JPS62207717A - Sol of crystalline tin oxide and its preparation - Google Patents

Abstract

PURPOSE:To obtain sol of crystalline tin oxide capable of providing superfine particles of tin oxide by only heating the sol by allowing a water-soluble tin compd. to react with a specified bicarbonate to form gel, and treating the sol hydrothermally after adding ammonia. CONSTITUTION:After forming gel by the reaction of a water-soluble compd. (e.g. SnCl4, etc.) with alkali metal bicarbonate or ammonium bicarbonate, ammonia is added to the sol, and the sol is treated hydrothermally to prepare sol of crystalline thin oxide. The sol has crystalline shape of thin oxide providing extremely fine <=300Angstrom particle size in aq. soln. state forming stable sol. It is possible to obtain superfine particles of tin oxide by only drying the sol. The sol is useful as transparent electrode for solar cell, liquid crystal element, transparent switch, etc., for promption of electric conduction of discharge tubes, prevention of clouding of windows of automobiles and aircrafts, etc., and antistatic treatment of glass fiber, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a crystalline tin oxide sol and a method for producing the same.

Tin oxide is used in transparent conductive membranes, gas sensors, ceramic pigments,
It is an industrial material used in many fields such as catalysts.

(Prior art) The tin oxide raw material powder used for these purposes is usually
It is produced by pyrothermally oxidizing metal tin, or by thermally decomposing metastannic acid obtained by acid treatment of tin scraps.

However, the tin oxide powder obtained by these methods generally has a coarse and irregular particle size, which poses a problem especially when applied to fields where uniform fineness is required.

On the other hand, the liquid phase method is known as a method for obtaining uniform fine powder without going through a solid phase, and this method has been widely studied for tin oxide as well. The thermal decomposition behavior of compound solutions has been investigated.

All of these solutions are treated according to their purpose,
For example, in the case of creating a transparent conductive film, it is coated on a substrate and then fired.

The desired points in this case are as follows, according to Ohji.

■The generated tin oxide particles must be uniform and fine;
゛■No by-products.

■The firing temperature must be low.

■Do not generate gases that require special treatment during firing.

Conventionally, water-soluble tin salt compounds such as stannic chloride have been considered as raw materials for tin oxide, but these do not meet the requirements (1), (2), and (3), especially (3), and are not suitable. In addition, organic tin compounds that are liquid at room temperature, such as stannous octoate, are being considered, but due to various problems such as wettability with substrates, there are few that satisfy (1), and they are generally expensive. At present, it cannot be said that it is necessarily beneficial.

(Problems to be Solved by the Invention) In view of these circumstances, the present inventors have conducted extensive research in order to obtain a crystalline tin oxide sol that is excellent in the various properties mentioned above that are desired when applied to ceramic materials, etc. As a result of these efforts, the present invention has been completed.

(Means for Solving the Problems) That is, the present invention relates to a crystalline tin oxide sol and a method for producing the same. , relates to a method for producing a crystalline tin oxide sol, which comprises reacting a water-soluble tin compound with an alkali metal monocarbonate or an ammonium bicarbonate to form a gel, then adding ammonia and hydrothermally treating the gel. Note that crystalline tin oxide has the chemical formula 5n0
2, and in X-ray diffraction, cassiterite (Cassiter
it@).

(Function) First, the crystalline tin oxide sol with a particle size of 300X or less, which is the invention of Mizui 1, will be explained in detail.

Conventionally, a method has been proposed for producing a colloidal solution of tin hydroxide by using an aqueous inorganic tin salt solution as a raw material and removing or neutralizing MMi contained therein by some method. A method of producing a sol by adding and mixing an amount of sodium hydroxide sufficient to make PM 0.9 to 1.4 to an acidic hydrochloric acid aqueous solution of stannic chloride (Japanese Patent Application Laid-Open No. 51-5103), stannic chloride A method of obtaining a sol by treating an aqueous tin solution with an anion exchange resin, etc.
Methods for obtaining a sol by hydrolyzing tin alkoxide by various means have also been proposed.

However, the sols obtained by these methods are either amorphous or some kind of hydroxide of tin, and are not crystalline sols of tin oxide.

On the other hand, the crystalline tin oxide sol of the present invention has a tin oxide crystal form and provides very fine colloidal particles of 3ooX or less in an aqueous solution state to form a stable sol solution.

