JP5822388B2 - Method for producing toner for electrophotography - Google Patents

Description

  The present invention relates to a method for producing 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 an electrophotographic toner obtained by the method.

  To meet the recent demands for speeding up and downsizing, a toner capable of being fixed at a lower temperature is demanded.

  In many cases, the toner is produced by melt-kneading a composition mainly composed of a colorant and a binder resin, pulverizing and classifying the obtained kneaded product. Accordingly, there is a demand for a method for producing a highly productive toner that generates less coarse particles and fine powder during pulverization.

  On the other hand, a toner using activated carbon as a colorant has been proposed.

  In Patent Document 1, by using activated carbon as a black colorant as an alternative to low resistance carbon black, there is no charge variation and toner scattering, and the tone reproducibility and fine line reproducibility of image quality are good. Thus, it is disclosed that the unevenness of the halftone portion does not occur.

  Patent Document 2 also discloses a toner that uses activated carbon as a black colorant as an alternative to carbon black, stabilizes image density / fogging, has less environmental dependency, and gives a high-quality image even when used repeatedly. Proposed.

JP-A-61-203463 JP 2003-280277 A

  However, toner using activated carbon has not been sufficient to achieve both low-temperature fixability and productivity.

  An object of the present invention is a method for producing a toner excellent in productivity, which generates less fine powder and coarse particles during pulverization, and a method for producing an electrophotographic toner capable of obtaining a toner excellent in low-temperature fixability, and the method The present invention provides an electrophotographic toner obtained by the above process.

The present invention
[1] A method for producing an electrophotographic toner comprising soybean-derived porous carbon powder and a binder resin,
Step 1: Melt-knead a component containing a binder resin and 2.5 to 20 parts by weight of a soy-derived porous carbon powder having a volume median particle size of 0.3 to 50 μm with respect to 100 parts by weight of the binder resin. A step of obtaining a resin mixture, and a step 2: pulverizing and classifying the resin mixture obtained in step 1, and a method for producing an electrophotographic toner, and [2] the production method according to the above [1] The present invention relates to an electrophotographic toner obtained.

  The method of the present invention is a method for producing a toner for electrophotography having a high productivity with less generation of fine powder and coarse particles during pulverization. Furthermore, the electrophotographic toner obtained by the method of the present invention is excellent in low-temperature fixability.

The method for producing the electrophotographic toner of the present invention includes:
Step 1: Melt-knead a component containing a binder resin and 2.5 to 20 parts by weight of a soy-derived porous carbon powder having a volume median particle size of 0.3 to 50 μm with respect to 100 parts by weight of the binder resin. A step of obtaining a resin mixture, and step 2: a step of pulverizing and classifying the resin mixture obtained in step 1,
In which a soybean-derived porous carbon powder is used. A toner having excellent low-temperature fixability can be obtained with high productivity by the method of the present invention. The reason for this is not clear, but activated carbon with a porous structure made from plant material controls the specific surface area and pore size to some extent by adjusting the conditions of chemicals used, firing process, activation process, etc. Although possible, the structure depends largely on the starting material. The soy-derived porous carbon powder has a multi-porous structure in which finely entangled fibers form 1 to 30 μm voids and further form 1 to 10 μm voids, The 10 μm void is filled with resin, and the 1 to 30 mm void is maintained. As a result, it is considered that an appropriate hardness is exhibited at the time of pulverization and generation of fine powder is suppressed.

  Further, soybean-derived porous carbon powder has high thermal conductivity, and can efficiently melt toner particles. In particular, within a specific particle size range, the soy-derived porous carbon powder is uniformly dispersed in the resin during melt-kneading, and as a result, it is uniformly dispersed in the toner particles, so that there is no variation in the fixing of the toner particles. The effect of improving the fixability by the soybean-derived porous carbon powder is more prominent in fixing at low temperatures.

[Soybean-derived porous carbon powder]
In the present invention, the soybean-derived porous carbon powder is preferably a baked product obtained by carbonizing and baking soybean hulls. For example, at a temperature of about 900 ° C., using a carbonization apparatus such as a stationary furnace or a rotary kiln. It is obtained by baking soybean hulls in an inert gas atmosphere such as nitrogen gas or in a vacuum (International Publication No. 2010/035829 [0023]). When used in the method of the present invention, the fired product is preferably pulverized and classified.

  Examples of commercially available soy-derived porous carbon powders include “Phytoporous SH905”, “Phytoporous SH930”, “Phytoporous SH3030” (manufactured by Nisshin Oilio Co., Ltd.), and the like.

