JPH0959020A - Zinc stannate hydrate sol and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject sol useful as a microfiller to be used as a high- refractive index hard-coating agent to be provided on the surface of e.g. plastic lens, films or plastic molded products, and for flame-retarding treatment of various resins or fibers. SOLUTION: This sol is obtained by dispersing, in a liquid medium, particles of a zinc stannate hydrate having a primary particle diameter of 2-200nm and expressed by the formula xZnO.ySnO2 .zH2 O [where, the molar ratio: x/y/z is 1:(0.83-1.43):(1.00-5.00)]. Specifically, this sol is obtained by reaction between a zinc salt and a stannate in the presence of hydrogen peroxide, or by neutralizing a zinc salt and a stannate with an acid in the presence of hydrogen peroxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a zinc stannate hydrate sol and a method for producing the same. The zinc stannate hydrate sol obtained in the present invention is a fiber mixed with a microfiller used for a plastic lens, a film, a hard coating agent having a high refractive index applied to the surface of a plastic molded product, or various resin emulsions. It can be used as a flame-retardant fiber by dispersing it in a flame-retardant treatment agent or a polymer such as modacrylic resin.

[0002]

2. Description of the Prior Art Zinc stannate hydrate is a product of the Journal of the American Ceramic Society (Jour.
nal of the American Ceram
icSociety) 1953, Volume 36, 20
It is disclosed as ZnSnO ₃ .4H ₂ O on page 7 and as ZnSnO ₃ .3H ₂ O on Acta Cryst, 1960, Volume 13, page 601.

In recent years, some manufacturing methods by the wet method have been reported. For example, in British Patent No. 2230255, sodium stannate (Na ₂ SnO ₃ .3H ₂ O) is used.
It discloses a method for producing a zinc stannate hydrate powder by mixing an aqueous solution and an aqueous zinc salt solution to form a zinc stannate hydrate precipitate, and filtering and drying the precipitate.
JP-A-5-24831, JP-A-5-24832, JP-A-5-24833, and JP-A-5-248.
No. 34 and JP-A-5-24835, an acidic aqueous solution containing stannic and zinc ions is mixed with an aqueous alkali metal hydroxide solution, ammonium carbonate, ammonium hydrogen carbonate, or an aqueous ammonia solution to form crystals. Powder is produced by precipitating a soluble zinc stannate hydrate or an amorphous zinc stannate hydrate as particles having a particle diameter of 0.2 to 1.0 μm, filtering and drying. These crystalline zinc stannate hydrate and amorphous zinc stannate hydrate powders are
It is used by being dispersed in a polymer as an addition type flame retardant.

[0004]

In the conventional method for producing zinc stannate hydrate, zinc stannate hydrate is added to the polymer in order to impart flame retardancy and smoke emission suppression of toxic gases to the polymer. It does not relate to a method for producing a sol containing fine colloidal particles, but to obtain a powder of the product.

The present invention can be used as a transparent flame retardant aid such as a halogen-containing resin or modacrylic resin, or as a microfiller (colloid particles contained in a hard coating agent) for a hard coating agent of a plastic lens. To provide a stable zinc stannate hydrate sol,
The resin using this zinc stannate hydrate sol has high flame retardancy, and the hard coat agent using this zinc stannate hydrate sol has a high refractive index.

[0006]

The invention of the present application is 2 to 200
have a primary particle size of nm and have the general formula xZnO.ySn
In O ₂ · zH ₂ O, x: y: z is 1: 0.83 to
This is a sol in which particles of zinc stannate hydrate represented by a molar ratio of 1.43: 1.00 to 5.00 are dispersed in a liquid medium.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The particles of zinc stannate hydrate dispersed in the sol of the present invention have a primary particle diameter of 2 to 200 nm.
(Nanometer), preferably 5-100 nm.
Here, the primary particle diameter is not the diameter of particles in an aggregated form, but the diameter of one particle when individually separated, and can be measured by an electron microscope.

The zinc stannate hydrate in the above particles has the general formula xZnO.ySnO ₂ .zH ₂ O [x: y: z is 1:
0.83 to 1.43: 1.00 to 5.00],
ZnSnO having a stoichiometric composition in which ZnO: SnO ₂ = 1: 1
_It can also be expressed as ₃ · zH ₂ O [ZnO · SnO ₂ · zH ₂ O]. z is 3.00 to 5.00], or ZnO:
SnO ₂ = 1: Zn having a nonstoichiometric composition of 0.83 to 1.43
O · (SnO ₂ ) _a · zH ₂ O [where a is 0.83 to
1.43 and z are 1.00 to 5.00].

Examples of the liquid medium in which the particles of the zinc stannate hydrate are dispersed include an aqueous medium and a hydrophilic organic solvent such as methanol, ethanol and isopropanol. As a first method, the method for producing a sol of the present invention comprises the following steps (a), (b) and (c); (a): zinc salt and stannate in an aqueous medium in the presence of hydrogen peroxide. To obtain an aqueous medium in which colloidal particles of zinc stannate hydrate having a Zn / Sn molar ratio of 0.7 to 1.2 are dispersed, (b): obtained in step (a) A step of heating an aqueous medium in which colloidal particles of zinc stannate hydrate are dispersed at a temperature of 30 to 200 ° C .; and (c): colloidal particles of zinc stannate hydrate obtained in the step (b), And a step of removing the electrolyte from the dispersed aqueous medium.

As the zinc salt used in the step (a), any zinc salt of an inorganic acid or an organic acid can be used as long as it is water-soluble. Examples thereof include zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, zinc gluconate, and the like, and these can be used alone or as a mixture of two or more kinds. However, zinc salts of inorganic acids such as zinc chloride and zinc sulfate are preferable from the viewpoint of production cost of the sol and wastewater treatment, and these can be used alone or as a mixture of two or more kinds. These zinc salts are 0.1 to 0.1 in terms of ZnO.
It can be used as an aqueous solution having a concentration of 20% by weight.

The stannate used in the step (a) is preferably a water-soluble alkali metal stannate, such as sodium stannate (Na ₂ SnO ₃ .3H ₂ O) and potassium stannate (K ₂ SnO _3). 3H ₂ O), which can be used alone or as a mixture. These stannates can be used as an aqueous solution having a concentration of 0.1 to 20% by weight in terms of SnO ₂ .

Hydrogen peroxide used in step (a) is H
₂ O ₂ can be used as an aqueous solution of 5 to 60% by weight. In the step (a), a zinc salt and a stannate are reacted in an aqueous medium at a Zn / Sn molar ratio of 0.7 to 1.2 in the presence of hydrogen peroxide to obtain a ratio of 0.7 to 1.2. Zn / S
It is possible to obtain colloidal particles of zinc stannate hydrate having an n molar ratio. The Zn / Sn molar ratio during the above reaction is 0.7.
When it is less than 1.2, tin oxide (SnO ₂ ) colloidal particles are generated, which is not preferable.
H) ₂ Colloidal particles are generated, which is not preferable.

In the step (a), the reaction between the zinc salt and stannate in the presence of hydrogen peroxide is carried out in an aqueous medium in which an aqueous solution of zinc salt to which hydrogen peroxide solution is added and an aqueous solution of stannate are mixed. Is preferred. The hydrogen peroxide solution can be added to either or both of the zinc salt aqueous solution and the stannate aqueous solution, but since the stannate aqueous solution is alkaline, it is added to the zinc salt aqueous solution. Things are more preferable. In the step (a), the amount of hydrogen peroxide present in the aqueous medium is 0.5 to ₂ in terms of H ₂ O ₂ / Zn molar ratio.
It can be set to 0.0, preferably 1.0 to 18.0. Hydrogen peroxide has a function of controlling the particle size of colloidal particles when zinc salt and stannate react with each other to produce colloidal particles of zinc stannate hydrate, and the above H ₂ O ₂ / Zn
When the molar ratio is less than 0.5, some colloidal particles of zinc stannate hydrate have a primary particle diameter of more than 200 nm, and when added in excess of 20.0, hydrogen peroxide is added. Is excessive and not economical.

In the step (a), the aqueous stannate solution and the aqueous zinc salt solution to which hydrogen peroxide solution is added are mixed together by a method in which both solutions are simultaneously mixed, or one of the solutions is dropped into the other solution. Both methods yield colloidal particles of zinc stannate hydrate with a Zn / Sn molar ratio of 0.7-1.2. However, in order to avoid agglomeration, the zinc salt aqueous solution added with hydrogen peroxide solution,
The method of dropping in an aqueous stannate solution is more preferable. This dropping is performed at a temperature of 20 to 80 ° C. for 0.5 to 5 hours. It is preferable to drop the aqueous solution of zinc salt to which the hydrogen peroxide solution has been added with a metering pump into the aqueous solution of stannate while stirring using a stirring machine such as Disper. The zinc stannate hydrate produced in the aqueous medium by this mixing is 0.1
It is preferable to mix both solutions so that the concentration becomes ˜20% by weight, preferably 1.0 to 10% by weight. The pH of this mixed solution is 3 to 12, preferably 5 to 9. If necessary, add an aqueous acid solution or alkaline solution to adjust the pH.
Can be adjusted. If the pH is less than 3, the unreacted zinc salt remains and the yield decreases, and if the pH exceeds 12, the unreacted stannate remains and the yield decreases, which is not preferable.

