JP2002363783A - Ion-exchange membrane electrolytic cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably operate an ion-exchange membrane electrolytic cell for a long time. SOLUTION: In the clam type ion-exchange membrane electrolytic cell in which a chamber frame and an ion-exchange are clamped through a gasket, the gasket contains >=50 mass % elastic polymer, the elastic material contains <=9 mass % of a process oil to the elastic polymer, 80 mass % or above of the elastic polymer is EPDM or EPM, and 3-30 mass % of the EPDM or EPM to the elastic polymer has the Mooney viscosity ML (1+4) of <=30 at 100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ion exchange membrane electrolytic cell, and more particularly to an ion exchange membrane electrolytic cell having a gasket having excellent corrosion resistance.

[0002]

2. Description of the Related Art Conventionally, in the salt electrolysis by the ion exchange membrane method, a filter press type electrolytic cell in which chamber frames constituting an electrode chamber and an ion exchange membrane are alternately arranged and fastened has been used. . In this electrolytic cell, a gasket is interposed between the chamber frame and the ion exchange membrane to prevent the electrolyte and gas from leaking out of the electrolytic cell.

As a gasket, a mixture of EPDM (ethylene-propylene-diene rubber) or EPM (ethylene-propylene rubber) and a process oil for improving moldability has been used from the viewpoint of sealing properties and creep properties. Was. However, this gasket did not have sufficient corrosion resistance to hypochlorous acid generated by the reaction between chlorine generated in the anode chamber of the electrolytic cell and hydroxide ions in the cathode chamber.

The following method is known as a method for solving this problem. That is, a method of homogeneously mixing polytetrafluoroethylene with an elastic polymer (Japanese Patent Laid-Open No.
181287), a method using a soft fluororesin (Japanese Unexamined Patent Publication No. 3-64490), a method in which a fluororubber is arranged in a portion in contact with a liquid or a gas, and an EPDM or EPM is arranged outside thereof, and both are integrally molded (Japanese Unexamined Patent Publication No. 3-17068
9, JP-A-4-32593). These methods increase the manufacturing cost of gaskets, EPDM and E.
There were problems such as inferior sealing properties and creep resistance properties than PM.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a conventional EP.
Provided is an ion exchange membrane electrolytic cell having a gasket having excellent corrosion resistance while having the same sealability, creep resistance, and manufacturing cost as DM and EPM, and having excellent ion exchange membrane durability.

[0006]

The present invention is a clamping type ion exchange membrane electrolytic cell in which a chamber frame and an ion exchange membrane are clamped with a gasket interposed therebetween, wherein the gasket contains 50% by mass of an elastic polymer. An elastic body containing at least 9% by mass of a process oil with respect to the elastic polymer, wherein at least 80% by mass of the elastic polymer is EPDM or EPM, and the elastic polymer of the EPDM or EPM is contained. 3-30% by mass is Mooney viscosity ML (1 + 4) 1
Provided is an ion exchange membrane electrolytic cell having a temperature of 00 ° C. of 30 or less.

Until now, gaskets using EPDM or EPM have been mixed with process oil in order to improve the moldability during production. However, in tests by the present inventors, an electrolytic cell using such a gasket was used. It was confirmed that the gasket deteriorated because the process oil deteriorated due to hypochlorous acid and chlorine gas. In order to improve the corrosion resistance of the gasket, it has been found that it is effective to reduce the amount of process oil mixed in the gasket as much as possible.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the mixing ratio of a process oil to an elastic polymer of a gasket is 9% by mass.
It is as follows. Therefore, the amount of process oil deteriorated by hypochlorous acid and chlorine gas is small, so that the gasket as a mixture is less deteriorated and the corrosion resistance is improved. The mixing ratio is 6% by mass or less, more preferably 3% by mass.
It is desirable that the content is not more than mass%.

[0009] The gasket of the present invention contains 50% by mass or more of an elastic polymer. For gaskets, in addition to elastic polymers and process oils, reinforcing agents such as fine silica, clay and talc, fillers such as metal oxides and metal hydroxides, pigments, antioxidants, stabilizers, processing aids ,
An internal release agent or the like may be added and blended.

