GB851605A - Novel drawn polymers and process for the production thereof - Google Patents

Abstract

A drawn polymer comprises a cold-drawn and preshrunk olefinic polymer having a drawn thickness within the range 0,1-100 mils, having not more than 5% shrinkage at up to 250 DEG F. and having a tensile strength of at least 30,000 p.s.i. at a temperature within 65 to 100 DEG F. Specified polymers are those of ethylene, propylene, 1-butene, 1-pentane and 1-berene and their interpolymers prepared by the low-pressure processes using as catalyst either chromium oxide associated with at least one of the porous oxides silica, alumina, zirconia and thoria or a mixture of a compound of the formula Al R3, where R is hydrogen or a saturated aliphatic, cycloaliphatic or aromatic hydrocarbon radical, and a compound of titanium, zirconium, chromium or molybdenum, e.g. the halides or tetra-alkoxides and tetravalent titanium salts of organic carboxylic acids. The drawn polymer may be in the form of a translucent or transparent filament or film and may be made by extruding or otherwise extending an olefin polymer having a density of at least 0,94 and a crystallinity of at least 70%, cold drawing this polymer at between room and softening temperature, and heating this cold-drawn polymer at below its softening point. The extended polymer may be quenched, e.g. in a quench medium at 32-150 DEG F., before being cold-drawn, preferably at 100-260 DEG F. and especially while immersed in an inert fluid at 225-260 DEG F. The cold-drawn polymer may be heated at above 160 DEG F., e.g. in boiling water for 5 to 30 minutes. Specifications 790,195 and 804,641 are referred to.