JPH0556290B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing stannous oxide, which is easily soluble in acids and is particularly suitable for plating. [Prior Art] Stannous oxide is widely used in the plating industry for preparing tin plating baths or as a tin ion additive. Conventionally, methods for producing stannous oxide include (1) adding an alkaline aqueous solution to an acidic aqueous solution of a stannous salt and reacting the resulting slurry, and (2) boiling the resulting slurry. 400 in an inert atmosphere such as gas
A common method is to bake it at about ℃. However, these methods require boiling or
The stannous oxide that is obtained and requires a calcination process has poor solubility in acids, is irregular in shape, has a low bulk density, and has a relatively large angle of repose, and has many disadvantages in terms of handling. It was hot. [Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing stannous oxide that does not have the above-mentioned drawbacks. [Means for solving the problem] In order to achieve this objective, the inventors of the present application have conducted extensive research and found that
However, they discovered that stannous hydroxide can be easily converted to stannous oxide, and also discovered the conditions for producing nearly spherical stannous oxide that is easily soluble in acids at low temperatures of 30°C or below, and arrived at the method of the present invention. This is what I did. That is, the method of the present invention involves adding alkali carbonate to a small amount of water to prepare an aqueous solution with a pH of 6.2 to 9.3, preferably 6.5 to 9.0, and adding the aqueous solution to the aqueous solution while maintaining the temperature at 10 to 30°C and stirring. , an acidic aqueous solution in which a stannous salt was dissolved and an aqueous alkali carbonate solution such as sodium carbonate or potassium carbonate were added at the same time by blowing into the bottom of the aqueous solution while maintaining the pH and temperature of the aqueous solution, and after 30 minutes. After aging the produced stannous oxide for about 1 hour, the produced stannous oxide is separated and dried. [Function] The concentration of the acidic aqueous solution of the stannous salt used in the present invention is not particularly limited;
A concentration of about 250 to 350 g/g is preferable. This aqueous solution is 4 to 10 ml per minute, preferably 4 to 8 ml per minute.
ml, and is supplied with an aqueous alkali carbonate solution in an amount that maintains the PH of the reaction tank at a predetermined value, for example, by a roller pump.
Adjusted with a control meter. In the method of the present invention, the pH in the reaction tank is 6.2-6.2.
9.3 The reason why it is preferably in the range of 6.5 to 9.0 is that anything other than this produces white 5SnO.2H ₂ O. Next, the reason why the temperature in the reaction tank is set in the range of 10 to 30°C is that below 10°C, 5SnO 2H ₂ O similar to the above is produced, and above 30°C, stannous oxide, which is easily soluble in acids, is produced. However, if the crystal shape does not lose its spherical shape as shown in Figure 1, and the temperature is further increased to 60°C or higher, the resulting crystal becomes a polyhedron as shown in Figure 2, making it difficult to handle. This is because it will cause trouble. The stannous salt used in the present invention includes chloride,
Similar products can be obtained using sulfates and other salts. In addition, when reacting an acidic aqueous solution of a stannous salt with an aqueous alkali carbonate solution, about 100 to 200 ml of ionized water or a repeated solution of the crystal mother liquor obtained by the method of the present invention is adjusted to a predetermined pH in advance. The purpose of reacting by blowing stannous salt and alkali carbonate into the solution is mainly to control the pH during treatment to a predetermined value. The method of the present invention can be applied either batchwise or continuously. In particular, when the process is carried out continuously, argon,
It is preferable to purge with nitrogen or the like. After completion of the reaction, all crystals become almost spherical after 30 minutes or more of ripening. Particular attention should be paid to the pH value of the reaction solution when carrying out the method of the present invention. The PH range during treatment is allowed to range from 6.2 to 9.3, but for example, the reaction may be started using the batch method, with an initial PH of 6.2, an intermediate PH of 8.0, and a final PH of 9.0. The method of the present invention does not allow the PH to be freely varied during the reaction even if the PH is within the permissible range. The PH fluctuation range of the reaction solution, which can be said to be a feature of the method of the present invention, is within ±0.2 to 0.3 of the predetermined PH value. That is, when the pH at the beginning of the reaction is 6.5, the pH range is preferably between 6.2 and 6.7 until the end of the reaction. The stannous oxide obtained by the method of the present invention is not only easily soluble in mineral acids such as sulfuric acid, inorganic acids such as hydroborofluoric acid, and organic acids such as phenolsulfonic acid and cresolsulfonic acid, but also has a shape. Since it is approximately spherical, has a large bulk density, and a small angle of repose, it is easy to handle and suitable for plating. [Example] Examples will be described below. Example An acidic hydrochloric acid aqueous solution containing industrial stannous chloride at a concentration of 300 g/dissolved using ionized water and a small amount of hydrochloric acid, and 150 g/contains sodium carbonate, a first class reagent. Aqueous solution with a volume of 5
Aqueous sodium hydroxide solution was added to 100ml of ionized water in a glass container in advance to maintain the specified temperature and pH.
value, stir it lightly using a magnetic stirrer, and place it in a reaction tank equipped with a PH control meter.
Using a roller pump, the above temperature and
It was added while maintaining the pH, and after the addition was completed, it was treated by a batch method in which it was kept for 30 minutes each time to ripen, and then it was filtered by suction, washed five times with a small amount of water, and vacuum dried. The shape was observed, and the composition, bulk density, and angle of repose were measured by X-ray diffraction. The results are shown in Tables 1 and 2.

