JP2019067957A - Bond magnet and composition for bond magnet - Google Patents

Abstract

To provide a composition for a bond magnet, by which a bond magnet superior in both of heat resistance and magnetic characteristic can be obtained while ensuring moldability.SOLUTION: A composition of the present invention comprises one or more kinds of rare earth magnet particles and a binding resin, and is used for manufacturing a bond magnet. The rare earth magnet particles include at least Nd-based magnet particles in which a rare earth element is Nd, and the total amount of the rare earth magnet particles is 90-95 mass% to a whole amount of the composition. The binding resin consists of polyamide 66(PA66) in which a total amount of terminal groups consisting of carboxyl and amino groups is 175 mmol/kg or less to a total amount of the binding resin. Even if PA66 of which the total amount of the terminal groups is adjusted touches the rare earth magnet particles serving to bring about a catalyst effect, the start of the increase in viscosity is delayed. So, the stable moldability can be ensured even if the content of the rare earth magnet particles is large. A bond magnet which can be obtained from the composition like this would be superior in both of magnetic characteristic and heat resistance.SELECTED DRAWING: Figure 2A

Description

  The present invention relates to a bonded magnet composition comprising rare earth magnet particles and a bonding resin.

  In order to exhibit high magnetic properties, rare earth magnets are used in various devices such as electric appliances and automobiles for which energy saving and weight reduction are desired. The rare earth magnet is a compact magnet made of a sintered body of a rare earth magnet powder (referred to as “magnet powder” as appropriate) or a hot compact, and the magnet powder is bonded resin (binder resin) by injection molding, compression molding, extrusion molding, etc. And bonded magnets. Recently, bonded magnets having a high degree of freedom in forming and suitable for the production of lightweight parts and the like tend to be used frequently.

  When a bonded magnet is used, not only the improvement of its magnetic properties but also the kneadability for obtaining a magnet raw material (composition) such as a compound by heating and kneading the magnet powder and the binder resin, and melting the binder resin It is also important to ensure moldability when injection molding and the like. Descriptions related to this are in the following patent documents.

Unexamined-Japanese-Patent No. 7-226312 JP-A-9-162019 JP 2003-342468 A JP-A-9-71721

Patent document 1 and patent document 2 are end-adjusted 12-nylon (PA12) which is a kind of aliphatic polyamide resin, and Sm ₂ Fe ₁₇ N ₃ powder (average particle diameter is about 4 μm) which is a kind of rare earth magnet powder. Proposed a composition consisting of These patent documents disclose that the recyclability and magnetic properties of an injection-molded bonded magnet can be compatible by using this composition.

  However, a bonded magnet using PA12 having a low melting point (softening point) as a bonding resin is inferior in heat resistance, and its use is limited. Moreover, as long as PA12 having a low melting point (softening point) is used, coexistence of the content of the magnet powder and the formability can be made without adjusting the end.

  Patent Document 3 proposes a composition comprising an end-regulated aromatic polyamide resin and an Nd—Fe—B based magnetic powder which is a kind of rare earth magnet powder. It is described in the patent document that the moldability and heat resistance of a bonded magnet can be compatible by using this composition.

  However, since the aromatic polyamide resin used in Patent Document 3 has a very high melting point, it tends to solidify in the mold due to the temperature decrease when the molten mixture is injected into the mold. Therefore, the composition according to Patent Document 3 is significantly inferior in formability, orientation, etc. to the composition using PA12. In particular, when the content of the magnet powder is increased, it is considered that it is difficult for the composition according to Patent Document 3 to secure formability suitable for mass production.

  Patent Document 4 proposes a composition comprising an end-adjusted polyamide 6 resin and a strontium ferrite magnetic powder which is a kind of rare earth oxide magnet powder. It is described in the patent document that the fluidity is improved by using this composition.

  However, in the case of a bonded magnet using polyamide described in Patent Document 4, particularly polyamide 66, there is a problem in retention stability that thickening of the composition occurs and formability is significantly reduced when a given time or more passes in a processing temperature range. was there. Therefore, the composition according to Patent Document 4 has a possibility of thickening due to retention at the time of mass production, and it has been difficult to secure formability suitable for mass production.

