JP2014236195A - Method of producing magnetic particles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing rare-earth-iron-nitrogen-based magnetic particles having a high coercive force and an excellent squareness ratio efficiently.SOLUTION: A method of producing magnetic particles represented by RFeNM(in the formula, R represents at least one kind of rear-earth elements including Y, M represents a metal element, and 3≤v≤30, 5≤w≤15, 0<x≤2.5) includes a step for obtaining a precipitate containing R ions and Fe ions from a solution containing R ions and Fe ions, a step for obtaining oxide particles containing R element and Fe element from the precipitate, and a step for obtaining a mixture by mixing oxide particles and a solution or a sol containing a metal element M and a medium.

Description

  The present invention relates to a method for producing magnetic particles.

  Anisotropic rare earth-iron-nitrogen based magnetic powder has excellent magnetic properties and has attracted attention as a magnetic powder for rare earth bonded magnets replacing NdFeB based magnetic powder. For example, a bonded magnet of a desired shape can be easily obtained by melting and solidifying a compound (magnetic material) obtained by mixing rare earth-iron-nitrogen based magnetic powder and thermoplastic resin with an injection molding machine. Can be formed. In this way, injection molded products using rare earth-iron-nitrogen based magnetic materials are rich in shape freedom and can be integrally molded with other members. ing.

  Along with the expansion of the field of application of bond magnets, bond magnets that can be used even in harsh environments have been demanded, and the use of high heat and water resistant resins as thermoplastic resins has been demanded. In particular, the use of polyphenylene sulfide resin (PPS) is indispensable for automotive applications. In a bonded magnet using a high heat resistance and high water resistance resin such as PPS, it is indispensable to treat at a high temperature at the time of molding. However, in general, rare earth-iron-nitrogen based magnetic materials are known to be deteriorated in magnetic properties, in particular, coercive force, when the surface is oxidized when heated to 280 ° C. or higher, which is the melting point of PPS. Yes. In order to solve this, in consideration of demagnetization when molded at 280 ° C. or higher, a rare earth-iron-nitrogen based magnetic material with high coercive force, high heat resistance (coercive force of molded product of 15 kOe or more) — There is a need for an iron-nitrogen based magnetic material or a rare earth-iron-nitrogen based magnetic material having both characteristics.

In relation to the above, a method of improving the characteristics of a magnetic material by including a metal component M in a rare earth-iron-nitrogen based magnetic material has been proposed (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses that the coercive force of the nitride magnetic material is prevented from decreasing by allowing the metal component M to coexist in the main phase of the rare earth-iron-nitrogen based magnetic material. Patent Document 1 mentions a high-frequency melting method, an arc melting method, a rapid quenching method, a gas atomizing method, a reduction diffusion (R / D) method, a mechanical alloying method, and an HDDR method as methods for adding the metal component M.
Patent Document 2 includes Zr and Ti as the metal component M to be added. From a solution in which at least one compound of lanthanoid elements including Y, an iron compound, and a Zr compound or a Ti compound is dissolved. A method for producing a rare earth-iron-nitrogen based magnetic powder is disclosed in which an insoluble salt is produced, calcined, and then subjected to a reduction diffusion reaction.

JP 06-1112019 A JP 2008-91873 A

The intrinsic coercive force of the magnetic powder compact specifically disclosed in Patent Document 1 is about 5.6 kOe, and it was difficult to say that it was sufficiently large. Moreover, in the manufacturing method disclosed in Patent Document 1, in order to include the metal component M in the main phase of the rare earth-iron-nitrogen based magnetic material, a large-scale facility is required and coarse pulverization is performed before nitriding. It was necessary, and the pulverization treatment caused a decrease in coercive force, and the heat resistance was sometimes affected.
Although the magnetic powder disclosed in Patent Document 2 has a high coercive force, a magnetic material having a higher coercive force and a better squareness ratio is required.
An object of the present invention is to provide a method for producing magnetic particles capable of efficiently producing rare earth-iron-nitrogen based magnetic particles having a high coercive force and an excellent squareness ratio.

  As a result of diligent research to solve the above problems, by adding the metal element M by a specific addition method, a high coercive force (for example, 15 kOe or more, preferably 17 kOe or more) and an excellent squareness ratio (for example, 0. The inventors have found that rare earth-iron-nitrogen based magnetic particles having a balance of 250 or more, preferably 0.290 or more can be efficiently produced, and the present invention has been completed. That is, specific means for solving the above problems are as follows.

Method of manufacturing a magnetic particle of the present _invention, in _{R v Fe (100-v-} w-x) N w M x ( wherein, R represents at least one rare earth element including Y, M represents a metal element 3 ≦ v ≦ 30, 5 ≦ w ≦ 15, 0 <x ≦ 2.5), and R ions and Fe ions are extracted from a solution containing R ions and Fe ions. A step of obtaining a precipitate containing, a step of obtaining oxide particles containing R element and Fe element from the precipitate, and a step of mixing a solution or sol containing oxide particles and metal element M and a medium to obtain a mixture; A method for producing magnetic particles containing By adding the metal element M in a solution or sol state, rare earth-iron-nitrogen based magnetic particles having both a high coercive force (for example, 15 kOe or more) and an excellent squareness ratio (for example, 0.250 or more) are obtained. It can be manufactured efficiently.

  The concentration of the metal element M in the solution or sol containing the metal element M and the medium is preferably 5 to 40% by mass. As a result, the amount of liquid to be added can be reduced, the drying step performed as necessary, or the drying time can be shortened, and magnetic particles can be produced more efficiently.

