JPS6134725B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel fluorinated copolymer useful as a raw material for producing fluorinated cation exchange membranes or cation exchange resins having sulfonic acid groups and/or carboxylic acid groups, and a method for producing the same. In recent years, there has been a growing movement to develop new chemical processes using fluorinated cation exchange membranes and cation exchange resins that have excellent chemical resistance and heat resistance. A typical example of this trend is in industries that produce caustic soda and chlorine through the electrolysis of table salt, which has advantages in terms of pollution prevention and energy conservation compared to the conventional mercury method and diaphragm method. It is possible to produce caustic soda with the same quality as the mercury method.
The ion exchange membrane method is attracting a lot of attention. The most important factor influencing the economic efficiency of the ion exchange membrane method is the characteristics of the cation exchange membrane used, which must satisfy the following conditions. (1) High current efficiency and low electrical resistance. For high current efficiency, the membrane needs to have a sufficiently large ion exchange capacity and a low water content, resulting in a high fixed ion concentration within the membrane. On the other hand, in order to have a low electrical resistance, it is advantageous for the water content to be high. Since the water content varies depending on the type of ion exchange group, ion exchange capacity, and concentration of the external liquid, an optimal combination thereof is required. (2) Can withstand high temperature chlorine and alkali for long periods of time. Cation exchange membranes made of fluorinated polymers generally withstand the above atmospheres well, but some types of ion exchange groups may not have sufficient chemical stability, so it is necessary to use appropriate ion exchange groups. It is important to choose. (3) In a highly concentrated alkali, the forces of swelling and contraction that act under conditions of high temperature and high electrical density, the force of delamination due to intense mass transfer, and the vibration of the membrane due to gas generation. , to withstand forces that tend to cause bending and cracking for a long period of time. In general, the physical strength of a membrane is determined by the physical structure of the membrane,
Since it varies depending on the polymer composition, ion exchange capacity, type of ion exchange group, etc., it is necessary to realize an optimal combination of these. (4) The manufacturing method is easy and the cost is low. Conventionally, several fluorinated cation exchange membranes have been proposed for use in electrolysis of aqueous solutions of alkali metal halides. For example, by hydrolyzing a copolymer of tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octensulfonyl fluoride, a fluorinated cation exchanger with a sulfonic acid group in the side chain is used. It is known as a membrane. However, since this conventionally known fluorinated cation exchange membrane consisting only of sulfonic acid groups has a high water content, it is easy for hydroxyl ions migrating and diffusing from the cathode chamber to permeate, resulting in electrolysis. The disadvantage was that the current efficiency was low. In particular, for example 20
When performing electrolysis while obtaining caustic soda solution with a high concentration of % or more, the current efficiency was extremely low, and this resulted in an economical disadvantage compared to the conventional salt electrolysis using the mercury method or the diaphragm method. In order to improve this shortcoming of low current efficiency, when the exchange capacity of sulfonic acid groups is lowered to, for example, 0.7 milliequivalent or less per gram of H-type dry resin, the moisture content in the membrane decreases and the ions fixed in the membrane are reduced. Since the concentration is relatively high compared to a membrane with a high exchange capacity, it was possible to somewhat prevent a decrease in current efficiency during electrolysis. For example, when obtaining caustic soda with a concentration of 20% during the electrolysis of common salt, the current efficiency could be improved to approximately 80%.
However, when reducing the exchange capacity of the membrane to improve current efficiency, the electrical resistance of the membrane increases significantly.
Not only is it impossible to carry out electrolysis economically, but no matter how high the membrane resistance is, the current efficiency remains low.
It has been extremely difficult to produce an industrial sulfonic acid type fluorinated cation exchange membrane that has been improved to nearly 90%. On the other hand, JP-A-50-120492, JP-A-51-126398
In the issue, a fluttering pair -ion replacement membrane having a carboxylic acid group is disclosed as an exchange group. Since these membranes have a low water content in their carboxylic acid groups, the concentration of fixed ions in the membrane can be increased, and current efficiency of over 90% can be achieved. Chemically, it is also sufficiently stable under commonly used conditions. However, when compared with the same ion exchange capacity, membranes with carboxylic acid groups have higher electrical resistance than membranes with sulfonic acid groups, and they have the disadvantage that the electric power consumption becomes significantly higher, especially when used at high current densities. Not only that, but also because the moisture content of the entire membrane is low, when used for a long period of time under harsh conditions in highly concentrated alkali, the membrane gradually shrinks and becomes hard and brittle, resulting in delamination and cracking. Another drawback was that current efficiency decreased. In order to improve the drawbacks of membranes having only carboxylic acid groups, a fluorinated polymer having a carboxylic acid group or a group convertible to a carboxylic acid group (hereinafter referred to as a precursor) and a sulfonic acid group or JP-A No. 52-36589 discloses that a fluorinated polymer containing the precursor is laminated into a film or formed into a blend film, and then hydrolyzed to form a cation exchange group.
No. 53-132089. However, these polymers have problems because they have poor compatibility, making it difficult to completely adhere or blend them, and tend to cause peeling or cracking during use under harsh conditions. Moreover, blended materials are completely inadequate from the viewpoint of fully utilizing the high current efficiency of the carboxylic acid group and the low electrical resistance of the sulfonic acid group, and exhibit only intermediate performance between the two. In addition, the above-mentioned patent publication and Japanese Patent Application Laid-open No. 52-
A vinyl monomer having a carboxylic acid group or a precursor thereof, as disclosed in No. 23192,
A cation exchange membrane that is formed by terpolymerizing a vinyl monomer having a sulfonic acid group or its precursor with a fluorinated olefin, forming it into a membrane, and then hydrolyzing it is also an intermediate material. It only shows good performance. On the other hand, JP-A-52-24176, JP-A-53-104583
No. 53-116287, JP-A No. 54-6887, etc. disclose a method in which a carboxylic acid group is formed by chemical treatment on one surface layer of a fluorinated cation exchange membrane having a sulfonic acid group. are listed. These membranes effectively prevent migration and diffusion of hydroxyl ions due to the presence of carboxylic acid groups, and exhibit high current efficiency. In addition, because carboxylic acid groups exist only in the thin layer on the cathode side, and sulfonic acid groups with high water content exist in the rest of the membrane, the membrane has low electrical resistance and is extremely superior in terms of power consumption. It is. However, although these membranes exhibit stable performance for an industrially satisfactory period under normal usage conditions, as shown in the comparative example, under harsh conditions such as high electrical density and high temperature, There are problems in that spots or blisters occur, the carboxylic acid layer peels off from the sulfonic acid layer, and the carboxylic acid layer cracks, resulting in a decrease in current efficiency. Although the cause of this phenomenon is not clear, one factor is presumed to be the polymer structure of the fluorinated cation exchange membrane, which is used as a raw material and has a sulfonic acid group or a derivative thereof. That is, these membranes are made by copolymerizing a fluorinated olefin and a sulfur-containing fluorinated vinyl ether represented by the following formula and molded into a membrane, or by hydrolyzing it to remove sulfonic acid groups. It is manufactured by chemically treating a film with (n=an integer of 0 to 2) Among these monomers, those with n=0 are
As described in No. 47-2083, etc., in order to cause a cyclization reaction in the vinylation step as shown in the following formula (1) and convert this cyclic sulfone into CF ₂ = CFOCF ₂ CF ₂ SO ₂ F, However, many additional reactions are required, making it extremely difficult to produce industrially, and depending on the conditions, cyclization may occur during polymerization, deteriorating the polymer's physical properties. Therefore, those with n=1 are usually used industrially, but this does not mean that the obtained sulfonic acid type membrane and the chemical treatment disclosed in the above patent publication report The ion exchange capacity of the membrane formed on the surface layer of the sulfonic acid type membrane is
Not only does it have the disadvantage that it cannot be made very large, but the side chain

