JPH09134811A - Resin bonded composition for magnet and resin bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for a magnet which has superior moldability (melting and flowing property) and mechanical strength. SOLUTION: In this composition wax is added to a mixture of magnetic powder which has anisotropic magnetic filed (HA) of at least 50kOe and polyamide resin. The polyamide resin is constituted of modified polyamide resin having a terminal group being modified and the wax is mixture of paraffin wax and fatty acid amide wax. The resin bonded type composition for a magnet is obtained by being heated and molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a resin-bonded magnet, and more particularly to a composition for providing a resin-bonded magnet having excellent moldability (melt fluidity) and mechanical strength. Related to the magnet used.

[0002]

2. Description of the Related Art Permanent magnets such as ferrite magnets, alnico magnets, and rare earth magnets are used in various applications including motors. However, since these magnets are mainly produced by a sintering method, they are generally brittle, and it is difficult to obtain thin magnets or complicated shapes. Also, shrinkage during sintering is 15-20.
%, High dimensional accuracy cannot be obtained, and post-processing such as polishing is required to increase the accuracy.

[0003] The resin-bonded magnet solves these drawbacks and opens up new applications, and is made by using a thermoplastic resin such as nylon as a binder and filling it with magnetic powder. However, resin magnets using a thermoplastic resin as a binder, when filled with magnetic powder at 80% by weight or more, the viscosity at the time of melt molding rapidly increases and molding becomes difficult. Molding is performed by adding a lubricant for thermoplastic resins such as stearic acid-based metal soap and paraffin, but there is a limit. Further, as the filling amount of the magnetic powder increases, the mechanical strength decreases.

[0004]

In recent years, small motors,
Resin-bonded magnets used for audio equipment, OA equipment, etc.
Due to the demand for miniaturization of devices, there is a demand for magnetic devices having high magnetic properties, excellent dimensional accuracy, and low cost. However, the moldability (melt flow property) and mechanical strength of the conventional resin-bonded magnet composition obtained only with the magnetic powder, polyamide resin and lubricant are not always sufficient for use in the above-mentioned applications. Early improvement of the composition for mold magnets has been desired.

Accordingly, the present invention has been made to solve the drawbacks of the conventional polyamide resin-bonded magnet composition, and to provide a magnet composition having excellent moldability (particularly, melt fluidity) and mechanical strength. Aim.

[0006]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have made various studies by changing the kind and amount of polyamide resin, and as a result, the anisotropic magnetic field (H _A ) Fifty
In a composition in which magnetic powder of kOe or more and a polyamide resin are mixed, the polyamide resin is a modified polyamide resin having a terminal group modified with a monocarboxylic hydrocarbon, and a paraffin wax and a fatty acid amide wax are further added. It was found that a composition for resin-bonded magnet having excellent moldability (melt flowability) and mechanical strength can be obtained by adding the mixture of the above, and the present invention was completed.

That is, according to the present invention, the anisotropic magnetic field (H _A ) is 5
A composition in which a wax is added to a mixture of a magnetic powder of 0 kOe or more and a polyamide resin, wherein the polyamide resin is a modified polyamide resin whose end group is modified with a monocarboxylic hydrocarbon, and the wax is paraffin. A resin-bonded magnet composition characterized by being a mixture of a system wax and a fatty acid amide wax, and a mixing ratio of the modified polyamide resin of 4 to 50 parts by weight based on 100 parts by weight of the magnetic powder. The resin-bonded magnet composition is characterized in that the mixing ratio of the paraffin wax is 0.05 to 10 parts by weight, and the mixing ratio of the fatty acid amide wax is 0.05 to 10 parts by weight.

Further, there is provided a resin-bonded magnet obtained by thermoforming these resin-bonded magnet compositions.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The magnetic powder used in the present invention includes an anisotropic magnetic field ( _HA ).
However, if the magnetic powder is 50 kOe or more, a magnetic powder usually used for a resin-bonded magnet can be used. For example, rare earth cobalt-based, rare earth-iron-boron, rare earth-iron-
And nitrogen-based magnetic powder.

In the above resin-bonded magnet composition, the inventors of the present invention use the Sm—Co ₅ type alloy powder by the reduction diffusion method or the Sm—Fe—N type alloy powder as the magnetic powder. It has been confirmed that a resin-bonded magnet having a particularly high magnetic property such as 93 wt% or more can be obtained. The Sm-Co ₅ magnetic powder obtained by the reduction diffusion method is preferably pulverized by a jet mill, a ball mill or the like. The preferred particle size of these magnetic powders is 7 μm or less on average, and particularly preferably 5 μm or less on average.

