JP7380379B2 - Dispersion manufacturing method - Google Patents

Description

The present invention relates to a method for producing a dispersion.

Inorganic particles can impart various performances, such as a refractive index adjustment effect and a heat ray shielding function, to parts, members, and materials. Therefore, it is used in various technical fields such as cosmetics, resin products, and optical parts.

When unmodified, inorganic particles generally have hydroxyl groups on their surfaces. Therefore, inorganic particles are usually hydrophilic. Therefore, when adding inorganic particles to a hydrophobic material, the surface of the inorganic particles is modified to be hydrophobic using a surface modifier such as a silane coupling agent.

As inorganic particles whose surfaces have been modified to be hydrophobic, for example, cosmetic pigments in which the surface of the pigment is coated with a specific silane coupling agent such as n-octyltriethoxysilane are known (for example, (See Patent Document 1). When blended into cosmetics, this pigment for cosmetics has high water repellency, yet has a moist feel, is not heavy, and has high adhesion to the skin.
Further, as a dispersion containing inorganic particles whose surface has been modified to be hydrophobic, for example, the surface has been modified with a surface modifier having one or more reactive functional groups, and the dispersed particle size is 1 nm or more and 20 nm or less. An inorganic oxide transparent dispersion containing inorganic oxide particles is known (for example, see Patent Document 2).

Japanese Patent Application Publication No. 2001-181136 International Publication No. 2007/049573

By the way, as a method for surface-modifying inorganic particles with a surface-modifying material in a liquid phase, for example, a mixed solution is prepared by mixing not only the inorganic particles and the surface-modifying material but also a dispersion medium, and then the mixed solution is dispersed. One example is a method of distributed processing using machines. When such surface-modified inorganic particles are mixed with a highly hydrophobic material, they are not sufficiently dispersed in the material and aggregate. As a result, there has been a problem in that turbidity such as white turbidity occurs in highly hydrophobic materials. Further, the obtained dispersion liquid had a broad particle size distribution, and the performance of the inorganic particles was sometimes not fully exhibited.

The present invention has been made in view of the above circumstances, and provides a method for producing a dispersion liquid that suppresses aggregation and prevents the occurrence of cloudiness such as cloudiness even when mixed with a highly hydrophobic material. The purpose is to provide a dispersion liquid with a sharp particle size distribution.

In order to solve the above problems, one aspect of the present invention includes a step B of mixing a surface modification material, inorganic particles, and an alcohol solvent to obtain a mixed solution, and dispersing the inorganic particles in the mixed solution. , a step C of obtaining a dispersion in which the inorganic particles are dispersed, and a step D of adding a hydrophobic solvent to the dispersion, and the step D of adding the hydrophobic solvent includes heating the dispersion, and then a step d1 of adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate; a step d2 of adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate while heating the dispersion; or a step d2 of adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate. A step d3 of heating the dispersion after adding the inorganic particles at a rate that does not agglomerate the inorganic particles, the content of the inorganic particles in the mixed solution is 10% by mass or more and 46% by mass or less, and the content of the inorganic particles in the mixed solution is Provided is a method for producing a dispersion liquid, wherein the total content of the surface modification material and the inorganic particles is 65% by mass or more and 93% by mass or less.

One aspect of the present invention further includes a step A of mixing the surface modification material and water to obtain a hydrolyzed solution containing the hydrolyzed surface modification material, and a step B of obtaining the mixed solution. In this case, the mixed liquid may be obtained by mixing the hydrolyzed liquid, the inorganic particles, and the alcoholic solvent.

In one aspect of the present invention, the amount of water added to the hydrolysis solution may be 0.5 mol or more and 5 mol or less with respect to 1 mol of the surface modification material.

According to the present invention, there is provided a method for producing a dispersion liquid in which aggregation is suppressed and generation of turbidity such as white turbidity is prevented even when mixed with a highly hydrophobic material, and a dispersion liquid with a sharp particle size distribution is provided. be able to.

A method for producing a dispersion liquid and an embodiment of the dispersion liquid of the present invention will be described.
It should be noted that the present embodiment is specifically explained in order to better understand the gist of the invention, and is not intended to limit the invention unless otherwise specified. In the present invention, changes, omissions, substitutions, additions, etc. can be made to numerical values, amounts, materials, types, times, temperatures, orders, etc. without departing from the spirit of the invention.

[Dispersion manufacturing method]
Preferred embodiments of the present invention will be described in detail below.
<1. Idea of the inventors>
First, prior to a detailed description of the present invention, the ideas that the present inventors and others came up with leading up to the present invention will be explained.

As mentioned above, conventionally, when inorganic particles are surface-modified with a surface-modifying material in a liquid phase, a mixed solution is prepared by mixing not only the inorganic particles and the surface-modifying material but also a dispersion medium, and then the mixture is The liquid was dispersed using a dispersion machine. When such surface-modified inorganic particles are mixed with a highly hydrophobic material, they are not sufficiently dispersed in the material and aggregate. As a result, there has been a problem in that turbidity such as white turbidity occurs in highly hydrophobic materials. In such a case, the inorganic particles cannot fully exhibit the desired performance.

The dispersion medium is usually added for the purpose of uniformly dispersing the inorganic particles and causing the surface modification material to uniformly modify the surfaces of the inorganic particles. Conventionally, when a dispersion medium is not used, the viscosity of the dispersion increases. As a result, it was thought that the surface modification material would not adhere sufficiently to the surface of the inorganic particles. That is, conventionally, a dispersion medium was considered essential for surface modification of inorganic particles in a liquid phase. We directly dispersed inorganic particles into high concentrations of surface-modified materials without the use of a dispersion medium or with a small amount. As a result, the present inventors have found that uniform dispersion of inorganic particles can be achieved in a dispersion liquid, and that it is possible to uniformly modify the inorganic particles with a surface modification material.

Next, in the dispersion liquid obtained in this way, since the viscosity of the mixed liquid at the time of dispersion was high, it was difficult to make the particle size distribution sufficiently sharp.
Therefore, the present inventors have also discovered that a dispersion liquid with a sharp particle size distribution can be obtained by mixing a small amount of a hydrophilic solvent into the mixed liquid.

The mechanism is presumed as follows.
When inorganic particles are directly dispersed in a surface-modified material, the viscosity of the mixture is higher than when a solvent is added, so the dispersion effect due to collisions with dispersion media such as beads is reduced. Furthermore, since the alcohol produced by hydrolysis during dispersion volatilizes, the viscosity of the liquid mixture increases during dispersion, further reducing the dispersion effect.
Therefore, it is assumed that by adding a small amount of a hydrophilic solvent, the viscosity of the mixed liquid during dispersion is lowered, and the increase in viscosity of the mixed liquid during dispersion is suppressed, thereby suppressing the decrease in dispersion efficiency. Ru.

Next, the dispersion liquid obtained in this way has a high solid content (concentration), so it has a high viscosity and poor handling properties. However, when a hydrophobic solvent was added to the obtained dispersion in order to lower the solid content, the particles coagulated due to the low hydrophobicity of the particle surface, making it impossible to obtain a uniform dispersion.

Therefore, the present inventors have also discovered that by heating the obtained dispersion and gradually adding a hydrophobic solvent, it is possible to adjust the dispersion to a low solid content.

The mechanism is presumed as follows.
By heating the dispersion liquid, polymerization of the surface modification material attached to the inorganic particles progresses, and the hydrophobicity of the particle surfaces improves. Even if the polymerization reaction progresses too much, inorganic particles will aggregate, so by gradually adding a hydrophobic solvent to the dispersion while the polymerization reaction is in progress, the surface will gradually become hydrophobic while suppressing the excessive polymerization reaction. and hydrophobic solvents can be gradually mixed.

