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

A process for preparing nylon staple fibers having a load-bearing capacity of greater than 3.2 to 5.0 grams per denier measured as tenacity (T7) 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 T7 tenacity greater than 3.2 to 5.0 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 carried out at a temperature of from 80° C. to 125° C. 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.