JP3236702B2 - Continuous melting equipment for plating ion source powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous melting apparatus for plating ion source powder in electroplating.

[0002]

2. Description of the Related Art Electroplating is based on a method of replenishing ions consumed by plating, a method using a soluble anode made of a metal to be plated, and a method using an insoluble anode while replenishing plated ions separately. They are roughly divided into In the former method, since the anode is consumed by energization, the anode in the plating bath often needs to be replaced, and there are many disadvantages. Therefore, the latter electroplating process using an insoluble anode tends to be adopted.

In electroplating using this insoluble anode,
It is necessary to replenish the consumed metal ions as needed. Therefore, for example, in electrogalvanizing, zinc is replenished to the plating solution by using zinc hydroxide, zinc carbonate, or zinc oxide alone or in combination (Japanese Patent Laid-Open Publication No. H11-163873). No. 50-85531). In particular, when zinc oxide is used, it is dispersed in water in advance and then charged into a plating solution to prevent the occurrence of agglomeration (mamako) (Japanese Patent Publication No. 58-13639). However, there are still problems as described below.

(1) When zinc oxide is dispersed in water and added to a plating solution, the water balance as a dissolution system may be lost, so that an evaporator is required as a water removing means. (2) When performing the above dispersion treatment, an expensive high-speed stirrer such as a homogenizer having a function of pulverizing zinc oxide is required. (3) When the zinc oxide subjected to the dispersion treatment as described above is supplied into the plating solution, the zinc oxide aggregates in the plating solution.
The growth produces a hardly soluble solid, which not only reduces the dissolution rate, but also reduces the zinc oxide yield. (4) The plating solution contains iron ions eluted from the steel sheet, but when the pH of the plating solution exceeds 2.1, the iron ions are formed as hydroxides on the surface of zinc oxide,
Prevents dissolution of zinc oxide. (5) When filtered through a filter cloth, a hard-to-filter substance (a substance composed of zinc hydroxide or the like) is generated. (6) Zinc oxide has a slow dissolution rate, and requires at least 7 minutes for complete dissolution even when the dissolution conditions are satisfied.

[0005] Fig. 1 shows the results of an experiment in which the solubility of zinc oxide was investigated. The experiment was performed with a plating solution of 1 m ³ (pH: 1.7
5 kg of zinc oxide powder was placed in the dissolution tank containing 5)
8kg and 10kg were added and stirred and dissolved. As a result, if the input amount of the zinc oxide powder was 8 kg / m ³ or less, the solubility was good. Five minutes after the start of the dissolution, 95% or more was dissolved,
After a minute, it was found to be completely dissolved. In this regard, when the input amount becomes 10 kg / m ³ , although the solubility is considerably reduced,
After 7 minutes it was found to be almost completely dissolved. Therefore, in order to completely dissolve zinc oxide powder, 7
It is necessary to stay for more than a minute.

[0006] The applicant company has been disclosed in Japanese Patent Laid-Open No. 62-27598.
In the publication, a method of dissolving zinc metal particles using a centrifugal separator and / or a filter was proposed. However, since there is a large difference in dissolution characteristics between zinc metal and zinc oxide, this technique was simply used as it is. Then, zinc oxide cannot be dissolved efficiently.

Further, in the iron or iron alloy electroplating using an insoluble anode, a very unstable Fe ²⁺ ions in the plating solution, for example, Fe ² by the electrode reaction in the residual oxygen and the anode surface in the plating solution ⁺ Ions are easily oxidized to Fe ³⁺ ions. Since Fe ³⁺ ions cause adverse effects such as a decrease in deposition efficiency, it is necessary to reduce the concentration in the plating solution as much as possible. Therefore, in this type of electroplating, reduction of Fe ³⁺ ions is indispensable.

As a method of reducing Fe ³⁺ of the iron-based plating solution to Fe ²⁺ , there is a method of adding iron powder to the plating solution and dissolving / reducing it. For this oxidation-reduction reaction, a vertical dissolution tank is used, and a method disclosed in, for example, JP-A-3-2399 is known. However, this method has a problem in that undissolved iron powder staying in the vertical melting tank flows out of the system as it is, so that pipes and pumps are damaged. In addition, there is a problem that residues are mixed in the downstream filtration process, which makes sludge treatment difficult. This tendency is remarkable especially when the flow rate of the dissolving tank is increased in accordance with the plating operating conditions.

On the other hand, JP-A-59-126799 discloses a method of recovering undissolved residues carried over from a dissolving tank and returning it to the dissolving tank. However, the above method has the following problems. (1) No specific method is described for a device for collecting unreacted metal powder (particles) carried over from the reaction tank. (2) It takes as long as 60 minutes for the unreacted iron powder to reach 0%, and the time required to reduce Fe ³⁺ ions, which is an operational problem in continuous electroplating, becomes longer. Failure may occur.

