JP2014214061A - Hydrophobic inorganic oxide powder, and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hydrophobic inorganic oxide particles obtained by surface-treating inorganic oxide particles synthesized by a sol-gel process, and having a small primary particle diameter and a narrow particle size distribution width, which do not strongly agglomerate and are excellent in disintegration property and extremely satisfactory in dispersibility into resin, and a method of simply and easily producing the particles.SOLUTION: The hydrophobic inorganic oxide particles have a median diameter of the particles of 0.05-1.5 μm by a laser diffraction and scattering particle size distribution measurement method, a variation coefficient of not greater than 35%, and satisfy the following requirements (1)-(2). (1) The hydrophobicity degree is 40-70 vol%. (2) The particle amount remaining on a sieve after placing 10 g of the hydrophobic inorganic oxide particles powder on the sieve having a sieve opening of 45 μm (a sieve having a diameter of 75 mm in accordance with JIS Z8801), and vibrating up and down for 60 sec by 1 mm of amplitude and 60 Hz of frequency is not greater than 40 mass%; agglomerated particle amount (%)=particle amount remaining on the sieve/10×100.

Description

  The present invention relates to a novel hydrophobic inorganic oxide powder and a method for producing the same. Specifically, it has the characteristics that the particle size distribution width obtained by the sol-gel method is narrow, has a primary particle size of a small particle size, has excellent crushability, and has excellent dispersibility when added to a resin. Hydrophobic inorganic oxide particles are provided.

  A sol-gel method is known as one method for producing inorganic oxide particles such as silica, titania, zirconia, and alumina. This production method is a method for obtaining inorganic oxide particles by hydrolysis and polycondensation reaction of a metal alkoxide such as tetramethoxysilane in an organic solvent containing water in the presence of an acidic catalyst or a basic catalyst. The sol-gel method is characterized in that fine inorganic oxide particles having a spherical shape and a relatively uniform particle size can be obtained.

  Incidentally, in recent years, the electrophotographic technology of copying machines and printers has been increased in speed and definition, and an additive that enhances the durability and transferability of toner is required. As such an additive, it has been reported that sol-gel silica (hydrophobic inorganic oxide particles) having a narrow particle size distribution width and a hydrophobic surface is effective (see Patent Document 1).

  As a method for producing such a surface-solubilized sol-gel method silica, for example, a method for obtaining a hydrophobized silica by adding a silazane compound to silica sol and reacting it has been reported (patent) Reference 2). The recovery of the silica after the surface treatment in this method is carried out by distilling off the solvent from the slurry containing the silica after the surface treatment. Such a recovery method can be easily applied when taking out from the flask in a laboratory scale, but when this method is applied to an actual large-scale manufacturing plant, the sol-gel method in which the reaction vessel is hydrophobized. Scrapeing out silica is difficult and impractical.

  Here, since the small particle | grains with a particle size of 1 micrometer or less manufactured by the sol-gel method will pass a filter paper and a filter cloth, the solid-liquid separation by filtration is very difficult. Therefore, as a method for solid-liquid separation of the inorganic oxide particles from the dispersion, a method of sedimenting and decanting the particles by the solvent distillation method or centrifugation is employed. And the inorganic oxide particle is obtained by drying the wet body of the inorganic oxide particle obtained by these methods.

  However, in the solid-liquid separation step in the inorganic oxide particle dispersion, strong aggregates of the inorganic oxide particles are generated, and further, strong aggregates of the inorganic oxide particles are generated by the drying step. For this reason, when such particles are used as an external additive for toner, dispersibility in the toner resin is poor, so that effective fluidity cannot be imparted to the toner or the photosensitive drum may be damaged. For this reason, it is difficult to use, and it is necessary to crush the inorganic oxide particle aggregate using a crushing device such as a jet mill. Although the crushing process such as jet mill has a certain effect, it is not sufficient. In addition, there was also a problem that the production efficiency was very poor in terms of energy, time, and work, including the solid-liquid separation process that was the previous process.

JP 2002-108001 A JP 2006-151764 A

  The present invention has been made in view of the above situation. That is, an object of the present invention is a hydrophobic inorganic oxide powder obtained by surface-treating inorganic oxide particles having a narrow primary particle size with a narrow particle size distribution width synthesized by a sol-gel method. Thus, it is to provide a particle having excellent crushability without being strongly aggregated and having extremely good dispersibility in a resin, and a method for easily producing the particle.

  The present inventors have intensively studied to solve the above problems. As a result, a specific surface treatment agent was added to the inorganic oxide particle dispersion obtained by hydrolysis and polycondensation reaction of metal alkoxide in a mixed solvent of alcohol and water in the presence of a basic catalyst to make it hydrophobic. Hydrophobic inorganic oxide powder obtained by adjusting the inorganic oxide particle dispersion and spray-drying the dispersion under specific conditions is excellent in crushability without strongly agglomerating, It was found that the dispersibility when added to was extremely good.

That is, in the present invention, the median diameter of the particles in the laser diffraction / scattering particle size distribution measurement method is in the range of 0.05 to 1.5 μm, the variation coefficient is 35% or less, and the following (1) to ( It is a hydrophobic inorganic oxide powder characterized by satisfying the requirement 2).
(1) Degree of hydrophobicity is 40 to 70% by volume
(2) Place 10 g of the hydrophobic inorganic oxide particle powder on a sieve having a mesh size of 45 μm (diameter 75 mm, compliant with JIS Z8801), and vibrate up and down for 60 seconds at an amplitude of 1 mm and a frequency of 60 Hz. After that, the amount of aggregated particles remaining on the sieve is 40% by mass or less. However, the amount of aggregated particles (%) = the amount of residual particles (g) / 10 (g) × 100
Moreover, according to the said method, the crushing strength of this hydrophobic inorganic oxide powder in a crushing strength measuring method can be 0.01 N or less. When 1 part by mass of the particles is added to 100 parts by mass of the resin, the coverage of the particles with the resin can be 4% or more.

