JP5235365B2 - Method for producing toner for electrophotography - Google Patents

Description

  The present invention relates to an electrophotographic toner used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method and the like, and a method for producing the same.

  In recent years, a toner capable of fixing at a lower temperature has been demanded from the viewpoint of speeding up and downsizing of the apparatus, and a toner using polyester as a binder resin has been studied. On the other hand, various waxes are known as the most effective toner raw materials for improving the releasability such as filming resistance of the toner, and the method of rolling and quenching the melt-kneaded product in the cooling process in order to highly disperse the wax. Is known (see Patent Documents 1 to 3).

On the other hand, as a study on a toner production method, a method of performing a heat treatment step on a production intermediate such as a melt-kneaded product or a classified product has been proposed (see Patent Documents 4 to 6).
JP-A-6-151153 Japanese Patent Laid-Open No. 10-293413 JP 2003-50480 A JP 2005-308995 A JP 2006-65015 A JP 2006-65077 A

  However, synthetic ester waxes, amide waxes, carnauba waxes and the like that are generally compatible with polyester are dispersed to such an extent that it is difficult to ensure the effect of the wax on the fixability. Therefore, in order to improve the fixability, a large amount of wax is added, and the technology related to the cooling process as described above is disclosed. However, when the melt-kneaded material is pulverized after the cooling process, the wax eventually becomes an interface. Therefore, filming is easier. Furthermore, the compatible part of these waxes and polyester can cause filming and toner spent where the toner is fused to the carrier. These problems are particularly noticeable in printing durability at a high printing rate in which toner is rapidly replaced.

  An object of the present invention is to provide an electrophotographic toner having excellent fixing properties and preventing filming and toner spent, and a method for producing the same.

The present invention includes a melt-kneading step of melt-kneading a raw material of toner base particles containing a binder resin and a wax, a pulverizing step of pulverizing the obtained melt-kneaded product, and classifying the obtained pulverized product to obtain toner base particles. An electrophotographic toner manufacturing method comprising at least a classification step and an external addition step of mixing the obtained toner base particles and an external additive, wherein the binder resin comprises at least a carboxylic acid component and an alcohol component. Polyester obtained by condensation polymerization is contained, and the wax contains 0.1 to 4 parts by weight of carnauba wax with respect to 100 parts by weight of the binder resin. After the melt-kneading step, the formula (A):
Tg ₁ ≤ t ≤ Tw (A)
(In the formula, Tg ₁ is the glass transition point (° C.) of the object to be treated in the heat treatment step, and T w is the melting point (° C.) of the wax having the lowest melting point among the waxes)
The present invention relates to a method for producing an electrophotographic toner in which a heat treatment step is performed at a heating temperature t (° C.) satisfying the above, and an electrophotographic toner obtained by the production method.

  According to the method of the present invention, an electrophotographic toner having excellent fixability and preventing filming and toner spent can be produced.

  In the present invention, the toner mother particles containing the binder resin and the wax are melt-kneaded, a pulverizing step of pulverizing the obtained melt-kneaded product, the obtained pulverized product is classified, and the toner mother particles are classified. When a toner is produced by a method including at least a classification step to be obtained and an external addition step of mixing the obtained toner base particles and an external additive, polyester as a binder resin and a specific amount of carnauba wax as a wax are used. The main feature is that the heat treatment step is performed under a specific temperature condition after the melt-kneading step. Although details are unknown, carnauba wax is difficult to bleed out on the surface of the object to be treated even in the heat treatment step, and the wax whose crystal structure is broken due to compatibility with polyester in the melt-kneading step is recrystallized by heat treatment. Therefore, according to the method of the present invention, it is presumed that a toner having excellent fixability and improved durability can be produced.

  In the method of the present invention, the binder resin contains at least a polyester obtained by condensation polymerization of a carboxylic acid component and an alcohol component.

