JPH04154888A - Mesophase pitch having ultra-low softening point and low viscosity, its production and production of high-strength and high-modulus carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the subject pitch capable of performing stable spinning or molding in high carbonizing yield and a low cost containing a large amount of optically anisotropic phase by removing an organic solvent-insoluble part from a polymer of condensed polycyclic hydrocarbon, etc., and separating by using a specific gravity difference. CONSTITUTION:Condensed polycyclic hydrocarbon or a substance containing the hydrocarbon is polymerized in the presence of hydrogen fluoride-boron trifluoride at 200-400 deg.C under 5-100atm to obtain a pitch. Then, said pitch is subjected to solvent-extracting treatment to remove an organic solvent-insoluble part composed of aromatic hydrocarbon having >=10.0 solubility parameter, a nitrogen-containing six-membered heterocyclic compound or a mixture thereof as principal components, then subjected to separation by a specific gravity difference to afford the objective pitch having <=220 deg.C softening point, <=100 poise viscosity at 250 deg.C and >=1000 average molecular weight and containing >=90wt.% optically anisotropic phase.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention generally relates to a technology for producing carbon fibers and other carbon materials having high strength and high modulus of elasticity. ,
An ultra-low softening point, low viscosity mesophase pitch containing 90% or more of an optically anisotropic phase obtained by polymerizing a condensed polycyclic hydrocarbon such as anthracene, a method for producing the same, and use of the mesophase pitch The present invention relates to a method for producing carbon fibers with high strength and high modulus.

In recent years, low-cost, high-performance carbon fibers that constitute lightweight, high-strength, and high-elastic composite materials have been used in aircraft, automobiles, construction, and various other industrial fields. There is a strong demand for high-strength, high-density moldable carbon materials that can be molded and used for various purposes.

Conventionally, PAN-based carbon fibers made from polyacrylonitrile have been widely used as carbon fibers with high strength and high modulus of elasticity, but they have the problems of expensive raw materials and poor carbonization yields. are doing.

On the other hand, research and development of carbon fibers or moldable carbon materials using petroleum-based pitch or coal-based pitch as raw materials has been actively conducted in recent years because the raw materials are cheaper and the carbonization yield is better. It is being done.

For example, to obtain carbon fibers with high strength and high modulus from carbonaceous raw material pitch such as petroleum pitch or coal pitch,
It is known that it is necessary to obtain a mesophase pitch in which the optically anisotropic phase is substantially 100%.

For example, Japanese Patent Application Laid-Open No. 54-55625 discloses a mesophase phase in which the optically anisotropic phase is substantially 100% by carrying out long-term thermal decomposition polycondensation using a combination of inert gas bubbling and stirring. A method for obtaining pitch is also disclosed in Japanese Patent Application Laid-Open No. 54-1
Publication No. 60427 discloses a method for obtaining mesophase pitch having substantially 100% optically anisotropic phase by a solvent extraction method. However, the mesophase pitch for pitch-based carbon fibers obtained by these methods had a high softening point of 330° C. or higher.

On the other hand, Japanese Patent Publication No. 61-38755 discloses a method in which a pitch containing an optically anisotropic phase is produced by heat-treating the raw material pitch, and then a specific gravity separation is performed, whereby the optically anisotropic phase is substantially removed. Discloses a method for obtaining a mesophase pitch that is generally 100%.

According to this method, the softening point is about 230 to 320°C, and the softening point is about 230 to 320°C.
Compared to the mesophase pitch for pitch-based carbon fibers as described in Publication No. 160427, a mesophase pitch with substantially 100% optically anisotropic phase having an extremely low softening point can be obtained. Therefore, 280~
It has the advantage that it can be stably spun at a spinning temperature of 380°C.

Recently, as the commercial demand for carbon fibers or carbon materials for molding has increased, carbon fibers with better carbonization yields and lower costs are needed.
Furthermore, it is desired to develop a mesophase pitch with a lower softening point and lower viscosity so that it can be spun or molded more stably.

In order to meet this demand, we polymerized condensed polycyclic hydrocarbons such as naphthalene in the presence of hydrogen fluoride (HF) and boron trifluoride (BF3) to contain substantially 100% optically anisotropic phase. Mitsubishi Gas Chemical Co., Ltd. has proposed a method for producing menphase pitch (Japanese Patent Application Laid-open No. 1-139621, Japanese Patent Application Laid-open No. 1-254796, Japanese Patent Application No. 1-30
9482).

