Method for producing resin particle dispersion and method for producing toner for developing electrostatic images

Abstract

The present invention provides a method for producing a resin particle dispersion containing resin particles that are used to produce a toner that suppresses offset when a toner image is fixed to a recording medium. [Solution] The method for producing a resin particle dispersion includes step (1) of mixing a resin composition containing resin and inorganic particles with a basic compound and a surfactant by applying heat and shear force, and step (2) of emulsifying the mixture by adding an aqueous medium while applying shear force after step (1). In step (1), the resin composition and the basic compound are mixed, and then the surfactant is added, or the resin composition is mixed with the basic compound and the surfactant simultaneously.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a resin particle dispersion and a method for producing a toner for developing electrostatic images. [Background technology]

[0002] Patent Document 1 discloses resin microparticles containing a polyester resin and a basic dye, in which the volume average particle size of the resin microparticles is 0.05 μm or more and 1 μm or less, and the concentration ratio of the basic dye at the center of gravity of the resin microparticles to the surface portion at a depth of 10 nm or less from the surface of the resin microparticles is 0.8 or more.

[0003] Patent Document 2 discloses a method for producing a resin particle dispersion, which includes a melting step of adding a surfactant and a basic compound to a resin mixture containing an amorphous resin and a crystalline resin in the absence of an organic solvent and forming a molten mixture while applying shear force, and an emulsification step of adding an aqueous medium to the molten mixture while applying shear force to emulsify the mixture, wherein the surfactant content in the molten mixture is 1% by mass or more and 5% by mass or less relative to the total mass of the resin in the molten mixture, and the basic compound content in the molten mixture is 0.05 mol or more and 0.2 mol or less relative to 1 kg of the resin in the molten mixture.

[0004] Patent Document 3 discloses a method including melt-mixing a resin in the absence of an organic solvent; optionally adding a surfactant to the resin; and adding a basic agent and water to the resin to form an emulsion of resin particles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-127428 [Patent Document 2] Patent Publication No. 2021-046477 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-191271 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a method for producing a resin particle dispersion containing resin particles that are used in toner production and that can produce a toner that suppresses offset when a toner image is fixed to a recording medium. [Means for solving the problem]

[0007] Specific means for solving the above problems include the following aspects. <1> (1) a step of mixing a resin composition containing a resin and inorganic particles, a basic compound, and a surfactant by applying heat and shear force; Following the step (1), a step (2) of emulsifying the mixture by adding an aqueous medium while applying a shear force, In the step (1), the resin composition and the basic compound are mixed together, and then the surfactant is mixed therewith, or the resin composition is mixed with the basic compound and the surfactant at the same time. A method for producing a resin particle dispersion. <2> The proportion of the inorganic particles in the resin composition is 0.1% by mass or more and 20% by mass or less. <1> 1. A method for producing a resin particle dispersion liquid according to claim 1. <3> The inorganic particles include at least one selected from the group consisting of silica particles, alumina particles, and titania particles. <1> or <2> 1. A method for producing a resin particle dispersion liquid according to claim 1. <4> No organic solvent is used in the steps (1) and (2). <1> ~ <3> 10. A method for producing a resin particle dispersion liquid according to any one of the above. <5> <1> ~ <4> obtaining a resin particle dispersion by the method for producing a resin particle dispersion according to any one of the above items; aggregating the resin particles in the resin particle dispersion to form aggregated particles; and heating the dispersion containing the aggregated particles to fuse and coalesce the aggregated particles to form toner particles. A method for producing a toner for developing electrostatic images. [Effects of the Invention]

[0008] <1> , <3> or <4> According to the method, a method for producing a resin particle dispersion liquid containing resin particles capable of producing a toner that suppresses offset when a toner image is fixed to a recording medium is provided, compared to a production method in which a surfactant is mixed with a resin composition before a basic compound is mixed in step (1). <2> According to the present invention, there is provided a method for producing a resin particle dispersion containing resin particles that can produce a toner that suppresses offset when a toner image is fixed to a recording medium, compared to a production method in which the proportion of inorganic particles in the resin composition is less than 0.1 mass % or more than 20 mass %. <5> According to the present invention, there is provided a method for producing a toner for developing an electrostatic image, which can produce a toner that suppresses offset when a toner image is fixed to a recording medium. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0010] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0011] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[0012] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0013] When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0014] In the present disclosure, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the composition may contain multiple types of particles corresponding to each component. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0015] In the present disclosure, "(meth)acrylic" is an expression that includes both acrylic and methacrylic, and "(meth)acrylate" is an expression that includes both acrylate and methacrylate.

[0016] In this disclosure, "developer" refers to "electrostatic image developer," "carrier" refers to "electrostatic image developing carrier," and "toner" refers to "electrostatic image developing toner."

[0017] In the present disclosure, a method for producing toner particles by aggregating and coalescing material particles in a dispersion medium is referred to as an EA (Emulsion Aggregation) method.

[0018] <Method of manufacturing resin particle dispersion> The method for producing a resin particle dispersion according to the present disclosure includes step (1) of mixing a resin composition containing a resin and inorganic particles with a basic compound and a surfactant by applying heat and shear force, and step (2) of emulsifying the resin composition by adding an aqueous medium while applying shear force, wherein in step (1), the resin composition and the basic compound are mixed and then the surfactant is added, or the resin composition is mixed with the basic compound and the surfactant at the same time. In step (1), the surfactant is not mixed with the resin composition before the basic compound.

[0019] The method for producing a resin particle dispersion according to the present disclosure provides a resin particle dispersion containing resin particles to be used in toner production, the resin particles enabling production of a toner that suppresses offset when a toner image is fixed to a recording medium.

[0020] In step (1) of the manufacturing method of the present disclosure, the surfactant is not mixed with the resin composition before the basic compound. The resin particles provided by the manufacturing method of the present disclosure can produce a toner that suppresses offset when a toner image is fixed to a recording medium, compared to resin particles provided by a manufacturing method in which the surfactant is mixed with the resin composition before the basic compound. While the detailed mechanism is unknown, the resin particles produced by the mixing order of the present disclosure contain inorganic particles well dispersed within the resin particles, and the inorganic particles are also well dispersed within the toner particles. As a result, it is presumed that the toner particles exhibit appropriate elasticity, suppressing offset when a toner image is fixed to a recording medium. Furthermore, the manufacturing method of the present disclosure uses a resin composition in which a resin and inorganic particles are premixed in step (1). This also allows the inorganic particles to be well dispersed within the resin particles.

[0021] In step (1), the resin composition and the basic compound are mixed together, and then the surfactant is mixed therewith, or the basic compound and the surfactant are simultaneously mixed into the resin composition. From the viewpoint of further dispersing the inorganic particles in the toner particles, it is preferable to mix the resin composition and the basic compound together, and then the surfactant is mixed therewith.

[0022] [Resin composition] The resin composition contains at least a resin and inorganic particles. The resin composition is preferably a powder composition or a granular composition. Examples of the form of the resin composition include the following forms (1) to (3), and further include a mixture of at least two forms selected from forms (1) to (3).

[0023] Form (1): A powder composition or granular composition containing resin powder or resin particles and inorganic particles. Form (2): A powder composition or granular composition comprising a resin powder or resin particles, and a resin powder or resin particles containing inorganic particles therein. Form (3): A powder composition or granular composition comprising a resin powder or resin particles, and a resin powder or resin particles having inorganic particles attached to the surface thereof.

[0024] The resin composition of form (1) is produced by mixing resin powder or resin particles with inorganic particles. The resin compositions of Forms (2) and (3) are produced, for example, by mixing resin powder or resin particles with toner. The toner may be unused toner or toner recovered from an image forming apparatus. The resin composition may contain a colorant, wax, metal soap, etc. derived from the toner.

