FR2512076A1 - PROCESS FOR THE PREPARATION OF CARBON FIBERS WITH HIGH MECHANICAL RESISTANCE AND HIGH MODULE FROM BRAI - Google Patents

Abstract

PROCESS FOR PREPARING HIGH QUALITY CARBON FIBERS. A MESOPHASE BRAI CONTAINING 1 TO 40 BY WEIGHT OF A MESOPHASE IS MELTED AND THREADED, THE FIBER OBTAINED IS RENDERED INFUSIBLE IN THE AIR AND CARBONIZED IN AN INERT GAS ATMOSPHERE. MESOPHASE BRAI CAN ITSELF BE OBTAINED BY HYDROGENATION AND THERMAL TREATMENT OF ORDINARY BRAI WITH AN AROMATICITY INDEX OF NOT LESS THAN 0.6. THE CARBON FIBERS OBTAINED HAVE A RESISTANCE OF 200 TO 350KGMM AND A MODULE OF ELASTICITY OF 10 TO 40TONNESMM.

Description

12076

  Process for the preparation of high carbon fibers

  mechanical resistance and high modulus.

  The present invention relates to a method of

  preparation of high strength carbon fiber

  high modulus from mesophase pitches

  of pitch with a high degree of aromaticity.

  According to their mechanical strength, the carbon fibers can be classified into two groups: general purpose carbon fibers ("general performance", "GP") and high-quality carbon fibers ("high performance").

"HP").

  GP carbon fibers have a resistance of 70

  at 140 kg / mm 2 and a module of 3 to 5 tonnes / mm and are

  commonly adorned with optically isotropic pitches.

  Among the main applications of carbon fibers

  GP, abrasive materials,

  heat, antistatic materials,

  slippery, filters, packings and applica-

  Similar applications These applications exploit certain

  properties of carbon in the form of fibers and, in most

  of the cases, do not require high carbon fiber

resistance and high module.

  On the other hand, HP carbon fibers have a high strength, from 200 to 350 kg / mm 2 and a high modulus,

  from 10 to 40 tonnes / mm 2 and are commonly prepared for

  shot of a polyacrylonitrile The main applications

  HP carbon fibers are contained in

  sites obtained by combining these fibers with residues

  These composite materials obtained from HP carbon fibers, compared

  other industrial materials, have both an excellent

  slow mechanical resistance and an excellent module by

  are used as special materials for the manufacture of rocket and aircraft parts and in sports articles such as golf clubs, tennis rackets and fishing rods. It is expected that in the future, the demand for HP carbon fibers for automotive, building and similar building materials will increase in a

marked measure.

  However, because the HP carbon fiber

  produced from polyacrylonitrile are very costly

  the composite materials containing these

  are rarely used in indoor applications.

  ordinary industries, despite the high mechanical resistance

  It would therefore be highly desirable to find a process for preparing carbon fibers.

HP at a low price.

  A number of processes for the preparation of

  low-priced HP carbon fiber from metal pitches

  sophase obtained by heat treatment of inexpensive pitches, have already been proposed in Japanese patent applications published under No. 8634/74, 7533/78, 1810/79 and JA patent applications made available to the public No. 55 According to these processes, HP carbon fibers can be prepared by treating a pitch at a relatively low temperature, close to 400.degree. C., for a duration ranging from several hours to several tens of hours, thus forming a mesophase pitch containing from 40 to 100% by weight of a mesophase, which is melted and spun; a crude fiber is obtained in which the mesophase is oriented along the axis of the fiber, the raw fiber is rendered infusible in the air, the infusible fiber is carbonized and, if desired,

  subject the charred fiber to graphitization.

  However, the preparation of a pitch in mesophase

  in the processes described above includes accelerating

  polycondensation of the pitch by heat treatment for several hours to several tens of hours, so that the degree of condensation of the mesophase formed in the early stages of treatment

  the heat is stronger than that of the mesophase pro-

  in the later stages of treatment.

  degree of condensation of the mesophase has a distribution

  It is a very broad solution, which leads to a decrease in the ability of the mesophase pitch to uniform melting. In the case of interest, there is also a decrease in the mesophase pitchability. In addition, when the pitch is treated

  at a temperature of 430 ° C or above, polycondensa-

  the mesophase is often accelerated to the point where the

  high degree of condensation that is achieved renders

  the fusion of mesophase pitch can then be

  necessary to eliminate such an insoluble and intractable mesophase

  fuse of pitch in mesophase before spinning.

