JP2013170110A - Nonpolar organic solvent dispersion of titanium oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a comparatively inexpensive dispersion formed by dispersing titanium oxide particles uniformly in a nanoparticle level into a low-polarity organic solvent which is considered to be difficult to have dispersion of titanium oxide particles therein, without water inclusion that causes contamination, and without using a dispersant or a stabilizer.SOLUTION: A nonpolar organic solvent dispersion of titanium oxide is formed by dispersing, into a nonpolar organic solvent, hydrophobic titanium oxide fine powder obtained by performing a dry surface treatment with a silane coupling agent and/or a silicone compound on the surface of titanium oxide fine powder obtained by hydrolyzing a volatile titanium compound in a vapor-phase flame containing hydrogen.

Description

  The present invention relates to a non-polar organic solvent dispersion of titanium oxide in which titanium oxide fine particles are uniformly dispersed in a non-polar (non-proton) solvent without using a dispersant, a stabilizer or the like.

The demand for a titanium oxide dispersion is high, and many documents and patents have already been published.
For example, in an academic review, the concept of a general technique of “control of aggregation and dispersion behavior of nanoparticles in liquid” is introduced (Non-patent Document 1).
Here, first, when hydrophilic particles such as metal oxide are dispersed in a hydrophilic solvent such as water or alcohol, it is stated that some modification is performed on the particle surface.
For example, polyacrylic acid, carboxylate, polyimine-based dispersants, etc. are used, and if the solvent is aqueous, anionic and cationic surfactants are adsorbed to increase the surface potential of the particles. Alternatively, a method of dispersing by a steric hindrance effect by a hydrophilic group adsorbed on the particle surface and a hydrophobic group not adsorbed has been devised.

  In addition, when dispersing hydrophilic particles in nonpolar solvents, hydrophilic ceramic raw material particles in low-polar organic solvents such as toluene, MMA, and THF have poor wettability. In addition to the agent, it has been introduced that the surface is modified with a silane coupling agent to improve the wettability with a solvent by introducing a hydrocarbon chain.

  Typical examples of conventional technology for dispersing titanium oxide particles in an aqueous solvent include the following.

Patent Document 1: Aqueous containing oxide particles characterized by an asymmetric distribution of the particle size of oxide particles and produced by a thermal decomposition method of titanium containing alkali metal, alkaline earth metal, ammonium ion or the like as a dispersant Dispersion Patent Document 2: Titanium dioxide and the carboxyl group of hydrophilic polymer are chemically modified with an ester bond, so that they are excellent in dispersibility and stability in aqueous solvents in a wide pH range as well as near neutrality. Further, surface-modified titanium dioxide fine particles and dispersions thereof Patent Document 3: Inorganic oxide ultrafine particles containing titanium oxide having a rutile-type crystal structure with a molar ratio of tin to titanium (Sn / Ti) of 0.001 to 2 In the presence of a tin compound, a titanium compound aqueous solution having a Ti concentration of 0.07 to 5 mol / l is reacted in a pH range of −1 to 3 to form a nucleus (A) containing silicon oxide. Coated inorganic oxide ultrafine particles having a coating layer (B) Patent Document 4: Surface obtained by dispersing surface-modified titanium dioxide fine particles in which the surface of titanium dioxide is modified with a hydrophilic polymer having a carboxyl group in an aqueous solvent Modified titanium dioxide fine particle dispersion

  Moreover, there exists the following technique about dispersion | distribution to a nonpolar solvent.

Patent Document 5: Metal oxide fine particles having a step of introducing metal oxide fine particles whose surface has been treated with a surface treating agent into a dispersion medium made of (meth) acrylic monomer, and a step of adding oxo acid containing phosphorus or sulfur A method for producing a dispersion. Here, by adding a surface treating agent together with an organic solvent, a dispersing agent for extracting metal oxide fine particles is added and dispersed in the organic solvent.
Patent Document 6: A step of heat-treating an aqueous solution containing a tin compound and a titanium compound having a titanium concentration of 0.1 M or more and 0.25 M or less to produce titanium oxide fine particles, and a surface in the aqueous solution by a fat-soluble surface modifying molecule Is a wet process in which titanium oxide fine particles modified with an additive are added to an aqueous solution to extract rutile-type titania into a nonpolar organic solvent phase, with high reproducibility and high dispersibility in nonpolar organic solvents such as toluene Rutile-type titanium oxide fine particles having the following formula are produced.
Patent Document 7: A hard coat composition containing a curable silicone compound as an essential component and is a technique for mixing with a resin, and can be obtained as a colloidal dispersion in the process of preparing the hard coat composition This includes a process in which a silicon compound as a coating agent is added to a surface-treated titanium oxide (containing water) according to a known technique. Here, in part, a general technique that can be dispersed in water and / or an organic solvent by a so-called silane coupling process to form a sol is shown. In addition, when using an organic solvent, the organic solvent with high polarity is considered preferable.
Patent Document 8: Titanium oxide fine particle dispersion comprising a transparent organic solvent dispersion of titanium oxide fine particles containing a dispersion stabilizer, wherein the dispersion stabilizer is mainly composed of an organic acid having a refractive index of 1.50 or more. .
Patent Document 9: An organic solvent dispersion of titanium oxide fine particles having excellent transparency, in which titanium oxide fine particles of nano-level rutile type crystals are dispersed, and containing at least a mixed organic solvent and an organic acid. An organic solvent dispersion of titanium oxide fine particles.
Patent Document 10: Titanium raw material is heated and vaporized by a direct current arc plasma method, and the titanium vapor is oxidized and cooled, whereby the pH of a 20% by weight aqueous dispersion is 2.8 to 4.0, and the average particle Titanium dioxide ultrafine particles having a diameter in the range of 5 to 70 nm are used. A non-aqueous dispersion of titanium dioxide ultrafine particles is obtained by dispersing in an organic solvent together with a dispersant, and it is necessary to disperse together with the dispersant.
Patent Document 11: Ultrafine titanium oxide powder having an average primary particle diameter of 0.01 to 0.1 μm produced by a vapor phase method, β-diketone, titanate and / or aluminum cup in an organic solvent A photocatalyst coating material containing a ring agent and titanium alkoxide or a partial hydrolyzate thereof. This is a technique in which a reagent having a dispersion effect is added to a dispersion for dispersion.
Patent Document 12: Hydrophobic properties of various particles such as carbon black coated with a polymer by graft polymerization of monomers using a double bond in a hydrocarbon chain introduced by a coupling agent and further crosslinking reaction An electrophoretic liquid has been invented that enhances and enhances the stability of the suspension in the solvent due to the suspension of the polymer. In the former stage, silica coating treatment or the like is performed in a sodium silicate aqueous solution, which is accompanied by treatment in an aqueous solution.

  The hydrophobic titanium oxide fine powder used in the present invention is described in Patent Document 13.

