JPS6128378B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel ion exchange resin. Specifically, it is a polymeric material having a carbon to which at least one fluorine atom is bonded to a carbon to which a sulfonyl group is bonded, and at least the surface layer of the polymeric material has a sulfonic acid amide group and a carboxylic acid group. This is an ion exchange resin characterized by a mixture of. Conventionally, ion exchange resin membranes having acid amide bonds in the surface layer have the property of allowing ions with a lower charge to more easily permeate in the selective permeability of the same kind of ions, and ion exchange resin membranes made of specific fluorine-containing resins have been known. By adding an anion exchange substance or an amino group having dissociable hydrogen to the surface layer of the membrane through an acid amide bond, it is possible to obtain a diaphragm that can electrolyze an aqueous alkali metal salt solution with high current efficiency. Are known. Also, a sulfonic acid type ion exchange resin membrane having a carboxylic acid group layer on the surface has been similarly proposed as a diaphragm for electrolysis of aqueous solutions of alkali metal salts. It is known that such an ion exchange resin membrane can improve current efficiency when used for electrolysis. A more detailed study of these ion-exchange resin membranes shows that when a cation-exchange membrane with carboxylic acid groups on the surface layer is used for electrolysis, the current efficiency for caustic alkali production reaches close to 95% even on an industrial scale. It is expected that the voltage between the electrodes can be increased, and even in that case, it is possible to maintain the interelectrode voltage within a reasonable range. However, since prevention of mixing of alkali metal salts such as common salt into the caustic alkali due to diffusion is not sufficient, increasing the concentration of the alkali metal salts supplied to the anode chamber increases the concentration of the salts in the caustic alkali. There is. Therefore, if the concentration of the anode chamber solution is made relatively low, the voltage between the electrodes will naturally increase, which is not preferable. On the other hand, in the case of a cation exchange resin membrane with acid amide bonds added to the surface layer, the effect of preventing the diffusion of alkali metal salts is large, and the improvement in current efficiency is also due to the acid amide bonds and, by extension, the bonds. Although it would be possible to increase the current efficiency to 90% or more as the amount (or size) of the atomic groups increases, the increase in the electrical resistance of the membrane would be large, and the increase in the current efficiency during electrolysis would increase. The voltage between the electrodes becomes too high. On the other hand, in order to keep the electrical resistance within a reasonable range, the current efficiency of the produced caustic alkali must be sacrificed to some extent. The present invention is an improved electrolytic diaphragm that is suitable for producing an ideal electrolytic diaphragm that maintains the electrolytic voltage within a reasonable range while obtaining sufficient current efficiency and that reduces the diffusion of alkali metal salts into the produced caustic alkali. This was finally completed as a result of intensive research aimed at providing a cation exchange resin. That is, the gist of the present invention is that the carbon to which the sulfonyl group is bonded has at least one carbon atom bonded thereto, preferably a polymeric substance,
A perfluoro polymeric material, at least in the surface layer of the polymeric material, a sulfonic acid amide group (A) and a carboxylic acid group (B) are present in a molar ratio of (A)/(A)+(B). 0.01～0.
