JPS6044332B2 - Ion exchange membrane bonding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for bonding ion exchange membranes, and particularly to a method for bonding cation exchange membranes useful as diaphragms for chloralkali electrolysis.

In industry, it is often necessary to join ion exchange membrane sheets into complex shapes.

In this case, it is technically difficult to make a complicated shaped object in advance with a film, and it is often not rational in terms of cost since it is necessary to manufacture a mold suitable for each case. One example of this is the production of asbestos, which produces chlorine and caustic soda by electrolyzing table salt.
There are cases where

In other words, asbestos diaphragm electrolytic cells currently in use include the so-called diamond cell manufactured by Diamond Jamrock and the so-called granol cell manufactured by PPG, but these are thin electrodes combined with perforated plate electrodes. , or is constructed by covering a finger-shaped electrode with an asbestos diaphragm over a tapered finger-shaped electrode (generally referred to as a finger electrode) with its tip bent and the gap between the pair of electrode plates increasing. It is an electrolytic cell.

On the other hand, the so-called ion-exchange membrane electrolysis method, which uses a cation-exchange membrane as a diaphragm, is currently being adopted industrially due to its various excellent advantages, so the existing asbestos diaphragm tank can be converted to an ion-exchange membrane tank. It is becoming necessary to do so.

However, these current electrolytic cells have complex electrode structures, and it is extremely difficult to pre-form a cation exchange membrane into a shape that tightly fits these electrodes due to the large size of the formed membrane. And it is expensive,
A method by which sheet-like cation exchange membranes can be formed into complex shapes by bonding is desired in industry. The usual method for joining membranes is to overlap the parts of the membranes to be joined, place an adhesive between them, and heat and press them. However, when using this method, the joined part becomes a little thicker and is easily damaged. . The present inventors have studied a joining method in which the joint part has the same thickness as the other parts of the sheet, avoiding such thickening of the joint part, and as a result, they have arrived at the present invention. Two ion exchange membranes that are not treated with tertiary amines, quaternary ammonium bases, or their salts are paired with a slight gap between the sides, and made of thin resin that is not treated with the above treatment to cover the gap. The gist of this invention is a method for joining ion exchange membranes, which is characterized by placing a film on the film and applying pressure and heat to this part.

Various cation exchange membranes and anion exchange membranes are used as ion exchange membranes, but perfluorohydrocarbons with carboxylic acid, sulfonic acid, and phosphonic acid as ion exchange groups are particularly used for chloralkali electrolysis. A type of cation exchange membrane is preferably used.

The ion exchange membrane used in the present invention also includes a processed membrane obtained by processing the above-mentioned ion exchange membrane as described below.

That is, the ion-exchange membrane has a gas- and liquid-permeable porous layer on at least one surface that does not function as an electrode, including the one disclosed in Japanese Patent Application No. 111815-1983.

The material of the thin resin film placed on the opposite side of the ion exchange membrane as described above is not particularly limited, but it is preferably of the same quality as the ion exchange membrane to be joined.

Furthermore, it has almost the same physical properties as the ion exchange membrane to be bonded, but has a slightly lower melting point, that is, about 5 to 10'C. It is better. To explain the perfluorohydrocarbon-based cation exchange membrane which is suitable for chlor-alkali electrolysis and uses rubonic acid groups as the ion-exchange membrane, fiber-reinforced membranes are preferably used as the membrane for chlor-alkali electrolysis from various points of view. Therefore, as a thin resin film for joining this diaphragm, the above-mentioned cation exchange membrane before fiber reinforcement has exactly the same electrochemical properties but a slightly lower melting point (i.e., the melt flow characteristics are slightly lower). is used as a preferred combination.

Next, a method of pressurizing and heating will be explained.

The joining sides of the ion exchange membranes to be joined are arranged on a flat plate at approximately equal intervals, approximately 2 TIUn or less apart. Next, a thin resin film is placed to cover the gap. The width of this film is preferably 10 to 15 Tnm, although it depends on the distance between the gaps, the thickness of the ion exchange membrane, and the thickness of the film. In addition, the film melts when heated and flows into the gap, but the entire amount of the film does not completely melt and fill the gap, so the film remaining on the ion exchange membrane・The thickness of the film is such that the thickness of the film is not substantially increased at the joint portion, that is, the thickness of the ion exchange membrane is 315 mm.
It is best to use a film with a thickness of ~1 cm.

If the thickness is within the above range, even if the film remains on the ion exchange membrane during heating and pressurization, it will be thermally deformed and become thinner, so that the thickness of the bonded portion will not be substantially increased.
The volume of the film must of course be larger than the volume of the gap formed on the opposing sides of the ion exchange membrane, but if it is too large, too much film will remain on the ion exchange membrane. This was not good and ended up being 1.
It is preferable to have a volume of about 0 to 1 mm.

