JP2003246906A - Fluorine-containing copolymer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new useful composition capable of achieving high tensile strength on handling and high durability under practical conditions, and useful as a raw material for producing a reinforced and cross-linked fluorine-containing cation exchange membrane, a gas diffusion electrode and a membrane electrode conjunctive material. <P>SOLUTION: This composition comprises 100 pts. mass specific fluorine- containing terpolymer containing SO<SB>2</SB>F and SO<SB>2</SB>NHR as functional groups and 10-10,000 pt. mass specific liquid fluorooligo ether. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fluorine-containing cation exchange membrane useful as a membrane for electrolysis and a membrane for fuel cells, a gas diffusion electrode, a membrane electrode assembly, etc.
The present invention relates to a composition comprising a non-electrolyte SO ₂ F type functional group-containing fluorine-based terpolymer and a liquid fluorooligoether.

[0002]

2. Description of the Related Art Fluorine-containing cation exchange membranes are widely used as membranes for salt electrolysis, membranes for fuel cells and the like. Fluorine-containing cation exchange membranes are required to have high strength and high durability under handling conditions and practical conditions. As a method for achieving these, a reinforcing method using a polytetrafluoroethylene porous film (see, for example, Japanese Patent Publication No. 11-50
1964) and a cross-linking method by sulfonimidation (for example, JP 2000-188013 A).

However, Japanese Patent Publication No. 11-501964
In the reinforcing method described in the publication, the strength at the time of handling the film can be improved, but the solution of the raw material is electrolyte type (SO ₃
Since it is formed from a fluorine-based copolymer containing functional groups such as H-type), sufficient adhesion between the resins of the fluorine-based copolymer containing functional groups and between the resin and the base polytetrafluoroethylene resin It was difficult to impart strength, and long-term resistance was not sufficient. JP 2000-188013 A
In the crosslinking method described in the publication, durability (high temperature resistance)
However, since the cross-linking structure lacks homogeneity, the dimensional stability and strength during handling such as film treatment and installation were insufficient.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and provides reinforcement and crosslinking capable of achieving both high strength to withstand stress during handling and high durability under practical conditions. It is an object of the present invention to provide a novel composition which is extremely useful as a raw material for producing such a fluorinated cation exchange membrane, a gas diffusion electrode, a membrane electrode assembly and the like.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have found that a non-electrolyte SO ₂ F type functional group-containing fluorine-based terpolymer (sulfone) in which formation of a complete solid structure (crystal structure, etc.) is inhibited. It has been found that the above object can be achieved by a composition comprising a fluorinated terpolymer containing a sulfonamide group which is an imide cross-linking precursor) and a fluoro oligoether, and has completed the present invention. .

That is, the present invention is as follows. [1] It is composed of the repeating units represented by the chemical formulas (1), (2) and (3), and the molar ratio of the repeating units is represented by the chemical formula (2).
2 to 20 units of the chemical formula (1) per 1 mol of the unit of
Mol, the unit of the chemical formula (3) is 0.001 to 1 mol, based on 100 parts by mass of the perfluoro copolymer, one or two or more of the repeating units represented by the chemical formula (4), the degree of polymerization 6 to. A fluorocopolymer-containing composition containing 100 to 100 parts by mass of a liquid fluorooligoether.

[0007]

[Chemical 5]

[0008]

[Chemical 6]

[0009]

[Chemical 7]

[0010]

[Chemical 8] (In the formula, n and n ′ are each independently an integer of 0 to 2,
m and m ′ are each independently an integer of 1 to 4, R is H,
(Unsubstituted hydrocarbon group or substituted hydrocarbon group, R _f is a perfluoroalkylene group having 1 to 4 carbon atoms)

[2] The repeating unit-(R _f -O)-is
_{- (CF (CF 3) -CF} 2 -O) -, - (CF 2 CF 2 C
F ₂ -O), or - (CF ₂ -O) and - (CF ₂ -CF
YO)-, and the fluorine-containing copolymer-containing composition according to [1]. (In the formula, Y is F or CF ₃
[3] The liquid fluorooligoether is contained in an amount of 200 to 10000 parts by mass with respect to 100 parts by mass of the perfluorocopolymer, and the perfluorocopolymer is dispersed in the fluorooligoether. The fluorine-containing copolymer-containing composition according to [1] or [2]. [4] The average particle size of the perfluoro copolymer is 100 μm
The fluorine-containing copolymer-containing composition according to [3], characterized in that:

The present invention will be described in detail below. (Composition) The composition of the present invention comprises the repeating units represented by the chemical formulas (1), (2) and (3), and the molar ratio of the repeating units is 1 mol of the unit of the chemical formula (2). The unit of (1) is 2 to 20 mol, the unit of the chemical formula (3) is 0.001 to 1 mol, and is composed of one or more kinds of the repeating unit represented by the chemical formula (4). It contains a liquid fluorooligoether having a degree of polymerization of 6 to 100.

(Perfluoro Copolymer Contained in Composition) The perfluoro copolymer contained in the composition of the present invention has a melt index measured by using an apparatus having an orifice inner diameter of 2.09 mm and a length of 8 mm. When measured, the temperature is 250
Under the conditions of ~ 290 ° C and a load of 21.2N, usually 0.01
It is preferably in the range of ˜500 g / 10 minutes (converted value).

