JPS6031216B2 - Manufacturing method of cation exchange membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a cation exchange membrane, and more particularly to a method for producing a cation exchange membrane, in which a polymer film having an acid halide group and a fluorine atom bonded to each other has a phenolic hydroxyl group and a vinyl group. The present invention relates to a method for producing a cation exchange membrane having particularly good electrolytic performance by contacting the membrane with an aromatic compound that does not have an aromatic compound.

In recent years, there has been an urgent need to establish a method for producing alkali metal salt hydroxide, hydrogen gas, oxygen gas, halogen gas, etc. by electrolysis of aqueous alkali metal salt solutions to obtain highly pure alkali metal hydroxide. ing.

The core of this technology is a cation exchange membrane that separates the anode chamber and the cathode chamber. Research and improvement of ion exchange membranes continues. The basic properties of a cation exchange membrane that can meet the above objectives are oxidation resistance, alkali resistance, and heat resistance. For this purpose, fluorine-containing cation exchange membranes have been developed, but in general, fluorine-containing cation exchange membranes are used to obtain concentrated alkali metal hydroxides, maintain high current efficiency, and have a low lightning tank. Maintaining voltage is not easy. Therefore, various methods of improving fluorine-containing cation exchange membranes have been proposed or attempted. For example, a method of forming a sulfonic acid amide layer by treating the surface of a perfluorocarbon sulfonic acid type membrane in contact with caustic soda with ammonia, monoalkylamine, diamine, or polyamine, a method of forming an anionic thin layer, and a method of forming an anionic thin layer. There are methods of forming a thin layer of , a method of forming a layer having carboxylic acid groups, and a method of using a fluorine-containing intestinal ion exchange membrane having only carboxylic acid groups. The present inventors conducted various studies on the reaction between the sulfonyl halide groups and aromatic rings of the polymer membrane by reacting a reactive aromatic compound with a polymer membrane having sulfonyl halide groups. As a result of this progress, we unexpectedly discovered that alkali metal The present invention was completed based on the discovery that electrolytic performance is significantly improved when salt electrolysis is carried out.

That is, the present invention provides a polymer film having a fluorine atom bonded to an acid halide group and a fluorine atom bonded to at least a carbon at the Q position with respect to the halide group, and a phenolic hydroxyl group bonded to the phenolic hydroxyl group for at least one month. This is a method for producing a cation exchange membrane, which is characterized in that after contacting with an aromatic compound having the above-mentioned properties and not having a vinyl group, hydrolysis treatment is performed as necessary. The polymer film used in the present invention has a fluorine atom and a halogen halide group bonded to each other, and it is necessary that a fluorine atom is bonded to at least the carbon at the Q position with respect to the acid halide group. be.

The acid halide group in this case is not particularly limited as long as it is a conventionally known acid halide group. That is, sulfonic acid halides, carboxylic acid halides, phosphoric acid halides, phosphorous halides, etc. The halides include fluoride, chloride,
Although there are no particular limitations on fromide and iota-11ide, chloride, furomide, and iota-11ide are particularly preferred. Furthermore, as the polymer film-like material in which a fluorine atom is bonded to at least the carbon at the Q position relative to the acid halide group, it is most desirable to use a polymer film in which the acid halide group is bonded to a perfluorocarbon polymer chain. For example, a copolymer of perfluoro(3,6-dioxa-4-methyl-7-octensulfonyl fluoride) and tetrafluoroethylene, or a cation exchange membrane made by hydrolyzing it, is used as phosphorus pentachloride. , phosphorus trichloride, phosphorus oxychloride, thionyl chloride, phosphorus pentabromide, fluorine gas, etc., are bonded to groups converted to acid halide groups by conventionally known methods. On the other hand, in the present invention, aromatic compounds having a phenolic hydroxyl group bonded for at least one month and having no vinyl group to be reacted with a polymer film having an acid halide group include phenol, pyrogallol, resorcinol, and tecol. ,
Hydroquinone, phloroglucin, gallic acid, naphthols, naphthalene diols, or their humble conductors, compounds with halogens, alkyl groups, alkoxy groups, amino groups, sulfonic groups, nitro groups, phosphoric acid groups, carboxylic acid groups, etc. Examples include cresols, ethylphenols, chlorophenols, iodophenols, methoxyphenols, dimethoxyphenols, methoxycatechols, diisopropylcatechols, hexahydroxybesozene, chlorresorcinols, methylhydroquinones, and dihydroxynaphthalenes. , tetrahydroxyanthracenes, bis→hydroxyphenyl)-methanes, etc., which are soluble in organic and inorganic solvents are desirable.

Next, the means by which these aromatic compounds having a phenolic hydroxyl group and not having a vinyl group are brought into contact with an acid halide group is not particularly limited.

