JPH11333457A - Production of electrolytic water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic water making method capable of simply washing electrolytic water having washing capacity more excellent than that of electrolytic water made by a conventional electrolizing method. SOLUTION: The anode soln. supplied to a water electrolyzing tank 1 demarcated into two or three chambers by an ion exchange membrane 2 is passed through a cooling jacket 16 before supply to be cooled so as to advance electrolytic reaction at 0-20 V. By performing electrolytic reaction at low temp., a precursor of radicals excellent in washing capacity can be contained in the formed electrolytic water in large quantities and the consumption of electrodes is suppressed to continue stable electrolysis over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anode water (acidic water) and / or a cathode water (alkali water) having an excellent cleaning effect.
More specifically, the present invention relates to a method for producing anodic water and / or cathodic water having an excellent cleaning effect used for cleaning electronic devices such as semiconductors and liquid crystals.

[0002]

2. Description of the Related Art In the manufacture and cleaning of highly integrated electronic components such as liquid crystals and semiconductor wafers, sulfuric acid, hydrofluoric acid, hydrogen peroxide, hydrochloric acid, etc. conventionally prepared specifically for such applications. Has been used. These will be used in the future depending on the application, but they are obtained by specially refining products manufactured by the corresponding chemical processes, and the metal components mixed in from the catalyst etc. in the manufacturing process The operation is complicated to perform the removal and the like, resulting in an expensive product. Further, even if the refining operation is carefully performed, it is not always possible to sufficiently cope with the decrease in the allowable impurity amount accompanying the advancement of electronic devices, and a new alternative method is required.

[0003] One of the alternatives is the use of ozone water. In particular, high-concentration ozone water produced by electrolysis is known to be extremely effective for cleaning electronic devices. However, the use of ozone water alone may not be sufficient, and there is an increasing need for a treatment liquid that has other functions that ozone water does not have, such as an oxidizing action and a reducing action, and that does not contain any metal components. The treatment liquid includes so-called anodic water or superacid water. The anodic water usually has a pH of 2.7 or less and an oxidation-reduction potential (OR
P) is 1.1 V or more and has an oxidizing power, so that it has an effect of decomposing organic substances and dissolving and removing metal precipitates, and is used for cleaning electronic devices, though slightly. I have. Simultaneously with the production of the anode water, cathode water having a pH of 10 or more and an ORP of 0 V or less is produced as a by-product in the cathode chamber of the electrolytic cell. So-called electrolyzed water having oxidizing or reducing properties produced by a relatively simple operation of electrolysis of water (the former is referred to as acidic water or anodic water, and the latter is referred to as cathodic water or alkaline water) is converted into high-purity acid or alkali, Alternatively, it has been reported that when used in place of a reagent such as hydrogen peroxide, a cleaning effect equivalent to that of the reagent can be obtained and a remarkable cost reduction can be achieved.

[0004] Ordinary electrolyzed water, for example, anodic water, can be easily obtained by supplying dilute hydrochloric acid as an anolyte solution raw material for electrolysis. In addition, when ozone or the like is generated only by supplying pure water, water having a high ORP can be obtained. The raw material chloride ions are supplied to the cathode chamber and sent to the anode chamber through the membrane,
It is also reported that the desired electrolyzed water can be obtained more economically. The production efficiency of anode and cathode water varies depending on operating conditions such as the type of feed water, the type of electrode catalyst, and the current density. Further, it is preferable that the effective anode and cathode water contain a high concentration of radicals which enhance the cleaning effect. In semiconductor cleaning, it is necessary to reduce impurities generated and mixed in an electrolytic cell as much as possible, and it is required that heavy metal impurities due to electrodes are not generated. An iridium oxide-based catalyst is a preferable electrode catalyst capable of suppressing the generation of these impurities. However, the catalyst does not have sufficient resistance to chlorine gas and ozone gas which stably generate radicals, and thus does not significantly contribute to an increase in the cleaning effect. If radicals can be generated in a stable state, electrolyzed water with an excellent cleaning effect can be obtained.However, the generation efficiency of these radicals depends not only on the catalyst but also on other electrolysis conditions such as the type of supply water and current density. Also depends.