  In the present invention, the hydrophobic inorganic oxide powder is produced by adding a surface treating agent to the inorganic oxide particle dispersion obtained by hydrolysis and polycondensation of metal alkoxide in the presence of a basic catalyst to make it hydrophobic. In the production method of preparing a dispersion containing the treated hydrophobic inorganic oxide particles and obtaining the inorganic oxide powder from the dispersion by spray drying, the spray drying is performed by a spray dryer, and the drying condition is an inlet temperature of 80. Is in the range of ~ 300 ° C, the difference (ΔT) between the drying chamber inlet and outlet temperatures is in the range of 30 to 175 ° C, and the dispersion spray rate is 1.5 to 40 kg / h with respect to the drying chamber volume of 1 m3. It is the range of these.

  Since the effect can be expected more remarkably, in the composition of the mixed solvent constituting the dispersion liquid containing the hydrophobic inorganic oxide powder, the water concentration is preferably 20% by mass or less.

  Furthermore, after the manufacturing method, secondary drying may be performed in the range of 80 to 200 ° C., or second hydrophobization may be performed.

  Since the hydrophobic inorganic oxide powder produced by the method of the present invention has a weak cohesive force, for example, when it is added to a resin to prepare a toner, it is easily crushed by the share of the disperser and is uniform in the toner resin. Can be dispersed.

  In addition, by the method of the present invention, a hydrophobic inorganic oxide powder having a hydrophobized surface and having excellent crushability without being strongly aggregated can be easily produced. Moreover, since the inorganic oxide particle dispersion is directly spray-dried by a spray dryer, the hydrophobic inorganic oxide powder can be obtained in a short time without requiring a solid-liquid separation step as in the prior art. Can do.

  Hydrophobic inorganic oxide particles produced by the method of the present invention are excellent in pulverization, are hydrophobized by surface treatment, and are based on a sol-gel method reaction, so the particle size distribution width is narrow. In particular, it is useful as an external additive for toner for electrophotography.

  Hereinafter, the present invention will be described in detail.

The hydrophobic inorganic oxide powder of the present invention comprises spherical inorganic oxide particles obtained by a sol-gel method, and the median diameter of the particles in the laser diffraction / scattering particle size distribution measurement method is 0.05 to 1. It is a hydrophobic inorganic oxide powder characterized by being in the range of 5 μm, having a coefficient of variation of 35% or less, and satisfying the following requirements (1) to (2).
(1) Degree of hydrophobicity is 40 to 70% by volume
(2) Place 10 g of the hydrophobic inorganic oxide particle powder on a sieve having a mesh size of 45 μm (diameter 75 mm, compliant with JIS Z8801), and vibrate up and down for 60 seconds at an amplitude of 1 mm and a frequency of 60 Hz. After that, the amount of aggregated particles remaining on the sieve is 40% by mass or less. However, the amount of aggregated particles (%) = the amount of residual particles (g) / 10 (g) × 100
Examples of the inorganic oxide of the present invention include periodic table group 4 metals such as titanium, zirconium and hafnium, periodic table group 13 metals such as boron, aluminum, gallium and indium, and periodic table group 14 metals such as germanium and tin. And metal oxides such as silica (silicon oxide) and composite oxides composed of these elements.

  Among the inorganic oxides, oxides of silicon, titanium, zirconium, aluminum, and composite oxides composed of these elements are preferable, and silica and composite oxides containing silicon, particularly silica, are effective in the present invention. It is preferable because it appears remarkably.

  The inorganic oxide powder of the present invention has a median diameter of 0.05 to 1.5 μm. In general, inorganic oxide particles having such a small particle size tend to form strong aggregates, but according to the present invention, they can have a median diameter equivalent to that of primary particles. A more preferable median diameter is 0.07 to 0.80 μm.

  The median diameter of the hydrophobic inorganic oxide powder is measured by a laser diffraction / scattering particle size distribution measurement method. Specifically, 0.1 g of the hydrophobic inorganic oxide powder after drying is put into a glass container having an inner diameter of 4 cm and a height of 11 cm, and 50 g of ethanol is added to obtain a measurement solution. Here, a 4.5 cm portion from the tip of the probe (tip inner diameter: 7 cm) is immersed, and an ultrasonic wave is applied at an output of 20 W for 30 seconds to be dispersed. The median diameter and the coefficient of variation of the obtained dispersion are measured in the range of 0.04 to 2000 μm by polarization scattering intensity difference measurement using Beckman Coulter Co., Ltd., Coulter LS230. The coefficient of variation is calculated from the following formula.

Coefficient of variation (%) = standard deviation of particle diameter (μm) / number average value of particle diameter (μm) × 100
The coefficient of variation in the hydrophobic inorganic oxide powder of the present invention is 35% or less, preferably 30% or less, and more preferably 25% or less. That is, the first feature of the hydrophobic inorganic oxide particles of the present invention is that they are easily broken into fine particles and have few aggregated particles by a slight physical application such as ultrasonic dispersion.

  The median diameter and coefficient of variation need to be calculated by a laser diffraction / scattering particle size distribution measurement method. For example, in the measurement of the median diameter and coefficient of variation by image observation / analysis with an electron microscope, even aggregated particles are measured as independent particles, and vice versa. May be significantly different.

  The inorganic oxide powder of the present invention has a hydrophobicity of 40 to 70% by volume. Particles having a degree of hydrophobicity of less than 40% by volume tend to form strong aggregates due to water crosslinking between the hydroxyl groups on the particle surface. On the other hand, particles exceeding 70% by volume are difficult to produce by a hydrophobization reaction in an aqueous solution as in the present invention. Preferably it is 45-65 volume%.

  The inorganic oxide powder of the present invention is characterized by having such a high dispersibility as described above while having such a hydrophobic property. Some inorganic oxide particles such as silica produced by a conventionally known sol-gel method have a median diameter and a coefficient of variation within the range specified in the present invention. In the present invention, a strong agglomeration and a narrow coefficient of variation and high dispersibility as in the present invention have not been obtained.

  The method for measuring the degree of hydrophobicity in the present invention is as follows. 0.2 g of hydrophobic inorganic oxide particles are added to a 250 mL beaker containing 50 mL of water and stirred with a magnetic stirrer. Here, methanol is added dropwise using a burette, and titration is performed with the end point where the total amount of the sample powder is dispersed and suspended in the solution. The volume percentage (%) of methanol in the methanol-water mixed solvent at the end point is defined as the degree of hydrophobicity.

