JPH08138929A - Rare earth plastic magnet - Google Patents

Abstract

PURPOSE: To obtain a rare earth plastic magnet which is high in heat resistance and comparatively high in magnetic properties by a method wherein high heat- resistant engineering plastic and cyanate ester compound are used as organic binder, rare earth alloy powder is compounded with the organic binder, the compound is injection-molded, and the molded body is hardened. CONSTITUTION: High heat-resistant engineering plastic A and cyanate ester compound B are used as organic binder, wherein the weight ratio of A to B is set to 80:20 to 20:80. 60 to 75% by volume of rare earth alloy powder is compounded. The compound is injection-molded, and the molded body is hardened. Moreover, one or more selected out of polyphenylene ether, polysulfone, polyether sulfone, polyether imide, and polyarylate are used as high heat- resistant engineering plastic. Cyanate ester compound is of monomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth plastic magnet having excellent heat resistance, and to a plastic magnet having various shapes easily molded by injection molding.

[0002]

[Prior Art and Problems] Plastic magnets
Although it is inferior in magnetic properties to the sintered magnet, it is being used in a wide range of applications because it has an advantage that a magnet having a complicated shape can be manufactured by molding. Furthermore, although there are many types of plastic magnets, rare earth plastic magnets are generally oxidized during use in a high temperature atmosphere and the magnetic force is reduced, so there is a limit to use in a high temperature state. On the other hand, molding methods such as compression molding, injection molding, and extrusion molding are known for molding plastic magnets. However, plastic magnets capable of injection molding with excellent mass productivity are used to ensure injection moldability. However, there is a problem that the amount of the organic binder (plastic) to be mixed must be larger than that for the compression molding, and the magnetic properties are lower than those of the compression molding.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to manufacture a rare earth plastic magnet having high heat resistance and relatively high magnetic properties by injection molding. In other words, in order to obtain a high heat resistant plastic magnet, a high heat resistant engineering plastic is used as an organic binder, which has a high melting point and a high viscosity, so that it is difficult to mix a large amount of rare earth alloy powder. . On the other hand, there is a problem that the rare earth alloy powder is oxidized when the molded product is used at high temperature. The present invention aims to provide a rare earth plastic magnet that solves these problems.

[0004]

Means for Solving the Problems That is, the present invention provides a rare earth plastic magnet obtained by binding rare earth alloy powder with an organic binder, wherein the organic binder is a highly heat resistant engineering plastic (A) and a cyanate ester compound ( B) is used, (A): (B)
In a weight ratio of 80:20 to 20:80, and the rare earth alloy powder is mixed in an amount of 60 to 75% by volume, and the mixture is injection-molded and then cured. It is the obtained rare earth plastic magnet.

The present invention will be described in more detail below. The cyanate ester compound is a polyfunctional cyanate ester having two or more cyanato groups (-OCN) in the molecule or a cyanate ester prepolymer, and a preferable one is the following general formula (1). R (OCN) _n (1) (wherein n is an integer of 2 or more and usually 5 or less, R is an aromatic organic group which may include a heterocycle, The above cyanato group is a compound represented by (bonded to the aromatic ring of the organic group).

Specific examples of such cyanate ester compounds include 1,3- or 1,4-dicyanatobenzene,
1,3,5-tricyanatobenzene, 1,3-, 1,4-,
1,6-, 1,8-, 2,6- or 2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene, 4,4-
Dicyanatobiphenyl, bis (4-dicyanatophenyl) methane, bis (3,5-dimethyl-4-dicyanatophenyl) methane, 2,2-bis (4-cyanatophenyl) propane, 2,2-bis ( 3,5-Dibrolo-4-cyanatophenyl) propane, 2,2-bis (3,5-dibromo-4-cyanatophenyl) propane, 2,2-bis (3,5-dimethyl-4-cyanato) Phenyl) propane, bis (4-cyanatophenyl) ether, bis (4
-Cyanitophenyl) thioether, bis (4-cyanatophenyl) sulfone, tris (4-cyanatophenyl) phosphite, tris (4-cyanatophenyl) phosphate, many obtained by reaction of novolac with cyanogen halide. Functional novolac cyanates (US Pat. No. 4,022,755; 3,448,079).
No.), a polyfunctional polycarbonate cyanate obtained by reacting a polycarbonate oligomer having a terminal --OH group with halogen and cyan (US Pat. No. 4,026,9).
No. 13; German Patent No. 2,611,796), and styryl obtained by reacting cyanogen halide with poly-hydroxy-styryl-pyridine obtained by reacting hydroxybenzene aldehydes with alkyl-substituted pyridines. -Pyridine-cyanate (U.S. Pat. No. 4,578,
No. 439) and the like. In addition to these, U.S. Pat. Nos. 3,553,244; 3,755,402; 3,740,348; 3,595,900; 3,694,410. No. 4,166,946, British Patent No. 1,305,967; No. 1,060,933, German Patent No. 1,190,184; Cyan described in No. 1,195,764, etc. Acid esters may also be used. The above-mentioned polyfunctional cyanate ester is a prepolymer obtained by polymerization in the presence of a mineral acid, a Lewis acid, a salt such as sodium carbonate or lithium chloride, or a phosphoric acid ester such as tributylphosphine. It can also be used as a prepolymer with a polymerizable amine. The monomer of the cyanate ester compound or the low molecular weight compound thereof is more preferably low in viscosity.