  It can therefore be seen that the process of the technical

  than earlier to prepare a mesophase pitch is far from being the best method of preparing a

  raw material for HP carbon fiber.

  The object of the present invention is to provide a

  perfected to prepare HP carbon fibers.

  The invention also aims to provide a

  improved process for the preparation of HP carbon fibers in which mesophase pitch is used, the mesophase content of which is lower than that of mesophase pitches previously used and which, therefore, has a higher

excellent spinning ability.

  Still another object of the invention is to provide an improved process for preparing HP carbon fibers, comprising pre-preparing a mesophase pitch such as

described above.

  The method according to the invention for preparing

  HP carbon particles is characterized in that it comprises the following operating stages: one melts and spins a

  mesophase pitch containing from 1 to 40% by weight of a

  The spun fiber is rendered infusible in the air, the infusible fiber is carbonized in an inert gas atmosphere and, if appropriate, the charred fiber is subjected to graphitization. The term "mesophase content" as used in this application refers to the content of quinoline-insoluble material as determined by the procedure of the industry standard.

Japanese JIS K-2425.

  Mesophase pitch used as raw material

  In the process according to the invention, the mesophase content is 1 to 40% by weight, unlike the mesophase pitches used in the prior art processes.

  Thus, the pitch in mesophase according to the invention possesses

  a significantly improved ability to spin.

  Other features and advantages of the invention

  more clearly from the detailed description of the

  FIG. 1 is an optical microphotograph of a mesophase pitch used in the process according to the invention; Fig. 2 is an optical microphotograph of a crude fiber obtained by melt spinning the mesophase pitch of Fig. 1; and Figure 3 is an electron photomicrograph

  carbon fiber prepared by the process according to the invention.

  vention. In a preferred embodiment of the invention, high-aromatic pitches, for example depolymerized carbon, coal tar, coal tar pitch, are used as the raw material for the preparation of mesophase pitches. ethylene distillate oil pitch, etc. The term "depolymerized coal" as used in the present application applies to any pitch-like material obtained by depolymerizing the coal in a hydrocarbon solvent under hydrogen pressure and then in

  eliminating a possibly undissolved residue and the sol-

  of the product obtained, such a highly aromatic pitch is

  hydrogenation in a hydrocarbon solvent

  presence of a hydrogenation catalyst.

  In the practice of the invention, it is not sufficient merely to subject the hydrogenation pitch: it is important to improve the degree of hydrogenation of the pitch and, at the same time, to suppress its polycondensation.

  the hydrogen content of the hydrogenated pitch must be higher than

  less than 10%, and preferably 15 to 50%,

  the starting pitch, and at least 90% of the hydrogenated pitch should have a molecular weight in the range of 400 to 600. The "molecular weight" referred to herein is determined by chromatography with a pernhalation gel.

  appropriate hydrogenation conditions and catalytic

  It is essential to meet these requirements. From the reaction mixture obtained in the hydrogenation described above, the materials are removed.

  insoluble solids from the starting pitch, and the sol-

  It is also possible to eliminate

  insoluble solids from the starting pitch before the

  by using appropriate techniques such as melt filtration, centrifugation,

  solvent extraction and similar techniques.

  The hydrogenated pitch is then treated at elevated temperature and

  under vacuum for a short time This treatment with

  is preferably carried out under the following conditions:

  the temperature is not less than 480 ° C; the du-

  during which the pitch is maintained at this temperature.

  ture does not exceed 30 minutes, and the absolute pressure does not exceed

  it is not 40 mm Hg We obtain then a pitch in mesophase

  containing from 1 to 40% by weight of a mesophase.

  As noted above, the treatment

  of the hydrogenated pitch is carried out at a high temperature

  evacuated for a short time so that the formation of a mesophase takes place intensively

2512076.

  for a short time, leading to a mesophase at a

  degree of condensation very uniform In addition,

  isotropic from the optical point of view of the hydrogenated pitch,

  which can hardly be converted into a meso-

  phase and can not form a homogeneous melt

  with the mesophase, are removed as an oil

  Thus, the mesophase pitch obtained in these conditions can be uniformly melted and

  in addition to excellent spinning ability On the other hand, se-

  the invention, the mesophase content of the pitch in mesopha-

  can be lowered to a level much lower than

  those, ranging from 40 to 100% by weight, of mesophase pitches

  are used in the processes of the prior art.

