JP6646563B2 - Manufacturing method of soft pitch - Google Patents

Description

  The present invention relates to a method for producing a soft pitch. The present invention particularly relates to a method for producing a soft pitch suitable for a carbon material such as an electrode and a special carbon material.

  Electrodes such as artificial graphite electrodes and aluminum refining electrodes, and carbon materials such as graphite crucibles for metal melting and specialty carbon materials such as granulated activated carbon are used as binders made from aggregates such as coke and coal tar etc. It is manufactured by kneading and molding soft pitch (impregnated pitch) and then firing.

  Conventionally, the soft pitch has been produced through a distillation step of distilling coal tar as a raw material and fractionating a low-boiling oil (naphthalene oil) containing naphthalene.

  Further, as disclosed in Patent Document 1, there is known a technique for producing a synthetic tar by mixing soft pitch obtained by tar distillation and distilled oil.

JP 2006-28423 A

  The soft pitch produced through the above conventional distillation process has a small proportion of components having a boiling point of 250 ° C. or less, so that the boiling point distribution is biased to 250 ° C. or more, and the soft pitch in the soft pitch at a specific temperature during firing of the carbon material. There was a problem that components volatilized rapidly. As a result, internal cracks in the product (carbon material) were generated, and the yield was reduced accordingly.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a soft pitch that can suppress rapid volatilization of components in the soft pitch at a specific temperature.

The present invention has the following aspects.
[1] A tar distillation step of distilling a dehydrated tar obtained by dehydrating coal tar into an intermediate pitch having a boiling point of 120 ° C. or more and a softening point of 70 ° C. or less, and a naphthalene oil having a boiling point of 300 ° C. or less. A naphthalene oil distillation step of distilling the naphthalene oil obtained in the tar distillation step to obtain a light oil having a boiling point of 120 to 200 ° C .; the intermediate pitch obtained in the tar distillation step; Mixing the light oil obtained in the oil distillation step to obtain a soft pitch having a softening point of 70 ° C. or lower.
[2] The method for producing a soft pitch according to [1], wherein the soft pitch has a viscosity at 50 ° C. of 1.5 to 5.0 Pa · s and a fixed carbon amount of 30% by mass or more.

ADVANTAGE OF THE INVENTION According to the manufacturing method of the soft pitch of this invention, the soft pitch which can suppress rapid volatilization of the component in a soft pitch at a specific temperature can be provided.
ADVANTAGE OF THE INVENTION According to the manufacturing method of the soft pitch of this invention, the rapid volatilization of the component in a soft pitch at a specific temperature at the time of baking of a product (carbon material) can be suppressed, and the crack and deformation inside a product (carbon material) are prevented. The yield can be improved.
The soft pitch of the present invention is particularly suitable as an impregnated pitch for a carbon material (electrode, special carbon material).

FIG. 1 is an explanatory diagram illustrating an embodiment of a method for producing a soft pitch according to the present invention. FIG. 2 is a graph in which the mass reduction ratio at each temperature of the intermediate pitch and the soft pitch is measured.

  Hereinafter, an embodiment of a method for manufacturing a soft pitch according to the present invention will be described with reference to FIG. However, the present invention is not limited to the following embodiments.

  FIG. 1 is an explanatory diagram illustrating one embodiment of a method for producing a soft pitch of the present invention. The method for producing a soft pitch according to the present invention includes a tar distillation step of distilling a dehydrated tar obtained by dehydrating coal tar to separate it into an intermediate pitch and a naphthalene oil, and the naphthalene oil obtained in the tar distillation step. To obtain light oil, and a mixing step of mixing the intermediate pitch obtained in the tar distillation step and the light oil obtained in the naphthalene oil distillation step to obtain a soft pitch And

<Tar distillation process>
In the tar distillation step, the coal tar 1 (raw material tar 1) is charged into the dehydration distillation tower 6, and the coal tar 1 is subjected to a dehydration treatment to fractionate components having a boiling point of 100 ° C. or less to obtain a dehydrated tar 2. The dehydrated tar 2 has a boiling point of 100 to 600C. In addition, the boiling point in this specification means the boiling point at normal pressure unless otherwise specified.
Next, the dehydrated tar 2 is withdrawn from the bottom of the dehydration distillation column 6, charged into a vacuum distillation column 7 and distilled by atmospheric distillation or vacuum distillation to separate naphthalene oil 3 and intermediate pitch 4.

