JP6022866B2 - Method for producing alkaline earth metal atom titanium oxide dispersion - Google Patents

Description

  The present invention relates to a method for producing an alkaline earth metal atom titanium oxide dispersion.

In recent years, metal oxides having a high refractive index have been used as fillers such as sealing materials, lens materials, light condensing materials, and high dielectric materials. In particular, if the primary particle diameter of the metal oxide is several tens of nanometers or less, the filler can impart high transparency to the dispersion.
However, even if the primary particle diameter of the metal oxide nanoparticles is several tens of nanometers or less, the transparency is significantly lowered when the nanoparticles are aggregated in the dispersion medium.

In Patent Document 1, the average primary particle diameter is 50 nm or less, the average aspect ratio is 1.0 to 1.2, the refractive index is 1.8 to 2.6, and MTiO ₃ {wherein M is an alkaline earth metal titanium oxide powder comprising a compound represented by the following formula: M is at least one selected from the group consisting of Ba, Sr, Ca and Mg.

International Publication No. 2011-004750 Pamphlet

However, the alkaline earth metal atom titanium oxide dispersion produced in Patent Document 1 becomes a yellow colored dispersion, and there is room for improvement in transparency.
Therefore, the problem to be solved by the present invention is to provide a method for producing an alkaline earth metal atom titanium oxide dispersion excellent in dispersibility and transparency.

  The inventors of the present invention intensively studied to solve the above problems, and as a result of repeated experiments, the present invention was completed. That is, the present invention is as follows.

  [1] A method for producing a dispersion of an alkaline earth metal atom titanium oxide, comprising a step of adding and dispersing an alkaline earth metal and an alkoxytitanium in an alcohol solvent having a dissolved oxygen concentration of 2.00 ppm or less.

  [2] The method according to [1], wherein the alcohol solvent is an alcohol having an alkoxy group.

  [3] The method according to [1] or [2], wherein water is further added after the alkaline earth metal and the alkoxytitanium are added to the alcohol solvent.

  [4] The method according to any one of [1] to [3], wherein the alkaline earth metal is barium.

  [5] The method according to any one of [1] to [4], wherein an average primary particle diameter of the alkaline earth metal atom titanium oxide is 1 nm to 50 nm.

  [6] The method according to any one of [1] to [5], further comprising a step of storing the dispersion of the alkaline earth metal atom titanium oxide in an inert gas atmosphere.

  According to the present invention, an alkaline earth metal atom titanium oxide dispersion having very high dispersion transparency and no coloring can be produced.

  Hereinafter, modes for carrying out the present invention (hereinafter abbreviated as “embodiments”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  The present embodiment includes a step of adding and dispersing an alkaline earth metal and alkoxytitanium in a solvent, and an alkaline earth having an dissolved oxygen concentration of 2.00 ppm or less is used as the solvent. It is a manufacturing method of a metal atom titanium oxide dispersion liquid.

  Examples of the alkaline earth metal atom titanium oxide of the present embodiment include barium titanate, strontium titanate, calcium titanate, and magnesium titanate. Further, barium strontium titanate can be produced by mixing Ba and Sr during production.

  In the present embodiment, alcohol having a dissolved oxygen concentration of 2.00 ppm or less is used as a solvent. In addition, components other than alcohol may be mixed in the solvent at the concentration of inevitable impurities.

Examples of the alcohol that can be used as the solvent include monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol; polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, glycerin, trimethylolpropane, and hexanetriol. A dihydric alcohol such as 2-methoxyethanol, 2-ethoxyethanol, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether; Ether: Diethylene glycol monomethyl ether, diethylene glycol Bruno ethyl ether, diethylene glycol monopropyl ether, ethers of polyhydric alcohols such as diethylene glycol monobutyl ether; and the like. The alcohol preferably has an alkoxy group in order to improve the transparency and dispersibility of the dispersion. Furthermore, monohydric alcohol or ether of dihydric alcohol is preferable from the viewpoint of dispersibility, and ether of dihydric alcohol, particularly 2-methoxyethanol or 2-ethoxyethanol is more preferable from the viewpoint of transparency.
These alcohols may be used alone or in combination of a plurality of alcohols.

