JPH0148314B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing pitch, which has excellent performance as a raw material for producing carbon fibers. Currently, carbon fiber is mainly manufactured using polyacrylonitrile as a raw material. However, when polyacrylonitrile is used as a raw material, there are disadvantages in that the raw material is expensive, the original fibrous shape is easily destroyed during heating and carbonization, and the carbonization yield is also poor. In recent years, focusing on this point, many methods have been reported for producing carbon fibers using pitch as a raw material.
When pitch is used as a raw material, it is expected that carbon fibers can be produced at low cost because the raw material is inexpensive and the carbonization yield is usually as high as 85 to 95%. However, carbon fibers obtained using pitch as a raw material have a higher modulus of elasticity than polyacrylonitrile carbon fibers, but have a problem in that they are inferior in strength. Therefore, if this problem could be solved and the modulus of elasticity could be further improved, it would be possible to produce carbon fibers with high strength and high modulus at low cost from pitch. Recently, commercially available petroleum pits have been heat-treated to obtain pitches containing optically anisotropic liquid crystals called mesophases, and pitches containing this mesophases have been converted into precursor pits (hereinafter referred to as molten). Carbon fibers with improved elastic modulus and strength can be obtained by melt-spinning this precursor pitch, making it infusible, and then carbonizing or graphitizing it. It was reported (Japanese Unexamined Patent Publication No. 19127-1983). However, whether or not a pitch can form a liquid crystal is determined by various factors, and the physical properties such as the structure, softening point, and viscosity of the liquid crystal greatly depend on the raw material pitch. Said Japanese Unexamined Patent Application Publication No. 1973-
No. 19127 relates to a method for preparing pitch containing mesophase (hereinafter abbreviated as mesophase pitch), but does not mention anything about the raw material pitch for forming high quality mesophase pitch. As mentioned above, a high-quality mesophase pitch largely depends on the raw material pitch, and if an optimal raw material pitch can be found, it will be possible to produce carbon fibers with even better elastic modulus and strength. Therefore, finding this optimal raw material pitch is an important challenge in this technical field. For example, coal tar pitch contains substances that are insoluble and infusible in carbon black-like quinoline, and these not only cause non-uniformity of the precursor pitch and deteriorate spinnability, but also reduce the strength and strength of carbon fibers. Adversely affects elastic modulus. On the other hand, many commercially available petroleum pitches and other synthetic pitches contain almost no substances that are insoluble and infusible in quinoline. Insoluble high molecular weight components are produced. In other words, when these pitches are heat-treated, thermal decomposition and polycondensation reactions occur simultaneously, and the low molecular weight components gradually increase in molecular weight.
It becomes a high molecular weight component that is insoluble in quinoline, and at the same time, the high molecular weight component further increases in molecular weight. Along with this, the softening point of pitch also increases. If this quinoline insoluble matter is similar to the carbon black-like substance in coal tar, it will have an adverse effect on the steps after spinning as described above. Furthermore, even if the substance is different from the carbon black-like substance mentioned above,
The presence of a large amount of quinoline insolubles and a high softening point have an adverse effect on the melt spinning stage. In other words, in order to melt-spun a precursor pitch, it is necessary to raise the spinning temperature until the precursor pitch reaches a viscosity that allows spinning, and if the softening point of the precursor pitch is too high, the spinning temperature may As a result, the molecular weight of the insoluble portion of quinoline becomes even higher, and the pitch is thermally decomposed and light gas is generated, making it impossible to form a uniform precursor pitch and making it difficult to spin. It becomes virtually impossible. Thus, the precursor pitch must have a relatively low softening point and a suitable viscosity for spinning. Furthermore, it must not substantially contain volatile components during spinning or carbonization. For this reason, precursor pitch for carbon fiber production is prepared by removing the generated quinoline insoluble matter by means such as pressurization and solvent separation (Japanese Patent Application Laid-Open No. 47-9804, 50 −142820,
55-1342, 55-5954). however,
