# US 9,752,256 B2 · Process for making a yarn having improved strength retention and yarn made thereby

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- Number: US 9,752,256 B2
- Document ID: US9752256B2
- Status: Granted
- Kind: B2
- Application number: 14/804,439
- Filed: 2015-07-21
- Published: 2016-02-04
- Granted: 2017-09-05
- Earliest claimed: 2014-07-31
- Assignees: E. I. Du Pont de Nemours and Company
- Applicants: E I Du Pont De Nemours and Company
- Inventors: Mehdi Afshari; Walter Randall Hall, III
- Web page: https://patentgrep.com/patent/US9752256B2

## CPC

- D01D 5/06: Wet spinning methods {(D01D5/0046 takes precedence)}
- D01D 10/02: Heat treatment (heating for finishing D02J13/00)
- D01D 10/06: Washing or drying
- D01F 6/605: {from aromatic polyamides}
- D02G 3/02: Yarns or threads characterised by the material or by the materials from which they are made
- D10B 2331/021: aromatic polyamides, e.g. aramides
- D01D: MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01F: CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D02G: CRIMPING OR CURLING FIBRES, FILAMENTS, THREADS, OR YARNS; YARNS OR THREADS
- D10B: INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES

## 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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

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

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 1)

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

### Claim 8 (depends on 1)

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

### Claim 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.

### Claim 10 (depends on 9)

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

### Claim 11 (depends on 10)

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

### Claim 12 (depends on 11)

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

### Claim 13 (depends on 1)

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.

### Claim 14 (depends on 13)

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

### Claim 15 (depends on 13)

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