JPH01149059A - Manufacture of electrostatic charge image developing toner - Google Patents

Abstract

PURPOSE:To bring out the pulverizing ability and the energy efficiency of a pulverizing device to their utmost and to manufacture a toner capable of forming an image high in density and small in fog with a correct consumption of the toner by finely pulverizing the crude toner with high impact by using a jet mill, and further giving comparatively low impact to it as compared with the first impact for a short time. CONSTITUTION:The crude material to be pulverized 1 is fed to a first classifying means 2, the classified particles larger than a prescribed particle size range 3 is fed to a high impact pulverizing means 4, the pulverized particles are again fed to the means 2, the finer particles are fed to a low impact treating means 5, the treated particles are fed to a second classifying means 6, and classified into particles finer than a prescribed size range 7 and particles in the prescribed size range 8. The jet mill is used for the means 4, and the low impact treatment is executed, for example, by giving impact to the particles between a rotor and a liner, thus permitting deterioration of the image density due to the high impact pulverization to be covered by the low impact treatment, and an image high in density to be obtained, and both of the treatment capacity of the device and the energy efficiency to be enhanced.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, and the like. [Prior art] Conventionally, as an electrophotographic method, the U.S. Patent No. 2,297°89
Although many methods are known, as described in Japanese Patent Publication No. 1, Japanese Patent Publication No. 42-23810, Japanese Patent Publication No. 43-24748, etc., they generally utilize photoconductive substances and perform various methods. forming an electrical latent image on the photoreceptor by means;
The latent image is then developed using toner, and if necessary, the toner image is transferred to a transfer material such as paper, and then fixed by heat, pressure, solvent vapor, or the like to obtain a copy. Methods for charging the developing particles or developer include: ■Charge injection method, which makes toner conductive and injects charge; ■Dielectric polarization method, which uses dielectric polarization under an electric field; and ■Corona charger, etc., which charge charged ions. There is an ion flow charging method in which particles are exposed to a shower, and a triboelectric charging method in which the toner is charged by rubbing the toner against an object at a position where the frictional charging series is different from that of the toner. Among these methods, the triboelectric charging method is currently widely used because it can be adjusted to a sufficient amount of charge using insulating toner particles and is reproducible. Conventionally, as a method for producing this toner, a so-called pulverization method is generally used, in which toner raw materials are melt-kneaded, cooled and solidified, and then finely pulverized and classified to form a toner. In the case of the pulverization method, applying a high impact during the pulverization step has the effect that the pulverization processing capacity of the apparatus is high and that less energy is required per unit weight of toner. However, since triboelectric charges are used to charge the developer, subtle differences in the surface condition of the toner affect image quality, resulting in low image density and increased scattering around characters. This tends to be particularly noticeable under low temperature and low humidity conditions and high temperature and high humidity conditions. On the other hand, relatively low-impact pulverization yields high image density and solid images, but the processing speed of the pulverizer is significantly reduced and the energy required per unit weight of toner is excessive. There is a problem with this. If the impact force is weakened too much, this tendency becomes more pronounced, and phenomena such as an increase in toner consumption per image and an increase in fogging occur, which becomes an obstacle to efficiently obtaining good image quality. There is. [Problems to be Solved by the Invention] An object of the present invention is to provide a toner manufacturing method that overcomes the above-mentioned problems in the toner manufacturing method. That is,
An object of the present invention is to provide a method for producing toner that maximizes the crushing ability and energy efficiency of a crushing device, has high image density, has appropriate toner consumption, and has low fog. [Means and effects for solving the problems] The present invention comprises a process of melting and kneading toner raw materials such as a binder, a colorant, a charge control agent, etc., cooling and solidifying the mixture, and a process of finely pulverizing the kneaded product. In a method for producing toner for electrostatic charge development, which includes a classification step of classifying finely pulverized particles to obtain a desired particle size distribution, the pulverization step involves performing high-impact pulverization using a jet mill. Furthermore, apart from this pulverization step, the present invention is characterized in that it includes a modification step in which a comparatively lower impact than during pulverization is applied to the toner for a short period of time. FIG. 1 is a flow diagram of the method of the present invention. ``The pulverized raw material is sent to the first classification means together with the particles pulverized by the high-impact pulverization means, and is classified into coarse powder and fine powder. The coarse powder is sent to high impact means to be crushed and then sent to first classification means. The fine powder side (i.e., the pulverized product) is processed by a low-impact means and then classified by a second classification means, and is divided into a classified product having a particle size within the specified particle size and a classified fine powder consisting of particles with a particle size below the specified particle size. It will be done. The high-impact crushing means shown in the above flow diagram includes a second
A jet mill as shown in the figure is used, and the second-(a)
The figure shows a state diagram of pulverization by a jet mill. Powder from a hopper 23 passes through a conical throttle valve 24.
The high-pressure gas is ejected from the accelerating tube 25, collides with the opposing collision plate 2B, and is pulverized and discharged from the discharge port 27. Here, it is desirable to use a collision plate having a collision surface perpendicular to the acceleration tube or a collision plate substantially perpendicular to the acceleration tube, and the air pressure of the compressor is 5. It is desirable to use an air pressure of 5 kg/cm2 to 10 kg/cm2, which is the upper limit of the air pressure of the high-pressure gas conventionally used in jet mills or higher. Figure 2-(b) shows an example of an impingement plate that is substantially perpendicular to the air flow in the accelerator tube, preferably less than 20° with respect to the direction perpendicular to the air flow in the accelerator tube. is the impingement plate 26' having an angle of less than 10°. When a powder containing a resin with a relatively low softening point and glass transition point, such as toner, is pulverized with high impact using a perpendicular collision plate, a fused substance is formed on the collision plate due to local heat generation, resulting in continuous pulverization failure. However, in this case, if a collision plate 26' as shown in FIG. 2-(b) is used, highly efficient and high-impact crushing without the generation of fused materials becomes possible, especially in a high pressure region. Another method of high-impact grinding is to put the powder into a compressor