JP2010266804A - External additive of electrophotographic toner, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica fine particle as an external additive for preventing burial in electrophotographic toner resin. <P>SOLUTION: This external additive of the electrophotographic toner is a fine particle having a core shell structure having silica compound in a shell layer, and the specific gravity is 1.8 or lower. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hybrid fine particle capable of greatly reducing the embedding in a toner resin when used as an external additive for an electrophotographic toner.

  In electrophotographic toner, silica fine particles are mainly used as an external additive. These silica fine particles adhere to the surface of the toner and exhibit effects such as improvement in toner fluidity, charging efficiency, and transferability. However, recent toners tend to reduce the amount of heat applied when fixing the toner due to the reduction in power consumption, and thus the softening point of the toner resin is lowered. For this reason, there are many problems that silica fine particles added as an external additive are buried in the toner resin. When an external additive such as silica fine particles is embedded in the toner resin, effects such as improvement in toner fluidity, charging efficiency, and transferability are reduced.

  Therefore, a method of adding external additives having different particle sizes (for example, see Patent Document 1) and a method of modifying the surface of silica with a specific group (for example, see Patent Document 2) are known. However, although these methods can prevent the burying of external additives to some extent, they cannot be completely prevented, and further improvements have been required.

JP-A 64-68765 JP 2007-171713 A

  Accordingly, the problem to be solved by the present invention is to provide silica fine particles as an external additive that can be prevented from being embedded in an electrophotographic toner resin.

  Accordingly, the present inventors have intensively studied and found an external additive capable of preventing the burying in the toner resin for electrophotography, leading to the present invention. That is, the present invention is an external additive for an electrophotographic toner, which is a fine particle having a core-shell structure having a silica compound in an outer shell layer and having a specific gravity of 1.8 or less.

  The external additive for an electrophotographic toner using the silica fine particles of the present invention can prevent burying in an electrophotographic toner resin.

4 is a photograph showing a state where fine particles 3 of Example 3 are attached to the surface of polymer beads. 4 is a photograph showing a state in which wet silica fine particles of Comparative Example 1 are attached to the surface of polymer beads.

  The external additive for the electrophotographic toner of the present invention is a fine particle having a silica compound in the outer shell layer and a specific gravity of 1.8 or less. When all of the fine particles are made of a silica compound, the specific gravity of the fine particles is not lower than 1.8 because the specific gravity of silica is around 2. Therefore, the fine particles have a core-shell structure, and the core (inner shell) portion needs to be a substance having a light specific gravity. Substances with low specific gravity include, for example, organic matter and air, and metal oxides with high specific gravity such as aluminum oxide, titanium oxide, zinc oxide, etc., are porous and contain air. The specific gravity will be lighter. However, hollow fine particles in which voids are created in the particles and the inner shell part is made into air, and fine particles whose inner shell part is porous are time-consuming and expensive to manufacture, and mass production is difficult, If the shell portion (outer shell) is thin, it may collapse due to collision with the toner resin, and therefore the inner shell portion is preferably organic.

  The organic substance forming the inner shell of the hybrid fine particles that is the external additive of the electrophotographic toner of the present invention may be any material as long as it is a fine particle organic substance. For example, polyethylene, polypropylene, polystyrene, polyacrylate , Synthetic resins such as nylon, phenolic resin, epoxy resin, urethane resin, and urea resin; and natural polymers such as cellulose, chitin, and chitosan. When these materials are in a large form, they may be made into fine particles by pulverization, granulation or the like, but in the case of synthetic resins, they may be made into fine particles at the production stage. Examples of the method for producing fine particles include emulsion polymerization. The fine particles produced by emulsion polymerization have an almost spherical shape, and can be produced freely from small to large particle sizes depending on the reaction conditions, and the obtained fine particles have the advantage of very little variation. . That is, when produced by emulsion polymerization, spherical fine particles having a uniform particle size can be easily obtained. As an external additive for an electrophotographic toner, since the particle size is preferably uniform, a synthetic resin obtained by emulsion polymerization is preferable as an organic material used as a raw material of the hybrid fine particles of the present invention.

