JPH08293411A - Bond magnet - Google Patents

Abstract

PURPOSE: To enhance the magnetic performance of a bond magnet by using furan resin as a binder, which is treated by baking after hardening, for the bond magnet created by bonding magnetic powder with a binder. CONSTITUTION: A bond magnet is furan resin with the binder baked in vacuum and thus the binder is shrunk by the baking treatment of the furan resin, magnetic powder is adhered more closely each other, and magnet performance can be improved. For the hardening of furan resin used as the binder, normally an acidic catalyst is used; however, the acidic catalyst tends to easily leave spaces between magnetic powder for rare earth type Nd2 -Fe14 -B, Sm2 -CO17 and Sm2 -Fe17 -N3 magnetic powder having high magnetic performance; and thus it is better to add only a small amount of acidic catalyst; and 0.01 equivalent to 0 equivalent is adequate for 100g of magnetic powder. Weight decrease factor for baked furan resin is 2 to 90% because of the improvement of magnetic characteristics and mechanical strength but 5 to 60% is more desired. By doing this, the density of the bond magnet can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonded magnet in which magnetic powder is bonded with a furan resin which has been hardened and baked.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional bonded magnet is prepared by kneading finely divided magnetic powder with a thermoplastic resin or thermosetting resin or a low melting point metal as a binder to coat the finely divided magnetic powder. , Extruded, molded into a predetermined shape by a molding method such as compression / injection, after the curing step if the comprehensive material is thermosetting, after molding if the binder is thermoplastic or low melting point metal, It is magnetized to make bonded magnets.

However, in the conventional example, the volume ratio of the binder and air bubbles which are the non-magnetic components in the bond magnet is the smallest, and even the bond magnet obtained by compression molding using the epoxy resin as the total material is 20% or more. Therefore, the maximum energy product (BHm
It was as low as 50th that ax) was stably obtained.

Therefore, in order to improve the BHmax value of the bonded magnet, the non-magnetic component is reduced and the pressure at the time of molding is increased so that the magnetic powder interval is made as close as possible and close to the density peculiar to the magnetic material. Is being carried out.

However, among the non-magnetic components, the binder is
It is difficult to reduce the amount of binder because the binding force of the bond magnet will decrease if it is not included above a certain level, and it is also difficult to reduce the amount of internal bubbles due to galling of magnetic particles even if the molding pressure is increased. However, the mold life of the molding machine is shortened by increasing the molding pressure.

Furthermore, for low BHmax values, Arnco type, Sm-Co ₅ type, isotropic N type, rather than ferrite type are used.
d ₂ -Fe ₁₄ -B system, Sm ₂ -Co ₁₇ system, anisotropic Nd ₂
Materials having higher magnetic properties, such as —Fe ₁₄ —B system and Sm ₂ —Fe ₁₇ —N ₃ system, are used for bonded magnets. For the above reasons, when compared with the same material, bonded magnets have a higher bond strength than bonded magnets. The magnetic performance of the magnet is always low.

[0007]

Therefore, the problem to be solved by the present invention is the magnet performance of the bonded magnet, which is lower than that of the sintered magnet.

[0008]

A bonded magnet according to the present invention is characterized in that it is a furan resin in which a binder is hardened and then fired.

In the bonded magnet according to the present invention, the binder is a furan resin which is fired in a vacuum. Therefore, the firing treatment of the furan resin causes the binder to shrink and the magnetic powder to approach to improve the magnet performance. Can be done.

The furan resin used as the binder of the present invention is cured by using an ordinary acidic catalyst, but Nd ₂ —Fe ₁₄ —B system, Sm ₂ —Co ₁₇ system, and Sm ₂ — having high magnet performance are used.
Since rare earth-based materials such as Fe ₁₇ -N ₃ and magnetic powders are easily removed, it is preferable not to add a small amount of an acidic catalyst, and 0.01 equivalent to 0 equivalent is suitable for 100 g of magnetic powder. One equivalent is the number of grams obtained by dividing the molecular weight of the acidic catalyst by the number of hydrogen atoms capable of reacting as an acid.

Further, in order to cure the furan resin and further improve the magnetic properties by firing without being adversely affected by acid, the liquid furan resin is condensed with a binder at the time of pressure molding without using an acidic catalyst. By advancing in advance, heat-curing after pressure molding, and further firing, the magnet performance can be improved by contraction of the binder.

The furan resin is a thermosetting resin having a furan ring, which is a liquid substance or a semi-solid substance before molding, and is a furfuryl alcohol / furfural cocondensation type,
Furfuryl alcohol type, furfural / phenol cocondensation type, furfural / ketone cocondensation type, furfuryl alcohol / urea cocondensation type, furfuryl alcohol / phenol cocondensation type and the like are used. The weight ratio of the furan resin in the bonded magnet is 20% to 0.5%, and more preferably 10% to 1. 5%.

