CA1064658A - Method for producing solid carbon material having high bulk density and flexural strength - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Solid carbon article having high bulk density of at least 1.90 g/cm3 and high flexural strength of at least 900 kg/cm2 can be produced by sequential steps of preparing, by means of poly-condensation of a raw pitch material, a specific precursory car-bon material which has an atomic ratio H/C of 0,4 to 0.6, a quino-line soluble of 2 to 15 weight %, a fixed carbon content of 80 to 93 weight % and a degree of heat shrinkage of at least 2 %; pul-verizing the precursory carbon material into a fine powder having a particle size of up to 10 microns; shaping the pulverized mat-erial into a desired article at a room temperature; and carboniz-ing and further graphitizing said article in an inert atmosphere.

Description

This invention relates to a shaped solid carbon article, and particularly to a solid carbon article havin~ a high bulk density and flexural strength.
Heretofore, most solid carbon articles have been manufac- ~ ~
tured by molding a mixture of calcined coke powder and binding ~ ~;
pitch, followed by carbonizing or further graphitizing. However, the mechanical strength of the product tends to be low due to de-composition of the binding material during carbonization and graphitization. If coke powders could be solidified by sintering as in powder metallurgy with~ut using any binding material, the product would have a much higher mechanical strength. However, commercially available coke, per se, can not be sintered and some :
binding material is always necessary.
One method proposed for manufacturing solid carbon mater- i ials without using any binding material comprises densifying light pitch to obtain spherulite therefrom, separating the spherulite .. ~
from the liquid phase by solvent extraction, press-molding the spherulite into a shaped article, and carbonizing or further gra-::
~ phitizing the article. According to this method, it is possible ~ ~
.
to obtain a solid carbon article of high density without using any binder. However, spherulite is obtained from the light pitch in a very low yield and it is not easy to separate it from the ;-~
liquid phase. Moreover, some cracks are apt to grow~in the car~
bonized or graphiti2ed spherulite. This method has never been practically adopted industrially.
We have now devised a method of producing a solid carbon article having a bulk density of at least 1.90 g/cm and a flex~
ural strength of at least 900 kg/cm2 from a raw pitch material without using any binder. -According to the present invention there is provided -- 1 -- , ;
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a method of producin~ solid carbon article which comprises the sequential steps of heating a raw pitch material at a tempera~
ture of from 350 to 550Cin an inert atmosphere in order to ob-tain a polycondensed pitch as a precursory carbon material; pul-verizing the precursory carbon material; press-forming the pul-verized precursory carbon material into the desired article with-.
:~ out using any binder at a room temperature; carbonizing the press~
formed article at a temperature of at least 1000C in an inert atmosphere; and graphitizing the carbonized article at a tempera- - ~-.
ture of from 2000 to 3000Cin an inert atmosphere; an improvement : ~
~ ;:
characterized in that, the heat-treatment of the raw pltch mater-ial is carried out so as to obtain a precursory carbon material which has a hydrogen-to-carbon atomic ratio H/C of from 0.4 to .:
0.6, a quinoline soluble (as herein defined) of from 2 to 15 by weight, a fixed carbon content (as herein defined) of 80 to 93 % by weight and a degree of heat shrinkage (as herein defined) ~. ;-` of at least 2 %; and the precursory aarbon material is pulverized ~ to a particle size of 10 microns at most before the press-forming .. , ,.: ~
step, in order to obtain a shaped solid carbon article having a ;~ 20 bulk density of at least 1.90 g/cm3 and a flexural st~ength of at least 900 kg/cm2.
This object can be attained in accordance with this in~
- vented method which comprises the steps of heating a raw pitch material at a temperature of from 350 to 550C in an inert atmos-. . ,~ ,. ~ .
phere in order to obtain a polycondensed pitch as a precursory carbon material having a hydrogen-to-carbon atomic ratio H/C of from 0.4 to 0.6, a quinoline soluble (as herein defined) of from