  This also contributes to a great extent to the improvement

  ration of spinnability in mesophase pitch.

  The mesophase pitch prepared by the method described above is melted and spun; the spun fiber is then

  made infusible in the air The infusible fiber is carbon

  inert gas atmosphere and, if desired,

  Subsequent graphitisation This gives an HP carbon fiber whose strength is not less than 200 kg / mm 2 and the modulus is not less than 10 tonnes / mm 2

  Thus, the mesophase pitches serving as

  of high-strength, high-modulus HP carbon fibers can be prepared from quite common and inexpensive pitches without the use of any solvent, reagent or

particular techniques.

  In the process according to the invention, a high aromatic degree pitch is used as raw material. Among the suitable pitches are depolymerized carbon,

  coal tar, coal tar pitch (derived from

  coal) as well as the ethylene (and therefore oil-derived) petroleum pitches. It is also possible to prepare high aromatic degree pitches by treating a heavy oil rich in aliphatic hydrocarbons with a high degree of aromaticity. temperature of 350 to 450 ° C

  for a period of 15 minutes to 10 hours, then to

  The pitches which can advantageously be used as raw material in the process according to the invention have an aromaticity index which is not less than 0.6 L "aromaticity index" of which it is question is a parameter that has been proposed by Takeya and collators, (Journal of the Japan Fuel Society, 46, 927 (1967)) and which is defined by the following equation: aromaticity index = C / H Ha / x Ho / y C / H where C is the total number of carbon atoms, H is the total number of hydrogen atoms, Ha is the number of hydrogen atoms placed in positions a and Ho is

  the number of hydrogen atoms placed in positions X or

  above For the purposes of the invention, it is assumed that x and y

are equal to 2.

  Pitches with a lower aromaticity index

  at 0.6 are not suitable because they give a low return

  mesophase pitch, which is less capable of uniform melting, with a final product, ie a

  HP carbon fiber, the mechanical strength of which is

  drie, not to mention other disadvantages.

  There is no particular limitation to the nature of the hydrocarbon solvent used in the process according to

  the invention and any one of

  practically dissolve the described raw material

  above Solvents with a high degree of aromaticity

  for this purpose, for example, heavy oils

  from coal, for example an absorbing oil

  bante, creosote oil, medium tar oil,

  anthracene oil, etc., as well as slight fractions of

  oil-based heavy oils such as ethylene pellet oil, FCC cracking oil, etc. Aliphatic hydrocarbon-rich solvents are unsuitable because they are not capable of sufficiently dissolving the raw material according to the invention and do not allow

  to perform a regular hydrogenation.

  The amount of hydrocarbon solvent used is preferably selected such that the weight ratio of starting pitch to hydrocarbon solvent is 1: 2 or above and is preferably in the range of 1: 3 to 1:10 If the weight ratio between the starting pitch and the hydrocarbon solvent is lower

  at 1: 2, it is difficult to separate the catalyst and the

  insoluble solids of the resulting reaction mixture

to hydrogenation.

  The preferred conditions for the hydrogenation in the process according to the invention are a temperature in the range of 400 to 5000 C, and preferably 430 to

  480 ° C, a manometric pressure of hydrogen in the

  range from 50 to 300 bar (50 to 300 kg / cm 2 G) and preferably

  from 70 to 200 bar (70 to 200 kg / cm 2 G), and a duration of

  at this temperature which does not exceed 240 mn and

  preferably within the range of 5 to 60 minutes.

  spinning study of the mesophase pitch obtained under these conditions.

  tions is improved when the hydrogenation is carried out

  at a higher temperature for a shorter time.

