Phosphorous-coated rare earth magnetic powder, magnet, bonded magnet, and bonded magnet composition

Abstract

The present disclosure relates to: a phosphorus-coated rare earth magnetic powder comprising a rare earth magnetic powder and a phosphorus-containing coating part that contains phosphorus, the phosphorus-containing coating part covering at least a portion of the surface of the rare earth magnetic powder and having a specific resistivity of 1 Ω•cm or greater as measured under a pressure of 64 MPa; a magnet containing the phosphorus-coated rare earth magnetic powder; a bonded magnet; and a bonded magnet composition.

Description

Phosphorus-coated rare earth magnetic powder, magnets, bonded magnets, and compositions for bonded magnets

[0001] This invention relates to phosphorus-coated rare-earth magnetic powder, magnets, bonded magnets, and compositions for bonded magnets.

[0002] Conventionally, rare earth magnetic powders such as Sm-Co, Nd-Fe-B, and Sm-Fe-N have been subjected to phosphoric acid treatment to form a phosphorus-containing coating, such as phosphate, on their surface, in order to obtain good magnetic properties or to suppress the deterioration of magnetic properties.

[0003] For example, Patent Document 1 discloses a method for producing phosphate-coated SmFeN-based anisotropic magnetic powder, which includes a phosphoric acid treatment step to obtain SmFeN-based anisotropic magnetic powder coated with phosphate on its surface by adding an inorganic acid to a slurry containing SmFeN-based anisotropic magnetic powder, water, and a phosphoric acid compound to adjust the pH of the slurry to 1 or more and 4.5 or less. It is stated that this method yields phosphate-coated SmFeN-based anisotropic magnetic powder having excellent coercivity.

[0004] International Publication No. 2022 / 107461

[0005] Phosphorus-coated rare earth magnetic powder, which has a phosphorus-containing coating such as a phosphate that covers at least a portion of the surface of the rare earth magnetic powder, generally exhibits superior magnetic properties compared to rare earth magnetic powder without a phosphorus-containing coating. However, if exposed to a relatively high temperature atmosphere, for example, exceeding 200°C, during or after manufacturing, the magnetic properties may deteriorate, and phosphorus-coated rare earth magnetic powder with sufficient magnetic properties may not be obtained.

[0006] One embodiment of the present invention aims to provide a phosphorus-coated rare-earth magnetic powder having excellent magnetic properties. Another embodiment of the present invention aims to provide a phosphorus-coated rare-earth magnetic powder that retains its excellent magnetic properties even when exposed to a relatively high-temperature atmosphere during or after manufacturing.

[0007] Furthermore, another embodiment of the present invention aims to provide a magnet and a bonded magnet having excellent magnetic properties, and a composition for a bonded magnet capable of obtaining a bonded magnet having excellent magnetic properties.

[0008] The phosphorus-coated rare earth magnetic powder according to an embodiment of the present invention has a rare earth magnetic powder and a phosphorus-containing coating portion containing phosphorus, and the phosphorus-containing coating portion covers at least a part of the surface of the rare earth magnetic powder, and the resistivity measured under a pressure of 64 MPa is 1 Ω·cm or more.

[0009] The magnet according to another embodiment of the present invention contains the above phosphorus-coated rare earth magnetic powder. Further, the bonded magnet according to another embodiment of the present invention contains the above phosphorus-coated rare earth magnetic powder and a resin. The composition for a bonded magnet according to a further embodiment of the present invention contains the above phosphorus-coated rare earth magnetic powder and a resin and / or a resin precursor.

[0010] According to an embodiment of the present invention, a phosphorus-coated rare earth magnetic powder having excellent magnetic properties can be provided. Further, according to an embodiment of the present invention, a phosphorus-coated rare earth magnetic powder capable of maintaining excellent magnetic properties even when exposed to a relatively high-temperature atmosphere during or after production can be provided.

[0011] According to another embodiment of the present invention, a magnet and a bonded magnet having excellent magnetic properties can be provided. Further, according to another embodiment of the present invention, a composition for a bonded magnet capable of obtaining a bonded magnet having excellent magnetic properties can be provided.

[0012] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. In this specification, the numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

[0013] <Phosphorus-Coated Rare-Earth Magnetic Powder> The phosphorus-coated rare-earth magnetic powder according to one embodiment of the present invention has a rare-earth magnetic powder and a phosphorus-containing coating portion containing phosphorus, and the phosphorus-containing coating portion covers at least a part of the surface of the rare-earth magnetic powder, and the resistivity measured under a pressure of 64 MPa is 1 Ω·cm or more. In one aspect of this embodiment, the phosphorus-coated rare-earth magnetic powder has a resistivity measured under a pressure of 64 MPa of 10 ３ Ω·cm or more. Further, in one aspect of this embodiment, the phosphorus-coated rare-earth magnetic powder has a resistivity measured under a pressure of 64 MPa of 10 ４ Ω·cm or more, further 10 ５ Ω·cm or more, further 5×10 ５ Ω·cm or more, and can be 10 ６ Ω·cm or more, preferably 5×10 ６ Ω·cm or more, more preferably 10 ７ Ω·cm or more in some cases.

[0014] In the phosphorus-coated rare-earth magnetic powder in which the phosphorus-containing coating portion covers at least a part of the surface of the rare-earth magnetic powder, those having a resistivity measured under a pressure of 64 MPa of 1 Ω·cm or more, more preferably 10 ３ Ω·cm or more have excellent magnetic properties. The phosphorus-coated rare-earth magnetic powder having a resistivity measured under a pressure of 64 MPa of 1 Ω·cm or more, more preferably 10 ３ Ω·cm or more retains excellent magnetic properties even when exposed to a relatively high-temperature atmosphere during or after production, for example, an atmosphere with a temperature exceeding 200 °C, or even an atmosphere with a temperature exceeding 250 °C.

[0015] For example, in one aspect of this embodiment, the phosphorus-coated rare-earth magnetic powder can have a coercivity reduction rate ΔiHc of 20% or less after being held at 300 °C in the atmosphere for 6 hours, as defined by the following formula. The coercivity reduction rate ΔiHc after being held at 300 °C in the atmosphere for 6 hours is more preferably 18% or less, and even more preferably 15% or less. ΔiHc (%) = (iHc ０ - iHc) / iHc０ ×100 (where iHc is the coercive force after holding at 300°C in the atmosphere for 6 hours, and iHc ０ is the coercive force before holding at 300°C in the atmosphere for 6 hours.)

[0016] Here, when comparing the rare-earth magnetic powder that is the core of the phosphorus-coated rare-earth magnetic powder with the phosphorus-containing coating part that covers at least a part of the surface of the rare-earth magnetic powder, usually, the phosphorus-containing coating part has higher electrical insulation than the rare-earth magnetic powder (core). However, there is a practical limit to the amount of the phosphorus-containing coating part, and the conventional phosphorus-coated rare-earth magnetic powder had a resistivity of less than 1 Ω·cm measured under a pressure of 64 MPa. The phosphorus-coated rare-earth magnetic powder of the present embodiment has a high resistivity, and this high resistivity is considered to reflect the state of the phosphorus-containing coating. In the phosphorus-coated rare-earth magnetic powder of the present embodiment, it is considered that a uniform phosphorus-containing coating is formed. As a result, the phosphorus-coated rare-earth magnetic powder of the present embodiment has excellent heat resistance as described above, and it is considered that even when exposed to high temperatures during manufacturing, after manufacturing, or during use, its magnetic properties such as excellent coercive force are maintained.

[0017] As described above, in the present embodiment, the resistivity of the phosphorus-coated rare-earth magnetic powder measured under a pressure of 64 MPa is 1 Ω·cm or more, and 10 ３ Ω·cm or more is preferable. In one aspect of the present embodiment, the resistivity of the phosphorus-coated rare-earth magnetic powder measured under a pressure of 64 MPa can be 10 ４ Ω·cm or more, and 10 ５ Ω·cm or more is preferable, 5×10 ５ Ω·cm or more is more preferable, 10 ６ Ω·cm or more is more preferable, 5×10 ６ Ω·cm or more is more preferable, 10 ７ Ω·cm or more is even more preferable. There is no particular problem if the resistivity of the phosphorus-coated rare-earth magnetic powder is too high, and its upper limit is not particularly limited. For example, 10 １２It is approximately Ω·cm or less. Here, the resistivity of phosphorus-coated rare earth magnetic powder measured under a pressure of 64 MPa is the resistivity measured by the four-probe method in a mold equipped with electrodes, where the phosphorus-coated rare earth magnetic powder was placed and pressed under a pressure of 64 MPa.

