Emulsion graft-copolymers with high grafting yield - obtd. by pre-activating aq. emulsion of graft substrate with initiator and oxygen, before adding the grafting monomers, etc.

摘要

A particulate graft copolymer (I) is claimed, esp. a latex for the prodn. of impact-modified thermoplastic moulding materials; (I) is obtd. by radical polymerisation of monomer(s) (II) in an aq. emulsion of a graft substrate (III); the process involves (a) adding to the emulsion of (III) cpds. (IV) which produce free radicals at above room temp., (b) passing an oxygen-contg. gas into the emulsion and (c) heating to the decompsn. temp. of (IV), and then adding (II) together with a reducing agent; steps (a)-(c) can be carried out simultaneously or separately in any order. (III) is a rubber with Tg below 0 deg.C, pref. a polydiene or an elastomeric poly-(-18C, pref. 4-8C alkyl)-acrylate; (II) is styrene, alpha-methylstyrene, alkyl (meth)acrylate or (meth)acrylonitrile, pref. styrene, MMA or acrylonitrile; (IV) is a water-soluble initiator, pref. a per-disulphate, and the oxygen-contg. gas is air; the emulsion is heated to 30-90 deg.C; the reducing agent is an inorganic sulphite, bisulphite or sulphoxylate, and is added together with a transition metal salt. USE/ADVANTAGE - Pre-activation of the graft substrate with initiator and oxygen results in an increased grafting yield and therefore an increased impact-modifying effect. The prods. (I) are useful as moulding materials for the prodn. of window sections, garden furniture, boats, signs, automobile parts, toys, etc.