Composition containing ethylene-vinyl alcohol copolymer, and preparation method thereof

Abstract

The invention relates to a composition containing an ethylene-vinyl alcohol copolymer, and a preparation method thereof. The composition comprises 90-95wt% of the ethylene-vinyl alcohol copolymer and 5-10wt% of an ethylene-vinyl alcohol micro-molecular oligopolymer, and the molecular structure of the ethylene-vinyl alcohol copolymer contains 1-2%mol of a 1,2-glycol structure. The preparation method of the composition comprises the following steps: polymerizing 50-80 parts of a vinyl acetate monomer, 20-50 parts of an alcoholic solvent and 0.0001-0.001 parts of an initiator at 80-140DEG C under 30-70kg/cm<2>, and carrying out a saponification reaction to obtain the composition. The molecular structure of the composition contains 1-2%mol of the 1,2-glycol structure having a viscosity reducing effect, and also contains 5-10mol% of the micro-molecular oligopolymer having a plasticising effect, so it is in favor of the melting processing property of the ethylene-vinyl alcohol copolymer, and the problems of the bad repeated utilization of the routine ethylene-vinyl alcohol copolymer, the easy migration of inorganic salt additives to the surface of the polymer, and environment pollution are overcome. The preparation method has the advantages of simple process, safety, environmental protection, high product quality, and suitableness for industrial production.

Description

technical field [0001] The present invention relates to a composition containing ethylene-vinyl alcohol copolymer, in particular to a composition containing ethylene-vinyl alcohol copolymer with improved melting processability and a preparation method thereof. Background technique [0002] Ethylene-vinyl alcohol copolymer (EVOH) is a crystalline polymer with a chain molecular structure. Its properties mainly depend on the mole fraction of comonomers, and its gas barrier properties, moisture barrier properties and processing properties change with the ethylene content. When the ethylene content increases, the gas barrier properties decrease, the moisture resistance performance improves, and the resin is easier to process . If the ethylene content is less than 20%, stable melt processability cannot be guaranteed, and if the ethylene content is greater than 50%, the gas barrier properties will be severely damaged. Therefore, the ethylene content in EVOH is generally kept betwe...

AI Technical Summary

Problems solved by technology

Ethylene-vinyl alcohol copolymers have both the processability of polyethylene and the high barrier properties of vinyl alcohol polymers, but in order to ensure sufficient gas barrier properties, EVOH usually contains vinyl alcohol structures, and vinyl alcohol polymers Due to the existence of a large number of hydroxyl groups, the crystallinity is high, and the melting point is high, close to the decomposition temperature, so the dehydration of hydroxyl groups is easy to occur during melt processing, which will deteriorate the quality of the polymer.

The increase of the vinyl alcohol unit content can increase the macromolecular force and improve the barrier property, but its melt processing stability decreases. Although the melt processability can be improved to a certain extent by adding some additives afterward, the external additives have a certain effect. To a certain extent, the gas barrier properties of the polymer will inevitably be reduced, and it will migrate to the surface with time, causing certain pollution

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