JP2016168524A - Composite particle and mixing method of particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide composite particles with which a predetermined function as the composite particles can be exhibited even when two kinds of particles with a size of nano-micron order are mixed with each other, and to provide a mixing method of particles, with which the two kinds of particles can uniformly be mixed.SOLUTION: Composite particles are obtained by dry-mixing first particles with average primary particle size of 1 μm or less and second particles with average primary particle size of 1 μm or less with each other, in which stirring of the first particles and the second particles and crushing of aggregates of the first particles are simultaneously performed in dry-mixing, and the ratio of the average primary particle size of the first particles and the average primary particle size of the second particles ((second particles)/(first particles)) is 0.02-0.25.SELECTED DRAWING: None

Description

  The present invention relates to composite particles and a particle mixing method.

  Conventionally, two or more types of particles are mixed to produce composite particles. Usually, the composite particles have a predetermined function (for example, improved handling property and improved mixing property) by attaching the secondary material particles to the surface of the main material particles. Examples of applications of such composite particles include toner particles and toner additive particles (for example, Patent Document 1).

  As a composite particle, various attempts have been made to combine a secondary material particle having a nano-order particle size with a main material particle having a micro-order particle size. Combining secondary particles having nano-order particle diameter with particles has not been sufficiently studied.

JP-A-11-24312

  When the inventors of the present invention mix main material particles having a nano-order particle size (for example, an average primary particle size of 1 μm or less) and sub-material particles having a nano-order particle size, The problem that the effect of adding is not sufficiently obtained was found.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to develop a predetermined function as a composite particle even when two kinds of particles having a nano-order particle size are mixed. An object of the present invention is to provide composite particles that can be obtained, and to provide a particle mixing method that can uniformly mix the two kinds of particles.

The composite particles of the present invention are composite particles obtained by dry-mixing aggregates of first particles having an average primary particle diameter of 1 μm or less and second particles having an average primary particle diameter of 1 μm or less. In the dry mixing, the stirring of the first particles and the second particles and the crushing of the aggregates of the first particles are performed simultaneously, and the average primary particle diameter of the first particles, The ratio of the second primary particles to the average primary particle size (second particles / first particles) is 0.02 to 0.25.
In one embodiment, the average secondary particle diameter of the composite particles is 80% or less with respect to the average particle diameter of the aggregate of the first particles.
In one embodiment, the mixing amount of the second particles is 0.1 to 10 parts by weight with respect to 100 parts by weight of the mixing amount of the first particles.
According to another aspect of the present invention, a particle mixing method is provided. This particle mixing method is a method of mixing first particles having an average primary particle diameter of 1 μm or less and second particles having an average primary particle diameter of 1 μm or less, and an aggregate of the first particles is obtained. Stirring the first particles and the second particles while crushing.
In one embodiment, the particle mixing method uses a mixing device including a stirring blade and a crushing blade.
In one embodiment, the input amount of the second particles is 0.1 to 10 parts by weight with respect to 100 parts by weight of the input amount of the first particles.
In one embodiment, the ratio (second particle / first particle) between the average primary particle size of the first particles and the average primary particle size of the second particles is 0.02 to 0. .25.

  The composite particles of the present invention are particles obtained by dry-mixing first particles having an average primary particle diameter of 1 μm or less and second particles having an average primary particle diameter of 1 μm or less. According to the present invention, during the dry mixing, the first particles and the second particles are agitated and the aggregates of the first particles are simultaneously pulverized, whereby the second particles as sub-material particles. It is possible to provide composite particles having a high additive effect. Further, according to the present invention, the first particles and the second particles are agitated while the aggregates of the first particles are crushed, thereby uniformly mixing the particles having a small particle diameter. The resulting particle mixing method can be provided.

(A) is a figure which shows the result of the surface elemental analysis and SEM image element mapping of the composite particle in Example 1. FIG. (B) is a figure which shows the result of the surface element analysis and SEM image element mapping of the composite particle in the comparative example 1. It is a figure which shows the coating film formed with the coating material produced by the reference examples 2 and 3. FIG.

A. Composite Particles The composite particles of the present invention are obtained by dry-mixing first particles having an average primary particle diameter of 1 μm or less and second particles having an average primary particle diameter of 1 μm or less. The composite particles may be in a form in which the first particles and the second particles are attached to each other. The average primary particle diameter is calculated by calculating the diameter of a predetermined number of randomly selected particles (the maximum length of the particles (cross section)) and calculating the arithmetic average thereof. Details of the average primary particle size evaluation method will be described later.

  The first particles can be subjected to mixing as an aggregate in which single particles are aggregated, and the aggregate of the first particles is crushed as a result of the mixing operation with the second particles. More specifically, the composite particles of the present invention are obtained by dry mixing in which the agglomeration of the first particles and the second particles and the crushing of the aggregates of the first particles are simultaneously performed. Note that the aggregate of the first particles is an aggregate formed by reversibly aggregating single particles, and is an aggregate in a state of being aggregated in a state where the grain boundaries of the single particles remain (so-called 2 Secondary agglomerates).

  In the present invention, even if the particles to be mixed are both extremely small (average primary particle size is 1 μm or less), that is, particles that are likely to aggregate (secondary aggregation) because of their large specific surface area and high surface energy. Even when the aggregate of the first particles is crushed (that is, in a state where the secondary particle diameter of the first particles is reduced and / or in a state where the first particles are made into single particles), Since the particles and the second particles are brought into contact with each other, the amount of the second particles adhering to the first particles is increased, and as a result, composite particles exhibiting a desired function can be obtained. For example, as will be described later, it is possible to obtain a composite particle having a high degree of hydrophobicity by mixing hydrophilic first particles and hydrophobic second particles.

