Patent ID: 8921482

Claim:
A water repellent composition to be used for treatment of a hydrophobic substrate, which comprises a fluorinated copolymer comprising structural units based on the following monomer (a), structural units based on the following monomer (b) and structural units based on the following monomer (c), and a medium, wherein the proportion of the structural units based on the monomer (a) is from 50 to 90 mass % and the proportion of the structural units based on the monomer (b) is from 5 to 30 mass % of the structural units (100 mass %) based on all monomers present in the fluorinated copolymer: monomer (a): a compound represented by formula (1): (Z-Y) n X (1) wherein Z is a C 4-6 perfluoroalkyl group Y is a C 1-4 alkylene group, n is 1, and X is a group represented by formula (3-3): —OC(O)CR═CH 2 wherein R is a hydrogen atom, a methyl group or a halogen atom; monomer (b): a (meth)acrylate having no polyfluoroalkyl group and having a C 1-6 alkyl group; monomer (c): vinyl chloride or vinylidene chloride.