Nylon staple fiber suitable for use in abrasion resistant, high strength nylon blended yarns and fabrics

Abstract

Included is the preparation of high strength nylon staple fibers having a denier per filament of about 1.0 to 3.0, a tenacity T at break of at least about 6.0, and a load-bearing capacity, T7, of greater than about 2.5, including greater than 3.2. Such nylon staple fibers are produced by preparing tows of relatively high molecular weight nylon filaments (RV of 65 to 100), drawing and annealing such tows via a two-stage drawing and annealing operation and then cutting or otherwise converting the drawn and annealed tows into the desired high strength nylon staple fibers. The nylon staple fibers so prepared can be blended with a companion fiber such as cotton staple fibers to produce nylon/cotton (NYCO) yarns.

1 . A process for preparing nylon staple fibers, said process comprising melt-spinning nylon polymer into filaments, quenching said filaments and forming one or more tows from a multiplicity of said quenched filaments, subjecting said tow(s) to drawing and annealing, and converting said drawn and annealed tow(s) into staple fibers suitable for forming into spun yarn; wherein;
 A) the nylon polymer melt spun into filaments has a formic acid relative viscosity (RV) of from 65 to 100;   B) the drawing and annealing of the tow(s) is carried out in a two-stage continuous operation conducted at a total effective draw ratio of from 2.3 to 4.0, said operation comprising a first drawing stage wherein from 85% to 97.5% of the drawing of the tow(s) occurs and a second annealing and drawing stage wherein said tow(s) is/are subjected to an annealing temperature of from 145° C. to 205° C.; said operation being followed by a cooling step wherein said drawn and annealed tow(s) is/are cooled to a temperature of less than 80° C.; and   C) the tow(s) is/are maintained under a controlled tension throughout said two stage continuous operation.   
     
     
         2 . A process according to  claim 1  wherein said staple fibers have a denier per filament of from 1.0 to 3.0, a tenacity at break of at least 6.0 grams per denier and a load-bearing capacity of greater than 2.5, grams per denier measured as tenacity (T 7 ) at 7% elongation. 
     
     
         3 . A process according to  claim 1  wherein the relative viscosity (RV) of the nylon polymer ranges from 70 to 85. 
     
     
         4 . A process according to  claim 1  wherein said staple fibers have a denier per filament of from 1.55 to 1.8, a tenacity at break greater than 6.5 grams per denier, and a load-bearing capacity of from 3.0 to 5.0 grams per denier measured as tenacity (T 7 ) at 7% elongation. 
     
     
         5 . A process according to  claim 4  wherein said drawing and annealing of said multifilament tow(s) is conducted at a total effective draw ratio of from 2.5 to 3.0. 
     
     
         6 . A process according to  claim 1  wherein said staple fibers have a denier per filament of from 2.1 to 3.0, a tenacity at break of greater than 6.5 grams per denier, and a load-bearing capacity of from 3.0 to 4.0 grams per denier measured as tenacity (T 7 ) at 7% elongation. 
     
     
         7 . A process according to  claim 6  wherein said drawing and annealing of said multifilament tow(s) is conducted at a total effective draw ratio of from 3.25 to 3.75. 
     
     
         8 . A process according to  claim 1  wherein said nylon polymer is prepared by subjecting nylon flake material to solid phase polymerization (conditioning) to attain the desired relative viscosity (Rv) and by then melt spinning said polymer into filaments. 
     
     
         9 . A process according to  claim 1  wherein said first drawing stage is carried out at a temperature of from 80° C. to 125° C., and said second annealing and drawing stage is carried out at a temperature of from 165° C. to 205° C. 
     
     
         10 . A process according to  claim 1  wherein said nylon polymer is selected from the group consisting of polyhexamethylene adipamide (nylon 6,6) and polycaproamide (nylon 6). 
     
     
         11 . Nylon staple fibers prepared by a process according to  claim 1 . 
     