  Examples of the alcohol component include polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane and polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane, which are represented by the formula (I):

(In the formula, RO is an alkyleneoxy group, R is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average number of added moles of alkylene oxide, and the sum of x and y is 1 to 16, preferably 1.5-5)
Aromatic diols such as alkylene oxide adducts of bisphenol represented by: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Aliphatic diols such as hexanediol, 1,4-butenediol, 1,3-butanediol and neopentyl glycol, and trihydric or higher polyhydric alcohols such as glycerin.

  Examples of carboxylic acid components include oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, etc. Aliphatic dicarboxylic acids; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid; And anhydrides of these acids, alkyl (1 to 3 carbon atoms) esters; rosins; rosins modified with fumaric acid, maleic acid, acrylic acid, and the like. Such acids, anhydrides of these acids, and alkyl esters of these acids are collectively referred to herein as carboxylic acid compounds.

  The aromatic dicarboxylic acid compound and the aliphatic dicarboxylic acid compound may be used in combination with the carboxylic acid component of the same polyester. However, in the present invention, in order to more highly control the dispersion of the wax, the phase with the wax is used. A polyester (polyester A) obtained by using an aromatic dicarboxylic acid compound that has good solubility and contributes to improving the dispersibility of wax, and a polyester (polyester) obtained by using an aliphatic dicarboxylic acid compound that is relatively incompatible with wax. B) is preferably used in combination, and the weight ratio (A / B) of polyester A to polyester B is preferably 5/95 to 60/40, more preferably 10/90 to 50/50. In the present invention, from the viewpoint of improving the dispersibility of the wax, terephthalic acid is preferable as the aromatic dicarboxylic acid compound. From this viewpoint, the content of the aromatic dicarboxylic acid compound of polyester A is 20 mol in the carboxylic acid component. % Or more is preferable, 50 mol% or more is more preferable, and 90 mol% or more is more preferable. Further, from the viewpoint of preventing toner spent, fumaric acid is preferred as the aliphatic dicarboxylic acid compound. From this viewpoint, the content of the aliphatic dicarboxylic acid compound of polyester B is preferably 20 mol% or more, more preferably 50 mol% or more, and still more preferably 90 mol% or more in the carboxylic acid component.

  The alcohol component may contain a monovalent alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid compound as appropriate from the viewpoints of molecular weight adjustment and offset resistance improvement.

  The polyester is obtained by polycondensing an alcohol component and a carboxylic acid component at 180 to 250 ° C., for example, in an inert gas atmosphere, if necessary, in the presence of an esterification catalyst.

  The softening point of the polyester is preferably 80 to 150 ° C, more preferably 85 to 145 ° C, and still more preferably 90 to 145 ° C.

  The acid value of the polyester is preferably 50 mgKOH / g or less, more preferably 1 to 30 mgKOH / g. Further, the glass transition point is preferably 40 to 80 ° C, more preferably 50 to 70 ° C, from the viewpoints of pulverization and storage.

  In the present invention, the polyester may be a polyester modified to such an extent that the characteristics are not substantially impaired. Examples of the modified polyester include grafting and blocking with phenol, urethane, epoxy and the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. And a composite resin having two or more kinds of resin units including a polyester unit.

  In the present invention, in addition to polyester, a range in which other binder resins do not impair the effects of the present invention may be used as appropriate. Examples of other binder resins include binder resins other than polyesters such as vinyl resins, epoxy resins, polycarbonates, and polyurethanes. The content of the polyester is not particularly limited, but is preferably 80% by weight or more, and more preferably 90% by weight or more in the binder resin from the viewpoint of low-temperature fixability.

  The wax in the present invention contains carnauba wax from the viewpoint of low-temperature fixability, toner spent and filming prevention. The content of carnauba wax is 0.1 to 4 parts by weight, preferably 0.5 to 3 parts by weight, more preferably 1 to 2.5 parts by weight with respect to 100 parts by weight of the binder resin from the viewpoint of toner spent and filming prevention. Part.

