JP2008096729A - Method for producing electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an electrophotographic toner having excellent fogging properties by preventing the flocculation of particles in a classifying step thereby improving a classification yield. <P>SOLUTION: The method for producing the electrophotographic toner includes: a step where a raw material mixture including a binding resin and a coloring agent is melted and kneaded; a step where the kneaded material is cooled and solidified, and is thereafter coarsely pulverized; a step where the coarsely pulverized material is pulverized; and a step where the pulverized material is classified by an air flow classifying machine with a louver for introducing the same into a device with a carrier air. In the classifying step, the carrier air is admixed with water of 1.5 to 8 pts.mass per 100 pts.mass of the processing amount of the pulverized material or alkali electrolyzed water of 1 to 8 pts.mass per 100 pts.mass of the processing amount of 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 including a classification step with good classification efficiency.

  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.

  As a typical air classifier used in the toner classification process, a dispersion separator (manufactured by Nippon Pneumatic Industry Co., Ltd.) as shown in FIG. 1 is known. The powder material supply unit to the classification chamber of the airflow classifier shown in FIG. 1 has a cyclone shape, and a guide cylinder 11 is provided upright at the center of the upper surface of the upper cover 10. A supply cylinder 12 is connected to the upper outer peripheral surface of the motor 11. The supply cylinder 12 is connected to the outer periphery of the guide cylinder 11 so that the powder material supplied via the supply cylinder 12 is introduced in the tangential direction of the inner circumference of the guide cylinder.

  When the powder material is supplied from the supply cylinder 12 into the guide cylinder 11, the powder material descends while turning along the inner peripheral surface of the guide cylinder 11. In this case, since the powder material descends from the supply tube 12 along the inner peripheral surface of the guide tube 11, the distribution and concentration of the powder material flowing into the classification chamber 13 become uneven (the guide tube to the classification chamber). The powder material flows only from a part of the inner peripheral surface), and the dispersion is poor. Further, when the processing amount is increased, there is a problem that the powder material is more likely to be aggregated, and further, the dispersion is not sufficiently performed, so that high-precision classification cannot be performed.

  In addition, when the amount of air for conveying the powder material is large, the amount of air flowing into the classification chamber is large, so that the center direction speed of the swirling particles in the classification chamber increases and the separation particle size increases. There is.

  Therefore, normally, when the separation particle diameter is reduced, air is extracted from the guide cylinder upper part 14 by controlling with a damper. However, if the amount of air to be extracted is large, part of the powder material is discharged and lost. The problem may occur.

  As an air classifier that solves such a problem, there is one described in Patent Document 1. As shown in FIG. 2, this airflow classifier includes a cylindrical main body casing 1 and a lower casing 2, and a hopper 3 for discharging coarse powder is connected to the lower part thereof. A classification chamber 4 is formed inside the main casing 1, and an upper portion of the classification chamber 4 is an annular guide chamber 5 attached to the upper portion of the main casing 1 and a conical (umbrella-shaped) upper portion whose central portion is raised. It is closed by a cover 6.

  A plurality of louvers 7 arranged in the circumferential direction are provided on a partition wall between the classification chamber 4 and the guide chamber 5, and the powder material and air fed into the guide chamber 5 are transferred to the classification chamber 4 from between the louvers 7. It is swirling and flowing.

  A classification louver 9 arranged in the circumferential direction is provided at the lower part of the main body casing 1, and classification air that causes a swirling flow from the outside to the classification chamber 4 is taken in via the classification louver 9.

  In the airflow classifier configured as described above, air and powder material are supplied to the classification chamber 4 via the louver 7, and when supplied to the classification chamber 4 via the louver 7, the airflow classifier is significantly different from the conventional method. There is an advantage that an improvement in dispersion can be obtained.

However, recent toners with a small particle diameter (6.0 μm or less) often have agglomeration during classification, and it is not sufficient to deal with the above-mentioned device side alone.
Japanese Patent Laid-Open No. 5-23611

  The present invention has been made under the circumstances as described above, and an object of the present invention is to provide a method for producing an electrophotographic toner having good fog characteristics by preventing aggregation of particles in the classification step to improve the classification yield. And

  In order to solve the above problems, the first aspect of the present invention includes a step of melt kneading a raw material mixture containing a binder resin and a colorant, a step of coarsely pulverizing the kneaded product after cooling and solidifying, and crushing the coarsely pulverized product And a step of classifying the pulverized product with an airflow classifier having a louver that introduces the pulverized product into the apparatus using the carrier air. In the classifying step, 1.5% per 100 parts by mass of the pulverized material processing amount is added to the carrier air. Provided is a method for producing an electrophotographic toner, which comprises adding ˜8 parts by mass of water.

  The second aspect of the present invention comprises a step of melt kneading a raw material mixture containing a binder resin and a colorant, a step of coarsely pulverizing the kneaded product after cooling and solidifying, a step of pulverizing the coarsely pulverized product, and a pulverized product. Comprising a step of classifying with an air classifier having a louver introduced into the apparatus by means of carrier air, and in the classifying step, 1 to 8 parts by mass of alkaline electrolyzed water per 100 parts by mass of the pulverized material processing amount is added to the carrier air. A method for producing an electrophotographic toner is provided.