  The degree of hydrophobicity of the hydrophobic inorganic oxide particles of the present invention can be controlled by the amount of surface treatment agent added and the treatment time in the hydrophobization step in the production method described later. For example, when hexamethyldisilazane is used as the surface treatment agent and 50 parts by mass is added to 100 parts by mass of the inorganic oxide particles and the treatment is performed for 1 hour, the hydrophobicity of the hydrophobic inorganic oxide particles is 55% by volume. It is. As the amount of the surface treatment agent used increases, the degree of hydrophobicity tends to increase, and as the treatment time increases, the degree of hydrophobicity tends to increase.

  Further, the inorganic oxide powder of the present invention is obtained by placing 10 g of the hydrophobic inorganic oxide particle powder on a sieve having a mesh size of 45 μm (a sieve having a diameter of 75 mm and conforming to JIS Z8801), an amplitude of 1 mm, and a frequency of 60 Hz. The amount of agglomerated particles remaining on the sieve after shaking up and down for 60 seconds is 40% by mass or less (provided that the amount of agglomerated particles (%) = the amount of residual sieve particles (g) / 10 (g) × 100 Is). More preferably, it is 30 mass% or less, More preferably, it is 25 mass% or less. This value of 40% by mass or less indicates that no strongly aggregated giant particles are contained.

  The crushability of the hydrophobic inorganic oxide powder of the present invention can be evaluated by a crushing strength measurement method. Specifically, the hydrophobic inorganic oxide particles are passed through a sieve having an aperture of 1.4 mm, subsequently passed through a sieve having a mesh of 0.71 mm, and the hydrophobic inorganic oxide powder remaining on the sieve having an aperture of 0.71 mm is measured. Used for. The particles are placed on an upper pan balance, loaded with a metal spatula, the load when the powder is crushed is recorded, and the crushing strength is calculated by the following formula.

Crushing strength (N) = Load (g) × 9.80665 × 10 ⁻³
This measurement is repeated 60 times, and the average value is taken as the crushing strength. A smaller value of the crushing strength indicates that the particles are more easily broken, and the crushing strength of the hydrophobic inorganic oxide powder of the present invention is preferably 0.01 N or less.

  Further, the hydrophobic inorganic oxide particles of the present invention are extremely excellent in crushability and dispersibility in resins, and therefore can be suitably used as an external additive for toner. For example, when the hydrophobic inorganic oxide powder is added to the toner resin, the dispersibility of the particles in the resin can be evaluated based on the coverage of the inorganic oxide particles on the resin surface. That is, 0.1 g of hydrophobic inorganic oxide powder and 20 g of styrene-acrylic resin particles having a median diameter of 6.1 μm were placed in a 100 mL polyethylene container and mixed for 60 minutes with a shaker. The obtained mixed particles are observed in 50 fields at a magnification of 10,000 using a field emission scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number “S-5500”). Using an image analysis system (manufactured by Asahi Kasei Co., Ltd., trade name “IP-1000PC”), the average value of the resin surface coverage is calculated from the obtained image by the following formula. A higher surface coverage indicates that the toner is more suitable as an external additive for toners. In the case of the hydrophobic inorganic oxide particles of the present invention, this coverage is higher, usually 4% or more.

Surface coverage (%) = area of the portion covered with inorganic oxide particles / area of styrene-acrylic resin particles × 100
Next, a method for producing the hydrophobic inorganic oxide powder of the present invention will be described.

  In the present invention, first, inorganic oxide particles are produced by a sol-gel method under a basic catalyst, that is, metal alkoxide is hydrolyzed and polycondensed to obtain a dispersion containing inorganic oxide particles. .

  A method for producing a dispersion containing inorganic oxide particles by a sol-gel method is known, and in the present invention, this step can be carried out without any particular change from the prior art. However, in the present invention, in order to perform a hydrophobization treatment using a surface treatment agent, a mixed solvent of water and an organic solvent is used as a solvent, and a metal alkoxide as a raw material in the presence of an appropriate basic catalyst is used. A method of hydrolysis and polycondensation is preferably employed. Further, as described later, since a more remarkable effect can be expected by controlling the water concentration of the mixed solvent contained in the dispersion to be dried, suitable water can be used during the production of inorganic oxide particles by the sol-gel method. A concentration range is preferable.

  Of course, it is also possible to produce inorganic oxide particles using only water as the solvent used in the sol-gel method. In this case, it is necessary to add an organic solvent to the dispersion to adjust the liquid composition to a suitable mixed solvent composition during the hydrophobic treatment with the surface treatment agent and drying.

<Metal alkoxide>
The metal alkoxide used in the present invention is not particularly limited and can be appropriately selected and used according to the inorganic oxide particles to be produced.

Specific examples of titanium alkoxide include titanium tetraisopoxide, titanium tetra-n-butoxide and the like;
Examples of zirconium alkoxide include zirconium n-butoxide, zirconium t-butoxide and the like;
Examples of boron alkoxides include trimethyl borate and triethyl borate;
Examples of aluminum alkoxides include aluminum n-butoxide, aluminum isopropoxide and the like;
Examples of silicon alkoxides (alkoxysilanes) include methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and the like;
Examples of alkoxides of Group 4 elements other than silicon include germanium (IV) isopropoxide, germanium (IV) butoxide,
Each can be mentioned.

  Among the above metal alkoxides, titanium tetraisopropoxide, titanium tetra n-butoxide, zirconium n-butoxide, aluminum n-butoxide, aluminum isopropoxide, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxy Silane, tetraisopropoxysilane and tetrabutoxysilane are preferred, and among these, titanium tetraisopropoxide, zirconium n-butoxide, tetramethoxysilane and tetraethoxysilane are easily available industrially and are handled. Is more preferable, and methyltrimethoxysilane, tetramethoxysilane, and tetraethoxysilane are particularly preferable.

  In the production method of the present invention, the metal alkoxide as described above may be used alone or in combination of two or more. When using 2 or more types together, the composite inorganic oxide particle containing a silica can be obtained by mixing and using especially alkoxysilane and metal alkoxides other than alkoxysilane.

  In addition, after obtaining silica particles having a constant diameter by hydrolysis and polycondensation of alkoxysilane, it is also possible to perform hydrolysis and polycondensation by adding a metal alkoxide other than alkoxysilane. It is possible to obtain composite inorganic oxide particles in which other metal oxides are bonded to the surface of the core particles made of.

  When the metal alkoxide is solid at normal temperature and pressure, it can be used as it is, or it can be diluted with an organic solvent described later. When the metal alkoxide is solid at normal temperature and pressure, it can be used by dissolving or dispersing in an organic solvent.

