JP2003342468A - Resin composition for bonded magnet and bonded magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition for a bonded magnet excellent in moldability, and a bonded magnet excellent in mechanical strength and heat resistance. <P>SOLUTION: This resin composition comprises a magnetic powder and an aromatic polyamide resin. The polyamide resin has such characteristics that the molar ratio of the amount of remaining terminal carboxyl groups to that of remaining terminal amino groups is 1.0 or lower or that an aliphatic diamine component for producing the polyamide resin comprises a linear diamine and a branched diamine, the molar ratio of the content of the linear diamine to that of the branched diamine being less than 4.0. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin composition for a bonded magnet which is excellent in moldability and a bonded magnet which is excellent in mechanical strength and heat resistance.

[0002]

2. Description of the Related Art As is well known, bonded magnets are molded by using a thermoplastic resin such as a polyamide resin or ethylene-ethyl acrylate copolymer as a binder, and filling this with magnetic powder such as ferrite particle powder or rare earth magnetic powder. These magnets are used in large amounts because they are lighter in weight, less prone to cracking, and have better workability because they have better workability than magnets manufactured by the sintering method.

However, the bonded magnet using the above-mentioned thermoplastic resin as a binder has a drawback that it has a low heat resistance, and cannot be used in applications requiring excellent heat resistance.

Among the thermoplastic resins, a bonded magnet using a polyphenylene sulfide resin, which is excellent in heat resistance, has been proposed, but it has a problem in productivity because its moldability is poor and the molded product is brittle.

The bond magnet is molded by injection molding or extrusion molding. In the case of injection molding, sprue and runners are generated, and it is necessary to recycle these in order to reduce material loss. Polyphenylene sulfide resin The bonded magnet using is also problematic in that, when recycled, the moldability and the strength of the molded product are further reduced.

A bond magnet using an aromatic polyamide resin as a heat-resistant resin other than the polyphenylene sulfide resin has also been proposed. However, the heat-resistant aromatic polyamide resin is brittle because the crystallinity is too high as compared with the usual aliphatic polyamide, and it is difficult to handle because of poor moldability such as fluidity and recyclability. Various organic additives are used for improvement, but since the molding temperature is very high, most organic compounds are decomposed and gasified, and the original effect of improving fluidity and preventing resin deterioration is obtained. In addition to being difficult to be prevented, there is a problem that the molding failure and the mold are contaminated by the gas.

Conventionally, as seen in Patent Documents 1 to 7, various attempts have been made to improve the properties of bonded magnets by specifying the constituent units of polyamide resin.

[0008]

[Patent Document 1] Japanese Patent Laid-Open No. 7-26312

[Patent Document 2] Japanese Patent Application Laid-Open No. 9-190914

[Patent Document 3] Japanese Patent Laid-Open No. 9-283314

[Patent Document 4] Japanese Patent Laid-Open No. 11-302539

[Patent Document 5] Japanese Patent Laid-Open No. 9-71721

[Patent Document 6] Japanese Patent Laid-Open No. 2000-3809

[Patent Document 7] Japanese Patent Laid-Open No. 2000-348918

[0009]

The resin composition for a bonded magnet excellent in moldability and the bonded magnet excellent in mechanical strength and heat resistance are currently most demanded. A resin composition and a bonded magnet have not been obtained yet.

That is, the above-mentioned Patent Document 1 describes a resin composition for a bonded magnet in which a terminal group of a polyamide resin is adjusted, but the content ratio of a terminal carboxyl group and a terminal amino group is not taken into consideration. In other words, it is hard to say that it is a resin composition for bonded magnets having excellent moldability.

Further, in the above-mentioned Patent Document 2, a polyamide resin containing a benzene ring in the main chain and a melting point of 270 ° C. and a crystallinity of 35%
Although a bonded magnet having the following polyamide resin as a basic component is described, the content ratio of the terminal carboxyl group and the terminal amino group and the ratio of the linear and branched chain of the aliphatic diamine are considered. Therefore, it cannot be said that the moldability is sufficient.

Further, the above-mentioned Patent Document 3 describes a bonded magnet using a polyamide resin comprising a terephthalic acid component, a dicarboxylic acid component other than terephthalic acid, and a diamine component. However, it has a terminal carboxyl group and a terminal amino group. The content ratio and the ratio of the linear and branched chain of the aliphatic diamine are not considered, and it cannot be said that the moldability is sufficient.

Further, the above-mentioned Patent Document 4 describes a bonded magnet using a polyamide resin composed of a terephthalic acid component and an aliphatic diamine, but the content ratio of the terminal carboxyl group and the terminal amino group is taken into consideration. However, since the linear diamine component of the aliphatic diamine is contained in a large amount, it is difficult to say that the mechanical strength is sufficient.

Further, the above-mentioned Patent Documents 5 and 6 describe a bonded magnet using a polyamide resin in which the terminal carboxyl group concentration or the terminal amino group concentration in the polyamide resin is specified. Since a carboxyl group-containing organic compound is used for the above, the concentration of the carboxyl group in the resin composition is unnecessarily high, and it is hard to say that it is a bonded magnet excellent in recyclability.

