JPH11292520A - Metal oxide sol with fluorinated surface and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aquasol or organosol which has an extremely small average particle size and an excellent dispersion state, which is stable without aggregation and which enables controlling of hydrophilicity or hydrophobicity, by reacting a molecular fluorine gas with a metal oxide sol dispersed in a liquid dispersion medium. SOLUTION: A metal oxide sol such as titanium oxide, aluminum oxide and silicon oxide, which have 1-500 nm avarag particle diameter of primary particles dispersed in a liquid dispersion medium such as water or an org. solvent is reacted with a molecular fluorine gas to obtain a metal oxide sol having a fluorinated surface. The fluorination reaction is preferably carried out at -20 to 200 deg.C reaction temp. within 3 hours reaction time by using a fluorine gas diluted with nitrogen or argon. By controlling the reaction time or the concn. of the source fluorine gas, the surface fluorination rate is controlled to control the hydrophobicity or hydrophilicity of the metal oxide sol. The obtd. sol is excellent in dispersibility, resistance against acid and alkali, light resistance, weather resistance and shielding property, and is effective as an additive.

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 a metal oxide sol having a surface fluorinated in a liquid phase, and a metal oxide sol having a substantially surface fluorinated obtained by the method. It is. More specifically,
By fluorinating the surface of metal oxide particles to control from hydrophilic to hydrophobic side, the stability, water repellency and dispersibility of the sol are improved. And a method for producing the same.

[0002]

2. Description of the Related Art Metal oxides are widely used as raw materials for paints, matte synthetic fibers, printing inks, cosmetics, milky glass, etc., and as colorants or pigments for rubbers and resins. Usually, the surface of the metal oxide is covered with a hydroxyl group, and shows a hydrophilic property. Therefore, when it is blended with a hydrophobic material such as a resin, a paint or a cosmetic, a surface treatment is performed. For example, in order to improve the dispersibility of titanium oxide in hydrophobic materials, treatment with higher fatty acids, treatment with organosilicon compounds, silica / alumina treatment, treatment with various coupling agents, and many other surface treatments have been attempted. It has been implemented. Similarly, for aluminum oxide and silicon oxide, surface treatment with a silylating agent or the like has been attempted on the particle surface.

[0003] These methods all aim at controlling the hydrophobicity or hydrophilicity of the surface of the metal oxide particles or the surface activity thereof by replacing and eliminating the hydroxyl groups on the surface of the metal oxide particles. However, when the metal oxide particles are blended with a highly hydrophobic substance such as a fluororesin, it is desirable that the particles be even more hydrophobic and oleophobic. It is necessary to form a surface covered with. In addition, when compounding with a material requiring weather resistance, it was necessary to reduce the photocatalytic action in order to prevent deterioration of the material. When blended with such a resin or the like, the metal oxide having a fluorinated particle surface is advantageously an organosol suspended in a hydrophobic solvent.

[0004] The present inventors have previously prepared such a surface-fluorinated metal oxide by directly fluorinating a metal oxide in the form of fine powder with fluorine gas, whereby the solid surface was fluorinated. It has been developed to produce metal oxides. In order to obtain a stable sol-like organosol of fluorinated metal oxide, a method of synthesizing fine metal oxide in the gas phase and then dispersing it in a solvent was attempted. In general, oxides cannot be dispersed well in an organic solvent that is a dispersion medium, and in this state, fluorination of a metal oxide is possible, but the fluorination rate is not so high, and fluorination does not proceed well. It has been found.
On the other hand, a metal oxide in a state of extremely excellent dispersibility, that is, an organosol or aquasol state metal oxide produced by a liquid phase method is extremely stable. It is considered possible to manufacture products (titanium oxide, silicon oxide, etc.). A sol having a stable dispersion state and excellent sol state is a sol made in a liquid phase system. Further, it is considered that a metal oxide having a fluorinated surface can easily form a good dispersed state because the surface energy can be reduced by fluorination, and can be expected to improve properties such as lubricating properties.

