JP2009231673A - Rare earth bond magnet composition and its injection-molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare earth bond magnet composition with good molding stability, and to provide an injection-molded product using the same, which is excellent in machanical strength (extraction strength) at high temperatures. <P>SOLUTION: A composition for rare earth bond magnet includes a rare earth-transition metal-based magnet particle and a polyphenylene-sulfide resin, wherein an amount of NO radical is measured at 50°C and room temperature by an electron spin resonance device by putting the rare earth-transition metal-based magnet particle into an aqueous solution of TEMPOL, and an amount of radical of the rare earth-transition metal-based magnet particle calculated from the difference with the measured amount of NO radical is ≤75%. An injection-molded product is obtained by injecting the rare earth bond magnet composition at a nozzle temperature of 230-350°C using an injection molding machine for inject molding. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rare earth bonded magnet composition and an injection molded body thereof, and more particularly relates to a rare earth bonded magnet composition having good molding stability and an injection molded body excellent in mechanical strength at high temperature using the same.

A resin-bonded magnet (bonded magnet) is a composite material composed of magnet powder and a binder such as a thermoplastic resin or a thermosetting resin. Bond magnets manufactured by an injection molding method using a thermoplastic resin as a binder are excellent in shape flexibility. Sr ferrite and Ba ferrite are mainly used as magnet powders, but rare earth magnet powders, particularly NdFeB-based magnet powders are increasingly used in accordance with demands for miniaturization and high performance.
The composition for bonded magnets for injection molding is called a compound, and is produced by mixing the magnet powder and a resin binder and kneading them at a temperature equal to or higher than the melting point of the resin. The obtained compound is pelletized by crushing or cutting and supplied to an injection molding machine. The compound plasticized in the cylinder of the injection molding machine is injected into a mold having a predetermined shape, cooled and solidified, and then taken out from the mold as a magnet molded product.

  In order to obtain a magnet having excellent magnetic properties, it is naturally necessary to increase the content of the magnetic powder. However, when the content is increased, there arises a problem that the mechanical strength of the obtained magnet is lowered. Further, as the amount of the magnetic powder increases, the dispersibility of the magnetic powder decreases and the fluidity of the composition decreases. When the fluidity is lowered, the orientation of the magnetic particles is also lowered, so that a magnet having magnetic properties corresponding to the amount of the magnetic powder cannot be obtained. Moreover, due to the deterioration of fluidity, not only the power load (kneading torque) required for kneading increases, but also the moldability of the composition deteriorates, and it may not be possible to form a magnet having a desired shape.

In the bond magnet, a polyamide resin is widely used as a binder. However, when using magnetic powder containing iron, iron with high surface acidity has strong acid-base interaction with basic polyamide resin, causing chemisorption, and as a result, the fluidity of the composition is reduced. Further, the kneading torque is increased so that the extruding operation cannot be performed by the extruder.
Then, in order to solve such a problem, it has been proposed to blend a metal deactivator and a radical scavenger as a deterioration preventing agent in the polyamide resin binder (see Patent Document 1). Thereby, although the fluidity | liquidity fall of a composition can be suppressed, the obtained bonded magnet is not enough in heat resistance.

  On the other hand, a bond magnet using a polyphenylene sulfide (PPS) resin, which has better heat resistance and solvent resistance than polyamide resin, is known. When PPS resin is used, the nozzle temperature of the injection molding machine is usually set to 280 to 350 ° C., which is higher than that of the polyamide resin, and the mold temperature is set to 120 ° C. or higher. In particular, when the mold temperature is set lower than this, the crystallinity of PPS is lowered, and the mechanical strength of the magnet molded product is lowered.

  Conventionally, Sr ferrite and Ba ferrite have been mainstream as magnet powders, but rare earth magnet powders have recently been used in accordance with demands for miniaturization and high performance of magnets. Among rare earth magnet powders, SmCo-based and SmFeN-based PPS compounds rarely cause a deformation phenomenon such as a molded product protruding from a mold during injection molding.

However, in the NdFeB PPS compound, when injection molding is performed at such a temperature setting, the sprue or runner breaks when the molded product is taken out from the mold, the molded product itself is damaged, or the molded product is still taken out when taken out. However, since it deforms softly, stable continuous molding may not be possible.
Hereinafter, the mechanical strength when taking out a molded product from such a mold is referred to as “takeout strength”. There is not necessarily a correlation between the take-out strength and the mechanical strength of the molded product at room temperature, but even if the mechanical strength at room temperature is sufficient, the take-out strength may be low and continuous molding may not be possible. How to improve is a problem.

Thus, various attempts have been made to solve such problems. For example, as a rare earth-based bonded magnet composition containing a rare earth-transition metal magnet powder and a PPS resin, at least 70% by weight of the PPS resin has a melt viscosity (measured at 300 ° C. and a shear rate of 600 s ⁻¹ ) of 200 poise. A composition having the above-described crosslinked PPS resin has been proposed (see Patent Document 2). However, this is produced mainly for the purpose of improving the recyclability of the bonded magnet, and does not mention the radical amount of the magnet or the take-out strength of the injection molded body.

Also, by setting the nozzle temperature and mold temperature lower than the above during injection molding, it may be possible to avoid a decrease in take-out strength, but the crystallinity of the molded product will be reduced and the mechanical strength at room temperature will be reduced. To do. Accordingly, there is a need for a rare earth bonded magnet composition that has high takeout strength and can be stably injection molded.
JP 2003-82236 A JP 2006-5304 A

  An object of the present invention is to provide a rare earth bonded magnet composition having good molding stability and an injection molded article having excellent mechanical strength at high temperature using the same, in view of the above-mentioned conventional problems.

