JPH09197718A - Method of manufacturing toner for developing electrostatic latent image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly and finely disperse an offset preventive agent into a binder resin by re-kneading the agents after kneading in a kneading machine. SOLUTION: The specifically compounded materials are continuously charged into a hopper 1 of a kneading and cooling equipment, while these materials are melted in a cylinder-like kneading machine 3 heated on the outer side by a heater 2, the materials are kneaded. While the kneaded matter 5 is discharged by a screw 4, the kneaded matter is continuously rekneaded by two rolls 6. Cooling water is admitted through pipings 7 respectively into these rolls 6 and the cooling water after the admission therein is discharged through pipings 8. The resin pool 5a of the kneaded matter 5 is formed between the rolls 6 having an adequate spacing and, therefore, rekneading is well executed. The kneaded matter 5 transferred to a roller 10 is primarily crushed by a roller 13 having cutting blades 12 on the outer peripheral apart, is then subjected to secondary coarse pulverizing by a pulverizing machine 14 and in succession, finely pulverized by a jet grinding machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner for developing an electrostatic latent image, and more particularly to a toner for developing an electrostatic latent image in which a polyolefin as an anti-offset agent is uniformly and finely dispersed in a binder resin. The present invention relates to a toner manufacturing method.

[0002]

2. Description of the Related Art In general, a toner is a binder resin made of a molten thermoplastic resin, a colorant such as polyolefin or carbon black as an offset preventing agent, and a charge control for imparting a required triboelectric chargeability to the toner. It is produced by kneading and dispersing various compounding agents such as agent particles, cooling, finely pulverizing to a required particle size using a jet mill, and then classifying.

In order for a toner obtained by such a pulverization method to form a high quality copied image, it is necessary that the above-mentioned respective compounding agents are uniformly and finely dispersed in individual toner particles. When the compounding agent is not uniformly and finely dispersed in each toner particle, the toner has a wide charge distribution range, and
Particles consisting only of the compounding agent are unevenly distributed in the toner particles, and as a result, a copy image is fogged or lacks in stability, and filming of the photoconductor and contamination in the copying machine occur.

However, conventionally, even if the molten binder resin and the compounding agent are kneaded for a long period of time, it is still not easy to uniformly disperse the compounding agent in the binder resin, and the compounding agents are not individually dispersed. It was often non-uniformly dispersed in the toner particles.

By the way, there is a phenomenon in which a toner image transferred onto paper or the like is transferred to a heat roller in the fixing process. In order to prevent this phenomenon called offset, the fixing temperature of the binder resin (about 160 to 200 ° C.) It is generally performed to increase the melt viscosity and to add an offset preventive agent. The offset preventive agent is added to prevent transfer of toner to the heat roller and adhesion when the toner image transferred to paper or the like is fixed by applying heat and pressure simultaneously by a heat roller or the like.
Its function is to allow the offset preventing agent dispersed in the toner to seep to the toner surface by heat and pressure, and form a coating film having a releasing property on the heat roller on the toner surface. In order to exert such a function, it is desirable that the offset preventive agent quickly melts at the above temperature to have a low viscosity, and in order to quickly transfer to the toner surface, it has a small interaction with the binder resin. Is desirable.

As can be seen from the above, the melting behavior of the binder resin and the offset preventive agent are completely different, and the interaction is small, so it is very difficult to uniformly and finely disperse the offset preventive agent by kneading. . However, if the offset preventive agent is not well dispersed, problems such as image defects such as fog and filming may occur as described above.

Further, Japanese Patent Application Laid-Open No. 7-152205 discloses a kneading / cooling device for producing a toner for developing an electrostatic latent image as shown in FIGS. 3 and 4. In the figure, materials such as a binder resin, an offset preventive agent, and a colorant, which are fed from the raw material hopper 21, are mixed in a kneading machine 22.
After kneading, the kneaded material 23 is rolled by rolling rolls 24, 24 as shown in FIG.
Or the kneaded product 2 as shown in FIG.
3 is rolled by a cooling drum 26 and a rolling roll 24, then cooled by a cooling drum 26 and a cooling belt 25 ', and then pulverized and classified to produce an electrostatic latent image developing toner. And, in the same publication, since the kneaded material temperature immediately after passing through the rolling roll can be cooled to the softening temperature of the binder resin or less by having such a configuration, re-aggregation of the offset preventive agent can be made difficult to occur. Is listed.
However, this publication does not describe re-kneading for positively dispersing the compounding agent in the binder resin.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and its purpose is to achieve the above-mentioned various kinds of toners for producing electrostatic latent image developing toner. It is an object of the present invention to provide a method for producing a toner for developing an electrostatic latent image, which can solve the problem and disperse the offset preventive agent in the binder resin uniformly and finely.

