JPS5922930A - Method for adhering metal closely onto base layer of carboxylic acid of cation exchange membrane - Google Patents

Abstract

PURPOSE:To adhere a metal closely onto a COOH layer of a cation exchange membrane with improved adhesive property, by sticking a polymer having sulfonic acid groups having a high ion exchange capacity to the surface of the cation exchange membrane, and chemically plating the surface of the COOH layer. CONSTITUTION:A perfluorocarbon polymer layer having sulfonic acid groups having within 0.90-1.5meg/g range dried resin exchange capacity is formed on the surface of a COOH layer of a cation exchange membrane, e.g. prepared by using a monomer of the formula [R is CF3 or CF2OCF3; n is 0-5; m and n are 0 or 1; p is 1-6; X is SO2F, SO2Cl or COOR1 (R1 is 1-5C alkyl)], and the resultant polymer layer is then chemically plated with a metal, e.g. Pt, Pd, Lu, Ag or Ni, etc. to adhere the metal onto the surface of the COOH layer. USE:Usable for the electrolysis of halides, etc.

Description

[Detailed description of the invention] Provides a changing membrane, a method for producing the same, an aqueous solution,
It particularly concerns its use in the electrolysis of halides.

A method of producing alkali hydroxide by electrolyzing alkali chloride in an electrolytic cell divided into an anode chamber and a cathode chamber by a cation exchange membrane (In recent years, energy saving development has been progressing in ion exchange deprocessing, and from this point of view Therefore, in this type of technology, efforts are being made to lower the electrolysis voltage as much as possible.

Conventionally, this method has been based on the material of the anode and cathode. Various methods have been proposed, such as considering the composition and shape, or specifying the composition of the ion-exchange membrane used or the type of ion-exchange group, but although they all have certain effects, they are not necessarily sufficient for industrial use. It wasn't satisfying.

On the other hand, in recent years, the SP]lii electrolytic method and the so-called electrolytic wave technique have been attracting attention. Some of these devices aim to reduce the electrolytic voltage by integrating the electrode layer and the cation exchange membrane, and have achieved considerable effects. In addition, a method has been proposed in which a cation exchange membrane is integrated with a porous layer that does not have electrode activity, such as a metal acid, a compound, etc., and is used as a diaphragm in salt electrolysis (Japanese Patent Application Laid-Open No. 56-75585. Japanese Patent Publication No. 1983
-112487, JP-A-56-108888, etc.).

As described above, one trend toward reducing the electrolytic voltage is to cover the surface of the cation exchange membrane with a layer made of certain metals, metal oxides, or the like.

As a method for covering a cation exchange membrane with a layer containing metal and/or metal oxide, there is a dry method (Japanese Patent Application Laid-Open No. 1983-1993) in which catalyst particles are sintered and formed using a binder such as PTFE and then hot-pressed onto the membrane surface. -52297, etc.), the so-called chemical plating method (%
Publication No. 56-36875, Japanese Unexamined Patent Publication No. 56-156985), etc. are known.

The present inventors developed the dry method from the above points of view.

As a result of repeated research on silver content regarding the electrolytic performance of diaphragms using the wet method, we came to the following conclusions.

1. In the dry method, it is difficult to uniformly adhere the metal layer onto the membrane surface, and it is difficult to achieve reproducibility in the electrolytic performance of the membrane. The layer cannot be avoided from separating from the film surface.

λ With the wet method, it is easier to obtain reproducibility than with the dry method. However, since the metal is deposited only on the surface of the film, the separation of the remaining edges is more difficult than the dry method. Furthermore, if the fixing conditions are made stricter for the purpose of improving this point, the current efficiency will be lowered.

The present inventors conducted further studies based on such a conclusion, and as a result, they arrived at the present invention.

That is, first, a perfluorocarbon polymer layer having an exchange capacity of 0.90 to 1.5 mθυ and a sulfo/acid group of the dry resin is formed on the surface of the carboxylic acid base layer of the cation exchange membrane, and then chemical plating is applied. gold on the carboxylic acid base layer of the cation exchange membrane)? This article provides a method for fixing 4.

The monomers used in the production of the cation exchange membrane used in the present invention are, for example, represented by the following general formula % [where R= -CF, , -C! F, -0-OF.

n=0 or 1-5 m=o or 1 o=0 or 1. P=1~6 X=502F, So, Cl, C0OR, (R,
Specific examples of the polymer used in the production of the cation exchange membrane produced using the above-mentioned single-phase material (1-5 alkyl group), ON, cow) include, for example, the following polymers. .

(Group A) OF, -CF-0-CF, -CF, -8o, Fchi OF, -OF, -8o, F 0F, -OF, -8o, IP 1 C.F.

0F-OF, -0-OF.

OF, =C! ? , -8o,? O.F.

