JPH06650B2 - Titanium oxide / cerium oxide composite sol and transparent thin film formed from this sol - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a titanium oxide / cerium oxide composite sol excellent in dispersibility in a dispersion medium, long-term stability, light resistance, and the like, and a method for producing the same. It relates to an excellent transparent thin film formed.

[0002]

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION Titanium oxide is used as a compounding agent or surface coating agent for plastics or the like by utilizing its ultraviolet ray shielding power or high refractive index, or as it is compounded in a cosmetic base material and is exposed to ultraviolet rays. It is used in the production of cosmetics with a shielding effect.

Titanium oxide used for these purposes is
Ultrafine particles are preferable, and colloidal titanium oxide (titanium oxide sol) is particularly preferable from the viewpoints of dispersibility in a medium, stability and the like. As such a titanium oxide sol, the present inventors have proposed a titanium oxide sol having various characteristics not found in the conventional titanium oxide sol in "Titanium oxide sol and its manufacturing method" (Japanese Patent Application No. 62-252953).

The inventors of the present invention have conducted extensive studies to obtain a titanium oxide sol having further excellent characteristics, and have found that the titanium oxide / cerium oxide composite sol obtained by a specific method has excellent characteristics. The present invention has been completed.

[0005]

An object of the present invention is to provide a method for producing a titanium oxide / cerium oxide composite sol capable of providing a transparent thin film having a high refractive index as well as an excellent shielding ability against ultraviolet rays in the UV-A region, and It is intended to provide a transparent thin film formed from a composite sol.

[0006]

SUMMARY OF THE INVENTION A titanium oxide / cerium oxide composite sol according to the present invention is prepared by adding hydrogen peroxide to a dispersion of hydrated titanium oxide and hydrated cerium oxide to obtain the hydrated titanium oxide and hydrated cerium oxide. It is characterized by melting and then heating the resulting solution.

The transparent thin film according to the present invention is characterized in that it is formed by containing the titanium oxide / cerium oxide composite fine particles obtained as described above.

[0008]

DETAILED DESCRIPTION OF THE INVENTION A method for producing a titanium oxide / cerium oxide composite sol according to the present invention will be described.

First, in the present invention, a mixed gel or sol of hydrated titanium oxide and hydrated cerium oxide, or a coprecipitated gel or sol of both is prepared. The mixed gel of hydrated titanium oxide and hydrated cerium oxide is, for example, a hydrated titanium oxide gel obtained by neutralizing and hydrolyzing an aqueous solution of a titanium salt such as titanium chloride or titanyl sulfate, and a cerium salt such as diammonium cerium nitrate. It is obtained by mixing with a hydrated cerium oxide gel obtained by neutralizing and hydrolyzing. Alternatively, a hydrated titanium oxide gel or a hydrated cerium oxide gel may be prepared in advance, and an aqueous solution of cerium salt or an aqueous solution of titanium salt may be added thereto for neutralization and hydrolysis to give a mixed gel.

The mixed sol can be obtained by peptizing the mixed gel prepared by the above method with an acid such as nitric acid or hydrochloric acid. The coprecipitated gel of hydrated titanium oxide and hydrated cerium oxide is obtained by neutralizing and hydrolyzing a mixed aqueous solution of titanium salt and cerium salt. Also, if this coprecipitated gel is peptized with an acid, a sol can be obtained. These mixed gels or sols, or coprecipitated gels or sols are not limited to the above methods, and can be prepared by conventionally known methods. In the present specification, “hydrated titanium oxide” and “hydrated cerium oxide” are generic terms including titanium oxide, cerium oxide hydrate, titanium hydroxide, and cerium hydroxide.

The ratio of titanium oxide and cerium oxide in the gel or sol obtained by these methods is such that the CeO ₂ / TiO ₂ (weight ratio) in the final product is at least 0.0.
It is desirable to adjust it to be 5, preferably 0.1. The Ce O ₂ / Ti O ₂ (weight ratio) is less than 0.05, sometimes the effect of adding the cerium oxide does not effectively expressed.

Further, when the proportion of cerium oxide increases,
Since it becomes difficult to dissolve it with hydrogen peroxide in the next step, C
The e O ₂ / Ti O ₂ (weight ratio) is preferably about 20 or less.

