Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
  • H01F1/10—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure
  • H01F1/11—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure in the form of particles
  • H01F1/113—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure in the form of particles in a bonding agent
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
  • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
  • H01F1/06—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder
  • H01F1/08—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
  • H01F1/083—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together in a bonding agent
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
  • H01F41/0266—Moulding; Pressing

Definitions

• This invention relates to a magnetic powder material and resin bonded-type magnets, more particularly, to a magnetic powder material suitable for compression molding, resin-bonded type magnet excellent in heat resistance, chemical resistance, etc., and a method for producing them.
• thermosetting resin such as an epoxy resin, etc.
• the resulting resin-bonded type magnetic powder material is poor in preservability and also poor in production stability. Further, at preparation, it takes one hour or more for thermosetting processing so that productivity is low.
• a critical temperature for use of the resulting resin-bonded type magnet is 120°C or so, which is impractical, and it also lacks dimensional stability with a lapse of time.
• the crystalline resin such as PPS or PEEK requires a high temperature for fusion molding such as 350°C or higher, so that there is a disadvantage that magnetic powder of the rare earth is likely to be oxidized at molding.
• An object of the present invention is to provide a resin-bonded type magnet having excellent heat resistance and chemical resistance as well as excellent magnetic characteristics.
• Another object of the present invention is to provide a resin-bonded type magnet which is excellent in dimensional stability with a lapse of time, dimensional stability at molding, etc. in addition to the above mentioned characteristics.
• a further object of the present invention is to provide a magnetic powder material suitable for molding of the above resin-bonded type magnet.
• a further object of the present invention is to provide methods for preparing the above resin-bonded type magnet and magnetic powder material by simple procedures with high productivity and efficiency.
• the present invention relates to a magnetic powder material which comprises magnetic powder to which a crystalline thermoplastic resin with heat resistance is coated or adhered in amount of 0.1 to 5% by weight.
• the present invention relates to a resin-bonded type magnet comprising a compression molded material of the above magnetic powder material. Further, the present invention relates to a method for preparing the above magnetic powder material which comprises, to a mixture obtained by dissolving a crystalline thermoplastic resin with heat resistance in a solvent and dispersing magnetic powder, effecting (1) addition of a bad solvent of said resin, or (2) volatilization or evaporation of the solvent in said mixture, or (3) cooling said mixture.
• the present invention relates to a method for preparing the above magnetic powder material which comprises dissolving by heating a crystalline thermoplastic resin with heat resistance in a solvent, and then dispersing and mixing a gel obtained by cooling and magnetic powder, and crushing the resultant simultaneously with volatilizing or evaporating the solvent.
• the present invention relates to a method for preparing the above resin-bonded type magnet, characterized in that the above magnetic powder material is compression molded.
• thermoplastic resin excellent in heat resistance
• various ones can be used, but generally those having a melting point of 200°C or higher, preferably 230°C or higher. Among them, those having at least one -S- bond or -O- bond in the chemical bond skeleton.is particularly preferred.
• Specific examples of these resins include polyether ether ketone (PEEK), polyether ketone, polyphenylenesulfide (PPS), polysulfide ketone, etc.
• the molecular weight of these resins should optionally be selected in view of the above matters.
• a limiting viscosity thereof in ⁇ -­chloronaphthalene solvent at 206°C is 0.1 dl/g or higher, preferably 0.15 to 0.3 dl/g and in case of PEEK, a limiting viscosity thereof in p-chlorophenol solvent at 60°C is 0.3 dl/g or higher, preferably 0.3 to 0.85 dl/g.
• the type of the magnetic powder is not particularly limited and various ones can be optionally selected depending on the purposes.
• Specific examples thereof include ferrite powder such as BaO ⁇ 6Fe2O3, MnO ⁇ ZnO ⁇ ­Fe2O3, ⁇ -Fe3O4 PbO ⁇ 6Fe2O3, SrO ⁇ 6Fe2O3, etc.; arnico powder such as MCA160, MCA230, MCB500, MCB580, MCB4DOH, etc.
