Cross-linkable polymer composition

A polymerization process which includes the steps of:

• (a) polymerizing a mixture of ethylenically unsaturated monomers, at least 70% of all ethylenically unsaturated bonds of the monomers being of a methacrylic nature, in the presence of one or more chain transfer agents of the formula
• 3
• wherein R1 and, if present, each R2 are, independently, the same or different and selected from conventional radical stabilizing groups, n is, on average, 0-10, to form a first polymer with unsaturated carbon-carbon end groups, said first polymer being essentially free of organic solvents and said monomers being selected such that the first polymer is water-soluble or water-dispersible;
• and
• (b) aqueous emulsion polymerizing a mixture comprising ethylenically unsaturated monomers in the presence of the first polymer to form a dispersion of a water-insoluble second polymer.