Process for producing mesophase pitch

A mesophase pitch suitable for carbon products, particularly for carbon fibers, which has a mesophase content of at least 40%, preferably at least 60%, and a larger mesophase domain, is produced by adding at least one part by weight of at least one of an alcohol and a phenol to 100 parts by weight of heavy bitumens, subjecting the resulting mixture to pretreatment by heating at least at 250.degree. C., and then subjecting the pretreated mixture to heat treatment until mesophases are formed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for producing a mesophase pitch for 
high quality carbon products such as carbon fibers, needle-like pitch 
cokes, etc., and carbon products, particularly carbon fibers, produced 
from the mesophase pitch. 
2. Description of the Prior Art 
Carbon products such as carbon fibers, needle-like cokes or synthetic 
graphite electrodes made of the mesophase pitch as raw material have a 
graphite-like crystal structure, and thus have distinguished mechanical 
and electrical characteristics such as high Young's modulus, high 
electroconductivity, etc. 
According to the conventional process for producing carbon products from 
pitches, the softening point, molecular weight, etc. of a pitch are 
adjusted by heat treatment, extraction, etc. to give a raw material for 
carbon products. Thus prepared pitch is then molded into desired shapes, 
for example, fiber form, etc., and carbonized or graphitized. 
Generally, optically anisotropic portions called "mesophase" are formed in 
an optically isotropic pitch, as the pitch is heated, and the mesophase 
portions gradually increase in their proportion through repetition of 
their growth, agglomeration, and deformation. 
The mesophase has a liquid crystal structure in which planar condensed 
aromatic molecules are regularly oriented. Mesophase pitch having a high 
degree of orientation can be readily converted to graphite-like crystals 
by carbonization and graphitization, and thus carbon products having a 
well developed graphite-like structure can be obtained from such a 
mesophase pitch. 
On the other hand, the production of carbon products from a pitch requires 
a molding step, and thus the pitch must have a good moldability. To this 
end, the mesophase pitch must have a good flowability. 
For example, in the production of carbon fibers from a pitch, the degree of 
crystal size and the degree of crystal orientation in carbon fibers 
greatly depend on whether the condensed aromatic molecules in the pitch 
for carbon fibers can be oriented in the axial direction of fibers in the 
melt-spinning step or not. Thus, it can be said that the desirable pitch 
for the carbon fibers must be a mesophase pitch containing a group of 
regularly oriented condensed aromatic molecules and also must have a 
sufficient flowability. These are common requirements for all the raw 
material pitches for synthetic graphite products. 
Usually the condensed aromatic molecules grow larger and the content of 
mesophase becomes higher. The regularity and orientation are improved, but 
at the same time the softening point will become higher, resulting in a 
lower flowability and poorer workability. In the production of carbon 
fibers, the pitch having a substantially 100% mesophase content can hardly 
flow when subjected to melt-spinning. When the spinning temperature is 
elevated to obtain a sufficient flowability, the pitch will be partially 
decomposed or sometime coked. 
Thus, it has been so far desired in the production of a raw material pitch 
for carbon products to produce a mesophase pitch having a lower softening 
point, in other words, a pitch having a higher mesophase content, so long 
as the softening point is on the same level. In the case of a mesophase 
pitch having a good flowability, mesophase spherulites themselves can 
readily agglomerate mutually during heat treatment to give large domains 
or continuous mesophases can be developed. Solubility in a solvent such as 
quinoline, etc. is one of indices for evaluating the characteristics of 
the mesophase pitch. A mesophase pitch containing a quinoline-soluble 
mesophase has a lower melting point and a higher flowability, and thus has 
an advantage of easy melt-spinning for the production of carbon fibers. 
Thus, a mesophase pitch has been now regarded as the most desirable raw 
material for producing high performance carbon fibers, and studies of the 
processes have been so far extensively made. Some of the so far proposed 
processes for producing a mesophase pitch containing a quinoline-soluble 
mesophase are given below: 
U.S. Pat. No. 4,209,500 discloses production of a mesophase pitch having a 
substantially 100% mesophase content and containing a pyridine-soluble 
mesophase by passing an inert gas through a pitch heated and stirred at 
380.degree. to 430.degree. C., where a treatment time of 2 to 60 hours and 
a large amount of the inert gas are required. 
U.S. Pat. No. 4,208,267 discloses production of pitch portions, which can 
be readily converted to a mesophase pitch containing a quinoline-soluble 
mesophase by treating a pitch with a specific solvent, where the pitch 
portions are called neomesphase-forming fractions (NMF fractions), but the 
NMF fractions obtainable from the pitch are very small. 
