EP0024694B1 - Procédé de préparation de particules aciculaires ferromagnétiques de fer, et leur application - Google Patents

Procédé de préparation de particules aciculaires ferromagnétiques de fer, et leur application Download PDF

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Publication number
EP0024694B1
EP0024694B1 EP80104979A EP80104979A EP0024694B1 EP 0024694 B1 EP0024694 B1 EP 0024694B1 EP 80104979 A EP80104979 A EP 80104979A EP 80104979 A EP80104979 A EP 80104979A EP 0024694 B1 EP0024694 B1 EP 0024694B1
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EP
European Patent Office
Prior art keywords
goethite
iron
particles
iron particles
magnetic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP80104979A
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German (de)
English (en)
Other versions
EP0024694A2 (fr
EP0024694A3 (en
Inventor
Werner Dr. Steck
Wilhelm Dr. Sarnecki
Laszlo Dr. Marosi
Manfred Dr. Ohlinger
Werner Dr. Loeser
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BASF SE
Original Assignee
BASF SE
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Publication date
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Publication of EP0024694A2 publication Critical patent/EP0024694A2/fr
Publication of EP0024694A3 publication Critical patent/EP0024694A3/de
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Publication of EP0024694B1 publication Critical patent/EP0024694B1/fr
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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
    • 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
    • H01F1/065—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 obtained by a reduction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
    • B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
    • 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
    • H01F1/061—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 with a protective layer

