Abstract: A process for producing carbo-chain homopolymers, block- and random copolymers of conjugated dienes and vinylaromatic monomers comprising polymerization of dienes, vinyl- or di-vinylaromatic monomers or copolymerization thereof in a medium of a hydrocarbon solvent at a temperature ranging from -30.degree. to +150.degree. C. in the presence of an organolithium catalyst of the formula R(Li).sub.x, wherein R is a hydrocarbon radical or a diene polymer, x is an integer of from 1 to 4, and a modifying additive which is a compound comprising a product of interaction between a phenolamine resin and an alkali metal and having the general formula: ##STR1## wherein n is an integer of from 1 to 10;M is sodium or potassium;R is an alkyl with 2 to 20 carbon atoms or an arylalkyl with 7 to 20 carbon atoms;R.sub.1 is an alkyl with 1 to 6 carbon atoms, an arylalkyl with 7 to 9 carbon atoms or hydrogen;this modifying additive is used in an amount of from 0.07 to 2.0 g/equiv. per one g/equiv. of active lithium.

Abstract: A process for producing high-impact polystyrene which comprises polymerization of styrene in the presence of a reinforcing agent, i.e. a conjugated diolefin polymer, random copolymer, graft-copolymer or block-copolymer of a conjugated diolefin with styrene or a mixture of said copolymers and an anionic catalyst based on organic derivatives of alkali metals or adducts thereof in a medium of inert hydrocarbon solvents such as aliphatic, cycloaliphatic and aromatic solvents or mixtures thereof. On completion of polymerization the resulting polymer is subjected to cross-linking by means of peroxide compounds or redox systems, followed by isolation of the desired product.The process for producing high-impact polystyrene according to the present invention makes it possible to shorten the technological cycle due to increased polymerization rate, to facilitate production technology, and to manufacture polystyrene with improved properties.