  As a method for obtaining fine particles by emulsion polymerization, any method may be used as long as it is a known method for emulsion polymerization. For example, monomers such as ethylene, propylene, styrene, and acrylate are mixed with water and a surfactant ( What is necessary is just to emulsify with an emulsifier and polymerize with a polymerization initiator. Since the size and particle size distribution of the synthetic resin particles obtained are determined by conditions such as monomer type, monomer concentration, reaction temperature, emulsifier concentration, initiator concentration, etc., these conditions are specified when the particle size is specified. The emulsion polymerization may be carried out by appropriately adjusting the above.

Specific emulsions obtained by the above emulsion polymerization include, for example, urethane emulsion, acrylate emulsion, styrene emulsion, vinyl acetate emulsion, SBR (styrene / butadiene) emulsion, ABS (acrylonitrile / butadiene / styrene) emulsion. , BR (butadiene) emulsion, IR (isoprene) emulsion, NBR (acrylonitrile / butadiene) emulsion, or a mixture thereof.
Examples of the urethane emulsion include polyether polyol, polyester polyol, and polycarbonate polyol.

  Examples of the acrylate emulsion include (meth) acrylic acid (ester) alone, (meth) acrylic acid (ester) / styrene, (meth) acrylic acid (ester) / vinyl acetate, (meth) acrylic acid (ester) / Acrylonitrile, (meth) acrylic acid (ester) / butadiene, (meth) acrylic acid (ester) / vinylidene chloride, (meth) acrylic acid (ester) / allylamine, (meth) acrylic acid (ester) / vinylpyridine, (meth ) Acrylic acid (ester) / alkylolamide, (meth) acrylic acid (ester) / N, N-dimethylaminoethyl ester, (meth) acrylic acid (ester) / N, N-diethylaminoethyl vinyl ether, cyclohexyl methacrylate, Epoxy-modified, urethane-modified, etc. Compounds, and the like.

  Examples of the styrene emulsion include styrene alone, styrene / acrylonitrile, styrene / butadiene, styrene / fumaronitrile, styrene / maleonitrile, styrene / cyanoacrylate, styrene / phenylvinyl acetate, styrene / chloromethylstyrene, styrene / Polymers such as dichlorostyrene, styrene / vinyl carbazole, styrene / N, N-diphenylacrylamide, styrene / methyl styrene, acrylonitrile / butadiene / styrene, styrene / acrylonitrile / methyl styrene, styrene / acrylonitrile / vinyl carbazole, styrene / maleic acid, etc. Is mentioned.

Examples of vinyl acetate emulsions include vinyl acetate alone, vinyl acetate / styrene, vinyl acetate / vinyl chloride, vinyl acetate / acrylonitrile, vinyl acetate / maleic acid (ester), vinyl acetate / fumaric acid (ester), vinyl acetate / Polymers such as ethylene, vinyl acetate / propylene, vinyl acetate / isobutylene, vinyl acetate / vinylidene chloride, vinyl acetate / cyclopentadiene, vinyl acetate / crotonic acid, vinyl acetate / acrolein, vinyl acetate / alkyl vinyl ether and the like can be mentioned.
Among the emulsions listed above, an acrylate emulsion and a styrene emulsion are preferred because a desired particle size can be easily obtained.

  Any emulsifier that can be used in the above emulsion polymerization can be used as long as it is a known surfactant, and examples thereof include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant. .

  Examples of the anionic surfactant include higher fatty acid salts, higher alcohol sulfate esters, sulfurized olefin salts, higher alkyl sulfonates, α-olefin sulfonates, sulfated fatty acid salts, sulfonated fatty acid salts, and phosphate ester salts. , Fatty acid ester sulfate ester salt, glyceride sulfate ester salt, fatty acid ester sulfonate salt, α-sulfo fatty acid methyl ester salt, polyoxyalkylene alkyl ether sulfate ester salt, polyoxyalkylene alkyl phenyl ether sulfate ester salt, polyoxyalkylene Alkyl ether carboxylate, acylated peptide, sulfate ester salt of fatty acid alkanolamide or its alkylene oxide adduct, sulfosuccinate ester, alkylbenzene sulfonate, alkyl naphthalene sulfonate Salt, alkylbenzimidazole sulfonate, polyoxyalkylene sulfosuccinate, N-acyl-N-methyltaurine salt, N-acyl glutamic acid or salt thereof, acyloxyethane sulfonate, alkoxyethane sulfonate, N-acyl -Β-alanine or salt thereof, N-acyl-N-carboxyethyltaurine or salt thereof, N-acyl-N-carboxymethylglycine or salt thereof, acyl lactate, N-acyl sarcosine salt, and alkyl or alkenylaminocarboxy One type or a mixture of two or more types such as methyl sulfate can be mentioned.