[0010] 80% by mass or more of the elastic polymer is EP
DM or EPM. As other elastic polymers, hydrocarbon polymers, substituted hydrocarbon polymers, and the like can be used. For example, natural rubber, polybutadiene, styrene
It is a hydrocarbon polymer such as butadiene copolymer or butyl rubber, or a substituted hydrocarbon copolymer such as polychloroprene or nitrile rubber. Further, two or more kinds of elastic polymers may be used as a mixture.

When the gasket of the present invention is manufactured, the amount of the process oil is smaller than that of the conventional gasket, so that the moldability may be impaired. In the present invention, JIS K accounts for 3 to 30% by mass of the EPDM or EPM contained in the gasket with respect to the elastic polymer.
Mooney viscosity ML (1 + 4) 10 specified in 6300
EP of 0 ° C. (hereinafter simply referred to as Mooney viscosity) of 30 or less
Since it is DM or EPM, moldability is improved. It is more preferred that EPDM or EPM having a Mooney viscosity of 20 or less be contained in an amount of 3 to 30% by mass based on the elastic polymer. In particular, it is preferable that EPDM or EPM having a Mooney viscosity of 10 or less be contained in an amount of 3 to 30% by mass based on the elastic polymer.

When a process oil is used in the present invention, a petroleum oil is preferably used as the process oil, and a naphthenic oil or a paraffin oil is particularly preferable. Further, two or more process oils may be used as a mixture.

In the production of the gasket of the present invention, it is preferable that the elastic polymer and, if necessary, the process oil and other additives are sufficiently uniformly mixed. The mixing can be carried out by a conventionally used rubber kneading roll, kneader or Banbury mixer. The mixing conditions are not particularly limited, for example, 30 to 8
By kneading at a temperature of about 0 ° C. for about 10 to 60 minutes, sufficient dispersion and mixing can be achieved.

Further, such an addition mixture can be appropriately dissolved and dispersed in a solvent to form a suspension. Further, so-called wet mixing in which mixing is performed in a solvent from the beginning is also possible. In such a case, a solution mixture can be obtained by using a mixer such as a roll, a ball mill, and a homogenizer. The mixing conditions are desirably determined by selecting optimal conditions according to the type and purpose of the raw materials and the mixture used.

The gasket of the present invention is obtained by subjecting the mixture obtained as described above to molding by a continuous molding method such as extrusion, transfer, roll coating, brushing, impregnation, etc. in addition to molding. can get.

The gasket obtained as described above is
Preferably it is vulcanized. As a vulcanization method, a method conventionally used conventionally can be adopted. For example, a method in which heating is performed while applying pressure in a mold, or a method in which the material is extruded, molded using a calender roll or the like, and then heated in a heating furnace or a steam pot may be employed.

The vulcanization conditions and the like are desirably determined by selecting optimum conditions according to the raw materials used and the blending. The temperature at the time of vulcanization may be 60 to 250 ° C, preferably about 120 to 200 ° C. The heating time is not particularly limited, but is in the range of 1 minute to 3 hours, preferably in the range of 5 minutes to 2 hours, depending on the type of the organic peroxide. When the heating temperature is increased, the heating time can be shortened. It should be noted that reheating treatment of the obtained vulcanized product can also be employed, which is useful for improving physical properties.

The electrolytic cell of the present invention comprises, for example, one or a plurality of anodes, one or a plurality of cathodes, and one or more gaskets. A clamping type electrolytic cell having a separator between them is used, and is used by clamping at a high pressure. The tightening pressure of the electrolytic cell is not particularly limited.
5 to 40 kg / cm ² , especially ²⁰ to 35 kg / cm ²
cm ² is preferred.

As the anode, titanium or titanium coated with a metal oxide is preferably used. As the cathode, a metal plate coated with stainless steel, nickel or a nickel compound is preferably used.
As the ion exchange membrane, sulfonic acid type perfluorocarbon polymer ion exchange membrane (Flemion membrane manufactured by Asahi Glass Co., Ltd.,
Nafion membrane manufactured by DuPont or Aciplex membrane manufactured by Asahi Kasei Corporation) is preferably used. The material of the chamber frame is not particularly limited, but titanium is preferably used as the anode chamber frame, and stainless steel or nickel is preferably used as the cathode chamber frame.