Further, the above-mentioned Patent Document 7 describes a bonded magnet using a polyamide resin containing a linear or branched alkylene group, but the content ratio of the terminal carboxyl group and the terminal amino group is considered. However, the mechanical strength is not sufficient because it contains a large amount of linear components.

Therefore, it is a technical object of the present invention to provide a resin composition for a bonded magnet which is excellent in moldability and a bonded magnet which is excellent in mechanical strength and heat resistance.

[0017]

The above technical problems can be achieved by the present invention as follows.

That is, the present invention is a resin composition for a bonded magnet, comprising a magnetic powder and an aromatic polyamide resin,
Ratio of residual amount of terminal carboxyl group and residual amount of terminal amino group of aromatic polyamide resin ([terminal carboxyl group]
A resin composition for a bonded magnet, which comprises using an aromatic polyamide resin having a ratio of / [terminal amino group]) of 1.0 or less (invention 1).

The present invention also provides a resin composition for a bonded magnet, comprising a magnetic powder and an aromatic polyamide resin,
The aliphatic diamine constituting the aromatic polyamide resin is composed of a linear diamine and a branched diamine, and the molar ratio of the content of the linear diamine and the content of the branched diamine ([linear diamine ] / [Branched diamine]) is less than 4.0 aromatic polyamide resin is used, a resin composition for a bonded magnet (invention 2).

The present invention also provides a resin composition for a bonded magnet, which comprises magnetic powder and an aromatic polyamide resin,
The molar ratio of the residual amount of the terminal carboxyl groups and the residual amount of the terminal amino groups of the aromatic polyamide resin ([terminal carboxyl group] / [terminal amino group]) is 1.0 or less, and
The aliphatic diamine constituting the aromatic polyamide resin is composed of a linear diamine and a branched diamine, and the molar ratio of the content of the linear diamine and the content of the branched diamine ([linear diamine ] / [Branched diamine]) is less than 4.0 aromatic polyamide resin is used, a resin composition for a bonded magnet (invention 3).

Further, the present invention is a bond magnet comprising the resin composition for a bond magnet according to any one of the present inventions 1 to 3 (the present invention 4).

The structure of the present invention will be described in more detail as follows.

First, the aromatic polyamide resins of the present inventions 1 to 3 will be described.

The aromatic polyamide resin in the present inventions 1 to 3 is an aromatic polyamide resin containing terephthalic acid and an aliphatic diamine as constitutional units, for example, modified 6T nylon or 9T nylon which is a semi-aromatic polyamide. . In addition, an aromatic polyamide resin modified with another substance such as a random copolymer of an aromatic polyamide resin and another monomer, a block copolymer or a graft copolymer, or a resin blended with another thermoplastic resin is used. May be. In particular, it is preferable to use 9T nylon, which has an excellent balance between thermal stability and moldability.

The solution viscosity of the aromatic polyamide resin in the present inventions 1 to 3 is preferably 1.1 dl / g or less. 1.
When it exceeds 1 dl / g, when a bonded magnet is produced by mixing magnet powder in an amount necessary for obtaining magnetic characteristics in a practical range, fluidity is low and injection molding becomes difficult. It is more preferably 1.05 dl / g or less. The lower limit is about 0.5 dl / g. If it is less than 0.5 dl / g, the molded product and the strength during molding may decrease.

Next, the aromatic polyamide resin in the first invention will be described.

The aromatic polyamide resin in the resin composition for a bonded magnet of the present invention 1 has a molar ratio of the residual amount of terminal carboxyl groups to the residual amount of terminal amino groups in the resin:
[Terminal carboxyl group] / [Terminal amino group] (hereinafter,
This is referred to as "end group ratio". ) Is 1.0 or less. When the terminal group ratio exceeds 1.0, the resin causes a crosslinking reaction or the like to increase the viscosity, so that kneading or injection molding becomes difficult. It is preferably 0.9 or less, and more preferably 0.8 or less. The lower limit of the terminal group ratio is about 0.1.

In order to adjust the ratio of the end groups of the aromatic polyamide resin, the amount of the remaining end groups may be adjusted by a commonly used method. For example, when synthesizing an aromatic polyamide resin, a method of adjusting the amount of terminal groups by adding an end modifier to the above polyamide resin monomer, or when synthesizing an aromatic polyamide resin, dicarboxylic acid (terephthalic acid) And a method of changing the ratio of the aliphatic diamine.

The residual amount of terminal amino groups of the aromatic polyamide resin is preferably 0.5 mol% or more, and the upper limit is 1.
It is about 25 mol%. The content of the terminal amino group is 0.
If it is less than 5 mol%, resin deterioration such as a crosslinking reaction is promoted and moldability may be deteriorated.

Next, the aromatic polyamide resin of the second invention will be described.

