JPH1012472A - Manufacture of rare-earth bond magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare-earth bond magnet having a low hole rate, high dimensional precision, excellent moldability and excellent magnetic characteristics. SOLUTION: First, rare-earth magnetic powder, binder resin composed of thermoplastic resin and antioxidant are mixed with predetermined ratios and the mixture is kneaded at a temperature higher than the heat deformation temperature. Then the kneaded mixture is granulated or rectified to obtain grains. The grains are subjected to the compression molding at a 1st temperature at which the thermoplastic resin is softened or melt and then cooled to a 2nd temperature which is at least lower than the 1st temperature while the pressure is applied and the thermoplastic resin is solidified to obtain a rare-earth bond magnet. It is recommended that the 2nd temperature is lower than the melting point or the heat deformation temperature of the thermoplastic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a rare earth bonded magnet and a composition for a rare earth bonded magnet.

[0002]

2. Description of the Related Art Rare earth bonded magnets are manufactured by pressing a mixture (compound) of a rare earth magnet powder and a binder resin (organic binder) into a desired magnet shape. The molding method by the pressure molding is roughly classified into a compression molding method, an injection molding method and an extrusion molding method.

[0003] In the compression molding method, the compound is filled in a press die, and the compound is compression-molded at a predetermined temperature to obtain a molded body. Then, when the binder resin is a thermosetting resin, it is cured. This is a method of making a magnet. This method
Compared with other methods, molding is possible even with a small amount of the binder resin, so that the amount of resin in the obtained magnet is reduced, which is advantageous for improving magnetic properties.

The extrusion molding method is a method of extruding a heated and melted compound from a mold of an extrusion molding machine, solidifying it by cooling, cutting it into a desired length, and forming a magnet.
In this method, the degree of freedom for the shape of the magnet is large, there is an advantage that a thin, long magnet can be easily manufactured, but in order to ensure the fluidity of the melt during molding,
It is necessary to increase the addition amount of the binder resin compared to that of the compression molding method, and therefore, the resin amount in the obtained magnet is large,
There is a disadvantage that the magnetic properties tend to decrease.

The injection molding method is a method in which the compound is heated and melted, and the molten material is poured into a mold in a state where the compound has sufficient fluidity, and is molded into a predetermined magnet shape. In this method, the degree of freedom with respect to the shape of the magnet is greater than in the extrusion molding method, and in particular, there is an advantage that a magnet having a different shape can be easily manufactured. However, since the fluidity of the melt during molding requires a higher level than that of the extrusion molding method, the amount of the binder resin to be added needs to be further increased as compared with that of the extrusion molding method. However, there is a disadvantage that the amount of resin in the magnet is large and the magnetic properties tend to deteriorate.

[0006]

Among the above-mentioned methods, compression molding which can form a magnet having the highest magnetic performance has the following disadvantages.

First, the manufactured rare earth bonded magnet is:
Although the density of the molded article is high, the porosity tends to increase, so that the mechanical strength is weak and the corrosion resistance is poor. Therefore, particularly in the compression molding method, high pressure molding in which the molding pressure is as high as 70 kgf / mm ² or more has been utilized, or a method such as applying a corrosion-resistant coating treatment after molding has been used. However, high-pressure molding imposes a heavy burden on the molding machine, and in the case of performing anticorrosion coating treatment, a step for that purpose is added, which lowers productivity and increases production costs due to the complexity of the production process. Invite.

Second, in a compound using a thermosetting resin, since the resin is in an uncured state, a change in physical properties due to the curing of the resin and a change in physical properties due to water absorption occur. Change. As a result, even when molded under the same conditions, the dimensions and density of the molded body change, making it difficult to perform stable molding. In addition, when a thermosetting resin is used, a curing (curing) step is required, which not only leads to an increase in the number of steps and cost, but also a change in dimensions due to a reaction of the resin during the curing. In order to secure the target dimensions, it is necessary to correct the mold dimensions, and it is not easy to secure the dimensions.

In the case of conventional compression molding, both thermosetting resins which are solid and liquid at room temperature are used. Among them, when the former solid resin is used, the material supply property is relatively good, but the moldability is poor, and the porosity tends to be higher. In addition, the dispersibility of the resin and the magnet powder is poor, and as a result, the mechanical strength decreases. On the other hand, when the latter liquid resin is used, it is possible to obtain a high-density molded body, but the physical properties of the resin are sensitively affected by the environment (temperature, humidity) at the time of molding, and the The filling property decreases.

[0010] For this reason, the target dimensions of the magnet are varied, that is, the dimensional accuracy is poor, and the stability of molding is lacking. In particular, in the case of a small magnet, this disadvantage becomes remarkable. Since the size variation is large in this way, it is necessary to adjust the size by secondary processing such as cutting and polishing after forming the target magnet product larger than the target size in order to secure the target size of the final magnet product. As a result, the number of steps is increased, and a defective material is generated by processing, so that the productivity is reduced and the manufacturing cost is increased. Further, in order to eliminate such defects, special measures must be taken for the structure and the molding process of the molding machine, and the molding machine is significantly consumed and the molding cycle time becomes long.

Further, one of the first and second drawbacks described above is that the compound manufacturing method, manufacturing conditions, temperature conditions during molding, cooling conditions after molding, and the like are inappropriate. ing.

Accordingly, an object of the present invention is to provide a method of manufacturing a rare earth bonded magnet which can easily manufacture a low porosity rare earth bonded magnet having excellent moldability, magnetic properties and dimensional stability. .

[0013]

This and other objects are achieved by the present invention which is defined below as (1) to (17).

(1) A method for producing a rare-earth bonded magnet in which rare-earth magnet powder is bound by a binding resin made of a thermoplastic resin, wherein the rare-earth magnet powder and the binding resin are mixed and kneaded to obtain a kneaded product. A step of producing, a step of granulating or sizing the kneaded product to form a granular material, and a step of press-molding the binder resin at a first temperature at which the binder resin is in a softened or molten state using the granular material. And cooling at least to a second temperature lower than the first temperature in a pressurized state.

(2) The kneading is performed at a temperature equal to or higher than the thermal deformation temperature of the binder resin and in such a state that the surface of the rare earth magnet powder is covered with the melted or softened binder resin component. The method for producing a rare-earth bonded magnet according to 1).

(3) The method for producing a rare earth bonded magnet as described in (1) or (2) above, wherein the content of the rare earth magnet powder in the kneaded material is 90 to 99 wt%.

(4) The method for producing a rare earth bonded magnet according to any one of the above (1) to (3), wherein the kneaded material contains an antioxidant.

(5) The method for producing a rare-earth bonded magnet according to (4), wherein the content of the antioxidant in the kneaded material is 0.1 to 2% by weight.