  The inventors of the present invention have made extensive studies to achieve the above object. When a compound is prepared by mixing a magnetic powder containing at least one of Nd or Pr with a PPS resin binder, a differential scanning calorimeter (DSC) is used. It has been found that the crystallization temperature Tc2 of the PPS resin is significantly lowered and cannot be continuously formed, whereas the crystallization temperature Tc2 of the PPS resin is not so lowered in the compound in which the Sm-based magnet powder is mixed with the PPS resin binder. . Then, by reducing the intrinsic radical strength of the rare earth bonded magnet powder to a specific amount or less, it is found that the decrease in the crystallization temperature Tc2 of the PPS resin is suppressed, and continuous molding becomes possible, thereby completing the present invention. It came to.

That is, according to the first invention of the present invention, in a rare earth-bonded magnet composition containing a rare earth-transition metal magnet powder and a polyphenylene sulfide resin, the rare earth-transition metal system represented by the following formula (1): There is provided a composition for a rare earth bonded magnet, wherein the radical amount (MR) of the magnet powder is 75% or less.
MR (%) = {1−I (50) / I (RT)} × 100 (1)
(In the formula, I (RT) is an electron spin resonance (ESR) of a rare earth-transition metal magnet powder in a 4-hydroxy-2,2,6,6-tetra-methylpiperidine-N-oxyl (TEMPOL) aqueous solution. (It is NO radical intensity when measured at 23 ° C. using an apparatus, and I (50) is NO radical intensity measured at 50 ° C.)

  According to the second aspect of the present invention, in the first aspect, the rare earth-transition metal magnet powder contains at least one of Nd or Pr as the rare earth element. Things are provided.

  According to a third aspect of the present invention, there is provided the rare earth bonded magnet composition according to the first aspect, wherein the rare earth-transition metal magnet powder has an average particle size of 10 to 200 μm. The

  According to the fourth invention of the present invention, in the first invention, the surface of the rare earth-transition metal magnet powder is at least one surface treatment selected from a phosphoric acid compound, a silica compound, or a triazine thiol derivative. A rare earth bonded magnet composition is provided which is coated with an agent.

  According to a fifth aspect of the present invention, there is provided a rare earth bonded magnet composition according to the first aspect, wherein 50% by weight or more of the total polyphenylene sulfide resin is a linear polyphenylene sulfide resin. Provided.

According to a sixth aspect of the present invention, in the fifth aspect, the melt viscosity of the linear polyphenylene sulfide resin is 10 to 200 Pa · s (310 ° C., shear rate 1200 s ⁻¹ ). A composition for rare earth bonded magnets is provided.

  According to the seventh invention of the present invention, in the first invention, the content of the polyphenylene sulfide resin is 5 to 30% by mass with respect to the entire composition. Things are provided.

  Furthermore, according to the eighth invention of the present invention, there is provided a rare earth bonded magnet composition characterized in that, in the first invention, the crystallization temperature Tc2 of the polyphenylene sulfide resin is 200 to 250 ° C. .

  On the other hand, according to the ninth invention of the present invention, there is provided an injection molded product according to the first to eighth inventions, wherein the rare earth bonded magnet composition is injection molded by an injection molding machine at a nozzle temperature of 230 to 350 ° C. Provided.

  The rare earth bonded magnet composition of the present invention uses a polyphenylene sulfide having excellent heat resistance and solvent resistance as a resin binder, and the radical degree of the rare earth-transition metal magnet powder is below a specific value. The mechanical strength (takeout strength) when taking out is high, and continuous molding is possible. Therefore, the productivity of bonded magnets is improved, and the obtained bonded magnets can be used in many fields where high heat resistance, solvent resistance, and mechanical strength are required. It has high usability.

  Hereinafter, the rare earth bonded magnet composition of the present invention and an injection molded article using the same will be described in detail.

1. Rare earth bonded magnet composition The rare earth bonded magnet composition of the present invention is a rare earth bonded magnet composition containing a rare earth-transition metal magnet powder and a polyphenylene sulfide resin. The radical amount (MR) of the magnet powder is 75% or less.

(1) Rare earth-transition metal magnet powder The magnet powder used in the present invention contains a rare earth element and a transition metal such as Fe, and particularly contains at least one kind of Nd or Pr as the rare earth element. is there.
Examples of such magnet powder include NdFeB-based magnet powder manufactured by a liquid quenching method and NdFeB-based magnet powder manufactured by a method called HDDR method or d-HDDR method. It may be a thing or an anisotropic thing.

  Moreover, you may contain other rare earth elements, such as Y, La, Ce, Gd, Dy, and Tb, other than Nd or Pr. Furthermore, Co, Ni, Mn, Cu, etc. other than Fe may be contained as a transition metal. Further, as additive elements for improving heat resistance and weather resistance, Cu, Zn, Ga, Ge, Mn, Cr, V, Zr, Ti, Zr, Nb, Mo, Sn, Hf, Ta, W, P, S, Si and C may be contained.

  A compound is prepared from rare earth bonded magnet powder containing Sm, for example, SmCo magnet powder or SmFeN magnet powder and PPS resin, and the strength is not reduced even if this is injection molded. Deformation phenomenon such as protrusion does not occur remarkably. However, when a compound is prepared with an element containing at least one of Nd or Pr as a rare earth element and this is injection-molded, the take-out strength is reduced, and deformation phenomena such as the protrusion of the molded product from the mold frequently occur. The present invention is directed to a rare earth bonded magnet powder containing at least one of Nd or Pr as a rare earth element that causes such a decrease in take-out strength.

