JP4521801B2 - Organic solvent-dispersed titanium oxide sol and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic solvent-dispersed titanium oxide sol and a method for producing the same, and in particular, has excellent compatibility with a hydrophilic organic solvent or a hydrophilic organic solvent-based polymer and liquid stability, and increases the thickness of a film when forming a thin film. Therefore, it is an object of the present invention to provide a titanium oxide sol that is easy to use and useful for improving the functions of various materials.
[0002]
[Prior art]
Titanium oxide, known as a white pigment, has a large refractive index and dielectric constant, and has the property of being easily excited by ultraviolet rays. Utilizing these properties, ultraviolet absorbers, optical materials, electrical / electronic materials, It is also used for photocatalysts, decorative materials, video display materials, adsorbing materials, cosmetic materials, Gretchel dye-sensitized solar cells, image storage materials, and the like. The form of titanium oxide used for such applications is often a film. Such a film is a method in which a titanium oxide precursor such as titanium alkoxide or an organic titanium compound is baked on a substrate, and a titanium oxide sol is mixed with a binder component. Then, a method of forming a film is known.
The former is also called a sol-gel method or an alkoxide method, and can form a thin film made of only titanium oxide. However, the film tends to collapse due to stress during baking, and it is generally difficult to form a film of several micrometers or more.
On the other hand, the latter can be thickened by selecting a binder, and since titanium oxide fine particles are used instead of the precursor, a desired film can be obtained at a lower temperature. Titanium oxide sol is more stable than titanium oxide precursor and is suitable for industrial use.
[0003]
Except when sintered at high temperature, titanium oxide generally has a hydroxyl group on the particle surface and is hydrophilic, so it is generally used as a water-dispersed sol. The water-dispersed titanium sol can be mixed with a hydrophilic solvent such as ethanol within a certain range, but when the amount of the organic solvent to be mixed increases, the form of the sol breaks and gels, Precipitation may occur.
Furthermore, when the content of components such as a binder increases, phase separation may occur, and an organic solvent-type stable titanium oxide sol is desired.
[0004]
Among inorganic oxide sols, silica sols can easily be esterified on the surface, and therefore, alcohol-dispersed silica sols can be easily produced. Such silica sols are used in various applications.
Further, tin oxide sols are disclosed in JP-B-5-87445 and JP-B-6-19074 in hydrophilic solvents (alcohols such as ethanol and ethylene glycol, ethers such as methyl cellosolve, and amines such as methanolamine). And amides such as dimethylformamide).
[0005]
By the way, various techniques are also disclosed regarding the titanium oxide sol.
JP-A-63-215520 discloses a neutral titania sol containing an oxycarboxylic acid, but such a sol is not suitable for thickening and cannot be used.
JP-A-3-257758 discloses a propylene glycol-type metal oxide sol. In order to improve the wettability of the coating film, this sol is mixed with water-soluble propylene glycol in the water-soluble sol. It was only done.
Japanese Examined Patent Publication No. 6-74204 describes an aqueous sol used for sunscreen cosmetics composed of fine particles of metatitanic acid using a water-soluble polyhydric alcohol as a stabilizer.
JP-A-10-167727 discloses a modified titanium oxide sol treated with a compound such as crown ethers, polyethylene glycols, or polypropylene glycols as a compound having phase transfer activity.
JP-A-9-248467 and JP-A-9-100124 describe a method for producing a sol using titanium alkoxide as a stabilizer or a raw material.
Japanese Patent Publication No. 7-100611 describes an alcohol-dispersed titanium sol in which water of a water-soluble titanium oxide sol is replaced with isopropyl alcohol.
However, a lower alcohol such as isopropyl alcohol has a high vapor pressure of the solvent, and there is no problem in the production of a thin film. However, when a thick film is to be produced, it cannot be formed into a thick film because it is too dry. There is a problem.
[0006]
[Problems to be solved by the invention]
Therefore, the present inventors have completed the present invention described in detail below as a result of intensive studies on a titanium oxide sol that is stable against an organic solvent and can easily obtain a thick film of titanium oxide. .
