Note: Descriptions are shown in the official language in which they were submitted.
2012627
FIELD OF THE INVENTION
The present invention relates to a method for
controlling the aggregate size and structure of
carbon blacks.
BACKGROUND
Carbon blacks are generally produced in a
furnace-type reactor by pyrolyzing a hydrocarbon
feedstock with hot combustion gases to produce
combustion products containing particulate carbon
black.
In one type of a furnace carbon black reactor,
such as shown in US Patent N 3,401,020 to Kester et
al., or US Patent N 2,785,964 to Pollock, herein-
after "Kester" and "Pollock" respectively, a fuel,
preferably hydrocarbonaceous, and an oxidant,
preferably air, are injected into a first zone and
react to form hot combustion gases. A hydrocarbon
feedstock in either gaseous, vapor or liquid form is
also injected into the first zone whereupon
pyrolysis of the hydrocarbon feedstock commences. In
this instance, pyrolysis refers to the thermal
decomposition of a hydrocarbon. The resulting
combustion gas mixture, in which pyrolysis is
occurring, then passes into a reaction zone where
-- 1 --
,,,
"~,
20~Z6Z7
._
completion of the carbon black forming reaction occurs.
In another type of a furnace carbon black reactor, a liquid or
gaseous fuel is reacted with an oxidant, preferably air, in the
first zone to form hot combustion gases. These hot combustion
gases pass from the first zone, downstream through the reactor,
into a reaction zone and beyond. To produce carbon blacks, a
hydrocarbonaceous feedstock is injected at one or more points
into the path of the hot combustion gas stream. The
hydrocarbonaceous feedstock may be liquid, gas or vapor, and may
be the same or different than the fuel utilized to form the
combustion gas stream. The first (or combustion) zone and the
reaction zone may be divided by a choke or zone of restricted
diameter which is smaller in cross section than the combustion
zone or the reaction zone. The feedstock may be injected into the
path of the hot combustion qases upstream of, downstream of,
and/or in the restricted diameter zone. Furnace carbon black
reactors of this type are generally described in U.S. Patent
Reissue No. 28,974 and U.S. Patent No. 3,922,335.
Although two types of furnace carbon black reactors and
processes have been described, it should be understood that
201Z6Z7
the present invention can be used in any other furnace carbon
black reactor or process in which carbon black is produced by
pyrolysis and/or incomplete combustion of hydrocarbons.
In both types of processes and reactors described above,
and in other generally known reactors and processes, the hot
combustion gases are at a temperature sufficient to effect
pyrolysis of the hydrocarbonaceous feedstock injected into the
combustion gas stream. In one type of reactor, such as
disclosed in Kester, feedstock is injected, at one or more
points, into the same zone where combustion gases are being
formed. In other type reactors or processes the injection of
the feedstock occurs, at one or more points, after the
combustion gas stream has been formed. In either type of
reactor, since the hot combustion gas stream is continually
flowing downstream through the reactor, pyrolysis continually
occurs as the mixture of feedstock and combustion gases
passes through the reaction zone. The mixture of feedstock
and combustion gases in which pyrolysis is occurring is
hereinafter referred to, throughout the application, as "the
effluent". The residence time of the effluent in the reaction
zone of the reactor is sufficient, and under conditions
Z012627
suitable, to allow the formation of carbon blacks. "Residence
time" refers to the amount of time which has elapsed since the
initial contact between the hot combustion gases and the
feedstock. After carbon blacks having the desired properties
are formed, the temperature of the effluent is further lowered
to stop pyrolysis. This lowering of the temperature of the
effluent to stop pyrolysis may be accomplished by any known
manne~, such as by injecting a quenching fluid, through a
quench, into the effluent. As generally known to those of
ordinary skill in the art, pyrolysis is stopped when the desired
carbon black products have been produced in the reactor. One
way of determining when pyrolysis should be stopped is by
sampling the effluent and measuring its toluene extract level.
Toluene extract level is measured by ASTM Dl618-83 "Carbon
~lack Extractables - Toluene Discoloration~. The quench is
generally located at the point where the toluene extract level
of the effluent reaches an acceptable level for the desired
carbon black product bein~ produced in the reactor. After
pyrolysis is stopped, the effluent generally passes through a
bag filter system to separate and collect the carbon blacks.