  The metal element M is preferably a metal element having a higher melting point than Fe, and more preferably at least one metal element selected from the group consisting of W, Cr, Mo, Zr, and Nb. When the metal element M is in such an embodiment, the particle growth during the formation of the magnetic material is more effectively suppressed, and it is possible to produce magnetic particles having better characteristics.

  The method for producing magnetic particles preferably further includes a step of reducing the obtained mixture, and the step of reducing the mixture more preferably includes a step of reducing and diffusing an oxide containing R element. By reducing the obtained mixture, magnetic particles having more excellent characteristics can be produced.

The composite material of the present invention is a composite material containing magnetic particles obtained by the above-described method for producing magnetic particles and a resin. By including the magnetic particles, the magnetic properties are excellent.
The bonded magnet of the present invention is a composite material containing magnetic particles obtained by the above-described method for producing magnetic particles and a resin. By including the magnetic particles, the magnetic properties are excellent.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the magnetic particle which can manufacture the rare earth-iron-nitrogen type magnetic particle with a high coercive force and the outstanding square ratio efficiently can be provided.

  Hereinafter, although an embodiment concerning the present invention is explained in full detail, it is an example for embodying the technical idea of the present invention, and the present invention is not limited to the following embodiment and an example. Note that in this specification, the term “process” is not limited to an independent process, and even if it cannot be clearly distinguished from other processes, the term “process” is used if the intended purpose of the process is achieved. included. Moreover, the numerical range shown using "to" shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively. Further, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition.

<Method for producing magnetic particles>
Method of manufacturing a magnetic particle of the present _invention, in _{R v Fe (100-v-} w-x) N w M x ( wherein, R represents at least one rare earth element including Y, M represents a metal element 3 ≦ v ≦ 30, 5 ≦ w ≦ 15, 0 <x ≦ 2.5), and R ions and Fe ions are extracted from a solution containing R ions and Fe ions. A step of obtaining a precipitate containing (hereinafter also referred to as “first step”), a step of obtaining oxide particles containing R element and Fe element from the precipitate (hereinafter also referred to as “second step”), A method of producing magnetic particles comprising a step of mixing oxide particles and a solution or sol containing a metal element M and a medium to obtain a mixture (hereinafter also referred to as “third step”).

By mixing a solution or sol containing the metal element M and the medium with the oxide particles containing the R element and the Fe element, the metal can be obtained in a shorter time than when the powder containing the metal element M is mixed with the oxide particles. A mixture in which the element M is more uniformly dispersed can be obtained, and magnetic particles can be efficiently produced. By preparing magnetic particles from the mixture thus obtained, magnetic particles having high coercive force and excellent squareness ratio can be efficiently obtained. Further, the obtained magnetic particles are excellent in heat resistance. This is because, for example, a liquid material such as a solution or sol containing the metal element M has a self-diffusion property, and therefore, in a shorter time than a powder (solid) that needs to be dispersed only by an external force. It can be considered that the metal element M can be uniformly dispersed.
In addition, by using a solution or sol containing the metal element M, magnetic particles having superior productivity and superior characteristics can be produced compared to the case of using a powder (particularly nanopowder) containing the metal element M. Can do. That is, for example, the time required for the production of magnetic particles can be shortened, and the production cost, particularly the raw material cost can be reduced.

(Magnetic particles)
The magnetic particles have a composition represented by the following formula (I).
_{R v Fe (100-v-} w-x) N w M x (I)
In the formula, R represents at least one rare earth element including Y, and M represents a metal element. v, w, and x satisfy 3 ≦ v ≦ 30, 5 ≦ w ≦ 15, and 0 <x ≦ 2.5, respectively.

R in the formula (I) is not particularly limited as long as it is at least one of rare earth elements including Y. Among them, R is preferably at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. More preferably, it is at least one selected from the group consisting of Sm, Eu, Tb and Dy.
R in formula (I) may be a single type or a combination of two or more types.

M in the formula (I) represents a metal element. The metal element represented by M is preferably a metal element having a melting point higher than that of Fe (iron, melting point 1538 ° C.) from the viewpoint of further improving magnetic properties by suppressing particle growth in the produced magnetic particles. More preferably, it is a metal element having a melting point of 1600 ° C. or higher, and further preferably a metal element having a melting point of 2000 to 3500 ° C. Specific examples of the metal element M include W (tungsten, melting point 3422 ° C.), Cr (chromium, melting point 1907 ° C.), Mo (molybdenum, melting point 2623 ° C.), Zr (zirconium, melting point 1855 ° C.) and Nb (niobium, melting point). At least one selected from the group consisting of 2477 ° C.), and more preferably at least one selected from the group consisting of W, Mo and Nb.
The metal element M in the formula (I) may be a single type or a combination of two or more types.

  It is also preferable that the metal element M has a compound (preferably its oxide, chloride, ammonium salt, etc.) soluble in water, acid or alkali. Here, the term “dissolvable” means that the solubility at 25 ° C. is 0.1 g or more with respect to 100 g of the solvent.

v, w, and x are not particularly limited as long as 3 ≦ v ≦ 30, 5 ≦ w ≦ 15, and 0 <x ≦ 2.5, respectively. Among them, from the viewpoint of magnetic properties, the mol% [{x / (100−w−x)} × 100] of the metal element M with respect to the total amount of the rare earth elements R and Fe is 0.00 <{x / (100−w −x)} × 100 ≦ 1.00 is preferably satisfied, and 0.05 ≦ {x / (100−w−x)} × 100 ≦ 0.50 is more preferable.
Furthermore, when manufacturing magnetic particles using a sol containing the metal element M, it is preferable to satisfy 0.05 ≦ {x / (100−w−x)} × 100 ≦ 0.40.