Further, the furan resin forms a three-dimensional network structure by the curing reaction, and is baked by the curing shrinkage stress caused thereby, so that the volatile thermal decomposition products and the built-in moisture are efficiently scattered, and the furan resin 10 ^-3 to contract
It is preferable to perform firing at mmHg or less, particularly 10 ⁻⁴ mmHg or less.

The weight reduction rate of the furan resin fired at this time is 2% to 90 from the viewpoint of improving magnetic properties and mechanical strength.
%, More preferably 5% to 60%.

[0015]

【Example】

 (Embodiment 1) The present invention will be described below with reference to FIG.

As the magnetic material, isotropic Nd ₂ -Fe _{14 is used.}
-B type magnetic powder (trade name: MQP-B, manufactured by GM, USA) 2
As a binder, a furfuryl alcohol / furfural co-condensation type liquid furan resin (trade name: VF-303, manufactured by Hitachi Chemical Co., Ltd.) was used as an acidic catalyst for 100 g of crushed particles having a particle size of 50 μm or less. Acrylic acid (CH
₂ : CHCOOH) added from 0 to 0.0001,
0.001 and 0.01 equivalents were changed respectively (the addition amount of the furan resin to the magnetic powder is 2.5 wt% constant),
What was covered with magnetic powder was prepared. On the other hand, as a comparative sample, the same magnetic powder was used and an epoxy resin (trade name: # 26
Magnetic powder (5, made by Sumitomo 3M) was coated on the magnetic powder at 2.5 wt%. A diameter of 10 mm obtained by adding 0.3 wt% of zinc stearate as a lubricant to the magnetic powder coated with the binder (based on the magnetic powder coated with the fixing material).
Then, 1.2g is put into the molding die of No. 1, compression molding is performed with a pressing force of 5 ton / cm ² , and after taking out from the die, 150 ° C.
The binder was heat-cured for 1 hour. The maximum energy product B from the external dimensions after curing, from the weight to the density and from the self-recording magnetometer
Hmax was determined. Then, the tablet-shaped molded product after curing is put in a vacuum furnace of 1 × 10 ⁻⁵ mmHg, the binder is baked at a temperature rising rate of 2 ° C./min for 240 ° C./30 minutes, and further heated to 2 ° C./min. The following table shows the results of the density and BHmax value obtained from the external dimensions and the weight after curing after firing at 280 ° C./30 minutes at a temperature rate and returning to normal temperature and pressure.
The change in weight of the binder at this time was a little less than 10% from the time when the curing was completed. BHmax value is MG
Oe, density is g / cc

[0017]

[Table 1]

An acid curing catalyst is added to the furan resin in an amount of 0 to 0.0.
It can be seen that, when 1 equivalent is added, the density is increased by firing, and the performance of the magnet is significantly improved as compared with the bonded magnet using the epoxy resin as the binder.

(Example 2) As in Example 1, the liquid furan resin was placed in a container and left in a dryer at 90 ° C for 0 minutes.
It was shaken for 30 minutes, 60 minutes, and 90 minutes to accelerate the curing of the liquid furan resin. These were diluted with acetone, and similarly to Example 1, the isotropic Nd ₂ —Fe ₁₄ —B based magnetic powder was sprayed with acetone so that the furan resin component was 2.5 wt%, and coated on the magnetic powder. 1.2g of zinc stearate, which is a lubricant, was added to the magnetic powder coated with each furan resin, and 1.2g was put into a molding die having a diameter of 10mm, and compression molding was performed at a molding pressure of 5tom / cm ^2. The tablet-shaped molded product was taken out, and the density and BHmax value obtained from the external dimensions after curing at 150 ° C. for 1 hour and the weight after curing were measured. Then, these molded products are placed in an atmosphere of 1 × 10 ⁻⁵ mmHg, and the temperature is increased at 2 ° C./min.
Baking with 280 ° C./30 minutes at a heating rate of ℃ / min, the density obtained from the external dimensions of the tablet-shaped molded product at room temperature and normal pressure and the weight after completion of curing, and the BHma obtained from a self-recording magnetometer
The x values are shown in the table below.

Here, the condensation reaction was promoted and the viscosity in the thickened state was measured using an E-type viscometer manufactured by Toki Sangyo Co., Ltd. at a cone angle of 3 ° and 25 ° C. of the cone plate.

[0021]

[Table 2]

As described above, if the furan resin whose curing reaction is accelerated in advance is used, the effect of baking can be sufficiently enhanced without fear of deterioration due to acid without using an acidic catalyst.

The same effect can be expected when the method of accelerating the curing is carried out by heating the liquid resin alone, or by heating after coating the magnetic powder to accelerate the curing.

