JP2011105553A - Method for hydrophobizing treatment of inorganic oxide fine particle, method for producing dispersion, inorganic oxide fine particle and dispersion thereof, and resin composition and application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple, reliable and highly efficient means of uniformly dispersing inorganic oxide fine particles of ZrO<SB>2</SB>or the like in a resin by hydrophobizing inorganic oxide fine particles of ZrO<SB>2</SB>or the like nanodispersed in water without aggregating, so that the inorganic oxide fine particles of ZrO<SB>2</SB>or the like can exist as nanoscale particles, e.g. of ≤30 nm, particularly ≤20 nm in an organic solvent such as toluene, and to provide optical members and optical parts having a high refractive index by using the means. <P>SOLUTION: A method for hydrophobizing treatment of inorganic oxide fine particles includes: mixing an aqueous dispersion of inorganic oxide fine particles produced by dispersing inorganic oxide fine particles in water with a ≥4C carboxylic acid to produce a mixed liquid; and removing the water from the mixed liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for hydrophobizing inorganic oxide fine particles and a method for producing a dispersion useful for use in optical parts and the like, and relates to inorganic oxide fine particles, a dispersion thereof, a resin composition, and an application.

In recent years, research on optical materials has been actively conducted, and particularly in the field of lens materials, high refractive index, low dispersibility (that is, high Abbe number), heat resistance, transparency, easy moldability, light weight, and moisture resistance. The development of materials with excellent chemical resistance and solvent resistance is strongly desired. Plastic lenses are lighter and harder to break than inorganic materials such as glass, and can be easily processed into various shapes. Therefore, not only spectacle lenses and camera lenses, but also optical materials with special shapes such as for display panels in recent years. Is popular. On the other hand, since plastics generally have a lower refractive index than glass, it is required to increase the refractive index of the material itself in order to reduce the thickness of the optical member.
For this reason, conventionally, in the field of display panels and the like, inorganic oxide particles such as titanium oxide and zirconium oxide are dispersed and contained in a resin to realize an inorganic particle composite plastic having a high refractive index and excellent transparency. It has been tried. For example, since ZrO ₂ has a high refractive index peculiar to inorganic oxides, application to a high refractive index optical material is expected by compounding with a polymer.

In order to achieve a plastic compound with high refractive index and excellent transparency, in order to prevent light scattering by the composite inorganic particles, the size of the composite inorganic particles is compared with the wavelength of visible light. It is known that it is necessary to make it sufficiently small, and preferably, nano particles such as ZrO ₂ having a size of 20 nm or less are composited with a polymer material at a nano level to maintain transparency. It is expected that the refractive index of the polymer material can be improved.

On the other hand, as a method conventionally known as a method for producing a large amount of nanoparticles such as ZrO ₂ having a size of 20 nm or less while ensuring the uniformity of size, as described in, for example, cited documents 1 to 3, A method is generally known in which fine molecules of zirconium oxide (zirconia particles) are obtained by dissolving a liquid molecule containing zirconium in an aqueous phase and neutralizing it with an alkali. The zirconia particles obtained in this way are generally present as a dispersed phase dispersed in an aqueous phase and generally have high hydrophilicity. For this reason, in order to uniformly disperse the hydrophilic zirconia particles in the resin without aggregating them, a treatment for increasing the affinity with the organic solvent or the resin by hydrophobizing its surface Is required.

  Conventionally, inorganic particles existing as a dispersed phase dispersed in an aqueous phase are made inorganic by using, for example, an organic solvent such as toluene or a uniform dispersion in a resin by using, for example, a silane coupling agent or a surfactant. Modifying the surface of the particles (see Patent Document 1), preparing a dispersion using phosphoric acid or phosphorous acid ester as a dispersant (Patent Document 2), and further aromatic carboxylic acids such as phthalic acid It has been proposed to produce a composite with a transparent resin by modifying the surface of inorganic particles with an organic acid such as a lower carboxylic acid such as acid or propionic acid (Patent Document 3).

However, in spite of these proposals, conventionally, inorganic oxide fine particles such as ZrO ₂ nano-dispersed in water are agglomerated without being agglomerated as they are, as nanoscale particles, transferred to an organic solvent such as toluene, In fact, no simple, reliable, and efficient means for uniformly dispersing these in the resin has yet been found.

JP 2007-119617 A JP 2008-201634 A JP 2009-191167 A

From the background as described above, the present invention hydrophobizes inorganic oxide fine particles such as ZrO ₂ nano-dispersed in water without agglomeration, and in an organic solvent such as toluene, for example, 30 nm or less, further 20 nm. By making it possible to exist as the following nano-scale particles, it provides a simple, reliable and efficient means for uniformly dispersing inorganic oxide fine particles such as ZrO ₂ in the resin, and also provides high refraction. It is an object to provide an optical member and an optical component having a high rate.

  The present invention is characterized by the following.

  1: Mixing a carboxylic acid having 4 or more carbon atoms into an aqueous dispersion of inorganic oxide fine particles obtained by dispersing inorganic oxide fine particles in water to remove the water from the mixture A process for hydrophobizing inorganic oxide fine particles, comprising the step of:

  2nd: The process of removing water from the said liquid mixture is the water and water-insoluble organic solvent which suspend the said inorganic oxide microparticles | fine-particles by mixing a water-insoluble organic solvent and an amphoteric organic solvent in the said liquid mixture. And forming the mixed solution containing the water-soluble organic solvent and evaporating and removing water and the water-soluble organic solvent from the mixed solution. Processing method.

