JPS6336501A - Manufacture of compound magnet - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a composite magnet with excellent magnetic properties. More specifically, in a method for producing a composite magnet in which magnetic powder is kneaded and molded with a resin, the magnetic powder is kept in close contact with a monomer capable of radical polymerization in advance, and the polymerization reaction is carried out in the presence of acidic sulfite ions. The present invention relates to a method for producing a composite magnet, the feature of which is to modify the surface of the magnetic powder by coating the powder with an IJ polymer.

[Conventional technology]

It is well known to mix and knead magnetic powder and a binder and to produce a composite magnet by extrusion molding, compression molding, or injection molding. Composite magnets are less prone to cracking and do not require secondary processing, making them suitable for complex shapes and thin-walled shapes. i!
With improvements in magnetic properties near L, the use of small motors, sensors, relays, OA equipment, etc., is increasing.

[Problem that the invention seeks to solve]

On the other hand, a drawback of composite magnets is that non-magnetic binders and additives are mixed in as components.

One example is that the magnetic properties deteriorate by the volume.

In order to improve this drawback, it is necessary to increase the amount of magnetic powder packed and to increase the degree of orientation of the magnetic powder.

However, in general, when the amount of magnetic powder mixed in is increased, flow during molding becomes poor, moldability deteriorates, or a product cannot be obtained.

Moreover, even if the shape is barely formed, the degree of orientation of the magnetic powder decreases, making it impossible to obtain satisfactory magnetic properties.

One of the methods to improve such problems is to surface-treat magnetic powder with various coupling agents to improve the filling rate and mechanical strength. This method has the effect of changing the surface of the magnetic powder from hydrophilic to oleophilic, effectively preventing l-11 from forming with the binder, and thus improving the filling rate, orientation, and mechanical strength. Although this method can particularly improve magnetic properties compared to conventional methods, there is a strong desire to make magnets lighter, thinner, and shorter, especially for motor magnets used in office automation equipment, and further improvements in magnetic properties are desired. ing.

In view of these circumstances, it is an object of the present invention to provide a manufacturing method for further improving magnetic properties.

[Means for solving problems]

That is, the present invention provides a method for manufacturing a composite magnet formed by kneading and molding magnetic powder with a resin, in which the magnetic powder is maintained in advance in close contact with a monomer capable of radical polymerization,
The magnetic powder is characterized in that the surface is modified by carrying out a polymerization reaction in the presence of acidic sulfite ions and coating it with the powdered polymer, and further, by kneading this magnetic powder with a polyamide resin. It was discovered that a remarkable effect can be obtained by combining the two, and this led to the completion of the present invention.

According to the invention, the magnetic powder has the general formula MO, 6Fe2Q3
(However, M is Ca", Ba" r Sr", and P
A ferrite powder having magnetobrambite-type crystals coated with divalent metal ions such as b++ is used.

In addition, resins include polyolefin resins such as polyethylene and polypropylene, nylon-6, nylon-12t nylon 610. Nylon 11. Polyamide resins such as nylon 66, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyphenylene sulfide, polyether ether ketone, deriether sulfone, and these Modified type resins such as these are suitable, but polyamide resins in particular can significantly exhibit the effect of the surface treatment according to the present invention.

In addition, in the case of coating the ferrite powder with a polymer in the present invention, the radical polymerizable or radical copolymerizable monomer used is acrylic acid.

Acrylic acid esters such as methacrylic acid and methyl acrylate, butyl acrylate, methyl methacrylate, and ethyl methacrylate; aromatic vinyl compounds such as thylstyrene methacrylate; tzenes such as butadiene, isogrene, and chloroprene; and acrylonitrile. I can list many.

In the method of the present invention, one or more monomers selected from the above radical polymerizable or radical copolymerizable monomers are used.

If the amount of monomer used in the present invention is too large, it will cause a decrease in mechanical strength and heat resistance, and if it is too small, it will not be possible to completely cover the ferrite powder and the surface treatment effect will not be exerted. 0.1-1 by weight
0%, preferably in the range of 0.5% to 7%.

In addition, sulfite water, sulfite gas, sulfite aqueous solution, acidic sulfite aqueous solution, etc. are used as the substance that provides the dispersible sulfite ions used in the present invention. The amount of sulfite ion is in the range of 90.1 to 50 parts by weight, preferably 05 to 30 parts by weight, based on 100 parts by weight of the monomer, in terms of sulfite.

