JPS6218593B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of pitch for raw material for carbonaceous processed products using petroleum heavy residual oil. In particular, the present invention relates to carbonaceous processing for the purpose of easy processability, particularly to a manufacturing method for obtaining a raw material pitch suitable for manufacturing carbon fibers.

Currently, in order to produce carbon fibers with excellent strength and elastic modulus using Pits as a raw material, there are two methods: (1) stretching carbon fibers made of isotropic carbon under high temperature conditions of 2500°C or higher, and (2) non-stretching them. There are two main methods: using isotropic pitch as a raw material.

A typical method (2) is to produce carbon fibers using pitch containing a large amount of mesophase as a raw material. Patent Publication No. 1986-8634 discloses a method for producing carbon fiber using a large planar polycyclic structure formed by condensing seven or more rings as a basic skeleton as a raw material,
When the same raw material is molded into fibers, the polished surface parallel to the fiber axis can be observed with a polarizing microscope and
Linear observation shows that the planar molecules are oriented in the direction of the fiber axis. Furthermore, the same orientation is confirmed by X-ray observation even when carbonized or graphitized materials are infusible.

Also, in Patent Publication Publication No. 55-37611, 40~
A method for producing high modulus, high strength carbon fibers from mesophase pitch having a mesophase content of 90% by weight is disclosed. In this case, the mesophase is defined as one that can be visually observed by polarized light microscopy and is essentially insoluble in organic solvents such as quinoline and pyridine. On the other hand, in Published Patent Publication No. 160427/1984, the fraction separated from isotropic carbonaceous pitch by solvent extraction method is
Disclosed is a method for producing pitch, which generates an optically anisotropic phase of 75% or more by heating for 10 minutes or less. In addition to the method for manufacturing pitch, the claims of the patent include pitch fiber, and in the detailed description of the invention, it is stated that the purpose is to manufacture carbon fiber. There is no mention of the fact that high-strength, high-modulus carbon fibers can be produced from pitch using this method.

Therefore, as far as these patents are concerned, regardless of the possibility, high strength and high modulus carbon fibers are achieved by using pitch containing a large amount of mesophase. It is certainly possible to produce high-strength, high-modulus carbon fibers by spinning pitch containing a large amount of mesophase and subjecting it to infusibility, carbonization, and graphitization under appropriate conditions.
However, it is very difficult to melt-spun pitch containing a large amount of mesophase, especially pitch containing 40% by weight or more of mesophase. Therefore, in order to industrially stably produce carbon fibers with high strength and high modulus using pitch containing a large amount of mesophase as a raw material, it is necessary to overcome the difficulty of spinning.

As a result of intensive research on this point, we have found that using pitch, which has properties different from conventional methods, has extremely excellent spinnability and at the same time makes it possible to produce carbon fibers with a high modulus of elasticity. That is, the properties of the pitch are within a very limited range of 7-18% by weight of quinoline-insoluble content and 70-85% by weight of toluene-insoluble content, and the production method is also different from conventional methods. The reason why the properties of pitch were defined by the amounts of quinoline-insoluble matter and toluene-insoluble matter is as follows.

As mentioned above, in the conventional method, the properties of pitches are mainly determined by the mesophase content, but there are substances that correspond to each stage in a continuous manner between mesophases and potential substances that become the source of mesophases. It is difficult to clearly distinguish these in a complex mixture such as pitch. For example, attempts have been made to polish the pitch and observe mesophases using a reflective polarization microscope, and to estimate the amount of mesophases based on the area of the optically anisotropic region recognized through this observation. However, even if optical anisotropy is observed using this method, it cannot be concluded that all the substances present in that region are mesophases. Mesophases that are insoluble in quinoline and pyridine can certainly be observed as optically anisotropic substances, but conversely, even if the presence of mesophases is recognized in areas where optical anisotropy is observed, not all of them are mesophases. do not have. In other words, even in areas that are recognized as optically anisotropic, it is quite possible that substances other than mesophase may also be present, and especially in pitches produced from mixtures such as heavy petroleum oil as precursor raw materials, mesophase may be present. It is more reasonable to think that substances other than mesophase and mesophase coexist. Therefore, determining the amount of mesophase from the area of a portion that happens to be observed as an optically anisotropic region by a reflective polarization microscope is not an appropriate method except in special cases. The main component of the pitch produced in the present invention is a substance that is very similar to mesophase but is not mesophase, and therefore has extremely excellent spinnability. As a result of trying various methods for defining such substances, we have found that it is possible to define them by the amounts of quinoline-insoluble matter and toluene-insoluble matter, as described above.

The outline of the present invention is as follows. In other words, petroleum-based heavy residual oil with a boiling point of 400°C or higher and a sulfur content of 1.5% by weight or less is heat-treated at a temperature of 380 to 415°C for a heating time of 12 to 30 hours, and then heated to a temperature of 380°C or lower. Pitch is produced by separating and removing insoluble substances by the action of gravity or centrifugal force, followed by vacuum distillation to separate and remove light fractions with a boiling point of 400°C or less, and contains 7 to 70% of quinoline insoluble matter.
The content is 18% by weight, and the toluene insoluble content is in the range of 70 to 85% by weight.

