JPH0770470A - Production of inorganic compound - Google Patents

Abstract

PURPOSE:To obtain an excellent titanium oxide maintaining dispersion stability in an organic solvent for a long period of time because of strong bonding of an acid anhydride derivative to the surface of titanium oxide particles and being difficult to be isolated. CONSTITUTION:Hydroxyl group existing on the surface of titanium oxide particles is reacted with an acid anhydride to modify the surface of the titanium oxide particles with a derivative of the acid anhydride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an inorganic compound by modifying the particle surface of the inorganic compound with an organic molecule.

[0002]

2. Description of the Related Art Inorganic compounds are pigments, ultraviolet absorbers, decoration materials, catalysts, photocatalysts, catalyst carriers, adsorbents, deodorants, bioreactors, fillers, optical materials, electronic / electrical materials,
It is used for various purposes such as photoelectric conversion materials, but in order to improve the filling property, it is often used after the inorganic compound is uniformly dispersed in an organic solvent. However, since the inorganic compound originally has a large number of hydroxyl groups on the particle surface, it has hydrophilicity, and particles are easily aggregated in an organic solvent, resulting in extremely poor dispersion stability. Therefore, in order to improve dispersion stability in an organic solvent, acetic acid, trifluoroacetic acid, an organic carboxylic acid such as benzoic acid or an alkylamine such as hexylamine, dodecylamine, tetradecylamine is added to the surface of the inorganic compound particles. A method for modifying the particle surface of the inorganic compound by reacting it with hydroxyl groups of the above has been proposed (Journal of the Chemical Society of Japan, 1982, (7), P1).
141-1146).

[0003]

In the above-mentioned method of the prior art, although the dispersion stability is slightly improved, the modified substance is released from the particle surface of the inorganic compound and is dissolved in the organic solvent, so that it is sufficient. There is a problem that the dispersion stability cannot be obtained and the inorganic compound particles aggregate with each other.

[0004]

Means for Solving the Problems As a result of various investigations for improving the dispersion stability of inorganic compound particles, the present inventors have made it possible to react a hydroxyl group present on the surface of an inorganic compound particle with an acid anhydride. When the particle surface of the inorganic compound is modified with the derivative of the acid anhydride, the acid anhydride derivative is firmly bonded to the surface of the particle of the inorganic compound and is not easily desorbed, so that the dispersion stability is excellent over a long period of time. That is, the present invention has been completed and the present invention has been completed. That is, the present invention is to provide an inorganic compound having excellent dispersion stability in an organic solvent.

In the present invention, a hydroxyl group existing on the surface of an inorganic compound particle is reacted with an acid anhydride, and the particle surface of the inorganic compound is modified with a derivative of the acid anhydride and treated. In the present invention, inorganic compounds include various inorganic materials such as titanium oxide, silicon oxide, aluminum oxide, zinc oxide, tin oxide, iron oxide, tungsten oxide, barium titanate, barium sulfate, aluminum phosphate, molybdenum sulfide, cadmium sulfide, and activated carbon. Compounds can be used. The above-mentioned inorganic compound is obtained by a known method, and its particle size is 1
A range of up to 1000 nm, especially 3 to 500 nm is suitable. In the present invention, the inorganic compound obtained by a known method may be subjected to a treatment such as normal pressure, reduced pressure, or pressure, drying or firing.

The present invention is preferably applied to an inorganic compound such as an inorganic oxide which requires a high degree of dispersion stability, particularly titanium oxide. In the present invention, titanium oxide includes, in addition to titanium oxide, those generally called hydrous titanium oxide, hydrated titanium oxide, metatitanic acid, orthotitanic acid, titanium hydroxide and the like, and the crystal system thereof does not matter. . Such titanium oxide, titanyl sulfate, titanium tetrachloride, titanium compounds such as organic titanium compounds, in the presence of seeds for nucleation, if necessary, a method of hydrolysis, if necessary seeds for nucleation. In the presence, titanyl sulfate, titanium tetrachloride, a method of neutralizing by adding an alkali to titanium compounds such as organic titanium, titanium tetrachloride, a method of vapor phase oxidation of organic titanium compounds, the above, obtained by the method of It can be obtained by, for example, a method of firing a pottery.

In the present invention, the acid anhydride is a compound in which two molecules of carboxylic acid such as an aliphatic carboxylic acid, an aromatic carboxylic acid, an alicyclic carboxylic acid and a heterocyclic carboxylic acid are condensed by losing one molecule of water. Therefore, it is a compound represented by the general formula (RCO) ₂ O. In the present invention, for example, succinic anhydride, maleic anhydride, glutaric anhydride, butyric anhydride, valeric anhydride, phthalic anhydride, benzoic anhydride, cinnamic anhydride,
Glutaric anhydride, glutaconic anhydride, diglycolic anhydride, diphenic anhydride, etc. can be used. In the present invention, an acid anhydride having a benzene ring, which has a large effect of imparting lipophilicity to an inorganic compound, is preferable, and an acid anhydride in which at least one hydrogen of the benzene ring is replaced with a halogen atom such as a fluorine atom is preferable. . In addition, the derivative of the acid anhydride is a compound formed by a structural change of a small portion of the acid anhydride.
And an acyl group represented by the general formula RCO. The modification amount of the acid anhydride derivative can be appropriately set, but it is 0.
1-20% by weight is suitable.

