US20160201205A1

US20160201205A1 - Anode and process for manufacturing same

Info

Publication number: US20160201205A1
Application number: US14/909,830
Authority: US
Inventors: Noriaki SUGAMOTO; Tatsuo KIBE; Tetsuro Kamo; Tsuyoshi Iwasa; Tetsuji Kawakami; Kou TAKADA; Toshio Morimoto
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 2013-08-13
Filing date: 2014-07-23
Publication date: 2016-07-14
Also published as: TW201510284A; KR20160041907A; WO2015022846A1; JP6011488B2; CN105452535A; JP2014208871A

Abstract

The present invention controls a temperature rise due to resistance in electrolysis, and prevents an anode from falling off A holding member is attached in surface contact with one side of an electrode plate made of a low melting metal or a low melting alloy having a melting point of not less than 100° C. and not more than 250° C., the holding member having a length equal to or longer than the length of said one side and being made of a metal or an alloy having a melting point higher than the melting point of the electrode plate.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an anode for electrolysis, and a process for manufacturing the same, and in particular, relates to an anode for electrolyzing a low melting metal or a low melting alloy, and a process for manufacturing the same. The present application claims priority based on Japanese Patent Application No. 2013-168271 filed in Japan on Aug. 13, 2013. The total contents of the Patent Application are to be incorporated by reference into the present application.
2. Description of Related Art
Electrolysis is the decomposition and purification of a substance by passing a direct current through an anode and a cathode in pairs in a state in which the anode and the cathode are immersed in an electrolytic solution or a fused salt, and thereby causing a chemical change in an electrode surface.
Examples of electrolysis techniques include hydrometallurgical reining and metal plating wherein a voltage is applied to a metal used as an anode, whereby the metal decomposed in the anode is deposited on a surface of the cathode in a high purity state, or a coating of the metal is formed.
On the other hand, adjustment of an electrolytic solution to obtain an appropriate pH makes it possible that, when a metal decomposed in an anode is dissolved in the electrolytic solution and moved to a cathode, before deposited on the cathode, the metal is precipitated as a hydroxide and thereby isolated (for example, see Patent Literature 1).
As disclosed in Patent Literature 2, in many cases, an anode for electrolysis is an anode 100 illustrated in FIG. 10. The anode 100 is formed in the shape of a plate having a projection 101 in the upper side thereof, and is electrically connected to an electric supply unit 102 by hooking or hanging the projection 101 on or from the electric supply unit 102.
In electrolysis employing such anode 100, an exothermic phenomenon caused by electric resistance occurs between the projection 101 of the anode 100 and the electric supply unit 102. In the anode 100, this exothermic phenomenon is prevented as much as possible because the phenomenon leads to an energy loss. However, it is unable to entirely prevent the generation of heat.
Furthermore, this exothermic phenomenon does not cause a temperature rise to such an extent as to soften and melt an anode made of a common metal, such as copper. However, in the case where a low melting metal, such as tin or indium, or a low melting alloy is employed as the anode 100, when a high voltage or current is passed, there arise a problem that the anode 100 is softened and deformed due to the generation of heat, and a problem that the projection 101 is melted at a contact point between the projection 101 and the electric supply unit 102, the contact point having the highest temperature, whereby the anode 100 cannot support itself and falls off into an electrolytic bath.
For such problems, the anode 100 having a common integral form as illustrated in FIG. 10 cannot reduce the generation of heat when a high voltage or current is passed, because a contact area between the projection 101 and the electric supply unit 102 is very small. Therefore, it is difficult to prevent the anode 100 from falling off Hence, in the case of employing the anode 100, an electrolysis treatment needs to be completed within a short time by the time the anode 100 falls off, whereby workability decreases, and furthermore, there is no way except that electrolysis is performed with a low voltage or current, whereby the efficiency of metal deposition is reduced.
Besides, Patent Literature 3 discloses a process wherein, as illustrated in FIG. 11, holes 104 are formed for an anode at two points on the upper side of an electrode plate 103; conductive connection jigs 105 are passed through the holes 104 to hang the electrode plate 103 from a metal bar 106 for electric supply; and the metal bar 106 and an electric supply unit 107 are electrically connected. Furthermore, Patent Literature 4 discloses a process wherein, as illustrated in FIG. 12, ribbon-shaped metal hangers 109 are attached to two portions of an electrode plate 108 to hang the electrode plate 108 from a metal bar 110 for electric supply, and the metal bar 110 and the electric supply unit 111 are electrically connected.
However, according to the process described in Patent Literature 3, the conductive connection jigs 105 and the electrode plate 103 are only in point contact with each other at the respective holes, and therefore, a temperature rise at contact portions cannot be controlled when a high voltage or current is passed, and consequently, when a low melting metal, such as tin or indium, is employed for the electrode plate 103 for an anode, the electrode plate 103 is softened and melted, and falls off
The process described in Patent Literature 4 has been often employed for an electrode on a cathode side, but such structure has been employed also for an anode. According to the process described in Patent Literature 4, as illustrated in FIG. 12, the electrode plate 108 is joined to the metal hangers 109 with rivets at two portions. To bring the metal hangers 109 into firm contact with the metal bar 110, a thin metal having good processability is employed for the metal hangers 109, and accordingly, the metal hangers 109 are easily deformed, and therefore deformed also at the time of joining by a rivets, and hence, it is hard to say that the surfaces of the hangers 109 and the surface of the electrode plate 108 are sufficiently joined. Furthermore, in terms of the purpose of using the hangers 109, a metal wider than needed is not commonly employed as long as the electrode plate 108 can be sufficiently held. According to the process disclosed in Patent Literature 4, a temperature rise is somewhat controlled, compared with the case of a point contact like the process described in Patent Literature 3, but, the process disclosed in Patent Literature 4 is not sufficiently effective for an electrode plate made of a low melting metal, such as tin or indium, or a low melting alloy, and accordingly, the electrode plate is softened when a high voltage or current is passed, and the electrode plate 108 is put its own weight thereon, such as the weight of a portion being in the vicinity of a joining portion between the metal hanger 109 and the electrode plate 108 and having no holding portion at the upside, and accordingly, the electrode plate 108 begins to be deformed due to its own weight, and falls off
Patent Literature 1: Japanese Patent No. 2829556
Patent Literature 2: Japanese Patent Application Laid-Open No. H11-229171
Patent Literature 3: Japanese Patent No. 4911668
Patent Literature 4: Japanese Patent Application Laid-Open No. 2004-043846