[0018] The phosphorus-coated rare-earth magnetic powder according to this embodiment may not have a coating containing electrically insulating silica and / or resin, and in that case, it can still have the high resistivity described above. Furthermore, the phosphorus-coated rare-earth magnetic powder according to this embodiment may not have any coating other than the phosphorus-containing coating.

[0019] The phosphorus (P) content in phosphorus-coated rare earth magnetic powder is usually PO ４ In terms of conversion, 0.1% by mass or more and 5% by mass or less is preferred, 0.5% by mass or more and 3% by mass or less is more preferred, and 1% by mass or more and 2.5% by mass or less is even more preferred. The phosphorus (P) content is PO ４ When the phosphorus content is 0.1% by mass or more, a sufficiently high phosphorus-containing coating effect can usually be obtained. However, if the amount of phosphorus-containing coating is too high, the overall magnetic properties of the phosphorus-coated rare earth magnetic powder may decrease, but if the phosphorus (P) content is PO ４ If the phosphorus content is 5% by mass or less, sufficiently excellent magnetic properties can be obtained. The phosphorus (P) content in phosphorus-coated rare earth magnetic powder can be measured by ICP emission spectroscopy (ICP-AES), and PO ４ Expressed in terms of molecular weight.

[0020] In this embodiment, the phosphorus-containing coating that covers at least a portion of the surface of the rare-earth magnetic powder (core) is a coating containing phosphorus (P), and can be, for example, a coating containing a phosphate. Examples of phosphates include phosphates of metal components contained in the rare-earth magnetic powder that is the core. When the rare-earth magnetic powder is an Sm-Fe-N type magnetic powder, examples include samarium phosphate and iron phosphate. The phosphorus-containing coating may also contain metal components other than the metal components contained in the rare-earth magnetic powder (added metal components). The added metal components are not particularly limited, but examples include Mo, W, V, Cr, Al, Zn, Mn, Cu, Zr, Ba, Ca, Mg, Sr, and rare-earth metals such as Sm, La, Pr, Ce, Nd, and Dy. The phosphorus-containing coating may contain one type of phosphate, or it may contain two or more types of phosphates. The phosphorus-containing coating may also contain phosphorus (P) in the form of a compound other than a phosphate. Furthermore, the phosphorus-containing coating may also contain compounds other than phosphorus-containing compounds, or individual metals and nonmetals. The above-mentioned added metal components may be contained in the form of phosphates or in other forms.

[0021] The rare earth magnetic powder (core) is not particularly limited, and any rare earth magnetic powder can be suitably applied. Examples of rare earth magnetic powders include Sm-Co magnetic powder, Nd-Fe-B magnetic powder, and Sm-Fe-N magnetic powder.

[0022] In one embodiment of this invention, the rare earth magnetic powder (core) is preferably an Sm-Fe-N magnetic powder. Examples of Sm-Fe-N magnetic powders include Th ２ Zn １７ It has a crystal structure of type Sm ｘ Fe １００－ｘ－ｙ N ｙExamples include nitrides composed of the rare earth metal samarium (Sm), iron (Fe), and nitrogen (N), represented by . Here, x is preferably 8.1 atomic% or more and 10 atomic% or less, y is preferably 13.5 atomic% or more and 13.9 atomic% or less, and the remainder is mainly Fe. Examples of Sm-Fe-N magnetic powders include Sm ２ Fe １７ N ３ These are examples. Furthermore, the Sm-Fe-N magnetic powder may contain additive metal elements other than samarium (Sm) and iron (Fe). The additive metal elements are not particularly limited, but examples include La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, and Lu.

[0023] In one embodiment of this invention, the phosphorus-coated rare-earth magnetic powder may further have coatings other than the phosphorus-containing coating on at least a portion of the surface of the rare-earth magnetic powder and / or on at least a portion of the surface of the phosphorus-containing coating. The coatings other than the phosphorus-containing coating may be provided directly on at least a portion of the surface of the rare-earth magnetic powder and / or on at least a portion of the surface of the phosphorus-containing coating, or they may be provided via other coatings.

[0024] In one embodiment of this invention, the phosphorus-coated rare-earth magnetic powder may further include, for example, a silicon-containing coating portion. The silicon-containing coating portion may be provided directly on at least a portion of the surface of the rare-earth magnetic powder and / or on at least a portion of the surface of the phosphorus-containing coating portion, or it may be provided via other coating portions.

[0025] The silicon-containing coating is usually preferably one that contains silicon (Si) in the form of silica, but it may also contain silicon (Si) in the form of other compounds. Furthermore, the silicon-containing coating may also contain compounds other than silicon-containing compounds, or elements of metals and nonmetals.

[0026] A phosphorus-coated rare-earth magnetic powder further having a silicon-containing coating, preferably a silicon-containing coating containing silica, typically has a higher resistivity compared to one without a silicon-containing coating, due to the electrical insulation properties of the silicon-containing coating. In one embodiment of this present invention, the phosphorus-coated rare-earth magnetic powder further having a silicon-containing coating has a resistivity of 5 × 10⁻¹⁰ when measured under a pressure of 64 MPa. ５ It can be Ω·cm or more, and 10 ６ It is preferable that it be Ω·cm or more, and 5 × 10 ６ It is more preferable that it be Ω·cm or more, 10 ７ It may be even more preferable that the resistivity be Ω·cm or greater. Furthermore, in one embodiment of this embodiment, the phosphorus-coated rare earth magnetic powder having a silicon-containing coating further has a resistivity of 10 when measured under pressure of 64 MPa. ８ Ω·cm or more, and even 10 ９ Ω·cm or more, and even 10 １０ Ω·cm or more, and even 10 １１ It can be greater than or equal to Ω·cm.

[0027] Furthermore, the phosphorus-coated rare earth magnetic powder of this embodiment may further have coatings other than the phosphorus-containing coating and the silicon-containing coating. In one embodiment of this embodiment, the phosphorus-coated rare earth magnetic powder may further have, in addition to the phosphorus-containing coating, an iron oxide-containing coating, for example, an iron oxide-containing coating, and may further have an iron oxide-containing coating and, preferably, a silicon-containing coating containing silica.

[0028] Furthermore, in one embodiment of this product, the phosphorus-coated rare-earth magnetic powder may be surface-treated. For example, the phosphorus-coated rare-earth magnetic powder may be surface-treated (coupling treated) with a coupling agent such as a silane coupling agent. In particular, when applied to bonded magnets, it is generally preferable to treat the phosphorus-coated rare-earth magnetic powder with a coupling agent because it can improve wettability with the resin and the strength of the resulting bonded magnet.

[0029] <Method for producing phosphorus-coated rare earth magnetic powder> Below, an example of a method for producing phosphorus-coated rare earth magnetic powder according to this embodiment will be described, but the phosphorus-coated rare earth magnetic powder according to this embodiment is not limited to those produced by the following method.

[0030] The core rare-earth magnetic powders can be manufactured by known methods. While not particularly limited, Sm-Co magnetic powders can be manufactured, for example, by the method disclosed in Japanese Patent Application Publication No. 08-260083. Nd-Fe-B magnetic powders can be manufactured, for example, by the HDR method disclosed in International Publication No. 2003 / 85147. Sm-Fe-N magnetic powders can be manufactured, for example, by the method disclosed in Japanese Patent Application Publication No. 11-189811.

