JPS62187861A - Manufacture of toner for development of electrostatically charged image - Google Patents

Abstract

PURPOSE:To efficiently obtain a particle group which has a fine particle size distribution by using a specific classifying means. CONSTITUTION:The section of a side wall has shapes 32 and 51 and the bottom surface is rectangular and divided into three by classifying fences like knife-edge type classifying edges 27 (39) and 28 (40) fixed to or fitted in the bottom surface in parallel at specific intervals. A raw material supply nozzle 26 which has an opening in a classifying chamber is provided on a vertical wall 32 almost opposite the rising start point of a curved wall 51 and a counder block 30 which is folded downward in the prolongation direction of the base tangent of the nozzle to draw an elliptic arc is projected on the vertical side wall 32; and the upper part of the classifying chamber is formed in an upright rectangular cylinder shape and a knife-edge type air intake edge 29 (41) is provided lengthwise at the center of a top wall, which is provided with intake pipes 24 and 25 having aperture in the classifying chamber.

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention provides efficient pulverization and pulverization of solid particles having a binder resin.
The present invention relates to a manufacturing method for obtaining an electrostatic image developing toner having a predetermined particle size by performing classification.

[Prior art]

In image forming methods such as electrophotography, electrostatic photography, and electrostatic printing, a torch is used to develop an electrostatic image. - The process of pulverizing and classifying raw material solid particles to obtain the final product in the production of toner for electrostatic image development, where the final product is required to be fine particles, has conventionally been shown in the flowchart of FIG. This method is generally adopted. The method is 1. For example, when predetermined materials such as a binder resin 1 and a coloring agent are melt-kneaded, cooled to solidify, and then pulverized, and the pulverized solid particles are used as a pulverized raw material, the pulverized material is 1
The coarse powder, which is continuously or sequentially supplied to the classifier and classified, and whose main component is coarse particles with a specified particle size or more, is sent to the crusher and crushed, and then circulated to the first classifier again. Ru. Other powders whose main components are particles within the specified particle size range and particles below the specified particle size are sent to the second classifier, which separates medium powder whose main component is particles with the specified particle size and smaller than the specified particle size. This is because it is classified into a fine powder whose main component is a group of particles.

As a specific example under this conventional method, from a solid particle group consisting of pulverized particles, a predetermined amount average particle diameter (for example, a Coulter Counter manufactured by Coulter Electronics Inc. (USA) is used) It is a method of expressing measurement results, and is expressed as a weight average particle diameter (hereinafter simply referred to as "average particle diameter"), excluding the fine powder region, that is, for example, the average particle diameter is 10~15ILm
In order to obtain a particle group in which the number of particles of 5 ILm or less is 1% or less.

Grind and classify the powder to a predetermined average particle size using an impact crusher or jet crusher equipped with a classification mechanism to remove the coarse powder, and then pass the crushed product after removing the coarse powder to another classifier. The fine powder is removed to obtain the desired medium powder.

One problem with such conventional methods is that the process using a pulverizer equipped with a classification mechanism to remove coarse powder and the process using a classifier to remove fine powder are performed in separate steps. In addition to being large in number and complicated to operate,
In the case of long-term operation, heat generation may occur, and unavoidable adhesion to powder may occur.

In addition, the original purpose of the classification mechanism for removing coarse powder is to send only particles of a certain particle size or above to the crusher, but conventional classifiers have a very long residence time of several minutes. After removing the coarse powder area, some of the particles may coagulate with each other, or fine particles may adhere to the coarse particles and cause the problem to occur again.

There is a tendency for over-grinding to occur as it is returned to the crusher. This causes problems such as a decrease in pulverization efficiency and a decrease in yield in a classifier for removing the fine powder region in the next step. Moreover, in the case of the second disintegrating machine, which is intended to remove especially fine powder, aggregates composed of extremely fine particles may be formed, and it is difficult to remove the aggregates as fine powder. . In that case, such aggregates will be mixed into the final product, making it difficult to obtain a product with a precise particle size distribution, and the aggregates will disintegrate in the toner and become extremely fine particles, causing a reduction in image quality. Become. For this reason, even if it is possible to obtain a desired product with a precise particle size distribution using the conventional method, the process becomes complicated and the classification yield decreases, resulting in poor production efficiency and high costs. This tendency becomes more pronounced as the predetermined particle size becomes smaller.

