Shaped polyethylene articles of intermediate molecular weight and high modulus
First Claim
1. A process for producing shaped polyethylene articles which comprises the steps of:
- (a) forming a solution of polyethylene in a first solvent, said polyethylene having a weight average molecular weight between about 200,000 and 4,000,000 kilograms/kg mole;
(b) extruding said solution through an apertures to form a solution product;
(c) stretching the solution product above the temperature at which a gel will form, at a stretch ratio of at least about 3;
1;
(d) cooling the solution product to form a first gel containing first solvent;
(e) extracting the first solvent form the first gel with a second solvent to form a second gel containing second solvent, substantially free of the first solvent;
(f) drying the gel containing the second solvent to form a xerogel substantially free of solvent; and
,(g) stretching at least one of the first gel,the second gel, and the xerogel, the total stretch ratio being sufficient to produce a polyethylene article having a tenacity of at least about 13 grams/denier and a modulus of at least about 350 grams/denier.
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Accused Products
Abstract
Solutions of intermediate molecular weight polymers from about 200,000 to about 4,000,000, such as polyethylene, in a relatively non-volatile solvent are extruded through an aperture at constant concentration and thereafter stretched at a ratio of at least about 3:1 prior to cooling to form a first gel. The first gels are extracted with a volatile solvent to form a second gel, and the second gel is dried to form a low porosity xerogel. Stretching occurs with any one or more of the first gel, second gel or xerogel. The polyethylene products produced by our process include products having a molecular weight between about 200,000 and about 4,000,000 a tenacity of at least about 13 grams/denier, a modulus of at least about 350 gram/denier, a porosity of less than 10% by volume, a crystalline orientation function of at least about 0.95, and a main melting temperature of at least about 140° C.
106 Citations
20 Claims
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1. A process for producing shaped polyethylene articles which comprises the steps of:
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(a) forming a solution of polyethylene in a first solvent, said polyethylene having a weight average molecular weight between about 200,000 and 4,000,000 kilograms/kg mole; (b) extruding said solution through an apertures to form a solution product; (c) stretching the solution product above the temperature at which a gel will form, at a stretch ratio of at least about 3;
1;(d) cooling the solution product to form a first gel containing first solvent; (e) extracting the first solvent form the first gel with a second solvent to form a second gel containing second solvent, substantially free of the first solvent; (f) drying the gel containing the second solvent to form a xerogel substantially free of solvent; and
,(g) stretching at least one of the first gel, the second gel, and the xerogel, the total stretch ratio being sufficient to produce a polyethylene article having a tenacity of at least about 13 grams/denier and a modulus of at least about 350 grams/denier. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification