JPH0438123B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Purpose [Field of Industrial Application] The present invention relates to a plastic magnet roll, and is useful, for example, as a magnet roll for magnetic brush phenomenon. [Prior Art] Conventional examples of plastic magnet rolls are disclosed, for example, in JP-A-5-94940, JP-A-55-165606, and JP-A-56-108207. These are magnet rolls for copying machines, and have an integral structure in which a plastic magnet made of magnetic powder and a synthetic resin binder is formed around a metal shaft. [Problems to be solved by the invention] In conventional magnet rolls, the metal shaft and the plastic magnet have different thermal deformation rates, so the plastic magnet can crack due to temperature changes during manufacturing or use. There is a risk that the metal shaft may be deformed by the plastic molding pressure during manufacturing, and the residual stress may cause the molded magnet roll to warp, resulting in the following limitations. (i) Long rolls whose length is larger than their diameter cannot be manufactured by a manufacturing method that involves large temperature fluctuations, such as injection molding, and cannot be used in an environment with large temperature fluctuations. (ii) In order to make long rolls, it is necessary to reduce the mixing ratio of magnetic powder or use a synthetic resin with high ductility as the synthetic resin binder. However, this method has drawbacks such as a decrease in magnetic force and a decrease in heat resistance. In order to solve the above-mentioned problems, the inventor of the present invention created a mixture of a fibrous material whose surface has already been treated with a silane coupling agent, a magnetic powder whose surface has been treated with a silane coupling agent, and a synthetic resin binder. Completed a plastic magnet consisting of the following materials and filed an application (Japanese Patent Application Laid-Open Nos. 59-237306 and 237307).
However, as a result of further research on other coupling agents, the present invention was completed. The present invention provides a plastic magnet roll that has excellent resistance to temperature changes and has high processing accuracy. (B) Structure of the Invention This invention involves molding a mixture of a fibrous material whose surface has been treated with a coupling agent, a magnetic powder whose surface has been treated with a coupling agent, and a synthetic resin binder, and a molded product thereof. It has been experimentally found that the mechanical properties are further improved without compromising the magnetic properties. This makes it possible to integrally mold this mixture with a metal roll shaft to obtain a plastic magnet roll that does not cause cracks or cracks, and furthermore, it is possible to mold the entire mixture, including the roll shaft, from the same material. A feature of this invention is that it has made it possible to obtain a plastic magnet roll that is sufficiently usable. As the above-mentioned fibrous material, glass fiber is preferable from the point of view of cost, etc., but carbon fiber, aromatic polyamide fiber, whisker, etc. can also be used. As the magnetic powder, conventionally known magnetic powders can be used, and specific examples include barium ferrite, strontium ferrite, and lead ferrite. Examples of the coupling agent include silane coupling agents, aluminum coupling agents, titanate coupling agents, and zircoaluminate coupling agents. Coupling agents for surface-treating fibrous materials and coupling agents for surface-treating magnetic powders include combinations of the same type of coupling agents such as a titanate coupling agent, a titanate coupling agent, and a silane coupling agent and an aluminum coupling agent. There are different combinations of drugs. Specific examples of the synthetic resin binder include thermosetting resins such as phenolic resins, epoxy resins, and unsaturated polyester resins, thermoplastic resins such as polyamide resins, polyethylene resins, polyethylene terephthalate resins, ABC resins, and ethylene-vinyl acetate copolymers. Examples include resin. The preferred mixing ratio of the above fibrous substance, magnetic powder and synthetic resin binder is: - Fibrous substance: 0.5-12% by weight - Magnetic powder: 65-87% by weight - Synthetic resin binder: 12.5-23% by weight. The mixing ratio of magnetic powder is determined based on magnetic properties, workability, and mechanical strength. Moreover, if the mixing ratio of the fibrous material is larger than this, the magnetic properties will deteriorate, and if it is smaller than this, no reinforcing effect on mechanical strength will be recognized. When the above fibrous material is glass fiber, the cut length is 2 to 6 mm and the filament diameter is 5 to 20 μm.
m is preferable; if it deviates from these ranges, the reinforcing effect of the molded article will be reduced, and the dispersibility with the binder and the fluidity of the mixture during molding will be lost. In addition, the average particle diameter of the above magnetic powder is 0.5~
1.5 μm is preferred. This value was determined based on the orientation characteristics of the powder particles, the combined effect with the binder in terms of mechanical strength, and the wear of the mold during injection molding. The above-mentioned magnetic powder and fibrous material are surface-treated with a coupling agent before molding, which improves, in particular, (1) the dispersibility of the fibrous material and magnetic powder, and (2) the binder and the fibrous material. Improvements can be seen in the blending (kneading) properties with the magnetic powder and the magnetic powder, and (3) the bonding properties (mechanical strength) of the fibrous material with the binder and the magnetic powder. The production of the plastic magnet roll of this invention is as follows:
Made by injection molding. In other words, the roll shaft is inserted into the mold, or the roll shaft is integrated with the roll body, and a mixture of magnetic powder, fibrous material, and synthetic resin binder is heated and melted in the space. The molded product is then injection-filled, cooled, and then removed as a molded product. The plastic magnet roll is magnetized simultaneously with the molding by a magnetizing device provided in the molding die. It is known that the main cause of cracks in plastic magnet rolls is internal residual stress caused by inhibition of molding shrinkage of the plastic magnet due to the metal roll shaft. In the plastic magnet roll of the present invention constructed as described above, its mechanical strength is improved, and in particular, the shrinkage rate during molding and cooling is reduced. Table 1 shows plastic magnet rolls made of glass fiber surface-treated with an aluminum-based coupling agent according to the present invention, magnetic powder surface-treated with a silane-based coupling agent, and a synthetic resin binder, and a conventional one. An example of the shrinkage rate at time is shown.

