JPH0618130B2 - Permanent magnet material composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a permanent magnet material composition, and more particularly to a permanent magnet material composition having excellent magnetic properties and mechanical strength.

"Prior Art and Problems" Alloy magnets containing rare earth metals and transition metals as main components (hereinafter referred to as rare earth magnets) have superior magnetic characteristics to conventional ferrite-based and alnico-based magnets. Therefore, in recent years, it has been used in various fields mainly for small motors. Such rare earth magnets are sintered magnets manufactured by powder metallurgy and plastic molded magnets fixed with an organic binder (hereinafter referred to as plastic magnets).
However, sintered magnets have the drawbacks of low mechanical strength and poor dimensional accuracy, and plastic magnets are being widely used to compensate for these drawbacks.

Since such a plastic magnet uses a synthetic resin, which is a non-magnetic material, as a binder, it has a drawback that magnetic properties are inferior to those of a sintered magnet. Therefore, in order to make the magnetic properties of the plastic magnet the same, it is necessary to increase the content of the rare earth magnetic powder, and increase the pressure during pressure molding to reduce the porosity and improve the packing density of the rare earth magnetic powder. .

However, conventional rare-earth plastic magnets have a low strength of the molded body before being hardened and solidified when the content of the rare-earth magnetic powder is high, and are easily damaged or deformed, or the mechanical strength of the molded body after curing is low. There is a problem. Further, when the pressure is increased to reduce the porosity, a large load is applied to the molding die during compression molding, and the die is likely to be damaged.

"Means for Solving the Problems" In view of the problems of the above-mentioned conventional techniques, the present invention reduces the load on the mold at the time of molding and improves the density of the molded body to improve the magnetic properties. As a result of intensive research to provide a rare earth plastic magnet having high mechanical strength and excellent dimensional stability, it was found that the intended purpose can be achieved by blending a specific silane coupling agent. The present invention has been completed.

That is, the present invention relates to an intermetallic compound magnetic powder containing a rare earth metal and a transition metal as main components, a synthetic resin as a binder, and a general formula [R ₁ -R ₂ ] _4-n Si- (R ₃ ). _n (R ₁ : a perfluoroalkyl group having 1 to 20 carbon atoms, R ₂ : an alkyl group having 1 to 3 carbon atoms, R ₃ : an alkoxy group, n: 1 to 3) The content is a permanent magnet material composition as a basic component.

As the intermetallic compound magnetic powder containing a rare earth metal and a transition metal as main components used in the present invention, SmCo ₅ , Sm ₂ Co ₁₇ , or R-Fe-B system alloy magnet (R is Nd and / or Pr, or Magnetic powders known as those obtained by substituting a part of these with one or more rare earth elements), and other materials, such as iron, copper, zirconium and other metals for improving magnetic properties. You may add. Among these, R-Fe-B based alloy magnets (R is Nd and / or Pr, or a part of them replaced with one or more rare earth elements) having high magnetic properties are preferable. Further, Nd-Fe-B based magnetic powder is particularly preferable.

The intermetallic compound magnetic powder is in the form of powder, but in order to improve the density of the compact and obtain high magnetic properties, the particle size distribution should be as wide as possible within the range of the particle size used. There is a need to. That is, the intermetallic compound magnetic powder that can be used in the present invention is preferably a mixture of particle groups having different particle sizes in the range of 1 μm to 1 mm. The maximum particle size in these particle groups can be appropriately selected according to the target minimum thickness of the molded body.

Specific silane coupling agents used in the present invention include general formula [R ₁ -R ₂ ] _4-n Si- (R ₃ ) _n (R ₁ : a perfluoroalkyl group having 1 to 20 carbon atoms, R ₂ Is a compound represented by an alkyl group having 1 to 3 carbon atoms, R ₃ : an alkoxy group, and n: 1 to 3). The compound reduces friction of the intermetallic compound magnetic powder at the time of molding, and has a high packing density. The molded product of is obtained, and the magnetic properties are greatly improved. The method of adding the silane coupling agent is not particularly limited, but it is preferable to apply the silane coupling agent to the magnetic powder in advance. As a coating method, as it is or after diluting it with a diluent, it is coated with a granulating blender, a ribbon blender, a rotary blade mixer or the like.

In the present invention, a thermosetting resin or a thermoplastic resin can be used as the binder, but in order to obtain the intended composition, the binder is mixed more uniformly with the intermetallic compound magnetic powder. It is desirable that the binder itself has a role of reducing friction between the magnetic powders of the intermetallic compound during compression molding. That is, it is preferable to use a liquid thermosetting resin as the binder of the present invention, whereby the binder has a low viscosity and is not only uniformly distributed on the surface of the intermetallic compound magnetic powder, but also at the time of compression molding. Friction between the intermetallic compound magnetic powders is reduced, a compact having a high packing density can be easily obtained, and the magnetic properties are greatly improved. Furthermore, when such a binder is used, a compact having a desired compact density and high magnetic properties can be obtained even when the compression molding pressure is lowered, and the load on the molding die can be reduced.
The value from an industrial point of view is extremely high.

The liquid thermosetting resin that can be used in the present invention is a liquid at room temperature and is a phenol resin, an epoxy resin, a urea resin, a melamine resin, a furan resin, an unsaturated polyester resin, or the like, but a phenol resin, particularly a resol-type phenol. Resins are preferred.