[0009]

In order to achieve the above object, the present invention provides an offset preventive agent by re-kneading after kneading in a kneader in order to uniformly and finely disperse an anti-offset agent in a binder resin. It is characterized by further improving the dispersibility of the agent.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a material containing a binder resin, an offset preventive agent and a colorant is kneaded, cooled,
Then, in the method of producing a toner for electrostatic latent image development by pulverizing and then classifying, it is a method of kneading with a kneader, re-kneading with a roll, and then cooling. When the offset preventing agent is polyolefin, the viscosity of the binder resin at the re-kneading temperature is η _R , and the viscosity of the polyolefin is η _P , the condition of 0.2 ≦ η _R / η _P ≦ 20 is satisfied. Therefore, it is preferable to adjust the re-kneading temperature.
Further, when the re-kneading time is t, it is preferable to set the re-kneading time so that 3 seconds ≦ t ≦ 12 seconds. As this polyolefin, for example, polypropylene can be used.

According to the present invention, a material containing a binder resin, an offset preventing agent and a colorant is kneaded in a kneader and then re-kneaded with a roll so that the offset preventing agent is uniformly dispersed in the material. Can be dispersed in. In order to effectively carry out the re-kneading, the viscosity of the binder resin at the re-kneading temperature and the viscosity of the polyolefin as the offset preventing agent are important. Now, the re-kneading temperature T (120 ° C ≤
When the viscosity of the binder resin at T ≦ 160 ° C. is η _R and the viscosity of the polyolefin is η _P , then η _R / η _P >
If the viscosity condition is 20, the polyolefin melts during kneading, the binder resin and the polyolefin phase-separate macroscopically, and the polyolefin is not uniformly and finely dispersed in the binder resin. Therefore, it is preferable to adjust the re-kneading temperature so that η _R / η _P ≦ 20. On the other hand, η _R / η _P
If the viscosity conditions are such that <0.2, the viscosity of the binder resin becomes too low and the dispersibility of the binder resin and the compounding agent deteriorates. Therefore, it is preferable to adjust the re-kneading temperature so that 0.2 ≦ η _R / η _P.

Further, as a condition for effectively carrying out the re-kneading, the re-kneading time is also important. This is because, if the re-kneading time is t, if t <3 seconds, the re-kneading time is insufficient and the polyolefin cannot be uniformly dispersed in the binder resin, so t ≧ 3 seconds. Is preferred.
On the other hand, the longer the re-kneading time, the more the dispersibility of the polyolefin in the binder resin improves, but it is not preferable to extremely reduce the roll rotation speed from the viewpoint of productivity. Therefore, it is preferable to set t ≦ 12 seconds.

Further, the thickness h of the re-kneaded product immediately after passing the roll
With respect to the above, when the thickness of the re-kneaded product becomes too thick, re-expansion of the resin easily causes re-aggregation of the polyolefin, so that h ≦ 1.3 mm is preferable. On the other hand, if the thickness of the re-kneaded product is too thin, the re-kneaded product may be broken, so h ≧ 0.5 mm is preferable.

[0014]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. The materials having the formulations shown in the following Table 1 are continuously charged into the hopper 1 of the kneading / cooling device having the structure as shown in FIG. 1 (a), and the materials are cylindrically kneaded with the outside heated by the heater 2. Kneading was performed while melting in the machine 3. Then, the kneaded product 5 was continuously re-kneaded by the two rolls 6 while being discharged by the screw 4. As shown in FIG. 1B, cooling water is introduced into the rolls 6 and 6 through pipes 7 and 7, respectively, and the cooling water after the passage is discharged through the pipes 8 and 8. Further, as shown in FIG. 1B, since the resin reservoir 5a of the kneaded material 5 is formed between the rolls 6 having the proper gap, the re-kneading is performed well. Table 2 shows the re-kneading temperature, the viscosity of the kneaded product at the re-kneading temperature, the re-kneading time, and the thickness of the kneaded product after the re-kneading.
Table 2 shows the evaluation of the dispersibility of the polyolefin at the re-kneading temperature.

