GB807198A - Improvements in or relating to polymeric materials - Google Patents

Abstract

A copolymer of vinyl or allyl salicylate and ethylene, containing at least 50 per cent by weight of polymerized ethylene and from 3 to 50 per cent polymerized salicylate, prepared in the presence of a free-radical producing catalyst is purified by solvent extraction and may be fabricated as a sheet, film or filament, or used in solution as a coating composition. The copolymer may contain, up to 20 per cent of the total polymer, polymers of vinyl monomers such as isobutylene, vinyl acetate, 1,3-butadiene, and methyl methacrylate. The polymerization may be by emulsion methods using catalysts such as ammonium persulphate, hydrogen and benzoyl peroxide and azonitriles and in Example I ethylene is added under pressure to an emulsion of vinyl salicylate in water containing potassium dihydrogen phosphate, sodium dodecylsulphate and benzoyl peroxide adjusted to a pH of 6. After heating under pressure a white spongy copolymer is separated by steam distillation. The monomers may be polymerized (Examples II to X) in solution, in benzene or chlorobenzene, with di-t-butyl peroxide, or t-butyl alcohol with a ,a 1-azo diisobutyronitrile, and the products steam distilled and extracted with acetone. The copolymers are soluble in benzene, toluene, xylenes, tetrahydronaphthalene, di-n-butyl ether, tetrahydrofurane and cyclohexanone, and may be cast, hot pressed, moulded or extruded as shaped articles such as sheets, films or filaments. The copolymers may be cross-linked by chelation with polyvalent metals such as aluminium, zirconium, zinc, magnesium, beryllium, titanium, copper, manganese, iron, cobalt, nickel, chromium, cadmium, boron, tin, xandium, vanadium and bismuth by (1) transchelation using the process described in Specification 791,325, by treating with a chelate of a polyvalent metal and a volatile chelating agent (listed), and the mixtures may be cross-linked by evaporation (see Examples XI-XX and XXII to XXIV); (2) by alcoholysis (Example XXI) in which the copolymer is reacted with a polyvalent metal alcoholate prepared from the above metals and volatile alkanols. The process is irreversible and can be carried out at room temperatures or at 100-200 DEG C. to maintain plasticity sufficient for shaping, or in solution for example benzene or toluene; (3) by treating the copolymer, preferably in solution, with a solution of a metal salt or oxide dissolved in methanol, aqueous methanol or water. Salts such as cupric, ferric or aluminium acetates and zinc propionate are preferred and the chelate is separated as an insoluble precipitate. The chelates may also be formed as sheets, films or filaments or other shaped articles, either concurrently with the removal of the volatile chelating agent, or at high temperatures or from solutions in, for example, benzene, toluene, xylenes, methanol, ethanol, n-butanol, di-n-butyl ether, tetrahydrofurane, methyl isobutyl ketone or cyclohexanone. In an alternative method the unchelated shaped copolymer is treated with a polyvalent chelating metal alcoholate in a suitable solvent and a surface chelation is obtained. A coating composition may comprise the unchelated copolymers in solution in a volatile solvent which may optionally include a polyvalent chelating metal. The products may be used as wrapping materials for food, books, wire and fabric and as ultra-violet light screens and protective coatings for paints, and have good resistance to embittlement at low temperatures. The chelated copolymers have enhanced strength, are resistant to heat and organic solvents and hence have wider application in the above fields. U.S.A. Specification 2,299,862 is referred to.ALSO:Vinyl salicylate is prepared by reacting salicylic acid with excess vinyl acetate in the presence of mercuric acetate and concentrated sulphuric acid. The slurry is stirred at 25 DEG C. for five days, filtered and sodium acetate added. Excess vinyl acetate is removed at 25 DEG C. under reduced pressure and the residue filtered. After washing with benzene, the filtrate is distilled under reduced pressure and the 62-85 DEG C. fraction refractionated to yield vinyl salicylate boiling at 72-73 DEG C. at 2.5 mm. pressure. Allyl salicylate is prepared by ester-interchange between methyl salicylate and allyl alcohol by refluxing with a sodium methylate catalyst. Excess allyl alcohol is removed by distillation under reduced pressure and a solution in diethyl ether washed and redistilled to give allyl salicylate boiling at 82 DEG C. at 2 mm. pressure. Specification 791,325, [Group IV (a)], and U.S.A. Specification 2,299,862 are referred to.