CF, -8o, F (Group B) " Ft C! F-OF.

0-OF, -0000H.

0? .

OF.

OF, -0000H.

■ OF, -CF, -OF, -OF, -000C! H.

OF, -OF, -COF C! ? , -(3F-0-OF, -CF, -COOCH.

OF.

0000H.

O0 1 OF30F, -OF, -OF, -00700 1 OF, C! F, -OF, -C! F,-C! 0
OcH.

0 0 1st grade CFsCF.

Out C00C horse Oo 1 OF, CF, -0F2-00F 0 I CF, OF.

F. The exchange group capacity at 0.5 to 1.0 me
A range of q/f' dry resins can be used.

The polymer shown in Group B is a perfluorocarbon polymer that becomes a carboxylic acid group and has a chloro group, and has an exchange group capacity of α6 to t 5 meq when converted to a carboxylic acid group.
/f/dry resin can be used.

Among these polymers, Group A polymers are used either by chemically treating the surface of the membrane to convert the sulfonic acid groups on the surface into carboxylic acid groups, or in a laminated form with a membrane of Group B polymers. .

The cation exchange membrane used in the present invention is 50μ to 5μ
A thickness of 0.00 μm is generally used, and an appropriate thickness is selected in consideration of the specific conductivity and current efficiency of the film.

In the first step of the present invention, a polymer layer having sulfonic acid groups is formed on the carboxylic acid base layer. The polymers used to form the polymer layer having sulfonic acid groups include:
The above-mentioned Group A polymers can be used, but the exchange capacity of the polymers used is in the range of 19 to 1.5 meq/F/dry resin.

A method for forming a polymer layer having a sulfonic acid group on the surface of a carboxylic acid base layer is, for example, by attaching the polymer to the carboxylic acid ester base layer of a cation exchange membrane by coating or heat-pressing, and then hydrolyzing it. Here are some ways to do it. At this time, it is also possible to use a polymer in which a metal, metal oxide, or inorganic substance such as zeolite is appropriately mixed. Of course, the method for forming the polymer layer on the carboxylic acid base layer is not limited to the above method.

In the second step of the invention, the formed polymer layer is chemically plated. The metal to be fixed to the sulfonic acid base layer formed on the carboxylic acid base layer of the cation exchange membrane is not particularly limited as long as it has a sufficient catalytic effect on the cathode reaction, but platinum, palladium, Platinum group metals such as ruthenium and iridium, silver and nickel, or mixtures thereof are used. These metals are fixed to the membrane by chemical plating. However, the chemical plating method itself is a normal method and there are no particular restrictions. For example, a metal salt solution to be plated is placed on the cathode side of a cation exchange membrane, and a reducing agent solution is placed on the anode side, and the metal salt solution permeates into the membrane. A method of plating using the difference in speed (Patent Publication No. 55-58954), in which a membrane is immersed in a metal salt solution, the membrane is impregnated with the metal salt, and then the membrane is immersed in a reducing agent. A method of depositing metal on the membrane surface,
A method using an electroless plating solution can be selected as appropriate, and the above methods may be combined.

Further, if the electrical conductivity of the fixed metal is 1Ω-10-1 or more, the purpose can be sufficiently achieved, and a conductivity of 5\ can be easily achieved by chemical plating.

The effects of the present invention can be roughly explained as follows.

When chemical plating is applied on a carboxylic acid base layer, there is a major problem of poor adhesion. This is because metal ions cannot be completely adsorbed because the pKa of carboxylic acid groups is larger than that of sulfonic acid groups, and the water content of the layer containing carboxylic acid groups is smaller than that of sulfonic acid groups. It is thought that this decreases the density of the adhered Kinro and reduces the adhesion.

In order to solve this problem, a layer to be chemically plated may have a high water content and a functional group with a low pKa.

Therefore, in the present invention, a cation exchange membrane with extremely good adhesion is produced by chemically plating a polymer having a large exchange membrane and a sulfonic acid group with a small pKa on the layer to be chemically plated. I was able to get it.

Below, we will show examples that specifically demonstrate the effects. Note that the present invention is not limited in any way by these specific examples.

Example 1 CF, =OF, and OF, =OF'-0-OF, -
0F-0-OF, -OF.

C.F.

and then hydrolyzed to increase the exchange capacity to 190
mθq/? - Obtained a dry resin cation exchange membrane.

Subsequently, the membrane was subjected to sulfonyl chloride treatment with phosphorus pentachloride (
2 mils) and then treated with a reducing agent to obtain a two-layer structure film of sulfonic acid groups and carboxylic acid groups. Subsequently, the carboxylic acid group was esterified with a methanol/hydrochloric acid system.

