JP2603116B2 - Method for producing isotropic bitch for carbon fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a petroleum-based carbon fiber precursor.

[Conventional technology]

In order to produce a carbon fiber precursor pitch from petroleum heavy oil, it is necessary to appropriately modify and adjust the heavy oil.

For example, Japanese Patent Application Laid-Open No. 61-190587 proposes a method in which a solvent is extracted after heat treatment and a second-stage heat treatment is performed in order to further improve the molecular weight range.

Japanese Patent Publication No. 60-57478 discloses a method in which pitch obtained by heat treatment is subjected to hot filtration to remove insoluble components, and further subjected to reduced pressure treatment.

The use of a solvent to remove insoluble components not only complicates steps such as dissolving the pitch and recovering the solvent, but is uneconomical in every respect. Further, in the hot filtration method and the like, there is a problem that the unmelted component easily causes clogging of the filter, resulting in poor productivity and the like.

[Problems to be solved by the invention]

Conventional petroleum-based carbon fibers are inexpensive as raw materials, but are not necessarily economical because they have to go through complicated steps as described above. SUMMARY OF THE INVENTION An object of the present invention is to produce general-purpose carbon fiber starting from a petroleum-based raw material and using a production process that is simple and requires few processing steps.

[Means for solving the problem]

Therefore, the inventor of the present application has selected a material having high aromaticity,
As a result of studying how to efficiently remove low-boiling components,
The present invention has been reached.

That is, the present invention is to decatalyze a fluid catalytic cracking oil of petroleum, and to use a fraction having a boiling point of 400 ° C. or higher obtained by pre-distillation as a raw material, and perform centrifugal molecular distillation under reduced pressure at a temperature of 250 ° C.
This is a method for producing an isotropic pitch for carbon fiber, in which a fraction having a boiling point of 500 ° C. or less is removed by distillation at 350 ° C. to obtain a pitch having a softening point of 180 ° C. or more.

Hereinafter, the present invention will be described in more detail.First, one of the features is that a fraction having a boiling point of 400 ° C. or more obtained by decatalyzing and predistilling a fluid catalytic cracking oil of petroleum as a raw material is selected. .

The raw material of the carbon fiber precursor pitch is preferably a highly aromatic one. The fluid catalytic cracking oil contains a large amount of aromatic compounds, and preferably has an aromatic index of 50% or more. Coal tar pitch is superior in that it has a large amount of aromatic compounds. However, coal tar pitch contains a large amount of insoluble solids, and requires solvent extraction or the like to remove it, which complicates the process.

Since the fluid catalytic cracking oil selected in this way contains a small amount of catalyst, the catalyst is removed by, for example, an electrostatic oil purification treatment, and then a fraction under 400 ° C is removed by a normal vacuum distillation apparatus. And use it as raw material oil.

The second feature of the present invention is that the raw material obtained above is distilled at a temperature of 250 to 350 ° C. under reduced pressure by a centrifugal molecular distillation apparatus to remove a fraction having a boiling point of 500 ° C. or less, and a softening point of 180 ° C. or more. Is to get the pitch. Isotropic pitch for carbon fiber,
If light fractions are included, nozzle fouling will occur during melt spinning,
Stable spinning operation cannot be performed due to yarn breakage. Also,
The presence of a large amount of light components has disadvantages such as difficulty in infusibilizing pitch yarn. Because of this, the boiling point is 500
It is necessary to remove components below ℃. In addition, when high temperature and long time are required for removing light components, insoluble solids are generated, so at a relatively low temperature, preferably 350 ° C. or less,
It is preferable to remove the light fraction in a short time.

As a result of various studies on methods for removing light fractions at a relatively low temperature and in a short time, good results were obtained when the raw material was treated in a thin film form at a temperature of 250 to 350 ° C under reduced pressure in a centrifugal molecular distillation apparatus. I knew it could be done.

The feature of the centrifugal molecular distillation apparatus used in the present invention is that a sample is supplied to the center of a rotary evaporating surface in the shape of a flower pot rotating at a high speed, and the liquid is spread on the rotating surface by the action of centrifugal force to form a thin film. This is an apparatus of the type in which the sample is heated, the sample is evaporated, and the sample is condensed on the opposing condensing surface. Compared to a pot-type molecular distillation apparatus and a falling-film molecular distillation apparatus, it has the following features.

 Liquid heating time is very short.

 A uniform and extremely thin liquid film can be obtained.

 There is almost no pressure loss.

 Good evaporation efficiency, heat efficiency and degree of separation.

 Low risk of foaming.

 High viscosity liquid can be processed.

Next, the mechanism of the centrifugal molecular distillation apparatus will be described with reference to FIG. The condensation dome (1) and the main body plate (2) are flange-connected via an O-ring, and the inside of the main body is maintained at a high vacuum by a vacuum pump through an exhaust port (3). The sample is rotated by a feed pump through a preheater, feed pipe, etc.
It is supplied to the center and forms a uniform thin film that does not cause mist scattering by the action of centrifugal force. Subsequently, the main body sheath heater (6) provided at the lower part of the evaporating dish evaporates mainly by giving latent heat of evaporation, and is condensed on the opposite condensing surface (7) and collected in the distilling gooder (8). Further, the distillation residue liquid is collected in a residue gooder (9) and each of them is discharged out of the apparatus.