[0007]
[Means for Solving the Problems]
That is, in the present invention, the oxycarboxylic acid is in the range of oxycarboxylic acid / titanium oxide (molar ratio) = 0.03 to 3.0 and primary to tertiary amine cationic surfactants and quaternary ammonium salt cationic types. The present invention relates to an organic solvent-dispersed titanium oxide sol containing a cationic surfactant selected from surfactants in a range of cationic surfactant / titanium oxide (molar ratio) = 0.05 to 0.2. Furthermore, the present invention provides an oxycarboxylic acid obtained by adding a cationic surfactant in the presence of a water-dispersed titanium oxide sol stabilized with an oxycarboxylic acid and then substituting the aqueous solvent with an organic solvent. Acid / titanium oxide (molar ratio) = 0.03 to 3.0 and a cationic surfactant in a range of cationic surfactant / titanium oxide (molar ratio) = 0.05 to 0.2 The present invention relates to a method for producing an organic solvent-dispersed titanium oxide sol.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The organic solvent-dispersed titanium oxide sol of the present invention will be described based on its production method. The titanium oxide sol of the present invention may be either an amorphous titanium oxide sol or a crystalline titanium oxide sol. However, when used for the production of a thick film of titanium oxide, the anatase type because the titanium oxide sol concentration of the present invention can be made high, and the shrinkage during drying is less than that of amorphous titanium oxide. It is desirable to use a crystalline titanium oxide sol.
[0009]
The anatase type crystalline titanium oxide sol can be a commercially available product, for example, trade name “Tynoch” (manufactured by Taki Chemical Co., Ltd.), or an alkaline aqueous solution of a water-soluble titanium such as titanium chloride or titanium sulfate. An alkaline compound such as a metal hydroxide or an ammonium compound is added to form a titanium gel, an oxycarboxylic acid is added thereto, and this is hydrothermally treated at 100 ° C. or higher to produce anatase type crystalline titanium oxide sol. You can also.
Moreover, it can manufacture also by adding oxycarboxylic acid to the powder and slurry of anatase type titanium oxide, and carrying out wet grinding.
Regarding dispersion of these aqueous dispersion medium titanium oxide sols in an organic solvent, it is possible to mix a hydrophilic organic solvent such as alcohol to some extent with the titanium oxide sol using water as a dispersion medium. The lower the concentration of titanium sol, the more organic solvent can be contained.
[0010]
However, when a film is formed using such a sol solution, the sol component aggregates and the film becomes cloudy or a smooth film cannot be obtained. As a matter of course, when the concentration of the titanium oxide sol is low, a desired film thickness cannot be obtained even if the film can be successfully formed.
For this reason, a high-concentration titanium oxide sol that can be substantially dispersed in an organic solvent is required. At first, we focused on silica sols that are commercially available after being dispersed in various organic solvents, and tried to disperse silica sol in titanium oxide sol and disperse it in organic solvent. However, simply mixing both does not improve the dispersibility. It was.
[0011]
Therefore, as a result of intensive investigations on the improvement of dispersibility of titanium oxide sol, by adding a cationic surfactant in the presence of a water-dispersed titanium oxide sol stabilized with oxycarboxylic acid, a substantially organic solvent can be obtained. It was found that it can be dispersed.
[0012]
The water-dispersed titanium oxide sol stabilized with oxycarboxylic acid used in the present invention is obtained by stabilizing the above-described titanium oxide sol by adding oxycarboxylic acid.
Examples of the oxycarboxylic acid used in the present invention include lactic acid, citric acid, glycolic acid, malic acid, tartaric acid, glyceric acid, α-oxybutyric acid, mandelic acid, tropic acid and the like. Among these, apple Most preferred is the use of acids, tartaric acid, and citric acid. That is, the use of the oxycarboxylic acid is desirable from the viewpoint of the liquid stability of the sol composition and the thickening of the film when the composition is used in relation to the hydrophilic organic solvent described later.
[0013]
Regarding the amount of oxycarboxylic acid used, the oxycarboxylic acid / titanium oxide (molar ratio) is used in a range of 0.03 to 3.0. When this molar ratio is less than 0.03, the liquid stability of the titanium oxide sol deteriorates, and a precipitate is formed with time. When a film is formed using this, a non-uniform film quality is obtained. Further, when the molar ratio exceeds 3.0 and the amount of oxycarboxylic acid increases, the film quality of the film prepared using this sol solution is remarkably deteriorated.
