JP4702396B2 - Bonded magnet composition and bonded magnet using the same - Google Patents

Description

  The present invention relates to a composition for a bonded magnet and a bonded magnet using the same, and more specifically, for a bonded magnet having excellent fluidity at low-temperature melting, good injection moldability, and excellent mechanical properties such as magnetic properties and rigidity. The present invention relates to a composition and a bonded magnet using the composition.

  Ferrite magnets, alnico magnets, rare earth magnets, and the like are incorporated and used as motors in various products including general home appliances, communication / acoustic equipment, medical equipment, and general industrial equipment. These magnets are mainly manufactured by a sintering method, but magnets manufactured by a sintering method are fragile and difficult to be thinned, so it is difficult to form a complicated shape, and shrinks by 15 to 20% during sintering. Therefore, dimensional accuracy cannot be improved, post-processing such as polishing is required, and there are significant restrictions in terms of application.

  In contrast, resin-bonded magnets (called bonded magnets) are easily filled with magnetic powder using thermoplastic resins such as polyamide resins and polyphenylene sulfide resins, and thermosetting resins such as epoxy resins and phenol resins as binders. New applications are being developed. In particular, an injection-molded magnet manufactured by injection molding using a thermoplastic resin as a binder has a feature that the shape flexibility is excellent compared to other bond magnets such as a compression-molded magnet and an extrusion-molded magnet.

An injection-molded magnet is manufactured by injecting a bonded magnet composition melted inside a cylinder of an injection molding machine into a mold. The mold is provided with a cavity having a predetermined product shape and a runner for the melted bonded magnet composition called sprue or runner. The temperature of the mold is set so that it is not higher than the melting point of the thermoplastic resin used in the composition. Therefore, the injected molten composition is rapidly cooled and solidified in the mold, and the magnet molded product. As taken out.
Here, for example, in the case of a bonded magnet composition using a polyamide resin as a binder, the mold temperature is often set to about 80 to 110 ° C. In order to shorten the molding cycle and improve productivity, the mold temperature may be set lower to shorten the cooling time. Also, in the case where an orientation magnetic field is generated in the cavity by embedding a rare earth sintered magnet in the die, the die is prevented in order to prevent the orientation magnetic field from decreasing according to the temperature coefficient α (Br) of the rare earth sintered magnet. The temperature may be set as low as possible. For example, α (Br) of the Nd—Fe—B sintered magnet is −0.11% / K. Therefore, when the mold set temperature changes by 80 ° C., the orientation magnetic field changes by 9%. In these cases, the mold temperature may be set to less than 80 ° C, and further to 10 to 50 ° C.
The lower the mold set temperature, the faster the melted bonded magnet composition cools as it passes through the sprue and runner, so the composition fills well before reaching the cavity or within the cavity. It becomes solidified before, and molding defects called short shots are likely to occur.

One countermeasure is to incorporate a hot sprue or hot runner system that can be heated into the mold to avoid solidification with the sprue runner. It is difficult to incorporate a mold having a structure. Another possible method is to raise the cylinder temperature of the injection molding machine to sufficiently raise the temperature of the injected composition. However, when the magnetic powder is a rare earth magnetic powder, it is oxidized by placing it in a high temperature. There is a possibility that the magnetic powder due to the deterioration of the characteristics, and the desired magnet performance cannot be obtained. In addition, a method has been proposed in which the melt viscosity of the composition is lowered and the flow resistance is reduced, so that the sprue and the runner are quickly passed and filled. In order to realize this, a binder having a high MI (melt flow index) value is selected, a lubricant or the like is added, or the powder properties of the magnetic powder are adjusted.

For example, a mixture of (a) a homopolymerized polyamide resin and (b) any of a copolymerized polyamide, a polyamide-based elastomer, and a polyester-based elastomer, where (b) / (a + b) is in a specific range, There has been proposed a method for manufacturing a compound for a bonded magnet in which the melt viscosity of the compound is lowered by use and the solidification rate of the once melted compound is set within a specific range (see Patent Document 1).
According to this, it is expected that a bonded magnet with good orientation and excellent magnetic properties can be obtained, but even if the melt viscosity of the composition is simply lowered, the backflow is generated inside the cylinder of the injection molding machine. There was a problem that it would not be effective unless it occurs or is an expensive ultra-high speed injection molding machine.
In addition, as another problem, even when the set temperature of the mold is a normal 80 to 110 ° C., when the time for the molten bonded magnet composition to reach the product cavity from the sprue bush of the mold is long In the course of injection filling, the melt viscosity of the composition may increase and molding defects may occur.

On the other hand, the melt fluidity of the composition for bonded magnets can be improved and good melt fluidity can be maintained even if the filling amount of magnetic powder is increased in order to increase the magnetic force of the molded product. In order to obtain a bonded magnet molded product that can suppress a decrease in molding processability due to a decrease in property, a polymer fatty acid-based polyether ester amide block copolymer is included in a main resin of a thermoplastic resin as a resin binder. A composition for a bonded magnet has been proposed (for example, Patent Document 2). In addition, a bonded magnet composition using a resin binder in which a polymer fatty acid-based polyamide block copolymer is contained in a main resin made of a thermoplastic resin has been proposed (for example, Patent Document 3).
These use a thermoplastic resin as the main material resin, and add a small amount of polymerized fatty acid-based polyether ester amide block copolymer or polymerized fatty acid-based polyamide block copolymer to the resin binder. With this resin binder, the problem relating to the improvement of the bond magnet injection moldability could not be solved sufficiently.

In the composition for bonded magnets using these polymerized fatty acid-based polyether ester amide block copolymers and polymerized fatty acid-based polyamide block copolymers, the inventors focused on the temperature dependence of the melt viscosity and started solidification thereof. It succeeded in improving by making the difference of temperature and solidification completion temperature more than a specific value (patent document 4). However, miniaturization and thinning of injection molded bodies have progressed, and better injection moldability has been demanded.
JP 2001-85209 A Japanese Patent Laid-Open No. 2001-123067 JP 2001-240740 A JP 2005-72564 A

  An object of the present invention is to provide a bonded magnet composition that is excellent in fluidity and injection moldability during low-temperature melting and a bonded magnet that is excellent in mechanical strength such as rigidity.

