JPH09148113A - Resin bonded type magnet composition and resin bonded type magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition and magnet having excellent forming property (melting fluidity) and mechanical strength by constituting these elements of the terminal group denatured polyamide resin wherein an end group specifies the denatured number average molecular weight as well as a specific polyamide resin obtained by the condensing reaction of a specific dicarbonic acid to a specific diamine. SOLUTION: A polyamide adopts an end group denatured polyamide resin of number average molecular weight not exceeding 10,000 wherein the end group is denatured by monocarboxyl group hydrocarbon as well as an end group denatured polyamide resin in the number average molecular weight exceeding 30,000. Besides, a specific polyamide resin produced by condensing reaction of dicarbonic acid represented by a formula I (D represents hydrocarbon having carbon atoms at least exceeding 20) to diamine represented by another formula II is adopted. Next, this polyamide is mixed with magnet particles to obtain a resin bonded type magnet composition. Finally, this resin junction type magnet composition is heat.molded to produce the resin bonded type magnet.

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. Also, 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 have made various studies by changing the type and amount of polyamide, and as a result, have an anisotropic magnetic field (H _A ) of 50 kOe.
In the above mixture of magnetic powder and polyamide, the polyamide is a terminal group-modified polyamide resin having a number average molecular weight of 10,000 or less whose terminal group is modified with a monocarboxylic group hydrocarbon, an end group-modified polyamide resin having a number average molecular weight of 30,000 or more, and , A special polyamide resin obtained by the condensation reaction of the dicarboxylic acid represented by [Formula 1] and the diamine represented by [Formula 2] has excellent moldability (melt flowability) and mechanical strength. It has been found that a resin-bonded magnet composition having the same can be obtained, and in the same manner, the polyamide is a terminal-group-modified polyamide oligomer having a number average molecular weight of 1000 or less in which an end group is modified with a monocarboxylic group hydrocarbon, and a number average molecular weight. 10000 or more end group-modified polyamide resin, and dicarboxylic acid represented by [Formula 1] and [Formula 2] It was found that a resin composition for magnets having excellent moldability (melt flowability) and mechanical strength can be obtained by using a special polyamide resin obtained by a condensation reaction with a diamine to complete the present invention. did.

That is, according to the present invention, the anisotropic magnetic field (H _A ) is 5
A composition obtained by mixing a magnetic powder of 0 kOe or more with a polyamide, wherein the polyamide is a terminal carboxyl group-modified polyamide resin having a number average molecular weight of 10,000 or less modified with a monocarboxylic group hydrocarbon, and a number average molecular weight of 30,000 or more. Terminal-modified polyamide resin and special polyamide resin obtained by condensation reaction of dicarboxylic acid represented by [Formula 1] and diamine represented by [Formula 2], for resin-bonded magnet The composition and the magnetic powder are 100 parts by weight, and the mixing ratio of the modified polyamide resin having the number average molecular weight of 10,000 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 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, and further the dicarboxylic acid represented by [Formula 1]. And a resin bound magnet composition, wherein the mixing ratio of the special polyamide resin obtained by the condensation reaction is 0.5 to 50 parts by weight of a diamine represented by [Equation 2].

Further, according to the present invention, the anisotropic magnetic field (H _A ) is 5
A composition obtained by mixing a magnetic powder of 0 kOe or more and a polyamide, wherein the polyamide is a terminal carboxyl group-modified polyamide oligomer having a number-average molecular weight of 1000 or less and a number-average molecular weight of 1000, the terminal phase of which is modified with a monocarboxylic group hydrocarbon.
Resin bond comprising 0 or more terminal group-modified polyamide resin and a special polyamide resin obtained by a condensation reaction of a dicarboxylic acid represented by [Formula 1] and a diamine represented by [Formula 2] The above-mentioned number average molecular weight of 10000, based on 100 parts by weight of the composition for mold magnet and magnetic powder.
The mixing ratio of the following modified polyamide oligomer is 2 to 48
By weight, 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 amount of the modified polyamide is 4 to 50 parts by weight.
A resin characterized in that the mixing ratio of the special polyamide resin obtained by the condensation reaction of the dicarboxylic acid represented by [Formula 1] and the diamine represented by [Formula 2] is 0.5 to 50 parts by weight. It is a composition for a combined magnet.