(First step)
The method for producing magnetic particles includes a first step of obtaining a precipitate containing R ions and Fe ions from a solution containing R ions and Fe ions. In the first step, a precipitate containing a metal component constituting the main phase of the magnetic particles is precipitated from a solution containing R ions and Fe ions. Specifically, for example, R (preferably Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc.) and Fe are ionized. A precipitate containing R ions and Fe ions (R) is added to the reaction tank solution containing the metal ions by adding a precipitant capable of coprecipitation of these metal ions to reduce the solubility of the metal ions. -Fe precipitate).

In the production method of the present invention, the rare earth elements R and Fe constituting the main phase of the magnetic particles are uniformly dissolved and mixed in the solvent as R ions and Fe ions, respectively. Therefore, it is necessary to prepare a solution in which the rare earth elements R and Fe, which are metal components constituting the main phase of these magnetic particles, are dissolved. For example, an acid aqueous solution can be used as a solvent that can ionize and dissolve these metal components alone or in common. Preferred acids include mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid, and the above-described metal ions can be dissolved at a high concentration. Another method for preparing a metal ion solution may be to dissolve chlorides, sulfates, nitrates, and the like of these metal components in water.
The solution containing R ions and Fe ions is not limited to an aqueous solution, but an organic metal compound in the form of a metal alkoxide or the like, an organic solvent, for example, an alcohol such as methanol or ethanol, a ketone such as acetone, a hydrocarbon such as cyclohexane, It may be a solution dissolved in ether such as tetrahydrofuran.

  The content ratio of R ions and Fe ions in the solution containing R ions and Fe ions is preferably set according to the content ratio in the main phase of the magnetic particles. The content ratio of R ions and Fe ions (R ions: Fe ions) is preferably a molar ratio of 1.5: 17 to 3.0: 17, and 2.0: 17 to 2.5: 17. It is more preferable.

As a substance that generates a precipitate as a salt insoluble with these metal ions from a solution in which the above metal ions are dissolved, anions (nonmetal ions) such as hydroxide ions, carbonate ions, and oxalate ions are preferably used. can do. That is, any material solution capable of supplying these anions can be suitably used for the first step. For example, ammonia, caustic soda, and the like can be given as substances that supply hydroxide ions. Examples of the substance that supplies carbonate ions include ammonium bicarbonate and sodium bicarbonate. Oxalic acid is mentioned as what supplies an oxalate ion.
In the case of a solution in which a metal alkoxide is dissolved in an organic solvent, for example, by adding water, a precipitate can be deposited in the form of a metal hydroxide. In addition to water, any substance that reacts with metal ions to form an insoluble salt is applicable to the present invention. Moreover, as a method for producing an insoluble salt of hydroxide as a precipitate, a so-called sol-gel method can be preferably used.

In the first step, by controlling the precipitation reaction between metal ions and non-metal ions, the distribution of the constituent components in the precipitate particles constituting the precipitate is uniform, the particle size of the particle shape is sharp. An ordered alloy particle raw material can be obtained. The use of such alloy particle raw materials further improves the magnetic properties of the magnetic particles that are the final product. This precipitation reaction can be controlled by appropriately setting reaction conditions such as the supply rate of metal ions and non-metal ions, the reaction temperature, the concentration of the reaction solution, the stirring state of the reaction solution, and the pH during the reaction. For setting these conditions, for example, first, various reaction conditions are selected to optimize the yield of the precipitate, the independence of the precipitate particles (particle shape), and the particle size distribution of the precipitate particles are sharp. Each condition may be determined while confirming that there is a microscopic observation. Needless to say, the form of the precipitate varies greatly depending on what kind of chemical species is selected as a raw material and what kind of precipitation reaction is applied. By this precipitation reaction (first step), the particle diameter, particle shape, particle size distribution and the like of the magnetic particles as the final magnetic material are approximately determined. As described above, the control of the precipitation reaction is very important in that the properties of the alloy particle raw material are closely reflected in the magnetic material.
The particle size of the precipitate particles obtained in the first step is preferably 0.05 μm to 20 μm, more preferably a size and distribution such that almost all particles are in the range of 0.1 μm to 10 μm. Moreover, it is preferable that an average particle diameter exists in the range of 0.1 micrometer-10 micrometers. In the precipitate particles thus obtained, the rare earth element R and Fe are present in a sufficiently mixed state.
The particle size distribution of the precipitate particles obtained in the first step is measured using a laser diffraction wet particle size distribution meter, and the average particle size corresponds to 50% cumulative volume from the small particle size side in the particle size distribution. Measured as the particle size.

  The first step is preferably a step in which a precipitate is obtained by mixing an acid aqueous solution containing R ions and Fe ions and an aqueous solution containing hydroxide ions from the viewpoint of the magnetic properties of the obtained magnetic particles. And a step of obtaining a precipitate by mixing an acid aqueous solution containing at least one selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid, and an aqueous solution containing hydroxide ions, containing R ions and Fe ions. More preferred.

  Specifically, as the first step, a method of adding a solution containing nonmetallic ions to a solution containing R ions and Fe ions, and a method of adding a solution containing R ions and Fe ions to a solution containing nonmetallic ions And a method of adding a solution containing R ions and Fe ions and a solution containing non-metal ions to a solvent (preferably water). Among them, the first step is a method in which a solution containing R ions and Fe ions and a solution containing non-metal ions are dropped into a solvent (preferably water) from the viewpoint that the properties of the precipitate particles can be easily adjusted. It is preferable.

