JP4608665B2 - Rare earth bonded magnet compound, rare earth bonded magnet, and method for producing them - Google Patents

Description

  The present invention relates to a compound for a rare earth bonded magnet, a rare earth bonded magnet, and a production method thereof.

  In recent years, the demand for bonded magnets obtained by molding a compound containing magnet powder and a resin binder into a predetermined shape can be easily obtained as a magnet having a complicated shape or a thin shape. . In the present specification, the magnet powder includes an alloy powder that is not magnetized.

  In particular, rare earth bonded magnets using rare earth permanent magnet powders with excellent magnetic properties are expected to be applied in various fields, and their practical application is progressing. As the rare earth-based permanent magnet powder, MQ powder sold by Magnequench International, which is the R-Fe-B magnet powder having the most excellent magnetic properties, has been used conventionally. On the other hand, resin binders are roughly classified into thermosetting resins (including vulcanized rubber) and thermoplastic resins (including thermoplastic elastomers).

  In recent years, sheet-like bonded magnets are being developed for application to electronic components such as small motors. When applying a sheet-like bond magnet to a motor, it is desirable to have flexibility in order to curl the sheet-like bond magnet annularly.

  For example, in Patent Document 1, a flexible resin binder such as magnet powder and rubber is kneaded with a pressure kneader, the obtained kneaded material is pulverized to a size of about 5 mm, and then rolled into a sheet by a roll. A method for producing a sheet-like bonded magnet by heat-treating a rolled magnet material is described.

  The method described as an Example in Patent Document 1 includes the following steps. First, a film containing a rust inhibitor and an epoxy resin main agent is formed on the surface of the magnet powder. The obtained mixture is kneaded with a rubber binder, a curing agent and a curing accelerator in a pressure kneader, and then pulverized. A sheet-like magnet material is obtained by rolling the obtained powder with a heated roll. Next, after preheating the sheet-like magnet material for about 8 hours, the rubber binder is vulcanized by heating to about 170 ° C. Furthermore, a flexible sheet-like bonded magnet can be obtained by performing a reheat treatment at 130 ° C. for 60 minutes.

  However, when vulcanized rubber (thermosetting resin) is used as described above, a complicated process is required, which causes a problem of an increase in cost and a decrease in throughput. In addition, when vulcanized rubber is used, there is a problem that the flexibility is relatively low.

On the other hand, Patent Document 2 describes a bonded magnet using a thermoplastic resin. According to Patent Document 2, a sheet-like bonded magnet having excellent flexibility is obtained by using a mixture of a thermoplastic elastomer and a thermoplastic resin having a maleic anhydride structure as a resin binder. It is described that the magnet powder is preferably an SmFeN system having high magnetic properties even when miniaturized. This sheet-like bonded magnet is manufactured by the following process. First, after magnet powder and a resin binder are kneaded, they are pulverized by a crusher to form pellets. The obtained magnet powder composition (compound) is formed into a sheet by extruding and rolling, and further subjected to heat treatment to obtain a sheet-like bonded magnet. According to Patent Document 2, this sheet-like bonded magnet has a Shore D hardness of 33 to 55, a tensile strength of 32 to 60 kgf / cm ² , and cracks occur when a 1 mm thick sheet is wound around a 10 mm diameter cylinder. Does not occur.
JP-A-5-47576 JP 2001-68316 A

  However, in the method described in Patent Document 2, the properties of the compound are pellets, and an extrusion and rolling process is required to form a sheet-like bonded magnet. This is due to the following reason. In general, a compound obtained by kneading magnet powder and resin using a kneader, a screw extruder, a kneading open roll, or the like has low fluidity and is an indeterminate lump. Therefore, since it cannot be processed into a uniform sheet as it is, it is formed into a sheet having a shape close to the final product by once heating and melting the pellet-like compound after forming a pellet having a constant particle diameter. Thereafter, processing is further performed to the size and shape of the final product.

  As described above, when the method described in Patent Document 2 is used, a sheet-like bonded magnet containing a thermoplastic elastomer as a resin binder can be obtained. However, there are problems in that the cost is high because many steps are required. It has not been used for.

  This invention is made | formed in view of the said various points, The main objective is to provide the sheet-like bond magnet which contains a thermoplastic elastomer as a resin binder at low cost.

  The compound of the present invention is a bonded magnet compound containing a rare earth alloy powder and a thermoplastic elastomer, wherein the content of the rare earth alloy powder in the compound is 80% by mass or more, and the thermoplastic elastomer at room temperature. The Shore A hardness is 10 or less.

  Another compound of the present invention is a bonded magnet compound containing a rare earth alloy powder and a thermoplastic elastomer, wherein the content of the rare earth alloy powder in the compound is 80% by mass or more, and the porosity of the compound Is a sheet-like compound with 3% or more. The porosity of the compound is preferably 30% or less. The thermoplastic elastomer preferably has a Shore A hardness of 10 or less at room temperature.

  In one embodiment, the rare earth alloy powder preferably has an average particle size of 20 μm or more and 150 μm or less, and a ratio of a minor axis direction size to a major axis direction size of the powder particles of 0.5 or more and 1.0 or less.

  In one embodiment, the rare earth alloy powder preferably includes a nanocomposite magnet powder having at least one hard magnetic phase and at least one soft magnetic phase in the same metal structure.

In one embodiment, the nanocomposite magnet powder includes a composition formula T _100-xyz Q _x R _y M _z (T is Fe or one or more elements selected from the group consisting of Co and Ni and Fe). Transition metal element, Q is at least one element selected from the group consisting of B and C, R is one or more rare earth elements substantially free of La and Ce, M is Ti, Al, Si, V , Cr, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and one or more metal elements selected from the group consisting of Pb)
A nanocomposite powder having a composition in which composition ratios x, y, z, and m satisfy 10 <x ≦ 25 atomic%, 1 ≦ y <10 atomic%, and 0.5 ≦ z ≦ 10 atomic%, respectively. Is preferred.