[0031] [Phosphoric Acid Treatment Process] In the phosphoric acid treatment process, a slurry containing rare earth magnetic powder, a phosphoric acid compound, and water is stirred while maintaining the pH of the slurry between 1 and 4.5 by adding an acid or base as needed, thereby forming a phosphorus-containing coating (phosphorus-containing coating) on ​​at least a portion of the surface of the rare earth magnetic powder. Here, the slurry shall contain only water as the solvent and shall not contain any organic solvents. Compounds containing metals such as Mo, W, V, Cr, Al, Zn, Mn, Cu, Zr, Ba, Ca, Mg, Sr, and rare earth metals such as Sm, La, Pr, Ce, Nd, and Dy may be added to the slurry as additive metal components.

[0032] In this phosphoric acid treatment process, the metal components contained in the rare earth magnetic powder react with the phosphoric acid components contained in the phosphoric acid compound, causing the phosphate of the metal components contained in the rare earth magnetic powder to precipitate on the surface of the magnetic powder, forming a phosphorus-containing coating. When compounds containing metals such as Mo, W, V, Cr, Al, Zn, Mn, Cu, Zr, Ba, Ca, Mg, Sr, or rare earth metals such as Sm, La, Pr, Ce, Nd, and Dy are added, the metal components contained in these added metal-containing compounds will also be contained in the phosphorus-containing coating.

[0033] In the phosphoric acid treatment step, the pH of the slurry is maintained between 1 and 4.5, but it is preferable to maintain the pH of the slurry between 1.6 and 4.5, and more preferably between 2 and 4.5. In this embodiment, within this range, the pH of the slurry is initially kept low by adding acid as needed, and then the pH is raised by adding a base to complete the phosphoric acid treatment. When adding acid, it is preferable to maintain the pH of the slurry at 3 or below, and after adding the base, it is preferable to raise the pH of the slurry to 3 or above, preferably above 3. The time for adding acid to keep the pH low is usually preferably 10 minutes or more, and more preferably 30 minutes or more.

[0034] The content of rare earth magnetic powder in the slurry is preferably, for example, 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 20% by mass or less.

[0035] The phosphorus (P) content in the slurry is, for example, PO ４ In terms of converted amount, it is 0.5% by mass or more and 10% by mass or less, preferably 0.7% by mass or more and 10% by mass or less, and more preferably 0.8% by mass or more and 5% by mass or less from the viewpoint of reactivity between the metal component and the phosphoric acid component and productivity.

[0036] Examples of phosphate compounds include inorganic phosphates and phosphates such as orthophosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, zinc phosphate, calcium phosphate, hypophosphorous acid, hypophosphite, pyrophosphate, and polyphosphate, as well as organic phosphates. These may be used individually or in combination of two or more.

[0037] As described above, compounds containing metals such as Mo, W, V, Cr, Al, Zn, Mn, Cu, Zr, Ba, Ca, Mg, Sr, and rare earth metals such as Sm, La, Pr, Ce, Nd, and Dy can be added to the slurry as additive metal components. Examples of metal-containing compounds to be added include metal oxoates such as molybdate, tungstate, vanadate, and chromate; metal chlorides such as aluminum chloride, zinc chloride, manganese chloride, copper chloride, zirconium chloride, calcium chloride, magnesium chloride, and strontium chloride; and rare earth chlorides such as samarium chloride, lanthanum chloride, praseodymium chloride, cerium chloride, neodymium chloride, and dysprosium chloride. In addition, oxidizing agents such as sodium nitrate and sodium nitrite, and chelating agents such as EDTA can also be added to the slurry. These may be used individually or in combination of two or more. In this embodiment, metal-containing compounds such as these metal oxoates and other additives are added to improve the properties of the phosphorus-containing coating and the phosphorus-coated rare earth magnetic powder. However, if the amount added is too large, the properties of the resulting phosphorus-coated rare earth magnetic powder may deteriorate, and it is generally preferable to use 1% by mass or less.

[0038] The acid to be added is not particularly limited, but from the viewpoint of wastewater treatment, inorganic acids are preferred. Examples of inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. Organic acids can also be used, and examples of organic acids include acetic acid, formic acid, and tartaric acid. Only one type of acid may be used as the added acid, or two or more types may be used in combination.

[0039] The base to be added is not particularly limited, but from the viewpoint of wastewater treatment, an inorganic base is preferred. Examples of inorganic bases include sodium hydroxide, potassium hydroxide, and ammonia. These inorganic bases are preferably added as aqueous solutions. Only one type of base may be used, or two or more types may be used in combination.

[0040] In this embodiment, it is preferable to prepare in advance a slurry containing rare earth magnetic powder and water, and an aqueous solution (which may also be a slurry) containing a phosphate compound, water, and optionally added metal-containing compounds and other additives, and then mix them. The phosphorus (P) content in the aqueous solution containing the phosphate compound to be prepared (phosphate aqueous solution) is, for example, PO ４ In terms of converted amount, 5% by mass or more and 50% by mass or less is preferred, and 10% by mass or more and 30% by mass or less is more preferred. The pH of the aqueous solution containing the prepared phosphoric acid compound (aqueous phosphoric acid solution) is preferably 1 to 4.5, and more preferably 1.5 to 4. The pH of the aqueous phosphoric acid solution can be adjusted with dilute hydrochloric acid, dilute sulfuric acid, etc.

[0041] Furthermore, when stirring the slurry containing rare earth magnetic powder, phosphate compound, and water while maintaining a pH of 1 to 4.5, the temperature is usually room temperature, and if necessary, it may be heated or cooled in a range of preferably 40°C or lower.

[0042] [Oxidation process after phosphoric acid treatment] After the phosphoric acid treatment process, the phosphorus-coated rare earth magnetic powder obtained may be subjected to oxidation treatment as needed. When the core rare earth magnetic powder is an Sm-Fe-N type magnetic powder, it is preferable to perform oxidation treatment after the phosphoric acid treatment process. By oxidizing phosphorus-coated rare earth magnetic powder whose core is an Sm-Fe-N type magnetic powder, a coating containing iron oxide (iron oxide-containing coating) is formed, which may improve the oxidation resistance of the phosphorus-coated rare earth magnetic powder. Furthermore, by oxidizing phosphorus-coated rare earth magnetic powder, it is possible to suppress undesirable oxidation-reduction reactions, decomposition reactions, and alterations that occur on the surface of the magnetic powder when the phosphorus-coated rare earth magnetic powder is exposed to high temperatures during magnet manufacturing, etc., and as a result, a magnet with excellent magnetic properties may be obtained.

[0043] The oxidation treatment can be carried out by heat-treating the rare earth magnetic powder (phosphorus-coated rare earth magnetic powder) after phosphoric acid treatment in an oxygen-containing atmosphere. The reaction atmosphere is preferably a mixed gas atmosphere of oxygen and an inert gas, such as nitrogen or argon containing oxygen. The oxygen concentration in the mixed gas is preferably 3% to 30% by volume, and more preferably 3.5% to 25% by volume. During the oxidation reaction, it is preferable to exchange the gas at a flow rate of 2 L / min to 10 L / min per 1 kg of magnetic powder.

[0044] The oxidation temperature is preferably 150°C to 380°C, and more preferably 170°C to 350°C. If the oxidation temperature is below 150°C, the effects of improved oxidation resistance due to the formation of the iron oxide-containing coating may not be fully obtained. If the oxidation temperature exceeds 380°C, the overall magnetic properties of the phosphorus-coated rare earth magnetic powder, such as coercivity, may decrease. In one embodiment of this product, the oxidation temperature is more preferably 200°C to 350°C, and even more preferably 230°C to 350°C. By setting the oxidation temperature to 200°C or higher, and even more preferably 230°C or higher, the heat resistance of the phosphorus-coated rare earth magnetic powder can be improved, and the heat resistance of the resulting magnet and bonded magnet can be improved. Furthermore, in the manufacture of bonded magnets, it becomes possible to use binder resins that require relatively high temperatures for magnet molding, and as a result, the range of selectable binder resins can be broadened. The oxidation time (heat treatment time) is usually preferably 3 hours to 10 hours.

[0045] [Silica Treatment Process] After the phosphoric acid treatment process, or after the subsequent oxidation process, the phosphorus-coated rare earth magnetic powder may be subjected to silica treatment as needed. By silica treatment of the surface of the phosphorus-coated rare earth magnetic powder to form a silicon-containing coating containing silica (hereinafter also referred to as a silica thin film), the oxidation resistance of the phosphorus-coated rare earth magnetic powder may be further improved.

