JP2011006767A - Cathode gasket for electrolytic cell and electrolytic cell comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode gasket for an electrolytic cell which has reduced creep, has excellent fracture resistance, further does not brake an ion exchange membrane upon electrolysis, and has excellent corrosion resistance.SOLUTION: In the cathode gasket 1 for an electrolytic cell sealing a space between an ion exchange membrane and an electrolytic chamber frame in an electrolytic cell used for an ion exchange membrane process and having an opening part 10 formed almost at the center, the cathode gasket 1 for the electrolytic cell includes a reinforcing member arranged at the inside thereof, and the reinforcing member is not arranged at the inside region with a prescribed length of the gasket 1 for an electrolytic cell from the inner circumferential edge part of the opening part 10.

Description

  The present invention relates to a cathode gasket for an electrolytic cell and an electrolytic cell including the same.

  In electrolysis using an aqueous alkali metal chloride solution such as saline, an ion exchange membrane method is used. The ion exchange membrane method uses an electrolytic cell provided with an ion exchange membrane (hereinafter referred to as “ion exchange membrane method electrolytic cell”). As an ion exchange membrane electrolytic cell, a filter press type electrolytic cell is generally used in which a cathode chamber frame attached with a cathode and an anode chamber frame attached with an anode are closely attached via an ion exchange membrane and a gasket and tightened by hydraulic pressure or the like. Has been used.

  The ion exchange membrane method produces high-concentration alkali metal hydroxide, chlorine gas, hydrogen gas, etc. using alkali chloride such as salt as a raw material. Therefore, leakage of electrolyte and gas from the electrolytic cell is not only dangerous for explosion and fire but also harmful for the environment. Therefore, by interposing a gasket between the chamber frame and the ion exchange membrane, and tightening the ion exchange membrane and the gasket, alkali metal hydroxide, chlorine gas, hydrogen gas, etc. generated by electrolysis are outside the electrolytic cell. To prevent leakage. Therefore, the gasket is required to be resistant to corrosive electrolytes and gases and to be used for a long time. For this reason, a gasket obtained by molding a rubber sheet is often used.

  However, when the ion exchange membrane and the gasket are tightened for a long period of time, the gasket gradually creeps and becomes thin. As a result, the rubber elasticity of the gasket is reduced, and the sealing performance of the electrolyte and gas may be reduced. As the gasket creeps further, the ion exchange membrane is stretched following the spread of the gasket. As a result, the ion exchange membrane may be broken. When the ion exchange membrane is broken, the ion exchange membrane needs to be replaced or repaired even though the membrane performance (current efficiency, etc.) of the ion exchange membrane is still sufficient, so that the economic loss is great. Therefore, Patent Document 1 discloses a rubber gasket lined with a reinforcing core material (reinforcing cloth) in order to prevent the ion exchange membrane from being broken.

Japanese Patent Laid-Open No. 55-164088

  However, the gasket lined with the reinforcing core material as disclosed in Patent Document 1 has a problem that the reinforcing core material is exposed to the electrolytic surface during electrolysis and breaks the ion exchange membrane. On the other hand, the gasket that does not allow the reinforcing core material to be inserted to the tip of the electrolytic surface has a large creep in the portion that does not contain the reinforcing core material. Therefore, when tightening pressure is applied, the gasket may break and the ion exchange membrane may break. .

  The present invention has been made in view of the above circumstances, and has a low creep, excellent rupture resistance, and does not damage the ion exchange membrane during electrolysis, and has an excellent corrosion resistance. And an electrolytic cell including the same.

  As a result of intensive research to solve the above problems, the inventors of the present invention sealed the gap between the ion exchange membrane and the electrolytic chamber frame in the electrolytic cell used for the ion exchange membrane method, and were formed at a substantially central position. An electrolytic cell cathode gasket having an opening, including a reinforcing member disposed inside the electrolytic cell cathode gasket, and having a predetermined length of the electrolytic cell cathode gasket from an inner peripheral end of the opening. By adopting a structure in which the reinforcing member is not disposed in the internal region, the creep is small, the fracture resistance is excellent, and the ion exchange membrane is not damaged during electrolysis, and the corrosion resistance is excellent. The inventors have found that the cathode gasket can be used as a tank, and have completed the present invention.