  In the present invention, the composite particles are obtained by dry mixing. The dry mixing means mixing performed without using a liquid. Conventional dry mixing methods tend to agglomerate particles for mixing compared to wet mixing methods in which particles are mixed using a liquid. Therefore, not only the mixing of particles having a nano-order particle diameter but also the mixing of particles having a micron-order particle diameter is insufficient in effect due to the particle mixing, making practical application difficult. On the other hand, in this invention, the said conventional problem can be eliminated, and also by employ | adopting a dry-mixing method, the crushing of 1st particle | grains is performed effectively. As a result, even when the particles having nano-order particle diameters are mixed with each other, two kinds of particles can be mixed well to obtain composite particles exhibiting a desired function.

  The second particles before mixing may be aggregated particles, single particles, or a state in which these particles coexist. In the present invention, composite particles having good characteristics as described above can be obtained even when the aggregated second particles are used.

  The average secondary particle diameter of the composite particles is preferably 0.3 μm to 7 μm, more preferably 0.3 μm to 5 μm, and still more preferably 0.3 μm to 3 μm. Thus, it is one of the effects of the present invention that composite particles having a small secondary particle diameter can be obtained. The average secondary particle diameter of the composite particles and the average particle diameter (described later) of the aggregates of the first particles can be measured by a laser diffraction method (volume basis).

  The average secondary particle size of the composite particles is preferably 80% or less, more preferably 75% or less, with respect to the average particle size of the aggregates of the first particles (aggregates before mixing). More preferably, it is 70% or less, particularly preferably 65% or less, and most preferably 10% to 65%. In one embodiment, the average secondary particle diameter of the composite particles obtained after mixing is smaller than the average particle diameter of the aggregates of the first particles (aggregates before mixing).

  In addition to the first particles and the second particles, the composite particles may further include other particles.

  Details of the first particles and the second particles will be described in Section B.

B. Particle Mixing Method The particle mixing method of the present invention is a method of mixing first particles having an average primary particle diameter of 1 μm or less and second particles having an average primary particle diameter of 1 μm or less. Stirring the first particles and the second particles while crushing the aggregates of the particles.

  According to the particle mixing method, particles having an extremely small particle diameter can be mixed uniformly, and contact (increased contact area, increased number of contacts, etc.) between the first particle and the second particle can be promoted. More specifically, by mixing while crushing the aggregate of the first particles, the nano-level particles are mixed with each other, and contact between the first particles and the second particles (increased contact area, increased number of contacts, etc.) ) Is considered to be promoted. Further, the composite particles of the above item A can be obtained by the particle mixing method.

  In the particle mixing method, the first particles and the second particles are charged into a predetermined mixing device. Aggregates (secondary particles) obtained by agglomerating single particles can be used as the first particles introduced into the mixing apparatus. According to the particle mixing method of the present invention, even if particles that are easily aggregated are used, uniform mixing is possible, and composite particles having excellent characteristics can be obtained. Further, the second particles put into the mixing device may be aggregated particles, single particles, or a state in which these particles coexist.

  The mixing amount (input amount) of the second particles is preferably 0.1 parts by weight to 10 parts by weight, more preferably 0, with respect to 100 parts by weight of the mixing amount (input amount) of the first particles. .2 to 8 parts by weight, more preferably 0.3 to 6 parts by weight. Within such a range, particles having an extremely small particle diameter can be mixed uniformly.

  Other materials may be further added to the mixing apparatus. The substance is not particularly limited, and for example, another particle, a resin material, an additive, or the like can be input.

  Preferably, the mixing apparatus includes a mixing container, and further includes a stirring blade for stirring the mixture and a crushing blade (so-called chopper) for crushing the aggregate (aggregated particles) in the mixing container. ). Preferably, the stirring blade and the crushing blade are each rotated by an independent rotating shaft. According to the mixing method of the present invention, particles having a very small particle diameter can be uniformly mixed by simultaneously operating the stirring blade and the crushing blade.

  As the mixing container, a container having any appropriate shape is used. A cylindrical container is used, more preferably a cylindrical container. The volume of the mixing container is preferably 150% by volume to 1000% by volume, more preferably 150% by volume to 800% by volume, and even more preferably 160% by volume to 600% by volume with respect to the total volume of the mixture. It is. The volume of the mixing container is, for example, 5L to 1500L.

  The agitating blade has a function of prompting the entire mixture to roll within the mixing vessel. The stirring blade can be any suitable shape as long as the mixture can be stirred. Preferably, the stirring blade is attached to a rotating shaft extending in the axial direction of the cylindrical mixing container. The mixing device may include a plurality of stirring blades. The rotation diameter of the stirring blade is preferably 80% or more and less than 100%, more preferably 90% to 99% with respect to the diameter of the mixing vessel.