When the above-mentioned compound having a phenolic hydroxyl group is in a liquid state, a polymer film having an acid halide group may be impregnated with the compound, or if it is a solid, it may be dissolved in an appropriate organic or inorganic solvent. The film-like material may be impregnated. As the above-mentioned organic/inorganic solvents, alcohols, ketones, ethers, organic acids, carbon tetrachloride, halogenated hydrocarbons such as chloroform, aromatic compounds, water, etc. can be used without any restriction. When bringing these aromatic compounds with phenolic hydroxyl groups or aqueous solutions containing them into contact with polymer membranes having acid halide groups, it is best to immerse the membrane in the solution and soak the liquid. is desirable, or it may be preferable to flow the liquid at a constant flow rate over the membrane surface of the membrane-like material depending on the case. The above contact temperature is not particularly limited as long as the aromatic compound having a phenolic hydroxyl group or the solution containing it is within the temperature range from which it does not coagulate. You can achieve your purpose. Furthermore, when an aromatic compound having a phenolic hydroxyl group is dissolved in a suitable solvent, it can be used at a concentration up to a saturated solution, or when the solubility is low, it may be made into a slurry. The above-mentioned contact time is generally industrially significant from 1 minute to 200 hours, but there is no particular problem if the contact time is further extended for 20 hours or more. Note that when bringing into contact, only one side of the membrane may be brought into contact, or both sides of the membrane may be brought into contact, but it is particularly preferable to bring into contact only one side of the membrane. In addition, if you want to advance the reaction to the inside of the polymer membrane, you can use a solvent that has the ability to swell the polymer membrane, or if you want to cause the reaction to occur only in a thin layer on the surface of the membrane, A solvent having poor affinity for the film-like material may be used. As described above, by bringing an aromatic compound having a phenolic hydroxyl group into contact with a polymer film having a halide group, the resulting polymer film is mixed with an aqueous solution of an alkali metal hydroxide or an organic solvent. The remaining acid halide groups are converted into enteric ion exchange groups by immersion in a solution.

When this cation exchange membrane is used, for example, as a barrier in an electrolytic reaction in which an aqueous alkali metal salt solution is electrolyzed to obtain an alkali metal hydroxide, it exhibits extremely high current efficiency. Although the mechanism of action is not fully understood, the phenolic hydroxyl group and the acid halide group form an ester bond, and due to the remarkable hydrophobic bonding of the aromatic ring, the water content of the membrane decreases and the fixed ion concentration decreases. As a result of the reaction between the acid halide group and the reactive aromatic ring, a phenolic hydroxyl group, which is a weakly acidic cation exchange group, is introduced at the same time as the hydrophobically binding aromatic ring, and the fixed ion of the membrane is improved. There is a possibility that the concentration increases, that another new functional group having ion exchange ability is generated, and that the acid halide group is converted to an inert group that does not have ion exchange ability. In general, in ion-exchange membranes, the selective permeability between ions of opposite sign (ring ratio, current efficiency), which is important as the electrochemical properties of the membrane, and the electrical resistance of the membrane are contradictory elements. It is necessary to increase the fixed ion concentration by increasing the exchange capacity of the membrane and lowering the amount of water in the building, but increasing the fixed ion concentration will increase the electrical resistance of the membrane.

Therefore, in order to keep the transference number high and the electrical resistance low, a layer with a high concentration of fixed ions is formed only on the membrane surface where there is a high possibility that ions having the same sign of charge as the ion exchange group of the membrane will enter. is desirable. That is, in the present invention, as described above, the polymer membrane having acid halide groups has phenolic hydroxyl groups only on one membrane surface in a thin layer with a thickness that does not substantially increase the electrical resistance of the membrane. It is effective to react with an aromatic compound. The cation exchange membrane obtained in the present invention can be used without any restriction in systems using conventionally known cation exchange membranes.

For example, diaphragms for electrolysis of organic salts, organic acids, and organic bases; diaphragms for electrolysis of inorganic salts, inorganic acids, and inorganic bases; cation exchange membranes for electrodialysis; fuels It is suitably used as an electrolyte in batteries, an electrolyte in devices that electrolyze water to generate hydrogen and oxygen, or diffusion dialysis and other systems that generally contain an oxidizing agent. The contents of the present invention will be specifically explained with reference to the following examples, but the contents of the present invention are not restricted by the following examples.

In the examples, the electrical resistance of the membrane was 3. Arc-NaCI
The measurement was performed at 8,000 ℃ by placing a membrane between 1,000 cycles of AC and 6.0N-NaOH.

