JPS6119638A - Repair of cation-exchange membrane for electrolysis of aqueous solution of alkali metal chloride - Google Patents

Abstract

PURPOSE:To repair an ion-exchange membrane having major defects such as pinholes, breakages, peeling etc. with good workability, by melt-bonding a specified repairing material to a defective cation-exchange membrane for the electrolysis of an aqueous solution of an alkali metal chloride. CONSTITUTION:A repairing material of a thickness of 5-700mum comprising a perfluoropolymer which contains 0.5-1.9meq/g of an acid residue such as -COOH, -SO3H or -P(O)(OH)2 is abutted against the defective part of a material to be repaired comprising a cation-exchange membrane for the electrolysis of an aqueous solution of an alkali metal chloride which has defects such as pinholes, breakage, or peeling, contains ion-exchange groups comprising alkali metal salts, and has an exchange capacity of 0.5-1.9meq/g, and is heated and pressed at 100-260 deg.C and 0.2-200kg/cm<2> for 1sec-10min to be melt-bonded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for repairing a cation exchange membrane for aqueous alkali metal chloride solution electrolysis.

[Prior art 1: As a method for producing high-grade alkali hydroxide and chlorine,
Electrolysis using a cation exchange membrane as a diaphragm is widely practiced. In this case, a pinhole.

If a membrane with defects such as damage or peeling is used as a diaphragm as is, fatal problems such as a decrease in product purity and current efficiency will occur, so either replace it with a non-defective one or repair such defects by some method. There is a need,
The latter is preferable from an economic standpoint.

Conventionally, as such a repair method, a method has been proposed in which the ion exchange group of the repaired material is in an acid or ester type state and a similar membrane-like repair material is melt-bonded (Japanese Patent Publication No. 57-22
However, in this method, if the ion exchange group of the material to be repaired is in the form of an alkali metal salt, it is essential to first convert it into an acid or ester form. There was an operational difficulty in that prior to electrolysis, it had to be converted back into an alkali metal salt form. As another method, a method has been proposed in which a repair material powder is dispersed in a medium that is solvable and soluble in both the repaired material and the repair material, and the powder is applied to the defective part and dried (JP-A-58
'Refer to Publication No. 87286). However, although this method is effective for small defects, it cannot be applied when the defects become large to a certain extent, and furthermore, there are limitations such as contamination of the working environment by volatile solvents.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art as described above. The aim is to provide a repair method that can be applied to

[Means for Solving the Problems] The repair method of the present invention involves melt-bonding a repair material to a repaired material consisting of a cation exchange membrane for aqueous alkali metal chloride electrolysis that has defects such as pinholes, damage, or peeling. In the repair method for at least repairing defects, the ion exchange group of the repaired material is of an alkali metal salt type, and the repair material is made of a perfluoropolymer having acid residues.

In the present invention, the form, material, type of exchange group, exchange capacity, etc. of the cation exchange membrane to be repaired are not limited as long as the ion exchange group is an alkali metal salt type. , various types can be adopted. for example,
The form is not limited to single-layer membranes, but also multi-layer membranes having two or more layers with different types of exchange groups or exchange capacities, and fabrics made of perfluoropolymer fibers or polytetrafluoroethylene fibrils. It is also possible to employ a membrane reinforced by the above-mentioned membranes, etc., or a membrane with a hydrophilic porous layer provided on at least one surface thereof. As for the material, perfluoro-based materials can be preferably used from the viewpoint of acid/alkali resistance, oxidation resistance, chlorine resistance, etc.

The type of exchange group is 1000M (M represents an alkali metal. The same applies hereinafter).

-500M, -P (0) (ON)2, -C(CF
* ) 20M etc. is exemplified, and the exchange capacity is 0.5
~1.9, particularly about 0.8 to 1.8 millimeter/gram dry resin (hereinafter referred to as meq/g) may be employed.

In the present invention, it is important to use a repair material made of a perfluoropolymer having acid residues. Surprisingly, those in which the portion corresponding to the acid residue is esterified or in the form of an acid halide are better in terms of melt fluidity than those with acid residues. Nevertheless, the adhesion to the repaired material is poor, and non-perfluoropolymer-based materials have poor durability, both of which are disadvantageous. In addition, perfluoropolymers that do not have acid residues have poor adhesion to the material to be repaired, and the membrane twitches during electrolysis at the site to be repaired, which is inconvenient as it becomes a starting point for wrinkles.

The composition, manufacturing method, etc. of the perfluoropolymer having acid residues used as a raw material for the repair material in the present invention are not particularly limited, and various embodiments are possible. The type of acid residue is -GOOH.