  Examples of the rare earth transition metal alloy powder include isotropic or anisotropic magnetic powder produced by a method called liquid quenching method, HDDR method, or d-HDDR method. The HDDR method or the d-HDDR method is a method in which a rare earth transition metal alloy is heated and occluded to make the metal structure non-uniform, and then the alloy is heated under reduced pressure to dehydrogenate the structure. This is a method for producing a magnetic powder for bonded magnets that is recombined to form fine crystal grains of less than 1 μm. Further, a part of the rare earth transition metal alloy powder may be replaced with an oxide powder such as ferrite magnetic powder or silica so that desired magnetic properties and physical properties can be obtained.

  In addition, rare earth transition metal magnet powders exist from fine particles having an average particle size of 5 μm or less to coarse particles having a particle size exceeding 500 μm. In the present invention, the average particle size is 10 to 200 μm, preferably 50 to 100 μm. Is good. If the average particle diameter exceeds 200 μm, the surface smoothness of the molded product is deteriorated and the radical amount may be increased, which is not preferable. On the other hand, if the average particle size is smaller than 10 μm, the effect of improving the oxidative deterioration of the alloy powder that occurs during kneading or injection molding is reduced, which is not preferable.

Further, in a compound in which the take-out strength is lowered, the crystallization temperature Tc2 of the PPS resin measured by a differential scanning calorimeter (DSC) is greatly lowered. That is, Tc2 which is usually 230 to 250 ° C. is a composition with low take-off strength when measured while raising the temperature to 340 ° C. at 20 ° C./min for 2 minutes in an inert gas atmosphere and lowering the temperature at the same rate. In products, it falls below 200 ° C.
Therefore, in the present invention, the magnetic powder production conditions are controlled more strictly than before so that the radical amount (MR) of these rare earth bonded magnet powders is 75% or less, and the decrease in Tc2 is suppressed.

Here, the amount of radicals in the magnet powder was determined by using an electron spin resonance (ESR) apparatus and 4-hydroxy-2,2,6,6-tetra-methylpiperidine-N-oxyl (TEMPOL) having radicals stable at room temperature. It is determined by measuring the amount of NO radicals in the aqueous solution. That is, first, the TEMPOL aqueous solution and the magnetic powder are brought into contact at room temperature (23 ° C.). At room temperature, the radicals in the magnet powder hardly react with the TEMPOL NO radicals. First, in this state, the initial NO radical amount is measured as the ESR intensity. Next, when this mixed solution is heated to 50 ° C., the TEMPOL NO radicals are consumed and reduced by the radicals of the magnet powder.
Therefore, the consumption rate of NO radicals before and after heating can be calculated and used as the radical amount of the magnet powder. At this time, the higher the radical consumption rate, the greater the amount of radicals in the magnet powder. In the present invention, such TEMPOL NO radical consumption rate is referred to as “radical amount” of the magnet powder.

  In general, resins are known to undergo radical oxidative degradation, but compared to polyamides, which are most often used as bonded magnet resin binders, PPS is particularly effective when combined with rare earth bonded magnet powders of the above composition. It is remarkable and the degree of deterioration is large. Therefore, the present invention realizes the production of a composition that can be stably molded by controlling the radical amount of the rare earth bonded magnet powder, which is a radical source, to 75% or less. If the radical amount of the magnet powder exceeds 75%, the PPS resin in the composition deteriorates, and the above-described problem occurs when the molded product is taken out from the mold.

(2) Control of radical amount of magnet powder Various methods can be considered to control the radical amount of magnet powder. For example, the specific surface area and surface treatment of magnet powder can be adjusted. The amount of radicals can be reduced as the specific surface area is smaller or the surface of the magnet powder is inactive.

  Since the specific surface area is affected by the particle size distribution and powder shape, the specific surface area can be reduced by increasing the particle size, sharpening the particle size distribution, reducing the unevenness of the powder surface, making the shape closer to a sphere, etc. .

  On the other hand, the surface can be inactivated by, for example, forming an oxide film on the surface by gradually oxidizing the powder, or by appropriately performing a surface treatment with a phosphoric acid compound, a silica compound, or a triazine thiol derivative. Even if it is surface-treated, there is no effect if the radical amount of the magnet powder exceeds 75%.

  As a method of slow oxidation, specifically, there is a method of circulating an inert gas whose oxygen concentration is adjusted within a range of 0.1 to 20% while stirring magnetic powder in a mixer. You may heat and process at the temperature of 200 degrees C or less as needed.

  Examples of the phosphoric acid compounds include JP-A-60-13826, JP-A-69-1501, JP-A-02-46703, JP-A-11-251124, JP-2003-007521, and the like. What is described is applicable. Specifically, magnet powder is mixed with a solution obtained by mixing 10 to 30 g of 85% phosphoric acid and 1 to 2 kg of an organic solvent with respect to 1 kg of magnet powder, and heated to 100 to 200 ° C. in vacuum to be dried. That's fine.

  In addition, examples of the silica-based compound include tetramethyl orthosilicate and tetraethyl orthosilicate. If this is used, a film can be effectively formed on the surface of the magnet powder by the sol-gel reaction. For example, with respect to 1 kg of magnet powder, a silica compound may be mixed with a solution obtained by mixing 30 to 80 g and water 0.1 to 0.5 g, and heated to 50 to 150 ° C. in vacuum to be dried.

  Examples of the triazine thiol derivative include 2,4,6-trimercapto-s-triazine in addition to triazine thiol. A film can be formed by diluting this with alcohol such as methanol, ethanol, 2-propanol, etc., stirring and mixing with magnet powder in a mixer, and then removing the solvent by volatilization in an inert gas atmosphere. For example, with respect to 1 kg of magnet powder, the triazine thiol derivative 3 to 8 g may be mixed with a solution obtained by mixing 100 to 300 g of alcohol, heated to 50 to 150 ° C. in vacuum, and dried.

