JPH0713759B2 - Method for manufacturing toner for developing electrostatic image - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to efficient pulverization / solidification of solid particles having a binder resin.
The present invention relates to a manufacturing method for performing classification to obtain a toner for developing an electrostatic charge image having a predetermined particle size.

[Prior art]

In the image forming methods such as electrophotography, electrostatic photography and electrostatic printing, toner is used to develop an electrostatic image.

The process of pulverizing and classifying raw solid particles in the production of a toner for developing an electrostatic image which requires that the final product is a fine particle to obtain the final product is conventionally shown in the flow chart of FIG. The method is generally adopted. The method is, for example, when a predetermined material such as a binder resin and a colorant is melt-kneaded, cooled and solidified, and then crushed, and the crushed solid particle group is used as a crushed product of the raw material, the crushed product is It is continuously or sequentially supplied to the 1 classifier and classified, and the classified coarse powder containing a coarse particle group of a specified particle size or more as a main component is sent to a pulverizer and pulverized, and then circulated to the first classifier again. To be done. Particles within other specified particle size ranges and powders containing particles below the specified particle size as the main component are sent to the second classifier, and medium powder containing particles having the specified particle size as the main component and below the specified particle size. It is classified into a fine powder whose main component is a particle group of.

Then, as a specific example under this conventional method, a predetermined weight average particle size (particle size is measured by, for example, a Coulter Counter manufactured by Coulter Electronics (USA)) from a solid particle group including crushed particles. A method of expressing the results, which is expressed as a weight average particle size, which will be simply referred to as "average particle size" hereinafter), excluding the fine powder region, that is, for example, an average particle size of 10 In order to obtain a particle group having particles of ˜15 μm and particles of 5 μm or less of 1% or less, a predetermined average particle size is determined by an impact type crusher or a jet crusher equipped with a classification mechanism for removing coarse powder areas. After crushing to classify and removing the coarse powder, the crushed product is put into another classifier to remove the fine powder to obtain a desired intermediate powder.

Regarding such a conventional method, as a problem, since the treatment by the pulverizer having the classifying mechanism for removing the coarse powder and the treatment by the classifier for removing the fine powder are performed in separate steps, In addition to the large number and complicated operation,
When operating for a long period of time, heat may be generated and a large amount of unavoidable adhesion or the like may occur on the powder.

Also, regarding the classification mechanism for the purpose of removing coarse powder, the original purpose is to send only particle groups of a certain size or more to the pulverizer, but the conventional classifier has a very long residence time of several minutes. After removal of the coarse powder region, some of the particle groups aggregate with each other, or fine particles adhere to the coarse particles and are returned to the pulverizer again, so that overpulverization tends to occur. Therefore, there are problems that the pulverization efficiency is lowered, and the yield in the classifier for removing the fine powder region in the next step is lowered. Further, in the second classifier for the purpose of removing the fine powder, it is difficult to remove the agglomerate as the fine powder because the agglomerate composed of the ultrafine particles may occur. In that case, such aggregates are likely to be mixed in the final product, and as a result, it becomes difficult to obtain a product having a fine particle size distribution, and the aggregates are broken down in the toner to become ultrafine particles, which causes deterioration of image quality. Become. For this reason, even if a desired product having a fine particle size distribution can be obtained under the conventional method, the process becomes complicated and the classification yield is lowered, resulting in poor production efficiency and high cost. Is inevitable. This tendency becomes more remarkable as the predetermined grain size becomes smaller.

[Object of the Invention]

The present invention is to solve the above-mentioned various problems in the conventional method for producing an electrostatic charge image developing toner, and an object thereof is to provide an electrostatic charge image developing toner having a fine particle size distribution. It is to provide a manufacturing method for efficiently generating.
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 μm).

[Constitution and effect of the invention]

The present invention is to melt-knead a mixture of a binder resin, a colorant, and various additives, cool the molten mixture, and then pulverize the solid particles to produce a fine particle product having a definite predetermined particle size distribution (as a toner). Used) is efficiently produced in a short time.