• rare earth cobalt powder such as SmCo5, PrCo5, NdCo5, MMCo5 (here, MM represents a Misch metal ), SmPrCo5, SmPrNdCo5, SmMMCo5, R2Co17 (wherein R represents a series of rare earth elements of atomic numbers from 58 to 71), Sm2Co17, Pr2Co17, Sm2 (Co, Fe, Cu)17 and Sm2 (Co, Fe, Cu, M)17 (wherein M represents Ti, Zr or Hf).
• rare earth ⁇ iron ⁇ boron powder Nd2Fe14B, Nd2Fe12Co2B, Pr2Fe14B, etc.
• Fe-Cr-Co magnetic powder Mn-Al-C magnetic powder, Pt-Co magnetic powder, Pt-Fe magnetic powder, cunife magnetic powder, etc.
• the above magnetic powder can be used as it is by mixing with the above thermoplastic resin, but in order to prevent oxidation of the magnetic powder and improve adhesiveness into a binder (the themoplastic resin), it is preferred to surface treat them with a coupling agent in an amount of 5% by weight or less, particularly 0.5 to 2.0% by weight based on the magnetic powder.
• coupling agents which can be used include various ones but titanate series and silane series ones are preferable.
• the titanate series coupling agents include isopropyltriisostearoyl titanate, isopropyltrioctanoyl titanate, isopropyltris(dioctylpyrophosphate)titanate, isopropyldimethacrylisostearoyl titanate, isopropyltri(N-­aminoethyl-aminoethyl) titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropylisostearoyldiacryl titanate, isopropyltri(dioctylphosphate)titanate, isopropyltricumylphenyl titanate, tetraisopropylbis(dioctylphosphite)titanate, tetraoctylbis(
• the silane series coupling agents include ⁇ -mercapto-propyl-trimethoxysilane, 2-styryl-ethyltrimethoxysilane, N- ⁇ -(aminoethyl) ⁇ -amino­propyl-trimethoxysilane, ⁇ -(3,4-epoxycyclohexyl)ethyl­trimethoxysilane, ⁇ -aminopropyl-trimethoxysilane, ⁇ -glycidoxy-propyltrimethoxysilane, phenyltrimethoxysilane, methyldimethoxysilane, etc. and these may be used singly or in combination.
• the titanium series coupling agents and the silane series coupling agent can be used in combination.
• the surface treatment by the coupling agent can be carried out by wetting magnetic powder with 5 to 20% by volume of the coupling agent solution (using an alcohol or toluene as a solvent), and then drying it at a temperature not less than room temperature, preferably 120 to 150°C. According to the surface treatment due to the coupling agent, water repellent property and lubricity are applied to the magnetic powder so that the mechanical strength, etc. of the resin-bonded type magnet obtained after molding can be improved.
• the magnetic powder material in the present invention can be obtained by coating or adhering the above crystalline thermoplastic resin with heat resistance onto the above magnetic powder with a ratio of 0.1 to 5% by weight, preferably 1 to 4% by weight.
• a ratio of 0.1 to 5% by weight preferably 1 to 4% by weight.
• the method for preparing the magnetic powder material by coating or adhering the thermoplastic resin on or to the magnetic powder there may be mentioned the method in which said resin and magnetic powder are mixed in the temperature range between the crystal fusion initiating temperature and the melting point of the resin, and then the mixture is cooled to coat thereon or adhere thereto; by utilizing the crystallinity of the resin.
• the crystalline thermoplastic resin with excellent heat resistance is coated on or adhered to the magnetic powder by the method as mentioned above (1) or (2), and at this time, the amount of the resin to be coated or adhered is 0.1 to 5% by weight (ratio based on the total magnetic powder material) as already mentioned. If the coated or adhered amount is less than 0.1 % by weight, the resin cannot act as the binder and the shape when molded cannot be retained. Also, if it exceeds 5% by weight, magnetic characteristics are decreased.
• An amount of the coated resin can be calculated by dissolving the resin of the magnetic powder material to remove with p-chlorophenol or ⁇ -chloronaphthalene, etc., having strong dissolving power and measuring the weight decreased.
