JP2000226214A - Production of high-purity alkali stannate compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an alkali stannate compound, containing neither anions such as chloride ion, sulfate ion, nitrate ion, and the like except stannate ion nor metal tin component, and not requiring great energy. SOLUTION: A raw material tin such as metal tin, as alloy or another material containing tin is thrown into an aqueous solution of an alkali hydroxide such as potassium hydroxide, sodium hydroxide or lithium hydroxide. A fixed reaction temperature is maintained while constantly making the aqueous solution of alkali hydroxide flow on the surface of the raw material tin by stirring or circulating the aqueous solution of the alkali hydroxide and a reaction is carried out by dripping a hydrogen peroxide solution as a reaction promoter to a reaction solution to give an aqueous solution of stannate containing an insoluble component. The insoluble component is filtered off from the aqueous solution of stannate. Crystal of potassium stannate, sodium stannate or lithium stannate is obtained by a method for concentration under reduced pressure, evaporation, crystallization or centrifugation from the aqueous solution of stannate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-purity alkali stannate compound, and more particularly, to a method for improving the adhesiveness in soldering of electric parts and the like in recent years, which is widely used in the electronic industry. Alkali stannate compounds such as potassium stannate, sodium stannate, etc. used for tin plating applied (compounds represented by the general formula M2SnO3.XH2O. In the above formula, M is lithium, sodium or potassium, and X is (The number of moles of crystallization water is shown.)

[0002]

2. Description of the Related Art Known methods for obtaining potassium stannate, sodium stannate or lithium stannate include tin hydroxide, carbonate or oxide and either potassium hydroxide, sodium hydroxide or lithium hydroxide. And eutectic or melting using a small excess of alkali hydroxide with respect to the molar ratio in the composition formula.

[0003]

According to this method, a baking furnace is required, and a large amount of energy is required for performing a solid-phase reaction at a high temperature of 500 ° C. or more. Furthermore, depending on the state of the tin compound used, the reactivity of the alkali stannate compound may be affected and the yield may decrease, so it is necessary to strictly control the reaction, which increases the production cost. It is not a good idea from the viewpoint of energy saving, because it causes a lot of energy.

In addition, since it is produced via another tin compound, it is inevitable that impurities from the tin raw material and salts produced as a by-product during the formation of the tin compound are mixed, and it is difficult to obtain a high-purity alkali stannate compound. Met.

As another method, there is a method of producing a predetermined alkali stannate compound by electrolyzing a metal salt. As a modification of the electrolysis method, Japanese Patent Application Laid-Open No. 60-21814 discloses a production method of performing electrolysis while blowing air (a production method of alkali stannate).

Further, it has been proposed to mix metal tin and alkali hydroxide and directly introduce the mixture into a firing furnace such as an electric furnace or a gas furnace to produce an alkali stannate compound. It is hardly a good idea.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an anion other than stannate such as chloride ion, sulfate ion and nitrate ion, and metal tin. It is an object of the present invention to provide a method for producing an alkali stannate compound which does not contain a metal component of tin contained in the compound and does not require much energy.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a reaction accelerator is used when metal tin is introduced into an aqueous solution of alkali hydroxide to cause the reaction between alkali hydroxide and metal tin. It has been found that an aqueous solution containing a high-yield and high-purity alkali stannate compound can be produced by using a hydrogen peroxide solution as a solvent, and the present invention has been completed based on this finding. That is, the present invention is a method of introducing a raw material tin such as metal tin, or an alloy or other material containing tin into an aqueous alkali hydroxide solution of any of potassium hydroxide, sodium hydroxide, and lithium hydroxide. Is maintained at a predetermined reaction temperature while constantly flowing over the surface of the raw material tin by stirring or circulating, and the reaction is carried out while dropping hydrogen peroxide solution as a reaction accelerator into the reaction solution to contain insoluble components. After obtaining the aqueous stannate solution, the insoluble matter is filtered off, and then concentrated under reduced pressure from the aqueous stannate solution, evaporation, crystallization, or a method such as centrifugation, potassium stannate, sodium stannate,
Another object of the present invention is to provide a method for producing a high-purity alkali stannate compound, which comprises obtaining lithium stannate crystals.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION According to the method of the present invention, metallic tin or a raw material tin such as an alloy containing tin or other products is charged into an aqueous solution of potassium hydroxide, sodium hydroxide or lithium hydroxide in an alkali hydroxide, The reaction is maintained at a reaction temperature while constantly flowing the surface of the raw material tin by stirring or circulating an aqueous alkali hydroxide solution, and the reaction is carried out while dropping a hydrogen peroxide solution as a reaction accelerator into the reaction solution. After obtaining a stannate aqueous solution containing an insoluble matter, the insoluble matter is filtered off. Thereafter, potassium stannate, sodium stannate, or lithium stannate crystals are obtained from the aqueous stannate solution by a method such as concentration under reduced pressure, evaporation, crystallization, or centrifugation.