[Purpose of the invention]

The present invention solves the various problems described above in the conventional method for producing toner for developing electrostatic images, and includes:
The purpose is to provide a manufacturing method for efficiently producing an electrostatic image developing toner having a precise particle size distribution. Another object of the present invention is to provide a method for efficiently producing a high quality toner having a small particle size (for example, 2 to 8 gm).

[Structure and effect of the invention]

The present invention melt-kneads a mixture consisting of a binder resin, 9 colorants, and various additives, cools the molten mixture, and then pulverizes the resulting solid particles. The present invention relates to a method for efficiently manufacturing products in a short period of time.

The method of the present invention uses pulverized material as a raw material, and FIG. 1 is a flow chart showing an overview of the method. That is, the method of the present invention sends the raw material to a multi-division classification zone and divides it into at least three particle size categories, namely, large particle size category (coarse powder mainly composed of coarse particles), medium particle size category (coarse powder mainly composed of coarse particles), and medium particle size category (coarse powder mainly composed of coarse particles). The particles in the large particle size category are divided into medium-sized powder (mainly composed of particles with a specified particle size) and small particle size category (fine powder whose main component is particles with a specified particle size or less), and the particles in the large particle size category are crushed as appropriate. The raw material is pulverized by a means 1, and is recycled to the multi-division classification zone together with the newly introduced raw material, where it is subjected to the same classification process as described above. Particles with particle diameters within the specified range of the medium particle size category and particles with a particle size below the specified particle size of the small particle size category are respectively taken out from the multi-divided classification area by appropriate extraction means. The group has an optimal particle size distribution and can be used as a toner as is. On the other hand, the particles in the small particle size category taken out may be recycled to the melting process and reused.

As the means for providing the multi-divided classification area, for example, a second
A multi-division classifier of the type shown in the figure or FIG. 3 may be exemplified as one specific example. In FIGS. 2 and 3, the side wall cross section has a shape shown by 32.51, and the bottom surface is rectangular and is divided into three parts parallel to the bottom surface at predetermined intervals in the longitudinal direction. . Curved 1! ! A raw material supply nozzle 26 that opens into the classification chamber is provided on a portion of the vertical wall 32 facing the substantially upright starting point of the nozzle 51, and is bent downward with respect to the extension direction of the bottom tangent of the nozzle to form a long elliptical arc shape. A Coanda block 30 is provided protrudingly on the vertical side wall 32, the upper part of the classification chamber forms an upright rectangular tube shape, and a knife ridge type etching 29 (or 41) is provided in the longitudinal direction at the center of the top wall, and furthermore, on the top wall. A popular tube 24,25 is provided which opens into the classification chamber. The positions of the classification edges 27 (or 39), 28 (or 40) vary depending on the size of the chamber of the multi-divided classification zone and the type of raw material to be processed. - Also, on the bottom of the chamber, there are exhaust pipes 21, 22, 23 that open into the chamber corresponding to each fraction area.
will be established. The discharge pipes 21, 22, 23 may each be provided with opening/closing means such as valve means.

The classification edges 27 (or 39), 28 (or 40) are provided so as to project into the indoor space with the edge portion facing L, and the inlet edge 29 (or 40) is provided with the edge portion facing downward from the top wall. It is usually installed in an indoor space, but if you want to make the particle group of the medium particle size category into a very limited particle size range, the 1 classification edge 28 and the inlet edge 29 are set as 40.41 in Fig. 3. As shown in , the fixed position may be left as is, and the rising part for the former and the hanging part for the latter may be tilted so that they are on the outside of the airflow, respectively.
The raw material is supplied into the classification chamber via the raw material supply nozzle 26 according to a verification curve depending on the type of raw material.

The classification operation of raw materials in the multi-division classification zone configured as described above is carried out, for example, as follows.

