JPH0339017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydrophobic rutile type fine particle titanium oxide.

Titanium oxide has a high refractive index and is used as a white pigment in many fields. Furthermore, titanium oxide has unique absorption and scattering properties for ultraviolet rays. These titanium oxides have a particle size that exhibits the best hiding power for each application as a white pigment, but as the distance between the particle sizes becomes larger than the optimum diameter, the hiding power decreases, especially in the direction smaller than the optimum diameter. The bigger it gets,
It is known that this tendency becomes remarkable.

Utilizing these properties, titanium oxide with a small particle size is used as a transparent or relatively transparent ultraviolet shielding agent. In this case, the degree of transparency and the UV-shielding effect are determined by the particle size, and the transparency increases inversely with the particle size.
There are other useful uses for fine-particle titanium oxide, taking advantage of its large specific surface area.

As is well known, there are two types of titanium oxide: anatase type and rutile type. The anatase type is photochemically active, and its properties such as weather resistance and light resistance are inferior to the rutile type. Rutile-type titanium oxide is produced by vapor-phase thermal decomposition of titanium tetrachloride, the so-called chlorine method, and also by the sulfuric acid method, in which hydrolyzed titanium oxide obtained by hydrolyzing a titanyl sulfate solution is calcined at high temperatures. In addition, in this sulfuric acid method, in order to facilitate the transition to rutile type by firing,
It is common practice to add substances that promote metastasis. The rutile-type titanium oxide produced in this way is used in a variety of applications as a white pigment with excellent hiding power, weather resistance, and light resistance, and its particle size varies from 0.15 to 0.4 μm depending on each application. It is generally within the range of .

However, rutile-type fine particle titanium oxide, which is transparent or relatively transparent and exhibits excellent UV-shielding properties, must be significantly smaller than the particle size of titanium oxide, which is generally used as a white pigment, and the maximum However, it is generally less than 0.1 μm.
Must be in the range 0.005-0.1 μm. However, it is extremely difficult to produce such rutile-type fine particle titanium oxide with a particle size of 0.1 μm or less using the sulfuric acid method, which is a common manufacturing method for rutile-type titanium oxide used as a white pigment. .

The present inventors have discovered that rutile-type titanium oxide obtained by hydrolyzing titanyl sulfate solution, titanium tetrachloride solution, etc. is treated with caustic alkali, and heated in hydrochloric acid. Focusing on titanium sol, which has a crystalline structure, we attempted to produce rutile-type fine particle titanium oxide.

treating the hydrous titanium oxide with caustic alkali,
Titanium sol, which has a rutile-type crystal structure obtained by aging in hydrochloric acid, is basically added as a nuclear material to promote the transition to rutile-type by calcination during the production of titanium oxide using the sulfuric acid method. However, until now, it has not been used as a raw material for producing rutile-type fine particle titanium oxide. The reason is that this is not necessary when used as a nuclear material that promotes the transition to a rutile type by firing, but in order to use it as a rutile type fine particle titanium oxide, it is necessary to separate and purify it. This is thought to be because it is extremely difficult. That is, the titanium sol having the rutile crystal structure generally has a crystal structure of 100 to 200
It is made of rutile-type fine titanium oxide with a specific surface area of m ² /g. This rutile-type fine titanium oxide has a strong affinity with water and forms a strong hydration layer with water molecules. Therefore, filtration and washing operations are extremely difficult, and extremely strong adhesion occurs during drying, making redispersion difficult.

In the present invention, a fatty acid having 7 or more carbon atoms or a water-soluble salt thereof is reacted with a water-soluble polyvalent metal salt in the titania sol dispersion, and titanium oxide is dispersed using the polyvalent metal salt of the fatty acid produced. By coating the particles, filtration and washing with water are facilitated, and firm adhesion during drying is prevented, so that hydrophobic rutile type fine particle titanium oxide can be easily obtained.