  As the degree of adjustment of these specific surface areas and surface treatments, the particle size can be increased within a range that does not impair the magnetic properties, or the film thickness is increased so that the radical amount of the magnet powder is 75% or less. It is preferable to set conditions.

(3) Polyphenylene sulfide resin The polyphenylene sulfide resin (PPS resin) used in the injection molding composition of the present invention is a thermoplastic resin having a structure in which benzene rings and sulfur atoms are alternately bonded, and the rare earth transition metal. It is a component that functions as a binder for magnet powder.

Examples of the PPS resin include cross-linked, straight-chain, and semi-linear (also referred to as partially cross-linked or semi-cross-linked) resins. In the present invention, any of them can be used, and they may be used in combination, but the effect is remarkable when a linear type is used.
So far, for bonded magnets, a cross-linked type is used when rigidity is required, and a linear type or semi-linear type is used when toughness is required. Moreover, the molecular weight of the PPS resin used for the bond magnet is 20,000 to 80,000, and a low molecular weight PPS resin has a low melt viscosity. In contrast, the high molecular weight PPS resin is excellent in physical properties, but the physical properties are inferior. However, since the viscosity is high, if the filling rate of the magnetic powder is increased, the moldability is inferior.
In the present invention, when the PPS resin is distinguished by the crosslinking rate, the crosslinking type PPS resin has a crosslinking rate of 26% or more (for example, 30 to 40%), and the semi-linear type PPS resin has a crosslinking rate of 5%. ˜25%, linear PPS resin refers to those having a crosslinking rate of less than 5%.

  The linear PPS resin and semi-linear PPS resin can be easily synthesized by a conventionally known method. The semi-linear PPS resin may be shortened in the heat treatment time or the processing temperature when the linear PPS resin is partially crosslinked by heat treatment. Since the crosslinking is promoted, the crosslinking rate of the semi-linear PPS resin can be adjusted even if the oxygen content in the heat treatment atmosphere is reduced. What is necessary is just to adjust the crosslinking rate of a semi linear PPS resin by combining the said method suitably in the case of actual manufacture.

  Here, as the linear PPS resin, H-1 (trade name), LR-03 (trade name), Touprene PPS LN-1 (trade name), manufactured by Tooprene Co., Ltd., LC manufactured by Tooprene Co., Ltd. Commercial products such as -5 (trade name), manufactured by Kureha Co., Ltd., trade names: W-203A and W-214A can also be used. As the semi-linear PPS resin, commercially available products such as T-2 (trade name) manufactured by Toprene Co., Ltd. may be used. In addition, as the cross-linked PPS resin, a commercially available product such as K-1G (trade name) manufactured by Toprene Co., Ltd. can also be used.

The melt viscosity of the PPS resin may be selected appropriately depending on the type of the alloy powder. Generally, the melt viscosity at 310 ° C. and a shear rate of 1000 s ⁻¹ is 20 to 300 Pa · s. It is preferable. When the viscosity is less than 20 Pa · s, although the alloy powder can be highly filled, the mechanical strength of the molded body is lowered, which is not preferable. When the melt viscosity exceeds 300 Pa · s, the moldability is remarkably lowered, which is not preferable.

In the present invention, a PPS resin is used as the resin binder, but 50% by weight or more of the total resin is a linear PPS resin having a melt viscosity of 10 to 200 Pa · s (310 ° C., shear rate of 1200 s ⁻¹ ). Desirably, the melt viscosity is more preferably 20 to 60 Pa · s. On the other hand, when the melt viscosity is less than 10 Pa · s, the mechanical strength at normal temperature is lowered, and when it exceeds 200 Pa · s, the take-out strength is not sufficiently increased even in a molded body formed by combining with magnetic powder. Furthermore, the fluidity of the composition is reduced.

If necessary, polyester resin such as liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, etc., which is a thermoplastic resin other than polyphenylene sulfide resin, less than 50% by weight of the total resin; Non-linear PPS resin; 6 Polyamide resins such as nylon, 6,6 nylon, 4,6 nylon, 11 nylon, 12 nylon, and aromatic nylon; polyacetal resin; polyether ether ketone resin; monomer units of these resins and other types of monomers Copolymers; and those resins modified with fatty acids or the like can be substituted.
The shape of the resin may be any of a pellet shape, a bead shape, a powder shape, and a paste shape, but a powder shape is preferable in terms of obtaining a uniform mixture.

(4) Heavy metal deactivator Addition of a heavy metal deactivator as a resin stabilizer is effective in improving the take-out strength. However, this effect on the take-out strength appears only when a magnetic powder controlled by performing a treatment to reduce the amount of radicals is used. small.
The heavy metal deactivator has a function of preventing the deterioration of the PPS resin by forming a chelate compound with the metal component element of the rare earth transition metal alloy powder.

In the present invention, at least one selected from oxalic acid derivatives, salicylic acid derivatives, and hydrazine derivatives is used as the heavy metal deactivator. Among these, salicylic acid derivatives and / or hydrazine derivatives are preferable, and those having a melting point of 200 ° C. or higher, more preferably 300 ° C. or higher are preferably used.
Examples of such heavy metal deactivators include oxalyl-bis (benzylidene hydrazide), N, N-dibenzal (oxal hydrazide), 2,2′-oxamidobis [ethyl 3 (3,5-di-t- Oxalic acid derivatives such as butyl-4-hydroxyphenyl) propionate]; N-salicyloyl-N′-aldehyde azine, decamethylenecarboxylic acid disalicyloyl hydrazide, 3- (N-salicyloyl) amino-1,2,4- Salicylic acid derivatives such as triazole; 2 ′, 3-bis [[3- [3,5-di-t-butyl-4-hydroxyphenyl] propionyl]] propionohydrazide, isophthalic acid bis (2-phenoxypropionylhydrazine), etc. The hydrazine derivative of can be mentioned.
When a heavy metal deactivator having a melting point lower than 200 ° C. is used, there arises a problem that the return material takeout strength becomes insufficient. The reason is presumed that the heavy metal deactivator gradually volatilizes during kneading.