It is an ion exchange resin mixed at a ratio of 50%. In the present invention, the surface layer portion may include at least the surface and the vicinity of the surface, for example, 20μ
A certain degree is sufficient, and anything beyond that will not have a particularly large effect. Generally, in the case of a cation exchange resin membrane, it may be about 0.001 to 50% of the total thickness of the membrane. In any case, the key point is that a mixed layer of carboxylic acid groups and sulfonic acid amide groups exists, and the mixing ratio is such that the number of moles of sulfonamide (A) is equal to the number of moles of carboxylic acid group (B). It is preferable to keep the molar ratio of (A)/(A)+(B) (molar ratio) within the range of 0.01 to 0.50. The amino compound constituting the sulfonic acid amide is not particularly limited. Therefore, on the surface layer of the ion exchange resin

It suffices if there is a bond of the formula (wherein R ₁ and R ₂ are selected from H or other substituents). However, in order to make the electrical resistance as low as possible, it is preferable that at least one of R ₁ and R ₂ is hydrogen, and R ₁ or R ₂ is usually alkyl, aryl, aminophenyl, hydrazyl. or substituted hydrazyl or -
(CH ₂ ) _o NH ₂ , -(CH ₂ CH ₂ NH) - _o H (where n is an integer), or those in which some of the hydrogens bonded to these carbons are replaced with fluorine. The polymeric substance that is the basis of the ion exchange resin of the present invention is not particularly limited, but for many uses, a substance having a perfluorocarbon main chain is preferable. In addition, the ion exchange group for expressing the ion exchange ability of the ion exchange resin is -SO ₂ -Me [However,
Me is -OH, primary or secondary amino group, -OM (M
is an alkali gold layer, a dissociative substance such as NH ₄ )]
Although ion exchange groups such as sulfonyl groups are preferred, other ion exchange groups may also be used. Although there are no particular limitations on the means for making the ion exchange resin of the present invention contain both a sulfonic acid amide group and a carboxylic acid group, in general, a fluorine-based polymeric substance having a sulfonyl halide group has at least a primary amino group and a secondary amino group. What is necessary is to react with a compound having one or more compounds under cooling, at room temperature, or under heating. When it is desired to have sulfonic acid amide groups and carboxylic acid groups present in an ion exchange resin as uniformly and as a thick film, the reaction is carried out in a solvent that swells the polymeric substance, or an amino compound that swells the resin is used. Just use it. The amino compound used in this case is not particularly limited as long as it has one or more primary and/or secondary amines bonded to it, and includes primary amines such as methylamine and ethylamine, dimethylamine, and diethylamine. secondary amine,
Diamines and polyamines such as ethylenediamine, diethylenetriamine, and polyethyleneimine are used. A basic solution containing ammonium ions is also preferably used. Moreover, amines having a heterocycle or an aromatic ring such as piperidine, aniline, N-methylaniline, etc. are also suitably used. It is known that a fluorine-containing polymeric substance having a sulfonic acid halide group is reacted with a primary or secondary amine to form a sulfonic acid amide bond. The present inventors have studied this reaction in detail and found that during this reaction, a functional group that is neither a sulfonic acid group nor a sulfonyl halide group, nor a sulfonic acid amide group is simultaneously generated as a sulfonic acid amide group.
It was found that when immersed in an organic solvent bath containing an alkali metal salt hydroxide, it was decomposed, but when heated, additional carboxylic acid groups were formed. The inventors have also found that the formation of carboxylic acid groups is significantly easier to generate when a sulfonyl chloride is reacted with an amino compound than when a sulfonyl fluoride is reacted than when a sulfonamide group is reacted. In this case, the generation rate is faster if the heating is performed in an atmosphere containing oxygen. Generally, the heating temperature is
The temperature should be 50℃ or higher and lower than 250℃, preferably 70℃.