Perhaps because it contains [Formula], unless the copolymerization ratio of the fluorinated olefin to the sulfur-containing fluorinated vinyl ether is about 6 or more,
This is also the reason why it is not possible to obtain a physically strong film, and it also occurs when a film containing the above-mentioned carboxylic acid groups and sulfonic acid groups is used under harsher conditions than normal conditions. It is also expected that this is a cause of cracks in the carboxylic acid layer. Since the molecular weight of n=2 is even larger, the above drawback is further amplified. Furthermore, copolymers of fluorinated vinyl monomers that do not have an ether bond and tetrafluoroethylene, such as trifluorovinylsulfonyl fluoride, disclosed in Japanese Patent Publication No. 41-13392, have the disadvantage of poor film-forming properties. There is. Furthermore, JP-A-52-28588, JP-A-52-23192
The general formula CF ₂ = CX ¹ (OCF ₂ CFX ² ) _a O _b (CFX ³ ) _c SO ₂ X ⁴ [However, X ¹ is F or CF ₃ , X ² , X ³ is F or C ₁
~ _C10 perfluoroalkyl group, ^X4 is F,
OH, OR ¹ , OM and NR ² R ³ (R ¹ is a C ₁ to C ₁₀ alkyl group, R ₂ and R ₃ are H or one of R ¹ , M
is an alkali metal or quaternary ammonium group), a
is an integer of 0 to 3, b is 0 or 1, and c is an integer of 0 to 12] A fluorinated cation exchange membrane produced from a fluorinated vinyl compound and a copolymer of the same and a fluorinated olefin. is listed. However, the method for producing the fluorinated vinyl compound is not specifically disclosed, nor is the precursor of the compound taught. Moreover, as can be seen from the description of the specification of the publication, the preferred form is X ¹ =F, X ² =CF ₃ , X ³ =F, or CF ₃ , X ⁴
=F, a=0-1, b=1, c=1-3, in the examples and as preferred representative examples, conventionally known (a is the same as above) That is, only those in which c=2 and copolymers and membranes derived therefrom are listed. In the field of ion exchange membrane methods, there is a strong need to develop membranes that exhibit high current efficiency and low electrical resistance even when used under harsher conditions, have a longer lifespan, and are lower in cost. In the process of continuing their earnest efforts to develop such a membrane, they have finally completed the present invention. The gist of the invention consists of the following repeating units, (A) and
(B), (A) (-CA ₁ A ₂ - CA ₃ A ₄ ) - (A ₁ , A ₂ are F or H, A ₃ is F, Cl or H, A ₄ is F , Cl, CF ₃ , -OR _F , H or CH ₃ , R _F is a C ₁ to _{C 5} perfluoroalkyl group) (B) (k=0 or 1, l=an integer from 3 to 5, Z is -
S- or _-SO2- , Y= _C1 to _C10 alkyl group, aryl group, Cl or _C1 to _C10 perfluoroalkyl group) The ratio of the number of repeating units of (A) and (B) is (A)/(B)=1~
16, a novel fluorinated copolymer and its production method. In the above formula, when heat resistance and chemical resistance are particularly required, such as when manufacturing fluorinated cation exchange membranes for aqueous electrolysis of alkali metal halides, the repeating unit (A) is , (L=F, Cl, CF ₃ , -OR _F or H, R _F are the same as above) It is preferable, and the case where L=F is particularly preferable. Moreover, k=0 is preferable in order to produce a membrane or resin that has high ion exchange capacity and is physically tough. Moreover, it is preferable that (A)/(B)=1.5-14, and (A)/(B)=3-11 is more preferable. In addition, it is preferable that l = 3 because it is easy to manufacture the monomer, the physical properties of the obtained polymer can be increased, and the range of variation in the physical properties of the polymer can be widened, and Y is a C ₁ to C ₁₀ alkyl group or an aryl group. Of these, Y is preferably C ₁ to C ₁₀
More preferred are those having an alkyl group. Considering the aspects of polymerizability and moldability, Z is -S-,
Particularly preferred are those in which Y is an alkyl group of _C1 to _C10 , and among these, those of _C1 to _C5 are most preferred. The above copolymer is essentially a random copolymer, and its molecular weight is usually in the range of 8,000 to 1,000,000, and when the melt index is measured using an apparatus with an orifice inner diameter of 2.1 mm and length of 8 mm, the temperature is 250.
℃, load 2.16Kg, usually 0.001g/10 minutes ~
The range is 500g/10 minutes. The above copolymer can be conveniently identified by measuring the infrared absorption spectrum (IR) or surface infrared absorption spectrum (ATR) of the film-like product as shown in Examples. The copolymer composition can be estimated by converting all S-containing end groups into ion exchange groups such as sulfonic acid groups or carboxylic acid groups, and then measuring the ion exchange capacity, performing elemental analysis, or a combination of these. This is done by Furthermore, the side chain structure of the copolymer according to the present invention is S
After converting the terminal group containing , to an ion exchange group such as a sulfonic acid group, a carboxylic acid group, or a sulfinic acid group, a removal group reaction is performed, and the IR or ATR of the product is
It can be identified by measuring. The fluorinated copolymer of the present invention comprises at least one monomer selected from the group of olefins represented by the following general formula, CA ₁ A ₂ =CA ₃ A ₄ (A ₁ , A ₂ , A ₃ , A ₄ is the same as above), preferably at least one monomer selected from the group of fluorinated olefins represented by the following general formula, and CF ₂ =CFL (L = F, Cl, CF ₃ , -OR _F or H, R _F is C ₁
~ _C5 perfluoroalkyl group) Produced by copolymerizing at least one monomer selected from the group of sulfur-containing vinyl ethers represented by the following general formula. (k, l, Z, and Y are the same as above) In this case, other vinyl compounds may be mixed and copolymerized in small amounts, or divinyl compounds such as perfluorobutadiene and perfluorodivinyl ether, or CF It is also possible to carry out crosslinking by copolymerizing a fluorinated vinyl compound having a terminal group capable of carrying out a crosslinking reaction such as _2I . The fluorinated olefin used in the present invention includes:
Those containing no H are preferred in terms of heat resistance and chemical resistance, and among these, tetrafluoroethylene is the most preferred. Among the sulfur-containing fluorinated vinyl ethers used in the present invention, those with k = 0 are preferred because they can increase the ion exchange capacity and produce physically strong membranes, but of course, if k = 1 is used in small amounts, They may be used in combination. Further, one in which l=3 is preferable from the viewpoint of ease of production and physical properties of the obtained polymer. If l=6 or more, it is difficult to manufacture and the ion exchange capacity cannot be sufficiently increased.
= Inferior to 3 to 5. Moreover, those in which Y is a _C1 to _C10 alkyl group or aryl group are preferable from the viewpoint of ease of production of the vinyl monomer, and those in which Y is a _C1 to _C10 alkyl group are more preferable. In addition, considering the aspects of polymerizability and moldability, it is particularly preferable that Z=-S- and Y is an alkyl group of C ₁ to C ₁₀ , and among these, those of C ₁ to _{C 5} are the most preferable. preferable. In the present invention, specific examples of sulfur-containing fluorinated vinyl ethers preferably used are as follows: (k=0 or 1 preferably 0, R is C ₁ to C ₁₀
alkyl or aryl groups). The sulfur-containing fluorinated vinyl ether used in the present invention is a sulfur-containing fluorinated vinyl ether containing the following formula, which has been conventionally used in producing fluorinated cation exchange membranes or cation exchange resins having sulfonic acid groups and/or carboxylic acid groups. Compared to sulfur-fluorinated vinyl ether, (n is the same as above) Even in the case of k = 0, the terminal structure or the number of ring members is different, so the cyclization reaction as described above does not occur substantially or very little in the vinylation process. k=0 can be easily obtained. Furthermore, during polymerization, the physical properties of the polymer do not deteriorate due to the cyclization reaction. Therefore, since k=0 can be mainly used for polymerization, the side chain has