  The amount of heavy metal deactivator is preferably 0.1 to 10% by weight of the amount of polyphenylene sulfide resin. If the amount is less than 0.1% by weight, the decrease in the crystallization temperature of the polyphenylene sulfide resin in the molded product after injection molding cannot be suppressed, and tends to be less than 170 ° C. This is not preferable because the mechanical strength is reduced.

(5) Other additives A lubricant, a stabilizer, and the like can be added to the rare earth-based bonded magnet composition of the present invention as an additive other than the heavy metal deactivator as necessary.

  Examples of the lubricant include waxes such as paraffin wax, liquid paraffin, polyethylene wax, polypropylene wax, ester wax, carnauba wax, and micro wax; stearic acid, 1,2-oxystearic acid, lauric acid, palmitic acid, oleic acid Fatty acids such as calcium stearate, barium stearate, magnesium stearate, lithium stearate, zinc stearate, aluminum stearate, calcium laurate, zinc linoleate, calcium ricinoleate, zinc 2-ethylhexoate (metal) Soaps); stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, lauric acid amide, hydroxystearic acid amide, methyl Fatty acid amides such as ethylene bis-stearic acid amide, ethylene bis-stearic acid amide, ethylene bis-lauric acid amide, distearyl adipic acid amide, ethylene bis-oleic acid amide, dioleyl adipic acid amide, N-stearyl stearic acid amide; Fatty acid esters such as butyl; Alcohols such as ethylene glycol and stearyl alcohol; Polyethers composed of polyethylene glycol, polypropylene glycol, polytetramethylene glycol and modified products thereof; Polysiloxanes such as dimethylpolysiloxane and silicon grease; Fluorine compounds such as oil, fluorine-based grease, fluorine-containing resin powder; and silicon nitride, silicon carbide, magnesium oxide, alumina, silicon dioxide, disulfide Ribuden and inorganic compound powder and the like. These lubricants may be used alone or in combination of two or more. The blending amount of the lubricant may be usually 1 to 10 parts by weight with respect to 100 parts by weight of the magnet powder.

  Stabilizers include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [2- { 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy} -4- {3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy} -2,2 , 6,6-tetramethylpiperidine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,2,3-triazaspiro [4,5] undecane-2,4-dione, 4, -Benzoyloxy-2,2,6,6-tetramethylpiperidine, dimethyl-1- (2-hydroxyethyl) succinate-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly [ [6- 1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidyl) imino] hexamethylene [ [2,2,6,6-tetramethyl-4-piperidyl] imino]], 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1, Hindered amine stabilizers such as 2,2,6,6-pentamethyl-4-piperidyl); and antioxidants such as phenols, phosphites, and thioethers. These stabilizers may be used alone or in combination of two or more. The amount of the stabilizer may be usually 0.05 to 10 parts by weight with respect to 100 parts by weight of the magnet powder.

2. Production of Rare Earth Bond Magnet Composition The rare earth bond magnet composition of the present invention is produced by mixing and kneading the specific magnetic powder and the PPS resin.

  The blending amount of the PPS resin may be usually 5 to 100 parts by weight, preferably 5 to 30 parts by weight, and more preferably 5 to 20 parts by weight with respect to 100 parts by weight of the magnet powder. If the blending amount is less than 5 parts by weight, the kneading resistance (torque) of the composition is remarkably increased, the fluidity is lowered, and molding may be difficult. On the other hand, when the amount is more than 100 parts by weight, a bonded magnet having desired magnetic properties cannot be obtained.

  In this invention, the compounding quantity of magnetic powder is 70 to 97 weight% with respect to the whole composition, Preferably it is 80 to 95 weight%. When the blending amount is less than 70% by weight, the magnetic properties of the obtained magnet are deteriorated. On the other hand, if it exceeds 97% by weight, the fluidity of the composition is extremely lowered and molding becomes difficult, or even if the fluidity can be maintained and molded, the orientation of the magnetic particles deteriorates, Magnetic properties commensurate with the content rate may not be obtained. Moreover, since there are too few binder components, the mechanical strength of a magnet falls and it cannot use as components.

The mixing means of each component is not particularly limited, for example, a blender such as a ribbon blender, tumbler, nauter mixer, Henschel mixer, super mixer, etc .; Banbury mixer, kneader, roll, kneader ruder, single screw extruder, twin screw Examples thereof include a method using a kneader such as an extruder.
Further, in the kneading, it is preferable to control the supply amount of the raw material and the rotation number of the blade and screw so that the temperature of the composition is 380 ° C. or lower, preferably 360 ° C. or lower. When the temperature of the composition exceeds 380 ° C., deterioration of the PPS resin due to heat proceeds, and the take-out strength decreases.
The shape of the composition obtained is in the form of powder, beads, pellets or a mixture thereof, and pellets are preferred from the viewpoint of ease of handling.

  The state of the obtained composition can be confirmed not only by actually performing injection molding but also by the crystallization temperature Tc2 of the PPS resin by a differential scanning calorimeter (DSC). In an inert gas atmosphere, when measured while raising the temperature to 340 ° C. at 20 ° C./min for 2 minutes and then lowering the temperature at the same rate, Tc2 is 200 to 250 ° C. in the bonded magnet composition of the present invention. The more preferable state is 220 to 250 ° C. When a plurality of Tc2 exothermic peaks are observed, the one with the larger calorific value falls within this range. In a composition with low takeout strength, Tc2 is less than 200 ° C.