U.S. Pat. No. 4,184,942 discloses an increased production of NMF fractions 
by heat-treating a pitch in advance, followed by separation of NMF 
fractions, where the heat treatment, solvent extraction, and further heat 
treatment must be carried out, resulting in complicating of the process. 
As described above, the prior art processes require a large amount of a 
special gas, or a specific solvent, or a complicated process or prolonged 
treatment time for producing a mesophase pitch containing a 
quinoline-soluble mesophase, and thus still have problems to be solved. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a process for producing a 
novel mesophase pitch free from the problems of the prior art processes. 
Another object of the present invention is to provide a process for 
producing a mesophase pitch having a mesophase content of at least 40%, a 
low softening point and an improved flowability. 
Another object of the present invention is to provide a mesophase pitch 
having a high quinoline-soluble mesophase content and large domains of 
mesophase. 
Still another object of the present invention is to provide carbon 
products, particularly carbon fibers, produced from the said mesophase 
pitch as a raw material. 
According to the present invention, a mesophase pitch having a mesophase 
content of at least 40% can be produced by adding at least one of an 
alcohol and a phenol to heavy bitumens, pretreating the resulting mixture 
by heating at a temperature of at least 250.degree. C. for at least 5 
minutes, and further by heat-treating the pretreated mixture until 
mesophases are formed.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be described in detail below. As a result of 
extensive studies on the production of a mesophase pitch for high 
performance carbon products which can overcome the said drawbacks of the 
prior art processes, the present inventors have found that a mesophase 
pitch suitable for higher performance carbon products can be obtained by 
adding at least one of an alcohol and a phenol to heavy bitumens, and 
pretreating the resulting mixture by heating, and further heat-treating 
the pretreated mixture, and have established the present invention. 
The term "mesophase" herein used refers to an optically anisotropic 
structure which can be determined by observing the polished surface of a 
cooled and solidified pitch by a polarization microscope. The mesophase 
content of the mesophase pitch refers to a proportion of the anisotropic 
structure thus determined. 
The function of an alcohol so far used in relation to the heavy bitumens 
has been nothing but that of an extracting agent for extracting an oil 
fraction as unsuitable matters for producing the carbon products from the 
heavy bitumens. A major portion or most of the heavy bitumens is insoluble 
in an alcohol, and the alcohol as a treating agent for the heavy bitumens 
for producing carbon products has not been taken into account at all. 
Furthermore, in the production of carbon products from the raw material 
heavy bitumens, it has been only known that oxygen, sulfur, etc. contained 
in the raw material will inhibit graphitization through a carbonizing step 
in the process for obtaining carbon products and that the reaction of 
heavy bitumens with an alcohol would add more oxygen to the bitumens, and 
thus is not regarded at all as a means for producing a raw material pitch 
for producing the carbon products in the conventional sense. 
Heretofore, the reaction of heavy bitumens with a phenol or successive heat 
treatment have not been studied at all. Phenols are contained in coal tar, 
coal-liquefied oil, etc. as raw materials for pitch. According to the 
conventional process for producing pitches as their heavy residues, 
phenols are removed in advance with a chemical such as caustic soda, etc., 
or stripped together with an oil fraction by distillation, and thus no 
phenols are contained in the pitches as the heavy residues. 
Pitches are used substantially as a raw material for carbon products, and 
the oxygen in the raw material has been regarded, together with sulfur, 
etc. as inhibiting matters for graphitization of carbon products. Thus, in 
the conventional production of pitches for carbon product, phenols are 
intentionally removed from the raw material heavy bitumens on this ground. 
According to an extreme case, a phenol-aldehyde resin which can be 
synthesized from phenol as one of raw materials is a typical raw material 
for non-graphitized carbon products [S. Ohtani and Y. Sanada: Tansoka 
KogaKu Kogaku-no Kiso (Foundation of Carbonizing Technology), published by 
Ohm Publishing Company, Tokyo (1980), page 117]. 
Thus, the reaction with a phenol and successive heat treatment have not 
been so far regarded at all as a means for producing a raw material for 
carbon products that require a graphite-like structure in the conventional 
sense. 
The present inventors have made extensive studies of reactions of heavy 
bitumens with various compounds contrary to the said conventional sense, 
and have found that a mesophase pitch having more distinguished properties 
and applicable as a raw material for producing carbon products than the 
pitch obtained by mere heat treatment of heavy bitumens can be produced by 
pretreating heavy bitumens with at least one of an alcohol and a phenol by 
heating, and heat-treating the pretreated mixture until mesophases are 
formed in the mixture. 
