GB779807A - Thermal stabilization of ethylene polymers - Google Patents

Abstract

Solid polymers or copolymers of ethylene. e.g. with styrene, vinyl chloride or acetate, vinylidene chlorofluoride and methyl methacrylate are stabilized against oxidative degradation during thermal processing by incorporating a zinc di-(saturated hydrocarbon) substituted diorthocarbamate. Compounds of the formula <FORM:0779807/IV(a)/1> where R1, R11, R111, R1111 are alkyl groups or R1 and R11 together and/or R111 and R1111 together constitute a polymethylene or alkyl polymethylene group which may contain 4 to 5 carbon atoms, may be used in up to 1 per cent by weight. Alkyl groups mentioned are methyl, ethyl, n-propyl, isopropyl, n-, sec-, iso- and t-butyl, amyl, hexyl, octyl and dodecyl groups and the polymethylene groups may be those derived from piperidine, pyrrolidine, 2-methyl pyrrolidine, hexahydrocollidines, hexahydropicolines and hexahydrolutidines. Examples are the mixed zinc salt of diethyl and dimethyldithiocarbamic acid, zinc pentamethylene-, 2-methyltetramethyl-, tetramethylene - 3 - ethylpentamethylene-, di - (sec. - amyl)-, di - (2 - ethylhexyl) dithiocarbamates. The dithiocarbamates may be incorporated as solids, or in solution in, for example, carbon disulphide, benzene, toluene or chloroform by mixing, cold milling, or extrusion or by addition to a benzene or xylene solution of polyethylene. The solution may be cast or spun into films or fibres. Articles of improved heat resistance may be obtained by moulding and subjecting the shaped article to additional heating and exposure to ultra-violet light.