In general, in water electrolysis, oxygen is generated using water as a raw material on the anode side which loses electrons (formula). Hydrochloric acid is added to promote the production of free chlorine and hypochlorous acid (formula). Ozone is also generated depending on the selection of the catalyst (formula). _{2H 2 O → O 2 + 4H} + + 4e 2Cl - → Cl 2 + 2e Cl 2 + H 2 O → HClO + H + + Cl - 3H 2 O → O 3 + + 6H + + 6e hydrogen ions produced at the anode reaction formula is partly cathode , But remains in the anode and is acidic. The high ORP is also derived from free chlorine and hypochlorous acid ORP. In terms of equilibrium theory, the former takes precedence in oxygen generation and chlorine generation, but the latter also progresses in many electrodes, and it is easy to advance chlorine discharge ahead of oxygen by selecting a catalyst. The current efficiency of the chloride ion oxidation reaction depends on the concentration and p
H dependent.

[0006] The above-mentioned ozone is generally unstable, and is known to generate active OH radicals and O radicals by reaction with water. However, ozone has been reported to be fairly stable in clean pure water with a half-life of several hours. This suggests that the generation of radicals by ozonolysis requires a certain amount of stimuli such as impurities and ultraviolet rays and a catalyst. Therefore, in order to generate radicals, a small amount of a catalyst is dissolved, or a substance that promotes the decomposition of ozone is fixed in the piping of the cell and brought into contact with the electrolyzed water. However, when ozone or active chlorine is decomposed by contact with the contaminant to be treated to generate radicals, this is not necessary. In the elementary process of the electrode reaction, adsorbed ions and discharge intermediate species of water molecules are generated. That is, chemical species corresponding to radicals are generated on the electrode surface. It is also conceivable that these react with the solution molecules to generate radical species. The following is presumed as a reaction process of radical generation in the presence of chloride ions. Parentheses in the formula indicate chemical species on the electrode surface, and. Indicates a radical. Cl ⁻ → (Cl) + e (Cl) + H ₂ O → ClOH ⁻ + H ⁺ ClOH ⁻ → Cl ⁻ + .OH

Further, the generation of radicals by the following reaction process is expected from the oxidation of water. H ₂ O → (OH) + H ⁺ + e (OH) + Cl ⁻ → ClOH ⁻ ClOH ⁻ → Cl ⁻ + OH Cathode water having a reducing ability is originally derived from hydrogen gas. At the cathode of a cell having a cation exchange membrane, hydrogen is generated from hydrogen ions transferred from the anode side or from cathode water. Hydrogen radicals may be generated depending on the electrode and electrolysis conditions. Hydrogen peroxide, which can be generated directly or indirectly by electrolysis using oxygen as a raw material, becomes a raw material that generates radicals like ozone,
Effective for cleaning. The electrolyzed water produced by electrolysis as described above has a higher cleaning ability as it contains more active species such as radicals, and has been widely used especially for cleaning electronic devices that require particularly high purity. The probabilities of producing high-capacity electrolyzed water are being sought.

[0008]

An object of the present invention is to provide an electrolytic water having an excellent cleaning effect, particularly an anode water and a cathode water which are effective for cleaning liquid crystals and semiconductors in the electronics industry.
It is an object of the present invention to provide a method for producing electrolyzed water capable of stably and efficiently obtaining high ORP anode water or low ORP cathode water.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method for obtaining electrolyzed water by energizing a water electrolyzer partitioned into two or three chambers by an ion exchange membrane, wherein the electrolysis reaction is carried out at 0 to 20 ° C. A method for producing electrolyzed water, characterized in that:

Hereinafter, the present invention will be described in detail. The feature of the present invention is that by maintaining the temperature of the electrolytic solution of the electrolytic reaction low, the generation efficiency of radicals and other active chemical species having excellent cleaning ability which contribute to the increase in the cleaning function of the generated electrolytic water is increased. In order to maximize the cleaning effect. The reason for this is not clear, but can be guessed as follows. Active chemical species such as radicals that contribute to the improvement of the cleaning performance described above have a relatively short life, and once the chemical species is generated from the precursors such as ozone and free chlorine, the cleaning performance is high for a relatively short time. After that, the radicals disappear and the cleaning ability is greatly reduced. The concentration of the generated chemical species is proportional to the concentration of the precursor.