The aliphatic diamine constituting the aromatic polyamide resin in the resin composition for a bonded magnet of the present invention 2 is
Consisting of a linear diamine (n-form) and a branched diamine (i-form), the molar ratio of the content of the linear diamine (n-form) and the content of the branched diamine (i-form). : [Content of linear diamine (n-form)] / [content of branched diamine (i-form)] (hereinafter referred to as "n / i ratio") is less than 4.0, and preferably Is 3.0 or less. n /
When the i ratio is 4.0 or more, the melting point and crystallinity of the aromatic polyamide resin become high, and a bonded magnet excellent in mechanical strength cannot be obtained. As the content of the branched chain diamine increases, the melting point and crystallinity of the aromatic polyamide resin decrease, and the toughness suitable for the bonded magnet can be obtained. The lower limit of the n / i ratio is about 0.8.

The aromatic polyamide resin has an n / i ratio of 4.0.
In order to adjust the amount to be less than, for example, when synthesizing the polyamide resin, the mixing amount of the linear diamine (n-form) and the branched chain diamine (i-form) may be adjusted.

When ferrite powder particles are used as the magnetic powder, high packing, high orientation rate and high fluidity are required to improve magnetism, so that the n / i ratio is preferably 1.5 or less.

The melting point of the aromatic polyamide resin satisfying the n / i ratio is preferably 250 ° C. or higher. The upper limit is 320 ° C
Is less than. If the temperature is lower than 250 ° C, the heat resistance of the molded article is lowered, and therefore it is not suitable for applications requiring high heat resistance. Three
If the temperature is 20 ° C. or higher, the temperature approaches the decomposition temperature of the resin itself, making the molding process difficult. In addition, the crystallinity and hardness of the aromatic polyamide resin are increased, and the toughness is reduced. As a result, runner breakage during injection molding, cracking of the molded product, etc. occur and productivity is reduced.

Next, the aromatic polyamide resin in the present invention 3 will be described.

The aromatic polyamide resin in the resin composition for a bonded magnet of the present invention 3 has a terminal group ratio of 1.0 or less and an n / i ratio of less than 4.0. By simultaneously satisfying the terminal group ratio and the n / i ratio, it is possible to prevent deterioration of resin during molding, viscosity increase, runner breakage during molding, cracking of molded products and chipping, and to improve mechanical strength and heat resistance. An excellent bonded magnet can be obtained with high productivity.

The magnetic powder used in the present invention is preferably ferrite particle powder or rare earth magnetic powder.

The ferrite particle powder is preferably a magnetoplumbite type ferrite particle powder, and the magnetoplumbite type ferrite particle powder is represented by the formula AO.nFe ₂ O ₃
(However, A is Ba, Sr or Ba-Sr, n = 5.0-
6.5) barium ferrite particle powder, strontium ferrite particle powder, barium-strontium ferrite particle powder, and 0.1 to 7.0 mol% of Ti, Mn, Al and La in these ferrite particle powders.
It is a particle powder containing one or more elements selected from Zn, Bi and Co.

The average particle diameter of the ferrite particle powder is 1.0
.About.5.0 .mu.m is preferable, and more preferably 1.0 to 2.
Is 0 .mu.m, BET specific surface area is preferably 1 to 10 m ² / g, more preferably from 1 to 5 m ² / g, a coercive force IHc is 119~557kA / m (1500~7000
Oe) is preferable, and more preferably 119 to 398 kA.
/ M (1500 to 5000 Oe), and the residual magnetization is 1
00-300 mT (1000-3000 G) is preferable, and more preferably 100-200 mT (1000-2).
000G).

The rare earth magnetic powder is an intermetallic compound composed of at least one rare earth element and at least one transition metal among the constituent elements. For example, rare earth cobalt-based,
Magnetic powders of rare earth-iron-boron type, rare earth-iron-nitrogen type and the like can be mentioned. In particular, rare earth-iron-boron magnetic powder,
When the rare earth-iron-nitrogen based magnetic powder is used, a bonded magnet having excellent magnetic properties can be obtained.

The average particle size of the rare earth magnetic powder is 1 to 120.
μm is preferable, more preferably 1 to 80 μm,
The BET specific surface area is preferably 0.5 to ⁵ m ² / g, more preferably 0.5 to ³ m ² / g, and the coercive force IHc is preferably 239 to 1591 kA / m (3.0 to 20 kOe), and more preferably Is 318 to 1114 kA / m
(4.0-15 kOe) and the residual magnetization is 0.3-
It is preferably 1.8 mT (3.0 to 18 kG), more preferably 0.5 to 1.3 mT (5.0 to 13 kG).

The Nd-Fe-B system magnetic powder may be directly used for kneading. However, when the Nd-Fe-B system magnetic powder is a flaky powder, it should be ground with a jet mill, atomizer, ball mill or the like to have an average particle size of 100 μm or less in order to obtain higher fluidity and magnetic properties. Is desirable.

It is desirable that these magnetic powders be subjected to various surface treatments in order to deteriorate the magnetic properties due to oxidation, improve the compatibility with the resin, and improve the strength of the molded product.

Examples of the surface-treatable material include silane coupling agents, titanium coupling agents, aluminum coupling agents, siloxane polymers, organic phosphoric acid surface treating agents, inorganic phosphoric acid surface treating agents and the like. In particular, the strength of the molded product can be significantly improved by previously treating the surface of the magnetic powder with a silane coupling agent.