[0010]

SUMMARY OF THE INVENTION The present invention advantageously overcomes the above-mentioned problems, and minimizes mixing of the undissolved portion of the plating ion source powder into a plating solution and promotes its dissolution. Accordingly, it is an object of the present invention to propose a continuous dissolving apparatus for a plating ion source powder capable of supplying a plating solution having a desired concentration quickly and at low cost without the need for a particularly large-scale apparatus.

[0011]

That is, the present invention provides a plating solution dissolving tank having a stirring function, a plating ion source powder supply device, a cyclone for separating the undissolved portion of the powder from the plating solution, and a plating solution. A continuous dissolving of the plating ion source powder, comprising a pump and a pipe for feeding from the melting tank to the cyclone, and a pipe for returning the undissolved portion of the plating ion source powder separated in the cyclone to the melting tank. Device.

FIG. 2 schematically shows a preferred example of a continuous melting apparatus according to the present invention. In the figure, reference numeral 1 denotes a vertical dissolution tank for accommodating a plating solution, 2 denotes a motor, 3 denotes a stirring blade, 4 denotes a supply device for a plating ion source powder, 5 denotes a hopper, 6 denotes a cyclone, and 7 denotes a liquid sending pump. Numeral 8 denotes a pipe for feeding the plating solution in the vertical dissolving tank to the cyclone 6 via the liquid feed pump 7, and 9 a pipe for returning the undissolved portion of the plating ion source powder separated by the cyclone 6 to the dissolving tank. Road. . In the present invention, the plating solution is guided from the vertical dissolution tank 1 to the solution sending pump 7, and the pressure is increased by the solution sending pump 7 to supply the plating solution to the cyclone 6. In the cyclone 6, a swirling flow is generated, and the undissolved portion of the plating ion source powder having a higher specific gravity than the plating solution flows downward and returns to the vertical dissolution tank 1, while the plating solution flows upward and is supplied to the next step. I do.

Here, it is important to ensure the cyclone separation function in order to effectively use the above-mentioned apparatus. According to an investigation by the inventor regarding this point, it was found that if the particle size of the zinc oxide powder was about 50 μm or less, the zinc oxide powder could be dissolved in the plating solution without particular stirring. Therefore, the cyclone needs to have a performance of 5 μ−50% removal (corresponding to 50 μ−100% removal) or more.

[0014]

The apparatus of the present invention can easily separate the undissolved components in the plating solution with the above-described extremely simple equipment configuration, and can efficiently return the undissolved components to the vertical dissolution tank.
In addition, since extremely fast liquid flow occurs in the cyclone, the dissolution of the plating ion source powder is promoted. For example, in the case of zinc oxide, fine particles having a size of about 50 μm or less are easily dissolved. On the other hand, when iron powder is used as the plating ion source powder, the reduction efficiency of Fe ³⁺ is significantly increased. In addition, even when the amount of liquid flowing into the dissolving tank increases, the plating ion source powder circulates through the pump, the pipeline, the cyclone, and the tank, so that carry-over does not occur. Further, since the undissolved components do not flow out of the vertical dissolving tank system, there is no damage to the pipes, pumps, etc., thus contributing to prolonging the life of the dissolving apparatus.

[0015]

【Example】

Example 1 Using a continuous melting apparatus according to the present invention as shown in FIG. 2 and a conventional apparatus without a cyclone such as the apparatus of the present invention, melting and reduction of iron powder were performed in the following manner. The effective capacities of the vertical dissolution tank and cyclone used are as follows. Vertical dissolution tank effective volume: 15 m ³ cyclone effective volume: 0.1 m ³ Incidentally, in the present invention apparatus, to vertical dissolver 1 month, pump lift: 35m, flow rate 180 m ³ / h as the 1 Three units and three cyclones were installed.

The following results were obtained by dissolving and reducing iron powder using the conventional apparatus under the following conditions. Iron powder input of the vertical dissolution tank: 172 g / h vertical undissolved iron powder amount was reduced to the plating solution of pH = 2.1 Vertical dissolution tank in the dissolution tank: 0.438 kg / m ³ ie, cyclones When no was used, 0.438 kg / m ^{3 of} undissolved iron powder flowed out of the system.

On the other hand, when the apparatus of the present invention is used under the same conditions of the iron powder input amount and the pH, the amount of undissolved iron powder in the vertical dissolution tank: 0.476 kg / m ^{3 in the} cyclone filtrate Undissolved iron powder: 0.004 kg / m ³ Cyclone Return undissolved iron powder in the filtrate: 0.947 kg / m ³ Plating solution supply to cyclone: 180 m ³ / h, undissolved iron outside the system Powder outflow was minimized. Also, since the reduction efficiency of Fe ³⁺ increased, the plating solution volume
The concentration of Fe ³⁺ in 150 m ³ / h was constantly reduced to about 3 g / m ³ , and iron powder consumption was reduced from 180 kg / h to 115 kg / h.

Example 2 Next, zinc oxide powder was melted using a continuous melting apparatus according to the present invention shown in FIG. 3 and a conventional apparatus shown in FIG. In each of the figures, the outline of the configuration is common to that of FIG. 2 described above, and thus the same reference numerals are used. In the figures, reference numeral 10 denotes a plating solution circulation tank, 11 denotes a solution sending pump, and 12 denotes a clean plating solution sending pipe. ,
13 is an overflow pipe.