  According to the present invention, after cooling and solidifying and kneading the kneaded material, water or alkaline electrolyzed water is added to the carrier air when the pulverized material is classified by an air classifier having a louver that is introduced into the apparatus by carrier air. Therefore, aggregation of particles is hindered, the classification yield can be greatly improved, and an electrophotographic toner having good fog characteristics of the toner 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 material containing a binder resin and a colorant is cooled and solidified, coarsely pulverized and finely pulverized, and then the pulverized material is transported into the apparatus by conveying air. When classifying by an air classifier equipped with a louver to be introduced into, 1.5 to 8 parts by mass of water is added to the carrier air per 100 parts by mass of the pulverized material processing amount.

  In this way, when the pulverized product is introduced into the apparatus via the louver by the carrier air, by adding water to the carrier air and classification, the aggregation of the pulverized particles during classification can be reduced. As a result, the classification yield can be greatly 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 carrier air is 1.5 to 8 parts by mass with respect to 100 parts by mass of the pulverized product. If the amount of water is less than 1.5 parts by mass, the effect of adding water cannot be obtained, that is, the amount of ultrafine powder is large and the classification yield is low. The classification yield cannot be improved.

  The method for producing an electrophotographic toner according to the second embodiment of the present invention includes a louver that cools and solidifies a kneaded material containing a binder resin and a colorant, and then pulverizes the pulverized material into the apparatus using carrier air. When carrying out classification with an airflow classifier comprising: alkaline electrolyzed water is added to the carrier air.

  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 carrier air may be less than that of water, and is 1 to 8 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 1 part by mass, the effect of addition of alkaline electrolyzed water cannot be obtained, that is, the amount of ultrafine powder is large and the classification yield is low. The amount of ultrafine powder is large, and the classification yield cannot be improved.

  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 materials are measured and 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. The coarsely pulverized product thus obtained is finely pulverized and then classified to a predetermined particle size by an airflow classifier to obtain a toner particle matrix.

  The airflow classifier includes, for example, a louver 7 for introducing the pulverized material into the apparatus by carrier air as shown in FIG. 2, and water or alkaline electrolyzed water is added to the carrier air in the form of water vapor. The Therefore, a vaporizer for vaporizing water or alkaline electrolyzed water is connected to the carrier air introduction path of the airflow classifier.

  In this case, the particles introduced into the air classifier by the carrier air to which water or alkaline electrolyzed water is added via the louver 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.

  The resulting coarsely pulverized product is finely pulverized to a mass average particle diameter of 5.8 μm with a collision plate type pulverizer (“IDS-10” manufactured by Nippon Pneumatic Industry Co., Ltd.) adjusted to a pulverization pressure of 0.5 MPa, and further classified. Machine (Nippon Pneumatic Kogyo Co., Ltd. “DSX-10” was classified at a throughput of 30 kg / h to obtain 6.0 μm colored fine particles. Introduced into the classification room.

  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 added to a Henschel mixer. To obtain a toner.

  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. In addition, water vapor | steam addition amount shows the mass part of the water vapor | steam addition amount per 100 mass parts of classification treatment amount.

  From Table 1 above, the following is clear. That is, the range of 1.5-8 mass parts with respect to 100 mass parts of Examples 1, 4, and 7 which added alkaline electrolyzed water in the range of 1-8 mass parts with respect to 100 mass parts of process amounts. In Examples 2, 3, 5 and 6 to which water was added, the amount of ultrafine powder was as low as 26% or less, the classification yield was as high as 66% or more, and excellent results were obtained with little fogging. .

  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 1% by mass, and the amount of alkaline electrolyzed water added is less than 1% by mass. In Comparative Example 3 and Comparative Example 4 in which the amount of water added was as large as 10% by mass, the amount of ultrafine powder was as large as 27% or more, and the classification yield was as low as 62% or less. Further, Comparative Example 1 and Comparative Example 4 had more fog than Comparative Examples 2 and 3.

Sectional drawing which shows the structure of the dispersion separator which is a typical example of an airflow classifier. Sectional drawing which shows the structure of an airflow classifier provided with the louver which supplies air and a powder material to a classification chamber via the louver.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main body casing, 2 ... Lower casing, 3 ... Coarse powder discharge hopper, 4 ... Classification room, 5 ... Guide room, 6 ... Upper cover, 7 ... Louver, 9 ... Classification louver, 10 ... Upper cover, 11 ... Guide Tube, 12 ... supply tube, 13 ... classification room.

Claims (2)

A step of melt-kneading a raw material mixture containing a binder resin and a colorant;
A step of coarsely pulverizing the kneaded product after cooling and solidifying,
Comprising a step of pulverizing the coarsely pulverized product, and a step of classifying the pulverized product with an air classifier having a louver that introduces the pulverized product into the apparatus by carrier air,
In the classifying step, 1.5 to 8 parts by mass of water per 100 parts by mass of the pulverized material processing amount is added to the carrier air. A step of melt-kneading a raw material mixture containing a binder resin and a colorant;
A step of coarsely pulverizing the kneaded product after cooling and solidifying,
Comprising a step of pulverizing the coarsely pulverized product, and a step of classifying the pulverized product with an air classifier having a louver that introduces the pulverized product into the apparatus by carrier air,
In the classification step, 1 to 8 parts by mass of alkaline electrolyzed water is added to the carrier air per 100 parts by mass of the pulverized material processing amount.

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