JPS6325602B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new method for producing a fluorine-containing polymer having a carboxyl group, which is made of a fluorine-containing polymer having a sulfonyl group, and more specifically, a simple method for efficiently converting the sulfonyl group of the fluorine-containing polymer into a carboxyl group. This method provides a method. Conventionally, there have been many proposals regarding methods for converting sulfonyl groups in fluorine-containing polymers into carboxyl groups. For example, a method proposed by the present inventors in which a sulfonyl group (sulfonic acid group) is converted into a sulfonyl halide group and then oxidized in the presence of an organic solvent (JP-A-53-132069, 54-83982), There is a method of reaction (Japanese Patent Laid-Open No. 54-20981), a method of reaction with amines (Japanese Patent Laid-Open No. 54-21478), and another method is a method of treatment with a reducing agent such as hydriodic acid (Japanese Patent Laid-Open No. 52-1999). 24177) etc. However, since most of these proposed methods involve multiple steps, they are inevitably disadvantageous economically, including in terms of equipment. The present inventors have already proposed a method to eliminate the above-mentioned disadvantages (Japanese Patent Application No. 131,646/1982).
That is, this is a method in which a fluorine-containing polymer having a sulfonyl group is irradiated with ultraviolet rays in the presence of nitrogen oxides.
This method allows carboxyl groups to be produced efficiently in a short period of time, making it possible to significantly shorten the number of steps compared to conventional methods. However, since highly corrosive and harmful nitrogen oxides are used, some improvements have to be made in terms of equipment, such as the selection of materials for the irradiation chamber and the structure of the irradiation chamber to prevent leakage of nitrogen oxides. was necessary. Therefore, the present inventor conducted further research to improve the above-mentioned disadvantages, and found that a fluorine-containing polymer having a sulfonyl group can stably and well adsorb nitrogen oxides, thereby completing the present invention. It came to this. According to the present invention, a fluorine-containing polymer having a carboxyl group is characterized by adsorbing nitrogen oxides onto the fluorine-containing polymer having a sulfonyl group, and then irradiating the same with ultraviolet rays in the absence of nitrogen oxides. A manufacturing method is provided. That is, in the present invention, a fluorine-containing polymer having a sulfonyl group is placed in a suitable adsorption device, and nitrogen oxides are adsorbed onto the fluorine-containing polymer under appropriate conditions. After purging the inside of the adsorption device with a non-toxic gas to remove nitrogen oxides, the fluorine-containing polymer adsorbing nitrogen oxides is taken out. Thereafter, the fluorine-containing polymer having adsorbed nitrogen oxides is irradiated with ultraviolet rays using an ultraviolet irradiation device, thereby easily obtaining a fluorine-containing polymer having carboxyl groups. In the present invention, since ultraviolet irradiation is performed after nitrogen oxides are adsorbed, nitrogen oxides can be effectively used and the amount of pollutants used can be reduced.According to ultraviolet and infrared spectra, nitrogen It was also confirmed that oxides were fixed (adsorbed) as at least ^NO It has great industrial merits, such as being greatly simplified and making it possible to continuously produce a fluorine-containing polymer having carboxyl groups using a simple device. The fluorine-containing polymer having a sulfonyl group used in the present invention is particularly preferably a perfluorocarbon polymer, such as perfluorosultone.