  In one embodiment, the thermoplastic elastomer preferably includes one selected from the group consisting of styrene, olefin, ester, urethane, and alloys thereof.

  In one embodiment, the thermoplastic elastomer comprises polystyrene-poly (ethylene / propylene) block-polystyrene (SEPS).

  The compound of an embodiment is a sheet and has a thickness of 0.5 mm or more and 5 mm or less. In one embodiment, the width is 10 mm or more and the length is 100 mm or more.

  A bonded magnet according to the present invention includes a bonded magnet layer formed of any one of the above compounds. The bonded magnet may be formed only from the bonded magnet layer formed from the bound.

  In one embodiment, a protective layer is further provided on the bonded magnet layer. The protective layer may be provided on one side of the bonded magnet layer or on both sides.

  In one embodiment, the protective layer is formed from a thermoplastic resin.

  The bonded magnet of the present invention is a bonded magnet formed from any one of the above compounds.

In certain embodiments, the maximum magnetic energy product is 40 kJ / m ³ or greater.

  In some embodiments, the bonded magnet is sheet-like.

  An electronic component according to the present invention includes any one of the above bonded magnets.

  The method for producing a compound of the present invention comprises (a) a step of preparing a rare earth alloy powder and a thermoplastic elastomer, and (b) kneading the thermoplastic elastomer and the rare earth alloy powder in a state where the open roll is heated, Including a step of producing a magnet compound containing 80% by mass or more of the rare earth alloy powder, and a step of (c) processing the compound into a sheet by passing it through an open roll near room temperature. And

  In one embodiment, the porosity of the sheet-like compound obtained by the step (c) is 3% or more. The porosity of the compound is more preferably 5% or more, and preferably 30% or less.

  In one embodiment, the Shore A hardness of the thermoplastic elastomer at room temperature is 10 or less.

  In one embodiment, the rare earth alloy powder has an average particle size of 20 μm or more and 150 μm or less, and a ratio of a minor axis size to a major axis size of the powder particles is 0.5 or more and 1.0 or less.

  In one embodiment, the rare earth alloy powder includes a nanocomposite magnet powder having at least one hard magnetic phase and at least one soft magnetic phase in the same metal structure.

  In one embodiment, the thermoplastic elastomer includes one selected from the group consisting of styrene, olefin, ester, urethane, and alloys thereof.

  In one embodiment, the thermoplastic elastomer comprises polystyrene-poly (ethylene / propylene) block-polystyrene (SEPS).

  The method for producing a bonded magnet according to the present invention includes a step of heating and compressing a sheet-like compound produced by any one of the above production methods.

  Another method for producing the bonded magnet of the present invention includes a step of laminating a thermoplastic resin film on one or both sides of a sheet-like compound produced by any one of the above production methods, and a step of heating and compressing the laminate. It is characterized by including.

  According to the present invention, a flexible sheet-like bonded magnet (flexible sheet magnet) can be manufactured by a simple process. Since the compound of the present invention can be in the form of a sheet from the compounding stage, it is possible to efficiently produce bond magnets having various shapes including a sheet-like bond magnet. For example, an annular bonded magnet can be manufactured by curling a sheet-like compound. In addition, since a thermoplastic elastomer is used as the resin binder, recycling is easy, it is environmentally friendly, and costs can be kept low. In particular, a compound (and a bond magnet) using a resin elastomer having a Shore A hardness of 10 or less has an advantage that it can be re-kneaded without going through a heating step and can be easily recycled.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

 The present inventor has intensively studied the kind of binder resin, the kneading method and properties of the compound for the purpose of providing a sheet-like bonded magnet containing a thermoplastic elastomer as a resin binder at low cost, and arrived at the present invention.

  First, as a rare earth magnet powder, an R—Fe—B nanocomposite magnet powder, which has been developed recently, was selected as a powder for an R—Fe—B bond magnet. The R-Fe-B nanocomposite magnet powder is a magnet powder having at least one hard magnetic phase and at least one soft magnetic phase in the same metal structure. For example, SPRAX- available from NEOMAX I and SPRAX-II (SPRAX is a registered trademark of NEOMAX).

The R—Fe—B-based nanocomposite magnet powder includes, for example, a composition formula T _100-xyz Q _x R _y M _z (T is Fe or one or more elements selected from the group consisting of Co and Ni and Fe Transition metal element including: Q is at least one element selected from the group consisting of B and C; R is one or more rare earth elements substantially free of La and Ce; M is Ti, Al; Expressed by one or more metal elements selected from the group consisting of Si, V, Cr, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb) The composition ratios x, y, z, and m satisfy the following conditions: 10 <x ≦ 25 atomic%, 1 ≦ y <10 atomic%, and 0.5 ≦ z ≦ 10 atomic%, respectively.

This nanocomposite magnet powder forms a rapidly solidified alloy having a thickness of 60 μm or more and 300 μm or less by cooling a molten alloy of a predetermined composition by a roll quenching method such as a melt spinning method or a strip cast method, and by heat treatment The rapidly solidified alloy is crystallized to produce an alloy having permanent magnet characteristics, and the alloy is obtained by pulverizing the alloy to an average particle size of 20 μm to 150 μm. The alloy having the permanent magnet characteristics obtained by this crystallization has an average crystal grain size of iron-based boride which is a soft magnetic phase such as fine Fe ₃ B or Fe ₂₃ B ₆ having an average crystal grain size of 5 nm or less. Since the R ₂ Fe ₁₄ B phase, which is a hard magnetic phase of 10 to 100 nm, has a fine crystal structure that is uniformly distributed in the same metal structure, it can be easily broken in various directions by the pulverization process. The ratio of the size of the minor axis to the size of the major axis of the powder particles (referred to as the aspect ratio) is 0.5 or more and 1.0 or less, and the powder particles are flaky and very flat (the aspect ratio is less than 0.3). Compared with MQ powder composed of Moreover, it is not a perfect spherical shape, but is a lumpy lump.

