JP5004492B2 - Silica-based composite oxide fine particles and method for producing the same - Google Patents

Description

  The present invention relates to silica-based composite oxide fine particles and a method for producing the same. In particular, the present invention relates to silica-based composite oxide fine particles having a nano-level particle diameter and a method for producing the same.

  As a raw material, a method for producing so-called silica-based composite oxide fine particles such as silica-titania, silica-alumina, silica-zirconia, etc. by a sol-gel method using a combination of a silicon alkoxide and a metal alkoxide other than silicon is known. ing. Such silica-based composite oxide fine particles can exhibit various characteristics that cannot be obtained by silica alone. For example, the refractive index of the produced particles can be adjusted by changing the compounding ratio of silica and a metal oxide other than silica. Thereby, for example, when used as a filler to be added to a resin material, the refractive index of the resin material and the refractive index of the filler are aligned while providing performance as a filler such as imparting rigidity and lowering the thermal expansion coefficient. Thus, the transparency of the resin material can be maintained.

Nanoparticles are required in the field of nanocomposites, which are composites of polymers and nanoparticles, and coating materials. Patent Document 1 is characterized in that colloidal silica having a particle diameter of 3 to 100 nm is generated in a solvent by adding alkyl silicate to a reaction medium having a predetermined alkali concentration, hydrolyzing and polymerizing. A method for producing an aqueous silica sol is described.
Japanese Patent No. 3584485

  The method described in Patent Document 1 is a method for producing a water-soluble silica sol containing nanoparticles composed of silica alone, using a single alkyl silicate as a raw material, and does not describe the production of composite oxide fine particles. Absent. Further, in this method, even if silicon alkoxide and metal alkoxide other than silicon were used as raw materials, composite oxide fine particles having a nano-level particle diameter could not be obtained.

  Then, this invention makes it a subject to provide the silica type complex oxide microparticles | fine-particles which have a particle size of nano level, and its manufacturing method.

  As a result of intensive studies on the above-mentioned problems, the present inventor has found that composite oxide fine particles having a nano-level particle diameter are formed by different hydrolysis rates of silicon alkoxides and metal alkoxides other than silicon. And found that the above-mentioned problems can be solved by aligning the hydrolysis rate of silicon alkoxide and metal alkoxide other than silicon, and completed the following invention. It came to do.

  1st this invention is silica type complex oxide microparticles | fine-particles containing silica and metal oxides other than silica, Comprising: The content rate of metal oxides other than a silica is less than 50 mol%, The metal oxide is one or more selected from the group consisting of titania, zirconia, and alumina, and is a silica-based composite oxide fine particle having an average particle diameter of 1 nm to 100 nm.

  The fine particles of the present invention are silica-based composite oxide fine particles having an average particle diameter of 1 nm to 100 nm, which have been difficult to produce conventionally. The refractive index of the fine particles of the present invention can be adjusted by adjusting the content of silica and a metal oxide other than silica. Taking advantage of this property, for example, when added as a filler of a transparent resin material, by aligning the refractive index of the resin material and the refractive index of the fine particles of the present invention, while maintaining the transparency of the resin material, nano-level filler The function as can be provided. Specifically, it is used as a material for a PET film coating agent, an antireflection film (high refractive index layer), a spectacle lens hard coating agent, an inkjet transparent ink receiving layer, a composite high refractive index resin bead, an abrasive, etc. Can do.

  In addition, nanocomposites, which are composites of nano-order fine particles and polymers, have been developed as high-performance materials. The fine particles of the present invention can be used as fine particles capable of adjusting the refractive index of the nanocomposite. Moreover, the filling rate of a filler can be made high by adding the particle | grains which have a large and small diameter as a filler added to a resin material. In this case, as the small-diameter filler, by using the fine particles of the present invention having a refractive index comparable to that of the resin matrix, the filler filling rate is increased to give strength and the like. Transparency can be maintained.

  The second aspect of the present invention is a step (S1) of partially hydrolyzing a silicon alkoxide with water to form a partially hydrolyzed product, an alkoxide of a metal other than silicon selected from the group consisting of titanium, zirconium, and aluminum, Alternatively, a complex prepared by mixing an alkoxide of a metal other than silicon and a complexing agent and the partial hydrolyzate are mixed so that the ratio of the metal other than silicon is less than 50 mol%. The step of preparing the composite alkoxide raw material (S2), the step of hydrolyzing and condensing the composite alkoxide raw material in a solvent or dispersion medium having a water content of 60 to 100% by mass (S3), and an average particle diameter of 1 nm This is a method for producing silica composite oxide fine particles of ˜100 nm.

  When particles are synthesized by the sol-gel method, generally, first, a nucleation process for nucleation and a grain growth process for growing the generated nuclei are performed. Since the hydrolysis rate of alkoxides of metals such as titanium, zirconium, and aluminum (hereinafter, these metals may be referred to as “special foreign metals”) is much faster than that of silicon alkoxides, specific foreign metals When composite oxide particles are obtained by a sol-gel method using a simple mixture of alkoxides of silicon and alkoxides of silicon, nucleation and grain growth of oxides of specific different metals are prioritized. For this reason, it is very difficult to control the particle composition and particle diameter. In particular, in the initial stage of nucleation and particle growth, since it is strongly influenced by the difference in hydrolysis rate, as a so-called nanoparticle having an average particle diameter of 1 nm to 100 nm, it has a uniform composition, “specific foreign metal and silicon. It is even more difficult to obtain “composite oxide particles”.

  The present inventor prepares a composite alkoxide raw material, and hydrolyzes and condenses it under specific conditions, thereby maintaining the uniformity of the composition of the “composite oxide particles of a specific different metal and silicon” while maintaining the uniformity of the composition. It has succeeded in forming and growing it.

  Regarding the preparation of the composite alkoxide raw material, the preparation method varies depending on the composition of the composite oxide fine particles to be obtained. When the content of the oxide of the specific different metal is relatively low, for example, less than 25 mol%, a composite alkoxide prepared by simply mixing a partial hydrolyzate of silicon alkoxide with a specific different metal alkoxide The raw material can be used, but when the content ratio of the oxide of the specific dissimilar metal is relatively high, for example, when it is 25 mol% or more and less than 50 mol%, the composite alkoxide raw material can be used. Cannot achieve the goal.