Heavy bitumens for use in the present invention includes, for example, coal 
tar, coal-liquefied heavy oil, petroleum-topping bottoms, petroleum 
cracking bottoms, and pitch fractions prepared from these oils and 
bottoms, and in view of the yield of pitch for the carbon products, the so 
called pitch fraction cut from the oil fractions is preferable. The pitch 
can be obtained by separating a portion or the whole of an oil fraction 
from coal tar, coal-liquefied oil, petroleum cracking bottoms, etc. 
containing the pitch matters, or also by converting heavy coal tar oil, 
etc. containing no pitch matters to a pitch. In any way, a pitch contains 
hydrocarbons having condensed aromatic rings as major components, and a 
pitch having a softening point of 0.degree. to 200.degree. C. is a 
preferable raw material. Particularly preferable is a coal tar pitch 
having a softening point of 30.degree. to 150.degree. C. 
The alcohol for use in the present invention includes compounds having an 
alcoholic hydroxyl group, for example, saturated alcohols such as 
methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, 
octanol, etc.; unsaturated alcohols such as allyl alcohol, etc.; 
halogenoalcohols such as ethylene chlorohydrin, etc.; polyhydric alchols 
such as ethylene glycol, diethylene glycol, triethylene glycol, glycerine, 
etc.; aminoalcohols such as ethanolamine, etc., and can be used alone or 
in a mixture thereof. For example, distillation bottoms of alcohol, etc. 
can be also used. 
The phenol for use in the present invention includes compounds having a 
phenolic hydroxyl group, for example, monohydric phenol such as phenol, 
cresol, xylenol, etc., dithydric phenols such as resorcinol, hydroquinone, 
etc.; polyhydric phenols such as hydroxyhydroquinone, etc., and can be 
used alone or in a mixture thereof. For example, distillation bottoms of 
phenol, etc., can be also used. 
At least one part by weight, preferably at least two parts by weight, more 
preferably at least 5 parts by weight of at least one of an alcohol and a 
phenol is added to 100 parts by weight of heavy bitumens. Hereinafter 
"parts by weight" will be referred to merely by "parts". Below one part, 
the softening point of the resulting mesophase pitch for the carbon 
products is less lowered, whereas, above 200 parts, there is no remarkable 
effect on lowering of the softening point. 
In the present invention, it is important to add at least one part of at 
least one of an alcohol and a phenol from the outside to 100 parts of 
heavy bitumens. FIG. 1 graphically shows the relationship between the 
amount of an alcohol or a phenol added to a coal tar pitch in the 
pretreatment and the softening point of the resulting mesophase pitches 
after the heat treatment. 
The pretreatment of heavy bitumens with at least one of an alcohol and a 
phenol is carried out by heating at a 250.degree. C. or higher, preferably 
in a range of 300.degree. to 550.degree. C. 
The pretreatment means a thermal reaction in which the heavy bitumens and 
at least one of an alcohol and a phenol take part. At a lower temperature 
than 250.degree. C., no thermal reaction proceeds, whereas at a higher 
temperature than 550.degree. C., the coking reaction of heavy bitumens 
vigorously proceeds. The pretreatment time depends on the heating 
temperature, and for less than 5 minutes the reaction does not proceed 
substantially, with less effect on the lowering of the softening point of 
mesophase pitch. For a prolonged pretreatment time, the coking reaction 
may be initiated due to the pretreatment at a higher temperature to the 
contrary, and no better effect will be obtained on the lowering of the 
softening point. Thus, the pretreatment time of up to about 5 hours will 
be enough. 
In the pretreatment, it is necessary to seal an alcohol or a phenol in the 
heavy bitumens, and thus the pretreatment is carried out under a higher 
pressure than the autogeneous pressure of the alcohol or the phenol. When 
the boiling point of an alcohol or a phenol is low, the pressure may often 
exceed its critical point. 
The effects of the pretreatment are given below: 
Mesophases are formed in the heavy bitumens by heat-treating the pretreated 
mixture of the heavy bitumens and at least one of an alcohol and a phenol. 
As the heat treatment is intensified, the proportion of mesophases is 
increased, resulting in ultimate coking. With increasing mesophase 
content, the softening point of mesophase pitch will be elevated. As shown 
in FIG. 1, the softening point of mesophase pitch obtained from the coal 
tar pitch pretreated with an alcohol or a phenol by pretreatment is a few 
to a few tens .degree. C. lower than that of the mesophase pitch obtained 
from the coal tar pitch prepared without the pretreatment if the mesophase 
content is on the same level. This suggests that the mesophase pitches 
obtained in this invention have a higher flowability. 
Observation through a polarization microscope of a microstructure of 
mesophase pitches having continuous mesophases, obtained by pretreatment 
of at least one of an alcohol and a phenol and also without the 
pretreatment, reveals, as shown in FIGS. 2 to 9, that the mesophases 
obtained from the heavy bitumens pretreated by at least one of an alcohol 
and a phenol has larger domains than those of the mesophase obtained 
without the pretreatment, if the mesophase content is on the same level, 
that is, has less defects in lamination of planar condensed aromatic 
molecular layers. 