BRIEF SUMMARY OF THE INVENTION

Therefore, the present invention is proposed in view of such actual circumstances, and an object of the present invention is to provide an anode and a process for manufacturing same, the anode being capable of controlling a temperature rise at a connection portion between an electrode plate made of a low melting metal or a low melting alloy and a holding member configured to hold the electrode plate and to electrically connect the electrode plate to an electric supply unit, and capable of achieving long hours of electrolysis without the electrode plate melting and falling off In particular, an object of the present invention is to provide an anode and a process for manufacturing the same, the anode being capable of achieving long hours of electrolysis without an electrode plate falling off even when a high voltage or current is passed through the electrode plate.
An anode that achieves the above-mentioned object according to the present invention is characterized in that a holding member is attached in surface contact with the vicinity of one side of at least one major surface of an electrode plate, the electrode plate being made of a low melting metal or a low melting alloy having a melting point of not less than 100° C. and not more than 250° C., the holding member having a length equal to or longer than the length of said one side and being made of a metal or an alloy having a melting point higher than the melting point of the electrode plate.
A process for manufacturing an anode that achieves the above-mentioned object according to the present invention is characterized in that a low melting metal or a low melting alloy having a melting point of not less than 100° C. and not more than 250° C. is cooled and solidified in a mold; a solidified low melting metal or a solidified low melting alloy is taken out of the mold to obtain an electrode plate; and a holding member is attached in surface contact with the vicinity of one side of at least one major surface of the obtained electrode plate, the holding member having a length equal to or longer than the length of said one side and being made of a metal or an alloy having a melting point higher than the melting point of the electrode plate, whereby an anode is manufactured.
According to the present invention, a holding member is attached in surface contact with the vicinity of one side of at least one major surface of an electrode plate, the holding member having a length equal to or longer than the length of said one side, whereby a temperature rise caused by electric resistance between the electrode plate and the holding member is controlled to prevent the electrode plate from melting, and furthermore, even when the electrode plate is somewhat softened by resistance heating, the entire vicinity of one side of at least one major surface of the electrode plate is held, whereby the electrode plate is prevented from falling off and long hours of electrolysis is achieved. Furthermore, according to the present invention, even when a high voltage or current is passed, the attachment of the holding member in surface contact with the electrode plate makes it possible to control a temperature rise caused by electric resistance, and thereby to prevent the electrode plate from melting, and thus, long hours of electrolysis is achieved.
Furthermore, according to the present invention, an anode is efficiently manufactured in such a manner that the use of a low melting metal or a low melting alloy having a melting point of not less than 100° C. and not more than 250° C. for an electrode plate allows the metal or the alloy to be easily melted, and, by cooling, solidifying, and casting the molten metal or the molten alloy, an electrode plate is obtained, and only by the attachment of a holding member in surface contact with the vicinity of one side of at least one major surface of the obtained electrode plate, a temperature rise caused by electric resistance at a connection portion between the electrode plate and the holding member is controlled, whereby the electrode plate is prevented from melting, and furthermore, the electrode plate is prevented from falling off when softened by resistance heating.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of an anode to which the present invention is applied.

FIG. 2 is an exploded perspective view of said anode.

FIG. 3 is an exploded perspective view of an anode having an electrode plate with a groove portion formed therein.

FIG. 4 (A) is a plan view illustrating a relationship between a mold and a fixing plate, and FIG. 4 (B) is a side view illustrating said relationship.

FIG. 5 is a perspective view illustrating a relationship among the mold, the fixing plate, and a bar.

FIG. 6 is a perspective view of a mold for manufacturing the electrode plate having a groove portion.

FIG. 7 is a schematic diagram of an electrolysis apparatus.

FIG. 8 is a schematic diagram illustrating an arrangement of electrodes in an electrolytic bath.

FIG. 9 is a plan view of an anode used in Comparative Example.

FIG. 10 is a plan view of a conventional anode.

FIG. 11 is a plan view of a conventional anode.

