JP2000260616A - Ferromagnetic fine powder for plastic magnet and resin composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart an oxidation resistance by covering the surface of the ferromagnetic metal nitride fine powder with a thin film made of an inorganic phosphoric compound including no organic groups. SOLUTION: A ferromagnetic metal nitride is ground into fine powder in an inert gas atmosphere by a wet ball mill grinding method using a dispersion medium consisting of one kind of a hydrophobic organic solvent such as toluene, hexane, and benzene or a mixed solution of two or more kinds of such hydrophobic organic solvents. The average grain diameter of the ferromagnetic metal nitride fine powder is about 2 μm or below. Before applying an oxidation treatment to the ground ferromagnetic metal nitride fine powder, a treatment solution is brought into contact with the powder to remove the solvent in a drying process and evenly form a thin film made of an inorganic phosphoric compound including no organic groups on the surface of the powder. As for the treatment solution, phosphoric acid is mixed and dispersed in an organic solvent made of one kind of an alcoholic solvent such as methyl alcohol and ethyl alcohol or made of a mixture of two or more kinds of such alcohol solvents.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferromagnetic fine powder for kneading and molding together with a plastic material to produce a so-called plastic magnet and a resin composite material using the fine powder.

[0002]

2. Description of the Related Art In recent years, a ferromagnetic material as a raw material for a plastic magnet has been required to have high characteristics and at the same time low cost. In order to achieve high characteristics at the lowest possible cost, Nd- isotropic ferromagnetic material is required. Fe-Co-B-based alloy (trade name: MQP-B, company name: Mac Penquenchi International)
Is the most widely adopted. While this ferromagnetic material can achieve high characteristics, its high price limits the cost reduction of the product. Some Sm-Co alloys are also used as ferromagnetic materials to achieve higher characteristics, but their use is very limited due to their higher cost, and they have not yet become widespread. .

Under these circumstances, Sm-Fe-N-based metal nitrides are low in cost because they do not contain expensive elements such as Co, and have a magnetic property equal to or higher than that of Nd-Fe-Co-B-based alloys. Due to its properties, it is attracting attention as a next-generation magnet. Also, the Sm—Fe—N ferromagnetic metal nitride is Nd
-Since the magnetic properties are higher than those of Fe-Co-B-based alloys, even higher properties can be achieved even if the same weight of ferromagnetic fine powder is mixed with the resin, and Nd-Fe-Co-B-based alloys are used. When the magnetic properties equivalent to those of the plastic magnet manufactured by the above method are obtained, for example, when the BHmax is about 7.5 MGOe, the required weight of the ferromagnetic fine powder is 10%.
Approximately 15% less. Further, Nd-Fe-Co-B
Since the raw material price is low, the system alloy is a ferromagnetic material which is excellent in cost performance in manufacturing a resin composite material for a plastic magnet.

[0004] It is known that the Sm-Fe-N ferromagnetic metal nitride alloy is improved in magnetic properties, particularly coercive force, by pulverizing it to a particle size close to a single magnetic domain.
Practically, it is desirable to grind to an average particle size of 2 μm or less. For this reason, especially in the case where a product is obtained by injection molding after being blended with a resin composite material, the surface of the product obtained compared with the case of using an Nd-Fe-Co-B-based alloy having an average particle diameter of 20 µm or more is used. This has the advantage that the property is good and the variation of the magnetic properties on the product surface is very small.
As described above, it has been found that the Sm—Fe—N ferromagnetic metal nitride is an excellent material that can simultaneously realize low cost, high characteristics, and high quality of a plastic magnet. .

[0005] However, although the Sm-Fe-N ferromagnetic metal nitride alloy is a metal nitride, the metal element is also exposed on the surface of the particles. It will be easier to progress. For example, an average particle size of 2-3
When handling a fine powder of μm in the air, oxidation easily proceeds, and furthermore, ignition may occur due to friction or the like that may occur in the process, which is extremely dangerous. Furthermore, even after it is made into a product, it becomes susceptible to oxidation due to the humidity in the atmosphere, so it is indispensable to apply a surface coat for rust prevention in order to actually make it into a product, so even if the raw material cost is low, the final product There is a disadvantage that the cost merit is reduced at the stage of making.

On the other hand, Z
There is known a method of preventing oxidation by plating a film of n, Ni or the like to form a film, but the cost is high and it has not been put to practical use.

