JPS58176222A - Fixation of metal on cation exchange membrane - Google Patents

Abstract

PURPOSE:To fix a metal on the surface of a cation exchange membrane so as to form a metal coating which is capable of being chemically plated uniformly and has excellent adhesion, by impregnating the cation exchange membrane with a reducing agent, then impregnating the membrane with a metal which forms negative metal complex ions in a solution and thereby effecting chemical plating. CONSTITUTION:A cation exchange membrane, e.g., a membrane obtained from a polymer of the formula (wherein R' is -CF3 or -CF2-O-CF3, n is 0 or 1-5, m is 0 or 1, o is 0 or 1, p is 1-6, x is -SO3M (M is H or a metal atom), -SO2F, -SO2Cl, -COOM (M is the same as above), -COOR1 (R1 is 1-5C alkyl), -CN or COF) is impregnated with a reducing agent (e.g., hydrazine) and then impregnated with a metal salt forming negative metal complex ions in a solution (e.g., aqueous solution of H2PtCl6) to effect chemical plating. It is possible to obtain a cation exchange membrane having a metallic layer fixed extremely strongly and uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a cation exchange membrane having metals adhered to its surface, a method for its preparation, and its use in aqueous solution, particularly halide electroestrus.

In recent years, energy saving development has been progressing in the 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 (ion exchange membrane method). From this point of view, in this type of technology, efforts are being made to lower the electrolysis voltage as much as possible.

Conventionally, various methods have been proposed to achieve this, such as considering the material composition and shape of the anode and cathode, or specifying the composition of the ion exchange membrane used and the type of ion exchange group. Although all of these books had certain effects, they were not necessarily completely satisfactory from an industrial standpoint.

On the other hand, in recent years, a technique called the 8P Shōdenneho method has been attracting attention. This book aims to reduce electrolysis voltage by integrating an electrode layer and a cation exchange membrane, and has achieved considerable results. Furthermore, a method has been proposed in which a cation exchange membrane and a porous layer having no electrode activity, such as a metal oxide, are integrated, and this is used as a diaphragm in salt electrolysis.

(%Sho 56-75583. JP-A-Sho 56-.11248
7, Japanese Unexamined Patent Publication No. 56-108888, etc.).

In this way, as a method to reduce the electrolytic voltage,
One method that has become popular is to cover the surface of a cation exchange membrane with a layer made of a certain metal, metal oxide, or the like.

A method for covering a cation exchange membrane with a layer containing a metal and/or metal oxide is a dry method (specifically, a method in which one catalyst particle is sintered and formed using a binder such as PT1'FFi and then hot-pressed onto the membrane surface). 53-52797).

Sawa 873 where all metal can be deposited on the membrane surface in a solution using a reducing agent
．． 1% Kaisho 56-136985) township is known.

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

As a result of extensive research into the electrolytic performance of diaphragms using the wet method, we have come to the following conclusions.

1. In the dry method, it is difficult to uniformly adhere the metal layer to the membrane surface, and it is also difficult to achieve reproducibility in the electrolytic performance of the membrane.

Furthermore, during electrolysis, the gold layer cannot be avoided from detaching from the film surface.

It is easier to obtain reproducibility with the wet method than with the dry method. However, since the metal is deposited non-uniformly only on the film surface, the degree of metal separation is seven times higher than that of the dry method.

Furthermore, for the purpose of revising this point, we set the yd1 condition to −! −, it will cause a decrease in current efficiency.

Based on this conclusion, the present inventors conducted further research and found that a reducing agent was present on the membrane surface or in the membrane, and then negative metal lead ions were impregnated in a solution. The present invention was completed by discovering that it is possible to obtain a cation exchange membrane having a metal layer very strongly and evenly bonded to the cation exchange membrane by chemical plating. The effects of the present invention can be roughly explained as follows.