• a polar solvent having high dissolving power which can dissolve the above crystalline thermoplastic resin with heat resistance, and may include, for example, N-­methylpyrrolidone, ⁇ -chloronaphthalene, dichloroacetic acid, 1,3-dimethyl-2-imidazolidinone, dimethylsulfoxide, dimethylacetamide, dimethylformamide, p-chlorophenol, etc.
• the kind of the solvent to be used should be optionally selected depending on the kinds or molecular weights of the resin, and generally, it is preferred that ⁇ -chloronaphthalene is used when PPS is employed as the resin, and dichloroacetic acid or ⁇ -chloro-naphthalene is used when PEEK is used as the resin.
• an amount of the solvent may be varied depending on the amount of the resin supplied, or kinds, grain size distribution, wettability, adhesiveness to the resin of the magnetic powder, etc.
• an anisotropic one such as ferrite magnetic powder or samarium cobalt magnetic powder
• a ratio of the amount of the resin to the solvent i.e. a polymer concentration (amount of charged resin (g)/amount of solvent (dl)) is preferably 0.1 to 5 (g/dl).
• the resin in a solvent in order to dissolve the resin in a solvent, it is carried out by charging the above solvent and the resin in a powder state in a suitable stirring tank and then heating while stirring.
• the heating temperature at this time is to be raised, for example, to 190°C or higher when N-­methylpyrrolidone is used as the solvent, and to 250°C or higher when ⁇ -chloronaphthalene is used. Heating and stirring are preferably continued to uniformly dissolve the resin.
• the method employed for the resin coating can be optionally selected depending on kinds of resin solution or magnetic powder to be used or conditions thereof.
• the solubility thereof can be made lower so that the resin can be precipitated on the magnetic powder.
• the bad solvent means a solvent in which the resin is insoluble or little soluble.
• the dropwise addition of the bad solvent is preferably started at temperatures wherein the hot solution of the resin is uniformly dissolved. That is, the temperature whereat almost all the resin in the solution does not start to precipitate upon cooling, and is preferably the temperature not more than the boiling point of the bad solvent.
• an organic solvent other than ⁇ -chloronaphthalene (in the range of 205 to 250°C) and water for PPS an organic solvent other than dichloroacetic acid (150°C ⁇ ), ⁇ -chloronaphthalene (205 to 250°C) and p-chloro­phenol (50°C ⁇ ), and water for PEEK can be employed; so that it may be optionally selected depending on the molecular weight of the resin to be used, concentration of the resin and solubility of the resin depending on the dissolution temperature.
• Specific examples of the bad solvents include water, methanol, isopropyl alcohol, acetone, toluene, etc.
• solvent with high boiling point such as N-methylpyrrolidone, ⁇ -chloronaphthalene, 1,3-dimethyl-2-­imidazolidinone, dimethylsulfoxide, dimethylacetamide, dimethylformamide, etc. may be used as the bad solvent depending on the temperature.
• the added amount of the bad solvent depends on the concentraion of the resin solution, but generally an amount equivalent to the amount of the basic solvent or more is preferred.
• the method in which the solvent is volatilized and evaporated to precipitate the resin on the magnetic powder may be carried out, for example, by supplying with a liquid transferring pump, a mixed slurry (mixture) of the magnetic powder, the resin solution and a low boiling point solvent having high solubility to the resin to a heating tube overheated and explosively blowing out in a room with high temperature and vacuum, to evaporate (volatilize) the solvent in a moment.
• the resin By cooling a hot solution of the resin (a mixed solution of magnetic powder dispersed in a solution of dissolved resin) and decreasing the solubility of the resin, the resin can be precipitated on the magnetic powder. Further, the low molecular weight component, which is a part of the solution and cannot be precipitated, can be precipitated by adding a bad solvent.
• it can be carried out by mixing the hot solution of the resin uniformly dissolved with magnetic powder in a stirring tank having a jacket, and cooling the mixture to room temperature while effecting dispersion and stirring with a wet dispersing and stirring apparatus and flowing cold water through the jacket.
