PROCESS FOR PRODUCING HIGH TENACITY, HIGH MODULUS CRYSTALLINE THERMOPLASTIC ARTICLE AND NOVEL PRODUCT FIBERS

摘要

Prodn. of novel high strength, high modulus thermoplastic articles of indefinite length (pref. fibres) comprises (a) extruding a soln. in a first solvent of crystalline polyethylene (PE), polypropylene (PP), polycocymethylene, polybutene-1, polyvinylidene fluoride or poly-4-Me-pentene-1 of wt. average mol. length (7-71) times 10 power 4 backbone atoms through an aperture at constant concn. and without temp. loss; (b) cooling the soln. adjacent to and downstream of the aperture so as to form a rubbery gel contg. the first solvent; (c) extracting this gel with a second solvent to form a gel free of the first solvent; and (d) drying this second gel to form a xerogel free of both solvents. At least one of the gels is stretched at a total stretch ratio depending on the polymer; for polyethylene the ratio is one sufficient to give tenacity at least 20 g/den. and modulus at least 600 g/den.; for polypropylene the ratio is sufficient to give tenacity at least 10 g/den. and modulus at least 180 g/den.; and for the other polymers the ratio is at least 10:1. The claimed prods. are polyethylene and polypropylene fibres with specified properties and also specified polyolefin gel fibres. The fibres are of high strength, extraordinarily high modulus and great toughness. They are dimensionally and hydrolytically stable and creep resistant under sustained loads and so are esp. useful in marine ropes and cables, e.g. mooring lines. Other uses are as reinforcement pressure vessels, hoses, belts, automobiles or building construction.