Low density ion-modified polyethylene (LDPE) film and process for its preparation

摘要

An ionomer-modified polyethylene, that is, an ethylene/carboxylic acid copolymer in which at least some of the acidic groups are neutralized, is preparable by a one-stage procedure by reacting ethylene with unsaturated carboxylic acids and salts of such unsaturated carboxylic acids in the presence of a free radical polymerization initiator, under the conditions employed in the production of high pressure polyethylene (LDPE). The concentration of salt which is incorporated in the polymer is kept at no more than 1 mol %, relative to converted ethylene and other comonomers respectively. Advantageously, the unsaturated carboxylic acids and their salts are added to the copolymerization reaction as a homogeneous solution in a suitable solvent. The ionomer-modified polyethylenes based on low density polyethylene (LDPE), in which 30-95% of the carboxyl groups are neutralized and the neutralized carboxyl groups represent 0.1-0.8 mol % of the total number of moles of all monomers are suitable as a film material having high strength, good drawability and high tear propagation resistance.