JPH09148114A - Composition for resin-bonded magnet and resin-bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition and magnet having excellent forming property (melting fluidity) and mechanical strength by a mixture of and end group modi fied polyamide resin of number average molecular weight not exceeding a specific number and the end group modified polyamide resin of a number aver age molecular not exceeding a specific number. SOLUTION: Modified polyamide is a mixture of an end group modified polyamide resin of a number average molecular weight not exceeding 10000 and another end group modified polyamide resin of a number average molecular weight exceeding 30.000 wherein the end group is modified by monocarboxyl group hydrocarbon. Furthermore, assuming magnet particles to be 100wt.%, 2-24wt.% of modified polyamide resin of a number average molecular weight not exceeding 10.000, 2-24wt.% of the modified polyamide resin in the number average molecular weight exceeding 30.000 and 4-50wt.% of the total modified polyamide as well as 0.5-50wt.% of ethylene-ethylacrylate copolymer mixed with one another to obtain the title resin bonded type magnet composition.

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 object, the present inventors conducted various studies by changing the types and amounts of polyamide resin and additives, and as a result, found that the anisotropic magnetic field (H
_A ) _A mixture of a magnetic powder having 50 kOe or more and a modified polyamide, wherein the modified polyamide has a number average molecular weight of 100 having a terminal group modified with a monocarboxyl group hydrocarbon.
End-group modified polyamide resin of 00 or less and number average molecular weight 3
A resin-bonded magnet composition having excellent moldability (melt flowability) and mechanical strength, which is a mixture with a terminal group-modified polyamide resin of 0000 or more, and which is further added with an ethylene-ethyl acrylate copolymer resin. It was found that the modified polyamide was end-modified with a monocarboxyl hydrocarbon and the end group-modified polyamide oligomer having a number average molecular weight of 1000 or less and the terminal group-modified polyamide resin having a number average molecular weight of 10,000 or more were obtained. It was found that a resin-bonded magnet composition having excellent moldability (melt flowability) and mechanical strength can be obtained by adding an ethylene-ethyl acrylate copolymer resin. completed.

That is, according to the present invention, the anisotropic magnetic field (H _A ) is 5
A composition in which an ethylene-ethyl acrylate copolymer resin is added to a mixture of a magnetic powder of 0 kOe or more and a modified polyamide, wherein the modified polyamide has a number average molecular weight of 10 whose end groups are modified with a monocarboxylic group hydrocarbon.
000 or less end group-modified polyamide resin and end group-modified polyamide resin having a number average molecular weight of 30,000 or more, and a resin-bonded magnet composition, and the magnetic powder as 100 parts by weight, The mixing ratio of the modified polyamide resin having an average molecular weight of 10,000 or less is 2 to
48 parts by weight, the mixing ratio of the modified polyamide resin having the number average molecular weight of 30,000 or more is 2 to 48 parts by weight, and the total amount of the modified polyamide is 4 to 50 parts by weight. Further, the ethylene-ethyl acrylate copolymer resin. The resin-bonded magnet composition is characterized in that the mixing ratio is 0.5 to 50 parts by weight.

In the present invention, the anisotropic magnetic field (H _A ) is 50
A composition in which an ethylene-ethyl acrylate copolymer resin is added to a mixture of a magnetic powder having a kOe or more and a modified polyamide, wherein the modified polyamide has a number average molecular weight of 100 whose end groups are modified with a monocarboxylic group hydrocarbon.
A composition for a resin-bonded magnet, which is a mixture of an end group-modified polyamide oligomer having a number average molecular weight of 0 or less and a terminal group-modified polyamide resin having a number average molecular weight of 10,000 or more, and the above number based on 100 parts by weight of magnetic powder. The mixing ratio of the modified polyamide oligomer having an average molecular weight of 1,000 or less is 2 to 48 parts by weight, and the mixing ratio of the modified polyamide resin having the number average molecular weight of 10,000 or more is 2 to 48 parts by weight.
And the total of the modified polyamide is 4 to 50 parts by weight, and further, the mixing ratio of the ethylene-ethyl acrylate copolymer resin is 0.5 to 50 parts by weight. is there.