Next, hydrogen peroxide is added to the gel and / or sol obtained by the above method to dissolve the hydrated titanium oxide and the hydrated cerium oxide to prepare a uniform aqueous solution. At this time, it is preferable to heat to 50 ° C. or higher. The amount of hydrogen peroxide added is H ₂ O ₂ / (TiO ₂ +
If the CeO ₂ ) (weight ratio) is 1 or more, the hydrated titanium oxide and the hydrated cerium oxide can be completely dissolved. When H ₂ O ₂ / (Ti O ₂ + Ce O ₂ ) is less than 1, hydrated titanium oxide and hydrated cerium oxide may not be completely dissolved and may remain. In addition, H ₂ O ₂ / (Ti O ₂ +
The larger the weight ratio of CeO ₂ ) is, the greater the solubility of hydrated titanium oxide and hydrated cerium oxide is, and the reaction is completed in a short time. However, if too much hydrogen peroxide is used,
A large amount of unreacted hydrogen peroxide remains in the system, which is not economical and may affect the next step. Therefore,
The weight ratio of H ₂ O ₂ / (TiO ₂ + Ce O ₂ ) is 1 to 6,
It is preferably in the range of 2 to 5. When hydrogen peroxide in this range is used, the hydrated titanium oxide and the cerium oxide hydrate are about 0.
It dissolves completely in 5-8 hours.

If the concentrations of hydrated titanium oxide and hydrated cerium oxide are too high, it takes a long time to dissolve them, and undissolved substances are precipitated, or the obtained aqueous solution becomes too viscous. Therefore, the concentration in the aqueous solution after dissolution is (TiO ₂ + C
It is desirable that the amount of eO ₂ ) is about 10% by weight or less, preferably about 5% by weight or less.

Then, the aqueous solution is adjusted as it is or after the (TiO ₂ + Ce O ₂ ) concentration is adjusted by adding water to the aqueous solution, and then heated to 60 ° C. or higher, preferably 80 ° C. or higher for hydrolysis. . By doing so, a titanium oxide / cerium oxide composite sol in which particles of composite titanium oxide and cerium oxide are dispersed can be obtained.

The term "titanium oxide / cerium oxide composite sol" as used herein means a mixed sol of titanium oxide particles and cerium oxide particles, a state in which titanium oxide and cerium oxide are chemically bound, that is, in the crystal structure of titanium oxide. In which some of the titanium atoms in the above were replaced with cerium atoms, or a sol in which composite oxide particles in which cerium atoms were confined between titanium oxide crystal lattices were dispersed or titanium oxide and cerium oxide were physically bound It means a sol in which single particles are dispersed or a mixed sol of these.

The sol obtained by the above method is about 4
The sol is a stable sol in which fine particles having an average particle diameter in the range of ˜300 mμ are dispersed and has excellent light resistance. However, for the purpose of further improving the long-term stability and light resistance of the produced sol, an aqueous solution dissolved in hydrogen peroxide is used. Alternatively, the sol can be produced by heating and hydrolysis in the presence of a specific inorganic compound. That is, Group II of the periodic table such as Zn and Group II of Al
One or more elements selected from Group I, Group IV such as Ti, Zr, Si and Sn, Group V such as V and Sb, Group VI such as W and Group VIII such as Fe After mixing the inorganic compound and the above aqueous solution, the obtained mixture is heated to 60 ° C. or higher to be hydrolyzed.

The above inorganic compounds include salts, oxides,
It is used in the form of hydroxide or oxyacid or oxyacid salt. When the above-mentioned oxyacid salt is used, it is preferable to use it after desalting the oxyacid salt with a cation exchange resin or the like. These inorganic compounds may be used in solid form or as an aqueous solution, but are preferably used in the form of gel or sol. When the inorganic compound is used in the form of a sol, the average particle size of dispersed particles is about 30 m.
It is desirable that the thickness is μ or less, preferably about 15 mμ or less. For example, in the case of silicon, an alkali silicate,
Silica gel, silica sol or silicic acid solution is used. Here, the silicic acid solution means a low-polymerized solution of silicic acid obtained by dealkalizing an aqueous alkali silicate solution by an ion exchange method or the like.

When the mixing amount of the inorganic compound is increased, the long-term stability and light resistance of the obtained sol are improved, and a sol having a high concentration can be obtained. However, after these effects reach a predetermined level, even if the mixing amount of the inorganic compound is further increased, the effect of improving long-term stability, light resistance, etc. does not increase. On the other hand, if the amount of the inorganic compound mixed is small, the effect of mixing the inorganic compound may not be exhibited.

In consideration of the above, the amount of the inorganic compound to be mixed is determined by adding hydrogen peroxide to the dispersion liquid of hydrated titanium oxide and cerium oxide oxide, and adding the hydrated titanium oxide and cerium oxide oxide. A value obtained by converting the weight of titanium and cerium in an aqueous solution obtained by dissolution (hereinafter referred to as a hydrogen peroxide-dissolved aqueous solution) into (TiO ₂ + Ce O ₂ ) and the weight of the inorganic compound into an oxide (MO _x ). Ratio with value (T
i O ₂ + Ce O ₂ ) / MO _x (weight ratio) is 0.25 to
It is preferably in the range of 200.

