JPS6347389A - Method for electrolyzing aqueous solution of alkali metal salt - Google Patents

Abstract

PURPOSE:To obtain a highly concd. alkali metal hydroxide soln. with high current efficiency by spreading a cation exchange membrane having a specified ion exchange membrane layer contg. fluorine on the cathode side between anode and cathode and by electrolyzing an aq. soln. of an alkali metal salt. CONSTITUTION:When a cation exchange membrane is spread between anode and cathode in an electrolytic cell and an aq. soln. of an alkali metal salt is electrolyzed to produce the hydroxide of the alkali metal, a cation exchange membrane having a cross-linked sulfonic acid type ion exchange membrane layer contg. fluorine on at least the cathode side is used as the cation exchange membrane. The pref. ion exchange capacity of the ion exchange membrane layer is about 0.4-1.3 milli equivalent per 1g dry resin and the pref. concn. of ions fixed by the layer in pure water is >=about 3.0 milli equivalent per 1g H2O. Thus, an alkali metal hydroxide soln. having >=about 30wt% concn. is obtd. with >=about 90% current efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for electrolyzing an aqueous alkali metal salt solution. Specifically, the present invention provides an electrolysis method that uses a specific cation exchange membrane as a diaphragm and is suitable for producing particularly highly concentrated alkali metal hydroxide solutions with high current efficiency.

[Prior art and its problems] Conventionally, the electrolysis technology of aqueous alkali metal salt solutions has progressed, particularly in the development of a method to obtain chlorine and sodium hydroxide by electrolyzing a sodium chloride aqueous solution in an electrolytic cell using an ion exchange membrane as a diaphragm. , efforts are being made to improve the power consumption rate through increasingly higher current efficiency and lower sliding voltage. Among these technical trends in ion-exchange membrane electrolysis, improvements in fluorine-containing ion-exchange membranes have been primarily studied to improve current efficiency, and various proposals have already been made.

In particular, in industrial ion-exchange membrane electrolysis, in order to obtain high-concentration sodium hydroxide with high current efficiency, ion-exchange membranes are generally made of fluorine-containing resin and have a carboxylic acid type membrane layer at least on the cathode side. Use is recommended. Therefore, such a fluorine-containing carboxylic acid type ion exchange membrane generally involves converting the sulfonic acid type into a carboxylic acid type by oxidizing or reducing at least one side of the fluorine-containing sulfonic acid type ion exchange membrane, Alternatively, it is manufactured by a method of laminating a fluorine-containing sulfonic acid type membrane and a fluorine-containing carboxylic acid type membrane.

However, fluorine-containing carboxylic acid type ion exchange membranes have problems with long-term stability under harsh atmospheres such as high-concentration and high-temperature alkali hydroxide generated during electrolysis, and as mentioned above, fluorine-containing This method is complicated because it requires multiple synthesis steps after producing a sulfonic acid type ion exchange membrane.

On the other hand, fluorine-containing sulfonic acid type ion-exchange membranes are said to be chemically more stable than the above-mentioned fluorine-containing carboxylic acid type ion-exchange membranes, but they tend to undergo dimensional changes due to swelling and contraction during electrolysis. It is said that this is easy to occur and causes a decline in membrane performance over time, making it impossible to obtain highly concentrated alkali hydroxide with high current efficiency. For example, in Japanese Patent Application Laid-open No. 49-1497, tetrafluoroethylene F3 and CF 2 =CFOCF 2 CFOCF 2
Using a perfluorosulfonic acid type ion exchange membrane with a non-crosslinked structure obtained by copolymerizing CF2SO2F, 3
It is described that 7% sodium hydroxide can be obtained with a current efficiency of 80%. Also, JP-A-55-160030
Also in the publication, tetrafluoroethylene and CF 2
= CFOCF 2 CF 2 CF 2 Using a cation exchange membrane synthesized from 2S02F, 35% sodium hydroxide is obtained with a current efficiency of 65%. Furthermore, JP-A-57-25332 discloses tetrafluoroethylene, CF2=CFOCF2CF2SO2F and CF2
= Using a cation exchange membrane obtained by polymerizing CF 2 CF2G1, 12% sodium hydroxide can be exchanged with 91% current efficiency, 20% sodium hydroxide can be exchanged with 83% current efficiency, and 32% sodium hydroxide can be exchanged with 32% sodium hydroxide. It is described that each is obtained with a current efficiency of 74%.

