Process for the preparation of polymer dispersions

A process for the preparation of a dispersion of a condensation polymer in which the links between the reactants which form the polymer involve atoms other than carbon and in which a low molecular weight by-product is eliminated during the polymerisation reaction by which said polymer is made in an organic liquid medium in which the polymer is insoluble, the process comprising heating in the said liquid medium at the polymerisation temperature one or more condensation polymer-forming reactants, the reactant or at least one of the reactants being present in the liquid disperse phase of an emulsion of which the liquid continuous phase is constituted by the aforesaid liquid medium, said reactant being selected from the group consisting of a reactant which is liquid at normal temperature, a reactant which is melted by heating in the organic liquid medium at a temperature not higher than the polymerisation temperature, and a reactant which is a solid which cannot be melted at the reaction temperature and which is dissolved in a second, inert liquid which is substantially immiscible with the organic liquid medium, there being also present dissolved in the said liquid medium a polymeric material having a single polymer chain of molecular weight between 1000 and 20,000 which carries at least one reactive group capable of taking part in the condensation polymer-forming reaction, said single polymer chain being a homopolymer or a random copolymer but not a block or graft copolymer.