In step (a), the aqueous medium contains oxycarboxylic acid, a salt thereof, or a mixture thereof in a molar ratio within 1.5 times, preferably 0.0
It can be contained 5 to 1.5 times. By adding this oxycarboxylic acid or its salt, a zinc stannate hydrate sol having high dispersibility and transparency can be obtained. The above-mentioned oxycarboxylic acid or a salt thereof is water-soluble, and examples of the oxycarboxylic acid include gluconic acid, tartaric acid, and citric acid, and the oxycarboxylic acid salt is gluconic acid.
Examples thereof include an alkali metal salt of tartaric acid or citric acid, an ammonium salt, or an organic base salt. As the alkali metal salt, sodium gluconate, potassium citrate, or the like, and as the organic base salt, propylamine gluconate, monoethanol tartrate. Examples include amines. The oxycarboxylic acid or a salt thereof can be added after the colloidal particles of zinc stannate hydrate are formed, but it is preferably added before or during the formation of the colloidal particles. The above-mentioned oxycarboxylic acid or a salt thereof can be contained in an aqueous medium by adding it to either an aqueous solution of stannate or an aqueous solution of zinc salt, but an aqueous solution of zinc salt to which hydrogen peroxide solution is added. Among the methods of adding the above to the stirred stannate aqueous solution, the above-mentioned oxycarboxylic acid or its salt is preferably added to the stannate aqueous solution. These oxycarboxylic acids and their salts are directly or
It can be added to the aqueous stannate solution as an aqueous solution having a concentration of ˜50% by weight.

In step (b), the aqueous medium in which the colloidal particles of zinc stannate hydrate obtained in step (a) are dispersed is maintained at a temperature of 30 to 200 ° C., preferably 60 to 100 ° C. The heat aging is carried out for 1 to 50 hours, preferably 1 to 10 hours. When the heating temperature exceeds 100 ° C, an autoclave or the like is required. Heat aging time 0.1
If the time is less than the time, the effect is small and it may be more than 50 hours, but it is not economical. The aqueous medium in which the colloidal particles of zinc stannate hydrate obtained in the step (b) are dispersed has an improved sol dispersibility and transparency of the sol obtained by adding an alkaline substance to make it alkaline at pH 9-12. You can As the alkaline substance, amine, hydroxylated fourth
Examples thereof include primary ammonium and alkali metal hydroxides, and amines are particularly preferable. Examples of this amine include monoethanolamine and isopropylamine.

In the step (c), cations (alkali metal) excessively contained in the aqueous medium (zinc stannate hydrate aqueous sol) in which the colloidal particles of the zinc stannate hydrate obtained in the step (b) are dispersed. Electrolytes such as ions) and anions (acid radicals) can be removed by a combination of ultrafiltration and water washing. When the electrolyte is removed by the ultrafiltration method, it can be performed at 100 ° C. or lower, preferably room temperature to 60 ° C., depending on the material of the ultrafiltration membrane to be used. If necessary, the electrolyte may be reduced by further treating with a cation exchange resin or an anion exchange resin. The anion exchange resin is used in a hydroxyl group type, a commercially available anion exchange resin can be used, and the anion can be easily reduced by a method of passing the sol through a column packed with the anion exchange resin. Passing temperature is 0
It is preferable that the temperature is -60 ° C, and the liquid is passed through the space velocity (SV) at 1-10 h ^-1 . The cation exchange resin is used in a hydrogen form, and a commercially available cation exchange resin can be used. It is carried out by directly adding a necessary amount of the cation exchange resin and stirring.
By removing the excessive electrolyte in the step (c), the zinc stannate hydrate sol of the present invention having good transparency and sufficient stability can be obtained. The sol obtained in the step (c) is
It has a pH of 3 to 12, preferably 5 to 11, and contains zinc stannate hydrate in a concentration of 5 to 20% by weight. And
The zinc stannate hydrate particles in the obtained sol are 2 to 200.
have a primary particle size of nm and have the general formula xZnO.ySn
In O ₂ · zH ₂ O, x: y: z is 1: 0.83 to
It was represented by a molar ratio of 1.43: 1.00 to 5.00. Zinc stannate hydrate particles in the obtained sol,
The ratio of zinc, tin and water of crystallization can be confirmed by methods such as fluorescent X-ray analysis and differential thermal analysis.

When it is desired to further increase the concentration of the sol obtained in the step (c), in the step (d), a small amount of an organic base, an organic acid or the like is added as a stabilizer, and the mixture is subjected to rotary evaporation or ultrafiltration. It is possible to concentrate up to 40% by weight with a device such as a device. Examples of the organic base used include alkylamine, alkanolamine or quaternary ammonium hydroxide, such as n-propylamine,
Examples include isopropylamine, diisobutylamine, ethylenediamine, monoethanolamine, triethanolamine and the like. An oxycarboxylic acid such as glycolic acid, tartaric acid or citric acid can be used as the organic acid. The aqueous medium of the aqueous sol obtained in the step (c) or the step (d) added thereafter can be made into an organosol by the step (e) of substituting with a hydrophilic organic solvent. This substitution can be performed by a usual method such as a distillation method or an ultrafiltration method. Examples of the hydrophilic organic solvent include lower alcohols such as methanol, ethanol and isopropanol, linear amides such as dimethylformamide, N, N'-dimethylacetamide, cyclic amides such as N-methyl-2-pyrrolidone and ethylcellosolve. Examples thereof include glycol ethers and ethylene glycol. The particles in the organosol obtained by the step (e) are the same as those in the aqueous sol obtained by the step (c).
It has a secondary particle size and a component molar ratio.

The sol production method of the present invention comprises, as a second method, the following (a '), (b'), (c ') and (d').
Step; (a '): Zinc salt and stannate are neutralized with an acid in an aqueous medium in the presence of hydrogen peroxide to give Z of 0.7 to 1.2.
a step of obtaining an aqueous medium containing an aggregate of colloidal particles of zinc stannate hydrate having an n / Sn molar ratio, (b '): colloid of zinc stannate hydrate obtained in step (a') Aqueous medium containing agglomerates of particles, 30-2
Heating at a temperature of 00 ° C., (c ′): removing the electrolyte from an aqueous medium containing an aggregate of colloidal particles of zinc stannate hydrate obtained in the step (b ′), and (d) '): A step of peptizing the aggregate of colloidal particles of zinc stannate hydrate in the aqueous medium obtained in (c').

As the zincate used in step (a '), any zincate can be used as long as it is water-soluble.
As these zincates, alkali metal zincates are preferable, and examples thereof include sodium zincate and potassium zincate. Zinc alkali metal salts of the above are (as a general _{formula, M 2 O · ZnO · nH} 2 O, where M is an alkali metal atom) normal salt for susceptible to the hydrolysis, M ₂ O
It is preferably used as an alkaline aqueous solution having a composition with a / ZnO molar ratio of 2.0 or more. The above zincate is Zn
It is preferable to use an aqueous solution of 0.1 to 20% by weight as O.

The stannate used in the step (a ') is preferably a water-soluble alkali metal stannate, for example,
Sodium stannate _{(Na 2 SnO 3 · 3H 2} O) , potassium stannate _{(K 2 SnO 3 · 3H 2} O) can be mentioned, and these can be used alone or as a mixture.
These stannates are 0.1 to 20% by weight as SnO _2.
It can be used as a concentrated aqueous solution.

Hydrogen peroxide used in the step (a ') is
It can be used as an aqueous solution of 5 to 60% by weight as H ₂ O ₂ . In the step (a '), by mixing zincate and stannate in the presence of hydrogen peroxide at a Zn / Sn molar ratio of 0.7 to 1.2 and neutralizing with an acid in an aqueous medium. , An aggregate of colloidal particles of zinc stannate hydrate having a Zn / Sn molar ratio of 0.7 to 1.2 can be obtained. If the Zn / Sn molar ratio at the time of mixing the zincate and stannate is less than 0.7, tin oxide (SnO ₂ ) colloidal particles are generated, which is not preferable. OH) ₂ colloidal particles are generated, which is not preferable.

In the step (a '), 0.7 to 1.2
The colloidal particles of zinc stannate hydrate having a Zn / Sn molar ratio of 2 have a primary particle diameter of 2 to 200 nm, but the colloidal particles having these primary particle diameters form an aggregate, The aqueous medium containing the agglomerates of these colloidal particles of zinc stannate hydrate can be said to be a slurry. (A ')
Examples of the acid used in the step include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and sulfamic acid, and organic acids such as formic acid, acetic acid and oxalic acid, and the inorganic acid is preferable from the viewpoint of production cost and wastewater treatment. These acids can be used as an aqueous solution having a concentration of 0.1 to 20% by weight.

In the step (a '), the reaction of neutralizing the zincate and the stannate with an acid in the presence of hydrogen peroxide is carried out by using an aqueous solution containing the zincate and the stannate and a hydrogen peroxide solution. It is preferable that the reaction is carried out in an aqueous medium in which an acid aqueous solution added with is mixed. The aqueous solution containing zincate and stannate is preferably obtained by mixing an aqueous zincate solution and an aqueous stannate solution. The hydrogen peroxide solution can be added to either an aqueous solution containing zincate and stannate or an aqueous acid solution. However, a mixed aqueous solution of zincate and stannate is alkaline. Therefore, it is preferable to add it to the aqueous acid solution. In the reaction of neutralizing the zincate and the stannate with an acid in the presence of hydrogen peroxide in the step (a ′), the amount of hydrogen peroxide present in the aqueous medium is the molar amount of H ₂ O ₂ / Zn. The ratio can be set to 0.5 to 20.0, preferably 1.0 to 18. Hydrogen peroxide has the function of controlling the particle size of colloidal particles when neutralizing zincate and stannate with an acid to form aggregates of colloidal particles of zinc stannate hydrate,
When the H ₂ O ₂ / Zn molar ratio is less than 0.5, some colloidal particles of zinc stannate hydrate have a primary particle diameter of 200.
If it exceeds 20.0 nm, it is not economical.