  The rotation speed of the stirring blade is preferably 50 rpm to 500 rpm, more preferably 100 rpm to 400 rpm. When the rotational speed is represented by a peripheral speed, the peripheral speed is preferably 0.5 m / second to 8 m / second, more preferably 1 m / second to 6 m / second. If it is such a range, uniform mixing can be performed and crushing with a crushing blade can also be performed efficiently. More specifically, when the rotation speed of the stirring blade is less than 50 rpm, or when the peripheral speed is less than 0.5 m / sec, there is a possibility that uniform mixing cannot be performed. In addition, when the rotation speed of the stirring blade exceeds 500 rpm, or when the peripheral speed exceeds 8 m / second, the phenomenon of particle rolling becomes remarkable, and the particles are not efficiently supplied to the crushing blade, so that excellent composite particles are obtained. May not be obtained.

  The said crushing blade | wing has a function which gives a shearing force to the substance which contacted or approached this. The crushing blade may have any suitable shape as long as it exhibits such a function. Preferably, the crushing blade is attached to a rotating shaft that protrudes from the side surface of the mixing container. Preferably, the axis of rotation is directed to the center of the mixing vessel. A plurality of crushing blades may be provided on the rotating shaft, and a plurality of the rotating shafts may be provided on the mixing device. The crushing blade is a blade smaller than the stirring blade. The rotation diameter of the crushing blade can be set to any appropriate diameter depending on the characteristics of the particles to be mixed. The rotation diameter of the crushing blade is preferably 1/15 to 1/4, more preferably 1/10 to 1/5 of the diameter of the mixing vessel.

  The crushing blade preferably rotates at a higher speed than the stirring blade. The rotational speed of the crushing blade is preferably 1000 rpm to 20000 rpm, more preferably 2000 rpm to 10000 rpm, and still more preferably 3000 rpm to 6000 rpm. When the rotational speed is represented by a peripheral speed, the peripheral speed is preferably 15 m / second to 65 m / second, and more preferably 20 m / second to 60 m / second. If it is such a range, crushing by a crushing blade can be performed efficiently, and the crushing of particles can be prevented. More specifically, when the rotational speed of the crushing blade is less than 1000 rpm, or when the peripheral speed is less than 15 m / sec, the aggregate of the first particles cannot be sufficiently crushed, and the desired characteristics are obtained. There exists a possibility that the composite particle which has may not be obtained. Further, when the rotational speed of the crushing blade exceeds 20000 rpm, or when the peripheral speed exceeds 65 m / sec, the first particles themselves may be pulverized. Moreover, when using the crushing blade | wing rotating at high speed, the drive device of a special specification is needed and it is disadvantageous also from a cost surface.

  A commercially available mixing device may be used as the mixing device. Examples of commercially available mixing equipment include product names “Apex Granulator”, “Pro-Share Mixer” manufactured by Taiheiyo Kiko Co., Ltd., product names “Hemisphere Mixer”, “Axial Mixer” manufactured by Sugiyama Heavy Industries, Ltd., and Earth Technica Co., Ltd. The product name “High Speed Mixer”, the product name “Julia Mixer” manufactured by Deoksugaku Kosakusha Co., Ltd., the product name “Ladyge Mixer” manufactured by Matsubo, the product name “Vertical Granulator” manufactured by Paulek, etc. . Moreover, you may use the mixing apparatus as described in Unexamined-Japanese-Patent No. 2008-229461 as said mixing apparatus.

  The mixing time of the particle mixing method can be set to any appropriate time depending on the characteristics of the particles to be mixed. Preferably it is 1 minute-2 hours, More preferably, it is 3 minutes-1 hour, More preferably, it is 5 minutes-30 minutes.

B-1. First Particle Examples of the first particle include organic particles (resin particles), inorganic particles, organic-inorganic composite particles, metal particles, and the like. Among them, particles (for example, organic particles) that are usually composed of a material that easily aggregates are suitable for the particle mixing method of the present invention, and even when using the particles, uniform mixing is possible. Composite particles having excellent properties can be obtained.

  Examples of the organic particles include natural polymer particles and synthetic polymer particles. Specific examples of natural polymer particles include, for example, proteins such as glue, gelatin, casein, and albumin; natural rubbers such as gum arabic and tragacanth; glucosides such as saponin; alginic acid and propylene glycol alginate, and triethanol alginate. Examples thereof include particles composed of alginic acid derivatives such as amine and ammonium alginate; cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and ethylhydroxycellulose. Specific examples of synthetic polymer particles include, for example, phenol resins, furan resins, xylene / formaldehyde resins, ketone / formaldehyde resins, urea resins, melamine resins, aniline resins, alkyd resins, unsaturated polyester resins, epoxy resins, and the like. Curable resin: polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyacrylate, polymethacrylate, polyvinyl chloride, polyvinylidene chloride, fluoroplastic, polyacrylonitrile, polyvinyl ether, polyvinyl ketone, polyether, polycarbonate, thermoplastic polyester, Polyamide, diene plastic, polyurethane plastic, aromatic polyamide, polyphenylene, polyxylylene, polyphenylene oxide, polysulfone, silicon Particles composed of thermoplastic resins such as fat and the like.

