Porous membrane, composite membrane, and method for producing porous membrane

Patent metadata

Field	Value
Publication number	US-12097470-B2
Application number	US-201917413734-A
Country	US
Kind code	B2
Filing date	Dec 24, 2019
Priority date	Dec 26, 2018
Publication date	Sep 24, 2024
Grant date	Sep 24, 2024

Abstract

The present invention relates to a porous membrane including a polymer including a polyvinylidene fluoride-based resin as a main component, and a branched polyvinylidene fluoride-based resin as the polyvinylidene fluoride-based resin, in which the polymer has a value of a of 0.32 to 0.41 and a value of b of 0.18 to 0.42, each of which is determined by approximation according to the formula 1 below from a radius of gyration <S 2 > 1/2 and an absolute molecular weight M w of the polymer which are measured by GPC-MALS (gel permeation chromatograph equipped with a multi-angle light scattering detector). <S 2 > 1/2= bM w a (Formula 1).

First claim

The invention claimed is:

1. A porous membrane comprising a polymer comprising a polyvinylidene fluoride-based resin as a main component, and a branched polyvinylidene fluoride-based resin as the polyvinylidene fluoride-based resin,
wherein:
a proportion of the polyvinylidene fluoride-based resin in the polymer is 55 mass % or more,
a proportion of the branched polyvinylidene fluoride-based resin in the polyvinylidene fluoride-based resin is 10 mass % to 100 mass %,
the branched polyvinylidene fluoride-based resin has a weight average molecular weight of 50,000 Da to 1,000,000 Da,
wherein the polymer has a value of “a” of 0.32 to 0.41 and a value of “b” of 0.18 to 0.42, where “a” represents a value specific to the polymer for determining a radius gyration and “b” represents a proportionality constant specific to the polymer for determining a radius gyration, each of which is determined by approximation according to the formula 1 below from a radius of gyration <S 2 > 1/2 and an absolute molecular weight M w of the polymer which are measured by GPC-MALS (gel permeation chromatograph equipped with a multi-angle light scattering detector):
< S 2 > 1/2 =bM w a   (Formula 1),

the porous membrane has an average surface pore diameter of 3 nm to 16 nm, and a pure water permeability at 25° C. and 50 kPa of 0.1 m 3 /m 2 /hr to 0.8 m 3 /m 2 /h, and
the branched polyvinylidene fluoride-based resin is a star-shape branched polyvinylidene fluoride-based resin.

2. The porous membrane according to claim 1 , wherein the polymer includes a hydrophilic resin.

3. The porous membrane according to claim 1 , having a three-dimensional network structure.

4. The porous membrane according to claim 1 , wherein an amount of the branched polyvinylidene fluoride-based resin is 15 mass % to 100 mass %.

5. A composite membrane comprising the porous membrane according to claim 1 and another layer, wherein the porous membrane is disposed on a surface portion thereof.

6. The composite membrane according to claim 5 , wherein the other layer is a support.

7. A method for preparing the porous membrane according to claim 1 , the method comprising:
a polymer solution preparation step (A) of dissolving the polymer in a solvent to obtain a polymer solution; and
a porous membrane formation step (B) of coagulating the polymer solution in a non-solvent to form the porous membrane,
wherein the polyvinylidene fluoride-based resin subjected to the polymer solution preparation step (A) has a crystallinity of 35% or more.

Assignees

• Toray Industries

Inventors

• SHIMURA Shun
• Hanakawa Masayuki
• Iwai Kenta
• Yasuda Takaaki

Classifications

• B01D2325/02832

  1-10 nm · CPC title

• B01D69/1071

  Woven, non-woven or net mesh · CPC title

• B01D69/108

  Inorganic support material · CPC title

• B01D2325/02833

  more than 10 and up to 100 nm · CPC title

• B01D69/12

  Composite membranes; Ultra-thin membranes · CPC title