JPS60255604A - Preparation of mesocarbon microbead - Google Patents

Abstract

PURPOSE:To obtain the titled beads in high purity by an extremely simple operation without using solvent, by heat-treating a heavy oil or pitch to form mesophase pitch containing spherule of mesophase, centrifuging it under heating. CONSTITUTION:A heavy oil or pitch is heated 300-500 deg.C, to form spherules of mesophase. By this heat teatment, mesophase pitch in a state wherein spherules of mesophase are dispersed into an optically isotropic parent phase pitch is obtained. Then, the mesophase pitch is centrifugal while being heated at 200- 350 deg.C. Consequently, the spherules of mesophase can be separated from the parent phase pitch and collected, to give mesocarbon microbeads.

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for producing mesocarbon microbeads from heavy oils or pitches. [Technical background of the invention and its problems] Mesocarbon microbeads (hereinafter abbreviated as MC) are generated during the process of liquid-phase carbonization of coal tar, heavy petroleum oil, or pitch. Optically anisotropic liquid crystal spherules (menphase spherules) with a diameter of several gm to several hundred 1 Lm are
It is the name of something isolated from the optically isotropic pitch of the parent phase. In recent years, due to the demand for advanced use of coal-based or petroleum-based heavy oil or pitch, this MC has developed into high-density carbon materials, conductive composite materials, carbon for electrical resistance, toner for electrophotography,
It is a substance that is expected to be used in a wide range of fields as a raw material for high-performance carbon materials such as carbon fibers, carbon sheets, activated carbon beads, and carbon molecular sieves. In order to isolate such MC, Japanese Patent Application Laid-Open No. 56-967
In Publication No. 10, a mixture of mesophase pitch containing mesophase spherules obtained by heat-treating heavy oil and a solvent that dissolves only the parent phase is passed through a hydrocyclone to produce light liquid, medium liquid, A method is disclosed in which MC is separated by separating into a heavy liquid and then removing the solvent in the heavy liquid, and in JP-A-56-125210, pitches are heat treated to generate mencarbon spherules. JP-A-57-78487 discloses a method in which the small spheres are separated from the pitch matrix by a static separation method using a separation aid consisting of an aromatic solvent and a fatty solvent. The primary heat-treated pitch containing the generated mesophase spherules is cooled below its softening point, and then subjected to secondary heat treatment to separate the mesophase spherules precipitated in the secondary heat treatment. We have proposed a method for recovering the assembled mesophase spherules by solvent extraction. These methods use a solvent for MC@@, but since all of them use 10 parts by weight or more of solvent per 1 part by weight of pitch, the amount of processing increases, and it takes time to recover and purify the solvent. This method has the drawback of increasing manufacturing costs due to the need for secondary processing. As a method that does not use a solvent for MC isolation, JP-A-57-
In Publication No. 200213, after heating heavy oil to 400 to 500°C to obtain a pitch containing mesophase spheres,
We have proposed a method of agglomerating menphase spherules by applying turbulent flow at 0 to 400°C and separating them from the matrix pitch. This method focuses on the fact that the final product is a carbon molded body, so it does not necessarily have to be a small sphere, and produces a bulk mesophase that is a combination of mesophase small spheres. This is inappropriate as a manufacturing method. Furthermore, since the obtained aggregate still contains about 20 to 70% matrix pitch,
It is unsuitable as a method for isolating MC. [Object of the Invention] The present invention has been researched and developed in view of the above-mentioned ε.
Therefore, various problems associated with the use of solvents can be eliminated, and mencarbon microbeads can be separated from the matrix pitch with high purity by an extremely simple operation of centrifugation under heating. The goal is to provide a method for manufacturing beads. [Summary of the Invention] The gist of the present invention for achieving the above object is to heat-treat heavy oils or pitches at a temperature of 350 to 50°C to produce mesophase pitch containing menphase spherules at 200 °C. This is a method for producing mencarbon microbeads, characterized in that the mesophase spherules are separated from the parent phase by centrifugation at a temperature of ~350"C. The mesophase spherules are separated from the parent phase. This is difficult because (1) the viscosity of the matrix pitch is high, and (2) the difference in specific gravity between the mesophase spherules and the matrix pitch is small. Therefore, the viscosity of the matrix pitch is lowered by heating and centrifugation is performed. This led to the discovery that the mesophase spherules and the matrix pitch, which have a small difference in specific gravity, could be separated by this method, and this led to the present invention. The viscosity is lowered by heating the mesophase pitch contained therein to 200 to 350°C, and the mesophase spherules, which have a small difference in specific gravity, are separated from the parent phase pitch by centrifugation.