That is, the desired solid content is adjusted by adding a hydrophobic solvent in an amount that does not cause the inorganic particles to aggregate, and allowing the polymerization reaction of the surface modification material to proceed to an extent that it is compatible with the added amount of hydrophobic solvent. A dispersion liquid can be obtained.

Furthermore, the present inventors have found that when the dispersion obtained in this way is mixed with a highly hydrophobic material, the inorganic particles can be dispersed in the material without agglomeration, and the occurrence of turbidity is suppressed. This discovery led to the present invention.

The reason why inorganic particles are not dispersed in a highly hydrophobic material and turbidity occurs when a large amount of dispersion medium is used during dispersion is not clear, but it is thought to be as follows. If a large amount of dispersion medium is used, the surface modification material present near the inorganic particles becomes diluted during dispersion. As a result, it is thought that the reactivity of the surface modification material with respect to the inorganic particles decreased, and a sufficient amount of the surface modification material did not adhere to the inorganic particles. Furthermore, when a large amount of a hydrophobic solvent is used as a dispersion medium during dispersion, inorganic particles having hydroxyl groups on the surface are not sufficiently dispersed in the first place. Furthermore, when a large amount of a hydrophilic solvent is used as a dispersion medium, the miscibility between the hydrophilic solvent and the highly hydrophobic material contained in the dispersion liquid is insufficient.

It is also conceivable to attach the surface modification material to the surface of the inorganic particles in a dry manner using a Henschel mixer, a spray dryer, or the like. In this case, the inorganic particles aggregate and the surface modification material does not adhere uniformly to the surfaces of the inorganic particles. Furthermore, when performing dry modification, it is difficult to use a sufficient amount of surface modification material. As a result, when inorganic particles are mixed with a highly hydrophobic material, the inorganic particles are not dispersed in the material, resulting in turbidity.

<Method for producing dispersion>
Next, a method for producing a dispersion liquid according to this embodiment will be explained.

The method for producing a dispersion liquid according to the present embodiment includes a step B of mixing a surface modification material, inorganic particles, and a hydrophilic solvent to obtain a mixed liquid, and dispersing the inorganic particles in the mixed liquid to obtain the inorganic The process includes a step C of obtaining a dispersion liquid in which particles are dispersed, and a step D of adding a hydrophobic solvent to the dispersion liquid. In the step D of adding the hydrophobic solvent, after heating the dispersion liquid, a step d1 of adding the solvent at a rate that does not cause the inorganic particles to aggregate; a step d2 of adding the hydrophobic solvent while heating the dispersion at a rate that does not cause the inorganic particles to aggregate; or a step d2 of adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate. step d3 of heating the dispersion after adding at a rate that does not cause aggregation, the content of the inorganic particles in the mixed solution is 10% by mass or more and 46% by mass or less, and the surface modification in the mixed solution is performed. The total content of the material and the inorganic particles is 65% by mass or more and 93% by mass or less.

Note that the total content of the surface modification material and the inorganic particles does not include alcohol generated by hydrolysis of the surface modification material, which will be described later. That is, the total content of the surface modification material and the inorganic particles means the total content of the surface modification material, the hydrolyzed surface modification material, and the inorganic particles. It goes without saying that the above total content includes the content of inorganic particles attached to the surface modification material.

In addition, in this embodiment, prior to each of the above steps, there is a step A (hydrolysis step) of mixing the surface modification material and water to obtain a hydrolysis solution containing the hydrolyzed surface modification material. It's okay.
Each step will be explained in detail below.

(Step A (hydrolysis step))
In the hydrolysis step, the surface modification material and water are mixed to obtain a hydrolysis solution containing the hydrolyzed surface modification material. By using a liquid mixture in which at least a portion of the surface modification material has been previously hydrolyzed in this way, the surface modification material can easily adhere to the inorganic particles in the dispersion step described later.

As such a surface modification material, a surface modification material having a reactive functional group is preferably used. Examples of the surface modification material having a reactive functional group include surface modification materials having at least one functional group selected from the group of alkenyl groups, H--Si groups, and alkoxy groups. In particular, a surface modification material having an alkoxy group is preferably used in this embodiment because it can react with water and be hydrolyzed.

Examples of the alkenyl group include straight chain or branched alkenyl groups having 2 to 5 carbon atoms. Specific examples include vinyl group, 2-propenyl group, prop-2-en-1-yl group, and the like.
Examples of the alkoxy group include straight chain or branched alkoxy groups having 1 to 5 carbon atoms. Specific examples include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, and butoxy group.

Examples of the surface modification material having at least one functional group selected from the group of alkenyl groups, H-Si groups, and alkoxy groups include the following silane compounds, silicone compounds, and fatty acids containing carbon-carbon unsaturated bonds. It will be done. These surface modification materials may be used alone or in combination of two or more.

Examples of the silane compound include silane compounds containing an alkyl group and an alkoxy group, silane compounds containing an alkenyl group and an alkoxy group, silane compounds containing an H-Si group and an alkoxy group, other silane compounds containing an alkoxy group, H-Si Examples include silane compounds containing groups.

Examples of silane compounds containing an alkyl group and an alkoxy group include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, isobutyltrimethoxysilane, Examples include methylphenyldimethoxysilane and methylphenyldiethoxysilane.

Examples of the silane compound containing an alkenyl group and an alkoxy group include vinyltrimethoxysilane, methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, and the like.

Examples of the silane compound containing an H--Si group and an alkoxy group include diethoxymonomethylsilane, monoethoxydimethylsilane, diphenylmonomethoxysilane, and diphenylmonoethoxysilane.

Examples of other silane compounds containing an alkoxy group include phenyltrimethoxysilane.

Examples of the silane compound containing an H-Si group include dimethylchlorosilane, methyldichlorosilane, diethylchlorosilane, ethyldichlorosilane, methylphenylchlorosilane, diphenylchlorosilane, phenyldichlorosilane, trimethoxysilane, dimethoxysilane, monomethoxysilane, and trimethoxysilane. Examples include ethoxysilane.

Examples of the silicone compound include silicone compounds containing an H--Si group and silicone compounds containing an alkoxy group.

Examples of the silicone compound containing an H--Si group include methylphenyl silicone, dimethyl silicone, methyl hydrogen silicone, methyl phenyl hydrogen silicone, diphenyl hydrogen silicone, and the like.

Examples of silicone compounds containing alkoxy groups include alkoxy-terminated phenyl silicone, alkoxy-terminated methylphenyl silicone, alkoxy-containing methylphenyl silicone, alkoxy-containing dimethyl silicone, alkoxy-terminated trimethyl single-terminated dimethyl Examples include silicone, alkoxy group-containing phenyl silicone, and the like.

The silicone compound may be a monomer, an oligomer, or a resin (polymer). It is preferable to use monomers or oligomers because surface modification is easy.

Examples of fatty acids containing carbon-carbon unsaturated bonds include methacrylic acid and acrylic acid.

Among the above-mentioned surface modification materials, silane compounds containing an alkyl group and an alkoxy group are preferred as the surface modification material from the viewpoint of low viscosity and easy dispersion of inorganic particles in the dispersion step described below.

The number of alkoxy groups in the silane compound containing an alkyl group and an alkoxy group is preferably 1 or more and 3 or less, and more preferably 3. The number of carbon atoms in the alkoxy group is preferably 1 or more and 5 or less.

The number of alkyl groups in the silane compound containing an alkyl group and an alkoxy group is preferably 1 or more and 3 or less, and more preferably 1. The number of carbon atoms in the alkyl group is preferably 1 or more and 5 or less, more preferably 1 or more and 3 or less, and even more preferably 1 or more and 2 or less.
The total number of alkyl groups and alkoxy groups in the silane compound containing an alkyl group and an alkoxy group is 2 or more and 4 or less, and preferably 4.

