JPH0820762B2 - Method of manufacturing toner for electrostatic charge development - Google Patents

Description

The present invention relates to a method for producing a toner for developing an electrostatic charge image in electrophotography, electrostatic recording, electrostatic printing and the like.

[Prior Art] Conventionally, as an electrophotographic method, many methods are known as described in US Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 43-24748. However, in general, a photoconductive substance is used to form an electrical latent image on a photoconductor by various means, and then the latent image is developed with a toner, and if necessary, a transfer material such as paper is transferred. After the toner image is transferred, it is fixed by heating, pressure or solvent vapor to obtain a copy.

As a method of charging the visualized particles, that is, the developer, a charge injection method of electrically conducting the toner to inject a charge,
Dielectric polarization method that uses dielectric polarization under an electric field, ion current charging method that applies shower of charged ions to particles such as corona charger, and friction between an object and a toner at a position whose frictional charging series is different from that of the toner. There is a triboelectrification method and the like. Among them, the triboelectrification method is widely used at present because it can be adjusted to a sufficient charge amount by using insulating toner particles and has reproducibility.

Conventionally, as a method for producing this toner, a so-called pulverization method is generally used, in which a toner raw material is melt-kneaded, cooled and solidified, and then finely pulverized and classified to form a toner. In the case of the crushing method,
Grinding with a high impact in the crushing process has an effect that the crushing capacity of the apparatus is high and the energy required per unit weight of the toner is small.

However, since the frictional band charge is used to charge the developer, a slight difference in the surface state of the toner affects the image quality, resulting in a low image density and increased scattering around the characters. In particular, this tends to be remarkable under low temperature and low humidity and high temperature and high humidity.

On the other hand, when the crushing with a relatively low impact is carried out, the image density is high and a solid image is obtained, but the processing speed of the crusher is remarkably reduced, and the energy required per unit weight of the toner is excessive. There is a problem. If the impact force is weakened too much, this tendency becomes remarkable, and a phenomenon such as an increase in toner consumption per image or an increase in fog occurs, which is a hindrance to obtaining efficient and 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 which overcomes the above-mentioned problems in the toner manufacturing method. That is, it is an object of the present invention to provide a method for producing a toner having a high image density, a proper toner consumption amount, and a low fog while maximizing the pulverizing ability and energy efficiency of a pulverizing device.

[Means and Actions for Solving Problems] The present invention relates to a binder, a colorant, which is a raw material of a toner,
A toner for electrostatic charge development having a step of melting and kneading a charge control agent and the like to solidify by cooling, a step of finely pulverizing the kneaded product, and a classification step of classifying the finely ground particles to obtain a desired particle size distribution. In the manufacturing method, the finely pulverizing step is to perform high impact fine pulverization using a jet mill, and after this fine pulverizing step, a relatively lower impact than that during fine pulverization is applied to the toner for 0.01 seconds to 3 minutes. It is characterized by having a reforming step.

FIG. 1 is a flow chart relating to the method of the present invention. The pulverized raw material is sent to the first classifying unit together with the particles pulverized by the high impact pulverizing unit and classified into coarse powder and fine powder. The coarse powder is sent to the high impact means, crushed, and further sent to the first classification means. The fine powder side (that is, the pulverized product) is processed by the low impact means and then classified by the second classification means, and is classified into a classified product having a particle size within a specified particle size and a classified fine powder composed of particles having a particle size within the specified particle size. To be

A jet mill as shown in FIG. 2 is used for the high-impact crushing means shown in the above flow chart.
The figure (a) shows the state diagram of pulverization by a jet mill. The powder from the hopper 23 is ejected from the accelerating pipe 25 by the high-pressure gas through the conical squeeze valve 24, collides with the opposing collision plate 26, is pulverized, and is discharged from the discharge port 27.
Here, as the collision plate, it is desirable to use a collision plate having a collision surface at right angles to the acceleration tube or a collision plate substantially perpendicular to the acceleration tube. Further, a 5.5kg / cm ² ~10kg / cm ² as air pressure of the compressor, it is desirable to ground using upper limit or more values of the air pressure of the high pressure gas used in the conventional jet mill.

FIG. 2- (b) shows an example of a collision plate that is substantially perpendicular to the air flow in the accelerating pipe, and is preferably 20 ° or less, preferably 20 ° or less with respect to the direction perpendicular to the air flow in the accelerating pipe. Is
A collision plate 26 'having an angle of 10 ° or less. When powder containing resin having a relatively low softening point and glass transition point such as toner is crushed with a high-impact collision plate at a right angle, a fusion product is formed on the collision plate due to local heat generation, etc. However, in this case, if the collision plate 26 'as shown in FIG. 2- (b) is used, it is possible to perform highly efficient high impact crushing without generation of deposits, especially in a high pressure region.