Until now, a method of treating a metal oxide with a fluorine compound is disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 59-184263.
Japanese Patent Application Publication No. JP-A-2003-115139 discloses a method of adding sodium fluoride to a suspension slurry of titanium oxide and performing stirring treatment. However, in this method, when the titanium oxide is ultra-fine particles, the coagulation becomes strong in the drying step, and good dispersibility cannot be obtained even if the particles are pulverized. In this method, a fluorine atom is not directly bonded to a titanium atom, and it is difficult to say that the surface of titanium oxide is fluorinated. JP-A-61-215216 discloses that, when producing hydrophobic spherical titanium oxide particles,
A method using an organic fluorine compound as a hydrophobicity-imparting substance is disclosed, but also in this case, the titanium oxide surface is not substantially fluorinated. Also, JP-A-3-4091
No. 9 discloses a method in which a fluorocarbon gas is brought into contact with ultrafine titanium oxide and the surface is fluorinated at a high temperature of 200 to 400 ° C. However, since the reaction temperature is 200 ° C. or higher, thermal efficiency is not necessarily high. Not good. It has been known that metal oxides such as titanium oxide sol, aluminum oxide sol, and silicon oxide sol directly fluorinate the surface of metal oxide particles using fluorine gas in a liquid phase. Absent.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to a metal oxide aquasol or a metal oxide having an extremely small average particle diameter, excellent dispersion state, stable without aggregation, and capable of adjusting hydrophobicity and hydrophilicity. An object of the present invention is to provide an organosol and a method for producing the same.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve such a conventional problem. As a result, when the metal oxide sol is reacted with fluorine gas, the surface is substantially fluorinated. Therefore, they have found that a metal oxide sol having water / oil repellency, little particle aggregation, and a narrow particle size distribution can be obtained. In addition, the present inventors have found that, among metal oxides whose surfaces are fluorinated, the surface fluorinated titanium oxide sol has improved light resistance, water repellency and dispersibility as compared with conventional particulate titanium oxide, and When mixed with a thermoplastic resin as a shielding material, it was confirmed that it was a metal oxide capable of reducing the deterioration of the thermoplastic resin and was suitable for a transparent thin film or the like. Based on the above findings, the present invention provides the following surface fluorinated metal oxide sol and a method for producing the same.

The present invention provides [1] a method for producing a metal oxide sol having a fluorinated surface, comprising reacting a molecular fluorine gas with a metal oxide sol dispersed in a liquid dispersion medium, [2] The method for producing a surface-fluorinated metal oxide sol according to the above [1], wherein the molecular fluorine gas is a fluorine-containing gas diluted with nitrogen or argon gas, [3] reaction time and / or raw material fluorine The method for producing a surface-fluorinated metal oxide sol according to the above [1] or [2], wherein the surface fluorination metal oxide sol having a controlled surface fluorination rate is adjusted by adjusting the gas concentration, [4] ]
The method for producing a surface-fluorinated metal oxide sol according to any one of the above [1] to [3], wherein the fluorinated metal oxide sol is at least one of titanium oxide, aluminum oxide and silicon oxide. ,

[5] A metal oxide sol in which the surface of metal oxide particles is substantially fluorinated and dispersed in the liquid dispersion medium obtained by the method according to any one of the above [1] to [4], [6] The metal oxide sol according to the above [5], wherein the fluorinated metal oxide sol is at least one of titanium oxide, aluminum oxide and silicon oxide. [7] The metal oxide sol according to [5] or [6], wherein the surface of the metal oxide particles is substantially fluorinated, wherein the average particle diameter of the metal oxide in the sol is 200 nm or less, and [ 8]
The above object is attained by developing a metal oxide sol in which the surface of the metal oxide particles is substantially fluorinated according to any one of the above [5] to [7], wherein the dispersion medium is water or an organic solvent. Settled.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Method for Producing Metal Oxide Sol] In the present invention, a metal oxide sol used as a raw material
The production method is not limited as long as it is a stable aquasol or organosol. The average particle diameter of the metal oxide sol used in the present invention is 1 to 500 nm, and preferably 1 to 50 nm when the metal oxide sol whose surface has been fluorinated requires transparency. For example, as a conventional method of manufacturing a sol of titanium oxide, hydrous titanium oxide obtained by heat treatment of an aqueous solution of titanium sulfate or an aqueous solution of titanium tetrachloride is treated with sodium hydroxide or the like,
Further, it is known that a titania hydrosol having a rutile-type crystal structure can be obtained by a method of producing by aging in hydrochloric acid or by heating a solution obtained by dropping titanium tetrachloride in a solution of hydrochloric acid or the like. ing. Further, a method has been proposed in which an aqueous solution of hydrous titanium oxide and an alkali metal is heat-treated and then aged with an aqueous hydrochloric acid solution to produce a rutile type titanium oxide sol (Japanese Patent Application Laid-Open No. 62-235215). Furthermore, a method has been proposed in which a water-soluble titanium compound is reacted with an ammonium compound, a gel is prepared, and then a hydrothermal treatment is performed at 100 ° C. or more, and a hydrosol of crystalline titanium oxide is produced with an acid (Japanese Patent Application Laid-Open No. 62-207718). ing.