  Third: the hydrophobicity of the second inorganic oxide fine particles, wherein the water-insoluble organic solvent is at least one kind of aromatic hydrocarbon, and the amphoteric organic solvent is at least one kind of alcohol. Processing method.

  Fourth: Hydrophobizing treatment of the second or third inorganic oxide fine particles described above, further comprising a step of evaporating and removing the water-insoluble organic solvent after performing the step of removing water from the mixed solution Method.

  Fifth: The step of removing water from the mixed solution is a step of removing water by freeze-drying the mixed solution, wherein the first inorganic oxide fine particle hydrophobizing method is characterized.

  Sixth: Dispersing the inorganic oxide fine particles hydrophobized by any one of the first to fifth inorganic oxide fine particles in an organic solvent containing at least one aromatic hydrocarbon. A method for producing a featured inorganic oxide fine particle dispersion.

  Seventh: The sixth method for producing an inorganic oxide fine particle dispersion, wherein the organic solvent contains a polymerizable compound.

  Eighth: A method for producing an inorganic oxide fine particle-dispersed resin composition comprising polymerizing and curing a polymerizable compound contained in the inorganic oxide fine particle dispersion produced by the seventh method.

  Ninth: Inorganic oxide fine particles, wherein a carboxylic acid having 4 or more carbon atoms is adsorbed as a carboxylate on the surface of the particles.

  Tenth: An inorganic oxide fine particle dispersion characterized in that the ninth inorganic oxide fine particles are dispersed in an organic solvent.

  Eleventh: The tenth inorganic oxide fine particle dispersion, wherein the organic solvent is at least one of aromatic hydrocarbons.

  Twelfth: The inorganic oxide fine particle dispersion liquid according to any one of the ninth and tenth aspects, wherein the organic solvent contains at least one polymerizable compound.

  Thirteenth: An inorganic oxide fine particle-dispersed resin composition, wherein the ninth inorganic oxide fine particles are dispersed and contained in a resin.

  14th: A plastic member characterized in that the 13th resin composition is at least a part of its structure.

  Fifteenth: An optical component in which the fourteenth plastic member is at least a part of its configuration.

In the present invention, the inorganic oxide fine particles having an average particle diameter of, for example, 30 nm or less can be subjected to a hydrophobic surface treatment with a specific compound of carboxylic acid having 4 or more carbon atoms as a hydrophobic surface treatment agent. Thus, nanoscale fine particles of oxide such as ZrO ₂ can be uniformly dispersed in an organic solvent such as toluene in the form of primary particles without agglomeration.

In addition, by using a dispersion in which nanoscale fine particles of oxide such as ZrO ₂ were uniformly dispersed in an organic solvent such as toluene, the polymerizable compound was mixed and polymerized to form a nanodispersed composite of nanoparticle. A resin is formed.

That is, according to the present invention, inorganic oxide fine particles such as ZrO ₂ nano-dispersed in water can be hydrophobized and finely dispersed in an organic solvent such as toluene. It is possible to uniformly disperse, and a new technical means that is simple, reliable, and efficient is provided, and an optical member and an optical component having a high refractive index are thereby provided.

It is the figure which showed the example of the result of styrene polymerization. It is the figure which showed the example of the result of styrene polymerization and styrene-MMA copolymerization. It is the figure which showed the example of a measurement of refractive index. It is a ¹ H NMR spectrum diagram in the case of acetic acid. It is a ¹ H NMR spectrum diagram in the case of hexanoic acid. Hexanoic acid treatment (bottom), acid treatment (suspended) is a diagram showing the results of direct drying IR measurement of ZrO ₂ fine particles by (upper).

The inorganic oxide particles constituting the nano fine particles targeted by the present invention are inorganic oxide particles whose average particle diameter is in the nanoscale range of, for example, 30 nm or even 20 nm or less and dispersed in the aqueous phase. is there. As the kind of inorganic oxide, ZrO ₂ (zirconium oxide), TiO ₂ (titanium oxide), SnO ₂ (tin oxide), SiO ₂ (which can be used for transparent high refractive index inorganic particle / resin composites are used. Various examples such as silicon oxide) can be exemplified. Among them, in the present invention, mention may be made of an optical member, the ZrO ₂ in terms of the use as an optical component as a preferred one.

  As long as these inorganic oxide fine particles to be an object of the present invention are dispersed in an aqueous phase, the production method, components, crystal structure and the like are not particularly limited.

  As long as the inorganic oxide fine particles to be subjected to the hydrophobization treatment method according to the present invention are dispersed in the aqueous phase, the production method, components, crystal structure, and the like are not particularly limited. . The particles described as “fine particles” in the present invention are typically those having an average particle diameter of 30 nm or less obtained by dynamic light scattering (DLS). Needless to say, the present invention can be applied to particles having a particle size that can be uniformly dispersed without causing precipitation.

  As described above, the present invention has a predetermined hydrophobicity in the process of replacing the surface of the inorganic oxide fine particles having hydrophilicity and dispersed in the aqueous phase with the organic solvent in the aqueous phase or from the aqueous phase. It is hydrophobized by modification with a chemical surface treatment agent to improve the affinity with organic substances such as organic solvents and resins. In this case, the hydrophobic surface treating agent in this case is essential to be a fatty acid carboxylic acid having 4 or more carbon atoms, and is an essential feature.