  The volume-median particle size of the soy-derived porous carbon powder is 0.3 μm or more from the viewpoint of improving the productivity of the toner, the viewpoint of improving the low-temperature fixability, and the viewpoint of maintaining an appropriate image density, preferably It is 0.5 μm or more, more preferably 2.0 μm or more, and further preferably 5.0 μm or more. From the viewpoint of improving toner productivity, it is 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less. Taking these viewpoints together, the volume-median particle size of the soybean-derived porous carbon powder is 0.3 to 50 μm, preferably 0.5 to 30 μm, more preferably 2.0 to 20 μm, and still more preferably 5.0 to 10 μm.

  The maximum diameter of the soy-derived porous carbon powder is preferably 100 μm or less, and more preferably 50 μm or less, from the viewpoint of improving toner productivity.

The specific surface area of the soybean-derived porous carbon powder, from the viewpoint of improving the toner productivity is preferably 2~1000m ² / g, more preferably 5~500m ² / g, 300~500m ² More preferably, it is / g.

  The content of the soybean-derived porous carbon powder is 2.5 parts by weight with respect to 100 parts by weight of the binder resin from the viewpoint of improving the productivity of the toner, the viewpoint of improving the low temperature fixability, and the viewpoint of improving the image density. The amount is preferably 3 parts by weight or more, more preferably 4 parts by weight or more, and still more preferably 5 parts by weight or more. From the viewpoint of improving toner productivity, it is 20 parts by weight or less, preferably 15 parts by weight or less, more preferably 10 parts by weight or less, and further preferably 8 parts by weight or less. Summing up these viewpoints, the content of the soy-derived porous carbon powder, that is, the use amount of the soy-derived porous carbon powder in Step 1 is 2.5 to 20 parts by weight with respect to 100 parts by weight of the binder resin. Preferably it is 3-15 weight part, More preferably, it is 4-10 weight part, More preferably, it is 5-10 weight part, More preferably, it is 5-8 weight part.

[Colorant]
As the colorant, only the aforementioned soybean-derived porous carbon powder may be used as the colorant, but all of dyes and pigments used as the colorant for toner can be used in combination. When obtaining a black toner, carbon black may be used in combination because it is easily available.

  When carbon black is used in combination, the content of carbon black in the toner base particles is preferably 0.5 parts by weight or more with respect to 100 parts by weight of the binder resin from the viewpoint of improving the image density. Further, from an economic viewpoint, the amount is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and further preferably 5 parts by weight or less. Taking these viewpoints together, the content of carbon black in the toner base particles is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and still more preferably 0.5 to 5 parts per 100 parts by weight of the binder resin. Parts by weight.

  The content of the colorant in the toner base particles is combined with the content of the soybean-derived porous carbon powder, from the viewpoint of improving the productivity of the toner, the viewpoint of improving the low-temperature fixability, and the viewpoint of improving the image density. The amount is preferably 2.5 parts by weight or more, more preferably 3 parts by weight or more, still more preferably 4 parts by weight or more, and still more preferably 5 parts by weight or more with respect to 100 parts by weight of the binder resin. Further, from the viewpoint of improving the productivity of the toner and from an economical viewpoint, it is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, further preferably 12 parts by weight or less, and even more preferably 8 parts by weight or less. To summarize these viewpoints, the content of the colorant in the toner base particles is preferably 2.5 to 20 parts by weight with respect to 100 parts by weight of the binder resin, together with the content of the soybean-derived porous carbon powder. More preferably, it is 3-15 weight part, More preferably, it is 4-12 weight part, More preferably, it is 5-8 weight part.

[Binder resin]
The binder resin used in the present invention preferably contains polyester from the viewpoint of improving the low-temperature fixability of the toner. The content of polyester is preferably 80% by weight or more, more preferably 90% by weight or more in the binder resin, and more preferably only polyester is used as the binder resin, but the effect of low-temperature fixability is not impaired. In the range, resins other than polyester may be contained. Examples of other binder resins include vinyl resins, epoxy resins, polycarbonates, polyurethanes, and the like.

  The polyester used in the present invention is obtained by polycondensation of an alcohol component composed of a divalent or higher alcohol and a carboxylic acid component composed of a divalent or higher carboxylic acid compound.

  The dihydric alcohol has 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, more preferably 3 to 6 carbon atoms from the viewpoint of improving the productivity of the toner and the low temperature fixability of the toner. The aliphatic diols are preferred. Specific examples of the divalent aliphatic diol having 2 to 20 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1.9-nonanediol, neopentyl glycol, 1,4-butenediol, etc. 4-Butanediol and 1,6-hexanediol are preferred.

  The content of the divalent aliphatic diol having 2 to 20 carbon atoms is preferably 50 mol% or more in the alcohol component from the viewpoint of improving the productivity of the toner and the low temperature fixability of the toner. More preferably, mol% or more is more preferable, 90 mol% or more is more preferable, and substantially 100 mol% is still more preferable.