[0025] -resin- The resin of the resin composition serves as a binder resin for toner particles. Examples of the resin include resins containing carboxylic acid and / or carboxylic acid ester as a polymerization component. Specific examples include polyester resins, styrene (meth)acrylic resins, (meth)acrylic resins, and resins modified with these.

[0026] The resin is preferably a polyester resin. Examples of the polyester resin include amorphous polyester resin and crystalline polyester resin. As the polyester resin, only amorphous polyester resin may be used, only crystalline polyester resin may be used, or amorphous polyester resin and crystalline polyester resin may be used in combination.

[0027] -Amorphous polyester resin- The amorphous polyester resin may be a commercially available product or a synthetic product. Examples of amorphous polyester resins include condensation polymers of polycarboxylic acids and polyhydric alcohols, and resins obtained by modifying these polymers.

[0028] Examples of polycarboxylic acids that are polymerization components of amorphous polyester resins include aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids. The polycarboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower (e.g., carbon number 1 to 5) alkyl esters thereof. The polycarboxylic acids may be used alone or in combination of two or more. As the polycarboxylic acid, it is preferable to use an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid.

[0029] Examples of polyhydric alcohols that are polymerization components of amorphous polyester resins include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,1 Examples of the polyhydric alcohol include 1-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanedecanediol, alicyclic diols (for example, cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A), and aromatic diols (for example, an ethylene oxide adduct of bisphenol A and a propylene oxide adduct of bisphenol A). Among these, aromatic diols and aliphatic diols are preferred as the polyhydric alcohol, and aromatic diols are more preferred. As the polyhydric alcohol which is a polymerization component of the amorphous polyester resin, a trihydric or higher polyhydric alcohol having a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0030] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50°C or higher and 70°C or lower, more preferably 52°C or higher and 65°C or lower, and even more preferably 54°C or higher and 60°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K7121-1987 "Method for measuring transition temperature of plastics."

[0031] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the amorphous polyester resin is preferably 1,500 or more and 100,000 or less, and more preferably 2,000 or more and 95,000 or less. The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less.

[0032] The weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight measurement by GPC is performed using a measuring device HLC-8120GPC (Tosoh Corporation) and a column TSKgel SuperHM-M (diameter 15 cm, Tosoh Corporation) with a solvent of tetrahydrofuran. The weight average molecular weight and number average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0033] -Crystalline polyester resin- The crystalline polyester resin may be a commercially available product or a synthetic product. Examples of the crystalline polyester resin include a polycondensation product of a polycarboxylic acid and a polyhydric alcohol. The crystalline polyester resin is preferably a polycondensation product using a linear aliphatic polymerizable monomer rather than a polymerizable monomer having an aromatic ring, since it easily forms a crystalline structure.

[0034] Examples of polycarboxylic acids that are polymerization components of crystalline polyester resins include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalene-2,6-dicarboxylic acid), anhydrides thereof, and lower (e.g., having 1 to 5 carbon atoms) alkyl esters thereof. The polycarboxylic acid may be a tricarboxylic or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the tricarboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). As the polycarboxylic acid, a dicarboxylic acid having a sulfonic acid group and a dicarboxylic acid having an ethylenic double bond may be used in combination with these dicarboxylic acids. The polycarboxylic acids may be used alone or in combination of two or more.

[0035] Examples of polyhydric alcohols that are polymerization components of crystalline polyester resins include aliphatic diols (for example, straight-chain aliphatic diols having 2 to 20 carbon atoms in the main chain). Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanedecanediol. As the polyhydric alcohol, which is a polymerization component of the crystalline polyester resin, a trihydric or higher alcohol having a crosslinked or branched structure may be used in combination with the diol. Examples of the trihydric or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0036] The melting temperature of the crystalline polyester resin is preferably 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower, and even more preferably 60°C or higher and 85°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for measuring transition temperatures of plastics."

[0037] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0038] -Styrene (meth)acrylic resin, (meth)acrylic resin- Examples of styrene (meth)acrylic resins include resins obtained by polymerizing the following styrene-based monomers and (meth)acrylic acid-based monomers. Examples of (meth)acrylic resins include resins obtained by polymerizing the following (meth)acrylic acid-based monomers.

[0039] Examples of styrene-based monomers include styrene, α-methylstyrene, vinylnaphthalene; alkyl-substituted styrenes such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene; halogen-substituted styrenes such as 2-chlorostyrene, 3-chlorostyrene, and 4-chlorostyrene; and fluorine-substituted styrenes such as 4-fluorostyrene and 2,5-difluorostyrene. Preferred styrene-based monomers are styrene and α-methylstyrene. One type of styrene-based monomer may be used alone, or two or more types may be used in combination.

[0040] Examples of (meth)acrylic acid monomers include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, and (meth)acrylic acid. Examples of the (meth)acrylic acid monomer include isoheptyl, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, t-butylphenyl (meth)acrylate, terphenyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-carboxyethyl (meth)acrylate, 2-carboxypropyl (meth)acrylate, 3-carboxypropyl (meth)acrylate, 4-carboxybutyl (meth)acrylate, (meth)acrylonitrile, and (meth)acrylamide. One type of (meth)acrylic acid monomer may be used alone, or two or more types may be used in combination.

[0041] As the (meth)acrylic acid monomer, a (meth)acrylic acid lower alkyl ester is preferred. In the (meth)acrylic acid lower alkyl ester, the "lower alkyl" means a carbon number of 1 to 5, preferably a "lower alkyl" having 2 to 4 carbon atoms, more preferably 3 or 4 carbon atoms. Examples of (meth)acrylic acid lower alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, etc. Among these, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate are preferred, and n-butyl (meth)acrylate is particularly preferred.

[0042] The polymerization ratio of the styrene-based monomer to the (meth)acrylic acid-based monomer (mass basis, styrene-based monomer:(meth)acrylic acid-based monomer) is preferably 30:70 to 70:30, more preferably 40:60 to 60:40, and even more preferably 45:55 to 55:45.

[0043] -Inorganic particles- Inorganic particles include SiO2 (silica), Al2O3 (alumina), TiO2 (titania), CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, CaTiO3, SrTiO3, etc.

[0044] The inorganic particles are preferably at least one selected from the group consisting of silica particles, alumina particles, and titania particles, and more preferably silica particles.

[0045] The surfaces of the inorganic particles are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobic treatment agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the inorganic particles.

[0046] The average primary particle size of the inorganic particles is preferably 1 nm or more and 80 nm or less, more preferably 3 nm or more and 60 nm or less, and even more preferably 5 nm or more and 40 nm or less, from the viewpoint of suppressing offset when a toner image is fixed to a recording medium.

[0047] In this embodiment, the primary particle size of inorganic particles is the diameter of a circle having the same area as the primary particle image (so-called circle equivalent diameter), and the average primary particle size of inorganic particles is the particle size that is the cumulative 50% from the smallest diameter side in the number-based distribution of primary particle sizes. The primary particle size of inorganic particles is determined by image analysis of at least 300 inorganic particles.

[0048] The mass proportion of the inorganic particles in the resin composition is preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.5 mass % or more and 8 mass % or less, and even more preferably 1 mass % or more and 5 mass % or less, from the viewpoint of suppressing offset when a toner image is fixed to a recording medium.

[0049] Hereinafter, the steps (1) and (2) of the method for producing a resin particle dispersion will be described separately for "solvent-free emulsification" and "solvent emulsification," which are examples of embodiments of the method.

