Binder for anti-fouling paints

DETAILED DESCRIPTION We claim: 1.
A self-polishing anti-fouling marine paint comprising a pigment, a biocide for marine organisms which is different from the pigment, and a film-forming polymeric binder which is hydrolysable in seawater and contains units corresponding to an ester of an olefinically unsaturated acid having the formula: ##STR8## where each Ar independently is an aryl group and R' is a hydrogen atom, an alkyl group or aryl group.
2.
An anti-fouling marine paint according to claim 1, wherein R' and each Ar are all independently aryl groups.
3.
An anti-fouling marine paint according to claim 2, wherein said polymer contains units corresponding to triphenylmethyl acrylate or methacrylate.
4.
An anti-fouling marine paint according to claim 1, wherein at least one of the groups Ar is a phenyl group substituted by one or two electron-releasing groups.
5.
An anti-fouling marine paint according to claim 4, wherein said polymer contains units corresponding to diphenyl(p-methoxyphenyl)methyl acrylate or methacrylate.
6.
An anti-fouling marine paint according to claim 1, said polymer contains 25-40 percent of units of said formula.
7.
An anti-fouling marine paint according to claim 1, wherein said polymer also contains units of an alkyl acrylate having at least two carbon atoms in the alkyl group.
8.
A paint according to claim 1, wherein said pigment comprises cuprous oxide, cuprous thiocyanate or zinc ethylene bis(dithiocarbamate).
9.
An anti-fouling marine paint comprising a pigment which is a sparingly soluble copper or zinc compound having a solubility in sea water of from 0.
5 to 10 parts per million by weight and acts as a biocide for marine organisms and a film-forming binder which is a hydrolysable polymer containing units corresponding to an ester of an olefinically unsaturated acid and having the formula ##STR9## where each Ar independently is an aryl group and R' is a hydrogen atom, an alkyl group or aryl group.
10.
A paint according to claim 9 wherein said pigment comprises cuprous oxide, cuprous thiocyanate or zinc ethylene bis(dithiocarbamate)