The mesophase pitch containing substantially 100% of the optically anisotropic phase produced by the method described in JP-A-1-139621 is more infusible than conventional coal- and petroleum-based mesophase pitches. Good properties (, carbonization yield,
Furthermore, the mesophase pitch obtained by this method, which has 100% optically anisotropic phase, has a softening point of 180 to 4, according to the values in the above publication.
00°C (200°C according to the measurement method in this specification, which will be explained later)
~420°C), usually 200 to 240°C (220 to 260°C according to the measurement method herein described later),
Compared to conventional mesophase pitch, the spinning temperature can be lowered, spinning is easier, and high-strength carbon fibers can be obtained by firing.

However, if a mesophase pitch with a lower softening point and lower viscosity can be obtained, spinning and molding at even lower temperatures will be possible.
] capability to produce carbon fiber and other carbon materials at low cost.
This will be a breakthrough for stable production.

Therefore, an object of the present invention is to produce carbon fibers and other carbon materials with low yI, which can be spun and molded at low temperatures.
Moreover, stable production is possible! The objective is to provide mesophase big with ultra-low softening point and low viscosity.

Another object of the present invention is to polymerize a condensed polycyclic hydrocarbon such as naphthalene or a substance containing the same in the presence of hydrogen fluoride or boron trifluoride to produce carbon fibers with high strength and high elastic modulus. is a method for producing the ultra-low softening point, low-viscosity mesophase pitch containing 90% or more of an optically anisotropic phase, which can be suitably used for producing a high-strength, high-density carbon material for molding. The goal is to provide the following.

Still another object of the present invention is to provide a method for producing carbon fibers with high strength and high elastic modulus using the ultra-low softening point and low viscosity mesophase pitch.

In the process of further research and development of mesophase pitch obtained by polymerizing condensed polycyclic hydrocarbons such as naphthalene, which has excellent properties as described above, the present inventors It has been found that by further lowering the softening point and viscosity, it is possible to perform shaping such as spinning and molding at even lower temperatures, and to realize low-cost and stable production of carbon + A materials such as carbon fibers.

In other words, in order to lower the softening point and viscosity of mesophase pitch obtained by polymerizing condensed polycyclic hydrocarbons such as naphthalene, whether in catalytic polymerization or thermal polymerization, generally lowering the reaction temperature, decreasing the amount of catalyst, etc. to reduce the degree of polymerization (
However, in this case, the optically anisotropic phase is not generated, or even if it is generated, it is only in a very small amount, so it is virtually impossible to create a mesophase pitch containing 90% or more of the optically anisotropic phase. It's impossible.

The present inventors used such naphthalene-based pitch etc. as a raw material, and in order to obtain an ultra-low softening point, low viscosity mesophase pitch containing an optically anisotropic phase of 90% or more,
As a result of intensive study of the molecular structure, molecular weight distribution, association characteristics, etc. of pitch, we found that pitch with the following characteristics can achieve an ultra-low softening point and low viscosity.

In other words, in order to be a mesophase pitch with an ultra-low softening point and low viscosity, (1) the molecular structure must contain many side chain alkyl groups, naphthene rings, etc.

(2) In terms of molecular weight distribution, it should not contain high molecular weight components (components with a molecular weight of several thousand or more).

(3) In order to stably maintain an optically anisotropic phase of 90% higher without containing high molecular weight components, the average molecular weight must be 100%.
0 or more, preferably 1000 to 1500.

is necessary.

Furthermore, the present inventors have discovered that mesophase pitch having such characteristics can be produced extremely effectively by the following production method. That is, (A) in the first step, as described in JP-A-1-139621, a condensed polycyclic hydrocarbon such as naphthalene or the like is contained in the presence of hydrogen fluoride and boron trifluoride. The material is polymerized to create mesophase pitch containing an optically anisotropic phase. This pitch is characterized by its molecular structure, which includes many side chain alkyl groups, naphthene rings, etc.

(B) In the second stage, from the pitch obtained in the first stage,
Aromatic hydrocarbons or nitrogen-containing six-membered heterocyclic compounds having a solubility parameter of 10.0 or more, and mixtures containing them as main components, which are insoluble in organic solvents, are removed. This operation removes high molecular weight components generated during the polymerization reaction process. As mentioned above, this high molecular weight component must be removed because it hinders the achievement of a low softening point and low viscosity.

(C) In the third step, the lower layer portion is extracted from the mesophase pitch obtained in the second step by specific gravity separation to obtain mesophase pitch having an optically anisotropic phase of 90% or more.