Silane compounds as such surface modification materials are, for example, selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane and ethyltripropoxysilane. It may contain one type or two or more types.

The viscosity of the surface modification material at 25° C. is preferably, for example, 50 mPa·s or less.
When the viscosity of the surface modification material is 50 mPa·s or less, inorganic particles can be dispersed in the surface modification material without containing a large amount of dispersion medium. Note that the viscosity here refers to a viscosity measured in accordance with JIS Z 8803:2011 "Method for measuring liquid viscosity."

Moreover, the content of the surface modification material in the hydrolysis solution is not particularly limited, and can be the remainder of other components in the hydrolysis solution, but the content of the surface modification material in the hydrolysis solution is For example, the content is preferably 60% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 97% by mass or less, and even more preferably 80% by mass or more and 95% by mass or less.

Moreover, in the hydrolysis step, the hydrolysis liquid contains water. Water serves as a substrate for the hydrolysis reaction of the surface modified material.
The content of water in the hydrolysis solution is not particularly limited, and can be appropriately set, for example, depending on the amount of the surface modification material. For example, the amount of water added to the hydrolysis solution is preferably 0.5 mol or more and 5 mol or less, more preferably 0.6 mol or more and 3 mol or less, and 0.7 mol or less, per 1 mol of the surface modification material. More preferably, the amount is 2 mol or less. Thereby, while allowing the hydrolysis reaction of the surface modification material to proceed sufficiently, it is possible to more reliably prevent agglomeration of inorganic particles in a dispersion prepared using an excessive amount of water.

Alternatively, the content of water in the hydrolyzed solution is, for example, preferably 1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less based on 100% by mass of the hydrolyzed solution. , more preferably 1% by mass or more and 10% by mass or less.

Moreover, a catalyst may be added to the hydrolysis liquid. As the catalyst, for example, an acid or a base can be used.
The acid catalyzes the hydrolysis reaction of the surface modification material in the hydrolysis solution and in the mixed solution prepared containing the acid. The base catalyzes a condensation reaction between the hydrolyzed surface modification material and a functional group on the surface of the inorganic particle, such as a hydroxyl group or a silanol group. This makes it easier for the surface modification material to adhere to the inorganic particles, improving the dispersion stability of the inorganic particles.

The above-mentioned "acid" refers to an acid based on the so-called Brønsted-Lori definition. Here, the term "acid" refers to a substance that provides protons in the hydrolysis reaction of the surface modification material.

The above-mentioned "base" refers to a base based on the so-called Brønsted-Lori definition. Here, the term "base" refers to a substance that accepts protons in the hydrolysis reaction and subsequent condensation reaction of the surface modification material.

The acid that can be used in the method for producing a dispersion liquid according to the present embodiment is not particularly limited as long as it can supply protons in the hydrolysis reaction of the surface modification material. Such acids include, for example, inorganic acids or organic acids.
Examples of the inorganic acid include hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, boric acid, and phosphoric acid.
Examples of organic acids include acetic acid, citric acid, and formic acid.
These acids may be used alone or in combination of two or more.

The base that can be used in the method for producing a dispersion liquid according to the present embodiment is not particularly limited as long as it can accept protons in the hydrolysis reaction of the surface modification material or the subsequent condensation reaction. Examples of such bases include sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, ammonia, and amines. These bases may be used alone or in combination of two or more.

Among the above catalysts, it is preferable to use an acid as the catalyst. As the acid, inorganic acids are preferred from the viewpoint of acidity. Among inorganic acids, hydrochloric acid is more preferred.

The content of the catalyst in the hydrolysis solution is not particularly limited, but for example, it is preferably 10 ppm or more and 1000 ppm or less, more preferably 20 ppm or more and 800 ppm or less, and even more preferably 30 ppm or more and 600 ppm or less. Thereby, side reactions of the surface modification material can be suppressed while sufficiently promoting hydrolysis of the surface modification material.

Moreover, the hydrolyzate may contain a hydrophilic solvent. The hydrophilic solvent promotes the miscibility of water and the surface modification material in the hydrolysis solution, and further promotes the hydrolysis reaction of the surface modification material.

Examples of the hydrophilic solvent include alcohol solvents, ketone solvents, nitrile solvents, and the like. These hydrophilic solvents may be used alone or in combination of two or more.

Examples of alcoholic solvents include branched or linear alcohol compounds having 1 to 4 carbon atoms and ether condensates thereof. These alcoholic solvents may be used alone or in combination of two or more.
The alcohol compound contained in the alcohol solvent may be a primary alcohol, a secondary alcohol, or a tertiary alcohol. The alcohol compound contained in the alcoholic solvent may be a monohydric alcohol, a dihydric alcohol, or a trihydric alcohol.

Examples of alcoholic solvents include methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butyl alcohol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, methanediol, 1,2-ethanediol, 1,2- Propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-butene-1,4-diol, 1, Examples include 4-butynediol, glycerin, diethylene glycol, 3-methoxy-1,2-propanediol, and the like.

Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

Examples of nitrile solvents include acetonitrile and the like.

Among the above-mentioned hydrophilic solvents, alcoholic solvents are preferred from the viewpoint of having excellent affinity with both water and hydrophobic solvents and promoting their mixing. The number of carbon atoms in the alcohol compound constituting the alcohol solvent is preferably 1 or more and 3 or less, more preferably 1 or more and 2 or less.
Among the above-mentioned alcoholic solvents, methanol and ethanol are preferred, and methanol is more preferred from the viewpoint of being able to fully exhibit the effects of the above-mentioned alcoholic solvents.

The content of the hydrophilic solvent in the hydrolysis solution is not particularly limited, but is preferably, for example, 60% by mass or less, and more preferably 50% by mass or less. Thereby, the contents of the surface modification material and water in the hydrolysis solution can be sufficiently increased. Further, the content of the hydrophilic solvent in the hydrolysis solution is, for example, preferably 10% by mass or more, and more preferably 15% by mass or more. This can further promote the mixing of the surface modification material and water. As a result, the hydrolysis reaction of the surface modification material can proceed efficiently. Note that the hydrolysis solution may not contain any hydrophilic solvent other than the compound derived from the hydrolysis reaction.

In this embodiment, when a compound having an alkoxy group, for example, a silane compound having an alkoxy group, is used as a surface modification material, an alcohol compound derived from an alkoxy group is contained in the mixed liquid because this is hydrolyzed. . Since the hydrolysis reaction proceeds even with water adsorbed by inorganic particles, it can occur in any of the hydrolysis step, mixing step, and dispersion step. Therefore, unless there is a step to remove alcohol compounds, the final dispersion liquid will contain alcohol compounds.

In the hydrolysis step, the hydrolyzate may be maintained at a constant temperature for a predetermined period of time after being prepared. Thereby, hydrolysis of the surface modification material can be further promoted.
In the hydrolysis step, the temperature of the hydrolysis solution is not particularly limited, and can be changed as appropriate depending on the type of surface modification material. The temperature of the hydrolyzate is, for example, preferably 5°C or more and 65°C or less, more preferably 30°C or more and 60°C or less.

Further, the time for holding the hydrolyzate at a constant temperature (holding time) is not particularly limited, but for example, it is preferably 10 minutes or more and 180 minutes or less, and more preferably 30 minutes or more and 120 minutes or less. .

In addition, in holding the above-mentioned hydrolyzed liquid, the hydrolyzed liquid may be appropriately stirred.
Moreover, the hydrolysis step can be performed as necessary, or may be omitted.