[0007]

When a composite material for a plastic magnet is produced by blending a ferromagnetic metal nitride fine powder with a resin, in order to obtain a high holding force in practical use, an average particle size is required. It is desirable to grind to 2 μm or less,
Thereafter, if necessary, a process such as surface treatment such as coupling and kneading is performed. Since the pulverized ferromagnetic metal nitride fine powder is very easily ignited, it has to be handled in an inert atmosphere, which is very costly in terms of equipment. However, oxidation-resistant treatment such as plating is costly and impractical, and a technique for imparting oxidation resistance at low cost is practically essential.

In particular, in the kneading step of compounding a thermoplastic resin to form a composite or the step of molding and processing the obtained resin compounded composition, it is necessary to maintain the temperature at a high temperature of, for example, 200 ° C. or higher. If the length is long, the melt viscosity of the resin composite material will increase due to oxidation of the ferromagnetic metal nitride, making the kneading and molding steps difficult, and eventually causing the resin composite material to become clogged in the kneader or molding machine. Is a major problem. In addition, when performing injection molding, it is common practice to purge the inside of the molding machine and inject the resin composite material heated to a high temperature out of the molding machine. There is a risk that the purge material will ignite due to the accelerated oxidation of the material.

Further, even after forming the molded product, the ferromagnetic metal nitride in the composite material is easily oxidized due to the humidity in the air, which causes a problem that the magnetic force caused by the oxidation is reduced. As a result of intensive studies, the present invention has completed a ferromagnetic fine powder for a plastic magnet and a resin composite material using the fine powder, and will be clarified below.

[0010]

[Purpose] To manufacture low-cost, safe ferromagnetic fine powder that is difficult to ignite during handling in the atmosphere, and to mix and mix with resin to reduce the trouble caused by viscosity increase due to thermal oxidation in the molding process. It is an object of the present invention to provide a resin composite material that prevents and further prevents rust.

[0011]

The ferromagnetic fine powder for a plastic magnet of the present invention has a high oxidation resistance by covering the surface of a ferromagnetic metal nitride fine powder with a thin film of an inorganic phosphate compound containing no organic group. It is characterized by having been given.

The resin composite material for a plastic magnet of the present invention contains the above ferromagnetic fine powder in a resin.

A resin composite material may be prepared by mixing a ferromagnetic fine powder and a ferromagnetic compound powder such as a ferromagnetic ferrite fine powder having characteristics different from those of the ferromagnetic fine powder into a resin.

[0014]

Function and Effect The ferromagnetic fine powder of the present invention is provided with oxidation resistance because its surface is covered with an inorganic phosphate compound, and does not contain organic components in the acid-resistant coating film. Therefore, heat resistance is significantly improved. By selecting processing conditions, it can withstand high temperatures of 500 ° C. or more, eliminates ignition during handling in the air, and is required for kneading, molding, etc., which is necessary when a resin composite material containing a resin is added. Since the thermal oxidation of the ferromagnetic metal nitride fine powder in the step of processing at a high temperature can be prevented, an increase in melt viscosity caused by this can be suppressed, and high fluidity of the resin composite material is realized. Thereby, troubles such as clogging of the kneading machine and the molding machine and ignition of the purge material can be prevented.

Further, in the ferromagnetic fine powder which has been subjected to the oxidation-resistant treatment, an effect can be seen in that the surface is covered with the inorganic phosphoric acid compound, thereby stabilizing against external oxidation due to humidity or the like. This means that when a resin composite material is used as a product,
There is an advantage that a coating process for rust prevention, which is usually required, can be omitted.

[0016]

EXAMPLE A ferromagnetic metal nitride was subjected to wet ball milling using a dispersion medium comprising one or a mixture of two or more hydrophobic organic solvents such as toluene, hexane and benzene in an inert atmosphere. Crush into fine powder. Immediately before performing the oxidation treatment on the pulverized ferromagnetic metal nitride powder, the treatment liquid is brought into contact with the ferromagnetic metal nitride powder, and the solvent is removed in a drying step, so that the surface is uniformly made of a phosphoric acid compound. The film is coated to obtain a ferromagnetic powder.

The treatment liquid is quickly added to the ferromagnetic metal nitride fine powder in an organic solvent comprising one or a mixture of two or more of alcohol solvents such as methyl alcohol and ethyl alcohol. It is prepared by mixing and dispersing 10% by weight, preferably 0.5 to 5% by weight of phosphoric acid.