It has been found that the desired mesophase pitch with an ultra-low softening point and low viscosity can be produced very suitably by this method.

The present invention has been made based on this new knowledge.

To summarize, the present invention is obtained from a condensed polycyclic hydrocarbon or a substance containing the same, and has a softening point of less than 220°C and 250°C.
The viscosity is 10.00 poise or less, the average molecular weight is 1
000 or more, it is an ultra-low softening point, low viscosity mesophase pitch characterized by containing 90% or more of an optically anisotropic phase.

To explain further, the ultra-low softening point, low viscosity mesophase pitch according to the present invention is basically a condensed polycyclic hydrocarbon such as naphthalene or a substance containing this in the presence of hydrogen fluoride or boron trifluoride. The molecular structure contains many side chain alkyl groups, naphthene rings, etc.

When an alkyl side chain and a naphthene ring are present in the aromatic ring skeleton,
It is thought that the van der Waals radius expands, the intermolecular bonding force weakens, and this acts to lower the softening point and viscosity.

Furthermore, in terms of molecular weight distribution, the mesophase pitch of the present invention does not contain high molecular weight components and has an average molecular weight of 1000 or more, preferably 1000 to 1500. If a high molecular weight component, that is, a component with a molecular weight of several thousand or more, is contained in the mesophase pitch, it will increase the softening point and viscosity. If it does not reach 1000, it becomes extremely difficult to stably maintain 90% or more of the optically anisotropic phase in the mesophase pitch.

In addition, the average molecular weight is 1000 or less, and the optically anisotropic phase is 9
If it is less than 0%, stable spinning is difficult and the physical properties of the obtained carbon fiber tend to be poor.

In this way, the molecular structure contains many side chain alkyl groups, naphthene rings, etc., and in terms of molecular weight distribution, it does not contain high molecular weight components, and has an average molecular weight of 1000 or more.
By setting preferably 1000 to 1500, 9
It stably maintains an optically anisotropic phase of 0% or more, and further has a softening point of less than 220°C, preferably 170 to 215°C.
At the same time, an ultra-low softening point, low viscosity mesophase pitch having a viscosity of 1000 voids or less, preferably 5 to 800 voids at 250° C. is realized.

Note that the meaning of the phrase "optically anisotropic phase" used in this specification is not necessarily uniformly used in academic circles or in various technical documents, so in this specification, "Optically anisotropic phase" is one of the pitch constituents, and when a cross section of a pitch lump solidified near room temperature is polished and observed under crossed nicols with a reflective polarizing microscope, it is When rotated, it means the part where brilliance is observed, that is, the part is optically anisotropic.On the other hand, the part where brilliance is not observed, that is, is optically isotropic, is called optically isotropic phase. .

The optically anisotropic phase is mainly composed of molecules with a chemical structure in which the planarity of polycyclic aromatic condensed rings is more developed than in the optically isotropic phase, and the planes aggregate and associate in a stacked manner. It is considered to be in a kind of liquid crystal state at the melting temperature. Therefore, when this is extruded from a thin spinneret and spun, the planes of the molecules are aligned nearly parallel to the direction of the fiber axis, so carbon fibers made from this optically anisotropic pitch exhibit high elasticity. . In addition, the optically anisotropic phase is quantified by observing it under crossed Nicols with a polarizing microscope, taking a photograph, and measuring the area ratio occupied by the optically anisotropic part, which is essentially a volume percentage.
represents.

Moreover, in this specification, "mesophase pitch" means a pitch containing an optically anisotropic phase.

Furthermore, in this specification, the term "softening point of pitch" refers to the solid-liquid transition temperature of pitch, but using a differential scanning calorimeter, the absorption or release of latent heat when pitch melts or solidifies is measured. It is determined from the temperature that shows the peak.

The softening points described in the above-mentioned Japanese Patent Application Laid-Open No. 1-254796 are measured by the capillary method, and the values measured by the differential scanning calorimeter in this specification are based on the capillary method. The value is approximately 20°C higher than the base value.

The viscosity was measured using a high temperature rotational viscometer using a concentric cylinder method.

Regarding the method of measuring the average molecular weight, the molecular weight of pitch components is measured by dissolving the soluble part in a chloroform solvent and measuring it by vapor pressure equilibrium method (VPO), and using metallic lithium and ethylene diamine for the insoluble part. After being solubilized by a mild hydrogenation reaction, it was measured by the vapor pressure equilibrium method described above, and the average molecular weight was determined therefrom.