  As a result of intensive studies to achieve the above object, the present inventors have used a polymerized fatty acid type polyamide resin synthesized using a specific amine component (polyethylene glycol dialkylamine) and an acid component as a resin binder. Is a composition for bonded magnets in which a rare earth-transition metal magnetic powder is mixed, and has a supercooling degree ΔT of 15 ° C. or higher evaluated by a differential scanning calorimeter, which is excellent in injection moldability. The present invention was completed by confirming that a bonded magnet having excellent mechanical strength and magnetic properties can be obtained by injection molding the composition for bonded magnet having a high degree of supercooling.

That is, according to the first aspect of the present invention, in the bonded magnet composition comprising the rare earth-transition metal magnetic powder (A) and the polymerized fatty acid-based polyamide block copolymer (B), the polymerized fatty acid-based polyamide block The copolymer (B) has a structure composed of a polymerized fatty acid residue mainly composed of dimer acid and a polyethylene glycol dialkylamine residue, and the degree of supercooling of the composition represented by the following formula (1) There is provided a bonded magnet composition characterized in that ΔT is 15 ° C. or higher.
ΔT = Tc (5) −Tc (50) (1)
[In the formula, Tc (5) is obtained by using a differential scanning calorimeter, the composition was heated to 280 ° C. at 20 ° C./min in a nitrogen stream, held for 2 minutes, and then −5 ° C. / Solidification temperature measured by cooling to near room temperature with min, Tc (50) is the solidification temperature measured with a cooling rate of −50 ° C./min]

According to the second invention of the present invention, in the first invention, the rare earth-transition metal magnetic powder (A) is at least selected from SmCo magnetic powder, NdFeB magnetic powder, and SmFeN magnetic powder. There is provided a bonded magnet composition characterized by being one type.
According to a third aspect of the present invention, there is provided the composition for a bonded magnet according to the first aspect, wherein the dimer acid is an unsaturated fatty acid having 20 to 48 carbon atoms.
According to a fourth aspect of the present invention, there is provided the bonded magnet composition according to the first aspect, wherein the polyethylene glycol dialkylamine has an alkyl group having 2 to 20 carbon atoms. .
According to a fifth aspect of the present invention, in the first aspect, the polymerized fatty acid-based polyamide block copolymer (B) further comprises an aliphatic diamine residue having 2 to 12 carbon atoms and a carbon number of 6 to 6. There is provided a composition for a bonded magnet comprising a structure consisting of 18 aliphatic dicarboxylic acid residues.
According to a sixth invention of the present invention, in the fifth invention, the aliphatic diamine is ethylenediamine, 1,4-diaminobutane, tetramethylenediamine, methylpentamethylenediamine, hexamethylenediamine, nonamethylenediamine. , Undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, bis- (4,4'-aminocyclohexyl) methane, metaxylylenediamine para There is provided a composition for a bonded magnet, which is at least one selected from the group consisting of xylylenediamine, isophoronediamine, and norbornanediamine.
According to a seventh aspect of the present invention, in the fifth aspect, the aliphatic dicarboxylic acid is selected from the group consisting of adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid, eico There is provided a composition for a bonded magnet, which is at least one selected from the group consisting of sandioic acid, eicosadienedienedioic acid, diglycolic acid, and 2,2,4-trimethyladipic acid.
Furthermore, according to the eighth invention of the present invention, in the first invention, the number average molecular weight of the polymerized fatty acid-based polyamide block copolymer (B) is 20,000-60,000. A bonded magnet composition is provided.

  On the other hand, according to the ninth invention of the present invention, there is provided a bond magnet according to any one of the first to eighth inventions, wherein the bond magnet composition is injection molded.

  The composition for bonded magnets of the present invention uses a specific polymerized fatty acid-based polyamide block copolymer having a structure composed of a polymerized fatty acid residue mainly composed of dimer acid and a polyethylene glycol dialkylamine residue, and Since the degree of supercooling of the composition is high, solidification of the composition injected and filled in the mold and rapidly cooled can be delayed, and the moldability is excellent. Therefore, by using this composition for bonded magnets, a thin and small bonded magnet can be easily manufactured by injection molding.

  Hereinafter, the composition for bonded magnets of the present invention and the bonded magnet obtained using the composition will be described in detail.

1. The composition for bonded magnets The composition for bonded magnets according to the present invention contains a rare earth-transition metal magnetic powder (A) and a polymerized fatty acid-based polyamide block copolymer (B).

(A) Rare earth-transition metal magnetic powder As rare earth-transition metal magnetic powder (A), rare earth-iron magnetic powder, rare earth-iron-boron magnetic powder, rare earth-cobalt magnetic powder, etc. Various magnetic powders used as raw materials can be used and are not particularly limited, but magnetic powders containing rare earth elements that are liable to deteriorate magnetic properties due to oxidation at high temperatures are effective. These may be a mixture (hybrid), and are not only anisotropic magnetic powder but also isotropic magnetic powder.

As rare earth elements, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), Examples include holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and one or more of these groups are selected and can be used alone or as a mixture. As the rare earth element, Sm, Nd, Pr, Y, La, Ce, Gd and the like are preferable, and either Nd or Sm is particularly preferable.
On the other hand, examples of the transition metal element include iron (Fe), cobalt (Co), nickel (Ni), and manganese (Mn), and one or more are selected from these groups. In addition to this, in transition metal element, you may contain either Cr, V, or Cu. A particularly preferred transition metal element is either Fe or Co.
In addition to the main components of the magnetic powder, C, Al, Si, P, Ca, Ti, Mn, Ni, Zn, Ga, Zr, Nb, Mo, Ag, In, Sn, Hf, Ta, W, When one or more selected from Re, Os, Ir, Pt, or Au is added to the magnetic powder in an amount of 7% by weight or less, the heat resistance of the magnetic powder can be improved.
As the rare earth-transition metal magnetic powder, for example, one kind selected from rare earth-cobalt, rare earth-iron-boron, rare earth-iron-nitrogen magnetic powder, or a mixture of two or more kinds can be used. Rare earth-iron-nitrogen based magnetic powder is preferred.