A similar titanium oxide sol can be obtained by using a mineral acid such as hydrochloric acid or nitric acid instead of oxycarboxylic acid. However, since the viscosity of the sol becomes too high, a high concentration cation described later is used. A titanium oxide sol surface-treated with a type surfactant cannot be obtained, and is not suitable for the use of the present invention.
[0014]
Next, a cationic surfactant is added to the water-dispersed titanium oxide sol containing the oxycarboxylic acid produced as described above to obtain a precipitate of titanium oxide.
Next, the precipitate is washed and filtered to obtain a wet cake.
A hydrophilic organic solvent is added thereto, and the solution is dehydrated by heating and concentrating to obtain the organic solvent-dispersed titanium oxide sol of the present invention.
As another method, the organic solvent-dispersed titanium oxide sol of the present invention can also be obtained by drying the wet cake and redispersing it in an organic solvent.
As another method, when using an organic solvent having low solubility in water, the organic solvent dispersed type of the present invention can also be obtained by adding an organic solvent to the titanium slurry and extracting titanium oxide into the organic solvent phase. A titanium sol can be obtained.
[0015]
The types of cationic surfactants used are primary amine cationic surfactants such as octadecylamine acetate, secondary amine cationic surfactants such as oxyethylene dodecylamine, and polyoxyethylene dodecylamine. And tertiary amine cationic surfactants and quaternary ammonium salt cationic surfactants such as dialkyldimethylammonium chloride. Among these, use of quaternary ammonium salt cationic surfactants Is most preferable from the viewpoint of solubility.
Particularly preferred quaternary ammonium salt cationic surfactants include, but are not limited to, dialkyldimethylammonium chloride, alkyltrimethylammonium chloride, and alkyldimethylbenzylammonium chloride.
[0016]
Regarding the amount of the cationic surfactant used, the larger the particle size of the titanium oxide sol, the smaller the amount of the cationic surfactant used. Conversely, the smaller the particle size, the smaller the cationic interface. The amount of active agent used is increased. The amount used is in the range of 0.05 to 0.27 molar ratio to the amount of TiO _{2 in} titanium oxide.
When the amount of the surfactant used deviates from this range and is less than 0.05, the dispersibility of the sol is significantly lowered. On the other hand, when the amount of the surfactant used exceeds 0.27, the stability of the sol is deteriorated.
[0017]
Organic solvents that can be used in the present invention are alcohols such as methanol, ethanol, 1-propanol, 2-butanol, hexanol, butyl carbitol, 1-methoxy-2-propanol, 2-butoxyethanol, ketones such as methyl ethyl ketone, 4 -Esters such as butyrolactone can be exemplified.
[0018]
The water content in the organic solvent of the titanium oxide sol containing the surfactant is desirably 10% by mass or less.
[0019]
When the concentration of the titanium oxide sol is low, it is difficult to increase the thickness of the titanium oxide film. In the conventional sol, when the titanium oxide concentration is, for example, 15% by mass or more as TiO ₂ , the liquid thickens and gels, so that the water content in the dispersion medium cannot be reduced to 17% by mass or less.
However, in the organic solvent-dispersed titanium oxide sol of the present invention, the amount of water in the dispersion medium can be 10% by mass or less. Such a thing becomes possible by the following methods, for example.
That is, a cationic surfactant is added to a water-dispersed titanium oxide sol stabilized with oxycarboxylic acid, and after sufficiently reacting the surfactant with the titanium oxide sol, 4-butyrolactone having a high vapor pressure is used as an organic solvent. When 4-butyrolactone is added, dehydration is performed by heating the sol solution.
At the time of heating, water preferentially evaporates until the liquid temperature of the surfactant-containing titanium oxide sol solution reaches 100 ° C., but an amount of the organic solvent corresponding to the vapor pressure of the organic solvent at the liquid temperature also evaporates. When the evaporation of water is substantially completed, the liquid temperature rises to a temperature close to the external heating temperature. Therefore, for example, when external heating is performed at 140 ° C., the heating is terminated when the liquid temperature reaches 120 ° C. Dehydration is complete when the liquid temperature reaches 120 ° C. Even if heating is performed at 120 ° C. or higher for a long time, the amount of evaporation of the organic solvent increases, which is not economical. For this reason, there is no particular limitation on the heating time.