The ultra-low softening point, low viscosity mesophase pitch according to the present invention described above is produced by polymerizing a condensed polycyclic hydrocarbon or a substance containing the same in the presence of hydrogen fluoride and boron trifluoride to obtain optical anisotropy. Producing a pitch containing a phase, and removing from this pitch an aromatic hydrocarbon or nitrogen-containing six-membered heterocyclic compound with a solubility parameter of 10.0 or more, and a portion insoluble in an organic solvent consisting of a mixture containing these as the main component. After that, the lower layer can be extracted by specific gravity separation to produce it in a very suitable manner. Hereinafter, a method for manufacturing such ultra-low softening point, low viscosity menphase pitch will be explained in more detail.

・Starting materials Raw materials used in the production method of the present invention include naphthalene, methylnaphculene, anthracene, phenanthrene,
Condensed polycyclic hydrocarbons such as acenaphthene, acenaphthylene, and pyrene, or mixtures thereof, or substances containing one or more of these condensed polycyclic hydrocarbons, including various petroleum fractions and residues from petroleum processing processes. Also included are oil and coal tar fractions.

These raw materials are particularly suitable for raw materials containing low concentrations of nitrogen compounds, sulfur compounds, and oxygen compounds, which are basic compounds that strongly bind to hydrogen fluoride (HF) and boron trifluoride (BF3), which are polymerization catalysts. Are suitable.

・First step (polymerization) The above condensed polycyclic hydrocarbon or a substance containing it is polymerized in the presence of hydrogen fluoride/boron trifluoride as a polymerization catalyst to form a mesophase containing an optically anisotropic phase. Manufacture pitch. At this time, it is preferable that the mesophase pitch contains 50 to 100% of the optically anisotropic phase, and if the optically anisotropic phase is 50% or less, the yield in the second stage and subsequent stages, which will be explained later, will be improved. This is not preferable because it significantly reduces the

The amount of the polymerization catalyst is preferably 0.1 to 20 mol of hydrogen fluoride and 0.05 to 1.0 mol of boron trifluoride per mol of condensed polycyclic hydrocarbon. Even if hydrogen fluoride is used in an amount exceeding 20 moles, or boron trifluoride is used in an amount exceeding 1.0 moles, the reaction rate does not increase, and the amount of catalyst circulation increases. Therefore, the reactor becomes large, which is not preferable. Also less than 0.1 mole of hydrogen fluoride, 0.0 boron trifluoride
If the amount is less than 5 moles, it is not possible to obtain mesophase pitch containing 100% of the optically anisotropic phase.

In the production method of the present invention, hydrogen fluoride alone or boron trifluoride alone is not effective as a polymerization catalyst (it is necessary to use a combination of both).

By using hydrogen fluoride and boron trifluoride together, a strong protic acid is formed, which forms a complex with a condensed polycyclic hydrocarbon that is a base.

The polymerization reaction temperature is 200 to 400°C, preferably 2
50-320'C. If the temperature exceeds 400°C, polymerization will proceed excessively and the softening point of the resulting menphase pitch will become high. Furthermore, at temperatures lower than 200° C., menphasic pitch containing 100% of the optically anisotropic phase cannot be obtained.

The time required for polymerization varies depending on the type of raw materials, polymerization reaction temperature, and amount of catalyst, but is usually 5 to 300 minutes, preferably 30 to 240 minutes.

Moreover, the pressure of the polymerization reaction is 5 to 100 atmospheres, preferably 2
The pressure is 0 to 50 atmospheres.

The polymerization reaction is carried out by supplying raw materials and a catalyst into a corrosion-resistant reactor equipped with a stirrer and stirring the mixture. The reaction operation may be a batch operation or a continuous operation.

The condensed polycyclic hydrocarbon (A r ) as a raw material forms a complex by mixing with a catalyst, rapidly polymerizes, and forms a polymer body.

HF + BF3 + (Ar), -'! + Responsibility A
r) nBF4- (1) The complex of this polymer has the formula (1
), the volatile components HF and BF3 are distilled off at that temperature after the completion of polymerization and recovered as a catalyst. At this time, some polymerized oil is recovered and at the same time, polymerized pitch can be separated.

The separation and recovery of the catalyst from the pitch can be carried out specifically by the following method.

As a method for separating the catalyst in batches, after the completion of the polymerization reaction, the temperature is maintained as it is, HF and BP are extracted from the reactor as a gas phase under an appropriate pressure, and the polymer is recovered as molten pitch. The heating method for this is either indirect heating from the outside through a jacket, etc., or direct heating by supplying heated steam of a relatively inert auxiliary agent such as benzene, toluene, or halogenated hydrocarbon into the reactor. You may do so.

