JPS5936724A - Pitch composition of raw material for carbon fiber - Google Patents

Abstract

PURPOSE:The titled pitch composition, consisting of a quinoline-soluble optically isotropic pitch, having specified values of average molecular weight of structural nunits, number of condensed rings and specific gravity, and capable of giving carbon fibers having a high strength and modulus. CONSTITUTION:A pitch composition which is an optically isotropic pitch, substantially 100% soluble in quinoline, consisting essentially of a polycyclic aromatic condensate, and having 200-400 average molecular weight of the structural units measured by the mass spectrometry (MS), 2-6 number of condensed rings and within 1.25-1.31 specific gravity range at 20 deg.C. Preferably, the pitch contains carbon (A) having 129-2,150ppm chemical shift, carbon (B) having 980- 129ppm chemical shift and carbon (C) having 13-53ppm chemical shift based on the TMS in the 13C-NMR respectively in the following ratios: 15-25%, 55-65% and 10-20%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to pitch compositions useful as raw materials for the production of carbon fibers. More specifically, high temperature heat treatment - melt spinning -
Through a series of steps including infusibility treatment and carbonization treatment, a new pitch composition that can form a core fiber with high strength and high modulus that could not be achieved with conventional pitch yarn carbon fibers. relating to things.

Currently, carbon fibers mainly produced include PAN-based carbon fibers made from polyacrynitrile (PAN) fa fibers and pitch-based carbon fibers made from carbon-based or petroleum-based pitches.

However, high-strength, high-modulus, high-performance carbon fiber, which is mainly used as a reinforcing material for resins in composite materials, is PA.
N-based materials are the mainstream, and only pitch-based products with a relatively low strength of 200)C9/- or less are manufactured.

Attempts have been made to produce pitch-based carbon fibers with higher performance, and the following proposals have been made so far regarding the production of pitch for carbon fiber production.

(-) A method of hydrogen-treating or heat-treating a specific condensed polycyclic aromatic compound to produce pitch for carbon fibers (equity [45-
No. 28013 2% Publication No. 49-8634).

(b) A method in which a first heat treatment is performed in the presence of a petroleum-based tar or a pinch of Lewis acid catalyst, and then the catalyst is removed and a second heat treatment is performed to produce membrane face pitch (Japanese Patent Publication No. 53 -7533).

(c) A method of heating pitch under a flow of inert gas or under reduced pressure to produce mesophase pitch with a predetermined mesophase content (%1 Jllili No. 53-86717,
JP-A No. 53-86718).

(d) A method of treating optically isotropic pitch with a solvent (benzene, thormone, beptane, etc.) and heating the insoluble part to form neomesophase (Japanese Patent Application Laid-Open No. 54-16042
7. % Open Show 55-58287゜ JP Open Show 55-13080
No. 9),.

However, even with these methods, carbon with advanced performance comparable to PAN-based carbon fiber! Since pitch-based carbon fibers cannot be obtained, up to now, pitch-based carbon fibers have been used in fields where low strength is required, such as asbestos substitutes. In addition, among the above methods, the method using a membrane pitch has poor spinnability (melt spinning at an economical spinning speed is difficult) because the viscosity of the pitch used as the spinning stock solution is very high. There is also a manufacturing problem.

In view of the above-mentioned current situation in the production of pitch-based carbon fibers, the present inventors have conducted extensive research to develop a method for producing A fibers of excellent quality using pitches as raw materials. 1WPI is converted into an optically anisotropic menses at the infusibility/carbonization step after spinning! We would like to propose a new method for manufacturing carbon fibers using a pre-methoface pitch of 4.0 (Publication No. 56-117470), K.K.

C%' (No. 80670/1983) proposed a method suitable for industrially producing such pre-methoface pitch.

Further, as a result of intensive research on pitch compositions capable of forming high-performance pitch-based carbon Ii fibers, the present inventors found that optical fibers soluble in the inclusionary K100% Kirin, which is the raw material for the Primesoface pitch, were found. The chemical structure and properties of isotropic pitch are particularly important, and the basic structure of the polycyclic condensed compound at this stage is carried into the spinning dope as it is, improving spinnability at the spinning stage and carbonization stage. It is important that the average molecular weight, number of condensed rings, specific gravity, etc. of the structural units of this Zoo chiquinoline soluble optically isotropic pitch are within specific ranges (among them, Those with specific chemical shifts in lac-NMR, 'H-NMR, etc., and whose aromatization degree and H/C value fall within specific ranges) are particularly useful as raw material pitch for high-performance carbon fibers. This is what we have discovered and arrived at the present invention.

