Process for making a yarn having improved strength retention and yarn made thereby

Patent metadata

Field	Value
Publication number	US-9752256-B2
Application number	US-201514804439-A
Country	US
Kind code	B2
Filing date	Jul 21, 2015
Priority date	Jul 31, 2014
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

The invention relates to a continuous process for making a yarn comprising filaments of poly (paraphenylene terephthalamide) and the yarn made thereby, the process utilizing a coagulation bath having a temperature of at least 20° C., washing with an aqueous liquid, and drying the filaments under a tension of 0.3 to 1.0 grams per denier wherein the filaments are dried for 0.4 to 0.9 seconds at a temperature of from 250 to 325° C. The yarn has a tenacity of at least 22 gpd, an elongation at break of at least 3.2 percent, and a tensile modulus of from 530 to 700 gpd; the yarn further has a heat-aged strength retention (HASR) of at least 93 percent and the filaments in the yarn have a D110 crystallinity of at least 55 angstroms.

First claim

What is claimed is:

1. A yarn comprising filaments of poly (paraphenylene terephthalamide) and having a yarn tenacity of at least 22 gpd, an elongation at break of at least 3.2 percent, and a tensile modulus of from 530 to 700 gpd;
the yarn having a heat-aged strength retention (HASR) of at least 93 percent; and the filaments in the yarn having an apparent crystallite size of from 55 to 80 angstroms.

2. The yarn of claim 1 having a yarn tenacity of at least 24 gpd.

3. The yarn of claim 1 having HASR of at least 95 percent.

4. The yarn of claim 1 wherein the tensile modulus is less than 650 gpd.

5. The yarn of claim 1 wherein the elongation at break is 3.5 percent or greater.

6. The yarn of claim 1 having a linear density of from 500 to 3000 denier.

7. The yarn of claim 1 having a dipped cord strength of greater than 20 gpd.

8. The yarn of claim 1 having a dipped cord percentage tenacity retention of greater than 90 percent.

9. A dipped cord comprising a yarn comprising filaments of poly (paraphenylene terephthalamide) and having a yarn tenacity of at least 22 gpd, an elongation at break of at least 3.2 percent, and a tensile modulus of from 530 to 700 gpd; the yarn having a heat-aged strength retention (HASR) of at least 93 percent; and the filaments in the yarn having an apparent crystallite size of from 55 to 80 angstroms.

10. The dipped cord of claim 9 wherein the yarn has a yarn tenacity of at least 24 gpd.

11. The dipped cord of claim 10 wherein the yarn has HASR of at least 95 percent.

12. The dipped cord of claim 11 wherein the yarn has a tensile modulus that is less than 650 gpd.

13. A process for producing the yarn of claim 1 comprising filaments of poly (paraphenylene terephthalamide), the yarn having a heat-aged strength retention (HASR) of at least 93 percent and the filaments in the yarn having an apparent crystallite size of from 55 to 80 angstroms, comprising the following steps:
i) in a continuous process, spinning a polymer dope through a spinneret having a plurality of orifices and coagulating the dope into a plurality of filaments in an aqueous coagulation bath having a temperature of at least 20° C.;
ii) washing the filaments with an aqueous liquid; and
iii) drying the filaments under a tension of 0.3 to 1.0 grams per denier; wherein the filaments are dried for 0.4 to 0.9 seconds at a temperature of from 250 to 325° C.

14. The process of claim 13 wherein the yarn has a HASR of at least 95 percent.

15. The process of claim 13 wherein the tension in step iii) is 0.3 to 0.7 grams per denier.

Assignees

• Du Pont

Inventors

• Afshari Mehdi
• Hall Iii Walter Randall

Classifications

• D01D10/02 Primary

  Heat treatment (heating for finishing D02J13/00) · CPC title

• D01D5/06 Primary

  Wet spinning methods {(D01D5/0046 takes precedence)} · CPC title

• D02G3/02

  Yarns or threads characterised by the material or by the materials from which they are made · CPC title

• D10B2331/021

  aromatic polyamides, e.g. aramides · CPC title

• D01F6/605 Primary

  from aromatic polyamides · CPC title