Method for producing zirconia nanoparticles

Abstract

The present invention provides a method for producing zirconia nanoparticles, which can easily produce zirconia nanoparticles that have excellent dispersibility in organic solvents. [Solution] A method for producing zirconia nanoparticles includes a formation step of heating a sealed reaction vessel having a first compartment containing a precursor solution and a second compartment containing water to form zirconia nanoparticles in the first compartment, wherein the precursor solution contains zirconium alkoxide and at least one aliphatic compound selected from the group consisting of aliphatic carboxylic acids and aliphatic amines, and the proportion of the aliphatic carboxylic acid in the aliphatic compound is 80 mol % or more.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing zirconia nanoparticles. [Background technology]

[0002] Group 4 metal oxides have characteristics such as a large band gap, high dielectric constant and high refractive index, and their nanoparticles are expected to be applied in a variety of fields.

[0003] For example, Patent Document 1 describes a method for producing zirconia nanoparticles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-139378 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of further expanding applications, there is a demand for zirconia nanoparticles that have excellent dispersibility in organic solvents (particularly aprotic solvents, nonpolar solvents, etc.).

[0006] An object of the present disclosure is to provide a method for producing zirconia nanoparticles that can easily produce zirconia nanoparticles that have excellent dispersibility in organic solvents and have a crystalline structure. [Means for solving the problem]

[0007] The present disclosure relates to, for example, the following [1] to [7]. [1] A method for producing zirconia nanoparticles by heating a sealed reaction vessel having a first compartment containing a precursor solution and a second compartment containing water, the precursor solution contains zirconium alkoxide and at least one aliphatic compound selected from the group consisting of aliphatic carboxylic acids and aliphatic amines; The ratio of the aliphatic carboxylic acid to the aliphatic compound is 80 mol % or more. Method for producing zirconia nanoparticles. [2] The method according to [1], wherein the aliphatic carboxylic acid has a hydrocarbon group having 8 to 24 carbon atoms. [3] The method according to [1] or [2], wherein the aliphatic carboxylic acid has a carbon-carbon double bond. [4] The manufacturing method according to any one of [1] to [3], wherein the second compartment contains a mixed solution containing water and an alcohol. [5] [4] The method according to [4], wherein the content of the water is 1% by volume or more based on the total volume of the mixed solution. [6] a washing step of washing the zirconia nanoparticles formed in the first compartment; a dispersing step of dispersing the washed zirconia nanoparticles in an organic solvent; The method according to any one of [1] to [5], further comprising: [7] The method according to [6], wherein the organic solvent is an aprotic solvent or a nonpolar solvent. [Effects of the Invention]

[0008] According to the present disclosure, there is provided a method for producing zirconia nanoparticles that can easily produce zirconia nanoparticles that have excellent dispersibility in organic solvents and have a crystalline structure. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows the results of dynamic light scattering (DLS) in Example 1. [Figure 2] FIG. 2 shows the results of powder X-ray diffraction (XRD) of Example 1. [Figure 3] FIG. 3 shows the results of dynamic light scattering (DLS) in Example 2. [Figure 4] FIG. 4 shows the results of powder X-ray diffraction (XRD) of Example 3. [Figure 5] FIG. 5 is a diagram showing the results of observation of Comparative Example 2 using a transmission electron microscope. [Figure 6] FIG. 6 is a diagram showing the results of powder X-ray diffraction (XRD) of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present disclosure will be described in detail below.

[0011] The method for producing zirconia nanoparticles of this embodiment includes a formation step of heating a sealed reaction vessel having a first compartment containing a precursor solution and a second compartment containing water to form zirconia nanoparticles in the first compartment.

[0012] The precursor solution contains zirconium alkoxide and at least one aliphatic compound selected from the group consisting of aliphatic carboxylic acids and aliphatic amines, and the proportion of aliphatic carboxylic acids in the aliphatic compounds is 80 mol % or more.

