JP2021134398A - Method for monitoring detachability and method for manufacturing titanium metal foil - Google Patents

Abstract

To provide a method for monitoring detachability capable of easily checking whether a titanium metal foil can be successfully detached when an attempt is made to detach the titanium metal foil from an electrode.SOLUTION: A method for monitoring detachability of a titanium metal foil from a metallic electrode includes a measuring step of checking whether a load per unit width when detaching the titanium metal foil is less than or equal to 1.0 N/mm.SELECTED DRAWING: None

Description

The present invention relates to a method for monitoring peelability and a method for producing a metallic titanium foil.

Titanium sponge can usually be produced by the so-called Kroll process. On the other hand, in order to produce a sheet-like material such as a foil with a relatively thin thickness of metallic titanium, the above-mentioned sponge titanium is melted and cast into a titanium ingot or titanium slab, and then forged, rolled or other. It is necessary to perform the required processing. Therefore, it cannot be said that sheet-shaped metallic titanium such as foil can be produced efficiently and at low cost in such a process requiring melting and processing.

Under such circumstances, a molten salt electrolytic precipitation method in which metallic titanium is precipitated using a molten salt bath instead of the above-mentioned melting and processing has attracted attention from the viewpoint of reducing energy consumption and cost in the manufacturing process. ing.

Regarding the molten salt electrolytic precipitation method, Patent Document 1 states, "A method for producing a titanium foil or a titanium plate by a molten salt electrolytic precipitation method using a constant current pulse, from glassy carbon, graphite, Mo and Ni. After forming a titanium electrodeposition film on the surface of a cathode electrode composed of one or more selected ones, one or both of a step of applying an external force to the titanium electrodeposition film and a step of removing at least a part of the cathode electrode are performed. Thereby, a method for producing a titanium foil or a titanium plate, which separates the titanium electrodeposition film from the cathode electrode, has been proposed. According to the examples of Patent Document 1, a relatively small titanium electrodeposition film deposited on a cathode electrode made of glassy carbon, graphite or Ni can be peeled off by a physical external force or the like. There is. It has also been shown that the cathode made of nickel may not be able to be peeled off due to physical external force. Reaching is required for cathodes made of molybdenum.

International Publication No. 2018/159774

It would be cost effective if the titanium foil could be peeled off from a metal electrode instead of glassy carbon. Nickel is an impurity in the production of titanium sponge by the Kroll process, and it is desirable to avoid using a nickel electrode as an electrode for electrodepositing metallic titanium. However, if the metal titanium foil is continuously peeled off even though the metal electrode and the metal titanium foil are firmly bonded to each other and the metal titanium foil cannot be peeled off mechanically, the metal titanium foil breaks. The metal titanium foil with a sharp fracture surface may run wild (flutter), and the safety of the manufacturing site cannot be ensured.

Here, the present inventors have found that the metallic titanium foil deposited on the metal electrode can be mechanically peeled off by appropriately controlling the temperature and pulse current conditions of the molten salt bath. ..

When the metal titanium foil deposited on the metal electrode is peeled off by the action of a physical external force or the like, wrinkles may occur in the peeled metal titanium foil. The peeled metal titanium foil has a difference in smoothness between the surface in contact with the electrode and the surface in contact with the molten salt bath. Therefore, it may be desired to smooth the surface by rolling. The peeled metal titanium foil can be passed through a rolling roll and rolled into a long sheet, but even if the wrinkled metal titanium foil is rolled as described above, the wrinkles can generally be removed by the rolling process. Wrinkles remain on the rolled material without being able to do so. In addition, it is not realistic to always visually monitor the presence or absence of wrinkles on the metal titanium foil after peeling during mass production.

Therefore, an object of the present invention is to provide a peelability monitoring method capable of easily confirming whether or not the metal titanium foil can be peeled off satisfactorily when the metal titanium foil is to be peeled off from the electrode. ..

That is, the present invention is a method of monitoring the peelability of the metal titanium foil from the metal electrode on one side, and the load per unit width during the peeling operation of the metal titanium foil is 1.0 N / mm or less. It is a peelability monitoring method including a measurement step for confirming that.

In one embodiment of the peelability monitoring method according to the present invention, it is confirmed in the measurement step whether the load per unit width is 0.2 N / mm or less.

In one embodiment of the peelability monitoring method according to the present invention, the angle formed by the direction of peeling the metal titanium foil from the electrode and the surface of the electrode is 45 ° to 100 ° as measured from the surface of the electrode. It will be within the range.

In one embodiment of the peelability monitoring method according to the present invention, an electrodeposition step of obtaining the metallic titanium foil by electrodepositing metallic titanium on the electrode by molten salt electrolysis is further included before the measurement step. ..