(Process B (mixing process))
In the mixing step, a surface modification material, inorganic particles, and a hydrophilic solvent are mixed to obtain a mixed liquid. In the mixing step, water and a catalyst may be mixed in addition to the surface modification material, inorganic particles, and hydrophilic solvent. In addition, when the hydrolysis liquid is obtained by the above-mentioned hydrolysis process, a mixed liquid is obtained by mixing the hydrolysis liquid, inorganic particles, and a hydrophilic solvent.

In the mixing step, the content of inorganic particles in the mixed liquid is 10% by mass or more and 46% by mass or less, and the total content of the surface modification material and inorganic particles in the mixed liquid is 65% by mass or more and 93% by mass or less. The mixing is performed as follows.

The content of the hydrophilic solvent in the mixed liquid is preferably 5% by mass or more and 15% by mass or less, and more preferably 7% by mass or more and 13% by mass or less. By mixing the hydrophilic solvent in the above range, the dispersion efficiency of the inorganic particles is improved and the surface modification reaction of the surface modification material to the inorganic particles is also promoted.

As the hydrophilic solvent to be mixed with the surface modification material and the inorganic particles, the same hydrophilic solvent as used in the above hydrolysis step can be used.

Thus, in this embodiment, the total content of the surface modification material and inorganic particles in the mixed liquid is very large. A small amount of a dispersion medium such as an organic solvent or water, which was conventionally thought to be essential, is mixed. Even in such cases, by going through the dispersion process, it is possible to uniformly disperse the inorganic particles in the mixed liquid, and also achieve uniform adhesion of the surface modification material to the inorganic particles (surface modification). be done.

Here, the surface modification material "adhering" to the inorganic particles refers to the surface modification material coming into contact with or bonding to the inorganic particles through interaction between them. Examples of contact include physical adsorption. Further, examples of the bond include ionic bond, hydrogen bond, covalent bond, and the like.

If the total content of the surface modification material and inorganic particles in the mixed liquid is less than 65% by mass, components other than the surface modification material and inorganic particles, such as dispersion medium, will be too large and will not be used in the dispersion step described below. The surface modification material cannot be sufficiently attached to the surface of the inorganic particles. As a result, many hydroxyl groups remain on the surface of the inorganic particles, and when the resulting dispersion is mixed with a highly hydrophobic material, the inorganic particles aggregate, causing the highly hydrophobic material to become cloudy. The total content of the surface modification material and inorganic particles may be 65% by mass or more, preferably 70% by mass or more, and more preferably 75% by mass or more.

If the total content of the surface modification material and the inorganic particles in the mixed solution exceeds 93% by mass, the viscosity of the mixed solution will become too high, and the surface modification material will not be sufficiently absorbed by the inorganic particles in the dispersion process described below. Cannot be attached to surfaces. The total content of the surface modification material and inorganic particles may be 93% by mass or less, preferably 91% by mass or less, and more preferably 89% by mass or less.

Further, as described above, the content of inorganic particles in the mixed liquid is 10% by mass or more and 46% by mass or less. As a result, the amount of the surface modification material relative to the inorganic particles can be kept within an appropriate range, the surface modification material can be uniformly attached to the surface of the inorganic particles, and an increase in the viscosity of the mixed liquid can be suppressed. I can do it.

When the content of inorganic particles in the mixed liquid is less than 10% by mass, the amount of surface modification material is excessive relative to the inorganic particles, and the excess surface modification material induces aggregation of inorganic particles in the resulting dispersion. . The content of inorganic particles in the liquid mixture is preferably 20% by mass or more, more preferably 30% by mass or more.

If the content of the inorganic particles in the mixed liquid exceeds 46% by mass, the amount of surface modification material will be insufficient relative to the inorganic particles, and a sufficient amount of the surface modification material will not adhere to the inorganic particles. Moreover, as a result of the content of inorganic particles becoming too large, the viscosity of the liquid mixture becomes too high, making it impossible to sufficiently disperse the inorganic particles in the dispersion step described below. The content of inorganic particles in the liquid mixture is preferably 43% by mass or less, more preferably 40% by mass or less.

The content of the surface modification material relative to the content of inorganic particles in the mixed liquid is not particularly limited, but for example, when the inorganic particles are 100 parts by mass, it is preferably 100 parts by mass or more and 800 parts by mass or less, and 140 parts by mass or less. It is more preferably 180 parts by mass or more and 400 parts by mass or less, and even more preferably 180 parts by mass or more and 400 parts by mass or less. Thereby, the amount of the surface modification material relative to the inorganic particles can be kept within an appropriate range, and the surface modification material can be uniformly attached to the surfaces of the inorganic particles.

The inorganic particles contained in the liquid mixture are not particularly limited. Examples of inorganic particles include zirconium oxide particles, titanium oxide particles, silica particles, zinc oxide particles, iron oxide particles, copper oxide particles, tin oxide particles, cerium oxide particles, tantalum oxide particles, niobium oxide particles, tungsten oxide particles, Europium oxide particles, yttrium oxide particles, molybdenum oxide particles, indium oxide particles, antimony oxide particles, germanium oxide particles, lead oxide particles, bismuth oxide particles, hafnium oxide particles, potassium titanate particles, barium titanate particles, strontium titanate particles , potassium niobate particles, lithium niobate particles, calcium tungstate particles, yttria-stabilized zirconia particles, alumina-stabilized zirconia particles, silica-stabilized zirconia particles, calcia-stabilized zirconia particles, magnesia-stabilized zirconia particles, scandia-stabilized zirconia particles, hafnia-stabilized zirconia particles, ytterbia-stabilized zirconia particles, ceria-stabilized zirconia particles, india-stabilized zirconia particles, strontium-stabilized zirconia particles, samarium oxide-stabilized zirconia particles, gadolinium oxide-stabilized zirconia particles, antimony-doped tin oxide Inorganic oxide particles containing at least one selected from the group consisting of particles and indium-doped tin oxide particles are preferably used.

The type of inorganic particles can be appropriately selected depending on the use of the resulting dispersion. For example, when using the inorganic particles in the obtained dispersion as a material for a sealing member of a light emitting element, from the viewpoint of improving transparency and compatibility with the sealing resin (resin component), the mixed liquid is It is preferable that the inorganic particles include at least one selected from the group consisting of zirconium oxide particles, titanium oxide particles, and silica particles. Further, from the viewpoint of improving the refractive index of the sealing member, the inorganic particles preferably have a refractive index of 1.7 or more. Examples of the inorganic particles that improve the refractive index of the sealing member include particles other than silica particles among the above-mentioned inorganic oxide particles. When used as a material for a sealing member, the inorganic particles are more preferably at least one of zirconium oxide particles and titanium oxide particles, and particularly preferably zirconium oxide particles.

Note that the inorganic particles may be dispersed in the liquid mixture as primary particles, or may be dispersed as secondary particles obtained by agglomerating primary particles. Usually, the inorganic particles are dispersed as secondary particles in the mixed liquid.

The average primary particle diameter of the inorganic particles is, for example, preferably 3 nm or more and 200 nm or less, more preferably 5 nm or more and 170 nm or less, and even more preferably 10 nm or more and 100 nm or less. When the average primary particle diameter of the inorganic particles is within the above range, the transparency of the dispersion becomes high. Further, when used as a material for a sealing member of a light emitting element, for example, an LED (light emitting diode), the brightness of the light emitting element (LED) can be improved.

The average primary particle diameter of the inorganic particles can be measured, for example, by observation using a transmission electron microscope. First, a collodion film containing inorganic particles collected from a dispersion is observed using a transmission electron microscope to obtain a transmission electron microscope image. Next, a predetermined number of inorganic particles, for example 100, are selected from the transmission electron microscope image. Then, the longest straight line segment (maximum major axis) of each of these inorganic particles is measured, and the measured values are arithmetic averaged.

