Process and apparatus for the production of a low-shrinkage aliphatic polyamide yarn, and low-shrinkage yarn

Abstract

An apparatus 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.

1 - 25 . (canceled) 
     
     
         26 . An apparatus for production of a low-shrinkage aliphatic polyamide yarn, comprising:
 a spinneret in which polyamide is extruded through to form filaments;   a quenching unit following the spinneret to cool and combine the filaments to form at least one yarn;   a first pair of inlet rolls following the quenching unit for a first drawing of the yarn;   a second multi-stage drawing apparatus following the first pair of inlet rolls, wherein the second multi-stage drawing apparatus comprises at least three pairs of heatable draw rolls;   means for increasing the temperature of the pairs of draw rolls from a temperature of a first pair of the 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 the 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 the heatable draw rolls that is operated at a temperature of 5° C. to 20° C. below the melting point of the yarn; and   an at least three-stage relaxation zone, following the second multi-stage drawing apparatus, in which the yarn is relaxed from 4% to 10% in a temperature range of 5° C. to 15° C. below the melting point of the yarn, wherein the at least three-stage relaxation zone comprises at least first and second pairs of rolls and a reel device.   
     
     
         27 . The apparatus according to  claim 26 , wherein the pairs of draw rolls are operated at a peripheral speed of 400 m/min to 4000 m/min. 
     
     
         28 . The apparatus according to  claim 26 , wherein the polyamide comprises at least 90% by weight, monomeric units derived from caprolactam, or monomeric units derived from hexamethylenediamine and adipic acid (AH salt), or mixtures thereof.