  Incidentally, most of the bond magnets currently marketed (mass-produced) use either PA12 or polyphenylene sulfide (PPS) as a bonding resin. As described above, PA12 is poor in heat resistance. Although PPS has a high melting point and is excellent in heat resistance, when the temperature is raised from the melting point to a certain degree or more, the rare earth magnet powder is rapidly oxidized and its magnetic characteristics are degraded. For this reason, the injection temperature can not be raised much higher than the melting point of PPS, and the molten mixture of PPS becomes easy to solidify when injected into the mold, and the formability is inferior. In addition, the injection temperature when PPS is used can not be as high as 50 to 100 ° C. higher than the melting point, as in the case of injection temperature when PA 12 is used, so when a molten mixture consisting of PPS is injection molded into a mold The fluidity (viscosity) also decreases due to the decrease of the resin temperature. As a result, it is also difficult for a bond magnet using PPS to secure its density and degree of orientation sufficiently.

  This tendency is remarkable when the content (filling ratio) of the magnet powder is increased to enhance the magnetic properties of the bonded magnet. For this reason, when priority is given to magnetic properties over heat resistance, PA12 is used as a bonding resin, and when heat resistance is prioritized over magnetic properties, PPS is used as a bonding resin. Both PA12 and PPS are thermoplastic resins, and they themselves exhibit stable high fluidity (low viscosity) in the temperature range above the melting point regardless of the heat history. This tendency is the same even when PA12 or PPS coexists with rare earth magnet particles. For this reason, PA12 and PPS do not cause thickening when they are kneaded with a magnet powder.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a bond magnet composition and the like which can obtain a bond magnet having excellent magnetic properties and heat resistance while securing formability. To aim.

  As a result of intensive studies to solve this problem, the present inventor found that PA66, which has a melting point higher than that of PA12, is the same thermoplastic resin as PA12 and PPS, but when it coexists with high content rare earth magnet particles, It has been found that PPS produces a unique thickening phenomenon that does not occur substantially. Based on this new finding, the inventor has completed the present invention described below.

<< Composition for Bonded Magnets >>
The composition for a bonded magnet according to the present invention is a composition comprising one or more rare earth magnet particles and a bonding resin and used for producing a bonded magnet, wherein the rare earth magnet particles are Nd-based magnets wherein the rare earth element is Nd. The total amount of the rare earth magnet particles is 90 to 95% by mass with respect to the whole composition, and the total amount of terminal groups consisting of carboxyl groups and amino groups is the whole of the combined resin. It consists of polyamide 66 (PA66) below 175 mmol / kg.

  When the composition for a bonded magnet of the present invention (also referred to simply as a "composition") is used, the magnetic properties and heat resistance are improved by increasing the content of rare earth magnet powder while securing stable formability. It is possible to obtain a bonded magnet in which the

Bond magnet
The present invention can also be grasped as a bonded magnet using the composition described above. For example, the present invention may be a bonded magnet made of an injection molded body of a composition for a bonded magnet.

"Production method"
(1) The present invention can also be grasped as a method for producing the composition described above. For example, the present invention is a method for producing a composition comprising a kneading step of kneading one or more rare earth magnet powders and a binding resin, wherein the rare earth magnet powder contains at least Nd-based magnet particles whose rare earth element is Nd. The total amount of the rare earth magnet powder is 90 to 95% by mass with respect to the whole composition, and the total amount of terminal groups consisting of carboxyl groups and amino groups is 175 mmol / m to the whole of the composition. It may be a method for producing a bonded magnet composition consisting of polyamide 66 (PA 66) of not more than kg.

(2) The present invention can also be grasped as a method of manufacturing the bonded magnet described above. For example, the present invention may be a manufacturing method of a bonded magnet including an injection step of filling a cavity with a molten mixture which is a mixture of a bonding resin and rare earth magnet powder which is heated to heat the composition described above. When the rare earth magnet powder is a rare earth anisotropic magnet powder, the injection step may be a step of filling the molten mixture into the cavity in the orienting magnetic field.

<< Others >>
(1) The PA 66 referred to in the present specification also includes PA 66 which has not been terminally adjusted, PA 66 which has been terminally adjusted, and PA 66 which has been modified by condensation polymerization or crosslinking reaction. In order to distinguish them, they are referred to as “unmodified PA 66”, “modified PA 66”, and “deteriorated PA 66” as appropriate.