The temperature is preferably at least ℃ but less than 200℃. When such sulfonic acid amide groups and carboxylic acid groups coexist, they may be present uniformly from the surface layer to the interior of the ion exchange resin, or may be present only in the surface layer. Alternatively, in the case of a film-like material, it may be present only on one film surface or only on both surface layers. When only the surface layer of the ion exchange resin is a mixed layer of sulfonamide groups and carboxylic acid groups, the sulfonyl halide group may be present only in the surface layer of the ion exchange resin, or the sulfonyl halide group may be A method has been implemented in which the amine is uniformly present in a molecular substance, and the reaction time with the amine, the ratio of the amine to the solvent, and the molecular weight of the amine are selected, and the rate of diffusion into the membrane is controlled. , is selected as appropriate depending on the purpose. Furthermore, the method for producing the ion exchange resin of the present invention is not limited to the above-mentioned method. Polymerization or condensation may be carried out by impregnating polymers. Conversely, a monomer capable of polymerization or condensation, in which a fluorine atom is bonded to a carbon bonded to a sulfonic acid amide group, is impregnated into a polymer having a carboxylic acid group or an ion exchange resin. A condensation reaction may be carried out. In those cases, the proportion of carboxylic acid groups and sulfonic acid amide groups is preferably within the above range. The outline of the present invention has been explained above, and the ion exchange resin of the present invention has a sulfonic acid amide group (A) and a carboxylic acid group (B) in a molar ratio of (A)/(A) + (B) of 0.001. ~0.5
There is no particular restriction as long as it is within the range of, but at the same time, other cation exchange groups in an amount smaller than the amount of carboxylic acid groups,
For example, sulfonic acid groups, phosphoric acid groups, phosphorous acid groups, phenolic hydroxyl groups, thiol groups, as well as sulfuric acid esters, phosphoric acid esters, phosphorous ester groups, etc. may coexist. The content of the present invention will be specifically explained with reference to the following examples, but the present invention is not limited to the following examples. The presence and quantitative ratio of sulfonic acid amide groups and carboxylic acid groups were determined using an infrared reflection absorption spectrum and an X-ray microanalyzer. 10% caustic soda - 1680 cm ^-1 when immersed in methanol solution
The group for which absorption was observed at 1780 cm ^-1 when the same membrane was immersed in 3N-HNO ₃ was identified as carboxylic acid, and the sulfonic acid amide group was identified as a broad absorption near 3200 cm ^-1. Identification was made by the observed peaks. The ratio of sulfonic acid amide groups to carboxylic acid groups was determined by immersing the ion exchanger in a 10% KOH methanol solution at 80°C for 4 hours, then washing it with ethanol to remove excess KOH. The amount of potassium in the cross section of the membrane was determined using an X-ray microanalyzer. The amount of sulfur in the same cross section of this ion exchanger was determined and the two were compared.
Assuming that the amount of sulfur and potassium present in the product directly hydrolyzed to form carboxylic acid groups is 1.0, the measurement was made by the ratio to this or by other means. In addition, in the examples, in the case of a film-like material, the electrical resistance is
1000 by placing a membrane between 3.5N NaCl and 6.0N−NaOH
Measured at 80°C with cycle alternating current. In addition, to evaluate the electrochemical properties of the obtained membrane, electrolysis of a saturated alkali metal salt aqueous solution,
The test was carried out using a multichamber electrodialysis device paired with a neutral diaphragm. The equipment used for electrolysis of aqueous alkali metal salt solutions was a two-chamber electrolytic cell with an effective current-carrying area of 0.5 ^dm2.The anode was an insoluble anode made of a titanium wire mesh coated with titanium oxide and ruthenium oxide, and the cathode was made of soft iron. A wire mesh was used. Current density is 30A/d
m ² and the electrolysis temperature was 80-90°C. In addition, electrodialysis is used to dealkalize an aqueous solution containing a dilute alkali and recover the concentrated alkali on the concentration ^side . It was concentrated by electrodialysis. Example 1 Tetrafluoroethylene and perfluoro(3.
A copolymer film of 6-dioxa-4-methyl-7-octensulfonyl fluoride) was mixed with 600 parts of water,
400 parts of dimethyl sulfoxide, 15 parts of potassium hydroxide
A potassium sulfonate type cation exchange membrane was obtained by immersing the membrane in a bath consisting of 300 ml of water and hydrolyzing it. The membrane had a thickness of 0.25 mm and an exchange capacity of 0.91 meq/g dry membrane (H type). Next, this film was heated at 60°C.
After immersing the membrane in 3N nitric acid to completely convert it into the acid form, the membrane was tightened in a device that can react on only one side to uniformly disperse phosphorus pentachloride crystals on one side, and then heated to 150℃. The crystals of phosphorus pentachloride were sublimed between heated plates 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 at 1060 cm ^-1 on the surface of the film, and on the reacted film surface, these absorptions disappeared and a new absorption appeared at 1430 cm ^-1 . Next, this membrane was immersed in a 29% ammonia aqueous solution for 5 hours, then immersed in 1N hydrochloric acid for 5 hours, thoroughly washed with 1N hydrochloric acid, and then immersed in air at 50°C for 6 hours at 110°C. Heated at ℃ for 18 hours.
