Separation membrane and method for producing separation membrane

Patent metadata

Field	Value
Publication number	US-11794150-B2
Application number	US-202017786707-A
Country	US
Kind code	B2
Filing date	Dec 23, 2020
Priority date	Dec 23, 2019
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

The present invention relates to a separation membrane including a thermoplastic polymer selected from a cellulose ester and a polyamide, in which, when regions obtained by dividing a cross-sectional surface perpendicular to a longitudinal direction of the separation membrane into 5 at an equal interval are defined as regions 1 to 5, all the regions 1 to 5 have a number average pore diameter changing rate α i of −0.25 to 0.25, and at least one of the regions 1 to 5 is a region P that satisfies conditions (a) and (b): (a) a value of area average pore diameter D s /number average pore diameter D n is 2.50 to 6.00; and (b) a number average W of fine pores that are located at a distance smaller than L a from a center of respective coarse pores is 10 to 30.

First claim

The invention claimed is:

1. A separation membrane comprising, as a main component A, a thermoplastic polymer selected from the group consisting of a cellulose ester and a polyamide,
wherein, when regions obtained by dividing a cross-sectional surface perpendicular to a longitudinal direction of the separation membrane into 5 at an equal interval in order from one surface of the separation membrane in a thickness direction of the separation membrane are defined as regions 1 to 5,
an average pore diameter obtained by weighting with a pore area ratio of pores extracted in each region to a total area of all the pores is defined as an area average pore diameter D s in each region,
an average pore diameter obtained by weighting with a number ratio of pores extracted in each region to the number of all pores is defined as a number average pore diameter D n in each region,
a pore having a pore diameter larger than the area average pore diameter D s is defined as a coarse pore,
a pore having a pore diameter smaller than the number average pore diameter D n is defined as a fine pore,
an average of closest distance between coarse pores is defined as L a , and
a number average W of the fine pores that are located at a distance smaller than L a from a center of the respective coarse pores is calculated,
all the regions 1 to 5 have a number average pore diameter changing rate α i defined by the following Formula of −0.25 or more and 0.25 or less, and
at least one of the regions 1 to 5 is a region P that satisfies the following conditions (a) and (b):
(a) a value of the area average pore diameter D s /the number average pore diameter D n is 2.50 or more and 6.00 or less; and
(b) the number average W of the fine pores is 10 or more and 30 or less,
α i =( D i −D i+1 )/ D i

(D i : Number average pore diameter of region i),
it is noted that the number average pore diameter changing rate in the region 5 is defined by the following formula,
α 5 =( D 5 −D 4 )/ D 5 .

2. The separation membrane according to claim 1 , wherein an area ratio occupied by the fine pores in the region P is 3% or more and 20% or less.

3. The separation membrane according to claim 1 , wherein (L a −D s )/D n of the region P is 2.1 or more and 7.5 or less.

4. The separation membrane according to claim 1 , wherein a variation coefficient of L a in the region P is 50% to 0.1%.

5. The separation membrane according to claim 1 , wherein all of the regions 1 to 5 are the region P.

6. The separation membrane according to claim 1 , wherein an area ratio of pores having a pore diameter of 1600 nm to 3000 nm to all pores in the region P is 50% or more.

7. The separation membrane according to claim 1 , wherein a variation coefficient of the pores having a pore diameter of 1600 nm to 3000 nm in the region P is 40% or less.

8. The separation membrane according to claim 1 , wherein a content of the main component A is 95 mass % or more when a total content of components of the separation membrane is defined as 100 mass %.

9. The separation membrane according to claim 1 , further comprising a hydrophilic polymer other than the main component A, wherein an element ratio of the hydrophilic polymer to the main component A is 15 atomic % or more in a surface concentration calculated by X-ray photoelectron analysis (ESCA) measurement.

10. The separation membrane according to claim 1 , further comprising at least one selected from the group consisting of a cellulose ester, a cellulose ether, a polyamide, a poly-fatty acid vinyl ester, polyvinylpyrrolidone, polyethylene oxide, polypropylene oxide, a polyacrylic acid ester, a polymethacrylic acid ester, and a copolymer thereof as a component other than the main component A.

11. The separation membrane according to claim 1 , further comprising at least one selected from the group consisting of a polyacrylic acid ester, a polymethacrylic acid ester, and a copolymer thereof as a component other than the main component A.

12. The separation membrane according to claim 1 , further comprising at least one selected from the group consisting of a polyvinylpyrrolidone and a copolymer containing a polyvinylpyrrolidone component as a component other than the main component A.

13. The separation membrane according to claim 12 , further comprising a copolymer of fatty acid vinyl and vinylpyrrolidone as a component other than the main component A.

14. The separation membrane according to claim 1 , having a hollow fiber shape.

15. The separation membrane according to claim 1 , wherein an area ratio occupied by macro voids to an entire cross-sectional area in the cross-sectional surface perpendicular to the longitudinal direction of the separation membrane is 10% or less.

Assignees

• Toray Industries

Inventors

• EIMURA Hiroki
• Takada Koichi
• Otsuka Marina
• Hanakawa Masayuki

Classifications

• B01D71/5211

  Polyethylene glycol or polyethyleneoxide · CPC title

• B01D71/441

  Polyvinylpyrrolidone · CPC title

• B01D71/401

  Polymers based on the polymerisation of acrylic acid, e.g. polyacrylate · CPC title

• B01D71/48

  Polyesters · CPC title

• B01D69/02 Primary

  characterised by their properties · CPC title