Therefore, for example, in Japanese Patent Application Laid-open No. 60-243292, 10 (CF 2 )a-A (n is 1 to 3
, A is a sulfonic acid type ion exchange group) and has a specified short side chain type ion exchange group and has an ion exchange capacity of 0.
．． 5-1.2 meq/g dry resin surface yi
A manufacturing method has been proposed in which a fluorine-containing sulfonic acid type ion exchange membrane having a fluorine-containing sulfonic acid type ion exchange membrane is used to protect the concentration of the generated alkali hydroxide to 40% by weight or more and conduct electrolysis at a high current efficiency of 90% or more.

The object of the present invention is to use a fluorine-containing sulfonic acid type ion exchange membrane made of raw materials that are relatively easy to synthesize, and to conduct a high concentration of alkali metal hydroxide at a high current density, for example, 30% or more of sodium hydroxide. The present invention provides an electrolysis method that achieves a current efficiency of 90% or more and a low sliding voltage.

[Means for Solving the Problems] In order to achieve the above object, the present inventors, as a result of intensive research, have developed an anode having a sulfonic acid type fluorine-containing ion exchange membrane layer having a crosslinked structure at least on the cathode side. The inventors discovered that a highly concentrated alkali hydroxide can be obtained with high current efficiency by using an ion exchange membrane, leading to the completion of the present invention.

That is, the present invention provides a method for electrolyzing an aqueous alkali metal salt solution to produce an alkali metal hydroxide using an electrolytic cell in which a cation exchange membrane is disposed between an anode and a cathode. This is a method for electrolyzing an aqueous alkali metal salt solution, characterized by using a cation exchange membrane having a sulfonic acid type fluorine-containing ion exchange membrane layer having a crosslinked structure on its side.

In the present invention, it is important to use a specified cation exchange membrane having a sulfonic acid type fluorine-containing ion exchange membrane layer having a crosslinked structure. The structure is not particularly limited as long as it has a sulfonic acid type fluorine-containing ion exchange membrane layer having a structure. For example, the entire membrane can be made up of only a sulfonic acid type fluorine-containing ion exchange membrane layer with a crosslinked structure.

The membrane layer other than the sulfonic acid type fluorine-containing ion exchange membrane J- (cathode side surface layer) having a crosslinked structure (
For example, it may be constructed with another ion exchange membrane layer (via an intermediate layer if necessary). At this time, the sulfonic acid type fluorine-containing 8-layer ion exchange layer having a crosslinked structure has an ion exchange capacity of 0.4 to 1.5% in order to obtain 30% by weight or more of sodium hydroxide with a current efficiency of 90% or more. 3 milliequivalent/g dry resin, fixed ion concentration in pure water is 3.0 milliequivalent f
It is preferable that it is 1,/g-H20 or more.

The method for producing the cation exchange membrane used in the present invention is not particularly limited. For example, ■ a method of polymerizing a fluorine-containing divinyl compound and a fluorine-containing vinyl compound having a sulfonic acid group or a functional group that can be converted into a sulfonic acid group, and introducing a sulfonic acid group if necessary, ■ an ion exchange group or ion exchange A fluorine-containing vinyl monomer having a sulfonic acid group or a functional group convertible to a sulfonic acid group, a fluorine-containing divinyl monomer, and a polymerization initiator on a non-crosslinkable film polymer having a functional group convertible to a sulfonic acid group. A method of casting and polymerizing a mixture consisting of;
Methods such as casting and polymerizing a monomer mixture that forms a non-crosslinked polymerized membrane containing an ion exchange group or a fluorine-containing vinyl monomer convertible to an ion exchange group are particularly preferably used.