The softening point of the pitch obtained with the above device is 180 ° C
When the softening point is lower than 180 ° C., yarn breakage often occurs during spinning, and the infusibilization step after spinning requires a long time, resulting in reduced productivity. The obtained pitch having a softening point of 180 ° C. or higher can be used as isotropic pitch for carbon fiber as it is, and is sequentially turned into carbon fiber through the steps of spinning, infusibilizing, and carbonizing.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

Example 1 A fluid catalytic cracking oil was treated by an electrostatic oil purification method to remove a catalyst, and then a fraction having a boiling point of 400 ° C or lower was removed by preliminary distillation to obtain a raw material A. The properties of raw material A are shown in Table 1.

Next, the raw material A was distilled by a centrifugal molecular distillation apparatus to obtain a pitch. Table 2 shows the distillation conditions and the properties of the obtained isotropic pitch.

When the obtained isotropic pitch was melt-spun at a spinning temperature of 230 ° C, the yarn was not broken and the spinnability was extremely good.
This spinning pitch is infusibilized at 300 ° C, and then 1000 ° C.
To obtain a carbon fiber. Table 2 shows the properties of the carbon fibers.

Example 2 The same fluid catalytic cracking oil as in Example 1 was subjected to an electrostatic oil purification treatment and a preliminary distillation treatment. The conditions of the pre-distillation were stricter than those in Example 1, and a raw material B having a softening point higher than that of the raw material A was obtained. Table 1 shows the properties of the raw material B. This material B was subjected to centrifugal molecular distillation under the same conditions as in Example 1 to obtain an isotropic pitch. The obtained isotropic pitch had a higher softening point pitch than that of Example 1. This pitch enabled stable continuous spinning at a spinning temperature of 253 ° C.

Comparative example 1 It carried out similarly to Example 1 except having set the centrifugal molecular distillation temperature to 240 degreeC. The softening point of the formed pitch was 140 ° C., the nozzle became dirty during spinning, and continuous spinning was not possible.

Comparative Example 2 Example 1 except that the centrifugal molecular distillation temperature was 360 ° C.
Was performed in the same manner as described above. The softening point of the generated pitch was 230 ° C. When the pitch was observed with a polarizing microscope, a mesophase sphere of several microns was observed. When this pitch was spun, nozzle clogging occurred and continuous spinning was not possible.

Comparative Example 3 Raw material A was distilled by a Bessel-type reduced pressure simple distillation apparatus to obtain a pitch. Pitch temperature 400 ℃, pressure 5mmHg, holding time 1
Distillation over time resulted in the formation of a pitch containing a few microns of mephas at a softening point of 170 ° C. When the formed pitch was spun, the nozzle clogged and spinning was impossible.

[Effects of the Invention] In the present invention, by selecting a fraction having a boiling point of 400 ° C or higher obtained by decatalyzing and pre-distilling a fluidized catalytic cracking oil of petroleum as a raw material, it is possible to avoid insoluble solids that are undesirable in carbon fibers. And a centrifugal molecular distillation apparatus is used to remove a fraction having a boiling point of 500 ° C or less and a softening point of 180 ° C.
By using the above-mentioned pitch, a highly aromatic isotropic pitch for carbon fiber could be obtained by a production process which is simpler and requires less processing steps than the conventional method.

As a result, carbon fibers could be produced more economically than the conventional method.

[Brief description of the drawings]

FIG. 1 shows a centrifugal molecular distillation apparatus used in the present invention. (1): Condensing dome, (2): Body plate (3): Exhaust port, (4): Feed nozzle (5): Evaporating dish, (6): Sheath heater (7): Condensing surface, (8): Distilling goodder (9): Good residue, (10): Distilling outlet (11): Residual discharging outlet, (12): Main body drive motor (13): Motor cylinder, (14): Shaft sealing device Fig. 2 Is a flow sheet of the centrifugal molecular distillation apparatus used in the present invention. (15): Main body of centrifugal molecular distillation apparatus (16): Raw material tank, (17): Residue tank (18): Distillation tank, (19): Feed pump (20): Preheater, (21): Cold trap (22): Oil diffusion pump (23): Mechanical booster pump (24): Oil rotary pump, (25): Thermometer (26): Vacuum gauge

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Toshiaki Suzuki 2-7-3 Marunouchi, Chiyoda-ku, Tokyo Showa Shell Sekiyu KK (56) References JP-A-61-61602 (JP, A)

Claims (1)

(57) [Claims] 1. A fraction having a boiling point of 400 ° C. or higher obtained by decatalyzing and predistilling a fluidized catalytic cracking oil of petroleum as a raw material and distilling at a temperature of 250 to 350 ° C. under reduced pressure using a centrifugal molecular distillation apparatus. A process for removing a fraction having a boiling point of 500 ° C. or lower to obtain a pitch having a softening point of 180 ° C. or higher.