The reaction temperature in the precipitation reaction can be appropriately selected according to the material used. The reaction temperature in the precipitation reaction can be, for example, 30 to 50 ° C., and preferably 35 to 45 ° C.
The concentration of the reaction solution in the precipitation reaction can be appropriately selected according to the material used. For example, the concentration of the reaction solution in the precipitation reaction is preferably 0.65 mol / l to 0.85 mol / l, more preferably 0.7 mol / l to 0.85 mol / l, as the total concentration of metal ions.
The pH in the precipitation reaction can be appropriately selected according to the material used. For example, the pH in the precipitation reaction is preferably 5 to 9, and more preferably 6.5 to 8.

  The first step may further include other steps such as a step of separating and washing the resulting precipitate particles. Examples of the step of separating and washing the precipitate particles include a method of adding a solvent (preferably water) to the obtained precipitate particles and mixing them, and then removing at least a part of the solvent. The method for removing the solvent can be appropriately selected from commonly used methods such as filtration and decantation.

(Second step)
The method for producing magnetic particles includes a second step of obtaining oxide particles containing R element and Fe element (hereinafter also simply referred to as “oxide particles”) from the precipitate obtained in the first step. The second step is not particularly limited as long as the precipitate obtained in the first step can be converted into oxide particles, and conversion conditions and the like can be appropriately selected according to the properties of the precipitate.
For example, the oxide particles can be obtained by heat-treating the precipitate particles constituting the precipitate obtained from the precipitation reaction. When the precipitate particles are converted into oxide particles by heat treatment, the precipitate is preferably desolvated before the heat treatment. By removing the solvent before the heat treatment, conversion to oxide particles by the heat treatment tends to be easier. Further, when the precipitate particles have a high solubility in a solvent at a high temperature, it is particularly preferable to remove the solvent sufficiently. By sufficiently removing the solvent, it is possible to effectively prevent the particles from re-dissolving in the remaining solvent and agglomerating the particles or changing the particle size distribution, particle size, etc. .

  The method for removing the solvent is not particularly limited and can be appropriately selected according to the solvent to be used. Specific examples of the method for removing the solvent include a method of drying in an oven at 70 to 200 ° C. for 5 to 12 hours when water is used as the solvent.

It is considered that the conversion of the precipitate particles into the oxide particles by the heat treatment is due to the decomposition of the nonmetal ions as a result of heating the insoluble salt composed of metal ions and nonmetal ions. Therefore, the heat treatment is preferably performed in the presence of oxygen, and can be performed, for example, in an air atmosphere. For the same reason, it is preferable that the nonmetallic ion constituting the precipitate particle contains an oxygen atom as a constituent element. Examples of non-metal ions containing oxygen atoms include inorganic ions such as hydroxide ions, carbonate ions and oxalate ions, and organic acid ions such as citrate ions. Compounds that can supply non-metallic ions include compounds that supply hydroxide ions such as ammonia and caustic soda, compounds that supply carbonate ions such as ammonium bicarbonate and sodium bicarbonate, and compounds that supply oxalate ions such as oxalic acid. And so on.
However, in the case where an insoluble organic acid salt forms a hydroxide by hydrolysis like an alkoxide, it is preferable to convert it into oxide particles after heat-treating it once.

  The temperature and time of the heat treatment are not particularly limited as long as the precipitate particles can be converted into oxide particles, and can be appropriately selected according to the types of metal ions and nonmetal ions constituting the precipitate particles. For example, it can be set to several hours at a temperature of 800 to 1300 ° C., and preferably set to several hours (for example, 1 to 3 hours) at a temperature of 900 to 1100 ° C. The heat treatment apparatus is not particularly limited, and can be appropriately selected from commonly used heat treatment apparatuses. For example, when a heating furnace is used for the heat treatment, it is preferable that the atmosphere in the heating furnace is sufficiently supplied with air using a blower or the like, or oxygen is introduced into the furnace to perform the heat treatment.

  The oxide particles obtained as described above are oxide particles in which the rare earth elements R and Fe are sufficiently mixed microscopically in the particles, and the shape and particle size distribution of the precipitate particles are reflected. is there.

(Third process)
The method for producing magnetic particles includes a third step of mixing the oxide particles obtained in the second step with a solution or sol containing the metal element M and the medium to obtain a mixture. By mixing the oxide particles with a liquid material that is a solution or sol containing the metal element M and the medium, the metal element M can be easily and uniformly distributed on the surface of the oxide particles in a short time. By uniformly distributing the metal element M on the surface of the oxide particles, the magnetic properties of the finally obtained magnetic particles, particularly Hk, are improved, and magnetic particles having an excellent squareness ratio can be obtained.
On the other hand, when the metal element M is mixed with the oxide particles using a powder containing the metal element M instead of a liquid material containing the metal element M, it takes a long time to uniformly mix the metal component M. It is difficult to sufficiently improve the magnetic properties of the finally obtained magnetic particles.