Above all, when the titanium halide is hydrolyzed in the presence of a hydrophilic or hydrophobic organic solvent using 1 to 5 times the theoretical amount of water required for the hydrolysis of the titanium halide, the average A crystalline titanium oxide sol having a particle diameter of 20 nm or less can be easily produced. When this method is used, it is easy to control the crystal form of rutile, anatase, etc. at a low temperature, there is almost no particle aggregation, the average particle diameter is small, and a fine particle metal oxide sol having a narrow particle size distribution is efficiently produced. It can be used as a metal oxide sol suitable as a raw material of a metal oxide having a surface fluorinated according to the present invention.

It is well known that fluorine is a very active substance and reacts with many substances to fluorinate the partner substance. Therefore, when the fluorine gas is brought into contact with the metal oxide sol dispersed in the liquid phase, it reacts with the organic solvent or water used as the dispersion medium, and the fluorination of the metal oxide sol in the dispersion medium is not difficult. Surprisingly, when the metal oxide sol is brought into contact with fluorine gas, the fluorine gas almost instantaneously reacts with the metal oxide particles almost instantaneously and reacts with the organic solvent or water as the dispersion medium. Since the reaction of this is slow, the reaction with the dispersing medium is very slight, and it has been found that the presence of these dispersing media does not hinder the fluorination reaction of the metal oxide sol. The present invention has been made based on this finding. In this case, a small part of the fluorine gas reacts with a substance other than the metal oxide to generate by-products such as hydrogen fluoride, which can be easily removed by treatment with a basic ion exchange resin or the like. It does not hinder the production of fluorinated metal oxide sols.

[Fluorination of metal oxide sol]
The method for producing a metal oxide sol having a fluorinated surface is characterized by reacting the metal oxide sol with fluorine, substantially fluorinating the particle surface, and optionally controlling the fluorination ratio. Things. Here, “substantially” means that almost the entire surface of the metal oxide sol is fluorinated, but it is not necessary that the metal oxide sol be 100% fluorinated. Also, the surface need not necessarily be uniformly fluorinated. Incidentally, the fluorination rate of the particle surface is determined by XPS (X-ray photoel).
The ratio is determined from the total amount of elements existing from the particle surface to a depth of about 100 angstroms determined by electron spectroscopy (X-ray photoelectron spectroscopy). For example, in the fluorination of titanium oxide, all (ie, 100%) of the titanium in the titanium oxide is TiF
₄ , the fluorine content of the particles becomes (4F
/ TiF ₄ ) × 100 = 61.3% by weight.

The metal oxide used as a raw material in the present invention means a metal oxide. Specific examples include oxides such as titanium, aluminum, silicon, silver, copper, zirconium, zinc, tin, germanium, and tantalum. In particular, oxides of titanium, aluminum, and silicon are preferable. The specific surface area, crystal type and the like of the metal oxide sol used as the raw material are not particularly limited, and various types may be used. The particle size is usually 500 nm or less in average primary particle size, preferably 200 n
m, particularly preferably 1 to 50 nm. Regarding its crystal form, for example, titanium oxide may be any of amorphous, anatase, brookite, and rutile. Aluminum oxide may be any of amorphous, α-alumina and γ-alumina. Silicon oxide may be either silicic anhydride or synthetic silicic acid.

