JP2024102932A - Electrode for chloralkali electrolysis using ion exchange membrane method, its manufacturing method and zero gap type ion exchange membrane electrolytic cell using same - Google Patents

Abstract

[Problem] The object of the present invention is to provide an anode for electrolysis that can be used in ion-exchange membrane salt electrolysis and can maintain an extremely low electrolysis voltage in so-called zero-gap electrolysis. [Solution] The electrode for ion-exchange membrane chlor-alkali electrolysis according to the present invention has an electrode substrate made of a pure titanium porous plate having a thickness t, and a hydrophilic electrode active material coating layer formed on the surface of the electrode substrate. The electrode substrate is a roll-pressed product of expanded metal, and the apparent thickness P of the roll-pressed product is 1.1t or more and 2t or less. [Selected Figure] Figure 3

Description

This disclosure relates to an anode for the so-called zero gap method, which is used in close contact with an ion exchange membrane in ion exchange membrane salt electrolysis, and which has a long life and can maintain a low electrolysis voltage.

Chloralkali electrolysis, in which salt water is electrolyzed to obtain chlorine from the anode and caustic alkali and hydrogen from the cathode, is the most important electrolysis used around the world for the manufacture of basic inorganic chemicals, with an annual production scale of over 60 million tons of caustic soda, making it the largest industrial electrolysis process. However, like other processes, industrial electrolysis requires a large amount of electricity, so there is a need to reduce this as much as possible, and various attempts are being made to achieve this. The ion exchange membrane method itself is a method that has evolved from the mercury method and diaphragm method of the past, and its extremely high product quality and energy-saving properties can be seen from the fact that most current processes use this method.

Even in this situation, as industrial electrolysis develops, it is an important mission to further reduce the power consumption of industrial electrolysis. To achieve this, the gap between the anode and cathode, which was initially about 2 mm, was changed to a so-called zero gap by improving the ion exchange membrane and further hydrophilizing the surface of the ion exchange membrane, in which the anode and cathode are pressed together. This reduced the electrolysis voltage, increased the current density, and expanded production capacity.

However, no significant improvements have been made to the anode up to the present. This is because the anode is originally used with the ion exchange membrane and the anode in close contact due to the specific gravity difference between the anolyte and the catholyte, the original electrode overvoltage is suppressed to an extremely small value of 30 mV to 50 mV by the so-called DSA (Dimensionally Stable Anode), and there is little room for improvement, and from the viewpoint of improving productivity, the main focus has been on responding to the demand for stable operation at a higher current density and further extending the life of the anode due to the extended life of the ion exchange membrane. During this time, the anode current density has increased several times from the original ² to 3 kA/m2 to the current 6 kA/ ^m2 to 8 kA/ ^m2 . Recently, new electrodes have been proposed, mainly electrode substrates.

In the anode structure for ion exchange membrane electrolysis, a titanium plate is used as the base material, and is made into a perforated plate to remove any air bubbles that may have formed. In addition, expanded metal is often used because the titanium can be used without waste when making the holes. It is known that the conditions for this expanded metalization can make the electrolysis voltage lower and more efficient, and proposals have been made for this purpose. The data on which this is based was presented by one of the inventors in Non-Patent Document 1. In other words, the size of the mesh (also called the mesh) of the expanded metal is often expressed by the opening period LW of the long sides and the opening period SW of the short sides, and this shows the relationship between the opening period LW of the long sides and the cell voltage. This shows that the smaller LW is, the lower the cell voltage. In other words, the smaller the mesh is, the lower the cell voltage is.

Patent document 1 indicates that the electrode plate should be a perforated plate with a perimeter of the hole portion of 2 m or more for an effective flat electrode plate unit size of 100 x 100 mm.

Patent Document 2 shows that an expanded metal with a thickness of 0.05 mm to 0.3 mm is used as the anode. By using such a thin anode and placing it as close as possible to the ion exchange membrane, it is possible to operate at a low voltage.

Patent Document 3 shows electrolysis using the zero-gap method, in which the anode smooths the expanded metal completely to the thickness of the original plate so that it adheres closely to the ion exchange membrane. This reduces the electrolysis voltage so that the anode is almost in close contact with the ion exchange membrane.

Patent Document 4 shows an electrode structure made of expanded metal that is very thin, has small mesh, and has an extremely small opening ratio.

In Patent Document 5, expanded metal is used as the anode, but the plate thickness is 0.1 to 0.5 mm, and the shape of the formed mesh is SW/LW = 0.45 to 0.55.

Patent document 6 discloses an insoluble metal electrode that includes applying a first substantially aqueous coating solution containing a valve metal oxide and at least two platinum group metal oxide precursors to an electrode support, treating the first coating solution to obtain a first metal oxide coating layer on the electrode support, and applying a second substantially organic coating solution containing a valve metal oxide and at least one platinum group metal oxide precursor to the first coating layer.

Japanese Unexamined Patent Publication No. 56-146884 Japanese Unexamined Patent Publication No. 58-130286 Japanese Patent No. 4453973 WO2018/131519 publication WO2015/108115 publication Special Publication No. 2007-507612

Electrochemistry and Industrial Physical Chemistry Vol. 56, No. 5 p306 (1988)

Non-Patent Document 1 indicates that the smaller the mesh, the lower the cell voltage, but does not show any relationship to SW, so the relationship to shape is unclear. Also, although it indicates that an aperture ratio of around 50% is good, it does not indicate what size is optimal.

Patent Document 1 does not disclose the shape of the perforated plate. This would mean that a plate with cuts could simply be used as the base material, but in that case, there would be no way for air bubbles generated on the ion exchange membrane side to escape. This would mean that it would be impossible to maintain a low voltage, making the invention incomplete, and the numbers are quite puzzling. However, it does disclose that the holes are important.

In Patent Document 2, the operating conditions may differ from those of the present day, but when the actual electrode area is taken into consideration, the cross-sectional electrode area is small due to the thinness of the plate, and it is clear that this is completely incompatible with the current electrolysis conditions that require high current density. Also, it is likely that if there is no physical protection on the back side of the anode, the anode will be more likely to deform due to pressure from the cathode chamber.

In Patent Document 4, the plate thickness is 0.5 to 1.2 mm, which is close to the electrode substrates commonly used today, but there is a restriction on the relationship between the mesh size and the aperture ratio, and applying this restriction results in a small mesh, which, except under special conditions, makes it difficult to remove air bubbles generated on the ion exchange membrane side of the anode to the back side of the anode, and at the same time, there is a possibility that the supply of electrolyte to this area will be insufficient, which is problematic.

