JP2017160481A - Method for cleaning metal foil, method for producing metal foil, and functional water generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning metal foil capable of reducing the residue in the surface of metal foil.SOLUTION: Provided is a method for cleaning metal foil comprising: an acidic electrolytic water cleaning step where metal foil is cleaned with acidic electrolytic water generated from an anode by electrolyzing an electrolyte aqueous solution dissolved with an electrolyte; a hydrogen water cleaning step where the metal foil is cleaned with hydrogen water in which pH being 7.0 to below 9.0, Electrical Conductivity value being 20.0 mS/m and oxidation reduction potential being below -300 mV; and a drying step where the metal cleaned with the hydrogen water is dried.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a metal foil manufacturing method, a metal foil cleaning method, and a cleaning liquid generator that adjust the surface state of a metal foil such as copper or aluminum to a good state.

  Conventionally, rolled copper foil has been used for circuit materials for flexible printed wiring boards and current collectors for battery electrode plates. In these applications, the rolled copper foil is not used as a simple substance, but is used by coating the rolled copper foil with an adhesive, a paint, a resin, a solvent, or a mixture thereof. For flexible printed wiring board circuit material applications, rolled copper foil is coated with an adhesive and a resin film is bonded to form a wiring board, and then the rolled copper foil is coated with an ultraviolet curable paint to form an electrical wiring circuit. To do. Moreover, in the use of the collector of a battery electrode plate, the slurry which mixed the active material of a battery, the adhesive agent, and the solvent is coated on a rolled copper foil, and an electrode plate is produced. However, since oil such as rolling oil is present on the surface of the rolled copper foil, the adhesion is poor and problems such as peeling and uneven coating occur.

  The method for producing a rolled copper foil is to reduce the thickness of an ingot obtained by melting and casting copper by repeating hot rolling, cold rolling and intermediate annealing, and finally the predetermined thickness is obtained by cold rolling. Finish like so. Oils such as rolling oil used in cold rolling and rust prevention oil that suppresses oxidation of the surface adhere to the surface of the rolled copper foil thus manufactured. Moreover, the machine oil mixed unavoidable in the manufacturing process of copper foil has adhered to the surface. Oils such as rolling oil adhering to these surfaces are removed by washing the rolled copper foil with a washing liquid containing a surfactant. Further, washing and drying are performed to remove the cleaning liquid (see, for example, Patent Document 1).

JP 2000-313980 A

  By the way, such a cleaning method has a problem that a large amount of residue remains on the surface, for example, the oil and the surfactant cannot be completely removed.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a metal foil cleaning method, a metal foil manufacturing method, and a functional water generator that can reduce surface residue. .

In order to solve such a problem, in the metal foil cleaning method of the present invention,
An acidic electrolyzed water washing step for washing the metal foil with acidic electrolyzed water generated from the anode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved;
a hydrogen water cleaning step of cleaning the metal foil with hydrogen water having a pH of 7.0 or more and less than 9.0, an EC (Electrical Conductivity) value of less than 20.0 mS / m, and a redox potential of less than −300 mV; ,
A drying step of drying the metal foil washed with the hydrogen water;
A method for cleaning a metal foil, comprising:

In the method for producing a metal foil of the present invention,
A rolling step of rolling solid metal;
An acidic electrolyzed water washing step for washing the metal foil with acidic electrolyzed water generated from the anode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved;
a hydrogen water cleaning step of cleaning the metal foil with hydrogen water having a pH of 7.0 or more and less than 9.0, an EC (Electrical Conductivity) value of less than 20.0 mS / m, and a redox potential of less than −300 mV; ,
A drying step of drying the metal foil washed with the hydrogen water.

Furthermore, in the functional water generator of the present invention,
An electrolytic cell for generating acidic electrolyzed water from the anode and electrolyzing alkaline electrolyzed water from the cathode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved;
A filter part that filters the alkaline electrolyzed water and removes impurities such as salts that are not volatilized by heating and evaporation;
An acidic electrolyzed water supply unit for supplying the acidic electrolyzed water generated by the electrolytic cell;
And a hydrogen water supply unit that supplies alkaline electrolyzed water filtered by the filter unit as hydrogen water.

  INDUSTRIAL APPLICABILITY The present invention can realize a metal foil cleaning method, a metal foil manufacturing method, and a functional water generating device that can reduce surface residue.

It is a flowchart which shows the washing | cleaning method. It is a basic diagram explaining a washing | cleaning process. It is an approximate line figure showing the composition of the functional water generating device by other embodiments.