  In order to obtain nanoparticles having a high content of the oxide of the specific foreign metal in this way, before mixing with the partial hydrolyzate of silicon alkoxide, the alkoxide of the specific foreign metal and the complexing agent are added. It is necessary to reduce the hydrolysis rate by mixing in advance to form a complex. By forming the complex, the hydrolysis rate is set to be approximately the same as the hydrolysis rate of the silicon alkoxide, whereby silica-based composite oxide fine particles having an average particle diameter of 1 nm to 100 nm can be obtained.

  That is, in the method for producing silica-based composite oxide fine particles of the second aspect of the present invention, (I) the step of preparing the composite alkoxide raw material is an alkoxide of a metal other than silicon selected from the group consisting of titanium, zirconium, and aluminum. And a partial hydrolyzate of silicon alkoxide so that the proportion of metal other than silicon is less than 25 mol%, and a production method that is a step of preparing a composite alkoxide raw material, and (II) composite The step of preparing the alkoxide raw material includes a complex prepared by mixing an alkoxide of a metal other than silicon selected from the group consisting of titanium, zirconium, and aluminum and a complexing agent, a partial hydrolyzate of the alkoxide of silicon, Is mixed so that the proportion of metal other than silicon is 25 mol% or more and less than 50 mol%. Includes two methods of the production method is a step of preparing a composite alkoxide raw material by.

  In the production method of the second aspect of the present invention, the ratio of the metal other than silicon (specific foreign metal) is specified by “mol%”, and the “mol%” means in the partially hydrolyzed product. The number of moles of silicon (here, the number of moles corresponds to the number of gram atoms of Si) is the number of moles of the specified foreign metal in the alkoxide or complex of the different foreign metal. This corresponds to the value represented by {M / (Si + M)} × 100 (%), where M is equivalent to the number of gram atoms of a different metal.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

<Silica complex oxide fine particles>
The silica-based composite oxide fine particles of the present invention contain silica and a metal oxide other than silica. Examples of metal oxides other than silica include titania, zirconia, and alumina. Of these, titania is preferable. Titanium alkoxides have a slower hydrolysis rate than other zirconium and aluminum alkoxides. Therefore, in the production method of the present invention described below, it is relatively easy to make the hydrolysis rate uniform with that of silicon alkoxide by forming a complex.

  A metal oxide other than silica may be combined with silica alone, or two or more metal oxides other than silica may be combined with silica. For example, as a metal oxide other than silica, both titania and zirconia may be used to form silica-titania-zirconia ternary silica-based composite oxide particles, or both alumina and titania may be used. Alternatively, silica-alumina-titania ternary silica-based composite oxide particles may be used.

  In the silica-based composite oxide particles of the present invention, the content of metal oxides other than silica is less than 50 mol%, preferably 0.1 mol% or more and less than 50 mol%, more preferably 1 mol% or more and 50 mol%. Is less than. The “content ratio of metal oxides other than silica” here means that the number of moles of silicon constituting the silica is Si, and the number of moles of metal elements constituting the metal oxide other than silica is M. M / (Si + M)} × 100 (%). In the case of the ternary silica-based composite oxide particles as described above, M is the total number of moles of metal elements other than silica.

  The average particle size of the silica-based composite oxide particles of the present invention is in the range of 1 nm to 100 nm, preferably in the range of 5 nm to 50 nm, more preferably in the range of 10 nm to 50 nm. A composite oxide fine particle having such a particle size has not been obtained so far.

  The silica-based composite oxide particles of the present invention can be confirmed in particle shape by using a scanning or transmission electron microscope. Further, the average particle diameter of the particles can be measured by analysis using the electron microscope image, a highly accurate particle size distribution meter, or the like. Preferably, the average particle diameter can be determined by analyzing the above electron microscope image using a commercially available image analyzer.

  In the silica-based composite oxide particles of the present invention, components of silica and metal oxides other than silica are generally chemically bonded, and these components cannot be physically separated. . The fact that both components are chemically bonded can be confirmed by measuring the infrared spectrum and refractive index (particle optical transparency).

  The silica-based composite oxide particles of the present invention are synthesized as a slurry of an organic solvent containing water, but are generally used as a slurry in which this is replaced with a desired solvent. There is no particular limitation on the method of solvent replacement, but a process by repeated concentration and dilution by ultrafiltration is preferably used. Further, the present particles can be used after drying and firing as required. What is necessary is just to select suitably the temperature in the case of drying and baking in the range of 100 to 1300 degreeC. The specific surface area of the silica-based composite oxide particles of the present invention is not particularly limited. When firing at a high temperature, the specific surface area decreases, and those dried at a low temperature tend to increase the specific surface area. When firing at a temperature exceeding 1300 ° C., the particles may sinter, and there is a concern that the monodispersibility may be impaired.

  Most of the composite oxide particles of the present invention are amorphous, but may be a mixture of amorphous and partially crystalline. When it is amorphous before firing and the above firing temperature is low, it remains amorphous, but when the firing temperature is high, part of the metal oxide other than silica may be crystalline. In general, these properties can be analyzed by means such as X-ray diffraction. In general, when the optically transparent properties of the particles are to be used, it is preferable that the particles are amorphous. Particularly, when the particle diameter is 40 nm or more, the particles are amorphous or only a part of the particles. It is preferable that the crystal is transformed into a crystalline state. For that purpose, the above-mentioned firing temperature is preferably 1100 ° C. or less, more preferably 1050 ° C. or less, and further preferably 1000 ° C. or less.

Furthermore, the density and refractive index of the silica-based composite oxide particles of the present invention cannot be generally specified because they vary depending on the type and content of the metal oxide other than silica and the firing temperature of the particles. Most commonly, the true density is in the range of 1.5-5 g / cm ³ and the refractive index is in the range of 1.4-3. For example, for silica-titania composite oxide particles, when the titania content is in the range of 30 to 50 mol%, the true density is 2.6 to 3.0 g / cm. ^The refractive index was in the range of 1.65 to 1.85.