[0013] In the formation process, water vaporized in the second compartment is supplied to the precursor solution in the first compartment, where zirconium alkoxide is hydrolyzed in the precursor solution to form zirconia nanoparticles with a crystalline structure. The presence of a specific aliphatic compound in the precursor solution stabilizes the formation of zirconia nanoparticles in the precursor solution. Furthermore, the presence of an aliphatic carboxylic acid in the precursor solution modifies the surface of the zirconia nanoparticles with the aliphatic carboxylic acid, resulting in excellent dispersibility of the zirconia nanoparticles in organic solvents (especially aprotic solvents, nonpolar solvents, etc.).

[0014] According to the findings of the present inventors, aliphatic carboxylic acids and aliphatic amines can be used as components that contribute to the stabilization of zirconia nanoparticles in the precursor solution, and by increasing the proportion of aliphatic carboxylic acids (setting the proportion of aliphatic carboxylic acids in the aliphatic compounds to 80 mol %), the dispersibility of zirconia nanoparticles in organic solvents (particularly aprotic solvents, nonpolar solvents, etc.) becomes significantly better.

[0015] The reaction vessel may have any structure as long as it has a first compartment and a second compartment and water vaporized in the second compartment can be supplied to the first compartment. The reaction vessel may also be a sealable, pressure-resistant vessel capable of creating a high pressure inside.

[0016] The reaction vessel may be, for example, an autoclave reaction vessel with a small vessel for holding the precursor solution disposed therein. In this case, the inside of the small vessel is the first compartment, and the outside of the small vessel within the autoclave reaction vessel is the second compartment.

[0017] The reaction vessel may also be an autoclave reaction vessel with a small container for containing water disposed inside the reaction vessel, in which case the inside of the small container becomes the second compartment and the outside of the small container inside the reaction vessel becomes the first compartment.

[0018] The precursor solution may include a zirconium alkoxide, at least one aliphatic compound selected from the group consisting of an aliphatic carboxylic acid and an aliphatic amine, and a solvent.

[0019] Zirconium alkoxides include, for example, Zr(OR 1 )4(R 1 R represents an alkyl group. 1 The alkyl groups in may be linear, branched, or cyclic. 1 may be the same or different from each other.

[0020] R 1The alkyl group may have, for example, 1 to 8 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms.

[0021] R 1 The alkyl group may be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group, a t-butyl group, or the like, and from the viewpoint of the stability of the zirconium alkoxide, a t-butyl group or an n-butyl group is preferred.

[0022] The content of zirconium alkoxide in the precursor solution may be, for example, 0.5 mol % or more, 1 mol % or more, or 2 mol % or more, based on the total amount of zirconium alkoxide, aliphatic compound, and solvent. The content of zirconium alkoxide in the precursor solution may be, for example, 20 mol % or less, 15 mol % or less, 10 mol % or less, 8 mol % or less, or 6 mol % or less, based on the total amount of zirconium alkoxide, aliphatic compound, and solvent.

[0023] The aliphatic carboxylic acid may be a compound in which a hydrocarbon group not containing an aromatic ring is bonded to a carboxyl group.

[0024] The number of carbon atoms in the hydrocarbon group of the aliphatic carboxylic acid may be, for example, 8 or more, or, from the viewpoint of further improving the dispersibility of zirconia nanoparticles, may be 12 or more, or 16 or more. The number of carbon atoms in the hydrocarbon group of the aliphatic carboxylic acid may be, for example, 24 or less, 22 or less, 20 or less, or 18 or less.

[0025] The hydrocarbon group contained in the aliphatic carboxylic acid may be a saturated hydrocarbon group or an unsaturated hydrocarbon group.

[0026] The aliphatic carboxylic acid may have a carbon-carbon double bond. That is, the hydrocarbon group of the aliphatic carboxylic acid may have a carbon-carbon double bond. Aliphatic carboxylic acids having a carbon-carbon double bond tend to have a low melting point and are easy to handle at room temperature.

[0027] The aliphatic carboxylic acid may be a compound having one or more carboxyl groups, or may be a compound having one carboxyl group.

