| 摘要 |
Impact - resistant thermoplastic moulding compositions comprise a homogeneous mixture of (A) a graft copolymer consisting of (1) an elastomeric copolymer of di-n-butyl fumarate and butadiene in a weight ratio of from 80:20 to 40:60 to which there has been grafted (2) 20 to 100% by weight, with reference to component (1), of either styrene or a styrene-acrylonitrile mixture containing up to 30% by weight of acrylonitrile; and (B) a copolymer of styrene and acrylonitrile in a weight ratio of from 60:40 to 90:10, the weight ratio of (A) to (B) being from 70:30 to 90:10 with the proviso that component (1) is present in an amount of 10 to 35% by weight with reference to the total polymer mixture. Component (1) may additionally comprise up to 20% by weight of units of another monomer, e.g. acrylic and methacrylic esters, vinyl ketones, vinyl esters and vinyl ethers, specified compounds being acrylonitrile, methyl, ethyl and n-butyl acrylate, vinyl acetate and propionate, and methyl isopropenyl ketone. The preparation of component (1) and the subsequent graft polymerization are carried out in aqueous emulsion using anionic emulsifiers and initiators such as persulphates, peroxides, hydroperoxides and azo-compounds (e.g. potassium persulphate, benzoyl peroxide, lauroyl peroxide or azo-diisobutyronitrile) or redox systems (e.g. cumene or t-butylcumene hydroperoxide with sodium hydroxymethyl sulphinate); activators such as triethanolamine or ferrous ethylenediamine tetraacetic acid complex may also be present. The polymers (A) and (B) can be combined by mixing together aqueous dispersions of each, or an aqueous dispersion of (A) with a suspension of (B) in methanol; the polymers may also be mixed in powder form, e.g. in an extruder or on mixing rolls. In the examples, component (1) is prepared by polymerizing di-n-butyl fumarate and butadiene, with or without acrylonitrile or methyl isopropyl ketone, in aqueous emulsion containing sodium paraffin sulphonate or sodium alkyl sulphonate as emulsifier and a redox catalyst, monomers and various catalyst components being added during the course of polymerization.
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