In this perfluoro copolymer, the molar ratio (p) of the units of the chemical formula (1) is 2 to 20 to 1 mol of the units of the chemical formula (2). The ratio (p ') is 0.001-1, preferably 0.01-
It is 0.1. When p is less than 2, it becomes difficult to achieve a sufficient degree of polymerization of the film obtained from the above composition, and when it is more than 20, it gives a sufficiently high ionic conductivity to the film. I can't. When p'is less than 0.001, sufficient cross-linking effect (heat resistance) cannot be obtained after introducing the imide cross-linking structure. Sufficient adhesion between the base material and the base material cannot be obtained. The values of p and p ′ are appropriately selected according to the application and can be adjusted by appropriately selecting the polymerization conditions.

Two or more kinds of perfluoro copolymers may be mixed in the composition of the present invention. The perfluoro copolymer contained in the composition of the present invention is a non-electrolyte SO ₂ F
Since it contains a side chain terminal functional group of the mold, it has a great feature in that the adhesive strength between the resins and between the resin and the base material can be increased by heating and melting during film production, and the durability can be improved.

(Fluoro-oligoether Contained in Composition) The fluoro-oligoether contained in the composition of the present invention is a liquid fluoro-oligoether composed of one or more repeating units represented by the chemical formula (4). Is. The oligomer represented by the chemical formula (4) may be an oligomer composed of one kind of repeating unit or an oligomer composed of two or more kinds of repeating units. Examples of the latter include those in which two or more kinds of repeating units are randomly bonded, and those in which blocks of each repeating unit are bonded. "Liquid"
Means that it shows a liquid state or an oil state even at a temperature of 60 ° C. or lower and shows fluidity.

The degree of polymerization of fluoro oligoether is 6 to 1
00, preferably 6 to 60. If the degree of polymerization is less than 6, the boiling point is low and the vapor pressure is large, so removal of monomers and polymerization solvents, formation of stable compositions with perfluorocopolymers, and handling at high temperatures (160 ° C or higher) are required. It is difficult, and if it exceeds 100, the polymerization yield will be low, which is economically disadvantageous, and the viscosity will be too high, and handling will be difficult. The fluorooligoether has a high degree of molecular freedom due to its ether bond, and thus a fluorooligoether having a higher molecular weight can be used. Therefore, there is an advantage that the vapor pressure is low even at a high temperature. Due to its ether structure, the fluorooligoether exhibits oil-like property, that is, fluidity even if it is a high molecular weight substance, and therefore it is possible to use up to 100 high molecular weight substances.

There is no restriction on the chemical structure of the molecular chain end group of the fluoro-oligoether, but when treated at high temperature, it is preferable that the structure is stable at that temperature, and a carboxylic acid group is added to the molecular chain end. A structure not having is more preferable.
Examples of fluoro oligoether, as easily available commercially _{available, - (CF (CF 3)} -CF 2 -
_{O), - (CF 2 CF} 2 CF 2 -O) -, or - (CF ₂ -
O) and _{- (CF 2 -CFY-O)} - include those having repeating units of, but not limited thereto. These are, for example, Krytox from DuPont.
(Registered trademark), Demnam (registered trademark) from Daikin
Available as FOMBLIN® from Ausimont. All of these fluoro-oligoethers have a CF ₃ group at the end of the molecular chain and have a thermally extremely stable structure, which is preferable.

Full containing three or more different repeating units
As the oligo-oligoether, for example,-(CF₂−
O),-(CF (CF₃) -O) -and- [CF (CF
₃) -CF ₂Examples of the structural unit include -O]-
To be These fluoro oligoethers used alone
Alternatively, two or more kinds may be mixed and used. Fluo
As a lower oligoether, it is usually at 0-100 ° C
Kinematic viscosity is 0.1-5 cm²/ Sec liquid
The body is preferably used, from low viscosity to high viscosity
It is appropriately selected according to the purpose and purpose.

(Ratio of Composition) The composition of the present invention is characterized by containing 10 to 10000 parts by mass of fluoro oligoether with respect to 100 parts by mass of perfluoro copolymer. When the amount of fluorooligoether is less than 10 parts by mass, the effect of the present invention becomes small, and when the amount of fluorooligoether exceeds 10,000 parts by mass, it is economically disadvantageous.

When the amount of fluorooligoether is 200 parts by mass or more based on 100 parts by mass of the perfluorocopolymer, the perfluorocopolymer particles having an average particle diameter of 100 μm or less are stably dispersed in the fluorooligoether. Can be taken. The “average particle size” of the dispersed particles is measured by a laser diffraction type particle size distribution measuring device using a dispersion diluted with fluoro oligoether so that the content of the perfluoro copolymer is about 0.1% by mass. The average particle diameter measured and calculated is shown.

The composition of this constitution usually has a cloudy, paste-like form. The ratio of the perfluoro copolymer and the fluoro oligoether capable of forming this stable structure is determined by the equivalent weight (EW) of the perfluoro copolymer, the molecular weight, the SO ₂ F type functional group and the SO ₂ NHR type functional group. The ratio of
And, depending on the properties and molecular weight of the fluoro oligoether. The compositions of the present invention are suitable for many applications and have long-term storage stability. In a composition having a dispersed particle size of 100 μm or less, liquid fluorooligoether is excessively present, and finely dispersed particles of a perfluorocopolymer swelled by being solvated with fluorooligoether are stably contained in the fluorooligoether. It has a dispersed structure.
Therefore, the properties of the composition of the present invention are maintained and do not change even if the amount of fluorooligoether is increased excessively.

When the composition containing the surplus fluoro-oligoether is left to stand for a long time, a paste-like substance (gel-like substance) that becomes cloudy usually precipitates and separates into two phases. It has no effect on the characteristics. in this case,
It can be used as a homogeneous composition by stirring at the time of use. Further, in this stable composition, it is possible to increase the concentration of the perfluorocopolymer without deteriorating the original properties of the composition by removing the excess fluorooligoether by decanting or vacuum filtration. is there.

