CA1309369C - Process for the production of an anisotropic pitch for carbon fibres - Google Patents
Process for the production of an anisotropic pitch for carbon fibresInfo
- Publication number
- CA1309369C CA1309369C CA000587816A CA587816A CA1309369C CA 1309369 C CA1309369 C CA 1309369C CA 000587816 A CA000587816 A CA 000587816A CA 587816 A CA587816 A CA 587816A CA 1309369 C CA1309369 C CA 1309369C
- Authority
- CA
- Canada
- Prior art keywords
- pitch
- fibres
- production
- constituents
- carbon fibres
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 12
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 12
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 239000011337 anisotropic pitch Substances 0.000 title claims abstract description 5
- 238000000034 method Methods 0.000 title claims description 14
- 239000011295 pitch Substances 0.000 claims abstract description 52
- 238000012545 processing Methods 0.000 claims abstract description 13
- 239000011294 coal tar pitch Substances 0.000 claims abstract description 11
- 239000002904 solvent Substances 0.000 claims abstract description 11
- 238000004821 distillation Methods 0.000 claims description 9
- SMWDFEZZVXVKRB-UHFFFAOYSA-N Quinoline Chemical compound N1=CC=CC2=CC=CC=C21 SMWDFEZZVXVKRB-UHFFFAOYSA-N 0.000 claims description 8
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 claims description 4
- MWPLVEDNUUSJAV-UHFFFAOYSA-N anthracene Chemical compound C1=CC=CC2=CC3=CC=CC=C3C=C21 MWPLVEDNUUSJAV-UHFFFAOYSA-N 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 239000007789 gas Substances 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 claims description 2
- 239000011269 tar Substances 0.000 claims 1
- 238000000605 extraction Methods 0.000 abstract description 3
- 239000000470 constituent Substances 0.000 description 23
- 238000004939 coking Methods 0.000 description 7
- 239000002245 particle Substances 0.000 description 6
- 239000011302 mesophase pitch Substances 0.000 description 5
- 230000003287 optical effect Effects 0.000 description 4
- 230000000704 physical effect Effects 0.000 description 4
- 238000009987 spinning Methods 0.000 description 4
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 239000002956 ash Substances 0.000 description 3
- 238000007664 blowing Methods 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 239000011280 coal tar Substances 0.000 description 3
- 229940108066 coal tar Drugs 0.000 description 3
- 238000005984 hydrogenation reaction Methods 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 235000002918 Fraxinus excelsior Nutrition 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000000706 filtrate Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 229920002239 polyacrylonitrile Polymers 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- LBUJPTNKIBCYBY-UHFFFAOYSA-N 1,2,3,4-tetrahydroquinoline Chemical compound C1=CC=C2CCCNC2=C1 LBUJPTNKIBCYBY-UHFFFAOYSA-N 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- 230000003466 anti-cipated effect Effects 0.000 description 1
- 239000003849 aromatic solvent Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000002802 bituminous coal Substances 0.000 description 1
- 239000011336 carbonized pitch Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000011312 pitch solution Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 239000011338 soft pitch Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10C—WORKING-UP PITCH, ASPHALT, BITUMEN, TAR; PYROLIGNEOUS ACID
- C10C1/00—Working-up tar
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10C—WORKING-UP PITCH, ASPHALT, BITUMEN, TAR; PYROLIGNEOUS ACID
- C10C3/00—Working-up pitch, asphalt, bitumen
- C10C3/02—Working-up pitch, asphalt, bitumen by chemical means reaction
- C10C3/04—Working-up pitch, asphalt, bitumen by chemical means reaction by blowing or oxidising, e.g. air, ozone
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Textile Engineering (AREA)
- Working-Up Tar And Pitch (AREA)
- Inorganic Fibers (AREA)
Abstract
ABSTRACT
Anisotropic pitch for the production of carbon fibres is produced from blown coaltar pitch by extraction with a pitch solvent and thermal processing of the solvent-free soluble fraction in a vacuum.
