Very low creep, ultra high modulus, low shrink, high tenacity polyolefin fiber having good strength retention at high temperatures and method to produce such fiber

• US 5,578,374 A
• Filed: 02/08/1995
• Issued: 11/26/1996
• Est. Priority Date: 06/17/1985
• Status: Expired due to Term

• Current Assignee: Alliedsignal Inc.
• Original Assignee: Alliedsignal Inc.
• Inventors: Tam, Thomas Y., Dunbar, James J., Wincklhofer, Robert C., Kavesh, Sheldon, Weedon, Gene C., Prevorsek, Dusan C.
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): GRAY, JILL M
• Application Number:
  US08/385,238
• Time in Patent Office: 657 Days
• Field of Search: 428/364, 428/902, 428/394, 264/210.7, 264/210.8, 264/290.5, 264/205, 526/348.1, 524/108
• US Class Current: 428/364
• CPC Class Codes: D01F 6/04 from polyolefins
• CPC Class Codes: D07B 2205/2014 High performance polyolefins, e.g. Dyneema or Spectra
• CPC Class Codes: D07B 2401/2005 Elongation or elasticity
• CPC Class Codes: D07B 2801/10 Smallest filamentary entity of a rope or strand, i.e. wire, filament, fiber or yarn
• CPC Class Codes: Y10S 428/902 High modulus filament or fiber
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber
• CPC Class Codes: Y10T 428/2967 Synthetic resin or polymer
• CPC Class Codes: Y10T 442/30 Woven fabric [i.e., woven strand or strip material]
• CPC Class Codes: Y10T 442/60 Nonwoven fabric [i.e., nonwoven strand or fiber material]

Abstract

By poststretching, at a temperature between about 135° and 160° C., a polyethylene fiber, which has already been oriented by drawing at a temperature within 5° C. of its melting point, an ultra high modulus, very low creep, low shrink, high tenacity polyolefin fiber having good strength retention at high temperatures is obtained. The poststretching can be in multiple stages and/or with previous annealing. The poststretching should be done at a draw rate of less than 1 second^-1. Tensile modulus values over 2,000 g/d for multifilament yarn are consistently obtained for ultrahigh molecular weight-polyethylene, with tensile strength values above 30 g/d while at the same time dramatically improving creep (at 160° F. (71.1° C.) and 39,150 psi load) by values at least 25% lower than fiber which has not been poststretched. Shrinkage is improved to values less than 2.5% of the original length when heated from room temperature to 135° C. Performance at higher temperature is improved by about 15° to 25° C.

Claims

1. A polyolefin fiber having a weight average molecular weight of at least 250,000, a tenacity of at least 20 g/d if the weight average molecular weight of the fiber is in the range of about 250,000 to less than 800,000 and a tenacity of at least 32 g/d if the weight average molecular weight of the fiber is at least 800,000 and a creep rate, measured at 160°

F. (71.1°

C.) and 39, 150 psi load, less than one-half that value given by the following equation;

space="preserve" listing-type="equation">percent/hr=1.11×

10.sup.10 (IV).sup.-2.78 (Modulus).sup.-2.11

where IV is the intrinsic viscosity of the fiber measured in decalin at 135°

C., d/l/g, and Modulus is the tensile modulus in grams per denier of the article measured by ASTM 885-81 at 110%/minute strain rate, zero strain.

2. The fiber of claim 1, wherein the total fiber shrinkage measured at 135°

C. is less than 2.5 percent.

3. A polyethylene fiber having a weight average molecular weight of at least 250,000, said fiber having been made by a process which comprises the steps of producing a highly oriented fiber having a weight average molecular weight of at least 250,000, drawing the highly oriented fiber at least twice wherein one of the drawing steps is conducted at a temperature within 10°

C. of the melting point and a later of the drawing steps is conducted at a drawing rate of less than about 1 second^-1 at a temperature within about 10°

C. of said highly oriented fiber, said fiber having a tenacity if the weight average molecular weight is about 250,000 but less than 800,000 of at least 20 g/d if the weight average molecular weight is at least 800,000, of at least 32 g/d and exhibiting, when compared to a fiber produced by the process, excluding only the later of the drawing steps, at least a ten percent increase in tensile modulus and at least a twenty percent decrease in creep rate measured at 160°

F. under 39,150 psi load.

4. The fiber of claim 3 wherein said creep rate is less than one-half that value given by the following equation:

space="preserve" listing-type="equation">percent/hr=1.11×

10.sup.10 (IV).sup.-2.78 (Modulus).sup.-2.11

where IV is the intrinsic viscosity of the article measured in decalin at 135°

C., dl/g, and Modulus is the tensile modulus in grams per denier of the article measured by ASTM 885-81 at 110%/minute strain rate, zero strain.

5. A polyethylene fiber having a weight average molecular weight of at least 800,000, a tenacity of at least 32 g/d, and a creep value less than 5% when measured at 23°

C. and at 30% of breaking load for five days.

6. A polyethylene fiber having a weight average molecular weight of at least 800,000, a tenacity of at least 32 g/d, and a creep rate less than 0.25%/hr when measured at 160°

F., 39,150 psi.