JPH02290227A - Gasket for electrodialyzing tank - Google Patents

Abstract

PURPOSE:To maintain a stable electrodialyzing performance over an extended period of time by attaching a gasket frame and a spacer firmly into an integral form by means of a thermoplastic elastomer interposed between the inner peripheral edge of the gasket frame and the outer peripheral edge of the spacer. CONSTITUTION:In a gasket with a spacer 2a provided in an electric nonconducting part and/or conducting part of a gasket frame 1a, the spacer 2a is of such size as to keep its outer peripheral edge out of contact with the inner peripheral edge of the gasket frame 1a. And the gasket frame 1a and the spacer 2a are firmly attached into an integral form by a thermoplastic elastomer interposed between the inner peripheral edge of the gasket frame 1a and the outer peripheral edge of the spacer 2a. As a result, this method provides no liq. leakage even with a lower pressure applied for the gasket attachment than in the case of the conventional gasket for use in electrodialysis and, unlike the prior art gasket attaching methods, there is no problem of damages to ion-exchange membrane at the gasket attachment and a stable electrodialyzing performance can be maintained over an extended period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gasket 7 for an electrodialysis tank suitable for use in a clamp-type electrodialysis device.

In particular, the present invention provides an o.c. lrrf or more and is used on an industrial scale, and is made by arranging a large number of cation exchange membranes and anion exchange membranes alternately between electrodes via gaskets, and tightening them. Electrodialyzers are generally widely used for concentrating and desalting salts.

At this time, in order to maintain the dialysis performance as high as possible and maintain it stably for a long period of time, it is necessary to uniformly disperse the fluid flowing into the dialysis space and the room formed by the gasket. A spacer made of a rope is inserted inside.

The position of this spacer is held stably to maintain a uniform flow state of the supply liquid during electrodialysis, and the gap between the gasket frame and spacer that occurs when the spacer is simply inserted into the notch of the gasket frame is In order to prevent the membrane from collapsing and to improve the efficiency of assembly and disassembly of the dialysis machine, a gasket frame and a spacer are integrated, for example, as disclosed in JP-A-57-171404 and JP-A-Sho. 58-1 Publication No. 12006, JP-A-5238
Various proposals have been made in Japanese Utility Model Application No. 483, Japanese Utility Model Application Publication No. 49-99842, Japanese Utility Model Application Publication No. 57-165206, Japanese Unexamined Utility Model Publication No. 61-21703, etc.

(Problems to be Solved by the Invention) In recent years, power saving has been desired also in electrodialysis. For this reason, the thickness of the ion exchange membrane and dialysis chamber (i.e.
The current trend is to reduce the thickness of the current-carrying spacer as much as possible.

Under such circumstances, when the gasket frame and the current-carrying part, or the current-carrying part and the tideway part are integrated using conventionally known techniques, the following problems arise.

That is, Utility Model Application No. 41-99842, Utility Model Application No. 57
-165206, Japanese Patent Application Laid-open No. 61-21703, when they are fixed and integrated using adhesives such as epoxy adhesives, rubber adhesives, or hot melt adhesives, It takes a long time for the adhesive to harden.

A further problem is that since the hardness of the fixed portion is high, when tightened, the ion exchange membrane in contact with the fixed portion is damaged, and furthermore, liquid leakage occurs.

Also, Utility Model Application Publication No. 57-165206, Utility Model Application Publication No. 49
-9 9 8 4 Even when fixed and integrated by heat welding as shown in Publication No. 2, damage to the ion exchange membrane and liquid leakage occur due to hardness of the fixed part, poor smoothness of the fixed part, etc. becomes a problem.

Also, JP-A-57-171404, JP-A-58-
Publication No. 112006 discloses a structure in which a gasket frame made of a vulcanized rubber sheet, glue, unvulcanized rubber, and a reticulated net spacer is used to fix and integrate a gasket frame and a spacer that can withstand practical use on an industrial scale. The gasket is
Tokukai V again! ! Publication No. 52-38483 discloses the integration of the current-carrying part spacer and the gasket frame in a configuration of "gasket frame - unvulcanized rubber - spacer".
These are vulcanized at a high temperature of 150''C in order to ensure that the bonding strength of the integrated portion is sufficient for practical use.

