JP3487652B2 - Method for producing functional group-containing perfluorocarbon copolymer, and functional group-containing perfluorocarbon copolymer composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a functional group-containing perfluorocarbon-based copolymer in an aqueous system, and a functional group-containing perfluorocarbon-based copolymer composition. TECHNICAL FIELD The present invention relates to a method for producing a functional group-containing perfluorocarbon-based copolymer having excellent and high melt-moldability that is suppressed or prohibited in an aqueous system, and a functional group-containing perfluorocarbon-based copolymer composition.

[0002]

BACKGROUND OF THE INVENTION Functional group-containing perfluorocarbon copolymers are widely used as base materials for cation exchange membranes for salt electrolysis, diaphragms for fuel cells and the like. As the functional group-containing perfluorocarbon-based copolymer, carboxylic acid-type functional group-containing perfluorocarbon-based copolymers and sulfonic acid-type functional group-containing perfluorocarbon-based copolymers are particularly useful.

For example, in a cation-exchange membrane electrolysis method of sodium chloride, a carboxylic acid-type cation obtained by converting a functional group of a carboxylic acid-type functional group-containing perfluorocarbon-based copolymer into a cation-exchange group on the cathode chamber side of the membrane. A layer having an ion exchange group is provided, and a sulfonic acid type cation exchange group obtained by converting the functional group of the sulfonic acid type functional group-containing perfluorocarbon-based copolymer into a cation exchange group is provided on the side of the anode chamber of the membrane. It is known that the provision of the layer having this is effective for producing high-purity caustic soda, and high current efficiency and low electrolysis voltage can be obtained. Regarding the production techniques of the carboxylic acid type functional group-containing perfluorocarbon type copolymer and the sulfonic acid type functional group-containing perfluorocarbon type copolymer, both the aqueous technique and the non-aqueous technique have been clarified.

Regarding the manufacturing technique in a non-aqueous system, for example, JP-A-57-92026 and US Pat. No. 352.
8954, U.S. Pat. No. 3,642,742, U.S. Pat. No. 4,138,426, U.S. Pat.
As described in Japanese Patent No. 267364, chlorofluorocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane are used as a solvent as a medium, and the ozone layer depletion has a negative impact on the global environment. Due to a problem, it cannot be implemented.

Regarding the technique for producing a perfluorocarbon type copolymer containing a carboxylic acid type functional group in an aqueous system, for example, Japanese Patent Publication No. 57-53371 and Japanese Patent Laid-Open No. 53-4.
No. 9090, JP-A-55-161810 and JP-A-56-45911, the obtained carboxylic acid functional group-containing perfluorocarbon copolymer is used as a group for a cation exchange membrane. When used as a material, the salt electrolysis method has not yet obtained sufficiently high current efficiency to be an economical method.

Regarding the technique for producing a sulfonic acid type functional group-containing perfluorocarbon type copolymer in an aqueous system, for example, JP-A-55-160008 and JP-B-48-
20788, JP-A-62-288617,
Japanese Patent Publication No. 62-501079, WO94 / 0350
3 and JP-A-6-184244, JP-A-55-160008 and JP-B-48-
According to the method described in 20788, it is extremely difficult to stably produce a sulfonic acid type functional group-containing perfluorocarbon-based copolymer having a low equivalent weight, and JP-A-62-288617 and Japanese Patent Publication No. 62-5010
According to the methods described in Japanese Patent Publication No. 79 and WO94 / 03503, a low equivalent weight of a sulfonic acid type functional group-containing perfluorocarbon-based copolymer can be produced, but the sulfonic acid obtained is obtained by the method described in the literature. The mold functional group-containing perfluorocarbon-based copolymer has extremely low melt moldability. A uniform and good film cannot be obtained, and it is not practical at all for producing a thin film which is useful and essential for industrial use. Further, in the method described in JP-A-6-184244, the function of the copolymer obtained cannot be sufficiently enhanced, and the copolymer having a high molecular weight sufficient to give practically sufficient strength is obtained. Difficult to get coalesced.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a copolymer of a functional group-containing perfluorocarbon monomer and a perfluoroolefin, which has a significantly improved function in an aqueous system. It is an object of the present invention to provide a production method, and a highly functional functional group-containing perfluorocarbon-based copolymer composition, in which melt moldability is significantly improved, and a high current efficiency and a salt electrolysis method are used. An object of the present invention is to provide a functional group-containing perfluorocarbon-based copolymer composition which can realize low power consumption and can be an excellent base material for a cation exchange membrane, and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have conducted various studies on a copolymerization reaction of a functional group-containing perfluorocarbon monomer represented by the following general formula (1) and a perfluoroolefin represented by the following general formula (2) in an aqueous system. As a result of repeated studies, it has been found that the cause of deteriorating the function of the copolymer is a homopolymer-like heteropolymer of perfluoroolefin (2) produced in the aqueous phase. The heterogeneous polymer remarkably lowers the melt moldability of the copolymer and also substantially lowers the ion exchange function after the functional group is converted into a cation exchange group. In order to suppress / prohibit the formation of the perfluorocarbon monomer (1), the functional group-containing perfluorocarbon monomer (1) is finely divided into particles with an average particle diameter of 2 μm or less and dispersed in water, and active radicals are chain-transferred in the aqueous phase. It was effective to add the resulting water-soluble organic chain transfer agent to polymerize, and it was found that the function of the functional group-containing perfluorocarbon copolymer can be significantly improved thereby, and the present invention was completed. It was

That is, according to the present invention, a copolymer of a functional group-containing perfluorocarbon monomer represented by the following general formula (1) and a perfluoroolefin represented by the following general formula (2) is produced in an aqueous system. In the method described above, the functional group-containing perfluorocarbon monomer (1) is atomized to an oil droplet average particle size of 2 μm or less and dispersed in water, and an aliphatic alcohol having 1 to 6 carbon atoms and 2 to 6 carbon atoms are used. The present invention relates to a method for producing a functional group-containing perfluorocarbon-based copolymer, which comprises polymerizing by adding a water-soluble organic chain transfer agent consisting of one or more selected from ethers, At that time, depending on the progress of the polymerization reaction (functional group-containing perfluorocarbon monomer (1)
The method for producing a functional group-containing perfluorocarbon-based copolymer, characterized in that the reaction pressure of the perfluoroolefin (2) is lowered to perform polymerization, according to the increase in the conversion rate of A functional group-containing perfluorocarbon-based copolymer composed of the following repeating units (a) and (b) and the following repeating unit (b) alone whose content w [wt%] is defined by the following formula (1): The polymer is composed of two polymers and has an equivalent weight (EW) of 6
50-1650 [g-copolymer composition / eq. -Functional group], the functional group-containing perfluorocarbon-based copolymer composition.

[0010]

Embedded image CF ₂ ═CF—O— (CF ₂ CF (CF ₃ ) —O) _n — (CF ₂ ) _m −Z ... (1) (wherein, m is an integer of 2 to 4) , Z is CO ₂ R (R is an alkyl group having 1 to 3 carbon atoms) or SO ₂ F. When Z = CO ₂ R, n is 1 or 2, and when Z = SO ₂ F, n is It is an integer of 0 to 2.)

[0011]

Embedded image CF ₂ ═CFX (2) (wherein X is F, Cl or CF ₃ ).

[Chemical 7] (A);-[CF₂CF (-O- (CF₂CF (CF₃) -O)_n-(CF₂) _m -Z)]- (In the formula, m is an integer of 2 to 4, and Z is CO.₂R (R is
It is an alkyl group having 1 to 3 carbon atoms. ) Or SO₂At F
It Z = CO₂When R, n is 1 or 2, Z = SO₂Of F
At this time, n is an integer of 0 to 2. )

[0012]

Embedded image (b);-[CF ₂ CF ₂ ]-

[Formula 2] w = (ΔH / 16) × 100 ≦ 0.4 [when EW = 650 to 1000] w = (ΔH / 16) × 100 ≦ (EW-930) / 175 [where EW = 1000 to 1650 When] (1) (In the formula, ΔH is an endothermic peak at 300 to 340 ° C, which is measured by a differential scanning calorimeter (DSC) and is based on melting of crystals of the homopolymer of the repeating unit (b). [J / g-functional group-containing perfluorocarbon-based copolymer composition], where EW is the equivalent weight (EW) of the functional group-containing perfluorocarbon-based copolymer composition [g-copolymer composition /Eq.-functional group].)

As the dispersant used in the present invention, the dispersants and emulsifiers conventionally used in the aqueous polymerization of perfluoromonomers can be used in a wide range without any particular limitation. For example, a surface active compound such as potassium salt, sodium salt, ammonium salt of perfluorosulfonic acid, or potassium salt, sodium salt, ammonium salt of perfluorocarboxylic acid can be used. As the dispersant, a perfluorocarboxylic acid type surfactant that is easily removed in the treatment after polymerization is preferable, and particularly, C ₆ F ₁₃ COONH ₄ and C ₇ F ₁₅ COONH are preferable.
Perfluorocarboxylic acid type surfactants such as ₄ or C ₈ F ₁₇ COONH ₄ are preferred.

The dispersant is 0.001 to 10 with respect to water.
It is used in a concentration of about wt%, preferably about 0.05 to 2 wt%. If the concentration of the dispersant is too low, the oil droplets of the functional group-containing perfluorocarbon monomer (1) that have been finely divided and dispersed will be insufficiently stabilized, and the oil droplets will not settle.
Coalescence may occur, and if the concentration of the dispersant is too high, the production of different polymers in the aqueous phase may increase. It is more preferable that the concentration of the dispersant is such that the dispersant does not form micelles after the functional group-containing perfluorocarbon monomer (1) is made into fine particles and dispersed. Further, the dispersant is preferably added before atomizing / dispersing the functional group-containing perfluorocarbon monomer (1), but it is also possible to add it after atomizing / dispersing.

As the buffer used in the present invention, conventionally known and publicly used buffers can be used in a wide range.
For example, a buffer such as sodium dihydrogen phosphate / disodium hydrogen phosphate is used. The buffer has a pH of 7
The following are preferable, those having a pH of 3 to 7 are more preferable, and those having a pH of 4 to 7 are particularly preferable. When the pH is higher than 7, the functional group-containing perfluorocarbon monomer (1) is hydrolyzed, and when the pH is too low, metal ions such as ferrous iron are eluted from the reaction tank to cause polymerization initiator. In some cases, it may be difficult to control the copolymerization reaction to accelerate the decomposition of the particles, or the stability of the dispersed particles may be reduced to cause the particles to settle or coalesce. The buffering agent is 0.01 to 5% by weight, preferably 0.0
It is used at a concentration of about 5 to 2% by weight. The buffering agent is preferably added before the granulation of the functional group-containing perfluorocarbon monomer (1). The reason is that if it is not added before the atomization, the pH of the liquid is extremely lowered during the atomization / dispersion process, and the oil droplets of the functional group-containing perfluorocarbon monomer (1) settle and coalesce. Because it may cause.

The polymerization initiator used in the present invention includes
Water-soluble polymerization of inorganic peroxides such as potassium persulfate and ammonium persulfate, redox initiators such as ammonium persulfate-ferrous sulfate, ammonium persulfate-ammonium hydrogen sulfite, and water-soluble organic peroxides such as disuccinoyl peroxide. Initiators, azo compounds such as azobisisobutyronitrile, diacyl peroxides such as benzoyl peroxide, dipentafluoropropionyl peroxide, peroxyesters such as t-butylperoxyisobutyrate, diisopropylbenzene Oil-soluble polymerization initiators such as hydroperoxides such as hydroperoxide can be used over a wide range.

The polymerization initiator preferably has a high activity at the reaction temperature, and the concentration of the polymerization initiator is 0.
0001% to 30% by weight, preferably about 0.001% to 10% by weight. If the concentration of the initiator is too large, the molecular weight tends to decrease, so that the strength is sufficiently high. In some cases, a copolymer having a molecular weight cannot be obtained. As the polymerization initiator used in the present invention, it is preferable to use a water-soluble polymerization initiator, because when a water-soluble polymerization initiator is used, the functional group-containing perfluorocarbon monomer (1) is made into fine particles. This is because even if it is added after dispersion, it is easy to distribute it evenly and the operability is excellent.

The functional group-containing perfluorocarbon monomer (1) used in the present invention is roughly classified into the following general formula (1) where Z is CO ₂ R (R is 1 to 1 carbon atoms).
3 is an alkyl group. ) A carboxylic acid type functional group-containing perfluorocarbon monomer having the general formula (1)
There are two types of sulfonic acid type functional group-containing perfluorocarbon monomers in which Z is SO ₂ F.

The carboxylic acid type functional group-containing perfluorocarbon monomer (Z = CO ₂ R) used in the present invention is preferably one in which R = CH ₃ in the above general formula (1).

Embedded image CF ₂ ═CF—O—CF ₂ CF (CF ₃ ) —O
_{- (CF 2) 2 -CO 2} CH 3, CF 2 = CF-O-C
_{F 2 CF (CF 3) -O-} (CF 2) 3 -CO 2 C
_{H 3, CF 2 = CF-} O- (CF 2 CF (CF 3) -
_{O) 2 - (CF 2)} 2 -CO 2 CH 3, CF 2 = CF-
_{O- (CF 2 CF (CF 3} ) -O) 2 - (CF 2) 3 -
A compound such as CO ₂ CH ₃ is used.

The sulfonic acid type functional group-containing perfluorocarbon monomer (Z = SO ₂ F) used in the present invention is, for example,

[Of 10] _{CF 2 = CF-O- (CF} 2) 2 -SO
_{2 F, CF 2 = CF-} O- (CF 2) 3 -SO 2 F, C
_{F 2 = CF-O-CF} 2 CF (CF 3) -O- (C
_{F 2) 2 -SO 2 F,} CF 2 = CF-O-CF 2 CF
_{(CF 3) -O- (CF 2} ) 3 -SO 2 F, CF 2 = C
_{F-O- (CF 2 CF (} CF 3) -O) 2 - (CF 2)
_2- SO ₂ F, CF ₂ = CF-O- (CF ₂ CF (CF
_{3) -O) 2 - (CF} 2) 3 -SO 2 F, compounds such as are used.

As the perfluoroolefin (2) in the present invention, tetrafluoroethylene, chlorotrifluoroethylene or hexafluoropropylene is used, and tetrafluoroethylene is preferred. In the atomization of the functional group-containing perfluorocarbon monomer (1) used in the present invention, known and officially used dispersers and emulsifiers can be used over a wide range without particular limitation. For example, an ultrasonic crusher, a homogenizer, an emulsifying machine such as a colloid mill mixer can be used. It is necessary that the average particle size of the oil droplets of the functional group-containing perfluorocarbon monomer (1) after fine-graining is 2 μm or less, and the functional group-containing perfluorocarbon monomer (1) has a large difference in specific gravity from water and is extremely small. Since it is easy to settle, it is preferable to reduce the average particle size to 1 μm or less in order to stabilize the oil droplets of the monomer and prevent the separation of the monomer due to settling and coalescence.

