Method for manufacturing toner for electrostatic charge image development
Patent Information
- Application Number
- JP2022188308
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-11-25
- Publication Date
- 2025-09-17
Abstract
Description
[Technical field]
[0001] The present invention relates to a method for producing a toner for developing electrostatic images used in developing latent images formed in electrophotography, electrostatic recording, electrostatic printing and the like. [Background technology]
[0002] As a binder resin for toner, it is known that a crystalline polyester resin is effective in improving the low-temperature fixing property of the toner, and its combined use with an amorphous resin is also being considered.
[0003] Patent Document 1 discloses a toner that contains at least a crystalline polyester and a release agent, and is characterized in that the toner contains first silica fine particles having a volume average particle diameter of 50 nm or less inside the toner, and also contains second silica fine particles produced by a sol-gel method and having a volume average particle diameter of 50 nm or more and 200 nm or less on the toner surface.
[0004] Patent Document 2 discloses a method for producing a toner for developing electrostatic images, the method including a step of melt-kneading a mixture containing a binder resin and a wax, the binder resin containing an amorphous resin and a crystalline resin, the amorphous resin containing an amorphous polyester (A) obtained by condensation polymerization of an alcohol component containing an aliphatic diol (a) having 3 or 4 carbon atoms and having a hydroxy group bonded to a secondary carbon atom and an aliphatic diol (b) consisting of at least one of α,ω-linear alkanediols having 2, 4, 6 or 8 carbon atoms, and a carboxylic acid component, and the mass ratio of the amorphous resin to the crystalline resin (amorphous resin / crystalline resin) is 55 / 45 to 95 / 5.
[0005] Patent Document 3 discloses an invention relating to a pulverized toner produced by a melt kneading method, which contains an amorphous polyester A and a crystalline polyester C, in which the amorphous polyester A is a polycondensate of an alcohol component containing an aliphatic diol having a hydroxyl group bonded to a secondary carbon atom having 3 to 5 carbon atoms, and a carboxylic acid component containing an aromatic dicarboxylic acid compound, and the crystalline polyester C is a polycondensate of an alcohol component containing an aliphatic diol, and a carboxylic acid component containing an aliphatic dicarboxylic acid compound. [Prior art documents] [Patent documents]
[0006] [Patent Document 1] JP 2019-159022 A [Patent Document 2] JP 2014-85587 A [Patent Document 3] JP 2018-59964 A Summary of the Invention [Problem to be solved by the invention]
[0007] However, when a toner is produced using a crystalline polyester resin and an amorphous resin, although an amorphous polyester resin obtained using an aliphatic diol having a relatively short carbon chain has high compatibility with the crystalline polyester resin compared to a resin obtained using an aromatic diol such as an alkylene oxide adduct of bisphenol A, further improvement is required in terms of the grindability and durability of the kneaded product.
[0008] The present invention relates to a method for producing a toner for developing electrostatic images, which has excellent grindability and durability. [Means for solving the problem]
[0009] The present invention relates to a method for producing a toner for developing electrostatic images, which contains a crystalline polyester resin C and an amorphous polyester resin A, wherein the crystalline polyester resin C is a polycondensate of an alcohol component containing 80 mol % or more of ethylene glycol and a carboxylic acid component containing 80 mol % or more of an aliphatic dicarboxylic acid compound, and the amorphous polyester resin A is a polycondensate of an alcohol component containing 80 mol % or more of an aliphatic diol having a carbon number of 2 to 6 and a carboxylic acid component, the method including a step of melt-kneading a mixture containing the crystalline polyester resin C and the amorphous polyester resin A using an open-roll type twin-screw kneader equipped with two rolls having different circumferential speeds, and the set temperature of the raw material supply side of the high-rotation roll having the higher circumferential speed of the open-roll type twin-screw kneader is 150° C. or less. Effect of the Invention
[0010] According to the method of the present invention, a toner for developing electrostatic images having excellent grindability and durability can be produced. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] The present invention has a major feature in that, when producing a toner for developing electrostatic images containing a crystalline polyester resin and an amorphous resin, a crystalline polyester resin and an amorphous resin obtained using a predetermined raw material monomer are used, and an open-roll type twin-screw kneader in which a high-speed rotation roll is adjusted to a predetermined temperature is used in the melt-kneading step. The reason why a toner for developing electrostatic images having excellent grindability and durability can be obtained by the method of the present invention is not clear, but is presumed to be as follows.
[0012] When an amorphous polyester resin (amorphous polyester resin A) obtained by using an aliphatic diol having 2 to 6 carbon atoms as the main component of the alcohol component is melt-kneaded in a twin-screw extruder, the low molecular weight components of the amorphous polyester resin A tend to volatilize, resulting in a decrease in the grindability of the kneaded product. This is thought to be because the twin-screw extruder is a closed kneader, and it is difficult to control the temperature during kneading, so the temperature becomes very high, and the low molecular weight components volatilize during cooling immediately after kneading. In contrast, by using an open-roll type twin-screw kneader in which the high-speed roll is adjusted to a predetermined temperature, it is possible to adjust the high-speed roll to a predetermined temperature and simultaneously perform cooling using the low-speed roll, even though it is an open-type kneader, so that excessive temperature rise can be suppressed during kneading and when cooling immediately after kneading. Furthermore, by using a crystalline polyester resin (crystalline polyester resin C) obtained by using ethylene glycol as the main component of the alcohol component, since the number of carbon atoms of the alcohol component of the crystalline polyester resin C and the alcohol component of the amorphous polyester resin A are close, that is, the distance between the ester groups is close, the interaction between the two works strongly, supplementing the low molecular weight components in the amorphous polyester resin A and improving the dispersibility of the crystalline polyester resin C in the amorphous polyester resin A. As a result, it is presumed that the volatilization of the low molecular weight components is suppressed, and the grindability of the kneaded product is improved, and the exposure of the low molecular weight components and the crystalline polyester resin C to the toner particle surface is suppressed, resulting in a toner with excellent durability.