2 to 15 % by weight, a fixed carbon content (as herein defined) ~7 ,~.' of from 80 to 93 % by weight, a degree of heat shrinkage (as :~

herein defined) of at least 2 ~; pulverizing the precursory carbon ". ~ ..
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material to a particle size of up to 10 microns; press forming the pulverized precursory carbon material into a desired shape without using a binder at a room temperature; carbonizing said shaped article at a temperature of at least 1000C in an inert atmosphere; and graphitizing the carbonized article at a tempera-ture of from 2000 to 3000Cin an inert atmosphere, The present invention will best be understood and appre-ciated from the following description of the process and examples taken in connection with the accompanying drawings, in which~
Fig. 1 is a polarization microscopic photograph showing the texture of the sectional surface of a precursory carbon mat-erial which is not used in this invention; ;~
Fig, 2 is a polarization microscopic photograph showing the texture of the sectional surface of a precursory carbon mat-;~ erial used in the present invention;
Fig. 3 is a polarization microscopic photogxaph showingthe texture of the sectional surface of commercially avaiIable green petroleum coke which is not used in this invention; ~-Fig. 4 is a polarization microscopic photograph showing the texture of the sectional surface of a spherulite article which is insoluble in quinoline and has been calcined at 1000 C; ~'~
Fig. 5 is a polarization microscopic photograph showing the texture of the sectional surface of an article not according to the invention, made of a precursory carbon material having a particle size of about 100 microns and which has been calcined at `~
i 1000C;
Fig. 6 is a polarization microscopic photograph showing the texture of the sectional surface of a molded and calcined article not according to the invention made of a precursory carbon -material having a particle size of about 100 microns; and

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~0~4b5i8 ,, Fig. 7 i9 a polarization microscopic photograph showing the texture of the sectional surface of a molded and calcined ~ -article of this invention made of a precursory carbon material having a particle size of about 3 microns.
"Quinoline soluble" means the proportion by weight of a material which is soluble in quinoline, measured by the method of ASTM D 2318.
"Fixed carbon content" means the residual welght percen-tage of a material after calcining it in an inert atmosphere up to a temperature of 1000 C in increments of 5C per minute. ;
"Degree of heat shrinkage" is defined hereinafter.
The precursory carbon material is obtained by heating a - coal pitch, petroleum pitch or a mixture of the two at a tempera~
ture of from 350 to 550C in an inert atmosphere. Although the other kinds of pitch such as synthetic pitch obtained by thermal decomposition of polyvinyl chloride or tetrabenzophenazine can be used, these are inferior to coal or petroleum pitch economically. ^
Generally, when pitch is carbonized, there is obtained a coke having swollen portions or stratified cracks. Therefore, it . ~ :
has hitherto seemed impossible to prepare faultless solid carbon articles having no swollen portions or cracks therein. We have ;- ;
found, however, that when the precursory carbon material describ~
ed above is used, it is possible to produce faultless solid car~
bon articles having no swollen portion or crack.
The precursory carbon material has mainly a mesophase structure, though it is porous in macrostructure, and is similar in appearance to uncalcined petroleum coke.
We investigated the relation between the mean particle ,~ , size of mechanically pulveri~ed precursory carbon material and the amount of cracks generated in the article obtained by shaping and ~ 4 ~
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carbonizing said pulverized precursory carbon material. We have found that faultless solid carbon materials could be obtained when the precursory carbon material had a mean particle size of ~ ~-lO microns at most.
We have found that a very dense solid carbon material, free from any swollen portion, can be obtained without using any binding material by sintering a pulverized precursory carbon material having a quinoline soluble of 2 to 15 per cent by weight and having an atomic ratio H/C of from 0.4 to 0.6. If the atom-ic ratio H/C is less than 0.4 the sintering of the precursory car-bon material does not produce good resultsO When the ratio is ~-greater than 0.6, dense products can not be produced due to the generation of swollen portions in the carbonization step. If the quinoline soluble is less than 2 per cent by weight, a high den-sity product would not be obtained, and similarly when more than 15 per cent by weight, the precursory carbon material is softened or generates swollen portions during the carbonization.
; The fine powders of precursory carbon material are solidified compactly by sintering to each other. The sintering of the material can be easily evaluated by measuring the degree of heat shrinkage thereof using a flow tester. This flow tester mainly consists of a metallic cylinder havlng an inner cross-sectional area of l.00 cm which has an electrical heater and a thermo-couple. The bottom of the cylinder has a hole l mm in diameter. After one gram of the fine powder of precursory carbon material is charged into the cylinder, a piston having a weight of 10 kg is inserted into the cylinder onto the sample mat-erial charged. The height h of the sample material in the cylin-der is measured. ~hen the sample material is heated up to 500C -in increments of 6C per minute, and the height h' of the heated `