  The wax in the present invention preferably further contains various waxes known as mold release agents other than the carnauba wax. The wax other than carnauba wax is preferably an ester wax other than carnauba wax, more preferably an ester of pentaerythritol and a fatty acid, from the viewpoint of compatibility with polyester and low-temperature fixability. 15-25 are preferable and, as for carbon number of this fatty acid, 17-23 are more preferable.

  The melting point of the ester wax other than carnauba wax is preferably 60 to 100 ° C., more preferably 70 to 95 ° C., and further preferably 75 to 90 ° C. from the viewpoints of filming, toner spent and fixability.

  The content of the ester wax other than the carnauba wax is preferably 0.1 to 5 parts by weight and more preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner base particles of the present invention further include a colorant, a charge control agent, a magnetic powder, a fluidity improver, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, and an anti-aging agent. In addition, additives such as a cleaning property improver may be appropriately contained.

  As the colorant, all of dyes and pigments used as toner colorants can be used, such as carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Isoindoline, Disazo Yellow and the like can be used, and the toner of the present invention may be either black toner or color toner. The content of the colorant is preferably 1 to 40 parts by weight and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner for electrophotography of the present invention includes a melting step of melt-kneading a raw material of toner base particles containing a binder resin containing polyester, a wax containing the carnauba wax, and a colorant used as appropriate, and the obtained melt-kneading Obtained by a pulverization step of pulverizing the product, a classification step of classifying the obtained pulverized product to obtain toner base particles, and an external addition step of mixing the obtained toner base particles and an external additive, and melt kneading After the process, a heat treatment process is performed under a specific temperature condition.

From the viewpoint of promoting re-domaining (unification) and recrystallization of the wax, the heat treatment step is performed by the formula (A):
Tg ₁ ≤ t ≤ Tw (A)
(In the formula, Tg ₁ is the glass transition point (° C.) of the object to be treated in the heat treatment step, and T w is the melting point (° C.) of the wax having the lowest melting point among the waxes)
The heat treatment process is performed at a heating temperature t (° C.) that satisfies the above. Formula (A) is
Preferably Tg ₁ + 3 ≦ t ≦ Tw−5,
More preferably, Tg ₁ + 3 ≦ t ≦ Tw−10,
It is.

  The heat treatment process may be performed after the melt-kneading process, and the melt-kneading process and after refers to a stage after the melt-kneading process. Specific steps include each step described later, that is, between the melt-kneading step and the pulverization step, between the pulverization step and the classification step, between the classification step and the external addition step, after the external addition step, and after the pulverization step. However, when it is composed of coarse pulverization and fine pulverization as described later, it may be performed between coarse pulverization and fine pulverization, but it is possible to selectively prevent the presence of wax at the interface and shape control. From the viewpoint, it is preferably performed after the coarse pulverization step, more preferably after the classification step, and further preferably after the external addition step.

  The time for the heat treatment step is preferably 2 to 36 hours, and more preferably 5 to 30 hours, from the viewpoints of productivity and recrystallization, wax redomaining (unification), and toner shape control.

  Further, the relative humidity during the heat treatment step is preferably 10 to 70%, more preferably 20 to 60%, from the viewpoint of solving electrostatic aggregation of the external additive and preventing aggregation of the toner particles.

  An oven or the like can be used for the heat treatment step. For example, when an oven is used, the heat treatment step can be performed by maintaining the melt-kneaded material at a constant temperature in the oven. Further, a thermo-hygrostat or a vibrating fluidized bed (VIA-16D type (manufactured by Chuo Kako Co., Ltd.)) can also be used.

  Hereinafter, each process other than the heat treatment process will be described.

  Melt kneading of the raw material of the toner base particles can be performed using a known kneader such as a closed kneader, a single or twin screw extruder, or an open roll type kneader, but a twin screw extruder is used. Is preferred. The temperature of the melt-kneading is not particularly limited as long as the raw materials are sufficiently mixed. The raw materials such as the binder resin, wax, and colorant used in the melt-kneading process are preferably mixed using a Henschel mixer and then used in the melt-kneading process.