Petroleum-based heavy residual oils that are precursor raw materials (substances that serve as raw materials for manufacturing pitucci) include atmospheric distillation residual oil of crude oil, hydrodesulfurization residual oil, hydrocracked residual oil, pyrolysis residual oil, and contact oil. It may originate from cracked residual oil, solvent-extracted oil (extract) that is a by-product during lubricant production, but it must have a boiling point of 400°C or higher calculated at normal pressure and a sulfur content of 1.5% by weight or less. It is.
Otherwise, it will be difficult to achieve the required heating at normal pressure, and the properties of the produced pitches will be poor. Here, the sulfur content is measured by the method specified in JIS K-2541. Heat treatment is performed under normal pressure at a temperature of 380 to 415.
Heat treatment is performed at a temperature in the range of 12 to 30 hours. Operations such as gas blowing and depressurization are not performed during the heat treatment, and light fractions generated during the heat treatment are prevented from exiting the system as much as possible. If the light fraction is discharged from the system, it becomes difficult to separate insoluble substances later. In addition, the heat treatment is performed within the above-mentioned condition range, but with regard to the combination of heating temperature and heating time, substantial optical anisotropy is observed even when the substances remaining in the system are polished after the heat treatment and observed with a reflective polarization microscope. It is preferable to set conditions such that there is no such occurrence. If optical anisotropy is observed here, spinnability deteriorates.

The following method is used to determine whether optical anisotropy occurs in the substance remaining in the system after heat treatment. The heat-treated product is crushed to a diameter of approximately 3 mm, then reduced and a sample is collected.The sample of the heat-treated product is embedded in a resin such as unsaturated polyester and hardened, and after polishing, a reflective polarizing microscope is used. It is used to observe at a magnification of 250 times or more under crossed Nicols to determine the development of optical anisotropy. Next, the heat-treated substance is heated to a temperature of 380° C. or below using gravity or centrifugal force to separate and remove insoluble substances at a set temperature. Heat treatment temperature 380℃
The reason for the following is to prevent the generation of optically anisotropic substances due to this heating. By separating and removing this insoluble material, it is possible to remove the material that does not melt during spinning. Next, the substance from which insoluble substances have been separated and removed is vacuum distilled to a boiling point of 400.
Separate and remove the low boiling point fraction below ℃ (converted to normal pressure). The conditions of each step are appropriately set so that the properties of the pitch produced through these steps are in the range of 7 to 18% by weight of quinoline insoluble content and 70 to 85% by weight of toluene insoluble content. If the quinoline-insoluble content of the produced pitch is 7% by weight or less and the toluene-insoluble content is 70% by weight or less, spinnability is good, but carbon fibers with high elastic modulus cannot be produced. On the other hand, if the quinoline insoluble content exceeds 18% by weight, spinnability deteriorates, and yarn breaks occur frequently during spinning, making stable spinning difficult.
Within such a fairly limited range of pitch properties, both spinnability and production of high modulus carbon fibers can be satisfied. Here, quinoline insoluble content and toluene insoluble content are JIS
Measured by the method specified in K-2425.
As described above, the present invention makes it extremely easy to spin fibers by producing a pitch with a property range that was considered to be quite difficult to use as a raw material for high modulus carbon fiber in the conventional method. This simultaneously makes it possible for the fiber to have a high modulus of elasticity.

The present invention will be explained in more detail with reference to Examples below.

Example 1 Solvent extracted oil (boiling point
400℃ or higher, sulfur content 0.5% by weight) to 410℃, 16
After heat treatment for an hour, the insoluble substances are allowed to settle while being heated to 360°C, and the insoluble substances are separated and removed using a decanting method.The substances from which the insoluble substances have been removed are then vacuum distilled at a temperature below 400°C. The low boiling point fraction was separated and removed to obtain pitch. The quinoline-insoluble content of this pitch was 15.4% by weight, the toluene-insoluble content was 73.2% by weight, and the n-heptane soluble content was 1.2% by weight.
When this pitch was melt-spun using a spinning nozzle with a nozzle hole of 0.5 mmφ at a spinning temperature of 364°C, the pitch fiber diameter was 20 μm for 10 minutes without a single yarn breakage. This pitch fiber is heated at 260℃ in an air atmosphere.
After being made infusible by heating, the material was fired and carbonized at 2000° C. in an inert gas atmosphere to have a tensile strength of 15.6Ton/cm ² and an elastic modulus of 2400Ton/cm ² .