[0028] From the viewpoint of easy handling, the aliphatic carboxylic acid is preferably a liquid at room temperature. The melting point of the aliphatic carboxylic acid may be, for example, 50°C or lower, 40°C or lower, 30°C or lower, or 20°C or lower.

[0029] Examples of the aliphatic carboxylic acid include oleic acid, elaidic acid, myristoleic acid, linoleic acid, and 2-hexyldecanoic acid.

[0030] The aliphatic amine may be a compound in which an amino group is bonded to a hydrocarbon group that does not contain an aromatic ring.

[0031] The number of carbon atoms in the hydrocarbon group of the aliphatic amine may be, for example, 8 or more, or, from the viewpoint of further improving the dispersibility of zirconia nanoparticles, may be 12 or more, or 16 or more. The number of carbon atoms in the hydrocarbon group of the aliphatic amine may be, for example, 24 or less, 22 or less, 20 or less, or 18 or less.

[0032] The hydrocarbon group contained in the aliphatic amine may be a saturated hydrocarbon group or an unsaturated hydrocarbon group.

[0033] The aliphatic amine may have a carbon-carbon double bond. That is, the hydrocarbon group of the aliphatic amine may have a carbon-carbon double bond. Aliphatic amines having a carbon-carbon double bond tend to have a low melting point and are easy to handle at room temperature.

[0034] The aliphatic amine may be a compound having one or more amino groups, or may be a compound having one amino group.

[0035] From the viewpoint of easy handling, the aliphatic amine is preferably a liquid at room temperature. The melting point of the aliphatic amine may be, for example, 50°C or lower, 40°C or lower, or 30°C or lower.

[0036] Examples of the aliphatic amine include compounds in which the carboxy group of the above-mentioned aliphatic carboxylic acid is substituted with an amino group, such as oleylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine.

[0037] The proportion of aliphatic carboxylic acids in the aliphatic compounds (total of aliphatic carboxylic acids and aliphatic amines) is 80 mol% or more, and from the viewpoint of further improving the dispersibility of zirconia nanoparticles in organic solvents, it may be 85 mol% or more, 90 mol% or more, 95 mol% or more, 97 mol% or more, or even 100 mol%.

[0038] The content of the aliphatic compound (total amount of aliphatic carboxylic acid and aliphatic amine) in the precursor solution may be, for example, 1 mole or more per mole of zirconium alkoxide, and from the viewpoint of more efficiently reacting the zirconium alkoxide, it may be 2 moles or more, or 4 moles or more. Furthermore, the content of the aliphatic compound (total amount of aliphatic carboxylic acid and aliphatic amine) in the precursor solution may be, for example, 50 moles or less per mole of zirconium alkoxide, and from the viewpoint of reducing excess aliphatic compound, it may be 40 moles or less, 30 moles or less, 20 moles or less, 15 moles or less, or 10 moles or less.

[0039] The solvent in the precursor solution may be any solvent that can dissolve the zirconium alkoxide and the aliphatic compound (aliphatic carboxylic acid and aliphatic amine).

[0040] Examples of the solvent in the precursor solution include alcohol-based solvents such as methanol, ethanol, isopropanol, and 1-butanol; glycol-based solvents such as ethylene glycol and propylene glycol; and ether-based solvents such as octyl ether, diphenyl ether, and dibenzyl ether.

[0041] The second compartment may contain a mixed solution containing water and an alcohol. When the second compartment contains water, the zirconia nanoparticles are more likely to be obtained as zirconia nanocrystals having a crystalline structure.

[0042] Examples of the alcohol in the mixed solution include methanol, ethanol, isopropanol, and 1-butanol, with methanol and ethanol being preferred from the viewpoint of solubility.

[0043] The proportion of water in the mixed solution (the water content based on the total volume of the mixed solution) may be, for example, 1% by volume or more, 5% by volume or more, or 10% by volume or more. The proportion of water in the mixed solution (the water content based on the total volume of the mixed solution) may be, for example, 99% by volume or less, 95% by volume or less, 90% by volume or less, 85% by volume or less, or 80% by volume or less.