In addition, as a method for continuously separating the catalyst, a distillation column is used, the polymerization reaction liquid is continuously fed into the above-mentioned inert auxiliary agent, and vaporized HF and BFa are extracted from the top of the column. Pitch is recovered from the bottom of the column as an auxiliary solution.

In either method, the temperature required to recover the catalyst is the same as the polymerization temperature, and the pressure during recovery is 0 to 30 atm, preferably 1 to 5 atm.

The polymerized pitch thus obtained is substantially HF
, does not contain BF3, optically anisotropic phase is 50-100%
This is the mesophase pitch.

Further, as a result of analysis, it was found that the mesophase pitch contains many side chain alkyl groups, naphthene rings, etc. as molecular structural characteristics.

Typically, the side chain alkyl carbon content was 3-11% and the naphthenic carbon content was 7-15%.

・Second stage (solvent extraction) In the mesophase pitch obtained in the first stage,
It contains high molecular weight components produced during the polymerization reaction, that is, components with a molecular weight of several thousand or more. This high molecular weight component increases the softening point and viscosity and needs to be removed.

The present inventors believe that such a high molecular weight component is an organic solvent, preferably an aromatic hydrocarbon or a nitrogen-containing six-membered heterocyclic compound having a solubility parameter of 10.0 or more, and a mixture containing these as main components. It has been found that removal can be achieved extremely efficiently by using an organic solvent of 1O12 to 11.2% and removing the portion insoluble in the organic solvent.

To explain further, when using an organic solvent with a solubility parameter of less than 10.0, such as benzene with a solubility parameter of 9.1, the amount of optically anisotropic phase contained in the benzene-soluble component is extremely reduced, and in some cases becomes zero, and pitch containing an optically anisotropic phase cannot be obtained even by specific gravity separation operation such as centrifugation in the third stage, which will be explained later.

In addition, even if organic solvents have a solubility parameter of 10.0 or more, solvents with polar groups such as butanol (solubility parameter 11°4) and hexanol (solubility parameter 10°6) have low compatibility with pitch, and therefore cannot be used in the present invention. Not suitable as a solvent.

Examples of organic solvents that can be suitably used in the present invention include quinoline (solubility parameter: 10°7) and pyridine (solubility parameter: 10.6).

Furthermore, in the solvent extraction process, the organic solvent may be used alone or in combination.

Further, the conditions for such a solvent extraction treatment are such that the solvent to pitch ratio (volume) is 1 to 5:1, the temperature is 50 to 200 DEG C., and the pressure is in the range from atmospheric pressure to 5.0 Kg/cm2.G.

This solvent extraction process removes high molecular weight components having a molecular weight of several thousand or more, which were generated during the oversizing of the first stage polymerization reaction.

- Third stage (specific gravity difference separation) The solvent-insoluble matter is removed by the solvent extraction treatment in the second stage, thereby reducing the proportion of the optically anisotropic phase in the mesophase pitch. According to the results of research experiments conducted by the present inventors, for example, if the mesophase pitch obtained in the first step contains 100% optically anisotropic phase, the mesophase pitch obtained in the second step The content of optically anisotropic phase in tuna is reduced to 60%. This is because the optically anisotropic phase portion composed of high molecular weight components disappears by removing the high molecular weight components.

Therefore, according to the present invention, in order to obtain mesophase pitch containing 90% or more of the optically anisotropic phase from this pitch, specific gravity separation is performed in the third step to extract the lower layer portion. The lower layer portion is mesophase pitch containing 90% or more of an optically anisotropic phase.

To explain further, the purpose of this specific gravity separation step is simply not to take out the optically anisotropic phase in the pitch obtained in the second step, and thermal decomposition and polycondensation are further carried out during this step. The coalescence and growth of the optically anisotropic phase should be avoided, and the specific gravity separation treatment temperature and treatment time should be appropriately selected in consideration of this point. Therefore, in general, the specific gravity separation is carried out at a temperature of 400°C or lower, preferably 170 to 350°C, in an inert atmosphere.
The optically anisotropic phase portion with high density is accumulated in the lower layer, separated from the optically isotropic phase portion with lower density in the upper layer by the difference in specific gravity, and the optically anisotropic phase portion in the lower layer is Extract only the tropic phase part.

In particular, in order to shorten the heating time (and to perform the specific gravity difference separation more quickly and efficiently in accordance with the purpose of the present invention, specific gravity difference separation by a static method in which the heating time is kept at a predetermined temperature and in a substantially stationary state is preferred). It is more preferable to employ specific gravity separation by centrifugation than separation.

