EP0105110B1 - Verfahren zur Herstellung nadelförmiger, im wesentlichen aus Eisen bestehender ferromagnetischer Metallteilchen - Google Patents

Verfahren zur Herstellung nadelförmiger, im wesentlichen aus Eisen bestehender ferromagnetischer Metallteilchen Download PDF

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Publication number
EP0105110B1
EP0105110B1 EP83107240A EP83107240A EP0105110B1 EP 0105110 B1 EP0105110 B1 EP 0105110B1 EP 83107240 A EP83107240 A EP 83107240A EP 83107240 A EP83107240 A EP 83107240A EP 0105110 B1 EP0105110 B1 EP 0105110B1
Authority
EP
European Patent Office
Prior art keywords
iron
oxide
iii
metal particles
feooh
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
EP83107240A
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German (de)
English (en)
French (fr)
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EP0105110A3 (en
EP0105110A2 (de
Inventor
Werner Dr. Steck
Peter Dr. Rudolf
Wilhelm Dr. Sarnecki
Werner Dr. Loeser
Jenoe Dr. Kovacs
Helmut Dr. Jakusch
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BASF SE
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BASF SE
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Publication date
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Publication of EP0105110A3 publication Critical patent/EP0105110A3/de
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Publication of EP0105110B1 publication Critical patent/EP0105110B1/de
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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