Since it is possible to obtain a fluorinated copolymer containing substantially no or only a small amount of [Formula], the content of fluorinated olefin can be increased even with membranes and resins with the same ion exchange capacity. Physically tough membranes and resins with high capacity can be produced. The vinyl monomer used in the present invention can be synthesized, for example, by the following route. or In the above route, The fluorine-containing carboxylic acid obtained by the reaction is reacted with SF ₄ or SOCl ₂ or POl ₅ and then
React with NaF or KF to form RSO ₂ CF ₂ CF ₂ COF
and when used instead of RSCF ₂ CF ₂ COF above, can be obtained. Furthermore, in the above route, if an arylthioether salt is used instead of RSNa, a vinyl monomer in which Y is an aryl group can be obtained. Furthermore, it is also possible to synthesize sulfur-containing vinyl ethers with different terminal shapes by reacting these vinyl monomers or their intermediate raw materials with appropriate reagents. For example, by treating -CF ₂ SR with Cl, It can be converted into the form -CF ₂ SCl or -CF ₂ SO ₂ Cl, or it can be converted into -CF ₂ SO ₃ M by treating -CF ₂ SO ₂ R with an alkali containing an oxidizing agent. You can also do that. Also, in the above route,
Instead of RSCF ₂ CF ₂ COF, Y―Z― derived from carboxylic acid fluoride obtained by the following formula
When (CF ₂ ) _3-4 COF is used, a sulfur-containing fluorinated vinyl ether with l=4-5 can be obtained. The copolymerization ratio between the olefin contained in the copolymer and the sulfur-containing fluorinated vinyl ether can be adjusted by appropriately selecting the monomer charge ratio and polymerization conditions. The copolymers of the present invention are made by conventional polymerization methods known for use in the homopolymerization or copolymerization of fluorinated ethylene. Methods for producing the copolymer of the present invention include a non-aqueous polymerization method and an aqueous polymerization method, and the polymerization temperature is generally 0 to 200°C, preferably 20 to 100°C. Pressure is 0~200Kg/ ^cm2 , preferably 1~50
Kg/ ^cm2 . Non-aqueous polymerizations are often carried out in fluorinated solvents. A suitable non-aqueous solvent is inert 1,1,2-trichlor-1,
2,2-trichloroethane or perfluorohydrocarbons such as perfluoromethylcyclohexane, perfluorodimethylcyclobutane, perfluorooctane, perfluorobenzene, etc. Aqueous polymerization methods for producing copolymers include emulsion polymerization methods, in which the monomers are contacted with an aqueous medium containing a free radical initiator and an emulsifier to obtain a slurry of polymer particles; There is a suspension polymerization method in which a dispersion of polymer particles is prepared by contacting the polymer particles with an aqueous medium containing both a dispersion stabilizer that is inactive against meridization, and this dispersion is precipitated. Free radical initiators used in the present invention include oxidation-reduction catalysts such as ammonium persulfate and sodium hydrogen sulfite; organic peroxides such as t-butyl peroxide and benzoyl peroxide; and azobisisobutyronitrile. Examples include azobis-based compounds such as; fluorine radical generators such as N ₂ F ₂ ; After polymerization, the polymer is molded into a film or particles, if necessary. For this molding, a general technique of melting and molding a thin film can be used. When the copolymer of the present invention is used as a raw material for a fluorinated cation exchange membrane, the above membrane-like material is further combined with a membrane-like material made from a copolymer having a high copolymerization ratio of sulfur-containing fluorinated vinyl ether. It is possible and sometimes preferable to glue them together. In this case, the membrane material used for gluing may be made from a copolymer of monomers selected from the group of sulfur-containing fluorinated vinyl ethers and the group of fluorinated olefins, but As, A copolymer using the above may be used as a raw material. In order to lower the electrical resistance, it is preferable that the thickness of the film-like material used for gluing occupies 1/2 to 19/20 of the total thickness after gluing. The membrane may be lined with a mesh of mechanical reinforcing material or the like to help increase strength. A mesh made from polytetrafluoroethylene fibers is most suitable for such a backing, although porous polytetrafluoroethylene sheets and the like are also useful. It is also possible to increase the strength by mixing fibrous polytetrafluoroethylene when forming it into a membrane. When using a membrane material with a glued structure,
It is preferable to embed the reinforcing substance from the side of the membrane material having a high copolymerization ratio of sulfur-containing fluorinated vinyl ether. The thickness of the film-like material is usually 2,500 microns or less, preferably 1,000 microns or less, particularly preferably,
It is 500 microns or less, and the lower limit is determined by the required mechanical strength. The copolymer film of the present invention is substantially composed of the following repeating units (C) and (D) by converting all S-containing terminal groups to sulfonic acid groups, and ( C)

[Formula] (L is the same as above) (D) (k, l, and M are the same as above) The ratio of the number of repeating units of (C) and (D) is (C)/(D) = 1.5
It is possible to form a novel fluorinated cation exchange membrane having sulfonic acid groups of ~14, preferably 3 to 11. This membrane is useful as a melting membrane for aqueous alkali metal halide electrolysis, water electrolysis, or fuel cells. Superior to cation exchange membranes. Further, the film-like material of the copolymer of the present invention is substantially composed of the above repeating units (C) and (D) and the following repeating unit (E), and (E) (k, M are the same as above, m=l-1) The ratio of the number of repeating units of (C), (D), and (E) is (C)/[(D)+(E)]=1.5~ It is also possible to provide a novel fluorinated cation exchange membrane having carboxylic acid groups and sulfonic acid groups, preferably from 3 to 11, more preferably from 3.5 to 6. When this membrane is used for aqueous electrolysis of alkali metal halides, it is preferable to have a structure in which the carboxylic acid groups are unevenly distributed in the surface layer on one side of the membrane. The ratio of the number of carboxylic acid groups on the surface to the total number of ion exchange groups on the surface (hereinafter referred to as carboxylic acid group density) satisfies the following conditions (a) and (b). Favorable in terms of performance. (a) The density of carboxylic acid groups on one surface is 20% or more. (b) The carboxylic acid group density gradually decreases from the surface toward the inside, and the maximum gradient is 20%/micron or less. The above membrane has excellent electrolytic performance such as high current efficiency and low electrical resistance, and is much more stable than conventional membranes even under harsh electrolytic conditions than those normally used. In addition, it can maintain excellent electrolytic performance for a long period of time, is easy to manufacture, and is inexpensive. The reason why the above membrane exhibits excellent electrolytic performance is that the carboxylic acid group density is 20 to 100% on one surface, preferably 40% or more, and more preferably 60% or more, and The carboxylic acid group density gradually decreases over time, and its maximum gradient is per micron of film thickness.
It has a structural feature of 20 to 0.1%, preferably 15% or less, and more preferably 10% or less. Here, the thickness from the surface with higher carboxylic acid group density to the cross section substantially parallel to the surface where the carboxylic acid group density is 0% is 1/2 or less, preferably 1/4 of the total thickness. More preferably, it is 1/6 or less, the lower limit is 100 Å, and the opposite surface has a structure having substantially only sulfonic acid groups. When using the above membrane for electrolysis of an aqueous alkali metal halide solution, it is preferable to use the surface with a higher density of carboxylic acid groups facing the cathode. Due to the presence of acid groups, it contracts and the fixed ion concentration increases, which effectively prevents hydroxide ions from penetrating into the membrane, migrating within the tank, and diffusing, resulting in high current efficiency. The density of carboxylic acid groups on the surface depends on various factors such as the ratio of the number of repeating units in the membrane (C)/[(D)+(E)] and the current density used in electrolysis, temperature, and alkali concentration. Although it is possible to appropriately select the optimal value according to the manufacturing conditions by adjusting the manufacturing conditions, in general (C)/
The larger [(D)+(E)] is, the lower the carboxylic acid group density may be. On the other hand, in a preferred embodiment of the above-mentioned membrane, the carboxylic acid groups are mainly present in the thin layer on one surface side, and substantially only the sulfonic acid groups are present in the remaining majority, so that the alkali metal The electrical resistance when ions move from the anode chamber to the cathode chamber is extremely low compared to, for example, a membrane containing only carboxylic acid groups. Even if the above-mentioned membrane is used in contact with highly concentrated alkali under harsher conditions than normally used,
One of the reasons why it is much more stable than conventional membranes and can maintain excellent electrolytic performance for a long time is because of the repeating units (C), (D), and (E) mentioned above.
There is a structural feature of the polymer that it consists essentially of: Here, k=0 is preferable since it is possible to obtain a physically strong membrane having a high ion exchange capacity, but a part of k=1 may be mixed. It is preferable that l=3 because the monomer can be easily produced. Those with l of 6 or more are inferior to those with l of 3 to 5 because it is difficult to industrially produce the monomer and the ion exchange capacity cannot be sufficiently increased. Also L
=F is particularly preferred from the viewpoint of heat resistance and chemical resistance. The above polymer structural features are based on the structural features of the sulfur-containing fluorinated vinyl ether of the following formula used in manufacturing the above membrane. (k, l, Z, Y are the same as above) The above monomer is used as a raw material for conventional sulfonic acid type membranes or sulfonic acid type membranes with carboxylic acid groups formed on the surface layer by chemical treatment. Compared to sulfur-containing fluorinated vinyl ether, (n is the same as above) Even in the case of k = 0, the terminal structure or the number of ring members is different, so the cyclization reaction as described above does not occur substantially in the vinylation step, or It can be made very small, and one where k=0 can be easily obtained. Furthermore, during polymerization, the physical properties of the polymer do not deteriorate due to the cyclization reaction. Therefore, since k=0 can be mainly used for membrane production, the side chain

