JP2000003824A - Manufacture of resin-bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a resin-bonded magnet, which exhibits superior moldability in the case of composition and a configuration of a molded object difficult to be molded in the conventional art. SOLUTION: In a manufacturing method of a resin-bonded magnet which injection-molds composition having magnetic powder and resin binder as the main component, the cavity of a metal molds is opened and the metal mold is filled with heat softened composition. In the course of the metal mold being filled with the composition, or after filling, the cavity of the metal mold is closed. By compressing the charged composition with a mold clamping force of the metal mold, an molded object is obtained.

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 resin-bonded magnet having high magnetic properties, and more particularly, to a composition or a molded article which has been conventionally difficult to mold by a special injection molding method. The present invention relates to a method for forming a resin-bonded magnet exhibiting improved moldability.

[0002]

2. Description of the Related Art Magnets such as ferrite magnets, alnico magnets, and rare earth magnets are mainly produced by a sintering method in which magnetic powder is sintered. Since green compacts before sintering are generally brittle,
It is difficult to obtain thin or complicated shapes. Further, since the shrinkage during sintering is as large as 15 to 20%, a product having high dimensional accuracy cannot be obtained, and a process such as polishing is required after sintering to increase the dimensional accuracy.

[0003] The resin-bonded magnet solves these drawbacks and opens up new applications. Known resin-bonded magnets include an injection molded article or an extruded article using a thermoplastic resin such as a polyamide resin or a polyphenylene sulfide resin as a binder, and a compression molded article using a thermosetting resin such as an epoxy resin as a binder. ing.

[0004]

However, conventional resin-bonded magnets manufactured by injection molding using a thermoplastic resin as a binder have a high moldability, such as torque during kneading before injection molding and melting during molding. Due to the problem of fluidity, the quality and quantity of the magnetic powder to be mixed were limited. For this reason, it has not been possible to obtain a resin-bonded magnet composition in which the properties after molding, especially the magnetic properties of a product having a complicated irregular shape, which is difficult to mold, are improved. Extrusion molding is also limited to simple-shaped products, and it has not been possible to obtain products with complex irregular shapes.

[0005] A resin-bonded magnet manufactured by compression (press) molding using a thermosetting resin as a binder,
Due to the characteristics of the molding method, it is not only impossible to mold a complicated and irregularly shaped product as in the case of the extrusion molding method, but molding in a magnetic field is difficult and there is a limit in improving the properties.

In recent years, resin-coupled magnets used in small motors, audio equipment, OA equipment, and the like have been required to have smaller and more complicated shapes due to the demand for smaller equipment and have excellent magnetic properties. The conventional resin-bonded magnets obtained by each of the above molding methods have insufficient moldability, and it is difficult to satisfy these requirements, for example, the magnetic powder content cannot be increased. Early improvement was desired.

Accordingly, the present invention solves the weak points of the conventional resin-bonded magnet molding and provides a method for producing a resin-bonded magnet which exhibits excellent moldability even in the case of a composition or a molding having been conventionally difficult to mold. The purpose is to provide.

[0008]

A method of manufacturing a resin-bonded magnet according to the present invention is a method of manufacturing a resin-bonded magnet by injection molding a composition containing a magnetic powder and a resin binder as main components. Open the mold cavity and fill the mold with the heat-softened composition, close the mold cavity during or after the composition is filled into the mold, and fill with the mold clamping force. The molded composition is obtained by compressing the composition.

The following describes a method for obtaining a molded article by closing the cavity of the mold while the composition is being filled into the mold and compressing the filled composition with the mold clamping force of the mold. A method called `` injection press molding '', in which the cavity of the mold is closed after the composition is completely filled in the mold, and a method of obtaining a molded body by compressing the filled composition with the mold clamping force of the mold, This is called "injection compression molding".

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic powder used in the production method of the present invention is generally used for resin-bonded magnet moldings such as rare-earth-transition metal-based magnetic powder and iron oxide-based magnetic powder. Can be used.

More specifically, rare earth-transition metal magnetic powders include rare earth-iron-cobalt-boron (for example, Nd-Fe-Co-B) and rare earth-iron-boron (for example, Nd). -Fe-B system), magnetic powders of rare earth-iron-nitrogen system (for example, Sm-Fe-N system), rare earth-cobalt system (for example, Sm-Co system) and the like. Examples of iron oxide-based magnetic powder include Ba ferrite-based magnetic powder,
A magnetic powder such as an Sr ferrite is used.