  The silica-based composite oxide fine particles of the present invention are composite oxide fine particles having a nano-level (1 nm to 100 nm) particle size, which could not be produced conventionally, and the silica and metal oxides other than silica in the particles. By adjusting the content rate, the refractive index of the obtained fine particles can be adjusted. Thereby, when using as a filler of a resin material, the transparency of the resin material can be ensured while providing the performance as a nanofiller by matching the refractive index of each resin material. Moreover, it can be used as fine particles whose refractive index can be adjusted while maintaining the transparency of the nanocomposite.

<Method for producing silica-based composite oxide fine particles>
FIG. 1 shows a process diagram of a production method for silica-based composite oxide fine particles of the present invention. The method for producing silica-based composite oxide fine particles of the present invention includes a step S1 of partially hydrolyzing silicon alkoxide with water to form a partially hydrolyzed product, other than silicon selected from the group consisting of titanium, zirconium, and aluminum. Metal alkoxide of metal (specific different metal) or complex prepared by mixing alkoxide of metal other than silicon and complexing agent, and the partial hydrolyzate, the proportion of metal other than silicon is 50 mol% Step S2 for preparing a composite alkoxide raw material by mixing so as to be less than, and Step S3 for hydrolyzing and condensing the composite alkoxide raw material in a solvent or dispersion medium having a water content of 60 to 100% by mass. is doing.

  The production method of the present invention is a method for forming nanoparticles by hydrolyzing and condensing a metal alkoxide raw material. In the present invention, as a raw material, a composite alkoxide raw material is formed in advance by a predetermined method from a silicon alkoxide and a metal alkoxide other than silicon, and the composite alkoxide raw material is hydrolyzed and condensed under specific conditions. By this method, it is possible to produce silica-based composite oxide fine particles having a nano-level particle diameter that could not be produced conventionally and in which silica and a metal oxide other than silica are uniformly dispersed. is there. Hereafter, each process in this invention is demonstrated.

(Partial hydrolyzate formation step S1)
The silicon alkoxide is partially hydrolyzed (step S1). The alkoxide of silicon is not particularly limited as long as it forms a silicon oxide by hydrolysis / condensation reaction in a solvent or dispersion medium having a water content of 60 to 100% by mass described below. And known compounds can be used. For example, a silicon alkoxide represented by the general formula Si (OR) ₄ or SiR ′ _n (OR) _4-n , or a low condensate obtained by partially hydrolyzing and condensing silicon alkoxide is industrially available. It is easy to do and is preferably used. These silicon alkoxides may be used in combination of two or more. In the above general formula, R and R ′ are alkyl groups, and are preferably lower alkyl groups such as a methyl group, an ethyl group, an isopropyl group, and a butyl group. n is an integer of 1 to 3.

  When partially hydrolyzing the silicon alkoxide, it is preferable to use an organic solvent such as alcohol compatible with both the alkoxide and water. When an organic solvent such as alcohol is not used, the silicon alkoxide and water tend to phase separate, and partial hydrolysis may not proceed or the reaction may be very slow. Moreover, in order to advance partial hydrolysis rapidly, it is preferable to add a catalyst to the water. An acid is suitable as the catalyst, and specific examples include hydrochloric acid, sulfuric acid, nitric acid, oxalic acid and the like, but there is no particular limitation. As the acid concentration, it is preferable to use an acid having a pH in the range of 1 to 4. Unlike the case where an alkali catalyst is used, when an acid catalyst is used, it is difficult for condensation of the hydrolyzate to occur, so that the formation of particles before the step S2 can be prevented.

  Hereinafter, the matter considered by the present inventor as the mechanism of partial hydrolysis will be described. The case where tetramethyl silicate is used as the silicon alkoxide (alkoxysilane) will be described. Part of the alkoxide of silicon is hydrolyzed by partial hydrolysis, and a silanol group (SiOH) is generated in the molecule (see the following formula 1). In step S2, the silanol group reacts with an alkoxide of a metal other than silicon to generate a composite alkoxide of silicon and a metal other than silicon. The hydrolysis reaction of alkoxysilane proceeds sequentially, and it is considered that alkoxyhydroxysilane according to the following formula is generated as a main product according to the amount of water used. It is considered that the mixture has a distribution (mixture of compounds having different degrees of hydrolysis).

式（１）において、「Ｍｅ」はメチル基を表している（以下、同様である。）。また、「ｎ」は１〜４の整数である。

In the formula (1), “Me” represents a methyl group (the same applies hereinafter). “N” is an integer of 1 to 4.

In the production method of the present invention, in order to obtain composite oxide particles having a uniform composition, it is preferable to control the amount of water used when the silicon alkoxide is partially hydrolyzed with water. As can be seen from the formula (1), the amount of water used in the alkoxysilane partial hydrolysis reaction is a factor that determines the number of silanol groups (Si—OH groups) introduced into the silane compound to be generated. The number of silanol groups in one molecule of the partial hydrolyzate affects the uniformity of the composite alkoxide raw material prepared in step S2. That is, in the preparation step S2 of the composite alkoxide raw material, when the partial hydrolyzate is mixed with an alkoxide of a specific dissimilar metal, the alkoxy group and silanol group of the alkoxide react (dealcoholization reaction) to cause Si- OM (wherein M represents a specific dissimilar metal atom) bond is formed, and Si _a · M _b · (OR) _c · (OH) _d (where a, b, c, and d are each 1 A composite alkoxide raw material is formed as shown by the number of Si atoms, M atoms, OR groups, and OH groups contained in the molecule.

  From the viewpoint of producing composite oxide fine particles having a uniform composition, it is preferable to prepare a composite alkoxide raw material having a composition corresponding to the composition of the composite oxide fine particles as a target product without forming a gel in step S2. However, for that purpose, it is important to control the number of silanols that one molecule of the alkoxysilane partial hydrolyzate has, and also the amount of silanol groups contained in the entire product of the partial hydrolysis reaction. For example, if the amount of silanol groups is small compared to the amount of alkoxides of specific foreign metal, unreacted alkoxides of specific foreign metal will remain, whereas if the amount of silanol groups is too large, silanol Alkyl groups or an alkoxy group bonded to Si react with each other or a Si-O-Si bond is formed, resulting in gelation or particle formation.

  For this reason, in step S1, it is preferable to control the amount of water used so as to satisfy the condition represented by the following formula (2).