Anisotropic pitch for the production of carbon fibres is produced from blown coaltar pitch by extraction with a pitch solvent and thermal processing of the solvent-free soluble fraction in a vacuum.
Description
3~i9 The present invention relates to the production of a highly anisotropic pre-product for carbon fibres, this being pro-duced from coaltar pitch.
The production of carbon fibres from coaltar pitch is known. Because of the lower raw-material costs and the higher yields, it is to be anticipated that the fibres produced from coaltar pitch can be produced at a lower cost than that incurred by the production from polyacrylnitrile. However, it is not pos-sible to produce high-strength carbon fibres with a tenslle strength of more than 2 GPa breaking elongation of more than 1%, as can be done from polyacrylnitrile. Only anisotropic pitches are suitable for this purpose. For this reason, intensive research aimed at developing such pitches is being carried on world-wide.
A pitch of this type has liquid-crystaline properties, in particular an ordered arrangement of large planar aromatic molecules whilst retaining its fluidity. Pitches of this type are referred to as "mesophase pitches~, wherein, in addition to the predominantly anisotropic phase, there can also be an isotropic phase. The assessment of anisotropy is carried out by observatlon of the ground surfaces of the pitch using a polariza-tion microscope.
In addition to anisotropy, a pitch that is suitable for the production of hlgh-strength carbon fibres should also have the following properties: the lowest possible content of solid particles in order to avoid defects in the fibres; a low flow temperature in order to avoid polymerization during processing; a high carbon content, a high level of coking residue, and a low content of volatile constituents in order to achieve a high yield and simplification of the spinning, stabilization, and carboniza-tion processes; and a low content of constituents that are insol-uble in chinoline with a high content of constituents that areinsoluble in toluent (high ~ -range = TI-QI).
13~9369 It is obvious that purposeful refinlng of the multi-substance pitch is necessary in order to achieve a characteristic profile of this type. The careful separatlon of the solid part-icles within the pitch is essential and belongs to the prior art.
It is known from the literature that the direct produc-tion of mesophase pitches from filtered coaltar or petroleum pitches by means of t~ermal processing only leads to modest results:
In the case of a processing time that is too brief, there is a high isotropic fraction and this reduces the yield and has a negative effect on the strength of the fibres. In the case of more extensive processing, infusible particles are formed from the high-molecular constituents of the pitch and these make spinning more difficult and cause a deterioration of the quality of the fibres.
Fractionation of the pitch with the aim of ccncentrating the distribution of the molecular weight has been described in numerous publications.
Starting from a soft pitch, in the process described in EP O 17 29 55 Al(l), mesophases are formed in a first thermal processing and the insoluble pitch constituents that are formed are removed by extraction with an aromatic solvent and subsequent filtration. The filtrate is processed by distillation in order to separate the solvent and then subjected to a second thermal processing which produces a highly anisotropic pitch for the production of carbon fibres; however, this has a high flow point and a large content of constituents that are insoluble in chinoline. The physical properties of the carbonized fibres are inadequate.
Another method for the production of spinnable mesophase pitch involves hydrogenation of the pitch. In the process as described in DE 3 33 05 75 C2(2) pitch is hydrogenated with a hydrogenating agent, e.g., tetrahydrochinoline and thermally processed in a . ~, , . ,~, 93~i9 ,~
vacuum to form the mesophases after filtration and the removal of the solvent by distillation.
These measures reduce the flow point and the physical properties of the fibres, carbonized at 1500C, are improved.
A more complex process for forming spinnable pitch is described in EP 0 24 75 65 Al(3):
The insoluble constituents are filtered off from bituminous coal after extraction with xylene. The soluble fraction is subjected to thermal-pressure processing, flashed for the separation of the low molecular constituents by distillation, and the heavy phase is hydrogenated. After separation of the hydrogenating agent by means of distillation, the mesophase is formed by thermal processing.
A disadvantage in the two last processes for forming spinnable pitch is the great technical cost involved in producing the high pressures and temperatures that are required for hydrogenation of the pitch. In particular, the last process, which involves additional thermal-pressure processing, flashing, and distillation is costly and can cancel out the cost advantage provided by the use of less expensive raw materials.