  If the hydrogenation temperature is below 400 ° C. and the hydrogen pressure is less than 50 bar / cm 2 G, the starting pitch is not entirely

  hydrogenated and it becomes difficult to obtain a hydro-

  -generate possessing the properties desired for use

  In the process according to the invention, on the other hand, if the temperature

  hydrogenation temperature is greater than 5000 C and the duration

  greater than 240 minutes, the starting pitch undergoes a polycon-

  excessive densification and it becomes difficult to get a

  hydrogenated pitch having the properties desired for

  In addition, the mesophase pitch prepared from this hydrogenated pitch is difficult to melt uniformly. Moreover, if the hydrogen pressure is greater than 300 bar (300 kg / cm 2 G). the hydrogenated pitch that is obtained is not much higher,

  for the preparation of a mesophase pitch, with

  drogenes obtained at a hydrogen pressure

  not exceeding 300 bar (300 kg / cm 2 G).

  The hydrogen content of the hydrogenated pitch obtained by hydrogenation under the conditions described above is greater by at least 10%, and preferably from 15 to 50%, than that of the starting pitch, and at least 90% of the pitch. hydrogen

  have a molecular weight in the range of 400 to 600.

  If the starting pitch is hydrogenated under conditions

  other than those described above and-if the hydrogenated pitch does not meet all the requirements set out above, the mesophase pitch prepared from pitch

  hydrogenated is difficult to uniformly melt.

  not only a decrease in the spinning ability of the

  pitch in mesophase but also a decrease in the

  mechanical resistance of carbon fiber obtained in

final duit.

  Naturally, if the starting pitch is not hydro-

  generated but treated directly with heat in the process according to the invention, a pitch in mesophase is obtained which does not

  can not be uniformly melted and is totally

  provided with the ability to spin.

  nation is essential for the preparation of

  sophase suitable for use in the process according to the invention.

  The hydrogenation catalyst used in the

  assigned according to the invention preferably contains at least one component selected from the group consisting of iron, cobalt,

  molybdenum, copper, tungsten, nickel,

  tine and rhodium, and the oxides and sulphides of these metals.

  The hydrogenation catalyst is preferably added to the starting pitch in amounts of 1 to 20% by weight and more preferably 2 to 10% by weight. If the amount of catalyst added is less than 1% by weight, the duration of hydrogenation is too long and if it is superior

  at 20% by weight, no additional benefit is obtained.

  When the hydrogenation has been carried out under the conditions

  As described above, the reaction mixture is removed from the hydrogenation catalyst and the solids.

  insoluble material from the starting pitch, for example by

  Spraying or centrifugation The hydrocarbon solvent is then removed, for example by vacuum distillation, and a hydrogenated pitch suitable for use in the reaction is obtained.

  method according to the invention There is no limitation

  the conditions observed for the removal of the hydro-carbonated solvent, and it is not necessary to eliminate all the hydrocarbon solvent used. However, if it is desired to ensure that the hydrogenated pitch has the properties described above. above, it is possible to choose the distillation conditions so that the base temperature is

  in the range of 200 to 300 ° C and the absolute pressure

  read in the range of 5 to 20 mm Hg.

  The hydrogenated pitch obtained under these conditions is then treated at elevated temperature and under vacuum for a short time, to form a mesophase pitch containing from 1 to 40% by weight, and preferably from 5 to 30% by weight, by weight. A mesophase The heat treatment conditions must be chosen so that the mesophase pitch obtained contains from 1 to 40% by weight of a mesophase. This operation is preferably carried out under the following conditions: the temperature is not

  less than 480 ° C and is preferably located in the

  from 500 to 550 OC, the duration of the maintenance at that temperature

  erage does not exceed 30 minutes and is preferably

  interval of 2 to 15 minutes, and the absolute pressure does not exceed

  The mesophase content is less than 1% by weight, it is impossible to obtain from the mesophase pitch by the standard operating procedure. , to an HP carbon fiber, and if it is greater than 40% by weight, the pitch in mesophase has a marked decrease

  Moreover, if the temperature ob-

  When the heat treatment is less than 48 ° C, if the duration of the maintenance at this temperature is greater than min and if the absolute pressure is greater than 40 mmHg, it is impossible to obtain a mesophase pitch suitable for uniform melting and excellent spinning ability. When the mesophase pitch obtained by the heat treatment described above is observed using a reflected polarized light microscope, it is found that at least 60%

  pitch in mesophase are optically anisotropic.

