JP3180977B2 - Treatment method for electroless plating aging solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless plating aging solution which efficiently separates and removes a plating metal component and a reducing agent component remaining in an electroless plating aging solution and renders the electroless plating aging solution harmless. Regarding the processing method.

[0002]

2. Description of the Related Art Electroless plating technology has been widely used in the production of decorative plated articles, but recently, in the production of functional electronic components such as magnetic disks and magnetic tapes, nickel plating or nickel plating by the electroless method has been used. Cobalt plating has been applied, and its application field has been extremely expanded. Generally, the electroless plating method is performed by immersing a substrate to be plated in a plating solution prepared in advance and reacting it for an empirically determined time. However, a large amount of plating metal ions such as Ni ²⁺ and a reducing agent component such as sodium hypophosphite necessarily remain in the liquid after the treatment due to an increase in oxidation products during the reaction. .

Conventionally, a solution which has completed such a certain plating reaction is called a plating aging solution, and in many cases, is discarded by means such as dumping into the sea. However, from the viewpoints of pollution prevention and environmental purification requirements and the recovery and reuse of contained valuable metal components, plating aging solution treatment techniques have been actively developed, and some of them have been put into practical use. . Of these, the recovery of valuable metals is mainly a method of separating and recovering nickel ions dissolved in the plating aging solution.For example, (1) a method of precipitating and recovering nickel by an electrolytic method,
(2) a method of injecting a large amount of iron powder or palladium salt into the plating aging solution to induce self-decomposition to separate and recover the solution; (3) a method of adsorbing the ion-exchange resin; and (4) an aluminum plating aging solution made alkaline. A method in which nickel is precipitated by charging a plate or foil and then recovered with nitric acid, and nickel remaining in the mother liquor is adsorbed by a chelating resin (Japanese Patent Laid-Open No. 51-6136). Method of applying plating aging solution to raw material in the production of electroless plating powder
-276979) and the like.

Further, recently, with respect to the treatment of the plating aging solution, the mica powder is subjected to electroless plating to recover nickel, and the mother liquor is oxidized with hydrogen peroxide or the like to be converted into orthophosphate ions, which are then converted into calcium ions ( A method of reacting with Ca ²⁺ ) to precipitate and separate as calcium phosphite or calcium phosphate has been reported [“Study on technology for treating waste liquid of chemically difficult-to-phosphorus-based chemical plating” (Product Research Institute Research Report No. 121). However, all of the above methods are difficult to implement due to operational or economic disadvantages.

[0005]

The object of the invention is to be Solved by the present inventors have found that hypophosphorous
Although systematic research has been carried out on a rational treatment method for the electroless plating aging solution containing acid ions , in this process, an effective means for separating and removing dissolved components different from the above-mentioned prior art has been elucidated. That is, when the same electroless plating aging solution is added at a constant flow rate to a slurry in which powder is dispersed in a diluted electroless plating aging solution in a specific pH range while stirring, dissolved plating metal ions form a plating film on the powder surface. When the zinc compound is reacted with the mother liquor after the plating powder is further separated and the plating powder is separated, the reducing agent component and the like precipitate as a zinc phosphite composition containing zinc phosphite as a main component, After the treatment, it was confirmed that the solution could be purified into a disposable liquid containing no harmful components.

The present invention has been developed on the basis of the above findings, and its object is to efficiently separate dissolved components such as a plating metal and a reducing agent from an electroless plating aging solution containing hypophosphite ions. An object of the present invention is to provide a method for treating an electroless plating aging solution that can be removed and made harmless to a state in which it can be disposed of.

[0007]

To achieve the above object, the method for treating an electroless plating aging solution according to the present invention is as follows.
The slurry is prepared by dispersing the powder in a dilute solution adjusted to pH around the electroless plating aging solution containing phosphite ions , and the same electroless plating aging solution is controlled while heating and stirring the slurry. A first separation step of separating and removing the powder after the addition treatment at the set flow rate, and reacting a zinc compound with the mother liquor after the first separation step to precipitate a composition containing zinc phosphite as a main component. Are sequentially performed in a second separation step of separating and removing the slag.