  The naphthalene oil 3 has a boiling point of 300 ° C. or less. The naphthalene oil 3 is a distillation fraction containing naphthalene as a main component, and its boiling point range is 120 to 300 ° C.

The intermediate pitch 4 is a residue after the naphthalene oil 3 is distilled off, has a boiling point of 120 ° C. or higher, and a softening point of 70 ° C. or lower. The boiling range of the intermediate pitch 4 is 120 to 600 ° C. The softening point of the intermediate pitch 4 is preferably in the range of 45 to 70 ° C.
The intermediate pitch 4 is not subjected to heat treatment or hydrogenation. When the intermediate pitch 4 is subjected to these treatments, the boiling point of the intermediate pitch 4 rises, and the boiling point distribution of the soft pitch 10 obtained by mixing the intermediate pitch 4 is biased, so that a rapid volatilization at a specific temperature occurs. May not be able to be suppressed.

<Naphthalene oil distillation process>
In the naphthalene oil distillation step, the naphthalene oil 3 obtained in the tar distillation step is charged into a naphthalene distillation column 8 and distilled by atmospheric distillation to obtain a light oil 5. The boiling point range of the light oil 5 is 120 to 200 ° C.

<Mixing process>
In the mixing step, the intermediate pitch 4 obtained in the tar distillation step and the light oil 5 obtained in the naphthalene oil distillation step are charged into a mixing tank 9 and mixed to obtain a soft pitch 10.
Such a soft pitch 10 is excellent in the effect of suppressing rapid volatilization of components in the soft pitch 10 at a specific temperature. This is considered to be because the boiling point distribution of the soft pitch 10 becomes gentle by mixing the intermediate pitch 4 and the light oil 5 produced through the above-described steps to produce the soft pitch 10.

  The mixing ratio between the intermediate pitch 4 and the light oil 5 can be appropriately adjusted in consideration of the viscosity and the like of the soft pitch 10 to be manufactured. From the viewpoint that a smoother boiling point distribution can be obtained, it is preferable to mix the light oil 5 with 1 to 10 parts by mass and more preferably 1 to 5 parts by mass with respect to the intermediate pitch 4 of 100 parts by mass.

(Soft pitch 10)
The soft pitch 10 is manufactured through the above steps. The boiling range of the soft pitch 10 is 120 to 600 ° C. The soft pitch of the soft pitch 10 is 70 ° C. or less. The soft pitch of the soft pitch 10 is preferably 45 to 70 ° C.
Further, through the above steps, a soft pitch 10 having a viscosity at 50 ° C. of 1.5 to 5.0 Pa · s and a fixed carbon amount of 30% by mass or more can be produced. The viscosity of the soft pitch 10 at 50 ° C. is more preferably 1.5 to 3.0 Pa · s. The fixed carbon amount of the soft pitch 10 is more preferably 35% by mass or more. Further, the mass reduction rate when the soft pitch 10 is heated at 150 ° C. for 48 hours in a nitrogen atmosphere is preferably 2% by mass or more.
The soft pitch 10 according to the present invention is excellent in the effect of suppressing rapid volatilization of components in the soft pitch 10 at a specific temperature. In particular, it is excellent in the effect of suppressing rapid volatilization at a specific temperature during molding and firing of a carbon material, and can be suitably used as a carbon material impregnating pitch. By using the soft pitch 10 as a raw material for a carbon material, cracking and deformation during the forming and firing of the carbon material are suppressed, thereby contributing to an improvement in yield.