~- Generally a single quench is utilized. Kester, however,
201Z627
discloses the use of two quenches to control certain
propertieS of carbon blacks. Kester relates to controlling the
modulus-imparting properties of carbon blacks by heat
treatment. This heat treatment is achieved by regulating the
water flow rates to two water spray quenches, positioned in
series, in the effluent smoke in a carbon black furnace. The
modulus of a carbon black relates to the performance of the
carbon black in a rubber product. As explained in the article by
Schaeffer and Smith, ~Effect of Heat Treatment on Reinforcing
Properties of Carbon Black~ (Industrial and Engineering
Chemistry, Vol. 47, No. 6; June 1955, page 1286), hereinafter
"Schaeffer", it is generally known that heat treatment will
effect the modulus-imparting properties of carbon black.
However, as further explained in Schaeffer, the change in the
modulus-imparting properties of carbon blacks produced by
heat treating results from a change in the surface chemistry
of the carbon blacks. Therefore, positioning the quenches as
suggested by Kester, in order to subject the combustion gas
stream to different temperature conditions, affectS the
modulus-imparting properties of carbon black apparently by
changing the surface chemistry of the carbon blacks rather
Z012627
than by affecting the morphology of the carbon blacks in any
discernible way. Moreover, in Kester, both quenches are
located in a position in the reaction zone where significant
pyrolysis of the feedstock has already occurred. Thus, it
would appear that, in Kester's process, by the time the
effluent reaches the first quench, the CTAB, tint, DBP and
Sto~es diameter properties of the carbon blacks have been
defined. This supports the conclusion that the change in the
modulus-imparting properties in Kester does not result from a
change in the morphological properties of the carbon blacks.
Still further, Kester does not attach any significance to the
position of the first quench, relative to the point of injection
of feedstoc~ or residence time, and does not disclose means
for selecting the position of the first quench.
U.S. Patent No. 4,230,670 to Forseth, hereinafter Forseth,
suggests the use of two quenches to stop pyrolysis. The two
quenches are located inches apart at the point where a single
quench would be located. The purpose of the two quenches is
to more completely fill the reaction zone with quenching fluid
to more effectively stop pyrolysis. In Forseth however, by the
time the effluent reaches the quenches, the CTAB, Tint, DBP
_ 2012627
and Stokes diameter properties of the carbon blacks
have been defined.
U.S. Patent No. 4,265,870, to Mills et al., and
U.S. Patent No. 4,316,876, to Mills et al., suggest
using a second quench located downstream of the first
quench to prevent damage to the filter system. In both
patents the first quench completely stops pyrolysis and
is located at a position generally known to the art,
and by the time the effluent reaches the first quench,
the CTAB, Tint, DBP and Stokes diameter properties of
the carbon blacks have been defined. The second quench
further reduces the temperature of the combustion gas
stream to protect the filter unit.
U.S. Patent No. 4,358,289, to Austin,
hereinafter "Austin", also relates to preventing damage
to the filter system by the use of a heat exchanger
after the quench. In this patent also, the quench
completely stops pyrolysis and is located at a position
generally known to the art. In Austin, by the time the
effluent reaches the first quench, the CTAB, tint, DBP
and Stokes diameter properties of the carbon blacks
have been defined.
U.S. Patent No. 3,615, 211 to Lewis, hereinafter
Lewis,
X 7
--~ 2012627
relates to a method for improving the uniformity of
carbon blacks produced by a reactor, and for extending
the life of a reactor. To improve uniformity and extend
reactor life, Lewis suggests using a plurality of
quenches, located throughout the reaction zone, to
maintain a substantially constant temperature in the
reaction zone. A certain quantity of quenching fluid is
injected at the quench located furthest upstream in the
reactor, with a greater amount of quenching fluid
injected at each subsequent downstream quench. The
quench located furthest downstream stops pyrolysis. By
maintaining a constant temperature in the reaction zone
the apparatus of Lewis promotes uniformity int he
carbon blacks produced by the apparatus. However, the
plurality of quenches does not control the morphology
of carbon blacks produced by the apparatus.