In this heating dehydration method, it is preferable to carry out at 80 ° C. or lower when using vacuum distillation instead of atmospheric distillation.
[0020]
The titanium (TiO ₂ ) concentration of the sol composition of the present invention is in the range of 5 to 40% by mass, more preferably 10 to 30% by mass. When the amount is 5% by mass or less, as described above, the organic solvent-dispersed titanium sol can be obtained relatively easily. Therefore, it is not necessary to perform the operation as in the present invention. On the other hand, when it is 40% by mass or more, even if the composition is devised, the viscosity becomes too high and the sol stability is deteriorated.
[0021]
The organic solvent-dispersed titanium oxide sol of the present invention thus obtained is excellent in compatibility and stability with an organic solvent or an organic solvent-based polymer, and is particularly suitable for various uses that do not like water, such as thickening. Material. By the way, an inorganic binder, an organic binder, or an organic-inorganic composite binder that can be mixed with the organic solvent to be used can be added to and mixed with the organic solvent-dispersed titanium oxide sol of the present invention.
As such a binder, for example, a photocurable resin or a composite binder containing them can be cited as a good example.
[0022]
【Example】
The present invention will be further described with reference to the following examples. In addition, unless otherwise indicated,% shows the mass% altogether.
[0023]
[Example 1]
Ammonium water (NH ₃ = 2%) 2212 g (NH ₃ / Cl equivalent ratio = 1.3) is gradually added to 2000 g of titanium oxychloride aqueous solution (TiO ₂ = 2%) under normal temperature stirring to form titanium hydroxide gel. It was. This was washed with filtered water until the chlorine ions in the filtrate became 100 ppm or less with respect to the titanium gel (TiO ₂ ) to obtain a gel with TiO ₂ = 10% and NH ₃ = 0.3%.
To 400 g of this gel, 54 g of malic acid was added so that malic acid / TiO ₂ (molar ratio) = 0.8, and this was put in an autoclave and hydrothermally treated at 120 ° C. for 6 hours to obtain crystalline titanium oxide sol (TiO 2 ₂ = 6.5%). As a result of analyzing this sol by X-ray diffraction, an anatase-type titanium oxide peak was observed, and the crystallite size obtained from the Debye-Scherrer equation using the first peak was 6 nm.
The obtained sol was washed using an ultrafiltration device to sufficiently remove excess malic acid, and the titanium oxide sol obtained was malic acid / TiO ₂ (molar ratio) = 0.3.
Next, to this titanium oxide sol (TiO ₂ = 15%, malic acid = 7.6%, pH = 2.5), ion-exchanged water 2900g and alkyldimethylbenzylammonium chloride 10% aqueous solution (cation F2 manufactured by NOF Corporation) were added. And kept for 1 hour, and then a wet cake was obtained by suction filtration. To this wet cake, 72 g of 4-butyrolactone was added, and dehydration was performed by distillation under reduced pressure at a liquid temperature of 60 ° C. using an evaporator. Distillation was performed until no distillation occurred, whereby the cationic surfactant-containing titanium oxide sol of the present invention was obtained. As a result of subjecting this sol to analysis, TiO ₂ = 15%, surfactant = 5%, malic acid = 7.6%, (surfactant / TiO ₂ (molar ratio) = 0.08, malic acid / TiO ₂ (molar ratio) ) = 0.3, 4-butyrolactone / TiO ₂ (molar ratio) = 4.4), and the water content in the dispersion medium was 2.0%.
[0024]
A resin coating film formation test was conducted using the obtained organic solvent-dispersed titanium oxide sol of the present invention.