Therefore, when producing electrolyzed water containing a precursor such as ozone or free chlorine by water electrolysis, in order to increase the cleaning ability in actual use, it is necessary to not only increase the concentration of the precursor but also increase the concentration of the precursor. It is desirable that the body does not decompose, but is decomposed only at the time of actual cleaning, and the cleaning ability is exhibited. The decomposition of the precursor generated when the temperature of the produced electrolyzed water is high proceeds, and the solubility of the generated precursor is further reduced according to Henry's law. Will decrease. Further, depending on the type of the precursor, there is a case where it is easier to generate the material at a low temperature in an equilibrium theory. When electrolysis is performed at a low temperature, there is a disadvantage that the cell voltage is increased, but there is an advantage that electrolyzed water having excellent cleaning ability can be provided. Further, when the electrolysis is performed at a low temperature, the elution of the electrode substance is suppressed, the life of the electrode is extended, and the effect of preventing impurities from being mixed into the generated electrolyzed water is also produced.

The present inventors have studied a wide range of preferred temperatures for the electrolytic reaction in the production of electrolyzed water, that is, the temperature of the electrolytic solution in which a precursor for generating a chemical species having a high cleaning ability as described above has reached the present invention. It is. Conventional electrolyzed water production is performed without cooling, so the temperature of the electrolysis reaction is 25-50 ° C
It was about. According to the study of the present inventors, radicals are hardly detected in electrolyzed water generated by electrolysis at these temperatures, and thus the cleaning ability is insufficient. On the other hand, the generation of radicals is observed in the electrolytic water generated when the electrolytic reaction is carried out at 0 to 20 ° C. as in the present invention, and the elution of the electrode material is further reduced, and a longer electrode life can be expected than in the conventional electrolytic reaction. . In the electrolytic reaction of the present invention, 0 to 20 ° C. is the temperature of the electrolytic solution, and the electrolytic bath itself is cooled during the electrolytic reaction, or the electrolytic solution supplied to the electrolytic bath is cooled to perform the electrolytic reaction. The temperature of the electrolyte is maintained at 0 to 20 ° C. When the electrolysis reaction is carried out at a temperature exceeding 20 ° C., the reaction itself is close to or the same as the conventional electrolysis reaction, there is little or no radical, and the elution of the electrode substance becomes remarkable. Further, the obtained anode water ORP is reduced. The lower limit of the reaction temperature is 0 ° C., which is the freezing point of water.

The method of the present invention is carried out using an electrolytic cell partitioned into two or three chambers by an ion exchange membrane, and other requirements are not particularly limited. The ion exchange membrane is preferably a perfluorocarbon ion exchange membrane having good corrosion resistance (for example, NAFION of DuPont, FLEMION of Asahi Glass Co., Ltd., ACIPLEX of Asahi Kasei Corporation), and the ion exchange membrane is a conventional neutral membrane. Unlike the case, the anolyte and the catholyte hardly mix because the liquid permeability is almost zero. Therefore, the efficiency decreases due to the partial mixing of the generated anolyte (anode water) and the catholyte (cathode water). Can be avoided, and operation under a high current density becomes possible, and a desired amount of washing water can be obtained in a short time. In the present invention, highly oxidizable hypochlorite ion (ClO ⁻ ) is often generated on the anode side,
The ion exchange membrane has extremely high resistance to the ions and can be operated stably.

The above-mentioned ion exchange membrane may be used alone, but in order to prevent contamination of ions or gas generated at the counter electrode, a noble metal layer is formed on at least one of the ion exchange membranes. Are preferably arranged so as not to contact the electrodes. In this case, hydrogen and oxygen that have permeated the membrane at the noble metal layer are recombined to form water and eliminate the effect on the counter electrode, or the noble metal layer acts as a physical shield plate to prevent mixing of the electrolyte. You. In order to completely eliminate the influence of the counter electrode, it is possible to provide an intermediate chamber between a plurality of ion exchange membranes to form a three-chamber structure. However, as a simpler method, at least one hydrogen atom permeable membrane is required. The electrolytic cell may be configured with a hydrogen storage alloy or metal foil interposed. Examples of the material of the foil include Pd, Pd-Au, and Pd-Ag. In this case, the foil functions as a bipolar electrode plate. That is, the permeating protons are separated into hydrogen and electrons in the atomic state, and after they are led to the opposite surface, they are regenerated into protons by their recombination, resulting in the flow of electricity. Exhibits an excellent shielding effect on substances.