If necessary, the magnetic powder may be silane-based,
A titanium-based or aluminum-based surface treatment agent, that is, a coupling agent, can be used in a range of 0.1 to 3.0 parts by weight based on 100 parts by weight of the magnetic powder. Examples of these coupling agents include silane-based vinyltriethoxysilane, γ-aminopropyltriethoxysilane, N
-(Β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, etc. Also, titanium-based isopropyltriisostearoyl Titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl tri Typical examples include decylbenzene sulfonyl titanate and the like, and acetoalkoxy aluminum diisopropylate as the aluminum type.

Further, in the composition, the polyamide resin which is an essential component functions as a binder for the magnetic powder, and as the polyamide resin used in the present invention, the polyamide resin is a monocarboxyl group hydrocarbon and has an end group. It is characterized in that it is a modified modified polyamide resin. As long as this condition is satisfied, for example, 6 nylon, 6-6 nylon, 11 nylon, 12 nylon,
6-12 Copolymer nylon, aromatic nylon, etc., such as homopolymers of these, copolymers with other types of monomers, mixing with end group-treated products with other substances, etc. are acceptable, but consider moldability. Then, 11 nylon or 12 nylon is preferable.

The molecular weight of the modified polyamide resin used in the present invention is not particularly limited, but preferably has a number average molecular weight of 1,000 to 30,000, more preferably a number average molecular weight of 500.
0 to 20000 is more preferable. If a modified polyamide resin having a number average molecular weight of less than 1,000 is used outside the range of this molecular weight, the strength of the molded product will be reduced, and 3000
If it exceeds 0, the formability is deteriorated.

On the other hand, when less than 4 parts by weight of the end group-modified polyamide resin is filled in 100 parts by weight of the magnetic powder, the kneading torque and the fluidity are remarkably reduced, which makes molding difficult, and 50 parts by weight. If it exceeds, the desired magnetic characteristics cannot be obtained. Therefore, the filling amount of the terminal group-modified polyamide resin is preferably 4 to 50 parts by weight.

The shape of these modified polyamide resins is not particularly limited, such as powder, beads and pellets, but powder is preferable in view of uniform mixing with magnetic powder.

The paraffin wax used in the present invention is
The main component is linear saturated hydrocarbon (n-paraffin), side chain saturated hydrocarbon (isoparaffin), cyclic saturated hydrocarbon (cycloparaffin), etc., and the number of carbon atoms in one molecule is 1
8-50 simple substance or complex, molecular weight 200-7
Fifty can be used. In addition, composite types such as aromatic hydrocarbons and special hydrocarbons other than these can of course be used, and one or more kinds of them may be added to the composition without being restricted by the degree of polymerization or the molecular weight. be able to. As these paraffin waxes, those having a melting point of 40 to 70 ° C. are preferably used.

These paraffin waxes are usually added in a proportion of 0.05 to 10 parts by weight with respect to 100 parts by weight of magnetic powder, preferably 0.1 to 5 parts by weight, more preferably 0.1. It is 1 to 3 parts by weight. The wax is
The magnetic powder and the polyamide resin may be mixed at the same time. If the amount of the wax added is less than 0.05 parts by weight with respect to 100 parts by weight of the polyamide resin, the moldability decreases,
As a result, the content of the magnetic powder cannot be increased, so that a magnet having high magnetic properties cannot be obtained. The addition amount is 1
If it exceeds 100 parts by weight, desired physical properties (especially mechanical strength) cannot be obtained.

The fatty acid amide wax of the present invention (the same applies to amides as amide) is a saturated fatty acid monoamide wax such as lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide. Unsaturated fatty acid monoamide wax such as oleic acid amide, erucic acid amide, and ricinoleic acid amide, stearyl stearic acid amide, oleyl oleic acid amide, stearyl oleic acid amide,
Substituted amides such as oleyl stearic acid amide, stearyl erucic acid amide, oleyl palmitic acid amide, methylol stearic acid amide, methylol amides such as methylol behenic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, ethylenebiscabrin Acid amide, ethylenebislauric acid amide,
Ethylenebishydroxystearic acid amide, ethylenebisbehenic acid amide, hexamethylenebisstearic acid amide, hexamethylenebisbehenic acid amide, hexamethylenebishydroxystearic acid amide, N, N-distearyl adipic acid amide, N, N-di Saturated fatty acid bisamides such as stearyl sebacic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N, N-dioleyl sebacic acid amide unsaturated fatty acid bisamide, m-xylene bisstearic acid amide, N, N- Examples thereof include aromatic bisamides such as distearyl isophthalic acid amide, and the like, and one or more of these can be added to the composition for use. As the fatty acid amide wax, it is preferable to use a bisamide wax.

