To obtain a composition useful for, e.g. imparting hydrophilicity to heat exchanger fins, by using as the constituent a copolymer produced by copolymerizing a mixture containing an oxyalkylene-containing vinyl monomer, a hydroxylated vinyl monomer, a COOH-containing vinyl monomer and an Si-containing vinyl monomer.

The composition contains a copolymer obtained by copolymerizing a vinyl monomer mixture containing preferably 10-50 wt.% vinyl monomer of formula I, preferably 5-30 wt.% hydroxylated vinyl monomer, preferably 5-30 wt.% COOH-containing vinyl monomer, and preferably 1-10 wt.% vinyl monomer of formula II. In the formulas, R1 and R3 are each H or CH3; R2 and R4 to R6 are each a hydrocarbon group; x is 2 or greater; q is 1 or greater; and y is 3 or smaller. The copolymer used preferably comprises one having a glass transition temperatures of -50 to 30°C and a weight-average molecular weight of 10,000 to 100,000. Examples of solvents preferably used for the composition include water, alcoholic solvents and Cellosolve solvents.