<Basic catalyst>
As the catalyst used in the sol-gel method, a known catalyst used for the production of inorganic oxides by the reaction of the sol-gel method can be used. In the sol-gel method, an acidic catalyst may be used, but it is preferable to use a basic catalyst because it is easy to obtain spherical particles having a uniform particle diameter. Here, in the sol-gel method, first, preliminary hydrolysis is performed under an acidic catalyst, followed by particle growth. In this case, an acidic catalyst is used during preliminary hydrolysis, and a basic catalyst is used during particle growth. The method using is preferably employed.

  The basic catalyst used in the present invention can be suitably used as long as it is a known basic catalyst used for producing inorganic oxide particles by a sol-gel method reaction. Examples of such basic catalysts include amine compounds and alkali metal hydroxides. In particular, it is preferable to use an amine compound from the viewpoint that the amount of impurities containing a metal other than the metal element constituting the target inorganic oxide particles is small and high purity inorganic oxide particles can be obtained. Examples of such amine compounds include ammonia, methylamine, dimethylamine, trimethylamine, and ethylamine. Among these, it is preferable to use ammonia because it is highly volatile and easy to remove, and the reaction rate of the sol-gel method is high.

  These basic catalysts can be used alone or in combination of two or more.

  As the above basic catalyst, an industrially available one can be used as it is (as it is in a commercially available form), or it can be used after diluting with a solvent such as ammonia water. Is also possible. In particular, it is preferable to dilute the basic catalyst in water and use it as an aqueous solution whose concentration is adjusted as necessary, in terms of easy control of the reaction progress rate. The concentration in the case of using an aqueous solution as the basic catalyst is preferably in the range of 1 to 30% by mass because it is easily available industrially and the concentration can be easily adjusted.

  The usage rate of the basic catalyst may be appropriately determined in consideration of the reaction rate of the hydrolysis and polycondensation reaction of the metal alkoxide. As the use ratio of the basic catalyst, the amount of the basic catalyst in the reaction solution is preferably 0.1 to 60% by mass with respect to the mass of the metal alkoxide to be used, and 0.5 to 40% by mass. It is more preferable to use in the range of%.

<Solvent>
In the present invention, as a solvent used for the hydrolysis and polycondensation reaction of the metal alkoxide, water can be used alone, but the resulting inorganic oxide particles are subjected to a hydrophobic treatment with a surface treatment agent. A mixed solvent of water and an organic solvent is preferably used in order to uniformly perform the treatment at the time of implementation. Here, in the present invention, when the dispersion of the inorganic oxide particles is subjected to a drying step, a more remarkable effect can be expected by controlling the water concentration of the mixed solvent contained in the dispersion. It is preferable to produce in a water concentration range.

Although the said organic solvent will not be restrict | limited especially if it is compatible with water, The organic solvent which melt | dissolves 10g or more of water per 100g at normal temperature and a normal pressure is suitable. Specifically, alcohols such as methanol, ethanol, isopropyl alcohol, butanol;
Ethers such as diethyl ether, tetrahydrofuran and dioxane;
Examples thereof include amide compounds such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

  Among them, since alcohol is a by-product during the reaction of the sol-gel method, it is possible to use alcohol such as methanol, ethanol, isopropyl alcohol, butanol among the above to disperse the inorganic oxide particles after the reaction. This is particularly preferable from the viewpoint that various organic components in the liquid are prevented from being present and can be easily removed by heating.

  In the sol-gel method, when a mixed solvent is used, the water concentration in the mixed solvent depends on the particle size of the target inorganic oxide particles and the dispersion containing the inorganic oxide particles after the reaction by the sol-gel method. The concentration of the inorganic oxide particles, as will be described in detail later, is appropriately determined from the viewpoint of the concentration at which the surface treatment agent can be uniformly dispersed in the dispersion and the water concentration suitable for drying. It ’s fine.

  In addition, if the amount of water used is too small relative to the metal alkoxide of the raw material, the reaction rate will be slow, and conversely if too large, when the inorganic oxide particles are taken out from the dispersion, drying will be insufficient and pulverization will occur. Cause it to get worse. Therefore, it is preferable to set it as the range of 24-55 mass% with respect to a metal alkoxide, and it is more preferable to set it as the range of 35-45 mass%.

  In the present invention, water is sufficient if it satisfies the above-mentioned use amount when the sol-gel reaction is carried out in the reactor, and may be preliminarily present in the reactor. When the metal alkoxide is continuously supplied to the reactor, it may be additionally supplied according to the amount. Furthermore, you may add the other component added to a reactor, for example, one part with a basic catalyst.

<Reaction conditions>
The hydrolysis and polycondensation reaction in the present invention, that is, the sol-gel method, is preferably carried out in the presence of a basic catalyst as described above. Known conditions can be adopted as the reaction conditions, and the contact method between the metal alkoxide and the basic catalyst is not particularly limited, and may be appropriately determined in consideration of the configuration of the reaction apparatus and the reaction scale. A specific example of the reaction method of the sol-gel method is as follows. Examples include a method in which water or a mixed solvent of water and an organic solvent and a basic catalyst are charged into a reactor, and a solution obtained by diluting a metal alkoxide or metal alkoxide with an organic solvent and an aqueous solution of a basic catalyst are added simultaneously. be able to. According to this method, spherical inorganic oxide particles having good reaction efficiency and uniform particle diameter can be produced efficiently and with good reproducibility, which is preferable. In this case, for example, after adding a part of the metal alkoxide first, the remaining metal alkoxide and the basic catalyst can be added simultaneously.

  Moreover, when using together 2 or more types of metal alkoxide, each may be mixed and added simultaneously, or each may be added sequentially. In particular, when producing composite inorganic oxide particles containing silica, first, a preliminary hydrolysis and polycondensation reaction is performed using one type of metal alkoxide, and then another type of metal alkoxide is added to react. By continuing, a composite inorganic oxide particle can be manufactured.

  The metal alkoxide and the basic catalyst are preferably added dropwise to the reaction solution. Here, dripping in the liquid means that when the above raw material is dripped into the reaction liquid, the position of the dripping port tip means that the tip of the dripping port is immersed in the reaction liquid. Although it is not limited, it is desirable to set the position where stirring is sufficiently performed, such as in the vicinity of the stirring blade, and the dripping material can quickly diffuse into the reaction solution.

