CA1227005A - Process for producing carbon fibers - Google Patents
Process for producing carbon fibersInfo
- Publication number
- CA1227005A CA1227005A CA000462682A CA462682A CA1227005A CA 1227005 A CA1227005 A CA 1227005A CA 000462682 A CA000462682 A CA 000462682A CA 462682 A CA462682 A CA 462682A CA 1227005 A CA1227005 A CA 1227005A
- Authority
- CA
- Canada
- Prior art keywords
- carbon fibers
- pitch
- cross
- filament yarns
- spinning
- 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
Links
- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 48
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 48
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000009987 spinning Methods 0.000 claims abstract description 45
- 238000002074 melt spinning Methods 0.000 claims abstract description 9
- 229920001187 thermosetting polymer Polymers 0.000 claims abstract description 8
- 239000011302 mesophase pitch Substances 0.000 claims description 25
- 239000011295 pitch Substances 0.000 claims description 21
- 239000002994 raw material Substances 0.000 claims description 15
- 238000003763 carbonization Methods 0.000 claims description 6
- 241000234282 Allium Species 0.000 claims description 4
- 235000002732 Allium cepa var. cepa Nutrition 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- 208000012886 Vertigo Diseases 0.000 claims 1
- 238000010000 carbonizing Methods 0.000 abstract 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- 238000001125 extrusion Methods 0.000 description 7
- 239000000835 fiber Substances 0.000 description 7
- 230000000704 physical effect Effects 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 240000005220 Bischofia javanica Species 0.000 description 2
- 235000010893 Bischofia javanica Nutrition 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000000295 fuel oil Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 229920002239 polyacrylonitrile Polymers 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000004523 catalytic cracking Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000011280 coal tar Substances 0.000 description 1
- 239000011294 coal tar pitch Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000003760 hair shine Effects 0.000 description 1
- 239000003562 lightweight material Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000386 microscopy Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000011269 tar Substances 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
Classifications
-
- 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
- D01F9/32—Apparatus therefor
- D01F9/322—Apparatus therefor for manufacturing filaments from pitch
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D4/00—Spinnerette packs; Cleaning thereof
- D01D4/02—Spinnerettes
-
- 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
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Inorganic Fibers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for producing filament yarns of high strength, high modulus carbon fibers having superior properties can be obtained from a pitch containing mesophase in an amount of 70% to 100% by using, in melt-spinning of the pitch, spinning nozzles having a cross-sectional area at the nozzle outlet part greater than the cross-sectional area of the narrowest part of the passage for spinning dope inside the nozzles, and subsequently thermosetting and then carbonizing the pitch.
A process for producing filament yarns of high strength, high modulus carbon fibers having superior properties can be obtained from a pitch containing mesophase in an amount of 70% to 100% by using, in melt-spinning of the pitch, spinning nozzles having a cross-sectional area at the nozzle outlet part greater than the cross-sectional area of the narrowest part of the passage for spinning dope inside the nozzles, and subsequently thermosetting and then carbonizing the pitch.
Description
~1 2~
TITLE OF THE INVEN~ION
Process for producing carbon fibers BACKGROUND OF THE INVENTION
1. Field o~ the Invention This invention relates to a process for producing carbon fibers. More particularly, it relaies to a process for producing filament yarns of high strength, high modules carbon fibers having flawless, superior properties from a pitch containing a specified amount of mesophase, as a raw material, by melt-spinning using spinning no~zles (spinnerettes) having a specified structure in extrusion holes for spinning dope.
A term "mesophase" herein referred to is one of the components constituting the pitch and it means an optically anisotropic part of the pitch ~hich shines brilliantly when the section of a lump of pitch solidified at a temperature close to room temperature is polished and observed through the crossed nicols of reflection type polarizing microscopy~ A pitch mostly composed of meso-phase is callad mesophase pitch. The content of mesophase in a mesophase pitch is calculated from the percentage o~
the area of optically anisotropic part obtained by obser-vation under a reflection type polarizing microscope.
TITLE OF THE INVEN~ION
Process for producing carbon fibers BACKGROUND OF THE INVENTION
1. Field o~ the Invention This invention relates to a process for producing carbon fibers. More particularly, it relaies to a process for producing filament yarns of high strength, high modules carbon fibers having flawless, superior properties from a pitch containing a specified amount of mesophase, as a raw material, by melt-spinning using spinning no~zles (spinnerettes) having a specified structure in extrusion holes for spinning dope.