As the fluorine-containing divinyl compound that constitutes the fluorine-containing polymer having a crosslinked structure of the above-mentioned cation exchange membrane,
For example, CF3 CF, = CFO (CF to CFO). ~, (CF to C, O
), ~,.

CF3 (CFCFaO)a-jCF=CF,.

CF3 CF,=CFO(CF2CF2). -, (CF Yu), -
KaF3 (OCFCF). -30CF=CF.

CF3 CF2= CF (CF,),,-,. (OCF CF
2) 6~.

0CF=CF2゜ CF2 = CF (CF,), -, CF = CF.

At least one compound represented by CF2=CFO(CF2)2~0CF= which is particularly easy to polymerize.
CF2 is preferred.

Further, as a fluorine-containing vinyl compound having a sulfonic acid group or a functional group convertible to a sulfonic acid group, for example, CF3 CFa= CF O (CFzCFO) o-J (C
Fa) a -3S 0AX (X is CQ, l FI O
HI 0CH310C2H51ONa, OK, NH2,
NHCH2CHzNHztNHCH2CH2N” (C
H3) is a type of 3CQ-).

CF2=CFSO2F, CF2=CFSO3CH+CF
2=At least one compound represented by CFO(CF2CF2)1-3I.

In order to obtain the desired ion-exchange membrane having a crosslinked structure, it is necessary to use the entire monomer of the fluorine-containing vinyl compound and the fluorine-containing vinyl compound having a sulfonic acid group or a functional group that can be converted into a sulfonic acid group. It is generally desirable to maintain the proportion of the fluorine-containing divinyl compound at 30% by weight or more. That is, in a monomer mixture of a fluorine-containing compound having a sulfonic acid group or a functional group to be added to the sulfonic acid group and a fluorine-containing divinyl compound, the charging ratio of the fluorine-containing divinyl compound is 30% by weight or more. As the amount increases, the polymerization rate can be increased, and a polymer having a three-dimensional crosslinked structure can be obtained with a high polymerization rate. On the other hand, if the proportion of the fluorine-containing divinyl compound charged is less than 30% by weight, the polymerization rate will be low and an ion exchange resin having the desired crosslinked structure cannot be obtained. In addition, as the charging ratio of the fluorine-containing divinyl compound is increased to 30% by weight or more, the exchange capacity of the obtained ion exchange membrane decreases. preferable. On the other hand, as the content of the fluorine-containing divinyl compound in the total monomer increases, the ion exchange capacity of the fluorine-containing ion exchange membrane decreases and the membrane resistance increases, so the charging ratio should be 90% or less. is preferred. Furthermore, in addition to the above-mentioned fluorine-containing vinyl compounds, CF2C
F2 (CFLCFO). ~3 (CF2)24F3 0CFY.

CF 3 Clear CF = CFO (CF2CF2). ~, (CF,C
F20)1~3F2Y (Y is -CN, -COF, -COOH, -C0OR1
, -COOM, -CONR2R3, -CONHCH2C
H2N1(2 and -C0NHCH2CH2N” (CH
3) 3■-, where R1 is a carbon number of 1 to 10
．． Preferably 1 to 3 alkyl groups, each R2 and R3 being hydrogen or one of R1, and M being sodium, potassium or cesium).

CF2=CFCOOCH3, CF2=CFCOF.

CF 2 = CF O (CF 2) 2 ~ P (OCH
3) 2゜CF2=CFOCF2 (CF2CF2)1~
．． HIH3 CF2=CF2 (CF2CF). ~30Rf (
R is a perfluoroalkyl group having 1 to 10 carbon atoms),
CF2=CF2. CF2:CF(Jl, CF3CF:C
F2. CF2=CF2. Fluorine-containing monomers such as CF2=CH2 and polytetrafluoroethylene.

Fine powders, oligomers such as copolymers of tetrafluoroethylene and hexafluoropropylene, copolymers of tetrafluoroethylene and alkyl vinyl ethers, or perfluorohexane, perfluorohebbutane, polyfluoroethers, trichlorotrifluoroethane, perfluoro A solvent such as polyether can be added to adjust the viscosity of the solution and the sinterability of the resulting film.