In the step (a '), the aqueous solution containing zincate and stannate is mixed with the aqueous acid solution to which hydrogen peroxide solution is added. The method is performed by dropping an aqueous solution into the other aqueous solution.
Aggregates of colloidal particles of zinc stannate hydrate having an n molar ratio are obtained. However, in order to avoid the formation of flocs, a method of dropping an aqueous acid solution containing hydrogen peroxide into an aqueous solution containing zincate and stannate is preferable. This dropping takes 20 to 80 over 0.5 to 5 hours.
Performed at a temperature of ° C. It is preferable to add an aqueous acid solution containing hydrogen peroxide solution to the aqueous solution containing zincate and stannate under stirring with a metering pump using a stirring machine such as a disper. It is preferable to mix both solutions so that the zinc stannate hydrate produced in the aqueous medium by this mixing has a concentration of 0.1 to 20% by weight, preferably 1.0 to 10% by weight. The pH of this mixed solution is 3 to 12, preferably 5 to 9. If the pH is less than 3, a part of the produced zinc stannate hydrate dissolves in the acid as a zinc salt, so that the yield decreases, and if the pH exceeds 12, some of the stannate and the zinc salt are partially formed. Since it remains unreacted, the yield decreases, which is not preferable.

In step (a '), the oxycarboxylic acid, a salt thereof, or a mixture thereof is added to the aqueous medium in a molar ratio of 1.5 times or less with respect to Sn in the stannate, preferably 0.05 to It can be contained 1.5 times. A zinc stannate hydrate sol having high dispersibility and transparency can be obtained by adding the above-mentioned oxycarboxylic acid or a salt thereof. As the above-mentioned oxycarboxylic acid or a salt thereof, a water-soluble one is used, and examples of the oxycarboxylic acid include gluconic acid, tartaric acid,
Examples include citric acid, and as the oxycarboxylic acid salt, gluconic acid, tartaric acid, or an alkali metal salt such as citric acid,
Examples thereof include ammonium salts and organic base salts, examples of the alkali metal salt include sodium gluconate, and examples of the organic base salt include propylamine gluconate. Oxycarboxylic acids and salts thereof are (a ') to (d')
It can be added at any stage of the process, but before the formation of aggregates of colloidal particles of zinc stannate hydrate, during the formation of aggregates, or in the sol obtained by peptizing the aggregates. It is preferable to add. When added before the formation of the agglomerates of colloidal particles of zinc stannate hydrate, the above-mentioned oxycarboxylic acid or its salt was prepared by adding an aqueous solution containing zincate and stannate or hydrogen peroxide solution. It is possible to add it to any aqueous solution of the acid aqueous solution so that it is contained in the aqueous medium, but the acid aqueous solution to which hydrogen peroxide solution is added is changed to an aqueous solution containing a stirred zincate and stannate. Among the dropping methods, the above-mentioned oxycarboxylic acid or its salt is preferably added to an aqueous solution containing zincate and stannate. These oxycarboxylic acids and salts thereof can be added directly or as an aqueous solution having a concentration of 1 to 50% by weight to an aqueous solution containing zincate and stannate.

In the step (b '), the aqueous medium containing the aggregate of colloidal particles of zinc stannate hydrate obtained in the step (a') is heated at 30 to 200 ° C, preferably 60 to 10 ° C.
At a temperature of 0 ° C. for 0.1 to 50 hours, preferably 1 to 10
Heat aging takes place over time. When the heating temperature exceeds 100 ° C, an autoclave or the like is required. If the heat aging time is 0.1 hours or less, the effect is small, and it may be more than 50 hours, but it is not economical.

In step (c '), cations (alkali metal ions) contained in excess are extracted from the aqueous medium containing the aggregate of colloidal particles of zinc stannate hydrate obtained in step (b'). Electrolytes such as anions (acid radicals) are removed. The electrolyte is removed by washing by a method such as decantation, centrifugal filtration, and ultrafiltration. Removal by these filtration methods is 100 ° C or less, preferably 25
It can be performed at -60 ° C.

In the step (d '), an aqueous medium (slurry) containing a zinc stannate hydrate colloidal agglomerate obtained by washing and removing the excess electrolyte obtained in the step (c') is dispersed,
The sol can be produced by dispersing and peptizing with a device such as a sand grinder, an attritor or a ball mill. At this time, as a dispersion aid, by adding an inorganic base such as alkali metal hydroxide or ammonia, or an organic base such as amines to adjust the pH, the particles of zinc stannate hydrate can be more efficiently water-soluble. It is possible to produce a sol dispersed in a medium. The above-mentioned oxycarboxylic acid, a salt thereof or a mixture thereof can be added to the sol thus obtained in a molar ratio of 1.5 times or less with respect to Sn of zinc stannate hydrate.

The sol obtained by the step (d ') has a pH of
It has a pH of 3 to 12, preferably 5 to 11, and contains zinc stannate hydrate in a concentration of 5 to 30% by weight. And the zinc stannate hydrate particles in the obtained sol have a particle size of 2 to 200 nm.
With a primary particle diameter of xZnO.ySnO ₂
· ZH ₂ O in the x: y: z is 1: 0.83 to 1.4
It was represented by a molar ratio of 3: 1.00 to 5.00.

The sol obtained by the step (d ') can be treated with a cation exchange resin or an anion exchange resin in order to further reduce the electrolyte in the zinc stannate hydrate sol. The anion exchange resin is used in a hydroxyl group type, a commercially available anion exchange resin can be used, and the anion can be easily removed by a method of passing a sol through a column packed with the anion exchange resin. The temperature of the liquid passing is preferably 0 to 60 ° C., and the liquid passing is preferably ¹ to 10 h ^{−1 in} space velocity (SV). Further, the cation exchange resin is used in a hydrogen form, and a commercially available cation exchange resin can be used. The treatment with the cation exchange resin can remove the cations by directly adding a necessary amount to the sol under stirring. The zinc stannate water of the present invention having good transparency at pH 3 to 12 and sufficient stability because the excessive electrolyte removal in the step (c ') facilitates the peptization in the step (d'). Japanese sol can be obtained. If it is desired to further increase the concentration of the sol obtained in the step (d '), it can be concentrated to 40% by weight by adding a stabilizer such as an organic base or an organic acid in the step (e'). Examples of the organic base used include alkylamine, alkanolamine or quaternary ammonium hydroxide, such as n-propylamine, isopropylamine, diisobutylamine, ethylenediamine,
Examples include monoethanolamine and triethanolamine. An oxycarboxylic acid such as glycolic acid, tartaric acid or citric acid can be used as the organic acid. The aqueous medium of the aqueous sol obtained by the step (d ') or the step (e') added thereafter can be made into an organosol by the step (f ') of substituting with a hydrophilic organic solvent.
This substitution can be performed by a usual method such as a distillation method or an ultrafiltration method. Examples of the hydrophilic organic solvent include lower alcohols such as methanol, ethanol and isopropanol, linear amides such as dimethylformamide, N, N'-dimethylacetamide, cyclic amides such as N-methyl-2-pyrrolidone and ethylcellosolve. Examples thereof include glycol ethers and ethylene glycol.
The particles in the organosol obtained by the step (f ') are
It has the same primary particle size and component molar ratio as the particles in the aqueous sol obtained in step (e ').

The sol in which the particles of the zinc stannate hydrate of the present invention are dispersed in a liquid medium can be produced by the third method which is a combination of the above-mentioned first method and second method. That is, the third method is the step (a ″): neutralizing a stannate and a zinc salt with an acid and a zinc salt in an aqueous medium in the presence of hydrogen peroxide,
A step of obtaining an aqueous medium containing an aggregate of colloidal particles of zinc stannate hydrate having a Zn / Sn molar ratio of 0.7 to 1.2, step (b ″): obtained in step (a ″) A step of heating an aqueous medium containing an aggregate of colloidal particles of zinc stannate hydrate at a temperature of 30 to 200 ° C., a step (c ″): a zinc stannate water obtained in the step (b ″) A step of removing an electrolyte from an aqueous medium containing an aggregate of colloidal particles of a hydrate, and a step (d ″) of colloidal particles of zinc stannate hydrate in the aqueous medium obtained in the step (c ″) It comprises the step of peptizing the aggregates.

In the step (a ") of the third method, the reaction of neutralizing zincate and stannate with acid and zinc salt in the presence of hydrogen peroxide contains zincate and stannate. It is preferable that the zinc stannate hydrate produced by the conventional method is used in an aqueous medium in which an aqueous solution of hydrogen peroxide and an aqueous solution of zinc salt and an aqueous solution of zinc salt are mixed. A precipitate is formed, and the particle size is large at 0.3 to 1.0 μm, and it does not become a sol even if the excess electrolyte is removed by filtration and washing, etc. Also, if wet pulverization treatment with a sand grinder or an attritor is performed to a certain extent. It is possible to form a sol by dispersion, but it is difficult to form a sol with high stability and transparency.

