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EP0172955B1 - Méthode pour la production d'un brai précurseur pour une fibre de carbone - Google Patents

Méthode pour la production d'un brai précurseur pour une fibre de carbone Download PDF

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Publication number
EP0172955B1
EP0172955B1 EP19840305857 EP84305857A EP0172955B1 EP 0172955 B1 EP0172955 B1 EP 0172955B1 EP 19840305857 EP19840305857 EP 19840305857 EP 84305857 A EP84305857 A EP 84305857A EP 0172955 B1 EP0172955 B1 EP 0172955B1
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Prior art keywords
pitch
mesophase
solvent
stage
temperature
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EP19840305857
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German (de)
English (en)
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EP0172955A1 (fr
Inventor
Kozo C/O Research Laboratories Yudate
Ken C/O Research Laboratories Nakasawa
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JFE Steel Corp
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Kawasaki Steel Corp
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Priority to DE8484305857T priority Critical patent/DE3476685D1/de
Priority to EP19840305857 priority patent/EP0172955B1/fr
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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
    • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues
    • D01F9/155—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues from petroleum pitch
    • 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
    • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues
    • D01F9/15—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues from coal pitch

Definitions

  • the present invention relates to a method for producing a precursor pitch for carbon fiber preparation and is concerned with a method wherein coal tar soft or middle pitch is subjected to heat-treatment to form mesophase pitch.
  • the production of carbon fibers is generally classified into methods using synthetic fibers such as polyacrylonitrile, etc. as the raw material and methods using a petroleum pitch or a coal tar pitch as the raw material.
  • the former method has the drawbacks that the raw material fiber is expensive and the carbonization yield of the raw material fiber is low.
  • pitch having a good spinnability has poor infusibility
  • pitch having a good infusibility has poor spinnability.
  • Presently commercially available carbon fibers are almost always formed using petroleum pitch as the raw material. But, when petroleum pitch is used as the raw material, it is essential to effect the removal of insoluble solid components to adjust the raw material pitch and a variety of specific physical chemical treatments such as hydrogenation, heat treatment and the like have to be carried out and these steps involve much labour and time.
  • coal tar pitch When coal tar pitch is used as the raw material, it is necessary to separate and remove microparticles of free carbon having a diameter of less than 1 11m contained in the pitch as an insuluble solid component and in order to improve the spinnability and infusibility, specific adjustments of the pitch, such as by using a plurality of solvents, hydrogenation, heat treatment and the like, are carried out.
  • Carbon fibers obtained by melt-spinning precursor pitch having such properties and subjecting the spun fiber to infusibilizing and carbonizing treatments have excellent graphitization and orientation and have the desired strength and Young's modulus properties.
  • the inventors have diligently studied to obtain a precursor pitch having the above described properties and have found a method for producing precursor pitch for carbon fiber which satisfactorily satisfies concurrently the above described requirements for precursor pitch for carbon fibers. In this method free carbon in the coal tar pitch can be easily removed and specific treatments such as hydrogenation and the like are not needed.
  • EP-A-008984 describes a process for the production of a pitch for use in the preparation of carbon fibers.
  • a suitable starting material is subjected to a first heat treatment to remove volatile matter and is then allowed to settle to form an upper layer and a lower layer.
  • the lower layer is a pitch which is largely an optically anisotropic phase.
  • the upper layer is again subjected to heat treatment to obtain an optically anistropic pitch which can be melt spun to form a carbon fibre.
  • Suitable starting materials are carbonaceous heavy oils, tars and pitches obtained from the petroleum or coal industry.
  • the coal tar pitch is heat-treated in the first stage to form mesophase. Then a solvent insoluble portion including the mesophase is separated and removed by extraction using an aromatic solvent, whereby free carbon contained in the pitch can be easily removed and pitch containing no free carbon is obtained.
