JPH0123405B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing carbon molded bodies such as carbon electrodes, and more particularly to a method for manufacturing carbon molded bodies from coal-based binder pitch or petroleum-based binder pitch and carbonaceous aggregate. Technical background of the invention and its problems In recent years, for example, carbon electrodes have (a) large mechanical strength and thermal conductivity due to ultra-high power operation associated with larger and more efficient electric furnaces; (b) It has a small coefficient of thermal expansion and modulus of elasticity, and (c) it has excellent so-called thermal shock resistance.
Products that meet various requirements such as low electrical resistance and (d) high density are required. For this reason, needle coke with high density and high crystallinity has been mainly used as an aggregate for manufacturing carbon molded bodies such as carbon electrodes. Coal-based binder pitch or petroleum-based binder pitch is used to produce carbon compacts such as carbon electrodes from aggregates such as needle coke, and the properties of the resulting carbon compacts depend on the properties of this binder pitch. Changes greatly. For this reason, many proposals have been made for improving the binder pitch used in producing carbon molded bodies, and conventionally the method of applying thermal modification treatment to coal-based pitch or petroleum-based pitch has been mainly adopted. However, when a binder pitch obtained by a thermal modification method is used to produce a carbon molded article, there are disadvantages in that the softening point of the binder pitch increases due to the thermal modification treatment, and the so-called graphitization property deteriorates. On the other hand, research has also been conducted to modify the binder pitch by adding additives to the binder pitch, thereby producing carbon molded bodies with desired properties. For example, Japanese Patent Publication No. 45-22949 discloses a method for producing a binder pitch, which comprises adding 1 to 15% by weight of carbon black having a particle size of 1 μm or less to the binder pitch, followed by heat treatment at 300 to 400°C. However, this method has the drawback that the graphitizability of the resulting binder pitch deteriorates, and also has the major problem of requiring heat treatment after addition of carbon black. In addition, Japanese Patent Publication No. 51-20397 discloses that 10% or less of mesocarbon microbeads are added to coal-based or petroleum-based pitch, and the resulting mixture is heated to a temperature above the softening point of the pitch and below 400°C. A method for manufacturing a binder pitch used for manufacturing a carbon electrode characterized by the following is disclosed. However, this method also has a major problem in that it is necessary to perform heat treatment after adding mesocarbon microbeads to coal-based or petroleum-based pitch, and it is not necessarily preferable from the point of view of cost. OBJECTIVES AND SUMMARY OF THE INVENTION The present invention aims to solve the drawbacks associated with the prior art as described above, and aims to solve the problems associated with the prior art as described above. The object of the present invention is to provide a method for producing a carbon molded body with excellent properties. In the method for producing a carbon molded body according to the present invention, when producing a carbon molded body by mixing and firing a coal-based pitch or petroleum-based binder pitch and carbonaceous aggregate, bulk mesophase is added to the binder pitch or the carbonaceous aggregate. It is characterized by being added to the carbonaceous aggregate in advance or to the mixture of the binder pitch and carbonaceous aggregate. It is desirable that the bulk mesophase is added in an amount of 20% by weight or less, preferably 15% by weight or less, and more preferably 3 to 5% by weight of the binder pitch. The carbon molded body obtained by the method for manufacturing a carbon molded body according to the present invention exhibits excellent properties in terms of graphitizability, mechanical strength, thermal shock resistance, bulk density, electrical resistance value, and the like. DETAILED DESCRIPTION OF THE INVENTION In the present invention, a coal-based binder pitch or a petroleum-based binder pitch is used as a binder pitch for carbonaceous aggregate. As the coal-based binder pitch, medium binder pitch, hard binder pitch, etc. are used.