That is, the present invention is as follows.
[1]
An electrolytic cell cathode gasket that seals between an ion exchange membrane and an electrolytic chamber frame in an electrolytic cell used in an ion exchange membrane method, and has an opening formed at a substantially center,
A reinforcing member disposed inside the electrolytic cell cathode gasket,
The electrolytic cell cathode gasket, wherein the reinforcing member is not disposed in an inner region of a predetermined length of the electrolytic cell cathode gasket from an inner peripheral end of the opening.
[2]
The cathode gasket for electrolytic cells according to [1], wherein the predetermined length is 2.5 mm or more.
[3]
[1] or [2] electrolytic cell cathode gasket, wherein at least a part of the surface of the electrolytic cell cathode gasket is covered with a coating material containing a fluororesin.
[4]
The electrolytic cell according to [3], wherein at least a part of a boundary surface between a portion where the reinforcing member is disposed and a portion where the reinforcing member is not disposed is covered with the covering material. Cathode gasket for use.
[5]
[3] or [4] electrolytic cell cathode gasket, wherein at least a part of the surface of the portion where the reinforcing member is disposed is covered with the covering material.
[6]
The cathode gasket for electrolytic cells according to any one of [3] to [5], wherein at least a part of the coating material is inherent in the negative electrode gasket for electrolytic cells.
[7]
The cathode gasket for an electrolytic cell according to any one of [3] to [6], wherein at least a part of a surface in contact with the cathode chamber frame is covered with the covering material.
[8]
An ion exchange membrane;
An anode chamber;
A cathode chamber;
An anode gasket for an electrolytic cell disposed between the ion exchange membrane and the anode chamber;
The cathode gasket for an electrolytic cell according to any one of [1] to [7], disposed between the ion exchange membrane and the cathode chamber;
Electrolyzer containing.

  The cathode gasket for an electrolytic cell of the present invention has small creep, excellent rupture resistance, and further excellent corrosion resistance without damaging the ion exchange membrane.

It is a perspective view of 1st embodiment of the cathode gasket for electrolytic cells which concerns on this embodiment. It is sectional drawing which follows the XX 'line | wire of FIG. It is a partial cross section figure at the time of mounting | wearing the electrolytic cell with the cathode gasket for electrolytic cells which concerns on this embodiment. It is a partial cross section figure of 2nd embodiment of the cathode gasket for electrolytic cells which concerns on this embodiment. It is a partial cross section figure of 3rd embodiment of the cathode gasket for electrolytic cells which concerns on this embodiment. It is a partial cross section figure of 4th embodiment of the cathode gasket for electrolytic cells which concerns on this embodiment. It is a partial cross section figure of 5th embodiment of the cathode gasket for electrolytic cells which concerns on this embodiment. It is a graph which shows the creep performance of the gasket of Examples 1, 2 and Comparative Examples 1, 2.

  Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. In addition, the dimensional ratio of drawing is not restricted to the ratio of illustration. And this invention can be deform | transformed suitably and implemented within the range of the summary.

  The cathode gasket for an electrolytic cell according to the present embodiment (hereinafter simply referred to as “cathode gasket”) seals between the ion exchange membrane and the electrolytic chamber frame in an electrolytic cell used for the ion exchange membrane method, and is substantially at the center. A cathode gasket having an opening formed therein, including a reinforcing member disposed inside the cathode gasket, wherein the reinforcement extends from an inner peripheral end of the opening to an inner region of a predetermined length of the cathode gasket. It is a cathode gasket in which no member is arranged.

  FIG. 1 is a perspective view of a first embodiment of a cathode gasket according to the present embodiment. FIG. 2 is a cross-sectional view taken along the line XX ′ in FIG. FIG. 3 is a partial cross-sectional view when the cathode gasket according to the present embodiment is attached to the electrolytic cell. The cathode gasket 1 has an opening 10 formed at substantially the center thereof, and has a SUS core material 16 and a nylon 6 core material 18 as reinforcing members therein. And the surface of the gasket main body 12 of the cathode gasket 1 is covered with the coating | covering material 14 containing a fluororesin.

