EP-4741460-A1 - BINDER PITCH FOR PRODUCING CARBON MATERIAL AND METHOD FOR PRODUCING CARBON MATERIAL

Abstract

A method for producing a carbon material using pitch having a softening point of 70°C to 120°C, a fixed carbon content of 50.0% by mass or more, a quinoline insoluble matter of 18.0% by mass or less, an initial boiling point of 320°C or more, and a Casson yield value at the softening point +100°C of 0.18 Pa or more, as a binder pitch.

Inventors

• ISHIKAWA, YUTARO
• NISHI, NOBUHIRO

Assignees

• Resonac Corporation

Dates

Publication Date

20260513

Application Date

20240423

Claims (4)

1. A binder pitch for producing a carbon material, wherein the binder pitch has a softening point of 70°C to 120°C, a fixed carbon content of 50.0% by mass or more, a quinoline insoluble matter of 18.0% by mass or less, an initial boiling point of 320°C or more, and a Casson yield value at the softening point +100°C of 0.18 Pa or more.
2. The binder pitch for producing a carbon material according to claim 1, wherein the carbon material is a graphite electrode.
3. A method for producing a carbon material using pitch having a softening point of 70°C to 120°C, a fixed carbon content of 50.0% by mass or more, a quinoline insoluble matter of 18.0% by mass or less, an initial boiling point of 320°C or more, and a Casson yield value at the softening point +100°C of 0.18 Pa or more, as a binder pitch.
4. The method for producing a carbon material according to claim 3, wherein the carbon material is a graphite electrode.

Description

TECHNICAL FIELD The present disclosure relates to a method for producing carbon materials, such as a graphite electrode, and binder pitch. BACKGROUND Carbon materials, such as a graphite electrode used in an electric furnace for remelting iron are produced by kneading and forming aggregates, such as coke, and pitch (referred to as "binder pitch") at a temperature equal to or higher than the softening point of the binder pitch, followed by baking, and then graphitizing. Since it is necessary that the carbon material have properties such as high mechanical strength, high electrical conductivity, and high thermal conductivity, the carbon material preferably has high density. However, the baked body has a structure having a large number of pores due to volatilization of low-molecular-weight components in the binder pitch during the baking step, etc. Therefore, in the production process, impregnating the baked body with pitch (referred to as "impregnation pitch") followed by re-baking several times reduces the porosity and results in the obtained carbon material having high density. The coking value of the binder pitch in the formed body in the baking step is referred to as a carbon yield. The higher the carbon yield, the more the density of the obtained baked body, which is preferable, since the number of subsequent impregnations with the impregnation pitch and re-baking can be reduced. In general, the higher the fixed carbon content of the pitch, the higher the carbon yield. Therefore, it is preferable to use such pitch as a binder pitch. As a method of increasing the fixed carbon content of the binder pitch, a method of removing light components in the pitch by distillation, etc., is known, but at the same time, the softening point also increases. In general, when kneading aggregates, such as coke, and a binder pitch, a temperature higher than the softening point by about 50°C or more is required. Therefore, when the softening point is high, there is a problem that the equipment load becomes large. In order to solve this problem, there is a method of adding a cutback oil to pitch having a high fixed carbon content and a high softening point (Patent Literature 1). [Citation List] [Patent Literature] [PTL 1] US 6352637 B2 SUMMARY OF INVENTION [Technical Problem] The method described in Patent Literature 1 has a problem that the initial boiling point of the obtained pitch is lowered, since it is necessary to add a cut-back oil having a relatively low boiling point. When the initial boiling point is too low, there is a problem that the amount of light components volatilized during kneading is large, so that the viscosity increases during kneading, and the kneadability is lowered. As described above, it is difficult to achieve both favorable kneadability and a high carbon yield only from the viewpoint of the fixed carbon content and the softening point, which have been considered important so far. The present disclosure provides a binder pitch capable of achieving both favorable kneadability and a high carbon yield, and a method for producing a high density carbon material using the binder pitch. [Solution to Problem] When a formed body is baked, softening and a decrease in viscosity of the binder pitch in the formed body occur with an increase in temperature. At this time, when the outflow of the binder pitch from the formed body occurs, the carbon yield decreases. In order to suppress the outflow of the binder pitch during baking, it is considered effective to use pitch capable of maintaining a relatively high viscosity even during baking. However, such pitch generally has a high softening point, and therefore has a problem of lowering the kneadability. The present inventors considered that, in order to suppress the outflow of the binder pitch during baking without lowering the kneadability, a binder pitch, whose viscosity tends to decrease in a state in which the binder pitch flows to some extent, such as during kneading, and which maintains a high viscosity in a state in which the binder pitch hardly flows, such as during baking, is preferable. Based on this consideration, the present inventors have combined a new viewpoint of rheological properties of the binder pitch with the characteristics that have been conventionally considered important, such as the fixed carbon content and the softening point of the binder pitch, and conducted intensive studies. As a result, the present inventors have found that a higher carbon yield can be obtained and a higher density carbon material can be obtained, when pitch having a similar fixed carbon content but a higher Casson yield value is used as the binder pitch, thereby completing the present invention. That is, the contents of the present disclosure relate to the following [1] to [4]. [1] A binder pitch for producing a carbon material, wherein the binder pitch has a softening point of 70°C to 120°C, a fixed carbon content of 50.0% by mass or more, a quinoline insoluble