(6) The method for producing a rare earth bonded magnet according to any one of the above (1) to (5), wherein the granulation or sizing is performed by pulverization.

(7) The granular material has an average particle size of 10 μm.
The method for producing a rare-earth bonded magnet according to any one of the above (1) to (6), which has a thickness of 2 mm.

(8) The method for manufacturing a rare earth bonded magnet according to any one of the above (1) to (7), wherein the pressure molding is compression molding.

(9) The method for manufacturing a rare earth bonded magnet according to any one of the above (1) to (8), wherein the second temperature is a melting point of the binding resin.

(10) The method for manufacturing a rare earth bonded magnet according to any one of the above (1) to (8), wherein the second temperature is a thermal deformation temperature of the binder resin.

(11) The method for manufacturing a rare-earth bonded magnet according to any one of (1) to (10), wherein a difference between the first temperature and the second temperature is 20 ° C. or more.

(12) The rare earth bond according to any one of (1) to (11), wherein the cooling in the pressurized state is performed continuously without releasing the pressurization during the pressurizing. Manufacturing method of magnet.

(13) The rare earth bond according to any one of the above (1) to (12), wherein the pressure at the time of cooling in the pressurized state is equal to or less than the molding pressure at the time of the pressure molding. Manufacturing method of magnet.

(14) The production of the rare-earth bonded magnet according to any one of the above (1) to (13), wherein the pressure during cooling in the pressurized state is kept constant at least up to the melting point of the binder resin. Method.

(15) Any of the above (1) to (13), wherein the pressure at the time of cooling in the pressurized state is kept constant at least up to a temperature between the first temperature and the second temperature. A method for producing a rare-earth bonded magnet according to any one of the above.

(16) The method for producing a rare-earth bonded magnet according to any one of the above (1) to (15), wherein the cooling rate at the time of cooling in the pressurized state is 0.5 to 100 ° C./sec.

(17) The molding pressure during the pressure molding is 6
The method for producing a rare-earth bonded magnet according to any one of the above (1) to (16), which is 0 kgf / mm ² or less.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a rare earth bonded magnet of the present invention will be described in detail.

The method for producing a rare-earth bonded magnet of the present invention comprises:
It mainly has the following steps.

<1> Production of Kneaded Product of Rare Earth Bonded Magnet Composition First, a rare earth bonded magnet composition (hereinafter simply referred to as “composition”)
Adjust). This composition is mainly composed of a rare earth magnet powder and a binder resin (binder). Further, it preferably contains an antioxidant, and other additives are added as necessary. These components are mixed using, for example, a mixer such as a Henschel mixer or a stirrer, and further kneaded as described later to obtain a kneaded material.

Hereinafter, each of these components will be described.

1. Rare earth magnet powder The rare earth magnet powder is preferably made of an alloy containing a rare earth element and a transition metal. In particular, the following [1]-
[4] is preferred.

[1] A rare earth element mainly composed of Sm and C
a transition metal mainly composed of o (hereinafter, referred to as a basic component)
Sm-Co alloy).

[2] R (where R is at least one of rare earth elements including Y), a transition metal mainly composed of Fe, and B (hereinafter, R-Fe-B)
System alloy).

[3] A rare earth element mainly composed of Sm and F
A material mainly composed of a transition metal mainly composed of e and an interstitial element mainly composed of N (hereinafter, referred to as an Sm-Fe-N-based alloy).

[4] R (where R is at least one of rare earth elements including Y) and a transition metal such as Fe as basic components and having a magnetic phase at the nanometer level (hereinafter referred to as “nanocrystal Magnet ").

[5] A mixture of at least two of the above-mentioned compositions [1] to [4]. In this case, the advantages of the respective magnet powders to be mixed can be obtained, and more excellent magnetic properties can be easily obtained.

Representative Sm-Co alloys include SmCo ₅ and Sm ₂ TM ₁₇ (where TM is a transition metal).

Representative R-Fe-B alloys include Nd-Fe-B alloys, Pr-Fe-B alloys, and N-Fe-B alloys.
d-Pr-Fe-B-based alloy, Ce-Nd-Fe-B-based alloy, Ce-Pr-Nd-Fe-B-based alloy, in which part of Fe is replaced by another transition metal such as Co or Ni And the like.

[0043] Typical examples of the Sm-Fe-N based alloy was prepared by nitriding the Sm ₂ Fe ₁₇ alloy Sm ₂ Fe
₁₇ N ₃ .

The rare earth elements in the magnet powder include Y, La, Ce, Pr, Nd, Pm, Sm, Eu,
Examples include Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and misch metal, and one or more of these may be included. Further, as the transition metal, F
e, Co, Ni and the like, and one or more of these can be included. Further, in order to improve magnetic properties, B, Al, Mo,
Cu, Ga, Si, Ti, Ta, Zr, Hf, Ag, Z
n or the like can be contained.

The average particle size of the magnet powder is not particularly limited, but is preferably about 0.5 to 100 μm.
About 0 μm is more preferable. The particle size of the magnet powder or the like can be measured by, for example, the FSSS (Fischer Sub-Sieve Sizer) method.

Further, even if the particle size distribution of the magnet powder is uniform,
Although it may be dispersed to some extent (varies),
In order to obtain good moldability at the time of molding with a small amount of a binder resin as described later, the latter is preferable. Thereby, the porosity of the obtained bonded magnet can be further reduced.
In the case of the above [5], the average particle size may be different for each composition of the magnet powder to be mixed.

The method for producing the magnet powder is not particularly limited.
For example, an alloy ingot is produced by melting and casting, and the alloy ingot is crushed to an appropriate particle size (classified), and a quenched ribbon manufacturing apparatus used to manufacture an amorphous alloy is used to form a ribbon. Quenched flakes (a collection of fine polycrystals) may be produced, and the flakes (ribbons) may be pulverized to an appropriate particle size (further classified), or any other material obtained.

The content of the above magnetic powder in the kneaded material is preferably about 90 to 99 wt%, and 93 to 99 wt%.
More preferably, it is about 99% by weight, and 95 to 99% by weight.
More preferably, it is in the order of magnitude. If the content of the magnet powder is too small, the magnetic properties (especially the magnetic energy product) cannot be improved, and if the content of the magnet powder is too large, the content of the binder resin becomes relatively small, and the moldability increases. Decrease.

2. Binding resin (binder) As the binding resin (binder), a thermoplastic resin is used. When a thermoplastic resin is used as the binding resin, it is advantageous in obtaining a magnet having a low porosity as compared with the case where a thermosetting resin is used.However, in the present invention, temperature conditions during molding to be described later, Lower porosity can be achieved in combination with cooling conditions.