The fluorination reaction of the metal oxide sol of the present invention is carried out by a liquid phase method, for example, as follows. That is, the above-described raw material metal oxide sol is directly charged into a reactor such as an autoclave, and after the reactor is heated to a predetermined temperature, a reaction is performed for a predetermined time while flowing a molecular fluorine-containing gas into the reactor. The surface is fluorinated. In this case, the reactor is filled with: (1) a metal oxide sol is prepared and filled by a sol-gel method in a metal alkoxide in a solvent. (2) The obtained metal oxide sol is filled by hydrolyzing a metal halide in a solvent. (3) A commercially available metal oxide sol is filled as it is. Any of these may be used. The heating temperature of the reactor, in other words, the reaction temperature, is usually -20 to 200 ° C, especially 0 to 15 ° C.
0 ° C. is preferred. The reaction time is adjusted by adjusting the fluorination rate of the target metal oxide and the amount of molecular fluorine to be supplied (the supply amount of gas and the content of molecular fluorine). Normal 3
The reaction is performed under conditions such that the target reaction is completed within an hour, preferably within one hour. In the reaction, the supply rate of the molecular fluorine gas is not fixed according to the target fluorination rate, but is usually 0.1 to 100 ml / g (metal oxide).
Min, particularly preferably 0.5 to 50 ml / g.
・ It is a minute. When the amount is small, a batch type reaction is also possible. Furthermore, although the concentration of fluorine gas can be used even at 100%,
0.01% by volume or more, preferably 0.1% by volume or more, more preferably 1% by volume or more of a fluorine-containing gas diluted with nitrogen, argon, or the like can be used. By adjusting the concentration of the molecular fluorine gas and / or the reaction time, the fluorination rate on the surface of the metal oxide particles can be easily controlled.

The surface fluorinated metal oxide sol obtained by the above production method of the present invention maintains the particle shape and high specific surface area of the raw material, and has an average primary particle diameter of 500 nm or less,
It is preferably 200 nm or less, more preferably 1 to 50 nm fine particles or ultrafine particles. As the dispersion medium used in the present invention, water or an organic solvent is used. Examples of the organic solvent include alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, ketones, esters, ethers, ketone ethers, ketone esters, ester ethers, and the like. And mixtures thereof.

Specific examples of these organic solvents include methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, nonanol,
Benzyl alcohol, methylcyclohexanol, ethanediol, propanediol, butanediol, pentanediol, hexanediol, octanediol,
Alcohols such as hexanetriol; butyl formate, pentyl formate, methyl acetate, ethyl acetate, propyl acetate;
Butyl acetate, pentyl acetate, hexyl acetate, benzyl acetate, 3-methoxybutyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, methyl propionate, ethyl propionate, ethyl propionate, butyl propionate, pentyl propionate and the like Esters; amides such as dimethylformamide, dimethylacetamide, diethylformamide, diethylacetamide; ketones such as dimethylketone, methylethylketone, pentanone, hexanone, methylisobutylketone, heptanone, diisobutylketone; nitriles such as acetonitrile; diethylether; Ethers such as dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether; anisole, tetrahydrofuran, tet Cyclic ethers such as hydropyran; dimethoxyethane, diethoxyethane, dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol ethers such as ethylene glycol dibutyl ether; methylal, acetal such as acetal; pentane, hexane, heptane; Paraffinic hydrocarbons such as octane, nonane, decane, dodecane, etc .; toluene, xylene, ethylbenzene, cumene, missitylene,
Cyclic hydrocarbons such as tetralin, butylbenzene, cymene, diethylbenzene, pentylbenzene, dipentylbenzene, cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, and decalin; chloromethane, dichloromethane, trichloromethane, tetrachloromethane, chloroethane, dichloroethane, Trichloroethane, tetrachloroethane, pentachloroethane, chloropropane, dichloropropane, trichloropropane, chlorobutane, dichlorobutane, trichlorobutane, chloropentane, chlorobenzene, dichlorobenzene, chlorotoluene, dichlorotoluene, bromomethane, bromoethane, bromopropane, bromobenzene,
Halogenated hydrocarbons such as chlorobromoethane; and the like.