  The oxygen concentration in the alcohol solvent can be measured using a dissolved oxygen concentration meter. The oxygen concentration is preferably 2.00 ppm or less, more preferably 1.50 ppm or less from the viewpoint of dispersibility of the alkaline earth metal atom titanium oxide dispersion to be produced, while 1 from the viewpoint of the transparency of the dispersion. More preferred is 0.000 ppm or less. Examples of the method for adjusting the oxygen concentration in the solvent include a method of bubbling an inert gas in the solvent, a method of distilling the solvent under an inert atmosphere, and a method of treating the solvent with a deoxygenation column.

  In the present embodiment, examples of the alkaline earth metal include barium, strontium, calcium, and magnesium, and these may be used alone or at the same time. From the viewpoint of imparting the best dispersibility to the dispersion, it is preferable to use barium alone.

  In the present embodiment, as the alkoxy titanium (also referred to as “titanium alkoxide”), for example, tetraethoxy titanium, tetra (i-propoxy) titanium, tetra (n-butoxy) titanium, tetra (2-ethylhexyloxy) titanium, Examples include tetraoctyloxy titanium. As alkoxytitanium, tetraethoxytitanium, tetra (i-propoxy) titanium, or tetra (n-butoxy) titanium is preferable from the viewpoint of dispersibility of the produced dispersion, and tetraethoxytitanium, or from the viewpoint of availability, Tetra (i-propoxy) titanium is particularly preferred.

  In the present embodiment, alkaline earth metal atoms and titanium alkoxide are dissolved and premixed in an alcohol solvent whose oxygen concentration is adjusted to 2.00 ppm or less by bubbling with an inert gas under an inert gas atmosphere. It is preferable to add water later for hydrolysis.

  In this specification, an inert gas is a low-reactivity gas used for chemical synthesis, chemical analysis, or storage of a highly reactive substance, and examples thereof include noble gases such as nitrogen and argon.

  The premixing time is not particularly limited, but is preferably 5 minutes to 24 hours, and more preferably 10 minutes to 12 hours. The premixing time is preferably 5 minutes or longer in order to sufficiently dissolve the alkaline earth metal and titanium alkoxide in the alcohol solvent, while 24 hours or shorter is preferable in order to prevent the solution from being colored. The inventors do not wish to be bound by any particular theory, but assume that the cause of the coloration of the solution is the formation of an oxoalkoxide complex of an alkaline earth metal alkoxide by dissolved oxygen.

  The temperature of the premixing is not particularly limited, but is 0 to 40 ° C. higher than the boiling point of the solvent and between 30 ° C. and 200 ° C. from the solubility point of the alkaline earth metal and titanium alkoxide. From the viewpoint of refluxing the reaction solution and further increasing the solubility, the temperature is more preferably 10 ° C to 30 ° C higher than the boiling point of the alcohol solvent. By heating the reaction solution at a temperature equal to or higher than the boiling point of the solvent, the internal solution is refluxed, so that the dissolution efficiency is improved and the dispersion transparency of the dispersion after the hydrolysis step is improved. In addition, the boiling point in this embodiment points out the boiling point in 1 atmosphere.

  The concentrations of the alkaline earth metal and titanium alkoxide during the premixing are each preferably 0.02 to 0.30 M with respect to the total amount of solution, and the primary particle size distribution of the generated alkaline earth metal titanium oxide is From a viewpoint of making it uniform, it is more preferable that it is 0.06M-2.2M. It is preferably 0.02M or more from the viewpoint of efficient premixing reaction, and is preferably 0.3M or less from the viewpoint of solubility of alkaline earth metal and titanium alkoxide. It is preferable from the viewpoint of the purity of the alkaline earth metal titanium oxide to be produced that the concentration ratio of the alkaline earth metal and the titanium alkoxide is equal in molar ratio.