Here, when the inorganic particles are aggregated, the aggregate particle diameter of this aggregate is not measured. The maximum major axis of a predetermined number of inorganic particles (primary particles) constituting this aggregate is measured, and these measured values are arithmetic averaged to obtain the average primary particle diameter.

In the mixing step, an organic solvent other than the hydrophilic solvent may be further mixed with the mixed solution as long as it does not interfere with the hydrolysis reaction.

Examples of organic solvents other than hydrophilic solvents include aromatic solvents, saturated hydrocarbon solvents, and unsaturated hydrocarbon solvents. These organic solvents may be used alone or in combination of two or more.
Note that when the surface modification material is hydrolyzed in the mixing step, a compound derived from the surface modification material, such as an alcohol solvent, is contained in the mixed liquid.

The content of the organic solvent in the liquid mixture is not particularly limited as long as it satisfies the above-mentioned contents of the inorganic particles and surface modification material.

The mixed liquid may contain components other than those mentioned above as necessary, such as general additives such as dispersants, dispersion aids, antioxidants, fluidity regulators, thickeners, pH adjusters, preservatives, etc. may be mixed.

(Process C (dispersion process))
In the dispersion step, inorganic particles are dispersed in the mixed liquid to obtain a dispersion liquid (first dispersion liquid) in which the inorganic particles are dispersed.
Dispersion of the inorganic particles can be performed using a known disperser. As the dispersing machine, for example, a bead mill, a ball mill, a homogenizer, a disperser, a stirrer, etc. are suitably used.

In the dispersion process, the inorganic particles are dispersed in the mixed liquid by applying the minimum amount of energy without applying excessive energy so that the particle size (dispersed particle size) of the inorganic particles in the dispersion liquid is almost uniform. It is preferable to disperse.

(Process E (removal process))
In this embodiment, a step E for removing the hydrophilic solvent may be provided between the dispersion step C and the addition step D.
In the removal step, the hydrophilic solvent contained in the dispersion and the alcohol produced by the hydrolysis reaction are removed. By providing the removal step, the efficiency of step D described below can be improved.
Although the method for removing the hydrophilic solvent is not particularly limited, for example, an evaporator can be used.
The removal step may be performed until the hydrophilic solvent is completely removed, or may be performed until about 5% by mass of the hydrophilic solvent remains.
Note that since the hydrophilic solvent is also removed in the following addition step, this step does not need to be performed.

(Step D (addition step))
In the addition step, a hydrophobic solvent is added to the above dispersion to adjust the dispersion to a desired solid content (concentration).
As mentioned above, the hydrophobic solvent may be added gradually to prevent the inorganic particles from agglomerating. Therefore, the hydrophobic solvent may be added after the dispersion is heated, the dispersion may be heated after the hydrophobic solvent is added, or the dispersion may be heated and the hydrophobic solvent is added at the same time. Good too.
That is, the addition step may be a step d1 of adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate after heating the dispersion, and adding the hydrophobic solvent while heating the dispersion. Step d2 may include adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate, or heating the dispersion after adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate. It may be step d3.

The speed at which the inorganic particles do not aggregate is not particularly limited. For example, the hydrophobic solvent may be added continuously at a rate such that the solid content is reduced in the range of 3% by mass to 20% by mass in 1 hour. The amount of hydrophobic solvent added may be adjusted as appropriate, such that when the heating temperature is high, the amount of hydrophobic solvent added is increased, and when the heating temperature is low, the amount of hydrophobic solvent added is decreased.

For example, the hydrophobic solvent may be added stepwise every 30 minutes, every 1 hour, or every 2 hours so that the solid content is reduced in the range of 3% by mass to 20% by mass. If the heating temperature is high, increase the amount of hydrophobic solvent added at one time, and if the heating temperature is low, reduce the amount of hydrophobic solvent added at one time. may be adjusted accordingly.

The heating temperature is not particularly limited as long as it is a temperature at which the polymerization reaction of the surface modification material proceeds. The heating temperature is preferably, for example, 35°C or higher and 80°C or lower. By setting the heating temperature to 35° C. or higher, the polymerization reaction of the surface modification material can proceed. On the other hand, by setting the heating temperature to 80° C. or lower, aggregation of inorganic particles due to rapid reaction of the surface modification material can be suppressed.

The heating time may be carried out as appropriate until the adjustment of the solid content is completed, and is preferably, for example, 4 hours or more and 12 hours or less. When the heating time is 4 hours or more, the polymerization reaction of the surface modification material proceeds and it becomes possible to mix it with the hydrophobic solvent. On the other hand, by setting the heating time to 12 hours or less, agglomeration of inorganic particles due to excessive progress of the polymerization reaction of the surface modification material can be suppressed.

The hydrophobic solvent is not particularly limited as long as it is compatible with the material to be mixed with the dispersion of this embodiment. Examples of the hydrophobic solvent include aromatics, saturated hydrocarbons, unsaturated hydrocarbons, and the like. These hydrophobic solvents may be used alone or in combination of two or more. Among these, aromatics, particularly aromatic hydrocarbons, are preferred. Aromatics have excellent compatibility with methyl silicone, and thereby contribute to improving the viscosity characteristics of the resulting composition and the quality (transparency, shape, etc.) of the formed sealing member.

Examples of aromatic hydrocarbons include benzene, toluene, ethylbenzene, 1-phenylpropane, isopropylbenzene, n-butylbenzene, tert-butylbenzene, sec-butylbenzene, o-xylene, m-xylene, p-xylene, Examples include 2-ethyltoluene, 3-ethyltoluene, 4-ethyltoluene and the like. These aromatic hydrocarbons may be used alone or in combination of two or more.

Among these aromatic hydrocarbons, toluene, o-xylene, m-xylene, p-xylene, -At least one selected from the group consisting of xylene and benzene is particularly preferably used.

The content of the hydrophobic solvent contained in the final dispersion may be adjusted as appropriate so as to provide a desired solid content. The content of the hydrophobic solvent is, for example, preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and 60% by mass or more and 80% by mass or less. is even more preferable. This makes it easier to mix the dispersion liquid with the resin component described below, especially the methyl silicone.

Through the above steps, a dispersion liquid can be obtained. In the dispersion produced using the dispersion production method according to the present embodiment, the inorganic particles are uniformly dispersed, and the surfaces of the inorganic particles are uniformly and sufficiently modified with the surface modification material. Furthermore, when a highly hydrophobic material and a dispersion are mixed, the inorganic particles can be uniformly dispersed in the highly hydrophobic material, resulting in turbidity of the highly hydrophobic material, e.g. Clouding is prevented. Therefore, the intended function of the inorganic particles is exerted without substantially affecting the color tone of the highly hydrophobic material.

The dispersion produced using the dispersion production method according to the present embodiment can have a low solid content, and therefore can be easily mixed with a hydrophobic material. That is, the dispersion produced using the dispersion production method according to the present embodiment can reduce the effort of mixing with a hydrophobic material in a subsequent step, and is easy to handle.

<Dispersion>
The dispersion according to the present embodiment includes inorganic particles, one or more surface modification materials at least partially attached to the inorganic particles, and a hydrophobic solvent, and the surface modification material includes at least a silane compound, The dispersion liquid and methylphenyl silicone are mixed so that the mass ratio of the total mass of the inorganic particles and the surface modification material to the methylphenyl silicone is 30:70, and the hydrophobic solvent is removed. The viscosity is 100 Pa·s or less, and D90/D10 is 1.0 or more and 2.4 or less, where D90 is the 90% particle diameter by volume of the inorganic particles and D10 is the 10% particle diameter by volume of the inorganic particles. It is.