Usually, the spacer used for electrodialysis is a polyolefin-based reticulated proboscis with a low heat deformation temperature, generally having a thickness of 0.2 to 1 lTIIfi. Therefore, JP-A-57-1
Under the vulcanization conditions at 150°C shown in JP-A No. 71404 and JP-A-52-38483, the spacer, which has the function of ensuring a uniform flow state of the supply liquid during electrodialysis, is deformed (wrinkled). It was extremely difficult to adhere and integrate without it.

(Means for Solving the Problems) As a result of intensive research to solve the above problems, the present inventors found that when the gasket frame and spacer are fixedly integrated using a thermoplastic elastomer, the gasket frame and spacer near the fixed part are The present invention was completed by discovering that it is possible to obtain an industrial-scale electrodialysis tank gasket that does not undergo deformation, has excellent thickness accuracy at the fixed part, and has a hardness of the fixed part equal to or less than that of the gasket frame, and has completed the present invention. reached.

That is, the present invention provides a gasket in which a spacer is inserted into the current-carrying part or the current-carrying part and the channel part of the gasket frame, and the spacer has a size such that its outer circumferential edge does not touch the inner circumferential edge of the gasket frame, and the spacer has a size that does not touch the inner circumferential edge of the gasket frame. This gasket for an electrodialysis tank is characterized in that the gasket frame and the spacer are fixed and integrated by a thermoplastic elastomer interposed between the peripheral edge and the outer peripheral edge of the spacer.

As the gasket frame material of the present invention, it is obvious to those skilled in the art and does not require further explanation, but vulcanized rubber made from natural rubber and synthetic rubber, polyethylene, polypropylene, ethylene-ethyl acrylate copolymer, Synthetic resins such as ethylene-vinyl acetate copolymer are used, and the thickness is 0.2 to 2 m, and JIS
It is preferable to have a hardness of 30 to 95 degrees on the A scale.

The way to make it is to punch it out and use it as a gasket frame, or
Alternatively, it is preferable to make a band-like object from the sheet, and as shown in FIG. 5, a gasket frame is formed by abutting the ends of the band-like object and joining by adhesive or other means. Usually, a rubber adhesive is used as the adhesive.

In the present invention, the spacer is preferably a mesh spacer conventionally used in dialysis. For example, lattice-like, honeycomb-like, or mikoshiro fibers are preferable, and diagonal mesh-like ones are particularly preferable. Further, the material thereof is a synthetic resin such as polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, etc., and preferably contains polyolefin as the main component. Thickness is 0. It is preferable to have 2 to 2 cylinders and a Rockwell R hardness of 50 to 100 degrees.

Further, the spacers used for the current carrying part and the tideway part may be of different types or may be of the same type, but from the viewpoint of ease of manufacture and handling, it is preferable to use the same type of spacer.

The thermoplastic elastomer used in the present invention refers to a polymer consisting of a polymer block (soft segment) that is in a rubber state at room temperature and a polymer block (hard segment) that is in a glass or crystalline state.

Polymers with such a structure can have rubber elasticity similar to conventional vulcanized rubber in the soft segment, a plastic deformation prevention function in the hard segment, and also have plastic fluidity similar to conventional plastics. Therefore, it is widely known that it has excellent workability.

The present invention was also achieved by taking full advantage of the characteristics of this thermoplastic elastomer.

That is, in the gasket of the present invention, in which a thermoplastic elastomer is interposed between the gasket frame and the spacer, and the elastomer is fixed and integrated, the elastomer itself is a thermoplastic with a low softening point, and under the fixed conditions, Perhaps due to its high fluidity, the elastomer flows smoothly during adhesion, and as a result, less stress is generated when the inclusions flow.