The water-soluble organic chain transfer agent used in the present invention includes aliphatic alcohols having 1 to 6 carbon atoms and 2 carbon atoms.
~ 6 ethers. They are,
It has a solubility in water of 0.1% by weight or more with respect to water, has a large effect of suppressing / inhibiting the formation of a heterogeneous polymer in water, and forms a molecular chain terminal having high thermal stability, which is preferable. Specific examples of the water-soluble organic chain transfer agent used in the present invention include alcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol and cyclohexanol, and ethyl ether,
Ethers such as propyl ether and tetrahydrofuran. The water-soluble organic chain transfer agent is preferably an aliphatic alcohol having 1 to 6 carbon atoms, more preferably an aliphatic alcohol having 1 to 4 carbon atoms, and particularly preferably methanol.

The amount of the water-soluble organic chain transfer agent added is in the range of 0.001% by weight to 50% by weight with respect to water.
It is preferably in the range of 0.01% by weight to 20% by weight.
If the amount added is too small, the effect of suppressing / inhibiting the formation of heterogeneous polymers in the water phase will be insufficient, and if the amount added is too large, the molecular weight will decrease significantly and sufficient strength will be imparted. Inability to obtain a high molecular weight copolymer, and functional group-containing perfluorocarbon monomer (1)
In some cases, the dispersion stability of the oil droplets decreases, and the oil droplets may easily settle and coalesce.

The method of adding the water-soluble organic chain transfer agent used in the present invention is not particularly limited, and known and publicly-used methods are widely adopted. The water-soluble organic chain transfer agent may be added before atomizing the functional group-containing perfluorocarbon monomer (1) or after atomizing. When it is added at the time of reaction after fine-graining, it may be added all at once in the initial stage, may be added several times or may be added continuously. Further, in the present invention, two or more of the above water-soluble organic chain transfer agents may be used in combination.

In the present invention, the above water-soluble organic chain transfer agent and a hydrophobic chain transfer agent such as alkanes such as pentane, hexane, heptane and octane or a gaseous chain transfer agent such as hydrogen, methane and ethane. And may be used together for the purpose of adjusting the molecular weight of the functional group-containing perfluorocarbon-based copolymer. The method of adding or introducing these chain transfer agents is not particularly limited, and well-known and publicly-used methods are widely adopted. Further, the water-soluble organic chain transfer agent itself used in the present invention is also used as a chain transfer agent as a molecular weight modifier of the copolymer for the purpose of adjusting the molecular weight of the functional group-containing perfluorocarbon copolymer. be able to.

In the present invention, when a copolymer having a deliberately reduced molecular weight is produced, or when a reaction is performed up to a high conversion rate of the functional group-containing perfluorocarbon monomer (1), for example, butanol such as butanol is used. A method of using a water-soluble organic chain transfer agent having a relatively large distribution to the functional group-containing perfluorocarbon monomer (1), and two or more kinds of water-soluble organic systems such as using two kinds of methanol and butanol The method using a chain transfer agent works effectively in reducing the amount of the water-soluble organic chain transfer agent added and improving the stability of the latex. In particular, a method of using two or more water-soluble organic chain transfer agents in which one or more selected from aliphatic alcohols having 2 to 6 carbon atoms is used in combination with methanol is preferable because of excellent operability. The addition amount of is a minimum amount necessary and sufficient to suppress / prohibit the formation of a heterogeneous polymer in the aqueous phase, and has 2 to 6 carbon atoms.
It is preferable to adjust the molecular weight of the copolymer with a water-soluble organic chain transfer agent selected from the aliphatic alcohols.

The decrease in the reaction pressure of the perfluoroolefin (2) in the present invention depends on the progress of the polymerization reaction.
It is carried out by controlling the reaction pressure according to the conversion rate of the functional group-containing perfluorocarbon monomer (1) to the functional group-containing perfluorocarbon copolymer. As a method for controlling the reaction pressure, a publicly-known or publicly-used general control method can be adopted without particular limitation. For example, the amount of perfluoroolefin (2) supplied to the reaction tank from outside the system (or the amount of discharge to the outside of the system) and the reaction pressure of the perfluoroolefin (2) in the reaction tank are interlocked to perform cascade control. Method etc. are adopted. The amount of the perfluoroolefin (2) supplied to the reaction vessel from outside the system (or the amount discharged to the outside of the system) and the control amount of the reaction pressure in the reaction vessel are the functional group-containing contents obtained by changing the respective control amounts. It is preferable to determine the change in equivalent weight (EW) of the perfluorocarbon-based copolymer on the basis of the results of actual tests, because the controlled amount is the target functional group-containing perfluorocarbon-based copolymer. Equivalent weight (EW), functional group-containing perfluorocarbon monomer (1) / water weight ratio, reaction temperature, filling state of the polymerization distribution liquid into the reaction tank (gas phase of perfluoroolefin (2) / polymerization distribution liquid phase) This is because it depends on many factors, such as the ratio of.

In the present invention, as described above, the functional group-containing perfluorocarbon monomer (1) is atomized to an oil droplet average particle size of 2 μm or less and dispersed in water, and the water-soluble organic chain transfer agent (carbon A water-soluble organic chain transfer agent which is one or more selected from aliphatic alcohols having 1 to 6 and ethers having 2 to 6 carbon atoms is added to carry out the copolymerization reaction. As the polymerization reaction conditions and the like, a wide range of known and publicly used general conditions used for the homopolymerization or copolymerization of fluorinated ethylene can be adopted. The polymerization temperature is generally 0 to 200 ° C., preferably 2
It is 0 to 90 ° C. Initial reaction pressure is 1 to 200 kg / c
m ² , preferably 1 to 50 kg / cm ² .

In the present invention, the functional group-containing perfluorocarbon monomer (1) / water weight ratio is 0.05 to 2
In the range of 0.1 to 0.5, and preferably in the range of 0.1 to 0.5. When the ratio of the functional group-containing perfluorocarbon monomer (1) is too large, the oil droplets of the monomer tend to settle and coalesce, and separation from water easily occurs.
If the ratio of the functional group-containing perfluorocarbon monomer (1) is too small, the reactor and the separation / recovery equipment for the copolymer become large, which is disadvantageous in terms of work operation.

In the present invention, the concentration (solid content concentration) of the functional group-containing perfluorocarbon copolymer produced in the latex is 40% by weight or less, preferably 30%.
It is carried out by controlling the content to be not more than weight%. If the concentration of the copolymer is too high, the copolymer may aggregate and precipitate, which is disadvantageous in terms of work and operation. In the present invention, in order to achieve a higher conversion ratio of the functional group-containing perfluorocarbon monomer (1), an appropriate water-soluble organic chain transfer agent is used and the functional group-containing perfluorocarbon monomer (1) is used. By reducing the fluorocarbon monomer (1) / water weight ratio, it is possible to obtain a functional group-containing perfluorocarbon-based copolymer having high functionality without causing aggregation / precipitation of the copolymer in water. It is also possible to achieve extremely high conversion rates of 50% to 90% or more, which have not been achieved by publicly known and publicly known methods.

In the present invention, in addition to the functional group-containing perfluorocarbon monomer (1) and the perfluoroolefin (2), other components, for example, perfluorovinyl ether represented by the following general formula (3), or the following: One kind or two or more kinds of the diolefin represented by the general formula (4) can be used in combination. The functional group-containing perfluorocarbon monomer (1) includes a carboxylic acid type functional group-containing perfluorocarbon monomer (functional group-containing perfluorocarbon monomer in which Z = CO ₂ R in the general formula (1)) and a sulfonic acid type. Functional group-containing perfluorocarbon monomer (in the general formula (1), Z = S
It is also possible to use two or more kinds of functional group-containing perfluorocarbon monomers which are O ₂ F together.

[0032]

Embedded image CF ₂ ═CFOR _f (3) (In the formula, R _f is a perfluoroalkyl group having 1 to 10 carbon atoms.)

Embedded image CF ₂ ═CF—O— (CF ₂ CF ₂ —O) _p —CF═CF ₂ (4) (In the formula, p is an integer of 2 to 10.)

Further, for example, 1,1,2-trichloro-
1,2,2-trifluoroethane, perfluoromethylcyclohexane, perfluorodimethylcyclobutane,
It is also possible to add an inert fluorocarbon solvent such as perfluorooctane or perfluorobenzene.
The above-mentioned addition of the perfluorovinyl ether, diolefin or fluorocarbon solvent may be carried out before the functional group-containing perfluorocarbon monomer (1) is made into fine particles or dispersed, or the functional group-containing perfluorocarbon monomer (1) may be added. You may carry out after fine-graining and dispersion. Fine-grained and dispersed functional group-containing perfluorocarbon monomer (1)
In order to make the concentration of the component uniform in the oil droplets of
It is preferable to add the functional group-containing perfluorocarbon monomer (1) before finely granulating and dispersing.

The functional group-containing perfluorocarbon-based copolymer produced by the present invention has an equivalent weight (EW) of 65.
0 to 1650 [g-copolymer / eq. -Functional group], and is appropriately selected depending on the intended use, and can be adjusted by appropriately selecting the polymerization conditions. Further, the copolymer usually has a molecular weight of 8,000 to 1,000,000.
When the melt index is measured with a device having an orifice inner diameter of 2.09 mm and a length of 8 mm, the melt index is usually 0.01 g / 10 at a temperature of 250 ° C. to 290 ° C. and a load of 2.16 kg. The range is from minutes to 500 g / 10 minutes.

According to the production method of the present invention, a functional group having excellent melt moldability and a high function over a very wide range of equivalent weight (EW) from low equivalent weight (EW) to high equivalent weight (EW). The containing perfluorocarbon-based copolymer can be stably produced. The functional group-containing perfluorocarbon-based copolymer composition of the present invention comprises a functional group-containing perfluorocarbon-based copolymer composed of the following repeating units (a) and (b) and a content w in the following formula (1). A homopolymer of the following repeating unit (b) defined by [% by weight] is composed of two kinds of polymers and has an equivalent weight (E
W) is 650 to 1650 [g-copolymer composition / eq.
-Functional group].

[0036]

[Chemical 13] (A);-[CF₂CF (-O- (CF₂CF (CF₃) -O)_n-(CF₂) _m -Z)]- (In the formula, m is an integer of 2 to 4, and Z is CO.₂R (R is
It is an alkyl group having 1 to 3 carbon atoms. ) Or SO₂At F
It Z = CO₂When R, n is 1 or 2, Z = SO₂Of F
At this time, n is an integer of 0 to 2. )

[0037]

Embedded image (b);-[CF ₂ CF ₂ ]-

[Formula 3] w = (ΔH / 16) × 100 ≦ 0.4 [when EW = 650 to 1000] w = (ΔH / 16) × 100 ≦ (EW-930) / 175 [where EW = 1000 to 1650] When] (1) (In the formula, ΔH is an endothermic peak at 300 to 340 ° C, which is measured by a differential scanning calorimeter (DSC) and is based on melting of crystals of the homopolymer of the repeating unit (b). [J / g-functional group-containing perfluorocarbon-based copolymer composition], where EW is the equivalent weight (EW) of the functional group-containing perfluorocarbon-based copolymer composition [g-copolymer composition /Eq.-functional group].)

The above-mentioned homopolymer of the repeating unit (b) is a polymer close to polytetrafluoroethylene containing almost no functional groups, but the homopolymer contains about 1 mol% or less of the above. The repeating unit (a) may be contained, and even in this case, the equivalent weight (EW) becomes a copolymer of 10,000 or more, and the functional group cannot be substantially measured. Is a heterogeneous polymer that cannot be converted into an ion-exchange group or a functional group can be converted into an ion-exchange group, but hardly exhibits the function as an ion-exchange group.

The functional group-containing perfluorocarbon copolymer composition of the present invention is prepared by coagulating and destroying the latex obtained by the copolymerization reaction to precipitate the copolymer, and then thoroughly washing it with water and / or an organic solvent. Remove the inorganic salts and dispersants, then
By drying, it is usually obtained as a powdery copolymer composition. These post-treatment methods for latex are not particularly limited, and publicly known and publicly used general techniques can be widely used. As a method for coagulating and breaking the latex, general techniques such as freeze breaking, shear breaking, salting out, and acid breaking can be used. The washing of the copolymer is carried out for the purpose of sufficiently removing impurities such as an inorganic salt and a dispersant in the copolymer, and water, a mixed solvent of water / organic solvent and an organic solvent are used as a washing solvent. A cleaning solvent such as water, a water / methanol mixed solvent, or methanol is used because of its simple operation, easy removal, and the like. The copolymer composition is dried for the purpose of removing the cleaning solvent and the remaining functional group-containing perfluorocarbon monomer (1), and for example, a vacuum drying method at a temperature of about 50 ° C to 150 ° C is used. . After the polymerization, the functional group-containing perfluorocarbon-based copolymer composition of the present invention is formed into a film or granules if necessary. For this molding, a general technique of melting and forming a thin film or pellet can be used.

The functional group-containing perfluorocarbon-based copolymer composition of the present invention has extremely excellent melt moldability,
The shrinkage in the cooling process at the time of melt molding, which is the cause of the deterioration of the melt moldability, hardly occurs, and the “swell” described later, which is an index of the shrinkage in the cooling process at the time of melt molding, is 40.
% Or less, to produce a thin film that is useful and indispensable for industrial use, by the conventional publicly known and publicly known melt extrusion film forming method, without causing edge breakage, thickness unevenness, surface roughness, etc. Is possible, 0.5 mil to 1 mi
Even an extremely thin film of 1 or less can be continuously and stably produced by using the functional group-containing perfluorocarbon-based copolymer composition alone.

The cation exchange membrane obtained by converting the functional group-containing perfluorocarbon copolymer composition of the present invention is widely used as a diaphragm in, for example, diffusion dialysis and alkali halide electrolysis. In particular, when a cation exchange membrane obtained by converting a carboxylic acid type functional group-containing perfluorocarbon-based copolymer composition is used as a diaphragm in a cation exchange membrane electrolysis method of sodium chloride, 96% to 9%
An extremely high current efficiency of 8% can be obtained. Such high current efficiency has not yet been obtained in the case of using a carboxylic acid type functional group-containing perfluorocarbon copolymer produced by a conventionally known method in an aqueous system.