  The melt-kneaded product obtained by the melt-kneading process is rolled and cooled. The method of rolling and cooling is not particularly limited. Examples of the rolling means include a rolling roll and a rolling drum, and examples of the cooling means include an air cooling method, a water cooling method, and a steel cooling belt method. The thickness after rolling can be adjusted by adjusting the interval between the rolling rolls and the rolling drum.

  The thickness of the melt-kneaded product that is subjected to cooling after rolling is preferably 3 mm or more from the viewpoint of improving the dispersibility of the wax and productivity.

  The pulverization step is a step of pulverizing the obtained melt-kneaded product to a volume median particle size of preferably 20 μm or less, more preferably 10 μm or less, from the viewpoint of improving durability.

  The pulverization process may be performed in multiple stages. For example, the melt-kneaded product may be coarsely pulverized to about 1 to 5 mm and further finely pulverized. Moreover, in order to improve the productivity at the time of a grinding | pulverization and a classification process, you may grind | pulverize, after mixing melt-kneaded material with inorganic fine particles, such as hydrophobic silica.

  The pulverizer used in the pulverization step is not particularly limited. For example, examples of the pulverizer suitably used for the coarse pulverization include an atomizer and a rotoplex, but a hammer mill or the like may be used. Further, examples of the pulverizer suitably used for fine pulverization include a jet mill, a collision plate mill, and a rotary mechanical mill.

  Examples of the classifier used in the classification process include an airflow crusher, an air classifier, an inertia classifier, and a sieve classifier. In the classification step, the pulverized product which has been removed due to insufficient pulverization may be subjected to the pulverization step again, and may be repeated with the pulverization step and the classification step as necessary.

After the melt-kneading step, an external addition step is performed in which the toner base particles obtained through the pulverization step and the classification step are mixed with an external additive, and the external additive is externally added to the toner surface. The volume median particle size (D ₅₀ ) of the toner base particles is preferably 4 to 12 μm, and more preferably _{5 to} 10 μm. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  Examples of the external additive include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide. Among these, silica having a small specific gravity is preferable from the viewpoint of preventing embedding.

From the viewpoint of environmental stability, the silica is preferably hydrophobic silica that has been subjected to a hydrophobic treatment. The hydrophobizing method is not particularly limited, and examples of the hydrophobizing agent include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), silicone oil, methyltriethoxysilane, and the like. And DMDS are preferred. The treatment amount of the hydrophobizing agent is preferably 1 to 7 mg / m ² per surface area of the inorganic fine particles.

  As the external additive, from the viewpoint of preventing free silica, and when the heat treatment step is performed after the external addition step, the average particle size is preferably 12 to from the viewpoint of preventing embedding in the toner in the heat treatment step. It is preferable to use silica (silica A) of 120 nm, more preferably 35 to 80 nm, still more preferably 40 to 60 nm. From the viewpoint of imparting fluidity, silica (silica) having an average particle diameter smaller than that of silica A together with silica A More preferably, B) is used.

  The external addition amount of silica A is preferably 0.3 parts by weight or more, more preferably 0.3 to 5.0 parts by weight, and more preferably 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the toner base particles from the viewpoint of preventing aggregation during the heat treatment. Further preferred.

  The average particle size of silica B is preferably 10 to 30 nm, more preferably 10 to 20 nm, from the viewpoint of imparting fluidity.

  Further, the ratio of the average particle diameter of silica A and silica B (silica A / silica B) is preferably 1.2 to 10, more preferably 1.5 to 5, and further preferably 2.0 to 3.0.

  The external addition amount of silica B is preferably 0.1 parts by weight or more, more preferably 0.1 to 4.0 parts by weight, and more preferably 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the toner base particles from the viewpoint of preventing aggregation during the heat treatment. Further preferred.

