Patent ID: 8609795

Claim:
A water and oil repellent composition, which comprises a copolymer comprising repeating units of the following monomer (a) and repeating units of the following monomer (b), wherein the total content of said repeating units is at least 80 mass % of repeating units of said copolymer: Monomer (a): an ethylenically polymerizable monomer having a perfluoroalkyl group, which forms a homopolymer having no melting point or a melting point of at most 55° C. attributable to fine crystals derived from the perfluoroalkyl group, and having a glass transition point of at least 20° C., Monomer (b): an ethylenically polymerizable monomer having no polyfluoroalkyl group and having a cross-linkable functional group, wherein the monomer (a) is a compound represented by (Z—Y) n X provided that the symbols in the formula have the following meanings: Z: a perfluoroalkyl group having at most 6 carbon atoms, Y: a bivalent organic group or a single bond, n: 1 or 2, X: a polymerizable unsaturated group, which is —CR═CH 2 , —COOCR═CH 2 , —OCOCR═CH 2 , —OCH 2 -φ-CR═CH 2 or —OCH═CH 2 when n is 1, and is >CH(CH 2 ) m CR═CH 2 , >CH(CH 2 ) m COOCR═CH 2 , >CH(CH 2 ) m OCOCR═CH 2 , or —OCOCH═CHCOO— when n is 2, wherein R is a hydrogen atom, a methyl group or a halogen atom, φ is a phenylene group and m is an integer of from 0 to 4, wherein the polymerization units of monomer (a) and the polymerization units of monomer (b) are present in a mass ratio of 70.0-99.9 to 0.1-30.0, respectively.