  Examples of the inorganic particles include inorganic pigments, inorganic nitrides, clay minerals, and the like. Specific examples of inorganic pigments include, for example, titanium dioxide, zinc white, bengara, chromium oxide, iron black, cobalt blue, alina white, iron oxide yellow, viriadine, fluidized zinc, lithopone, cadmium yellow, vermilion, cadmium red, Examples include yellow lead, molybdate orange, zinc chromate, strontium chromate, white carbon, ultramarine blue, precipitated barium, calcium carbonate, white lead, bitumen, margaret violet, carbon black and the like. Specific examples of the inorganic nitride include silicon nitride, aluminum nitride, boron nitride, titanium nitride, zirconium nitride, tantalum nitride, niobium nitride, and the like. Specific examples of clay minerals include, for example, talc, pyrophyllite, smectite (saponite, hectorite, saconite, stevensite, montmorillonite, beidellite, nontronite, etc.), vermiculite, mica (phlogopite, biotite, chinwald mica, etc.) , Muscovite, paragonite, ceradonite, sea chlorite, etc.), chlorite (clinochlore, chamosite, nimite, penantite, sudowite, dombasite, etc.), brittle mica (clinentite, margarite, etc.), sulite, serpentine (anti Golite, lizardite, chrysotile, amicite, cronstedite, burcherin, greenerite, garnierite, etc.) and kaolin (kaolinite, dickite, nacrite, halloysite, etc.).

  Examples of the organic-inorganic composite particles include particles described in JP 2011-89069 A.

  Examples of the metal particles include platinum, gold, palladium, silver, copper, nickel, chromium, tin, zinc, aluminum, iron, cobalt, rhodium, ruthenium, lead, bismuth, tungsten, titanium, nickel, and the like. Particles.

  The first particle may have a core-shell structure.

  The average primary particle diameter of the first particles is preferably 1 μm or less, more preferably 10 nm to 900 nm, still more preferably 30 nm to 800 nm, particularly preferably 50 nm to 800 nm, and most preferably 50 nm. ~ 700 nm. In the present invention, even particles having such a small particle diameter and large surface energy that are easily aggregated and difficult to be aggregated can be uniformly mixed. In addition, since the particles are mixed with the second particles in a state where the aggregation is appropriately released, composite particles having excellent characteristics can be obtained.

  As described above, the first particles can be subjected to mixing in the form of aggregates. The average particle diameter of the first particle aggregate (aggregate before mixing) is not particularly limited, and is, for example, 1 μm to 15 μm.

B-2. Second particles Examples of the second particles include organic particles (resin particles), inorganic particles, organic-inorganic composite particles, and metal particles. Specific examples of the organic particles, inorganic particles, organic-inorganic composite particles, and metal particles are as described in the above section B-1. The second particle may have a core-shell structure.

  The average primary particle diameter of the second particles is preferably 1 μm or less, more preferably 1 nm to 900 nm, further preferably 3 nm to 800 nm, particularly preferably 5 nm to 800 nm, and most preferably 5 nm. ~ 200 nm.

  The ratio of the average primary particle diameter of the first particles to the average primary particle diameter of the second particles (second particles / first particles) is preferably 0.02 to 0.25, more preferably. Is 0.03-0.2, more preferably 0.04-0.15. Within such a range, composite particles having excellent characteristics can be obtained. Further, according to the particle mixing method of the present invention, even particles having a particle size ratio in such a range can be efficiently mixed, and the composite having a high effect of adding the second particles as a secondary material Particles can be obtained.

C. In one embodiment of composite particles composed of amino resin particles and hydrophobic inorganic oxides, amino resin particles are used as the first particles, and hydrophobic inorganic oxides are used as the second particles. The composite particle A is provided by the particle mixing method. The composite particles A are given hydrophobicity by a hydrophobic inorganic oxide. According to the particle mixing method of the present invention, hydrophobic addition with a hydrophobic inorganic oxide can be sufficiently performed even when amino resin particles having a very small particle diameter are used. Moreover, according to the particle mixing method of the present invention, the degree of hydrophobicity can be adjusted in correlation with the mixing time, and the degree of hydrophobicity can be increased by extending the mixing time.

  The composite particle A can be suitably used as an additive for toner. The toner additive containing the composite particles A can improve the chargeability of positively charged toner and negatively chargeable toner.

  In the particle mixing method for producing the composite particle A, the amount of the hydrophobic inorganic oxide mixed (input amount) is preferably 0.1 with respect to 100 parts by weight of the amino resin particle mixed amount (input amount). Parts by weight to 10 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight, and still more preferably 0.5 parts by weight to 5 parts by weight. Within such a range, composite particles A having a high degree of hydrophobicity can be obtained (for example, composite particles A having a degree of hydrophobicity of 30% or more, preferably 30% to 70%). Such composite particles A are excellent in fluidity, handling properties, mixing properties, and the like.

C-1. Amino resin particles The average primary particle diameter of the amino resin particles is preferably 1 μm or less, more preferably 780 nm or less, further preferably 20 nm to 780 nm, further preferably 30 nm to 600 nm, Preferably it is 30 nm-500 nm, Most preferably, it is 30 nm-200 nm. Within such a range, it is possible to obtain a toner additive that does not easily fall off from the surface of the toner particles.

  At least the surface layer of the amino resin particles is formed of an amino resin. The amino resin particles may be formed of only an amino resin, or may have a core-shell structure in which a shell layer is formed of an amino resin.

  As said amino resin, the condensate of an amino compound and formaldehyde is mentioned, for example. As an amino compound, urea, thiourea, a polyfunctional amino compound etc. are mentioned, for example. Of these, polyfunctional amino compounds are preferably used, and polyfunctional amino compounds having a triazine-returned structure are more preferably used. Examples of the polyfunctional amino compound having a triazine ring structure include melamine; an amino compound represented by the general formula (1); a diaminotriazine compound represented by the general formula (2) or the general formula (3); And guanamine compounds such as cyclohexanecarboguanamine, cyclohexenecarboguanamine, acetoguanamine, norbornenecarboguanamine, and spiroguanamine. Among these, melamine and benzoguanamine are preferable. Only 1 type may be used for an amino compound and 2 or more types may be used for it.

