JPH10273319A - Binder for metal oxide sol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a binder capable of coating a metal oxide sol without requiring specific treating facilities, in forming a film for sufficiently exhibiting optical functions of a metal oxide sol selected from titanium, cerium, niobium and tantalum with respect to a binder for the metal oxide sol. SOLUTION: Since this binder for a metal oxide sol is selected from titanium, cerium, niobium and tantalum, comprising a basic alkali metal stannate having a composition in a range of M/Sn (M is an alkali metal) of 0.05-0.5 (molar ratio), in forming a film for sufficiently exhibiting optical functions of a metal oxide sol, the metal oxide sol can be coated with requiring specific treating facilities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder for a metal oxide sol, and particularly to a binder for forming a thin film for sufficiently exhibiting an optical function of a metal oxide sol selected from titanium, cerium, niobium and tantalum. An object of the present invention is to provide a binder capable of coating these metal oxide sols without requiring any processing equipment.

[0002]

2. Description of the Related Art Properties specific to elements such as titanium, cerium, niobium, and tantalum, such as ultraviolet absorbing ability, photocatalytic ability,
Conventionally, only a vapor deposition method has been used as a method for producing a transparent thin film for sufficiently exhibiting functions such as infrared reflectivity. However, this method is unsuitable for large-sized substrates, and even if applicable, it is difficult to produce it in large quantities and at low cost, and it can only be used for special small members.

[0003] Sols such as titanium, cerium, niobium, and tantalum have been developed, and it has been found that when these are used, a transparent thin film can be obtained by a coating method like a paint.
The film strength is weak only by coating and drying, and sufficient film strength cannot be obtained even after baking (heat treatment).
The improvement was desired.

Accordingly, the present inventors have studied a method using a binder as a simple and industrial method for improving film strength.
When water glass is mixed with sols such as titanium, cerium, niobium, and tantalum, the compatibility is poor and a transparent film cannot be produced.When a metal oxide sol such as silica sol is used, a simple mixture of sols is used. However, it did not lead to improvement of the film strength. Hydrolysis products of alkoxysilane were also examined, but although some improvement effects were seen, the film strength was not sufficient because of the sol-gel method. Poor solubility, many restrictions when finishing into a coating agent, making it impractical.

[0005]

SUMMARY OF THE INVENTION UV absorption, photocatalyst,
As applications using functions such as infrared reflection have expanded,
There is an increasing demand for transparent thin films having high strength, and moreover, for outdoor use, water resistance is also required. However, as described above, a thin film made of only sol cannot cope with these new uses. In particular, for ultraviolet absorption and photocatalyst applications, the inorganic composition must be inorganic in view of weather resistance and oxidative decomposition by the photocatalyst.
At present, nothing satisfying these demands has been obtained.

[0006]

In such a situation, the present inventors have focused on a solution of a basic salt as a binder which is excellent in transparency and can be mixed with a metal oxide sol. As a result of examining the strength development, it was found that the basic alkali metal stannate satisfies the above required conditions.

[0007] By the way, the following documents are known as sols using tin compounds, and the following contents are described respectively. JP-A-63-185820
Patent Publication No. 1 discloses a technique for modifying a titania sol by adding a silicon compound or a zirconium compound to a titania sol precursor. Is described.

[0008] Japanese Patent Publication No. 87446/1993 discloses an inorganic compound selected from one or more of the elements of Groups III, IV, V, VI and VII of the periodic system. A method for producing a modified titanium oxide sol by heating an aqueous titanic acid solution obtained by adding hydrogen peroxide to a hydrous titanic acid gel or sol in the presence of and dissolving the hydrous titanic acid has been described. I have. Japanese Patent Publication No. 4-27168 discloses a crystalline titanium oxide-tin oxide sol in which titanium oxide and tin oxide are dissolved. JP 63-35668
The publication describes a method of producing a sol containing colloid particles by gradually hydrolyzing an aqueous solution of a tin compound, and then drying and calcining the sol, followed by grinding to obtain a conductive fine powder. .

