JPH0432593A - Gasket for electrolytic cell and its production - Google Patents

Abstract

PURPOSE:To produce a gasket for the electrolytic cell having a long service life by integrally forming a composition consisting of fluororubber and EPDM rubber in a specified ratio by the vulcanization reaction of a peroxide. CONSTITUTION:A composition consisting of 25-95wt.% fluororubber and 75-5wt.% EPDM rubber or EPM rubber and added with a peroxide is charged into a frame-shaped metallic mold and heated at 140-190 deg.C for 3 to 30min under the pressure of the mold. The composition is then taken out of the mold, heated at 140-190 deg.C for 1 to 8hr and integrally formed. In this case, the total content of Mg and Ca in the rubber is preferably controlled to <= about 0.01wt.%. Since the vulcanization reaction of the rubber composition is thus carried out in two stages, a frame-shaped gasket for the electrolytic cell having a long service life and with the maintenance cost reduced is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gasket used for sealing an electrolytic cell and a method for manufacturing the same.

[Conventional technology] Conventionally, electrolytic cell seals were made of EPD, which has relatively good corrosion resistance.
M rubber or EPM rubber molded bodies were used.

The gasket of the electrolytic cell is subject to deterioration due to the sodium hypochlorite in the electrolytic cell at high temperatures.

That is, the lifespan of ion exchange membranes used in electrolytic cells is approximately 5 years due to corrosion and permanent distortion during use, whereas the lifespan of EPDM rubber or EPM rubber gaskets is shorter. Shutdown maintenance is often required, reducing device manufacturing efficiency. Furthermore, replacing the gasket involves handling an expensive ion exchange resin membrane that is extremely thin and easily damaged, so this operation requires great care and takes a long time. When replacing this gasket, in the unlikely event that
If the ion exchange membrane is damaged, the damage will be enormous.

From this point of view, it is effective to make the life of the gasket match the life of the ion exchange membrane or to exceed the life of the ion exchange resin.

[Problems to be Solved by the Invention] An object of the present invention is to provide a gasket for an electrolytic cell that has a long life.

[Means to solve the problem] The durability of an electrolytic cell gasket depends on its chemical resistance, but if the material of the electrolytic cell gasket is replaced with fluororubber, which has high chemical resistance, the life of the gasket will be extended. Since fluororubber is expensive, this method cannot be economically adopted.

The present inventor has developed a method using fluororubber mixed with peroxide and EPDM.
We discovered that an integrally molded gasket made of a composition made of rubber or EPM rubber has better corrosion resistance than a single EPDM rubber or EPM rubber, and is cheaper than a single fluororubber, reaching the point where it can be used on a regular basis. The present invention was completed based on this.

That is, the present invention consists of the following gaskets and methods of manufacturing the same.

1. A frame-shaped gasket for an electrolytic cell, characterized in that a composition consisting of 25 to 95% by weight of fluororubber and 75 to 5% by weight of EPDM or EPM rubber is integrally molded by a vulcanization reaction with peroxide. .

2 In the frame-shaped gasket, the outer peripheral portion is made of 20 to 70% by weight of fluororubber and 80% by weight of EPDM or EPM rubber.
A composition consisting of ~30% by weight is arranged, and a fluororubber and E having a fluororubber content of 10% or more by weight or more than the composition are arranged.
1. A gasket for an electrolytic cell, characterized in that a composition with PDM or EPM is placed on the inner periphery and integrally bonded by a co-vulcanization reaction with peroxide.

3 Fluororubber mixed with peroxide in a frame-shaped mold 25-9
A composition consisting of 5% by weight and 75 to 5% by weight of EPDM rubber or EPM rubber was charged, and 1% was added under pressure using a mold.
Heated at 40-190°C for 3-30 minutes, then removed from the mold and heated at 140-190°C for 1-8
A method for producing a gasket for an electrolytic cell, characterized by integrally molding it by heating for a period of time.

4 A composition consisting of 20 to 75% by weight of fluororubber mixed with peroxide and 80 to 25% by weight of EPDM or EPM rubber is charged to the outer peripheral part of the frame-shaped mold, and the composition of the outer peripheral part is charged to the inner peripheral part. Fluororubber content is 10
A composition of fluororubber and EPDM or EPM in an amount greater than 1% by weight is charged, and the mixture is heated to 140-190% by weight under pressure using a mold.
℃ for 3 to 30 minutes, then taken out from the mold and heated at 140 to 190℃ for 1-/8 hours to integrally bond and mold.Production of an electrolytic cell gasket. Method.

The gasket of the present invention has a frame-like shape, and the frame-like shape here corresponds to the shape of the rectangular ion exchange membrane of the electrolytic cell.
As shown in FIG. 1, it means a frame shape with a rectangular peripheral portion remaining.