  In the divalent alcohol component, as an alcohol component other than the aliphatic diol having 2 to 20 carbon atoms, the formula (I):

(In the formula, RO and OR are oxyalkylene groups, R is an ethylene and / or propylene group, x and y indicate the number of added moles of alkylene oxide, each being a positive number, and the sum of x and y. 1 to 16 is preferable, 1 to 8 is more preferable, and 1.5 to 4 is more preferable. The alkylene oxide adduct of bisphenol A, hydrogenated bisphenol A, and the like can be given.

  Examples of trihydric or higher alcohols include trihydric or higher polyhydric alcohols having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms. Specific examples include sorbitol, 1,4-sorbitan, pentaerythritol, glycerol, trimethylolpropane, and the like.

  Examples of the divalent carboxylic acid compound include dicarboxylic acids having 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, and more preferably 3 to 10 carbon atoms, and their acid anhydrides and alkyls (1 to carbon atoms). 3) Derivatives such as esters. Specifically, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, an alkyl group or alkenyl group having 1 to 20 carbon atoms And an aliphatic dicarboxylic acid such as succinic acid substituted with.

  Examples of the trivalent or higher carboxylic acid compound include, for example, a polyvalent carboxylic acid having 4 to 30 carbon atoms, more preferably 4 to 20 carbon atoms, and still more preferably 4 to 10 carbon atoms, and more, and acid anhydrides thereof. Products, derivatives of alkyl (1 to 3 carbon atoms) esters and the like. Specific examples include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), and the like.

  In addition, a monovalent alcohol may be appropriately contained in the alcohol component, and a monovalent carboxylic acid compound may be appropriately contained in the carboxylic acid component from the viewpoint of adjusting the softening point of the polyester.

  From the viewpoint of reducing the acid value of the polyester, the equivalent ratio (COOH group / OH group) of the carboxylic acid component and the alcohol component in the polyester is preferably 0.70 to 1.10, and more preferably 0.75 to 1.00.

  The polycondensation reaction between the alcohol component and the carboxylic acid component is carried out by polycondensation at a temperature of about 120 to 250 ° C. in the presence of an esterification catalyst, a polymerization inhibitor, etc. in an inert gas atmosphere as necessary. Can be manufactured. Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin (II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamate. The amount of the esterification catalyst used is preferably 0.01 to 1.5 parts by weight, more preferably 0.1 to 1.0 part by weight, based on 100 parts by weight of the total amount of the alcohol component and the carboxylic acid component. The amount of the polymerization inhibitor used is preferably 0.001 to 0.5 parts by weight and more preferably 0.01 to 0.1 parts by weight with respect to 100 parts by weight of the total amount of the alcohol component and the carboxylic acid component.

  The softening point of the polyester is preferably from 70 to 160 ° C, more preferably from 90 to 150 ° C, more preferably from 105 to 149, from the viewpoint of improving the low temperature fixability and high temperature offset resistance of the toner and improving the productivity of the toner. More preferably.

  The softening point of the polyester can be controlled by adjusting the types and composition ratios of the alcohol component and carboxylic acid component, the amount of catalyst, and the like, and selecting reaction conditions such as reaction temperature, reaction time, and reaction pressure.

  In the present invention, from the viewpoint of improving toner productivity, it is preferable to use two or more polyesters as the binder resin.

  When two or more polyesters are used, the softening point of the entire binder resin is within the above range from the viewpoint of improving the low-temperature fixability and high-temperature offset resistance of the toner and improving the toner productivity. It is preferable. That is, 100-150 degreeC is preferable, 120-140 degreeC is more preferable, and 130-135 degreeC is further more preferable. The softening point of the entire binder resin can be obtained by a weighted average, that is, the sum of the products of the respective softening points and content ratios.

  When two or more polyesters are used, the softening point of at least one polyester (polyester A) is preferably 135 to 160 ° C. from the viewpoint of improving the high-temperature offset resistance of the toner and improving the low-temperature fixability. -150 ° C is more preferred.

  The softening point of the other polyester (polyester B) is preferably from 70 to 135 ° C, more preferably from 90 to 120 ° C, from the viewpoint of improving the high temperature offset resistance of the toner and improving the low temperature fixability.

  The difference in softening point between polyester A and polyester B is preferably 20 ° C. or higher, and more preferably 25 ° C. or higher, from the viewpoint of improving the high temperature offset resistance of the toner and improving the low temperature fixability.

  The amount of polyester A is preferably 50 to 90% by weight and more preferably 55 to 70% by weight in the binder resin from the viewpoint of improving the high temperature offset resistance of the toner and improving the low temperature fixability. In the present specification, simply “amount” means both the content and the blending amount.