  The external addition step is preferably a dry mixing method in which the external additive and the toner base particles are mixed using a high-speed stirrer such as a Henschel mixer or a super mixer, a V-type blender or the like. The external additives may be mixed in advance and added to a high-speed stirrer or a V-type blender, or may be added separately.

  After the external addition step, it is preferable to perform a sieving step of removing coarse powder (aggregates) by sieving the toner. When the heat treatment step and the sieving step are performed after the external addition step, the heat treatment step is preferably performed between the external addition step and the sieving step.

  The electrophotographic toner of the present invention can be used as it is as a one-component developing toner as it is, but the toner of the present invention is excellent in durability and more effective in suppressing the toner spent on the carrier. Since it is remarkably exhibited, it is preferable to use it as a two-component developer by mixing with a carrier.

In the present invention, from the viewpoint of image characteristics, it is preferable to use a carrier with low saturation magnetization that weakens the area around the magnetic brush. Saturation magnetization of the carrier is preferably ^{40~100Am 2 / kg, 50~90Am 2 /} kg is more preferable. The saturation magnetization is preferably 100 Am ² / kg or less from the viewpoint of adjusting the hardness of the magnetic brush and maintaining gradation reproducibility, and preferably 40 Am ² / kg or more from the viewpoint of preventing carrier adhesion and toner scattering.

  As the core material of the carrier, those made of known materials can be used without particular limitation, for example, ferromagnetic metals such as iron, cobalt, nickel, magnetite, hematite, ferrite, copper-zinc-magnesium ferrite, Examples include alloys and compounds such as manganese ferrite and magnesium ferrite, and glass beads. Among these, iron powder, magnetite, ferrite, copper-zinc-magnesium ferrite, manganese ferrite, and magnesium ferrite are preferable from the viewpoint of chargeability. From the viewpoint of image quality, ferrite, copper-zinc-magnesium ferrite, manganese ferrite and magnesium ferrite are more preferable.

  The surface of the carrier is preferably coated with a resin from the viewpoint of preventing spent. The resin that coats the carrier surface varies depending on the toner material. For example, fluororesin such as polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin such as polydimethylsiloxane, polyester, styrenic resin, Acrylic resins, polyamides, polyvinyl butyral, amino acrylate resins, and the like can be used, and these can be used alone or in combination of two or more. However, when the toner is negatively charged, the chargeability and surface From the viewpoint of energy, a silicone resin is preferable. The method for coating the core material with the resin is not particularly limited, for example, a method in which a coating material such as a resin is dissolved or suspended in a solvent and applied to the core material, or a method of simply mixing with a powder.

  In the two-component developer obtained by mixing the toner and the carrier, the toner to carrier weight ratio (toner / carrier) is preferably 1/99 to 10/90, and more preferably 2/98 to 8/92.

  Further, since the toner of the present invention is excellent in durability, it can be suitably used in an image forming method using a high-speed developing device having a linear speed of 750 mm / sec or more, preferably 850 to 2000 mm / sec.

[Softening point of object to be subjected to resin and heat treatment process]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample is heated at a heating rate of 6 ° C / min. While applying a load of 1.96 MPa with a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. . The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Glass transition point of resin]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C, and the sample was cooled to 0 ° C at a temperature drop rate of 10 ° C / min. The temperature at the intersection of the extended line of the baseline below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Glass transition point (Tg ₁ ) of workpiece to be subjected to heat treatment process]
The endotherm obtained when the sample is heated from -20 ° C to 160 ° C at a rate of 10 ° C / min using a differential scanning calorimeter (DSC Q20, manufactured by TA Instruments Japan) In the curve, the temperature at the intersection of the baseline extension below the peak temperature observed at the lowest temperature among the endothermic peaks and the tangent showing the maximum slope from the peak rise to the peak apex Read as the transition point (Tg ₁ ).