In the present invention, for example, the above-mentioned acid anhydride is added to a dispersion liquid in which the above-mentioned inorganic compound is dispersed in a solvent, or the solvent in which the acid anhydride is present is added to the inorganic compound, The hydroxyl group present on the particle surface of the inorganic compound and the acid anhydride are reacted by mixing the dispersion liquid of the compound and the solvent in which the acid anhydride is present. As the solvent, benzene, chloroform, carbon disulfide, ethers, nitriles and the like are preferable. The reaction temperature can be appropriately set, but a temperature from room temperature to the boiling point of the solvent used is suitable. In the case of preparing the above-mentioned inorganic compound dispersion liquid, it is preferable to add a dispersant, wet pulverize, or classify to adjust the particle diameter as close as possible to a single particle of the inorganic compound. Further, the concentration of the inorganic compound dispersion liquid is preferably about 50 to 1200 g / l.

Next, the reaction product is separated from the dispersion, washed if necessary, and dried. In the present invention, in addition to the acid anhydride derivative, an organic carboxylic acid, an alkylamine, an organic compound such as an alkanolamine and aluminum, silicon, titanium, antimony, a hydrous oxide of a metal such as tin or cerium, Oxides or hydroxides may be treated.

[0010]

【Example】

Example 1 100 mg of titanium oxide (P-25, manufactured by Degussa) was used.
After drying under reduced pressure at a temperature of 00 ° C. for 2 hours, under a nitrogen atmosphere,
Containing 4.5 mmol of tetrafluorophthalic anhydride,
Inject 50 ml of dehydrated acetonitrile with a syringe,
The mixture was stirred and refluxed for 12 hours. Then, the solvent after the completion of the reaction was distilled off, and the obtained titanium oxide was put into dehydrated cyclohexane, dispersed by ultrasonic waves, and then centrifuged to remove the supernatant liquid. This operation was repeated until there was no absorption of acid anhydride from the ultraviolet spectrum of the supernatant. The obtained wet cake was dried under reduced pressure for 6 hours to obtain titanium oxide (Sample A) of the present invention modified with a derivative of tetrafluorophthalic anhydride. As a result of elemental analysis, the modification amount of the acid anhydride derivative of Sample A was 6.5% by weight based on the weight standard of TiO ₂ .

Comparative Example Titanium oxide (Sample B) was obtained in the same manner as in Example 1 except that tetrafluorophthalic anhydride was not added.

Samples obtained in Examples and Comparative Examples (A,
B) 10 mg of each was dispersed in 10 ml of acetonitrile by ultrasonic waves and then centrifuged (rotation speed 4000 r
pm) for 20 minutes. The sample B of the comparative example was completely precipitated by centrifugation, while the sample A of the example was dispersed even after the centrifugation. Then, when the supernatant liquid of the sample A of Example after centrifugation was filtered with a membrane filter made of PTFE (pore size: 0.2 μm), the filtrate was clouded and found to be highly dispersed.

Next, the samples (A, B) obtained in the examples and comparative examples were ultrasonically dispersed in acetonitrile, diluted to a certain concentration, and then allowed to stand, and 350 n
The time variation of the absorbance of m was examined to evaluate the dispersion stability of each sample. The result is shown in FIG. The sample B of the comparative example is 24
Complete sedimentation within hours. On the other hand, the sample A of the example is 4
It can be seen that no sedimentation occurs even after 5 hours. In addition,
When modified with benzoic acid in the same amount as in Example A,
The modified product was eluted in acetonitrile as the dispersion solvent, and no improvement in the dispersion stability of titanium oxide was observed. From these facts, the inorganic compound modified with the acid anhydride derivative of the present invention, particularly the inorganic compound modified with the derivative of tetrafluorophthalic anhydride is excellent in dispersion stability and can be dispersed even in acetonitrile. I found out.

[0014]

INDUSTRIAL APPLICABILITY The present invention is a method of reacting a hydroxyl group present on the surface of an inorganic compound particle with an acid anhydride to modify the particle surface of the inorganic compound with a derivative of the acid anhydride. This is a very useful method industrially because it is possible to obtain an inorganic compound having excellent dispersion stability over a long period of time because the derivative of an anhydride is firmly bound to the surface of the particles of the inorganic compound and is difficult to be desorbed. Moreover, the present invention, by appropriately selecting the acid anhydride to be used, it is possible to disperse while maintaining the primary particle size of the inorganic compound, it is also possible to disperse in the state of particles where several primary particles are collected. The dispersion state of the inorganic compound particles can be controlled. The inorganic compound obtained by the method of the present invention can be used in various applications such as pigments and catalysts, and can also be expected to be used as a novel functional material having unprecedented unique physical properties.

[Brief description of drawings]

FIG. 1 is a diagram showing the change with time of the absorbance of dispersion liquids of samples (A, B) obtained in Examples and Comparative Examples.

Claims (4)

[Claims] 1. A method for producing an inorganic compound, which comprises reacting a hydroxyl group present on the surface of an inorganic compound particle with an acid anhydride to modify the particle surface of the inorganic compound with a derivative of the acid anhydride. 2. The method for producing an inorganic compound according to claim 1, wherein the inorganic compound is an inorganic oxide. 3. The method for producing an inorganic compound according to claim 2, wherein the inorganic oxide is titanium oxide. 4. The method for producing an inorganic compound according to claim 1, wherein the acid anhydride is an optionally substituted phthalic anhydride.