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sample material is measured. The degree of heat shrinkage S of the sample material is defined herein as calculated by the follow-ing formula: `~
S 1~) = h h h x 100 If any material runs out through the bottom hole of thecylinder during the operation period, then the precursory carbon material is unfit for use.
When the degree of heat shrinkage i5 less than 2 %, the sintering property of the precursory carbon material is not good ~`~
enough to obtain the desired solid carbon article. When the de~
gree is at least 2 %, the packing of sintered solid carbon mat~
erial, which has been carbonlzed by heating up to 1000C, becomes ";~
grea~er than 95 ~ even if the packing of the precursory carbon -~
material shaped into a desired form at room temperature is only -~ ;
about 80 %. Consequently, a final solid carbon product having a `~
bulk density of at least 1.90 gjcm2 can be obtained by carboniz-ing or further graphitizing the press--formed precursor. The final ;~ -carbon product of a high bulk density and a high flexural strength of at least 900 kg/cm has not hitherto been known in the art.
Since the precursory carbon material is press-formed with- ~;
out using any binder and carboniz~ed and further graphitlzed by ordinary means, the process of producing a final solid carbon art-icle of this invention is very simple to effect. It is not neces-sary to effect any heat-molding process or penetrating process for ~
the purpose of densifyiny the product. ~ ~-The method of this invention can be modified by adding an adjuvant to the pulverized precursory carbon material before the step of press-forming in order to improve the workability and ~-sintering property of the material.

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The adjuvant is the one selected from the group consist-ing of an organic substance of high molecular weight containing hydroxyl groups, an ester or ether of such an organic substance, a fatty acid, an ester of a fatty acid and a metallic salt of a fatty acid, the adjuvant being a fluid at a temperature of at least 100C, and having a boiling or decomposition point of at least 150C and a fixed carbon content of 20 % at most; and where-in the amount o adjuvant used is from 3 bo 60~ by weight based on the weight of pulverized precursory carbon material. ;~`~
The organic compounds having a hydroxyl gxoup therein may be, for example, an alkylene glycol such as ethylene glycol and propylene glycol, a polyalkylene glycol such as polyethylene gly- ,!
col and polypropylene glycol, cyclohexanol, glycerin, polyvinyl ;~
alcohol and higher alcohols. The hydrocarbons used for the adju-vant are, for example, fluid paraffin, lubricating oil, light pet~
roleum oil, tar oil, anthracene oil, naphthalene and alkylnaphtha-lenes. The fatty acid may be, for example, laurlc acid, myristic ~ acid, palmitic acid~ stearic acid and oleic acid, and esters and ;~ metallic salts of these acids can ~also be used.
Since the expected effect of using the above-mentioned adjuvant is to improve the workability and sintering of the pre- -~ ~
cursory carbon material, the adjuvant should wet the material. ~ ~`
Thus the adjuvant should be fluid or wax-like at room temperature, and must be fluid at a temperature of at least 100C. If an ad- :
juvant is used which has a boiling or decomposition point of less than 150 C, cracks may be generated on the surface layer of the carbonized article. Further, if the fixed carbon content of the ~;
adjuvant is more than 20 per cent by weight, the homogeneity of the final product would be injured or swollen portions are generat-ed therein.