−0.06X + 3.5 <Y <−0.06X + 4.5 (2)
{In Formula (2), “X” represents the content (mol%) of a metal oxide other than silica in the target silica-based composite oxide fine particles, and “Y” is the number of moles of water used. Is a value obtained by dividing by the number of moles of alkoxide of a metal other than silicon used in step S2. }

  Note that the above equation (2) is determined experimentally, and data as the basis thereof is shown in FIG. 1 of JP-A-2003-252616. In this publication, since the conditions for hydrolysis / condensation of the raw material alkoxide are different from the conditions in step S3 in the present invention, the nanoparticle was not successfully produced, but the composite prepared by the same method as in the present invention was used. Since complex oxide particles having a uniform composition can be produced using an alkoxide raw material, it can be understood that the above conditions are preferably satisfied as partial hydrolysis conditions for producing a good composite alkoxide raw material.

  In fact, also in the present invention, when the amount of water is smaller or larger than the above range when partially hydrolyzing silicon alkoxide, the content of water is in a solvent or dispersion medium of 60 to 100% by mass. When the composite alkoxide raw material is hydrolyzed / condensed to obtain silica-based composite oxide particles, it becomes difficult to control the reaction, so that many fused particles are formed, or in extreme cases, particles are synthesized during particle synthesis. Has been confirmed to aggregate.

  Moreover, it is more preferable that the amount of water in the partial hydrolysis in step S1 satisfies the condition represented by the following formula (3).

−0.06X + 3.7 <Y <−0.06X + 4.3 (3)
(“X” and “Y” in formula (3) represent the same meaning as in formula (2) above.)

(Composite alkoxide raw material preparation step S2)
In the production method of the present invention, in step S2, an alkoxide of a metal other than silicon (specific foreign metal) selected from the group consisting of titanium, zirconium, and aluminum, or an alkoxide of the specific different metal and a complexing agent. The complex alkoxide raw material is prepared by mixing the complex prepared by mixing and the partial hydrolyzate prepared above so that the ratio of the specific different metal is less than 50 mol%.

  As described above, the hydrolysis rate of alkoxysilane and the hydrolysis rate of alkoxides of specific dissimilar metals are greatly different. Therefore, when both are simply mixed and subjected to hydrolysis / condensation, the composite oxidation has a uniform composition. It is difficult to obtain physical fine particles. On the other hand, once the composite alkoxide is formed, the difference in hydrolysis rate between the two is relaxed, and composite oxide particles having a uniform composition can be obtained.

  However, there is a limit to the effect of the composite, and when the content of the oxide of the specific foreign metal is relatively low, for example, less than 25 mol%, the partial hydrolyzate of silicon alkoxide and the specific foreign metal Even a composite alkoxide raw material prepared simply by mixing with an alkoxide (hereinafter referred to as a “normal composite alkoxide raw material” in order to distinguish this composite alkoxide raw material from a complex alkoxide raw material to be complexed as described later) is sufficient. An effect can be obtained. However, when the content of the oxide of the specific dissimilar metal is relatively high, for example, 25 mol% or more and less than 50 mol%, “a partial hydrolyzate of the silicon alkoxide and the alkoxide of the specific dissimilar metal are mixed. It is difficult to obtain a sufficient relaxation effect by “compositing by things”.

  Therefore, in the present invention, when the content ratio of the oxide of the specific different metal is relatively high, a complex prepared by mixing the alkoxide of the specific different metal and the complexing agent, and a partial hydrolyzate of silicon alkoxide Are mixed so that the proportion of the specific different metal is 25 mol% or more and less than 50 mol%, in order to distinguish this composite alkoxide raw material from the above-mentioned normal composite alkoxide raw material “ A method of preparing a “complexed complex alkoxide raw material”) is employed. By reducing the hydrolysis rate of the alkoxide of the specific different metal by complexing and approaching the hydrolysis rate of the alkoxysilane, composite oxide fine particles having a uniform composition even when the content ratio of the specific different metal is high are obtained. It becomes possible.

  In the above description, the content ratio of the specific dissimilar metal has been described with 25 mol% as the boundary. However, the reactivity of the normal composite alkoxide raw material does not change suddenly at 25 mol%, for example, 25%. It is possible to obtain the desired nanoparticles if the conditions are selected even if more than the usual composite alkoxide raw material is used. Further, the case of using the complexed composite alkoxide raw material is not limited to the case where it exceeds 25 mol%, and is less than 25 mol% (for example, the mol% of the specific dissimilar metal is 0.1 to 25 mol%). %)), There is no problem and the desired nanoparticles can be obtained.

Hereinafter, the preparation method of the normal composite alkoxide raw material and the preparation method of the complexed composite alkoxide raw material will be described in detail.
(Normally a method for preparing composite alkoxide raw materials)
Usually, the composite alkoxide raw material can be prepared by mixing an alkoxide of a metal other than silicon selected from the group consisting of titanium, zirconium, and aluminum and a partial hydrolyzate of alkoxysilane.

As the alkoxide of the specific different metal, titanium alkoxide (Ti (OR) ₄ ), zirconium alkoxide (Zr (OR) ₄ ), and aluminum alkoxide (Al (OR) ₃ ) can be used. R is an alkyl group, and is preferably a lower alkyl group such as a methyl group, an ethyl group, an isopropyl group, or a butyl group.

  Usually, when preparing the composite alkoxide raw material, the mixing ratio of the partial hydrolyzate of alkoxysilane and the alkoxide of the specific dissimilar metal is such that the silica and the oxide of the specific dissimilar metal in the finally obtained silica-based composite oxide fine particles. It depends on what ratio you want to mix. That is, based on the number of moles of Si atoms (number of grams of atoms) contained in the partial hydrolyzate of alkoxysilane used, the composition of the composite oxide fine particles to be obtained (mol% of the desired specific dissimilar metal) Accordingly, the number of moles (gram atoms) of the specific foreign metal (M) required is determined, and an appropriate amount of the alkoxide of the specific foreign metal may be used.

  For example, when producing silica-based composite oxide fine particles containing 80 mol% of silica and 20 mol% of titania, the number of moles of silicon in the partial hydrolyzate is Si, and the number of moles of titanium in the alkoxide of titanium is Ti. , {Ti / (Si + Ti)} × 100 = 20, and the partially hydrolyzed product and titanium alkoxide are mixed.

