JPH0439763B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Purpose [Field of Industrial Application] The present invention relates to a plastic magnet roll having a metal shaft, and is useful, for example, as a magnet roll for magnetic brush development. [Prior Art] Conventional examples of plastic magnet rolls are disclosed, for example, in JP-A-53-94940, 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 may crack or break due to temperature changes during manufacturing or use. As a result, the following restrictions apply. (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. The present invention provides a plastic magnet roll with excellent resistance to temperature fluctuations. (B) Structure of the Invention The present invention is for molding a mixture of a fibrous material whose surface has 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. It was experimentally found that the mechanical properties of the molded articles were significantly improved without compromising the magnetic properties. Therefore, it is a feature of the present invention that this mixture is integrally molded with a metal roll shaft, thereby making it possible to obtain a plastic magnet roll that is free from cracks and cracks. 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. Before molding, the magnetic powder and fibrous material are each surface-treated with a silane coupling agent as follows. In other words, 0.2 to 2.0% by weight of the silane coupling agent based on the magnetic powder or fibrous material is mixed with 2 to 5 times the amount of water or an aqueous alcohol solution (water/alcohol ratio 1/9) until completely dispersed. , this is added to magnetic powder or fibrous material and thoroughly stirred and mixed, then 100 to 150
Dry for 1 hour at ℃. Through this treatment, the surfaces of the magnetic powder and fibrous material are treated to form a monomolecular film. The silane coupling agents include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane,
Vinyl silanes such as vinyltris(β-methoxyethoxy)silane, vinyltriacetoxysilane,
Methacryloxysilanes such as γ-methacryloxypropyltrimethoxysilane, epoxysilanes such as β-(3,4 epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, N-β(aminoethyl )
γ-aminopropyltrimethoxysilane, N-β
(Aminoethyl) Aminosilanes such as γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, mercaptosilanes such as γ-mercaptopropyltrimethoxysilane, etc. Can be mentioned. Specific examples of the synthetic resin binder include thermosetting resins such as phenol resins, epoxy resins, and unsaturated polyester resins, thermoplastic resins such as polyamide resins, polyethylene resins, polyethylene terephthalate resins, ABS 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. Furthermore, 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-mentioned fibrous material is glass fiber, the cut length is 2 to 6 mm, and the filament diameter is 5 to 6 mm.
A thickness of 20 μm is preferable, and if it is outside this range, 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. Furthermore, in the above surface treatment, the silane coupling agent was selected from among the various coupling agents because of (1) dispersibility of the fibrous material and magnetic powder, and (2) the relationship between the binder, the fibrous material, and the magnetic powder. This is because the most significant effects were observed in blending (kneading) properties, and (3) bonding properties (mechanical strength) between the binder and the fibrous material and magnetic powder. The production of the plastic magnetic roll of this invention is as follows:
Made by injection molding. That is, a roll shaft is inserted into a mold, and a mixture of magnetic powder, fibrous material, and synthetic resin binder is heated and melted and injected into the space, and after cooling, it is taken out as a molded product. The plastic magnet roll is magnetized by a magnetizing magnetic field provided in the mold.
This is done at the same time as molding. 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 an example of the shrinkage rate during molding and cooling of the plastic magnet roll according to the present invention and the conventional one.

〔Example〕

In the longitudinal cross-sectional view shown in FIG. 1a and the front view shown in FIG. Roll shaft 2 has a diameter of 6 mm and a length
Made of 236.7mm stainless steel. A roll body 3 is formed around the roll shaft 2. The roll body 3 is made of glass-reinforced nylon containing 30% by weight of glass fibers treated with a silane coupling agent.
A1030GFL (manufactured by Nippon Unicar Co., Ltd.) 25% by weight (i.e., 7.5% by weight of glass fiber treated with a silane coupling agent and 17.5% by weight of nylon) is used as a binder, and the silane coupling agent A-1100 (manufactured by Nippon Unicar Co., Ltd.) is used as a binder. Contains 75% by weight of barium ferrite with a particle size of 1.2 μm and an outer diameter of 17.6
mm, length is 207mm. The manufacturing method for this magnet roll 1 involves inserting the roll shaft 2 into a mold that has a finished outer diameter of 17.6 mm and a finished length of 207 mm, and then inserting the above-mentioned mixture of barium ferrite and glass-reinforced nylon into the mold.
It is heated to melt at ℃ and then injected and filled into a mold. According to this, the roll main body 3 did not have any cracks or cracks. At this time, if only nylon containing no glass fibers is used as the binder, and if either or both of the glass fibers and barium ferrite are not treated with a silane coupling agent, the roll body 3 will have a circular shape. A circumferential crack and a shaft crack occurred. (c) Effects of the Invention The plastic magnet roll of the present invention is formed by mixing a synthetic resin binder with a fibrous material and magnetic powder each treated with a silane coupling agent, and molding the mixture into an integral structure with a metal roll shaft. It is. Therefore, the synthetic resin binder is modified,
Since the shrinkage rate during molding is significantly reduced and the mechanical strength after molding is improved, 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.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, with FIG. 1a being a side sectional view and FIG. 1b being a front view. 1... Magnet roll, 2... Roll shaft, 3... Roll body.

Claims (1)

[Claims] 1. A mixture of (a) a fibrous material whose surface is treated with a silane coupling agent, (b) a magnetic powder whose surface is treated with a silane coupling agent, and (c) a synthetic resin binder is made of metal. A plastic magnet roll characterized by being formed around a roll axis. 2 The mixture contains 0.5 to 12% by weight of fibrous material, 65 to 87% by weight of magnetic powder, and 12.5 to 23% of synthetic resin binder.
% by weight of a plastic magnet roll according to claim 1. 3. The plastic magnet roll according to claim 1, wherein the fibrous material is glass fiber having a cut length of 2 to 6 mm and a filament diameter of 5 to 20 μm.