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The mixing of adjuvant and hase precuxsory carbon mater-ial can be carried out by any conventional mixing precedure. The mixture may be pelletized in order to facilitate the subsequent shaping step. The amount of adjuvant used is from 3 to 60 per cent by weight, preferably 5 to 35 per cent by weight based on the weight of pulverized precursory carbon material - -Among the advantages of using above-mentioned adjuvants are the following~
(1) The molding pressure can be decreased in the step of shaping.
(2) Some stickiness is imparted to the uncarbonized mater-ial by the interaction between the precursory carbon material and the adjuvant, as a result of which the uncarbonized fine material ;~ -~
becomes easy to handle and the breakage loss of the shaped articles ~-is notably reduced.
~3) Since any rubbish generated during the handling period ~;
of the uncarbonized material does not scatter owing to its sticki-ness, the working environment is kept in good condition. ~

(4) Internal strains in the shaped body during the initial ~;
period of carbonization are relieved due to the thermal charact-eristics of the precursory aarbon material and adjuvant. According~
ly, sintered articles having any form and dimension can be easily produced without any breaking losses. ~ ;
Among the articles which may be made according to this invention are many kinds of electrode for iron refining and elec-trolysis; high grade rubbing carbons used for mechanical seals, disk brakes for aeroplanes, bearings, vanes and electric brushes;
crucibles and jig-and-fixtures used for semiconductor manufactur-ing; nozzles for continuous casting apparatus; dies for sintering machines; refractories for high temperature treating apparatus;

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impermeable carbon materials; graphite materials for atomic power apparatus; etc.
The process of this invention will be more fully under-stood by referring to the following examples.

Samples of a by-product pitch, which was produced in manu-facturing ethylene by high temperature thermal cracking of naphtha, were heat-treated at 410C in varying times. The treatments were carried out in a nitrogen atmosphere, and various polycondensation products were obtained. Each of the samples obtained was observ-ed under a polarization microscope. The quinoline soluble was measured uslng one gram of each sample, which was pulverized to - have a particle size passing through a 60 Tyler mesh sieve, and soaked in 100 c.c. of quinoline for 16 hours at 40C. The in- ~;
solubles were filtered off and washed first with a small amount of quinoline, and then wlth benzene, whereafter they were dried at 100C. The weight percent of quinoline soluble was calculated using these data. The characteristics of the polycondensates ob- ~
tained are shown in Table 1. ~ ?

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In Table 1, the polycondensed pitches of No. 1 and No. .~-7 are not of the style used in this invention. The polarization microscopic photographs of Sample Nos. 1, 3 and 7 are shown in Figs. 1, 2 and 3~ respectively.
Each of -the precursory carbon materials shown in Table 1 was pulverized using a ball mill so as to have a particle size of ].0 microns at most. The pulverized material was press-molded into a disk 50 mm thick and 90 mm in diameter at room temperature .-and under a pressure of 1000 kg/cm . The disk was carbonized by heating up to 1000C in increments of 15C per hour in a coke ,~
breeze bed, followed by graphitization at 2400C. The character-..
istics of carbonized products and graphitized products are shown in Table 2.

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E~AM~LE 2 One hundred parts by weight of each of the precursory carbon materials prepared in Example 1 were mixed wlth 20 parts by weight of tar oil as an adjuvant using a Eenschel mixer. Each of the mixtures was shaped into a disk 50 mm thick and 90 mm in ;
diameter,and each disk was carbonized and further graphitized in a like manner as in Example l.The characteristics of the products are shown in Table 3.
As is clear from Tables 2 and 3, a comparatlvely low mold~

ing pre~sure could be employed, when tar oil was used as an ad-juvant, to obtain a graphitized article having a bulk density of at least 1.9 kg/cm ; whereas a molding pressure of at least 1,000 ;~
kg/cm2 was necessary when tar oil was not used.