  Usually, the preparation of the composite alkoxide raw material can be suitably performed by mixing a reaction solution obtained by partial hydrolysis of alkoxysilane and a predetermined amount of the alkoxide of a specific different metal under stirring. The liquid temperature during mixing is preferably maintained at 5 to 50 ° C. The stirring time depends on the reaction temperature, but about 10 minutes to 2 hours is sufficient.

  For example, when a reaction solution obtained by performing a partial hydrolysis reaction as shown in the following formula (4) and tetraisopropyl titanate (tetraisopropoxy titanium) which is an alkoxide of a specific different metal are mixed, the following formula It is considered that the complexing reaction as shown in (5) occurs.

(Method for preparing complexed complex alkoxide raw material)
The complexed composite alkoxide raw material is prepared by mixing an alkoxide of a specific different metal and a complexing agent to form a complex, and then mixing this complex and the partial hydrolyzate prepared above. As the alkoxide of the specific different metal, those described in the method for preparing the composite alkoxide raw material can be used.

  As complexing agents, (1) alkylene glycols (ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerol, etc.), (2) glycol alkyl ethers (ethylene glycol monoethyl ether, ethylene) Glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, etc.), (3) glycol aryl ethers (ethylene glycol monophenyl ether, etc.), (4) β-dicarbonyl Compound (acetylacetone, etc.), (5) Amines (ethylenediamine, diethanolamine) Triethanolamine), (6) hydroxy acetone, (7) acetals (acetone dimethyl acetal), (8) carboxylic acids (acetic, lactic, and citric acid, etc.) and the like. Among these, amines such as triethanolamine, β-dicarbonyl compounds, hydroxyacetone, and carboxylic acids are preferable.

  The complexing reaction can be performed by mixing an alkoxide of a specific different metal and a complexing agent in a polar solvent, preferably an alcohol. The reaction temperature may be 5 ° C to the boiling point of the solvent, and the reaction proceeds sufficiently even at room temperature. Moreover, although reaction time is based also on reaction temperature, it is about 10 minutes-about 2 hours normally.

  In the complexing reaction, the amount ratio between the alkoxide of the specific different metal and the complexing agent is important from the viewpoint of controlling the hydrolysis rate of the alkoxide of the specific different metal. In order to obtain composite oxide fine particles having a uniform composition, it is preferable to adjust the hydrolysis rate of the complex to be formed to the same level as the hydrolysis rate of the alkoxysilane. Since the hydrolysis rate of the complex can be controlled by changing the quantitative ratio between the alkoxide of the specific different metal and the complexing agent, the above viewpoints depend on the combination of the alkoxide of the specific different metal and the complexing agent to be used. From this, a suitable quantitative ratio may be determined as appropriate. Such a quantitative ratio can be easily determined by a simple experiment.

  In the following, tetraisopropyl titanate (also referred to as tetraisopropoxytitanium; hereinafter sometimes abbreviated as “TPT”) is used as the alkoxide of a specific dissimilar metal, and triethanolamine (hereinafter, “ An example of an experiment using “TEA” may be abbreviated as “TEA”.

  This experiment was conducted in order to confirm the relationship between the amount ratio of TPT and TEA and the hydrolysis rate of the obtained complex, and was conducted according to the following procedure. That is, “50% by mass methanol solution in which TPT and TEA were mixed in various proportions” separately prepared in the same amount as the ammonia water in a predetermined amount of 0.3% ammonia water was stirred using a stirrer ( The rate of hydrolysis was evaluated by measuring the time from immediately after completion of addition until the solution was gelled. In addition, the gelation time was calculated | required as the time of gelatinizing when the motion of the stirring bar stopped by the viscosity increase of the solution. The results are shown in Table 1. In another experiment, when tetramethyl silicate was used as the silicon alkoxide and the experiment was performed under the same conditions, the gelation time was 14 minutes.

  From the above results, it was found that when TEA / TPT = 0.5, it was closest to the gelation time (14 minutes) when tetramethyl silicate was used. Thus, in the embodiment described below, TEA / TPT = 0.5. However, the idea of the present invention is to make the hydrolysis rate of an alkoxide of a specific different metal and the hydrolysis rate of a silicon alkoxide (alkoxysilane) at the same level. Therefore, if this idea is achieved, the blending ratio of TEA and TPT is not limited to the above value.

  In addition, when TEA / TPT = 0.5, when the TEA and TPT are mixed, the present inventor believes that the complex shown below is formed.

（式（６）において、「ｉＰｒ」はイソプロピル基を表している（以下、同様である。）。）

(In Formula (6), “iPr” represents an isopropyl group (hereinafter the same).)

  A complexed composite alkoxide raw material is prepared by mixing the complex thus prepared and a partial hydrolyzate of alkoxysilane. At this time, the complex and the partial hydrolyzate of alkoxysilane are usually mixed in the same manner as the mixture of the partial hydrolyzate of alkoxysilane and the alkoxide of the specific dissimilar metal when preparing the composite alkoxide raw material. it can.

(Hydrolysis / condensation step S3)
In the method of the present invention, silica-based composite oxide particles are produced by hydrolyzing and condensing the composite alkoxide raw material prepared above in a solvent containing a catalyst. At this time, in order to obtain silica-based composite oxide fine particles having an average particle diameter of 1 nm to 100 nm, the hydrolysis / condensation must be performed in a solvent or dispersion medium having a water content of 60 to 100% by mass. . When hydrolysis / condensation is carried out in a solvent or dispersion medium having a water content of less than 60% by mass, the nucleation is slow and the nuclei once formed grow rapidly, so the average particle size is 1 nm. ˜100 nm particles cannot be obtained. From the viewpoint of obtaining fine particles having such a particle size efficiently with good reproducibility, the content of water in the solvent or dispersion medium is preferably 70% by mass or more, particularly preferably 75% by mass or more.

  In addition, since water is consumed by the hydrolysis / condensation reaction of the composite alkoxide raw material and alcohol is produced as a by-product, the concentration of water in the solvent or dispersion medium decreases when the reaction is performed in batch, From the start to the end of the reaction, the concentration of water in the solvent or dispersion medium is preferably 60% by mass or more, particularly 70% by mass or more.