  The addition time of metal alkoxide and basic catalyst (the time from the start of addition to the end of addition) is very important in producing particles having a narrow particle size distribution width. If this time is too short, the particle size distribution range tends to be widened. Conversely, if the time is too long, stable particle growth cannot be achieved. Therefore, in order to obtain inorganic oxide particles having a narrow particle size distribution width and a uniform particle size, it is necessary to select an addition time suitable for the growth of the particles. From such a point of view, the addition time is preferably in the range of 0.2 to 8 hours when the desired particle size is 0.1 μm.

  The reaction temperature is not particularly limited as long as the reaction of the sol-gel method proceeds promptly, and may be appropriately selected according to the particle size of the target inorganic oxide particles. When inorganic oxide particles having a median diameter of 0.01 to 1.5 μm are obtained, the reaction temperature may be appropriately selected within the range of 0 to 60 ° C. In order to advance the reaction of the sol-gel method with certainty, aging may be performed after the dropping of the metal alkoxide and the basic catalyst is completed. The aging temperature is preferably about the same as the reaction temperature, 0 to 60 ° C., and the aging time is preferably 0.25 to 5 hours. In order to obtain inorganic oxide particles having a desired particle size, a method of adding a metal alkoxide and a basic catalyst again after aging and growing the particle size of the inorganic oxide particles may be used.

<Dispersion of inorganic oxide particles>
In the present invention, the dispersion obtained by the sol-gel method described above contains inorganic oxide particles corresponding to the metal alkoxide element used as a raw material. It will be obvious to those skilled in the art which composition of inorganic oxide particles can be obtained depending on the type, amount and order of addition of the metal alkoxide used.

  Of these inorganic oxides, oxides of silicon, titanium, zirconium or aluminum, and composite inorganic oxides containing a plurality of these elements are preferred. In particular, from the viewpoint of good reactivity with the surface treatment agent and excellent physical properties when applied to an external additive for toner, a composite inorganic oxide containing silica or silicon and other metal elements is particularly preferable. Further, silica is particularly preferable.

  In general, the particle size of the inorganic oxide particles obtained by the reaction of the sol-gel method has a median size of 0.01 to 5 μm, but the production method of the present invention is applicable regardless of the particle size of the inorganic oxide particles. can do. In particular, the present invention is effective when drying small particles having a median diameter of 1.5 μm or less, in which generally strong aggregates are easily formed.

  The inorganic oxide particles produced by the sol-gel method are characterized by a narrow particle size distribution width. The particle size distribution width of the inorganic oxide particles obtained by the above production method is very narrow. For example, the variation coefficient, which is one of the indexes indicating the spread of the particle size distribution, can be 25% or less.

<Hydrophobic treatment>
In the present invention, the inorganic oxide particles obtained by the sol-gel method are subjected to a hydrophobic treatment by contacting with a surface treatment agent in a dispersion state without being dried to obtain hydrophobic inorganic oxide particles. Once solid-liquid separation occurs, strong agglomeration tends to occur, and the hydrophobic inorganic oxide powder of the present invention cannot be obtained. As the surface treatment agent, at least one surface treatment agent selected from the group consisting of silicone oil, silane coupling agent and silazane is preferably used.

  Moreover, in the said hydrophobization process, in order to disperse | distribute a surface treating agent effectively in the dispersion liquid containing an inorganic oxide particle, the mixed solvent of water and an organic solvent is used as a solvent which comprises a dispersion liquid. The composition of the mixed solvent, that is, the water concentration is such that the water concentration in the mixed solvent is 20% by mass or less in order to uniformly disperse the surface treatment agent in the mixed solvent and perform the hydrophobic treatment efficiently. It is preferable to adjust so that.

  It is efficient to adjust the water concentration of the mixed solvent by adjusting the solvent composition of the reaction solution obtained by the sol-gel reaction. That is, it is preferable to adjust the water concentration to the above range by adding water or an organic solvent to the composition of the mixed solvent constituting the reaction solution. As the organic solvent used for such adjustment, the organic solvents exemplified above are used without particular limitation.

  Of course, when using the dispersion liquid in which the water concentration of the mixed solvent is within the preferable range at the time of completion of the sol-gel reaction, it is not necessary to make the above adjustment.

  In the present invention, as the silicone oil, a known silicone oil that is usually used for the surface treatment of inorganic oxide particles can be used without particular limitation, and the performance of the surface-treated inorganic oxide particles that are required. It may be appropriately selected and used depending on the situation.

  Specific examples of the silicone oil include, for example, dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, epoxy-modified silicone oil, carboxyl-modified silicone oil, carbinol-modified silicone oil, Examples thereof include methacryl-modified silicone oil, polyether-modified silicone oil, and fluorine-modified silicone oil.

  Of the above, the use of dimethyl silicone oil is particularly preferred in that the hydrophobicity of the inorganic oxide particles can be efficiently increased.

  The amount of silicone oil used is not particularly limited, but if it is too small, the surface treatment will be insufficient, and if it is too large, the post-treatment will be complicated, so 0.05 to 80 parts per 100 parts by mass of the inorganic oxide particles used. It is preferable to set it as a mass part, and it is more preferable to set it as 0.1-60 mass parts.

  As said silane coupling agent, the well-known silane coupling agent normally used for surface treatment can be used, and it selects suitably according to the performance of the surface treatment inorganic oxide particle to require. Use it.

  Specific examples of the silane coupling agent include, for example, methyltrimethoxysilane, methyltriethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-matacrylic. Examples include royloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 4-styryltrimethoxysilane. Among these, the use of methyltrimethoxysilane, methyltriethoxysilane, hexyltrimethoxysilane, or decyltrimethoxysilane can increase the hydrophobicity of the inorganic oxide particles efficiently.

  The amount of the silane coupling agent to be used is not particularly limited. However, if the amount is too small, the surface treatment becomes insufficient, and if the amount is too large, the post-treatment becomes complicated. -80 mass parts is preferable, and it is more preferable to set it as 0.1-40 mass parts.

  As said silazane, the well-known silazane normally used for surface treatment can be especially used without a restriction | limiting. Of the silazanes, hexamethyldisilazane is preferably used because of its good reactivity and ease of handling.