These fatty acid amide waxes are usually added in a proportion of 0.05 to 10 parts by weight with respect to 100 parts by weight of the magnetic powder, preferably 0.1 to 5 parts by weight, more preferably, It is 0.1 to 3 parts by weight. The wax may be mixed with the magnetic powder and the polyamide resin at the same time.
The amount of the wax added was 100 parts by weight of the magnetic powder.
If the amount is less than 05 parts by weight, the molding processability is deteriorated, and as a result, the content of the magnetic powder cannot be increased, so that a magnet having high magnetic properties cannot be obtained. Also, if the addition amount exceeds 10 parts by weight, desired physical properties (especially mechanical strength)
Can not be obtained.

In addition to the above components, the composition of the present invention may contain other waxes for molding plastics, lubricants, various stabilizers and the like.

Examples of the lubricant include waxes such as polyethylene wax, polypropylene wax, ester wax, carnauba, and microwax, fatty acids such as stearic acid, 1,2-oxystearic acid, lauric acid, palmitic acid, and oleic acid. Fatty acid salts (metal soaps) stearic acid, such as calcium stearate, barium stearate, magnesium stearate, lithium stearate, zinc stearate, aluminum stearate, calcium laurate, zinc linoleate, calcium ricinoleate, and zinc 2-ethylhexoate. Amide, oleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, lauric acid amide, hydroxystearic acid amide, methylenebisstearic acid amide, ethylenebis Tearic acid amide, ethylenebislauric acid amide, distearyl adipic acid amide, ethylenebisoleic acid amide, dioleyl adipic acid amide, N-stearyl stearic acid amide and other fatty acid amides, butyl stearate and other fatty acid esters, ethylene glycol, Alcohols such as stearyl alcohol,
Polyethylene glycol, polypropylene glycol,
Polytetramethylene glycol and polyethers composed of these modified products, dimethylpolysiloxane, polysiloxanes such as silicon grease, fluorine-based oil, fluorine-based grease, fluorine compounds such as fluorine-containing resin powder, silicon nitride, silicon carbide, oxidation Inorganic compound powders such as magnesium, alumina, silicon dioxide and molybdenum disulfide may be mentioned.

As the stabilizer, bis (2,2,2
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 [ポ リ 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}], 2- (3,5-di-tert-butyl-4) Hindered amine based stabilizers such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) -2-hydroxybenzyl) -2-n-butylmalonate, as well as phenol based, phosphite based and thioether based stabilizers And the like.

In the present invention, the mixing method of the respective components is not particularly limited, and for example, a mixer such as a ribbon blender, a tumbler, a Nauter mixer, a Henschel mixer, a super mixer, or a Banbury mixer, a kneader, a roll, a kneader ruder, a single mixer. It is carried out using a kneader such as a twin-screw extruder or a twin-screw extruder.

The composition of the present invention can be obtained in the form of powder, beads, pellets or a mixture thereof by mixing the respective components, and pellets are preferable from the viewpoint of easy handling. The obtained composition is molded by various thermoplastic resin molding machines, preferably an injection molding machine and an extrusion molding machine.

[0025]

The present invention will be described more specifically below with reference to examples and comparative examples. The details, test methods, and evaluations of each component used in Examples and Comparative Examples will be illustrated, but the present invention is not limited to these without departing from the spirit of the present invention.

Resin-bonded magnet compositions and magnets were manufactured and evaluated by the following materials and methods. The materials used are shown below.

The terminal group-modified polyamide resin is obtained by adding desired stearic acid to 12 commercially available nylon and mixing and reacting in a nitrogen atmosphere at 300 ° C. under a pressure of 1 kg / cm ² for 3 hours. Was used after confirming the polystyrene-converted molecular weight by gel permeation chromatography.

A magnetic powder-Magnetic powder 1: SmCo ₅ type magnetic powder (trade name: RCo ₅ alloy, manufactured by Sumitomo Metal Mining Co., Ltd.) Anisotropic magnetic field: 246 kOe-Magnetic powder 2: Nd-Fe-B type magnetic powder ( (Product name: MQP-B, manufactured by General Motors, USA) Anisotropic magnetic field: 70.4 kOe

B Polyamide resin (polylaurolactam) PA1: Terminal group modified 12 nylon (number average molecular weight bar Mn = 11000) PA2: Terminal group modified 12 nylon (number average molecular weight bar Mn = 16500) PA3 : 12 nylon (UBE nylon 3014U, Ube Industries, Ltd.)

C Paraffin wax ・ PW 1 (trade name: Mobil Wax 130, manufactured by Mobil Oil Co., Ltd., melting point 55.8 ° C.) ・ PW 2 (trade name: Mobil Wax 140, manufactured by Mobil Oil Co., Ltd., melting point 61.5 ° C)

D Fatty acid amide wax ・ AW 1: ethylenebisstearic acid amide (trade name: Thripax E manufactured by Nippon Kasei Co., Ltd.) ・ AW 2: stearic acid amide (trade name: Amide AP-1, Nippon Kasei ( Co., Ltd.)

Next, the manufacturing method and evaluation method of each molded product are as follows. Mixing and Preparation of I Composition A predetermined resin and each additive system are added to each magnetic powder in a predetermined ratio (each part by weight), and thoroughly mixed and stirred in a planetary mixer (40 rpm, 80 ° C.). ) And then dried in a vacuum oven at 120 ° C for 24 hours. The mixture thus obtained was used as a 20 mmφ single extruder (L / D = 25, CR = 2.0, rotation speed = 20 r
pm, 5mmφ strand die, cylinder temperature 200
280 ° C., die temperature 280 ° C.), and a 5 mmφ × 5 mm resin-bonded magnet pellet compound was produced with a hot-cut pelletizer.

II Method for Evaluating Melt Fluidity Fluidity (MFR) Evaluation The pelletized composition obtained under the above kneading conditions was subjected to a Koka type flow tester manufactured by Shimadzu Corporation (temperature: 250).
° C, Load: 30kgf, Die shape: 1mmφ × 1m
m, preheat: 120 seconds) The fluidity was measured.

The results are shown in Tables 1 to 3. It has been found in the fluidity evaluation that if a fluidity of 1.5 g / min or more can be ensured, no problems will be caused in molding.

III Evaluation of Mechanical Strength (Three-Point Bending Strength) These pellet compounds were measured with a magnetic field injection molding machine (J-20MII) manufactured by Nippon Steel Works, Ltd., with a width of 5 mm and a length of 15 mm.
The same conditions are used for the test resin-bonded magnet of 2 mm x 2 mm (molding temperature 240-290 ° C, mold temperature 100-120 ° C).
The bending strength of the obtained magnet molded product was measured at room temperature with an autograph manufactured by Shimadzu Corporation at a head speed of 2 mm / min. The results are also shown in Tables 1 to 3. The bending strength is 5.0 kgf / mm
It is known that a mechanical strength of ^two or more is sufficient.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

As described above, the resin composition for a resin-bonded magnet of the present invention has improved moldability and mechanical strength as compared with the prior art, and is required for high-performance products, such as general home appliances, It is particularly useful in a wide range of fields, such as communication and audio equipment, medical equipment, and general industrial equipment.

Claims (3)

[Claims] 1. _A composition in which wax is added to a mixture of magnetic powder having an anisotropic magnetic field (H _A ) of 50 kOe or more and a polyamide resin, wherein the polyamide resin is a monocarboxyl group hydrocarbon and an end group. Is a modified polyamide resin modified by, wherein the wax is a mixture of a paraffin wax and a fatty acid amide wax. 2. The mixing ratio of the magnetic powder, the modified polyamide resin, and each wax is 4 to 50 parts by weight of the modified polyamide resin and 0.05 to 10 parts by weight of the paraffin wax, based on 100 parts by weight of the magnetic powder. The composition for a resin-bonded magnet according to claim 1, wherein the fatty acid amide wax is 0.05 to 10 parts by weight. 3. A resin-bonded magnet obtained by heat-molding the resin-bonded magnet composition according to claim 1 or 2.