In Patent Document 5, the expanded metal has a relatively large mesh size, but the mesh plate used is thin. The thin plate thickness allows air bubbles generated on the electrolytic surface in contact with the ion exchange membrane to escape relatively easily to the side of the electrode opposite the ion exchange membrane, i.e., the back side of the electrode. However, because the expanded metal plate is thin, as mentioned above, when considered three-dimensionally, the electrode surface area is inevitably small, the current density on the electrode surface is large, the electrode potential is high, and the electrode life may be shortened, which is problematic. This is particularly problematic for large current densities.

Patent Document 6 shows that the potential is lowered, but it only shows in a cyclic voltammogram that the surface area of the coating with the organic coating solution is increased, and makes no mention of bubbles or the like.

There are many other documents in addition to those mentioned above, and from these it can be seen that many electrode technologies have been proposed in the past to improve electrolysis performance. However, the anode structure is still insufficient for current operation. Moreover, although these electrodes are essentially made by combining an electrode substrate, shape, and an electrode active material coating applied to its surface, there has been almost no discussion of the combination. In particular, when the number of bubbles generated from the electrode increases, that is, when the current density increases, the finer the electrode surface becomes, the more important the combination of the electrode coating and electrode substrate, and even the bubbles themselves that are generated, but little research has been done on this topic.

The purpose of this disclosure is to provide an anode for electrolysis that can be used in ion exchange membrane salt electrolysis and that can maintain an extremely low electrolysis voltage in so-called zero gap electrolysis.

After extensive research, the inventors discovered that the above-mentioned problems could be solved by using expanded metal as an electrode substrate after it has been roll-pressed, and in this case, by performing roll-pressing so that the apparent thickness of the roll-pressed product is not as thin as the thickness of the sheet before the expanded metal is processed (hereinafter, also referred to as the original sheet) (hereinafter, a roll-pressed product that satisfies this condition will be referred to as a weakly pressed product), and thus completed the present invention. That is, the electrode for ion-exchange membrane chloralkali electrolysis according to the present invention is an electrode for ion-exchange membrane chloralkali electrolysis having an electrode substrate made of a pure titanium perforated plate and a hydrophilic electrode active material coating layer formed on the surface of the electrode substrate, the electrode substrate being a roll-pressed product of an expanded metal having a plate thickness of t mm, a long side opening period of LW mm, a short side opening period of SW mm, and a strand of W mm, the opening rate of the expanded metal being 20% or more and 60% or less, the ratio calculated by LW/SW being 1.5 or more and 3.5 or less, the plate thickness t of the perforated plate being 0.5 mm or more and 1.0 mm or less, the short side opening period SW being 2.0 mm or more and 5.5 mm or less, and the apparent thickness P mm of the roll-pressed product being 1.1t or more and 2t or less.

In the electrode for chloralkali electrolysis using the ion exchange membrane method according to the present invention, the pure titanium is preferably JIS Class 1 or JIS Class 2 titanium.

In the electrode for chloralkali electrolysis using the ion exchange membrane method according to the present invention, the hydrophilic electrode active material coating layer is preferably an oxide coating layer that contains ruthenium or ruthenium and iridium as the electrode active material and titanium or tin or titanium and tin as a stabilizing material.

In the electrode for chloralkali electrolysis using the ion exchange membrane method according to the present invention, it is preferable that the mesh shape of the expanded metal is diamond-shaped or tortoiseshell-shaped.

The manufacturing method of the electrode for chloralkali electrolysis by the ion exchange membrane method according to the present invention includes the steps of: preparing an expanded metal of a pure titanium perforated plate having a thickness of t mm, a long side opening period of LW mm, a short side opening period of SW mm, a strand of W mm, and an apparent thickness of K mm; roll-pressing the expanded metal to obtain a roll-pressed product having an apparent thickness of P mm as an electrode substrate; and forming a hydrophilic electrode active material coating layer on the surface of the roll-pressed product. The method is characterized in that the opening rate of the expanded metal is 20% or more and 60% or less, the ratio calculated by LW/SW is 1.5 or more and 3.5 or less, the plate thickness t of the perforated plate is 0.5 mm or more and 1.0 mm or less, the short side opening period SW is 2.0 mm or more and 5.5 mm or less, and the apparent thickness P mm of the roll-pressed product is 1.1t or more and 2t or less.

In the manufacturing method of the electrode for chloralkali electrolysis using the ion exchange membrane method according to the present invention, it is preferable to further include, between step 2 and step 3, step 4 of subjecting the roll-pressed product obtained in step 2 to a surface blasting treatment, and step 5 of etching the surface-blasted roll-pressed product with high-temperature hydrochloric acid to remove sharp protrusions and sharp edges on the surface.

In the manufacturing method of electrodes for chloralkali electrolysis using an ion exchange membrane method according to the present invention, it is preferable that the etching treatment using high-temperature hydrochloric acid in step 5 uses an etching solution having a hydrochloric acid concentration of 18% to 25% and a temperature of 90°C or higher and a boiling point or lower.

In the manufacturing method of the electrode for chlor-alkali electrolysis using the ion exchange membrane method according to the present invention, the step 3 preferably includes step 3-1 in which a coating liquid consisting of a dilute hydrochloric acid solution containing ruthenium or a dilute hydrochloric acid solution containing ruthenium and iridium is applied to the surface of the roll-pressed product, and thermal decomposition is repeated multiple times, and step 3-2 in which a coating liquid containing ruthenium and mainly composed of alcohol as a solvent or a coating liquid containing ruthenium and iridium and mainly composed of alcohol as a solvent is applied, and thermal decomposition is performed one or more times to make the surface of the electrode active material coating layer hydrophilic.

The present invention provides an anode for electrolysis that can be used in ion exchange membrane salt electrolysis and can maintain an extremely low electrolysis voltage in so-called zero gap electrolysis.

1A and 1B are schematic diagrams showing an example of the shape of an expanded metal, in which FIG. 1A shows a hole shape, and FIG. 1B is a schematic cross-sectional view of a bond taken along line A'. 1A and 1B are schematic diagrams showing the mesh shapes of an expanded metal, in which (a) shows a diamond shape and (b) shows a tortoiseshell shape. 1A and 1B are diagrams illustrating the removal of air bubbles, in which (a) shows a conventional electrode and (b) shows the electrode according to the present embodiment.

Next, the present invention will be described in detail with reference to an embodiment, but the present invention should not be interpreted as being limited to these descriptions. Various modifications of the embodiment may be made as long as the effects of the present invention are achieved.

The electrode for chloralkali electrolysis using an ion exchange membrane method according to this embodiment has an electrode substrate made of a perforated plate made of pure titanium and a hydrophilic electrode active material coating layer formed on the surface of the electrode substrate, in which the electrode substrate is a roll-pressed product of an expanded metal having a perforated plate thickness of t mm, a long-side opening period of LW mm, a short-side opening period of SW mm, and a strand of W mm, the opening rate of the expanded metal being 20% or more and 60% or less, the ratio calculated by LW/SW being 1.5 or more and 3.5 or less, the perforated plate thickness t being 0.5 mm or more and 1.0 mm or less, the short-side opening period SW being 2.0 mm or more and 5.5 mm or less, and the roll-pressed product having an apparent thickness P mm being 1.1t or more and 2t or less.