  The rapid cooling method is preferably a roll rapid cooling method such as a melt spinning method or a strip cast method. When the atomizing method, which is one of the rapid cooling methods, is used, spherical magnet powder particles can be obtained. The spherical solid powder obtained by pulverizing the rapidly solidified alloy obtained by the roll rapid cooling method can be obtained. This is because the powder particles are more agglomerated with a rougher surface as described above, and are therefore strongly bonded at the interface with the thermoplastic elastomer by the anchor effect, and the strength of the sheet-like bonded magnet can be obtained. When such nanocomposite magnet powder is used, it shows very good followability in movements such as bending of the bond magnet, and the magnetic powder content is increased to 95% by mass, similar to an injection-molded bond magnet using a nylon-based resin as a binder. However, there is no threshing that causes a practical problem.

In order to set the thickness of the rapidly solidified alloy to 60 μm or more and 300 μm or less, it is desirable to adjust the surface speed of the cooling roll within the range of 4 m / s to 20 m / s. If the surface speed of the chill roll is less than 4 m / s, the thickness of the rapidly solidified alloy exceeds 300 μm, but a hard quenched alloy structure with a large amount of α-Fe is formed. This is because R ₂ Fe ₁₄ B, which is a magnetic phase, does not precipitate and the permanent magnet characteristics may not be exhibited. On the other hand, when the roll surface speed exceeds 20 m / s, the thickness of the rapidly solidified alloy becomes thinner than 60 μm, and in the pulverization step after the heat treatment, the direction substantially perpendicular to the roll contact surface (the thickness of the alloy ribbon) Direction). As a result, the quenched alloy ribbon is easily broken into a flat shape, and the ratio of the minor axis size to the major axis size of the obtained powder particles may be less than 0.3.

  The average particle size of the R—Fe—B nanocomposite magnet powder particles is defined as 20 μm to 150 μm. If the particle size is smaller than 20 μm, the required magnetic properties cannot be obtained. This is because the moldability is adversely affected. From the same viewpoint, the thickness is more preferably 40 μm to 100 μm.

  Since the R-Fe-B nanocomposite magnet powder has the aspect ratio and / or shape as described above, it has an advantage that the bonding effect with the resin is strong due to the anchor effect and that the magnetic powder is less dropped. ing. Moreover, the content rate of the magnet powder in a compound can also be raised. Furthermore, the nanocomposite magnet powder has an advantage of excellent corrosion resistance. In the bonded magnet using MQ powder, in addition to the shape of the powder particles described above, the corrosion resistance is low, which is a reason why magnetic powder is likely to fall off (granulation). Since MQ powder contains a large amount of rare earth elements, it has low corrosion resistance and is corroded to the inside of the powder particles. Therefore, erosion occurs when corrosion progresses during use. In contrast, nanocomposite magnet powder has a low content of rare earth elements and excellent corrosion resistance, so it is difficult to corrode, and even if corrosion occurs, an oxide layer is only formed on the surface of the powder particles. Since corrosion does not proceed to the inside of the particles, degranulation does not occur.

  Further, the feature that the nanocomposite magnet powder is hardly oxidized is also advantageous in the compound manufacturing process. As will be described later, when producing a compound using an open roll for kneading, there is no need to use an inert atmosphere in order to suppress the oxidation of the magnet powder (or to the extent that oxidation can be sufficiently suppressed with simple equipment) (Inert atmosphere can be created). In order to produce a compound using MQ powder, the MQ powder will be oxidized unless oxygen is sufficiently blocked. For example, when kneading using an open roll in the atmosphere, it may even ignite. Further, as will be described later, there is a risk of oxidation when handled in the state of a sheet-like compound having a porosity of 3% or more.

Among the R-Fe-B nanocomposite magnet powders, SPRAX-II is preferably used from the viewpoint of magnetic properties and corrosion resistance. SPRAX-II is a so-called Ti-containing nanocomposite magnet powder, composition formula _{(Fe 1-m T m)} 100-abcn (B 1-p C p) a R b Ti c M n (T is Co and Ni One or more elements selected from the group consisting of: R is one or more elements selected from the group consisting of Y (yttrium) and rare earth metals; M is Al, Si, V, Cr, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and one or more elements selected from the group consisting of Pb) and a composition ratio (atomic ratio) a, b , C, m, n, and p are 10 <a ≦ 25 atomic%, 6 ≦ b <10 atomic%, 0.5 ≦ c ≦ 12 atomic%, 0 ≦ m ≦ 0.5, 0 ≦ n, respectively. R—Fe—B-based nanocomposite magnet powder satisfying ≦ 10 atomic% and 0 ≦ p ≦ 0.25 It is. Details of the composition and manufacturing method of the Ti-containing nanocomposite magnet powder are described in, for example, Japanese Patent Nos. 3264664, 3297676, and 3358735. Although it is preferable to use SPRAX-II as the rare earth alloy powder from the above-mentioned advantages, the rare earth alloy powder used in the compound of the present invention is not limited to this. For example, Sm—Fe—N magnet, Sm—Co magnet, Various known rare earth alloy powders for bonded magnets such as isotropic R—Fe—B (HDDR) magnets can be used. Of course, you may mix and use magnet powder as needed. However, for the reasons described above, it is preferable to adjust the average particle size to 20 μm or more and 150 μm or less, and the ratio of the minor axis size to the major axis size of the powder particles is 0.5 to 1.0. It is preferable to use a powder.