[0012] One ion exchange membrane is used and the ion exchange membrane is composed of a resin fiber support, or one of a plurality of ion exchange membranes is composed of a resin fiber support, or two or more ion exchange membranes are used. A membrane can be formed by sandwiching one resin fiber support between the membranes. In this case, the current distribution of the ion exchange membrane and the electrodes becomes non-uniform, and the radical generation rate stably even at a low current density. An increasing effect occurs. Fiber thickness is 0.
01 to 5 mm, fiber thickness 0.001 to 1 mm, porosity 20 to
Preferably it is 95%. The material is preferably a chemically stable insulating material, for example, a hydrocarbon resin such as polypropylene or polyethylene, a fluororesin such as PVDF, PTFE, or FEP, or a sintered ceramic fiber structure.

In order to maintain the purity of the generated anode water, the anode to be used is made of a metal such as noble metal, titanium, tantalum or the like which is stable against oxidation, or a conductive ceramic such as carbon or silicon carbide as a base material. It is preferable that the substrate is formed by supporting a noble metal such as platinum, ruthenium, and iridium, a conductive ceramic or diamond as a catalyst on the surface of the substrate. The amount of catalyst is 1 to 50 on the substrate surface.
The degree of formation of a catalyst layer having a thickness of μm is good, and the use of a conductive diamond as a catalyst is easy because radicals are easily generated due to poor activity in the electrolytic reaction of water and high overvoltage. The cathode used uses noble metals stable against reduction, metals such as titanium, zirconium and tantalum, carbon and conductive ceramics such as silicon carbide as base materials to maintain the purity of the generated cathode water.
It is preferable that the substrate is formed by supporting a noble metal such as platinum, ruthenium, and iridium, a conductive ceramic or diamond as a catalyst on the surface of the substrate. As the amount of the catalyst, a degree of forming a catalyst layer of 1 to 50 μm on the substrate surface is good,
Further, as a catalyst, the conductive diamond is poor in activity for the electrolytic reaction of water and has a high overvoltage, so that radicals are easily generated, and its use is preferred. Gas-liquid permeation on both sides of the ion exchange membrane of the two-chamber electrolytic cell as a solid electrolyte, or one anode side of two ion exchange membranes and the cathode side of another ion exchange membrane in the three-chamber electrolytic cell It is also possible to adopt a structure in which a anodic material and a cathodic material are adhered to each other. Further, a zero-gap type electrolytic cell in which plate-shaped anodes and cathodes are closely attached to both surfaces of the ion exchange membrane may be used.

The shapes of the anode and the cathode are not particularly limited, but a plate-like member having an aperture ratio of 40 to 80% is preferably used in order for the reaction to proceed smoothly. A stable film made of PTFE resin or the like may be formed on the surface. For the purpose of producing anode water, pure water and / or hydrochloric acid are supplied to the anode chamber of the above-mentioned electrolytic cell, and electricity is supplied between the anode and the cathode. When only pure water is supplied, the cation exchange membrane functions as an electrolyte to generate oxygen (which may contain ozone) by water electrolysis, and the oxygen dissolves in the anolyte to generate anodic water. Further, when hydrochloric acid is supplied to the anode chamber, chlorine ions are electrolytically oxidized to chlorine gas and further to hypochlorite ions, thereby producing anode water having a low pH and strong oxidizing power.

On the other hand, for the purpose of producing cathode water, pure water and / or ammonium hydroxide are supplied to the cathode chamber of the above-mentioned electrolytic cell, and electricity is supplied between the anode and the cathode. When only pure water is supplied, the cation exchange membrane functions as an electrolyte, hydroxyl ions are generated by water electrolysis, and cathode water is generated. Also, when ammonium hydroxide is supplied to the cathode compartment, the concentration of hydroxyl ions increases, and stronger cathode water is generated. The anode water or cathode water thus produced may contain a small amount of cations or anions, and in the method of the present invention, the obtained anode water or cathode water is placed in a cation provided outside the electrolytic cell. Alternatively, cationic or anionic impurities can be removed through an anion resin packed tower and through the packed tower to obtain more pure anode water or cathode water. The present invention can also be applied to electrolysis in which anode water is produced in the anode chamber while hydrogen peroxide is synthesized by supplying oxygen to the cathode chamber.

