Method for manufacturing toner for electrostatic image development, toner for electrostatic image development, and electrostatic image developer

Abstract

To provide a method for producing a toner for electrostatic charge image development which can shorten fusing time while suppressing occurrence of coarse powder.SOLUTION: A method for producing a toner for electrostatic charge image development includes a step A of preparing a first dispersion liquid where first aggregated particles containing a binder resin are dispersed, a step B of depositing resin particles onto the surface of the first aggregated particles in the first dispersion liquid and preparing second aggregated particles, and preparing a second dispersion liquid where the second aggregated particles are dispersed, a step C of raising the temperature of the second dispersion liquid to a fusion temperature at which the second aggregated particles in the second dispersion liquid are fused, and a step D of keeping the temperature of the second dispersion liquid at the fusion temperature, wherein at least one of the step C and the step D adds 20 mass% or more of a weak acid with respect to the mass of the second aggregated particles to the second dispersion liquid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an electrostatic charge image developing toner, an electrostatic charge image developing toner, and an electrostatic charge image developer.

Background Art

[0002] In Patent Document 1, an aggregating agent and a stabilizer are added to an aqueous dispersion containing at least polymer fine particles and colorant fine particles to associate a large number of the above fine particles, and the associated particles are heat-fused at a temperature not lower than the glass transition temperature of the polymer fine particles. In the method for manufacturing an electrostatic charge image developing toner, a method for manufacturing an electrostatic charge image developing toner in which at least the concentration of either the aggregating agent or the stabilizer, which is a nonionic surfactant, is changed during heat fusion is disclosed.

[0003] In Patent Document 2, a resin particle dispersion liquid in which crystalline polyester resin-containing binder resin particles are dispersed and a colorant dispersion liquid in which a colorant is dispersed are mixed, and an aggregating agent is added thereto to form aggregated particles. An aggregating particle forming step, and a fusing and unifying step of heating the aggregated particles and fusing and unifying them while adding an acid and a surfactant are disclosed. A method for manufacturing an electrostatic charge developing toner characterized by including the steps is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The object of this disclosure is to provide a method for manufacturing toner for electrostatic image development that can shorten the fusion time while suppressing the generation of coarse powder, compared to adding a strong acid to the second dispersion or adding a weak acid of less than 20% by mass relative to the mass of the second aggregated particles, in at least one of the following steps: step C, in which the second dispersion is heated to a fusion temperature at which the second aggregated particles in the second dispersion fuse; and step D, in which the second dispersion is held at the fusion temperature. [Means for solving the problem]

[0006] The means for solving the aforementioned problem include the following embodiments. <1> Step A involves preparing a first dispersion in which first aggregated particles containing a binder resin are dispersed, Step B involves attaching resin particles to the surface of the first aggregated particles in the first dispersion to produce second aggregated particles, and preparing a second dispersion in which the second aggregated particles are dispersed. Step C involves raising the temperature of the second dispersion to a fusion temperature at which the two aggregated particles in the second dispersion fuse together. Step D involves holding the second dispersion at the fusion temperature, Includes, A method for producing toner for electrostatic image development, comprising adding a weak acid of 20% by mass or more relative to the mass of the second aggregated particles to the second dispersion in at least one of the C and D steps.

[0007] <2> The weak acid is at least one selected from the group consisting of carbonic acid, phosphoric acid, carboxylic acid compounds, and sulfonic acid compounds. <1> A method for manufacturing toner for electrostatic image developing as described above. <3> The aforementioned weak acid is carbonic acid. <2> A method for manufacturing toner for electrostatic image developing as described above. <4> The addition of the weak acid to the second dispersion is carried out by adding carbonated water to the second dispersion. <3> A method for manufacturing toner for electrostatic image developing as described above. <5> The addition of the weak acid to the second dispersion is carried out by adding carbon dioxide to the second dispersion. <3> A method for manufacturing toner for electrostatic image developing as described above. <6> The addition of the weak acid is completed before the pH of the second dispersion reaches 7. <1> ~ <5> A method for manufacturing electrostatic image developing toner as described in any one of the following. <7> The weak acid is added in an amount of 90% by mass or less relative to the mass of the second aggregated particles. <1> ~ <6> A method for manufacturing electrostatic image developing toner as described in any one of the following. <8> The surfactant content in the second dispersion after step D is 5% by mass or less relative to the total solid content in the second dispersion. <1> ~ <7> A method for manufacturing electrostatic image developing toner as described in any one of the following. <9> <1> ~ <8> A toner for developing electrostatic images manufactured by the method for manufacturing electrostatic image developing toner described in any one of the following documents. <10> <1> ~ <8> An electrostatic image developer containing an electrostatic image developer toner manufactured by the method for manufacturing electrostatic image developer toner described in any one of the above. [Effects of the Invention]

[0008] <1> , <2> , <3> , <4> , or <5> According to the invention, a method for manufacturing toner for electrostatic image development is provided in which, compared to adding a strong acid to the second dispersion or adding a weak acid of less than 20% by mass relative to the mass of the second aggregated particles, the generation of coarse powder is suppressed and the fusion time is shortened, in at least one of step C, in which the temperature is raised to a fusion temperature at which the second aggregated particles in the second dispersion fuse, and step D, in which the second dispersion is held at the fusion temperature. <6> According to the invention, a method for manufacturing electrostatic image developing toner is provided that can suppress the generation of coarse powder compared to a case where the addition of a weak acid is terminated when the pH of the second dispersion becomes less than 7. <7> According to the invention, a method for producing electrostatic image developing toner is provided that can suppress the generation of coarse powder compared to the case in which a weak acid is added in an amount exceeding 90% by mass relative to the mass of the second aggregated particles. <8> According to the invention, a method for manufacturing electrostatic image developing toner is provided that facilitates wastewater treatment compared to the case where the surfactant content in the second dispersion after step D is more than 5% by mass relative to the total solid content in the second dispersion. <9> According to the invention, a toner for electrostatic image development with less coarse powder is provided. <10> According to the invention, an electrostatic image developer containing an electrostatic image developer toner with low coarse powder content is provided. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

[0010] In this disclosure, the numerical range indicated using "~" represents a range that includes the numbers before and after "~" as the minimum and maximum values, respectively.

[0011] In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0012] In this disclosure, the term "process" includes not only independent processes but also any process that cannot be clearly distinguished from other processes, provided that its intended purpose is achieved.

[0013] In this disclosure, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple types of the substance corresponding to each component in the composition, it means the total amount of those multiple types of substances present in the composition unless otherwise specified.

[0014] In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified.

[0015] In the present disclosure, “(meth)acryl” means at least one of acrylic and methacrylic, and “(meth)acrylate” means at least one of acrylate and methacrylate.