As an initiator for copolymerizing a fluorine-containing divinyl compound and a fluorine-containing vinyl compound having a sulfonic acid group or a functional group that can be converted into a sulfonic acid group, diacyls such as benzoyl peroxide, lauroyl peroxide, and isobutyryl peroxide can be used. Peroxide, hydroperoxide such as cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide.

Dialkyl peroxides such as di-t-butyl peroxide and trichloroacetyl peroxide; alkyl peresters such as t-butyl peroxyneodecanoate and -butyl peroxybiplate; bis(4-t-butylcyclohexyl) peroxide; Barcarbonates such as oxydicarbonate diisopropyl baroxidine carbonate.

Azo initiators such as azobisisobutyronitrile, azobisisochlorohexanecarbonitrile, succinic acid peroxide, general formula % formula %) (However, B is hydrogen or fluorine atom 1m is 1 to 24,
dipentafluoropropionyl peroxide, ditetrafluoroprobionyl peroxide, dihebutafluoroptyryl peroxide, di(trichlorooctafluorohexanoyl)peroxide, di(tetrachloroundecanoyl), where n is 1 to 10); Fluorine-containing diacyl peroxides such as Shiba-fluoro-2-n-propoxyprobionyl peroxide, Shiba-fluoro-2-isopropoxyprobionyl peroxide, and the like.

N F 3 p N 2 F 4 t N 2 F 2
*CF3C(NF2)=C(NF2)CF3゜CF3
It is possible to use a fluorine-containing nitrogen compound such as CF (NF2)C(NF)CF3, an initiator such as potassium persulfate, ammonium persulfate, or ultraviolet rays or ionizing radiation. Among these polymerization initiators, an initiator that is soluble in the monomer mixed solution, whose half-life temperature is below the boiling point of the monomer used under normal pressure, and which can produce a crosslinked resin at a high polymerization rate. is necessary. Initiators that meet these conditions include fluorine-containing sialic silver oxide and peroxydicarbonate.

CF 3 C(NF 2 ) = C(NF 2
) CF3.

It is preferable to use one or more polymerization initiators such as CF3C(NF2)C(NF)CF3. The amount of these initiators added is 0.1 to 10% by polymerization, preferably 0.5 to 5% by polymerization, based on the monomer.

Note that it is also possible to use these initiators after diluting them with an organic solvent. The polymerization temperature is -80°C to 400°C, preferably -10°C to 150°C, and the polymerization temperature may be raised stepwise to complete the polymerization.

In addition, polymerization is carried out in the presence of an inert gas such as nitrogen at a temperature of -70 mm.
It is preferable to carry out under a pressure of Hg to 20 kg/cTI+2. As the form of polymerization, bulk polymerization is recommended to achieve a high polymerization rate.

In addition to the above bulk polymer resin, polytetrafluoroethylene, a copolymer of ethylene and tetrafluoroethylene, a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, a copolymer of tetrafluoroethylene and perfluorovinyl sulfonyl fluoride , copolymer of tetrafluoroethylene and perfluorovinyl carboxylic acid ester, polyvinylidene fluoride, polyvinyl chloride.

Fabrics such as cloth and net made of polypropylene, etc.

It is preferable to use a nonwoven fabric 11!4+ film, porous film, tube, etc. as a support during polymerization.

Furthermore, the above-mentioned tetrafluoroethylene fibers are treated with metallic sodium, or tetrafluoroethylene and perfluoroalkyl vinyl ale, tetrafluoroethylene and perfluorovinylsulfonyl fluoride, or tetrafluoroethylene are added to the fibers made of tetrafluoroethylene. It is also possible to use m-products obtained by impregnation polymerization or graft polymerization of one type of perfluorovinyl carboxylic acid ester in the presence of a radical polymerization initiator or radiation. Or stainless steel.

Metals such as a wire mesh, punched metal, M-bound plate, etc. made of titanium, nickel, platinum, etc. can be used as the support.

Furthermore, in order to obtain an ion exchange membrane, (1) the block polymer polymerized into a cylindrical shape is cut;

(2) The monomer mixture is cast onto a flat plate and polymerized.