  • this method it is possible to easily produce a precursor pitch for carbon fibers which has a very high thermal stability, excellent spinnability and infusibility, a high carbonization yield and excellent graphitization and orientation without needing specific treatments such as hydrogenation and the like as hitherto.
  • the mesophase is formed from a temperature of about 350°C.
  • the formed amount increases and the mesophase grows to form large globular bodies.
  • the mesophase assembles and at about 500°C, the mesophase is wholly formed into an anisotropic body.
  • the fine particles of free carbon having a diameter of less than 1 11m and inorganic substances which become ash, which ar originally present in the coal tar pitch, stick around the mesophase globular bodies and hence are easily removed with the mesophase.
  • high molecular weight components having a high thermal reactivity which are present in the pitch and components having a small content of functional groups are preferentially polycondensed to remove these substances and form the mesophase, so that the resulting pitch is low in the amount of heteroatoms and is homogeneous and has excellent thermal stability.
  • the pitch is heat-treated at a temperature from about 350°C at which the mesophase is formed to about 500°C at which the whole coke formation proceeds, in the first stage.
  • the temperature of the heat treatment is too high, the mesophase is formed in a large amount and as a result, the yield of hard pitch lowers.
  • the temperature of the heat treatment is too low, the components having a high thermal reactivity are apt to remain in the hard pitch.
  • the temperature of the heat treatment is optimum at about 350°C-500°C as mentioned above and it is preferable to form 10-30% by weight of the mesophase within this temperature range.
  • the solvent insoluble portion including the mesophase is easily separated through spontaneous precipitation or filtration.
  • the separation of the mesophase by filtration does not cause clogging of the mesh of the filter, as tends to occur during the filtration of free carbon, and is very easy.
  • the solvent is removed by distillation to obtain pitch having no free carbon.
  • This pitch is heat-treated in the second stage to form mesophase, whereby the desired precursor pitch suitable for carbon fiber production is obtained.
  • This precursor has a softening point higher than 300°C and consists of 80-95% by weight of a benzene insoluble portion, 20-60% by weight of a quinoline insoluble portion and less than 800 ppm of ash.
  • the precursor pitch for carbon fiber obtained according to the present invention is so-called "bulk mesophase pitch" containing 20-60% by weight of a quinoline insoluble portion.
  • this pitch is observed with a polarizing microscope, it can be seen that an isotropic pitch component is dispersed in the whole optical anistropic texture.
  • the ratio of the optical anistropic texture observed under the polarizing microscope is 80-95%. It has been found that such a pitch has excellent spinnability and infusibility and can provide carbon fibers having high strength and Young's modulus.
  • the carbon fibers formed from the mesophase pitch have various properties which have never been seen in carbon fibers made of isotropic precursor pitch containing no mesophase.
  • carbon fibers made from the mesophase pitch according to the present invention show high Young's modulus even at a treating temperature of 1,000°C and both the tensile strength and the Young's modulus are noticeably more improved by a graphitizing treatment.
  • the most suitable precursor pitch for carbon fiber is a mesophase pitch having 80-95% by weight of benzene insoluble portion and 20-60% by weight of quinoline insoluble portion.
  • the benzene insoluble portion is less than 80% by weight and the quinoline insoluble portion is less than 20% by weight, the mesophase portion and the isotropic pitch portion in the mesophase pitch separate and such a pitch cannot be spun.
  • the benzene insoluble portion is more than 95% by weight and the quinoline insoluble portion is more than 60% by weight, the melt viscosity of the mesophase pitch is quite high and spinning is not feasible.
  • mesophase pitch having 80-95% by weight of benzene insoluble portion and 20-60% by weight of quinoline insoluble portion
  • the mesophase portion and the isotropic pitch portion are present in a uniform system, the melt viscosity at the spinning temperature is not high, and the spinnability is excellent.
  • a mesophase pitch having a softening point of higher than 300°C, 80-95% by weight of benzene insoluble portion and 20-60% by weight of quinoline insoluble portion is suitable as a precursor pitch for carbon fiber. It has a uniform system, excellent thermal stability, spinnability and infusibility, and has a high carbonization yield and few impurities, such as free carbon, heteroatoms, and inorganic substances. Carbon fibers formed therefrom have high strength and Young's modulus.