  When the water concentration of the solvent or dispersion medium is less than 100% by mass, the solvent or dispersion medium contains an organic solvent. At this time, as an organic solvent, alcohols such as methanol, ethanol, propanol, isopropanol, butanol, ethylene glycol and propylene glycol, ketones such as acetone and methyl ethyl ketone, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate, Other organic solvents that are compatible with water are used alone or in combination. Among these, lower alcohols such as methanol, ethanol, and isopropanol are preferable because of high compatibility with metal alkoxides and water and low viscosity.

Further, a metal alkoxide as a catalyst to hydrolysis, N _{(CH 3)} amines such as _3, ammonia, LiOH, NaOH, KOH, a base such as _{N (CH 3)} 4 OH can be suitably used. In particular, ammonia and amines are extremely suitable as a catalyst for hydrolysis because the produced silica-based composite oxide particles are calcined and no base remains in the particles. The amount of the catalyst added varies depending on the type of catalyst used, the type of water and organic solvent in the water-containing organic solvent, and the blending ratio. It is preferable to do this. In the case of ammonia most suitable as a catalyst, it is suitable to add so that the weight fraction as NH ₃ is 0.005% to 10%, preferably 0.01% to 7%.

  The composite alkoxide raw material is preferably dropped in the liquid. Dropping in liquid means that the tip of the dropping port is immersed in an aqueous solvent when the alkoxide raw material is dropped in the aqueous solvent. The position of the tip of the dropping port is not particularly limited as long as it is in the liquid, but a position where stirring is sufficiently performed such as in the vicinity of the stirring blade is desirable. For example, when the liquid is dropped from above the reaction liquid without dropping in the liquid, it is not preferable because the particles easily aggregate.

  Further, an alkaline aqueous solution prepared separately together with the composite alkoxy raw material may be simultaneously dropped into an aqueous solvent containing a catalyst. As this alkaline aqueous solution, 0.005 to 10% by mass of ammonia water or the like is suitable. In addition, it is alkaline with a supply ratio such that the number of moles of water in the alkaline aqueous solution is 1 to 6 times mole, preferably 2 to 5 times moles, with respect to the total number of moles of silicon and the specific foreign metal in the raw material. It is preferable to add the aqueous solution dropwise.

  Although it is not necessary to drop the alkaline aqueous solution in the liquid, dropping in the liquid near the stirring blade is preferable because stirring in the aqueous solvent is sufficiently performed. By simultaneously dropping the alkaline aqueous solution as described above, particles can be synthesized with a high solid content concentration, so that a synthesis with a high yield is possible.

  It is preferable that the raw material made of alkoxide is continuously dropped from the start to the end of the dropping. The term “continuous” as used herein means that an interval of preferably 10 minutes or longer, more preferably 3 minutes or longer is not left. The dropping speed is not necessarily constant, but it is desirable to change continuously when changing the dropping speed.

  The temperature of the reaction vessel when performing the hydrolysis may be in the range of 0 to 50 ° C., and is appropriately selected depending on the type of alkoxide used. In addition, a well-known thing is employ | adopted as a reaction container used for a hydrolysis, reaction conditions other than the above, without any limitation.

  The particles synthesized as described above have a content of metal oxides other than silica of less than 50 mol%, and have an average particle diameter of 1 nm to 100 nm, preferably 5 nm to 50 nm, more preferably 10 nm to 50 nm. This is a silica-based composite oxide fine particle.

  The particles after the synthesis are obtained as a colloidal particle dispersion dispersed in the reaction solution. Depending on the application, it may be used as it is, or after replacing the solvent of the reaction solution with an organic solvent such as water or alcohol.

  Further, after the particles are synthesized, they may be separated into solid and liquid by a method such as centrifugation, filtration, distillation, spray drying, etc. and taken out in the form of powder. The extracted powder can be dried. The drying temperature is preferably in the range of 50 to 300 ° C., and the drying time is preferably several hours to several days. The dried powder can be fired at higher temperatures. The firing temperature is preferably in the range of 100 to 1300 ° C., and the firing time is preferably in the range of 1 to 24 hours. The dried or fired particles can be crushed into individual particles using a ball mill, a jet mill or the like. The dried or fired particles can also be used after being dispersed in an appropriate solvent using a counter collision type dispersion device, a bead mill, or the like.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
Example 1 (SiO ₂ —TiO ₂ nanoparticles, Ti content: 45 mol%)
Into a 2 liter Erlenmeyer flask, 167.4 g of methyl silicate (Si (OMe) ₄ , manufactured by Tama Chemical Industry Co., Ltd., trade name: normal methyl silicate) was charged, and while stirring, 76.1 g of methyl alcohol and 0.04% by mass 18.0 g of hydrochloric acid was added, and methyl silicate was partially hydrolyzed by stirring at room temperature for about 20 minutes (this prepared solution is referred to as “solution A1”).

In addition to the above, 255.8 g of tetraisopropoxy titanium (Ti (O-iPr) ₄ , manufactured by Nippon Soda Co., Ltd., trade name: A-1 (TPT)), 255.8 g of methanol, and 134.3 g of triethanolamine were added. After stirring at room temperature for 30 minutes, it was mixed with Solution A1 and stirred for 30 minutes (this prepared solution is referred to as “Solution B1”).

  A reaction solution was prepared by mixing 1775.6 g of ion-exchanged water and 4.4 g of aqueous ammonia (25% by mass) in a glass reaction vessel (with an internal volume of 5 liters) equipped with a stirrer. Held on. The solution B1 was dropped into the reaction solution over about 5 hours. After completion of the dropwise addition, stirring was further continued for 1 hour, and then the solution in the system was taken out, transferred to a 5 liter beaker, and allowed to stand. The resulting solution was concentrated twice with a reverse osmosis membrane, and then diluted with water to double. This concentration / dilution operation was repeated five times to obtain an aqueous dispersion of fine particles.

  SEM observation was performed about the obtained particle | grains. As a result, particles having a particle diameter of 0.02 μm were obtained. Further, when X-ray fluorescence analysis was performed on the powder obtained by drying the aqueous dispersion, it was found that the ratio of Si and Ti was Si: Ti = 55: 45.

