JPH0230564B2 - PURASUCHITSUKUMAGUNETSUTOSOSEIBUTSU - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to plastic magnet compositions. In particular, the present invention relates to a novel plastic magnet composition having excellent magnetic performance and excellent formability. In order to improve the formability of various magnetic materials, which could previously only be formed by high-temperature sintering, and the fragility of the formed magnets, composite materials made by mixing these magnetic materials with various synthetic resins have been put into practical use in recent years. be. These are composites of magnetic powder mainly composed of ferrite or rare earth metals and synthetic resins such as polypropylene, polyvinyl chloride, and polyamide. These plastic magnet compositions make it possible to efficiently mold parts with complex shapes that were impossible with conventional magnetic materials, and they also produce molded products that are stronger than conventional products, making them particularly popular in recent years. The development is remarkable. However, it is difficult to avoid a decrease in magnetic performance due to the addition of synthetic resin and its poor dispersion, and there are many problems such as insufficient fluidity and partial non-uniformity of fluidity during injection molding, etc., which are hindering smooth development. Various attempts have been made to improve these drawbacks, and a method of treating the surface of magnetic powder with a coupling agent is known to be particularly effective. As this coupling agent, a silane coupling agent, a titanate coupling agent, etc. are used, and the treatment is carried out by mixing and contacting this with the desired magnetic powder, but from the viewpoint of uniform treatment, the temperature is relatively low. It is said that it is preferable to carry out the above treatment preferably at room temperature or lower. However, although the physical properties of plastic magnet compositions using magnetic powder surface-treated with such coupling agents are improved compared to those without surface treatment, they are still insufficient, and their magnetic properties are It was still not satisfactory in terms of moldability and moldability. In view of the above circumstances, the present inventors have conducted a detailed study on surface treatment methods for coupling agents, and have surprisingly found that by performing surface treatment at a high temperature of 100°C or higher, which has traditionally been considered disadvantageous, The present invention was achieved by discovering the fact that the magnetic properties and moldability of plastic magnet compositions using magnetic powder are significantly improved. Thus, according to the present invention, in a plastic magnet composition containing a magnetic powder and a synthetic resin as main components, the magnetic powder is treated with a coupling agent at a high temperature of 100° C. or higher and below the decomposition temperature of the coupling agent. There is provided a plastic magnet composition characterized in that it uses magnetic powder that has been surface-treated at high temperatures. As the magnetic powder used in the present invention, ferrite-based magnetic powder such as barium ferrite and strontium ferrite is used. The particle size is not particularly restricted, but relatively fine particles of 5 μm or less are generally preferred. As the synthetic resin used in the present invention, various thermoplastic resins and thermosetting resins can be used, and in some cases, elastomers can also be used. usually,
Thermoplastic resins are preferred, and polypropylene, polyvinyl chloride, and polyamides are more preferred. In particular, polyamides such as nylon-6, nylon-11, and nylon-12 have excellent heat resistance, chemical resistance, impact resistance, moldability, etc. It is excellent in this respect. The proportion of the magnetic powder in the total amount of the magnetic powder and synthetic resin is not particularly limited, but is preferably 80% by weight or more and 95% by weight or less. If it is less than 80% by weight, the magnetic performance of the composite material will not be sufficient, and if it is more than 95% by weight, it will be difficult to mold it. As coupling agents used in the present invention, common silane coupling agents, titanate coupling agents, aluminum coupling agents, phosphoric acid coupling agents, etc. are used. Titanate coupling agents are particularly preferred from the viewpoint of magnetic performance and moldability of the composite material. The type of coupling agent that is suitable varies depending on the type of plastic, but in the case of polyolefins such as polypropylene, a coupling agent with a long chain alkyl group is preferable, in the case of polyvinyl chloride, a coupling agent with a phosphoric acid group is preferable, and in the case of polyvinyl chloride, a coupling agent with a phosphoric acid group is preferable. In this case, a coupling agent containing a nitrogen atom is suitable. The amount of coupling agent to be used relative to the magnetic powder is not particularly limited, but 0.2 to 2 parts is appropriate.
If it is less than 0.2 part, the coupling effect will be insufficient, and if it is more than 2 parts, unreacted coupling agent will remain, often causing adverse effects. The temperature at which the surface treatment is performed is the most important factor in the present invention, and it is necessary to perform the surface treatment at a high temperature of 100° C. or higher and lower than the decomposition temperature of the coupling agent. A particularly preferred surface treatment temperature is 130°C to 180°C. Various methods are used for surface treatment, but for example, magnetic powder is placed in a Henschel mixer, dried at a high temperature such as 150°C, and then a predetermined amount of coupling agent is added dropwise while stirring, followed by stirring for about 10 minutes. Just continue. Note that it is also effective as a method for uniform treatment to dilute the coupling agent in advance with an inert high-boiling liquid and then add it dropwise. In addition to the above-mentioned main components, the composition of the present invention can also contain a lubricant, a molding aid, a heat stabilizer, an antioxidant, etc., if necessary. The plastic magnet composition produced by the method of the present invention can be molded into various shapes by compression molding, extrusion molding, injection molding, etc., and can be made into magnets by an appropriate magnetization method. Such compositions of the present invention can be used in electronic devices such as rotors and stators for motors, magnet rolls, generators, keyboard switches, etc.
It is useful as a magnet or its raw material in a wide range of fields such as mechatronics equipment and automobile parts. Next, examples of the present invention will be shown, but these are for illustrating the present invention and are not intended to limit it, of course. Example 1 Barium ferrite 340 with average particle size of 3 microns
g was placed in a hand mixer and dried at 150°C for 2 hours. Next, 2.7 g of isopropyl tristearoyl titanate was added dropwise to the mixture at a temperature of 150° C. over 3 minutes while stirring, and the surface treatment was then completed by stirring for an additional 5 minutes. To this was added 60 g of nylon-6 powder finer than 60 mesh, and the mixture was stirred and mixed for 5 minutes. A predetermined molded article was obtained by compression molding using this mixture. For compression molding, the mold temperature is 260℃ and the pressure is 200℃.
The test was carried out under the conditions of Kg/cm ² . Various physical properties were measured using this molded article, and the measuring methods were as follows. Bending test…according to JIS K7203, load speed 10
Measured in mm/min. Fluidity: Loaded at 260℃ using a melt indexer
The outflow amount was measured at 10Kg for 10 minutes. Nozzle radius 1mm. Magnetic properties: The magnetization curve and hysteresis roof are measured using an electromagnetic magnetizer and a DC magnetization property automatic recording device, and from this the residual magnetic flux density (Br),
Coercive force (Hc) and BH _nax were calculated to evaluate magnetic properties. The measurement sample is cylindrical with a diameter of 15 mm and a height of 20 mm.
It was magnetized using an Oersted magnetic field for 1 second. The results are shown in the table below.