That is, the present invention provides an optically isotropic pitch which is substantially 100% quinoline soluble and which is used as a raw material for carbon fibers and has a structural unit average molecular weight of 200 to 400 as measured by mass spectrometry (MS). , number of fused rings 2-6
This pitch composition is mainly composed of a polycyclic aromatic condensate, and has a specific gravity of 1.25 to 1.31 at 20°C.

In general, high-performance carbon fiber spinning pitch needs to have both molecular orientation to the extent that it can be oriented during the spinning process, and high molecular properties and fluidity to form threads. With conventional technology,
Attempts have been made to produce high-performance carbon: A#R fiber by placing emphasis on molecular orientation and using so-called membrane as a pitch for spinning.

However, when attempting to impart polymeric properties to conventional membrane pitch, fluidity and spinnability deteriorate, making spinning operations difficult. In addition, carbon fibers produced using such menface pitch as a spinning dope tend to have huge foliate domains in the carbon fiber precursor pitch fibers due to their highly developed orientation, resulting in a change in the structure of the final fiber. It is easy to cause a decrease in strength due to radial formation and vertical cracking of the fibers. This has led to the conventional efforts to produce carbon fibers comparable to PAN-based carbon fibers using pitch as a raw material. This is thought to be one of the reasons why it does not appear.

As a result of research, the present inventors have developed a raw material to produce a spinning pitch that has moderately lower molecular orientation than conventional spinning pitch, and has a well-balanced molecular orientation, polymeric properties, and fluidity. In the process of heat-treating pitch to adjust spinning pitch with a higher molecular weight, the basic structural units of the raw material pitch do not change significantly, and the basic structure of the pitch before heat treatment is brought into the spinning pitch. It was confirmed that this had an effect on the production of the final fiber.

In addition, the pitch before cape/treatment has a lower softening point and higher solubility in solvents than pitch for spinning. Therefore, removal of foreign substances such as free carbon, which is another factor that adversely affects the performance of carbon fibers, can be carried out much more efficiently and rigorously with the pitch before heat treatment.

From this point of view, unexploded sieves are essentially IO before heat treatment.
By focusing on the optically bulky pitch that is soluble in chiquinoline and controlling the chemical structure and properties of this pitch, we can improve the spinnability in the subsequent spinning process and further improve the properties of the final carbon fiber. 1412 is also improved.

By the way, according to the research of the present inventors, as mentioned above, it is necessary to slightly reduce the molecular orientation of the spinning pinch, and also to achieve a well-balanced balance between fluidity and polymer properties. It is effective to introduce into the pitch a hydrogenated structure that maintains the fused carbon ring structure and does not significantly reduce aromaticity. Such pitch has a chemical structure in which the nucleus is hydrogenated by m, and it is thought that the planarity of the molecule is appropriately distorted without destroying the basic carbon skeleton. In other words, it is most effective to control the molecular weight, degree of aromatization, and flatness of one molecule of pitch before heat treatment to an appropriate range.

The pitch composition of the present invention is based on this new finding, and first of all, the pitch composition of the present invention shows that substantially gold is soluble in quinoline. This is necessary in order to effectively remove foreign substances such as free carbon. In addition, quinoline-soluble pitches are pitches whose molecular weights are uniform to a certain extent, and are essential because they can be made into homogeneous pitches for spinning by subsequent heat treatment.

Furthermore, the pitch composition of the present invention can be analyzed by mass spectrometry analysis (
#1 structure average molecular weight measured by MS) is 200-400
It is mainly composed of a polycyclic aromatic condensate having 2 to 6 condensed rings. These are necessary to easily polymerize to an appropriate degree of polymerization by heat treatment and maintain fluidity. Therefore, if these values are l''\ than the above range, polymerizability during heat treatment will be lacking, while if it exceeds the above range, excessive polymerization will occur during heat treatment, resulting in spinning pitch lacking fluidity. only is formed.

In addition, the pitch composition of the present invention has a specific gravity in the range of 1.25 to 1.31 at 20°C. Here, the specific gravity is 1r18, which eliminates a pinch of aromaticity, and those with a specific gravity in the above range have aromaticity, but have appropriate distortion in the planarity of their molecules, and moderate molecular orientation. At the same time, it imparts fluidity to the pitch with increased molecular weight after heat treatment. If the specific gravity is less than 1.25, the aromaticity of the heat-treated spinning pitch becomes too low, and the development of molecular planarity (orientation) during the subsequent carbonization (#) process and the occurrence of molecular flatness (orientation) during the spinning process. Problems arise with potential orientation and pinch thermal stability. On the other hand, when the specific gravity exceeds 1.31, the fluidity of the pitch after heat treatment deteriorates, and orientation tends to develop to a high degree during the spinning process, which is not preferable.