Further, in another aspect, a monitoring step of carrying out any of the above-mentioned peelability monitoring methods and an electrodeposition step of obtaining the metallic titanium foil by electrodepositing metallic titanium on the electrode by molten salt electrolysis. It is a manufacturing method of the metal titanium foil including.

On another side, it is a method for manufacturing a metal titanium foil in which the load per unit width at the time of peeling operation of the metal titanium foil from the metal electrode is 1.0 N / mm or less.

In one embodiment of the method for producing a metallic titanium foil according to the present invention, the load per unit width during the peeling operation of the metallic titanium foil from the metal electrode is 0.2 N / mm or less.

According to one embodiment of the present invention, when the metal titanium foil is to be peeled from the electrode, it can be easily confirmed whether the metal titanium foil can be peeled off satisfactorily.

It is the schematic which shows an example of the internal structure of the electrolytic apparatus used in one Embodiment of the peelability monitoring method which concerns on this invention. It is the schematic which shows an example of the internal structure of the electrolytic apparatus used in one Embodiment of the peelability monitoring method which concerns on this invention. It is the schematic which shows the internal structure of the electrolytic apparatus in Examples 1 and 2 and Comparative Example 1. FIG. FIG. 3 is a schematic schematic cross-sectional view taken along the line III-III of FIG. 3A. It is the schematic which shows an example of the measuring method of the peeling strength using the peeling tester in one Embodiment of the peeling property monitoring method which concerns on this invention. It is a photograph which shows the evaluation result of the wrinkle of the metal titanium foil in Example 1. FIG. It is a photograph which shows the evaluation result of the wrinkle of the metal titanium foil in Example 4. It is the description of the part which can be the target of EPMA analysis of the sample in Examples 1 to 4 and Comparative Examples 1 and 2.

The present invention is not limited to each of the embodiments described below, and the components can be modified and embodied without departing from the gist thereof. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in each embodiment.

[Peelability monitoring method]
One embodiment of the peelability monitoring method according to the present invention includes an electrodeposition step and a measurement step. In the measurement step, it is confirmed whether the load per unit width at the time of the peeling operation is within a predetermined range. By doing so, it is possible to easily monitor whether the metal titanium foil can be peeled off, and further, the occurrence of wrinkles in the peeled metal titanium foil.

In the electrolyzer 1 shown in FIG. 1, the inside is in an inert gas atmosphere such as argon or in an appropriate depressurized state, the molten salt bath Bf is stored in the electrolytic cell 2, and the molten salt bath Bf is cylindrical or cylindrical and made of metal. The cathode 4 and the anode 5 held at a predetermined distance from the cathode 4 are immersed in the molten salt bath Bf, respectively. By energizing the electrode 3 from a power source (not shown) while rotating the cathode 4 around the central axis, metallic titanium is deposited on the surface of the cathode 4, so that the cathode 4 and the sheet in contact with the cathode 4 are formed. A laminate made of metal titanium foil Ts can be obtained. Then, as the cathode 4 rotates, the sheet-shaped metal titanium foil Ts of the laminated body is peeled off on the bath surface of the molten salt bath Bf using the blade 6, and the sheet-shaped and long metal titanium foil Ts is peeled off. Is wound up by the coil winder 7. As a result, the sheet-shaped metal titanium foil Ts can be continuously produced while being peeled from the surface of the cathode 4. In the above production, when the sheet-shaped metal titanium foil Ts is mechanically peeled from the surface of the cathode 4, wrinkles may or may not occur on the sheet-shaped metal titanium foil Ts after the peeling. For example, it is conceivable to constantly visually monitor the presence or absence of wrinkles in the continuously manufactured metallic titanium foil, but this is not desirable from the viewpoint of improving productivity.
Further, if the coil winding machine 7 is forced to wind the laminated body even though the peelability is low, that is, the peeling is difficult, the metal titanium foil Ts may be broken in the vicinity of the blade 6. Immediately after the fracture, the metal titanium foil having a sharp fracture surface violently (flutters), so that the safety of the manufacturing site cannot be ensured.

Therefore, the present inventors include a condition including the temperature of the molten salt bath, the average current density at the time of electrolysis, and the pulse current in which the energization stop period is periodically provided and the energization period and the energization stop period are alternately repeated. Was changed, and the peel strength between the electrode of the laminated body and the metal titanium foil obtained thereby and the presence or absence of wrinkles were confirmed, respectively. As a result, the present inventors have found a range of peel strength that enables safe mechanical peeling. Furthermore, it was found that there is a certain relationship between the peel strength and the occurrence of wrinkles in the peeled metallic titanium foil. In other words, in the present invention, it was possible to numerically determine whether or not mechanical peeling is possible, and further, the peel strength at which wrinkles are less likely to occur on the metal titanium foil after peeling. The wrinkles of the metal titanium foil can be confirmed by visual observation of the electrode side surface of the metal titanium foil.
Hereinafter, each step will be described.