Even in the case of centrifugation, the optically anisotropic phase-containing pitch is separated in an inert atmosphere above its softening point, generally below 400°C, preferably between 170 and 350°C, depending on the magnitude of the centrifugal force. ℃ range, the optically anisotropic phase portion with higher density is accumulated in the centrifugal direction, separated from the optically isotropic phase portion with lower density by the difference in specific gravity, and only the optically anisotropic phase portion is separated. Take out. The magnitude of the centrifugal force is preferably 1,000 G or more, particularly in the range of 10,000 to 40,000 G, in order to perform the centrifugal force effectively in a short time. still,
There are restrictions in terms of equipment for 50,000G or more.

Mesophase pitch separated by specific gravity separation contains 90% or more of an optically anisotropic phase.

The purpose of the third stage in the production method of the present invention is to obtain, for example, 6
The purpose is to increase the content of the optically anisotropic phase in the mesophase pitch, which has decreased to about 0%, to 90% or more. Polymerization, catalytic polymerization, etc. may also be considered, but these methods result in the formation of high molecular weight components again, resulting in an increase in the softening point and viscosity, which is not preferable. As mentioned above, in the present invention, by employing specific gravity difference separation,
It is possible to avoid high molecular weight due to polymerization and obtain mesophase pitch with a high content of optically anisotropic phase.

According to the above production method of the present invention, the softening point is less than 220°C, preferably 170 to 21.5°C, the viscosity at 250°C is 1000 poise or less, preferably 5 to 800 poise, and the average molecular weight is 1000 or more, preferably 1000 poise. ~1
500, a mesophase pitch containing more than 90% of the optically anisotropic phase is obtained.

The thus obtained menphase pitch according to the present invention can be suitably used as a carbon material for molding as it is, or can be spun into pitch fibers by a method well known to those skilled in the art. Carbon fibers (carbonized fibers or graphitized fibers) can be obtained by performing a firing treatment.

To briefly explain the manufacturing method of carbon fiber, first,
The mesophase pitch obtained in the present invention is heated, melted, and spun to produce pitch fibers. When the mesophase pitch of the present invention is used during spinning, 200
Spinning can be carried out at a low spinning temperature of ~290°C, usually 250°C or less.

The pitch fibers are infusible by heating in an oxidizing gas atmosphere in an infusibilizing furnace, generally at a temperature of 150 to 500"C. Examples of oxidizing gases include air, oxygen, air and oxygen,
Alternatively, a nitrogen mixed gas or the like can be used, and in some cases, a gas containing an oxidizing agent such as halogen, NO, or ozone is used. In addition, the heat treatment is performed at a temperature of 150 to 50
It can be carried out at a constant temperature within the range of 0°C or by increasing the temperature continuously or stepwise.

This infusible fiber is carbonized or graphitized by heating it to a temperature of 3200°C or less in an inert gas atmosphere such as nitrogen gas or argon gas, resulting in carbon fiber (carbonized fiber or graphitized fiber). Fiber) is obtained.

The carbon fiber thus obtained has a tensile strength of 2.5
High strength of GPa or more, tensile modulus of 250GPa or more,
It is a carbon fiber with a high elastic modulus, and is characterized by a particularly high elastic modulus.

Next, the present invention will be explained with reference to examples.

Examples 1 and 2 Naphthalene, hydrogen fluoride, and boron trifluoride in a molar ratio of 1:0
．． Mixed at a ratio of 45:0.14, 43II.

Reaction pressure in a corrosion-resistant reactor of 25 K g f/cr
The reaction was carried out at 260° C. for 3 hours. After the reaction, light components are removed while blowing nitrogen gas to reduce the optically anisotropic phase content to 1.
00% pitch A was obtained with a yield of 76% by weight.

This pitch A was dissolved in quinoline (solubility parameter 10.7) at 80°C for 30 minutes, the insoluble components were removed by centrifugation at 4000 G for 20 minutes, and the quinoline was removed from the soluble components. The content of anisotropic phase is 6
A pitch B of 0% was obtained.