Further, there is provided a resin-bonded magnet obtained by subjecting these resin-bonded magnet compositions to heat molding.

[0010]

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 it is a magnetic powder of 50 kOe or more, a magnetic powder usually used for a resin-bonded magnet can be used.
mCo ₅ system, Sm ₂ (Co, Fe, Zr, V) ₁₇ system, Sm
₂ (Co, Cu, Fe, Zr) ₁₇ type, Sm ₂ (Co, C
u, Fe, Zr, Te) ₁₇ based, Sm ₂ (Co, Cu, F)
e, Ta, Te) rare earth cobalt-based such as ₁₇ -based, Nd-F
e-Co-B system, Nd-Dy-Fe-B system, Nd-Fe
Rare earths such as B-based iron-boron-based, Sm-Fe-N-based,
Sm-Fe-Co-N system, Nd-Fe-Ti-N system, N
Rare earth-iron-nitrogen-based magnetic powders such as d-Fe-VN-based powders.

The present inventors have found that in the above-mentioned resin-bonded magnet composition, when the alloy powder obtained by the Sm—Co ₅ based reduction diffusion method or the Sm—Fe—N based alloy powder exemplified above is used as the magnetic powder. For example, it has been confirmed that a resin-filled magnet having a high filling of, for example, 93% by weight or more and having excellent magnetic properties 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.

[0012] The magnetic powder may be optionally replaced with a silane-based material.
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.

In the composition, the modified polyamide, which is an essential component, functions as a binder for magnetic powder. The modified polyamide used in the present invention includes a monocarboxyl hydrocarbon and a terminal group having a terminal group. A mixture of a modified modified polyamide resin having a number average molecular weight of 10,000 or less and a modified polyamide resin having a number average molecular weight of 30,000 or more, or a modified polyamide oligomer having a number average molecular weight of 1,000 or less whose terminal group is modified by a monocarboxyl group hydrocarbon It is characterized by comprising a mixture with a modified polyamide resin having an average molecular weight of 10,000 or more. As long as this condition is satisfied,
6 nylon, 6-6 nylon, 11 nylon, 12 nylon, 6-12 copolymer nylon, aromatic nylon, etc.
Mixing with these homopolymers, copolymers with other kinds of monomers, products with terminal group treatment with other substances, etc. may be used, but nylon 11 or nylon 12 is preferable in consideration of moldability.

In the first and second compositions for a resin-bonded magnet according to the present invention, the modified polyamide has a molecular weight of not more than 10,000 and not more than 30,000. The mixing ratio is 2 to 48 parts by weight as a modified polyamide resin having a number average molecular weight of 10000 or less and 2 to 48 parts by weight as a modified polyamide resin having a number average molecular weight of 30000 or more, based on 100 parts by weight of the magnet powder. Preferably, there is. Deviating from this mixing ratio, the number average molecular weight is 10
If the modified polyamide resin having a number average molecular weight of 30,000 or more exceeds 48 parts by weight, the mechanical strength of the molded product increases, but the moldability (melt fluidity) decreases. Therefore, it is not preferable. When the amount of the modified polyamide resin having a number average molecular weight of 10,000 or less exceeds 48 parts by weight, and when the amount of the modified polyamide resin having a number average molecular weight of 30,000 or more is less than 2 parts by weight, the moldability (melt fluidity) of the molded product is improved, This is not preferred because the target strength is reduced.

