Patent GB-1424657-A (GB)
Title: Emulsion polymerzation method to produce a polymeric styrene- acrylonitrile and/or methylmethacrylate-polyorganosiloxane composition and product
IPC: C08F283/12
Filed: 1974-04-24
Abstract: 1424657 Styrene-grafted polyorganosiloxanes DOW CORNING CORP 24 April 1974 [31 Jan 1974] 17874/74 Headings C3G and C3T A styrenic copolymer composition consists essentially of a continuous copolymer matrix having copolymer units derived from (i) styrene, alpha-methylstyrene and ring substituted chlorinated styrene and from (ii) acrylonitrile, methacrylonitrile, methyl methacrylate or a mixture of one of the said nitriles and methyl methacrylate, having dispersed therein gelled particles which are essentially free of inclusions of free styrenic copolymer, which have an average particle size of from 1000 to 10,000 Š where at least 50% fall within said particle size range, said gelled particles consisting of polyorganosiloxane and styrenic copolymer grafted to polyorganosiloxane, wherein said particles are present in an amount sufficient to provide a polyorganosiloxane gel ratio of at least 0.65, said polyorganosiloxane having units of the formulµ R 2 SiO, RSiO 1-5 , R 3 SiO 0-5  and SiO 2 , wherein there is for each 100 moles of R 2 SiO units, from 0 to 12 moles of RSiO 1À5  units, from 0 to 1.5 moles of R 3 SiO 0À5  units and from 0 to 5 moles of SiO 2  units, wherein R is a monovalent radical selected from methyl, phenyl, vinyl and allyl where at least 60% of the R groups are methyl and 0.5 to 8% are vinyl or allyl, said polyorganosiloxane in the ungrafted state having a weight average molecular weight of at least 10,000, the amount of polyorganosiloxane being from 5 to 70% by weight based on the total weight of the styrenic copolymer composition, said copolymer units providing from 95 to 30% by weight of said composition in a ratio of 10 to 95% by weight of styrene units, 0 to 60% of nitrile units and 0 to 70% of methyl methacrylate units, the said styrenic copolymer composition having a room temperature notched Izod impact strength of greater than 1-0 foot pounds per inch of notch, wherein the notch is 45 degrees and 0-1 inch deep for a compression moulded sample. The styrenic copolymer composition is produced by polymerizing the said monomers in an aqueous emulsion of the polyorganosiloxane comprising a redox polymerization catalyst. Examples are given in which (a) emulsified polyorganosiloxanes prepared from (i) mixed polydimethylsiloxane cyclics, mixed polymethyl vinyl siloxane cyclics and tetraethoxy silane or methyltrimethoxy silane or (ii) a mixture of the said mixed cyclics are grafted with styrene and acrylonitrile using a cumene hydroperoxide/dextrose/ferrous sulphate heptahydrate catalyst system; (b) emulsified polyorganosiloxanes prepared from the said mixture of mixed cyclics is grafted with styrene and methyl methacrylate as in (a); and (c) emulsified polyorganosiloxanes prepared from mixed polydimethylsiloxane cyclics, mixed polymethylvinylsiloxane cyclics and tetraethoxysilane are grafted with styrene, alpha-methylstyrene and acrylonitrile as in (a). The copolymer compositions produced are blended with styreneacrylonitrile copolymer.