[0013] In the present invention, the crystalline polyester resin C is a polycondensate of an alcohol component containing ethylene glycol and a carboxylic acid component containing an aliphatic dicarboxylic acid compound.
[0014] The crystallinity of a resin is represented by a crystallinity index defined as the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, i.e., the value of [softening point / maximum endothermic peak temperature]. A crystalline resin is a resin having a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 or less. On the other hand, an amorphous resin is a resin in which no endothermic peak is observed, or if an endothermic peak is observed, the crystallinity index is greater than 1.4, preferably greater than 1.5, more preferably 1.6 or more, or less than 0.6, preferably 0.5 or less. The crystallinity of the resin can be adjusted by the type and ratio of the raw material monomers, and the production conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. In the case of a crystalline resin, the maximum endothermic peak temperature is the melting point.
[0015] The content of ethylene glycol in the alcohol component is 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and 100 mol% or less. When the alcohol component contains a monoalcohol, the content is preferably 98 mol% or less, more preferably 95 mol% or less.
[0016] Examples of other alcohol components include aliphatic diols other than ethylene glycol, such as 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol; alkylene oxide adducts of bisphenol A; aromatic diols such as bisphenol A; hydrogenated bisphenol A; sorbitol, pentaerythritol, glycerin, and trimethylolpropane; and other trihydric or higher alcohols.
[0017] Examples of the aliphatic dicarboxylic acid compound include succinic acid (carbon number: 4), fumaric acid (carbon number: 4), adipic acid (carbon number: 6), suberic acid (carbon number: 8), azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), dodecanedioic acid (carbon number: 12), tetradecanedioic acid (carbon number: 14), succinic acid having an alkyl group or an alkenyl group on the side chain, anhydrides of these acids, and alkyl esters of these acids having a carbon number of 1 to 3. Here, when the aliphatic dicarboxylic acid compound is an alkyl ester, the carbon number of the alkyl group is not included in the above carbon number.
[0018] From the viewpoint of hydrophobicity, the carbon number of the aliphatic dicarboxylic acid compound is preferably 4 or more, more preferably 8 or more, even more preferably 10 or more, and still more preferably 12 or more, and from the viewpoint of low-temperature fixability, the carbon number is preferably 16 or less, more preferably 14 or less.
[0019] The aliphatic dicarboxylic acid compound may be either a saturated aliphatic dicarboxylic acid compound or an unsaturated aliphatic dicarboxylic acid compound, but from the viewpoint of durability, it is preferably a saturated aliphatic dicarboxylic acid compound.
[0020] From the viewpoint of durability, the content of the aliphatic dicarboxylic acid compound in the carboxylic acid component is 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and 100 mol% or less. When the carboxylic acid component contains a monocarboxylic acid compound, the content is preferably 98 mol% or less, more preferably 95 mol% or less.
[0021] Examples of other carboxylic acid components include aromatic dicarboxylic acid compounds such as phthalic acid, isophthalic acid, and terephthalic acid, and trivalent or higher carboxylic acid compounds such as trimellitic acid and pyromellitic acid.
[0022] Furthermore, the alcohol component and / or the carboxylic acid component of the crystalline polyester resin C preferably contains a monofunctional monomer.
[0023] Examples of monofunctional monomers contained in the alcohol component include aliphatic monoalcohols such as capric alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and behenyl alcohol.
[0024] Examples of monofunctional monomers contained in the carboxylic acid component include aliphatic monocarboxylic acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, and aliphatic monocarboxylic acid compounds such as alkyl esters of these acids in which the alkyl group has 1 to 3 carbon atoms.
[0025] From the viewpoint of improving hydrophobicity, the monofunctional monomer preferably contains an aliphatic monocarboxylic acid compound and / or an aliphatic monoalcohol.
[0026] The carbon number of the aliphatic monoalcohol is preferably 10 or more, more preferably 12 or more, and even more preferably 14 or more from the viewpoint of hydrophobicity, and is preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less from the viewpoint of low-temperature fixability.
[0027] From the viewpoint of hydrophobicity, the carbon number of the aliphatic monocarboxylic acid compound is preferably 10 or more, more preferably 12 or more, and even more preferably 14 or more, and from the viewpoint of low-temperature fixability, it is preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less. Here, when the aliphatic monocarboxylic acid compound is an alkyl ester, the carbon number of the alkyl group is not included in the above carbon number.
[0028] The content of the monofunctional monomer in the raw material monomers (in the total amount of the alcohol component and the carboxylic acid component) is preferably 1 mol % or more, more preferably 3 mol % or more, and even more preferably 5 mol % or more, and from the viewpoint of low-temperature fixing property, it is preferably 30 mol % or less, more preferably 20 mol % or less, and even more preferably 15 mol % or less.
[0029] In this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol component and the carboxylic acid component.
[0030] The equivalent ratio of the carboxy group of the carboxylic acid component to the hydroxyl group of the alcohol component (COOH group / OH group) is preferably 0.8 or more, more preferably 0.9 or more, from the viewpoint of durability, and is preferably 1.2 or less, more preferably 1.1 or less, from the viewpoint of low-temperature fixability.
[0031] The crystalline polyester resin C can be produced, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and if necessary, in the presence of an esterification promoter, a polymerization inhibitor, etc., at a temperature preferably of 120°C or higher and 230°C or lower.
