JP2017212353A - Method for manufacturing magnet alloy powder for bond magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing magnet alloy powder for a bond magnet, which has a high coercive force with stability and excellent weather resistance.SOLUTION: Provided is a method for manufacturing magnet alloy powder for a bond magnet. The method is arranged to obtain magnet alloy powder for a bond magnet by pulverizing rare earth element-containing iron-based magnet alloy powder in an organic solvent. The method comprises: a finely pulverizing process; and a heating/drying process. The finely pulverizing process includes the steps of: previously preparing a chromium-containing phosphoric acid solution by adding to 5-30 wt% of metal chromium powder to a phosphoric acid solution and then removing metal chromium powder remaining as a result; and pulverizing the rare earth element-containing iron-based magnet alloy powder in the organic solvent, in which the chromium-containing phosphoric acid solution is added to the organic solvent to form a protective coating on the surface of the rare earth element-containing iron-based magnet alloy powder. The heating/drying process includes the steps of: performing a solid-liquid separation on a slurry including the rare earth element-containing iron-based magnet alloy powder, which is obtained in the finely pulverizing process; and heating and drying the resultant rare earth element-containing iron-based magnet alloy powder.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a magnet alloy powder for bonded magnets, and more specifically, relates to a method for producing a magnet alloy powder for bonded magnets having a stable and high coercive force and excellent weather resistance.

  In recent years, ferrite magnets, alnico magnets, rare earth magnets, and the like have been incorporated and used as motors and sensors in various products including general household electrical appliances, communication / acoustic equipment, medical equipment, and general industrial equipment. Although these magnets are mainly manufactured by a sintering method, they are fragile and difficult to be thinned, so it is difficult to mold them into complex shapes. Also, since they shrink by 15 to 20% during sintering, the dimensional accuracy cannot be increased. Post-processing such as polishing is necessary, and there are significant restrictions in terms of application.

  On the other hand, bonded magnets (resin-bonded magnets) use a thermoplastic resin such as polyamide resin or polyphenylene sulfide resin as a binder, or an epoxy resin, bis-maleimide triazine resin, unsaturated when used in combination with a curing agent. Since thermosetting resins such as polyester resins and vinyl ester resins can be used for easy manufacture by filling them with magnet alloy powder, new applications are being developed.

  Among the magnet materials, rare earth-iron-boron permanent magnets (hereinafter sometimes referred to as iron magnets containing rare earth elements) have the best magnetic properties among magnets in practical use. Because of the disadvantages of electrical conductivity and poor temperature characteristics of corrosion resistance and magnetic properties, chromate is used on the base metal film of Al or Zn to improve the electrical insulation, heat resistance, and corrosion resistance of the magnet. It has been proposed that a coating is provided and further coated with a polyimide resin by vapor deposition polymerization (see Patent Document 1).

However, in the above coating method, an Al or Zn base metal film is formed in advance, but the adhesion between the magnet and the polyimide film is not sufficient, and there is a problem that peeling occurs locally or from the end of the required surface. In order to improve it, after forming a base metal film on the surface of an iron-based magnet containing a rare earth element, the metal film is subjected to a phosphate treatment, and then the phosphate film and the adhesive After applying a good silane coupling agent, it has been studied to deposit a polyimide resin on the silane coupling surface.
Phosphate coating has the role of increasing the corrosion resistance by filling the pores and recesses of the porous and uneven base metal coating by phosphating to make the surface of the phosphate coating uniform, and the base metal coating and silane coupling agent It also has the role of improving the adhesion of the polyimide coating, thereby contributing to the improvement of corrosion resistance, and the adhesion between the phosphate coating of the underlying layer and the silane coupling and between the silane coupling and the polyimide coating is good. In addition, it is said that a polyimide resin having excellent electrical insulation, corrosion resistance, and heat resistance can be applied to the local or required surface of the R-Fe-B permanent magnet surface (see Patent Document 2).

  As described above, 1) In the method of resin coating after performing a base treatment for forming a reactive chemical conversion film such as phosphate treatment or chromate treatment, an oxide film on the surface of an iron-based magnet containing rare earth elements and the main component of the magnet It is difficult to obtain a uniform and stable conversion coating on the surface of the magnet due to the presence of the active rare earth element. 2) Hexavalent chromium, trivalent chromium on the surface of the iron-based magnet containing the rare earth element In the method in which a coating layer containing silica and silica is formed by performing a coating-type chromate treatment, and a resin coating film is formed on the coating layer, the surface of the rare earth magnet is porous. Further, corrosion from the pores cannot be suppressed, sufficient corrosion resistance cannot be obtained, and there is a problem of swelling of the upper resin coating film.

  In order to solve these problems, a compound layer containing at least one element selected from the group consisting of zirconium, chromium, vanadium, tungsten, titanium, manganese, molybdenum, and silicon is purified from an inorganic salt containing the above metal. A surface treatment solution dissolved in water is prepared, and an iron-based magnet piece containing a rare earth element is immersed in the surface treatment solution to be deposited on the surface of the iron-based magnet containing the rare earth element, thereby having high corrosion resistance. It is disclosed that an iron-based sintered magnet containing a rare earth element can be obtained (see Patent Document 3).

  On the other hand, when producing a bonded magnet by kneading iron-based magnet alloy powder containing rare earth elements with a resin binder, it is necessary to pulverize the magnet alloy powder to 150 μm or less. Although pulverization is performed in an inert gas or an organic solvent, the magnet alloy powder after pulverization is extremely active, and when exposed to the air, the magnet alloy powder rapidly oxidizes and deteriorates the magnetic properties. A method of gradually oxidizing by introducing a slight amount of oxygen into an inert atmosphere is employed.

Bond magnets obtained by molding using iron-based magnet alloy powders containing rare earth elements are prone to rust in salt water, so even if the magnet alloy powder produced by the above method is used, In a severely corrosive environment, it was not fully satisfactory for rust control.
Therefore, rusting is suppressed by forming a coating film such as a thermosetting resin on the surface of the bonded magnet obtained by molding, and phosphates such as aluminum phosphate and zinc phosphate are contained on the molded body surface. Providing a coating treatment with a paint to suppress rusting has been proposed (see, for example, Patent Document 4).

  In addition, the surface of the magnetic alloy powder is treated with zinc phosphate, then treated with inorganic chromic acid, and further impregnated with a synthetic resin in the voids of the molded product obtained by heat-curing after compression molding (for example, Patent Documents) 5) has been proposed. Further, vapor deposition of zinc or aluminum on the surface of the magnetic alloy powder (for example, see Patent Document 6), formation of a polymer film on the surface of the magnetic alloy powder (for example, see Patent Document 7), and further, magnetic alloy powder Techniques such as metal plating of Ni and Sn on the surface (see, for example, Patent Document 8) have also been proposed.