<Electrodeposition process>
In the electrodeposition step, metallic titanium is electrolyzed on the electrode by molten salt electrolysis using an electrolyzer. By doing so, a laminate having an electrode and a metal titanium foil in contact with the electrode is obtained. In order to improve the electrodeposition efficiency of metallic titanium (that is, to facilitate electrodeposition), the molten salt bath contains lower titanium chloride such as titanium dichloride or titanium trichloride, and then the anode and cathode are energized. You can do it. Lower titanium chloride can be produced, for example, by adding titanium tetrachloride to titanium sponge.

(Electrolyzer)
In the present invention, various electrolyzers can be used. An example of the electrolytic device 100 shown in FIG. 2 is a batch type, and is an electrode 120 including an electrolytic cell 110 in the shape of a closed container for storing the molten salt bath Bf, and an anode 121 and a cathode 122 arranged by being immersed in the molten salt bath Bf. And a power source 130 connected to the anode 121 and the cathode 122 and energizing the anode 121 and the cathode 122. Since the electrolyzer 1 shown in FIG. 1 can continuously electrodeposit metallic titanium by rotating the cathode 4, it is not a batch production but a continuous production.

(Molten salt)
The molten salt constituting the molten salt bath Bf in the electrolytic cells 2 and 110 can be a mixture of one or more halides. Typical halides include chlorides such as _{MgCl 2} , NaCl, KCl, CaCl _{2 and LiCl.}

The molten salt bath Bf preferably contains two or more kinds selected from the group consisting of _{MgCl 2} , NaCl, KCl, CaCl _{2, and LiCl.} By including two or more of these, the molten state of the molten salt bath Bf can be maintained satisfactorily even at a low temperature to some extent, so that the metal titanium foil can be deposited in the molten salt bath in a low temperature range. However, the content of the above-mentioned halides such as chlorides can be appropriately determined based on the specific type of salt, molar standard, and mass standard in consideration of the operating temperature and the like. The molar content is measured by ICP emission spectrometry.

A metal titanium source for depositing the metal titanium foil on the electrode may be added in advance to the molten salt bath Bf. The metallic titanium source is lower titanium chloride, and preferably contains at least TiCl _x (X = 2 to 3). It is preferable that TiCl _x (X = 2 to 3) contains TiCl ₂ as a main component, and TiCl ₃ may be contained in an amount equal to or less than the molar amount of TiCl _{2. The amount of TiCl x} (X = 2 to 3) in the molten salt bath can be appropriately set, and for example, it is 1 to 10% by mass.

(Anode / Cathode)
The anodes 5 and 121 and the cathodes 4 and 122 can be, for example, rod-shaped, long strip-shaped, plate-shaped, cylindrical or other columnar or lump-shaped, which are used while moving. If you want to set the distance between the electrodes of the anodes 5 and 121 and the cathodes 4 and 122 within a specific range, make the shapes of the anodes 5 and 121 and the cathodes 4 and 122 in the vertical cross section similar to each other. Is preferable. For example, when a tubular, rod-shaped, or columnar cathode is used and the anode is arranged outside the cathode, the anode 221 may also be tubular as in the electrolytic device 200 shown in FIG. 3A. The electrolytic device 200 shown in FIG. 3A has substantially the same configuration as the electrolytic device 100 shown in FIG. 2, except that the shapes of the anode 221 and the cathode 222 are changed. Further, a rod-shaped or columnar cathode 222 having a fixed axial position and being rotatable may be used, and a plate-shaped anode 221 having an arc-shaped cross section may be used at the facing portion. Even in this case, the facing portions of the anode 221 and the cathode 222 can maintain substantially the same distance between the electrodes.

Here, among the anodes 5, 121, 221 and the cathodes 4, 122, 222 immersed in the molten salt bath Bf in the electrolytic cells 2, 110, 210, examples of the anodes 5, 121, and 221 include metallic titanium. .. As the metallic titanium, for example, sponge titanium, titanium scrap, a titanium rod and / or a titanium plate and the like can be used. When the sponge titanium is used as an anode, the lumpy sponge titanium may be installed in a Ni-made basket and the Ni-made basket may be energized. Since Ni has a lower ionization tendency than Ti, it is possible to elute only titanium sponge as an anode without eluting Ni.