Specifically, the present invention provides a method for producing an electrostatic charge image developing toner, in which particles of a predetermined particle size range are classified and collected from solid colored particles having a binder resin generated by pulverization to obtain toner. The solid colored particle group is introduced into a constant quantity feeder, the solid colored particle group is supplied from the constant quantity feeder to a raw material supply nozzle, and the solid coloring is carried out in a multi-division classification area which is fractionated into at least three by a classification fence. A particle group is introduced from the raw material supply nozzle and moved along a curved line to separately collect coarse powder containing a coarse particle group as a main component in the first fractionation area, and a predetermined particle in the second fractionation area. Separately collects the medium powder mainly composed of particle groups in the diameter range,
A fine powder containing a group of particles having a predetermined particle size or less as a main component is divided and collected in the third fraction area, and the coarse powder thus divided is sent to a pulverizing step via a cyclone to be finely pulverized, The present invention relates to a method for producing a toner for developing an electrostatic charge image, which comprises introducing a finely pulverized coarse powder into the constant quantity feeder, supplying the raw material supply nozzle, and performing classification in the multi-division classification area.

The method of the present invention uses a pulverized material as a raw material, and FIG. 1 is a flowchart showing the outline of the method. That is, according to the method of the present invention, the raw material is sent to the multi-division classification zone and at least three kinds of particle size classifications, that is, a large particle size classification (coarse powder containing coarse particles as a main component) and a medium particle size classification (within the specified range) Classify the particles into a large particle size group (medium powder) and a small particle size class (fine particles whose size is less than the specified particle size) and crush the large particle size group appropriately. It is pulverized by a means, is recycled to the multi-division classification zone together with the newly introduced raw material, and is subjected to the classification treatment similar to the above. A group of particles having a prescribed internal diameter in the medium particle size category and a group of particles having a prescribed particle size or less in the small particle size category are respectively taken out from the multi-division classification area by an appropriate take-out means. The group of particles taken out from the medium particle size area has an optimum particle size distribution and can be used as a toner as it is. On the other hand, the particles in the small particle size section that are taken out may be recycled by being recycled to the melting step.

As means for providing the multi-division classification area, for example, the second
A multi-division classifier of the type shown in FIGS. 3 and 4 can be exemplified as one of the specific examples. In FIGS. 2 and 3, the side wall cross section has a shape indicated by 32, 51, the bottom surface is rectangular, and the knife edge type in which the bottom portion is fixed or fixed in parallel to the bottom surface in the longitudinal direction at a predetermined interval in parallel. Classification 27 (or 3)
9), 28 (or 40) such as a classification fence is divided into three. A vertical wall that faces the upright fulcrum of the curved wall 51.
A raw material supply nozzle 26 that opens into the classification chamber is provided in the upper portion 32, and a Coanda block 30 in the shape of an elliptical arc is formed by bending the nozzle downwardly with respect to the extension direction of the bottom tangent of the nozzle and projecting it onto the vertical side wall 32. The upper part of the classification chamber has an upright rectangular tube shape.
In the center of the top wall, there is a knife-edge type air intake edge 29 in the longitudinal direction.
(Or 41) is provided, and the top walls are provided with air intake pipes 24 and 25 that open to the classification chamber. Classification Edge 27 (or 39), 2
The position of 8 (or 40) differs depending on the size of the chamber in the multi-division classification area and the type of raw material to be treated. In addition, discharge pipes 21, 22, 23 that open to the inside of the chamber are provided on the bottom of the chamber so as to correspond to the respective fractionation areas. The discharge pipes 21, 22 and 23 may each be provided with opening / closing means such as valve means.

Classifying edges 27 (or 39), 28 (or 40) are provided so that the edge part is upward and protrude into the indoor space, and the intake air edge 29 (or 40) is inside the top wall with the edge part downward. Normally, it is provided in the space, but when trying to make the particle group of the medium particle size category have a very limited particle size range,
As shown by 40 and 41 in FIG. 3 for the classification edge 28 and the intake edge 29, leave the fixed position and tilt the rising part for the former and the hanging part for the latter so that they are outside the air flow. May be. The supply of the raw material into the classification chamber through the raw material supply nozzle 26 is performed according to a calibration curve corresponding to the type of raw material.

The classification operation of the raw material in the multi-division classification area configured as described above is performed, for example, as follows. That is, when the powder raw material is supplied from the raw material supply nozzle 26, the powder moves by drawing the curved line 35 by the action of the Coanda block 30 due to the Coanda effect and the action of gas such as inflowing air at that time.
Large particles (coarse particles) according to the size of each particle
Is the outside of the air stream, that is, the fraction outside the classification edge 28, the intermediate particles (particles with a specified internal diameter) are the classification between the edges 28 and 27, and the small particles (particles below the specified diameter) are classified It is divided into fractions inside the edge 27, with large particles coming out of outlet 21, intermediate particles coming out of outlet 22, and small particles coming out of outlet 23.
Will be discharged respectively.