As the petroleum binder pitch, naphtha tar pitch produced as a by-product during naphtha cracking, decant oil produced as a by-product during fluid catalytic cracking, pitch obtained by heat treating petroleum heavy oil, etc. are used. In the present invention, coal-based binder pitch or petroleum-based pitch can be used alone as the binder pitch, or a mixture of coal-based binder pitch and petroleum-based pitch can also be used as the binder pitch. Examples of the carbonaceous aggregate include coal-based coke, coal-based needle coke, petroleum-based coke, and petroleum-based needle coke, and needle coke is particularly preferred for high-grade artificial graphite electrodes. The bulk mesophases used in the present invention are petroleum heavy oils such as normal pressure residual oil of petroleum, vacuum residual oil, catalytic cracking decant oil, pyrolysis tar, hydrocarbons such as coal tar, oil sand oil, etc. Mesophase small spheres (mesocarbon microbeads) that are generated in the heat treatment pit when heavy oil is heat treated to a temperature of 400 to 500°C are aggregated and separated from the matrix pit. It is a substance rich in physical activity. One of the methods for manufacturing such bulk mesophases
An example is disclosed in Japanese Unexamined Patent Publication No. 57-200213 filed by the present applicant, in which heavy oil is heated to a temperature of 400 to 500°C to perform a polycondensation reaction to produce pits containing mesophase spherules. After getting it, the pitch is 250 ~
By cooling to 400°C and applying turbulent flow, mesophase spherules are aggregated and coalesced, and bulk mesophase is obtained by separating this from the parent phase. The apparatus for producing such bulk mesophases is disclosed in the patent application filed in 1983 by the applicant.
It is disclosed in Publication No. 139467. The bulk mesophase is pre-added to a coal-based or petroleum-based binder pitch, or added to a mixture of a coal-based or petroleum-based binder pitch and carbonaceous aggregate. Additionally, in some cases, the bulk mesophase may be pre-added to the carbonaceous aggregate and mixed with a coal-based binder pitch or a petroleum-based binder pitch. This means that bulk mesophase can be added at any point in the process of industrially manufacturing carbon compacts, from blending the particle size of the aggregate to mixing the binder pitch to the coalescence process. ing. The bulk mesophase is added in an amount of 20% by weight or less, preferably 15% by weight or less, more preferably 3 to 5% by weight, based on the weight of the coal-based binder pitch or petroleum-based binder pitch.
If the amount of bulk mesophase added is too small, the effects of adding bulk mesophase, such as improving graphitization or increasing bonding strength, will not be sufficiently obtained. If it exceeds 20% by weight, the bending strength, thermal shock resistance, etc. of the obtained carbon molded article tend to decrease slightly, which is not preferable. When producing carbon molded bodies from binder pitch and aggregate, bulk mesophase can be added to the binder pitch or carbonaceous aggregate in advance, or by adding it to the mixture of binder pitch and aggregate. As a result, the following effects can be obtained. (a) Even when bulk mesophase is added to the binder pitch, the softening point of the binder pitch hardly increases. Therefore, mixing and molding can be carried out under exactly the same temperature conditions as in the case of ordinary binder pitch. The bulk density of the obtained carbon molded body is improved. (b) The bending strength of the obtained carbon molded body is significantly improved, and the electrical resistance value is also decreased. This is considered to be because the bulk mesophase added to the binder pitch becomes a nucleus in the binder, increasing the bonding force. (c) The thermal shock resistance of the obtained carbon molded body is improved. (d) When an extruded body is formed by extrusion molding a composition for producing a carbon molded body consisting of binder pitch, aggregate, and bulk mesophase, the bulk density of the extruded body is improved. This is thought to be because the wetting properties of the binder pitch with respect to the aggregate are improved by the addition of bulk mesophase. (e) Bulk mesophase is a highly crystalline carbon precursor and has excellent graphitization properties, so that graphitization of a composition for producing a carbon molded body to which bulk mesophase is added is improved. (F) Binder pitches to which bulk mesophases have been added in advance do not require heat treatment to be applied to the binder pitches after adding bulk mesophases, compared to binder pitches to which mesocarbon microbeads have been added. , is exceptional in this respect. That is, excellent effects can be obtained simply by adding bulk mesophase. The bulk mesophase added to the binder pitch preferably has a particle size of 20 mesh or finer, preferably 60 mesh or finer. A wide variety of conventional methods can be used to produce a carbon molded body from a carbon molded body manufacturing composition containing a binder pitch, an aggregate, and a bulk mesophase.
For example, a binder pitch to which bulk mesophase is added and aggregate are mixed, preferably 10 to 50 parts by weight of the binder pitch is 26 to 100 parts by weight of the aggregate.
Mix thoroughly to make ~30 parts by weight, extrude this to form an extrudate, and then extrudate the extrudate.