As the rare earth-iron-nitrogen based magnetic powder, for example, the magnetic powder is 20 to 25% by weight of Sm, 2.1 to 4.0% by weight of N, and the balance is essentially composed of Fe as an essential element. An intermetallic compound having a Th2Zn17 crystal structure, which is a metal, is desirable.
If Sm is less than 20% by weight, the coercive force HcJ of the bonded magnet is reduced, and if it exceeds 25% by weight, the residual magnetic flux density Br of the bonded magnet is reduced, while N is less than 2.1% by weight or 4.0. When the weight percentage is exceeded, the coercive force HcJ of the bonded magnet decreases. If 30% by weight or less of the remaining Fe is replaced with Co, the saturation magnetization and the Curie temperature of the magnetic powder increase, and the temperature coefficient α (Br) of the bonded magnet can be kept low.
As another magnetic powder, 20 to 25% by weight of Sm, 3.5 to 5.5% by weight of N, 1.0 to 10% by weight of Mn, and the balance is essentially composed of Fe as an essential element. It is desirable to include an intermetallic compound having a Th2Zn17 type crystal structure which is a metal.
If the Sm is less than 20% by weight, the coercive force HcJ of the bonded magnet is reduced, and if it exceeds 25% by weight, the residual magnetic flux density Br of the bonded magnet is decreased, while N is less than 3.5% by weight. If it exceeds 5% by weight, the coercive force HcJ of the bonded magnet is lowered. If 30% by weight or less of the remaining Fe is replaced with Co, the saturation magnetization and the Curie temperature of the magnetic powder increase, and the temperature coefficient α (Br) of the bonded magnet can be kept low.

The physical properties of the rare earth-transition metal magnetic powder are not particularly limited, but from the viewpoint of the melt fluidity of the obtained bonded magnet composition, the orientation of the magnetic powder, the filling rate, etc., the rare earth-transition metal magnetic The average particle size of the powder is preferably 1 to 100 μm. Furthermore, in the case of obtaining a small thin magnet, it is preferably 1 to 50 μm, preferably 1 to 50 μm, in order to improve the fluidity of the composition and increase the magnet density and magnetic properties. More preferably it is.
However, the anisotropic Nd—Fe—B based magnetic powder produced by the HDDR method has a case where the magnetic properties may be lowered when the average particle size is 0.1 to 10 μm. It is preferable to be set to ˜100 μm.
In the present invention, one or more kinds of magnetic powders of ferrite magnetic powders such as Sr ferrite and Ba ferrite and metal magnetic material powders such as alnico and iron chrome cobalt are used in accordance with the required magnetic properties. A powder mixed with the material powder can be used.
The mixing ratio of the ferrite magnetic powder to the rare earth-transition metal magnetic powder can be arbitrarily set. However, if the amount of the rare earth magnetic powder is set to be larger than the target magnetic characteristics, the rare earth magnetic powder and the ferrite magnetic powder are mixed. Since the total amount can be reduced, a composition for a bond magnet having a low melt viscosity can be obtained. Conversely, if the amount of ferrite is set to be large, the cost performance of the composition can be improved.

In addition, in the magnetic powder containing rare earth elements, it is desirable to use a powder whose surface is uniformly coated with a metal compound film such as Zn or a phosphate film having an average of 3 to 100 nm. The phosphate coating is a composite phosphate containing at least iron phosphate and a rare earth element phosphate, and is a coating that protects the surface of the magnetic powder. If the average thickness of the phosphate coating is less than 3 nm, sufficient weather resistance cannot be obtained, and if it exceeds 100 nm, the magnetic properties deteriorate and the kneading properties and moldability also deteriorate.
In the present invention, the surface of the magnetic powder is uniformly coated with a metal phosphate (a-1) containing iron and rare earth elements as metal components, and any one of aluminum, zinc, manganese, copper or calcium is used. More preferably, the metal phosphate (a-2) containing the above as a metal component is uniformly coated with a composite film. Here, uniformly coated means that 80% or more, preferably 85% or more, more preferably 90% or more of the surface of the magnetic powder is covered with the composite metal phosphate coating.

The metal phosphate (a-1) is samarium phosphate, iron phosphate or the like, which is formed by reacting phosphoric acid with the rare earth or iron constituting the magnetic powder. Metal phosphates are also included. On the other hand, the metal phosphate (a-2) is, for example, aluminum phosphate, zinc phosphate, manganese phosphate, copper phosphate, calcium phosphate, or a metal salt in which two or more of these are combined. In addition to aluminum, zinc, manganese, copper and calcium, the metal component may be chromium, nickel, magnesium, etc., and these metal phosphates may be contained in the composite metal phosphate coating.
The metal phosphate (a-1) or the metal phosphate in which the metal phosphate (a-2) is complexed is a component that increases the bonding strength with the resin binder and increases the corrosion resistance of the magnetic powder. Although sufficient salt water resistance can be obtained only with the metal phosphate (a-1), in order to further increase the salt water resistance, metal components of the metal phosphate (a-2), that is, aluminum, zinc, manganese, copper Or a composite phosphate containing at least one selected from calcium in an amount of 30% by weight or more, particularly 50% by weight or more, more preferably 80% by weight or more based on the total amount of metal components of the composite phosphate coating. Is preferred. The film thickness of the magnetic powder (A) is preferably 1 to 100 nm, particularly 10 to 80 nm on average. When the average thickness is less than 1 nm, sufficient salt water resistance and mechanical strength cannot be obtained. On the other hand, when the average thickness exceeds 100 nm, the magnetic properties deteriorate, and when a bonded magnet is produced, kneadability and formability deteriorate. . The film thickness of the multilayered coating film can be confirmed from an electron micrograph of the cross section of the magnetic powder coated with the multilayered coating film.
The magnetic powder on which the composite metal phosphate coating is formed is preferably further coated with a silicate coating or a silane coupling agent-treated coating. The individual thicknesses of the silicate coating or the silane coupling agent-treated coating are not particularly limited, but it is preferable that all are 5 to 40 nm.

(B) Polymerized fatty acid-based polyamide block copolymer The resin binder used in the present invention is a specific polymerized fatty acid-based polyamide block copolymer (hereinafter also simply referred to as a polyamide block copolymer), and has a dimer in the molecular structure. A supercooling degree ΔT of a composition in which a structure comprising a polymerized fatty acid residue containing an acid as a main component and a polyethylene glycol dialkylamine residue is introduced and the polyamide block copolymer is blended with magnetic powder is 15 Use one that will be at or above ° C.
The polymerized fatty acid-based polyamide block copolymer contains a structure composed of an aliphatic diamine residue having 2 to 12 carbon atoms and an aliphatic dicarboxylic acid residue having 6 to 18 carbon atoms. preferable.