Furthermore, it can be processed at lower temperatures and pressures than conventionally known techniques, such as gaskets that are fixed and integrated with unvulcanized rubber interposed therebetween.

For these two reasons, there is no deformation of the spacer and gasket frame near the fixed portion, and the thickness accuracy of the fixed portion is excellent. For this reason, there is no liquid leakage (leakage) even at a lower tightening pressure than conventional gaskets for electrodialysis tanks, and the ion exchange membrane does not leak at the fixed parts, which was a problem with gaskets fixed and integrated using conventional methods. There is no damage to the electrodialysis, and stable electrodialysis performance can be maintained over a long period of time.

Furthermore, by making the hardness of the thermoplastic elastomer lower than that of the gasket frame material, liquid leakage can be prevented even with a lower fastening pressure. As a result, damage to the ion exchange membrane at the adhesion site can be further reduced,
The effects of the present invention can be further exhibited.

Therefore, the hardness of thermoplastic elastomer is 30-95°.
(JIS A) is preferred.

As the thermoplastic elastomer that can be used in the present invention, currently commercially available styrene-based, polyester-based, polyolefin-based, polyurethane-based, and 1,2-polybutadiene-based elastomers can be used without limitation, but the compatibility with the gasket frame material Those with good quality are selected. For example, when natural rubber or styrene-butadiene rubber is used as the gasket frame material, a styrene-based thermoplastic elastomer is preferable from the viewpoint of adhesion strength between the gasket frame and the thermoplastic elastomer. Furthermore, it is particularly preferable that the soft segment is based on styrene-butadiene and the hard segment is based on polystyrene.

The fixation and integration of the thermoplastic elastomer and the spacer is achieved by embedding the spacer in the thermoplastic elastomer.

Furthermore, since the spacer is a thin mesh made of synthetic resin such as polyvinyl chloride, polyvinylidene chloride, polyethylene, or polypropylene, which has a low heat distortion temperature, the resin flows easily when heated and pressurized to bond and integrate. , the appropriate one is selected.

As a guideline, there is "resin flow characteristics" which is widely known in the field of plastic processing.

For example, using a Shimadzu flow tester CFT-500 type, orifice;
Load: 50 kgf/cII1, temperature: 150°C
Resin flow force under the conditions of
A thermoplastic elastomer having a temperature of sec or more is preferable in that it prevents deformation of the spacer in the vicinity of the bonded portion between the gasket frame material and the thermoplastic elastomer. The upper limit is not particularly limited, but is 1 0 0 x 1 0-'c++17sec
The degree is chosen.

The method for manufacturing the gasket for an electrodialyzer according to the present invention will be described below.

In order to fix and integrate the gasket frame and spacer with thermoplastic elastomer, first, make the spacer large enough so that its outer edge does not come into contact with the inner edge of the gasket frame.
For example, the spacer is inserted into the gasket frame such that the gap between the outer peripheral edge of the spacer and the inner peripheral edge of the gasket frame is 0.5 to 5 spaces, preferably 1 to 2 spaces.

On the other hand, the thermoplastic elastomer is formed into a sheet and cut into strips of a suitable size, for example, 5IIIil width and Xi,000 body length. The molding thickness of this thermoplastic elastomer is -10 to +30% of the thickness of the gasket frame material.
Preferably it is 0 to +15%.

Next, a method of setting the thermoplastic elastomer will be described. First, the gap between the inner edge of the gas cap and the inner edge is 0.5 to 5.
A thermoplastic elastomer cut into a strip is placed on the outer periphery of the spacer inserted so as to have a thickness of IIIffl, preferably 1 to 2 mm. The way to place it is to set it so that it rests on the outer periphery of the spacer so that when the gasket frame and the thermoplastic elastomer are fixed and integrated, at least one mesh is completely filled with the thermoplastic elastomer. . In addition, at this time, the inner circumferential edge of the gasket frame and the thermoplastic elastomer are the inner circumferential edge of the gasket frame (notched cross section) and one part of the cross section of the thermoplastic elastomer opposite thereto.
part, preferably with your fingertips etc. so that 20% or more of it touches,
It is desirable to set the gasket so as to press down on the thermoplastic elastomer in order to improve the adhesion strength between the gasket frame and the thermoplastic elastomer.