When these means are used, the processing equipment becomes complicated and the processing cost increases, which is not preferable from an economic point of view. It would be most preferable if a pitch having excellent performance could be used as the raw material pitch to prevent the formation of high molecular weight components that would become quinoline-insoluble components during the heating step of mesophase formation. The present inventors have completed the present invention as a result of intensive research into these problems. That is, the present inventors suppressed the formation of high molecular weight components at the stage of preparing the precursor pitch, had an optimal viscosity, and created a composition in which the aromatic planes were easily arranged in an orderly manner at the early stage of carbonization. We have discovered a raw material pitch that has excellent performance. In other words, the present invention keeps the softening point relatively low;
The present invention also provides a method for producing a raw material pitch that easily forms a mesophase. The present invention will be explained in detail below. In the present invention, a precursor pitch obtained by heating a raw material pitch is melt-spun, and then infusible and carbonized or graphitized to produce carbon fiber. Heavy oil with a boiling point of 200℃ or higher obtained during fluid catalytic cracking
For 100 parts by volume, (2) a fraction with a boiling point range of 160 to 400°C produced when the raw material pitch is heat-treated is brought into contact with hydrogen in the presence of a hydrogenation catalyst; The aromatic nucleus of the aromatic hydrocarbon contained in
Hydrogenated oil 10-200 obtained by 10-70% nuclear hydrogenation
Add part by volume, temperature 370~480℃, pressure 2~5
The present invention relates to a method for producing a raw material pitch for carbon fiber, characterized in that it is obtained by heat treatment at Kg/cm ² ·G. When the mesophase reaction is carried out using the raw material pitch obtained by the present invention, not only the production of quinoline-insoluble components is suppressed, but also the pitch is modified,
It was completely unexpected that the final product, carbon fiber, could have a high modulus of elasticity and high strength. On the other hand, when coal tar pitch, commercially available petroleum pitch, or synthetic pitch was heat-treated to form a mesophase according to the method of JP-A-49-19127, the resulting pitch had a softening point of 340°C or higher. thing,
In many cases, melt spinning was virtually impossible, such as in cases where solids were deposited, or even if solids were not deposited, the quinoline insoluble content reached 70% or more. Even if melt spinning is possible, the strength of the carbon fiber obtained by further infusibility, carbonization, and graphitization is 120 to 200 Kg/mm ² and the elastic modulus is 12 to 20 tons/mm.
It was about ^mm2 . Furthermore, when a material with a high softening point was spun, pores were present in the spun material due to the generation of thermal decomposition gas. In the present invention, the heavy oil with a boiling point of 200℃ or higher obtained by fluid catalytic cracking of petroleum, which is used as component (1) of the raw material pitch, refers to the heavy oil obtained from natural petroleum such as kerosene, light oil, or atmospheric residual oil. Alternatively, by fluid catalytic cracking in the presence of a synthetic silica-alumina catalyst or zeolite catalyst at 450 to 550°C and normal pressure to 20 kg/cm ² G, the substance that is produced as a by-product when producing light oil such as gasoline can be The boiling point range is 200-550
℃, preferably heavy oil within the range of 300-550℃. In the present invention, the hydrogenated oil used as component (2) of the raw material pitch is one whose boiling point range is substantially within the range of 160 to 400°C, preferably 170 to 350°C when the raw material pitch is heat-treated. The fraction is brought into contact with hydrogen in the presence of a hydrogenation catalyst to partially hydrogenate the aromatic nuclei of aromatic hydrocarbons contained in the fraction. The hydrogenation catalyst used at this time may be a catalyst used in a normal hydrogenation reaction, for example, an inorganic solid such as bauxite, activated carbon, diatomaceous earth, zeolite, silica, titania, zirconia, alumina or silica gel is used as a carrier, copper etc. metals of group IB of the periodic table, metals of group B of the periodic table such as chromium, molybdenum, metals of group B of the periodic table such as cobalt, nickel, palladium or platinum in the form of metals or in the form of oxides or sulfides. Those supported on a carrier are used. Hydrogenation conditions vary depending on the type of catalyst used, but usually the temperature is 120 to 450°C, preferably 150 to 350°C, and the pressure is 20 to 100 Kg/cm ² G, preferably 30 to 70 Kg/cm. ²・G takes place. Further, when the hydrogenation treatment is carried out in a batch manner, the appropriate hydrogenation treatment time is 0.5 to 3 hours. When carried out in a continuous manner, a space velocity (LHSV) of 0.5 to 3.0 is selected. To give an example of hydrogenation conditions, 2wt% Raney
When the process is carried out batchwise using nickel as a catalyst, the pressure is preferably 40 to 50 kg/cm ² G, the temperature is 160 to 170°C, and the treatment time is 1 to 1.5 hours. When using the formula, the pressure is 30 to 50 kg/cm ² G, the temperature is about 330°C,
A space velocity (LHSV) of about 1.5 is preferably adopted. The aromatic nuclei of aromatic hydrocarbons contained in the fraction are partially hydrogenated by the hydrogenation reaction, but the nuclear hydrogen percentage at this time is 10 to 70%, preferably 15%.