In the above resin-bonded magnet composition, the Nd-Fe-B-based alloy powder obtained by the liquid quenching method, the Sm-Co-based alloy powder, and the Sm-F
When an e-N-based alloy powder is used, for example, a highly filled composition of 90% by weight or more can be easily molded, and as a result, a resin-bonded magnet having excellent magnetic properties can be obtained.
In particular, when an Sm-Co-based or Sm-Fe-N-based anisotropic alloy powder is used, the effect of the present invention is large, and the ratio to high magnetic characteristics is remarkable.

Nd-Fe- obtained by the liquid quenching method
Since the B-based magnetic powder has a unique scale-like shape, it is preferable to grind it with a jet mill, a ball mill, or the like. The preferred particle size of these magnetic powders is 20 on average.
It is 0 μm or less, particularly preferably 100 μm or less on average.

These magnetic powders can of course be used as they are, but it is desirable to coat the surfaces with various surface treating agents in order to minimize oxidation deterioration during kneading and molding.

Materials that can be surface-treated include silane coupling agents such as vinyltriethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N-
(Β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, etc. Also, as a titanium-based coupling agent, isopropyl triisostearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N -Aminoethyl-aminoethyl) titanate, tetraoctylbis (ditridecylphosphite) titanate, isopropyltrioctanoyl titanate, isopropyldimethacrylisostearoyl titanate, isopropyltridecylbenzenesulfonyl titanate, etc .; Alkoxy aluminum diisopropylate, phosphoric acid surface treatment agent, chromic acid surface treatment agent, zinc phosphate surface treatment agent, phosphoric acid Ngan-based surface treatment agent, iron phosphate-based surface treating agent, phosphoric acid such as calcium phosphate surface treatment agents, and the like phosphate-based surface treatment agent.

In particular, by preliminarily treating the surface of the magnetic powder with these phosphoric acid-based surface treating agents and phosphate-based surface treating agents and forming the composition in a subsequent step, it is possible to minimize the decrease in magnetic properties. Has been confirmed. Also, an organosiloxane-based surface film, a mixed surface film of an organosiloxane-based and organosilica sol, a mixed surface film of an organosiloxane-based and acrylic monomer, a polyorganosilsesquioxane (ladder-type organosiloxane-based polymer) -based surface film, It has been confirmed that the use of magnetic powder formed with a single or mixed inorganic coating film such as a methyldisilazane-based surface film, polysilazane (perhydropolysilazane), silicon oxide, etc. can minimize deterioration of magnetic properties. is made of.

The resin binder used in the method of the present invention comprises:
It works as a binder for the magnetic powder. The resin used is not particularly limited. For example, in the case of a thermoplastic resin, nylon 6, nylon 6, nylon 11, nylon 12, nylon 6, 6, nylon 12, aromatic nylon, or any of these molecules may be used. Polyamide resin such as partially modified denatured nylon, linear polyphenylene sulfide resin, crosslinked polyphenylene sulfide resin, semi-crosslinked polyphenylene sulfide resin, low density polyethylene, linear low density polyethylene resin, high density polyethylene resin, ultra high molecular weight polyethylene Resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, ionomer resin, polymethylpentene resin, polystyrene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile Styrene copolymer resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyvinyl formal resin, methacrylic resin, polyvinylidene fluoride resin, poly (trifluorochloroethylene) resin, tetrafluoroethylene resin Ethylene-hexafluoropropylene copolymer resin, ethylene-tetrafluoroethylene copolymer resin, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin, polytetrafluoroethylene resin, polycarbonate resin, polyacetal resin, polyethylene terephthalate resin, Polybutylene terephthalate resin, polyphenylene oxide resin, polyallyl ether allyl sulfone resin, polyether sulfone resin, polyether ether ketone resin, polyarylate resin, Aromatic polyester resins, cellulose acetate resins, various elastomers and rubbers, and the like.

Random copolymers, block copolymers, graft copolymers with these homopolymers and other monomers,
An end group modified product with another substance may be used. Further, naturally, a system in a blend of two or more kinds of these thermoplastic resins is also included. The melt viscosity and molecular weight of these thermoplastic resins are desirably low as long as the desired mechanical strength is obtained, and the shape is not particularly limited, such as powder, beads, and pellets, considering the uniform mixing with the magnetic powder. Powder is preferred.