As the cation exchange membrane, the carboxylic acid-type functional group-containing perfluorocarbon-based copolymer composition of the present invention may be used alone, or the sulfonic acid-type functional group-containing perfluorocarbon-based copolymer of the present invention may be used. It may have a structure in which it is present as a layer with the polymer composition and / or a structure in which a network of fibers of another fluorocarbon polymer is present in the film as a reinforcing material for mechanical strength. Using the cation exchange membrane as a diaphragm, a layer having a carboxylic acid type cation exchange group obtained by converting the carboxylic acid type functional group-containing perfluorocarbon-based copolymer composition of the present invention is directed to the cathode chamber side, and electrolysis is performed. The anode chamber and the cathode chamber of the tank are divided into sections, and while supplying a salt solution having a concentration of 1 to 5 N to the anode chamber, conventional general electrolysis conditions: a current density of 5
By electrolyzing at 70 A / dm ² and a temperature of 20 to 100 ° C., a caustic soda aqueous solution having a high concentration of 20 wt% to 35 wt% or more is stably produced from the cathode chamber for a long time with high current efficiency and low power consumption. it can.

The sulfonic acid type functional group-containing perfluorocarbon-based copolymer composition of the present invention is used as a base material of a diaphragm for a fuel cell in addition to the use as a base material of the diaphragm in the above-mentioned alkali halide electrolysis method. It is also used as a material, and in this case, the sulfonic acid type functional group contained in the acid type (S
It is used after being converted to O ₃ H type). In any of these applications, it is desired to provide a copolymer having a low equivalent weight for the purpose of achieving low resistance, but in the sulfonic acid functional group-containing perfluorocarbon copolymer composition of the present invention, Even in an extremely low equivalent weight (EW) range of 800 to 900, the "melt index", which is an index of the molecular weight, is 60 [g / 10 minutes] or less at 270 ° C., which is a practically sufficiently high molecular weight. According to the present invention, a low equivalent weight and a high molecular weight, which have not been heretofore available,
In addition, it is possible to provide a copolymer composition having excellent melt moldability and function.

In the present invention, the functional group-containing perfluorocarbon-based copolymer having a high function as described above (carboxylic acid type functional group-containing perfluorocarbon type copolymer and sulfonic acid type functional group-containing perfluorocarbon type copolymer) The essential requirement for the stable production of is that the functional group-containing perfluorocarbon monomer (1) is finely pulverized to 2 μm or less and dispersed in water, and that active radicals can be chain-transferred in the aqueous phase. Organic chain transfer agent (water-soluble organic chain transfer agent consisting of one or more selected from aliphatic alcohols having 1 to 6 carbon atoms and ethers having 2 to 6 carbon atoms) There are two. Furthermore,
By reducing the reaction pressure of the appropriate perfluoroolefin (2) according to the progress of the copolymerization reaction, which is the third requirement (according to the increase in the conversion of the functional group-containing perfluorocarbon monomer (1)), A functional group-containing perfluorocarbon-based copolymer having a high function can be obtained while maintaining the homogeneity of the composition of the copolymer up to a high conversion rate of the functional group-containing perfluorocarbon monomer (1).

In order to explain the features of the present invention in more detail, the mechanism and operation of the present invention will be described below, but the present invention is not limited to the above description. Regarding the method for producing a copolymer of a functional group-containing perfluorocarbon monomer (1) and a perfluoroolefin (2) in an aqueous system, the monomer (1) is a carboxylic acid-type functional group-containing perfluorocarbon monomer (the above-mentioned general formula (1 ₂ ) and Z = CO ₂ R)) and a sulfonic acid type functional group-containing perfluorocarbon monomer (Z = SO ₂ F in the general formula (1)). There is.

Regarding the method for producing a carboxylic acid type functional group-containing perfluorocarbon type copolymer in an aqueous system,
For example, JP-B-57-53371 and JP-A-53-53
49090, JP-A-55-161810,
Although described in JP-A-56-45911, in these documents, a carboxylic acid type functional group-containing perfluorocarbon monomer (1) having a structure used in the present invention and a perfluoroolefin (2) Although a description including a method for producing a polymer is made, as a specifically described copolymer, a carboxylic acid type functional group-containing perfluorocarbon monomer represented by the following general formula (5) and a perfluoroolefin are described. It is only a copolymer with (2), and there is no description regarding a copolymer of a carboxylic acid type having a structure used in the present invention: a functional group-containing perfluorocarbon monomer (1) and a perfluoroolefin (2).

[0047]

Embedded image _{CF 2 = CF-O- (CF} 2) m -CO 2 R ··· (5) wherein, m = 2 to 4 integer, R represents is an alkyl group having 1 to 3 carbon atoms . The carboxylic acid type functional group-containing perfluorocarbon monomer (5) corresponds to the functional group-containing perfluorocarbon monomer (1) used in the present invention where Z = CO ₂ R and n = 0. ]

The present inventors have conducted a copolymerization reaction of a perfluorocarbon monomer containing a carboxylic acid type functional group in which Z = CO ₂ R in the general formula (1) with a perfluoroolefin (2), and a carboxylic acid type As a result of various studies and studies on the copolymerization reaction of the functional group-containing perfluorocarbon monomer (5) and the perfluoroolefin (2), it was found that the two reactions are completely different. According to the conventionally known method described in the above literature, a copolymer having a high function of a carboxylic acid type: functional group-containing perfluorocarbon monomer (1) and perfluoroolefin (2) is stably produced. It is not possible. For example, in the general formula (5), m = 2,
The reaction between the following carboxylic acid functional group-containing perfluorocarbon monomer (6) in which R = CH ₃ and tetrafluoroethylene in which X = F in the general formula (2) is described in the above-mentioned document. While the copolymer can be easily and stably produced by the method, in the general formula (1), n = 1, m = 2, Z = CO ₂ R, R = C
In the reaction of the following carboxylic acid type functional group-containing perfluorocarbon monomer (7) which is H ₃ and tetrafluoroethylene where X = F in the general formula (2), the obtained copolymer is It had problems and was not practical at all.

[0049]

Embedded image CF ₂ ═CFO (CF ₂ ) ₂ CO ₂ CH ₃ (6)

Embedded image CF ₂ ═CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ CO ₂ CH ₃ (7)

That is, the copolymer of carboxylic acid type functional group-containing perfluorocarbon monomer (7) obtained by the conventional production method and tetrafluoroethylene is said to cause excessive shrinkage during cooling during melt molding. There's a problem. For this reason, for example, in melt extrusion film formation, the extruded film suffers from edge breakage, uneven thickness, and surface roughness, so that a uniform and excellent film cannot be obtained. Further, when the copolymer is used as a base material of a cation exchange membrane for salt electrolysis, although it is possible to appropriately select the equivalent weight (EW), a current efficiency of 90 to 92% can only be obtained, or Even if a current efficiency of 93 to 95% is obtained, a large increase in power consumption occurs and it is not practical.

Furthermore, in the production of the copolymer, the reaction is unstable and it is difficult to obtain a copolymer having a low equivalent weight (EW), and a copolymer having a high equivalent weight (EW) is easily produced. In addition, not only the gas pressure of tetrafluoroethylene at the time of polymerization but also the equivalent weight (EW) of the obtained copolymer changes greatly, and the copolymer obtained as the polymerization initiator concentration increases. Of the carboxylic acid type functional group-containing perfluorocarbon monomer (6) and tetrafluoroethylene do not exist in the copolymerization reaction.

As described above in the reaction between the carboxylic acid type functional group-containing perfluorocarbon monomer (6) and tetrafluoroethylene, and the reaction between the carboxylic acid type functional group-containing perfluorocarbon monomer (7) and tetrafluoroethylene. The large difference is based on the difference in solubility in water between the carboxylic acid-type functional group-containing perfluorocarbon monomer (6) and the carboxylic acid-type functional group-containing perfluorocarbon monomer (7).
This is due to the difference in the field of the copolymerization reaction between the two. Carboxylic acid type functional group-containing perfluorocarbon monomer (6)
Is sufficiently hydrophilic and can be sufficiently supplied to the aqueous phase under normal and general conditions. Therefore, in the aqueous phase, the carboxylic acid functional group-containing perfluorocarbon monomer (6)
It is possible to produce a copolymer of homogeneous composition with propylene and tetrafluoroethylene.

On the other hand, in a perfluorocarbon monomer containing a carboxylic acid type functional group having a greater hydrophobicity, such as the perfluorocarbon monomer containing a carboxylic acid type functional group (7), the carboxylic acid type functional group to the aqueous phase is added. Since the contained perfluorocarbon monomer (7) is scarcely supplied, a target copolymer is scarcely produced in the aqueous phase, and a heteropolymer close to a homopolymer of tetrafluoroethylene is produced. On the other hand, in the oil phase of the carboxylic acid type functional group-containing perfluorocarbon monomer (7), the target copolymer is produced. That is, in a reaction of a highly hydrophobic monomer such as a carboxylic acid type functional group-containing perfluorocarbon monomer (7) with tetrafluoroethylene in an aqueous system, water that produces only a heteropolymer like a tetrafluoroethylene homopolymer is produced. There are two reaction fields, one is the in-phase reaction and the other is the reaction field in which the carboxylic acid functional group-containing perfluorocarbon monomer oil that forms the target copolymer is in the reaction phase. Become. The above-mentioned difference in the reaction was recognized as a clear difference in the produced particles from the result of observing the latex obtained by the polymerization with an electron microscope.

Further, a latex of a copolymer of tetrafluoroethylene and a carboxylic acid type functional group-containing perfluorocarbon monomer having a large hydrophobicity such as carboxylic acid type functional group-containing perfluorocarbon monomer (7) is allowed to stand for about 1 day or more. By doing so, it is possible to separate the upper layer (aqueous phase) and the lower layer (oil phase: slurry layer), and from the aqueous phase, a heteropolymer like a homopolymer of tetrafluoroethylene was confirmed. By observing the aqueous phase with an electron microscope, the diameter is 0. Flat spherical particles reaching several μm to 10 μm or more were observed. Take out this polymer IR
It was confirmed that the polymer was a polymer close to a homopolymer of tetrafluoroethylene containing almost no carboxylic acid type functional group by the analysis. Further, the polymer was tested by a differential scanning calorimeter (DSC), and a large endothermic peak corresponding to melting of crystals of a homopolymer of tetrafluoroethylene was confirmed. On the other hand, by treating the lower layer (slurry layer) of the two-layer separation liquid of the above-mentioned latex and taking out the polymer, the target is set in the oil phase (in the oil droplets) of the carboxylic acid type functional group-containing perfluorocarbon monomer (7). It was confirmed that a copolymer was produced.

A copolymer produced only in the oil phase,
That is, the copolymer obtained by removing the heterogeneous polymer hardly causes shrinkage in the cooling process during melt molding, and a good film can be obtained in melt extrusion film formation. It was found that high current efficiency can be achieved when used as a base material of a cation exchange membrane for salt electrolysis. That is, in a copolymerization reaction of a carboxylic acid type: a highly hydrophobic monomer such as a functional group-containing perfluorocarbon monomer (1) and a perfluoroolefin (2) in an aqueous system, a water-soluble polymerization initiator may be used. Since the desired copolymerization reaction mainly occurs in the carboxylic acid type functional group-containing perfluorocarbon monomer phase (within the monomer oil droplets), on the other hand, it appears competitively as a homopolymer of perfluoroolefin (2) in the aqueous phase. The formation of the heterogeneous polymer and the incorporation of the polymer into the target copolymer by the batch treatment of the latex significantly reduce the melt moldability of the resulting copolymer, and the functional groups are cation exchanged. After being converted into a group, the substantial ion exchange function is reduced.

Such a perfluoroolefin (2)
In the case of a homopolymer-like heteropolymer-containing copolymer, devitrification (whitening) is often observed in the melt-molded copolymer, and further, in the molten state of the copolymer, Especially, devitrification (whitening) was confirmed. this is,
It is considered that the homopolymer-like heteropolymer of the perfluoroolefin (2) and the copolymer are not completely mixed and are phase-separated, and cause the function of the copolymer to be deteriorated. It is thought that it has become.

The method for producing a carboxylic acid-type functional group-containing perfluorocarbon-based copolymer in an aqueous system has been described in detail above. It is the same. However, even if the same functional group-containing perfluorocarbon monomer (1) contains a sulfonic acid type functional group (SO ₂ F group), it is more hydrophobic. Therefore, the present invention provides a carboxylic acid type functional group-containing perfluorocarbon monomer. In the case of n in the general formula (1)
Is applied only to the monomer of 1 or 2, whereas in the case of the sulfonic acid type functional group-containing perfluorocarbon monomer, it is also applied to the monomer of which n is 0 in the general formula (1) (n = 0 to 0). 2).

As described above, in order to enhance the function of the copolymer, it is important to use the highly hydrophobic functional group-containing perfluorocarbon monomer (1) as the main reaction site. For this purpose, It is an essential requirement that the functional group-containing perfluorocarbon monomer (1), which has a large specific gravity and tends to settle, coalesce, and separate, is finely dispersed and stabilized to have an average particle size of 2 μm or less by the method of the present invention. Become. The functional group-containing perfluorocarbon monomer (1)
In the method of only finely granulating and dispersing, for example, although it is possible to relatively reduce the production of the heterogeneous polymer in water by adopting a method of significantly reducing the concentration of the polymerization initiator, The method alone does not sufficiently enhance the function of the copolymer, and as described in, for example, JP-A-62-288617 and WO94 / 03503, a copolymer having a lower equivalent weight is used. Although it is possible to obtain a melt moldability that can be practical,
It was impossible. Therefore, in the manufacturing method of the present invention,
The addition of a water-soluble organic chain transfer agent, which is another of the essential requirements, is a very important requirement.
The details will be described below.

In producing the highly functional functional group-containing perfluorocarbon-based copolymer in the present invention, the functional group-containing perfluorocarbon monomer (1) is finely divided and dispersed to an average oil droplet size of 2 μm or less. In addition, it is essential to add a water-soluble organic chain transfer agent capable of chain transfer of active radicals in the aqueous phase. In the present invention, a homopolymer-like heteropolymer of perfluoroolefin (2) produced in the aqueous phase by adding a water-soluble organic chain transfer agent capable of chain transfer of active radicals in the aqueous phase. Surprisingly,
It can be drastically reduced to ˜1 / 100 or less, and this effect is explained as follows.