[0032] Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamine. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 1 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the esterification promoter include gallic acid. The amount of the esterification promoter used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the polymerization inhibitor include tert-butylcatechol. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, more preferably 0.1 part by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.
[0033] In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc., and among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended with a polyisocyanate compound are preferred.
[0034] The softening point of the crystalline polyester resin C is preferably 50°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher from the viewpoint of durability, and is preferably 120°C or lower, and more preferably 110°C or lower from the viewpoint of low-temperature fixability.
[0035] The melting point of the crystalline polyester resin C is preferably 60° C. or higher, more preferably 70° C. or higher, from the viewpoint of durability, and is preferably 130° C. or lower, more preferably 120° C. or lower, from the viewpoint of low-temperature fixability.
[0036] The acid value of the crystalline polyester resin C is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, from the viewpoint of low-temperature fixability, and is preferably 20 mgKOH / g or less, more preferably 15 mgKOH / g or less, from the viewpoint of durability.
[0037] The content of crystalline polyester resin C in the total amount of crystalline polyester resin C and amorphous polyester resin A is preferably 3 mass % or more, more preferably 5 mass % or more, and even more preferably 8 mass % or more from the viewpoint of low-temperature fixability, and is preferably 30 mass % or less, more preferably 25 mass % or less, and even more preferably 20 mass % or less from the viewpoint of durability.
[0038] The amorphous polyester resin A is a polycondensation product of an alcohol component containing an aliphatic diol having 2 to 6 carbon atoms and a carboxylic acid component.
[0039] Examples of the aliphatic diol having 2 to 6 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol.
[0040] The content of the aliphatic diol having 2 to 6 carbon atoms is 80 mol % or more, preferably 90 mol % or more, more preferably 95 mol % or more, and 100 mol % or less in the alcohol component from the viewpoint of durability and crushability, and when the alcohol component contains a trihydric or higher alcohol, it is preferably 95 mol % or less, more preferably 90 mol % or less. Note that, when two or more resins are used in combination as the amorphous polyester resin, the content of the aliphatic diol is the weighted average value calculated by adjusting the content of the aliphatic diol used in each resin in the alcohol component to the mass ratio of the resin.
[0041] Examples of other alcohol components include aliphatic diols having 7 or more carbon atoms, alkylene oxide adducts of bisphenol A, aromatic diols such as bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, trimethylolpropane, and other trihydric or higher alcohols.
[0042] From the viewpoints of durability and grindability, the carboxylic acid component preferably contains an aromatic dicarboxylic acid compound.
[0043] Examples of the aromatic dicarboxylic acid compound include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.
[0044] The content of the aromatic dicarboxylic acid compound in the carboxylic acid component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more, and is 100 mol% or less. When the carboxylic acid component contains a trivalent or higher carboxylic acid compound, the content is preferably 98 mol% or less, more preferably 95 mol% or less.
[0045] Examples of other carboxylic acid components include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with a hydrocarbon group, aliphatic dicarboxylic acids such as glutaric acid, adipic acid, and sebacic acid, trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.
[0046] In addition to the alcohol component and the carboxylic acid component, polyethylene terephthalate (PET) may be used. PET, or ethylene glycol and terephthalic acid produced by depolymerization of a portion of it, are used as raw material monomers in a polycondensation reaction and are incorporated into polyester resin. PET is an equimolar polycondensation product of ethylene glycol and terephthalic acid, and the ethylene glycol and terephthalic acid that make up PET are regarded as the alcohol component and the carboxylic acid component, respectively.
[0047] The PET may be new virgin PET or recycled PET. Recycled PET is made by collecting used PET, washing it as necessary, and separating it from other materials before crushing it. The crushed material is then depolymerized to break it down into monomer units, which are then used to resynthesize the material.
[0048] The IV value of PET is preferably 0.40 or more, more preferably 0.45 or more, even more preferably 0.50 or more, and even more preferably 0.55 or more, and from the viewpoint of low-temperature fixability and uniform depolymerization, it is preferably 0.85 or less, more preferably 0.80 or less, even more preferably 0.75 or less, and even more preferably 0.70 or less. The IV value is an intrinsic viscosity and is an index of molecular weight.
[0049] The alcohol component may appropriately contain a monohydric alcohol, and the carboxylic acid component may appropriately contain a monovalent carboxylic acid compound.
[0050] From the viewpoint of adjusting the softening point of the polyester resin, the equivalent ratio of the carboxy group of the carboxylic acid component to the hydroxyl group of the alcohol component (COOH group / OH group) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.75 or more, and is preferably 1.2 or less, more preferably 1.15 or less.
[0051] The polycondensation reaction conditions of the alcohol component and the carboxylic acid component of the amorphous polyester resin are similar to those of the crystalline polyester resin, except that the suitable reaction temperature is preferably 130°C or more, more preferably 170°C or more, and preferably 250°C or less, more preferably 240°C or less.
[0052] The softening point of the amorphous polyester resin A is preferably 90° C. or higher, more preferably 100° C. or higher, from the viewpoint of durability, and is preferably 150° C. or lower, more preferably 140° C. or lower, from the viewpoint of low-temperature fixability and grindability.
[0053] From the viewpoints of low-temperature fixability and fixing width, the amorphous polyester resin A may be composed of resins having different softening points. The difference in softening point between the two resins is preferably 10° C. or more, more preferably 12° C. or more, and is preferably 60° C. or less, more preferably 30° C. or less, and even more preferably 20° C. or less.
[0054] The softening point of the amorphous resin having the higher softening point (resin AH) is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher, from the viewpoint of fixing width, and is preferably 180°C or lower, more preferably 160°C or lower, and even more preferably 140°C or lower, from the viewpoint of low-temperature fixing ability.