(2) PA 66 comes in contact with rare earth magnet particles, and the total amount of its end groups decreases as it becomes a composition and even a bonded magnet. In other words, PA 66 maximizes the total amount of end groups in the raw material stage before contacting with the rare earth magnet particles. Therefore, in the present invention, the total amount of the end groups of PA 66 constituting the composition or the bonded magnet is defined with the total amount of the end groups of PA 66 obtained in the raw material stage as the upper limit.

  The term "mmol / kg" as used herein means the amount (mmol) of end groups present in 1 kg of PA66.

(3) Unless otherwise specified, "x to y" in the present specification includes the lower limit x and the upper limit y. Ranges such as “a to b” may be newly established as new lower limit values or upper limit values for arbitrary numerical values included in various numerical values or numerical ranges described in the present specification.

It is an explanatory view showing signs that molecules of non-modified PA66 contact with rare earth magnet particles and it becomes a denatured PA 66 with a large molecular weight. It is explanatory drawing which shows a mode that the functional group in the terminal of PA66 becomes a non-reactive substituent by terminal adjustment. It is a graph which shows the time-dependent change of the torque required for kneading | mixing of PA66 and rare earth magnet powder. It is a scatter diagram which shows the relationship between the total amount of the terminal group of PA66, and the thickening start time or solidification time.

  To the components of the present invention, one or more components arbitrarily selected from the specification can be added. The contents described in the present specification can be appropriately applied not only to the composition and the bonded magnet of the present invention but also to a method of manufacturing them. Even a methodical component can be an entity-related component. Whether or not which embodiment is the best depends on the target, required performance, and the like.

<< Rare Earth Magnet Particles (Powder) >>
(1) The rare earth magnet particles may contain at least Nd magnet particles, and may contain one or more other rare earth magnet particles. Furthermore, the composition of the present invention may contain a small amount of magnet particles (for example, ferrite particles) other than rare earth magnet particles.

Nd-based magnet particles may be rare earth element Nd, but usually, Nd-TM-B magnet particles, more specifically, Nd ₂ TM ₁₄ B ₁ (TM: transition metal element, particularly Fe) is mainly used It is a magnet particle to be a phase. However, the Nd-based magnet particles may contain various modifying elements that enhance their magnetic properties. The modifying element may be an element dissolved in the main phase or an element constituting the grain boundary phase. Such an element is, for example, one or more of Co, Ni, Al, Cu, Ga, Nb, Ti, V, Zr, Cr, Mn, Hf, W, Ta, Zn, Sn and the like.

Examples of rare earth magnet particles other than Nd magnet particles include Sm magnet particles and the like. Sm-based magnet particles are Sm-TM-N-based magnet particles, Sm-TM-based magnet particles, and the like. Sm-TM-N based magnet particles are, for example, magnet particles having Sm ₂ Fe ₁₇ N as a main phase, and Sm-TM based magnet particles are, for example, magnets having SmCo ₅ or Sm ₂ Co ₁₇ as a main phase. It is a particle.

(2) The rare earth magnet particles preferably have an average particle diameter of 1 to 300 μm, and more preferably 5 to 250 μm. If the average particle size is too small, the total surface area of the particles will increase and PA 66 will tend to thicken. When the average particle size is too large, the particles are likely to be broken, and due to the miniaturization of the particles and the appearance of a new surface, the total surface area of the particles also increases and the PA 66 tends to be thickened.

  The average particle diameter of the Nd-based magnet particles is, for example, 40 to 250 μm, 60 to 200 μm, or 80 to 150 μm. Such Nd-based magnet particles are produced, for example, by hydrogen treatment (HDDR or the like).

  Sm-based magnet particles usually have a smaller average particle size than Nd-based magnet particles. The average particle diameter is, for example, 1 to 20 μm, and further 3 to 15 μm. By using a mixed powder of coarse powder composed of Nd-based magnet particles and fine powder composed of Sm-based magnet particles, higher content of magnet powder can be achieved, and fluidity during kneading or molding can be rather improved. .