Since titanium oxide is an essential and useful material for various applications, as described above, conventionally, many inventions and proposals have been made regarding techniques for dispersing titanium oxide in an aqueous solution system or an organic solvent system. .
However, titanium oxide synthesized in an aqueous system contains a large amount of residual adsorbed water inside the particle, and if it is strongly adsorbed at the molecular level, it is difficult to dry sufficiently, so it is used for dispersion in an aqueous solvent. Except in some cases, there was a problem that it was difficult to use in applications where mixing of water was not desired.

  In addition, there is a technology that makes it easy to disperse the surface of titanium oxide particles dispersed in an aqueous solvent by applying a surface modification with a coupling agent or the like. Aggregation is likely to occur, the bulk density becomes high, and a separate work / process for crushing and sieving is required, and the work causes a problem of increased contamination.

  Therefore, in order to eliminate the need to take it out of the solution system once, there is an invention in which the titanium oxide particles surface-modified in an aqueous solvent are extracted into an organic solvent. There has been a problem that a dispersant, a stabilizer, or the like introduced into an organic solvent to be extracted or dissolved in an aqueous solvent is also mixed.

  In addition to titanium oxide synthesized by a wet process, even if titanium oxide is produced in the gas phase, once the surface modification or modification treatment is performed in an aqueous solvent, it is described above. The same problem occurs as well.

Titanium oxide itself has physicochemical properties and characteristics that are hydrophilic, and itself is difficult to uniformly disperse in an organic solvent, particularly a non-aqueous, low-polarity organic solvent.
For this reason, in order to obtain a dispersion of titanium oxide particles using an organic solvent, a surfactant having a dispersing effect is separately added and dispersed in the solvent to stabilize the dispersion state or in the solution. Then, use a technique such as modifying the surface of titanium oxide particles with a coupling agent to make it easier to disperse in a solvent, or first preparing a dispersion in an aqueous solution and then extracting it to an organic solvent, etc. The technology has been proposed.
However, in the conventional method, the dispersion of the titanium oxide particles in the nonpolar organic solvent cannot obtain a uniform dispersion state unless a dispersant is added, and there is a problem of contamination derived from the dispersant due to the use of the dispersant. was there. Further, in the dispersion of titanium oxide particles containing a dispersant, not only the titanium oxide but also the dispersant remains after the solvent is removed by evaporation, and cannot be used for applications requiring only titanium oxide. .

Japanese Patent No. 4338636 JP 2005-289660 A JP 2007-197278 A Japanese Patent No. 3775432 JP 2010-095679 A JP 2009-215119 A JP 2004-238418 A Japanese Patent No. 4725510 JP 2010-138020 A JP-A-11-278844 Japanese Patent No. 3291563 US2002 / 0185378A1 Japanese Patent No. 3417291

Hidehiro and Yotoyuki Iijima, “Aggregation and Dispersion Behavior Contral of Nanoparticles in Liquid Phase” J. Soc. Powder Technol, Japan, 46, 606-614 (2009)

  The present invention has been made in view of the above-described conventional situation, and it is difficult to disperse titanium oxide particles without contamination of water causing contamination, and without using a dispersant or a stabilizer. It is an object of the present invention to provide a relatively inexpensive dispersion liquid in which titanium oxide particles are uniformly dispersed at the nanoparticle level in an organic solvent having a low polarity.

  As a result of intensive investigations to solve the above problems, the present inventors have determined that the surface of titanium oxide fine powder obtained by hydrolyzing a volatile titanium compound in a gas-phase flame containing hydrogen is treated with silane. Hydrophobic titanium oxide fine powder obtained by surface treatment with a coupling agent and / or silicone compound is uniform at a nanoparticle level in a nonpolar organic solvent without using a dispersant or stabilizer. It was found to be dispersible.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] The surface of titanium oxide fine powder obtained by hydrolyzing a volatile titanium compound in a gas-phase flame containing hydrogen is surface-treated with a silane coupling agent and / or a silicone compound in a dry process. A non-polar organic solvent dispersion of titanium oxide obtained by dispersing a hydrophobic titanium oxide fine powder obtained in a non-polar organic solvent.

[2] In [1], the titanium oxide constituting the hydrophobic titanium oxide fine powder has a BET specific surface area of 40 to 150 m ² / g, a crystal structure of anatase and rutile, and a ratio of anatase of 0.3 A non-polar organic solvent dispersion of titanium oxide, characterized by being -0.98 titanium oxide.

[3] In [1] or [2], the nonpolar organic solvent is one or more selected from the group consisting of methyl ethyl ketone, ethyl acetate, benzene, diethyl ether, and toluene. Nonpolar organic solvent dispersion of titanium oxide.

[4] The nonpolar organic material of titanium oxide according to any one of [1] to [3], wherein the silane coupling agent is represented by the following general formula (I) or (II): Solvent dispersion.
X _4-n SiR _n (I)
(In the formula (I), X represents a hydroxyl group, an alkoxy group, or a halogen atom, R represents an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 0 to 3).
R ′ ₃ SiNHSiR ′ ₃ (II)
(In the formula (II), R ′ represents an alkyl group having 1 to 3 carbon atoms, and some R ′ may be other substituents such as a hydrogen atom or a vinyl group.)

[5] A nonpolar organic solvent dispersion of titanium oxide according to any one of [1] to [3], wherein the silicone compound is represented by the following general formula (III):

(In the formula (III), R ^a represents a methyl group or an ethyl group, and R ^b represents a hydrogen atom, a methyl group, an ethyl group, or an alkyl group which may be substituted with a vinyl group, a phenyl group or an amino group. X ′ represents a hydroxyl group, an alkoxy group, a halogen atom or an alkyl group, and m represents an integer of 1 to 500.)

[6] In any one of [1] to [5], the hydrophobic titanium oxide fine powder has a hydrophobicity measured by a transmittance method of 70% or more. Polar organic solvent dispersion.

[7] In any one of [1] to [6], the hydrophobic titanium oxide fine powder is obtained by mixing and heat-treating the titanium oxide fine particles and the silane coupling agent and / or silicone compound. A non-polar organic solvent dispersion of titanium oxide,

[8] In any one of [1] to [7], the hydrophobic titanium oxide fine powder is mixed with a stirring blade, dissolver, ball mill, kneader, sand mill, roll mixer, ultrasonic homogenizer, homomixer, tower mill, wet jet. A nonpolar organic solvent dispersion of titanium oxide, which is dispersed in the nonpolar organic solvent by one or more mechanical / physical means of either a mill or a bead mill.

[9] The nonpolar organic solvent dispersion of titanium oxide according to any one of [1] to [8], wherein the concentration of the hydrophobic titanium oxide fine powder is 0.1 to 40% by weight.

According to the present invention, titanium oxide fine powder in which titanium oxide fine powder is uniformly dispersed at a nanoparticle level in a nonpolar organic solvent without using a dispersant or a stabilizer or without passing through an aqueous dispersion. A nonpolar organic solvent dispersion is provided.
That is, according to the present invention, a hydrophobic function is imparted to the surface of titanium oxide obtained by hydrolysis in a gas phase flame by a dry treatment using a silane coupling agent and / or a silicone compound. Since the dispersibility with respect to the polar organic solvent is good and a uniform dispersion can be obtained without the need for components such as a dispersant, a surfactant and a stabilizer for stabilizing the dispersion, these It is possible to avoid mixing of impurities due to the use of components, for example, mixing of phosphoric acid and tin.