As another means of high impact crushing, put powder in a feed tank of air pressure of compressor air and introduce it into the accelerating pipe together with the compressor air, and accelerate it at the same time as the powder like a conventional jet mill. By eliminating relatively low pressure air around the atmospheric pressure introduced into the pipe,
Means for accelerating the powder are also available.

By crushing with such a high impact crushing means,
The pulverizing ability and pulverizing efficiency of the pulverizer can be remarkably improved as compared with the condition in which the image quality is taken into consideration. Particularly, the smaller the particle size distribution is, the more remarkable this effect is. The crusher system is effective both when the particle size of a few mm is directly used as the target toner particle size and when the particle size of the raw material is set to about 10 to 100 μ and the target toner particle size is crushed.

On the other hand, examples of the low impact means include a method of applying an impact between a rotating rotor, a blade or a hammer and a liner facing the rotating rotor, or an impact between a plurality of rotating pins.

FIG. 3 is a schematic cross-sectional view of a low impact treatment device using a combination of a rotor and a liner. In the figure, 31 is a rotating shaft, 32 is a casing, 33 is a liner, 34 is a blower blade, 35 is a rotor (with blade), 36 is an outlet, 37 is a product outlet, 38 is a return passage, 39 is a raw material inlet, 40 Is an inlet, 41 is a jacket, and 42 is a return closing valve.

The peripheral speed of the rotating rotor is 10 to 200 m / sec, preferably
It is preferably 30 to 150 m / sec, and the temperature is preferably in the temperature range of glass transition point -5 ° C to glass transition degree -30 ° C.
If it is too high, it will melt in the apparatus, and if it is too low, a cost for cooling energy will be required, which is not preferable in practice.

FIG. 4 is a liner for the low impact treatment device shown in FIG.
The positional relationship between 33 and the rotating rotor 35 is shown. Liner 33
The distance between the rotor and the rotor 35 is the circumference of the line that connects the tip of the protrusion to the inner circumference of the liner and the locus of the protrusion of the rotor.
The difference between the radii of two circles. The same applies to blades and hammers instead of this rotor. Good results have been obtained with a distance between the blade or hammer and the liner of the order of 0.5-10 mm, preferably 1-5 mm.

FIG. 5 is a schematic cross-sectional view of a pin mill type low impact treatment device. 51 is a casing, 52 is a pin, 53 is an inlet, 54
Is a material input port, 55 is a circulation blower, 56 is a return path, and 57
Is a product outlet, 58 is an outlet, 59 is a rotor, 60 is a rotating shaft connected to the rotor, and 61 is a jacket. In this pin mill type, not only the minimum distance between pins is 0.5 to 5 mm, but also the maximum distance is 5 to 10 mm or less, preferably 5 m
Good results have been obtained by setting it to m or less.

In Fig. 3 and Fig. 5, the type is recyclable to control the residence time. However, when the residence time is short, the wind speed and the length of the part to which the impact is applied are controlled to make it a transient system. Perform processing.

Since the purpose of the low impact treatment is to modify the surface characteristics, not to make it spherical, the residence time in the apparatus is extremely short, and the time varies depending on the properties of each toner and the peripheral speed of the rotor. At a speed of 200 m / sec, it is 0.01 to 2 seconds,
Select from 0.01 seconds to 3 minutes depending on the conditions. Therefore, there is little influence on the shape and the surface of the toner, and when the ratio of the short diameter to the long diameter of the toner is 0.60 to 0.70 when pulverized, it is about to shift to about 0.65 to 0.85, and the toner surface state is When viewed under a microscope, unlike spheroidization, no significant changes are found.

If this low impact treatment time (residence time) is set to be longer than the above-mentioned time, phenomena such as increase in toner consumption and increase in fog due to deterioration in cleaning property will be increased. Conversely, if it is too short, surface characteristics will be improved. The quality effect becomes weaker, and the toner scattering in the character portion tends to increase.

In addition, the peripheral speed of the low-impact means is relatively high 100
In the region of ~ 150m / sec, the crushing may be partially performed and the particle size may shift, so attach a wind classifier to the low impact means and make the inlet particle size of the low impact means about 1 to 2μ coarser than the outlet particle size. It is also possible to treat the material if the material has good pulverizability. In this case, the processing capacity and efficiency of the pulverizer in the previous step will be further improved.