On the other hand, C! F, = CF, and CF, = C! F-0-OF,
-OF -0-OF, -■ V3 (3F2-8O,F Which copolymer exchange container is 1.
Copolymerization was carried out to give a dry resin of 0 meq/liter. Subsequently, the copolymer was thermocompression bonded (160°C, 150 Kg/cm') onto the ester layer of the film obtained above.
,Ta.

Next, the film was hydrolyzed with methanol/10% caustic soda to obtain a cation exchange membrane. Next, the thermocompression bonded layers were set for reaction treatment.

Next, add H, PtC1, *6 to 1 t of 2.5% ammonia water.
After dissolving H,0(1f) and allowing it to stand for 2 hours, the membrane was treated at room temperature for 4 hours. After thorough washing with water, the salt electrolytic cell was assembled so that the carboxylic acid layer faced the cathode side.

An expanded titanium metal coated with ruthenium oxide was used as an anode, and an expanded metal made of iron was used as a cathode. Saturated salt solution is supplied to the anode chamber and water is supplied to the cathode chamber to maintain the caustic soda concentration of the cathode chamber solution at 35% while maintaining the temperature at 90°C, current, and density at 30 AA! When electrolyzed with
The voltage was &15 volts and the current efficiency was 95%.

No "peeling" occurred even after three months of operation.

Comparative Example 1 A carboxylic acid layer was chemically plated on the film used in Example 1 in the same manner as in Example 1 without applying thermocompression bonding.

When the same operation as in Example 1 was carried out, the voltage was 3.30 volts and the current efficiency was 92%. 6 after about 1 month of driving
"Peeling" had occurred.

Comparative Example 2 The film used in Example 1 was thermocompressed and subjected to the treatment of the present invention. When the same operation as in Example 1 was performed, the voltage was 3.32 volts and the current efficiency was 95%. Ta.

Comparative Example 3 When the two-layer structure membrane used in Example 1 was operated in the same manner as in Example 1, the voltage was 545 volts and the current efficiency was 95%.

Example 2 OF, =(!F, and OF, =C!F-0-OF, -0F-0-OF,
-OF, -80,FCF.

A film obtained from a copolymer with (exchange capacity α9mθv9 when converted to sulfonic acid group, dry resin) and
, =CF, and CF, =OF-0-OF, -0F-0
-CF, -(3F, -C!0OCH.

Film obtained from copolymer with CF3 (exchange capacity 1.0 meq/f when converted to carboxylic acid group, dry resin)
These were heat-pressed and formed into a single film.

Next, on both sides of the film, CF, =CF, and CF,
=Cl0-CF, -0F-0-OF2-OF, -8
o, F0F.

Copolymer with (exchange membrane when converted to sulfonic acid group)
1.0 meq/? Drying [11! lr) by thermocompression bonding (16
0'C.

1sOKp/α2).

Next, the film was hydrolyzed with methanol/10% caustic soda to obtain a cation exchange membrane.

The membrane was dissolved in 1 t of 2.5% ammonia water with H,PtO7,-
It was immersed for 30 minutes at room temperature in a solution in which 6H,0(12) was dissolved and left for 2 hours. After thoroughly washing with water,
Reduce 1- with NaBH4 (α01%) for 2 hours at °C.

When the cation exchange membrane thus obtained was operated in the same manner as in Example 1, it exhibited the following performance.

Current efficiency 95% Electric voltage 510 ports Even after 3 months of operation, 6(su) did not occur.

Comparative Example 4 The membrane used in Example 2, that is, C! F, =OF, and O
F, =C! F-0-OF, -0F-0-OF, -OF
, -8o, ? A film obtained from a copolymer with Fs (exchange film amount α9 meq/f when converted to sulfonic acid group, dry resin) and C
! F, =CF, and C! F, =OF-0-OF, -0F-0-OF,
-(1!F, -000CH.

0F.

A film obtained from a copolymer with (exchange membrane t1. Omeq/?・dry resin when converted to carboxylic acid groups) is thermo-compressed and formed into a single film, and then mixed with methanol/10% caustic soda. It was hydrolyzed to obtain cation exchange. When the membrane was operated in the same manner as in Example 1, the performance was as follows.

Current efficiency: 95% Voltage: 555 volts Comparative Example 5 When the same method as in Example 1 was used in Example 2 without performing chemical plating, the performance was as follows.

Current efficiency: 95% Voltage: 52 o volts Comparative Example 6 The membrane used in Comparative Example 4 was directly chemically plated in the same manner as in Example 2, and then operated in the same manner as in Example 1. It was as follows.

Current efficiency 92% Electric voltage 3.15 volts After one month of operation, peeling occurred.

Example 3 CF, =CF, and CF, =CF-0-OF, -CF-0-CF, -
CF, -000cH.

OF.

A film obtained from a copolymer with (exchange capacity 1.3 meυ when converted to carboxylic acid groups, now dry resin).