When positive metal complex ions are used, since the exchange groups in the membrane are anion groups, these ions will selectively enter the exchange groups, resulting in non-uniform adsorption. , the performance of the membrane will be degraded. In addition, when the membrane is impregnated with negative metal complex ions, the adsorption part of the membrane, which is uniformly impregnated, is scratched, and reduction occurs in the reducing agent during treatment with the reducing agent. Impossible to plate. In order to solve the above-mentioned drawbacks, by first impregnating the membrane with an additive and then impregnating it with negative metal complex ions, the stiffening agent can be uniformly applied to the membrane surface and inside the membrane. Because / is introduced and the attracting agent is present in -, chemical plating occurs easily.As a result, uniform chemical plating occurs and the metal is fixed to the surface with excellent adhesion. I can do that.

The cation exchange membrane that can be used in the present invention can be obtained from the following polymers: A perfluorocarbon polymer having a cation exchange group and/or a group that can become a cation exchange group. These groups include sulfonic acid groups (
-8o, M (where M is a hydrogen atom or a metal atom), 18ot'F, which is a precursor of a sulfonic acid group, -
F2O, C1, carboxylic acid group (-C!OOM, where M is a hydrogen atom or a metal atom), -C which is a precursor of a force A/boxylic acid group! OF.

-cooR (R is an alkyl group having 1 to 5 carbon atoms) and -C
I can list N. As the polymer, for example,
Examples include electrocombinants represented by the following general formula.

77/ +OF2-CF,-)-Sho OF,-CF-)-Mouse.

Yo C.F.

cy-n' [However, R/= -clF, , -ay, -o-a
y.

n 20-matasha 1 to 5 m 20-matasha 1 0 = (] or 1. p = 1 to 6 x = -90, M (ad hydrogen atom or society II atom).

-C1 to song, F, -8 1000M (M is a hydrogen atom or a metal atom).

-cooy+, (R, = 1 to 5 alkyl group).

-CI+, -COF) Furthermore, a polymer obtained by adding a third component or a fourth component to the above two-component system and bundling it can also be used.

% [Specific combing, for example, the following can be shown.

(He group) ■ (!'F,-(?-0(7,-〇'F,-80.F Atsushi α, -CF-Kui, -α, Partial, F c’y.

wood C.F.

Suga cv-air.

'i't OF, -CF, -8(1,F OF, -('! Bird-80, C1 C.F.

cv-CF, -o-CF.

OF, -CP, -80,F CF, -1”n, F (8th group) O.F.

J-CTI 0-OF, -coocz C.F.

OF.

CFtF, -COOOa.

CFt-ay, -CFt-CFF, -cooca.

(!F, -(!F, -C!OF 1 CF, -CFF-007, -OF, -Cαχ old.

C.F.

coocH.

0 0 1 (! FM CF, -CF, -OF, -C
(1F'0 0 II CF, CP, -CIF, -CF, -
COQIT.

0 0 １　　　　　　floor CF, CF.

T゛ Coo(!FT.

II CF, (!?.

(!F-OF.

0-to the mouth-CF,-C! OF o coocH.

C.F.

In these polymers, the exchange group capacity should be set to (Lamenu dry resin ~ 1.5 meq/g dry resin!!
It is preferable to section.

In the present invention, it is possible to use these polymers formed into a film alone, but it is also possible to use a sulfonic acid group or a group that can be converted into a diagnostic group and a carboxylic acid group or a group that can be converted in general. It is also possible to use a polymer in which a polymer having a sulfonic acid group or a group that can be converted to the above-mentioned type and a polymer having a carboxylic acid-based group that can be converted to the above-mentioned type are layered on each side. can.

Such a film-like material is composed of a polymer having a sulfonic acid group or a group that can be converted into the above (for example, a group (A) polymer), and a polymer having a carboxylic acid group or a group that can be converted to the above (for example, a polymer of group (A)). (B) group polymers) can be obtained by forming them into a film shape and then gluing them together, or a film form of a polymer having only a sulfonic acid group or a group that can be converted into the above group. It can also be obtained by chemically treating only one side of the substance to change these groups to carboxylic acid groups.

Furthermore, it can also be obtained by chemically treating only one side of a film-like polymer having only carboxylic acid groups or groups that can be converted into the above-mentioned groups to convert these groups into sulfonic acid groups. The thickness of the film used is generally 50 μm to 500 μm, 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, the ion exchange membrane obtained from such a polymer membrane is impregnated with a reducing agent.