  The “average particle diameter” as referred to in the present specification is specified by measurement using a laser diffraction type particle size distribution measuring device (Nanotrac Wave II manufactured by Microtrac Bell Inc.).

(3) It is considered that thickening of PA 66 is caused by the catalytic action of rare earth magnet particles (particularly, active rare earth elements) to promote condensation polymerization reaction or crosslinking reaction of PA 66 and increase of its molecular weight. From this point of view, the rare earth magnet particles may be isotropic magnet particles or anisotropic magnet particles.

  However, a bonded magnet obtained by molding a molten mixture of rare earth anisotropic magnet particles and a molten bonding resin in a magnetic field exhibits higher magnetic properties due to the orientation of the rare earth anisotropic magnet particles. When the composition of the present invention is used, thickening of PA 66 is suppressed even during molding in a magnetic field, and the fluidity of the molten mixture is secured. A bonded magnet with high magnetic properties in orientation is obtained.

Bonding resin
(1) Thickening Generally, the molecular formula of unregulated PA66 (unmodified PA66) is HO [CO (CH ₂ ) ₄ CONH (CH ₂ ) ₆ NH] _n H or (C ₁₂ H ₂₂ N ₂₎ O ₂ ) _n (n is an integer) or the like, and the terminal of each molecule (polymer) is a carboxyl group (COOH) or an amino group (NH ₂ ). The PA 66 itself is a thermoplastic resin and does not cause thickening or solidification even by heating, kneading, etc. alone.

  However, when each molecule of unmodified PA 66 comes into contact with magnet particles containing transition metal elements, rare earth elements, etc., for example, as shown in FIG. 1A as an example, a dehydration (condensation) reaction between a carboxyl group and an amino group And cross-linking reaction, etc., and it can be converted to a polymerised modified PA 66. It is considered that, due to the increase in molecular weight, thickening and solidification that do not occur alone occur in the coexistence with the rare earth magnet particles.

  The binding resin of the invention consists of end-regulated PA66 (modified PA66). As shown in FIG. 1B, at least a portion of the carboxyl group and / or amino group at the end of the unmodified PA66 is substituted with a non-reactive or low-reactive end group, as shown in FIG. 1B. It is believed that there is. As a result, it is inferred that the modified PA 66 according to the present invention does not show a sharp thickening phenomenon even when in contact with the catalytic rare earth magnet particles.

  FIG. 2A actually shows how the kneading torque changes with time when each of the unmodified PA 66 or the mixture of the modified PA 66 and the Nd—Fe—B based magnet powder is heat-kneaded. In addition, this experiment was performed using the laboplast mill mentioned later, and the data which concerns on unmodified | non-modified PA66 and modified PA66 respond | correspond to the sample 20 shown in Table 1, and the sample 22, respectively.

  As is clear from FIG. 2A, although any of the PAs 66 exhibits a thickening phenomenon, the unmodified PA 66 starts thickening at about 1200 seconds (about 20 minutes) after the start of kneading. On the other hand, in the case of the modified PA 66, the start of the thickening is greatly delayed, and the inherent low viscosity of the PA 66 is maintained for approximately 2400 seconds (40 minutes) from the start of the kneading.

  The kneading time (heating time) for producing the composition (compound or the like) is about 600 to 1,500 seconds (10 to 25 minutes). In the unmodified PA 66, rapid thickening may occur during kneading, but if the modified PA 66 is used, kneading can be completed before thickening occurs, and stable kneading can be performed.

  In addition, when injection molding of a bonded magnet, the time required for the heating-started raw material (composition) to be melted and to be completely filled in the cavity of the mold (electromagnetic part) is usually about 30 to 300 seconds. It is. Even if the heat histories of kneading and molding are combined, injection molding can be completed sufficiently within the thickening start time by using the modified PA 66, and it can be said that stable moldability can be secured.

  In this specification, the time when the kneading torque shows 1.2 times the minimum torque after the start of kneading is referred to as the thickening start time, and when the kneading torque becomes maximal (peak) after the start of kneading (the first derivative The next time it becomes zero) is called solidification time.

