JPS5833249B2 - Fluorine-containing cation exchange resin membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel fluorine-containing cation exchange resin membrane, more specifically, an improved fluorine-containing cation exchange resin membrane having excellent performance as a diaphragm in diaphragm electrolysis of an electrolyte, particularly an aqueous alkali chloride solution. This invention relates to ion exchange resin membranes.

For example, CF2-CFOCF2CF(CF3)OCF20F2S included in the above polymerizable fluorine-containing compounds having a sulfonic acid group or a functional group convertible to the sulfonic acid group
A copolymer consisting of perfluorovinyl ether called O2F and a fluorinated olefin compound, such as tetrafluoroethylene, is already known (Japanese Patent Publication No. 4820788). It has also been proposed to use a cation exchange resin membrane composed of a fluorine-containing copolymer which has been decomposed to convert its -8O2F to -8O3H as a diaphragm in diaphragm electrolysis of alkali chloride.

(Unexamined Japanese Patent Publication No. 48-78097) However, KaS
When using a cation exchange resin membrane made of a fluorine-containing copolymer as an electrolytic diaphragm for alkali chloride, it is necessary to use a membrane S with excellent oxidation resistance, chlorine resistance, and alkali resistance, and a If the concentration is increased, for example, in the case of sodium hydroxide, if the concentration is increased to about 20% by weight or more, it becomes impossible to achieve a current efficiency of 85% or more.

The present inventor has repeatedly conducted research and examination on seven species in order to improve cation exchange resin membranes composed of fluorine-containing polymers having functional groups that can be converted into sulfonic acid groups or group groups. As a result, a novel fluorine-containing cation exchange resin membrane having the following structure was achieved.

That is, the present invention provides a perfluorocarbon polymer having a functional group convertible to a sulfonic acid group or a group group consisting of a copolymer of a polymerizable fluorine-containing compound having the following general formula (1) and a fluorinated olefin. From the formed first film-like material having an ion exchange capacity of 0.6 to 2 milliequivalents/1 dry resin and a copolymer of a polymerizable fluorine compound and a fluorinated olefin having the following general formula (2) carboxylic acid group,
An ion exchange capacity of 0.000 is formed from a perfluorocarbon polymer having a weakly acidic cation exchange group selected from phosphonic acid groups and hydroxyl groups or a functional group convertible to a group group.
6 to 2 milliequivalents/1 dry resin and a second film-like material with a thickness of 10μ or more is laminated and integrated, and if necessary, a functional group or weakly acidic that can be converted into a sulfonic acid group in the above-mentioned film-like material. The present invention relates to a fluorine-containing cation exchange resin membrane characterized in that the functional groups convertible to cation exchange groups are respectively converted to sulfonic bases or weakly acidic cation exchange groups.

(X is -F or -CF3, Y, Y' are -F
or a perfluoroalkyl group having 1 to 10 carbon atoms,
l is 6-3, m is O-1, n is O-12, A is -
A group selected from F, -OH1-0M, -OR,※※ and -NR1R2, R1 is an alkyl group having 1 to 10 carbon atoms, R2 and R3 are F or R1, and M is an alkali metal or a quaternary group. class ammonium group) (X, Y, YI, ■, m and n are represented by the above general formula (1
), B is a weakly acidic cation exchange group selected from a carboxylic acid group, a phosphonic acid group, and a hydroxyl group, or a functional group that can be converted into a group group). When an ion exchange resin membrane is used as a diaphragm for alkali chloride diaphragm electrolysis, it has high current efficiency and
Compared to conventional cation exchange resin membranes made only of fluorine-containing polymers that have low electrical resistance and have functional groups that can be converted into sulfonic acid groups or group groups, they have better alkali resistance, chlorine resistance,
Although the oxidation resistance is similarly excellent, the fluorine-containing cation exchange resin membrane of the present invention has a current efficiency of 90% or more even when the concentration of sodium hydroxide produced is 20% or more. It has extremely excellent performance in that it can maintain the following properties.

The first fluorinated polymer having a functional group convertible to a sulfonic acid group or a group group constituting the fluorinated cation exchange resin membrane of the present invention preferably has the following general formula (1). In the coating composed of a copolymer of a first polymerizable fluorine-containing compound and a fluorinated olefin, X is fluorine or -CF3, Y,
Y'' is fluorine or a perfluoroalkyl group having 1 to 10 carbon atoms, ■ is 0 to 3, m = 0 to 1,
n is O-12, A is fluorine, -OH1-0M
, -0R1 and -NR2R3, R1 is an alkyl group having 1 to 10 carbon atoms, R2,
R3 is hydrogen or R1, and M is an alkali metal or a quaternary ammonium group.