[0055] Furthermore, the softening point of the amorphous resin having the lower softening point (resin AL) is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher from the viewpoint of durability, and is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower from the viewpoint of low-temperature fixability.
[0056] The mass ratio of resin AH to resin AL (resin AH / resin AL) is preferably 10 / 90 or more, more preferably 20 / 80 or more, even more preferably 30 / 70 or more, and is preferably 90 / 10 or less, more preferably 80 / 20 or less, even more preferably 70 / 30 or less.
[0057] The glass transition temperature of the amorphous polyester resin A is preferably 40° C. or higher, more preferably 50° C. or higher, from the viewpoint of durability, and is preferably 80° C. or lower, more preferably 70° C. or lower, and even more preferably 68° C. or lower, from the viewpoint of low-temperature fixability.
[0058] The acid value of the amorphous polyester resin A is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, from the viewpoint of low-temperature fixability, and is preferably 20 mgKOH / g or less, more preferably 18 mgKOH / g or less, from the viewpoint of durability.
[0059] The number average molecular weight of the amorphous polyester resin A is preferably 1,000 or more, more preferably 1,500 or more, and even more preferably 2,000 or more from the viewpoint of durability, and is preferably 6,000 or less, more preferably 5,000 or less, and even more preferably 4,000 or less from the viewpoint of low-temperature fixability and grindability.
[0060] The weight average molecular weight of the amorphous polyester resin A is preferably 4,000 or more, more preferably 6,000 or more, and even more preferably 8,000 or more from the viewpoint of durability, and is preferably 500,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less from the viewpoint of low-temperature fixability and grindability.
[0061] The content of amorphous polyester resin A in the total amount of crystalline polyester resin C and amorphous polyester resin A is preferably 70 mass% or more, more preferably 75 mass% or more, and even more preferably 80 mass% or more from the viewpoint of durability, and is preferably 97 mass% or less, more preferably 95 mass% or less, and even more preferably 92 mass% or less from the viewpoint of grindability.
[0062] The mass ratio of crystalline polyester resin C to amorphous polyester resin A (crystalline polyester resin C / amorphous polyester resin A) is preferably 3 / 97 or more, more preferably 5 / 95 or more, and even more preferably 8 / 92 or more, from the viewpoint of low-temperature fixability and grindability, and is preferably 30 / 70 or less, more preferably 25 / 75 or less, and even more preferably 20 / 80 or less, from the viewpoint of durability.
[0063] In the toner, the crystalline polyester resin C and the amorphous polyester resin A are contained as binder resins.
[0064] Other examples of the binder resin include vinyl resins such as styrene-acrylic resin, epoxy resin, polycarbonate, polyurethane, and composite resins containing two or more of these resins.
[0065] The total content of the crystalline polyester resin C and the amorphous polyester resin A in the binder resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass.
[0066] In addition, the content of the binder resin in the toner is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and is preferably less than 100% by mass, more preferably 98% by mass or less, even more preferably 95% by mass or less.
[0067] In addition to the binder resin, the toner may contain additives such as a colorant, a release agent, a charge control agent, a magnetic powder, a flowability improver, a conductivity adjuster, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property improver.
[0068] As the colorant, dyes, pigments, magnetic materials, etc. used as colorants for toners can be used. For example, carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. can be mentioned. In the present invention, the toner may be either a black toner or a color toner.
[0069] From the viewpoint of improving the image density and low-temperature fixability of the toner, the content of the colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the binder resin.
[0070] Examples of the release agent include hydrocarbon waxes such as polypropylene wax, polyethylene wax, polypropylene-polyethylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts. These may be used alone or in combination of two or more.
[0071] The melting point of the release agent is preferably 60° C. or higher, more preferably 70° C. or higher, from the viewpoint of durability, and is preferably 160° C. or lower, more preferably 140° C. or lower, even more preferably 120° C. or lower, and even more preferably 110° C. or lower, from the viewpoint of low-temperature fixability.
[0072] The content of the release agent is, from the viewpoint of the low-temperature fixability and grindability of the toner and the viewpoint of dispersibility in the binder resin, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 7 parts by mass or less, relative to 100 parts by mass of the binder resin.
[0073] The charge control agent is not particularly limited, and may contain either a positively chargeable charge control agent or a negatively chargeable charge control agent.
[0074] Examples of the positively charged charge control agent include nigrosine dyes such as "Nigrosine Base EX", "Oil Black BS", "Oil Black SO", "Bontron N-01", "Bontron N-04", "Bontron N-07", "Bontron N-09", and "Bontron N-11" (all manufactured by Orient Chemical Industries Co., Ltd.); triphenylmethane dyes containing a tertiary amine as a side chain; quaternary ammonium salt compounds such as "Bontron P-51" (manufactured by Orient Chemical Industries Co., Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX Examples of such resins include "VP435" (manufactured by Clariant), etc.; polyamine resins, such as "AFP-B" (manufactured by Orient Chemical Industry Co., Ltd.); imidazole derivatives, such as "PLZ-2001" and "PLZ-8001" (both manufactured by Shikoku Kasei Corporation); and styrene-acrylic resins, such as "FCA-701PT" and "FCA-201-PS" (manufactured by Fujikura Kasei Co., Ltd.).
[0075] Examples of the negatively chargeable charge control agent include metal-containing azo dyes such as "Varifast Black 3804", "Bontron S-31", "Bontron S-32", "Bontron S-34", and "Bontron S-36" (all manufactured by Orient Chemical Industry Co., Ltd.), "Aizenspiron Black TRH", and "T-77" (manufactured by Hodogaya Chemical Industry Co., Ltd.); metal compounds of benzilic acid compounds such as "LR-147" and "LR-297" (all manufactured by Nippon Carlit Co., Ltd.); metal compounds of salicylic acid compounds such as "Bontron E-81", "Bontron E-84", "Bontron E-88", and "Bontron E-304" (all manufactured by Orient Chemical Industry Co., Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Industry Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts such as "COPY CHARGE NX VP434 (Clariant), nitroimidazole derivatives, and organometallic compounds.
