JPH0246704A - Manufacture of compound magnet - Google Patents

Abstract

PURPOSE:To enhance the magnetic properties and corrosion resistance by a method wherein, in the manufacturing process of a compound magnet to pressure-mold a mixture of rare earth magnetic powder and a binder, the rare earth magnetic powder is surface-processed with a fluorine coupling agent. CONSTITUTION:The rare earth magnetic power contains alloy powder represented by a general formula R2T14B (where R represents rare earth group element including yttrium, likewise T: transition metal and B: boron). The fluorine base coupling agent is oligomer structure as represented by the formula I where n=1-3, iPrO: isopropyl radical, Mi: -CF2-(OCF-CF2)x-(OCF2)y-OCF3, x=1-10, y=1-10. The pressure molding falls under injection molding or compression molding. The surface of magnetic powder may be modified by either one out of the following tow processes i.e., the coupling agent itself or the same melted into a small amount of solvent is dripped or sprayed while agitating the magnetic powder or the coupling agent melted into a large amount of the solvent is mixed with the magnetic powder to be agitated and then the solvent is dried up to be removed.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a composite magnet obtained by pressure molding from a mixture of magnetic powder and a binder, and particularly relates to a method for manufacturing a composite magnet obtained by pressure molding a mixture of magnetic powder and a binder, and in particular, the powder filling amount when rare earth magnetic powder is used. This relates to improvements in corrosion resistance and corrosion resistance.

[Prior Art] Composite magnets have the following characteristics that cannot be obtained with sintered magnets, so demand for them has increased significantly in recent years.

(1) Radial anisotropy can be easily obtained.

(2) Less brittle than sintered magnets.

(3) Products with high dimensional accuracy can be obtained without post-processing.

(4) Thin-walled products can be easily obtained.

On the other hand, a drawback of composite magnets is that when a non-magnetic binder is added, the magnetic properties deteriorate depending on the amount of the binder. To improve this, it is necessary to mix as much magnetic powder as possible and, in the case of anisotropic powder, to bring the degree of orientation close to 100%.

[Problems to be Solved by the Invention] When producing a mixture of rare earth magnetic powder and a binder by injection molding, generally when a large amount of this magnetic powder is mixed in, the melt viscosity of the mixed material increases, and it becomes extremely difficult to process the mixture during injection molding. The flow becomes poor, and the moldability deteriorates or the product cannot be obtained. As methods for improving this drawback, addition of plasticizers and lubricants, and surface treatment of magnetic powder with various coupling agents have been proposed, but these methods are still not sufficient.

In addition, when manufacturing a mixture of rare earth magnetic powder and binder by compression molding, methods such as increasing the molding pressure, adjusting the particle size of the powder, and adding a lubricant have been proposed. Improvements are being made, but users are demanding even higher standards. Furthermore, a major drawback common to injection molding and compression molding is that the magnetic powder is easily corroded because it is rare earth-based. In the case of composite magnets used in electronic and electrical parts, corrosion tests are generally conducted at high temperature and high humidity (for example, 80° C., 95% RH), and the occurrence of corrosion is fatal. In order to solve this problem, the addition of antioxidants, the surface coupling method of magnetic powder, and the coating of molded products have been carried out, but these methods are still not sufficient in terms of corrosion resistance and cost.

Therefore, the technical problem of the present invention is to provide a method for manufacturing a rare earth composite magnet with improved magnetic properties and corrosion resistance.

[Means for Solving the Problems] The present inventors believe that the solution to these problems essentially lies in modifying the surface of the magnetic powder, so the present inventors have developed a method for improving both high lubricity and high hydrophobicity. As a result of extensive research into surface modifiers with this function, we discovered that a titanium coupling agent in which rare earth magnetic powder is preliminarily treated with a fluorine-based oligomer exhibits a remarkable effect, leading us to complete the present invention. Ta.

According to the present invention, there is provided a method for producing a composite magnet in which a mixture of a rare earth magnetic powder and a binder is pressure-molded, which comprises surface-treating the rare earth magnetic powder with a fluorine-based coupling agent. A method for manufacturing a magnet is obtained.

According to the present invention, there is obtained the method for manufacturing a composite magnet, wherein the fluorine-based coupling agent has an oligomer structure as shown in the following formula [I].

[I] (iPrO)n -Ti-(OCO-[M])4
-n22 In the method for manufacturing a composite magnet of the present invention, it is desirable that the rare earth magnetic powder contains samarium cobalt powder.