A term "mesophase" herein referred to is one of the components constituting the pitch and it means an optically anisotropic part of the pitch ~hich shines brilliantly when the section of a lump of pitch solidified at a temperature close to room temperature is polished and observed through the crossed nicols of reflection type polarizing microscopy~ A pitch mostly composed of meso-phase is callad mesophase pitch. The content of mesophase in a mesophase pitch is calculated from the percentage o~
the area of optically anisotropic part obtained by obser-vation under a reflection type polarizing microscope.
2. Description o the Prior Art Recently, there has been a demand for high strength ~2~ S
and high modulus light-weight materials in various fields, e.g. in aircraftr motor vehicle and other ~ndustries, and in this connection, a demand for carbon fibers provided with the above-mentioned properties is rapidly increasing.
S It is well known that ~he starting material for high strength, high modulus carbon fibers available now in the marke-t are mostly polyacrylonitrile fibers. However these polyacrylonitrile fihers are not only expensive but also give only a low yield of carbon fibers, e.g. about 45~.
This fact also increases the production cost of the ultimate products of carbon fibers.
As one method for producing high strength, high modulus carbon fibers at a low cost, there are descrip-tions in the official ga2ette of Japanese Patent Publica-tion No. 1810 (197~) issued to Union Carbide Corporation and it is a well known fact that mesophase-containing pitches are excellent raw materials for filament yarn's of high strength, high modulus carb~n ~ibers~ In the raw materials of high strength, high modulus carbon fibers, the content and the physical properties of mesophase gi~e a great influence upon the physical properties of car~on fibers. The higher the mesophase content, the better the quality of mesophase, and the greater the improvement o the physical properties of carbon fibers. Further, pitch o low m~sophase content i~ not adequate as a raw matarial 7~
for high strengthr hi~h modulus-carbon fibers because both the strength and modulus of the carbon fibers obtained therefrom are lo~l.
As for the structure of the cross-section of pitch-derived carbon fibers, it has been known that roughly random shape ~orderless), radial shape kadiated), onion shape (concentric circle shape), etc. of carbon arrangement exist (Examples of literature The l~th biennial conference on carbon, July 329 (1975); Pittburg and Ceramics 11 (1976) No. 7, Nos 612-621) These structures depend greatly upon the physical properties o~ raw material pitch. When mel~-spinning is carried out by using a spinning no~zle in which a narrow channel, as a passage or molten pitch, is a straight tube having a circular cross-section as commonly used case, filaments of carbon fibers thus obtained show a structure in which carbonaceous material is radially oriented because the higher the mesophase content o~ a raw material pitch, the higher the orientation degree of carbonaceous material of the filament produced by melt-spinning, and after thermosetting and carboni7ation,obtained carbon fibers have noticeable radial structure.
Filaments of carbon fi~e~s having radial structure ~orm very often bi~ cracks extending from the circumference of cross-section toward the center of a filament and resultant carbon iber~ utterly lose their value as articles of ~2~010~
- 4 - :
commerce.
It is an object of the present invention to provide a process for producing carbon fibers in which the above-mentioned problems of prior art processes for producing pitch-derived carbon fibers have been overcome and products having excellent properties can constantly be made without forming a crack or cracks~
It is another object of the present invention to provide spinning nozzles capable of providing high strength, high modulus carbon fibers having nearly circular cross-section and containing no crackes at all.
The above mentioned objects can be attained by the process and the nozzles of the present invention.
SU~ARY OF T~E INVENTION
The present invention resides in a process for producing high strength, high modu].us filament yarns of carbon fibers which comprises su~jecting a pitch having a mesophase content of 70% or higher to melt-spinning using spinning nozzles having a cross-sectional area at their nozzle outlet part greater than the cross-sectional area of the narrowest part inside the nozzles and suhjecting the resultant filament yarns to thermosetting and carbon-ization to obtain high strength high modulus filament yarns without cracks in the cross-section of the carbon 25- fibers.
~2~:7~
In the process of the present invention, melt spinning is carried out at a temperature which is higher than the softening temperature of mesophase pitch ~y from 40C to 140C preferably from 55C to 120C using spinning nozzles having a cross-sectional area at their nozzle outlet greater than the cross-sectional area of the narrow-est part inside the nozzles, preferably by two times or more.
DETAILED DESCRIPTION OF THE INVENTION
The inventor of the present application has discovered after comprehensive studies that the properties of car~on fibers can be notably improved by eliminating the formation of crac~s in the cross-section of carbon fibers made from raw material mesophase pitch containing mesophase in an amount of 70~ or higher.
