EP0441616B1 - Aimant anisotropique à liant plastic du type Nd-Fe-B et procédé de sa fabrication - Google Patents

Aimant anisotropique à liant plastic du type Nd-Fe-B et procédé de sa fabrication Download PDF

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Publication number
EP0441616B1
EP0441616B1 EP91300981A EP91300981A EP0441616B1 EP 0441616 B1 EP0441616 B1 EP 0441616B1 EP 91300981 A EP91300981 A EP 91300981A EP 91300981 A EP91300981 A EP 91300981A EP 0441616 B1 EP0441616 B1 EP 0441616B1
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EP
European Patent Office
Prior art keywords
magnetic powder
magnetic
weight
epoxy resin
bonded magnet
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP91300981A
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German (de)
English (en)
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EP0441616A2 (fr
EP0441616A3 (en
Inventor
Shizuo Furuyama
Kiyoshi Kojima
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Panasonic Holdings Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
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Publication date
Priority claimed from JP2030844A external-priority patent/JPH03234002A/ja
Priority claimed from JP2215366A external-priority patent/JP2990759B2/ja
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Publication of EP0441616A2 publication Critical patent/EP0441616A2/fr
Publication of EP0441616A3 publication Critical patent/EP0441616A3/en
Application granted granted Critical
Publication of EP0441616B1 publication Critical patent/EP0441616B1/fr
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0578—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together bonded together