It is generally desirable, however, to be able
to control the morphology of carbon blacks such that
carbon blacks well suited to a particular end use may
be produced. It is also desirable to increase the
aggregate size and structure of carbon blacks for a
given surface area, since increased aggregate size and
structure, as represented by higher DBP,
` 8
- - 2012627
lower tint, and larger Stokes Diameter, makes the carbon
blacks better suited for certain end uses.
Accordingly an object of the present invention is to
provide a method for controlling the aggregate size and
structure of carbon blacks.
An additional object of the present invention is to
produce carbon blacks having larger aggregate size and higher
structure for a given surface area.
SUMMARY OF T~E INVENTION
We have discovered a method which achieves these
desirable objects. We have discovered that we can control the
morphology of carbon blacks produced in a furnace carbon black
process, ~y lowering the temperature of the effluent without
stopping pyrolysis, preferably up to about 800 degrees F,
within a specified residence time of up to about 0.002 second
downstream from the furthest downstream point of injection
of feedstock. The lowering of the temperature may be
accomplished by locating a first quench at or within about 4
feet downstream of the furthest downstream point of
injection of feedstock and injecting quenching fluid.
According to the present invention the production of carbon
20~2627
blacks may be controlled to produce carbon blacks having
specific morphological properties such as larger aggregate
size and increased structure as shown by higher DBP, lower
tint, and increased Stokes diameter for a given surface area
(CTAB). We have further discovered that these morphological
propertieS of carbon blacks may be further controlled by
varying the amount by which the temperature of the effluent is
lowered and/or varying the residence time from the time of
the furthest downstream injection of feedstock until the
temperature of the effluent is lowered.
In more detail, the present invention relates to a method
for controlling the aggregate size and structure of the carbon
blacks produced by a furnace carbon black reactor by lowering
the temperature of, but not stopping pyrolysis in, the effluent
(the mixture of combustion gases and feedstock in which
pyrolysis is occurring) at a residence time between about 0.0
second and about 0.002 second, preferably between a~out 0.0
and about 0.0015 second, downstream from the furthest
downstream point of injection of feedstock. The temperature
of the effluent is lowered, within the above specified
residence time, preferably up to about 800 degrees F and more
1 0
ZO~X6Z7
preferably between about 50 and about 800 degrees F. The
temperature of the effluent may be lowered by a quench,
preferably a quench injecting quenching fluid into the effluent,
located at point in the reactor whereby the effluent is
quenched between about o.o and 0.002 second, preferably
between about 0.0 and a~out 0.0015 second, downstream from
the furthest downstream point of injection of feedstock.
Typically, in order for the effluent to be quenched within the
specified residence time, the quench will be located at or
within about 4 feet from the furthest downstream point of
injection of feedstock. The quench lowers the temperature of
the effluent, preferably up to about 800 degrees F, and more
preferably between about 50 and about 800 degrees F, but does
not stop pyrolysis. According to the present invention, the
amount by which the temperature of the effluent is lowered
and the residence time at which the lowering of the
temperature of the effluent occurs may be varied.
- independently or simultaneously to control the aggregate size
and structure of carbon blacks being produced by the reactor.
In a reactor using a quench, injecting a quenching fluid, to
lower the temperature of the effluent within the specified
-- 2012627
residence times, this varying of the amount the
temperature of the effluent is lowered and the
residence time at which the lowering of the temperature
of the effluent occurs may be accomplished by varying
the quantity of quenching fluid injected from the
quench and varying the location of the quench
respectively. After carbon blacks with the desired
properties have been formed pyrolysis is stopped.
The present invention allows the production of a
carbon black product having larger aggregate size and
structure for a given surface area than the carbon
black products produced by a similar process wherein
the temperature of the effluent is not lowered within
the specified residence time.
An advantage of the process of the present
inventiQn is that the aggregate size and structure of
carbon blacks may be controlled.
Another advantage of the process of the present
invention is that carbon blacks having larger aggregate
size and structure, as shown by higher DBP's, lower
tints, and increased Stokes' diameters, for a given
surface area, as shown by CTAB, may be produced.