In chlor-alkali electrolysis using the ion exchange membrane method, the main reaction at the anode is the chlorine generation reaction, and the chlorine gas generated by electrolysis is electrically resistant because the bubbles are not conductive. Therefore, it is necessary to consider how quickly to remove the bubbles from around the anode, and to keep the area around the electrode constantly filled with liquid, which is a requirement for stable continuation of electrolysis at a low electrolysis voltage.

In this embodiment, the electrode base material is an expanded metal made of pure titanium. Expanded metal has the characteristics that it is relatively easy to make a perforated plate for the electrode, and that, although it is a perforated plate, it has a high titanium utilization rate of 100% compared to other base materials such as punched plates, and is relatively inexpensive. Here, it is preferable that the pure titanium is JIS Class 1 or JIS Class 2 titanium.

In this embodiment, the thickness of the base plate, i.e., the plate thickness t of the perforated plate, is 0.5 mm to 1.0 mm. If the plate thickness is smaller than 0.5 mm, the cross-sectional area of the perforated portion of the electrode surface area effective for electrolysis is reduced, so that the actual surface area of the electrode as a whole is reduced, and as a result, the actual current density increases, and as a result, the electrode overvoltage increases slightly, and the life of the electrode may be shortened. Furthermore, the physical strength may be insufficient. On the other hand, if the thickness of the base plate is larger than 1.0 mm, the weight of the titanium increases, making it expensive, and it becomes difficult to make the mesh size small. In addition, the current concentrates on the front side of the electrode, that is, on the ion exchange membrane side, and the back side cannot be used effectively, so that the effective actual surface area may be reduced. For these reasons, the thickness t of the electrode substrate base plate is 0.5 mm to 1.0 mm, preferably 0.6 mm to 0.9 mm, and more preferably 0.7 mm to 0.8 mm.

When the expanded metal is produced, the outer shape of the expanded metal expands by the number of holes to be made porous, and the rate at which the plate expands is its aperture ratio. In other words, if the length of the original plate is 1000 mm and the length of the expanded metal produced from it is 2000 mm, the aperture ratio is (2000-1000)/2000=0.5, or 50%. When the aperture ratio is 30%, the length of the porous plate is x, and x is expressed by the formula 1.
(Math 1)x=0.3x+1000
From (Equation 1), it is found that x is approximately 1429 (mm).

The mesh size of this expanded metal is determined by the repeat period in the stretched direction, SW, and the repeat period in the perpendicular direction, LW. In other words, a small mesh has small LW and SW, and the expanded metal has a large number of repeat periods per unit size. Also, as the ratio of LW to SW, LW/SW, increases, the opening of the holes in the porous section becomes elongated, and as LW/SW decreases, that is, approaches 1, the holes become closer to a square.

For such meshes, it is desirable for the current distribution inside the ion exchange membrane, which has a relatively high electrical resistance, to be uniform, and to achieve this, it is better for the expanded metal to have small mesh. However, in reality, the air bubbles generated by electrolysis need to be expelled through the openings, i.e. the mesh of the expanded metal, and for this to happen, a certain degree of hole size is essential. Furthermore, even if there are openings, it is difficult for the air bubbles to escape through narrow gaps, such as thin openings. After careful consideration of this issue, it was found that it would be sufficient to bring the relationship between the opening rate and the size of the holes in the expanded metal within a certain range.

Figure 2 shows specific examples of preferred mesh shapes for expanded metal. Figure 2(a) shows a diamond shape, and (b) shows a tortoiseshell shape.

The aperture ratio of the expanded metal used here is 20% to 60%, preferably 22% to 55%, more preferably 25% to 50%, and even more preferably 35% to 40%. If the aperture ratio is less than 20%, the titanium area per surface, i.e., the electrode area, will increase, but in return the gaps in the expanded metal will become smaller, which will cause the problem that it will be difficult for the generated bubbles to escape to the opposite side of the ion exchange membrane, i.e., to the back side of the electrode. Therefore, when making it into an expanded metal, it is desirable to make it three-dimensional even slightly to increase the gaps. It is desirable to make the apparent thickness thicker than the original plate thickness. This will make the actual electrode area larger and make it possible for bubbles to escape to the opposite side of the ion exchange membrane more effectively. On the other hand, if it exceeds 60%, the effective area as an electrode will become smaller, which will cause a problem of increased voltage. The stretch ratio of the expanded metal used during production is 1.25 to 2.50 times the length of the original plate, preferably 1.28 to 2.22 times, more preferably 1.33 to 2.00 times, and even more preferably 1.54 to 1.67 times.

In other words, normal expanded metal is made by expanding a plate to make it porous, and then rolling it to the thickness of the original plate to make it porous with a smooth surface. In contrast, in this embodiment, roll pressing is performed as follows. That is, the original plate (thickness t mm) is expanded to make it porous. The apparent thickness of the porous body before roll pressing at this time is T mm. Then, the porous body is roll pressed and pressed to a thickness 1.1 to 2.0 times that of the original plate. In other words, the apparent thickness P mm of the roll pressed product is set to 1.1t or more and 2t or less. The roll pressed product is not pressed to the thickness of the original plate, so it can be said to be a weakly pressed product.

Here, an example of a porous body produced by expanding metal processing of a plate will be considered. Figure 1 shows a schematic diagram of a porous body produced by expanding metal processing. As shown in Figure 1, the thickness of the plate before expanding metal processing and the thickness of the porous body are the same, and are denoted as t (mm). The opening period of the long side of the porous body is denoted as LW (mm), the opening period of the short side is denoted as SW (mm), and the strand is denoted as W (mm). The apparent thickness of the expanded metal before roll pressing is denoted as T (mm). In this case, T is expressed by (Equation 2).
(Math. 2) T = 2W/SW・{t+√(SW ² - 4W ² )}

As shown in Figure 1 (b), the manufacturing conditions for expanded metal usually result in an apparent thickness T that is expressed by the formula 2, which is determined by the original plate thickness (t) and the plate feed width (strand (W)) during the manufacturing of the expanded metal. If the expanded metal were treated as a flat plate, the metal portion would be inclined relative to it, and would be significantly thicker than the original plate. When it is made into expanded metal, its opening ratio is given by the strand and the repeat period in the extension direction, SW.

If the actual measured apparent thickness of the expanded metal before roll pressing is K, K has the relationship of (Equation 3) with respect to the calculated apparent thickness T of the expanded metal obtained by (Equation 2).
(Equation 3) K = α T
Here, 0.7≦α≦1.0
α is a correction coefficient. During the actual expanded metal processing, the ends of the metal parts tend to become rounded or distorted, so the actual measured value tends to be slightly smaller than the calculated value.