  Thus, in the heat treatment stage involved in the process according to the invention,

  high temperature for a short time a hydrogen pitch

  which has been prepared under special conditions of hydro-

  the duration necessary to bring the hydrogenated pitch to a given temperature is very short,

  order of 1 or 2 minutes, so that the formation of a meso-

  phase takes place intensively during a short

  This prevents the formation of an inactive mesophase

  luble and infusible and we obtain a pitch in mesophase

  uniformly and with excellent

spinning study.

  The mesophase pitch, containing from 1 to 40% by weight of a mesophase, is then melted and spun at a temperature of 320 to 400 ° C. Its spinnability is as good as that of the optically isotropic pitches used for

  the preparation of carbon fiber GP In addition, the di-

  meter of the formed raw fiber is very uniform along the axis of the fiber, indicating good fuse

  pitch in mesophase according to the invention.

  Although less than 40% of mesophase pitch according to

  the invention are optically isotropic, this pitch in meso

  In addition, during spinning, the mesophase is oriented along the axis of the fiber and this orientation is retained in the fiber of the fiber.

carbon or graphite formed.

  The resulting raw fiber is then rendered infusible in air. The operation is preferably carried out under the following conditions: the temperature is in the range of 260 to 3400 C, and preferably 270 to 320 ° C, the duration the maintenance at this temperature does not exceed mn and is preferably in the range of 5 to 30 min, and the heating rate does not exceed 3.30 C / min

  and is preferably in the range of 0.5 to 2.00 C / min.

  If the temperature is below 2600 C, the raw fiber does not become sufficiently infusible. As a result, the fibers melt or sinter together during carbonization.

  subsequent, and one does not obtain an HP carbon fiber.

  If the temperature is higher than 3400 C and the duration of the maintenance at this temperature greater than 60 minutes, the fiber is too oxidized and the carbon fiber obtained has lost

its mechanical resistance.

  The infusible fiber is then carbonized in a

inert gas atmosphere.

  This operation is preferably performed in

  the following conditions: the temperature is not below

  below 800 ° C and is preferably in the mean

  1,000 to 1,500 ° C, the duration of maintenance at that temperature.

  re is not less than 5 minutes and is preferably

  10 to 30 minutes, and the rate of reheating

  fage does not exceed 70 C / min and is preferably

  the range from 2 to 50 C / min If the temperature is below

* re at 8000 C and the duration of temperature maintenance lower than

  At 5 minutes, the fiber is not completely carbonized and a high strength carbon fiber is not obtained. If the heating rate is greater than C / min, the carbon fiber undergoes a partial melting.

  therefore a decrease in its mechanical strength.

  In addition, if one wishes to increase the fiber modulus

  of carbon, it is subjected to graphitization in an atmosphere

  inert gas, preferably at a temperature of

2,000 to 3,000 C.

  Carbon fibers (including graphite fibers)

  made by the process according to the invention have a strength of 200 to 350 kg / mm 2 and a modulus of 40 tonnes / mm Thus, they compare favorably

  HP carbon fibers obtained from a polyacryloid

  nitrile, both in appearance and resistance

  However, the process according to the invention makes it possible to prepare HP carbon fibers from pitches that are themselves inexpensive and easy to supply, with a low cost price, ease of use, and without resorting to any solvents, reagents or techniques

special.

  The examples which follow illustrate the invention without, however, limiting its scope; in these examples, the indications of parts and% are by weight

unless otherwise stated.

Example 1

  A pitch of coal tar (containing 91.43% carbon, 4.68% hydrogen, 0.97% nitrogen, 1.09% of

  sulfur and 1.83% oxygen in the analysis according to the

  Japanese standard JIS M-8813, with an aromaticity index of 0.95) and 5% of an iron oxide

  catalyst and 3 times the weight of the pitch of an oil absorbing

  After thorough mixing, hydrogen is heated to a temperature

  re 4600 C under a hydrogen pressure of 100 bars (100 kg / cm 2 G) while maintaining this temperature

  for 10 minutes. The reaction mixture is removed by filtration.

  silicate and insoluble solids from coal tar pitch.

  filtrate at a bottom temperature of 2500 C under a pressure of

  absolute pressure of 10 mmHg; this gives a hydro-pitch

  gene consisting of 91.97% carbon, 5.61% hydrogen,

  0.88% nitrogen, 0.41% sulfur and 1.13% oxygen, that is,

  that is, its hydrogen content has increased by about 20% compared to that of coal tar pitch used

  as a raw material The distribution is also determined

  molecular weight determination by gel permeation chromatography using quinoline as a solvent; it is found that 92% of the braihydrogen has a molecular weight

in the range of 400 to 600.