FIG. 12 is a plan view of a conventional anode.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an anode to which the present invention is applied, and a manufacture of said anode will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following detailed description unless otherwise specified.
<1. An Anode>
An anode 1 illustrated in FIG. 1 and FIG. 2 to which the present invention is applied is an anode to be used for electrolysis and used by being hooked on or hung from an electric supply unit of an electrolysis apparatus. The anode 1 is such that a holding member 3 to hold an electrode plate 2 in electrolysis is attached to a holding member attaching surface 2 a positioned in the vicinity of one side of both major surfaces of the electrode plate 2.
The electrode plate 2 is made of a low melting metal or a low melting alloy having a melting point of not less than 100° C. and not more than 250° C., and formed in the shape of, for example, a square or rectangular plate. Examples of the low melting metal include tin and indium, and examples of the low melting alloy include an alloy of indium and tin (for example, In-9.6 wt % Sn), and an alloy of indium and gallium (for example, In-6.3 wt % Ga).
The thickness of the electrode plate 2 is suitably determined in consideration of, for example, the prevention of the electrode plate 2 from falling off the holding member 3 due to the own weight of the electrode plate 2, and the fact that the thickness of the anode 1 becomes thinner as electrolysis proceeds. For example, the thickness of the electrode plate 2 is preferably not less than 2 mm and not more than 15 mm. An electrode plate 2 having a thickness of not more than 2 mm is not preferable because such thin thickness sometimes causes the electrode plate 2 to be broken when handled, and furthermore, causes pitting corrosion of the anode 1 for electrolysis to easily occur. On the other hand, an electrode plate 2 having a thickness of not less than 15 mm is not preferable because such thickness causes the electrode plate 2 to be heavy in weight and thereby easily fall off and be handled with difficulties, and furthermore, when the anode 1 becomes thinner as electrolysis proceeds, the distance between electrodes becomes larger and voltage remarkably rises.
Low melting metal or low melting alloy, which forms the electrode plate 2, has the characteristic of becoming softer as the metal or the alloy has a higher purity or temperature is higher. Therefore, the electrode plate 2 obtained by molding a low melting metal or a low melting alloy into the shape of a plate is kept being hung in an electrolytic solution by a holding member 3 that has a large contact area with a holding member attaching surface 2 a, and is attached thereto, the holding member attaching surface 2 a being positioned in the upper side of the electrode plate 2 at the time of an installation to an electrolysis apparatus.
The holding member 3 is attached to the holding member attaching surface 2 a of the electrode plate 2, holds the electrode plate 2 in an electrolytic solution in electrolysis, and electrically connects the electrode plate 2 to an electric supply unit provided in an electrolysis apparatus.
The holding member 3 has a melting point higher than the melting point of the electrode plate 2, and is made of a metal or an alloy having high electrical conductivity. The use of a metal or an alloy having a melting point higher than the melting point of the electrode plate 2 makes it possible that, even when resistance becomes higher at a contact portion between the electrode plate 2 and the holding member 3 and temperature rises accordingly, the falling of the electrode plate 2 due to the melting of the holding member 3 prior to that of the electrode plate 2 is prevented. Examples of the metal that forms the holding member 3 include silver, copper, and gold, and examples of the alloy that forms the holding member 3 include an alloy of said metals, and among them, in terms of cost, copper is preferably employed because of its inexpensiveness.
Furthermore, the holding member 3 is preferably such that a metal or an alloy having a high melting point and high electrical conductivity is employed as a core material, and coated with a metal having an ionization tendency low enough not to cause corrosion by an electrolytic solution. Examples of the metal for the coating include noble metals, such as platinum, and titanium in order to prevent formation of a non-conducting film on the core material due to corrosion or the like, and among them, in terms of cost, titanium is preferably employed because of its inexpensiveness. In the case where corrosion resistance against an electrolytic solution is not highly required, a metal having high electric conductivity and wear resistance is more preferably selected.
Coating of the core material can be performed by a common process, such as welding processing, plating, or cladding. Also there is no problem about a partial coating on only a portion having a risk of corrosion. In the case where there is no risk of corrosion or the like by an electrolytic solution, a core material with no coating may be employed alone as the holding member 3.
The shape of the holding member 3 is not particularly limited as long as the holding member 3 can be attached in surface contact with the vicinity of one side of at least one major surface of the electrode plate 2, that is, the holding member attaching surface 2 a, and is capable of holding the electrode plate 2 and electrically connecting the electrode plate 2 to an electric supply unit.
Examples of the holding member 3 include a member illustrated in FIG. 1 and FIG. 2. The holding member 3 illustrated in FIG. 1 is electrically connected to the electrode plate 2 via conductive connecting members 6; electrically connects the electrode plate 2 to an electric supply unit; holds the electrode plate 2 in an electrolytic solution; and has an electrode plate holding member 4, the conductive connecting members 6 configured to electrically connect the electrode plate 2 to the electrode plate holding member 4, and bolts 5 for attaching the conductive connecting member 6 to the electrode plate 2 and the electrode plate holding member 4.
The electrode plate holding member 4 has a structure in which the lower end portion of the electrode plate holding member 4 is connected to the electrode plate 2 via the conductive connecting member 6, and, to hook or hang the electrode plate 2 on or from an electric supply unit, the upper end portion of the electrode plate holding member 4 projects like an arm in the horizontal direction. This projecting portion serves as an electric supply connection portion 4 a to be electrically connected to an electric supply unit. The electric supply connection portion 4 a may be formed in the shape of a bar or a plate extending in the lateral direction. The form of the electric supply connection portion 4 a is preferably a structure that allows a contact area with the electric supply unit to be sufficiently secured, and prevents the distance between anodes and cathodes from being too large when the anodes and the cathodes are arranged alternately (refer to FIG. 8).