[Formula] Vinyl monomer with sulfonyl fluoride group obtained from oligomerization with hexafluoropropylene oxide after ring opening or

[Formula] (in the above formula, Y is a fluorine trifluoromethyl group or a perfluoroalkyl group; m and n are integers of 0 to 5) or other fluorine-containing vinyl monomers such as vinylidene fluoride, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene,
These include copolymers with hexafluoropropylene and the like. In addition, through post-treatment of fluorine-containing polymers,
Those into which a sulfonyl group has been introduced can also be used. The sulfonyl group referred to in the present invention generally refers to -
CF _{2 SO 2} X=
ONH ₄ ). Particularly preferred among these sulfonyl groups are sulfonic acid groups and their ammonium salts because they are easily available. A typical production example of a fluorine-containing polymer having these sulfonyl groups is a mixture of a fluorine-containing vinyl monomer and a vinyl monomer having a sulfonyl fluoride group (the composition depends on the content of sulfonyl groups in the fluorine-containing polymer). The powder thus obtained is polymerized by a known polymerization method, that is, in the presence of an initiator, at a polymerization temperature of room temperature to 200°C and a pressure of 1 to 250 Kg/cm ² by solution, emulsion or suspension polymerization. The polymer is used after being appropriately formed into, for example, granules or a film. Furthermore, in some cases, a molded membrane material may be preferably lined with a reinforcing material (such as a net) to increase its mechanical strength. When the fluorine-containing polymer having carboxyl groups obtained by the method of the present invention is used as an ion exchange membrane for electrolysis, the content of sulfonyl groups in the fluorine-containing polymer before the treatment of the present invention is 0.2 to 2.5 mm. Equivalent weight/
Gram resin is preferred from its electrochemical standpoint. Incidentally, -SO ₂ F contained in the fluorine-containing polymer obtained above can be converted into a desired sulfonyl group as described above according to the following reaction. (1) Sulfonic acid group or its salt (2) Sulfinic acid group or its salt Examples of nitrogen oxides to be adsorbed onto a fluorine-containing polymer having a sulfonyl group include NO ₂ (or N ₂ O ₄ ),
N ₂ O ₃ , N ₂ O ₅ , a mixture of NO and NO ₂ , or a suitable mixture of these gases are preferably used. In addition, depending on the conditions during adsorption, compounds that can generate the above-mentioned nitrogen oxides may also be used. For example, nitric acid, nitrites and their salts. Among these, NO ₂ (or N ₂ O ₄ ) is used because it is easily available and easy to handle.
Gaseous nitrogen oxides of N ₂ O ₃ or a mixture of NO and NO ₂ are preferred. The method for adsorbing these nitrogen oxides onto a fluorine-containing polymer having a sulfonyl group is not particularly limited, and many commonly used known methods can be applied. For example, in the case of a granular fluorine-containing polymer, it is packed in a cylindrical container, and the nitrogen oxide is placed in the container either as is or in batches diluted with an appropriate inert gas (e.g. nitrogen, helium, argon, etc.). Adsorption takes place if introduced in a continuous manner or continuously. In some cases, when a particularly large amount of adsorption is desired, the adsorption may be carried out under pressure. In the case of a film-like material, the formwork and the film-like material are alternately sandwiched between a so-called filter press type adsorption device, and nitrogen oxide or another inert gas diluted with nitrogen oxide or other inert gas is introduced through a nozzle attached to the formwork. This allows it to be absorbed. In another method, it is possible to place a support on which a number of membrane-like materials are attached in parallel in a curtain-like manner into an adsorption container, and to cause the support to be adsorbed onto a number of membrane-like materials at once. Although the adsorption amount of nitrogen oxides on the fluorine-containing polymer cannot be definitively determined depending on the purpose of use of the fluorine-containing polymer obtained by the present invention, it can be adjusted by adjusting the partial pressure of nitrogen oxides and the temperature. The present invention can be achieved if the amount of sulfonyl groups (milliequivalents/gram) in the fluorine-containing polymer used is 0.01 or more, preferably 0.1 or more. The amount of nitrogen oxides adsorbed on such a fluorine-containing polymer can be determined from the change in partial pressure of nitrogen oxides before and after adsorption. The amount of adsorption can also be determined by back-extracting the nitrogen oxides adsorbed by the water contained and quantifying the amount of extracted nitrogen oxides according to a conventional method. Next, the fluorine-containing polymer that has adsorbed nitrogen oxides is irradiated with ultraviolet light. As the irradiation method, a method commonly used in photochemical reaction systems is preferably used. In general, a known ultraviolet source such as a mercury lamp that emits ultraviolet rays of about 1800 to 4000 angstroms (although of course ultraviolet rays on the higher energy side than this range is also effective) can be used. The present invention can be fully achieved if the reactor is designed to uniformly irradiate the fluorine-containing polymer adsorbed with nitrogen oxides with the ultraviolet rays from the lamp and whose temperature can be controlled. The ultraviolet irradiation atmosphere may be under reduced pressure, in the presence of an inert gas such as nitrogen, helium, or argon, or under increased pressure. If the fluorine-containing polymer having a sulfonyl group is in the form of particles, it is preferable to irradiate it with ultraviolet rays under flowing conditions using means such as vibration or stirring. Further, in the case of a film-like fluorine-containing polymer, the position with the ultraviolet source may be fixed and ultraviolet rays of a certain intensity may be irradiated in batches. Further, when the fluorine-containing polymer is large relative to the ultraviolet light source, especially in the case of a film-like material, the film-like material may be irradiated with the ultraviolet light source while being moved continuously or intermittently. Thus, according to the method of the present invention, it is industrially advantageous that the conversion from sulfonyl groups to carboxyl groups is rapid and that the process is carried out continuously. The amount of ultraviolet rays to be irradiated and the irradiation time depend on the purpose of use of the fluorine-containing polymer obtained by the treatment of the present invention, the type of fluorine-containing polymer used, the amount of nitrogen oxide adsorption, the reaction temperature, and the shape of the reaction apparatus. etc., it cannot be determined unambiguously. Generally, if the amount of ultraviolet rays and the irradiation time are too large or too long, the elimination reaction of the sulfonyl group may occur preferentially, giving undesirable results. Therefore, it is desirable to determine the amount of ultraviolet rays and the irradiation time in advance through experiments, depending on the intended use of the fluorine-containing polymer obtained by the treatment of the present invention. Generally, the present invention can be sufficiently achieved with a dose of several mW/cm ² and an irradiation time of several minutes to several hours. In the method of the present invention, the temperature at which the fluorine-containing polymer having a sulfonyl group is treated by irradiating ultraviolet light is generally preferably in the range of room temperature to 250°C.