The optimum amount of phosphoric acid has a correlation with the particle size and specific surface area of the ferromagnetic metal nitride fine powder. The same oxidation resistance can be obtained with a smaller amount. In addition, it is important to keep the amount of the alcohol solvent used at the time of preparing the treatment liquid to a minimum amount necessary for sufficiently dispersing the phosphoric acid in order to prevent the esterification reaction from proceeding. .

In the present invention, the term "ferromagnetic metal nitride fine powder" means ferromagnetic, for example, R _a M _b Fe _(1-abcde)
N _c H _d O _e (R is a rare earth element including yttrium, M is N
In addition to transition metal elements such as i, V, and Cr, Nb, Mo, Ta, W, Ru,
One or two metal elements such as Rh, Pd, Hf, Re, Os, Ir
A, b, c, d and e are each 0.
05 ≦ a ≦ 0.20, 0 ≦ b ≦ 0.49, 0.10 ≦ c ≦ 0.25, 0.000
(1 ≦ d ≦ 0.05, 0.0001 ≦ e ≦ 0.10)
Alloy nitride fine powder having the following composition: Also, "phosphoric acid"
The term includes not only phosphoric acid (H ₃ PO ₄ ) but also inorganic phosphates and other inorganic phosphorus compounds. Also, "ferromagnetic compound powder having characteristics different from ferromagnetic metal nitride fine powder"
For example, ferrite-based oxide, Sm-Co-based alloy, Nd
-Fe-B alloy, Al-Ni alloy, Mn-Al-C
It is a fine powder of a ferromagnetic compound such as a system alloy.

After the coupling treatment is performed by bringing the oxidation-resistant ferromagnetic metal fine powder into contact with a coupling agent, the mixture is blended with the resin using a universal mixer, a mixer, or the like, to obtain a resin composite material composition. obtain. A lubricant such as wax may be added to improve the fluidity. As the "coupling agent" here, aminosilane-based, titanate-based,
Includes one or a combination of two or more of the aluminate-based coupling agents. The “resin” includes thermoplastic resins such as polyethylene, polyamide, and elastomer, thermosetting resins such as epoxy, and rubber.

After the obtained composition is processed into a pellet or a sheet-like semi-finished product, it is formed into a molded product by an injection molding machine, an extrusion molding machine or a compression molding machine. Further, the compounded composition of the resin composite material can be directly fed into a molding machine to produce a molded product.

[0022]

The [Example 1] film treatment apparatus Figure 3 for use in the present invention is used in the practice of the method of the present invention, shows an oxidation prevention coating apparatus of the ferromagnetic metal nitride fine powder, patent applicant previously proposed This is a known device disclosed in Japanese Patent No. 2602979. The coating apparatus also serves as a pulverizer for pulverizing metal particles, and uses a water-insoluble inert organic solvent that does not dissolve water, such as toluene, hexane, or a hydrocarbon solvent such as heptane, as a pulverization aid, After performing wet grinding in the grinding aid and under an inert atmosphere to pulverize the metal particles, a coating treatment can be immediately performed. A lid plate (13) is airtightly placed on the cylindrical stirring tank (1) having an open upper surface,
A stirrer (2) is suspended in the stirring tank. Stirrer (2)
A plurality of scrapers (2) are arranged in a stirring tank (1) in a radial direction on a rotating shaft (21) penetrating freely and airtightly through a central portion of a lid (13).
A shaft formed by projecting 2) and projecting outward from the lid plate (13)
(21) The variable speed rotation drive device (23) is connected to the upper end. The stirring tank (1) has a double structure, and a cooling water filling chamber (10) is provided between the inner wall and the outer wall. A cooling water supply port (11) and a discharge port (12) are connected to the chamber. ing. An inert gas supply pipe (4) and a gas pressure gauge (5) are connected through the cover plate (13).

Metal particles to be ground in a stirring tank (1), diameter 5
mm steel balls and toluene, benzene, n-
A water-insoluble organic solvent such as hexane or one or a mixture of two or more of them is charged as a grinding aid and covered. The agitation tank (1) is filled with an inert gas such as N2 or Ar from the inert gas supply pipe (4), and the agitation tank (1) is maintained at a slightly higher pressure than the atmospheric pressure to ensure the invasion of the outside air. The stirring body (2) is rotated in this state. The steel balls and metal particles repeatedly collide, and the metal particles are crushed. A supply pipe (61) for the coating treatment liquid is connected to the stirring tank (1). Cover plate (13)
, A coating liquid supply pipe (61) is inserted into the stirring tank (1), and the processing liquid tank (6) is connected to the supply pipe (61).
A lid (62) is hermetically attached to the upper opening of the tank (6),
Further, an inert gas filling pipe (63) is connected to the upper part of the tank (6), and the gas layer between the liquid surface of the tank (6) and the lid is always filled with the inert gas to maintain the pressure above the atmospheric pressure. It is maintained to prevent the outside air from flowing into the tank (6). Further, a liquid thermometer (7) for measuring the temperature of the liquid in the stirring tank (1) is provided so as to penetrate the cover plate (13).