  However, even if any of the above methods is applied to an iron-based magnet alloy powder containing a rare earth element (for example, an Nd-Fe-B-based or Sm-Fe-N-based bonded magnet alloy powder), the oxidation resistance is not Although improved, there is a problem that the properties of the powder surface are rough and the magnetic properties deteriorate. In addition, in order to obtain a sufficient oxidation resistance effect by forming a film, it is necessary to have a film thickness of about several tens of μm, so that the volume fraction of the material that exhibits magnetic characteristics decreases, and the magnetic characteristics decrease. There is also a problem of inviting. In addition, since the fine powders aggregate when forming the coating, the direction of magnetic anisotropy becomes uneven, and the magnetic properties of the magnet compact using the magnetic fine powder cannot be avoided.

  In addition, when iron-based magnet powder containing rare earth elements is pulverized in an inert gas or a solvent to a particle size of about several μm, the magnet powder after pulverization is extremely active, so before the coating treatment is performed on the compact. When exposed to the atmosphere, oxidation rusting proceeds rapidly and the magnetic properties deteriorate. In order to solve this, the present applicant in Patent Document 9 pretreated the pulverized magnet powder with an acidic solution to activate the surface of the magnet powder, and then in the phosphate aqueous solution, It was proposed to form a phosphate film by immersing the treated magnetic powder. As a result, the drawbacks of the conventional resin-bonded magnet composition were eliminated, and a resin-bonded magnet excellent in moldability and excellent in magnetic properties and physical properties (particularly mechanical strength) could be provided.

  However, when phosphate is added after the completion of pulverization, the pulverized magnet powder is agglomerated with each other by the magnetic force, and a portion not covered with the phosphate film is generated on the contact surface of the magnet powder. Once such magnet powder is kneaded with the bond magnet resin, the agglomerated magnet powder is partially crushed by the shearing force of kneading, and the active powder surface without a film is exposed. For this reason, the bond magnet obtained by molding such magnet powder easily corrodes and deteriorates magnetic properties when used in a practically important humidity environment. Since the rare earth-iron-nitrogen based magnet powder shows a nucleation type coercive force expression mechanism, if such a region is generated in part, the coercive force is remarkably lowered.

  In other words, the magnet powders that are aggregated together by magnetic force, although the surface of the aggregated powder is protected with a film, the protection against individual magnet powders is not sufficient, so the weather resistance in a dry environment is improved, but practical use There has been a problem that the weather resistance under the humidity environment, which is important, has not been improved to a satisfactory extent.

Therefore, the present applicant has proposed that phosphoric acid be added when the magnet alloy powder is pulverized in an organic solvent in order to knead the iron-based magnet powder containing a rare earth element with a resin to be used as a bonded magnet ( (See Patent Document 10). Thereby, the magnet powder which was excellent in weather resistance and suppressed the fall of the coercive force in a humidity environment was able to be obtained.
However, the coercive force does not decrease after being left for 24 hours in an environment of 80 ° C. and 90% relative humidity, but the magnetic property of the magnet powder, particularly, the decrease in coercive force becomes apparent when left for 200 hours. In some cases, coercive force and weather resistance varied among production lots.

JP-A-9-260120 JP-A-9-326308 JP 2000-199074 A JP 2000-208321 A Japanese Patent Laid-Open No. 1-14902 JP-A-64-15301 JP-A-4-257202 Japanese Patent Laid-Open No. 7-142246 JP-A-11-251124 JP 2002-124406 A

  In view of the above-mentioned problems of the prior art, the object of the present invention is a method for producing a magnet alloy powder for bonded magnets that has a stable and high coercive force, excellent weather resistance, and reduced variations in coercive force and weather resistance. Is to provide.

As a result of intensive studies to achieve the above object, the present inventors have obtained a magnet alloy powder for a bond magnet by pulverizing an iron-based magnet alloy powder containing a rare earth element in an organic solvent. When pulverizing the iron-based magnet alloy powder containing the rare earth element in an organic solvent, the phosphoric acid solution containing chromium prepared in advance using the metal chromium powder is added to the organic solvent and pulverized. Solid-liquid separation of a finely pulverizing treatment step for forming a protective film on the surface of the iron-based magnet alloy powder containing the rare earth element, and a slurry containing the iron-based magnet alloy powder containing the rare earth element obtained in the finely pulverizing treatment step And heat drying treatment step of heating and drying the obtained iron-based magnet alloy powder containing rare earth elements,
It has been found that a magnet alloy powder for bonded magnets excellent in weather resistance can be obtained by providing the above, and the present invention has been completed.

  That is, according to the first invention of the present invention, there is provided a manufacturing method for obtaining a magnet alloy powder for a bonded magnet by pulverizing an iron-based magnet alloy powder containing a rare earth element in an organic solvent. After adding 5 to 30% by weight of chromium powder and leaving it at 20 to 60 ° C. for 24 hours or more, a phosphoric acid solution containing chromium is prepared by removing the remaining metal chromium powder and containing the rare earth element. When pulverizing the iron-based magnet alloy powder in an organic solvent, the phosphoric acid solution containing chromium is added to the organic solvent and pulverized, and a protective coating is formed on the surface of the iron-based magnet alloy powder containing the rare earth element. The finely pulverizing treatment step to be formed, and the slurry containing the iron-based magnet alloy powder containing the pulverized rare earth element are subjected to solid-liquid separation, and heating to dry the iron-based magnet alloy powder containing the separated rare earth element is heated. A drying process, Method for producing a magnetic alloy powder for bonded magnets, wherein it is provided.

  According to the second invention of the present invention, in the first invention, the amount of the phosphoric acid solution containing chromium added to the organic solvent is 1 kg of iron-based magnet alloy powder containing rare earth elements to be crushed. There is provided a method for producing a magnet alloy powder for bonded magnets, characterized in that phosphoric acid is 0.1 mol to 0.5 mol.

  Furthermore, according to the third invention of the present invention, in the first or second invention, the organic solvent contains one or more alcohols selected from ethanol or 2-propanol (IPA). A method for producing a magnet alloy powder for a bonded magnet is provided.

According to the method for producing a magnet alloy powder for bonded magnets of the present invention, when the iron-based magnet alloy powder containing a rare earth element is pulverized in an organic solvent in the pulverization treatment step, the organic solvent contains chromium. By adding a phosphoric acid solution and pulverizing, a protective coating containing chromium and phosphoric acid can be immediately formed on the newly fractured surface generated by pulverization during pulverization of the iron-based magnet alloy powder containing the rare earth element. Therefore, if a bonded binder is produced by mixing and molding a resin binder using the obtained magnet alloy powder, an iron-based bonded magnet containing a rare earth element with excellent weather resistance can be obtained while maintaining high magnetic properties. Can do.
Therefore, the iron-based bonded magnet containing rare earth elements having excellent weather resistance obtained by the present invention is extremely useful in a wide range of fields such as general home appliances, communication / acoustic equipment, medical equipment, general industrial equipment, and the like. The industrial value of the magnet alloy powder for bonded magnets according to the present invention is very high.