16 hours in a 10% caustic soda methanol solution;
When the infrared reflection spectrum was taken after immersion at 41°C, extremely strong absorption was observed at 1680 cm ^-1 , and from 3200 cm -1.
Broad absorption was observed at 3500 cm ^-1 . Therefore, when the ratio of potassium to sulfur was calculated using a fluorescent X-ray microanalyzer, the ratio of sulfonic acid amide groups to carboxylic acid groups was 1:5 for a surface layer of 20 microns. When this membrane was further used to electrolyze saturated saline solution according to the method described in the specification, the current efficiency was 95% when 7.5N-NaOH was obtained, and there was no change even after 3 months. The battery voltage was 3.55V. On the other hand, the membrane hydrolyzed without heat treatment obtained 7.5N-NaOH, had a current efficiency of 82%, and a cell voltage of 4.55V. In addition, the membrane that was hydrolyzed without reacting with ammonia was 7.5N−
NaOH was obtained and the current efficiency was 52%. In addition,
The electrical resistance of the membrane is 1.5Ω− for a membrane containing only sulfonic acid groups.
cm ² , the membrane of the present invention having both a sulfonic acid amide group and a carboxylic acid group had a resistance of 2.5 Ω-cm ² , and the membrane immediately hydrolyzed after immersion in ammonia water had a resistance of 5.9 Ω-cm ² . Furthermore, when the salt concentration in the caustic soda obtained from the cathode chamber was analyzed, it was 8 ppm in terms of 48%-NaOH for the membrane of the present invention, 38 ppm for the membrane reacted with ammonia, and 38 ppm for the membrane reacted with ammonia. teeth
It was 230ppm. Example 2 Tetrafluoroethylene and perfluoro(3.
A copolymer film of 6-dioxa-4-methyl-7-octensulfonyl fluoride) was immersed in a bath consisting of 600 parts of water, 400 parts of dimethyl sulfoxide, and 15 parts of caustic soda for hydrolysis treatment to obtain sodium sulfonate. type cation exchange membrane. The thickness of this film is
At 0.15 mm, the exchange capacity was 0.83 meq/g dry membrane (Type H). This membrane was immersed in 60% concentrated nitric acid at 60°C to completely convert it to the acid form, and then clamped into a device that can react on only one side to uniformly form phosphorus pentachloride crystals on one side of the membrane. disperse,
This was placed between hot plates kept at 150°C, and the phosphorus pentachloride crystals were sublimated and left for one hour. After taking out the membrane, washing it with water and drying it under reduced pressure, we observed the membrane surface that had reacted with phosphorus pentachloride vapor and the unreacted membrane surface using reflection infrared absorption spectroscopy. has an absorption of 1060cm ^-1 , and the absorption of 1060cm ^-1 disappears on the reaction-treated membrane surface.
A new absorption was observed at 1430 cm ^-1 . Next, this membrane was mixed with 400 parts of ethylenediamine and 100 parts of water.
After 24 hours at room temperature in a bath consisting of water, dimethyl sulfoxide, and caustic soda, the unreacted sulfonyl chloride groups were hydrolyzed. This membrane
After thoroughly washing with 1N hydrochloric acid, washing with water and drying under reduced pressure,
ESCA (Electron Spectroscopy Chemical
Analysis), the film surface treated with phosphorus pentachloride had a C of 292.5eV, 294.0eV, and 297.0eV.
Absorption based on the -F bond and C _1s absorption based on C-H absorption were observed at 285 eV, and absorption based on N _1s was observed at 400 eV. On the other hand, on the membrane surface not treated with phosphorus pentachloride, only a slight C--H absorption was observed at around 285 eV, which was thought to be due to membrane contamination. Absorption of N _1s at 400 eV was not observed at all. When this membrane was used to electrolyze saturated saline according to the method described in the specification, the result was 6.0N-
Obtain NaOH with current efficiency of 88% and cell voltage of 3.95V
It was hot. The amount of salt in caustic soda converted to 48% is
It was 53ppm. When this membrane was used for continuous electrolysis for one month, the current efficiency was 86%.