In the case of a thermosetting resin, for example, epoxy resin, vinyl ester epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, urea resin, benzoguanamine resin, bismaleimide triazine resin, diallyl phthalate resin, Furan resin, thermosetting polybutadiene resin, polyimide resin, polyurethane resin, silicone resin, xylene resin, etc. are included, and naturally, these basic compositions, other monomers, and blends of two or more of these resins are also included. It is. The viscosity, molecular weight, properties, and the like of these thermosetting resins are not particularly limited as long as the desired mechanical strength and moldability can be obtained. Is desirable.

When these resins are added in an amount of more than 100 parts by weight with respect to 100 parts by weight of the magnetic powder in the composition, desired magnetic properties cannot be obtained and the effects of the present invention cannot be obtained. On the other hand, if the amount is less than 5 parts by weight, the moldability is remarkably reduced and a desired molded product cannot be obtained. Therefore, the mixing amount of these resins is preferably 5 parts by weight or more and 100 parts by weight or less based on 100 parts by weight of the magnetic powder.

In the present invention, in addition to these resin binders, a plastic molding lubricant, various stabilizers, and the like can be added to the resin-bonded magnet for molding.

Examples of the lubricant include waxes such as paraffin wax, liquid paraffin, polyethylene wax, polypropylene wax, ester wax, carnauba and micro wax, stearic acid, 1,2-
Fatty acids such as oxystearic acid, lauric acid, palmitic acid and oleic acid, calcium stearate, barium stearate, magnesium stearate, lithium stearate, zinc stearate, aluminum stearate, calcium laurate, zinc linoleate, calcium ricinoleate , Fatty acid salts (metal soaps) such as zinc 2-ethylhexoate, stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, lauric acid amide, hydroxystearic acid amide, methylenebisstearic acid amide, Ethylenebisstearic acid amide, ethylenebislauric amide, distearyladipamide, ethylenebisoleic amide, dioleyladipamide, N-stearylstearin Amides such as fatty acid amides, fatty acid esters, ethylene glycol and butyl stearate,
Alcohols such as stearyl alcohol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethers composed of modified products thereof, dimethylpolysiloxane, polysiloxanes such as silicon grease, fluorine-based oil, fluorine-based grease,
Examples include fluorine compound such as fluorine-containing resin powder, and inorganic compound powder such as silicon nitride, silicon carbide, magnesium oxide, alumina, silicon dioxide, and molybdenum disulfide.

As the stabilizer, bis (2,2,
6,6, -tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6, -pentamethyl-4-
Piperidyl) sebacate, 1- [2- {3- (3,5-
Di-tert-butyl-4-hydroxyphenyl) propionyloxy {ethyl] -4- {3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy}
-2,2,6,6-tetramethylpiperidine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-
1,2,3-triazaspiro [4,5] undecane-
2,4-dione, 4-benzoyloxy-2,2,6,
6-tetramethylpiperidine, dimethyl succinate-1-
(2-hydroxyethyl) -4-hydroxy-2,2,
6,6-tetramethylpiperidine polycondensate, poly [[6
-(1,1,3,3-tetramethylbutyl) imino-
1,3,5-triazine-2,4-diyl] [(2,
2,6,6-tetramethyl-4-piperidyl) imino]
Hexamethylene [[2,2,6,6-tetramethyl-4
-Piperidyl) imino]], bis (1,2,2,6,6-pentamethyl-4-piperidyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate ), Antioxidants such as phenolic, phosphite, thioether and the like.

In the present invention, the method of mixing the components of the pre-molding composition is not particularly limited, and for example, a ribbon blender,
Tumbler, Nauta mixer, Henschel mixer,
The mixing can be carried out using a mixer such as a super mixer or a planetary mixer, or a kneader such as a Banbury mixer, a kneader, a roll, a kneader ruder, a single screw extruder, a twin screw extruder, or the like.

[0025]

The present invention will now be described more specifically with reference to examples and comparative examples. The details, test methods, and evaluations of each component used in the examples and comparative examples are illustrated, but are not limited thereto without departing from the gist of the present invention.

A composition and a magnet for a resin-bonded magnet were manufactured and evaluated by the following materials and methods. The materials used are shown below.

