JPS5980902A - Manufacture of bond magnet - Google Patents

Abstract

PURPOSE:To obtain an isotropic bond magnet easily by a simple equipment by a method wherein a magnetic field such as a pulse magnetic field or a static magnetic field is applied to a magnetized surface to give an isotropic property and after solidification or hardening, magnetization to the same direction as the isotropic property has been given is performed. CONSTITUTION:Magnetic particles and binder and coupling material or the like added when necessary are mixed and kneaded at the temperature not less than the softening point or the melting point of the binder and after being cooled, pulverized and peletized or granuled compound is obtained. The compound is supplied into a hopper 1 and mixed and kneaded and compressed by a kneader screw 2 and cut by a shredder 3 and extruded by an auger 6 through a tapered borrel 7 and a die 8. The extruded body is cut to a prescribed length at an outlet of the die. Reduction ratio at the extrusion is expressed by the ratio So/S of the area So of the auger and the area S of the outlet of the die. The suitable ratio is 3-100 and especially a range of 20-70 is desirable. When the reduction ratio is too small, it is difficult to obtain a uniform extruded body and when the reduction ratio is too large, cracking is easy to be produced when the extruded body is formed. The extruded body is treated by a process such as hardening by heating, hardening by radiation, solidification by cooling or application of a magnetic field and then magnetized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing ferrite magnets used in electronic copying machines, two-rotation audio equipment, and the like.

As methods for molding bonded magnets such as plastic magnets and rubber magnets used in small DC motors, magnet rotating machines, etc., injection molding, compression molding, and extrusion molding are usually used. Among these molding methods, in order to obtain an anisotropic bonded magnet with particularly high magnetic properties, magnetic field molding is performed, in which a kneaded material composed of a modifying grain, a lubricant, etc. is heated and compressed in a magnetic field. In addition, testing of injection molding in a magnetic field has recently begun, and disk-shaped anisotropic plastic magnets have been produced.

The extrusion molding method is applied to the production of cylindrical or plate-shaped rubber magnets and plastic magnets used in small motors and the like. Further, JP-A-49-75536 discloses that a long cylindrical ferrite magnet for a magnet roll is formed by extrusion molding.

Among the various molding methods mentioned above, the extrusion molding method has high molding efficiency, does not require a mold with a complicated structure like the injection molding method, and can be continuously molded every month, which greatly improves production and efficiency. In addition, anisotropy is imparted during extrusion molding, which can be expected to improve magnetic properties, but this is not sufficient to satisfactorily overcome the properties of an anisotropic ferrite bonded magnet. Therefore, as a method to strengthen the anisotropy in extrusion molding, extrusion molding in a magnetic field is generally used.
7'1\, Japanese Patent Publication No. 47-34192, for sintered magnets, proposals have been made to use a special nozzle in addition to applying a magnetic field. In order to obtain an anisotropic bonded magnet by extrusion molding in this way, molding in a magnetic field is generally used, but the applied external magnetic field becomes a resistance during extrusion molding. In order to strengthen the anisotropy,
When the external magnetic field is strengthened, particularly in screw-type continuous extruders, auger slippage occurs, often making molding difficult or impossible. Furthermore, the magnetic field device itself becomes larger and larger.

An object of the present invention is to provide a manufacturing method that allows anisotropic bonded magnets to be easily obtained by extrusion molding using a simple device.

The method for manufacturing a bonded magnet of the present invention includes magnet plumbite type magnetic particles as a main component, a binder as necessary,
In a method for producing a bonded magnet, the method comprises extrusion molding a kneaded material containing a surface modifying material and a particulate additive, and solidifying or hardening the obtained molded product using an appropriate method such as heat treatment or radiation treatment. , Applying a magnetic field such as a pulsed magnetic field or a static magnetic field to the magnetized surface of the molded body to impart -C anisotropy, and then, after solidification or hardening, magnetizing in the same direction as the direction in which the anisotropy is imparted. It is characterized by

Hereinafter, the details of the present invention will be explained based on the drawings.