(2) Total Amount of End Groups A plurality of modified PA66s having different total amounts of end groups (total amount of carboxyl group and amino group) were prepared using chemical modifiers (end modifiers, capping agents). The modified PA 66 or unmodified PA 66 and the rare earth magnet powder were heated and kneaded as described above to determine the relationship between the total amount of terminal groups and the thickening start time or solidification time. The results thus obtained are shown in FIG. 2B. In addition, unmodified PA66 had a total amount of terminal groups of 224 mmol / kg. As apparent from FIG. 2B, the thickening start time and the solidification time are rapidly extended in the range in which the total amount of terminal groups is 175 mmol / kg or less, 150 mmol / kg or less, 125 mmol / kg or less, and 100 mmol / kg or less. It is understood that

(3) Chemical Modifier The terminal adjustment of PA66 can be performed, for example, by reacting unmodified PA66 with a chemical modifier. As a result, the terminal functional group, the carboxyl group and / or the amino group, is replaced by another non-reactive functional group. As the chemical modifier, various carbodiimide compounds, carboxylic acids, amines and the like can be used. Among them, when a carbodiimide compound is used as a bonded magnet composition, it is preferable because generation of a gas during molding is small, moldability is stable, and bonded magnet strength is obtained.

(4) Thickening (molecular weight increase) of rare earth magnet particles PA66 can occur by contact with rare earth magnet particles, but the degree (thickening start time) is the content, size (specific surface area), type of rare earth magnet particles It changes with constituent elements, component composition etc.

  For example, the higher the content of the rare earth magnet particles and the smaller the size (average particle diameter) of the PA 66, the higher the probability that the end groups of the PA 66 contact the rare earth magnet particles, and the PA 66 tends to be thickened. For this reason, when the content of fine rare earth magnet particles (for example, SmFeN magnet particles) is greatly increased (for example, 50 mass% or more), even if the modified PA 66 is used, the significant delay in the start of thickening is Absent.

  On the other hand, the fluidity of the molten mixture is improved when some fine rare earth magnet particles are mixed, rather than only coarse rare earth magnet particles (for example, NdFeB magnet particles), and rather, not only formability but also rare earth The degree of orientation of the magnet particles and thus the magnetic properties of the bonded magnet may be enhanced. In addition, with only coarse rare earth magnet particles, there is a limit to improvement in the content, and particle refinement due to cracking or the like may also occur.

  Based on such circumstances, for example, when coarse Nd-based magnet particles are contained in an amount of 90% by mass or more, 91% by mass or more, further 92% by mass or more with respect to the entire composition, the total amount of PA66 end groups is 100 mmol / It is preferable to set it as kg or less, 85 mmol / kg or less, and further 75 mmol / kg or less.

  In the case where coarse Nd-based magnet particles and fine Sm-based magnet particles are mixed and the total (total) of rare earth magnet particles is 90% by mass or more, the total amount of terminal groups of PA66 is 150 mmol / It may be not more than kg, not more than 125 mmol / kg, and further not more than 100 mmol / kg. At this time, it is preferable that the Sm based magnet particles be 1 to 40% by mass, 5 to 35% by mass, and further 15 to 30% by mass with respect to the entire composition.

  Specifically, for example, Nd magnet particles have an average particle diameter of 40 to 150 μm and are contained at 65 to 89% by mass with respect to the whole composition, and Sm magnet particles have an average particle diameter of 1 to 20 μm. The total amount of the end groups of PA66 may be 150 mmol / kg or less.

(5) Others The modified PA 66 preferably has a weight average molecular weight (Mw) of 12,000 to 40,000 and more preferably 13,000 to 30,000. If the Mw is too small, the strength of the bonded magnet will be low, and if the Mw is too large, the kneadability and formability, the content of magnet particles, the degree of orientation, etc. may be reduced as in the case of thickening.

The total amount of terminal groups as referred to herein is calculated from the peak intensities measured by ¹ H-NMR (nuclear magnetic resonance spectroscopy). Moreover, Mw as referred to herein is specified by measurement by gel permeation chromatography (GPC). In addition, unless otherwise indicated, the molecular weight as used in this specification means a weight average molecular weight.

  The composition or bonded magnet of the present invention may contain, in addition to the modified PA 66 and the rare earth magnet particles, a coupling agent, a lubricant and a small amount of resin other than PA 66. Also, the magnet particles may be surface-treated in advance with a coupling agent.