(3) Pour the monomer mixture into the slit and polymerize.

(4) A viscous monomer mixture obtained by polymerizing the monomer mixture to some extent is applied to a reinforcing material made of polytetrafluoroethylene, and both sides are sandwiched between films of tetrafluoroethylene, stainless steel, polyester, polyvinyl alcohol, polyethylene, etc. and polymerized. do. Further, by performing polymerization using a release film roughened by subjecting such a release film to blasting or grinding, the surface of the polymerized film is roughened.

(5) A low polymer obtained by polymerizing the monomer mixture to some extent is coated on a terafluoroethylene support using a doctor knife or the like, and then sandwiched between release films and polymerized.

(6) A drum in which a support made of tetrafluoroethylene and a release film are concentrically wound is placed in an autoclave, the drum is evacuated, and the degassed monomer mixture is poured into the autoclave and polymerized.

(7) On the film-like material obtained by polymerizing the monomer mixture, a mixture of monomers of the same or different types, or a monomer mixture obtained by partially polymerizing them, is present, or a mixture of these monomers is added. By superimposing the impregnated films and then polymerizing them, a membrane-like material having a multi-N structure is obtained.

(8) After immersing a fluorine-containing ion exchange membrane or a fluorine-containing base ion exchange membrane in a monomer mixture, it is sandwiched between films such as polytetrafluoroethylene and subjected to impregnation polymerization.

The monomer mixture is a solution containing a fluorine-containing divinyl compound, a fluorine-containing vinyl compound having an ion exchange group or a functional group convertible to an ion exchange group, and a polymerization initiator.

In order to introduce sulfonic acid groups into the copolymer thus obtained, a cation exchange membrane can be obtained by performing a hydrolysis treatment using an alkaline solution of KOH or NaOH.

The surface of the ion exchange membrane thus obtained can also be roughened by grinding. Also Ti02-Zr0
Thin film made of 2-polytetrofluoroethylene etc., Ru
O2-1n203-polytetrafluoroethylene, N1
- A thin film made of polytetrafluoroethylene or the like, a vapor-deposited metal film, etc. can be bonded to one or both sides of the film.

The present invention is characterized by the use of the above-described specific cation exchange membrane, and is not particularly limited in other respects.

For example, the electrolytic cell itself used in the present invention is not particularly limited, and any conventionally known electrolytic cell can be used as is.

The anode is generally known as a dimensionally stable electrode (DSE), and is a perforated plate made of titanium or the like, such as bunched metal, expanded metal, or wire mesh, with many holes of about 0°5 to 10++ ua on each side. with a porosity of 30
% or more of the porous plate is coated with lutetium oxide, platinum oxide, palladium oxide, or platinum group metals such as platinum, iridium, palladium, or their oxides, or these metals or their oxides are coated with titanium oxide, zirconium oxide, etc. The electrodes are coated with a mixture of materials such as, and the cathode is made of mild steel.

A porous plate made of nickel or the like and having the same shape as the anode is used as it is, or it is coated with nickel or sintered material using a bath of an active substance such as a sulfur-containing nickel compound. Further, the anode chamber of the electrolytic cell is generally made of titanium, and the cathode chamber is made of iron, but it may be advantageous to use nickel plating or lining if necessary. As for the structure and materials of the electrolytic cell, conventionally known structures and materials may be used without any restriction.

Electrolysis is carried out at a concentration of 3.0 in the aqueous alkali metal salt solution in the anode chamber.
~5N, especially 3.5~4N for sodium chloride aqueous solution.
By maintaining the temperature at 5N, alkali metal hydroxides such as caustic soda are produced in the cathode chamber. In this case, a high concentration of caustic alkali can be obtained only by the water molecules accompanying the ions moving from the anode chamber to the cathode chamber through the ion exchange membrane, but there is also the risk of causing damage such as a decrease in current efficiency. Generally, it is preferable to supply water or dilute caustic alkali to the cathode chamber of the electrolytic cell and conduct electrolysis while maintaining an appropriate concentration. Of course, it is also possible to use a recirculation method in which a portion of the cathode chamber solution is extracted and supplied again. In the present invention, it is generally preferable to obtain about 30 to 48% caustic alkali.

