JP5176380B2 - Surface-modified zirconia particles, surface-modified zirconia particle dispersion and composite, and method for producing surface-modified zirconia particles - Google Patents

Description

  The present invention relates to a surface-modified zirconia particle, a surface-modified zirconia particle dispersion and composite, and a method for producing the surface-modified zirconia particle. More specifically, the present invention is suitably used as a filler material for resin, and has transparency, refractive index and mechanical properties. Surface-modified zirconia particles capable of improving properties, surface-modified zirconia particle dispersion liquid in which the surface-modified zirconia particles are dispersed in a dispersion medium, and a composite obtained by combining the surface-modified zirconia particles and a resin, The present invention relates to a method for producing the surface-modified zirconia particles.

  Conventionally, attempts have been made to improve the mechanical properties and the like of a resin by combining it with a resin using an inorganic oxide such as silica as a filler. As a method of combining the filler and the resin, a method of mixing a dispersion in which an inorganic oxide is dispersed in water and / or an organic solvent and a resin is generally used. By mixing by the method, an inorganic oxide particle composite plastic in which inorganic oxide particles are composited as the second phase can be produced.

As inorganic oxide fillers for improving the refractive index of plastics, oxide fine particles such as zirconia and titania are used as high refractive index fillers.
In particular, zirconia has both a weak acid point and a weak base point on the particle surface at the same time, and has a function as an acid-base bifunctional catalyst having excellent catalytic activity and reaction selectivity. Among them, zirconia combined with sulfate ions or the like is used as a super strong acid catalyst that is an acid stronger than concentrated sulfuric acid.

Moreover, in order to make an inorganic oxide filler into a composite with a resin, a dispersion liquid in which the inorganic oxide filler is dispersed in an aqueous solvent or an organic solvent has been developed, and an improvement in the refractive index of the resin has been studied.
As an example of this composite, a zirconia particle composite plastic in which a zirconia particle having a particle size of 10 to 100 nm and a resin are combined has been proposed (for example, see Patent Document 1).
Japanese Patent Laying-Open No. 2005-161111

By the way, in the conventional zirconia particles, when the surface is modified with an organic surface modifier having a C—C bond such as an alkoxysilane compound or a siloxane compound, the organic compound remaining on the surface is oxidized by the surface activity. There was a problem that the surface turned yellow.
When zirconia particles whose surface is yellowed are dispersed in a transparent resin to form a composite, problems such as coloring of the composite or reduction in transparency occur, resulting in problems with transparency and coloring. There is a problem that the range of use of the composite plastic is limited.

  The present invention has been made to solve the above-mentioned problems, and is a surface-modified zirconia particle capable of improving transparency, refractive index, and mechanical properties without yellowing the surface, and the surface modification. Provided are a surface-modified zirconia particle dispersion in which zirconia particles are dispersed in a dispersion medium, a composite obtained by combining the surface-modified zirconia particles and a resin, and a method for producing the surface-modified zirconia particles. For the purpose.

  As a result of intensive studies on a method for preventing the surface of the surface-modified zirconia particles from being yellowed, the present inventors have performed neutralization treatment on the surface of the surface-modified zirconia particles whose surface has been modified with an organic surface modifier. For example, the surface of the surface-modified zirconia particles can be prevented from yellowing over a long period of time, and as a result, the transparency, refractive index and mechanical properties of the surface-modified zirconia particles can be improved. The headline and the present invention were completed.

That is, the surface-modified zirconia particles of the present invention are obtained by neutralizing the surface of the surface-modified zirconia particles whose surface is modified with an organic surface modifier, including the organic surface modifier. Is characterized in that it is one or more selected from the group of alkoxysilane compounds, siloxane compounds, surfactants, and titanium coupling agents.

The hydrogen ion index (pH) when the surface containing the organic surface modifier is wetted with water is preferably 4 or more and 10 or less.

  The surface-modified zirconia particle dispersion of the present invention is characterized in that the surface-modified zirconia particles of the present invention are dispersed in a dispersion medium.

  The composite of the present invention is characterized in that the surface-modified zirconia particles of the present invention are dispersed in a resin.