Next, heat pressing is performed using a press machine having a pressing surface larger than the area of the set thermoplastic elastomer.

The temperature at this time is above the softening point of the thermoplastic elastomer used, and the spacer used is made of synthetic resin and has a thickness of 0.
．． Because it is susceptible to thermal deformation in the form of two to two shells,
It is selected based on the aim that no deformation of the surface area near the fixed part occurs.

The pressure varies depending on the ``resin flow characteristics'' of the thermoplastic elastomer used and the ``material'' and ``shape'' of the spacer, but the pressure at the fixed site is 0. 5-10 kg/c
n{, preferably 2 to 5 kg/cA, is desirable in terms of thickness accuracy of the fixed site and prevention of deformation (mesh deformation, thickness unevenness, etc.) of the spacer near the fixed site.

The setting of the certain time is based on the gap between the inner circumferential edge of the gasket frame and the outer circumferential edge of the spacer (0.5 to 5 mm, preferably 1 to 5 mm).
The amount of thermoplastic elastomer softened by heating press and flowing into the mesh of the spacer (2mm) and the spacer is controlled. The amount of the thermoplastic elastomer that wraps around the inner peripheral edge (notch cross section) of the gasket frame and its uniformity greatly affect the bonding strength between the gasket frame and the thermoplastic elastomer, so strict management is required. Also, if the time is too long, the spacer will undergo thermal deformation. Taking these into consideration, a period of several seconds to several minutes is usually desirable.

At this time, if necessary, it is preferable to apply a suitable brimer, such as Brimmer 10R manufactured by No-tape Kogyo ■, to the inner periphery of the gasket frame as a pretreatment in order to increase adhesive strength.

The portion to be fixed may be the entire inner peripheral edge of the gasket frame, or may be a portion thereof. However, considering ease of handling during assembly, disassembly, and cleaning of the gasket, it is desirable that the adhesive be fixed by 20% or more, and more preferably on all sides.

Further, the thickness of the fixed portion is preferably -IO to +10%, preferably -5 to +5% of the thickness of the gas cant frame.

(Example) Examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1 Vulcanized styrene-butadiene synthetic rubber with JIS A hardness of 80 degrees and thickness of 0.5 mm (Nikkiko Lastomer Q)
MM Solblen 1204) Sheet, width 30mm x length 698mm and medium 67+mm x length 355 111[+
The material was cut into strips at a number ratio of 1:1. Then, the second
At the position indicated by the broken line in the figure, connect with rubber adhesive (■ThreeBond 1521 manufactured by ThreeBond), with an area of 20,
I made a 6dtrf picture frame gasket frame.

Next, a round hole 3 with a diameter of 22 marks is made in the upper and lower medium wide band-like parts,
Seven 3" square holes with a side of 39 mm were drilled alternately so that the center spacing between the holes was even.Furthermore, for the part where the 39 mm square holes were drilled, 39 mm was drilled toward the inside of the gasket frame.
1TIII I made a notch 1 width and made a notched gasket frame l as shown in Figure 3.

Next, a diagonal mesh spacer made of polypropylene with a thickness of 0.52 mm, a W-thickness pitch of 5 m x 3 m, and a Rockwell R hardness of 90 degrees was cut so that there was a gap of 1 cylinder within this notched gasket frame. , inserted.

The cut spacer 2 has a shape as shown in FIG. In Fig. 4, when this spacer is inserted into the gasket frame, there is a spacer in the upper and lower part of the gasket frame 1 at the center position of the seven protruding parts of the spacer shown by 5, which becomes the groove when forming the gasket. Drill in advance a total of 7 holes 3 or 22 mm in diameter at the center positions of the 3 or 4 22 mm diameter holes 3 drilled in the wide band part, and 22 mm diameter holes 3 at the top and bottom, with the holes 3 centered at the horizontal line. Oita.