  The amount of silazane used is not particularly limited, but if it is too small, the surface treatment becomes insufficient, and if it is too large, the post-treatment becomes complicated, so 0.05 to 150 parts per 100 parts by mass of the inorganic oxide particles used. A mass part is preferable and it is more preferable to set it as 1-120 mass parts.

  Said surface treating agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  Of the above surface treatment agents, it is preferable to use at least one selected from the group consisting of silicone oils and silazanes, because the hydrophobic inorganic oxide particle powder obtained has good crushability, and silazanes are used. More preferably.

  The method for adding the surface treating agent is not particularly limited, and for example, if it is liquid at normal temperature and normal pressure, it may be dropped into the dispersion or sprayed. Dropping is preferred because of its simplicity in operation. If it is gaseous, a method of bubbling may be considered.

  After the addition of the surface treatment agent, the time for which the surface treatment agent and the inorganic oxide particles are brought into contact with each other for a predetermined time (treatment time), and the temperature of the dispersion liquid (treatment temperature) at that time are not particularly limited, and the surface to be used What is necessary is just to determine in consideration of the reactivity of a processing agent. For example, the treatment time is preferably 0.1 to 48 hours, more preferably 0.5 to 24 hours. The treatment temperature is preferably 0 to 60 ° C. which is the same as the production temperature of the inorganic oxide particles.

<Dry>
In order to obtain the hydrophobic inorganic oxide powder of the present invention from the dispersion of inorganic oxide particles hydrophobized by the above method, it is necessary to perform spray drying under specific conditions.

  The spray drying in the present invention is preferably carried out at a water concentration of the mixed solvent contained in the hydrophobic inorganic oxide particle dispersion, that is, a water concentration of the mixed solvent constituting the dispersion is 20% by mass or less. As described above, the inorganic oxide particles may be produced so as to be in the above water concentration range when the inorganic oxide particles are produced by the sol-gel method, or the concentration may be adjusted by adding an organic solvent before drying.

  In the present invention, a spray dryer is preferably used for spray drying. A spray dryer apparatus is not specifically limited, A commercially available thing can be used. In the present invention, it is important to control the drying conditions in order to obtain hydrophobic inorganic oxide particles having good crushability.

  As the drying conditions, first, the drying chamber inlet temperature needs to be 80 to 300 ° C. 100-250 degreeC is more preferable, and 120 degreeC-200 degreeC is especially preferable. When the inlet temperature exceeds 300 ° C., the functional group derived from the surface treatment agent bonded to the surface of the inorganic oxide particles tends to be decomposed, and the hydrophobicity is lowered. On the other hand, when the inlet temperature is 80 ° C. or lower, the amount of heat necessary for drying the inorganic oxide particles is insufficient, the drying becomes insufficient, the amount of aggregated particles increases, and the crushability deteriorates.

  As a second condition, the difference (ΔT) between the drying chamber inlet temperature and the outlet temperature needs to be 30 to 175 ° C. 30-125 degreeC is more preferable, and 30-75 degreeC is especially preferable. If ΔT is greater than 175 ° C., the humidity in the drying chamber increases and drying tends to be insufficient. Conversely, if ΔT is set to 30 ° C. or less, it is necessary to slow the dispersion spray rate, which is disadvantageous in terms of productivity. Become.

Thirdly, the dispersion spray rate needs to be 1.5 to 40 kg / h with respect to the drying chamber volume of 1 m ³ . On the other hand, since ΔT also changes depending on the dispersion spray speed, the amount of hot air fed into the drying chamber may be adjusted so that ΔT is in the above range and the dispersion spray speed is in the above range.

  The hydrophobic inorganic oxide powder obtained by drying by spray drying may be subjected to secondary drying. The secondary drying method is not particularly limited, and a known method such as blow drying or drying under reduced pressure can be selected. The drying temperature is preferably from 80 to 200 ° C, particularly preferably from 100 to 150 ° C. Although these drying times are not particularly limited, sufficiently dried hydrophobic inorganic oxide particles can be obtained by performing the drying for 0.5 to 48 hours.

<Second hydrophobic treatment>
In the present invention, to the hydrophobic inorganic oxide powder obtained as described above, at least one surface treatment agent selected from the group consisting of silicone oil, silane coupling agent and silazane is added, A second hydrophobizing step for further hydrophobizing the hydrophobic inorganic oxide particles may be provided. As the surface treatment agent, the above-described surface treatment agent can be used. However, the surface-treated inorganic oxide obtained by using a treatment agent that can be chemically bonded directly to the functional group on the surface of the inorganic oxide particles is obtained in comparison with the case of using a treatment agent that has no reactivity. It is preferable because the powder is excellent in pulverization.

  The ratio of the surface treatment agent used in the second hydrophobization treatment step is as follows, depending on the type.

  Silicone oil: preferably 0.01 to 50 parts by mass, more preferably 0.01 to 20 parts by mass with respect to 100 parts by mass of the hydrophobic inorganic oxide powder; silane coupling agent: 100 parts by mass of the hydrophobic inorganic oxide powder Preferably 0.1 to 100 parts by mass, more preferably 0.2 to 50 parts by mass; and silazane; preferably 0.10 to 150 parts by mass with respect to 100 parts by mass of the hydrophobic inorganic oxide powder. Parts, more preferably 0.2 to 100 parts by mass.

  The second hydrophobizing treatment step is preferably performed by a so-called dry step. That is, it is a method in which the surface treatment agent is added to the hydrophobic inorganic oxide powder dried by spray drying and stirred by an appropriate method. The method for adding the surface treatment agent to the inorganic oxide powder can be appropriately determined depending on the form of the surface treatment agent to be used. For example, when the surface treatment agent is a low-viscosity liquid at the process temperature and process pressure, it may be added dropwise to the inorganic oxide powder, or may be sprayed onto the inorganic oxide powder. On the other hand, when the surface treatment agent is a high-viscosity liquid or solid, it can be added in the same manner as in the case of a low-viscosity liquid after being diluted with a small amount of an arbitrary organic solvent. Furthermore, when the surface treatment agent is a gas, it can be performed by stirring the inorganic oxide powder and the surface treatment agent in a sealed state in a container.

  This second surface treatment step is preferably performed in the presence of water from the viewpoint of securing a sufficient amount of silanol groups capable of reacting with the surface treatment agent on the surface of the inorganic oxide particles. In this case, the proportion of water used is preferably 30 parts by mass or less and more preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of the inorganic oxide particles.