  Various methods for producing resin binders and compounds (mainly kneading methods) were studied.

  First, the use of a low-hardness thermoplastic elastomer developed recently was examined as the thermoplastic elastomer. From the viewpoint that the flexibility of the sheet-like bonded magnet is not impaired even if the content of the magnet powder is increased, a low hardness elastomer having a Shore A hardness of 0 to 10 at room temperature (close to a gel at room temperature) Selected). In particular, those having a Shore A hardness of 1 or less are preferred.

  However, even when a low-hardness thermoplastic elastomer is used, when the magnetic powder is blended so as to be 80% by mass with respect to the entire compound, the melt flow rate (fluidity) is extremely reduced, It was impossible to perform kneading and extrusion with a twin-screw kneader or the like. Similarly, kneading with a pressure kneader was not easy. Similarly, when the magnetic powder was blended at a high ratio, the resulting compound was brittle, and it was not possible to produce a compound having a fixed shape such as a pellet. The true specific gravity of the R—Fe—B magnet powder is about 7.5, and the specific gravity of the low-hardness thermoplastic elastomer is about 0.9.

  Therefore, it was examined to use an open roll for kneading which is often used for kneading natural rubber having no fluidity or kneading a special filler in a large amount to a thermoplastic resin. Furthermore, if a sheet-like compound can be taken out directly when kneading is completed using an open roll for kneading, the sheet can be directly subjected to hot-pressing, which greatly improves the manufacturing process. In consideration of the need for a preforming step for producing a more uniform sheet, the inventors have intensively studied a production method using an open roll for kneading.

  The low-hardness type, which is close to a gel, only stretches when melted with an open roll heated by itself, so that even if it is pulled, it is stretched as an elastomer even if it is pulled from one side of the rotating roll surface and pulled. It is difficult to take out in sheet form. Further, when the content of the magnet powder is increased (for example, 80% by mass or more), the bonding strength (cohesive force) of the thermoplastic elastomer in a molten state is reduced, and one side of the compound kneaded and wound around the rotating roll Even if it is cut and pulled, it will be cut easily at that part, and the compound cannot be taken out in sheet form. Also, if the compound is wound around the rotating roll and the roll is forcibly cooled to cool and solidify the compound, the viscosity (adhesiveness) of the thermoplastic elastomer will decrease, resulting in an indeterminate lump. The sheet fell off from the roll surface and could not be taken out. In addition, the rotation of the roll was stopped while the compound was wound around the roll surface, and the temperature of the roll was cooled and an attempt was made to take out through a sufficient cooling process. In this case, the compound adhered to the roll surface. , Even if I cut one side and pulled it, it broke.

  Therefore, paying attention to the fact that the low-hardness elastomer itself is close to a gel at room temperature and has adhesiveness, the compound obtained by once melting and kneading is removed from the roll as an irregular lump. After cooling to room temperature and then trying to form a sheet by passing a lump of the compound once through the gap of the roll cooled to near room temperature, a sheet-like compound could be formed. This is because, as will be described later, since the sheet is formed while the air is engulfed by the shearing force of the open roll, the sheet is rich in voids (porosity of 3% or more, preferably 5% or more). Conceivable.

  This sheet-like compound has excellent flexibility, and even if it is lowered with one side thereof, it is not broken by its own weight and has excellent handling properties. In addition, it has excellent uniform dispersibility of magnetic powder and its thickness is constant, so it is easy to perform secondary molding, and it is possible to manufacture highly accurate and flexible sheet-like bonded magnets with no variation in shape and density. It is.

  The sheet-like compound has a thickness of 0.5 mm to 5 mm, a width of 10 mm or more, a length of 100 mm or more, typically a width of 30 mm or more, and a length of 600 mm or more. The thickness of the sheet-like compound is The thickness is preferably about 1.5 times the thickness of the final bonded sheet magnet.

  The sheet-like compound can produce a bonded magnet by a molding method such as press molding or injection molding. According to the method of the present invention, a sheet-like bonded magnet having a thickness of 0.2 mm to 5 mm, a width of 2 mm or more, and a length of 2 mm or more can be produced, and further, a large sheet having a width of 500 mm or more and a length of 500 mm or more. Bond magnets can also be manufactured.

  Moreover, since the compound is a sheet form, the sheet-like bond magnet manufactured using the sheet-like compound of this invention is excellent in the uniformity of the density of the bond magnet obtained. This is an effect that is difficult to obtain when a pellet-like (or other lump-like) compound is used. Further, since the R-Fe-B nanocomposite magnet powder has an equiaxed shape, the obtained compound has very excellent fluidity, and as a result, such a sheet-like shape is obtained. A sheet-like bonded magnet obtained by using a compound has magnetic properties with extremely high uniformity.

  As the thermoplastic elastomer, specifically, as the base resin, it is preferable to use a styrene-based, olefin-based, ester-based, urethane-based, or alloy thereof, and to further strengthen the bond between the resin and the magnetic powder. In consideration of the compatibility of resins such as acid-modified styrene-based elastomers and olefin-based elastomers, which have an excellent effect on metal binding properties, 5 modifiers for 100 parts by weight of the base resin. It is desirable to mix and use a modifier of about part by weight.

  The mixing ratio of the magnet powder and the thermoplastic elastomer is preferably 80% by mass or more in terms of the content of the magnet powder with respect to the entire compound. This is because, within such a range, necessary magnetic characteristics can be obtained, and a necessary magnetic flux density can be obtained even when used as a permanent magnet used in electronic parts such as motors, actuators and sensors. The content of the R—Fe—B nanocomposite magnet powder is preferably 85% by mass or more, and more preferably 90% by mass or more in applications where a higher magnetic flux density is desired. Further, from the viewpoint of flexibility of the sheet-like bonded magnet, the content of the magnet powder is preferably 96% by mass or less, and more preferably 95% by mass or less. The magnet powder may be subjected to a known silane coupling agent treatment or the like in order to improve the adhesion with the thermoplastic elastomer. The silane coupling agent may be mixed in the kneading step.