The high heat resistant engineering plastic is a heat resistant engineering plastic having a glass transition temperature of 150 ° C. or higher, and examples thereof include polyphenylene ether, polysulfone, polyether sulfone, polyetherimide and polyarylate. Of these, polyphenylene ether is preferred. Here, polyphenylene ether is a phenol represented by the following general formula.

[0008]

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(Wherein R ₄ is a lower alkyl group having 1 to 3 carbon atoms, R ₃ and R ₅ are independently a hydrogen atom or a lower alkyl group having 1 to 3 carbon atoms, and at least one of hydroxyl groups is A lower alkyl substituent must be present at the ortho position.) A phenylene ether obtained by polycondensation of one or more of the following: a polyphenylene ether as the backbone obtained by graft-polymerizing a vinyl aromatic compound to this polyphenylene ether. Means a graft copolymer having This polyphenylene ether may be a homopolymer or a copolymer. The polyether sulfone, a heat-resistant thermoplastic resin represented by trade name developed by the British company ICI "Victrex", a benzene ring ether (-O-) and sulfone - of (-SO ₂₎ are those joined by each group, the polysulfone, a heat-resistant thermoplastic resin typified developed by US Union carbide "U del polysulfone" benzene ring isopropylidene (-C (CH _3)
2 -), ether (-O-) and sulfone (-SO ₂ -)
Polyetherimide is a heat-resistant thermoplastic resin typified by "Ultem" developed by GE in the United States, and bisphenol A is an ether bond of phthalic anhydride m. It is bonded at the -position, condensed with m-phenylenediamine, and then linked by imide bond. Polyarylate is a polyester composed of diphenol, and bisphenol and phthalic acid or a derivative thereof. It is obtained by polycondensation, and is typified by "U polymer" manufactured by Unitika Ltd.

The rare earth alloy is a magnetic alloy containing a rare earth metal such as Sm-Nd, and is a Sm-Co type or Nd-Fe-type.
Examples thereof include B type and Nd-Fe-B type in which Dy (dysprosium), Co and Mo are added. These may be surface-treated in order to enhance corrosion resistance.

As for the composition ratio of each component, the weight ratio (A) :( B) of the high heat resistant engineering plastic (A) and the cyanate ester compound (B) is 80:20 to 2
The range is 0:80, preferably 45:55 to 3
It is 0:70. If the component ratio (A) is more than 80:20, the resin viscosity becomes too high, and the addition amount of the rare earth alloy powder cannot be increased. As a result, the molded product has poor magnetic properties. On the other hand, when the amount of the component (A) is less than 20:80, the thermoplastic properties are too small and injection molding (short-time molding) becomes difficult. The amount of rare earth alloy powder is 60 to 75% by volume of the whole, and it is preferable that the amount is as large as possible in view of magnetic characteristics, but if it exceeds 75% by volume, kneading and molding are substantially difficult, which is not preferable.

The present invention can be used as a composition in which other thermosetting monomers or prepolymers or resin components are blended, if necessary, and further other fibrous reinforcing materials, fillers, It can also be used as a mixture of various known additives such as dyes, pigments, thickeners, coupling agents and flame retardants. Further, the above-prepared composition can be used by coating it on a reinforcing substrate or the like.

As the thermosetting monomer or prepolymer, acrylates such as polyfunctional (meth) acrylate, polyfunctional alkyl (meth) acrylate, tri (meth) acryloxyisocyanurate, and epoxy (meth) acrylate. Allyl compounds such as diallyl phthalate, divinyl benzene, diallyl benzene, trialkenyl isocyanurate, triallyl assocyanurate; dicyclopentadiene and its prepolymers; xylene resins; polyfunctional epoxy compounds; polyfunctional maleimide compounds The kind is illustrated. On the other hand, as a resin component, polyvinyl formal, other polyvinyl acetal resin; phenoxy resin; OH group or COOH
Non-crosslinked (non-vulcanized) rubbers such as polybutadiene, butadiene-acrylonitrile copolymer, polychloroprene, butadiene-styrene copolymer, polyisoprene, butyl rubber, natural rubber; polyethylene; , Polypropylene, polybutene,
Poly-4-methylpentene-1, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyltoluene,
Polyvinylphenol, AS resin, ABS resin, MBS
Vinyl compound polymers such as resins, polytetrafluoroethylene, polytetrafluoroethylene-hexafluoropropylene, and polyvinylidene fluoride; polycarbonates, polyesters, polyamides, polyamideimides, polyesterimides, polyphenylene sulphite, etc. A polymer (prepolymer) can be mentioned.