As a process for eliminating cracks in the cross-section of carbon fibers, it has been found that the use of spinning nozzles having a cross-sectional area of the outlet of the noz21es greater than the cross-sectional 2~ area of the narrowes-t part o the thin passage for spinning dope inside the nozzles, praferably having a ratio of the cross-sectiona-l area at tne outlet of the nozzle to that of the narrowest part of the thin passage for spinning dope inside the nozzles o two or greater as shown herein-after in the drawing o Figures 1, 2 and 3 and also the use of a spinning temperature higher than the softeningtemperature (as measured by Koka type flow tester) by 40 to 140C, preferably by 55~ - 120C in the melt-spinning, followed by usual treatments of thermosetting and carbonization provides filament yarns of carbon fiber which are excellent in quality and have no crack at all, and thus the process of the present invention has been completed.
Detailed description will be given as to the above mentioned spinning temperature. Although optimum spinning temperature somewhat varies depending on the mesophase content in the mesophase pitch and physical properties of mesophase, the results of ~ experimentS
show that, if spinning is carried out at a temperature which is not higher than the softening point of mesophase pitch by 40C, the viscosity of the mesophase pitch is too high for spinning resu~ting in poor spinnability.
On the other and if spinning is carried out at a temper-ature higher than the softening temperature of the 0 mesophase pitch by 140C or ~ore, the reduction of .s Viscoslty of mesophase ~ eh, increase of ~e~am~tLo~
of spinning nozzles, and change of properties of mesophase pitch occur, resulting in increase of breakaqe of spun filaments and sta~le spinning becomes difficult. Accord-ingly, it is proper to select a ~pinning temperatu.re in 3L2;~7~ S
the range of 40 to 140C, preferably 55 to 120C
higher than -the softening temperature of~ ~ mesophase.~; t' The softening temperature of mesophase~is in the range of 190C to 240C.
As for a raw material of mesophase pitch used in the process of the present invention, petroleum-origin heavy oil, such as topped crude (reduced C. or long residue), vacuum residue (short residue), residue of thermal catalytic cracking of vacuum gas oil, tar or pitch produced, as a by-product of heat treatment of these residues and a coal-origin heavy oil such as coal tar, coal tar pitch and a coal liquified product can be mentioned. Mesophase pitch can be produced by subjecting one or more of these raw materials to heat treatment under non-oxidative atmosphere l, to form mesophase, causing the resulting mesophase to grow by aging, and separating the part mostly consisting of mesophase.
The inventors of the present application have found that filaments of carbon fibers having superior qualities can be produced at an inexpensive price according to the process of the present invention if the content of mesophase in mesophase pitch is 70% or greater, preferably 90~ or higher. A mesophase pitch containing lower than 70~ mesophase, when suhjected to spinning according to an usual manner and then to thermosetting and carhonization, ~2~27~S
provides carbon ~iber filaments which do not form radial structure in cross-section due to its low degree of carbon orientation. Therefor, although no crack is formed, both tensile strength and modulus of resulting filaments are low, and the carbon fibers have little value as articles of commerce.
When mesophase pitch is used, as a ra~Y material of filament yarn of carbon fibers, the higher the mesophase content, the better the quality of the carbon fibers When mesophase pitch containing 70% or more, preferably 90% or more mesophase is melt-spun by causing velocity change to the flow of mesophase pitch inside the nozzles by using spinning nozzles having a cross-sectional area at their nozzle outlet part greater than that of the narrowest part of the passage way ~or spinning dope inside the nozzles, preEerably in a ratio of the areas of 2 or grater, filament yarns of car~on fibers free of crackes in the cross-section can be obtained.
BRIEF DESCRIPTION OF THE ~RAWING5 Figure 1 is a view of vertical cross-section through the center of one type of a nozzle oE this inven-tion. Figure 2 is also a vertical cross-section through the center of another type of nozzle. Figure 3 is also a vertical cross-section through the center of a further C~ fe.
ty~e of nozzle o~ thi~i invention. Fig~res~4 ~ 7 ~a-~
~iL227~5 _ g _ photograph~of a cross-section of the filament yarns of carbon fibers made by using the nozzle of the present invention and observed under a SEM. Figure 8 is a photo-graph o~ the cross-section of the filaments of carbon fibers made by using the nozzle of the referential example.
Examples o~ nozzle shapes of the spinnerettes used in the process of the present invention are illust-rated in the drawings. However, it is to be noted that the shape of the spinning nozzles used in the present invention should not be limited to tho-se shown in these drawings. Further, the cross-section of the nozzle should not be limited only to circular shape. It is only limited to the condition defined in the scope o~ claim.
In each drawings, 1 is an inlet part of spinning dope. 2 is narrowest tube part. 3 is an outlet part of extruding hole.
Following examples are offered by way of illust-ration and not by ~ay o~ limitation.
