lt of a polymerizable mixture of phosphates of each of the formulae OR THEIR PARTIAL ALKYLENE OXIDE ADDITION PRODUCTS, IN WHICH R1 is hydrogen or methyl, R2 is an alkylene or halogenated alkylene group, B is a polymerizable monomer and C is an unsaturated polyester, whereby a water-in-oil emulsion is prepared, adding a polymerization catalyst to the emulsion and curing the emulsion.