  The amount of polyester B is preferably 10 to 50% by weight and more preferably 30 to 45% by weight in the binder resin from the viewpoint of improving the high temperature offset resistance of the toner and improving the low temperature fixability.

  The weight ratio of polyester A to polyester B (polyester A / polyester B) is preferably 50/50 to 90/10 from the viewpoint of improving the high-temperature offset resistance of the toner and improving the low-temperature fixability. 45-70 / 30 is more preferable.

  As the polyester, either a crystalline polyester or an amorphous polyester can be used, or a mixture of both can be used. From the viewpoint of improving the low-temperature fixability of the toner, it is preferable to use a mixture of a crystalline polyester and an amorphous polyester.

  The weight ratio of crystalline polyester to amorphous polyester (crystalline polyester / amorphous polyester) is preferably 5/95 to 50/50, more preferably 5/95 to 40/60, and 5/95 to 20 / 80 is more preferred.

  Here, the crystallinity of the resin is represented by the crystallinity index defined by the ratio between the softening point and the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the value of [softening point / maximum endothermic peak temperature]. The crystalline resin has a crystallinity index of 0.6 to 1.4, preferably 0.7 to 1.2, more preferably 0.9 to 1.2, and the amorphous resin is a resin having a value of 1.4 or less than 0.6. The crystallinity of the resin can be adjusted by the types and ratios of the raw material monomers, production conditions (for example, reaction temperature, reaction time, cooling rate) and the like. The highest endothermic peak temperature refers to the temperature of the peak on the highest temperature side among the observed endothermic peaks. The maximum peak temperature is the melting point if the difference from the softening point is within 20 ° C., and the peak due to the glass transition if the difference from the softening point exceeds 20 ° C.

  The maximum peak temperature of the endothermic polyester is preferably from 50 to 130 ° C, more preferably from 60 to 120 ° C, and even more preferably from 65 to 115 ° C from the viewpoint of improving the low-temperature fixability of the toner and improving the productivity. .

  The glass transition temperature of the polyester is preferably from 50 to 85 ° C., and from 55 to 80 ° C., from the viewpoint of improving the low-temperature fixability of the toner, improving the productivity of the toner, and improving the storage stability of the toner. More preferred. The glass transition temperature is a physical property unique to an amorphous resin.

  The glass transition temperature of the polyester can be controlled by the type and composition ratio of the alcohol component and carboxylic acid component.

  The acid value of the polyester is preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less, and even more preferably 20 mgKOH / g or less from the viewpoint of improving the chargeability and improving the dispersibility of the additive.

  The acid value of the polyester can be controlled by adjusting the types and composition ratios of the alcohol component and the carboxylic acid component, the amount of the catalyst, etc., and selecting the reaction conditions such as the reaction temperature, reaction time, and reaction pressure.

  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 or blocking with phenol, urethane, epoxy or the like by the method described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc. Polyester.

  The toner of the present invention may further contain a release agent, a charge control agent and the like.

[Release agent]
As the release agent, low molecular weight polypropylene, low molecular weight polyethylene, low molecular weight polypropylene polyethylene copolymer, aliphatic hydrocarbon wax such as microcrystalline wax, paraffin wax, Fischer-Tropsch wax and oxides thereof, carnauba wax, Examples include montan wax, sazol wax and their deoxidized wax, ester waxes such as fatty acid ester wax, fatty acid amides, higher alcohols and the like. Among these, paraffin wax is preferable from the viewpoint of improving the low-temperature fixability of the toner.

  The content of the release agent is preferably 1 to 20 parts by weight, more preferably 1.5 to 10 parts by weight, and more preferably 2 to 4 parts by weight with respect to 100 parts by weight of the binder resin from the viewpoint of improving the low-temperature fixability of the toner. Part is more preferable.

  The melting point of the release agent is preferably 60 to 160 ° C., more preferably 70 to 150 ° C. from the viewpoint of improving the low-temperature fixability of the toner and the storage stability.

[Charge control agent]
As the charge control agent, either a negative charge control agent or a positive charge control agent can be used.

  Examples of the negatively chargeable charge control agent include metal-containing azo dyes, copper phthalocyanine dyes, metal complexes of salicylic acid alkyl derivatives, nitroimidazole derivatives, and benzyl acid boron complexes. Examples of metal-containing azo dyes include “Varifirst Black 3804”, “Bontron S-28”, “Bontron S-31”, “Bontron S-32”, “Bontron S-34”, “Bontron S-36” ( As mentioned above, “T-77”, “Eisenspiron Black TRH” (manufactured by Hodogaya Chemical Co., Ltd.) and the like can be mentioned. Examples of metal complexes of alkyl derivatives of salicylic acid include “Bontron E-81”, “Bontron E-82”, “Bontron E-84”, “Bontron E-85” (above, manufactured by Orient Chemical Co., Ltd.) and the like. It is done. Examples of the benzyl acid boron complex include “LR-147” (manufactured by Nippon Carlit).