[0008] Hypophosphite ions to be treated by the present invention
The type of electroless plating aging solution containing is not particularly limited, but is typically an electroless plating aging solution using nickel, cobalt or a nickel-cobalt alloy as a plating metal source using sodium hypophosphite as a reducing agent. . The composition of the electroless plating aging solution varies depending on the bath composition and the plating conditions, but taking the normal composition of the nickel plating aging solution as an example, nickel ions 4 to 7 g / l, oxycarboxylate ions (chelating agent) 30 to 55 g / l, hypophosphite ion 25-5
5 g / l, phosphite ions 80-100 g / l, sulfate ions 30-45 g / l. However, the electroless plating aging solution to be treated in the present invention is not limited to the above composition.

[0009] The first separation step of the present invention, hypophosphorous acid ion
Ni ⁺ , Co dissolved from electroless plating aging solution containing
^This is the step of separating and removing plating metal ions such as ²⁺ . In this step, first, the powder is dispersed in a dilute solution obtained by adjusting the pH of the electroless plating aging solution to near neutrality to form a slurry. The pH of the aging solution is adjusted to pH5 using an acid or an alkali agent.
The pH is controlled in the range of 5 to 8.5, preferably in the vicinity of pH 7. Dilution of the electroless plating solution can be performed before and after pH adjustment, and is preferably diluted to 5 to 20 times with water.

[0010] The powder to be dispersed in the diluent is a base material for coating and capturing the plating metal, and is a powder that can be easily dispersed to form a homogeneous slurry and that can be subjected to electroless plating. The material, shape, etc. are not limited as long as it is provided. However, the most preferred powder for the purposes of the present invention is iron or its alloys. The reason for this is that when iron or its alloy is used as a base material, it is not necessary to perform a pretreatment for supporting a noble metal salt serving as a plating catalyst nucleus. Is expected.

The powder is mildly warmed, preferably 60
It is added to the diluted electroless plating aging solution whose pH has been adjusted at a liquid temperature of up to 70 ° C., and sufficiently stirred and dispersed. Dispersing the powder in the electroless plating aging solution diluted in this way is
This is because the treatment can be performed extremely rationally in view of the treatment purpose of the plating aging solution and the plating reaction. That is, if the powder is a metal, the oxide film on the surface is removed by the reducing agent component in the liquid, so that the plating catalyst nucleus is formed by the displacement precipitation action, and the conventional pretreatment for forming the catalyst nucleus using palladium or the like is performed. Does not require any. Therefore, when a powder other than a metal powder such as iron powder is used as the base material, it is natural that it is necessary to perform a plating pretreatment which is usually adopted in advance.

If the slurry is continuously heated and agitated, the powder metal ions dissolved in the electroless plating aging solution will react with the powder, causing a foaming phenomenon. At the time when this reaction is started, the same electroless plating aging solution is added at a controlled flow rate while continuing to heat and stir to maintain the reaction. Here, the controlled flow rate refers to an electroless control in which the adjusted pH and temperature levels are maintained in a constant range from the start to the end, and the metal ion concentration in the liquid is controlled to be substantially close to zero at all times. It means the addition flow rate of the plating aging solution. In this case, the presence or absence of the metal ions can be identified by the degree of coloration of the slurry liquid, so that the presence or absence can be easily determined.

When the electroless plating aging solution is added to the slurry, an alkali agent or hypophosphite may be added at the same time as necessary. The alkaline agent is
It is added in order to keep the pH of the solution around neutral at all times, and is usually carried out by interlocking with a pH controller or by flowing a calculated amount of sodium hydroxide solution at a constant rate. In addition, hypophosphite ions in the aging solution are generally present in a molar amount several times as large as the plating metal ions, so that the reducing power is not insufficient even in a normal case without additional addition. If the concentration of hypophosphite in the solution is not sufficient to completely reduce the metal ions, the insufficient amount of hypophosphite is used alone or mixed with the above-mentioned sodium hydroxide solution. And add.

When the addition of a predetermined amount of the electroless plating aging solution is completed, stirring is continued until the reaction is completed. By this treatment, Ni ²⁺ and Co ²⁺ remaining dissolved in the electroless plating solution are dissolved.
Such metal ions are reduced and deposited as a dense plating film on the surfaces of the powder particles. The powder on which the plating film is formed is separated from the slurry by a solid-liquid separation operation such as a filtration treatment.