As the thermoplastic resin, for example, polyamide (eg, nylon 6, nylon 46, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, nylon 6-12, nylon 6-66), thermoplastic polyimide , Liquid crystal polymers such as aromatic polyester resins, polyphenylene oxide, polyphenylene sulfide, polyethylene, polypropylene, ethylene-
Polyolefins such as vinyl acetate copolymers, modified polyolefins, polyethers, polyacetals, and the like, or copolymers, blends, and polymer alloys containing these as main components, and one or more of these are mixed. Can be used.

Of these, polyamides or copolymers thereof, which are excellent in moldability and mechanical strength, and mainly liquid crystal polymers and polyphenylene sulfide in view of improvement in heat resistance, are easy to mold. From the viewpoints of properties and low cost, those mainly composed of polyolefin are preferred.
These thermoplastic resins are also excellent in kneadability with magnet powder.

The thermoplastic resin used has a melting point of 120.
C. or higher, preferably 122 ° C. to 400 ° C.
More preferably, it is 125 ° C. to 350 ° C. When the melting point is lower than the lower limit, the heat resistance of the magnet molded body is reduced, and it is difficult to secure sufficient temperature characteristics (magnetic or mechanical). On the other hand, when the melting point exceeds the upper limit, the temperature at the time of molding increases, and oxidation of the magnet powder and the like is likely to occur.

In order to further improve the moldability, the thermoplastic resin used has an average molecular weight (degree of polymerization) of 10%.
It is preferably about 000 to 60000, and 1000
More preferably, it is about 0 to 35,000.

The content of the binder resin in the kneaded product is preferably about 1 to 10% by weight, and 1 to 8% by weight.
%, More preferably about 1 to 5% by weight. If the content of the binder resin is too large, the magnetic properties (particularly, the maximum magnetic energy product) cannot be improved, and the dimensional accuracy tends to decrease. On the other hand, when the content of the binding resin is too small, the moldability is reduced.

3. Antioxidant The antioxidant is used to prevent deterioration of the rare earth magnet powder due to oxidation and alteration due to oxidation of the binder resin (produced by the metal component of the rare earth magnet powder acting as a catalyst) during the production of a kneaded product. It is an additive added to the composition. The addition of the antioxidant prevents oxidation of the rare-earth magnet powder and contributes to improving the magnetic properties of the magnet, and also improves the thermal stability during kneading and molding of the rare-earth bonded magnet composition. And plays an important role in ensuring good moldability with a small amount of binder resin.

The antioxidant volatilizes or deteriorates at the time of kneading, molding into a magnet, or the like. Therefore, a part of the antioxidant remains in the manufactured rare earth bonded magnet.

As the antioxidant, any antioxidant can be used as long as it can prevent or suppress the oxidation of rare earth magnet powder and the like. Examples thereof include amine compounds, amino acid compounds, nitrocarboxylic acids, hydrazine compounds, cyanide compounds, and the like. A chelating agent that forms a chelate compound for a metal ion, particularly an Fe component, such as a sulfide, is preferably used. It goes without saying that the type, composition and the like of the antioxidant are not limited to these.

When such an antioxidant is added, the content of the antioxidant in the kneaded product is preferably about 0.1 to 2% by weight, more preferably about 0.5 to 1.5% by weight. Is more preferred. In this case, the content of the antioxidant is preferably about 2 to 150%, more preferably about 30 to 100%, based on the content of the binding resin.

In the present invention, it goes without saying that the amount of the antioxidant to be added may be equal to or less than the lower limit of the above range, or may not be added.

The added amount of the binder resin and the antioxidant is
The decision is made in consideration of the following.

That is, when the amount of the binder resin is small, the amount of the magnet powder relatively increases, the viscosity of the kneaded material during kneading increases, the kneading torque increases, and the resin tends to be oxidized by heat generation. Becomes At this time, if the amount of the antioxidant is small, the oxidation of the resin cannot be sufficiently suppressed, and the viscosity of the kneaded product (resin melt) increases, and the kneading property increases.
Moldability is reduced, and a magnet having low porosity, high mechanical strength, and excellent dimensional stability cannot be obtained. In addition, when the amount of the antioxidant is large, the amount of the resin relatively decreases, and the mechanical strength of the molded body tends to decrease.

On the other hand, when the amount of the binder resin is large, the amount of the magnet powder is relatively reduced, and the influence of the magnet powder on the resin is reduced, so that oxidation of the resin becomes difficult. Therefore, even if the amount of the antioxidant is small, the oxidation of the resin can be suppressed.

As described above, when the content of the binding resin is relatively large, the content of the antioxidant can be reduced,
Conversely, if the content of the binding resin is small, it is necessary to increase the content of the antioxidant.

Therefore, the total content of the binder resin and the antioxidant in the kneaded product is preferably 1.0 to 8.0 wt%, more preferably 2.0 to 6.0 wt%. . By setting the content in such a range, it is possible to improve the moldability at the time of molding, the ease of molding, and the prevention of oxidation of the magnet powder and the like, and a magnet having low porosity, high mechanical strength, and high magnetic properties can be obtained.

4. Other additives In the kneaded material, if necessary, for example, a plasticizer (for example, a fatty acid salt such as zinc stearate, a fatty acid), a lubricant (for example, silicone oil, various waxes, a fatty acid, alumina, silica) , Various inorganic lubricants such as titania) and other various additives such as molding aids may be added.

The addition of a plasticizer improves the fluidity during molding, so that similar characteristics can be obtained with a smaller amount of binder resin added, and compression molding can be performed with a lower molding pressure. I do. The same applies to the addition of a lubricant. The addition amount of the plasticizer is preferably about 0.01 to 0.2 wt%, and the addition amount of the lubricant is 0.05 to 0.5 wt%.
It is preferably about wt%.

The above rare earth magnet powder, the binder resin, preferably an antioxidant, and other additives as necessary are mixed and kneaded to produce a kneaded product.

The mixing is performed using a mixer such as a Henschel mixer or a stirrer.

The kneading is carried out using a kneader such as a twin screw extruder, a roll type kneader or a kneader.

This kneading is preferably carried out at a temperature not lower than the heat distortion temperature of the binder resin used (measured by a method according to ASTM D648), more preferably at a temperature not lower than the melting point of the binder resin used.

For example, when polyamide (heat deformation temperature: 145 ° C., melting point: 178 ° C.) is used as the binder resin, the preferable kneading temperature is about 150 to 280 ° C. The kneading time varies depending on the type of the binder resin and various conditions such as the kneading temperature, but is usually about 5 to 40 minutes.