  Here, examples of the carboxylic acid having 4 or more carbon atoms include saturated or unsaturated carboxylic acids having 4 to 18 carbon atoms. Examples of these carboxylic acids include monovalent fatty acid carboxylic acids such as butanoic acid, isobutanoic acid, methacrylic acid, hexanoic acid, octanoic acid, oleic acid, linoleic acid, and lauric acid. These may be used alone, or a plurality of types may be mixed and used. In particular, when the inorganic oxide fine particles after hydrophobization treatment are used dispersed in a resin, a carboxylic acid that easily improves the affinity with the resin should be selected and used according to the type of the resin. Is desirable. Further, by using a thiocarboxylic acid having 4 or more carbon atoms in which an oxygen atom constituting the carboxyl group of the carboxylic acid is substituted with a sulfur atom, or a dithiocarboxylic acid having 4 or more carbon atoms, an inorganic material having a higher refractive index than that in the case of using the carboxylic acid. Fine oxide particles can be obtained.

  Although it is not clear about the direct cause of causing affinity for organic solvents by hydrophobizing the fatty acid carboxylic acid having 4 or more carbon atoms to the hydrophilic inorganic oxide fine particles dispersed in the aqueous phase. From the results of infrared absorption shown below, it is considered that the carboxylic acid having 4 or more carbon atoms is adsorbed on the surface of the inorganic oxide fine particles to cause hydrophobicity.

  In addition, in the surface modification of the inorganic oxide fine particles with the carboxylic acid, the affinity to the organic solvent or the resin composition tends to increase as the amount of the carboxylic acid as a hydrophobizing surface treatment agent generally used for the surface modification increases. It was seen. On the other hand, when excessive modification is performed, the volume ratio of the inorganic oxide in each dispersed particle is reduced, and the effect of improving the refractive index when dispersed in the resin composition as an optical member is lowered. For this reason, the amount of carboxylic acid used for modification should be the minimum amount necessary for uniform dispersion depending on the resin composition used when the main purpose is to increase the refractive index of the resin. Is preferred. Typically, the use of a carboxylic acid having a mass of 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less based on the inorganic oxide fine particles to be modified is a viewpoint of high refractive index. Is preferable. On the other hand, in order to reliably obtain high transparency according to the application, a hydrophobic treatment using about 100% by mass of carboxylic acid is performed on the inorganic oxide fine particles to be modified, thereby ensuring a reliable hydrophobicity. Can be processed.

  The surface modification of the inorganic oxide fine particles with carboxylic acid in the present invention is performed by the following steps. That is, by mixing and stirring an appropriate amount of a fatty acid carboxylic acid having 4 or more carbon atoms as a hydrophobizing surface treatment agent in a transparent aqueous dispersion in which hydrophilic inorganic oxide fine particles having an average particle size of about 20 nm or less are dispersed. White turbidity can be generated in the dispersion. This white turbidity is caused by the surface of the inorganic oxide fine particles having hydrophilicity being hydrophobized to form an interface between the particles and the aqueous phase, which indicates that the inorganic oxide fine particles have been hydrophobized. It is.

  In order to disperse the hydrophobized inorganic oxide fine particles in an organic solvent or a resin composition, it is necessary to remove water from the cloudy dispersion. In the present invention, as an intermediate means for finally uniformly dispersing in the resin composition, (1) a dispersion in which the hydrophobic inorganic oxide fine particles are suspended is freeze-dried and A method of drying and separating inorganic oxide fine particles, and (2) mixing a predetermined amount of a water-insoluble organic solvent and an amphoteric organic solvent in a dispersion in which the hydrophobized inorganic oxide fine particles are suspended. Then, a mixed solution of water, a water-insoluble organic solvent and an amphoteric organic solvent is used as a medium to form a dispersion in which inorganic oxide fine particles are suspended, and then water and the amphoteric organic solvent are mainly azeotropically distilled. A method for obtaining a dispersion in which inorganic oxide fine particles hydrophobized in a water-insoluble organic solvent are uniformly dispersed transparently, and (3) the inorganic oxide in the water-insoluble organic solvent obtained above. Non-dispersion from a dispersion in which fine particles are uniformly dispersed in a transparent manner It is preferable to use any of the methods the soluble organic solvent removed by evaporation to separate acquires inorganic oxide particles revealed.

  In other words, the inorganic oxide fine particles obtained by the above methods (1) and (3) can be easily applied to an organic solvent such as toluene or styrene on the condition that an appropriate hydrophobic treatment is performed. The inorganic oxide fine particles are uniformly dispersed by mixing the hydrophobic inorganic oxide fine particles with an appropriate resin composition containing an organic solvent and performing polymerization or the like. A dispersed inorganic particle composite plastic can be obtained. Also, an inorganic particle composite plastic in which inorganic oxide fine particles are uniformly dispersed can be obtained by appropriately performing polymerization or the like by mixing the resin composition with the dispersion obtained by the method (2).