Of course, even outside this range, for example around 10°C, the reaction proceeds, albeit slowly, and even at temperatures above 250°C, the formation of carboxyl groups can be observed in some cases. Other side reactions, such as partial elimination of carboxyl groups, especially in the case of fluorine-containing polymers, are not preferred because physical defects such as deformation and deterioration of strength are observed. The fluorine-containing polymer obtained by processing according to the method of the present invention has an infrared spectrum (KBr method if the polymer is granular, ATR method or transmission method if the polymer is film-like)
As a result of measurement, a new absorption band appears at 1780 cm ^-1 that was not observed before treatment, and it shifts to 1680 cm ^-1 after alkali treatment, indicating that it is caused by the carboxyl group linked to the perfluoroalkyl group. In addition, depending on the processing conditions, an absorption band at 1610 cm ^-1 that is assumed to be caused by perfluoronitro groups is observed. On the other hand, the absorption band of sulfonic acid groups that is strongly observed at 1060 cm ^-1 before treatment (when the sulfonyl group is a sulfonic acid group) generally disappears when the treatment conditions are strengthened, and most of the sulfonic acid groups are not reacted. Resulting in. Furthermore, when the treatment conditions are weakened, most of the sulfonic acid groups remain and a small amount of carboxyl groups are observed to be produced. Accordingly, in the present invention, depending on the processing conditions, it is possible to arbitrarily produce a product ranging from a state containing a small amount of carboxyl group in the sulfonic acid group to a state in which there are almost no sulfonic acid groups and only carboxyl groups are present. The present invention is an advantageous method for efficiently converting a sulfonyl group into a carboxyl group in one step, but it also forms a thin layer in which carboxyl groups exist with a uniform thickness on the surface layer of a granular or film-like fluorine-containing polymer. Has features that can be configured. Such thin layers can be easily distinguished by staining. For example, a fluorine-containing polymer treated according to the present invention is dyed in an acidic aqueous solution of crystal violet containing a swelling solvent such as alcohol, a thin section of the cross section is cut, and the carboxyl polymer is observed under a microscope. The layer in which the group is present can be confirmed. Furthermore, since the method of the present invention is a reaction using ultraviolet light in a gas phase, the above-mentioned granular,
In addition to thread-like and film-like forms, bag-like forms can also be suitably processed. For example, by arranging an ultraviolet ray source so that ultraviolet rays can be uniformly irradiated onto the center of a cylindrical object or the inner surface of the cylindrical object that has previously adsorbed nitrogen oxides, and applying the treatment according to the present invention, the present invention can be applied to bag-like objects as well. Able to adapt. The fluorine-containing polymer having a carboxyl group obtained by the treatment of the present invention can be used in conventionally known applications without any limitations. For example, if a polymer having carboxyl groups is in the form of particles, it is useful for catalysts, PH controllers, special ion exchange resins, and the like.