The present invention will be explained in more detail with reference to drawings of embodiments. In the following description, for the sake of simplicity, the case where EPDM is used is described, but EPM can also be used in the same way instead of EPDM or mixed therewith.

The gasket of the first aspect of the present invention is shown in the above item 1, and the rectangular frame-shaped gasket l shown in FIG.
Fluororubber and EP shown in Section 1! A blend composition with DM is integrally molded using peroxide.

The blending ratio of fluororubber can be 25 to 95% by weight, preferably 35 to 90% by weight. The larger the blending ratio of fluororubber, the higher the electrolyte corrosion resistance, and the higher the EPDM content, the better the sealing performance. For the gasket of the present invention, an appropriate blending ratio can be selected depending on the usage conditions.

EPDM mixed with fluororubber is characterized by having properties that combine the electrolyte corrosion resistance of fluororubber and the sealing properties of EPDM.

The method for producing a gasket according to the first aspect of the present invention is to perform the first vulcanization reaction by heating at 140 to 190° C. for 3 to 30 minutes under pressure using a mold, and then taking it out from the mold.
It is characterized in that it is heated at 140 to 190°C for 1 to 8 hours to perform a second vulcanization reaction and then molded.

The manufacturing method of the present invention is characterized in that the second stage of oven vulcanization completely decomposes the peroxide, thereby preventing vulcanization from proceeding after molding and causing distortion during use.

If heating for complete decomposition of the peroxide is performed in the mold, the rotation rate of the mold will be poor, so in the present invention, the second stage of vulcanization is performed in an oven after being removed from the mold. Increase mold productivity.

A second aspect of the present invention is that the outer peripheral portion 2 in FIG. A composition consisting of fluororubber and EPDM rubber, or a composition consisting only of fluororubber, which is more than 10% by weight than the rubber around the outside, is placed via the interface 4, and is integrated by a co-vulcanization reaction with peroxide. This is a specially bonded gasket for electrolytic cells.

The gasket according to the second aspect of the present invention is characterized in that, when manufacturing the gasket, the blended rubber layers of fluororubber and EPDM having different compounding ratios constituting the gasket are simultaneously molded by peroxide vulcanization.

In the present invention, by performing peroxide vulcanization, the peel strength of the interface can be increased, and the productivity of the mold can be increased by two-stage vulcanization molding.

As described above, the gasket according to the second aspect of the present invention contains fluororubber in the outer part as well, so that a small amount of electrolyte leaks from the seal part in the inner peripheral part of the gasket to the seal in the outer peripheral part of the gasket. The outer part has the effect of preventing corrosion, and the inner part that comes into direct contact with the electrolyte contains 10% more fluororubber by weight, and the outer part has a slightly corrosion-resistant seal. It has the advantage of being able to maintain a perfect seal while arranging good rubber and using fluororubber efficiently.

If the blending ratio of fluororubber is not increased by 10% by weight or more,
The above effects are insufficient.

It is desirable that the different rubbers in the gasket molded product of the second aspect of the present invention have approximately the same hardness and permanent deformation in order to avoid peeling at the interface during use.

In addition, the rubber used for the gasket of the present invention may have a low content of magnesium compounds and carunium compounds that adversely affect reactions in the electrolytic cell, for example, the total amount of magnesium and carunium in these compounds may , 0.02% by weight or less, preferably 0.02% by weight in the rubber.
It is desirable that the content be 0.01% by weight or less.

It is desirable that the two rubber compositions used for this purpose be blended so that the hardness of both rubber molded products is the same and the content of magnesium and calcium is as low as possible.

Therefore, the organic peroxide used is one that does not contain a diluent, or one that contains an inorganic substance that does not contain trace amounts of magnesium or calcium, such as silica, as a diluent.

Further, if the vulcanization molding of the dissimilar rubber according to the second aspect of the present invention is carried out by a normal vulcanization reaction using sulfur, the rubber deteriorates severely and peeling of the interface is likely to occur during use of the gasket.

Generally, when a molded body is produced by joining or laminating two types of rubber and co-vulcanizing them, the joint portion of the two types of rubber tends to peel off.

The strength socket of the present invention is characterized in that by vulcanization molding using peroxide, a durable bonding surface that is stable even at high temperatures can be obtained at the interface.

The gasket of the present invention has an inner peripheral portion 3 as shown in Table 1.
The corrosion resistance is not much different from that of fluororubber alone; the corrosion resistance slightly increases as the fluororubber content increases, and the sealing performance increases as the EPDM or EPM content increases.

When the gasket of the first aspect of the present invention is placed in a mold,
The process is very convenient in that the compounded rubber composition can be extruded from an extruder into a mold and molded.