According to the above method (1), it is possible to hydrophobize hydrophilic inorganic oxide fine particles present in the aqueous phase very easily, and the hydrophobized inorganic oxide obtained by lyophilization. The fine particles can then be uniformly dispersed on a nanoscale in an appropriate organic solvent or resin composition. In order to hydrophobize the inorganic oxide fine particles by the method (1), the mixing amount of the hydrophobized surface treatment agent is determined in consideration of the dispersibility of the hydrophobized surface treatment agent used in the aqueous phase. It is desirable. Typically, an effective hydrophobization treatment can be achieved by performing a hydrophobization treatment by mixing about 30 to 100% by mass of a carboxylic acid with respect to inorganic oxide fine particles dispersed in an aqueous phase to be modified. It becomes possible.
On the other hand, the methods (2) and (3) are desirable in that good hydrophobicity can be efficiently performed even with a small amount of a hydrophobic surface treatment agent. The reason why efficient hydrophobic treatment can be performed by the methods (2) and (3) using both a water-insoluble organic solvent and an amphoteric organic solvent for the hydrophobic treatment is not clear. Due to the presence of the solvent, the hydrophobized surface treatment agent is more uniformly present in the dispersion, and the water phase barrier existing on the surface of the inorganic oxide fine particles disappears, so that the hydrophobized surface treatment agent is inorganic oxidized. It can be considered that the fine particles are efficiently supplied to the surface of the fine particles.

  In the above, the amphoteric organic solvent means that it is water-soluble and has compatibility with a water-insoluble organic solvent. Typical examples of such an amphoteric organic solvent include alcohols such as methanol, ethanol, propanol and butanol, and acetone. These may be used as single or plural kinds. The amphoteric organic solvent used is mainly used to produce a uniform liquid phase containing water and a water-insoluble organic solvent and to remove water from the liquid phase by azeotroping with water. The Therefore, it is preferable to produce a uniform liquid phase containing water and a water-insoluble organic solvent in a small amount and to have a relatively low boiling point. In general, alcohol having a relatively small molecule having 3 or less carbon atoms having high compatibility with water, acetone, or the like is preferably used.

  In addition, typical examples of the water-insoluble organic solvent include aromatic hydrocarbons such as toluene, xylene, and benzene, and alicyclic hydrocarbons such as cyclohexane. These may be used singly or in combination. The water-insoluble organic solvent is for dispersing and holding the hydrophobized inorganic oxide fine particles, and preferably has a low vapor pressure that does not cause excessive evaporation when water is removed. Moreover, it is preferable to select and use a thing with high compatibility with the target resin compound after that. Moreover, it is also possible to use styrene etc. which become a resin by polymerization under appropriate conditions as the water-insoluble organic solvent.

  As for the aqueous dispersion of inorganic oxide fine particles, it is desirable from the viewpoint of processing efficiency that the inorganic oxide fine particles contain as high a concentration as possible within the range in which the fine inorganic oxide fine particles can be uniformly dispersed. Generally, it can be taken as a standard that the content of inorganic oxide fine particles is in the range of 5 to 50% by mass.

  Regarding the mixing ratio of the aqueous dispersion and the water-insoluble organic solvent, as described above, the water-insoluble organic solvent is for dispersing and holding the hydrophobic-treated inorganic oxide fine particles, and can achieve its purpose. Must be above the minimum amount. On the other hand, an excessive amount of the water-insoluble organic solvent is undesirable because it reduces the blending ratio of the inorganic oxide fine particles in the resin composition. Specifically, for example, when zirconia particles are used as the inorganic oxide fine particles and toluene is used as the water-insoluble organic solvent, about 0.3 to 5 ml per gram of zirconia particles contained in the aqueous dispersion to be used. Is preferred. In addition, when a water-insoluble organic solvent evaporates at the time of azeotropic removal of water, it is also possible to add a water-insoluble organic solvent suitably.

  The amphoteric organic solvent is desirably used in a proportion higher than the amount capable of producing a liquid phase as a mixed solution by dissolving both the aqueous dispersion and the water-insoluble organic solvent. On the other hand, when an excessive amount is used, it is not desirable because the vapor pressure of water is excessively reduced during the azeotropic removal of water. In addition, when performing azeotropic removal of water in multiple steps, it is not always necessary to dissolve all the aqueous dispersion and the water-insoluble organic solvent in each azeotropic removal, A good hydrophobizing treatment can be performed by mixing an amount of an amphoteric organic solvent capable of dissolving water. The specific amount of the amphoteric organic solvent used is determined by the type and amount of the water-insoluble organic solvent to be used. For example, 10 ml of the aqueous dispersion and about 1 ml of toluene as the water-insoluble organic solvent are used. In some cases, when methanol is used as the amphoteric organic solvent, it is preferable to use about 20 to 100 ml of methanol.

  In the evaporation process in which water is removed by azeotropy with the amphoteric organic solvent, depending on the type and amount of the amphoteric organic solvent to be used, the temperature of the mixed solution can be increased. The gas phase pressure that equilibrates to this is appropriately determined. As typical azeotropic removal conditions for water, when methanol is used as the amphoteric organic solvent, the gas phase pressure is reduced within a range that does not cause bumping in the liquid phase while maintaining the liquid phase at about room temperature. By doing so, it is possible to efficiently remove water from the liquid phase. The azeotropic removal of water is performed until the water contained in the liquid phase is almost completely removed, and the liquid phase is no longer cloudy and becomes sufficiently transparent. For this purpose, a process of repeatedly adding and mixing the amphoteric organic solvent and the evaporation process a plurality of times, or a process of continuously reducing the water content by replenishing the amphoteric organic solvent while carrying out the evaporation step. Is desirable. In this case, when the water-insoluble organic solvent evaporates at the same time and the amount thereof decreases, it is preferable to replenish appropriately.