air feed tank and introduce it together with the compressor air into an accelerator tube, which accelerates the powder at the same time as in a conventional jet mill. It is also possible to use means to further accelerate the powder by eliminating relatively low-pressure air near atmospheric pressure introduced into the tube. By pulverizing with such a high-impact pulverizing means, the pulverizing capacity and pulverizing efficiency of the pulverizer can be significantly improved compared to the conditions in terms of image quality.In particular, the smaller the particle size distribution, the more effective this effect is. becomes noticeable. The pulverizer system is effective both when directly reducing the particle size of several square centimeters to the desired toner particle size, and when pulverizing the raw material particle size to about 10 to 100 l to the desired toner particle size. On the other hand, examples of low-impact means include methods in which impact is applied between a rotating rotor, blade, or hammer and a liner facing it, or between a number of rotating pins. Figure 3 is a schematic cross-sectional view of a low-impact treatment device that combines a rotor and a liner.
is a casing, 33 is a liner, 34 is a blower blade, 35
36 is a rotor (with blades), 36 is an outlet, 37 is a product outlet, 38 is a return path, 39 is a raw material inlet, 40 is an inlet, 41 is a jacket, and 42 is a return closing valve. The circumferential speed of the rotating rotor is 10 to 200 ra/sec,
Preferably it is 30 to 150 m/sea, and the temperature is preferably from the glass transition point -5°C to the glass transition temperature -30°C. If it is too high, it will melt in the equipment, and if it is too low Both of these methods are undesirable from a practical point of view. Figure 4 shows the liner 3 of the low impact treatment equipment shown in Figure 3.
The distance between the liner 33 and the rotor 35, which indicates the positional relationship between the liner 33 and the rotating rotor 35, is defined by the two circumferences: the circumference obtained by connecting the tips of the protrusions toward the inner circumference of the liner, and the locus of the protrusions of the rotor. The same is true for blades or hammers instead of this rotor. Good results have been obtained with a spacing between the blade or hammer and the liner of about 0.5 to 10 mm, preferably 1 to 5III+. FIG. 5 is a schematic sectional view of a pin mill type low impact processing device. 51 is a casing, 52 is a pin, 53 is an inlet, 54 is a raw material input port, 55 is a circulation blower, 156 is a return path, 57 is a product extraction port, 58 is an outlet, 59 is a rotor, and 60 is a rotating shaft connected to the rotor. , 61 is a jacket. In this pin mill type, not only the minimum spacing between pins is 0.5 to 5cm, but also the maximum spacing is 5mm.
Good results have been obtained by setting the thickness to 10 mm or less, preferably 5!1 layers or less. In addition, in Figures 3 and 5, the type is recyclable in order to control the retention time, but if the retention time is short, the one-time type can be used, especially by controlling the wind speed and the length of the part that applies impact. Perform processing. Since the purpose of low-impact treatment is to modify the surface properties rather than spheroidization, the residence time in the device is extremely short and varies depending on the nature of the individual toner and the circumferential speed of the rotor, but e.g. Speed 200 proverbs/sea 0.01 seconds to 2
The time is approximately 0.01 seconds to 3 minutes depending on the conditions. Therefore, there is little effect on the shape and toner surface.
When crushed, the ratio of the short axis to long axis of the toner is 0.60 to 0.70.
However, when observing the state of the toner surface using a scanning electron microscope, no particularly large change was found, unlike spherical formation. If this low-impact processing time (residence time) is made too long than the above-mentioned time, phenomena such as increased toner consumption and increased fog due to decreased cleaning performance will be exacerbated, while if it is too short, the surface characteristics will not be improved. There is a tendency for the quality effect to become weaker and toner scattering in character areas to increase. Note that the circumferential speed of the low impact means is relatively high, 100
- In the region of -150 m/sec, some pulverization occurs and the particle size may shift, so a wind classifier is attached to the low-impact means, and the inlet particle size of the low-impact means is 1 to 2 times smaller than the outlet particle size.
It is also possible to process the material as coarsely as IL if the material has good pulverizability. In this case, the throughput and efficiency of the pulverizer in the previous step will be further improved. By performing this low-impact processing, the drop in density caused by high-impact pulverization in the previous process is covered, making it possible to obtain sharper images, and greatly improving both the processing capacity and energy efficiency of the equipment. be able to. [Example] Example 1 Styrene butyl acrylate-divinylbenzene copolymer (UW 300,000) 90 parts by weight Nigrosine
2 parts by weight Hiwax 200p (polyethylene wax made by Mitsui Petrochemicals) 4 parts by weight Magnetic material (specific surface area 8 m2/g) 60 parts by weight
The resulting kneaded material was cooled and crushed using a hammer mill using a 2+am screen. (Volume average diameter measured by Coulter counter). At this time, the collision plate used was a conical one having an angle of 10° with respect to the 90° plane of the air flow direction of the accelerator tube, the compressor air pressure was 6.5 kg/intestinal 2, and the air amount was The powder was pulverized at a controlled rate of 6.5 m3/win. Thereafter, the toner was modified using the surface treatment device shown in Fig. 3 under the conditions that the rotational speed was 130 m/sec, the clearance between the liner and the log was 5 m, and the temperature on the exit side of the device was 40°C. I did it. Next, the volume average diameter was 1iI using an Albine jig-zag classifier.
L, 6.351 L or less was cut into fine powder so that the number average was 20% or less to obtain a classified finished product. At this time, the capacity of the crusher was 26 kg/hr. Examples 2 and 3 As shown in Table 1, the examples were carried out in exactly the same manner as in Example 1, except that the compressor air pressure and air amount in the high-impact pulverization process and the crushing function in the second classification process were changed. A classified finished product (toner) according to No. 2 was obtained. In addition, the classified finished product according to Example 3 (toner ) was obtained. Comparative Examples 1 to 3 Except for not performing any low impact treatment under the conditions shown in Table-1,
Classified finished products (toner) according to Comparative Examples 1 to 3 were obtained in the same manner as in Example 1. (Left below) Next, to 6100 parts by weight of the toner of each example and comparative example,
Colloidal silica treated with amine silicone oil 0
．． 5 parts by weight was added and mixed in a mixer with rotating blades to obtain a product toner, which was used to produce a Canon copier NP3.
Illustrated at 525. The energy efficiency and investment efficiency in obtaining the toners according to each of the above examples and comparative examples are shown in Table 2 and Table 3, respectively. Furthermore, the results of the illustrations are shown in Table 4. (Hereinafter, blank space) As described above, according to the method of the present invention, energy efficiency,
It can be seen that the investment efficiency is greatly improved, and the quality is equivalent to that of Comparative Example 2, which is conventional.

