Process for the Production of a Low-Shrinkage Aliphatic Polyamide Yarn

Abstract

A process for production of a low-shrinkage aliphatic polyamide fibre, in which polyamide is extruded through a spinneret to form filaments, then cooled and combined to form at least one yarn. The at least one yarn is subjected to drawing between the spinneret and a pair of inlet rolls, then in a further multi-stage drawing step is subjected to 4-fold to 6-fold drawing by pairs of draw rolls. The pairs of draw rolls successively heat the yarn and at least the last pair of draw rolls has a temperature of 5° C. to 20° C. below the melting point of the yarn. The yarn is relaxed by from 6% to 10% in a subsequent at least three-stage relaxation zone and is kept in a temperature range of 5° C. to 15° C. below the melting point of the yarn, and is subsequently wound up on a reel device.

What is claimed is: 
     
         1 . An method for production of a low-shrinkage aliphatic polyamide yarn, comprising steps of:
 extruding a polyamide through a spinneret to form filaments;   quenching the filaments from the spinneret to cool and combine the filaments to form at least one yarn;   conducting a first drawing of the quenched yarn through a first pair of inlet rolls;   following the first drawing, conducting a second drawing through a multi-stage drawing apparatus that includes at least three pairs of heatable draw rolls;   increasing the temperature of the at least three pairs of draw rolls from a temperature of a first pair of heatable draw rolls that is operated at a temperature of 5° C. below to 30° C. above the glass transition temperature of the yarn, to a temperature of a second pair of heatable draw rolls that operate at a temperature from 130° C., to 40° C. below a melting temperature of the yarn, to a temperature of a last pair of heatable draw rolls that is operated at a temperature of 5° C. to 20° C. below the melting point of the yarn; and   following the second drawing, relaxing the yarn from 4% to 10% in a temperature range of 5° C. to 15° C. below the melting point of the yarn via at least a three-stage relaxation zone comprising at least first and second pairs of rolls and a reel device that winds the yarn.   
     
     
         2 . The method according to  claim 1 , further including operating all pairs of draw rolls at a peripheral speed of 400 m/min to 4000 m/min. 
     
     
         3 . The method according to  claim 1 , wherein the extruding step includes extruding a polyamide comprising at least 90% by weight, monomeric units derived from caprolactam, or monomeric units derived from hexamethylenediamine and adipic acid (AH salt), or mixtures thereof.