  The specific structure of the molecular chain includes a structure represented by the general formula (1) and a structure represented by the general formula (2).

  In the formula (1), R1 is a polyethylene glycol residue having 2 to 20 carbon atoms, R2 is an alkyl chain residue having 2 to 20 carbon atoms, and X containing them is a polyethylene glycol dialkylamine residue. R3 is a polymerized fatty acid residue mainly composed of a dimer acid having 20 to 40 carbon atoms.

  However, in Formula (2), R4 is a C2-C12 aliphatic diamine residue, and R5 is a C6-C18 aliphatic dicarboxylic acid residue.

The polymerized fatty acid type polyamide block copolymer includes a soft skeleton of polyethylene glycol amine and dimer acid in its skeleton. That is, it has a unique structure in which a soft skeleton of polyethylene glycol amine and dimer acid and a skeleton of dicarboxylic acid having a relatively long hydrocarbon chain are block copolymerized.
This structure is similar to the polymerized fatty acid-based polyetheresteramide block copolymer (B-2) described in Patent Document 4, but with the polymerized fatty acid-based polyamide block copolymer (B) of the present invention. Are distinctly different in that they have ester bonds. The reason why the injection moldability is improved in such a composition is not yet clear, but since the degree of supercooling ΔT of the composition for bonded magnets is large, when the injected composition is rapidly cooled in the mold, it is relatively Solidification will proceed slowly. This is effective for injection molding small and thin products because the composition solidifies slowly in the mold. In the conventional polyamide block copolymer, the regularity of the molecular structure is lower than that of the homopolymer polyamide. However, in the polymerized fatty acid-based polyamide block copolymer according to the present invention, a polymerized fatty acid residue mainly composed of dimer acid is used. In addition, since it includes a structure composed of polyethylene glycol dialkylamine residues, the regularity is further disturbed and lowered. Therefore, it is presumed that the crystallinity of the resin is lowered and the supercooling phenomenon becomes remarkable.

  The polymerized fatty acid-based polyamide block copolymer (B) used in the present invention preferably has a number average molecular weight of 20,000 to 60,000, more preferably 25,000 to 35,000. When the number average molecular weight is less than 20,000, the melt viscosity is remarkably reduced, and may be separated from the magnetic powder during the molding process, or the strength of the bond magnet formed with the composition may be remarkably reduced. When the molecular weight exceeds 60,000, sufficient melt fluidity cannot be obtained during molding. If injection molding is attempted at a high temperature in order to improve fluidity, a magnet having excellent magnetic properties cannot be obtained due to oxidative degradation of the magnetic powder. Here, the number average molecular weight is calculated by quantifying the acid value and amine value of the resin by a titration method.

The polymerized fatty acid-based polyamide block copolymer (B) used in the present invention is described in detail in JP-A-5-320335, JP-A-5-320336, etc., except that polyethylene glycol dialkylamine is used and no glycol is used. It can be produced by diverting the described method.
The polymerized fatty acid-based polyamide block copolymer (B) is produced by mixing polyethylene glycol dialkylamine with a specific dimer acid (I), dicarboxylic acid (B), and diamine (C) and polycondensing them. In addition, although mixing of dicarboxylic acid (b) is preferable, its use may be omitted.

  The polyethylene glycol dialkylamine is not particularly limited depending on the number of carbon atoms and the structure thereof, but those having 6 to 44 carbon atoms are preferable. Specific examples include polyethylene glycol diethylamine, polyethylene glycol diisopropylamine, polyethylene glycol dipropylamine, polyethylene glycol dioctylamine, polyethylene glycol diethylhexylamine, and polyethylene glycol dioleylamine. Of these, polyethylene glycol dipropylamine is particularly preferred.

As the dimer acid (a), a polymerized fatty acid obtained by polymerizing an unsaturated fatty acid having 20 to 48 carbon atoms, for example, a monobasic fatty acid having one or more double bonds or triple bonds having 10 to 24 carbon atoms is used. Used. Specific examples include natural animal and vegetable oil fatty acids such as soybean oil fatty acid, tall oil fatty acid and rapeseed oil fatty acid, polymerized fatty acids obtained by purifying these from oleic acid, linoleic acid, erucic acid, and the like, and ester derivatives thereof. It is done.
Commercially available polymerized fatty acids usually contain dimer acid (dimerized fatty acid) as the main component, but also contain fatty acids as raw materials and fatty acids higher than trimer, but dimer acid (dimerized fatty acid). It is desirable that the content is 70% or more, preferably 95% or more, and the degree of unsaturation is reduced by hydrogenation. In particular, commercially available products such as pre-poles 1004 and 1009, pre-pole 1010 (manufactured by Unikema) and Empor 1008 (manufactured by Cognis) are preferred. Mixtures of these and ester derivatives are also used.

The dicarboxylic acid (b) that can be used together with the polymerized fatty acid is an aliphatic or aromatic dicarboxylic acid having 6 to 22 carbon atoms and ester derivatives thereof. For example, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid, eicosandioic acid, eicosadiene dienedioic acid, diglycolic acid, 2,2,4-trimethyladipic acid Xylene dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, and ester derivatives thereof may be used.
In particular, azelaic acid, sebacic acid, dodecanedioic acid, and a mixture thereof are preferable from the viewpoints of polymerizability, copolymerization with polymerized fatty acid, and physical properties of the obtained polyamide copolymer.

  The diamine (c) is preferably a diamine having 2 to 20 carbon atoms, and specifically includes ethylenediamine, 1,4-diaminobutane, tetramethylenediamine, methylpentamethylenediamine, hexamethylenediamine, nonamethylenediamine, unamethylene. Decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, bis- (4,4'-aminocyclohexyl) methane, metaxylylenediamine, paraxylylene Examples thereof include alicyclic diamines such as range amine, isophorone diamine and norbornane diamine, and aliphatic diamines such as dimer diamine derived from a polymerized fatty acid having 20 to 48 carbon atoms. In addition, caprolactam may be blended.