• the cooling rate and precipitating time may optionally be selected since the time of forming precipitates is different depending on the solubility of the resin or dissolution conditions, but generally it is preferred to provide a precipitating time of one hour or more after cooling to room temperature for 1 to 2 hours. If no precipitation time is provided, it may cause delay in precipitation of the resin due to its supercooled state.
• bad solvents to be used include water, methanol, isopropyl alcohol, acetone, toluene, etc.
• a hot concentrated solution When cooled, it does not stop at a jelly-like state but rather as solid material such as wax or soap.
• it can be effected to coat the resin on the magnetic powder simultaneously with grinding thereof. That is, by adding dropwise a hot solution of the resin to magnetic powder preheated to a temperature which is the same as the hot solution of the resin under high speed dispersion and stirring, and cooling, the resin can be coated on the magnetic powder and grinding can be carried out simultaneously by precipitating and solidifying the resin.
• a dry type disperser such as Henshel mixer, high speed mixer and super mixer, etc can be used. At the time of disperse by these mixers, grinding ability can be increased by adding a ball made of ceramics such as an alumina, etc.
• the concentration of the resin solution is preferably 2 (g/dl) or more. If it is less than 2 (g/dl), it becomes a jelly-like state and aggregation is inevitable so that it is impossible to carry out coating and grinding simultaneously.
• the solution concentration may optionally be selected at which coating and grinding can be carried out simultaneously and easily in the concentraion range wherein the resin is dissolved in the solvent uniformly, and generally it is preferred to 5 to 25 (g/dl). Also, by drying under reduced pressure at a temperature of 100°C or higher while carrying out dispersion and grinding simultaneously in a mixer, the solvent can be removed.
• the resin-coated magnetic powder obtained by this method is subjected to compression molding without removing the solvent to carry out desolvation (solvent removal) simultaneously with compression molding. Also, when desolvation is effected before molding, after adding a bad solvent so as to become a slurry containing 30 to 50% by weight of the magnetic powder, the solvent can be removed with the bad solvent by using an instantaneous vacuum drying device.
• a gel (solid component) previously prepared from a resin solution and magnetic powder are dispersed and mixed, and then removal of the solvent was carried out while effecting dispersion and grinding whereby adhering to or coating on the magnetic powder can be carried out.
• a Henshel mixer in method (3) can be used.
• balls may be used in combination. The size, hardness or number of balls may be optionally determined depending on grinding ability.
• the concentration of the resin solution is preferably 5 to 25 g/dl. If it is less than 5 g/dl, an amount of the solvent to be used increases so that productivity decreases, while if it exceeds 25 g/dl, dispersion of a gel is likely to become ununiform.
• grinding treatment is carried out, if necessary.
• an impact type mill for example, a sample mill produced by Fuji Powdal K.K., or an atomizer
• a hammer mill for example, a sample mill produced by Fuji Powdal K.K., or an atomizer
• This is to supply a resin-coated magnetic powder from a hopper via a feeder to a hammer-shaped rotary wing rotating with high speed (6000 to 12000 rpm), to collide with the hammer, whereby the grinding treatment is carried out.
• This grinding is generally carried out at a normal temperature and normal pressure, but it may be carried out at a low temperature by using a coolant such as dry ice, etc. or a liquid nitrogen atomsphere. Also, in case of using a rare earth magnetic powder, in order to avoid oxidation due to collision, it is preferred to effect the procedure at a low temperature under an inert gas atmosphere such as liquid nitrogen, etc.
• the shearing force to be applied may be optionally selected depending on the number of rotation and numbers of grinding treatments.
• the magnetic powder material of the present invention can be prepared. Also, for preparing a resin-­bonded type magnet of the present invention, the resin-coated (or adhered) magnetic powder material obtained by the above methods is, if necessary, ground, and then molded. For molding, various means such as the hot compression molding, the cold compression molding, etc can be used. Among these, the cold compression molding is the particularly optimum one since productivity is high and there is no fear in lowering magnetic characteristics.