[Table] As is clear from Table 1, unless the addition rate of the aqueous solution of stannous acid chloride is 8 ml/min or less, most of the products will not be spherical and will be mostly polygonal. In Experiments Nos. 4 and 5, the yield of tin and the solubility in acids did not decrease significantly, but they were inferior in terms of handling, and many of them were polyhedral or polygonal with a width of about 50 μm. The products of Experiment Nos. 1 to 3 were approximately spherical with an average particle size of 30 to 40 μm.

[Table] As can be seen from Table 2, in experiments No. 9 to 11 where the PH or temperature during treatment was outside the range of the method of the present invention, stannous oxide was not obtained, and only the treatment temperature was determined according to the method of the present invention. In experiments Nos. 6 to 8, which were higher than the method, stannous oxide was obtained, but only polyhedral crystals as shown in FIG. 2 were obtained.
The product produced by the method of the present invention had a spherical shape with almost uniform particle size as shown in Figure 1 (Experiment No. 13), and was superior to other products in both bulk density and angle of repose. Incidentally, when the impurities in Experiment No. 13 were quantified, they were as shown in Table 3.

[Table] Next, the solubility of each product in Table 2 in phenolsulfonic acid was investigated. The dissolution test was conducted so that the concentration of free phenolsulfonic acid after dissolution was 71.0 g/Sn and 20.0 g/Sn, and the degree of turbidity of the dissolved aqueous solution was determined by its absorbance using an absorption photometer (manufactured by Hitachi). It can be said that the closer the absorbance is to 0, the higher the solubility. The results are shown in Table 4.

【table】

〔Effect of the invention〕

It is possible to efficiently produce spherical stannous oxide that is more easily soluble in acids than stannous salts. Since it is spherical, handling such as cutting out from a hopper is extremely easy. Another advantage is that a product with high purity can be obtained at almost room temperature.

[Brief explanation of the drawing]

Figure 1 is a 500x scanning electron micrograph showing the structure of the stannous oxide crystal obtained in Experiment No. 13 using the method of the present invention, and Figure 2 is a photograph obtained in Comparative Example Experiment No. 6. 1 is a 500x scanning electron micrograph showing the structure of a stannous oxide crystal.

Claims (1)

[Claims] 1. A method for producing stannous oxide by reacting an acidic aqueous solution of a stannous salt with an aqueous alkali carbonate solution, in which an alkali is added to water to prepare an aqueous solution with a pH of 6.2 to 9.3. This is maintained at a temperature of 10 to 30°C, and an acidic aqueous solution of a stannous salt and an alkali carbonate aqueous solution are simultaneously added to the bottom of the aqueous solution while maintaining the PH and temperature of the aqueous solution. A method for producing spherical stannous oxide easily soluble in acid, which comprises adding the stannous oxide by blowing and aging the produced stannous oxide. 2. The rate of addition of the acidic aqueous solution of stannous salt is 4 to 8 times per minute an aqueous solution with a concentration of 300 g of tin.
ml. A method for producing spherical stannous oxide easily soluble in acid according to claim 1.