Preferred treatment conditions when performing the second surface treatment step are as follows.
Treatment temperature: preferably 100-500 ° C, more preferably 150 ° C-350 ° C;
Treatment pressure: preferably 3 × 10 ⁵ Pa or less, more preferably 1 × 10 ⁴ to 2 × 10 ⁵ Pa; and treatment time: preferably 1 to 300 minutes, more preferably 5 to 180 minutes.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. The measuring method of various physical properties in the present invention is as follows.
(1) Measurement of median diameter and coefficient of variation The measurement of the median diameter of hydrophobic inorganic oxide particles was performed by a laser diffraction scattering method.
0.1 g of the hydrophobic inorganic oxide particles after drying was put into a glass container having an inner diameter of 4 cm and a height of 11 cm, and 50 g of ethanol was poured. A 4.5 cm portion from the tip of the probe (7 cm inside diameter at the tip) was immersed therein, and was dispersed by applying ultrasonic waves at an output of 20 W for 30 seconds.

The median diameter and variation coefficient of the obtained dispersion liquid were measured in the range of 0.04 to 2000 μm by polarization scattering intensity difference measurement using Beckman Coulter Co., Ltd., Coulter LS230. The coefficient of variation was calculated from the following formula.
Coefficient of variation (%) = standard deviation of particle diameter (μm) / number average value of particle diameter (μm) × 100
A narrower coefficient of variation indicates a narrower particle size distribution width.

(2) Measurement of degree of hydrophobicity 0.2 g of hydrophobic inorganic oxide particles were added to a 250 mL beaker containing 50 mL of water and stirred with a magnetic stirrer. Here, methanol was added dropwise using a burette, and titration was performed with the end point where the entire amount of the sample powder was dispersed and suspended in the solution. The volume percentage (%) of methanol in the methanol-water mixed solvent at the end point was defined as the degree of hydrophobicity.

(3) Measurement of crushing strength Crushing strength was measured as an index for evaluating the crushability of hydrophobic inorganic oxide particles.
The hydrophobic inorganic oxide particles were passed through a sieve having an aperture of 1.4 mm, followed by passing through a sieve having a mesh of 0.71 mm, and the hydrophobic inorganic oxide particles remaining on the sieve having an aperture of 0.71 mm were used for measurement. The particles were placed on a pan balance, loaded with a metal spatula, the load when the particles were crushed was recorded, and the crushing strength was calculated by the following formula.
Crushing strength (N) = Load (g) × 9.80665 × 10 ⁻³
This measurement was repeated for 60 particles, and the average value was taken as the crushing strength. A smaller value of the crushing strength indicates that the particles are more easily broken (excellent crushability).

(4) Measurement of the amount of aggregated particles 10 g of the hydrophobic inorganic oxide particles are placed on a sieve having a mesh opening of 45 μm (a sieve having a diameter of 75 mm and conforming to JIS Z8801), and vertically for 60 seconds at an amplitude of 1 mm and a vibration frequency of 60 Hz. After the vibration, the weight of the particles remaining on the sieve was measured, and the value calculated from the following formula was used as the aggregated particle amount.

Aggregated particle amount (%) = sieve remaining amount (g) / 10 (g) × 100
(5) Measurement of resin surface coverage 0.1 g of hydrophobic inorganic oxide particles and 20 g of styrene-acrylic resin particles having a median diameter of 6.1 μm were placed in a 100 mL polyethylene container and mixed for 60 minutes with a shaker. . The obtained mixed particles were observed in 50 fields at a magnification of 10,000 using a field emission scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, model number “S-5500”). Using an image analysis system (product name “IP-1000PC” manufactured by Asahi Kasei Co., Ltd.), an average value of the resin surface coverage was calculated from the obtained image according to the following formula. A higher surface coverage indicates a more suitable external additive for toner.

Surface coverage (%) = area of the portion covered with inorganic oxide particles / area of styrene-acrylic resin particles × 100
Example 1
A 5 L separable flask was charged with 1,040 g of methanol as an organic solvent and 150 g of 15 mass% aqueous ammonia as a basic catalyst, and stirred at 35 ° C. Here, 1940 g of tetramethoxysilane as a metal alkoxide and 700 g of 5% by mass ammonia water as a basic catalyst were dropped into the liquid. The dropwise addition was carried out by adjusting the speed so as to finish in 5 hours. After completion of dropping, aging was performed for 0.5 hour. The mass of the silica particle dispersion obtained by this reaction is 3830 g, the water concentration of the mixed solvent in the dispersion is 8.6% by mass, and the content of silica in the dispersion is 20% by mass (the amount of silica is 766 g). It is.

  After completion of dropping, 230 g of hexamethyldisilazane (equivalent to 30 parts by mass with respect to 100 parts by mass of silica) was added as a surface treatment agent. After the addition, the mixture was stirred at 35 ° C. for 1 hour to obtain a hydrophobic silica particle dispersion. The water concentration in the mixed solvent in the dispersion at this time was 9.2% by mass.

  The hydrophobic silica particle dispersion obtained above is spray-dried with a spray dryer at an inlet temperature of 200 ° C., ΔT 75 ° C., and a dispersion spray rate of 2.5 kg / h, whereby 650 g of hydrophobic silica particle powder is obtained. Got.

  Various measurements were performed on the dispersion and silica particles in this example according to the methods described above. The measurement results are shown in Table 1.

Example 2
The drying with a spray dryer was carried out in the same manner as in Example 1 except that the inlet temperature was changed to 140 ° C. and ΔT 30 ° C. The measurement results are shown in Table 1.

Example 3
The drying with a spray dryer was performed in the same manner as in Example 1 except that the inlet temperature was changed to 300 ° C. and ΔT 175 ° C. The measurement results are shown in Table 1.

Example 4
The same procedure as in Example 1 was performed except that the spray speed of the dispersion liquid dried by the spray dryer was changed to 40 kg / h. The measurement results are shown in Table 1.

Example 5
The hydrophobic silica obtained in Example 4 was subjected to secondary drying at 120 ° C. and normal pressure for 24 hours. The measurement results are shown in Table 1.