[0016] In the present disclosure, “toner” refers to “toner for electrostatic charge image development”, “developer” refers to “electrostatic charge image developer”, and “carrier” refers to “carrier for electrostatic charge image development”.

[0017] <Method for manufacturing toner for electrostatic charge image development> The method for manufacturing the toner according to this embodiment is Step A of preparing a first dispersion liquid in which first aggregated particles containing a binder resin are dispersed; Step B of producing second aggregated particles by attaching resin particles to the surface of the first aggregated particles in the first dispersion liquid and preparing a second dispersion liquid in which the second aggregated particles are dispersed; Step C of heating the second dispersion liquid to a fusing temperature at which the second aggregated particles in the second dispersion liquid fuse; Step D of holding the second dispersion liquid at the fusing temperature; and includes In at least one of Step C and Step D, a weak acid of 20% by mass or more with respect to the mass of the second aggregated particles is added to the second dispersion liquid.

[0018] For example, a method of obtaining toner particles is known in which binder resin particles or the like are aggregated using a flocculant such as a metal salt, and further binder resin is attached to the surface of the obtained first aggregated particles to form second aggregated particles, and then the second aggregated particles are heated and fused. Such a method is called the EA (Emulsion Aggregation) method, and is a method of aggregating material particles in a dispersion medium in which the material particles are dispersed, and then fusing and combining the aggregated particles to manufacture toner particles. In the process of fusing the second aggregate particles, the second aggregate particles are heated to a certain temperature or higher to promote their fusion, and the circularity of the fused and combined second aggregate particles (i.e., toner particles) is adjusted to a desired value. At this time, there is a method of heating the second aggregate particles to a high temperature, but this method takes a long time, so the hydrolysis of the binder resin contained in the second aggregate particles progresses, resulting in softened parts, and coarse powder (so-called coarse particles) may be generated due to adhesion between the toner particles. Therefore, one method to promote the fusion of the second aggregated particles is to adjust the pH of the system by adding an acid to the dispersion in which the second aggregated particles are dispersed. In this method, the second aggregated particles can be fused and coalesced to the desired degree of circularity in a short fusion time. However, depending on the type of acid, a localized decrease in repulsive force may occur on the surface of the second aggregated particles, causing adhesion between particles and potentially generating coarse powder. Furthermore, depending on the amount of acid added, it may not be possible to sufficiently promote the fusion of the second aggregated particles.

[0019] According to the toner manufacturing method of this embodiment, having the configuration described later, it is possible to suppress the generation of coarse powder while shortening the fusion time. In the toner manufacturing method according to this embodiment, in at least one of steps C and D, which are steps for fusing the second aggregated particles, a weak acid of 20% by mass or more relative to the mass of the second aggregated particles is added to the second dispersion in which the second aggregated particles are dispersed. By adding a weak acid in this way, it is presumed that the reduction in local repulsive force on the surface of the second aggregated particles can be suppressed, and as a result, the generation of coarse powder can be suppressed. Furthermore, it is presumed that by specifying the amount of weak acid added as described above, the fusing of the second aggregated particles can be sufficiently promoted, and the fusion time to the desired circularity can be shortened. In this disclosure, "fusion time" means the time from when the second dispersion reaches the fusion temperature in step C until the second aggregated particles (i.e., toner particles) after fusion and coalescence reach the desired circularity.

[0020] The following describes in detail each step in the toner manufacturing method according to this embodiment, and the materials used in each step. In the toner manufacturing method according to this embodiment, toner particles with a core-shell structure are obtained.

[0021] [Process A] In the toner manufacturing method according to this embodiment, first, step A is performed. Step A is a step in which a first dispersion liquid is prepared in which first aggregated particles containing a binder resin are dispersed. The first dispersion containing the first aggregated particles is obtained by agglomerating at least the binder resin particles in a dispersion containing at least the binder resin particles. The dispersion used to obtain the first dispersion may contain, in addition to the binder resin particles, at least one of the mold release agent particles and the coloring agent particles. Therefore, the first aggregated particles contained in the first dispersion may be obtained by agglomerating the binder resin particles along with at least one of the mold release agent particles and the coloring agent particles. In other words, the first aggregated particles contained in the first dispersion may contain the binder resin along with at least one of the mold release agent and the coloring agent.

[0022] The dispersion used to obtain the first dispersion is prepared by separately preparing a resin particle dispersion containing binder resin particles, a release agent particle dispersion containing release agent particles, and a colorant particle dispersion containing colorant particles, and mixing these particle dispersions. The order in which these particle dispersions are mixed is not limited.

[0023] In the following explanation, aspects common to resin particle dispersions, mold release agent particle dispersions, and colorant particle dispersions will be collectively referred to as "particle dispersions."

[0024] One example of a particle dispersion is a dispersion in which a material is dispersed in a dispersion medium in the form of particles using a surfactant.

[0025] A water-based medium is preferred as the dispersion medium for the particle dispersion. Examples of water-based mediums include water and alcohol. Water with reduced ion content, such as distilled water or ion-exchanged water, is preferred. These water-based mediums may be used individually or in combination of two or more.

[0026] The surfactant used to disperse the material in the dispersion medium may be anionic, cationic, or nonionic surfactant. Examples include anionic surfactants such as sulfate esters, sulfonates, phosphates, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Surfactants may be used individually or in combination of two or more. Nonionic surfactants may be used in combination with anionic or cationic surfactants.

[0027] Known dispersion methods for dispersing materials in particulate form in a dispersion medium include rotary shear homogenizers, ball mills with media, sand mills, and dyno mills.

[0028] One method for dispersing resins in particulate form within a dispersion medium is phase inversion emulsification. Phase inversion emulsification involves dissolving the resin in a hydrophobic organic solvent in which the resin is soluble, neutralizing the organic continuous phase (O phase) by adding a base, and then adding an aqueous medium (W phase) to perform a phase inversion from W / O to O / W, thereby dispersing the resin in particulate form within the aqueous medium.

[0029] The volume-average particle size of the particles dispersed in the particle dispersion is preferably 30 nm to 460 nm, more preferably 50 nm to 300 nm, even more preferably 60 nm to 250 nm, and even more preferably 80 nm to 200 nm. The volume-average particle size of particles in a particle dispersion refers to the particle size at which the cumulative total from the smallest diameter side reaches 50% in the particle size distribution measured by a laser diffraction particle size distribution analyzer (for example, LA-700 manufactured by Horiba, Ltd.).

[0030] The particle content in the particle dispersion is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less, and even more preferably 15% by mass or more and 30% by mass or less.