The conductive connecting member 6 is formed in the shape of a plate that has a length equal to or longer than the length of the holding member attaching surface 2 a of the electrode plate 2 so as to at least bring the conductive connecting member 6 into contact with the entirety of the holding member attaching surface 2 a of the electrode plate 2 formed in the shape of a plate and that has a width enough to make an integral connection between the electrode plate 2 and the electrode plate holding member 4 by a bolt 5. A metal having excellent electric conductivity is preferably employed for the conductive connecting member 6. Since this conductive connecting member 6 is connected in surface contact with the electrode plate 2, even when temperature rises at a connection portion between the electrode plate 2 and the conductive connecting member 6 due to electric resistance, heat diffuses, whereby the electrode plate 2 can be prevented from melting, and even when a high voltage or current is passed, the electrode plate 2 can be prevented from melting. Furthermore, even if temperature rises due to electric resistance and the electrode plate 2 is somewhat softened, the electrode plate 2 can be prevented from falling off because the entirety of the holding member attaching surface 2 a of the electrode plate 2 is connected to the conductive connecting member 6.
A process for connecting the electrode plate 2 to the holding member 3 is such that, as illustrated in FIG. 1 and FIG. 2, with the electrode plate 2 and the electrode plate holding member 4 butting against each other, a connection portion between the electrode plate 2 and the electrode plate holding member 4 is sandwiched from the sides, that is, sandwiched from both major-surface sides of the electrode plate 2 by two conductive connecting members 6, and the bolts 5 each are passed through the electrode plate 2 and the two conductive connecting members 6 and through the electrode plate holding member 4 and said two conductive connecting members 6, and said bolts 5 are tightened with not-illustrated nuts. At this time, through-holes 9 in one of the two conductive connecting members 6 may be used as screw holes for the respective bolts 5, and, without using a nut, the electrode plate 2 and the electrode plate holding member 4 may be fastened using the conductive connecting members 6 and the bolts 5. Thus, the electrode plate 2 and the holding member 3 that has the electrode plate holding member 4 and the two conductive connecting members 6 are united, and the electrode plate 2 and the electrode plate holding member 4 are electrically connected by the bolts 5 and the conductive connecting members 6. As illustrated in FIG. 2, through- holes 7, 8, and 9 for passing the bolts 5 therethrough are formed beforehand in the electrode plate 2, the electrode plate holding member 4, and the conductive connecting members 6, respectively. In the case where the connection is performed by such connecting process, as exemplified in FIG. 1, four bolts 5 are attached to each of the electrode plate 2 and the electrode plate holding member 4, but the connection is not limited to this, and the connection is performed using a plurality of bolts 5, preferably not less than three bolts 5, more preferably three or four bolts 5 in order to firmly fix the electrode plate 2 to the holding member 3 and avoid a complicated operation. It is beneficial that the bolts 5 are symmetrically well spaced out at equal intervals.
Furthermore, as illustrated in FIG. 3, an electrode plate 2 may have a groove portion 7 a in place of the through-hole 7 through which a bolt 5 is passed. The groove portion 7 a is provided in a periphery portion of the electrode plate 2, the periphery portion facing the electrode plate holding member 4; is opened on the side of the upper end portion, which faces the electrode plate holding member 4; and is formed in the shape of a groove by making a cut having a width equal to or larger than the diameter of the bolt 5. The groove portion 7 a is not limited to the U-shaped groove portion illustrated in FIG. 3, and may be, for example, a triangular or square groove, and may have any shape as long as the bolt 5 passes through the groove portion 7 a of the electrode plate 2, whereby the electrode plate 2 can be attached to the electrode plate holding member 4.
Even in the case where the electrode plate 2 illustrated in FIG. 3 is employed, the electrode plate 2 can be connected to the holding member 3 as in the case of employing the electrode plate illustrated in FIG. 1. Both of the major surfaces of the electrode plate 2 and the electrode plate holding member 4 butting against each another are sandwiched by two conductive connecting members 6, and the bolts 5 pass through each of the groove portion 7 a of the electrode plate 2 and the two conductive connecting members 6, and the electrode plate holding member 4 and said two conductive connecting members 6, and said bolts 5 are tightened with not-illustrated nuts. The sandwiching of the electrode plate 2 by the two conductive connecting members 6 allows the electrode plate 2 to be attached without falling of the electrode plate holding member 4 even in the case of employing the groove portion 7 a formed in the shape of a groove.
In the electrode plate 2 illustrated in FIG. 3, a portion through which the bolt 5 passes is not a through-hole but a groove-shaped groove portion 7 a, whereby the electrode plate 2 can be easily attached to and removed from the electrode plate holding member 4. For example, when the electrode plate 2 is replaced during continuous operation, without removing the bolts 5 to completely separate the two conductive connecting members 6 from the electrode plate 2 and the electrode plate holding member 4, the used electrode plate 2 can be easily removed from the holding member 3 only by loosening the bolts 5. Then, with a state in which the used electrode plate 2 has been removed from the holding member 3, a new electrode plate 2 is inserted between the conductive connecting members 6 so that the bolt 5 is fitted in the groove portion 7 a, and the bolt 5 is tightened, whereby the electrode plate 2 can be easily fixed. Thus, the electrode plate 2 having the groove portion 7 a formed therein can be easily attached and removed, and therefore, makes it possible to improve working efficiency.
The holding member 3 illustrated in FIG. 1 holds the electrode plate 2 in an electrolytic solution in such a manner that the electrode plate 2 and the electrode plate holding member 4 are sandwiched by the two conductive connecting member 6, and a connection state is maintained with the bolts 5 and the conductive connecting members 6. Furthermore, the holding member 3 electrically connects the electrode plate 2 to the electrode plate holding member 4 via the conductive connecting members 6, and thereby electrically connects the electrode plate 2 to the electric supply unit on which the electric supply connection portion 4 a is hooked.
The holding member 3 is not limited to a member illustrated in FIG. 1, and, as a simpler process, for example, there may be adopted one-touch attaching/detaching by making use of the sandwiching force of a spring or other tools. However, in this case, compared with the holding member 3 illustrated in FIG. 1, for example, a design idea to bring the holding member into firm surface contact with the electrode plate 2 at the time of sandwiching the electrode plate 2 is needed, and the number of movable portions is increased, and hence, measures against corrosion by an electrolytic solution are more important, and maintenance or the like is more complicated. Therefore, for a long period of use, the more simply structured holding member 3 that is illustrated in FIG. 1 and uses the bolt 5 is preferable. It should be noted that as long as the holding member 3 is capable of holding the electrode plate 2 and electrically connecting the electrode plate 2 to an electric supply unit, the holding member 3 may be a holding member configured to be attached only to the holding member attaching surface 2 a of one major surface of the electrode plate 2.