The content ratio of the magnetic powder in the resin composition for bonded magnets is preferably 80 to 95% by weight. If it is less than 80% by weight, the required magnetic properties cannot be obtained, which is not preferable. If it exceeds 95% by weight, the mechanical strength of the obtained bonded magnet is lowered, and the moldability such as fluidity and recyclability is extremely lowered, which is not preferable.

The resin composition for a bonded magnet according to the present invention contains a resin other than an aromatic polyamide resin, a plastic molding lubricant, and various other materials in order to improve moldability, heat resistance, prevent oxidative deterioration, and prevent rust. The stabilizer and the like can be optionally contained.

As the resin which can be added, an aliphatic polyamide resin having an affinity with an aromatic polyamide resin is preferable, and in consideration of the stability of the resin, a polyethylene resin, a polypropylene resin, a polybutene resin and a polymethylpentene resin are preferable. Olefinic resins such as resins are preferred.

As the lubricant, for example, carboxylic saturated / unsaturated fatty acid type such as propionic acid, stearic acid, linoleic acid, oleic acid, malonic acid, glutaric acid, adipic acid, maleic acid and fumaric acid, and compounds thereof , For example, metal soaps such as calcium stearate, magnesium stearate and lithium stearate, fatty acid amides such as hydrodystearic acid amide, ethylenebislauric acid amide and ethylenebisoleic acid amide, waxes such as paraffin wax,
Examples thereof include dimethylpolysiloxane, polysiloxanes such as silicon oil, and fluorine compounds such as fluorine-containing oil.

As the stabilizer, in addition to the hindered amine stabilizer, pentaerythrityl-tetrakis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate] and other hindered / less hindered phenolic systems, N, N′-bis [3- (3,5-di-t-
Examples thereof include metal deactivators such as butyl-4-hydroxyphenyl) propionylhydrazine, and antioxidants such as phosphite-based and thioether-based antioxidants. Especially hindered /
The combined use of rehindered phenol type and phosphite type or metal deactivator is effective.

Further, pigments, various modifiers for plastics, compatibilizers and the like may be added as needed, but when they are added, they cause decomposition and gasification at the time of molding. It is preferable to use.

The resin composition for a bonded magnet according to the present invention 1 has an MFR value of 100 to 500 g / 10 min.
The torque rise time of the plastomill is preferably 15-60 min.

The MFR value of the resin composition for bonded magnets according to the present invention 2 is preferably 70 to 500 g / 10 min. The bonded magnet using the resin composition for a bonded magnet according to the present invention 2 has an IZOD impact strength of 10 to 20 according to the evaluation method described below.
The bending strength is preferably kJ / m ² and 100 to 180 MPa.

The resin composition for bonded magnets according to the present invention 3 has an MFR value of 100 to 500 g / 10 min,
The torque rise time of the plastomill is preferably 22 to 60 minutes. A bonded magnet using the resin composition for a bonded magnet according to the present invention 3 has an IZOD according to the evaluation method described below.
Impact strength is 10 to 20 kJ / m ² and bending strength is 1
It is preferably from 00 to 180 MPa.

Next, a method for producing the resin composition for a bonded magnet according to the present invention will be described.

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

After mixing the above components, a resin composition for a bonded magnet having a shape of powder, pellets or a mixture thereof is obtained, but pellets are preferable from the viewpoint of easy handling.

A bond magnet can be obtained by molding the obtained resin composition for a bonded magnet with various thermoplastic resin molding machines, preferably an injection molding machine or an extrusion molding machine.

[0058]

BEST MODE FOR CARRYING OUT THE INVENTION A typical embodiment of the present invention is as follows.

The amount of the reactive end groups of the aromatic polyamide resin was determined by measuring the end group concentration by the NMR measurement from the ratio of the main chain to the end groups. Device: JEOL GX-400 (JEOL Ltd.) Solvent: Deuterated trifluoroacetic acid (1/4) Sample concentration: 1.0%

The solution viscosity of the aromatic polyamide resin was determined as follows.

That is, the dried aromatic polyamide resin 5
Dissolve 0 mg with concentrated sulfuric acid to adjust 25 cc of sulfuric acid solution,
It was introduced into an Ubbelohde viscometer (30 ° C./water 20) through a glass filter of 15AG P100, and the dropping time of the sulfuric acid solution was measured in a constant temperature water bath of 30 ° C. The measurement was repeated until the time difference between the two times was within 0.15 seconds, and the average of the two falling times was defined as t. Only concentrated sulfuric acid was measured in the same manner, and the fall time (blank value) was set to t ₀ . According to the following formula, the solution viscosity (η _inh ) was obtained by rounding off to the nearest three decimal places. η _inh (dl / g) = (ln (t / t ₀ )) ÷ (4 ×
Resin weight (g))

The melting point of the aromatic polyamide resin is JIS
According to K7121, it measured by the differential scanning calorimetry (DSC) using DSC220 (made by Seiko Instruments Inc.).