In the presence of a water-soluble organic chain transfer agent capable of chain transfer in the aqueous phase, the -CF ₂ * (or -CFX *) active radical at the terminal of the oligomer radical chain growing in the aqueous phase undergoes chain transfer. However, the increase in the molecular weight of the homopolymer-like heteropolymer of the perfluoroolefin (2) produced in the aqueous phase is suppressed. As a result, the diameter of 0. The production of flat spherical particles of several μm to 10 μm or more is significantly suppressed / prohibited, and the production rate of the heterogeneous polymer is significantly reduced. This was clarified by observing the latex obtained by the polymerization with an electron microscope. The heterogeneous polymer has an extremely high molecular weight when no water-soluble organic chain transfer agent is present in the aqueous phase, and is surprising when the high molecular weight heterogeneous polymer is mixed in the target copolymer. It was surprisingly found that the melt moldability can be remarkably reduced even when the amount of the mixture is only 0.1 to 1% by weight based on the copolymer. The influence on the melt moldability becomes significantly smaller as the molecular weight of the heterogeneous polymer decreases, and the molecular weight of the heterogeneous polymer (and formation of the heterogeneous polymer is changed by the water-soluble organic chain transfer agent used in the present invention). It has been found that the amount) can be significantly reduced, and thereby the melt moldability of the copolymer can be significantly improved, and the present invention has been completed.

The -CF ₂ * (or -CFX *) active radical at the chain end of the oligomer radical that is growing in the aqueous phase is chain-transferred to the water-soluble organic chain transfer agent added in the present invention, so that it is more active. It is considered that the consumption of perfluoroolefin (2) in water is suppressed by generating small and stable (less reactive) radicals. On the other hand, the copolymerization reaction of the target functional group-containing perfluorocarbon monomer (1) and the perfluoroolefin (2) in the functional group-containing perfluorocarbon monomer phase (in the monomer oil droplets) causes the activity in the aqueous phase. Radicals do not have a significant effect because they occur as they enter the functional group-containing perfluorocarbon monomer phase (within the monomer oil droplets) from the aqueous phase. For example, the copolymerization reaction rate does not drop significantly. As a result, the formation of a homopolymer-like heteropolymer of perfluoroolefin (2), which causes the function of the copolymer to be reduced, is almost complete with respect to the production of the intended copolymer. Since it can be made so small that it can be neglected, it is possible to obtain substantially only the target functionalized functional group-containing perfluorocarbon-based copolymer. That.

In addition, a sulfonic acid type functional group-containing perfluorocarbon-based copolymer (copolymerization of the functional group-containing perfluorocarbon monomer having Z = SO ₂ F in the general formula (1) and the perfluoroolefin (2)) Union)
In the production of, from its application, low equivalent weight and high molecular weight are required, but for such purpose, the production method of the present invention has the following features, and the conventional solution polymerization method or bulk method is used. It is extremely suitable because it has an advantage that a copolymer having a higher molecular weight than the copolymer obtained by the polymerization method can be obtained. That is, for the purpose of obtaining a high molecular weight copolymer having excellent functions such as melt moldability, the formation or inhibition of the homopolymer-like heteropolymer of perfluoroolefin (2) in the aqueous phase is suppressed or prohibited, Moreover, the concentration of the chain transfer agent in the sulfonic acid type functional group-containing perfluorocarbon monomer oil phase, which is the site for producing the desired copolymer, may be minimized. For example, a water-soluble organic system such as methanol having a very large water solubility. By using a chain transfer agent, the chain transfer agent is hardly distributed to the sulfonic acid type functional group-containing perfluorocarbon monomer phase, which is the site of the desired copolymerization reaction (that is, the molecular weight of the desired copolymer is On the other hand, the formation of heterogeneous polymers in the water phase can be greatly suppressed and prohibited, and the high molecular weight and low equivalent weight contribute to the functions such as melt moldability. It is characterized in that it produced excellent copolymer.

According to the production method of the present invention, the functional group-containing perfluorocarbon monomer (1) is in the oil phase (in the oil droplets).
Since only the copolymerization reaction of (1) becomes dominant, the copolymer having a low equivalent weight (EW) can be changed to a copolymer having a high equivalent weight (EW) without being largely influenced by the conditions such as the concentration of the polymerization initiator. Up to a wide range, it is possible to stably produce a functional group-containing perfluorocarbon-based copolymer.

As described above, in producing a functional group-containing perfluorocarbon-based copolymer having a high function in the present invention, the functional group-containing perfluorocarbon monomer (1) is pulverized to an average particle size of 2 μm or less. Water-soluble organic chain transfer agent capable of causing active radical chain transfer in the aqueous phase when dispersed in water (one selected from aliphatic alcohols having 1 to 6 carbon atoms and ethers having 2 to 6 carbon atoms) Alternatively, it is extremely important to add a water-soluble organic chain transfer agent consisting of two or more kinds. However, when the reaction is carried out under a constant pressure of the perfluoroolefin (2) according to a conventionally known and publicly-known method, the functional group-containing perfluorocarbon of the functional group-containing perfluorocarbon monomer (1) is only required for the above two requirements. Since the equivalent weight (EW) of the obtained copolymer increases significantly as the conversion rate to the system copolymer increases, it is difficult to improve the conversion rate, and it is difficult to improve the conversion rate in industrial applications. This is not an economical production method due to the large size of the recovery device and the great loss of the functional group-containing perfluorocarbon monomer (1).

The inventors of the present invention can produce the highly functional functional group-containing perfluorocarbon copolymer as described above up to a high conversion rate of the functional group-containing perfluorocarbon monomer (1). To provide a way
As a result of further intensive studies and investigations, the increase in the equivalent weight (EW) of the functional group-containing perfluorocarbon-based copolymer with the progress of the reaction showed that the perfluoroolefin ( It is not due to the increase in the production of heteropolymers like homopolymer of 2), but is produced within the oil phase (within the monomer oil droplets) of the functional group-containing perfluorocarbon monomer (1), which is the main site of the copolymerization reaction. It has been found that this is due to an increase in the equivalent weight (EW) of the copolymer itself.

The increase in the equivalent weight (EW) of the produced copolymer is due to the functional group-containing perfluorocarbon monomer (1).
It has been found that the conversion rate of 5 to 20% is as low as about 5 to 20%, and that when the conversion rate exceeds 30 to 50%, a further large increase in equivalent weight (EW) occurs. This means that in the copolymerization reaction of the above-mentioned carboxylic acid type functional group-containing perfluorocarbon monomer (6) and tetrafluoroethylene, a copolymer is produced under a constant pressure up to a conversion rate of 40 to 50%. This is in contrast to the fact that a copolymer having a homogeneous composition with almost no change in the equivalent weight (EW) of the functional group-containing perfluorocarbon monomer can be obtained. It reflects the difference in the place of the polymerization reaction.

With an increase in the conversion rate of the functional group-containing perfluorocarbon monomer (1), the equivalent weight (EW) of the functional group-containing perfluorocarbon-based copolymer as described above was increased (composition heterogeneity). In order to suppress / prohibit, it was found that the reduction of the reaction pressure of the perfluoroolefin (2) according to the progress of the copolymerization reaction, which is the important third requirement in the present invention, is effective, and the present invention It came to completion. Surprisingly, according to the method of the present invention, 50 to 90 which could not be achieved by the conventionally known and publicly available methods.
It is possible to stably produce a functional group-containing perfluorocarbon-based copolymer having a uniform composition and a high function up to a conversion rate as high as 10% or more.

Even when the reaction of the perfluoroolefin (2) is carried out under a constant pressure according to a conventionally known method, by optimizing various polymerization conditions,
For example, the conversion rate of the functional group-containing perfluorocarbon monomer (1) as described above can be obtained by optimizing the shape of the polymerization stirring blade to lower / optimize the stirring strength, and lowering the stirring strength as the reaction progresses. The equivalent weight of the functional group-containing perfluorocarbon-based copolymer (E
Although it was possible to sufficiently suppress an increase in W) (homogenization of composition), it was difficult to produce a copolymer having a function equivalent to that of the copolymer produced by the method of the present invention. It was

The cause of the increase in the equivalent weight (EW) of the copolymer with the increase in the conversion rate as described above is estimated as follows. The main place for the reaction to form the functional group-containing perfluorocarbon copolymer is in the oil phase (in the monomer oil droplets) of the functional group-containing perfluorocarbon monomer (1). As the copolymerization reaction proceeds, a copolymer is formed in the oil phase and the concentration of the copolymer increases, while the concentration of the functional group-containing perfluorocarbon monomer (1) in the oil phase increases. Decreases.

However, perfluoroolefin (2)
The change in concentration of the oil in the oil phase is small,
Therefore, as the conversion rate of the functional group-containing perfluorocarbon monomer (1) increases, the concentration ratio of the perfluoroolefin (2) and the functional group-containing perfluorocarbon monomer (1) in the oil phase increases, and Equivalent weight of the functional group-containing perfluorocarbon-based copolymer (E
W) will increase. This is because the portion of the structural unit of the functional group-containing perfluorocarbon monomer (1) incorporated in the molecular chain of the copolymer produced by the copolymerization reaction in the oil phase, including the side chain having the functional group, is also the original. This can be explained by the fact that the perfluoroolefin (2) can be dissolved in the same manner as the monomer.

As described above, in the method of the present invention, by decreasing the reaction pressure of the perfluoroolefin (2), the composition is uniform until the conversion of the functional group-containing perfluorocarbon monomer (1) is high. It is possible to produce a functional group-containing perfluorocarbon-based copolymer having a high function. A specific method for decreasing the reaction pressure of the perfluoroolefin (2) will be described below. The production method of the present invention is characterized in that the reaction pressure of the perfluoroolefin (2) is lowered while the reaction pressure of the perfluoroolefin (2) is lowered in accordance with the increase in the conversion rate of the functional group-containing perfluorocarbon monomer (1) in the oil phase. By doing so, it is possible to maintain a constant composition of the copolymer to be produced, to achieve an unprecedentedly high conversion rate, and to produce a copolymer having a high function, and if the same purpose can be achieved by the same principle, The specific method is not particularly limited. Therefore, the present invention is not limited to the following specific methods.

In order to obtain a copolymer whose composition does not change up to a high conversion of the functional group-containing perfluorocarbon monomer (1), the reaction pressure of the perfluoroolefin (2) in the reaction vessel is set to the functional group-containing perfluoroolefin (2). It is necessary to carry out the reaction while controlling the pressure according to the conversion rate of the fluorocarbon monomer (1) in the oil phase. This is because the concentration of the perfluoroolefin (2) in the monomer oil phase, that is, the solubility of the perfluoroolefin (2) in the monomer oil phase is controlled by the reaction pressure of the perfluoroolefin (2). It is thought that it depends.

The control method and conditions are, in practice, the equivalent weight (EW) of the target functional group-containing perfluorocarbon-based copolymer, the functional group-containing perfluorocarbon monomer (1) / water weight ratio, and the reaction temperature. , The filling state of the polymerization distribution liquid into the reaction tank (ratio of gas phase of perfluoroolefin (2) / polymerization distribution liquid phase), etc. This is because the solubility of the perfluoroolefin (2) in the aqueous phase is greatly different from the solubility of the functional group-containing perfluorocarbon monomer (1) of the perfluoroolefin (2) in the oil phase, and the solubility of the perfluoroolefin (2) )
It is based on the fact that the gas pressure in the gas phase changes due to the consumption of.

Here, when the perfluoroolefin (2) is not supplied from outside the system of the reaction vessel, the perfluoroolefin (2) is consumed in the copolymerization reaction and the perfluoroolefin (2) is consumed. The gas pressure of will decrease. At the same time, the conversion of the functional group-containing perfluorocarbon monomer (1) increases with the progress of the copolymerization reaction. At a certain pressure of the perfluoroolefin (2) and a certain conversion of the functional group-containing perfluorocarbon monomer (1) when the reaction proceeds a little from a certain point, the equivalent weight (EW) of the copolymer instantaneously generated at this point ) Is smaller than the equivalent weight (EW) of the copolymer produced before that, it is necessary to supply the perfluoroolefin (2) from outside the system of the reaction tank to suppress the decrease in gas pressure. On the contrary, when the equivalent weight (EW) of the copolymer instantaneously formed at this point is larger than the equivalent weight (EW) of the copolymer formed earlier than that, the amount of par It is necessary to discharge the fluoroolefin (2) to reduce the gas pressure.

Thus, depending on the progress of the copolymerization reaction,
By controlling the supply and / or the discharge of the perfluoroolefin (2) from the outside of the reaction vessel, the perfluoroolefin (2) corresponding to the conversion rate of the functional group-containing perfluorocarbon monomer (1). Achieves gas pressure of
Thereby, the composition change (EW change) of the obtained copolymer is obtained.
Can be made smaller. Under the conditions usually adopted, the gas pressure of the perfluoroolefin (2) greatly decreases with the progress of the copolymerization reaction. Therefore, the gas of the perfluoroolefin (2) is always supplied from the outside of the reaction vessel. It tends to suppress an excessive decrease in pressure. That is, the pressure of the perfluoroolefin (2) is controlled by controlling the supply amount of the perfluoroolefin (2) to the reaction tank (reaction system), and the change of the equivalent weight (EW) of the copolymer is controlled. The method is taken. An example of a specific method will be described below,
It is preferable to determine this method / condition based on the result of actual test in order to obtain a copolymer having a homogeneous composition.

First, the target equivalent weight (EW)
The initial reaction pressure of the gas of perfluoroolefin (2) required to obtain the copolymer of (1) is determined. This is determined from the relationship between the gas reaction pressure and the equivalent weight (EW) of the produced copolymer in the extremely low region where the conversion rate of the functional group-containing perfluorocarbon monomer (1) is preferably about 1 to 4%. .

Next, the required gas reaction pressure of the perfluoroolefin (2) is determined according to the increase in the conversion rate of the functional group-containing perfluorocarbon monomer (1). At this time, as described above, when the other reaction conditions and the like are different, the control method and the control amount are different. Therefore, it is necessary to determine and fix these in advance according to the purpose. First, the amount of perfluoroolefin (2) supplied from outside the reaction vessel system is arbitrarily determined. Next, the pressure range of the gas to be dropped during the reaction of all the perfluoroolefin (2) is arbitrarily determined. For each, the reaction was carried out by performing cascade control so that the supply amount of perfluoroolefin (2) and the pressure drop width were proportional to each other, and the actual equivalent weight (EW) of each copolymer obtained was used to determine the initial reaction. Determine the appropriate pressure (pressure drop width) required to achieve the same equivalent weight (EW) as From the weight and equivalent weight (EW) of the obtained copolymer, the conversion rate of the functional group-containing perfluorocarbon monomer (1) reacted during this period can be obtained.