The dispersion liquid of this embodiment is manufactured by the method for manufacturing a dispersion liquid according to the above-mentioned embodiment.
That is, the dispersion liquid of this embodiment includes step B of mixing a surface modification material, inorganic particles, and a hydrophilic solvent to obtain a mixed liquid, and dispersing the inorganic particles in the mixed liquid so that the inorganic particles are A step C of obtaining a dispersed dispersion liquid and a step D of adding a hydrophobic solvent to the dispersion liquid, the content of the inorganic particles in the mixed liquid is 10% by mass or more and 46% by mass or less, It is obtained by a method for producing a dispersion liquid in which the total content of the surface modification material and the inorganic particles in the mixed liquid is 65% by mass or more and 93% by mass or less.

Therefore, in the dispersion liquid of this embodiment, the inorganic particles are uniformly dispersed in the surface modification material, and the surfaces of the inorganic particles are uniformly and sufficiently modified by the surface modification material. Furthermore, when a highly hydrophobic material is mixed with the dispersion liquid of this embodiment, the inorganic particles can be uniformly dispersed in the highly hydrophobic material, and clouding of the highly hydrophobic material can be suppressed. I can do it. As a result, the intended function of the inorganic particles is exhibited without substantially affecting the color tone of the highly hydrophobic material.

As mentioned above, in the dispersion liquid of this embodiment, by directly dispersing inorganic particles in a surface modification material, a dispersion liquid having a sharp particle size distribution can be obtained, and the inorganic particles can be mixed with a hydrophobic material. Now you can. It is presumed that in the dispersion liquid of this embodiment, more surface modification material adheres to the inorganic particles than in conventional dispersion liquids, and that the particles are densely coated. However, it is unclear what condition the surface of the inorganic particles is in that allows the dispersion to mix with the hydrophobic material. Therefore, it is impossible to directly specify the characteristics of the dispersion liquid of this embodiment based on the state of the surface of the inorganic particles modified with the surface modification material. Given that the dispersion includes inorganic particles, one or more surface modification materials at least partially attached to the inorganic particles, and a hydrophobic solvent, it is possible to mix the inorganic particles with the hydrophobic material. The ability to mix inorganic particles with a hydrophobic material is important in determining the surface condition of the inorganic particles, including the structure of the surface modification material, the degree of polymerization in the dispersion, and the shape, particle size, and particle size of the inorganic particles. Considering that it is presumed to be caused by a complex interplay of many factors such as distribution and specific surface area, this is almost impossible.

Further, the dispersion liquid of the present embodiment can obtain the above-mentioned effects more markedly in the case of inorganic particles that are difficult to disperse, for example, fine inorganic particles.

The surface modification material in this embodiment contains at least a silane compound, but may or may not contain a silicone compound. That is, only a silane compound may be used as the surface modification material.
The content of the silane compound in the surface modification material is preferably 60% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 90% by mass or less.
When the content of the silane compound is within the above range, the hydrophobicity of the surface of the inorganic particles can be increased to such an extent that the inorganic particles can be uniformly mixed into the hydrophobic material.

When selecting a silicone resin as the hydrophobic material to be mixed with the dispersion liquid of this embodiment, it is preferable to attach the silicone compound to the surface of the inorganic particles. The content of the silicone compound in the surface modification material contained in the dispersion of the present embodiment is preferably 0% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.
When the silicone compound content is within the above range, inorganic particles can be mixed more easily when a silicone resin is used as the hydrophobic material.

When the dispersion of this embodiment and methylphenyl silicone are mixed so that the mass ratio of the total mass of inorganic particles and surface modification material to methylphenyl silicone is 30:70, and the hydrophobic solvent is removed. The viscosity of is 100 Pa·s or less.
The methylphenyl silicone is KER-2500-B manufactured by Shin-Etsu Chemical Co., Ltd.

It is preferable to completely remove the hydrophobic solvent using an evaporator or the like, but since it is difficult to completely remove the hydrophobic solvent, about 5% by mass may remain.
The viscosity is measured using a rheometer (trade name: Rheostress RS-6000, manufactured by HAAKE) at 25° C. and a shear rate of 1 (1/S).

Removal of the hydrophobic solvent brings the particles closer together, increasing the viscosity of the composition (composition containing inorganic particles, surface modification material, and silicone). Therefore, the viscosity after removing the hydrophobic solvent means the viscosity of the composition measured within 1 hour after removing the hydrophobic solvent from the dispersion.

The viscosity of the composition is preferably 90 Pa·s or less, more preferably 80 Pa·s or less, even more preferably 70 Pa·s or less, and particularly preferably 60 Pa·s or less. The lower limit of the viscosity of the composition is preferably about the same as the viscosity of KER-2500-B manufactured by Shin-Etsu Chemical Co., Ltd., and may be 1 Pa·s or 5 Pa·s. , 10 Pa·s.

If the viscosity of the composition is within the above range, the composition can be easily handled in subsequent steps.

In the dispersion according to the present embodiment, D90/D10 is 1.0 or more and 2.4, where D90 is the 90% volume-based particle diameter of the inorganic particles and D10 is the 10% volume-based particle diameter of the inorganic particles. It is as follows. D90/D10 is an index of the shape of the particle size distribution of the inorganic particles, and serves as an index of the uniformity of the particle diameter of the inorganic particles. When D90/D10 is within the range described above, the particle size of the inorganic particles in the dispersion becomes relatively uniform, and the particle size distribution is sharp. Further, the inorganic particles having such a uniform particle size in the dispersion according to the present embodiment can be relatively stably and uniformly dispersed even in highly hydrophobic materials. Such a range of D90/D10 can be achieved relatively easily by the method for producing a dispersion liquid according to the present embodiment described above.

In the dispersion according to the present embodiment, the volume-based 50% particle diameter D50 of the inorganic particles is not particularly limited, but is preferably, for example, 30 nm or more and 400 nm or less, and more preferably 40 nm or more and 300 nm or less. Generally, inorganic particles having a particle size within the above range tend to aggregate due to a high specific surface area. However, in the dispersion liquid according to the present embodiment, the surface modification material is uniformly and sufficiently adhered to the inorganic particles, so that stable dispersion of the inorganic particles is possible. Further, even when the dispersion liquid is mixed with a highly hydrophobic material, aggregation of the inorganic particles is suppressed, and the inorganic particles can be stably dispersed in the highly hydrophobic material.

In addition, D10, D50, and D90 of the inorganic particles are the particle diameters D10, D50, and D90 of the inorganic particles when the cumulative percentage of the scattering intensity distribution obtained by the dynamic light scattering method is 10%, 50%, and 90%, respectively. It is. D10, D50 and D90 of the inorganic particles can be measured using a dynamic light scattering particle size distribution analyzer (for example, manufactured by HORIBA, model number: SZ-100SP). According to this particle size distribution meter, D10, D50, and D90 of inorganic particles can be measured using a quartz cell with an optical path length of 10 mm x 10 mm for a dispersion whose solid content is adjusted to 5% by mass with a hydrophobic solvent. be able to.

In addition, in this specification, "solid content" refers to the residue when volatile components are removed from the dispersion liquid. For example, when 1.2 g of the dispersion is placed in a magnetic crucible and heated on a hot plate at 100°C for 1 hour, the components that remain without volatilizing (inorganic particles, surface modification materials, etc.) are considered solid content. I can do it.

In addition, D10, D50, and D90 of inorganic particles are measured and calculated based on the diameter of the dispersed inorganic particles, regardless of whether the inorganic particles are dispersed as primary particles or secondary particles. be done. Further, in this embodiment, D10, D50, and D90 of the inorganic particles may be measured as D10, D50, and D90 of the inorganic particles to which the surface modification material is attached. In the dispersion, there may be inorganic particles to which the surface modification material is attached and inorganic particles to which the surface modification material is not attached, so the D10, D50, and D90 of the inorganic particles are usually can be measured as a value.

