EP2076476A2 - Polycrystalline corundum fibers and method for the production thereof - Google Patents

Polycrystalline corundum fibers and method for the production thereof

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Publication number
EP2076476A2
EP2076476A2 EP07802225A EP07802225A EP2076476A2 EP 2076476 A2 EP2076476 A2 EP 2076476A2 EP 07802225 A EP07802225 A EP 07802225A EP 07802225 A EP07802225 A EP 07802225A EP 2076476 A2 EP2076476 A2 EP 2076476A2
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EP
European Patent Office
Prior art keywords
fibers
corundum
microns
oxide
periodic table
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.)
Withdrawn
Application number
EP07802225A
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German (de)
French (fr)
Inventor
Norbert Roesch
Bernd Clauss
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Clariant International Ltd
Original Assignee
Clariant Finance BVI Ltd
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Filing date
Publication date
Application filed by Clariant Finance BVI Ltd filed Critical Clariant Finance BVI Ltd
Publication of EP2076476A2 publication Critical patent/EP2076476A2/en
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/62227—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products obtaining fibres
    • C04B35/62231—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products obtaining fibres based on oxide ceramics
    • C04B35/62236—Fibres based on aluminium oxide
    • C—CHEMISTRY; METALLURGY
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/30—Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/632—Organic additives
    • C04B35/634—Polymers
    • C04B35/63404—Polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C04B35/63444—Nitrogen-containing polymers, e.g. polyacrylamides, polyacrylonitriles, polyvinylpyrrolidone [PVP], polyethylenimine [PEI]
    • C—CHEMISTRY; METALLURGY
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
    • C04B2235/3206—Magnesium oxides or oxide-forming salts thereof
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3205—Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
    • C04B2235/3208—Calcium oxide or oxide-forming salts thereof, e.g. lime
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
    • C04B2235/3222—Aluminates other than alumino-silicates, e.g. spinel (MgAl2O4)
    • C—CHEMISTRY; METALLURGY
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/327—Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
    • C04B2235/3272—Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
    • C—CHEMISTRY; METALLURGY
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/44—Metal salt constituents or additives chosen for the nature of the anions, e.g. hydrides or acetylacetonate
    • C04B2235/444—Halide containing anions, e.g. bromide, iodate, chlorite
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/52—Constituents or additives characterised by their shapes
    • C04B2235/5208—Fibers
    • C04B2235/5264—Fibers characterised by the diameter of the fibers
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/74—Physical characteristics
    • C04B2235/78—Grain sizes and shapes, product microstructures, e.g. acicular grains, equiaxed grains, platelet-structures
    • C04B2235/781—Nanograined materials, i.e. having grain sizes below 100 nm
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/74—Physical characteristics
    • C04B2235/78—Grain sizes and shapes, product microstructures, e.g. acicular grains, equiaxed grains, platelet-structures
    • C04B2235/782—Grain size distributions
    • C04B2235/784—Monomodal
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/80—Phases present in the sintered or melt-cast ceramic products other than the main phase
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2913—Rod, strand, filament or fiber
    • Y10T428/298—Physical dimension

Definitions

  • the present invention relates to novel polycrystalline corundum fibers and a process for their preparation, wherein aluminum chlorohydrate serves as a starting compound.
  • Ceramic fibers have been produced for many years and used in various fields. They are characterized by the high
  • the ceramic fibers based on aluminum oxide and aluminum oxide / silicon dioxide (MuINt) are used as insulating material in furnace construction, in the aerospace and automotive industries.
  • alumina fibers and mullite fibers are used as starting materials corresponding precursors of metal oxides.
  • Silica is often used to stabilize the crystal phases and to suppress crystal growth (EP 0 318 203 and EP 0 206 634). Further additives for influencing the crystal structure and the crystal growth in the fibers, e.g. MgO and iron oxide are described in EP 0 294 208.
  • Aluminum salts such as aluminum chlorohydrate (EP 0 318 203) or aluminum formate acetate mixed salts (EP 0 294 208) are used as precursors for the production of aluminum oxide and mullite fibers.
  • Aluminum salts such as aluminum chlorohydrate (EP 0 318 203) or aluminum formate acetate mixed salts (EP 0 294 208) are used as precursors for the production of aluminum oxide and mullite fibers.