In the kneading step, the mixture thus obtained is kneaded while being heated and melted using a batch kneader such as a Brabender, a Banbury mixer, a Henschel mixer, a helical rotor, a roll, a single screw extruder, a twin screw extruder or the like. For kneading, a batch kneader such as a kneader may be used, or a continuous kneader such as an extruder may be used. Since the crystallization temperature of the PPS resin decreases with temperature and shearing force, the conditions may be set by adjusting the set temperature, the structure of the stirring blade, and the rotational speed in any kneader.
The composition for bonded magnets of the present invention is obtained by extruding the kneaded product obtained above into a strand shape or a sheet shape, and then cutting the kneaded material into a block shape by hot cutting or cold cutting. Thereafter, it can be cooled and solidified, and further pulverized into pellets or the like. The bonded magnet composition thus obtained is excellent in low temperature fluidity and injection moldability.

3. Injection molding The injection molding method is preferable in that the degree of freedom of the shape of the molded body is large, and the surface properties and magnetic properties of the obtained magnet are excellent, so that it can be incorporated as it is as a part of an electronic component. After the composition is heated and melted at a temperature equal to or higher than the melting point of the resin, preferably in the range of 230 to 350 ° C., the melt is molded in a magnetic field using this injection molding method to obtain a bonded magnet. it can.

Moreover, it is desirable that the obtained molded body is magnetized before use. For the magnetization, an electromagnet that generates a static magnetic field, a condenser magnetizer that generates a pulsed magnetic field, or the like is used. The magnetization magnetic field, that is, the magnetic field strength is preferably 1200 kA / m (15 kOe) or more, and more preferably 2400 kA / m (30 kOe) or more.
The bonded magnet thus obtained has excellent magnetic properties and excellent mechanical strength such as rigidity. In addition, for example, it is used for small and flat complex shaped products such as motor parts for electronic equipment, and has features such as mass production, no post-processing, insert molding, etc. It is suitable for an integrally molded part.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples.

In the following Examples and Comparative Examples, each characteristic evaluation of the PPS resin, the injection molding magnet composition, and the injection molded magnet was performed as follows.
<Rare earth magnet powder>
(1) Isotropic NdFeB magnet powder MQP-B (manufactured by Magnequench International)
(2) Anisotropic NdFeB magnet powder 1 (HDDR-B manufactured by Neomax Co., Ltd.)
(3) Anisotropic NdFeB magnet powder 2 (MFP-12, manufactured by Aichi Steel Corporation)

<PPS resin>
(1) Polyphenylene sulfide: Dainippon Ink Chemical Co., Ltd., trade name: H-1G, melt viscosity 10 Pa · s, linear type (2) Polyphenylene sulfide: Dainippon Ink Chemical Co., Ltd., trade name: LR -1G, melt viscosity 50 Pa · s, linear (3) polyphenylene sulfide: manufactured by Touprene Co., Ltd., trade name: LC-5, melt viscosity 300 Pa · s, linear (4) polyphenylene sulfide: Kureha Co., Ltd. Product name: W-203A, melt viscosity 30 Pa · s, linear type (5) Polyphenylene sulfide: Kureha Co., Ltd., product name: W-214A, melt viscosity 140 Pa · s, linear type

<Heavy metal deactivator>
(1) Salicylic acid derivative 1: 3- (N-salicyloyl) amino-1,2,4-triazole (2) Salicylic acid derivative 2: Decamethylene carboxylic acid disalicyloyl hydrazide (3) Hydrazine derivative 1: 2 ', 3 -Bis-[[3- [3,5-di-tert-butyl-4-hydroxyphenyl] propionyl]] propionohydrazide

<Radical amount evaluation>
5 cc of a 1 mM TEMPOL aqueous solution diluted to 10% with ethyl alcohol was prepared, and 100 mg of magnet powder was added. After stirring for 5 minutes at 23 ° C., the mixture was allowed to stand, 0.5 cc of the supernatant was taken, put into a sample tube having a diameter of 0.8 mm, and ESR measurement was performed. The ESR measuring apparatus was JES-FA200 type manufactured by JEOL, and the NO radical intensity was measured under the conditions of a probe head of 7 mm-MAS, a resolution of 2.35 μT, a sweep width of 0.01 mT, a sweep time of 4 minutes, and a frequency of 9.0 GHz. This intensity is I (RT).
Next, 5 cc of a TEMPOL aqueous solution diluted with ethyl alcohol at the same ratio was heated to 50 ° C., and 100 mg of magnet powder was added, followed by stirring for 5 minutes while maintaining 50 ° C. 0.5 cc of the supernatant obtained after standing was put in a sample tube, and NO radical intensity I (50) was measured in the same manner. In the present invention, the radical amount (MR) of the magnet powder is expressed by the formula (1) which is the NO radical consumption rate.
MR (%) = {1−I (50) / I (RT)} × 100 (1)

<Tc2 measurement>
Using DSC3100S manufactured by Mac Science, the composition sample was heated from room temperature to 350 ° C. at 20 ° C./min in a nitrogen stream, held for 5 minutes, and then cooled to room temperature at 20 ° C./min. The crystallization temperature Tc2 of the sample was read at the top of the exothermic peak when the temperature was lowered.