Since it is possible to create a structure that contains substantially no or only a small amount of [Formula], the content of fluorinated olefin can be increased even with the same ion exchange capacity, resulting in a physically strong membrane with a high ion exchange capacity. In addition, although the mechanism is not clear, it prevents the carboxylic acid layer from peeling or cracking and maintains stable performance even when used under harsher conditions than normal conditions. becomes possible. Another reason why the above film is stable even under harsh conditions is the ratio of the number of repeating units (C), (D), and (E) that substantially constitute the film: (C)/ [(D)+
(E)] is generally in the range of 1.5 to 14, preferably 3 to 11, more preferably 3.5 to 6. If this ratio is less than 1.5, the membrane tends to swell during use and cannot maintain stable performance for a long period of time. If it is larger than 14, the membrane tends to shrink and the electrical resistance becomes high, making it impractical. The ion exchange capacity of the above-mentioned membrane is expressed as an equation that depends on the structure of repeating units, the ratio of the number of repeating units, and the density of carboxylic acid groups, as shown in the following equation. Ion exchange capacity = 1000/[r(81+M _L ) +d(142+166k+50m) +(1-d)(178+166k+50l)] (meq/gr dry H-type resin) [Here, r is (A)/[(B)+( C)] M _L : Formula weight of atomic group L d: Carboxylic acid group density] Conventionally, the ion exchange capacity of ion exchange membranes has been described, for example, in JP-A-50-120492, JP-A-51-130495,
USP No. 4065366, JP-A-52-36589, JP-A-52
- As disclosed in No. 24176, etc., specific numerical values have been specified. However, according to the research conducted by the present inventors, it is not the ion exchange capacity itself that governs the swelling and contraction behavior of membranes when the type of ion exchange group is given, but the fluorination that constitutes the copolymer. Copolymerization ratio of olefin and fluorinated vinyl ether having an ion exchange group and

The presence or absence of [Formula] is most important, and in order to obtain a physically strong film that has sufficiently low electrical resistance and has little swelling or shrinkage even when used for electrolysis,

It is necessary to mainly use fluorinated vinyl ether that does not have [formula], and adjust the above copolymerization ratio within a certain range. Therefore, the ion exchange capacity is determined by the above formula,
It will be expressed. It is not clear why the above copolymerization ratio has a decisive influence on the swelling and shrinkage behavior of the membrane, but for the sake of explanation, as a fluorinated olefin,
When the most preferred tetrafluoroethylene is used, X-ray diffraction of the membrane shows that the tetrafluoroethylene is partially crystallized, and the degree of crystallization is largely dependent on the above copolymerization ratio. Therefore, this crystalline region acts as a pseudo-crosslinking point,
It is presumed that it controls the swelling and shrinking behavior of the membrane. In the above membrane, substantially

When producing a membrane that does not contain [Formula] or contains only a small amount of it and has the same ion exchange capacity, the copolymerization ratio of tetrafluoroethylene is set to sulfur-containing vinyl ether,

It can be made larger than when using the formula [Formula], and the membrane can have both high ion exchange capacity and physical toughness. Even if the above-mentioned membrane is used in contact with highly concentrated alkali under harsher conditions than normally used,
Another reason why it is much more stable than conventional membranes is that, as mentioned above, the carboxylic acid group density is gradually varied with a gradient within a certain range. A membrane containing a carboxylic acid group, which is disclosed in JP-A-52-36589, JP-A-53-132089, etc.
As mentioned above, the membrane that has a structure in which a membrane containing a sulfonic acid group is glued together has incomplete adhesion, and under the above harsh conditions, it will peel off from the bonded part and cause blisters in a short period of time. Easy to occur. On the other hand, according to the knowledge of the present inventors,
No. 24176, JP-A No. 104583, JP-A-53-
Even if it is possible to control the gradient of carboxylic acid group density to some extent with a film in which carboxylic acid groups are generated through chemical treatment, as disclosed in No. 116287, JP-A-54-6887, etc., Perhaps because of the problem with the polymer structure mentioned above, the carboxylic acid layer is more likely to peel or crack under severe conditions than the above-mentioned films. On the other hand, as shown in the examples, the above film shows no abnormalities such as peeling of the carboxylic acid layer or cracking even under high current densities of 110 A/dm ² or higher and at high temperatures of 95°C or higher. Moreover, it can maintain stable performance for a much longer period of time than conventional membranes. The above film is substantially composed of the above-mentioned repeating unit (C) and the following repeating unit (F) on the surface with a lower density of carboxylic acid groups, (F) (p=0 or 1, q=an integer of 3 to 5, M is the same as above) The ratio of the number of repeating units of (C) and (F) is (C)/(F)<(C)/(D ) or (C)/[(D)+(E)] It is possible to have a structure in which fluorinated cation exchange membranes are laminated, and this is preferable from the viewpoint of lowering the electrical resistance of the membrane. In this case, it is preferable that p = 0 and q = l because a physically strong film with low electrical resistance can be obtained and it is easy to manufacture. The thickness of the ion exchange membrane is preferably 1/2 to 19/20 of the thickness of the entire membrane after lamination. Furthermore, the film-like material of the copolymer of the present invention is composed of the above-mentioned repeating units (C) and (E), and the ratio of the number of repeating units of (C) and (E) is (C)/(E). )=1.5-14, preferably 3-11, and it is also possible to form a fluorinated cation exchange membrane having substantially only carboxylic acid groups. A method for producing a fluorinated cation exchange membrane having the above-mentioned carboxylic acid groups and sulfonic acid groups from a membrane-like product of the copolymer of the present invention will be described below. Fluorinated cation exchange membranes having only groups can also be produced using some of these reactions. The first step of producing a fluorinated cation exchange membrane having carboxylic acid groups and sulfonic acid groups from the copolymer of the present invention is obtained by the method described above. In a film-like product substantially composed of the following repeating units (C) and (B), the terminals of some or all of the repeating units (B) may be optionally substituted with a sulfonyl halide group, preferably a sulfonyl chloride group -CF ₂ SO ₂ Cl or sulfonyl fluoride - CF ₂ SO ₂ F with the general formula B ₂ (AB _d-2 ) _e (A=P or S, when A=P, B=halogen and d=3 or 5, A When =S, B=F and d=4, e
= 0 or 1). (C)