In particular, in the case of membrane-like materials, the present invention provides extremely high-performance ion exchange membranes for salt electrolysis, which have been actively researched in recent years. That is, as a preferred embodiment of an ion exchange membrane for salt electrolysis, one having a sulfonic acid group on one side and a carboxyl group on the other side has been proposed. It is easy to control thin layers with carboxyl groups of several microns to several tens of microns, so it is possible to make the layer containing carboxyl groups, which is a relatively high resistance layer, extremely thin, making it possible to Electrolytic membranes can be produced dramatically more efficiently in one process and with simple equipment. Furthermore, the film-like material obtained by the present invention can be applied to energy-saving devices that have been actively researched recently, such as S, P, and E (Solid Polymer).
Electrolyte) method, or coating the surface where carboxyl groups are present with platinum etc.
It can also be applied to a method of roughening the surface of a film-like object to prevent the adhesion of air bubbles, a method of attaching inorganic powder to the surface of a film-like object, and the like. Examples are shown below to specifically explain the present invention, but the present invention is not limited thereto. Example 1 Tetrafluoroethylene and perfluoro(3,
A copolymer of 6-dioxa-4-methyl-7-octensulfonyl fluoride), which has an exchange capacity of 0.91 (milligram equivalent/gram dry resin) when the sulfonyl fluoride group is hydrolyzed to form a sulfonic acid group. A transparent film with a thickness of 0.18mm is
The sulfonic acid groups were converted to H ⁺ form by immersion in 1N HCl. On the other hand, a germicidal lamp GL is placed in the center of a glass cylinder with an inner diameter of 8 cm and has two nozzles at the top and bottom of the cylinder.
-15 (manufactured by Toshiba) was attached to the inner periphery of the reactor so that the surface was uniformly exposed to ultraviolet rays, and the above-mentioned H ⁺ type film was attached at 15 cm x 20 cm. This reactor was immersed in an oil bath, and the temperature was raised to 160° C. while introducing nitrogen through a nozzle at a flow rate of 50 c.c./m. After raising the temperature,
The introduction of nitrogen was stopped, a vacuum pump was connected to the nozzle, and vacuum drying was continued for another hour. After drying, the reaction vessel was evacuated to −76 cmHg. Nitrogen oxide (NO) and nitrogen dioxide (NO ₂ ) were introduced through nozzles at 5 cmHg each, and nitrogen was introduced to bring the pressure to atmospheric pressure. The film was left in this state for 45 minutes to allow nitrogen oxides to be adsorbed onto the film. The pressure drop inside the reactor was 3 cmHg. Thereafter, nitrogen was introduced into the reactor to clean the inside of the reactor. The reactor was degassed using a vacuum pump to ensure thorough cleaning. Nitrogen was again introduced into the reactor up to atmospheric pressure. The germicidal lamp was turned on and irradiation started. After 1 hour of irradiation, the lamp was turned off and nitrogen was introduced into the reactor for cleaning. The film was taken out and a portion thereof was cut out and subjected to infrared spectrum measurement (ATR method). The remaining portion was heated for 30 minutes in methanol-water containing 20% NaOH (volume ratio 1/1) to remove ion exchange groups.
After converting into Na ⁺ form, it was subjected to dyeing tests, electrolytic tests, etc. As a result, in the red spectrum of the irradiated surface, an absorption band attributable to carboxyl groups with medium intensity was observed at 1780 cm ^-1 , and a new, albeit weak absorption band was observed at 1610 cm ^-1 . On the other hand, the absorption band of sulfonic acid groups at 1060 cm ^-1 observed on the unirradiated surface was hardly observed. A portion of the Na ⁺ film (approximately 5 mm x 10 mm) was placed in a staining solution in which 100 mg of crystal violet was dissolved in 100 c.c. of a mixed solvent of 0.5N-HCl-methanol (volume ratio 3:7). It was soaked for 15 hours at room temperature. After washing with water, the cross section was cut into thin sections using a microtome and observed under a microscope. As a result, 15 μm of one surface was not stained at all in a layered manner, and the other parts were stained dark green.
It was found that carboxyl groups were present at a thickness of 15μ from the surface. Table 1 shows the measurement results of the electrolytic test for the film after ultraviolet treatment and the untreated film. The electrolytic test was carried out using a two-chamber cell consisting of a titanium anode chamber and a nickel cathode chamber and an effective current-carrying area of 0.5 dm ² . A titanium lath material coated with titanium oxide and ruthenium oxide was used as the anode, and a soft iron lath material was used as the cathode. A film is placed between the anode chamber and the cathode chamber, with the anode in close contact with the cathode, with a gap of 2 mm (for those irradiated with ultraviolet rays, the irradiated surface should face the cathode) to increase the Ca concentration in the anode chamber.