In the surface treatment solution, the metal particles are pulverized to a desired particle size, and the alcoholic solvent is rapidly mixed with the necessary amount of phosphoric acid in a separate container within about 10 minutes immediately before the coating treatment is performed. Thus, the esterification of phosphoric acid was suppressed as much as possible, and this was transferred to the tank (6). If the ferromagnetic metal nitride fine powder is used in a range from room temperature to about 200 ° C., even if the ferromagnetic metal nitride fine powder treated with the processing solution with advanced esterification has sufficient acid resistance, It shows chemical properties. However, for the purpose of being kneaded with a resin at a high temperature of 200 ° C. or more and being molded, the ferromagnetic metal nitride fine powder is treated with a solution avoiding the above-mentioned phosphoric esterification and covered with an inorganic phosphate thin film. Must be used.

Treatment Method 250 g of Sm-Fe-N ferromagnetic metal nitride fine powder (manufactured by Sumitomo Metal Mining Co., Ltd.) and 500 g of n-hexane having an average particle size of about 20 μm were weighed, and a powder having a diameter of about 5 mm was obtained. 3 kg of a steel ball is put into the stirring tank (1) of the above-mentioned processing apparatus, and the gas layer between the liquid surface and the lid (13) is purged with nitrogen.
It was pulverized for an hour to obtain a ferromagnetic metal nitride fine powder having an average particle diameter of 2 μm or less.

A predetermined amount of phosphoric acid is mixed and dispersed in 20 g of methanol within 10 minutes immediately before the oxidation-resistant treatment, and the prepared oxidation-resistant treatment solution is charged into a treatment apparatus which has been purged with nitrogen. The oxidation-resistant treatment was performed by stirring for 30 seconds in an atmosphere. The solvent is removed by maintaining the slurry-like mixture composed of the treated ferromagnetic metal nitride fine powder and the solvent at 60 to 100 ° C. while evacuating with a vacuum pump using a vacuum dryer to remove the solvent. Magnetic fine powder was obtained (sample No. 1 to sample No. 7, sample No. 1 is a comparative example).

Table 1 summarizes the sample weight and the oxidation initiation temperature when the amount of phosphoric acid added for the oxidation resistance treatment was changed. The oxidation start temperature was evaluated at the temperature at which the sample weight increased by 0.5% of the initial value when the sample was heated at a rate of 5 ° C / min under a flow of dry air (20 ml / min). Temperature. It can be said that the higher this temperature is, the more stable it is against thermal oxidation.

The amount of phosphoric acid added during the oxidation-resistant treatment is determined by the specific surface area of the object to be treated and the required heat-resistant temperature, and is, for example, 1 to 10 with respect to a ferromagnetic metal nitride fine powder having an average particle size of about 2 μm. An oxidation-resistant film having an oxidation start temperature of 200 ° C. or more was obtained in the range of weight%. Like sample No. 7, sample 25
If the addition amount of phosphoric acid is 25%, which is 10% of 0 g, the oxidation start temperature reaches 512 °. If the amount of phosphoric acid to be added is large (for example, 15%), the esterification reaction proceeds between the excess phosphoric acid and the alcoholic solvent in the drying step after the treatment, and the produced ester exerts an adhesive effect. This causes problems such as solidification of the ferromagnetic metal nitride fine powder and adhesion to the container. In addition, for example, sample No.
As shown in FIG. 3, the amount of phosphoric acid added during the oxidation resistance treatment is
Even when the amount is as small as 0.1%, the oxidation onset temperature is lower than that of the sample to which a large amount of phosphoric acid is added, but a sufficient effect was observed to prevent ignition in handling in the air.