Next, a 0.55 mm thick sheet made by calendering a pellet of 1,2-polybutadiene thermoplastic elastomer (JSR RB830 manufactured by Japan Synthetic Rubber) using a heat transfer roll was cut into 5 pieces. It was made into a string-like object. The hardness of this string-like material was 70 degrees in JIS A hardness.

In addition, "resin flow characteristics" are measured using the Shimadzu flow tester CF.
Using T-500 type, orifice; l order φ x 5ffI
IIL, load. 5 0 kgf/cfil, temperature; 1
5. Resin flow rate under 50°C condition. IX
It was 10-”cnf/sec.

This string-shaped thermoplastic elastomer is stretched over its entire length so that one side is in contact with the gasket frame notch cross section (inner periphery) and covers the gap between the gasket frame notch and the outer periphery of the spacer inserted into the notch. (In this state, the thermoplastic elastomer has a shape as shown in Figure 5. Also, in this state, the thermoplastic elastomer has a shape of 4ffIII1
), 110°C for 2 minutes
Heat pressing was performed at 3 kg/cm to embed the thermoplastic elastomer into the mesh of the spacer, and then press the vulcanized rubber. By fixing it to the cut-out section of the gasket frame and integrating the gasket frame and spacer, the liquid passage width is 26 m.
It has 7 shore roads of m and has a thickness of 0. 300 gaskets for electrodialysis tanks with a diameter of 5 mm and an effective current carrying area of 19.6 drrf.
I made one.

The average thickness of the completed gasket where the thermoplastic elastomer is filled and fixed is 0.5121Ilfll.
Met. The completed gas get is shown in Figure 1.

In Fig. 1, 1a is a gasket body made of vulcanized rubber, 2a is a spacer whose metal edge is fixed and integrated with the gasket, 3a is a communication hole for diluted liquid flow and concentrated liquid flow, and 4a
indicates a portion filled and fixed with thermoplastic elastomer.

150 gaskets made by the above method were used for the dilution chamber in the form of 3 holes and 4 holes, and 150 gaskets were used for the 4-hole inlet 3.
Asahi Kasei Aciplex OK for use in concentration chamber in the form of a hole exit
Using 150 sheets of -182 (cation exchange membrane) and 150 sheets of A-182 (anion exchange membrane), they were assembled in the order of forming an electrodialysis tank, and temporarily tightened with a fastening frame. The time required for this assembly was 8 hours by two people.

Next, the assembled product was attached to a filter press type electrodialysis tank, and after fastening with a hydraulic press, it was transferred to a concentration chamber.
Seawater was flowed into the dilution chamber at a linear velocity of 5 Cm/sec, but liquid leaked from the dialysis tank to the outside (hereinafter referred to as
There was a leak outside the tank), so I tightened it up using a hydraulic press and the leak outside the tank was reduced to ``0''.

The pressure at this time is 1.0 kg/C per effective current carrying area.
It was IIIG.

Next, we set the supply to the dilution chamber at 0.2 cm/sec, stopped the supply to the concentration chamber, and measured the leakage of seawater into the concentration chamber (hereinafter referred to as tank leak) in this state. The rate was 1.0 cc/min per chamber.

Next, the supply to the dilution chamber was set to 5 cm/sec, and the supply to the concentration chamber was set to 0.5 cm/sec, and in this state, a DC voltage was applied, and continuous operation was performed for 10 days at 79 Amρ. The average salt concentration of the concentrate was 203 g/ffi.

After this, it was disassembled, but the fixed part of the gasket did not come off, and there was no deformation of the membrane.

Furthermore, after measuring the fastening pressure and the leak inside the tank at which the leak outside the assembled tank was "0" again, the operation was repeated 4 times by operating for 10 days and then disassembling.