A saturated saline solution of 0.5 ppm or less was supplied and discharged at a salt concentration of 3.5N. On the other hand, pure water was supplied to the cathode chamber so that the concentration of NaOH was 11N. Current density
The power was adjusted to 30 A/dm ² and the temperature in the polar chamber was 90°C.

[Table] Example 2 Made of the copolymer used in Example 1, thickness 0.13
A film having an exchange capacity of 0.81 (milligram equivalent/gram dry resin) in mm was made into H ⁺ form as in Example 1. After drying the film under reduced pressure at 100℃ for 1 hour,
Transferred into a separable flask with two nozzles. At room temperature, a mixed gas of nitrogen oxide, nitrogen dioxide, and argon (volume ratio: 5:1:50, respectively) was introduced through one nozzle at a flow rate of 100 c.c./min for 1 hour, and then discharged through the other nozzle. Thereafter, the film adsorbing nitrogen oxides was divided into two parts, and one part was placed in the reactor used in Example 1 after the temperature was raised to 150℃. Instead, helium was sealed at a pressure approximately 0.5 atmospheres higher than atmospheric pressure. A sterilization lamp was turned on and irradiated for 30 minutes. At this time, the intensity of the ultraviolet lamp is determined by the irradiated surface of the film.
It was 1.5mW/ ^cm2 . After irradiation, the inside of the reactor was cleaned with nitrogen and the film was taken out. An untreated film, a film on which nitrogen oxides were simply adsorbed, and a film of the present invention subjected to the above treatment were treated with NaOH/MeOH-H ₂ O in the same manner as in Example 1.
It was immersed in water for 10 hours at room temperature. Wash more with water
It was made into Na ⁺ type. When these three films were dried under reduced pressure and their infrared spectra were measured, it was found that only the ultraviolet irradiated side of the film treated according to the present invention had a wavelength of 1680 cm.
An absorption band assigned to the ^-1 carboxylate group (Na ⁺ salt) was observed, and the others gave an infrared spectrum exactly the same as the untreated one. On the other hand, in the dyeing test, an undyed layer with a thickness of about 8 μm was observed inside the irradiated surface of the film treated according to the present invention. On the other hand, the other films were uniformly dyed green throughout. Further, when an electrolytic test was conducted using the apparatus of Example 1, the film of the present invention produced 10N NaOH, had a cell voltage of 3.30V, and a current efficiency (NaOH) of 94% and 50%.
The NaCl concentration in NaOH was 40 ppm. On the other hand, the cell voltage of the untreated film and the film that only adsorbed nitrogen oxides was 3.23V and 3.25V, respectively.
The current efficiency was also 54% and 55%, respectively. Example 3 Tetrafluoroethylene and perfluoro(3,
The exchange capacity when hydrolyzed with a copolymer of 6-dioxa-4-methyl-7-octensulfonyl fluoride (6-dioxa-4-methyl-7-octensulfonyl fluoride) is 0.71 (milligram equivalent/gram dry resin), A film-like material obtained by sandwiching and heat-sealing denier thread (50 strands per inch both vertically and horizontally), with a thickness of 0.35 mm, and converting the sulfonic acid group into H ⁺ type using the usual method. did. This film-like substance
It was installed in a reactor made of stainless steel and equipped with a window (10 cm x 15 cm, made of quartz) that allows ultraviolet rays to be irradiated from one side. A flat heater was attached to the stainless steel plate on the other side to control the temperature of the irradiated surface. Two mercury lamps SHL-100UV-2 (manufactured by Toshiba) were installed in parallel at a distance of 4 cm from the quartz window. A mixture of nitrogen and nitrogen dioxide (20:1 by volume) was introduced into the reaction chamber at a flow rate of 100 c.c./min while the temperature was raised. The introduction continued for 2 hours. The temperature of the reactor is
The temperature had reached 130℃. Then switch to nitrogen 50
A flow rate of cc/min was introduced. After confirming that no nitrogen dioxide was detected in the nitrogen flowing out from the reactor by ultraviolet absorption spectrum, the mercury lamp was turned on. After 2 hours of continuous irradiation, the temperature of the reactor was
The temperature had risen to 140℃. The mercury lamp was turned off, the reaction chamber was flushed with nitrogen, and the membrane was removed from the reactor.