In the composition of the present invention, 1 part of fluoro-oligoether is added to 100 parts by mass of perfluoro copolymer.
When it contains 0 to 200 parts by mass, it itself forms a stable dispersed structure in its composition. Further, even when the fluoro oligoether exceeds 200 parts by mass with respect to 100 parts by mass of the perfluoro copolymer, for example, a low EW and an extremely high molecular weight perfluoro copolymer (for example, EW is 1000 or less, and , A perfluoro copolymer having a melt index of 0.01 to 1 g / 10 min (converted value) may have a rubber-like morphology, and this composition also forms a stable dispersion structure in the composition. .

The composition of the present invention is a novel one which cannot be produced by the melt kneading method which is a conventional technique, and in addition, it has extremely excellent melt moldability and meltability due to the plasticizing effect of the fluorooligoether contained therein. It has an extrusion film forming property. From the above characteristics, the mass ratio of the perfluoro copolymer and the fluoro oligoether is:
Usually, depending on the purpose and application, when forming the composition of the present invention from a polymerization solution composition containing a perfluorocopolymer, or the amount of fluorooligoether added before the polymerization and the polymerization method and conditions. Determined by

(Method for Producing Composition) The method for producing the composition of the present invention is divided into two methods: a method of adding a fluorooligoether after polymerization and a method of previously adding a fluorooligoether before polymerization. (A) Method for producing a composition in which a fluoro-oligoether is added after polymerization In order to produce the composition of the present invention, at least one functional group-containing perfluorocarbon monomer represented by the chemical formula (5) and the chemical formula (6) are used. At least one functional group-containing perfluorocarbon monomer represented and a perfluoro copolymer obtained by copolymerizing three or more monomers containing tetrafluoroethylene are used.

[0027]

[Chemical 9] (In the formula, n is an integer of 0 to 2 and m is an integer of 1 to 4.)

[0028]

[Chemical 10] (N 'in the formula is an integer of 0 to 2, m'is an integer of 1 to 4, R
Is H, an unsubstituted hydrocarbon group or a substituted hydrocarbon group. )

For this copolymerization, a known solution polymerization method or bulk polymerization method used for homogeneous polymerization or copolymerization of fluorinated ethylene can be used. A wide range of polymerization conditions can be selected as long as the produced perfluoro copolymer does not become a completely solid substance. In order to produce a finely dispersed composition, it is preferable to select polymerization conditions that allow the resulting perfluoro copolymer to swell sufficiently.

When carrying out solution polymerization, the polymerization temperature is 10 to 8
The temperature is preferably 0 ° C., more preferably 20 to 60 ° C., and the initial reaction pressure is preferably 0.1 to 2 MPa, more preferably 0.1 to 1 MPa. As the polymerization solvent, a wide range of known fluorine-containing solvents can be used. For example, CF
_{2 ClCFCl 2 (CFC113), CClF} 2 CF 2 CF
HCl (HCFC225cb), CF ₃ CHFCHFC
An inert fluorine-containing solvent such as F ₂ CF ₃ (HFC43-10mee), perfluoromethylcyclohexane, perfluorodimethylcyclobutane, perfluorooctane or perfluorobenzene is preferably used.

In the production of a polymerization liquid composition containing a perfluorocopolymer, it is preferable that the fluorine-containing solvent is usually used in a proportion of 50 to 1000 parts by mass based on 100 parts by mass of the total amount of the monomers. In addition to this, bulk polymerization using the functional group-containing perfluorocarbon monomer itself as a polymerization solvent can also be adopted. Examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile, diacyl peroxides such as benzoyl peroxide and dipentafluoropropionyl peroxide, and peroxyesters such as t-butylperoxyisobutyrate. A wide range of oil-soluble polymerization initiators such as hydroperoxides such as diisopropylbenzene hydroperoxide can be used.

For the purpose of controlling the molecular weight of the perfluoro copolymer, well-known and known chain transfer agents such as alkanes such as pentane and hexane and alkanols such as methanol and ethanol can be added. By the above-mentioned method, a perfluoro copolymer in which the functional group-containing perfluorocarbon monomer represented by the chemical formulas (5) and (6) and tetrafluoroethylene are terpolymerized is produced. Alternatively, a functional group-containing perfluorocarbon monomer other than the above may be used at the same time. Further, the perfluorovinyl ether represented by the chemical formula (7) may be used in combination at a ratio of 10 mol% or less based on the total amount of the above monomers.

CF ₂ = CFOR _f (7) (R _f is a perfluoroalkyl group having 1 to 10 carbon atoms.)

Examples of the functional group-containing perfluorocarbon monomer represented by the chemical formula (5) include SO represented by the chemical formulas (8), (9), (10) and (11).
Those having ₂ F type non-electrolyte type functional groups are used.

[0035]

[Chemical 11]

[0036]

[Chemical 12]

[0037]

[Chemical 13]

[0038]

[Chemical 14]

As the functional group-containing perfluorocarbon monomer represented by the chemical formula (6), for example, the chemical formula (1
SO as shown in 2), (13), (14) and (15)
₂ Those having an NHR type functional group are used.

[0040]

[Chemical 15]

[0041]

[Chemical 16]

[0042]

[Chemical 17]

[0043]

[Chemical 18]

R in these monomers is a hydrogen atom, or an unsubstituted hydrocarbon group or a substituted hydrocarbon group having 1 to 10 carbon atoms, preferably a hydrogen atom or a non-substituted hydrocarbon group having 1 to 4 carbon atoms. A substituted hydrocarbon group or a substituted hydrocarbon group, more preferably a hydrogen atom. Specific examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a t-butyl group and the like. If necessary, an ether group or a fluorine atom may be used as a substituent. It may contain a different halogen group.