[0031] -Binding resin- Examples of binder resins include vinyl resins consisting of monomer homopolymers of styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (e.g., ethylene, propylene, butadiene, etc.), etc., or copolymers of two or more of these monomers. Examples of binder resins include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin; mixtures of these with the aforementioned vinyl resins; and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These binding resins may be used individually or in combination of two or more types.

[0032] Polyester resin is preferred as the binder resin. Examples of polyester resins include amorphous polyester resin and crystalline polyester resin.

[0033] In this embodiment, "crystalline" of the polyester resin refers to having a clear endothermic peak rather than a stepwise change in endothermic quantity in differential scanning calorimetry (DSC). Specifically, it refers to the fact that the full width at half maximum of the endothermic peak measured at a heating rate of 10°C / min is within 10°C. In this embodiment, "amorphous" in the polyester resin refers to a full width at half maximum exceeding 10°C, exhibiting a stepwise change in endothermic capacity, or not showing a clear endothermic peak.

[0034] -Amorphous polyester resin- 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.

[0035] 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, alkenyl succinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), their anhydrides, or their lower alkyl esters (e.g., with 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids. Polycarboxylic acids may be used in combination with dicarboxylic acids, or with trivalent or higher carboxylic acids that have a cross-linked or branched structure. Examples of trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, their anhydrides, or their lower alkyl esters (e.g., having 1 to 5 carbon atoms). Polycarboxylic acids may be used individually or in combination of two or more.

[0036] 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, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc.). Among these, aromatic diols and alicyclic diols are preferred as polyhydric alcohols, and aromatic diols are more preferred. As the polyhydric alcohol that is the polymerization component of amorphous polyester resin, a trivalent or higher polyhydric alcohol that has a crosslinked or branched structure may be used in combination with the diol. Examples of trivalent or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. Polyhydric alcohols may be used individually or in combination of two or more types.

[0037] The glass transition temperature (Tg) of amorphous polyester resin is preferably 50°C to 80°C, and more preferably 50°C to 65°C. The glass transition temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, from the "extracorporeal glass transition onset temperature" described in the method for determining the glass transition temperature in JIS K 7121-1987 "Method for Measuring the Transition Temperature of Plastics".

[0038] The weight-average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 to 1,000,000, and more preferably 7,000 to 500,000. The number-average molecular weight (Mn) of the amorphous polyester resin is preferably between 2,000 and 100,000. The molecular weight distribution (Mw / Mn) of the amorphous polyester resin is preferably 1.5 to 100, and more preferably 2 to 60. Weight-average molecular weight and number-average molecular weight are measured by gel permeation chromatography (GPC). GPC molecular weight measurement is performed using a Tosoh GPC-HLC-8120GPC analyzer, a Tosoh TSKgel SuperHM-M (15cm) column, and THF solvent. The weight-average molecular weight and number-average molecular weight are calculated from these measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0039] Amorphous polyester resins can be obtained by known manufacturing methods. Specifically, for example, they can be obtained by a method in which the polymerization temperature is set to 180°C or higher and 230°C or lower, and the reaction system is subjected to reduced pressure as needed, while removing water and alcohol generated during condensation. If the monomers of the raw materials do not dissolve or miscible at the reaction temperature, a high-boiling point solvent may be added as a solubilizer to dissolve them. In this case, the polycondensation reaction should be carried out while distilling off the solubilizer. If there are monomers with poor miscibility in the copolymerization reaction, it is advisable to condense the poorly miscible monomers with the acid or alcohol to be polycondensed with them beforehand, and then polycondense them with the main component.

[0040] -Crystalline polyester resin- Crystalline polyester resin may be a commercially available product or a synthetic product. Examples of crystalline polyester resins include polycondensates of polycarboxylic acids and polyhydric alcohols. Because crystalline polyester resins readily form a crystalline structure, polycondensates using linear aliphatic polymerizable monomers are preferred over polymerizable monomers having aromatic rings.

[0041] 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., phthalic acid, isophthalic acid, terephthalic acid, dibasic acids such as naphthalene-2,6-dicarboxylic acid, etc.), their anhydrides, or their lower alkyl esters (e.g., having 1 to 5 carbon atoms). Polycarboxylic acids may be used in combination with dicarboxylic acids, or with trivalent or higher carboxylic acids that have a crosslinked or branched structure. Examples of trivalent carboxylic acids include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalentricarboxylic acid, etc.), their anhydrides, or their lower alkyl esters (e.g., having 1 to 5 carbon atoms). In addition to these dicarboxylic acids, polycarboxylic acids with sulfonic acid groups and dicarboxylic acids with ethylenic double bonds may also be used in combination. Polycarboxylic acids may be used individually or in combination of two or more.

[0042] -Release agent- Examples of release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum-based waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. However, the release agents are not limited to these.

[0043] The melting temperature of the release agent is preferably 50°C to 110°C, and more preferably 60°C to 100°C. The melting temperature of the release agent is determined from the DSC curve obtained by differential scanning calorimetry (DSC), according to the "melting peak temperature" described in JIS K7121:1987 "Method for determining the transition temperature of plastics".

[0044] -Coloring agent- Examples of colorants include carbon black, chrome yellow, Hansa yellow, benzidine yellow, surene 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, risole red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, and Pigments such as ultramarine blue, chalcioyl blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate; dyes such as acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thioindico, dioxazine, thiazine, azomethine, indico, phthalocyanine, aniline black, polymethine, triphenylmethane, diphenylmethane, and thiazole; and others. A single coloring agent may be used alone, or two or more may be used in combination.

[0045] The coloring agent may be a surface-treated coloring agent as needed, and may be used in combination with a dispersant.

[0046] A dispersion liquid obtained by mixing multiple types of particle dispersions is called a "mixed dispersion liquid."

[0047] It is preferable to adjust the pH of the mixed dispersion to a range of 3 to 4 after mixing multiple types of particle dispersions. Means for adjusting the pH of the mixed dispersion include adding an acidic aqueous solution such as nitric acid aqueous solution, hydrochloric acid aqueous solution, or sulfuric acid aqueous solution.

[0048] The mass ratio of particles contained in the mixed dispersion is preferably within the following range. When the mixed dispersion contains release agent particles, the mass ratio of binder resin particles to release agent particles is preferably 100:3 to 100:30, more preferably 100:5 to 100:25, and even more preferably 100:8 to 100:20. When the mixed dispersion contains coloring agent particles, the mass ratio of binding resin particles to coloring agent particles is preferably 100:5 to 100:35, more preferably 100:7 to 100:30, and even more preferably 100:9 to 100:25.