  Note that a sheet-like bonded magnet may be formed by laminating two or more of the above-mentioned sheet-like compounds (sometimes referred to as compound layers) and heating and compressing them. Furthermore, you may provide a protective layer in the single side | surface or both surfaces of the bond magnet obtained by heat-compressing a sheet-like band. In the bonded magnet provided with the protective layer, a layer obtained by heating and compressing the sheet-like compound may be referred to as a bonded magnet layer. The protective layer is typically a resin layer.

  When another resin layer is laminated on one side or both sides of the sheet-like bonded magnet, the thickness of the resin layer is preferably 50 μm or less, and preferably 20 μm to 30 μm in consideration of the influence on the magnetic properties. As a method of providing the resin layer, a general coating technique such as spraying, dipping, or electrodeposition is also possible.

  Among the resins, it is preferable to use a thermoplastic resin. When a thermoplastic resin film is used, a sheet-like bonded magnet having a protective layer can be produced by the following steps.

  A thermoplastic resin film is placed on the surface of the sheet-like compound before the sheet-like compound is heated and compressed, and the sheet-like compound and the thermoplastic resin film are simultaneously heated and compressed, so that the thermoplastic resin is applied to the surface of the bond magnet layer. The sheet-like bonded magnet provided with the protective layer formed from can be obtained. When this process is adopted, there is an advantage that the heat compression step does not increase. Of course, only the sheet-like compound is heated and compressed to form a bonded magnet layer (sheet-like bonded magnet), and then a thermoplastic resin film is placed on the surface and heat-sealed to heat the bonded magnet layer to the surface. You may obtain the sheet-like bond magnet provided with the protective layer formed from the plastic resin. Thus, a very uniform resin layer can be formed by heat-compressing or heat-sealing a thermoplastic resin film with a hot press. Moreover, you may adhere | attach a resin film using a normal temperature press, a calender roll, etc. with an adhesive agent. As the material of the thermoplastic resin film, polypropylene having a low melting point and high compatibility with the thermoplastic elastomer used for the binder is desirable, but various thermoplastic resin films can be used depending on other required performance and physical properties.

  Table 1 below shows the types and characteristics of typical thermoplastic resin films. Table 1 is a comparative table showing the compatibility and characteristics when the film used for the protective layer of the sheet-like bonded magnet having excellent flexibility according to the present invention is formed by melt lamination.

  The compatibility in Table 1 was evaluated as follows. Each thermoplastic resin film is laminated on a sheet-like compound, heated and compressed, and then cooled to room temperature. The film is peeled off from the center of the sheet-like bonded magnet (peeling test), and evaluated by the presence or absence of cohesive failure. did. The state of destruction was visually observed. Here, the cohesive failure means that the interface failure between the protective layer and the bonded magnet layer does not occur and the protective layer breaks, or the bonded magnet layer breaks and a part of the bonded magnet layer adheres to the protective layer. Including the case of When cohesive failure occurred (that is, when interface failure did not occur), it was judged that the compatibility between the material forming the protective layer and the thermoplastic elastomer of the bonded magnet layer was good.

  As can be seen from Table 1, it can be seen that polypropylene, polyethylene, and polystyrene films do not cause interface breakdown (interface peeling), and are preferable as a material for the protective layer in terms of surface hardness and flexibility. A urethane film can be used for applications in which flexibility is important. In addition, when employ | adopting the process of bonding a thermoplastic film to a sheet-like bond magnet (bond magnet layer) using an adhesive agent, compatibility is not required.

  As described above, when a protective layer (resin layer) is laminated on the bonded magnet layer, it is possible to further prevent the magnet powder from falling off and to prevent slight magnet powder from falling off due to bending or rubbing. In addition, the R-Fe-B nanocomposite magnet powder has a particle size larger than that of the ferrite magnet powder or the Sm magnet powder, so that the surface of the bond magnet may be roughened (surface roughness increases). In such a case, the roughness of the magnet surface can be reduced by laminating the protective layer.

  The sheet-like bonded magnet can be used as it is, or it can be cut with a shearing machine, laser cutter, etc., cut into various sizes and shapes, or punched. May be. Moreover, you may shape | mold so that many small magnets can be taken in the case of shaping | molding.

  In addition, when using the hot press molding method when forming bonded magnets, various shapes of magnets can be easily manufactured at low cost by devising the mold shape, and manufactured from the sheet-like compound of the present application. The flexible bonded magnets are electronic components such as small motors, servo motors, linear motors, actuators and sensors, sensing devices, linear sliding devices, office equipment, industrial equipment, health equipment, home It can be used for various purposes such as goods.

The bonded magnet manufactured from the sheet-like compound of the present invention is excellent in flexibility and has a tensile strength of> 0.3 MPa and an elongation of> 10%. As magnetic properties, the content of the nanocomposite magnet powder is 85% by mass or more, the maximum magnetic energy product (BH) _max is 40 kJ / m ³ or more, 90% by mass or more, and (BH) _max is 48 kJ / m ³ or more. Can be achieved.

  Using this property, for example, by using a ring-shaped mold or cutting a sheet-shaped bonded magnet into a ring shape, and using a rubber band-shaped magnet, it can be easily mounted on an electronic component such as a small motor. It is possible to use. Alternatively, by using the flexibility of the sheet-like compound, it can be molded after being mounted on a predetermined part or the like using a curling device or the like in the compound state.

  FIG. 1 shows photographs of several sheet-like bonded magnets according to the present invention. In addition, the cigarette for size reference is also shown in FIG.