Definitions

  • the invention relates to a process for the production of acicular ferromagnetic iron particles by tempering a goethite provided with a shape-stabilizing surface coating to form ⁇ -iron (III) oxide and reduction with hydrogen at 275 to 425 ° C., and to the use of the iron particles thus obtained as a magnetic material in the production of magnetic recording media.
  • ferromagnetic metal powders and metal thin layers are of particular interest for the production of magnetic recording media, since in this way the energy product and the information density can be increased considerably and such recording media compared to the current state result in narrower signal widths and better signal amplitudes .
  • the mechanical properties of such information media can be influenced within a wide range by a suitable selection of the polymeric organic binder systems, but the magnetic properties are then excluded to place further demands on the shape, size and dispersibility of the metal particles.
  • the corresponding metal particles must exhibit magnetic single-range behavior.
  • the anisotropy that is present or can additionally be achieved by the magnetic alignment in the strip should be caused by external influences, such as, B. temperature or mechanical stress, to be little affected, ie the small particles should be shape-anisotropic, in the preferred case needle-shaped, and they should generally be between 10 and 10 3 nm in size.
  • the catalytic acceleration of the reduction of preferably needle-shaped starting compounds generally results in needles which are far smaller than the starting product, and which also has a low length / thickness ratio.
  • the end product has a fairly large particle size spectrum.
  • the particle size dependence of coercive force and remanence in magnetic substances is very strong in the order of magnitude of the single-range particles. If there are also the influences which arise from a proportion of superparamagnetic particles which can arise as fragments in the above-mentioned procedure, such magnetic materials are unsuitable for use in the production of magnetic recording media. In such heterogeneous mixtures, the magnetic field strength, which is necessary to remagnetize the particles, is very different, and the distribution of the remanent magnetization as a function of the applied external field also results in a less steep remanence curve.
  • the object of the invention was therefore to provide a method for producing acicular ferromagnetic iron particles, with which it is easy to produce distinctly shape-anisotropic particles with high values for coercive field strength and in particular remanence and relative remanence.
  • acicular ferromagnetic iron particles can be obtained by reacting an aqueous solution of an iron (II) salt with aqueous solutions of alkali metal hydroxides, oxidizing the resulting suspensions of iron (II) hydroxide with oxygen-containing gases to goethite, and applying a shape-stabilizing coating on the surface of the goethite, tempering the goethite treated in this way to the x-iron (111) oxide and then reducing it with hydrogen at 275 to 425 ° C to acicular ferromagnetic iron particles with the required properties if the goethite provided with a shape-stabilizing coating is used 250 to 450 ° C in a water vapor atmosphere with a water vapor partial pressure of is annealed at least 30 mbar for 10 minutes to 10 0 hours.
  • the goethite provided with a shape-stabilizing coating is annealed for 10 minutes to 10 hours at 250 to 450 ° C. in a water vapor-containing atmosphere with a water vapor partial pressure of 30 to 1013 mbar.
  • goethite used in the process according to the invention by the so-called alkaline process is known and is described in detail, for example, in DE-AS 1 204 644, 2 550 225, 2 550 307 and 2 550 308.
  • These goethite needles are characterized by a BET specific surface area of 20 to 75 m 2 / g, an average particle length between 0.2 and 1.5 and preferably between 0.3 and 1.2 ⁇ m and a length-to-thickness Characterized ratio of at least 10, advantageously 10 to 40.
  • goethite particles required for the process according to the invention are now provided in a known manner with a shape-stabilizing surface coating which helps to maintain the outer shape during the further reworking steps.
  • the treatment of goethite with an alkaline earth metal and a carboxylic acid or another organic compound which has at least two groups capable of chelating with the alkaline earth metal is suitable for this purpose.
  • Also known and described in DE-OS 2 646 348 is the shape-stabilizing finishing of goethite on its surface with hydrolysis-resistant oxygen acids of phosphorus, their salts or esters and aliphatic mono- or polybasic carboxylic acids.
  • Possible hydrolysis-resistant substances are phosphoric acid, soluble mono-, di- or triphosphates such as potassium, ammonium dihydrogen phosphate, disodium or dilithium orthophosphate, trisodium phosphate, sodium pyrophosphate and metaphosphates such as sodium metaphosphate.
  • the compounds can be used alone or as a mixture with one another.
  • the esters of phosphoric acid with aliphatic monoalcohols with 1 to 6 carbon atoms such as. B.
  • Carboxylic acids in the process are saturated or unsaturated aliphatic carboxylic acids with up to 6 carbon atoms and up to 3 acid groups, it being possible for one or more hydrogen atoms in the aliphatic chain to be substituted by hydroxyl or amino radicals.
  • Oxidic and oxitricarboxylic acids such as oxalic acid, tartaric acid and citric acid are particularly suitable.
  • the goethite which has been given a shape-stabilizing effect in the manner described, is then annealed for 10 minutes to 10 hours at temperatures between 250 to 450 ° C. in a water vapor-containing atmosphere with a water vapor partial pressure of at least 30 mbar.
  • the end product is a needle-shaped ⁇ -iron (III) oxide provided with the surface coating formed according to the previous equipment.
  • This tempering can be carried out discontinuously or continuously.
  • Reactors such as muffle furnaces, rotary tube furnaces or vortex furnaces are suitable for batch drainage.
  • air, inert gases or air-inert gas mixtures can be passed over or through the stationary or moving iron oxide, these gases being loaded beforehand with the appropriate amount of water vapor.
  • the gases or gas mixtures are expediently saturated with water vapor at temperatures between 40 ° C. and the boiling point of the water, in particular between 50 ° C. and the boiling point of the water, and are introduced into the tempering reactors in this state.
  • the water can of course also be used in the form of steam itself or in a mixture with other gases.
  • the tempering can be particularly favorable in continuous reactors, e.g. B.
  • the ⁇ -iron (III) oxide provided with a shape-stabilizing surface coating is reduced in a manner known per se with hydrogen at 275 to 425, preferably at 300 to 400 ° C. It is advisable to passivate the finely divided iron powders obtained in this way by passing an air or oxygen-inert gas mixture over them, since the pyrophoric character of the needle-shaped iron particles with a length between 0.1 to 0.8 J-Lm and a length to thickness ratio of 5 to 25: 1 can be controlled.
  • the needle-shaped particles are particularly easy to orient magnetically, and important electroacoustic values, such as depth and height controllability, are improved.
  • the iron particles produced according to the invention are dispersed in a known manner in polymeric binders.
  • Known compounds such as homopolymers and copolymers of polyvinyl derivatives, polyurethanes, polyesters and the like are suitable as binders for this purpose.
  • the binders are used in solutions in suitable organic solvents, the further additives such. B. to increase the conductivity and abrasion resistance of the magnetic layers.
  • a uniform dispersion is obtained, which is applied to rigid or flexible carrier materials such as foils, plates or cards, the magnetic particles contained therein are aligned by a magnetic field and the layer is solidified by drying.
  • the nitrogen surface S N2 determined according to BET was primarily used to characterize the acicular iron (III) oxide hydroxides used. Electron microscope images provide information on the appearance and dimensions (L / D ratio) of the iron oxide hydroxide particles.
  • the magnetic values of the iron powder were measured with a vibration magnetometer at a magnetic field of 160 or 800 kA / m.
  • Specific remanence (M r / p ) and saturation (M m / p ) are given in nTm 3 / g.
  • remanent coercive field strength H R is an important assessment variable.
  • half of the particles are remagnetized at the field strength H R in terms of volume. It thus represents a characteristic quantity for recording processes, which in particular determines the operating point in magnetic recording.
  • the more non-uniform the remanent coercive field strength of the individual magnetic particles in the recording layer the wider the distribution of the magnetic fields, which can remagnetize a limited volume of the recording layer. This is particularly effective if the border area between oppositely magnetized areas should be as narrow as possible due to high recording densities or short wavelengths.
  • a value h 5 for the total width of the remanence curve and h 25 for the steepness of the remanence curve is determined from the constant field demagnetization curve. The values are determined according to and
  • the number index at the letter H indicates how many of the particles are magnetized in percent.
  • 70 parts of a goethite finished on the surface according to Example 1 are also annealed in a tube furnace at 350 ° C. for one hour, but under a pressure of 25 mbar.
  • the negative pressure in the reaction chamber is generated by a vacuum pump and kept constant by metering in air dried over silica gel via a vacuum valve.
  • the resulting surface-finished ⁇ -iron (III) oxide with a surface S N2 of 50 m 2 / g is then reduced to metal in the same way as described in Example 1.
  • the magnetic values measured on the acicular iron particles are shown in Table 1.
  • Example 2 The procedure is as described in Example 2, but the surface finish of goethite is reduced without additional treatment as in Example 2.
  • the magnetic properties of the resulting pyrophoric and passivated iron particles are listed in Tables 1 and 2.
  • 800 parts of the passivated iron particles produced according to Example 2 are in a 600-volume steel cylinder mill, which contains 9000 parts of steel balls with a diameter between 4 and 6 mm, with 456 parts of a 13 percent solution of a thermoplastic polyester urethane from adipic acid, 1,4-butanediol and 4,4'-diisocyanatodiphenylmethane in a solvent mixture of equal parts of tetrahydrofuran and dioxane, 296 parts of a 10 percent solution of a polyvinylformal binder containing 82 percent vinyl formal, 12 percent vinyl acetate and 6 percent vinyl alcohol units, in the solvent mixture mentioned, 20 parts butyl stearate and a further 492 Parts of the solvent mixture mentioned are mixed and dispersed for 4 days.
  • the electroacoustic properties of these tapes are measured in accordance with DIN 45 512 with a tape speed of 4.75 cm / sec, a bias current J H ⁇ of 23 mA and an equalization of 70 ⁇ sec.
  • Table 3 shows the values for the modulation at 333 Hz (A T ) and at 10 kHz (A H ).
  • the values for the magnetic tape were set to 0 dB according to comparative experiment 7.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Hard Magnetic Materials (AREA)
  • Magnetic Record Carriers (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Paints Or Removers (AREA)