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

[0010]

Embedded image However, D is a dicarboxylic acid having a hydrocarbon-based structure having at least 20 carbon atoms.

[0011]

[Chemical 6]

[0012]

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.

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 a silane type,
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 modified polyamide which is an essential component functions as a binder for the magnetic powder, and as the modified polyamide used in the present invention, the modified polyamide is a monocarboxylic hydrocarbon and an end 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 and having an end group modified with a monocarboxylic 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 resin-bonded magnet compositions according to the first and second aspects of the present invention, the modified polyamide has a molecular weight of a 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. Characteristically, the mixing ratio is 2 to 48 parts by weight as a modified polyamide resin having a number average molecular weight of 10,000 or less and 2 to 48 parts by weight as a modified polyamide resin having a number average molecular weight of 30,000 or more with respect to 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.

Further, in the resin-bonded magnet compositions according to the third and fourth aspects 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. The mixing ratio is a number average molecular weight of 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 mixed 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 and molding becomes 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.

Examples of the monocarboxylic group hydrocarbon used for modifying the terminal group used in the present invention include 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 special polyamide resin obtained by the condensation reaction of the dicarboxylic acid represented by [Formula 1] and the diamine represented by [Formula 2] of the present invention is not restricted by the degree of polymerization or the molecular weight. One or two or more kinds of them can be added to the composition, but one having a melting point of 150 ° C. or lower is preferable. Further, the molecular structure in the dicarboxylic acid represented by [Formula 1] is not particularly limited as long as the -D- moiety is a hydrocarbon system having 20 or more carbon atoms, and other atoms such as oxygen atom and nitrogen are used. Various elements such as atoms, sulfur atoms, phosphorus atoms, boron atoms and silicon atoms may be contained. In addition, the structure of the molecule is not limited to linear, cyclic, branched, or a composite of these, and there is no problem even if a double bond is included in the molecule. On the other hand, the molecular structure in the diamine represented by [Formula 2] is not limited at all. The shape of the special polyamide resin obtained by the condensation reaction of these dicarboxylic acid and diamine may be either powder or pellet, but powder is preferable in view of mixing and dispersibility.

[0022]

Embedded image However, D is a dicarboxylic acid having a hydrocarbon-based structure having at least 20 carbon atoms.

[0023]

Embedded image The special polyamide resin is added in an amount of 0.5 to 50 parts by weight, preferably 1.0 to 10 parts by weight, based on 100 parts by weight of the magnetic powder. The special polyamide resin is
The magnetic powder and the modified polyamide may be mixed at the same time. When the addition amount of the special polyamide resin is less than 0.5 parts by weight with respect to 100 parts by weight of the magnetic powder, moldability is deteriorated,
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 5
If it exceeds 0 parts by weight, desired physical properties (especially heat resistance and mechanical strength) cannot be obtained.

In addition to the above-mentioned components, the composition of the present invention may contain a plastic molding lubricant, various stabilizers, and the like.

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, 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 these modified products, 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 (2,2,2
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 each component is not particularly limited, for example, a mixer such as a ribbon blender, a tumbler, a Nauter mixer, a Henschel mixer, a super mixer, 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, but pellets are preferable because they are easy to handle. The obtained composition is molded by various thermoplastic resin molding machines, preferably an injection molding machine and an extrusion molding machine.

[0029]

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.

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

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

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 kO
e ・ 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 terminal group modified polyamide resin (polylaurolactam) PA 1: terminal 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 Special polyamide resin ・ Special PA 1 (trade name: Macromelt 6813, manufactured by Henkel Hakusui Co., Ltd.) ・ Special PA 2 (trade name: Macromelt 6202, manufactured by Henkel Shiramizu Co., Ltd.)

Next, the manufacturing method and evaluation method of each molded product will be described as follows. Mixing and Preparation of Composition I To a total amount of each magnetic powder, a predetermined resin and each additive system are added in a predetermined ratio (each part by weight), and sufficiently mixed and stirred in a planetary mixer (40 rpm, 80 ° C.). ) Then, 12
It was dried in a vacuum oven at 0 ° C. for 24 hours. The mixture obtained by these is used as a 20 mmφ single extruder (L /
D = 25, CR = 2.0, rotation speed = 20 rpm, 5 mm
φ strand die, cylinder temperature 200 ~ 280 ℃,
It was extruded at a die temperature of 280 ° C., and a hot-cut pelletizer was used to prepare a pellet compound for resin-bonded magnets of 5 mmφ × 5 mm.