The method for mixing the hydrogen peroxide-dissolved aqueous solution and the inorganic compound is not particularly limited, and a predetermined amount of the hydrogen peroxide-dissolved aqueous solution and the inorganic compound may all be mixed at a time.
Alternatively, the hydrogen peroxide-dissolved aqueous solution and a part of the inorganic compound may be first mixed and heated, and the rest of both may be added as the reaction proceeds. Further, a method in which the whole amount of the inorganic compound and a part of the hydrogen peroxide-dissolved aqueous solution are first mixed and heated, and then the remaining aqueous solution is added may be used.

The inorganic compound is not necessarily mixed after the hydrated titanium oxide and the hydrated cerium oxide are dissolved in the hydrogen peroxide, but is mixed at the gel or sol stage before being dissolved in the hydrogen peroxide. Alternatively, they may be mixed at the time of preparing a gel or sol of hydrated titanium oxide and cerium hydrate. In short, it is sufficient that the above-mentioned inorganic compound is present in the reaction system when the aqueous solution after being dissolved in hydrogen peroxide is heated and hydrolyzed.

In the titanium oxide / cerium oxide composite sol thus obtained, particles having an average particle diameter of 4 to 300 mμ are dispersed in an aqueous dispersion medium, and the dispersibility, long-term stability and light resistance are improved. It is an excellent and stable sol in a wide pH range (3 to 12).

The titanium oxide / cerium oxide composite sol obtained by the production method according to the present invention can be directly used for various purposes, but it may be appropriately prepared by a known method such as vacuum evaporation and ultrafiltration. It can also be used after being concentrated to a concentration. In addition, depending on the use, it can be mixed with an organic solvent such as alcohol or glycol or solvent-substituted to obtain an organic solvent-dispersed sol.

Further, even if the titanium oxide / cerium oxide composite sol of the present invention having water as a dispersion medium is mixed with an organic solvent such as alcohol, glycol, glycerin, or solvent substitution, the composite sol has an interface. It is very stable without the addition of activators. Therefore, the composite sol according to the present invention can also be used as an organic sol using the above organic solvent as a dispersion medium.

[0026]

The titanium oxide / cerium oxide composite sol according to the present invention is extremely stable in a wide pH range of 3 to 12, and is a sol in which fine particles having a particle size in the range of 4 to 300 mμ are uniformly dispersed. Excellent in stability, long-term stability and light resistance. In addition, since it contains cerium oxide, 320
It also has an excellent shielding effect against ultraviolet rays in the range of 400 nm, particularly in the range of 340 to 380 nm, as compared with titanium oxide sol having the same concentration.

The titanium oxide / cerium oxide composite sol according to the present invention can be used for various purposes by utilizing the above characteristics. Mixing a water-dispersed sol with an organic solvent or solvent substitution to form an organic solvent-dispersed sol and using this as a compounding agent for plastics and paints can prevent deterioration of plastics by ultraviolet rays and discoloration of pigments in paints. You can expect an effect. Further, when blended with a plastic film for food packaging, it can be stored for a long period of time as compared with conventional packaging materials. Dispersion in raw material plastic for contact lenses (for example, HEMA) produces contact lenses that have the effect of protecting the retina by ultraviolet rays.

A coating solution prepared by mixing and dispersing the above-mentioned organic solvent-dispersed sol in a coating solution for forming a transparent film is applied to glass,
If a transparent thin film is applied to the glass surface, an ultraviolet shielding glass can be obtained. In addition, by utilizing the fact that titanium oxide / cerium oxide in the composite sol according to the present invention has a high refractive index, a coating liquid containing the composite sol according to the present invention is applied to a plastic lens, and the surface is coated. A high refractive index lens can be made by forming a transparent thin film.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0030]

Example 1 5 g of cerium chloride and Ti as Ce O ₂
Dissolve 5 g of titanium tetrachloride as O ₂ in pure water to obtain 10
A mixed aqueous solution of 00 g was prepared. Aqueous 15% ammonia water was gradually added to this to obtain a coprecipitated gel of hydrated titanium oxide and hydrated cerium oxide.