The results for each 10-day period are shown in Table 1 below.

After the fifth operation in Table 1, the unit was disassembled, and there was no detachment of the fixed part of the gasket, and no deformation of the spacer.

Furthermore, there were no wrinkles, sharpness, or pinholes in the film.

Example 2 In Example 1, a 0.5 mm thick sheet made of EEA (ethylene-ethylene acrylate copolymer resin, WN-930 manufactured by Nippon Unicar Co., Ltd.) was used as the gasket frame material. In the same manner as above,
We made 300 gaskets for electrodialysis tanks, each having a thickness of 0.5 mm and an effective current-carrying area of 19.6 drW, each having 7 channels of valence. The average thickness of the part of the completed gasket filled with thermoplastic elastomer and fixed thereto was 0.525 mm. The completed gasket is similar to that shown in Figure 1.

However, in FIG. 1, 1a is a gasket body made of EEA sheet.

The gasket made by the above method and the same type of membrane as used in Example 1 were assembled in the same manner. It took two people 8 hours to assemble.

Next, when the fastening pressure at which leakage outside the tank becomes "0" was measured using the same method as in Example 1, it was found to be 1.
4kg/cdG, and the tank leakage is 1.4cc/min.
It was a room.

Furthermore, liquid and electricity were applied in the same manner as in Example 1, and 10
After continuous operation for several days, the average salt concentration of the concentrate was 198g/I! ．． Met.

After that, I disassembled it, but the fixed part of the gasket came off,
There were no changes in the membrane or spacer.

Example 3 In Example 1, the member used to integrate the gasket frame and spacer was changed from a 1,2-polybutadiene-based thermoplastic elastomer to a styrene-based thermoplastic elastomer with a soft segment of polybutadiene and a hard segment of polystyrene (Asahi Kasei Corporation). ■I made 300 gaskets instead of Toughbrain 315).

The hardness of the thermoplastic elastomer used here is JIS
A hardness is 60 degrees, and "resin flow characteristic J is Example 1.
When measured in the same manner as 5,2 X 1 0-3
cot/sec.

The average thickness of the fixed part of the completed gasket is 0.5
It was 2 mm.

The gasket made by the above method and the same type of membrane as used in Example 1 were assembled in the same manner. It took two people 8 hours to assemble.

Next, when the fastening pressure at which leakage outside the tank becomes "0" was measured in the same manner as in Example 1, it was found that 1 per effective current-carrying area.
．． 3 kg/c4 G, and the tank leakage is 1.2
cc/min/chamber.

Furthermore, liquid and electricity were applied in the same manner as in Example 1, and 10
Continuous operation was carried out for several days, and the average salt concentration of the concentrate was 202 g/f.

After that, I disassembled it, but the fixed part of the gasket came off,
There were no changes in the membrane or spacer.

Example 4 In Example 1, only the Shiodo spacer 5 was fixed to the gasket frame cutout section using thermoplastic elastomer, and the gasket 300 was made by integrating the gasket frame and spacer.
I made one.

The average thickness of the thermoplastic elastomer fixed portion of the completed gasket was 0.510 mm.

The completed gasket is shown in Figure 7.

In FIG. 7, lb is a gasket body made of vulcanized rubber, 2b is a spacer whose outer peripheral edge is partially fixed and integrated with the gasket, 3b is a communication hole for the diluted liquid flow and concentrated liquid flow, and 4b is a thermoplastic elastomer. Fixed part of 5
b indicates the Shiodo spacer.

The gasket made by the above method and the same type of membrane as used in Example 1 were assembled in the same manner. It took two people 8 hours to assemble.

Next, when the fastening pressure at which leakage outside the tank becomes "0" was measured in the same manner as in Example 1, it was found to be 1.
3 kg/cdG, and the tank leakage is 1.5 cc/min.
It was a room.

Furthermore, liquid and electricity were applied in the same manner as in Example 1, and 10
Continuous operation was carried out for several days, and the average salt concentration of the concentrate was 197 g/f.