The kneading is sufficiently performed so that the surface of the rare earth magnet powder is covered with the molten or softened binder resin component. When kneading at the kneading temperature, the kneading time for obtaining such a state varies depending on the type of the binder resin and the kneading machine to be used, various conditions such as the kneading temperature, but is usually about 5 to 90 minutes. Preferably
More preferably, it is about 5 to 60 minutes.

By kneading under these conditions, the efficiency of kneading is improved, and the kneading can be carried out more uniformly in a shorter time than in the case of kneading at room temperature, while the viscosity of the binder resin is reduced. Since the mixture is kneaded, the binder resin uniformly covers the periphery of the rare earth magnet powder, which contributes to a decrease in the porosity in the kneaded material, that is, a decrease in the porosity in the manufactured magnet.

When n kinds of thermoplastic resins are mixed and used as the binder resin, the “thermal deformation temperature (or melting point) of the binder resin used” can be converted, for example, as follows. .

When the total amount of the thermoplastic resins is 1 part by weight, the amounts of the respective thermoplastic resins are A ₁ , A ₂ ...
The thermal deformation temperature (or melting point) of the thermoplastic resin to be used is A ₁ T ₁ + A, where T ₁ , T ₂ ...
₂ T ₂ +... An Tn This conversion is also applied to the case where n kinds of thermoplastic resins are mixed and used in the following steps.

<2> Production of Granulated Material The kneaded product produced in the above <1> is granulated or sized to produce a granular material having a predetermined particle size.

The method of granulation or sizing is not particularly limited, but is preferably performed by pulverizing the kneaded material. This pulverization is performed using, for example, a ball mill, a vibration mill, a crusher, a jet mill, a pin mill, or the like.

Further, the granulation can be carried out using a granulator such as an extrusion granulator, and further, the granulation by the granulator and the pulverization can be carried out in combination.

The particle size of the granular material can be adjusted by classification using a sieve or the like.

The average particle size of the granular material is preferably about 10 μm to 2 mm, more preferably about 20 μm to 2 mm, and still more preferably about 50 μm to 2 mm. When the average particle diameter of the granular material is 2 mm or more, particularly when the size of the magnet to be molded is small, that is, when the size of the gap of the molding die is small, the filling amount of the granular material into the mold is finely adjusted. Is difficult and the quantitativeness is poor.
The dimensional accuracy of the bonded magnet cannot be improved. On the other hand, granules having an average particle size of 10 μm or less may be difficult or troublesome to produce (granulate). If the average particle size is too small, the porosity of the obtained bonded magnet increases. Show the trend.

Such a granular material may have a certain degree of variation in the particle size, but preferably has a uniform particle size. Thereby, the packing density in the mold is increased, and a bonded magnet with low porosity and high dimensional accuracy can be obtained.

The granular material referred to here is distinguished from pellets (mass) having a large particle size.

<3> Pressure molding Pressure molding is performed using the granular material obtained in <2>.
Hereinafter, typical compression molding will be described.

The granulated product is placed in a mold (gap) of a compression molding machine.
And compression-molded in a magnetic field (the orientation magnetic field is, for example, 5 to 20 kOe, and the orientation direction can be any of vertical, horizontal, and radial directions) or in the absence of a magnetic field.

This compression molding is performed by warm molding. That is, the temperature of the material at the time of molding is set to a predetermined temperature (first temperature) at which the thermoplastic resin (bonding resin) to be used is in a softened or molten state, for example, by heating a molding die.

The first temperature is a temperature equal to or higher than the thermal deformation temperature of the thermoplastic resin used. Further, the temperature is preferably set to a temperature equal to or higher than the melting point of the thermoplastic resin to be used, more preferably a predetermined temperature in the range from the melting point to about (melting point + 200) ° C., and from the melting point to (melting point + 130) ° C.
More preferably, the predetermined temperature is in the range up to the extent.

For example, when the thermoplastic resin to be used is polyamide (melting point: 178 ° C.), a particularly preferable material temperature (first temperature) at the time of molding is about 180 to 300 ° C.

By molding at such a temperature, the fluidity of the molding material in the mold is improved, and the molding material is not only cylindrical, block-shaped, but also cylindrical (ring-shaped), plate-shaped,
A shape having a thin portion such as a curved plate, a small size,
Even long ones can be mass-produced with low porosity, high mechanical strength, good and stable shape and dimensions.

[0089] molding pressure in the compression molding is preferably 60 kgf / mm ² or less, more preferably 2~50kgf / mm ² approximately, and further preferably 5~40kgf / mm ² approximately.
In the present invention, since the molding is performed at the first temperature as described above, the bonded magnet having the advantages as described above can be molded (shaped) even at such a relatively low molding pressure.

<4> Cooling After the pressure molding, the compact is cooled. This cooling is performed at a predetermined temperature (second temperature) that is at least lower than the first temperature.
Perform under pressure until Hereinafter, this is referred to as “cooling under pressure”.

By performing such cooling under pressure,
Since the state of low porosity during molding is maintained as it is, a rare-earth bonded magnet having low porosity, high dimensional accuracy, and excellent magnetic properties can be obtained.

The second temperature (decompression temperature) is used to reduce the porosity and improve the dimensional accuracy of the obtained bonded magnet.
Preferably, the temperature is as low as possible.
The temperature is preferably the melting point of the thermoplastic resin used or lower, and more preferably the thermal deformation temperature (softening point) of the thermoplastic resin used or lower.

The difference between the first temperature and the second temperature is preferably 20 ° C. or more, and more preferably 50 ° C. or more. The greater the temperature difference, the greater the effect of reducing the porosity and improving the dimensional accuracy.

When the content of the magnet powder is relatively large, a bonded magnet having a low porosity can be easily obtained even if the second temperature is set higher. Therefore, for example, when the content of the magnetic powder in the kneaded material is, for example, 94% by weight or more, the second temperature is set to a temperature near the melting point of the thermoplastic resin to be used or a temperature higher than or equal to the melting point (up to about + 10 ° C.). In this case, the porosity can be reduced (4.5% or less or 4.0% or less).

Further, the cooling under pressure may be performed after the pressure during the pressure molding is once released or relaxed, but it is preferably performed continuously without releasing the pressure during the pressure molding. This is preferable for simplifying the process and improving the dimensional accuracy.

The pressure during cooling under pressure may be constant or may vary, but it is preferable that the pressure is kept constant at least up to the melting point (particularly the heat deformation temperature) of the thermoplastic resin used. When the pressure at the time of cooling under pressure changes, for example, it may include a pattern in which the pressure increases or decreases continuously or stepwise.