That is, according to the present invention, the surface of the fine rutile-type titanium oxide dispersed particles in the titania sol is made of hydrophobic fatty acids produced by the reaction of the fatty acid or its water-soluble salt with a water-soluble polyvalent metal salt. As the particles are coated with polyvalent metal salts, the dispersed particles of titanium oxide become hydrophobic and have no affinity for water.
Since the formation of a strong hydration layer with water molecules does not occur, subsequent filtration and washing become easier. In addition, strong adhesion of titanium oxide, which makes redispersion difficult during drying, does not occur. The obtained microparticle titanium oxide becomes hydrophobic by coating its surface with a polyvalent metal salt of a hydrophobic fatty acid, which eliminates the formation of a hydration layer with water, making it easier to unravel and , the dispersibility in paints and resins is improved, resulting in better transparency and ultraviolet shielding properties.

Examples of fatty acids or water-soluble salts thereof that can be used in the present invention include fatty acids having a carbon number such as capric acid, lauric acid, myristic acid, stearic acid, coconut oil fatty acid, tallow fatty acid, oleic acid, linoleic acid, and linolenic acid. Examples include seven or more higher fatty acids, and water-soluble salts of fatty acids include salts of the above fatty acids with alkali metals, ammonia, organic amines, and the like.

As the water-soluble polyvalent metal salt to be reacted with the above fatty acid or its water-soluble salt, water-soluble salts of polyvalent metals such as calcium, magnesium, and aluminum are used. These should be added in an amount such that the coating amount of the polyvalent metal salt of fatty acid formed on the surface of the dispersed particles of titanium oxide is 1 to 20%, preferably 5 to 10%, of the titanium oxide in the titania sol. Bye.

The operation for coating the surface of the dispersed particles of titanium oxide in the titania sol dispersion with a polyvalent metal salt of a fatty acid includes adding an alkaline solution, a fatty acid or a water-soluble salt thereof, or an aqueous solution thereof to the titania sol dispersion. The water-soluble polyvalent metal salt or its aqueous solution may be gradually added while stirring, the reaction may be completed by continuing to stir even after the addition is completed, the mixture may be filtered, washed if necessary, and then dried to remove moisture. At this time, the dispersed particles of titanium oxide become hydrophobic due to the surface coating with the polyvalent metal salt of hydrophobic fatty acid, lose hydrophilicity, and no longer form a strong hydration layer with water molecules. , subsequent filtration,
Cleaning becomes extremely easy, and strong adhesion does not occur during drying. Then, the obtained rutile type fine particle titanium oxide becomes hydrophobic due to the surface coating with the polyvalent metal salt of fatty acid.

The thus obtained hydrophobic rutile type fine particle titanium oxide generally has a particle diameter of 0.005 to 0.015 μm, and has good transparency and ultraviolet shielding properties.

In the present invention, the reason why a higher fatty acid having 7 or more carbon atoms is used as the fatty acid is to make the polyvalent metal salt of the fatty acid that coats the surface of the dispersed particles of titanium oxide hydrophobic. When the fatty acid is a lower fatty acid with a small number of carbon atoms, the polyvalent metal salt of the fatty acid obtained becomes water-soluble and the objective cannot be achieved. In addition, when reacting with the above fatty acid or its water-soluble salt, the use of a polyvalent metal salt is as follows:
This is to make the polyvalent metal salt of fatty acid that coats the surface of the titanium oxide dispersed particles hydrophobic. When a monovalent metal salt is used instead of the polyvalent metal salt mentioned above, only a water-soluble salt is obtained when reacted with a fatty acid or its water-soluble salt, and the surface of the dispersed particles of titanium oxide is Since it is hydrophobic, it cannot be coated strongly and the purpose cannot be achieved.

Further, in the present invention, the obtained hydrophobic rutile type fine particle titanium oxide is used as is, and is not calcined (usually heat treatment performed at 500° C. or higher). When fired, the polyvalent metal salt of fatty acid that coats the surface of titanium oxide particles is decomposed by heat, disappears, loses its hydrophobicity, and forms a strong affinity layer with water molecules. This is because the dispersibility in paints and resins decreases.