FIG. 1 shows a schematic sectional view of a screw type extrusion molding machine. The screw and auger sections, respectively indicated by 2 and 6 in the figure, are made of Jawood on the outside and can be heated with oil. First, magnetic plumbite type particles are prepared as a raw material, but if the particle size of the particles is small, the particle filling rate with respect to the binder will decrease, while if the particle size becomes large, the particles will form a multi-domain, so the coercive force r l-10 decreases rapidly. The average particle size of the particles is preferably in the range of about 0.7 to 1.9 μm. Further, if dislocations, defects, etc. are present in the particles, the magnetic properties will deteriorate, so it is necessary to use particles annealed at about 800° C. to 1100° C. The binders used include polyamide resins, phenolic resins, tyrene-vinyl acetate copolymer resins, polypropylene, polyamideimide, polystyrene, polyphenylene-1-nulphide, and rubber-based polymers, chloroprene-butadiene, chlorosulfonated polyethylene, and nitrile. Various polymers such as rubber and acrylic rubber are known and used. Furthermore, in order to improve the wettability between the magnetic particles and the binder, coupling agents such as organosilicon compounds (JP-A-52-28696) and organic titanium compounds (JP-A-5E-AS3O4) can be added. , resulting in improved impact resistance and chipping resistance. Furthermore, toluene sulfonic acid amide (Japanese Patent Application Laid-Open No. 1989-1999) was added for the purpose of increasing particle orientation, that is, anisotropy, by reducing friction between magnetic particles.
152198), stearic acid metal salts (Japanese Patent Application Laid-Open No. 1983-1989-
91803) etc. may be added. The ratio of the solid powder containing magnetic powder to the binder varies depending on the type of binder and the particle size of the powder, but is powder/binder -70 to 9.
Approximately 0 wt% is desirable. When the amount of binder is 30 wt% or more, although anisotropy is promoted, the absolute amount of magnetic particles is small, and as a result, the C magnetic force is reduced. On the other hand, if the binder amount is 90 wt% or more, extrusion molding itself becomes difficult, and anisotropy itself becomes difficult because the resistance between powder particles becomes large. The above-mentioned magnetic particles and binder, as well as a coupling material added as necessary, etc., are placed in a pressure heating kneader (for example, Moriyama Seisakusho D 3-7.5 type, etc.).
By doing this, the mixture is sufficiently mixed at a temperature above the softening point or melting point of the binder, and after cooling, it is crushed to obtain a pellet or granular compound. the compound first
The material is charged into the hopper 1 shown in the figure, cross-compressed by the cross-wire screw 2, and then cut by the shredder 3. At this time, the vacuum chamber 4 is degassed by a vacuum pump 5, and the molded body is extruded by an extrusion auger 6 through a tapered barrel 7 and a mold 8, and cut into a predetermined length at the mold outlet. The drawing ratio during extrusion molding is determined by the auger area of the extrusion molding machine being SO,
If the mold exit area is S, it is expressed as 3o/S,
This ratio is preferably in the range of 3 to 100, more preferably 20 to 70. That is, if the drawing ratio is too small, it is difficult to obtain a uniform molded product, while if the drawing ratio is too large, cracks are likely to occur during molding. Depending on the type of binder, the molded product thus obtained is subjected to treatments such as heat curing, single-width copper wire hardening, cooling rotation, or magnetization, and then magnetized to become a final product.

Regarding the method of manufacturing bonded magnets by extrusion molding described above,
As a result of various studies, we found that compared to isotropic bonded magnets made by conventional extrusion molding, by loading the extruded body in a rheological state into a magnetizing device and applying a pulsed magnetic field once or multiple times as necessary. It was found that the magnetic force was about 40% higher.

Below, we will explain the case where the application of this pulsed magnetic field is applied to a cylindrical compact, but the same applies when applying static magnetic lift or when applying to a compact in the shape of a plate, ring, etc. effect can be obtained. First, the yoke 9 is prepared as shown in FIG. 2, and then the molded body 1o is inserted into the yoke, but after magnetization, the molded body is prevented from being attracted to the yoke by its own magnetic force! Then, it is preferable to cover the surface with an insulating material such as rubber, vinyl, or cloth, or a conductive material 11 such as A (1° ausdenoid stainless steel, brass, etc.). If the molded product is at a high temperature, it is preferable to use glass foam or bar that maintains heat resistance and heat retention as the covering material, but it is preferable to use asbestos, etc. It is necessary to consider cooling the yoke with water.Next, a pulsed magnetic field is instantaneously generated by energizing the coil (not shown) of the yoke 9.By applying this pulsed magnetic field, the rheological molded body is deformed and the ferrite particles are orientation occurs.