[0044] The reaction temperature in the forming step may be, for example, 120° C. or higher, 140° C. or higher, 160° C. or higher, or 180° C. or higher. The reaction temperature in the forming step may be, for example, 300° C. or lower, 230° C. or lower, or 200° C. or lower.

[0045] In the formation step, the time for maintaining the reaction temperature (hereinafter referred to as the reaction time) may be, for example, 5 hours or more, 10 hours or more, or 15 hours or more. The reaction time in the formation step may be, for example, 48 hours or less, 36 hours or less, or 24 hours or less.

[0046] In the forming step, zirconia nanoparticles are formed in the first compartment, and the formed zirconia nanoparticles are precipitated in the first compartment.

[0047] The manufacturing method of this embodiment may further include a washing step of washing the zirconia nanoparticles formed in the first compartment, and a dispersing step of dispersing the washed zirconia nanoparticles in an organic solvent.

[0048] The washing method in the washing step is not particularly limited, and may be, for example, a washing method using centrifugation, filtration, or the like.

[0049] The washing step may be, for example, a step of dispersing the zirconia nanoparticles recovered from the first compartment in a low-polarity solvent to obtain a dispersion, adding a polar solvent to the dispersion, and re-recovering the zirconia nanoparticles by centrifugation.

[0050] Examples of low-polarity solvents include halogenated solvents such as chloroform and dichloromethane, aromatic hydrocarbon solvents such as toluene and benzene, aliphatic hydrocarbon solvents such as hexane and octane, and alicyclic hydrocarbon solvents such as cyclohexane.

[0051] Examples of polar solvents include alcohol solvents such as methanol, ethanol, isopropanol, and 1-butanol; ketone solvents such as acetone and methyl ethyl ketone; and acetonitrile.

[0052] The amount of polar solvent added is not particularly limited, and may be, for example, 40% by volume or more, 50% by volume or more, 60% by volume or more, or 70% by volume or more, where the total amount of the low-polarity solvent and the polar solvent is 100% by volume. Furthermore, the amount of polar solvent added may be, for example, 95% by volume or less, or 90% by volume or less, where the total amount of the low-polarity solvent and the polar solvent is 100% by volume.

[0053] The washing step may be a step of performing the above-mentioned centrifugation multiple times.

[0054] The dispersion step is a step of dispersing zirconia nanoparticles in an organic solvent to obtain a dispersion liquid.

[0055] The organic solvent may be an aprotic solvent or a non-polar solvent.

[0056] Examples of organic solvents include halogenated solvents such as chloroform and dichloromethane, aromatic hydrocarbon solvents such as toluene and benzene, aliphatic hydrocarbon solvents such as hexane and octane, and alicyclic hydrocarbon solvents such as cyclohexane.

[0057] According to the production method of this embodiment, zirconia nanoparticles that are excellent in dispersibility in organic solvents (particularly, aprotic solvents, nonpolar solvents, etc.) can be obtained.

[0058] The zirconia nanoparticles may be zirconia nanocrystals, which can be confirmed by powder X-ray diffraction.

[0059] The average primary particle size of the zirconia nanoparticles may be, for example, 1 nm or more, or 2 nm or more, or may be, for example, 20 nm or less, or 15 nm or less, 10 nm or less, or 8 nm or less.

[0060] The average primary particle size of the zirconia nanoparticles is measured using a transmission electron microscope.

[0061] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. [Example]

[0062] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0063] Example 1 A precursor solution was prepared by mixing 2.5 mmol of zirconium(IV) butoxide, 7.93 mL (25 mmol) of oleic acid, and 2.92 mL (50 mmol) of ethanol at room temperature and stirring for 15 minutes. A water / ethanol mixture (water / ethanol = 20 / 80 (volume ratio)) was also prepared.