• the molding pressure may be set at or more than a pressure that causes plastic deformation to the binder resin, but generally it is optionally selected within the range of not less than 1 t/cm2. Also, a temperature is sufficient at a room temperature.
• the binder resin causes plastic deformation to adhere therewith so that strength of the molded material obtained is increased, whereby a resin-bonded type magnet having excellent physical properties can be obtained.
• the crystalline thermoplastic resin is used as the binder resin, particularly, compression molding is possible even at a room temperature.
• the amorphous thermoplastic resin it is hard or impossible to effect cold compression molding at not more than the glass transition temperature since elongation at breakage is small.
• an anisotropic resin-bonded type magnet can be obtained while the procedure is carried out by applying a magnetic field. In this case, it is effective to apply a magnetic field of 15 kOe or more. Also, if the cold compression molding is effected without applying a magnetic field, an isotropic resin-bonded type magnet which is capable of magnetizing to all directions can be obtained.
• heat treatment may be carried out. This heat treatment may only be carried out by allowing the magnet to stand at a temperature not less than the softening (pour) point or the melting point of the resin for several minutes. By this heat treatment, the resin is fused and crystallized whereby recombination is progressed and the strength of the resin-­bonded type magnet can further be improved.
• magnetization after molding is carried out by the conventional method such as applying a magnetic field of 20 kOe or more.
• a magnetic powder material to which a resin is coated or adhered by the other methods may be used, and the magnetic powder material obtained by the method for preparing the magnetic powder material of the present invention may be molded to a magnet obtained by the other methods, but by combining both methods of the present invention, production stability and mass productivity can be improved, whereby magnets having excellent characteristics can easily be obtained.
• the magnetic powder material and the resin-bonded type magnet of the present invention are good in preservability as compared with the case where a thermosetting resin is used as a binder since its chemical stability with a lapse of time is excellent.
• a practically endurable magnet can be prepared easily, which is excellent in heat resistance, chemical resistance, water absorption resistance, dimensional stability with a lapse of time, dimensional stability at molding, linear expansion coefficient, etc. And yet, a magnet can be molded by the cold compression molding, without heating, so that production step is simple and inexpensive in costs such as equipment and working, and also excellent in production stability and mass productivity.
• the resin-bonded type magnet in the present invention can be widely and effectively utilized for various electric and electronic devices including motors, etc. used in places with high temperature circumstances or requiring chemical resistance.
• a magnetic powder material suitable with the above method for preparing the resin-bonded type magnet can be effectively prepared.
• Ferrite powder Strontium ferrite SrO 6Fe2O3 OP-71 produced by Nippon Bengara Industry K.K. (a product surface treated with a silane coupling agent) Rare earth cobalt powder Samarium cobalt 2-17 series; Sm2Co17 R-30 produced by Shinetsu Chemical Industries, Ltd. (32 mesh under):
• a bortex pulverizer Into a bortex pulverizer, 3 kg of magnetic powder and 5 liters of isopropanol were introduced, and after replacing the atmosphere with N2 gas therein sufficiently, pulverization was carried out for 7 minutes and classified to obtain a powder having an average particle size of 37 ⁇ m.
• the resulting magnetic powder (3 kg) was introduced into a supermixer and the temperature was raised to 100°C under a N2 gas atmosphere, and 300 g of an isopropanol solution containing 10 % of a silane coupling agent (A-1120 produced by Nippon Unicar K.K. (N- ⁇ -aminoethyl- ⁇ -amino-propyl­trimethoxy-silane)) was added dropwise over 5 minutes.
• a silane coupling agent A-1120 produced by Nippon Unicar K.K. (N- ⁇ -aminoethyl- ⁇ -amino-propyl­tri
• Neodium series magnetic powder (Rare earth-iron-boron powder): Nd2Fe14B MQ-II powder produced by General Motors Co., Ltd.
• Polyphenylene sulfide (PPS) Examples 1 to 5,7,8 and 11 are produced by Philips Co., Ltd. and others are produced by Idemitsu Petrochemical Co., Ltd. (limiting viscosity 0.2 dl/g, 206°C, ⁇ -chloronaphthalene).
