Ion exchange membrane for alkali chloride electrolysis, production method, and alkali chloride electrolysis apparatus

Patent metadata

Field	Value
Publication number	US-2017218527-A1
Application number	US-201715491371-A
Country	US
Kind code	A1
Filing date	Apr 19, 2017
Priority date	Nov 10, 2014
Publication date	Aug 3, 2017
Grant date	—

Abstract

To provide an ion exchange membrane for alkali chloride electrolysis which has high membrane strength and low membrane resistance, thereby capable of reducing the electrolysis voltage during alkali chloride electrolysis. In this ion exchange membrane ( 1 ) for alkali chloride electrolysis, a reinforcing material 20 formed by weaving reinforcing yarns 22 and sacrificial yarns 24 is disposed in a layer (S) 14 , and layer (S) 14 has elution portions 28 formed by elution of at least portions of the sacrificial yarns 24 . In a cross section perpendicular to reinforcing yarns of the warp, the average distance (d1) from the center of a reinforcing yarn 22 to the center of the adjacent reinforcing yarn 22 , the total area (P) obtained by adding the cross-sectional area of an elution portion 28 and the cross-sectional area of a sacrificial yarn 24 remaining in the elution portion 28 , the number (n) of elution portions between adjacent reinforcing yarns 22 , and the ion exchange capacity of a layer (Sa) located on the most anode side in the layer (S) 14 during alkali chloride electrolysis, are controlled to be within specific ranges, respectively.

First claim

What is claimed is:

1 . An ion exchange membrane for alkali chloride electrolysis to be used as installed in an alkali chloride electrolytic cell provided with a cathode and an anode so as to partition inside of the electrolytic cell into a cathode chamber on the cathode side and an anode chamber on the anode side, characterized in that
said ion exchange membrane for alkali chloride electrolysis has a layer (S) comprising a fluorinated polymer having sulfonic acid functional groups, and a reinforcing material disposed in said layer (S) substantially in parallel to the layer (S); said layer (S) is a laminate of a single layer (Sa) disposed at the most anode side, at least one layer (Sb) disposed on the cathode side than the layer (Sa), and the reinforcing material disposed between the layer (Sa) and the layer (Sb), or in the layer (Sb); the reinforcing material is a woven fabric using reinforcing yarns for the weft and warp and optionally using sacrificial yarns for the weft and warp, in a cross section of the layer (S) perpendicular to the length direction of the reinforcing yarns, the average distance (d1) from the center of a reinforcing yarn to the center of the adjacent reinforcing yarn is from 750 to 1,000 μm; in the layer (S), elution portions formed by elution of the sacrificial yarns are present; the total area (P) of the cross-sectional area of an elution portion and the cross-sectional area of a sacrificial yarn remaining in the elution portion is from 500 to 5,000 μm 2 ; and the average number of elution portions between adjacent reinforcing yarns is from 4 to 6; and the ion exchange capacity of said layer (Sa) is at least 1.15 meq/g dry resin.

2 . The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein the ion exchange capacity of the layer (Sb) is lower than the ion exchange capacity of the layer (Sa).

3 . The ion exchange membrane for alkali chloride electrolysis according to claim 1 , which has at least one layer (C) comprising a fluorinated polymer having carboxylic acid functional groups, on the most cathode side surface of the layer (S).

4 . The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein a relationship is established to satisfy the following formula (1) in a cross section perpendicular to the length direction of the reinforcing yarns:
0.5≦{ d 2/ d 1×( n+ 1)}≦1.5  (1)
provided that symbols in the formula (1) have the following meanings,
d1: the average distance from the center of a reinforcing yarn to the center of the adjacent reinforcing yarn,
d2: the average distance from the center of an elution portion to the center of the adjacent elution portion,
n: the average number of elution portions that exist between adjacent reinforcing yarns.

5 . The ion exchange membrane for alkali chloride electrolysis according to claim 4 , wherein a relationship is established to satisfy the following formula (1′) at all measurement points measured to determine the average distance (d1) and the average distance (d2) in a cross section perpendicular to the length direction of the reinforcing yarns:
0.5≦{ d 2′/ d 1×( n+ 1)}≦1.5  (1′)

provided that the symbols in the formula (1′) have the following meanings,
d2′: the distance from the center of an elution portion to the center of the adjacent elution portion at an optional measurement point,
d1 and n: the same as above.