[0046] Silica treatment (formation of a silica thin film) can be carried out by known methods. For example, a silica thin film can be formed on the surface of phosphorus-coated rare earth magnetic powder by stirring and mixing a slurry containing phosphorus-coated rare earth magnetic powder, alkyl silicate, and a solvent (preferably water) under basic conditions.

[0047] [Silane Coupling Treatment Process] After the phosphoric acid treatment process, or after the subsequent oxidation process, or after the silica treatment process, the phosphorus-coated rare earth magnetic powder may be further treated with a silane coupling agent. By treating the surface of the phosphorus-coated rare earth magnetic powder with silane coupling, the magnetic properties of the phosphorus-coated rare earth magnetic powder may be further improved, and when applied to bonded magnets, the wettability with the binder resin and the strength of the magnet can be improved.

[0048] The silane coupling agent can be selected according to the type of resin and is not particularly limited, but examples include 3-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, and γ-Mel. Captopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyl Trichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, oleidopropyltriethoxysilane, γ-isocyanatetopropyltriethoxy Examples of silane coupling agents include silanes, polyethoxydimethylsiloxane, polyethoxymethylsiloxane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)tetrasulfan, γ-isocyanatetopropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, t-butylcarbamatetrialkoxysilane, and N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine.These silane coupling agents may be used individually or in combination of two or more.

[0049] The amount of silane coupling agent added is preferably 0.2 parts by mass or more and 0.8 parts by mass or less, and more preferably 0.25 parts by mass or more and 0.6 parts by mass or less, per 100 parts by mass of phosphorus-coated rare earth magnetic powder. If the amount of silane coupling agent added is less than 0.2 parts by mass, the effect of the silane coupling agent tends to be small. If the amount of silane coupling agent added exceeds 0.8 parts by mass, aggregation of the magnetic powder may occur, which may reduce the magnetic properties of the phosphorus-coated rare earth magnetic powder and the magnet containing it.

[0050] Silane coupling treatment (treatment with a silane coupling agent) can be carried out by known methods. For example, silane coupling treatment can be performed by stirring a slurry containing phosphorus-coated rare earth magnetic powder, a silane coupling agent, and a solvent (water or an organic solvent) under basic conditions.

[0051] Furthermore, surface treatment can also be performed using coupling agents other than silane coupling agents.

[0052] After each of the following steps—phosphoric acid treatment, oxidation, silica treatment, and silane coupling treatment—the phosphorus-coated rare earth magnetic powder can be filtered, dehydrated, and dried by conventional methods.

[0053] As described above, a phosphorus-coated rare earth magnetic powder is obtained that has a silicon-containing coating containing silica in addition to a phosphorus-containing coating, and has also undergone silane coupling treatment. In the production of the phosphorus-coated rare earth magnetic powder of this embodiment, the oxidation step, silica treatment step, and silane coupling treatment step after the phosphoric acid treatment step are not essential and may be performed as needed.

[0054] <Method for Manufacturing Sm-Fe-N Magnetic Powder> As described above, in one embodiment of this embodiment, the rare earth magnetic powder that is the core of the phosphorus-coated rare earth magnetic powder is preferably Sm-Fe-N magnetic powder. An example of a method for manufacturing Sm-Fe-N magnetic powder will be described below, but the Sm-Fe-N magnetic powder contained in the phosphorus-coated rare earth magnetic powder according to this embodiment is not limited to those manufactured by the following method.

[0055] Sm-Fe-N magnetic powders are not particularly limited, but can be manufactured by a method including, for example, the following steps: mixing a solution containing Sm and Fe with a precipitant to obtain a precipitate containing Sm and Fe (precipitation step); calcining the precipitate to obtain an oxide containing Sm and Fe (oxidation step); heat-treating the oxide in a reducing gas-containing atmosphere to obtain a partial oxide (pretreatment step); reducing the partial oxide (reduction step); and nitriding the alloy particles obtained in the reduction step (nitriding step).

[0056] [Precipitation Process] In the precipitation process, the Sm and Fe raw materials are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe. ２ Fe １７ N ３ When obtaining the main phase, the molar ratio of Sm to Fe (Sm:Fe) is preferably 1.5:17 to 3.0:17, and more preferably 2.0:17 to 2.5:17. If necessary, raw materials such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, and Lu may be added to the solution.

[0057] The Sm and Fe raw materials are not limited as long as they can be dissolved in a strongly acidic solution. For example, in terms of availability, samarium oxide can be used as the Sm raw material, and iron sulfate (FeSO4) can be used as the Fe raw material. ４ Examples include: The concentration of the solution containing Sm and Fe can be adjusted as appropriate within the range in which the Sm and Fe raw materials are substantially soluble in the acidic solution. Sulfuric acid is an example of an acidic solution in terms of solubility.

[0058] An insoluble precipitate containing Sm and Fe is obtained by reacting a solution containing Sm and Fe with a precipitating agent. Here, the solution containing Sm and Fe only needs to be a solution containing Sm and Fe when it reacts with the precipitating agent. For example, the raw materials containing Sm and Fe may be prepared as separate solutions, and each solution may be added dropwise to react with the precipitating agent. Even when preparing the raw materials as separate solutions, the concentrations of the solutions should be adjusted appropriately within the range in which each raw material is substantially soluble in the acidic solution. The precipitating agent is not limited to alkaline solutions that react with a solution containing Sm and Fe to produce a precipitate, and examples include aqueous ammonia and aqueous sodium hydroxide, with aqueous sodium hydroxide being preferred.

[0059] For the precipitation reaction, a method is preferred in which a solution containing Sm and Fe and a precipitant are added dropwise to a solvent such as water, as this allows for easy adjustment of the particle properties of the precipitate. By appropriately controlling the supply rate of the solution containing Sm and Fe and the precipitant, the reaction temperature, the concentration of the reaction solution, and the pH during the reaction, a precipitate with a homogeneous distribution of constituent elements, a sharp particle size distribution, and a well-formed powder shape can be obtained. Using such a precipitate tends to improve the magnetic properties of the resulting Sm-Fe-N magnetic powder. The reaction temperature is preferably 0 to 50°C, and more preferably 35 to 45°C. The concentration of the reaction solution is preferably 0.65 to 0.85 mol / L, and more preferably 0.7 to 0.84 mol / L, as the total concentration of metal ions. The reaction pH is preferably 5 to 9, and more preferably 6.5 to 8.

[0060] The powder particles obtained in the precipitation process roughly determine the particle size, shape, and particle size distribution of the final Sm-Fe-N magnetic powder. When the particle size of the obtained particles is measured using a laser diffraction wet particle size analyzer, it is preferable that the size and distribution of the entire powder fall approximately within the range of 0.05 to 20 μm, more preferably 0.1 to 10 μm. Furthermore, the average particle size (D50) is measured as the particle size corresponding to 50% of the volume cumulative from the smallest particle size side in the particle size distribution, and is preferably within the range of 0.1 to 10 μm.

[0061] After separating the precipitate, it is preferable to desolvent the separated material to prevent the precipitate from redissolving in the remaining solvent during the subsequent oxidation heat treatment, which can lead to aggregation of the precipitate, changes in particle size distribution, powder particle size, etc., as the solvent evaporates. Specifically, a method for desolvation is to dry the material in an oven at 70 to 200°C for 5 to 12 hours, for example, when water is used as the solvent.

[0062] The process may include a step of separating and washing the precipitate after the precipitation step. The washing step is performed when the conductivity of the supernatant solution is 5 mS / m ２ Continue as needed until the following is achieved. For example, to separate the precipitate, a solvent (preferably water) can be added to the obtained precipitate and mixed, followed by filtration, decantation, or other methods.

[0063] [Oxidation Process] In the oxidation process, an oxide containing Sm and Fe is obtained by calcining the precipitate formed in the precipitation process. For example, the precipitate can be converted into an oxide by heat treatment. When heat treating the precipitate, it is necessary to do so in the presence of oxygen, for example, in an atmospheric environment. Also, because it is necessary to do so in the presence of oxygen, it is preferable that the nonmetallic portion of the precipitate contains oxygen atoms.