     
         12 . An article comprising nylon staple fibers made from nylon having a formic acid relative viscosity (RV) of from 65 to 100, more preferably from 70 to 85, wherein said fibers have a denier per filament of from 1.0 to 3.0, a tenacity of at least 6.0 grams per denier and a load-bearing capacity of greater than 2.5, grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         13 . The article of  claim 12  wherein said nylon staple fibers have a denier per filament of from 1.55 to 1.75, a tenacity at break of greater than 6.5 grams per denier, and a load-bearing capacity of from 3.0 to 5.0 grams per denier measured as tenacity (T 7 ) at 7% elongation. 
     
     
         14 . The article of  claim 12  wherein said nylon staple fibers have a denier per filament of from 2.1 to 3.0, a tenacity at break of greater than 6.5 grams per denier, and a load-bearing capacity of from 3.0 to 5.0 grams per denier measured as tenacity (T 7 ) at 7% elongation. 
     
     
         15 . The article of  claim 12  wherein said nylon staple fibers are made from nylon polymer material selected from the group consisting of polyhexamethylene adipamide (nylon 6,6) and polycaproamide (nylon 6). 
     
     
         16 . The article of  claim 12  wherein said nylon staple fibers range in length from 2 to 13 centimeters (0.79 to 5.12 inches). 
     
     
         17 . The article of  claim 12  wherein said article comprises a textile yarn suitable for weaving into fabrics to improve abrasion resistance of said fabric, said yarn comprising blended cotton staple fibers and nylon staple fibers in a weight ratio of cotton staple fibers to nylon staple fibers ranging from 20:80 to 80:20. 
     
     
         18 . A textile yarn suitable for weaving into fabrics to improve abrasion resistance of said fabric, said yarn comprising blended cotton staple fibers and nylon staple fibers in a weight ratio of cotton staple fibers to nylon staple fibers ranging from 20:80 to 80:20; wherein substantially all of said nylon staple fibers are made from nylon having a formic acid relative viscosity (RV) of from 65 to 100, said nylon fibers being further characterized by having a denier per filament of from 1.0 to 3.0, a tenacity of at least 6.0 grams per denier and a load-bearing capacity of greater than 2.5, grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         19 . A textile yarn according to  claim 17  which exhibits a Lea product value of at least 2800 or a breaking tenacity of at least 18 cN/tex, based on a standard 50:50 nylon:cotton ratio. 
     
     
         20 . An NYCO fabric woven from textile yarns according to  claim 17 . 
     
     
         21 . A NYCO fabric woven from textile yarns in both a warp and weft (fill) direction wherein said textile yarns woven in at least one direction comprise blended cotton staple fibers and nylon staple fibers in a weight ratio of cotton staple fibers to nylon staple fibers ranging from about 20:80 to 80:20; and further characterized in that said nylon staple fibers are made from nylon having a formic acid relative viscosity (RV) of from 65 to 100, more preferably from 70 to 85, said nylon fibers further having a denier per filament of from 1.0 to 3.0, a tenacity of at least 6.0 grams per denier and a load-bearing capacity of greater than 2.5, grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         22 . A NYCO fabric according to  claim 20  wherein the yarns woven in the fill direction comprise nylon staple fibers having a denier per filament of from 1.6 to 1.8 and the yarns woven in the warp direction comprise nylon staple fibers having a denier per filament of from 2.3 to 2.7. 
     
     
         23 . A NYCO fabric according to  claim 20  having a fabric weight of 200 grams/m 2  (6.0 oz/yd 2 ) or less. 
     
     
         24 . A 2×1 twill NYCO fabric according to any of  claims 20  to  23  having a grab strength of 190 lbs or greater in the warp direction and 80 lbs or greater in the fill direction, measured in accordance with ASTM D 5034. 
     
     
         25 . A 2×1 twill NYCO fabric according to  claim 20  having a Taber Abrasion Resistance of at least 600 cycles to failure, and more preferably at least 1200 cycles to failure, measured in accordance with ASTM D 3884. 
     
     
         26 . A 2×1 twill NYCO fabric according to  claim 20  having a Flex Abrasion of at least 55,000 cycles, more preferably 65,000 cycles to failure as measured in accordance with ASTM D 3885.