In order to carry out the above-mentioned method, it is usual to use an integrated device system in which mutual devices are connected by a communication means such as a pipe, and a preferable example of such a device is used.
Shown in the figure. The integrated device shown in FIG. 4 is a three-division classifier 2
(The type shown in FIG. 2 or FIG. 3. Details are as described above.), Crusher 3, collection cyclone 4, collection cyclone 5, quantitative feeder 6, vibrating feeder 7, The collection cyclone 8 and the collection cyclone 9 are connected by a communication means.

In this apparatus, so-called pulverized material is sent to a collection cyclone 5 via a material supply conduit 31 equipped with an on-off valve 1, then to a constant quantity feeder 6, and then to a vibrating feeder 7 to supply a material supply nozzle. It is introduced into the three-division classifier 2 by 26. At the time of introduction, the pulverized material can be sucked and introduced into the three-division classifier 2 by utilizing the suction force of the collection cyclones 4, 8 and / or 9. The introduction by suction is preferable because the sealing property of the system is not strictly required as compared with the introduction by pressure. At the time of suction introduction, it varies depending on the specific gravity and particle diameter of the particles, but it is preferable to introduce the pulverized material into the three-division classifier 2 at a flow rate of usually 50 to 200 m / sec in terms of classification accuracy and classification efficiency. Since the size constituting the classification area of the classifier 2 is usually [10 to 50 cm] × [10 to 50 cm], the pulverized material can be dispensed into three or more kinds of particle groups in an instant of 0.1 to 0.01 seconds or less. Then, the three-division classifier 2 divides the particles into large particles (coarse particles), intermediate particles (particles having a specified internal particle diameter), and small particles (particles having a specified particle diameter or less).

After that, the large particles are sent to the collection cyclone 4 through the discharge conduit 21, and then sent to the pulverizer 3 to be crushed, and the collection cyclone 5 together with the powder raw material newly introduced through the raw material supply conduit 31. Then, it is sent to a constant quantity feeder and subjected to classification treatment in the same manner as described above. Intermediate particles are
It is discharged to the outside of the system through the discharge conduit 22 and collected by the collecting cyclone 9 to be collected as much as the toner product 91. The small particles are discharged to the outside of the system through the discharge conduit 23, repaired by the collecting cyclone 8, and then recovered as the non-specified fine powder 81. The collection cyclones 4, 8 and 9 also function as suction decompression means for sucking and introducing the pulverized raw material into the classification area through the nozzle 26.

As the crusher 3, an impact crusher, a jet crusher or the like can be used. That is, examples of the impact type crusher include a turbo mill manufactured by Turbo Kogyo Co., Ltd., and examples of the crusher using a jet include Supersonic Jet Mill PJM-I manufactured by Japan New Matic Industry Co., Ltd. and Micron Jet manufactured by Hosokawa Micron. To be Examples of the multi-division classifier in the method of the present invention include means such as Elbow Jet manufactured by Nittetsu Mining Co., Ltd.

As described above, the method of the present invention removes the coarse powder particle group and the fine powder particle group at the same time by the specific classification means, and the coarse particle group is crushed and supplied to the quantitative feeder for recirculation, It is possible to efficiently obtain a group of particles having a fine particle size distribution within a predetermined particle size range quickly from the pulverized product. Further, the method of the present invention requires fewer steps, so that the product cost can be reduced as compared with the conventional method.

Furthermore, the method of the present invention has almost no residence time in the classifying area, so that it is difficult to generate agglomerates as seen in the classifier for removing the coarse powder area in the related art, and the crusher has a specified particle size. Since only the above coarse particles are sent, the load on the crusher is small, the crushing efficiency is very good, and over-crushing does not occur. It is also possible to very efficiently remove the fine powder region, and the classification yield can be satisfactorily increased. Further, in the conventional classification method for classifying the intermediate powder region and the fine powder region, it is difficult to generate agglomerates that cause fog in the developed image composed of fine particles, and if they occur, they can be removed from the intermediate powder region. Although difficult, according to the method of the present invention, even if the agglomerates are mixed in the pulverized product, the agglomerates are broken down by the Coanda effect and / or the high speed movement to be removed as fine powder, and the breakage is avoided. Even if there are agglomerates, they can be removed to the coarse powder area at the same time, and thus the agglomerates can be removed efficiently.

