U.S. patent number 3,865,713 [Application Number 05/367,449] was granted by the patent office on 1975-02-11 for carbonaceous reagent for carbonaceous binder used in the manufacture of fired carbon articles and carbon-bonded refractories.
This patent grant is currently assigned to Kureha Kagaku Kogyo Kabushiki Kaisha. Invention is credited to Kiro Asano, Yoshio Kawai, Kiyoshi Yamaki.
United States Patent |
3,865,713 |
Kawai , et al. |
February 11, 1975 |
CARBONACEOUS REAGENT FOR CARBONACEOUS BINDER USED IN THE
MANUFACTURE OF FIRED CARBON ARTICLES AND CARBON-BONDED
REFRACTORIES
Abstract
A carbonaceous reagent is provided for modifying a carbonaceous
binder used in the manufacture of fired carbon articles and
carbon-bonded refractories. The reagent serves to increase the
carbonization yield of the binder. The reagent contains one or more
functional groups each of which has one or more oxygen atom, has an
atomic ratio of oxygen to carbon of from 0.05 to 0.30, and a
carbonization yield per se of at least 50 percent.
Inventors: |
Kawai; Yoshio (Tokyo,
JA), Asano; Kiro (Tokyo, JA), Yamaki;
Kiyoshi (Tokyo, JA) |
Assignee: |
Kureha Kagaku Kogyo Kabushiki
Kaisha (Tokyo, JA)
|
Family
ID: |
13061904 |
Appl.
No.: |
05/367,449 |
Filed: |
June 7, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Jun 12, 1972 [JA] |
|
|
47-57655 |
|
Current U.S.
Class: |
208/6;
208/44 |
Current CPC
Class: |
C01B
32/00 (20170801); C04B 35/532 (20130101); C04B
35/013 (20130101) |
Current International
Class: |
C04B
35/01 (20060101); C04B 35/532 (20060101); C01B
31/00 (20060101); C04B 35/528 (20060101); C10c
003/04 () |
Field of
Search: |
;208/6,44 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: O'Keefe; Veronica
Attorney, Agent or Firm: Flynn & Frishauf
Claims
What we claim is:
1. A method for preparing a carbonaceous reagent for a carbonaceous
binder used in the manufacture of fired carbon articles and
carbon-bonded refractories in order to increase the carbonization
yield of said binder, which comprises oxidizing a carbonaceous raw
material at a temperature of from 15.degree.C. to 400.degree.C.
with an oxidizing agent to provide an atomic ratio of oxygen to
carbon therein of from 0.05 to 0.30.
2. The method of claim 1, wherein an oxygen containing functional
group is introduced into said raw material by said oxidation.
3. A method according to claim 1, wherein the carbonaceous raw
material is one selected from the group consisting of a tar, a
pitch and a coal.
4. A method according to claim 3, wherein the tar is coal tar or
petroleum tar.
5. A method according to claim 3, wherein the pitch is coal pitch
or petroleum pitch.
6. A method according to claim 3, wherein the coal is anthracite or
bituminous coal.
7. A method according to claim 1, wherein the oxidizing agent is a
gas selected from the group consisting of oxygen, ozone, air,
sulfur trioxide and nitrogen dioxide.
8. A method according to claim 1, wherein the oxidizing agent is an
aqueous solution of an acid selected from the group consisting of
nitric acid, sulfuric acid, a mixed acid of nitric and sulfuric
acids, hypochlorous acid and dichromic acid.
9. A method for preparing a carbonaceous reagent for a carbonaceous
binder used in the manufacture of fired carbon articles and
carbon-bonded refractories in order to increase the carbonization
yield of said binder, which comprises oxidizing a carbonaceous raw
material at a temperature of from 15.degree. to 400.degree.C. with
an oxidizing agent to introduce therein an oxygen-containing
functional group, and heating the oxidized carbonaceous raw
material for aging at a temperature of from 250.degree. to
500.degree.C. in an atmosphere of inactive gas, whereby the atomic
ratio of oxygen to carbon in the reagent falls within the range of
from 0.05 to 0.30.
