GB682420A - Improvements in or relating to the polymerisation of ethylene - Google Patents

Abstract

Solid ethylene polymers are made by polymerizing liquid ethylene in bulk, solution, emulsion or dispersion, at a temperature below 9.6 DEG C. in the presence of a catalyst capable of producing free radicals at this temperature, but excluding organic azo compounds. Polymerization may be effected in batches or continuously, and the product may be obtained as beads. The catalyst may be a mixture of an oxidizing agent and a metal compound having more than one valency state together with a supplementary reducing agent for the metal compound if it is not in its lower valency state, or a metal alkyl in combination with a metal or salt having more than one valency or an azo disulphonate, e.g. of potassium and water, or nitrosoacetanilide. The oxidizing catalyst may be a peroxide, e.g. benzoyl and methyl isobutyl ketone peroxides, a persalt, e.g. ammonium persulphate, an organic hydroperoxide, e.g. 1-hydroxycyclohexyl-1-hydroperoxide, a peracid, e.g. succinic acid peroxide, an alkyl acyl peroxide, e.g. t-butyl perbenzoate, or a polyperoxide. Specified metal compounds are ferrous chloride tetrahydrate, ferric acetylacetonate, cupric sulphate, nickelous sulphate hexahydrate, silver nitrate, manganese chloride and cobaltous nitrate hexahydrate. Supplementary reducing agents mentioned are sodium bisulphite, d- or l-ascorbic acid, d-isoascorbic acid, sodium - formaldehyde - sulphoxylate dihydrate, triethanolamine, benzoin, benzenesulphinic acid, dihydroxy maleic acid, formamidine sulphinic acid, butyraldehyde, sorbose, levulose, inosose, fructose and glucose. Specified metal alkyls are sodium butyl, lithium butyl or amyl, zinc hexyl, zinc butyl, lithium butyl or amyl, zinc hexyl, zinc dibutyl, magnesium butyl and potassium octadecyl. Metals and salts which may be used in conjunction with the alkyls are nickel, e.g. on kieselguhr, cobalt, iron, platinum, copper, silver, gold, copper sulphate, copper nitrate, silver nitrate, nickel chloride, cobalt chloride and iron sulphate. Solvents for the polymerization may be methanol or t-butanol and mixtures with water. Emulsifying agents may be the potassium or sodium salts of long chain aliphatic carboxylic acids or of long chain sulphates or sulphonates, polyethylene oxide condensates and quaternary ammonium salts. The polymers have a moisture permeability of less than 10 grams of water transmitted per hour per 100 sq. metres of surface area through a one mil. thick film at 39.6 DEG C. with a 100 per cent relative humidity on one side of the film and zero on the other, a bending modulus of between 100,000-200,000 lbs./sq. inch, a melting point of 108 DEG to 128.4 DEG C. and a density of from 0.9709 to 1.096 gms./c.c. at 25 DEG C. The polymers may be used for fibres, films, sheathing for wire, chemical equipment, polishes, abrasion-resistant adjuvants for finishes and coatings, e.g. for paper and cardboard. They may also be mixed with polymers produced from gaseous ethylene, polyisobutylene, natural and synthetic rubbers, and waxes, e.g. paraffin. Specification 632,316 is referred to.