[0064] A small container containing the precursor solution was placed inside a Teflon (registered trademark) container for autoclave, and a water / ethanol mixed solution was placed on the outside of the small container inside the Teflon (registered trademark) container. The Teflon (registered trademark) container was placed inside a stainless steel pressure vessel, sealed, and heated at 180°C for 18 hours. After heating, the white precipitate in the small vessel was collected and redispersed in 10 mL of hexane, 30 mL of ethanol was added, and the mixture was centrifuged to obtain zirconia nanoparticles.

[0065] The resulting zirconia nanoparticles were dispersed in toluene to obtain a transparent dispersion, and powder X-ray diffraction (XRD) confirmed that the resulting zirconia nanoparticles had a crystalline structure of ZrO2 (a mixture of tetragonal and monoclinic).

[0066] Fig. 1 shows the results of dynamic light scattering (DLS) in Example 1. Fig. 2 shows the results of powder X-ray diffraction (XRD) in Example 1.

[0067] Example 2 Zirconia nanoparticles were obtained in the same manner as in Example 1, except that "7.93 mL (25 mmol) of oleic acid" in the precursor solution was changed to 7.28 mL (25 mmol) of 2-hexyldecanoic acid.

[0068] The obtained zirconia nanoparticles were dispersed in toluene, and were found to be well dispersed, yielding a transparent dispersion.

[0069] FIG. 3 shows the results of dynamic light scattering (DLS) in Example 2.

[0070] Example 3 Zirconia nanoparticles were obtained in the same manner as in Example 1, except that the amount of zirconium (IV) butoxide used was changed from 2.5 mmol to 6.25 mmol.

[0071] The resulting zirconia nanoparticles were dispersed in toluene to obtain a transparent dispersion, and powder X-ray diffraction (XRD) confirmed that the resulting zirconia nanoparticles had a crystalline structure of ZrO2 (a mixture of tetragonal and monoclinic).

[0072] FIG. 4 shows the results of powder X-ray diffraction (XRD) of Example 3.

[0073] (Comparative Example 1) Zirconia nanoparticles were obtained in the same manner as in Example 1, except that "7.93 mL (25 mmol) of oleic acid" in the precursor solution was changed to 4.76 mL (15 mmol) of oleic acid and 3.22 mL (10 mmol) of oleylamine.

[0074] When the obtained zirconia nanoparticles were dispersed in toluene, some of them aggregated, and good dispersibility was not obtained.

[0075] (Comparative Example 2) Zirconia nanoparticles were obtained in the same manner as in Example 1, except that ethanol was used instead of the water / ethanol mixed solution.

[0076] The obtained zirconia nanoparticles were confirmed to be amorphous particles by transmission electron microscopy and powder X-ray diffraction (XRD).

[0077] Fig. 5 is a diagram showing the results of observation by a transmission electron microscope of Comparative Example 2. Fig. 6 is a diagram showing the results of powder X-ray diffraction (XRD) of Comparative Example 2.

Claims

1. A method for producing zirconia nanoparticles by heating a sealed reaction vessel having a first compartment containing a precursor solution and a second compartment containing water, the precursor solution contains zirconium alkoxide and at least one aliphatic compound selected from the group consisting of aliphatic carboxylic acids and aliphatic amines; the proportion of the aliphatic carboxylic acid in the aliphatic compound is 80 mol % or more; Method for producing zirconia nanoparticles.

2. The method according to claim 1, wherein the aliphatic carboxylic acid has a hydrocarbon group having 8 to 24 carbon atoms.

3. The method according to claim 1, wherein the aliphatic carboxylic acid has a carbon-carbon double bond.

4. The method of claim 1 , wherein the second compartment contains a mixed solution containing water and an alcohol.

5. The method according to claim 4 , wherein the content of the water is 1% by volume or more based on the total volume of the mixed solution.

6. a washing step of washing the zirconia nanoparticles formed in the first compartment; a dispersing step of dispersing the washed zirconia nanoparticles in an organic solvent; The method of claim 1 further comprising:

7. The method according to claim 6, wherein the organic solvent is an aprotic solvent or a nonpolar solvent.

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