When the membrane was taken out and analyzed after electrolysis, a slight infrared absorption spectrum of sodium carboxylate was observed at 1680 cm ^-1 in this case as well. Separately, a membrane treated with phosphorus pentachloride was similarly immersed in an aqueous ethylenediamine solution for 24 hours.
Heat treatment was carried out at 130°C for 24 hours in an air vent. Next, it was immersed in the same hydrolysis bath as above for hydrolysis treatment. The film is prepared by the method described in the specification.
After equilibrating with KOH, washing with water and drying, measure the potassium distribution in the cross section of the membrane with an X-ray microanalyzer.
Next, the distribution of sulfur was similarly observed. By strength ratio to thick film containing only sulfonic acid groups -
When we calculated the ratio of COOH and −SO ₂ NHR, we found that
A value of 7:3 was obtained for 12 microns.
The formation of -COOH was confirmed by observing the film surface using an infrared reflection spectrum. That is, for the surface treated with phosphorus pentachloride and heat-treated, strong absorption was observed at 1780 cm ^-1 after immersion in 2N hydrochloric acid, and for the surface not heat-treated, absorption was slightly observed at the same location. On the other hand, no such absorption was observed on the membrane surface that had not been treated with phosphorus pentachloride. After being treated with this ethylenediamine aqueous solution, the heat-treated membrane was electrolyzed with the same saturated saline solution to obtain 6.0N NaOH and the current efficiency was
At 94%, the battery voltage is 3.75V, and it remains 94% even after one month.
% current efficiency. in NaOH equivalent to 48%
The amount of NaCl was 7 ppm. In addition, in the case of a sulfonic acid type membrane that does not react with phosphorus pentachloride or an aqueous ethylenediamine solution, the current efficiency is
The obtained 6.0N caustic soda was 62%, the cell voltage was 3.65V, and the amount of salt in the 48% converted caustic soda was 260 ppm. In addition, 6.0N−NaOH and 1000 cycles of AC
The electrical resistance of the membrane in 1.0N HCl was as shown in Table 1.

[Table] Example 3 Tetrafluoroethylene and perfluoro(3.
The following reaction was carried out using a 5 mil thick film of a copolymer of 6-dioxane-4-methyl-7-octensulfonyl fluoride. The exchange capacity of the copolymer when hydrolyzed was 0.91 meq/g dry film. (1) A membrane containing a sulfonyl fluoride group was installed in an apparatus capable of reacting only one side of the membrane, and only one side was brought into contact with a solution prepared by adding 2 parts of water to 18 parts of ethylenediamine at room temperature for 4 hours. The membrane was then immersed in the hydrolysis bath described in (2) to convert the sulfonyl fluoride groups inside the membrane to sulfonate. (2) A film containing sulfonyl fluoride groups was immersed in a solution containing 400 parts of dimethyl sulfoxide, 600 parts of water, and 15 parts of potassium hydroxide at 80°C for 3 hours to convert the sulfonyl fluoride groups into sodium sulfonate. Then, it was immersed in 60% nitric acid to convert it into a sulfonic acid group, and then dried under reduced pressure. This was immersed at 130°C in a solution of 2 parts of phosphorus pentachloride and 10 parts of phosphorus oxychloride, and heated under reflux. The reaction was carried out. This was washed with carbon tetrachloride, washed with water, and then dried to obtain a film-like material having sulfonyl chloride groups.
When we measured the infrared reflection and absorption spectrum of the surface of this, absorption was observed at 1060 cm ^-1 before reflection, but after the reaction, the absorption disappeared and 1430 cm ^-1
A new strong absorption was observed. This membrane was used to react with isopropylamine, ethylamine, and ethylenediamine. It was then immersed in a 1:1 mixture of water and methyl alcohol containing 10% caustic soda to hydrolyze unreacted sulfonyl chloride groups and convert them into sulfonic acid groups. The reaction temperature was room temperature in all cases. (3) The film-like material having a sulfonyl chloride group synthesized in (2) is installed in a device that can react only on one side, and only one side is brought into contact with butyl alcohol.