The pitch composition of the present invention preferably satisfies the above conditions and also has the following chemical shift in nuclear magnetic resonance spectroscopy such as "C-NMR" and "H-NMR." That is, (in 1118C-NMR, the chemical shift based on TM11! is 129-1504 carbon A content... 15-25
Carbon B content of %80-129p%...55-6
5% 13~53 charcoal gc content...10~2
A preferred temperature is 0 tfb. What satisfies this condition is a pitch characteristic that favorably distorts molecular orientation. In other words, this pinch prepares a suitably distorted planarity in the pitch for spinning, and preferably lowers the molecular orientation. ■Because it has a fairly high aromaticity, it is also quite stable thermally and maintains its condensed ring structure even after heat treatment. (2) Since the aromatic nucleus is partially hydrogenated (rich in active hydrogen), a desirable increase in molecular weight occurs during heat treatment, but fluidity is maintained. In addition, even in systems where menface coexists, the compatibility with menface is good, and the spinnability is good.Furthermore, during the infusibility treatment, the partially hydrogenated area is quickly oxidized, and the infusibility treatment can be carried out efficiently. (2) The spinning pitch produced by heat treatment recovers molecular flatness during the carbonization (firing) process following spinning, and develops good crystallinity and orientation.

(In 21'H-NMR, the chemical shift based on TMS is 5-10-hydrogen HA...40-80%1.7
~4pP hydrogen HB...15-401%)
That's preferable. In addition, hydrogen Hc with a chemical shift of 1.1 to 1.7 ppm...5% or less (
Particularly preferably 3% or less) 0.3 to 1.1 pp of hydrogen HD...5 or less (
Particularly preferably 1tI6 or less).

In addition, hydrogen HE with the same chemical shift of 2.5 to 3 pIm...8 to 11%3 to
Hydrogen for 4 fermentations ■...8-17% Hydrogen for 1.7-2+2 ferments HG...5-7 H is suitable, and in addition to the above conditions, 5-7 pplI hydrogen HX1...6~15q6
is particularly preferable. This HH is considered to be hydrogen derived from a double bond, and indicates that the aromatic nucleus is partially hydrogenated.

Those that satisfy the conditions specified by these H-NMR measurement values have considerably high aromaticity, and therefore can be used as spinning pitches with latent orientation, and also have a fused ring structure. Due to its partially hydrogenated structure (containing active hydrogen), subsequent heat treatment results in a spinning pitch that maintains good fluidity despite having a favorable molecular weight. Since the amount is small, it has the advantage of preventing excessive polymerization and development of orientation during heat treatment.

(3) the degree of aromatization is within the range of 0.3 to 0.5;
And it is preferable that H/C is within the range of 0.55 to 0.8. This means that the aromatic nucleus is in a particularly favorable state of partial hydrogenation.

Next, the average molecular weight of the structural unit in the present invention.

Aromatization degree, 'H-NMR, 13C-NMR, H/
The method for measuring C@ will be explained.

(1) Structural unit average molecular weight Measured by mass spectrometry (MS). For MS, a JEOL JMS-D300 spectrometer was used as the device, and a ridge method was used as the ionization method.

(2) Aromatization degree KBr Infrared absorbance analysis (I) measured by tablet method
R), it is calculated by the following formula.

Aromatization degree - 3050cut-" strength / (3050cm-" strength +
2925fi-' intensity) The IR measuring device used is the IR-27G model manufactured by Shimadzu Corporation.

(3) Testing 1 A JEOL PS-too'5 spectrometer was used as a measuring device, and the chemical shift was expressed as a γ value using TMS as an internal standard.

The NMR spectra were measured using CDC (S).

(4) Diεzu'1 A JEOL FIGS-100 type spectrometer was used as a measuring device, and the chemical shift was expressed as a γ value using TMS as an internal standard.

NMR spectra were measured using CDCl3 as a solvent (・, gated coupling non-NOE mode, <7 seconds of Luss repetition time.

(51H/C Calculated according to the following formula from elemental analysis measured according to JIS M-8813.

)1/C=(H analysis value/l)/(c analysis value/12) The pitch composition of the present invention having various characteristics as described above,
This is filtered to remove free carbon and the like, and then heat treated to form a polymer while maintaining the special basic structure of the polycyclic condensed compound.