As mentioned above, the obtained hydrophobic rutile type fine particle titanium oxide is used as it is without being calcined, and in the present invention, an organic polymer flocculant is not used in the intermediate step. This is because when an organic polymer flocculant is used, if it is used as is without firing, the organic polymer flocculant remaining on the surface of titanium oxide particles will inhibit the basic properties of titanium oxide, for example. This is because transparency and ultraviolet shielding properties are reduced. Furthermore, when an organic polymer flocculant is used, the coating of the titanium oxide particle surface with the polyvalent metal salt of fatty acid is inhibited.

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

Example 1 95 kg of hydrous titanium oxide slurry obtained by thermally decomposing a titanyl sulfate solution, filtering and washing by a conventional method
(equivalent to 10 kg of _TiO2 ), 48% caustic soda solution
73 kg was added with stirring and heated at 95°C for 2 hours. Next, 48 kg of 35% hydrochloric acid was added to 205 kg of slurry obtained by thoroughly washing the treated material with stirring.
A titanium sol was prepared by heating at 95°C for 2 hours.

This titania sol showed a rutile crystal structure by X-ray diffraction. 253 kg of titania sol obtained in this way, 16.8 kg of 48% caustic soda solution, 0.95 kg of sodium stearate, and sodium aluminate solution.
Add 0.70Kg (equivalent to 0.11Kg in terms of Al ₂ O ₃ ) with stirring, heat at 80℃, adjust the pH value to 7.0,
Dispersed particles of titanium oxide were coated with aluminum stearate, and then the dispersed particles were filtered, washed with water, and dried at 105°C. The average particle diameter of the hydrophobic rutile-type fine particle titanium oxide obtained in this way is
It was 0.012 μm.

By the coating treatment with aluminum stearate as described above, the filtration workability of the titania sol was significantly improved compared to that of the untreated titania sol shown in Comparative Example 1 below, and the processing capacity was improved by 8.1 times. Also,
This dried product was soft and easy to break up. The obtained rutile-type fine particle titanium oxide is hydrophobic due to the surface coating with aluminum stearate, and its dispersibility in vinyl chloride resin is improved as described in Comparative Example 1 below.
As will be explained later based on FIG. 1, the transparency and ultraviolet shielding properties were excellent.

Comparative Example 1 Rutile-type fine particle titanium oxide having an average particle diameter of 0.012 μm was obtained in the same manner as in Example 1, except that the titania sol prepared in the same manner as in Example 1 was not coated with aluminum stearate.

Figure 1 shows a thin film prepared by blending the hydrophobic rutile type fine particle titanium oxide obtained in Example 1 and the rutile type fine particle titanium oxide obtained in Comparative Example 1 with vinyl chloride resin using a spectrophotometer (manufactured by Shimadzu Corporation). , UV-200) is a graph showing the results of measuring light transmittance. The above vinyl chloride resin thin film was created under the following conditions. The vinyl chloride resin used was Zeon 103EP manufactured by Nippon Zeon.

Compound Zeon 103EP 66 parts Barium stearate 1.9 parts Cadmium stearate 1.9 parts Tin-based stabilizer KS-20 1.9 parts Plasticizer DOP 30 parts Microparticle titanium oxide 0.25 parts The above ingredients were kneaded using two heated rolls.
A 100 μm thin film was molded from the obtained vinyl chloride resin composition and used as a sample for transmittance measurement.

In FIG. 1, curve A shows the transmittance of the hydrophobic rutile-type fine particle titanium oxide of Example 1 with respect to the wavelength of light, and curve B shows the transmittance of the rutile-type fine particle titanium oxide of Comparative Example 1 with respect to the light wavelength. However, as is clear from the comparison between Curve A and Curve B, in the visible region where the wavelength is about 430 nm or more, Curve A is located above Curve B, and the hydrophobicity of Example 1 is This shows that the rutile type fine particle titanium oxide has higher transparency than the rutile type fine particle titanium oxide of Comparative Example 1. Furthermore, in the ultraviolet region with a wavelength of about 400 nm or less, curve A is located lower than curve B, and the transmittance is reversed. It has a higher ultraviolet absorption power than the rutile-type fine particle titanium oxide, indicating that it has excellent ultraviolet shielding properties. This difference in transmittance is due to the fact that the hydrophobic rutile type fine particle titanium oxide of Example 1 has better dispersibility in vinyl chloride resin than the rutile type fine particle titanium oxide of Comparative Example 1. .

