Hydrophilic porous membrane and method for producing hydrophilic porous membrane

Patent metadata

Field	Value
Publication number	US-12005401-B2
Application number	US-202117405126-A
Country	US
Kind code	B2
Filing date	Aug 18, 2021
Priority date	Feb 26, 2019
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

Abstract

Provided are a hydrophilic porous membrane including a porous membrane and a hydroxyalkyl cellulose retained in the porous membrane, in which the average pore size differs between two surfaces of the porous membrane, the hydroxyalkyl cellulose distributed in the thickness direction of the hydrophilic porous membrane exhibits two or more peaks of detection intensity in GPC, and the weight-average molecular weight Mwmin of the peak that is detected latest among the above-mentioned peaks is less than 100,000; and a method for producing a hydrophilic porous membrane, the method including separately preparing a hydrophilizing liquid including a hydroxyalkyl cellulose having a smaller weight-average molecular weight and a hydrophilizing liquid including a hydroxyalkyl cellulose having a larger weight-average molecular weight, and applying each of the hydrophilizing liquids on two surfaces of the porous membrane or sequentially on one surface thereof.

First claim

What is claimed is:

1. A hydrophilic porous membrane comprising:
a porous membrane; and
a hydroxyalkyl cellulose retained in the porous membrane,
wherein an average pore size differs between two surfaces of the porous membrane,
the hydroxyalkyl cellulose distributed in a thickness direction of the hydrophilic porous membrane exhibits two or more peaks of detection intensity in gel permeation chromatography, and
a weight-average molecular weight Mw min of a peak that is detected latest among the peaks is less than 100,000.

2. The hydrophilic porous membrane according to claim 1 ,
wherein in a case where the hydrophilic porous membrane is divided in the thickness direction into two parts having an equal thickness, namely, part A and part B, from a side of a surface with a smaller average pore size,
the detection intensity of the peak that is detected latest in the gel permeation chromatography of the hydroxyalkyl cellulose retained in the part A is higher than that of the hydroxyalkyl cellulose retained in the part B.

3. The hydrophilic porous membrane according to claim 2 ,
wherein the hydrophilic porous membrane has a layered dense region with a minimum pore size in an inner part,
a pore size continuously increases in the thickness direction from the dense region toward at least one membrane surface of the porous membrane, and
the dense region is located in the part A.

4. The hydrophilic porous membrane according to claim 3 , wherein an average pore size of the dense region is 0.01 to 5 μm.

5. The hydrophilic porous membrane according to claim 1 , wherein a weight-average molecular weight Mw max of a peak that is detected earliest among the peaks satisfies the following relationship:
30,000≤ Mw max /d max ≤130,000

in the formula, d max represents an average pore size [μm] at a surface on a side where the average pore size of the porous membrane is larger.

6. The hydrophilic porous membrane according to claim 1 , wherein the porous membrane contains polyethersulfone or polysulfone.

7. The hydrophilic porous membrane according to claim 2 , wherein the porous membrane contains polyethersulfone or polysulfone.

8. The hydrophilic porous membrane according to claim 3 , wherein the porous membrane contains polyethersulfone or polysulfone.

9. The hydrophilic porous membrane according to claim 4 , wherein the porous membrane contains polyethersulfone or polysulfone.

10. The hydrophilic porous membrane according to claim 1 , wherein the hydroxyalkyl cellulose is hydroxypropyl cellulose.

11. The hydrophilic porous membrane according to claim 6 , wherein the hydroxyalkyl cellulose is hydroxypropyl cellulose.

12. The hydrophilic porous membrane according to claim 1 , wherein a total mass of the hydroxyalkyl cellulose is 0.02% to 3% by mass with respect to a total mass of the porous membrane.

Assignees

• Fujifilm Corp

Inventors

• Ishii Akihiro
• Umehara Takeshi

Classifications

• B01D2325/0231

  Dense layers being placed on the outer side of the cross-section · CPC title

• B01D69/1071

  Woven, non-woven or net mesh · CPC title

• B01D2325/34

  Molecular weight or degree of polymerisation · CPC title

• B01D2325/36

  Hydrophilic membranes · CPC title

• B01D2325/023

  Dense layer within the membrane · CPC title