The pressure during cooling under pressure (when the pressure changes with time, the average pressure thereof) is preferably equal to or less than the molding pressure during pressure molding. It is more preferable that the pressure up to the melting point of the resin is equal to the molding pressure during pressure molding. When cooling under pressure between the melting point of the thermoplastic resin to be used and the heat deformation temperature, the pressure during that time is 40% of the molding pressure during pressure molding.
It is preferably about 100%, more preferably about 50% to 80%.

In the present invention, it goes without saying that cooling may be continued under non-pressurization (under normal pressure) after cooling under pressure (after depressurization). Further, after cooling under non-pressure, cooling under pressure may be performed again.

The cooling rate during cooling under pressure (when the cooling rate changes over time, the average value thereof) is not particularly limited, but is preferably 0.5 to 100 ° C./sec.
More preferably, it is 0 ° C./sec. If the cooling rate is too fast, rapid cracking due to cooling may cause fine cracks inside the molded body, which may cause a decrease in mechanical strength.In addition, the internal stress increases due to cooling, and When the material is removed, strain or deformation may occur due to stress relaxation, and dimensional accuracy may decrease. On the other hand, if the cooling rate is too slow,
The molding cycle time increases and productivity decreases.

When cooling is continued after depressurization, the cooling rate is not particularly limited, and the same cooling rate as described above can be used.

The cooling rates during cooling under pressure and during cooling after depressurization may be constant or variable.

In this step, any cooling method such as natural air cooling, forced air cooling, water cooling, oil cooling, or a combination of water cooling and air cooling may be employed.

The rare earth bonded magnet manufactured by the method of the present invention as described above has the following excellent characteristics. That is, the porosity is low, preferably 4.5% (vol%)
Or less, more preferably 3.5% or less, still more preferably 2.0% or less. As described above, since the porosity is low (= high density), the mechanical strength is high, the corrosion resistance is excellent, and the dimensional accuracy is high, and even when mass-produced, the dimensional variation is small and the dimensional stability is excellent. ing.

Further, it is excellent in magnetic properties. In particular, isotropic magnets have excellent magnetic properties due to the composition of the magnet powder and the large content of the magnet powder.

That is, in the case of a rare-earth bonded magnet formed in the absence of a magnetic field, the maximum magnetic energy product (BH) max is preferably at least 6 MGOe, more preferably at least 8 MGOe,
In the case of a rare earth bonded magnet formed in a magnetic field, the maximum magnetic energy product (BH) max is 12 MGOe or more, more preferably 13 MGOe or more.

The shape and dimensions of the rare-earth bonded magnet obtained according to the present invention are not particularly limited. For example, regarding the shape, for example, a columnar shape, a prismatic shape, a cylindrical shape, an arc shape (tile shape), and a flat plate Any shape, such as a shape, a curved plate shape, etc., is possible, and the size can be any size from a large one to a very small one.

[0107]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

(Example 1) The following magnet powder, a binder resin (thermoplastic resin) and additives were mixed, the mixture was kneaded, and the kneaded product was granulated (granulated) to obtain a granular material. The granular material is filled in a mold of a molding machine, compression-molded (warm molding) in the absence of a magnetic field, cooled while maintaining the same pressurized state at the time of molding, and solidified by bonding resin. Rare earth bonded magnets (Sample Nos. 1 to 9) in which magnet powders were bonded were manufactured. The content of each substance indicates the amount in the kneaded material.

Structure Nd-Fe-B based magnet powder: Nd _12.0 Fe _77.8 Co _4.3
B _5.9 , 96.0 wt% Thermoplastic resin: A to G described in Table 1, 2.8 wt% each Antioxidant: hydrazine antioxidant, 1.2 wt% Mixing: Mixing using Henschel mixer.

Kneading: Kneading with a twin screw extruder. See Table 2 for kneading temperatures.

Screw rotation speed: 100 to 300 rpm. Kneading time 5 to 15 minutes Granulation (granulation): The kneaded product is pulverized and classified to have an average particle size of 0.1.
Adjusted to 8mm grain.

Molding: The granular material was put into a mold, and heated to a predetermined molding temperature (first temperature) to perform pressure molding.

See Table 2 for the molding temperature and molding pressure.

Cooling: While maintaining the pressurized state, the sample was cooled to the depressurizing temperature (second temperature), and after depressurizing, further cooled to room temperature, and a sample was taken out.

The cooling method was air cooling. See Table 2 for decompression temperatures.

The cooling rate under cooling under pressure is 1 ° C./sec.

Molded product shape: cylindrical shape (outside diameter φ30 mm × inside diameter φ28 mm × height 7 mm) Flat plate shape (20 mm square × thickness 3 mm) (for measuring mechanical strength) The magnetic performance (magnetic flux) of the obtained rare-earth bonded magnet was measured. Density Br, coercive force iHc, maximum magnetic energy product (BH) max),
When the density, porosity, mechanical strength, and corrosion resistance were examined, the results were as shown in Table 3 below.

The evaluation of each measurement item in Table 3 was performed according to the following method.

Magnetic performance: After pulse magnetization at 40 kOe,
Measured with a DC magnetometer at a maximum applied magnetic field of 25 kOe. Alternatively, a magnet piece of 5 mm square × 1 mm thickness is cut out from a molded sample, and measured by VSM.

Density: Measured by Archimedes' method (underwater method).

Porosity: Calculated from the weighed composition and the measured value of the density of the molded article.

Mechanical strength: Measured by a punching shear test. The test machine uses an autograph manufactured by Shimadzu Corporation.
The shearing speed was 1.0 mm / min using a circular punch (outer diameter: 3 mm).

A flat magnet was used for the sample.

Corrosion resistance: A molded magnet was put into a constant temperature and humidity chamber at a temperature of 80 ° C. and a humidity of 90%, and the time until rust was generated on the magnet surface was measured. Surface observation was taken out of the tank every 50 hours and observed with an optical microscope (× 10). After 500 hours,
Observations were made every 500 hours.

[0125]

[Table 1]

[0126]

[Table 2]

[0127]

[Table 3]

As is evident from Table 3, the rare-earth bonded magnets according to the present invention using the thermoplastic resin as the binder resin (Samples Nos. 1 to 9) were all empty despite the low molding pressure. The porosity is as low as 1% or less, and a high-density bonded magnet having almost the same theoretical density can be obtained.
A magnet with very high mechanical strength was obtained.

Further, even when the magnet surface was not coated, it had sufficient corrosion resistance. It is presumed that this is because the binding resin uniformly covers the surface of the magnet powder due to the small number of holes.

With respect to each of the magnets of Sample Nos. 1 to 9, an electron micrograph (SEM) of a cut surface thereof was taken and observed. Were confirmed to be uniformly dispersed.

Further, the magnetic flux density Br and the coercive force iHc, the maximum magnetic energy product (BH) max, are high, indicating that the magnetic properties are excellent.