[Formula] (L is the same as above) (B) (k, l, Z, and Y are the same as above) The reaction used in this step differs depending on the types of Z and Y, so it will be explained for each type. (a) In the case of Z=-S-: Generally, halogen and a film-like substance can be reacted to convert it into a sulfonyl halide group, but from the viewpoint of reactivity and ease of handling, it is preferable to use chlorine; via −CF ₂ SCl or directly, −
Generates CF ₂ SO ₂ Cl. Although a wide range of reaction conditions can be selected, the reaction temperature is generally in the range of 0 to 300°C, and constant pressure or increased pressure is used. Further, chlorine may be used in a dry state, or dissolved in water, an organic solvent such as acetic acid trifluoroacetic acid, or an inorganic solvent such as S ₂ Cl ₂ . In the case of Z=-S-, Z=-SO _2- can be oxidized to sulfone or sulfoxide. This oxidation treatment is usually carried out in an aqueous solution for 30
Although it is carried out at a temperature of ~200°C, it is also possible to coexist an organic solvent such as acetic acid or trifluoroacetic acid to speed up the penetration of the oxidizing agent into the membrane. The sulfoxide produced by the above oxidation treatment can be converted to -CF ₂ SO ₂ Cl with chlorine. (b) For sulfone with Z=-SO ₂ -: Z=-S-
Although it is possible to convert to _a sulfonyl chloride group in the same manner as in the case _of
It is also possible to do this. This hydrolysis is carried out under conditions of 30 to 200°C using a solution in which caustic soda or caustic potash is dissolved in water or a mixed solvent of water and an organic solvent such as alcohol or dimethyl sulfoxide, and an oxidizing agent is added if necessary. It can be done with The sulfonic acid group obtained in this way can be obtained by using phosphorus pentachloride vapor or its solution in phosphorus oxychloride, halogenated organic compounds, etc.
It can be easily converted into a sulfonyl chloride group by reacting with the method and conditions described in JP-A-134888, JP-A-54-4289, and the like. Further, phosphorus trichloride may be used in combination with chlorine. It is also possible to convert it into a sulfonyl fluoride group by reacting with a fluorinating agent such as SF ₄ . In this case, the reaction temperature is in the range of 30 to 300°C, and the reaction is usually carried out under pressure of 1 to 100 atmospheres. When a vinyl monomer having a sulfonic acid group is used for polymerization, it is difficult to mold it as it is, so it is possible to convert it into a sulfonyl fluoride group by the method described above and then mold it into a membrane. In addition, when a vinyl monomer having a terminal group with poor thermal stability such as a sulfonyl chloride group is used for polymerization, it can be hydrolyzed once to form a sulfonic acid group, and then converted to a sulfonyl fluoride group using the method described above. After that, it is possible to perform molding. The second step of producing a fluorinated cation exchange membrane having a carboxylic acid group and a sulfonic acid group from the copolymer of the present invention involves the use of the terminal part of the repeating unit (G) obtained by the above method or All sulfonyl halide groups, preferably sulfonyl chloride groups or sulfonyl fluoride groups, are converted to carboxylic acid groups, but it is most preferable to use sulfonyl chloride groups in terms of reactivity and ease of production. (G) (k, l are the same as above, X is halogen, preferably F or Cl) Such a conversion generally converts a film-like material having a repeating unit (G) into 52
-24177, JP-A-53-132094, etc., by treating with the reducing agent, reaction method, and reaction conditions, and directly bonding to the S atom via the sulfinic acid group or directly.- This is accomplished by converting CF ₂ − into a carboxylic acid group. Examples of the reducing agent used in the present invention include hydroiodic acid, hydrobromic acid, hypophosphorous acid, hydrosulfuric acid, arsenous acid, phosphorous acid, sulfite, nitrous acid, formic acid,
Reducing inorganic acids such as oxalic acid, their metal salts,
Ammonium salts and hydrazines are preferred from the viewpoint of reactivity and ease of handling, but among these, reducing inorganic acids are most preferred. These reducing agents may be used alone or in combination if necessary. The structure in which the carboxylic acid groups are unevenly distributed only on one side of the membrane, which is an excellent feature of the above membrane, allows the first stage reaction, or preferably the second stage reaction, to be carried out from one side of the membrane. It can be easily achieved by doing this. In the case of a film-like material having a bonded structure, it is preferable to carry out these reactions from the side opposite to the side on which the bonding was performed. In addition, adjusting the density gradient of carboxylic acid groups to a desired shape can be achieved by adjusting factors such as temperature, time, pressure, solvent composition, etc. of the first or second stage reaction.
This can be achieved by appropriately adjusting the reaction rate and balancing the reaction rate with the diffusion rate of the reaction reagent into the membrane, but from the viewpoint of ease of control, it is preferable to adjust it in the second stage reaction. A preferred method of adjusting carboxylic acid group density is
A reaction is carried out using a solution in which at least one organic compound selected from the group of C ₁ to _{C 12} alcohols, carboxylic acids, sulfonic acids, nitriles, or ethers is dissolved in the aqueous solution of the above reducing agent. However, it is particularly preferable to use carboxylic acids as the organic compound. The amount of these organic compounds added is appropriately selected within the range of 100 PPM or more depending on the type of membrane, reducing agent, organic compound, etc. used, and reaction conditions. Examples of alcohols used in the above method include methanol, ethanol, propanol, ethylene glycol, diethylene glycol,
Examples include 4-butanediol, 1,8-octanediol, and glycerin. Examples of carboxylic acids and sulfonic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, n-citrusic acid, caproic acid, n-heptanoic acid, caprylic acid, lauric acid, fluoroacetic acid, chloroacetic acid, Bromoacetic acid, dichloroacetic acid, malonic acid, glutaric acid, trifluoroacetic acid, perfluoropropionic acid, perfluorobutyric acid, perfluorochitzoic acid, perfluorocaproic acid, perfluoro n-heptanoic acid, perfluorocaprylic acid,
Perfluoroglutaric acid, trifluoromethanesulfonic acid, perfluoroheptanesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, heptanesulfonic acid, etc., preferably acetic acid , propionic acid, caprylic acid, trifluoroacetic acid, perfluorocaprylic acid, and perfluorobutyric acid. In addition, examples of nitriles include acetonitrile,
Examples include propionitrile and adiponitrile, and examples of ethers include diethyl ether, tetrahydrofuran, dioxane, glyme, and diglyme. Some of these organic compounds may cause chemical changes depending on the reducing agent used.
It is better to avoid such combinations. The gradient of the density of carboxylic acid groups in the membrane can be determined by staining a cross section of the membrane with an appropriate dye and measuring the degree of staining, as shown in Examples, or by dyeing the membrane substantially parallel to the surface. The surface infrared absorption spectrum (hereinafter abbreviated as ATR) is measured while scraping the surface, and calculation can be made from the change in the intensity of the absorption peak caused by the carboxylic acid group. In addition, in the above membrane and other fluorinated cation exchange membranes, the side chain structure to which the ion exchange group is attached causes a deexchanged group reaction, and the ATR or IR absorption spectrum of the product can be measured. Identified by Furthermore, the copolymer composition is estimated by combining measurement of ion exchange capacity, elemental analysis, and the like. In addition to the above-mentioned method using a reducing agent,
-CF ₂ I
It is also possible to convert the repeating unit (B) into a carboxylic acid group, or to directly obtain a carboxylic acid group by irradiating a film-like material containing the repeating unit (B) with ultraviolet rays, electron beams, etc. Also, JP-A-53-104583, JP-A-53-116287
As described in No. 1, etc., a film-like material having a sulfonyl halide group, a sulfinic acid group obtained as an intermediate in the above method, or a film-like material having -CF ₂ I can be used as a compound having a carbonyl group. Alternatively, by reacting ionic or radically with a compound having an unsaturated bond under conditions that cause SO ₂ or iodine atoms to be eliminated, -CF ₂ - is more than that obtained by a method using a reducing agent. It is also possible to obtain carboxylic acid groups. However, these methods are difficult to control the carboxylic acid group density gradient, require multiple steps for the reaction, are expensive, require expensive reagents, are difficult to suppress side reactions, and have side chain It is inferior to the method using a reducing agent in that it does not become perfluorinated and the membrane is physically damaged during processing, and therefore the membrane produced by the method using a reducing agent are much more preferable than those produced by the method described above. The third step of producing a fluorinated cation exchange membrane having carboxylic acid groups and sulfonic acid groups from the copolymer of the present invention is to convert all remaining unterminated groups containing S atoms into sulfonic acid groups. This can be achieved by applying the oxidation reaction mentioned in the first stage reaction or the reaction such as hydrolysis described in JP-A-52-24176, JP-A-52-24177, etc. , can be easily done. As mentioned above, the above-mentioned fluorinated cation exchange membrane having carboxylic acid groups and sulfonic acid groups can be derived from a common starting material into carboxylic acid groups and sulfonic acid groups through a simple reaction. It has the excellent features of being easy to use and low cost. A cation exchange membrane having sulfonic acid groups and carboxylic acid groups produced from the copolymer of the present invention is extremely preferably used for electrolysis of aqueous alkali metal halide solutions. That is, conventional general electrolytic conditions;
It is of course used for electrolysis under the conditions of current density 10-70A/ ^dm2 , temperature 20-100℃, alkali metal halide concentration 1-5N, and alkali concentration 1-20N, as well as current density 70-200A/dm. ² , temperature 100~
It can be used with stable performance for a long time even under harsh conditions such as 150℃. In addition, the copolymer of the present invention can be made into granules during polymerization or molding, and then converted into a membrane into a fluorinated cation exchange membrane, according to a method for producing general ion exchange resins. Applying the above reaction to be used, it is composed of the following repeating units (A) and (D) and/or (E), (A) (-CA ₁ A ₂ - CA ₃ A ₄ ) - (A ₁ , A ₂ , A ₃ , A ₄ are the same as above) (D) (k, l, M are the same as above) (E) (k, m, and M are the same as above) The ratio of the number of repeating units of (A), (D), and (E) is (A)/[(D)+(E)]=0.5 to 16. It is also possible to use a refined granular ion exchange resin. These ion exchange resins can be processed into any shape such as granules, membranes, fibers, strings, etc., and have heat resistance,
Taking advantage of its superior chemical resistance compared to hydrocarbon-based substances, it is generally useful for separation processes that utilize adsorption, such as adsorption separation of metal ions and separation of organic polymer substances. It can be widely used as an acid catalyst for reactions. Furthermore, the copolymer according to the present invention can be used in the form of fibers or strings as an ion conductive reinforcing material for fluorinated cation exchange membranes. In addition, the copolymer can be used for various purposes by blending with other fluorine-based or hydrocarbon-based copolymers, or can be used as it is or mixed with an appropriate catalyst to form lubricants and interfaces. It can also be used as an activator. It is also useful as a raw material for fluorine-based elastomers. Examples are shown below, but the technical scope of the present invention is not limited thereto. Example 1 10g of
CF ₂ = CFO (CF ₂ ) ₃ SC ₂ H ₅ , 0.1 g of ammonium persulfate and water were added and emulsified with ammonium perfluorooctanoate as an emulsifier, and tetrafluoroethylene was added at a temperature of 50°C and a pressure of 15 kg/cm ² . The copolymer of the present invention was obtained by polymerizing while additionally adding sodium bisulfite used as a co-catalyst. Elemental analysis showed that the sulfur content of this copolymer was 4.23%. When we measured the infrared absorption spectrum of this copolymer as a thin film, we found that there were ^ethyl groups and
Ether group near 990cm ^-1 , C-S near 740cm ^-1
- Absorption that seems to be based on C is observed. When the melt index of the above copolymer was measured using a device with an orifice inner diameter of 2.1 mm and length of 8 mm, it was found that the melt index of the above copolymer was measured at a temperature of 250°C and a load of 2.16 kg.
It was 1.6g/10 minutes. After molding this copolymer into a film with a thickness of 250μ, it was treated with chlorine gas at 120°C for 20 hours, and then
It was treated with saturated chlorine water at 83°C for 20 hours. Measuring the ATR of this film-like substance revealed that it was observed before chlorination.
The absorption of ethyl group around 3000cm ^-1 has disappeared,
Instead, absorption due to sulfonyl chloride groups appeared around 1420 cm ^-1 . After hydrolyzing a part of the film with an alkali, the ion exchange capacity was measured to be 1.3 meq/g dry resin, and the ratio of repeating units of this film, i.e. was 4.4. One side of this film containing sulfonyl chloride groups was mixed with 57% hydroiodic acid and glacial acetic acid at a volume ratio of 15:
After treatment with a solution mixed at a ratio of 1:1 at 72°C for 18 hours, it was hydrolyzed with an alkali, and further treated with a 5% aqueous sodium chlorite solution at 90°C for 16 hours to obtain a cation exchange membrane. When the ATR of this exchange membrane was measured, absorption due to carboxylate type was observed at 1690 cm ^-1 on the side treated with hydroiodic acid, and on the untreated side.
Sulfonate type absorption was observed at 1060 cm ^-1 . In addition, when the cross section of the membrane is dyed with malachite green aqueous solution adjusted to pH = 2, 12
The thickness of μ was stained blue and the rest was stained yellow. The density gradient of carboxylic acid groups in the blue-dyed layer was measured by the following method. A membrane with the same exchange capacity but with all exchange groups converted to carboxylic acid groups was prepared in the same manner as above.
The ATR of this film is measured, and the absorbance of the carboxylic acid base at 1690 cm ⁻¹ is calculated by the baseline method, and the absorbance is set to 100. The surface layer of the above-mentioned film on the side having the carboxylic acid base is uniformly scraped off, the ATR of the surface is measured, the absorbance of the carboxylic acid group is calculated, and the ratio A% to the absorbance of the entire surface carboxylic acid film is calculated. On the other hand, the film thickness before and after the surface layer is scraped off is measured, and the difference Bμ is calculated. That is, the carboxylic acid density at a thickness of Bμ from the surface layer is A%. The density of carboxylic acid groups when scraped from the surface layer of one side of the membrane obtained in this example was 100% on the surface, 88% at a thickness of 5μ from the surface, 68% at a thickness of 10μ, and 15%.
It is 46% at a thickness of μ, 26% at a thickness of 20μ, and 0% at a thickness of 29μ.The relationship between thickness and density is shown in Figure 1, and the maximum density gradient is 4.4
%/μ. The electrolytic performance of the membrane was measured as follows. Using an electrolytic layer consisting of an anode chamber and a cathode chamber via the membrane, with a current-carrying area of 0.06 dm ² (2 cm x 3 cm),
The membrane is assembled with the side having carboxylic acid groups facing the cathode side. A dimensionally stable metal electrode is used as the anode, and an iron plate is used as the cathode. A saturated saline solution is poured into the anode chamber, and the pH is maintained at 3 while adding hydrochloric acid.
In the cathode chamber, water is added to keep the concentration constant while circulating a 10N caustic soda aqueous solution. The anode and cathode chambers were each kept at 95℃.
Current efficiency was calculated by dividing the amount of caustic soda produced in the cathode chamber per hour by the theoretical amount calculated from the amount of current applied by applying current at a current density of 110 amperes/dm ² . Changes in current efficiency and cell voltage over time were as shown in the table below.