It was confirmed that an oxidation-resistant effect was obtained even when the pulverizing step and the oxidation-resistant treatment were performed separately. Pulverization was performed in a nitrogen atmosphere for 1 hour in the same manner as in the above step, and drying was performed using a vacuum dryer without performing heat treatment. In order to prevent ignition at the time of taking out, after sufficiently cooling to room temperature, it was first replaced with nitrogen and then gradually replaced with air, and then taken out. Subsequently, a predetermined amount of phosphoric acid was added to the obtained ferromagnetic metal nitride fine powder within 10 minutes immediately before the coating treatment.
g of methanol was added to a treatment apparatus together with an oxidation-resistant treatment liquid prepared by mixing and dispersing in methanol, and the mixture was stirred for 30 seconds under a nitrogen atmosphere to perform an oxidation-resistant treatment. The obtained slurry mixture was dried by the above method to obtain a heat-resistant ferromagnetic fine powder (Sample No. 8).

[0030]

[Table 1]

[0031]

[Specific Example 2] Among the oxidation-resistant ferromagnetic fine powders produced in Specific Example 1, samples No. 1 and No. 4 were used to prepare a resin-containing composite material. 1 part by weight of an aminosilane coupling agent with respect to 100 parts by weight of the oxidation-resistant ferromagnetic fine powder,
Polyamide 12 was added in an amount of 10.1 parts by weight and mixed and stirred in a universal mixer for 3 minutes to obtain a resin composite material composition. The obtained resin composite material composition is processed into pellets by a single-screw extruder (cylinder section set temperature: 250 ° C.), and then the pellets are injected into an injection molding machine (cylinder section temperature: 2).
Injection molding is performed at 60 ° C, mold set temperature 100 ° C)
A test piece (10 × 10 × 7 mm) was prepared and used for evaluation.

FIG. 1 shows the results of examining the change in the magnetic characteristics of the test piece surface when the test piece was held at 80 ° C. and 90% RH. The evaluation of the magnetic properties was carried out by keeping the above condition for a predetermined time and then taking out the test chamber, and measuring the flux value on the test piece surface after 30 minutes or more and the temperature was sufficiently lowered.

[0033]

EXAMPLE 3 Sample No. 4 of the oxidation-resistant ferromagnetic fine powder produced in Example 1 was mixed with strontium ferrite at 1:
1 part by weight, 1 part by weight of aminosilane coupling agent and 11 parts by weight of polyamide 12 were added to 100 parts by weight of the mixed fine powder, and mixed and stirred in a universal mixer for 3 minutes to obtain a resin composite. A material composition was obtained. A test piece (10 × 10 × 7 mm) was prepared from the resin composite material composition thus obtained by the method of Example 2, and the same evaluation was performed.

FIG. 2 shows a test piece made of a resin composite material prepared by mixing the ferromagnetic fine powder of sample No. 4 and strontium ferrite in a resin at a ratio of 1: 1 at 80 ° C.
It is the result of investigating the change of the magnetic characteristic when holding in 90% RH. The comparative example in the figure is a measurement result of a test piece similarly manufactured using the ferromagnetic fine powder of Sample No. 1.

As is clear from Table 1, in the case of fine powder having an average particle size of 2.0 μm or less, the amount of phosphoric acid added was 0.1%.
%, The oxidation start temperature was higher than that of the comparative example, which indicates that the oxidation resistance to thermal oxidation was improved.

When the pulverizing step and the oxidation-resistant treatment are performed separately, even though the amount of phosphoric acid added is the same, the oxidation onset temperature is lower than in the case where the pulverization and the oxidation-resistant treatment are performed simultaneously, but the obtained oxidation-resistant effect is small. The effect of the oxidation resistance treatment was recognized. This is because a part of the surface of the ferromagnetic fine powder has already been oxidized in the drying step after the pulverization, and a thicker phosphoric acid compound film is required to stop the oxidation which easily proceeds by heat.

As a comparative example, in sample No. 1 which was not subjected to the oxidation resistance treatment, the metal nitride was pulverized in a nitrogen atmosphere,
Since ignition occurred during handling of the ferromagnetic metal nitride fine powder in the atmosphere, it became necessary to handle the powder after pulverization under a nitrogen atmosphere. On the other hand, with respect to all of the samples No. 2 to No. 8 subjected to the oxidation resistance treatment of the present invention, ignition of the ferromagnetic fine powder and clogging of the molding in the compounding step, kneading step, and injection molding step in the air. There were no problems caused by oxidation, such as ignition of the purged material.