~50%, most preferably 15-35%. Incidentally, the nuclear hydrogenation rate is defined by the following formula, and the number of aromatic ring carbon atoms in the following formula is as indicated by ASTM D-2140-66. Nuclear hydrogenation rate = (number of aromatic ring carbons before hydrogenation treatment) - (
(Number of aromatic ring carbon atoms after hydrogenation treatment)/Number of aromatic ring carbon atoms before hydrogenation treatment The method for preparing the raw material pit of the present invention is to combine heavy oil as component (1) and hydrogenated oil as component (2). It is obtained by mixing in a specific ratio and heat-treating under specific conditions. The mixing ratio of component (1) heavy oil and component (2) hydrogenated oil is component (1):component (2) in a volume ratio of 1:0.1 to 2, preferably 1:0.2 to 1.5. It is necessary.
The heat treatment temperature is 370-480℃, preferably
Perform at a temperature within the range of 390-460°C. If the heat treatment temperature is lower than 370°C, the reaction progresses slowly and takes a long time, which is uneconomical. Further, heat treatment at a temperature higher than 480° C. causes problems such as caulking, which is not preferable. The heat treatment time is determined in consideration of the heat treatment temperature; when the temperature is low, the heat treatment is performed for a long time, and when the temperature is high, the heat treatment is performed for a short time. Normally
Processing times within the range of 15 minutes to 20 hours, preferably 30 minutes to 10 hours can be employed. Regarding the pressure, the reaction can be carried out under any desired pressure, but the pressure is preferably such that the active ingredients in the raw materials do not substantially distill out of the system unreacted, specifically 2 to 50 Kg/cm ² ·G, preferably 5 to 30Kg/cm ²・G is adopted. After the heat treatment, it is also preferable to remove light components by distillation or the like, if necessary. To explain the present invention with reference to FIG. 1, heavy oil, which is the component (1) of the raw material pitch of the present invention, is introduced from line 1, and hydrogenated oil, which is component (2), is introduced from line 3. After (1) and component (2) are mixed in a predetermined ratio, heat treatment is performed under predetermined conditions to prepare a raw material pitch. The prepared raw material pitch is then heat treated under specific conditions. The fraction produced at this time with a boiling point range of 160 to 400°C is extracted from line 2, subjected to partial nuclear hydrogenation treatment, and then returned through line 3 as a component of the raw material pitch. When carrying out the present invention, component (2) of the raw material pitch of the present invention is not present at the initial stage, but other oils may be substituted for component (2) of the present invention, or heat treatment may be performed without using component (2) of the present invention. At this time, the hydrogenated oil produced by partially hydrogenating the fraction with a boiling point range of substantially 160 to 400°C is substituted as component (2) of the raw material pitch of the present invention from the next step. The present invention can be achieved by following these steps. When other oils are substituted for component (2) of the present invention in the first step, the oils to be substituted include, for example:
The boiling point range obtained when petroleum is steam cracked is
Hydrogenated oil obtained by partial nuclear hydrogenation of a fraction within the range of 160 to 400℃, partial nuclear hydrogenation of a fraction with a boiling point range of 160 to 400℃ obtained when fluid catalytic cracking of petroleum is performed. Hydrogenated oil, component of the raw material pitch of the present invention (1)