The solution containing the metal element M and the medium can be prepared by dissolving the metal element M alone or a compound thereof in the medium. The compound of the metal element M is not particularly limited as long as it can be dissolved in the medium, and can be appropriately selected from commonly used compounds. Examples of the compound of the metal element M include oxides, chlorides, carbides, ammonium salts, and the like, and at least one selected from the group consisting of oxides and ammonium salts is preferable.
Examples of the medium constituting the solution include water, alcohol, acetone and the like, and it is preferable to use water. When water is used as the medium, the compound of the metal element M may be dissolved using an acid or an alkali.
The solution containing the metal element M is preferably a compound containing the metal element M dissolved in water using an acid or alkali, and an oxide containing the metal element M dissolved in water using an alkali. More preferably.

The sol containing the metal element M and the medium can be prepared by dispersing a simple substance of the metal element M or a compound thereof in the medium. The compound of the metal element M is not particularly limited as long as it can be dispersed in the medium, and can be appropriately selected from commonly used compounds. Examples of the compound of the metal element M include oxides, chlorides, carbides, ammonium salts, and the like, and at least one selected from the group consisting of oxides and ammonium salts is preferable.
Examples of the medium constituting the sol include water, alcohol, acetone and the like, and it is preferable to use water.

The particle size distribution in the sol containing the metal element M and the medium is not particularly limited as long as the sol is formed. The average particle size of the sol is preferably 0.05 μm to 1.00 μm, and more preferably 0.1 μm to 0.7 μm. The average particle size of the sol is measured as a particle size corresponding to 50% volume accumulation from the small particle size side by measuring the particle size distribution using a laser diffraction wet particle size distribution meter.
The sol containing the metal element M and the medium can be prepared, for example, by pulverizing a simple substance of the metal element M or a compound thereof in the medium using a colloid mill. Moreover, you may use it selecting from a commercial sol suitably.

The concentration of the metal element M in the solution or sol containing the metal element M and the medium is preferably 1% by mass to 40% by mass from the viewpoint of dispersibility with the oxide particles, and 5% by mass to 35% by mass. More preferably.
When using a solution, the concentration of the metal element M is preferably 5% by mass to 25% by mass and more preferably 10% by mass to 20% by mass from the viewpoint of dispersibility with the oxide particles. .
When using a sol, the concentration of the metal element M is preferably 15% by mass to 30% by mass and more preferably 20% by mass to 30% by mass from the viewpoint of dispersibility with the oxide particles. .

The mixing method in the third step is not particularly limited as long as the oxide particles, the metal element M, and the solution or sol containing the medium can be mixed, and can be appropriately selected from commonly used mixing methods. The mixing method in the third step preferably includes a dispersion treatment that imparts a strong shearing force from the viewpoint of magnetic properties. The dispersion apparatus used for the dispersion treatment is not particularly limited as long as a strong shearing force can be applied to the mixture of the oxide particles, the metal element M, and the solution or sol containing the medium. Specific examples of the dispersing device include a ball mill, a bead mill, and a roll mill.
The processing time of the distributed processing can be appropriately selected according to the dispersing device, the manufacturing scale, and the like. For example, it can be 1 hour to 12 hours, and is preferably 2 hours to 10 hours. By using a solution or sol containing the metal element M and the medium in the third step, the dispersion process can be performed in a very short time compared to the case where the metal element M is used as a solid and dispersed to the same degree of dispersion. It can be carried out. The dispersion state of the metal element M can be determined from the magnetic properties of the obtained magnetic particles.
The treatment temperature of the dispersion treatment is not particularly limited, and can be, for example, 20 to 100 ° C, and more preferably 25 to 95 ° C.

In the third step, it is preferable to perform a premixing process prior to the dispersion process. Thereby, a magnetic characteristic can be improved more efficiently. Specific examples of the mixing apparatus used for the preliminary mixing treatment include a V blender, a mixer having a stirring blade, and a shaker. The mixing device used for the premixing treatment is preferably capable of imparting a strong shearing force to the mixture of the oxide particles, the metal element M and the solution or sol containing the medium.
The treatment time for the preliminary mixing treatment can be appropriately selected according to the mixing apparatus, production scale, etc., and is preferably 0.1 hours to 5 hours from the viewpoint of productivity, and preferably 0.1 hours to 1. More preferably, it is 5 hours.
The treatment temperature in the premixing treatment is not particularly limited, and can be, for example, 20 to 100 ° C, and more preferably 25 to 95 ° C.

  Specifically, as the premixing treatment, a method of operating the mixing device after charging the mixing device with the oxide particles, the metal element M and the medium or a sol containing the medium, and charging the mixing device with the oxide particles. Examples thereof include a method of gradually adding a solution or sol containing the metal element M and the medium while operating the apparatus. It is preferable to select the mixing method of the premixing process in consideration of the shearing force of the mixing device.

The mixture obtained in the third step may contain a medium contained in a solution or sol containing the metal element M, but it is preferable that at least a part of the medium is removed. It is more preferable to remove the mass% or more.
The method for removing the medium can be appropriately selected according to the type of the medium. As a method for removing the medium, for example, when the medium is water, a method of heat drying at a temperature of 50 to 250 ° C. for 0.5 hour to 15 hours is preferable, and a temperature of 100 to 200 ° C. for 1 hour to More preferably, the method is a heat drying treatment for 10 hours.

  The mixture obtained above is an oxide particle having the metal element M on the surface, and the oxide particle is a mixture containing particles reflecting the shape, particle size distribution and the like of the above-described precipitate particles. The metal element M is preferably in a state of being uniformly distributed on the surface of the oxide particles. By reducing the mixture, magnetic particles having excellent magnetic properties can be produced.