The water used in the present invention is not particularly limited, and general tap water, distilled water, ion-exchanged water and the like can be used. Among these, distilled water or ion-exchanged water is preferable, and ion-exchanged water having an electric conductivity of 2 μm / cm or less is particularly desirable. The surface fluorinated metal oxide sol obtained according to the present invention exhibits water and oil repellency and is also excellent in acid resistance and alkali resistance. Further, it has good dispersibility in a hydrophobic substance, and is advantageous when added to a Teflon resin for the purpose of improving light resistance, weather resistance, hiding power, whiteness, controlling the refractive index, and absorbing ultraviolet light. Therefore, the surface fluorinated metal oxide sol of the present invention is extremely useful as an additive for paints, synthetic resins, cosmetics and the like that require weather resistance. Also, according to the method of the present invention,
Moreover, the surface of the metal oxide sol can be efficiently fluorinated by controlling the surface at an arbitrary ratio, which is extremely useful in industry.

Among the metal oxides, titanium oxide is known to have a photocatalytic function for generating OH radicals on the surface by light. Therefore, when titanium oxide is blended and used with a polymer or the like, the polymer near the surface of the titanium oxide is oxidized due to this catalytic action, and the deterioration proceeds. Therefore, in order to prevent the polymer from deteriorating, it is necessary to completely coat the titanium oxide surface to prevent this photocatalysis. On the other hand, this photocatalytic action also has the effect of decomposing dirt by the catalytic action if titanium oxide is present when dirt adheres to the polymer surface. The photocatalytic action of the titanium oxide whose surface is fluorinated according to the present invention can be adjusted by adjusting the fluorination rate.

The following results were obtained by studying the regulation of photocatalytic action by fluorination of titanium oxide particles. Metal oxide sol whose surface has been fluorinated with a changed fluorination rate,
A titanium oxide sol whose surface was not fluorinated was prepared, and a liquid phase oxidation reaction of tetralin was performed using the sol, and their photocatalytic effects were measured. That is, a heat-resistant glass reactor 5 having a capacity of about 100 ml and connected to a glass tube as shown in FIG. 1 was prepared with reference to Kato et al. [Industrial Chemistry Magazine, 63 , 5, 748 to 750 (1960)]. 20 ml of tetralin is put in advance, 0.02 g of titanium oxide sol whose surface is fluorinated is used as titanium oxide, and the reaction temperature is kept at 40.1 ° C. in a thermostatic oven 2. While irradiating with an ultraviolet lamp 1 in a gas atmosphere, the pressure at every predetermined time is measured by a differential pressure gauge (Differential Pressure Ga).
u.g. 4), the pressure measurement is plotted against time and its slope (pressure change: mmH ₂ O / min)
Is the oxygen absorption rate. For comparison, a similar test was performed on a system using titanium oxide in a titanium oxide sol that was not fluorinated and tetralin containing no titanium oxide. Table 1 shows the results.

[0021]

[Table 1] As described above, the photocatalytic effect is suppressed as the fluorination rate increases.

In the case of titanium oxide sol as a raw material of the present invention, a halogen is prepared by using 1 to 5 times the theoretical amount of water necessary for hydrolysis of titanium halide in the presence of a hydrophilic or hydrophobic organic solvent. When titanium oxide is hydrolyzed to produce crystalline titanium oxide sol (both rutile type and anatase type) having an average particle diameter of 20 nm or less, a higher concentration than conventional amorphous titanium oxide sol production methods is used. It can be obtained in a stable sol. For this reason, when a titanium oxide-silica multilayer infrared reflecting film is to be prepared, the surface of the present invention requires only one coating or a small number of coatings when using a fluorinated crystalline titanium oxide sol. A reflective film having a desired film thickness and reflectivity can be obtained. In addition, the fluorinated titanium oxide sol obtained according to the present invention has excellent stability, and therefore, it is difficult to form a uniform film using a conventional titanium oxide powder during work such as coating. Even after storage for a period, the titanium oxide sol maintains a uniform dispersion, and a uniform coating film can be obtained by applying the titanium oxide sol. This is very effective in the production of a titanium oxide-based ceramic coating film. In addition, since the crystalline titanium oxide sol is uniformly dispersed in water or an organic solvent, handling is easy,
At the time of use, it can be diluted to an appropriate concentration or mixed with other materials.