Other conditions during electrolysis, such as the temperature of salt water and caustic alkali during electrolysis, are usually 60 to 100°C, preferably 8°C.
Electrolysis is carried out at a temperature of about 0 to 90° C., a current density of up to about 50 A/dm2, an internal pressure of the tank during electrolysis usually below 1 atm (gauge), and a cathode chamber pressure slightly higher than an anode chamber pressure.

[Effects] The method of electrolyzing an aqueous alkali metal salt solution using the sulfonic acid type ion exchange membrane having a crosslinked structure of the present invention has a higher It is possible to obtain high concentrations of alkali metal hydroxides with high current efficiency and low sliding voltages. Furthermore, since it has a cross-linked structure, it has the characteristic that the dimensional change of the membrane during electrolysis is small.

[Examples] Hereinafter, the present invention will be explained based on Examples, but the present invention is not particularly limited to the following Examples.

Example 1 A porous membrane made of polytetrafluoroethylene with a thickness of 150 mm and an average pore diameter of 10 μm, and a polytetrafluoroethylene-hexafluoroethylene copolymer made of a tetrafluoroethylene-hexafluoroethylene copolymer with both surfaces roughened with No. 400 abrasive paper. After spirally wrapping a 100μ release film around a glass rod, it was placed in a stainless steel autoclave, and CF2 = CFOC was heated under reduced pressure.
F2CF20CF=CF27.0 parts by weight, CF3CF2
COO CF 2 CFOCF 2 CF 2 So 2 F
A monomer mixture consisting of 3.0 parts by weight and 0.2 parts by weight of (CF3CF2COO)2 was introduced, and 6 kg/
l? Polymerization was carried out at 30° C. for 2 days under nitrogen pressure of m2. After polymerization, the release film was removed and the resulting film-like polymer was exposed to N.
8 parts by weight of aOH15j, 30 parts by weight of dimethyl sulfoxide, and 55 parts by weight of water at 85°C.
The sulfonyl fluoride groups were converted to sodium sulfonate groups over time. The ion exchange capacity of this ion exchange membrane was 0.65 millifl/g of dry resin.

Using this cation exchange membrane, a two-chamber electrolytic cell (effective area:
50(2)2. Anode ruthenium dioxide showcased titanium electrode,
Cathode: iron, distance M between membrane and cathode: 4 mm, membrane and anode in close contact,
A 5N-NaC aqueous solution was supplied to the anode chamber using an electrolysis temperature of 90 DEG C. and a current density of 30 A/dm2 to produce a 33% sodium hydroxide aqueous solution. As a result, the electrolytic voltage was 3.51 V and the current efficiency was 93%.

Example 2 A porous film made of polytetrafluoroethylene with a thickness of 100μ and an average pore diameter of 5μ and a release film made of polytetrafluoroethylene with a thickness of 50μ were spirally wound around a glass rod, and then wrapped around a glass rod. Put it in an autoclave and under reduced pressure CF2=CFOCF2 CF20CF=CF2
7.2 parts by weight.

A monomer mixture consisting of 2.8 parts by weight of CF2=CFOCF2CF2SO2F and 3 parts by weight of (CF3CF2CF2COO)zO was introduced and polymerized at 20°C for 2 days under nitrogen pressure of 6 kg/am2. After polymerization, the obtained film-like polymer was hydrolyzed by the method of Example 1, and a 33% sodium hydroxide solution was produced in a two-chamber electrolytic cell in the same manner as in Example 1, and electrolytic evaluation was performed. The voltage was 3.32V and the current efficiency was 95%. After boiling this membrane with pure water,
After converting the ion exchange group into a sulfonic acid type with an IN hydrochloric acid aqueous solution, the ion exchange capacity was measured, and the fixed ion concentration was determined by measuring the water content after washing with water. Futa. Note that the ion exchange capacity was 0.95 meq/g dry resin.