[0049] The volume-average particle size of the binder resin particles contained in the mixed dispersion is preferably 30 nm to 460 nm, more preferably 50 nm to 300 nm, even more preferably 60 nm to 250 nm, and even more preferably 80 nm to 200 nm. The volume-average particle size of particles in a particle dispersion refers to the particle size at which the cumulative total from the smallest diameter side reaches 50% in the particle size distribution measured by a laser diffraction particle size distribution analyzer (for example, LA-700 manufactured by Horiba, Ltd.).

[0050] The total mass of the binder resin particles contained in the mixed dispersion is preferably 50% by mass or more and 90% by mass or less, more preferably 55% by mass or more and 90% by mass or less, and even more preferably 60% by mass or more and 90% by mass or less, relative to the total amount of toner particles produced.

[0051] A preferred method for obtaining a first dispersion containing the first aggregated particles is, for example, The process involves adding a coagulant to the mixed dispersion while stirring it, It is preferable that the method includes adding a flocculant to the mixed dispersion, and then heating the mixed dispersion while stirring to raise its temperature.

[0052] Examples of flocculants include surfactants with opposite polarity to the surfactant contained in the mixed dispersion, inorganic metal salts, and metal complexes with a valency of 2 or higher. One type of flocculant may be used alone, or two or more types may be used in combination.

[0053] 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.

[0054] As a flocculant, a metal salt compound with a valency of 2 or higher is preferred, a metal salt compound with a valency of 3 or higher is more preferred, and a trivalent inorganic aluminum salt compound is even more preferred. Examples of trivalent inorganic aluminum salt compounds include aluminum chloride, aluminum sulfate, polyaluminum chloride, and polyaluminum hydroxide.

[0055] The amount of flocculant added is not limited. When using a trivalent metal salt compound as a flocculant, the amount of trivalent metal salt compound 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, per 100 parts by mass of the binder resin.

[0056] When heating the mixed dispersion, the target temperature of the mixed dispersion 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 - 10°C) or lower. If the mixed dispersion contains multiple types of binder resin particles with different Tg values, the lowest temperature among the Tg values ​​is defined as the Tg of the binder resin particles.

[0057] As described above, a first dispersion is obtained in which first aggregated particles containing a binder resin (preferably containing a binder resin, a release agent, and a coloring agent) are dispersed.

[0058] [B process] In the toner manufacturing method according to this embodiment, step B is performed after step A. Step B is a process of preparing a second dispersion in which resin particles are attached to the surface of the first aggregated particles in the first dispersion to create second aggregated particles, and the second dispersion in which the second aggregated particles are dispersed. One method for producing the second aggregated particles is to mix a first dispersion containing the first aggregated particles with a dispersion containing resin particles, thereby causing the resin particles to adhere to the surface of the first aggregated particles.

[0059] As the dispersion containing resin particles to be mixed with the first dispersion, it is preferable to use at least one selected from the binder resin particle dispersions used to obtain the first aggregated particles in step A, with a polyester resin particle dispersion being more preferable. In other words, it is preferable to produce second aggregated particles by attaching binder resin particles to the surface of the first aggregated particles.

[0060] A preferred method for obtaining a second dispersion containing the second aggregated particles is, for example, The first dispersion containing the first aggregated particles is stirred while adding a dispersion containing resin particles to the first dispersion. The method includes adding a dispersion containing resin particles, and then heating the dispersion containing first aggregated particles with resin particles attached to its surface while stirring.

[0061] When heating a dispersion containing first aggregated particles with resin particles attached to its surface, the target temperature of the dispersion is preferably a temperature based on the glass transition temperature (Tg) of the resin particles, for example, (Tg-30°C) or higher and (Tg-10°C) or lower.

[0062] In this manner, a second dispersion is obtained in which second aggregated particles, each having resin particles attached to the surface of the first aggregated particles, are dispersed.

[0063] [E process] In the toner manufacturing method according to this embodiment, after step B and before step C, step E may be performed to stop the growth of the second aggregated particles after they have grown to a desired size. One method for stopping the growth of the second aggregated particles is to add a chelating agent to the flocculant used in step A.

[0064] 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 chelating agent added is preferably 0.01 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of binder resin particles, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass.

[0065] One way to stop the growth of the second aggregated particles is to increase the pH of the second dispersion. A means of increasing the pH of the second dispersion is to add at least one substance selected from the group consisting of aqueous solutions of alkali metal hydroxides and aqueous solutions of alkaline earth metal hydroxides. Examples of aqueous solutions of alkali metal hydroxides or alkaline earth metal hydroxides include aqueous solutions of sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, with aqueous solution of sodium hydroxide being preferred. The pH of the second dispersion is preferably between 8 and 10.

[0066] In this way, a second dispersion is obtained in which the second aggregated particles, which have grown to the desired size, are dispersed.

[0067] [C process and D process] In the toner manufacturing method according to this embodiment, steps C and D are performed after step B or after step E. Step C is a process of raising the temperature of the second dispersion to the fusion temperature at which the second aggregated particles in the second dispersion fuse together. Furthermore, step D is a process of holding the second dispersion at the fusion temperature. Through steps C and D, the second aggregated particles fuse together and coalesce to obtain toner particles. In the toner manufacturing method according to this embodiment, at least 20% by mass or more of a weak acid relative to the mass of the second aggregated particles is added to the second dispersion in at least one of steps C and D. In other words, in the process of raising the temperature of the second dispersion in step C, and in the process of maintaining the temperature of the second dispersion in step D, a weak acid of 20% by mass or more relative to the mass of the second aggregated particles is added to the second dispersion.

[0068] In step C, the temperature is raised to the fusion temperature at which the second aggregated particles fuse. This fusion temperature is preferably above the glass transition temperature (Tg) of the binder resin, and more preferably above (Tg + 10°C) and below (Tg + 40°C) of the binder resin. If the second aggregated particles contain multiple types of binder resins with different Tg values, the highest temperature among the Tg values ​​is defined as the Tg of the binder resin. The heating rate to reach the fusion temperature is preferably, for example, 0.1°C / min or more and 2.0°C / min or less, and more preferably 0.2°C / min or more and 1.0°C / min or less.

[0069] In step D, the second dispersion, which was heated in step C, is held at the fusion temperature. The holding time is the time it takes for the second aggregated particles to fuse and coalesce, and for the coalesced particles (i.e., toner particles) to reach the desired circularity. The circularity of the coalesced particles in the second dispersion is measured intermittently over time, and when the desired circularity is reached, step D is terminated. From the above, the retention time varies depending on the circularity of the toner particles to be obtained.