  Resin composition compatible with the water-insoluble organic solvent in a dispersion in which the inorganic oxide fine particles hydrophobized in the water-insoluble organic solvent obtained by the above steps are uniformly dispersed in a nanoscale. An inorganic particle composite plastic in which inorganic oxide fine particles are uniformly dispersed can be obtained by appropriately mixing the materials and performing polymerization or the like.

  Further, the hydrophobic oxide-modified inorganic oxide fine particles obtained by further evaporating and removing the water-insoluble organic solvent from the dispersion liquid are again re-dispersed uniformly in a water-insoluble organic solvent on a nanoscale to obtain a transparent material. It is possible to obtain a dispersion liquid, and by mixing with a water-insoluble organic solvent or a resin composition as necessary, an inorganic particle composite plastic in which inorganic oxide fine particles are uniformly dispersed can be obtained. The organic solvent as the dispersion medium in this case may be a nonpolar hydrocarbon, for example, an aromatic hydrocarbon such as toluene or benzene, and may be a monomer compound or oligomer compound such as polymerizable styrene, methacrylic acid or methacrylate. There may be. The organic solvent may contain a polymerizable compound. These may be used as single or plural kinds.

  When the organic solvent is a polymerizable compound or contains a polymerizable compound, it can be made into an inorganic oxide fine particle-dispersed polymerizable composition, which is polymerized and cured to produce inorganic oxide fine particles. A dispersed plastic can be formed. Various types of polymerizable compounds are considered. These are used as compounds that form a transparent resin.

  For example, as the transparent resin, various materials such as polystyrene, polymethyl methacrylate (PMMA), polyether, polycarbonate, epoxy resin, polyurethane, styrene, MMA copolymer, polyester, and phenol resin are considered.

  In the resin composition in which the surface-modified inorganic oxide fine particles of the present invention are dispersedly contained, the content of the inorganic oxide fine particles is determined according to the expected refractive index and the like, but to ensure transparency. Is preferably considered to be in the range of 80% by mass or less of the total amount.

  By using such a resin composition as a molded product having a predetermined formation, an optical member or an optical component can be configured. It goes without saying that various means such as thermal polymerization by heating, polymerization by containing a polymerization initiator, and photopolymerization by light irradiation may be employed for the polymerization oxidation.

  In the resin composition in which the nanoscale inorganic oxide fine particles hydrophobized according to the present invention are dispersed, the inorganic oxide fine particles have a sufficiently small size compared to the wavelength of visible light, and the inorganic oxide fine particles Since there is substantially no interface between the resin and the resin, light scattering is small and sufficient transparency can be obtained. Compared with the conventional method of providing a relatively thick hydrophobic coating on the surface of the inorganic oxide fine particles with a silicon coupling agent, etc., the inorganic oxide fine particles are hydrophobized with a relatively small amount of the hydrophobizing surface treatment agent. In order to eliminate the interface with the resin, compared with the inorganic oxide fine particles provided with a hydrophobic coating film by an existing method, a high effect of improving the refractive index can be obtained when dispersed in the resin.

Hereinafter, the case where ZrO ₂ nanoparticles are used as the inorganic oxide particles will be described in more detail as an example. Of course, the present invention is not limited to the following examples.
[Example]

The ZrO ₂ particles dispersed in an aqueous phase, means for the hydrophobic treatment to redispersible ZrO ₂ particles into water-insoluble organic solvent in the aqueous phase was studied.
<1> to various surface treatment agents according to ZrO ₂ surface-modified ZrO ₂ fine particles aqueous dispersion and has a uniformly dispersed transparent in the aqueous phase of the particles (ZrO ₂ content 11.61wt%) 3mL In the conditions shown in Table 1, various surface treatment agents were added to 30% by mass with respect to ZrO ₂ contained in the aqueous dispersion, and the mixture was mixed for about one hour in a 10 mL eggplant flask with a stirrer chip set. Went. As the ZrO ₂ fine particle aqueous dispersion, a product made by Sumitomo Osaka Cement was used. Depending on the surface treatment agent used, the dispersion liquid after mixing the surface treatment agent showed white turbidity and maintained the transparency.
<2> Removal of water by freeze-drying The liquid mixture obtained by adding and mixing the various surface treatment agents obtained above is dried by ordinary freeze-drying to remove water and dispersed in the aqueous phase. The ZrO ₂ particles were powdery.
<3> Confirmation of dispersibility in water-insoluble organic solvent The powder composed of the ZrO ₂ particles obtained above is mixed by adding toluene, which is a water-insoluble organic solvent, as a dispersion medium, and each powder is dispersed in toluene. The particle diameter of ZrO ₂ particles dispersed in toluene was measured by dynamic light scattering (DLS). The results are summarized in Table 1.

As shown in Table 1, when methacrylic acid or hexanoic acid, which is a predetermined amount of carboxylic acid having 4 or more carbon atoms, is used as a surface treatment agent, at least a part of ZrO ₂ particles is uniformly dispersed in toluene. And was observed to be transparent. Moreover, the particle diameter of the ZrO ₂ particles present in toluene was about 10 nm, and it was confirmed that the particles were dispersed on the nanoscale.

On the other hand, when acetic acid or propionic acid was used as the hydrophobizing surface treatment agent, almost all of the ZrO ₂ particles were not dispersed in toluene but precipitated.

From the results shown in Table 1, it is possible to hydrophobize ZrO ₂ fine particles dispersed in the aqueous phase by using a carboxylic acid having 4 or more carbon atoms as a hydrophobizing surface treatment agent. It became clear that redispersion in a state where the nanoscale was maintained in the solvent became possible.

