High impact polystyrene is made by (1) polymerising styrene in the presence of (a) a polymer of a conjugated diene or a random copolymer, graft polymer or block copolymer of a conjugated diene with styrene, or a mixt. of these as reinforcing agent; (b) an anionic catalyst comprising organic derivs. of alkali metals, or adducts of these; and (c) a reaction medium consisting of inert aliphatic, cycloaliphatic or aromatic hydrocarbons or mixts. of these, and (2) after the polymerisation, structuring the polymer using a per cpd. or an oxidn.-redn. system. Pref. reinforcing agent is a butadiene-styrene-butadiene block copolymer with 3-12 arms in which each arm contains 1-2 polybutadiene blocks and 1-2 polystyrene blocks and the total content of bound butadiene is 30-80 wt. After the polymerisation and before the structuring process, additional polymeric reinforcing agent can be added to the mixt. to give a polymer compsn. contg. 4-30 wt.% bound diolefin. The structuring process is pref. carried out using an organic per cpd. such as isopropylbenzenehydroperoxide, tert.butylhydroperoxide, tert.butylperoxide, dicumylperoxide, tert.butylperbenzoateperoxide, isopropylcyclohexylbenzenehydroperoxide, as oxidising agent and SO2 as reducing agent.
展开▼