  Hereinafter, a manufacturing method for obtaining a magnet alloy powder for a bonded magnet by pulverizing an iron-based magnet alloy powder containing a rare earth element of the present invention in an organic solvent, and a rare earth element excellent in weather resistance while maintaining high magnetic properties. The iron-based bond magnets included will be described in detail.

1. Method for producing magnet alloy powder for bonded magnet The method for producing magnet alloy powder for bonded magnet according to the present invention comprises adding 5 to 30% by weight of metal chromium powder to a phosphoric acid aqueous solution in advance at 20 to 60 ° C. for 24 hours or more. After leaving, prepare a phosphoric acid solution containing chromium, excluding the residual metallic chromium powder, and when pulverizing the iron-based magnet alloy powder containing the rare earth element in an organic solvent, Pulverizing treatment step of adding a phosphoric acid solution containing chromium and crushing to form a protective film on the surface of the iron-based magnet alloy powder containing the rare earth element;
A slurry containing the finely pulverized rare earth element-containing iron-based magnet alloy powder is subjected to a solid-liquid separation, and a heat-drying treatment step for heating and drying the separated iron-based magnet alloy powder containing the rare earth element is provided. Yes.

(1) Iron-based magnet alloy powder containing a rare earth element In the present invention, the iron-based magnet alloy powder containing a rare earth element as a raw material for the magnet alloy powder for bonded magnets is a magnet powder containing rare earth elements and iron as main components (hereinafter referred to as the main components). Or simply “rare earth magnet powder”).

  As the rare earth element, for example, at least one element selected from Sm, Gd, Tb, and Ce, or, in addition to the rare earth element, selected from Pr, Nd, Dy, Ho, Er, Tm, and Yb. Those containing at least one kind of element are preferred. The main raw material of the rare earth magnet alloy powder of the present invention is preferably Sm, which is superior in weather resistance and thermal stability to Nd which is easily oxidized and weak at high temperatures.

  When Sm is contained as the rare earth element, in order to obtain a high coercive force, a higher coercive force can be obtained by setting the Sm content to 60% by weight or more, preferably 90% by weight or more of the whole rare earth. Preferable examples of the iron-based magnet alloy powder containing rare earth elements include, for example, rare earth-iron-nitrogen-based magnet alloy powder. In addition, in the iron-based magnet alloy powder containing a rare-earth element, a rare-earth magnet powder having a composition in which part of Fe is replaced with Co is also preferable, and examples thereof include a rare-earth-iron-cobalt-nitrogen based magnet powder.

(2) Manufacture of iron-based magnet alloy powders containing rare earth elements Iron-based magnet alloy powders containing rare earth elements include casting methods and reduction diffusion methods. The obtained iron-based magnet alloy powder containing rare earth elements is suitable.

Hereinafter, a method for producing rare earth-iron-nitrogen based magnet alloy powder will be described as an example. However, the iron-based magnet alloy powder containing rare earth elements used in the present invention is not limited to this rare earth-iron-nitrogen based magnet powder.
In the reduction diffusion method, first, a predetermined amount of rare earth oxide powder, iron powder, and other raw material powders are mixed, and further, a reducing agent sufficient to reduce the rare earth oxide powder is added and mixed, and then this mixture is reacted. In a non-oxidizing atmosphere (an atmosphere in which oxygen is not substantially present), the temperature is raised to and maintained at a temperature at which the reducing agent melts, for example, 800 ° C. or higher, and a temperature at which the rare earth-iron alloy does not melt. Then, the rare earth oxide is reduced to a rare earth element by heat treatment, and the rare earth oxide is diffused in the iron powder to synthesize a rare earth-iron alloy.

  The rare earth oxide powder is not particularly limited, but is made of at least one rare earth element selected from Sm, Gd, Tb and Ce, or is further made of Pr, Nd, Dy, Ho, Er, Tm and Yb. Those containing at least one selected rare earth element are preferred. In particular, those containing Sm are preferred. When Sm is contained, in order to obtain a high coercive force, Sm is set to 60% by mass or more, preferably 90% by mass or more of the entire rare earth element. The rare earth oxide powder has a predetermined amount of Mn, Ca, Cr, Nb, Mo, Sb, Ge, Zr, V, Si, Al in order to improve coercive force, improve productivity, and reduce costs. 1 or more types, such as Ta, Cu, or Cu, may be added. The particle size of the rare earth oxide powder is not particularly limited, but is preferably 10 μm or less from the viewpoint of reactivity and workability.

The iron powder is not particularly limited, and reduced iron powder, gas atomized powder, water atomized powder, carbonyl iron powder, electrolytic iron powder, and the like can be used. Moreover, you may use the iron powder which substituted 20 mass% or less of iron with cobalt.
In addition, as a particle diameter of iron powder, the average particle diameter is 35-45 micrometers, and the powder which a powder with a particle diameter of 5-60 micrometers occupies 80 volume% or more is preferable. If the iron powder to be used is too large, it takes a very long time for the rare earth element to diffuse into Fe when synthesizing the rare earth-Fe, while the small iron powder is expensive in terms of production cost. Not suitable for use.

  The reducing agent is not particularly limited, and alkali metals, alkaline earth metals, hydrides thereof, and the like can be used. In terms of handling safety and cost, granular metallic calcium sieved to 5 mesh (Tyler mesh) or less is preferable.

  The rare earth oxide powder, iron powder, and reducing agent are weighed in predetermined amounts and then thoroughly mixed together. For mixing, for example, a known mixing device such as a V-shaped blender or an S-shaped blender can be used.

  Next, the reaction product obtained by the reduction diffusion treatment is charged into a sealed container, and after evacuation, the reaction product is subjected to hydrogen treatment under a predetermined condition, thereby allowing the reaction product to occlude hydrogen. This improves the pulverization property of the reaction product and the disintegration property in water, and the reaction product can be finely pulverized by subsequent water disintegration treatment and water washing treatment without crushing treatment. Can be suppressed.

Moreover, since the hydrogen treatment has the effect of improving the disintegration property of the reduced product and dissociating the sintered particles, the excess rare earth element-rich phase can be easily removed by pickling. Here, the mechanism of the hydrogen treatment having such an effect will be specifically described below. For example, an Sm—Fe alloy synthesized by reduction diffusion has Sm around the main phase (Sm ₂ Fe ₁₇ N ₃ ). A rich phase (SmFe ₂ , SmFe ₃ ) exists, and when the Sm-Fe alloy is put in a reaction vessel and left in hydrogen, the main phase and the Sm rich phase are Sm ₂ Fe ₁₇ Hx, SmFe ₂ Hx, SmFe, respectively. Varies with ₃ Hx. At this time, the Sm-rich phase around the main phase has a larger lattice expansion coefficient than the main phase, so the Sm-rich phase breaks, and as a result, the reduced product collapses.