FIG. 1 is a schematic longitudinal sectional view illustrating an electrolytic cell that can be used in the method of the present invention. The electrolytic cell main body 1 has a frame-shaped anode chamber gasket 3 and a cathode chamber gasket 4 sandwiching a perfluorocarbon-based cation exchange membrane 2, and each gasket 3, 4 on a surface opposite to the cation exchange membrane 2. It is provided with an anode chamber wall plate 5 and a cathode chamber wall plate 6 having a function of flowing an electrolytic solution and having at least a portion in contact with the inner electrolytic solution made of a fluororesin. A porous anode 7 made of a powder of a platinum group metal or an oxide thereof is provided in close contact with the anode surface of the cation exchange membrane 2, and platinum or carbon is provided on the cathode surface of the cation exchange membrane 2. The porous sheet-shaped cathode 8 made of is provided in close contact. An anode current collector 9 and a cathode current collector 10 are connected to the anode 7 and the cathode 8, respectively, and electricity is supplied through the current collector.

An anolyte flow passage is provided inside the anode chamber wall plate 5.
An anolyte dissolved in hydrochloric acid or the like supplied from an anolyte inlet 12 enters the anode chamber through the anode chamber opening 13 and comes into contact with the anode 7 to form a high oxidizing power such as hypochlorous acid. Oxidized to a compound with redox potential and converted to anolyte as anolyte outlet
Retrieved from 14. A cooling jacket 16 is provided around the extension pipe 15 on the tip side from the anolyte inlet 12, and a refrigerant such as liquid nitrogen or ethylene glycol is introduced from the refrigerant inlet 17 to bring the anolyte in the extension pipe 15 to a desired temperature. And then supply it to the anode chamber. On the other hand, a catholyte flow passage 18 is formed inside the cathode chamber wall plate 6,
Ultrapure water supplied as necessary from the catholyte inlet 19 enters the cathode compartment through the cathode compartment opening 20 and is brought into contact with the cathode 8 together with the migration water from the anode containing ions, and is reduced. It is taken out from the exit 21. In the production of washing water using the illustrated electrolytic cell, since the anolyte before being supplied to the anode chamber is cooled by the refrigerant in the extension pipe 15, the electrolytic reaction in the anode chamber is performed at a low temperature of 0 to 20 ° C. Can be provided, the anode water containing a large amount of radical precursors necessary for improving the cleaning ability is provided, furthermore elution of the electrode substance is prevented,
A stable electrolytic reaction can be continued for a long time.

[0018]

EXAMPLES Next, examples of the production of electrolyzed water by the method for producing electrolyzed water according to the present invention will be described, but the examples do not limit the present invention.

[0019]

Example 1 Three films of Nafion 117 (manufactured by DuPont) were stacked as a cation exchange film, and a film having a platinum coating formed by electroless plating was used on one of the central films. On the anode chamber side of the cation exchange membrane, a titanium mesh coated with an iridium oxide catalyst generated by thermal decomposition with an electrode area of 10 cm ² was adhered as an anode, and a carbon sheet coated with a platinum catalyst was formed on the cathode chamber side. As a cathode, and a silver fiber sintered plate (2 mm thick) was connected as a cathode current collector. These members were fastened with bolts and nuts to form a two-chamber electrolytic cell. Ultrapure water (18 M ohm cm) whose pH was adjusted to 2.5 with hydrochloric acid was supplied to the anode chamber side of the electrolytic cell at a rate of 10 cc / min.
A current was passed, and the supply water tank, cell, and piping were cooled such that the cell temperature at this time was 20 ° C. or less. Add DMPO (radical stabilizer) to the generated anode water at the outlet
When 10 mM was added and radicals were detected by the ESR apparatus, a peak corresponding to OH radicals was detected. It was confirmed that the anode gas contained 500 ppm of ozone and the anolyte contained 100 ppm of dissolved chlorine. Exit ORP is 1100
mV and the total concentration of heavy metals was 50 ppt.