  Examples of the positively chargeable charge control agent include nigrosine dyes, triphenylmethane dyes, quaternary ammonium salt compounds, polyamine resins, and imidazole derivatives. Nigrosine dyes include, for example, “Nigrosine Base EX”, “Oil Black BS”, “Oil Black SO”, “Bontron N-01”, “Bontron N-07”, “Bontron N-09”, “Bontron N-11” (Above, manufactured by Orient Chemical Industry Co., Ltd.). Examples of the triphenylmethane dye include a triphenylmethane dye containing a tertiary amine as a side chain. Examples of quaternary ammonium salt compounds include “Bontron P-51”, “Bontron P-52” (manufactured by Orient Chemical Co., Ltd.), “TP-415” (Hodogaya Chemical Co., Ltd.), and cetyltrimethylammonium bromide. , "COPY CHARGE PXVP435", "COPY CHARGE PSY" (manufactured by Clariant). Examples of the polyamine resin include “AFP-B” (manufactured by Orient Chemical Industries). Examples of the imidazole derivative include “PLZ-2001”, “PLZ-8001” (manufactured by Shikoku Kasei Co., Ltd.) and the like.

  The content of the charge control agent is preferably 0.5 to 5 parts by weight and more preferably 0.7 to 3 parts by weight with respect to 100 parts by weight of the binder resin from the viewpoint of improving the charging stability of the toner.

  The toner of the present invention further includes additives such as magnetic powder, fluidity improver, conductivity modifier, extender pigment, fibrous substance, reinforcing filler, antioxidant, anti-aging agent, cleaning improver and the like. You may contain suitably.

<Toner production method>
The toner of the present invention is obtained by a method including the following steps 1 and 2.
Step 1: Step of melting and kneading components containing binder resin and soybean-derived porous carbon powder to obtain a resin mixture Step 2: Step of pulverizing and classifying the mixture obtained in Step 1

Furthermore, in the present invention, it is preferable from the viewpoint of improving the fluidity and chargeability of the toner to include the following step 3 in which the toner obtained in step 2 is used as toner base particles and externally added.
Step 3: A step of externally adding the toner base particles obtained in Step 2

  Step 1 can be performed using a known kneader such as a closed kneader, a uniaxial or biaxial kneader, or a continuous open roll type kneader, but is preferably performed with a biaxial kneader. A biaxial kneader is a closed-type kneader in which two kneading shafts are covered by a barrel and improves the dispersibility of soybean-derived porous carbon powder, colorant, and charge control agent in the binder resin. From the viewpoint, a type in which the rotation direction of the shaft can rotate in the same direction is preferable. As a commercial product, from the viewpoint of improving productivity, the twin screw extruder PCM series manufactured by Ikekai Tekko Co., Ltd., which is good at high speed twin screw engagement is preferable.

  The toner raw material is preferably mixed in advance with a mixer such as a Henschel mixer or a ball mill and then supplied to the kneader.

  The melt kneading in the biaxial kneader is performed by adjusting the barrel set temperature (temperature of the inner wall surface of the extruder), the peripheral speed of biaxial shaft rotation, and the raw material supply speed. The barrel set temperature is preferably 80 to 140 ° C., from the viewpoint of improving dispersibility in the binder resin of the soybean-derived porous carbon powder and colorant and charge control agent, and from the viewpoint of improving productivity, 120 ° C. is more preferable.

  The peripheral speed of the biaxial shaft rotation is 0.1 to 1 m / sec from the viewpoint of improving dispersibility in the binder resin of soybean-derived porous carbon powder, colorant, and charge control agent, and productivity. Is preferred.

  The feed rate of the raw material to the biaxial kneader is appropriately adjusted according to the allowable capacity of the kneader to be used, the barrel set temperature and the peripheral speed of the shaft rotation.

  Step 2 is a step of pulverizing and classifying the resin mixture obtained in Step 1. The resin mixture obtained in Step 1 is preferably cooled to 40 ° C. or lower while being rolled to a thickness of 1 to 3 mm, and then subjected to a pulverization step and a classification step.

  The pulverization process may be performed in multiple stages. For example, the resin mixture may be coarsely pulverized to about 0.1 to 5 mm and further pulverized.

  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. Moreover, examples of the pulverizer suitably used for fine pulverization include a fluidized bed type counter jet mill, a collision plate jet mill, and a mechanical mill.