Example 2 (SiO ₂ —TiO ₂ nanoparticles, Ti content: 10 mol%)
In a 2 liter Erlenmeyer flask, 548.0 g of methyl silicate (Si (OMe) ₄ , manufactured by Tama Chemical Industry Co., Ltd., trade name: normal methyl silicate) was charged, and while stirring, 274.0 g of methyl alcohol and 0.04 mass% 28.8 g of hydrochloric acid was added, and the methyl silicate was partially hydrolyzed by stirring at room temperature for about 20 minutes (this prepared solution is referred to as “Solution A2”).

Separately from the above, 113.6 g of tetraisopropoxy titanium (Ti (O-iPr) ₄ , Nippon Soda Co., Ltd., trade name: A-1 (TPT)) and 227.2 g of isopropyl alcohol were added and stirred at room temperature for 30 minutes. Thereafter, it was mixed with the solution A2 and stirred for 30 minutes (this prepared solution is referred to as “solution B2”).

  A reaction solution is prepared by mixing 1184.0 g of ion-exchanged water and 4.4 g of ammonia water (25% by mass) in a glass reaction vessel (with an internal volume of 5 liters) equipped with a stirrer. Held on. The solution B2 was dropped into the reaction solution over about 5 hours. After completion of the dropwise addition, stirring was further continued for 1 hour, and then the solution in the system was taken out, transferred to a 5 liter beaker, and allowed to stand. The resulting solution was concentrated twice with a reverse osmosis membrane, and then diluted with water to double. This concentration / dilution operation was repeated five times to obtain an aqueous dispersion of fine particles.

  SEM observation was performed about the obtained particle | grains. As a result, particles having a particle diameter of 0.01 μm were obtained. Further, when X-ray fluorescence analysis was performed on the powder obtained by drying the aqueous dispersion, it was found that the ratio of Si and Ti was Si: Ti = 9: 1.

Example ₃ (SiO ₂ -ZrO 2 based nanoparticles, Zr content: 45 mol%)
In preparing the solution B1, instead of tetraisopropoxy titanium, 345.3 g of tetra-tert-butoxyzirconium (Zr (O-tBu) ₄ , manufactured by Wako Pure Chemical Industries, Ltd.) was used, and the amount of methanol was 345.3 g. Except that, SiO ₂ —ZrO ₂ -based fine particles were obtained in the same manner as in Example 1.

  SEM observation was performed about the obtained particle | grains. As a result, particles having a particle diameter of 0.01 μm were obtained. Further, when X-ray fluorescence analysis was performed on the powder obtained by drying the aqueous dispersion, it was found that the ratio of Si and Zr was Si: Zr = 55: 45.

Example ₄ (SiO 2 _-Al 2 _{O 3} based nanoparticles, Al content: 45 mol%)
When preparing solution B1, instead of tetraisopropoxy titanium, 183.8 g of triisopropylaluminum (Al (O-iPr) ₃ , manufactured by Wako Pure Chemical Industries, Ltd.) was used, except that the amount of methanol was 183.8 g. Obtained SiO ₂ —Al ₂ O ₃ -based fine particles in the same manner as in Example 1.

  SEM observation was performed about the obtained particle | grains. As a result, particles having a particle diameter of 0.02 μm were obtained. Further, when X-ray fluorescence analysis was performed on the powder obtained by drying the aqueous dispersion, it was found that the ratio of Si and Al was Si: Al = 55: 45.

Example 5 (Examples of hydrolysis and condensation in an aqueous solution of SiO ₂ —TiO ₂ -based nanoparticles, Ti content: 45 mol%, 65 mass%)
Into a 2 liter Erlenmeyer flask, 167.4 g of methyl silicate (Si (OMe) ₄ , manufactured by Tama Chemical Industry Co., Ltd., trade name: normal methyl silicate) was charged, and while stirring, 76.1 g of methyl alcohol and 0.04% by mass 18.0 g of hydrochloric acid was added, and the methyl silicate was partially hydrolyzed by stirring at room temperature for about 20 minutes (this prepared solution is referred to as “solution A5”).

In addition to the above, 255.8 g of tetraisopropoxy titanium (Ti (O-iPr) ₄ , manufactured by Nippon Soda Co., Ltd., trade name: A-1 (TPT)), 255.8 g of methanol, and 134.3 g of triethanolamine were added. After stirring at room temperature for 30 minutes, it was mixed with solution A5 and stirred for 30 minutes (this prepared solution is referred to as “solution B5”).

  A reaction liquid is prepared by mixing 1153 g of ion-exchanged water, 621 g of methanol, and 4.4 g of aqueous ammonia (25% by mass) in a glass reaction vessel (with an internal volume of 5 liters) equipped with a stirrer. Held at 0C. The solution B5 was dropped into the reaction solution over about 5 hours. After completion of the dropwise addition, stirring was further continued for 1 hour, and then the solution in the system was taken out, transferred to a 5 liter beaker, and allowed to stand. The resulting solution was concentrated twice with a reverse osmosis membrane, and then diluted with water to double. This concentration / dilution operation was repeated five times to obtain an aqueous dispersion of fine particles.

  SEM observation was performed about the obtained particle | grains. As a result, particles having a particle size of 0.05 μm were obtained. Further, when X-ray fluorescence analysis was performed on the powder obtained by drying the aqueous dispersion, it was found that the ratio of Si and Ti was Si: Ti = 55: 45.

Comparative Example 1 (Comparative Example of Example 1 in which hydrolysis and condensation were performed in a 50% by mass aqueous solution)
Into a 2 liter Erlenmeyer flask, 167.4 g of methyl silicate (Si (OMe) ₄ , manufactured by Tama Chemical Industry Co., Ltd., trade name: normal methyl silicate) was charged, and while stirring, 76.1 g of methyl alcohol and 0.04% by mass 18.0 g of hydrochloric acid was added, and methyl silicate was partially hydrolyzed by stirring at room temperature for about 20 minutes (this adjusted solution is referred to as “solution A1 ′”).