Example 1 A distillate fraction higher than 404C, as initial distilling point, o~ residue of thermal calalytic cracking o~ vacuum gas oil was su~ected to heat treatment at 420C for 2 hours while sending there methane gas and further to heating at 320C for 16 hours to cause mesophase to grow by aging and a part consisting mostly of mesophase ~iL2~ 3S
was separated. The mesophase content o~ this mesophase pitch was 91% according to the measurement under a reflection type polarizing microscope and the softening point (as measured by a Koka type flow tester) was 215C.
Using this mesophase pitch as a raw material, and using spinning nozzles shown in Figure l (having 100 extrusion holes i.e. passage ~or spinning dope, a diameter at the inlet part of spinning dope of 2.5 mm, a diameter at the narrowest thin tube part of 0.15 mm, the length of the narrowest thin tube part of 0.3 mm, an angle of cone expanding toward the outlet part of 90, a diameter at the outlet part of 0.3 mm), spinning was carried out at a spinning temperature of 300C, and a spinning velocity o 210 m/min Res~ltant filament yarns of pitch fibers were subjected to thermosetting at 300C and then to carboniza-tion at 2500C to procluce products. When the cross-section of these filaments of carbon fibers was observed under a scanning type electron microscope(SEM), it was found that ~ost O~
the structure of the cross-section thereof was of radial shape and there was no crac~ formed. Further, resultant filaments of carbon fibers had a tensile strength of 278 kg/mm2, a modulus of elasticity of 49 $tmm2 and an elongation of 0 57~.
Example 2 Using the mesophase pitch as u~ed in Example 1 ~22~70~5 as a raw material and using spinning nozzles of Figure L, (100 extrusion holes), in which the diameter of spinning dope introducing part is 2.5 mm~, the diameter of the thinnest tube part is 0.1 mm~, the length of the thinnest tube part is 0.1 mm, the cone angle of a frustum expanding toward outlet is 45, and the diameter of outlet part is 0.2 mm~, filament yarns of carbon fibe~s were produced by spinning at a spinning temperature of 307C and at a spinninq velocity of 500 m/min followed by other proces-sings in same manner as in Example 1. When the cross-s~ction of the resultant carbon fiber was observed with a scanning type electron microscope, it has an onion like structure in the cross-section as shown in Fig. 5, and no crack was found Exam~le 3 Using the mesophase pitch used as in Example 1 as a raw material, and using spinning nozzles of.Fi~ure 2 (100 extrusion holes) in which the diameter of spinning dope introducing part is 2.5 mm0, the diameter of the thinnest tu~e part is 0.1 mm~, the length of the thinnest tube part-is 0.1 mm.~t and the diameter ~t the outlet part ~ ,n/S~
is O . 25 mm~. (Expanding by fo;ming a ho~ u~, filame~t.
yarns of carbon fibers were ~roduced by sp.inning at a spinning tempe~ratur~ oE 280~C and a sDinning velocity of 180 mlmin_ followed by other processings in the same ~L22~
manner as in Example 1~ The representative cross-sectional structure of resultant carbon fibers was a mixture of radial, onion, and random patterns as shown in Figure 6.
There was found no crack at all.
Example 4 -100% Mesophase pitch having a so~tening point of 235~C was obtained after the same processing as in Example 1 except that longer time was necessary for sepa-rating the mesophase pitch. Using this pitch and nozzles as used in Example 2, filament y~rns of carbon fibers were produced by spinning at a spinning temperature of 304C
and a spinning velocity o~ 150 m/min. followed by other processings in the same manner as in Example 1. Represent-ative cross-sectional structuLe o resultant fibers was lS a mixture of radial and random patterns as shown in Figure 7. There was found no crack at all.
Comparative Example 1 Using a mesophase pitch as used in Example 1 as a raw material and using spinning nozzles having e~trusion holes, in which thin tube parts of the extrusion holes are o~ a straight tube having a diameter of 0.3 mm in cross-section and 0 3 mm in len~th and also having a diameter of 0 3 mm at the outlet part~ filament yarns of car~on Eibers were- produced under the same conditions for spinninq, tharmosetting and carbonization as in Example 1. When the ~L2270~)S
cross-section of the resultant filaments of carbon fibers was observed under a scanning type electron microscope, the structure of the cross-section of the filaments yarn of carbon fibers was of radial shape as shown in Figure 8 S but there were formed crac~s at an angle of about 90~. t Resultant filaments of carbon fibers had a tensile strength of 157 kg/mm a modulus of elasticity of 38 $/mm and an elongation of 0.41~.