Further, the cathodes 4, 122 and 222 made of metal can be appropriately selected, and examples thereof include molybdenum and titanium.
When the cathodes 4, 122 and 222 are molybdenum, the electrodeposition of metallic titanium gives a laminate including the cathodes 4, 122 and 222 and the metallic titanium foil deposited on the surface of the cathode, and the laminate is obtained. , A diffusion layer containing Ti and Mo may be provided at the boundary between the metallic titanium foil and the cathodes 4, 122 and 222. On the other hand, when the cathodes 4, 122 and 222 are made of titanium, the electrodeposition of metallic titanium gives a laminate including the cathodes 4, 122 and 222 and the metallic titanium foil deposited on the surface of the cathode. Even in this case, the metallic titanium foil is peeled off.
In the present specification, the diffusion layer means a layer in which the proportion of Ti represented by the following formula (1) is in the range of 1% to 99%.
Ti ratio (%) = (Ti concentration (mass%)) / (Ti concentration (mass%) + Mo concentration (mass%)) x 100 ... (1)
An example of a method for measuring the thickness of the diffusion layer will be described below.
A sample piece containing a metal electrode and a metal titanium foil is collected from the laminate. Next, at least three test pieces are collected from the sample piece. In the EPMA analysis, the cross section of the test piece (see FIG. 6) is measured for the amount of Ti and Mo along the thickness direction, and the thickness of the layer within the range of the above Ti ratio is determined. The maximum value of the above thicknesses of at least three test pieces is defined as the thickness of the diffusion layer.

As the shape of the cathode, for example, as shown in FIGS. 3A and 3B, it is preferable that at least a part of the surface of the cathode on which metallic titanium is deposited has a curved surface shape. When such a cathode is used, metallic titanium can be electrodeposited on the cathode surface while rotating the cathode, which contributes to miniaturization of the apparatus during continuous production. That is, it contributes to the production as illustrated in FIG. The electrolyzer 200 shown in FIGS. 3A and 3B includes a cylindrical or cylindrical cathode 222 having a cylindrical surface and a cylindrical anode 221 arranged so as to surround the cathode 222.
When both the surface of the anode and the surface of the cathode have a curved shape, it is easy to maintain a constant distance between the electrodes even if the cathode is moved, so that metallic titanium can be uniformly deposited over a wide area of the surface of the cathode. From this point of view, the surface of the anode and the surface of the cathode may have curved surfaces similar to each other.

(Temperature of molten salt bath)
The electrodeposition of metallic titanium is performed in the molten salt bath Bf. The temperature of the molten salt bath Bf is controlled, for example, in the range of 350 ° C. to 600 ° C. The upper limit side of the temperature of the molten salt bath Bf may be 515 ° C. or lower. In the electrodeposition of metallic titanium at a temperature lower than the above temperature, metallic titanium is unlikely to precipitate on the cathode. In addition, electrodeposition of metallic titanium in an aqueous solution is usually impossible. Due to the presence of water, hydrogen gas is preferentially generated over the precipitation of metallic titanium. Therefore, metallic titanium is electrodeposited on the electrode in the molten salt bath Bf controlled within the above temperature range.

(Average current density)
Average current density of the cathode 4,122,222 is, for example, ^{0.01A / cm 2 ~0.09A / cm 2} . As a result, efficient precipitation of metallic titanium, formation of an appropriate diffusion layer when a diffusion layer is formed, and suppression of dendrite growth can be achieved, and anodes 5, 121, and 221 are well dissolved. Will be done. The average current densities of the cathodes 4, 122 and 222 can be calculated by ^{the formula: average current density (A / cm 2} ) = average current (A) ÷ electrolytic area (cm ^2). Here, the electrolytic area is calculated by the formula: electrolytic area (cm ² ) = cathode immersion surface area = cathode diameter (cm) × π × cathode height (cm) in the case of a cathode having a cylindrical surface, for example. Further, the average current is an average value of currents flowing at a predetermined time for obtaining the average current density.

(Pulse current)
The current flowing through the electrode may be a pulse current in which an energization stop period is periodically provided to set the current value to zero (that is, no energization is performed), and the energization period and the energization stop period are alternately repeated. The pulse current can be realized by ON / OFF control in which the supply of the current for depositing the metallic titanium and the stop of the current supply are alternately repeated. By using the ON / OFF control pulse current, the titanium concentration in the vicinity of the cathode decreases during energization, but titanium is supplied to the vicinity of the cathode by diffusion when the energization is stopped. That is, it is considered that the non-uniformity of the concentration of Ti dissolved in the molten salt bath Bf due to diffusion when the current supply is stopped is eliminated or alleviated. As a result, it is considered that metallic titanium having excellent smoothness and higher purity can be obtained on the surfaces of the cathodes 4, 122 and 222.