Subsequently, using this point as a new standard, an appropriate pressure at a higher conversion rate was obtained in the same manner, and this was sequentially repeated to obtain the perfluoroolefin (2) from the outside of the reaction vessel system. 2) and the gas pressure of the perfluoroolefin (2), and the relationship between the conversion rate of the functional group-containing perfluorocarbon monomer (1) and the gas pressure of the perfluoroolefin (2). In order to reduce the change with time of the equivalent weight (EW) accompanying the progress of the copolymerization reaction, in the above method, the amount of perfluoroolefin (2) supplied from the outside of the reaction vessel was set small and tested. Then, the supply amount of perfluoroolefin (2) from the outside of the reaction tank and the perfluoroolefin (2)
It is preferable to determine the relationship between the gas pressures of 1 and 2 in more detail.

By the above-mentioned method, an appropriate condition for reducing the reaction pressure of the perfluoroolefin (2) is determined,
It is possible to reduce the change with time of the equivalent weight (EW) accompanying the progress of the copolymerization reaction, and it is possible to obtain a highly functional copolymer. The method for determining the reaction pressure drop conditions and control method will be described.

First, by the same method as described above, the initial reaction pressure of the perfluoroolefin (2) gas required to obtain the desired equivalent weight (EW) of the copolymer is determined. This initial pressure can be easily determined by determining the water-soluble organic chain transfer agent, since it depends only on the temperature and is hardly influenced by other factors. Next, the reaction completion pressure at the intended monomer conversion of the functional group-containing perfluorocarbon monomer (1) is determined. This end pressure is
When the monomer conversion rate is 100%, the reaction pressure is −
1 kg / cm ² (absolute pressure 0 kg / cm ² ), and it can be calculated by approximating that the monomer conversion rate and the reaction completion pressure have a proportional relationship (linear relationship). Then, the total supply amount of the perfluoroolefin (2) to be supplied from the outside of the system of the reaction tank is determined from the determined initial reaction pressure to the determined reaction end pressure. This total supply amount (w _T ) is calculated from the weight of the perfluoroolefin (2) (w _P ) converted into the copolymer by the copolymerization reaction (in the vapor phase part). Equivalent to the difference between the weight of the perfluoroolefin (2) at the initial reaction pressure (w _I ) and the weight at the end pressure of the reaction (w _F ) in the liquid phase portion). Weight (w _I −w _F
Becomes ) Is subtracted (w _T = w _P − (w _I −w
_F ). ) Can be approximated. The weight (w _P ) of the perfluoroolefin (2) converted to the copolymer by the copolymerization reaction is the equivalent weight (EW) of the target copolymer,
It is calculated from the molecular weight of the functional group-containing perfluorocarbon monomer (1), the conversion rate of the target functional group-containing perfluorocarbon monomer (1), and the charged weight of the functional group-containing perfluorocarbon monomer (1). On the other hand, the weight (w _I −w _F ) corresponding to the difference between the weight of the perfluoroolefin (2) in the polymerization tank system at the initial reaction pressure and the weight at the reaction end pressure is approximately It is obtained by actual measurement as follows. A functional group-containing perfluorocarbon monomer (1) dispersion liquid, which has been finely pulverized and crushed, and a water-soluble organic chain transfer agent are charged in a polymerization tank, and then the temperature is raised to the reaction temperature. Next, under constant temperature conditions, the perfluoroolefin (2) is supplied from outside the system, and the pressure is increased while sufficiently dissolving it. The weight of the perfluoroolefin (2) supplied from the outside of the system in the process of increasing the pressure from the previously determined reaction completion pressure to the reaction initial pressure is actually measured, and is set as the weight (w _I -w _F ) corresponding to the difference. By subtracting the weight corresponding to this pressure difference from the weight of the perfluoroolefin (2) converted into the copolymer obtained by the above-mentioned method, the perfluoroolefin (from the outside of the system into the reaction tank during the polymerization reaction ( It is the total supply of 2).

The initial reaction pressure obtained as described above,
The ratio of the pressure drop amount of perfluoroolefin (2) during the reaction to the supply amount of perfluoroolefin (2) from outside the system, depending on the reaction completion pressure and the total amount of perfluoroolefin (2) supplied from outside the system. The reaction is carried out while cascade-controlling the supply amount of perfluoroolefin (2) from outside the system so that the value is always constant, so that the composition is homogeneous and the coequivalent weight of the target equivalent weight (EW) is almost the same. You can get coalesced. When a large reaction tank is used, some latex is extracted during the above reaction and the change in equivalent weight (EW) with time is confirmed.
The reaction end pressure, the total amount of perfluoroolefin (2) supplied from the outside of the system, and the control method can be finely adjusted and optimized, and the target equivalent weight (EW) and homogeneous composition can be obtained. A polymer can be easily obtained.

In addition, in the functional group-containing perfluorocarbon monomer such as the functional group-containing perfluorocarbon monomer (1) of the present invention, the functional group-containing perfluorocarbon monomer is used in spite of using the water-soluble polymerization initiator. The target copolymerization reaction is taking place in the fluorocarbon monomer phase (within the monomer oil droplets), which is essentially the same as general suspension polymerization. The water-soluble polymerization initiator is changed to an oil-soluble polymerization initiator. Can be used. Even when an oil-soluble polymerization initiator is used, as in the case of using a water-soluble polymerization initiator, the perfluoro group that causes a decrease in the function of the copolymer due to the active radical species released from the oil phase in water. Since the homopolymer-like heteropolymer of the olefin (2) can be produced, the method of the present invention works effectively.

Thus, the functional group-containing perfluorocarbon-based copolymer composition of the present invention has substantially improved function as compared with the conventional one in which there is almost no mixing of a heteropolymer such as a homopolymer of perfluoroolefin (2). It is excellent in melt moldability and is useful and indispensable for industrial use without causing edge cuts, uneven thickness, or surface roughness in the extruded film during melt extrusion film formation. The membrane can be easily and stably manufactured. Further, the carboxylic acid type: functional group-containing perfluorocarbon-based copolymer composition of the present invention is 96 in the salt electrolysis method.
It can be used as an excellent base material for a cation exchange membrane, which can realize a high current efficiency of up to 98% and a low power consumption. Further, the sulfonic acid type: functional group-containing perfluorocarbon-based copolymer composition of the present invention can be used. It is possible to provide a material having a low equivalent weight and a high molecular weight, which has not been heretofore available, and can be an excellent base material such as a cation exchange membrane and a diaphragm for a fuel cell, which can realize low resistance. In the above description, in order to clarify the high function of the functional group-containing perfluorocarbon-based copolymer composition of the present invention, in particular, the use as a base material of a cation exchange membrane for salt electrolysis will be described in detail. However, the use of the copolymer composition of the present invention is not limited to such use.

[0084]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. The treatment of the latex after the copolymerization reaction in Examples and Comparative Examples was carried out as follows. While stirring the latex after the reaction at room temperature to 40 ° C,
After dropping it into an aqueous solution of 0.5 N hydrochloric acid or 0.5 N sulfuric acid or a methanol / water mixed solution to completely aggregate and precipitate,
Centrifugal filtration / separation was performed to obtain a liquid-containing copolymer. Next, washing and centrifugal filtration of the copolymer were repeated 3 times or more using a mixed solution of water / methanol = 50/50 (volume ratio) to sufficiently remove the inorganic salt and the dispersant. The resulting liquid-containing copolymer was vacuum dried at 90 ° C to 110 ° C to obtain a powdery or blocky copolymer.

In the examples and comparative examples, fine graining and
Average particle size of dispersed monomer oil droplets, equivalent weight (EW) of copolymer, melt index, swell, conversion rate of functional group-containing perfluorocarbon monomer, endotherm of 300 to 340 ° C. based on melting of crystals of heterogeneous polymer The peak endothermic amount ΔH, the weight fraction of the heterogeneous polymer in the aqueous phase (upper layer) obtained by separating the latex after the polymerization reaction into two layers, and the current efficiency in the use example were obtained as follows.

(1) The “average particle size” of the functional group-containing perfluorocarbon monomer oil droplets that have been finely divided and dispersed is the ultracentrifugal automatic particle size distribution analyzer CAPA- manufactured by Horiba, Ltd.
It was measured using 700. (2) “Equivalent weight (E) of the copolymer (copolymer composition)
W) "was measured as follows. When the copolymer is a carboxylic acid type functional group-containing perfluorocarbon type copolymer, the following measurements were carried out after converting all the carboxylic acid type functional groups contained in the copolymer to methyl ester type.

A film having a thickness of about 200 μm is formed by press molding, and the weight is precisely weighed. Let this weight be w ₁ [g]. Next, this film is treated with a mixed solution of 3N cesium hydroxide aqueous solution / 50% by volume methanol at 60 ° C. for 16 hours or more to obtain a complete cesium salt type. continue,
The film is taken out and washed with running water at room temperature for 30 minutes or more, and then washed with ion exchanged water at 90 ° C. for 12 hours or more (the liquid renewal is repeated 5 times or more) to completely remove the Donan salt in the film. After taking out the film and vacuum drying at 150 ° C. for 16 hours or more, it is further dried at room temperature for 3 days or more in a desiccator containing phosphorus pentoxide until the weight is completely reduced. Precisely weigh the weight of this film, w
₂ [g] W ₁ [g] measured as described above
And w ₂ [g], in the case of a carboxylic acid type functional group-containing perfluorocarbon-based copolymer (copolymer composition), based on the following formula (2), the sulfonic acid type functional group-containing perfluorocarbon-based copolymer In the case of a polymer (copolymer composition), the equivalent weight (EW) [g-copolymer (copolymer composition) / eq. -Functional group] is calculated.

[0088]

[Formula 4] EW [g-copolymer (copolymer composition) / eq. Of carboxylic acid type functional group-containing perfluorocarbon-based copolymer (copolymer composition) —CO ₂ CH ₃ group]: EW = (117.870) (w ₁ ) / (w ₂ −w ₁ ) ... (2)

[Formula 5] EW [g-copolymer (copolymer composition) / eq. Of sulfonic acid type functional group-containing perfluorocarbon-based copolymer (copolymer composition) —SO ₂ F group]: EW = (129.906) (w ₁ ) / (w ₂ −w ₁ ) ... (3)

(3) The "melt index" of the copolymer (copolymer composition) has a functional group of CO ₂ CH ₃ type or S.
In the O ₂ F type copolymer (copolymer composition),
Measured using a melt indexer S-01 type manufactured by Toyo Seiki Seisakusho, an orifice having an inner diameter of 2.09 mm and a length of 8 mm was used, and the load was 2.1 at a temperature of 250 ° C to 290 ° C.
It is represented by the weight of the copolymer flowing out in 10 minutes under the condition of 6 kg [g / 10 minutes]. The melt index serves as an index of the molecular weight of the functional group-containing perfluorocarbon-based copolymer, and the larger the molecular weight, the smaller the melt index. In the examples, those not particularly described show values at a temperature of 270 ° C.

(4) The "swell" of the copolymer (copolymer composition) is measured by the following method and indicates the degree of shrinkage during the cooling process in melt molding, and this value is small. The smaller the degree of shrinkage, the better the melt moldability, which is an index of the melt moldability of the copolymer.
The "swell" is obtained by measuring the diameter D [mm] of the yarn of the copolymer extruded from the orifice in the measurement of the "melt index" and comparing it with the inner diameter of the orifice. The swell [%] is given by the following equation (4).

[Formula 6] Swell (%) = ((D / 2.09) -1) × 100 (4)

(5) The "conversion rate" of the functional group-containing perfluorocarbon monomer is the conversion rate x [%], and the molecular weight of the functional group-containing perfluorocarbon monomer is w [g / mo].
1], the weight of the charged functional group-containing perfluorocarbon monomer is w ₃ [g], and the weight of the functional group-containing perfluorocarbon-based copolymer (copolymer composition) obtained by the reaction is w ₄ [g] , The above formula (2) or the above (3)
Equivalent weight calculated by the formula: EW [g-copolymer (copolymer composition) / eq. -Functional group], the following formula (5)
It is represented by.

[Formula 7] x (%) = (w ₄ × w / (EW)) / w ₃ × 100 (5)

(6) “Endothermic amount ΔH [J / g-of endothermic peak at 300 to 340 ° C. based on melting of crystals of different polymer
Functional group-containing perfluorocarbon-based copolymer composition] "
Is a copolymer (copolymer composition) having a functional group of CO ₂ CH ₃ type or SO ₂ F type, using a DSC device: DSC-100 manufactured by Seiko Denshi Kogyo Co., Ltd. as follows. It was measured. Using a sealed sample container made of Al with a capacity of 15 microliters, sample: about 20 mg on the sample side (weigh accurately), Al on the reference side: about 15 mg
Temperature rise from room temperature to 380 ° C: 5 ° C / min
300 to 340 in the obtained DSC curve
The endothermic amount of the endothermic peak (crystal melting peak) at ℃ was calculated. The calorific value is based on normal DSC measurement conditions (for example, Al
Using an open sample container manufactured by, sample weight: 2-30 mg,
Temperature rising rate: 5 to 20 ° C / min, temperature range: room temperature to 40
It is possible to measure even at 0 ℃, and it is possible to calculate almost the same amount of heat, but DSC due to thermal decomposition of the sample
Since disturbance of the base line (corrosion due to HF gas, etc.) may occur and affect the measurement data, the measurement was performed using the sealed sample container as described above.

(7) "Weight fraction of heterogeneous polymer in aqueous phase (upper layer) obtained by separating two layers of latex after polymerization reaction" was calculated as follows. After the polymerization reaction, the latex is allowed to stand overnight or more under a nitrogen atmosphere to completely separate the two layers,
The upper layer (aqueous phase) and the lower layer (monomer layer: slurry layer) are taken out separately. (At this time, if the boundary between the separated two layers is unclear, the boundary is taken out as the lower layer.) Thereafter, 0.5 to 1N hydrochloric acid or sulfuric acid is generated in each layer, and a precipitate is formed at all. It is added until it disappears, the precipitate is taken out, washed repeatedly with water and methanol, and then 110 ° C.
Vacuum dry overnight and then weigh each polymer. With the weight of the polymer taken out from the aqueous phase as w ₅ and the weight of the polymer taken out from the slurry layer as w ₆ , the weight fraction of the heterogeneous polymer is calculated by the following formula (6).