~ ~3~)9369 The properties of the spinnable pitches and carbonized pitch fibres produced by the patents adduced above as examples are set out in Table 1:
Table 1 Processes as in (1) (2) (3) Properties-spinnable pitch Flow point 350 330 316 Optical anisotropy %-vol 94 100 90 Toluene insoluble %-wt93,7 85 95,5 constituents Chinoline insoluble %-wt 45 45 16 constituents Properties carbon fibres Tensile strength GPa 1,3 2,76 2,67 Modules of elasticity GPa 86 196 153 Carbonisation end C 1000 1500 1000 temperature It can be seen from the prior art that up to now it has only been possible to produce carbonated pitch fibres with a tensile strength of more than 2 GPa and a breaking elongation of more than 1% by using hydrogenated pitches.
~3~g3~9 The present invention provides a more simple process for the production of a anisotropic pitch without hydrogenation, from which fibres that have a tensile strength of more than 2 GPa at a breaking elongation of more than 1% can be spun.
According to the present invention a coaltar pitch is blown in a temperature range of 330-400C for 8-12 hours with 1 to 10.10-3 kg/kg pitch.h of a gas that contains oxygen and then extracted with a pitch solvent, and the soluble pitch fraction is heated with a heating rate of 1-50 K/min. at a pressure of 0.5-50 mbar to a temperature between 400 and 480C after the distilla-tion removal of the solvent, the end temperature being maintained for up to 50 minutes.
slowing coaltar pitch with air is known. This serves to increase the softening point and the coking residue. Pitch that has been treated in this manner is used, for example, as the charging stock for pitch coking in horizontal-chamber ovens. It has also been proposed that coaltar pitch be filtered, blown with air, and then spun (Fuel, 1981, Vol. 60, pp. 848-850). Here, too, blowing is used to raise the softening point, in order that the pitch fibres do not adhere to each other during subsequent processing. Bituminous coaltar pitch should be understood to be the residue from the distillation processing of high temperature bitumlnous coaltar, preferably a bituminous coaltar normal pitch wlth a softenlng point (Kraemer-Sarnow) of approximately 70C.
All pitch solvents, the solvent behavlour of whlch correspond to pyridine, chinoline or anthracene oil, can be used as the sol-vent.
The present invention ls described in greater detail below on the basis of an Example:
Example 500 kg of bituminous coaltar pitch with a softening ~Q9369 point (Kraemer-Sarnow) of 70C were heated to 335C in a heated retort whilst being stirred and blown for ten hours with 6.10-3 kg air/kg pitch.h until the temperature rose to 393C. The air was forced into the liquid pitch through pipes that ended a short distance above the bottom of the retort.
The following substance data applies to the pitch blown in this manner:
Flow point 160C
Toluene-insoluble constituents 52%-wt Chinoline-insoluble constituents 21%-wt Coking residue (Alcan) - 68%-wt Ashes (900C) 0.2%-wt ~"~9369 The blown pitch was ground and 1 part by weight of pitch was dissolved in 2 parts by weight chinoline at 180C whilst being stirred. After approximately 2 hours the undissolved constituents of the pitch were separated from the soluble constituents by sedimentation. The liquid phase was drawn off and filtered through a sintered metal filter (pore width: 1 micron) so as to separate off the finest solid particles. The chinoline was distilled off from the pitch solution at a pressure of 200 mbar to a sump temperature of 300C.
The following substance data apply to the remaining pitch fraction:
Flow point 170 C
Toluene-insoluble constituents 46%-wt Chinoline-insoluble constituents less than 1%-wt Coking residue (Alcan) 65%-wt Ashes (900C) The pitch fraction was heated at a pressure of 5 mbar in 60 minutes from 250 to 440C and the end temperature was maintained for 20 minutes.
