JPS6026143B2 - Method for improving film with ion exchange ability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in films having cation exchange chambers.

Specifically, ions present on at least one surface of a film having an ion exchange group in its side chain and an ion exchange group having at least one fluorine atom bonded to the carbon to which the ion exchange group is bonded. This is a method of eliminating the ion exchange facility of the exchange group, and is a method of converting intestinal ion exchange groups such as sulfonic acid groups, carboxyl groups, phosphate groups, etc. into corresponding acid halide groups. The acid halide group in the present invention is not necessarily stable and can be further converted into another functional group by heating, acid or alkali. Therefore, among the films having ion-exchange ability obtained by the present invention, those whose ion-exchange ability is reduced or eliminated only on the surface can be used as a cation-exchange membrane for electrodialysis to selectively remove low-charge ions. Improvements in the permeability property and conversely the anion ring rate, especially the transport number of hydroxyl ions, can be seen in terms of usage, and it can be effectively used as an intermediate treatment product for the second improvement means. For example, the film obtained according to the present invention is further treated with ammonia, amine, polyamine, amino alcohol, etc. to bond hydrophilic groups such as amino groups, acid amide bonds, hydroxyl groups, or hydrophobic groups such as alkyl groups only to the surface. In addition, it is also possible to introduce a different type of ion exchange group or anion exchange group from the ion exchange group that the treated film had. As an example of such a film, for example, a film that originally has sulfonic acid groups is subjected to the treatment of the present invention to form a sulfonyl halide group on at least one surface layer portion, and this is converted into a carboxy group by oxidation or reduction. be able to. In this case, by converting all the sulfonic acid groups present in the film into sulfonyl halide groups by the treatment of the present invention, substantially all the ion exchange groups can be changed to carboxylic acid groups, and the surface layer of the film can be made very shallow. (For example, 20
If a sulfonyl halide group is used, an ion exchange membrane having both sulfonic acid and carboxylic acid exchange groups with carboxylic acid groups on the thin layer can be obtained. Such an ion exchange membrane is effective as a membrane for electrolysis of common salt. In the present invention, it is possible to use a film having intestinal ion exchange ability, which has an intestinal ion exchange group in its side chain and has at least one fluorine atom bonded to the carbon to which the ion exchange group is bonded. This is essential, and the process of the present invention can be performed smoothly with such a structure.

Further, as processing agents, phosphorus pentachloride, phosphorus tribromide, and phosphorus triiodide have all been experimentally confirmed to achieve the object of the present invention. All of these processing agents are solids, and there are no suitable solvents that can dissolve them in high concentrations. Therefore, it is extremely difficult to react uniformly with a solid material having a large surface area such as a film. Therefore, a solid-gas system reaction using vapors (including those caused by evaporation and sublimation) of these processing agents may be considered. Of course, if sufficient temperature and uniform air flow are maintained, it is possible to achieve the desired purpose in such a reaction system, but normally the concentration of the processing agent accompanying the carrier gas is low, or the processing agent is not uniform over the entire surface of the film. Concentration and temperature are difficult to obtain. For this reason, industrialization has been difficult, such as requiring a long time for the reaction or making uniform treatment difficult. The present invention proposes a method for performing extremely uniform treatment in a relatively short time, and the present invention proposes a method for performing extremely uniform treatment in a relatively short time. After vapor-depositing at least one type of halogen compound from phosphorus pentachloride, phosphorus tribromide, and phosphorus triiodide on at least one surface of the film having intestinal ion exchange ability that binds atoms, and wrinkling this, 1
This is a method for improving an ion-exchangeable film, characterized in that the ion-exchange ability of intestinal ion-exchange groups present at least on the surface of the film is lost by heating the film to a temperature of 4 to 180 qo.

One of the features of the present invention is that the processing agent is first uniformly deposited on the film.

By vapor depositing in this way, in the next reaction step,
Since the reaction can be carried out extremely uniformly and in the presence of a concentrated processing agent, it is possible to achieve uniform processing and shorten processing time. The means for depositing the processing agent on the film is not particularly limited, but for example, as shown in FIG. 1 described below,
This can be easily achieved by bringing a film maintained at a temperature below the vaporization temperature of the processing agent into contact with the processing agent vapor deposition.

Furthermore, for a film on which a processing agent has been uniformly deposited, consideration must be given to storage or reaction conditions so that the vapor deposition processing agent does not re-vaporize.

Next, heating is usually used to react the processing agent.
Within the range of 4 to 18 pi, the lower the temperature, the longer the treatment time, for example several hours, and the higher the temperature, the shorter time treatment, for example several minutes.