[0070] In the toner manufacturing method according to this embodiment, a weak acid is added to the second dispersion in at least one of steps C and D. The addition of the weak acid to the second dispersion may be carried out in step C, in step D, or in both steps C and D. It is preferable to add the weak acid in step D, as adding it when the aggregated particles have fused to a certain extent increases the amount of weak acid relative to the surface area of ​​the aggregated particles, thereby enhancing the coalescence-promoting effect. Furthermore, the addition of a weak acid to the second dispersion may be done once or two or more times. For example, the weak acid may be added to the second dispersion once or two or more times in step C, and furthermore, the weak acid may be added to the second dispersion once or two or more times in step D.

[0071] -Addition of a weak acid- The weak acid used in the toner manufacturing method according to this embodiment refers to inorganic acids and organic acids with a pKa of 2 or higher, as described in the Basic Edition II of the Chemical Handbook (Maruzen Co., Ltd.), etc. As a weak acid, it is preferable that it be at least one selected from the group consisting of carbonic acid, phosphoric acid, and carboxylic acid compounds, from the viewpoint of availability and reactivity upon addition. Examples of carboxylic acid compounds include acetic acid and citric acid. As a weak acid, one type may be used alone, or multiple types may be used in mixture. As a weak acid, carbonic acid is preferred from the viewpoint that it can be added in aqueous solution or as a gas.

[0072] In the toner manufacturing method according to this embodiment, the addition of a weak acid to the second dispersion is preferably done by adding carbonated water to the second dispersion or by introducing carbon dioxide gas to the second dispersion. In particular, the addition of a weak acid to the second dispersion is preferably done by introducing carbon dioxide gas to the second dispersion, from the viewpoint of having a high effect in suppressing the generation of coarse powder.

[0073] The addition of carbonated water to the second dispersion can be carried out in step C, in step D, or in both steps C and D, as long as it is possible to add 20% or more by mass of carbon dioxide relative to the mass of the second aggregated particles. Furthermore, the addition of carbonated water to the second dispersion can be done in one go, or in two or more separate steps.

[0074] Furthermore, in the carbonated water added to the second dispersion, the carbon dioxide concentration is preferably 0.05 mol / L or more and 0.70 mol / L or less, and more preferably 0.10 mol / L or more and 0.60 mol / L or less, from the viewpoint of exhibiting an effect of suppressing the generation of coarse powder.

[0075] Furthermore, the addition of carbon dioxide to the second dispersion may be carried out in step C, in step D, or in both steps C and D, provided that a weak acid of 20% by mass or more relative to the mass of the second aggregated particles is added. Furthermore, carbon dioxide may be added to the second dispersion once or two or more times. As a method for adding carbon dioxide to the second dispersion, carbon dioxide can be blown into the container containing the second dispersion at a pressure of, for example, 0.05 MPa to 0.60 MPa for a period of 2 seconds to 30 seconds. The amount of carbon dioxide added to the second dispersion can be controlled by adjusting the pressure and duration of carbon dioxide injection into the container containing the second dispersion.

[0076] Furthermore, the carbon dioxide added to the second dispersion should preferably have a high purity; for example, a purity of 90% or higher is more preferable.

[0077] In the toner manufacturing method according to this embodiment, the amount of weak acid added to the second dispersion is 20% by mass or more, preferably 25% by mass or more, and more preferably 30% by mass or more, relative to the mass of the second aggregated particles, from the viewpoint of exhibiting an effect of suppressing the generation of coarse powder. On the other hand, if too much weak acid is added to the second dispersion, the pH of the second dispersion containing the weak acid may drop too low, reducing the repulsive force between the second aggregated particles. This can lead to particle adhesion and the generation of coarse powder. Therefore, for the reasons stated above, it is preferable to complete the addition of the weak acid before the pH of the second dispersion reaches 7, and more preferably before the pH of the second dispersion reaches 7.2. Furthermore, for the reasons mentioned above, it is preferable that the weak acid be added in an amount of 90% by mass or less, preferably 80% by mass or less, relative to the mass of the second aggregated particles. In other words, it is preferable that the addition of the weak acid be completed before the amount of weak acid added reaches 90% by mass (preferably 80% by mass) relative to the mass of the second aggregated particles.

[0078] Furthermore, when using a weak acid other than carbonic acid, it is preferable to prepare an aqueous solution containing the weak acid and add it to the second dispersion. In this case, there are no particular restrictions on the concentration of the weak acid in the aqueous solution, but for example, it is preferable that the concentration of carbonic acid is within a similar range as described above.

[0079] The surfactant content in the second dispersion after step D is preferably 5% by mass or less relative to the total solid content in the second dispersion. In order to keep the surfactant content in the second dispersion after step D below the above upper limit, it is desirable not to use surfactants in steps C and D. Generally, using a surfactant in at least one of steps C and D promotes the fusion of the second aggregated particles, but in the toner manufacturing method according to this embodiment, as described above, by using a weak acid and setting the amount of weak acid added above a certain level, the fusion of the second aggregated particles can be promoted without using a surfactant. As a result, it is also possible to shorten the fusion time. Furthermore, the surfactant used when manufacturing toner particles in the EA method is discharged along with the cleaning solution, etc., but the treatment of wastewater containing surfactants can be very burdensome and costly. By keeping the surfactant content in the second dispersion after step D below the above upper limit, wastewater treatment becomes easier.

[0080] In this way, toner particles having the desired circularity can be obtained.

[0081] [Other processes] After the completion of step D, the toner particles in the dispersion are subjected to known washing, solid-liquid separation, and drying steps to obtain dried toner particles. From the viewpoint of electrostatic charge, the washing process should be thoroughly performed by displacement washing with ion-exchanged water. From the viewpoint of productivity, the solid-liquid separation process should be performed by suction filtration, pressure filtration, etc. From the viewpoint of productivity, the drying process should be performed by freeze-drying, air-flow drying, fluidized bed drying, vibratory fluidized bed drying, etc.

[0082] [Process of adding external additives] The toner manufacturing method of this embodiment preferably includes a step of adding an external additive to the toner particles. External addition of additives to toner particles is performed by mixing the dry toner particles with the external additive. Mixing is carried out using, for example, a V-blender, Henschel mixer, or Redigge mixer. Furthermore, if necessary, coarse toner particles may be removed using a vibrating screen separator or a wind screen separator.

[0083] Examples of external additives include inorganic particles. These inorganic particles include SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n Examples include Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4.

[0084] The surface of the inorganic particles used as an external additive should preferably be 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, but examples include silane-based coupling agents, silicone oil, titanate-based coupling agents, and aluminum-based coupling agents. These may be used individually or in combination of two or more. The amount of hydrophobic treatment agent is typically, for example, 1 to 10 parts by mass per 100 parts by mass of inorganic particles.