  Nonionic surfactants include, for example, polyoxyalkylene alkyl ether, polyoxyalkylene alkenyl ether, polyoxyethylene polyoxypropylene alkyl ether (addition form of ethylene oxide and propylene oxide may be random or block) .), Polyethylene glycol propylene oxide adduct, polypropylene glycol ethylene oxide adduct, glycerin fatty acid ester or ethylene oxide adduct thereof, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, alkyl polyglucoside, fatty acid monoethanolamide or ethylene oxide thereof Adduct, fatty acid-N-methylmonoethanolamide or its ethylene oxide adduct, fatty acid dietano Ruamido or an ethylene oxide adduct, a sucrose fatty acid ester, alkyl (poly) glycerol ether, polyglycerol fatty acid esters, polyethylene glycol fatty acid esters, fatty acid methyl ester ethoxylates, N- long chain alkyl dimethyl amine oxides, and the like.

Examples of the cationic surfactant include alkyl (alkenyl) trimethyl ammonium salt, dialkyl (alkenyl) dimethyl ammonium salt, alkyl (alkenyl) quaternary ammonium salt, mono- or dialkyl (alkenyl) containing ether group, ester group or amide group. ) Quaternary ammonium salt, alkyl (alkenyl) pyridinium salt, alkyl (alkenyl) dimethylbenzyl ammonium salt, alkyl (alkenyl) isoquinolinium salt, dialkyl (alkenyl) morphonium salt, polyoxyethylene alkyl (alkenyl) amine, alkyl (alkenyl) amine Examples thereof include salts, polyamine fatty acid derivatives, amyl alcohol fatty acid derivatives, benzalkonium chloride, and benzethonium chloride.
Examples of the amphoteric surfactant include carboxybetaine, sulfobetaine, phosphobetaine, amide amino acid, imidazolinium betaine surfactant and the like.
Among the above surfactants, anionic surfactants, nonionic surfactants and cationic surfactants are preferable.

  In addition, a reactive surfactant having a double bond in the molecule can also be used. Examples of such reactive surfactant include, for example, JP-A-58-203960 and JP-A-61-222530. JP-A 63-023725, JP-A 63-091130, JP-A 04-256429, JP-A 06-239908, JP-A 08-041113, JP-A 2002-301353. Etc. are mentioned.

  When the emulsion is produced, the above-mentioned emulsifier can be arbitrarily used within the range of the usual use amount, but is preferably 0.1 to 20% by mass, more preferably 0.2 to 0.2% with respect to the raw material monomer. 10 mass%, More preferably, 0.5-8 mass% can be added and used.

  When producing the hybrid fine particles of the present invention, the organic fine particles, which are the inner shell, are dispersed in water or a mixture of water and an organic solvent, and then the silica compound that forms the outer shell layer is coated. Therefore, the fine particles obtained by the emulsion polymerization can be used for the next reaction as they are. On the other hand, the fine compound obtained by pulverization or the like can be dispersed in water as long as it is dispersed in water, and if it is not dispersed in water, it can be dispersed in water using a dispersant or the like. What is necessary is just to disperse. As the dispersant that can be used, the surfactants listed above as emulsifiers can be used.

  In order to form the silica compound layer in the outer shell layer, a specific silicon compound may be reacted with the fine particles in the inner shell. Examples of such silicon compounds include tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; monomethyltrimethoxysilane, dimethyldimethoxysilane, trimethylmonomethoxysilane, monoethyltrimethoxysilane, Alkyl alkoxysilane compounds such as diethyldimethoxysilane and triethylmonomethoxysilane; phenylalkoxysilane compounds such as phenyltrimethoxysilane, diphenyldimethoxysilane and triphenylmonomethoxysilane; aminopropyltrimethoxysilane and (aminoethyl) aminopropyldimethoxysilane Aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxy Amino group-containing silane compounds such as silane and aminobutyltriethoxysilane; Vinyl group-containing silane compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; 3-glycidoxypropylmethylethoxysilane, 3-glycidoxypropyltriethoxy Glycidyl group-containing silane compounds such as silane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxy (Meth) acrylic group-containing silane compounds such as propyltrimethoxysilane; chlorosilane compounds such as monochlorosilane, dichlorosilane, and trichlorosilane; silicates such as sodium silicate and potassium silicate.

