To obtain a coating film having excellent weathering resistance by copolymerizing a malonate-group-containing monomer (a) with a malonate-group- free monofunctional ethylenically unsaturated monomer (b) by solution polymerizaiton.

Component (a) is represented by formula I (wherein R1 is H or methyl; R2 and R3 are each a 2-6 C alkylene; R4 is a 1-10 C alkyl; (n) is 1-10; and (m) is 0-6 when n=1 and is 0 when n>1) and is exemplified by a 2-1-10 C alkoxymalonylethyl (meth)acrylate. Component (b) is a common acryl monomer (e.g. ethyl acrylate) or a non-acryl monomer (e.g. styrene) used in the production of acryl resins for coating materials and partially consists of an epoxy acryl monomer (e.g. glycidyl acrylate). The obtained acrylic polymer has a number-average molecular weight of 1,000-1000,000, an equivalent of the active hydrogen atoms of active methylene groups of 100-10,000 and an epoxy equivalent of 200-10,000.