The toner for developing an electrostatic image is usually melted and kneaded with raw materials such as a styrene resin, a styrene-acrylic resin, or a polyester resin, a colorant (or / and a magnetic material), an offset inhibitor, and a charge control agent, and then cooled, It is manufactured by crushing and classifying. At this time, since it is difficult to obtain a melt in which each raw material is uniformly dispersed in the kneading step, the pulverized pulverized product contains particles unsuitable as toner particles (for example, a colorant or magnetic particles). However, in the conventional pulverizing and classifying method, the residence time of the particles is long in the pulverizing and classifying process, and thus inappropriate particles are likely to aggregate Since it was difficult to remove the substance, the characteristics of the toner were significantly deteriorated. Since the method of the present invention immediately classifies into three or more fractions after pulverization, it is difficult to generate the agglomerates, and even if they occur, it is possible to remove the agglomerates to the coarse powder region, and thus particles of a uniform component are obtained. And a product having a fine particle size distribution can be obtained. As a result, the toner obtained by the method of the present invention has a stable triboelectric charge amount between toner particles or between a toner and a sleeve and between a toner and a toner carrier such as a carrier. Therefore, the development fog and the toner scattering around the edges of the latent image, which have not been sufficiently solved in the past, are extremely small, a high image density is obtained, and the halftone reproducibility is improved. Furthermore, the initial characteristics are maintained even when the developer is continuously used for a long period of time,
High-quality images can be provided for a long period of time. further,
Even when used under high temperature and high humidity environmental conditions, the presence of ultrafine particles and aggregates thereof is small, so the triboelectric charge amount of the developer is stable and hardly changes compared to normal temperature and normal humidity.
Fog and reduction in image density are small, and development that is faithful to the latent image is provided. Furthermore, the transfer efficiency is also excellent. Even when used under low temperature and low humidity conditions, the triboelectrification amount distribution shows almost no change from that at room temperature and normal humidity, and since the developer component having an extremely large electrification amount is removed, there is no reduction in image density or fog. The toner obtained by the method of the present invention has the characteristic that there is almost no roughness or scattering during transfer.

In addition, medium powder with small particle size (for example, average particle size 3 to 7μ)
The present invention can be carried out more efficiently than in the conventional method when producing

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

Example 1 Toner raw material consisting of the mixture of the above formulation is about 1.0 at about 180 ° C.
After melting and kneading for an hour, it is cooled and solidified, and then 100
Coarsely pulverized to particles of ˜1000 μ, and then pulverized to a pulverized product having a weight average particle diameter of 100 μ by an ACM Pulverizer manufactured by Hosokawa Micron. The multi-division classifier 2 shown in Fig. 2 is used to classify the obtained pulverized product into three kinds of coarse powder, medium powder and fine powder by utilizing Coanda effect at an amount of 1.0 kg per minute. It was installed on an Elbow Jet EJ-45-3 machine (manufactured by Nippon Steel Mining Co., Ltd.). At the time of introduction, the pulverized material is supplied at a flow rate of about 100 m / sec by the suction force derived from the decompression in the system by the suction decompression of the collection cyclones 8, 9 and 4 communicating with the discharge ports 21, 22, 23. Introduced on 26. The pulverized material introduced was classified instantly for 0.01 seconds or less. The collection cyclone 9 which collects the classified medium powder contains about 12μ volume average particle size (0.5% by weight of particles with a particle size of 5.04μ or less, 0.1% by weight of particles with a particle size of 20.2μ or more). % Or less, which can be regarded as substantially not contained), and a preferable intermediate powder as a toner was obtained with a classification yield of 85% by weight. The classification yield here means the ratio of the amount of the finally obtained intermediate powder (product) to the total amount of the supplied pulverized material. When the obtained intermediate powder was observed with an electron microscope, substantially no aggregates of about 5 μ or more in which ultrafine particles were aggregated were found.