The unrolled expanded metal with apparent thickness K is roll pressed to make the apparent thickness P mm of the roll pressed product 1.1t to 2t. At this time, there is almost no change in LW, SW, W, and t before and after roll pressing.

For the anode in ion-exchange membrane salt electrolysis, an inclined structure is roll-pressed to the thickness (t) of the original plate to make it a simple perforated plate. This makes it easy to handle, but has little effect, especially when the perforations of the perforated plate are relatively large. However, the bubbles that are generated first flow in the plate thickness direction, perpendicular to the ion-exchange membrane, and then flow along with the liquid flow, resulting in a problem of poor bubble removal. This is because when the plate is thin and the aperture ratio is low, the apparent perforations become small, and in the case of chlorine, which has much larger bubbles than hydrogen, the bubble removal condition becomes poor.

In this embodiment, this is pressed by roll pressing to a thickness 1.1 to 2.0 times that of the original plate. This makes the porous section tilted, and by using this tilt to tilt the porous section upward from the ion exchange membrane side to the back side of the electrode, air bubbles can be removed without resistance by following the flow of the air bubbles.

Figure 3 shows an explanatory diagram of the escape of air bubbles. When the expanded metal is smoothed to the same thickness as the original plate, as is used in normal ion exchange membrane electrolysis, the contact surface between the expanded metal and the ion exchange membrane is maximized, and it is thought that electrolysis can be performed most efficiently. However, in reality, the air bubbles generated by electrolysis should move to the opposite side of the ion exchange membrane, that is, the back side of the electrode, and then flow upward. However, they are blocked by the cross section of the electrode, and first come out horizontally, and then they have to rise by the buoyancy of the air bubbles themselves. This resistance prevents the air bubbles from escaping, and the amount of air bubbles in the liquid increases, albeit slightly, as the rising speed slows (see Figure 3 (a)). In other words, there is a problem in that the electrical resistance of the electrolyte increases substantially.

In this embodiment, these factors are taken into consideration, and the ion exchange membrane actually swells slightly during use, and even if the anode has slight unevenness due to the pressure of the catholyte, it follows this unevenness and adheres closely to the anode. The unevenness that allows this is preferably 1.2 to 2.0 times the thickness of the pure titanium plate before processing, and more preferably 1.2 to 1.5 times. This allows the generated bubbles to rise diagonally upward on the opposite side of the ion exchange membrane, minimizing resistance without moving horizontally (see Figure 3 (b)). Depending on the degree of swelling of the ion exchange membrane, it may be better to slightly change the degree of smoothing of the electrode to 1.4 to 2.0 times, and it is desirable to select appropriately depending on the ion exchange membrane.

The LW/SW ratio, which is related to the size and shape of the mesh of the expanded metal, is 1.5 to 3.5, preferably 1.6 to 2.5, and more preferably 1.7 to 2.0. The LW/SW ratio shown here is related to the aspect ratio of the diamond opening of the expanded metal, and as the LW/SW ratio increases, the long diameter of the diamond becomes larger relative to the short diameter, so that even if the opening area is the same, the mesh opening becomes narrower and it becomes difficult for air bubbles to escape. Therefore, it is desirable for the opening to be close to a diamond with an aspect ratio close to 1:1. To achieve this, it is desirable for the LW/SW ratio to be close to 1, but from the perspective of the workability of titanium, it is thought that the limit is about 1.5, and if it is smaller than that, processing becomes difficult. If the LW/SW ratio is larger than 3.5, depending on the size of the mesh, thin parts will appear in the diamond opening, and there is a high possibility that air bubbles will not escape completely.

In this embodiment, the short side opening period SW is 2.0 mm or more and 5.5 mm or less, preferably 2.0 mm or more and 5.0 mm or less, and more preferably 2.2 mm or more and 4.5 mm or less. The size of SW is determined by the strand (W) and opening rate of the expanded metal, but in the case of ion exchange membrane method salt electrolysis, when manufacturing the expanded metal, it is determined to be as small as possible within the range where generated bubbles can easily escape. Furthermore, in order to manufacture the expanded metal stably, the plate thickness (t) and strand (W) are sometimes made approximately the same size. The SW of the expanded metal is determined by these factors.

Next, a method for manufacturing an electrode for chloralkali electrolysis using an ion exchange membrane method according to this embodiment will be described. The method for manufacturing an electrode for chloralkali electrolysis using an ion exchange membrane method has the following steps:

(Step 1)
An expanded metal is prepared, which is a pure titanium porous plate having a thickness of t mm, a long side opening period of LW mm, a short side opening period of SW mm, a strand of W mm, and an apparent thickness of K mm.
(Step 2)
The expanded metal is roll-pressed to obtain a roll-pressed product having an apparent thickness of P mm as an electrode substrate.
(Step 3)
A hydrophilic electrode active material coating layer is formed on the surface of the roll-pressed product.

In the roll-pressed product, the opening rate of the expanded metal is 20% or more and 60% or less, the ratio calculated by LW/SW is 1.5 or more and 3.5 or less, the plate thickness t of the perforated plate is 0.5 mm or more and 1.0 mm or less, the short side opening period SW is 2.0 mm or more and 5.5 mm or less, and the apparent thickness Pmm of the roll-pressed product is 1.1t or more and 2t or less.

So far, we have been talking about the shape of the electrode substrate, but the size of the chlorine gas bubbles generated from the anode is usually more than 100 times the size of the hydrogen bubbles generated from the cathode, and it varies depending on the hydrophilicity of the electrode surface, the hydrophilicity of the ion exchange membrane, and even the unevenness of the electrode surface. The porous parts of the anode expand metal are relatively small because they are arranged in large numbers and finely. Although the bubbles are easily removed at an angle in this embodiment, it is desirable for smaller bubbles to pass through the electrode part. To achieve this, a hydrophilic electrode active material coating layer is provided. It is also preferable to further process the electrode substrate surface.

In the manufacturing method of the electrode for chlor-alkali electrolysis using the ion exchange membrane method according to this embodiment, it is preferable to further include, between steps 2 and 3, step 4 of subjecting the roll-pressed product obtained in step 2 to a surface blasting treatment, and step 5 of etching the surface-blasted roll-pressed product with high-temperature hydrochloric acid to remove sharp protrusions and sharp edges on the surface.

(Step 4)
For this purpose, it is preferable to make the surface of the expanded metal substrate uneven by blasting or the like, remove burrs, and further smooth the corners and edges. In particular, smoothing the corners is important in this embodiment because the porous portion is inclined and may come into contact with the ion exchange membrane at an acute angle, so that the ion exchange membrane is not damaged at the corners. For example, in the case of sandblasting, it is preferable to use white alumina shot, a powder with an average particle size of about 0.5 mm, as a medium and perform the treatment at a pressure of about 0.2 to 0.5 MPa. However, this is adjusted according to the thickness of the titanium base plate used. Of course, it is also possible to use a medium such as SiC powder or zircon sand if the same characteristics can be obtained.