The heat treatment is preferably terminated when the quinoline-soluble component is contained in a small amount (at least 30%, preferably 50 to 70%), and those heat-treated to this stage have good spinnability.Heat treatment can be carried out under reduced pressure, or can be carried out under normal pressure after removing the solvent contained in the composition.

The pitch composition of the present invention is produced by processing raw material pitch and then hydrogenating it using a specific hydrogenation solvent. However, it cannot be produced by a method that involves a membrane phase, such as the conventionally known neo-mesophase or dormant mesophase. □ Next, the pitch composition of the present invention is made from the raw pitch,
Further, an example in which this is heat-treated to produce pitch for spinning will be specifically explained. Raw material pitches include coal-based heavy oils such as coal cool, coal tar pitch, and coal liquefied petroleum, atmospheric residual oil from petroleum, vacuum distillation residual oil, and tar, pitch, and oil sand produced as by-products of heat treatment of these residual oils. .

Although petroleum-based heavy oils such as bitumen can be used, coal tar pinch is preferred because it facilitates the production of the pitch composition of the present invention.

The pitch composition of the present invention is produced by refining the commercially available raw material pitch and then subjecting it to a first stage treatment by heating it in a specific hydrogenation solvent. Next, pitch for spinning is produced by performing a second stage treatment of heating the solvent to a high temperature after or while removing the solvent, if any.

As the hydrogenation solvent used in the first stage treatment, tetrahydroquinoline (hereinafter abbreviated as THQ) is most suitable.
A mixture of quinoline and THQ may also be used;
Heat with hydrogen at 340-450° C. for 10-60 minutes in the presence of a catalyst (cobalt-molybdenum based, iron oxide based).

The product thus treated is subjected to the next second stage treatment.

In the second stage treatment, the THQ treatment pitch is 450°C or higher, preferably 45°C, under reduced pressure, e.g., a pressure of 50mM9 or lower.
Hold at 0-550°C for 5-60 minutes. In this case, instead of such a reduced pressure treatment, after THQ is removed, the temperature may be 450 to 550 at normal pressure.

The pitch composition of the present invention was applied to the #41 stage treatment in JP-A No. 5
No. 9-36724 (6) can be easily manufactured by appropriately selecting the processing conditions within the above range depending on the composition and properties of the raw material pinch.

The spinning pitch obtained by heat-treating the pitch composition of the present invention as described above has appropriate viscoelastic properties at the spinning temperature and has extremely good melt spinnability.

Melt spinning can be performed by a method known per se.

For example, the pinch composition of the present invention is extruded from a spinneret having spinning holes with a diameter of 0.1 to 0.8 fins at a temperature 50 to 100°C higher than the softening point, and the filament discharged from the spinneret is spun (taken up) at a speed of It can be easily made into fibers by winding at 300 to 150 o@/min. The obtained pitch fibers were then heated to 250-350°C in the presence of WI element at a heating rate of 3°C/min and maintained for 5-30 minutes to make them infusible. is further heated to 1000 to 1500° C. at a heating rate of 2 to b in an inert gas, and carbonized by maintaining this temperature for 10 to 30 minutes.

The carbon fibers made from the pitch composition of the present invention become completely oriented during the carbonization process, forming carbon fibers with a dense structure that is fully oriented and does not contain large domains.

The obtained carbon fiber has a high strength of 200 to 9/- or more and to
It has a modulus of ton/- or more, and has extremely excellent performance.

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

In addition, the fiber diameter (thread diameter) of the carbon fiber in each example.

Tensile strength, elongation rate, and modulus are JI8 Xt 760
Measured according to 1 "Carbon Fiber Test Method".

Note that the fiber diameter was measured using a helium-neon laser.

Example-1 It coal tar medium pitch 134g and THQ 402g
8US-:116 equipped with an electromagnetic induction rotating stirring device.
After replacing the autoclave sufficiently with oxygen, the internal pressure was set to Okf/asiG, and after sealing it, the autoclave was heated to 43℃ while stirring.
After increasing the temperature to G"C and reaching 430℃,
It was maintained for a minute.

Thereafter, the mixture was cooled to room temperature, stirring was stopped, and the contents were taken out. The undissolved contents were removed from the contents using A4 qualitative paper under reduced pressure using a water jet and a 7-filter filter. The mother liquor thus obtained was
A pitch for carbon fiber spinning was prepared by heat treatment in a 90'C10sn+Torr atmosphere, and carbon fibers were obtained by spinning, infusibility, and sintering, and the physical properties were investigated.