Finally, the outer peripheral shape of the molded body becomes a polygonal shape with protruding portions corresponding to the magnetic poles. After orientation, the desired bonded magnet can be obtained by cooling with a thermoplastic binder, or by heating or irradiating with a width copper wire hardening type binder, respectively.

When observing the flow of magnetic lines of force in the cross section of the cylindrical magnet molded body obtained by the method of the present invention, it becomes anisotropic as shown in Figure 3.
It is clear that there are That is, when paper was placed on top of this cylindrical molded body and iron powder was scattered thereon, the iron powder was arranged along the lines of magnetic force as shown in FIG. In applying the above-mentioned pulsed magnetic field, the coil of the yoke may be connected to an instantaneous DC power source that inputs, for example, a commercial AC power source, boosts and rectifies it to a predetermined DC voltage, charges a group of capacitors, and discharges it via a sistor. Further, as for the magnitude of the pulsed magnetic field, if it is about 10 K Oe or more, it is sufficient to obtain a normal anisotropic ferrite magnet. Also,
For a cylindrical magnet used in a magnet roll, a magnetic field of around 20 Oe is sufficient, although it depends on the type of binder.

As a result of various experiments, the present invention was applied to a cylindrical bonded magnet with an external diameter of 20 to 73 mm for magnet rolls, and the result was Br2000 G.
We confirmed that the above can be obtained. Also, the thickness is 3~30m
l111 width 30-100mm, length ioo ~500m
3 r 2000Q even for a plate-shaped bonded magnet of about m
We confirmed that the above can be obtained. The present invention can be applied to magnets of various shapes by changing the shape of the mold.
In addition to the above, rod-shaped or cylindrical bonded magnets can of course be manufactured.

Example 1 Annealed 3r fluorite particles 87 with an average particle size of 1.3 μm
Part, Toray Nylon 6 (Grade CM1017) 12
．． 5 parts, toluenesulfonic acid amide (JP-A-55-91
803) A composition consisting of 0.5 parts (parts are important parts) was prepared, melted and mixed using a pressure kneader, and then ground to a size of 3 to 5 mm to obtain pellets for molding. Using the above compound, using the extrusion molding machine shown in FIG.
A cylindrical molded body with a diameter of 0.00 mm was obtained. Then 200℃
The molded body cooled to a certain temperature was inserted into an asbeth 1-cylinder with an inner diameter of φ31, and the temperature was raised to about 230 to 240°C, and then inserted into a symmetrical 8-pole magnetized yoke as shown in Fig. 3. A pulsed magnetic field of 20 KQe was applied. After cooling and assimilation, the molded body was taken out from the asbestos capsule to obtain an anisotropic bonded magnet A. Table 1 shows the results of magnetic measurements. Incidentally, as long as the asbestos capsule is oriented as quickly as possible, almost the same magnetic properties can be obtained.

B in Table 1 is the characteristic of the bonded magnet when no pulsed magnetic field is applied. Further, C is a characteristic of an isotropic integrally sintered magnet obtained by the rubber press method, and the dimensions are the same in all cases. As is clear from Table 1, according to the method of the present invention, long cylindrical magnets with superior magnetic properties than ordinary bonded magnets, as well as isotropic sintered magnets, despite their low density bonded magnets can be obtained.