  As shown in FIG. 1, the sheet-like bonded magnet of the present invention is highly flexible and has sufficient strength for handling and curling. Therefore, as illustrated in FIG. 1, it can be curled or can be easily cut into various shapes.

[Rare earth nanocomposite magnet powder]
Nd: 6 atomic%, Pr: 1 atomic%, B: 12 atomic%, C: 1 atomic%, Ti: 4 atomic%, balance is made of Fe and inevitable impurities, and the raw materials are weighed. It put into an alumina crucible. Thereafter, the raw material was melted by a high-frequency heating method to produce a molten alloy having the above composition. The molten metal temperature was set to 1350 ° C. Thereafter, the alumina crucible was tilted, and this molten metal was directly supplied onto a cooling roll rotating at a surface peripheral speed of 10 m / s through a chute to produce a rapidly solidified alloy. The average thickness of the obtained rapidly solidified alloy was 85 μm. This rapidly solidified alloy is crystallized by heat treatment by holding at 700 ° C. for 5 minutes, then pulverized, and Nd—Fe—B nanocomposite magnet powder having an average particle size of 75 μm (Ti-containing nanocomposite magnet powder) Got. It was confirmed using a powder X-ray diffraction method that the obtained magnet powder was a Ti-containing nanocomposite magnet powder. From the X-ray diffraction pattern, Nd ₂ Fe ₁₄ B phase and Fe ₃ B phase were confirmed. Moreover, as a result of observing with SEM, the particles of the magnet powder have an individual shape, and the ratio of the minor axis size to the major axis size (aspect ratio) is 0.5 to 1. It was equiaxed with 0.0. When the magnetic powder was observed with a transmission electron microscope, the average grain size of the crystal grains constituting the metal structure was about 20 nm. Incidentally, the magnetic properties of the magnet powder obtained was measured with a vibration type magnetometer (VSM), remanence B _r is 830MT, maximum magnetic energy product (BH) _max is 105kJ / m ^3, the holding force H _cJ is It was 660 kA / m.

  Below, the detail of manufacture of a sheet-like compound and manufacture of a sheet-like bond magnet is demonstrated.

  The resin binder is 80% by mass of Septon JS10NS (Shore A hardness of 1 degree or less) SEP manufactured by Kuraray Co., Ltd. as a thermoplastic elastomer, and M-1943 is modified SEBS manufactured by Asahi Kasei Chemicals Co., Ltd. as a modifier. Of 20% by mass was used.

  20 g of an aqueous solution obtained by diluting a silane coupling agent to 50% by mass is prepared for 1 kg of the rare earth nanocomposite magnet powder, and the aqueous solution is sprayed while stirring the rare earth nanocomposite magnet powder with a mixer and heated until dried. Stir.

  In order to melt the resin binder and blend the rare earth-based nanocomposite magnet powder, an 8-inch kneading open roll manufactured by Kansai Roll Co., Ltd. was used.

  First, the roll surface temperature was heated to 160 ° C., 66.7 g of the resin binder was melted on the roll, and the magnetic powder subjected to the surface treatment was blended and kneaded. If the compound is only a general resin, it is possible to take out the sheet-like compound by cutting out the compound on the roll surface at the stage when this kneading is finished, but a high ratio blending of rare earth nanocomposite magnet powder was performed. In some cases, the compound was fragile and could not be taken out in the form of a sheet, so the compound lump was scraped off from the roll surface in an irregular shape once with a scraper and cooled to room temperature.

  Next, the compound lump cooled to room temperature was put into an open roll that was forcibly cooled to room temperature with tap water. The open roll machine for kneading is a structure that improves the kneading effect by changing the rotational speed of the two rolls to increase the kneading effect by applying a shearing force to the compound mass in order to increase the kneading effect. By applying the shearing force and the pressure passing between the rolls, the above-mentioned irregularly shaped compound lump was formed into a sheet molded product having a width of 430 mm, a length of 638 mm, and a thickness of 0.77 mm. This sheet was a sheet that could be handled sufficiently without being cut even when it was lowered with its upper side.

  A similar manufacturing method further widens the gap between two rolls to produce six sheets each having a different thickness, and a small piece having a width of 10 mm and a length of 40 mm as a test sample piece from each sheet. Were cut out and designated as AF.

  Table 2 below shows the measured values of these six sheets. The specific gravity was measured using EW-200SG manufactured by Alpha Mirage Co., Ltd., and the tensile strength (maximum breaking strength) was measured using STROGRRAPH-VE5D manufactured by Toyo Seiki Seisakusho.

  Next, in order to determine the mass that would break at its own weight for these samples, in the sheets A to F, when looking at the relationship between the mass and the maximum breaking strength, the breaking strength was higher than the own weight in all sheets. It was much better. That is, in the width dimension of the sheet samples A to F, the length dimension that is broken by its own weight and cannot be handled is the case where the mass (self weight) exceeds the maximum breaking strength.

  From this, a sheet formed into a sheet molded product having a width of 430 mm, a length of 638 mm, and a thickness of 0.77 mm by passing a shearing pressure between the above-mentioned rolls to form the above-mentioned irregularly shaped compound lump has a top side. It can be seen that even if it is supported and lowered, it does not break and has sufficient strength for handling.

  A sheet-like compound that is cold-rolled with an open roll is a sheet that can handle sufficient handling, does not require pre-forming for hot-pressing in the final molding, and has a final sheet shape with excellent density distribution. Manufacture is possible.

  FIG. 2 shows an example of the result of determining the relationship between the void ratio of these sheet-like compounds and the work of fracture. The rupture work on the vertical axis was determined as the product of the maximum rupture elongation and the maximum rupture strength in the tensile test. The tensile strength (maximum breaking strength) was measured using STROGRAPH-VE5D manufactured by Toyo Seiki Seisakusho. The porosity was calculated | required by calculation from the specific gravity measured using Alpha Mirage EW-200SG.