II Melt Flowability Evaluation Method Flowability (MFR) Evaluation The pelletized composition obtained under the above kneading conditions was measured by a high-performance 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 6. 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 Mechanical Strength (3-point Bending Strength) Evaluation These pellet compounds were used in a magnetic field injection molding machine (J-20MII) manufactured by Japan Steel Works, Ltd. to measure width 5 mm × length 15 m.
An m × 2 mm thick resin-bonded test magnet was molded under the same conditions (molding temperature 240 to 290 ° C., mold temperature 100 to 120 ° C.), and the bending strength of these magnet molded products obtained was determined by Shimadzu Corporation ( Using an Autograph manufactured by Co., Ltd., the head speed was set to 2 mm / min and the temperature was determined at room temperature. Table 1 also shows the results.
To Table 6 below. It is known that mechanical strength is sufficient if the bending strength is 5.0 kgf / mm ² or more.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

INDUSTRIAL APPLICABILITY As described above, the resin-bonded magnet composition of the present invention has improved moldability and mechanical strength as compared with conventional ones, and is used for applications requiring high-performance products, for example, general household electric appliances, It is especially useful in a wide range of fields including communication / audio equipment, medical equipment, and general industrial equipment.

HOOC-D-COOH [Formula 1] H2N-R-NH2 [Formula 2]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location (C08L 77/06 C08K 3:20)

Claims (5)

[Claims] 1. _A composition comprising a mixture of a magnetic powder having an anisotropic magnetic field (H _A ) of 50 kOe or more and a polyamide, the polyamide having a number average molecular weight of 10,000 modified with a monocarboxyl group hydrocarbon. The following terminal group-modified polyamide resin, terminal group-modified polyamide resin having a number average molecular weight of 30,000 or more, and a special compound obtained by the condensation reaction of the dicarboxylic acid represented by [Formula 1] and the diamine represented by [Formula 2] A composition for a resin-bonded magnet, which is a polyamide resin. Embedded image However, D is a dicarboxylic acid having a hydrocarbon-based structure having at least 20 carbon atoms. Embedded image 2. The modified polyamide resin having a mixing ratio of the magnetic powder, the modified polyamide and the special polyamide of 100 or less with respect to 100 parts by weight of the magnetic powder has a number average molecular weight of 10,000 or less.
48 parts by weight, the modified polyamide resin having a number average molecular weight of 30,000 or more is 2 to 48 parts by weight, the total of the two types of modified polyamides is 4 to 50 parts by weight, and the special polyamide resin is 0.5 to 50 parts by weight. The composition for resin-bonded magnets according to claim 1, wherein the composition is parts by weight. 3. _A composition in which a magnetic powder having an anisotropic magnetic field (H _A ) of 50 kOe or more and a polyamide are mixed, wherein the polyamide has a number average molecular weight of 1000 and a terminal group modified with a monocarboxyl group hydrocarbon. The following terminal group-modified polyamide oligomer, a terminal group-modified polyamide resin having a number average molecular weight of 10,000 or more, and a special compound obtained by a condensation reaction of a dicarboxylic acid represented by [Formula 1] and a diamine represented by [Formula 2] A composition for a resin-bonded magnet, which is a polyamide resin. Embedded image However, D is a dicarboxylic acid having a hydrocarbon-based structure having at least 20 carbon atoms. Embedded image 4. The modified polyamide oligomer having a mixing ratio of the magnetic powder, modified polyamide and special polyamide of 2 to 48 parts by weight and the number average molecular weight of 10000 or more per 100 parts by weight of the magnetic powder. The modified polyamide resin is 2 to 48 parts by weight, the total of the two types of modified polyamides is 4 to 50 parts by weight, and the special polyamide resin is 0.5 to 50 parts by weight. The composition for resin-bonded magnets according to item 3. 5. A resin-bonded magnet obtained by heat-forming the resin-bonded magnet composition according to claim 1.