  In FIG. 3, when the gasket is attached to the electrolytic cell, the cathode gasket 1 is disposed between the ion exchange membrane 2 and the cathode chamber frame 3, and the anode gasket 5 is disposed between the ion exchange membrane 2 and the anode chamber frame 4. Be placed. In this way, by sandwiching the ion exchange membrane 2 between the cathode gasket 1 and the anode gasket 5, it is possible to seal between the chamber frame of the electrolysis chamber (cathode chamber, anode chamber) and the ion exchange membrane. Here, arrow A indicates the cathode side, arrow B indicates the ion exchange membrane side, and arrow C indicates the electrolytic cell side. The electrolytic solution in the cathode chamber is in contact with the surface of the cathode gasket 1 on the electrolytic cell side C.

  In the cathode gasket 1, reinforcing members (SUS core material 16 and nylon 6 core material 18) are not disposed in the inner region of the predetermined length L from the inner peripheral end S of the opening 10 (see FIG. 2). When performing electrolysis, the inner peripheral end S is in contact with the electrolytic solution, and is a portion that is easily corroded by the electrolytic solution or electrolytic solution. Here, the region where the reinforcing member is not disposed inside the cathode gasket 1 is a region where the reinforcing member is not exposed to the surface even when the cathode gasket 1 is corroded by electrolysis or generated caustic soda during electrolysis. It is.

  The predetermined length L is preferably 2.5 mm or more, more preferably 2.7 mm or more, and further preferably 3 mm or more from the inner peripheral end S of the cathode gasket 1. By setting the lower limit of the predetermined length L to the above numerical value, it is possible to prevent the reinforcing member from protruding to the electrolytic surface due to corrosion during electrolysis and damaging the ion exchange membrane. Further, the predetermined length L is preferably 6 mm or less, more preferably 5.5 mm or less, and further preferably 5 mm or less from the inner peripheral end S of the cathode gasket 1. By setting the upper limit of the predetermined length L to the above numerical value, it is possible to prevent the creep resistance of the portion where the reinforcing member is not disposed from being significantly deteriorated. The method of adjusting the length of the predetermined length L is not particularly limited. For example, the raw rubber is placed under the mold at the site corresponding to the tip of the gasket on the electrolytic cell side and vulcanized with a hot press. Can do.

  The shape of the cathode gasket of this embodiment is not particularly limited, and a rectangular frame such as a rectangle is preferable. The size of the rectangle depends on the size of the electrolytic cell and the like, but is usually about 1200 × 2400 mm which is an electrolysis area, and the width (sealing width) is about 35 mm.

Although the thickness of a cathode gasket is not specifically limited, The range of 2.5 mm-4.5 mm is preferable, More preferably, it is about 3.1 mm. Usually, a surface pressure of about 20 kg / cm ² is applied to the gasket during electrolysis, but the thickness of the cathode gasket of the present embodiment is set to the above numerical value range so that the thickness of about 2.5 mm is applied when the surface pressure is applied. Can be adjusted.

  The material of the gasket main body of the present embodiment is not particularly limited, and can be composed of various materials. However, an elastic material having high sealing properties is preferable, and the hardness is 60 ° according to JIS K6301A Hs (Hardness spring). What is -90 degrees is preferable.

  The material of the gasket body is not particularly limited. For example, natural rubber, isoprene rubber, styrene / butadiene rubber, butyl rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, chloroprene rubber, silicone rubber, fluorine rubber, An acrylic rubber etc. are mentioned. Among these, from the viewpoint of chemical resistance and hardness, vulcanized molded products of ethylene / propylene / diene rubber (EPDM rubber) and ethylene / propylene rubber (EPM rubber) are preferable. As the crosslinking method, known methods such as sulfur vulcanization and peroxide crosslinking can be used.