It is obvious from the foregoing that the mesophase pitch obtained 
according to the present invention has a higher flowability than the 
mesophase pitch obtained from the heavy bitumens without the pretreatment 
with at least one of an alcohol and a phenol, that is, only by the heat 
treatment. 
Details of mechanism of the pretreatment of heavy bitumens with at least 
one of an alcohol and a phenol have not been clarified yet. However, it 
has been found that the following products have been formed when an 
alcohol was added to the heavy bitumens. That is, proton nuclear magnetic 
resonance ('H-NMR) spectra of the oil fraction from coal tar pitch 
pretreated with isopropanol reveals that a peak formation characteristic 
of acetone at .delta. value of 2.1 ppm, which is not contained in the raw 
material coal tar pitch, is observable. According to infrared (IR) spectra 
of an oil fraction from the coal tar pitch pretreated with n-butanol or 
sec-butanol, peaks of carbonyls, which are not contained in the raw 
material coal tar pitch, appear at about 1640 cm.sup.-1 and about 1700 
cm.sup.-1. Thus, it seems that the hydrogen is transferred from the 
alcohol to the coal tar pitch, while the alcohol itself is converted to a 
carbonyl compound, but as is obvious also from the said example of 
isopropanol, the carbonyl can be formed from only a small amount of the 
added alcohol, while a considerable amount of the alcohol remains as such 
in the pitch. It also seems that the thermal reaction of pitch becomes 
peculiar in the presence of an alcohol. Details of the mechanism thus has 
not been clarified yet. 
Said effects obtained by pretreatment of heavy bitumens with a phenol seem 
to be due to the fact that the thermal reaction of heavy bitumens is made 
peculiar by the addition of a phenol thereto, but the details of reaction 
mechanism have not been clarified yet, either. 
Lowering of the softening point of the mesophase pitch obtained by 
pretreatment of heavy bitumens with at least one of an alcohol and a 
phenol and by successive heat treatment depends on the amount of at least 
one of the alcohol and phenol added. In FIG. 1, changes in softening 
points of mesophase pitches are plotted against the amount of the 
isopropanol or phenol added for pretreating the coal tar pitch. In this 
case, pretreatment conditions are set with varied amounts of isopropanol 
or phenol at 320.degree. C. or 375.degree. C., 90 minutes, under the 
autogeneous pressure. Then, the pretreated pitches are heat-treated at 
various temperatures under various pressures for various periods of time. 
Thus, the mesophase pitches having various mesophase contents are 
obtained. These softening points are closely related to mesophase contents 
in range of 10-90%. Thus, the softening points of mesophase pitch having 
70% mesophase contents are determined and the softening points are plotted 
against the amount of the isopropanol or phenol added for pretreating the 
coal tar pitch. It is obvious from FIG. 1 that the softening point can be 
considerably lowered by adding even a small amount of an alcohol or a 
phenol for pretreatment. 
The effects of lowering the softening point of a mesophase pitch are 
remarkable in the production of carbon fibers from the mesophase pitch. 
Pitch-based carbon fibers are produced at first by melt-spinning the 
mesophase pitch, and usually spinning of the mesophase pitch is carried 
out at a temperature 20.degree. to 60.degree. C. higher than the softening 
point. At a higher spinning temperature, a portion of the pitch undergoes 
thermal decomposition, resulting in gas generation or coking. Thus, the 
spinning temperature itself has an upper limit, which is about 380.degree. 
to about 400.degree. C. On the other hand, it is said that the carbon 
fibers produced from the mesophase pitch can be distinguished in physical 
properties such as modulus of elasticity, etc., only when the mesophase 
pitch for spinning has a higher mesophase content, for example, 40% or 
higher, preferably 60% or higher. 
Even if the heavy bitumens are heat-treated according to the present 
invention until a higher mesophase content is obtained, the softening 
point can be made lower by a few to a few tens .degree. C. than that of 
the heavy bitumens without the pretreatment with at least one of an 
alcohol and a phenol. This means that the mesophase pitch having even a 
higher mesophase content can be spun satisfactorily into carbon fibers, 
and thus the present invention is very advantageous for producing high 
quality carbon fibers. To obtain such effects, it is desirable to add at 
least one part, preferably at least two parts, more preferably at least 
five parts of at least one of an alcohol and a phenol to 100 parts of the 
heavy bitumens, and conduct pretreatment of the resulting mixture by 
heating. The pretreatment is desirably carried out under pressure for at 
least 5 minutes, as described before. 