  This hydrogenated pitch is immersed in a salt bath at 5100 ° C., immediately exposed to an absolute pressure of

  mm Hg and maintained at this temperature for 10 minutes.

  Mesophase pitch is obtained with a mesophase content

27.6%.

  This mesophase pitch is melted and spun at a time

  3500 C and at a drawing speed of 800 m / min -

  The resulting raw fiber is rendered infusible by heating in air at a temperature of 280.degree.

  heating up to 1.00 C / min and maintaining the same temperature

  For 5 minutes, an infusible fiber is obtained, which is heated in an argon atmosphere at a temperature of 1500 ° C. at a heating rate of 50 ° C./min while maintaining at 1.0000 ° C. for 15 minutes. A carbon fiber is obtained with

  a yield of 88.9% compared to the raw fiber.

  The carbon fiber obtained has an average diameter of 12.8 microns, a mechanical strength of 235 kg / mm 2 and a modulus of 16.2 tons / mm

Example 2

  The hydrogenated pitch obtained in Example 1 is treated with heat as described in this example, but at a temperature of 520 ° C. and with a holding time at this temperature of 5 minutes. A mesophase pitch at a temperature of

mesophase content of 17.5%.

  This mesophase pitch is spun at a temperature of 350 ° C. and a drawing speed of 1000 m / min; a raw fiber is obtained which is then treated as described in

  Example 1 gives a carbon fiber with a yield of

  88.2% of the raw fiber.

  The carbon fiber obtained has an average diameter of 11.2 microns, a resistance of 288 kg / mm and a modulus of 14.9 tons / mm

Example 3

  The hydrogenated pitch obtained in Example 1 is treated

  to heat as described in this example but at a

  at a temperature of 530 ° C. and with a holding time at this temperature of 4 minutes. A mesophase pitch at a temperature of

mesophase content of 11.6%.

  This mesophase pitch is spun at a temperature of 3450 ° C and a drawing speed of 1400 m / min; a crude fiber is obtained which is treated as described in Example 1 for conversion into carbon fiber. The yield of carbon fiber is 89.4% relative to the raw fiber. The carbon fiber obtained has an average diameter of 1 micron, a resistance of 310 kg / mm 2 and a modulus of 17.9 tonnes / mm. A comparison of the results obtained in Examples 1 to 3 shows that the spinning ability mesophase pitch (which can be evaluated by fiber diameter and draw speed) and mechanical strength of the final carbon fiber are improved when increasing the temperature of the heat treatment (at which the pitch is hydrogenated is vacuum treated) and is

  the duration of the heat treatment.

Example 4

  The carbon fiber obtained is subjected to the example

  ple 3 to graphitization by heating in atmosphere

  of argon at a temperature of 2800 ° C at a rate of

  heating 10 OC / min and maintaining at a temperature of 2800 ° C for 5 mm The graphite fiber is obtained with a

  85.9% yield compared to the raw fiber.

  The graphite fiber obtained has an average diameter of 9.8 microns, a resistance of 210 kg / mm and a modulus of 38.5 tons / mm.

Example 5

  An Australian lignite is ground to a particle size of 250 microns or below and its weight is added to an average tar oil 3 times.

  at a temperature of 4100 C under pressure

  hydrogen bar of 50 bar (50 kg / cm 2 G) and maintained

  at this temperature for 60 minutes in order to completely dissolve

  The lignite components which are soluble in the solvent are removed. Any undissolved residues of the reaction mixture are removed by filtration and the filtrate is distilled under vacuum;

  This produces distilled coal which is distilled.

  It is carried out at a bottom temperature of 350 ° C.

  under an absolute pressure of 10 mm Hg

  risé consists of 89,27% carbon, 5,14% hydrogen, 0,96% nitrogen, 0,34% sulfur and 4,29% oxygen and it has

an aromaticity index of 0.80.