Example 3 A cloth made of 200 denier polytetrafluoroethylene threads woven at 50 threads per inch vertically and horizontally was laminated with a porous film made of polytetrafluoroethylene having a thickness of 50 μm and an average pore diameter of 3 μm, and a release film made of No. 1500 was used. Using FEP films with both sides roughened with abrasive paper, these were spirally wound around a glass rod, placed in a stainless steel autoclave, and then CF2 = CFOC was heated under reduced pressure.
F2CF20CF=CF26 parts by weight, CF2=CFO(
CF2) sOcF=cF21 parts by weight.

A monomer mixture consisting of 3 parts of CF2=CFOCF2CF2CF2SO2F and 20.3 parts by weight of (CF3CF2CF2COO) was introduced and combined under a pressure of 6 kg/am2 of nitrogen at 25°C for 2 days. After polymerization,
The membrane-like polymer was taken out, hydrolyzed by the method of Example 1, and electrolytically evaluated with the polytetrafluoroethylene porous membrane side facing the cathode. As a result, the sliding voltage was 3.35 V and the current efficiency was 94% with 33% NaOH.

Example 4 CF2=CFOCF2CF20CF=CF26 parts by weight.

C.F.

CF2=CFOCF2CFOCF2CF2SO2F 4
After partially polymerizing a monomer consisting of 2 parts by weight of CF3CF2COO at 10°C for 4 hours, a 200 denier thread made of polytetrafluoroethylene was vertically polymerized.
Apply to 60 strands/inch of woven cloth and coat both sides with FEP.
The sample was covered with a release film, and further sandwiched between glass plates on both sides, and polymerized at 30° C. for 2 days under nitrogen pressure. After polymerization, take out the membrane polymer and stick it to a stainless steel mold on one side of the membrane polymer.
= CF2 0.7F5 parts by weight, CF3 CF 2 =CF OCF 2 CF OCF 2 C
F2S O2F0.25 parts by weight 1 (CF3CF
After partially polymerizing 20.03 parts by weight of 2COO) at 10°C for 8 hours, it was cast and laminated at 30°C for 1 day under a nitrogen pressure of 6 kg/am2. After polymerization, it was hydrolyzed by the method of Example 1, and electrolysis was performed in the same manner as in Example 1 with the laminate polymerized side facing the cathode side. As a result, N
When the aOH was 33%, the sliding voltage was 3.4.4V and the current efficiency was 95%.

Example 5 CF3 CF2=CFOCF2CFOCF2CF2SO2F 9
A mixture of parts by weight and 21 overlapping parts of (CF3CF2CO2) was poured into an autoclave with a horizontal bottom to produce CF2.
= Introduce CF2 gas, pressurize to 4kg Z mark 2 and 30℃
A non-crosslinked resin layer was polymerized. After absorbing CF2=CF210 parts by weight, the remaining CF2=CF2 was discharged and replaced with nitrogen.

After this, CF2=CFOCF2CF20CF=CF21
0 parts by weight.

A monomer mixed solution consisting of 5 parts by weight of CF3 CF2=CFOCF2CFOCF2CF2SOF and 20.5 parts by weight of (CF3CF2CO2) was cast onto the above non-crosslinked resin layer, and 6 kg
/(2) Polymerization of the second crosslinked resin layer was carried out at 30° C. under a nitrogen pressure of 2 for 2 days.

After polymerization, the obtained film-like polymer was hydrolyzed by the method of Example 1, and electrolytic evaluation was performed with the second crosslinked resin layer facing the cathode side. As a result, the electrolytic voltage was 3.30 with 33% NaOH.
V, the current efficiency was 94%.

Claims (1)

[Claims] 1) In a method of electrolyzing an aqueous alkali metal salt solution to generate an alkali metal hydroxide using an electrolytic cell configured with a cation exchange membrane disposed between an anode and a cathode, the cation exchange membrane comprises at least A method for electrolyzing an aqueous alkali metal salt solution, characterized by using a cation exchange membrane having a crosslinked sulfonic acid type fluorine-containing ion exchange membrane layer on the cathode side.