  The hydrolysis time is not particularly limited, but is preferably 10 minutes to 24 hours, and more preferably 20 minutes to 12 hours. The hydrolysis time is preferably 10 minutes or more from the viewpoint of increasing the crystallinity of the produced alkaline earth metal atom titanium oxide, while it is preferably within 24 hours from the viewpoint of productivity.

  The temperature of the hydrolysis is not particularly limited, but is preferably 0 to 40 ° C. higher than the boiling point of the solvent and between 30 ° C. and 200 ° C. from the viewpoint of increasing the crystal efficiency. In view of further refluxing and dispersibility, the temperature is more preferably 10 ° C. to 30 ° C. than the boiling point of the solvent. By heating the reaction solution at a boiling point or higher, reflux occurs in the inner liquid, crystal formation efficiency is improved, and dispersion transparency of the dispersion liquid after the hydrolysis step is improved.

  The concentration of water used for hydrolysis is preferably 1M to 40M, more preferably 2M to 30M, and still more preferably 2 to 20M with respect to the alcohol solvent. 1M or more is preferable from the viewpoint of crystal generation efficiency, and 40M or less is preferable from the viewpoint of dispersibility of the alkaline earth metal atom titanium oxide.

  By adding a silane coupling material such as alkoxysilane and an organic phosphonic acid surface modifier to the dispersion liquid of this embodiment, the surface modification reaction can be continued and the dispersion state is maintained in different solvents. The dispersion medium can be replaced.

  The average primary particle diameter of the alkaline earth metal atom titanium oxide of the present embodiment is preferably 1 nm to 50 nm, and more preferably 3 nm to 30 nm. The average primary particle size is preferably 1 nm or more from the viewpoint of crystallinity, and is preferably 50 nm or less from the viewpoint of transparency of the dispersion. In the present disclosure, the average primary particle diameter means a number average value. The average primary particle diameter can be determined by direct observation with a transmission electron microscope (TEM).

  In order to prevent coloring or aggregation of the oxide nanoparticles, the alkaline earth metal atom titanium oxide dispersion is preferably stored in an inert atmosphere. Although it does not restrict | limit especially as an inert gas used at the time of storage, Nitrogen gas or argon gas is preferable from a versatility viewpoint.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.
Each physical property in the Examples was measured according to the following (1), (2), (3), (4) and (5).

(1) Measurement of the average primary particle diameter of alkaline earth metal atom titanium oxide The particle dispersion is dropped on a fine sample capturing film (collodion film), dried, and then transmitted through an electron microscope (TEM) (2000-FX). , Manufactured by JEOL Ltd.) and the number average of the primary particle diameters of 50 particles was calculated.

(2) Identification of Alkaline Earth Metal Atom Titanium Oxide Particles / Crystal Sizes A portion of the alkaline earth metal atom titanium oxide dispersion is dried to obtain an X-ray diffraction (XRD) apparatus (RU-200X, manufactured by Rigaku Corporation). X-ray powder diffraction was performed to confirm that the diffraction pattern coincided with the diffraction pattern of the alkaline earth metal atom titanium oxide, and the crystallite size was calculated from the peak width.

(3) Determination of Dissolved Oxygen Concentration in Alcohol Solvent The dissolved oxygen concentration in the alcohol solvent was measured under a nitrogen environment using an O2 converter model 4100e / 2HX, sensor InPro6800 (manufactured by METTLER TOLEDO).

(4) Measurement of dispersion secondary particle diameter by dynamic light scattering device (DLS) The dispersion secondary particle diameter of the dispersion was measured using DLS (FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.). According to the cumulant measurement based on the scattering intensity distribution, the dispersion having a dispersion secondary particle size of 30 nm or less was graded as ◯, 30 nm to 250 nm as Δ, and 250 nm or more as x.

