Patent ID: 8747715
Filing Date: 2014-06-10
Classification: B29C,D01D,D01F,F41H

Abstract:
1. A process for producing gel spun yarn made from ultra high molecular weight polyethylene (UHMW PE), the process comprising the steps of: feeding a slurry that comprises an UHMW PE and a spinning solvent to an extruder to produce a liquid mixture, the UHMW PE having an intrinsic viscosity (IV) in decalin at 135° C. of at least about 30 dl/g; wherein a 10 wt. % solution of said UHMW PE dissolved in mineral oil at 250° C. has a Cogswell extensional viscosity (λ) in accordance with the formula: passing the liquid mixture through a heated vessel to form a homogeneous solution comprising the UHMW PE and the spinning solvent; providing the solution from the heated vessel to a spinneret to form a solution yarn; drawing the solution yarn that issues from the spinneret at a draw ratio of from about 1.1:1 to about 30:1 to form a drawn solution yarn; cooling the drawn solution yarn to a temperature below the gel point of the UHMW PE polymer to form a gel yarn; drawing the gel yarn in one or more stages at a first draw ratio DR1 of from about 1.1:1 to about 30:1; drawing the gel yarn at a second draw ratio DR2; removing spinning solvent from the gel yarn in a solvent removal device to form a dry yarn; drawing the dry yarn at a third draw ratio DR3 in at least one stage to form a partially oriented yarn; the partially oriented yarn having an intrinsic viscosity of greater than about 19 dl/g; transferring the partially oriented yarn to a post drawing operation; and drawing the partially oriented yarn at a post drawing temperature in the post drawing operation to a fourth draw ratio DR4 of from about 1.8:1 to about 15:1 to form a highly oriented yarn product having a tenacity of greater than about 45 g/d (40.5 g/dtex) and a modulus of greater than about 1400 g/d.