Further, in the method for manufacturing a composite magnet of the present invention, the rare earth magnetic powder may include an alloy powder represented by the general formula R2Tl4B (where R is a rare earth element containing yttrium, T is a transition metal, and B is boron). desirable.

Furthermore, in the method for manufacturing a composite magnet of the present invention, a method for manufacturing a composite magnet is obtained, wherein the pressure molding is injection molding or compression molding.

That is, the rare earth magnetic powder used in the present invention has the general formula
Samarium cobalt powder represented by SmCo5 and Sm2CO+7, etc., and alloy powder represented by the general formula R2T, 4B (R is a rare earth element including yttrium, T is a transition metal, and B is boron) (the best example is neodymium iron-boron). ) is used. The particle size of each particle is not particularly limited, but from the viewpoint of magnetic properties, it is about 5μ for SmCo, Sm2
The COHy type has a thickness of 10 to 40μ, the sintered type of R2T and 4B has a thickness of 2 to 50μ, and the quenched type has a thickness of 2 to 200μ.

The surface modifier for magnetic powder used in the present invention is a titanium-based coupling agent having fluorine-based oligomers as branches represented by the following structural formula.

(hereinafter abbreviated as FTi) (iPrO)n -Ti-(OCO-[M])4-.

n-1 to 3 iPrO: isobrobyl group M: -CF2(OCF-CF2
) (OCF 2 ) OCF 3x-1
~10y-1~10 The amount of FTi used in the present invention is arbitrary, but from an economical point of view and for the purpose of fully utilizing its effects, the amount of FTi used in the rare earth magnetic powder (below 0.1vt% is ineffective). , 1wL%
Even if you add more than that, there will be a surplus) 0.1~lvt%
is desirable. The surface modification treatment conditions for magnetic powder are generally known as a dry method, in which FTi is dissolved directly or in a small amount of solvent, and then dripped or sprayed while stirring the magnetic powder, and a wet method, in which FTi is dissolved in a large amount of solvent, Any method may be used in which the solvent is dissolved and stirred and mixed with the magnetic powder, and then the solvent is dried and removed. Further, heat treatment after mixing FTi with the magnetic powder is suitably carried out for 5 minutes to 30 minutes in an inert gas atmosphere at 80 to 150°C. This inert gas atmosphere is preferably N2 or A.

The surface-treated powder particles have a coating formed by adsorption of a coupling agent on their surfaces.

Note that the present invention is not limited to these surface modification treatment conditions.

The magnetic powder subjected to the surface modification treatment according to the present invention is then subjected to pressure molding such as injection molding or compression molding. First, when used for injection molding, it is kneaded with any thermoplastic resin. The cross-crossing is carried out using a heated kneader-screw or twin-screw extruder at a temperature above the melting point or softening point of the resin.

The obtained mixed wire material is pelletized and then subjected to injection molding.

On the other hand, when used for compression molding, it is mixed with any thermosetting resin, a predetermined molded product is obtained using a compression molding machine, and then cured by curing treatment.

The thus obtained molded product was subjected to magnetic property evaluation and moisture resistance testing in comparison with conventional methods, and we were able to obtain a product with performance that significantly exceeded the currently available products.

[Example] A more specific explanation will be given below using examples.

Example 1 97 parts of neodymium iron and boron magnetic powder (manufactured by GM) were put into a super mixer, and while vigorously stirring, 5 parts of FTto dissolved in a small amount of isopropanol was added dropwise over 5 minutes, and then heated to 100°C. for 15 minutes, then the solvent was removed in vacuo.

25 parts of a one-component epoxy resin was added to this mixture and mixed for an additional 3 minutes.

The obtained treated product was pressurized with a compression molding machine at 6 tons/c to obtain a molded product of 13φ■×10111Il. The molded article was cured at 120°C for 2 hours. The density of this thing is 6.
2g/c+n3, and the magnetic properties are (BH)max 1
It showed a high value of 0.2 MGOe.

A corrosion resistance test was also conducted, and the results are summarized in Table 1.

In the corrosion resistance test, the presence or absence of rust was confirmed with the naked eye in a constant temperature and humidity test under predetermined conditions, and the time at which rust was observed was recorded.

Comparative Example I The same procedure as in Example 1 was carried out except that 3 parts of epoxy resin was used instead of using FTi. The results are shown in Table 1.

Comparative Example 2 All examples were the same as Example 1 except that isopropyl triisostearoyl titanate (hereinafter abbreviated as STi) was used instead of FTi.
I did it in the same way. The results are shown in Table 1.