10. A carbonaceous reagent for a carbonaceous binder used in the
manufacture of fired carbon articles and carbon-bonded
refractories, said reagent increasing the carbonization yield of
said binder, characterized in that said reagent contains a
functional group having an oxygen atom, has an atomic ratio of
oxygen to carbon of from 0.05 to 0.30, and a carbonization yield
per se of at least 50 percent.
11. A carbonaceous reagent according to claim 10, wherein the
functional group is selected from the group consisting of
carboxyl-, carbonyl-, hydroxy-, ether- and peroxy groups.
Description
This invention relates to carbonaceous reagents useful for
modifying carbonaceous binders used in the manufacture of fired
carbon articles and carbon-bonded refractories, and to a method for
forming said reagents. The reagents are capable of increasing the
carbonization yield of said binders when said articles or
refractories are fired, thereby providing products of high density
and great mechanical strength.
As used herein, the term "carbonization yield of a binding
material" is defined to mean an amount in percent by weight of a
residual mass derived from an original binding material when heated
up to 1,000.degree.C in increments of 5.degree.C per minute in an
atmosphere of inert gas.
Shaped and fired carbon articles, for example, carbon electrodes
are manufactured from coke, anthracite, graphite or carbon black
finely divided for use as a filler by adding to the filler a proper
amount of binding material such as tar, pitch, phenolic resin or
furan resin, kneading the mixture, and molding the kneaded mass,
followed by firing. In a special case, these binding materials
themselves are fired for carbonization and may be made into carbon
articles by the same process as described above with no use of
fillers. In any case, the binding material, when fired, is
generally carbonized to an appreciably low degree and gives forth
volatile matter possibly to make the resulting product undesirably
porous, presenting difficulties in providing articles of high
density and great mechanical strength. To compensate for such
defects, it is customary practice to impregnate fired material with
tar or pitch and again fire the impregnated mass so as to enable
the final product to increase in density and mechanical strength
and decrease in specific electric resistance.
To eliminate the above-mentioned troublesome procedure, it is
considered advantageous to use a binder giving as high a
carbonization yield as possible. Therefore, the world tends to
accept the so-called heavy pitch, which provides a high
carbonization yield. This heavy pitch has an aromatic structure and
a large molecular weight, and in consequence indicates a high
softening point and melt viscosity. However, these properties
present great difficulties in kneading a mixture of heavy pitch and
filler and molding or extruding the kneaded mass, imposing
considerable limitation on application of the heavy pitch.
On the other hand, study is in progress to add a small amount of
reagent to pitch used as a binder. Attempts have been made to use,
for example, dinitronaphthalene or 2,3-naphthoquinone as a reagent.
However, such a reagent itself is not only carbonized to a low
extent and mostly volatilized when fired, but is also extremely
expensive, failing to be put to industrial application in any
way.
It is accordingly the object of this invention to provide an
inexpensive reagent having a high carbonization yield per se and
little soluble in a binding material preventing the softening point
thereof from being raised.
To this end, the reagent of this invention is prepared by oxidizing
tar, pitch or coal by an oxidation process to introduce therein
functional groups containing oxygen atoms to such an extent that
the atomic ratio of oxygen to carbon in said reagent falls within
the range of from 0.05 to 0.30.
Other important objects and advantageous features of this invention
will be apparent from the following description and accompanying
drawings, wherein the specific embodiments of the invention are set
forth in detail.
FIG. 1 is a curve diagram showing the relationship between the
carbonization yield of a binder pitch and the mixing ratio of the
reagent to the binder pitch used in Example 1;
FIG. 2 is a curve diagram showing the relationship between the
atomic ratios of oxygen to carbon and hydrogen to carbon in a
reagent and the temperature at which the reagent itself was
heat-treated in Example 2; and
FIG. 3 is a curve diagram showing the relationship between the
carbonization yield of a modified binder pitch and the atomic ratio
of oxygen to carbon in the heattreated reagent of Example 2.
The reagent of this invention not only presents a high
carbonization yield itself but also is little soluble in a binder,
preventing the binder mixed with said reagent from being raised in
the softening point. Further, the reagent acts as a sort of filler
in the steps of kneading a mixture of raw carbonaceous material and
binder and molding or extruding the kneaded mass.