[0064] The heat treatment temperature in the oxidation process (hereinafter also referred to as the oxidation temperature) is not particularly limited, but is preferably 700 to 1300°C, and more preferably 900 to 1200°C. If the oxidation temperature is below 700°C, oxidation may be insufficient. If the oxidation temperature exceeds 1300°C, it tends to be difficult to obtain the desired shape, average particle size, and particle size distribution of the magnetic powder. The heat treatment time is also not particularly limited, but is preferably 1 to 3 hours.

[0065] The resulting oxides exhibit sufficient microscopic mixing of Sm and Fe within the oxide particles, and the precipitate shape and particle size distribution are reflected in the oxide particles.

[0066] [Pretreatment step] In the pretreatment step, an oxide containing Sm and Fe is heat-treated in a reducing gas atmosphere to obtain a partial oxide in which a portion of the oxide has been reduced.

[0067] Here, a partial oxide refers to an oxide in which a portion of the oxide has been reduced. The oxygen concentration of the partial oxide is not particularly limited, but it is preferably 10% by mass or less, and more preferably 8% by mass or less. If the oxygen concentration of the partial oxide exceeds 10% by mass, the heat generated by reduction with Ca in the reduction process increases, and the firing temperature rises, which tends to result in the formation of particles with abnormal particle growth. Here, the oxygen concentration of the partial oxide can be measured by non-dispersive infrared absorption spectroscopy (ND-IR).

[0068] Reducing gases include hydrogen (H ２ ), carbon monoxide (CO), methane (CH4) ４ A suitable hydrocarbon gas such as ) can be selected, but hydrogen gas is preferred in terms of cost. The flow rate of the reducing gas is adjusted appropriately within a range where oxides do not scatter. The heat treatment temperature in the pretreatment step (hereinafter also referred to as the pretreatment temperature) is preferably in the range of 300 to 950°C, more preferably 400°C or higher, particularly preferably 750°C or higher, and more preferably less than 900°C. When the pretreatment temperature is 300°C or higher, the reduction of oxides containing Sm and Fe proceeds efficiently. Furthermore, when the pretreatment temperature is 950°C or lower, particle growth and segregation of oxide particles are suppressed, and the desired particle size can be easily maintained.

[0069] [Reduction Process] In the reduction process, the partial oxide obtained in the pretreatment process is reduced to alloy particles by heat treatment in the presence of a reducing agent, preferably at 920 to 1200°C. For example, reduction is carried out by contacting the partial oxide with calcium molten material or calcium vapor. From the viewpoint of magnetic properties, the heat treatment temperature is preferably 950 to 1150°C, and more preferably 980 to 1100°C. From the viewpoint of suppressing uneven particle growth, the heat treatment time is preferably less than 120 minutes, and more preferably less than 90 minutes. Furthermore, from the viewpoint of carrying out the reduction reaction more uniformly, the heat treatment time is preferably 10 minutes or more, and more preferably 30 minutes or more.

[0070] Metallic calcium is used, for example, in granular or powder form, with a particle size of 10 mm or less being preferable. This allows for more effective suppression of aggregation during the reduction reaction. Furthermore, metallic calcium can be added in a ratio of 1.1 to 3.0 times the reaction equivalent (the stoichiometric amount required to reduce Sm oxide, and including the amount required to reduce Fe if it is in oxide form), with 1.5 to 2.0 times being preferable.

[0071] In the reduction process, a disintegration accelerator can be used as needed, along with the reducing agent, metallic calcium. This disintegration accelerator is used as appropriate to promote the disintegration and granulation of the product during the washing process described later, and examples include alkaline earth metal salts such as calcium chloride and alkaline earth metal oxides such as calcium oxide. These disintegration accelerators are used in a ratio of 1 to 30 parts by mass, preferably 5 to 28 parts by mass, per 100 parts by mass of Sm oxide used as the Sm source.

[0072] [Nitriding Process] In the nitriding process, Sm-Fe-N magnetic powder is obtained by nitriding the alloy particles obtained in the reduction process. In this method, the porous mass containing alloy particles obtained in the reduction process is immediately heat-treated in a nitrogen atmosphere without pulverization, allowing the alloy particles to be nitrided uniformly.

[0073] The heat treatment temperature (hereinafter also referred to as the nitriding temperature) for nitriding alloy particles is preferably 300 to 600°C, more preferably 400 to 550°C, and the nitriding treatment can be carried out by replacing the atmosphere with a nitrogen atmosphere within this temperature range. The heat treatment time should be set to a length that ensures sufficiently uniform nitriding of the alloy particles.

[0074] The product obtained after the nitriding process may contain not only magnetic particles (Sm-Fe-N magnetic powder) but also by-products such as calcium oxide and unreacted metallic calcium, which may form a sintered mass. In this case, the product can be immersed in cooling water to separate the calcium oxide and metallic calcium from the magnetic particles as a calcium hydroxide suspension. Furthermore, the magnetic particles may be washed with acetic acid or the like to thoroughly remove any remaining calcium hydroxide.

[0075] As described above, Sm-Fe-N magnetic powder can be obtained.

[0076] The average particle size of Sm-Fe-N magnetic powder is usually preferably between 2 μm and 5 μm, and more preferably between 2.5 μm and 4.8 μm. If the average particle size is 2 μm or larger, the amount of magnetic powder packed into the bonded magnet can be increased, which may improve magnetization. Also, if the average particle size is 5 μm or smaller, the coercivity of the bonded magnet may be improved. Here, the average particle size is the particle size measured under dry conditions using a laser diffraction particle size distribution analyzer.

[0077] The particle size D50 of the Sm-Fe-N magnetic powder is preferably 2.5 μm or more and 5 μm or less, and more preferably 2.7 μm or more and 4.8 μm or less. The particle size D10 is preferably 1 μm or more and 3 μm or less, and more preferably 1.5 μm or more and 2.5 μm or less. The particle size D90 is preferably 3 μm or more and 7 μm or less, and more preferably 4 μm or more and 6 μm or less. Here, D50 is the particle size corresponding to 50% of the cumulative value of the particle size distribution based on volume of the Sm-Fe-N magnetic powder. D10 is the particle size corresponding to 10% of the cumulative value of the particle size distribution based on volume of the Sm-Fe-N magnetic powder. D90 is the particle size corresponding to 90% of the cumulative value of the particle size distribution based on volume of the Sm-Fe-N magnetic powder.

[0078] The span of the Sm-Fe-N magnetic powder, as defined by the following formula, is preferably 2 or less, and more preferably 1.5 or less, from the viewpoint of the coercivity of the resulting magnet. Span = (D90 - D10) / D50 The particle size distribution of the Sm-Fe-N magnetic powder is preferably monodisperse from the viewpoint of the angularity of the demagnetizing properties of the resulting magnet.

[0079] The circularity of Sm-Fe-N magnetic powder is not particularly limited, but is preferably 0.5 or higher, and more preferably 0.6 or higher. If the circularity is less than 0.5, the fluidity will be poor, and stress will be placed between particles during molding, which may reduce the magnetic properties. Here, the circularity is measured by binarizing SEM images taken at 3000x magnification using image processing, and the circularity is determined for each particle. The circularity defined here refers to the average value of the circularity obtained by measuring approximately 1000 to 10000 particles. Generally, the circularity increases as there are more particles with smaller particle sizes, so the circularity is measured for particles of 1 μm or larger. The following definition formula is used for measuring circularity: Circularity = 4πS / L ２ (In the formula, S is the two-dimensional projected area of ​​the particle, and L is the two-dimensional projected perimeter.)

[0080] <Magnets, bonded magnets, and compositions for bonded magnets> A magnet according to one embodiment of the present invention comprises phosphorus-coated rare earth magnetic powder as described above, i.e., rare earth magnetic powder and a phosphorus-containing coating portion, wherein the phosphorus-containing coating portion coats at least a part of the surface of the rare earth magnetic powder, and includes phosphorus-coated rare earth magnetic powder having a resistivity of 1 Ω·cm or more as measured under a pressure of 64 MPa. A bonded magnet according to one embodiment of the present invention comprises phosphorus-coated rare earth magnetic powder as described above and a resin. Furthermore, a composition for bonded magnets according to one embodiment of the present invention comprises phosphorus-coated rare earth magnetic powder as described above and a resin and / or a resin precursor.

