JPH0399405A - Resin bonded type rare-earth magnet - Google Patents

Abstract

PURPOSE:To obtain high density while a high powder fludity is being maintained when a molding operation is conducted by a method wherein a mixture, formed by mixing the magnetic powder with organic resin which becomes a binder and a microcapsule containing a lubricant and an organic solvent, is used as a magnet raw material. CONSTITUTION:A lubricant and an organic solvent are contained in a microcapsule, and the mixture of the microcapsule and the resin-coated magnetic powder, in a B-stage hardened state, is used as a magnet raw material. When the raw material powder is put in a mold and a compact-molding operation is conducted, the microcapsule contained in the raw material is destructed by the pressure of molding, and the lubricant and the organic solvent in the capsule are brought out to outside. The brought out lubricant enters between powder, and the frictional resistance between powder is lessened. Also, the organic solvent dissolves the solid-state binder of the B stage on powder surface, and the organic solvent works as a liquid lubricant. A high density resin-bonded type magnet is obtained by the above-mentioned double lubricational actions. Also, as the microcapusule is merely mixed into the dried magnetic powder, the raw material powder has excellent fluidity, and it can be filled in the mold easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin bonded rare earth magnet. [Conventional technology 1] When manufacturing resin-bonded magnets, a method of adding resin to serve as a binder to magnetic powder is to mix liquid resin with a device such as a Ni-Goo or a roll mill, and then mechanically mill around the magnetic powder. A commonly used method is to coat the but. With this method, it is difficult to apply resin around all the powder, resulting in variations in the performance of the magnet as a product due to differences in the cross-wire state.Also, since the resin is liquid, the powder after cross-wire becomes sticky. The disadvantage is that the powder has poor fluidity, making it difficult to fill the mold with the powder during molding. One way to solve this problem is to dissolve the resin in an organic solvent, immerse the magnetic powder in it, and then evaporate the solvent while stirring to coat the magnetic powder with the resin, or to coat the magnetic powder with the resin. A method of granulation using a moving bed has come into use. Powders obtained by these methods have individual powder surfaces completely coated with resin, and since the resin is in a B-stage solid state, the powder after coating is smooth and has good fluidity. have. [Problem to be solved by the invention] In the powder obtained by the method using a resin dissolved in an organic solvent, the resin serving as a binder is in a B-stage solid state on the surface of the magnetic powder. Mechanically mixed wires are significantly different from mechanically kneaded ones because liquid resin exists between the magnetic powders even during molding, so there is less frictional resistance between the powders and high-density compacts can be easily obtained. However, since the powder in the B-stage solid state does not have a liquid that acts as a lubricant during molding, the frictional resistance between the powders is large, making it difficult to obtain a high-density compact. The present invention is intended to solve these problems, and its purpose is to provide a resin-bonded rare earth magnet with high density while maintaining high powder fluidity during molding. [Means for Solving the Problems] The present invention is characterized in that a mixture of magnetic powder coated with an organic resin serving as a binder, and microcapsules containing a lubricant and an organic solvent is used as a magnet raw material. Microcapsules are already widely used in fields such as adhesives, printing, and medicine, but what is used in the fields of adhesives and printing is to put adhesive or ink inside microcapsules and use external pressure to release the capsules. When the paper is destroyed, the adhesive or ink inside comes out, allowing for adhesion or printing. In the present invention, a lubricant and an organic solvent are encapsulated in microcapsules, and a mixture of the microcapsules and magnetic powder coated with a resin in a B-stage hardening state is used as a magnet raw material. When raw material powder is put into a mold and compacted, the microcapsules in the raw material are destroyed by the pressure of molding, and the lubricant and organic solvent inside the capsules are expelled. The released lubricant enters between the powders and reduces the frictional resistance between the powders.
The organic solvent also dissolves the B-stage solid binder on the powder surface and acts as a liquid lubricant. These dual lubrication effects result in a high-density resin-bonded magnet. Furthermore, since the microcapsules are simply mixed with smooth magnetic powder, the raw material powder has good fluidity and can be easily filled into molds. [Examples] The present invention will be described in detail below based on Examples. (Example 1) Nd-Fe-B magnetic powder first obtained by the quenched ribbon method (average particle size = 25 μm, maximum diameter = 177 μm)
An epoxy resin dissolved in triethane was added thereto in an amount of 2 wt %, and the solvent was evaporated while stirring to obtain a resin-coated magnetic powder. Olive oil and triethane were added to an aqueous gelatin solution and emulsified, an aqueous gum arabic solution was added, and the pH was adjusted to 4-4.3 with acetic acid to precipitate a coacervate phase. Add formalin aqueous solution to this and adjust the pH to 8.5 with NaOH.
gelatin-gum arabic microcapsules (average particle size 20μ) that encapsulate olive oil by
m) was obtained. 2 wt % of microcapsules were added to the resin-coated magnetic powder and mixed well to obtain a raw material powder. Using the obtained raw material powder, 1O*10*1 in the absence of a magnetic field
It was molded into a 0 mm block and fired at l 50c for 1 hour. After firing, the molded body was checked for performance and density. For comparison, a similar test was also conducted on a molded product without adding microcapsules. The results are shown in Table 1. Table 1 It can be seen from Table 1 that the addition of microcapsules increases the density and improves the performance. (Example 2) Fluidized bed granulation was performed using Sm--Co magnetic powder and a methyl ethyl ketone solution (corresponding to 2.5 wt% of the weight of the epoxy resin) as an epoxy resin to obtain resin-coated magnetic powder. 1.5 wt % of microcapsules containing oleic acid and triethane were added to this powder, and the same test as in Example 1 was conducted. The results are shown in Table 2. Table 2 It can be seen from Table 2 that the addition of microcapsules increases the density and improves the performance. [Effect of the invention 1] As described above, the present invention provides a resin-bonded magnet that maintains the high powder fluidity of conventional resin-coated magnetic powder and has higher density and performance than conventional resin-coated magnetic powder. It became possible to do so. that's all

Claims (1)

[Claims] In resin-bonded rare earth magnets obtained by adding an organic resin to magnetic powder containing rare earth metals in the basic composition, the magnetic powder is coated with an organic resin as a binder as a magnet raw material, and a lubricant and an organic solvent are used during production. A resin-bonded rare earth magnet characterized by using a mixture of encapsulated microcapsules.