JPH0262146B2 - - 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 composition having excellent magnetic properties and excellent moldability. Conventional permanent magnets include Alnico magnets as cast magnets, and sintered ferrite magnets using iron oxide.In particular, sintered ferrite magnets are used in heavy electrical appliances, home appliances,
Used in many electronic devices. In recent years, demand for high-magnetic samarium-cobalt alloy magnets has increased due to the demand for smaller, more precise electronic equipment and higher performance and reliability. However, these magnets are an obstacle to expanding their use because they are brittle and require secondary processing such as cutting and polishing. In order to improve these problems, composite materials of magnetic materials and various synthetic resins have been put into practical use. These are composites of magnetic powder mainly made of ferrite or rare earth metals and plastics such as polyamide and polypropylene, and can be efficiently molded into complex shapes that were impossible with conventional magnetic materials. I can do it. However, there are problems such as a decrease in magnetic force due to the addition of plastic and variations in magnetic force due to poor dispersion, as well as poor fluidity during injection molding. As a method to improve these problems, surface treatment of magnetic powder has been carried out, but it is still not sufficient. As a result of extensive research into the surface treatment of magnetic powders, the inventors of the present invention have discovered that among many coupling agents, aluminum-based coupling agents are particularly excellent as surface treatment agents. The aluminum coupling agent used in the present invention has been conventionally known as a dispersant for fillers, pigments, etc., but as far as the inventors know, it is not known to be used for treating magnetic powder in plastic magnet compositions. It has not been done. Thus, according to the present invention, in a plastic magnet composition containing magnetic powder and synthetic resin as main components, magnetic powder whose surface has been previously treated with an aluminum-based coupling agent is used as the magnetic powder. A plastic magnet composition is provided. In particular, the surface treatment of the present invention imparts lubricity to the magnetic powder and improves dispersion and moldability, thereby making it possible to obtain excellent magnetic properties. The composition of the present invention has particularly excellent moldability, and can have excellent magnetic properties by orienting it in a magnetic field during injection molding. Examples of the aluminum coupling agent used in the present invention include acetalkoxyaluminum diethylate, acetalkoxyaluminum diisopropylate, acetalkoxyaluminum diisopropylate, and acetalkoxyaluminum diisopropylate.
Examples include acetoalkoxyaluminum dialkylates such as di-n-butyrate and acetoalkoxyaluminum diethylhexylate, but the most preferred is acetolower alkoxyaluminum diisopropylate. The amount added is preferably 0.5 parts or more and 1.5 parts or less based on the magnetic powder. If the amount is less than 0.5 part, the coupling agent treatment effect will be insufficient, and if it is more than 1.5 parts, unreacted coupling agent will remain and often have an adverse effect. The magnetic powder used in the present invention includes barium ferrite, strontium ferrite, calcium ferrite, lead ferrite, and sodium ferrite.
Examples include magnetic powders of ferrites such as lanthanum ferrite and rare earths such as samarium cobalt, and among these, magnetoplumite magnetic powders are preferred. The particle size is not particularly limited, but relatively fine particles of 5 microns or less are preferred. As the synthetic resin used in the present invention, various thermoplastic resins and thermosetting resins are used, such as polyolefin resins and polyamide resins. Especially nylon-6, nylon-12
These polyamides have excellent heat resistance, chemical resistance, impact resistance, moldability, etc. The proportion of magnetic powder in the total amount of magnetic powder and synthetic resin is not particularly regulated, but it is 80%
It is preferably at least 95% by weight. 80% by weight
Below, the moldability is good, but the magnetic properties are insufficient. Moreover, if it exceeds 95% by weight, it becomes difficult to mold and becomes brittle. In this invention, the surface treatment of the magnetic powder can be carried out by directly mixing aluminum coupling agents in a predetermined ratio since they are usually liquid, but in some cases it may be carried out in the presence of a volatile solvent. The process may be carried out under conditions where at least the magnetic powder and the aluminum-based coupling agent can come into uniform contact with each other. In this case, the surface treatment is carried out at room temperature or at a high temperature around the decomposition temperature of the aluminum coupling agent (but below the decomposition temperature; e.g.
It can be carried out at a temperature of around 320℃). Surface treatment with a coupling agent is generally carried out at a temperature below 100°C. However, it has been found that it is effective even at high temperatures of 100°C or higher, which is about the decomposition temperature of the coupling agent. Various methods can be used as specific surface treatment methods, but for example, it is appropriate to charge the magnetic powder into a Henschel mixer, drop a predetermined amount of the coupling agent while stirring, and then further stir. The composition of the present invention can also contain a lubricant, a heat stabilizer, etc., if necessary, in addition to the above-mentioned main components. The plastic magnet material produced by the method of the present invention can have excellent magnetic properties by being oriented in a magnetic field. These are used in a wide range of fields such as small precision motors, instrument parts, and small generators. The present invention will be explained below with reference to Examples. Example 1 8.8 kg of anisotropic strontium ferrite with an average particle size of 1.2 μ was placed in a Henschel mixer, and 70 g of acetomethoxyaluminum diisopropylate was added dropwise while stirring at room temperature, followed by further stirring for 10 minutes for surface treatment. Obtain strontium ferrite powder. To this was added 1.2 kg of nylon-6 powder finer than 60 mesh, and the mixture was stirred and mixed for 10 minutes. This mixture was formed into pellets using a twin-screw extruder, and further subjected to magnetic field molding by injection molding. The molding conditions in this case are 6 in a magnetic field of 12000 Oe.
The molded product was magnetized for seconds, and various physical properties were measured on this molded product. The measurement method is as follows. A Fluidity Using a melt indexer, load 10 at 260℃
The outflow amount for 10 minutes was measured in the case of Kg (nozzle radius 1.0 mm). B Magnetic properties The hysteresis curve is measured using a DC magnetization property automatic recording device, and from this the residual magnetic flux density (Br), coercive force (BHc), intrinsic coercive force (IHc), and the maximum energy product (B.Hmax) are calculated from these. The magnetic properties were evaluated. In addition, the measuring material is 20 mm in diameter.
It is cylindrical with a height of 10 mm and a height of 10 mm.

[Table] Comparative Example 1 in the table was not treated with a coupling agent. Comparative Example 2 was treated with isopropyltri(N-aminoethylaminoester) titanate at room temperature, and when compared with Example 1, both fluidity and magnetic properties were inferior. Example 2 The processing temperature of the coupling agent in Example 1 was changed to 140°C.
The experiment was conducted in the same manner except for the following. The results are shown in the table below.

[Table] Comparative Example 3 was treated with isopropylene tri(N-aminoethylaminoester) titanate at 140°C. Example 3 An experiment was carried out in exactly the same manner as in Example 1, except that acetomethoxyaluminum diethylhexylate was used as the coupling agent. The results are shown below.

[Table] Example 4 An experiment was conducted in the same manner as in Example 1 except that 1.1 kg of nylon-12 powder passing through 120 mesh was used as the synthetic resin. The results are shown in the table below.

[Table] Example 5 A blend was prepared in the same manner as in Example 1, except that 1.2 kg of polypropylene powder that passed through 100 meshes was used as the synthetic resin, and its various performances were measured.
The results are shown in the table below.

【table】

Claims (1)

[Scope of Claims] 1. A plastic magnet composition containing magnetic powder and synthetic resin as main components, characterized in that magnetic powder whose surface has been previously treated with an aluminum-based coupling agent is used as the magnetic powder. Plastic magnet composition.