JPS60221319A - Manufacture of stannous oxide - Google Patents

Abstract

PURPOSE:To manufacture stannous oxide easy to handle, having high stability and high solubility in an acid, and suitable for use as a component for preparing a tinning bath by reacting an acidic aqueous soln. of a stannous salt with an aqueous soln. of sodium carbonate under specified conditions. CONSTITUTION:The acidic aqueous soln. of the stannous salt (A) such as stannous chloride and an aqueous soln. of sodium carbonate (B) are added to a reactor little by little, and they are mixed by stirring at 6.5-8.4pH and 70-85 deg.C to form a white precipitate of stannous hydroxide (5SnO.2H2O). Stirring is continued while keeping said conditions, and by a proceeding reaction the white precipitate of stannous hydroxide is converted into black particles of stannous oxide (SnO) having >=2 bulk density and <=40 deg. angle of repose.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing stannous oxide, particularly stannous oxide whose bulk density and angle of repose are selectively controlled and which is easily soluble in inorganic acids and organic acids. .

Stannous oxide is widely used in the plating industry for preparing tin plating baths or as a tin ion additive. Generally, an aqueous alkali solution is added to an acidic aqueous solution of a stannous salt to react, precipitate the stannous hydroxide, and then boil the resulting slurry to convert the stannous hydroxide to stannous oxide. manufactured by the method. The stannous salt only needs to be soluble in the aqueous acid solution, and stannous chloride is generally used. The alkali used in the reaction is generally an aqueous solution of alkali carbonate, ammonia, or alkali hydroxide. A slurry of white precipitate is obtained by stirring and mixing the aqueous solutions of these reactive raw materials. Although this white precipitate is generally called stannous hydroxide, it is actually a hydrate of stannous oxide, and is a compound having a composition of 5Sn0.2O.

For convenience, this precipitate is referred to herein as stannous hydroxide. The obtained stannous hydroxide is usually treated by boiling it together with the mother liquor, or by heating the stannous hydroxide that has been collected separately at a temperature of about 400°C in an inert atmosphere such as carbon dioxide gas to form a black oxide. Usually, it is made of stannous or SnO. In any case, conventional methods require considerable heat energy for boiling or roasting. Moreover, according to this method, the bulk density of the produced stannous oxide is relatively low, the angle of repose is relatively large, which may cause difficulties in handling, and the disadvantage is that it has low solubility in acids. It recognized.

The present inventors have determined that the conditions for converting from stannous hydroxide to stannous oxide in the above-mentioned prior art are that stannous hydroxide and stannous oxide in a low temperature range, especially in order to carry out the conversion in a lower temperature range than in the conventional method. The stability of tin was investigated in detail. As a result, by selecting the slurry temperature and u value within an extremely narrow range, the conditions under which stannous hydroxide can be easily converted to stannous oxide even when the slurry temperature is in the low temperature range of 100°C or lower, the produced stannous oxide Tin has a high bulk density and a small angle of repose, making it easy to handle.It also has a high bulk density and a small angle of repose, making it easy to handle. It has been found that it is possible to obtain stannous oxide that is easily soluble even in organic acids that are difficult to dissolve tin.

According to the present invention, in the method for producing stannous oxide by the reaction of an acidic aqueous solution of a stannous salt and an aqueous sodium carbonate solution, the rainwater solution is adjusted to have a pH of 6.5 to 8.4. temperature 7
After mixing and reacting while maintaining the temperature in the range of 0°C to 85°C, the mixture was further mixed as described above.

An improved method for producing stannous oxide is provided, which comprises stirring for a sufficient period of time such that the stannous oxide particles produced at a temperature exhibit a bulk density of 2 or more and an angle of repose of 40° or less. Ru.

The basic points elucidated by the present inventors regarding the conversion mechanism from stannous hydroxide to stannous oxide are as follows. The stability region of tin and stannous oxide was confirmed. FIG. 1 is a graph showing how the stability regions of 5sno, 2birds, and SnO change based on changes in temperature. The results shown in Figure 1 were obtained using sodium carbonate in the alkaline aqueous solution, and 5SnO.2H,
It can be seen that even when the heating conditions for the O slurry are limited to 100° C. or lower, there is a stable region of SnO over a fairly wide range of single values. Such a phase diagram shows chloride as a stannous salt,
No change occurs even when sulfates and other salts are used.

However, when sodium hydroxide is used as the alkaline aqueous solution, the stability region of SnO is reduced in the right and lower parts of the region shown in Figure 1, making it less stable than when sodium carbonate is used. It was found that the area became narrower.

