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Producing high tenacity, high modulus crystalline article such as fiber or film

  • US 4,551,296 A
  • Filed: 01/20/1984
  • Issued: 11/05/1985
  • Est. Priority Date: 03/19/1982
  • Status: Expired due to Term
First Claim
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1. A process for producing a high strength, high modulus shaped thermoplastic article of substantially indefinite length which comprises the steps:

  • (a) forming a solution of a thermoplastic crystalline polymer selected from the group consisting of polyethylene, polypropylene, polyoxymethylene, polybutene-1, poly(vinylidene fluoride) and poly(4-methylpentene-1) in a first, non-volatile solvent at a first concentration of about 2 to 15% by weight of polymer per unit weight of first solvent, said thermoplastic polymer having a weight average molecular length between about 7×

    104 and about 71×

    104 backbone atoms and the solubility of said thermoplastic polymer in said first solvent at a first temperature being at least said first concentration;

    (b) extruding said solution through an aperture, said solution being at a temperature no less than said first temperature upstream of the aperture and being substantially at the first concentration both upstream and downstream of the aperture;

    (c) cooling the solution adjacent to and downstream of the aperture to a second temperature below the temperature at which a gel is formed to form a gel containing first solvent of substantially indefinite length;

    (d) extracting the gel containing first solvent with a second, volatile solvent for a sufficient contact time to form a gel containing second solvent which gel is substantially free of first solvent and is of substantially indefinite length;

    (e) drying the gel containing second solvent to form a xerogel of substantially indefinite length free of first and second solvent; and

    ,(f) stretching at a sufficient temperature at least one of;

    (i) the gel containing the first solvent,(ii) the gel containing the second solvent and,(iii) the xerogel at a total stretch ratio;

    (i) in the case of polyethylene which is sufficient to achieve a tenacity of at least about 20 g/denier and a modulus of at least about 600 g/denier,(ii) in the case of polypropylene which is sufficient to achieve a tenacity of at least about 10 g/denier and a modulus of at least about 160 g/denier, and(iii) in the case of polyoxymethylene, polybutene-1, poly(vinylidene fluoride) or poly(4-methylpentene-1) of at least about 10;

    1.

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