Example 2 Annealed 3r fluorite particles 86 with an average particle size of 1.5 μm
Phenol resin RM4000 manufactured by Asahi Organic Industrial Co., Ltd.
A molded powder obtained by kneading 8 parts of D and 6 parts of water at room temperature was molded and oriented in the same manner as in Example 1 at room temperature. However, the molded body was inserted into the yoke shown in FIG. 3 after wrapping the outer surface with vinyl having a thickness of 0.3 mm. The obtained anisotropic molded body was dried at room temperature and then
Heat curing was performed at 70°C. The obtained magnetic properties are 3r
=2600G. It has reached IH O = 3500Qe, which shows that it has extremely high performance of 1C for a cylindrical magnet that is difficult to anisotropy. Also, using the same compound, 30W-10T-300Ω (m
After extrusion molding the plate-shaped molded product in m), the upper and lower surfaces of the molded product were covered with 0.31 vinyl, and then the molded product was inserted into a parallel magnetic field yoke with a gap of 13n++u, and heated at 20K.
The orientation of Oe is adjusted by applying a pulsed magnetic field twice. Then, after drying, hardening is performed under the same conditions as the cylindrical magnet. The magnetic properties obtained are Sr = 2
It was 700G Ito1c==36300e.

As described above, according to the present invention, the following effects can be obtained.

(1) Injection molding method, which is comparatively different from compression method,
High-performance anisotropic bond using a simple mold device and a comparatively simple 8'J magnetizing yoke! You can get i stones.

(2) Impression force of pulsed magnetic field 04 for imparting anisotropy,
Since a normal magnetizing yoke can be used, there is no need to provide two special devices. Moreover, a commercially available general-purpose power supply is sufficient.

(3) Since extrusion molding is used, the Bon 1: magnet can be obtained in various shapes such as a cylindrical plate shape and an arc shape by simply changing the shape of the mold. Furthermore, both thermoplastic and thermosetting resins can be used. Also, rubber magnets can also be made by not performing vulcanization in the post-process.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing one example of an extrusion molding machine used in the present invention, Fig. 2 is a sectional view for explaining the application of a pulsed magnetic field in the present invention, and Fig. 3 is a sectional view showing an example of an extrusion molding machine used in the present invention. The figure is a diagram showing the flow of magnetic lines of force in a cylindrical long bonded magnet obtained according to the present invention. 1: Hopper 2: Mixing screw 3: Extrusion screw (auger) 8: Mold 9: Yoke
10: Molded body 11: Insulator or conductor Fig. 1 - 9 - Fig. 2 @ /1 Fig. 3

Claims (1)

[Claims] 1 Mainly composed of magnet plumbite type magnetic particles,
A bonded magnet is produced by extrusion molding a hybrid material to which a surface modifying material, a binder, and particulate additives are added as necessary, and assimilating or hardening the resulting molded product by an appropriate method such as heat treatment or radiation treatment. The manufacturing method is characterized in that a magnetic field such as a pulse is applied to the magnetized surface of the molded body to impart anisotropy, and then, after solidification or hardening, the molded body is magnetized in the same direction as the anisotropic direction. A method for manufacturing a bonded magnet. 2. After covering a cylindrical or ring-shaped molded product obtained by extrusion molding with an insulator or conductor, or after storing it in a storage container molded from the material of the insulator or conductor, in a direction perpendicular to the axis. The method for manufacturing a bonded magnet according to claim 1, characterized in that a magnetic field is applied to the molded body in a parallel direction. 3. The method for manufacturing a bonded magnet according to claim 2, characterized in that the magnetic field applied to the molded body is a magnetic field of about 5 KOe or more. 4 After covering the surface of the plate-shaped molded body with an insulator or conductor or storing it in a container made of the material of the insulator or conductor, a pulsed magnetic field of about 10 KOe or more is applied to the molded body once or multiple times. and the 3r value of the final product is 200O.
A method for manufacturing a bonded magnet according to claim 1, characterized in that the bonded magnet is G or more. 5. A pulsed magnetic field of approximately IQK Oe or more is momentarily applied once or multiple times to a cylindrical or ring-shaped molded body with an outer diameter of 10 mm, so that the surface density BO of the final product is 10
Claim 1 characterized in that it is 0OG or more.
A method for producing a bonded magnet as described in . 6. It is characterized by forming an arc-shaped molded body with an outer diameter of approximately 10 mm or more by extrusion molding, coating at least the upper and lower surfaces of the molded body with an insulator, and then applying a pulsed magnetic field of about 10 KOe or more. A method for making bond magnets.