By appropriately adjusting the temperature of the molten salt bath, the average current density, the pulse current, and the like, a metallic titanium foil having a target thickness can be obtained.

<Measurement process>
In the measurement step, the peel strength between the electrode and the metal titanium foil in the laminated body is measured, and it is confirmed whether the peel strength is 1.0 N / mm or less. The peel strength may be a load (N) per unit width (mm). In the measuring step, using a peeling tester to measure the peeling strength between the electrode and the metallic titanium foil is only an example of monitoring. For example, a sample (test piece) that can be set in a peeling tester can be collected from a part of the laminated body produced by the batch method, and the peeling strength can be determined in advance. If the result is good, the metal titanium foil may be peeled off from the laminate. When metallic titanium is continuously electrodeposited as in the electrolytic device 1 shown in FIG. 1, it is preferable to measure the peel strength over time and perform monitoring.

(Peeling strength)
The peel strength between the metal electrode and the metal titanium foil in the laminated body can also be measured using a peel tester as described above. While the peel strength is being measured, the angle between the direction of peeling the metallic titanium foil from the electrode and the surface of the electrode may be 100 ° or less as measured from the surface of the electrode, and further in the range of 45 ° to 100 °. It is preferable to keep it inside. When the cathode is cylindrical or cylindrical and the surface of the cathode is curved, the angle may be measured with the tangent line of the surface of the cathode at the peeling base point of the metal electrode and the metal titanium foil as the electrode surface. By adjusting the angle at the time of peeling strength measurement as described above, plastic deformation due to bending of the metal titanium foil can be appropriately suppressed during peeling.
At this time, the peel strength is preferably 1.0 N / mm or less, more preferably 0.2 N / mm or less.
When the peel strength is 1.0 N / mm or less, the mechanical peelability is good, so that continuous electrodeposition of metallic titanium and continuous peeling of the metallic titanium foil from the cathode are possible. That is, it can be said that continuous production of long metal titanium foil is possible. On the other hand, if the peeling strength exceeds 1.0 N / mm, the metallic titanium foil may break during the peeling operation, so that it is possible to determine that the mechanical peeling is stopped on the production line.
Further, when the peeling strength is in the range of more than 0.2 N / mm and 1.0 N / mm or less, wrinkles may occur irregularly on the metal titanium foil after peeling. That is, it is not possible to accurately predict when wrinkles will occur. In this case, it may be necessary to observe the surface of the peeled metal titanium foil on the cathode side in the production line to confirm the presence or absence of wrinkles.
Further, when the peeling strength is 0.2 N / mm or less, the metal titanium foil after peeling can accurately suppress the occurrence of wrinkles.
Next, an example of a method for measuring the peel strength using a peel tester is shown.
First, a 70 mm × 10 mm sample is collected from a part of the laminate using a cutter or the like. Next, as shown in FIG. 4, the sample 500 is placed on the stage 550 (horizontal plane) of the 90 ° peeling tester, the metal titanium foil 510 is peeled off by 10 mm from the end of the sample 500, and the peeled portion is chucked. Sandwich with. Next, the end of the sample 500 on the stage 550 and the end of the cathode 122 opposite to the end are fixed with fixing jigs 511 and 512, respectively. Then, the chuck is raised vertically upward V at 20 mm / sec, and the stage 550 is moved in the horizontal direction H at 20 mm / sec. At this time, the peel strength is determined according to the following formula (2). In the example of FIG. 4, since the surface of the cathode 122, which is an electrode, and the horizontal direction coincide with each other, the angle between the peeling direction of the metallic titanium foil and the surface of the cathode is 90 ° as measured from the surface of the cathode 122. be.
Peeling strength = (average load (N) in displacement of 5 mm to 25 mm after the start of peeling) / (width of the metal titanium foil parallel to the direction perpendicular to the direction of moving the stage (mm)) ... (2)