Comparative Example 1 The following magnet powder and a binder resin (thermosetting resin) were mixed, the mixture was kneaded, and the kneaded product was granulated (regulated) to obtain a granular material. The granular material is filled in a mold of a molding machine, compression-molded (cold molding or warm molding) in a magnetic field-free state, and then the binder resin is cured to form a rare-earth bonded magnet (sample Nos. 10 to 15). Was manufactured.
The content of each substance indicates the amount in the kneaded material.

Structure Nd-Fe-B based magnet powder: Nd _12.0 Fe _77.8 Co _4.3
B _5.9, 96.0wt% thermosetting resin: as described in Table 4, (a curing agent) 4.0 wt% mixed: in the case of using a solid resin at room temperature, mixed in a V-blender.

When a resin that is liquid at room temperature is used, it is mixed with a stirrer.

Kneading: Kneading using a kneader. See Table 5 for kneading temperatures.

Kneader rotation speed 50-250 rpm. Kneading time 30 minutes.

Granulation (sizing): The kneaded material is adjusted to particles having an average particle diameter of 0.8 mm or less by pulverization and classification.

Molding: The granular material was charged into a mold and molded under pressure at a predetermined molding temperature.

The molding temperature and the molding pressure are shown in Table 5.

Cooling: Cooling to the decompression temperature (sample No.
10 and 11), and after depressurizing, further cool to room temperature,
A sample was taken.

The cooling method was air cooling. See Table 5 for decompression temperatures.

The cooling rate was 2 ° C./sec.

Heat treatment: The temporary molded product is placed in a thermostat and the thermosetting resin is cured.

For curing conditions, see Table 4.

Molded product shape: cylindrical shape (outside diameter φ30 mm × inside diameter φ28 mm × height 7 mm) Flat plate shape (20 mm square × thickness 3 mm) (for measuring mechanical strength) The magnetic performance (maximum) of the obtained rare-earth bonded magnet The magnetic energy product (BH) max), density, porosity, mechanical strength, and corrosion resistance were examined. The results are as shown in Table 6 below. The evaluation method for each item is the same as that in the first embodiment.

[0146]

[Table 4]

[0147]

[Table 5]

[0148]

[Table 6]

As is clear from Table 6, a comparative magnet (sample No. 10) using a thermosetting resin as the binding resin was used.
In (15) to (15), the porosity is high and the density of the molded magnet is low even when the molding pressure is set to 70 kgf / mm ² , as well as when the molding pressure is set to 20 kgf / mm ² . As a result, the mechanical strength of the magnet is low and the corrosion resistance is low.

For each of the magnets of Sample Nos. 10 to 15, an electron micrograph (SEM) of the cut surface was taken.
Observation revealed that there were many pores inside.
In addition, the distribution of the pores was non-uniform, with many pores in the center and few near the surface due to pressure transmission during pressure molding. Further, segregation of the resin component was observed.

When the molding pressure was set to 20 kgf / mm ² , there was a large variation in mechanical strength in the sample.
As a result, cracks and cracks were generated at places other than the place where the load was applied by the circular punch, so that accurate measurement of mechanical strength could not be performed. On the other hand, the molding pressure was set to 70 kgf / mm ²
In this case, the resin component in the kneaded material leaked, and as a result, burrs occurred.

Example 2 The following magnet powder, a binder resin (thermoplastic resin), and additives were mixed, the mixture was kneaded, and the kneaded product was granulated (granulated) to obtain a granular material. The granular material is filled in a mold of a molding machine, compression-molded (warm-forming) in a magnetic field, and cooled while maintaining the same pressurized state at the time of molding. 16-19). The content of each substance indicates the amount in the kneaded material.

Structure Sm-Co based magnet powder: Sm (Co _bal. Fe _0.32 Cu
_{0.06 Zr 0.016) 7. 8, 95.0wt} % thermoplastic resin: PPS resin, 4.2 wt% antioxidant: hydrazine based antioxidant, 0.8 wt% mixed: using a V-type mixer a mixture.

Kneading: Various kneading machines were used. Table 7 shows the kneading conditions.
See

Granulation (sizing): The kneaded material was adjusted to particles having an average particle diameter of 0.8 mm by pulverization and classification.

Molding: The granular material was charged into a mold and heated to a predetermined molding temperature (first temperature).
kOe) while applying pressure.

The molding temperature was 320 ° C. and the molding pressure was 20 kgf /
It was mm ^2.

Cooling: While maintaining the pressurized state, the sample was cooled to a depressurizing temperature (second temperature) of 150 ° C., and after depressurizing, further cooled to room temperature, and a sample was taken out.

The cooling method was air cooling.

The cooling rate under cooling under pressure is 5 ° C./sec.

[0161] Molded product shape: rectangular parallelepiped (11 mm long x 8 mm wide x
Height 7mm, height direction is orientation direction. ) Flat plate shape (20mm square x 3mm thickness) (for measuring mechanical strength) Magnetic properties (maximum magnetic energy product (BH) max), density, porosity, mechanical strength, corrosion resistance Was as shown in Table 8 below. The evaluation method for each item is the same as that in the first embodiment.

[0162]

[Table 7]

[0163]

[Table 8]

As is clear from Table 8, the rare-earth bonded magnets according to the present invention (samples Nos. 16 to 19) all had a low porosity of 1% or less, and high-density bonded magnets were obtained. As a result, mechanical strength and corrosion resistance were high.

Further, electron micrographs (SEM) of the magnets of Sample Nos. 16 to 19 were taken and observed in the same manner as described above.
It was confirmed that the binder resin component was uniformly dispersed around the magnet powder.

Further, it can be seen that the maximum magnetic energy product (BH) max is high and the magnetic properties are excellent.

Comparative Example 2 The following magnet powder, a binder resin (thermoplastic resin), and an additive were mixed, and the mixture was filled in a mold of a molding machine and compression-molded in a magnetic field (warm molding). )
Then, rare earth bonded magnets (Sample Nos. 20 and 21) were manufactured. The content of each substance indicates the amount in the mixture.

Structure Sm-Co based magnet powder: Sm (Co _bal. Fe _0.32 Cu
_{0.06 Zr 0.016) 7. 8, 95.0wt} % ( Sample No. 2
0), 96.0 wt% (Sample No. 21) Thermoplastic resin: PPS resin, 4.2 wt% (Sample No. 21)
20) 3.2 wt% (Sample No. 21) Antioxidant: hydrazine-based antioxidant, 0.8 wt% Mixing: Mixing using a V-type mixer.

Molding: The mixture was put into a mold and heated to a predetermined molding temperature, whereupon it was molded under pressure while applying a transverse magnetic field (15 kOe).