Photosensitive polymer (40% methacrylic acid, 30% methyl methacrylate, 30% styrene copolymer, concentration 35%, weight average molecular weight 43000, acid value 95) obtained by dissolving 35 g of the sol of the present invention in 4-butyrolactone The solution was added to 10 g of the solution, and further 3 g of a photopolymerization initiator (IC-369 manufactured by Ciba Geigy Co.) was added thereto to prepare a liquid having a viscosity of 100,000 mPa / s. Using this, a pattern having a thickness of 150 μm was produced on a glass plate by screen printing, and then the pattern was cured by being exposed to a high-pressure mercury lamp.
Thereafter, the compact was fired at 550 ° C. to obtain a titanium oxide thick film. By baking, the film thickness contracted to 70% of the initial film thickness, but no cracks were observed and a good pattern was obtained.
[0025]
[Example 2]
1700 g of ammonia water (NH ₃ = 2%) (NH ₃ / Cl equivalent ratio = 1.0) is gradually added to 2000 g of titanium oxychloride aqueous solution (TiO ₂ = 2%) to produce titanium hydroxide gel. It was. This was washed with filtered water to obtain a gel with TiO ₂ = 5%, NH ₃ = 0.1%, and Cl = 0.1%.
Add 15.8 g of citric acid / monohydrate to 400 g of this gel so that the citric acid / TiO ₂ (molar ratio) = 0.3, put it in a thermostatic bath at 60 ° C., hold it for 24 hours, Obtained. The obtained sol was washed using an ultrafiltration device to sufficiently remove excess citric acid. As a result of analyzing this sol by X-ray diffraction method, a clear peak of anatase-type titanium oxide was not seen, and this sol was an amorphous titanium oxide sol (TiO ₂ = 4.8%, citric acid = 1.1%, pH = 3) Met.
Next, 760 g of ion-exchanged water and 43.5 g of didecyldimethylammonium chloride 10% aqueous solution (cation 2DB-500E manufactured by NOF Corporation) were added to 200 g of this titanium oxide sol and held for 1 hour, followed by suction filtration to obtain a wet cake. . The wet cake was dried at 60 ° C. to obtain a titanium oxide powder containing a cationic surfactant. To this, 30 g of 4-butyrolactone was added and dispersed to obtain an organic solvent-dispersed titanium oxide sol (TiO ₂ = 20%) of the present invention. As a result of subjecting this sol to analysis, TiO ₂ = 20%, citric acid = 4.6%, cationic surfactant = 8.3%, (cationic surfactant / TiO ₂ (molar ratio) = 0.09, citric acid / TiO 2 ₂ (molar ratio) = 0.1, and the water content in the dispersion medium was 4.6%, and this sol can be arbitrarily diluted with isopropyl alcohol, and there is no problem with a mixed solvent. It was found to be stable.
[0026]
[Example 3]
To 5000 g of sulfuric acid aqueous titanium sulfate solution (TiO ₂ = 2%, SO ₄ = 8%), 6500 g of sodium hydroxide aqueous solution (Na ₂ O = 4%) was added with stirring to produce a titanium gel.
This was washed with filtered water and washed well until the electric conductivity (mS / cm ² ) of the filtrate was 1/500 or less of the reaction mother liquor, and a TiO ₂ = 8% gel was obtained. This gel was dried and heat-treated at 300 ° C. for 1 hour to obtain 110 g of anatase-type titanium oxide powder (TiO ₂ = 90%).
To 60 g of this titanium oxide powder, 10 g of tartaric acid and 230 g of ion-exchanged water were added and wet-pulverized, followed by processing with a centrifugal separator with a centrifugal force of 4000 G, and the supernatant was separated. The supernatant was a titanium oxide sol having TiO ₂ = 15%, tartaric acid = 3.6%, and an average particle size of 0.2 μm.
A cationic surfactant is obtained by adding 50 g of tetradecyldimethylbenzylammonium chloride 10% aqueous solution (cation M2 manufactured by NOF Corporation) to 200 g of this water-dispersed sol, holding it for 1 hour, washing, filtering with suction, and drying at 60 ° C. A titanium oxide powder was obtained. 106 g of ethanol was added thereto and dispersed to obtain an organic solvent-dispersed titanium oxide sol (TiO ₂ = 20%) of the present invention. As a result of subjecting this sol to analysis, TiO ₂ = 20%, tartaric acid = 4.8%, cationic surfactant = 2.5%, (cationic surfactant / TiO ₂ (molar ratio) = 0.03, tartaric acid / TiO ₂ ( Molar ratio) = 0.1, and the amount of water in the dispersion medium was 2.0%.