The material after re-kneading is placed on a belt 11 which continuously circulates between the rollers 9 and 10 and transferred to the roller 10. The kneaded material transferred to the roller 10 has a cutting blade on the outer peripheral portion. Roller 13 with 12 is used for primary coarse crushing, followed by secondary coarse crushing by crusher 14, followed by fine crushing by jet crusher (not shown), wind classifier (not shown). ), A powder having a particle diameter of about 5 to 20 μm was obtained. Next, 100 parts by weight of this powder and 0.3 part by weight of fine silicic acid powder were dry-mixed to obtain a toner. Further, this toner was mixed with a carrier (silicone-coated carrier) so that the toner concentration was 5% by weight to obtain a two-component toner. Table 2 shows the characteristics (contamination of carrier and occurrence of filming of photoconductor) when 100,000 sheets were copied by a commercial plain paper electrostatic copying machine using this two-component toner.

[0016]

[Table 1]

[0017]

[Table 2]

From Table 2, the following points are clear. Since the toners of Examples 1 and 2 have good dispersibility of polyolefin, the carrier was not contaminated and filming was not observed on the photoreceptor. However, in the toner of Comparative Example 1, since the binder resin has a low viscosity, the re-kneading time is short, and the thickness of the re-kneaded product is too thick, the dispersibility of the polyolefin is poor, and the carrier is contaminated and the photosensitive material is exposed. Filming occurred on the body.

Further, since the viscosity of the polyolefin of the toner of Comparative Example 2 was too low, the dispersibility of the polyolefin was poor, the carrier was contaminated, and filming occurred on the photoreceptor.

FIG. 2 shows an example in which the roll 15 and the roll 16 are interposed between the roll 6 and the roll 9 in FIG. 1 and re-kneading is performed by a so-called inverted L-shaped calender. The same effect as the case can be expected.

[0021]

According to the present invention, the offset preventive agent can be dispersed uniformly and finely in the binder resin, so that the carrier is not contaminated and filming does not occur on the photosensitive member. A duplicate image can be obtained.

[Brief description of drawings]

FIG. 1 (a) is a diagram showing a schematic configuration including a cross section of a kneading / cooling device suitable for carrying out a method for producing a toner for electrostatic latent image development of the present invention, and FIG. 1 (b) is a diagram It is an expansion perspective view of the roll 6 part of 1 (a).

FIG. 2 is a diagram showing a schematic configuration including a cross section of another kneading / cooling device suitable for carrying out the method for producing a toner for electrostatic latent image development of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional kneading / cooling device for carrying out a method for manufacturing a toner for developing an electrostatic latent image.

FIG. 4 is a schematic configuration diagram of another conventional kneading / cooling device for carrying out the method for manufacturing a toner for developing an electrostatic latent image.

[Explanation of symbols]

 3 ... Kneading machine 4 ... Screw 5 ... Kneading material 5a ... Resin pool 6 ... Roll

Claims (4)

[Claims] 1. A method for producing a toner for developing an electrostatic latent image by kneading a material containing a binder resin, an offset preventing agent and a colorant, cooling, pulverizing and then classifying the material, and kneading with a kneader. Then, a method for producing a toner for developing an electrostatic latent image, which comprises re-kneading with a roll and then cooling. 2. When the offset preventing agent is polyolefin, the viscosity of the binder resin at the re-kneading temperature is η _R , and the viscosity of the polyolefin is η _P , 0.2 ≦
The method for producing a toner for electrostatic latent image development according to claim 1, wherein the re-kneading temperature is adjusted so as to satisfy the condition of η _R / η _P ≦ 20. 3. When the offset preventing agent is polyolefin, the viscosity of the binder resin at the re-kneading temperature is η _R , and the viscosity of the polyolefin is η _P , 0.2 ≦
When the re-kneading temperature is adjusted so that the condition of η _R / η _P ≦ 20 is satisfied and the re-kneading time is t, 3
2. The method for producing a toner for developing an electrostatic latent image according to claim 1, wherein the re-kneading time is set so that seconds ≦ t ≦ 12 seconds. 4. The electrostatic latent image according to claim 1, wherein the thickness of the re-kneaded product immediately after passing the roll is h, 0.5 mm ≦ h ≦ 1.3 mm. Method for producing developing toner.