JPS6115092B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses a cation exchange resin in which a fluorine atom is bonded to at least the carbon atom at the alpha position with respect to a cation exchange group, in particular a perfluorocarbon main chain, and a cation exchange group bonded to the side chain. The present invention relates to a method for converting a cation exchange group of a cation exchange resin into an acid chloride group. Ion exchange resins are used for a variety of purposes, so they need to be durable under the conditions of use.
Various considerations have been made. One of these is an ion exchange resin with a structure in which at least one fluorine atom is bonded to the carbon atom at the alpha position to the cation exchange group, that is, the carbon atom to which the ion exchange group is bonded. has been done. Such cation exchange resins, especially those with perfluorocarbon as the main chain and ion exchange groups in the side chains, have particularly good chemical resistance and oxidation resistance, so they are formed into cation exchange membranes and coated with alkali metal salts. It is suitably used as a diaphragm for electrolysis. On the other hand, ion exchange resins are more suitable for various usage modes, and various modifications have been attempted. However, the object of the present invention, which is an extremely stable cation exchange resin, is difficult to chemically change unless it is subjected to extremely violent reaction conditions, and it is difficult to adequately control the reaction under such violent conditions. It is. Therefore, there is a need for a method of introducing active groups in order to modify the above-mentioned stable ion exchange resins. Therefore, the present invention provides a method for converting the ion exchange group of a cation exchange resin having high chemical resistance, that is, chemically stable, into an acid chloride group. The present inventors have already discovered that at least one side of an acid (hydrogen ion) type fluorine-containing cation exchange membrane, which has a fluorine atom bonded to a carbon atom at the alpha position relative to a cation exchange group, is coated with phosphorus pentachloride. Japanese Patent Application No. 52-68823 proposes a method for converting a cation exchange group into an acid chloride group, which is characterized by bringing the cation exchange group into contact with steam under conditions such that the cation exchange group does not substantially dissociate. When applying the above method, since it is a gas phase reaction, it has various advantages, but it is inevitable that some acid anhydride groups will be produced as by-products at the same time as the cation exchange groups are converted to acid chloride groups. Ta. This acid anhydride group can be converted into an ion exchange group again by subsequent hydrolysis treatment, etc., and although it does not pose a problem to the ion exchange resin, it reduces the production rate of acid chloride groups, so it can be further converted into an ion exchange group. It was also meaningful to make improvements. The method of the present invention provides a cation exchange resin in which a fluorine atom is bonded to at least an α-position carbon atom with respect to a cation exchange group, and the counter ion of the cation exchange group is an ammonium ion or a substituted ammonium ion. It is characterized in that the cation exchange resin, which is an ion, is brought into contact with the vapor of phosphorus pentachloride under conditions such that the cation exchange group is not substantially removed. One embodiment in which the present invention is effectively applied is the use of an alkali metal salt as a diaphragm in an electrolytic cell. In this case, the membrane is used as an ion exchange membrane, and it may be particularly desirable to exchange only the ion exchange groups on the surface with acid chloride groups.
Therefore, in such a case, among all the ion exchange groups that the cation exchange resin has, the counter ion of the ion exchange group on the surface portion is ammonium or substituted ammonium ion, and the counter ion of the internal ion exchange group is hydrogen ion. Alternatively, it is also preferable to contact the phosphorus pentachloride vapor in the form of metal ions such as alkali metals. In the present invention, ammonium ions or substituted ammonium ions are used as counter ions of cation exchange groups. The advantage is that the ion exchange group is converted to an acid chloride group at a high rate, and the by-product of an acid anhydride group is small. That is, Figure 1 shows the relationship between phosphorus pentachloride vapor and phosphorus pentachloride vapor over a certain period of time for the ammonium ion type (a cation exchange group whose counter ion is an ammonium ion, abbreviated as follows) and the hydrogen ion type. The relationship between the contact temperature and the amount of reduction in ion exchange groups (indicated by an increase in the electrical resistance of the membrane) is shown. From this figure, it can be seen that when the ammonium ion type is used, the formation of acid chloride groups is easier than when the hydrogen ion type is used. In other words, the reaction can be carried out at lower temperatures. Furthermore, in Figure 2, the acid chloride groups and acid anhydride groups of ammonium ion type cation exchange membranes and hydrogen ion type cation exchange membranes are shown when they are brought into contact with phosphorus pentachloride vapor under the same conditions. The relationship between the production ratio of chemical substances and temperature is shown. This figure shows that acid anhydride groups are rarely produced in the ammonium ion type. The method of converting into ammonium ion or substituted ammonium ion type in the present invention is not limited, but usually uses a solution of ammonia, amines, etc.
