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

Patent metadata

Field	Value
Publication number	US-11066751-B2
Application number	US-201816156360-A
Country	US
Kind code	B2
Filing date	Oct 10, 2018
Priority date	Apr 13, 2016
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

To provide an ion exchange membrane for alkali chloride electrolysis which is a membrane having a high water permeability and being capable of maintaining a low electrolysis voltage while suppressing the amount of water supplied to a cathode chamber to be minimum, and which is capable of forming an aqueous alkali hydroxide solution having a high caustic alkali quality. The ion exchange membrane for alkali chloride electrolysis comprises a layer 12 made of a fluorinated polymer having carboxylic acid functional groups, and a layer 14A and a layer 14B made of a fluorinated polymer having sulfonic acid functional groups, wherein a reinforcing material 20 containing reinforcing threads 22 is disposed between the layer 14A and the layer 14B, the thickness when dried, of the layer 12 is from 9 to 28 μm, the layer 14B includes a layer having an ion exchange capacity of from 1.3 to 2.5 meq/g, the thickness when dried, of the layer 14B is from 6 to 100 μm, the layer 14A includes a layer having an ion exchange capacity of from 0.9 to 1.25 meq/g, and the thickness when dried, of the layer 14A is from 40 to 110 μm.

First claim

What is claimed is:

1. An ion exchange membrane for alkali chloride electrolysis comprising a layer (C) made of a fluorinated polymer having carboxylic acid functional groups at the surface on a cathode side, and a layer (S) made of a fluorinated polymer having sulfonic acid functional groups at the surface on an anode side, characterized in that a reinforcing material comprising reinforcing threads is disposed in the layer (S) made of a fluorinated polymer having sulfonic acid functional groups,
the thickness when dried, of the layer (C) made of a fluorinated polymer having carboxylic acid functional groups is from 9 to 28 μm,
in the layer (S) made of a fluorinated polymer having sulfonic acid functional groups,
a layer (Sb) located on the anode side of the reinforcing material includes a layer made of a fluorinated polymer having sulfonic acid functional groups with an ion exchange capacity of from 1.3 to 2.5 meq/g dry resin, and has a thickness when dried, of from 6 to 100 μm, and
a layer (Sa) located on the cathode side of the reinforcing material includes a layer made of a fluorinated polymer having sulfonic acid functional groups with an ion exchange capacity of from 0.9 to 1.25 meq/g dry resin, and has a thickness when dried, of from 40 to 110 μm.

2. The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein at least a part of the fluorinated polymer having sulfonic acid functional groups constituting the layer (Sb) made of a fluorinated polymer having sulfonic acid functional groups located on the anode side of the reinforcing material is a polymer having structural units represented by the following formula (U1):

wherein Q 1 is a perfluoroalkylene group which may have an etheric oxygen atom, Q 2 is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom, R f1 is a perfluoroalkyl group which may have an etheric oxygen atom, X 1 is an oxygen atom, a nitrogen atom or a carbon atom, when X 1 is an oxygen atom, a is 0, when X 1 is a nitrogen atom, a is 1, when X 1 is a carbon atom, a is 2, Y 1 is a fluorine atom or a monovalent perfluoro organic group, r is 0 or 1, and M is a hydrogen atom, an alkali metal or a quaternary ammonium base.

3. The ion exchange membrane for alkali chloride electrolysis according to claim 2 , wherein the structural units represented by the formula (U1) are structural units based on a monomer represented by the formula (M1):

wherein R F11 is a single bond or a C 1-6 linear perfluoroalkylene group which may have an etheric oxygen atom, and R F12 is a C 1-6 linear perfluoroalkylene group.

4. The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein the ion exchange capacity of at least a part of the fluorinated polymer having carboxylic acid functional groups constituting the layer (C) made of a fluorinated polymer having carboxylic acid functional groups is from 0.5 to 2.0 meq/g dry resin.

5. The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein the layer (Sa) located on the cathode side of the reinforcing material is a layer composed of two or more layers.

6. The ion exchange membrane for alkali chloride electrolysis according to claim 5 , wherein among the layers forming the layer (Sa) located on the cathode side of the reinforcing material, a layer (Sa- 1 ) located on the most cathode side is a layer made of a fluorinated polymer having sulfonic acid functional groups with a thickness when dried, of from 1 to 55 μm and an ion exchange capacity of from 0.9 to 1.25 meq/g dry resin.

7. The ion exchange membrane for alkali chloride electrolysis according to claim 1 , wherein the reinforcing material comprises reinforcing threads and sacrificial threads.

8. The ion exchange membrane for alkali chloride electrolysis according to claim 1 , which further has an inorganic particle layer at the outermost surface of at least one side.

9. A method for producing an ion exchange membrane for alkali chloride electrolysis as defined in claim 1 , characterized by laminating a layer (C′) made of a fluorinated polymer having groups convertible to carboxylic acid functional groups, a layer (S′a) made of a fluorinated polymer having groups convertible to sulfonic acid functional groups, a reinforcing fabric and a layer (S′b) made of a fluorinated polymer having groups convertible to sulfonic acid functional groups, in this order to obtain a reinforced precursor membrane, and then, contacting the reinforced precursor membrane with an aqueous alkaline solution, to convert the groups convertible to ion exchange groups in the reinforced precursor membrane to ion exchange groups.

10. The method for producing an ion exchange membrane for alkali chloride electrolysis according to claim 9 , wherein the reinforcing fabric is made of reinforcing threads and sacrificial threads, and the reinforcing precursor membrane is brought in contact with an aqueous alkaline solution to convert the groups convertible to ion exchange groups to ion exchange groups, and to dissolve at least a part of the reinforcing threads in the reinforcing fabric to form a reinforcing material.

11. The method for producing an ion exchange membrane for alkali chloride electrolysis according to claim 9 , wherein the aqueous alkaline solution is a mixture of a water-soluble organic compound, a hydroxide of an alkali metal and water.

12. An alkali chloride electrolysis apparatus characterized by comprising an electrolytic bath provided with a cathode and an anode, and an ion-exchange membrane for alkali chloride electrolysis as defined in claim 1 that partitions a cathode chamber on the cathode side and an anode chamber on the anode side in said electrolytic bath.

13. A method for producing an alkali hydroxide, characterized by electrolyzing an alkali chloride by using the alkali chloride electrolysis apparatus as defined in claim 12 .

14. The method for producing an alkali hydroxide according to claim 13 , wherein the alkali chloride is electrolyzed while supplying oxygen to the cathode chamber.

15. The method for producing an alkali hydroxide according to claim 13 , wherein the content of the alkali chloride to the alkali hydroxide in the aqueous alkali hydroxide solution to be produced, is at most 25 ppm.

Assignees

• Agc Inc

Inventors

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

Classifications

• C25B9/23

  comprising ion-exchange membranes in or on which electrode material is embedded · CPC title

• B01J39/05

  in the strongly acidic form · CPC title

• B01J39/20

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

• C25B13/08 Primary

  based on organic materials · CPC title

• B01J47/12

  characterised by the use of ion-exchange material in the form of ribbons, filaments, fibres or sheets, e.g. membranes (electrodialysis or electro-osmosis B01D61/42) · CPC title