The fluorooligoether represented by the chemical formula (4) was added to the polymerization liquid composition containing the perfluorocopolymer of the present invention at a temperature of about 40 ° C. or lower, and the mixture was stirred and mixed, then 150 Unreacted functional group-containing perfluorocarbon monomers and low-boiling compounds such as fluorine-containing solvents are removed at a temperature of not higher than 0 ° C. As a method of removing the low boiling point compound, a method of extracting and removing with a hydrocarbon solvent is preferably used. The temperature at the time of removing is preferably 150 ° C. or lower, more preferably 40 ° C. or lower, and usually it is preferably carried out at room temperature under normal pressure.

In addition to the above-mentioned method, for example, in order to obtain the desired composition, a polymerization solution containing the above-mentioned perfluorocopolymer, which is formed by adding necessary fluorooligoether and then stirring and mixing. A hydrocarbon solvent is added to the composition, stirred and mixed, and then allowed to stand to separate the two layers, and a dispersion of the lower layer perfluoro copolymer and fluoro oligoether (concentration of perfluoro copolymer By this, the form changes from a paste form to a rubber form to a powder form and usually becomes a cloudy dispersion. Then, if necessary, the solvent may be repeatedly washed with a hydrocarbon-based solvent to extract and remove the functional group-containing perfluorocarbon monomer, which is a low boiling point compound, and the fluorine-containing solvent contained therein.

The hydrocarbon solvent is preferably compatible with the compound such as the functional group-containing perfluorocarbon monomer to be washed and removed, which is not compatible with the fluorooligoether and is separated into two layers. Therefore, an ordinary solvent is used as the hydrocarbon solvent. Some examples thereof are alkanols such as methanol and ethanol, alkanes such as hexane and heptane, ethers such as diethyl ether, ketones such as acetone, and esters such as ethyl acetate. For the purpose of efficiently removing the residual fluorine-containing compound having a low molecular weight, these hydrocarbon solvents and fluorine-containing solvents may be mixed and used.

In order to almost completely remove the remaining low boiling point compound, it is preferable to carry out heating under reduced pressure, but when a large amount of the low boiling point compound remains, this is carried out at the time of heat fixing at high temperature or melt molding processing. This is because a void may occur. This heating under reduced pressure is preferably performed at a temperature of 150 ° C. or lower, and preferably 90 ° C. or lower. The addition of the fluoro oligoether may be performed after the polymerization liquid composition and / or the fluoro oligoether is diluted with the fluorine-containing solvent and / or the functional group-containing perfluorocarbon monomer.

(B) Method for producing a composition in which a fluorooligoether is added in advance before the polymerization When the composition of the present invention is produced, a method in which the fluorooligoether is added in advance before the initiation of the polymerization is adopted. You may. this is,
Fluoro-oligoether is thermally and chemically stable,
Moreover, it is inactive in the polymerization.

In the method in which the fluoro oligoether is added in advance before the initiation of the polymerization, in addition to the bulk polymerization using the functional group-containing perfluorocarbon monomer itself as the polymerization solvent, and the solution polymerization using the fluorine-containing solvent as the polymerization solvent. Thus, water can also be used as a polymerization solvent. In the case of bulk polymerization and solution polymerization, usually, a fluoro oligoether may be added at any stage before the initiation of polymerization, but in the case of aqueous polymerization such as suspension polymerization using water as a polymerization solvent and emulsion polymerization. The fluoro oligoether is preferably used in a form of being dissolved in advance in a functional group-containing perfluorocarbon monomer. The reason for this is that a composition of homogeneous composition can be produced.

The polymerization conditions when the fluorooligoether is added in advance before the start of the polymerization are exactly the same as the above-mentioned polymerization conditions, but the amount of the fluorooligoether to be added depends on the desired composition. The conversion rate of the functional group-containing perfluorocarbon monomer and the gas pressure of tetrafluoroethylene are determined. When water is used as a polymerization solvent, usually a surfactant and, if necessary, a buffering agent are added for polymerization. As the polymerization initiator used in the aqueous polymerization, well-known water-soluble initiators can be widely used in addition to the oil-soluble initiator described above. Examples of water-soluble initiators include potassium persulfate, inorganic peroxides such as ammonium persulfate, redox initiators such as ammonium persulfate-ferrous sulfate, ammonium persulfate-ammonium bisulfite, and disuccinoyl peroxide. Such a water-soluble organic peroxide.

In the treatment after the bulk polymerization and the solution polymerization and after the polymerization in an aqueous system, the produced polymer is aggregated and the surfactant, the salt and the like are washed and removed based on the known method, as described above. In the same manner as in the method for producing the composition in which the fluoro oligoether is added after the polymerization, 1
The low boiling point compound in the composition obtained at 50 ° C. or lower is removed to produce the composition of the present invention. (Method for producing a fluorinated cation exchange membrane using the composition as a raw material) The composition of the present invention is used for producing a fluorinated cation exchange membrane (a membrane for electrolysis or a membrane for a fuel cell), a membrane electrode assembly, etc.
It can be widely used for various purposes. For this manufacturing method, the method proposed by the present inventors in PCT / JP01 / 08443 can be adopted, and extremely high adhesiveness to a substrate and structural stability can be realized.