-3O3H, -P(0)(OH)2, (:(CFs
)20H etc., and from the viewpoint of availability -COO)l
From the viewpoint of melt fluidity, 100OH can be preferably employed. The content is usually 0.5 to 1.8, particularly 0.8 to 1.8, from the viewpoint of melt fluidity.
8 meq/g can be adopted. A method for producing such a polymer involves combining a perfluoroolefin, especially tetrafluoroethylene, a perfluorounsaturated compound having an acid residue or a group convertible thereto, especially a perfluorovinyl ether type compound, and a desired compound. A monomer mixture containing a co-educated 11E compound such as perfluoroalkyl vinyl ether added as appropriate is copolymerized by acting on a polymerization initiation source, and if necessary, it is formed into a form such as a film or the like in a bulk state or by a conventional method. A preferred example is a method of converting a group convertible into an acid residue in the post-copolymer into an acid residue.

In addition, when selecting such a polymer, from the viewpoints of easy availability and prevention of wrinkles in the membrane after repair, select a polymer that has the same type of acid residue as the ion exchange group of the material to be repaired, and The difference between its content and exchange capacity is preferably 0.8me
It is desirable to select one with a small value of about q/g or less. The acid residue is -COOH, and the ion exchange group is -GO.
The combination of ONa can be particularly preferably employed from the viewpoint of durability, electrolytic performance, and the like.

In the present invention, the form of the repair material is not particularly limited, and may be appropriately selected depending on the form and thickness of the material to be repaired, such as film, filament, cloth, powder, etc., as well as the form and size of the defect. From 5 to 7001 LII, preferably from 50 to 40
Good results are achieved by employing film thicknesses of the order of 0 gm. Such repair materials include reinforcing materials and fillers.

It is also possible to contain pigments and the like as appropriate.

The conditions for melt joining the repair material and the repaired material are not particularly limited, but the temperature is 100 to 260°C, preferably about 180 to 250°C, and the pressure is 0.2 to 200°C.
kg/CTl1, preferably 5 to 100 kg/cyd
The degree of crimping can be adopted, and the crimping time is 1 second to l
About 0 minutes is sufficient.

In the present invention, if the material to be repaired has an ion-exchange group or an alkali metal salt type, a special pretreatment process is usually not necessary, but cleaning the area to be repaired by washing it with water will remove any dirt and electrolyte that may have adhered to it. It is preferable to remove such materials in order to achieve more perfect bonding. Furthermore, if the material to be repaired has a porous layer made of inorganic particles or the like on its surface, it is preferable to remove such a layer from the repaired portion before performing the repair.

[Example] Example 1 Tetrafluoroethylene [TFE] and perfluoro-
Methyl 3-oxa-1-heptenoate [CF2 = G, F
A copolymer (polymer I) with an ion exchange capacity of 1.44 meq/g obtained by copolymerizing O(C:F,)3 (:ooCH3) was press-formed into a film at 230°C to a thickness of 280 g m.
It was made into a film. This film is designated as O. Next, the film was treated with a 25% aqueous sodium chloride solution at 70° C. for 16 hours to hydrolyze it into sodium-type ion-exchanged S. This ionic membrane is designated as A. Next, the ionic membrane A was treated with 2N hydrochloric acid to prepare a film in which the functional group had a carboxylic acid residue. This film is designated as B. A hole of approximately Q, 2 crn' was made in the sodium type ion membrane A, and then this hole was covered with a film B having acid residues at 230°C.
.

Heat and pressure bonding was carried out for 1 minute under the condition of 20 kg/crn'. The repaired membrane thus obtained has achieved strong bonding,
No peeling was observed at the repaired area even after being left in water at 100°C for 30 minutes.

In addition, the same repaired membrane as above was separately subjected to an electrolytic test. For electrolysis, an anode with a low oxygen overvoltage made by coating a titanium punched metal with a solid solution of ruthenium oxide, indium oxide, and titanium oxide, and an anode with a low hydrogen overvoltage by electrodepositing Raney nickel on a 5US-304 punched metal. A negative electrode was used. A 5N aqueous sodium chloride solution is supplied to the anode chamber, which is divided into two parts of the electrolytic cell by a repair membrane, and water is supplied to the cathode chamber. When electrolysis was carried out at 90°C and 30 A/dm' while maintaining the concentration at 35% by weight, the current efficiency 7 days after the start of electrolysis was 85%, and the voltage was 3. It was OV. The salt content in the produced caustic soda solution was 30 ppm. After continuing electrolysis for 20 days, the membrane was observed, but no abnormality was observed. These electrolytic data were not significantly different from the data for non-perforated ionic membrane A.