• PEEK Polyether ether ketone
• Ultradisperser produced by IKA Co., Ltd. (rotary number: 10000 rotations per minute).
• LFG-GS-1 Type (agitator rotary number: 2000 rotations per minute) produced by Shinko Industry Co., Ltd.
• magnets were prepared by cold compression molding.
• Magnet powder, a binder resin and ⁇ -chloronaphthalene or p-chlorophenol as a solvent were mixed in a flask and the binder was dissolved by heating to 240°C under an argon stream, and then the mixture was gradually cooled to 50°C over 4 hours while stirring to coat the surface of the magnetic powder with the binder resin by precipitation. After washing the residual solvent, it was dried.
• a weight (W2) of the ççresulting magnetic powder removing the coated resin was measured and a decreased weight was made as the amount of the coated resin.
• the amount of the coated resin (% by weight) was calculated from the following equation (hereinafter the same). Provided that when the strontium ferrite powder was used, the powder was ground by a grinding machine after coating with the resin.
• the resulting samples were subjected to heat treatment in an oven of an argon atmosphere for 3 minutes, and then magnetization was carried out in a magnetic field of 20 kOe to obtain permanent magnets.
• Example 19 In the same manner as in Example 19 except for replacing the ferrite powder with samarium cobalt series magnetic powder, resin coating was carried out as in Example 19 under an inert atmosphere of argon stream.
• the ferrite magnetic resin-coated powder obtained in the above Examples 13, 16, 19 and 22 were effected grinding twice by using a grinding machine (produced by Fuji Powdal K.K., Sample mill) at 10000 rpm, respectively, and the rare earth series magnetic resin-coated powder obtained in Examples 14, 15, 17, 18, 20, 21, 23 and 24 were effected grinding once by useing the same machine and flowing a liquid nitrogen with copresence thereof at 6000 rpm, respectively.
• anisotropic ferrite magnetic resin-coated powder of the above Examples 13, 16, 19 and 22 after grinding, and the anisotropic ferrite magnetic resin-coated powder obtained in Examples 25, 28, 31 and 34 were subjected to compression molding at room temperature and an applied pressure of 3 ton/cm2 in a magnetic field of 10 kOe.
• the anisotropic samarium cobalt magnetic resin-coated powder of the above Examples 14, 17, 20 and 23 after grinding, and the anisotropic samarium cobalt magnet resin-­coated powder obtained in Examples 26, 29, 33 and 36 were subjected to compression molding at room temperature and an applied pressure of 6 ton/cm2 in a magnetic field of 10 kOe.
• the isotropic neodium magnetic resin-coated powder of the above Examples 14, 18, 21 and 24 after grinding, and the isotropic neodium magnetic resin-coated powder obtained in Examples 27, 30, 32 and 35 were subjected to compression molding at room temperature and an applied pressure of 7 ton/cm2 in a non-magnetic field.
• a test piece for measuring thermal deformation temperature mentioned hereinafter was molded to a square pillar shape having 8 X 14 x 7 mm and a test plece for measuring bending strength was molded to a shape of 40 x 4 x 3 mm, respectively.
• each magnet After the above compression molding, it was exposed at 350°C for 3 minutes and then at 260°C for 5 minutes. Provided that rare earth ones were subjected under an inert atmosphere of argon stream.
• the chemical resistance was according to JIS-K7114 and visual inspection and measurements of changes in weight and dimension were carried out.
• Table 3 Chemicals Chemical resistance Chemicals Chemical resistance Hydrochloric acid (10 %) o Toluene o Sulfuric acid (10 %) o Xylene o dil. Nitric acid (5 %) o Methyl alcohol o conc.
• Standard dimension Dimension immediately after thermal treatment (room temperature)
• Test piece Approximate dimension 8 x 14 x 7 mm Changed ratio in dimension after heat treatment (%) PPS 0.012 PEEK 0.010

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• 1989
  • 1989-07-06 EP EP19890112316 patent/EP0350781A3/fr not_active Withdrawn
  • 1989-07-12 KR KR1019890010003A patent/KR900002355A/ko not_active Application Discontinuation

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