  In the present invention, first, a polyamide oligomer is synthesized using (a) a polymerized fatty acid having 20 to 48 carbon atoms, (b) a dicarboxylic acid, and (c) a diamine having 2 to 20 carbon atoms. (A) to (c) are mixed at a ratio satisfying the structural formula of the polymerized fatty acid-based polyamide block copolymer (B). For example, the weight ratio of (a) to (b) is (b) / (b) is 0.3 to 5.2, and the total amino groups are substantially equivalent to the total carboxyl groups. To polycondense. When (i) / (b) is less than 0.3, the resulting polyamide copolymer has insufficient flexibility. On the other hand, when it is greater than 5.2, it is too soft and the heat resistance is significantly reduced. The intended polyamide copolymer cannot be obtained. Thereafter, the polyamide oligomer is further reacted with (d) polyethylene glycol dialkylamine and (ii) a polymerized fatty acid having 20 to 48 carbon atoms.

For example, in a reaction vessel sufficiently substituted with nitrogen, (a) a polymerized fatty acid, (b) azelaic acid and / or sebacic acid, and (c) hexamethylene diamine are combined. The weight ratio of (a) to (a) / (b) is 0.3 to 5.2, and all amino groups are charged to be substantially equivalent to the total carboxyl groups, and a predetermined amount of molecular weight regulator. In the presence of a small amount of a polycondensation catalyst (phosphoric acid or the like), the temperature is raised to 170 to 280 ° C. and reacted for 1 to 3 hours, and then further reacted for 0.5 to 2 hours under reduced pressure of about 160 mmHg.
Thereafter, the obtained polyamide oligomer is further reacted with (d) polyethylene glycol dialkylamine and (b) a polymerized fatty acid having 20 to 48 carbon atoms. A reaction vessel is charged with a polyamide oligomer, (d) polyethylene glycol dialkylamine, (i) a polymerized fatty acid having 20 to 48 carbon atoms, and in the presence of a predetermined amount of molecular weight regulator and a small amount of polycondensation catalyst (phosphoric acid, etc.). After raising the temperature to 200 to 300 ° C. and reacting for 1 to 3 hours, the reaction is further carried out for 0.5 to 2 hours under a reduced pressure of about 160 mmHg. A polymer is obtained. As the molecular weight modifier, carboxyl group-containing hydrocarbons such as acetic acid, propionic acid, butyric acid, valeric acid, lauric acid, palmitic acid, stearic acid, and behenic acid can be used.
In the present invention, a resin binder soft segment (a component having a flexible structure exhibiting entropy elasticity at a low glass transition temperature) and a hard segment (hydrogen bond or high glass) are synthesized by changing the amount of raw material to be polycondensed. Polymerized fatty acid-based polyamide block copolymers having different supercooling degrees ΔT can be obtained by adjusting the skeleton and ratio of the component that constrains the intermolecular molecules forming the transition temperature phase and the like.

2. Supercooling degree ΔT
In the present invention, the polymerized fatty acid-based polyamide block copolymer (B) includes a structure composed of a polymerized fatty acid residue mainly composed of dimer acid and a polyethylene glycol dialkylamine residue, and has the following formula (1): The degree of supercooling ΔT of the composition represented by is characterized by being 15 ° C. or more.
ΔT = Tc (5) −Tc (50) (1)
[In the formula, Tc (5) is obtained by using a differential scanning calorimeter, the composition was heated to 280 ° C. at 20 ° C./min in a nitrogen stream, held for 2 minutes, and then −5 ° C. / Solidification temperature measured by cooling to near room temperature with min, Tc (50) is the solidification temperature measured with a cooling rate of −50 ° C./min]

The degree of supercooling ΔT is determined by measuring the solidification temperature by cooling the melted composition under different cooling conditions using a differential scanning calorimeter, and determining the ease of solidification of the composition for bonded magnets injected into the mold. It is an index for grasping.
In general, the solidification temperature of a molten thermoplastic resin decreases as the cooling rate increases, and its behavior is affected by the resin composition and impurities. The injected resin is rapidly cooled in the mold, but in order to obtain a good molded product, the filling must be completed before the resin is solidified. Since it takes time for approximately 10 -2 ^{to 10} 0 ^sec in the injection filling, as the solidification of the resin is slow good molded article can be obtained when it is rapidly cooled in the mold.
Therefore, in the present invention, when the sample is heated to 280 ° C. at 20 ° C./min in a nitrogen stream and held for 2 minutes and then cooled to near room temperature at −50 ° C./min, the solidification temperature of the sample (crystal Temperature) is Tc (50). Further, the solidification temperature is measured in the same manner except that the cooling rate is −5 ° C./min, and is set as Tc (5).
Here, the reason why the cooling rates were set to −50 ° C./min and −5 ° C./min is that temperature measurement with a differential scanning calorimeter can be followed within this range. In the production of bonded magnets, the cooling rate of the composition in the mold is much faster than −50 ° C./min, but evaluation under such cooling conditions is difficult. If the solidification temperature difference Tc (5) -Tc (50) is small, the composition is easily solidified in the mold. Conversely, if the solidification temperature difference Tc (5) -Tc (50) is large, solidification is difficult. Therefore, injection filling is good.

The degree of supercooling ΔT differs between the bonded magnet composition obtained by kneading the resin binder itself and the magnetic powder. For example, in a polymerized fatty acid-based polyamide, even if its own supercooling degree ΔT is 30 ° C. or more, the supercooling degree of the composition can be reduced to 15 ° C. or less by adding a small amount of magnetic powder. There is something that falls. However, other polymerized fatty acid polyamides have a supercooling degree ΔT of 30 ° C. or higher, but the supercooling degree of the composition is 15 ° C. or lower even if the blending amount of the magnetic powder used is increased. Some of them do not drop.
In the present invention, it is important to employ a polymerized fatty acid-based polyamide block copolymer in which the degree of supercooling ΔT of the latter composition is 15 ° C. or more as the resin binder. Here, a resin binder whose ΔT of the composition is less than 15 ° C. is not preferable because the effect of improving the injection moldability is small.

