Water repellent composition, its production method, hydrophobic substrate treating agent composition and article

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)nX (1)
• wherein
• Z is a C4-6 perfluoroalkyl group
• Y is a C1-4 alkylene group,
• n is 1, and
• X is a group represented by formula (3-3):
• —OC(O)CR═CH2
• 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 C1-6 alkyl group;
• monomer (c):
• vinyl chloride or vinylidene chloride.