In the continuous melting apparatus according to the present invention shown in FIG. 3, the zinc oxide powder cut out from the hopper 5 by the supply device 4 is supplied to the melting tank 1. On the other hand, the plating solution is supplied from the plating solution circulation tank 10 to the dissolution tank 1 by the solution sending pump 11. In the dissolving tank 1, the plating solution and the zinc oxide powder are stirred and dissolved by a stirring device including a motor 2 and a stirring blade 3. The plating solution pressurized by the solution sending pump 7 is supplied to the cyclone 6, and the clean plating solution from which zinc oxide has been removed by the cyclone 6 is supplied to the plating solution circulating tank 10 through the clean plating solution sending pipe 12. Is returned to. On the other hand, the undissolved slurry of zinc oxide separated by the cyclone 6 is returned to the dissolution tank 1 through the return line 9. As a result, the zinc oxide stays in the dissolution tank 1 until the dissolution is completed.

On the other hand, in the conventional apparatus shown in FIG. 4, the zinc oxide powder and the plating solution are supplied to the dissolving tank 1 and stirred and dissolved in the dissolving tank 1 in the same manner as in FIG.
The plating solution supplied to the dissolution tank 1 is sequentially overflowed, and a plating solution circulation tank is provided by an overflow pipe 13.
Returned to 10. Here, what determines the residence time of the zinc oxide in the dissolving tank 1 is the volume of the dissolving tank 1 and the amount of the plating solution supplied by the liquid feed pump 11. When dissolving zinc oxide on an industrial scale, a dissolving tank of ³⁰ to 50 m ³ is required based on the results shown in FIG. 1 described above, but such a dissolving tank is impractical, and in practice, it is about 20 m ^3. Therefore, undissolved zinc oxide flows out of the dissolution tank 1 and remains as sludge in the plating solution circulation tank 10.

When such sludge is sent to the plating tank,
As a workaround, a cushion tank is provided on the way from the dissolution tank 1 to the plating solution circulation tank 10 so that zinc oxide is brought into the plating solution circulation tank 10. However, in this case, the yield of zinc oxide must be reduced. Attempts have also been made to recover zinc oxide using a filtration-type filter, but in this case, as described above, a filter cloth-like substance that is difficult to filter is generated, and in fact, it cannot be used in processes. is there.

The classification conditions in the cyclone were set to 5 μ- using each of the dissolving devices disclosed in FIGS. 3 and 4 described above.
Dissolution of zinc oxide powder was carried out to remove 50% (50μ-100%). When the conventional equipment was used, the dissolution yield was only 84% and sludge was deposited in the liquid circulation tank. When the apparatus of the present invention was used, the dissolution yield was 95% or more, and the cleanliness of the plating solution was extremely good. Therefore, no sludge was deposited in the solution circulation tank.

[0023]

As described above, according to the present invention, not only the undissolved portion of the plating ion source powder can be recovered quickly and easily, but also the dissolution thereof can be promoted. Thus, the plating ion source powder can be dissolved. In addition, since outflow of undissolved components to the outside of the system can be suppressed to a minimum, not only the yield of the plating ion source powder can be improved but also the life of the melting device can be extended.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a stirring time and a dissolution rate of a zinc oxide powder.

FIG. 2 is a schematic view of a preferred continuous melting apparatus according to the present invention.

FIG. 3 is a schematic view of a preferred continuous dissolution apparatus according to the present invention used in an example.

FIG. 4 is a schematic view of a conventional continuous melting apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical dissolution tank 2 Motor 3 Stirrer blade 4 Plating ion source powder supply device 5 Plating ion source powder hopper 6 Cyclone 7 Liquid feed pump 8 Line 9 Return line 10 Plating solution circulation tank 11 Liquid feed pump 12 Clean plating solution Liquid supply piping 13 Overflow piping

Continuation of the front page (72) Inventor Takao Ikenaga 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. None) Inside the Mizushima Works, Kawasaki Steel Corporation (72) Inventor Hiroshi Nakano 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (No address) Inside the Mizushima Works, Kawasaki Steel Corporation (56) JP, A) JP-A-4-88200 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C25D 21/14

Claims (3)

(57) [Claims] 1. A plating solution dissolving tank having a stirring function.
Supply device for plating ion source powder, cyclone for separating undissolved portion of the powder from plating solution, pump and conduit for feeding plating solution from dissolution tank to cyclone, and plating ion source powder separated by cyclone A continuous dissolving device for plating ion source powder, comprising a conduit for returning undissolved matter to a dissolving tank. 2. The continuous dissolving apparatus according to claim 1, wherein the plating ion source powder is a zinc oxide powder. 3. The continuous dissolving apparatus according to claim 1 or 2, wherein the cyclone has a classification specification of 5 μ-50% (50 μ-100%) or more.