Further, the electrochemical properties of the obtained membrane were evaluated using a multi-chamber electrodialysis device that combines electrolysis of a saturated alkali metal salt aqueous solution and a neutral diaphragm. The device used for electrolysis of aqueous alkali metal salt solutions has an effective current carrying area of 0. In the feared two-chamber electrolytic cell, the anode was an insoluble anode made of a titanium wire mesh coated with titanium oxide and ruthenium oxide, and the cathode was a metal wire mesh. Current density is 30A/
The electrolysis temperature was 80-9000℃. In addition, electrodialysis is used to dealkalize an aqueous solution containing dilute alkali and recover the concentrated alkali on the concentration side. , and concentrated by electrodialysis. Example 1 Tetrafluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octensulfonyl fluoride)
A copolymerized film of 60 parts of water and 4 parts of dimethyl sulfoxide
00 parts of sodium hydroxide and 15 parts of caustic soda were soaked and hydrolyzed to obtain a sodium sulfonate type intestinal ion exchange membrane.

The thickness of this membrane was 0.25 mm, and the exchange capacity was 0.91 meq/g dry membrane (Japan type). This film is 6000
After completely converting to the acid form by immersing it in 60% concentrated nitric acid, it was dried under reduced pressure and tightened in a device that allows only one side to react, to uniformly disperse phosphorus pentachloride crystals on one membrane surface. This was placed between hot plates maintained at 150 qo, and the phosphorus pentachloride crystals were sublimated and left for 1 hour. After taking out the membrane, washing it with water and drying it under reduced pressure, we analyzed the membrane surface that had reacted with phosphorus pentachloride vapor and the unreacted membrane surface using reflection infrared absorption spectroscopy.
Absorption was observed in Ka-1 and 109-ratio Ne-1, but these absorptions disappeared on the reacted film surface and new 580c-1
, absorption appeared at the position of 1430 cM-1. Next, this film was immersed in a solution of 25 parts of cyclohexanone and 5 parts of pyrocatechin at 35q0 for 4 hours, thoroughly washed with methanol and water, and the reflection infrared absorption spectrum was measured again. 580 on the membrane surface treated with phosphorus
Ka-1, 1430 skin-1 absorption disappears, 1410 skin-
1, 1790 arc-1, 3200-3400 skin-1, 29
A new absorption appeared at -1 of 50c.

This membrane was immersed in a 10% caustic soda ethanol solution, hydrolyzed, washed with water, dried under reduced pressure, and the surface of the membrane treated with phosphorus pentachloride was observed again using an infrared reflection spectrum. 1680 skin-1, 3200-34
Infrared absorption spectra were observed for 00ka-1 and 2950ka-1. 0. treated under the same conditions as above. When we made a membrane large enough to be incorporated into a two-chamber electrolytic cell and electrolyzed it using saturated saline as the anolyte, we found 7. After obtaining state-NaOH, the current efficiency was 95%, the tank voltage was 3.72 V, and the NaCI in caustic soda was 48%, 1&me in terms of NaOH. Note that electrolysis was performed with the membrane surface treated with phosphorus pentachloride facing the cathode. In addition, the above film was subjected to a reaction treatment for 2 hours in 8,000 ml of concentrated nitric acid, and the results were measured using a reflection infrared spectrum.
200~3400c-1, 2950 arc-1, 1410
The absorption of Hada-1 became weaker, and the absorption band of 1790 Hada-1 remained.

As a result of electrolysis of saturated saline using the membrane subjected to this treatment, the cell voltage was 5.3V, 7. The current efficiency during state-NaOH acquisition was 85%. On the other hand, electrolysis of saturated saline was carried out using a membrane having only sulfonic acid groups.7. Obtained state-NaOH and current efficiency is 51
%, the cell voltage was 3.65 V, and the amount of NaCI in the caustic soda was 48% NaOH equivalent.

Example 2 A copolymer of tetrafluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octensulfonyl fluoride) was placed between two 2 mil thick sheets made of polytetrafluoroethylene. A plain woven fabric (50 400 denier threads per inch both vertically and horizontally) was sandwiched and heat fused to form a single polymer membrane.

A 2 mil thick sheet of the same copolymer was heat-fused and bonded to one side of this. This was immersed in a hydrolyzate consisting of 40 parts of dimethyl sulfoxide, 60 parts of water, and 15 parts of sodium hydroxide at 80°C for 3 hours to hydrolyze the sulfonyl fluoride groups and convert them into sodium sulfonate. Its exchange capacity was 0.83 milliequivalents/gram dry membrane (Japan type). This membrane was immersed in 60 qo, 60% concentrated nitric acid for 1 hour to convert sodium sulfonate into sulfonic acid groups, and then dried under reduced pressure and dissolved in 2 parts of phosphorus pentachloride and 1 part of phosphorus oxychloride. 130pm in things
A heating reflux reaction was carried out by immersion in water. The membrane was taken out, washed with carbon tetrachloride, and then washed with water to obtain a membrane having sulfonyl chloride groups. On the other hand, when a sheet of the same copolymer without reinforcing cloth was immersed in the same phosphorus pentachloride-phosphorus oxychloride reaction bath under the same conditions and the post-reflection infrared absorption spectrum was taken, it was found that before the reaction, it was 580c. -1,850
Absorption was observed in Hada-1 and 1060 Hada-1, but after the reaction, the absorption spectra disappeared and new absorption was observed in 1430 Hada-1.

