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High tenacity polyethylene yarn

  • US 20080305331A1
  • Filed: 06/08/2007
  • Published: 12/11/2008
  • Est. Priority Date: 06/08/2007
  • Status: Active Grant
First Claim
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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 UHMVVPE 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.

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