[Table] In the table, Reference Example 1 was not treated with a coupling agent, and Reference Example 2 was treated with a surface treatment at 20°C. As is clear from the table, Example 1
Compared to Reference Examples 1 and 2, it is particularly superior in fluidity (ie, moldability) and magnetic properties. Although the flexural modulus of Example 1 is slightly lower than that of the others, this does not pose any practical problem and rather reflects the toughness of the molded product. Examples 2 to 5 Using strontium ferrite with an average particle size of 2μ in Example 1 and isopropyl-tri(N-aminoethyl-aminoethyl) titanate as a coupling agent, compositions were prepared by varying the surface treatment temperature. Various physical properties were measured in the same manner as in 1. The results are shown in the table below. Reference example 3 in the table
Samples 5 to 5 have low processing temperatures and are outside the scope of the present invention.

[Table] Example 6 An experiment was conducted in the same manner as in Example 1 except that 3.4 g of acetalkoxyaluminum diisopropylate was used as the coupling agent and the treatment temperature was 120°C. The results are shown in the table below. Note that Reference Example 6 is the result when the treatment temperature was 20°C.

【table】

【table】

[Table] Example 7 The results of an experiment conducted in exactly the same manner as in Example 1 except that γ-aminopropyltriethoxysilane was used as the coupling agent are shown in the table below. Note that Reference Example 7 is the result when the treatment temperature was 20°C.

[Table] Example 8 An experiment was conducted in exactly the same manner as in Example 2 except that 42 g of nylon-12 powder that passed through 120 mesh was used as the resin. The results are shown below. Density (g/cc) 3.70 Breaking bending strength (Kg/cm ² ) 620 Flexural modulus (Kg/cm ² ) 65000 Fluidity (g/10 min) 2.6 Magnetic properties Br (Gauss) 1550 Hc (Oersted) 2750 BH _nax ×10 ^-6 0.52 Example 9 A blend was prepared in exactly the same manner as in Example 1 except that 50 g of polypropylene powder that passed through 100 meshes was used as the resin, and its various performances were measured. The results were as follows. Density (g/cc) 3.28 Breaking bending strength (Kg/ ^cm2 ) 520 Flexural modulus (〃) 51000 Fluidity (g/10 min) 6.6 Magnetic properties Br (Gauss) 1360 Hc (Oersted) 2580 BH _nax ×10 ^{- 6} 0.41

Claims (1)

[Claims] 1. In a plastic magnet composition whose main components are magnetic powder and synthetic resin, the magnetic powder is surface-treated with a coupling agent at a high temperature of 100°C or higher and at a temperature below the decomposition temperature of the coupling agent. A plastic magnet composition characterized by using ferrite magnetic powder.