[0020]

Example 2 Electrolysis performance when the cell temperature was changed in the electrolytic system of Example 1, that is, when the temperature was 10, 20, 30, or 40 ° C., the voltage, the generated ozone concentration, the presence or absence of radicals, the ORP
And the amounts of heavy metal impurities are summarized in Table 1. As can be seen from Table 1, when the temperature is lowered, the cell voltage increases, but particularly at 10 or 20 ° C., the amount of generated radicals and the ozone concentration increase.

[0021]

[Table 1]

[0022]

Example 3 A two-chamber electrolytic cell was constructed and electrolyzed in the same manner as in Example 1 except that hydrochloric acid was not added to the anode side. 10m of DMPO in the generated anode water at the outlet
When M was added and radicals were detected by an ESR apparatus, a peak corresponding to OH radicals was detected. 500 ppm of ozone is detected in the anode gas, and the ORP at the outlet is
1100 mV and the total concentration of heavy metals was 5 ppt.

[0023]

Embodiment 4 Table 2 summarizes the electrolytic performance of the electrolytic system of Example 3 when the cell temperature was changed. As can be seen from Table 2, when the temperature is lowered, the cell voltage increases, but particularly at 10 or 20 ° C., the amount of generated radicals and the ozone concentration increase.

[0024]

[Table 2]

[0025]

According to the present invention, there is provided a method for obtaining electrolyzed water by energizing a water electrolysis tank partitioned into two or three chambers by an ion exchange membrane, wherein the electrolysis reaction is carried out at 0 to 20 ° C. This is a method for producing electrolyzed water. In the method of the present invention, the electrolytic reaction during the production of electrolyzed water is performed at a relatively low temperature of 0 to 20 ° C.
Ozone and free chlorine, which are the precursors of radical generation with excellent cleaning ability, remain in the produced electrolytic water without being decomposed and are decomposed during actual cleaning to efficiently produce short-lived radicals in the required amount. To be able to generate. Therefore, according to the method of the present invention, it is possible to produce electrolyzed water (anode water and cathodic water) having better washing ability than before. In addition, in the method of the present invention, since the electrolysis is performed at a low temperature, elution of the electrode substance can be reduced, the impurity concentration in the generated electrolytic water can be reduced, and the life of the electrode and the electrolytic cell can be prolonged.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view illustrating an electrolytic cell that can be used in the method of the present invention.

[Explanation of symbols]

1 ・ ・ ・ Electrolyzer main body 2 ・ ・ ・ Cation exchange membrane 2 3 ・
..Anode compartment gasket 4 ・ ・ ・ Cathode compartment gasket 5 ・ ・ ・ Anode compartment wall plate 6 ・
..Cathode room wall plate 7 ・ ・ ・ Anode 8 ・ ・ ・ Cathode 9 ・ ・
・ Anode current collector 10 ・ ・ ・ Cathode current collector 11 ・ ・ ・ Anolyte flow passage 12 ・ ・ ・ Anolyte inlet 13 ・ ・ ・ Anode chamber opening 14
・ ・ ・ Anolyte outlet 15 ・ ・ ・ Extension pipe 16 ・ ・ ・ Cooling jacket 17 ・ ・ ・ Coolant inlet 18 ・ ・ ・ Cathode flow passage
19 ・ ・ ・ Cathode liquid inlet 20 ・ ・ ・ Cathode chamber opening 21 ・ ・
・ Cathode solution outlet

Continued on the front page (72) Inventor Yoshinori Nishiki 1-3-1304, Fujisawa 1-chome, Fujisawa-shi, Kanagawa Prefecture (72) Inventor Naoya Hayami 33 Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Toshiba Production Technology Research Institute ( 72) Inventor Naoaki Sakurai 33, Shinisogo-cho, Isogo-ku, Yokohama-shi, Kanagawa Pref.

Claims (1)

[Claims] 1. A method for obtaining electrolyzed water by energizing a water electrolysis tank partitioned into two or three chambers by an ion exchange membrane,
A method for producing electrolyzed water, wherein the electrolysis reaction is performed at 0 to 20 ° C.