JP2001302219A - Method for producing nickel hypophosphite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inexpensively producing a high-purity product of nickel hypophosphite hexahydrate useful as a reducing agent and a nickel source in an electroless nickel plating under a pollution-free condition. SOLUTION: Barium hexahydrate or calcium hexahydrate is reacted with nickel sulfate in a water system and slightly water-soluble or water-insoluble calcium sulfate or barium sulfate is separated and nickel hypophosphite hexahydrate is obtained from the separated solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for producing nickel hypophosphite for use in electroless nickel plating. More particularly, the present invention relates to a method for producing barium hypophosphite or calcium hypophosphite and nickel sulfate in an aqueous system. And a method for producing nickel hypophosphite hexahydrate from the obtained separated solution after first separating a precipitate of barium sulfate or calcium sulfate having low solubility in water.

[0002]

2. Description of the Related Art As a basic composition of electroless nickel plating, nickel sulfate has been used as a nickel source, and sodium hypophosphite has been used as a reducing agent. However, as the plating progresses, sodium sulfate is generated, which not only shortens the life of the plating bath but also increases the cost of treating the waste sodium sulfate, and a drastic improvement is required. As a solution, a method of using nickel hypophosphite alone, which is a nickel source and a reducing agent, has been proposed. (JP-A-4-
210480)

[0003] Although the superiority of the nickel hypophosphite method is apparent in principle, the biggest reason that this method has not become the mainstream of electroless nickel plating is that nickel hypophosphite is too small. Being expensive.

It is well known that sodium hypophosphite is reacted with an acidic nickel salt, nickel sulfate, nickel nitrate or nickel chloride, to obtain nickel hypophosphite hexahydrate. However, in these methods, a neutral salt is produced as a by-product, which needs to be dissolved in water and separated from crystals. In this case, a considerable amount of nickel hypophosphite dissolves in water, resulting in a decrease in yield and a disadvantage of costly detoxification treatment.

A method for reacting hypophosphorous acid with nickel hydroxide or nickel carbonate has been proposed in JP-A-9-2809. These methods are superior to the above-described production methods, because by-products of neutral salts are avoided,
The starting materials, hypophosphorous acid, nickel hydroxide or nickel carbonate, are more expensive than the corresponding sodium hypophosphite, for example, nickel sulfate, which is problematic for industrial implementation.

There is no question that nickel sulfate is the cheapest nickel source. However, barium hypophosphite or calcium hypophosphite has little demand and is therefore often viewed as a very expensive chemical, but can be easily produced from yellow phosphorus and barium hydroxide or calcium hydroxide (Chiya Toshizo "New Edition Inorganic Chemistry" p. 728-729, published in Sangyo Tosho 47) In terms of price, mass production is possible at a price close to that of sodium hypophosphite.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing nickel hypophosphite hexahydrate at low cost and to produce a production method in which by-products which must be detoxified are extremely reduced. It is in.

[0008]

Means for Solving the Problems Nickel sulfate, nickel nitrate and nickel chloride are subjected to metathesis reaction in an aqueous system with sodium, magnesium, calcium and barium salts of hypophosphorous acid. Table 1 shows the solubility in water at 25 ° C. of the substance produced together with the above.

Of the various substances shown in Table 1, barium sulfate hardly dissolves in water. In addition, the solubility of calcium sulfate is low, and although not shown in the table, the solubility does not increase even at a high temperature.
It can be seen that the solubility at 0.0 ° C. can be easily and completely removed from the aqueous system due to the solubility of 0.067). The reaction formula according to the present invention is shown in Chemical formula 1.

[0011]

Embedded image Ba (H ₂ PO ₂ ) ₂ + NiSO ₄ → Ni (H ₂ PO ₂ ) ₂ + BaSO ₄ (1) Ca (H ₂ PO ₂ ) ₂ + NiSO ₄ → Ni (H ₂ PO ₂ ) ₂ + CaSO ₄ (2)

[0009]

[Table 1]

Hereinafter, the present invention will be described in detail. In the reaction between barium hypophosphite or calcium hypophosphite and nickel sulfate, both components may be aqueous solutions, or either may be a transparent solution, and may be a solid or a mixture of solid and liquid. .

The reaction temperature is preferably from 40 to 80 ° C. 4
When the temperature is lower than 0 ° C., not only does the reaction rate slow down,
Since the generated nickel hypophosphite cannot be completely dissolved,
It is necessary to increase the amount of intervening water for a part of it to be mixed into the precipitate or to completely dissolve it, and there is a concern that the yield of nickel hypophosphite may be reduced. If the reaction temperature is higher than 80 ° C., thermal decomposition of hypophosphite is apprehended.

In relation to the reaction temperature, the amount of water involved in the reaction is important. The key point of the present invention is to separate the produced barium sulfate or calcium sulfate to obtain an aqueous solution of nickel hypophosphite. The lower the concentration (the greater the amount of intervening water), the lower the yield, On the other hand, if the concentration is too high, it cannot be completely dissolved in water, and the yield also decreases. A water content of 10 to 40 moles per mole of nickel hypophosphite is preferred.

The mode of separating barium sulfate or calcium sulfate from the aqueous solution of nickel hypophosphite is not limited. In addition to general filtration, centrifugation is also effective. Especially at the same temperature as the reaction temperature to increase the separation efficiency,
The method of centrifugation is excellent.

As a method for obtaining nickel hypophosphite hexahydrate from an aqueous solution of nickel hypophosphite, there is a general method of precipitating a crystal, followed by filtration and drying. However, in this method, a solution remaining in the filtrate remains. There is a problem in the treatment of nickel hypophosphite, but rather a method of directly drying the aqueous solution by vacuum stirring is preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto.

EXAMPLE 1 31.2 g of water was added to 26.7 g of barium hypophosphite and heated to about 60.degree. 27.3 g of solid nickel sulfate hexahydrate was gradually added to this mixture and a partial aqueous solution of barium hypophosphite. The reaction mixture was milky green and was filtered immediately after the addition was completed, yielding only 6 g of filtrate. However, the presence of green crystals obtained when recrystallizing nickel hypophosphite from water was confirmed in this filtrate. Next, a total of 70 g from the 77 g
g was transferred to another beaker, 50 g of water was added, the mixture was again heated to 60 ° C. and filtered again. The amount of the filtrate was about 60 g. When these were allowed to stand overnight, about 8 g from the filtrate, trace amounts of crystals were found on the surface of the filtration residue, and not a few crystals were found on the back side of the filter paper and the funnel.

Example 2 27.0 g of water was added to 17.0 g of calcium hypophosphite, heated to about 60 ° C., and further prepared in advance.
51.6 g of a 30% aqueous solution of 30% nickel sulfate was added,
Stirred at 60 ° C. for 30 minutes. The reaction mixture was filtered, the filtrate was cooled and air-dried to obtain about 11.0 g of nickel hypophosphite hexahydrate.

As described above, according to the present invention, barium hypophosphite or calcium hypophosphite is reacted with nickel sulfate in an aqueous system, and barium sulfate which is substantially insoluble in water or calcium sulfate which is hardly soluble in water. Was removed, and nickel hypophosphite hexahydrate could be obtained from the obtained separated solution.

Claims (1)

[Claims] 1. A barium hypophosphite or calcium hypophosphite is reacted with nickel sulfate in an aqueous system to remove barium sulfate or calcium sulfate having low solubility in water. A method for producing hexahydrate.