[0050] [Solvent-free emulsification] Solvent-free emulsification is a method in which no organic solvent is used in the production of a resin particle dispersion. Specifically, solvent-free emulsification is The method includes step (1) of mixing a resin composition, a basic compound, and a surfactant by applying heat and shear force, and step (2) of emulsifying the resin composition, a basic compound, and a surfactant by adding an aqueous medium while applying shear force, following step (1), and no organic solvent is used in steps (1) and (2).

[0051] In step (1), the resin composition and the basic compound are mixed together, and then the surfactant is mixed therewith, or the resin composition and the basic compound and the surfactant are simultaneously mixed therewith. When the basic compound and the surfactant are simultaneously mixed into the resin composition, the basic compound and the surfactant may be mixed separately, or a mixture in which the basic compound and the surfactant are mixed in advance may be used.

[0052] In the solventless emulsification, steps (1) and (2) are preferably carried out using a kneading extruder. A kneading extruder is a device that applies heat and shear force to a material to be treated while continuously conveying the material. The structure of a kneading extruder is generally broadly divided into a material inlet, a barrel, and a die, from upstream to downstream. A screw is provided inside the barrel. A heater that heats the inside of the barrel is provided around the barrel. The screw may be a single-screw type or a twin-screw type, with the twin-screw type being preferred.

[0053] The L / D (ratio of screw length L to screw diameter D) of the kneading extruder is preferably 30 or more and 90 or less, more preferably 40 or more and 80 or less, and even more preferably 50 or more and 70 or less, in the entire process of steps (1) and (2).

[0054] Examples of basic compounds include hydroxides of alkali metals such as lithium, sodium, and potassium; oxides of alkaline earth metals such as magnesium and calcium; hydroxides of alkaline earth metals such as magnesium and calcium; etc. Among these, alkali metal hydroxides and alkaline earth metal hydroxides are preferred, alkali metal hydroxides are more preferred, potassium hydroxide and sodium hydroxide are even more preferred, and sodium hydroxide is particularly preferred.

[0055] The amount of the basic compound used is an amount that can emulsify and disperse the mixture. Specifically, the amount of the basic compound used is preferably an amount that results in a neutralization rate of 30% or more and 80% or less according to the following formula (1): Formula (1): Neutralization rate (%) = mb×n×56.1÷Mwb÷AV×1000, mb is the amount (g) of basic compound used per 1 g of resin, n is the valence of the basic compound, Mwb is the molecular weight of the basic compound, AV is the acid value of the resin (mg KOH / g).

[0056] The surfactant may be any of anionic surfactants, cationic surfactants, and nonionic surfactants. Examples include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soap-based surfactants; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. One surfactant may be used alone, or two or more surfactants may be used in combination. A nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant. Anionic surfactants are preferred as the surfactant, and sulfonate surfactants are more preferred. The amount of surfactant used is such that the emulsified particles can be kept dispersed.

[0057] The aqueous medium is preferably water with a reduced ion content, such as distilled water or ion-exchanged water. The aqueous medium is preferably used by adjusting its temperature to a range of 35°C or higher and 100°C or lower, more preferably within ±5°C of the internal barrel temperature of the kneading extruder.

[0058] The temperature inside the barrel of the kneading extruder in step (1) is preferably 70°C or higher and 140°C or lower, more preferably 80°C or higher and 110°C or lower, and even more preferably 90°C or higher and 100°C or lower. The temperature inside the barrel of the kneading extruder in step (2) is preferably 70°C or higher and 140°C or lower, more preferably 80°C or higher and 110°C or lower, and even more preferably 90°C or higher and 100°C or lower.

[0059] When using a twin-screw kneading extruder, the average feed rate of the mixture fed from step (1) to step (2) is 0.15 kg / (h cm) when the feed rate (kg / h) is divided by the cube of the shaft diameter (cm). 3 ) or more 5.0kg / (h cm 3 ) or less is preferable, and 0.5 kg / (h·cm 3) or more 4.0kg / (h cm 3 ) or less is more preferable, and 0.8 kg / (h·cm 3 ) or more 3.0kg / (h cm 3 ) The following is more preferred.

[0060] [Solvent emulsification] Specifically, the solvent emulsification is A step (1-1) of mixing a resin composition with an organic solvent in which the resin constituting the resin composition is soluble while applying heat, thereby dissolving the resin constituting the resin composition in the organic solvent; Following the step (1-1), a step (1-2) of mixing the basic compound and the surfactant by applying heat and shear force; Following the step (1-2), there is a step (2) of emulsifying the mixture by adding an aqueous medium while applying a shear force. In the step (1-2), the basic compound is mixed first, and then the surfactant is mixed, or the basic compound and the surfactant are mixed simultaneously.

[0061] The solvent emulsification is preferably carried out in steps (1-1), (1-2), and (2) in a stirring vessel equipped with a stirring means and a heating / cooling means. The stirring means is preferably a stirring means having a rotating shaft and a stirring blade. The heating / cooling means is preferably a means for applying and / or removing heat from the wall surface of the stirring vessel.

[0062] When the resin constituting the resin composition is a polyester resin, examples of organic solvents in which the polyester resin is soluble include ethyl acetate, isopropanol, 2-butanol, methyl ethyl ketone, and mixed solvents thereof. Among these, organic solvents or mixed solvents having a boiling point of 60°C or higher and lower than 100°C are preferred.

[0063] Ammonia water is suitable as the basic compound.

[0064] The amount of the basic compound used is an amount that can emulsify and disperse the mixture. Specifically, the amount of the basic compound used is preferably an amount that results in a neutralization rate of 50% or more and 100% or less according to the following formula (1): Formula (1): Neutralization rate (%) = mb×n×56.1÷Mwb÷AV×1000, mb is the amount (g) of basic compound used per 1 g of resin, n is the valence of the basic compound, Mwb is the molecular weight of the basic compound, AV is the acid value of the resin (mg KOH / g).

[0065] The surfactant may be any of anionic surfactants, cationic surfactants, and nonionic surfactants. Examples include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soap-based surfactants; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. One surfactant may be used alone, or two or more surfactants may be used in combination. A nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant. Anionic surfactants are preferred as the surfactant, and sulfonate surfactants are more preferred. The amount of surfactant used is such that the emulsified particles can be kept dispersed.

[0066] The aqueous medium is preferably water with a reduced ion content, such as distilled water or ion-exchanged water. The aqueous medium is preferably used at a temperature adjusted to a range of 35°C or higher and 100°C or lower (preferably a range of 35°C or higher and 55°C or lower).

[0067] The temperature of the material to be treated placed in the stirring tank in steps (1-1) and (1-2) is preferably 25°C or higher and 60°C or lower, more preferably 30°C or higher and 55°C or lower, and even more preferably 35°C or higher and 50°C or lower. In step (2), the temperature of the material contained in the stirring tank is preferably 25°C or higher and 60°C or lower, more preferably 30°C or higher and 55°C or lower, and even more preferably 35°C or higher and 50°C or lower.

[0068] The aqueous medium is preferably added dropwise in step (2). The time for dropping a specified amount of aqueous medium (twice the amount of resin) in step (2) is preferably 10 to 150 minutes, more preferably 20 to 140 minutes, and even more preferably 30 to 130 minutes.

[0069] After the addition of the aqueous medium is completed, it is preferable to remove the organic solvent by reducing the pressure inside the stirring tank and / or bubbling the emulsion. Thereafter, a surfactant may be added to improve the dispersion stability of the particles. Examples of surfactants include the anionic surfactants, cationic surfactants, and nonionic surfactants described above.

[0070] <Method of manufacturing toner for developing electrostatic images> The toner of the present disclosure is preferably produced by a wet method such as an EA method (aggregation-coalescence method), a suspension polymerization method, a solution-suspension method, or an ester elongation method. Of these, the EA method is preferred. There are no limitations on these methods, and any known method may be used.