  Next, the obtained rare earth-iron-based alloy ingot is cooled to room temperature by air cooling and furnace cooling, and then poured into pure water, subjected to a disintegration treatment, and remaining as calcium oxide, calcium metal, etc. Dissolve and remove the agent. As the water washing treatment, a slurry mainly composed of alloy powder is obtained by performing stirring and decantation a predetermined number of times.

  Further, pickling treatment is performed on the obtained slurry. In the pickling treatment, the remaining calcium hydroxide and the like are removed, and the rare earth element rich phase generated by the rare earth element added excessively to keep the surface state of the magnet powder active is removed. At this time, acetic acid, hydrochloric acid, nitric acid, sulfuric acid or the like is used as the acid used for the pickling treatment.

  A rare earth-iron-nitrogen based alloy powder can be obtained by performing a water washing treatment for removing acid from the obtained alloy powder and drying the alloy powder.

In the present invention, after the above hydrogen treatment and wet treatment, the reaction product is heated in an atmosphere of nitrogen gas or ammonia under predetermined treatment conditions, and nitrogen is introduced into the alloy, thereby nitriding It can be a thing. Nitriding is preferably performed by heating at a temperature of 300 to 500 ° C. for 3 hours or more, for example, 5 to 10 hours.
The production of iron-based magnet alloy powders containing rare earth elements is described in detail in Patents 5071160, 4440747, 4345588, and 4241461 by the present applicant, which are incorporated herein by reference. And

(3) Fine grinding treatment of iron-based magnet alloy powder containing rare earth element In the present invention, when producing magnet alloy powder for bonded magnets by grinding iron-based magnet alloy powder containing rare earth element in an organic solvent, A phosphoric acid solution containing a predetermined amount of chromium is added to an organic solvent and pulverized, and a fine pulverization treatment is performed to form a protective film on the surface of the iron-based magnet alloy powder containing the rare earth element.

  In the present invention, first, a phosphoric acid solution containing an organic solvent and specific chromium, which are materials for the treatment liquid, is prepared.

(Organic solvent)
There are no particular restrictions on the organic solvent, and alcohols such as 2-propanol, ethanol and methanol, lower hydrocarbons such as pentane and hexane, aromatics such as benzene, toluene and xylene, ketones, and mixtures thereof However, from the viewpoint of safety, it is preferable that at least one alcohol selected from ethanol and 2-propanol is contained.

(Phosphoric acid solution containing chromium)
The phosphoric acid solution containing chromium used in the present invention is obtained by adding 5 to 30% by weight of metal chromium powder to a phosphoric acid aqueous solution and leaving it at 20 to 60 ° C. for 24 hours or more, and then collecting only the supernatant. It was obtained by removing the metal chromium powder. If the standing time is 24 hours or longer, the shorter the time, the better. The upper limit is not specified, but it is preferably 36 hours or less in consideration of production efficiency.

  The solubility of chromium in the phosphoric acid aqueous solution varies depending on the temperature, the mixing method and time, the particle size of the chromium metal powder, and the like. If it is less than 20 degreeC, the solubility of chromium will be very small, and a solubility will improve by heating, but if it exceeds 60 degreeC, the reactivity with phosphoric acid will become high and the coverage to the magnet powder required in this invention will deteriorate.

  There is no restriction | limiting in particular by the kind of phosphoric acid, The normal orthophosphoric acid marketed, for example, 85% concentration phosphoric acid aqueous solution can be used. In addition to orthophosphoric acid, disodium hydrogen phosphate, pyrophosphoric acid, metaphosphoric acid, manganese phosphate, zinc phosphate, aluminum phosphate, and the like may be used, but orthophosphoric acid is preferred from the viewpoint of cost.

In the present invention, metal chromium powder is used. As the metal chromium powder, for example, a commercially available metal chromium powder having a size of 63 μm or a coarse powder obtained by finely pulverizing metal chromium pieces in a mortar may be used.
In addition, various metal compounds can be used as chromium. However, even if there is a trace amount of transition metal element that can be contained in the metal chromium powder or an oxide film that is inevitably generated on the surface, the object of the present invention is not impaired. .
A general-purpose filtration device can also be used as the supernatant recovery means.

  Here, if the metal chromium powder is less than 5% by weight, the effect of the phosphoric acid solution containing chromium cannot be obtained, and the coercive force is lowered and the weather resistance is deteriorated under high temperature and high humidity. If the amount of the metal chromium powder to be added exceeds 30% by weight, the effect of improving the weather resistance due to the addition of the phosphoric acid solution containing chromium will be saturated, so it is not economical to add more metal chromium powder. Further, if the temperature is less than 20 ° C., the weather resistance deteriorates, and even if the temperature exceeds 60 ° C., the effect of improving the weather resistance is saturated, which is not preferable from the viewpoint of safety and energy saving. If the standing time after adding metallic chromium to the phosphoric acid aqueous solution is less than 24 hours, the weather resistance may not be sufficient.

The solution prepared in advance in the present invention cannot strictly define the chemical state of phosphoric acid and chromium, but the state in which chromium and phosphoric acid are separately present as ions has better coating performance on magnet powder. Presumed to be higher.
More preferably, 10-25% by weight of metal chromium powder is added to the phosphoric acid aqueous solution and left at 25-50 ° C. for 24-30 hours, and then only the supernatant is recovered to remove the metal chromium powder. It is an aqueous solution.

  The amount of the phosphoric acid solution containing chromium to be added to the organic solvent is not generally determined because it is related to the particle size, surface area, etc. of the magnet powder after pulverization. It is preferable that it is 0.1 mol-0.5 mol of phosphoric acid with respect to 1 kg of a system magnet alloy powder. More preferably, it is 0.2 mol-0.4 mol of phosphoric acid with respect to 1 kg of iron-based magnet alloy powder containing rare earth elements, and more preferably 0.25 mol-0.35 mol. If the added amount is less than 0.1 mol of phosphoric acid, the surface of the pulverized magnet powder is not sufficiently covered, so that the weather resistance is not improved. As a result, the magnetic properties are extremely deteriorated. When the addition amount exceeds 0.5 mol of phosphoric acid, the surface coating treatment of the magnet powder is sufficiently performed, but the coating thickness is increased, so that the magnetic properties are deteriorated, and the weather resistance is not further improved.

(Fine grinding)
Next, when producing magnet alloy powder for bonded magnets by pulverizing iron-based magnet alloy powder containing rare earth elements in an organic solvent, the phosphoric acid solution containing chromium obtained by the above method is placed in the organic solvent. A fine pulverization treatment is performed to add a fixed amount and pulverize to form a protective film on the surface of the iron-based magnet alloy powder containing the rare earth element.
The means for the fine pulverization treatment is not particularly limited, but it is desirable to employ a stirring medium mill such as a ball mill or a bead mill that uses ceramic balls or beads as the pulverizing medium and stirs in an organic solvent. The rare earth-iron-nitrogen based alloy powder can be slurried by putting it in, for example, a stirring medium mill and finely pulverizing it to a predetermined particle size. The rotational speed of the stirring medium mill is 1 to 5 m / s, preferably 1.5 to 3 m / s, although it depends on other conditions.