Moreover, the non-polar organic solvent dispersion of titanium oxide of the present invention is realized by realizing a non-polar organic solvent dispersion of titanium oxide fine particles, which could not be realized conventionally without using a dispersant or a stabilizer. Can be applied as a constituent component of applications such as paints, inks, composites with resins, films, etc. that could not be applied with dispersions using polar solvents. Since the property is excellent, it is possible to provide a uniform coating film, coating, or film on the surface of the target product.
These are also effective for ensuring the homogeneity of the product using titanium oxide as a raw material, such as the size, surface state, and filling rate, and for providing optical homogeneity of the optical product.

  In particular, in the process of removing the solvent from the non-polar organic solvent dispersion of titanium oxide according to the present invention, an additive such as an unnecessary dispersant other than titanium oxide does not precipitate, and therefore it is formed of titanium oxide fine particles. In products of any shape such as surface coatings, films and solids, there is no risk of unnecessary substances concentrating or agglomerating at the interface of titanium oxide, and it should be used effectively for applications that require high purity and homogeneous materials Can do.

In Example 1, it is a chart which shows the particle diameter distribution of the titanium oxide dispersion particle in a dispersion liquid when stirring with a stirring blade was performed for 30 minutes. In Example 1, it is a chart which shows the particle size distribution of the titanium oxide dispersion | distribution particle | grains in a dispersion liquid when the dispersion | distribution process by an ultrasonic homogenizer was performed for 10 minutes after stirring with a stirring blade. In Example 1, it is a chart which shows the particle size distribution of the titanium oxide dispersion | distribution particle | grains in a dispersion liquid when the dispersion | distribution process by a bead mill was performed for 60 minutes after stirring with a stirring blade.

  Hereinafter, embodiments of the nonpolar organic solvent dispersion of titanium oxide of the present invention will be described in detail.

[Hydrophobic titanium oxide fine powder]
First, the non-polar organic solvent dispersion of titanium oxide of the present invention may be referred to as a hydrophobic titanium oxide fine powder dispersed in a non-polar organic solvent (hereinafter referred to as “the hydrophobic titanium oxide fine powder of the present invention”). ) Will be described according to the manufacturing method.

<Synthesis of titanium oxide>
First, a volatile titanium compound such as TiCl ₄ is hydrolyzed in a gas-phase flame containing hydrogen to synthesize titanium oxide constituting the hydrophobic titanium oxide fine powder.
Compared with wet titanium oxides etc. that are generally produced by the sulfuric acid method that is commercially available, this dry titanium oxide is synthesized in a hydrogen-containing flame in the gas phase, so there is basically no or no residual water. The water content is extremely small.
Also, since the internal specific surface area is small, the particles are easily hydrophobized uniformly to the inside, and as the bulk density is low, the degree of aggregation of the particles is low, so that the particles are easily dispersed as fine particles in a solvent. have.

As a volatile titanium compound used as a starting material, titanium alkoxide such as Ti (OCH ₃ ) ₄ and Ti (OC ₂ H ₅ ) ₄ can be used in addition to TiCl ₄ .

When titanium oxide produced by decomposing such a volatile titanium compound has a BET specific surface area of less than 40 m ² / g, the resulting hydrophobic titanium oxide fine powder is crushed or ground in a nonpolar organic solvent. When the BET specific surface area is larger than 150 m ² / g, the cohesive strength of titanium oxide increases and dispersion in a nonpolar organic solvent becomes difficult.
Therefore, the BET specific surface area of the obtained dry titanium oxide is preferably 40 to 150 m ² / g, particularly 50 to 110 m ² / g.

The dry titanium oxide obtained is not particularly limited in the ratio of rutile and anatase, but if the ratio of anatase (hereinafter sometimes referred to as “anatase ratio”) is less than 0.3, the surface of the titanium oxide surface Since the activity is too weak, it is difficult to uniformly modify the surface, and the hydrophobicity of the resulting hydrophobic titanium oxide fine powder becomes poor. When the anatase ratio is greater than 0.98, the surface activity is too strong, and therefore, the surface modifier is partially decomposed and it is difficult to uniformly modify the surface.
Therefore, in the present invention, the obtained dry titanium oxide has anatase and rutile crystal structures, and the anatase ratio is particularly preferably 0.3 to 0.98.
In addition, anatase ratio can be calculated | required by the method described in the term of the below-mentioned Example.

Thus, the titanium oxide having a BET specific surface area of 40 to 150 m ² / g and an anatase ratio of 0.3 to 0.98 is, for example, a volatile titanium compound in the presence of a hydrogen-containing gas at 600 to 1800 ° C. It can manufacture by thermally hydrolyzing on the conditions whose titanium concentration in source gas is 5-250 g / m < ³ > in conversion of titanium dioxide.

<Surface treatment>
In the present invention, the dry titanium oxide surface modifier obtained as described above is preferably a silane coupling agent represented by the following general formula (I) or (II) and / or the following general formula (III): Surface treatment is performed dry using a silicone compound represented by

X _4-n SiR _n (I)
(In the formula (I), X represents a hydroxyl group, an alkoxy group, or a halogen atom, R represents an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 0 to 3).

R ′ ₃ SiNHSiR ′ ₃ (II)
(In the formula (II), R ′ represents an alkyl group having 1 to 3 carbon atoms, and some R ′ may be other substituents such as a hydrogen atom or a vinyl group.)

(In the formula (III), R ^a represents a methyl group or an ethyl group, and R ^b represents a hydrogen atom, a methyl group, an ethyl group, or an alkyl group which may be substituted with a vinyl group, a phenyl group or an amino group. X ′ represents a hydroxyl group, an alkoxy group, a halogen atom or an alkyl group, and m represents an integer of 1 to 500.)

  In the general formulas (I) and (II), when a long-chain alkylsilane coupling agent having an alkyl group represented by R having a carbon number greater than 18 is used, surface modification may occur due to steric hindrance. It is difficult to carry out uniformly and is easy to aggregate.

  In the silane coupling agent represented by the general formula (I), R particularly represents an alkyl group having 1 to 10 carbon atoms, and X represents a hydroxyl group, an alkoxy group having 1 to 3 carbon atoms, or a halogen such as Cl. Atoms are preferred, specifically, methyltrimethoxysilane, dimethyltrimethoxysilane, dimethyltriethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, Examples include n-octadecyltrimethoxysilane, dimethyldichlorosilane, and methyltrichlorosilane.

  In the silane coupling agent represented by the general formula (II), R ′ is particularly preferably an alkyl group having 1 to 2 carbon atoms, specifically, hexamethyldisilazane and the like. Examples of those in which 'is substituted with a hydrogen atom include tetramethyldisilazane, and those in which' is substituted with a vinyl group include divinyltetramethyldisilazane.