In the anode 1 having the above-mentioned configuration, even in the case where the electrode plate 2 is made of a low melting metal or a low melting alloy, the electrode plate 2 is in surface contact with the holding member 3, for example, with the conductive connecting members 6 illustrated in FIG. 1, and accordingly, even when resistance heating occurs in a connection portion therebetween, heat diffuses and a temperature rise is controlled, whereby the electrode plate 2 can be prevented from melting, and furthermore, even when the electrode plate 2 is somewhat softened by resistance heating, the holding member 3 holds the entirety of the holding member attaching surface 2 a of the electrode plate 2, whereby the electrode plate 2 can be prevented from falling off and electrolysis can be performed for long hours. In the anode 1, the electrode plate 2 is in surface contact with the holding member 3, and therefore, even when a high voltage or current is passed through the electrode plate 2, electrolysis can be performed for long hours without the electrode plate 2 falling off Furthermore, in the anode 1, even in the case where the thickness of the electrode plate 2 is larger, for example, not less than 8 mm, the electrode plate 2 is held without falling off the holding member 3, and therefore, electrolysis can be performed for long hours.
<2. A Process for Manufacturing the Anode>
As to a process for manufacturing the anode 1, first, a process for manufacturing the electrode plate 2 will be described. The electrode plate 2 is manufactured by casting by the use of a mold that fits the shape of the electrode plate 2.
Specifically, the electrode plate 2 to be used for the anode 1 illustrated in FIG. 1 and FIG. 2 is formed by the use of a mold 10 illustrated in FIG. 4 and FIG. 5, the mold being such that a depression portion 10 a corresponding to the size of the electrode plate 2 is formed in, for example, a graphite carbon plate having a sufficient thickness. The use of the mold 10 made of graphite carbon allows heat to be easily conducted to a metal poured into the depression 10 a at the time of heating, whereby the metal can be easily melted, and furthermore, allows a solidified metal to be removed from the mold 10 after cooling.
Besides graphite carbon, polytetrafluoroethylene and high melting metals can be employed for the mold 10 in terms of heat resistance. However, polytetrafluoroethylene is not preferably employed because polytetrafluoroethylene has low heat conductivity, and accordingly, it takes much time to melt a metal. High melting metals are not preferably employed because the wettability between a molten low melting metal or low melting alloy and the high melting metals is higher, and accordingly, when the metal or alloy is cooled and solidified and then removed from the mold, the metal or alloy has difficulties in being removed from the mold. Hence, graphite carbon is preferably employed as a material having excellent heat conductivity, causing less deformation due to thermal expansion, and having an excellent release property. The size of the mold 10 is determined by the thickness and the length and width of the electrode plate 2. In the depression 10 a of the mold 10, an angle may be provided so as to make the inner wall widen from the bottom toward the opening in order that a cooled and solidified electrode plate 2 can be more easily removed.
In casting by the use of the above-mentioned mold 10, a through-hole 7 through which a bolt 5 for attaching a holding member 3 passes is formed in a holding member attaching surface 2 a of an electrode plate 2 on which the holding member 3 is attached. For example, a process for forming the through-hole 7 is such that, as illustrated in FIG. 4 and FIG. 5, during the melting of a low melting metal or a low melting alloy in the mold 10, a bar 11 having the same diameter as that of the bolt 5 is inserted from the opening side of the mold 10, whereby a portion into which the bar 11 is inserted serves as the through-hole 7. To fix the bar 11 in the molten low melting metal or the molten low melting alloy, there is used a fixing plate 13 that is formed to have the approximately same size as the width of the mold 10 and have a passing hole 12 for passing the bar 11 therethrough.
With being parallel to the mold 10 and without being suspended above the mold 10, the fixing plate 13 covers an opening portion of the mold 10. Furthermore, the fixing plate 13 has a structure by which, every time casting is carried out, accuracy of position is securely maintained so that the fixing plate 13 appropriately covers the mold 10. Therefore, as illustrated in FIG. 5, an accuracy maintaining member 14 having the same height as the thickness of the mold 10 and having the same length as the short sides of the fixing plate 13 is attached to the bottom of one of the short sides of the fixing plate 13 so as to make a shape like the letter L.
This accuracy maintaining member 14 is fit into the fixing plate 13 so as to slide along the outer surface of the mold 10 when the mold 10 is covered with the fixing plate 13. The accuracy maintaining member 14 is formed to have the same height as the height of the mold 10, thereby allowing accuracy of the height of the fixing plate 13 to be maintained, and furthermore, the accuracy maintaining member 14 is formed to have the same length as the length of the fixing plate 13, thereby allowing accuracy of position of a passing hole 12 for passing the bar 11 therethrough to be maintained by aligning an end portion 14 a of the accuracy maintaining member 14 with a corner portion 10 b of the mold 10. The structure of the accuracy maintaining member 14 is not limited to the above-mentioned structure as long as high accuracy of position is maintained.
As the bar 11 to form the through-hole 7, there is preferably employed a bar that is heat resistant and has poor wettability with metal so as to be easily removed even after the solidification of a low melting metal or a low melting alloy. For example, a bar 11 made of polytetrafluoroethylene is preferably employed.
As to the size of the bar 11, the bar 11 needs to have a length sufficient for penetrating the electrode plate 2 to be cast and needs to have a diameter equal to the diameter of the bolt 5. The number of the bars 11 and intervals between the bars 11 to be inserted are made to match the number and the position of the bolts 5.
In the case where the electrode plate 2 is manufactured using such mold 10 or the like, when a low melting metal or a low melting alloy is heated to the melting point thereof or higher in the mold 10 and a state is created where the low melting metal or the low melting alloy is sufficiently melted and spreads in the mold 10, the fixing plate 13 in a state where the bar 11 passes through the passing hole 12 is made to cover the mold 10 so that the bar 11 faces a portion at which the through-hole 7 is to be formed, and the bar 11 is inserted into the molten metal. Then, the metal is cooled and solidified by still standing in the state where the bar 11 is inserted thereinto. Then, the bar 11 is removed from the passing hole 12, and a solidified metal is removed from the mold 10, whereby an electrode plate 2 having the through-hole 7 formed therein is obtained. In this process for manufacturing the electrode plate 2, the mold 10 is preferably heated until the bar 11 is inserted in order to maintain the molten state of the low melting metal or the low melting alloy.