From such features, the reagent itself may be deemed as a special
raw carbonaceous material.
Moreover, with the reagent of this invention, functional groups
introduced therein improve the wetting of the reagent to a binder,
attaining an easy and homogeneous mixture thereof. When the kneaded
mass is fired, the functional groups of the reagent react with the
binder prominently to increase the carbonization yield of the
binder. Therefore, application of the reagent does not exert any
harmful effect on the molding or extrusion of the kneaded mass, but
facilitates the manufacture of carbon articles of high density and
mechanical strength and low specific electric resistance. The
reagent of this invention can be applied in manufacturing for not
only the fired carbon artciles but also refractories using a
carbonaceous binder.
The raw material of the reagent of this invention may consist of
ordinary tar or pitch, those obtained by polycondensation which is
derived from heat-treatment and/or oxidation of petroleum. The
reagent should preferably be formed of a raw material of highly
aromatic structure so as to permit the easy introduction of
functional groups in said raw material by oxidation and enable the
resultant reagent to have a low solubility and meltability and to
have a high carbonization yield itself.
The raw material of the reagent may consist of not only the
above-mentioned types of tar and pitch but also finely ground coal.
The preferred coals are anthracite and a bituminous type low in ash
content, but any other kind of coal is acceptable.
Oxidation of the raw materials of the reagent is generally effected
by various processes. Most convenient is the use of oxidizing gas,
for example, oxygen, ozone, air, sulfur trioxide, or nitrogen
dioxide. It is also possible to treat the raw materials of the
reagent with an oxidizing aqueous solution of nitric acid, sulfuric
acid, mixed acid thereof, hypochlorous acid or dichromic acid.
It does not matter whether the raw materials of the reagent are
oxidized in the form of powders, fibers, molten mass or solution.
While not subject to any particular limitation in temperature, the
oxidation is generally carried out at 15.degree. to 400.degree.C so
as to prevent undue oxidation. If the raw materials are again
heat-treated for aging at lower temperatures than about
500.degree.C in an atmosphere of inert gas after the
above-mentioned oxidation, then the raw materials will present a
prominent effect.
The oxidation causes the hydrocarbon molecules constituting the raw
materials of the reagent to contain functional groups having an
oxygen atom in the form of a carboxyl-, carbonyl- (of quinone,
ketone or aldehyde type), hydroxy- (of phenol or alcohol type),
ether-, or peroxy group. Said oxidation also gives rise to
polycondensation among te hydrocarbon molecules, and this causes
the reagent prominently to decrease in solubility in binding
materials and indicate a low meltability thereof. Depending on the
kind of oxidizing agent used, some amount of, for example, nitro
group, halogen group or sulfur group may sometimes be carried into
the raw materials of the reagent, which, however, does not obstruct
the function of the reagent.
The functional groups can be identified or their amounts can be
quantitatively determined by the infrared spectrum analysis,
elementary analysis or ordinary chemical analysis. The quantitative
analysis of the individual functional groups is difficult to carry
out and also unnecessary. It is sufficient to determine the atomic
ratio of the total oxygen atoms to the carbon atoms contained in
the reagent. The indispensable requisite for the reagent of this
invention is that the atomic ratio of oxygen to carbon be defined
within the range of 0.05 to 0.30 or preferably 0.10 to 0.25. It has
been found that where the above-mentioned requisite is fully met,
the atomic ratio of hydrogen to carbon falls within the range of
about 0.2 to 0.8. If the atomic ratio of oxygen to carbon decreases
from 0.05, then the reagent will not fully display its effect.
Again where said ratio increases over 0.3, the reagent does not
indicate any increased effect. Therefore, any process resulting in
such excessively large atomic ratio of oxygen to carbon is not only
useless but also undesirably reduces the carbonization yield of the
reagent per se.
The oxidation in producing the reagent gives rise to cross linking
among its molecules and minimizes the content of volatile matter,
enabling the reagent to present a high carbonization yield. The
reagent thus prepared has a carbonization yield of at least 50
percent, generally ranging from 60 percent to 92 percent.