  In order to make the silicon compound react with the organic fine particles in the inner shell, for example, the organic fine particles as the inner shell are dispersed in 0.1 to 30% by mass in water or a mixture of water and an organic solvent, and 0 to 50 A silicon compound is added at a temperature, and the reaction is carried out by stirring at the same temperature for 1 to 48 hours. Thereafter, the temperature of the system may be raised to 60 to 80 ° C. and aging may be performed for 1 to 20 hours. Catalysts that can be used include strong acids such as sulfuric acid and toluenesulfonic acid; metal halides such as titanium tetrachloride, hafnium chloride, zirconium chloride, aluminum chloride, gallium chloride, indium chloride, iron chloride, tin chloride, boron fluoride; water Sodium hydroxide, potassium hydroxide, sodium methylate, alkali metal or alkaline earth metal hydroxides or carbonates such as sodium carbonate; metal oxides such as aluminum oxide, calcium oxide, barium oxide, sodium oxide And organic metal compounds such as tetraisopropyl titanate, dibutyltin dichloride, and dibutyltin oxide.

  The outer shell layer obtained by reacting the silicon compound with organic fine particles becomes a silica layer in the case of a tetraalkoxysilane compound, a chlorosilane compound, or a silicate, and an alkyl-modified silicon compound or an amino-modified silicon compound is modified. It becomes a silica layer (for example, it becomes an alkyl-modified silica in the case of an alkylalkoxysilane compound, and an amino group-modified silica in the case of an amino group-containing silane compound).

  The silicon compound may be reacted in an arbitrary amount with respect to the organic fine particles in the inner shell. Preferably, the silicon atom of the silicon compound is 0.5 to 30 parts by mass with respect to 100 parts by mass of the organic fine particles in the inner shell. More preferably, the reaction may be performed so as to be 1 to 20 parts by mass, and more preferably 0.8 to 10 parts by mass. If the amount of the silicon compound is too small, the outer shell layer may not be formed well, and if the amount of the silicon compound is too large, the particles may be fused or aggregated.

  Here, the fine particles obtained by reacting the silicon compound with the organic fine particles as described above may contain impurities derived from raw materials and catalysts. If these impurities are contained in the toner, the charge amount may be low or the charge amount may be difficult to control. Therefore, it is preferable to limit the content of these impurities in the hybrid fine particles of the present invention. Specifically, the total amount of metal elements and halogen elements as impurities is 100 ppm or less, preferably 50 ppm or less, more preferably 10 ppm or less.

  As a manufacturing method that does not contain impurities, for example, a tetraalkoxysilane compound may be used as a raw material and reacted with organic fine particles without a catalyst. Among the tetraalkoxysilane compounds, tetramethoxysilane and tetraethoxysilane are preferable because the reaction is easily controlled, and tetramethoxysilane is more preferable. In addition, although a chlorosilane compound and a silicate react without a catalyst, when these raw materials are used, a chloro compound, an alkali metal, etc. will remain in the system as impurities. In addition, raw materials for forming modified silica such as alkyl alkoxysilanes and amino group-containing silane compounds are not suitable for non-catalytic reactions because of poor reactivity.

  As described above, the outer shell layer of the particles obtained by reacting with the tetraalkoxysilane compound is coated with silica. However, as a toner external additive, it is preferable to use a silica modified surface for charge control. Therefore, it is preferable that the hybrid fine particles of the present invention obtained using a tetraalkoxysilane compound as a raw material further react with a silicon compound that forms a modified silica layer.