Claims (3)

1. Procédé de préparation de particules de fer ferromagnétiques aciculaires par réaction d'une solution aqueuse d'un sel de fer (III) avec une solution aqueuse d'hydroxydes de métal alcalin. oxydation en goethite des suspensions d'hydroxyde de fer(II) ainsi obtenues avec des gaz oxygénés, application d'un revêtement stabilisant la forme sur la surface de la goethite, recuit de la goethite ainsi traitée pour la transformer en oxyde de fer(III)-α puis réduction avec de l'hydrogène entre 275 et 425° C pour transformer cet oxyde en particules de fer ferromagnétiques aciculaires, caractérisé par le fait que la goethite munie d'un revêtement stabilisant la forme est recuite pendant 10 minutes à 10 heures, entre 250 et 450° C, en atmosphère contenant de la vapeur d'eau, à pression partielle de vapeur d'eau d'au moins 30 mbars.
2. Procédé selon la revendication 1, caractérisé par le fait que la goethite employée reçoit sur sa surface des acides oxygénés du phosphore, résistant à l'hydrolyse, leurs sels ou esters, à raison de 0,2 à 2% en poids de phosphore, par rapport à la goethite, et des acides carboxyliques aliphatiques, mono- ou polybasiques, à 1 à 6 atomes de carbone, à raison de 0,02 à 1,2% en poids de carbone, par rapport à la goethite, puis est recuite durant 10 minutes à 10 heures entre 250 et 450° C en atmosphère contenant de la vapeur d'eau, à pression partielle de vapeur d'eau comprise entre 30 et 1013 mbars.
3. Utilisation des particules de fer ferromagnétiques aciculaires préparées selon la revendication 1 ou 2 pour la fabrication de supports d'enregistrement magnétiques.
EP80104979A 1979-09-01 1980-08-21 Procédé de préparation de particules aciculaires ferromagnétiques de fer, et leur application Expired EP0024694B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19792935358 DE2935358A1 (de) 1979-09-01 1979-09-01 Verfahren zur herstellung nadelfoermiger ferromagnetischer eisenteilchen und deren verwendung
DE2935358 1979-09-01

Publications (3)

Publication Number Publication Date
EP0024694A2 EP0024694A2 (fr) 1981-03-11
EP0024694A3 EP0024694A3 (en) 1981-08-26
EP0024694B1 true EP0024694B1 (fr) 1983-09-28

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ID=6079797

Family Applications (1)

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EP80104979A Expired EP0024694B1 (fr) 1979-09-01 1980-08-21 Procédé de préparation de particules aciculaires ferromagnétiques de fer, et leur application

Country Status (4)