By carrying out this low impact treatment, it is possible to cover the decrease in concentration that was caused by the high impact pulverization in the previous process, and it becomes possible to obtain a solid image, and the processing capacity and energy efficiency of the device are greatly improved. You can

Example 1 Styrene butyl acrylate-divinylbenzene copolymer (w≈300,000) 90 parts by weight Nigrosine 2 parts by weight Hiwax 200p (polyethylene wax manufactured by Mitsui Petrochemical) 4 parts by weight Magnetic material (specific surface area 8 m ² / g) 60 parts by weight The components of the above formulation were heat-kneaded in a roll mill at 150 ° C for about 30 minutes, the resulting kneaded product was cooled, and the coarsely crushed product was roughly crushed with a hammer mill on a 2 mm screen to produce a new product. Matic I-5-DS5 crusher with a toner particle size of 10.5μ
(Volume average diameter measured by Coulter counter). At this time, the collision plate moves 90 ° in the direction of air flow in the acceleration tube.
Use a cone with an angle of 10 ° with respect to the plane of °, and set the compressor air pressure to 6.5 kg / m ² and the air amount.
It was crushed while controlling to 6.5 m ³ / min.

After that, with the surface treatment device shown in FIG. 3, the rotation speed is 130 m / sec and the clearance between the liner and the rotor is 5 m.
The toner was modified under the condition that the temperature at the outlet side of the apparatus was 40 ° C.

Next, using a Zine Zaku classifier manufactured by Alpine, a volume average diameter of about 11
Fine particles were cut so that the number average of μ and 6.35 μ 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 same procedure as in Example 1 was carried out except that the compressor air pressure and air amount in the high impact fine powder process and the crushing functional force in the second classification process were changed. A classified finished product (toner) according to No. 2 was obtained.

Further, the classified finished product (toner) according to Example 3 is exactly the same as Example 1 except that the toner particle size in the first classification step, the rotation speed in the low impact treatment step, and the crushing functional force in the second classification step are changed. ) Got.

Comparative Examples 1 to 3 Classification finished products (toners) according to Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 except that the low impact treatment was not performed under the conditions shown in Table 1.

Next, for each 100 parts by weight of the toner of each Example and Comparative Example,
Colloidal silica treated with amino silicone oil 0.
5 parts by weight was added and mixed by a mixer having a rotary blade to obtain a product toner, and this was used to perform drawing on a Canon copier NP3525.

The energy efficiency and investment efficiency in obtaining the toner according to each of the above Examples and Comparative Examples are shown in Table 2 and Table 3, respectively. Further, the results of drawing out are shown in Table-4.

As described above, according to the method of the present invention, it is understood that both energy efficiency and investment efficiency are significantly improved, and the quality is equivalent to that of the comparative example 2 which has been conventionally performed.

[Effect of the Invention] The present invention combines a low impact surface modification treatment step after a fine impact pulverization step with a high impact jet mill that does not particularly consider image quality.

Therefore, as a jet mill, it is possible to perform grinding with extremely high efficiency in terms of both processing capacity and energy efficiency per device. At the same time, with an inexpensive, low-power, low-impact device
By performing the processing for 0.01 seconds to 3 minutes, it is possible to increase the image density and properly control the toner consumption amount. Even with such a low impact device installed as a post process of the jet mill, the investment required to obtain the required production capacity and the energy efficiency are better than those of the conventional methods.

In addition, another great effect of the present invention is that, regardless of the crushing process, the process of this low-impact treatment matches the developing device to obtain higher density, toner consumption per image, and fogging. It is now possible to control.

[Brief description of drawings]

FIG. 1 is a flow chart of the present invention, FIG. 2 shows an example of high impact crushing means, FIG. 2- (a) shows its state diagram, and FIG. 2- (b) shows high impact crushing means. FIG. 3 shows an example of a collision plate of FIG. 3, FIG. 3 is a schematic cross-sectional view of a low impact treatment device by combining a rotor and a liner, and FIG. 4 is a diagram showing a positional relationship between the liner and the rotor of the device shown in FIG. FIG. 5 is a schematic cross-sectional view of a pin mill type low impact treatment device. 25 …… Accelerating pipe, 26, 26 ′ …… Collision plate 33 …… Liner, 35 …… Rotor 52 …… Pin, 59 …… Rotor

Claims (1)

[Claims] 1. A binder, a colorant, which is a raw material of a toner,
A toner for electrostatic charge development having a step of melting and kneading a charge control agent and the like to solidify by cooling, a step of finely pulverizing the kneaded product, and a classification step of classifying the finely ground particles to obtain a desired particle size distribution. In the manufacturing method, the finely pulverizing step is to perform high impact fine pulverization using a jet mill, and after this fine pulverizing step, a relatively lower impact than that during fine pulverization is applied to the toner for 0.01 seconds to 3 minutes. A method for producing a toner for electrostatic charge development, comprising a modification step.