  • US Pat. No. 3,808,015 assumes mixtures of aluminum oxide particles (13-80% proportion) and corresponding binders, such as, for example, aluminum chlorohydrate.
  • the aluminum oxide particles used according to US Pat. No. 3,808,015 are intended a Korundierenverotti of 99.5% less than 5 microns, 98% less than 3 microns and 50% greater than 0.2 microns.
  • water-soluble polymers such as polyethylene oxide or polyvinyl alcohol added.
  • the invention relates to polycrystalline corundum fibers consisting essentially of corundum and an oxide of elements of the I. or II. Main group of the Periodic Table, wherein the crystallites of these corundum fibers have the following particle size distribution: 0 to 0.15 microns (34%), 0.15 to 0.29 micron (55%) and 0.29 to 0.43 micron (11%). Preferred is a particle size distribution of 0 to 0.06 microns (34%); 0.06 to 0.122 microns (55%) and 0.122 to 0.3 microns (11%). With this particle size distribution, the corundum fibers according to the invention differ significantly from the corundum fibers according to EP 294 208, which according to the information there have a completely different particle size distribution and have a significantly higher particle size.
  • the corundum fibers according to the present invention preferably contain 0.01 to 20% by weight of an oxide of the 1st or 2nd main group.
  • oxides are in particular CaO and MgO.
  • Another object of the present invention is a method for producing the corundum fibers described above.
  • This method consists in mixing an aqueous solution of aluminum chlorohydrate with an oxide former of elements of main groups I and II of the Periodic Table and nuclei promoting the formation of ⁇ -alumina, adding a water-soluble polymer to this mixture, spinning fibers and these fibers calcined at temperatures higher than 1100 0 C.
  • the aluminum chlorohydrate used has the formula Al 2 (OH) x Cl y , where x is a number from 2.5 to 5.5 and y is a number from 3.5 to 0.5 and the Sum of x and y is always 6.
  • x is a number from 2.5 to 5.5
  • y is a number from 3.5 to 0.5
  • the Sum of x and y is always 6.
  • Preference is given to starting from 50% aqueous solutions, as they are commercially available.
  • Such a solution is mixed with nuclei which promote the formation of the ⁇ -modification of Al 2 O 3 .
  • nuclei cause a lowering of the temperature for the formation of the ⁇ -modification in the subsequent thermal treatment.
  • germs are preferably in question finely disperse corundum, diaspore or hematite.
  • C1-Al 2 O 3 nuclei having an average particle size of less than 0.1 ⁇ m.
  • This starting solution additionally contains oxide formers in order to produce the oxides MeO of the elements of the I. and II. Main group of the Periodic Table.
  • the chlorides in particular the chlorides of the elements Ca and Mg, but also other soluble or dispersible salts such as oxides, oxychlorides, carbonates or sulfates.
  • the amount of oxide generator is such that the finished fibers contain from 0.01% to 20% by weight of the oxide MeO.
  • the oxides of I. and II. Main group may be present as a separate phase in addition to the alumina or with this real mixed oxides such. Form spinels etc.
  • the term "mixed oxides" in the context of this invention should be understood to include both types.
  • oxide formers of elements of the I. and II. Main group and crystallization nuclei still a water-soluble polymer is added, by means of which the rheology for the spinnability of the mass is adjusted.
  • Suitable polymers include polyvinyl alcohols, polyethylene oxides, polyvinylpyrrolidones and other water-soluble, organic polymers, it being possible for the polymer content to be in the range from 10 to 40% by weight (based on the oxide content of the mixture).
  • the spinning dope according to the invention is blown or expressed through nozzles, wherein the resulting green fibers are collected as short fiber. It is also possible to produce long fibers with the spinning composition according to the invention, in which case the thread is taken up and wound on bobbins. The green fiber thus obtained is in a subsequent
  • Calcination step converted into the desired corundum fiber Starting from the spinning dope according to the invention, the formation of ⁇ -alumina takes place at temperatures above 1100 ° C.
  • the fibers thus obtained consist of at least 80% of aluminum oxide and at least 70% of ⁇ -Al 2 O 3 (corundum).