[Table] When the film was observed after electricity was applied, no physical damage such as blisters, cracks, or peeling was observed. Comparative example 1 10g of
CF ₂ = CFOCF ₂ 〓 / 〓 CF ₂ CF 2 CF ₂ f ₂ F and 0.1 g of ammonium perforated sulfate and water, emulsify perilloro octaric acid as an emulsifier, and at a temperature of 50 ° C. /
cm ² , polymerization was carried out while additionally adding sodium bisulfite used as a cocatalyst. After partially hydrolyzing the obtained polymer with an alkali, the ion exchange capacity was measured and found to be 1.3 meq/g - dry resin. The proportion of repeating units in this polymer, i.e. was 3.3. After washing the above polymer with water, it was molded into a film with a thickness of 250 μm and hydrolyzed with an alkali, but the mechanical strength of the film was low and could not be evaluated. Comparative Example 2 Polymerization was carried out in the same manner as in Comparative Example 1 except that the pressure of tetrafluoroethylene was changed to 5 kg/cm ² . The resulting polymer had an exchange capacity of 0.89 meq/g dry resin. The proportion of repeating units in this polymer, i.e. was 6.8. After washing the above polymer with water, it was molded into a film with a thickness of 250 μm and hydrolyzed with an alkali. After thoroughly drying this film-like material, it was immersed in a solution of phosphorus pentachloride and phosphorus oxychloride mixed at a weight ratio of 1:3.
°C, process for 20 hours. When the ATR of this film was measured, a specific absorption due to sulfonyl chloride groups appeared at 1420 cm ^-1 . One side of the membrane was treated with 57% hydroiodic acid at 83°C for 20 hours, then hydrolyzed with alkali, and further treated with 5% aqueous sodium hypochlorite solution at 90°C for 16 hours. When the ATR of this film-like substance was measured, it was found that the surface treated with hydroiodic acid had 1690
A characteristic absorption of the carboxylate type was observed at cm ^-1 . Furthermore, when a cross section of the membrane was stained in the same manner as in Example 1, a thickness of 8.6 μm from the surface layer was stained blue, and the rest was stained yellow. This membrane was subjected to electrolytic evaluation in the same manner as in Example 1, with the side having carboxylic acid groups facing the cathode side. The current efficiency and voltage were as shown in the table below.