A Magnetic powder Metal powder 1: Nd-Fe-B based magnetic powder (average particle size 1
(Product name: MQP-B, manufactured by Magnequench International Co., Ltd.) Metal powder 2: Strontium ferrite magnetic powder (Product name: MA-951, manufactured by Toda Kogyo Co., Ltd.)

B Resin binder ・ Resin 1: Polyamide resin modified with terminal amine group (trade name: DAIAMID-1709P, manufactured by Daicel Huls Co., Ltd.) ・ Resin 2: polyphenylene sulfide resin (trade name: FORTRON KPS W-214) , Manufactured by Kureha Chemical Industry Co., Ltd.)

Next, the manufacturing method and evaluation method of each molded product will be described as follows.

1. Mixing and Preparation of Composition To a total amount of each metal powder, a predetermined resin is added in a predetermined ratio (each part by weight).
The specified amount was added to 00 parts by weight, and the mixture was thoroughly mixed and stirred in a planetary mixer.

The mixture obtained as described above was used for a thermoplastic resin binder-based composition only in a φ20 mm single extruder (L / D = 25, CR = 2.0, rotation speed = 20 rpm,
5mmφ strand die, cylinder temperature 200-30
The mixture was extruded at 0 ° C. and a die temperature of 230 to 300 ° C., and a pellet compound of about φ5 mm × 5 mm was prepared using a hot cut pelletizer.

2. Injection molding method These pellet compounds are supplied to Meiki Seisakusho (M
-50C-DM), the normal injection molding method and the injection compression molding method (the mold is usually closed immediately before molding, but by setting the mold clamping pressure lower than usual, the composition pressure at the time of injection can be slightly reduced. The mold is opened, and after the injection is completed, the molding is completed by finally compressing with the maximum mold clamping pressure), the injection press molding method (injection with the mold opened about several millimeters immediately before molding,
After the injection is completed, final flow and shaping are performed while pressing with the maximum mold clamping pressure, and molding is completed.) According to each molding method, a rectangle having a thickness of 1 mm, a width of 10 mm and a length of 120 mm is evaluated by magnetic properties. For evaluation, a cylindrical resin-bonded magnet of φ10 mm × 15 mm was molded under the same temperature conditions (molding temperature 220 to 330 ° C., mold temperature 100 to 130 ° C.), and the obtained molded products were described later. The method was evaluated. The molding was performed in a magnetic field using a mold capable of generating a magnetic field only when strontium ferrite magnet powder was used.

3. Each evaluation method ・ Evaluation of moldability The molding conditions in each rectangular molding were evaluated as follows. If molded without any problems, “○”, barely molded, but “表面” if the surface is rough, “x” if a completely filled compact is not obtained, and the results are shown in Table 1.
To Table 3 below.

Evaluation of Magnetic Properties of Molded Body The magnetic properties of these cylindrical molded bodies were determined using a thiophy-type self-recording magnetic flux system. The results are shown in Tables 1 to 3.

Evaluation of variation in density of compacts 20 mm at the center and 20 mm at the end of these rectangular compacts
The portion was cut, the specific gravity was determined by an underwater replacement method, and the specific gravity difference of the same molded body was determined. The results are shown in Tables 1 to 3. The specific gravity difference is preferably as close to 0 as possible. It is known that if it exceeds 2%, it is not practical.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

As described above, the method of manufacturing the resin-bonded magnet of the present invention is limited to a special injection molding method.
It can provide excellent moldability and magnet products for compositions and product shapes that have been difficult to mold in the past.For example, in a wide range of fields such as general home appliances, communication and audio equipment, medical equipment, and general industrial equipment, etc. Particularly useful.

Claims (2)

[Claims] 1. A method for producing a resin-bonded magnet, which comprises injection-molding a composition containing a magnetic powder and a resin binder as main components, wherein a cavity softened by opening a mold cavity is filled into the mold. A resin-coupled magnet, wherein a cavity of the mold is closed while the composition is being filled into the mold, and a molded body is obtained by compressing the filled composition with a mold clamping force of the mold. Manufacturing method. 2. A method of manufacturing a resin-bonded magnet in which a composition mainly composed of a magnetic powder and a resin binder is injection-molded, wherein a cavity of the mold is opened, and the thermally softened composition is filled into the mold. After the filling of the composition into the mold is completed, the cavity of the mold is closed, and the filled composition is compressed by the mold clamping force of the mold to obtain a molded body. Production method.