Flowability of resin composition for bonded magnet (MF
R) is a melt indexer (model P-101, manufactured by Toyo Seiki Seisakusho Co., Ltd.) with a heating cylinder temperature of 330 ° C. and a load of 10
It was measured under the condition of kgf.

The resin deterioration characteristic was evaluated by using a pellet-shaped resin composition for a bonded magnet 60 cc (calculated value from the compound true density) with a Labo Plastomill (type 30C-150,
(Toyo Seiki Seisakusho Co., Ltd.), the mixture was kneaded at a temperature of 330 ° C. and a screw rotation speed of 50 rpm, and the kneading torque during kneading was measured. Kneading torque is 1.5k from the start of kneading
The time required to exceed g · m was defined as the torque rise time.

The injection moldability when rare earth magnetic powder was used as the magnetic powder was evaluated in the following three stages. ○: Continuous molding possible △: Rarely short shots ×: Always short shots (bond magnets cannot be molded)

The injection moldability when ferrite particle powder was used as the magnetic powder was evaluated in the following three stages. ○: Continuous molding is possible △: Runner sprue is rarely broken ×: Runner sprue is always broken (bond magnet cannot be molded)

The magnetic characteristics of the injection molding machine (model J-20M
II, manufactured by Japan Steel Works Ltd., φ10 mm x 7 m
A cylindrical bonded magnet of m was injection-molded and measured at room temperature using a rare earth temperature coefficient measuring device (model TRF-5BH-25auto, manufactured by Toei Industry Co., Ltd.).

The mechanical strength of the injection molding machine (model J-20
80 mm x 12 using MII, manufactured by Japan Steel Works, Ltd.
A mm × 3 mm plate-shaped bonded magnet was injection-molded, and the bending strength was measured with an autograph (model AG-10kNI, manufactured by Shimadzu Corporation). The IZOD impact value was measured with an Izod impact tester (manufactured by Yasuda Seiki Seisakusho).

The deflection temperature under load is determined by the injection molding machine (model J-
125 mm using 20MII, manufactured by Japan Steel Works, Ltd.
Injection-molded a plate-shaped bonded magnet of × 13 mm × 4 mm, H
It was measured with a DT tester (model S-3M, manufactured by Toyo Seiki Seisakusho Co., Ltd.).

<Production of Bonded Magnet I (Invention 1)> Nd
-Fe-B system magnetic powder (90.5% by weight, average particle size 70
μm, coercive force 748 kA / m (9.4 kOe), remanent magnetization 875 mT (8750 G)) and 5 with 2-propanol
A silane coupling agent (0.5% by weight) diluted with 0% (A-1100, manufactured by Nippon Unicar Co., Ltd.) was added to a Henschel mixer and heated at 100 ° C. with stirring to be Nd-Fe-B type. The magnetic powder was surface-treated. Next, aromatic polyamide resin (9.0% by weight, solution viscosity 0.7 dl / g, terminal group ratio 0.3, melting point 303 ° C., residual amount of terminal amino group 1.01 mol%) (trade name: Genestar, Kuraray (Manufactured by Mitsui Chemical Co., Ltd.) was added and mixed and stirred sufficiently. The obtained mixture was mixed with a 20 mmφ twin-screw extruder (rotation speed 96 rp
m, 3 mmφ die, cylinder temperature 310 ° C.) and then cut to obtain a pellet-shaped resin composition for a bonded magnet of 3 mmφ × 4 mm.

The MFR showing the fluidity of the pellet-shaped resin composition for a bonded magnet is a heating cylinder temperature of 330 ° C. and a load of 10 kg.
It was 220 g / 10 min under the condition of f, and the torque rise time was 36 min.

The obtained pellet-shaped resin composition for a bonded magnet was injection molded (molding temperature: 280 to 320 ° C.) by an injection molding machine (model J-20MII, manufactured by Japan Steel Works, Ltd.).
Mold temperature is 110 to 140 ° C.), cylindrical rare earth-based bonded magnet of φ10 mm × 7 mm and 80 mm × 12 mm × 3
A plate-shaped rare earth-based bonded magnet having a thickness of mm was obtained. Injection moldability is
Continuous molding was possible (○).

The magnetic properties of the obtained bond magnet are as follows: residual magnetic flux density is 530 mT (5.3 kG) and coercive force is 716 k.
A / m (9.0 kOe), maximum magnetic energy product is 4
It was 5.3 kJ / m ³ (5.7 MGOe). The deflection temperature under load was 209 ° C.