The electrolytic cell of the present invention can be widely used in electrolytic cells having a diaphragm such as electrolysis of an aqueous solution of an alkali chloride such as salt, water electrolysis, and hydrochloric acid electrolysis. When salt is electrolyzed in the electrolytic cell, a saline solution is introduced into the anode chamber of the electrolytic cell,
Chlorine generated during electrolysis is taken out of the anode chamber, the aqueous solution is taken out of the electrolytic cell through the separator, and hydrogen and alkali hydroxide generated by electrolysis are taken out of the cathode chamber.

[0021]

The present invention will be described in detail with reference to Examples (Example 1) and Comparative Examples (Examples 2 and 3). In the examples, “parts” means “parts by mass”.

Example 1 EPDM having Mooney viscosity of 38
(Manufactured by Nippon Synthetic Rubber Co., trade name EP21) 100 parts, MT
30 parts of carbon, 10 parts of EPDM having Mooney viscosity of 8 (manufactured by Mitsui Chemicals, Inc., trade name: EP4010), 3 parts of triallyl isocyanurate, 1 part of organic peroxide (manufactured by NOF CORPORATION, trade name: Parkadox 14), After uniformly mixing with a two-roll kneader, the mixture was formed into a sheet. Next, change this to 16
Press vulcanization at 0 ° C for 30 minutes, and then
Secondary vulcanization was performed at 80 ° C. for 1 hour to obtain a gasket having a thickness of 2 mm.

[Example 2] In place of EPDM having a Mooney viscosity of 8, 10 parts of a naphthenic process oil (trade name: R1000, manufactured by Japan Energy Co., Ltd.) was used.
A gasket was obtained in the same manner as in Example 1. This gasket is a gasket conventionally used.

Example 3 A gasket was obtained in the same manner as in Example 1 without using EPDM having a Mooney viscosity of 8 and using no process oil.

[Evaluation of Formability] The gaskets of Examples 1 and 2 exhibited good moldability, and there was no roughness on the gasket surface.
The gasket of Example 3 had a high viscosity at the time of kneading, so molding was difficult, and the surface of the gasket was slightly roughened.

[Evaluation of Corrosion Resistance] A test piece having a length of 5 cm and a width of 2 cm was cut out from the gaskets of Examples 1 to 3, and the weight was measured. The test piece was sandwiched between titanium meshes at a position of 15 to 20 cm from the lower side in the anode chamber frame of an ion exchange membrane electrolytic cell (trade name: AZEC-M3, manufactured by Asahi Glass Co., Ltd.). Using this electrolytic cell, salt electrolysis was performed for 1 week under the conditions of a current density of 4 kA / m ² , 90 ° C., and a concentration of hypochlorite ion in the anolyte at the outlet of the electrolytic cell of 3 g / L. The weight change rate was calculated. The weight change rate was -13% for Example 1, -19% for Example 2, and 5% for Example 3.

[0027]

According to the present invention, an ion exchange membrane electrolytic cell having a gasket excellent in corrosion resistance and excellent in durability of the ion exchange membrane can be obtained.

Claims (2)

[Claims] 1. A clamping type ion exchange membrane electrolytic cell in which a chamber frame and an ion exchange membrane are clamped with a gasket interposed therebetween, wherein the gasket contains 50% by mass or more of an elastic polymer, and the process oil is elastic. An elastic body containing 9% by mass or less based on the polymer, and 80% by mass or more of the elastic polymer is E
PDM or EPM, wherein said EPDM or EPM
Among them, an ion exchange membrane electrolytic cell having a Mooney viscosity of ML (1 + 4) 100 ° C. of 30 to 30% by mass based on the elastic polymer. 2. The ion-exchange membrane electrolytic cell according to claim 1, wherein the ion-exchange membrane electrolytic cell is an electrolytic cell of an alkali chloride aqueous solution.