Other advantages of the present invention will
become
12
;~O~Z6Z7
apparent from the following description and claims.
8RIEF DESCRIPTION OF THE DRAWING
The figure is a cross sectional view of one embodiment of the
present invention in a carbon black reactor, showing the
location of a first and a second quench.
DETAILED DESCRIPTION OF T~E INVENTION
The figure depicts one possible embodiment of the
present invention. Although a portion of one type of carbon
black reactor is depicted in the figure, as previously explained
the present invention can be used in any carbon black furnace
reactor in which carbon black is made by pyrolysis and/or
incomplete combustion of hydrocarbons. Further, although the
following description explains an embodiment of the present
invention utilizing a quench, injecting a quenching fluid, to
lower the temperature of the effluent, as will be understood
by those of ordinary skill in the art, the present invention
encompasses any method for lowering the temperature of the
effluent, preferably by the amounts specified, within the
specified residence times from the point of injection of
feedstock nearest the reaction zone. Similarly, although the
following description describes using a second quench to stop
201Z627
pyrolysis, as will be understood by those of ordinary skill in
the art, the present invention encompasses any method for
stopping pyrolysis.
In the figure, a portion of a carbon black reactor 10,
having, for example, a reaction zone 12, and a zone of
restricted diameter 20, is equipped with a first quench 40,
located at point 60, and a second quench 42, located at point
62, for injecting quenching fluid 50. The quenching fluid 50
may be the same or different for each quench. The direction of
flow of the hot combustion gas stream through reactor 10, and
zones 12 and 20 is shown by the arrow. Quenching fluid 50 can
be injected by first quench 40 and second quench 42
counter-currently, or preferably co-currently, to the direction
of the combustion gas stream. Point 14, is the furthest
downstream point of injection of feedstock 30. As will be
understood by those having ordinary skill in the art, 14, the
furthest downstream point of injection of feedstock can be
varied. The distance from 14, the furthest downstream point
of injection of feedstock, to the point of the first quench 60 is
r~presented by L-l and the distance from the furthest
downstream point of injection of feedstock, 14 to the point of
14
201Z627
t~e second quench 62 is represented by L-2.
According to the depicted embodiment of the present
invention, the first quench 60 is positioned to lower the
temperature of the effluent (the mixture of combustion gases
and feedstock in which pyrolysis is occurring~ no later than
0.002 second, and preferably between 0.0 and 0.0015 second,
residence time from the furthest downstream point of
injection of feedstock. Typically, in order for the effluent to
be quenched within the specified residence time, the first
quench will be located at or within about 4 feet from the
furthest downstream point of injection of feedstock.
Therefore L-1 will be between about o.0 and about 4 feet.
Quenching fluid is injected through the first quench 60 in order
to lower the temperature of the effluent, preferably by an
amount up to 800 degrees F, more preferably by an amount
between about 50 and about 800 degrees F, provided, however,
that the quenching fluid injected through first quench 60 will
not stop pyrolysis.
Additionally, according to the present invention the
residence time from the furthest.downstream point of
in`jection of feedstock until the tèmperature of the effluent
~-- 2012627
(the mixture of combustion gases and feedstock in which
pyrolysis is occurring) is initially lowered, and the
amount by which the temperature of the effluent is
lowered, may be varied independently or simultaneously
to control the aggregate size and structure of the
carbon blacks produced by the reactor. In the
embodiment of the present invention shown in the
figure, varying L-1 will vary the residence time from
the time of the furthest downstream injection of
feedstock to the time at which the temperature of the
effluent is lowered. By varying the amount of quenching
fluid injected the amount by which the temperature of
the effluent is lowered may be varied.
As explained in the preceding paragraph, in the
embodiment of the present invention shown in the
figure, depending on the aggregate size and structure
desired typically L-1 ranges from about 0.0 feet to
about 4 feet. Quenching fluid 50 lowers the temperature
of the effluent, preferably by an amount up to about
800 degrees F, more preferably by an amount between
about 50 and about 800 degrees F, provided, however,
that pyrolysis will not be stopped at first quench 60
by the quenching fluid 50.
16
Z~2~Z7
After carbon blacks with the desired properties have
been produced pyrolysis is stopped at point 62 by quench 42.