The coprecipitated gel thus obtained was dehydrated and washed, and then 110 g of this coprecipitated gel was added with 115 g of 35% hydrogen peroxide and 25 g of pure water and then heated to 80 ° C. 250 g of a yellowish orange brown transparent aqueous solution of hydrogen peroxide was obtained. P of this hydrogen peroxide solution
H was 8.7. This aqueous solution is converted into an oxide (TiO ₂ +
The mixture was diluted with pure water to 0.1% by weight as CeO ₂ ) and then heated at 95 ° C. for 96 hours. After 96 hours, a pale yellowish-white transparent titanium oxide / cerium oxide composite sol was obtained. The pH of this sol is 6.8 and the minimum is 6m.
Microparticles having a particle size of μ and a maximum of 20 mμ were dispersed, and the specific surface area (BET method) of this particle was 256 m ² / g. Further, it was stable even when this sol was concentrated to a concentration of 20% by weight (Ce O ₂ + Ti O ₂ ) by a vacuum evaporation method.

A part of the sol obtained above was diluted as an oxide (TiO ₂ + Ce O ₂ ) to a concentration of 0.05% by weight, and the diluted sol was placed in a quartz cell having a thickness of 1 mm to obtain a spectrophotometric value. The light transmittance of 260 to 500 nm was measured with a meter (type 330 manufactured by Hitachi, Ltd.).

The results are shown in FIG. 1 (curve A). The coating solution containing the sol thus obtained was coated on a plastic lens to form a transparent thin film on the plastic surface.

[0034]

Example 2 250 g of a hydrogen peroxide-dissolved aqueous solution obtained in the same manner as in Example 1 was mixed with 15 g of silica sol having an average particle size of 7 mμ and a SiO ₂ concentration of 10% by weight and 9.7 kg of pure water. It heated at 150 degreeC for 10 hours. After 10 hours, a pale yellowish-white transparent titanium oxide / cerium oxide composite sol was obtained. The pH of this sol is 7.3, the dispersed particle size is 7 to 21 mμ, and the specific surface area of the particles is 26.
It was 6 m ² / g. This sol was stable even when concentrated to 27% by weight in the same manner as in Example 1. The light transmittance measured by the same method as in Example 1 was almost the same as in Example 1.

[0035]

Example 3 As Ce O ₂ , 10 g of ceric ammonium nitrate was dissolved in pure water to prepare a 0.5 wt% aqueous solution of Ce O ₂ . Add 15% ammonia water to this, p
After H was gradually added to 9.0, dehydration and washing were carried out to obtain 100 g of hydrous cerium oxide gel. 112 g of 5 wt% hydrochloric acid was added thereto to dissolve the hydrated cerium oxide.

[0036] Then, Ce O ₂ / Ti O ₂ to the aqueous solution
After adding the titanium tetrachloride aqueous solution so that it became = 1 (weight / weight), 15% ammonia water was gradually added to adjust pH to 8.0. The mixed gel of hydrated titanium oxide and hydrated cerium oxide thus obtained was dissolved in hydrogen peroxide in the same manner as in Example 1. As a result, a pale yellow-orange brown transparent peroxide having a pH of 9.2 was dissolved. 500 g of a hydrogen-dissolved aqueous solution was obtained.

Next, 500 g of this hydrogen peroxide-dissolved aqueous solution
Then, 780 g of a silicic acid solution (5% by weight of SiO ₂ ) obtained by dealkalizing an aqueous solution of water glass with a cation resin and 720 g of pure water were mixed and then heated to 172 ° C. When heated for 16 hours, a pale yellowish milky white titanium oxide / cerium oxide composite sol having a pH of 7.5 was obtained. The particle size of the dispersed particles in this sol was in the range of 7 to 19 mμ, and the specific surface area of the particles was 243 m ² / g.

In addition, (Ce O ₂ + Ti O ₂ ) 25% by weight
20 g of concentrated sol and 5 g of carbopol were added to pure water 75
After uniformly dissolving the liquid dissolved in g, a 5 μm thick film was formed on a quartz plate with a doctor blade, and the light transmittance was measured with a spectrophotometer (Model 330 manufactured by Hitachi, Ltd.).

The results are shown in FIG. 2 (curve A).

[0040]

Example 4 In Example 3, Ce O ₂ / Ti O ₂ =
Example 3 was repeated except that 1 (weight / weight) was changed to 4, resulting in a pH of 6.8 and a dispersed particle size of 6 to 4
A composite sol having a particle size of 0 mμ and a particle specific surface area of 350 m ² / g was obtained. The sol was stable even when concentrated to 30% by weight. The light transmittance of the sol measured by the same method as in Example 3 is shown in FIG. 2 (curve B).