The sol in which the particles of the zinc stannate hydrate of the present invention are dispersed in a liquid medium is the first method in which a zinc salt and a stannate are reacted in an aqueous medium in the presence of hydrogen peroxide, or zinc. It can be produced by the second method in which the acid salt and stannate are neutralized with an acid in the presence of hydrogen peroxide in an aqueous medium. Hydrogen peroxide can control the particle size of zinc stannate hydrate colloidal particles generated during the reaction, and as a result, the primary particle size becomes about 2 to 200 nm, and even if secondary aggregation occurs, The degree of aggregation is weak, and after removing excess electrolyte, it can be easily deflocculated to produce a zinc stannate hydrate sol. It is presumed that this is because the surface of stannic acid is in a peroxide state due to the presence of hydrogen peroxide.

Zinc stannate hydrate particles in the sol obtained by the first method of the present invention were analyzed by X-ray diffraction, and were produced by TK, Index Toza Xray.
Powder Data File In Organic (AST
M, Index to the X-ray Powder
Zinc stannate hydrate (ASTM No. 20-, described in R Data File Inorganic).
1455, ZnSnO ₃ .3H ₂ O,) peak pattern. Although the peak of crystalline zinc stannate hydrate is also shown, it is very small, and it was confirmed that most of them are amorphous zinc stannate hydrate.

The zinc stannate hydrate particles in the sol obtained by the second method of the present invention were analyzed by X-ray diffraction and
ASTM (No.20-1455, ZnSnO ₃ · 3H
The peak pattern of crystalline zinc stannate hydrate coincides with the peak pattern of ₂ O,). The crystallinity of the particles obtained by this second method is high.

[0037]

【Example】

Example 1 Sodium stannate (Na ₂ SnO ₃₎ was added to 2391.8 g of water.
・ 3H ₂ O, manufactured by Showa Kako Co., Ltd., containing 55% by weight as SnO ₂ ) 146.8 g was dissolved to prepare an aqueous solution of sodium stannate (containing 3.3% by weight as SnO ₂ ). Sodium stannate / sodium gluconate mixed aqueous solution 2 with addition of 51.4 g of sodium gluconate
500 g was prepared. Separately, 63.5 g of zinc chloride (ZnCl ₂ ) was dissolved in 1686.5 g of water to prepare an aqueous zinc chloride solution, and 750 g of hydrogen peroxide solution having a concentration of 35% by weight was added therein.
Was added to prepare 2500 g of a mixed aqueous solution of zinc chloride / hydrogen peroxide.

Step (a): The zinc chloride aqueous solution / hydrogen peroxide mixed aqueous solution prepared above is added to the sodium stannate / sodium gluconate mixed aqueous solution for about 1 hour under stirring with a disperser using a metering pump and reacted. A zinc stannate hydrate colloidal solution was obtained. This zinc stannate hydrate colloidal solution has a pH of 8.5, oxycarboxylic acid / SnO ₂
Molar ratio 0.44, H ₂ O ₂ 5.25 wt%, ZnO / S
The nO ₂ molar ratio was 0.87, and the concentration was 2.4% by weight in terms of ZnO + SnO ₂ .

Step (b): 200 g of hydrochloric acid having a concentration of 5% by weight is added to the zinc stannate hydrate colloidal solution obtained in the step (a).
Was added to adjust the pH to about 6, and then the mixture was heated and aged at 90 ° C. for 5 hours, and after cooling, 25.3 g of isopropylamine was added and stirred for 8 hours by disper stirring to deflocculate the zinc stannate hydrate colloidal solution 5225. 0.3 g was obtained. PH of this thing
Is 9.32, conductivity 24.2 ms / cm, ZnO + Sn
It was 2.3% by weight in terms of O ₂ .

Step (c): Excess electrolyte in the zinc stannate hydrate colloidal solution obtained in step (b) is washed with 36 liters of water by an ultrafiltration method to remove water by washing with zinc stannate. 2572 g of Japanese sol was obtained. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 5 nm as observed by a transmission electron microscope and a ZnO / SnO ₂ molar ratio of 0.70. And the general formula xZnO.ySnO
_{In 2} · zH ₂ O, x: y: z is 1: 1.43: 3.
It was 90. To this sol, 50 ml of a cation exchange resin (Amberlite IR-120B, used in hydrogen form) was added and stirred to further remove cations. The cation exchange resin was separated to obtain 2937 g of sol. The obtained sol has a pH
The electrical conductivity was 7.44 and the electrical conductivity was 172 μs / cm.

Step (d): 0.5 g of isopropylamine was added to the sol obtained in the step (c) and concentrated under reduced pressure using a rotary evaporator to obtain concentrated sol 10.
09 g were obtained. The obtained sol had a pH of 8.00 and an electric conductivity of 4
03 μs / cm, converted to ZnO + SnO ₂ 11.2
% By weight, and the yield was 95%. 11 of this thing
The refractive index of the dried product at 0 ° C. was 1.70, and it was an amorphous zinc stannate hydrate by X-ray diffraction measurement.

Step (e): The sol obtained in the step (d) was stirred with 8.3 g of diisobutylamine and 5.
After 1 g was added to make an adjusted sol, the mixture was put into a rotary evaporator and 21 liters of methanol was gradually added under reduced pressure to distill off water in the sol to obtain 495.6 g of zinc stannate hydrate methanol sol. . The obtained sol had a specific gravity of 0.960 and a viscosity of 21.0 c. p. , PH (1
+1) 8.60, conductivity (1 + 1) 446.5 μs / c
m, a concentration of 22.8% by weight in terms of ZnO + SnO ₂ ,
The water content was 0.86% by weight. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 5 nm and a ZnO / SnO ₂ molar ratio of 0.70 as observed by a transmission electron microscope. The general formula xZnO.ySnO ₂ .zH ₂
In O, x: y: z was 1: 1.43: 3.90.

Example 2 Sodium stannate (Na ₂ SnO ₃₎ was added to 1945.7 g of water.
・ 3H ₂ O, manufactured by Showa Kako Co., Ltd., containing 55% by weight as SnO ₂ ) 147.0 g was dissolved to prepare an aqueous solution of sodium stannate (containing 3.3% by weight as SnO ₂ ). Gluconic acid aqueous solution (Fujisawa Pharmaceutical Co., Ltd.)
63.0 g was added to prepare 2155.7 g of sodium stannate / gluconic acid mixed aqueous solution. Separately, zinc chloride (ZnCl) was added to 1302.8 g of water.
₂ ) 65.9 g was dissolved to prepare a zinc chloride aqueous solution, and 750 g of 35 wt% hydrogen peroxide solution was added thereto to prepare 218.7 g of a zinc chloride / hydrogen peroxide mixed aqueous solution.

Step (a): The zinc chloride aqueous solution / hydrogen peroxide mixed aqueous solution prepared above is added to the sodium stannate / gluconic acid mixed aqueous solution for about 1 hour while stirring with a disperser using a metering pump to react the stannic acid. A zinc hydrate colloidal solution was obtained. This zinc stannate hydrate colloidal solution has a pH
6.8, oxycarboxylic acid / SnO ₂ molar ratio 0.30,
H ₂ O ₂ 6.13 wt%, ZnO / SnO ₂ molar ratio 0.1.
90, a concentration of 2.8% by weight in terms of ZnO + SnO ₂ .

Step (b): The zinc stannate hydrate colloidal solution obtained in the step (a) is heat-aged at 92 ° C. for 5 hours, cooled, 25.0 g of isopropylamine is added, and the mixture is stirred with a disper for 8 hours. , Zinc stannate hydrate colloidal solution 43
06.9 g was obtained. The product had a pH of 9.28, an electric conductivity of 24.7 ms / cm, and a conversion of ZnO + SnO ₂ to 2.
It was 78% by weight. Step (c): Excess electrolyte in the zinc stannate hydrate colloidal solution obtained in step (b) is treated with water 30 by ultrafiltration.
Water was removed by washing with liter to obtain 2792 g of zinc stannate hydrate sol. This had a pH of 10.42 and an electric conductivity of 377 μs / cm. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 5 nm as observed by a transmission electron microscope. The transmission electron micrograph is shown in FIG. The ZnO / SnO ₂ molar ratio is 0.8
It was 5. From the result of thermogravimetric analysis (TG) shown in FIG. 3, the weight loss was 15.18% at a temperature of 322 ° C., and x: y: in the general formula xZnO · ySnO ₂ · zH ₂ O.
The z was 1: 1.18: 3.40. This sol was passed through a column packed with an anion exchange resin (Amberlite IRA-410, used in a hydroxyl group type) to further remove anions. This sol had a pH of 11.05 and an electric conductivity of 289 μs / cm. Cation exchange resin (Amberlite IR-120B, used in hydrogen form)
100 ml was added and stirred to remove cations. The cation exchange resin was separated to obtain 4077 g of sol. The obtained sol had a pH of 7.98 and an electric conductivity of 98.6 μs / cm.

Step (d): The sol obtained in the step (c) was concentrated at a liquid temperature of 30 ° C. by an ultrafiltration device to obtain 930 g of concentrated sol. The obtained sol had a pH of 7.83, an electric conductivity of 213 μs / cm, and a ZnO + SnO _{2 value} of 1
It was 1.8% by weight, and the yield was 91.5%. The X-ray diffraction measurement of this product dried at 110 ° C. revealed that it was almost amorphous zinc stannate hydrate. The result of the X-ray diffraction measurement is shown in FIG.

