JP2001110620A - Composition for resin magnet and resin magnet molded object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for a resin magnet which is superior in fluidity in melting and can maintains satisfactory melting fluidity, when the fill of magnetic powder is increased and realize high magnetization of a molded object without lowering molding workability. SOLUTION: In a composition for a resin magnet which is formed by dispersing and mixing magnetic powder into resin binder, the resin binder contains a main material resin, composed of thermoplastic resin and polymerized fatty acid based polyamide elastomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is obtained by mixing and dispersing magnetic powder in a resin binder, and is suitably used as a molding material for a resin magnet molding such as a magnet roller used in an electrophotographic apparatus or an electrostatic recording apparatus. Resin magnet composition,
And a resin magnet molded product obtained by molding the resin magnet composition into a desired shape.

[0002]

2. Description of the Related Art Conventionally, as a developing roller for visualizing an electrostatic latent image on a latent image holding member such as a photosensitive drum, in an electrophotographic apparatus such as a copying machine or a printer or an electrostatic recording apparatus.
A so-called jumping phenomenon, in which a magnet roller formed of a resin magnet is provided in a rotating sleeve, and a magnetic developer (toner) carried on the surface of the sleeve flies onto the latent image holding member by the magnetic force characteristics of the magnet roller, There is known a developing method for supplying a toner to the surface of a latent image holding member to visualize an electrostatic latent image.

Conventionally, the above-mentioned magnet roller is prepared by injection molding or extrusion molding of a composition for a synthetic resin magnet in which a magnetic powder is mixed with a binder of a thermoplastic resin using a mold having a magnetic field formed around the composition. It is manufactured by forming it into a roller shape and magnetizing it to desired magnetic properties.

Further, with the recent development of electrophotographic apparatuses and the like, there is a tendency that a more complicated magnetic force pattern is required for the magnet roller. A desired magnetic force pattern is also formed by molding a plurality of magnet pieces with magnetized magnetic poles from the above-described resin magnet composition and bonding them around the shaft.

[0005] Further, resin magnets are widely used not only for the above-mentioned magnet roller but also for various uses. In particular, in electric and electronic devices, they are used for various uses as one of precision parts.

[0006]

The above-mentioned magnet roller and other resin magnets are prepared by mixing magnetic powder such as ferrite or rare earth magnet with polyamide resin such as polyamide-6, polyamide-12, polyphenylene sulfide, ethylene-ethyl acrylate copolymer or the like. It is manufactured by molding a synthetic resin magnet composition kneaded and dispersed in a synthetic resin into a desired shape.However, in the above-described magnet rollers and resin magnets for electric / electronic devices requiring high dimensional accuracy, At present, satisfactory dimensional accuracy is not always obtained.

[0007] In other words, magnet rollers used in electrophotographic equipment and electrostatic recording devices and resin magnets used in other electric and electronic equipment are required to have extremely strict quality with respect to dimensional accuracy and dimensional environmental changes. When molding the resin magnet composition to obtain a resin magnet such as a magnet roller, sufficient dimensional accuracy cannot be obtained due to shrinkage of the resin after molding, or even when good dimensional accuracy is obtained during molding. There is a problem that expansion or warpage occurs due to moisture absorption or the like depending on the use environment, and dimensional accuracy is reduced.

The present invention has been made in view of the above circumstances, and it is possible to prevent a decrease in dimensional accuracy due to shrinkage after molding as much as possible, and to effectively prevent the occurrence of expansion and warpage due to environmental changes. It is an object of the present invention to provide a resin magnet composition capable of reliably obtaining a resin magnet molded article having excellent dimensional accuracy, and a resin magnet molded article obtained by molding the resin magnet composition.

[0009]

Means for Solving the Problems and Embodiments of the Invention In order to achieve the above object, the present inventor first studied the root cause of the decrease in dimensional accuracy and obtained the following findings. (1) When a crystalline resin such as polyamide or polyolefin is used as the binder resin, the crystallization of the binder resin rapidly proceeds upon cooling after molding, and the shrinkage or sink occurs, or the molded product is warped. Often do. (2) When a hygroscopic resin such as polyamide is used as the binder resin, the molded product may expand due to moisture absorption depending on the environment in which the molded product is used as a final product, resulting in dimensional defects.

Accordingly, the present inventors have further studied to solve these problems, and as a result, it has been found that an appropriate amount of an ultrafine powder inorganic filler having an average particle diameter of 1 μm or less is added to a binder resin separately from magnetic powder. Thereby, in the cooling step after molding, crystallization of the binder resin is delayed or inhibited, shrinkage can be suppressed, dimensional accuracy can be improved, and permeation of water molecules in the composition is suppressed, and moisture absorption is suppressed. The dimensional change can be suppressed at the same time, and the above-mentioned disadvantages relating to the dimensional accuracy can be effectively solved, and a resin magnet molded article having good dimensional accuracy and capable of maintaining the same can be obtained reliably. To complete the present invention.