  When pulverizing with the above-mentioned pulverizer, it is desirable to supply an inert gas so that the iron-based magnet alloy powder containing the rare earth element is hardly oxidized. The pulverization time varies depending on the size of the pulverizer, the particle size of the rare earth magnet powder to be processed, the processing amount, and the like, and is set so as to obtain the desired magnetism.

  In the present invention, a phosphoric acid solution containing chromium prepared in advance is used, but phosphoric acid can be further added in the pulverization step. The amount of phosphoric acid described above means the total amount added finally to the slurry, and the desired phosphoric acid concentration is such that the newly fractured surface generated by grinding the rare earth magnet powder is immediately surface-treated. There is no particular limitation as long as phosphoric acid is always present in the solution. For example, when pulverizing with a medium stirring mill or the like, all necessary amounts are added to the organic solvent used as a solvent at one time before pulverization. Or may be gradually added during pulverization.

  By the above-mentioned fine pulverization treatment, the average particle diameter of the pulverized rare earth magnet alloy powder is approximately 1 to 5 μm, preferably 2 to 4 μm, and the surface of the magnet powder contains chromium having a suitable thickness. It is uniformly coated and stabilized. Here, being uniformly coated means that 80% or more, preferably 85% or more, more preferably 90% or more of the surface of the rare earth magnet powder is covered with a phosphate film containing chromium.

  According to the fine pulverization method, even when the rare earth magnet alloy powder is pulverized and a new surface is formed, it reacts instantaneously with phosphoric acid containing chromium in the organic solvent, and the organic solvent is substantially free of oxygen. In combination with this, a phosphate film containing chromium is formed on the surface of the rare earth magnet alloy powder. Also, even if the magnetic powder once formed with a phosphate film containing chromium on the surface may be agglomerated due to its magnetic force, the contact surface is already stabilized by the film, and corrosion due to crushing It does not occur.

  When the fine pulverization process is performed without adding chromium-containing phosphoric acid to the fine pulverization process of the present invention, the iron-based magnet alloy powder containing the rare earth element is pulverized, the agglomerated particles are released, and the new surface is removed. Even if it occurs, the new surface cannot be subjected to surface treatment, and the particle size of the obtained powder becomes uneven, or a defect occurs on the surface of the powder, so that high quality magnet powder cannot be produced.

  In addition, even if a processing agent such as phosphoric acid containing chromium is added after the fine pulverization of the iron-based magnet alloy powder containing the rare earth element, the pulverized magnet powder is agglomerated with each other due to magnetic force, etc. No film is formed on the surface where the powders are in contact. Therefore, since the obtained rare earth magnet alloy powder has insufficient formation of a phosphate film containing chromium, when the bonded magnet is kneaded with a resin binder, the agglomerated rare earth magnet alloy powder is kneaded. The active powder surface that is partially crushed by the shearing force and is not formed with a film is exposed. For this reason, in a bonded magnet obtained by molding such rare earth magnet powder, corrosion easily occurs in a practically important humidity environment, and the magnetic properties are deteriorated. In particular, in a magnet powder showing a nucleation type coercive force expression mechanism such as a samarium-iron-nitrogen alloy, the coercive force is remarkably lowered when such a region is generated.

(4) Solid-liquid separation of slurry containing iron-based magnet alloy powder containing rare earth element, heat treatment Iron-based magnet alloy powder containing rare earth element obtained in the fine pulverization process, phosphoric acid containing chromium and organic solvent The slurry containing is supplied to a solid-liquid separator. The slurry is treated with a solid-liquid separator to remove most of the liquid, and becomes an iron-based magnet alloy powder cake containing a rare earth element having a liquid content of 5 to 30% by weight, for example.

As the solid-liquid separation device, a filter type filter such as a Nutsche type filter or a centrifugal filter, a decanter type centrifugal separator or the like can be used. However, the solid-liquid separation is performed in consideration of the powder properties, filterability, etc. of the slurry. It is necessary to select a device.
For example, in a filter type filter, the influence of powder properties on filterability is large, and the liquid content may be difficult to control as an apparatus parameter. Moreover, since the slurry containing the iron-based magnet alloy powder containing rare earth elements has very poor filterability, it takes a lot of time to filter with a filter, and it is often difficult to achieve a low liquid content.

  Here, the liquid content of the iron-based magnet alloy powder cake containing the rare earth element obtained is adjusted to 5 to 30% by weight, preferably 10 to 30% by weight. If the liquid content exceeds 30% by weight, the magnet powder aggregates and becomes agglomerate during the heat treatment in the next step, and a process for crushing them separately is required. In addition, the heat treatment is unfavorable because the treatment time becomes long and the production efficiency is lowered. On the other hand, if the liquid content is less than 5% by weight, it may ignite in the atmosphere or oxidize and generate heat, which may deteriorate the magnetic properties.

Next, the iron-based magnet alloy powder cake containing rare earth elements obtained by solid-liquid separation is heat-dried.
Specifically, the obtained iron-based magnet alloy powder cake containing rare earth elements is transferred to a heat treatment apparatus, and then heat-treated in a specific temperature range in vacuum or in an inert gas. For this heat treatment, a mixer type dryer, a processed product stationary type box type dryer or the like can be used.

  The heat treatment is preferably performed in a temperature range of 150 ° C. or higher, in a vacuum or in an inert gas such as nitrogen or Ar, for the obtained iron-based magnet alloy powder cake containing rare earth elements, and 150 to 220 ° C. In particular, it is preferable to perform the heat treatment in a temperature range of 160 to 180 ° C. When the heat treatment is performed at a temperature lower than 150 ° C., the rare earth magnet alloy powder is not sufficiently dried, and the hydrogen taken into the magnet alloy powder is not sufficiently removed, so that the magnetic properties are deteriorated. In addition, when heat treatment is performed at a temperature exceeding 220 ° C., there is a problem that the magnetic properties are deteriorated because the rare earth magnet powder is thermally damaged.

In the case where the heat treatment is performed in a vacuum, it is desirable that the heat treatment tank is maintained at a vacuum degree of 1.33 × 10 ³ Pa or less, preferably 6.66 × 10 ² Pa or less. If the degree of vacuum is worse than this, the magnetic properties may deteriorate. This is presumably because, when the degree of vacuum is poor, the heat treatment time must be lengthened, so that the influence of the oxidation of the alloy magnet powder surface increases.

  The heat treatment time varies depending on the size of the apparatus, the particle diameter of the magnetic alloy powder to be treated, the amount of treatment, and the like, and cannot be defined generally, but it is desirable that the heat treatment time be as short as possible. For example, when 50 kg of magnetic alloy powder is processed with a 100-liter stirring type dryer, it is preferably within 2 hours, particularly within 90 minutes, after the temperature of the alloy powder reaches a predetermined temperature. The longer the heat treatment time, the more likely it is due to oxidation, but the residual magnetic flux density decreases. However, if it is shorter than 10 minutes, a stable phosphate film containing chromium may not be formed.