Step (e): To 312 g of the sol obtained in the step (d), 1.52 g of tartaric acid and 2.28 g of diisobutylamine were added with stirring to obtain an adjusted sol, which was then placed in a rotary evaporator under reduced pressure. Water in the sol was distilled off while gradually adding 13 liters of methanol to obtain 232 g of zinc stannate hydrate methanol sol.
The obtained sol has a specific gravity of 0.930 and a viscosity of 28.1 c.
p. , PH (1 + 1) 8.18, conductivity (1 + 1) 20
0 μs / cm, converted to ZnO + SnO ₂ were 18.8 wt% and water was 0.77 wt%. Particles of zinc stannate hydrate in this sol were observed by a transmission electron microscope.
The secondary particle diameter is 5 nm, and the ZnO / SnO ₂ molar ratio is 0.1.
85. Then, the general formula xZnO · ySnO ₂ ·
In zH ₂ O, x: y: z is 1: 1.18: 3.40.
Met.

Example 3 4849.6 g of water was added to potassium stannate (K ₂ SnO ₃ · 3).
H ₂ O, manufactured by Showa Kako Co., Ltd., containing 50.4% by weight as SnO ₂ ) was dissolved to prepare an aqueous potassium stannate solution (SnO ₂ 2.0% by weight). Acid aqueous solution (manufactured by Fujisawa Pharmaceutical Co., Ltd., content 50)
(% By weight) 104.9 g was added to prepare 5154.9 g of a potassium stannate / gluconic acid mixed aqueous solution. Separately water 34
91.4 g of zinc chloride (ZnCl ₂ ) was dissolved in 03.9 g to prepare a zinc chloride aqueous solution, and 989.2 g of 35 wt% hydrogen peroxide solution was added thereto to add a zinc chloride / hydrogen peroxide mixed aqueous solution 4484. 5 g was prepared.

Step (a): The zinc chloride aqueous solution / hydrogen peroxide mixed aqueous solution prepared above is added to the potassium stannate / gluconic acid mixed aqueous solution for about 1 hour with stirring using a metering pump under a disper stirring to cause reaction. 9639.4 g of a zinc hydrate colloidal solution was obtained. This zinc stannate hydrate colloidal solution had a pH of 7.0 and a gluconic acid / SnO ₂ molar ratio of 0.
40, H ₂ O ₂ 3.59% by weight, ZnO / SnO ₂ molar ratio 1.00, and a concentration of 1.62% by weight in terms of ZnO + SnO ₂ .

Step (b): The zinc stannate hydrate colloidal solution obtained in the step (a) is then heat-aged at 90 ° C. for 5 hours, cooled, and added with 25.0 g of isopropylamine. After stirring for an hour, 9664.4 g of zinc stannate hydrate colloidal liquid was obtained. The pH of this product is 9.
45, conductivity 19.0 ms / cm, ZnO + SnO
₂ 1.61% by weight.

Step (c): Excess electrolyte in the zinc stannate hydrate colloidal solution obtained in step (b) is washed with 32 liters of water by an ultrafiltration method to remove water by washing with zinc stannate. 2990 g of Japanese sol was obtained. Particles of zinc stannate hydrate in this sol were observed by a transmission electron microscope.
The secondary particle size is 5 nm and the ZnO / SnO ₂ molar ratio is 1.
02. Then, the general formula xZnO · ySnO ₂ ·
In zH ₂ O, x: y: z is 1: 0.98: 3.80.
Met. This sol was passed through a column packed with an anion exchange resin (Amberlite IRA-410, used in a hydroxyl group type) to further remove anions. This sol had a pH of 10.23 and an electric conductivity of 474 μs / cm. Furthermore, cation exchange resin (Amberlite IR-1
20B, used in hydrogen type) 70 ml was added and stirred to remove cations. Separated the cation exchange resin, 3151 g
The sol of The obtained sol has a pH of 7.87 and an electric conductivity of 1.
It was 73 μs / cm.

Step (d): To the sol obtained in the step (c), 5.6 g of citric acid and 8.5 g of diisobutylamine were added and concentrated under reduced pressure using a rotary evaporator to obtain 1096 g of concentrated sol. . The obtained sol is Z
It was 13.2% by weight of nO + SnO ₂ . 1 of this thing
The refractive index of the dried product at 10 ° C. was 1.70, and a small peak of crystalline zinc stannate hydrate was observed by X-ray diffraction measurement, but most were amorphous zinc stannate hydrate.

Step (e): The sol obtained in step (d) is put into a rotary evaporator, and 63 liters of methanol is gradually added under reduced pressure to distill off water in the sol to hydrate zinc stannate. Thing methanol sol 64
1.6 g was obtained. The obtained sol had a specific gravity of 0.960 and a viscosity of 21.0 c. p. , PH (1 + 1) 8.60, electric conductivity (1 + 1) 446.5 μs / cm, and ZnO + SnO ₂ had a concentration of 22.6% by weight and a water content of 0.80% by weight. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 5 nm as observed by a transmission electron microscope.
The O / SnO ₂ molar ratio was 1.02. Then, in the general formula xZnO.ySnO ₂ .zH ₂ O, x: y: z was 1: 0.98: 3.80.

Example 4 Sodium stannate (Na ₂ SnO ₃₎ was added to 4960.9 g of water.
・ 3H ₂ O, manufactured by Showa Kako Co., Ltd., containing 55% by weight of SnO ₂ ) 183.6 g was dissolved to prepare an aqueous solution of sodium stannate (containing 3.3% by weight of SnO ₂ ). 10.0 g of tartaric acid was added to prepare 5154.5 g of a mixed aqueous solution of sodium stannate / tartaric acid. Separately, 91.2 g of zinc chloride (ZnCl ₂ ) was added to 3311.7 g of water.
To prepare an aqueous solution of zinc chloride, in which 35 wt%
Hydrogen peroxide solution (989.2 g) was added to prepare a zinc chloride / hydrogen peroxide mixed aqueous solution (4392.1 g).

Step (a): The zinc chloride aqueous solution / hydrogen peroxide mixed aqueous solution prepared above is added to the sodium stannate / tartaric acid mixed aqueous solution for about 1 hour with stirring using a metering pump and reacted to give zinc stannate. 9546.6 g of a hydrate colloidal solution was obtained. This zinc stannate hydrate colloidal solution had a pH of 8.0, a tartaric acid / SnO ₂ molar ratio of 0.10,
H ₂ O ₂ 3.59% by weight, ZnO / SnO ₂ molar ratio 1.
0, and the concentration was 1.63 wt% as ZnO + SnO ₂ .

Step (b): The zinc stannate hydrate colloidal solution obtained in the step (a) is heated and aged at 90 ° C. for 4 hours, cooled, 20.0 g of isopropylamine is added, and the mixture is stirred with a disper for 10 hours. , Zinc stannate hydrate colloidal liquid 9
566.6 g was obtained. This had a pH of 9.86, an electric conductivity of 14.6 ms / cm, and ZnO + SnO ₂ 1.62% by weight.

Step (c): The excess electrolyte in the zinc stannate hydrate colloidal solution obtained in the step (b) is removed by water injection washing with 30 liters of water by an ultrafiltration method. 2873 g of Japanese sol was obtained. The pH of this product is 1
The electric conductivity was 0.28 and the electric conductivity was 368 μs / cm. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 5 nm and a ZnO / SnO ₂ molar ratio of 0.98 as observed by a transmission electron microscope. And the general formula xZnO.yS
In nO ₂ · zH ₂ O, x: y: z is 1: 1.02:
It was 3.40. This sol was passed through a column packed with an anion exchange resin (Amberlite IRA-410, used in a hydroxyl group type) to further remove anions. This sol has a pH of 10.86 and an electric conductivity of 260 μs / c.
m. Further, 70 ml of a cation exchange resin (Amberlite IR-120B, used in hydrogen form) was added and stirred to remove cations. Separate the cation exchange resin 4
058 g of sol was obtained. The obtained sol had a pH of 7.43,
The electric conductivity was 23.2 μs / cm.

Step (d): To the sol obtained in the step (c), 6.0 g of tartaric acid and 9.0 g of diisobutylamine were added with stirring, and the mixture was concentrated under reduced pressure using a rotary evaporator to obtain 1214 g of concentrated sol. Obtained. The obtained sol has a specific gravity of 1.170 and a viscosity of 28.1 c. p. , PH
7.84, conductivity 3200 μs / cm, ZnO + SnO
It was ₂ 11.8% by weight. The 110 ° C. dried product had a refractive index of 1.72 and was an amorphous zinc stannate hydrate by X-ray diffraction measurement. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 7 to 15 nm as observed by a transmission electron microscope, and had a ZnO / SnO ₂ molar ratio of 0.98.
Met. Then, the general formula xZnO.ySnO ₂ .zH
_{In 2} O, x: y: z was 1: 1.02: 3.40.