The shape of the polymerized fatty acid-based polyamide block copolymer may be any of a pellet shape, a bead shape, a powder shape, and a paste shape, and a powder shape is desirable in terms of obtaining a uniform mixture.
In the above-mentioned polymerized fatty acid-based polyamide block copolymer, a part of the polymer is separated by distillation, chromatographic separation, or the like within a range in which the degree of supercooling ΔT is maintained at 15 ° C or more, or other polymerized fatty acid type polyamide is mixed. can do. Moreover, another thermoplastic resin can also be mix | blended as needed.
For example, linear polyphenylene sulfide, crosslinked polyphenylene sulfide, semi-crosslinked polyphenylene sulfide, low density polyethylene, linear low density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, ethylene Ethyl acrylate copolymer resin, ionomer resin, polymethylpentene, polystyrene, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl Formal, methacrylic resin, polyvinylidene fluoride, polytrifluorinated ethylene, tetrafluoroethylene-hexafluoropropylene copolymer resin, ethylene Fluoroethylene copolymer resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, polytetrafluoroethylene, polycarbonate, polyacetal, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polyallyl ether-allyl sulfone resin, polyether sulfone , Polyether ether ketone, polyarylate, aromatic polyester resin, cellulose acetate resin, various elastomers and rubbers.
Further, random copolymers with these homopolymers, other types of monomers, block copolymers, graft copolymers, end group-modified products with other substances, and the like can also be used. Furthermore, a system in which two or more types of thermoplastic resins are blended is also included.

3. Production of composition for bonded magnet In the present invention, to produce a composition for bonded magnet, a specific polymerized fatty acid-based polyamide block copolymer (B) and a specific magnetic powder (A) are blended as essential components, Knead.

  The amount of the polymerized fatty acid-based polyamide block copolymer is usually preferably 5 to 100 parts by weight with respect to 100 parts by weight of the magnetic powder. Furthermore, a preferable compounding quantity is 5-50 weight part. When the blended amount of the polymerized fatty acid-based polyamide block copolymer is less than 5 parts by weight, the kneading resistance (torque) of the composition is increased, the fluidity is lowered, and it becomes difficult to mold the magnet. On the other hand, if the amount exceeds 100 parts by weight, desired magnetic properties cannot be obtained.

  In the composition of the present invention, various additives (C) shown below can be used as necessary as long as the object of the present invention is not impaired. For example, for the purpose of improving the heat resistance of the polymerized fatty acid-based polyamide block copolymer and the magnetic powder, stabilizers such as a heat aging inhibitor and an antioxidant can be added.

Examples of such stabilizers include primary antioxidants such as hindered amines and hindered phenols, sulfur-based and phosphorus-based secondary antioxidants, and in particular, triphenyl which is a phosphorus-based secondary antioxidant. Phosphites such as trisnonylphenyl borophyte and tris (2,4-di-t-butylphenyl) phosphite are preferred.
The stabilizer can be added at any stage of the mixing process, the kneading process, and the molding process, and may be added in advance to the polyamide resin.

The mixture thus obtained is kneaded while being heated and melted using a batch kneader such as a Brabender, a Banbury mixer, a Henschel mixer, a helical rotor, a roll, a single screw extruder, a twin screw extruder or the like. The kneading temperature should just be more than melting | fusing point of a polymeric fatty acid type polyamide block copolymer, Preferably it is the range of 180-300 degreeC, In order to prevent the high temperature oxidation of a magnetic powder, the range of 180-250 degreeC is especially preferable. .
The composition for bonded magnets of the present invention is obtained by extruding the kneaded product obtained above into a strand shape or a sheet shape, and then cutting the kneaded material into a block shape by hot cutting or cold cutting. Thereafter, it can be cooled and solidified, and further pulverized into pellets or the like. The bonded magnet composition thus obtained is excellent in low temperature fluidity and injection moldability.

4). Bond Magnet The bond magnet of the present invention is obtained by heating and melting the above composition at a temperature equal to or higher than the melting point of the resin, preferably in the range of 200 to 250 ° C., and then using an injection molding method, an extrusion molding method, a compression molding method, or the like. By molding the melt in a magnetic field, it can be obtained as a molded body.

In particular, the injection molding method is preferable in that the degree of freedom of the shape of the molded body is large, the surface properties and magnetic properties of the obtained magnet are excellent, and it can be incorporated as an electronic component as it is.
The obtained molded body is desirably magnetized before use. For the magnetization, an electromagnet that generates a static magnetic field, a condenser magnetizer that generates a pulsed magnetic field, or the like is used. The magnetization magnetic field, that is, the magnetic field strength is preferably 1200 kA / m (15 kOe) or more, more preferably 2400 kA / m (30 kOe) or more.
The obtained bonded magnet is excellent in magnetic properties and mechanical strength such as rigidity. For example, it is used for small and flat complex shaped products such as motor parts for electronic equipment, and has features such as mass production, no post-processing, insert molding, etc. It is suitable for.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples. In the following Examples and Comparative Examples, the degree of supercooling ΔT of the bonded magnet composition was measured and evaluated as follows.

<Degree of supercooling ΔT of composition>
The degree of supercooling ΔT of the composition for bonded magnets was evaluated with a differential scanning calorimeter (DSC3100S manufactured by Mac Science). That is, about 30 mg of a sample was heated to 280 ° C. at 20 ° C./min in a nitrogen stream of 100 ml / min, held for 2 minutes, and then cooled to near room temperature at −50 ° C./min. The peak temperature (crystallization temperature) of the exothermic peak due to solidification at this time is defined as Tc (50). The solidification temperature is measured in the same manner except that the cooling rate is −5 ° C./min, and is set to Tc (5). Difference in solidification temperature measured, that is, Tc (5) −Tc (50): If the degree of supercooling ΔT was 15 ° C. or higher, it was accepted, and if it was less than 15 ° C., it was rejected. If a plurality of exothermic peaks due to solidification are observed, the determination is made by adopting the peak temperature with the larger calorific value.

