JP2008077012A - Method for manufacturing electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for an electrophotographic toner which is excellent in fog characteristics by preventing aggregation of pulverized particles to improve classification yield in a production process. <P>SOLUTION: The method includes steps of: mixing a source material containing a binder resin and a colorant; melting and kneading the source material mixture; cooling and solidifying the kneaded material and then coarsely pulverizing the material; mixing water of 1 to 10 parts by mass or an alkaline electrolytic water of 0.5 to 10 parts by mass based on 100 parts by mass of the coarse pulverized product; pulverizing the mixture; and classifying the pulverized material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an electrophotographic toner, and more particularly, to a method for producing an electrophotographic toner having good fog characteristics with a high classification yield.

  In general, image formation by electrophotography is performed by developing and visualizing an electrostatic image with charged toner, and transferring and fixing the toner image obtained by development onto a sheet. As a method for producing such a toner used for image formation, there are a pulverization method, a polymerization method, and the like. In general, the pulverization method dominates.

  A general production method of the pulverization method is to mix raw materials such as a binder resin, a colorant, a release agent, and a charge control agent in a dry manner, then melt and knead with a twin-screw extruder or the like, and after cooling and solidifying, Crushing is performed to obtain a kneaded crushed material. Thereafter, fine pulverization is performed with a jet mill or the like, and the particle size is adjusted with a classifier so as to obtain an appropriate particle size distribution. Further, the toner is obtained by performing surface treatment by mixing with silica etc. in a mixer.

  The required performance of electrophotographic toners in recent years has become increasingly sophisticated. The main requirements for toners are to reduce the particle size, reduce oil, fix at low temperature, increase transfer efficiency, and improve image quality. As an elemental technology common to these toners, it is necessary to disperse a toner internal additive such as a pigment, a charge control agent, and a release agent finely and uniformly in the binder resin.

  In particular, when the toner particle size is reduced, the cohesive force due to electrostatic force and van der Waals force between particles increases, and the amount of fine powder increases, so the classification yield in the classification process after pulverization decreases. There is a need to solve this problem.

  On the other hand, a method has been proposed in which water is added to a raw material mixture and kneaded to achieve uniform dispersion of the charge control agent (see, for example, Patent Document 1).

However, according to this method, it is possible to improve the dispersibility of the charge control agent, but it is not possible to reduce the cohesive force of the particles after pulverization and to improve the classification yield.
JP-A-4-313762

  The present invention has been made under the circumstances as described above, and provides a method for producing an electrophotographic toner having good fog characteristics by preventing aggregation of pulverized particles and improving classification yield in the production process. With the goal.

  In order to solve the above problems, the first aspect of the present invention includes a step of mixing a raw material containing a binder resin and a colorant, a step of melting and kneading the raw material mixture, and a step of coarsely pulverizing the kneaded product after cooling and solidifying. An electrophotographic toner manufacturing method comprising a step of mixing 1 to 10 parts by mass of water, a step of pulverizing the mixture, and a step of classifying the pulverized product with respect to 100 parts by mass of the coarsely pulverized product.

  The second aspect of the present invention includes a step of mixing a raw material containing a binder resin and a colorant, a step of melt kneading the raw material mixture, a step of coarsely pulverizing the kneaded product after cooling and solidifying, and 100 parts by mass of the coarsely pulverized product. In contrast, the present invention provides a method for producing an electrophotographic toner comprising a step of mixing 0.5 to 10 parts by mass of alkaline electrolyzed water, a step of pulverizing the mixture, and a step of classifying the pulverized product.

  According to the present invention, the kneaded product is cooled and solidified, coarsely pulverized, and then water or alkaline electrolyzed water is added to the coarsely pulverized product to prevent particle aggregation and improve the classification yield. Thus, an electrophotographic toner having good fog characteristics can be obtained.

  Embodiments of the present invention will be described below.

  In the method for producing an electrophotographic toner according to the first embodiment of the present invention, a kneaded product containing a binder resin and a colorant is cooled and solidified, coarsely pulverized, and then a predetermined amount of water is added to the coarsely pulverized product. This is further pulverized and classified.

  Thus, by adding water to the coarsely pulverized product, pulverization and classification, aggregation of the pulverized particles during classification can be reduced, and as a result, the classification yield is improved. The reason why the agglomeration of the pulverized particles during classification can be reduced in this way is that water has a function of eliminating static electricity, and therefore, during classification, the pulverized particles are prevented from aggregating due to static electricity. . When the pulverized particles agglomerate, the amount of ultrafine powder increases and the classification yield also decreases. However, since the electrostatic aggregation of the pulverized particles is dissociated by the presence of water, the classification yield is improved. In addition, electrostatic adhesion to the wall of the classifier is also reduced.

  In the method for producing an electrophotographic toner according to the first embodiment of the present invention, the amount of water added to the coarsely pulverized product is 1 to 10 parts by mass with respect to 100 parts by mass of the coarsely pulverized product. If the amount of water is less than 1 part by mass, the effect due to the addition of water cannot be obtained, that is, the amount of ultrafine powder is large and the classification yield is low. In many cases, the classification yield cannot be improved.

