PROCESS FOR OBTAINING AQUEOUS POLYMERIC DISPERSIONS

摘要

A process for obtaining an aqueous polymer dispersion comprising the following steps:- formation of a monomer preemulsion in water by using surfactants;-transfer into the reactor of the basic charge containing a surfactant solution and a part of the preemulsion;- step C.1 polymerization start; - step C.2 polymerization of the monomeric mixture;- step C.3 removal of the residual monomers;wherein: A) from the start and up to a time in the range from -40% to +20% with respect to the instant wherein the polydispersity index of the particle sizes increases, the preemulsion is fed and the surfactant concentration in the reactor is not higher than 0.7% by weight;B) subsequently and till the polymerisation end, the remaining part of preemulsion is fed and the surfactant concentration in the dispersion is higher than that in step A) but lower than 5% by weight with respect to the dispersion weight.