  It does not specifically limit as a reinforcement member of a cathode gasket, For example, SUS, iron, nickel, nylon 6, polyester, etc. are mentioned. Among these, SUS and nylon 6 are preferable from the viewpoint of tensile strength.

  Since the cathode gasket expands and contracts due to the influence of temperature and humidity, when the cathode gasket is attached to the electrolytic cell, it is usually attached to the ion exchange membrane with the cathode gasket extended to some extent. For this reason, in this embodiment, reinforcing members having different degrees of elasticity are used, reinforcing members having a low degree of elasticity (for example, SUS core material) are arranged from the inner peripheral side to the outer peripheral side of the cathode gasket, and reinforcement with a high degree of elasticity is achieved. It is preferable to arrange a member (for example, nylon 6 core material) along the periphery of the frame of the cathode gasket (see FIG. 2). As described above, it is preferable to lining the reinforcing member woven with reinforcing members having different degrees of expansion and contraction on the cathode gasket, since creep can be further reduced while maintaining the excellent sealing performance of the cathode gasket. From the viewpoint of effectively preventing breakage of the ion exchange membrane due to creep, the reinforcing member is preferably lined in the vicinity of the ion exchange membrane side of the cathode gasket.

  Prior to backing the reinforcing member to the cathode gasket, it is preferable to perform an adhesion treatment of the reinforcing member in order to further improve the adhesion between the gasket body and the reinforcing member. A conventionally known technique can be used for the bonding treatment. For example, a treatment using an adhesive such as “Chemlock” (trade name), “Sixon” (trade name), “Megham” (trade name), etc., manufactured by Road Far East.

  Moreover, it does not specifically limit as a method of lining a reinforcement member to a cathode gasket, A conventionally well-known technique can be utilized. For example, when raw rubber is used as the gasket body, raw rubber, a vulcanizing agent, an antioxidant, a plasticizer and a reinforcing agent are mixed and then calendered with a rotating roll to obtain a thin rubber plate. In addition, there is a method in which a reinforcing member is sandwiched between two thin rubber plates, passed through a rotating roll, and then vulcanized with a hot press.

  The surface of the cathode gasket 1 is preferably covered with a coating material 14 containing a fluororesin. It is more preferable to cover the inner peripheral end S of the cathode gasket 1 in contact with the electrolytic solution and at least a part of the surface of the cathode gasket 1 in contact with the ion exchange membrane 2 with a covering material 14 (see FIG. 3). More preferably, the surface of the cathode gasket 1 in contact with the ion exchange membrane 2 covered with the covering material 14 includes a range of 5 to 18 mm from the inner peripheral end S in contact with the electrolytic solution. In this case, the symbol L ′ in FIG. 3 is in the range of 5 to 18 mm.

  When the cathode gasket slides out of the electrolytic cell during electrolysis, a gap is formed between the cathode gasket and the electrolytic cell, and gas and electrolyte leak to the outside of the electrolytic cell. Conventionally, for the purpose of partially increasing the surface pressure and improving the sealing performance of the cathode gasket, a projecting shape is provided on the cathode side (arrow A side in FIG. 3) of the cathode gasket. However, the surface in contact with the electrolyte has a lower clamping pressure than other parts, and high-concentration caustic soda or the like tends to enter and stay between the cathode gasket and the ion exchange membrane. As a result, the present inventors have found that the hypochlorous acid concentration increases with time and corrosion proceeds. In addition, the ion exchange membrane can be damaged by penetration of chlorine on the anode side and caustic soda on the cathode side into the membrane, and salt is precipitated in the membrane. In order to prevent this, in the present embodiment, it is preferable to attach an anode gasket at the same position as the seal portion on the anode side in order to improve the circulation of the electrolytic solution and prevent the retention of chlorine gas. On the cathode side, in order to prevent the permeation of caustic soda, it is preferable that the inner peripheral edge S of the cathode gasket is put into the electrolytic cell by about 5 mm from the sealing portion of the electrolytic cell frame (see FIG. 3).

