Terpolymérisation acrylonitrile‐styène‐acrylate de méthyle, 2. Synthèse de terpolymères homogènes en composition par polymérisation en émulsion

Previous Kinetic studies of the emulsion polymerisation of the three component system acrylonitrile (A) — styrene (S) — methyl acrylate (M) have shown that S is much more reactive than A and M, which have practically the same reactivities. As a consequence, in batch process a large copolymer composition drift is observed versus conversion. To avoid this damageable drift, two techniques were investigated, to get homogeneous macromolecules. (1) Application of the well known “semi‐continuous technique” which appeared not to be totally satisfactory, since the initial batch polymer fraction generally has a composition different from the further polymer when the monomer feed is added under starving conditions; a mixture of various macromolecules is the result. (2) The use of the composition controlled reactor, developed in this laboratory, which consists in a continuous monitored readjustment of monomer feed composition. However, due to the heterogeneous medium of an emulsion copolymerization, the copolymer exerts a small chemical heterogeneity which may be practically negligible at high monomer/water ratio. It is finally proposed that a thermodynamic approach might overcome such a behaviour and insure an actual control of the copolymer composition.