  Further, the silicone compound represented by the general formula (III) is difficult to impart hydrophobicity if it is a low molecule, and if it is a polymer, it can be imparted hydrophobicity but tends to aggregate.

In the silicone compound represented by the general formula (III), R ^b is preferably a hydrogen atom, a methyl group or the like, and X ′ is preferably a hydroxyl group, a methoxy group or a methyl group, and m is 15 to 300. Preferably there is.
As the silicone compound, dimethylpolysiloxane having a molecular weight of about 1000 to 20000, methylhydrogenpolysiloxane, α, ω-hydroxyorganopolysiloxane, alkyl-modified silicone oil and the like are suitable.

  Such surface modifiers may be used singly, or two or more kinds may be used simultaneously, or two or more kinds may be used stepwise.

  The surface modification treatment can be performed by either a dry method or a wet method, but in the present invention, the surface modification treatment is performed by a dry method in order to prevent water contamination as much as possible. Also, the dry method is desirable from the viewpoint of aggregation problems and processing costs, and from the viewpoint of waste liquid processing and environmental considerations.

  The dry surface treatment can be performed by adding a silane coupling agent and / or a silicone compound dropwise in an inert gas atmosphere to titanium oxide fine powder while stirring and heating and stirring at 50 to 400 ° C. for about 0.1 to 3 hours. good.

  In this surface modification treatment, if the amount of the silane coupling agent and / or silicone compound used is too small, the surface modification cannot be carried out sufficiently, and if it is too much, aggregates increase. Therefore, the addition amount of the silane coupling agent and / or the silicone compound is preferably 0.1 to 50% by weight, particularly 1 to 30% by weight, based on titanium oxide.

  The hydrophobic titanium oxide fine powder of the present invention thus obtained has a hydrophobicity measured by a transmittance method of preferably 70% or more, more preferably 80% or more. This is preferable because it can be stably and uniformly dispersed in a solvent.

[Dispersion of hydrophobic titanium oxide fine powder in nonpolar organic solvent]
Next, a method for producing a nonpolar organic solvent dispersion of titanium oxide of the present invention by dispersing the hydrophobic titanium oxide fine powder obtained as described above in a nonpolar organic solvent will be described.

<Non-polar organic solvent>
The nonpolar organic solvent used in the present invention is composed of molecules having small electric dipoles, and is generally an organic solvent having a low dissolving power when used as a solvent. Although it will not be restrict | limited especially if it is a small organic solvent, Specifically, benzene, carbon tetrachloride, diethyl ether, methyl ethyl ketone, ethyl acetate, hexane, chloroform, toluene, xylene, methyl isobutyl ketone, butyl acetate, etc. are mentioned. Of these, methyl ethyl ketone, ethyl acetate, benzene, diethyl ether, and toluene are preferable.
These may be used alone or in combination of two or more.

<Distribution method>
The method for dispersing the hydrophobic titanium oxide fine powder of the present invention in the nonpolar organic solvent as described above is not particularly limited as long as it can be uniformly dispersed. For example, there are various names and names such as stirring blades, dissolvers, ball mills, kneaders, sand mills, roll mixers, homomixers, tower mills, ultrasonic homogenizers, wet jet mills and bead mills. Examples thereof include a method of stirring, mixing, and pulverizing by a mechanical or physical method. Such distributed processing may be performed in combination of two or more.

  The dispersion treatment time is appropriately determined according to the concentration of the hydrophobic titanium oxide fine powder in the dispersion, the dispersion treatment means, etc. so that a uniform dispersion can be obtained.

<Hydrophobic titanium oxide fine powder concentration>
In the non-polar organic solvent dispersion of titanium oxide of the present invention, the concentration of the hydrophobic titanium oxide fine powder in the dispersion is preferably 0.1 to 40% by weight, particularly preferably 0.5 to 30% by weight.
If the concentration of the fine powder of hydrophobic titanium oxide in the dispersion is too low, it will be difficult to apply to various applications, and if it is too high, it will be difficult to obtain a uniform dispersion, resulting in problems such as a long time for dispersion treatment. .

<Other ingredients>
The hydrophobic titanium oxide fine powder of the present invention can be uniformly dispersed in a nonpolar organic solvent without using a dispersant or a stabilizer.
Here, the dispersants and stabilizers that are not used in the present invention are those generally used for improving the dispersibility of the fine particles. For example, polyacrylic acid, carboxylate, polyimine-based dispersants Various kinds of hydrocarbon compounds, tin compounds, phosphorus compounds such as phosphoric acid and phosphonic acid / phosphinic acid, aluminum compounds, sulfur compounds such as sulfuric acid and sulfonic acid, silane coupling agents, curable silicones, and the like powders Dispersing aids and stabilizers other than the solvent component (in the present invention, these are referred to as “dispersing agents”).
Also, the moisture mixed in by the titanium oxide synthesis process is an undesirable contaminant.
The non-polar organic solvent dispersion of titanium oxide according to the present invention does not contain any of these dispersants, and there is no problem of contamination due to the dispersant or residual of the dispersant after volatilizing the non-polar organic solvent. Therefore, it is preferable. Here, being substantially free means that the concentration in the dispersion is, for example, 0.05% by weight or less.

  The non-polar organic solvent dispersion of titanium oxide of the present invention may contain components other than the above-described dispersant, for example, silicon compounds such as silicon oxide, chlorine compounds, etc., but most preferably hydrophobic Composed of fine titanium oxide fine powder and the aforementioned nonpolar organic solvent. The dispersion of the present invention may contain only one kind of hydrophobic titanium oxide fine powder, and the BET specific surface area, the anatase ratio, the hydrophobicity, and the different hydrophobicity of the surface treatment agent used. Two or more kinds of titanium oxide fine powder may be contained.

<Dispersity>
As a uniform dispersion state of the hydrophobic titanium oxide fine powder in the nonpolar organic solvent dispersion of titanium oxide of the present invention, the particle size distribution is 10 nm to 3 μm, particularly 20 nm to 0.5 μm, and D ₅₀ is 30 to 300 nm. It is preferable in various uses that it is 40-100 nm.
The particle size distribution of the titanium oxide in the dispersion is based on the dynamic light scattering method, for example, “Microtrac UPA-EX”, “Microtrac MT3300II” manufactured by Nikkiso Co., Ltd., “LA-920” manufactured by Minato Seisakusho. , “LB-500” or the like, and D ₅₀ can be obtained from the measurement result of the particle size distribution as a center value (D ₅₀ ) indicating the boundary between fine particles and coarse particles. However, in the present invention, the measurement was performed using “Microtrac MT3300II” manufactured by Nikkiso Co., Ltd.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

In the following, the BET specific surface area, anatase ratio of the titanium oxide fine powder, the hydrophobicity of the hydrophobic titanium oxide fine powder, the particle size distribution of the hydrophobic titanium oxide fine powder or the titanium oxide fine powder in the dispersion, and D ₅₀ Is measured by the following method.