Next, this pitch B was heated at 320°C under a nitrogen stream for 100
Centrifugation was performed for 30 minutes in OOG, and pitch C containing no optically isotropic phase was obtained with a yield of 60% by weight. Pitch C has an optically anisotropic phase content of 100% and a softening point of 213°C, 2
Viscosity at 50°C is 662 poise, average molecular weight is 10
◎ The pitch C obtained in this way was filled into a spinning machine having a nozzle with an inner diameter of 0.3 mm, and spinning was continued for 1 hour at a spinning temperature of 248°C and a winding speed of 500 m/min. However, pitch fibers having a constant outer diameter of 12.5 μm could be continuously and stably spun without yarn breakage.

The obtained pitch fibers were heated at 220°C in an oxidizing dust atmosphere.
Oxidized for 30 minutes and further heated for 250 minutes under an inert gas atmosphere.
Graphitized fibers were obtained by graphitizing at 0°C. The tensile properties of this single fiber are as follows: fiber diameter is l1μm, strength is 3.0G
Pa and elastic modulus were 840 GPa.

1 liter of methylnaphthalene, hydrogen fluoride, and boron trifluoride in a molar ratio of 1
:0.45:0.15 in a corrosion-resistant reaction tank of 18β at a reaction pressure of 25 K g f / cr rd.
The reaction was carried out at 260°C for 3 hours. After the reaction, remove light components while blowing nitrogen gas to achieve optically anisotropic phase content of 100%.
Pitch D was obtained in a yield of 75% by weight.

By removing the quinoline dissolved content from this pitch D under the same conditions as in Example 1, a pitch E having an optically anisotropic phase content of 60% was obtained.

Next, pitch E was centrifuged under the same conditions as in Example 1 to obtain pitch F containing no optically isotropic phase at a yield of 60% by weight. Pitch F has an optically anisotropic phase content of 100%
The softening point was 208°C, the viscosity at 250°C was 208 poise, and the average molecular weight was 1030.

Next, the pitch F thus obtained was spun using the same spinning machine as in Example 1 at a spinning temperature of 233°C and a winding speed of 500°C.
Spinning was performed continuously for 1 hour under the conditions of m/min, but pitch fibers having a constant outer diameter of 12 um could be continuously and stably spun without any yarn breakage.

The obtained pitch fibers were rendered infusible and fired under the same conditions as in Example 1 to obtain graphitized fibers. The tensile properties of this single fiber include a fiber diameter of 9.9 μm, a strength of 3.7 GPa, and an elastic modulus of 740.
'GPa.

1 seed■ Yuanthracene, hydrogen fluoride, and boron trifluoride in a molar ratio of 1:
Mixed in the ratio of 0.45:0.14 and reacted at a reaction pressure of 25 K g f/c rrr in a corrosion-resistant reactor of 184 26
The reaction was carried out at 5°C for 14 hours. After the reaction, light components were removed while blowing nitrogen gas, and pitch G having an optically anisotropic phase content of 100% was obtained at a yield of 78% by weight.

Insoluble matter was removed from pitch G using a mixed solvent of 10% benzene and 90% quinoline to obtain pitch H having an optically anisotropic phase content of 60%.

Furthermore, Pitch H was centrifuged at 320° C. under a nitrogen stream and at 10,000 G for 15 minutes to obtain Pitch II containing 98% of the optically anisotropic phase at a yield of 60% by weight. Pitch ■ has a softening point of 214°C and a viscosity of 550 poise at 1250°C.
The average molecular weight was 1240.

The pitch ■ thus obtained was spun using the same spinning machine as in Example 1 at a spinning temperature of 245°C and a winding speed of 500 m.
Spinning was carried out continuously for 1 hour under the conditions of /min, but pitch fibers having a constant outer diameter of 12 μm could be continuously and stably spun without any yarn breakage.

The obtained pitch fibers were rendered infusible and fired under the same conditions as in Example 1 to obtain graphitized fibers. The tensile properties of this single fiber are as follows: fiber diameter is 9.9 μm, strength is 3.0 GPa, and elastic modulus is 71
It was 0.6Pa.

ratio” and “example”.

Pitch A of Example 1, which had an optically anisotropic phase content of 100%, had a softening point of 265°C, a viscosity at 250°C that was unmeasurable, and an average molecular weight of 1320.

This pitch A could not be spun at 250° C. using the same spinning machine as in Example 1. Further, when spinning was carried out under the conditions of a spinning temperature of 298° C. and a winding speed of 500 m/min, pitch fibers with an outer diameter of 12 μm were obtained.

The obtained pitch fiber was heated to 230" in an oxidizing gas atmosphere.
C160 minutes to oxidize and infusible, further under an inert gas atmosphere for 25 minutes
Graphitized fibers were obtained by graphitizing at 00'C. The tensile properties of this single fiber are as follows: fiber diameter: 9.7 gm, strength: 3
．． 2 GPa, and the elastic modulus was 680 GPa. It can be seen that this fiber is inferior to the graphitized fiber of Example 1 obtained by the present invention in terms of elastic modulus.