Comparative ~xample 2 Using the mesophase pitch as used in Example 4 as a raw material, and using spinning nozzles having extrusion holes in which thin tube parts of the extrusion hole are of a straight tube having a cross-sectional diameter of 0.1 mm, a length of 0.1 mm and a diameter at lS the outlet being also 0.1 mm, filament yarns of carbon ~ibers were produced under the same condition for spinning, thermosetting and carbonization as in Example 4. Resultant filaments of carbon fibers had a structure of a radial pattern in cross-section as in Comparativ~ Example 1, and 20 cracks were formed.
and high modulus light-weight materials in various fields, e.g. in aircraftr motor vehicle and other ~ndustries, and in this connection, a demand for carbon fibers provided with the above-mentioned properties is rapidly increasing.
S It is well known that ~he starting material for high strength, high modulus carbon fibers available now in the marke-t are mostly polyacrylonitrile fibers. However these polyacrylonitrile fihers are not only expensive but also give only a low yield of carbon fibers, e.g. about 45~.
This fact also increases the production cost of the ultimate products of carbon fibers.
As one method for producing high strength, high modulus carbon fibers at a low cost, there are descrip-tions in the official ga2ette of Japanese Patent Publica-tion No. 1810 (197~) issued to Union Carbide Corporation and it is a well known fact that mesophase-containing pitches are excellent raw materials for filament yarn's of high strength, high modulus carb~n ~ibers~ In the raw materials of high strength, high modulus carbon fibers, the content and the physical properties of mesophase gi~e a great influence upon the physical properties of car~on fibers. The higher the mesophase content, the better the quality of mesophase, and the greater the improvement o the physical properties of carbon fibers. Further, pitch o low m~sophase content i~ not adequate as a raw matarial 7~
for high strengthr hi~h modulus-carbon fibers because both the strength and modulus of the carbon fibers obtained therefrom are lo~l.
As for the structure of the cross-section of pitch-derived carbon fibers, it has been known that roughly random shape ~orderless), radial shape kadiated), onion shape (concentric circle shape), etc. of carbon arrangement exist (Examples of literature The l~th biennial conference on carbon, July 329 (1975); Pittburg and Ceramics 11 (1976) No. 7, Nos 612-621) These structures depend greatly upon the physical properties o~ raw material pitch. When mel~-spinning is carried out by using a spinning no~zle in which a narrow channel, as a passage or molten pitch, is a straight tube having a circular cross-section as commonly used case, filaments of carbon fibers thus obtained show a structure in which carbonaceous material is radially oriented because the higher the mesophase content o~ a raw material pitch, the higher the orientation degree of carbonaceous material of the filament produced by melt-spinning, and after thermosetting and carboni7ation,obtained carbon fibers have noticeable radial structure.
Filaments of carbon fi~e~s having radial structure ~orm very often bi~ cracks extending from the circumference of cross-section toward the center of a filament and resultant carbon iber~ utterly lose their value as articles of ~2~010~
- 4 - :
commerce.
It is an object of the present invention to provide a process for producing carbon fibers in which the above-mentioned problems of prior art processes for producing pitch-derived carbon fibers have been overcome and products having excellent properties can constantly be made without forming a crack or cracks~
It is another object of the present invention to provide spinning nozzles capable of providing high strength, high modulus carbon fibers having nearly circular cross-section and containing no crackes at all.
The above mentioned objects can be attained by the process and the nozzles of the present invention.
SU~ARY OF T~E INVENTION
The present invention resides in a process for producing high strength, high modu].us filament yarns of carbon fibers which comprises su~jecting a pitch having a mesophase content of 70% or higher to melt-spinning using spinning nozzles having a cross-sectional area at their nozzle outlet part greater than the cross-sectional area of the narrowest part inside the nozzles and suhjecting the resultant filament yarns to thermosetting and carbon-ization to obtain high strength high modulus filament yarns without cracks in the cross-section of the carbon 25- fibers.
~2~:7~
In the process of the present invention, melt spinning is carried out at a temperature which is higher than the softening temperature of mesophase pitch ~y from 40C to 140C preferably from 55C to 120C using spinning nozzles having a cross-sectional area at their nozzle outlet greater than the cross-sectional area of the narrow-est part inside the nozzles, preferably by two times or more.
DETAILED DESCRIPTION OF THE INVENTION
The inventor of the present application has discovered after comprehensive studies that the properties of car~on fibers can be notably improved by eliminating the formation of crac~s in the cross-section of carbon fibers made from raw material mesophase pitch containing mesophase in an amount of 70~ or higher.