[0085] Examples of external additives include resin particles (such as polystyrene, polymethyl methacrylate, and melamine resin) and cleaning activators (for example, metal salts of higher fatty acids represented by zinc stearate, and fluorine-based high molecular weight particles).

[0086] The amount of external additive added is preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less, relative to the mass of the toner particles.

[0087] <Toner> The toner produced by the manufacturing method according to this embodiment is preferably an externally added toner, in which an external additive is added to the toner particles. The form of the external additive is as described above.

[0088] The toner produced by the manufacturing method according to this embodiment includes toner particles having a core-shell structure, which comprises a core and a shell layer covering the core. In particular, it is preferable that the toner particles with a core-shell structure have, for example, a core containing a binder resin, a release agent, and a colorant, and a shell layer containing a resin.

[0089] The binder resin content is preferably 40% to 95% by mass, more preferably 50% to 90% by mass, and even more preferably 60% to 85% by mass, relative to the total toner particles.

[0090] If the toner particles contain a release agent, the release agent content is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, relative to the total toner particles.

[0091] If the toner contains a colorant, the colorant content is preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, relative to the total toner particles.

[0092] The volume-average particle size of the toner particles 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 size of toner particles is measured using a Coulter Multisizer II (Beckman Coulter), and the electrolyte is measured using an ISOTON-II (Beckman Coulter). For measurement, 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate) as a dispersant. This is then added to 100 ml to 150 ml of the electrolyte. The electrolyte containing the suspended sample is dispersed in an ultrasonic disperser for 1 minute. The particle size distribution of particles with a diameter of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled is 50,000. The particle size distribution is plotted from the smallest diameter side, and the particle size at which the cumulative distribution reaches 50% is defined as the volume-average particle size D50v.

[0093] The average circularity of the toner particles is preferably 0.94 to 1.00, and more preferably 0.95 to 0.98. The average circularity of a toner particle is calculated as (perimeter of a circle with the same area as the particle projection) / (perimeter of the particle projection). This is determined by sampling 3500 toner particles using a flow-type particle image analyzer (FPIA-3000, manufactured by Sysmex Corporation).

[0094] <Developer> The toner produced by the manufacturing method according to this embodiment may be used as a one-component developer, or it may be mixed with a carrier and used as a two-component developer.

[0095] There are no particular restrictions on the carriers, and known carriers can be used. Examples of carriers include coated carriers in which a resin is coated on the surface of a core material made of magnetic powder; magnetic powder dispersed carriers in which magnetic powder is dispersed in a matrix resin; and resin-impregnated carriers in which resin is impregnated into porous magnetic powder. A magnetic powder dispersion type carrier or a 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 thereof is coated with resin.

[0096] Examples of magnetic powders include magnetic metals such as iron, nickel, and cobalt; and magnetic oxides such as ferrite and magnetite.

[0097] 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, styrene-acrylic acid ester copolymer, straight silicone resin or modified thereof containing organosiloxane bonds, fluororesin, polyester, polycarbonate, phenolic resin, epoxy resin, etc. The coating resin and matrix resin may also contain conductive particles and other additives. Examples of conductive particles include metals such as gold, silver, and copper, carbon black, titanium dioxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0098] To coat the surface of the core material with resin, one method is to coat it with a coating layer-forming solution prepared by dissolving the coating resin and various additives (used as needed) in a suitable solvent. The solvent is not particularly limited and should be selected considering the type of resin used and its suitability for coating. Specific resin coating methods include the immersion method, in which the core material is immersed in a coating layer forming solution; the spray method, in which the coating layer forming solution is sprayed onto the surface of the core material; the fluidized bed method, in which the coating layer forming solution is sprayed onto the core material while it is suspended by fluidized air; and the kneader coater method, in which the carrier core material and the coating layer forming solution are mixed in a kneader coater, and then the solvent is removed.

[0099] In a two-component developer, the mixing ratio (mass ratio) of toner and carrier is preferably toner:carrier = 1:100 to 30:100, and more preferably 3:100 to 20:100. [Examples]

[0100] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following explanation, unless otherwise specified, "parts" and "%" refer to mass. Synthesis, processing, and manufacturing were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0101] <Preparation of particle dispersion> [Preparation of polyester resin particle dispersion (P)] • Polyoxypropylene(2,2)-2,2-bis(4-hydroxyphenyl)propane: 80 moles • Ethylene glycol: 10 moles • Cyclohexanediol: 10 moles Terephthalic acid: 80 moles Isophthalic acid: 10 moles n-dodecenyl succinic acid: 10 moles The above materials were placed in a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube, and the inside of the reaction vessel was replaced with dry nitrogen gas. Next, 0.25 parts of titanium tetrabutoxide were added as a catalyst per 100 parts of monomer. The reaction was carried out with stirring at 170°C for 3 hours under a nitrogen gas stream, and then the temperature was raised to 210°C over 1 hour. Next, the pressure inside the reaction vessel was reduced to 3 kPa, and the reaction was carried out with stirring under reduced pressure for 13 hours to obtain a polyester resin. The glass transition temperature (Tg) of the obtained polyester resin was 58°C.

[0102] In a jacketed reaction vessel equipped with a condenser, thermometer, dropping device, and anchor vanes, 200 parts polyester resin, 100 parts methyl ethyl ketone, and 70 parts isopropyl alcohol were added. The polyester resin was dissolved while stirring at 100 rpm in a water-circulating constant temperature bath, maintaining the temperature at 70°C. Next, the stirring speed was increased to 150 rpm, the water-circulating constant temperature bath was set to 66°C, and 10 parts of 10% aqueous ammonia were added over 10 minutes. Then, 600 parts of deionized water, kept at 66°C, were added dropwise at a rate of 5 parts / minute to invert the phase and obtain an emulsion. 600 parts of the emulsion and 525 parts of deionized water were placed in a round-bottom flask and placed in an evaporator equipped with a vacuum control unit via a trap bulb. The round-bottom flask was heated in a 60°C water bath while rotating, and the pressure was reduced to 7 kPa while taking care to prevent bumping to remove the solvent. When the amount of recovered solvent reached 825 parts, the pressure was returned to atmospheric pressure, and the round-bottom flask was cooled with water to obtain a dispersion. Deionized water was added to adjust the solid content concentration to 20% to obtain polyester resin particle dispersion (1). The volume-average particle size of polyester resin particle dispersion (1) was 180 nm.

[0103] [Preparation of mold release agent particle dispersion (W)] • Paraffin wax (Nippon Seiro Co., Ltd., HNP-9, melting point 75℃): 50 units • Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK): 5 parts • Ion-exchanged water: 200 copies The above materials were mixed and heated to 95°C, then dispersed using a homogenizer (IKA Ultra-Turrax T50). Next, the mixture was dispersed using a pressure-discharge type Gorin homogenizer, and water was added to adjust the solid content to 20% to obtain the release agent particle dispersion (W). The volume-average particle size of the release agent particle dispersion (W) was 190 nm.