Example 5 1422.8 g of sodium hydroxide was dissolved in 2188.4 g of water, and 368.8 g of zinc oxide was added and dissolved therein to prepare 4004.2 g of a sodium zincate aqueous solution. This had a ZnO content of 9.21% by weight, a Na ₂ O content of 25.61% by weight, and a Na ₂ O / ZnO molar ratio of 3.65. To 3842.5 g of water, 500.6 g of the above sodium zincate aqueous solution and sodium stannate (Na ₂ SnO ₃ ·.
3H ₂ O, manufactured by Showa Kako Co., Ltd., containing 55% by weight of SnO ₂ ) 163.3 g of sodium zincate,
Sodium stannate mixed aqueous solution (ZnO 1.02% by weight,
SnO ₂ 1.99% by weight, ZnO / SnO ₂ molar ratio 0.1.
95) was prepared, and 93.6 g of an aqueous gluconic acid solution (manufactured by Fujisawa Pharmaceutical Co., Ltd., content: 50% by weight) was added to prepare 4600 g of a sodium zincate / sodium stannate / gluconic acid mixed aqueous solution. Separately, 555.8 g of 35 wt% hydrochloric acid was dissolved in 3203.2 g of water, and 441.0 g of hydrogen peroxide aqueous solution of 35 wt% was added thereto to prepare 4200 g of a hydrochloric acid / hydrogen peroxide mixed aqueous solution.

Step (a '): The hydrochloric acid / hydrogen peroxide mixed aqueous solution prepared above is added to the sodium zincate / sodium stannate / gluconic acid mixed aqueous solution for about 1 hour under stirring with a disperser using a metering pump to carry out reaction. Then, a slurry liquid of an aggregate of zinc stannate hydrate colloidal particles was obtained. This product had a gluconic acid / SnO ₂ molar ratio of 0.40 and a pH of 6.
7. 1.75% by weight of H ₂ O ₂ and a ZnO / SnO ₂ molar ratio of 0.95.

Step (b '): 5% by weight to the zinc stannate hydrate colloidal aggregate slurry liquid obtained in the step (a')
After adding 252 g of hydrochloric acid to adjust the pH to 5.00, heat aging was carried out at 90 ° C. for 4 hours. The pH of this product is 5.8.
0, the electric conductivity was 54 ms / cm, and it was 1.55% by weight in terms of ZnO + SnO ₂ . Step (c ′): Excessive electrolyte in the zinc stannate hydrate colloidal aggregate slurry liquid obtained in step (b ′) is removed by washing with 24 liters of water by an ultrafiltration method to remove stannic acid. 1000 g of zinc hydrate aggregate slurry was obtained. 3.0 g of isopropylamine was added to this slurry to adjust the pH to 8.60. The conductivity of this thing is 62
It was 0 μs / cm.

Step (d '): 1200 g of glass beads (1.0 to 1.2 mmφ) was added to the zinc stannate hydrate colloidal aggregate slurry obtained in the step (c'), and wet-dispersed in a ball mill for 71 hours. After deflocculating, the glass beads were separated, and the obtained sol was further subjected to anion exchange resin (IR
The solution was passed through a column packed with A-410) to obtain 3052.7 g of zinc stannate hydrate sol. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 7 nm and a ZnO / SnO ₂ molar ratio of 0.80 as observed by a transmission electron microscope. And the general formula xZnO.ySnO ₂ .zH ₂ O
X: y: z was 1: 1.25: 3.40.

Step (e '): Step (d') The obtained sol is concentrated using an ultrafiltration device to obtain a concentrated sol 126.
9 g were obtained. The obtained sol had a pH of 9.80 and an electric conductivity of 73.
It was 0 μs / cm, and was 9.06% by weight in terms of ZnO + SnO ₂ . Step (f ′): 633 g of sol obtained in step (e ′)
By adding 1.72 g of diisobutylamine and 1.15 g of citric acid to the prepared sol under stirring to prepare an adjusted sol, the mixture was put into a rotary evaporator and 13 liters of methanol was gradually added under reduced pressure to distill off water in the sol. 322 g of zinc stannate hydrate methanol sol was obtained. The obtained sol had a specific gravity of 0.910 and a viscosity of 21.6 c. p. , PH
(1 + 1) 8.25, conductivity (1 + 1) 253.5 μs
/ Cm, converted to ZnO + SnO ₂ and had a concentration of 15.3% by weight and a water content of 0.56% by weight. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 7 to 15 nm as observed by a transmission electron microscope and a ZnO / SnO ₂ molar ratio of 0.80. And the general formula xZnO.ySnO
_{In 2} · zH ₂ O, x: y: z is 1: 1.25: 3.
It was 40. The 110 ° C. dried product of this sol has a refractive index of 1.72, and according to the X-ray diffraction measurement, ASTM No. Two
0-1455, ZnSnO ₃ .3H ₂ O coincided with the peak pattern.

Example 6 To 3898.5 g of water, 500.6 g of the aqueous solution of sodium zincate prepared in Example 5 and sodium stannate (Na ₂ Sn) were added.
O ₃ · 3H ₂ O, Showa Kako Co., Ltd., 5 as SnO ₂
163.3 g (containing 5% by weight) is dissolved and a mixed aqueous solution of sodium zincate and sodium stannate (1.
01 wt%, SnO ₂ 1.97 wt%, ZnO /
SnO ₂ molar ratio of 0.95) was prepared, and 37.6 g of citric acid was added thereto to prepare 4600 g of a mixed aqueous solution of sodium zincate / sodium stannate / citric acid. Separately, 524.9 g of 35 wt% hydrochloric acid was dissolved in 3234.1 g of water, and 441.0 g of hydrogen peroxide aqueous solution of 35 wt% was added thereto to prepare 4200 g of a hydrochloric acid / hydrogen peroxide mixed aqueous solution.

Step (a '): The hydrochloric acid / hydrogen peroxide mixed aqueous solution prepared above is added to the sodium zincate / sodium stannate / citric acid mixed aqueous solution for about 1 hour while stirring with a disperser using a metering pump and reacted. Then, a slurry liquid of an aggregate of zinc stannate hydrate colloidal particles was obtained. This product had a citric acid / SnO ₂ molar ratio of 0.40 and H ₂ O _{2 of} 1.7.
It was 5 wt% and the ZnO / SnO ₂ molar ratio was 0.95.

Step (b '): The zinc stannate hydrate colloidal aggregate slurry liquid obtained in the step (a') was heated and aged at 90 ° C for 5 hours. The pH of this product is 8.0
0, the electric conductivity was 54 ms / cm, and it was 1.55% by weight in terms of ZnO + SnO ₂ . Step (c ′): The excess electrolyte in the zinc stannate hydrate colloid aggregate aggregate slurry liquid obtained in the step (b ′) was removed by washing with 36 liters of water by an ultrafiltration method. 1498 g of zinc stannate hydrate aggregate slurry was obtained. This slurry has a pH of 8.60 and an electric conductivity of 686 μs /
cm.

Step (d '): Glass beads (1.0 to 1.2 mmφ) 15 were added to the slurry obtained in the step (c').
00g was added, wet dispersion deflocculation was performed for 72 hours with a ball mill, glass beads were separated, and the obtained sol was passed through a column packed with an anion exchange resin (IRA-410) to obtain zinc stannate hydrate sol. 2576 g were obtained. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 10 to 30 nm as observed with a transmission electron microscope, and ZnO / Sn
The O ₂ molar ratio was 0.90. And the general formula xZnO
· YSnO ₂ · zH ₂ O in x: y: z is 1: 1.
It was 11: 3.20.

Step (e '): The sol obtained in the step (d') was concentrated under reduced pressure using a rotary evaporator to obtain 1345.4 g of concentrated sol. The obtained sol had a pH of 8.58, an electric conductivity of 530 μs / cm, and ZnO + S.
It was 10.1% by weight in terms of nO ₂ . Step (f '): 672 g of sol obtained in step (e')
After adding 2.04 g of diisobutylamine and 1.36 g of citric acid with stirring to prepare an adjusted sol, the mixture was put into a rotary evaporator and 13 liters of methanol was gradually added under reduced pressure to distill off water in the sol. 322 g of zinc stannate hydrate methanol sol was obtained. The obtained sol has a specific gravity of 0.960 and a viscosity of 2.8 c. p. , PH (1
+1) 8.15, conductivity (1 + 1) 139.5 μs / c
m, 21.0 wt% concentration converted to ZnO + SnO ₂ ,
The water content was 0.53% by weight. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 10 to 70 nm and a ZnO / SnO ₂ molar ratio of 0.90 as observed by a transmission electron microscope. And the general formula xZnO.ySnO
_{In 2} · zH ₂ O, x: y: z is 1: 1.11: 3.
20. The refractive index of a 110 ° C. dried product of this sol is 1.74, and according to the X-ray diffraction measurement, the ASTM No. Two
0-1455, ZnSnO ₃ .3H ₂ O coincided with the peak pattern.

Example 7 In 7872 g of water, 1001.2 g of the aqueous solution of sodium zincate prepared in Example 5 and sodium stannate (Na ₂ SnO _{2) were} added.
₃ · 3H ₂ O, Showa Kako Co., Ltd., as SnO ₂ 55
326.8 g (containing 100% by weight) is dissolved and 9200 g of a mixed aqueous solution of sodium zincate and sodium stannate (1.00% by weight as ZnO, 1.95% by weight as SnO ₂ ;
A ZnO / SnO ₂ molar ratio of 0.95) was prepared. Separately, 1116.6 g of 35 wt% hydrochloric acid was dissolved in 5519.4 g of water, and 1764.0 g of 35 wt% hydrogen peroxide solution was dissolved therein.
Was added to prepare 8400 g of a hydrochloric acid / hydrogen peroxide mixed aqueous solution.