Japanese Patent Application Laid-Open No. 2-120374 discloses that an aqueous solution of an acid salt of indium or tin or a mixed solution of both of them and an aqueous alkali solution is reacted with an aqueous solution of 240 to 320 in a reducing atmosphere.
There has been disclosed a method for producing transparent conductive ultrafine particles, which is characterized by heating to ° C. JP-A-52-100554 discloses an example of using a tin compound as a binder. The present invention relates to a binder having excellent water resistance and strength in a transparent functional thin film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The binder for a metal oxide sol of the present invention will be described in more detail below. The method for producing a basic alkali metal stannate of the present invention will be described.Aqueous solution of an acidic stannate such as tin chloride is hydrolyzed with an alkaline aqueous solution such as ammonia water, and the obtained tin hydroxide gel is purified. Wash well to remove by-product salts as much as possible. M / Sn (provided that the tin hydroxide gel thus obtained is
M represents an alkali metal) = Alkali metal hydroxide such as sodium hydroxide, lithium hydroxide, potassium hydroxide or the like is added so as to be 0.05 to 0.5 (molar ratio) to dissolve the gel.

When M / Sn (molar ratio) is low, it can be dissolved at an early stage by heating. When an alkaline stannate such as a commercially available sodium stannate is used, a basic stannic acid having a predetermined M / Sn (molar ratio) is obtained by subjecting the cation exchange resin to a dealkali metal treatment. An aqueous alkali metal salt solution can also be obtained. There is no particular limitation on the concentration of the basic alkali metal stannate aqueous solution, but it is preferable to use tin oxide at about 10 to 15% by weight.

The composition of the basic alkali metal stannate is M /
Sn = 0.05 to 0.5 (molar ratio), but M / Sn
If it is less than 0.05 (molar ratio), the binding strength is weak, and it is not sufficient as a binder. When M / Sn = 0.5 (molar ratio) or more, the salt concentration becomes high, so that the compatibility with the sol becomes poor and a transparent film cannot be obtained. Examples of the type of the alkali metal include lithium, sodium, and potassium, and lithium is most preferable from the viewpoint of the strength and water resistance of the thin film.

Metal oxide sol selected from titanium, cerium, niobium and tantalum (hereinafter referred to as metal oxide sol)
Is preferably an alkali-stable sol. Generally, when a neutral or acidic stable sol is used, when mixed with a basic alkali metal stannate, the sol gels,
When this is used as a coating agent, a transparent thin film cannot be obtained.

However, when a neutral or acidic stable sol must be used, a dilute neutral or acidic stable sol is slowly added to a dilute aqueous solution of a basic alkali metal stannate while stirring. As a result, a stable coating agent that does not show gelation can be obtained. After that, it is concentrated and used at a concentration that can be practically used.

As for the mixing ratio between the binder and the metal oxide sol, when the function of the metal oxide sol is emphasized, the usage ratio of the binder (solid content) is 5 in total with the sol (solid content).
10 to 10% by weight is desirable.
-60% by weight, especially 40-50% by weight is desirable. The larger the M / Sn (molar ratio) of the basic alkali metal stannate, the easier it is to gel and the more difficult it is to form a transparent film.
Therefore, it is necessary to adjust the mixing ratio.

As described above, it is desirable to change the mixing ratio depending on the application and the desired strength. Although not particularly limited, the mixing ratio is approximately 5 to 60% by weight. If it is less than 5% by weight, the bonding strength with the sol particles is weak, and if it is more than 60% by weight, the transparency of the sol is lowered and it is not practical.

When the binder of the present invention is mixed with a metal oxide sol and used as a coating agent, it may be merely applied to a substrate and dried. However, in order to fully exert the function of the binder. , It is desirable to perform a heat treatment, and by performing the heat treatment at 300 ° C. or more, the water resistance and the film strength are remarkably improved. The binder of the present invention exerts its effects best when the metal oxide sol is used as a coating agent, as is clear from the above description,
Particularly, it is suitable as a coating agent for outer walls of glass, buildings and the like, tiles, tiles, plastics and the like.