[Table] Example 1 In FIG. 1a showing a longitudinal sectional view and FIG. It is inserted into the sleeve 4 and used for development. The roll body 2 is made of stainless steel and has a diameter of 17.6 mm and a length of 207 mm, and a roll shaft 3 that has a diameter of 6 mm and a shaft length of 256 mm.
The sleeve 4 is made of aluminum and has an inner diameter of 19.6 mm and an outer diameter of 21.6 mm. 5 and 6 are flanges attached to both ends of the sleeve 4, and 7 and 8 are metal bearings that support the roll shaft 3. The manufacturing method of this magnet roll 1 is to insert and fix the roll shaft 3 into a mold, and then combine 6.25% by weight of glass fibers and 6-nylon fibers treated with a coupling agent.
A mixture of 18.75% by weight and 75% by weight of barium ferrite with an average particle diameter of 0.9 μm treated with a coupling agent is injected and filled, simultaneously magnetized and molded. After cooling, the molded product is taken out from the mold, its dimensions are corrected, and it is mounted in the sleeve 4. In this case, if the axial warpage of the magnet roll is less than 0.3 mm, it will be difficult to install and a load will be applied to the rotation of the magnet roll, so it will be considered defective. In this example, coupling agents for ferrite treatment and glass fiber treatment were combined as shown in Table 2, and a total of 80 magnet rolls, 10 of each combination, were manufactured. It was not seen in all of them. Moreover, the warpage in the axial direction was kept within 0.3 mm, and all of them were installed in Sleeve 4 without modification.

[Table] Example 2 In the longitudinal cross-sectional view shown in FIG. 2, reference numeral 11 is a long magnet roll according to another example of the present invention, which is a roll used for recovering toner during electrostatic copying. The roll body 12 has a diameter of 14 mm and a length of 440 mm.
The roll shafts 13 and 14 have a diameter of 6 mm and a shaft length of 15 mm.
It is. The roll body 12 and the roll shafts 13 and 14 are integrally molded and made of 9% by weight glass fiber treated with a coupling agent and 21% by weight 6-nylon.
and 70% by weight of barium ferrite with an average particle diameter of 1.0 μm treated with a coupling agent. The manufacturing method of this magnet roll 11 involves heating and melting the mixture of barium ferrite, glass fiber, and nylon at 270°C, injecting and filling the mixture into a mold that can obtain the finished dimensions of each part described above, and simultaneously depositing the mixture. It is magnetic. In this way, 80 magnet rolls were manufactured in the same manner as in Example 1, but no cracks or cracks were observed in all of them. On the other hand, if a roll with a conventional metal penetrating shaft is manufactured using a conventional material, in the dimensional relationship of the above embodiment, if the length of the roll body 12 exceeds 200 mm, the roll body Several circumferential cracks were observed in the part. For the 80 magnetic rolls, coupling agents for ferrite treatment and glass fiber treatment were combined as shown in Table 3, and 10 of each combination were manufactured. Inspect all items after manufacturing,
The mechanical properties of the treatment coupling agent combinations are shown in Table 4 as average values. According to this, it is shown that the combinations of magnet rolls No. 1 to No. 3, No. 6, and No. 7 are preferable in terms of bending elastic modulus and the like.

[Table] (C) Effects of the Invention The plastic magnet roll of the present invention is made by mixing a synthetic resin binder, a fibrous material and a magnetic powder each treated with a coupling agent, and forming an integral structure with a metal roll shaft. The entire roll shaft, including the roll shaft, is integrally molded from the same material. Therefore, the shrinkage rate during molding is reduced and the mechanical strength after molding is improved, so that cracks and cracks are prevented from occurring. Furthermore, the magnetic powder and the fibrous material are each
Since the particle surface is treated with a coupling agent and the adhering moisture is removed, the occurrence of conventional cracks and cracks caused by gasification of moisture is also prevented. In addition, treatment with a coupling agent improves the physical properties of the magnetic powder surface and the fibrous material surface, and makes it possible to control the viscosity and plasticity of the binder, thereby improving processability and moldability. A magnet roll that is physically and magnetically balanced can be obtained. In particular, when the entire product including the roll shaft is integrally molded, the amount of plastic magnet increases by the volume occupied by the conventional through shaft, which means that the magnetic force is stronger than before.
It is also advantageous that the dimensional accuracy of the magnet roll is improved and its weight is reduced.

[Brief explanation of drawings]

1A and 1B are a longitudinal sectional view and a transverse sectional view showing one embodiment of the invention, and FIG. 2 is a longitudinal sectional view showing another embodiment of the invention. 1,11...Plastic magnet roll, 2,1
2...Roll body, 3...Metal roll shaft, 1
3,14...Roll axis.

Claims (1)

[Claims] 1. A plastic magnet made of a fibrous material and magnetic powder surface-treated with a coupling agent and a synthetic resin binder is formed around the roll shaft,
A plastic magnet roll characterized by its integral structure. 2. The plastic magnet roll according to claim 1, wherein the roll shaft is a metal shaft. 3. The plastic magnet roll according to claim 1, wherein the roll shaft is made of the same material as the plastic magnet and integrally formed with the plastic magnet. 4. Any one of claims 1 to 3, wherein the coupling agent for treating the fibrous material is any one of a silane coupling agent, an aluminum coupling agent, a titanate coupling agent, and a zircoaluminate coupling agent. Plastic magnet rolls listed in. 5. Any one of claims 1 to 4, wherein the coupling agent for treating the magnetic powder is any one of a silane coupling agent, an aluminum coupling agent, a titanate coupling agent, and a zircoaluminate coupling agent. Plastic magnet roll as described.