<< Application >>
Since the bonded magnet of the present invention is excellent in heat resistance, it is suitable not only for electromagnetic devices used in a normal temperature range, but also for electromagnetic devices used in a high temperature range and electromagnetic devices that become hot during use. For example, the bonded magnet of the present invention is suitable as a field source of a vehicle-mounted electromagnetic device (motor, generator, etc.) that is required to have heat resistance of 150 ° C. or more, and further 200 ° C. or more.

  Various compounds (compositions for bonded magnets) as raw materials of bonded magnets were manufactured using PA 66 having different total amounts of end groups. In addition, bonded magnets were also manufactured by injection molding using each compound. The formability at each production and the magnetic properties of each bonded magnet were evaluated. The present invention will be described in more detail based on such specific examples.

<< Production of samples >>
(1) Raw Material A commercially available PA66 (manufactured by Unitika), which had not been terminally adjusted, and a carbodiimide compound (stabucksol I, manufactured by Line Chemie, Inc.) to be a terminal regulator of PA66, were prepared.

  In addition, NdFeB anisotropic magnet powder (MF18P manufactured by Aichi Steel Co., Ltd.) as Nd magnet powder (coarse powder) and SmFeN anisotropic magnet powder (Sumitomo Metal Co., Ltd.) as Sm magnet powder (fine powder) A Minebek's SmFeN alloy fine powder C) was prepared.

(2) End Adjustment The end adjustment of PA66 is carried out by supplying a mixture obtained by dry blending unmodified PA66 and a predetermined amount of carbodiimide compound to the main hopper of a twin-screw extruder (TEM26SS manufactured by Toshiba Machine Co., Ltd., screw diameter 26 mm), After melt-kneading at 280 ° C., extruding in the form of a strand and cooling and solidifying it, it was obtained by cutting with a pelletizer. In this way, two types of modified PA66 in which the total amount of end groups differs were obtained. The modified PA66 and the unterminated PA66 (unmodified PA66) were subjected to the production of the samples shown below.

(3) Production of Compound For each sample, a mixture of each rare earth magnet powder and each PA 66 weighed to a mass ratio shown in Table 1 is subjected to 280 using a biaxial kneader (TEM-26SS manufactured by Toshiba Machine Co., Ltd.). It knead | mixed, heating at ° C. The kneaded material thus obtained was cut with a pelletizer to obtain pellets (φ 3 mm × 3 mm) of the resin composition.

(4) Production of Bonded Magnet For each sample, the compound was charged into the hopper of an injection molding machine (EC-100 manufactured by Toshiba Machine Co., Ltd.) and heated, and the molten mixture was filled into the cavity of the mold. In this way, a bonded magnet of length 127 mm × width 12 mm × thickness 3 mm was obtained. Injection molding was performed with a mold temperature of 120 ° C. and a nozzle temperature of 280 ° C. while applying an orienting magnetic field to the mold cavity.

<< Measurement >>
(1) Total Amount of Terminal Groups The concentrations of the carboxyl group and the amino group which are terminal functional groups of each PA 66 were determined as follows. The sample was dissolved in a mixed solution of trifluoroacetic acid-d (CF ₃ COOD) and heavy water (D ₂ O), and ¹ H-NMR measurement was performed. Based on the peak intensity of the obtained spectrum, the total amount of —NH ₂ end and —COOH end was calculated. The carboxyl group concentration, amino group concentration and their total concentration (total amount) of each PA 66 are shown together in Table 1.

(2) Magnetic properties For each sample, the magnetic properties (residual magnetic flux density: Br, coercivity: iHc, maximum energy product: BHmax) of the bond magnet are recorded in a direct current magnetization characteristic automatic recording apparatus (Riken Electronics Co., Ltd. Model BHU-20) ) At room temperature. The obtained results are shown together in Table 1.

(3) Formability (kneading torque)
For each sample, a mixture of rare earth magnet powder weighed to the mass ratio shown in Table 1 and each PA 66 is heat-kneaded using Labo Plastomill (R-60 manufactured by Toyo Seiki Co., Ltd.), and torque required during kneading ( The change over time of the kneading torque was measured. At this time, heating temperature: 280 ° C., screw rotation speed: 50 rpm (constant).