  On the other hand, as described in Japanese Patent Application Laid-Open No. 06-111201, when a high-frequency melting method, an arc melting method, a rapid cooling method, a gas atomizing method, or the like is used as a method for introducing the metal element M into the main phase, the coercive force In order to prevent the decrease in the temperature, it is necessary to perform annealing, and the introduction method of the metal element M is complicated and it is difficult to say that the method is sufficiently satisfactory for practical use.

(Reduction process)
The method for producing magnetic particles preferably further includes a reduction step of reducing the mixture obtained in the third step to obtain alloy particles. The method of reducing the mixture containing oxide particles to obtain alloy particles can be applied by appropriately selecting from the reduction methods usually used in the method for producing magnetic particles. As the reduction method, for example, the method described in Japanese Patent No. 4590920 can be preferably applied to the present invention. Specifically, the reduction step is preferably a reduction method including a pretreatment step of reducing a part of the oxide particles having the metal element M on the surface and a reduction diffusion step of reducing and diffusing the rare earth oxide.

(Pretreatment process)
The method for producing magnetic particles includes, as a part of the reduction process, a pretreatment process (hydrogen reduction process) in which a part of the metal oxide contained in the mixture obtained in the third process is reduced to obtain a partially reduced product. It is preferable. In the pretreatment step, part of the metal oxide contained in the mixture is heat-treated in a reducing atmosphere with a reducing gas, so that oxygen combined with Fe is converted into water (H ₂ O) and carbon monoxide. It can be gradually removed in the form of (CO) or the like. The reducing gas can be appropriately selected from commonly used reducing gases, and examples thereof include hydrocarbon gases such as hydrogen (H ₂ ), carbon monoxide (CO), and methane (CH ₄ ). In this case, for example, the temperature of the heat treatment is preferably set in the range of 300 to 900 ° C, and more preferably in the range of 400 to 800 ° C. When the temperature of the heat treatment is 300 ° C. or higher, the reduction of the Fe oxide proceeds efficiently. Further, when the temperature is 900 ° C. or lower, oxide particles are prevented from growing and segregating, and a desired particle diameter can be maintained.
Moreover, when using hydrogen as reducing gas, it is preferable to adjust the thickness of the mixture layer provided to a pre-processing process to 20 mm or less, and also to adjust the dew point in a reaction furnace to -10 degrees C or less. Thereby, the aggregation prevention effect by the metal element M can be obtained more effectively.
The pressure of the reducing atmosphere in the pretreatment process is not particularly limited.

(Reduction diffusion process)
The method for producing magnetic particles includes a reduction diffusion step in which the rare earth oxide contained in the oxide particles having the metal element M, which is a mixture obtained in the third step, is reduced and diffused to obtain alloy particles as the reduction step. Furthermore, it is preferable to include. In the reduction-diffusion process, oxide particles having the metal element M on the surface and metal calcium are mixed and heat-treated in an inert gas atmosphere or in vacuum, so that the rare earth oxide contained in the oxide particles is calcium-fused. Reduced and diffused in contact with body or its vapor.

  Metallic calcium is used in the form of particles or powder, but the particle diameter is preferably 10 mm or less. Thereby, aggregation at the time of reductive diffusion reaction can be controlled more effectively. In addition, metallic calcium is a reaction equivalent (a stoichiometric amount necessary for reducing the rare earth oxide, and if Fe is in the form of an oxide, it includes the amount necessary for reducing this). It can be added at a rate of 1.1 to 3.0 times, and preferably added at a rate of 1.5 to 2.0 times.

  In the reduction-diffusion process, a disintegration accelerator can be used as needed together with metallic calcium as a reducing agent. This disintegration accelerator is appropriately used for promoting the disintegration and granulation of the product in the water washing step described later, and examples thereof include calcium chloride disclosed in JP-A-63-105909. Examples thereof include alkaline earth metal salts and alkaline earth oxides such as calcium oxide. These disintegration promoters are used in a proportion of 1 to 30% by mass, preferably 5 to 30% by mass, based on the rare earth oxide used as the rare earth source.

  In the reduction diffusion step, the oxide particles having the metal element M on the surface, metal calcium as a reducing agent, and a disintegration accelerator used as necessary are mixed, and the mixture is an inert atmosphere other than nitrogen, For example, the heat treatment is performed in argon gas. The temperature of the heat treatment in the reduction diffusion treatment is in the range of 700 to 1200 ° C, preferably in the range of 800 to 1100 ° C. Although the heat treatment time of the reduction diffusion treatment is not particularly limited, it can be carried out in a time range of 10 minutes to 10 hours and preferably in a range of 10 minutes to 2 hours from the viewpoint of performing the reduction reaction more uniformly.

(Nitriding process)
The method for producing magnetic particles preferably further includes a nitriding step of nitriding the alloy particles obtained in the reduction step to obtain magnetic particles. Here, the alloy particles are alloy particles having rare earth R—Fe as a main phase obtained by reducing oxide particles. In particular, when the reduction diffusion step is performed as the reduction step, the alloy particles are obtained in a porous mass, so that the nitridation step can be performed by immediately heat-treating in a nitrogen atmosphere without performing the pulverization treatment, thereby making the nitridation uniform. Done.

  On the other hand, in the case of obtaining magnetic particles by nitriding an alloy produced by the method specifically disclosed in JP-A-06-1122019, the nitriding time becomes longer when the crystal grain size of the alloy particles is 500 μm or more. It is necessary to perform a coarse pulverization treatment before the nitriding treatment. When the coarse pulverization process is performed, oxidation of the particle interface, distortion of the alloy particles, and the like are likely to occur, and the coercive force may be lowered.