  To this depolymerized charcoal is added 2% of a

  cobalt-molybdenum lysate and 3 times its Doids by a fraction

  After thorough mixing, the mixture is hydrogenated by heating at a temperature of 450 ° C. under a hydrogen pressure of 150 bar.

  (150 kg / cm 2 G) and keeping at this temperature

  After 10 minutes After separating the solid and liquid phases by filtration, the filtrate is distilled at a bottom temperature of 2000 ° C. under an absolute pressure of 10 mmHg; a hydrogenated pitch of 89.41% of carbon, 6.24% of hydrogen, 1.04% of nitrogen, 0.28% of sulfur and 3.03% of oxygen is obtained. that is, its hydrogen content increased by about 21% compared to that of the depolymerized carbon used as a raw material. On the other hand, the molecular weight distribution was measured by

  gel permeation chromatography with quinoline serine

  solvent; it is found that 91% of the hydrogenated pitch has

  a molecular weight in the range of 400 to 600.

  This hydrogenated pitch is immersed in a salt bath at 520 ° C., immediately exposed to an absolute pressure of

  mm Hg and maintained at this temperature for 5 minutes.

  Mesophase pitch is obtained at a mesophase content

7.1%.

  This mesophase pitch is spun at a temperature of 335 ° C and a drawing speed of 1400 m / min.

  infusible raw fiber by heating it in the air at a time

  300 C at a heating rate of 2.0 C / min and maintaining it at 300 ° C. for 5 minutes. An infusible fiber is obtained which is heated in an argon atmosphere at a temperature of 1000 ° C. to a temperature of 1000 ° C. heating rate of 5 C / min and maintained at 1000 C for 15 minutes; a carbon fiber is obtained with a yield of 87.4% compared to

the raw fiber.

  The carbon fiber obtained has a diameter of 10.0 microns, a resistance of 262 kg / mm 2 and a modulus of 21.2 tons / mm 2

Example 6

  At a petroleum pitch of ethylene pellet riddled with

  light fractions (consisting of 94.26% carbon, 5.53% hydrogen, 0.00% nitrogen, 0.07% sulfur and 0.14% oxygen, aromaticity index of 0.76) 7% of a catalyst iron oxide and 3 times its

  weight of anthracene oil After thorough mixing,

  gene by heating at a temperature of 470 C under a pressure of

  hydrogen pressure of 100 bar (100 kg / cm 2 G) and maintaining at 470 C for 5 min. The catalyst is separated and

  the insoluble solids of the reaction mixture by

  and the filtrate is distilled at a bottom temperature of 300 ° C. under an absolute pressure of 10 mmHg; a hydrogenated pitch is thus obtained which consists of 92.89% of carbon, 6.91% of hydrogen, 0.05% of nitrogen, 0.03% of sulfur and 0.12% of oxygen. that is, its hydrogen content increased by about 25% over that of ethylene pellet oil stripped of light fractions. The molecular weight distribution was also measured by gel permeation chromatography. using quinoline as the solvent; it is found that 95% of the hydrogenated pitch has a molecular weight in

the range of 400 to 600.

  This hydrogenated pitch is immersed in a bath at 530 ° C, immediately exposed to an absolute pressure of

  mm Hg and maintained at this temperature for 4 minutes.

  Mesophase pitch is obtained with a mesophase content

13.1%.

  This pitch is spun at a temperature of 3400 C and at a drawing speed of 1200 m / min; a raw fiber is obtained which is then treated as described in Example 1 for conversion into carbon fiber & the fiber yield

of carbon is 89.6%.

  The carbon fiber obtained has an average diameter of 11.4 microns, a mechanical strength of 239 kg / mm 2 and a modulus of 14.2 tons / mm. In most cases, the mesophase pitch according to the invention does not consist of not entirely in an optically anisotropic structure and also contains a structure

optically isotropic.

  In fact, all the mesophase pitches described in Examples 1 to 6 consist in part of a structure

  optically isotropic but they can be uniformly fused

  During spinning, the mesophase is oriented along the axis of the fiber and this orientation is transferred into the final carbon fiber. For example, the mesophase pitch shown in Figure 1 contains about 15% With an optically isotropic structure, the raw fiber obtained by spinning mesophase pitch has an orientation along the axis of the fiber, as illustrated in FIG. 2. In addition, it can be seen from the examination of FIG. orientation of the raw fiber has been

  transferred into the carbon fiber.