In the pretreatment, the softening point of a mesophase pitch, or lowering 
of the lowering of pretreatment temperature, shortening of reaction time, 
and reduction in the amount of at least one of an alcohol and a phenol can 
be attained by adding 0.01 to 5 parts of a basic substance such as caustic 
alkali, alkali carbonate, tar bases, etc. to 100 parts of heavy bitumens. 
For example, when 100 parts of isopropanol were added to 100 parts of coal 
tar pitch, and one part of caustic potassium was added thereto as a basic 
substance, and when the pretreatment was carried out at 320.degree. C. 
under pressure for 90 minutes and an oil fraction was removed therefrom by 
distillation after the pretreatment, it was found by 'H-NMR spectrum 
measurement of the oil fraction that acetone was formed in an amount about 
3 times as large as that obtained when no basic substance was added, and 
also it was found that the mesophase pitch obtained by successive heat 
treatment had a softening point about 20.degree. C. lower than that of the 
mesophase pitch obtained by the pretreatment without the basic substance 
and by the successive heat treatment under the same conditions. 
After the pretreatment of heavy bitumens, a mesophase pitch having a 
mesophase content of at least 40% can be obtained by successive heat 
treatment. The successive heat treatment for mesophase formation can be 
carried out according to the conventional procedure, for example, by 
heating at 350.degree. to 500.degree. C. under reduced pressure, by 
heating at 350.degree. to 500.degree. C. with blowing of an inert gas, or 
by heating under the atmospheric pressure, followed by conducting 
distillation under reduced pressure or blowing of an inert gas to remove 
an oil fraction therefrom and to increase the mesophase content. In any 
heat treatment procedure, those skilled in the art can readily determine, 
through easy experiments, conditions for producing a mesophase pitch 
having a desired mesophase content for carbon products, such as heat 
treatment temperature, heat treatment time, degree of pressure reduction, 
amount of inert gas, etc. A typical mesophase pitch can be obtained by 
heat treatment at 400.degree. C. or higher under a pressure of 50 Torr or 
lower. 
It is preferable to remove low boiling components such as unreacted alcohol 
or phenol or formed aldehydes, ketones and so on from the pretreated heavy 
bitumens before the heat treatment. The removal can be carried out by 
distillation, settling, centrifuge, etc. However, the heat treatment is 
usually carried out at an elevated temperature under the atmospheric 
pressure or reduced pressure, or together with blowing of an inert gas, 
and thus the formed low boiling components can be removed spontaneously 
without any intentional separation in advance. Thus, the pretreated heavy 
bitumens can be transferred from the pretreatment directly to the heat 
treatment for mesophase formation. An alcohol is less soluble in the heavy 
bitumens, and can undergo phase separation only by settling the pretreated 
mixture. Thus, it is convenient to remove the alcohol therefrom by the 
settling. A phenol has a large difference in boiling point from the heavy 
bitumens, and thus it is preferable to remove the phenol therefrom by 
distillation. 
Quinoline-insoluble matters in the heavy bitumens usually lower the quality 
of mesophase pitch for carbon products. Particularly in the case of carbon 
fibers, the presence of quinoline-insoluble matters is not preferable, 
because they may clog spinning nozzles during the spinning. It may be 
sometimes necessary to remove the quinoline-insoluble matters from the raw 
material heavy bitumens also in the present invention, depending on the 
end use. Such removal can be carried out, before or after the pretreatment 
with at least one of an alcohol and a phenol, according to the 
conventional procedures, for example, by solvent extraction using 
quinoline or other solvents, melt filtration, centrifuge, etc. 
High quality carbon products such as carbon fibers, needle-like pitch 
cokes, etc. can be produced from the present mesophase pitch according to 
the conventional procedures. For example, carbon fibers or graphitized 
fibers can be produced by melt-spinning the present mesophase pitch at a 
temperature 20.degree. to 60.degree. C. higher than the softening point, 
thermosetting the spun fibers in an atmosphere of air or oxygen, etc., and 
then heating the fibers at 1,000.degree. to 2,000.degree. C. in an inert 
atmosphere, or successively at 2,000.degree. to 3,000.degree. C. 
The present mesophase pitch has a lower melting point in contrast to the 
higher mesophase content, and thus can be melt-spun at a lower spinning 
temperature, and thus high quality carbon fibers can be readily and stably 
produced from the present mesophase pitch without coking. 
PREFERRED EMBODIMENTS OF THE INVENTION 
The present invention will be described in detail below, referring to 
Examples, Comparative Examples, and Drawings, where the ratio of materials 
is expressed in parts and percentages are by weight, unless otherwise 
mentioned. 