[Acid value of resin and wax]
Measured according to the method of JIS K0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Hydroxyl value of wax]
Measured according to the method of JIS K0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Melting point of wax (Tw)]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C, and the sample was cooled to 0 ° C at a temperature drop rate of 10 ° C / min. The maximum peak temperature of heat of fusion is taken as the melting point.

[Volume-median particle diameter of toner (D ₅₀ )]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) 5% electrolyte dispersion condition: 10 mg of measurement sample is added to 5 ml of dispersion, and dispersed for 1 minute with an ultrasonic disperser. Then, 25 ml of the electrolytic solution is added, and further dispersed with an ultrasonic disperser for 1 minute.
Measurement conditions: Add 100 ml of electrolyte and dispersion in a beaker, measure 30,000 particles at a concentration that can measure the particle size of 30,000 particles in 20 seconds, and determine the volume-median particle size ( determine the D _50).

[Average particle size of external additives]
The average particle size of the external additive refers to the number average particle size. The particle size (average value of major axis and minor axis) of 500 particles is measured from a scanning electron microscope (SEM) photograph, and the average value is averaged. The particle size.

[Carrier saturation magnetization]
(1) Fill a plastic case with a lid of 7 mm outer diameter (6 mm inner diameter) and 5 mm height while tapping the carrier, and calculate the mass of the carrier from the difference between the weight of the plastic case and the weight of the plastic case filled with the carrier. .
(2) Set the plastic case filled with the carrier in the sample holder of the magnetic property measuring device `` BHV-50H '' (VSMAGNETOMETER) of RIKEN ELECTRONICS CO., LTD., While vibrating the plastic case using the vibration function, Saturation magnetization is measured by applying a magnetic field of 79.6 kA / m. The obtained value is converted into saturation magnetization per unit mass in consideration of the mass of the filled carrier.

Example of polyester production The raw material monomers (alcohol component and carboxylic acid component) shown in Table 1 were placed in a 5-liter glass four-necked flask together with 8 g of tin (II) 2-ethylhexylate as an esterification catalyst, and the temperature A total, a stainless steel stirrer, a flow-down condenser and a nitrogen introduction tube were attached, and the reaction was carried out at 220 ° C. for 8 hours with stirring in a nitrogen stream in an electric heating mantle, followed by reaction at 8.3 kPa for 1 hour. Furthermore, it was made to react until it reached a desired softening point at 210 degreeC, and resin A and B was obtained.

Production example 1 of ester wax
A 4-neck round flask equipped with a stirrer, a thermocouple, and a nitrogen introduction tube was charged with 4 mol of behenic acid per 1 mol of pentaerythritol, and heated at 130 ° C. for 5 hours in a nitrogen atmosphere to carry out an esterification reaction. The reaction product was purified with methyl ether to obtain an ester of pentaerythritol and behenic acid (ester wax A). Wax A had an acid value of 0.4 mgKOH / g, a hydroxyl value of 1.6 mgKOH / g, and a melting point of 82.7 ° C.

Production example 2 of ester wax
A 4-neck round flask equipped with a stirrer, thermocouple, and nitrogen inlet tube was charged with 1 mol of behenic acid per 1 mol of behenyl alcohol, and heated at 130 ° C. for 3 hours in a nitrogen atmosphere to carry out an esterification reaction. The reaction product was purified with methyl ether to obtain an ester of behenyl alcohol and behenic acid (ester wax B). Wax B had an acid value of 0.1 mgKOH / g, a hydroxyl value of 1.2 mgKOH / g, and a melting point of 78.7 ° C.

Example 1 (Reference Example)
80 parts by weight of resin A and 20 parts by weight of resin B as binder resins, 2 parts by weight of “Carnauba wax C1” (manufactured by Kato Yoko Co., Ltd., melting point: 87 ° C.), 2 parts by weight of wax A, and “ After mixing 1 part by weight of “T-77” (made by Hodogaya Chemical Co., Ltd., iron azo dye) and 6 parts by weight of carbon black “NIPEX60” (made by Degussa) as a colorant with a Henschel mixer for 60 seconds, Immediately after being melt-kneaded at 100 ° C., it was cooled to a sheet having a thickness of 3 mm using a cooling roller, and roughly pulverized to about 2 mm with a hammer mill.