[0076] From the viewpoint of the charging stability of the toner, the content of the charge control agent is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the binder resin.
[0077] In the present invention, a mixture containing crystalline polyester resin C, amorphous polyester resin A, and, if necessary, additives such as a colorant, a release agent, and a charge control agent, is subjected to a step of melt-kneading using an open-roll type twin-screw kneader.
[0078] The mixture to be melt-kneaded may be kneaded all at once or in portions, but it is preferable to mix the mixture in advance in a mixer such as a Henschel mixer or a ball mill and then supply the mixture to an open roll type twin-screw kneader.
[0079] The open-roll type twin-screw kneader is an extruder having two rolls, a melt-kneading section that is open and not sealed, and can easily dissipate the heat of kneading generated during melt-kneading. The open-roll type twin-screw kneader used in the present invention is provided with a raw material supply port and a kneaded material discharge port provided along the axial direction of the rolls, and is preferably a continuous open-roll type twin-screw kneader from the viewpoint of production efficiency.
[0080] The open-roll type twin-screw kneader used in the present invention is a kneader equipped with two rolls with different circumferential speeds, i.e., a high-speed roll with a high circumferential speed and a low-speed roll with a low circumferential speed. In the present invention, from the viewpoint of improving the dispersibility of the crystalline polyester resin, it is preferable that the high-speed roll functions as a heating roll and the low-speed roll functions as a cooling roll, that is, it is preferable that the set temperature of the high-speed roll is higher than the set temperature of the low-speed roll. When the set temperatures of the rolls are different between the raw material input side and the kneaded product discharge side, it is preferable that the set temperature of the high-speed roll is higher than the set temperature of the low-speed roll at least on the raw material input side, and it is more preferable that the set temperature of the high-speed roll is higher than the set temperature of the low-speed roll on both the raw material input side and the kneaded product discharge side.
[0081] The temperature of the rolls can be adjusted, for example, by the temperature of a heat medium passed through the inside of the roll. Each roll may have its interior divided into two or more sections through which heat mediums of different temperatures are passed.
[0082] The temperature of the raw material input side of the high-speed rotation roll is 150°C or less, preferably 145°C or less, and more preferably 140°C or less, from the viewpoint of suppressing volatilization of low molecular weight components, and is preferably 80°C or more, more preferably 85°C or more, and even more preferably 90°C or more, from the viewpoint of melting the crystalline polyester resin.
[0083] On the other hand, the temperature of the discharge side of the kneaded material of the high-speed rotation roll is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher, from the viewpoint of improving the dispersibility of the crystalline polyester resin, and is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower.
[0084] The temperature of the raw material input side of the low rotation roll is preferably 25°C or higher, more preferably 40°C or higher, from the viewpoint of reducing the mechanical force during melt kneading and suppressing heat generation, and is preferably 80°C or lower, more preferably 70°C or lower.
[0085] From the viewpoint of improving the dispersibility of the crystalline polyester resin, the temperature of the kneaded material discharge side of the low rotation roll is preferably 25°C or higher, more preferably 30°C or higher, and is preferably 80°C or lower, more preferably 50°C or lower.
[0086] In both the high rotation roll and the low rotation roll, the temperature of the raw material input side is preferably higher than that of the kneaded product discharge side, and the temperature difference between the raw material input side and the kneaded product discharge side of the high rotation roll is preferably 5° C. or more, more preferably 20° C. or more, even more preferably 25° C. or more, and preferably 60° C. or less, more preferably 50° C. or less, and even more preferably 35° C. or less, from the viewpoint of preventing the kneaded product from coming off the roll and reducing the mechanical force during melt kneading and suppressing heat generation. The temperature difference between the raw material input side and the kneaded product discharge side of the low rotation roll is preferably 5° C. or more, and preferably 50° C. or less, from the viewpoint of improving the dispersibility of the crystalline polyester resin and reducing the mechanical force during melt kneading and suppressing heat generation.
[0087] The temperature of the raw material input side of the high rotation roll and the low rotation roll refers to the set temperature of the raw material input end, and the temperature of the kneaded material discharge side refers to the set temperature of the kneaded material discharge end.
[0088] The peripheral speed of the high rotation roll is preferably 2 m / min or more, more preferably 10 m / min or more, even more preferably 25 m / min or more, and preferably 100 m / min or less, more preferably 75 m / min or less, and even more preferably 50 m / min or less, from the viewpoint of improving the dispersibility of the crystalline polyester resin, and from the viewpoint of reducing the mechanical force during melt kneading and suppressing heat generation. From the same viewpoint, the peripheral speed of the low rotation roll is preferably 1 m / min or more, more preferably 5 m / min or more, even more preferably 15 m / min or more, and preferably 90 m / min or less, more preferably 60 m / min or less, and even more preferably 30 m / min or less. In addition, the ratio of the peripheral speeds of the two rolls (low rotation roll / high rotation roll) is preferably 1 / 10 or more, more preferably 3 / 10 or more, and preferably 9.9 / 10 or less, more preferably 8 / 10 or less.
[0089] There are no particular limitations on the structure, size, material, etc. of each roll. The roll surface has grooves used for kneading, and the shape of these grooves may be linear, spiral, wavy, or uneven.