Ion exchange may be performed by a conventional method. In particular, when converting a hydrogen ion type cation exchange resin to an ammonium ion and/or substituted ammonium ion type, the desired ammonia and/or
Alternatively, it can be achieved by an exchange reaction between gas and solid phase by contacting the cation exchange resin with the vapor of amines. In this case, by measuring the amount of decrease in the vapor pressure of ammonia and/or amines, the amount of ammonium ions and/or substituted ammonium ions adsorbed by ion exchange on the cation exchange resin can be determined. It becomes possible to control the amount of ammonium ions and/or substituted ammonium ions adsorbed on the ion exchange resin. Therefore, when the cation exchange groups of the cation exchange resin are partially converted into ammonium ions or substituted ammonium ions, exchange between gas and solid phase is extremely advantageous. In the present invention, a substituted ammonium ion refers to one of the hydrogen atoms constituting the ammonium ion.
Substituted with 1 to 4 substituents, such as alkyl groups such as methyl, ethyl, propyl, and butyl; aryl groups such as phenyl and naphthyl; alkyl, pyridyl, and other substituents; The form that acts on ion exchange resins is amines. In this case, the amines are not limited to monoamines and diamines, but may also be high molecular weight substances such as polyvinylpyridine and polyethylenepolyamine. When introducing substituted ammonium ions only into the ion exchange groups in the surface layer of the cation exchange resin, high molecular weight amines are more convenient because they are less likely to penetrate into the resin. When such high molecular weight amines are used, it is convenient to introduce substituted ammonium ions into the cation exchange group in water, an organic substance, or a mixed solvent thereof. Next, the method of contacting the cation exchange resin with phosphorus pentachloride is not particularly limited, but generally the partial pressure of phosphorus pentachloride is 100 mmHg or more, preferably 200 mmHg.
or more, and it is desirable that substantially no water be present at the time of contact. Therefore, the cation exchange resin should be dried before contacting the phosphorus pentachloride vapor. Generally, the conditions for the reaction between the ion exchange group of the cation exchange resin and phosphorus pentachloride, which is the object of the present invention, differ depending on the type of the ion exchange group. For example, in the case of a sulfonic acid group, the temperature is 80 to 190°C, preferably 120 to 170°C, and in the case of a carboxylic acid group, the temperature is
The temperature is 80 to 180°C, preferably 100 to 160°C, for several minutes to several tens of hours each, and is appropriately selected depending on what percentage of the exchange groups of the cation exchange resin to be treated is to be converted into acid chloride groups. In any of the above cases, conditions in which the ion exchange group itself substantially decomposes and disappears should be avoided, and one of the judgments is that the inner layer of the ion exchange resin up to at least 5 μm in the surface layer should be avoided. It is advisable to confirm in advance through preliminary experiments the conditions under which 3% or more of the ion exchange groups will not be decomposed, that is, temperature, partial pressure of phosphorus pentachloride vapor, and reaction time. The ion exchange resin used in the present invention described above is not particularly limited as long as it has a fluorine atom bonded to the α-position carbon atom, and in particular, perfluorocarbon-based cation exchange membranes such as perfluoroalkyl vinyl ether A copolymer of sulfonyl fluoride and tetrafluoroethylene, specifically, perfluoro(3,6-dioxa-4-methyl-7-octensulfonyl fluoride) was used as the main component as perfluoroalkyl vinyl ether sulfonyl fluoride. Polymer membranes are preferred. The cation exchange group is preferably a sulfonic acid group, but other carboxylic acid groups, phosphorous acid groups, phosphoric acid groups, etc. are also suitable, and one or more of these groups are used in an amount of 0.3 meq/g dry membrane (H type ) or more cation exchange resins can be used without any restrictions. According to the present invention, the cation exchange resin into which an acid chloride group has been introduced can be reacted with another compound, such as a compound having at least one primary or secondary amine, by utilizing the reactivity of the acid chloride group. A method of forming an acid amide bond on the membrane surface, a method of bonding other functional groups via an acid amide bond, a method of forming a crosslinked structure, a method of forming an ester bond, a method of reduction treatment, oxidation Various improvements can be made, such as a treatment method, a method of decomposing the acid chloride group, or