  Examples of the silicon compound (modified silicon compound) for forming the modified silica include alkyl alkoxysilanes such as monomethyltrimethoxysilane, dimethyldimethoxysilane, trimethylmonomethoxysilane, monoethyltrimethoxysilane, diethyldimethoxysilane, and triethylmonomethoxysilane. Compound: Phenylalkoxysilane compound such as phenyltrimethoxysilane, diphenyldimethoxysilane, triphenylmonomethoxysilane; aminopropyltrimethoxysilane, (aminoethyl) aminopropyldimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, Amino group-containing silane compounds such as aminopropylmethyldiethoxysilane and aminobutyltriethoxysilane; vinyltrimethoxysilane Vinyl group-containing silane compounds such as vinyltriethoxysilane; 3-glycidoxypropylmethylethoxysilane; glycidyl group-containing silane compounds such as 3-glycidoxypropyltriethoxysilane; 3-methacryloxypropylmethyldimethoxysilane; (Meth) acrylic group-containing silane compounds such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and nonafluorohexyl Fluorine atom-containing silane compounds such as trimethoxysilane, nonafluorohexyltriethoxysilane, tridecafluorohexyltrimethoxysilane, and tridecafluorohexyltriethoxysilane, and mixtures thereof. It is.

  These modified silicon compounds may be reacted directly with the fine particles coated with silica, and react even without using a catalyst during the reaction. Here, the reactivity of the modified silicon compound will be described in detail. As described above, alkylsilane, amino-modified silane, and the like are inferior in reactivity compared to tetraalkoxysilane, and therefore generally do not react without a catalyst. However, modified silicon compounds such as alkylsilanes and amino-modified silanes have the property of reacting when attached to a substrate with high affinity, and silica is one of the substrates with the highest affinity. Therefore, the modified silicon compound easily reacts with the fine particles coated with silica even without a catalyst. Thereby, the fine particles on which the modified silica layer is further formed do not contain impurities derived from the catalyst.

  Any amount of the modified silicon compound may be allowed to react, but if the amount is too small, the effect may not be exhibited. If the amount is too large, the particles may agglomerate. The silicon atom of the modified silicon compound is 0.01 to 5 mol, more preferably 0.1 to 3 mol, still more preferably 0.5 to 2 mol, per 1 mol of silicon atom of the tetraalkoxysilane compound. The reaction may be as follows. As a specific reaction method, for example, fine particles having a silica layer are dispersed in 0.1 to 30% by mass in water or a mixture of water and an organic solvent, and a modified silicon compound is added at 0 to 50 ° C., The reaction is allowed to stir at the same temperature for 1 to 48 hours. Thereafter, the temperature of the system is raised to 60 to 80 ° C. and aging is performed for 1 to 20 hours.

  The external additive of the electrophotographic toner of the present invention can be easily produced from small particles to large particles depending on the conditions of emulsion polymerization. Specifically, if the particle size is 10 to 350 nm, it can be produced freely, and the obtained hybrid fine particles can be produced with small variation in particle size and with uniform size. Has the advantage.

  The external additive for the electrophotographic toner of the present invention is produced in water or in a mixed solution of water and an organic solvent, but is dried and powdered after production. Any drying method may be used as long as it is a known method. For example, heat drying, vacuum drying, spray drying, or a combination of these methods may be used.

  Here, the embedding of the external additive in the toner resin will be described. The reason why the external additive of the electrophotographic toner is buried in the toner resin is that the specific gravity of the external additive such as silica is large in addition to the current situation that the toner resin is softened. The external additive added to the toner is mixed and collides with the toner resin at a constant speed and adheres to the surface of the toner resin, but when the kinetic energy of the external additive exceeds a certain amount, the surface of the toner resin The external additive cannot be withstood and is buried in the toner resin. As is well known, the kinetic energy depends on the speed and mass of the substance, but since it is virtually impossible to control the speed of the external additive, it may be most effective to control the mass of the external additive. Recognize. Silica fine particles that are most commonly used as an external additive are substances having a specific gravity of about 2.0. If the specific gravity can be lowered, energy at the time of collision with the toner resin can be reduced.

  The external additive for an electrophotographic toner of the present invention is a hybrid fine particle having a core-shell structure having an organic substance in the inner shell and a silica compound in the outer shell layer. Since the outer shell layer has a silica compound, it is similar in appearance to conventional silica fine particles, but since the inner shell is an organic substance, the specific gravity as particles is greatly reduced compared to silica. For example, if the organic substance is polystyrene, the specific gravity is about 1.05 to 1.07, and if the organic resin is ABS resin, the specific gravity is about 1.04. Therefore, the specific gravity of the hybrid fine particles of the present invention using these organic substances is less than 2.0 and becomes 1.8 or less, preferably 1.6 or less, more preferably 1.4 or less. That's fine. Due to the decrease in specific gravity, the kinetic energy when colliding with the toner resin surface can be reduced, and the embedding of the external additive in the toner resin can be prevented.

