초록

A process for preparing ultra-high molecular weight polyethylene (UHMWPE) multi-filament yarns having improved tensile properties and the yarns and articles thereby produced.

대표청구항 ▼

What is claimed is: 1. A process of producing a high strength polyethylene multi-filament yarn comprising the steps of: a) forming a slurry of an ultrahigh molecular weight polyethylene (UHMWPE) having an initial intrinsic viscosity (IV0) at least about 10 dl/g and an antioxidant in a solvent for s

What is claimed is: 1. A process of producing a high strength polyethylene multi-filament yarn comprising the steps of: a) forming a slurry of an ultrahigh molecular weight polyethylene (UHMWPE) having an initial intrinsic viscosity (IV0) at least about 10 dl/g and an antioxidant in a solvent for said UHMWPE having an atmospheric pressure boiling point at least about 180° C. at a temperature that is below the temperature at which the UHMWPE will dissolve in said solvent, the weight ratio of said UHMWPE to said solvent being from about 5:95 to about 95:5 and the weight ratio of said antioxidant to said solvent being from about 10 parts per million to about 1000 parts per million; b) feeding said slurry to an intermeshing co-rotating twin screw extruder wherein the screws in said twin screw extruder are comprised of multiple segments having a root diameter of Dr millimeters, an outside diameter of Do millimeters, the ratio Dr/Do is R, the rotational speed of the screws is ω revolutions per minute and following relationships are satisfied 0.84 ≥ R ≥ 0.55 ω ⁢ ⁢ D 0 ⁡ ( ( 1 + R ) ( 1 - R ) ) ≥ 70 , 000 , millimeters ⁢ / ⁢ ⁢ min c) forming a liquid mixture in said extruder of said UHMWPE and said antioxidant, in said solvent at a temperature from about 140° C. to about 320° C., the intrinsic viscosity of the UHMWPE in said mixture being reduced to a value of from about 0.2 IV0 to about 0.7 IV0 in passing through said extruder; d) passing said liquid mixture through a heated vessel at a temperature at least about 140° C., said vessel having a volume such that the average residence time in said vessel is from about 2 to about 120 minutes, whereby a solution of the UHMWPE is formed; e) passing the thus-formed solution through a spinneret to form solution filaments; f) passing said solution filaments from said spinneret through a short gaseous space into a liquid quench bath at a temperature less than about 35° C. wherein said solution filaments are rapidly cooled to form gel filaments; g) removing the solvent from the gel filaments to form solid filaments; and h) stretching at least one of the solution filaments, the gel filaments and the solid filaments in one or more stages to a combined stretch ratio of at least about 10:1, wherein a stretch of at least about 2:1 is applied to the solid filaments to form a high strength multi-filament UHMWPE yarn, said UHMWPE yarn having a tenacity at least about 40 g/d, and having an intrinsic viscosity from 0.2 IV0 to 0.65 IV0. 2. The process of claim 1, wherein said antioxidant is selected from the group consisting of tetrakis[methylene(3,5-di-ter-butylhydroxyhydrocinnamate)]methane, tris(2,4-di-tert-butylphenyl) phosphite, octadecyl 3,5-di-tert-butyl-4-hyroxyhydrocinnamate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6 (1H,3H,5H)-trione, 2,5,7,8 tetramethyl-2(4′,8′,12′-trimethyltridecyl)chroman-6-ol, α-tocopherol, and their mixtures. 3. The process of claim 1, wherein the weight ratio of said antioxidant to said solvent is from about 10 parts per million to about 100 parts per million. 4. The process of claim 1, wherein said twin screw extruder is run liquid full with the extruder feed zone flooded with said slurry under an inert gas blanket. 5. The process of claim 1, wherein the average residence time of said liquid mixture in said twin screw extruder is not more than about 1.5 minutes. 6. The process of claim 1 wherein substantially all of said screw segments in said twin screw extruder are forwarding conveying flight segments. 7. The process of claim 1, wherein the temperature of the mixture exiting said twin screw extruder is from about 220° C. to about 320° C. 8. The process of claim 1, wherein the liquid in said liquid quench bath is selected from the group consisting of water, ethylene glycol, ethanol, iso-propanol, a water soluble anti-freeze and their mixtures, and wherein said liquid quench bath temperature is from about minus 35° C. to about 35° C. 9. The process of claim 1, wherein said high strength multi-filament yarn comprises at least about 100 filaments. 10. The process of claim 9, wherein said high strength multi-filament yarn has an intrinsic viscosity less than or equal to about 18 dl/g.