Then, a through-hole 8 is formed in an end portion of the electrode plate holding member 4, the end portion being to be connected to the conductive connecting member 6, and through-holes 9 configured to pass the bolts 5 therethrough are formed at positions of the conductive connecting member 6 so as to face the through-hole 7 of the electrode plate 2 and the through-hole 8 of the electrode plate holding member 4. Examples of a process for forming the through- holes 8 and 9 include cutting using a common drill.
Next, the holding member 3 is attached to the holding member attaching surface 2 a of the electrode plate 2 obtained as mentioned above, whereby an anode 1 is manufactured. The electrode plate 2 and the electrode plate holding member 4 are made to butt against each other, and a butted portion is sandwiched from both sides thereof by the two conductive connecting members 6, and the bolts 5 are made to pass through the through- holes 7, 8, and 9 of the electrode plate 2, the electrode plate holding member 4, and the conductive connecting member 6, respectively, and the bolts 5 are tightened with nuts to unite the electrode plate 2 and the holding member 3, whereby the anode 1 is obtained.
The process for manufacturing the anode 1 in the case of employing a holding member 3 illustrated in FIG. 1 was described above, but, depending on the structure of a holding member 3, the holding member 3 is attached by a process suitable for said structure.
The process for manufacturing the anode 1 that includes the electrode plate 2 having the through-hole 7 was described above, and next, a process for manufacturing an anode 1 that includes an electrode plate 2 having a groove portion 7 a will be described.
An electrode plate 2 having a groove portion 7 a can be manufactured using a mold 15 illustrated in FIG. 6. The mold 15 is such that a depression portion 15 a having a size corresponding to the size of the electrode plate 2 is formed in a graphite carbon plate having a sufficient thickness, and a projection portion 15 b projected from the inner wall of the plate at a position corresponding to the groove portion 7 a is formed in the plate. In the depression portion 15 a of the mold 15, an angle may be provided so as to make the inner wall widen from the bottom toward the opening in order that a cooled and solidified electrode plate 2 can be more easily removed.
In the manufacture of the electrode plate 2, a low melting metal or a low melting alloy is heated to the melting point thereof or higher in the mold 15, and the low melting metal or the low melting alloy is sufficiently melted and spreads in the mold 15, and then, the metal is cooled and solidified. Then, a solidified metal is removed from the mold 15 to obtain an electrode plate 2 having the groove portion 7 a formed therein.
According to this process for manufacturing the electrode plate 2, a through-hole 7 does not need to be formed as mentioned above, and therefore, a low melting metal or a low melting alloy as an electrode material does not need to be melted and maintained in the mold 15, and hence, the low melting metal or the low melting alloy may be melted in another container, and then poured into the depression 15 a of the mold 15 to obtain the electrode plate 2.
Since the projection portion 15 b to form the groove portion 7 a is formed in the mold 15, the electrode plate 2 having the groove portion 7 a formed therein can be manufactured only by melting a low melting metal or a low melting alloy in the mold 15 and cooling and solidifying the metal, or by pouring a molten low melting metal or a molten low melting alloy into the mold 15 and cooling and solidifying the metal. Thus, the electrode plate 2 having the groove portion 7 a formed therein can be more easily and more efficiently manufactured than the electrode plate 2 having the through-hole 7 formed therein.
In the case of employing the electrode plate 2 having the groove portion 7 a formed therein, an anode 1 may be obtained in such a manner that, first, the bolt 5 is passed through the through- holes 8 and 9 of the electrode plate holding member 4 and the conductive connecting member 6, and the bolt 5 is loosely tightened with a nut, and then, the electrode plate 2 is inserted so that the bolt 5 fits into the groove portion 7 a of the electrode plate 2, and then, the bolt 5 is firmly tightened with a nut, whereby the electrode plate 2 and the holding member 3 are united.
According to the above-mentioned process for manufacturing the anode 1, the use of a low melting metal or a low melting alloy having a low melting point of not less than 100° C. and not more than 250° C. for the electrode plate 2 allows the metal or the alloy to be easily melted; and the molding of a molten low melting metal or a molten low melting alloy by the use of a mold allows an electrode plate 2 to be obtained; only by the attachment of the holding member 3, for example, the conductive connecting member 6 in FIG. 1, in surface contact with the holding member attaching surface 2 a of an obtained electrode plate 2, an anode 1 can be efficiently manufactured, the anode being such that a temperature rise due to resistance in a connection portion between the electrode plate 2 and the holding member 3 is controlled, the electrode plate 2 does not melt, and the electrode plate 2 is prevented from falling off even if the electrode plate 2 is somewhat softened by resistance heating. Furthermore, according to the above-mentioned process for manufacturing the anode 1, even when a high voltage or current is passed, attachment of the holding member 3 in surface contact with the electrode plate 2 makes it possible to efficiently manufacture the anode 1, wherein a temperature rise due to electric resistance is controlled, the electrode plate 2 is prevented from melting, and the electrode plate 2 is prevented from falling off
Furthermore, according to the process for manufacturing an anode 1, in the case where an anode 1 illustrated in FIG. 1 is manufactured so as to have a configuration illustrated in FIG. 2, when a through-hole 7 of the electrode plate 2 to pass the bolt 5 therethrough is formed, the electrode plate 2 having the through-hole 7 formed therein can be easily manufactured only by inserting the bar 11 whose position is fixed by the fixing plate 13 into a molten low melting metal or a molten low melting alloy as illustrated in FIG. 4 and FIG. 5. Thus, in the case where the anode 1 illustrated in FIG. 1 is manufactured so as to have the configuration illustrated in FIG. 2, the use of the electrode plate 2 having the through-hole 7 makes it possible to produce an anode only by connecting the conductive connecting member 6 to this electrode plate 2 by the bolt 5, and therefore, the anode 1 can be efficiently manufactured.
In the case where an anode 1 having a configuration illustrated in FIG. 3 is manufactured, an electrode plate 2 having a groove portion 7 a formed therein can be obtained only by pouring a molten low melting metal or a molten low melting alloy into a mold 15 as illustrated in FIG. 6, and thus, the electrode plate 2 can be more easily manufactured. Furthermore, in the case where the anode 1 having the configuration illustrated in FIG. 3 is manufactured, in a state in which a bolt 5 is loosened without completely separating the conductive connecting member 6 from the electrode plate holding member 4, the electrode plate 2 is inserted between two conductive connecting members 6 so that the bolt 5 enters the groove portion 7 a, and then, by firmly tightening the bolt 5, the electrode plate 2 and the electrode plate holding member 4 can be connected. In the case of employing the electrode plate 2 having the groove portion 7 a formed therein, in particular, the used electrode plate 2 can be easily replaced with a new electrode plate 2, and therefore, the anode 1 can be more efficiently manufactured.