  In the cathode gasket, there is a possibility that it may become the starting point of the corrosion within a range of 5 to 18 mm from the inner peripheral end S (see reference numeral L ′ in FIG. 3). Therefore, corrosion can be more effectively prevented by covering the surface in this range with a coating material. In this case, the covering material preferably covers the entire surface in the range of 5 to 18 mm from the inner peripheral end S (see FIG. 2). Since the entire surface of the cathode gasket on the ion exchange membrane side (see arrow B in FIG. 3) where partial corrosion can occur is covered with a coating material, corrosion can be more effectively prevented. Moreover, you may coat | cover so that a coating | covering material may be wrapped to the cathode side (refer code | symbol A of FIG. 3), and the same effect can be acquired by this.

  The method for covering the surface of the cathode gasket with a coating material containing a fluororesin is not particularly limited, and can be performed by a known method. For example, the method etc. which affix a fluororesin sheet | seat on the cathode gasket surface via an adhesive agent etc. are mentioned.

  Examples of the fluororesin used as the coating material include ethylene tetrafluoride (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene / hexafluoropropylene (FEP), vinylidene fluoride ( PVDF). Among these, PTFE or PFA is preferable from the viewpoint of corrosion resistance.

  The thickness of the coating material is not particularly limited, but is preferably 300 μm or less from the viewpoint of not adversely affecting the sealing property and obtaining corrosion resistance by hypochlorite ions.

  FIG. 4 is a cross-sectional view of the second embodiment of the cathode gasket according to the present embodiment. In the present embodiment, it is preferable that at least a part of the covering material 14a containing the fluororesin is inherent in the cathode gasket 1a. By disposing at least a part of the covering material 14a inside the gasket body 12a, it is possible to prevent the covering material 14a from being peeled off from the gasket body 12a, and to cover the gasket surface more reliably. As described above, when the covering material 14a is folded back from the surface on the ion exchange membrane side of the cathode gasket 1a to the cathode side, it is preferable to back the covering material 14a with rubber or the like in order to maintain the sealing performance on the cathode side. In the gasket body 12a, the reinforcing members (SUS core material 16a and nylon 6 core material 18a) are inherently folded. Such an internal structure can effectively prevent the covering material 14a from being peeled off from the surface of the gasket body 12a on the ion exchange membrane side. As a result, since the surface on the ion exchange membrane side can be more reliably covered with the coating material, corrosion that may occur on the surface on the ion exchange membrane side can be more reliably prevented.

  In particular, it is more preferable that the covering material 14a is present on the outer peripheral side in the inner region of the predetermined length from the inner peripheral end S (that is, the region where the reinforcing member is not disposed). By adopting a structure in which the covering material 14a does not exist on the inner peripheral side of the inner region, it is possible to prevent the reinforcing member from being exposed to the surface even if the cathode gasket 1a is corroded by caustic soda generated during electrolysis.

  As a manufacturing method of the cathode gasket 1a, for example, raw rubber is disposed on the lower part of the mold corresponding to the cathode side and the lower part of the mold corresponding to the tip on the electrolytic cell side. And the method of putting the semi-vulcanized rubber which backed the reinforcing member wrapped with the fluororesin sheet on the part of the gasket equivalent to the front-end | tip at the side of an electrolytic cell, and vulcanizing | curing with a hot press is mentioned.

  FIG. 5 is a cross-sectional view of a third embodiment of the cathode gasket according to the present embodiment. In this embodiment, it is preferable that at least a part of the surface in contact with the cathode chamber frame is covered with the covering material. That is, the cathode gasket 1b is covered with the covering material 14b so as to enclose not only the surface on the ion exchange membrane side where partial corrosion can occur but also the cathode side surface of the cathode gasket. Thereby, corrosion by the electrolyte etc. which penetrate | invades from the clearance gap between a cathode chamber frame and a cathode gasket can also be prevented.