Next, an example in the case of using a rotating electrode as in the electrolytic device 1 shown in FIG. 1 will be shown.
In the electrolyzer 1 shown in FIG. 1, for example, energization of the electrode 3 is started while rotating the cathode 4 in the direction of arrow DR1, and energization is stopped when the cathode 4 makes one round. Next, a cut is made in a part of the sheet-shaped metal titanium foil Ts electrodeposited on the cathode 4 with a cutter, and the sheet-shaped metal titanium foil Ts electrodeposited about half a circumference from the cut portion is peeled off from the cathode 4. In this process, there is an opportunity to measure the peel strength using a force gauge. Next, the tip of the peeled sheet-shaped metal titanium foil Ts is wound around the coil winder 7.
The energization of the electrode 3 is resumed, and the coil winder 7 is rotated in the direction of the arrow DR2 to perform continuous collection. The peel strength can be continuously confirmed by the driving force of the coil winder 7 or a tension meter or the like.
By providing the coil winder 7 with a moving mechanism (not shown), the distance between the coil winder 7 and the cathode 4 can be appropriately adjusted. For example, when winding the tip of the peeled sheet-shaped metal titanium foil Ts around the coil winder 7, the distance between the coil winder 7 and the cathode 4 is brought closer. On the other hand, at the start of winding the sheet-shaped metal titanium foil Ts, tension is applied to the sheet-shaped metal titanium foil Ts so as not to loosen, and the coil winder 7 and the cathode 4 are separated from each other.

<Manufacturing method of metallic titanium foil>
In one embodiment of the method for producing a metallic titanium foil according to the present invention, the metallic titanium foil is formed by electrodepositing metallic titanium on the electrode by the monitoring step of carrying out the peelability monitoring method and the molten salt electrolysis. It may include an electrodeposition step of obtaining.

For example, when the metal titanium foil is manufactured by the batch method using the electrolytic devices 100, 200 and the like shown in FIGS. 2 and 3A to 3B, a sample is taken from a part of the laminate in advance and the peel strength thereof is measured. By doing so, it is possible to easily monitor the mechanical peelability and the occurrence of wrinkles on the metal titanium foil after the peeling.

Further, for example, when the metal titanium foil is continuously produced while rotating the metal electrode by using the electrolyzer 1 or the like shown in FIG. 1, it is continuously produced by the driving force of the coil winder 7, the tension meter, or the like. The peel strength can be measured and monitoring can be performed. Here, if the load per unit width during the peeling operation exceeds 1.0 N / mm, the electrodeposition of the metal titanium foil can be temporarily stopped because there is a risk of breakage. After that, the electrodes may be maintained and the production of the metallic titanium foil may be resumed. Examples of the maintenance include replacement of metal electrodes.

In one embodiment of the method for producing a metallic titanium foil according to the present invention, the load per unit width at the time of the peeling operation of the metallic titanium foil from the metal electrode may be 1.0 N / mm or less. The load per unit width during the peeling operation is preferably 0.2 N / mm or less. When the metal titanium foil is continuously produced while rotating the metal electrode by using the electrolytic device 1 or the like shown in FIG. 1, the peeling strength is continuously produced by the driving force of the coil winder 7 or the tension meter or the like. Can be monitored. Therefore, it is preferable to manufacture the metal titanium foil while adjusting the driving force of the coil winder 7 and the like so that the load per unit width at the time of peeling is within a desired range.

The present invention will be specifically described with reference to Examples and Comparative Examples. The following examples and comparative examples are merely specific examples for facilitating the understanding of the technical contents of the present invention, and the technical scope of the present invention is not limited by these specific examples.

(Manufacturing of metal titanium foil)
The electrolyzer 200 shown in FIGS. 3A and 3B was installed. The dimensional shape of the bath portion of the electrolytic cell 210 of the electrolytic device 200 was 470 mmΦ × 500 mm depth. Note that FIGS. 3A and 3B show an outline of the device configuration, and the scale thereof is not always accurate. Next, 140 kg of molten salt (MgCl ₂ : NaCl: KCl = 2: 1: 1 (molar ratio conversion)) was put into the electrolytic cell 210 of the electrolyzer 200 to raise the temperature of the molten salt to 700 ° C. bottom. Then, titanium sponge was immersed in the bath, and titanium tetrachloride was added thereto to obtain a molten salt bath Bf containing _{about 7% by mass of lower titanium chloride (TiCl 2} and TiCl _3). After obtaining this molten salt bath Bf, the temperature of the molten salt bath Bf was controlled to 500 to 520 ° C.

Next, an anode 221 made of metallic titanium and a cathode 222 made of metallic molybdenum were prepared. A titanium plate was used, and a cylindrical anode 221 having an inner diameter (diameter) of 160 mm was used. On the other hand, the molybdenum plate was a cylindrical cathode 222 having an inner diameter (diameter) of 100 mm and a height of 250 mm. In the electrolytic cell 210 of the electrolyzer 200, the cylindrical cathode 222 is positioned inside the cylindrical anode 221 and the height direction of the anode 221 and the cathode 222 is substantially parallel to the depth direction of the molten salt bath Bf. The anode 221 and the cathode 222 were arranged so as to be. The distance between the electrodes was kept constant over the entire circumference of the anode 221 and the cathode 222. That is, the central axis of the anode 221 and the central axis of the cathode 222 are at the same position.