As a result, the average molecular weight of the structural unit measured by M8 of the raw pitch composition was 23G, and it was thought that the number of condensed rings was 4 to 5. The specific gravity at 20°C measured using water as a medium is 1.257, and the specific gravity of a pinch in commercially available coal tar is 1.257.
．． 284, indicating a decrease in aromaticity.

In order to investigate this situation in more detail, we used "C-NMR."

``H-NMR, IR, and elemental analysis were conducted.

Measured using CDCj as a solvent, good decoupling, non-NOE mode, and pulse repetition time of 7 seconds (abbreviated as gated ■ method).1-C-NMR results, chemical shift based on tetramethylsilane (TMS). 129-1
The proportions of carbon A appearing at 50% m, carbon B appearing at 80-129M, and carbon C appearing at 13-53 furnace are A -20.5% and B = respectively, relative to the total detected carbon excluding the solvent.
58.6 inches, C=17.6%, pitch A-35.8%, B-55.3 days in commercially available coal tar.

When compared with C=8.0'%, the total of tertiary aromatic carbon and olefinic carbon hardly changes due to T 11 Q treatment, while quaternary aromatic carbon slightly increases and aliphatic carbon increases. It was obvious that he was doing this.

Furthermore, IH-NMR measured using CDCj as a solvent
As a result, HA-a 3.1%, n, -a 1.1
%.

Hc-3,5%, HD-0,9%, HG-5,8%, H
, -9,2%, HF-t 2.8%, HH-11,2
%Met,.

This is HA-88.5% pitch in commercially available coal tar.
, HB = 9.6%, If(= 1.6%
+ Hl) ” O% e HG-0,8chi, HF,
HB, HG, which correspond to various naphthene hydrogens,
HT! ,, HF and 'Hc, which corresponds to side chain hydrogen, increase significantly while
, it is shown that the increase in HD is small. These data indicate that pitch in commercially available coal tar has a special structure in which aromatic rings are partially hydrogenated while maintaining the polycyclic condensed skeleton. This special S structure exerts a strain on the molecular planarity and increases pitch mobility, and the strain is easily repaired by dehydrogenation occurring during the carbonization (firing) process. It is thought that there are.

In addition, the degree of aromatization was calculated from the IR measured by the KBr molding method using the following formula (% formula %), and from the elemental analysis measured according to JIBM-8813, the following formula: HlC-(H analysis value, "-1)/(C The HIC values determined according to analysis value/12) were 0.43 and 0.70, respectively.These aromatization degrees and HIC values indicate a still high degree of aromatization for a hydrogenated pitch. , demonstrating the possibility of facile planar structure restoration through effective hydrogenation and carbonization (calcination) processes.

The raw pitch composition was heated at 465°C and 10 Torr T1.
The mixture was heat-treated under stirring in a nitrogen atmosphere for 5 minutes to obtain pitch for carbon fiber spinning. The spinning pitch is approximately 1 at 330°C.
It becomes a homogeneous liquid with a viscosity of 000 poise.

The spinning pitch was put into a cylinder equipped with a constant-speed descending plunger, and after sufficient defoaming, it was discharged at 370°C and heated to 100°C.
It was wound with a fast wave of 01 rL/min, and the pitch was set to +k Ha. The pitch fibers are heated at 200°C to 300°C in an air stream.
After heat treatment at a heating rate of 2°C/min until
The carbon fibers were heat treated at 0''C for 15 minutes to make them infusible fibers, and then carbonized (fired) in a nitrogen stream for 15 minutes at 1500C to make carbon fibers.The carbon fibers had a thread diameter of 8.5μ.

It had a strength of 2 sakg/-, a modulus of 16 ton/-, and an elongation of 1.5%.

The physical properties of carbon fiber made by directly applying the same treatment to commercially available coal tar pitch are as follows: strength: 75 kg/mtA;
The modulus was as low as 4 tons/-.

Comparative Example-1 Pinch 10'Op' in the same commercially available coal tar as used in Example-1 was charged into a glass three-lough flask equipped with a stirrer, and after heat treatment at normal pressure of 400°C in a nitrogen stream for 10 hours,
Take out and add 65III to 1 part by weight of the heat treated pinch.
After reduction at 80 to 90° C. with metal lithium in an amount equal to the weight of the skeleton pitch in dehydrated ethylene diamine (T), neutralization was performed by a conventional method, water washing and filtration were repeated to obtain hydrogenated coal tar pitch. A part of the hydrogenated pitch was sampled, and Example-
The remaining fibers were subjected to the same analysis as in Example 1, and the remaining fibers were heat-treated to make pitch for spinning, then made into carbon fibers according to Example 1, and their physical properties were measured.