In addition, blasting with iron grit or iron shot can be used to roughen the surface, but this requires high blast pressure and blasting tends to leave iron in the titanium base material, which requires excessive etching of the base material to remove, so although it is not impossible, its use is not recommended.

(Step 5)
After blasting, it is preferable to etch the surface with a high-temperature hydrochloric acid solution in order to completely remove the blasting powder remaining on the surface, to smooth the sharp irregularities generated by blasting, and to activate the surface of the substrate. The reason why hydrochloric acid is used as the etching acid is that it has a strong etching effect and smoothes the sharp irregularities generated by blasting, etc., and this improves the separation of bubbles generated during electrolysis, so that the bubbles leave the substrate surface before they grow large, and the bubbles become small and quickly escape from the anode part. Furthermore, countless fine titanium hydrides are generated on the surface of the titanium substrate by hydrochloric acid etching, so that when an electrode coating is applied to the surface, it has extremely strong adhesion. The conditions for hydrochloric acid etching are a hydrochloric acid concentration of 18% to 25%, and a temperature of 90°C to 107°C (boiling) are preferable. The treatment time is preferably 10 to 15 minutes, and the weight reduction of titanium is preferably about 30 to 70 g/ ^m2 -projected surface, but is not limited to this.

A composite oxide-type electrode coating is applied to the surface of the substrate thus prepared. At least the surface of this electrode coating must be hydrophilic. This allows the generated gas (chlorine gas) to separate easily, and the bubbles become finer and easier to remove. The hydrophilic coating used here is preferably formed by a normal pyrolytic coating method. The solvent of the coating liquid is preferably a liquid mainly composed of alcohol. However, the electrode prepared in this way has the problem that the electrode wears out at a relatively high rate. Therefore, in consideration of durability, it is recommended that the base be coated using a normal hydrochloric acid solvent liquid, and then the surface be coated with a pyrolytic coating from the liquid that will become the hydrophilic coating described here. In other words, it is possible to laminate two or more types of coatings. Of course, if necessary, only one type of hydrophilic coating may be used.

More specifically, step 3 preferably includes step 3-1 of applying a coating liquid consisting of a dilute hydrochloric acid solution containing ruthenium or a dilute hydrochloric acid solution containing ruthenium and iridium to the surface of the roll-pressed product, and repeating thermal decomposition multiple times, and step 3-2 of applying a coating liquid containing ruthenium and mainly composed of alcohol as a solvent, or a coating liquid containing ruthenium and iridium and mainly composed of alcohol as a solvent, and performing thermal decomposition coating one or more times to make the surface of the electrode active material coating layer hydrophilic.

The components of the electrode coating are not specified here, but it is preferable that the electrode active material coating layer is an oxide coating layer consisting of two components, ruthenium or ruthenium and iridium, as the electrode active material, titanium or tin or two components of titanium and tin as stabilizers, and further containing other components as necessary. These can be used by improving conventional components. However, the electrode coating on the electrode surface must be strongly hydrophilic. Furthermore, when a long-life electrode is required as in the current situation, it is preferable to use a composite oxide in which ruthenium and iridium are used as the electrode materials and titanium is added as a stabilizer.

For hydrophilic coatings, it is desirable to use an alcohol-based liquid such as n-butanol or iso- or n-propanol as the solvent for the coating liquid containing these electrode active materials, rather than an aqueous solution, and to carry out the coating under adjusted coating conditions. This makes it possible to obtain a coating layer with a strong hydrophilic surface. Furthermore, since the hydrophilic coating produced in this way has the characteristic that the electrode active material is consumed slightly more than when dilute hydrochloric acid is used as the solvent, it is also recommended to apply an aqueous coating to the base layer and then layer a coating using an alcohol-based liquid on the surface on top of the base layer.

The electrode coating layer made from the aqueous solution system here is initially hydrophobic and has the characteristic of having a slightly high potential, but after several months to three years of electrolysis, the potential decreases and the layer becomes hydrophilic. Therefore, by using such an electrode coating with two or more layers for continuous use, it is possible to maintain a low potential and hydrophilicity over the lifespan of a long period of time.

This allows the current to be extremely excellent at a large current density of 6 kA/m ² to 8 kA/m ² , and together with low overvoltage, minimizes the effects of bubbles generated by electrolysis, i.e., allows electrolysis at a low electrolysis voltage.

This embodiment allows electrolysis at an extremely low electrolysis voltage in zero-gap ion-exchange membrane chlor-alkali electrolysis, with excellent chlorine generation efficiency and a long and stable anode life. In other words, by tilting the mesh of the porous portion of the expanded metal slightly upward from the ion-exchange membrane side toward the opposite side (back side) of the ion-exchange membrane, air bubbles can be removed more easily. In addition, by improving the electrode surface and making the electrode coating itself hydrophilic, air bubbles can be removed more easily, and the air bubbles can be smaller in diameter and more easily removed from the electrode. As a result, even if the current density is increased and the air bubble rate around the electrode is increased, the generated air bubbles remain small and escape to the rear at a faster rate. As a result, even if the current density is increased, the increase in voltage can be minimized and the voltage itself can be kept low.

When electrodes with a longer life are required, a compact electrode coating is applied to the base using a coating liquid of an aqueous solvent, and then a hydrophilic electrode coating of a hydrophilic alcohol solvent system is layered on the surface, which allows the cell voltage to be low from the beginning and enables stable electrolysis over a long period of time.

<Test 1>
A pure titanium plate with a thickness of t=0.8 mm was used to prepare an expanded metal (diamond-shaped mesh) with SW=3.0 mm, LW=5.0 mm, and an opening ratio of 40%. The strand (W) was approximately 0.9 mm, and the apparent thickness of the expanded metal was 1.8 to 1.9 mm. A porous titanium body with a different apparent thickness was prepared from this expanded metal by roll pressing. The porous titanium body was blasted at a pressure of 0.2 MPa using white alumina sand as a medium. The surface was then cleaned and activated by etching in a 20% hydrochloric acid solution at 95°C for 10 minutes. The surface of the porous titanium body thus prepared was coated with an electrode material. That is, the coating liquid was prepared by dissolving iridium chloride, ruthenium chloride, and titanium butoxide in n-butyl alcohol. The composition of the metal components in the coating liquid was iridium:ruthenium:titanium=16.7:33.3:50.0 in terms of metal molar ratio. This coating liquid was applied with a brush to the surface of the blasted and etched titanium porous body, dried at 60°C, and then pyrolyzed at 510°C for 10 minutes. The application, drying, and pyrolysis operations were repeated 10 times, resulting in the formation of a composite oxide coating with a total amount of iridium and ruthenium equivalent to 8 g/ ^m2 per projected surface of the titanium porous body. Using these as electrodes, the following electrolysis tests 1-1 to 1-7 were carried out.