(5) Transmittance measurement The dispersion was placed in a 1 cm quartz cell, and the transmittance of light having a wavelength of 400 nm was measured using a spectrophotometer (U-4100, manufactured by Hitachi High-Tech). A dispersion having a transmittance of 80% or more was graded as ◯, a dispersion having a transmittance of 70% or more and less than 80% as Δ, and a dispersion having a transmittance of less than 70% as x.

[Example 1]
288 mL of 2-methoxyethanol (manufactured by Wako Pure Chemical Industries, Ltd., purity 99% or more) was placed in a 1 L separable flask substituted under a nitrogen atmosphere. Under a nitrogen atmosphere, 2-methoxyethanol was bubbled with nitrogen for 2 hours to bring the dissolved oxygen amount to 0.00 ppm. In the 2-methoxyethanol, 6.56 g (0.08 M) of metal barium (manufactured by Kanto Chemical Co., Ltd., purity 99% or more) and 10.05 mL of tetraethoxy titanium (0.08 M) (manufactured by Tokyo Chemical Industry Co., Ltd., purity 97% or more) And heated at 130 ° C. for 2 hours with stirring to completely dissolve the metal barium and tetraethoxytitanium. After 2 hours, a solution obtained by dissolving 43.2 mL (4M) of ion-exchanged water with 2-methoxyethanol was bubbled with N _{2 so} that the dissolved oxygen amount was 0.00 ppm, and the total amount of the solution was 600 mL. And added to a solution of tetraethoxytitanium. The mixture was stirred for 3 hours at 130 ° C. using an oil bath to obtain a dispersion of barium titanate. TEM observation revealed that nanoparticles having an average primary particle size of 7 nm were obtained. The XRD peak was confirmed to match that of barium titanate, and the crystallite size was identified as 6.7 nm. Table 1 also shows the evaluation results of the dispersed secondary particle size and the dispersed transparency.

[Example 2]
288 mL of 2-methoxyethanol was placed in a 1 L separable flask that was replaced under a nitrogen atmosphere. Under a nitrogen atmosphere, 2-methoxyethanol was bubbled with nitrogen for 2 hours to make the dissolved oxygen amount 0.03 ppm. In the 2-methoxyethanol, 4.21 g (0.08M) of metal strontium (Aldrich, 99% or more) and 10.05 mL (0.08M) of tetraethoxytitanium are added and heated at 130 ° C. for 2 hours with stirring. The metal strontium and tetraethoxy titanium were completely dissolved. After 2 hours, a solution obtained by dissolving 162 mL (15 M) of water with 2-methoxyethanol was bubbled with N ₂ to make the dissolved oxygen amount 0.02 ppm, so that the total amount of the solution was 600 mL, and metal strontium and tetraethoxy titanium. Was added to the solution. The mixture was stirred at 130 ° C. for 3 hours using an oil bath to obtain a dispersion of strontium titanate. TEM observation revealed that nanoparticles having an average primary particle size of 10 nm were obtained, and confirmed that the XRD peak coincided with strontium titanate, and the crystallite size was identified as 10 nm. Table 1 also shows the evaluation results of the dispersed secondary particle size and the dispersed transparency.

[Example 3]
288 mL of 2-methoxyethanol was placed in a 1 L separable flask that was replaced under a nitrogen atmosphere. The amount of dissolved oxygen was adjusted to 0.08 ppm by bubbling 2-methoxyethanol with nitrogen under a nitrogen atmosphere for 2 hours. In the 2-methoxyethanol, 6.59 g (0.08 M) of metal barium and 10.05 mL (0.08 M) of tetraethoxytitanium were added and heated at 130 ° C. for 2 hours with stirring. Was completely dissolved. After 2 hours, a solution obtained by dissolving 162 mL (15 M) of water with 2-methoxyethanol was bubbled with N ₂ to make the dissolved oxygen amount 0.02 ppm, so that the total amount of the solution was 600 mL, and metal barium and tetraethoxy titanium. Was added to the solution. The mixture was stirred for 3 hours at 130 ° C. using an oil bath to obtain a dispersion of barium titanate. TEM observation revealed that nanoparticles having an average primary particle size of 21 nm were obtained, confirming that the XRD peak coincided with barium titanate, and the crystallite size was identified as 19.5 nm. Table 1 also shows the evaluation results of the dispersed secondary particle size and the dispersed transparency.