  Examples of the classifier used in the classification process include an airflow classifier, an inertia classifier, and a sieve classifier. In the classification step, the pulverized product that has been 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.

The volume median particle size (D ₅₀ ) of the toner base particles obtained in step 2 is preferably 3 to 15 μm, more preferably 4 to 12 μm, from the viewpoint of improving the image quality of the toner. 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.

  Step 3 is a step in which the toner base particles obtained in Step 2 are externally added.

  In the toner of the present invention, it is preferable to use inorganic fine particles as an external additive in order to improve transferability. Specific examples include inorganic particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as resin particles such as melamine resin fine particles and polytetrafluoroethylene resin fine particles. Among these, silica is preferable, and from the viewpoint of preventing silica from being embedded in the binder resin, it is more preferable that silica having a low specific gravity is contained.

  Silica is preferably hydrophobic silica that has been subjected to a hydrophobic treatment, from the viewpoint of toner transferability.

  The number average particle diameter of the external additive is from 10 to 250 nm, preferably from 10 to 200 nm, more preferably from 15 to 90 nm, from the viewpoint of improving the chargeability, fluidity and transferability of the toner.

  The content of the external additive is preferably 0.05 to 5 parts by weight with respect to 100 parts by weight of the toner base particles before being processed with the external additive, from the viewpoint of improving the chargeability, fluidity and transferability of the toner. More preferably, it is 0.1-4 weight part, More preferably, it is 0.3-3 weight part.

  For mixing the toner base particles and the external additive, it is preferable to use a mixer equipped with a stirring tool such as a rotary blade, a high speed mixer such as a Henschel mixer or a super mixer is preferable, and a Henschel mixer is more preferable.

  The toner of the present invention can be used in an image forming apparatus of a one-component development system or a two-component development system as a one-component development toner as it is or as a two-component development toner mixed with a carrier.

  Also, the fixing method is not particularly limited, but an oilless fixing type image forming apparatus can also be suitably used. The oilless fixing is a method using a fixing device having a heat roll fixing device that does not include an oil supply device. The oil supply device has an oil tank and has a mechanism for quantitatively applying oil to the surface of the heat roll, as well as a device having a mechanism for bringing a roll pre-impregnated with oil into contact with the heat roll, etc. including.

[Softening point of resin]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample is heated at a heating rate of 6 ° C / min, and a load of 1.96 MPa is applied by a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. Plot the plunger drop amount of the flow tester against the temperature, and let the softening point be the temperature at which half of the sample flowed out.

[Maximum peak temperature of resin endotherm]
Using a differential scanning calorimeter (Q Instruments Japan Co., Ltd., Q-100), weigh 0.01 to 0.02 g of the sample into an aluminum pan and cool it from room temperature to 0 ° C at a temperature drop rate of 10 ° C / min. Then, it was left still for 1 minute. Then, it measured with the temperature increase rate of 50 degrees C / min. Among the observed endothermic peaks, the temperature of the peak on the highest temperature side is defined as the highest endothermic peak temperature. If the maximum peak temperature is within 20 ° C of the softening point, the melting point is assumed.

[Glass transition temperature 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.

[Acid value of the resin]
Measured by 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 a mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Volume median particle size of soybean-derived porous carbon powder and activated carbon]
Measuring machine: Laser diffraction particle size measuring machine (Horiba, LA-920)
Measurement method: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) is dissolved in distilled water to a concentration of 10% by weight, 10 mg of a measurement sample is added to 5 ml of the obtained solution, and ultrasonic waves are added. Disperse with a disperser for 3 minutes to prepare a dispersion. After adding distilled water to the measurement cell, the sample dispersion is added, and the volume median particle size (D ₅₀ ) is measured.

[Specific surface area of soybean-derived porous carbon powder]
The BET specific surface area is measured under the following conditions using Micromeritics FlowSorbIII (manufactured by Shimadzu Corporation).
・ Sample amount: 0.1g
・ Deaeration condition: 40 ℃, 10 minutes ・ Adsorption gas: Nitrogen gas

[Melting point of release agent]
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 melting point is the maximum peak temperature of the heat of fusion

[Number average particle diameter of external additives]
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 taken as the number average particle size.

[Volume-median particle size of toner]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 100μm
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) is dissolved in the electrolyte so as to have a concentration of 5% by weight.
Dispersion conditions: 10 mg of a measurement sample was added to 5 ml of the dispersion, and dispersed for 1 minute with an ultrasonic disperser, then 25 ml of the electrolyte was added, and further dispersed for 1 minute with an ultrasonic disperser. Prepare sample dispersion.
Measurement conditions: The sample dispersion is added to 100 ml of the electrolytic solution so that the particle size of 30,000 particles can be measured in 20 seconds, and 30,000 particles are measured. Determine the median particle size (D ₅₀ ).