Sample No. 1, which had not been subjected to the oxidation resistance treatment, generated heat due to an increase in the pressure in the kneader due to the high viscosity of the molten resin composite material during the kneading process, and finally the temperature exceeded the set temperature of the kneader. Was also as high as 30-40C. Furthermore, when the obtained resin composite material is injection-molded, the molding temperature is set to 250 ° C. due to low fluidity.
Can not be filled with resin composite material in the mold
It was necessary to raise the temperature to 70 ° C. Unnecessarily exposing the resin composite material to a high temperature in this way should be avoided because it causes thermal damage to the resin and adversely affects product quality such as a decrease in strength due to deterioration of the resin. On the other hand, in the samples No. 2 to No. 8 subjected to the oxidation resistance treatment, the material temperature during the kneading is stable throughout the range of about 255 to 260 ° C., and the injection molding is sufficiently performed at the molding temperature of 250 ° C. Since it is possible, thermal damage to the resin composite material can be minimized, and quality deterioration can be avoided.

As is clear from comparison between Sample 1 and Sample 4 in FIG. 1, the flux value on the surface of the test piece of Sample 1 sharply decreased from the measurement 20 hours after the start of the endurance test, and it was 500 hours. Later, it was demagnetized to 58% of the initial value. On the other hand, in the case of Sample 4, which is a resin composite material manufactured using the ferromagnetic fine powder subjected to the oxidation resistance treatment, there is almost no decrease from the start to the end of the test, and the test start 50
After 0 hour, the initial value was reduced to only 95% of the initial value, indicating that the molded article of the resin composite material has an oxidation resistance effect against oxidation due to humidity.

As can be seen from FIG. 2, in the comparative example, the open flux value on the test piece surface sharply decreased from the measurement 20 hours after the end of the endurance test, and demagnetized to 67% of the initial value after 500 hours. I was On the other hand, in the present invention, which is a resin composite material prepared using the ferromagnetic fine powder subjected to the oxidation resistance treatment, the decrease is hardly observed from the start to the end of the test, and the initial value is 500 hours after the start of the test. It is only reduced to 96% at most, and it is understood that the same oxidation resistance effect can be obtained in the resin composite material molded article even when mixed with the ferromagnetic ferrite fine powder.

From the above results, it can be seen that not only the stability of the ferromagnetic metal nitride fine powder itself against oxidation was significantly improved by performing the anti-oxidation treatment, but also that the ferromagnetic metal nitride fine powder was used alone or mixed with the ferromagnetic ferrite fine powder. It can be seen that the oxidation resistance of the product obtained by molding the resin composite material mixed with the resin was significantly improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a change in magnetic properties when a test piece manufactured using ferromagnetic fine powders of Sample No. 1 and Sample No. 4 is placed in 80 ° C. and 90% RH.

FIG. 2 shows a change in magnetic properties when a test piece manufactured using a resin composite material manufactured by mixing ferromagnetic fine powder and strontium ferrite in a resin at a ratio of 1: 1 is maintained at 80 ° C. and 90% RH. It is a graph.

FIG. 3 is a sectional view of a coating apparatus.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/10 H01F 1/10 F term (Reference) 4J002 BB031 CD001 CL001 DF016 FB076 5E040 AA01 AA03 AA06 AA09 AA19 AB03 BB03 BC01 CA01 NN01 NN06

Claims (5)

[Claims] 1. A ferromagnetic fine powder for a plastic magnet, wherein the ferromagnetic metal nitride fine powder is provided with oxidation resistance by covering the surface with a thin film of an inorganic phosphate compound containing no organic group. 2. The ferromagnetic metal nitride fine powder has an average particle size of 2
The ferromagnetic fine powder for a plastic magnet according to claim 1, which has a size of not more than μm. 3. A plastic magnet characterized in that the ferromagnetic metal nitride fine powder is coated with a fine powder provided with oxidation resistance by covering the surface with a thin film of an inorganic phosphate compound containing no organic group. For resin composite materials. 4. A ferromagnetic fine powder which is provided with oxidation resistance by uniformly covering the surface of a ferromagnetic metal nitride fine powder with a thin film of an inorganic phosphate compound containing no organic group; A resin composite material for a plastic magnet, characterized in that a ferromagnetic compound fine powder such as a ferromagnetic ferrite fine powder having different properties from the above is blended in a resin. 5. The ferromagnetic metal nitride fine powder has an average particle size of 2
5. The ferromagnetic fine powder for a plastic magnet according to claim 3, which has a size of not more than μm.