Example 2 Distilling the residual oil by-produced from the catalytic cracking process to reduce the boiling point
The fraction below 400°C was removed to obtain a heavy residual oil with a boiling point of 400°C or above. The sulfur content of this heavy residual oil is 1.27% by weight. This heavy residual oil with a boiling point of 400℃ or higher is
After heat treatment for 20 hours at 360°C, the insoluble substances were allowed to settle while being heated to 360°C, and the insoluble substances were separated and removed using a decanting method.Then, the substances from which the insoluble substances had been removed were vacuum distilled. Pitch was obtained by separating and removing the low boiling point fraction below 400°C. The quinoline insoluble content of this pitch is 16.5% by weight, and the toluene insoluble content is 77.4%.
The n-heptane soluble content was 1.2% by weight. This pitch is spun at a spinning temperature of 365℃ and a nozzle hole diameter of 0.5mm.
When melt spinning was carried out using a spinning nozzle with a diameter of φ, no yarn breakage occurred even once in 10 minutes when the pitch fiber diameter was 20 μm. This pitch fiber is placed in the air atmosphere.
After infusibility at 260℃, 2000℃ in an inert gas atmosphere
The tensile strength of the carbonized one by firing at ℃ is 16.9Ton/cm ² ,
The elastic modulus was 4100Ton/ ^cm2 .

Comparative Example 1 The same heavy residual oil from catalytic cracking as used in Example 2, with a boiling point of 400°C or higher, was heated at 410°C for 20 hours while blowing _N2 gas, and then reduced to 400°C by vacuum distillation. The low boiling point fraction below ℃ was separated and removed to obtain pitch. This pitch had a quinoline insoluble content of 29.7% by weight, a toluene insoluble content of 62.4% by weight, and an n-heptane soluble content of 1.1% by weight. Spinning temperature of this pitch
When melt spinning was carried out at 365° C. using a spinning nozzle with a nozzle hole diameter of 0.5 mmφ, thread breakage occurred an average of 8 times in 10 minutes for pitch fibers with a diameter of 20 μm. This pitch fiber was made infusible at 260° C. in an air atmosphere and then fired at 2000° C. in an inert gas atmosphere, and had a tensile strength of 7.8 Ton/cm ² and an elastic modulus of 2100 Ton/cm ² .

Comparative Example 2 The same heavy residual oil from catalytic cracking used in Example 2 with a boiling point of 400°C or above was heated at 410°C for 5 hours while blowing _N2 gas, and then reduced to 400°C by vacuum distillation. The low boiling point fraction below ℃ was separated and removed to obtain pitch. The quinoline insoluble content of this pitch is 5.6
The toluene-insoluble content was 45.7% by weight, and the n-heptane soluble content was 2.0% by weight. When this pitch was melt-spun using a spinning nozzle with a nozzle hole diameter of 0.5 mmφ at a spinning temperature of 363℃, the pitch fiber diameter was 20μ.
The yarn did not break even once in 10 minutes.
This pitch fiber was made infusible at 260°C in an air atmosphere and then fired at 2000°C in an inert gas atmosphere, resulting in a tensile strength of 6.6Ton/cm ² and an elastic modulus of 410Ton/cm ² .
It was hot.

Comparative Example 3 Distilling the residual oil by-product from the catalytic cracking process to reduce the boiling point
A heavy residual oil with a temperature of over 400℃ was obtained. This heavy residual oil was obtained. The sulfur content of this heavy residual oil was 2.7% by weight. This heavy residual oil was heat-treated at 410°C for 20 hours, then heated to 360°C and allowed to settle, allowing insoluble substances to settle out. After removing the organic substances, vacuum distillation was performed to separate and remove the low boiling point fraction below 400°C to obtain pitch. The quinoline-insoluble content of the pitch is
22.5% by weight, toluene insoluble content 68.7% by weight, n-
The heptane soluble content was 1.2% by weight. When this pitch was melt-spun at a spinning temperature of 365° C. using a spinning nozzle with a nozzle hole diameter of 0.5 mm, fiber breakage occurred an average of 6 times in 10 minutes at pitch fiber diameter of 20 μm. This pitch fiber was made infusible at 260°C in an air atmosphere and then fired at 2000°C in an inert gas atmosphere, resulting in a tensile strength of 11.0Ton/cm ² and an elastic modulus.
It was 1790Ton/ ^cm2 .

Claims (1)

[Claims] 1. Sulfur content 1.5 at a boiling point of 400°C (converted to normal pressure) or higher
After heat treatment of petroleum heavy residual oil of less than % by weight,
It consists of separating and removing insoluble substances while heating at a temperature of 380°C or less, and then vacuum distilling to remove a fraction with a boiling point of 400°C or less (normal pressure equivalent). A method for producing pitchchi having a toluene insoluble content of 70 to 85% by weight. 2 In claim 1, a low boiling point fraction produced by heating petroleum heavy residual oil with a boiling point of 400°C or more and a sulfur content of 1.5% by weight or less under normal pressure without blowing gas is removed from the system. temperature while suppressing
A method for producing pitutchi characterized by heat treatment at 380 to 415°C for a heating time of 12 to 30 hours. 3. The method for producing pituti according to claim 1, characterized in that insoluble substances are separated and removed by the action of gravity or centrifugal force while heating the heat-treated product at a temperature of 380° C. or lower.