EXAMPLE 1 
100 parts of coal tar pitch (A) having a softening point of 82.degree. C., 
11% toluene insolubles (T1) and 0% quinoline-insolubles (QI) and 50 parts 
of isopropanol were charged into an autoclave, and subjected to 
pretreatment by heating at 320.degree. C. for 90 minutes after the air in 
the autoclave was replaced with a nitrogen gas and the autoclave was 
tightly sealed. The pretreatment pressure was 80 kg/cm.sup.2 gage. 
After the pretreatment, the resulting pretreated mixture was cooled, and a 
supernatant containing unreacted isopropanol was removed thereform by 
decantation. 
The pitch residue was then taken into a test tube, and subjected to heat 
treatment by heating at 450.degree. C. under 4 Torr in a nitrogen 
atmosphere for 15 minutes to obtain a mesophase pitch. A picture of the 
mesophase pitch, taken through a polarization microscope, is shown in FIG. 
2. It is seen that the mesophase domains are larger than those of FIG. 6. 
COMATIVE EXAMPLE 1 
Coal tar pitch (A) was taken into test tubes without pretreatment and 
subjected directly to heat treatment under the same conditions as in 
Example 1, except that the heat treatment time was changed variously to 
obtain mesophase pitches having various mesophase contents. FIG. 6 shows 
the picture of mesophase pitch having about the same mesophase content as 
that of Example 1 as shown in FIG. 2. 
EXAMPLE 2 
100 parts of coal tar pitch (B) having a softening point of 82.degree. C., 
11% toluene insolubles and 0% quinolineinsolubles and 50 parts of phenol 
were charged into an autoclave, and subjected to pretreatment by heating 
at 375.degree. C. for 90 minutes after the air in the autoclave was 
replaced with a nitrogen gas and the autoclave was tightly sealed. The 
pretreatment pressure was 20 kg/cm.sup.2 gage. 
After the pretreatment, an oil fraction was removed from the resulting 
mixture by distillation at 300.degree. C. under 10 Torr. 
Then, the pitch residue was then taken into a test tube, and subjected to 
heat treatment by heating at 450.degree. C. under 4 Torr in a nitrogen 
atomosphere for 15 minutes to obtain a mesophase pitch. A picture of the 
mesophase pitch, taken through a polarization microscope, is shown in FIG. 
3. It is seen that the mesophase domains are larger than those of FIG. 7. 
COMATIVE EXAMPLE 2 
Coal tar pitch (B) was taken into test tubes without pretreatment and 
subjected directly to heat treatment under the same conditions as in 
Example 2, except that the heat treatment time was changed variously to 
obtain mesophase pitches having various mesophase contents. FIG. 7 shows 
the picture of mesophase pitch having about the same mesophase content as 
that of Example 2 as shown in FIG. 3. 
EXAMPLE 3 
Coal tar soft pitch (C) having a softening point of 36.degree. C., 11% TI 
and 5% QI was filtered with heating to obtain a pitch having a softening 
point of 36.degree. C., 11% TI and a trace of QI. 
Then, 100 parts of the filtered pitch and 200 parts of isopropyl alcohol 
were charged into an autoclave, and subjected to pretreatment by heating 
at 335.degree. C. for 90 minutes after the air in the autoclave was 
replaced with a nitrogen gas and the autoclave was tightly sealed. The 
pretreatment pressure was 131 kg/cm.sup.2 gage. 
After the pretreatment, an oil supernatant containing unreacted isopropyl 
alcohol was separated from the resulting mixture by decantation. 
Then, the pitch residue was taken into a test tube, and subjected to heat 
treatment by heating at 470.degree. C. under 10 Torr in a nitrogen 
atmosphere for 15 minutes to obtain a mesophase pitch. After cooling, the 
surface of the mesophase pitch was polished and observed by a polarization 
microscope. The surface was as shown in FIG. 4 and it is seen therefrom 
that the mesophase domains are larger than those of FIG. 8. 
COMATIVE EXAMPLE 3 
The same filtered coal tar soft pitch as used in Example 3 was taken into a 
test tube without the pretreatment, and subjected to heat treatment by 
heating at 470.degree. C. under 10 Torr in a nitrogen atmosphere for 15 
minutes, but coked. Thus, the heat treatment temperature was changed to 
450.degree. C., and the same soft pitch as above was subjected to heat 
treatment by heating at 450.degree. C. under 10 Torr in a nitrogen 
atmosphere, except that the heat treatment time was changed variously, to 
obtain mesophase pitches having various mesophase contents. The surfaces 
of the thus obtained mesophase pitches were polished and observed by a 
polarization microscope. FIG. 8 shows one example thereof, which has about 
the same mesophase content as that of the mesophase pitch of Example 3. 