Example 1
Isotropic NdFeB magnet powder MQP-B was ball milled to an average particle size of 72 μm using ethanol as a solvent. This pulverized slurry was put into a mixer and dried at 80 ° C. with stirring in a 10% O ₂ —N ₂ gas stream. The radical amount of the obtained powder was evaluated and found to be 63%.
This magnet powder was blended as 89 wt% and PPS resin W-203A 11 wt%, and kneaded by a last mill (manufactured by Toyo Seiki Seisakusho). The maximum temperature of the kneaded material was 351 ° C. The Tc2 of the collected sample was 229 ° C.
Next, after pulverizing the obtained kneaded material, it is put into an injection molding machine (J-35M manufactured by Nippon Steel Works), under the conditions of a nozzle temperature of 305 ° C., a mold temperature of 130 ° C., and a cooling time of 5 seconds. A total of 70 shots of a plate-like molded body having a width of 8 mm, a thickness of 2 mm, and a length of 40 mm were injection-molded. Sprues and runners did not break, and all could be molded stably. The results are shown in Table 1.

(Example 2)
The mixture was kneaded and molded in the same manner as in Example 1 except that 89.0 wt% of the magnet powder, 10.0 wt% of the PPS resin W-203A, and 1.0 wt% of the salicylic acid derivative 1 as a heavy metal deactivator were blended. The maximum temperature of the kneaded product during kneading was 353 ° C. Tc2 of the obtained composition was 235 degreeC.
All 70 shots were injection molded stably. The results are shown in Table 1.

(Example 3)
Except for using W-214A as the PPS resin, it was blended, kneaded and molded in the same manner as in Example 1. The maximum temperature of the kneaded product during kneading was 359 ° C. The obtained composition had a Tc2 of 206 ° C.
During 70 shots of injection molding, molding was interrupted by two sprue breaks. The results are shown in Table 1.

(Comparative Example 1)
Isotropic NdFeB magnet powder MQP-B was ball milled to an average particle size of 72 μm using ethanol as a solvent. This pulverized slurry was put into a mixer and dried at 60 ° C. with stirring in a 7% O ₂ —N ₂ gas stream. When the radical amount of the obtained powder was evaluated, it was 82%.
This magnet powder was used for kneading and molding in the same manner as in Example 2. The maximum temperature of the kneaded product during kneading was 355 ° C. Tc2 of the obtained composition was lowered to 196 ° C., and sprue breakage and runner breakage occurred in almost all shots of 70 shot injection molding. The results are shown in Table 1.

(Comparative Example 2)
The compounding, kneading and molding were performed in the same manner as in Example 3 except that the magnet powder of Comparative Example 1 was used. The maximum temperature of the kneaded product during kneading was 357 ° C. Tc2 of the obtained composition had fallen to 153 degreeC.
In the injection molding, when the molded product is taken out from the mold at a mold temperature of 130 ° C., the molded product is not yet solidified, and the plate-shaped molded product is deformed. Although the deformation could be reduced by lowering the mold temperature to 90 ° C., the sprue breakage was not lost. Since the mold temperature was lowered to 90 ° C., the DSC measurement of this molded product confirmed an exothermic peak Tc1 associated with recrystallization of the PPS resin at 142 ° C. during the temperature rise, and the molded product with a low degree of crystallinity. I found out. The results are shown in Table 1.

Example 4
An anisotropic NdFeB magnet powder 1 having an average particle size of 115 μm obtained by classifying and removing fine powder of 50 μm or less with a sieve is mixed with a solution obtained by mixing 30 g of 85% phosphoric acid and 2 kg of ethanol with 1 kg of magnet powder. Stir for minutes. Next, the filtered magnet powder was heated to 130 ° C. in vacuum to obtain a powder surface-treated with a phosphoric acid compound. The obtained powder had a surface covered with a uniform phosphate film having a thickness of 20 nm. When the radical amount of this magnet powder was evaluated, it was 41%.
This magnet powder was mixed at 85 wt%, PPS resin LR-1G at 14.5 wt%, and the heavy metal deactivator hydrazine derivative 1 at 0.5 wt%, and kneaded with a plastmill. The maximum temperature of the kneaded material was 344 ° C. The Tc2 of the collected sample was 232 ° C.
Next, after pulverizing the obtained kneaded material, it was put into an injection molding machine, and under conditions of a nozzle temperature of 305 ° C., a mold temperature of 130 ° C., and a cooling time of 5 seconds, the width 8 mm × thickness 2 mm × length 40 mm A total of 70 shots of the plate-like molded body were injection molded. Sprues and runners did not break, and all could be molded stably. The results are shown in Table 1.

(Example 5)
It was compounded, kneaded and molded in the same manner as in Example 4 except that LC-5 was used as the PPS resin and salicylic acid derivative 2 was used as the heavy metal deactivator. The maximum temperature of the kneaded product during kneading was 359 ° C. Tc2 of the obtained composition was 203 degreeC.
During injection molding of 70 shots, sprue breakage and runner breakage occurred at 13 shots of about 1/5, and molding was interrupted. The results are shown in Table 1.

(Comparative Example 3)
The amount of 85% phosphoric acid added in Example 4 was 10 g, and the heating temperature was 70 ° C. to obtain a phosphoric acid-based surface treated powder. Although the surface of the obtained powder was covered with a film having a film thickness of 5 nm, it was not a uniform phosphate film. When the radical amount of this powder was evaluated, it was 78%.
This magnet powder was used for blending, kneading and molding in the same manner as in Example 4. The maximum temperature of the kneaded material during kneading was 349 ° C. Tc2 of the obtained composition was lowered to 184 ° C., and sprue breakage and runner breakage occurred in almost all shots of 70 shot injection molding. The results are shown in Table 1.