In the dispersion according to this embodiment, the average primary particle diameter of the inorganic particles is preferably 3 nm or more and 200 nm or less, more preferably 5 nm or more and 170 nm or less, and even more preferably 10 nm or more and 100 nm or less. When the average primary particle diameter of the inorganic particles is within the above range, the transparency of the dispersion becomes high. Further, when the inorganic particles contained in the dispersion according to the present embodiment are used as a material for a sealing member of a light emitting element, for example, an LED, the brightness of the light emitting element (LED) can be improved.

Note that the types and contents of the inorganic particles and surface modification material in the dispersion liquid, as well as other components, are the same as those of the above-mentioned mixed liquid, and therefore their explanations will be omitted.
However, if a decomposition reaction such as hydrolysis occurs when the surface modification material is attached to the inorganic particles, the content of the surface modification material in the dispersion may be lower than the content of the surface modification material in the mixed liquid. It can be small. Therefore, the total content of the surface modification material and inorganic particles in the dispersion may also be smaller than the total content of the surface modification material and inorganic particles in the mixed solution. Furthermore, the amount of compounds produced by the decomposition reaction, such as alcohol compounds, can increase in the dispersion compared to in the case of a mixed solution.

As described above, even when the dispersion according to the present embodiment is mixed with a highly hydrophobic material, the inorganic particles can be uniformly dispersed in the highly hydrophobic material, and the dispersion of the highly hydrophobic material can be uniformly dispersed. It is possible to suppress cloudiness. Furthermore, even when the dispersion according to the present embodiment is mixed with a highly hydrophobic material, the viscosity of the composition after mixing is low, making it easy to handle the composition.
Examples of highly hydrophobic materials include organic solvents, resin materials, oils and fats, etc. that contain a large amount of carbon and hydrophobic groups. More specifically, for example, silicone containing a large number of methyl groups and the like can be mentioned.

Moreover, when the dispersion liquid according to this embodiment is used, uniform dispersion of fine inorganic particles in a highly hydrophobic material can be achieved. Therefore, the dispersion liquid according to the present embodiment is suitable as a material for optical members such as members for which fine inorganic particles are required to be uniformly dispersed in highly hydrophobic materials, such as sealing members for light emitting elements. There is. Therefore, the dispersion liquid according to this embodiment can be a dispersion liquid for optical members, particularly a dispersion liquid for sealing members of light emitting elements.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that the embodiments described below are merely examples of the present invention, and do not limit the present invention.

[Example 1]
(Preparation of dispersion)
(i) Hydrolysis step 90.78 parts by mass of methyltrimethoxysilane (product name: KBM-13, manufactured by Shin-Etsu Kogyo Kagaku Co., Ltd.) as a surface modification material, 9.21 parts by mass of water, and 0.0 parts by mass of hydrochloric acid (1N). 01 parts by mass were added and mixed. Next, this mixed solution (first mixed solution) was stirred at 60° C. for 30 minutes, and methyltrimethoxysilane was hydrolyzed to obtain a hydrolyzed solution. Note that the amount of methyltrimethoxysilane added to the hydrolysis solution was 0.7 mol, and the amount of water added was 0.5 mol. That is, the amount of water was 0.8 mol with respect to 1 mol of the surface modification material.

(ii) Mixing step 30 parts by mass of zirconium oxide particles having an average primary particle diameter of 12 nm (manufactured by Sumitomo Osaka Cement Co., Ltd.), 60 parts by mass of the above hydrolyzed solution, and 10 parts by mass of isopropyl alcohol are mixed, and the mixed solution (second A mixed liquid) was obtained. The content of zirconium oxide particles in the mixed solution (second mixed solution) is 30% by mass, the content of methyltrimethoxysilane is 54.5% by mass, and the total content of zirconium oxide particles and methyltrimethoxysilane is , 84.5% by mass.

(iii) Dispersion process After dispersing this liquid mixture in a bead mill for 6 hours, the beads were removed to obtain a dispersion liquid (first dispersion liquid).

(iv) Addition step The obtained dispersion (first dispersion) was heated at 60° C. for 2 hours. Next, toluene was added to the dispersion so that the solid content was 40% by mass, and the mixture was heated at 60° C. for 2 hours.
Next, toluene was added to the dispersion so that the solid content was 30% by mass, and the mixture was heated at 60° C. for 1 hour.
Next, toluene was added to the dispersion so that the solid content was 20% by mass, and the dispersion was heated at 60° C. for 1 hour to obtain the dispersion of Example 1 (second dispersion).

(Evaluation of particle size distribution of dispersion)
A part of the obtained dispersion of Example 1 was collected, and the solid content was adjusted to 5% by mass with toluene. D10, D50, and D90 of the zirconium oxide particles in the dispersion were measured using a particle size distribution meter (manufactured by HORIBA, Measurement was carried out using a model number: SZ-100SP). As a result, D10 was 35 nm, D50 was 54 nm, and D90 was 81 nm. D90/D10 was 2.3.

(Evaluation of transparency of dispersion)
A part of the obtained dispersion of Example 1 was collected, the solid content was adjusted to 15% by mass with toluene, and the dispersion was put into a quartz cell, and the transmittance at a wavelength of 600 nm when the optical path length was 10 mm was Measurement was performed using a spectrophotometer (model number: V-770, manufactured by JASCO Corporation) using an integrating sphere. As a result, the transmittance was 25%.

(Evaluation of compatibility with hydrophobic resin)
10 g of Example 1 dispersion liquid whose solid content was adjusted to 15% by mass was mixed with 3.5 g of methylphenyl silicone (product name: KER-2500-B, manufactured by Shin-Etsu Chemical Co., Ltd.). That is, the total mass of zirconia and surface modification material and methylphenyl silicone were mixed in a mass ratio of 30:70.
Next, toluene was removed from this mixed solution using an evaporator to obtain a composition.
Visual observation of the appearance of the obtained composition revealed that it was a transparent composition.

(Evaluation of viscosity of composition)
The viscosity of the obtained composition was measured using a rheometer (product name: Rheostress RS-6000, manufactured by HAAKE) at 25° C. and a shear rate of 1 (1/s).
As a result, the viscosity of the composition after toluene was removed was 30.5 Pa·s.

[Example 2]
Example 2 was carried out in the same manner as in Example 1, except that zirconium oxide particles with an average primary particle size of 90 nm (manufactured by Sumitomo Osaka Cement Co., Ltd.) were used instead of zirconium oxide particles with an average primary particle size of 12 nm. Such a dispersion was obtained.
The content of zirconium oxide particles in the mixed solution obtained in the mixing step is 30% by mass, the content of methyltrimethoxysilane is 54.5% by mass, and the total content of zirconium oxide particles and methyltrimethoxysilane is: It was 84.5% by mass.

In the same manner as in Example 1, the particle size distribution of the dispersion of Example 2 was measured. As a result, D10 was 79 nm, D50 was 102 nm, and D90 was 165 nm. D90/D10 was 2.1.
The transmittance of the dispersion liquid of Example 2 whose solid content was adjusted to 15% by mass was measured in the same manner as in Example 1, and the result was 19%.

The dispersion liquid of Example 2 whose solid content was adjusted to 15% by mass was mixed with methylphenyl silicone in the same manner as in Example 1, and toluene was removed to obtain a composition. Visual observation of the appearance of the obtained composition revealed that it was a transparent composition.

The viscosity of the obtained composition was measured in the same manner as in Example 1. As a result, the viscosity of the composition after toluene was removed was 25.3 Pa·s.

