Patent GB-994924-A (GB)
Title: High polymer compositions having high light transmission and toughness
IPC: C08L33/10
Filed: 1963-07-30
Abstract: Transparent thermoplastic moulding compositions comprise an admixture of (1) from 50 to 95 parts by weight of a polymer composed of at least one polymerizable monomer containing ethylenic unsaturation and (2) from 5 to 50 parts by weight of a natural or synthetic rubber having grafted thereon a polymer composed of at least one monomer possessing ethylenic unsaturation, the refractive indices of said components (1) and (2) being within 0.009 of one another, both components (1) and (2) being transparent.  Methods are described for obtaining components (1) and (2) with the desired refractive index agreement; these methods are based on correlating the various refractive indices of the homo- and co-polymerized monomers and the rubbers used in preparing the components (1) and (2). Component (1) is preferably a polymer containing at least 50% by weight of an alkyl methacrylate in which the alkyl group contains from 1 to 6 carbon atoms. These esters may be copolymerized with ethylenically unsaturated alcohol esters, esters of ethylenically unsaturated acids, vinyl cyclic compounds including vinyl aromatic hydrocarbons, ethylenically unsaturated ethers, ethylenically unsaturated amides and their N-substituted derivatives, acrylonitrile and substituted acrylonitriles, ethylenically unsaturated ketones, ethylene, vinyl halides and vinylidene halides; or any of these monomers can instead be polymerized or copolymerized without the methacrylate esters.  As the parent rubber of component (2), there may be used polybutadiene, poly(methyl methacrylate/butadiene), poly(styrene/butadiene), natural or synthetic polyisoprene, polyisobutylene, poly(isobutylene/isoprene), poly(acrylonitrile/butadiene), poly(alkyl acrylate), and rubbery polyurethane and poly(ethylene/propylene). The monomer which is grafted on to the rubber may be selected from any of those set forth above in respect of component (1), the specified alkyl methacrylates again being preferred.  The polymer components may have incorporated therein light stabilizers, heat stabilizers, antioxidants, lubricants, plasticizers, pigments, fillers and dyes. The components (1) and (2) may be blended in any known manner; the preferred procedure comprises treating a stream of each of the components, i.e. a polymer solution and a rubbery latex, in a devolatilizer-extruder.  In the examples, component (2) is polybutadiene, styrene-butadiene copolymer, polyisoprene or acrylonitrile-butadiene copolymer, each of which has grafted thereon a polymer derived from a mixture of methyl methacrylate, styrene and acrylonitrile, or polybutadiene having grafted thereon a polymer of a mixture of methyl methacrylate and acrylonitrile. Component (1) is a polymer of the monomers used for grafting in the preparation of the corresponding component (2), i.e. a methyl methacrylate-styrene-acrylonitrile terpolymer or a methyl methacrylate-acrylonitrile copolymer.  In the examples, component (2) is obtained by graft polymerizing in aqueous emulsion in the presence of cumene hydroperoxide and dihydroxyacetone; component (1) is obtained by polymerizing the monomers (a) in toluene in the presence of 2,5-dimethyl - 2,5 - di - (t. - butylperoxy) - hexane and lauryl mercaptan, (b) in xylene in the presence of 2,5-dimethyl-2,5-di-(t.-butylperoxy)-hexane and dodecyl mercaptan, and (c) in aqueous emulsion in the presence of ammonium persulphate and dodecyl mercaptan.