(Comparative Example 4)
Compounding, kneading and molding were carried out in the same manner as in Example 4 except that anisotropic NdFeB magnet powder 1 having an average particle size of 74 μm from which fine powder of 50 μm or less was not sieved and removed was used. The radical content of this powder was 87%. The maximum temperature of the kneaded material was 352 ° C. Tc2 of the obtained composition had fallen to 138 degreeC.
In injection molding, when a molded product was taken out from the mold at a mold temperature of 130 ° C., the molded product was not yet solidified, and the plate-shaped molded product was deformed. Even when the cooling time was 15 seconds, the deformation was not eliminated. Although the deformation could be reduced by lowering the mold temperature to 90 ° C., the sprue breakage was not lost. The results are shown in Table 1.
In addition, DSC measurement of a molded product having a mold temperature of 90 ° C. confirmed an exothermic peak Tc1 accompanying recrystallization of the PPS resin at 137 ° C. during the temperature increase, and it was found that the molded product had a low crystallinity. . The results are shown in Table 1.

(Example 6)
By mixing anisotropic NdFeB magnet powder 2 having an average particle size of 86 μm with a solution in which 5 g of a triazine thiol derivative is mixed with 250 g of ethanol with respect to 1 kg of magnet powder, the mixture is heated to 80 ° C. in a vacuum and dried. A magnet powder surface-treated with a triazine thiol derivative was obtained. The obtained powder was covered with a uniform triazine thiol derivative film having a film thickness of 10 nm. When the radical amount of this powder was evaluated, it was 71%.
The magnet powder was blended in an amount of 87 wt%, PPS resin LR-1G 12.5 wt%, and hydrazine derivative 1 as a heavy metal deactivator 0.5 wt%, and kneaded with a plastmill. The maximum temperature of the kneaded product was 352 ° C. The Tc2 of the collected sample was 224 ° C.
Next, after pulverizing the obtained kneaded material, it was put into an injection molding machine, and a plate-like molded body having a width of 8 mm, a thickness of 2 mm and a length of 40 mm was obtained under the conditions of a nozzle temperature of 305 ° C. and a mold temperature of 130 ° C. A total of 70 shots were injection molded. Sprues and runners did not break, and all could be molded stably.

(Example 7)
Compounding, kneading and molding were performed in the same manner as in Example 6 except that the PPS resin was changed to H-1G. The maximum temperature of the kneaded material during kneading was 339 ° C. Tc2 of the obtained composition was 236 degreeC. All 70 shots of injection molding were stable. The results are shown in Table 1.

(Comparative Example 5)
A surface-treated magnet powder was obtained in the same manner as in Example 6 except that anisotropic NdFeB magnet powder 2 having an average particle size of 32 μm was used. When the radical amount of the obtained powder was evaluated, it was 79%.
This powder was blended, kneaded and molded in the same manner as in Example 6. The maximum temperature of the kneaded material was 357 ° C. Tc2 of the obtained composition was 192 degreeC.
In almost all of the 70 shot injection moldings, sprue breakage and runner breakage occurred, and stable molding was not possible. The results are shown in Table 1.

<< Evaluation >> As seen in Examples 1 to 7, the composition for rare earth bonded magnet of the present invention has a high takeout strength by using a rare earth-transition metal magnet powder having a radical amount of 75% or less. Shot injection molding is stable.
On the other hand, in Comparative Examples 1 to 5 that are out of the present invention, since the rare earth-transition metal magnet powder having a radical amount exceeding 75% is used, the takeout strength is low, and in almost all 70 shots, the sprue is reduced. Breakage and runner breakage occurred, and stable molding was not achieved. In particular, when Comparative Example 3 is seen, it can be seen that when the surface treatment of the magnet powder is incomplete and the radical amount exceeds 75%, stable molding cannot be performed.

Claims (9)

In the composition for a rare earth bonded magnet including the rare earth-transition metal magnet powder and the polyphenylene sulfide resin, the radical amount (MR) of the rare earth-transition metal magnet powder represented by the following formula (1) is 75% or less. A composition for a rare earth bonded magnet, characterized in that:
MR (%) = {1−I (50) / I (RT)} × 100 (1)
(In the formula, I (RT) is an electron spin resonance (ESR) of a rare earth-transition metal magnet powder in a 4-hydroxy-2,2,6,6-tetra-methylpiperidine-N-oxyl (TEMPOL) aqueous solution. (It is NO radical intensity when measured at 23 ° C. using an apparatus, and I (50) is NO radical intensity measured at 50 ° C.)   2. The rare earth bonded magnet composition according to claim 1, wherein the rare earth-transition metal magnet powder contains at least one of Nd and Pr as the rare earth element.   The rare earth-bonded magnet composition according to claim 1, wherein the rare earth-transition metal magnet powder has an average particle size of 10 to 200 µm.   2. The rare earth bond according to claim 1, wherein the surface of the rare earth-transition metal magnet powder is coated with at least one surface treatment agent selected from a phosphoric acid compound, a silica compound, or a triazine thiol derivative. Magnet composition.   2. The composition for a rare earth bonded magnet according to claim 1, wherein 50% by weight or more of the total polyphenylene sulfide resin is a linear polyphenylene sulfide resin. 6. The composition for a rare earth bonded magnet according to claim 5, wherein the linear polyphenylene sulfide resin has a melt viscosity of 10 to 200 Pa · s (310 ° C., shear rate of 1200 s ⁻¹ ).   Content of polyphenylene sulfide resin is 5-30 mass% with respect to the whole composition, The composition for rare earth bond magnets of Claim 1 characterized by the above-mentioned.   2. The rare earth bonded magnet composition according to claim 1, wherein the polyphenylene sulfide resin has a crystallization temperature Tc2 of 200 to 250 ° C. 3.   An injection-molded product obtained by injection-molding the rare-earth bonded magnet composition according to any one of claims 1 to 8 with an injection molding machine at a nozzle temperature of 230 to 350 ° C.