  The specific gravity of the organic particles that are the inner shells of the hybrid fine particles of the present invention in a state where the particles are filled in the particles without gaps is about 1.05, although it depends on the type of the organic material. However, there is a method in which the specific gravity is less than 1.05. In order to make the specific gravity less than 1.05, the organic substance in the inner shell may be made porous. In order to obtain a porous shape, for example, after reacting a silicon compound with an organic substance in the inner shell, the reactant is put in an organic solvent capable of dissolving the organic substance, and then treated, whereby a part of the inner shell is processed. Can be dissolved and removed. However, these treatments require time and cost. Further, if a part of the inner shell is removed, the strength of the particles is lowered, and the particles may be collapsed when colliding with the toner resin. Therefore, it is preferable that a part of the inner shell is not removed and the specific gravity is 1.05 or more. Examples of the organic solvent include benzene, toluene, xylene, hexane, tetrohydrofuran, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, chloroform, dichloromethane, dichloroethane, and the like. Can be mentioned.

  The electrophotographic toner of the present invention is a toner containing the external additive of the electrophotographic toner of the present invention. As the usable toner, any of black toner and color toner can be used, and it can be used for any one of electrophotographic systems such as magnetic one component, non-magnetic one component, and two component. Any toner binder resin can be used as long as it is generally used. For example, a styrene / acrylic copolymer resin, a polyester resin, an epoxy resin, and the like can be used without particular limitation. The toner production method can be applied not only to mainstream pulverization / kneading methods but also to toners obtained by polymerization methods such as suspension polymerization and emulsion polymerization. As other usable raw materials, any materials that are usually used for toners can be used. For example, black colorants, color colorants such as cyan, magenta, and yellow, positive charge and negative charge control agents. And mold release agents such as wax. Further, if necessary, silica compound particles other than the external additive of the present invention may be combined, oxide fine particles other than silica such as titania and alumina, and lubricants such as Teflon (registered trademark), zinc stearate, polyvinylidene fluoride and the like. Alternatively, other additives such as fixing aids such as polyethylene and polypropylene can be used in combination.

  The amount of the external additive of the electrophotographic toner of the present invention added to the toner is not particularly limited as long as the obtained toner has desired characteristics, but preferably 0.05 to 5% by mass, More preferably, the content is 0.1 to 4% by mass and can be added to the toner by a known method.

  Hereinafter, the present invention will be specifically described by way of examples. In the following examples and the like,% and ppm are based on mass unless otherwise specified.

Example 1
In a 1000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer, 50 g of styrene monomer, 500 g of distilled water and 4 g of dodecyltrimethylammonium chloride as an emulsifier were substituted with nitrogen, and the temperature was raised to 70 ° C. while stirring. . After the temperature rise, 0.7 g of water-soluble azo polymerization initiator V-50 (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an initiator and reacted at 70 ° C. for 3 hours to obtain a milky white polystyrene emulsion. It was. 100 g of the obtained polystyrene emulsion was put into a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer, and 886.9 g of distilled water was further added to perform nitrogen substitution. After adjusting the temperature in the system to 25 ° C., 13.2 g of tetramethoxysilane (2.4 g in terms of silicon atom) was added while stirring the system, and the reaction was continued for 24 hours at 25 ° C. Then, the temperature was raised to 70 ° C. The mixture was further heated for 6 hours to obtain a 2.3% aqueous solution of the external additive 1 of the present invention.

Example 2
Manufactured in the same manner as in Example 1 except that 50 g of styrene monomer was changed to 40 g of styrene monomer and 10 g of vinylpyridine, and 4 g of dodecyltrimethylammonium chloride was changed to 4 g of ammonium dodecylbenzenesulfonate. Thus, a 2.3% aqueous solution of the external additive 2 of the present invention was obtained.

Example 3
950 g of a 2.3% aqueous solution of the hybrid fine particle 1 obtained in Example 1 was placed in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer, and 1.6 g of dimethyldimethoxysilane ( 0.37 g in terms of silicon atoms) was added, reacted at 25 ° C. for 24 hours, then heated to 70 ° C. and further reacted for 6 hours to obtain a 2.5% aqueous solution of external additive 3 of the present invention. .