The mesophase pitch produced in this manner has the following properties:
.. .
o~ ~3Q9369 Flow point 320 C
Optical anisotropy more than 90%-vol Toluene-insoluble constituents 85%-wt Chinoline-insoluble constituents 18%-wt Coking residue (Alcan) g4%-wt Pressure filter test (1 micron) practically no infusible particles present The mesophase pitch can be spun at 380C, without any rupture of the fibres. Pitch fibres are stabilized up to a temperature of 350C in air and then carbonized up to 1200C. The carbon fibres obtained in this manner are characterized by the following data:
Diameter 9-10 microns Tensile strength 2.4 GPa Modulus of elasticity 210 GPa The physical properties exceed those of fibres produced from pitch that has been thermally processed twice (EP 0 17 29 55 Al) and correspond more or less to those fibres produced from hydrogenated and thermally processed pitches.
The influence of blowing on the pitch and the fibre properties is demonstrated by the following comparative example:
,.
1 ~ ~9 3 6 9 - lD -Comparative Example The same starting pitch as in the example was filtered after the addition of secondary fil~ering agents at 270C. The filtrate is distinguished by the following properties:
Softening point (Kraemer-Sarnow) 70~C
Toluene-insoluble constituents 22%-wt Chinoline-insoluble constituents less than 0.1%-wt Ash trace The filtered pitch is thermally processed under the same conditions as in the above example. In order to achieve an optical anisotropy of at least 90%-vol., the end temperature must be increased to 465C and the maintenance period extended to 30 minuteS. The mesophase pitch produced in this manner is distinguished by the following characteristics:
Flow point 340~C
Optical anisotropy 90%-vol.
Toluene-insoluble constituents 88%-wt Chinoline-insoluble constituents 51%-wt Coking residue (Alcan) 95%-wt Filter test (1 micron) 0.5%-wt infusible particles ~3Q93~:;9 ~Z
The mesophase pitch can be first spun at 405C. There were frequent fibre breakages. The service life of the filter elements arranged ahead of the spinning nozzles is very low.
The carbon fibres carbonized up to 1200C can be characterized by the following typical properties:
Diameter 9-11 microns Tensile strength 1.6 GPa Modulus elasticity 230 GPa The tensile strength thus corresponds to that of pitches that have been thermally processed twice. The elongation fraction is, however, below 1~.
Comparison of the analytical data shows clearly that formation of the mesophase is favourably influenced by blowing with air as a pre-treatment for the pitch. The mesophase according to the present invention has, most surprisingly, a lower flow point and a lower content of chinoline insoluble constituents at a higher level of anisotropy. This means that spinning is simplified and the physical properties of the carbonized fibres are greatly improved.
~ ~;'. ' Z
The production of carbon fibres from coaltar pitch is known. Because of the lower raw-material costs and the higher yields, it is to be anticipated that the fibres produced from coaltar pitch can be produced at a lower cost than that incurred by the production from polyacrylnitrile. However, it is not pos-sible to produce high-strength carbon fibres with a tenslle strength of more than 2 GPa breaking elongation of more than 1%, as can be done from polyacrylnitrile. Only anisotropic pitches are suitable for this purpose. For this reason, intensive research aimed at developing such pitches is being carried on world-wide.
A pitch of this type has liquid-crystaline properties, in particular an ordered arrangement of large planar aromatic molecules whilst retaining its fluidity. Pitches of this type are referred to as "mesophase pitches~, wherein, in addition to the predominantly anisotropic phase, there can also be an isotropic phase. The assessment of anisotropy is carried out by observatlon of the ground surfaces of the pitch using a polariza-tion microscope.
In addition to anisotropy, a pitch that is suitable for the production of hlgh-strength carbon fibres should also have the following properties: the lowest possible content of solid particles in order to avoid defects in the fibres; a low flow temperature in order to avoid polymerization during processing; a high carbon content, a high level of coking residue, and a low content of volatile constituents in order to achieve a high yield and simplification of the spinning, stabilization, and carboniza-tion processes; and a low content of constituents that are insol-uble in chinoline with a high content of constituents that areinsoluble in toluent (high ~ -range = TI-QI).