That is, these electrodes were used as anodes and installed in an experimental zero-gap type ion exchange membrane electrolytic cell, and the potential and electrolysis voltage were measured. The operating temperature was 85°C, and after performing preliminary electrolysis for 10 hours at a current density of 0.6 A/ ^cm2 , the potential as an anode was measured at a current density of 0.1 A/ ^cm2 . Thereafter, the anode potential and electrolysis voltage were measured at a current density of 0.6 A/ ^cm2 . Here, the anolyte was 200 g-NaCl/L, but the pH was not adjusted. As shown in Table 1, the anode potential of Tests 1-2 to 1-6 increased slightly as the electrode inclination width (electrode thickness ratio) increased, but the electrolysis voltage was found to be lower than that of the conventional expanded metal electrode (Test 1-1) in which the base material thickness was obtained by pressing, and was 2.95 V or less. In addition, the electrolysis voltage of Test 1-7 exceeded 2.95 V. This is because the electrode was thick due to insufficient pressing, and the electrolysis current was concentrated on the front side of the electrode.

<Test 2>
For a pure titanium plate having a thickness of t=0.6 mm, LW=4.0 mm and SW=2.5 mm were prepared, and the open area ratio was changed. The apparent thickness before the roll press was 1.7 mm at an open area ratio of 10%, and 1.0 mm at an open area ratio of 70%. The thickness P of these expanded metals was set to 0.9 mm by roll press. This was 1.5 times the original plate thickness. The titanium porous body thus obtained was used as an electrode substrate and pretreated, and then coated with an electrode material and used as an anode to measure the characteristics. The titanium porous body electrode substrate prepared was blasted at a pressure of 0.2 MPa using SiC powder as a medium to provide unevenness on the surface and to homogenize the surface condition. Then, etching was performed for 10 minutes at 90° C. with a 20% hydrochloric acid aqueous solution. The same coating liquid as in Test 1 was used for this, and coating was performed under the same conditions to prepare an anode. For these anodes, the same experimental zero-gap type ion exchange membrane electrolytic cell as in Test 1 was used, and electrolysis was performed under the same conditions to measure the potential and electrolysis voltage. The results are shown in Table 2. In the case of Test 2-1, where the aperture ratio was 10%, the effective electrode area was certainly large, but the aperture was very small, and therefore air bubbles accumulated between the electrode and the ion exchange membrane, making it difficult to pass electricity at a high current density. The electrolysis voltage was far above 2.95 V. In Test 2-7, it was also observed that the effective area of the electrode itself became smaller as the aperture ratio increased, resulting in an increase in the electrolysis voltage (3.20 V).

<Comparative test>
The titanium porous body of Test 2 was processed in the same manner as the original plate, except that the expanded metal was pressed to a thickness of 0.6 mm, and the surface treatment and coating were also the same to prepare anodes. Electrolysis was performed on these bodies under the same conditions as Test 2, and the electrolysis voltage was measured. The results are shown in Table 3.

As shown in Table 3, the electrolysis voltage was significantly higher than 2.95 V in all cases. This resulted in a large power consumption.

<Test 3>
For a pure titanium plate having a thickness of 1.0 mm, an opening ratio of 50% and SW of 3.0 mm were used to produce expanded metals having LW=4.0 mm, 6.0 mm, 7.0 mm, 8.0 mm, 10.0 mm, and 12.0 mm. Among these, for the LW=4.0 mm of test 3-1, it was possible to manufacture the expanded metal, but it was found that cracks occurred partially and it was not suitable for the purpose. Except for the LW=4.0 mm portion, the expanded metal was processed by roll pressing so that the apparent thickness was 1.2 mm. These were first subjected to hydrophobic electrode coating under the following conditions, and the surface was subjected to hydrophilic electrode coating to produce an anode. As a comparative example, a sample was prepared that was subjected to only hydrophobic electrode coating (test 3-7).

The surfaces of the expanded metals prepared as above were blasted at a pressure of 0.25 MPa using white alumina as blast powder. Then, they were etched for 10 minutes with a 20% aqueous hydrochloric acid solution held at 100°C. After preparation in this way, the following pyrolysis coating was performed. First, two types of coating liquids with the same composition but different raw materials were prepared. In other words, the metal components of the coating were iridium, ruthenium, and titanium, and the composition was iridium:ruthenium:titanium = 30:30:40 (molar ratio) in terms of metal mass ratio in both cases. Coating liquid 1 was prepared by using iridium chloride, ruthenium chloride, and an aqueous titanium tetrachloride solution as raw materials, and dissolving these in a 10% aqueous hydrochloric acid solution. Coating liquid 2 was prepared by using iridium chloride, ruthenium chloride, and orthotitanium butoxide as raw materials, and dissolving these in n-butanol.

The coating conditions were: iridium + ruthenium was applied with a brush to a titanium surface at 1 g/m ² (projected surface), dried at 60° C. for 10 minutes, then heated and pyrolyzed at 480° C. for 10 minutes, and then cooled. This operation was repeated as many times as necessary. That is, the operation of applying, drying, and pyrolyzing with the coating liquid 1 was repeated five times, and then the operation of applying, drying, and pyrolyzing with the coating liquid 2 on the surface was repeated five more times to form an anode. As a comparative example, an anode was prepared as Test 3-7 by repeating the application, drying, and pyrolyzing with the coating liquid 1 only ten times.

Electrolysis was carried out on the anodes thus fabricated under the same conditions as in Test 1, and the results are shown in Table 4. As shown in Table 4, when LW/SW was greater than 3.5 times, as in Test 3-6, the small mesh area expanded, which led to poor air bubble removal and the electrolysis voltage exceeding 2.95 V. In Test 3-7, the electrolysis voltage was higher than in Test 3-5, possibly due to the large air bubbles generated by electrolysis due to the hydrophobic coating.