  Next, modes for carrying out the present invention will be described with reference to the drawings.

<Embodiment>
Generally, acidic electrolyzed water that exhibits acidity, alkaline electrolyzed water that exhibits alkalinity, and neutral electrolyzed water that exhibits almost neutrality are known as electrolyzed water. Has been.

  Alkaline electrolyzed water is often used for oil stains. This is because oil stains can be emulsified due to the nature of alkali.

  However, the inventors of the present application have found that oil stains can be effectively removed without forming scales on the surface of the metal foil by washing with acidic electrolyzed water and then with hydrogen water.

  As shown in FIG. 1, the cleaning method of the present invention has a two-step cleaning process in which two types of cleaning water (acidic electrolyzed water and hydrogen water) are used. That is, cleaning with acidic electrolyzed water is performed in step SP1, and cleaning with hydrogen water is performed in step SP2. In step SP3, the remaining washing water is removed by drying.

  That is, in the acidic electrolyzed water washing step (step SP1), most of the oil adhering to the metal foil is removed by the acidic electrolyzed water and the oxide scale is removed. In the subsequent hydrogen water washing step (step SP2), the oil remaining on the metal foil is removed, and the acidic electrolyzed water used in the acidic electrolyzed water washing step is neutralized using the reducing power of the hydrogen water, and further the metal Protect the foil surface from oxidation. In the drying step (step SP3), moisture remaining on the metal foil surface is removed.

  After the metal foil is processed into a thin foil by rolling or the like, the metal foil moves to a cleaning step using the cleaning method of the present invention. The metal foil is applied to a foil (thickness of about 1 to 300 μm) made of an easily oxidizable metal such as a copper foil or an aluminum foil, but is preferably used for a metal foil of 10 μm, particularly 20 μm or more. This is because the metal foil has a certain degree of stiffness (rigidity), so that wrinkles are not easily mixed in the cleaning process. The cleaning method of the present invention can be applied to metal foils manufactured by various methods. However, the cleaning method of the present invention is used when manufactured by a thinning method by rolling a solid metal. Is preferred. This is because a large amount of oil is used when rolling the metal.

  As a cleaning method, after the foil forming step of the metal foil, the cleaning water is sprayed on the both surfaces of the metal foil flowing on the line for a predetermined time (for example, for 3 to 10 seconds) or the stored cleaning water is passed through. It is executed by letting Moreover, you may combine these methods according to washing water. In the drying step, the metal foil is dried with hot air or hot air of about 40 ° C to 130 ° C.

  For example, the cleaning method of the present invention is used in a manufacturing factory for manufacturing a copper foil. Of course, it is also possible to wash | clean the copper foil manufactured in another factory using this invention. As shown in FIG. 2, in the copper foil manufacturing factory, after the copper foil is rolled to an arbitrary thickness by the rolling process FL, the process proceeds to the cleaning process WS. The cleaning process WS includes an electrolyzed water cleaning process WS1, a hydrogen water cleaning process WS2, and a drying process WS3.

  In the electrolyzed water cleaning step WS1, the acidic electrolyzed water generated by the electrolyzed water generating device 1 is supplied to the cleaning tank 2. In the washing tank 2, acidic electrolyzed water is stored, and a collision flow is formed so as to collide with the immersed copper foil. The electrolytic bath is supplied with the newly generated acidic electrolyzed water as needed, and the acidic electrolyzed water is circulated by extracting the acidic electrolyzed water inside the cleaning bath 2 and removing the oil by a filter or floating separation. And reused.

  By using acidic electrolyzed water exhibiting acidity as cleaning water, the surface of the copper foil is oxidized and corroded. In the electrolyzed water washing step WS1, by washing in a water bath of acidic electrolyzed water, an effect of dissolving the copper foil by oxidation and removing the oxide scale can be expected.

After the electrolyzed water cleaning step WS1, the copper foil is promptly sent to the hydrogen water cleaning step WS2. In the hydrogen water cleaning step WS2, the hydrogen water generated by the hydrogen water generating device 3 is injected from the injection unit 3A onto the surface of the copper foil. Cleaning is performed by an injection method in which new cleaning water (hydrogen water) is always supplied, thereby removing a small amount of remaining oil and neutralizing acidic electrolyzed water. Moreover, until it dries by drying process WS3, a copper foil surface is maintained in a reduced state and corrosion of the copper foil surface is prevented. Further, since the reducing species exhibiting a reducing action is hydrogen (H ₂ ), it does not vaporize in the drying process and does not remain on the metal surface to form a scale.