When the ZrO ₂ fine particles dispersed in the aqueous phase are transferred to the water-insoluble organic solvent, the surface treatment agent is hydrophobized in the process, and the ZrO ₂ fine particles are uniformly dispersed in the water-insoluble organic solvent. The means for obtaining the liquid was studied.
<1> different in 100mL eggplant flask equipped with a surface-modified stirrer chip of ZrO ₂ particles by the hydrophobic surface treatment agent, various hydrophobic surface treatment in an amount corresponding to 10～100Wt% relative ZrO ₂ to be processed 10 mL of ZrO ₂ fine particle aqueous dispersion (ZrO ₂ content 11.61 wt%) was added to and mixed with 1 mL of toluene as a water-insoluble organic solvent and 30 mL of methanol as an amphoteric organic solvent. . As the ZrO ₂ fine particle aqueous dispersion, a product made by Sumitomo Osaka Cement was used. In the obtained mixed solution, the water-insoluble organic solvent toluene and water are dissolved in methanol, which is the miscible organic solvent, to form a uniform liquid phase, and white turbidity caused by ZrO ₂ fine particles is generated. It was.

  After stirring the liquid mixture obtained above at room temperature for 1 hour, the dispersion medium was removed by evaporation using a rotary evaporator until the volume became about 3 to 5 mL. Evaporation removal of the dispersion medium was performed by reducing the atmosphere to a pressure that does not cause bumping in the liquid phase while keeping the mixed liquid at room temperature.

The mixed liquid remaining in the eggplant flask after the first removal of the dispersion medium by evaporation was cloudy, and the liquid phase was separated into two phases. To the mixture, 30 mL of methanol and 1 mL of toluene were further added to form a cloudy dispersion with no interface again, and the evaporation was performed again until about 3 to 5 mL. Obviously, by repeating this operation several times, depending on the type and amount of the surface treatment agent used, the dispersion can be changed from cloudy to colorless and transparent, and the remaining liquid phase can be made into a single phase. became. In this example, a toluene dispersion of ZrO ₂ fine particles was obtained by replacing the water / ethanol / toluene mixed solvent with a solvent containing only toluene by 5 to 6 operations. The particle diameter of the ZrO ₂ fine particles in the obtained toluene dispersion was measured by dynamic light scattering (DLS).

Table 2 summarizes the toluene dispersion of ZrO ₂ particles obtained in this example.

As is apparent from the results in Table 2, when alcohol or amine is used as the surface treatment agent, white turbidity remains, so that the ZrO ₂ particle surface does not have sufficient affinity for toluene. It was inferred that there was an interface between them. On the other hand, when a fatty acid carboxylic acid having 4 or more carbon atoms is used, the toluene dispersion may become transparent by mixing 10 to 100% by mass with respect to the amount of ZrO ₂ particles. It was observed that the surface of the ZrO ₂ particles had an affinity for toluene, and it was assumed that there was no substantial interface between them.
<2> Surface modification state As described above, the surface modification of ZrO ₂ fine particles in which a carboxylic acid having 4 or more carbon atoms is dispersed in an aqueous phase as a hydrophobizing surface treatment agent causes aggregation in toluene. It is possible to disperse without. FIG. 5 shows a ¹ H NMR spectrum measurement result of a toluene dispersion of ZrO ₂ fine particles obtained by adding toluene as a hydrophobizing surface treatment agent corresponding to 20% by mass with respect to the ZrO ₂ fine particles (toluene replacement). The lower part is shown in comparison with the measurement result of hexanoic acid (upper part). As is clear from FIG. 5, in toluene in which ZrO ₂ fine particles hydrophobized with hexanoic acid are dispersed, a signal corresponding to a broad peak of hexanoic acid is obtained, and hexanoic acid is adsorbed on ZrO ₂ fine particles. It was inferred that

FIG. 4 shows, as a comparative example, ¹ H NMR spectrum measurement results (lower stage) of a toluene dispersion of ZrO ₂ particles that have been clouded by performing substitution with toluene using acetic acid as a surface treatment agent. Shown in comparison with (top). In toluene containing ZrO ₂ particles hydrophobized with acetic acid, no signal due to acetic acid was observed.

In addition, FIG. 6 is obtained by adding 20% by mass of hexanoic acid as a hydrophobizing surface treatment agent to the ZrO ₂ fine particles as described above and performing toluene substitution, followed by vacuum drying at room temperature. and ZrO ₂ results of IR measurement of the fine particles (lower), ZrO ₂ fine particle aqueous dispersion in a hydrophobic surface treatment agent as a result of IR measurement of the dried resultant ZrO ₂ particles after the addition of acetic acid and (middle) The results are shown in comparison with IR measurement results (upper) of ZrO ₂ particles obtained by further baking ZrO ₂ particles obtained by directly drying an aqueous dispersion of ZrO ₂ fine particles at 400 ° C.

From FIG. 6, both ZrO ₂ particles to which hexanoic acid and acetic acid were added showed absorption due to carboxylate, while those with hexanoic acid showed absorption due to CH ₃ etc. in the vicinity of 3000 cm ⁻¹ . From these facts, it is presumed that both acetic acid and hexanoic acid are adsorbed on the ZrO ₂ fine particles, but it is presumed that the influence on the hydrophobicity is different due to the difference in the number of carbon atoms. That is, the reason why the ZrO ₂ particles hydrophobized by the hydrophobizing method according to the present invention are dispersed without agglomerating into aromatic hydrocarbons to produce a transparent dispersion is as described above. It is presumed that the carboxylic acid having 4 or more carbon atoms added as a treating agent is adsorbed on the surface of the ZrO ₂ particles in the carboxylate state.