It was heated to 110° C. and air was blown to oxidize the sulfonyl chloride groups to convert them to carboxylic acid groups, and then immersed in the hydrolysis bath described in section (2) to convert them into sodium carboxylate. According to the reflection infrared absorption spectrum of the reaction surface, the absorption of the sulfonyl chloride group observed at 1430 cm ^-1 disappeared, and strong absorption corresponding to the carboxylic acid group was observed at 1680 cm ^-1 after hydrolysis. Electrolysis was carried out with the reacted membrane surface facing the cathode, and 8.0 normal caustic soda was regularly obtained from the cathode chamber. For membranes reacted with amino compounds, the electrolytic performance was measured for membranes that were hydrolyzed immediately after the reaction and membranes that were heat-treated for an appropriate time, and the amount of carboxylic acid groups and sulfonic acid amide groups were measured using X-rays. Measured with a microanalyzer. The Koki membrane was immersed in KOH to form potassium ions, and the amount of potassium and sulfur in the membrane was analyzed using an X-ray microanalyzer to determine the ratio. The membrane used for the measurement with the X-ray microanalyzer was a sulfonyl chloride type membrane immersed in a reaction bath and reacted from both sides of the membrane to the inside. These data are summarized in Table 3. The values shown in the table were determined by setting the amount of potassium and sulfur in the unreacted potassium sulfonate film as measured by an X-ray microanalyzer as 100.

【table】

[Table] Example 4 Water permeability of the cation exchange membrane synthesized in Example 2 with an electrical resistance of 3.2 Ω-cm ² and the styrene-divinylbenzene base with a quaternary ammonium base as the anion exchange group. Using pairs of anion exchange membranes with a capacity of 0.01 cc/hr・cm ²・cmH ₂ O, six pairs were made and an anode chamber and a cathode chamber were provided on both sides, and 0.5N NaOH
An attempt was made to concentrate it by electrodialysis. current density 10
The flow rate of the diluted caustic soda solution is 6 cm/sec at A/dm ² .
Desalt by batch method to 0.2N NaOH with
Caustic soda was concentrated and recovered. Example 1 on the concentration chamber side
Electrodialysis was performed with the membrane surface treated with phosphorus pentachloride facing the membrane, and 7.5N caustic soda was used as a concentrated solution to increase the current efficiency.
I was able to get it at 65%. On the other hand, when the caustic soda solution was concentrated in the same manner using the membrane treated with phosphorus pentachloride in Example 2 and only hydrolyzed without reacting with ethylenediamine, 6.0N NaOH was obtained and the current efficiency was It was 45%. In addition, there is a water column of 30 on the desalination room side.
Electrodialysis was performed by applying a pressure of cm.

Claims (1)

[Scope of Claims] 1. A polymeric substance having a carbon to which a sulfonyl group is bonded and at least one fluorine atom bonded thereto, the polymeric substance having at least a surface layer containing sulfonic acid amide. Group (A) and carboxylic acid group
An ion exchange resin in which (B) and (A)/(A) + (B) (molar ratio) are mixed at a ratio of 0.01 to 0.50. 2. The ion exchange resin according to claim 1, wherein the sulfonic acid amide group has a dissociable hydrogen atom. 3. The ion exchange resin according to claim 1, which is a film-like material having a size of 1 cm or more in each of at least two directions. 4 The sulfonyl group is a pendant side chain, R(-OCF ₂ CFY)- _o (where R represents the main chain,
2. The ion exchange resin according to claim 1, wherein Y represents a fluorine atom or _-CF3 , and n is bonded via a fluorine atom or -CF3, and n is 1 to 5. 5. The ion exchange resin according to claim 1, which has a thin layer containing a mixture of sulfonic acid amide groups and carboxylic acid groups only on one surface of the membrane-like material. 6. The method according to claim 1, which is a membrane-like material reinforced with tetrafluoroethylene polymer fibers.