[0071] The toner manufacturing method of the present disclosure uses, as material particles, at least resin particles obtained by the resin particle dispersion manufacturing method of the present disclosure. The resin particles serve as a binder resin for toner particles, and inorganic particles are dispersed in the binder resin. Hereinafter, the resin particles obtained by the resin particle dispersion manufacturing method of the present disclosure are also referred to as "binder resin particles containing inorganic particles."

[0072] The method for producing a toner according to the present disclosure includes aggregating and coalescing material particles including inorganic particle-containing binder resin particles in a dispersion medium to obtain toner particles. Specifically, the toner manufacturing method of the present disclosure includes aggregating inorganic particle-containing binder resin particles in a dispersion containing inorganic particle-containing binder resin particles to form aggregated particles, and heating the dispersion containing the aggregated particles to fuse and coalesce the aggregated particles to form toner particles.

[0073] Each step and material of the EA method will be explained in detail below.

[0074] [Aggregation step (first aggregation step)] In the aggregating step, at least inorganic particle-containing binder resin particles are aggregated in a dispersion containing at least inorganic particle-containing binder resin particles to form aggregated particles.

[0075] When the toner manufacturing method of the present disclosure includes the second aggregation step (a step for forming a shell) described below, the above aggregation step is referred to as the “first aggregation step.” The first aggregation step is a step for forming a core in a toner having a core-shell structure.

[0076] The dispersion liquid to be subjected to the aggregation step contains at least inorganic particle-containing binder resin particles. The dispersion liquid to be subjected to the aggregation step may further contain release agent particles. The dispersion liquid to be subjected to the aggregation step may further contain colorant particles. The dispersion liquid to be subjected to the aggregation step may further contain binder resin particles that do not contain inorganic particles. The binder resin particles containing inorganic particles and the binder resin particles not containing inorganic particles are collectively referred to as "binder resin particles."

[0077] The dispersion liquid to be subjected to the aggregation step is prepared, for example, by preparing a resin particle dispersion liquid (binder resin particle dispersion liquid containing inorganic particles) obtained by the method for producing a resin particle dispersion liquid of the present disclosure, a binder resin particle dispersion liquid containing no inorganic particles, a release agent particle dispersion liquid, and a colorant particle dispersion liquid, and then mixing these particle dispersion liquids. The order in which these particle dispersion liquids are mixed is not limited.

[0078] Hereinafter, the common features of the release agent particle dispersion liquid and the colorant particle dispersion liquid will be collectively referred to as "particle dispersion liquid."

[0079] An example of an embodiment of the particle dispersion is a dispersion in which a material is dispersed in the form of particles in a dispersion medium by a surfactant.

[0080] The dispersion medium for the particle dispersion is preferably an aqueous medium. Examples of aqueous media include water and alcohol. The water is preferably water with a reduced ion content, such as distilled water or ion-exchanged water. These aqueous media may be used alone or in combination of two or more.

[0081] The surfactant used to disperse the material in the dispersion medium may be any of anionic surfactants, cationic surfactants, and nonionic surfactants. Examples include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soap-based surfactants; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. One surfactant may be used alone, or two or more surfactants may be used in combination. A nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant.

[0082] Methods for dispersing a material in a particulate form in a dispersion medium include known dispersion methods such as a rotary shear homogenizer, a ball mill having media, a sand mill, and a dyno mill.

[0083] The volume average particle size of the particles dispersed in the particle dispersion is preferably 30 nm or more and 300 nm or less, more preferably 50 nm or more and 250 nm or less, and even more preferably 80 nm or more and 200 nm or less. The volume average particle size of particles in a particle dispersion refers to the particle size that is the cumulative 50% particle size from the smallest diameter side in the particle size distribution measured using a laser diffraction particle size analyzer. The number of particles measured was 10,000.

[0084] The content of particles contained in the particle dispersion is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, and even more preferably 15% by mass to 30% by mass.

[0085] The materials constituting the particles of each of the release agent particle dispersion liquid and the colorant particle dispersion liquid will be described below.

[0086] -Mold release agent- Examples of release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. There are no particular limitations on the release agent, and it can be selected appropriately depending on the purpose. Hydrocarbon waxes and ester waxes are preferred as release agents. One type of release agent may be used alone, or two or more types may be used in combination.

[0087] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, more preferably 60°C or higher and 100°C or lower, and even more preferably 75°C or higher and 95°C or lower. The melting temperature of the release agent is determined from a DSC curve obtained by differential scanning calorimetry (DSC) in accordance with the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121:1987 "Method for measuring transition temperatures of plastics."

[0088] -Coloring agent- Examples of colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, and ultramarine blue. pigments such as phthalocyanine blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate; dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based; and inorganic pigments such as titanium compounds and silica. The colorant may be used alone or in combination of two or more kinds.

[0089] The colorant is not limited to a substance that absorbs light in the visible light region, but may be, for example, a substance that absorbs light in the near-infrared region, or may be a fluorescent colorant. Examples of colorants that have absorption in the near-infrared region include aminium salt compounds, naphthalocyanine compounds, squarylium compounds, and croconium compounds. Examples of fluorescent colorants include the fluorescent colorants described in paragraph 0027 of JP 2021-127431 A.

[0090] The colorant may be a colorant having luster. Examples of the luster colorant include metal powders such as aluminum, brass, bronze, nickel, stainless steel, and zinc; mica coated with titanium oxide or yellow iron oxide; coated flaky inorganic crystal substrates such as barium sulfate, layered silicates, and layered aluminum silicates; single-crystal plate-like titanium oxide, basic carbonates, bismuth oxychloride, natural guanine, flaky glass powder, and metal-deposited flaky glass powder.

[0091] The colorant may be used alone or in combination of two or more kinds. The colorant may be surface-treated as needed, and may be used in combination with a dispersant.

[0092] The toner particles may contain a colorant or may not contain a colorant. The toner may be a toner that does not contain a colorant in the toner particles, that is, a so-called transparent toner.

[0093] Hereinafter, a dispersion liquid obtained by mixing a plurality of types of particle dispersion liquids will be referred to as a "mixed dispersion liquid."

[0094] The mass ratio of the particles contained in the mixed dispersion is preferably in the following range. When the mixed dispersion contains release agent particles, the mass ratio of the binder resin particles to the release agent particles (binder resin particles:release agent particles) is preferably 100:1 to 100:40, more preferably 100:2 to 100:30, and even more preferably 100:5 to 100:20. When the mixed dispersion contains colorant particles, the mass ratio of the binder resin particles to the colorant particles (binder resin particles:colorant particles) is preferably 100:1 to 100:100, more preferably 100:2 to 100:40, and even more preferably 100:5 to 100:20.

[0095] After mixing the plurality of particle dispersions, it is preferable to adjust the pH of the mixed dispersion to a range of 3 to 4. Examples of a means for adjusting the pH of the mixed dispersion include adding an acidic aqueous solution such as a nitric acid aqueous solution, a hydrochloric acid aqueous solution, or a sulfuric acid aqueous solution.

[0096] The aggregation step may be carried out, for example, by adding a flocculant to the mixed dispersion while stirring the mixed dispersion; After adding the aggregating agent to the mixed dispersion, the mixed dispersion is heated while being stirred to increase the temperature of the mixed dispersion.

[0097] Examples of the flocculant include a surfactant having an opposite polarity to the surfactant contained in the mixed dispersion, an inorganic metal salt, and a divalent or higher metal complex. One type of flocculant may be used alone, or two or more types may be used in combination.

[0098] Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide.

[0099] The flocculant is preferably a divalent or higher metal salt compound, more preferably a trivalent metal salt compound, and even more preferably a trivalent inorganic aluminum salt compound, such as aluminum chloride, aluminum sulfate, polyaluminum chloride, or polyaluminum hydroxide.