In addition, when processing deep inside the film, it depends on the thickness of the film, but for example, if the film is about 0.1 rib, it can be easily processed to the center, and if the film is about 0.8 Even if treatment is performed from both sides, considerably high temperatures and long periods of time are required to convert all ion exchange groups.
However, when treating only the surface layer of the t film, for example, a shallow portion of 20 μm or less, 20 minutes at 160° C., for example, is sufficient. Examples of suitable means for carrying out the invention are shown below.

FIG. 1 shows two general means of evaporation. A film with ion exchange ability that has a cation exchange group in its side chain and has at least one fluorine atom bonded to the carbon to which the ion exchange group is bonded, such as ion exchange phlegm manufactured by DuPont. The hydrolyzate of a copolymer of perfluoro(alkyl vinyl ethersulfonyl fluoride) and tetrafluoroethylene is moved 1' in the direction of the arrow and supported by Nipprol 11 and 12 on the dust box 2. pass. The vapor deposition box 2 contains a processing agent, that is, at least one type of halogenated phosphorus compound among phosphorus pentachloride, phosphorus tribromide, and phosphorus triiodide, and is heated by a heating device 3 to The room is filled with processing agent vapor. In some cases, it may be effective to keep the vapor deposition box under reduced pressure. In this way, the processing agent vapor condenses or precipitates and solidifies on the low-temperature film.The film on which the processing agent is vapor-deposited may be a film cut to an appropriate length, or it may be rolled up to the maximum length. It may also be a film.

Film coated with a processing agent can be stored by stacking two films together so that their vapor-deposited surfaces are in contact with each other, or by rolling up another film on the vapor-deposited surface. The present invention can be achieved by immediately heating the film to 140°C or higher in that state.In addition, in the case of the largest length, the vapor-deposited film that has been rolled up or the film that comes out of the coating process is not rolled up. , heating rolls 4, 5, and 6 as shown in Figure 2.Three heating rolls are shown in Figure 2, but the number, shape, etc. may vary depending on the heating time. It is decided as appropriate.
FIG. 3 shows an example of another embodiment. In this example, the largest film 1 is placed in the vapor deposition box 2 and then continuously sent to the reaction process. The vapor deposition box 2 is a box that is shielded from outside air as much as possible, and suction is carried out through a pipe 8 if necessary, and the processing agent is evaporated in another device not shown in this figure, and only the vapor or the vapor is removed. Steam is introduced through pipe 9 with nitrogen or other inert carrier gas. Alternatively, the processing agent may be evaporated inside the dust collecting box 2. For example, in one embodiment, a wire mesh shelf filled with a processing agent is provided in the upper part of the vapor deposition box, and processing agent vapor is generated by heating. This corresponds to the case where the top and bottom of FIG. 1 are turned upside down. In this case, it is also effective to reduce the pressure inside the box in advance. In short, it is important to form a uniform layer of the processing agent on the film to be processed, and for this purpose it is necessary to maintain a uniform concentration of the processing agent vapor within the deposition box.

Usually, the time required for vapor deposition is much shorter than when the film is directly reacted with processing agent vapor. Therefore, it is extremely easy to maintain a uniform vapor concentration inside the box for that short period of time, compared to the case of direct reaction, where the vapor concentration inside the box must be maintained uniformly over a long period of time required for the reaction. This is a huge advantage in implementing this method. It is preferable that the Aoi box is heated or kept warm.

It is also preferable to pass cooling water for cooling the film through the deposition box in order to increase the deposition effect. The film on which the processing agent has been deposited is continuously led to the next reaction step. The reaction step is preferably carried out in a box-like object 7 that is substantially shut off from outside air, similar to a normal vapor deposition box. Here, while the film is sandwiched between the endless belts 15 supported by the rolls 10 and moves, a reaction occurs due to the heat of the heating device 16. In this case, in order to prevent the vapor-deposited processing agent from being diffused, it is also preferable to introduce the vapor of the processing agent through the pipe 13. Furthermore, since the processing agent is generally a powerful chemical, it may be preferable from a sanitary standpoint to suck it up through the pipe 14 to prevent it from leaking outside. Example 1 A copolymer of perfluoroalkyl pinylethersulfonyl fluoride containing perfluoro(3,6-dioxa-4-methyl-7-octensulfonyl fluoride) as a main component and tetrafluoroethylene was hydrolyzed. A sulfonic acid type intestinal ion exchange membrane was used.