  The nitriding treatment of the alloy particles is performed by lowering the temperature from the heating temperature range for the reduction to a temperature of 300 to 600 ° C., particularly 400 to 550 ° C., and replacing the atmosphere with a nitrogen atmosphere in this temperature range. The heat treatment time in the nitriding treatment may be set to such an extent that the alloy particles are sufficiently nitrided, for example, about 2 to 30 hours.

(Washing process)
When the reduction diffusion process is performed in the reduction process, the reaction product obtained after the nitriding process includes, in addition to magnetic particles, by-produced CaO, unreacted metallic calcium, etc., and a sintered lump state in which these are combined. It may be. In that case, it is preferable to introduce this reaction product into cooling water and separate CaO and metallic calcium from the magnetic particles as a calcium hydroxide (Ca (OH) ₂ ) suspension. Further, the remaining calcium hydroxide is preferably removed sufficiently by washing the magnetic particles with acetic acid or the like. When the reaction product is put into water, the composite sintered mass reaction product collapses, that is, pulverizes, due to the oxidation of metallic calcium with water and the hydration reaction of by-product CaO.
After the water washing step, through a drying step, substantially spherical magnetic particles having an average particle size of 0.5 μm to 10 μm can be obtained.

<Composite material>
The composite material of the present invention includes magnetic particles obtained by the above-described method for producing magnetic particles and a resin. The composite material may further contain other components as required. By including the magnetic particles, a composite material having a high coercive force can be formed.

Details of the magnetic particles in the composite material are as described above.
In addition, the resin contained in the composite material is not particularly limited, and can be appropriately selected from resins usually used according to the purpose and the like. The resin may be a thermosetting resin or a thermoplastic resin, and is preferably a thermoplastic resin. Specific examples of the thermoplastic resin include polyphenylene sulfide resin (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyamide (PA), polypropylene (PP), and polyethylene (PE). it can.

  The mixing ratio of the magnetic particles and the resin in the composite material can be appropriately selected according to the purpose and the like. The mixing ratio of resin to magnetic particles (resin / magnetic particles) is preferably 0.10 to 0.15, and more preferably 0.11 to 0.14.

  The method for producing the composite material is not particularly limited as long as the magnetic particles and the resin can be mixed, and can be applied by appropriately selecting from commonly used mixing methods. Specifically, the method of mixing at 280-330 degreeC using a kneader can be mentioned, for example.

<Bond magnet>
The bonded magnet of the present invention includes magnetic particles obtained by the above-described method for producing magnetic particles and a resin. The bonded magnet may further contain other components as necessary. By including the magnetic particles, a bonded magnet having a high coercive force can be configured.

  The bonded magnet can be manufactured using, for example, the composite material. Specifically, for example, the composite material can be manufactured by a manufacturing method including an alignment process in which easy magnetic domains are aligned with an alignment magnetic field while heating the composite material, and a magnetization process in which pulse magnetization is performed with a magnetic field.

The heating temperature in the alignment step can be appropriately selected according to the resin. The heating temperature is preferably 90 to 200 ° C, for example, and more preferably 100 to 150 ° C. The magnitude of the alignment magnetic field in the alignment step can be set to 720 kA / m, for example.
Moreover, the magnitude | size of the magnetizing magnetic field in a magnetizing process can be 1500-2500 kA / m, for example.

  Since the composite material and bonded magnet of the present invention are excellent in heat resistance and have a high coercive force, for example, the composite material and bonded magnet should be suitably applied to applications such as automobile motors (especially water pumps) that are required to be used at high temperatures. Can do.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” is based on mass.

<Example 1>
(Raw material preparation)
First, an Fe—Sm sulfuric acid solution was prepared. In 2.0 kg of pure water, 5.0 kg of FeSO ₄ · 7H ₂ O was mixed and dissolved. Further, 0.49 kg of Sm ₂ O _{3 and} 0.74 kg of 70% sulfuric acid were added and stirred well to dissolve completely. Next, pure water is added to the obtained solution, and finally the Fe ion concentration is adjusted to 0.726 mol / l and the Sm ion concentration is 0.112 mol / l. did.

  Next, the Fe-Sm sulfuric acid solution obtained above was added dropwise to 2 kg of pure water maintained at 35 ° C. with stirring, and at the same time, 15% ammonia solution was added dropwise to adjust the pH to 7-8. did. As a result, a precipitate of Fe—Sm hydroxide, which is a hardly soluble salt, was obtained. The resulting precipitate was slurried.

  The obtained slurry was washed with pure water, and then the precipitate was separated. The separated precipitate was dried in an oven at 80 ° C. for 10 hours. Then, it baked at 1000 degreeC in air | atmosphere for 1 hour. After cooling, red Fe-Sm oxide particles were obtained as a raw material powder.

(Addition of metal element M)
After 100 g of the obtained raw material powder and a tungsten solution having an amount of 0.19 g of tungsten as the metal element M were mixed in a mixer (Wonder Crush Mill WDL-1, rotational speed 25000 rpm) for 10 minutes, The mixture containing the oxide particles and the metal element M was obtained by dispersing for 3 hours using a ball mill. The resulting mixture was dried at 100 ° C. for 3 hours.
The tungsten solution was prepared by dissolving tungsten oxide (WO ₃ ) in 28% ammonia water so that the concentration of tungsten oxide was 17%.