Formula (1), R ^1, identical or different, represent an alkyl group which may be a hydrogen atom or a substituent, at least one of R ¹ is an alkyl group which may have a substituent. In general formula (1), R ¹ is preferably a hydrogen atom or a hydroxyalkyl group.

In General Formula (2), R ² is the same or different, and is a hydrocarbon group having 1 to 2 carbon atoms (—CH ₂ —, —CH ₂ CH ₂ —, —, which is a linear structure or a structure having a side chain. CH _(CH 3) -) is.

In general formula (3), R ³ is any one of a linear structure, a structure having a side chain, a structure having an aromatic ring which may have a substituent, and a structure having an alicyclic ring which may have a substituent. It is a C1-C8 hydrocarbon group which is. The structure having an aromatic ring or the structure having an alicyclic ring may be a structure having a side chain.

  In one embodiment, 10% to 100% by weight of the amino compound is a guanamine compound. The content ratio of the guanamine compound in the amino compound is preferably 20% by weight to 100% by weight, more preferably 40% by weight to 100% by weight, and further preferably 50% by weight to 100% by weight. More preferably 60% to 100% by weight, still more preferably 70% to 100% by weight, still more preferably 80% to 100% by weight, and still more preferably 90% to 100% by weight. More preferably, it is 95 to 100% by weight, and most preferably 100% by weight. Within such a range, it is possible to obtain a toner additive capable of preventing fogging and image density reduction.

  When the amino resin particles are formed only from an amino resin, the resin particles can be obtained by reacting the amino compound and formaldehyde (addition condensation reaction) by any appropriate method. Examples of a method for producing resin particles formed from an amino resin include, for example, JP 2000-256432 A, JP 2002-293854 A, JP 2002-293855 A, JP 2002-293856 A, and the like. JP 2002-293857, JP 2003-55422, JP 2003-82049, JP 2003-138823, JP 2003-147039, JP 2003-171432, JP 2003. And the production methods described in JP-A-176330, JP-A-2005-97575, JP-A-2007-186716, JP-A-2008-101040, and the like. Specifically, for example, the above-mentioned amino compound (preferably a polyfunctional amino compound) and formaldehyde are preferably subjected to an addition condensation reaction in a basic aqueous medium to form a condensate oligomer, and the condensate oligomer is dissolved. Alternatively, resin particles formed from an amino resin having a crosslinked structure can be produced by mixing and curing an acid catalyst such as dodecylbenzenesulfonic acid or sulfuric acid in an aqueous medium to be dispersed. It is preferable that both the step of generating the condensate oligomer and the step of obtaining the amino resin particles having a crosslinked structure are performed in a state of being heated at a temperature of 50 to 100 ° C. In order to control the particle diameter of the amino resin-crosslinked particles, the step of forming the amino resin particles having a crosslinked structure is preferably performed in the presence of a surfactant. In addition, after the said hardening, you may obtain amino-type resin particles through processes, such as the aggregation process which aggregates particle | grains by arbitrary appropriate methods, a solid-liquid separation process, a particle | grain drying process, a grinding | pulverization process.

  When the amino resin particles have a core-shell structure, for example, the resin particles are obtained by dispersing particles that form a core layer in the basic aqueous medium, and the amino compound and formaldehyde in the aqueous medium as described above. And a condensate oligomer can be obtained by curing the condensate oligomer as described above.

  When the amino resin particles have a core-shell structure, the average particle size of the particles serving as the core layer is preferably 10 nm to 700 nm, more preferably 20 nm to 400 nm, and still more preferably 30 nm to 150 nm.

  When the amino resin particles have a core-shell structure, the total thickness of the shell layer is preferably 10% or more, more preferably 15% to 500%, with respect to the average particle diameter of the particles serving as the core layer. More preferably, it is 20% to 400%, and particularly preferably 30% to 350%.

  Any appropriate material can be selected as a material for forming the core layer. An organic material or an inorganic material may be used as a material constituting the core layer particles.

  Examples of the organic material forming the core layer include vinyl polymer fine particles. As the vinyl polymer fine particles, polymer fine particles obtained by using any appropriate polymerizable monomer and any appropriate crosslinkable monomer as required can be adopted.

  The polymerizable monomer may be a compound containing at least one ethylenically unsaturated group in the molecule. Specifically, for example, monomers having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate; methoxypolyethylene glycol (meth) acrylate Monomers having a polyethylene glycol component such as, butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, isoamyl acrylate, lauryl (meth) acrylate, benzyl methacrylate, methacryl Alkyl (meth) acrylates such as acid tetrahydrofurfuryl; trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, pentanefluoropropyl (meth) acrylate, octafluoroamyl (meth) acrylate, etc. Fluorine atom-containing (meth) acrylates; aromatic vinyl compounds such as styrene, α-methylstyrene, vinyl tolman, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-ethylstyrene; glycidyl (Meth) acrylate; (meth) acrylic acid; (meth) acrylamide; (meth) acrylonitrile; The said polymerizable monomer may be used independently and may use 2 or more types together.

