ANTIFOULING COMPOSITION

An antifouling coating composition comprises a binder system which includes (A) a first silyl ester copolymer comprising a triisopropylsilyl methacrylate monomer, (B) a second silyl ester copolymer comprising a triisopropylsilyl acrylate monomer, and (C) 5 to 40 wt.% monocarboxylic acid or a derivative thereof, wherein components (A) and (B) are different and the weight ratio of (A):(B) is 55:45 to 95:5. The acid or derivative thereof may be a C6-20 cyclic monocarboxylic acid, such as rosin. Copolymers (A) or (B) may comprise a hydrophilic monomer, such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, or tetrahydrofurfuryl (meth)acrylate. The binder system preferably comprises 20-70 wt.% copolymer (A) and 2-45 wt.% copolymer (B) on a dry solids basis. The composition may contain a biocide and less than 15 wt.% silyl ester copolymers other than (A) and (B). When combined, (A) and (B) may have a glass transition temperature of more than 10ºC and less than 70ºC.