  In the drying step WS3, drying with warm air or hot air is performed. There is no limitation on the drying temperature, and warm air of about 40 ° C to 130 ° C is used. The temperature of the warm air is appropriately selected according to the length of the drying device 5, the line speed (that is, the drying time), the air volume, the presence or absence of the formation of an oxide film, and the like.

  Next, the cleaning water used in the cleaning method of the present invention will be described.

  In the electrolyzed water cleaning step WS1, acidic electrolyzed water is used. As the acidic electrolyzed water, electrolyzed water containing oxygen (oxygen gas and ozone gas) generated on the anode side by electrolyzing dissolved water obtained by dissolving an electrolyte in raw water is used. As the raw water, it is preferable to use high-purity water from which impurities are removed by filtration through a filter such as a RO (Reverse Osmosis) membrane filter.

  There is no restriction | limiting in particular as electrolyte, Although it is possible to use various substances, it is preferable to exhibit acidity as acidic electrolysis water, and salt, hydrochloric acid, sodium carbonate, etc. are used suitably. Although there is no restriction | limiting in particular as an electrolytic cell, The thing of 2 tank type or 3 tank type which can isolate | separate only acidic electrolyzed water is used suitably.

  The acidic electrolyzed water is preferably pH 2.0 to pH 4.0 (pH 2.0 or more and less than pH 4.0. The following is used in the same meaning), more preferably pH 2.5 to pH 3.5. . If the pH is too small, the oxidizing action becomes strong and the metal foil after washing is excessively oxidized, which is not preferable. On the other hand, if the pH is too high, sufficient detergency cannot be obtained.

  The acidic electrolyzed water preferably has a redox potential of 500 mV to 1500 mV, more preferably 700 mV to 1200 mV. If the redox potential is too large, the metal foil after washing is excessively oxidized, which is not preferable. Further, if the redox potential is too small, it is not preferable because sufficient detergency cannot be obtained.

  The acidic electrolyzed water preferably has an EC (Electrical Conductivity) value of 20 mS / m or more, more preferably 40 mS / m or more. This is because the effect of removing oxide scale is enhanced by acidic substances such as chlorine and carbonic acid caused by the electrolyte. In addition, an increase in the acidic substance is expected to improve the wettability to the metal surface.

As the acidic electrolyzed water, so-called fine bubbles having a nano-order (about 10 to 1000 nm) diameter may be contained. After producing the acidic electrolyzed water, the fine bubbles can be contained in the acidic electrolyzed water by using a fine bubble generator by a high-speed swirling method or a pressure release method. As for the fine bubble generator, for example, Non-Patent Document 1 (
https://staff.aist.go.jp/m.taka/takahashi2.pdf) and Patent Document 2 (Japanese Patent Application No. 2015-34628). The fine bubbles are preferably contained in an amount of 0.2 × 10 ⁸ particles / ml or more in order to obtain a sufficient effect.

  Thereby, the surface tension as acidic electrolyzed water can be reduced, fine scratches on the surface of the metal foil can be entered, and the detergency can be improved. The material of the fine bubble is not particularly limited, but air or a specific gas can be appropriately selected and used. Moreover, as fine bubbles, the gas generated at the anode in the electrolytic cell (oxygen, chlorine, etc.) can be temporarily separated by standing, etc., and mixed with the acidic electrolyzed water again, thereby enhancing the effect as acidic electrolyzed water. It is. The structure of this electrolyzed water generating apparatus is described in Patent Document 3 (Patent Registration No. 5628403).

  Although it does not specifically limit about water temperature, The thing of about 0 degreeC-80 degreeC, More preferably, about 20 degreeC-60 degreeC is used suitably. It is appropriately selected depending on the type of oil used and the type of metal to be cleaned.

  In the hydrogen water cleaning step WS2, hydrogen water is used. As hydrogen water, water containing hydrogen generated on the cathode side is used by electrolyzing raw water using a solid electrolyte or the like. As the raw water, it is preferable to use high-purity water from which impurities are removed by filtration through a filter such as a RO (Reverse Osmosis) membrane filter. Although there is no restriction | limiting in particular as an electrolytic cell, The thing of 3 tank type | molds which has the electrolyte tank packed with the fixed electrolyte is used suitably.

  As hydrogen water, it is preferable to show the value of pH 7.0-pH 9.0. If the pH is too low, the reducing action becomes small, and if the pH is too high, it means that the concentration of impurities other than water and hydrogen is high, which is not preferable.