<BET specific surface area>
It was measured by the BET method.

<Anatase ratio>
Titanium oxide fine powder pressed flat on a sample holder with a glass plate was measured with an X-ray diffractometer (manufactured by Philips), and was the strongest interference line of anatase crystal structure of the obtained diffraction intensity (101 diffraction intensity) (I _a) and the strongest interference line of the rutile-type crystal structure value determined content of the anatase type crystal structure (a) using the following equation from the diffraction intensity (I _R) of the (110) Anatase ratio was used.
A (%) = 100 / (1 + 1.265 × I _A / I _R )
(Ref. R. A. Spurr, H. Myers, Anal. Chem. 29, 760 (1957))

<Hydrophobic rate>
1 g of hydrophobic titanium oxide fine powder is weighed into a 200 mL separatory funnel, 100 mL of pure water is added thereto, stoppered, shaken with a turbula mixer for 10 minutes, and then allowed to stand for 10 minutes. After standing, 20 to 30 mL of the lower layer was withdrawn from the funnel, and the lower layer mixed solution was dispensed into a 10 mm quartz cell.

<Particle size _{distribution, D 50>}
Measurement was performed by a dynamic light scattering method using “Microtrac MT3300II” manufactured by Nikkiso Co., Ltd. Further, it determined central value indicating the boundary of the fine particles and coarse particles from the measurement results (D _50).

[Example 1]
BET specific surface area of 90 m is obtained by thermal hydrolysis of gaseous titanium tetrachloride in a flame containing hydrogen atoms at a temperature of 1,000 ° C. and a titanium concentration of 80 g / m ^{3 in} terms of titanium dioxide. Titanium oxide fine powder having an anatase ratio of ² / g and anatase ratio of 0.85 was produced.
100 parts by weight of this titanium oxide fine powder is put into a mixer, 20 parts by weight of n-octyltrimethoxysilane is added dropwise with stirring in a nitrogen atmosphere, heated and stirred at 150 ° C. for 2 hours, and then cooled to cool the surface. Processed.
The hydrophobicity of the obtained hydrophobic titanium oxide fine powder was 97%.

10 parts by weight of this hydrophobic titanium oxide fine powder was added to 90 parts by weight of methyl ethyl ketone taken in a container having a stirring blade while stirring, and stirring was continued for 30 minutes to obtain a milky white uniform dispersion. .
When a part of this dispersion was sampled and the particle size distribution was measured, as shown in FIG. 1, the particle size distribution was 60 nm to 2 μm, D ₅₀ was 210 nm, and a sufficiently homogeneous dispersion was obtained by stirring. It was confirmed that
An ultrasonic homogenizer was allowed to act on a part of the remaining dispersion for 10 minutes, and a part of the dispersion was sampled to measure the particle size distribution. As shown in FIG. 2, the particle size distribution was 38 nm to 0.45 μm. D ₅₀ is next 75 nm, dispersed particles becomes more fine particles, it was confirmed that the dispersion has been promoted.
The remaining dispersion liquid was continuously mixed and dispersed with 30 μm stabilized zirconia beads for 60 minutes while dispersing the liquid with a beads mill (manufactured by Nippon Coke, MSC mill). When the particle size distribution of the dispersion liquid sample was measured, as shown in FIG. 3, the particle size distribution was 35 nm to 0.25 μm, D ₅₀ was 65 nm, and the coarse particles were further reduced by the bead mill to become fine particles. It was confirmed that dispersion was promoted.

  After the stirring, homogenization, and dispersion after mill mixing were each transferred to a transparent glass container and allowed to stand for observation, but after several days, neither sample sedimentation nor solvent separation was observed. .

In addition, 20 parts by weight of the above-mentioned hydrophobic titanium oxide fine powder was added to 80 parts by weight of methyl ethyl ketone taken in a container having a stirring blade while stirring, and stirring was continued for 1 hour to obtain a milky white uniform dispersion. Got.
When this dispersion is dispersed with an ultrasonic homogenizer and a bead mill, respectively, as described above, it may be necessary to lengthen the treatment time, but as described above, no sedimentation of particles is observed and stable. A dispersion was obtained.
Further, the proportion of the above-mentioned hydrophobic titanium oxide fine powder was increased to 30 parts by weight, added to 70 parts by weight of methyl ethyl ketone with stirring, and stirred for 1 hour, and then dispersed with an ultrasonic homogenizer to obtain a milky white uniform powder. A dispersion was obtained. Similarly to the above, this dispersion was also a stable dispersion with no sedimentation of particles.
However, although mixing was possible even when the hydrophobic titanium oxide fine powder exceeded 30 parts by weight and 40 parts by weight, when the weight part of the powder was increased to 40 parts by weight, stirring with a stirring blade became increasingly difficult. The limit of the appropriate concentration as a dispersion was considered to be 30% by weight.

[Comparative Example 1]
The titanium oxide fine powder having a BET specific surface area of 90 m ² / g produced in Example 1 is hydrophilic. Without surface treatment, 10 parts by weight was taken and added to 90 parts by weight of methyl ethyl ketone taken in a vessel having a stirring blade, and stirring was continued for 30 minutes to obtain a white mixture.
When a part of the sample was collected and allowed to stand while stirring, some particles settled, and after 1 hour, a part of the solvent separated as a supernatant, and was sufficiently dispersed and stabilized. Not observed.
In addition, an ultrasonic homogenizer was allowed to act on a part of the mixture collected during stirring for 10 minutes and allowed to stand to observe. As in the case of mixing with a stirring blade, the particles settled and the solvent was removed after 1 to 2 hours. Separation was seen.
Furthermore, a part of the stirred sample was put into the sample folder of the bead mill, and pulverization and dispersion were tried while circulating the mixed solution. Even after the sample was milled for 1 hour, it was removed from the mill and left to stand. As time passed, sedimentation of the particles and separation of the solvent became apparent after 1 to 2 hours.
From this result, it was confirmed that hydrophilic titanium oxide is not easily dispersed stably in a nonpolar solvent.

[Example 2]
A dispersion was produced in the same manner as in Example 1, except that ethyl acetate was used as the nonpolar organic solvent.
That is, 10 parts by weight of hydrophobic titanium oxide fine powder was added to 90 parts by weight of ethyl acetate in a container having a stirring blade while stirring, and stirring was continued for 30 minutes to obtain a milky white uniform dispersion. It was.
As in Example 1, a part of this was sampled and the particle size distribution was measured. As in FIG. 1, the particle size distribution was 68 nm to 1.8 μm and D ₅₀ was 220 nm, which was sufficiently homogeneous by stirring. A good dispersion was obtained.
An ultrasonic homogenizer was allowed to act on a part of the remaining dispersion for 10 minutes, and a sample was collected from the part to measure the particle size distribution. As in FIG. 2, the particle size distribution was 45 nm to 0.42 μm. D ₅₀ is 80nm, and the further becomes fine particles, dispersed was promoted.
The remaining dispersion liquid was continuously mixed and dispersed with 30 μm stabilized zirconia beads for 60 minutes while dispersing the liquid with a bead mill, and the particle size distribution of the dispersion liquid was measured. As shown in FIG. Furthermore, the particle size distribution was 38 nm to 0.25 μm, D ₅₀ was 70 nm, and the coarse particles were further reduced by the bead mill to become fine particles, which promoted dispersion.
After the stirring, homogenization, and dispersion after mill mixing were each transferred to a transparent glass container and allowed to stand for observation, but after several days, neither sample sedimentation nor solvent separation was observed. .