As mentioned above, the reagent of this invention is substantially
insoluble in the binding materials and contains functional groups
having affinity with the binding materials, and can be uniformly
dispersed therein due to good wettability. Further, the reagent
undergoes little chemical reaction with the binding materials at
kneading and molding temperature, preventing the softening point or
viscosity of the mixed binding materials from being elevated and
consequently causing the mixture of filler and binder to be little
reduced in moldability.
High temperature firing after molding gives rise to a chemical
reaction between the reagent and binder, leading to not only the
binding of the molecules of both constituents but also a chain
reaction therebetween, thereby promoting polycondensation among the
binder molecules. Accordingly, mere addition of a small amount of
reagent to the binder considerably improves its carbonization
yield, providing fired articles of increased density, mechanical
strength, corrosion resistance and electric conductivity.
While varying with the particle size distribution of the filler,
the mixing ratio of the filler to the binder and the kind of binder
used, it may be generalized that the reagent should preferably be
added at the ratio of 1 to 50 weight parts per 100 weight parts of
the binder. As previously described, it is possible to apply the
reagent itself as a filler, using very little filler or with its
use entirely omitted. In such case, 2.5 to 100 weight parts of the
binder are mixed with 50 weight parts of the reagent. In a special
case, carbon articles can be prepared from reagent and a binder
(cf. Example 5).
The modifier of this invention has a variety of applications such
as carbon electrodes, carbon blocks, carbon articles used with
mechanical or electric machinery, amorphous carbon material to be
stamped for use as lining, carbon paste for Soederberg electrodes
and refractories.
The reagent of the present invention will be more fully understood
by reference to the following examples.
EXAMPLE 1
Into the steam superheated to about 2,000.degree.C was introduced a
vapour of petroleum naphtha preheated to 350.degree.C. The vapour
was thermally cracked for 0.003 second at 1,100.degree.C, followed
by quenching, obtaining residual tar with a yield of about 20
percent by weight in addition to ethylene, acetylene, benzene and
naphthalene. The tar was later distilled up to 300.degree.C at
vacuum of 5 mmHg to remove light weight components, producing pitch
in an amount about half the original weight of the tar.
The pitch indicated a hydrogen to carbon atomic ratio of 0.51
calculated from measure of contents of hydrogen and carbon using
the elementary analysis. The carbonization yield of said pitch was
64 percent. One gram of the pitch was put in a cylinder 1 cm.sup.2
in cross sectional area which was provided at the lower end with a
nozzle 1 mm in diameter used in a Flow Tester. When the pitch was
increasingly heated in increments of 10.degree.C per minute at a
pressure of 10 Kg/cm.sup.2, the pitch indicated a softening point
of 218.degree.C as measured from the temperature at which the pitch
commenced to run out. The aforesaid hydrogen to carbon atomic ratio
in the pitch suggested that it consisted of a large amount of
polycondensed aromatic components. This assumption was also
confirmed by the IR spectrum and the NMR spectrum using carbon
disulfide as a solvent.
After being crushed, the pitch was heated for oxidation to
250.degree.C by raising the temperature in increments of 1.degree.C
per minute in air containing 3 percent by volume of nitrogen
dioxide gas, obtaining a product having the properties given in
Table 1 below.
Table 1 ______________________________________ Properties of
Oxidized Pitch ______________________________________ Softening
point Difficult to measure (above 400.degree.C) Elementary analysis
(% by weight) C 81.5 H 2.8 O 15.3 N 0.3 Hydrogen to carbon atomic
ratio 0.428 Oxygen to carbon atomic ratio 0.141 Solubility in
anthracene oil Less than 2 % by weight Carbonization yield of its
own 75 % ______________________________________
The instrumental analysis such as the IR spectrum method and
ordinary chemical analysis qualitatively proved that the oxidized
pitch obtained contained carboxyl-, carbonyl-, hydroxyl- and nitro
groups, and oxygen of ether type.
The oxidized pitch, that is, a reagent of this invention was
pulverized to such a particle size as passed the 100 Tyler mesh
screen. The powders obtained were mixed in various proportions with
coal tar binder pitch of which softening point and carbonization
yield were 78.degree.C and 46 percent respectively. Every 5 grams
of the mixed mass was placed in a porcelain crucible having a
capacity of 30 c.c., and was heated to 1,000.degree.C by raising
temperature in increments of 5.degree.C per minute in an atmosphere
of nitrogen. FIG. 1 presents the carbonization yields of the binder
pitch at different mixing ratios of the reagent to the binder
pitch. Said yield was calculated by deducting the amount of
carbonized modifier pitch from the amount of total residue.
