GB1121885A - Modified bulk polymerisation process - Google Patents

Abstract

Acrylonitrile and a monovinyl aromatic compound are grafted on to a rubber by a process comprising (a) polymerizing with vigorous agitation in an initial polymerization zone a mixture comprising 39 to 93.1% by weight of a monovinyl aromatic compound which is styrene, an alkyl- or halogen-substituted styrene or a mixture thereof, 4-9 to 26% of acrylonitrile, 2 to 30% of rubber and 0 to 5% of additives at 60 DEG to 140 DEG C. until 10 to 45% conversion of the initial monomers to polymer is obtained; (b) passing the resulting mixture to at least one additional zone wherein said mixture is further polymerized at a temperature up to 220 DEG C. until 85 to 100% conversion of monomers to polymer is obtained; (c) passing the resulting polymer to a devolatilization zone wherein said polymer is heated to a temperature of 80 DEG to 240 DEG C. under a pressure of 0 to 760 mm. Mg abs. and (d) recovering said devolatilized polymer, during which process from 3 to 30% of an alkyl aromatic diluent having a boiling point of 100 DEG to 200 DEG C. is added to the polymerizable mixture at step (a) or step (b), the per cent by weight of said diluent being based on the weight of the total reaction mixture. Styrene, preferably together with a minor amount of alphamethyl styrene is the preferred monovinyl aromatic compound. The preferred diluent is ethyl benzene, which may be used together with another chain regulator, e.g. tert.-dodecyl mercaptan. The polymerization may be carried out in the presence of lubricants and antioxidants, e.g. the mineral oil, trisnonylphenyl phosphite and 2,6-ditert.-butyl methylphenol used in the examples, in which styrene and acrylonitrile are grafted on to polybutadiene.