EP0443431A2 - Hollow carbon fibres - Google Patents

Hollow carbon fibres Download PDF

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Publication number
EP0443431A2
EP0443431A2 EP19910102053 EP91102053A EP0443431A2 EP 0443431 A2 EP0443431 A2 EP 0443431A2 EP 19910102053 EP19910102053 EP 19910102053 EP 91102053 A EP91102053 A EP 91102053A EP 0443431 A2 EP0443431 A2 EP 0443431A2
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EP
European Patent Office
Prior art keywords
carbon fibers
ring
fibers according
weight
fibers
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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Withdrawn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
EP19910102053
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German (de)
French (fr)
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EP0443431A3 (en
Inventor
Erich Prof.Dr. Fitzer
Wolfgang Metzler
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BASF SE
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BASF SE
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Publication date
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Publication of EP0443431A2 publication Critical patent/EP0443431A2/en
Publication of EP0443431A3 publication Critical patent/EP0443431A3/en
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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
    • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/253—Formation of filaments, threads, or the like with a non-circular cross section; Spinnerette packs therefor

Definitions

  • the invention relates to hollow carbon fibers based on polyacrylonitrile precursor fibers and their use for the production of high-performance composite materials.
  • Hollow carbon fibers based on pitch fibers and polyacrylonitrile fibers are known.
  • the cross-sectional area of the fibers is generally in the form of a uniform, closed ring.
  • High-performance composite materials that have been produced with such hollow fibers have the advantage of better fiber / matrix adhesion and higher compressive strength, based on the fiber weight, compared to those based on compact fibers.
  • it has been shown that the damage tolerance of such composite materials still needs improvement for some applications.
  • the invention was therefore based on the object of providing hollow carbon fibers which give high-performance composite materials with improved damage tolerance.
  • EP-A 232 051 describes carbon fibers with a cross-sectional area in the form of a ring that is not completely closed, the carbon fibers being produced from pitch fibers.
  • the explanations in this publication give the impression that carbon fibers shaped in this way cannot be produced from polyacrylonitrile fibers.
  • the hollow carbon fibers according to EP-A 232 051 have a diameter of more than 30 ⁇ m. Such fibers are not suitable for the production of high-performance composite materials because they do not have a sufficiently reinforcing effect in the composite.
  • EP-A 232 051 are correct insofar as it is not possible to produce carbon fibers with a cross-sectional area in the form of a not completely closed ring from the usual solution-spun polyacrylonitrile fibers using the processes described therein.
  • the preferred process for producing the hollow carbon fibers according to the invention is therefore based on melt-spun polyacrylonitrile precursor fibers.
  • Such fibers are e.g. in the as yet unpublished European patent application 89 11 5373.6 and in the publications cited therein.
  • the underlying polyacrylonitrile preferably consists of at least 85% by weight of acrylonitrile units; it can contain up to 15% by weight of units of conventional comonomers, e.g. Contain methyl acrylate, styrene, methyl methacrylate or itaconic acid.
  • this acrylonitrile polymer 100 parts by weight of this acrylonitrile polymer are mixed with 10-30 parts by weight of water, 5-30 parts by weight of acetonitrile or nitromethane, and optionally other organic liquids, e.g. 1-10 parts by weight of a C1-C4 alkanol mixed and melted.
  • the melt is pressed out through a nozzle head which has C-shaped nozzle openings.
  • a spatial extension is expediently provided at one end of the C-shaped nozzle opening (see FIG. 1) and serves as a reservoir for the polyacrylonitrile melt during the subsequent stretching.
  • the nozzles can have a diameter between 50 and 200 microns.
  • the hollow carbon fibers obtained preferably have an outer diameter of 5 to 20 ⁇ m and a wall thickness of 0.5 to 5 ⁇ m.
  • the distance between the ends of the non-closed ring depends on the size of the reservoir described above and on the stretching conditions.
  • the ring can either be completely open (FIG. 2), the distance between the ring ends being a maximum of 2 ⁇ m, preferably 0.1-1 ⁇ m, or the ring ends, which are rounded, can touch, so that the point of contact has a reduced wall thickness has (Figure 3).
  • polyacrylonitrile fibers are oxidized in a conventional manner at 200-300 ° C and carbonized at 1000-2000 ° C. It has been shown that these processes run much faster if the cross section of the stretched polyacrylonitrile fiber is in the form of an open ring. The fiber does not change its shape significantly during oxidation and carbonization, i.e. the shape of the cross-sectional area is retained.
  • the carbon hollow fibers according to the invention are outstandingly suitable for the production of specifically light, high-strength and rigid composite materials.
  • they are used in the form of rovings using customary methods thermosetting plastics, such as epoxy resins, bismaleimide resins or cyanate resins, or impregnated with thermoplastic plastics, such as polyether sulfones, polyether ketones or polyimides.
  • thermosetting plastics such as epoxy resins, bismaleimide resins or cyanate resins
  • thermoplastic plastics such as polyether sulfones, polyether ketones or polyimides.
  • the composite materials are characterized by particularly high resistance to buckling and buckling and have a higher damage tolerance than comparable composite materials based on carbon hollow fibers with a cross-sectional area in the form of a closed ring, that is to say the composite material can absorb higher loads without causing a load Damage comes. In terms of numbers, this is expressed in an increased fracture energy G 1c .