Definitions

  • the invention relates to a process for the production of acicular ferromagnetic metal particles consisting essentially of iron by reducing acicular iron (III) oxide hydroxide provided with a shape-stabilizing surface coating or the iron (III) oxide obtained therefrom by dewatering by means of decomposable organic compounds and hydrogen.
  • Acicular ferromagnetic metal particles are of particular interest for the production of magnetic recording media because of their high saturation remanence and high coercive force.
  • the object of the invention was therefore to provide a method for producing acicular ferromagnetic metal particles consisting essentially of iron, with which it is possible in a simple manner to obtain pronounced shape-anisotropic particles which are distinguished by a high degree of fineness, a narrow particle size distribution and a high coercive field strength.
  • acicular ferromagnetic metal particles consisting essentially of iron are formed by reducing acicular iron (III) oxide hydroxide provided with a shape-stabilizing surface coating or the iron (III) oxide obtained therefrom by dewatering, to which additionally decomposable organic compounds are applied can be produced according to the task if the pretreated iron (III) oxide hydroxide or iron (III) oxide in a first stage in an inert gas atmosphere at a temperature between 270 and 650 ° C to FeO x with values for x from 1.33 to 1.44 and in a second stage by means of hydrogen at a temperature between 270 and 450 ° to the metal.
  • the starting material for the process according to the invention is iron (III) oxide hydroxide in the form of a-FeOOH and ⁇ -Fe00H in a mixture of 80 to 100% a-FeOOH and 0 to 20% ⁇ -FeOOH or 70 to 100% ⁇ -FeOOH and 0 to 30% a-Fe00H suitable.
  • the corresponding iron (III) oxide hydroxides expediently have a BET surface area of at least 20 and up to 120 m 2 / g, the average particle length is between 0.10 and 1.5 ⁇ m with a length-to-thickness ratio of at least 5, expediently 8 to 40.
  • iron (III) oxides obtained from the iron (III) oxide hydroxides mentioned by dewatering at more than 250 ° C. can also be used.
  • Correspondingly modified iron oxides are used in a known manner as starting materials for producing metal particles which contain further alloy constituents, such as cobalt, nickel and / or chromium, in addition to iron.
  • iron (III) oxide hydroxides or iron (III) oxides are now provided in a known manner with a shape-stabilizing surface coating, which helps to maintain the outer shape during the further processing steps. Suitable for this is e.g. B. the treatment of iron (III) oxide hydroxides or oxides with an alkaline earth metalation and a carboxylic acid or another organic compound which has at least two groups capable of chelating with the alkaline earth metalation. These processes are described in DE-A-24 34 058 and 2434096.
  • Also known and described in DE-A-26 46 348 is the shape-stabilizing treatment of the iron (III) oxide hydroxides or oxides on their 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.
  • esters of phosphoric acid with aliphatic monoalcohols with 1 to 6 carbon atoms such as. B. use tert-butyl ester of phosphoric acid.
  • 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.
  • Equipment is the known surface coatings with tin compounds (DE-C-19 07 691) or with silicates or Si0 2 (JP-A-121 799/77 and JP-A-153 198/77).
  • Suitable organic compounds are all organic substances which are decomposable in the temperature range between 270 and 650 ° C. in the presence of the iron oxide hydroxides or iron oxides. So are u. a. longer-chain carboxylic acids and their salts, amides of long-chain carboxylic acids, long-chain alcohols, starch, oils, polyalcohols, waxes, paraffins and polymeric substances such. B. polyethylene. A high boiling point or sublimation point is advantageous in order to avoid losses of organic matter before the reduction effect begins.
  • the iron (III) oxide hydroxides or oxides are mechanically mixed with the solid or liquid organic substances or coated with them in a suitable solution or suspension of the substance. Shape stabilization and application of the organic substance can also simultaneously or immediately one after the other, for. B. in an aqueous suspension of the particles.
  • the organic compounds can also be present during or before the crystal growth of the iron (III) oxide hydroxides.
  • the organic substance is already at the beginning of the Fe00H synthesis, e.g. B. added before the precipitation of Fe (OH) 2 .
  • the addition after nucleation has ended or during or after the growth stage is also suitable.
  • the shape-stabilizing surface coating is subsequently formed in the aqueous suspension of the particles or after the filter cake has been freed from inorganic salts in water.
  • carbon contents 0.5 to 20% by weight, based on Fe00H or Fe 2 0 3, are sufficient.
  • the reductions and, if appropriate, the dewatering of FeOOH to Fe 2 O 3 before and at the start of the reduction can be carried out batchwise or continuously, for. B. each in its own reactor.
  • the type of product used, for. B: Fe00H or Fe 2 0 3 and the reduction process can use cocurrent or countercurrent operation of solids and gas or steam streams.
  • the organic reduction to FeO x can be carried out simultaneously with the dewatering of FeOOH and at the same point in the reactor or, in the case of a continuous procedure, the dewatering to Fe 2 0 3 and the organic reduction to FeO x in a reactor by addition of the organic matter take place locally at the appropriate location of the reactor.
  • the acicular ferromagnetic metal particles obtainable by the process according to the invention still largely have the shape stemming from the starting materials and, despite the preceding conversion reaction, they are uniform and particularly fine-particle according to the starting material. As a result, they are characterized by high values with regard to their magnetic properties, such as the coercive force and above all the remanence.
  • the high squareness of the hysteresis loop indicates a narrow switching field thickness distribution due to the uniform shape.
  • Such metal particles are outstandingly suitable as magnetic materials for the production of magnetic recording media.
  • these substances are expediently passivated before further processing. This means encasing the metal particles with an oxide layer by controlled oxidation in order to eliminate the pyrophoricity caused by the large free surface area of the small particles. For example, this is achieved by passing an air / nitrogen mixture over the metal powder.
  • the passivation can also be carried out by wetting the pigments with organic solvents in the presence of oxygen or with other known oxidation and / or coating processes.
  • the metal particles obtainable by the process according to the invention can be oriented magnetically particularly easily.
  • important electroacoustic values, such as depth and height controllability, and especially the noise due to the fine nature of the material have been improved.
  • Example 2 A ⁇ -FeOOH which had been treated with oxalic acid / phosphoric acid in accordance with Example 1 was reduced directly with hydrogen as indicated in Example 1.
  • the coercive field strength of the pyrophoric material was 63.1 kA / m.
  • a ⁇ -FeOOH with a specific surface area of 30 m 2 / g was provided with a tin oxide coating in accordance with the information in DE-AS 19 07 691 by neutralizing the acidic SnCl 2 -containing aqueous suspension of the particles.
  • the amount of tin was 1% by weight based on FeOOH.
  • a coating of 3% by weight of olive oil was produced in the same dispersion by adding olive oil.
  • the Fe00H equipped in this way was reduced to the metal in a hydrogen stream (30 NI / h) at 370 ° C. for 7 hours.
  • the measurement results of the pyrophoric material (py) and of a material (pa) passivated with acetone in the presence of air are given in Table 1.
  • the specific surface area of the metal particles is 26.6 m 2 / g.
  • the powder obtained showed an H c of 87.3 [kA / m] and an M r / ⁇ of 61 [nTm3 / g ] in the pulse magnetometer.
  • sample A 80 g of sample A were dewatered in air at different temperatures (sample B). The conditions and results are summarized in the table.
  • the measurement of the magnetic properties was carried out in a measuring field of 160 kA / m, the coercive field strength H e in [kA / m], remanent magnetization M, and saturation magnetization M m in [mT] as well as the guideline factor Rf, the remanence longitudinal / transverse, specified.
  • the noise-to-noise ratio RG A against the reference band IEC IV and the copy loss K o were determined. The results are shown in Table 5.
  • Example 5 The procedure was as described in Example 10, but the metal particles obtained in Example 5 were used. The results are shown in Table 5.
  • Example 10 The procedure was as described in Example 10, but the metal particles obtained according to Example 7 'were used. The results are shown in Table 5. (See table 5 page 7 f.)