As a process for eliminating cracks in the cross-section of carbon fibers, it has been found that the use of spinning nozzles having a cross-sectional area of the outlet of the noz21es greater than the cross-sectional 2~ area of the narrowes-t part o the thin passage for spinning dope inside the nozzles, praferably having a ratio of the cross-sectiona-l area at tne outlet of the nozzle to that of the narrowest part of the thin passage for spinning dope inside the nozzles o two or greater as shown herein-after in the drawing o Figures 1, 2 and 3 and also the use of a spinning temperature higher than the softeningtemperature (as measured by Koka type flow tester) by 40 to 140C, preferably by 55~ - 120C in the melt-spinning, followed by usual treatments of thermosetting and carbonization provides filament yarns of carbon fiber which are excellent in quality and have no crack at all, and thus the process of the present invention has been completed.
Detailed description will be given as to the above mentioned spinning temperature. Although optimum spinning temperature somewhat varies depending on the mesophase content in the mesophase pitch and physical properties of mesophase, the results of ~ experimentS
show that, if spinning is carried out at a temperature which is not higher than the softening point of mesophase pitch by 40C, the viscosity of the mesophase pitch is too high for spinning resu~ting in poor spinnability.
On the other and if spinning is carried out at a temper-ature higher than the softening temperature of the 0 mesophase pitch by 140C or ~ore, the reduction of .s Viscoslty of mesophase ~ eh, increase of ~e~am~tLo~
of spinning nozzles, and change of properties of mesophase pitch occur, resulting in increase of breakaqe of spun filaments and sta~le spinning becomes difficult. Accord-ingly, it is proper to select a ~pinning temperatu.re in 3L2;~7~ S
the range of 40 to 140C, preferably 55 to 120C
higher than -the softening temperature of~ ~ mesophase.~; t' The softening temperature of mesophase~is in the range of 190C to 240C.
As for a raw material of mesophase pitch used in the process of the present invention, petroleum-origin heavy oil, such as topped crude (reduced C. or long residue), vacuum residue (short residue), residue of thermal catalytic cracking of vacuum gas oil, tar or pitch produced, as a by-product of heat treatment of these residues and a coal-origin heavy oil such as coal tar, coal tar pitch and a coal liquified product can be mentioned. Mesophase pitch can be produced by subjecting one or more of these raw materials to heat treatment under non-oxidative atmosphere l, to form mesophase, causing the resulting mesophase to grow by aging, and separating the part mostly consisting of mesophase.
The inventors of the present application have found that filaments of carbon fibers having superior qualities can be produced at an inexpensive price according to the process of the present invention if the content of mesophase in mesophase pitch is 70% or greater, preferably 90~ or higher. A mesophase pitch containing lower than 70~ mesophase, when suhjected to spinning according to an usual manner and then to thermosetting and carhonization, ~2~27~S
provides carbon ~iber filaments which do not form radial structure in cross-section due to its low degree of carbon orientation. Therefor, although no crack is formed, both tensile strength and modulus of resulting filaments are low, and the carbon fibers have little value as articles of commerce.
When mesophase pitch is used, as a ra~Y material of filament yarn of carbon fibers, the higher the mesophase content, the better the quality of the carbon fibers When mesophase pitch containing 70% or more, preferably 90% or more mesophase is melt-spun by causing velocity change to the flow of mesophase pitch inside the nozzles by using spinning nozzles having a cross-sectional area at their nozzle outlet part greater than that of the narrowest part of the passage way ~or spinning dope inside the nozzles, preEerably in a ratio of the areas of 2 or grater, filament yarns of car~on fibers free of crackes in the cross-section can be obtained.
BRIEF DESCRIPTION OF THE ~RAWING5 Figure 1 is a view of vertical cross-section through the center of one type of a nozzle oE this inven-tion. Figure 2 is also a vertical cross-section through the center of another type of nozzle. Figure 3 is also a vertical cross-section through the center of a further C~ fe.
ty~e of nozzle o~ thi~i invention. Fig~res~4 ~ 7 ~a-~
~iL227~5 _ g _ photograph~of a cross-section of the filament yarns of carbon fibers made by using the nozzle of the present invention and observed under a SEM. Figure 8 is a photo-graph o~ the cross-section of the filaments of carbon fibers made by using the nozzle of the referential example.
Examples o~ nozzle shapes of the spinnerettes used in the process of the present invention are illust-rated in the drawings. However, it is to be noted that the shape of the spinning nozzles used in the present invention should not be limited to tho-se shown in these drawings. Further, the cross-section of the nozzle should not be limited only to circular shape. It is only limited to the condition defined in the scope o~ claim.
In each drawings, 1 is an inlet part of spinning dope. 2 is narrowest tube part. 3 is an outlet part of extruding hole.
Following examples are offered by way of illust-ration and not by ~ay o~ limitation.