  Further, like the cathode gasket 1b, the covering material 14b covers at least a part of the surface in contact with the ion exchange membrane, a part in the gasket body 12b, and at least a part of the surface in contact with the cathode chamber frame. More preferably. As a result, not only the surface on the ion exchange membrane side but also the surface on the cathode chamber side can be more reliably covered with the covering material 14b. As a result, not only the corrosion that can occur on the surface of the ion exchange membrane side, but also the corrosion caused by the electrolyte entering from the gap between the cathode chamber frame and the cathode gasket can be prevented more reliably.

  FIG. 6 is a cross-sectional view of a fourth embodiment of the cathode gasket according to the present embodiment. In the cathode gasket 1c, at least a part of boundary surfaces Yc and Yc ′ between the portion where the reinforcing member (SUS core material 16c and nylon 6 core material 18c) is disposed and the portion where the reinforcing core material is not disposed. Is preferably covered with a covering material 14c containing a fluororesin.

  In a portion where the reinforcing member is not disposed, creep is large, and the ion exchange membrane is stretched following the spread of the cathode gasket, so that the ion exchange membrane may break. Further, the cathode gasket is easily broken at a portion where the reinforcing member is not disposed. Covering the boundary surface between the portion where the reinforcing member is disposed and the portion where the reinforcing member is not disposed with a covering material, the creep at the portion where the reinforcing member is not disposed is reduced, and the cathode gasket is broken. Resistance can be further improved. Furthermore, it is possible to prevent the ion exchange membrane from being broken during electrolysis. And from a viewpoint which can prevent corrosion more effectively, it is more preferable that the boundary surface Yc by the side of the ion exchange membrane of the gasket main body 12c is covered with the coating | covering material 14c.

  When the surface of the cathode gasket is covered with a fluororesin sheet, it is preferable to perform a surface treatment on the fluororesin sheet for the purpose of improving the adhesion between the fluororesin sheet and rubber. The surface treatment method is not particularly limited, and a conventionally known method can be used. As the surface treatment method, for example, ions are generated by a chemical etching method in which the solution is immersed in a liquid ammonia-metal sodium (1 mass%) solution or a naphthalene + tetrahydrofuran-metal sodium solution for several seconds, and discharge is performed. Examples include sputter etching processing, plasma processing, and the like that are applied to the surface of the resin sheet for etching.

  FIG. 7 is a cross-sectional view of a fifth embodiment of the cathode gasket according to the present embodiment. In the cathode gasket 1d, at least a part of the surface of the portion where the reinforcing member (SUS core material 16d and nylon 6 core material 18d) is disposed inside the gasket body 12d is covered with a covering material 14d containing a fluororesin. Yes. Such a structure is preferable because corrosion can be more effectively prevented.

  The cathode gasket of this embodiment can be used for an electrolytic cell used for an ion exchange membrane method. Specifically, an ion exchange membrane, an anode chamber, a cathode chamber, an anode gasket arranged between the ion exchange membrane and the anode chamber, and an arrangement between the ion exchange membrane and the cathode chamber. It can be used as an electrolytic cell including the cathode gasket of this embodiment.

  The cathode gasket of this embodiment exhibits sufficiently high sealing properties, small creep, and excellent rupture resistance. Further, the ion exchange membrane can be prevented from being damaged. Therefore, it can be operated without replacing the gasket for a long time, which is economically superior.

  The present embodiment will be described in more detail with reference to the following examples, but the present embodiment is not limited to the following examples.

[Example 1]
The cathode gasket shown in FIGS. 1 and 2 was produced. The gasket body 12 made of EPDM (made by JSR, trade name “EP-24”) having a rectangular frame shape with an outer dimension of about 2400 mm, a height of about 1200 mm, and a thickness of about 3.1 mm is attached to a fluororesin (PTFE sheet). , Manufactured by Nippon Valqua Co., Ltd., trade name “VALFLON”). As the reinforcing member, SUS core material (0.3 mmφ, 30 mesh) 16 and nylon 6 core material (0.35 mmφ, 20 mesh) 18 were used.