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Fibers (AREA)
  • Artificial Filaments (AREA)

Abstract

Hollow carbon fibres are described which have a cross-sectional area in the shape of a ring which is not completely closed. They are produced by spinning a polyacrylonitrile melt through a spinner head having C-shaped spinneret orifices, drawing, oxidising and carbonising the fibres. The hollow carbon fibres are suitable for the production of high performance composite materials. <IMAGE>

Description

Die Erfindung betrifft Kohlenstoff-Hohlfasern auf Basis von Polyacrylnitril-Precursorfasern, sowie ihre Verwendung zur Herstellung von Hochleistungsverbundwerkstoffen.The invention relates to hollow carbon fibers based on polyacrylonitrile precursor fibers and their use for the production of high-performance composite materials.

Kohlenstoff-Hohlfasern auf der Basis von Pechfasern und von Polyacrylnitrilfasern sind bekannt. Die Querschnittsfläche der Fasern hat im allgemeinen die Form eines gleichmäßigen, geschlossenen Rings. Hochleistungsverbundwerkstoffe, die mit derartigen Hohlfasern hergestellt wurden, haben gegenüber solchen auf Basis von kompakten Fasern den Vorteil der besseren Faser/Matrix-Haftung und der höheren Druckfestigkeit, jeweils bezogen auf das Fasergewicht. Es hat sich jedoch gezeigt, daß die Schadenstoleranz solcher Verbundwerkstoffe für manche Anwendungszwecke noch verbesserungsbedürftig ist.Hollow carbon fibers based on pitch fibers and polyacrylonitrile fibers are known. The cross-sectional area of the fibers is generally in the form of a uniform, closed ring. High-performance composite materials that have been produced with such hollow fibers have the advantage of better fiber / matrix adhesion and higher compressive strength, based on the fiber weight, compared to those based on compact fibers. However, it has been shown that the damage tolerance of such composite materials still needs improvement for some applications.

Der Erfindung lag also die Aufgabe zugrunde, Kohlenstoff-Hohlfasern bereitzustellen, die Hochleistungsverbundwerkstoffe mit verbesserter Schadenstoleranz ergeben.The invention was therefore based on the object of providing hollow carbon fibers which give high-performance composite materials with improved damage tolerance.

Es wurde gefunden, daß diese Aufgabe gelöst wird durch Kohlenstoff-Fasern mit einer Querschnittsfläche in Form eines Rings, der nicht ganz geschlossen ist, wobei die Kohlenstoff-Fasern aus schmelzgesponnenen Polyacrylnitril-Fasern hergestellt wurden.It has been found that this object is achieved by carbon fibers with a cross-sectional area in the form of a ring which is not completely closed, the carbon fibers being produced from melt-spun polyacrylonitrile fibers.

Die EP-A 232 051 beschreibt Kohlenstoff-Fasern mit einer Querschnittsfläche in Form eines Rings, der nicht ganz geschlossen ist, wobei die Kohlenstoff-Fasern aus Pechfasern hergestellt wurden. Die Ausführungen dieser Druckschrift erwecken den Eindruck, daß aus Polyacrylnitril-Fasern derartig geformte Kohlenstoff-Fasern nicht hergestellt werden können. Die Kohlenstoff-Hohlfasern nach EP-A 232 051 haben einen Durchmesser von mehr als 30 µm. Solche Fasern sind zur Herstellung von Hochleistungsverbundwerkstoffen nicht geeignet, da sie im Verbund nicht eine ausreichend verstärkende Wirkung aufweisen.EP-A 232 051 describes carbon fibers with a cross-sectional area in the form of a ring that is not completely closed, the carbon fibers being produced from pitch fibers. The explanations in this publication give the impression that carbon fibers shaped in this way cannot be produced from polyacrylonitrile fibers. The hollow carbon fibers according to EP-A 232 051 have a diameter of more than 30 µm. Such fibers are not suitable for the production of high-performance composite materials because they do not have a sufficiently reinforcing effect in the composite.