Further, although it has been described that the curing is promoted without using the acidic catalyst, it is naturally applicable to the case where the acidic catalyst is used, but it is easy to apply it to a region where the acidic catalyst is small. However, when a relatively large amount of catalyst is used, the condensation reaction proceeds faster,
It is necessary to take measures such as lowering the acceleration temperature or shortening the acceleration temperature. If the reaction of the coating resin proceeds too much, the binding force of the magnetic particles becomes insufficient during heat curing after molding, which causes a problem such as falling of the magnetic particles from the bonded magnet.

(Example 3) Sm ₂ -Co ₁₇ as magnetic powder
Prepare magnetic powder (trade name: R30, manufactured by Shin-Etsu Chemical Co., Ltd.) for system anisotropy to 250 μm or less, furan resin (trade name: VF-30)
3 Hitachi Chemical Co., Ltd.) was heated at 90 ° C./90 minutes to promote hardening, and coated with 2.5 wt% of the magnetic powder. 0.3 wt% of zinc stearate as a lubricant was added to these to obtain a size of 5 mm × 5 mm. Put 0.9g into the mold and 5 in the magnetic field
A prismatic molded product was obtained with a pressure of ton / cm ² . As a comparative sample, an epoxy resin (trade name: # 265, manufactured by Sumitomo 3M Limited) was coated on the same magnetic powder in an amount of 2.5 wt%, and the same amount of lubricant was added to the same magnetic powder. I got a thing. The binder was cured at 150 ° C. for 1 hour in each of these molded products, the density was determined from the outer mold size and weight, and the BHmax value was determined using a self-recording magnetometer. Then, place these molded products in a vacuum furnace at 1 × 10 ⁻⁵ mm
In a Hg atmosphere, the temperature was raised to 400 ° C./30 minutes under a temperature rising condition of 1 ° C./minute, the binder was fired, and the temperature was returned to normal temperature and normal pressure.
When the x value was calculated

[0026]

[Table 3] Met. At this time, the weight change of the binder by firing in this example was -30 wt% based on the time of curing. As shown in the examples, the BHmax is increased by firing.
The value can be improved. Volume shrinkage can be expected as the firing temperature is higher, but it is 28 with isotropic Nd ₂ -Fe ₁₄ -B based magnetic powder.
Although it was performed only up to 0 ° C., it was up to 400 ° C. in the Sm ₂ —Co ₁₇ system. This is determined in consideration of the properties of the magnetic powder to be used, since it causes the precipitation of α-Fe and the deterioration of the magnetic properties accompanying the phase transformation. In addition, the rate of temperature rise must be determined depending on the wall thickness of the molded product, and if the rate of temperature rise is too fast, thermal decomposition rapidly occurs inside the molded product, causing cracks, blisters, cracks, etc. of the molded product. Therefore, it is necessary to select the heating rate considering the wall thickness.

As can be seen from Table 3 of the examples, the density of the molded product is higher than that of the case of molding under the same pressure as compared with the epoxy resin, and the higher density can be achieved by firing. This means that if an attempt is made to obtain the same performance as the epoxy resin, the molding pressure can be made lower than that, and the life of the molding die can be extended.

The cured furan resin used in the present invention is very stable to acid, and the bond magnet is dipped in hydrochloric acid or the like.
When the residual resin component after removing the magnetic powder was measured by FT-IR (Fourier transform spectrophotometer), it was found that carbonization proceeded by firing as shown in FIGS. 3 and 4. It should be noted that the carbon precursor is still in the state of firing at 1100 ° C.

A furan resin cured product obtained by curing the furan resin alone at 150 ° C. for 1 hour was fired at 1 × 10 ⁻⁵ mmHg at various temperatures for 1 hour to obtain a weight ratio and a volume based on the cured product. When I calculated the ratio

[0030]

[Table 4] Met.

[0031]

As described above, according to the present invention,
As a binder that binds magnetic powder, it is possible to increase the density of the bond magnet by curing the furan resin and then firing it, and to greatly improve the low magnet performance, which was the disadvantage of conventional bond magnets. Made possible

[Brief description of drawings]

FIG. 1 is a process drawing according to an embodiment of the present invention.

FIG. 2 is a process diagram illustrating a conventional example.

FIG. 3 FT-I in curing / baking of the binder of the present invention
R curve diagram.

FIG. 4 is an FT-IR curve diagram for firing the binder of the present invention.

Claims (3)

[Claims] 1. A bond magnet obtained by binding magnetic powders with a binder, wherein the binder is a furan resin that has been subjected to a curing treatment and a firing treatment. 2. The bond magnet according to claim 1, wherein an acidic catalyst equivalent for curing treatment is used in an amount of 0 to 0.01 per 100 g of the magnetic powder. 3. The weight reduction rate of the binder due to the firing treatment is 2
The bonded magnet according to claim 1 or 2, characterized in that it is ˜90%.