  • the average diameter of the corundum crystallites is less than 300 nm and the average diameter of all crystallites is less than 0.5 ⁇ m. Due to the small size of the crystallites and their homogeneous distribution fibers of the invention show high tensile modulus and a very good mechanical strength while maintaining flexibility.
  • the long fibers according to the invention are particularly suitable for the production of ceramic fiber fabrics and as starting material for the production of ceramic matrix and metal matrix composite materials.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Structural Engineering (AREA)
  • Nanotechnology (AREA)
  • Physics & Mathematics (AREA)
  • Composite Materials (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Thermal Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Inorganic Fibers (AREA)
  • Artificial Filaments (AREA)

Abstract

The invention relates to polycrystalline corundum fibers substantially consisting of corundum and an oxide of the elements of the main groups I or II of the periodic table. The crystallites of said corundum fibers have the following grain size distribution: 0 to 0.15 micrometers (34 %), 0.15 to 0.29 micrometers (55 %) and 0.29 to 0.43 micrometers (11 %). Said corundum fibers are produced by mixing nuclei and an oxide former of the elements of the main groups I. and Il of the periodic table with an aluminium chlorohydrate, by adding a water-soluble polymer, then by spinning fibers from said mixture and by calcining said fibers at temperatures above 1100°C.

Description

Beschreibung description
Polykristalline Korundfasern und Verfahren zu deren HerstellungPolycrystalline corundum fibers and process for their preparation
Die vorliegende Erfindung betrifft neue polykristalline Korundfasern und ein Verfahren zu ihrer Herstellung, wobei Aluminiumchlorohydrat als Ausgangsverbindung dient.The present invention relates to novel polycrystalline corundum fibers and a process for their preparation, wherein aluminum chlorohydrate serves as a starting compound.
Keramische Fasern werden seit vielen Jahren hergestellt und in unterschiedlichen Bereichen eingesetzt. Sie zeichnen sich durch die hoheCeramic fibers have been produced for many years and used in various fields. They are characterized by the high
Chemikalienbeständigkeit, hohe thermische Stabilität und bemerkenswerte mechanische Eigenschaften aus. Während Kurzfasern eine enorme Bedeutung in Hochtemperatur- Isoliermaterial als Ersatz für Asbest erlangt haben, stellen die erhältlichen Filamentfasern Nischenprodukte dar, die aufgrund des hohen Preises nur in begrenztem Umfang für Spezialanwendungen eingesetzt werden.Chemical resistance, high thermal stability and remarkable mechanical properties. While short fibers have gained tremendous importance in high-temperature insulation as a substitute for asbestos, the available filament fibers are niche products which, due to the high price, are only used to a limited extent for special applications.
Als Isoliermaterial finden die keramischen Fasern auf Basis Aluminiumoxid und Aluminiumoxid / Siliciumdioxid (MuINt) Anwendung im Ofenbau, in der Luft- und Raumfahrt und im Automobilbereich.The ceramic fibers based on aluminum oxide and aluminum oxide / silicon dioxide (MuINt) are used as insulating material in furnace construction, in the aerospace and automotive industries.
Bei der Herstellung dieser Aluminiumoxidfasern und Mullitfasern dienen als Ausgangsmaterialien entsprechende Vorstufen der Metalloxide. Zur Stabilisierung der Kristallphasen und zur Unterdrückung von Kristallwachstum wird häufig Siliciumdioxid verwendet (EP 0 318 203 und EP 0 206 634). Weitere Zusätze zur Beeinflussung der Kristallstruktur und des Kristallwachstums in den Fasern, wie z.B. MgO und Eisenoxid, sind beschrieben in EP 0 294 208.In the preparation of these alumina fibers and mullite fibers are used as starting materials corresponding precursors of metal oxides. Silica is often used to stabilize the crystal phases and to suppress crystal growth (EP 0 318 203 and EP 0 206 634). Further additives for influencing the crystal structure and the crystal growth in the fibers, e.g. MgO and iron oxide are described in EP 0 294 208.