[Example 3]
A dispersion was produced in the same manner as in Example 1 except that toluene was used as the nonpolar organic solvent.
That is, 10 parts by weight of hydrophobic titanium oxide fine powder was added to 90 parts by weight of toluene in a container having a stirring blade while stirring, and stirring was continued for 30 minutes to obtain a milky white uniform dispersion. .
In the same manner as in Example 1, a part of this dispersion was sampled and an ultrasonic homogenizer was allowed to act for 10 minutes. A sample was sampled from the part and the particle size distribution was measured. It was 2 μm.
After the stirring, the homogenized dispersion was transferred to a transparent glass container and allowed to stand to observe. After 2 to 3 hours, no precipitation of particles and separation of the solvent were observed.
After 24 hours from the homogenization treatment, changes and differences were observed in the state of cloudiness between the upper part and the lower part of the dispersion.

[Comparative Example 2]
In Comparative Example 1, the same operation was performed except that ethyl acetate was used as the nonpolar organic solvent.
That is, 10 parts by weight of hydrophilic titanium oxide fine powder not subjected to surface treatment was added to 90 parts by weight of ethyl acetate taken in a container having a stirring blade while stirring, and stirring was continued for 30 minutes. A white mixture was obtained.
When a part of this was collected and allowed to stand, some particles settled, and after 1 hour, a part of the solvent was observed as a supernatant, and it was confirmed that sufficient dispersion and stabilization were not achieved. It was.
In addition, an ultrasonic homogenizer was allowed to act on a part of the mixture collected during stirring for 10 minutes and allowed to stand to observe. As in the case of mixing with a stirring blade, the particles settled and the solvent was removed after 1 to 2 hours. Separation was seen.

[Comparative Example 3]
In Comparative Example 1, the same operation was performed except that toluene was used as the nonpolar organic solvent, and the liquid after stirring for 30 minutes or the dispersion liquid after ultrasonic homogenization treatment was allowed to stand. Sedimentation was observed, and a portion of the solvent was observed as a supernatant after 1 hour.

  From Comparative Examples 2 and 3, it was confirmed that the hydrophilic titanium oxide was hardly dispersed stably in the nonpolar solvent.

[Example 4]
BET specific surface area is 120 m ² / g by thermal hydrolysis in gaseous titanium tetrachloride in a flame in which hydrogen atoms are mixed at a temperature of 900 ° C. and a titanium concentration of 40 g / m ^{3 in} terms of titanium dioxide. g. A fine titanium oxide powder having an anatase ratio of 0.90 was produced.
100 parts by weight of this titanium oxide fine powder is put into a mixer, 20 parts by weight of n-butyltrimethoxysilane is added dropwise with stirring in a nitrogen atmosphere, heated and stirred at 150 ° C. for 2 hours, and then cooled to cool the surface. Processed.
The hydrophobicity of the obtained hydrophobic titanium oxide fine powder was 95%.

10 parts by weight of this hydrophobic titanium oxide fine powder was added to 90 parts by weight of methyl ethyl ketone taken in a container having a stirring blade while stirring, and stirring was continued for 30 minutes to obtain a milky white uniform dispersion. .
When a part of this dispersion was collected and the particle size distribution was measured, the particle size distribution was 65 nm to 1.8 μm, D ₅₀ was 200 nm, and it was confirmed that a sufficiently homogeneous dispersion was obtained by stirring. It was done.
An ultrasonic homogenizer was allowed to act on a part of the remaining dispersion for 10 minutes, and a part of the dispersion was sampled and the particle size distribution was measured. The particle size distribution was 40 nm to 0.42 μm, and D ₅₀ was 72 nm. Furthermore, it became a fine particle, and it was confirmed that dispersion | distribution was accelerated | stimulated.
The remaining dispersion was continued to be mixed and dispersed with 30 μm stabilized zirconia beads for 60 minutes while dispersing the liquid with the bead mill. When the particle size distribution of the dispersion liquid sample was measured, it was found that the particle size distribution was 36 nm to 0.23 μm, D ₅₀ was 62 nm, the coarse particles were further reduced by the bead mill to become fine particles, and the dispersion was accelerated. confirmed.

  After the stirring, homogenization, and dispersion after mill mixing were each transferred to a transparent glass container and allowed to stand for observation, but after several days, neither sample sedimentation nor solvent separation was observed. .

20 parts by weight of the above-mentioned hydrophobic titanium oxide fine powder is added to 80 parts by weight of methyl ethyl ketone taken in a container having a stirring blade while stirring, and stirring is continued for 30 minutes to obtain a milky white uniform dispersion. It was.
In the same manner as above, when this dispersion was dispersed with an ultrasonic homogenizer and a bead mill, respectively, it may be necessary to lengthen each treatment time. A dispersion was obtained.
Similarly to Example 2, even when ethyl acetate was used as the solvent, good dispersibility was obtained by dispersing with stirring, an ultrasonic homogenizer, and a bead mill.
Further, 30 parts by weight of hydrophobic titanium oxide fine powder was added to 70 parts by weight of methyl ethyl ketone while stirring, and after stirring for 1 hour, the mixture was dispersed with an ultrasonic homogenizer to obtain a milky white uniform dispersion. Similar to the above, no sedimentation of particles was observed, and it was confirmed that the dispersion was stable.
However, although mixing was possible even when the hydrophobic titanium oxide fine powder exceeded 30 parts by weight and 40 parts by weight, when the weight part of the powder was increased to 40 parts by weight, stirring with a stirring blade became increasingly difficult. The limit of the appropriate concentration as a dispersion was considered to be 30% by weight.

  The hydrophobic titanium oxide fine powder obtained by surface treatment in the same manner as described above using iso-butyltrimethoxysilane, which is an isomer, instead of n-butyltrimethoxysilane was also used for methyl ethyl ketone and ethyl acetate. Or dispersed homogeneously in toluene with a stirring blade, an ultrasonic homogenizer, a bead mill, etc., and the resulting dispersion shows no sedimentation of the powder and separation of the solvent after standing for 1 week to standing for 1 month, A result equivalent to the above was obtained.

