JPH0793207B2 - Resin-bonded permanent magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-bonded permanent magnet obtained by press molding a mixture of an epoxy resin using imidazole and its derivative as a curing agent and rare earth magnet powder in a magnetic field. Is.

[0002]

2. Description of the Related Art Resin-bonded permanent magnets are superior to sintered magnets in (1) dimensional accuracy of molded products. (2) Less chipping and cracking. (3) Complex shapes are possible.

Since it has advantages such as the above, it is currently receiving attention.
However, the performance of resin-bonded magnets is lower than that of sintered magnets by the proportion of the resin contained, and the orientation is also reduced, so generally only about 1/2 to 1/3 the performance of sintered magnets is shown. Not done. Therefore, it is necessary to reduce the amount of resin as much as possible to improve the performance. In addition, the amount of resin is small, and (1) it has a strong adhesive force, (2) it has good heat resistance, (3)
Resins used for permanent magnets need to meet the requirements such as chemical resistance. Resins used in permanent magnets include thermosetting, thermoplastic, and rubber-based materials, but in the case of thermoplastic resins and rubber-based materials, a large amount of resin is filled, resulting in a large decrease in performance. It becomes a poor permanent magnet. It can be said that among the remaining thermosetting resins, those that satisfy the above conditions are limited to epoxy resins.

[0004]

The epoxy resin is mainly composed of two liquids (a main agent and a curing agent), and when heated, the curing agent reacts with the epoxy group contained in the main agent to cause polymerization,
As a result, a strong cured product can be obtained. There are various kinds of this curing agent, but the curing agent most often used is an aliphatic amine curing agent, which is characterized by strong adhesive force and good mechanical properties. For this reason, the curing agent for the epoxy resin that has been conventionally used for permanent magnets is also the aliphatic amine type. However, the aliphatic amine-cured epoxy resin has a problem in heat resistance, and when used in a permanent magnet, the limit operating temperature of the permanent magnet was only 100 ° C. Further, there is also a problem with solvent resistance, and therefore, resin-bonded magnets have not been used in applications requiring high reliability. Furthermore, aliphatic amines have the drawbacks of requiring great care when used because they are highly toxic, and that many mixtures cannot be prepared and stored at once due to their short pot life.

[0005]

SUMMARY OF THE INVENTION The present invention uses imidazole and its derivatives as a curing agent for epoxy resins in order to eliminate such drawbacks.

The structural formulas of imidazole and its derivatives used in the present invention are shown below.

[0007]

[Chemical 1]

(In the formula, R1, R2 and R5 are a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group,
An aryl group, and an alkyl group in which at least one or more hydrogen atoms in the molecule are substituted with a cyano group or a hydroxyl group, a cycloalkyl group, and an annealing group. ) The curing of the epoxy resin with the imidazole-based curing agent is slow at low temperatures and violent at high temperatures. Therefore, the pot life of the epoxy resin becomes long, and it becomes possible to manufacture and store a large amount of a mixture of the magnet powder and the epoxy resin. Further, imidazole-cured epoxy resin is generally known to have good heat resistance and chemical resistance, and this greatly contributes to the improvement of heat resistance and chemical resistance of the resin-bonded magnet. Imidazole was less volatile and less toxic than aliphatic amines, and thus was safer during work.

As described above, the epoxy resin using imidazole as the curing agent is most suitable for the resin-bonded magnet, and improves the temperature characteristics and reliability of the magnet, which have been weak points in the past.
It also plays a major role in cost reduction.
The rare earth magnet powder used is R ₂ TM ₁₇ system (R is a lanthanum-based metal element containing Y, La, Ce, Pr, Nd, P).
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
One or a combination of two or more of m, Yb and Lu, and TM represents a transition metal. ) Use powder. This R ₂ TM ₁₇
The system powders have much higher magnetic performance than the SmCo ₅ magnet powder and the alnico and ferrite magnet powders.
Even when used in a resin-bonded magnet, high performance can be maintained. The amount of epoxy resin added is 1 to magnet powder.
6 wt% is appropriate, and if it is more than this, problems such as a decrease in density and seepage of resin during press molding occur.

As described above, the permanent magnet and the method for producing the same according to the present invention are excellent in heat resistance and chemical resistance because they are formed by press molding a mixture of an epoxy resin using imidazole as a curing agent and rare earth magnet powder. Permanent magnets can be manufactured at low cost.

[0011]

EXAMPLES Next, the present invention will be described in detail with reference to examples.