[Table] After electricity was applied, blisters were observed when the current-carrying surface of the membrane was observed, and when looking at the cross section, 5 μm from the surface of the carboxylic acid layer was observed.
However, it had peeled off. Comparative Example 3 In Comparative Example 1, the pressure of tetrafluoroethylene was changed to 5 Kg/cm ² and polymerization was carried out in the same manner. A part of the obtained polymer was hydrolyzed and the ion exchange capacity was measured, and it was found to be 0.83 meq/g dry resin. This polymer was molded into a film with a thickness of 50μ. This film is called an a-film. Meanwhile, in a 500 c.c. stainless steel autoclave
Add 16 g of CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ , 0.17 g of ammonium persulfate and water, and emulsify with ammonium perfluorooctanoate as an emulsifier.
Tetrafluoroethylene was polymerized at a temperature of 50° C. and a pressure of 7 kg/cm ² using sodium hydrogen sulfite as a promoter. When a part of the obtained polymer was hydrolyzed and the ion exchange capacity was measured, it was 1.10meq/g.
It was dry resin. This polymer was molded into a film with a thickness of 100μ. This film is called the b film. Film A and film B were stacked and press-molded to create a laminated film. After hydrolyzing this membrane with alkali,
Electrolytic performance was measured in the same manner as in Example 1 with the surface of the b membrane facing the cathode side. The results are shown in the table below.

[Table] After energization, blisters were generated all over the energized surface of the membrane, and when the cross section of the membrane was observed, peeling had occurred exactly at the boundary where membranes A and B were pasted together. Comparative Example 4 In Example 1, instead of CF ₂ = CFOCF ₂ CF ₂ SC ₂ H ₅

Copolymerization was carried out using [Formula] and CF ₂ =CFO(CF ₂ ) ₄ COOCH ₃ in accordance with Example 2 of JP-A No. 120492/1983 while blowing in tetrafluoroethylene. This polymer was molded into a film with a thickness of 250 μm, and after hydrolysis with an alkali, the electrolytic performance was measured in the same manner as in Example 1. The results were as shown in the table below.

[Table] Comparative Example 5 One side of the sulfonyl chloride film obtained in Comparative Example 2 was coated with CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ .
50 in perfluorodimethylcyclobutane solution containing 5 wt% and catalytic amount of azobisisobutyronitrile.
It was treated at ~60°C for 5 hours. After the treatment, the membrane was hydrolyzed with a 2.5N caustic soda/50% methanol aqueous solution. The ATR of the treated surface is 1690cm ^-1
Characteristic absorption of carboxylate type was observed in the specimen, and when cross-sectionally dyed with malachite green, a thickness of 4 μm from the surface layer of the treated surface was stained blue. When electrolysis was carried out in the same manner as in Example 1 with the side having the carboxylic acid group facing the cathode side, the results shown in the table below were obtained.

[Table] After energization, blisters were formed all over the energized surface of the membrane. Examples 2 to 7 In Example 1, the reducing agent and treatment conditions for treating one side of the membrane material having sulfonyl chloride groups were as shown in the table below. The electrolytic performance, surface density and maximum density gradient of carboxylic acid groups are shown in the table below.

[Table] After energizing, there are blisters, peeling, and
No cracks were observed. Example 4 In Example 1, CF ₂ = CFO (CF ₂ ) ₃ SC ₂ H ₅

[Formula] was added in a molar ratio of 4:1 and polymerization was carried out in the same manner. When the obtained polymer was subjected to the same treatment as in Example 1, the same results as in Example 1 were obtained. Example 5 Polymerization was carried out in the same manner as in Example 1 except that the pressure of tetrafluoroethylene was 17 Kg/cm ² . The ion exchange capacity of a portion of the obtained polymer was measured in the same manner as in Example 1, and it was found to be 0.75 meq/g dry resin. The proportion of repeating units in this polymer, i.e. was 10. The above polymer was molded into a film with a thickness of 50 μm. This film-like substance is called a c-film. The thickness of the sulfide type polymer obtained in Example 1 was 100 mm.
It was molded into a μ membrane. This film is called a d film. c.
After overlapping and press-molding the membrane and d-membrane to form a laminated membrane-like product, with the d-membrane side facing down, a multifilament with a weft of 400 denier and a warp of 200 denier multifilament x 2 with length and width per inch of 25
The membrane was placed on top of a polytetrafluoroethylene fabric with a thickness of approximately 0.15 mm, and the fabric was heated while being vacuumed to embed the fabric inside the d-membrane for reinforcement. This reinforcing material-containing laminated film was treated with chlorine in the same manner as in Example 1 to form a sulfonyl chloride type laminated film. The c-film side of the laminated film-like material is 57
After treatment at 83℃ for 20 hours with a solution containing 10% hydroiodic acid and glacial acetic acid in a volume ratio of 10:1, hydrolyzed with alkali, and further treated with 5% sodium hypochlorite at 90℃. Treated for 16 hours. When the cross section of the membrane is stained with a malachite green aqueous solution adjusted to pH 2, a thickness of 11μ from the surface layer on the C membrane side is stained blue.
The rest were stained yellow. The maximum density gradient of carboxylic acid groups in the blue-dyed layer was measured to be 4.9%/μ, and the density of carboxylic acid groups on the surface was 92%. The electrolytic performance was measured toward the cathode side on the C membrane side in the same manner as in Example 1, with the alkali concentration set to 6N, and the results were as shown in the table below. After energization, there are blisters, peeling, and
No cracks were observed.