The coating treatment conditions of the present invention can be carried out as follows. 1 part by weight of ferrite powder was suspended in 1 to 10 parts by weight of water, and after adjusting the liquid to neutrality (pH 6 to 8), a monomer and a polymerization initiator for donating sulfite ions were added and the mixture was heated at 10°C.
The coating process is carried out at a temperature in the range from ~100<0>C, preferably from 20 to 70<0>C.

The treatment time is 1 to 4 hours and almost 100% of the monomer is converted to polymer. Next, the resulting suspension of coated powder is neutralized, dehydrated, and dried.

The magnetic powder treated according to the present invention is then mixed and kneaded with a resin, and then made into pellets. Kneading is done using heating kneader-1-
It can be carried out using a screw or twin screw extruder. Of course, the surface-treated magnetic powder may be subjected to compression molding.

〔Example〕

Examples of the present invention will be explained in more detail below.
It goes without saying that the present invention is not limited to these examples.

Example-1 Add 5 kg of strontium ferrite powder (average particle size 1 μm) and 50 ml of water to a reaction vessel equipped with a stirrer and a thermometer.
Stir vigorously for 30 minutes at °C. p)I at this time was 11. After adjusting this solution to pH 3 with IN hydrochloric acid, methyl acrylate monomer was 200.9 and sodium hydrogen sulfite was 52! j was added thereto, and the reaction was carried out at 50° C. for 2 hours with stirring.

After the reaction is completed, the reaction solution is cooled and purified with an aqueous INN card solution.
It was set as H7.5.

This material was dehydrated and dried, and the amount of coverage was measured: 12
It was 5g.

543 g of nylon-6 powder was mixed with 5 kg of coated ferrite powder obtained in this manner and kneaded in a twin-screw extruder, and then left to obtain a molding material. Injection molding was performed.The results are shown in Table-1.

Comparative Example-1 The same procedure as in Example-1 was carried out except that the ferrite powder was used without surface treatment. The results are shown in Table-1.

Comparative example-2 Strontium ferrite (average particle size 1μ) 5 kg
was placed in a Suhar mixer, heated to 120°C, 50I of a Nran coupling agent (γ-aminopropyltriethoxysilane) was added, and the mixture was further stirred at 120°C for 30 minutes to perform surface treatment. - The powder was pelletized in the same manner as in Example-1 and subjected to injection molding. The results are shown in Cloth-1.

Examples 2 to 6 Examples 2 to 6 of Examples 2 to 6 were carried out in exactly the same manner as in Example 1, except that the resin shown in Table 2 was used and the volume ratio of ferrite powder was changed to 60 inches. The results are shown in Shishi-2.

The following Examples 7 to 10 were carried out in the same manner as in Example 1 except that the monomers and catalysts shown in Table 3 were used. The results are shown in Table-3.

In addition, the ratio of ferrite powder free content and magnetic properties in composite magnets with surface treatment according to the present invention (in the case of Example 1), silane coupling method, and untreated case are also shown. The relationship is shown in Figure 1.

〔Effect of the invention〕

As described above, according to the present invention, by discovering a very effective surface treatment method, we were able to obtain a composite magnet with significantly improved magnetic properties, and also with excellent formability. I was able to have it.

Therefore, its industrial value is great.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between ferrite powder content and magnetic properties in composite magnets in which the surface treatment according to the present invention is performed, the silane coupling method, and the untreated case. Figure 1 a78Ft 8'? QO91 ferrite powder (1, Z) Procedural amendment C spontaneous) 1986? 29th of the month

Claims (1)

[Claims] 1. A method for producing a composite magnet by kneading and molding magnetic powder with a resin, in which the magnetic powder is maintained in advance in close contact with a monomer capable of radical polymerization, and acidic sulfite ions are 1. A method for producing a composite magnet, which comprises coating the powder with a polymer by carrying out a polymerization reaction in the presence of a polymer. 2. The magnetic powder has the general formula MO. Ferrite having a magnetoplumbite crystal structure represented by 6Fe_2O_5 (where M is a divalent metal ion such as Ca^+^+, Ba^+^+, Sr^+^+, and Pb^+^+) The method for manufacturing a composite magnet according to claim 1, wherein the composite magnet is a powder. 3. The method for manufacturing a composite magnet according to claim 1, wherein the resin is a polyamide resin.