In the present invention, an industrially preferred concentration of the aqueous alkali hydroxide solution is 1% by weight or more and 50% by weight or less, preferably 5% by weight or more and 25% by weight or less, based on the weight of the alkali hydroxide. . When the concentration is less than 5% by weight, the concentration of the aqueous alkali stannate solution is low, which is not preferable because the productivity is lowered. Also 2
When the content exceeds 5% by weight, the amount of the liquid becomes insufficient, and it is difficult to bring the metallic tin having a flower shape or the like below the liquid level, and the stirring operation cannot be performed. When the aqueous caustic alkali solution is circulated, if the concentration of the caustic alkali exceeds 25% by weight, crystals of alkali stannate are precipitated in the reaction solution, which is likely to cause clogging of the circulation pump, which causes inconvenience during production. At the same time, the aqueous solution of hydrogen peroxide as a reaction accelerator is self-decomposed in a concentrated alkaline aqueous solution without participating in the reaction, and as a result, the effective utilization rate of the aqueous hydrogen peroxide is reduced.

The amount of the alkali hydroxide used must be at least 2 mol in order to obtain an aqueous solution containing 1 mol of stannate. At the same time, if there is no free alkali metal component, the stannate hydrolyzes. Therefore, it is preferable to add the stannate in excess of 0.1% by weight or more as the free alkali metal concentration in the aqueous solution.

The concentration of hydrogen peroxide solution as a reaction accelerator is 1% by weight or more and 99% by weight or less, preferably 10% by weight or less.
% By weight or more and 60% by weight or less. When the content is 10% by weight or less, the concentration of the low-concentration aqueous alkali stannate solution decreases,
Productivity decreases. When the content is 60% by weight or more, the hydrogen peroxide solution does not participate in the reaction and catalytically decomposes with the metal tin and the alkali aqueous solution, resulting in a lower effective utilization rate of the hydrogen peroxide solution. As a result, the raw material cost increases. Not a good idea.

The tin used as a raw material to be introduced into the aqueous alkali hydroxide solution may be tin, pellets, flakes, or other highly reactive metal tin, as well as tin pieces, tin-plated products, and tin alloys.

In the reaction vessel, when reacting the raw material tin with the alkali hydroxide, crystals of the stannate as a product are deposited and cover the tin surface, thereby preventing the reaction from proceeding smoothly. For this purpose, the reaction solution containing a reaction accelerator containing tin in an alkali hydroxide solution is stirred or a counter solution is circulated by a pump so that the reaction solution constantly flows on the tin surface. .

The reaction temperature between tin and alkali hydroxide is 10
The reaction temperature is at least 20 ° C and at most 90 ° C. In order to keep this reaction, which is an exothermic reaction, at 20 ° C. or lower, not only a large amount of cooling water is required, but introduction of expensive equipment such as chiller equipment is inevitable in summertime production. In order to obtain the crystals of alkali stannate, an operation of concentrating the aqueous solution is required. At this time, a part of the remaining hydrogen peroxide solution is decomposed and foamed at a stretch, resulting in a very dangerous state. This is not a good idea from the viewpoint of ensuring worker safety. When the reaction is performed at 90 ° C. or higher, the hydrogen peroxide solution as a reaction accelerator is decomposed without participating in the reaction, and the effective utilization rate of the hydrogen peroxide solution is reduced.
As a result, the cost of raw materials rises, which is not advisable.