<Manufacture of Bonded Magnet II-1 (Invention 2): Rare Earth Bonded Magnet> Nd-Fe-B magnetic powder (89.5% by weight, average particle size 70 μm, coercive force 748 k)
A / m (9.4 kOe), remanent magnetization 875 mT (875
0G)) and a silane coupling agent (0.5 wt%) diluted to 50% with 2-propanol (A-1100, manufactured by Nippon Unicar Co., Ltd.) are charged into a Henschel mixer and heated at 100 ° C. with stirring. Then, the Nd-Fe-B based magnetic powder was subjected to surface treatment. Then, aromatic polyamide resin (9.5% by weight, solution viscosity 0.68 dl / g, n /
i ratio 1.0, terminal group ratio 0.3, melting point 275 ° C., terminal amino group concentration 0.86 mol%) (Brand name: Genestar,
(Manufactured by Kuraray Co., Ltd.) and an olefinic additive (0.5% by weight) (Viscor 550P, manufactured by Sanyo Chemical Industry Co., Ltd.) were added and sufficiently mixed and stirred. The resulting mixture is 2
The resin composition for a bond magnet was extruded with a 0 mmφ twin-screw extruder (rotation speed: 96 rpm, 3 mmφ die, cylinder temperature: 290 ° C.) and cut into a pellet-shaped resin composition of 3 mmφ × 4 mm.

The MFR showing the fluidity of the pellet-shaped resin composition for a bonded magnet is a heating cylinder temperature of 330 ° C. and a load of 10 kg.
450g / 10min under the condition of f, and the torque rise time is 3
It was 6 minutes or more.

The obtained pellet-shaped resin composition for a bonded magnet was injection molded (molding temperature: 280 to 320 ° C.) by an injection molding machine (model J-20MII, manufactured by Japan Steel Works, Ltd.).
Mold temperature is 110 to 140 ° C.), cylindrical rare earth-based bonded magnet of φ10 mm × 7 mm and 80 mm × 12 mm × 3
A plate-shaped rare earth-based bonded magnet having a thickness of mm was obtained.

The magnetic characteristics of the obtained bonded magnet are remanent magnetism.
Flux density is 500 mT (5.0 kG), coercive force is 724 k
A / m (9.1 kOe), maximum magnetic energy product is 4
0.6 kJ / m^Three(5.1 MGOe). IZO
D impact strength is 14.0 kJ / m ^TwoAnd the bending strength is 1
It was 17 MPa. The deflection temperature under load is 202 ° C.
It was

<Manufacture of Bonded Magnet II-2 (Invention 2): Ferrite Bonded Magnet> Ferrite particle powder (85.7% by weight, strontium ferrite, average particle diameter 1.3 μm, BET specific surface area value 1.65 m ² / G,
Coercive force 223 kA / m (2.8 kOe), remanent magnetization 17
7mT (1770G)) and 50% diluted with 2-propanol Silane coupling agent (0.5% by weight) (A
-1100, manufactured by Nippon Unicar Co., Ltd.) was put into a Henschel mixer and heated at 100 ° C. with stirring to perform surface treatment of the ferrite particle powder. Then, aromatic polyamide resin (13.8 wt%, solution viscosity 0.90 dl
/ G, n / i ratio of 1.0, melting point of 275 ° C., terminal amino group concentration of 0.5 mol%) (trade name: Genesta, manufactured by Kuraray Co., Ltd.) was added and sufficiently mixed and stirred. The resulting mixture is
It was extruded with a 20 mmφ twin-screw extruder (rotation speed 96 rpm, 3 mmφ die, cylinder temperature 290 ° C.) and then cut into a 3 mmφ × 4 mm pellet-shaped resin composition for a bonded magnet.

The MFR showing the fluidity of the pellet-shaped resin composition for a bonded magnet is a heating cylinder temperature of 340 ° C. and a load of 10 kg.
It was 100 g / 10 min under the condition of f.

The obtained pellet-shaped resin composition for a bonded magnet was injection molded (molding temperature: 280 to 320 ° C.) with an injection molding machine (model J-20MII, manufactured by Japan Steel Works, Ltd.).
Mold temperature 110-140 ℃, orientation magnetic field 8kOe), φ
A cylindrical ferrite-based bonded magnet of 10 mm × 7 mm and a plate-shaped ferrite-based bonded magnet of 80 mm × 12 mm × 3 mm were obtained. The injection moldability was such that continuous molding was possible (∘), and the number of runner breaks was 0 out of 10.

The magnetic properties of the obtained bonded magnet are as follows: residual magnetic flux density is 250 mT (2.5 kG) and coercive force is 239 k.
A / m (3.0 kOe), maximum magnetic energy product is 1
It was 2.1 kJ / m ³ (1.52 MGOe).

<Production of Bonded Magnet III (Invention 3)>
Nd-Fe-B system magnetic powder (91.5 wt%, average particle size 70 μm, coercive force 748 kA / m (9.4 kOe), remanent magnetization 875 mT (8750 G)) and silane system diluted to 50% with 2-propanol. A coupling agent (0.5% by weight) (A-1100, manufactured by Nippon Unicar Co., Ltd.) was put into a Henschel mixer and heated at 100 ° C. with stirring to perform surface treatment of the Nd—Fe—B magnetic powder. It was
Then, aromatic polyamide resin (7.5 wt%, solution viscosity 0.65 dl / g, terminal group ratio 0.4, n / i ratio 1,
(Melting point: 275 ° C., residual amount of terminal amino group: 0.8 mol%)
(Trade name: Genesta, manufactured by Kuraray) and an olefinic additive (0.5% by weight) were added, and they were sufficiently mixed and stirred. The obtained mixture was mixed with a 20 mmφ twin-screw extruder (rotation speed 96 rp
m, 3 mmφ die, cylinder temperature 290 ° C.) and then cut to obtain a pellet-shaped resin composition for 3 mmφ × 4 mm bond magnet.