As a result, the specific gravity of the hydrogenated pinch was greatly reduced to 1,147, and the aromatization g, H/C was also 0.17.
．． 0.99, indicating a significant decrease in aromaticity.

Also, from "C-NMR and 'H-NMR, A='5.
8%, B=13.3%, C=77.8%, HA=
15.8%, HB=46.8%, Hc-19.7%
, HD= 11.7%, HG= 17.4 q6.
HE= 10.7 factor, HF= 11.0%, HH
= 7.6%. Such data shows that the polycyclic fused skeleton is considerably destroyed, and the aromatic ring is not only partially hydrogenated,
Indicates complete hydrogenation. The molecular planarity of pitch with such a structure cannot be restored by simple dehydrogenation (also, it is thermally unstable), so it is difficult to restore the molecular planarity of pitch by simple dehydrogenation. molecular chain scission,
It is thought that low-molecular substances are likely to be produced, and there is a high possibility that defects in carbon fibers will increase. The hydrogenated pitch was heat-treated in a N2 stream at normal pressure at 400° C. for 1 hour with stirring to obtain pitch for spinning, and then made into carbon fiber according to Example 1 and its physical properties were measured. As a result, the yarn diameter was 9 times, the strength was 150 kg/-, and the modulus was 1 o ton/-.

Comparative Example 2 Commercially available petroleum pitch (manufactured by Ashland) 409 was placed in a glass three-loaf flask with stirring roots, heat treated at 430'C for 5.5 hours in a nitrogen stream at normal pressure, and then taken out. The pitch was reduced in 65 ml of dehydrated ethylenediamine at 80-90'C with an equal weight part of metallic lithium to the heat-treated pitch, neutralized by a conventional method, washed with water, and filtered repeatedly to obtain a hydrogenated pitch.

A part of the hydrogenated pitch was sampled and analyzed in the same manner as in Example-1, and the rest was heat-treated to make pitch for spinning, and then made into carbon fiber according to Example-1, and its physical properties were measured.

As a result, the specific gravity of the hydrogenated pitch is as small as 1.10, and the degree of aromatization and H/C are also 0. Ql.

1.14, indicating a significant decrease in aromaticity.

Also, from '3C-NMR and 'H-NMR, A = 5
．． 3%.

B=12.7%, e-78.9%, H person=1 3. s%.

HB= 45.5%, Hc= 22.6%, HD=
13.4%.

HG=18.5%, HE=9.7%, HF=9.
1%"11=4.2%. The data show that the polycyclic condensed ring skeleton was considerably destroyed and the aromatic ring was not only partially hydrogenated but completely hydrogenated. .

Pitch with a curved structure cannot be restored to its molecular planarity by simple dehydrogenation, and is thermally unstable, so it cannot be used when preparing pitch for spinning or infusible.

It is thought that the heat applied during firing tends to cause molecular chain scission and generation of low-molecular substances, and there is a high possibility that defects in carbon fibers will increase.

The hydrogenated pitch was heated at normal pressure and 400°C in a N2 stream.

After heat treatment with stirring for 1 hour to prepare pitch for spinning, Example-
The physical properties of carbon fiber were measured according to 1.

As a result, the thread diameter was 9 layers and the strength was 140 kg/d.

The modulus was 10.5 tons/-.

Comparative Example 3 Two ounces of commercially available petroleum pinch (manufactured by A4hland) were placed in a three-hole glass flask equipped with a stirrer, and after heat treatment at 400'C in a nitrogen stream for 1 hour, the same weight of tetrahydrofuran (THp) as the crushed hindlimb heat-treated pitch was taken out. ) and stirred for 1 hour at room temperature in a nitrogen stream. After that,
The solution was filtered with N and pressure filter using S4 qualitative F paper and a gold cloth to remove insoluble matter. (To the f solution obtained, T
Four times the amount of toluene relative to HFK was added under stirring in a nitrogen stream, and stirring was continued for 1 hour. The precipitate was collected by filtering it through a pitchy G-4 glass filter, and then dried by conventional methods. A part of the solvent-fractionated pitch was sampled and analyzed in the same manner as in Example-1, and the remainder was heat-treated to make pitch for spinning, and then made into carbon fiber according to Example-1, and its physical properties were measured.