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Hard Magnetic Materials (AREA)
  • Compounds Of Iron (AREA)
  • Paints Or Removers (AREA)
  • Magnetic Record Carriers (AREA)
EP83107240A 1982-07-31 1983-07-23 Verfahren zur Herstellung nadelförmiger, im wesentlichen aus Eisen bestehender ferromagnetischer Metallteilchen Expired EP0105110B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3228669 1982-07-31
DE19823228669 DE3228669A1 (de) 1982-07-31 1982-07-31 Verfahren zur herstellung nadelfoermiger, im wesentlichen aus eisen bestehender ferromagnetischer metallteilchen

Publications (3)

Publication Number Publication Date
EP0105110A2 EP0105110A2 (de) 1984-04-11
EP0105110A3 EP0105110A3 (en) 1985-11-21
EP0105110B1 true EP0105110B1 (de) 1987-11-11

Family

ID=6169825

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83107240A Expired EP0105110B1 (de) 1982-07-31 1983-07-23 Verfahren zur Herstellung nadelförmiger, im wesentlichen aus Eisen bestehender ferromagnetischer Metallteilchen

Country Status (4)

Country Link
US (1) US4439231A (enExample)
EP (1) EP0105110B1 (enExample)
JP (1) JPS5944809A (enExample)
DE (2) DE3228669A1 (enExample)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60181210A (ja) * 1984-02-27 1985-09-14 Fuji Photo Film Co Ltd 強磁性金属粉末の製造方法
JPS6161404A (ja) * 1984-08-31 1986-03-29 Sony Corp 金属磁性粉末の製造方法
JPS6161405A (ja) * 1984-08-31 1986-03-29 Sony Corp 金属磁性粉末の製造方法
JPS61154013A (ja) * 1984-12-27 1986-07-12 Mitsui Toatsu Chem Inc 磁気記録用針状性鉄微粒子の製造方法
JPS61126628U (enExample) * 1985-01-28 1986-08-08
DE3516884A1 (de) * 1985-05-10 1986-11-13 Basf Ag, 6700 Ludwigshafen Verfahren zur herstellung nadelfoermiger, im wesentlichen aus eisen bestehender ferromagnetischer metallteilchen
JP2843124B2 (ja) * 1990-07-02 1999-01-06 花王株式会社 金属磁性粉末の製造方法
US5570017A (en) * 1992-09-30 1996-10-29 Canada Conveyor Belt Co., Inc. Apparatus and method of damage detection for magnetically permeable members using an alternating magnetic field and hall effect sensors
USD425189S (en) 1996-04-26 2000-05-16 Donaldson Company, Inc. Combined filter element and frame therefor
DE102010061495A1 (de) * 2010-12-22 2012-06-28 Bundesanstalt für Materialforschung und -Prüfung (BAM) Additive für die carbothermische Reduktion von Metalloxiden zu den entsprechenden Metallen

Family Cites Families (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1592398A1 (de) * 1967-02-08 1970-12-17 Bayer Ag Verwendung von hochkoerzitivem nadelfoermigem gamma-Fe2O3 zur Herstellung von Magnetogrammtraegern
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.
US3889319A (en) * 1973-10-23 1975-06-17 Crompton & Knowles Corp Method and system for producing blended textile fibrous materials
DE2434058C2 (de) * 1974-07-16 1985-12-19 Basf Ag, 6700 Ludwigshafen Nadelförmige, vorwiegend aus Eisen bestehende ferromagnetische Metallteilchen und Verfahren zu ihrer Herstellung
JPS51121799A (en) * 1975-04-18 1976-10-25 Fujitsu Ltd Manufacturing method of electlet and piezoeiectric material
JPS52122213A (en) * 1976-04-05 1977-10-14 Hitachi Ltd Production of ferromagnetic metal powder
JPS52144400A (en) * 1976-05-27 1977-12-01 Toda Kogyo Corp Process for preparing magnetic ironoxide particle for magnetic recording material
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
DE2731845A1 (de) * 1977-07-14 1979-01-25 Devender Dr Ing Dhingra Verfahren zur herstellung von metallpulvern
DE2743298A1 (de) * 1977-09-27 1979-04-05 Basf Ag Ferromagnetische, im wesentlichen aus eisen bestehende metallteilchen und verfahren zu deren herstellung
JPS5573803A (en) * 1978-11-25 1980-06-03 Hitachi Maxell Ltd Production of magnetic alloy powder
DE2935358A1 (de) * 1979-09-01 1981-03-26 Basf Ag, 67063 Ludwigshafen Verfahren zur herstellung nadelfoermiger ferromagnetischer eisenteilchen und deren verwendung
JPS5946282B2 (ja) * 1979-12-11 1984-11-12 戸田工業株式会社 金属鉄又は鉄を主成分とする合金磁性粒子粉末の製造法
JPS5754205A (ja) * 1980-09-17 1982-03-31 Hitachi Maxell Ltd Jiseifunnoseizohoho

Also Published As

Publication number Publication date
EP0105110A3 (en) 1985-11-21
EP0105110A2 (de) 1984-04-11
DE3228669A1 (de) 1984-02-02
JPS5944809A (ja) 1984-03-13
DE3374480D1 (en) 1987-12-17
JPH0475641B2 (enExample) 1992-12-01
US4439231A (en) 1984-03-27

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