GB1409282A - Elastomer production - Google Patents

Abstract

1409282 Elastomeric materials IMPERIAL CHEMICAL INDUSTRIES Ltd 11 April 1973 [16 May 1972] 22849/72 Headings C3R and C3P Elastomeric materials are prepared from a homogeneous composition comprising 60 to 95% by weight of the precursors of a cross-linked polyurethane and 40 to 5% by weight of at least one polymerizable ethylenically unsaturated material, the reaction of the polyurethane precursors being substantially completed before polymerization of the unsaturated material is allowed to proceed to the extent that the polymer so produced forms a separate phase, polymerization of the unsaturated material thereafter being completed, the precursors when reacted alone in the absence of the unsaturated material being capable of forming an elastomeric polyurethane having a glass-rubber transition temperature of 25‹ C. or less and the ethylenically unsaturated material containing at least one unsaturated material which contains two or more ethylenically unsaturated groups and being selected so as to produce, after polymerization, a cross-linked polymer having on average a M.W. between cross-links of not greater than 2500. The precursors of the polyurethane preferably do not contain groups reactive with the ethylenically unsaturated material and comprise at least one polyfunctional compound containing isocyanate-reactive groups and at least one polyisocyanate. The ethylenically unsaturated material comprises a polyfunctional ethylenically unsaturated monomer optionally in admixture with a monofunctional ethylenically unsaturated monomer. Suitable polyfunctional ethylenically unsaturated monomers include divinyl benzene, trivinyl benzene, divinyl toluene, divinyl naphthalene and unsaturated esters especially bis-esters of acrylic or methacrylic acid with a glycol, e.g. ethylene glycol dimethacrylate. Polyurethane-forming catalysts and free-radical initiators may be included in the reaction mixture. In a typical example, oxypropylated trimethylol propane, poly-(propylene glycol) and 4,4<SP>1</SP>-diphenylmethane diisocyanate are mixed and to the resulting solution is added ethylene glycol dimethacrylate, t-butyl peroctoate and dibutyl tin dilaurate. The solution is poured into a mould, the polyurethane reaction is effected and the temperature raised to polymerize the ethylene glycol dimethacrylate.