2. Magnet alloy powder for bonded magnet The magnet alloy powder for bonded magnet using the iron-based magnet alloy powder containing rare earth element according to the present invention is obtained by the above-described manufacturing method, and the surface of the iron-based magnet alloy powder containing rare earth element is chromium. As described above, the average particle diameter is 1 to 5 μm, preferably 2 to 4 μm. If the average particle size is less than 1 μm, the production cost is high, and if it exceeds 5 μm, the magnetic properties are deteriorated.

  The thickness of the phosphate film containing chromium necessary for protecting the magnet powder surface is usually 5 to 100 nm on average. When the average thickness of the phosphoric acid film containing chromium is less than 5 nm, sufficient weather resistance cannot be obtained, and when it exceeds 100 nm, the magnetic properties are deteriorated and the kneadability and moldability when producing a bonded magnet are reduced. It will decline.

3. Composition for Bond Magnet To produce a resin composition for a bond magnet using the magnet powder for bond magnet of the present invention, for example, a resin binder such as a known thermoplastic resin or thermosetting resin as shown below, Additives can be used.

As described above, the magnet powder for bonded magnets of the present invention is partly re-aggregated through heat drying treatment, but a protective film of phosphoric acid containing chromium is formed, and the cohesive force is Since the resin composition is weak, it is deagglomerated again when the resin composition is used, and the obtained resin composition for bonded magnets can be easily oriented in a magnetic field. Therefore, the obtained molded body has a high residual magnetization. In addition, since the dispersibility is improved, the flowability of the resin composition for bonded magnets using the magnet alloy powder is also improved, so that the moldability is excellent.
The resin binder is not particularly limited, and may be various thermoplastic resins alone or a mixture, or various thermosetting resins alone or a mixture, and the physical properties and properties of each may be within a range where desired characteristics can be obtained. It will never be done.

(Thermoplastic resin)
The thermoplastic resin is not particularly limited as long as it functions as a binder for the magnet alloy powder, and conventionally known ones can be used. Specific examples include 6 nylon, 6-6 nylon, 11 nylon, 12 nylon, 6-12 nylon, aromatic nylon, polyamide resins such as modified nylon partially modified from these molecules, and linear polyphenylene sulfide. Resin, cross-linked polyphenylene sulfide resin, semi-cross-linked polyphenylene sulfide resin, low density polyethylene, linear low density polyethylene resin, high density polyethylene resin, ultrahigh molecular weight polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, ethylene- Ethyl acrylate copolymer resin, ionomer resin, polymethylpentene resin, polystyrene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, polyvinyl chloride resin, polyvinylidene chloride Fatty, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyvinyl formal resin, methacrylic resin, polyvinylidene fluoride resin, polytrifluoroethylene chloride resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, ethylene- Tetrafluoroethylene copolymer resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, polytetrafluoroethylene resin, polycarbonate resin, polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene oxide resin, polyallyl ether allyl Sulfone resin, polyethersulfone resin, polyetheretherketone resin, polyarylate resin, aromatic polyester resin, cellulose acetate resin, each resin system mentioned above Elastomer, and the like, random copolymers of these homopolymers and other species monomer, block copolymers, graft copolymers, and end groups modified products with other substances.

  It is desirable that the melt viscosity and molecular weight of these thermoplastic resins be low as long as desired mechanical strength can be obtained for the obtained bonded magnet. Further, the shape of the thermoplastic resin is not particularly limited, such as powder, bead, pellet, etc., but powder is preferable in that it is uniformly mixed with the magnet alloy powder.

  The compounding quantity of a thermoplastic resin is 5-50 weight part normally with respect to 100 weight part of rare earth magnet powder, Preferably it is 5-30 weight part, More preferably, it is 5-15 weight part. When the blending amount of the thermoplastic resin is less than 5 parts by weight, the kneading resistance (torque) of the composition is increased, and the fluidity is lowered, making it difficult to mold the magnet. The amount of powder is small and desired magnetic properties cannot be obtained. Various coupling agents, lubricants, various stabilizers, and the like can be blended in order to improve the heat fluidity and the like of the composition for bonded magnets as long as the object of the present invention is not impaired.

(Thermosetting resin)
On the other hand, examples of the thermosetting resin include resins such as unsaturated polyester resin, vinyl ester resin, urethane (meth) acrylate resin, and polyester (meth) acrylate resin having radical polymerization reactivity. In addition, epoxy resin, polyvinyl butyral, and phenol resin can be used. Among these, unsaturated polyester resin or vinyl ester resin is preferable. Although not limited by the degree of polymerization or the molecular weight, a resin that is liquid at a temperature of 150 ° C. or lower and has a viscosity at 25 ° C. of 5000 mPa · s or lower is preferable from the viewpoint of moldability.

The unsaturated polyester resin is a thermosetting resin comprising an unsaturated polyester obtained by a polycondensation reaction between a polyhydric alcohol and a saturated polybasic acid and / or an unsaturated polybasic acid, and a monomer copolymerizable with the ester. is there.
Here, the polyhydric alcohol is not particularly limited, and examples thereof include hydrogenated bisphenol A, hydrogenated bisphenol F, bisphenol A propylene oxide adduct, bisphenol F propylene oxide adduct, and hydrogenated bisphenol S. Ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,6-hexanediol, dibromoneopentyl glycol, pentaerythrit diallyl ether, allyl glycidyl ether, etc. Can be mentioned.
These polyhydric alcohols may be used alone or in combination of two or more. In the present invention, those containing a polyhydric alcohol having a bisphenol skeleton, hydrogenated bisphenol A, hydrogenated bisphenol F or the like in at least a part of the molecular structure are more preferred.

  Saturated polybasic acids include phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, adipic acid, sebacic acid, het acid, tetrabromophthalic anhydride, etc. Can be mentioned. Examples of the unsaturated polybasic acid include maleic anhydride, fumaric acid, itaconic acid and the like, but are not particularly limited. These dibasic acids may be used alone or in combination of two or more.

  The vinyl ester resin can be obtained, for example, by addition reaction of an epoxy compound and an unsaturated monobasic acid. The epoxy compound used as a raw material for the vinyl ester resin is not particularly limited as long as it is a compound having at least one epoxy group in the molecule. Specifically, for example, an epibis type glycidyl ether type epoxy resin obtained by a condensation reaction between bisphenols such as bisphenol A and bisphenol S and epihalohydrin; phenol, cresol, novolak which is a condensate of bisphenol and formalin; Novolac type glycidyl ether type epoxy resin obtained by condensation reaction with epihalohydrin; glycidyl ester type epoxy resin obtained by condensation reaction of tetrahydrophthalic acid, hexahydrophthalic acid, benzoic acid and epihalohydrin; water-added bisphenol or glycols and epihalohydrin Glycidyl ether type epoxy resin obtained by condensation reaction with amine; Amine-containing glycidyl obtained by condensation reaction of hydantoin or cyanuric acid with epihalohydrin Ether type epoxy resins.