Als Vorstufen für die Herstellung von Aluminiumoxid- und Mullitfasern kommen Aluminiumsalze wie Aluminiumchlorohydrat (EP 0 318 203) oder Aluminiumformiat-acetat-Mischsalze (EP 0 294 208) zum Einsatz. InAluminum salts such as aluminum chlorohydrate (EP 0 318 203) or aluminum formate acetate mixed salts (EP 0 294 208) are used as precursors for the production of aluminum oxide and mullite fibers. In
US 3 808 015 wird hingegen von Mischungen aus Aluminiumoxidpartikeln (13 - 80 %-Anteil) und entsprechenden Bindern, wie z.B. Aluminiumchlorohydrat ausgegangen. Die gemäß US 3 808 015 benutzten Aluminiumoxidpartikel sollen eine Korundgrößenverteilung von 99,5 % kleiner 5 μm, 98 % kleiner 3 μm und 50 % größer 0,2 μm sind.US Pat. No. 3,808,015, on the other hand, assumes mixtures of aluminum oxide particles (13-80% proportion) and corresponding binders, such as, for example, aluminum chlorohydrate. The aluminum oxide particles used according to US Pat. No. 3,808,015 are intended a Korundgrößenverteilung of 99.5% less than 5 microns, 98% less than 3 microns and 50% greater than 0.2 microns.
Zur Verbesserung der Rheologie und Spinnbarkeit der Massen werden häufig wasserlösliche Polymere wie z. B. Polyethylenoxid oder Polyvinylalkohol zugesetzt.To improve the rheology and spinnability of the masses are often water-soluble polymers such. As polyethylene oxide or polyvinyl alcohol added.
Gegenstand der Erfindung sind polykristalline Korundfasern bestehend im Wesentlichen aus Korund und einem Oxid von Elementen der I. oder II. Hauptgruppe des Periodensystems, wobei die Kristallite dieser Korundfasern folgende Korngrößenverteilung aufweisen: 0 bis 0,15 Mikrometer (34 %), 0,15 bis 0,29 Mikrometer (55 %) und 0,29 bis 0,43 Mikrometer (11 %). Bevorzugt ist eine Korngrößenverteilung von 0 bis 0,06 Mikrometer (34 %); 0,06 bis 0,122 Mikrometer (55 %) und 0,122 bis 0,3 Mikrometer (11 %). Mit dieser Korngrößenverteilung unterscheiden sich die erfindungsgemäßen Korundfasern deutlich von den Korundfasern gemäß EP 294 208, die gemäß den dortigen Angaben eine völlig andere Korngrößenverteilung haben und eine wesentlich höhere Partikelgröße aufweisen.The invention relates to polycrystalline corundum fibers consisting essentially of corundum and an oxide of elements of the I. or II. Main group of the Periodic Table, wherein the crystallites of these corundum fibers have the following particle size distribution: 0 to 0.15 microns (34%), 0.15 to 0.29 micron (55%) and 0.29 to 0.43 micron (11%). Preferred is a particle size distribution of 0 to 0.06 microns (34%); 0.06 to 0.122 microns (55%) and 0.122 to 0.3 microns (11%). With this particle size distribution, the corundum fibers according to the invention differ significantly from the corundum fibers according to EP 294 208, which according to the information there have a completely different particle size distribution and have a significantly higher particle size.
Die Korundfasern gemäß der vorliegenden Erfindung enthalten vorzugsweise 0,01 bis 20 Gew.-% eines Oxids der I. oder II. Hauptgruppe. Derartige Oxide sind insbesondere CaO und MgO.The corundum fibers according to the present invention preferably contain 0.01 to 20% by weight of an oxide of the 1st or 2nd main group. Such oxides are in particular CaO and MgO.
Ein weiterer Gegenstand der vorliegenden Erfindung ist ein Verfahren zur Herstellung der zuvor beschriebenen Korundfasern. Dieses Verfahren besteht darin, dass man eine wässrige Lösung von Aluminiumchlorohydrat mit einem Oxidbildner von Elementen der I. und II. Hauptgruppe des Periodensystems und Kristallisationskeimen, die die Bildung von α-Aluminiumoxid fördern, mischt, diese Mischung mit einem wasserlöslichen Polymer versetzt, Fasern spinnt und diese Fasern bei Temperaturen höher als 11000C kalziniert.Another object of the present invention is a method for producing the corundum fibers described above. This method consists in mixing an aqueous solution of aluminum chlorohydrate with an oxide former of elements of main groups I and II of the Periodic Table and nuclei promoting the formation of α-alumina, adding a water-soluble polymer to this mixture, spinning fibers and these fibers calcined at temperatures higher than 1100 0 C.