In order to enhance the friction reducing effect of such a synthetic resin binder,
It is preferable to include a plasticizer in the binder.

Plasticizers that can be used in the present invention include polyester plasticizers, phthalic acid ester plasticizers, epoxidized oil plasticizers, fatty acid ester plasticizers, and others, which are selectively used according to the type of liquid thermosetting resin used. To do. For example, when a phenol resin is used, adipic acid polyester plasticizers, phthalic acid polyester plasticizers, phosphoric acid ester plasticizers, dibutyl phthalate, epoxidized soybean oil and the like are very suitable.

The composition of the present invention comprises an intermetallic compound magnetic powder, a synthetic resin as a binder, and a silane coupling agent,
The compounding ratio is preferably 0.1 to 5 parts by volume of the silane coupling agent with respect to 100 parts by volume of the magnetic powder of 50 to 90% by volume and the synthetic resin of 50 to 10% by volume. If the magnetic powder is less than 50% by volume, it is difficult to obtain the desired magnetic properties, while if it exceeds 90% by volume, the mechanical strength is lowered.
If the silane coupling agent is less than 0.1 part by volume, a sufficient effect of reducing friction cannot be obtained, and if it exceeds 5 parts by volume, the increase of the effect is not so remarkable and is rather economically undesirable. The plasticizer is added in the range of 2 to 25 parts by volume based on 100 parts by volume of the magnetic powder and the synthetic resin. Further, in order to improve the properties of the composition of the present invention, a lubricant, a heat stabilizer,
A small amount of other modifying additives may be added and used.

In molding the composition described above, a compression molding method such as hot pressing or cold pressing can be used, but when a liquid binder is used, the strength of the molded body after compression molding and before curing is large, There is no need to employ a hot press that is troublesome in various operations. That is, when molding the composition of the present invention, it is compression-fixed at room temperature and then cured and solidified at the curing temperature of the thermosetting resin used. By such a method, a molded product having high productivity and having good dimensional accuracy and magnetic properties can be obtained. Suitable pressure conditions for compression molding are ² to 8 t / cm ² .
At pressures below 2 t / cm ^{2, the} packing densities achieved with the compositions according to the invention may be inadequate;
Even if a pressure of more than / cm ² is applied, the packing density can no longer be remarkably improved, the load on the mold becomes large, and the mold is easily damaged. Further, when heat curing is performed after molding such a composition, it is more preferable to perform heat curing in nitrogen or an inert gas for the purpose of preventing deterioration of magnetic properties due to oxidation of the intermetallic compound magnetic powder. Is.

"Examples" Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 6 Nd-Fe-B based magnetic powders were mixed with a silane coupling agent, a synthetic resin and a plasticizer in a compounding ratio as shown in Table 1. Then, the obtained mixture was compression-molded at the pressure shown in Table 1 to obtain a cylindrical fixed molded body of 12.5 mmφ × 8 mm, and the molded body was heat-cured at 180 ° C. for 2 hours to give a good appearance. A molded body sample having the above was obtained. Table 1 shows the results of measuring the magnetic characteristics of the molded body sample with a BH tracer and the density of the molded body sample.

Further, using a mixture having the same composition as that of the cylindrical sample, a ring-shaped molded body having an outer diameter of 8 mm, an inner diameter of 6 mm and a height of 4 mm is prepared, and after heat curing, the ring-shaped molded body is diametrically moved at a speed of 5 mm / min. The load was applied, and the maximum load when the molded body was broken was measured, and is shown in Table 1 as radial crushing strength.

As a result, as shown in Table 1, the maximum energy product was 7.5 to 8.0 MGOe, which was significantly improved as compared with the comparative example.

Comparative Examples 1 to 3 Without using a silane coupling agent or using a known silane coupling agent or zinc stearate,
The same operation as in the example was carried out with the compounding ratios shown in the table.

As a result, the maximum energy products of the obtained molded products were all less than 7.0 MGOe.

[Operation / Effect] As described above, according to the present invention, friction during molding of the intermetallic compound magnetic powder is reduced, and the magnetic powder has high density and high magnetic characteristics.
Further, it is possible to provide a rare earth plastic magnet having excellent mechanical strength, and it can be used in various applications such as a field magnet for a small motor and a correction magnet for a TV.

Claims (2)

[Claims] 1. An intermetallic compound magnetic powder containing a rare earth metal and a transition metal as main components, a synthetic resin as a binder, and a general formula [R ₁ -R ₂ ] _4-n Si- (R ₃ ). _n (R ₁ : a perfluoroalkyl group having 1 to 20 carbon atoms, R ₂ : an alkyl group having 1 to 3 carbon atoms, R ₃ : an alkoxy group, n: 1 to 3). A permanent magnet material composition as a basic component. 2. Intermetallic compound magnetic powder 50 to 90% by volume
And 50 to 10% by volume of the synthetic resin and 100 parts by volume of the magnetic powder and the synthetic resin in total, the general formula [R ₁ -R ₂ ] _4-n -Si- (R ₃ ) _n (R ₁ : perfluoroalkyl group having 3 to 20 carbon atoms, _{R 2:} an alkyl group having 1 to 3 carbon atoms, _{R 3:} an alkoxy group, n: 1 to 3) silane coupling agent 0.1 represented by
The composition according to claim 1, which comprises 5 parts by volume as a basic component.