Example 1 A distillate fraction higher than 404C, as initial distilling point, o~ residue of thermal calalytic cracking o~ vacuum gas oil was su~ected to heat treatment at 420C for 2 hours while sending there methane gas and further to heating at 320C for 16 hours to cause mesophase to grow by aging and a part consisting mostly of mesophase ~iL2~ 3S
was separated. The mesophase content o~ this mesophase pitch was 91% according to the measurement under a reflection type polarizing microscope and the softening point (as measured by a Koka type flow tester) was 215C.
Using this mesophase pitch as a raw material, and using spinning nozzles shown in Figure l (having 100 extrusion holes i.e. passage ~or spinning dope, a diameter at the inlet part of spinning dope of 2.5 mm, a diameter at the narrowest thin tube part of 0.15 mm, the length of the narrowest thin tube part of 0.3 mm, an angle of cone expanding toward the outlet part of 90, a diameter at the outlet part of 0.3 mm), spinning was carried out at a spinning temperature of 300C, and a spinning velocity o 210 m/min Res~ltant filament yarns of pitch fibers were subjected to thermosetting at 300C and then to carboniza-tion at 2500C to procluce products. When the cross-section of these filaments of carbon fibers was observed under a scanning type electron microscope(SEM), it was found that ~ost O~
the structure of the cross-section thereof was of radial shape and there was no crac~ formed. Further, resultant filaments of carbon fibers had a tensile strength of 278 kg/mm2, a modulus of elasticity of 49 $tmm2 and an elongation of 0 57~.
Example 2 Using the mesophase pitch as u~ed in Example 1 ~22~70~5 as a raw material and using spinning nozzles of Figure L, (100 extrusion holes), in which the diameter of spinning dope introducing part is 2.5 mm~, the diameter of the thinnest tube part is 0.1 mm~, the length of the thinnest tube part is 0.1 mm, the cone angle of a frustum expanding toward outlet is 45, and the diameter of outlet part is 0.2 mm~, filament yarns of carbon fibe~s were produced by spinning at a spinning temperature of 307C and at a spinninq velocity of 500 m/min followed by other proces-sings in same manner as in Example 1. When the cross-s~ction of the resultant carbon fiber was observed with a scanning type electron microscope, it has an onion like structure in the cross-section as shown in Fig. 5, and no crack was found Exam~le 3 Using the mesophase pitch used as in Example 1 as a raw material, and using spinning nozzles of.Fi~ure 2 (100 extrusion holes) in which the diameter of spinning dope introducing part is 2.5 mm0, the diameter of the thinnest tu~e part is 0.1 mm~, the length of the thinnest tube part-is 0.1 mm.~t and the diameter ~t the outlet part ~ ,n/S~
is O . 25 mm~. (Expanding by fo;ming a ho~ u~, filame~t.
yarns of carbon fibers were ~roduced by sp.inning at a spinning tempe~ratur~ oE 280~C and a sDinning velocity of 180 mlmin_ followed by other processings in the same ~L22~
manner as in Example 1~ The representative cross-sectional structure of resultant carbon fibers was a mixture of radial, onion, and random patterns as shown in Figure 6.
There was found no crack at all.
Example 4 -100% Mesophase pitch having a so~tening point of 235~C was obtained after the same processing as in Example 1 except that longer time was necessary for sepa-rating the mesophase pitch. Using this pitch and nozzles as used in Example 2, filament y~rns of carbon fibers were produced by spinning at a spinning temperature of 304C
and a spinning velocity o~ 150 m/min. followed by other processings in the same manner as in Example 1. Represent-ative cross-sectional structuLe o resultant fibers was lS a mixture of radial and random patterns as shown in Figure 7. There was found no crack at all.
Comparative Example 1 Using a mesophase pitch as used in Example 1 as a raw material and using spinning nozzles having e~trusion holes, in which thin tube parts of the extrusion holes are o~ a straight tube having a diameter of 0.3 mm in cross-section and 0 3 mm in len~th and also having a diameter of 0 3 mm at the outlet part~ filament yarns of car~on Eibers were- produced under the same conditions for spinninq, tharmosetting and carbonization as in Example 1. When the ~L2270~)S
cross-section of the resultant filaments of carbon fibers was observed under a scanning type electron microscope, the structure of the cross-section of the filaments yarn of carbon fibers was of radial shape as shown in Figure 8 S but there were formed crac~s at an angle of about 90~. t Resultant filaments of carbon fibers had a tensile strength of 157 kg/mm a modulus of elasticity of 38 $/mm and an elongation of 0.41~.
