JPH0122967B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in anisotropic resin magnets, and provides resin magnets with excellent heat resistance. It has already been done to create anisotropic resin magnets by molding ferromagnetic powder with a large magnetic anisotropy constant using synthetic resin as a binder, and aligning the powder in a fixed direction using the force of a magnetic field. It is. The present inventors also developed anisotropic resin magnets in which powders such as barium ferrite magnets, strontium ferrite magnets, and rare earth cobalt magnets were bonded with various thermoplastic resins.
52-31079, 54-37679, 55-15853, JP 53-117799, JP 53-135497, and JP 54-
62259, already disclosed or proposed. Traditional technological development efforts for anisotropic resin magnets have been directed primarily toward improving magnetic properties, mechanical properties, and processability. Therefore, conventional products have a continuous withstand temperature of about 180 to 200 degrees Celsius, and cannot be used unless the environmental temperature is below 180 degrees Celsius.If the temperature exceeds that temperature, deformation, cracking, deterioration of magnetic properties, etc. may occur. was unavoidable. Recently, as the use of anisotropic resin magnets has expanded, including in automobile parts, there has been a demand for magnets that can withstand use at high temperatures. As a result of research to meet this requirement, the present inventors have found a system that can be put to practical use at temperatures up to at least 300°C.
We have developed an anisotropic resin magnet with excellent heat resistance. The anisotropic resin magnet with excellent heat resistance of the present invention is
A powder of a ferromagnetic material having a large magnetic anisotropy constant is kneaded with a binder consisting of a polyphenylene oxide resin or a mixture of a polyphenylene oxide resin and a polyphenylene sulfide resin, and the powder of the ferromagnetic material therein is It is formed by molding in a state in which the parts are aligned in a certain direction. Polyphenylene sulfide and polyphenylene oxide used as binders are both thermoplastic resins, but we adopted them because they have a significantly high softening temperature. Even when used in small amounts, the mixture with ferromagnetic powder The moldability is good;
It was confirmed that the molded product showed the expected heat resistance and also had high magnetic properties. Any ferromagnetic powder can be used, but
Of course, those having a large magnetic anisotropy constant are preferable, and the above-mentioned strontium ferrite, barium ferrite, rare earth cobalt, etc. are preferable. Since polyphenylene oxide resin and polyphenylene sulfide resin have good compatibility with each other, they can be used by mixing them in any proportion. Whether you use the former alone or both together,
The mixing ratio of ferromagnetic powder with powder is by weight:
It is preferable to select resin from the range of 70:30 to 94:6.
Needless to say, the higher the proportion of ferromagnetic powder in the mixture, the higher the magnetic properties of the resin magnet.
There is a limit to this, and if the ferromagnetic powder exceeds 90%, the moldability will deteriorate and the magnetic properties will deteriorate. Therefore, an appropriate mixing ratio should be determined with these balances in mind. The practical limit is usually 94%, although it varies somewhat depending on the case. The mixture can be molded by conventional means such as extrusion molding and injection molding, similar to the molding of conventional resin magnets, except that the melting temperature of the resin is high. Applying a magnetic field to the resin while it is in an unsolidified state to solidify the ferromagnetic powder while aligning it in a certain direction may also be done in accordance with what is established in the art. The anisotropic resin magnet of the present invention can withstand continuous use at temperatures up to 300°C, and its magnetic properties are
It is equivalent to or better than conventional resin magnets. This fact will be illustrated below with examples. Example 1 Barium ferrite magnet powder and polyphenylene oxide resin were mixed in various proportions and formed into molded products by injection molding. A test piece was taken from this molded product and tested for heat resistance and magnetic properties. Heat resistance was determined by making a test piece with a length of 80 x width of 15 x thickness of 3 mm from a molded product consisting of 86 parts of strontium ferrite and 14 parts of polyphenylene oxide resin (by weight), and holding one longitudinal end horizontally with a cantilever. Place it in a furnace while supporting it, and raise the temperature at a rate of 1°C/min.
The study was conducted by measuring the amount of deformation, which was the distance that the tip sagged due to softening. The graph in FIG. 1 shows how the amount of deformation increases as the temperature changes. For comparison, a conventional polyethylene resin magnet (polyethylene 88: strontium ferrite 12)
Similar measurements were also made for polyamide resin (nylon 86: strontium ferrite 14). In FIG. 1, the curve shows the amount of deformation of the heat-resistant resin magnet according to the present invention, and the curve and the curve show the amount of deformation of the polyethylene resin magnet and the polyamide resin magnet, respectively. On the other hand, the magnetic properties were determined by measuring the residual magnetic flux density Br, coercive force BH _C , and maximum energy product (BH) _nax using a disk-shaped test piece. The results are shown in Table 1 together with the density.

【table】

[Table] Next, magnet powder: resin = 86:14 was added to 300
The magnetic properties of
Changes in Br were tracked. The results are shown in the plot of FIG. It was confirmed that the magnetic properties did not deteriorate even after heating for 1000 hours. The appearance remains unchanged. In contrast, with conventional resin magnets, even when placed in an air bath at a lower temperature of 200°C, it was observed that the binder resin deteriorated and cracked. From the data in FIGS. 1 and 2, it will be easily understood that the anisotropic resin magnet of the present invention has excellent heat resistance. Also, the results in Table 1 are
This shows that the magnetic properties of the resin magnet of the present invention are at a level comparable to that of conventional products. Separately, the same test as above was conducted by changing the ferromagnetic material to strontium ferrite magnet powder. Similar trends were obtained, but the difference is that barium ferrite magnet powder can be blended in a slightly larger amount with the resin than strontium ferrite magnet powder. Regarding magnetic properties, both were almost the same. Example 2 A resin magnet using a strontium ferrite magnet as a ferromagnetic powder and a polyphenylene oxide resin and a polyphenylene sulfide resin as a binder was tested in the same manner as in Example 1 to improve heat resistance and magnetic properties. I looked into it. The results of the heat deformation test were almost the same as in Example 1 in which polyphenylene oxide resin was used alone. Characteristic values of magnetic properties and density are shown in Table 2.

【table】 [Brief explanation of drawings]

Both drawings are for explaining the heat resistance of the anisotropic resin magnet of the present invention, and FIG. This is a graph shown in comparison, and FIG. 2 is a graph tracking changes in the magnetic property Br when the same example was heated and held for a long time.

Claims (1)

[Claims] 1. Ferromagnetic powder with a large magnetic anisotropy constant,
An anisotropic resin magnet formed using a binder made of polyphenylene oxide resin or a mixture of polyphenylene oxide resin and polyphenylene sulfide resin. 2 70-94% by weight of ferromagnetic powder and binder
30 to 6% by weight of the anisotropic resin magnet according to claim 1.