The MFR showing the fluidity of the pellet-shaped resin composition for a bonded magnet is a heating cylinder temperature of 330 ° C. and a load of 10 kg.
It was 430 g / 10 min under the condition of f, and the torque rise time was 36 min or more.

The obtained pellet-shaped resin composition for a bonded magnet was injection molded (molding temperature: 280 to 320 ° C.) by an injection molding machine (model J-20MII, manufactured by Japan Steel Works, Ltd.).
Mold temperature is 110 to 140 ° C.), cylindrical rare earth-based bonded magnet of φ10 mm × 7 mm and 80 mm × 12 mm × 3
A plate-shaped rare earth-based bonded magnet having a thickness of mm was obtained.

Regarding the magnetic characteristics of the obtained bonded magnets, the residual magnetic flux density was 540 kT (5.4 kG), the coercive force was 724 kA / m (9.1 kOe), and the maximum magnetic energy product was 50.9 kJ / m ³ ( It was 6.5 MGOe).
The IZOD impact strength was 10.3 kJ / m ² and the bending strength was 102 Pa. The deflection temperature under load was 215 ° C.

[0086]

In general, the rare earth magnetic powder used for the bonded magnet is active, and the resin composition using the aromatic polyamide resin having a high melting point is heated at high temperature during kneading, injection and extrusion processing, so that the resin component is deteriorated. However, the resin composition was thickened and solidified, and the fluidity of the resin composition was poor. This phenomenon causes deterioration of moldability and reduction of strength of a molded product during processing and molding. Further, in order to reliably recycle defective molded products and runners, it is necessary to suppress the deterioration of the components of the aromatic polyamide resin as much as possible.

In the resin composition for a bonded magnet according to the first aspect of the present invention, the ratio of the terminal groups of the aromatic polyamide resin is reduced to increase the residual ratio of the terminal amino groups, thereby improving the fluidity and the torque rise time in the plastomill. I was able to do it. The reason for this is not yet clear, but the affinity between the aromatic polyamide resin and the magnetic powder is increased by decreasing the ratio of the end groups, and the fluidity is improved.
It is believed that the deterioration of the resin component could be suppressed. The improvement of fluidity is an improvement of moldability, and it can be expected that the processing temperature is lowered, the load on the processing machine is reduced, and the productivity is improved. The improvement of torque rise time in Plastmill is
It shows a decrease in the viscosity increasing rate of the resin due to a crosslinking reaction and the like, and the strength and recyclability are improved. As a result, since the resin composition for a bonded magnet according to the present invention is excellent in moldability such as fluidity and recyclability, the use amount of a commonly used lubricant or resin stabilizer is reduced, or the lubricant or resin is stabilized. It shows that no agent needs to be used.

A bonded magnet using an aromatic polyamide resin generally has a high bending strength, but has a low IZOD impact strength and a small shrinkage ratio, and therefore cracks of the product or a runner at the time of taking out the product by injection molding. There is a problem that continuous molding cannot be performed because of the breakage.

The resin composition for a bonded magnet according to the present invention 2 can be continuously molded by improving the toughness of the resin. This is because the crystallinity of the resin is lowered by increasing the content of the branched chain diamine, as a result, the toughness is improved, and sufficient toughness can be ensured against impact during mold opening and product ejection. It is considered that continuous molding has become possible. In addition, as the crystallinity of the resin decreases, the melting point and the crystallization speed may decrease. The lowering of the melting point can lower the molding temperature, and the deterioration of the resin and the magnetic powder during molding can be suppressed to the minimum. Although there is concern that the heat resistance of the bond magnet, which is the original purpose, may decrease due to the decrease in the melting point, the bending temperature under load of the bond magnet according to the present invention is 200 ° C. or higher, and the load when 6 nylon is used. Deflection temperature (170 ° C) and 12
It is higher than the deflection temperature under load (about 150 ° C.) when nylon is used, and shows a characteristic that can sufficiently withstand solder reflow and the like. It is considered that the decrease in the crystallization rate suppresses shrinkage cracks, sink marks, etc. due to a rapid temperature decrease during filling in injection molding.

As described above, by adjusting the n / i ratio of the aliphatic diamine to control the melting point of the aromatic polyamide resin, it is possible to manufacture a bonded magnet according to the required mechanical strength.

[0091]

EXAMPLES Next, examples and comparative examples will be given.

Resin compositions for bonded magnets according to the present invention Examples A to D, Comparative examples a to b: Embodiments of the invention except that the solution viscosity and the terminal group ratio of the aromatic polyamide resin were variously changed. : A bonded magnet was obtained in the same manner as in Production I of bonded magnet.

Table 1 shows the manufacturing conditions and various characteristics of the obtained bonded magnet at this time. 1 and 2 show changes with time of torque during kneading.

