Abstract: To provide a fluorinated copolymer capable of obtaining an article excellent in water and oil repellency, and friction durability of water and oil repellency. A fluorinated copolymer having units based on the following monomer a and units based on the following monomer b, wherein the proportion of the units based on the monomer a is from 20 to 50 mol % based on the total number of moles of units constituting the fluorinated copolymer, the mass average molecular weight is from 20,000 to 100,000, and the ratio of the half-width W1 of the peak of the fluorinated copolymer to the peak width W2 in a chromatogram obtainable by high performance liquid chromatography measurement is from 0.35 to 0.55: Monomer a: a compound represented by CH2?CH—Rf (Rf: a C1-8 perfluoroalkyl group; Monomer b: a monomer copolymerizable with the monomer a.

Abstract: To provide an antifouling processing agent composition capable of imparting oil repellency and antifouling properties (stain release properties), while suppressing a reduction in the water absorbency of a textile product. This antifouling processing agent composition comprises: a fluorinated polymer comprising from 30 to 70 mass % of units based on F(CF2)nY—OCOCR?CH2 (wherein Y is an alkylene group, and R is a hydrogen atom, an alkyl group, or a halogen atom) and from 20 to 60 mass % of units based on CH2?CR1—COO—(R2O)q—R3 (wherein R1 is a hydrogen atom or a methyl group, R2 is an alkylene group, and R3 is a hydrogen atom, an alkyl group, a (meth)acryloyl group, or a glycidyl group), and having a number average molecular weight of 3,000-500,000; and a fluorinated amphoteric surfactant having a C1-6 perfluoroalkyl group or a C3-9 perfluoroalkenyl group, and having a number average molecular weight of less than 3,000.