Therefore, the present invention is characterized in that a composition for a resin magnet obtained by dispersing and mixing magnetic powder in a resin binder contains an ultrafine inorganic filler having an average particle size of 1 μm or less, in addition to the magnetic powder. And a resin magnet molded product obtained by molding the resin magnet composition into a desired shape.

Hereinafter, the present invention will be described in more detail.
As described above, the resin magnet composition of the present invention is obtained by adding an ultrafine powder inorganic filler to a binder resin in addition to a magnetic powder.

As the binder resin, a resin which is conventionally known as a binder resin for a resin magnet can be used, for example, polyamide resin (polyamide-6, polyamide-12, etc.), polystyrene resin, polyethylene terephthalate resin (PET). , Polybutylene terephthalate resin (PBT), polyphenylene sulfide resin (PPS), ethylene-vinyl acetate copolymer resin (E
VA), ethylene ethyl acrylate resin (EEA),
Polyolefins such as epoxy resin, ethylene-vinyl alcohol copolymer resin (EVOH), polypropylene resin (PP), polyethylene, and polyethylene copolymer;
Modified polyolefins in which a reactive functional group such as a maleic anhydride group, a carboxyl group, a hydroxyl group, or a glycidyl group is introduced into the structure of these polyolefins are exemplified, and one or more of these may be used in combination. be able to. Although not particularly limited, the effect of the present invention is remarkable when a crystalline resin such as polyamide or polyolefin is used as the binder resin,
In particular, polyamide has a remarkable effect of suppressing dimensional change due to moisture absorption because it also has moisture absorbency.

The amount of the binder resin is not particularly limited, but may be from 5 to 5 parts of the entire resin magnet composition.
It is preferably about 0% by weight, particularly preferably 7 to 20% by weight. If the compounding amount of the binder resin is less than 5% by weight, there may be a problem in molding processing, and the mechanical strength of the molded product may be insufficient. On the other hand, if it exceeds 50% by weight, the filling amount of the magnetic powder may be insufficient and the magnetic properties may be insufficient.

Next, as the magnetic powder mixed and dispersed in the binder resin, a known magnetic powder conventionally used as a magnetic powder in a resin magnet can be used. Ferrite powder such as Ba ferrite, Sm-Co alloy, Sm-Fe-N alloy, Nd-
Rare earth alloy powders such as Fe-B alloy and Ce-Co alloy can be exemplified.

The magnetic powder used in the present invention is not particularly limited, but has an average particle size of 0.5 to 200.
μm, particularly preferably about 1 to 100 μm.

The above-mentioned magnetic powder can be subjected to a known pretreatment if necessary, and blended into the resin magnet composition. In this case, although not particularly limited, it is preferable to perform the coupling treatment using a known coupling agent such as a silane coupling agent or a titanate-based coupling agent, and the coupling treatment is performed. By using the magnetic powder, the melt fluidity of the composition can be effectively improved.

As the silane coupling agent, γ-
Aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ
-Aminopropyltrimethoxysilane, ureidopropyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane And γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane Etc. are particularly preferably used.

Examples of the titanate-based coupling agent include isopropyl bis (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl / aminoethyl) titanate, isopropyl triisostearoyl titanate, and diisopropyl bis (dioctyl pyrophosphate) titanate. , Tetraisopropylbis (dioctylphosphite) titanate, tetraoctylbis (ditridecylphosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, bis (dioctylpyrophosphate) Oxyacetate titanate, bis (dioctylpyrophosphate) ethylene titanate and the like are listed. Phosphate) titanate is particularly preferably used.

The amount of the magnetic powder is appropriately selected according to the strength of the magnetic force required for the desired molded product, and is not particularly limited.
It can be 0-95% by weight, especially 80-93% by weight.

The resin magnet composition of the present invention is obtained by mixing and dispersing the above magnetic powder in the above binder resin. In the present invention, the average particle size is reduced in order to prevent shrinkage after molding and decrease in dimensional accuracy due to moisture absorption. An appropriate amount of an ultrafine powdered inorganic filler having a diameter of 1 μm or less is added.

