Separation membrane and method for producing same

Patent metadata

Field	Value
Publication number	US-2017157572-A1
Application number	US-201515324399-A
Country	US
Kind code	A1
Filing date	Jul 7, 2015
Priority date	Jul 7, 2014
Publication date	Jun 8, 2017
Grant date	—

Abstract

An object of the present invention is to provide a separation membrane having high mechanical strength and being less likely to cause clogging and capable of continuously maintaining high water permeation performance. The present invention relates to a separation membrane characterized in that the average diameter D 1 of a spherical structure in a region within 10 μm from a first surface in a separation membrane having a spherical structure layer formed of a thermoplastic resin and the average diameter D 2 of a spherical structure in a region of 10 μm to 20 μm from a second surface satisfy the relational expression of D 1 >D 2 and the average diameter D 1 and the average diameter D 3 of a spherical structure in a third region satisfy the relational expression of 1.10<D 1 /D 3 <4.00.

First claim

1 - 8 . (canceled)

9 . A separation membrane having a spherical structure layer formed of a thermoplastic resin,
wherein the spherical structure layer has a first surface and a second surface, in the spherical structure layer, an average diameter D 1 of a spherical structure S 1 in a region within 10 μm from the first surface and an average diameter D 2 of a spherical structure S 2 in a region of 10 μm to 20 μm from the second surface satisfy a relational expression of D 1 >D 2 , and the average diameter D 1 and an average diameter D 3 of a spherical structure S 3 in a region of 10 μm to 20 μm from the first surface satisfy a relational expression of 1.10<D 1 /D 3 <4.00.

10 . The separation membrane according to claim 1 , wherein the average diameter D 1 and the average diameter D 3 satisfy a relational expression of 0.00 μm<(D 1 −D 3 )<2.00 μm.

11 . The separation membrane according to claim 1 , wherein the average diameter D 1 is from 2.00 μm to 4.00 μm, and the average diameter D 3 is 0.10 μm or more and less than 2.00 μm.

12 . The separation membrane according to claim 1 , wherein the average diameter D 3 and the average diameter D 2 satisfy a relational expression of −0.30 μm<(D 3 −D 2 )<0.30 μm.

13 . The separation membrane according to claim 2 , wherein the average diameter D 3 and the average diameter D 2 satisfy a relational expression of −0.30 μm<(D 3 −D 2 )<0.30 μm.

14 . The separation membrane according to claim 1 , wherein the thermoplastic resin is a polyvinylidene fluoride-based resin.

15 . The separation membrane according to claim 4 , wherein the thermoplastic resin is a polyvinylidene fluoride-based resin.

16 . The separation membrane according to claim 5 , wherein the thermoplastic resin is a polyvinylidene fluoride-based resin.

17 . A method for producing a separation membrane, the method comprising:
(a) a step of dissolving a polyvinylidene fluoride-based resin in a poor solvent to obtain a polyvinylidene fluoride-based resin solution; (b) a step of holding the polyvinylidene fluoride-based resin solution under conditions allowing primary nucleus formation to proceed; (c) a step of molding the polyvinylidene fluoride-based resin solution into a separation membrane shape; (d) a step of solidifying the polyvinylidene fluoride-based resin solution by solid-liquid thermally induced phase separation in a cooling bath; and (e) a step of imparting a temperature gradient in a separation membrane thickness direction to the polyvinylidene fluoride-based resin solution, between start of the step (c) and start of the step (d).

18 . The method for producing a separation membrane according to claim 9 , wherein a solution temperature T 1 ° C. at a time of the dissolution in the step (a) is a temperature not less than a crystallization temperature Tc° C., and the conditions allowing the primary nucleus formation to proceed in the step (b) are a pressure of 0.5 MPa or more and a temperature of (Tc+20)° C. to (Tc+55)° C.

19 . The method for producing a separation membrane according to claim 10 , wherein a time for holding under the conditions allowing the primary nucleus formation to proceed in the step (b) is 10 seconds or more.

20 . The method for producing a separation membrane according to claim 9 , wherein, in the step (e), an average temperature rise rate at a time of imparting the temperature gradient is from 30 to 700° C./min, and an imparting time thereof is from 0.1 to 5.0 seconds.

Assignees

• Toray Industries

Inventors

• Iwai Kenta
• Ishizaki Toshiyuki
• Kitade Tamotsu
• Komori Kenji
• Hanakawa Masayuki

Classifications

• C08J2327/16

  Homopolymers or copolymers of vinylidene fluoride · CPC title

• D01D5/24

  with a hollow structure; Spinnerette packs therefor (D01D5/38 takes precedence; producing tubes of plastic material B29D; addition of agents forming hollow filaments D01F1/08) · CPC title

• B01D69/085

  Details relating to the spinneret · CPC title

• B01D61/14

  Ultrafiltration; Microfiltration · CPC title

• B01D69/02

  characterised by their properties · CPC title