A thickness of 7 mils was obtained.

Then OF, ==CF, and OF, =CF-0-(:!F, -0F-0-(3F
, -OF, -8o,? Police OF.

Copolymer with (exchange capacity when converted to sulfonic acid group 1
．． 0 meq/f/dry resin) was thermocompression bonded (160°C, 15 QKf/cm2) onto both sides of the film.

Next, the film was hydrolyzed with methanol/10% caustic soda to obtain a cation exchange membrane.

The membrane was soaked in 2.5% ammonia water 11K H, PtC.
1,.6H20 (12) was dissolved and left for 2 hours, and the sample was immersed at room temperature for 30 minutes. After thorough washing with water, reduction was performed using NaBH4 (0.01%) at 50°C for 2 hours.

When the membrane was operated in the same manner as in Example 1, it exhibited the following performance.

Current efficiency 94% Electric voltage: 525 volts No "peeling" occurred even after 3 months of operation.

Comparative Example 7 The membrane used in Example 3, OF, =OF, and ay,
=CF-0-OF, -CF-0-CF, -OF,
-0000! H.

A cation exchange membrane was obtained by hydrolyzing a copolymer with CF3 (exchange membrane % when converted to carboxylic acid group: 1-5 meq/S', dry resin, thickness 7 mil) with methanol/10% caustic soda. I got it.

When the membrane was operated in the same manner as in Example 1, it exhibited the following performance.

Current efficiency 94% Voltage 545 ports Comparative Example 8 When the membrane used in Comparative Example 7 was directly coated with the chemical plating of Example 4 in the same manner as Example 1, the following performance was obtained. Indicated.

DC efficiency 93% Electricity voltage: 535 volts One peeling occurred after one month of operation.

Comparative Example 9 When the same operation as in Example 1 was performed in Example 3 without chemical plating, the following performance was exhibited.

Current efficiency: 94% Voltage: 535 volts Example 4 A cation exchange membrane similar to that used in Example 2, i.e.
OF, =OF, and CP, =C! F-0-OF, -0F-0-OF,
-OF, -80,'I! ■ Film obtained from copolymer with CF3 (exchange capacity when converted to sulfonic acid group (L9mθq/f・dry resin) and OF, =OF, and OF, =OF-〇-OF, -0F- 0-OF, -CP,
A film obtained from a copolymer with -000CH3CF3 (exchange capacity 1.0 mθq when converted to carboxylic acid group, /r dry resin) was thermocompressed and molded into a single film.

Next, CF on the carboxylic acid ester layer side of the film, =
CF, and OF, =OF-0-C! F, -0F-0-
The co-merger with OF, -OF, -8o and F-Kyo OF3 (exchange capacity 1.0 meq/f when converted to sulfonic acid group, dry resin) was thermocompressed (160'C).
;.

150Kf/cPII.

Next, the film was hydrolyzed with methanol 710% caustic soda to obtain a cation exchange membrane.

After setting the membrane so that the carboxylic acid layer side can react, it was treated with an aqueous solution of nickel sulfate (0.01%) for 30 minutes, thoroughly washed with water, and then treated with an aqueous solution of hydrazine ((101%) at 50°C for 2 hours. When the cation exchange membrane thus obtained was operated in the same manner as in Example 1, it exhibited the following performance.

Current efficiency 95% Electric voltage: 515 volts Even after 3 months of operation, no "1 peeling" occurred.

Example 5 In Example 2, OF, =OF, and OF, =O
F-0-OF, -0F-0-OF, -OF, 7S
When thermocompression bonding a copolymer with O, FFs (exchange capacity when converted to sulfonic acid group is 1.0 meq/P, dry resin), 40% Zr0t is added to the copolymer. A chemically plated cation exchange membrane was obtained in the same manner as in Example 2 except that it was crimped.

When the cation exchange membrane thus obtained was operated in the same manner as in Example 1, it exhibited the following performance.

Current efficiency 95% Electric voltage 505 volts No "peeling" occurred even after 5 months of operation.

Patent applicant: Toyo Soda Kogyo Co., Ltd.

Claims (1)

[Scope of Claims] 1. A method of fixing perfluorocarbon having an exchange capacity α90 to 1.5 m13q7 and having a sulfonic acid group of a dry resin on the surface of a carboxylic acid base layer of a cation exchange membrane. Z. The method according to claim 1, wherein a cation exchange membrane having a carboxylic acid group is used as the cation exchange membrane. The method according to claim 1, wherein a cation exchange membrane having a multilayer structure of a sulfonic acid base layer and a carboxylic acid base layer is used as the A IQ ion exchange membrane. 4. The method according to claim 1, 2 or 3, in which the metal to be fixed is selected from platinum, palladium, ruthenium, iridium, silver, nickel or a mixture thereof.