Composite porous hollow fiber membrane, composite porous hollow fiber membrane module, and operation method for composite porous hollow fiber membrane module

Patent metadata

Field	Value
Publication number	US-11235989-B2
Application number	US-201716312768-A
Country	US
Kind code	B2
Filing date	Jun 23, 2017
Priority date	Jun 24, 2016
Publication date	Feb 1, 2022
Grant date	Feb 1, 2022

Abstract

The present invention relates to a composite porous hollow-fiber membrane including a first layer and a second layer which each include a fluororesin-based polymer, in which at least a part of molecular chains of the fluororesin-based polymer is oriented in a longitudinal direction of the composite porous hollow-fiber membrane, the molecular chains of the fluororesin-based polymer have a degree of orientation it in the longitudinal direction of the composite porous hollow-fiber membrane of 0.4 or higher but less than 1.0, the degree of orientation it being calculated with the specific formula.

First claim

The invention claimed is:

1. A composite porous hollow-fiber membrane comprising a first layer and a second layer which each comprise a fluororesin-based polymer, wherein
at least a part of molecular chains of the fluororesin-based polymer is oriented in a longitudinal direction of the composite porous hollow-fiber membrane,
the molecular chains of the fluororesin-based polymer have a degree of orientation π in the longitudinal direction of the composite porous hollow-fiber membrane of 0.4 or higher but less than 1.0, the degree of orientation π being calculated with the following formula (1),
the first layer has a columnar texture oriented in the longitudinal direction of the composite porous hollow-fiber membrane,
the columnar texture has a short-side length of 0.5 μm to 3 μm and has an aspect ratio of 3 or higher,
the second layer has a three-dimensional network texture and has an average surface-pore diameter of 5.0 nm to 5.0 μm:
Degree of orientation π=(180°− H )/180°  (1),

provided that H is a half-value width (°) of a circumferential-direction diffraction intensity distribution of a wide-angle X-ray diffraction image, and
the short-side length and the aspect ratio of the columnar texture are measured by the following procedure:
the composite porous hollow-fiber membrane is cut along the longitudinal direction of the composite porous hollow-fiber membrane to obtain a section;
the section obtained is examined using a scanning electron microscope (SEM);
three arbitrarily selected fields of view each including five columnar textures are examined to obtain values of longitudinal length of the columnar textures, and an average value of the obtained values of longitudinal length of the columnar textures is determined as a representative value of the longitudinal lengths of the columnar textures;
in the three arbitrarily selected fields of view and at each of a given number of arbitrary measuring points, wherein the given number of arbitrary measuring points is a value obtained by dividing the longitudinal length (μm) by 1 μm while omitting any figures below the decimal point, a short-side length of one columnar texture is measured, and an average value of the obtained values of the short-side lengths is determined as a representative value of short-side length; and
the aspect ratio of the columnar texture is calculated from the representative value of longitudinal length and the representative value of short-side length.

2. The composite porous hollow-fiber membrane according to claim 1 , wherein the columnar texture has a short-side length of 0.5 μm to 3 μm and has an aspect ratio of 3 or higher.

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

4. The composite porous hollow-fiber membrane according to claim 1 , wherein the half-value width H is a half-value width of an intensity distribution obtained by wide-angle X-ray diffractometry, by scanning, in a circumferential direction, a crystal peak (2θ=20.4°) assigned to a (110) plane of poly(vinylidene fluoride).

5. The composite porous hollow-fiber membrane according to claim 1 , wherein, in a case where measuring points on the composite porous hollow-fiber membrane which are located at intervals of 1 cm in the longitudinal direction thereof are examined by wide-angle X-ray diffractometry, the degree of orientation π is 0.4 or higher but less than 1.0 in 80% or more of the measuring points.

6. The composite porous hollow-fiber membrane according to claim 1 , wherein the columnar texture has an average value v of a Raman orientation parameter obtained by Raman spectrometry of 3.0 or larger.