[Example 3]
In the addition step of Example 1, before heating the obtained dispersion (first dispersion), toluene was added to the dispersion so that the solid content was 55% by mass, and then this dispersion was Heated at 60°C for 2 hours.
Next, toluene was added to the dispersion so that the solid content was 40% by mass, and the mixture was heated at 60° C. for 2 hours.
Next, toluene was added to the dispersion so that the solid content was 30% by mass, and the mixture was heated at 60° C. for 1 hour.
Next, toluene was added to the dispersion so that the solid content was 20% by mass, and the dispersion was heated at 60° C. for 1 hour to obtain a dispersion of Example 3 (second dispersion).

In the same manner as in Example 1, the particle size distribution of the dispersion of Example 3 was measured. As a result, the dispersion had a D10 of 37 nm, a D50 of 59 nm, and a D90 of 83 nm. D90/D10 was 2.2.
In the same manner as in Example 1, the transmittance of the dispersion liquid of Example 3 whose solid content was adjusted to 15% by mass was measured and found to be 24%.
The dispersion liquid of Example 3 whose solid content was adjusted to 15% by mass was mixed with methylphenyl silicone in the same manner as in Example 1, and toluene was removed to obtain a composition. Visual observation of the appearance of the obtained composition revealed that it was a transparent composition.

The viscosity of the obtained composition was measured in the same manner as in Example 1. As a result, the viscosity of the composition after toluene was removed was 30.7 Pa·s or less.

[Comparative example 1]
In the addition step of Example 1, the obtained dispersion (first dispersion) was heated at 60°C for 2 hours, and then toluene was added to the dispersion at once so that the solid content was 20% by mass. did.
As a result, the particles agglomerated, making it impossible to obtain a dispersion.

[Comparative example 2]
In the addition step of Example 1, before heating the obtained dispersion (first dispersion), toluene was added to the dispersion so that the solid content was 40% by mass.
As a result, the particles agglomerated, making it impossible to obtain a dispersion.

[Comparative example 3]
In the mixing step, the mixing step and the dispersion step were carried out in the same manner as in Example 1, except that 20 parts by mass of the above hydrolyzed liquid and 50 parts by mass of isopropyl alcohol were used instead of 70 parts by mass of the above hydrolyzed liquid. went. The content of zirconium oxide particles in the mixed solution obtained in the mixing step is 30% by mass, the content of methyltrimethoxysilane is 18.2% by mass, and the total content of zirconium oxide particles and methyltrimethoxysilane is: It was 48.2% by mass.
The solid content of the dispersion was measured (at 100°C for 1 hour) and was found to be 38% by mass.

Toluene was added to the obtained dispersion (first dispersion) so that the solid content was 20% by mass, and the mixture was heated at 60° C. for 2 hours. Next, toluene in the same amount as the volatilized amount was added to the dispersion, and the mixture was heated at 60° C. for 2 hours. Next, toluene in the same amount as the volatilized amount was added to the dispersion, and the mixture was heated at 60° C. for 1 hour. Next, the same amount of toluene as the volatilized amount was added to the dispersion and heated at 60°C for 1 hour to promote surface modification. A dispersion liquid) was obtained.

In the same manner as in Example 1, the particle size distribution of the dispersion of Comparative Example 3 was measured. As a result, D10 was 42 nm, D50 was 95 nm, and D90 was 100 nm. D90/D10 was 2.4.
The transmittance of the dispersion liquid of Comparative Example 3 whose solid content was adjusted to 15% by mass was measured in the same manner as in Example 1, and the result was 40%.

The dispersion of Comparative Example 3 whose solid content was adjusted to 15% by mass was mixed with methylphenyl silicone in the same manner as in Example 1, but the particles agglomerated and a composition could not be obtained.

[Comparative example 4]
Example 1 except that in the mixing step of Example 1, 70 parts by mass of the hydrolyzate was mixed instead of 60 parts by mass of the hydrolyzate and 10 parts by mass of isopropyl alcohol, and no isopropyl alcohol was added. A dispersion liquid (first dispersion liquid) was obtained in the same manner.

The obtained dispersion (first dispersion) was heated at 60° C. for 2 hours. Next, toluene was added to the dispersion so that the solid content was 40% by mass, and the mixture was heated at 60° C. for 2 hours.
Next, toluene was added to the dispersion so that the solid content was 30% by mass, and the mixture was heated at 60° C. for 1 hour.
Next, toluene was added to the dispersion so that the solid content was 20% by mass, and the dispersion was heated at 60° C. for 1 hour to obtain a dispersion of Comparative Example 4 (second dispersion).

In the same manner as in Example 1, the particle size distribution of the dispersion of Comparative Example 4 was measured. As a result, D10 was 50 nm, D50 was 120 nm, and D90 was 150 nm. D90/D10 was 3.0.
The transmittance of a dispersion liquid whose solid content was adjusted to 15% by mass was measured in the same manner as in Example 1, and the result was 21%.

The dispersion liquid of Comparative Example 4 whose solid content was adjusted to 15% by mass was mixed with methylphenyl silicone in the same manner as in Example 1, and toluene was removed to obtain a composition. Visual observation of the appearance of the obtained composition revealed that it was a transparent composition. Visual observation of the appearance of the obtained composition revealed that it was a transparent composition.
The viscosity of the obtained composition was measured in the same manner as in Example 1. As a result, the viscosity of the composition was 40.6 Pa·s.

As described above, the dispersion liquids according to Examples 1 to 3, in which zirconium oxide particles were dispersed in a highly concentrated surface modification material, can obtain transparent compositions without becoming cloudy against highly hydrophobic resins. It was possible. On the other hand, when the dispersion according to Comparative Example 3 was mixed with a hydrophobic resin, it became cloudy and a transparent composition could not be obtained.

Furthermore, when comparing Examples 1 and 3 and Comparative Examples 1 and 2, it was found that the dispersion liquid dispersed in the highly concentrated surface modification material was improved by gradually adding toluene (hydrophobic solvent) while heating. It was confirmed that a dispersion liquid with a low solid content and high handling properties could be obtained.

In addition, by comparing Example 1 and Comparative Example 4, it was found that by mixing a small amount of a hydrophilic solvent and performing dispersion treatment, a dispersion with small D10, D50, and D90 and a narrow (sharp) particle size distribution was obtained. was obtained, and it was confirmed that the increase in viscosity when mixed with a hydrophobic material could be suppressed.

Claims (3)

Step B of mixing the surface modification material, inorganic particles, and alcoholic solvent to obtain a mixed solution;
Step C of dispersing the inorganic particles in the mixed liquid to obtain a dispersion in which the inorganic particles are dispersed;
step D of adding a hydrophobic solvent to the dispersion;
Step D of adding the hydrophobic solvent is a step d1 of adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate after heating the dispersion; heating the dispersion, adding the hydrophobic solvent to the inorganic particles; step d2 of adding at a rate that does not cause the particles to aggregate, or step d3 of heating the dispersion after adding the hydrophobic solvent at a rate that does not cause the inorganic particles to aggregate;
The content of the inorganic particles in the mixed solution is 10% by mass or more and 46% by mass or less, and the total content of the surface modification material and the inorganic particles in the mixed solution is 65% by mass or more and 93% by mass. The method for producing a dispersion liquid is as follows. Further, a step A of mixing the surface modification material and water to obtain a hydrolysis liquid containing the hydrolyzed surface modification material,
The method for producing a dispersion liquid according to claim 1, wherein in step B of obtaining the mixed liquid, the mixed liquid is obtained by mixing the hydrolyzed liquid, the inorganic particles, and the alcoholic solvent. The method for producing a dispersion liquid according to claim 2, wherein the amount of water added to the hydrolysis liquid is 0.5 mol or more and 5 mol or less with respect to 1 mol of the surface modification material.