As a result, the specific gravity of the solvent fractionated pitch was 1.289, and the degree of aromatization and H/C were 0.4 a and 0.4 o, respectively.
, e 4 Tea Tsuta. Also, 'sC-NMR1 and 'H-
From NMR, A = t 5.7 (11, B = 42.3
%, C = 40.7%, 1 (A-56,5%, H,
= 35.9%, Hc = 4.1%, HD = 1.7%
, HQ= 5.0chi, HE= Article 13.4, HF
= 4.7%, HH = 3.0%. These data indicate that it is composed of highly developed aromatic polycyclic condensed rings and has excellent molecular planarity.

The pitch of such a structure gives a highly developed mesophase during the preparative heat treatment to the spinning pinch, which is likely to form giant lobe-like domains in the carbon fiber and cause longitudinal cracks in the yarn. it is conceivable that.

The solvent fractionation pinch was heated in a N2 stream at normal pressure at 440°C for 15 minutes.
Example 1: Heat treated with stirring for minutes to prepare pitch for spinning.
Carbon fibers were prepared according to IK, and the physical properties were measured. As a result, some yarns were found to have vertical cracks, and the strength was 150 to 1.
00 kg/d.

The modulus varied in the range of 8 to 1 ston/-.

Comparative Example-4 200 g of pitch in the same commercially available coal tar as used in Example-1 was charged into a glass three-lough flask equipped with a stirrer.
After heat treatment in a nitrogen stream at normal pressure and 400° C. for 1 hour, the sample was taken out and subjected to solvent fractionation in accordance with Comparative Example 3 to obtain a solvent fractionated pitch.

A part of the solvent fractionation pitch was sampled and Example-1
The remaining fibers were subjected to the same analysis as above, and the remaining fibers were heat-treated and used as pitch for spinning, and then made into carbon fibers according to Example 1, and their physical properties were measured.

As a result, the specific gravity of the solvent fractionated pitch was 1.335, and the degree of aromatization and H/'C were 0.71 and 0.71, respectively.
55, indicating extremely high aromaticity. or,"
C-NMR, "A port 31.6% from H-NMR, B = 5
7.7%, C=8.8%, I(A-76,0%, 'H
B=17.5%, Hc-3,3fD, HD! 3.4
%, H, = 0.6%l H, = 4.8%,
H, -3.8%.

It was HH-1%. These data indicate that the polycyclic fused ring skeleton is well-developed and consists mostly of aromatic rings.

Pitch with such a structure is considered to have good molecular bending properties, and it gives a highly developed membrane during the heat treatment to prepare the carbon fiber for spinning. It is thought that this forms a huge foliate domain, which causes vertical cracks in the thread.

The solvent was separated at normal pressure, 450°C, and 1
After heat-treating for 0 minutes to prepare pitch for spinning, carbon fibers were prepared according to Example 1, and physical properties were measured. As a result, 1M in the thread
Cracks were observed, and the strength was 150-1 (10kg7 ma
The r modulus varied in the range kIII from 8 to 12 tons/-.

Comparative Example-5 The same commercially available coal tar pitch used in Onagare 1-1 was treated with quinoline m'91 (, PilA) to remove foreign substances and highly developed carbides in the pitch,
Then, quinoline was distilled off to obtain a quinoline-soluble component in pitch in coal tar. A part of the quinoline-soluble pitch was sampled and analyzed in the same manner as in Example-1, and the rest was heat-treated to make pitch for spinning, and then carbon fibers were produced according to Example-1.

As a result, the specific gravity of the quinoline-soluble pitch was 1.341, and the degree of aromatization and H/C were each 0.66° and 0.55, indicating high aromaticity. Also, “C-NMR, 1
From H-NMR, A -35.8%, B≠55.3%,
c = s, o 嗟, HA = 8 s, s tl
D, HB-9.6%, Ho=1.6%, HD=
O%, HG=0.8%.

HE=3.7%, HF=-2.7%, HH=1.9
%Met.

These data indicate that polycyclic fused rings are well developed and that the fused rings consist mostly of aromatic rings. Pitch with such a structure is considered to already have good molecular planarity, and in the heat treatment of 11 to form pitch for spinning, it gives a highly developed membrane surface, which creates giant leaf-like structures in the carbon fiber. It is thought that this forms domains and causes longitudinal cracks in the yarn.

The 1,000N soluble pitch was mixed with N in a stream of air while stirring.

It was heat-treated at 400° C. for 420 minutes at normal pressure to obtain pitch for spinning. Pitch for cough spinning was extremely easy to separate into a high viscosity part consisting of mesofaces and a low viscosity part mainly consisting of non-mesofaces, and it was extremely difficult to prepare pitch fibers according to Example 1. As a result of infusibility and firing of a small amount of barely obtained pitch fibers, longitudinal cracks were observed in the carbon fibers, and the strength varied from 80 to 140 kg/-* and the modulus varied from 7 to 1 ston/-.