Hydrogenated oil is produced by partially hydrogenating the fraction with a boiling point range of 160 to 400 degrees Celsius, which is produced when heavy oil used as oil is heat-treated at 380 to 480 degrees Celsius, and hydrogenated oil is produced when petroleum is steam cracked. Hydrogenated oil, naphthalene, which is produced by partial nuclear hydrogenation of the fraction with a boiling point range of 160 to 400 degrees Celsius that is produced when heavy oil with a boiling point of 200 degrees Celsius or higher is heat-treated at 380 degrees Celsius to 480 degrees Celsius. Preferred oils include nuclear hydrides of two- or three-ring aromatic hydrocarbons such as indene, anthracene, and phenanthreth, and oils similar to these. By using the raw material pitch of the present invention thus obtained, when heat-treated to form a mesophase, the production of high molecular weight components that are insoluble in quinoline is suppressed, and at the same time, the softening point of the pitch is prevented from increasing. Furthermore, it becomes a good precursor pitch having a composition in which the aromatic planes are easily arranged in an orderly manner. As a result, carbon fibers with extremely excellent elastic modulus and strength can be obtained. A known method can be used to produce carbon fiber using the raw material pitch obtained according to the present invention. That is, a raw material pitch is heat-treated to form a mesophase, the resulting precursor pitch is melt-spun, and then subjected to infusibility treatment and carbonization or further graphitization treatment to produce carbon fibers. The reaction at the stage of heat-treating the raw material pitch to convert it into a mesophase to obtain the precursor pitch is usually carried out at a temperature
It is carried out at 340 to 450°C, preferably 370 to 420°C, under normal pressure or reduced pressure and by bubbling inert gas such as nitrogen. The heat treatment time at this time can be arbitrarily performed depending on conditions such as temperature and amount of inert gas ventilation, but it is usually performed for 1 to 50 hours, preferably 3 to 20 hours. Inert gas ventilation rate is 0.7
~5.0 scfh/1b pitch is preferred. As a method for melt-spinning the precursor pitch, known methods such as an extrusion method, a centrifugation method, and an atomization method can be used. The pitch fiber obtained by melt spinning is then subjected to an infusible treatment in an oxidizing gas atmosphere. As the oxidizing gas, one or more of oxidizing gases such as oxygen, ozone, air, nitrogen oxide, halogen, and sulfur dioxide gas are usually used. This infusibility treatment is carried out under temperature conditions that do not soften or deform the melt-spun pitch fibers to be treated. for example
Temperatures of 20-360°C, preferably 20-300°C are employed. Further, the treatment time is usually 5 minutes to 10 hours. The infusible pitch fibers are then carbonized or further graphitized in an inert gas atmosphere to obtain carbon fibers. Carbonization is usually carried out at a temperature of 800-2500°C. Generally, the processing time required for carbonization is 0.5 minutes ~
It is 10 hours. Further, when graphitization is performed, it is carried out at a temperature of 2500 to 3500°C, usually for 1 second to 1 hour. In addition, during infusibility, carbonization or graphitization treatment,
If necessary, a slight load or tension may be applied to the object to be processed in order to prevent shrinkage, deformation, etc. The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto. Example 1 Heavy oil having the properties shown in Table 1 was produced by fluid catalytic cracking of vacuum residue (VGO) desulfurized oil of Arabian crude oil at 500°C using a silica-alumina catalyst.
I got (A). This heavy oil (A) was heat treated at a pressure of 15 kg/cm ² ·G and a temperature of 420° C. for 3 hours. This heat treated oil (B)
was distilled at 250°C/1 mmHg to remove light components, yielding pitch () with a softening point of 92°C. On the other hand, desulfurized oil from vacuum residual oil (VGO) of Arabian crude oil was heated to 500℃ using a silica-alumina catalyst.
Boiling point range 200-350 obtained by fluid catalytic cracking at
℃ fraction (C) (its properties are shown in Table 2) was heated using a nickel-molybdenum catalyst (NM-502) at a pressure of 35 Kg/cm ² G, a temperature of 332℃, and a space velocity (LHSV).