  Examples of the crosslinkable monomer include divinylbenzene, (poly) ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meta) ) Acrylate, tetramethylol methane tri (meth) acrylate, tetramethylolpropane tetra (meth) acrylate, dipentaerythritol hexaacrylate, diallyl phthalate and isomers thereof, triallyl isocyanurate and derivatives thereof, and the like. The said crosslinkable monomer may be used independently and may use 2 or more types together.

  Examples of the inorganic material forming the core layer include silica fine particles such as silicon alkoxide hydrolyzed condensate fine particles and sodium silicate hydrolyzed condensate fine particles.

  An organic-inorganic composite material may be used as a material for forming the core layer. Typically, the organic-inorganic composite material includes organic-inorganic composite fine particles containing polysiloxane as an inorganic component and a vinyl polymer as an organic component. The polysiloxane as the inorganic component is preferably a polysiloxane skeleton obtained by hydrolysis and condensation of an inorganic compound raw material containing a silicon compound having a (meth) acryloxy group.

Any appropriate form can be adopted as the form of the organic-inorganic composite fine particles. Specifically, for example,
a) A form in which polysiloxane, which is an inorganic component, is fine particles and dispersed in a vinyl polymer that is an organic component,
b) Form of core-shell structure in which polysiloxane as an inorganic component is a fine core particle, and a shell made of a vinyl polymer as an organic component is formed on the surface of the core particle;
c) a form of a core-shell structure in which a vinyl polymer as an organic component is a fine core particle, and a shell made of polysiloxane as an inorganic component is formed on the surface of the core particle;
d) A form in which polysiloxane as an inorganic component and vinyl polymer as an organic component are combined or mixed at a molecular level,
e) The form of the core-shell structure in which the fine particles in the state of d) become core particles, and a shell made of polysiloxane as an inorganic component is formed on the surface of the core particles.
Etc.

  Preferable methods for producing the organic / inorganic composite fine particles include, for example, methods described in JP-A-8-81561 and JP-A-2003-183327.

  The shape of the organic-inorganic composite fine particles is not particularly limited, and specifically, for example, a spherical shape, a needle shape, a plate shape, a scale shape, a pulverized shape, an uneven shape, an eyebrows shape, a candy sugar shape, etc. The shape can be mentioned.

C-2. Hydrophobic inorganic oxide As the hydrophobic inorganic oxide, hydrophobic silica, hydrophobic titania, hydrophobic alumina, hydrophobic zirconia, hydrophobic zinc oxide, hydrophobic tin oxide or hydrophobic tantalum oxide is preferably used. Only one type of hydrophobic inorganic oxide may be used, or two or more types may be used. The hydrophobic inorganic oxide can be obtained, for example, by hydrophobizing a hydrophilic inorganic oxide by any appropriate hydrophobizing treatment. Examples of the hydrophobizing treatment include a method of treating with a hydrophobizing agent such as hexamethyldisilazane (HMDS), dimethyldichlorosilane, silicone oil, methyltriethoxysilane. Moreover, positive chargeability can also be added to an inorganic oxide by this hydrophobic treatment.

A commercially available product may be used as the hydrophobic inorganic oxide. Examples of commercially available products include “Aerosil RY200”, “Aerosil RX200”, “Aerosil RX300”, “Aerosil R972”, “AeroXide TiO ₂ T805”, “AeroXide Alu C805” manufactured by Aerosil Japan. .

  The hydrophobicity of the hydrophobic inorganic oxide is preferably 45% or more, more preferably 50% or more, still more preferably 60% or more, and particularly preferably 60% or more and less than 100%. When the hydrophobicity of the hydrophobic inorganic oxide is in such a range, a toner additive capable of improving the chargeability of the toner can be obtained for a negatively chargeable toner. The degree of hydrophobicity can be measured by a methanol titration method. That is, in this specification, “hydrophobic degree” means that 0.2 g of hydrophobic inorganic oxide is suspended on the surface of 50 ml of water, and methanol is added little by little while gently stirring the water ( This refers to the percentage of methanol with respect to water + methanol based on the amount of methanol used when all the powder on the water surface is submerged in water. A more detailed measurement method for the degree of hydrophobicity will be described later.

  The average particle diameter of the hydrophobic inorganic oxide is 80 nm or less, preferably 50 nm or less, more preferably 5 nm to 40 nm. When the average particle diameter of the hydrophobic inorganic oxide is in such a range, a toner additive capable of improving the chargeability of the toner can be obtained for a negatively chargeable toner.

  The hydrophobic inorganic oxide is preferably a hydrophobic inorganic oxide (so-called hydrophobic fumed inorganic oxide) obtained by a gas phase method. If a hydrophobic fumed inorganic oxide having a small particle size and a uniform particle size is used, the effect of the present invention becomes remarkable.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.

[Average secondary particle size]
The average particle diameter of the aggregates of the first particles (that is, the average secondary particle diameter) and the average secondary particle diameter of the composite particles are measured by a dry particle size distribution measuring device (manufactured by Shimadzu Corporation; trade name “Shimadzu Laser Diffraction Particle Size Distribution”). Measurement was performed under the following measurement conditions using a measurement apparatus SALD-2300 "" Cyclone dry measurement unit DS5 ").
<Measurement conditions>
Dispersion pressure: 0.5 MPa
Use cup: Standard

[Average primary particle size]
SEM photograph (magnification: 100,000 times) in the imaging range where the total number of single particles is about 200, the diameter (particle (cross section) of 100 single particles randomly selected from the single particles taken ) Was measured with a caliper, and the arithmetic average was taken as the average primary particle size.