Die Ausführungen der EP-A 232 051 sind insoweit richtig, als es nicht möglich ist, nach den dort beschriebenen Verfahren aus üblichen, lösungsgesponnenen Polyacrylnitril-Fasern Kohlenstoff-Fasern mit einer Querschnittsfläche in Form eines nicht ganz geschlossenen Rings herzustellen.The statements of EP-A 232 051 are correct insofar as it is not possible to produce carbon fibers with a cross-sectional area in the form of a not completely closed ring from the usual solution-spun polyacrylonitrile fibers using the processes described therein.

Bei dem bevorzugten Verfahren zur Herstellung der erfindungsgemäßen Kohlenstoff-Hohlfasern geht man also von schmelzgesponnenen Polyacrylnitril-Precursorfasern aus. Solche Fasern sind z.B. in der noch nicht veröffentlichten europäischen Patentanmeldung 89 11 5373.6 sowie in den dort zitierten Druckschriften beschrieben. Das zugrundeliegende Polyacrylnitril besteht vorzugsweise zu mindestens 85 Gew.-% aus Acrylnitril-Einheiten, es kann bis zu 15 Gew.-% Einheiten von üblichen Comonomeren, wie z.B. Methylacrylat, Styrol, Methylmethacrylat oder Itaconsäure enthalten. 100 Gew.-Teile dieses Acrylnitril-Polymeren werden mit 10-30 Gew.-Teilen Wasser, 5-30 Gew.-Teilen Acetonitril oder Nitromethan, sowie ggf. weiteren organischen Flüssigkeiten, z.B. 1-10 Gew.-Teilen eines C₁-C₄-Alkanols vermischt und geschmolzen. Die Schmelze wird durch einen Düsenkopf ausgepreßt, der C-förmige Düsenöffnungen aufweist. Zweckmäßigerweise ist an einem Ende der C-förmigen Düsenöffnung eine räumliche Erweiterung vorgesehen (siehe Figur 1), die als Reservoir für Polyacrylnitril-Schmelze beim anschließenden Verstrecken dient. Die Düsen können einen Durchmesser zwischen 50 und 200 µm aufweisen. Die Extrusion durch den Düsenkopf erfolgt bei etwa 140-190°C, anschließend werden Wasser und die organischen Flüssigkeiten verdampft und die gesponnenen Fäden werden mindestens um das Fünffache, vorzugsweise um das Acht- bis Zwanzigfache verstreckt. Einzelheiten dieser Verfahrensschritte sind in der europäischen Patentanmeldung 89 11 5373.6 beschrieben.The preferred process for producing the hollow carbon fibers according to the invention is therefore based on melt-spun polyacrylonitrile precursor fibers. Such fibers are e.g. in the as yet unpublished European patent application 89 11 5373.6 and in the publications cited therein. The underlying polyacrylonitrile preferably consists of at least 85% by weight of acrylonitrile units; it can contain up to 15% by weight of units of conventional comonomers, e.g. Contain methyl acrylate, styrene, methyl methacrylate or itaconic acid. 100 parts by weight of this acrylonitrile polymer are mixed with 10-30 parts by weight of water, 5-30 parts by weight of acetonitrile or nitromethane, and optionally other organic liquids, e.g. 1-10 parts by weight of a C₁-C₄ alkanol mixed and melted. The melt is pressed out through a nozzle head which has C-shaped nozzle openings. A spatial extension is expediently provided at one end of the C-shaped nozzle opening (see FIG. 1) and serves as a reservoir for the polyacrylonitrile melt during the subsequent stretching. The nozzles can have a diameter between 50 and 200 microns. The extrusion through the die head takes place at about 140-190 ° C, then water and the organic liquids are evaporated and the spun threads are drawn at least five times, preferably eight to twenty times. Details of these process steps are described in European patent application 89 11 5373.6.

Die erhaltenen Kohlenstoff-Hohlfasern weisen vorzugsweise einen äußeren Durchmesser von 5 bis 20 µm und eine Wandstärke von 0,5 bis 5 µm auf.The hollow carbon fibers obtained preferably have an outer diameter of 5 to 20 μm and a wall thickness of 0.5 to 5 μm.