(Example 1)
Oleic acid, linoleic acid, azelaic acid, sebacic acid and hexamethylenediamine are reacted as raw materials at 190 ° C. in a nitrogen atmosphere to form a polyamide oligomer, and then polyethylene glycol diethylamine and linoleic acid are added to this polyamide oligomer uniformly. Polymerization was performed at 270 ° C. with stirring. A polyamide block copolymer A having a melting point of 184 ° C. was obtained. The number average molecular weight determined from the determination of acid value and amine value by titration method was 25,000.
Using this polyamide block copolymer A as a resin binder, 9% by weight of this polyamide and 91% by weight of Sm ₂ Fe ₁₇ N ₃ magnetic powder (SFN-C manufactured by Sumitomo Metal Mining) were kneaded at 200 ° C. with a lab plast mill. And pulverized with a plastic pulverizer.
With an injection molding machine in which the obtained bonded magnet composition was set at a nozzle temperature of 220 ° C., an evaluation die having a die temperature of 30 ° C. (width 8 mm, length 40 mm, thickness 2 mm, at the end in the 40 mm direction) Injection molding). A good thin plate injection-molded body having a surface skin layer formed thereon could be obtained. Further, the degree of supercooling ΔT of this composition was 15 ° C. (the degree of supercooling ΔT of the polyamide block copolymer A itself was 32 ° C.).

(Example 2)
Polymerization was carried out in the same manner as in Example 1 except that polyethylene glycol dipropylamine was used instead of polyethylene glycol diethylamine to obtain a polyamide block copolymer B having a melting point of 183 ° C. and a number average molecular weight of 29,000.
Using this polyamide block copolymer B as a resin binder, a bonded magnet composition was prepared in the same manner as in Example 1, and injection molded into an evaluation mold. A good thin plate injection-molded body having a surface skin layer formed thereon could be obtained. Further, the degree of supercooling ΔT of this composition was 28 ° C. (the degree of supercooling ΔT of the polyamide block copolymer B itself was 38 ° C.).

(Example 3)
Polymerization was carried out in the same manner as in Example 1 except that polyethylene glycol diisopropylamine was used instead of polyethylene glycol diethylamine to obtain a polyamide block copolymer C having a melting point of 182 ° C. and a number average molecular weight of 30,000.
Using this polyamide block copolymer C as a resin binder, a bonded magnet composition was prepared in the same manner as in Example 1, and injection molded into an evaluation mold. A good thin plate injection-molded body having a surface skin layer formed thereon could be obtained. Further, the degree of supercooling ΔT of this composition was 24 ° C. (the degree of supercooling ΔT of the polyamide block copolymer C itself was 35 ° C.).

Example 4
Polymerization was carried out in the same manner as in Example 1 except that polyethylene glycol dioctylamine was used instead of polyethylene glycol diethylamine to obtain a polyamide block copolymer D having a melting point of 179 ° C. and a number average molecular weight of 35,000.
Using this polyamide block copolymer D as a resin binder, a bonded magnet composition was prepared in the same manner as in Example 1 and injection molded into an evaluation mold. A good thin plate injection-molded body having a surface skin layer formed thereon could be obtained. Further, the degree of supercooling ΔT of this composition was 32 ° C. (the degree of supercooling ΔT of the polyamide block copolymer D itself was 37 ° C.).

(Example 5)
Example except that Sm ₂ Fe ₁₇ N ₃ magnetic powder is NdFeB-based magnetic powder (MQP-B manufactured by Magnequen), the magnetic powder content is 94% by weight, and the polyamide block copolymer B is 6% by weight. In the same manner as in No. 2, a bonded magnet composition was prepared and injection molded into an evaluation mold. A good thin plate injection-molded body having a surface skin layer formed thereon could be obtained. Further, the degree of supercooling ΔT of this composition was 24 ° C. (the degree of supercooling ΔT of the polyamide block copolymer B itself was 38 ° C.).

(Comparative Example 1)
Unlike oleic acid, linoleic acid, azelaic acid, sebacic acid, and hexamethylene diamine, unlike Example 1, polyethylene glycol dialkylamine was not added, and the reaction was performed at 250 ° C. in a nitrogen atmosphere with stirring with stearic acid. As a result, a polyamide block copolymer E having a melting point of 183 ° C. and a number average molecular weight of 27,000 was obtained.
As a resin binder, 9% by weight of this polyamide block copolymer E and 91% by weight of Sm ₂ Fe ₁₇ N ₃ magnetic powder (SFN-C manufactured by Sumitomo Metal Mining) were kneaded at 200 ° C. with a lab plast mill, and plastic pulverized. Crushed with a vessel. The obtained bonded magnet composition is an injection molding machine set at a nozzle temperature of 220 ° C., and has a thin plate-like cavity having a width of 8 mm, a length of 40 mm, and a thickness of 2 mm (a gate is provided at the end in the 40 mm direction). It was injection-molded into a 30 ° C mold.
The obtained molded body was not sufficiently filled in the 40 mm direction and was a short shot. When the nozzle temperature of the injection molding machine was gradually increased, it was finally filled at 270 ° C. The degree of supercooling ΔT of this composition was 12 ° C.

(Comparative Example 2)
Comparative Example 1 except that the Sm ₂ Fe ₁₇ N ₃ magnetic powder was NdFeB-based magnetic powder (MQP-B manufactured by Magnequench), the magnetic powder content was 94 wt%, and the polyamide block copolymer B was 6 wt%. A bonded magnet composition was prepared in the same manner as described above, and injection molded at a nozzle temperature of 220 ° C and a mold temperature of 30 ° C.
However, the obtained molded product was not sufficiently filled in the 40 mm direction and was a short shot. When the nozzle temperature of the injection molding machine was gradually raised, it was finally filled at 280 ° C. Further, the degree of supercooling ΔT of the composition was 10 ° C.

(Comparative Example 3)
Polymerization was carried out in the same manner as in Example 1 except that polyethylene glycol dimethylamine was used instead of polyethylene glycol diethylamine to obtain a polyamide block copolymer F having a melting point of 185 ° C. and a number average molecular weight of 23,000.
Using this polyamide block copolymer F as a resin binder, Sm ₂ Fe ₁₇ N ₃ magnetic powder was blended in the same manner as in Example 1 to prepare a bonded magnet composition, a nozzle temperature of 220 ° C., and a mold temperature of 30 °. C was injection molded.
However, the obtained molded body was not sufficiently filled in the 40 mm direction and was a short shot. When the nozzle temperature of the injection molding machine was gradually raised, it was finally filled at 250 ° C. Further, the degree of supercooling ΔT of the composition was 13 ° C. (ΔT of the polyamide block copolymer F resin was 16 ° C.). Even in the case of polyethylene glycol dialkylamine, it can be seen that when the degree of supercooling ΔT is less than 15 ° C., the injection moldability does not increase.