TABLE 3 (Using adjuvant) No. of I Mean particle Molding Bulk density precursor size of pressure when shaped precursor ~(kg/cm2) (g/cm3) ~ ;~

1 2.3 600 1.18 ` ~
2 2.0 600 1.19 " ~;;
3 2.0 600 1.20 4 2.4 600 1.20 ~;
' 5 2.3 600 1.20 `

6 2.3 600 1.15 2.4 600 1.13 "
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Carbonized article Graphitized artiele ;
. ~_ _ _ - ..~_ Bulk Flexural Porosity Bulk Flexural Porosity Specific denSit3y ~trength (vol. ~) density strength ~vol. %) electric (g/cm ) tkg/cm2) (g/cm3) (kg/cm2) tanee (~-cm~
Foamed _ _ _ _ 1.75 1,410 2.7 2.11 1,370 2.6 12 x 10-4 1.75 1,400 2.7 2.15 1,360 2.6 11 x 10-4 1.76 1,420 2.5 2.10 1,350 2.4 11 x 10-4 1.75 1,~15 2.7 2.00 1,310 2.3 10 x 10 L~ L~ L ~ 199 1 1000 4s ll3xl~-4l ~

From the polycondensed pitch Mo. 1 in Table 1, (Example 1), ..`
the pitehy substance was removed by extraetion using quinoline as a solvent to obtain spherulite, which was subsequently carbonized by heating up to l,000C in incxements of 15C per hour. The in- -ternal structure of the carbonized spherulite obtained was observ- ;
ed under a polarization microseope as shown in Fig. 4. The poly-e~ndensed piteh Mo. 3 in Table 1 was also treated in the same man- `
ner. The internal strueture of the earbonized spherulite obtained is shown in Fig. 5. As is elear from Figs. 4 and 5, both the sph-erulites have eraeks therein at intervals of 7 to 10 mierons.
The polycondensed piteh No. 3, Table 1, was pulverized into two powders, one of mean particle size 3 mierons and the other 100 mierons. These powders were press-molded, earbonized and graphitized in the same manner as in Example 1. The internal struetures of both the carbonized artieles and graphitized arti- -. .
cles are shown in Figs 7 and 6 respeetively, and the eharaeteris-ties of the artieles are presented in Table 4. ~-, ',~

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TABLE 4 - ~
.
_ O-- Mean particle Molding Bulk density when size of pressure shaped (g/cm3) precursor (~) (kg!cm2) . ,, __ Spherulite 40 1,000 1.18 No. 3 in Table 1 100 1,000 1.15 No. 3 in Table 1 3 1,000 1.18 _ . _ Carbonized article Graphitized article I l l r Bulk Flexural Porosity Bulk Flexural Poro- ~pecific Mean dia-densit ¦strength (vol. ~) density strength sity electric meter of (g/cm3) (kg/cm2) (g/cm3) (kg/cm2) (Vol.% tance bubble L__ (Q cm) (~) 1.45 300 19.0 1.80 290 18.0 25 x 10-4 5.0 ; ;~

1.52 400 16.0 1.85 38Q 15.0 18 x 10-~ 3.0 ~;~
1.73 1,400 3.0 2.11 1~390 ~.9 12 x 10-4 0.05 (`Tho products in the first and second lines are out of the scope of the invention). ~-, ~
Pitch obtained from crude petroleum oil by high temperature `~ ~
cracking, and middle pitch obtained from coal tar, were treated by ~ --polycondensation in a nitrogen atmosphere under the conditions shown in Table 5. Samples of the polycondensed pitches obtained were observed using a polarization microscope, showing a flow pat-tern and very little amount of spherulite. The characteristics of these polycondensed pitches and final graphitized products obtained ~ ~ "
from the above-mentioned polycondensed pitches in the same manner as in Example 1 are shown in Tables 5 and 6. As obvious from Table 6, the graphitized product of this invention has an exceedingly high bulk density and flexural strength.