As the reducing agent, for example, an aqueous solution of hydrazine, NuFIR, or Na II PO* may be used.

In the second step, the membrane is impregnated with metal salts that form negative metal complex ions in solution. Examples of metal salts that form negative metal complex ions in solution include K and p dissolved in hydrochloric acid.
Aqueous solution of acx, , a, ptcx.

Aqueous solution of Kt (Ni (c N) a), Km
Aqueous solution of (Ru (aN),).

A mixture of these liquids and the like can be mentioned.

The time for impregnating these salts into the membrane is several seconds to several tens of minutes, and the steps of impregnating the reducing agent and impregnating the above-mentioned salts may be repeated until the desired deposit is obtained.

Example 1 OF, Tsukasa F, and OF, MiF -0-CF, -0F-0
-α7-CF, -Gloss, F heat OF.

(exchange capacity Q, 92 mm IJ equivalents/g dry) film (5 mils) of copolymer with C
oo(! Shared electricity OF with Us.

After bonding with a film (2 mil) of the combined product (exchange capacity IIL 96 meq/g dry), hydrolysis was performed (7 to obtain a two-layer structure membrane of carboxylic acid groups and sulfonic acid groups).

Next, this layer was subjected to a diving treatment, and then set in a cell so that only the carboxylic acid base layer could be treated.

Next, after impregnating with 10 volumes of hydrazine aqueous solution, 1
An aqueous solution of 5 wt %)% Pt01s was contact impregnated onto the membrane surface. Next, after thoroughly washing with water, repeat the above treatment twice (
However, the time for one contact is 15 minutes. ) was repeated and then treated with 10 weight 14 NaOH aqueous solution at 60-70°C.

A salt electrolytic cell was assembled so that platinum was fixed on the carboxylic acid base layer obtained above and the carboxylic acid base layer of the ion exchange membrane faced the cathode. Titanium expanded metal coated with ruthenium oxide was used as the anode, and expanded metal made of iron was used as the cathode. The anode and the membrane were brought into contact with each other under pressure, and the cathode and the membrane were brought into contact with each other under pressure.

When saturated saline was supplied to the anode chamber and water was supplied to the cathode chamber, and the caustic soda concentration in the cathode chamber was maintained at 65%, electrolysis was carried out at a temperature of 90°C and a current density of 30A/-, the voltage was 320 volts and the current efficiency was It was 95-. Also, even after 6 months of operation, the voltage increased by only 20+mV. If a clear film is used after the above treatment, the voltage will be 4.
The current efficiency at 5 holts was 96-.

Comparative Example 1 Using the membrane used in Example 1, reducing agent and H, P t C
When the Is impregnation procedure was reversed, almost no zeta-filtration chemical plating was performed.

Example 2 (!?, -CF, and CFW-"C7'OC1'I
OF 0-01% CFW CooCHsCF.

A cation exchange membrane was obtained by forming a 7 mil thick film of a copolymer with (exchange volume: 14 mm/g dry) and then hydrolyzing it.

After fixing platinum using the present cation exchange membrane under the same conditions as shown in Example 1, the membrane was operated under the same conditions as in Example 1.

At 527 volts, the current efficiency was 95 cm, and the increase was only 2511 V after 6 months of operation.

When using a membrane that is not treated with the present invention, the voltage is 552 volts. What is the current efficiency? It was 5.

Patent applicant: Toyo Soda Kogyo Co., Ltd.

Claims (1)

[Claims] t. A cation exchange membrane characterized in that the cation exchange membrane is impregnated with a reducing agent, then impregnated with a metal salt that forms a negative metal complex ion in a solution, and then chemically plated. A method of attaching metal to 2. The method according to claim 1, wherein a cation exchange membrane in which the λ exchange group is a sulfonic acid group is used. (5) The method according to claim 1, which uses a cation exchange membrane whose exchange groups are carboxylic acid groups. The method according to claim 1, which uses a cation exchange membrane having a multilayer structure in which the exchange groups are composed of sulfonic acid groups and carboxylic acid groups. 5. The metal to be fixed is platinum, palladium, ruthenium,
A method according to claim 1.2.3 or 4, wherein nickel or a mixture thereof is selected.