Further, the classified coarse powder was collected by a collecting cyclone 4, introduced into a crusher 3 (supersonic jet mill PJM-I-10 manufactured by Nippon Neumatik Kogyo Co., Ltd.) and crushed. The pulverized powder was supplied to the raw material supply conduit 31, and was supplied to the constant quantity feeder 6 via the supply conduit 31 for classification by the multi-division classifier.

Using the obtained intermediate powder as a toner, hydrophobic silica 0.
3% by weight was mixed to adjust the developer, and the adjusted developer was supplied to the copier NP-270 (manufactured by Canon), and a copy test was carried out. A copy image with good fine line developability without fog was obtained. Was given.

Comparative Example 1 The pulverized product obtained in the same manner as in Example 1 was classified by the classification system configured as shown in FIG. Volume average particle size 100μ
The crushed material was introduced into the first classifier (Nippon Neumatik Industrial Co., Ltd., airflow classifier DS-10) at an amount of 1.0 kg per minute, and the classified coarse powder was pulverized (Nippon Neumatik Industrial Co., Ltd. supersonic speed). It was introduced into a jet mill PJM-10), pulverized, and then circulated to the first classifier. The medium powder and fine powder classified by the first classifier were introduced into the second classifier (DS-10) and classified into medium powder and fine powder. The obtained intermediate powder has a volume average particle size of about 12μ and a classification yield of 70% by weight. When observed by an electron microscope, the ultrafine particles are scattered about 5μ or more aggregates. Was found.

Using the obtained intermediate powder as a toner, hydrophobic silica 0.
A developer was prepared by mixing 3% by weight, and the prepared developer was supplied to a copying machine NP-270 (manufactured by Canon Inc.) and a copy test was conducted. As a result, fog was more generated than the copy image obtained in Example 1. There were many.

Examples 2 to 4 Volume average particle diameters of 50μ, 30μ and 20 in the same manner as in Example 1.
Each pulverized product of μ was prepared and classified and pulverized in the same manner as in Example 1. The results are shown in the table below.
still, Comparative Example 2 A pulverized product having a volume average particle size of about 20μ was prepared in the same manner as in Example 1, and a medium powder having a volume average particle size of about 5μ was produced in the same manner as in Comparative Example 1. The classification yield was 50 weight. %Met. still,
The smaller the particle size of the medium powder, the larger the difference in classification yield between the inventive example and the comparative example.

[Brief description of drawings]

FIG. 1 is a flow chart of the method of the present invention, and FIGS. 2 and 3 are sectional views of an apparatus which is one specific example for carrying out the method for multi-division and classification of solid particles of the present invention. FIG. 4 is a schematic diagram showing a classifier system for carrying out the method of the present invention. FIG. 5 is a flowchart of the conventional method. Explanation of symbols in the figure 1 …… Opening / closing valve 2 …… Solid particle multi-division classifier 3 …… Crusher 4 …… Collection cyclone 5 …… Collection cyclone 6 …… Quantitative feeder 7 …… Vibration feeder 8… … Collecting cyclone 9 …… Collecting cyclone 21,22,23 …… Exhaust port 24,25 …… Inlet port 26 …… Material supply nozzle 27,28 …… Classification edge 29 …… Inlet edge 30 …… Coanda Block 31 …… Raw material supply conduit 51 …… Curved side wall 32 …… Vertical side wall 33,24,36,37 …… Intake direction 35,38 …… Solid particle scattering direction

Claims (1)

[Claims] 1. A method for producing a toner for developing an electrostatic charge image, which comprises classifying particles from a group of solid colored particles having a binder resin formed by pulverization into toner particles in a predetermined particle size range. Is introduced into the quantitative feeder, the solid colored particles are supplied from the constant feeder to the raw material supply nozzle, and the solid colored particles are divided into at least three divided fractions by a classification fence. It is introduced from a raw material supply nozzle and moved along a curved line to separately collect coarse powder containing a coarse particle group as a main component in a first fractionation area, and particles in a predetermined particle size range in a second fractionation area. Separately collects medium powder mainly composed of groups,
A fine powder containing a group of particles having a predetermined particle size or less as a main component is divided and collected in the third fraction area, and the coarse powder thus divided is sent to a pulverizing step via a cyclone to be finely pulverized, A method for producing an electrostatic charge image developing toner, characterized in that finely pulverized coarse powder is introduced into the constant quantity feeder, supplied to the raw material supply nozzle, and classified in the multi-division classification area.