  In the method for producing surface-modified zirconia particles of the present invention, the surface-modified zirconia particles whose surfaces are modified with an organic surface modifier are mixed with water, and then the hydrogen ion index (pH) of the mixed solution is 4 or more and 10 The surface-modified zirconia particles are prepared in the following range, and then the surface-modified zirconia particles are separated from the mixed solution.

According to the surface-modified zirconia particles of the present invention, the surface of the surface-modified zirconia particles whose surface is modified with an organic surface modifier is subjected to neutralization treatment, and the organic surface modifier is obtained. Is selected from the group consisting of an alkoxysilane compound, a siloxane compound, a surfactant, and a titanium coupling agent, so that the influence of acid or base points on the surface can be reduced. Even when an organic compound remains on the surface, yellowing of the surface can be prevented, and the refractive index and mechanical properties of the surface-modified zirconia particles can be improved and transparency can be maintained.
Therefore, if the surface-modified zirconia particles are dispersed in the resin, a composite having a high refractive index, excellent transparency, and improved mechanical properties can be easily obtained.

  According to the method for producing surface-modified zirconia particles of the present invention, the surface-modified zirconia particles whose surface is modified with an organic surface modifier are mixed with water, and then the hydrogen ion index (pH) of the mixed solution is 4 or more. In addition, since the surface-modified zirconia particles are prepared in a range of 10 or less and then separated from the mixed solution, the surface-modified zirconia particles having improved transparency, refractive index and mechanical properties can be easily and inexpensively produced. .

The best mode for carrying out the method for producing the surface-modified zirconia particles, the surface-modified zirconia particle dispersion and composite, and the surface-modified zirconia particles of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

"Surface-modified zirconia particles"
The surface-modified zirconia particles of the present invention are zirconia particles whose surface is modified with an organic surface modifier and the surface is neutralized.
When the surface of the surface-modified zirconia particles is wetted with water, for example, the hydrogen ion index (pH) is preferably 4 or more and 10 or less, more preferably 4 or more and 9 or less, and still more preferably. 5 or more and 9 or less.

The organic surface modifier is preferably an organic compound having a C—C bond, and the organic compound is selected from the group of alkoxysilane compounds, siloxane compounds, surfactants, and titanium coupling agents. One or two or more are preferably used.
Of these surface modifiers, a silane coupling agent is particularly preferable as the alkoxysilane compound, and a modified silicone is preferable as the siloxane compound.

  Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyltrimethoxysilane, n-butyltriethoxysilane, and n-hexyltri. Methoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, p-styryltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3- Examples include acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc. .

Examples of the modified silicone include methoxy modified silicone, carboxy modified silicone, alcohol modified silicone, polyether modified silicone, epoxy modified silicone, mercapto modified silicone, amino modified silicone, methacrylate modified silicone, methyl hydrogen silicone and the like.
In addition, it is particularly preferable to use a modified silicone having a vinyl group and / or a functional group bonded to a silicon atom because the functional group bonded to the vinyl group and / or silicon atom contributes to a chemical reaction when the resin is cured. .

As the surfactant, an anionic surfactant, a cationic surfactant, an ionic surfactant such as an amphoteric surfactant, or a nonionic surfactant is preferably used.
Examples of the anionic surfactant include fatty acid sodium such as sodium oleate, sodium stearate and sodium laurate, fatty acid such as fatty acid potassium and sodium fatty acid ester sulfonate, and phosphoric acid such as sodium alkyl phosphate ester. And olefins such as sodium alpha olein sulfonate, alcohols such as sodium alkyl sulfate, and alkylbenzenes.
Examples of the cationic surfactant include alkyl methyl ammonium chloride, alkyl dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, and alkyl dimethyl benzyl ammonium chloride.

Examples of the zwitterionic surfactant include carboxylic acid systems such as alkylaminocarboxylates and phosphate ester systems such as phosphobetaine.
Examples of the nonionic surfactant include fatty acid-based compounds such as polyoxyethylene lanolin fatty acid ester and polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, and fatty acid alkanolamide.

  Examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tri (dodecyl) benzenesulfonyl titanate, neopentyl (diallyl) oxy-tri (dioctyl) phosphate titanate, neopentyl (diallyl) oxy-trineo Examples include dodecanoyl titanate.

Examples of the method for modifying the surface of the zirconia particles using the organic surface modifier include a wet method and a dry method.
The wet method is a method of modifying the surface of the zirconia particles by adding and mixing an organic surface modifier and zirconia particles in a solvent.
The dry method is a method of modifying the surface of the zirconia particles by putting the organic surface modifier and the dried zirconia particles into a dry mixer such as a mixer and mixing them.

The weight ratio of the modified portion of the surface-modified zirconia particles is preferably 5% by weight or more and 200% by weight or less of the total amount of the particles, more preferably 10% by weight or more and 100% by weight or less. Is 20% by weight or more and 100% by weight or less.
Here, the reason why the weight ratio of the modified part is limited to 5% by weight or more and 200% by weight or less is that if the weight ratio of the modified part is less than 5% by weight, it becomes difficult to dissolve the zirconia particles in the resin. On the other hand, if the weight ratio of the modified portion exceeds 200% by weight, the influence of the surface treatment agent on the resin properties increases, and the composite properties such as the refractive index decrease.

The method for neutralizing the surface of the surface-modified zirconia particles may be a dry method or a wet method, but is preferably a wet method.
In the wet method, surface-modified zirconia particles whose surface is modified with an organic surface modifier are mixed with water, and then an acid or a base is added to the mixed solution to increase the hydrogen ion index (pH) to 4 or more and 10 It is a method of preparing in the following range, preferably in the range of 5 or more and 9 or less, and then separating the surface-modified zirconia particles from this mixed solution.

In order to effectively cause the neutralization reaction, the concentration of the surface-modified zirconia particles in the mixed solution is preferably 1 to 50% by weight, more preferably 5 to 20% by weight.
Here, when the concentration of the surface-modified zirconia particles is less than 1% by weight, a large amount of an aqueous solvent is used as compared with the surface-modified zirconia particles, and thus the productivity is lowered. If it exceeds, the viscosity of the mixed solution increases and the efficiency of the neutralization treatment becomes worse.
As the solvent, water is preferable because it is necessary to adjust the hydrogen ion index (pH) by adding an acid or a base.

  As a method for separating the surface-modified zirconia particles from this mixed solution, separation methods such as filtration and centrifugation are preferably used.

"Surface-modified zirconia particle dispersion"
The surface-modified zirconia particle dispersion of the present invention contains the surface-modified zirconia particles of the present invention, that is, the surface-modified zirconia particles whose surface is modified with an organic surface modifier and the surface is neutralized in a dispersion medium. It is a dispersed dispersion.
The dispersed particle size of the surface-modified zirconia particles is preferably 1 nm or more and 20 nm or less. If the dispersed particle size is less than 1 nm, the crystallinity becomes poor and it becomes difficult to express the refractive index, mechanical properties, etc. If the dispersed particle size exceeds 20 nm, a dispersion or a composite is obtained. This is because the transparency is lowered in some cases.

The content of the surface-modified zirconia particles is preferably 1% by weight or more and 70% by weight or less, more preferably 1% by weight or more and 50% by weight or less, and further preferably 5% by weight or more and 30% by weight or less.
Here, the reason why the content of the surface-modified zirconia particles is limited to 1% by weight or more and 70% by weight or less is that this range is a range where the surface-modified zirconia particles can take a good dispersion state, and the content is 1% by weight. If it is less than%, the effect as surface-modified zirconia particles is reduced, and if it exceeds 70% by weight, gelation and aggregation precipitation occur, and the characteristics as a dispersion are lost.

The dispersion medium basically contains at least one of water, an organic solvent, a liquid resin monomer, and a liquid resin oligomer.
Examples of the organic solvent include alcohols such as methanol, ethanol, 2-propanol, butanol, and octanol, ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone. Esters such as diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, acetone, Methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, cyclohexanone, etc. Amides, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and amides such as dimethylformamide, N, N-dimethylacetoacetamide and N-methylpyrrolidone are preferably used. One of these solvents or Two or more kinds can be used.