That is, when a powder raw material is supplied from the raw material supply nozzle 26, the powder moves in a curved line 35 due to the Coanda effect and the action of gas such as air flowing in at that time, and each Depending on the particle size of fraction, small particles (
(particles with a specified particle size or less) are divided into fractions inside the classification edge 27, with large particles going through the outlet 21 and intermediate particles going through the outlet 21. ? Smaller particles are discharged from the discharge port 23, respectively.

In order to carry out the method described above, it is usual to use an integrated device system in which mutual devices are connected through communication means such as pipes, and a preferred example of such a device is shown in Fig. 4. The integrated device shown in FIG. 4 consists of a three-part classifier 2 (of the type shown in FIG. 2 or 3, the details of which are as explained above), a crusher 3, and a collector. Su Italon 4. Collection cyclone 5. A fixed quantity supply a6, a vibrating feeder 7, a collection cyclone 8, and a collection cyclone 9 are connected by a communication means.

In this device, the so-called pulverized raw material is sent to a collection cyclone 5 through a raw material supply conduit 31 equipped with an on-off valve 1t, then fed into a quantitative feeder 6, and then via a vibrating feeder 7 to a raw material supply nozzle. 3 by 26
It is introduced into the dividing classifier z. At the time of introduction, the pulverized material can be sucked and introduced into the three-part classifier z using the suction force of the collection cyclone 4.8 and/or 9.

In the case of suction introduction, the sealing performance of the system is not required to be as strict as in pressurized introduction, so it is preferable. Introducing the pulverized material into the dividing classifier 2 is preferable in terms of classification accuracy and classification efficiency. The size of the classification area of classifier 2 is usually (10~
50cm)X (10~50cm), so the crushed material is
, can be distributed to three or more types of particle groups instantly within 1 to 0.01 seconds. Then, by 3-part classification @2, large particles (
It is divided into coarse particles), intermediate particles (particles with a specified particle size), and small particles (particles with a specified particle size or less).

Thereafter, the large particles are sent to the collection cyclone 4 through the discharge conduit 21 and then sent to the crusher 4113 to be crushed and sent to the collection cyclone 5 together with the powder raw material newly introduced via the raw material supply conduit 31. Then, it is sent to a quantitative feeder and subjected to classification processing in the same manner as described above. Intermediate particles are collected. Small particles are discharged out of the system via the discharge conduit 23, repaired by the collection cyclone 8, and then recovered as non-standard fine powder 81. The collection cyclones 4, 8, 9 also function as suction and pressure reduction means for suctioning and introducing the pulverized raw material into the classification area through the nozzle 26.

For the crushing 4113, an impact crusher, a jet crusher, or the like can be used. That is, examples of impact-type crushers include Turbo Mill made by Turbo Kogyo Co., Ltd.; examples of crushers using jets include supersonic jet mill PJM-1 made by Nippon Pneumatic Kogyo Co., Ltd., and Micron Jet made by Micron Co., Ltd. for wire use. can be mentioned. Further, as a multi-division classifier in the method of the present invention, means such as Elpau Jet manufactured by Nippon Steel Mining Co., Ltd. can be mentioned.

As explained above, in the method of the present invention, coarse particles and fine particles are simultaneously removed using a specific classification means, and the coarse particles are crushed and recirculated, so that a predetermined amount can be quickly extracted from the crushed material. It is possible to efficiently obtain a group of particles that are within the particle size range and have a precise particle size distribution. Furthermore, since the method of the present invention requires fewer steps, product costs can be lowered compared to conventional methods.

Furthermore, since the method of the present invention has almost no residence time in the classification zone, it is difficult to form agglomerates like those seen in conventional classifiers for removing coarse particles, and the crusher has a certain specified particle size. Since only the coarse particles above are sent, the load on the crusher is small and the crushing efficiency is very good, and over-grinding does not occur. Therefore, the removal of fine particles can be done very efficiently, and the classification The yield can be improved satisfactorily. In addition, in the conventional classification method aimed at classifying the medium-powder area and the fine-powder area, aggregates that are composed of fine particles and cause fogging of the developed image are likely to occur, and if they occur, it is necessary to remove them from the medium-powder area. However, according to the method of the present invention, even if aggregates are mixed into the pulverized material, the aggregates are broken down and removed as fine powder due to the Coanda effect and/or high-speed movement, and the disintegration is removed. Even if there are any agglomerates that escape, they can be removed simultaneously to the coarse powder area, making it possible to remove the agglomerates efficiently.