EXAMPLE 2
The oxidized pitch obtained in Example 1 having the properties set
forth in Table 1 was heat-treated in an atmosphere of nitrogen at
temperatures of 300.degree., 400.degree. 500.degree., 600.degree.,
700.degree. and 900.degree.C respectively. The elementary analysis
was made of the each oxidized pitch thus heat-treated to determine
the atomic ratio of oxygen to carbon and hydrogen to carbon in the
pitch, the results being presented in FIG. 2.
20 parts by weight of each heat-treated oxidized pitch were mixed
with eighty parts by weight of the same petroleum pitch as used in
Example 1. The carbonization yield of the petroleum pitch mixed
with the heat-treated oxidized pitch was determined in the same
manner as in Example 1, the results being set forth in FIG. 3. As
apparent from FIGS. 1, 2 and 3, the oxidized pitch heat-treated at
temperatures of about 250.degree. to about 500.degree.C prominently
elevated the carbonization yield of a binder pitch. Where, however,
said heat-treatment was effected at higher temperatures than
500.degree.C, the oxidized pitch thus heat-treated indicated a
sharp decline in the oxygen to carbon atomic ratio and in
consequence a noticeable decrease in the ability to increase the
carbonization yield of the binder.
EXAMPLE 3
An oxidized pitch was prepared in the following manner.
Five hundred grams of blown asphalt having a penetration index of
10 to 20, composed of 85.5 weight percent carbon and 9.67 weight
percent hydrogen, the hydrogen to carbon atomic ratio thereof being
1.36, were melted at 380.degree.C. Nitrogen gas was made to bubble
through the molten asphalt for 60 minutes at the rate of 2 l per
minute for dry distillation, and further distilled 3 hours at
300.degree.C and vacuum of 10.sup..sup.-3 mmHg, obtaining pitch
having a softening point of about 180.degree.C with a yield of 29
percent by weight. The pitch was formed of 86.1 percent carbon and
7.62 percent hydrogen and indicated a hydrogen to carbon atomic
ratio of 1.06.
Those pulverized portions of the above-mentioned pitch which passed
through the 100 Tyler mesh screen were used. Said pulverized
portions were oxidized 3 hours at 70.degree.C in air containing 1.5
percent by volume of ozone. The oxidation was repeated in the same
air by raising the temperature to 260.degree.C in increments of
1.degree.C per minute. Final heat treatment was carried out 30
minutes at 350.degree.C in an atmosphere of nitrogen. A reagent
obtained consisted of 76.1 percent carbon, 3.63 percent hydrogen
and 20.1 percent oxygen, and indicated an oxygen to carbon atomic
ratio of 0.20, a hydrogen to carbon atomic ratio of 0.57, and a
carbonization yield of 65 percent.
On the other hand, 100 weight parts of calcined petrocoke having
the particle size distribution shown in Table 2 below and 33 weight
parts of an ordinary binder pitch were mixed to provide a
control.
Table 2 ______________________________________ Particle size
distribution of calcined petrocoke
______________________________________ % by weight Particle sizes
from 3 to 1.5 mm about 20 Particle sizes smaller than 1.5 mm and
over 200 Tyler mesh about 30 Particle sizes under 200 Tyler mesh
about 50 ______________________________________
To the above-mentioned calcined petrocoke, the binder pitch and the
reagent prepared from the aforesaid asphalt were mixed in the
proportions given in Table 3 below. Every mixed mass was kneaded,
extruded, baked and graphitized in succession. All the steps were
carried out as follows. Initially, the mixed mass was kneaded 40
minutes at 150.degree. to 160.degree.C and extruded at a pressure
of 50 Kg/cm.sup.2 into rods each 25.4 mm in diameter and 100 mm
long. The rods were buried in coke breeze and heated to
700.degree.C in 50 hours and maintained 2 hours at said
temperature. Later, the rods were heated to 2,600.degree.C in 3
hours and maintained 1 hour at said temperature to complete
graphitization.