<Test 4>
For a pure titanium plate having a thickness of 1.0 mm, an expanded metal having an aperture ratio of 40%, an LW of 6.0 mm, and an SW of 2.0 mm, 3.0 mm, 4.0 mm, and 5.0 mm was manufactured. The expanded metal was roll-pressed to an apparent thickness of 1.2 mm. The titanium expanded metals having the same apparent thickness were blasted in the same manner as in Test 1, and further etched in 20% hydrochloric acid held at 90° C. to purify and activate the surface, and then coated with an electrode material on the surface. The anode coating was an oxide system consisting of ruthenium, titanium, and tin. That is, an aqueous solution of ruthenium chloride, tin dichloride, and titanium tetrachloride was dissolved in a mixed solution of n-butanol and a 10% aqueous hydrochloric acid solution in a volume ratio of 1:1 to prepare a coating solution. The composition of the metal components in the coating solution was ruthenium:tin:titanium=15:15:70 in terms of metal molar ratio. This coating liquid was applied with a brush so as to be uniformly distributed over the entire surface of the titanium expanded metal that had been blasted and etched, and then dried at 110°C. After that, the coating liquid was pyrolyzed in circulating air at 470°C for 10 minutes using a muffle furnace. After repeating the application, drying, and pyrolysis operations 10 times, the electrode was made by heat treatment at 470°C for 1 hour in circulating air. As a result, the amount of coating was 10 g in terms of the amount of ruthenium per ¹ m2 of projected surface. The potential and the electrolysis voltage of the zero-gap type ion exchange membrane electrolytic cell were measured for the electrode thus prepared under the same conditions as in Test 4. In addition, when the bubbles that emerged due to electrolysis were observed, the growth of the bubbles on the electrode surface was extremely small, and it was confirmed that the electrode had a hydrophilic surface. The measurement results of the potential and electrolysis voltage are shown in Table 5. As shown in Table 5, the anode potential was almost the same including the comparative example, but in the comparative example of Test 4-4, although the porous portion was large, the distance between the holes was wide, so that the apparent electrolysis voltage was large. In addition, in Test 4-5, the strands were large, and the blind area on the surface of the ion exchange membrane was large, which was thought to have led to poor escape of the generated bubbles and increased the electrolysis voltage.

<Test 5-I>
The expanded metals were prepared with a pure titanium plate having a thickness of 0.5 mm, an aperture ratio of 20%, an LW of 4.0 mm, and an SW of 1.8 mm, 2.0 mm, 2.5 mm, 3.0 mm, and 4.0 mm. The expanded metals were roll-pressed to an apparent thickness of 0.9 mm. The titanium expanded metals having the same thickness were pretreated and coated with an electrode material under the same conditions as in Test 4 to prepare electrodes. The amount of electrode coating was 8 g in terms of ruthenium per ^m2 of projected surface. The potential and the electrolysis voltage of a zero-gap type ion exchange membrane electrolytic cell were measured for the electrodes prepared in this way under the same conditions as in Test 4. The measurement results are shown in Table 6.

As shown in Table 6, the anode potential is almost the same for both the comparative examples, but in the comparative example of Test 5-1, the SW is small, which may have caused the bubbles to escape poorly, and it is believed that the electrolysis voltage was high due to electrical resistance caused by the bubbles.

<Test 5-II>
For a pure titanium plate having a thickness of 0.5 mm, a titanium porous plate was produced by changing the strand and carrying out the same processing as in Test 5-1, except that the aperture ratio was set to 25%. These were used as electrode substrates and pretreated under the same conditions as in Test 5-1, and coated with an electrode material to produce an electrode. Measurements were also carried out as the electrode under the same conditions as in Test 5-1. The results are shown in Table 7.

As shown in Table 7, no significant changes were observed overall, but in Test 5-6, where SW = 1.8 mm, the mesh size was slightly smaller, which resulted in insufficient escape of generated air bubbles, just like in Test 5-1, and it is believed that this caused the electrolysis voltage to increase, possibly due to electrical resistance caused by the air bubbles.

The electrolysis electrode of the present invention is particularly useful as an anode for ion-exchange membrane chlor-alkali electrolysis. Thanks to the new electrode structure and electrode coating, the gas bubbles generated by electrolysis (chlorine gas containing a small amount of oxygen) can be peeled off from the substrate before they grow, and can be drawn to the back side of the electrode (the opposite side of the ion-exchange membrane) while minimizing the resistance of the substrate, making it possible to obtain an extremely low electrolysis voltage. In addition, low voltages can be maintained without problems even during long-term operation. Moreover, because of the long life possible, it can be used extremely usefully in ion-exchange membrane chlor-alkali electrolysis.

1 Electrode 2 Ion exchange membrane 3 Flow of generated bubbles

After extensive research, the inventors have found that the above-mentioned problems can be solved by forming an expanded metal into a roll-pressed product and then using it as an electrode base material, and in this case, by performing roll pressing so that the apparent thickness of the roll-pressed product is not reduced to the thickness of the sheet before processing of the expanded metal (hereinafter also referred to as the original sheet) (hereinafter, a roll-pressed product that satisfies this condition is also referred to as a weakly pressed product), and have completed the present invention. That is, the electrode for chloralkali electrolysis by ion exchange membrane process according to the present invention is an electrode for an anode of a zero-gap type ion exchange membrane electrolytic cell in which one anode electrode arranged for one ion exchange membrane is arranged in the thickness direction, and the electrode for chloralkali electrolysis by ion exchange membrane process has an electrode substrate made of a perforated plate made of pure titanium, and a hydrophilic electrode active material coating layer formed on the surface of the electrode substrate, characterized in that the electrode substrate is a roll-pressed product of an expanded metal having a plate thickness of the perforated plate of t mm, an opening period of the long sides of LW mm, an opening period of the short sides of SW mm, and a strand of W mm, the opening ratio of the expanded metal being 20% or more and 60% or less, and the ratio calculated by LW/SW being 1.5 or more and 3.5 or less, the plate thickness t of the perforated plate being 0.5 mm or more and 1.0 mm or less, the opening period SW of the short sides being 2.0 mm or more and 5.5 mm or less, and the apparent thickness P mm of the roll-pressed product being 1.1t or more and 2t or less.

The method for producing an electrode for chloralkali electrolysis using an ion exchange membrane process according to the present invention is a method for producing an electrode for an anode in a zero-gap type ion exchange membrane electrolytic cell in which one anode electrode is arranged for one ion exchange membrane in the thickness direction, and includes a step 1 of preparing an expanded metal having a perforated plate made of pure titanium with a plate thickness of t mm, a long-side opening period of LW mm, a short-side opening period of SW mm, a strand of W mm, and an apparent thickness of K mm; and a step 2 of rolling the expanded metal to form an electrode substrate having an apparent thickness of K mm. and a step 3 of forming a hydrophilic electrode active material coating layer on the surface of the roll-pressed product, wherein the opening ratio of the expanded metal is 20% or more and 60% or less, the ratio calculated by LW/SW is 1.5 or more and 3.5 or less, the plate thickness t of the porous plate is 0.5 mm or more and 1.0 mm or less, the opening period SW of the short side is 2.0 mm or more and 5.5 mm or less, and the apparent thickness Pmm of the roll-pressed product is 1.1t or more and 2t or less.