Toner for developing electrostatic images is usually prepared by melting and kneading raw materials such as styrene resin, styrene-acrylic resin, or polyester resin9, coloring agent (or magnetic material), offset inhibitor, charge control agent, etc., followed by cooling, Manufactured by pulverization and 9 classifications. At this time, since it is difficult to obtain a melt in which each raw material is uniformly dispersed in the kneading process, the pulverized material may contain particles unsuitable as toner particles (for example, containing colorants or magnetic particles). However, in the conventional pulverization and classification method, the residence time of particles during the pulverization and classification process is long, which makes unsuitable particles more likely to agglomerate, and the resulting agglomeration It was difficult to remove the particles, which significantly degraded the properties of the toner. Since the method of the present invention instantly classifies into three or more fractions after pulverization, the above-mentioned agglomerates are unlikely to occur, and even if they occur, the agglomerates can be removed to the coarse powder region, so particles with uniform components can be obtained. , and it is possible to obtain a product with a precise particle size distribution. As a result, the toner obtained by the method of the present invention has a stable friction zone Nt amount between toner particles or between a toner and a toner carrier such as a sleeve or a toner and a carrier. Therefore, development fog, which could not be solved satisfactorily in the past, and toner scattering around the edges of the Hg image are extremely reduced, high image density is obtained, and halftone reproducibility is improved. Furthermore, even when the developer is used continuously for a long period of time, the initial characteristics can be maintained and high quality images can be provided for a long period of time. Furthermore, even when used in high-temperature, high-humidity environments, there are few ultrafine particles and their aggregates, so the developer triboelectric charge is stable and hardly changes compared to normal temperature and humidity, reducing fogging and image density. There is little deterioration in image quality, and development can be performed that is faithful to the Wi image. Furthermore, the transfer efficiency is also excellent. Furthermore, even when used under low temperature conditions, the triboelectric charge distribution is almost the same as that at room temperature and humidity, and since developer components with extremely large charges are removed, there is no reduction in image density or fog. The toner obtained by the method of the present invention has the characteristics that there is almost no force or scattering during transfer, and there is no wart.

Also, medium powder with small particle size (for example, average particle size 3 to full)
The present invention can be carried out more efficiently than conventional methods when manufacturing.

Hereinafter, the present invention will be described in detail based on examples.

Example 1 A toner raw material consisting of a mixture of the above formulation was melt-kneaded at about 180° C. for about 1.0 hours, cooled and solidified, and coarsely ground into particles of 100 to 1 ooo4 in a hammer mill. The powder was pulverized into a pulverized product having a weight average particle size of 100 JL. In order to classify the obtained pulverized material into three types, coarse powder, medium powder, and fine powder, using the Coanda effect at a rate of 1.0 kg per minute, a multi-division classifier 2 shown in FIG. 2 is used. EJ-45-
It was introduced into a Type 3 machine (manufactured by 0 Tetsu Mining Co., Ltd.). When introducing
The pulverized material was introduced into the supply nozzle 26 at a flow rate of about 100 m/sec by the suction force derived from the reduced pressure in the system due to the suction reduced pressure of the collection cyclones 8.9 and 4 communicating with the discharge ports 21, 22 and 23. . The crushed material introduced is 0.01
The collection cyclone 9, which collects medium-sized powder classified instantly in seconds or less, has a volume average particle size of about 12 hiro (particle size 5
．． Contains 0.5% by weight of particles of 0.4 g or less, and has a particle size of 20
．． The content of particles of 2 #L or larger was 0.1% by weight or less, and could be considered to be substantially free of O. A medium powder suitable as a toner was obtained with a classification yield of 85% by weight.