A preferred representative example of such a compound is CF2=CFOCF2CF(CF3)OCF2CF2S
O2F1CF2-CFOCF2CF2SO2F, CF2
-CFSO2F and the like.

Further, the second fluorinated polymer having a functional group that can be converted into a cation exchange group or a group group that is weaker than a sulfonic acid group is preferably a second fluorinated polymer having the following general formula (2). It is formed from a copolymer of a polymerizable fluorine-containing compound and a fluorinated olefin.

In this N, X, Y, Y'', 1, m, and n are the same as above, but B is a carboxylic acid group (-COOH), a phosphonic acid group (PO3H2), or a hydroxyl group (-0H). Examples of functional groups that can be converted into these cation exchange groups include acid ester groups, acid amide groups, acid alkali metal salts, and quaternary ammonium bases.

Preferred representative examples of such compounds include CF2=CFOCF2CF(CF3)OCF2CF2C
OOCH3,CF2=CFO(CF2)s
C00CHs, CF2 = CF C(CF3)
20H1 and the like.

The fluorinated olefin to be copolymerized with the above-mentioned first and second polymerizable fluorinated compounds preferably has the following general formula (
3) is used.

Here, z and z' are fluorine or -CF3, and representative examples thereof include tetrafluoroethylene and hexafluoropropylene, with tetrafluoroethylene being particularly preferred.

Content of the first polymerizable fluorine-containing compound and the second polymerizable fluorine-containing compound in each of the first and second fluorine-containing polymers constituting the fluorine-containing cation exchange resin membrane of the present invention are important because they are related to the performance of the ion exchange resin membrane, and preferably 1 to 50 mol%, particularly preferably 2 to 40 mol%, of each of them is employed in the polymer.

If the content of these polymerizable fluorine-containing compounds is too low, the ion exchange ability will be low and the electrical resistance will be high. On the other hand, if the content is too high, the mechanical strength will be impaired and the ion exchange performance (current This is not preferable because it causes a decrease in efficiency.

Copolymerization of a fluorinated olefin and a first polymerizable fluorine-containing compound or a second polymerizable fluorine-containing compound to produce the first fluorine-containing polymer and the second fluorine-containing polymer. can be carried out by known means under the action of polymerization initiators such as peroxy compounds, azo compounds, ultraviolet light, ionizing radiation, with or without the use of inert organic solvents or aqueous media.

For example, Japanese Patent Publication No. 48-2223, Japanese Patent Publication No. 48-20
Copolymerization can be carried out by methods such as those described in Japanese Patent Publication No. 788, Japanese Patent Publication No. 48-41942, and US Pat. No. 3,282,875.

Various polymerization methods such as bulk polymerization, solution polymerization, and suspension polymerization can be employed as the polymerization method.

In producing the first and second fluorinated polymers, one or more of the above-mentioned first or second polymerizable fluorinated compounds and fluorinated olefins can be used.

In addition to these compounds, other components such as a fluoronitroso compound represented by the general formula A-CF2-N=O, a fluoroketone represented by the general formula A-CF2COCF2-A1, and a fluoroketone represented by the general formula % Fluorovinyl ether (Kommede, A1A
1 is hydrogen, fluorine, or a perfluoroalkyl group having 1 to 7 carbon atoms, and it is possible to copolymerize one or more of the following: a=0 to 3, b=O to 7. be.

The molecular weight of the fluorine-containing polymer thus produced is preferably about 5,000 to 500,000, particularly preferably about 10,000 to 500,000, in view of the necessity for film formation.

When the cation exchange resin membrane of the present invention is composed of the first fluorinated polymer produced as described above and the second fluorinated polymer, both of the above fluorinated polymers A method is adopted in which the two are formed into films separately, and then the films of the two copolymers are laminated to integrate them.

Known methods such as press molding, roll molding, extrusion molding, solution casting, dispersion molding, or powder molding can be used as a method for forming the above-mentioned fluorine-containing polymer into a film.

In the case of such membrane formation, the membrane must be non-porous and dense in order to increase the cation selectivity of the cation exchange resin membrane obtained therefrom.

For this reason, the membrane preferably has a water permeability of water column pressure im (6
100 + 711/
time/m2 or less, and further, 1OrrLl/hour/m2 or less.

Further, the film thickness is preferably 20 to 500μ, particularly 50μ
It is preferable to make it ~300μ.

In the case where both of the above-mentioned fluorine-containing polymers are respectively formed into films and then laminated, the thickness of the film after lamination is preferably made to fall within the above range.