Dem verwendeten Aluminiumchlorohydrat kommt die Formel AI2(OH)xCIy zu, wobei x eine Zahl von 2,5 bis 5,5 und y eine Zahl von 3,5 bis 0,5 ist und die Summe von x und y stets 6 beträgt. Bevorzugt geht man dabei von 50 %igen wässrigen Lösungen aus, wie sie kommerziell verfügbar sind. Eine solche Lösung wird mit Kristallisationskeimen versetzt, die die Bildung der α-Modifikation des AI2O3 fördern. Insbesondere bewirken solche Keime eine Herabsetzung der Temperatur für die Bildung der α-Modifikation bei der nachfolgenden thermischen Behandlung. Als Keime kommen bevorzugt infrage feinstdisperser Korund, Diaspor oder Hämatit. Besonders bevorzugt nimmt man feinstdisperse C1-AI2O3- Keime mit einer mittleren Teilchengröße von weniger als 0,1 μm. Im Allgemeinen reichen 0,1 bis 10 Gew.-% an Keimen bezogen auf das entstehende Aluminiumoxid aus.The aluminum chlorohydrate used has the formula Al 2 (OH) x Cl y , where x is a number from 2.5 to 5.5 and y is a number from 3.5 to 0.5 and the Sum of x and y is always 6. Preference is given to starting from 50% aqueous solutions, as they are commercially available. Such a solution is mixed with nuclei which promote the formation of the α-modification of Al 2 O 3 . In particular, such nuclei cause a lowering of the temperature for the formation of the α-modification in the subsequent thermal treatment. As germs are preferably in question finely disperse corundum, diaspore or hematite. It is particularly preferable to use very finely divided C1-Al 2 O 3 nuclei having an average particle size of less than 0.1 μm. In general, 0.1 to 10 wt .-% of germs based on the resulting alumina from.
Diese Ausgangslösung enthält zusätzlich noch Oxidbildner, um die Oxide MeO der Elemente der I. und II. Hauptgruppe des Periodensystems zu erzeugen. Hierfür kommen vor allem infrage die Chloride, insbesondere die Chloride der Elemente Ca und Mg, aber darüber hinaus auch andere lösliche oder dispergierbare Salze wie Oxide, Oxichloride, Carbonate oder Sulfate. Die Menge an Oxidbildner ist so bemessen, dass die fertigen Fasern 0,01 bis 20 Gew.-% des Oxids MeO enthalten. Die Oxide der I. und II. Hauptgruppe können als separate Phase neben dem Aluminiumoxid vorliegen oder mit diesem echte Mischoxide wie z.B. Spinelle etc. bilden. Der Begriff "Mischoxide" im Rahmen dieser Erfindung ist so zu verstehen, dass er beide Typen mit einschließt.This starting solution additionally contains oxide formers in order to produce the oxides MeO of the elements of the I. and II. Main group of the Periodic Table. For this purpose, especially in question the chlorides, in particular the chlorides of the elements Ca and Mg, but also other soluble or dispersible salts such as oxides, oxychlorides, carbonates or sulfates. The amount of oxide generator is such that the finished fibers contain from 0.01% to 20% by weight of the oxide MeO. The oxides of I. and II. Main group may be present as a separate phase in addition to the alumina or with this real mixed oxides such. Form spinels etc. The term "mixed oxides" in the context of this invention should be understood to include both types.