【Effect of the invention】

The present invention combines a low-impact surface modification treatment process in addition to a high-impact pulverization process using a jet mill that does not take image quality into account. Therefore, as a jet mill, it is possible to achieve extremely efficient pulverization in terms of both throughput and energy efficiency per unit. At the same time, by performing processing in a short time using an inexpensive, low-power, low-impact device, it becomes possible to increase image density and appropriately control toner consumption. Installing such low-impact equipment as a downstream step to a jet mill also requires less investment and is more energy efficient than traditional methods to achieve the required production capacity. Another major effect of the present invention is that regardless of the pulverization process, this low-impact processing process allows for better matching with the developing device, resulting in higher density, toner consumption per image, and capri, etc. It has become possible to control it.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of the present invention, FIG. 2 shows an example of a high-impact crushing means, FIG. 2-(a) shows its state diagram, and FIG. 2-(b) shows a high-impact crushing means. FIG. 3 is a schematic cross-sectional view of a low-impact processing device using a combination of a rotor and a liner, and FIG. 4 is a diagram showing the positional relationship between the liner and rotor of the device shown in FIG. 3. FIG. 5 is a schematic cross-sectional view of a pin mill type low impact processing device.

Claims (1)

[Claims] A process of melt-kneading the binder, colorant, charge control agent, etc. that are raw materials for toner, cooling and solidifying it, a process of pulverizing the kneaded material, and a classification of the pulverized particles to obtain the desired particle size distribution. In the method for producing toner for electrostatic charge development, the pulverization step involves performing high-impact pulverization using a jet mill; A method for producing a toner for electrostatic charge development, comprising a modification step of applying a low impact to the toner for a short period of time.