EXAMPLE 4 
100 parts of petroleum pitch (D) having a softening point of 120.degree. 
C., 5.5% benzene insolubles, a trace of QI, a specific gravity of 1.185 
and 0.1% ashes and 50 parts of sec-butanol were charged into an autoclave, 
and subjected to pretreatment by heating at 430.degree. C. for 30 minutes 
after the air in the autoclave was replaced with a nitrogen gas and the 
autoclave was tightly sealed. The pretreatment pressure was 170 
kg/cm.sup.2 gage. 
After the pretreatment, an oil fraction containing unreacted sec-butanol 
was removed from the resulting mixture by distillation at 300.degree. C. 
under 35 Torr, whereby a pitch having a softening point of 116.degree. C., 
4.8% TI, and a trace of QI was obtained. 
Then, the pitch was taken into a test tube, and subjected to heat treatment 
by heating at 470.degree. C. under 10 Torr in a nitrogen atmosphere for 20 
minutes to obtain a mesophase pitch. The surface of the mesophase pitch 
was polished and observed by a polarization microscope, as given in FIG. 
5. It is seen that the mesophase domains are larger than those of FIG. 9. 
COMATIVE EXAMPLE 4 
The same petroleum pitch (D) as used in Example 4 was taken into a test 
tube without the pretreatment, and subjected to heat treatment by heating 
at 470.degree. C. under 10 Torr in a nitrogen atmosphere for 20 minutes, 
but coked. Mesophase pitch could be obtained by heat treatment under the 
same conditions as above, except that the heat treatment time was changed 
to 15 minutes. The surface of the thus obtained mesophase pitch was 
polished and observed by a polarization microscope, as given in FIG. 9. 
EXAMPLE 5 
100 parts of coal tar pitch (A) having a softening point of 82.degree. C., 
11% TI and 0% QI and 50 parts of isopropanol were charged into an 
autoclave and subjected to pretreatment by heating at 320.degree. C. for 
90 minutes after the air in the autoclave was replaced with a nitrogen gas 
and the autoclave was tightly sealed. The pretreatment pressure was 77 
kg/cm.sup.2 gage. 
After the pretreatment, the resulting mixture was cooled, and a supernatant 
containing unreacted isopropanol was removed therefrom by decantation. 
Then, the resulting pitch residue was taken into a flask, and subjected to 
heat treatment by heating at 470.degree. C. under 6 Torr in a nitrogen 
atmosphere for 6 minutes to obtain a mesophase pitch. Yield of the 
mesophase pitch on the basis of the raw material coal tar pitch was 12%, 
and the mesophase pitch had a softening point of 330.degree. C. and a 
mesophase content of 92%. 
Then, the mesophase pitch was heated at 385.degree. C. and extruded through 
a nozzle, 0.5 mm in diameter, and wound onto a bobbin, whereby a pitch 
fiber having a diameter of 9 .mu.m was obtained. 
Then, the pitch fiber was thermoset in a hot air, and then heat-treated in 
an argon atmosphere at 2,500.degree. C., and the resulting graphitized 
fiber had a Young's modulus as high as 45 Ton/mm.sup.2. 
EXAMPLE 6 
100 parts of the same coal tar pitch as used in Example 5, 2 parts of 
sec-butanol and 0.02 parts of caustic potash were charged into an 
autoclave, and subjected to pretreatment by heating at 450.degree. C. for 
20 minutes after the air in the autoclave was replaced with a nitrogen 
gas, and the autoclave was tightly sealed. The pretreatment pressure was 6 
kg/cm.sup.2 gage. 
After the pretreatment and cooling, the resulting mixture was taken 
directly into a flask without removal of the oil fraction, and subjected 
to heat treatment by heating at 470.degree. C. under 4 Torr in a nitrogen 
atmosphere for 3 minutes to obtain a mesophase pitch. The mesophase pitch 
had a yield of 15% on the basis of the raw material coal tar pitch, a 
softening point of 308.degree. C. and a mesophase content of 78%. 
Then, the mesophase pitch was heated at 360.degree. C., extruded from a 
nozzle, 0.5 mm in diameter, and wound onto a bobin, whereby a pitch fiber 
having a diameter of 11 .mu.m was obtained. 
COMATIVE EXAMPLE 5 
The same coal tar pitch as used in Example 5 was treated under the same 
conditions as in Examples 5 and 6 without the addition of the alcohols. 
The mesophase pitch obtained in the same conditions as in Example 5 had a 
softening point of more than 400.degree. C. and a substantially 100% 
mesophase content. 