The obtained coarsely pulverized product is heat-treated by being left in a thermostatic bath at a temperature of 60 ° C. and a relative humidity of 40% for 10 hours, and then finely pulverized by an air jet type pulverizer and classified by an airflow classifier. Thus, negatively chargeable toner base particles having a volume-median particle size (D ₅₀ ) of 8.5 μm were obtained.

  100 parts by weight of the obtained toner base particles, hydrophobic silica “R-972” (manufactured by Nippon Aerosil Co., Ltd., average particle size 16 nm, hydrophobizing agent DMDS) 0.6 part by weight, and hydrophobic silica “NAX50” (Nippon Aerosil An average particle size of 40 nm, a hydrophobizing agent HMDS (1.0 part by weight) was mixed with a Henschel mixer for 3 minutes, and the coarse powder was removed with a sieve sieve having an opening of 100 μm to obtain a toner.

Example 2 (Reference Example)
Example 1 is the same as in Example 1 except that the heat treatment step for 5 hours in a constant temperature bath at 60 ° C. and 40% relative humidity was performed on the toner base particles before mixing with hydrophobic silica instead of the coarsely pulverized product. Similarly, a toner was obtained.

Example 3
The heat treatment process, which is allowed to stand for 5 hours in a constant temperature bath at a temperature of 60 ° C. and a relative humidity of 40%, is not coarsely pulverized, but after mixing toner base particles and hydrophobic silica, and removing coarse powder with a shaking sieve. A toner was obtained in the same manner as in Example 1 except that the previous toner was used.

Example 4 (Reference Example)
A toner was obtained in the same manner as in Example 1 except that the resin A was not used as the binder resin and the amount of the resin B used was changed to 100 parts by weight.

Example 5 (Reference Example)
A toner was obtained in the same manner as in Example 1 except that 2 parts by weight of wax B was used instead of wax A.

Comparative Example 1
A toner was obtained in the same manner as in Example 1 except that wax A was not used and the amount of “carnauba wax C1” was changed to 5 parts by weight.

Comparative Example 2
A toner was obtained in the same manner as in Example 2 except that the amount of “carnauba wax C1” used was changed to 5 parts by weight.

Comparative Example 3
A toner was obtained in the same manner as in Example 1 except that the amount of “carnauba wax C1” used was changed to 5 parts by weight.

Comparative Example 4
A toner was obtained in the same manner as in Example 1 except that the heat treatment was not performed.

Comparative Example 5
A toner was obtained in the same manner as in Example 1, except that 2 parts by weight of paraffin wax “HNP-9” (manufactured by Nippon Seiki Co., Ltd., melting point: 81.6 ° C.) was used instead of “Carnauba wax”.

Comparative Example 6
A toner was obtained in the same manner as in Example 1 except that the heat treatment was performed by allowing the coarsely pulverized product to stand in a constant temperature bath at 90 ° C. and 40% relative humidity for 1 hour.

Comparative Example 7
A toner was obtained in the same manner as in Example 1 except that 2 parts by weight of polypropylene wax “Mitsui High Wax NP055” (Mitsui Chemicals, melting point: 140.0 ° C.) was used instead of “Carnauba wax C1” and wax A. It was.

Comparative Example 8
A toner was obtained in the same manner as in Example 1 except that the heat treatment was performed by allowing the coarsely pulverized product to stand in a constant temperature bath having a temperature of 40 ° C. and a relative humidity of 40% for 10 hours.

Using the toners obtained in Examples 1 to 5 and Comparative Examples 1 to 8, 6 parts by weight of each toner and 94 parts by weight of ferrite carrier (volume average particle size: 60 μm, saturation magnetization: 68 Am ² / kg) are mixed. Thus, a two-component developer was obtained. Using the obtained two-component developer, the tests of the following Test Examples 1 to 3 were performed. The results are shown in Table 2.