The redispersibility of the ZrO ₂ particles obtained by evaporating and removing the water-insoluble organic solvent from the dispersion of the water-insoluble organic solvent in which the ZrO ₂ fine particles are dispersed was examined.
<1> Removal of water-insoluble organic solvent Each toluene dispersion obtained in Example 2 was vacuum-dried at room temperature for 24 hours to remove toluene, thereby obtaining a powder composed of ZrO ₂ particles.
<2> Confirmation of dispersibility in non-water-soluble organic solvent The powder made of ZrO ₂ particles obtained above was put into various dispersion media, and the redispersibility of ZrO ₂ particles in various dispersion media was examined. . The results are summarized in Table 3.

As is clear from the results in Table 3, ZrO ₂ particles that have been hydrophobized with carboxylic acids having 4 or more carbon atoms can be uniformly redispersed in a wide variety of water-insoluble organic solvents in a transparent state. It is clear that it has an affinity for water-insoluble organic solvents.

The influence of various treatment conditions when hydrophobizing with a hydrophobizing surface treatment agent in the process of transferring ZrO ₂ fine particles dispersed in an aqueous phase to a water-insoluble organic solvent was investigated. In particular, in this example, when hydrophobized surface treatment agent was used by selecting and mixing hexanoic acid (HA) and methacrylic acid (MA) among carboxylic acids having 4 or more carbon atoms, the hydrophobized surface treatment. The effect of the type of agent was investigated.
<1> Surface Modification of ZrO ₂ Fine Particles with Various Surface Treatment Agents No. 1 described in Table 4 was placed on an eggplant flask in which a stirrer chip was set. A mixture of ZrO ₂ fine particle aqueous dispersion (ZrO ₂ content 11.61 wt%), methanol, and toluene manufactured by Sumitomo Osaka Cement under conditions 1 to 4 with hexanoic acid and methacrylic acid as hydrophobizing surface treatment agents. The mixture was added to obtain a cloudy mixture consisting of a single-phase liquid phase. This mixture was evaporated and removed from the dispersion medium 5-6 times in the same manner as in Example 2 to obtain a toluene dispersion of ZrO ₂ particles. Table 4 shows the properties of the obtained ZrO ₂ fine particle toluene dispersion and the size of the ZrO ₂ particles in the dispersion measured by dynamic light scattering (DLS).

As is clear from the results in Table 4, it is transparent in a wide range regardless of the mixing ratio of ZrO ₂ fine particle aqueous dispersion, methanol, toluene, the mixing ratio of hexanoic acid and methacrylic acid as the hydrophobizing surface treatment agent, etc. It has been clarified that a toluene dispersion of ZrO ₂ particles can be obtained, and that the size of the ZrO ₂ particles can be generally maintained at 10 nm or less in any of the dispersions.

The ZrO ₂ particles toluene from toluene dispersion of ZrO ₂ particles obtained in Example 4 was obtained by vacuum drying, it was re-dispersed in styrene as a resin composition, a polystyrene resin obtained by polymerizing styrene The properties were examined.
<1> Production of Styrene Dispersion of Surface-Modified ZrO ₂ Fine Particles and Polymerization of Styrene As shown in Table 3, the ZrO ₂ fine particles obtained by the surface modification method according to the present invention can be redispersed in styrene. In this example, ZrO ₂ fine particles subjected to hydrophobic treatment by surface modification in Example 4 were dispersed in styrene as a resin composition at a ratio of 20 to 65% by mass, and a transparent styrene dispersion of ZrO ₂ particles. Got. This styrene dispersion of ZrO ₂ fine particles was transferred to a test tube, subjected to nitrogen bubbling in an ice bath for 10 minutes, and polymerized in an oil bath at 120 ° C. for 3 days to obtain polystyrene.
<2> Polystyrene resin in which ZrO ₂ fine particles are dispersed Table 5 shows the mixing ratio of the ZrO ₂ particles and styrene (St) used in this example and the properties of the obtained polystyrene. FIG. 1 shows an optical photograph of the obtained polystyrene.

As is clear from Table 5 and FIG. 1, when a hydrophobized surface treatment agent in which hexanoic acid (HA) and methacrylic acid (MA) are mixed at a ratio of 6: 4 to 3: 7 is used, both are ZrO. It was revealed that a composite with transparent polystyrene can be obtained without aggregation of the _two particles. In particular, when a hydrophobized surface treatment agent in which hexanoic acid and methacrylic acid were mixed at a ratio of 4: 6 to 3: 7 was used, a tendency to obtain a highly transparent polystyrene composite was observed.

In addition, as shown in the following Table 6 and FIG. Even when the ZrO ₂ particles hydrophobized under the condition 2 are contained in the proportions of 46.9% by mass and 64.7% by mass, the transparency of the polystyrene composite is not impaired. It became clear that the ZrO ₂ particles can be dispersed in the resin without impairing the transparency by using the ZrO ₂ fine particles subjected to the chemical treatment.