[0094]

[Table 1]

From the examples and comparative examples, the end group ratio was 1.0.
In the following cases, it can be confirmed that the torque rise time is long and the fluidity is excellent.

Resin Compositions for Bonded Magnets According to the Present Invention Examples E and F, Comparative Example c: n / Aromatic Polyamide Resin
A rare earth-based bonded magnet was obtained in the same manner as in the embodiment of the invention: Production of bonded magnet II-1 except that the i ratio was variously changed.

Table 2 shows the manufacturing conditions and various characteristics of the obtained rare earth-based bonded magnet at this time.

[0098]

[Table 2]

Resin compositions for bonded magnets according to the present invention Examples G to I, Comparative examples d and e: Embodiments of the invention except that the n / i ratio of the aromatic polyamide resin was variously changed. A ferrite-based bonded magnet was obtained in the same manner as in Magnet Production II-2.

Table 3 shows the manufacturing conditions and various characteristics of the obtained ferrite-based bonded magnet at this time.

[0101]

[Table 3]

From the examples and comparative examples, it can be confirmed that when the n / i ratio is less than 4.0, a bond magnet having high IZOD impact strength and high bending strength can be obtained. Further, it can be seen that it is more effective to decrease the n / i ratio than to increase the resin viscosity to improve the strength against runner breakage during molding.

A resin composition for a bonded magnet according to the present invention 3. Examples J to L, Comparative examples f to h: Embodiments of the invention described above except that the end group ratio and n / i ratio of the aromatic polyamide resin were changed: Bond magnets were prepared in the same manner as in Production III of bond magnets. Obtained.

Table 4 shows the production conditions and various characteristics of the obtained bonded magnet at this time. PA9T of the resin means 9T nylon which is an aromatic polyamide resin.

[0105]

[Table 4]

From the examples and comparative examples, the end group ratio was 1.0.
In the following cases, it can be confirmed that the torque rise time is long and the fluidity is excellent. When the n / i ratio is less than 4.0, a bonded magnet having high IZOD impact strength and bending strength is obtained. In Comparative Example g, although the end group ratio is a lower value compared to all Examples, Examples J to L
Inferior to all the characteristics in comparison with, the n / i ratio is 4.
It is 0 or more, and is considered to be caused by high crystallinity. From this, it is understood that the combined use of the adjustment of the terminal group ratio and the adjustment of the n / i ratio is effective.

[0107]

The resin composition for a bonded magnet according to the present invention is excellent in moldability because the ratio of the terminal amino group and the terminal carboxyl group of the aromatic polyamide resin is appropriately adjusted. It is suitable as a resin composition.

The resin composition for a bonded magnet according to the present invention is prepared by appropriately adjusting the content ratio of the linear diamine and the branched diamine of the aliphatic diamine constituting the aromatic polyamide resin. Since it has excellent moldability and toughness, it is suitable as a resin composition for bonded magnets.

Therefore, according to the present invention, it is possible to provide a bonded magnet excellent in mechanical strength and heat resistance.

[Brief description of drawings]

FIG. 1 shows changes with time of kneading torques of Examples A and B and Comparative Example a.

FIG. 2 shows changes with time of kneading torques of Examples C and D and Comparative Example b.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takayoshi Ohara             Toda Kogyo Co., Ltd. 1-4 Meiji Shinkai, Otake City, Hiroshima Prefecture             Ceremony company Otake factory F-term (reference) 4J002 CL031 DA08 GT00                 5E040 AA04 BB04 CA01 NN04

Claims (4)

[Claims] 1. A resin composition for a bonded magnet, comprising a magnetic powder and an aromatic polyamide resin, wherein the molar ratio of the residual amount of the terminal carboxyl groups of the aromatic polyamide resin to the residual amount of the terminal amino groups ([terminal A resin composition for a bonded magnet, characterized by using an aromatic polyamide resin having a carboxyl group] / [terminal amino group]) of 1.0 or less. 2. A resin composition for a bonded magnet, comprising a magnetic powder and an aromatic polyamide resin, wherein the aliphatic diamine constituting the aromatic polyamide resin comprises a linear diamine and a branched diamine. An aromatic polyamide resin having a molar ratio ([straight chain diamine] / [branched chain diamine]) of the chain diamine content to the branched chain diamine content of less than 4.0 is used. And a resin composition for a bonded magnet. 3. A resin composition for a bonded magnet, comprising a magnetic powder and an aromatic polyamide resin, wherein the molar ratio of the residual amount of terminal carboxyl groups and the residual amount of terminal amino groups of the aromatic polyamide resin ([terminal [Carboxyl group] / [terminal amino group]) is 1.0 or less, and the aliphatic diamine constituting the aromatic polyamide resin is composed of a linear diamine and a branched diamine, and the linear diamine is contained. For a bonded magnet, characterized in that an aromatic polyamide resin having a molar ratio ([straight chain diamine] / [branched chain diamine]) of less than 4.0 to the content of the branched chain diamine is used. Resin composition. 4. A bond magnet comprising the resin composition for a bond magnet according to any one of claims 1 to 3.