[0023]

Next, the fluorinated metal oxide sol of the present invention and the method for producing the same will be described in detail with particular reference to examples of titanium oxide, aluminum oxide and silicon oxide. Not restricted. In the description of the following examples, the fluorine content on the particle surface indicates the ratio (% by weight) of all the constituent elements on the sample surface measured by XPS, but does not include carbon due to contamination.

Example 1 4 g of an aqueous solution of titanium tetrachloride (containing 0.3 g of water) and 40 ml of dimethylformamide were added to a reactor (autoclave), and the mixture was heated at 100 ° C. for 1 hour to form a translucent gel. An anatase-type crystalline titanium oxide sol (particle diameter: 1 to 10 nm) was obtained. After the air in the reactor was removed by reducing the pressure of the anatase-type titanium oxide sol, a gas (fluorine content: 20% by volume) obtained by diluting fluorine gas with nitrogen gas was fed into the reactor for 15 minutes, and the surface treatment was performed. An almost transparent sol was obtained. A neutral to weakly acidic sol was obtained by adding a basic ion exchange resin to the sol and filtering the sol. After removing the solvent from the fluorinated surface-treated sol at a low temperature, the fluorine content was quantified by XPS. As a result, the fluorine atoms were 14%.

Example 2 4 g of an aqueous solution of titanium tetrachloride (containing 0.3 g of water) and 40 ml of toluene were added to the same reactor as in Example 1, and the mixture was heated at 100 ° C. for 1 hour, thereby producing a rutile-type crystalline titanium oxide sol. was gotten. Fluorine gas (fluorine content: 20% by volume) diluted with nitrogen gas was fed into the rutile-type titanium oxide sol for 15 minutes, and surface treatment was performed to obtain an almost transparent sol. A neutral to weakly acidic sol was obtained by adding a basic ion exchange resin to the sol and filtering the sol. After removing the solvent from the fluorinated surface-treated sol at a low temperature, the fluorine content was quantified by XPS. As a result, the content of fluorine atoms was 16%.

Example 3 4 g of titanium tetrapropoxide and 0.1 g of acetylacetone were added to 40 ml of ethanol and stirred in the same reactor as in Example 1 to obtain a crystalline titanium oxide sol. Fluorine gas (fluorine content: 10% by volume) diluted with nitrogen gas was fed into this crystalline titanium oxide sol for 15 minutes to perform a surface treatment, and an almost transparent sol was obtained. After ethanol was removed from the fluorinated surface-treated sol at a low temperature, the fluorine content was quantified by XPS. As a result, the content of fluorine atoms was 16%.

Example 4 A crystalline silicon oxide sol was obtained by adding 4 g of silyltetraethoxide and 40 ml of ethanol containing 1% water to an atmospheric pressure gas-phase flow reactor and heating to 50 ° C. . Fluorine gas (fluorine content: 10% by volume) diluted with nitrogen gas was fed into the crystalline silicon oxide sol for 15 minutes to perform a surface treatment, and an almost transparent sol was obtained. After ethanol was removed from the fluorinated surface-treated sol at a low temperature, the fluorine content was quantified by XPS. As a result, the content of fluorine atoms was 16%.

(Example 5) A fluorinated alumina sol can be obtained by subjecting a commercially available alumina sol to the same fluorine gas treatment. As a result of quantifying the fluorine content by XPS, the fluorine content was 15%.