A fired body is formed by firing at a temperature of 800 to 1000°C for about one hour to several days. Next, this fired body is heated to 2600 ~
A carbon formed body can be produced by graphitizing the fired body by heating at a temperature of 3000° C. for 1 hour to several days. In addition, in the above description, the present invention is explained for the case where a carbon molded body is formed by extrusion molding method etc. from a composition for producing a carbon molded body containing a binder pitch, an aggregate, and a bulk mesophase. However, the present invention is not limited thereto; for example, a primary sintered body obtained by firing aggregate, etc. is impregnated with pitch in order to improve its quality, and then secondary firing is performed to improve the quality of the primary sintered body. In the case of producing a carbon molded body, a coal-based pitch or a petroleum-based pitch to which bulk mesophase is added in advance can be used as the impregnating pitch. In this case as well, the resulting carbon molded product has excellent graphitization properties, as well as mechanical strength, thermal shock resistance, bulk density, and the like. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. Example 1 Coal-based binder pitch (softening point 109℃, fixed carbon content 56% by weight, quinoline insoluble content 4.2% by weight),
Bulk mesophase of 60 mesh or finer is added in an amount of 3% by weight of the coal-based binder pitch,
A binder pitch was prepared. Next, commercially available needle petroleum coke (particle size composition: 8 to 20 mesh) was added.
28 parts by weight of the binder pitch was added to 100 parts by weight (30% by weight of 20-35 meshes, 10% by weight of 20-35 meshes, 60% by weight of 100 meshes or less), the resulting mixture was loaded into a kneader, and heated at 160°C. The mixture was kneaded for 1 hour.
This mixture was then transferred to an extruder and 130
An extruded body was obtained by extrusion molding at ℃. This extruded body was placed in a firing furnace and heated to 1000℃ at a temperature increase rate of 200℃/hour.
After raising the temperature to 1,000°C, it was maintained at 1000°C for 1 hour to obtain a fired body. Next, this fired body is heated to 2800℃ in a graphitization furnace.
A graphitized carbon molded article was produced by heating to . The physical properties of the obtained carbon molded body are shown in the table. Example 2 A carbon molded body was produced in the same manner as in Example 1, except that 5% by weight of bulk mesophase was added to the coal-based binder pitch. The physical properties of the obtained carbon molded body are shown in the table. Example 3 A carbon molded body was produced in the same manner as in Example 1, except that 10% by weight of bulk mesophase was added to the coal-based binder pitch. The physical properties of the obtained carbon molded body are shown in the table. Example 4 A carbon molded body was produced in the same manner as in Example 1, except that 15% by weight of bulk mesophase was added to the coal-based binder pitch. The physical properties of the obtained carbon molded body are shown in the table. Comparative Example 1 A carbon molded body was produced in the same manner as in Example 1 except that no bulk mesophase was added to the coal-based binder pitch. The physical properties of the obtained carbon molded body are shown in the table.

【table】

[Table] The following can be seen from the table. (a) By adding bulk mesophase into the binder pitch in advance, the bending strength of the resulting carbon molded product is significantly improved, and the electrical resistance value is reduced. (b) Regarding the thermal shock resistance of the obtained carbon molded body, 3 to 5% by weight of
When a binder pitch containing bulk mesophase is used, thermal shock resistance is significantly improved, but when the amount of bulk mesophase added reaches 10 to 15% by weight, it tends to decrease slightly. (c) The bulk density can be improved by adding bulk mesophase to the binder pitch in advance in any of the extruded bodies, fired bodies and carbon molded bodies.

Claims (1)

[Claims] 1. When producing a carbon molded body by mixing and firing a coal-based binder pitch or petroleum-based binder pitch and carbonaceous aggregate, bulk mesophase is added to the binder pitch or carbonaceous aggregate. 1. A method for producing a carbon molded article, which comprises adding the binder to the binder pitch or to the mixture of the binder pitch and the carbonaceous aggregate in advance. 2. The method for producing a carbon molded article according to claim 1, wherein the bulk mesophase is added in advance to a coal-based binder pitch or a petroleum-based binder pitch. 3. The method for producing a carbon molded article according to claim 1, wherein bulk mesophase is added in an amount of 20% by weight or less of the weight of the coal-based binder pitch or petroleum-based binder pitch. 4. The method for producing a carbon molded article according to claim 1, wherein bulk mesophase is added in an amount of 15% by weight or less of the weight of the coal-based binder pitch or petroleum-based binder pitch. 5 Add bulk mesophase to 3-5% of the weight of the coal-based binder pitch or petroleum-based binder pitch.
The method for producing a carbon molded body according to claim 1, wherein the carbon molded body is added in an amount of % by weight.