In the third and fourth compositions for resin-bonded magnets of the present invention, the modified polyamide has a molecular weight of a modified polyamide oligomer having a number average molecular weight of 1,000 or less and a modified polyamide resin having a number average molecular weight of 10,000 or more. Characterized in that the mixing ratio is such that the number average molecular weight is 1000
It is preferable that the modified polyamide oligomer is 2 to 48 parts by weight as the following modified polyamide oligomer and 2 to 48 parts by weight as the modified polyamide resin having a number average molecular weight of 10,000 or more. Deviating from this mixing ratio, the modified polyamide oligomer having a number average molecular weight of 1,000 or less is less than 2 parts by weight, and the number average molecular weight is 1,000.
When the amount of the modified polyamide resin of 0 or more exceeds 48 parts by weight, the mechanical strength of the molded article is increased, but the moldability (melt fluidity) is undesirably reduced. Number average molecular weight 1
If the amount of modified polyamide oligomer of 000 or less exceeds 48 parts by weight, or if the amount of modified polyamide resin of number average molecular weight of 10,000 or more is less than 2 parts by weight, the moldability (melt flowability) of the molded product is improved, but the mechanical strength is improved. Is decreased, which is not preferable.

On the other hand, if the total amount of the modified polyamide is less than 4 parts by weight with respect to 100 parts by weight of the magnetic powder, the kneading torque and fluidity are remarkably reduced, making molding difficult. If the amount is more than 50 parts by weight, desired magnetic properties 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 polyamide resins is
The powder, beads, pellets and the like are not particularly limited, but powder is preferred from the viewpoint of uniform mixing with the magnetic powder.

The monocarboxyl group hydrocarbon used for modifying the terminal group used in the present invention includes, for example, pentanoic acid, heptanoic acid, octanoic acid, decanoic acid, dodecanoic acid,
Octadecanoic acid, benzoic acid and the like can be mentioned. As a method for modifying the terminal group of the polyamide resin, a method of adding these monocarboxyl hydrocarbons during polymerization of the polyamide resin or a method of mixing and reacting the polyamide resin and these monocarboxyl hydrocarbons in a closed heating solution There is.

The ethylene-ethyl acrylate copolymer resin of the present invention can be used in the composition by addition of one kind or two kinds or more without being restricted by the degree of polymerization or the molecular weight, but the molecular weight is preferably 10,000. It is better to use the above items. The powder may be in the form of powder or pellet, but powder is preferable in view of mixing and dispersibility.

These ethylene-ethyl acrylate copolymer resins are used in an amount of 0.5 to 5 with respect to 100 parts by weight of the magnetic powder.
It is added in a proportion of 0 parts by weight, preferably 1.0 to 2
It is 0 part by weight, more preferably 1.0 to 10 parts by weight. The additive may be mixed with the magnetic powder and the modified polyamide at the same time. When the amount of the additive added is less than 0.5 parts by weight with respect to 100 parts by weight of the magnetic powder, the molding processability deteriorates, and as a result, the content of the magnetic powder cannot be increased, resulting in high magnetic properties. I can't get a magnet. Further, if the addition amount exceeds 50 parts by weight, desired physical properties (especially mechanical strength) cannot be obtained.

In the composition of the present invention, a lubricant for plastic molding, various stabilizers and the like can be added in addition to the above-mentioned components.

Examples of the lubricant include waxes such as paraffin wax, liquid paraffin, polyethylene wax, polypropylene wax, ester wax, carnauba, and microwax, 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 and the like, stearamide, oleamide, erucamide, behenamide, palmitamide, lauric amide, ethylenebisstearic amide, ethylenebislauric acid Fatty acid amides such as amides, distearyl adipamides, ethylene bisoleic acid amides, dioleyl adipamides, N-stearyl stearamides, and fatty acid esters such as butyl stearate Le, ethylene glycol, alcohols such as stearyl alcohol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and polyethers consisting modification thereof,
Examples include fluorine compound such as fluorine-based oil, fluorine-based grease, and 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 (2,2,2)
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 method of mixing each component 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 or the like. It is carried out using a kneader such as a 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, but pellets are preferred in terms of easy handling. The obtained composition is molded by various thermoplastic resin molding machines, preferably an injection molding machine and an extrusion molding machine.

[0026]

The present invention will be described more specifically with reference to the following 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.