[0100] The amount of the flocculant to be added is not limited. When a trivalent metal salt compound is used as the flocculant, the amount of the trivalent metal salt compound to be added is preferably 0.01 parts by mass or more and 10 parts by mass or less, more preferably 0.05 parts by mass or more and 5 parts by mass or less, and even more preferably 0.1 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0101] The temperature that the mixed dispersion reaches when heated is preferably a temperature based on the glass transition temperature (Tg) of the binder resin particles, for example, (Tg-30°C) or higher and (Tg°C) or lower of the binder resin particles. When the mixed dispersion contains a plurality of types of binder resin particles having different Tg's, the lowest temperature among the Tg's is set as the Tg in the aggregation step.

[0102] [Second flocculation step] The second aggregation step is a step for the purpose of producing a toner having a core-shell structure, and is performed after the first aggregation step. The second aggregation step is a step for forming a shell.

[0103] The second aggregation step is a step of mixing a dispersion containing aggregated particles with a dispersion containing resin particles that will form the shell, and aggregating the resin particles that will form the shell onto the surfaces of the aggregated particles to form second aggregated particles.

[0104] The dispersion liquid containing the resin particles that will form the shell is preferably at least one selected from binder resin particle dispersion liquids for forming the core, more preferably a polyester resin particle dispersion liquid, and even more preferably an amorphous polyester resin particle dispersion liquid.

[0105] The second aggregation step may be, for example, adding a dispersion liquid containing resin particles to be shells to the dispersion liquid containing the aggregated particles while stirring the dispersion liquid containing the aggregated particles; and heating the dispersion containing the aggregated particles while stirring the dispersion containing the resin particles that will become the shells after adding the dispersion containing the aggregated particles.

[0106] When the dispersion liquid containing the aggregated particles is heated, the temperature that the dispersion liquid containing the aggregated particles reaches is preferably a temperature based on the glass transition temperature (Tg) of the resin particles that form the shell, for example, not less than (Tg-30°C) and not more than (Tg-10°C) of the resin particles that form the shell.

[0107] After the aggregated particles or the second aggregated particles have grown to a predetermined size, a chelating agent for the aggregating agent used in the aggregation step may be added to the dispersion containing the aggregated particles or the second aggregated particles in order to stop the growth of the aggregated particles or the second aggregated particles before the heating in the coalescence step is performed. Examples of chelating agents include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid; and aminocarboxylic acids such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA). The amount of the chelating agent added is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, relative to 100 parts by mass of the binder resin particles.

[0108] After the aggregated particles or the second aggregated particles have grown to a predetermined size, the pH of the dispersion containing the aggregated particles or the second aggregated particles may be increased in order to stop the growth of the aggregated particles or the second aggregated particles before the heating in the coalescence step is performed. The pH of the dispersion containing the aggregated particles or the second aggregated particles can be increased by adding at least one selected from the group consisting of an aqueous solution of an alkali metal hydroxide and an aqueous solution of an alkaline earth metal hydroxide. The pH of the dispersion containing the aggregated particles or the second aggregated particles is preferably 8 or more and 10 or less.

[0109] [Uniting process] The coalescence step is a step in which the dispersion liquid containing the aggregated particles is heated to fuse and coalesce the aggregated particles to form toner particles.

[0110] When a second aggregation step is performed before the coalescence step, the coalescence step is a step in which a dispersion containing the second aggregated particles is heated to fuse and coalesce the second aggregated particles to form toner particles. By performing the second aggregation step and the coalescence step, toner particles having a core-shell structure can be produced. The second aggregation step may be performed multiple times, and may be performed multiple times by changing the type and / or blending ratio of the resin in the resin particles, the presence and type of a colorant, and the presence and type of a release agent.

[0111] The form described below is common to the aggregated particles and the second aggregated particles.

[0112] The temperature reached by the dispersion liquid containing the aggregated particles is preferably equal to or higher than the glass transition temperature (Tg) of the binder resin, and specifically, is preferably 10° C. to 30° C. higher than the Tg of the binder resin. When the aggregated particles contain a plurality of binder resins having different Tg's, the highest temperature among the Tg's is taken as the glass transition temperature in the coalescence step.

[0113] After the coalescence step, the toner particles in the dispersion are subjected to a known washing step, solid-liquid separation step, and drying step to obtain dried toner particles. In the washing step, from the viewpoint of chargeability, it is preferable to perform sufficient substitution washing with ion-exchanged water. In the solid-liquid separation step, it is preferable to perform suction filtration, pressure filtration, etc., from the viewpoint of productivity. In the drying step, it is preferable to perform freeze drying, flash drying, fluidized drying, vibration-type fluidized drying, etc., from the viewpoint of productivity.

[0114] [Step of adding external additives] The method for producing the toner of the present disclosure preferably includes a step of externally adding an external additive to the toner particles. The external additive is added to the toner particles by mixing the dry toner particles with the external additive. The mixing can be performed using, for example, a V blender, a Henschel mixer, a Loedige mixer, etc. Furthermore, if necessary, coarse particles of the toner can be removed using a vibrating sieve, an air sieve, etc.

[0115] Examples of external additives include inorganic particles, such as SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, CaTiO3, SrTiO3, etc.

[0116] The surfaces of inorganic particles as external additives are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobic treatment agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the inorganic particles.

[0117] Examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate, and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based polymers).

[0118] The amount of the external additive added is preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass, based on the mass of the toner particles.

[0119] <Toner for developing electrostatic images> The toner produced by the production method of the present disclosure is preferably an externally added toner in which an external additive is externally added to toner particles. The form of the external additive is as described above.

[0120] The toner particles contain at least a resin and inorganic particles. The toner particles may further contain a release agent. The toner particles may further contain a colorant.

[0121] The content of the resin (preferably polyester resin) is preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, based on the total mass of the toner.

[0122] When the toner particles contain a crystalline polyester resin, the content of the crystalline polyester resin is preferably 3% by mass or more and 30% by mass or less, and more preferably 8% by mass or more and 20% by mass or less, of the total binder resin.

[0123] The content of inorganic particles (preferably at least one selected from the group consisting of silica particles, alumina particles, and titania particles) is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, and even more preferably 0.5% by mass or more and 5% by mass or less, based on the total amount of the toner.

[0124] When the toner contains a release agent, the content of the release agent is preferably from 1% by mass to 20% by mass, and more preferably from 5% by mass to 15% by mass, based on the total mass of the toner.

[0125] When the toner contains a colorant, the content of the colorant is preferably from 1% by mass to 30% by mass, and more preferably from 3% by mass to 15% by mass, based on the total mass of the toner.

[0126] The volume average particle diameter of the toner is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less. The volume average particle diameter of the toner is measured as follows. The particle size distribution of the toner was measured using a Coulter Multisizer II (Beckman Coulter, Inc.) and an ISOTON-II (Beckman Coulter, Inc.) electrolyte. For the measurement, 0.5 mg to 50 mg of the sample to be measured was added to 2 ml of a 5% by weight aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant. This was then added to 100 ml to 150 ml of electrolyte. The electrolyte containing the suspended sample was dispersed in an ultrasonic disperser for 1 minute, and the particle size distribution of particles ranging from 2 μm to 60 μm was measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles measured was 50,000. The particle size distribution was plotted from the smallest diameter end, and the particle size at which the cumulative 50% of the particle size reached the volume average particle size D50v.

[0127] The average circularity of the toner is preferably 0.94 or more and 1.00 or less, and more preferably 0.95 or more and 0.98 or less. The average circularity of the toner is calculated by dividing the perimeter of a circle having the same area as the projected image of the particle by the perimeter of the projected image of the particle. This is determined by measuring 3,500 particles using a flow particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation).