Also, when ZrO ₂ particles hydrophobized with hexanoic acid and methacrylic acid are dispersed in a dispersion medium in which styrene and methyl methacrylate as a resin composition are mixed at a mass ratio of 7: 3, and polymerized to form a composite. Also in (No. 7 in Table 6), a styrene-methyl methacrylate copolymer resin and a ZrO ₂ particle composite excellent in transparency were obtained.
<4> styrene -ZrO ₂ particle dispersion and for the refractive index of the polystyrene resin containing dispersed ZrO ₂ particles styrene -ZrO ₂ particle dispersion 3 The results of the refractive index measurement, which had been measured for refractive index with an Abbe refractometer It was shown to. The ZrO ₂ particles dispersed in styrene have been subjected to a hydrophobization treatment using a hydrophobizing surface treatment agent in which hexanoic acid and methacrylic acid are mixed in a ratio of 5: 5. FIG. 3 shows the theoretical value of the refractive index of the styrene-ZrO ₂ particle dispersion calculated from the Lorentz-Lorenz equation. The refractive index of the dispersion increased by dispersing the ZrO ₂ fine particles. In the dispersion containing 65 wt% ZrO ₂ fine particles, an increase in the refractive index of 0.087 was observed compared to the refractive index of styrene. .

Conventionally, when the surface of a ZrO ₂ particle is coated with a silicon coupling agent having a low refractive index for the purpose of dispersing the ZrO ₂ particle in a resin, the silicon cup is compared with the volume of the ZrO ₂ particle. Since the volume ratio of the ring agent and the like is increased, as a result, even if the coated ZrO ₂ particles are dispersed in the resin, the expected improvement in the refractive index cannot be obtained. It was. On the other hand, as shown in FIG. 3, since the rate of increase in the refractive index obtained in this example is almost in line with the theoretical value, it is adsorbed on the surface of the ZrO ₂ fine particles by the hydrophobic treatment according to the present invention. It is inferred that the carboxylic acid to be dispersed can be dispersed in the resin composition by hydrophobizing the ZrO ₂ fine particles in a very small amount.

Polymerizing styrene having dispersed therein the ZrO ₂ particles, when a polystyrene resin containing dispersed ZrO ₂ particles, the refractive index of the polystyrene resin containing 30 wt% of ZrO ₂ particles 1.620 (D line: 589 nm) becomes The refractive index was improved by polymerization of styrene. Similarly, those containing 50% by mass of ZrO ₂ particles have a refractive index of 1.630, and those containing 65% by mass of ZrO ₂ particles have a refractive index of 1.655 (both D line: 589 nm). It was confirmed that the refractive index of the polymerized polystyrene was improved by dispersing the ZrO ₂ fine particles that had been treated by the hydrophobization treatment.

Claims (15)

  A step of mixing a carboxylic acid having 4 or more carbon atoms into an aqueous dispersion of inorganic oxide fine particles obtained by dispersing inorganic oxide fine particles in water, and a step of removing water from the mixture; A method for hydrophobizing inorganic oxide fine particles, comprising:   The step of removing water from the mixed solution includes mixing water, a water-insoluble organic solvent, and a water-insoluble organic solvent in which the inorganic oxide fine particles are suspended by mixing a water-insoluble organic solvent and a water-soluble organic solvent in the liquid mixture. The hydrophobization of inorganic oxide fine particles according to claim 1, comprising a step of forming a mixed solution containing an organic solvent, and a step of evaporating and removing water and the amphoteric organic solvent from the mixed solution. Processing method.   The hydrophobic treatment for inorganic oxide fine particles according to claim 2, wherein the water-insoluble organic solvent is at least one kind of aromatic hydrocarbon, and the amphoteric organic solvent is at least one kind of alcohol. Method.   4. The method for hydrophobizing inorganic oxide fine particles according to claim 2, further comprising a step of evaporating and removing the water-insoluble organic solvent after performing the step of removing water from the mixed solution.   2. The method for hydrophobizing inorganic oxide fine particles according to claim 1, wherein the step of removing water from the mixed solution is a step of lyophilizing the mixed solution to remove water.   Dispersing the inorganic oxide fine particles hydrophobized by the method for hydrophobizing inorganic oxide fine particles according to any one of claims 1 to 5 in an organic solvent containing at least one aromatic hydrocarbon. A method for producing a featured inorganic oxide fine particle dispersion.   The method for producing an inorganic oxide fine particle dispersion liquid according to claim 6, wherein the organic solvent contains a polymerizable compound.   A method for producing an inorganic oxide fine particle dispersed resin composition comprising polymerizing and curing a polymerizable compound contained in an inorganic oxide fine particle dispersion produced by the method according to claim 7.   An inorganic oxide fine particle, wherein a carboxylic acid having 4 or more carbon atoms is adsorbed as a carboxylate on the surface of the particle.   An inorganic oxide fine particle dispersion, wherein the inorganic oxide fine particles according to claim 9 are dispersed in an organic solvent.   The inorganic oxide fine particle dispersion according to claim 10, wherein the organic solvent is at least one kind of aromatic hydrocarbon.   The inorganic oxide fine particle dispersion liquid according to claim 9, wherein the organic solvent contains at least one polymerizable compound.   An inorganic oxide fine particle-dispersed resin composition, wherein the inorganic oxide fine particles according to claim 9 are dispersed and contained in a resin.   14. A plastic member, wherein the resin composition according to claim 13 is at least a part of the structure.   An optical component, wherein the plastic member according to claim 14 is at least a part of its configuration.