The classification yield here refers to the ratio of the final medium powder (product) to the total amount of the supplied pulverized raw material. When the obtained medium powder was observed under an electron microscope, substantially no aggregates of about 5 tiles or more, which were ultrafine particles aggregated, were found.

Further, the classified coarse powder was collected by a collection cyclone 4, and introduced into a pulverizer 3 (supersonic jet mill PJM-I-10 manufactured by Nippon Pneumatic Industries Co., Ltd.) to be pulverized. The pulverized powder was supplied to the raw material supply conduit 31, and was supplied to the supply conduit 31 for classification by a multi-division classifier.

The obtained medium powder was used as a toner, and hydrophobic silica 0
．． Mix 31 i% and make the developer 7A! 1, copy machine N
When a copying test was carried out by supplying a developer adjusted to P-270 (manufactured by Canon), a copy image with good fine line developability and no fog was obtained.

Comparative Example 1 A pulverized product obtained in the same manner as in the example was classified using a classification system configured as shown in FIG.

The pulverized material with a volume average particle diameter of 100 liters was introduced into the first classifier (air classifier DS-10 manufactured by Nihon Newyachik Kogyo Co., Ltd.) at a rate of 1.0 Kg per minute, and the classified coarse powder was Crusher(
Supersonic jet mill PJM manufactured by Nippon Pneumatic Kogyo Co., Ltd.
-10), and after pulverization, it was circulated to the fiIJ1 classifier. The medium powder and fine powder classified by the first classifier were introduced into the second classifier (Ds-io) and classified into medium powder and fine powder. The obtained medium powder had a volume average particle diameter of about 12 mm, and was obtained with a classification yield of 70% by weight, but when observed with an electron microscope, it was found that there were aggregates of about 5 μm or more, which were extremely fine particles aggregated. was found doing so.

When a copying test was conducted by supplying the prepared developer to a copying machine NP-270 (Canon), there was more fog than the copied image obtained in Example 1.

Jikkyō” LL2A The volume average particle size was 50 gauze in the same manner as in Example 1.

A pulverized product of 30 Hiro and 20 Hiro was prepared, and the pulverized product was classified and pulverized in the same manner as in Example 1. The results are shown in the table below, and Example 2 approximately 50
Approximately 12 85 Example 3 Approximately 30
Approximately 7 82 Example 4 Approximately 20
Approximately 5 81 Comparative Example 2 A pulverized material with a volume average particle diameter of approximately 20 was prepared in the same manner as in Example 1, and a medium powder with a volume average particle diameter of approximately 5 was produced in the same manner as in Comparative Example 1. The yield was 50% by weight.

Incidentally, as the particle size of the medium powder became smaller, there was a tendency for the difference in the 5-class yield between the Examples of the present invention and the Comparative Examples to become larger.

[Brief explanation of drawings]

FIG. 1 is a flowchart of the method of the present invention, FIGS. 2 and 3 are cross-sectional views of an apparatus that is a specific example for implementing the solid particle multi-division classification method of the present invention, and FIG. 1 is a schematic diagram showing a classifier system for carrying out the method of the present invention; FIG. FIG. 5 is a flowchart of the conventional method. Explanation of symbols in the diagram

Claims (1)

[Claims] (1) In a method for producing toner for electrostatic image development, in which a group of solid colored particles having a binder resin produced by pulverization is classified and collected in a predetermined particle size range to form a toner, the toner is divided into at least three particles using a classification fence. Introducing the solid colored particle group into the multi-division classification zone formed by the fractionation and causing it to descend in a curved line, dividing and collecting the coarse powder mainly composed of the coarse particle group in the first fractionation zone, In the second fractionation area, the medium powder mainly composed of particles within a predetermined particle size range is divided and collected, and in the third fractionation area, the fine powder mainly composed of particles with a predetermined particle size or less is divided and collected. A method for producing a toner for developing an electrostatic image, characterized in that the coarse powder is collected, and the coarse powder is supplied to a pulverization step and then introduced into the multi-division classification zone.