Definitions

  • This invention relates to a plastic bonded magnet containing an anisotropic neodymium-iron-boron system magnetic powder.
  • magnets are used in various devices including stepping motors, spindle motors, torque motors, automotive motors, various actuators, speakers, and other magnetic-field generating devices.
  • the invention provides a plastic bonded magnet which comprises an anisotropic neodymium-iron-boron system magnetic powder and a resin binder characterised in that the magnetic powder has a rounded shape, from 10 to 20% by weight of the magnetic powder has a grain size in the range 10 to 49 ⁇ m, and from 80 to 90% by weight of the magnetic powder has a grain size in the range 50 to 500 ⁇ m.
  • the magnetic powder grain distribution used in the magnets of the invention can be obtained by kneading and dispersing the powder (together with a binder) in a high-speed shearing machine.
  • a higher (BH) max is obtained due to a substantially improved magnetic orientation in the compressed molded body of the plastic bonded magnet. Furthermore, an extended pot-life of molding compound and higher (BH) max value can be obtained by employing an epoxy resin as the binder and curing it with a latent hardening agent which is an amine adduct of the epoxy resin.
  • FIG. 1 there is shown a magnet of the invention wherein 1 is anisotropic neodymium-iron-boron system magnetic powder having a grain size distribution from 50 to 500 ⁇ m (microns), reference 2 is anisotropic neodymium-iron-boron system magnetic powder having grain sizes from 10 to 49 ⁇ m (microns), and 3 is the plastic resin binder.
  • the anisotropic neodymium-iron-boron system magnetic powder employed in this invention can be anisotropic neodymium-iron-boron system magnetic powder manufactured by upsetting its overquenched melt-spun ribbon.
  • the magnets may also comprise, in addition, elements such as zirconium, gallium, cobalt, praseodymium, and tin for improving temperature characteristics, anti-corrosion properties, and magnetic properties as will be understood by those skilled in the art.
  • the magnetic powder employed in the invention has excellent magnetic properties, (magnetization 4 ⁇ I, coercive force iH c ) which are substantially governed by the grain size distribution as shown in Figure 2.
  • the magnetic characteristics of the fine powder having grain sizes of 10 to 49 ⁇ m (microns) are significantly different from those of powder of greater grain size, as Fig. 2 illustrates.
  • the invention does not use exclusively powder having grain sizes less than 49 microns: such magnets would have inferior magnetic properties. Rather, the invention introduces a limited amount only of such powder into the molding composition to improve the magnetic orientation.
  • the magnetic orientation of the plastic bonded magnet is highly improved by introducing magnetic powder having fine grain sizes from 10 to 49 ⁇ m (microns) in an amount of 10 to 20% by weight. The reason for this cannot be attributed to higher magnetic powder density, but we believe it can be attributed to the improved flowability of the molding composition.
  • Magnetic powder having grain sizes less than 10 ⁇ m (microns) because of its poor magnetic characteristics.
  • the content of fine magnetic powder (10 to 49 ⁇ m (microns) should be limited to less than 20% by weight, but the orientation effect cannot be attained if its content is less than 10% by weight.
  • large sized magnetic powder having grain sizes more than 500 ⁇ m (microns) has excellent magnetic characteristics, it causes a reduction in mold density and as a result no improvement in residual magnetic flux density B r can be expected.
  • the molding composition will contain a suitable dispersing agent.
  • Fatty acids, silicone-coupling agents and various surface-active agents can be employed, we prefer to use a liquid fatty acid, eg. oleic acid. This ability to function as a dispersing agent is attributed to the higher affinity for the magnetic powder. This is not shown by any of the solid fatty acids.
  • the use of liquid fatty acids is particularly advantageous in compressive molding which is performed conventionally at room temperature since it improves productivity.
  • fatty acid additive Although it is important to keep the amount of fatty acid additive as low as possible, it is preferred to introduce at least 0.8% by weight thereof (based on the weight of the magnetic powder). An amount of fatty acid less than 0.7% by weight usually results in an inadequate affinity to the magnetic powder resulting in reduced density and (BH) max . On the other hand, if an excessive amount of fatty acid is used, eg. more than 1.3% by weight, oozing of binder tends to occur and lower strength of the molded magnet results.
  • binders Whilst various binders can be used in the present invention, for room temperature molding we prefer to use liquid epoxy resin to give good adhesion strength.
  • the total amount of binder is determined by the attainable magnetic characteristics and the strength of the molding.
  • the total amount of binder component used depends on the magnetic characteristics required and the strength of the molded magnet. If an amount of binder of less than 1.4% by weight is mixed with the magnetic powder, this would usually result in inadequate mold strength, but if more than 3.0% by weight is used, this would result in poor magnetic characteristics.
  • Any suitable curing or hardening agent can be used.
  • Amines and acid anhydrides are generally preferred. If an amine adduct of epoxy resin is used as a hardening agent for epoxy resin used as a binder, a substantially extended pot-life of the molding composition can be obtained relative to the use of a conventional amine system hardening agent.
  • the molding composition is preferably prepared in a high-speed shearing machine capable of pulverizing and mixing the magnetic powder, such as a Henschell mixer, upper-mill, high-speed mixer, or a micro-mill grinder.
  • a high-speed shearing machine capable of pulverizing and mixing the magnetic powder, such as a Henschell mixer, upper-mill, high-speed mixer, or a micro-mill grinder.
  • a plastic bonded magnetic material mixture consisting of 100 weight parts of anisotropic Nd-Fe-B system magnetic powder having grain sizes from 1 to 2 mm and 0.9 weight part of oleic acid as a dispersion agent, are ground in a micro-mill grinder for about five minutes, and 1.0 weight part of epoxy resin, eg. Epikote 828 (manufactured by Yuka-Shell Epoxy Co.), is added thereto, and ground for another ten minutes.
  • epoxy resin eg. Epikote 828 (manufactured by Yuka-Shell Epoxy Co.
  • the dispersion process is completed by adding 0.9 weight parts of acid anhydride, eg. Kayahard MCD (manufactured by Nihon Kayaku Co.), and 0.01 weight parts of catalytic imidazone, eg. Epikure EMI-24 (manufactured by Shikoku Kasei Kogyo Co.) thereto, and the mixing continued for another ten minutes.