Resin Production Example 1 [Resin A, B]
The raw material monomers and esterification catalyst excluding trimellitic anhydride shown in Table 1 were put into a 5 L four-necked flask equipped with a thermometer, a stainless steel stirring bar, a flow-down condenser and a nitrogen inlet tube, and under a nitrogen atmosphere, The temperature was raised to 180 ° C. with a mantle heater, and further raised to 230 ° C. over 10 hours. Thereafter, the reaction was carried out at 230 ° C., and after confirming that the reaction rate reached 95% or more, it was cooled to 210 ° C. and trimellitic anhydride was added. After reacting at normal pressure (101.3 kPa) for 1 hour, the reaction was continued at 40 kPa until the desired softening point was reached to obtain a polyester. The reaction rate means a value of the amount of produced reaction water / theoretical product water amount × 100.

Resin Production Example 2 [Resin C]
The raw material monomers and esterification catalyst excluding trimellitic anhydride shown in Table 1 were put into a 5 L four-necked flask equipped with a thermometer, a stainless steel stirring bar, a flow-down condenser and a nitrogen inlet tube, and under a nitrogen atmosphere, The temperature was raised to 235 ° C. with a mantle heater, and the reaction was carried out at 235 ° C. for 10 hours. Then, it was made to react at 8 kPa for 1 hour with 235 degreeC, it cooled to 210 degreeC, and the trimellitic anhydride was added. After reacting at normal pressure (101.3 kPa) for 1 hour, it was reacted at 40 kPa until the softening point reached 150 ° C. to obtain a polyester.

Resin Production Example 3 [Resin D]
The raw material monomer and esterification catalyst shown in Table 1 are put into a 5 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, a flow-down condenser and a nitrogen introduction tube, and up to 235 ° C with a mantle heater in a nitrogen atmosphere. The temperature was raised and the reaction was carried out at 235 ° C. for 10 hours. Thereafter, the mixture was reacted at 235 ° C. and 8 kPa until the softening point reached 113 ° C. to obtain a polyester.

Resin Production Example 4 [Resin E]
The raw material monomer, esterification catalyst, and polymerization inhibitor shown in Table 1 were placed in a 5 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple. The temperature was raised to 4 ° C. over 4 hours to react. The temperature was raised from 160 ° C to 200 ° C over 3 hours, reacted at 200 ° C for 30 minutes, and then reacted at 8 kPa until the softening point reached 111 ° C to obtain a polyester.

Example 1 of production of pulverized soybean-derived porous carbon powder [soybean-derived porous carbon powder A, B]
Soy-derived porous carbon powder "Phytoporous SH905" (Nisshin Oillio) 70g, Emulgen 109P (Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) 35g, and distilled water 245g made of 1 liter polyethylene The mixture was placed in a container and stirred with “TK Robomix” (manufactured by Primix) at a rotation speed of 7000 r / min for 30 minutes to prepare a dispersion. 300 g of the resulting dispersion and 1500 g of zirconia beads with a diameter of 0.8 mm were put into a 6-unit sand mill (TSG-6, manufactured by AIMEX), ground for 12 hours at a rotation speed of 2150 r / min, and then the beads were removed by filtration. A crushed product was obtained.
56 g of the obtained soybean-derived porous carbon powder, 28 g of Emulgen 109P, and 196 g of distilled water are placed in a 1 liter polyethylene container, `` TK Robomix '' (manufactured by Primix), for 30 minutes at a rotation speed of 7000 r / min. Stirring was performed to prepare a dispersion. 280 g of the obtained dispersion and 1200 g of zirconia beads having a diameter of 0.1 mm are put into a 6-unit sand mill (IMS Co., TSG-6) and pulverized to a desired volume-median particle size at a rotational speed of 2150 r / min. And the beads were removed by filtration. Vacuum-dried at 70 ° C. for 8 hours to obtain soybean-derived porous carbon powders A and B.

Production example 2 of pulverized soybean-derived porous carbon powder [soy-derived porous carbon powder C, D]
Soy-derived porous carbon powder "Phytoporous SH905" (Nisshin Oilio) 70g, Emulgen 109P (Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) 35g, distilled water 245g, 1 liter polyethylene container The mixture was stirred with “TK Robomix” (manufactured by Primix) at a rotational speed of 7000 r / min for 30 minutes to prepare a dispersion. 300 g of the obtained dispersion and 1500 g of zirconia beads having a diameter of 0.8 mm are put into a 6-unit sand mill (IMS Co., Ltd., TSG-6), and at a rotational speed of 2150 r / min, until the desired volume-median particle size is obtained. Grinding was performed and the beads were removed by filtration. Vacuum-dried at 70 ° C. for 8 hours to obtain soybean-derived porous carbon powders C and D.