[0041]

Example 5 As CeO ₂ , 10 g of ceric ammonium nitrate was dissolved in pure water to prepare a 2.0 wt% aqueous solution of CeO ₂ . Add 15% ammonia water to this, p
After H was gradually added to 9.0, dehydration and subsequent washing gave 118 g of hydrated cerium oxide gel. To this, 130 g of 5 wt% hydrochloric acid was added to dissolve the hydrated cerium oxide. Then add Ce to this aqueous solution.
An aqueous titanium tetrachloride solution was added so that O ₂ / Ti O ₂ = 1/9 (weight / weight), and then 5% ammonia water was gradually added to adjust the pH to 8.4. When the mixed gel of hydrated titanium oxide and hydrated cerium oxide thus obtained was dissolved in hydrogen peroxide in the same manner as in Example 1, the pH was
Was 9.2, and 250 g of a pale yellow-orange brown transparent aqueous solution was obtained.

Then, in the same manner as in Example 2, the pH was 7.
A titanium oxide / cerium oxide composite sol of No. 8 was obtained.
The particle size of the dispersed particles was 4 to 25 mμ, and the specific surface area of the particles was 180 m ² / g.

[0043]

Example 6 A titanium oxide / cerium oxide composite having a pH of 6.5 in the same manner as in Example 5 except that Ce O ₂ / Ti O ₂ was changed to 9.5 / 0.5 (weight / weight). A system sol was obtained. (Dispersion particle size = 4 to 65 mμ, particle specific surface area 170
m ² / g).

[0044]

Comparative Example 1 Titanium sulfate was dissolved in pure water to obtain an aqueous solution containing 0.4% by weight of TiO ₂ . While stirring this aqueous solution, gradually add 15% aqueous ammonia,
A white slurry solution of 8.5 was obtained. The slurry was filtered and then washed to obtain a hydrated titanium oxide gel cake having a solid content concentration of 9% by weight.

After adding 610 g of 33% hydrogen peroxide solution and 1300 g of pure water to 550 g of this cake, the mixture was heated at 80 ° C. for 5 hours.
After heating for 2.5 hours, a 2.0 wt% solution of TiO ₂ 2.5
I got Kg. This aqueous solution was yellowish brown and had a pH of 8.1.
Met.

Next, 13 g of silica sol having a particle size of 7 mμ and a concentration of 15% by weight, and 900 g of the above aqueous solution.
After being mixed with 1000 g of pure water, the mixture was heated at 95 ° C. for 624 hours. The solution was initially a yellowish brown liquid, but after 624 hours, a milky white transparent titanium oxide sol was obtained. The average particle size of the dispersed particles of this sol was 24 mμ.

A part of the obtained titanium oxide sol was diluted with pure water to have a TiO ₂ concentration of 0.05% by weight, and the light transmittance was measured by the same method as in Example 1. The results are shown in Fig. 1 (curve B).

As is clear from the comparison of the curves A and B, the titanium oxide / cerium oxide composite sol of the present invention is more UV-A-specific than the titanium oxide sol containing no cerium oxide.
It can be seen that the ultraviolet ray shielding effect in the region is excellent.

[Brief description of drawings]

1 is a curve showing a light transmittance of a titanium oxide / cerium oxide composite sol according to the present invention, and a curve B is a curve showing a light transmittance of a titanium oxide sol.

FIG. 2 is a curve A showing Ce O _{2 according} to the present invention.
/ Ti O ₂ = 1 (weight / weight) is a curve showing the light transmittance of a titanium oxide / cerium oxide composite sol, and curve B is similarly a titanium oxide / cerium oxide of Ce O ₂ / Ti O ₂ = 4. It is a curve which shows the light transmittance of a composite sol.

Claims (5)

[Claims] 1. A method comprising adding hydrogen peroxide to a dispersion of hydrated titanium oxide and hydrated cerium oxide to dissolve the hydrated titanium oxide and hydrated cerium oxide, and then heating the resulting solution. And a method for producing a titanium oxide / cerium oxide composite sol. 2. A hydrogen peroxide is added to a dispersion liquid of titanium and cerium oxide hydrate to dissolve the titanium oxide hydrate and cerium oxide hydrate, and the resulting solution is then added to the periodic table II.
Titanium oxide characterized by heating in the presence of an inorganic compound of one or more elements selected from Group III, III, IV, V, VI and VIII Method for producing cerium oxide composite sol. 3. A titanium oxide / cerium oxide composite sol produced by the method of claim 1 or 2. 4. A transparent thin film containing titanium oxide / cerium oxide composite fine particles. 5. A method for producing a transparent thin film, which comprises applying a coating solution containing the titanium oxide / cerium oxide composite sol produced by the method according to claim 1 or 2 to a substrate.