A pulse current was supplied to the anode 221 and the cathode 222 using the electrolytic device 200, and electrolysis was performed in the molten salt bath Bf. As shown in Table 1 below, by changing each condition and precipitating metallic titanium over the entire surface of the cathode 222 on the anode 221 side for Examples 1 to 4 and Comparative Examples 1 and 2, a laminate was obtained. Was done. At this time, the target thickness of the metallic titanium foil deposited on the cathode 222 was appropriately adjusted to be 90 to 150 μm.

After the completion of electrolysis, the laminate was lifted from the molten salt bath Bf, pickled, and further washed with water to remove the molten salt adhering to the surface of the cathode and the metallic titanium foil, respectively. Further, the laminate was dried. In any of Examples 1 to 4 and Comparative Examples 1 and 2, metallic titanium having a size equivalent to the surface area of the cathode immersed portion was deposited on the cathode 222.

[evaluation]
The cylindrical laminate was cut in the direction of the central axis with a cutter knife to form a plate-shaped laminate, and the surface of the cathode of the laminate was placed on a table. Then, in the central portion of the plate-shaped laminate, the longitudinal direction is 70 mm, the surface of the laminate on the metal titanium foil side and the width direction orthogonal to the longitudinal direction is 10 mm, and two samples are collected by a cutter knife. Obtained. The peel strength was measured and wrinkles were confirmed in one sample, and the thickness of the diffusion layer was measured in the other sample. In the measurement of peel strength, the stage 550 was moved along the longitudinal direction. The measurement method of each evaluation will be described below.

(Peeling strength)
For the above sample, the peel strength between the metallic titanium foil and the cathode was measured by the method described above. The results are shown in Table 2. In Comparative Examples 1 and 2, since the measurable load was exceeded during the measurement, the measurement was stopped in order to prevent debris from scattering due to the breakage of the metallic titanium foil. That is, in Comparative Examples 1 and 2, the peel strength was calculated based on the average value of the loads in the section where the peeling was possible from the peeling displacement of 5 mm.
<Peeling conditions>
Peeling tester: Digital force gauge ZTS-200N (measurable load: 200N) manufactured by Imada Co., Ltd. and slide table P90-200N for 90 degree peeling test
Peeling angle: 90 °
Peeling speed: 20 mm / min (same speed in vertical and horizontal directions)
Peeling strength: Average value of load (N) in the section of 20 mm from 5 mm to 25 mm of peeling displacement

(Evaluation of wrinkles)
Next, after peeling the metal titanium foil from the above sample, the presence or absence of wrinkles in the metal titanium foil was confirmed by visually observing the entire surface of the metal titanium foil in contact with the cathode. The results are shown in Table 2, FIG. 5A (Example 1), and FIG. 5B (Example 4) below, respectively. FIG. 5A shows the evaluation results without wrinkles, and FIG. 5B shows the evaluation results with wrinkles. In Comparative Examples 1 and 2, since the measurement was stopped during the measurement of the peel strength, no wrinkles on the surface of the metal titanium foil in contact with the cathode were confirmed.

(Thickness of diffusion layer)
The sample 500 shown in FIG. 6 includes a metal titanium foil 510, a diffusion layer 515, and a cathode 222 in this order from the top. Test pieces A to C of the sample 500 are cut with a cutter knife so that L1 is 5 mm, L2 is 28.5 mm, L3 is 28.5 mm, L4 is 5 mm, L5 is 4.5 mm, and L6 is 4.5 mm. was gotten. That is, three test pieces for EPMA analysis were obtained from one sample 500.
EPMA analysis was performed using an electron probe microanalyzer (SUPERPROBE JXA-8100, manufactured by JEOL Ltd.), and the amounts of Ti and Mo were measured along the thickness direction for the cross sections of test pieces A to C, and the maximum of them was measured. The value was taken as the thickness of the diffusion layer. The results are shown in Table 2 below.

(Confirmation of variation)
Next, a total of 10 batches of metallic titanium foil were produced under the same conditions as in Example 1. Then, a sample was prepared by the method described above, and the thickness of the diffusion layer of each production lot was measured based on the sample. As a result, the number of lots in which the maximum thickness of the diffusion layer was less than 4.0 μm was 10. Furthermore, even after the peelability test of all lots, no wrinkles were generated on the metal titanium foil.