  • acid anhydride eg. Kayahard MCD (manufactured by Nihon Kayaku Co.)
  • catalytic imidazone eg. Epikure EMI-24 (manufactured by Shikoku Kasei Kogyo Co.)
  • the molding composition so made is loaded into a die cavity, and is molded at room temperature using a pressure of 6 ton/cm2 (6 x 108 Pa) under application of a magnetic field of 15 KOe. After a hardening process conducted at 100°C for one hour, a plastic bonded magnet of the invention is produced.
  • a molded article before hardening is removed from a mold and immersed in acetone to remove resin components.
  • the magnetic powder obtained is dried in a nitrogen atmosphere. The grain size distribution of this magnetic powder was measured and found to be:
  • Example 1 For comparison purpose, the procedure of Example 1 is repeated except that magnetic powder having grain sizes from 300 to 500 um is used as starting material.
  • the grain size distribution in this case was measured and was found to be:
  • Example 1 is repeated except that magnetic powder having grain sizes from 3 to 4 mm is used.
  • the grain size distribution was found to be:
  • Example 1 is repeated except that this time the mixture is ground for 12 hours in a ball-mill using acetone as a solvent and then the acetone is evacuated.
  • the grain size distribution was found to be:
  • Example 1 The general procedure of Example 1 is followed except that an electromagnetic steel plate made of soft magnetic material is inserted in the die before the molding composition is injected. The molding is then conducted at room temperature under a pressure of 6 6 x 108 Pa (ton/cm2) and a magnetic field of 15 KOe. After a hardening process at 100°C for two hours, a plastic bonded magnet having an integrated electromagnetic steel plate made of soft magnetic material, is obtained. The adhesion between the soft steel plate and plastic bonded magnet was found adequately high.
  • the degree of magnetic orientation is defined as B r (//)/ (B r (//) + B r ( )]. This represents the ease of movement of magnetic powder under application of an external magnetic field, and a higher value means a higher magnetic orientation.
  • B r (//) and B r ( ) represent a residual magnetic flux density along the applied magnetic field and a residual magnetic flux density perpendicular to the applied magnetic field, respectively.
  • Table 1 shows that plastic bonded magnets having higher densities, degrees of magnetic orientation and (BH) max values can be obtained by the present invention.
  • FIGs. 3,4 and 5 Changes in grain configurations of magnetic powder are shown in Figs. 3,4 and 5.
  • Figure 3 shows a schematic configuration of raw magnetic powder material
  • Figure 4 is a schematic showing the rounded-off grains of powder after pulverization and mixing conducted by a high-speed shearing machine which is employed to prepare the magnet of Example 1.
  • Figure 5 is a schematic diagram showing grain configuration of magnetic powder after kneading and dispersion of the magnetic powder of Comparison 3, showing more squarish and smaller grain sizes compared with those shown in Figure 4.
  • This improvement of magnetic orientation is attributed to the improved flowability of the compressive molding composition containing fine magnetic powder having grain sizes from 10 to 49 ⁇ m in amounts from 10 to 20% by weight. Hitherto, the use of this type of magnetic powder had been avoided because of its lower magnetic characteristics.
  • Example 1 the improvement of (BH) max is attributed to the higher magnetic orientation and improved density due to using magnetic powder which is rounded-off during said high-speed shearing process.
  • the density of the magnet of Comparison 2 is 6.15 which is low because it contains magnetic powder having grain sizes from 1 to 2mm, and thus, the (BH) max is low also.
  • An anisotropic Nd-Fe-B system magnetic powder having an average grain size of 1mm and oleic acid are mixed at a weight ratio of 100 to 0.9, and this mixture is kneaded for 10 minutes in a high-speed mixer under a nitrogen atmosphere.
  • an epoxy resin eg. Epikote-828 manufactured by Yuka-Shell Epoxy Co.
  • a latent hardening agent eg. Amicure PN-23, manufactured by Ajinomoto Co.
  • the resulting molding composition is then loaded into a cavity for applying a compressive pressure of 6 ton/cm2 with an applied magnetic field of 15 KOe.
  • the anisotropic plastic bonded magnet is produced after hardening for one hour at 100°C.
  • Example 3 is repeated except that the materials are as follows:
  • Example 3 is repeated except that the materials used were:
  • the initial magnetic characteristics, (BH) max , of the magnets, and the pot-life of the molding compositions are shown in Table 2.
  • the pot-life was determined as follows. The molding composition is left still at room temperature, and samples are taken out every one hour and used to mold a sample plastic bonded magnet under the above-described conditions. The elapsed time at which a sample of the composition forms a magnet which shows a magnetic characteristic which is lower by 5 % than that of the initial magnet is defined as the pot-life of the composition.
  • the plastic bonded magnet shown in Example 3 wherein a latent hardening agent is used showed a value of (BH) max as high as 15 MGOe and a pot-life as long as 20 hours, which are very useful features.
  • the use of a high-speed shearing machine minimizes the possibility of stability damage of binder system due to the local heat produced at kneading.
  • the magnet produced by using an aliphatic amine hardening agent, shown in Comparison 4 had a value of (BH) max of 12 MGOe and a pot life of only 3 hours, and this has little practical value.
  • an aromatic amine hardening agent as shown in Comparison 5 gave a value of (BH) max of 15 MGOe which is reasonably high, the pot life of 6 hours is still considered inadequate for practical purposes.
  • the (BH) max of the magnet, and the pot-life of the composition are influenced by the type of hardening agent.
  • the difference between magnetic characteristics of the magnets can be attributed in part to the difference between the affinities of binders for the magnetic powder, which results in the difference between dispersibilities.
  • the difference between pot-lives can be attributed to the difference between thermal stabilities of the binder systems against local heat generation.
  • the latent hardening agent employed i.e. a hardening agent which does not start hardening until a certain time is elapsed after it is mixed with a primary epoxy agent, is much preferred. This hardening system has a high thermal stability, and is thus considered highly useful to extend the pot-life.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)