The kneading was carried out in a Z-type kneader having a capacity
of 1 l. There was no difficulty in kneading and extruding the
samples of the control. The graphitized samples indicated the
properties given in Table 3 below as measured by the methods
specified in the Japanese Industrial Standards (JIS) R 7201 to R
7202.
Table 3
__________________________________________________________________________
Composition of raw materials and properties of graphitized samples
__________________________________________________________________________
Sample number 1 2 3 4 (Control)
__________________________________________________________________________
Composition of raw materials (parts by weight): Calcined petrocoke
100 97 95 90 Binder pitch 33 33 33 33 Reagent 0 3 5 10
__________________________________________________________________________
Carbonization yield of binder pitch in the 51 58 62 68 graphitized
sample (% by weight):
__________________________________________________________________________
Properties of graphitized sample: Bulk density 1.523 1.549 1.564
1.579 Bending strength (Kg/cm.sup.2) 99 120 135 151 Specific
resistance (.OMEGA..cm .times. 10.sup..sup.-5) 84 73 71 70
Coefficient of thermal expansion (.times. 10.sup.4 /.degree.C) 1.23
1.14 1.08 0.99
__________________________________________________________________________
The carbonization yield of the binder pitch shown in Table 3 was
calculated by deducting the residual amount of the calcined
petrocoke and the reagent when they were graphitized singly.
EXAMPLE 4
Coal tar pitch composed of 92.30 wt. percent carbon, 4.50 wt.
percent hydrogen, 0.20 wt. percent sulfur, 1.12 wt. percent
nitrogen and 1.88 wt. percent oxygen, in which the oxygen to carbon
atomic ratio and the hydrogen to carbon atomic ratio were 0.01 and
0.59 respectively, was dry-distilled 1 hour at 380.degree.C while
nitrogen gas was made to bubble through the pitch as in Example 3,
and further distilled 1 hour at 270.degree.C at vacuum to obtain
with a yield of 52 percent a pitch having a softening point of
about 195.degree.C, containing 92.40 weight percent carbon and 3.67
weight percent hydrogen and indicating the hydrogen to carbon
atomic ratio of 0.48.
Five hundred grams of those pulverized portions of the pitch which
passed through the 100 Tyler mesh screen were placed in a 1 l
flask. Air was made to pass through the flask at the rate of 1 l
per minute while gently stirring the flask. The charged pitch was
heated from room temperature to 150.degree.C in 10 minutes, further
heated to 260.degree.C by raising temperature in increments of
1.degree.C per minute, and maintained 10 hours at that temperature
for oxidation. The oxidized pitch (reagent) thus obtained was
formed of 71.9 weight percent carbon, 2.81 weight percent hydrogen
and 23.64 weight percent oxygen, and indicated the oxygen to carbon
atomic ratio of 0.25 and the hydrogen to carbon atomic ratio of
0.47, and had its own carbonization yield of 62 percent.
A plurality of mixed samples were prepared by mixing a filler
formed of pulverized pitch coke having a particle size distribution
in which particle sizes ranging from 170 to 325 accounted for 25
percent by weight and those finer than 325 Tyler mesh occupied 75
percent by weight; a coal pitch binder having a softening point of
88.degree.C as measured by the ring and ball method; and the
aforesaid oxidized pitch in the proportions shown in Table 4. Each
mixture was kneaded 30 minutes at 150.degree.C, and the kneaded
mass was charged in a metal mold 5 cm wide, 5 cm high and 20 cm
long. The charge was molded at a pressure of 200 Kg/cm.sup.2 at
150.degree.C. The shaped samples were buried in coke breeze and
heated to 700.degree.C in 50 hours. Later, the samples were
transferred to a graphitizing furnace, heated to 2,700.degree.C in
4 hours and maintained 1 hour at that temperature to complete
graphitization. Thus were obtained samples of graphite electrode
used in NaCl electrolysis. The samples presented the properties
given in Table 4.