Claims (15)

  Process for the preparation of high quality carbon fibers, characterized in that it comprises the stages   following: one melts and spins a pitch in mesophase   From 1 to 40% by weight of a mesophase, the fiber is made   spun infusible in the air, and the carbon fiber   fuse in an inert gas atmosphere, thereby forming the sought carbon fiber.   Process for the preparation of HP carbon fibers, characterized by the following steps:   a) a pitch having an aromatic index is hydrogenated;   not less than 0.6 in a hydrocarbon solvent in the presence of a hydrogenation catalyst, and eliminates   the catalyst, the insoluble solids and the sol-   hydrocarbon derivative of the reaction mixture to obtain a hydrogenated pitch; b) treating the hydrogenated pitch with heat under vacuum to obtain a mesophase pitch containing from 1 to 40% by weight of a mesophase; (c) the pitch is melted and spun into mesophase; d) making the spun fiber infusible in the air; and e) the resultant infusible fiber is carbonized in a inert gas atmosphere.   The process according to claim 1 or 2, wherein   in that, after the carbonisation of the   in an inert gas atmosphere, the fiber is subjected to charred graphitization.   4. Process according to claim 2 or 3, characterized   characterized in that the hydrogenation catalyst contains at least one component selected from the group consisting of iron, cobalt, molybdenum, copper, tungsten, nickel,   platinum and rhodium, their oxides and sulphides.   Process according to Claim 4, characterized in that the catalyst is used in an amount of 1 to 20%   by weight relative to the starting pitch.   Process according to any one of the claims   2 to 5, characterized in that the hydrogenation of the starting pitch is carried out at a temperature in the range   400 to 500 ° C with a hold time at this temperature.   no more than 240 minutes and under pressure   hydrogen scale in the range of 50 to 300 bar.   Process according to any one of the claims   2 to 6, characterized in that the hydrogen content of the hydrogenated pitch is at least 10% greater than that of the starting pitch and at least 90% of the hydrogenated pitch   have a molecular weight in the range of 400 to 600.   Process according to any one of the claims   2 to 7, characterized in that the hydrogenated pitch is heat-treated at a temperature of not less than 4800 C, at an absolute pressure not exceeding 40 mm Hg,   with a holding time at this temperature which does not exceed it's not 30 minutes.   Process according to any one of the claims   2 to 8, characterized in that the pitch having a subscript   of not less than 0.6 is chosen in the group   formed by depolymerized coal, coal tar, coal tar pitch and coal oil pitch ethylene pellet.   Process according to any one of the claims   2 to 9, characterized in that the hydrogenation of the starting pitch is used, the pitch is used at a non-aromaticity index.   less than 0.6 and the hydrocarbon solvent in proportions   relative weight ratios of 1: 2 or more.   Process according to any one of the claims   2 to 10, characterized in that, after hydrogenation, the hydrocarbon solvent is removed by distillation under conditions such that the bottom temperature of the distillation zone is in the range of 200 to 300 ° C and the absolute pressure in the range of 5 to 20 mm Hg.   Process according to Claim 8, characterized   in that the heat treatment is carried out at a time   from 500 to 550 ° C under an absolute pressure of 3 to mm Hg in a period of 2 to 15 minutes.   Process according to any one of the claims   tions, characterized in that the pitch in meso-   phase is melted and spun at a temperature of 320 to 4000 C.   Process according to any one of the claims   tions, characterized in that the spun fiber is   rendered infusible at a reheating speed   3.30 C / min, a temperature in the range of 260 to 340 ° C and a holding time at this temperature which does not exceed 60 minutes.   Process according to any one of the claims   tions, characterized in that the infusible fiber   is carbonized in an inert gas atmosphere at a reheating rate of not more than 70 C / min, at a temperature of not less than 8000 C and a holding time of   temperature not less than 5 minutes.   Process according to Claim 3, characterized in that the graphitization is carried out at a temperature from 2,000 to 3,000 C.   Process according to any one of the claims   characterized in that the high quality carbon fibers have a mechanical strength of 350 kg / mm and a modulus of elasticity of 10 to 40 tonnes / mm