[0081] In magnets, bonded magnets, and compositions for bonded magnets, phosphorus-coated rare-earth magnetic powder may be used alone or in combination of two or more types. In bonded magnets, resin may be used alone or in combination of two or more types. In compositions for bonded magnets, resin and / or resin precursors may be used alone or in combination of two or more types.

[0082] The magnets and bonded magnets of this embodiment use phosphorus-coated rare-earth magnetic powder, which has excellent magnetic properties, and therefore possess excellent magnetic properties as magnets. Furthermore, the bonded magnet composition of this embodiment uses phosphorus-coated rare-earth magnetic powder, which has excellent magnetic properties, and therefore can produce bonded magnets with excellent magnetic properties.

[0083] The magnet of this embodiment contains phosphorus-coated rare-earth magnetic powder as described above, having a resistivity of 1 Ω·cm or more as measured under a pressure of 64 MPa, and may further contain resin or may not contain resin. Among the magnets, those that further contain resin in addition to phosphorus-coated rare-earth magnetic powder are called bonded magnets.

[0084] Resin-free magnets can be manufactured by known methods, such as sintering. The manufacturing conditions are not particularly limited and can be appropriately selected by referring to known methods.

[0085] Resin-free magnets, such as sintered magnets, may, if necessary, contain other components added to the magnet in addition to the phosphorus-coated rare-earth magnetic powder described above, such as sintering aids.

[0086] In the case of magnets that do not contain resin (such as sintered magnets), the content of magnetic powder in the magnet is not particularly limited, but generally, from the viewpoint of magnetic properties, 85% by mass or more is preferred, and 90% by mass or more is more preferred. The upper limit of the magnetic powder content in the magnet is not particularly limited and can be 100% by mass.

[0087] A magnet containing resin, i.e., a bonded magnet, can be manufactured from a bonded magnet composition containing the phosphorus-coated rare-earth magnetic powder described above and a resin and / or a resin precursor, by known methods such as compression molding, injection molding, transfer molding, extrusion molding, and potting. Injection molding and transfer molding are preferred because they allow for the production of bonded magnets in various shapes, from simple to relatively complex. The manufacturing conditions are not particularly limited and can be appropriately selected by referring to known methods.

[0088] The resin contained in the bonded magnet and the composition for the bonded magnet is not particularly limited and may be a thermosetting resin or a thermoplastic resin. The thermosetting resin and thermoplastic resin may be used individually or in combination of two or more. Alternatively, one or more thermosetting resins may be used in combination with one or more thermoplastic resins. The composition for the bonded magnet may contain, instead of resin, a precursor that is converted into resin during the manufacturing process of the bonded magnet.

[0089] Thermosetting resins are not particularly limited, but examples include epoxy resins, phenolic resins, unsaturated polyester resins, vinyl ester resins (epoxy acrylate resins), diallyl phthalate resins, urea resins, melamine resins, and urethane resins. Thermoplastic resins are not particularly limited, but examples include polyphenylene sulfide (PPS), polyamides (various nylon resins, etc.), polyesters, polycarbonates, polystyrene, ABS (acrylonitrile-butadiene-styrene copolymer), polyethylene, polypropylene, polyetheretherketone, liquid crystal polymers, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, cycloolefin polymers, and cycloolefin copolymers.

[0090] When using a thermosetting resin, the composition for bonded magnets may contain a curing agent and may also contain a curing accelerator. The curing agent and curing accelerator may be used individually or in combination of two or more types.

[0091] The curing agent and curing accelerator are not particularly limited and can be appropriately selected depending on the type of thermosetting resin, etc. For example, in the case of epoxy resin, the curing agent is not particularly limited, but examples include phenolic curing agents, hydrazide curing agents, acid anhydride curing agents, aromatic polyamine curing agents, alicyclic polyamine curing agents, tertiary amine curing agents, imidazole curing agents, and dicyandiamide. The curing accelerator is not particularly limited, but examples include urea curing accelerators such as dimethylurea, tertiary amine curing accelerators, imidazole curing accelerators, and aromatic amine curing accelerators.

[0092] The content of the curing agent and curing accelerator in the bonded magnet composition can be appropriately selected depending on the type of thermosetting resin, curing agent, and curing accelerator, and is not particularly limited.

[0093] In the case of bonded magnets containing resin, the content of magnetic powder in the bonded magnet is not particularly limited, but is generally preferred to be 80% by mass or more, and more preferably 85% by mass or more, from the viewpoint of magnetic properties. Similarly, the content of magnetic powder in the composition for bonded magnets is not particularly limited, but is generally preferred to be 80% by mass or more, and more preferably 85% by mass or more. The upper limit of the magnetic powder content in the bonded magnet and the magnetic powder content in the composition for bonded magnets is not particularly limited, but is, for example, about 95% by mass or less. When manufacturing bonded magnets by injection molding or transfer molding, from the viewpoint of the fluidity of the composition for bonded magnets during molding, the content of magnetic powder in the bonded magnet and the magnetic powder content in the composition for bonded magnets is generally preferred to be less than 95% by mass, and more preferably 93% by mass or less.

[0094] Bonded magnets and compositions for bonded magnets may, if necessary, contain other components added to the bonded magnets, in addition to the phosphorus-coated rare-earth magnetic powder, resin, curing agent, and curing accelerator described above, such as fillers (preferably inorganic fillers), lubricants, dispersants, antioxidants, heavy metal deactivators, crystal nucleating agents, flame retardants, plasticizers, ultraviolet absorbers, antistatic agents, colorants, mold release agents, thermoplastic elastomers, solidification retardants, etc.

[0095] Compositions for bonded magnets can be obtained, for example, by mixing and kneading phosphorus-coated rare-earth magnetic powder, a resin, and optionally added curing agents, curing accelerators, and other components. The mixing and kneading method and conditions are not particularly limited and can be appropriately selected by referring to known methods.

[0096] For example, a mixture containing phosphorus-coated rare-earth magnetic powder and a resin, and optionally including a curing agent, a curing accelerator, and other components, is kneaded using a kneader such as a single-screw kneader or a twin-screw kneader. The kneading temperature can be appropriately selected depending on the type of resin, curing agent, and curing accelerator used, and is not particularly limited, but for thermosetting resins, it can be, for example, 60 to 140°C, and for thermoplastic resins, it can be, for example, 180 to 300°C. The kneading time is also not particularly limited and can be appropriately selected, for example, 1 to 10 minutes.

[0097] For example, a pellet-shaped bonded magnet composition can be obtained by mixing and kneading phosphorus-coated rare-earth magnetic powder, resin, and optionally a curing agent, curing accelerator, and other components, then extruding the strand using a twin-screw extruder, air-cooling it, and finally cutting it into the desired size (e.g., several millimeters) using a pelletizer. This pellet-shaped bonded magnet composition can be suitably used for injection molding.

[0098] Furthermore, for example, a tablet-shaped bonded magnet composition can be obtained by mixing and kneading phosphorus-coated rare-earth magnetic powder, a resin, and optionally a curing agent, a curing accelerator, and other components, then grinding the mixture using a ball mill, a high-speed mill, etc., and compressing the resulting pulverized material (tablet molding). Compression molding can be performed, for example, by filling a mold with the pulverized material and applying pressure at, for example, about 2 to 20 MPa. This tablet-shaped bonded magnet composition can be suitably used in transfer molding.

[0099] In one embodiment of this product, bonded magnets can be manufactured from a bonded magnet composition by injection molding. For example, using an injection molding machine, the bonded magnet composition is heated and softened in a screw cylinder, then injected into the cavity of a mold to which a magnetic field is applied, aligning and oriented the easy magnetization axes of the magnetic powder, and then cooled. In the case of thermosetting resins, the resin hardens due to heating in the mold cavity, and in the case of thermoplastic resins, the resin solidifies due to cooling. The orientation magnetic field at that time can be generated using an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but is usually preferably 4 kOe or more, and more preferably 6 kOe or more. After that, the solidified / hardened material is removed from the mold, and if necessary, bonded magnets can be obtained by magnetizing with an air-core coil or magnetizing yoke. The magnitude of the magnetizing magnetic field is also not particularly limited, but is usually preferably 20 kOe or more, and more preferably 30 kOe or more.