[Surface element analysis of composite particles and SEM image element mapping]
Using ultra high resolution scanning electron microscope (manufactured by Hitachi High-Technologies Corporation; trade name “S-4800”, acceleration voltage: 10 kV, WD = 8 mm), surface element analysis and SEM image element mapping of composite particles The existence state of the second particles attached to the surface of the first particles was confirmed.

(Measurement of hydrophobicity)
The hydrophobicity of the composite particles was measured by the following method.
In a 200 ml glass beaker with a stirrer placed at the bottom, 50 ml of deionized water was added, and 0.2 g of sample particles were floated on the water surface, and then the stirrer was gently rotated for 5 minutes. Thereafter, the tip of the burette was submerged in the water in the beaker, and methanol was gradually introduced from the burette. 1 ml of methanol was introduced at intervals of 3 minutes. Methanol was introduced until the total amount of sample particles on the water surface was completely submerged (no sample particles floating on the water surface), and the amount of methanol introduced when the sample particles completely submerged in water (ml ) And the degree of hydrophobicity was determined based on the following formula.
Hydrophobic degree (%) = 100 × (methanol introduction amount ml / (deionized water amount ml + methanol introduction amount ml))

[Example 1]
The first particle (amino resin particles, Nippon Shokubai Co., Ltd.) was added to a mixing device (trade name “Apex Granulator APG-20V type” manufactured by Taiheiyo Kiko Co., Ltd.) equipped with a stirring blade and a crushing blade in a 20 L mixing container. Product name “Eposter S”, average primary particle size: 200 nm, average particle size of aggregate (average secondary particle size of first particles): 3.1 μm, and second particles (hydrophobic silica particles) 10 g of a product name “Aerosil R-972” manufactured by Nippon Aerosil Co., Ltd., average primary particle size: 16 nm) was added. Next, the rotational speed of the stirring blade was 200 rpm (circumferential speed: 3.2 m / second), the rotational speed of the crushing blade was 6000 rpm (circumferential speed: 34.5 m / second), and the mixing time was 30 minutes. Mixed.
As a result of mixing as described above, composite particles having an average secondary particle diameter of 2.1 μm were obtained.
Further, the degree of hydrophobicity was measured for the composite particles after 3 minutes, 5 minutes, 10 minutes, 20 minutes and 30 minutes had elapsed since the start of mixing. The results are shown in Table 1.
Further, surface element analysis and SEM image element mapping of the composite particles were performed. The result is shown in FIG.

[Example 2]
The first particle (silica particles, product name made by Nippon Shokubai Co., Ltd.) is added to a mixing device (product name “High Speed Mixer FS-25”, made by Earth Technica Co., Ltd.) having a stirring blade and a crushing blade in a 25 L mixing container. “Sea Poster KE-S100”, average primary particle size: 850 nm, average particle size of aggregate (average secondary particle size of first particles): 2.4 μm, and second particles (hydrophobic silica particles) 17.5 g of trade name “Aerosil R-972” manufactured by Nippon Aerosil Co., Ltd., average primary particle size: 16 nm) was added. Next, the rotational speed of the stirring blade was 350 rpm (circumferential speed: 7.3 m / second), the rotational speed of the crushing blade was 3500 rpm (circumferential speed: 21.1 m / second), and the mixing time was 30 minutes. Mixed.
As a result of mixing as described above, composite particles having an average secondary particle diameter of 1.5 μm were obtained.
Further, the degree of hydrophobicity was measured for the composite particles after 3 minutes, 5 minutes, 10 minutes, 20 minutes and 30 minutes had elapsed since the start of mixing. The results are shown in Table 1.

[Example 3]
As the first particles, polymethyl methacrylate-based crosslinked particles (average primary particle size: 55 nm, agglomerates) obtained by pulverizing Nippon Shokubai Co., Ltd. trade name “Eposter MX050W” (water-dispersed emulsion) with a spray dryer. Average particle diameter (average secondary particle diameter of the first particles): 8.7 μm).
In the mixing apparatus used in Example 1, 600 g of the first particles and 0.72 g of second particles (hydrophobic silica particles, trade name “Aerosil RY200” manufactured by Nippon Aerosil Co., Ltd., average primary particle size: 12 nm) and Was introduced. Next, the rotational speed of the stirring blade was 200 rpm (circumferential speed: 3.2 m / second), the rotational speed of the crushing blade was 6000 rpm (circumferential speed: 34.5 m / second), and the mixing time was 30 minutes. Mixed.
As a result of mixing as described above, composite particles having an average secondary particle diameter of 3.0 μm were obtained.

[Comparative Example 1]
In a mixing apparatus (product name “Supermixer 20B type”, manufactured by Kawata Corporation) having only a stirring blade in a 20 L mixing container, first particles (amino resin particles, product name “Eposter S” manufactured by Nippon Shokubai Co., Ltd.), Average primary particle size: 200 nm, average particle size of aggregates (average secondary particle size of first particles): 3.1 μm, and second particles (hydrophobic silica particles, trade name of Nippon Aerosil Co., Ltd.) Aerosil R-972 ") 10g. Subsequently, the above-mentioned particles were mixed by setting the rotation speed of the stirring blade to 1200 rpm and the mixing time to 30 minutes.
As a result of mixing as described above, composite particles having an average secondary particle diameter of 2.9 μm were obtained.
Further, the degree of hydrophobicity was measured for the composite particles after 3 minutes, 5 minutes, 10 minutes, 20 minutes and 30 minutes had elapsed since the start of mixing. The results are shown in Table 1.
Further, surface element analysis and SEM image element mapping of the composite particles were performed. The result is shown in FIG.