a method of craft polymerization using the decomposed point as an active site simultaneously with the decomposition. In particular, in the case of a sulfonyl chloride type, by treating it with an oxidizing agent, it can be converted into a carboxyl group and can be made into an ion exchange resin having both strong acid and weak acid ion exchange groups. The ion exchange resin modified in this way has various characteristics, but for example, only the surface layer of the ion exchange resin is ammonium ion or substituted ammonium ion type, and if it is internal or membrane-like, the ion exchange group on the back side is changed. A technique is to use hydrogen ion type or metal ion type and introduce acid chloride groups only to the surface layer by taking advantage of the difference in reactivity to phosphorus pentachloride, or to uniformly form ammonium ion or substituted ammonium ion type and introduce acid chloride groups only to the surface layer. The technique of introducing acid chloride groups through the action of phosphorus pentachloride can improve the anti-fouling properties and selective adsorption properties of ion exchange resins without changing the essence of the ion exchange resin. Furthermore, in the case of ion exchange membranes, permselectivity and the like can be improved. An important use of ion exchange membranes endowed with these properties is to use them as diaphragms for electrolytic cells for aqueous solutions of alkali metal salts using the ion exchange membrane method. Example 1 Nafion (trade name of perfluorosulfonic acid type cation exchange membrane, manufactured by Dupont) XR-120 was immersed in concentrated nitric acid at 45°C for 16 hours to completely convert it to the hydrogen ion type. After thorough washing with water, it was immersed in 3N ammonia water at room temperature for 2 days to convert it into ammonium ion form. The ammonium ion type membrane was thoroughly dried. Glass ampoule consisting of two chambers (total volume
40 c.c.), 10 cm ² of the above dried membrane was placed in one chamber, 0.4 g of phosphorus pentachloride powder was placed in the other chamber, and the ampoule was sealed. Place this ampoule in an oil bath at 160℃.
The reaction was carried out by immersion for 30 minutes. After the reaction, the ampoule was opened and the membrane was washed with water for 15 hours. After drying under reduced pressure, the reflection infrared spectrum was measured, and the absorption band at 1060 cm caused by the sulfonic acid group observed in the film before phosphorus pentachloride vapor treatment disappeared, and instead it was found to be caused by the sulfonyl chloride group at 1420 cm ^-1 . A strong absorption band was observed. Corresponds to acid anhydride group (-SQ ₂ -O-SO ₂ -)
An absorption band from 1460 to 1480 cm ^-1 was also observed, but the intensity ratio of the absorption to the sulfonyl chloride group was approximately 0.02.
It was found that most of the sulfonic acid groups were substantially changed to sulfonyl chloride groups. On the other hand, the membranes treated with concentrated nitric acid, the membranes treated with ammonia water, and the membranes treated with phosphorus pentachloride were heated for 15 minutes at room temperature in a mixed solution of isopropanol and water (volume ratio 1/1) containing 0.5% crystal violet. After time staining and observing the cross section of the membrane with an optical microscope, we found that
For the first two, the cross section of the membrane was uniformly stained dark brown, but after the phosphorus pentachloride treatment, about 20μ from both surfaces of the membrane cross section was not stained at all, and the remaining portion was stained dark brown. was. From this, it was found that a portion approximately 20μ from the membrane surface was a sulfonyl chloride group. Example 2 XR-425, a naphion converted into hydrogen ion and ammonium ion forms by the method of Example 1, was mixed with 4 times the amount (molar ratio to the cation exchange group in the membrane) of phosphorus pentachloride and the same amount as in Example 1. The mixture was sealed in an ampoule and reacted for 15 minutes at each reaction temperature shown in Table 1. After the reaction, the ampoule was opened and the treated membrane was washed with water under reflux for 3 hours. The membrane resistance of each treated membrane was measured in N-HCl at room temperature, and the reaction temperature and reaction progress {ion exchange group (-SO ₃ NH ₄₉
-SO ₃ H) becomes a non-ion exchange group (-SO ₂ Ol) by reaction with phosphorus pentachloride vapor, and the progress of the reaction was measured by the increase in membrane resistance. Examined. The results are shown in Table 1 and Figure 1.From these results, even hydrogen ion type membranes can be heated at 160℃.
Although the reaction proceeds sufficiently at temperatures above, ammonium ion type membranes are less effective than hydrogen ion type membranes.