  In the method for producing an electrophotographic toner according to the second embodiment of the present invention, a kneaded product containing a binder resin and a colorant is cooled and solidified, coarsely pulverized, and then a predetermined amount of alkaline electrolyzed water is added to the coarsely pulverized product. It is characterized by being added, further pulverized and classified. That is, in the electrophotographic toner manufacturing method according to the first embodiment described above, alkaline electrolyzed water is added instead of water.

  In this way, when alkaline electrolyzed water is used instead of water, in addition to the above-mentioned static elimination effect, a surface active effect such as a cleaning effect is exhibited, and the alkaline electrolyzed water is well adapted to fine particles after being finely pulverized. High anti-aggregation effect is demonstrated.

  The amount of alkaline electrolyzed water added to the coarsely pulverized product may be less than that of water, and is 0.5 to 10 parts by mass with respect to 100 parts by mass of the coarsely pulverized product. If the amount of alkaline electrolyzed water is less than 0.5 parts by mass, the effect due to the addition of alkaline electrolyzed water cannot be obtained, that is, the amount of ultrafine powder is large and the classification yield is low, whereas it exceeds 10 parts by mass. However, the amount of ultrafine powder is large, and the improvement of the classification yield cannot be obtained.

  Alkaline electrolyzed water is formed on the cathode side by electrolyzing water. In addition, acidic electrolyzed water is obtained from the anode side. In general, acids and alkalis are neutralized to form a salt, but acidic water and alkaline water have a characteristic that they do not form a salt even when neutralized. Therefore, acidic electrolyzed water and alkaline electrolyzed water are not acids or alkalis.

  That is, electrolyzed water is acidic and alkaline at pH because water molecules are electrolyzed and can be relatively biased to hydrogen ions. Therefore, even if the electrolyzed water is neutralized, no salt is formed and the water is returned to neutral water, so that it is not adversely affected by the salt.

  As water used for electrolysis, tap water, well water, salt water, etc. are usually used. Tap water and well water contain ions such as calcium, magnesium, sodium, and potassium, and salt water contains sodium ions, so electrolysis is possible.

  When electrolyzing a salt solution having a concentration of 2% or less, strong acidic hypochlorous acid water having a pH of 2.7 or less is obtained as acidic electrolyzed water from the anode, and strong alkaline electrolyzed water having a pH of 11 to 12 is obtained from the cathode.

  In the first and second embodiments of the present invention described above, examples of the binder resin include a polyester resin, a styrene acrylic resin, and an epoxy resin. In these, a polyester resin is preferable.

  A conventionally well-known thing can be used as a coloring agent.

A release agent, a charge control agent, and the like can be further added to the toner. Conventionally known release agents can be used as the charge control agent and the release agent. Examples of such a release agent include those having low polarity such as low molecular weight polyethylene, low molecular weight polypropylene and paraffin, and those having high polarity such as carnauba wax and ester. In addition, the emulsion type carboxyl group-modified polyolefin is modified so as to have a carboxyl group with an olefin unit such as ethylene, propylene, butene-1, and pentene-1 as a skeleton, and at least a part of the carboxyl group is formed with ammonia or amine. It is also possible to use neutralized polyethylene wax, polypropylene wax or the like. Of these waxes, carnauba wax is preferred.
The toner manufacturing methods according to the first and second embodiments of the present invention are performed as follows.

First, materials such as a binder resin, a colorant, a release agent, and a charge control agent are measured, and the measured materials are mixed by a mixer. As a mixing machine, arbitrary things, such as a Henschel mixer, a super mixer, a V-type blender, and a Nauta mixer, can be used.
The raw material mixture is then fed to a kneader where it is melt kneaded. As the kneading machine, any type of extrusion kneading machine such as a twin-screw extrusion kneading machine and a single-screw extrusion kneading machine, an open roll type kneading machine such as a continuous two-roll mill, a continuous three-roll mill, and a batch roll mill can be used. Things can be used.

  The melt-kneaded product discharged from the kneader is usually cooled and coarsely pulverized according to the method used for the production of toner. Water or alkaline electrolyzed water is added to the coarsely pulverized product thus obtained and mixed. For mixing, any of the above-described Henschel mixer, super mixer, V-type blender, nauter mixer, and the like can be used.

  Next, the mixture obtained by mixing water or alkaline electrolyzed water is finely pulverized, and then classified to a predetermined particle size to obtain a toner particle matrix. For coarse pulverization and fine pulverization, an airflow pulverizer such as a collision plate pulverizer can be used, and various airflow classifiers can be used for classification.

  In this case, the finely pulverized particles do not aggregate due to the presence of water or alkaline electrolyzed water, and the amount of ultrafine powder is small. Therefore, the classification yield is greatly improved. In addition, since the amount of ultrafine powder is small, adhesion to the wall of the classifier can be reduced, and fogging can be reduced.

  An electrophotographic toner can be obtained by adding an external additive such as silica to the toner particle matrix thus obtained, followed by mixing and stirring.

Examples Hereinafter, examples and comparative examples of the present invention will be shown to describe the present invention more specifically.