[0015] With the above process, hypophosphorous acid ions present in the electroless plating aging solution (H ₂ PO ₂ ^-) is oxidized phosphite ion (HPO ₃ ^{2 -)} was converted to H ₂ PO ₂ ^- is substantially absent. Therefore, the mother liquor after the first separation step is:
The liquid composition contains phosphite ions, sulfate ions, oxycarboxylate ions as chelating agents, and sodium ions. The second separation step of the present invention is a step of reacting the mother liquor with a zinc compound to form a precipitate mainly composed of zinc phosphite, and separating and removing the precipitate.

As the zinc compound to be reacted with the electroless plating aging solution, zinc oxide (zinc white), zinc hydroxide, zinc carbonate, basic zinc carbonate, zinc sulfate or zinc nitrate can be used. Among them, it is economical to use zinc oxide.

In the reaction between the electroless plating aging solution and the zinc compound, an auxiliary agent for improving the reactivity can be used if necessary. Examples of the auxiliary agent include alkali agents such as sodium, potassium and ammonium hydroxides, acidifying agents such as phosphorous acid, phosphoric acid, sulfuric acid and nitric acid, sodium borate and pH buffering agents such as sodium phosphate. At least one or two or more selected from organic phosphonic acids or soluble salts thereof (alkali salts, ammonium salts).

The reaction is carried out under stirring, preferably 40-80.
The reaction is carried out in a heated state at a final pH of 6 to 10, more preferably 6.5 to 8.5. The precipitation reaction is continued until no phosphite ions are found in the solution, and after the reaction is completed, the mixture is aged for a while. Next, the precipitate is separated and removed by a solid-liquid separation operation such as a filtration treatment. This precipitate is a composite composition containing zinc phosphite as a main component and a small amount of other components such as a chelating agent.

The electroless plating aging solution thus treated does not contain any components that only dissolve sodium sulfate and are harmful when discarded. Therefore, there is no problem in terms of environmental pollution or pollution even if the waste is discharged or discharged as it is or appropriately diluted. The separated and recovered metal plating powder can be reused as, for example, a conductive filler, a powder metallurgy material or a thermal spray material, and the zinc phosphite composition can be reused as a metal rust preventive pigment, an antioxidant or a resin additive. Can be planned.

[0020]

The method for treating an electroless plating aging solution according to the present invention comprises a first separation step for separating and removing plating metal components dissolved in the electroless plating aging solution containing hypophosphite ions, and a separate dissolving method. A second separation step for separating and removing the reducing agent component and the like. Among them, in the first separation step, a liquid state is formed for smoothly proceeding a plating reaction in a pre-process of dispersing the powder in a dilute solution obtained by adjusting the pH of the electroless plating aging solution to form a slurry. By adding an electroless plating aging solution acting as a chemical solution under specific flow rate conditions, the dissolved Ni
Plating metal ions such as ²⁺ and Co ²⁺ are coated on the powder surface by plating and completely separated and removed. In the next second separation step, it remains in the mother liquor through the reaction with the zinc compound.
Components such as a reducing agent such as hypophosphite ion and a chelating agent are formed as a precipitate having a composite composition containing zinc phosphite as a main component, and are separated and removed very efficiently.

By the respective processing operations in the first and second separation steps, the aging solution for electroless plating is smoothly rendered harmless. In addition, since the separated and collected material can be reused, intensive post-treatment of the electroless plating aging solution can be performed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

Example 1 (1) First Separation Step Nickel 0.075 mol / l, sodium hypophosphite 0.1%
Sodium hydroxide was added to a pH 4.78 electroless nickel plating aging solution having a liquid composition of 29 mol / l, sodium phosphite 1.37 mol / l, and malic acid 0.34 mol / l to neutralize ( (pH 7.0), and diluted 5-fold with water. 200 ml of this solution was placed in a 500 ml glass beaker, placed in a hot water bath and heated to 65 ° C. Then, while stirring the solution, 20 g of iron powder (“Atmel 300M” manufactured by Kobe Steel Ltd.) was added, and the mixture was sufficiently stirred and dispersed to prepare a slurry. After a while, when the foaming started, the same electroless nickel plating aging solution (239 ml) was stirred at 5 ml /
Min, and at the same time 160g / l of sodium hydroxide
60 ml of the solution were added at a flow rate of 1.25 ml / min. During this addition, little color reaction of the slurry was observed. After the entire amount of the electroless nickel aging solution was added, stirring was continued until foaming was cured. The slurry after the treatment was filtered, and the formed nickel-plated iron powder was separated and removed. The filtrate was colorless and transparent, and no nickel ion was detected by quantitative analysis.

