High load bearing capacity nylon staple fiber and nylon blended yarns and fabrics made therefrom

Abstract

Disclosed is the preparation of improved high strength nylon staple fibers having a denier per filament of 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 3.2. Such nylon staple fibers are produced by preparing tows of relatively uniformly spun and quenched nylon filaments, drawing and annealing such tows via a two-stage drawing and annealing operation using relatively high draw ratios 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 other fibers such as cotton staple fibers to produce nylon/cotton (NYCO) yarns which are also of desirably high strength.

1 . A process for preparing nylon staple fibers having a load-bearing capacity of greater than 3.2 grams per denier measured as tenacity (T 7 ) at 7% elongation, said process comprising the steps of 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 comprising;
 A) the nylon polymer melt spun into filaments has a formic acid relative viscosity (RV) of from 45 to 100;   B) said nylon polymer filaments are spun, quenched and formed into tows with both positional uniformity and uniformity of quenching conditions which are sufficient to permit use of draw ratios that provide the desired eventual staple fiber T 7  tenacity greater than 3.2 grams per denier;   C) 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 5.0, 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   D) 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 and a tenacity at break of at least 6.0 grams per denier. 
     
     
         3 . A process according to  claim 1 , wherein the relative viscosity (RV) of the nylon polymer ranges from 45 to 65. 
     
     
         4 . A process according to  claim 1 , wherein said staple fibers have a denier per filament of from 1.6 to 1.8, a tenacity at break of greater than 6.8 grams per denier, and a load-bearing capacity of from 3.3 to 4.5 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 is conducted at a total effective draw ratio of from 3.12 to 3.40. 
     
     
         6 . A process according to  claim 1  wherein said staple fibers have a denier per filament of from 2.3 to 2.7, a tenacity at break of from greater than 6.8 grams per denier, and a load-bearing capacity of from 3.3 to 5.0 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 is conducted at a total effective draw ratio of from 3.5 to 4.0. 
     
     
         8 . A process according to  claim 1  wherein said nylon polymer has an RV of from 50 to 60. 
     
     
         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 comprising 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 3.2 grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         13 . The article of  claim 12 , wherein said nylon staple fibers have a relative viscosity (RV) of from 45 to 65. 
     
     
         14 . The article of  claim 12 , wherein said nylon staple fibers have a denier per filament of from 1.6 to 1.8, a tenacity at break of from greater than 6.8 grams per denier, and a load-bearing capacity of from 3.12 to 3.40 grams per denier, grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         15 . The article of  claim 12 , wherein said nylon staple fibers have a denier per filament of from 2.3 to 2.7, a tenacity at break of greater than 6.8 grams per denier, and a load-bearing capacity of from 3.3 to 5.0 grams per denier measured as tenacity (T 7 ) at 7% elongation. 
     
     
         16 . The article of  claim 12 , wherein said nylon staple fibers comprise a nylon polymer material selected from the group consisting of polyhexamethylene adipamide (nylon 6,6) and polycaproamide (nylon 6). 
     
     
         17 . The article of  claim 12 , wherein said nylon staple fibers range in length from 2 to 13 centimeters (0.79 to 5.12 inches). 
     
     
         18 . The article of  claim 12 , wherein said article comprises a textile yarn comprising blended cotton staple fibers and said nylon staple fibers in a weight ratio of cotton staple fibers to nylon staple fibers ranging from 20:80 to 80:20. 
     
     
         19 . A textile yarn comprising blended nylon staple fibers and at least one companion staple fiber wherein substantially all of said nylon staple 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 3.2 grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         20 . The textile yarn of  claim 19  wherein said companion staple fiber comprises cotton and said cotton staple fibers and nylon staple fibers have a weight ratio of cotton staple fibers to nylon staple fibers ranging from about 20:80 to 80:20; characterized in that substantially all of said nylon staple 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 3.2 grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         21 . A textile yarn according to  claim 18  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. 
     
     
         22 . A nylon/cotton (NYCO) fabric woven from textile yarns according to  claim 18 . 
     
     
         23 . A nylon/cotton (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 20:80 to 80:20; and wherein said nylon staple 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 3.2 grams per denier, measured as tenacity (T 7 ) at 7% elongation. 
     
     
         24 . A NYCO fabric according to  claim 21  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. 
     
     
         25 . A NYCO fabric according to  claim 21  having a fabric weight of 200 grams/m 2  (6.0 oz/yd 2 ) or less. 
     
     
         26 . A 2×1 twill NYCO fabric according to  claim 21  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. 
     
     
         27 . A NYCO fabric woven from textile yarns in both a warp and weft (fill) direction wherein said textile yarns woven in both directions comprise 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; and further characterized in that the yarns woven in the weft (fill) direction comprise nylon staple fibers having a denier per filament of from 1.3 to 2.0 and the yarns woven in the warp direction comprise nylon staple fibers having a denier per filament of from 2.5 to 3.0.