  The hydrogen water preferably has a redox potential of less than −300 mV, more preferably less than −400 mV. A high oxidation-reduction potential (small absolute value) is not preferable because the reduction action is low.

  The acidic electrolyzed water preferably has an EC (Electrical Conductivity) value of less than 20 mS / m, more preferably less than 10 mS / m. A large EC value means that the concentration of impurities other than water and hydrogen is high, which is not preferable.

Fine bubbles may be included as hydrogen water. After producing the hydrogen water, the fine bubbles can be contained in the hydrogen water by using a fine bubble generator using a high-speed turning method or a pressure release method. Thereby, the surface tension as hydrogen water can be reduced, and it can also enter into the fine crack on the surface of metal foil, and can improve cleaning power. It is also possible to increase the hydrogen content by separating gas (such as hydrogen) generated at the cathode in the electrolytic cell as fine bubbles and mixing it with hydrogen again. The fine bubbles are preferably contained in an amount of 0.2 × 10 ⁸ particles / ml or more in order to obtain a sufficient effect.

  Although it does not specifically limit about water temperature, The thing of about 0 degreeC-80 degreeC, More preferably, about 20 degreeC-60 degreeC is used suitably. It is appropriately selected depending on the type of oil used and the type of metal to be cleaned.

  A copper foil (100 μm) was used as the metal foil, and the one that was cut to 150 cm &#10005; 50 cm was the object to be cleaned. The cleaning water shown in Table 2 was sprayed on the object to be cleaned for 5 seconds and then dried with hot air using a dryer. The temperature of the washing water was set to 50 to 55 ° C. In Tests 7 to 12 using two types of cleaning water, the cleaning water 1 was sprayed for 5 seconds, then the cleaning water 2 was sprayed for 5 seconds, and then hot-air drying was performed with a dryer.

  The cleaning effect was evaluated on a five-point scale of “1 to 5”. The most favorable product was evaluated as “5”, and the poor product was evaluated as “1”. The results are shown in Table 2. Note that “+ fine bubbles” indicates that fine bubbles are contained. “RO water” is high-purity water filtered using an RO membrane.

The impurity concentration in Table 1 is calculated by multiplying the EC value by 8. The water temperature is the temperature at the time of measurement, and is different from the temperature at the time of washing. The apparatus used for the measurement is shown below.
pH / redox potential / EC measuring instrument: WM-32EP (manufactured by Toa DKK Corporation)
Chlorine concentration meter: RC-2Z (manufactured by Kasahara Chemical Industry Co., Ltd.)
Bubble number meter / particle measuring device: Nanosite NS500 (Malvern)

  As shown in Tests 1 to 6 in Table 2, when comparing one-stage washing of RO water, RO water + fine bubbles, alkaline electrolyzed water, alkaline electrolyzed water + fine bubbles, acidic electrolyzed water and acidic electrolyzed water + fine bubbles, The acidic electrolyzed water was excellent. However, the surface of the copper foil was oxidized with acidic electrolyzed water. In the remarks column, the oxidized scale formed on the surface of the copper foil is indicated as “oxidized dot”, and the residue scale derived from the washing water is indicated as “scale”.

  As shown in Tests 7 to 12, the results of Tests 9 and 10 were good in the two-stage cleaning. In this experiment, the sample amount was small and the evaluation was made visually, so in the cleaning results, there was almost no difference due to the inclusion of fine bubbles, but the drying time was increased by including fine bubbles. Was shortened. Moreover, in the test 12 using a detergent, the drying time was considerably longer (more than twice) as compared with other samples.

According to the above configuration, in the method for cleaning a metal foil of the present invention, an acidic electrolyzed water cleaning step of cleaning the metal foil with acidic electrolyzed water generated from the anode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved,
a hydrogen water washing step of washing the metal foil with hydrogen water having a pH of 7.0 or more and less than 9.0, an EC (Electrical Conductivity) value of less than 20.0 mS / m, and a redox potential of less than −300 mV;
A drying step of drying the metal foil washed with the hydrogen water.

  This makes it possible to neutralize without leaving residue scale with hydrogen water while effectively removing oil with acidic electrolyzed water on a flat and large metal foil, so that the metal foil surface is washed cleanly. be able to.