The composition of the present invention may be used alone as a raw material for producing a fluorine-containing ion exchange membrane or a membrane electrode assembly, or solid particles such as electrode powder, alkali resistant inorganic particles and sacrificial particles may be uniformly dispersed. You may use it as a manufacturing raw material after making it into the composition. As the electrode powder, for example, an electrode powder composed of one or more kinds of platinum group metals and oxides thereof, or one kind of carbon powder carrying iron, nickel, stainless steel, Raney nickel, carbonyl nickel and platinum group metals. Alternatively, an electrode powder composed of two or more kinds is used.

As the alkali resistant inorganic particles, at least one kind of alkali resistant inorganic particles of oxides, nitrides and carbides of elements selected from Group IV of the Periodic Table is used. For example, alkali resistant particles such as zirconium oxide are used. Inorganic particles are used. As the sacrificial particles, for example,
1 selected from alkali-soluble polymer particles such as polyamide and polyester, metal particles such as aluminum powder, and neutral inorganic salt particles such as alkali metal halide salts
One kind or two or more kinds of solid particles are used. PCT / JP01 / 0
8443.

According to the production method using the composition of the present invention, in addition to the characteristics of the method described in PCT / JP01 / 08443, a part or all of the sulfonamide type functional groups contained by being treated with a Lewis base are contained. By converting the compound into a sulfonimide crosslinked structure, it has an excellent effect that a more durable and stronger structure can be realized. A wide range of Lewis bases can be adopted as the sulfonimide cross-linking structure, and various organic nitrogen compound-based Lewis bases (including saturated, unsaturated, cyclic and acyclic) can be used. For example, tertiary amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, dimethylaniline, N (CH ₂ CH ₂ OCF ₂ C
HFCF ₃ ) ₃ represented by partial substitution with a fluorine atom, tertiary amines, pyridine, alkyl-substituted pyridine, quinoline, 1,4-diazabicyclo [2.2.2] octane (DABCO), 1,8-diazabicyclo [5.4.
And various heterocyclic amines such as 0] -7-undecene (DBU), 1,5-diazabicyclo [4.3.0] -5-nonene (DBN), imidazole or its derivatives.

In this cross-linking reaction, the Lewis base itself may be used alone, or the above-mentioned fluorine-containing solvent, glymes,
Ethers such as diethyl ether and dioxane, hydrocarbon solvents such as polar solvents such as dimethyl sulfoxide and dimethylformamide, and mixed solvents thereof may be used as the solvent. In the crosslinking reaction, when a large amount of water is present in the reaction solution, the hydrolysis of the SO ₂ F type functional group in the perfluoro copolymer becomes remarkable, which hinders the uniform formation of the desired crosslinking structure. Therefore, it is preferable to prevent water from entering the system as much as possible during this treatment. The reaction temperature is generally 0 ° C or higher, preferably 40 ° C or higher, more preferably 60 ° C or higher, and the upper limit temperature is 20 ° C.
It is 0 ° C or lower, preferably 150 ° C or lower.

(Impregnated film obtained by impregnating a polytetrafluoroethylene porous film with a perfluoro copolymer) Impregnation according to the present invention obtained by impregnating a polytetrafluoroethylene porous film with a perfluoro copolymer of the present invention The film contains non-electrolyte SO ₂ F type functional groups,
Since it can be melt-molded and heat-fused, it is characterized by being extremely excellent in structural stability. Furthermore,
By introducing a sulfonimide crosslinked structure by a reaction of the contained SO ₂ F type functional group and the contained SO ₂ NHR type functional group with a Lewis base, it has an excellent effect that durability can be further increased.

As the porous film of the substrate, a porous film made of polytetrafluoroethylene is selected, and the reason is that polytetrafluoroethylene has high chemical and thermal stability. In this base film,
The membrane thickness, the average pore diameter of the pores, and the porosity are not limited and are widely adopted, and are selected according to the use and purpose.
For example, the film thickness is usually about 5 to 200 μm, the average pore diameter is usually about 0.1 to 100 μm, and the porosity is usually about 50 to 95%.

In the case of use as a membrane for a fuel cell, the functional group to be contained contains an aqueous solution of an alkali metal hydroxide or an aqueous solution of an alkali metal hydroxide using an organic solvent such as alcohols or dimethylsulfoxide as a swelling agent. The non-electrolyte SO ₂ F type functional group was converted to the acid type (SO ₃ H type) by the hydrolysis treatment at a temperature of 95 ° C. and the subsequent acid treatment using an inorganic acid such as hydrochloric acid and sulfuric acid. Later put to practical use. Well-known methods are widely used as methods for converting these functional groups.

The polytetrafluoroethylene porous film impregnated with the perfluoro copolymer of the present invention is
Since it has a non-electrolyte SO ₂ F type functional group that can be heat-fused, it is possible to increase the adhesive strength between the polytetrafluoroethylene porous film and the molecular chain composed of — (CF ₂ ) -chain in the manufacturing process thereof. In addition, since the impregnated perfluoro copolymer can form a strong solid structure, the stability of the structure of the impregnated film is extremely large, and further, the treatment with a Lewis base provides a sulfonimide crosslinked structure represented by the chemical formula (16). By introducing them, it is possible to simultaneously realize two of high strength and durability.

[0061]

[Chemical 19] (In the formula, R'is hydrogen, or an unsubstituted or substituted hydrocarbon,
q and q'are each independently an integer of 1 to 4)

This film has a dimensional stability in the process in which the functional group contained in the film is converted into a salt type or an acid type after the sulfonimide cross-linking structure is introduced and / or after being optionally compounded. , Excellent in dimensional stability during handling such as installation, and also excellent in dimensional stability even after the functional group is converted to a salt type or an acid type and put into practical use, and a strong structure can be maintained. Therefore, it has high durability.