In the case of the gasket of the second aspect of the present invention, before charging into a mold, raw rubber containing two or more of these rubbers is extruded using an extruder and cut along the entire circumference of the mold to form a gasket shape. Vulcanization can be performed by placing the material in a mold, connecting the cut surfaces, and then applying heat and pressure.

The vulcanization of the present invention is preferably carried out in two stages for the reasons mentioned above.

In the production method of the present invention, the first stage vulcanization conditions are 140 to 190°C, preferably 160 to 170°C under pressure by a mold.
Then, heat for 3 to 30 minutes, preferably 10 to 25 minutes, and then remove from the mold and heat for 10 to 25 minutes.
It can be carried out at 49 to 190°C, preferably 150 to 160°C, for 1 to 8 hours, preferably 3 to 6 hours.

In the second stage oven vulcanization of the present invention, it is desirable to decompose and remove residual peroxide as much as possible.

The peroxide used in the production method of the present invention is not particularly limited, and for example, peroxyketal (Perhex 3M
, Bar Hexa 0, Bar Hexa ■), hydroperoxide (Per Hexa 25H), dialkyl peroxide (Burk Mill D1 Bar Butyl P1 Per Hexa 25B1 Ver Hexa 25B), etc. can be used.

[Example] The manufacturing method of the present invention will be explained in more detail with reference to Examples.

Mechanical properties and corrosion resistance in an electrolytic cell were tested for a total of eight types of vulcanized molded rubber, two types of fluorine rubber, EPDM rubber, and five types of blended rubber of fluorine rubber and EPDM rubber used in the present invention.

The formulation and vulcanization conditions of each rubber and the test method for the vulcanized rubber were as follows, and the results of the physical properties and corrosion resistance tests were as shown in Table 1. Since the difference in hardness of the blended rubber obtained by these combinations is 10 or less, there is no risk of peeling at the interface.

<Blend of rubber used> ■) 7-element rubber G100 - Compound Daiel G100I 100 parts by weight Carbon black 20 parts by weight 25-dimethyl-2,5
(Tertiary butyl peroxy) hequinone - 31,511 parts triallylisocyanurate 4 parts by weight - Vulcanization conditions: Vulcanize at 160°C for 15 minutes using a mold press for test pieces, remove from the mold and heat to 160°C. A test piece was obtained by vulcanization for a period of time.

■EPDM Rubber E70 - Compound EP24 100 parts by weight Zinc White No. 1
5 parts 1 part stearic acid
1 part by weight Antioxidant MB 1 part by weight Antioxidant RD 1 part by weight Carbon black FEF 82 parts by weight Paraffinic process oil 25 parts by weight Triallylisocyanurate
1 part by weight dicumyl peroxide 3.2 parts by weight Hard clay 5 parts by weight Vulcanization conditions 1st stage 160°cxis 2nd stage in mold 1.60°C x 5 hours In oven ■ Blend rubber l Mainly fluororubber Fluororubber-EPDM Rubber Blend/Composition A composition obtained by blending the above formulations (1) and (2) at a ratio of 80:20 between fluororubber and EPDM rubber.

・Vulcanization conditions 1st stage 160℃ x 15 minutes 2nd stage in mold 160℃ x 5 hours In oven ■ Blend rubber 2 Fluororubber mainly composed of EPDM rubber - EPDM blend rubber A composition blended with EPDM rubber in a ratio of 20:80.

・Vulcanization conditions 1st stage 160°C x 15 minutes 2nd stage in mold 160°C x S time in oven ■Fluororubber G
A composition in which fluororubber Daiel G902 was blended in place of fluororubber Daiel G1001 in the formulation of 90 (1).

■Blend Rubber 3 - Composition A composition obtained by blending the formulations of ■ and ■ above in a ratio of 80 + 20 of fluororubber and EPDM rubber.

・Vulcanization conditions 1st stage 160℃ x 15 minutes In the mold 2nd stage 160℃ x 5 hours In oven ■ Blend Rubber 4 ・Composition The above compounding of ■ and ■ will result in a ratio of fluororubber and EPDM rubber of 60:40. Composition blended in proportions.

・Vulcanization conditions 1st stage 160℃ x 15 minutes 2nd stage in mold 160℃ x 5 hours In oven ■ Blend Rubber 5 ・Composition The ratio of fluororubber and EPDM rubber is 50:50 with the combination of ■ and ■ above. Composition blended in proportions.

・Vulcanization conditions 1st stage 160℃! X 15 minutes 2nd stage in mold 160
℃ x 5 hours in oven <Physical property test method> ■Hardness (H5) Measured according to JISK-6301.

■Tensile strength (TB) Measured according to JISK-6301.