  • the method for preparing the precursor for carbon fibers by heat-treating, in the second stage, the pitch containing no free carbon which has been obtained by the heat treatment in the first stage is a simple one which comprises heating the pitch under atmospheric pressure or a reduced pressure in an inert gas atmosphere to form the mesophase pitch as mentioned above.
  • the precursor pitch obtained has excellent thermal stability and is suitable for spinning, because the high molecular weight components having high thermal reactivity and heteroatoms present in the raw material pitch are removed by the heat treatment at the first stage.
  • the raw material for the pitch is coal tar pitch rich in aromatic materials and the heat treatment is applied at the first stage, the resulting pitch containing no free carbon is composed of relatively large aromatic molecules. Therefore, in the mesophase pitch obtained in the second stage, the mesophase component and the isotropic component are present in a uniform system.
  • the heat treatment of the pitch containing no free carbon in the second stage is intended to produce bulk mesophase pitch having 20-60% by weight of quinoline insoluble portion and 80-95% by weight of benzene insoluble portion and it has been found, from a large number of experiments, that the heat treatment temperature (T°C) and the time (8 min) for which this temperature should be held preferably have the following relationship:-
  • Ash which is an impurity in the precursor pitch causes the formation of voids in carbon fibers or deteriorates the strength, so that the amount of the remaining free carbon is preferred to be as small as possible.
  • the precursor pitch according to the present invention is very clean, as the ash content is less than 300 ppm, and is a very excellent carbon fiber precursor.
  • This precursor pitch is melt-spun at a temperature higher by 20 ⁇ 40°C than the softening point by means of the conventional melt-spinnning techniques.
  • the spun fibers may be subjected to an infusing treatment by air oxidation without effecting pretreatment or by using an oxidizing agent, such as ozone oxidation or sulfuric acid.
  • an oxidizing agent such as ozone oxidation or sulfuric acid.
  • the spun fibers are fired and carbonized by raising the temperature up to about 1,000°C in an inert gas such as Ar, N 2 to obtain carbon fibers.
  • an inert gas such as Ar, N 2
  • Coal tar soft pitch having a softening point in the range 50 to 75°C and containing free carbon was heated at 450°C in an inert gas atmosphere for 60 minutes to form 25% by weight of mesophase and then the thus treated pitch was extracted with tar oil (an aromatic solvent). The high molecular weight components, which were mainly mesophase, were then filtered off. The filtrate was vacuum-distilled to recover the solvent and to obtain pitch having a softening point of 90°C, 12% by weight of benzene insoluble portion, and a trace of quinoline insoluble portion and containing no free carbon.
  • This pitch was heat-treated at 465°C under a vacuum of 20 mmHg in N 2 inert gas atmosphere to obtain mesophase pitch having a softening point of 355°C, and consisting of 91.9% by weight of benzene insoluble portion and 55.2% by weight of quinoline insoluble portion.
  • mesophase pitch having a softening point of 355°C, and consisting of 91.9% by weight of benzene insoluble portion and 55.2% by weight of quinoline insoluble portion.
  • This mesophase pitch was melt-spun at 385°C at a take-up rate of 300-500 m/min and the spun fiber was oxidized in air at 320°C and subsequently carbonized at 1,000°C in an argon atmosphere to obtain a carbon fiber.
  • This fiber had a fineness of 12-14 ⁇ m. a tensile strength of 140 kg/mm 2 and Young's modulus of 8.4 t/mm 2 .
  • this fiber was graphitized at 2,600°C in argon atmosphere to obtain a graphite fiber.
  • This fiber had a fineness of 11-13 um, a tensile strength of 240 kg/mm 2 and Young's modulus of 48 t/mm 2 .
  • Coal tar soft pitch containing free carbon was directly extracted with tar oil without effecting a heat treatment.
  • a pitch having a softening point of 90°C and containing a trace of quinoline insoluble portion and still containing free carbon was obtained by filtration.
  • This pitch was heat-treated at 450°C under a vacuum of 20 mmHg in N 2 gas atmosphere for 60 minutes to obtain mesophase pitch having 82.8% by weight of benzene insoluble portion and 43.2% by weight of quinoline insoluble portion. Phase separation between the mesophase portion and the isotropic pitch portion occurred in the molten state and it was impossible to carry out spinning.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Textile Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Working-Up Tar And Pitch (AREA)
  • Inorganic Fibers (AREA)