[0128] <Developer> The toner produced by the production method of the present disclosure may be used as a one-component developer, or may be mixed with a carrier and used as a two-component developer.

[0129] The carrier is not particularly limited, and known carriers can be used, such as coated carriers in which the surface of a core material made of magnetic powder is coated with a resin, magnetic powder dispersion carriers in which magnetic powder is dispersed in a matrix resin, and resin-impregnated carriers in which porous magnetic powder is impregnated with a resin. The magnetic powder dispersion type carrier or resin impregnated type carrier may be a carrier in which the constituent particles of the carrier are used as a core material and the surface of the core material is coated with a resin.

[0130] Examples of magnetic powder include magnetic metals such as iron, nickel, and cobalt; and magnetic oxides such as ferrite and magnetite.

[0131] Examples of coating resins and matrix resins include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, acrylic ester copolymer, styrene-acrylic ester copolymer, resins having a cycloalkyl group, acrylic ester copolymers having a cycloalkyl group, straight silicone resins containing organosiloxane bonds or modified products thereof, fluororesin, polyester, polycarbonate, phenolic resin, and epoxy resin. Acrylic ester copolymer, styrene-acrylic ester copolymer, resins having a cycloalkyl group, and acrylic ester copolymers having a cycloalkyl group are preferred. The coating resin and matrix resin may contain other additives such as conductive particles. Examples of conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0132] To coat the surface of the core material with a resin, a method of coating with a coating layer-forming solution prepared by dissolving the coating resin and various additives (used as needed) in an appropriate solvent is exemplified. The solvent is not particularly limited and may be selected taking into consideration the type of resin used, its suitability for application, etc. Specific resin coating methods include an immersion method in which the core material is immersed in a solution for forming a coating layer; a spray method in which the solution for forming a coating layer is sprayed onto the surface of the core material; a fluidized bed method in which the solution for forming a coating layer is sprayed onto the core material while it is suspended in flowing air; and a kneader coater method in which the core material of the carrier and the solution for forming a coating layer are mixed in a kneader coater and then the solvent is removed.

[0133] The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner:carrier=1:100 to 30:100, and more preferably 3:100 to 20:100. [Example]

[0134] Hereinafter, the embodiments will be described in detail with reference to examples, but the embodiments are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, unless otherwise specified, synthesis, production, treatment, measurement, etc. were carried out at room temperature (25°C ± 3°C).

[0135] <Preparation of amorphous polyester resin (A)> Terephthalic acid: 20 parts Fumaric acid: 35 parts Bisphenol A ethylene oxide adduct: 10 parts Bisphenol A propylene oxide adduct: 135 parts The above materials were charged into a flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and distillation column. The temperature of the reaction solution was raised to 220°C over 1 hour, and 1 part of titanium tetraethoxide was added for every 100 parts of the above materials. The temperature of the reaction solution was raised to 230°C over 30 minutes while distilling off the resulting water. The dehydration condensation reaction was continued for 1 hour while maintaining the temperature at 230°C. The reaction mixture was then cooled to room temperature. Thus, an amorphous polyester resin (A) was obtained with an acid value of 12.0 mgKOH / g, a weight-average molecular weight of 18,000, and a glass transition temperature of 60°C.

[0136] <Preparation of Crystalline Polyester Resin (B)> Sebacic acid: 279 parts 1,6-Hexanediol: 163 parts Dibutyltin oxide (catalyst): 0.7 parts The above materials were placed in a heated and dried three-necked flask, the air in the flask was replaced with nitrogen gas to create an inert atmosphere, and the mixture was stirred and refluxed with mechanical stirring at 180°C for 6 hours, thereby obtaining a crystalline polyester resin (B) with a weight-average molecular weight of 29,000 and an acid value of 8.8 mgKOH / g.

[0137] <Preparation of Resin Composition> [Resin composition (1)] Amorphous polyester resin (A): 97 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 3 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (1).

[0138] [Resin composition (2)] Amorphous polyester resin (A): 99.99 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 0.01 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (2).

[0139] [Resin composition (3)] Amorphous polyester resin (A): 99.9 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 0.1 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (3).

[0140] [Resin composition (4)] Amorphous polyester resin (A): 99.5 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 0.5 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (4).

[0141] [Resin composition (5)] Amorphous polyester resin (A): 92 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 8 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (5).

[0142] [Resin composition (6)] Amorphous polyester resin (A): 80 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 20 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (6).

[0143] [Resin composition (7)] Amorphous polyester resin (A): 75 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 25 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (7).

[0144] [Resin composition (8)] Amorphous polyester resin (A): 97 parts Surface-treated alumina particles (average primary particle size 30 nm, dry-process alumina, surface treatment agent: octylsilane): 3 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (8).

[0145] [Resin composition (9)] Amorphous polyester resin (A): 97 parts Surface-treated titania particles (average primary particle size 40 nm, dry-process titania, surface treatment agent: octylsilane): 3 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (9).

[0146] [Resin composition (10)] Amorphous polyester resin (A): 50 parts ·Resin composition (1): 47 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 3 parts The surface-treated silica particles were added to the resin composition (1) and mixed at 10,000 rpm for 30 seconds using a sample mill. Then, the amorphous polyester resin (A) was added and mixed using a stirring mixer to obtain the resin composition (10).

[0147] [Resin composition (11)] Amorphous polyester resin (A): 97 parts Surface-treated silica particles (average primary particle size 40 nm, dry process silica, surface treatment agent: hexamethyldisilazane): 1.5 parts Surface-treated alumina particles (average primary particle size 30 nm, dry-process alumina, surface treatment agent: octylsilane): 1.5 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (11).

[0148] [Resin composition (12)] Amorphous polyester resin (A): 87 parts Crystalline polyester resin (B): 10 parts Surface-treated silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent: hexamethyldisilazane): 3 parts The above materials were stirred and mixed in a stirring mixer to obtain a resin composition (12).

[0149] <Production of Inorganic Particle-Containing Resin Particle Dispersion> [Resin particle dispersion containing inorganic particles (1)] The following materials were prepared: ·Resin composition (1): 100 parts Basic compound: 20% aqueous solution of sodium hydroxide: 3 parts Surfactant: 10% aqueous solution of sodium dodecylbenzenesulfonate (Neopelex G-15, Kao Corporation): 60 parts Ion-exchanged water (1): 100 parts of ion-exchanged water at 90°C Ion-exchanged water (2): 100 parts of 90°C ion-exchanged water Ion-exchanged water (3): 100 parts of 90°C ion-exchanged water

[0150] A twin-screw kneading extruder (model number: TEM26SS, Toshiba Machine Co., Ltd.) was prepared. The barrel of the twin-screw kneading extruder used in this example was made up of a plurality of connected barrel blocks, with an overall L / D of 50.

[0151] -Process (1)- The barrel temperature of the twin-screw kneading extruder was set to 90°C, and the screw rotation speed was set to 200 rpm. Resin composition (1) and a 20% aqueous solution of sodium hydroxide were fed into the raw material inlet of the twin-screw kneading extruder, and the twin-screw kneading extruder was started. A surfactant was fed from the fourth block of the barrel, and the mixture was kneaded and mixed to melt the resin, producing a mixture.

[0152] -Process (2)- While the twin-screw kneading extruder was operating, ion-exchanged water (1) was added from the barrel in the fifth block, ion-exchanged water (2) was added from the barrel in the seventh block, and ion-exchanged water (3) was added from the barrel in the ninth block, and the mixture was emulsified to obtain an inorganic particle-containing resin particle dispersion liquid (1). The solids concentration of the inorganic particle-containing resin particle dispersion liquid (1) was 25%. The particle size distribution of the particles in the inorganic particle-containing resin particle dispersion (1) was measured using a laser diffraction particle size distribution analyzer (model number: LA-700, Horiba, Ltd.). The volume average particle size is shown in Table 1.