Der Abstand zwischen den Enden des nicht geschlossenen Rings hängt von der Größe des oben beschriebenen Reservoirs sowie von den Verstreckungsbedingungen ab. Der Ring kann entweder ganz offen sein (Figur 2), wobei der Abstand zwischen den Ringenden maximal 2 µm, vorzugsweise 0,1-1 µm beträgt, oder die Ringenden, die abgerundet sind, können sich berühren, so daß die Berührungsstelle eine verminderte Wandstärke aufweist (Figur 3). Im Anschluß an den Streckprozeß werden Polyacrylnitril-Fasern auf übliche Weise bei 200-300°C oxidiert und bei 1000-2000°C carbonisiert. Es hat sich gezeigt, daß diese Prozesse wesentlich schneller ablaufen, wenn der Querschnitt der gestreckten Polyacrylnitril-Faser die Form eines offenen Rings aufweist. Während der Oxidation und Carbonisierung verändert die Faser ihre Form nicht wesentlich, d.h., die Form der Querschnittsfläche bleibt erhalten.The distance between the ends of the non-closed ring depends on the size of the reservoir described above and on the stretching conditions. The ring can either be completely open (FIG. 2), the distance between the ring ends being a maximum of 2 μm, preferably 0.1-1 μm, or the ring ends, which are rounded, can touch, so that the point of contact has a reduced wall thickness has (Figure 3). Following the stretching process, polyacrylonitrile fibers are oxidized in a conventional manner at 200-300 ° C and carbonized at 1000-2000 ° C. It has been shown that these processes run much faster if the cross section of the stretched polyacrylonitrile fiber is in the form of an open ring. The fiber does not change its shape significantly during oxidation and carbonization, i.e. the shape of the cross-sectional area is retained.

Die erfindungsgmäßen Kohlenstoff-Hohlfasern sind hervorragend geeignet zur Herstellung von spezifisch leichten, hochfesten und steifen Verbundwerkstoffen. Dazu werden sie in Form von Rovings nach üblichen Methoden mit duromeren Kunststoffen, wie z.B. Epoxidharzen, Bismaleinimidharzen oder Cyanatharzen, oder mit thermoplastischen Kunststoffen, wie z.B. Polyethersulfonen, Polyetherketonen oder Polyimiden imprägniert. Die Verbundwerkstoffe zeichnen sich durch besonders hohe Beul- und Knickfestigkeit aus und weisen eine höhere Schadenstoleranz auf als vergleichbare Verbundwerkstoffe auf Basis von Kohlenstoff-Hohlfasern mit einer Querschnittsfläche in Form eines geschlossenen Rings, d.h., der Verbundwerkstoff kann höhere Lasten aufnehmen, ohne daß es zu einer Schädigung kommt. Zahlenmäßig drückt sich das in einer erhöhten Bruchenergie G1c aus.The carbon hollow fibers according to the invention are outstandingly suitable for the production of specifically light, high-strength and rigid composite materials. For this they are used in the form of rovings using customary methods thermosetting plastics, such as epoxy resins, bismaleimide resins or cyanate resins, or impregnated with thermoplastic plastics, such as polyether sulfones, polyether ketones or polyimides. The composite materials are characterized by particularly high resistance to buckling and buckling and have a higher damage tolerance than comparable composite materials based on carbon hollow fibers with a cross-sectional area in the form of a closed ring, that is to say the composite material can absorb higher loads without causing a load Damage comes. In terms of numbers, this is expressed in an increased fracture energy G 1c .

Claims (7)

