NOVEL COMPOSITION FOR THE PRODUCTION OF VINYLAROMATIC MATERIALS WITH IMPACT STRENGTH IMPROVED BY A STRUCTURE-MODIFYING ADDITIVE

The present invention refers to an improved composition for the production of vinyl aromatic polymers modified with rubber, in which a substantial impact resistance improvement of the final product is produced by the incorporation of a structure modifying additive in different steps of the polymerization, preferably during the process of co-continuity of phases and specially, during the inversion of phases interval. The additive is an insaturated compound of formula: wherein: R 1 , R 3 each represents a saturated or unsaturated chain from C 1 to C 18 , being equal or different from one another, R 2 , R 4 , R 5 each represent, hydrogen, halogen or a carbonated chain from C 1 to C 18 , being equal or different from one another, "n" being an integer number equal or grater than 1 and where the additive can be used either without mixing it in a concentration within the range of 0.025 to 5% in weigth, or in mixtures with low molecular weight polymers in a weight ratio preferably from 5/1 to 1/5.