The binder for a metal oxide sol according to the present invention can be used as a coating agent by mixing it with a metal oxide sol, and can also be used as a coating material by adding various applications to these.

Hereinafter, the present invention will be described in more detail with reference to Examples. All percentages are by weight unless otherwise specified.

【Example】

(Example 1) Aqueous stannic chloride solution (SnO ₂ = 17.6%) 10
00 g of an aqueous solution of ammonium bicarbonate (NH ₃ = 3.0%) 34
94 g is added gradually with stirring to form a tin gel. At this time, the pH of the gel solution was 7.2. This gel was washed well, and washed until no chloride ion was recognized in the gel by qualitative analysis of chloride ion with silver nitrate. As a result, 545 g of a gel containing SnO ₂ = 32.1% and NH ₃ = 0.4% was obtained. To 100 g of this gel, 1.7 g of sodium hydroxide and 540 g of water were added and dissolved by heating at 90 ° C. for 2 hours to obtain a basic sodium stannate solution (Na / Sn).
(Molar ratio) = 0.2, SnO ₂ = 5%) 640 g was obtained. An alkali-stable cerium oxide sol (CeO ₂ = 10%) 10 stabilized with metaphosphoric acid was added to 50 g of the basic sodium stannate solution.
0 g was added to prepare an ultraviolet absorbing coating agent.

This coating agent was spray-coated on a transparent glass plate (thickness: 1 mm), dried at 100 ° C., and baked at 300 ° C. for 20 minutes. The coating thickness was 0.6 μm, and the transmittance of visible light was 98%. The film strength of this glass plate was measured by the general paint test method (J
As a result of measurement by IS K5400, Section 8-4, Pencil Scratch Value Tester Method, the pencil strength was 6H. Also,
For boiling water resistance, paint general test method (JIS K5)
As a result of performing the test according to the method described in No. 400 (8-8-20 boiling water resistance), no abnormality was found.

(Comparative Example 1) No. 3 water glass (SiO ₂ = 29)
%, Na = 7.3%) To 2100 g of water was added 100 g of water, and 232 g of 5% hydrochloric acid was gradually added to the diluted water glass with stirring to form silica gel. Sodium hydroxide on 100 g of fully washed silica gel (SiO ₂ = 7.5%)
0.97 g and water 49 g were added, and the mixture was heated and dissolved at 90 ° C. for 2 hours, and a basic sodium silicate solution (Na / Si (molar ratio) = 0.
(2, SiO ₂ = 5%) 150 g was obtained. 100 g of the sol of Example 1 was added to 50 g of the basic sodium silicate solution to prepare an ultraviolet absorbing coating agent. This coating agent was coated on a glass plate and baked in the same manner as in Example 1. Although the pencil hardness was 6H, in the boiling water test, the film was peeled off and did not have water resistance.

Example 2 Tin gel 10 obtained in Example 1
Then, 2.7 g of lithium hydroxide monohydrate and 218 g of water were added to 0 g, and the mixture was heated and dissolved at 90 ° C. for 2 hours, and a basic lithium stannate solution (Li / Sn (molar ratio) = 0.3, SnO ₂ = 10 %) 320
g was obtained. 66 g of this basic lithium stannate solution was added to 1000 g of an alkali-type titanium oxide sol (TiO ₂ = 6%) stabilized with an amine to prepare a photocatalytic coating agent. The glass plate of a 600 × 300 × 1.4 mm tunnel illuminator was brush-painted, and the solution was erected to remove excess liquid.
After natural drying, this was baked at 500 ° C. for 1 hour. The film thickness was 0.35 μm, and although interference colors were observed, a coat film having excellent transparency was obtained. The pencil hardness was 6H. 9
As a result of performing a boiling water test at 0 ° C. for 2 hours, there was no abnormality in the coating film. Further, the above glass piece was cut into 50 × 50 mm, and the glass piece was cut into 64 ml of 50 ppm acetic acid aqueous solution.
And irradiated with 6 W of black light (0.2 mW / cm ² of ultraviolet ray on the surface of the test piece) for 5 hours. As a result of analyzing the acetic acid concentration after irradiation, it was found to be 39 ppm, indicating an excellent photocatalytic activity.