(2) Second Separation Step The mother liquor after the first separation step is heated to 65 ° C., and while stirring, a 0.5 mol / l zinc sulfate solution is adjusted to an equivalent amount to phosphite ions. It was added and reacted. Then, the final pH was adjusted to 8.5 with a 10% by weight sodium hydroxide solution, and the mixture was aged by continuing stirring for 60 minutes. As a result, a white precipitate was formed. The precipitate was separated off by filtration.
X-ray diffraction of this white precipitate confirmed that zinc phosphite crystals were the main component.
-IR revealed that the composition was a composite composition containing a small amount of zinc malate.

(3) Composition of liquid after treatment When the mother liquor after the second separation step was analyzed, the dissolved component was only sodium sulfate and no other components were detected at all.

Example 2 (1) First Separation Step Nickel 0.106 mol / l, cobalt 0.178 mol / l
l, pH containing sodium hypophosphite 0.717 mol / l, phosphite 0.801 mol / l and chelating agent
Sulfuric acid was added to the 9.3 electroless nickel-cobalt alloy plating aging solution to adjust the pH to 8.0, and then diluted 5 times with water. 200 ml of this diluted solution was taken in a 500 ml glass beaker, heated to 80 ° C. in a hot water bath, and 20 g of the same iron powder as in Example 1 was charged with stirring and dispersed sufficiently to prepare a slurry. At the time when foaming started after a while, 93 ml of the same electroless nickel-cobalt alloy plating aging solution as above was added at a flow rate of 2 ml / min while stirring the slurry, and simultaneously, a 160 g / l solution of sodium hydroxide was added to 0 ml. It was added at a flow rate of 0.4 ml / min. During this addition, the slurry hardly developed any color. After the whole amount was added and stirring was continued until foaming subsided, the plated iron powder was separated by a filtration operation. The filtrate was colorless and transparent, and no detection of nickel and cobalt ions was observed.

(2) Second Separation Step The mother liquor after the first separation step was heated to 65 ° C., and a 10% by weight zinc oxide slurry was added thereto with stirring so as to be equivalent to phosphite ions to cause a reaction. . The final pH is then 8.
After adjusting to 0, stirring was continued to ripen to form a white precipitate.

(3) Composition of liquid after treatment As a result of analyzing the components dissolved in the mother liquor after the treatment, only sodium sulfate was detected and no other components were recognized.

[0029]

As described above, according to the treatment method of the present invention, the plating metal and the reducing agent component and the like remaining in the electroless plating aging solution can be efficiently separated and removed, and purified to a harmless state that can be discarded. be able to. In addition, since the separated and collected material can be reused for a new use, it is expected to have great utility as an intensive processing technique for an electroless plating aging solution that will increase in the future.

──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Kingo Takeuchi 9-15-1, Kameido, Koto-ku, Tokyo Japan Chemical Industry Co., Ltd. Research and Development Headquarters (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 18/00-18/54

Claims (2)

(57) [Claims] 1. A slurry is prepared by dispersing a powder in an electroless plating aging solution containing hypophosphite ions in a diluting solution whose pH has been adjusted to near neutrality, and a slurry is prepared. A first separation step of separating and removing the powder after adding an electrolytic plating aging solution at a controlled flow rate; and reacting a zinc compound with the mother liquor after the first separation step to form a zinc phosphite as a main component. 2. A method for treating an electroless plating aging solution, comprising sequentially performing a second separation step of separating and removing a precipitate of the composition. 2. A nickel- and / or cobalt electroless plating aging solution adjusted to pH 5.5 to 8.5.
2. The method for treating an electroless plating aging solution according to claim 1, wherein a 20-fold dilution is used.