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TAsLE 5 . . . :~
Raw Treat~ ITreat- Preaursor material ing ten~ ing ~
perature ~me A-tomic Q~oline Fixed Degree Mean Sample (C) (hr.) ratio soluble carbon of heat parti- No. of (H/C) (wt.~) (wt.%) shrink- cle size pre-age (%) (~) cursor _. ...................... . _ _ .

peitchleUm 390 20 0.47 4.G 90 10 2.1 1 Petroleum 390 24 0.46 3.0 92 5 2.3 2 `~

Middle 420 15 0.45 3.5 88 7 2.D 3 ; 10 Pcoatlhtar ~ ~ ?~
Middle 420 20 0. 43 3.0 90 5 2.1 4 ;
pitch fr~
coal tar TABLE 6 ; -~
I- _ _ Graphitized article Sample No. _ of pre-Bulk Flexural Por~sity Specific electric :
; cursor density strength (v~l. %) resistance (g/cm3) (kg/cm~) (Q-cm) . . _ ,~
1 lv9~- ' 1,19p 5.0 13.5 x 10-4 ~ `~
; 2 1.93 1,000 - 6.0 14.0 x 10-4 ;; ,~
3 2.05 1,270 ~1.5 13.0 x 10-4 4 1.95 1,200 5.0 13.5 x 10-4 .-., .

Each of the precursory carbon materials obtained in `~
; Example 4, whose characteristics are shown in Table 5, was mixed `
with various kinds of adjuvant shown in Table 7 below. To 100 ;~
weight parts of precursor the amounts of adjuvant indicated in Table 7 were added. The mixture were molded into disk, followed ~ -,'1 ., .
by carbonization and graphitization in the same manner as in Example 1. The characteristics of the carbonized articles and `
. : .
graphitized articles obtained are shown in Table 7. `'~

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TABLE 7 : -~
: .
, __ _ _ Precursor No. Ad~uvant and Molding Bulk density ~ .
weight part pressure when molded thereof (kg/cm~) (g/cm3) _ ~:
1 Polyethylene gl~col 3 700 1,12 . ..
" 10 700 1.15 ~, " 20 700 1.19 ~ -" 30 500 1.20 ~.
_ _ .'', '~' Stearic acid 20 700 1.10 Naphthalene10 700 1,10 -Alkyl- ~:
2 naphthalene10 700 1.13 Liquid -~
paraffin 10 700 1.13 ~-_ _ -~
~"., 3 Coal tar 10 700 1.16 Petroleum tar 15 700 1,18 .
" 30 500 1.18 .~
. . ', :, 4 Petroleum 15 700 1.17 d~ :
tar : . _ _ : ~
Controls: 4 Water 10 700 Cracks were generated .
on the sur~ace layer .: -~
Ethanol 10 .700 of the article after .~.-molding~
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--Carbonized article Graphitized article __ _~ _ I , ~, ~
F.lexural Porosity Bulk Flexural Porosity Specific :;
density 5trength (Vol. %) density Strength (Vol. %) electric (g/om3) (ky/cm2) (g/cm3) (kg/cm2) resistance . .. . (Q-cm) ~
,;:
1.59 1,000 8.9 1.91 1,050 9.2 11 x 10-4 , 1.65 1,200 5.5 1.92 1,100 5.9 10 x 10-4 . :, - 17 - ~ ~

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1.72 1,390 3.9 1.99 1,230 3.g 9.0 x 10~4 `:~:

1.73 1,400 3.8 1.98 :L,200 3.8 9.5 x 10-4 _ ~ _ I ~
1.60 1,000 8.0 1.90 900 8.5 11 x 10-4 1.63 1,150 5.7 1.93 1,100 6.0 10 x 10-4 :

1.65 1,200 5.5 1.95 1,100 5.9 10 x 10-4 .

1.60 1,100 7.0 1.90 1,000 9.3 10 ~ 10-4 1.60 1,100 7.0 1.90 1,000 7.1 10 x 10-4 ~ :~

1.69 1,290 5.01.95 1,150 5.0 9.6 x 10-4 `~ .