After that, I disassembled it, but the fixed part of the gasket came off,
There were no changes in the membrane or spacer.

Comparative Example 1 In Example 1, 300 gaskets were made by replacing the thermoplastic elastomer with unvulcanized styrene-butadiene synthetic rubber (Solprene 1240 manufactured by Asahi Kasei Kogyo Hatake) for the member used to integrate the gasket frame and spacer. Ta.

The method for integrating the gasket frame and spacer at this time is as follows.

That is, a thiuram-based vulcanization accelerator (Soccinol PZ manufactured by Sumitomo Chemical ■) is added to unvulcanized rubber having the same composition as the gasket frame material.
) was added at 1% and rolled at 60°C to a thickness of 0.5mm.
A sheet of this material was made, and then cut into a string-like material with a width of 5I.

Next, in the same way as in Example 1, adhesive was applied over the entire length of the cutout cross section of the gas gent frame with the spacer inserted inside (the unvulcanized rubber of the 5 mm wide string made earlier was dissolved in MEK). After coating this area with one side of the previously cut 5-width string-like unvulcanized rubber, lightly touch it with your fingers and temporarily attach it, and then heat this area at 150°C for 5 minutes. X5kg/cffl heat press is performed to embed unvulcanized rubber in the spacer, and by molding and vulcanizing, the gasket frame and spacer are fixed and integrated, and has 7 channels with a liquid passage width of 26 mm. 300 gaskets for an electrodialysis tank with a thickness of 0.5M and an effective current-carrying area of 19.6d were made.

The average thickness of the vulcanized portion of the unvulcanized rubber in the finished gasket was 0.55 m, but the spacers at 10 fixed sites in 8 out of 300 gaskets were deformed (wrinkled). The completed gasket is shown in Figure 8.

In Figure 8, . l c is a gasket frame made of vulcanized rubber sheet, 2C is a spacer integrated with the gasket frame, 3C is a communication hole for concentrated liquid flow and diluted liquid flow, 4C
5c shows the part where unvulcanized rubber is vulcanized and fixed, and 5c shows the Shiodo spacer.

It was assembled in the same manner as in Example 1 using the gasket made by the above method and the same type of membrane as in Example 1.

Next, when the fastening pressure and the leak inside the tank, which resulted in the leak rQJ outside the tank, were measured in the same manner as in Example 1, they were 1.8 kg/c+lIG and 2 cc/min/chamber, respectively.

Continuous operation was performed for 10 days by passing liquid and electricity under the same method and conditions as in Example 1, and the average salt concentration of the concentrated solution was 191 g/f.

After that, it was disassembled, but a crank was found in the membrane where the "wrinkle of the spacer at the fixed part" that was confirmed when it was manufactured was in contact with it. In addition, there was a feeling that the film surface in that area was slightly raised.

Further, the operation and disassembly were repeated in the same manner as in Example 1, and the results were as follows.

Table 2 Furthermore, as a result of disassembly after the fifth operation, many cracks were observed in the membrane in the areas where the "wrinkles of the spacer in the fixed area" that were confirmed during fabrication were present, and four membranes had holes. Was. In addition, there was a bulge at the location where the membrane adhered, and when the membrane was placed on a flat plate, the bulge increased by about 0.1 to 0.2 mm per membrane.

Comparative Example 2 In Example 1, a spacer having the same specifications as that used in Example 1 was inserted into a notched gasket as shown in FIG. 3 with a gap of 1 mm.

Next, using Ciba Geigy's epoxy adhesive "'Araldite Standard", 9 locations were glued (4d in Figure 9) to integrate the gasket frame and spacer, and the Shiodo 7 with a liquid passage width of 26 mm was bonded. We made 30 individual gaskets for electrodialysis tanks.

Note that the size of each bonded portion was approximately 15 fences φ.