The infrared spectrum and electrolytic performance were measured in the same manner as in Example 1. According to the infrared spectrum, the absorption band of carboxyl group at 1780 cm ^-1 is in the middle, and the absorption band of carboxyl group at 1610 cm ^-1
was recognized as weak. On the other hand, almost no sulfonic acid groups were observed. As a result of conducting an electrolysis test in the same manner as in Example 1, when 6N NaOH was produced, the cell voltage was 3.35V and the current efficiency was 95%.
When the concentration of NaOH was further increased to 9N, the cell voltage remained at 3.45V and the current efficiency remained at 95%. Example 4 Tetrafluoroethylene and CF ₂ =CF−
A copolymer of OCF ₂ CF ₂ OCF ₂ CF ₂ SO ₂ F, the exchange capacity when hydrolyzing the sulfonyl fluoride group is
A film having a thickness of 0.15 mm with a ratio of 1.1 (milligram equivalent/gram dry resin) was converted into H ⁺ form according to a conventional method and then subjected to the treatment of the present invention. After drying the film under reduced pressure, it was placed in the separable flask used in Example 2. After immersing the separable flask in an oil bath at 100°C, 550 c.c./cm of an equimolar mixture of nitrogen oxide and nitrogen dioxide and a mixture of nitrogen (volume ratio: 1:1:10, respectively) were poured through a nozzle.
It was introduced at a flow rate of minutes. After 30 minutes of introduction, only nitrogen was continued to be introduced to wash the inside of the flask. The film adsorbing nitrogen oxides was incorporated into the reactor used in Example 1. The temperature of the reactor was raised to 190°C, and the pressure inside the reactor was reduced to -76 cmHg using a vacuum pump. A germicidal lamp was turned on and ultraviolet rays were irradiated for 1 hour. I turned off the germicidal lamp and took out the film. After immersing it in NaOH/MeOH-H ₂ O for 5 hours at room temperature to convert it into Na ⁺ form, the infrared spectrum was measured, and a strong absorption band at 1680 cm ^-1 was observed on the irradiated surface, and a strong absorption band at 1060 cm ^- The absorption band ¹ was observed in a shoulder shape. On the other hand, the unirradiated side was exactly the same as that of the untreated film. As in Example 1, an electrolytic test was performed with the irradiated surface facing the cathode, and 12N NaOH was produced, the cell voltage was 3.30 V, and the current efficiency was 96%. Example 5 The H ⁺ type film used in Example 1 was immersed in 2% ammonia water at room temperature for one day to form the NH ₄ ⁺ type film. After washing with water and air drying, the film was subjected to the treatment of the present invention in exactly the same manner as in Example 1. When the infrared spectrum of the obtained film was measured, it was found that on the surface irradiated with ultraviolet rays, there were carboxyl groups at 1780 cm ^-1 .
Furthermore, an absorption band at 1060 cm ^-1 due to the sulfonic acid group was observed with similar intensity. Example 6 The NH ₄ ⁺ type film obtained in Example 5 was
-4289, one side of the film was brought into contact with phosphorus pentachloride vapor at a temperature of 150°C to convert the sulfonic acid groups on one side to sulfonyl chloride groups.
Furthermore, in a 10% sodium sulfite aqueous solution at 80°C.
The sulfonyl chloride group was converted into a sulfinic acid group (Na ⁺ salt) by immersion in water for 10 hours. The obtained film was immersed in a dilute aqueous HCl solution to form an H ⁺ form. The obtained film was subjected to the treatment of the present invention according to Example 1. The reaction temperature was raised to 110℃, and the nitrogen oxides were 10 cmHg of nitrogen oxide and 2 cmHg of nitrogen dioxide.
The method was exactly the same as in Example 1 except for the following. Also, the surface where sulfinic acid was present was irradiated. After changing the obtained film to Na ⁺ type, an electrolytic test similar to that in Example 1 was conducted, and the result was
Manufacture NaOH, cell voltage 3.41V, current efficiency 94%
It was hot. Furthermore, when we measured the infrared spectrum, a strong absorption band corresponding to carboxylate groups was observed at 1680 cm ^-1 on the irradiated surface, but absorption bands based on sulfinic acid at 1010 cm ^-1 and 930 cm ^-1 were almost completely absent. It was not recognized. Example 7 The copolymer used in Example 4 had a thickness of 0.2 mm with an exchange capacity of 0.3 (milligram equivalent/gram dry resin) when the sulfonyl fluoride group was hydrolyzed.