The exchange capacity of this is 0.91 meq/g dry resin (
The thickness was 0.15 skin. This is an excess of 60
After soaking in %HN03 at 60 qo for 16 hours to completely convert it into an acid form, it was washed with water and dried under reduced pressure. 15 x of this film
Insert the 20 arc into a vapor deposition box as shown in Figure 1 (approximately 10 in. x 12 skin in the opening) into which phosphorus pentachloride was poured for about 10 in. Without rotating the nib roll, heat to about 200°C from the bottom. A homogeneous vapor-deposited film of phosphorus pentachloride was obtained in 1 minute.The film was then sandwiched between ferro plates and heated under pressure at 150°C for 2 hours.

after that,. When the membrane was washed with water and the surface layer was examined using an infrared reflection spectrum, a strong absorption peak was observed at 142 Himatsu-1, and conversely, the sulfonic acid peak at 1060 Himatsu-1 had disappeared. After soaking this membrane in acidic crystal violet solution and leaving it for 16 hours, the cross section was examined under a microscope.
Approximately 10 microns on both sides of the membrane were not stained, and the center was clearly stained. Just to be sure, this film was coated with 10% Na.
After hydrolyzing the sulfonyl chloride groups into sulfonic acid groups by immersion in an OH-methanol solution, a dyeing test was performed again, and the cross section of the membrane was clearly dyed, and the absorption at 1420 orbital disappeared in the infrared reflection spectrum. , 106
Zero orbital absorption reappeared. Next, this membrane was made into an acid form with nitric acid again and analyzed for sulfur by fluorescent X-rays.The sulfur content was reduced by only 0.7% compared to the membrane before phosphorus pentachloride treatment, which had been soaked in nitric acid and made into an acid form. It wasn't. Example 2 Tetrafluoroethylene and perfluoro(
A hydrolyzate of a copolymer membrane of perfluoroalkyl vinyl ether sulfonyl fluoride containing 3,6-dioxer (4-methyl-7-octensulfonyl fluoride) as the main component, with an exchange capacity of 0.83 meq/g dry membrane. (Japanese type) was used.

This was slowly wound up using the apparatus shown in FIG. 1 so that the exposure time was 1 minute. Incidentally, during winding, a Teflon PFA (manufactured by DuPont) film was overlapped. The wound film was placed in an air bath at 150 pm for 1. The insects reacted well after heating for a while. When this film was tested on the same machine as in Example 1, almost the same results were obtained. This confirmed that continuous processing was possible. Example 3 A sodium sulfonate type membrane was used, which was obtained by hydrolyzing the same perfluoro(3,6-dioxer-4-methyl-7-octensulfonyl fluoride) copolymer film used in Example 1.

That is, the acid type membrane used in Example 1 was immersed in 0.5N saline solution for 5 hours, the acidic solution was neutralized with caustic soda, and the membrane was completely immersed in the solution. It was made into a sodium type. This waist is shown in Figure 1 in the evaporation box (opening approx.
The compound shown in Table 1 was placed in a chamber (0x12cm) for 10 nights, heated from the bottom to 200qo to form a vapor deposited film on the film surface for 20 minutes, and then sandwiched between iron plates. It was heated under the conditions shown in Table 1.

After washing thoroughly with water, 1. The electrical resistance of the membrane was measured by immersing it in a specified amount of hydrochloric acid to equilibrate it and performing 1000 cycles of alternating current.

That is, the degree to which the sodium sulfonate group was inactivated was compared. Furthermore, when we measured the infrared absorption spectrum due to reflection on the film surface, it was found that for each film, the absorption based on the sulfonic acid group at position 106 disappeared, and absorption was observed at the wavenumber corresponding to each sulfonyl halide group. .

Table 1

[Brief explanation of drawings]

FIG. 1 shows general means for evaporation in the present invention, where 1 is a film, 2 is a vapor deposition box, and 3 is a heating device. FIG. 2 shows one mode of processing a long film, and 4, 5, and 6 are heating rolls, respectively. Third
The figure shows an embodiment in which a long film is continuously processed, where 7 is a reaction step and 16 is a heating device.
Next Z diagram is 2nd diagram

Claims (1)

[Scope of Claims] 1. A film having cation exchange ability, which has a cation exchange group in its side chain and has at least one fluorine atom bonded to the carbon to which the ion exchange group is bonded. After vapor-depositing at least one type of halogenated phosphorus compound among phosphorus pentachloride, phosphorus tribromide, and phosphorus triiodide on at least one surface, this is reacted by heating at 140° to 180°C to form the film. 1. A method for improving an ion-exchangeable film, the method comprising eliminating the ion-exchange ability of at least the cation-exchange groups present on the surface. 2. The method according to claim 1, characterized in that a long film having ion exchange ability is used, and a halogenated phosphorus compound is first vapor-deposited on at least one surface of the film, and then continuously supplied to a heating step. Method.