  Further, the reinforcing member was prepared so as not to exist in an inner region within 2.5 mm from the gasket inner peripheral end S. The entire peripheral surface from the peripheral edge S of the gasket body 12 (unvulcanized rubber) to the ion exchange membrane side is covered with a PTFE sheet having a width of 28 mm and a thickness of 0.1 mm, and placed in a mold for sulfur vulcanization. went. The thickness of the obtained gasket was 3.00 mm.

<Tensile test>
In order to examine the fracture resistance of the gasket, a tensile test was performed under the following conditions.
For the measurement, an autograph “AG-5000G” manufactured by Shimadzu Corporation was used.
The measurement sample was cut by 35 mm in the direction along the periphery and fixed to the chuck attached to the measurement device. The width of the measurement sample other than the fixed part was set to be 10 mm.
Furthermore, the measurement sample was pulled between the inner peripheral portion and the outer peripheral portion at a pulling speed of 10 mm / min, and the load when the measurement sample broke was measured to obtain the maximum load resistance. When the maximum load capacity was large, it was evaluated that the gasket was excellent in fracture resistance. As a result of the measurement, the maximum load capacity was 253 kgf. The measurement results are shown in Table 1.

<Measurement of creep amount>
The creep amount was measured by the following method.
First, the measurement sample was cut 100 mm in the direction along the periphery. Subsequently, the measurement sample was sandwiched between 100 mm × 21 mm metal blocks. Four measurement samples sandwiched between metal blocks were stacked and placed in a thermostatic bath, and surface pressure was applied by a hydraulic cylinder. Further, the temperature of the thermostatic chamber was raised to 90 ° C., a predetermined surface pressure was applied, and a position change amount was measured with a digital gauge after 1 hour. This change in position was converted into a change in gasket thickness per sheet, and the change in gasket thickness was measured. When the gasket thickness decrease was small, it was evaluated that the resistance to creep was good. The measurement result of the amount of change in the thickness of the gasket with respect to the surface pressure is shown in FIG.

<Electrolysis>
A cathode gasket is mounted on the cathode side of an electrolytic cell (product name “NCZ” manufactured by Asahi Kasei Chemicals Co., Ltd.) having a current-carrying area of 270 dm ^2. The electrolytic cell was constituted by tightening with pressure, and the aqueous sodium chloride solution was electrolyzed. Using this electrolytic cell, electrolysis was performed under the conditions of 60 kA / m ² , electrolysis temperature 88 ° C., cathode caustic soda concentration 32% by mass, anodic salt concentration 195 to 210 g / L, anode cell pressure 40 kPa, cathode cell pressure 44 kPa. Went. After electrolysis for 1 year, the corrosion state of the cathode gasket was observed. The covered PTFE sheet was removed and the gasket surface was visually observed, but no corrosion occurred. Further, it was confirmed that the reinforcing core material was not exposed from the gasket surface, and the ion exchange membrane was not broken.

[Example 2]
Production and evaluation were performed in the same manner as in Example 1 except that the PTFE sheet was not attached to the cathode gasket. The thickness of the produced cathode gasket was 3.11 mm. As shown in Table 1, the maximum load capacity was 210 kgf. Moreover, the measurement result of the creep amount is shown in FIG.
Further, in the same manner as in Example 1, a cathode gasket was attached to a large electrolytic cell, and an aqueous sodium chloride solution was electrolyzed. After conducting electrolysis for one year, the corrosion state of the cathode gasket was observed. As a result, corrosion was confirmed at a position of 7 to 10 mm from the inner peripheral end S of the cathode gasket. The reinforcing core material was not exposed from the surface of the cathode gasket, and it was confirmed that the ion exchange membrane was not broken.

[Comparative Example 1]
Fabrication and testing were performed in the same manner as in Example 1 except that the reinforcing core material was not put into the cathode gasket and the PTFE sheet was not pasted. The thickness of the cathode gasket was 3.54 mm. In the absence of the core material, the creep was large and the maximum load capacity could not be measured. Moreover, the result of measuring the creep amount is shown in FIG. Since there was no reinforcing core material, it was confirmed that the cathode gasket had poor fracture resistance and large creep.