1.70 1,360 5.01.96 1,300 4.9 9.5 x 10-4 ;~

.64 1,190 6 21.92 1,050 6.0 10 x 10-4 . . ' ~:
Cracks were generated on the surface layer of the article after molding. .
EXAMPLE 6 .,`~
A pitch obtained by high temperature cracking of crude petroleum oil was heat-treated in a nitrogen atmosphere to pre~
pare a polycondensed pitch having a fixed carbon content of 91%, a quinoline soluble of 3.0~ andan atomic ratio H/C of 0.46. The polycondensed pitch was pulverized ta obtain a precursory carbon material having a mean particIe size of 4 microns. One hundred `.

parts by weight of this precursory carbon material were mixed : `~
with 60 parts by weight of anthracene oil as an adjuvant at a:
température of 50 C using a kneader.
The mixture was extruded into a bar 100 mm in diameter .~.:
at room temperature and pressure of 150 kg/cm2. The bar was heat-ed up to 700 C in increments of 3 C per hour in a coke breeze bed, followed by further heating up to 1000C in increments of 30C ,;~:~
per hour and thereafter graphitized at temperature of 2400 C. ~ -''; ' '' ~",' ,,, ",,, ,, .. ... .. . ' ' .. ..
: .:. : . . , ~", . : ..

The characteristics of the yraphitized article obtained are shown in Table 8. For comparison, the characterics of custo-mary graphitized article are also represented in Table 8.

TABLE 8 `
':
_ ~
Graphitized Bulk Flexural Porosity Specific ~.
article density Strength(Vol. ~) electric (g/cm3)(kg/cm2) _ (Q-cm) --.:
Ofamhile 1.90 1,000 9.06.8 x 10 4 ~

~.- 10 Customary -4 material -1.75 180 28.07.5 x 10 -- ,~.,. ,~ .

., . ~ ~ - . .. .

`~ `''' ~ .

~:~ 20 .i .

~, , .~ . ,, ~.

. ' . . .

. ~ :
.: .
~:. ~ .

.

: -- 19 --:' ',~'i~ : ' , .. , ~
.: . - . : ~
~' ' : ~' ' ~: '

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for producing a shaped solid carbon article having a bulk density of at least 1.90 g/cm3 and a flexural strength of at least 900 kg/cm2, which method includes the steps of: heating a raw pitch at a temperature of from 350°C to 550°C
in an inert gas atmosphere to effect polycondensation, thereby forming a precursory carbon material having a hydrogen-to-carbon atomic ratio H/C of from about 0.4 to about 0.6, a quinoline solubility of from 2% to 15% by weight, a fixed carbon content of from 80% to 93% by weight, and a degree of heat shrinkage of at least 2%; pulverizing the precursory carbon material to have particle sizes ranging up to 10 microns; press-molding the pulver-ized precursory carbon material into a desired form at room temp-erature; carbonizing said formed carbon material at a temperature of at least 1000°C in an inert atmosphere; and graphitizing said carbonized material at a temperature of from 2000°C to 3000°C in an inert atmosphere.

2. A method as defined in claim 1, wherein the pulver-ized precursory carbon material is mixed, before the press-molding step, with a workable and sintering adjuvant selected from the group consisting of higher hydrocarbons, higher organic compounds having a hydroxyl group in the molecule thereof, esters and ethers of said higher organic compounds, fatty acids and esters or metallic salts of said fatty acids; said adjuvant being a liquid at a temperature of at least 150°C and having a maximum fixed carbon content of 20 percent by weight; and the amount of said adjuvant being from 3% to 60% by weight, based on the weight of said pulverized precursory carbon material.

3. A method as defined in claim 2, wherein said higher hydrocarbon is selected from the group consisting of liquid paraffin, lubricating oil, light petroleum oil, tar oil, anthracene oil, naphthalene, alkylnaphthalenes, and hydrogenated substances of tar oil.

4. A method as defined in claim 2, wherein said higher organic compound having a hydroxyl group in the molecule thereof is selected from the group consisting of ethylene glycol, propylene glycol, cyclohexanol, glycerin, polyvinyl alcohol and higher alcohols.

5. A method as defined in claim 2, wherein said fatty acid is selected from the group consisting of lauric acid, myristic acid, palmitic acid, stearic acid and oleic acid.

6. A method as defined in claim 1, 2, or 3, wherein said raw pitch is selected from the group consisting of coal pitch, petroleum pitch and mixtures thereof.

7. A method as defined in claim 4 or 5 wherein said raw pitch is selected from the group consisting of coal pitch, petroleum pitch and mixtures thereof.