a metal oxide (e.g. zirconium oxide), a silane coupling agent, etc., and then is applied to a galvanized steel sheet to form a film with a thickess of 0.1-5μm. The methacrylic ester is one obtained from methacrylic acid and a 2C or higher alcohol, such as ethyl, isopropyl, or n-butyl methacrylate.
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