JP3285613B2 - Stabilization of persulfate aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for stabilizing an aqueous solution of persulfate. The present invention particularly relates to a method for stabilizing an aqueous persulfate solution with an alkali borate.

[0002]

2. Description of the Related Art Persulfate aqueous solutions are used in many fields as desizing agents and dye oxidizing agents in the textile industry, and as surface treatment agents for printed wiring boards in the electronics industry. In such a persulfate aqueous solution, the concentration of the persulfate decreases due to decomposition of the persulfate during transportation or storage period until use, and therefore, a stabilizer is usually added to prevent such a decrease.

The stability of an aqueous solution of persulfate is strongly affected by temperature, but is also affected by trace amounts of metallic impurities such as iron and copper. For this reason, chelating agents that block these metal impurities are used as stabilizers.

[0004] The aqueous solution of persulfate also produces an acid by its decomposition, which lowers the pH and thereby further reduces the stability. On the other hand, the stability of the persulfate solution can be improved to some extent by neutralizing the aqueous solution of persulfate, and a pH buffer is used for this neutralization. In particular, stabilizers which are considered to be useful in practice are phosphates or condensed phosphates.

[0005]

However, the known stabilizers have the following disadvantages in practice as stabilizers for persulfates.

That is, phosphates or condensed phosphates have good initial stability, but after a long time, the stabilizing ability is reduced due to hydrolysis or the like with the lapse of time, and decomposition of persulfate is reduced. There was a problem that it could not be prevented.

The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, have found that the addition of an alkali borate or a mixture thereof to an aqueous persulfate solution can stabilize the aqueous persulfate solution. Heading, the present invention has been completed.

[0008]

In order to solve the above-mentioned problems, the present invention provides an aqueous persulfate solution comprising adding an alkali borate or a mixture thereof to a 1 to 70% by weight aqueous persulfate solution. To provide a stabilization method.

Although the principle of stabilization of the aqueous solution of persulfate in the method of the present invention is not clear, the stability of the aqueous solution of persulfate is improved by the relatively strong and moderate pH buffering action of the alkali borate on the aqueous solution of persulfate. It is considered to be done.

[0010] The alkali borate in the present invention is not particularly limited. Representative examples include sodium tetraborate (borax), sodium metaborate, sodium octaborate, potassium borate, potassium metaborate, and ammonium borate, with sodium tetraborate (borax) being particularly preferred.

The persulfate concentration of the aqueous persulfate solution is usually
It is about 1 to 70% by weight. On the other hand, the amount of the alkali borate used depends on the concentration of metal impurities in the aqueous solution of persulfate and is generally difficult to specify. Preferably, it is used in such an amount that it becomes 10 to 10% by weight. The amount of the alkali borate used is generally independent of the concentration of the persulfate. When the concentration of metal impurities in the aqueous solution of persulfate is extremely low and the storage temperature is low, it may be effective to use the alkali borate in an amount of less than 0.01% by weight.

[0012]

According to the present invention, by using an alkali borate as a stabilizer for persulfate, it is possible to stabilize the aqueous solution of persulfate for a longer period of time as compared with the case where a known phosphate is used.

In this case, it is usually preferable to use one or more compounds among the alkali borates as a stabilizer, but if necessary, it does not preclude the use in combination with a conventional stabilizer. .

[0014]

The present invention will be described more specifically with reference to the following examples. In the examples, parts are parts by weight.

Example 1 A solution of 100 parts of an aqueous solution is prepared from 20 parts of sodium persulfate, 0.5 part of a stabilizer and the balance of ion-exchanged water. This aqueous solution was allowed to stand at 20 ° C., and the stability (pH buffering action) immediately after the preparation and after a predetermined period of time was compared. Table 1 shows the results
Shown in

[0016]

[Table 1]

Example 2 A solution of 100 parts of an aqueous solution is prepared from 20 parts of sodium persulfate, 1 part of a stabilizer and the balance of ion-exchanged water. This aqueous solution was left at 25 ° C., and the stability was compared immediately after preparation and after standing for a predetermined period. Table 2 shows the results.

[0018]

[Table 2]

The stabilization rate (%) in Table 2 is calculated by the following equation.

(Equation 1) Here, A is the concentration of the aqueous solution of sodium persulfate immediately after preparation, and B is the concentration of the aqueous solution of sodium persulfate after standing. The concentration of the aqueous solution of sodium persulfate is measured according to JIS K
Performed according to -8252.

[0020]

As described above, according to the present invention, by using an alkali borate or a mixture thereof as a stabilizer for an aqueous solution of persulfate, it can be compared with the case where another known stabilizer is used. As a result, the aqueous solution of persulfate can be stabilized for a long period of time, so that the aqueous solution of persulfate can be stored for a long period of time without substantially lowering its concentration.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 15/08 C11D 7/42 CA (STN)

Claims (1)

(57) [Claims] 1. A method for stabilizing an aqueous persulfate solution, comprising adding an alkali borate or a mixture thereof to a 1-70% by weight aqueous solution of persulfate.