[Example 4]
288 mL of 2-ethoxyethanol was placed in a 1 L separable flask that was replaced under a nitrogen atmosphere. The amount of dissolved oxygen was adjusted to 0.03 ppm by bubbling 2-ethoxyethanol with nitrogen under a nitrogen atmosphere for 2 hours. In the 2-ethoxyethanol, 6.59 g (0.08M) of metal barium and 10.05 mL (0.08M) of tetraethoxytitanium were added and heated at 130 ° C. for 2 hours with stirring. Was completely dissolved. After 2 hours, a solution obtained by dissolving 162 mL (15 M) of water with 2-ethoxyethanol was bubbled with N ₂ to make the dissolved oxygen amount 0.04 ppm, so that the total amount of the solution was 600 mL, and metal barium and tetraethoxy titanium. Was added to the solution. The mixture was stirred for 3 hours at 130 ° C. using an oil bath to obtain a dispersion of barium titanate. TEM observation revealed that nanoparticles having an average primary particle size of 23 nm were obtained, confirming that the XRD peak coincided with barium titanate, and the crystallite size was identified as 21.4 nm. Table 1 also shows the evaluation results of the dispersed secondary particle size and the dispersed transparency.

[Comparative Example 1]
288 mL of 2-methoxyethanol was placed in a separable flask having a volume of 1 L replaced under a nitrogen atmosphere to form a nitrogen atmosphere, but bubbling with nitrogen was not performed. The dissolved oxygen concentration of 2-methoxyethanol at that time was 8.2 ppm. In the 2-methoxyethanol, 6.59 g (0.08 M) of metal barium and 10.93 g (0.08 M) of tetraethoxytitanium were added and heated at 130 ° C. for 2 hours with stirring. Was completely dissolved. Two hours later, a solution obtained by dissolving 162 mL (15 M) of water with 2-methoxyethanol was added to a solution of barium metal and tetraethoxytitanium so that the total amount of the solution was 600 mL. The mixture was stirred for 3 hours at 130 ° C. using an oil bath to obtain a dispersion of barium titanate. TEM observation revealed that nanoparticles having an average primary particle size of 21 nm were obtained, confirming that the XRD peak coincided with barium titanate, and the crystallite size was identified as 20.4 nm. The dispersion was colored yellow. Table 1 also shows the evaluation results of the dispersed secondary particle size and the dispersed transparency.

  Since the alkaline earth metal atom titanium oxide dispersion of the present invention has high transparency and dispersibility, it is suitable for use in transparent optical materials such as lenses.

Claims (6)

Adding an alkaline earth metal and alkoxytitanium in an alcohol solvent having a dissolved oxygen concentration of 2.00 ppm or less and dispersing ;
Thereafter, a step of further adding a mixture of alcohol and water having a dissolved oxygen concentration of 2.00 ppm or less,
A method for producing a dispersion of an alkaline earth metal atom titanium oxide.   The method according to claim 1, wherein the alcohol solvent is an alcohol having an alkoxy group. The method of Claim 1 or 2 that the dissolved oxygen concentration of the said liquid mixture is 0.04 ppm or less.   The method according to claim 1, wherein the alkaline earth metal is barium.   The method according to any one of claims 1 to 4, wherein an average primary particle diameter of the alkaline earth metal atom titanium oxide is 1 nm to 50 nm.   The method according to claim 1, further comprising a step of storing the dispersion of the alkaline earth metal atom titanium oxide under an inert gas atmosphere.