  In addition, when the oil adhering to metal foil in the rolling process presses with respect to metal foil by rolling, it is thought that it is closely_contact | adhered to metal foil and has penetrate | infiltrated deeply. In the case of alkaline electrolyzed water, since it is well-familiar with the oil and has an emulsifying action, the action is started from the surface of the oil film, and it is considered that removal is difficult until the end because there is much oil. On the other hand, acidic electrolyzed water is not familiar with oil and conversely with metal, so it can act on the metal surface, and as a result, it penetrates between the oil film and the metal foil and peels off the oil film itself. It may be possible.

In the hydrogen water washing step,
The hydrogen water is
It contains 0.2 × 10 ⁸ fine bubbles / ml or more.

  Thereby, hydrogen water can enter the fine irregularities of the metal foil, can improve the cleaning power, and can shorten the drying time.

The acidic electrolyzed water is
The oxidation-reduction potential is 600 mV or more.

  Thereby, the acidic electrolyzed water can remove the oxide scale on the surface of the metal foil by dissolving the metal by oxidation.

In the acidic electrolyzed water washing step,
The acidic electrolyzed water is
It contains 0.2 × 10 ⁸ fine bubbles / ml or more.

  Thereby, acidic electrolyzed water can enter the fine unevenness | corrugation of metal foil, and can improve a cleaning power.

In the acidic electrolyzed water washing step,
Immerse the metal foil in the stored acidic electrolyzed water,
In the hydrogen water washing step,
The hydrogen water is jetted onto the metal foil.

  Thus, in the acidic electrolyzed water cleaning step, the surface of the metal foil is effectively cleaned by removing the oxide scale, while in the hydrogen water cleaning step, new hydrogen water is always sprayed to minimize the residue on the surface of the metal foil. Can be limited.

According to the above configuration, in the metal foil manufacturing method of the present invention, a rolling step of rolling a solid metal,
An acidic electrolyzed water washing step for washing the metal foil with acidic electrolyzed water generated from the anode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved;
a hydrogen water cleaning step of cleaning the metal foil with hydrogen water having a pH of 7.0 or more and less than 9.0, an EC (Electrical Conductivity) value of less than 20.0 mS / m, and a redox potential of less than −300 mV; ,
And a drying step of drying the metal foil washed with the hydrogen water.

  Thereby, since the oil used in the rolling process can be effectively removed, it is possible to produce a clean metal foil with almost no residue on the surface.

<Other embodiments>
In embodiment mentioned above, the case where acidic electrolyzed water was produced | generated with the electrolyzed water production | generation apparatus 1 and hydrogen water was produced | generated with the hydrogen water production | generation apparatus 3 which consists of another structure was described. The present invention is not limited to this, and can be generated by a single device.

  As shown in FIG. 4, the electrolytic cell 21 of the functional water generator 20 has an anode chamber 21A having an anode electrode and a cathode chamber 21B having a cathode electrode. In addition, there is no restriction | limiting in the structure of an electrolytic cell, It is possible to use the electrolytic cell of various structures, such as 1 tank type, 2 tank type, and 3 tank type electrolytic cells.

  The anode chamber 21 </ b> A supplies the generated acidic electrolyzed water to the electrolyzed water storage unit 22. The electrolyzed water storage unit 22 supplies the acidic electrolyzed water to the acidic electrolyzed water providing unit 23 in response to a request from the acidic electrolyzed water providing unit 23.

  The cathode chamber 21 </ b> B supplies the generated alkaline electrolyzed water to the filter unit 25. The filter unit 25 has, for example, a filter configuration such as an RO membrane, removes ionic substances from the alkaline electrolyzed water, and supplies the hydrogen water to the hydrogen water storage unit 26. The hydrogen water storage unit 26 supplies hydrogen water to the hydrogen water providing unit 27 in response to a request from the hydrogen water providing unit 27.

  Gases generated from the acidic electrolyzed water and hydrogen water generated in the anode chamber 21A and the cathode chamber 21B are separated by a gas-liquid separator (not shown), and each gas is supplied to a fine bubble generator (not shown). By doing this, fine bubbles may be contained in the acidic electrolyzed water and / or hydrogen water. In that case, it is preferable to supply hydrogen water after filtration by the filter unit 25 to the fine bubble generator.

  The functional water generating apparatus 20 having such a configuration can be used not only for cleaning metal foil but also as a cleaning water generating apparatus for general metal parts. In addition to cleaning, the functional water generator 20 can be used for all applications where both acid electrolyzed water and hydrogen water are required. For example, after sterilizing foods such as cut vegetables using acidic electrolyzed water, neutralization with hydrogen water makes it possible to remove the chlorine odor from the food.