Pressure is applied from above the film with a pressure plate equipped with a heater.

This pressure plate is preferably a Bakelite plate with a built-in nichrome wire heater, for example. The width of the nichrome wire heater is at least twice the distance formed by the opposing sides of the ion exchange membrane,
Moreover, it is preferable that it is 2/3 times or more of the film width. The reason for this is that if the width of the heater is less than twice the distance, the bonding edges of the ion-exchange membrane will not be sufficiently melted and will not be fully bonded to the molten film. Further, if the width of the heater is less than 2/3 times the width of the film, even if pressure is applied, the edges of the film will not be softened and deformed, and the film will become thick locally. Actual heating and pressurizing conditions can be appropriately selected depending on the physical properties and thickness of the ion exchange membrane and resin film.

For example, if both the ion exchange membrane and the resin film are perfluorohydrocarbon-based, which is a copolymer of tetrafluoroethylene and CF2=CFO(CF2)3C00CH3, the pressure is approximately 1k9/d1 and the temperature is 240 to 260°C1. The time is about 5 minutes. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Tetrafluoroethylene and CF2=CFO(CF2)3C00C
A known cation exchange membrane (10 cm
Prepare two sheets of x10cm x 280μ) and
Flow glass so that the rt sides are facing each other with an interval of 1.
It was placed on top of the lower mold via silicone rubber.

Next, a cation exchange membrane (1C71 x 10 cm x 150μ) made of a copolymer of tetrafluoroethylene and CF2=CFO (CF2)3C00CH3 was placed directly above the gap between the cation exchange membranes.

Next, a Bakelite heating plate containing a heater with a nichrome wire width of 10 TI$L was placed so that the center line of the heater coincided with the center line of the interval, and the lower surface of the heating plate (i.e., the surface in contact with the cation exchange membrane) was heated. was heated to 240'C with a heater and pressed at 1k9/d for 5 minutes.

The joint portion was completely smooth and had sufficient strength. Example 2 In place of the cation exchange membrane of Example 1, a cation exchange membrane with a porous layer manufactured as follows was used, and bonding was carried out in the same manner as in Example 1.

That is, an aqueous dispersion containing 7 J weight % of polytetrafluoroethylene (hereinafter referred to as PTFE) with a particle size of 1 μ or less based on w parts of a 2 weight % methylcellulose aqueous solution as a thickener.
5 parts of titanium oxide powder with a particle size of 2.5μ or less are mixed together, and after thoroughly mixing in advance, 2 parts of isopropyl alcohol is mixed.
1 part and 1 part of cyclohexanol were added and kneaded again to obtain a paste.

The paste was applied to a printing substrate with an ion exchange capacity of 1 using a printing plate with a mesh number of 2001 and a 60μ thick stainless steel screen with a screen mask of 8μ thick underneath and a polyurethane squeegee. .43n1
eq/y dry resin, polytetrafluoroethylene with thickness 210μ and CF2=CFO(CF2)3C00C
10 cm on one side of an ion exchange membrane made of H3 copolymer.
X10? Screen printed to size.

The printed layer obtained on one side of the ion exchange membrane was dried in air to solidify the paste.

On the other hand, do the same thing on the other side of the ion exchange membrane.
Titanium oxide with a particle size of less than 5 microns was screen printed. After that, the temperature was 140℃ and the molding pressure was 30kg/Cl.
After press-bonding the printed layer to the ion membrane under the conditions of l, 90°C125
The ionic membrane was immersed in a wt % aqueous solution of caustic soda to hydrolyze it and to elute methylcellulose. The titanium oxide layer obtained on the ion exchange membrane has a thickness of 20μ,
It had a porosity of 70% and contained 1.5 mg/d of titanium oxide.

The joint was completely smooth and had sufficient strength.

Claims (1)

[Claims] 1. The sides of two ion exchange membranes that are not treated with a tertiary amine, a quaternary ammonium base, or their salts are paired with a slight gap between them, and the gap is covered. A method for bonding ion exchange membranes, which comprises placing a thin resin film that has not been subjected to the above treatment, and pressurizing and heating this portion. 2. The ion exchange according to claim 1, wherein the heating is performed by a heating source having a heating width that is at least twice the width of the gap, and the heating width is at least 2/3 times the width of the thin resin film. Membrane bonding method. 3. The method for joining ion exchange membranes according to claim 1 or 2, wherein the gap is 2 mm or less.