The measurement conditions of each measurement value in the present invention are as follows.
[Measurement conditions of viscosity]
JIS Z 8803 (2011) Viscosity of liquid-Measured using a Brookfield B-type rotational viscometer according to the measurement method.
[Measurement conditions of softening point]
JIS K 2425 (2006) 8. It was measured in accordance with the method of measuring the softening point of tar pitch (ring and ball method).
[Measurement conditions of fixed carbon amount]
JIS K 2425 (2006) 11. It was measured using an electric furnace according to the fixed carbon content determination method.

The soft pitch 10 was manufactured according to the above embodiment.
First, 100 parts by mass of coal tar 1 is charged into a dehydration distillation column 6, and the raw material tar 1 is subjected to dehydration treatment to fractionate components having a boiling point of 100 ° C. or less to obtain 96 parts by mass of dehydrated tar 2. Was.

  Next, 96 parts by mass of the dehydrated tar 2 was withdrawn from the bottom of the dehydration distillation column 6, charged into the vacuum distillation column 7, and subjected to distillation under reduced pressure of 0.02 MPa to obtain 15 parts by mass of naphthalene oil 3. An intermediate pitch 4 of 81 parts by mass was obtained. The boiling range of the naphthalene oil 3 was 120 to 300 ° C. The intermediate pitch 4 had a softening point of 65 ° C., a boiling range of 120 to 600 ° C., a viscosity at 60 ° C. of 20 Pa · s, and a fixed carbon content of 37% by mass.

  Thereafter, 15 parts by mass of the naphthalene oil 3 was charged into a naphthalene distillation column 8 and subjected to atmospheric distillation to obtain 3 parts by mass of a light oil 5. The boiling point range of this light oil 5 was 120 to 200 ° C.

Finally, 3 parts by mass of the light oil 5 was mixed with 100 parts by mass of the intermediate pitch 4 to obtain a soft pitch 10.
The soft pitch 10 had a softening point of 60 ° C, a boiling range of 120 to 600 ° C, a viscosity at 50 ° C of 2.8 Pa · s, and a fixed carbon content of 35% by mass.

  For the intermediate pitch 4 and the soft pitch 10 manufactured as described above, the mass reduction ratio when the temperature is raised from room temperature (25 ° C.) to 600 ° C. (the mass at each temperature with respect to the total mass of the intermediate pitch 4 or the soft pitch 10) Was measured by a thermogravimetric analyzer (TGA). The results are shown in FIG.

  As shown in FIG. 2, in the soft pitch 10 manufactured by blending the light oil 5, the rapid volatilization at a specific temperature was suppressed as compared with the intermediate pitch 4 not blending the light oil 5. . This is probably because the soft pitch 10 was produced by mixing the intermediate pitch 4 and the light oil 5 to produce the soft pitch 10, and the boiling point distribution of the soft pitch 10 became gentle. In addition, since the rapid volatilization at a specific temperature is suppressed in this way, deformation and cracking during molding and firing of a carbon material (electrode, special carbon material) manufactured using the soft pitch 10 are prevented. It is possible to do.

1 Coal tar (raw material tar)
2 dehydrated tar 3 naphthalene oil 4 intermediate pitch 5 light oil 6 dehydrated distillation tower 7 vacuum distillation tower 8 naphthalene distillation tower 9 blending tank 10 soft pitch

Claims (2)

A tar distillation step of distilling the dehydrated tar obtained by dehydrating the coal tar to have an intermediate pitch having a boiling point of 120 ° C. or higher and a softening point of 70 ° C. or lower and a naphthalene oil having a boiling point of 300 ° C. or lower,
A naphthalene oil distillation step of distilling the naphthalene oil obtained in the tar distillation step to obtain a light oil having a boiling point of 120 to 200 ° C;
A mixing step of mixing the intermediate pitch obtained in the tar distillation step and the light oil obtained in the naphthalene oil distillation step to obtain a soft pitch having a softening point of 70 ° C. or less, Production method.   The method for producing a soft pitch according to claim 1, wherein the soft pitch has a viscosity at 50 ° C. of 1.5 to 5.0 Pa · s and a fixed carbon amount of 30% by mass or more.