■Elongation (EB) Measured according to JISK-6301.

(2) Compression set (C5) Measured according to JISK-6301 after standing at 100°C for 22 hours.

■Chemical resistance A test piece is immersed in a hypochlorous acid solution with an available chlorine concentration of 10%, and the weight change relative to the initial weight is measured in weight %. The immersion solution is updated every 24 hours and
Measure data for 2 days.

(Left below) From this table, it can be seen that by blending fluororubber, the electric corrosion resistance is improved more than expected from the blending ratio.

Moreover, from the results of Blend Rubber 2, it can be seen that when the fluororubber is blended at 20% by weight or less, the electrolyte corrosion resistance is significantly reduced.

Example 1 Rectangular shape with outer surface dimensions of 1000 mm x 15100 O, thickness of 2.5 mI++, and inner edge dimensions of 800 x 130
Fill a 0mm rectangular frame-shaped mold with blend rubber 1 compound and press it.16C),'C! The mixture was heated at 160° C. for 15 minutes, removed from the mold, and heated at 160° C. for 5 hours to produce a gasket.

Example 2 A gasket was manufactured using the same composition of EPDM rubber-based blend rubber 5 as used for the test in place of the blend rubber 1 of Example 1, and keeping the other conditions the same.

Example 3 Blend rubber 3 was placed in a width of 501+1 m around the inner side, and blend rubber 4 was placed in the remaining space of the mold outside of the blend rubber 3, and a gasket was made in the same mold as in Example 1 under the same conditions. was manufactured.

The side edge of the obtained gasket was punched out perpendicularly to the boundary surface 4 in the shape of dumbbell No. 3 according to JISK-6301, and the test piece was pulled and broken while holding the outer and inner edges. There was no peeling, and the outer periphery was broken.

[Effects of the invention] The gasket of the present invention has the corrosion resistance of fluororubber and EPDM.
Alternatively, the gasket has the sealing properties of EPM and has a long life in the electrolytic cell, which is longer than the life of the ion exchange resin membrane in the electrolytic cell, which has the advantage of reducing maintenance costs.

Moreover, the manufacturing method of the present invention allows peroxide to be completely decomposed, so no distortion occurs during use.

In addition, the manufacturing method of the present invention for the gasket of the second embodiment greatly strengthens the bonding at the interface between different types of rubber layers, thereby preventing delamination, which is a defect of composite multilayer rubber when used in electrolytic cells under high temperature compression. There is an advantage that a durable composite molded gasket can be manufactured without fear.

Furthermore, since a gasket containing less calcium or magnesium can be obtained, it does not adversely affect the electrolytic reaction.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a gasket according to one embodiment of the invention, and FIG. 2 is a plan view of another embodiment of the invention. The symbols in the figure are 1: gasket for electrolytic cell, 2: outer peripheral blended rubber part, 3: inner peripheral blended rubber part, 4: boundary surface. Patent applicant: Toyo Rubber Industries, Ltd.

Claims (1)

[Scope of Claims] 1. A frame-shaped gasket, characterized in that a composition consisting of 25 to 95% by weight of fluororubber and 75 to 5% by weight of EPDM or EPM rubber is integrally molded by a vulcanization reaction with peroxide. Gasket for electrolytic cells. 2 In the frame-shaped gasket, the outer peripheral portion is made of 20 to 70% by weight of fluororubber and 80% by weight of EPDM or EPM rubber.
A composition consisting of ~30% by weight is arranged, and a fluororubber and E having a fluororubber content of 10% or more by weight or more than the composition are arranged.
1. A gasket for an electrolytic cell, characterized in that a composition with PDM or EPM is placed on the inner periphery and integrally bonded by a co-vulcanization reaction with peroxide. 3 Fluororubber mixed with peroxide in a frame-shaped mold 25-9
A composition consisting of 5% by weight and 75 to 5% by weight of EPDM rubber or EPM rubber was charged, and 1% was added under pressure using a mold.
Heated at 40-190°C for 3-30 minutes, then removed from the mold and heated at 140-190°C for 1-8
A method for producing a gasket for an electrolytic cell, characterized by integrally molding it by heating for a period of time. 4 A composition consisting of 20 to 75% by weight of fluororubber mixed with peroxide and 80 to 25% by weight of EPDM or EPM rubber is charged to the outer peripheral part of the frame-shaped mold, and the composition of the outer peripheral part is charged to the inner peripheral part. Fluororubber content is 10
A composition of fluororubber and EPDM or EPM which is more than 10% by weight is charged and heated to 140 to 190% by weight under pressure with a mold.
℃ for 3 to 30 minutes, then taken out from the mold, heated at 140 to 190℃ for 1 to 8 hours, and integrally bonded and molded. .