Claims (4)

  1. Aimant à liant de matière plastique qui comprend une poudre magnétique anisotrope du système néodyme-ferbore et un liant de résine, caractérisé en ce que la poudre magnétique a une configuration arrondie, 10 à 20 % en poids de la poudre magnétique ayant une dimension granulaire comprise entre 10 et 49 µm et 80 à 90 % en poids de la poudre magnétique ayant une dimension granulaire comprise entre 50 et 500 µm.
  2. Aimant selon la revendication 1, dans lequel le liant de résine est une époxyde, et l'aimant comporte en outre un produit d'addition d'amine de résine époxyde comme agent durcisseur latent pour la résine époxyde.
  3. Procédé de fabrication d'un aimant à liant de matière plastique selon la revendication 1, comprenant les étapes suivantes : la préparation d'une poudre magnétique anisotrope du système néodyme-fer-bore et d'un liant de résine, le mélange de la poudre magnétique et du liant de résine, le moulage du mélange résultant dans un champ magnétique, et l'exécution d'un traitement de durcissement de l'article moulé, caractérisé en ce que 10 à 20 % en poids de la poudre magnétique ont une dimension granulaire comprise entre 10 et 49 µm et 80 à 90 % en poids de la poudre magnétique ont une dimension granulaire comprise entre 50 et 500 µm, et en ce que l'étape de mélange comprend une étape de pulvérisation et de dispersion simultanées de la poudre magnétique avec le liant de résine dans une machine à grande vitesse ayant un gradient élevé de vitesse.
  4. Procédé selon la revendication 3, dans lequel le liant de résine est une résine époxyde qui est polymérisée avec un produit d'addition d'une amine et d'une résine époxyde comme agent durcisseur latent de la résine époxyde.
EP91300981A 1990-02-09 1991-02-06 Aimant anisotropique à liant plastic du type Nd-Fe-B et procédé de sa fabrication Expired - Lifetime EP0441616B1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2030844A JPH03234002A (ja) 1990-02-09 1990-02-09 ネオジウム―鉄―ボロン系プラスチック磁石およびその製造方法
JP30844/90 1990-02-09
JP2215366A JP2990759B2 (ja) 1990-08-14 1990-08-14 ネオジウム−鉄−ボロン系プラスチック磁石の製造方法
JP215366/90 1990-08-14

Publications (3)

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EP0441616A2 EP0441616A2 (fr) 1991-08-14
EP0441616A3 EP0441616A3 (en) 1992-05-20
EP0441616B1 true EP0441616B1 (fr) 1994-11-02

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DE (1) DE69104858T2 (fr)

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Publication number Priority date Publication date Assignee Title
DE19902679C1 (de) * 1999-01-23 2000-11-16 Harman Audio Electronic Sys Lautsprecher
DE102006002875B4 (de) * 2006-01-19 2009-10-22 Beyer Dynamic Gmbh & Co. Kg Schallwandler-Magnetsystem
FR3052602B1 (fr) 2016-06-13 2020-09-18 Gulplug Systeme de connexion electrique

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4558077A (en) * 1984-03-08 1985-12-10 General Motors Corporation Epoxy bonded rare earth-iron magnets
EP0281295A3 (fr) * 1987-03-03 1990-05-30 Imperial Chemical Industries Plc Procédé et composition pour la production d'un aimant à liant

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Publication number Publication date
DE69104858D1 (de) 1994-12-08
DE69104858T2 (de) 1995-05-24
EP0441616A2 (fr) 1991-08-14
EP0441616A3 (en) 1992-05-20

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