[Formula 8] Weight fraction of different polymer (%) = (w ₅ / (w ₅ + w ₆ )) × 100 (6)

(8) "Current efficiency" was measured by performing the following electrolysis. Effective film area 1 dm ² , anode RuO ₂ / T
A perfluorocarbon-based copolymer composition containing a carboxylic acid-type functional group was converted by using the diaphragm described in each of the use examples in a small electrolytic cell composed of i-expanded metal, cathode active nickel / Fe expanded metal, and gap of 2 mm. The layer having a carboxylic acid type cation exchange group thus formed is directed to the cathode chamber side, and the cathode chamber and the anode chamber of the electrolytic cell are divided,
200 g / l of saline solution was supplied to the anode chamber, and water was supplied to the cathode chamber so that the concentration of each caustic soda aqueous solution was kept, and electrolysis was continuously performed at a current density of 40 A / dm ² and 90 ° C. .. The "current efficiency (%)" was calculated by measuring the production amount of the caustic soda aqueous solution obtained from the cathode chamber side by electrolysis.

(I) Carboxylic acid type functional group-containing perfluorocarbon-based copolymer (copolymer composition) CF ₂ ═CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ C
Regarding the production of the copolymer (copolymer composition) of O ₂ CH ₃ and tetrafluoroethylene, the following Examples 1 to 14 are given.
And Comparative Examples 1 to 6. The results are summarized in Tables 1 to 3.

In Example 2 and Comparative Examples 4 to 6, n-hexane, which is a hydrophobic chain transfer agent, was used as the molecular weight modifier of the copolymer. Further, in Examples 3 to 14, the water-soluble organic chain transfer agent was used also as the molecular weight adjusting agent of the copolymer. Examples 8 and 14 were carried out at a reaction temperature of 40 ° C, while all other examples and comparative examples were carried out at a reaction temperature of 50 ° C. In addition, while Example 7 and Example 11 used a 100-liter autoclave, all other Examples and Comparative Examples carried out the reaction using a 1-liter autoclave.

(Example 1) Ion-exchanged water: 450 g,
C ₇ F ₁₅ COONH ₄ : 1.25 g, Na ₂ HPO ₄
12H ₂ O: 2.5 g, NaH ₂ PO ₄ · 2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 CO 2 CH 3: addition of 100 g. Next, using a Nippon Seiki Biomixer ABM-4 type, while cooling so that the liquid temperature becomes 20 ° C. or lower, 2
A treatment was carried out at 0000 rpm for 15 minutes to finely crush and disperse the monomer. The average particle size of the monomer oil droplets was 0.55 μm. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature is set to 50 ° C and the pressure of tetrafluoroethylene is set to 15.5k.
It was set to g / cm ² .

Next, a solution prepared by dissolving 1.0 g of methanol in 50 g of ion-exchanged water was added, followed by (NH
₄ ) A solution prepared by dissolving 1.6 g of ₂ S ₂ O _{8 in} 10 g of ion-exchanged water was added to carry out polymerization. While supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene becomes constant, the reaction is carried out for 1 hour, and after the reaction is completed,
23.2 g of copolymer was obtained. The copolymer obtained is 2
Melt index at 70 ° C is 0.5g / 10
Min, swell is 8%, equivalent weight (EW) is 109
It was 0 g / eq. The swell at 270 ° C. after melt-kneading the copolymer at 270 ° C. was 22%. The DSC of the copolymer was measured and the heat of fusion ΔH of the crystals of the heterogeneous polymer was calculated.
05 [J / g]). The conversion rate of the functional group-containing perfluorocarbon monomer in the reaction was 9%.

Further, another batch reaction was carried out under exactly the same conditions to obtain a latex. The heterogeneous polymer in the aqueous phase measured by separating it into two layers is a trace amount (weight: about 100 mg), and the weight fraction is less than 0.5%.
Almost no heterogeneous polymer was found in the aqueous phase. (Hereinafter, except for Example 7 and Example 11, in other Examples and Comparative Examples, another batch of latex that was reacted under exactly the same conditions was used to separate two layers in Table 2. The weight fraction of the different polymers in the aqueous medium phase was calculated.)

Comparative Example 1 Polymerization was carried out in exactly the same manner as in Example 1, except that the monomer oil droplets were not atomized / crushed and that methanol was not used. The obtained copolymer has a melt index at 270 ° C. of less than 0.01 g / 10 minutes and cannot be measured.
Further, the film of the copolymer was violently devitrified (whitened). If the monomer oil droplets are not atomized or crushed, the monomers will rapidly coalesce and settle when the dispersion liquid is stopped stirring, and the average particle diameter of the monomer oil droplets cannot be measured. The average particle size of the monomer is estimated to be at least about 5 μm or more in the agitated state (during the copolymerization reaction), and even in the following comparative examples, it is exactly the same when the granulation and crushing of the monomer are not carried out. It was
In addition, white polymer deposits were observed in the latex after the polymerization reaction, but no functional groups could be detected in this polymer. In addition, the amount in Table 2 was calculated.

(Comparative Example 2) Polymerization was carried out in the same manner as in Example 1 except that the monomer oil droplets were not atomized or crushed. The obtained copolymer is 270 ° C.
The melt index in Example 1 was less than 0.01 g / 10 minutes and could not be measured, and the film of the copolymer was severely devitrified (whitened).

(Comparative Example 3) Polymerization was carried out in the same manner as in Example 1 except that methanol was not used. The film of the obtained copolymer was devitrified (whitened), and after the melt-kneading of the copolymer at 290 ° C., 27
The swell at 0 ° C. was 185%, and a large increase in the swell due to melt-kneading was observed.

(Example 2) Ion-exchanged water: 450 g,
C ₈ F ₁₇ COONH ₄ : 1.13 g, Na ₂ HPO ₄
12H ₂ O: 2.3 g, NaH ₂ PO ₄ 2H ₂ O:
After dissolving 1.4 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 CO 2 CH 3: in 150 g n-hexane: a solution obtained by dissolving 0.1 g. Next, using a Nippon Seiki Biomixer ABM-4 type, the liquid temperature was 2
20,000 rp while cooling to 0 ° C or less
m for 15 minutes, and the monomer was atomized, crushed and dispersed. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. 50 monomer dispersion
℃ and tetrafluoroethylene pressure 17.0kg / c
It was set to m ² . Next, a solution prepared by dissolving 1.0 g of methanol in 5 g of ion-exchanged water was added, followed by (NH ₄ ) ₂
Polymerization was carried out by adding a solution prepared by dissolving 2.7 g of S ₂ O _{8 in} 10 g of ion-exchanged water. The reaction was performed for 1 hour while supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene was constant.

(Comparative Example 4) Polymerization was carried out in the same manner as in Example 2 except that methanol was not added. The film made of the obtained copolymer was devitrified (whitened), and the swell at 270 ° C. after melt-kneading the copolymer at 270 ° C. was 235%. A large increase was confirmed.

(Example 3) Deionized water: 500 g,
C ₇ F ₁₅ COONH ₄ : 1.25 g, Na ₂ HPO ₄
12H ₂ O: 2.5 g, NaH ₂ PO ₄ · 2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 CO 2 CH 3: 100g and methanol: were added 10g. Next, using a Nippon Seiki Biomixer ABM-4 type, while cooling so that the liquid temperature is 20 ° C. or lower, treatment is carried out at 20,000 rpm for 15 minutes to finely pulverize and disperse the monomer. Let This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was 50 ° C. and the pressure of tetrafluoroethylene was 16.0 kg / cm ² . Next (NH ₄ )
Polymerization was carried out by adding a solution prepared by dissolving 1.6 g of ₂ S ₂ O _{8 in} 10 g of ion-exchanged water. The reaction was performed for 1 hour while supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene was constant.

Example 4 Polymerization was carried out in the same manner as in Example 3, except that n-butyl alcohol: 0.68 g was used instead of methanol. (Example 5) Polymerization was carried out in the same manner as in Example 3, except that 0.38 g of n-hexyl alcohol was used instead of methanol. (Example 6) In Example 3, except that 0.5 g of n-propyl ether was used instead of methanol.
Polymerization was carried out in exactly the same manner. The melt index and swell are the values at 250 ° C, and the melt-kneading was performed at 250 ° C.

Example 7 Ion-exchanged water: 22.5 kg
In addition, C ₇ F ₁₅ COONH ₄ : 58 g, Na ₂ HPO ₄ ·
12H ₂ O: 116 g, NaH ₂ PO ₄ · 2H ₂ O: 6
After dissolving 9 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 CO 2 CH 3: 4.6kg and methanol: 580 g was added. Next, using a Nippon Seiki Biomixer BMO-100 type, while cooling so that the liquid temperature becomes 20 ° C. or lower, at 20 rpm at 20 rpm.
After the treatment for a minute, the monomer was atomized, crushed and dispersed. This operation was performed twice, and the liquid for two times was charged into a 100-liter stainless steel autoclave. next,
It was sufficiently purged with nitrogen and further with tetrafluoroethylene. The temperature was 50 ° C. and the pressure of tetrafluoroethylene was 16.0 kg / cm ² . Next, (NH ₄ ) ₂ S ₂
Polymerization was carried out by adding a solution prepared by dissolving 0.18 kg of O _{8 in} 1 kg of ion-exchanged water. The reaction was performed for 1 hour while supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene was constant.

(Comparative Example 5) Characteristic 2 of the method of the present invention
For the purpose of showing the two requirements, namely, the effect of atomizing / crushing the monomer (1) and adding the water-soluble organic chain transfer agent, these two were not carried out, A copolymer having the same equivalent weight (EW) as the obtained copolymer was obtained as follows.

In a 1 liter stainless steel autoclave, ion-exchanged water: 450 g, C ₈ F ₁₇ COONH ₄ :
1.13 g, Na ₂ HPO ₄ .12H ₂ O: 2.3 g,
NaH ₂ PO ₄ .2H ₂ O: a solution in which 1.4 g was dissolved, and CF ₂ = CFOCF ₂ CF (CF ₃ ) O (C
_{F 2) 2 CO 2 CH 3} : in 150 g n-hexane: 0.
A solution prepared by dissolving 2 g was charged. Next, after thoroughly purging with nitrogen and then with tetrafluoroethylene, 50
℃ and tetrafluoroethylene pressure 10.0kg / c
It was set to m ² . Subsequently, a solution of (NH ₄ ) ₂ S ₂ O ₈ (0.5 g) in ion-exchanged water (10 g) was added to carry out polymerization. The reaction was carried out for 1 hour while supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene was constant, and 56.0 g of a copolymer was obtained after completion of the reaction. The film of the copolymer was violently devitrified (whitened), and after melting and kneading the copolymer at 270 ° C., 27
The swell at 0 ° C. was 265%, and it was confirmed that the swell was greatly increased by melt-kneading.

Comparative Example 6 Characteristic of the method of the present invention,
For the purpose of showing the effect of the addition of the water-soluble organic chain transfer agent, this was not carried out and a copolymer having the same equivalent weight (EW) as the copolymer obtained in Example 2 was prepared as follows. Obtained.

In a 1 liter stainless steel autoclave, ion-exchanged water: 450 g, C ₈ F ₁₇ COONH ₄ :
1.13 g, Na ₂ HPO ₄ .12H ₂ O: 2.3 g,
NaH ₂ PO ₄ .2H ₂ O: a solution in which 1.4 g was dissolved, and CF ₂ = CFOCF ₂ CF (CF ₃ ) O (C
_{F 2) 2 CO 2 CH 3} : in 150 g n-hexane: 0.
A solution of 15 g dissolved was added. Next, using a bio-mixer ABM-4 manufactured by Nippon Seiki Co., Ltd., while cooling the liquid temperature to 20 ° C. or lower, a total of 15 at 20,000 rpm.
After the treatment for a minute, the monomer was atomized, crushed and dispersed.

This was charged in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. Monomer dispersion at 50 ° C
And tetrafluoroethylene pressure 14.0 kg / cm
^{2. Then} , a solution of (NH ₄ ) ₂ S ₂ O ₈ (1.3 g) in ion-exchanged water (10 g) was added to carry out polymerization, and the pressure of tetrafluoroethylene was kept constant. While feeding ethylene, the reaction was carried out for 1 hour, and 48.3 g of a copolymer was obtained after the reaction was completed. The film of the copolymer is slightly devitrified (whitened), and the swell at 270 ° C. after melt-kneading the copolymer at 270 ° C. is 135%, and the swell is greatly increased by the melt-kneading. Was confirmed.

(Example 8) Ion-exchanged water: 450 g,
_{C 7 F 15 COONH 4: 2.5g} , Na 2 HPO 4 · 1
2H ₂ O: 2.5 g, NaH ₂ PO ₄ .2H ₂ O: 1.
After dissolving 5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 CO 2 CH 3: 100g and methanol: were added 40 g. Next, using a Biomixer ABM-4 manufactured by Nippon Seiki Co., Ltd. at 20,000 rpm for 15
After the treatment for a minute, the monomer was atomized, crushed and dispersed. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was 40 ° C. and the pressure of tetrafluoroethylene was 16.0 kg / cm ² . Next, 10 g of (NH ₄ ) ₂ S ₂ O _{8 was} added to 50 g of deionized water.
Polymerization was carried out by adding the solution dissolved in. The reaction was performed for 1 hour while supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene was constant.

(Example 9) Ion-exchanged water: 500 g,
C ₇ F ₁₅ COONH ₄ : 1.25 g, Na ₂ HPO ₄
12H ₂ O: 2.5 g, NaH ₂ PO ₄ · 2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 CO 2 CH 3: 100g and methanol: 12.5 g was added. Next, using a Biomixer ABM-4 type manufactured by Nippon Seiki Co., Ltd., a treatment was carried out at 20,000 rpm for 15 minutes, and the monomer was finely divided, crushed and dispersed. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was 50 ° C. and the pressure of tetrafluoroethylene was 16.5 kg / cm ² . Next, (NH ₄ ) ₂ S ₂ O ₈ : 1.6 g of ion-exchanged water 10
Polymerization was carried out by adding a solution dissolved in g. The reaction was carried out for 5.5 hours while supplying tetrafluoroethylene from the outside of the reaction tank so that the pressure of tetrafluoroethylene was kept constant at 16.5 kg / cm ² during the reaction. The resulting copolymer film was slightly devitrified (whitened).

Example 10 Example 10 was repeated except that the reaction was carried out while supplying tetrafluoroethylene from outside the reaction vessel so that the pressure of tetrafluoroethylene was kept constant at 10.5 kg / cm ² during the reaction. 6 just like 9
A time reaction was performed.