Example 6
500 g of the hydrophobic silica obtained in Example 1 was placed in a 20 L pressure vessel and heated to 230 ° C. After replacing the inside of the container with a nitrogen atmosphere, 20 g of water was sprayed while sealing the particles under atmospheric pressure and stirring the particles. Then, after stirring for 15 minutes, the pressure was released and 120 g of hexamethyldisilazane was sprayed. Stirring was continued for 60 minutes, and then the pressure was released and nitrogen purge was performed for 15 minutes to obtain 300 g of hydrophobic silica having a further improved degree of hydrophobicity. The measurement results are shown in Table 1.

Comparative Example 1
A 5 L separable flask was charged with 677 g of methanol as an organic solvent and 381 g of 4.0% by mass ammonia water as a basic catalyst, and stirred at 45 ° C. Here, 1940 g of tetramethoxysilane as a metal alkoxide and 700 g of 2.5% by mass ammonia water as a basic catalyst were dropped into the liquid. The dropwise addition was carried out by adjusting the speed so as to finish in 5 hours. After completion of dropping, aging was performed for 0.5 hour. The mass of the silica particle dispersion obtained by this reaction was 3830 g, and the content of silica in the dispersion was 20% by mass (the amount of silica was 766 g) as in Example 1. The water concentration in the mixed solvent constituting the dispersion at this time was 22.6% by mass.

  After completion of dropping, 230 g of hexamethyldisilazane (30 parts by mass with respect to 100 parts by mass of silica) was added as a surface treatment agent. After the addition, the mixture was stirred at 45 ° C. for 1 hour to obtain a hydrophobic silica particle dispersion. The water concentration in the mixed solvent constituting the dispersion at this time was 21% by mass.

  The hydrophobic silica particle dispersion obtained above was dried under the same conditions as in Example 1. Compared with the hydrophobic silica particles obtained in Example 1, the amount of agglomerated particles increased and the crushing strength was high. The measurement results are shown in Table 1.

Comparative Example 2
In Example 1, 750 g of hydrophobic silica was obtained by drying the surface-treated hydrophobic silica dispersion at 65 ° C. using a hot plate. Compared with the hydrophobic silica obtained in Example 1, the amount of agglomerated particles increased and the crushing strength was high. The measurement results are shown in Table 1.

Comparative Example 3
In Example 1, the hydrophobic silica dispersion after the surface treatment was subjected to centrifugation for 10 minutes at 13,000 rpm using a “table top high-speed cooling centrifuge 3K30C” manufactured by KUBOTA. Hydrophobic silica was obtained by drying for 24 hours at 120 ° C. and normal pressure. Compared with the silica obtained in Example 1, the amount of aggregated particles increased, and the crushing strength was high. The measurement results are shown in Table 1.

Comparative Example 4
The drying conditions of the spray dryer were the same as in Example 1 except that the drying chamber inlet temperature was 75 ° C., ΔT 50 ° C., and the dispersion spray rate was 5 kg / h. Compared with the hydrophobic silica obtained in Examples 1 to 6, the amount of aggregated particles increased, the crushing strength of the hydrophobic silica particles was high, and the dispersibility in the resin was also poor. The results are shown in Table 1.

Comparative Example 5
The drying conditions of the spray dryer were the same as in Example 1 except that the drying chamber inlet temperature was 350 ° C., ΔT 240 ° C., and the dispersion spray rate was 40 kg / h. Compared with the hydrophobic silica obtained in Examples 1 to 6, the degree of hydrophobicity decreased, the amount of aggregated particles increased, the crushing strength of the hydrophobic silica particles was high, and the dispersibility in the resin was also poor. The results are shown in Table 1.

Claims (10)

The median diameter of the particles in the laser diffraction / scattering particle size distribution measurement method is in the range of 0.05 to 1.5 μm, the coefficient of variation is 35% or less, and the following requirements (1) to (2) are satisfied. Hydrophobic inorganic oxide powder characterized by satisfying.
(1) Degree of hydrophobicity is 40 to 70% by volume
(2) Place 10 g of the hydrophobic inorganic oxide particle powder on a sieve having a mesh size of 45 μm (diameter 75 mm, compliant with JIS Z8801), and vibrate up and down for 60 seconds at an amplitude of 1 mm and a frequency of 60 Hz. After that, the amount of aggregated particles remaining on the sieve is 40% by mass or less. However, the amount of aggregated particles (%) = the amount of residual particles (g) / 10 (g) × 100   The hydrophobic inorganic oxide particles according to claim 1 obtained by a sol-gel method.   The hydrophobic inorganic oxide particles according to claim 2, wherein the crushing strength in the crushing strength measurement method is 0.01 N or less. The coverage of the particles when the hydrophobic inorganic oxide particles are added by 2 parts by mass with respect to 100 parts by mass of the resin is 4% or more. Hydrophobic inorganic oxide particles.   The hydrophobic inorganic oxide particle according to any one of claims 1 to 4, wherein the surface treatment agent is hexamethyldisilazane.   The hydrophobic inorganic oxide particle according to claim 1, which is an external additive for toner. A dispersion containing hydrophobic inorganic oxide particles hydrophobized by adding a surface treatment agent to an inorganic oxide particle dispersion obtained by hydrolysis and polycondensation reaction of a metal alkoxide in the presence of a basic catalyst. In the production method of adjusting and obtaining inorganic oxide particles from the dispersion by spray drying, the spray drying is performed by a spray dryer, the drying conditions are in the range of an inlet temperature of 80 to 300 ° C., and the drying chamber inlet and outlet temperatures The difference (ΔT) in the range of 30 to 175 ° C. and the spray rate of the dispersion liquid is in the range of 1.5 to 40 kg / h with respect to the drying chamber volume of 1 m ³ . Manufacturing method of hydrophobic inorganic oxide particles.   The manufacturing method of the hydrophobic inorganic oxide particle of Claim 7 whose water is 20 mass% or less in the composition of the mixed solvent which comprises the dispersion liquid containing the said hydrophobic inorganic oxide particle.   The manufacturing method of the hydrophobic inorganic oxide particle which implements secondary drying in the range of 80-200 degreeC after the manufacturing method of this hydrophobic inorganic oxide particle of Claim 7 or 8.   The manufacturing method of the hydrophobic inorganic oxide particle characterized by implementing 2nd hydrophobization after the manufacturing method of the hydrophobic inorganic oxide particle of any one of Claims 7-9.