The ultrafine inorganic filler may be an inorganic filler having an average particle size of 1 μm or less, and more specifically, a particle size of 1 μm or less as observed by a SEM photograph. Examples of this inorganic filler include synthetic silicate fillers such as synthetic aluminum silicate and synthetic calcium silicate; natural silicate fillers such as kaolin, clay, pyrophyllite, bentonite, sericite, and layered mica; silicic acid, aluminum hydrate , Barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, metal oxides, inorganic fibers, non-oxide whiskers such as silicon carbonate and silicon nitride, Zn
Metal oxide whiskers such as O, MgO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , potassium titanate, barium titanate,
Whiskers such as double oxide whiskers such as aluminum borate; and other mica, metal powder, carbon, glass and the like. In addition, although it is not particularly limited, among these, a silicate filler is particularly preferably used from the viewpoint that ultrafineness is possible.

The ultrafine inorganic filler has an average particle size of 1 μm or less, as described above, but more preferably has an average particle size of 0.5 μm or less, and particularly preferably has a mean particle size of 0.01 to 0.1 μm.
It is preferably 3 μm.

The method of finely dispersing the ultrafine inorganic filler in the composition for resin magnets is not particularly limited.
A filler that is mechanically pulverized and added, or a filler such as a silicate filler that cleaves itself and becomes finer, is allowed to coexist with the binder resin during the preparation of the binder resin. A method such as dispersing is appropriately adopted.

The amount of the ultrafine powder inorganic filler is not particularly limited, and an appropriate amount may be added as necessary. However, the amount is usually 0.1% depending on the amount of the magnetic powder and the amount of the binder resin.
It is preferably in the range of 1 to 10% by weight, particularly 0.5 to 5% by weight.

The composition for a resin magnet of the present invention contains the above binder resin, magnetic powder and ultrafine powder inorganic filler, and further disperses the above magnetic powder and ultrafine powder inorganic filler as necessary. , A suitable amount of a dispersant, a lubricant, a plasticizer and the like can be added.

As the above-mentioned dispersant, a phenol-based or amine-based dispersant can be used. As the above-mentioned lubricant, waxes such as paraffin wax and microsterin wax, fatty acids such as stearic acid and oleic acid, and the like can be used. These metal salts (calcium stearate, zinc stearate, etc.) are preferably used, and as the plasticizer, a monoester or polyester plasticizer, an epoxy plasticizer and the like are suitably used.

Further, a filler having a large reinforcing effect such as mica, whisker or talc, carbon fiber, glass fiber or the like is appropriately added to the composition for a resin magnet of the present invention as long as the object of the present invention is not hindered. Can be. That is, when the magnetic force required for the molded product is relatively low and the filling amount of the magnetic powder is relatively small, the rigidity of the molded product is likely to be low. In such a case, mica or A molded product can be reinforced by adding a filler such as whisker. In this case, the filler preferably used in the present invention is preferably mica or whisker, and the whisker is a non-oxide whisker made of silicon carbide, silicon nitride or the like, or Zn.
Metal oxide whiskers made of O, MgO, TiO ₂ , SnO ₂ , Al ₂ O _{3 and the} like, and double oxide whiskers made of potassium titanate, aluminum borate, basic magnesium sulfate, etc., are exemplified. Among them, double oxide whiskers are particularly preferably used because they can be easily combined with plastic.

The amount of the filler used is not particularly limited, but is usually about 1 to 10% by weight, and particularly about 2 to 5% by weight of the whole composition for resin magnets. These fillers are added as components completely different from the ultrafine powder inorganic filler.

Further, additives other than the above-mentioned magnetic powder dispersant, lubricant, plasticizer and filler may be added to the resin magnet composition of the present invention without departing from the object of the present invention. For example, an organic tin-based stabilizer or the like can be added in an appropriate amount as needed.

The resin magnet molded article of the present invention is formed by using the resin magnet composition of the present invention.
As a result, a decrease in dimensional accuracy due to shrinkage or moisture absorption after molding is prevented as much as possible, and a resin magnet molded product having good dimensional accuracy can be obtained.

In order to obtain the resin magnet molded product of the present invention, the above-described resin magnet composition of the present invention may be kneaded and melted and molded. Accordingly, an appropriate molding method such as an injection molding method, an extrusion molding method, a compression molding method, or the like can be employed.

The resin magnet molded article of the present invention is not particularly limited. However, since particularly high dimensional accuracy is required, a magnet roller used in an electrophotographic apparatus or an electrostatic recording apparatus, an electric / electronic It is suitably used as a motor magnet or the like used in equipment.