In particular, a film having a sulfonimide crosslinked structure can realize high durability. For example, in the polytetrafluoroethylene porous film impregnated with the perfluoro copolymer of the present invention, a part or all of the sulfonamide group of the chemical formula (3) is replaced with a sulfonimide crosslinked structure represented by the chemical formula (16). Chemical formulas (1), (3) and (17), which are formed by crosslinking with, followed by hydrolysis and acid treatment.

[0064]

[Chemical 20] (In the formula, m is an integer of 1 to 4 and n is an integer of 0 to 2)

The polytetrafluoroethylene porous film impregnated with the perfluoro copolymer consisting of the repeating unit shown in was heat-treated at 120 ° C. for 4 hours with a mixed solution of water / ethanol = 50/50 volume ratio. Even if the amount of the perfluoro copolymer to be dissolved and extracted is 50% by mass of the functional group-containing perfluoro copolymer originally contained.
The following structural stability (substantially 10% by mass or less) is exhibited.

Under a milder water-only system condition (a condition close to practical conditions), this polytetrafluoroethylene porous film dissolves and extracts perfluoro even when subjected to a high temperature history of 150 ° C. It shows excellent structural stability with almost no copolymer (substantially 0%).

In the case of a membrane obtained by previously impregnating a SO ₃ H type perfluorocarbon copolymer with a solution prepared by dissolving a SO ₃ H type perfluorocarbon copolymer in a water / alcohol mixed solution in advance, the above water / ethanol = 50. When a history of 120 ° C. for 4 hours in a mixed liquid of 50/50 volume ratio is given, the structure is almost completely destroyed (almost most resin exceeding 90% by mass is eluted and / or dropped), and further , This conventional impregnated membrane, even under milder water-only conditions,
This is in stark contrast to the almost complete structural destruction (almost most of the resin above 90% by weight elutes and / or falls off) when subjected to a high temperature history of 50 ° C.

Further, in this conventional impregnated membrane, the functional group contained in the fluorine-based copolymer as a raw material for production is of the electrolyte type (SO ₃ H type, SO ₃ Na type, etc.), so that the impregnation of the present invention is performed. Introducing a homogeneous sulfonimide crosslinked structure as in a membrane is practically impossible, and there is an essential problem that it is extremely difficult to improve durability.

(Method for producing impregnated film obtained by impregnating voids of polytetrafluoroethylene porous film with perfluoro copolymer) The voids of polytetrafluoroethylene porous film are impregnated with the perfluoro copolymer of the present invention According to the method for producing an impregnated film thus obtained, the composition of the present invention is applied to a polytetrafluoroethylene porous film and heated to 160 to 340 ° C. under pressure, so that the perfluoro coexists in the voids of the base film. At the same time as impregnating the polymer, it is heat-fixed to form a porous film containing a perfluoro copolymer containing a fluoro oligoether. Then, the fluoro oligoether is washed and removed using a fluorinated solvent.

The composition of the present invention used for this purpose preferably has an average particle size of dispersed particles of 100 μm or less. The reason for this is that even the pores of a polytetrafluoroethylene porous film having a small average pore size of 0.1 μm can be easily impregnated with a perfluoro copolymer (or a perfluoro copolymer containing a fluoro oligoether). Because you can. As long as a stable dispersion is formed, the composition of the present invention to be used usually preferably has a high ratio of perfluoro copolymer. This is because it is possible to impregnate the voids of the polytetrafluoroethylene porous film with a sufficient amount of the perfluoro copolymer in a single step, and it is also economically advantageous.

According to the method for producing a polytetrafluoroethylene porous film containing the perfluoro copolymer of the present invention, the composition of the present invention is applied to a substrate and heated to 160 to 340 ° C. under pressure. It is heated and impregnated with perfluoro copolymer (or perfluoro copolymer containing fluoro oligoether) in the voids of the film, and at the same time, it is fixed by heating. In this process, the solid structure of perfluoro copolymer is formed. It The heating temperature is selected to be 160 ° C. or higher from the viewpoint of forming a solid structure of the perfluoro copolymer, and 340 ° C. or lower from the viewpoint of thermal decomposability of the perfluoro copolymer.

As the pressing method, for example, a press molding method is adopted. It is heated to 160 to 340 ° C. simultaneously with the pressurization, but more strictly, it is preferable to raise the temperature from a low temperature of 160 ° C. or less to 160 to 340 ° C. in a pressurized state. The reason for this is that when heated to 160 to 340 ° C. before being pressed, a complete solid structure of the perfluoro copolymer is formed, making it difficult to impregnate the pores of the polytetrafluoroethylene porous film. This is because there are cases. The time required to raise the temperature under pressure is not limited.

The polytetrafluoroethylene porous film after being heat-treated under pressure contains the perfluoro copolymer in the voids and at the same time, the separated liquid fluorooligoether is a polytetrafluoroethylene porous film. Is discharged to the outside. Fluoro-oligoethers are easily washed and extracted with a fluorine-containing solvent at a temperature not higher than the normal pressure boiling point of the fluorine-containing solvent. Further, it is dried under reduced pressure at a temperature of about 110 ° C. or lower to remove the fluorine-containing solvent.

For the purpose of increasing the adhesive strength between the perfluoro copolymers contained in the voids of the polytetrafluoroethylene porous film, the interaction between the polytetrafluoroethylene and the perfluoro copolymer of the base material is For the purpose of increasing the adhesiveness and improving the adhesiveness, it is preferable that a heat treatment or a heat press treatment at 160 to 340 ° C. is subsequently added. Since the fluoro oligoether itself is thermally and chemically stable, it may remain in the perfluoro copolymer.