Claims (3)

1. Procédé pour la production d'un brai approprie pour la préparation de fibres de carbone ledit procedé comprenant les étapes consistant a
(i) chauffer dans un premier stade, un brai obtenu de l'industrie du charbon,
(ii) extraire le brai ayant été ainsi traité à chaud avec un solvant,
(iii) séparer et éliminer la fraction insoluble dans le solvant conjointement avec le carbone libre et (iv) chauffer, dans un second stade, la fraction soluble dans la solvant, caractérisé en ce que
(v) le brai obtenu de l'industrie du charbon est un brai de houille grasse ou moyenne ayant un point de ramolissement deb 50 à 75°C,
(vi) le brai de houille est chauffe, dans le premier stade, a une temperature de 350 à 500°C sous atmosphère de gaz inerte, pour former une mésophase,
(vii) le solvant est un solvant aromatique,
(viii) la fraction insoluble dans le solvant contient la mésophase, et
(ix) la fraction soluble dans le solvant ne contient pas de carbone libre et elle est chauffée, dans le second stade, sous atmosphère de gaz inerte sous la pression atmosphérique ou sous pression réduite, pour former un brai en mésophase en masse, contenant 20-60% en poids de fraction insoluble dans la quinoléne.
2. Procédé selon la revendication 1, dans lequel le traitement thermique de la fraction soluble dans le solvant dans le second stade est effectué dans les conditions suivantes
Figure imgb0008
Figure imgb0009
où T (°C) est la température du traitementtheremique et 8 (min) est la durée pendant laquelle ladite fraction est maintenue à cette température.
EP19840305857 1984-08-28 1984-08-28 Méthode pour la production d'un brai précurseur pour une fibre de carbone Expired EP0172955B1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE8484305857T DE3476685D1 (en) 1984-08-28 1984-08-28 A method for producing a precursor pitch for carbon fiber
EP19840305857 EP0172955B1 (fr) 1984-08-28 1984-08-28 Méthode pour la production d'un brai précurseur pour une fibre de carbone

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19840305857 EP0172955B1 (fr) 1984-08-28 1984-08-28 Méthode pour la production d'un brai précurseur pour une fibre de carbone

Publications (2)

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EP0172955A1 EP0172955A1 (fr) 1986-03-05
EP0172955B1 true EP0172955B1 (fr) 1989-02-08

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EP19840305857 Expired EP0172955B1 (fr) 1984-08-28 1984-08-28 Méthode pour la production d'un brai précurseur pour une fibre de carbone

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EP (1) EP0172955B1 (fr)
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Publication number Priority date Publication date Assignee Title
DE3821866A1 (de) * 1988-06-29 1990-01-18 Ruetgerswerke Ag Verfahren zur herstellung eines anisotropen pechs fuer kohlenstoffasern

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JPS58164687A (ja) * 1982-03-24 1983-09-29 Toa Nenryo Kogyo Kk 光学的異方性ピツチの製造方法

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EP0172955A1 (fr) 1986-03-05
DE3476685D1 (en) 1989-03-16

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