Process for manufacturing polyolefin films

摘要

A process for manufacturing a film of ultra-high molecular weight polyolefin comprising: (a) subjecting a starting ultra-high molecular weight polyolefin with a weight average molecular weight of at least 500 000 gram/mole in powder form to a compacting step using an isobaric press; and (b) subjecting the compacted polyolefin to a rolling step and at least one stretching step under such conditions that at no point during the processing of the polymer its temperature is raised to a value above its melting point. The process allows for the manufacture of ultra-high molecular weight polyolefin films of high quality.

主权项

1. A process for manufacturing a homogeneous film of ultra-high molecular weight polyolefin comprising:
applying a starting ultra-high molecular weight polyolefin with a weight average molecular weight of at least 500,000 gram/mole in powder form on a releasable support belt at a distance upstream from an isobaric double belt press comprising a lower belt, an upper belt on top of the lower belt, and pressure cushions to apply pressure to the polyolefin at a compaction zone between the lower and upper belts; preheating the support belt to increase a temperature of the ultra-high molecular weight polyolefin above a softening point of the ultra-high molecular weight polyolefin before entering the compaction zone; subsequently feeding the support belt with the ultra-high molecular weight polyolefin into the compaction zone between the upper and lower belts of the isobaric press; subjecting the support belt with the ultra-high molecular weight polyolefin to a compacting step using the isobaric press, wherein the compacting step is carried out at a temperature of at least 1° C. below an unconstrained melting point of the polyolefin and wherein the temperature is maintained within a temperature window of 2° C. to form a single layer film of compacted polyolefin; discharging the support belt and the single layer film of compacted polyolefin from the upper and lower belts of the isobaric press; separating the film of compacted polyolefin from the support belt; and subjecting the single layer film of compacted polyolefin to a rolling step and at least one stretching step at a temperature of at least 1° C. below the melting point of the polyolefin under process conditions.