13~9369 It is obvious that purposeful refinlng of the multi-substance pitch is necessary in order to achieve a characteristic profile of this type. The careful separatlon of the solid part-icles within the pitch is essential and belongs to the prior art.
It is known from the literature that the direct produc-tion of mesophase pitches from filtered coaltar or petroleum pitches by means of t~ermal processing only leads to modest results:
In the case of a processing time that is too brief, there is a high isotropic fraction and this reduces the yield and has a negative effect on the strength of the fibres. In the case of more extensive processing, infusible particles are formed from the high-molecular constituents of the pitch and these make spinning more difficult and cause a deterioration of the quality of the fibres.
Fractionation of the pitch with the aim of ccncentrating the distribution of the molecular weight has been described in numerous publications.
Starting from a soft pitch, in the process described in EP O 17 29 55 Al(l), mesophases are formed in a first thermal processing and the insoluble pitch constituents that are formed are removed by extraction with an aromatic solvent and subsequent filtration. The filtrate is processed by distillation in order to separate the solvent and then subjected to a second thermal processing which produces a highly anisotropic pitch for the production of carbon fibres; however, this has a high flow point and a large content of constituents that are insoluble in chinoline. The physical properties of the carbonized fibres are inadequate.
Another method for the production of spinnable mesophase pitch involves hydrogenation of the pitch. In the process as described in DE 3 33 05 75 C2(2) pitch is hydrogenated with a hydrogenating agent, e.g., tetrahydrochinoline and thermally processed in a . ~, , . ,~, 93~i9 ,~
vacuum to form the mesophases after filtration and the removal of the solvent by distillation.
These measures reduce the flow point and the physical properties of the fibres, carbonized at 1500C, are improved.
A more complex process for forming spinnable pitch is described in EP 0 24 75 65 Al(3):
The insoluble constituents are filtered off from bituminous coal after extraction with xylene. The soluble fraction is subjected to thermal-pressure processing, flashed for the separation of the low molecular constituents by distillation, and the heavy phase is hydrogenated. After separation of the hydrogenating agent by means of distillation, the mesophase is formed by thermal processing.
A disadvantage in the two last processes for forming spinnable pitch is the great technical cost involved in producing the high pressures and temperatures that are required for hydrogenation of the pitch. In particular, the last process, which involves additional thermal-pressure processing, flashing, and distillation is costly and can cancel out the cost advantage provided by the use of less expensive raw materials.
~ ~3~)9369 The properties of the spinnable pitches and carbonized pitch fibres produced by the patents adduced above as examples are set out in Table 1:
Table 1 Processes as in (1) (2) (3) Properties-spinnable pitch Flow point 350 330 316 Optical anisotropy %-vol 94 100 90 Toluene insoluble %-wt93,7 85 95,5 constituents Chinoline insoluble %-wt 45 45 16 constituents Properties carbon fibres Tensile strength GPa 1,3 2,76 2,67 Modules of elasticity GPa 86 196 153 Carbonisation end C 1000 1500 1000 temperature It can be seen from the prior art that up to now it has only been possible to produce carbonated pitch fibres with a tensile strength of more than 2 GPa and a breaking elongation of more than 1% by using hydrogenated pitches.
~3~g3~9 The present invention provides a more simple process for the production of a anisotropic pitch without hydrogenation, from which fibres that have a tensile strength of more than 2 GPa at a breaking elongation of more than 1% can be spun.
According to the present invention a coaltar pitch is blown in a temperature range of 330-400C for 8-12 hours with 1 to 10.10-3 kg/kg pitch.h of a gas that contains oxygen and then extracted with a pitch solvent, and the soluble pitch fraction is heated with a heating rate of 1-50 K/min. at a pressure of 0.5-50 mbar to a temperature between 400 and 480C after the distilla-tion removal of the solvent, the end temperature being maintained for up to 50 minutes.
slowing coaltar pitch with air is known. This serves to increase the softening point and the coking residue. Pitch that has been treated in this manner is used, for example, as the charging stock for pitch coking in horizontal-chamber ovens. It has also been proposed that coaltar pitch be filtered, blown with air, and then spun (Fuel, 1981, Vol. 60, pp. 848-850). Here, too, blowing is used to raise the softening point, in order that the pitch fibres do not adhere to each other during subsequent processing. Bituminous coaltar pitch should be understood to be the residue from the distillation processing of high temperature bitumlnous coaltar, preferably a bituminous coaltar normal pitch wlth a softenlng point (Kraemer-Sarnow) of approximately 70C.