It can be seen that the reaction proceeded satisfactorily even at a relatively low temperature of about 130°C. After measuring the membrane resistance, each treated membrane was placed in an ethanol-water (1:1 volume ratio) solution containing 10% caustic soda.
When the membrane resistance was measured in N-HCl at room temperature after immersion at 45°C for 15 hours to hydrolyze the sulfonyl chloride groups, the resistance was 0.70 to ^0.75Ωcm2 , which was about the same as the membrane resistance before treatment. It was found that the ion exchange group was not substantially eliminated by the steam treatment of phosphorus pentachloride.

[Table] Example 3 Nafion XR-120, which was converted into hydrogen ions and ammonium ions by the method of Example 1, was encapsulated in an ampoule with four times the amount (molar ratio to the cation exchange group in the membrane) of phosphorus pentachloride. The reaction was carried out for 30 minutes at each reaction temperature shown in Table 2. After the reaction, the treated membrane was washed with water, dried under reduced pressure, and then its reflection infrared spectrum was measured. 1420 cm ^-1 in the spectrum and
The absorption band from 1460 to 1480 cm ^-1 is determined by the sulfonyl chloride group and the acid anhydride (-SO ₂ -O-SO _{2 )} , respectively.
-), the intensity ratio of the acid anhydride group and the sulfonyl chloride group, the ratio of the absorption peak height {hereinafter simply expressed as I(-SO ₂ -O-SO ₂ -)/I(-SO ₂ Ol) } was determined for each reaction temperature in Table 2. The results are shown in Table 2 and Figure 2. These results show that the ammonium ion type membrane produces less acid anhydride groups and significantly more sulfonyl chloride groups than the hydrogen ion type membrane even at relatively low temperatures.

[Table] Example 4 Nafion KR-415 was completely converted into a hydrogen ion type by the method of Example 1, and then dried. A stainless steel reactor (reaction area 100 cm ² , reaction chamber volume 500 c.c.) in which only one side of the membrane can be in contact with the reaction reagent after drying under reduced pressure is used. After reducing the pressure to -760 mmHg, 50 mmHg of methylamine gas was introduced into the reaction chamber at room temperature. After introduction, the pressure of methylamine gas is 33mm
When the temperature decreased to Hg, the methylamine gas remaining in the reaction chamber was degassed using a vacuum pump. Reactor temperature
The temperature was raised to 140℃, and nitrogen containing saturated vapor of phosphorus pentachloride at 140℃ was introduced into the reactor at 760℃.
It was introduced up to mmHg. The reaction was continued in this state for 1 hour. After the reaction, take out the membrane, cut out a part for infrared spectrum measurement and staining, and leave it at room temperature for 3N−
Washing with HCl and water was performed for 8 hours each. or,
The remaining part was immersed in n-butanol at room temperature for 16 hours. After drying the sample for infrared spectrum measurement under reduced pressure, the phosphorus pentachloride vapor-treated surface and the end-treated surface were scraped with paper, and the transmitted infrared spectrum was measured. As a result, the one with the treated surface removed is 1060 cm
The sulfonic acid group at ^-1 was strongly observed, and the absorption bands corresponding to the sulfonyl chloride group at 420 cm ^-1 and the acid anhydride group at 1460 to 1480 cm ^-1 were hardly observed. On the other hand, the one with the finished surface removed is 1060 cm.