Comparative Example The same repair operation as in Example 1 was carried out except that O was used instead of Film B. In this case, when the repaired film was left in water at 100°C for 30 minutes, some peeling occurred in the repaired area.

Electrolysis was carried out under exactly the same conditions as in Example 1 using the same repaired membrane as in Section 2. The current efficiency 7 days after the start of electrolysis is 9
2%, the voltage was a, 73v, and the salt content in the produced sodium hydroxide solution was 150ppm, so the electrolysis was discontinued.

Example 2 In Example 1, instead of treating the film O with a 25% aqueous sodium chloride solution at 70°C for 3 hours at 1f to hydrolyze it into a sodium-type ion exchange membrane, it was treated with a 20% aqueous potassium solution. A repaired membrane was obtained in exactly the same manner as in Example 1, except that it was treated at 80° C. for 16 hours to be hydrolyzed to obtain a potassium type ion exchange membrane. In order to evaluate the adhesion of the repaired film, the repaired film was left in water at 100° C. for 30 minutes.

No peeling was observed in the film.

Example 3 TFE and perfluoro(3,6-thioxer 4-methyl-7-octensulfonyl fluorite) [CF,=C
FOCF2 CF (CF3)OCF7CF7 SO2F
The ion exchange capacity obtained by copolymerizing 1.1a+eq/
A copolymer (polymer II) of g was press-formed at 230°C to form an a+ film with a thickness of 200 p. The film was then treated with a 25% strength soda aqueous solution at 80° C. for 1θ hour, and then treated with 2N hydrochloric acid to obtain a film having sulfonic acid residues. This film is designated as C.

A hole of about 0.2 crn' was made in the same sodium carboxylate type ion film A as in Example 1.
Covered with 230℃, 20kg/crn' (7) Condition Te1
The separate volumes were heat-pressed. The bondability of the repaired membrane was evaluated in exactly the same manner as in Example 1, and no abnormalities were observed in the membrane.

Example 4 Polymer II was press-formed at 230°C to form a film with a thickness of 200 gm, and then dissolved in a 25% aqueous sodium hydroxide solution at 9%
A sodium type ion membrane was obtained by processing at 0°C for 216 hours. A hole of about 0.2 crn' was drilled in the membrane, then the hole was covered with the same film B as in Example 1, and heated at 230°C.
Heat and pressure bonding was carried out for 1 minute under the condition of 0 kg/crn'. The adhesion of the repaired film was evaluated in exactly the same manner as in Example 1, but no peeling was observed in the film.

Example 5 In Example 1, instead of film B as the repair material,
Film B has a thickness of BoALffi and an aperture ratio of 65% P.
Using reinforcing film D embedded with TFE cloth 1
Other than that, the same repair operation as in Example 1 was performed. In this case as well, no peeling of the repaired area was observed during the same boiling test.

Example 6 Polymer II was press-formed at 230°C to form a film a with a thickness of 50 μm. Polymer I was press-formed at 230°C to form a film b with a thickness of 50 g m. After blending with Union II in a ratio of 1=1, roll kneading at 130°C, press forming at 230°C to form a film with a thickness of 50 pLm.
Fills I and C were obtained. Next, each film was stacked in the order of a, c, b, and rolled for 200 minutes using a hot roll.
°C't1'' laminated. After the thus obtained laminated membrane was hydrolyzed in exactly the same manner as in Example 1, the membrane had a
I drilled a cm' hole. Next, the same film B as in Example 1
Then cover the a side of the laminated film with holes and heat it to 230℃.

The adhesion of the repaired film was evaluated in the same manner as in Example 1 by heat-pressing for 1 minute at 20 kg/crn', but no peeling of the repaired area was observed.

[Effects of the Invention] According to the repair method of the present invention, strong repair is possible by directly melt-bonding the repair material to the repaired material, and there is no need for complicated pretreatment of the repaired material or use of a special binder. This method greatly improves operability because it does not require the use of a special solvent, and it is also advantageous in terms of the working environment because it does not require the use of special solvents. Furthermore, it can be advantageously applied to repairing relatively large defects. Another advantage is that it can be subjected to electrolysis immediately after repair is completed without any special post-treatment.

Claims (1)

[Scope of Claims] A repair method for repairing defects by melt-bonding a repair material to a repaired material comprising a cation exchange membrane for aqueous alkali metal chloride electrolysis having defects such as pinholes, damage, or peeling, comprising: A method for repairing a cation exchange membrane for aqueous alkali metal chloride solution electrolysis, characterized in that the ion exchange group of the material to be repaired is an alkali metal salt type, and the repair material is made of a perfluoropolymer having acid residues.