Pitch A from Example 1 was extracted at 120°C for 20 hours with benzene with a solubility parameter of 9.1, and the benzene-soluble components were extracted with 38%
A yield of % by weight was obtained. Benzene was removed from this soluble component by drying under reduced pressure to obtain benzene-soluble pitch L. This pitch L did not contain an optically anisotropic phase, and pitch containing an optically anisotropic phase could not be obtained even by centrifugation.

Pitch B of Example 1 with a ratio I mouth coarseness has an optically anisotropic phase content of 60%.
However, the softening point was 214°C, the viscosity at 250°C was 336 voids, and the average molecular weight was 850.

An attempt was made to spin this pitch B using the same spinning machine as in Example 1, but the pressure fluctuations were severe and spinning was difficult.

Rujrohada A 20 kg of heavy residual oil produced as a by-product in the catalytic cracking process of petroleum is
Pitch J containing 25% of an optically anisotropic phase was obtained by filling a 5β reaction tank and carrying out thermal decomposition polycondensation at 415° C. for 14 hours with sufficient stirring under a nitrogen atmosphere.

Next, this pitch J was adjusted to 1000°C at 350°C under one nitrogen stream.
Centrifugation was performed at 0 G, and the optically anisotropic phase content was 100%.
Pitch K was obtained in a yield of 25% by weight. This pitch had a softening point of 272°C, a viscosity at 250°C which could not be measured, and an average molecular weight of 1430.

Next, this pitch was made using the same spinning machine as in Example 1.
Spinning was impossible at 0°C. In addition, the spinning temperature is 305°C,
Spinning was performed at a winding speed of 500 m/min to obtain pitch fibers with an outer diameter of 12 μm, and further infusible and fired under the same conditions as in Comparative Example 1 to obtain graphitized fibers. The tensile properties of this single fiber are fiber diameter 9.7μm and strength 3.4G.
Pa, and the elastic modulus was 520 GPa. It can be seen that this fiber has a strength comparable to that of the graphitized fiber of Example 1 obtained by the present invention, but is significantly inferior to the graphitized fiber of Example 1 in terms of elastic modulus. .

1. The ultra-low softening point, low viscosity mesophase pitch of the present invention constructed as described above can be spun and molded at low temperatures, and can be used to produce carbon fibers and other carbon materials at low cost. Moreover, stable production has become possible. Furthermore, by using the mesophase pitch of the present invention, carbon fibers having high strength and high elastic modulus, particularly high elastic modulus, can be produced.

Further, according to the present invention, a condensed polycyclic hydrocarbon such as naphthalene or a substance containing the same is polymerized in the presence of hydrogen fluoride and boron trifluoride, and then high strength is obtained by solvent extraction and specific gravity separation. , high modulus carbon fiber, especially high modulus carbon fiber,
Alternatively, the ultra-low softening point, low-viscosity mesophase pitch containing 90% or more of an optically anisotropic phase, which can be suitably used to produce a high-strength, high-density carbon material for molding, is highly efficient. Can be manufactured well.

Claims (1)

[Claims] 1) Obtained from a condensed polycyclic hydrocarbon or a substance containing the same, with a softening point of less than 220°C and a viscosity of 1 at 250°C
1,000 poise or less, an average molecular weight of 1,000 or more, and an ultra-low softening point, low viscosity mesophase pitch characterized by containing 90% or more of an optically anisotropic phase. 2) In the presence of hydrogen fluoride and boron trifluoride, a condensed polycyclic hydrocarbon or a substance containing it is polymerized to produce pitch containing an optically anisotropic phase, and from this pitch a solubility parameter of 10. It is characterized in that it is obtained as a lower layer portion by gravity separation after removing the organic solvent-insoluble portion consisting of zero or more aromatic hydrocarbons or nitrogen-containing six-membered heterocyclic compounds, and mixtures containing these as main components. A method for producing an ultra-low softening point, low viscosity mesophase pitch according to claim 1. 3) The mesophase pitch according to claim 1 is 200 to 29
Pitch fibers are spun at a temperature of 0°C, infusible at 150 to 500°C in an oxidizing gas atmosphere, and then carbonized by raising the temperature to 3200°C or less in an inert gas atmosphere. is a method for producing high-strength, high-modulus carbon fiber characterized by graphitization.