Abstract: A process for producing an aqueous dispersion of a thermosettable, solid, water insoluble, addition polymer which comprises polymerizing in water at least one .alpha.,.beta.-ethylenically unsaturated main monomer, which is very slightly soluble in water, with at least one .alpha.,.beta.-ethylenically unsaturated monomer containing a reactive group in the presence of a material selected from the group consisting of surface active agents, suspension agents and mixtures thereof and water soluble, polymerizable ionic monomers consisting of sulpho esters of the formula:R -- CO.sub.2 -- Q -- SO.sub.3 Mwherein R is selected from the group consisting of vinyl and .alpha.-substituted vinyl groups, Q is a divalent hydrocarbon radical having its valence bonds on different carbon atoms and M is a cation selected from the group consisting of sodium, potassium, lithium, ammonium, substituted ammonium compounds of the formula NR'.sub.4 wherein R' is alkyl (C.sub.1 -C.sub.4) or alkanolamine (C.sub.1 -C.sub.