^-1 , the absorption band from 1460 to 1480 cm ^-1 was hardly observed, and the absorption band at 1420 cm ^-1 was strongly observed. Furthermore, when a staining test was carried out under the same staining conditions using the staining solution of Example 1, about 15 μm from the surface of the phosphorus pentachloride vapor-treated side was not dyed at all, and the remaining portion was strongly stained deep purple. was. The thickness almost coincided with the thickness of the layer of sulfonic acid groups converted to methylammonium type calculated from the adsorption amount and exchange capacity of methylamine. Also, the membrane soaked in n-butanol and
500 c.c. of n-butanol was placed in a separate flask with a reflux device, and while blowing air from the bottom of the flask at a flow rate of 500 c.c./min, the temperature was raised to 110°C, and at this temperature for 8 hours. continued to react. After the reaction,
The membrane was taken out and washed with water. Furthermore, ethanol-water containing 10% caustic soda (volume ratio 1/
1) Hydrolysis of the terminally reacted sulfonyl chloride group was carried out in a mixed solution. After hydrolysis, a portion of the membrane was washed with water and its transmission infrared spectrum was measured using the method described above. The surface that has not been subjected to phosphorus pentachloride vapor treatment is coated with raw film (Nafion XR-
415), but on the surface treated with phosphorus pentachloride vapor treatment, the absorption band at 1420 cm ^-1 due to the sulfonyl chloride group disappeared and was replaced by the sodium form of the carboxylic acid at 1680 cm ^-1 . An absorption band corresponding to the salt type was observed. Furthermore, the electrolytic performance of saturated saline was measured with the hydrolyzed membrane facing the phosphorus pentachloride vapor treated side toward the cathode under the following conditions. condition

[Table] Results of electrolysis test under the above conditions, cell voltage
It had a current efficiency of _3.62 V and 92%. Examples 5 to 10 After converting the perfluorinated cation exchange resin into a hydrogen ion type by the method of Example 1, it was added to a mixed solution of 5% of the various amines shown in Table 3 and ethanol-water (volume ratio 1/1). It was immersed for 15 hours under stirring at room temperature to convert from hydrogen ion type to substituted ammonium type. After washing the obtained membrane with water and drying, it was sealed in an ampoule together with phosphorus pentachloride powder under reduced pressure in the same manner as in Example 1.
The reaction was carried out under the conditions shown below. Table 3 shows the reaction conditions, the staining results of the membrane after the reaction, and the measurement results of the infrared spectrum.

[Table] Example 11 Hydrogen ion type membrane obtained in Example 1 (10cm ² )
5% polyethyleneimine (molecular weight 1500~
2000) was immersed in an aqueous solution for 18 hours at room temperature with stirring.
After washing with water, it was thoroughly dried. 1 g of phosphorus pentachloride and membrane were sealed in a glass ampoule with a total volume of 90 c.c. and heated at 150°C.
The reaction was carried out by immersing it in an oil bath for 1 hour. After a predetermined period of time had elapsed, the ampoule was taken out from the oil bath and opened. After the reaction, the film-like substance was
After washing with HCl and water and drying under reduced pressure, a staining test, reflection infrared spectrum, and measurement of membrane resistance in N-HCl were performed. The staining test results showed that the cross section of the membrane was uniformly stained deep purple. In addition, as a result of measuring the reflection infrared spectrum, 1060 cm ^-1 corresponding to sulfonic acid group
A strong absorption band was observed, and a weak absorption band corresponding to the sulfonyl chloride group at 1420 cm ^-1 was observed. Also, the membrane resistance at room temperature in IN-HCl is 30
It was Ω・cm ² . Judging from the above results, it seems that the sulfonic acid groups on the surface are converted to sulfole halide groups in a layer so thin that it cannot be determined by a dyeing test.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the embodiment of the present invention (-×-), the treatment in the hydrogen ion type ion-exchange resin (-○-), and the amount of reduction in ion exchange groups due to reaction temperature measured by changes in membrane resistance. It is. FIG. 2 is a diagram showing the relationship between the production ratio of acid anhydride and acid chloride groups and temperature for ion exchange groups changed by the same treatment as in FIG. 1.

Claims (1)

[Scope of Claims] 1. A cation exchange resin in which a fluorine atom is bonded to at least the α-position carbon atom with respect to a cation exchange group, wherein the counter ion of the cation exchange group is an ammonium ion or a substituted A method for converting a cation exchange group into an acid chloride group, which comprises contacting a cation exchange resin, which is an ammonium ion, with a vapor of phosphorus pentachloride under conditions such that the cation exchange group is not substantially removed. 2. The method according to claim 1, wherein the counter ion is an ammonium ion. 3. The method according to claim 1, wherein the counter ion is a substituted ammonium ion having a substituent consisting of an alkyl group having 1 to 6 carbon atoms. 4. The method according to claim 1, wherein the counter ion is a pyridinium ion. 5. The method according to claim 1, wherein the cation exchange resin has a perfluorocarbon main chain and an ion exchange group bonded to the side chain. 6. The method according to claim 1, wherein the cation exchange resin is a cation exchange membrane. 7. The method according to claim 1, wherein the cation exchange group is a sulfonic acid group. 8. Claim 1, which is a cation exchange resin in which some of the counter ions of the cation exchange group are ammonium ions or substituted ammonium ions.
The method described in section. 9. The method according to claim 8, wherein a substituted ammonium ion having a molecular weight that does not substantially penetrate into the cation exchange resin is used as a counter ion.