Example 4
950 g of a 2.3% aqueous solution of the hybrid fine particles 1 obtained in Example 2 was placed in a 2000 ml four-necked flask equipped with a thermometer, a nitrogen inlet tube and a stirrer, and aminopropyltriethoxysilane was added while stirring the system. 3 g (0.83 g in terms of silicon) was added and reacted at 25 ° C. for 24 hours, then heated to 70 ° C. and further reacted for 6 hours to obtain a 2.8% aqueous solution of external additive 4 of the present invention. It was.

Example 5
In the production method of Example 1, except that 13.2 g of tetramethoxysilane was changed to 18.1 g of tetraethoxysilane (2.4 g in terms of silicon atom) and the reaction time at 25 ° C. was changed to 150 hours. The same method as in Example 1 was used to obtain a 2.2% aqueous solution of the external additive 5 of the present invention.

Comparative Example 1
Wet silica: Adelite AT-20Q (manufactured by ADEKA Corporation)
Comparative Example 2
Dry silica: Aerosil R974 (Nippon Aerosil Co., Ltd.)

<Measurement of specific gravity>
Specific gravity was measured according to JIS-R7212.
Weigh the empty specific gravity bottle 1 (M1), put the dried fine particles in the specific gravity bottle 1 and weigh (M2), and put the solvent (THF) in the specific gravity bottle 1 (sample of the same amount as M2) containing the sample. After defoaming and setting to 30 ° C., weighing (M3), only the solvent (THF) was placed in the specific gravity bottle 1 and weighing (M4). As described above, the specific gravity of the fine particles was calculated from the following formula using the four measurement results. The results are shown in Table 1.
Specific gravity = (M1-M2) ρ / {(M4-M1)-(M3-M2)}
ρ is the specific gravity of the solvent (THF) at 30 ° C

<Toner resin adhesion test>
Using the following equipment, polymer beads (Chemisnow MX-800S: manufactured by Soken Chemical Co., Ltd.) that are assumed to be a resin for toner in the following procedure, fine particles 3 of Example 3 and wet silica fine particles of Comparative Example 1 Each was mixed, and the state of fine particles adhering to the surface of each polymer bead was observed with an electron microscope (S-4800: manufactured by Hitachi High-Technologies Corporation). All fine particles were used after being dried by spray drying. The observed photographs are shown in FIGS.

<Mixing equipment>
Milcer: IFM-650D (manufactured by Iwatani Corporation)
Milcer cutter: IMF-6C (manufactured by Iwatani Corporation)
<Procedure for mixing>
1. Weigh 0.1 g of fine particles and 9.9 g of polymer beads in a Mircer container for a total of 10 g.
2. A miller cutter is attached to the miller container containing the above powder, and is set on the miller body.
3. Switch on and mix for 10 seconds.
4). The obtained mixed powder is observed with an electron microscope (magnification 200 times).

  Comparing the photographs of FIGS. 1 and 2, it can be seen that the fine particles of Comparative Example 1 are embedded in the polymer beads by about 1/3 to half. On the other hand, the fine particles of Example 3 are attached on the polymer beads and are hardly buried. Furthermore, it was confirmed that similar results were obtained for other examples.

Claims (8)

  An external additive for an electrophotographic toner, wherein the outer shell layer is a fine particle having a core-shell structure having a silica compound and has a specific gravity of 1.8 or less.   2. The external additive for an electrophotographic toner according to claim 1, wherein the external additive is a hybrid fine particle having a core-shell structure having an organic substance in an inner shell and a silica compound in an outer shell layer.   3. The external additive for an electrophotographic toner according to claim 2, wherein the organic substance in the inner shell is a resin obtained by emulsion polymerization.   4. The external additive for an electrophotographic toner according to claim 2, wherein the outer silica layer is formed of a reaction product of tetraalkoxysilane.   4. The external additive for an electrophotographic toner according to claim 2, wherein the outer shell silica layer is formed of a reaction product of a tetraalkoxysilane and a reaction product of a modified silicon compound.   6. The external additive for an electrophotographic toner according to claim 1, wherein the average particle diameter is 10 to 350 nm.   The method for producing an external additive for an electrophotographic toner according to claim 1, wherein a silicon compound is reacted with organic fine particles in the absence of a catalyst.   An electrophotographic toner comprising the external additive for an electrophotographic toner according to claim 1.

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