[0075]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below based on Examples, but the present invention is not limited to the Examples. In the present invention, the “extraction rate of perfluoro copolymer” of the polytetrafluoroethylene porous film impregnated with the perfluoro copolymer is measured by the following method.

The mass (W ₁ ) of the polytetrafluoroethylene porous film as the base material is precisely weighed in advance. The mass of this test piece is 1 g or less. First, a polytetrafluoroethylene porous film obtained by impregnating a perfluoro copolymer containing a target acid type (SO ₃ H type) functional group is used at 90 ° C. with 1N hydrochloric acid or 1N sulfuric acid. 8
Time to process. After that, it is thoroughly washed with running water, air-dried, and then dried under reduced pressure at 110 ° C. for 8 hours, and its mass (W ₂ ) is quickly weighed precisely.

This sample had a diameter of 28 mm and a height of 200 mm.
Then, 60 ml of a mixed solution of water / ethanol = 50/50 volume ratio (a sufficiently large amount relative to the test piece) is added. The test tube was placed in a 5 liter autoclave, and the outside of the test tube (inside the autoclave)
About 2 liters of a mixed solution of water / ethanol = 50/50 volume ratio was charged to the mixture, heated to an internal temperature of 120 ° C., heat-treated as it was for 4 hours after reaching 120 ° C., and then cooled to room temperature. . The temperature raising process from room temperature to 120 ° C. and the temperature lowering process from 120 ° C. to room temperature are each about 2
Do it over time.

After the heat treatment, the test piece was taken out from the test tube in the autoclave, and at room temperature, water / ethanol = 50 /
Sufficient washing is performed with a mixed solution having a volume ratio of 50. This 11
Dry under reduced pressure at 0 ° C. for 8 hours, and quickly weigh precisely its mass (W ₃ ). From the obtained mass values: W ₁ , W ₂ and W ₃ ,
The extraction ratio E (mass%) of the perfluoro copolymer is determined as follows. If the content of polytetrafluoroethylene in the test piece is unknown, add 24 more pieces to the above test piece.
It is heated and dissolved at a high temperature of 0 ° C. or higher to dissolve and drop all of the contained perfluoro copolymer,
After being dried under reduced pressure for an hour, it is precisely weighed, and this mass is defined as W ₁ .
The complete removal of the resin is confirmed by quantifying the remaining functional groups by IR or the like. E _{(weight%) = {1- (W 3} -W 1) / (W 2 -W 1)} ×
100

[0079]

Example 1 A 1-liter stainless steel autoclave was charged with 580 g of CF ₂ Cl—CFCl ₂ , 280 g of a monomer represented by the chemical formula (18), ₂ g of a monomer represented by the chemical formula (19), and 0.02 g of methanol as a molecular weight adjusting agent. After that, it was purged with nitrogen. Then, it was purged with tetrafluoroethylene (TFE).

[0080]

[Chemical 21]

[0081]

[Chemical formula 22]

The temperature is set to 25 ° C. and the TFE pressure is set to 0.1.
After adjusting to 65 MPa-G (gauge pressure), (n-C ₃ F ₇
COO-) ₂ was carried out the polymerization of CF ₂ Cl-CFCl ₂ solution containing 5 wt% was added 7 g. While the TFE is intermittently fed from outside the system of the autoclave, the TFE pressure is changed from an initial value of 0.165 MPa-G to an end value of 0.142 MPa-G.
It was lowered to and polymerized for 6 hours. After purging TFE in the system of the autoclave with nitrogen to bring it to atmospheric pressure, a polymerization liquid composition was obtained.

This polymerization liquid composition was mixed with Kry manufactured by DuPont.
tox (registered trademark) 143AD (this is-(CF (C
F₃) -CF₂A hexaf having a repeating unit of -O)-
It is an oligomer of luoropropene oxide,
Kinematic viscosity in 4.95 cm ²/ Sec liquid)
400 g was added at room temperature, mixed and stirred. By this
The polymerization liquid composition became cloudy. Then, at room temperature,
1 liter of n-hexane was added to the dispersion and mixed and stirred.
After that, let stand and separate into two layers, a colorless and transparent upper layer and a cloudy lower layer
Separated into layers.

The cloudy lower layer was taken out and washed with 1 liter of n-hexane 5 times at room temperature.
Remove the low boiling point compounds by drying under reduced pressure at 0 ° C for 16 hours,
460 g of a cloudy paste-like (gel-like) composition was obtained. After allowing this composition to stand for one week, the upper layer (colorless transparent liquid (Krytox (registered trademark) 143AD)) was removed, and a paste-like composition obtained by concentrating the perfluoro copolymer was taken out.

Subsequently, the composition was opened to 212 μm.
Through a stainless steel sieve to remove a small amount of foreign matter (large particles) contained therein to prepare a composition as a raw material. EW (S of the perfluorocopolymer contained in this composition
EW based on O ₂ F type functional group is 960, SO ₂ NH
The content of the type ₂ functional group is about 0.7 mol% with respect to the total amount of the functional group (the total amount of the SO ₂ F type functional group and the SO ₂ NH ₂ type functional group),
The melt index at 270 ° C. was 16 g / 10 minutes (converted value), and the concentration of the contained copolymer was 24 mass%.

Using this paste material as a raw material,
In this way, ADVANTEC MEMBRANE
FILTER (POLYMER: PTFE, CAT.N
O. : T300A293D), average pore size: 3 μm, thickness
Only: 60 μm, porosity: 82% (porosity is the base material PTFE
It is a value calculated by the density method with the true specific gravity of 2.2 as
7 cm x 7 cm square test piece film cut out from
O₂F type and SO₂NH ₂Perfluor containing type functional groups
The copolymer was impregnated.