  As is apparent from FIG. 2, the void ratio of these sheet-like compounds is as high as 8% to 25%, which is considered to contribute to flexibility. As a result of various studies, it has been found that it is difficult to produce a sheet-like compound having a porosity of less than 3%, and if the porosity of the sheet-like compound is more than 30%, handling properties are lowered, which is not preferable. The porosity of the sheet compound is more preferably 5% or more.

  In FIG. 3, the SEM photograph (100 times) of the fracture surface of a sheet-like compound (sample D) is shown.

  As can be seen from FIG. 3, the rugged granular Ti-containing nanocomposite magnet powder and voids are uniformly dispersed. Since it has such a structure, it is considered that sufficient strength can be obtained even if a thermoplastic elastomer having a Shore hardness of 1 or less at room temperature is used as a binder resin.

[Production and evaluation of sheet-like bonded magnet]
In producing the sheet-like bonded magnet, the sheet-like compound D produced above was used.

  FIG. 4 is a schematic diagram for explaining a process for forming a sheet-like bonded magnet from a sheet-like compound.

  A sheet-like bonded magnet is obtained by placing and pressing the sheet-like compound 4 between the board surfaces 1 and 2 of the hot press. The thickness of the sheet-like bonded magnet is defined by the spacer 3. In addition, in order to give a mold release effect, the board surfaces 1 and 2 may be subjected to fluorine resin processing.

  The hot-pressing process used SF-37 type | mold heating press made from Shin-Watan Metal. The spacer 3 is a spacer having an inner size of 120 mm × 120 mm × thickness of 1 mm, and its volume is 14.4 cubic centimeters. Since the finished specific gravity after the press was predicted to be about 4.9, the sample D sheet-like compound was cut into 70.6 g, which is the expected mass of the sheet-like bonded magnet after molding, and the structure shown in FIG. After pre-compression at 180 ° C., 0.3 MPa, 2 minutes using a SF-37 type heat press made of Shin rattan metal, 180 ° C., 10 MPa, heat compression for 2 minutes, forced cooling to 30 ° C., thickness A sheet-like bonded magnet having a thickness of 1.04 mm and a specific gravity of 4.94 was produced.

  When the tensile strength of the obtained sheet-like bonded magnet was evaluated using STROGRAPH-VE5D manufactured by Toyo Seiki Seisakusho, the maximum breaking strength was 400 gf, which was superior to the sheet-like compound.

  As for the flexibility, no cracks or breaks were caused even when it was wound into a cylindrical shape having a diameter of 5 mm. Moreover, there was no dropping of the magnetic powder that would be a practical problem, and a sufficiently practical sheet-like bonded magnet could be obtained.

[Production and evaluation of sheet-like bonded magnet with protective layer (with film)]
Furthermore, for the purpose of improving flexibility, improving tensile strength, and surface modification, a resin thin film layer is provided on both the front and back sides of the elastomeric magnetic material, so that a thermoplastic resin is formed on both sides of the sheet-like compound during compression molding by a hot press. A film was placed and melted by heat compression. The method is described below.

  FIG. 5 is a schematic diagram for explaining a process of forming a sheet-like bonded magnet having a protective layer. In the configuration of FIG. 4, the protective layers forming films 5 and 6 are arranged between the board surfaces 1 and 2 of the hot-press press and the sheet-like compound, and the film is pressed using the spacer 3 having a thickness of 1 mm. As the films 5 and 6 serving as protective layers, a film made of polypropylene, polyethylene, and thermoplastic urethane each having a thickness of 40 μm, and a polyester (PET) film having a thickness of 9 μm were used.

  After performing a pre-compression of 180 ° C., 0.3 MPa, and 2 minutes using a SF-37 type heating press manufactured by Shintan Metal Co., Ltd. 180 degreeC, 10 MPa, heat-compressed for 2 minutes, forcedly cooled to 30 degreeC, and produced the sheet-like bonded magnet provided with the protective layer made from polypropylene, polyethylene, thermoplastic urethane, and polyester. Four test pieces having a width of 10 mm and a length of 40 mm were cut out from each sheet-like bonded magnet.

  Table 3 below shows the measured values of the respective sheet-like bonded magnets. Specific gravity was measured using EW-200SG manufactured by Alpha Mirage Co., Ltd., and rupture strength was measured using STROGRRAPH-VE5D manufactured by Toyo Seiki Seisakusho. Each sample is four.

  Next, in order to determine the mass that would break due to its own weight for these samples, the relationship between the mass and the maximum breaking strength in the sheets of each protective layer was as follows. It was much better. Even when compared with Table 2, the maximum breaking strength is far superior, and it can be seen that the sheet-like bonded magnet provided with each protective layer has sufficient practicality.

  Next, Table 4 shows the results of evaluating the adhesion between the sheet-like bonded magnet and the aluminum plate. As the sheet-like bond magnet, a bond magnet (blank in Table 4) formed only from the sheet-like compound and a sheet-like bond magnet provided with a protective layer made of thermoplastic urethane were used. As the adhesive, four types of epoxy, cyanoacrylate, urethane and silicon were used. In the case of a cyanoacrylate adhesive, primer treatment was performed. The test piece had a width of 10 mm, a length of 40 mm, and a thickness of about 1 mm, and an adhesive was applied to a portion of 20 mm in the length direction, and was immediately attached to the aluminum plate surface. Thereafter, after 24 hours, a peel test was performed, and the destruction state was visually observed. For the peeling test, STROGRRAPH-VE5D manufactured by Toyo Seiki Seisakusho was used, the crosshead speed was 50 mm / min, and the load range was 20N. The numerical values in parentheses in Table 4 indicate the peel strength (unit: N).