All pitch solvents, the solvent behavlour of whlch correspond to pyridine, chinoline or anthracene oil, can be used as the sol-vent.
The present invention ls described in greater detail below on the basis of an Example:
Example 500 kg of bituminous coaltar pitch with a softening ~Q9369 point (Kraemer-Sarnow) of 70C were heated to 335C in a heated retort whilst being stirred and blown for ten hours with 6.10-3 kg air/kg pitch.h until the temperature rose to 393C. The air was forced into the liquid pitch through pipes that ended a short distance above the bottom of the retort.
The following substance data applies to the pitch blown in this manner:
Flow point 160C
Toluene-insoluble constituents 52%-wt Chinoline-insoluble constituents 21%-wt Coking residue (Alcan) - 68%-wt Ashes (900C) 0.2%-wt ~"~9369 The blown pitch was ground and 1 part by weight of pitch was dissolved in 2 parts by weight chinoline at 180C whilst being stirred. After approximately 2 hours the undissolved constituents of the pitch were separated from the soluble constituents by sedimentation. The liquid phase was drawn off and filtered through a sintered metal filter (pore width: 1 micron) so as to separate off the finest solid particles. The chinoline was distilled off from the pitch solution at a pressure of 200 mbar to a sump temperature of 300C.
The following substance data apply to the remaining pitch fraction:
Flow point 170 C
Toluene-insoluble constituents 46%-wt Chinoline-insoluble constituents less than 1%-wt Coking residue (Alcan) 65%-wt Ashes (900C) The pitch fraction was heated at a pressure of 5 mbar in 60 minutes from 250 to 440C and the end temperature was maintained for 20 minutes.
The mesophase pitch produced in this manner has the following properties:
.. .
o~ ~3Q9369 Flow point 320 C
Optical anisotropy more than 90%-vol Toluene-insoluble constituents 85%-wt Chinoline-insoluble constituents 18%-wt Coking residue (Alcan) g4%-wt Pressure filter test (1 micron) practically no infusible particles present The mesophase pitch can be spun at 380C, without any rupture of the fibres. Pitch fibres are stabilized up to a temperature of 350C in air and then carbonized up to 1200C. The carbon fibres obtained in this manner are characterized by the following data:
Diameter 9-10 microns Tensile strength 2.4 GPa Modulus of elasticity 210 GPa The physical properties exceed those of fibres produced from pitch that has been thermally processed twice (EP 0 17 29 55 Al) and correspond more or less to those fibres produced from hydrogenated and thermally processed pitches.
The influence of blowing on the pitch and the fibre properties is demonstrated by the following comparative example:
,.
1 ~ ~9 3 6 9 - lD -Comparative Example The same starting pitch as in the example was filtered after the addition of secondary fil~ering agents at 270C. The filtrate is distinguished by the following properties:
Softening point (Kraemer-Sarnow) 70~C
Toluene-insoluble constituents 22%-wt Chinoline-insoluble constituents less than 0.1%-wt Ash trace The filtered pitch is thermally processed under the same conditions as in the above example. In order to achieve an optical anisotropy of at least 90%-vol., the end temperature must be increased to 465C and the maintenance period extended to 30 minuteS. The mesophase pitch produced in this manner is distinguished by the following characteristics:
Flow point 340~C
Optical anisotropy 90%-vol.