Examples of the flame retardant include inorganic flame retardants such as antimony trioxide, brominated epoxy compounds, brominated diphenyl ether, and brominated compounds such as hexabromobenzene.

In the present invention, a known catalyst of a cyanate compound can be used in combination if necessary. As an example of the thermosetting catalyst, zinc octylate, alkyl tin oxide, carboxylate of alkyl tin oxide, organic metal salt such as iron acetylacetone, organic metal salt chelate, metal compound such as alkylitin oxide; benzoyl peroxide, Organic peroxides such as lauroyl peroxide, di-tert-butyl peroxide, dicumyl peroxide and di-tert-butyl perphthalate; imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole; triethylamine , Tertiary amines such as N-methylpyridine; phenols such as phenol and cresol; trimellitic anhydride and phthalic anhydride.

In the present invention, a lubricant can be used in the same manner as a general thermoplastic or thermosetting molding material in order to improve moldability during injection molding. Examples of such lubricants include fatty acid amides such as stearic acid amide and oleic acid amide; fatty acid metal salts such as calcium stearate and barium stearate; higher fatty acids such as stearic acid and palmitic acid; and waxes. In the present invention, a molded product can be obtained by injection-molding a mixture of each component into a desired shape and then curing it. This curing treatment is preferably performed at a temperature of 150 to 250 ° C. for 30 to 300 minutes.

[0017]

EXAMPLES Examples will be described below together with comparative examples. Table 1
And the compositions shown in Table 2 were melt-mixed and kneaded with a heating roll to prepare a molding compound. The adjustment results are shown in Tables 1 and 2.

[0018]

[Table 1]

[0019]

[Table 2]

The materials shown in Tables 1 and 2 were evaluated as follows, and the results are shown in Tables 3 and 4. (1) Moldability: Moldability of Examples 1 to 3 and Comparative Examples 1 and 2 under molding conditions of 180 ° C., 350 kg / cm ² , mold temperature 90 ° C., curing (post cure) 200 ° C. × 3 Hrs, The appearance of molded products of a rectangular sample of 10 mm × 120 mm × 4 mm and a ring-shaped sample having an inner diameter of 15 mm, an outer diameter of 18 mm and a thickness of 10 mm was observed. Moldability of Comparative Example 3 Under a molding condition of 330 ° C., 700 kg / cm ² , and mold temperature of 150 ° C., a rectangular sample of 10 mm × 120 mm × 4 mm, an inner diameter of 15 mm, an outer diameter of 18 mm, and a thickness of 10 m.
The appearance of the molded product of the ring-shaped sample of m was observed. Moldability of Comparative Example 4 Under a molding condition of 270 ° C., 530 kg / cm ² , and a mold temperature of 100 ° C., a rectangular sample of 10 mm × 120 mm × 4 mm, an inner diameter of 15 mm, an outer diameter of 18 mm, and a thickness of 10 m.
The appearance of the molded product of the ring-shaped sample of m was observed.

(2) Fluidity: Base 1.6 mm, Height 1.6
The test was carried out using a mm semicircular spiral flow mold. (180 ° C., 350 kg / cm ² ) (3) Bending strength: A rectangular sample of 10 mm × 120 mm × 4 mm was measured by JISK7203. (4) Magnetic properties: inner diameter 15 mm, outer diameter 18 mm, thickness 1
Measurement according to JIS C2501 was performed on a 0 mm ring-shaped sample. (5) Heat resistance: JIS K6918 (load 18.5 kg / in a rectangular sample of 10 mm x 120 mm x 4 mm)
The measurement in cm ² ) was performed.

[0022]

[Table 3]

[0023]

[Table 4]

Claims (3)

[Claims] 1. In a rare earth plastic magnet obtained by binding rare earth alloy powder with an organic binder, a high heat resistant engineering plastic (A) and a cyanate ester compound (B) are used as the organic binder, and (A) :( The weight ratio of B) is 80:20 to 20: 8.
0, and the rare earth alloy powder is 60% of the total.
To 75% by volume, a rare earth plastic magnet obtained by injection molding the composition and then curing. 2. The rare earth plastic according to claim 1, wherein the high heat resistant engineering plastic is one or more selected from the group consisting of polyphenylene ether, polysulfone, polyether sulfone, polyetherimide and polyarylate. magnet. 3. The rare earth plastic magnet according to claim 1, wherein the cyanate ester compound is a monomer.