EXAMPLES

Hereinafter, specific examples to which the present invention is applied will be described, but the present invention is not limited to these examples.

Example 1

In Example 1, an anode illustrated in FIG. 1 was produced to have the same configuration as that of an anode including an electrode plate having a through-hole formed therein as illustrated in FIG. 2.
An indium electrode plate having a thickness of 4 mm, a length of 27 cm, and a width of 27 cm was produced by melting and casting using a mold (refer to FIG. 5).
The mold was produced by making a depression portion having a depth of 15 mm, a length of 27 cm, and a width of 27 cm in a carbon graphite block having a thickness of 30 mm, a length of 30 cm, and a width of 30 cm. A fixing plate was produced in such a manner that a carbon graphite block having a length of 65 mm, a width of 35 mm, and a height of 35 mm was shaved to be in the form of a plate having a length of 60 mm, a width of 30 mm, and a height of 30 mm. The dimension d (refer to FIG. 4) of an accuracy maintaining member to be attached to the fixing plate was set to 30 mm, which was the same as the thickness of the carbon graphite block, and the length of the accuracy maintaining member was set to 30 mm, which was the same as the width of the fixing plate. In the fixing plate, four passing holes having a diameter of 5 mm were made at regular intervals. Here, the passing holes were arranged so as to be aligned on a line 15 mm distant from the upper side of the electrode plate at intervals of 6.8 cm. Furthermore, to form the passing holes for bolts, there were prepared four bars having a diameter of 5 mm and a length of 3 cm and made of Teflon (registered trademark).
Using, for example, the mold produced as mentioned above, an indium electrode plate was cast as follows. The produced mold was put on a large sized hot plate manufactured by AS ONE Corporation (HP-A2234M, 30 cm×30 cm), and 2000-g indium metal was put into the mold. With this state kept, the hot plate was heated to approximately 300° C. and maintained. At the time when the indium metal completely melted, an end portion of the accuracy maintaining member attached to the fixing plate was aligned with one corner of the mold and placed thereon, and the bars made of Teflon (registered trademark) were deeply inserted into the respective four passing holes, and then, cooling was performed. After the indium metal cooled down to room temperature, the bars made of Teflon (registered trademark) were pulled out and the fixing plate was removed, and then, the mold was turned upside down. A solidified indium metal was smoothly released and removed from the mold. An obtained indium electrode plate had a thickness of approximately 4 mm.
Next, the indium electrode plate was attached to a holding member manufactured as follows. The holding member was a copper material having the same shape as that of a holding member illustrated in FIG. 1, and produced in such a manner that an electrode plate holding member formed to narrow down from the upper side having a length of 40 cm towards the lower side having a length of 27 cm and a conductive connecting member and were prepared, and the surfaces of said members were coated with titanium. Four through-holes for passing 5-mm bolts therethrough were made so that the centers of the passing holes are aligned at intervals of 6.8 cm on a line 15 mm upwardly distant from the lower side of the electrode plate holding member. The bolts were passed through the through-holes of this holding member and the indium electrode plate, and said holding member and said indium electrode plate were joined using the bolts and nuts at four points. The length from the top to the bottom of an anode in which the indium electrode plate and the holding member were united was 40 cm.
Electrolysis was performed using the anode produced as mentioned above. An apparatus illustrated in FIG. 7 was employed as an electrolysis apparatus 20. An electrolytic solution 21 was produced in such a manner that 100 L of 1-mol/L ammonium nitrate solution was prepared, and nitric acid was added to this ammonium nitrate solution to achieve a pH of 4.0. The electrolytic solution 21 was poured into an electrolytic bath 23 provided with a liquid dispersing plate 22, and the electrolytic solution 21 was maintained at 25° C. Furthermore, as illustrated in FIG. 8, four anodes 24 and five cathodes 25 were arranged so that the distance between the centers of said electrodes was 2.0 cm, and the anodes 24 and the cathodes 25 were connected using a double-core polyvinyl chloride insulated and sheathed cable as a lead 26 (JIS C 3342, allowable current: 200A, nominal cross sectional area: 100 mm²) to be connected to a rectifier.
In the electrolysis apparatus 20, a 1 mol/L ammonium nitrate solution having a pH of 4.0 is in a regulating tank 27 that is provided to be adjacent to the electrolytic bath 23. The regulating tank 27 is connected to the electrolytic bath 23 via a circulating pump 28 to circulate the electrolytic solution 21. The regulating tank 27 comprises: a stirring rod 29 to stir the electrolytic solution 21; a pH electrode 30 to measure pH; a temperature control heater 31 to control and maintain the temperature of the electrolytic solution 21; and a cooler 32.
In the electrolysis apparatus 20 having such configuration, while an current was maintained so as to achieve a current density of 15 A/dm², electrolysis was performed.
During the electrolysis, the contact temperature between the indium electrode plate and the conductive connecting member ranged from 50° C. to 80° C., and deformation of the indium electrode plate due to a temperature rise was not observed. In Example 1, indium hydroxide was generated in the electrolytic solution by electrolysis for 6 consecutive hours, and an obtained slurry was solid-liquid separated.

Example 2

In Example 2, an anode illustrated in FIG. 1 was produced to have the same configuration as that of an anode including an electrode plate having a groove portion formed therein as illustrated in FIG. 3.
An indium electrode plate having a thickness of 8 mm, a length of 349 mm, and a width of 260 mm was produced by melting and casting using a mold (refer to FIG. 6).
The mold was produced in such a manner that a depression portion having a depth of 15 mm, a bottom length of 349 mm, and a bottom width of 260 mm was made on the inside of a carbon graphite block having a thickness of 30 mm, a length of 400 mm, and a width of 300 mm. More specifically, the inner wall of the mold was inclined so that the depression portion was 355 mm in length and 266 mm in width at a depth of 8 mm. Furthermore, in the mold, there were formed projection portions projected from one of the short sides of the mold. The projection portion had an angle so as to be 14 mm in width and 17 mm in length at the bottom of the depression portion of the mold, whereas 8 mm in width and 14 mm in length at a depth of 8 mm Three such projection portions were provided at regular intervals. The projection portion was shaped like the letter U in such a manner that one end portion of the projection portion, the one end being not connected to the short side of the mold, was made circular.
Then, a 2-L stainless-steel pot was put on a large sized hot plate manufactured by
AS ONE Corporation (HP-A2234M, 30 cm×30 cm), and 5000-g indium metal was put into the pot. With this state kept, the hot plate was heated to approximately 300° C. and maintained to completely melt the indium metal. This molten indium was poured into the above-mentioned mold. Then, the indium metal was left standing at room temperature for 15 minutes to be cooled and solidified, and then, the mold was turned upside down. The solidified indium metal was smoothly released and removed from the mold. Three groove portions were formed without problems in one side of an electrode plate, and thus, an indium electrode plate having a thickness of 8 mm, a length of 349 mm, and a width of 260 mm was obtained.
The attachment to the holding member was performed in the same manner as in Example 1, except that the number of attachment bolts was decreased from four to three. Furthermore, electrolysis was performed in the same manner as in Example 1.
In Example 2, indium hydroxide was generated by electrolysis for 12 hours, and an obtained slurry was solid-liquid separated.
<Example 3>In Example 3, there was produced an anode including an electrode plate obtained by changing the U-shaped groove portion in Example 2 to a triangular V-shaped groove portion. Other conditions were the same as in Example 2.
Also in Example 3, indium hydroxide was generated by electrolysis for 12 hours, and an obtained slurry was solid-liquid separated.
[Comparative Example]In Comparative Example, an anode 40 made of indium metal and having a width of 27 cm, a length of 40 cm, and a thickness of 4 mm was formed, the anode 40 having a portion 40 a laterally projecting by 6.5 cm to the left and by 6.5 cm to the right in the upper part of the anode 40 as illustrated in FIG. 9, and having a total width including the projecting portion 40 a of 40 cm. The projecting portion 40 a of the anode 40 was hooked on an electric supply unit 41, and electrolysis was performed under the same conditions as in Example 1.
Immediately after the start of the electrolysis, the temperature around a contact point between the projection 40 a of the anode 40 and the electric supply unit 41 began to rise gradually, and, 30 minutes later, just before the temperature reached 150° C., indium was softened and melted, whereby the anode 40 falls off, and accordingly, the electrolysis had to be terminated at this point.
From the above-mentioned Examples and Comparative Example, it is understood that, in the case where an electrode plate is made of a material having a low melting point, such as indium, and the electrode plate is in surface contact with a holding member as described in Examples 1 to 3, the electrode plate can be prevented from melting, and accordingly, electrolysis is enabled to be performed for long hours.
On the other hand, it is understood that, in the case where a contact area between the electrode plate and the electric supply unit is small as described in Comparative Example, a material having a low melting point, such as indium, melts, whereby electrolysis time is shorter, and accordingly, metal cannot be sufficiently deposited.