[Example 5]
BET specific surface area of 40 m is obtained by thermal hydrolysis of gaseous titanium tetrachloride in a flame containing hydrogen atoms at a temperature of 1,550 ° C. and a titanium concentration of 230 g / m ^{3 in} terms of titanium dioxide. Titanium oxide fine powder with ² / g and anatase ratio of 0.30 was produced.
100 parts by weight of this titanium oxide fine powder is put into a mixer, 30 parts by weight of n-octadecyltrimethoxysilane is added dropwise with stirring in a nitrogen atmosphere, heated and stirred at 150 ° C. for 2 hours, and then cooled to cool the surface. Processed.
The hydrophobicity of the obtained hydrophobic titanium oxide fine powder was 90%.

10 parts by weight of this hydrophobic titanium oxide fine powder was added to 90 parts by weight of methyl ethyl ketone in a container having a stirring blade while stirring, and stirring was continued for 30 minutes to obtain a uniform dispersion.
An ultrasonic homogenizer was allowed to act on a part of this dispersion for 10 minutes, and a part of the dispersion was collected to measure the particle size distribution. The particle size distribution was 60 nm to 0.65 μm.
The stirred dispersion and further homogenized dispersion were each transferred to a transparent glass container and allowed to stand for observation, but no sedimentation of the particles and separation of the solvent were observed after one week.
Also, 20 parts by weight of the hydrophobic titanium oxide fine powder obtained by the above surface treatment was taken and stirred in 80 parts by weight of methyl ethyl ketone in the same manner and then dispersed with an ultrasonic homogenizer. Although it may be necessary, as described above, no sedimentation of particles was observed, and a stable dispersion was obtained.

[Example 6]
BET specific surface area is 150 m by thermal hydrolysis in gaseous titanium tetrachloride in a flame in which hydrogen atoms are mixed at a temperature of 1,550 ° C. and a titanium concentration of 15 g / m ^{3 in} terms of titanium dioxide. Titanium oxide fine powder having an anatase ratio of ² / g and anatase ratio of 0.95 was produced.
100 parts by weight of this titanium oxide fine powder is put into a mixer, 25 parts by weight of methyl hydrogen polysiloxane is added dropwise with stirring in a nitrogen atmosphere, heated and stirred at 250 ° C. for 1 hour, and then cooled to effect surface treatment. did.
The hydrophobicity of the obtained hydrophobic titanium oxide fine powder was 95%.

10 parts by weight of this hydrophobic titanium oxide fine powder was added to 90 parts by weight of methyl ethyl ketone in a container having a stirring blade while stirring, and stirring was continued for 30 minutes to obtain a uniform dispersion.
An ultrasonic homogenizer was allowed to act on a part of this dispersion for 10 minutes, and a part of the dispersion was sampled and the particle size distribution was measured. The particle size distribution was 50 nm to 0.55 μm.
The stirred dispersion and further homogenized dispersion were each transferred to a transparent glass container and allowed to stand for observation, but no sedimentation of the particles and separation of the solvent were observed after one week.
Also, 20 parts by weight of the hydrophobic titanium oxide fine powder obtained by the above surface treatment was taken and stirred in 80 parts by weight of methyl ethyl ketone in the same manner and then dispersed with an ultrasonic homogenizer. Although it may be necessary, as described above, no sedimentation of the particles and separation of the solvent were observed even after one week, and a stable dispersion was obtained.

[Example 7]
BET specific surface area is 100m by thermally hydrolyzing gaseous titanium tetrachloride in a flame containing hydrogen atoms at a temperature of 1,100 ° C and a titanium concentration of 100g / m ^{3 in} terms of titanium dioxide. ^A fine titanium oxide powder having a ² / g and anatase ratio of 0.80 was produced.
100 parts by weight of this titanium oxide fine powder was put into a mixer, 10 parts by weight of hexamethyldisilazane was added dropwise with stirring in a nitrogen atmosphere, and the mixture was heated and stirred at 200 ° C. for 2 hours, and then cooled. Furthermore, with respect to 100 parts by weight of the obtained hydrophobic titanium oxide fine powder, a mixture of 10 parts by weight of dimethylpolysiloxane and 30 parts by weight of n-hexane was added dropwise with stirring in a nitrogen atmosphere, and the mixture was heated and stirred at 300 ° C. for 1 hour. And it surface-treated by cooling.
The hydrophobicity of the obtained hydrophobic titanium oxide fine powder was 90%.

10 parts by weight of this hydrophobic titanium oxide fine powder was added to 90 parts by weight of methyl ethyl ketone in a container having a stirring blade while stirring, and stirring was continued for 30 minutes to obtain a uniform dispersion.
An ultrasonic homogenizer was allowed to act on a part of the dispersion for 10 minutes, and a part of the dispersion was sampled to measure the particle size distribution. The particle size distribution was 70 nm to 0.45 μm.
The stirred dispersion and further homogenized dispersion were each transferred to a transparent glass container and allowed to stand for observation, but no sedimentation of the particles and separation of the solvent were observed after one week.
Further, 20 parts by weight of the hydrophobic titanium oxide fine powder obtained by the above surface treatment was taken, stirred in 80 parts by weight of methyl ethyl ketone in the same manner, and then the dispersion was dispersed with an ultrasonic homogenizer. However, as described above, no sedimentation of the particles and separation of the solvent were observed after one week, and a stable dispersion was obtained.

[Comparative Example 4]
The titanium oxide fine powder having a BET specific surface area of 120 m ² / g produced in Example 4 is hydrophilic. Without surface treatment, 10 parts by weight was taken and added to 90 parts by weight of methyl ethyl ketone taken in a vessel having a stirring blade, and stirring was continued for 30 minutes to obtain a white mixture.
When a part of the sample was collected and allowed to stand while stirring, some particles settled, and after 1 hour, a part of the solvent separated as a supernatant, and was sufficiently dispersed and stabilized. Not observed.
In addition, an ultrasonic homogenizer was allowed to act on a part of the mixture collected during stirring for 10 minutes and allowed to stand to observe. As in the case of mixing with a stirring blade, the particles settled and the solvent was removed after 1 to 2 hours. Separation was seen.
Furthermore, a part of the stirred sample was put into the sample folder of the bead mill, and pulverization and dispersion were tried while circulating the mixed solution. Even after the sample was milled for 1 hour, it was removed from the mill and left to stand. Over time, after 1 to 2 hours, sedimentation of particles and separation of nonpolar solvents became apparent.
Similar results were obtained when ethyl acetate or toluene was used as the nonpolar organic solvent.

[Comparative Example 5]
The titanium oxide fine powder having a BET specific surface area of 40 m ² / g produced in Example 5 is hydrophilic. Without surface treatment, 10 parts by weight were taken and added to 90 parts by weight of methyl ethyl ketone, which is a nonpolar solvent, taken in a container having a stirring blade, and stirring was continued for 30 minutes to obtain a white mixture. It was.
When a part of the sample was collected and allowed to stand while stirring, some particles settled, and after 1 hour, a part of the solvent separated as a supernatant, and was sufficiently dispersed and stabilized. Not observed.
In addition, an ultrasonic homogenizer was allowed to act on a part of the mixture collected during stirring for 10 minutes and allowed to stand to observe. As in the case of mixing with a stirring blade, the particles settled and the solvent was removed after 1 to 2 hours. Separation was seen.
Furthermore, a part of the stirred sample was put into the sample folder of the bead mill, and pulverization and dispersion were tried while circulating the mixed solution. Even after the sample was milled for 1 hour, it was removed from the mill and left to stand. Over time, after 1 to 2 hours, sedimentation of particles and separation of nonpolar solvents became apparent.
Similar results were obtained when ethyl acetate or toluene was used as the nonpolar organic solvent.