As the liquid resin monomer, acrylic or methacrylic monomers such as methyl acrylate and methyl methacrylate, and epoxy monomers are preferably used.
Moreover, as said liquid resin oligomer, a urethane acrylate oligomer, an epoxy acrylate oligomer, an acrylate oligomer, etc. are used suitably.

In addition to the above, this surface-modified zirconia particle dispersion may contain other inorganic oxide particles, resin monomers, and the like as long as the characteristics are not impaired.
Examples of the inorganic oxide particles other than the surface-modified zirconia particles include metal oxide particles such as tin oxide, titanium oxide, hafnium oxide, aluminum oxide, iron oxide, cerium oxide, and zinc oxide, and nonmetal oxide particles such as silicon oxide. Etc.
These inorganic oxide particles are preferable because they exhibit super strong acidity by supporting sulfuric acid, tungstic acid, and the like, and as a result, exhibit behavior similar to that of zirconia particles.

"Complex"
The composite of the present invention is a composite in which the surface-modified zirconia particles of the present invention, that is, the surface-modified zirconia particles whose surface is modified with an organic surface modifier and the surface is neutralized, are dispersed in a resin. is there.
The resin may be any resin that is transparent to light in a predetermined wavelength band such as visible light or near infrared, and is thermoplastic, thermosetting, light (electromagnetic wave) curing by visible light, ultraviolet light, infrared light, or the like. And curable resins such as electron beam curable by electron beam irradiation are preferably used.

  Examples of such resins include acrylates such as polymethyl methacrylate (PMMA) and polycyclohexyl methacrylate, polycarbonate (PC), polystyrene (PS), polyether, polyester, polyarylate, polyacrylate, polyamide, phenol- Formaldehyde (phenolic resin), diethylene glycol bisallyl carbonate, acrylonitrile / styrene copolymer (AS resin), methyl methacrylate / styrene copolymer (MS resin), poly-4-methylpentene, norbornene polymer, polyurethane, epoxy, Examples thereof include silicone, and silicone and epoxy are particularly preferable.

The silicone resin is preferably composed of at least the following components (a) to (c).
(A) Organopolysiloxane in which at least two functional groups bonded to silicon atoms in one molecule are alkenyl groups (b) Whether at least two functional groups bonded to silicon atoms in one molecule are hydrogen atoms Or a linear organopolysiloxane (c) hydrosilylation catalyst in which both ends of the molecular chain are blocked with hydrogen atoms

(A) As an alkenyl group in a component, a vinyl group, an allyl group, a pentenyl group, a hexenyl group etc. are mentioned, Especially a vinyl group is preferable.
Examples of functional groups bonded to silicon atoms other than alkenyl groups include alkyl groups such as methyl, ethyl, propyl, and butyl groups, aryl groups such as phenyl and tolyl groups, benzyl groups, and phenethyl groups. Examples thereof include an aralkyl group, and a methyl group is particularly preferable.

(B) Functional groups bonded to silicon atoms other than hydrogen atoms in the component include alkyl groups such as methyl group, ethyl group, propyl group and butyl group, aryl groups such as phenyl group and tolyl group, benzyl group and phenethyl. And an aralkyl group such as a group, and a methyl group is particularly preferable.
In addition, the content of the component (b) is preferably an amount such that the hydrogen atoms are in the range of 0.1 to 10 mol with respect to 1 mol of the total alkenyl groups contained in the component (a). The amount is preferably in the range of 0.1 to 5 mol, and more preferably in the range of 0.5 to 2 mol.

The catalyst for hydrosilylation reaction of component (c) is a catalyst for promoting a hydrosilylation reaction between an alkenyl group in component (a) and a hydrogen atom bonded to a silicon atom in component (b). Examples of such a catalyst include a platinum-based catalyst, a rhodium-based catalyst, a palladium-based catalyst, and the like, and a platinum-based catalyst is particularly preferable.
Examples of the platinum-based catalyst include fine platinum powder, chloroplatinic acid, platinum-olefin complex, platinum carbonyl complex and the like, and chloroplatinic acid is particularly preferable.