7. The composite porous hollow-fiber membrane according to claim 1 , wherein the fluororesin-based polymer is poly(vinylidene fluoride).

8. The composite porous hollow-fiber membrane according to claim 1 , wherein the first layer has a porosity of 50-80%.

9. The composite porous hollow-fiber membrane according to claim 1 , which has a pure-water permeation performance at 50 kPa and 25° C. of 0.1 m 3 /m 2 /hr or higher and a breaking strength of 25 MPa or higher.

10. A composite porous hollow-fiber membrane module comprising:
a tubular case having, in a height direction thereof, a first end and a second end;
a plurality of the composite porous hollow-fiber membranes according to claim 1 disposed in the tubular case;
a fluid inflow/outflow port located in a sidewall of the tubular case further toward the second-end side than the center of the tubular case; and
a fluid inflow/outflow port located in a first-end-side end face of the tubular case,
wherein hollows of the composite porous hollow-fiber membranes are opened on the second-end side and closed on the first-end side.

11. A method for operating the composite porous hollow-fiber membrane module according to claim 10 , the method comprising simultaneously performing the following step (A) and step (B):
(A) a step in which a liquid to be filtrated is introduced into the tubular case through the fluid inflow/outflow port located in the first-end-side end face, and the liquid to be filtrated is discharged from the tubular case through the fluid inflow/outflow port located in the sidewall on the second-end side; and
(B) a step in which a filtrate is taken out from the hollows of the composite porous hollow-fiber membranes toward the second end.

12. A method for operating the composite porous hollow-fiber membrane module according to claim 10 , the method comprising simultaneously performing the following step (B) and step (C):
(B) a step in which a filtrate is taken out from the hollows of the composite porous hollow-fiber membranes toward the second end; and
(C) a step in which a liquid to be filtrated is introduced into the tubular case through the fluid inflow/outflow port located in the sidewall on the second-end side, and the liquid to be filtrated is discharged from the tubular case through the fluid inflow/outflow port located in the first-end-side end face.

13. The method for operating the composite porous hollow-fiber membrane module according to claim 11 , wherein the step (B) and the following step (D) are repeatedly performed:
(D) a step in which, after the step (B), a fluid is filtrated by passing the fluid from the hollows of the composite porous hollow-fiber membranes on the second-end side to an outside of the composite porous hollow-fiber membranes.

14. The method for operating the composite porous hollow-fiber membrane module according to claim 13 , wherein the step (B) and the step (D) are repeatedly performed and the following step (E) is further performed:
(E) a step in which a gas is introduced into the tubular case through the fluid inflow/outflow port located in the first-end-side end face, and the gas is discharged from the tubular case through the fluid inflow/outflow port located in the sidewall on the second-end side.

15. The method for operating the composite porous hollow-fiber membrane module according to claim 12 , wherein the step (B) and the following step (D) are repeatedly performed:
(D) a step in which, after the step (B), a fluid is filtrated by passing the fluid from the hollows of the composite porous hollow-fiber membranes on the second-end side to an outside of the composite porous hollow-fiber membranes.

16. The method for operating the composite porous hollow-fiber membrane module according to claim 15 , wherein the step (B) and the step (D) are repeatedly performed and the following step (E) is further performed:
(E) a step in which a gas is in

Assignees

• Toray Industries

Inventors

• SHIMURA Shun
• Hanakawa Masayuki
• Iwai Kenta
• Kitade Tamotsu
• Kimura Masahiro

Classifications

• B01D67/00113 Primary

  Pretreatment of the casting solutions, e.g. thermal treatment or ageing · CPC title

• B01D69/12

  Composite membranes; Ultra-thin membranes · CPC title

• B01D63/031

  Two or more types of hollow fibres within one bundle or within one potting or tube-sheet · CPC title

• B01D69/087

  Details relating to the spinning process · CPC title

• B01D67/0088

  Physical treatment with compounds, e.g. swelling, coating or impregnation · CPC title