[Comparative Example 6]
The titanium oxide fine powder having a BET specific surface area of 150 m ² / g produced in Example 6 is hydrophilic. Without surface treatment, 10 parts by weight was taken and added to 90 parts by weight of methyl ethyl ketone taken in a vessel having a stirring blade, and stirring was continued for 30 minutes to obtain a white mixture.
When a part of the sample was collected and allowed to stand while stirring, some particles settled, and after 1 hour, a part of the solvent separated as a supernatant, and was sufficiently dispersed and stabilized. Not observed.
In addition, an ultrasonic homogenizer was allowed to act on a part of the mixture collected during stirring for 10 minutes and allowed to stand to observe. As in the case of mixing with a stirring blade, the particles settled and the solvent was removed after 1 to 2 hours. Separation was seen.
Furthermore, a part of the stirred sample was put into the sample folder of the bead mill, and pulverization and dispersion were tried while circulating the mixed solution. Even after the sample was milled for 1 hour, it was removed from the mill and left to stand. Over time, after 1 to 2 hours, sedimentation of particles and separation of nonpolar solvents became apparent.
Similar results were obtained when ethyl acetate or toluene was used as the nonpolar organic solvent.

[Comparative Example 7]
The titanium oxide fine powder having a BET specific surface area of 100 m ² / g produced in Example 7 is hydrophilic. Without surface treatment, 10 parts by weight was taken and added to 90 parts by weight of methyl ethyl ketone taken in a vessel having a stirring blade, and stirring was continued for 30 minutes to obtain a white mixture.
When a part of the sample was collected and allowed to stand while stirring, some particles settled, and after 1 hour, a part of the solvent separated as a supernatant, and was sufficiently dispersed and stabilized. Not observed.
In addition, an ultrasonic homogenizer was allowed to act on a part of the mixture collected during stirring for 10 minutes and allowed to stand to observe. As in the case of mixing with a stirring blade, the particles settled and the solvent was removed after 1 to 2 hours. Separation was seen.
Furthermore, a part of the stirred sample was put into the sample folder of the bead mill, and pulverization and dispersion were tried while circulating the mixed solution. Even after the sample was milled for 1 hour, it was removed from the mill and left to stand. Over time, after 1 to 2 hours, sedimentation of particles and separation of nonpolar solvents became apparent.
Similar results were obtained when ethyl acetate or toluene was used as the nonpolar organic solvent.

  Also from the results of the above Comparative Examples 4 to 7, it was confirmed that hydrophilic titanium oxide is difficult to be stably dispersed in a nonpolar solvent.

[Reference Example 1]
The zirconium component contained in the dispersions obtained in Examples 1, 2, and 4 was analyzed.
In order to prevent leakage of the zirconium component, the solvent of each dispersion liquid was evaporated, and the sample obtained by drying and solidifying the sample was heat-treated at 700 ° C. and solidified by observing with SEM-EDX, and each random Six points were selected for the component analysis.
As a result, the amount of the zirconium component was 0.00% below the detection limit and was not substantially detected.
That is, when dispersing titanium oxide in a nonpolar organic solvent, if balls or beads such as stabilized zirconium oxide generally used as a grinding medium are used, there is a concern about contamination by zirconium. Since a good dispersion result was obtained with a short mixing / dispersion time, it was confirmed that the contamination by the zirconium in the dispersion was not a problematic mixing amount.

Claims (9)

  Hydrophobic formed by dry-treating the surface of titanium oxide fine powder obtained by hydrolyzing a volatile titanium compound in a gas-phase flame containing hydrogen with a silane coupling agent and / or a silicone compound. A nonpolar organic solvent dispersion of titanium oxide obtained by dispersing a fine titanium oxide fine powder in a nonpolar organic solvent. In Claim 1, the titanium oxide which comprises the said hydrophobic titanium oxide fine powder has a BET specific surface area of 40-150 m < ² > / g, has a crystal structure of anatase and a rutile, and the ratio of anatase is 0.3-0. A nonpolar organic solvent dispersion of titanium oxide, which is 98 titanium oxide.   The nonpolar organic titanium according to claim 1 or 2, wherein the nonpolar organic solvent is one or more selected from the group consisting of methyl ethyl ketone, ethyl acetate, benzene, diethyl ether, and toluene. Organic solvent dispersion. 4. The nonpolar organic solvent dispersion of titanium oxide according to claim 1, wherein the silane coupling agent is represented by the following general formula (I) or (II): .
X _4-n SiR _n (I)
(In the formula (I), X represents a hydroxyl group, an alkoxy group, or a halogen atom, R represents an alkyl group having 1 to 18 carbon atoms, and n represents an integer of 0 to 3).
R ′ ₃ SiNHSiR ′ ₃ (II)
(In the formula (II), R ′ represents an alkyl group having 1 to 3 carbon atoms, and some R ′ may be other substituents such as a hydrogen atom or a vinyl group.) The nonpolar organic solvent dispersion of titanium oxide according to any one of claims 1 to 3, wherein the silicone compound is represented by the following general formula (III).

(In the formula (III), R ^a represents a methyl group or an ethyl group, and R ^b represents a hydrogen atom, a methyl group, an ethyl group, or an alkyl group which may be substituted with a vinyl group, a phenyl group or an amino group. X ′ represents a hydroxyl group, an alkoxy group, a halogen atom or an alkyl group, and m represents an integer of 1 to 500.)   The non-polar organic solvent for titanium oxide according to any one of claims 1 to 5, wherein the hydrophobic titanium oxide fine powder exhibits a value of a hydrophobicity measured by a transmittance method of 70% or more. Dispersion.   7. The hydrophobic titanium oxide fine powder according to claim 1, wherein the hydrophobic titanium oxide fine powder is obtained by mixing and heat-treating the titanium oxide fine particles and the silane coupling agent and / or silicone compound. A non-polar organic solvent dispersion of titanium oxide characterized.   8. The hydrophobic titanium oxide fine powder according to claim 1, wherein the hydrophobic titanium oxide fine powder is mixed with a stirring blade, a dissolver, a ball mill, a kneader, a sand mill, a roll mixer, an ultrasonic homogenizer, a homomixer, a tower mill, a wet jet mill, and a bead mill. A nonpolar organic solvent dispersion of titanium oxide, wherein the dispersion is dispersed in the nonpolar organic solvent by one or more mechanical / physical means.   The nonpolar organic solvent dispersion of titanium oxide according to any one of claims 1 to 8, wherein the concentration of the fine powder of hydrophobic titanium oxide is 0.1 to 40% by weight.

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