6 . The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein a relationship is established to satisfy the following formula (2) in a cross section perpendicular to the length direction of the reinforcing yarns:
0.5≦{ d 3/ d 1×( n+ 1)}≦1.5  (2)
provided that the symbols in the formula (2) have the following meanings,
d3: the average distance from the center of a reinforcing yarn to the center of the adjacent elution portion,
d1 and n: the same as above.

7 . The ion exchange membrane for alkali chloride electrolysis according to claim 6 , wherein a relationship is established to satisfy the following formula (2′) at all measurement points measured to determine the average distance (d1) and the average distance (d3) in a cross section perpendicular to the length direction of the reinforcing yarns:
0.5≦{ d 3′/ d 1×( n+ 1)}≦1.5  (2′)

provided that the symbols in the formula (2′) have the following meanings,
d3′: the distance from the center of a reinforcing yarn to the center of the adjacent elution portion at an optional measurement point,
d1 and n: the same as above.

8 . The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein the thicknesses of the reinforcing yarns in a cross section perpendicular to the length direction of the reinforcing yarns are from 70 to 160 μm.

9 . An alkali chloride electrolysis apparatus having an electrolytic cell provided with a cathode and an anode, and an ion exchange membrane for alkali chloride electrolysis as defined in claim 1 , wherein the ion exchange membrane for alkali chloride electrolysis is installed between the anode and the cathode in said electrolytic cell substantially in parallel to them, so as to partition inside of the cell into a cathode chamber on the cathode side and an anode chamber on the anode side.

10 . A method for producing an ion exchange membrane as defined in claim 1 , which comprises obtaining a reinforced precursor membrane having a reinforcing fabric composed of reinforcing yarns and sacrificial yarns, disposed in a precursor membrane comprising a fluorinated polymer having groups convertible to ion exchange groups, and then contacting the reinforced precursor membrane with an alkaline aqueous solution to convert the groups convertible to ion exchange groups, to the ion exchange groups, and at the same time to elute at least a portion of the sacrificial yarns in the reinforcing fabric, thereby to obtain an ion exchange membrane comprising a fluorinated polymer having the ion exchange groups, a reinforcing material having at least a portion of the sacrificial yarns in the reinforcing fabric eluted, and elution portions.

11 . The method for producing an ion exchange membrane for alkali chloride electrolysis according to claim 10 , wherein the ion exchange capacity of the layer (Sb) located on the cathode side than the layer (Sa) during alkali chloride electrolysis, is lower than the ion exchange capacity of the layer (Sa).

12 . The method for producing an ion exchange membrane for alkali chloride electrolysis according to claim 10 , which further has a layer (C) comprising a fluorinated polymer having carboxylic acid functional groups on the opposite side surface to the layer (Sa).

13 . The method for producing an ion exchange membrane for alkali chloride electrolysis according to claim 10 , wherein a relationship is established to satisfy the following formula (1) in a cross section perpendicular to the reinforcing yarns of the warp:
0.5≦{ d 2/ d 1×( n+ 1)}≦1.5  (1)
provided that symbols in the formula (1) have the following meanings,
d1: the average distance from the center of a reinforcing yarn to the center of the adjacent reinforcing yarn,
d2: the average distance from the center of an elution portion to the center of the adjacent elution portion,
n: number of elution portions between adjacent reinforcing yarns.

14 . The method for producing an ion exchange membrane for alkali chloride electrolysis according to claim 10 , wherein a relationship is established to satisfy the following formula (2) in a cross section perpendicular to the reinforcing yarns of the warp:
0.5≦{ d 3/ d 1×( n+ 1)}≦1

Assignees

• Asahi Glass Co Ltd

Inventors

• Yamaki Yasushi
• Kaneko Takayuki
• Kusano Hiromitsu
• Nishio Takuo

Classifications

• C08J5/225

  containing fluorine · CPC title

• B01J39/20

  obtained by reactions only involving unsaturated carbon-to-carbon bonds · CPC title

• C25B1/46 Primary

  in diaphragm cells · CPC title

• C08F214/262

  with fluorinated vinyl ethers · CPC title

• C08J2327/18

  Homopolymers or copolymers of tetrafluoroethylene · CPC title