Zu der wässrigen Mischung von Aluminiumchlorohydrat, Oxidbildner von Elementen der I. und II. Hauptgruppe und Kristallisationskeimen wird noch ein wässerlösliches Polymer zugegeben, mit dessen Hilfe die Rheologie für die Spinnbarkeit der Masse eingestellt wird. Als Polymer kommen in Frage Polyvinylalkohole, Polyethylenoxide, Polyvinylpyrrolidone und andere wasserlösliche, organische Polymere, wobei der Gehalt an Polymer im Bereich 10 - 40 Gew.-% (bezogen auf den Oxidgehalt der Mischung) liegen kann. Zur Erhöhung des Feststoffgehalts kann es noch vorteilhaft sein, der Spinnmasse Wasser zu entziehen. Dies kann unter Erwärmung bei Normaldruck oder im Vakuum erfolgen. Die erfindungsgemäße Spinnmasse wird durch Düsen geblasen oder ausgedrückt, wobei die entstehenden Grünfasern als Kurzfaser gesammelt werden. Es ist auch möglich, mit der erfindungsgemäßen Spinnmasse Langfasern herzustellen, wobei in diesem Fall der Faden aufgenommen und auf Spulen gewickelt wird. Die so erhaltene Grünfaser wird in einem anschließendenTo the aqueous mixture of aluminum chlorohydrate, oxide formers of elements of the I. and II. Main group and crystallization nuclei still a water-soluble polymer is added, by means of which the rheology for the spinnability of the mass is adjusted. Suitable polymers include polyvinyl alcohols, polyethylene oxides, polyvinylpyrrolidones and other water-soluble, organic polymers, it being possible for the polymer content to be in the range from 10 to 40% by weight (based on the oxide content of the mixture). To increase the solids content, it may still be advantageous to extract water from the dope. This can be done under normal pressure or under vacuum. The spinning dope according to the invention is blown or expressed through nozzles, wherein the resulting green fibers are collected as short fiber. It is also possible to produce long fibers with the spinning composition according to the invention, in which case the thread is taken up and wound on bobbins. The green fiber thus obtained is in a subsequent
Kalzinierungsschritt in die gewünschte Korundfaser überführt. Ausgehend von der erfindungsgemäßen Spinnmasse erfolgt die Bildung von α-Aluminiumoxid bei Temperaturen über 11000C. Die so erhaltenen Fasern bestehen zu mindestens 80 % aus Aluminiumoxid und mindestens zu 70 % aus α-Al2θ3 (Korund). Der durchschnittliche Durchmesser der Korundkristallite liegt unter 300 nm und der durchschnittliche Durchmesser aller Kristallite liegt unterhalb 0,5 μm. Bedingt durch die geringe Größe der Kristallite und deren homogene Verteilung zeigen die erfindungsgemäßen Fasern hohe Zugmodule und eine sehr gute mechanische Festigkeit bei Erhalt der Flexibilität.Calcination step converted into the desired corundum fiber. Starting from the spinning dope according to the invention, the formation of α-alumina takes place at temperatures above 1100 ° C. The fibers thus obtained consist of at least 80% of aluminum oxide and at least 70% of α-Al 2 O 3 (corundum). The average diameter of the corundum crystallites is less than 300 nm and the average diameter of all crystallites is less than 0.5 μm. Due to the small size of the crystallites and their homogeneous distribution fibers of the invention show high tensile modulus and a very good mechanical strength while maintaining flexibility.
Die erfindungsgemäßen Langfasern eigenen sich insbesondere zur Herstellung von Keramikfaser-Geweben und als Ausgangsmaterial für die Herstellung von Keramikmatrix- und Metallmatrix-Verbundwerkstoffen.The long fibers according to the invention are particularly suitable for the production of ceramic fiber fabrics and as starting material for the production of ceramic matrix and metal matrix composite materials.
Beispiel 1example 1
Eine 50 %ig wässrige Lösung von Aluminiumchlorohydrat wurde mit soviel Magnesiumchlorid versetzt, dass nach der Kalzinierung das Verhältnis von Aluminiumoxid zu Magnesiumoxid 99,5 : 0,5 Gew.-% betrug. Außerdem wurden der Lösung 2 % Kristallisationskeime (bezogen auf den Oxidgehalt) in Form einer Suspension aus Feinstkorund zugesetzt. Nachdem die Lösung durch Rühren homogenisiert wurde, erfolgte die Zugabe einer wässrigen Lösung von Polyvinylpyrrolidon. Nach der Aufkonzentrierung durch Abdampfen von Wasser im Vakuum wurde die Spinnmasse in einem Trockenspinnverfahren durch eine Mehrlochdüse versponnen. Die erhaltenen Grünfasem wurden langsam bis auf 11000C erhitzt. Die sich bildende Korundfaser zeigte Korundkristallite, die im Bereich 10 - 150 nm liegen (REM-Aufnahmen).To a 50% aqueous solution of aluminum chlorohydrate was added so much magnesium chloride that, after calcination, the ratio of alumina to magnesia was 99.5: 0.5% by weight. In addition, the solution 2% crystallization nuclei were added (based on the oxide content) in the form of a suspension of Feinstkorund. After the solution was homogenized by stirring, an aqueous solution of polyvinylpyrrolidone was added. After concentration by evaporation of water in vacuo, the dope was spun in a dry spinning process through a multi-hole die. The Grünfasem obtained were slowly heated up to 1100 0 C. The forming corundum fiber showed corundum crystallites which are in the range 10-150 nm (SEM images).