  As is apparent from Table 1, in the examples, composite particles having a high degree of hydrophobicity were obtained. In addition, as the mixing time was increased, the degree of hydrophobicity increased. On the other hand, in the comparative example, even when the mixing time was increased, the degree of hydrophobicity did not increase, and composite particles having a high degree of hydrophobicity were not obtained. By using a mixing device equipped with a stirring blade and a crushing blade and mixing the agglomerates of the first particles while crushing, it becomes a mixture of nano-level particles, and the contact between the first particles and the second particles Is considered to be promoted. For this reason, it is considered that the number of second particles adhering to the first particles increases as the mixing time increases, and composite particles having excellent characteristics are obtained. Further, in the evaluation of surface elemental analysis and SEM image element mapping on the surface of the composite particle, in Example 1 (FIG. 1 (a)), it is derived from the second particle compared to Comparative Example 1 (FIG. 1 (b)). From the fact that a large amount of Si is observed, it can be seen that the composite particles of the present invention are formed by adhering a large amount of second particles.

[Reference Example 1]
The first particles were stirred in the same manner as in Example 1 without introducing the second particles. Table 2 shows the degree of hydrophobicity of the first particles after stirring.
Further, the mixing operation was performed in the same manner as in Example 1 except that the mixing amount of the second particles was changed to the amount shown in Table 2. Table 2 shows the degree of hydrophobicity of the obtained composite particles.

[Reference Example 2]
(Preparation of paint containing composite particles obtained in Example 1)
An epoxy resin (trade name “Celoxite 2021P” manufactured by Daicel Corporation) is used as a binder resin, 1.6 parts by weight of the epoxy resin, and a curing agent (trade name “Sun Aid SI80L” manufactured by Sanshin Chemical Co., Ltd.) 0.0016 weight Part and a resin solution (resin concentration 20% by weight) containing 6.4 parts by weight of a methyl ethyl ketone solution.
In a 20 ml sample bottle, 8 parts by weight of the above resin solution and 6 parts by weight of the composite particles obtained in Example 1 are placed and mixed using Awatori Nertaro (Sinky Corp.) (kneading conditions 150 rpm-3 minutes). The defoaming conditions were 1500 rpm-2 minutes), and a coating material was prepared.
The obtained paint was applied to a glass plate using a 4 mil applicator (clearance: 100 μm) and dried at room temperature for 1 hour. Next, the coating layer was cured by heating (100 ° C., 20 minutes) to obtain a coating film.
When preparing the paint, the wettability of the composite particles to the resin solution was very good.
Moreover, the obtained coating film was in a uniform matte state as shown in FIG.
Further, when the 60 ° gloss of the obtained coating film was measured with a gloss meter (trade name “Reform Gloss Meter VG-2000” manufactured by Nippon Denshoku Industries Co., Ltd.), the 60 ° gloss was 5.2.

[Reference Example 3]
(Preparation of paint containing composite particles obtained in Comparative Example 1)
A coating film was obtained in the same manner as in Reference Example 2, except that the composite particles obtained in Comparative Example 1 were used in place of the composite particles obtained in Example 1.
When preparing the paint, it took time until the composite particles were wetted with the resin solution.
Moreover, although the obtained coating film was in a uniform matte state, as shown in FIG.
Furthermore, when the 60 ° gloss of the obtained coating film was measured with a gloss meter (trade name “Reform Gloss Meter VG-2000” manufactured by Nippon Denshoku Industries Co., Ltd.), the 60 ° gloss was 17.1.

  From the coating film state and the 60 ° gloss value in Reference Example 2 and Reference Example 3, it can be seen that the composite particles of the present invention hardly aggregate even with a weak mixing / dispersing force.

Claims (7)

A composite particle obtained by dry-mixing an aggregate of first particles having an average primary particle diameter of 1 μm or less and second particles having an average primary particle diameter of 1 μm or less,
During the dry mixing, the stirring of the first particles and the second particles and the crushing of the aggregates of the first particles are performed simultaneously,
The ratio of the average primary particle size of the first particles to the average primary particle size of the second particles (second particle / first particle) is 0.02 to 0.25.
Composite particles.   2. The composite particle according to claim 1, wherein an average secondary particle diameter of the composite particle is 80% or less with respect to an average particle diameter of the aggregate of the first particles.   The composite particles according to claim 1 or 2, wherein the mixing amount of the second particles is 0.1 to 10 parts by weight with respect to 100 parts by weight of the mixing amount of the first particles. A method of mixing first particles having an average primary particle diameter of 1 μm or less and second particles having an average primary particle diameter of 1 μm or less,
Stirring the first particles and the second particles while crushing the aggregates of the first particles;
Particle mixing method.   The particle mixing method according to claim 4, wherein a mixing device including a stirring blade and a crushing blade is used.   The particle mixing method according to claim 4 or 5, wherein the input amount of the second particles is 0.1 to 10 parts by weight with respect to 100 parts by weight of the input amount of the first particles.   The ratio (second particle / first particle) between the average primary particle size of the first particles and the average primary particle size of the second particles is 0.02 to 0.25. The composite particle according to any one of 4 to 6.