(Comparative Example 4)
Without using polyethylene glycol diethylamine, polyoxytetramethylene glycol and azelaic acid were added to polyamide oligomer reacted at 190 ° C under nitrogen atmosphere using oleic acid, linoleic acid, azelaic acid, sebacic acid and hexamethylenediamine as raw materials. The mixture was added and polymerized at 270 ° C. with stirring to obtain a polyamide elastomer (polyether ester amide block copolymer) X having a melting point of 171 ° C. and a number average molecular weight of about 10,000.
Using this polyamide elastomer X as a resin binder, a bonded magnet composition was prepared and injection-molded at a nozzle temperature of 220 ° C and a mold temperature of 30 ° C.
However, the obtained molded body was not sufficiently filled in the 40 mm direction and was a short shot. When the nozzle temperature of the injection molding machine was gradually increased, it was finally filled at 260 ° C. Further, the degree of supercooling ΔT of the composition was 12 ° C.

(Conventional example 1)
A composition for a bonded magnet containing Sm ₂ Fe ₁₇ N ₃ magnetic powder was prepared in the same manner as in Comparative Example 1 except that polyamide 12 having a number average molecular weight of 12,000 was used as a resin binder, and then injection molding was performed.
However, at a mold temperature of 30 ° C., filling was not possible even when the nozzle temperature was raised to 270 ° C., and filling was finally possible at a mold temperature of 110 ° C. and a nozzle temperature of 230 ° C. The degree of supercooling ΔT of this composition was 6 ° C.

(Conventional example 2)
Sm ₂ Fe ₁₇ N ₃ Magnetic powder was changed to NdFeB-based magnetic powder (MQP-B manufactured by Magnequench), the magnetic powder content was 94 wt%, and polyamide 12 was 6 wt%. A composition for a bonded magnet was prepared. The degree of supercooling ΔT of this composition was 4 ° C. Injection molding was performed at a nozzle temperature of 220 ° C and a mold temperature of 30 ° C.
However, at a mold temperature of 30 ° C., filling was not possible even when the nozzle temperature was raised to 230 ° C., but finally filling was possible when the mold temperature was 110 ° C. and the nozzle temperature was 240 ° C.

"Evaluation"
As seen in Examples 1 to 4, a polymerized fatty acid-based polyamide block copolymer according to the present invention having a structure composed of a polymerized fatty acid residue mainly composed of dimer acid and a polyethylene glycol dialkylamine residue is used as a resin binder. By using it, it is possible to knead the SmFeN-based magnetic powder to obtain a composition excellent in injection property with a supercooling degree ΔT of 15 ° C. or more, and a thin plate-like molded body having a good surface state is obtained. . In Example 5, NdFeB-based magnetic powder was used instead of SmFeN-based magnetic powder. Similarly, a supercooling degree ΔT of 15 ° C. or more can be obtained as a composition having excellent injection properties, and the surface state is A good thin plate-like molded body is obtained.
In contrast to the above examples, in conventional examples 1 and 2 using polyamide 12 (nylon 12), the composition could not be filled in the mold, and comparative examples 1 and 2 using polymerized fatty acid-based polyamide as the resin binder Then, the mold temperature could not be sufficiently filled at 30 ° C., and injection molding could be performed by increasing the nozzle temperature. In Comparative Example 3, the structure of the polymerized fatty acid-based polyamide block copolymer was different from that of the present invention, and the supercooling degree ΔT of the resin itself was smaller than 15 ° C., so that the injection moldability was insufficient. Further, Comparative Example 4 is a case where a polyamide elastomer (polyether ester amide block copolymer) different from the present invention is used, and the degree of supercooling ΔT of the resin itself is smaller than 15 ° C. Was insufficient.

Claims (9)

In the composition for a bonded magnet containing the rare earth-transition metal magnetic powder (A) and the polymerized fatty acid polyamide block copolymer (B),
The polymerized fatty acid-based polyamide block copolymer (B) has a structure comprising a polymerized fatty acid residue mainly composed of dimer acid and a polyethylene glycol dialkylamine residue, and is represented by the following formula (1). A bonded magnet composition having a supercooling degree ΔT of 15 ° C. or more.
ΔT = Tc (5) −Tc (50) (1)
[In the formula, Tc (5) is obtained by using a differential scanning calorimeter, the composition was heated to 280 ° C. at 20 ° C./min in a nitrogen stream, held for 2 minutes, and then −5 ° C. / Solidification temperature measured by cooling to near room temperature with min, Tc (50) is the solidification temperature measured with a cooling rate of −50 ° C./min]   The bonded magnet composition according to claim 1, wherein the rare earth-transition metal magnetic powder (A) is at least one selected from SmCo magnetic powder, NdFeB magnetic powder, and SmFeN magnetic powder.   The composition for bonded magnet according to claim 1, wherein the dimer acid is an unsaturated fatty acid having 20 to 48 carbon atoms.   The composition for bonded magnet according to claim 1, wherein the polyethylene glycol dialkylamine has an alkyl group having 2 to 20 carbon atoms.   The polymerized fatty acid-based polyamide block copolymer (B) further comprises a structure comprising an aliphatic diamine residue having 2 to 12 carbon atoms and an aliphatic dicarboxylic acid residue having 6 to 18 carbon atoms. The composition for bonded magnets according to claim 1.   The aliphatic diamine is ethylene diamine, 1,4-diaminobutane, tetramethylene diamine, methyl pentamethylene diamine, hexamethylene diamine, nonamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4-trimethylhexamethylene. At least one selected from the group consisting of diamine, 2,4,4-trimethylhexamethylenediamine, bis- (4,4′-aminocyclohexyl) methane, metaxylylenediamine paraxylylenediamine, isophoronediamine, and norbornanediamine. The composition for bonded magnets according to claim 5, wherein the composition is present.   The aliphatic dicarboxylic acid is adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid, eicosandioic acid, eicosadienedienedonic acid, diglycolic acid, and 2,2 The composition for bonded magnets according to claim 5, wherein the composition is at least one selected from the group consisting of 1,4-trimethyladipic acid.   The composition for bonded magnets according to claim 1, wherein the number average molecular weight of the polymerized fatty acid-based polyamide block copolymer (B) is 20,000 to 60,000.   The bonded magnet formed by the injection molding of the bonded magnet composition in any one of Claims 1-8.