The reaction time is 30 minutes or more and 24 hours or less, preferably 1 hour or more and 24 hours or less. When the reaction is completed within one hour, the reaction temperature rises at once, and the worker is exposed to a dangerous condition. Effective utilization rate of water decreases. As a result, the cost of raw materials rises, which is not an advantage. In the case of the reaction for 24 hours or more, it is preferable from the viewpoint of improving the effective utilization rate of the hydrogen peroxide solution, but it is not advisable because productivity is poor.

Although black impurities remain in the obtained aqueous stannate solution, these impurities can be easily separated by an operation such as filtration, and the obtained aqueous stannate solution is concentrated under reduced pressure, evaporated and evaporated.
High purity stannate crystals can be obtained by a method such as crystallization or centrifugation. Since the free alkali metal and the stannate are dissolved in the separated mother liquor after filtering the stannate crystals, the separated mother liquor can be used as an alkali hydroxide source in the next reaction, Waste from manufacturing can be reduced.

The black insoluble material remaining as an unreacted substance in the aqueous stannate solution after the reaction was completed was confirmed by X-ray fluorescence analysis to be a trace impurity contained in the metallic tin. The amount of substances other than tin in the residue almost coincides with the amount of impurities in the metal tin charged, and the product stannate contains very little.

After the unreacted or insoluble matter is filtered off from the aqueous solution containing stannate after the reaction, potassium stannate is removed from the aqueous stannate solution by a method such as concentration under reduced pressure, evaporation, crystallization, or centrifugation. Obtaining sodium stannate or lithium stannate crystals;
It has been elucidated that high purity alkali stannate compounds can be obtained.

As described above, according to the production method of the present invention, even if the purity of tin metal is low, it is possible to produce an alkali stannate compound containing no metal component other than tin. In addition, since a simple apparatus is used and no multi-step process is used, a high-purity product of a high-purity alkali stannate compound can be obtained efficiently in a short time, in large quantities, and at low cost.

[0021]

Next, the present invention will be described in more detail by way of examples.

Example 1 In a 1 liter reaction vessel, water was added to 0.048 kg of flaky caustic soda to prepare a 10% by weight solution, and 0.05935 kg of flaky metal tin was added thereto.
And the temperature of the solution was kept at 90 ° C. while stirring. 0.1476K 35% by weight hydrogen peroxide in a separate container
g was weighed and diluted to 10% by weight. This hydrogen peroxide solution was dropped into a mixed solution of metal tin and sodium hydroxide over 17 hours. After completion of the reaction, the insoluble matter was filtered off from the reaction solution, and the aqueous solution was transferred to a 1-liter eggplant-shaped flask and concentrated under reduced pressure by an evaporator to obtain a crystalline compound. Sodium acid was identified. The obtained sodium stannate crystal had a tin metal equivalent of 0.0572 Kg and a tin dissolution amount of 96.3.
%Met.

Example 2 Water was added to 2.01 kg of flaky caustic soda in a 20 liter reaction vessel to prepare a 12.5% by weight sodium hydroxide solution, and 2.98 kg of flaky metal tin was charged therein. The temperature of the solution was kept at 70 ° C. while stirring. In a separate container, 4.88 kg of 35% by weight of hydrogen peroxide was weighed and dropped into a mixed solution of metal tin and sodium hydroxide over 5 hours. After filtering the insoluble matter from the reaction solution, a part of the aqueous solution was transferred to an eggplant-shaped flask, and concentrated under reduced pressure by an evaporator to obtain a crystalline compound. The powder was identified as sodium stannate by X-ray diffraction.
23.56 kg of a sodium stannate solution having a stannic content of 12.3% by weight was obtained, which means that 96.9% of tin was dissolved.

Example 3 Into a 5 liter reaction vessel, water was added to 0.8625 kg of flaky caustic potassium (96% by weight), and a 19.8% by weight potassium hydroxide solution was prepared. 0.746 kg of metal tin was charged, and the temperature of the solution was kept at 70 ° C. while stirring. In a separate container, 1.22 kg of a 35% by weight aqueous hydrogen peroxide solution was weighed, and the aqueous hydrogen peroxide solution was dropped into a mixed solution of metal tin and potassium hydroxide over 6 hours. After filtering the reaction solution, a part of the aqueous solution was transferred to a 1-liter eggplant-shaped flask, and concentrated under reduced pressure using an evaporator to obtain a crystalline compound. The obtained crystals were identified as potassium stannate by X-ray diffraction. 6.03 kg of a potassium stannate solution having a stannic content of 11.59% by weight was obtained, which means that 93.7% of tin was dissolved.

