# US 7,608,329 B2 · Polylactic acid resin, textile products obtained therefrom, and processes for producing textile products

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- Number: US 7,608,329 B2
- Document ID: US7608329B2
- Status: Granted
- Kind: B2
- Application number: 12/199,245
- Filed: 2008-09-26
- Published: 2009-02-05
- Granted: 2009-10-27
- Earliest claimed: 1999-06-18
- Assignees: Toray Industries, Inc.
- Inventors: Hiroshi Kaijiyama; Hideo Ueda; Hiroji Yoshida; Toichi Ogura
- Web page: https://patentgrep.com/patent/US7608329B2

## CPC

- D01F 6/625: {derived from hydroxy-carboxylic acids, e.g. lactones}
- C08G 63/06: derived from hydroxycarboxylic acids
- Y10T 428/2913: Rod, strand, filament or fiber
- Y10T 428/2915: including textile, cloth or fabric
- Y10T 428/2922: Nonlinear [e.g., crimped, coiled, etc.]
- Y10T 428/2929: Bicomponent, conjugate, composite or collateral fibers or filaments [i.e., coextruded sheath-core or side-by-side type]
- Y10T 442/641: Sheath-core multicomponent strand or fiber material
- D01F: CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A polylactic acid resin suitable for use especially in textile products; textile products obtained from the resin as a raw material (a fiber, multifilament, monofilament, staple, false-twist yarn, long-fiber nonwoven fabric, etc.); and processes for producing these textile products. The polylactic acid resin is a resin consisting mainly of a polylactic acid and is characterized in that it is linear, has an L-isomer content of 95 mol % or higher, an Sn content of 30 ppm or lower, a monomer content of 0.50 wt. % or lower, and has a relative viscosity of 2.7 to 3.9 or has a weight-average molecular weight of 120,000 to 220,000 and a number-average molecular weight of 60,000 to 110,000. Each of the textile products comprises the polylactic acid resin as the main material. The textile products each comprises a polylactic acid that is excellent in processability and excellent fiber properties. The free textile products are problems in practical use.

## Claims

### Claim 1

A polylactic acid resin comprising a linear polylactic acid with a relative viscosity ηrel of in the range of 2.7 to 3.9, prepared from lactic acid monomers wherein at least 95 mol % of the lactic acid is an L-isomer, and wherein the resin contains 0 to 30 ppm of tin (Sn) and 0 to 0.5% by weight of residual monomer.

### Claim 2 (depends on 1)

A polylactic acid fiber comprising the polylactic acid resin according to claim 1.

### Claim 3 (depends on 1)

A process for producing a polylactic acid fiber by melt-spinning the polylactic acid according to claim 1.

### Claim 4 (depends on 1)

A polylactic acid fiber comprising the polylactic acid resin according to claim 1, wherein the polylactic acid fiber is a staple fiber.

### Claim 5 (depends on 4)

A polylactic acid fiber according to claim 4 having a tensile strength of 2.6 cN/dtex or more, an elongation of 80% or less, a contraction ratio in boiling water of 5.0% or less and a crimp number in the range of 4 to 18 crimps/25 mm.

### Claim 6

A binder fiber comprising a polylactic acid resin comprising a linear polylactic acid with a relative viscosity ηrel of in the range of 2.7 to 3.9, prepared from lactic acid monomers wherein at least 90 mol % of the lactic acid is an L-isomer, and wherein the resin contains 0 to 30 ppm of Sn and 0 to 0.5% by weight of residual monomer.

### Claim 7 (depends on 6)

The binder fiber according to claim 6 having a structure with a core and a sheath, wherein the core contains a polylactic acid resin wherein at least 98 mol % of the lactic acid is an L-isomer, and the sheath contains a polylactic acid resin wherein at least 90 mol % of the lactic acid is an L-isomer.

### Claim 8 (depends on 7)

The binder fiber according to claim 7 having a structure with a core and a sheath, wherein the proportion C (mol %) of L-isomer in polylactic acid of the core and the proportion S (mol %) of L-isomer in the polylactic acid of the sheath satisfies the relation: 2≦C−S≦8.

### Claim 9 (depends on 7)

The binder fiber according to claim 7 having a tensile strength of 2.6 cN/dtex or more, an elongation of 80% or less, a heat-contraction ratio at 80° C. of 15.0% or less, and a crimp number in the range of 4 to 18 crimps/25 mm.

### Claim 10 (depends on 6)

A process for producing a polylactic acid binder fiber according to claim 6 comprising the steps: spinning at a spinning temperature in the range of 210° C. to 240° C. and spinning speed in the range of 600 to 1,200 m/min, drawing at a draw magnification factor in the range of 3.0 to 5.0 at a draw temperature in the range of 40° C. to 70° C., and heat-treating at a temperature in the range of 60° C. to 90° C.