  The time from the start of kneading to the time when the kneading torque became 1.2 times the minimum value as the viscosity increase start time. When the thickening start time is more than 1500 seconds: ○, when the thickening start time is 1200 to 1500 seconds: Δ, and when the thickening start time is less than 1200 seconds: as ×, it is shown together in Table 1.

"Evaluation"
(1) The comparison of the sample 10 and the sample C1 shown in Table 1 reveals the following. When the rare earth magnet powder is only Nd magnet powder and the binder resin is unmodified PA 66, the formability is secured if the content of the Nd magnet powder is less than 90% by mass. However, if the content of the Nd-based magnet powder is 90 mass or more in order to secure sufficient magnetic properties, high magnetic properties are secured but it becomes difficult to secure formability.

(2) As apparent from the samples C3 and C4, when the rare earth magnet powder is only a fine Sm-based magnet powder, even if the content is less than 90% by mass, whether or not the terminal resin of the binding resin is adjusted Regardless, it has been difficult to ensure formability.

(3) From the samples 11 and 12, even if the content of the Nd-based magnet powder is 90% by mass or more, by using the modified PA 66, the magnetic properties of the bonded magnet are sufficiently secured while the formability is also secured. I also knew that I could do it. In particular, it was also found that when the total amount of end groups of the modified PA 66 is 100 mmol / kg or less, the formability and the magnetic properties of the bonded magnet are compatible with each other at a higher level.

(4) From Samples 20 to 22, even when the content of the whole rare earth magnet powder is made 90 mass% or more, by using a mixed powder of Nd magnet powder (coarse powder) and Sm magnet powder (fine powder) It has been found that the magnetic properties of the bonded magnet can be improved while securing the formability. In particular, it has also been found that by using the modified PA 66 in which the total amount of terminal groups is 175 mmol / kg or less, and further 150 mmol / kg or less, the moldability and the magnetic properties of the bonded magnet can be compatible in higher dimensions.

  From the above, it has become clear that, by using the composition of the present invention, a bonded magnet excellent in both heat resistance and magnetic properties can be obtained while securing kneadability and moldability.

Claims (8)

A composition comprising one or more rare earth magnet particles and a binding resin and used for producing a bonded magnet,
The rare earth magnet particles at least include Nd magnet particles in which the rare earth element is Nd,
The total amount of the rare earth magnet particles is 90 to 95% by mass with respect to the entire composition,
The composition for a bonded magnet, wherein the binding resin is a polyamide 66 (PA66) in which the total amount of terminal groups consisting of a carboxyl group and an amino group is 175 mmol / kg or less based on the entire binding resin. The Nd-based magnet particles are contained in an amount of 90% by mass or more based on the entire composition,
The bonded magnet composition according to claim 1, wherein the total amount of end groups of the PA 66 is 100 mmol / kg or less.   The composition for a bonded magnet according to claim 1, wherein the Nd-based magnet particles have an average particle diameter of 40 to 250 μm. The rare earth magnet particles further include Sm based magnet particles in which the rare earth element is Sm,
The composition for a bonded magnet according to any one of claims 1 to 3, wherein the Sm-based magnet particles have an average particle diameter of 1 to 20 m. The Nd-based magnet particles have an average particle diameter of 40 to 150 μm and are contained in an amount of 65 to 89% by mass based on the whole composition,
The rare earth magnet particles further include Sm based magnet particles in which the rare earth element is Sm,
The Sm-based magnet particles have an average particle size of 1 to 20 μm and are contained in an amount of 1 to 30% by mass with respect to the entire composition,
The bonded magnet composition according to claim 1, wherein the total amount of end groups of the PA 66 is 150 mmol / kg or less.   The bonded magnet composition according to any one of claims 1 to 5, wherein the rare earth magnet particles are rare earth anisotropic magnet particles.   The composition for a bonded magnet according to any one of claims 1 to 6, wherein the PA 66 has a weight average molecular weight (Mw) of 12000 to 40000.   The bonded magnet which consists of an injection molded body of the composition for bonded magnets in any one of Claims 1-7.