[0012] (Example _{1) Sm (Co bal Cu 0.07} Fe 0.3 Zr
_0.016 ) The alloy having the composition of _7.8 is melted in a high frequency melting furnace to form an ingot. This ingot is subjected to heat treatment such as solution treatment and aging treatment. Then, this ingot is pulverized with a jet mill to a size of about 2 to 80 μm.
Epoxy resin was mixed with the obtained powder, this mixture was inserted into a mold, and while applying an applied magnetic field of 16 (kG) , 3 ton / cm ² pressure was applied using an electromagnet and a hydraulic press, and after demagnetization , Remove the sample from the mold. This magnet molding is then heat-cured in a constant temperature bath.

The epoxy resin used is based on
A curing agent is added in an amount of 2 to 5 parts by weight in the case of imidazoles and 10 to 20 parts by weight in the case of aliphatic amines and well stirred, and when uniform, 2% by weight is added to the magnet powder.

Imidazole type curing agent 1-cyanoethyl-
The heat resistance and chemical resistance of the resin-bonded magnet using 2-ethyl-4-methylimidazole (Sample-1) and the magnet using the aliphatic amine-based curing agent (Samples 2 and 3) were compared. Table 1 represents the heat resistance, Table 2 represents the chemical resistance.

Demagnetization occurs when the magnet is heated after being magnetized. Among the demagnetizations, there are (1) reversible demagnetization and (2) irreversible demagnetization, and the irreversible demagnetization of the resin-bonded magnet has a considerably larger value than the sintered magnet. Table 1 shows the irreversible demagnetization rate when a resin-bonded magnet with a different hardening agent was magnetized and then left in a constant temperature bath for 1000 hours.

[0016]

[Table 1]

From Table 1, it can be seen that the irreversible demagnetization ratio of Sample 1 using imidazole is significantly lower than that of Samples 2 and 3 using the aliphatic amine curing agent.
Heat deterioration of resin that causes irreversible demagnetization and resin and magnet powder
It can be said that this is because the decrease in the adhesive force between the two was improved by imidazole.

Table 2 shows the results of examining the chemical resistance of the samples using the same curing agent as in Table 1.

[0019]

[Table 2]

It can be seen from Table 2 that the solvent resistance is remarkably improved when the imidazole-cured epoxy resin is used. As can be seen from this example, it is certain that the reliability of the resin-bonded magnets With Imi da tetrazole is greatly improved. The heat resistance experiment was conducted as follows. That is φ
Was 10 × 7mm cylindrical anisotropy direction is magnetized sample in 7mm long axis direction pulse method, measuring table made of plastics steel click in the measuring apparatus shown in FIG. 1 (3 ). Next, the signal obtained by pulling up the coil (2) attached to the tip of the cylinder (4) is read by the digital magnetometer (5). The sample of (1) is 120
Leave for 1000 hours in a constant temperature bath at 150 ° C and 150 ° C.
The chemical resistance test was conducted as follows. A 5 × 5 × 5 mm cube sample is prepared and left to stand for 120 hours at room temperature with each chemical. After that, the sample is taken out and the surface of the sample is wiped with dry gauze, and the weight is immediately measured to examine the rate of change in weight.

Example 2 With respect to a sample using imidazole and a sample using aliphatic amine, the pot life of the kneaded product was examined. In the experiment, the epoxy resin containing each curing agent and the magnetic powder were kneaded, and the kneaded product was allowed to stand at room temperature and then molded to observe the deterioration of magnetic performance. Imidazole curing agent than 2 (1 shear Bruno ethyl
2-ethyl-4 when using methylimidazole) and aliphatic hydrocarbon based curing agent (Jiechirua amino pro pin triethanolamine) that long to the working life of the imidazole comparison seen clearly a case of using. When the pot life is long, the kneaded product can be produced and stored in a large amount at one time, and the cost can be reduced. In addition, since imidazole has low volatility and low skin irritation toxicity, it can be said that it can be handled in a large amount.

[0022]

INDUSTRIAL APPLICABILITY As described above, the magnet of the present invention is much more reliable than conventional resin-bonded permanent magnets in heat resistance, chemical resistance, etc., and can be manufactured at low cost. application to new areas such as use motor also considered, the industrial significance with the present invention can be said to be large.

[Brief description of drawings]

FIG. 1 is a diagram showing a magnetic flux detection device in a thermal demagnetization test used in the present invention.

FIG. 2 is a graph showing the pot life of the kneaded product. (-○
−) Use of imidazole curing agent, (... ● ...) Use of aliphatic amine curing agent. The vertical axis represents the residual magnetic flux density Br,
The horizontal axis indicates the number of days elapsed after kneading, and the 0th day indicates the day of kneading.

[Explanation of symbols]

 1 ... Magnet 2 ... Coil 3 ... Measurement case (A) 4 ... Measurement case (B) 5 ... Digital magnetometer

Claims (1)

[Claims] 1. A mixture comprising an epoxy resin using imidazole and its derivative as a curing agent and rare earth magnet powder.
The resin-bound permanent magnets, characterized in that it is obtained by up press forming.