In addition to the above, 255.8 g of tetraisopropoxy titanium (Ti (O-iPr) ₄ , manufactured by Nippon Soda Co., Ltd., trade name: A-1 (TPT)), 255.8 g of methanol, and 134.3 g of triethanolamine were added. After stirring at room temperature for 30 minutes, it was mixed with solution A1 ′ and stirred for 30 minutes (this prepared solution is referred to as “solution B1 ′”).

  A reaction solution is prepared by mixing 885 g of ion-exchanged water, 885 g of methanol, and 4.4 g of aqueous ammonia (25% by mass) in a glass reaction vessel (with an internal volume of 5 liters) equipped with a stirrer. Held at 0C. The solution B1 'was dropped into the reaction solution over about 5 hours. After completion of the dropwise addition, stirring was further continued for 1 hour, and then the solution in the system was taken out, transferred to a 5 liter beaker, and allowed to stand. The resulting solution was concentrated twice with a reverse osmosis membrane, and then diluted with water to double. This concentration / dilution operation was repeated five times to obtain an aqueous dispersion of fine particles.

  SEM observation was performed about the obtained particle | grains. As a result, it was revealed that a large amount of particles having a particle size of 0.1 μm or more was contained.

Comparative Example 2 (Comparative Example of Example 2 in which hydrolysis and condensation were performed in a 50% by mass aqueous solution)
In a 2 liter Erlenmeyer flask, 548.0 g of methyl silicate (Si (OMe) ₄ , manufactured by Tama Chemical Industry Co., Ltd., trade name: normal methyl silicate) was charged, and while stirring, 274.0 g of methyl alcohol and 0.04 mass% 28.8 g of hydrochloric acid was added, and the methyl silicate was partially hydrolyzed by stirring at room temperature for about 20 minutes (this prepared solution is referred to as “Solution A2 ′”).

Separately from the above, 113.6 g of tetraisopropoxy titanium (Ti (O-iPr) ₄ , Nippon Soda Co., Ltd., trade name: A-1 (TPT)) and 227.2 g of isopropyl alcohol were added and stirred at room temperature for 30 minutes. Thereafter, it was mixed with the solution A2 ′ and stirred for 30 minutes (this prepared solution is referred to as “solution B2 ′”).

  A reaction liquid was prepared by mixing 590 g of ion-exchanged water, 590 g of methanol, and 4.4 g of aqueous ammonia (25% by mass) in a glass reaction vessel (internal volume of 5 liters) equipped with a stirrer. Held at 0C. The solution B2 'was dropped into the reaction solution over about 5 hours. After completion of the dropwise addition, stirring was further continued for 1 hour, and then the solution in the system was taken out, transferred to a 5 liter beaker, and allowed to stand. SEM observation was performed about the obtained particle | grains. As a result, a large amount of particles having a particle diameter of 0.1 μm or more was contained.

Comparative Example 3
Particles were synthesized in the same manner as in Example 1 except that triethanolamine was not used. As a result of SEM observation of the obtained particles, it was revealed that the particles contained a large amount of particles of 0.1 μm or more.

Comparative Example 4 (example in which no composite alcoside raw material is used)
In a 2 liter Erlenmeyer flask, 548.0 g of methyl silicate (Si (OMe) ₄ , manufactured by Tama Chemical Industry Co., Ltd., trade name: normal methyl silicate) was charged, and while stirring, 274.0 g of methyl alcohol and 0.04 mass% 28.8 g of hydrochloric acid was added, and the methyl silicate was partially hydrolyzed by stirring at room temperature for about 20 minutes (this adjusted solution is referred to as “Solution A4 ′”).

Separately from the above, 113.6 g of tetraisopropoxy titanium (Ti (OiPr) ₄ , Nippon Soda Co., Ltd., trade name: A-1 (TPT)) and 227.2 g of isopropyl alcohol were added and stirred at room temperature for 30 minutes (this The prepared solution is referred to as “Solution C4 ′”).

  A reaction solution is prepared by mixing 1184.0 g of ion-exchanged water and 4.4 g of ammonia water (25% by mass) in a glass reaction vessel (with an internal volume of 5 liters) equipped with a stirrer. Held on. The solution A4 'and the solution C4' were dropped into the reaction solution over about 5 hours from separate supply lines. After completion of the dropwise addition, stirring was further continued for 1 hour, and then the solution in the system was taken out, transferred to a 5 liter beaker, and allowed to stand. The obtained particles contained a large amount of coarse particles having a particle diameter of 100 μm or more.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the invention is limited to the embodiments disclosed herein. However, the silica-based composite oxide fine particles and the method for producing the same can be changed as appropriate without departing from the spirit or idea of the invention that can be read from the claims and the entire specification. Should be understood as being included in the scope.

It is the schematic which shows the manufacturing process of the silica type complex oxide fine particle of this invention.

Explanation of symbols

S1 Partial hydrolyzate formation process S2 Compound alkoxide raw material preparation process S3 Hydrolysis / condensation process

Claims (3)

A step of partially hydrolyzing silicon alkoxide with water to form a partially hydrolyzed product,
An alkoxide of a metal other than silicon selected from the group consisting of titanium, zirconium, and aluminum, or a complex prepared by mixing an alkoxide of a metal other than silicon and a complexing agent, and the partial hydrolyzate A step of preparing a composite alkoxide raw material by mixing so that the proportion of metal other than silicon is less than 50 mol%,
A method for producing silica-based composite oxide fine particles having an average particle diameter of 1 nm to 100 nm, comprising a step of hydrolyzing and condensing the composite alkoxide raw material in a solvent or dispersion medium having a water content of 60 to 100% by mass. In the step of preparing the composite alkoxide raw material, the alkoxide of a metal other than silicon selected from the group consisting of titanium, zirconium, and aluminum, and the partial hydrolyzate, the proportion of the metal other than silicon is 25 mol%. The method according to claim 1 , which is a step of preparing a composite alkoxide raw material by mixing so as to be less than. The step of preparing the composite alkoxide raw material comprises a complex prepared by mixing an alkoxide of a metal other than silicon selected from the group consisting of titanium, zirconium, and aluminum and a complexing agent, and the partial hydrolyzate. The method according to claim 1 , which is a step of preparing a composite alkoxide raw material by mixing so that the proportion of the metal other than silicon is 25 mol% or more and less than 50 mol%.

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