Tables 2 and 3 show the volume-median particle size (D ₅₀ ) and specific surface area of soybean-derived porous carbon powder and activated carbon used in Examples and Comparative Examples described later.

Examples 1-21, Comparative Examples 1-12
The specified amount of binder resin, colorant, paraffin wax “HNP-9” (manufactured by Nippon Seiki Co., Ltd., melting point 75 ° C.) 3 parts by weight, and charge control agent “Bontron E-84” (Orient Chemical Industries) 1 part by weight) was mixed with a Henschel mixer, and the resulting mixture was rotated in the same direction with a twin screw extruder PCM-30 (Ikegai Iron Works, shaft diameter 2.9 cm, shaft cross section 7.06 cm ² ) Kneading at a barrel set temperature of 100 ° C and a shaft speed of 200r / min (shaft rotation peripheral speed of 0.30m / sec) at a raw material supply speed of 10kg / hr. It cooled to 25 degreeC, making it into a sheet.

  The obtained sheet is coarsely pulverized to 1.0 mm or less with a hammer mill (Hosokawa Micron), and further, an I-2 type jet mill (Nippon Pneumatic) and a DS2 airflow classifier (Nippon Pneumatic) Using a device connected to the pulverizer, the pulverization pressure is fixed at 0.5 MPa, the pulverization feed amount (input amount per hour kg / hr) is adjusted, and pulverization and classification so that the volume median particle size is 6.5 μm. To obtain toner base particles.

  The following formula (1) was used as an index of productivity. The higher the value, the better the productivity. The results are shown in Table 4.

[Productivity] = [Amount of pulverized feed] × ([Amount of toner base particles obtained] / [Total amount of input coarsely pulverized product])

  500 g of the obtained toner mother particles and 10 g of hydrophobic silica “R972” (manufactured by Nippon Aerosil Co., Ltd., number average particle diameter: 16 nm) are put into a 5 L Henschel mixer (manufactured by Nippon Coke Industries, Ltd.), and the rotational speed is 3700 r / min. The mixture was stirred for 180 seconds and classified with a sieve having an opening of 100 μm to remove the coarse powder, thereby obtaining a toner.

Test example (fixability)
The printer “HL-2040” (manufactured by Brother Kogyo Co., Ltd.), modified so that unfixed images can be taken, is filled with toner, and a 2cm square solid unfixed image is printed. The oilless fixing method “DL-2300” 5 ° C from 100 ° C to 230 ° C with an external fixing device (manufactured by Konica Minolta Co., Ltd.) modified from an external fixing device (the fixing roll rotating speed is set to 265mm / sec and the fixing roll temperature in the fixing device is variable) The fixing process was performed on the unfixed image at each temperature while increasing the fixing temperature, and a fixed image was obtained. The image obtained at each fixing temperature is rubbed 5 times with a sand eraser (Part No. LION ER502R) applied with a load of 500 g, and the image density ratio before and after rubbing ([image density after rubbing / image density before rubbing] × 100 ) First exceeds 90% as the minimum fixing temperature, and is used as an index of low-temperature fixing property. The smaller the value, the better the low-temperature fixability. The results are shown in Table 4.

  From the above results, it can be seen that the toners of Examples 1 to 21 are superior in productivity and low temperature fixability as compared with Comparative Examples 1 to 12.

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

Claims (5)

A method for producing an electrophotographic toner comprising soybean-derived porous carbon powder and a binder resin,
Step 1: Melt-knead a component containing a binder resin and 2.5 to 20 parts by weight of a soy-derived porous carbon powder having a volume median particle size of 0.3 to 50 μm with respect to 100 parts by weight of the binder resin. A process for obtaining a resin mixture, and a process 2: a process for pulverizing and classifying the resin mixture obtained in process 1;   The production method according to claim 1, wherein in step 1, the soybean-derived porous carbon powder is a fired product obtained by carbonizing and firing soybean hulls.   The process according to claim 1 or 2, wherein in step 1, the binder resin is a polyester obtained by polycondensation of an alcohol component containing an aliphatic diol having 2 to 20 carbon atoms and a carboxylic acid component.   The manufacturing method in any one of Claims 1-3 whose usage-amount of the soybean origin porous carbon powder in the process 1 is 5-10 weight part with respect to 100 weight part of binder resin.   The manufacturing method in any one of Claims 1-4 whose volume median particle diameter of the soybean origin porous carbon powder in the process 1 is 5.0-10 micrometers.