In addition, when forming a film of the above-mentioned fluorine-containing polymer, an olefin polymer such as polyethylene or polypropylene, preferably polytetrafluoroethylene or a copolymer of ethylene and tetrafluoroethylene, etc. It can also be molded by blending other fluorine-containing polymers, and furthermore, it can be supported on a support made of cloth, net, or other woven fabric, nonwoven fabric, or porous film made of these polymers.

Furthermore, the thicknesses of the two types of fluorine-containing polymer membranes in the cation exchange resin membrane of the present invention do not necessarily have to be the same, and can be changed as appropriate depending on the performance of each copolymer.

However, according to research conducted by the present inventors, it has been found that it is appropriate for the second fluorine-containing polymer membrane to occupy at least 10 μm or more, more preferably 20 μm or more, in the ion exchange membrane.

Lamination of both membranes of fluorine-containing polymers can be carried out by any suitable means, but in any case it is necessary to integrate both membranes by lamination.

Thus, for example, preferably at 100-350°C,
Such lamination is carried out by pressing at a pressure of 0.5 to 100 kg/-.

Before and after the manufacturing process for the above-mentioned ion exchange resin membrane, preferably after film formation, the copolymer contains not the sulfonic acid group or the above-mentioned weakly acidic ion exchange group itself, but a functional group that can be converted into these groups. If so, these functional groups are converted into sulfonic acid groups or the above-mentioned weakly acidic ion exchange groups by appropriate treatment.

For example, when the functional group is an acid ester, acid nitrile, acid amide, or acid halide, by hydrolysis or neutralization with an acid or alkali alcohol solution, or when the functional group is a divalent bond. is converted into an acid group, which is an ion exchange group, by adding SO2F, COF2 or H3PO3.

The fluorine-containing cation exchange resin membrane of the present invention produced in this way can be produced by controlling the type and composition of the first and second fluorine-containing polymers. The ion exchange capacity is preferably 0.6 to 2 meq/1 dry resin, particularly preferably 0.8 to 1.5 meq/1
It is preferable to reduce the amount of resin to 1 dry resin.

The fluorine-containing cation exchange resin membrane of the present invention has various excellent performances as described above, and therefore can be widely adopted for various purposes, fields, and uses.

For example, it is suitably used in fields where corrosion resistance is particularly required, such as in diffusion dialysis, electrolytic reduction, and as diaphragms in fuel cells.

In particular, when used as a diaphragm for alkali chloride diaphragm electrolysis, it exhibits advantages such as high current efficiency and low electrical resistance that cannot be obtained with conventional ion exchange resin membranes.

When the fluorine-containing cation exchange resin membrane of the present invention is used for such alkali chloride electrolysis, any known diaphragm electrolysis method can be used.

However, in the present invention, an anode and a cathode are separated by a single cation exchange resin membrane to form an anode chamber and a cathode chamber, an aqueous alkali chloride solution is supplied to the anode chamber for electrolysis, and water is supplied from the cathode chamber. It is most advantageous when applied to a so-called two-chamber type tank for obtaining alkali oxide.

In this case, when using the laminated cation exchange resin membrane of the present invention, the surface made of the copolymer having the sulfonic acid group of the group ring as an exchange group should face the anode side of the tank, and the sulfonic acid group should be It has also been found that advantageous results can be obtained when the surface having a weakly acidic cation exchange group is placed toward the cathode side of the tank.

Thus, even in the case of the above-mentioned two-chamber type electrolytic cell, using a sodium chloride aqueous solution with a concentration of 2N or higher as a raw material,
In electrolysis at a current density of A/am, when the cation exchange resin membrane of the present invention is used, it exhibits high performance that cannot be obtained with conventional ion exchange resin membranes.

EXAMPLES Below, the present invention will be described in more detail by showing examples of the present invention, but it goes without saying that the present invention is not limited to these examples in any way.

Example 1 Tetrafluoroethylene and CF2-CFOCF2CF-OCF2-CF2sO2F reinforced with tetrafluoroethylene cloth (70 mesh)
A copolymer (exchange capacity: 0.83 mm IJ equivalent/1 polymer) film (thickness 250 μ) and a copolymer of tetrafluoroethylene and CF2-CFO(CF2)3-COOCH3 (exchange capacity: 1. 10-: IJ equivalent/l polymer) films (thickness 100μ) are stacked together, 0.8kg/cr
They were laminated by heating at 240° C. for 5 minutes under pressure in A.

The laminate was heated at 70° C. in a mixture of 15 ml of NaOH, 200 ml of dimethyl sulfoxide and 650 ml of water.
A cation exchange membrane was obtained by immersion for 4 hours and hydrolysis.