The molding temperature was 320 ° C. and the molding pressure was 20 kgf /
It was mm ^2.

Cooling: The temperature was cooled to 150 ° C., and a sample was taken out.

The cooling method was air cooling.

The cooling rate was 5 ° C./sec.

Molded product shape: rectangular parallelepiped (length 11 mm x width 8 mm x
Height 7mm, height direction is orientation direction. Flat plate shape (20 mm square x 3 mm thickness) (for measuring mechanical strength) Both magnets of Sample Nos. 20 and 21 leak resin during molding, and the edges and end faces of the molded product are punched by the molding machine. By adhering to the molded article, the molded article is scoured, and edges and the like are formed, and a desired shape cannot be obtained.

An electron micrograph (SE) of the molded part
M) was photographed and observed. As a result, the dispersion of the binder resin component was uneven, and the magnet powder portion and the binder resin portion were mixed.

As described above, sample No. 20
Since the magnets of Nos. 21 and 21 were defective,
An effective measurement such as mechanical strength could not be performed.

Example 3 The following magnet powder (two types), a binder resin (thermoplastic resin) and an additive were mixed, the mixture was kneaded, and the kneaded product was granulated (granulated). Granules are obtained, and the granules are filled in a mold of a molding machine, compression-molded (warm molding) in a magnetic field, and cooled while maintaining the same pressurized state at the time of molding. Magnet (Sample Nos. 22 to 3)
0) was prepared. The content of each substance indicates the amount in the kneaded material.

Structure Sm-Co based magnet powder: Sm (Co _0.672 Fe _0.22 Cu
_0.08 Zr _0.028 ) _8.35 , 70.5 wt% Sm-Fe-N magnet powder: Sm ₂ Fe ₁₇ N ₃ , 23.
4 wt% thermoplastic resin: polyamide resin (nylon 12);
0 wt% antioxidant: phenolic antioxidant, 1.0 wt% Mixing: mixing using a Henschel mixer.

Kneading: Kneading with a twin screw extruder. The kneading temperature is 150 to 300 ° C.

The screw rotation speed is 100 to 300 rpm. Kneading time 10 minutes Granulation (granulation): The kneaded material was adjusted to the particle size shown in Table 9 by pulverization and classification.

Molding: The granular material was put into a mold by a scouring method, and heated to 220 ° C. (first temperature). Then, pressure molding was performed while applying a horizontal magnetic field (15 kOe). The molding pressure was 10 kgf / mm ² .

Cooling: While maintaining the pressurized state, the sample was cooled to a depressurizing temperature (second temperature) of 100 ° C., and a sample was taken out.

The cooling method was water cooling.

The cooling rate in cooling under pressure is 20 ° C./sec.

Molded product shape: flat plate shape (width 15 mm × thickness 2.5 mm × height 5 mm, orientation in the height direction) For the obtained rare earth bonded magnet, the weight, density, porosity, and height of the magnet Was as shown in Table 9 below.

[0186]

[Table 9]

As is clear from Table 9, by setting the particle size of the granular material, excellent quantitative properties can be obtained, and a bonded magnet having low porosity and high dimensional accuracy can be obtained. In particular, when the particle size of the granular material is in the range of 0.01 to 2 mm, an extremely low porosity (1% or less) and high dimensional accuracy (a dimensional error of ± 5/10
(Within 0 mm).

(Example 4, Comparative Example 3) The following magnet powder, binder resin (thermoplastic resin) and additives were mixed, the mixture was kneaded, and the kneaded product was granulated (granulated). Get granules,
The granules were filled in a mold of a molding machine, compression-molded (warm-forming) in a magnetic field, and cooled while maintaining the same pressurized state at the time of molding to form a rare-earth bonded magnet (sample No. 31-4
2) was manufactured. The content of each substance indicates the amount in the kneaded material.

Structure Nd-Fe-B magnet powder: Nd _12.6 Fe _69.3 Co _12.0
B _6.0 Zr _0.1 , 97.0 wt% Thermoplastic resin: A or F in Table 1, 1.5 wt% each Antioxidant: hydrazine antioxidant, 1.4 wt% Lubricant: zinc stearate, 0.1 wt % Mixing: Mixing using Henschel mixer.

Kneading: Kneading is performed by a twin-screw extruder. The kneading temperature is 150 to 350 ° C.

Screw rotation speed 100-300 rpm. Kneading time 5 minutes Granulation (granulation): The kneaded material is pulverized and classified to obtain an average particle size of 0.1.
Adjusted to 3mm grain.

Molding: The granular material was put into a mold and heated to a molding temperature (first temperature) shown in Table 10, and then subjected to pressure molding while applying a radial magnetic field (15 kOe). The molding pressure was 15 kgf / mm ² .

Cooling: While maintaining the pressurized state, the sample was cooled to a depressurizing temperature (second temperature) of 100 ° C. After the depressurizing, the sample was further cooled to room temperature, and a sample was taken out.

The cooling method was water cooling.

The cooling rate in cooling under pressure is 30 ° C./sec.

Molded product shape: cylindrical shape (outside diameter φ20 mm × inside diameter φ18 mm × height 5 mm, pressurized in the height direction) Flat plate shape (20 mm square × 3 mm thick) (for measuring mechanical strength) Rare earth bond obtained Magnet (Example 4: Sample No. 3
2-36, 38-42, Comparative Example 3: Sample No. 31,
37), the magnetic performance (maximum magnetic energy product (BH)
max), density, porosity, and mechanical strength were as shown in Table 10 below. The evaluation method for each item is the same as that in the first embodiment.

[0197]

[Table 10]

Sample Nos. 32-36 and 38 in Table 10
When the molding temperature was equal to or higher than the thermal deformation temperature of the binder resin as in Examples 42 to 42 (Example 4), the binder resin was in a softened or molten state during molding, and molding was possible.

In particular, Sample Nos. 33 to 36, 40, 4
When the molding temperature is equal to or higher than the melting point of the binding resin as in 2, the porosity of the obtained magnet is further reduced, and the magnetic performance is further improved.

On the other hand, when the molding temperature is lower than the thermal deformation temperature of the binder resin as in Sample Nos. 31 and 37 (Comparative Example 3), the binder resin does not soften at the time of molding, so that the granular materials adhere to each other. Therefore, the shape could not be maintained, and molding was impossible or molding failure. Therefore,
Measurement was not possible for each measurement item.

Example 5, Comparative Example 4 The following magnet powder, a binder resin (thermoplastic resin) and an additive were mixed, the mixture was kneaded, and the kneaded product was granulated (granulated). Get granules,
The granules are filled in a mold of a molding machine, compression-molded (warm molding) in a magnetic field-free state, cooled while maintaining the same pressurized state at the time of molding, and then mixed with a rare-earth bonded magnet (sample No. . 43-5
2) was manufactured. The content of each substance indicates the amount in the kneaded material.