Here, when the magnet roller is made of the resin magnet molded product of the present invention, the magnet roller usually has a structure in which a roller body made of a resin magnet and shaft portions protruding from both ends of the roller body are provided. However, in this case, a shaft made of metal or the like may be set in a mold, and the roller body may be molded around the outer periphery with the resin magnet composition. The composition may be integrally molded. Furthermore, when high and complicated magnetic properties are required, a plurality of resin magnet pieces are formed using the resin magnet composition, and these are bonded to the outer periphery of a shaft made of metal or the like to form a roller body. May be. The magnetization may be performed simultaneously with molding by forming a magnetic field around the mold, or may be performed using a known magnetizing machine after molding.

[0035]

According to the composition for a resin magnet of the present invention, by adding an appropriate amount of the above ultrafine powder inorganic filler in addition to the magnetic powder, it is possible to reduce the dimensional accuracy due to shrinkage after molding and moisture absorption. Thus, it is possible to obtain a resin magnet having excellent dimensional accuracy, and capable of maintaining excellent dimensional accuracy for a long period of time.

[0036]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples] 18 kg of anisotropic Sr ferrite (“NF110” manufactured by Nippon Benzai Co., Ltd.) was used as a silane coupling agent (“A1160” manufactured by Nippon Yunika Co., Ltd.) 180
The resulting powder was stirred with a high-speed mixer and surface-treated to prepare a magnetic powder. This magnetic powder was added to 2.455 kg of polyamide-6 (“M1015D” manufactured by Unitika Ltd., molecular weight: about 10,000) in which 2.5% by weight of a silicate filler (layered silicate) having an average particle diameter of 0.1 μm was dispersed. And kneading machine (2
(A shaft kneader) and pelletized to obtain a pellet-shaped composition for a synthetic resin magnet.

The obtained composition for a synthetic resin magnet was molded into a desired shape while applying a magnetic field by an injection molding machine, and was magnetized to obtain a molded resin magnet. When the magnetic force of the obtained resin magnet molded product was measured, the residual magnetic flux density Br = 0.28
45T, maximum energy product (BH) max = 16.1k
J / m ³ .

Further, the composition for a resin magnet was prepared at 25 ° C./5
When the change in water absorption under 5% RH was evaluated, it was as shown in FIG. Further, when the above resin magnet molded product was left under high temperature and high humidity (40 ° C./90% RH), the state of dimensional change due to moisture absorption was examined.

COMPARATIVE EXAMPLE The procedure of Example 6 was repeated except that polyamide-6 containing no silicate filler ("M1015D" manufactured by Unitika Ltd., molecular weight: about 10,000) was used in place of polyamide-6 containing silicate filler. A pellet-shaped composition for a synthetic resin magnet was obtained in the same manner as in the example. Using the obtained composition for a synthetic resin magnet, a resin magnet molded product was molded in the same manner as in the example, and the magnetic force after magnetization was measured. The residual magnetic flux density Br = 0.2571T, and the maximum energy product (BH ) Max = 13.2 kJ / m ³ , which was slightly inferior in magnetic force characteristics.

In the same manner as in the example, the change in the water absorption of the composition for resin magnet at 25 ° C./55% RH was evaluated. The result was as shown in FIG. Further, in the same manner as in the example, the above resin magnet molded product was heated under high temperature and high humidity (40 ° C./9
When the state of dimensional change due to moisture absorption when left at 0% RH) was examined, it was as shown in FIG.

As described above, the resin magnet molded product obtained from the synthetic resin magnet composition of the embodiment according to the present invention has good magnetic force characteristics, and is shown in FIGS. Furthermore, the composition for a synthetic resin magnet of the example in which a silicate filler was added and dispersed was less likely to absorb moisture than the composition of the comparative example containing no silicate filler (FIG. 1), and the dimensional change due to moisture absorption was small. (FIG. 2).

[Brief description of the drawings]

FIG. 1 is a graph showing the hygroscopicity of the synthetic resin magnet compositions prepared in Examples and Comparative Examples.

FIG. 2 is a graph showing a dimensional change accompanying moisture absorption of a resin magnet molded product obtained from the synthetic resin magnet compositions prepared in Examples and Comparative Examples.

Claims (5)

[Claims] 1. A resin magnet composition obtained by dispersing and mixing magnetic powder in a resin binder, characterized by containing, in addition to the magnetic powder, an ultrafine powder inorganic filler having an average particle size of 1 μm or less. Composition. 2. The resin magnet composition according to claim 1, wherein the ultrafine inorganic filler is a silicate filler. 3. The resin magnet composition according to claim 1, wherein the amount of the ultrafine powder inorganic filler is 0.1 to 10% by weight of the whole composition. 4. A resin magnet molded product obtained by molding the resin magnet composition according to claim 1 into a desired shape. 5. The resin magnet molded product according to claim 4, which is a magnet roller used for a developing operation in an electrophotographic process.