Table 4
__________________________________________________________________________
Composition of raw materials and properties of graphite samples
__________________________________________________________________________
Sample number 5 6 7 8 (Control)
__________________________________________________________________________
Composition of raw materials (parts by weight): Pitch coke 100 97
95 90 Coal pitch binder 40 40 40 40 Oxidized pitch 0 3 5 10
__________________________________________________________________________
Carbonization yield of coal pitch in the graphite sample 53 59 63
69 (% by weight):
__________________________________________________________________________
Properties of graphite sample: Bulk density 1.60 1.62 1.63 1.69
Bending strength (Kg/cm.sup.2) 180 220 250 300 Specific resistance
90 85 80 76 (.OMEGA..cm .times. 10.sup..sup.-5) Weight loss by
electrolytic oxidation (mg/amp. hour) 1.30 1.02 0.90 0.69
__________________________________________________________________________
In Table 4, the carbonization yield by the coal pitch binder with
the graphite samples was calculated in the same manner as in Table
3. The weight loss by electrolytic oxidation was determined by the
process specified by the terminal committee of the Japan Soda
Industry Association.
EXAMPLE 5
Anthracite mined in North Vietnam was pulverized into fine
particles passing through the 100 Tyler mesh screen. The pulverized
mass was heated to 230.degree.C by raising temperature in
increments of 1.degree.C per minute in air containing 1.5 percent
by volume of nitrogen dioxide gas and maintained 30 minutes at that
temperature for oxidation. The mass thus treated indicated, as
measured by elementary analysis, the oxygen to carbon atomic ratio
of 0.14 and the hydrogen to carbon atomic ratio of 0.34, and a
carbonization yield of 85 percent. The oxidized anthracite was
fully insoluble in various types of pitch, and chemically analyzed
to contain 5 .times. 10.sup..sup.-4 mol/g of carbonyl group, 2
.times. 10.sup..sup.-4 mol/g of carboxyl group and 1 .times.
10.sup..sup.-4 mol/g of phenol type hydroxyl group.
The oxidized anthracite was used as both filler and reagent.
Namely, 70 parts by weight of powders of the oxidized anthracite
were mixed with 30 parts by weight of the pitch obtained by thermal
decomposition of naphtha in Example 1. The mixed mass was kneaded
at 250.degree.C and, after cooling, pulverized into fine particles
passing through the 200 Tyler mesh screen. Water was added as a
molding agent in the ratio of 5 parts by weight per 100 parts by
weight of the powders. The mass was molded into a round column 30
mm in diameter and 30 mm long at room temperature and a pressure of
300 Kg/cm.sup.2. The molded sample was buried in coke breeze and
heated to 1,000.degree.C by raising temperature in increments of
100.degree.C per hour for carbonization to obtain a homogeneous
compact article having a volumetric contraction coefficient of 35
percent, porosity of 14 percent, compressive strength of 2,600
Kg/cm.sup.2, Shore hardness of 110, bulk density of 1.39, and
carbonization yield of about 90 percent.
EXAMPLE 6
The pitch obtained by thermal decomposition of naphtha in Example 1
was pulverized into fine particles passing through the 200 Tyler
mesh screen. One hundred grams of the powders obtained were mixed
with 1 l of 8 N water solution of nitric acid. Both materials were
reacted 30 minutes at 40.degree.C. The reaction product was
filtered and washed with water. The resultant cake was dried 3
hours with hot air at 120.degree.C. Thus obtained reagent indicated
the oxygen to carbon atomic ratio of 0.069, the hydrogen to carbon
atomic ratio of 0.42 and the carbonization yield of 75 percent.
A mixture of said reagent and coal tar was used as a binder, and
there were prepared for trial samples of carbonaceous magnesia
refractory, whose properties are presented in Table 5 below.
Table 5 ______________________________________ Composition of raw
materials and properties of refractory samples
______________________________________ Sample Number 9 10 (Control)
______________________________________ Composition of raw materials
(parts by weight): Magnesia 100 93 Coal tar 15 15 Reagent 0 7
______________________________________ Carbonization yield of the
binder of the refractory samples 15 32 (% by weight):
______________________________________ Bending strength of
refractory 80 150 samples (Kg/cm.sup.2)
______________________________________
* * * * *