Composition Nanocrystalline Nd—Fe—B magnet powder: Nd _5.5 Fe ₆₆ B
_18.5 Co ₅ Cr ₅ , 98.0 wt% Thermoplastic resin: A or G in Table 1, each 1.0 wt% Antioxidant: Hydrazine antioxidant 1.0 wt% Mixing: Mixing using Henschel mixer.

Kneading: Kneading by a twin-screw extruder. The kneading temperature is 150 to 350 ° C.

The screw rotation speed is 100 to 300 rpm. Kneading time 10 minutes Granulation (granulation): The kneaded material is pulverized and classified to obtain an average particle size of 0.1.
Adjusted to 1mm grain.

Molding: The granules were put into a mold and heated to a predetermined molding temperature (first temperature), whereupon they were molded under pressure. The molding temperature is 200 ° C (resin A) and 300 ° C
(Resin G), the molding pressure was 25 kgf / mm ² .

Cooling: While maintaining the pressurized state, the sample was cooled to the depressurizing temperature (second temperature) shown in Table 11, and a sample was taken out. The cooling method was water cooling.

The cooling rate under cooling under pressure is 50 ° C./sec.

Molded product shape: cylindrical shape (outside diameter φ10 mm × inside diameter φ7 mm × height 7 mm, pressurized in the height direction) The obtained rare earth bonded magnet (Example 5: Sample No. 4
4-47, 49-52, Comparative Example 4: Sample No. 43,
48), the magnetic performance (maximum magnetic energy product (BH)
max), density, porosity, and outer diameter were examined.
As shown in FIG. The evaluation method for each item is the same as that in the first embodiment.

[0209]

[Table 11]

Sample Nos. 44 to 47 and 49 in Table 11
When the depressurization temperature is equal to or lower than the melting point of the binder resin or the difference between the depressurization temperature and the molding temperature is equal to or higher than 20 ° C. as in Examples 52 to 52, the porosity of the obtained magnet is low and the density is low. high,
High magnetic performance and high dimensional accuracy (Dimensional error is ± 5/1
00mm or less). Such characteristics are improved as the decompression temperature is lower.

In particular, sample Nos. 46, 47, 50, 5
When the depressurization temperature is equal to or lower than the thermal deformation temperature of the binder resin as in 1, it is possible to achieve a density close to the theoretical density, and to achieve an extremely excellent magnetic performance capable of sufficiently exhibiting the characteristics of the magnet powder. It becomes a magnet.

On the other hand, when the depressurizing temperature and the molding temperature were the same as in Sample Nos. 43 and 48 (Comparative Example 4), the dimensional accuracy was low and the porosity was low.
47, 49-52.

[0213]

As described above, according to the present invention, press molding is performed by warm forming using the granulated material of the kneaded material. By cooling in a state, a rare earth bonded magnet with excellent moldability, low porosity, high mechanical strength, high dimensional stability (dimensional accuracy), and excellent magnetic properties even with a small amount of binder resin is obtained. Can be provided.

In this case, when the particle size of the granular material is in a desired range, the porosity is extremely low, and the dimensional stability is further improved.

Further, since the thermoplastic resin is press-formed in a softened or molten state, a rare-earth bonded magnet having the above characteristics can be manufactured at a relatively low forming pressure, and the manufacturing is easy.

In particular, the second temperature (decompression temperature) at the time of cooling is a temperature lower than the melting point of the thermoplastic resin to be used, or a temperature lower than the heat deformation temperature, or the first temperature and the predetermined temperature or higher. In the case of deviation, a rare-earth bonded magnet with extremely low porosity and extremely high dimensional stability can be provided.

Claims (17)

[Claims] 1. A method for producing a rare-earth bonded magnet in which a rare-earth magnet powder is bound by a binding resin made of a thermoplastic resin, wherein the rare-earth magnet powder and the binding resin are mixed and kneaded to produce a kneaded product. Performing the step of granulating or sizing the kneaded material to obtain a granular material; and performing pressure molding at a first temperature at which the binder resin is softened or melted using the granular material. Cooling in a pressurized state to at least a second temperature that is lower than the first temperature. 2. The method according to claim 1, wherein the kneading is performed at a temperature equal to or higher than a thermal deformation temperature of the binder resin and in a state where the surface of the rare earth magnet powder is covered with a melted or softened binder resin component. 3. The method for producing a rare earth bonded magnet according to item 1. 3. The method for producing a rare earth bonded magnet according to claim 1, wherein the content of the rare earth magnet powder in the kneaded material is 90 to 99 wt%. 4. The method for producing a rare earth bonded magnet according to claim 1, wherein the kneaded material contains an antioxidant. 5. The method for producing a rare earth bonded magnet according to claim 4, wherein the content of the antioxidant in the kneaded material is 0.1 to 2% by weight. 6. The method for producing a rare-earth bonded magnet according to claim 1, wherein the granulation or sizing is performed by pulverization. 7. An average particle size of the granular material is 10 μm to 2 mm.
The method for producing a rare-earth bonded magnet according to any one of claims 1 to 6, wherein 8. The method for manufacturing a rare-earth bonded magnet according to claim 1, wherein the pressure molding is compression molding. 9. The method according to claim 1, wherein the second temperature is a melting point of the binder resin. 10. The method according to claim 1, wherein the second temperature is a thermal deformation temperature of the binder resin. 11. The method according to claim 1, wherein a difference between the first temperature and the second temperature is 20 ° C. or more. 12. The method for manufacturing a rare-earth bonded magnet according to claim 1, wherein the cooling in the pressurized state is performed continuously without releasing the pressurization in the press-forming. . 13. The method for producing a rare-earth bonded magnet according to claim 1, wherein a pressure during cooling in the pressurized state is equal to or less than a forming pressure during the press-forming. . 14. The method for manufacturing a rare earth bonded magnet according to claim 1, wherein the pressure during cooling in the pressurized state is kept constant at least up to the melting point of the binder resin. 15. The method according to claim 1, wherein the pressure during cooling in the pressurized state is kept constant at least up to a temperature between the first temperature and the second temperature. Manufacturing method of rare earth bonded magnet. 16. The method for manufacturing a rare earth bonded magnet according to claim 1, wherein a cooling rate during cooling in the pressurized state is 0.5 to 100 ° C./sec. 17. The molding pressure during the pressure molding is 60 kg.
The method for producing a rare-earth bonded magnet according to any one of claims 1 to 16, wherein the f / mm ² is not more than f / mm ² .