Toluene-insoluble constituents 88%-wt Chinoline-insoluble constituents 51%-wt Coking residue (Alcan) 95%-wt Filter test (1 micron) 0.5%-wt infusible particles ~3Q93~:;9 ~Z
The mesophase pitch can be first spun at 405C. There were frequent fibre breakages. The service life of the filter elements arranged ahead of the spinning nozzles is very low.
The carbon fibres carbonized up to 1200C can be characterized by the following typical properties:
Diameter 9-11 microns Tensile strength 1.6 GPa Modulus elasticity 230 GPa The tensile strength thus corresponds to that of pitches that have been thermally processed twice. The elongation fraction is, however, below 1~.
Comparison of the analytical data shows clearly that formation of the mesophase is favourably influenced by blowing with air as a pre-treatment for the pitch. The mesophase according to the present invention has, most surprisingly, a lower flow point and a lower content of chinoline insoluble constituents at a higher level of anisotropy. This means that spinning is simplified and the physical properties of the carbonized fibres are greatly improved.
~ ~;'. ' Z
Claims (4)
1. A process for the production of an anisotropic pitch for producing carbon fibres, in which a coaltar pitch is blown in a temperature range from 300-400°C for 8-12 hours with 1-10.10 3 kg/kg pitch.h of a gas that contains oxygen and then extracted with a pitch solvent and the soluble pitch fraction is heated after distillation removal of the solvent with a heating rate of 1-50 K/min. at a pressure of 0.5-50 mbar to a temperature between 400 and 480°C, the end temperature being maintained for up to 50 minutes.
2. A process as defined in claim 1, wherein the coal-tar pitch is a residue from the distillation processing of a high temperature tar with a softening point (Kraemer-Sarnow) of approximately 70°C.
3. A process as defined in claim 1 or 2, in which pyridine, chinoline, or anthracene oil is used as the pitch sol-vent.
4. A process as defined in claim 1 or 2, wherein the gas that contains oxygen is air.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3821866.6 | 1988-06-29 | ||
| DE3821866A DE3821866A1 (en) | 1988-06-29 | 1988-06-29 | PROCESS FOR PREPARING AN ANISOTROPIC PECH FOR CARBON FIBER |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1309369C true CA1309369C (en) | 1992-10-27 |
Family
ID=6357481
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000587816A Expired - Lifetime CA1309369C (en) | 1988-06-29 | 1989-01-10 | Process for the production of an anisotropic pitch for carbon fibres |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0348599B1 (en) |
| JP (1) | JPH0247190A (en) |
| CA (1) | CA1309369C (en) |
| DE (2) | DE3821866A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4892642A (en) * | 1987-11-27 | 1990-01-09 | Conoco Inc. | Process for the production of mesophase |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3484365A (en) * | 1966-10-24 | 1969-12-16 | Phillips Petroleum Co | Asphaltene oxidation |
| DE3476685D1 (en) * | 1984-08-28 | 1989-03-16 | Kawasaki Steel Co | A method for producing a precursor pitch for carbon fiber |
| JPS6187790A (en) * | 1984-10-05 | 1986-05-06 | Kawasaki Steel Corp | Method for manufacturing carbon fiber precursor pitch |
| US4773985A (en) * | 1985-04-12 | 1988-09-27 | University Of Southern California | Method of optimizing mesophase formation in graphite and coke precursors |
-
1988
- 1988-06-29 DE DE3821866A patent/DE3821866A1/en not_active Withdrawn
-
1989
- 1989-01-10 CA CA000587816A patent/CA1309369C/en not_active Expired - Lifetime
- 1989-03-14 DE DE8989104511T patent/DE58900206D1/en not_active Expired - Lifetime
- 1989-03-14 EP EP89104511A patent/EP0348599B1/en not_active Expired - Lifetime
- 1989-06-29 JP JP1165489A patent/JPH0247190A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE3821866A1 (en) | 1990-01-18 |
| EP0348599B1 (en) | 1991-08-07 |
| JPH0247190A (en) | 1990-02-16 |
| EP0348599A3 (en) | 1990-02-07 |
| EP0348599A2 (en) | 1990-01-03 |
| DE58900206D1 (en) | 1991-09-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |