Porous hollow fiber membrane

Patent metadata

Field	Value
Publication number	US-9901883-B2
Application number	US-201515539355-A
Country	US
Kind code	B2
Filing date	Dec 25, 2015
Priority date	Dec 26, 2014
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

An object of the present invention is to provide a porous hollow-fiber membrane having high strength while maintaining high pure-water permeation performance. A porous hollow-fiber membrane of the present invention is a porous hollow-fiber membrane including a fluororesin-based polymer, in which the porous hollow-fiber membrane has a columnar texture oriented in a longitudinal direction of the porous hollow-fiber membrane, and a molecular chain of the fluororesin-based polymer is oriented in the longitudinal direction of the porous hollow-fiber membrane.

First claim

The invention claimed is:

1. A porous hollow-fiber membrane comprising a fluororesin-based polymer,
wherein the porous hollow-fiber membrane has a columnar texture oriented in a longitudinal direction of the porous hollow-fiber membrane,
a molecular chain of the fluororesin-based polymer is oriented in the longitudinal direction of the porous hollow-fiber membrane,
an orientation degree π of the molecular chain calculated based on the following formula (1) is 0.4 or more and less than 1.0:
Orientation degree π=(180°- H )/180°  (1)

provided that H is a half-width)(°)of a diffraction intensity distribution in a circumferential direction of a wide-angle X-ray diffraction image, and
the columnar texture has a short-side length of from 0.5 μm to 3 μm, and has an aspect ratio of 3 or more.

2. The porous hollow-fiber membrane according to claim 1 , wherein the columnar texture has a thickness uniformity of 0.60 or more.

3. The porous hollow-fiber membrane according to claim 1 , wherein the half-width H is a half-width of an intensity distribution obtained by circumferentially scanning a crystal peak (2θ=20.4°) derived from a (110) plane of polyvinylidene fluoride in wide-angle X-ray diffraction measurement.

4. The porous hollow-fiber membrane according to claim 1 , wherein, when the wide-angle X-ray diffraction measurement is performed at measurement points at 1 cm intervals in the longitudinal direction of the porous hollow-fiber membrane, the orientation degree π is 0.4 or more and less than 1.0 at 80% or more of the measurement points.

5. The porous hollow-fiber membrane according to claim 1 , wherein the fluororesin-based polymer is polyvinylidene fluoride, and a Raman orientation parameter v of the molecular chain obtained by Raman spectroscopy is 3.0 or more.

6. The porous hollow-fiber membrane according to claim 1 , which has a porosity of from 50 to 80%.

7. The porous hollow-fiber membrane according to claim 1 , which has a pure-water permeation performance at 50 kPa and 25° C. of 0.7 m 3 /m 2 /hr or more and a breaking strength of 25 MPa or more.

8. The porous hollow-fiber membrane according to claim 1 , which is formed by thermally induced phase separation.

Assignees

• Toray Industries

Inventors

• Hanakawa Masayuki
• Iwai Kenta
• Ishizaki Toshiyuki
• Kitade Tamotsu
• Kimura Masahiro

Classifications

• B01D71/34 Primary

  Polyvinylidene fluoride · CPC title

• B01D69/08

  Hollow fibre membranes (manufacture of hollow fibres D01D5/24, D01F1/08) · CPC title

• B01D69/02

  characterised by their properties · CPC title

• B01D67/0013

  Casting processes · CPC title

• B01D67/00165

  Composition of the coagulation baths · CPC title