[0153] [Resin particle dispersion containing inorganic particles (C1)] An inorganic particle-containing resin particle dispersion (C1) was produced in the same manner as in the preparation of the inorganic particle-containing resin particle dispersion (1), except that the resin composition (1) was changed to the amorphous polyester resin (A).

[0154] [Resin particle dispersion containing inorganic particles (C2)] An inorganic particle-containing resin particle dispersion (C2) was produced in the same manner as in the preparation of the inorganic particle-containing resin particle dispersion (1), except that the 20% aqueous sodium hydroxide solution and the surfactant were added in the reverse order.

[0155] [Resin particle dispersion containing inorganic particles (2) to (7)] Each inorganic particle-containing resin particle dispersion was produced in the same manner as in the preparation of inorganic particle-containing resin particle dispersion (1), except that resin composition (1) was replaced with any of resin compositions (2) to (7).

[0156] [Resin particle dispersion containing inorganic particles (8)] The following materials were prepared: Organic solvent (1): Ethyl acetate: 40 parts Organic solvent (2): Isopropanol: 25 parts ·Resin composition (1): 100 parts Basic compound: 10% ammonia water: 10 parts Surfactant: 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7, Sanyo Chemical Industries, Ltd.): 5 parts Ion-exchanged water (4): 200 parts of ion-exchanged water at 40°C

[0157] -Process (1)- Organic solvent (1) and organic solvent (2) were charged into a stirring vessel equipped with a stirrer, condenser, heater, and thermometer to prepare a mixed solvent. While maintaining the temperature inside the stirring vessel at 40°C, resin composition (1) was charged and stirred for 60 minutes. Next, a basic compound was charged and stirred for 30 minutes. Next, a surfactant was charged and stirred for 30 minutes.

[0158] -Process (2)- While maintaining the temperature inside the stirring tank and continuing stirring, ion-exchanged water (4) was added dropwise over 90 minutes to emulsify the contents. While maintaining the temperature inside the stirring tank in the range of 40°C to 55°C, the pressure inside the stirring tank was reduced to 10 kPa to remove the organic solvent from the emulsion. Thereafter, the temperature inside the stirring tank was lowered to room temperature, and the emulsion was passed through a sieve and an appropriate amount of ion-exchanged water was added to obtain inorganic particle-containing resin particle dispersion (8). The solids concentration of inorganic particle-containing resin particle dispersion (8) was 25%. The particle size distribution of the particles in the inorganic particle-containing resin particle dispersion (8) was measured using a laser diffraction particle size distribution analyzer (model number: LA-700, Horiba, Ltd.). The volume average particle size is shown in Table 1.

[0159] [Resin particle dispersion containing inorganic particles (9)~(10)] Each inorganic particle-containing resin particle dispersion was produced in the same manner as in the preparation of inorganic particle-containing resin particle dispersion (1), except that resin composition (1) was changed to resin composition (8) or resin composition (9).

[0160] [Resin particle dispersion containing inorganic particles (11)] An inorganic particle-containing resin particle dispersion (11) was produced in the same manner as in the preparation of the inorganic particle-containing resin particle dispersion (1), except that in step (1), the surfactant was not added to the fourth block of the barrel, but was added to the raw material inlet simultaneously with the resin composition (1) and a 20% aqueous solution of sodium hydroxide.

[0161] [Resin particle dispersion containing inorganic particles (12) to (14)] Each inorganic particle-containing resin particle dispersion was produced in the same manner as in the preparation of inorganic particle-containing resin particle dispersion (1), except that resin composition (1) was changed to any of resin compositions (10) to (12).

[0162] Example 1: Production of toner and developer [Preparation of amorphous polyester resin particle dispersion (1)] Terephthalic acid: 20 parts Fumaric acid: 35 parts Bisphenol A ethylene oxide adduct: 10 parts Bisphenol A propylene oxide adduct: 135 parts The above materials were charged into a flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and distillation column. The temperature of the reaction solution was raised to 220°C over 1 hour, and 1 part of titanium tetraethoxide was added for every 100 parts of the above materials. The temperature of the reaction solution was raised to 230°C over 30 minutes while distilling off the resulting water. The dehydration condensation reaction was continued for 1 hour while maintaining the temperature at 230°C. The reaction mixture was then cooled to room temperature. This resulted in an amorphous polyester resin with an acid value of 12.0 mgKOH / g, a weight-average molecular weight of 18,000, and a glass transition temperature of 60°C.

[0163] A mixed solvent was prepared by adding 40 parts of ethyl acetate and 25 parts of 2-butanol to a vessel equipped with a temperature control device and a nitrogen purge device. 100 parts of amorphous polyester resin was gradually added to the mixed solvent and dissolved. A 10% aqueous ammonia solution (equivalent to three times the molar amount of the resin's acid value) was then added and stirred for 30 minutes. The atmosphere inside the vessel was then purged with dry nitrogen, the temperature of the reaction solution was maintained at 40°C, and 400 parts of ion-exchanged water was added dropwise at a rate of 2 parts / min while stirring the reaction solution, resulting in emulsification. After the addition of ion-exchanged water was completed, the emulsion was cooled to room temperature (20°C to 25°C), and dry nitrogen was bubbled through the emulsion while stirring for 48 hours, reducing the total amount of ethyl acetate and 2-butanol to 1000 ppm or less. Ion-exchanged water was added to the emulsion to adjust the solids concentration to 20%. Thus, an amorphous polyester resin particle dispersion (1) was obtained. The volume average particle size of the particles in the amorphous polyester resin particle dispersion (1) was 160 nm.

[0164] [Preparation of Release Agent Particle Dispersion (1)] Paraffin wax (HNP-9, Nippon Seiro Co., Ltd.): 100 units Ion-exchanged water: 350 parts Anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku Co., Ltd., 20% aqueous solution) : 1 copy The above materials were mixed and heated to 100°C, and dispersed using a homogenizer (Ultra Turrax T50, IKA), followed by a pressure discharge homogenizer (Manton-Gaulin high-pressure homogenizer, Gaulin). The particles were collected when the volume average particle size reached 200 nm. An appropriate amount of ion-exchanged water was added to obtain a release agent particle dispersion (1) with a solids concentration of 20%.

[0165] [Preparation of Colorant Particle Dispersion (1)] Cyan pigment (CI Pigment Blue 15:3, Dainichiseika Color & Chemicals Mfg. Co., Ltd.): 20 parts Ion-exchanged water: 80 parts Anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku Co., Ltd., 20% aqueous solution) : 2nd part The above materials were mixed and dispersed for 1 hour using a high-pressure impact disperser (Ultimizer HJP30006, manufactured by Sugino Machine Co., Ltd.), and the mixture was collected when the volume average particle size reached 180 nm. An appropriate amount of ion-exchanged water was added to obtain a colorant particle dispersion (1) with a solids concentration of 20%.

[0166] [Production of toner particles] -First coagulation process- ·Resin particle dispersion containing inorganic particles (1): 25 parts Amorphous polyester resin particle dispersion (1): 25 parts Release agent particle dispersion (1): 10 parts Colorant particle dispersion (1): 10 parts Ion-exchanged water: 9 parts Anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku Co., Ltd., 20% aqueous solution) : 1 copy The above materials were placed in a round stainless steel flask, and 0.1 N nitric acid was added to adjust the pH to 3.5. 30 parts of a nitric acid aqueous solution containing 10% polyaluminum chloride was then added. The liquid temperature was adjusted to 30°C using an oil bath, and the mixture was dispersed using a homogenizer (Ultra-Turrax T50, IKA). The liquid temperature was then raised to 45°C and maintained for 30 minutes to form primary aggregated particles.