First, two sheets of Kapton film were prepared by thinly and uniformly applying 3 g of the above paste-like material on one side. The film test piece was sandwiched between the two Kapton (registered trademark, manufactured by DuPont) films so that the paste-like material was in contact with the test piece, and air in the film test piece portion was removed. This was sandwiched between stainless plates having a thickness of 2 mm, set in a press molding machine heated to 270 ° C., immediately pressurized to 20 MPa, and treated for 5 minutes.

After cooling and pressing under a pressure of 20 MPa, the film test piece was taken out and washed with HFC43-10mee to remove fluoro oligoether, and then 110
It was dried under reduced pressure at ℃ for 2 hours. The film test piece was sandwiched between Kapton films, set again in a press molding machine heated to 270 ° C., and treated under a pressure of 20 MPa for 30 minutes. Two film test pieces were prepared as described above.
This film test piece was transparent because the resin containing SO ₂ F type and SO ₂ NH ₂ type functional groups completely filled the voids of the polytetrafluoroethylene porous film.

One of the film test pieces (test piece A) obtained by the above treatment was directly subjected to hydrolysis treatment and acid treatment, and the other film test piece (test piece B) was triethylamine / 1,4-. Immersion treatment was carried out for 3 hours under reflux of a mixed solution of dioxane = 3/5 volume ratio, and after a sulfonimide crosslinking reaction was performed, hydrolysis treatment and acid treatment were performed. As the hydrolysis treatment, 15% by mass of KOH and 30% by mass of DMS are used.
Treatment using an aqueous solution containing O was performed at 90 ° C. for 1 hour, and as acid treatment, treatment with 1N sulfuric acid was performed at 90 ° C. for 1 hour.

The contents of the perfluorocopolymer in these test pieces A and B were 77% by mass and 74% by mass, respectively (values after drying). The “extraction rates of perfluorocopolymer” measured using test piece A and test piece B were 31% by mass and 9% by mass, respectively. All films were able to maintain sufficient transparency.
In the test piece B (impregnated film having a sulfonimide cross-linked structure), resin elution / shedding can be greatly reduced,
It was confirmed that great durability could be realized.

It is considered that this is because the uniform crosslinked structure could be achieved even in the above-mentioned film having a low content of SO ₂ NH ₂ type functional groups of about 0.7 mol%. It should be noted that by sufficiently removing low molecular weight substances from the impregnated film after impregnating the composition of the raw material or the copolymer / before reheating and / or increasing the content of the SO ₂ NH ₂ type functional group. Thus, it is possible to further improve the durability.

[0092]

Comparative Example 1 The same polytetrafluoroethylene porous film as that used in the above example was used as a substrate, and a water / alcohol solution of a SO ₃ H type functional group-containing perfluorocopolymer (Dupont) was used according to the prior art. The “extraction rate of perfluorocopolymer” in the SO ₃ H type functional group-containing perfluorocopolymer impregnated film prepared by using Mitsui Co., Ltd. was 94% by mass. By the treatment in the extraction rate measurement, almost all the perfluoro copolymer was dissolved and dropped, and the original substrate film (polytetrafluoroethylene porous film) was returned.

[0093]

INDUSTRIAL APPLICABILITY The composition of the present invention is excellent in melt-molding processability because the contained perfluoro copolymer has a non-electrolyte SO ₂ F type functional group, and the formation of a complete solid structure is inhibited. It is useful as a raw material for producing a wide variety of fluorine-containing cation exchange membranes, for example, fluorine-containing cation exchange membranes such as electrolysis membranes and fuel cell membranes. Then, the composition of the present invention is improved in the adhesive strength between the resins constituting the film and between the resin and the substrate by heat fixing treatment, and the durability is enhanced by the introduction of the crosslinked structure.

Claims (4)

[Claims] 1. A repeating unit represented by the chemical formulas (1), (2), and (3), wherein the molar ratio of the repeating units is such that the unit of the chemical formula (1) is 1 mole of the unit of the chemical formula (2). 2 to 20 mol, and the unit of the chemical formula (3) is 0.001 to 1 mol per 100 parts by mass of the perfluoro copolymer,
A fluorocopolymer-containing composition comprising 10 to 10000 parts by mass of a liquid fluorooligoether having a polymerization degree of 6 to 100, which is composed of one or more of the repeating units represented by the chemical formula (4). [Chemical 1] [Chemical 2] [Chemical 3] [Chemical 4] (In the formula, n and n ′ are each independently an integer of 0 to 2,
m and m ′ are each independently an integer of 1 to 4, R is H,
(Unsubstituted hydrocarbon group or substituted hydrocarbon group, R _f is a perfluoroalkylene group having 1 to 4 carbon atoms) 2. The repeating unit-(R_f-O) -is-
(CF (CF₃) -CF ₂-O)-,-(CF₂CF₂CF
₂-O), or-(CF₂-O) and-(CF₂-CFY
-O)-is the fluorine.
-Based copolymer-containing composition. (In the formula, Y is F or CF.₃so
is there) 3. A liquid fluorooligoether in an amount of 200 to 100 relative to 100 parts by weight of the perfluorocopolymer.
The fluorocopolymer-containing composition according to claim 1 or 2, characterized in that the perfluorocopolymer is contained in an amount of 100 parts by mass and the perfluorocopolymer is dispersed in the fluorooligoether. 4. The average particle size of the perfluorocopolymer is 1
The fluorine-containing copolymer-containing composition according to claim 3, which has a diameter of 00 μm or less.