Example 6 Titanium oxide (1.68 g) having an average primary particle size of 50 nm was placed in an autoclave, and 40 ml of dimethylformamide was further added. However, dispersion was difficult for 1 minute. I let it. After the air in the autoclave was removed by reducing the pressure of this dispersion solution in the same manner as in Example 1, fluorine gas (fluorine content: 20% by volume) diluted with nitrogen gas was added to this reactor for 1 hour.
After passing for 5 minutes, the surface of the titanium oxide was fluorinated.
The titanium oxide sol whose surface was fluorinated gave a dispersion almost unchanged from the state before fluorination. A neutral to weakly acidic dispersion was obtained by adding a basic ion exchange resin to the dispersion and filtering the dispersion. After removing dimethylformamide at a low temperature, the fluorine content of the obtained surface fluorinated titanium oxide was quantified by XPS. As a result, the fluorine content was 3%. Thus, when using commercially available titanium oxide in the form of fine particles, when performing fluorination by the liquid phase method, fluorination can be performed without causing aggregation, but compared to titanium oxide sol produced by the liquid phase method. As a result, the fluorination rate was considerably reduced.

[0030]

According to the present invention, by reacting a molecular fluorine gas with a metal oxide sol dispersed in a liquid dispersion medium, the average particle diameter is extremely small, and the stable dispersion state without aggregation is excellent. A metal oxide having a fluorinated surface can be efficiently produced. In production, it is only necessary to bring molecular fluorine into contact with the metal oxide sol dispersed in the liquid dispersion medium, and since it is hardly affected by the dispersion medium, the production method is extremely simple, and the fluorination of the liquid phase is required. It can be manufactured as a sol in a state where the dispersion state is stable. The metal oxide whose surface is fluorinated increases hydrophobicity, and the hydrophobicity and hydrophilicity can be appropriately adjusted by adjusting the fluorination rate. When using this method,
Since only the surface of the metal oxide is fluorinated, its properties such as hydrophobicity and hydrophilicity can be controlled while maintaining the properties such as the crystal form of the metal oxide. The metal oxide sol having a fluorinated surface has light resistance, water repellency,
The dispersibility is improved, and it is easy to mix as an additive in a hydrophobic substance such as a fluororesin.

[Brief description of the drawings]

FIG. 1 is a schematic view of a reaction apparatus used in an experiment for confirming the catalytic action of a surface fluorinated titanium oxide on a photochemical reaction according to the present invention.

[Explanation of symbols]

 1 ultraviolet lamp 2 constant temperature bath 3 stirrer 4 differential pressure gauge 5 reactor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Omori 1-1-1, Onodai, Midori-ku, Chiba-shi, Chiba Prefecture Showa Denko KK Research Institute (72) Inventor Chozo Inoue 1 Onodai, Midori-ku, Chiba-shi, Chiba No. 1-1, Showa Denko KK Research Institute (72) Inventor Nobuaki Ishii 5-1-1, Okawa, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Denko KK Research Technology Center

Claims (8)

[Claims] 1. A method for producing a metal oxide sol having a fluorinated surface, comprising reacting a molecular fluorine gas with a metal oxide sol dispersed in a liquid dispersion medium. 2. The method for producing a surface-fluorinated metal oxide sol according to claim 1, wherein the molecular fluorine gas is a fluorine-containing gas diluted with nitrogen or argon gas. 3. A metal having a surface fluorinated according to claim 1, wherein a surface fluorinated metal oxide sol having a controlled surface fluorination rate is obtained by adjusting a reaction time and / or a raw material fluorine gas concentration. A method for producing an oxide sol. 4. The fluorinated metal oxide sol according to claim 1, wherein the fluorinated metal oxide sol is at least one of titanium oxide, aluminum oxide and silicon oxide. Manufacturing method. 5. A metal oxide sol in which the surface of metal oxide particles substantially fluorinated dispersed in a liquid dispersion medium obtained by the method according to claim 1 is fluorinated. 6. The metal oxide having a substantially fluorinated metal oxide particle surface according to claim 5, wherein the fluorinated metal oxide sol is at least one of titanium oxide, aluminum oxide and silicon oxide. Thing sol. 7. The metal oxide in the sol has an average particle diameter of 20.
The metal oxide sol according to claim 5 or 6, wherein the surface of the metal oxide particles is substantially fluorinated. 8. The metal oxide sol according to claim 5, wherein the dispersion medium is water or an organic solvent.