[0090] After the melt-kneading, the kneaded mixture is cooled appropriately until it reaches a pulverizable hardness, and then, if necessary, a pulverization step and a classification step are carried out to obtain toner particles. Here, "cooling" refers to cooling the kneaded mixture to 0°C or higher and 50°C or lower, or to cooling to the glass transition temperature of the binder resin in the kneaded mixture or lower.
[0091] In pulverizing the kneaded product, the kneaded product may be pulverized to the desired particle size all at once or in stages. From the viewpoint of efficient and more uniform pulverization, however, it is preferable to perform the pulverization in two stages: coarse pulverization and fine pulverization.
[0092] Examples of the crushing machine used for the coarse crushing include a hammer mill, a cutter mill, an atomizer, and a rotoplex.
[0093] In the coarse pulverization, it is preferable to pulverize until the maximum diameter is 3 mm or less. For example, a pulverized material having a maximum diameter of 3 mm or less can be obtained by appropriately coarsely pulverizing the kneaded material until the particle size is about 0.05 mm or more and 3 mm or less, and then passing the kneaded material through a sieve with 3 mm openings.
[0094] Examples of the pulverizer used for fine pulverization include jet mills such as a fluidized bed jet mill and an impact plate jet mill, and mechanical mills.
[0095] The degree of pulverization is preferably adjusted appropriately depending on the desired particle size of the toner particles.
[0096] Examples of classifiers used for classification include airflow classifiers, inertial classifiers, sieve classifiers, etc. In the classification step, the pulverized material removed due to insufficient pulverization may be subjected to the pulverization step again, and the pulverization step and the classification step may be repeated as necessary.
[0097] In the present invention, it is preferable to further include an external addition step of mixing the obtained toner particles with an external additive.
[0098] Examples of the external additive include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as resin particles such as melamine-based resin fine particles and polytetrafluoroethylene resin fine particles, and two or more of them may be used in combination. Among these, silica is preferred, and from the viewpoint of the durability of the toner, hydrophobic silica that has been subjected to a hydrophobic treatment is more preferred.
[0099] Examples of hydrophobic treatment agents for hydrophobizing the surface of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazane, silicone oil, aminosilane, octyltriethoxysilane (OTES), and methyltriethoxysilane.
[0100] From the viewpoints of the chargeability, fluidity, and durability of the toner, the average particle diameter of the external additive is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 90 nm or less.
[0101] From the viewpoint of the electrostatic chargeability, fluidity, and durability of the toner, the content of the external additive is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the toner particles before being treated with the external additive, and is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less.
[0102] The volume median particle size (D 50 ) is preferably 3 μm or more, more preferably 4 μm or more, and is preferably 15 μm or less, more preferably 10 μm or less. 50 ) refers to the particle size at which the cumulative volume frequency calculated by volume fraction is 50% calculated from the smallest particle size. In addition, when the toner is treated with an external additive, the volume median particle size of the toner particles before treatment with the external additive is regarded as the volume median particle size of the toner.
[0103] The toner obtained by the method of the present invention can be used as it is as a toner for one-component development, or as a toner for two-component development mixed with a carrier, in an image forming apparatus of a one-component development system or a two-component development system, respectively. EXAMPLES
[0104] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Physical properties of resins and the like can be measured by the following methods.
[0105] [Softening point of resin] Using a flow tester "CFT-500D" (Shimadzu Corporation), 1g of sample is heated at a temperature increase rate of 6℃ / min while applying a load of 1.96MPa with the plunger, and extruding the sample from a nozzle with a diameter of 1mm and a length of 1mm. The amount of plunger descent of the flow tester is plotted against the temperature, and the temperature at which half of the sample has flowed out is taken as the softening point.
[0106] [Maximum endothermic peak temperature of resin] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), weigh 0.01 to 0.02 g of sample into an aluminum pan, cool from room temperature (25°C) to 0°C at a rate of 10°C / min, and maintain at 0°C for 1 minute. Then, measure at a rate of 10°C / min. The temperature of the peak with the largest peak area among the observed endothermic peaks is regarded as the maximum endothermic peak temperature. For crystalline resins, the maximum endothermic peak temperature is regarded as the melting point.
[0107] [Glass transition temperature of amorphous resin] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan), 0.01 to 0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and cooled from that temperature at a rate of 10°C / min to 0°C. Next, the sample is heated at a rate of 10°C / min, and the endothermic peak is measured. The glass transition temperature is the temperature at the intersection of the extension of the baseline below the maximum endothermic peak temperature and the tangent line showing the maximum slope from the rising part of the peak to the top of the peak.
[0108] [Acid value of resin] Measurements are performed based on the method of JIS K 0070:1992, except that the measurement solvent is changed from the ethanol and ether mixture specified in JIS K 0070 to a mixture of acetone and toluene (acetone:toluene = 1:1 (volume ratio)) for amorphous resins, and a mixture of chloroform and dimethylformamide (chloroform:dimethylformamide = 7:3 (volume ratio)) for crystalline resins.