Test Example 1 [low temperature fixability]
After mounting the two-component developer on the copier “AR-505” (manufactured by Sharp) and adjusting the toner amount to 0.6 mg / cm ² , the image is taken out before fixing and unfixed image Got. Furthermore, using a non-contact fixing type image forming device "Vario stream 9000" (manufactured by Ossprinting Systems), an external fixing machine is used, and the linear temperature is 1000mm / sec. The temperature was raised to 150 ° C. to obtain a fixed image. "UNICEF Cellophane" (Mitsubishi Pencil Co., Ltd., width: 18mm, JISZ-1522) is pasted on the image fixed at each temperature, pressure is applied to the tape with a roller so that a load of 500g is applied, and then the tape is peeled off. The image density before and after peeling was measured.

  The image density was calculated as an image density (ID) by measuring five points on the image printing portion with a color meter “GretagMacbeth Spectroeye” (manufactured by Gretag).

The low-temperature fixability was evaluated by setting the temperature on the paper where the image density ratio (after tape peeling / before tape application × 100) after tape peeling and before tape sticking first exceeded 90% as the lowest fixing temperature. A minimum fixing temperature of less than 105 ° C. is judged good. The results are shown in Table 2. The paper used for the fixing test is a cardboard “CopyBond SF-70NA” (75 g / m ² ) manufactured by Sharp Corporation.

Test Example 2 [Toner spent]
The two-component developer is mounted on a two-component development-type image forming device “Vario stream 9000” (manufactured by Ossprinting Systems Co., Ltd.) equipped with an organic photoreceptor. After printing for 20 hours at a printing rate of 18%, the following The spent amount was measured according to the method. The results are shown in Table 2.

(1) The two-component developer is passed through a 20 μm mesh with a vacuum cleaner, and the carbon content of the remaining carrier is measured with a carbon analyzer (carbon analyzer: manufactured by HORIBA).
(2) The carrier whose carbon content is measured in (1) is washed with chloroform, and the toner adhering to the carrier is removed. After cleaning, the amount of carbon in the carrier is measured.
(3) The amount of spent toner is obtained by subtracting the amount of carbon measured in (2) from the amount of carbon measured in (1). In the table, it is shown in% by weight relative to the weight of the carrier.

Test Example 3 [Film resistance]
In Test Example 2, after printing for 20 hours, the presence or absence of filming on the organic photoreceptor was visually observed, and the filming resistance was evaluated according to the following evaluation criteria. The results are shown in Table 2.

[Evaluation criteria for filming resistance]
◎: Filming is not recognized at all ○: Filming is recognized a little ×: Filming is recognized

  From the above results, it can be seen that the toners of Examples 1 to 5 have good low-temperature fixability and the occurrence of toner spent and filming is suppressed as compared with the toners of Comparative Examples 1 to 8. .

  The toner for electrophotography obtained by the present invention is suitably used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (1)

A melt-kneading step of melt-kneading the raw material of the toner base particles containing the binder resin and the wax, a pulverizing step of pulverizing the obtained melt-kneaded product, a classification step of classifying the obtained pulverized product to obtain toner base particles, And an electrophotographic toner production method comprising at least an external addition step of mixing the obtained toner base particles and an external additive, wherein the binder resin polycondenses at least a carboxylic acid component and an alcohol component. The obtained polyester contains, and the wax contains 0.1 to 4 parts by weight of carnauba wax with respect to 100 parts by weight of the binder resin. After the external addition step, the formula (A):
Tg ₁ + 3≤t≤Tw- 10 (A)
(In the formula, Tg ₁ is the glass transition point (° C.) of the object to be treated in the heat treatment step, and T w is the melting point (° C.) of the wax having the lowest melting point among the waxes)
A method for producing an electrophotographic toner, wherein the heat treatment step is performed at a heating temperature t (° C.) satisfying the above.