Moreover, the compound which has an epoxy group in a molecule | numerator by addition reaction with these epoxy resins, polybasic acids, and / or bisphenols may be sufficient. Only one kind of these epoxy compounds may be used, or two or more kinds may be appropriately mixed. In the present invention, among these, those containing at least polyhydric alcohol having a bisphenol skeleton, hydrogenated bisphenol A, hydrogenated bisphenol F, and the like are more preferable.
Although it does not specifically limit as unsaturated monobasic acid, Specifically, acrylic acid, methacrylic acid, cinnamic acid, crotonic acid, etc. are mentioned. Moreover, you may use half esters, such as maleic acid and itaconic acid. Furthermore, these compounds are combined with polyvalent carboxylic acids such as fumaric acid, itaconic acid and citraconic acid, saturated monovalent carboxylic acids such as acetic acid, propionic acid, lauric acid and palmitic acid, and saturated polyvalent carboxylic acids such as phthalic acid. You may use together an acid or its anhydride, and compounds, such as a saturated or unsaturated alkyd whose terminal group is a carboxyl group. These unsaturated monobasic acids may use only 1 type and may mix 2 or more types suitably.

  The thermosetting resin contains an organic peroxide as a reaction initiator. In addition, an N-oxyl compound for improving the pot life, phenol, a polymerization inhibitor, a low shrinkage agent, and the like can be blended. Moreover, a copolymerizable monomer can be blended with these unsaturated polyester resin, vinyl ester resin and the like. Examples of the copolymerizable monomer include (I) vinyl monomers such as styrene, vinyl toluene, α-methyl styrene, methyl methacrylate, vinyl acetate, (II) diallyl phthalate, diallyl maleate, diallyl isophthalate, diallyl. Allyl monomers such as terephthalate, triallyl isophthalate, triallyl isocyanurate, diallyl tetrabromophthalate, (III) acrylics such as phenoxyethyl acrylate, 1,6-hexanediol acrylate, trimethylpropane triacrylate, 2-hydroxyethyl acrylate Examples include acid esters. These copolymerizable monomers may be used alone or in combination of two or more, and the addition amount of the monomer is not particularly limited.

  Various mixers, kneaders, and extruders can be used for mixing and kneading the rare earth magnet alloy powder and the resin binder.

4). Bond Magnet Resin composition for bonded magnet containing magnet powder for bonded magnet manufactured by the method of the present invention is an injection molding method, extrusion molding method, injection compression molding method, injection, which has been conventionally used for plastic molding and the like. A bonded magnet can be obtained by molding using various molding methods such as press molding and transfer molding. Among these molding methods, an injection molding method, an extrusion molding method, an injection compression molding method, and an injection press molding method are particularly preferable. Further, an anisotropic bonded magnet can be produced by applying a magnetic field during molding.

  When the above resin composition for bonded magnet uses a thermoplastic resin as a resin binder, it is heated and melted at the melting temperature of the resin and then molded into a magnet having a desired shape.

(Molding by injection molding method)
In the injection molding method, a composition containing a thermoplastic resin and magnet alloy powder is melted at a temperature of 250 ° C. or higher, supplied into the mold cavity, and then cooled to take out the molded body. In this case, as the resin binder, for example, as described above, thermoplastic resins such as polyamide, polybutylene terephthalate, liquid crystal resin, and polyphenylene sulfide can be used.
In addition, when using a composition containing a thermosetting resin and a magnet alloy powder, the composition is supplied into a mold cavity in a fluid state, and then heated to a temperature equal to or higher than the thermosetting temperature of the resin, The obtained molded body is taken out at room temperature.

  In general, in the injection molding method, when using iron-based magnet alloy powder containing rare earth elements with no surface coating, kneading torque when kneading and injection molding rare earth magnet alloy powder and specific resin binder May become difficult to form. When the iron-based magnet alloy powder containing rare earth elements of the present invention is used, the finely divided magnet powder itself is uniformly coated and stabilized with a phosphoric acid film containing chromium, so that it can be molded without any problems. Can do.

  The resin binder is added in a ratio of 2 to 50 parts by weight with respect to 100 parts by weight of the magnet powder for bonded magnet in a state including each component, but 3 to 20 parts by weight, and further 10 to 15 parts by weight. It is preferable to add a part. When the addition amount of the resin binder is less than 2 parts by weight with respect to 100 parts by weight of the magnet powder, the strength of the molded body is remarkably lowered and the fluidity at the time of molding is lowered. On the other hand, if it exceeds 50 parts by weight, desired magnetic properties cannot be obtained.

(Molding by compression molding method)
Moreover, when shape | molding by the compression molding method, the composition for bonded magnets obtained by mixing thermosetting resin liquefied with the solvent etc. with stirring with the magnet alloy powder of this invention is used. As the resin binder, for example, an epoxy resin, a polyvinyl butyral, a phenol resin, an unsaturated polyester, a vinyl ester, or the like can be used. The usage-amount of the resin binder is 0.5 to 15 weight% normally with respect to the rare earth-iron-nitrogen based magnet alloy powder of this invention, Preferably, it is 0.7 to 10 weight%. If the resin binder is too much, the magnetic properties of the resulting bonded magnet will be unsatisfactory, and if it is too small, the strength of the bonded magnet will be unsatisfactory.

  Examples of the present invention and comparative examples are shown below, but the present invention is not limited to these examples.

<Phosphate solution containing chromium>
The phosphoric acid solution containing chromium was prepared in the following manner prior to fine pulverization of the magnet powder. Addition of 20% by weight (Example 1), 10% by weight (Example 2), 25% by weight (Example 3), 3% by weight (comparison) of metallic chromium powder to 85% phosphoric acid aqueous solution Example 2), 40% by weight (Comparative Example 3) was added, and the solution was allowed to stand at 25 ° C. for 24 hours. As the metal chromium powder, CRE03PB manufactured by High Purity Chemical Laboratory Co., Ltd., having a purity of 99% and having a size of 63 μm, was used.

  In addition, the evaluation method of the iron-based magnet alloy powder containing rare earth elements used in Examples and Comparative Examples is as follows.

[Coercivity evaluation]
After measuring the coercive force of the obtained magnet powder sample at room temperature with a vibrating sample magnetometer (manufactured by Riken Denshi Co., Ltd.), after leaving it in an atmosphere of 80% relative humidity and 95% relative humidity for 24 hours and 200 hours, Measurement was performed with a vibrating sample magnetometer.