(Hydrogen reduction process)
100 g of the obtained dried mixture was put in a steel container so as to have a bulk thickness of 10 mm. The container was placed in a furnace and the pressure was reduced to 100 Pa. Then, the temperature was raised to 700 ° C. while introducing hydrogen gas, and the temperature was maintained for 15 hours.
As a result, oxygen combined with Sm was not reduced, and black composite oxide particles in which 95% of the oxygen combined with Fe was reduced were obtained.

(Reduction diffusion process)
Next, 2.5 times equivalent metal calcium (average particle size of about 6 mm) was prepared with respect to the amount of oxygen contained in the black composite oxide particles obtained above, and mixed with the composite oxide particles. . Specifically, 60 g of composite oxide particles and 19.2 g of calcium metal were mixed and placed in a furnace.
After evacuating the inside of the furnace, argon gas (Ar gas) was introduced. The temperature was raised to 1100 ° C. and maintained for 2 hours to obtain Fe—Sm—W alloy particles. Here, the metal calcium was in a granular form of about 1 mm to 20 mm.

(Nitriding process)
After the reduction diffusion step, after cooling to 100 ° C., evacuation is performed, and nitrogen gas is continuously introduced, the temperature is raised to 450 ° C., and maintained for 23 hours to obtain a reaction product containing magnetic particles. It was.

(Washing process)
The bulk reaction product obtained in the nitriding step was put into 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant was drained by decantation. The addition to pure water, stirring and decantation were repeated 10 times.
Next, 2.5 g of 99.9% acetic acid was added and stirred for 15 minutes. The obtained slurry was subjected to solid-liquid separation, followed by vacuum drying at 80 ° C. for 3 hours to obtain magnetic particles having metallic luster. The obtained magnetic particles are represented by Sm _9.7 Fe _76.7 N _13.4 W _0.09 .
Further, when the volume average particle diameter of the obtained magnetic particles was measured, it was 2.4 μm.

[Evaluation]
(Magnetic properties)
The obtained magnetic particles were packed in a sample container together with paraffin wax, the paraffin wax was melted with a dryer, and then the easy magnetization domains were aligned with an orientation magnetic field of 16 kA / m. This magnetically oriented sample was pulse magnetized with a magnetizing magnetic field of 32 kA / m, and residual magnetization, coercive force and Hk were measured using a VSM (vibrating sample magnetometer) with a maximum magnetic field of 16 kA / m. The squareness ratio was calculated from the coercive force and Hk. The results are shown in Table 1.

<Examples 2 to 19 and Comparative Examples 1 to 22>
In Example 1, the magnetic particles were prepared in the same manner as in Example 1 except that the type, addition form, addition amount, and dispersion time of the metal element M were changed as shown in Table 1, and evaluated in the same manner. . The results are shown in Table 1.
Of the addition forms, a metal oxide sol having a concentration of 30% and a volume average particle size of 0.11 μm was used as the sol. As the solid, metal oxide particles having a volume average particle diameter of 2.10 μm (W), 9.0 μm (Nb), 6.5 μm (Zr), and 1.5 μm (Cr) were used.

  From Table 1, it can be seen that the magnetic particles obtained by the method for producing magnetic particles of the present invention exhibit excellent residual magnetization, coercive force, squareness ratio, and Hk. Furthermore, it can be seen that comparable magnetic properties can be achieved in a very short time of dispersion treatment time of 1/8 compared to the case where the metal element M is added in a solid state.

The magnetic particles obtained in Example 4 were subjected to a surface treatment by a conventional method to form an oxidation-resistant film on the surface of the magnetic particles, and then a predetermined amount was put in a container, and 300 ° C. for 0.5 hours in the atmosphere. Heated. After cooling at room temperature, the coercive force was measured in the same manner as described above, and the maintenance ratio (%) of the coercive force after heating to the coercive force before heating was calculated. I found out that
Also, the magnetic particles obtained in Comparative Example 22 were similarly subjected to surface treatment and heated in the same manner. After allowing to cool at room temperature, the coercive force was measured by the same method as described above, and the retention rate (%) of the coercive force after heating with respect to the coercive force before heating was calculated to be 56%.
From the above, it can be seen that the magnetic particles obtained by the method for producing magnetic particles of the present invention are excellent in heat resistance.

Claims (8)

R _v Fe _(100-vwx) N _w M _x (wherein R represents at least one rare earth element including Y, M represents a metal element, 3 ≦ v ≦ 30, 5 ≦ w) ≦ 15, 0 <x ≦ 2.5)).
Obtaining a precipitate containing R ions and Fe ions from a solution containing R ions and Fe ions;
Obtaining oxide particles containing R and Fe elements from the precipitate;
Mixing oxide particles and a solution or sol containing a metal element M and a medium to obtain a mixture;
The manufacturing method of the magnetic particle containing this.   The method for producing magnetic particles according to claim 1, wherein the concentration of the metal element M in the solution or sol containing the metal element M and the medium is 5 to 40% by mass.   The method for producing magnetic particles according to claim 1, wherein the metal element M is a metal element having a melting point higher than that of Fe.   The method for producing magnetic particles according to any one of claims 1 to 3, wherein the metal element M is at least one metal element selected from the group consisting of W, Cr, Mo, Zr and Nb.   The method for producing magnetic particles according to any one of claims 1 to 4, further comprising a step of reducing the mixture.   The method for producing magnetic particles according to claim 5, wherein the step of reducing the mixture includes a step of reducing and diffusing an oxide containing an R element.   The composite material containing the magnetic particle obtained by the manufacturing method of any one of Claims 1-6, and resin.   The bonded magnet containing the magnetic particle obtained by the manufacturing method of any one of Claims 1-6, and resin.