Partial nuclear hydrogenation was performed by contacting with hydrogen at step 1.5 to obtain hydrogenated oil (D). At this time, the nuclear hydrogenation rate is
It was 32%. Next, 30 parts by volume of hydrogenated oil (D) were mixed with 70 parts by volume of heavy oil (A), and heat treated at a pressure of 15 kg/cm ² ·G and a temperature of 430° C. for 3 hours. This heat treated oil is heated to 250℃/1mm.
Light components were distilled off using Hg to obtain Pitch () with a softening point of 63°C. Add 500ml/nitrogen to 30g of this pitch ()
The mixture was stirred with ventilation for 10 minutes, and heat treated at a temperature of 400°C for 10 hours, and a fraction (E) with a boiling point range of 160 to 400°C distilled out during this heat treatment process was collected. Its properties are shown in Table 3. 2wt% of Raney nickel was suspended in this fraction (E) and subjected to partial nuclear hydrogenation for 1.5 hours at a temperature of 169°C and a hydrogen pressure of 40 to 50 kg/cm ² G, resulting in hydrogenated oil (F).
I got it. The nuclear hydrogenation rate at this time was 35%.

【table】

【table】

【table】

[Table] 70 parts by volume of heavy oil (A) and 30 parts by volume of hydrogenated oil (F) were mixed and heat treated at a pressure of 20 kg/cm ² ·G and a temperature of 430°C for 3 hours. This heat-treated oil was distilled under reduced pressure to remove light components to obtain raw material pitch with a softening point of 62°C. Next, add 600 g of nitrogen to 30 g of this raw material pitch.
Stir with ventilation at a rate of ml/min and heat treat at 400℃ for 12 hours. Softening point: 268℃, quinoline insoluble content.
A pitch was obtained with a mesophase content of 13.7% by weight and 60%. This pitch was melt-spun at 322°C using a spinning machine with a nozzle diameter of 0.5 mmφ and L/D = 1, and
Pitch fibers were prepared, and carbon fibers were obtained by infusibility, carbonization, and graphitization treatment under the conditions shown below. The processing conditions for infusibility, carbonization and graphitization are as follows. Γ Infusibility conditions: Heating in an air atmosphere at a heating rate of 2°C/min up to 200°C and 1°C/min up to 280°C, and held at 280°C for 15 minutes. Γ Carbonization conditions: Raised temperature at 10℃/min in nitrogen atmosphere.
Hold at 1000℃ for 30 minutes. Γ Graphitization conditions: Heat treatment in an argon stream at a heating rate of 50°C/min to 2500°C. The obtained carbon fiber had a tensile strength of 285 Kg/mm ² and a Young's modulus of 41 ton/mm ² . Comparative Example 1 Pitch () obtained in Example 1 was used as a raw material pitch and heat treated in the same manner as in Example 1 to obtain a material with a softening point of 303°C, a quinoline insoluble content of 21.1% by weight, and a mesophase content of 85%. I got Pituchi. This pitch was melt-spun at 361°C using the spinning machine used in Example 1 to produce pitch fibers of 16 to 20μ.
Carbon fibers were obtained by infusibility, carbonization and graphitization treatment in the same manner as above. This carbon fiber had a tensile strength of 132 Kg/mm ² and an elastic modulus of 19 ton/mm ² .

[Brief explanation of drawings]

FIG. 1 is a process sheet showing the carbon fiber manufacturing process of the present invention.

Claims (1)

[Claims] 1. After melt-spinning a precursor pitch obtained by heating a raw material pitch, infusibility treatment and carbonization or further graphitization treatment to produce carbon fiber, the raw material pitch (1) is subjected to fluid contact with petroleum. For 100 parts by volume of heavy oil with a boiling point of 200°C or more obtained when cracked, (2) a fraction with a boiling point range of 160 to 400°C produced when the raw material pitch is heated is treated as a hydrogenation catalyst. The aromatic nuclei of the aromatic hydrocarbons contained in the fraction are reduced by 10 to 70% by contacting with hydrogen in the presence of
Add 10 to 200 parts by volume of hydrogenated oil obtained by nuclear hydrogenation, and heat at a temperature of 370 to 480°C and a pressure of 2 to 50 Kg/cm ² G.
1. A method for producing a raw material pitch for carbon fiber, characterized in that the pitch is obtained by heat-treating the raw material pitch.