From Table 1, it can be seen that Example 1, in which neodymium iron boron magnetic powder was treated with FTi isopropanol solution, was compared with Comparative Example 1, which was not treated, and Comparative Example 2, which was treated with STt isopropanol solution. , magnetic properties, especially Br and (BH)
It was found that max was improved and corrosion resistance was also significantly improved.

Example 2 2-17 samarium cobalt powder (average particle size 15μ)
Surface modification and epoxy resin mixing were performed using the same conditions as in Example 1. This mixture was molded using a compression molding machine for 1,500 m
13φl under an applied magnetic field of 00e and a pressure of 5t/c-
A molded article of n+X 10 mm was obtained. The molded article was cured at 120°C for 2 hours.

The results are shown in Table 2.

Comparative Example 3 The same procedure as in Example 2 was carried out except that 3 parts of epoxy resin was used instead of FTi. The results are shown in Table 2.

Comparative Example 4 The same procedure as in Example 2 was carried out except that STi was used instead of FTi. The results are shown in Table 2.

From Table 2, FT 2-17 samarium cobalt powder
The sample of Example 2 treated with i isopropanol solution was
The magnetic properties, especially B
r and (BH)IIlax are improved, corrosion resistance, especially 80
It was found that the improvement was achieved at relatively high temperatures such as °C.

Example 3 94 parts of neodymium iron boron magnetic powder (manufactured by GM) was put into a super mixer, and while vigorously stirring, 5 parts of FTio dissolved in a small amount of isopropanol was added dropwise over 5 minutes, and then heated at 100°C. Let stand for 15 minutes then remove solvent in vacuo.

5.3 parts of nylon-12 powder and 0.2 part of zinc stearate were mixed with this mixture and stirred vigorously again. This mixture was continuously kneaded using a two-wheeled extruder and pelletized by hot cutting. This material was then injection molded to 10
A molded article of φa+mX10+gffl was obtained. At this time, the MI value (melt index value) was also examined to check the moldability. These results are shown in Table 3.

Comparative Examples 5 to 8 Comparative Examples 5 to 8 were carried out in the same manner as in Example 3 under the conditions shown in Table 3. The results are shown in Table 3.

From Table 3, 2-17 series samarium cobalt powder FT
i The sample of Example 3 treated with isopropanol solution has better magnetic properties (BH ) It was found that n+ax was improved, MI value increased, and corrosion resistance was significantly improved.

Example 4 94 parts of 2-17 samarium cobalt powder (average particle size 1
5μ) was put into a super mixer, and while stirring vigorously, 5 parts of FTio dissolved in a small amount of isopropanol was added dropwise over 5 minutes. Thereafter, the solvent was removed in vacuo, and 5.2 parts of nylon 12 powder and 0.2 parts of calcium stearate were added thereto, and the mixture was vigorously stirred again. This material was continuously kneaded using a twin-screw extruder and pelletized by hot cutting. This material was injection molded in a magnetic field and
A molded article of φ×10 was obtained. Moreover, the MI value was examined to check the moldability at this time. These results are shown in Table 4.

Comparative Examples 9 to 12 Comparative Examples 9 to 12 were carried out in the same manner as in Example 3 under the conditions shown in Table 4. The results are shown in Table 4.

From Table 4, FT 2-17 samarium cobalt powder
i The sample of Example 4 treated with an isopropanol solution has a higher magnetic property (BH) max than the samples of Comparative Examples 9 and 10 without surface treatment and the samples of Comparative Examples 11 and 12 whose surface was treated with an STi isopropanol solution. It was found that the corrosion resistance was significantly improved, the MI value increased, and the corrosion resistance was significantly increased compared to Comparative Examples 9 and 10 without surface treatment.

[Effects of the Invention] As explained above, according to the method for manufacturing a composite magnet of the present invention, the treatment effect of FTi of rare earth magnetic powder can be improved not only in the magnetic properties by increasing the density but also in the corrosion resistance. The industrial value is extremely large.

Claims (2)

[Claims] 1. 1. A method for producing a composite magnet in which a mixture of rare earth magnetic powder and a binder is pressure-molded, the method comprising surface-treating the rare earth magnetic powder with a fluorine-based coupling agent. 2. A first method characterized in that the fluorine-based coupling agent has an oligomer structure as shown in the following formula [I].
A method for manufacturing a composite magnet according to claim 1. (iPrO)_n-Ti-(OCO-[M])_4_-
_n (however, n = 1 to 3 iPrO: isopropyl group M: -CF_2-(OCF-CF_2)_x-(OCF
_2)_y-OCF_3 x=1~10 y=1~10)