Comparative Example-6 A part of the petroleum pitch obtained from FCC decant oil was sampled and analyzed in the same manner as in Example-1.The rest was heat treated and used as pitch for spinning.The buds were made into carbon fibers according to Example-1. It was created.

The specific gravity of the petroleum pitch was 1.241, and the degree of aromatization and H/C were 9.37° and 0.72, respectively. This compared to the pitch of the present invention, the degree of aromatization and H
/C is similar, but the specific gravity shows a considerably small value, suggesting the development of side chains substituting in the multi-fJit condensed ring. Also, “C-NMR.

``H-NMR yo''; l Meta-seeking h = t 4.6%
, n −, a 1.1 h, C-43, 3%, H=
54.89”t HB= 35.6%.

HD-4,6%, HD-1,8%, HG-3,7
%, H,=13.2%, H,=6.4%, H
, = 2.3chi.

Such data also indicate the development of polycyclic fused rings and short side chains replacing them. It also seems to have essentially good molecular planarity.

Pitch with such a structure has thermally unstable side chains that are cut during heat treatment to prepare pitch for spinning, which triggers a highly developed membrane surface, but tends to produce low-molecular components due to cutting. It is thought that this tends to lead to vertical cracking of carbon fibers due to highly developed membranes, phase separation of spinning pitch due to lack of compatibility between membranes and low molecular weight components, and lack of spinnability. . In the petroleum-based pinch N2 stream, under stirring and at normal pressure, at 400°C, too
It was heat treated and used as spinning pitch. The spinning pinch is
It is very easy to separate into a high viscosity part consisting of mesoface and a low viscosity part mainly consisting of non-mesophase.
It was extremely difficult to create pitch fibers according to Example 1. By reducing the winding speed to 300 m/7 min, the small amount of pitch fibers barely obtained was made infusible and fired. As a result, longitudinal cracks were observed in the carbon fibers, and the strength was 80 to 14.
s kg/-.

The modulus varied in the range of 7 to 14 tons/-.

Patent applicant: Director of the Agency of Industrial Science and Technology Makoto Ishizaka − Designated agent Director of Kyushu Industrial Technology Laboratory Hayashi Tei -

Claims (1)

[Scope of Claims] 1. An optically isotropic pitch that is substantially xoo% quinoline soluble and that is
) is mainly composed of a polycyclic aromatic condensate having 2 to 6 condensed rings, with an average molecular weight of the structural unit measured by 200 to 400, and the pitch has a specific gravity of 1.25 to 1.25 at 20°C.
A carbon fiber raw material pitch composition characterized in that the pitch is 1.31. 2. In C-NMR, chemical shift of 129-150 ppm carbon A based on tetramethylsilane (TMS) relative to all detected carbons excluding solvent, 80-1
29 ppm carbon B and 13-53 ppm carbon C
The proportions of A-15 to 25% and B = 55 to 65, respectively.
The pitch composition according to claim 1, wherein H and C=10 to 20%. 3. In 'H-NMR, the ratio of hydrogen HA with a chemical shift of 5 to 10 ppm and hydrogen HB of 1.7 to 4 ppm based on tetramethylsilane (TMs) relative to all detected hydrogen excluding the solvent is , respectively HA=40-80%,
The pitch composition according to claim 1 or 2, wherein HB=15 to 40 inches. 4. The chemical shift) The proportions of hydrogen H6 of 1.1 to 1.7 p- and water 1AHD of 0.3 to 1.11116 are Ho- = 0 to 5%,) ID = O to 5%, respectively.
The pitch composition according to claim 1, 2g4 or 3. 5. In 1H-NMR, the chemical shifts based on tetramethylsilane (TMS) with respect to all detected hydrogen excluding the solvent are hydrogen HIc of 2.5 to 3, hydrogen H1 of 3 to 4, and hydrogen H1 of 1.7 to 2. The proportion of hydrogen H6 at 2 mA is respectively H
The pitch composition according to claim 3 or 4, wherein H = 5 to 7%, H = 8 to 11%, H = 8 to 17%. 6. In 'H-NMR, the proportion of hydrogen HH with a chemical shift of 5 to 7111 m based on tetramethylsilane (TMS) to all detected hydrogen excluding the solvent is 6 to 15%. The pitch composition according to any one of Item 5. 7. The pitch according to any one of claims 1 to 6, having a degree of aromatization of 0.3 to 0.5 and a H/C of 0.55 to 0.8. Composition.