[Comparative Example 2]
Fabrication and testing were performed in the same manner as in Example 1 except that the reinforcing core material was not put into the cathode gasket. The thickness of the cathode gasket was 3.45 mm. In the absence of the core material, the creep was large and the maximum load capacity could not be measured. Moreover, the result of measuring the creep amount is shown in FIG. Since there was no reinforcing core material, it was confirmed that the rupture resistance and creep resistance of the cathode gasket were not sufficiently improved as compared with Comparative Example 1 simply by covering the surface of the cathode gasket with a fluororesin sheet.

[Comparative Example 3]
Fabrication was performed in the same manner as in Example 1 except that the reinforcing core material was made to exist up to the tip of the electrolytic surface on the inner peripheral portion of the cathode gasket and that a PTFE sheet was not pasted. When electrolysis was performed under the same conditions as in Example 1, it was confirmed that the SUS core material of the reinforcing core material was exposed from the inner peripheral edge S of the cathode gasket and was pierced and damaged by the ion exchange membrane.

  Table 1 shows the maximum load resistance of the cathode gaskets of Examples 1 and 2 and Comparative Examples 1 and 2. The creep performance of the cathode gaskets of Examples 1 and 2 and Comparative Examples 1 and 2 is shown in FIG.

  From the above, it was confirmed that the cathode gasket of each example had small creep and excellent rupture resistance, and further excellent corrosion resistance without damaging the ion exchange membrane.

  The cathode gasket for an electrolytic cell of the present invention can be suitably used in a wide range of fields including the field of ion exchange membrane method alkaline electrolysis for producing chlorine and alkali metal hydroxides.

1,1a, 1b, 1c Electrolytic cell cathode gasket (cathode gasket)
DESCRIPTION OF SYMBOLS 10 Opening part 12,12a, 12b, 12c Gasket main body 14,14a, 14b, 14c Cover material 16,16a, 16b, 16c SUS core material 18,18a, 18b, 18c Nylon 6 core material 2 Ion exchange membrane 3 Cathode chamber frame 4 Anode chamber frame 5 Anode gasket for electrolytic cell (anode gasket)
S inner peripheral edge A cathode side B ion exchange membrane side C electrolytic cell side

Claims (8)

An electrolytic cell cathode gasket that seals between an ion exchange membrane and an electrolytic chamber frame in an electrolytic cell used in an ion exchange membrane method, and has an opening formed at a substantially center,
A reinforcing member disposed inside the electrolytic cell cathode gasket,
The electrolytic cell cathode gasket, wherein the reinforcing member is not disposed in an inner region of a predetermined length of the electrolytic cell cathode gasket from an inner peripheral end of the opening.   The cathode gasket for an electrolytic cell according to claim 1, wherein the predetermined length is 2.5 mm or more.   3. The electrolytic cell cathode gasket according to claim 1, wherein at least a part of the surface of the electrolytic cell cathode gasket is covered with a coating material containing a fluororesin.   The at least one part of the boundary surface of the site | part in which the said reinforcement member is arrange | positioned inside, and the site | part in which the said reinforcement member is not arrange | positioned inside is covered with the said coating | covering material. Cathode gasket for electrolytic cell.   The cathode gasket for an electrolytic cell according to claim 3 or 4, wherein at least a part of a surface of a portion where the reinforcing member is disposed is covered with the covering material.   The cathode gasket for electrolytic cells as described in any one of Claims 3-5 in which at least one part of the said coating | covering material is inherent in the said cathode gasket for electrolytic cells.   The cathode gasket for electrolytic cells as described in any one of Claims 3-6 with which at least one part of the surface which contact | connects the said cathode chamber frame is covered with the said coating | covering material. An ion exchange membrane;
An anode chamber;
A cathode chamber;
An anode gasket for an electrolytic cell disposed between the ion exchange membrane and the anode chamber;
The cathode gasket for an electrolytic cell according to any one of claims 1 to 7, which is disposed between the ion exchange membrane and the cathode chamber,
Electrolyzer containing.

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