GB1332070A - Graded polymer particles - Google Patents

Abstract

1332070 Graded acrylic polymer particles FORD MOTOR CO Ltd 17 Nov 1971 [21 Dec 1970] 53427/71 Heading C3P Graded polymer particles comprise (a) a core of a crosslinked acrylic polymer derived from a major proportion of a monofunctional acrylate (i.e. an acrylate or methacrylate ester containing no reactive groups such as hydroxyl or epoxy groups) and a minor proportion of an ethylenically unsaturated monomer containing two or more non-conjugated terminal ethylenic groups; (b) an outer shell of a polymer derived from methyl methacrylate or a mixture of methyl methacrylate and one or more ethylenically unsaturated comonomers containing at least 30 mole per cent methyl methacrylate; and (c) an intermediate layer of a polymer derived from the monomer components of core (a) and shell (b). The particles generally have an average size of from 0À04 to 1 micron. They can be prepared by emulsion copolymerizing the core monomers to a conversion of from 50-90% by weight, then adding the shell monomer(s) and 'completing the emulsion polymerization. Alternatively, copolymerization of the core monomers can be carried out to completion, a mixture of core and shell monomers then added and copolymerized, and finally shell monomer(s) added and polymerized. The monofunctional acrylate in (a) is preferably a C 2 -C 8 monohydric alcohol ester of acrylic acid, e.g. n-butyl or 2-ethylhexyl acrylate; certain other acrylates such as dodecyl methacrylate and benzyl (meth)- acrylate are also useful. Suitable polyethylenically unsaturated crosslinking comonomers include alkylene di(meth)acrylates, trimethylolalkane tri(meth)acrylates, dimethylolcyclohexane dimethacrylate, (meth)allyl (meth)acrylate, diallyl esters and divinyl benzene. Additional comonomers such as styrene, alpha methyl styrene, and (meth)acrylonitrile may optionally be present in the core components. Comonomers for use in (b) include monofunctional acrylates as for (a), styrene and its substituted derivatives, acrylonitrile, methacrylonitrile, isobornyl methacrylate, diacrylates or divinyl hydrocarbons, and monomers containing a reactive group, e.g. glycidyl methacrylate, hydroxyethyl or hydroxypropyl (meth)acrylate, and acrylic or methacrylic acid. The graded polymer particles can be used to form moulded articles.