  Further, the content of the component (c) is an amount capable of promoting the curing of the composition, that is, hydrosilyl of an alkenyl group in the component (a) and a hydrogen atom bonded to a silicon atom in the component (b). There is no particular limitation as long as it is an amount capable of promoting the chemical reaction, and specifically, the metal atom in the present component is 0.01 to 500 ppm by weight with respect to the present composition. It is preferably within the range, more preferably within the range of 0.01 to 50 ppm.

The reason why the content of the metal atom in this component is limited as described above is that if the content is less than 0.01 ppm, the composition may not be sufficiently cured, while the content is This is because if it exceeds 500 ppm, the obtained cured product may have problems such as coloring.
About this silicone resin, unless the objective of this invention is impaired, you may contain a heat-resistant agent, dye, a pigment, a flame retardance imparting agent, etc. as other arbitrary components.

  Epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, biphenyl type epoxy resin, and other bifunctional glycidyl ether type epoxy resins, phenol novolac type Polyfunctional glycidyl ether type epoxy resin such as epoxy resin, orthocresol novolak type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, tris-hydroxyphenylmethane type epoxy resin, tetraphenylolethane type epoxy resin, tetraglycidyldia Mini diphenylmethane type epoxy resin, triglycidyl isocyanurate type epoxy resin, aminophenol type epoxy resin, aniline type epoxy resin, toluidine type epoxy Glycidyl amine type epoxy resins such as a resin is preferably used.

  As a curing agent for epoxy resin, any of polyaddition type, catalyst type and condensation type can be used. For example, diaminodiphenylmethane, diaminodiphenylsulfone, polyamide, dicyandiamide, diethylenetriamine, triethylenetetramine, hexahydro anhydride Examples thereof include phthalic acid and methyltetrahydrophthalic anhydride.

  Moreover, you may add antioxidant, a mold release agent, a coupling agent, an inorganic filler, etc. with respect to said silicone resin and an epoxy resin in the range which does not impair the characteristic.

In this composite, the content of the surface-modified zirconia particles is preferably 1% by weight or more and 80% by weight or less, more preferably 10% by weight or more and 80% by weight or less, and further preferably 10% by weight or more and 50% by weight or less. It is as follows.
Here, the reason why the content of the surface-modified zirconia particles is limited to 1% by weight or more and 80% by weight or less is that the lower limit of 1% by weight improves the composite properties such as refractive index and mechanical properties. This is because the upper limit of 80% by weight is the maximum value of the addition rate that can maintain the characteristics (flexibility and specific gravity) of the resin itself.

This complex can be produced by the following method.
First, the above-described surface-modified zirconia particle dispersion of the present invention and a resin monomer or oligomer are mixed using a mixer or the like to obtain a resin composition that is easy to flow.
Next, the resin composition is molded using a mold, or filled in a mold or a container, and then the molded body or filling is heated or irradiated with ultraviolet rays, infrared rays, etc. The object is cured.

Here, when the resin monomer or oligomer has a reactive carbon double bond (C = C), it can be polymerized / resinized simply by mixing.
In particular, there are various methods for curing a resin composition containing an ultraviolet (UV) curable resin such as an acrylic resin. Typically, a radical polymerization reaction initiated by heating or light irradiation is used. Mold molding method, transfer molding method and the like. Examples of this radical polymerization reaction include a polymerization reaction by heat (thermal polymerization), a polymerization reaction by light such as ultraviolet rays (photopolymerization), a polymerization reaction by gamma (γ) rays, or a method in which a plurality of these are combined. .

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
To a zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, dilute ammonia water in which 344 g of 28% ammonia water was dissolved in 20 L of pure water was added with stirring to prepare a zirconia precursor slurry.
Next, an aqueous sodium sulfate solution in which 300 g of sodium sulfate was dissolved in 5 L of pure water was added to this slurry with stirring. The amount of sodium sulfate added at this time was 30% by weight with respect to the zirconia converted value of zirconium ions in the zirconium salt solution.

Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.
Next, this solid material was pulverized with an automatic mortar and then baked in the air at 500 ° C. for 1 hour using an electric furnace.
Next, the fired product is put into pure water, stirred to form a slurry, washed using a centrifuge, and after sufficiently removing the added sodium sulfate, dried in a dryer, Zirconia particles were prepared.

Next, 5 g of a silane coupling agent AY43-048 (manufactured by Toray Dow Silicone Co., Ltd.) as a surface modifier was added to 10 g of the zirconia particles and dry-mixed to modify the surface of the zirconia particles with the surface modifier.
Next, the surface-modified zirconia particles were mixed with pure water so that the particle concentration was 5% by weight, and ammonia water was further added to obtain a suspension adjusted to pH 7.

Next, the surface-modified zirconia particles are recovered from this suspension by solid-liquid separation, and dried at 120 ° C. for 2 hours to produce the surface-modified and neutralized zirconia particles (Z1) of Example 1. did.
Next, 85 g of toluene as a dispersion medium was added to 15 g of the zirconia particles (Z1) and mixed, and then a dispersion treatment was performed to prepare the surface-modified zirconia particle dispersion (Z1) of Example 1.

  Next, 10 g of silicone oil (a mixture of methylhydrogenpolysiloxane and organopolysiloxane each having vinyl groups at both ends) is added to 100 g of this surface-modified zirconia particle dispersion (Z1), and chloroplatinic acid is added to silicone. A resin composition was prepared by adding 20 ppm to 100 parts by weight of oil and removing the solvent by vacuum drying.

Next, this resin composition was poured into a mold assembled with a glass plate so as to have a thickness of 1 mm, and then heated and cured at 150 ° C. for 2 hours to produce a composite of Example 1. The zirconia content of this composite was 50% by weight.
Next, the transparency of the composite was visually observed, and the composite was measured based on Japanese Industrial Standard JIS-Z 8722 “Color Measurement Method—Reflection and Transmission Object Color”. Was calculated. In addition, the same evaluation was performed on the composite heated at 150 ° C. for 24 hours.

"Example 2"
Particle synthesis was performed according to Example 1 to produce surface-modified and neutralized zirconia particles (Z1).
Next, 85 g of toluene as a dispersion medium was added to and mixed with 15 g of the zirconia particles (Z1), followed by dispersion treatment to prepare a surface-modified zirconia particle dispersion (Z1).

  Subsequently, to 100 g of this surface-modified zirconia particle dispersion (Z1), 7 g of epoxy resin: Epicoat 828 and 3 g of EpiCure 3080 as a curing agent (both manufactured by Japan Epoxy Resins Co., Ltd.) are added, and the solvent is removed by vacuum drying. A resin composition was prepared.

Next, this resin composition was poured into a mold assembled with a glass plate so as to have a thickness of 1 mm, and then cured by heating at 80 ° C. for 30 minutes to produce a composite of Example 2. The zirconia content of this composite was 50% by weight.
Next, the transparency of the composite was visually observed, and the composite was measured based on Japanese Industrial Standard JIS-Z 8722 “Color Measurement Method—Reflection and Transmission Object Color”. Was calculated. In addition, the same evaluation was performed on the composite heated at 110 ° C. for 24 hours.

“Comparative Example 1”
Particle synthesis was performed according to Example 1 to produce zirconia particles.
Next, 5 g of a silane coupling agent AY43-048 (manufactured by Toray Dow Silicone Co., Ltd.) as a surface modifier is added to 10 g of the zirconia particles and dry-mixed to modify the surface of the zirconia particles (Z2). ) Was produced.

Next, 85 g of toluene as a dispersion medium was added to and mixed with 15 g of the surface-modified zirconia particles (Z2), followed by dispersion treatment to prepare a surface-modified zirconia particle dispersion (Z2).
Next, 10 g of silicone oil (a mixture of methylhydrogenpolysiloxane and organopolysiloxane each having vinyl groups at both ends) is added to 100 g of this surface-modified zirconia particle dispersion (Z2), and chloroplatinic acid is added to silicone. A resin composition was prepared by adding 20 ppm to 100 parts by weight of oil and removing the solvent by vacuum drying.

