Porous hollow fiber membrane, method for producing same, and water purification method

Patent metadata

Field	Value
Publication number	US-2016325237-A1
Application number	US-201415108610-A
Country	US
Kind code	A1
Filing date	Sep 18, 2014
Priority date	Jan 10, 2014
Publication date	Nov 10, 2016
Grant date	—

Abstract

The porous hollow fiber membrane of the present invention contains a thermoplastic resin, and includes a surface having a surface porosity of 32 to 60% and a fine pore diameter of 300 nm or less, and has a compressive strength of 0.7 MPa or more. The porous hollow fiber membrane of the present invention may include at least two layers, and in this case, the surface of one layer has a thickness of backbone of 0.3 to 20 μm and a fine pore diameter of 0.3 to 10 μm, and the surface of the other layer has a surface porosity of 32 to 60% and a fine pore diameter of 0.05 to 0.3 μm.

First claim

1 . A porous hollow fiber membrane containing a thermoplastic resin, comprising a surface having a surface porosity of 32 to 60% and a fine pore diameter of 300 nm or less,
wherein the porous hollow fiber membrane has a compressive strength of 0.7 MPa or more.

2 . The porous hollow fiber membrane according to claim 1 ,
wherein the porous hollow fiber membrane contains a thermoplastic resin and comprises at least two layers, the surface of one layer has a thickness of backbone of 0.3 to 20 μm and a fine pore diameter of 0.3 to 10 μm, and the surface of other layer has a surface porosity of 32 to 60% and a fine pore diameter of 0.05 to 0.3 μm.

3 . The porous hollow fiber membrane according to claim 2 ,
wherein the fine pores of the surface of the one layer have an aspect ratio of 4 or more.

4 . The porous hollow fiber membrane according to claim 2 ,
wherein the fine pores of the surface of the one layer have an aspect ratio of 10 or more.

5 . The porous hollow fiber membrane according to claim 2 ,
wherein the one layer has a porosity of 50 to 65%, and the other layer has a porosity of 65 to 80%.

6 . A method for producing the porous hollow fiber membrane as defined in claim 5 ,
wherein the melt kneaded product when producing the one layer has a concentration of the thermoplastic resin of 37 to 45% by mass, and the melt kneaded product when producing the other layer has a concentration of the thermoplastic resin of 20 to 35% by mass.

7 . The production method according to claim 6 ,
wherein the raw material is three components of a thermoplastic resin, inorganic fine powder, and a solvent.

8 . The production method according to claim 7 ,
wherein the inorganic fine powder having a primary particle diameter of 10 nm or more is used when producing the one layer, and the inorganic fine powder having a primary particle diameter of 20 nm or less is used when producing the other layer.

9 . The production method according to claim 7 ,
wherein the inorganic fine powder having a primary particle diameter of 20 nm or more is used when producing the one layer, and the inorganic fine powder having a primary particle diameter of less than 20 nm is used when producing the other layer.

10 . The production method according to claim 7 ,
wherein the inorganic fine powder having a primary particle diameter of 20 nm or more is used when producing the one layer, and the inorganic fine powder having a primary particle diameter of 10 nm or less is used when producing the other layer.

11 . The production method according to claim 7 , comprising discharging a melt-kneaded raw material resin from a spinning orifice nozzle when forming a membrane, and then cooling and solidifying it with taking an idle running time of 1 second or more.

12 . The production method according to claim 7 , wherein a braid is used as the one layer.

13 . The production method according to claim 7 , wherein the inorganic fine powder is silica.

14 . The production method according to claim 6 , wherein the thermoplastic resin is polyvinylidene fluoride (PVDF).

15 . The production method according to claim 14 ,
wherein a solvent satisfying the conditions of a three-dimensional solubility parameter represented by the following equation is used when producing the one layer:
((σ dm −σ dp ) 2 +(σ pm −σ pp ) 2 +(σ hm −σ hp ) 2 ) 1/2 ≦7.8

wherein σ dm and σ dp represent dispersion force terms of solvent and polyvinylidene fluoride, respectively, σ pm and σ pp represent dipole bonding force terms of solvent and polyvinylidene fluoride, respectively, and σ hm and σ hp represent hydrogen bond terms of solvent and polyvinylidene fluoride, respectively.

16 . The production method according to claim 14 ,
wherein a solvent satisfying the conditions of a three-dimensional solubility parameter represented below is used when producing the other layer:
((σ dm −σ dp ) 2 +(σ pm −σ pp ) 2 +(σ hm −σ hp ) 2 ) 1/2 >7.8

wherein σ dm and σ dp represent dispersion force terms of solvent and polyvinylidene fluoride, respectively, σ pm and σ pp represent dipole bonding force terms of solvent and polyvinylidene fluoride, respectively, and σ hm and σ hp represent hydrogen bond terms of solvent and polyvinylidene fluoride, respectively.

17 . A water purification method comprising a step of filtering suspended water using the porous hollow fiber membrane as defined in claim 1 .

Assignees

• Asahi Chemical Ind

Inventors

• Okamura Daisuke
• Miki Yuki
• Hashino Masatoshi

Classifications

• B01D69/02

  characterised by their properties · CPC title

• B01D71/027

  Silicium oxide · CPC title

• B01D71/34 Primary

  Polyvinylidene fluoride · CPC title

• B01D2325/04

  Characteristic thickness · CPC title

• B01D2325/24

  Mechanical properties, e.g. strength · CPC title