  First, raw materials having the following composition were mixed with a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) and melt-kneaded with a twin-screw extrusion kneader.

Cross-linked polyester resin (softening point 141 ° C., glass transition point 62 ° C.) 93% by mass
Colorant (C.I Pigment Red 57: 1) 3% by mass
Mold release agent (Sanyo Chemical Co., Ltd., Biscol 660P) 3% by mass
Charge control agent (E-84, manufactured by Orient Chemical Co., Ltd.) 1% by mass
The obtained kneaded product was cooled in the air, and then coarsely pulverized with a Rotoplex (manufactured by Mitsui Mining Co., Ltd.), and passed through a sieve having an opening of 2 mm to obtain a coarsely pulverized product having a maximum diameter of 2 mm or less.

  As shown in Table 1 below, various amounts of water or alkaline electrolyzed water were added to 100 parts by mass of the coarsely pulverized product, and mixed for 1 minute with a Henschel mixer. Next, the mass average particle size was reduced to 5.8 μm with a collision plate type pulverizer (“IDS-10” manufactured by Nippon Pneumatic Industry Co., Ltd.) in which the crushed material to which water or alkaline electrolyzed water was added was adjusted to a pulverization pressure of 0.5 MPa. The resultant was pulverized and further classified with a classifier (“DSX-10” manufactured by Nippon Pneumatic Industry Co., Ltd.) to obtain 6.0 μm colored fine particles.

  Next, 100 parts by mass of the colored fine particles, 1 part by mass of hydrophobic silica (“R972” manufactured by Nippon Aerosil Co., Ltd.) and 0.5% of hydrophobic silica (“RX50” manufactured by Nippon Aerosil Co., Ltd.) are mixed with a Henschel mixer. A toner was obtained.

  The toner samples obtained in the above examples and comparative examples were measured and tested for the following characteristics to evaluate the characteristics.

1. Measurement of particle size and amount of ultrafine powder A small sample, purified water, and a surfactant were placed in a beaker and dispersed with an ultrasonic cleaner, and the sample was measured with Multisizer II (manufactured by Coulter Co., Ltd.). The aperture is 100 μm, the count is 50,000, the volume and number distributions are obtained, the median diameter of the volume distribution is the average particle diameter, and the ratio (%) of the number distribution of 2 μm or less is the amount of ultrafine powder. did.

2. Classification yield (%)
The classification yield (%) was determined by the following formula.

Classification yield = ((Total amount of classified product obtained) ÷ (Total amount of finely pulverized product charged)) × 100
3. Fog A non-magnetic one-component developing device “Casio Page Presto N-5” (manufactured by Casio Computer Co., Ltd .: 29 printers per minute (A4 horizontal), process speed 129 mm / sec) with toner mounted in a normal environment ( After printing 10,000 sheets of 5% print images continuously on plain paper (XEROX-P paper A4 size) at 25 ° C. and 50% RH), perform blank paper printing and open the front door while printing. By opening, the printing was forcibly terminated, and the fog toner on the OPC drum at that time was copied onto a mending tape, and compared visually.

  In comparison with Comparative Example 2, the case where there was less fog than in Comparative Example 2 was marked as ◯, the case where the amount of fog was equivalent to that in Comparative Example 2 was Δ, and the case where there was more fog than Comparative Example 2 was marked as x.

The above test results are shown in Table 1 below.

  From Table 1 above, the following is clear. That is, Examples 1, 3, and 7 in which 0.5 to 10 mass of alkaline electrolyzed water was added to 100 parts by mass of the coarsely pulverized product, and 1 to 10 masses of water were added to 100 parts by mass of the coarsely pulverized product. In Examples 2 and 4 to 6, excellent results were obtained in which the amount of ultrafine powder was as low as 25% or less, the classification yield was as high as 66% or more, and the fog was small.

  In contrast, Comparative Example 1 in which water or alkaline electrolyzed water is not added to the coarsely pulverized product, Comparative Example 2 in which the amount of water added is as small as 0.5% by mass, and Comparative Example 2 in which the amount of water added is as large as 12% by mass. In Example 3, the amount of ultrafine powder was as high as 27% or more, and the classification yield was as low as 64% or less. Further, Comparative Example 1 and Comparative Example 3 had more fog than Comparative Example 2.

Claims (2)

Mixing a raw material containing a binder resin and a colorant;
A step of melt-kneading the raw material mixture,
A step of coarsely pulverizing the kneaded product after cooling and solidifying,
A step of mixing 1 to 10 parts by mass of water with respect to 100 parts by mass of the coarsely pulverized product,
A method for producing an electrophotographic toner, comprising: a step of pulverizing a mixture; and a step of classifying the pulverized product. Mixing a raw material containing a binder resin and a colorant;
A step of melt-kneading the raw material mixture,
A step of coarsely pulverizing the kneaded product after cooling and solidifying,
A step of mixing 0.5 to 10 parts by mass of alkaline electrolyzed water with respect to 100 parts by mass of the coarsely pulverized product,
A method for producing an electrophotographic toner, comprising: a step of pulverizing a mixture; and a step of classifying the pulverized product.