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US (1) US4344791A (fr)
EP (1) EP0024694B1 (fr)
JP (1) JPS5638405A (fr)
DE (2) DE2935358A1 (fr)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS596502A (ja) * 1982-07-05 1984-01-13 Mitsui Toatsu Chem Inc 改良された強磁性鉄粉の製造方法
DE3228669A1 (de) * 1982-07-31 1984-02-02 Basf Ag, 6700 Ludwigshafen Verfahren zur herstellung nadelfoermiger, im wesentlichen aus eisen bestehender ferromagnetischer metallteilchen
JPS59157204A (ja) * 1983-02-23 1984-09-06 Chisso Corp 強磁性金属微粒子の製造方法
US4464196A (en) * 1983-08-24 1984-08-07 Hercules Incorporated Acicular ferromagnetic metal particles
JP2582764B2 (ja) * 1986-02-05 1997-02-19 バスフ アクチェン ゲゼルシャフト 本質的に鉄から成る針状強磁性金属粉末の製造方法
US5219554A (en) 1986-07-03 1993-06-15 Advanced Magnetics, Inc. Hydrated biodegradable superparamagnetic metal oxides
US5069216A (en) 1986-07-03 1991-12-03 Advanced Magnetics Inc. Silanized biodegradable super paramagnetic metal oxides as contrast agents for imaging the gastrointestinal tract
JPH03194905A (ja) * 1989-12-22 1991-08-26 Ishihara Sangyo Kaisha Ltd 磁気記録用金属磁性粉末の製造方法
SE9401392D0 (sv) * 1994-04-25 1994-04-25 Hoeganaes Ab Heat-treating of iron powders
US8911663B2 (en) * 2009-03-05 2014-12-16 Quebec Metal Powders, Ltd. Insulated iron-base powder for soft magnetic applications

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1204644B (de) * 1962-03-30 1965-11-11 Basf Ag Verfahren zur Herstellung von insbesondere als Ausgangsmaterial fuer die Herstellung von hochkoerzitivem ª†-Eisen(III)-oxyd geeignetem nadelfoermigem Eisenoxydgelb, alpha-OH
NL162233C (nl) * 1968-03-05 1980-04-15 Philips Nv Werkwijze ter bereiding van een in hoofdzaak uit ijzer bestaand magnetisch stabiel poeder, voor magnetische registratie.
NL163355C (nl) * 1969-04-08 1980-08-15 Philips Nv Werkwijze ter bereiding van een in hoofdzaak uit ijzer bestaand magnetisch stabiel metaalpoeder, voor magnetische registratie.
CH528320A (de) * 1969-04-17 1972-09-30 Stamicarbon Verfahren zur Herstellung von dauermagnetisierbare Teilchen enthaltenden Formkörpern zur magnetischen Speicherung von Informationen und Anwendung des Verfahrens zur Herstellung von flächenartigen Gebilden
DE2434096C2 (de) * 1974-07-16 1985-10-17 Basf Ag, 6700 Ludwigshafen Nadelförmige, vorwiegend aus Eisen bestehende ferromagnetische Metallteilchen und Verfahren zu ihrer Herstellung
DE2434058C2 (de) * 1974-07-16 1985-12-19 Basf Ag, 6700 Ludwigshafen Nadelförmige, vorwiegend aus Eisen bestehende ferromagnetische Metallteilchen und Verfahren zu ihrer Herstellung
DE2550225C3 (de) * 1975-11-08 1978-06-22 Basf Ag, 6700 Ludwigshafen Verfahren zur Herstellung von nadeiförmigem Y-Eisen(IID-oxid
DE2550307C3 (de) * 1975-11-08 1978-07-06 Basf Ag, 6700 Ludwigshafen Verfahren zur Herstellung von nadeiförmigem Y-Eisen(ni)-Oxid
DE2550308C3 (de) * 1975-11-08 1978-07-13 Basf Ag, 6700 Ludwigshafen Verfahren zur Herstellung von nadeiförmigem a-Eisen(III)-Oxidhydrat
DE2646348C2 (de) * 1976-10-14 1986-08-28 Basf Ag, 6700 Ludwigshafen Verfahren zur Herstellung von nadelförmigen, ferromagnetischen, im wesentlichen aus Eisen bestehenden Metallteilchen und deren Verwendung zur Herstellung von magnetischen Aufzeichnungsträgern
DE2714588C2 (de) * 1977-04-01 1986-06-05 Basf Ag, 6700 Ludwigshafen Verfahren zur Herstellung nadelförmiger ferromagnetischer Eisenteilchen
JPS5853689B2 (ja) * 1979-01-20 1983-11-30 戸田工業株式会社 針状晶金属鉄磁性粒子粉末の製造法

Also Published As

Publication number Publication date
US4344791A (en) 1982-08-17
JPS5638405A (en) 1981-04-13
DE3065058D1 (en) 1983-11-03
EP0024694A2 (fr) 1981-03-11
EP0024694A3 (en) 1981-08-26
DE2935358A1 (de) 1981-03-26

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