Next, this resin composition was poured into a mold assembled with a glass plate so as to have a thickness of 1 mm, and then heated and cured at 150 ° C. for 2 hours to produce a composite of Comparative Example 1. The zirconia content of this composite was 50% by weight.
Next, the transparency of the composite was visually observed, and the composite was measured based on Japanese Industrial Standard JIS-Z 8722 “Color Measurement Method—Reflection and Transmission Object Color”. Was calculated. In addition, the same evaluation was performed on the composite heated at 150 ° C. for 24 hours.

“Comparative Example 2”
Particle synthesis was performed according to Example 1 to produce zirconia particles.
Next, 5 g of a silane coupling agent AY43-048 (manufactured by Toray Dow Silicone Co., Ltd.) as a surface modifier is added to 10 g of the zirconia particles and dry-mixed to modify the surface of the zirconia particles (Z2). ) Was produced.

Next, 85 g of toluene as a dispersion medium was added to and mixed with 15 g of the surface-modified zirconia particles (Z2), followed by dispersion treatment to prepare a surface-modified zirconia particle dispersion (Z2).
Next, to this surface-modified zirconia particle dispersion (Z2) 100 g, 7 g of epoxy resin: Epicoat 828 and 3 g of EpiCure 3080 as a curing agent (both manufactured by Japan Epoxy Resins Co., Ltd.) are added, and the solvent is removed by vacuum drying. A resin composition was prepared.

Next, this resin composition was poured into a mold assembled with a glass plate so as to have a thickness of 1 mm, and then heated and cured at 80 ° C. for 30 minutes to produce a composite of Comparative Example 2. The zirconia content of this composite was 50% by weight.
Next, the transparency of the composite was visually observed, and the composite was measured based on Japanese Industrial Standard JIS-Z 8722 “Color Measurement Method—Reflection and Transmission Object Color”. Was calculated. In addition, the same evaluation was performed on the composite heated at 110 ° C. for 24 hours.
The above evaluation results are shown in Table 1.

According to these evaluation results, in Examples 1 and 2, the visual observation before heating was transparent, the YI value was as low as 0.5, and the visual observation after heating was slightly yellow. The YI value was as low as 2 to 3, and it was found that yellowing can be reduced by neutralizing the surface-modified zirconia particles.
On the other hand, in Comparative Examples 1 and 2, the visual observation before heating was transparent and the YI value was as low as 0.5, but the visual observation after heating was yellow and lost transparency, and the YI after heating was also low. The value was also as high as 12-18.

  The surface-modified zirconia particles of the present invention are modified with an organic surface modifier and neutralized on the surface, so that the surface-modified zirconia particles are not yellowed. Since it is possible to maintain transparency while improving the refractive index and mechanical properties of a composite in which particles are dispersed in a resin, it is necessary to maintain transparency in the long term, for example, Semiconductor laser (LED) sealing material, substrate for liquid crystal display device, substrate for organic EL display device, substrate for color filter, substrate for touch panel, substrate for solar cell, transparent plate, optical lens, optical element, The effect is great not only in optical waveguides but also in various other industrial fields.

Claims (5)

The surface containing the organic surface modifier of the surface-modified zirconia particles whose surface is modified with an organic surface modifier is neutralized ,
The surface-modified zirconia particles, wherein the organic surface modifier is one or more selected from the group consisting of an alkoxysilane compound, a siloxane compound, a surfactant, and a titanium coupling agent. The surface-modified zirconia particles according to claim 1, wherein a hydrogen ion index (pH) when the surface containing the organic surface modifier is wetted with water is 4 or more and 10 or less.   A surface-modified zirconia particle dispersion comprising the surface-modified zirconia particles according to claim 1 or 2 dispersed in a dispersion medium.   A composite comprising the surface-modified zirconia particles according to claim 1 dispersed in a resin.   Surface-modified zirconia particles whose surface is modified with an organic surface modifier are mixed with water, and then the hydrogen ion index (pH) of the mixed solution is adjusted to 4 or more and 10 or less, and then the mixed solution A method for producing surface-modified zirconia particles, wherein the surface-modified zirconia particles are separated from the surface.