Step (a '): The hydrochloric acid / hydrogen peroxide mixed aqueous solution prepared above is added to the sodium zincate / sodium stannate mixed aqueous solution for about 1 hour while stirring with a disperser using a metering pump to react the stannic acid. A slurry liquid of an aggregate of zinc hydrate colloid particles was obtained. The slurry liquid of the aggregate of the zinc stannate hydrate colloidal particles has a pH of 8.7,
H ₂ O ₂ 3.51% by weight, ZnO / SnO ₂ molar ratio 0.1.
95.

Step (b '): 5% by weight of the zinc stannate hydrate colloid aggregate slurry liquid obtained in the step (a')
After 140 g of hydrochloric acid was added to adjust the pH to 7.13, the mixture was heat-aged at 90 ° C. for 4 hours. The pH of this product is 10.5
5, the conductivity was 53 ms / cm, and it was 1.55% by weight in terms of ZnO + SnO ₂ . Step (c ′): 50 g of 5 wt% hydrochloric acid was added to the zinc stannate hydrate colloidal aggregate slurry liquid obtained in step (b ′) to adjust the pH to 6.80, and then excess electrolyte was decanted and limited. By the external filtration method, 40 liters of water was used to wash and remove water. The obtained zinc stannate hydrate aggregate slurry was 1788 g, and had a pH of 8.93 and an electric conductivity of 16
It was 2 μs / cm.

Step (d '): 750 g of water and 14.6 g of 15 wt% potassium hydroxide aqueous solution were added to 1434 g of the slurry obtained in the step (c') to adjust pH to 11.6, and then glass beads. (1.0 to 1.2 mmφ) filled with a sand glider for 24 hours for wet dispersion peptization,
2860 g of zinc stannate hydrate sol was obtained. The obtained sol had a pH of 11.25 and an electric conductivity of 1210 μs / cm. While stirring, 5.4 g of citric acid and 40 ml of a cation exchange resin (IR-120B) were added to the obtained sol, and after stirring for 1 hour, the resin was separated. The obtained sol has a pH of 6.8.
6. The conductivity was 188 μs / cm. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 5 to 30 nm as observed by a transmission electron microscope. The transmission electron micrograph is shown in FIG. The ZnO / SnO ₂ molar ratio was 0.95. Then, the thermogravimetric analysis (T
From the result of G), the weight loss is 15.39% at the temperature of 262 ° C.
In the general formula xZnO.ySnO ₂ .zH ₂ O, x: y: z was 1: 1.05: 3.10.

Step (e '): To the sol obtained in the step (d'), 8.1 g of diisobutylamine was added to adjust the pH to 9.
After setting to 90, it concentrated under pressure reduction using a rotary evaporator and obtained 1381 g of concentrated sol. The obtained sol has a specific gravity of 1.194 and a viscosity of 264c.s. p. , PH8.
52, electric conductivity: 2040 μs / cm, converted to ZnO + SnO ₂ was 19.1% by weight.

Step (f '): 1251 g of the sol obtained in the step (e') was put into a rotary evaporator, and 31% of methanol was gradually added under reduced pressure to distill off the water in the sol to remove stannic acid. 1036.3 g of zinc hydrate methanol sol was obtained. The obtained sol has a specific gravity of 0.970 and a viscosity of 17.5 c. p. , PH (1 + 1)
7.85, conductivity (1 + 1) 96.0 μs / cm, Zn
O + SnO ₂ converted to 23.6 wt% concentration, water content of 0.
It was 53% by weight. The particles of zinc stannate hydrate in this sol have a primary particle diameter of 5 to 5 as observed by a transmission electron microscope.
It was 30 nm and the ZnO / SnO ₂ molar ratio was 0.95. And the general formula xZnO.ySnO ₂ .zH ₂ O
X: y: z was 1: 1.05: 3.10. The refractive index of a 110 ° C. dried product of this sol is 1.78, and according to X-ray diffractometry, ASTM No. 20-145
5. It coincided with the peak pattern of ZnSnO ₃ .3H ₂ O. The result of the X-ray diffraction measurement is shown in FIG.

Example 8 1001.2 g of the aqueous solution of sodium zincate prepared in Example 5 and 2734.2 g of water and sodium stannate (Na ₂ S) were added.
nO ₃ .3H ₂ O, manufactured by Showa Kako Co., Ltd., containing 55% by weight as SnO ₂ ) 326.8 g was dissolved to obtain a mixed aqueous solution of sodium zincate and sodium stannate 4062.2 g.
(2.31 wt% as ZnO and 4.4 as SnO ₂
9 wt%, ZnO / SnO ₂ molar ratio 0.95) was prepared. Separately, 35% by weight hydrochloric acid 1116.
Dissolve 6 g, in which 88 wt% hydrogen peroxide water 88
Add 2.0 g and add hydrochloric acid / hydrogen peroxide mixed aqueous solution 4000
g was prepared.

Step (a '): While stirring in 1000 g of water, the hydrochloric acid / hydrogen peroxide mixed aqueous solution and the sodium zincate / sodium stannate mixed aqueous solution prepared above were simultaneously added in about 1 hour using a metering pump. The reaction was carried out to obtain a slurry liquid of an aggregate of zinc stannate hydrate colloidal particles. This has a pH of 9.0, H ₂ O ₂ 3.43% by weight,
The ZnO / SnO ₂ molar ratio was 0.95.

Step (b '): 5% by weight to the zinc stannate hydrate colloidal aggregate slurry liquid obtained in the step (a')
After adding 198.7 g of hydrochloric acid and adjusting the pH to 6.65, 90
It was heat-aged at 4 ° C. for 4 hours. The pH of this product is 8.
50, conductivity 73 ms / cm, ZnO + SnO ₂ 3.0
It was 2% by weight. Step (c ′): The excess electrolyte in the zinc stannate hydrate colloidal aggregate slurry liquid obtained in step (b ′) was removed by washing with 40 liters of water by an ultrafiltration method. 2355 g of zinc stannate hydrate aggregate slurry was obtained. This slurry has a pH of 8.85 and an electric conductivity of 170 μs /
cm.

Step (d '): 9.0 g of a 15 wt% potassium hydroxide aqueous solution was added to the slurry obtained in the step (c').
Was added to adjust the pH to 10.9, and then wet dispersion peptization was performed with a sand glider filled with glass beads (1.0 to 1.2 mmφ) for 24 hours to obtain zinc stannate hydrate sol 5
525 g were obtained. The obtained sol had a pH of 10.95 and an electric conductivity of 471 μs / cm. The obtained sol was further passed through a column packed with an anion exchange resin (IRA-410) to obtain 5883 g of zinc stannate hydrate sol. With stirring, 5.4 g of citric acid and 60 ml of a cation exchange resin (IR-120B) were added to the obtained sol, and after stirring for 1 hour, the resin was separated. The obtained sol had a pH of 4.47 and an electric conductivity of 54.3 μs / cm. The particles of zinc stannate hydrate in this sol had a primary particle diameter of 7 to 15 nm and a ZnO / SnO ₂ molar ratio of 0.95 as observed by a transmission electron microscope. And the general formula xZnO.ySnO
_{In 2} · zH ₂ O, x: y: z is 1: 1.05: 2.
80.

Step (e '): To the sol obtained in the step (d'), 8.1 g of diisobutylamine was added to adjust the pH to 8.
Then, the mixture was concentrated using a 90% post ultrafiltration device to obtain 1582 g of concentrated sol. The obtained sol has a specific gravity of 1.188,
Viscosity 2.8c. p. , PH 7.37, conductivity 1780μ
s / cm, converted to ZnO + SnO ₂ 17.1% by weight
Met.

Step (f '): To 1455 g of the sol obtained in the step (e'), 2.57 of diisobutylamine was stirred.
g, 1.25 g of citric acid to prepare an adjusted sol, which is then placed in a rotary evaporator and methanol 2 under reduced pressure.
806.6 g of zinc stannate hydrate methanol sol by distilling off water in the sol while gradually adding 4 liters
I got The obtained sol has a specific gravity of 1.140 and a viscosity of 2.0.
c. p. , PH (1 + 1) 6.93, conductivity (1 + 1)
302 μs / cm, converted to ZnO + SnO ₂ 30.
The concentration was 8% by weight and the water content was 0.71% by weight. The particles of zinc stannate hydrate in this sol have a primary particle diameter of 7 to 15 nm as observed by a transmission electron microscope, and ZnO / Sn
The O ₂ molar ratio was 0.95. And the general formula xZnO
· YSnO ₂ · zH ₂ O in x: y: z is 1: 1.
It was 05: 2.80. This sol has a refractive index of 1.78 when dried at 110 ° C.
No. 20-1455 and ZnSnO ₃ .3H ₂ O peak pattern.

Comparative Example 1 Sodium stannate (Na ₂ SnO ₃ .3) was added to 2360 g of water.
H ₂ O, Showa Kako Co., Ltd., 55 wt% as SnO ₂
2500 g of an aqueous solution of sodium stannate (containing 3.1% by weight as SnO ₂ )
It was created. Separately, in 2430.3 g of water, zinc chloride (ZnC
₆ 29.7 g of 1 ₂ ) was dissolved to prepare 2500 g of an aqueous zinc chloride solution.