REFERENCE SIGNS LIST

1: anode
2: electrode plate
2 a: holding member attaching surface
3: holding member
4: electrode plate holding member
5: bolt
6: conductive connecting member
7: through-hole
7 a: groove portion
8: through-hole
9: through-hole
10: mold
10 a: depression portion
10 b: corner portion
11: bar
12: through-hole
13: fixing plate
14: accuracy maintaining member
14: end portion
15: mold
15 a: depression portion
15 b: projection portion
20: electrolysis apparatus
21: electrolytic solution
22: liquid dispersing plate
23: electrolytic bath
24: anode
25: cathode
26: lead
27: regulating tank
28: circulating pump
29: stirring rod
30: pH electrode
31: heater
32: cooler

Claims

1. An anode, wherein a holding member is attached in surface contact with a vicinity of one side of at least one major surface of an electrode plate, the electrode plate being made of a low melting metal or a low melting alloy having a melting point of not less than 100° C. and not more than 250° C., the holding member having a length equal to or longer than a length of said one side and being made of a metal or an alloy having a melting point higher than the melting point of the electrode plate.

2. The anode according to claim 1,

wherein the holding member comprises: an electrode plate holding member configured to hold the electrode plate; and conductive connecting members configured to electrically connect the electrode plate to the electrode plate holding member and formed in a shape of a plate, and

wherein sides of a connection portion at which the electrode plate and the electrode plate holding member are connected are sandwiched by the two conductive connecting members, and tightening of a bolt passing through the electrode plate, the electrode plate holding member, and the two conductive connecting members so as to unite the electrode plate, the electrode plate holding member, and the two conductive connecting members allows the electrode plate and the electrode plate holding member to be electrically connected via the conductive connecting members.

3. The anode according to claim 2, wherein, in the electrode plate, a portion through which the bolt is passed comprises a through-hole or a groove portion.

4. The anode according to claim 1, wherein the electrode plate has a thickness of not less than 2 mm and not more than 15 mm The anode according to claim 1, wherein the low melting metal is indium or tin.

6. The anode according to claim 1, wherein the holding member is made of copper.

7. The anode according to claim 1, wherein a surface of the holding member is coated with a metal that is resistant to corrosion by an electrolytic solution for electrolysis.

8. A process for manufacturing an anode, wherein a low melting metal or a low melting alloy having a melting point of not less than 100° C. and not more than 250° C. is cooled and solidified in a mold, a solidified low melting metal or a solidified low melting alloy is taken out of the mold to obtain an electrode plate, and a holding member is attached in surface contact with a vicinity of one side of at least one major surface of the obtained electrode plate, whereby the anode is obtained, the holding member having a length equal to or longer than the length of said one side and being made of a metal or an alloy having a melting point higher than the melting point of the electrode plate.

9. The process for manufacturing the anode according to claim 8, further comprising:

inserting a bar into a portion corresponding to the vicinity of the one side of the major surface of the electrode plate in a state in which a low melting metal or a low melting alloy in the mold is molten, and forming the electrode plate so that said inserted bar portion serves as a through-hole;

forming a through-hole in an end portion of an electrode plate holding member being a constituent of the holding member and configured to hold the electrode plate;

sandwiching side faces of a connection portion between the electrode plate and the electrode plate holding member by two conductive connecting members, the conductive connecting members being in a shape of a plate having a through-hole formed at a position facing the through-holes of the electrode plate and the electrode plate holding member, being a constituent of the holding member, and being configured to electrically connect the electrode plate to the electrode plate holding member; and

passing a bolt through the through-hole of the electrode plate, the through-hole of the electrode plate holding member, and the through-holes of the two conductive connecting members, and tightening the bolt to unite the electrode plate, the electrode plate holding member, and the two conductive connecting members, and electrically connecting the electrode plate holding member to the electrode plate by the conductive connecting members.

10. The process for manufacturing the anode according to claim 8, wherein the mold is made of graphite carbon.

11. The process for manufacturing the anode according to claim 9, wherein the bar is made of polytetrafluoroethylene.

12. The process for manufacturing the anode according to claim 8, further comprising:

forming the electrode plate by using the mold having a projection portion projected from an inner wall so that, around a perimeter of the electrode plate, the electrode plate has a groove portion formed by said projection portion;

forming a through-hole in an end portion of an electrode plate holding member, the electrode plate holding member being a constituent of the holding member and being configured to hold the electrode plate;

sandwiching side faces of a connection portion between the electrode plate and the electrode plate holding member by two conductive connecting members, the conductive connecting members being in a shape of a plate having a through-hole formed at a position facing the groove potion of the electrode plate and the through-hole of the electrode plate holding member, being a constituent of the holding member, and being configured to electrically connect the electrode plate to the electrode plate holding member; and

passing a bolt through the groove portion of the electrode plate, the through-hole of the electrode plate holding member, and the through-holes of the two conductive connecting members, and tightening the bolt to unite the electrode plate, the electrode plate holding member, and the two conductive connecting members, and electrically connecting the electrode plate holding member to the electrode plate by the conductive connecting members.