In the method for producing an electrode for ion-exchange membrane-based chloralkali electrolysis according to the present invention, the step 3 preferably comprises a step 3-1 in which a coating liquid consisting of a dilute hydrochloric acid solution containing ruthenium or a dilute hydrochloric acid solution containing ruthenium and iridium is applied to the surface of the roll-pressed product, and thermal decomposition is repeated a plurality of times, and a step 3-2 in which a coating liquid containing ruthenium and mainly composed of an alcohol as a solvent or a coating liquid containing ruthenium and iridium and mainly composed of an alcohol as a solvent is applied, and thermal decomposition is performed one or more times to make the surface of the electrode active material coating layer hydrophilic . The zero-gap ion-exchange membrane electrolytic cell according to the present invention comprises an ion-exchange membrane, an anode consisting of the electrode for ion-exchange membrane-based chloralkali electrolysis according to the present invention in close contact with the ion-exchange membrane, and a cathode in close contact with the ion-exchange membrane from the opposite side to the anode, and is characterized in that the number of anode electrodes arranged for one ion-exchange membrane is one in the thickness direction.

After extensive research, the inventors have found that the above-mentioned problems can be solved by forming an expanded metal into a roll-pressed product and then using it as an electrode base material, and in this case, by performing roll pressing so that the apparent thickness of the roll-pressed product is not reduced to the thickness of the sheet before processing of the expanded metal (hereinafter also referred to as the original sheet) (hereinafter, a roll-pressed product that satisfies this condition is also referred to as a weakly pressed product), and have completed the present invention. That is, the electrode for chloralkali electrolysis by ion exchange membrane method according to the present invention is an electrode for an anode of a zero-gap type ion exchange membrane electrolytic cell in which one anode electrode arranged for one ion exchange membrane is arranged in the thickness direction, and the electrode for chloralkali electrolysis by ion exchange membrane method has an electrode substrate made of a perforated plate made of pure titanium, and a hydrophilic electrode active material coating layer formed on the surface of the electrode substrate, characterized in that the electrode substrate is a roll-pressed product of an expanded metal in which the perforated plate has a plate thickness of t mm, an opening period of the long sides of LW mm, an opening period of the short sides of SW mm, and a strand of W mm, the opening ratio of the expanded metal is 20% or more and 60% or less, and the ratio calculated by LW/SW is 1.5 or more and 3.5 or less, the plate thickness t of the perforated plate is 0.5 mm or more and 0.8 mm or less, the opening period SW of the short sides is 2.0 mm or more and 5.5 mm or less, and the apparent thickness P mm of the roll-pressed product is 1.4t or more and 2t or less.

The method for producing an electrode for chlor-alkali electrolysis by an ion exchange membrane method according to the present invention is a method for producing an electrode for an anode in a zero-gap type ion exchange membrane electrolytic cell in which one anode electrode is arranged for one ion exchange membrane in the thickness direction, and includes the steps of: step 1 of preparing an expand metal of a pure titanium perforated plate having a plate thickness of t mm, a long-side opening period of LW mm, a short-side opening period of SW mm, a strand of W mm, and an apparent thickness of K mm; step 2 of roll-pressing the expand metal to obtain a roll-pressed product having an apparent thickness of P mm as an electrode substrate; and step 3 of forming a hydrophilic electrode active material coating layer on a surface of the roll-pressed product, wherein the open area ratio of the expand metal is 20% or more and 60% or less, and the ratio calculated by LW/SW is 1.5 or more and 3.5 or less, the plate thickness t of the perforated plate is 0.5 mm or more and 0.8 mm or less, the short-side opening period SW is 2.0 mm or more and 5.5 mm or less, and the apparent thickness P mm of the roll-pressed product is It is characterized by being between 1.4 t and 2 t.

Claims (8)

An electrode base material made of a porous plate made of pure titanium;
and a hydrophilic electrode active material coating layer formed on the surface of the electrode substrate,
The electrode base material is a roll-pressed product of an expanded metal having a plate thickness of t mm, a long side opening period of LW mm, a short side opening period of SW mm, and a strand of W mm,
The opening ratio of the expanded metal is 20% or more and 60% or less,
The ratio calculated by LW/SW is 1.5 or more and 3.5 or less,
The plate thickness t of the porous plate is 0.5 mm or more and 1.0 mm or less,
The opening period SW of the short side is 2.0 mm or more and 5.5 mm or less,
The electrode for chloralkali electrolysis using an ion-exchange membrane process, wherein the apparent thickness P mm of the roll-pressed product is 1.1 t or more and 2 t or less. The electrode for chloralkali electrolysis using the ion exchange membrane method according to claim 1, characterized in that the pure titanium is JIS type 1 or JIS type 2 titanium. The electrode for chlor-alkali electrolysis using an ion exchange membrane method according to claim 1, characterized in that the hydrophilic electrode active material coating layer is an oxide coating layer containing ruthenium or ruthenium and iridium as an electrode active material, and titanium or tin or titanium and tin as a stabilizing material. An electrode for chloralkali electrolysis using an ion exchange membrane method according to claim 1, characterized in that the mesh shape of the expanded metal is rhombic or tortoiseshell shaped. A step 1 of preparing an expanded metal having a perforated plate made of pure titanium with a plate thickness of t mm, a long side opening period of LW mm, a short side opening period of SW mm, a strand of W mm, and an apparent thickness of K mm;
A step 2 of subjecting the expanded metal to roll press processing to obtain a roll press product having an apparent thickness of P mm as an electrode substrate;
Step 3: forming a hydrophilic electrode active material coating layer on the surface of the roll-pressed product;
having
The opening ratio of the expanded metal is 20% or more and 60% or less,
The ratio calculated by LW/SW is 1.5 or more and 3.5 or less,
The plate thickness t of the porous plate is 0.5 mm or more and 1.0 mm or less,
The opening period SW of the short side is 2.0 mm or more and 5.5 mm or less,
a roll-pressed product having an apparent thickness P mm of 1.1 t or more and 2 t or less. Between the step 2 and the step 3,
A step 4 of subjecting the roll-pressed product obtained in the step 2 to a surface blasting treatment;
A step 5 of etching the surface-blasted roll-pressed product with high-temperature hydrochloric acid to remove sharp protrusions and sharp edges on the surface;
The method for producing an electrode for chloralkali electrolysis using an ion exchange membrane process according to claim 5, further comprising the steps of: The method for manufacturing an electrode for chloralkali electrolysis using an ion exchange membrane method according to claim 6, characterized in that the etching treatment using high-temperature hydrochloric acid in step 5 uses an etching solution having a hydrochloric acid concentration of 18% to 25% and a temperature of 90°C or higher and a boiling point or lower. The step 3 is
A step 3-1 in which a coating liquid consisting of a dilute hydrochloric acid solution containing ruthenium or a dilute hydrochloric acid solution containing ruthenium and iridium is applied to the surface of the roll-pressed product, and thermal decomposition is repeated several times;
and Step 3-2 of applying a coating liquid containing ruthenium and having alcohol as a main component as a solvent or a coating liquid containing ruthenium and iridium and having alcohol as a main component as a solvent, and performing a coating step of thermally decomposing the coating at least once to make the surface of the electrode active material coating layer hydrophilic.

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