After freezing and crushing the film, put it through a sieve and
Granules of mesh were obtained. Remove granules according to the usual method.
After changing to H ⁺ form, it was dried under reduced pressure. The granular material was further placed in the stainless steel reactor used in Example 3 to the extent that it just covered the bottom plate of the reactor. The reactor was placed in an ultrasonic cleaner so that vibrations could be applied to the reactor. A mixture of nitrogen dioxide and helium (1:100 by volume) was introduced into the reactor at a flow rate of 100 c.c./min for 30 minutes while applying ultrasound. After the introduction, the temperature was increased while cleaning the inside of the reactor with nitrogen. When the temperature of the reactor reached 80° C., the two mercury lamps used in Example 3 were placed at a distance of 5 cm from the quartz tube and turned on. When irradiation continued for 3 hours, the temperature of the reactor reached 100°C. The mercury lamp was turned off, the ultrasound application was stopped, and the particulate material was removed. When the infrared spectrum of the particulate matter was directly measured using the ATR method, an absorption band at 1780 cm ^-1 due to carboxyl groups was observed with medium intensity, and an absorption band at 1060 cm -1 with medium intensity was observed.
Almost no absorption band of sulfonic acid at cm ^-1 was observed. On the other hand, when the granular material was sliced into rings and the thin sections were stained with crystal violet and observed under a microscope, it was found that 30 μm from the surface was not stained at all, and the inside was stained green. Example 8 The sulfinic acid group-containing film (H ⁺ type) obtained in Example 6 was dissolved in 1% ammonia water at room temperature for 10 minutes.
It was soaked for an hour to form NH ₄ ⁺ form. The obtained film was subjected to the treatment of the present invention in exactly the same manner as in Example 2. When the infrared spectrum of the film after treatment was measured, an absorption band of carboxyl groups with medium intensity was observed at 1780 cm ^-1 on the irradiated surface, and a shoulder-shaped absorption band due to sulfinic acid groups was observed. After oxidation at 80°C for 5 hours in an aqueous solution containing 20% NaOH and 3% NaClO, the same electrolytic test as in Example 1 was performed, and 8N NaOH was produced, the cell voltage was 3.40V, and the current efficiency was was 93%. Examples 9 to 16 Using the H ⁺ type film and reactor used in Example 1, the relationship between the amount of nitrogen oxides adsorbed and the amount of carboxyl groups produced was investigated. That is, after the film was installed in the reactor, a mixture of N ₂ O ₃ (an equimolar mixture of NO and NO ₂ ) and nitrogen was introduced. After adsorption at room temperature for 1 hour, a part of the film was cut out and 1%
Soaked in NaOH water. Leave it at room temperature for 20 hours,
The extracted nitrogen oxides were quantified. On the other hand, the remaining film was irradiated with ultraviolet rays at 160° C. for 1 hour after purging the inside of the reactor with nitrogen at atmospheric pressure.
After changing to the Na ⁺ form after irradiation, infrared spectra were measured to determine the relative abundance of carboxylate groups and sulfonic acid groups. These operations were repeated by changing the partial pressure of N ₂ O ₃ to examine the amount of adsorption and the degree of formation of carboxylate groups. The results are shown in Table-2.

【table】

【table】

Claims (1)

[Scope of Claims] 1. A method for producing a fluorine-containing polymer having a carboxyl group, which comprises adsorbing nitrogen oxides onto the fluorine-containing polymer having a sulfonyl group, and then irradiating the polymer with ultraviolet rays. 2. The method according to claim 1, wherein the sulfonyl group is a sulfonic acid group or an ammonium salt thereof. 3. The method according to claim 1, wherein the adsorption amount of nitrogen oxides is 0.01 or more in equivalent ratio to sulfonyl groups. 4. The method according to claim 1, wherein the fluorine-containing polymer is a perfluorinated polymer. 5. The method according to claim 1, wherein the fluorine-containing polymer is a copolymer of perfluoroolefin and perfluoroalkylsulfonyl vinyl ether. 6 Nitrogen oxides are NO ₂ , N ₂ O ₃ or NO and NO ₂
The method according to claim 1, which is a mixture of. 7. The method according to claim 1, wherein the fluorine-containing polymer is a film-like material.