[Specific examples of the invention]

The invention will now be described in further detail. The heavy oils or pitches used in the present invention include heavy oils such as coal tar and petroleum-based heavy oils, and pitches such as coal tar pitch and petroleum-based pitch. When these heavy oils or pitches are heated at a temperature of 300 to 500 degrees Celsius, they can be heated to several micrometers to several hundred grams in a few minutes to 5 hours.
Mesophase spherules of several to 40 mao1% are produced. At temperatures below 350°C, the mesophase formation rate is slow and almost no mesophase is formed;
At temperatures above 0'C, rapid polycondensation reactions occur, resulting in coke-like bulk mesophase and coke-like char. Therefore, a heat treatment temperature range of 350 to 500°C is suitable. By performing the heat treatment as described above, a menphase pitch in which mesophase spherules are dispersed in an optically isotropic matrix pitch can be obtained. Furthermore, centrifugation is performed while heating this mesophase pitch to a temperature of 200 to 350°C.
The temperature of 0°C is derived from Stokes' law by separately collecting the matrix pitch and mesophase spherules based on the conventional solvent separation method, measuring the specific gravity of each and the relationship between the viscosity and temperature of the matrix pitch. From the sedimentation rate calculated according to equation (1), the heating temperature that would give a sedimentation rate suitable for industrial centrifugation was selected. Here, vg: Sedimentation velocity of mesophase spherules [C layer/5
ecl Δρ: Specific gravity difference between mesophase spherules and matrix pitch E
g/ crn'1 d: Minimum particle size of mesophase spherules [Cl3 g: Gravitational acceleration 980 [g/sec] River viscosity
[c, p,] Sedimentation rate and heating temperature of mesophase spherules at a certain temperature for each of the coal tar pitches shown in Figure 1 that were heat-treated at 400°C for 5 minutes, 20 minutes, 40 minutes, and 680 minutes. Showing an open collar. As is clear from FIG. 1, as the heat treatment time becomes longer, the sedimentation rate of the menphase spherules becomes slower. The broken line a is the lower limit of the applicable range of industrial centrifuges. The one heated at 400°C for 5 minutes contains about 5% of mesophase spherules,
The applicable temperature of industrial centrifugal separators is 200°C or higher, and those heated at 400°C for 80 minutes produce approximately 30%
335 despite containing menphasic spherules of
Industrial centrifugation becomes possible at temperatures above ℃. However, when the temperature exceeds 350° C., new menphase microspheres are generated and the menphase microspheres coalesce. Therefore, the heating temperature for centrifugation is preferably 200 to 350°C. The obtained precipitate still contains about 5 to 10% of matrix pitch, so it can be washed to increase its purity if necessary, but this is difficult in terms of yield and amount of solvent used. This is fundamentally different from the solvent separation methods described above. [Example] Examples will be described below. Coal tar pitches 1 to 6 from which insoluble solids have been removed are heated at 430°C for 15°30°C under a reduced pressure of 5+smHg.
Mesophase pitch was obtained by heat treatment for 45 minutes. These mesophase pitches were heated to 10 x 10 G
The precipitate was collected by centrifugation at a centrifugal efficiency of ++see. Content of mesophase spherules in mesophase pitch (MaO 1%), centrifugation heating temperature, mesophase spherule content in precipitate (Ma 01%), and particle size measured from area ratio observed under a polarizing microscope. The range is shown in Table 1. Table 1 t: 1′ 1−・ − 1・ As is clear from Table 1, NOl has a temperature of
At 50°C (<200°C), the content of mesophase spherules in the precipitate was as low as 48 MaO1%, and separation was insufficient. Also,! '&) 6 has a centrifugation temperature of 40θ℃ (>35
(0°C), the particle size ranged from 5 to 1300 pm, and coalescence of mesophase spherules occurred. No. 2, 3, 4, and 5 have a centrifugation temperature of 200-3
At 50°C, the content of mesophase spherules in the precipitate was 90
% or more, and the particle size range was 5 to 60 ILm. Furthermore, the precipitates of Nb2 and 4 were molded at a pressure of 2 t/c, heated to 2800° C. in Ar gas, and fired. None of the graphitized molded products showed any deformation such as cracking or blistering, and their bulk densities were 1.98 and 2.00, respectively, and were of good quality. [Effects of the Invention] As described above, the present invention does not use any solvent at all, and therefore can eliminate the problems associated with the use of solvents, and can be performed using an extremely simple operation of centrifugation under heating. This is an industrially effective method that can produce highly pure mesocarbon microbeads with a high recovery rate.

[Brief explanation of the drawing]

Figure 1 shows Kotaltar pitch heated to 400°C for 5 minutes and 20 minutes.
FIG. 3 is a diagram showing the relationship between the sedimentation rate and heating temperature of mesophase spherules heated for 1, 40 minutes, and 80 minutes. a. Lower limit of the applicable range of industrial centrifuges Patent applicant Yoshihisa Nagai, Patent attorney representing Sumitomo Metal Industries, Ltd. Figure 1 Addition *L@ ('0

Claims (1)

[Claims] (1) By heating heavy oils or pitches at a temperature of 350 to 500°C and centrifuging the mesophase pitch containing the generated mesophase spherules at a temperature of 200 to 350°C, A method for producing mencarbon microbeads, which comprises separating the mesophase spherules from a parent phase.