[0109] [Number average molecular weight and weight average molecular weight of resin] The number average molecular weight and the weight average molecular weight are determined by gel permeation chromatography (GPC) according to the following method. (1) Preparation of sample solution The resin is dissolved in tetrahydrofuran to a concentration of 0.5 g / 100 mL, and then the solution is filtered through a fluororesin filter (manufactured by Sumitomo Electric Industries, Ltd., product name: FP-200) with a pore size of 2 μm to remove insoluble components, thereby obtaining a sample solution. (2) Molecular weight measurement Using the following measuring device and analytical column, tetrahydrofuran was used as the eluent at a flow rate of 1 mL per minute, and the column was stabilized in a thermostatic bath at 40°C. 100 μL of the sample solution was injected into the column and the measurement was performed. The molecular weight of the sample was calculated based on a calibration curve that had been prepared in advance. The calibration curve used here included several types of monodisperse polystyrene (Tosoh Corporation; 2.63 × 10 3 , 2.06×10 4 , 1.02×10 5 , GL Sciences Inc.; 2.10 x 10 3 , 7.00×10 3 , 5.04×10 4 ) is used as a standard sample. Measuring device: CO-8010 (product name, manufactured by Tosoh Corporation) Analytical column: GMH XL +G3000H XL (All are product names, manufactured by Tosoh Corporation)
[0110] [PET IV value] The viscosity can be determined by dissolving the material in a mixed solvent of phenol / tetrachloroethane (mass ratio) of 60 / 40 at a concentration of 4 g / L, measuring with an Ubbelohde viscometer, and calculating according to the following formula. IV=(-1+√(1+4kη)) / (2kC) (where k = 0.33, C = 0.004 g / mL, and η = (t1 / t0)-1 (t0: number of seconds it takes for the solvent alone to fall, t1: number of seconds it takes for the sample solution to fall).)
[0111] [Melting point of release agent] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.02 g of the sample is weighed into an aluminum pan and heated to 200°C, then cooled from 200°C to 0°C at a rate of 10°C / min. The sample is then heated at a rate of 10°C / min, the amount of heat is measured, and the maximum endothermic peak temperature is taken as the melting point.
[0112] [Average particle size of external additives] The average particle size refers to the number-average particle size, and is calculated by measuring the particle sizes (average of major and minor diameters) of 500 particles in a scanning electron microscope (SEM) photograph and averaging these by number.
[0113] [Volume median particle size of toner (D 50 )〕 Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.) Aperture diameter: 50μm Analysis software: "Multisizer (registered trademark) III version 3.51" (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) Dispersion liquid: Polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" (manufactured by Kao Corporation, HLB (Griffin) = 13.6) was dissolved in the electrolyte to adjust the concentration to 5% by mass. Dispersion conditions: 10 mg of the measurement sample is added to 5 mL of the dispersion liquid, and dispersed for 1 minute using an ultrasonic disperser (machine name: US-1, manufactured by SND Co., Ltd., output: 80 W). Then, 25 mL of electrolyte is added, and the mixture is further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion liquid. Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles could be measured in 20 seconds. Then, 30,000 particles were measured, and the volume median particle size (D 50 ) is required.
[0114] Resin manufacturing example 1 The alcohol component and carboxylic acid component shown in Table 1 were placed in a 5-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and the temperature was raised to 200°C over 8 hours in a nitrogen atmosphere in a mantle heater. Then, an esterification catalyst shown in Table 1 was added, and the reaction was carried out at 8.0 kPa until the softening point shown in Table 1 was reached, obtaining crystalline polyester resins (resins C1 to C6). The physical properties are shown in Table 1.
[0115] [Table 1]
[0116] Resin manufacturing example 2 The alcohol component, carboxylic acid component, esterification catalyst and esterification promoter shown in Tables 2 and 3 were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a dehydration tube equipped with a fractionating tube through which hot water of 98°C was passed, a stirrer and a thermocouple, and the mixture was kept at 180°C for 1 hour under a nitrogen atmosphere, and then heated from 180°C to 230°C at a rate of 10°C / h, and then polycondensed at 230°C for 5 hours. The reaction was further carried out at 230°C under a reduced pressure of 10 kPa until the softening points shown in Tables 2 and 3 were reached, to obtain amorphous polyester resins (resins AH1, AH2, AH6, AL1, AL2 and AL5). The physical properties are shown in Tables 2 and 3.
[0117] Resin manufacturing example 3 The alcohol component, carboxylic acid component, PET, esterification catalyst, and esterification promoter shown in Tables 2 and 3 were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, stirrer, and thermocouple, and the mixture was kept at 180°C for 1 hour under a nitrogen atmosphere, then heated from 180°C to 230°C at a rate of 10°C / h, and polycondensed at 230°C for 5 hours. The reaction was further carried out at 230°C under a reduced pressure of 10 kPa until the softening points shown in Tables 2 and 3 were reached, to obtain amorphous polyester resins (resins AH3, AH4, AL3, and AL4). The physical properties are shown in Tables 2 and 3.
[0118] Resin manufacturing example 4 The alcohol components shown in Table 2, carboxylic acid components other than trimellitic anhydride, esterification catalyst and esterification promoter were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a dehydration tube equipped with a fractionating tube through which hot water of 98 ° C. was passed, a stirrer and a thermocouple, and the mixture was kept at 180 ° C. for 1 hour under a nitrogen atmosphere, and then heated from 180 ° C. to 230 ° C. at a rate of 10 ° C. / h, and then polycondensed at 230 ° C. for 5 hours. The temperature was then lowered to 210 ° C., and trimellitic anhydride shown in Table 2 was added, reacted at 210 ° C. for 1 hour, and then further reacted at 210 ° C. under a reduced pressure of 10 kPa until the softening point described in Table 2 was reached, to obtain an amorphous polyester resin (resin AH5). The physical properties are shown in Table 2.
[0119] [Table 2]
[0120] [Table 3]
[0121] Examples 1 to 13 and Comparative Examples 2 and 3 100 parts by mass of the binder resin shown in Table 4, 5 parts by mass of a colorant "ECB-301" (manufactured by Dainichi Seikagaku Co., Ltd., phthalocyanine blue (PB15:3)), 3 parts by mass of a release agent "Carnauba Wax C1" (manufactured by Kato Yoko Co., Ltd., melting point: 83°C), 3 parts by mass of a release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 75°C), and 0.5 parts by mass of a charge control agent "Bontron E-304" (manufactured by Orient Chemical Industries Co., Ltd.) were mixed in a Henschel mixer.