Such a sol has been completely unknown in the past, and will create new uses in the field of application of tin oxide materials.

The characteristics of the crystalline tin oxide sol of the present invention are listed as follows.

First, as mentioned above, the colloidal particles have a uniform and fine crystalline structure of tin oxide.

Conventional sols made of amorphous or tin hydroxide crystals require firing at a temperature of at least 500°C or higher in order to use them as tin oxide materials, and at that time, colloidal particles are irreversibly destroyed. There is a problem that it is easy to aggregate and it is difficult to obtain fine tin oxide particles.

In contrast, the crystalline tin oxide sol of the present invention makes it possible to obtain ultrafine powder of tin oxide simply by drying it.

This is very useful in the production of tin oxide ceramics.

The colloidal particle size was measured by electron microscopic observation, and the colloidal particles of the sol of the present invention have a particle size of 300x or less.

Second, it does not generate corrosive gas during drying or firing.

The sol of the present invention contains only a small amount of ammonia as a stabilizer, and this ammonia easily evaporates during drying.

In comparison, conventional sols other than the alkoxide method contain a considerable amount of NZ roots and require considerable high temperature treatment to completely volatilize them.

For example, conventional sol containing chlorine generates harmful corrosive hydrogen chloride gas during firing, and is not suitable in terms of furnace selection and working environment.

For these reasons, the sol of the present invention is industrially useful.

Thirdly, the sol has excellent stability. Among the conventional products, the sols produced by the alkoxide method have particularly high purity, but on the other hand, they have a fatal defect of poor stability over time. The sol of the present invention has not only high purity but also good stability, and can be said to be of higher quality.

The crystalline IR tin oxide sol of the present invention, which has the above-mentioned excellent characteristics, is a novel substance that can be applied to the many uses mentioned above.

Next, a method for producing a crystalline tin oxide sol, which is the second invention, will be explained.

The second invention relates to the production of a crystalline tin oxide sol, which involves reacting a water-soluble tin compound with an alkali metal bicarbonate or an ammonium bicarbonate to form a gel, adding ammonia, and subjecting the gel to hydrothermal treatment. It's a method.

In the present invention, first of all, a water-soluble tin compound and an alkali metal bicarbonate or an ammonium bicarbonate are reacted to obtain a gel.

Examples of the water-soluble tin compound used in the present invention include stannic chloride and stannic sulfate, and examples of the alkali metal bicarbonate include sodium bicarbonate and potassium bicarbonate, but the invention is not limited to these. It's not a thing.

Further, if a gel manufactured using raw materials other than those mentioned above is used in the present invention, the object of the present invention cannot be achieved.

That is, gels produced using sodium carbonate, sodium hydroxide, ammonia, etc. in place of the bicarbonate have poor filterability and are easily aged. It is not possible to produce a crystalline tin oxide sol with excellent dispersibility.

Regarding the conditions for producing the gel, the temperature at which the water-soluble tin compound and the alkali metal bicarbonate or ammonium bicarbonate are reacted may be room temperature, and there is no need to particularly heat or cool the reaction.

The ratio of addition of both is not particularly limited, but for economic reasons, it is generally the equivalent of the alkali metal or ammonium (A) derived from the bicarbonate and the acid radical (B) derived from the water-soluble tin compound. The ratio A/B is carried out in the range of 0.9 to 2.0.

Regarding the order of addition, in particular @Unspecified School 1, the method of adding an aqueous solution of a water-soluble tin compound to an aqueous solution of an alkali metal bicarbonate or an ammonium bicarbonate is effective in cleaning the gel in the next step. This is desirable because it can be done efficiently.

The gel thus produced is then washed to remove impurities. Regarding the amount of residual impurities, it is preferable to have a small amount from the viewpoint of manufacturing and usage of crystalline tin oxide sol. However, only when the gel is manufactured using ammonium bicarbonate, even if only ammonia remains in the gel. No problem.

The cleaning means is not particularly limited, and any commonly used methods such as water filtration and repulp centrifugation can be used.

Further, a method of removing impurities by contacting with a suitable ion exchange tree 11 or the like may also be adopted.

After washing, ammonia is then added to the gel to adjust the pH.

Therefore, the amount of ammonia added increases the PR of the gel by 8 to 12,
Desirably, the amount is sufficient to make the range 9 to 11.