Furthermore, the present inventors have discovered that very specific SnO particles can be obtained only when sodium carbonate is used as the alkali source. According to this discovery, in the extremely narrow region shown as an ellipse in the upper right corner of the SnO stability region in Figure 1, that is, in the temperature range of pH 6.5 to 8.4° and 70 to 85°C. It has been found that the Sn0 particles produced have a bulk density of 2 or more and an angle of repose of 40' or less, providing an extremely excellent product for preparing a tin plating bath or as a tin ion additive. Although the details of this phenomenon are unknown, it is clear that the degree of crystal growth of stannous oxide during the conversion process from stannous hydroxide to stannous oxide is controlled by the temperature conditions mentioned above. This effect is first confirmed in the filtration step of the SnO powder produced.For example, in the SnO stable region of Fig. 1 other than the conditions of the present invention, the crystal growth of stannous oxide does not occur satisfactorily. The produced crystals are fine, have poor p-permeability, have a low bulk density, and have a large angle of repose, making it impossible to obtain the stannous oxide aimed at in the present invention.

In carrying out the present invention, an acidic aqueous solution of a stannous salt and an aqueous sodium carbonate solution are poured into a reaction vessel and the mixture has a pH of 6.5.
-8.4 Add little by little and stir and mix while keeping the temperature in the range of 70-85°C. This produces a white precipitate of stannous hydroxide, but when the resulting slurry is further stirred under the same conditions, the white stannous hydroxide is converted to black stannous oxide. Under these conditions, the production of stannous oxide having the appropriate bulk density and angle of repose, which is the objective of the present invention, is completed in about 30 minutes.

Figure 2 shows that an acidic aqueous solution of stannous chloride in hydrochloric acid and an aqueous sodium carbonate solution are stirred and mixed at 80°C with varying values.
It is a graph showing the change in the bulk density of the obtained precipitated product when this stirring was continued for 30 minutes. Also, the third
The figure is also a graph showing changes in the angle of repose of the precipitation product. From these graphs, it is clear that in order to simultaneously satisfy the desired bulk density of 2 or more and angle of repose of 400 or less in the production of the stannous oxide of the present invention, temperature conditions as well as...
It can be seen that value control is an important point.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A hydrochloric acid acidic aqueous solution of stannous chloride containing stannous at a concentration of 200 W/l and an aqueous solution containing 200 f/l Na2CO1 were heated at 80°C using a 2-ton glass reaction vessel.
pH8,50,8,30,6,60,3,50,2,
50 and 8.00, and temperatures of 90°C, 83°C, and 72°C
, 25°C.

The reaction was carried out by stirring and mixing under various conditions at 15°C, and the stirring was continued for 30 minutes while maintaining the same conditions. The black precipitate produced was washed door to door with water, vacuum dried, and the composition, bulk density, The angle of repose was measured. The results are shown in Table 1 in comparison with the measured values of other companies' products.

Table 1 As shown in Table 1 above, in order to simultaneously satisfy the bulk density and angle of repose of the stannous oxide product in a low-temperature reaction below 100'C, the value of the liquid as well as the temperature conditions must be extremely high. Should be limited to a narrow range.

Furthermore, the stannous oxide obtained by the method of the present invention has a higher bulk density and a smaller angle of repose than commercially available products, so it is easier to handle.

Example 2 Each side of Example 1 (Volumes 1 to 10) and other companies' classic products (Volume 11)
-12) were compared for their solubility in an aqueous phenolsulfonic acid solution at 40°C. The dissolution work was performed so that the liquid composition after dissolution was 71 f/l of free phenolsulfonic acid, Sn
The concentration was 20 f/l. The results are shown in Table 2.

Table 2 As shown in Table 2, stannous oxide obtained by the method of the present invention has extremely good solubility even in aqueous solutions of acids, such as phenolsulfonic acid, in which stannous oxide is difficult to dissolve. As shown, commercially available stannous oxide has extremely poor solubility in an aqueous solution of phenolsulfonic acid.

The effects of the present invention can be summarized as follows.

(a) Since the stannous oxide obtained by the present invention has a high bulk density and a small angle of repose, it is easy to handle.

(Note) Since the stannous oxide of the present invention has large crystal particles and a small specific surface area, it is less susceptible to oxidation in the air and has high stability.

(c) Since the stannous oxide of the present invention has high solubility in inorganic and organic acids, it is suitable as a material for preparing a tin plating bath and for adding tin ions.

[Brief explanation of the drawing]

FIG. 1Ii: 5 is a graph showing the stability region of Sn0.2H40 and SnO. Figure 2 shows the relationship between the bulk density of the particles in the SnO stable region when the reaction was carried out at 80°C and stirring was continued for 30 minutes, and Figure 3 is a graph showing the relationship between the angle of repose of the particles and the O Patent applicant: Sumitomo Metal Mining Co., Ltd. Agent: Patent attorney Yasu Kaizu Sando: Patent attorney Hirayama - Sachi Figure 1

Claims (1)

[Claims] In a method for producing stannous oxide by reaction between an acidic aqueous solution of a stannous salt and an aqueous solution of IJ carbonate, the rainwater solution is adjusted to have a pH of 6.5 to 8.4. Temperature 70℃~85℃
After mixing and reacting while maintaining the above range, the mixture is further heated at the above-mentioned -0 temperature for a sufficient time so that the produced stannous oxide particles exhibit a bulk density of 2 or more and an angle of repose of 40° or less. A method for producing stannous oxide, which comprises stirring.