(Embodiment 11) C ₇ F ₁₅ COONH ₄ : 5
8 g, Na ₂ HPO ₄ · 12H ₂ O: 116 g, NaH
_{2 PO 4 · 2H 2 O:} 69g of ion-exchanged water: 22.8
An aqueous solution dissolved in kg is put in the container (A), and CF ₂ =
CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ CO ₂ CH
₃ : 4.6 kg was put in the container (B), and the monomer was finely divided and dispersed by the following method using Microfluidizer M-110Y type manufactured by Microfluidex. From the container (A) and the container (B), while keeping the ratio of both liquids constant at a weight ratio of 5: 1, each liquid was continuously fed using a constant-volume liquid-feeding pump to join both liquids. After that, it was fed to a microfluidizer. Stroke pressure of microfluidizer is 1000kg / cm
^Then , the total amount was fed for 90 minutes to finely disperse and disperse the monomer. At this time, the treatment was continuously carried out while cooling so that the temperature of the dispersion liquid after atomization was 10 ° C. or lower at the outlet of the microfluidizer. The above operation was performed twice, and the liquid for two times was charged into a 100-liter stainless autoclave.

Next, nitrogen was thoroughly purged and then tetrafluoroethylene. The temperature was 50 ° C. and the pressure of tetrafluoroethylene was 16.8 kg / cm ² . Next, methanol: 1.15 kg was added, and (NH ₄ ) ₂ S was added.
Polymerization was carried out by adding a solution prepared by dissolving 0.18 kg of ₂ O _{8 in} 1 kg of ion-exchanged water. Tetrafluoroethylene pressure from initial 16.8 kg / cm ² to final 9.7 kg
The reaction was continued for 9.5 hours while continuously lowering so as to be / cm ² , and during this period, 5.5 kg of tetrafluoroethylene was continuously supplied from the outside of the system. During the reaction, the amount of tetrafluoroethylene supplied from outside the system was continuously controlled so that the ratio between the total amount of tetrafluoroethylene pressure drop and the total amount of tetrafluoroethylene supplied from outside the system was always constant.

(Example 12) Ion-exchanged water: 500 g
, C ₇ F ₁₅ COONH ₄ : 1.25 g, Na ₂ HPO
_{4 · 12H 2 O: 2.5g,} NaH 2 PO 4 · 2H
₂ O: After dissolving 1.5 g, CF ₂ = CFOCF ₂ C
_{F (CF 3) O (CF} 2) 2 CO 2 CH 3: 100g and methanol: 12.5 g was added. Next, using a bio mixer ABM-4 manufactured by Nippon Seiki Co., Ltd., 20,000 r
The resultant was treated with pm for 15 minutes to finely crush and disperse the monomer. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was 50 ° C. and the pressure of tetrafluoroethylene was 16.5 kg / cm ² . Next, a solution of (NH ₄ ) ₂ S ₂ O ₈ (1.6 g) dissolved in 10 g of ion-exchanged water was added to carry out polymerization.

Initially set tetrafluoroethylene pressure to 16.
The reaction was carried out for 8 hours by intermittently lowering the pressure from 5 kg / cm ² to the final 9.5 kg / cm ² as follows. First, the initial reaction pressure is 16.5 kg /
4 g of tetrafluoroethylene was supplied from the outside of the reaction vessel system so that the pressure was constant at cm ² . Next, with the supply of tetrafluoroethylene from outside the system of the reaction tank being cut off, the pressure was lowered by 0.5 kg / cm ² by the reaction to 16.0 kg / cm ² . Then, the pressure is 1
4 g of tetrafluoroelene was again fed from outside the system of the reaction tank so as to be constant at 6.0 kg / cm ² . Then, with the supply of tetrafluoroethylene from the outside of the reaction tank being shut off, the pressure was set to 0.5 kg / cm by the reaction.
^The pressure was lowered to ² and the pressure was set to 15.5 kg / cm ² . The above operation was repeated to reduce the pressure to 9.5 kg / cm ² .

(Example 13) Ion-exchanged water: 500 g
, C ₇ F ₁₅ COONH ₄ : 1.25 g, Na ₂ HPO
_{4 · 12H 2 O: 2.5g,} NaH 2 PO 4 · 2H
₂ O: After dissolving 1.5 g, CF ₂ = CFOCF ₂ C
F (CF ₃ ) O (CF ₂ ) ₂ CO ₂ CH ₃ : 100 g,
Methanol: 1.0 g and n-butyl alcohol: 0.
6 g was added. Next, Nippon Seiki Bio Mixer ABM
-4 type was used to perform a treatment at 20,000 rpm for 15 minutes to finely pulverize and crush the monomer to disperse the monomer. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was 50 ° C. and the pressure of tetrafluoroethylene was 16.5 kg / cm ² . Then (NH ₄ ) ₂
Polymerization was carried out by adding a solution prepared by dissolving 1.8 g of S ₂ O _{8 in} 10 g of ion-exchanged water. Tetrafluoroethylene pressure from 16.5 kg / cm ² initially to 6.5 kg / final
In the same manner as in Example 12, the pressure was intermittently reduced to reach cm ^2, and the reaction was carried out for 11 hours. When the pressure reached 10.0 kg / cm ² , a liquid in which 0.5 g of n-butyl alcohol was dispersed in 5 g of purified water was additionally added.

Example 14 Ion-exchanged water: 450 g
In addition, C ₇ F ₁₅ COONH ₄ : 2.5 g, Na ₂ HPO ₄
・ 12H ₂ O: 2.5 g, NaH ₂ PO ₄ .2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 CO 2 CH 3: 100g, methanol: were added 35 g. Next, using a Biomixer ABM-4 type manufactured by Nippon Seiki Co., Ltd., a treatment was carried out at 20,000 rpm for 15 minutes, and the monomer was finely divided, crushed and dispersed. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was 40 ° C. and the pressure of tetrafluoroethylene was 17.0 kg / cm ² . Then (N
_{H 4) 2 S 2 O 8} : 5.4g of polymerization was carried out by adding a solution of the ion-exchanged water 50 g. Tetrafluoroethylene pressure from 17.0 kg / cm ² to 1 final
At a pressure of 4.0 kg / cm ² , the pressure was intermittently lowered to 5.5 in the same manner as in Example 12.
A time reaction was performed.

(Use Example 1) Using each of the copolymers (copolymer composition) obtained in Examples 2 to 6, Example 8 and Examples 12 to 14, the following method was used. A diaphragm (cation exchange membrane) used for salt electrolysis was prepared.

After converting all the carboxylic acid type functional groups contained in the copolymer to methyl ester type, the mixture was melt-kneaded at 270 ° C. This copolymer was further press-molded at 270 ° C. to obtain a film having a thickness of about 200 μm. This film is saponified in an aqueous solution containing 30% by weight of KOH and 5% by weight of dimethylsulfoxide at 95 ° C. for 2 hours,
A film having a potassium salt type cation exchange group was prepared. Further, using a 0.1N caustic soda solution,
It equilibrated at 0 degreeC for 1 hour, and produced the film which has a cation exchange group of a sodium salt type. The current efficiency was measured using this film as a diaphragm. 300 in each case
Electrolysis is continued for more than a time, high current efficiency is obtained, and
The performance remained stable. The results are shown in Table 3.

With respect to each of the copolymers (copolymer compositions) obtained in Examples 9 and 10, a diaphragm was prepared in the same manner as described above, and the current efficiency was measured. The results are shown in Table 3. Although a sufficiently high current efficiency may be obtained with the diaphragm based on the copolymer of Example 9, the current efficiency is not stable, and the cell voltage is extremely higher than other diaphragms. It was confirmed that the cell voltage increased with time. The copolymer-based membrane of Example 10 had relatively stable performance, but low current efficiency. Current efficiency of the membrane based on the copolymer of Example 12,
And by comparing the current efficiency of the copolymer-based membrane of Example 10 having the same equivalent weight (EW) with the current efficiency of the copolymer-based membrane of Example 3. It was confirmed that the function of the copolymer can be maintained as it was at the initial stage by appropriately lowering the tetrafluoroethylene pressure during polymerization (by reducing the change with time in the composition (EW) accompanying the progress of the polymerization reaction).

For each of the copolymers (copolymer compositions) obtained in Comparative Examples 4 to 6, a diaphragm was prepared in the same manner as described above, and the current efficiency was measured. The results are shown in Table 3. Although a sufficiently high current efficiency may be obtained with the diaphragm based on the copolymer of Comparative Example 4, the current efficiency is not stable, and the cell voltage is extremely higher than other diaphragms. It was confirmed that the cell voltage increased with time. This increase in cell voltage was beyond the industrially acceptable range. The membranes made of the copolymers of Comparative Example 5 and Comparative Example 6 as the base material exhibited relatively stable performance, but only low current efficiency was obtained.

(Use Example 2) Using the copolymer (copolymer composition) obtained in Example 7, a diaphragm (cation exchange membrane) used for salt electrolysis was prepared by the following method. After converting all of the carboxylic acid type functional groups contained in the copolymer to methyl ester type, melt kneading extrusion was performed at 250 ° C. to form particles. Next, the pellets were subjected to extrusion film formation at 270 ° C. to obtain a film having a thickness of 1 mil. During the extrusion film formation, a uniform and good film was continuously obtained without any edge breakage, uneven thickness, or surface roughness. Next, the this film, having an equivalent weight of _{1025, CF 2 = CFOCF 2 CF} (CF 3) OCF
A film of 3.5 mil in thickness formed by extrusion forming a copolymer of ₂ CF ₂ SO ₂ F and tetrafluoroethylene is laminated at 240 ° C., and a carboxylic acid type copolymer of 4.5 mil in thickness is laminated. A film having a two-layer structure of a polymer / sulfonic acid type copolymer was prepared.

This two-layer structure film was used as film (A)
And Next, this two-layer structure film (A), a reinforcing material cloth (B) made into a 18 mesh by plain weaving using 200 denier PTFE yarn (B) and 1025 equivalent weight C
F ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO
A film (C) having a thickness of 1.5 mil formed by extrusion-molding a copolymer of ₂ F and tetrafluoroethylene, and comprising a carboxylic acid functional group-containing perfluorocarbon-based copolymer (A) With the layers facing outward,
(A) / (B) / (C) were laminated in this order and laminated at 235 ° C. to prepare a multilayer structure film (D). Next, this membrane (D) was saponified with an aqueous solution containing 30% by weight of KOH and 5% by weight of dimethylsulfoxide at 95 ° C. for 2 hours to obtain a cation exchange membrane having a potassium salt type cation exchange group. Further, it was equilibrated at 90 ° C. for 1 hour using a 0.1 N sodium hydroxide aqueous solution to obtain a cation exchange membrane having a sodium salt type cation exchange group. The current efficiency was measured using this cation exchange membrane as a diaphragm. Concentration 3
Current efficiency when obtaining 0.5 wt% caustic soda is 9
6.5% to 97.5%, cell voltage is 3.23 to 3.26V
And the performance remained stable over 500 hours.

(Use Example 3) Using the copolymer (copolymer composition) obtained in Example 11, a diaphragm (cation exchange membrane) used for salt electrolysis in the same manner as in Use Example 2. It was created. In the extrusion film-forming of the copolymer, as in the case of Use Example 2, there was no occurrence of edge cutting, unevenness in thickness, surface roughness, etc., and a uniform and good thickness of 1 mi was obtained.
1 film was obtained continuously. The current efficiency was measured using the prepared cation exchange membrane as a diaphragm. Concentration 3
Current efficiency when obtaining 0.5 wt% caustic soda is 9
6.5% to 97.5%, cell voltage is 3.23 to 3.26V
And the performance remained stable over 500 hours.

(II) Sulfonic Acid Type Functional Group-Containing Perfluorocarbon Copolymer (Copolymer Composition) CF ₂ ═CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ S
The production of a copolymer (copolymer composition) of O ₂ F and tetrafluoroethylene was described in Examples 15 to 27 and Comparative Examples 7 to 10 below. The results are shown in Table 4 and Table 5.
Are summarized in.

In Example 21 and Comparative Example 10, n-hexane, which is a hydrophobic chain transfer agent, was used as the molecular weight modifier for the copolymer. In addition, Examples 18 to 20
In Examples 22 to 27, the water-soluble organic chain transfer agent was used also as the molecular weight modifier for the copolymer. The reaction was carried out at a reaction temperature of 60 in all Examples and Comparative Examples below.
It was carried out at ° C. In addition, Example 21, Example 23, Example 24, and Comparative Example 10 used a 100-liter autoclave, but in all other Examples and Comparative Examples, the reaction was performed using a 1-liter autoclave.

(Example 15) Ion-exchanged water: 450 g
In addition, C ₇ F ₁₅ COONH ₄ : 1.0 g, Na ₂ HPO ₄
・ 12H ₂ O: 2.5 g, NaH ₂ PO ₄ .2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF
_{(CF 3) O (CF 2} ) 2 SO 2 F: addition of 150 g. Next, Nippon Seiki Co., Ltd. biomixer ABM-4
While using a mold to cool the liquid temperature to 20 ° C. or less, a treatment was performed at 20,000 rpm for a total of 30 minutes to finely pulverize and disperse the monomer. The average particle size of the monomer oil droplets was 0.60 μm. This was placed in a 1-liter stainless steel autoclave, thoroughly purged with nitrogen, and further purged with tetrafluoroethylene. The temperature is 60 ° C and the pressure of tetrafluoroethylene is 1
It was set to 6.0 kg / cm ² . Next, methanol: 1.0 g
Was added to 5 g of ion-exchanged water, and then (NH ₄ ) ₂ S ₂ O ₈ : 0.5 g of ion-exchanged water was added.
Polymerization was carried out by adding a solution dissolved in 0 g. The reaction was performed for 1 hour while supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene was constant. After the reaction was completed, 39.6 g of a copolymer was obtained.

The copolymer had a melt index at 270 ° C. of 1.5 g / 10 minutes and a swell of 8%.
The EW was 1025. The swell at 270 ° C. after melt-kneading the copolymer at 270 ° C. was 23%. The DSC of the copolymer was measured and the heat of fusion ΔH of the crystals of the heterogeneous polymer was calculated. However, the peak was so small that it could not be separated from the noise of the DSC curve and was below the detection limit (ΔH <
0.05 [J / g]). The conversion of the functional group-containing perfluorocarbon monomer in the reaction was 12%.