Using the cation exchange membrane thus obtained, rhodium-coated titanium was used for the anode and stainless steel was used for the cathode.
The surface of the membrane having the sulfonic acid group as an exchange group was placed facing the anode side, the distance between the two electrodes was 2.2 crL, and salt was electrolyzed under the following conditions.

Note that the effective area of the diaphragm is 25 crrL.

4N NaCl aqueous solution in the anode chamber and 8N Na in the cathode chamber.
OH was charged, a 4N NaCl aqueous solution was supplied to the anode chamber, and water was supplied to the cathode chamber at a current density of 20 A /
Electrolysis was performed at a liquid temperature of 92°C.

The NaOH aqueous solution overflowing the NaCl solution from the anode chamber was collected, and the current efficiency of the generated caustic soda was determined from the amount of generated caustic soda.

As a result, 13.2N of caustic soda was obtained with a current efficiency of 92%, and the sliding voltage was 4.44 volts.

Example 2 Copolymer of tetrafluoroethylene and CF2=CFOCF2CFOCF2CF2so2F (exchange capacity 0.91 meq/f?polymer)
A film (30μ thick) and a copolymer of tetrafluoroethylene and CF2-CFO(CF2)3COOCH3 (
A film with an exchange capacity of 1.44 meq/r polymer) (
250 μm in thickness) were stacked and laminated in the same manner as in Example 1.

After hydrolysis, the salt was electrolyzed in the same manner as in Example 1, with the side of the group ring having the sulfonic acid group as the exchange group facing the anode side.

As a result, 12-3N caustic soda was obtained with a current efficiency of 94%, and the sliding voltage was 4.30V.

Example 3 Tetrafluoroethylene and CF 2 =CFOCF2 CFO(CF 2 ) 2
802 F and 70 F using trichlorotrifluoroethane as a solvent and azopisisophthyronitrile as an initiator.
Copolymerized with 'C, ion exchange capacity 1.08 meq
/y' polymer was obtained.

The polymer was compression molded at 230'C into a 200μ thick film.

On the other hand, tetrafluoroethylene and CF2=CFO(CF2)2
COH was similarly bulk polymerized at 40°C using diisopropyl peroxydicarbonate as an initiator, and the ion exchange capacity was 1.2.
A 4 meq/'ff polymer was obtained and compression molded at 230°C to form a 30μ film.

Next, these two types of films were laminated at 200°C and then hydrolyzed in 25% caustic soda at 90°C for 16 hours to obtain a cation exchange membrane.

Using a cation exchange membrane obtained by Electrolysis of common salt was carried out in the same manner as in Example 1 using an electrolytic cell with an electrode spacing of 5 mm.

As a result, 10.3N of caustic soda was obtained with a current efficiency of 90%.

Comparative example Tetrafluoroethylene and CF2=CFOCF2-CF-〇CF2-CF2SO2
Salt was electrolyzed in the same manner as in Example 2 using a F copolymer (AR = 0.83 meq/?) film (thickness 100μ), and as a result, 13.4N of caustic soda had a current efficiency of 78. It was obtained in only 5%.

Claims (1)

[Scope of Claims] 1. A perfluorocarbon polymer having a sulfonic acid group or a functional group convertible to the sulfonic acid group, which is a copolymer of a polymerizable nitrogen-containing compound having the following general formula (1) and a fluorinated olefin. formed from ion exchange capacity 0.6-2
A first film-like material having milliequivalent/1 dry resin, and a carboxylic acid group, a phosphonic acid group, and a hydroxyl group consisting of a copolymer of a polymerizable fluorine compound and a fluorinated olefin having the following general formula (2). A polymer having a thickness of 10 μm or more and having an ion exchange capacity of 0.6 to 2 milliequivalents/1 dry resin is formed from a perfluorocarbon polymer having a weakly acidic cation exchange group or a functional group convertible to the group. The two membrane-like materials are laminated and integrated, and if necessary, the above-mentioned; or a fluorine-containing cation exchange resin membrane characterized by being converted to a weakly acidic cation exchange group (X is -F or -CF3, Y and Y' are F or a carbon number of 1 to 1) 10 perfluoroalkyl groups, l
is 6 to 3, m is 0 to 1, n is 0 to 12, and A is -F
, -OH1-0M, -0R1※※ and -NR1R2, R1 is an alkyl group having 1 to 10 carbon atoms, R2 and R3 are F or R1, and M is an alkali metal or quaternary ammonium. (X, Y, Y', ■, m and n are the same as in the above general formula (1), and B is a weakly acidic group selected from a carboxylic acid group, a phosphonic acid group, and a hydroxyl group) (a cation exchange group or a functional group that can be converted into a cation exchange group).