The membranes without reinforcement were used for infrared absorption spectroscopy, and the membranes with reinforcement were manufactured for evaluation of electrochemical performance.

The electrolytic performance was evaluated by electrolysis of saturated saline.
The two deposited membranes were contacted with the aromatic compounds having phenolic hydroxyl groups shown in the following table in the single-sided processing apparatus used in Example 1, and then dimethyl sulfoxide, water,
The infrared absorption spectrum was immersed in a hydrolyzed solution consisting of caustic soda, and the electrolytic performance was evaluated to obtain 8.0N-NaOH as a saturated saline solution. The membrane used for measuring the reflected infrared absorption spectrum was immersed in a solution of the above compound, and the membrane used for evaluating electrolytic performance was treated with a reaction apparatus capable of reacting only one side. The temperature during contact was maintained at 4.0°C. Note that electrolysis was performed with the membrane surface on which the phenolic compound was reacted facing the cathode. The results are shown in Table 1. Table 1 Example 3 A copolymer of tetrafluoroethylene and CF2/CFCF3OCF2CF-OCF2CF2CoF was heat-molded at 17,000 to form a polymer membrane with a thickness of 0.1 rib.

60q○ of this was added to a 10% NaOH ethanol solution.
The exchange capacity was 1.45 milliequivalents/g dry membrane when hydrolyzed by soaking with water. When electrolysis of saturated saline was carried out using this membrane, 7. State-NaOH was obtained from the cathode chamber and the current efficiency was 59%. A carboxylic acid fluoride type of this membrane that has not been hydrolyzed was soaked in a 10% methanol solution of Resorciso at 6000°C for 4 hours, washed with methanol, and then diluted with 10% N.
The remaining carboxylic acid fluoride was hydrolyzed by soaking in aOH-methanol solution.

The exchange capacity was measured in the same manner as above and was 1.15 meq/g dry membrane. Using this membrane, electrolysis of saturated saline solution was carried out in the same manner as in the previous example.7.
State-NaOH was obtained and the current efficiency was 92%. In addition, when the infrared absorption spectrum of this film was taken, it was found that 3200 arc-1, 2
New absorption was observed near 950 skin -1 and 285 skin -1. Example 4 The cation exchange membrane synthesized in Example 1 has an electrical resistance of 3.80 and a water permeation rate of 0.01 cc/hr.
・Pairs of non-charged membranes (made of polytetrafluoroethylene) with a skin temperature of 20% are used, five pairs are made, and an anode chamber and a cathode chamber are provided on both sides. An attempt was made to electrodialytically concentrate NaOH.

The flow rate of the caustic soda solution on the dilution side is 5 at a current density of 10 A/d.
0. skin/sec. The caustic soda was concentrated and recovered by a semi-batch electrodialysis method so that -NaOH was obtained. 8. Perform electrodialysis with the membrane surface treated with phosphorus pentachloride facing the concentration chamber side, and use it as a concentrated solution. The current efficiency of the caustic soda marked is 63%.
I was able to obtain it. On the other hand, the membrane treated with phosphorus pentachloride in Example 1 and before being reacted with the phenolic compound was used in the same manner as in Example 1, and the membrane was treated with 0.0% under the same conditions. Electrodialytic concentration of arc-NaOH was performed.

Claims (1)

[Scope of Claims] 1. A polymer film having a fluorine atom bonded to an acid halide group and a fluorine atom bonded to at least a carbon at the α position with respect to the halide group, and a phenolic hydroxyl group. A method for producing a cation exchange membrane, which comprises bringing the membrane into contact with an aromatic compound having at least one group and not having a vinyl group, and then subjecting the membrane to hydrolysis treatment if necessary. 2. The method according to claim 1, wherein the acid halide group is a sulfonic acid halide. 3. The method according to claim 1, wherein the acid halide group is a carboxylic acid halide. 4. The method according to claim 1, wherein the polymer film is perfluorinated. 5 Aromatic compounds having at least one phenolic hydroxyl group include phenol, pyrogallol, resorcinol, catechol, hydroquinone, phloroglucin, gallic acid,
Claim 1 is at least one selected from naphthols, naphthalene diols, and derivatives thereof.
The method described in section.