Comparative ~xample 2 Using the mesophase pitch as used in Example 4 as a raw material, and using spinning nozzles having extrusion holes in which thin tube parts of the extrusion hole are of a straight tube having a cross-sectional diameter of 0.1 mm, a length of 0.1 mm and a diameter at lS the outlet being also 0.1 mm, filament yarns of carbon ~ibers were produced under the same condition for spinning, thermosetting and carbonization as in Example 4. Resultant filaments of carbon fibers had a structure of a radial pattern in cross-section as in Comparativ~ Example 1, and 20 cracks were formed.
Claims (8)
1. In a process for producing filament yarns of carbon fibers by melt-spinning, thermosetting and carbonization of a pitch, a process characterized by subjecting a pitch having a mesophase content of 70% or higher to melt-spin-ning using spinning nozzles having a cross-sectional area at their nozzle outlet part greater than the cross-sectional area at the narrowest part of their thin tube part inside the nozzles.
2. A process for producing filament yarns of carbon fibers according to claim 1; in which a pitch is subjected to melt spinning at a temperature higher than the softening point of the mesophase pitch by 55°C to 120°C.
3. A process for producing filament yarns of carbon fibers according to claim 1, in which raw material pitch is 100%
mesophase.
mesophase.
4. A process for producing filament yarns of carbon fibers according to claim 1, in which raw material pitch has a mesophase content lower than 100% but 70% or higher.
5. A process for producing filament yarns of carbon fibers according to claim 1 in which the resultant filament yarns have the structure of radial pattern in the cross-section.
6. A process for producing filament yarns of carbon fibers according to claim 1 in which the resultant filament yarns has a structure of random pattern in the cross-section.
7. A process for producing filament yarns of carbon fibers according to claim 1 in which the resultant filament yarns have a structure of onion-like pattern in the cross-section.
8. A process for producing filament yarns of carbon fibers according to claim 1 in which the resultant filament yarns have a structure of partly radial, partly radom, or partly onion pattern or a mixture of the above-mentioned patterns in the cross-section.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58209856A JPS60104528A (en) | 1983-11-10 | 1983-11-10 | Preparation of carbon fiber |
| JP209856/1983 | 1983-11-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1227005A true CA1227005A (en) | 1987-09-22 |
Family
ID=16579753
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000462682A Expired CA1227005A (en) | 1983-11-10 | 1984-09-07 | Process for producing carbon fibers |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS60104528A (en) |
| CA (1) | CA1227005A (en) |
| GB (1) | GB2150924B (en) |
| IT (1) | IT1208695B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60259631A (en) * | 1984-05-31 | 1985-12-21 | Mitsubishi Chem Ind Ltd | Production of pitch carbon fiber |
| JPS6134223A (en) * | 1984-07-24 | 1986-02-18 | Dainippon Ink & Chem Inc | Production of pitch based carbon fiber |
| JPS6241320A (en) * | 1985-08-16 | 1987-02-23 | Kashima Sekiyu Kk | Carbon yarn having section with wavy structure |
| JP2593654B2 (en) * | 1987-03-27 | 1997-03-26 | 正三 渡部 | Industrial production of high-strength and high-elastic carbon fiber knitted and woven fabrics |
| JPH0274618A (en) * | 1988-09-10 | 1990-03-14 | Teijin Seiki Co Ltd | Melt-spinning of high-performance pitch-base carbon fiber |
| DE102017216034A1 (en) * | 2017-09-12 | 2019-03-14 | Rheinisch-Westfälische Technische Hochschule (Rwth) Aachen | Nozzle for extruding an extrudate from an extrudate mass |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1526263A (en) * | 1967-04-13 | 1968-05-24 | Pechiney Saint Gobain | Improvement in dies intended for the extrusion of fibers of small sections |
| US4322027A (en) * | 1980-10-02 | 1982-03-30 | Crown Zellerbach Corporation | Filament draw nozzle |
| JPS59168127A (en) * | 1983-03-15 | 1984-09-21 | Toray Ind Inc | Production of carbon fiber |
-
1983
- 1983-11-10 JP JP58209856A patent/JPS60104528A/en active Granted
-
1984
- 1984-09-07 GB GB08422594A patent/GB2150924B/en not_active Expired
- 1984-09-07 CA CA000462682A patent/CA1227005A/en not_active Expired
- 1984-09-10 IT IT8448824A patent/IT1208695B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| GB2150924B (en) | 1987-10-21 |
| IT8448824A0 (en) | 1984-09-10 |
| JPH0144805B2 (en) | 1989-09-29 |
| JPS60104528A (en) | 1985-06-08 |
| GB8422594D0 (en) | 1984-10-10 |
| IT1208695B (en) | 1989-07-10 |
| GB2150924A (en) | 1985-07-10 |
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