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

The end group-modified polyamide resin is obtained by adding a desired stearic acid to 12 commercially available nylon and mixing and reacting the mixture at 300 ° C. in a nitrogen atmosphere under a pressure of 1 kg / cm ² for 3 hours. It was used after confirming the molecular weight in terms of polystyrene resin by a chromatographic method.

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

B end group modified polyamide oligomer and resin (end group modified polylaurolactam) -PA 1: end group modified 12 nylon (number average molecular weight
PA Mn: PA 2: Terminal group-modified 12 nylon (number average molecular weight)
PA Mn: PA 3: end group modified 12 nylon (number average molecular weight)
PA Mn: 1100) -PA 4: Nylon-modified 12 nylon (number average molecular weight)
PA M5: PA 5: end group modified 12 nylon (number average molecular weight)
PA Mn: PA 6: Terminal group-modified 12 nylon (number average molecular weight)
PA Mn: PA 7: Terminal group modified 12 nylon (number average molecular weight)
PA Mn = 18000) ・ PA 8: Terminal group modified 12 nylon (number average molecular weight
PA Mn: Terminal group-modified 12 nylon (number average molecular weight)
Bar Mn = 35000)

C Polyethylene-ethyl acrylate (EEA) copolymer resin-EEA 1 (trade name: PES-220, manufactured by Nippon Unicar Co., Ltd.)-EEA 2 (trade name: PES-250, manufactured by Nippon Unicar 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 and 2. 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 these magnet molded products obtained was determined at room temperature at a head speed of 2 mm / min using an autograph manufactured by Shimadzu Corporation. The results are similarly shown in Tables 1 and 2. The bending strength is 5.0 kgf / mm ²
It is known that if the above is satisfied, the mechanical strength is sufficient.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

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.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08L 23:08)

Claims (5)

[Claims] 1. _A composition in which an ethylene-ethyl acrylate copolymer resin is added to a mixture of magnetic powder having an anisotropic magnetic field (H _A ) of 50 kOe or more and a modified polyamide, wherein the modified polyamide is a monocarboxyl. A composition for resin-bonded magnet, which is a mixture of an end group-modified polyamide resin having a number average molecular weight of 10,000 or less and a terminal group modified with a group hydrocarbon and an end group-modified polyamide resin having a number average molecular weight of 30,000 or more. . 2. Magnetic powder, modified polyamide and ethylene
The mixing ratio of the ethyl acrylate copolymer resin is 2 to 48 parts by weight of the modified polyamide resin having a number average molecular weight of 10,000 or less and 2 to 48 parts by weight of the modified polyamide resin having a number average molecular weight of 30,000 or more, based on 100 parts by weight of magnetic powder. And the total of the two modified polyamides is 4 to
The resin-bonded magnet composition according to claim 1, wherein the amount of the ethylene-ethyl acrylate copolymer resin is 50 to 50 parts by weight. 3. _A composition comprising an ethylene-ethyl acrylate copolymer resin added to a mixture of magnetic powder having an anisotropic magnetic field (H _A ) of 50 kOe or more and a modified polyamide, wherein the modified polyamide is a monocarboxyl. End group-modified polyamide oligomer having a number average molecular weight of 1000 or less modified by a terminal hydrocarbon with a group hydrocarbon and a number average molecular weight of 10,000
A composition for a resin-bonded magnet, which is a mixture with the above terminal group-modified polyamide resin. 4. Magnetic powder, modified polyamide and ethylene-
The mixing ratio of the ethyl acrylate copolymer resin is 2 to 48 parts by weight of the modified polyamide oligomer having a number average molecular weight of 1000 or less and 2 to 48 parts by weight of the modified polyamide resin having a number average molecular weight of 10000 or more, based on 100 parts by weight of magnetic powder.
The weight ratio of the modified polyamide is 2 to 50 parts by weight, and the ethylene-ethyl acrylate copolymer resin is 0.5 to 50 parts by weight. The resin-bonded magnet composition of 5. A resin-bonded magnet obtained by heat-forming the resin-bonded magnet composition according to claim 1.