Next, a total of 10 batches of metallic titanium foil were produced under the same conditions as in Example 4, and the thickness of the diffusion layer of each production lot was measured. As a result, the number of lots in which the maximum thickness of the diffusion layer was 4.0 μm or more and 5.4 μm or less was 8, while the number of lots in which the maximum thickness of the diffusion layer was less than 4.0 μm was 2. Furthermore, when the wrinkles of the metal titanium foil were confirmed by observing the surface in contact with the cathode after the peelability test of the lot in which the maximum thickness of the diffusion layer was 4.0 μm or more and 5.4 μm or less, 4 out of 8 were confirmed. As for, the metal titanium foil had wrinkles.

(Correlation between width of metallic titanium foil and peel strength)
In the same titanium foil production lot as in Example 1, the width of the sample was doubled (20 mm) and the load at the time of peeling was measured. As a result, the load per unit width in the peeling operation was 0.1 N / mm, which was the same as that of Example 1, but the load was double that of Example 1. That is, even if the width of the sample was changed, the load per unit width during the peeling operation did not fluctuate significantly.

(Discussion by Example)
In Examples 1 to 4, the peel strength between the electrode and the metallic titanium foil was 1.0 N / mm or less, so that the metallic titanium foil could be mechanically peeled from the metal electrode. By observing the surface of the metal titanium foil on the electrode side after peeling, the presence or absence of wrinkles could be easily evaluated. Further, in Example 1, it was confirmed that the peel strength between the electrode and the metal titanium foil was 0.2 N / mm or less, so that no wrinkles were generated in the metal titanium foil after the metal titanium foil was peeled off.

If the metal titanium foil is continuously peeled off while electrodepositing the metal titanium foil on the surface of the cylindrical electrode in the electrolyzer 1 shown in FIG. 1, the metal titanium foil is peeled off toward the coil winder 7. , The cathode can be transferred in the tangential direction of the cathode at the point where the tip of the blade and the cathode meet. On the other hand, in the peeling using the tensile tester in Examples 1 to 4, the metal titanium foil is transferred vertically upward, and the cathode is transferred horizontally by the stage. That is, the angle formed by the direction in which the metallic titanium foil is peeled from the cathode and the surface of the cathode (which may be the tangent line of the cathode at the contact point with the tip of the blade) is within the range of 45 ° to 100 ° as measured from the surface of the cathode. The peeling of the metal titanium foil by the tensile tester is common to the continuous peeling of the metal titanium foil by the electrolytic device 1 shown in FIG. Therefore, according to Examples 1 to 4, the peel strength between the metallic titanium foil and the cathode is measured, and it is confirmed whether the value is 1.0 N / mm or less, and further, at 0.2 N / mm or less. It is considered useful in monitoring to confirm the existence. In addition, these findings can be applied to the production of continuous metallic titanium foil as shown in FIG.

1,100,200 Electrolyzer 2,110,210 Electrolytic cell 3,120,220 Electrode 4,122,222 Cathode 5,121,221 Anode 6 Blade 7 Coil winder 130, 230 Power supply 500 Sample 510 Metal titanium foil 511 512 Fixing jig 515 Diffusion layer 550 Stage A, B, C Test piece Bf Molten salt bath H Horizontal direction Ts Long metal titanium foil V Vertically above

Claims (7)

A method of monitoring the peelability of a metallic titanium foil from a metal electrode.
A peelability monitoring method including a measurement step for confirming whether the load per unit width at the time of the peeling operation of the metal titanium foil is 1.0 N / mm or less. The peelability monitoring method according to claim 1, wherein it is confirmed in the measurement step whether the load per unit width is 0.2 N / mm or less. In the measurement step, claim 1 or 2 wherein the angle formed by the direction of peeling the metallic titanium foil from the electrode and the surface of the electrode is within the range of 45 ° to 100 ° as measured from the surface of the electrode. The peelability monitoring method described in 1. The peelability according to any one of claims 1 to 3, further comprising an electrodeposition step of obtaining the metallic titanium foil by electrodepositing metallic titanium on the electrode by molten salt electrolysis before the measuring step. Monitoring method. A monitoring step for carrying out the peelability monitoring method according to any one of claims 1 to 4,
An electrodeposition step of obtaining the metallic titanium foil by electrodepositing metallic titanium on the electrode by molten salt electrolysis, and
A method for manufacturing a metal titanium foil including. A method for manufacturing a metallic titanium foil, wherein the load per unit width at the time of peeling operation of the metallic titanium foil from the metal electrode is 1.0 N / mm or less. The method for producing a metallic titanium foil according to claim 6, wherein the load per unit width at the time of the peeling operation of the metallic titanium foil from the metal electrode is 0.2 N / mm or less.

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