[Table] Examples 6 to 9 The c-membrane side of the sulfonyl chloride-type laminated film obtained in Example 5 was treated with the reducing agent and treatment conditions shown in the table below, and the subsequent treatments were the same as in Example 5. I went to The electrolytic performance, carboxylic acid group density and maximum density gradient on the surface of the c-membrane side are shown in the table below.

[Table] After energizing, there are blisters, peeling, and
No cracks were observed. Example 10 1.
1,2-Trichloro-1,2,2-trifluoroethane, CF ₂ = CFO (CF ₂ ) ₃ SO ₂ C ₂ H ₅ and perfluoropropionyl peroxide as an initiator were added, and tetrafluoropropylene was added at a polymerization temperature of 45°C. Polymerization was carried out at an ethylene pressure of 15 kg/cm ² . The obtained polymer contained 4.10% by weight of sulfur according to elemental analysis. A portion of this polymer was hydrolyzed with an alkali to which potassium permanganate was added, and the ion exchange capacity was measured, and it was found to be 1.31 meq/g dry resin. Using the above sulfone type polymer, the thickness
After molding into a 250 μm membrane, it was hydrolyzed with an alkali containing potassium permanganate. Next, the film-like substance was mixed with phosphorus pentachloride and phosphorus oxychloride in a ratio of 1:3.
(Weight ratio) It was immersed in the solution and treated at 110°C for 20 hours. When the ATR of this film was measured, a characteristic absorption due to sulfonyl chloride groups appeared at 1420 cm ^-1 . One side of the sulfonyl chloride type film-like substance is 57
After treatment at 72℃ for 18 hours with a mixed solution of 15:1 (volume ratio) of % hydroiodic acid and propionic acid, hydrolyzed with alkali, and further treated with 5% sodium hypochlorite aqueous solution at 90℃ for 16 hours. Time processed. When a cross-section of the membrane was stained with an aqueous solution of malachite green, an 11-μ thick layer from the surface of one side was stained blue, and the rest was stained yellow. The surface density and maximum density gradient of carboxylic acid groups in the blue-stained layer are respectively
They were 100% and 5.1%/μ. Examples 11 to 14 One side of the sulfonyl chloride type membrane obtained in Example 10 was treated with the reducing agent and treatment conditions shown in the table below, and the same operations as in Example 10 were carried out. The surface carboxylic acid group density and the maximum density gradient of carboxylic acid groups of the obtained film-like material were as shown in the table below.

【table】

[Table] Example 15 A copolymer obtained by the same polymerization method as in Example 1 was formed into a strand by extrusion molding, and then a granular resin having a diameter of 1 mm was produced using a pelletizer. The functional groups in the resin were changed into sulfonyl chloride groups using the method described in Example 1, and then hydrolyzed to convert them into sulfonic acid groups.The ion exchange capacity was measured and found to be 1.3meq/ g It was a dry resin. Example 16 In a 300cc. stainless steel autoclave, 10g of
After adding and emulsifying CF ₂ =CFO(CF ₂ ) ₃ SCH ₃ , 1.0 g of sodium phosphate-hydrogen, 45 c.c. of purified water, and 0.45 g of ammonium perfluorooctanoate,
Adding 5 c.c. of a 0.62% aqueous solution of ammonium persulfate and maintaining the temperature at 40°C, tetrafluoroethylene was polymerized at a pressure of 13 Kg/cm ² , and the pressure of tetrafluoroethylene was controlled so that the polymerization rate was constant. . The resulting polymer contained 3.50% by weight of sulfur based on elemental analysis. This polymer at 280℃
When a thin film was made by press molding and the infrared absorption spectrum was measured, absorption due to methyl groups was observed at around 3000 cm ^-1 . When the above polymer was molded into a film with a thickness of 150 μm and treated with chlorine gas at 120° C. for 20 hours, the infrared absorption spectrum was measured, and the absorption of methyl groups around 3000 cm ⁻¹ disappeared. Further, the film-like material was treated at 100° C. for 48 hours with a saturated solution of chlorine in a 2:1 (volume ratio) mixed solution of perfluorobutyric acid and water. When the infrared absorption spectrum of the film-like material was measured, absorption due to sulfonyl chloride groups appeared around 1420 cm ^-1 . After hydrolyzing a part of the membrane with alkali, the ion exchange capacity was measured to be 1.04 meq/g dry resin, and the ratio of repeating units of this membrane, i.e. was 6.7. One side of the above sulfonyl chloride type film was treated with a mixed solution of 57% hydriodic acid and acetic acid at a ratio of 30:1 (volume ratio) at 72°C for 16 hours, and then hydrolyzed with an alkali and further treated for 5 hours. % sodium hypochlorite aqueous solution at 90°C for 16 hours. When a cross section of the membrane was stained with malachite green, a 12μ thick portion on one side was stained blue, and the rest was stained yellow. Electrolysis performance, carboxylic acid group density, and maximum density gradient were as follows when the membrane material was subjected to the same conditions as in Example 1 with the blue dyed surface facing the cathode side.

【table】 [Brief explanation of the drawing]

FIG. 1 shows the density gradient of carboxylic acid groups in an example of a cation exchange membrane obtained from the copolymer of the present invention.

Claims (1)

[Claims] 1. Substantially composed of the following repeating units (A) and (B), (A) (-CA ₁ A ₂ - CA ₃ A ₄ ) - (A ₁ , A ₂ =F _{( B ) _ _ _ _ _} (k=0 or 1, l=an integer from 3 to 5, Z=-
S— or —SO ₂ —, Y=C ₁ to C ₁₀ alkyl group, aryl group, Cl or C ₁ to _{C 10} perfluoroalkyl group,) The ratio of the number of repeating units of (A) and (B) is , (A)/(B)=1~
16, a novel fluorinated copolymer with a molecular weight of 8,000 to 1,000,000. 2 The repeating unit (A) is The copolymer according to claim 1, wherein L=F, Cl, CF ₃ , -OR _F or H, R _F are the same as above. 3 Claim 1 or 2 where k=0
Copolymer described in section. 4. The copolymer according to any one of claims 1 to 3, wherein l=3. 5. The copolymer according to any one of claims 1 to 4, wherein Y is a _C1 to _C10 alkyl group or an aryl group. 6 Claim 1 where (A)/(B)=1.5-14
The copolymer according to any one of Items 1 to 5. 7 Claim 1 having a membrane-like form
The copolymer according to any one of Items 1 to 6. 8 Olefin represented by the following general formula CA ₁ A ₂ = CA ₃ A ₄ (A ₁ , A ₂ , A ₃ , A ₄ are the same as below) and a sulfur-containing fluorinated vinyl ether represented by the following general formula, (k, l, Z, Y are the same as below) and the following repeating unit, (A) and
The molecular weight is 8,000 to 8,000, which is substantially composed of (B), and the ratio of the number of repeating units of (A) and (B) is (A)/(B) = 1 to 16.
Method for producing fluorinated copolymers of 1,000,000. (A) (-CA ₁ A ₂ - CA ₃ A ₄ ) - (A ₁ , A ₂ = F or H, A ₃ = F, Cl or H, A ₄ = F, Cl, CF ₃ , - OR _F , H or CH ₃ , R _F = C ₁ to C ₅ perfluoroalkyl group) (B) (k=0 or 1, l=an integer from 3 to 5, Z=-
S- or _-SO2- , Y= _C1 to _C10 alkyl group, aryl group, Cl or _C1 to _C10 perfluoroalkyl group,) 9 The free radical initiator is an oxidation-reduction catalyst, an organic peroxide 9. The method according to claim 8, which is selected from the group consisting of compounds, azobis compounds, and fluorine radical generators. 10. The method according to claim 8, wherein the solvent is water or a fluorinated organic solvent. 11 Polymerization temperature is 20-100℃, pressure is 1-50Kg/
9. The method according to claim 8, wherein cm ² .