Eine Röntgenstrukturanalyse zeigte, dass überwiegend α-Aluminiumoxid vorliegt. An X-ray structure analysis showed that predominantly α-alumina is present.

Claims

Patentansprüche: claims:
1. Polykristalline Korundfasern bestehend im Wesentlichen aus Korund und einem Oxid von Elementen der I. oder II. Hauptgruppe des Periodensystems, wobei die Kristallite dieser Korundfasern folgende Korngrößenverteilung aufweisen: 0 bis 0,15 Mikrometer (34 %), 0,15 bis 0,29 Mikrometer (55 %) und 0,29 bis 0,43 Mikrometer (11 %).1. Polycrystalline corundum fibers consisting essentially of corundum and an oxide of elements of the I. or II. Main group of the Periodic Table, wherein the crystallites of these corundum fibers have the following particle size distribution: 0 to 0.15 microns (34%), 0.15 to 0, 29 microns (55%) and 0.29 to 0.43 microns (11%).
2. Polykristalline Korundfasern nach Anspruch 1 , wobei die Kristallite dieser Korundfasern folgende Korngrößenverteilung aufweisen: 0 bis 0,06 Mikrometer2. polycrystalline corundum fibers according to claim 1, wherein the crystallites of these corundum fibers have the following particle size distribution: 0 to 0.06 microns
(34 %); 0,06 bis 0,122 Mikrometer (55 %) und 0,122 bis 0,3 Mikrometer (11 %).(34%); 0.06 to 0.122 microns (55%) and 0.122 to 0.3 microns (11%).
3. Polykristalline Korundfasern nach Anspruch 1 , dadurch gekennzeichnet, dass die Korundfasern 0,01 bis 20 Gew.-% eines Oxids der I. oder II. Hauptgruppe des Periodensystems enthalten.3. polycrystalline corundum fibers according to claim 1, characterized in that the corundum fibers contain 0.01 to 20 wt .-% of an oxide of the I. or II. Main group of the Periodic Table.
4. Verfahren zur Herstellung der polykristallinen Korundfasern nach Anspruch 1 , dadurch gekennzeichnet, dass man eine wässrige Lösung von Aluminiumchlorohydrat mit Keimen und einem Oxidbildner von Elementen der I. und Il Hauptgruppe des Periodensystems versetzt, ein wasserlösliches Polymer zugibt, daraus Fasern spinnt und diese Fasern bei Temperaturen von über 11000C kalziniert.4. A process for producing the polycrystalline corundum fibers according to claim 1, characterized in that one adds an aqueous solution of aluminum chlorohydrate with germs and an oxide former of elements of the I. and II main group of the periodic table, a water-soluble polymer admits, spinning fibers and these fibers calcined at temperatures above 1100 0 C calcined.
5. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass man Chloride von Elementen der I. oder II. Hauptgruppe des Periodensystems als Oxidbildner zugibt.5. The method according to claim 3, characterized in that one adds chlorides of elements of the I. or II. Main group of the Periodic Table as an oxide former.
6. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass man feinstdispersen Korund, Diaspor oder Hämatit als Keime zugibt.6. The method according to claim 3, characterized in that one admits microdispersed corundum, diaspore or hematite as germs.
7. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass man 0,1 bis 10 Gew.-% Keime, bezogen auf die fertige Korundfaser, zugibt. 7. The method according to claim 3, characterized in that 0.1 to 10 wt .-% of germs, based on the finished corundum fiber, admits.
EP07802225A 2006-09-28 2007-09-08 Polycrystalline corundum fibers and method for the production thereof Withdrawn EP2076476A2 (en)

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