According to the above configuration, the functional water generator of the present invention includes an electrolytic cell that generates acidic electrolyzed water from the anode and electrolyzed alkaline electrolyzed water from the cathode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved,
A filter part that filters the alkaline electrolyzed water and removes impurities such as salts that are not volatilized by heating and evaporation;
An acidic electrolyzed water supply unit for supplying the acidic electrolyzed water generated by the electrolytic cell;
And a hydrogen water supply unit that supplies alkaline electrolyzed water filtered by the filter unit as hydrogen water.

  Thereby, since the alkaline electrolyzed water originally discarded can be used as hydrogen water, acidic electrolyzed water and hydrogen water can be generated simultaneously.

  It has the 1st fine bubble production | generation part which generate | occur | produces a fine bubble between the said electrolytic vessel and an acidic electrolyzed water supply part.

  Thereby, fine bubble can be contained in acidic electrolyzed water, and detergency can be improved.

  It has a 2nd fine bubble production | generation part which generate | occur | produces a fine bubble between the said filter part and hydrogen water supply part, It is characterized by the above-mentioned.

  Thereby, a fine bubble can be contained in hydrogen water, and detergency can be improved.

  It has a gas-liquid separation part which isolate | separates gas from the said alkaline electrolyzed water, and supplies the isolate | separated gas with respect to a said 2nd fine bubble production | generation part.

  Thereby, since hydrogen can be supplemented as a fine bubble, the hydrogen concentration in hydrogen water can be secured.

  The present invention can be applied to, for example, a cleaning process used in a metal foil manufacturing factory.

1: Electrolyzed water generating device 2: Cleaning tank 3: Hydrogen water generating device 5: Drying device 20: Functional water generating device FL: Rolling process WS: Cleaning process WS1: Electrolyzed water cleaning process WS2: Hydrogen water cleaning process WS3: Drying process

Claims (10)

An acidic electrolyzed water washing step for washing the metal foil with acidic electrolyzed water generated from the anode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved;
a hydrogen water cleaning step of cleaning the metal foil with hydrogen water having a pH of 7.0 or more and less than 9.0, an EC (Electrical Conductivity) value of less than 20.0 mS / m, and a redox potential of less than −300 mV; ,
A drying step of drying the metal foil washed with the hydrogen water;
A method for cleaning a metal foil, comprising: In the hydrogen water washing step,
The hydrogen water is
The method for cleaning a metal foil according to claim 1, comprising 0.2 × 10 ⁸ fine bubbles / ml or more. The acidic electrolyzed water is
The method for cleaning a metal foil according to claim 1 or 2, wherein the oxidation-reduction potential is 600 mV or more. In the acidic electrolyzed water washing step,
The acidic electrolyzed water is
It contains 0.2 * 10 < ⁸ > pieces / ml or more of fine bubbles. The method for cleaning a metal foil according to any one of claims 2 to 3. In the acidic electrolyzed water washing step,
Immerse the metal foil in the stored acidic electrolyzed water,
In the hydrogen water washing step,
The said hydrogen water is sprayed on the said metal foil. The cleaning method of the metal foil in any one of Claims 1-4 characterized by the above-mentioned. A rolling step of rolling solid metal;
An acidic electrolyzed water washing step for washing the metal foil with acidic electrolyzed water generated from the anode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved;
a hydrogen water cleaning step of cleaning the metal foil with hydrogen water having a pH of 7.0 or more and less than 9.0, an EC (Electrical Conductivity) value of less than 20.0 mS / m, and a redox potential of less than −300 mV; ,
A drying step of drying the metal foil washed with the hydrogen water. An electrolytic cell for generating acidic electrolyzed water from the anode and electrolyzing alkaline electrolyzed water from the cathode by electrolyzing an aqueous electrolyte solution in which the electrolyte is dissolved;
A filter part that filters the alkaline electrolyzed water and removes impurities such as salts that are not volatilized by heating and evaporation;
An acidic electrolyzed water supply unit for supplying the acidic electrolyzed water generated by the electrolytic cell;
And a hydrogen water supply unit that supplies the alkaline electrolyzed water filtered by the filter unit as hydrogen water. The functional water generating device according to claim 7, further comprising a first fine bubble generating unit that generates fine bubbles between the electrolytic cell and the acidic electrolyzed water supply unit. The functional water generator according to claim 7 or 8, further comprising a second fine bubble generator that generates fine bubbles between the filter unit and the hydrogen water supply unit. The functional water generator according to claim 9, further comprising a gas-liquid separator that separates gas from the alkaline electrolyzed water and supplies the separated gas to the second fine bubble generator.

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