Under the same conditions as in Example 6, coking took place during the 
heat treatment. Thus, mesophase pitches were produced at a heat treatment 
temperature of 450.degree. under 4 Torr in a nitrogen atmosphere, while 
changing the heat treatment time variously. The thus obtained mesophase 
pitches having the approximately same mesophase contents as those of 
Examples 5 and 6, that is, 92% and 78%, respectively, had softening points 
of 385.degree. C. and 375.degree. C., respectively, and both could not be 
spun into fibers. 
EXAMPLE 7 
100 parts of the same coal tar pitch (B) as used in Example 2, and 100 
parts of phenol were charged into an autoclave and subjected to 
pretreatment by heating at 375.degree. C. for 90 minutes, after the air in 
the autoclave was replaced with a nitrogen atmosphere and the autoclave 
was tightly sealed. The pretreatment pressure was 23 kg/cm.sup.2 gage. 
After the pretreatment, the resulting mixture was distilled at 300.degree. 
C. under 10 Torr to remove an oil fraction therefrom, and a pretreated 
pitch was obtained thereby. 
The pretreated pitch was subjected to heat treatment by heating at 
470.degree. C. under 6 Torr in a nitrogen atmosphere for 8 minutes to 
obtain a mesophase pitch. The mesophase pitch had a yield of 9% on the 
basis of the raw material coal tar pitch, a softening point of 353.degree. 
C. and a substantially 100% mesophase content. 
Then, the mesophase pitch was heated at 380.degree. C., extruded through a 
nozzle, 0.5 mm in diameter, and wound onto a bobin, whereby a pitch fiber 
having a diameter of 12 .mu.m was obtained. 
The pitch fiber was thermoset in a hot air and then heat-treated in an 
argon atmosphere at 2,500.degree. C. and the resulting graphitized fiber 
had a Young's modulus as high as 47 Ton/mm.sup.2. 
EXAMPLE 8 
100 parts of the same coal tar pitch (B) as used in Example 2, 5 parts of 
cresol and 0.05 parts of caustic potah were charged into an autoclave, and 
subjected to pretreatment by heating at 320.degree. C. for 20 minutes, 
after the air in the autoclave was replaced with a nitrogen gas, and the 
autoclave was tightly sealed. The pretreatment pressure was 8 kg/cm.sup.2 
gage. 
After the pretreatment, the pretreated mixture was cooled and taken 
directly into a flask without removal of an oil fraction and subjected to 
heat treatment by heating at 470.degree. C. under 4 Torr in a nitrogen 
atmosphere for 5 minutes to obtain a mesophase pitch. The mesophase pitch 
had a yield of 10% on the basis of raw material coal tar pitch, a 
softening point of 330.degree. C. and a mesophase content of 80%. 
Then, the mesophase pitch was heated at 375.degree. C., extruded through a 
nozzle, 0.5 mm in diameter, and wound onto a bobbin, whereby a pitch fiber 
having a diameter of 10 .mu.m was obtained. 
The pitch fiber was thermoset in a hot air, and then heat treated in an 
argon atmosphere at 2,500.degree. C., and the resulting graphitized fiber 
had a Young's modulus as high as 40 Ton/mm.sup.2. 
COMATIVE EXAMPLE 6 
The same coal tar pitch (B) as used in Example 2 was heat-treated under the 
same conditions as in Examples 7 and 8 without pretreatment with phenol 
and cresol. Under the conditions of Example 7, coking took place during 
the heat treatment. Under the conditions of Example 8, the resulting 
mesophase pitch had a softening point of 384.degree. C. and a mesophase 
content of 90%. Then, mesophase pitches were produced by heat treatment by 
heating at 450.degree. C. under 4 Torr in a nitrogen atmosphere while 
changing the heat treatment time variously. The thus produced mesophase 
pitches having the same mesophase contents as in Examples 7 and 8, that 
is, 100% and 80%, respectively, had softening points of 395.degree. C. and 
372.degree. C., respectively, and both could not been spun into fibers. 
EXAMPLE 9 
The same coal tar pitch as used in Example 6 was pretreated under the same 
conditions as in Example 6, except that no caustic potash was added, and 
the pretreated mixture was subjected to heat treatment under the same 
conditions as in Example 6 without removal of the oil fraction to obtain a 
mesophase pitch. The mesophase pitch had a softening point of 332.degree. 
C., which was by 24.degree. C. higher than that of Example 6. 
As described in detail above, the present invention provides a process for 
producing a mesophase pitch for high performance carbon products by adding 
at least one of an alcohol and a phenol to heavy bitumens, and conducting 
pretreatment of the resulting mixture by heating, and then conducting heat 
treatment of the resulting pretreated mixture, and also provides carbon 
products, particularly carbon fibers produced from such a mesophase pitch. 
Thus, the present invention has a great industrial significance.