Example 1
1976 g of samarium oxide powder, 4221 g of iron powder, and 801.5 g of calcium were mixed and subjected to reduction diffusion treatment at 1150 ° C. for 270 minutes to obtain a reduction diffusion product. Thereafter, the reduced diffusion material was put into water, and acetic acid was added to make a 4 wt% acetic acid solution. Then, calcium oxide was removed while stirring to obtain a samarium-iron alloy powder.
Next, the obtained samarium-iron alloy powder was subjected to nitriding treatment at 450 ° C. under conditions using a mixed gas of ammonia gas 4.7 L / min and hydrogen gas 9.3 L / min for 350 minutes.
1 kg of the obtained samarium-iron-nitrogen alloy powder (average particle size 20 μm) was added to ethanol and an organic solvent (phosphoric acid concentration: 0.3 mol) in which 35 g of the prepared phosphoric acid solution containing chromium was added. The mixture was made into a slurry and finely pulverized using a medium stirring mill (manufactured by Ashizawa Finetech Co., Ltd.).
Next, the slurry containing the samarium-iron-nitrogen magnet alloy powder after pulverization was transferred to a filtration device for solid-liquid separation, and the liquid content was adjusted to 15% by weight. Thereafter, the dewatered magnet alloy powder cake is supplied to a drying device, maintained at a vacuum of 1.33 × 10 ³ Pa or less, and dried at 160 ° C. for 2 hours to be samarium-iron-nitrogen magnet alloy for bonded magnets. Powder was produced.
When the surface of the magnet alloy powder was observed with an SEM, a film containing chromium phosphate having a thickness of 30 μm was formed.
The weather resistance of the obtained rare earth-iron-nitrogen based magnet alloy powder was evaluated by the evaluation method based on the change in the coercive force. The results are shown in Table 1.

(Examples 2 and 3)
The type of phosphoric acid solution containing chromium was changed to use 10% by weight of chromium metal added (Example 2) or 25% by weight added (Example 3), or 35g of each solution was added. A samarium-iron-nitrogen magnet combination was produced in the same manner as in Example 1 except that it was put in an organic solvent.
The weather resistance of the obtained samarium-iron-nitrogen magnet alloy powder was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Comparative Example 1)
A samarium-iron-nitrogen magnet alloy powder was produced in the same manner as in Example 1 except that a samarium-iron-nitrogen magnet alloy powder slurry was made in ethanol without adding a phosphoric acid solution containing chromium.
The weather resistance of the obtained samarium-iron-nitrogen magnet alloy powder was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. Although it was pulverized in ethanol without adding phosphoric acid, the magnet alloy powder has no surface coating, and the initial coercive force is larger than when pulverized in an organic solvent with phosphoric acid added. Oxidation progressed when left in an atmosphere at 80 ° C. and a relative humidity of 95% for 24 hours, resulting in demagnetization.

(Comparative Examples 2 and 3)
As the phosphoric acid solution containing chromium, one containing 3% by weight of metal chromium (Comparative Example 2) or 40% by weight (Comparative Example 3) was used, and 35 g of each solution was added to an organic solvent. Except for this, a samarium-iron-nitrogen magnet combination was produced in the same manner as in Example 1.
The weather resistance of the obtained samarium-iron-nitrogen magnet alloy powder was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Comparative Example 4)
A samarium-iron-nitrogen magnet combination was produced in the same manner as in Example 1 except that chromium was not added and the organic solvent was added with 35 g of phosphoric acid alone.
The weather resistance of the obtained samarium-iron-nitrogen magnet alloy powder was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Summary)
From the evaluation results of Examples 1 to 3 shown in Table 1, the decrease in coercive force after being left in an atmosphere of 95% relative humidity at 80 ° C. for 24 hours and 200 hours is low, and according to the present invention, phosphorus containing a specific amount of chromium is used. It can be seen that the weather resistance of the samarium-iron-nitrogen magnet alloy powder surface-coated with acid is improved. If this magnet alloy powder is used, since it has excellent weather resistance and magnetic properties, it is possible to produce a bond magnet using a thermoplastic resin such as polyamide and PPS, and a thermosetting resin such as unsaturated polyester as a binder.

On the other hand, in Comparative Example 1, pulverization was performed in ethanol without adding phosphoric acid and chromium, but oxidation proceeded after leaving it for 24 hours, and it became non-magnetic.
Comparative Example 2 is a case where phosphoric acid having a low chromium content is added, and the decrease in coercive force after leaving in an atmosphere of 80 ° C. and 95% relative humidity for 200 hours is significantly large, and the weather resistance is low. I understand that. Comparative Example 3 is a case where phosphoric acid having a high chromium content is added, and it is recognized that the decrease in coercive force is small and the weather resistance is high, but the effect of weather resistance is different from Example 3 in which 25% by weight is added. Absent.
Further, Comparative Example 4 is a case where 35 g of phosphoric acid to which chromium is not added is put in an organic solvent, and, as in Comparative Example 2, after being left in an atmosphere of 80 ° C. and 95% relative humidity for 200 hours. It can be seen that the decrease in coercive force is remarkably large and the weather resistance after standing for a long time is low.
The magnet alloy powders as in Comparative Examples 1, 2, and 4 have insufficient weather resistance and magnetic properties, so a desired bonded magnet using a thermoplastic resin such as polyamide or PPS, or a thermosetting resin such as unsaturated polyester as a binder. Can not be manufactured. In Comparative Example 3, the amount of chromium used is large, which is not preferable in terms of economy.

  Since the magnet alloy powder for bonded magnets obtained by the present invention has excellent weather resistance and high properties such as coercive force, an iron-based bonded magnet containing a rare earth element can be formed by mixing a resin binder, and the resulting bond Magnets are extremely useful in a wide range of fields such as general home appliances, communication / acoustic equipment, medical equipment, general industrial equipment, and the like.

Claims (3)

A method for producing a magnet alloy powder for a bonded magnet by pulverizing an iron-based magnet alloy powder containing a rare earth element in an organic solvent,
Add 5-30% by weight of metal chromium powder to the phosphoric acid aqueous solution in advance and leave it at 20-60 ° C. for 24 hours or more, and then prepare a phosphoric acid solution containing chromium by removing the remaining metal chromium powder. When the iron-based magnet alloy powder containing the rare earth element is pulverized in an organic solvent, the phosphoric acid solution containing chromium is added to the organic solvent and pulverized, and the iron-based magnet alloy containing the rare earth element is added. A fine pulverization process for forming a protective coating on the powder surface;
The slurry containing the iron-based magnet alloy powder containing the finely pulverized rare earth element is subjected to solid-liquid separation, and the heat-drying treatment step for heating and drying the iron-based magnet alloy powder containing the separated rare earth element;
A method for producing a magnet alloy powder for bonded magnets.   The amount of the phosphoric acid solution containing chromium added to the organic solvent is 0.1 mol to 0.5 mol of phosphoric acid with respect to 1 kg of iron-based magnet alloy powder containing rare earth elements to be pulverized. The manufacturing method of the magnet alloy powder for bonded magnets of description.   The organic solvent contains 1 or more types of alcohol chosen from ethanol or 2-propanol (IPA), The manufacturing method of the magnet alloy powder for bonded magnets of Claim 1 or 2 characterized by the above-mentioned.