In other words, if the pH deviates from the above range, a sol with excellent dispersibility cannot be obtained. In this case, the necessary amount of ammonia added will vary depending on the amount and type of trace impurities remaining in the gel, or the 5n02 concentration of the gel. However, approximately 5nOt 1
It ranges from 0.05 to 1600 moles.

Next, water is added to this PR-prepared gel as necessary to adjust the concentration.

In this case, it is desirable that the Snow concentration be 15% or less. If the concentration exceeds this, the generated sol will not only be extremely viscous and difficult to handle, but also become non-uniform. .

The gel, which has a pH and concentration of vI4gl, is then hydrothermally treated. Through this treatment, crystals 5 with a particle size of 300^ or less
A tin oxide sol is produced.

Regarding the conditions of the hydrothermal treatment, generally speaking, the higher the treatment temperature and the longer the treatment time, the better the development of the crystal form and the production of colloid particles with a larger particle size.

For example, in order to produce a sol consisting of colloidal particles with a particle diameter of 80^, hydrothermal treatment at 200°C for 6 hours is required. A major feature of the present invention is that it is only necessary to manufacture lIL and crystalline tin oxide sol with an optimal particle size depending on each use, and that this can be controlled by selecting hydrothermal treatment conditions.

(Example) The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. Unless otherwise specified, all percentages indicate weight percent.

Example 1 Ammonium bicarbonate aqueous solution (NH, 2.9%) 1000
An aqueous solution of stannic chloride (SnO2) was added to the solution while stirring.
16.5%) were gradually added.

After filtering the generated gel, water injection filtration and cleaning were performed until no chloride ions were observed in the gel. As a result, 5
A gel containing nOt 36.5% and MHzo 60% was obtained.

Next, 112 parts of 1.0% ammonia water was added to 100 parts of the gel.
and 153 parts of water were added and mixed, pH 10.5, SnO
After preparing a 216° 0% gel slurry, it was transferred to an autoclave and subjected to hydrothermal treatment at 200° C. for 6 hours. As a result, a sol of the present invention containing 5 nOzlO, 0% was obtained.

This sol was dried at 110°C and subjected to powder X-ray diffraction using a conventional method. As a result, the d values of the main peaks were 3.35λ, 2.6
4λ, 1.77λ, 2.37λ, and 1.68λ, the crystal form was identified as cassiterite.

Further, this sol was observed under magnification using a transmission electron microscope, and the particle diameter was measured, and it was found to be about 8 OA. Furthermore, when this sol was allowed to stand at room temperature for one month, no sediment was observed and the sol properties remained intact.

Comparative Example PH10.5, SnO obtained by the same method as Example 1
, 10.0% gel slurry was heated at 95° C. for 6 hours in a reactor equipped with a reflux device.

The resulting product was a liquid containing a white precipitate, and the dry powder was found to be amorphous by X-ray diffraction.

' Example 2 Aqueous solution of stannic sulfate (S n O2
, 10.5%) was gradually added, and the gel formed was filtered off. Approximately 200 parts of water was added to this and repulped and mixed, followed by solid-liquid separation using a centrifuge to obtain a gel.

After repeating the repulping and centrifugation operations until sodium ions and sulfate groups in the gel are no longer observed, SnO*
38. A gel containing O% was obtained.

Next, 43 parts of 2.0% ammonia water and 617 parts of water were added and mixed to 100 parts of the gel, and the pH was adjusted to 9,7,5nO2.
After making a 5.0% gel slurry, this was transferred to an autoclave and subjected to hydrothermal treatment at 150° C. for 10 hours.

As a result, a solution containing 25.0% of 5n0 was obtained. Using this sol in the same manner as in Example 1,
As a result of X-ray diffraction and electron Wl@mirror observation, it was found that the sol was composed of colloidal particles of cassiterite crystalline particles with a particle size of about 6OA.

Further, when this sol was allowed to stand at room temperature for one month, no sediment was observed and the sol properties were maintained.

Claims (2)

[Claims] (1) Crystalline tin oxide sol with a particle size of 300 Å or less. (2) After producing a gel by reacting a water-soluble tin compound with an alkali metal bicarbonate or an ammonium bicarbonate,
A method for producing a crystalline tin oxide sol comprising adding ammonia and hydrothermal treatment.