[0122] The obtained raw material mixture was fed to a continuous open-roll type twin-screw kneader "Kneedex" (manufactured by Mitsui Mining Co., Ltd.) by a table feeder and kneaded to obtain a kneaded product. The continuous open-roll type twin-screw kneader used in this case had a roll outer diameter of 0.14 m and an effective roll length of 0.8 m, and the operating conditions were a rotation speed of the high rotation roll (front roll) of 75 r / min (circumferential speed 33 m / min), a rotation speed of the low rotation roll (rear roll) of 50 r / min (circumferential speed 22 m / min), and a roll gap of 0.1 mm. The heating and cooling medium temperatures in the rolls were set to the temperatures shown in Table 4 on the raw material input side of the high rotation roll, the temperature on the kneaded material discharge side was set to 90 ° C, the temperature on the raw material input side of the low rotation roll was set to 65 ° C, and the temperature on the kneaded material discharge side was set to 30 ° C. The supply speed of the raw material mixture was 10 kg / h, and the average residence time was about 5 minutes.
[0123] The kneaded product obtained was cooled to 25°C and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Toa Machinery Co., Ltd.) and a coarsely pulverized product having a particle size of 2 mm or less was obtained using a sieve with a mesh size of 2 mm. The coarsely pulverized product obtained was finely pulverized using a I-2 type pulverizer (manufactured by Nippon Pneumatic Co., Ltd.), classified, and the volume median particle size (D 50 ) yielded 6.5 μm toner particles.
[0124] Here, the crushing pressure (MPa) during fine crushing using the I-2 type crusher was measured, and the crushability of the kneaded material was evaluated. The results are shown in Table 4. A lower crushing pressure indicates better crushability.
[0125] 100 parts by mass of the obtained toner particles and, as external additives, 1.0 part by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, average particle size: 16 nm) and 1.0 part by mass of hydrophobic silica "RY-50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil, average particle size: 40 nm) were mixed in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 3000 r / min (circumferential speed: 32 m / sec) for 3 minutes to obtain a toner.
[0126] Comparative Example 1 A toner was obtained in the same manner as in Example 1, except that melt kneading was performed using a twin-screw extruder "PCM-30" (manufactured by Ikegai Iron Works Co., Ltd.) instead of the continuous open-roll type twin-screw kneader. The operating conditions of the twin-screw extruder were a barrel set temperature of 100°C, a shaft rotation speed of 200 r / min (circumferential speed of shaft rotation of 0.30 m / sec), and a mixture supply rate of 10 kg / h.
[0127] Test Example [Toner Durability] The toner was loaded onto a printing machine "Page Presto N-4" (Casio Computer Co., Ltd., fixing: contact fixing method, development: non-magnetic one-component development method, development roll diameter: 2.3 cm) and a diagonal stripe pattern with a blackening rate of 5.5% was continuously printed in an environment of 32°C temperature and 85% humidity. During the printing, a solid black image was printed every 500 sheets and the presence or absence of streaks on the image was checked. Printing was stopped when streaks appeared on the image and continued up to a maximum of 9,000 sheets. The number of printed sheets until streaks were visually observed on the image was taken as the number of sheets on which streaks appeared due to toner fusing and adhering to the developing roll, and durability was evaluated. The results are shown in Table 4. In the table, ">9000" means that no streaks appeared even on the 9000th printed sheet. The higher the number of sheets on which streaks did not appear, the better the durability of the toner.
[0128] [Table 4]
[0129] From the above results, it can be seen that the toners of Examples 1 to 13 have excellent grindability of the kneaded product and good durability, compared to Comparative Example 1, in which a twin-screw extruder was used for melt kneading, Comparative Example 2, which contains a crystalline polyester resin that does not use ethylene glycol, and Comparative Example 3, which contains an amorphous polyester resin that uses a small amount of aliphatic diol. [Industrial Applicability]
[0130] The toner for developing electrostatic images obtained by the method of the present invention is suitably used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing and the like.
Claims
1. 1. A method for producing a toner for developing electrostatic images, comprising: a crystalline polyester resin C and an amorphous polyester resin A; wherein the crystalline polyester resin C is a polycondensate of an alcohol component containing 80 mol % or more of ethylene glycol and a carboxylic acid component containing 80 mol % or more of an aliphatic dicarboxylic acid compound; and the amorphous polyester resin A is a polycondensate of an alcohol component containing 80 mol % or more of an aliphatic diol having 2 to 6 carbon atoms and a carboxylic acid component; the method comprises a step of melt-kneading a mixture containing the crystalline polyester resin C and the amorphous polyester resin A using an open-roll twin-screw kneader equipped with two rolls having different peripheral speeds; and wherein the set temperature of the raw material supply side of the high-speed rotation roll having the higher peripheral speed of the open-roll twin-screw kneader is 150° C. or less.
2. 2. The method according to claim 1, wherein the mass ratio of the crystalline polyester resin C to the amorphous polyester resin A is 3 / 97 or more and 30 / 70 or less.
3. 2. The method according to claim 1, wherein the carboxylic acid component of the crystalline polyester resin C contains an aliphatic dicarboxylic acid compound having 8 to 16 carbon atoms.
4. The method according to claim 1, wherein the carboxylic acid component of the crystalline polyester resin C contains a saturated aliphatic dicarboxylic acid compound.
5. The method according to claim 1, wherein the alcohol component and / or the carboxylic acid component of the crystalline polyester resin C contains a monofunctional monomer.
6. 2. The method according to claim 1, wherein the set temperature of the high rotation roll of the open roll type twin-screw kneader is higher than the set temperature of the low rotation roll.