Example 2 Titanium sol 248Kg prepared in the same manner as Example 1
48% caustic soda 16.5Kg, sodium laurate
0.94Kg and 0.83Kg of sodium aluminate solution (equivalent to 0.13Kg in terms of Al ₂ O ₃ ) were added with stirring, heated to 65℃, adjusted the pH value to 6.5, and dissolved the dispersed particles of titanium oxide into lauric acid. After coating with aluminum, the dispersed particles were filtered, washed with water, and dried at 105°C. The average particle diameter of the hydrophobic rutile type fine particle titanium oxide thus obtained was 0.012 μm.

Due to the coating treatment with aluminum laurate as described above, the filtration workability of the titania sol was significantly improved compared to the untreated titania sol shown in Comparative Example 1, and its processing capacity was improved by 5.6 times. In addition, the dried product was soft and easy to break up. The obtained hydrophobic rutile type fine particle titanium oxide had good dispersibility in the nitrocellulose paint, and as shown in FIG. 2, it had excellent transparency and ultraviolet shielding properties.

Figure 2 shows the transmission of light using a spectrophotometer for a paint containing nitrocellulose mixed with the hydrophobic rutile-type fine-particle titanium oxide obtained in Example 2 and the rutile-type fine-particle titanium oxide obtained in Comparative Example 1 above. This graph shows the results of measuring the ratio.
The above nitrocellulose paint was created under the following conditions.

Compounded nitrocellulose 6.6 parts Solvent (toluene/ethyl acetate/isopropanol = 1/1/1) 26.4 parts Plasticizer DOP 3 parts Fine titanium oxide 3 parts Glass beads (3 mmφ) 90 parts Each of the above ingredients was mixed with a paint conditioner. After being dispersed for 60 minutes, it was coated on cellophane paper with a bar coater to a thickness of 3 μm (dry film thickness), and this was used as a sample for transmittance measurement.

In FIG. 2, curve A shows the transmittance of the hydrophobic rutile-type fine-particle titanium oxide of Example 2 to the wavelength of light, and curve B shows the transmittance of the rutile-type fine-particle titanium oxide of Comparative Example 1 to the light wavelength. However, as is clear from the comparison between curve A and curve B, in the visible region where the wavelength is about 430 nm or more,
Curve A is located above curve B, and Example 2
This shows that the hydrophobic rutile-type fine-particle titanium oxide of Comparative Example 1 has higher transparency than the rutile-type fine-particle titanium oxide of Comparative Example 1. Furthermore, in the ultraviolet region with a wavelength of about 400 nm or less, curve A is located lower than curve B, and the transmittance is reversed. It has a higher ultraviolet absorption power than the rutile-type fine particle titanium oxide, indicating that it has excellent ultraviolet shielding properties. This difference in transmittance is due to the fact that, as in Example 1, the hydrophobic rutile-type fine particle titanium oxide of Example 2 has better dispersibility in the nitrocellulose paint than the rutile-type fine particle titanium oxide of Comparative Example 1. This is based on the fact that it is in good condition.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the transmittance of a vinyl chloride resin thin film blended with hydrophobic rutile type fine particle titanium oxide of Example 1 and a vinyl chloride resin thin film blended with rutile type fine particle titanium oxide of Comparative Example 1 with respect to the wavelength of light. Figure 2 is a graph showing the transmittance of the paint thin film containing the hydrophobic rutile type fine particle titanium oxide of Example 2 and the paint film containing the rutile type fine particle titanium oxide of Comparative Example 1 with respect to the wavelength of light. .

Claims (1)

[Claims] 1 In a dispersion of titania sol having a rutile crystal structure obtained by treating hydrous titanium oxide with caustic alkali and aging it in hydrochloric acid, a fatty acid having 7 or more carbon atoms or a water-soluble salt thereof and a water-soluble polyester are added. Rutile with a particle size of 0.1 μm or less, characterized by coating dispersed particles of titanium oxide with the polyvalent metal salt of a fatty acid produced by reacting with a valent metal salt, and then filtering and drying the dispersed particles. Manufacturing method of type microparticle titanium oxide.