The average thickness of the glued part of the completed gas get is 0.
．． 6+s, but the variation was large and the minimum part was 0.
It was 51mm, and 0.72mm at its maximum. Figure 9 shows the shape of the completed gasket.

In Fig. 9, 1d is the gasket body made of vulcanized rubber sheet, 2d is the spacer, 3d is the communication hole for the concentrated liquid flow and diluted liquid flow, and 4d is the adhesive between the gasket frame and the spacer using "Araldite Standard". 5d shows the Shiodo spacer.

The gasket made by the above method was assembled in the same manner as in Example 1, and the tightening pressure at which leakage outside the tank was "0" and the leakage inside the tank were measured, and the results were 2 kg/cfflG, respectively.
, 5cc/min.chamber. There were many cracks inside the tank, so when we dismantled it, we found many cracks and holes in the membrane where the epoxy resin came into contact.

(Effects of the Invention) In the present invention, a thermoplastic elastomer is interposed between the gasket frame and the spacer, and the integrated gasket can be produced using conventionally known techniques, for example, by using a thermoplastic elastomer. Since it can be processed at a lower temperature and pressure than a gasket that is fixed and integrated with vulcanized rubber interposed, there is no deformation of the spacer and gasket frame near the fixed part, and the thickness of the fixed part is excellent.

For this reason, there is no liquid leakage even at a lower tightening pressure than conventional gaskets for electrodialyzers, and damage to the ion exchange membrane at the sticking site, which was a problem with gaskets that were fixed and integrated using conventional methods, is avoided. Therefore, stable electrodialysis performance can be maintained over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a front view of the gasket prepared in Example 1. FIG. 2 is a front view of a gasket frame in which rubber sheets are joined together to form a picture frame. FIG. 3 is a front view of a notched gasket frame created by cutting a picture frame-shaped gasket frame. FIG. 4 is a front view of the spacer inserted into the notched gasket frame. FIG. 5 is a front view of a string-like thermoplastic elastomer used to fix and integrate the gasket frame body and the spacer in Example 1. FIG. 6 is a partial sectional view taken along line xx' of the gasket prepared in Example 1 shown in FIG. FIG. 7 is a front view of the gasket prepared in Example 4. FIG. 8 is a front view of the gasket prepared in Comparative Example 1. FIG. 9 is a front view of the gasket prepared in Comparative Example 2. FIG. 10 is a schematic diagram showing the configuration of a tightening type electrodialyzer. FIG. 11 is a schematic diagram showing a combination of a gasket frame and an ion exchange membrane in a stack constituting a clamping type electrodialyzer. 1 (la, lb, lc, ld), 19, 20・
...Gasket frame 2 (2a, 2b, 2c, 2d)
, 21, 22-...Subasa-3 (3a, 3b,
3c, 3d), 23... Diluted liquid flow and concentrated liquid flow communication hole (round hole) 3゛... Square holes 4a, 4b... Portion 4c fixed with thermoplastic elastomer... Part 4d fixed with unvulcanized rubber...
... Part 5 (5a.5b, 5c.5d) bonded with adhesive ... Shiodome spacer 1l ... Positive electrode frame l2 ... Liquid supply frame 13 ... Fastening frame 14... Stack 15... Cathode frame 16a... Press fixed plate 16b... Press movable plate 17... Anion exchange membrane 18... Cation exchange membrane D... Diluted solution C... Concentrated solution FIG. FIG. 5 FIG FIG. 3 FIG. 7 FIG. 8 FIG FIG (clam liquid frame) 14 (Star fishing)

Claims (1)

[Claims] (1) In a gasket in which a spacer is inserted into the current-carrying part or the current-carrying part and the channel part of the gasket frame, the spacer has a size such that its outer periphery does not come into contact with the inner periphery of the gasket frame, and the inner periphery of the gasket frame and the spacer A gasket for an electrodialysis tank, characterized in that a gasket frame and a spacer are fixed and integrated by a thermoplastic elastomer interposed between the outer peripheral edges of the gasket.