Step (a): The zinc chloride aqueous solution prepared above was added to the sodium stannate aqueous solution for about 1 hour while stirring with a disperser using a metering pump, and reacted to obtain a zinc stannate hydrate colloidal slurry solution. . This is ZnO /
SnO ₂ molar ratio 1.0, ZnO + SnO ₂ 2.3
The concentration was 7% by weight. Step (b): The zinc stannate hydrate colloidal slurry liquid obtained in the step (a) was stirred at 25 ° C. for 2 hours for aging. This product has a pH of 6.85 and an electric conductivity of 20.2 ms /
cm.

Step (c): The excess electrolyte in the zinc stannate hydrate colloidal slurry liquid obtained in step (b) was filtered and decanted to remove water by washing with water. As it was, the sol could not be formed. A transmission electron micrograph of the zinc stannate hydrate particles is shown in FIG. The pH of this slurry was 5.00 and the electric conductivity was 585 μs / cm.

Comparative Example 2 267.1 g of the aqueous solution of sodium zincate prepared in Example 5 was added to 2063.1 g of water and sodium stannate (Na ₂ Sn).
O ₃ · 3H ₂ O, Showa Kako Co., Ltd., 5 as SnO ₂
86.9 g (containing 5% by weight) is dissolved to prepare a mixed aqueous solution of sodium zincate and sodium stannate (1.0 as ZnO).
2% by weight, SnO ₂ as 1.98% by weight, ZnO / S
An nO ₂ molar ratio of 0.95) was prepared to prepare 2417.1 g of a mixed aqueous solution of sodium zincate / sodium stannate.
Separately, 295.7 g of 35 wt% hydrochloric acid was dissolved in 1991.9 g of water to prepare 2287.6 g of a hydrochloric acid aqueous solution.

Step (a '): The hydrochloric acid aqueous solution prepared above is added to a mixed aqueous solution of sodium zincate / sodium stannate for about 1 hour with stirring using a metering pump for about 1 hour to react with zinc stannate hydrate colloid. A slurry liquid of particle aggregates was obtained. This had a ZnO / SnO ₂ molar ratio of 0.95. Step (b '): 210 g of 5 wt% hydrochloric acid was added to the zinc stannate hydrate colloid aggregate slurry liquid obtained in step (a').
After adding and adjusting the pH to 7.07, heating and aging was performed at 90 ° C. for 4 hours. This is ZnO + SnO ₂ .
It was 47% by weight.

Step (c '): Excessive electrolyte in the zinc stannate hydrate colloid aggregate aggregate slurry liquid obtained in step (b') was removed by washing with 12 liters of water by ultrafiltration. . Zinc stannate hydrate aggregate slurry 658
g was obtained. This slurry has a pH of 6.30 and an electric conductivity of 147.
μs / cm. Step (d '): Slurry 30 obtained in step (c')
To 0 g, 1.1 g of 15% potassium hydroxide and 300 g of glass beads (1.0 to 1.2 mmφ) were added and wet-dispersed in a ball mill for 120 hours, but almost no peptization occurred and a sol was not formed. A transmission electron micrograph of this aggregate of zinc stannate hydrate is shown in FIG.

[0087]

The zinc stannate hydrate sol obtained according to the present invention has a primary particle diameter of 2 to 200 nm and high transparency, and its dry film has a refractive index of about 1.7 to 1.9. It also shows good light resistance, weather resistance, antistatic property, abrasion resistance, adhesion and the like. This sol exhibits sufficient stability to be supplied as an industrial product, and can be stably mixed with a resin emulsion, a modacrylic resin, a partial hydrolyzate of a silane coupling agent, or the like.

The sol of the present invention having such properties is
As a component for improving the refractive index, dyeability, chemical resistance, water resistance, light resistance, weather resistance, abrasion resistance, etc. for forming a hard coat film on the surface of plastic molded products such as plastic lenses and films Especially effective. The sol of the present invention can be used for flame retardant aids such as halogen-containing vinyl resins and modacrylic resins, flame retardants for fibers and papers, ultraviolet absorbing microfillers, far infrared emitting microfillers and the like. I can.

Further, the powder obtained by drying the sol of the present invention with a spray drier is useful as a flame retardant for halogen-containing resins, and the anhydrous product obtained by firing this powder at 300 ° C. or higher has a processing temperature of It can also be used as a flame retardant for high engineering plastics.

[Brief description of drawings]

FIG. 1 is a transmission electron micrograph showing a particle structure of a zinc stannate hydrate sol produced in Example 2, which has a magnification of 200,000 times.

FIG. 2 is an X-ray diffraction diagram of a powder obtained by drying the zinc stannate hydrate sol produced in Example 2 at 110 ° C.

FIG. 3 is a differential thermal analysis diagram of a powder obtained by drying the zinc stannate hydrate sol produced in Example 2 at 110 ° C.

FIG. 4 is a transmission electron microscope photograph showing the particle structure of the zinc stannate hydrate sol produced in Example 7, which has a magnification of 200,000 times.

FIG. 5 shows the zinc stannate hydrate sol prepared in Example 1
The X-ray-diffraction measurement figure of the powder obtained by drying at 10 degreeC.

FIG. 6 shows the zinc stannate hydrate sol prepared in Example 1
The differential thermal analysis figure of the powder obtained by drying at 10 degreeC.

FIG. 7 is a transmission electron micrograph showing a particle structure of a zinc stannate hydrate sol produced in Comparative Example 1, which has a magnification of 200,000 times.

8 is a transmission electron micrograph showing the particle structure of the zinc stannate hydrate sol produced in Comparative Example 2, which has a magnification of 200,000.

[Explanation of symbols]

 1 ... A curve showing the results of differential thermal analysis (DTA). 2 ... Curve showing the result of thermogravimetric analysis (TG).

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Neko Iijima 722-1, Tsuboi-cho, Funabashi-shi, Chiba Pref. Nissan Chemical Industry Co., Ltd.

Claims (11)

[Claims] 1. A primary particle size of _{2 to} 200 nm, and x in the general formula xZnO.ySnO ₂ .zH ₂ O:
y: z is 1: 0.83 to 1.43: 1.00 to 5.00
A sol in which particles of zinc stannate hydrate represented by the following molar ratio are dispersed in a liquid medium. 2. The following steps (a), (b) and (c); (a): a zinc salt and a stannate are reacted in the presence of hydrogen peroxide in an aqueous medium to give 0.7 to A step of obtaining an aqueous medium in which colloidal particles of zinc stannate hydrate having a Zn / Sn molar ratio of 1.2 are dispersed, (b): colloidal particles of zinc stannate hydrate obtained in step (a) Is heated at a temperature of 30 to 200 ° C., and (c): the electrolyte is removed from the aqueous medium in which the colloidal particles of zinc stannate hydrate obtained in the step (b) are dispersed. The method for producing a sol according to claim 1, comprising a step. 3. In the step (a), the amount of hydrogen peroxide present in the aqueous medium is 0. _{2 at} a molar ratio of H ₂ O ₂ / Zn.
It is 5 to 20.0, The manufacturing method of Claim 2. 4. In the step (a), the reaction between the zinc salt and stannate in the presence of hydrogen peroxide is an aqueous medium in which an aqueous solution of zinc salt to which hydrogen peroxide solution is added and an aqueous solution of stannate are mixed. The method for producing a sol according to claim 2 or 3, wherein 5. The method for producing a sol according to claim 2, wherein the aqueous medium has a pH of 3 to 12 in step (a). 6. The method according to claim 2, wherein in step (a), the aqueous medium contains oxycarboxylic acid, a salt thereof or a mixture thereof in a molar ratio of 1.5 times or less with respect to Sn in stannate. The method for producing the sol according to claim 5. 7. The following steps (a '), (b'), (c ') and (d'): (a '): zincate and stannate in an aqueous medium in the presence of hydrogen peroxide. Neutralize with acid in Z to 0.7-1.2
a step of obtaining an aqueous medium containing an aggregate of colloidal particles of zinc stannate hydrate having an n / Sn molar ratio, (b '): colloid of zinc stannate hydrate obtained in step (a') Aqueous medium containing agglomerates of particles, 30-2
Heating at a temperature of 00 ° C., (c ′): removing the electrolyte from an aqueous medium containing an aggregate of colloidal particles of zinc stannate hydrate obtained in the step (b ′), and (d) '): A method for producing a sol according to claim 1, which comprises the step of peptizing the aggregate of colloidal particles of zinc stannate hydrate in the aqueous medium obtained in step (c'). 8. The method according to claim 7, wherein in the step (a ′), the amount of hydrogen peroxide present in the aqueous medium is 0.5 to 20.0 in terms of H ₂ O ₂ / Zn molar ratio. Production method. 9. In the step (a ′), the reaction of neutralizing the zincate and the stannate with an acid in the presence of hydrogen peroxide is performed by an aqueous solution containing the zincate and the stannate, and a peroxide. The method for producing a sol according to claim 7 or 8, which is performed in an aqueous medium mixed with an aqueous acid solution added with hydrogen water. 10. In the step (a ′), p of an aqueous medium is used.
H is 3-12, The manufacturing method of the sol of any one of Claim 7 thru | or 9. 11. The step (a ′), wherein the oxycarboxylic acid, a salt thereof or a mixture thereof is contained in the aqueous medium within a molar ratio of 1.5 times with respect to Sn in the stannate. The method for producing the sol according to any one of claims 7 to 10.