  X indicates that the interface failure between the protective layer or the bonded magnet layer and the adhesive layer has mainly occurred, ◎ indicates that the protective layer or the bonded magnet layer has mainly caused cohesive failure, and △ indicates the intermediate layer. It was.

  Thus, the sheet-like bonded magnet of this example has excellent adhesiveness with respect to epoxy adhesives, cyanoacrylate adhesives, and the like.

[Evaluation of bonded magnet]
The magnetic properties of the sheet-like bonded magnet produced above were measured with a BH tracer manufactured by Metron Giken Co. As a result, the magnetic properties shown in Table 5 below were obtained.

  Thus, the sheet-like bonded magnet of the present example has excellent magnetic properties equivalent to or higher than those of conventional bonded magnets.

  According to the present invention, a sheet-like bonded magnet including a thermoplastic elastomer as a resin binder can be provided at a low cost. Moreover, since the compound for bond magnets can be provided in a sheet form, the production efficiency of various shapes of bond magnets can be improved.

2 is a photograph of a sheet-like compound according to the present invention. It is a graph which shows the relationship between the porosity of the sheet-like compound of the Example by this invention, and a fracture work. It is a SEM photograph of the fracture surface of a sheet-like compound (sample D) by the present invention. It is a schematic diagram for demonstrating the process for forming a sheet-like bonded magnet from a sheet-like compound. It is a schematic diagram for demonstrating the process of forming the sheet-like bonded magnet which has a protective layer.

Explanation of symbols

1, 2 Surface of hot press 3 Spacer 4 Sheet compound 5, 6 film (protective layer)

Claims (22)

A compound for a bond magnet comprising a rare earth alloy powder and a thermoplastic elastomer,
The content of the rare earth alloy powder in the compound is 80% by mass or more, the porosity of the compound is 5% or more and less than 30%, and the Shore A hardness of the thermoplastic elastomer at room temperature is 10 or less , A sheet-like compound having flexibility at room temperature . 2. The compound according to claim 1, wherein the rare earth alloy powder has an average particle size of 20 μm or more and 150 μm or less, and a ratio of a minor axis direction size to a major axis size of the powder particles is 0.5 or more and 1.0 or less. 3. The compound according to claim 1, wherein the rare earth alloy powder includes a nanocomposite magnet powder having at least one hard magnetic phase and at least one soft magnetic phase in the same metal structure. The nanocomposite magnet powder has a composition formula T _100-xyz Q _x R _y M _z (T is Fe or one or more elements selected from the group consisting of Co and Ni and a transition metal element containing Fe, Q Is at least one element selected from the group consisting of B and C, R is one or more rare earth elements substantially free of La and Ce, M is Ti, Al, Si, V, Cr, Mn, One or more metal elements selected from the group consisting of Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb)
The composition ratios x, y, z and m are respectively
10 <x ≦ 25 atomic%,
1 ≦ y <10 atomic%,
0.5 ≦ z ≦ 10 atomic%,
The compound of Claim 3 containing the nanocomposite powder which has the composition which satisfies these. The said thermoplastic elastomer is a compound in any one of Claim 1 to 4 containing 1 type selected from the group which consists of styrene type, olefin type, ester type, urethane type, and these alloys. 6. A compound according to claim 5 wherein the thermoplastic elastomer comprises polystyrene-poly (ethylene / propylene) block-polystyrene (SEPS). The compound according to any one of claims 1 to 6 , which has a thickness of 0.5 mm or more and 5 mm or less. The compound according to claim 7 , wherein the compound has a width of 10 mm or more and a length of 100 mm or more. Bonded magnet comprising a bonded magnet layer formed from a compound according to any one of claims 1 to 8. The bonded magnet according to claim 9 , further comprising a protective layer provided on the bonded magnet layer. The bonded magnet according to claim 10 , wherein the protective layer is made of a thermoplastic resin. The bonded magnet according to claim 11 , wherein the maximum magnetic energy product is 40 kJ / m ³ or more. Bonded magnet according to claims 9 to 12 in the form of a sheet. Electronic component comprising a bonded magnet according to any of claims 9 13. (A) preparing a rare earth alloy powder and a thermoplastic elastomer having a Shore A hardness of 10 or less at room temperature ;
(B) The step of kneading the thermoplastic elastomer and the rare earth alloy powder with the open roll heated to produce a magnet compound containing 80% by mass or more of the rare earth alloy powder;
(C) a step of processing the compound into a sheet by passing an open roll near room temperature; and
A method for producing a sheet-like compound having flexibility at room temperature . The manufacturing method of the compound of Claim 15 whose porosity of the sheet-like compound obtained by the said process (c) is 5 % or more and less than 30% . The rare earth alloy powder according to claim 15 or 16 , wherein an average particle diameter is 20 µm or more and 150 µm or less, and a ratio of a minor axis direction size to a major axis size of the powder particles is 0.5 or more and 1.0 or less. Compound manufacturing method. The rare earth alloy powder includes a nanocomposite magnet powder having at least one hard magnetic phase with at least one soft magnetic phase in the same metal in tissue production method of the compound according to any one of claims 15 17 . The method for producing a compound according to any one of claims 15 to 18 , wherein the thermoplastic elastomer includes one selected from the group consisting of styrene, olefin, ester, urethane, and alloys thereof. 20. The method for producing a compound according to claim 19 , wherein the thermoplastic elastomer comprises polystyrene-poly (ethylene / propylene) block-polystyrene (SEPS). Method for producing a bonded magnet comprising the step of heating and compressing the sheet over bets like compound according to any one of claims 1 to 8. Laminating a thermoplastic resin film on one side or both sides of the sheet over bets like compound according to any one of claims 1 to 8,
A method of manufacturing a bonded magnet including a step of heating and compressing the laminate.