[0100] In one embodiment of this product, bonded magnets can be manufactured from a bonded magnet composition by a transfer molding method. For example, using a transfer molding machine, the bonded magnet composition is heated and softened in a mold pot, then injected into a mold cavity (empty portion) to which a magnetic field is applied, aligning and oriented the easy magnetization axes of the magnetic powder, and then cooled. In the case of thermosetting resins, the resin hardens due to heating in the mold cavity, and in the case of thermoplastic resins, the resin solidifies due to cooling. The orientation magnetic field at that time can be generated using an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but is usually preferably 4 kOe or more, and more preferably 6 kOe or more. After that, the solidified / hardened material is removed from the mold, and if necessary, bonded magnets can be obtained by magnetizing with an air-core coil or magnetizing yoke. The magnitude of the magnetizing magnetic field is also not particularly limited, but is usually preferably 20 kOe or more, and more preferably 30 kOe or more. The injection pressure when injecting the softened bond magnet composition into the mold cavity is not particularly limited, but is usually preferably 5 to 30 MPa, and more preferably 5 to 15 MPa.

[0101] In injection molding and transfer molding, the temperature for softening the bond magnet composition can be appropriately selected depending on the type of resin, curing agent, and curing accelerator used, and is not particularly limited. For example, in the case of thermosetting resins, it can be 60 to 190°C, and in the case of thermoplastic resins, it can be 160 to 320°C. The heating time (softening time) for softening the bond magnet composition is also not particularly limited and can be appropriately selected, for example, 10 to 3600 seconds.

[0102] In injection molding and transfer molding, the temperature of the mold from which the bond magnet composition is injected or injected (in the case of thermosetting resins, the temperature at which the bond magnet composition is cured) can be appropriately selected depending on the type of resin, curing agent, and curing accelerator used, and is not particularly limited. For example, in the case of thermosetting resins, it can be 150 to 250°C, and in the case of thermoplastic resins, it can be 30 to 150°C. The time for which the bond magnet composition is held in the cavity of the mold is also not particularly limited and can be appropriately selected, for example, 20 to 180 seconds.

[0103] As stated above, the molding method used to manufacture bonded magnets using the bonded magnet composition is not limited to injection molding and transfer molding, but any known method such as compression molding, extrusion molding, or potting can be employed. The molding conditions in this case are not particularly limited and can be set appropriately by referring to known methods. Furthermore, the temperature setting of the molding machine and the settings of the orientation magnetic field and magnetization magnetic field can be performed, for example, in the same manner as described above.

[0104] The magnets and bonded magnets of this embodiment can be suitably used in a variety of applications. For example, they can be suitably used in applications requiring heat resistance, such as in-vehicle drive motors and auxiliary motors, and various pumps such as water pumps, oil pumps, and fuel pumps. Furthermore, the magnets and bonded magnets of this embodiment can be suitably used in home appliance applications such as air conditioner compressors and fan motors, and in aviation applications such as drive motors for aerodynamic mobility devices such as drones.

[0105] In the examples and comparative examples, the resistivity and phosphorus content (PO) of the phosphorus-coated Sm-Fe-N magnetic powder were measured. ４ The coercivity (iHc), converted, and coercivity (iHc) of bonded magnets were measured and evaluated as follows.

[0106] (Resistivity of phosphorus-coated Sm-Fe-N magnetic powder) The resistivity of phosphorus-coated Sm-Fe-N magnetic powder was measured using an automatic powder resistance measurement system MCP-PD600 (manufactured by Nitto Seikou Analytech Co., Ltd.) with a load of 20 kN and a pressure of 64 MPa, using the four-probe method. The resistivity was measured after phosphoric acid treatment (before oxidation treatment), and in the examples, it was also measured after silica treatment and silane coupling treatment.

[0107] (Phosphorus content in phosphorus-coated Sm-Fe-N magnetic powder) The phosphorus (P) content in phosphorus-coated Sm-Fe-N magnetic powder was measured by ICP emission spectrometry (ICP-AES), and PO ４ Converted to molecular weight.

[0108] (Coercivity (iHc) of phosphorus-coated Sm-Fe-N magnetic powder) The intrinsic coercivity (iHc) of phosphorus-coated Sm-Fe-N magnetic powder was measured using a VSM (vibrating sample magnetometer).

[0109] (Coercivity (iHc) of bonded magnets) The intrinsic coercivity (iHc) of bonded magnets was measured using a BH tracer.

[0110] <Example 1> 2.0 kg of pure water mixed with FeSO4 ４ 7H ２ O 5.0 kg was mixed and dissolved. Furthermore, Sm ２ O ３ 0.49 kg of sulfuric acid and 0.74 kg of 70% sulfuric acid were added and the mixture was stirred well until completely dissolved. Next, pure water was added to the resulting solution to adjust the final concentration to 0.726 mol / L for Fe and 0.112 mol / L for Sm, thus obtaining the SmFe sulfuric acid solution.

[0111] [Precipitation Process] The entire amount of the prepared SmFe sulfuric acid solution was added dropwise to 20 kg of pure water maintained at 40°C while stirring for 70 minutes from the start of the reaction, and at the same time, 15% ammonia solution was added dropwise to adjust the pH to 7-8. This obtained a slurry containing SmFe hydroxide. The precipitate (SmFe hydroxide) was separated from the obtained slurry by decantation, washed with pure water, and then the hydroxide was separated by solid-liquid separation. The separated hydroxide was dried in an oven at 100°C for 10 hours.

[0112] [Oxidation Process] The hydroxide obtained in the precipitation process was calcined in air at 1000°C for 1 hour. After cooling, red SmFe oxide was obtained as the raw material powder.

[0113] [Pretreatment Process] 100 g of SmFe oxide obtained in the oxidation process was placed in a steel container to a thickness of 10 mm. The container was placed in a furnace, the pressure was reduced to 100 Pa, and then the temperature inside the furnace was raised to 850°C while introducing hydrogen gas, and maintained at that temperature for 15 hours. This yielded a partial oxide in which a portion of the oxide was reduced.

[0114] [Reduction Process] 60 g of partial oxide obtained in the pretreatment process and 19.2 g of metallic calcium with an average particle size of approximately 6 mm were mixed and placed in the furnace. After evacuating the furnace, argon gas was introduced. Subsequently, the temperature inside the furnace was raised to 1045°C and held for 45 minutes to obtain Sm-Fe alloy particles.

[0115] [Nitriding Process] Subsequently, the temperature inside the furnace was cooled to 100°C, then the furnace was evacuated, and the temperature was raised to 450°C while introducing nitrogen gas. This temperature was maintained for 23 hours to obtain a bulk product containing Sm-Fe-N magnetic particles.

[0116] [Washing Process] The lumpy product obtained in the nitriding process was added to 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decanting was repeated 10 times. Next, 3 kg of pure water and 2.5 g of 99.9% acetic acid were sequentially added to the slurry after decantation and stirred for 15 minutes. After standing, the supernatant was drained by decantation. The process of adding to 3 kg of pure water, stirring, and decanting was repeated twice, followed by dehydration and drying, and then mechanical crushing treatment to obtain Sm-Fe-N magnetic powder (average particle size 3 μm).

