PROCESS FOR PRODUCING STRETCHED ARTICLE OF ULTRAHIGH- MOLECULAR WEIGHT POLYETHYLENE

摘要

A process for producing a stretched article of ultrahigh-molecular-weight polyethylene; which comprises (1) melt-kneading a mixture composed of (A) 15 to 80 parts by weight, per 100 parts by weight of components (A) and (B) combined, of ultrahigh-molecular-weight polyethylene having an inherent viscosity ¢n! of at least 5 dl/g, and (B) 85 to 20 parts by weight, per 100 parts by weight of components (A) and (B) combined, of an aliphatic compound (b1) of at least 8 carbon atoms having a melting point of at least 10.degree.C and a boiling point of at least 130.degree.C, wherein up to 80% by weight of the aliphatic compound (b1) may be replaced by a low softening point hydrocarbon polymer (b2) having a softening point of not more than 130.degree.C and a weight average molecular weight (Mw) of not more than 2,000, in a screw extruder while maintaining the mixture at a temperature ranging from the molting point of the mixture to 300.degree.C, (2) melt-extruding the molten mixture through a die kept at a temperature ranging from the melting point of the mixture to 300.degree.C, (3) cooling the resulting unstretched extrudate to solidify it, and (4) subjecting the unstretched solidified extrudate to a stretching treatment at a temperature ranging from the melting point or component (B) to a point 20.degree.C above the melting point of the mixture at a stretch ratio of either at least about 3:1 when step (2) is carried out while a draft is applied to the unstretched extrudate or at least about 10:1 when step (2) is carried out in the absence or a draft.