[0027]
[Example 4]
To 400 g of titanium oxide gel (TiO ₂ = 10%, NH ₃ = 0.3%) obtained by the same method as in Example 1, 70% glycolic acid (Wako Pure Chemical Industries) was used so that glycolic acid / TiO ₂ (molar ratio) = 0.5. 27.2 g (manufactured by Yakuhin Kogyo Co., Ltd.) was added, and this was put in an autoclave and hydrothermally treated at 120 ° C. for 6 hours to obtain a crystalline titanium oxide sol (TiO ₂ = 9.4%).
Next, 840 g of ion-exchanged water and 41.3 g of 10% aqueous solution of alkyldimethylbenzylammonium chloride (Cation F2 manufactured by NOF Corporation) were added to 100 g of this sol and held for 1 hour, followed by extraction with 40 g of isobutyl alcohol. An organic solvent-dispersed titanium oxide sol was obtained. As a result of subjecting this sol to analysis, TiO ₂ = 15%, cationic surfactant = 6.4%, glycolic acid = 7.1%, (cationic surfactant / TiO ₂ (molar ratio) = 0.1, glycolic acid / TiO 2 ₂ (molar ratio) = 0.5, and the water content in the dispersion medium was 10%.
[0028]
As a comparative example, 15.8 g of 60% nitric acid and 38.1 g of ion-exchanged water were added to 400 g of the above titanium oxide gel (TiO ₂ = 10%, NH ₃ = 0.3%) so that nitric acid / TiO ₂ (molar ratio) = 0.3. It was added and placed in a 40 ° C. incubator for 3 days to obtain amorphous titanium oxide sol (TiO ₂ = 6.5%). Next, 800 g of ion-exchanged water and 40 g of a 10% aqueous solution of alkyldimethylbenzylammonium chloride were added to 145 g of this sol, but no precipitate was formed and the reaction did not proceed.
[0029]
【The invention's effect】
The organic solvent-dispersed titanium oxide sol of the present invention is particularly excellent in compatibility with a hydrophilic organic solvent or a hydrophilic organic solvent-based polymer and liquid stability, and it is easy to increase the film thickness when forming a thin film. It is useful for improving the function of various materials, and is a material suitable for various applications that do not like water. For example, an excellent function can be imparted to a dielectric, a photoelectric conversion material, an ultraviolet cut material, a high refractive index material, a catalyst, a hard coat material, and the like, which is industrially beneficial.

Claims (6)

The oxycarboxylic acid is selected from the range of oxycarboxylic acid / titanium oxide (molar ratio) = 0.03 to 3.0 and primary to tertiary amine cationic surfactants and quaternary ammonium salt cationic surfactants. An organic solvent-dispersed titanium oxide sol containing the cationic surfactant in a range of cationic surfactant / titanium oxide (molar ratio) = 0.05 to 0.2.  The organic solvent-dispersed titanium oxide sol according to claim 1, wherein the oxycarboxylic acid is malic acid, tartaric acid or citric acid.  The organic solvent-dispersed titanium oxide sol according to claim 1 or 2, wherein the cationic surfactant is a quaternary ammonium salt cationic surfactant.  2. The organic solvent-dispersed titanium oxide sol according to claim 1, which comprises adding a cationic surfactant in the presence of a water-dispersed titanium oxide sol stabilized with oxycarboxylic acid and then replacing the aqueous solvent with an organic solvent. Manufacturing method.  The organic solvent dispersion according to claim 4, wherein the oxycarboxylic acid content of the water-dispersed titanium oxide sol stabilized with oxycarboxylic acid is in the range of oxycarboxylic acid / titanium oxide (molar ratio) = 0.03 to 3.0. Of manufacturing type titanium oxide sol.  The method for producing an organic solvent-dispersed titanium oxide sol according to claim 4 or 5, wherein the addition amount of the cationic surfactant is in the range of surfactant / titanium oxide (molar ratio) = 0.05 to 0.27.