[0104] [Preparation of colorant particle dispersion (C)] • Cyan pigment (Pigment Blue 15:3, Dainichi Seika Kogyo): 100 copies • Anionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen®): 2 parts • Ion-exchanged water: 400 units The above materials were mixed and dispersed for 60 minutes using a high-pressure impact disperser (Ultimizer HJP30006, Sugino Machine Co., Ltd.) to obtain a colorant particle dispersion (C) with a solid content of 20%. The volume-average particle size of the colorant particle dispersion (C) was 160 nm.

[0105] <Example 1> [Process A] • Ion-exchanged water: 200 copies • Polyester resin particle dispersion (P): 100 parts • Release agent particle dispersion (W): 9 parts • Coloring agent particle dispersion (C): 10 parts • Anionic surfactant (Tayca Co., Ltd., TaycaPower BN2060): 1 part The above materials were placed in a 2L cylindrical stainless steel container and stirred to obtain a mixed dispersion. Three parts of 0.3M nitric acid aqueous solution were added to the mixed dispersion to adjust the pH to 3.0. To the mixed dispersion, 2 parts of a 10% aqueous aluminum sulfate solution were added dropwise using a homogenizer (IKA Ultra-Turrax T50) at 6000 rpm while applying shear force, and the mixture was stirred for 5 minutes. Next, the mixed dispersion was heated to 45°C using a mantle heater and held for 30 minutes to produce first aggregated particles, thereby obtaining a first dispersion containing the first aggregated particles.

[0106] [B process] 25 parts of polyester resin particle dispersion (P) and 10 parts of deionized water were mixed, and the pH was adjusted to 3.0 to obtain resin particle dispersion (2). Resin particle dispersion (2) was added to the first dispersion containing the first aggregated particles, and the mixture was held for 10 minutes. Subsequently, in order to stop the growth of the second aggregated particles, a 1M sodium hydroxide aqueous solution was added, and the pH of the second dispersion containing the second aggregated particles was adjusted to 8.0.

[0107] [C process] Next, the second dispersion containing the second aggregated particles was heated to 98°C at a heating rate of 1°C / min.

[0108] [D process] The second dispersion was kept at 98°C after it reached this temperature, and after 30 minutes, the circularity of the second aggregated particles was measured and confirmed to be 0.93. Then, 12 parts of carbonated water adjusted to 0.2 mol / L were added. The pH of the second dispersion after the addition of carbonated water was 7.4. Subsequently, the circularity of the second aggregated particles was measured every 30 minutes, and the temperature of the second dispersion was kept at 98°C until the circularity reached 0.98. The time from when the second dispersion reached 98°C until the circularity of the second aggregated particles (i.e., toner particles) after fusion and coalescence reached 0.98 was 2 hours. The dispersion was then cooled to 30°C at a rate of 0.5°C / min. Next, the solid components were filtered off, washed with deionized water, and dried to obtain toner particles (1).

[0109] [Example 2] Toner particles (2) were obtained in the same manner as in Example 1, except that the amount of carbonated water added in step D was changed from 12 parts to 27 parts. Furthermore, the pH of the second dispersion after adding 27 parts of carbonated water was 6.8.

[0110] [Example 3] Toner particles (3) were obtained in the same manner as in Example 1, except that the amount of carbonated water added in step D was changed from 12 parts to 25 parts. Furthermore, the pH of the second dispersion after adding 25 parts of carbonated water was 7.1.

[0111] [Example 4] In step C, 9 parts of carbonated water adjusted to 0.2 mol / L were added to the second dispersion during the heating process, and in step D, no carbonated water was added, and the temperature of the second dispersion was maintained at 98°C until the circularity of the second aggregated particles reached 0.98. Otherwise, toner particles (4) were obtained in the same manner as in Example 1. Furthermore, the pH of the second dispersion after adding 9 parts carbonated water was 7.7.

[0112] [Example 5] In step C, 6 parts of carbonated water adjusted to 0.2 mol / L were added to the second dispersion during the heating process, and the amount of carbonated water added in step D was changed from 12 parts to 6 parts. Otherwise, toner particles (5) were obtained in the same manner as in Example 1. Furthermore, the pH of the second dispersion after adding a total of 12 parts of carbonated water was 7.4.

[0113] [Example 6] Toner particles (6) were obtained in the same manner as in Example 1, except that step D described below was performed.

[0114] [D process] The second dispersion was kept at 98°C for 30 minutes, and the circularity of the second aggregated particles was measured and confirmed to be 0.93. Then, carbon dioxide gas was blown into the cylindrical stainless steel container containing the second dispersion at a pressure of 0.2 MPa for 10 seconds. Subsequently, the circularity of the second aggregated particles was measured every 30 minutes, and the same carbon dioxide gas blowing was repeated three times until the circularity reached 0.98 (i.e., carbon dioxide gas was blown into the cylindrical stainless steel container at a pressure of 0.2 MPa for 10 seconds three times). The pH of the second dispersion after a total of four carbon dioxide gas blowings was 7.3. The temperature of the second dispersion was kept at 98°C during the repeated carbon dioxide gas blowing. The time from when the second dispersion reached 98°C until the circularity of the second aggregated particles (i.e., toner particles) after fusion and coalescence reached 0.98 was 2 hours. The dispersion was then cooled to 30°C at a rate of 0.5°C / min. Next, the solid components were filtered off, washed with deionized water, and dried to obtain toner particles (6).

[0115] [Example 7] In step D, carbon dioxide gas was blown into a cylindrical stainless steel container containing the second dispersion at a pressure of 0.2 MPa for 10 seconds a total of seven times, except that the procedure was the same as in Example 6 to obtain toner particles (7). The pH of the second dispersion after the carbon dioxide gas was blown in as described above was 6.9.

[0116] [Example 8] Toner particles (8) were obtained in the same manner as in Example 6, except that in step D, carbon dioxide gas was blown into a cylindrical stainless steel container containing the second dispersion at a pressure of 0.2 MPa for 11 seconds a total of six times. The pH of the second dispersion after the carbon dioxide gas was blown in as described above was 7.2.

[0117] [Example 9] In step C, carbon dioxide gas was blown into a cylindrical stainless steel container containing the second dispersion at a pressure of 0.2 MPa for 10 seconds, a total of three times, during the heating process. In step D, carbon dioxide gas was not blown in, and the temperature of the second dispersion was maintained at 98°C until the circularity of the second aggregated particles reached 0.98. Otherwise, toner particles (9) were obtained in the same manner as in Example 6. The pH of the second dispersion after the carbon dioxide gas was blown in as described above was 7.4.