[0117] [Phosphoric acid treatment process] As the phosphoric acid treatment solution, 85% orthophosphoric acid, sodium dihydrogen phosphate, sodium molybdate dihydrate, and pure water are mixed and PO ４ A solution was prepared with a concentration adjusted to 24% by mass. 1700 g of the Sm-Fe-N magnetic powder obtained in the water washing step was stirred in dilute hydrochloric acid for 1 minute to remove surface oxide film and contaminants. Then, drainage and water addition were repeated until the conductivity of the supernatant liquid was 100 μS / cm or less, to obtain a slurry containing 10% by mass of Sm-Fe-N magnetic powder. While stirring the obtained slurry, 600 g of the prepared phosphoric acid treatment solution was added to the treatment tank, and the pH of the slurry was controlled within the range of 2.5 ± 0.1 by adding 6% by mass hydrochloric acid as needed, and maintained for about 1 hour. After that, a 5% by mass sodium hydroxide aqueous solution was added to raise the pH of the slurry to about 4, and the phosphoric acid treatment was completed. Subsequently, phosphorus-coated Sm-Fe-N magnetic powder was obtained by suction filtration, dewatering, and vacuum drying. The resistivity of this phosphorus-coated Sm-Fe-N magnetic powder after phosphoric acid treatment was measured under a pressure of 64 MPa and was 4 × 10⁻⁶. ３ It was Ω·cm.

[0118] [Oxidation process after phosphoric acid treatment] 1000 g of the obtained phosphorus-coated Sm-Fe-N magnetic powder was gradually heated from room temperature in an atmosphere of a nitrogen and air mixture (oxygen concentration 21 vol%, flow rate 5 L / min), and heat-treated at a maximum temperature of 300°C for 6 hours to obtain oxidized phosphorus-coated Sm-Fe-N magnetic powder.

[0119] [Silica Treatment Process] Oxidized phosphorus-coated Sm-Fe-N magnetic powder, ethyl silicate 40, and 12.5% ​​by mass of ammonia water were mixed in a mixer in a mass ratio of 97.8:1.8:0.4. The resulting mixture was heated in a vacuum at 200°C to obtain phosphorus-coated Sm-Fe-N magnetic powder on which a thin silica film was formed on the particle surface.

[0120] [Silane Coupling Process] A phosphorus-coated Sm-Fe-N magnetic powder with a silica thin film formed on it was mixed with 12.5% ​​by mass of ammonia water in a mixer. Then, a 50% by mass ethanol solution of 3-aminopropyltriethoxysilane was added and the mixture was further mixed in the mixer. The mass ratio of the phosphorus-coated Sm-Fe-N magnetic powder with a silica thin film formed on it, the 12.5% ​​by mass ammonia water, and the 50% by mass ethanol solution of 3-aminopropyltriethoxysilane was 99:0.2:0.8. The mixture was dried at 100°C under a nitrogen atmosphere for 10 hours to obtain silane-coated phosphorus-coated Sm-Fe-N magnetic powder.

[0121] When the phosphorus (P) content in the phosphorus-coated Sm-Fe-N magnetic powder obtained in this way was measured, PO ４ This was converted to 1.8 mass%. Furthermore, when the resistivity of the phosphorus-coated Sm-Fe-N magnetic powder that had undergone silane coupling treatment was measured under a pressure of 64 MPa, it was 1 × 10⁻⁶. ７ The value was greater than Ω·cm (above the measurement limit).

[0122] [Mixing and Molding Process] A silane-coated phosphorus-coated Sm-Fe-N magnetic powder and a commercially available polyphenylene sulfide resin (H-1G, manufactured by DIC Corporation) were mixed in a mass ratio of 87:13 and kneaded in a twin-screw extruder to obtain a composition for bonded magnets. The kneading temperature at this time was 295°C.

[0123] The obtained bond magnet composition was heated to 310°C in the screw cylinder of an injection molding machine, and the molten composition was injection molded in a mold maintained at 150°C while applying a magnetic field of 9 kOe to obtain a cylindrical bond magnet molded product with a diameter of 10 mm and a height of 7 mm. The obtained bond magnet molded product was then placed in an air-core coil and magnetized with a magnetizing magnetic field of 60 kOe to obtain a bond magnet.

[0124] Table 1 shows the results of measuring and evaluating the resistivity of phosphorus-coated Sm-Fe-N magnetic powder after phosphoric acid treatment, the coercivity (iHc) of silane-coated phosphorus-coated Sm-Fe-N magnetic powder used in the manufacture of bonded magnets, and the coercivity (iHc) of the obtained bonded magnets.

[0125] <Comparative Example 1> A phosphorus-coated Sm-Fe-N magnetic powder was obtained in the same manner as in Example 8 of Patent Document 1 (International Publication No. 2022 / 107461). When the phosphorus (P) content in the obtained phosphorus-coated Sm-Fe-N magnetic powder was measured, PO ４ This was converted to 1.1% by mass. This phosphorus-coated Sm-Fe-N magnetic powder was subjected to oxidation treatment, silica treatment, and silane coupling treatment after phosphoric acid treatment.

[0126] Then, using the obtained phosphorus-coated Sm-Fe-N magnetic powder, a bonded magnet was obtained in the same manner as in Example 1.

[0127] Table 1 shows the results of measuring and evaluating the resistivity of phosphorus-coated Sm-Fe-N magnetic powder after phosphoric acid treatment, the coercivity (iHc) of silane-coated phosphorus-coated Sm-Fe-N magnetic powder used in the manufacture of bonded magnets, and the coercivity (iHc) of the obtained bonded magnets.

[0128]

[0129] Embodiments relating to this disclosure may include, for example, the following aspects: [Item 1] A phosphorus-coated rare earth magnetic powder comprising a rare earth magnetic powder and a phosphorus-containing coating portion, wherein the phosphorus-containing coating portion covers at least a portion of the surface of the rare earth magnetic powder, and the resistivity measured under a pressure of 64 MPa is 1 Ω·cm or more. [Item 2] A phosphorus (P) content is PO４ A phosphorus-coated rare earth magnetic powder as described in item 1, wherein the converted amount is 0.1% by mass or more and 5% by mass or less. [Item 3] A resistivity of 10 measured under pressure of 64 MPa. ３ Phosphorus-coated rare earth magnetic powder according to item 1 or 2, having a resistivity of Ω·cm or more. [Item 4] Phosphorus-coated rare earth magnetic powder according to any one of items 1 to 3, which does not have a coating portion containing electrically insulating silica and / or resin. [Item 5] Further having a silicon-containing coating portion containing silicon, and having a resistivity of 5 × 10 measured under pressure of 64 MPa. ５ [Item 6] A phosphorus-coated rare earth magnetic powder according to any one of items 1 to 3, wherein the phosphorus-coated rare earth magnetic powder is Ω·cm or greater. [Item 7] A magnet containing the phosphorus-coated rare earth magnetic powder according to any one of items 1 to 6. [Item 8] A bonded magnet containing the phosphorus-coated rare earth magnetic powder according to any one of items 1 to 6 and a resin. [Item 9] A composition for a bonded magnet containing the phosphorus-coated rare earth magnetic powder according to any one of items 1 to 6 and a resin and / or a resin precursor.

Claims

1. A phosphorus-coated rare earth magnetic powder comprising a rare earth magnetic powder and a phosphorus-containing coating portion, wherein the phosphorus-containing coating portion covers at least a portion of the surface of the rare earth magnetic powder, and the resistivity measured under a pressure of 64 MPa is 1 Ω·cm or more.

2. The phosphorus (P) content is PO ４ The phosphorus-coated rare earth magnetic powder according to claim 1, wherein the amount is 0.1% by mass or more and 5% by mass or less.

3. The specific resistivity measured under a pressure of 64 MPa is 10 ３ The phosphorus-coated rare earth magnetic powder according to claim 1 or 2, having a density of Ω·cm or more.

4. The phosphorus-coated rare earth magnetic powder according to claim 1 or 2, which does not have a coating portion containing electrically insulating silica and / or resin.

5. It further has a silicon-containing coating portion containing silicon, and the resistivity measured under a pressure of 64 MPa is 5 × 10⁻⁶. ５ The phosphorus-coated rare earth magnetic powder according to claim 1 or 2, having a density of Ω·cm or more.

6. The phosphorus-coated rare earth magnetic powder according to claim 1 or 2, wherein the rare earth magnetic powder is an Sm-Fe-N type magnetic powder.

7. A magnet comprising phosphorus-coated rare earth magnetic powder according to claim 1 or 2.

8. A bonded magnet comprising phosphorus-coated rare-earth magnetic powder according to claim 1 or 2 and a resin.

9. A composition for bonded magnets comprising the phosphorus-coated rare-earth magnetic powder according to claim 1 or 2, and a resin and / or a resin precursor.

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