Example 4 Water was added to 0.0117 kg of lithium hydroxide to prepare a 1.2% by weight solution in a 1 liter reaction vessel, and 0.006 kg of flaky metal tin was put into the solution and stirred. While performing, the temperature of the solution was kept at 90 ° C. In a separate container, weigh 0.0098 kg of hydrogen peroxide and place 1
Diluted to 0% by weight. This hydrogen peroxide solution was dropped into a mixed solution of metal tin and lithium hydroxide over 8 hours. After completion of the reaction, insoluble components were separated from the reaction solution by filtration. The aqueous solution was transferred to a 1-liter eggplant-shaped flask, and concentrated under reduced pressure by an evaporator. As a result, a crystalline compound was obtained. It was identified as lithium oxide. The obtained tin stannate crystal had a tin metal equivalent of 0.0051 kg.
And the amount of tin dissolved was 85.0%.

Example 5 Raw materials used in Example 2
Table 1 shows the results of analyzing the filtration residue and the product (sodium stannate) obtained by filtering the reaction solution with a fluorescent X-ray analyzer. It was confirmed that the impurity component in the metal was concentrated at a high concentration in the filtration residue, which was an insoluble component, and was hardly contained in the product.

[0027]

[Table 1]

Example 6 A reaction was carried out in the same manner as in Example 2 using a raw material containing a large amount of impurities. Table 2 shows the results of analyzing the raw materials to be used, the filtration residue obtained by filtering the reaction solution, and sodium stannate with a fluorescent X-ray analyzer. Impurity components in the metallic tin were found in high concentration in the filtration residue, which is an insoluble matter, and was hardly contained in the product.

[0029]

[Table 2]

(Comparative Example) 0.220 kg of α-stannic acid obtained by reacting metallic tin with nitric acid and 0.020% of sodium hydroxide
After sufficiently kneading 777 kg, 700 ° C. in an electric furnace,
It was baked for 8 hours. After cooling, the fired product was put into water, stirred sufficiently, filtered to remove insoluble components, and the aqueous solution was concentrated to obtain sodium stannate crystals. This crystal was analyzed for tin as a main component and trace components contained in the crystal. The results are as shown in Table 3. Compared with Example 5 and Example 6, it was confirmed that there were more impurity components.

[0031]

[Table 3]

[0032]

The method for producing a high-purity alkali stannate compound according to the present invention has the above-mentioned structure and action, so that metal tin is introduced into an aqueous alkali hydroxide solution to react the alkali hydroxide with metal tin. When the reaction is carried out, the use of aqueous hydrogen peroxide as a reaction accelerator makes it possible to mass-produce a high-yield and high-purity alkali stannate compound at low cost.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanori Yanagizuru 2-20-5 Shimotani, Taito-ku, Tokyo Inside Japan Chemical Industry Co., Ltd. (72) Inventor Tsuyoshi Sayaya 2-20-5 Shimotani, Taito-ku, Tokyo Japan Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. A raw material tin such as metallic tin or an alloy or other material containing tin is charged into an aqueous alkali hydroxide solution of any one of potassium hydroxide, sodium hydroxide and lithium hydroxide, and the aqueous alkali hydroxide solution is added. While maintaining the predetermined reaction temperature while constantly flowing on the surface of the raw material tin by stirring or circulating, and performing a reaction while dropping hydrogen peroxide water as a reaction accelerator into the reaction solution, tin containing insoluble components After obtaining an aqueous solution of a citrate, the insoluble matter is filtered off, and thereafter, potassium stannate, sodium stannate, or lithium stannate is concentrated from the stannate aqueous solution by a method such as concentration under reduced pressure, evaporation, crystallization, or centrifugation. A method for producing a high-purity alkali stannate compound, characterized by obtaining crystals of