Further, another batch of reaction was carried out under exactly the same conditions to obtain a latex. The amount of the heterogeneous polymer in the aqueous phase measured by separating it into two layers is a trace amount (weight: about 50 mg), the weight fraction is less than 0.5%, and the heterogeneous polymer is not present in the aqueous phase. It was hardly recognized. (Less than,
Except for Example 21, Example 23, Example 24 and Comparative Example 10, in other Examples and Comparative Examples, another batch of latex which was reacted under exactly the same conditions was used. The weight fraction of the different polymer in the aqueous phase separated into two layers was calculated. )

Example 16 The reaction was carried out in the same manner as in Example 15 except that the pressure of tetrafluoroethylene was changed to 12.0 kg / cm ² . (Example 17) A reaction was carried out in the same manner as in Example 15, except that the pressure of tetrafluoroethylene was changed to 9.0 kg / cm ² . (Example 18) In Example 15, methanol: 1.
The reaction was carried out in exactly the same manner except that a solution obtained by dissolving 0 g in 5 g of ion-exchanged water was a solution obtained by dissolving 9.5 g of methanol in 10 g of ion-exchanged water.

Comparative Example 7 The reaction was carried out in the same manner as in Example 15 except that methanol was not added. The film of the obtained polymer was slightly devitrified (whitened), and the swell at 270 ° C. after melt-kneading the copolymer at 270 ° C. was 245%. An increase was observed. (Comparative Example 8) The reaction was carried out in exactly the same manner as in Example 17, except that methanol was not added. 270 ° C. after melt-kneading the obtained copolymer at 270 ° C.
Swell was 143%, and a large increase in swell due to melt-kneading was observed. (Comparative Example 9) In Example 15, finely granulating the monomer
The reaction was performed in exactly the same manner except that the crushing was not performed. The film of the obtained copolymer was severely devitrified (whitened), and the melt index of the copolymer at 270 ° C. was less than 0.01 g / 10 minutes and could not be measured.

Example 19 In Example 15, a solution prepared by dissolving 1.0 g of methanol in 5 g of ion-exchanged water was added to 0.4 g of n-butyl alcohol in 1 ion-exchanged water.
The reaction was performed in exactly the same manner except that the solution was dissolved in 0 g. (Example 20) In Example 15, methanol: 1.
The reaction was performed in exactly the same manner except that a solution prepared by dissolving 0 g in 5 g of ion-exchanged water was used as a dispersion liquid in which 0.6 g of n-propyl ether was dispersed in 10 g of ion-exchanged water. The melt index and swell are the values at 250 ° C, and the melt-kneading was performed at 250 ° C.

(Example 21) Ion-exchanged water: 21 kg
In addition, C ₈ F ₁₇ COONH ₄ : 42 g, Na ₂ HPO ₄ ·
12H ₂ O: 106 g, NaH ₂ PO ₄ · 2H ₂ O: 6
After dissolving 3 g, CF ₂ = CFOCF ₂ CF (CF
₃ ) O (CF ₂ ) ₂ SO ₂ F: 7.0 kg solution of n-hexane: 5.0 g, and methanol: 50
g was added. Next, Nippon Seiki Bio Mixer BMO-
Using a 100 type, while cooling so that the liquid temperature was 20 ° C. or lower, treatment was carried out at 10,000 rpm for 60 minutes to finely pulverize and crush the monomer to disperse it. This operation was performed twice, and the liquid for two times was charged into a 100-liter stainless steel autoclave. Next, it was thoroughly purged with nitrogen and then with tetrafluoroethylene. The temperature is 60 ° C and the pressure of tetrafluoroethylene is 16.0 kg.
/ Cm ² . Next, a solution in which (NH ₄ ) ₂ S ₂ O ₈ : 52 g was dissolved in deionized water: 1 kg was added to carry out polymerization. The reaction was performed for 1 hour while supplying tetrafluoroethylene so that the pressure of tetrafluoroethylene was constant.

The polymer was melt-kneaded at 240 ° C., extruded and molded into particles, and the pellets were used to perform extrusion film formation at 270 ° C. When extrusion film formation, cuts and uneven thickness,
Roughness of the surface does not occur at all and it is uniform and good at 0.5 m
Thin films of 1 mil, 1 mil, 2 mil, and 5 mil could be continuously and stably obtained.

Comparative Example 10 The reaction was carried out in exactly the same manner as in Example 21, except that methanol was not added and the pressure of tetrafluoroethylene was set to 14.5 kg / cm ² . In addition, in order to obtain a copolymer having the same EW as that of the copolymer in Example 21, the pressure of tetrafluoroethylene was changed.

The film of the obtained copolymer was slightly devitrified (whitened), and the swell at 270 ° C. after melt-kneading the copolymer at 270 ° C. was 224%. A significant increase in swell was noted. The polymer was melt-kneaded and extruded at 240 ° C. to be formed into particles, and then the pellets were used to perform extrusion film formation at 270 ° C. in the same manner as in Example 21. At the time of extrusion film formation, a film having a thickness of 10 mil or less could not be obtained stably and continuously due to edge breakage. Further, the thickness of the obtained film was not constant, and unevenness of thickness of ± 50% was generated, and the surface was rough and devitrification was observed, which was not practical at all.

(Example 22) Ion-exchanged water: 500 g
In addition, C ₇ F ₁₅ COONH ₄ : 1.0 g, Na ₂ HPO ₄
・ 12H ₂ O: 2.5 g, NaH ₂ PO ₄ .2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 SO 2 F: 100g and methanol: 9.5 g was added. Next, using a Biomixer ABM-4 type manufactured by Nippon Seiki Co., Ltd., 20,000 rpm
For 30 minutes, the monomer was atomized, crushed and dispersed. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was set to 60 ° C. and the pressure of tetrafluoroethylene was set to 16.5 kg / cm ² .
Next, 2.3 g of (NH ₄ ) ₂ S ₂ O _{8 was} added to ion-exchanged water 1
Polymerization was carried out by adding a solution dissolved in 0 g. The reaction was carried out for 5.5 hours while supplying tetrafluoroethylene from outside the reaction vessel so that the pressure of tetrafluoroethylene was kept constant at 16.5 kg / cm ² during the reaction. The resulting copolymer film was slightly devitrified (whitened).

(Example 23) C ₇ F ₁₅ COONH ₄ : 4
2g, Na ₂ HPO ₄ · 12H ₂ O: 105g, NaH
_{2 PO 4 · 2H 2 O:} 63g of ion-exchanged water: 20.8
An aqueous solution dissolved in kg is put in the container (A), and CF ₂ =
CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ SO ₂ F:
7.0 kg was put in a container (B), and the monomer was finely divided and dispersed by the following method using Microfluidizer M-110Y type manufactured by Microfluidex Co., Ltd. From the container (A) and the container (B), while the ratio of both liquids was kept constant at a weight ratio of 3: 1, they were continuously fed using a constant-volume liquid-feeding pump to join both liquids. After that, it was fed to a microfluidizer. Stroke pressure of microfluidizer is 1000kg / c
The amount was m ² , and the total amount was fed over 90 minutes to finely disperse and disperse the monomer. At this time, the treatment was continuously carried out while cooling so that the temperature of the dispersion liquid after atomization was 10 ° C. or lower at the outlet of the microfluidizer. The above operation was performed twice, and the liquid for two times was charged into a 100-liter stainless autoclave.

Next, nitrogen was thoroughly purged and then tetrafluoroethylene. The temperature was 60 ° C. and the pressure of tetrafluoroethylene was 17.2 kg / cm ² . Next, 735 g of methanol was added, and (NH ₄ ) ₂ S ₂ O was added.
_8: 57 g of the polymerization was carried out by adding a solution of the ion-exchanged water 1 kg. The tetrafluoroethylene pressure was continuously reduced from the initial 17.2 kg / cm ² to the final 6.2 kg / cm ² , and 9.1 kg during this period.
While continuously supplying tetrafluoroethylene of No. 1 from outside the system, the reaction was performed for 8.5 hours. During the reaction, the amount of tetrafluoroethylene supplied from outside the system was continuously controlled so that the ratio between the total amount of tetrafluoroethylene pressure drop and the total amount of tetrafluoroethylene supplied from outside the system was always constant.

The obtained copolymer was melt-kneaded at 240 ° C., extruded and molded into granules.
Extrusion film formation was performed at ℃. In the extrusion film formation, there are no edge cuts, thickness irregularities, surface roughness, etc., and uniform and good thin films of 0.5 mil, 1 mil, 2 mil, and 5 mil can be continuously and stably obtained. It was

Example 24 In Example 23, 440 g of methanol, the initial reaction pressure of tetrafluoroethylene was 15.0 kg / cm ² , and the final pressure was 6.7 kg /.
cm ^2, except for using 8.5kg total tetrafluoroethylene amount supplied from the outside of the system was subjected to 8 hours in the same manner. The obtained copolymer was melt-kneaded at 230 ° C., extruded and molded into granules.
Extrusion film formation was performed at ℃. In the extrusion film formation, there are no edge cuts, thickness irregularities, surface roughness, etc., and uniform and good thin films of 0.5 mil, 1 mil, 2 mil, and 5 mil can be continuously and stably obtained. It was

Example 25 Ion-exchanged water: 500 g
In addition, C ₇ F ₁₅ COONH ₄ : 1.0 g, Na ₂ HPO ₄
・ 12H ₂ O: 2.5 g, NaH ₂ PO ₄ .2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 SO 2 F: 100g and methanol: 9.5 g was added. Next, using a Biomixer ABM-4 type manufactured by Nippon Seiki Co., Ltd., 20,000 rpm
For 30 minutes, the monomer was atomized, crushed and dispersed. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was set to 60 ° C. and the pressure of tetrafluoroethylene was set to 16.5 kg / cm ² .
Next, 2.3 g of (NH ₄ ) ₂ S ₂ O _{8 was} added to ion-exchanged water 1
Polymerization was carried out by adding a solution dissolved in 0 g. The tetrafluoroethylene pressure was changed from an initial value of 16.5 kg / cm ² to a final value of 3.5 kg / cm ^2, and the pressure was intermittently lowered as described below to carry out the reaction for 8 hours. First, 4 g of tetrafluoroethylene was supplied from the outside of the reaction tank system so that the pressure was constant at the initial reaction pressure of 16.5 kg / cm ² . Next, with the supply of tetrafluoroethylene from outside the system of the reaction tank shut off, the pressure was lowered by 0.5 kg / cm ² by the reaction and the pressure was reduced to 16.0 kg.
/ Cm ² . Subsequently, the pressure was 16.0 kg / cm ^2.
Then, 4 g of tetrafluoroerene was fed again from outside the system of the reaction tank so as to be constant. Then, with the supply of tetrafluoroethylene from the outside of the reaction vessel being shut off, the pressure was lowered by 0.5 kg / cm ² by the reaction and the pressure was reduced to 1
It was set to 5.5 kg / cm ² . The above operation was repeated to reduce the pressure to 3.5 kg / cm ² .

(Example 26) Deionized water: 450 g
In addition, C ₇ F ₁₅ COONH ₄ : 1.0 g, Na ₂ HPO ₄
・ 12H ₂ O: 2.5 g, NaH ₂ PO ₄ .2H ₂ O:
After dissolving 1.5 g, CF ₂ = CFOCF ₂ CF (C
_{F 3) O (CF 2)} 2 SO 2 F: 150g and methanol: 2.9 g was added. Next, using a Biomixer ABM-4 type manufactured by Nippon Seiki Co., Ltd., 20,000 rpm
For 30 minutes, the monomer was atomized, crushed and dispersed. This was placed in a 1-liter stainless steel autoclave, then sufficiently purged with nitrogen and further purged with tetrafluoroethylene. The temperature was 60 ° C. and the pressure of tetrafluoroethylene was 13.5 kg / cm ² .
Next, 2.3 g of (NH ₄ ) ₂ S ₂ O _{8 was} added to ion-exchanged water 1
Polymerization was carried out by adding a solution dissolved in 0 g. In the same manner as in Example 25, the pressure of tetrafluoroethylene was changed from the initial 13.5 kg / cm ² to the final 5.5 kg / cm ^2, and the pressure was intermittently lowered to carry out the reaction for 8 hours.

(Example 27) [0148] Methanol: 1.2 g and n-butyl alcohol: 0.6 g were used in place of methanol: 9.5 g, and the pressure of tetrafluoroethylene was 10.0 kg during the reaction. / Cm ² was reached, the reaction was carried out for 7.5 hours in the same manner as in Example 25 except that a liquid in which 0.5 g of n-butyl alcohol was dispersed in 5 g of ion-exchanged water was added. It was

[0149]

[Table 1]

[0150]

[Table 2]

[0151]

[Table 3]

[0152]

[Table 4]

[0153]

[Table 5]

[0154]

EFFECTS OF THE INVENTION According to the production method of the present invention, it is possible to suppress / prohibit the formation of a heterogeneous polymer in the aqueous phase, and to improve the melt moldability,
Also, a functional group-containing perfluorocarbon-based copolymer having an excellent function can be produced. The obtained copolymer composition is a functional group-containing perfluorocarbon-based copolymer composition having excellent melt moldability and excellent function after the functional group is converted into an ion-exchange group. It was

Continuation of front page (31) Priority claim number Japanese Patent Application No. 6-25877 (32) Priority date January 31, 1994 (January 31, 1994) (33) Country of priority claim Japan (JP) (56) References JP-A-62-288617 (JP, A) JP-A-61-223007 (JP, A) JP-A-60-221409 (JP, A) JP-A-6-184244 (JP, A) JP-A-56 -45911 (JP, A) JP-A-60-76516 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 214/18-214/28 C08F 2/16-2/30 C08F 216/14-216/20

Claims (2)

(57) [Claims] 1. A method for producing a copolymer of a functional group-containing perfluorocarbon monomer represented by the following general formula (1) and a perfluoroolefin represented by the following general formula (2) in an aqueous system, The functional group-containing perfluorocarbon monomer (1) is finely divided into oil droplets having an average particle size of 2 μm or less and dispersed in water, and selected from aliphatic alcohols having 1 to 6 carbon atoms and ethers having 2 to 6 carbon atoms. A method for producing a functional group-containing perfluorocarbon-based copolymer, which comprises polymerizing by adding a water-soluble organic chain transfer agent of one kind or two or more kinds. ## STR1 ## _{CF 2 = CF-O- (CF} 2 CF (CF 3) -
_{O) n - (CF 2)} m -Z ··· (1) ( in the formula, m is an integer of 2 to 4, Z is the CO ₂ R (R is an alkyl group having 1 to 3 carbon atoms. Or SO ₂ F, n is 1 or 2 when Z = CO ₂ R, and n is an integer of 0 to 2 when Z = SO ₂ F.) embedded image CF ₂ ═CFX ... (2) (In the formula, X is F, Cl or CF _3. ) 2. The polymerization is performed by decreasing the reaction pressure of the perfluoroolefin (2) in accordance with the progress of the polymerization reaction (in accordance with the increase in the conversion rate of the functional group-containing perfluorocarbon monomer (1)). The method for producing a functional group-containing perfluorocarbon-based copolymer according to claim 1.