Kohlenstoff-Fasern mit einer Querschnittsfläche in Form eines Rings, der nicht ganz geschlossen ist, dadurch gekennzeichnet, daß die Kohlenstoff-Fasern aus schmelzgesponnenen Polyacrylnitril-Fasern hergestellt wurden.Carbon fibers with a cross-sectional area in the form of a ring that is not completely closed, characterized in that the carbon fibers were made from melt-spun polyacrylonitrile fibers. Kohlenstoff-Fasern nach Anspruch 1, dadurch gekennzeichnet, daß sie einen äußeren Durchmesser von 5 bis 20 µm aufweisen.Carbon fibers according to claim 1, characterized in that they have an outer diameter of 5 to 20 µm. Kohlenstoff-Fasern nach Anspruch 1, dadurch gekennzeichnet, daß die Wandstärke des Rings 0,5 bis 5 µm beträgt.Carbon fibers according to claim 1, characterized in that the wall thickness of the ring is 0.5 to 5 µm. Kohlenstoff-Fasern nach Anspruch 1, dadurch gekennzeichnet, daß der Ring offen ist und der Abstand zwischen den Ringenden bis zu 2 µm beträgt.Carbon fibers according to claim 1, characterized in that the ring is open and the distance between the ring ends is up to 2 µm. Kohlenstoff-Fasern nach Anspruch 1, dadurch gekennzeichnet, daß der Ring abgerundete Enden aufweist, welche sich berühren, so daß die Brührungsstelle eine verminderte Wandstärke aufweist.Carbon fibers according to claim 1, characterized in that the ring has rounded ends which touch, so that the contact point has a reduced wall thickness. Verfahren zur Herstellung der Kohlenstoff-Fasern nach Anspruch 1, dadurch gekennzeichnet, daß man eine Schmelze, enthaltend 100 Gew.-Teile eines Acrylnitril-Polymeren, 10-30 Gew.-Teile Wasser und 5-30 Gew.-Teile Acetonitril oder Nitromethan aus einem Spinnkopf mit C-förmigen Düsenöffnungen auspreßt, die Fäden um mindestens das Fünffache verstreckt, und auf übliche Weise stabilisiert und carbonisiert.A process for producing the carbon fibers according to claim 1, characterized in that a melt comprising 100 parts by weight of an acrylonitrile polymer, 10-30 parts by weight of water and 5-30 parts by weight of acetonitrile or nitromethane is selected a spinning head with C-shaped nozzle openings, the threads are stretched at least five times, and stabilized and carbonized in the usual way. Verwendung der Kohlenstoff-Fasern nach Anspruch 1 in Form von Faserbündeln, zusammen mit duroplastischen oder thermoplastischen Kunststoffen, zur Herstellung von spezifisch leichten, hochfesten und steifen Verbundwerkstoffen.Use of the carbon fibers according to claim 1 in the form of fiber bundles, together with thermosetting or thermoplastic plastics, for the production of specifically light, high-strength and rigid composite materials.
EP19910102053 1990-02-22 1991-02-14 Hollow carbon fibres Withdrawn EP0443431A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19904005530 DE4005530A1 (en) 1990-02-22 1990-02-22 CARBON HOLLOW FIBERS
DE4005530 1990-02-22

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EP0443431A2 true EP0443431A2 (en) 1991-08-28
EP0443431A3 EP0443431A3 (en) 1992-02-19

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002000973A1 (en) * 2000-06-29 2002-01-03 R-R & D Centre N.V. Synthetic fibre, nozzle and method for manufacturing the same and thereof
WO2006010401A1 (en) * 2004-07-23 2006-02-02 Wabco Gmbh & Co. Ohg Fibre for an acoustic insulating material, especially for sound dampers in compressed air devices
US8006801B2 (en) 2004-07-24 2011-08-30 Wabco Gmbh Noise damper for a compressed air device
US8215448B2 (en) 2008-06-20 2012-07-10 Wabco Gmbh Sound damper for vehicle compressed air systems

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2945739A (en) * 1955-06-23 1960-07-19 Du Pont Process of melt spinning
US5149517A (en) * 1986-01-21 1992-09-22 Clemson University High strength, melt spun carbon fibers and method for producing same
US4935180A (en) * 1988-08-25 1990-06-19 Basf Aktiengesellschaft Formation of melt-spun acrylic fibers possessing a highly uniform internal structure which are particularly suited for thermal conversion to quality carbon fibers

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002000973A1 (en) * 2000-06-29 2002-01-03 R-R & D Centre N.V. Synthetic fibre, nozzle and method for manufacturing the same and thereof
WO2006010401A1 (en) * 2004-07-23 2006-02-02 Wabco Gmbh & Co. Ohg Fibre for an acoustic insulating material, especially for sound dampers in compressed air devices
CN1989036B (en) * 2004-07-23 2011-06-22 威伯科有限公司 Thermoplastic fibers for sound insulation
US8006801B2 (en) 2004-07-24 2011-08-30 Wabco Gmbh Noise damper for a compressed air device
US8215448B2 (en) 2008-06-20 2012-07-10 Wabco Gmbh Sound damper for vehicle compressed air systems

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Publication number Publication date
DE4005530A1 (en) 1991-08-29
EP0443431A3 (en) 1992-02-19

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