[0167] -Second coagulation process- While maintaining the temperature of the dispersion containing the first aggregated particles at 45° C., 20 parts of the amorphous polyester resin particle dispersion (1) was added, and the mixture was maintained for 60 minutes to form second aggregated particles.

[0168] -Combining process- A 0.1 N aqueous solution of sodium hydroxide was added to the dispersion containing the second aggregated particles to adjust the pH to 8.5, and the liquid temperature was raised to 84°C and maintained for 150 minutes. The liquid was then cooled to 20°C at a rate of 20°C / min, and the solid matter was filtered off, washed with ion-exchanged water, and dried. The dried matter was sieved to obtain toner particles (1). The volume average particle size of the toner particles (1) was 6.0 μm.

[0169] [Manufacturing of externally added toner] To 100 parts of toner particles (1), 1.5 parts of dimethylsilicone oil-treated dry-process silica particles with a primary particle size of 40 nm and 1.0 part of hydrophobic titanium oxide (product number: T805, Nippon Aerosil Co., Ltd.) were added and mixed using a sample mill at 10,000 rpm for 30 seconds.The mixture was then sieved using a vibrating sieve with 45 μm openings to obtain an externally added toner.

[0170] [Manufacture of carrier (1)] A dispersion was prepared by dispersing 14 parts of toluene, 5 parts of a cyclohexyl methacrylate-monoethylaminoethyl methacrylate copolymer (mass ratio 95:5, weight average molecular weight 60,000), and 0.2 parts of carbon black (product number: VXC-72, Cabot Japan Co., Ltd.) in a sand mill. The dispersion and 100 parts of ferrite particles (average particle size 35 μm) were placed in a vacuum degassing kneader, and the mixture was stirred under reduced pressure and dried to obtain carrier (1).

[0171] [Manufacturing of developer] 8 parts of the externally added toner and 92 parts of the carrier (1) were placed in a V-blender and stirred for 20 minutes, after which the mixture was sieved through a sieve with 212 μm openings to obtain a developer.

[0172] <Examples 2 to 14, Comparative Examples 1 and 2> In the same manner as in Example 1, except that the type of inorganic particle-containing resin particle dispersion was changed as shown in Table 1, each toner particle, toner with external additives, and developer were prepared.

[0173] Example 15 Toner particles, toner with external additives, and developer were prepared in the same manner as in Example 1, except that the materials used in the first aggregation step and the second aggregation step in the production of toner particles were changed as follows. -First coagulation process- ·Resin particle dispersion containing inorganic particles (1): 50 parts Release agent particle dispersion (1): 10 parts Colorant particle dispersion (1): 10 parts Ion-exchanged water: 9 parts Anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku Co., Ltd., 20% aqueous solution) : 1 copy -Second coagulation process- ·Resin particle dispersion containing inorganic particles (1): 20 parts

[0174] <Performance evaluation> [Fixing Offset] The developer was filled into the developing unit of a modified image forming apparatus, ApeosPortIV C4470 (Fujifilm Business Innovation Co., Ltd.). The process speed of the image forming apparatus was set to 175 mm / sec, and the fixing temperature was set to 160°C. A 20 cm x 25 cm solid image (toner loading amount 127 g / m) was printed on A4 size plain paper in an environment of 23°C temperature and 70% relative humidity. 2 ) were formed. The gloss was measured at five points (the center and four corners) of each solid image on the first, tenth, and 100th sheets. The gloss was measured using a gloss meter GM-26D (Murakami Color Research Laboratory Co., Ltd.) at an incident light angle of 75 degrees to the image. The difference between the maximum and minimum values ​​of the 15 measured values ​​(Δgloss) was classified as follows: The results are shown in Table 1. The smaller the Δgloss, the more the fixing offset is suppressed. A: Δgloss is less than 2.0 B: Δgloss is 2.0 or more and less than 4.0 C: Δ gloss is 4.0 or more and less than 6.0 D: Δ gloss is 6.0 or more and less than 8.0 E: Δ gloss is 8.0 or more

[0175] [Table 1]

[0176] The meanings of the abbreviations in Table 1 are as follows: PEs: Polyester resin

[0177] The method for producing a resin particle dispersion and the method for producing a toner for developing electrostatic images according to the present disclosure include the following aspects.

[0178] (Addendum) (((1))) (1) a step of mixing a resin composition containing a resin and inorganic particles, a basic compound, and a surfactant by applying heat and shear force; Following the step (1), a step (2) of emulsifying the mixture by adding an aqueous medium while applying a shear force, In the step (1), the resin composition and the basic compound are mixed together, and then the surfactant is mixed therewith, or the resin composition is mixed with the basic compound and the surfactant at the same time. A method for producing a resin particle dispersion. (((2))) The method for producing a resin particle dispersion according to (((1))), wherein the inorganic particles account for 0.1% by mass or more and 20% by mass or less in the resin composition. (((3))) The method for producing a resin particle dispersion according to (((1))) or (((2))), wherein the inorganic particles include at least one kind selected from the group consisting of silica particles, alumina particles, and titania particles. (((4))) The method for producing a resin particle dispersion liquid according to any one of (((1))) to (((3))), wherein no organic solvent is used in the steps (1) and (2). (((5))) obtaining a resin particle dispersion by the method for producing a resin particle dispersion according to any one of (((1))) to (((4))); aggregating the resin particles in the resin particle dispersion to form aggregated particles; and heating the dispersion containing the aggregated particles to fuse and coalesce the aggregated particles to form toner particles. A method for producing a toner for developing electrostatic images.

[0179] According to (((1))), (((3))), or (((4))), there is provided a method for producing a resin particle dispersion containing resin particles that can produce a toner that suppresses offset when a toner image is fixed to a recording medium, compared to a production method in which a surfactant is mixed with a resin composition before a basic compound is mixed with a resin composition in step (1). According to (((2))), a method for producing a resin particle dispersion containing resin particles that can produce a toner that suppresses offset when a toner image is fixed to a recording medium is provided, compared to a production method in which the proportion of inorganic particles in the resin composition is less than 0.1 mass % or more than 20 mass %. According to (((5))), a method for producing a toner for developing electrostatic images is provided, which can produce a toner that suppresses offset when a toner image is fixed to a recording medium.

Claims

1. (1) a step of mixing a resin composition containing a resin and inorganic particles, a basic compound, and a surfactant by applying heat and shear force; The method includes a step (2) of emulsifying the emulsion by adding an aqueous medium while applying a shear force, subsequent to the step (1), In the step (1), the resin composition and the basic compound are mixed together, and then the surfactant is mixed therewith, or the basic compound and the surfactant are simultaneously mixed into the resin composition. A method for producing a resin particle dispersion.

2. The method for producing a resin particle dispersion according to claim 1 , wherein the inorganic particles account for 0.1% by mass or more and 20% by mass or less of the resin composition.

3. The method for producing a resin particle dispersion according to claim 1 , wherein the inorganic particles include at least one kind selected from the group consisting of silica particles, alumina particles, and titania particles.

4. The method for producing a resin particle dispersion according to claim 1 , wherein no organic solvent is used in the steps (1) and (2).

5. Obtaining a resin particle dispersion by the method for producing a resin particle dispersion according to any one of claims 1 to 4; aggregating the resin particles in the resin particle dispersion to form aggregated particles; and heating the dispersion containing the aggregated particles to fuse and coalesce the aggregated particles to form toner particles. A method for producing a toner for developing electrostatic images.

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