Example 3 Potassium stannate solution (SnO ₂ = 3)
%) Was passed through a column containing a cation exchange resin (trade name “Amberlat IR-120B” manufactured by Organo Co., Ltd.).
A stannic acid solution (SnO ₂ = 2.5%) was obtained. 25 g of an aqueous potassium hydroxide solution (KOH = 0.8%) was added to 100 g of this solution, dissolved by heating, and a basic potassium stannate solution (K / Sn (molar ratio)) was added.
= 0.2, SnO ₂ = 2%). 8 g of this basic potassium stannate solution was mixed with 50 g of an alkali-stable tantalum sol (Ta ₂ O ₅ = 3%) stabilized with citric acid to prepare an infrared reflective coating agent. This coating agent was spin-coated on a slide glass and dried at 100 ° C. Thickness is 0.1μm, spectral energy distribution 1000 ~ 2
10% was reflected at an integration of 500 nm. The pencil hardness was 4H. The coating film was not abnormal in appearance, but the pH of the immersion water was increased by 0.4. When the slide glass after drying at 100 ° C. was baked at 300 ° C. for 1 hour, the pencil hardness was 6H, the coating film was of course normal in appearance, and the pH of the immersion water did not increase.

(Examples 4 to 8) In the same manner as in Example 2, a basic lithium stannate solution having a different Li / Sn molar ratio was prepared, and a coating agent was prepared in the same manner as in Example 2. Using this, a thin film (0.
4 μm) and heat-treated at 500 ° C. The physical properties of the thin films were measured.

[0025]

[Table 1] Paint general test method (JIS K5400) Pencil hardness: Section 8-4 Pencil scratch value tester Cross-cut test: Section 8-5 Cross-cut tape method Abrasion test: Number of times until rubbing and peeling off with tissue paper *: Amine-stabilized alkaline titanium oxide sol alone

(Example 9) The photocatalyst coating agent prepared in Example 2 has poor flexibility because it is a completely inorganic substance. A one-part cross-linkable acrylic emulsion (trade name "SC-509B" manufactured by Nippon Shokubai Co., Ltd.) at a solid content ratio of 10% was added to the coating agent. Because of the small amount of the acrylic emulsion, the choking of the weather resistance deterioration of the acrylic emulsion by the photocatalyst was not so noticeable, and the titanium particles were substantially reduced by the basic lithium stannate. It was fixed to the film, and there was almost no decrease in strength.

Example 10 40 g of the basic lithium stannate solution of Example 2 and 100 g of an alkaline niobium oxide sol (4% Nb ₂ O ₃ ) stabilized with citric acid were mixed well to prepare a coating agent. . This coating agent was spray-coated on a transparent glass plate and baked at 400 ° C. for 1 hour to form a thin film having a thickness of 0.9 μm on the glass plate. The pencil hardness of this thin film was 7H.

[0028]

The binder for a metal oxide sol according to the present invention comprises titanium, cerium, and the like comprising a basic alkali metal stannate.
Niobium, a binder for a metal oxide sol selected from tantalum, for example, a photocatalytic function of the metal oxide sol,
In the formation of thin films for fully exhibiting various functions such as ultraviolet absorbing ability, it is possible to form a film with high film strength without requiring special processing equipment, and it is excellent in water resistance, transparency and baking. When the treatment is performed, the water resistance and the film strength are further improved. The metal oxide sol binder of the present invention exerts its effects best when used as a coating agent for glass, plastic, outer walls, tiles, tiles, etc., or as a paint.

Claims (2)

[Claims] 1. A binder for a metal oxide sol selected from titanium, cerium, niobium and tantalum comprising a basic alkali metal stannate salt. 2. The composition of a basic alkali metal stannate having a composition of M
/ Sn (where M represents an alkali metal) = 0.05 to 0.
The binder for a metal oxide sol according to claim 1, wherein the binder is in a range of 5 (molar ratio).