[0118] [Example 10] In step C, carbon dioxide gas was blown into a cylindrical stainless steel container containing the second dispersion at a pressure of 0.2 MPa for 8 seconds, a total of two times, during the heating process. In step D, carbon dioxide gas was blown into a cylindrical stainless steel container containing the second dispersion at a pressure of 0.2 MPa for 10 seconds, a total of two times. Otherwise, toner particles (10) were obtained in the same manner as in Example 6. The pH of the second dispersion after the carbon dioxide gas was blown in as described above was 7.3.

[0119] [Example 11] In step D, toner particles (11) were obtained in the same manner as in Example 1, except that 14 parts of a phosphoric acid aqueous solution adjusted to 0.2 mol / L were added instead of carbonated water. Furthermore, the pH of the second dispersion after adding 14 parts of phosphoric acid aqueous solution was 7.3.

[0120] [Example 12] In step D, toner particles (12) were obtained in the same manner as in Example 1, except that 13 parts of an aqueous acetic acid solution adjusted to 0.2 mol / L were added instead of carbonated water. Furthermore, the pH of the second dispersion after adding 13 parts of aqueous acetic acid solution was 7.4.

[0121] [Comparative Example 1] Toner particles (C1) were obtained in the same manner as in Example 1, except that in step D, 5 parts of hydrochloric acid adjusted to 0.2 mol / L were added instead of carbonated water. Furthermore, the pH of the second dispersion after adding 5 parts hydrochloric acid was 6.8.

[0122] [Comparative Example 2] Toner particles (C2) were obtained in the same manner as in Example 1, except that in step D, 3 parts of a 0.2 mol / L aqueous phosphoric acid solution were added instead of carbonated water. Furthermore, the pH of the second dispersion after adding 3 parts of phosphoric acid aqueous solution was 7.5.

[0123] [Comparative Example 3] In step D, toner particles (C3) were obtained in the same manner as in Example 1, except that 6 parts of a 0.2 mol / L aqueous phosphoric acid solution and 7 parts of an anionic surfactant were added instead of carbonated water. Furthermore, the pH of the second dispersion after adding 6 parts of phosphoric acid aqueous solution was 7.2.

[0124] <Rating> [Evaluation of the amount of coarse flour 1] The toner dispersion containing 100g of toner particles obtained in each example was sieved through a 20μm mesh. The residue on the mesh was dried, and its mass (g) was determined. In this evaluation, the residue on the mesh was defined as coarse powder (i.e., coarse particles), and the proportion (mass %) of coarse powder in the toner particles was calculated using the following formula. Percentage of coarse powder (mass %) = Mass of coarse powder (residue on the screen) (g) / Mass of toner particles (100g) × 100 The amount of coarse flour was evaluated according to the following criteria. -standard- G1: The proportion of coarse powder is less than 1% by mass. G2: The proportion of coarse powder is 1% by mass or more and less than 2% by mass. G3: The proportion of coarse powder is less than 2% by mass or 3% by mass. G4: The proportion of coarse powder is 3% by mass or more.

[0125] [Evaluation of the amount of coarse flour 2] Using the previously described method for measuring the volume-average particle size of toner particles, the particle size distribution of toner particles obtained in each example was measured for particles ranging from 2 μm to 60 μm. The measured particle size distribution was plotted as a cumulative distribution of volume percentage from the smallest diameter side for each divided particle size range (channel), and in this evaluation, particles with a particle size of 15 μm or larger were defined as coarse powder (i.e., coarse particles). The volume percentage (volume %) of toner particles with a particle size of 15 μm or larger was determined from the particle size distribution obtained above. The amount of coarse flour was evaluated according to the following criteria. -standard- G1: The proportion of coarse powder is less than 0.5% by volume. G2: The proportion of coarse flour is 0.5% by volume or more and less than 1.0% by volume. G3: The proportion of coarse powder is 1.0% by volume or more and less than 2.0% by volume. G4: The proportion of coarse powder is 2.0% by volume or more.

[0126] [Evaluation of wastewater treatment] In each example, the following coagulation and precipitation properties were evaluated using deionized water (used washing solution) used to wash the toner particles. 300 mg of ferric chloride and 5 mg of polymer flocculant (anionic compound, manufactured by Kurita Water Industries) were added to 100 ml of used cleaning solution to form flocs. The state of these flocs was visually inspected and evaluated according to the following criteria. A grade of G3 or higher indicates a level that is not problematic for practical use. G1: The flocs are large, and the liquid transparency is extremely good. G2: The flocculation is slightly fine, but the transparency is good (level between G1 and G3). G3: Slightly less transparent, but not to the point of causing problems in practical use. G4: Flocculants form, but the settling is poor and discoloration is present (a level between G3 and G4). G5: The flocs are fine and the coloring is extremely poor.

[0127] The evaluation results are summarized in Table 1 below. Table 1 also shows the conditions for adding acid in steps C and D. In Table 1, "Presence or absence of surfactant addition" refers to the presence or absence of surfactant addition in steps C and D, and the numbers in parentheses represent the amount added.

[0128] [Table 1]

[0129] As is clear from Table 1, the manufacturing method of the example yields toner with less coarse powder, even with a shorter fusion time compared to the manufacturing method of the comparative example.

Claims

1. Step A involves preparing a first dispersion in which first aggregated particles containing a binder resin are dispersed, Step B involves attaching resin particles to the surface of the first aggregated particles in the first dispersion to produce second aggregated particles, and preparing a second dispersion in which the second aggregated particles are dispersed. Step C involves raising the temperature of the second dispersion to a fusion temperature at which the second aggregated particles in the second dispersion fuse together. Step D involves holding the second dispersion at the fusion temperature, Includes, A method for producing electrostatic image developing toner, comprising adding 25% by mass or more of carbonated water (where the carbon dioxide concentration in the carbonated water is 0.05 mol / L or more and 0.70 mol / L or less) or 25% by mass or more of carbon dioxide gas relative to the mass of the second aggregated particles to the second dispersion in at least one of the steps C and D.

2. The method for producing electrostatic image developing toner according to claim 1, wherein the addition of carbonated water or carbon dioxide is completed before the pH of the second dispersion reaches 7.

3. A method for producing electrostatic image developing toner according to claim 1 or claim 2, wherein the carbonated water or carbon dioxide is added in an amount of 90% by mass or less relative to the mass of the second aggregated particles.

4. A method for producing electrostatic image developing toner according to any one of claims 1 to 3, wherein the amount of surfactant in the second dispersion after step D is 5% by mass or less with respect to the total solid content in the second dispersion.

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