Point 62 is a point at which carbon blacks having the desired
properties have been produced by the reactor. As previously
explained, point 62 may be determined in any manner known to
the art, for selecting the position of a quench which stops
pyrolysis. One method for determining the position of the
quench which stops pyrolysis is by determining the point at
which an acceptable toluene extract level for carbon black
products desired from the reaction is achieved. Toluene
extract level may be measured by using ASTM Test D1618-83
"Carbon Black Extractables - Toluene Discoloration". L-2 will
vary according to the position of point 62.
The effectiveness and advantages of the present
invention will be further illustrated by the following example.
EXAMPLE
To demonstrate the effectiveness of the present
invention experiments were conducted in a carbon black
production process utilizing two quenches and varying the
residence time from the time of the furthest downstream
injection of feedstock until the time the temperature of the
20~2627
,
effluent was lowered and the amount by which the temperature
of the effluent was lowered. This residence time was ~raried
by varying L-l. The process variables for, and the results of,
the two sets of carbon black runs in the experiments, are
summarized in the Table set forth below. Set I comprises runs
1, 2, and 3 and Set II comprises runs 4, 5, and 6.
TABLE
Temp. Temp. T mp.
R- . Bet. 1 st Att. 2nd An.
nme 1~ 0 Ci 1st O Ci 2nd O ~d. D~t flut~
RUN SET (sec) oF n. F n. F CTAS Tint Dlsc. CDBP nm DPiP
--- 2520 ----- 2620 4 21350 109 2 120.5 68 109.5 98.8 186
2 1 .0007 2620 1 4 2220 17.0 1350100.7 1106 45 110.0 109.6 205
3 .0005 2620 1.0 2220 20.0 135094.3 102.2 73 113.4 126.9 232
4 - 2570 ---- 25~0 15.01350 91.6 114.6 77 95.2 94.1 148
11 .0004 2570 1 0 2270 34.0 135093.4 106 1 78 106.4 101.5 213
6 .0004 2570 1.0 2170 36.0 135091 4 1050 41 107.1 103.3 220
SET 1 Prehest . 900O F: GAS. 7.2 ksc~h: Air ~ 80 itacih Air/G~u . 11.11 Prlmary Comi~siion . 123~: CL ' a Zone Vol. . .
~s ~t ':
Inlectlon Zone Olameter - 4.2 In. Injection Zone ~ength 8 12 ~n. C~ n GaS Veioaty In Inlection Zon- . 2000 n.hec.:
oil . 125 gph Oil Inlection i res~ure . 230 pslg ~ o~ oo tips . 4 Oil ~ip d~ameter = 0.042 In. Reectlon Zone Oiameter . 13.5 In.
ll e liquid teedstock (oil) had tile ~ollowing c . 1~ .. H/C Ra~io . .91: Hydroqen . 6.89 wt % 7.00 wi.%:
Caroon 91.1 wt.% 90.8 wt.% Suitur . 1.1 wt.~ API Gravlty 15.6/15.6 C(60f) . 5.0: PiMCI (Vl~c-Gravl 141
Sf~ Il: Preheal . 11000 F GaS . 7 5 kscrh Air . 50 itllClh: Air/Gas . 10 6 Primary C~ . 118%: C- - ~n Zon- vol. -.85t.J.
. Inj~ctlon Zon Oiameter . 4.2 In. Inje~ion Zone Length . 12 In.; C~ Gaa V-icK ~ty In In~ on Zon- . 2300 n.h c.:
oii 136 gph: Oil In;ection Pre~ure . 270 ~ig ~ o~ oil ~ID- . 4; Oil ~p di~me~r~r . 0.042 In. Reaetlon Zone iDiameter 6 In.
The iiquid hed~tock (oli) had the toiiowing c .~ ~. R/C Ratio . t.06 I-iydrogen . 7.99 wt.% 7.99wt.%:
Carbon . 89.7 wt.% 89.5 wt.%: SuHur . 0.5 wt.%: API Gravity 1S.6/15.6 C(60F) . 0.5: iSMCI (~GGrov) . 123
In ~ S~t I and Sat ll the nuld tuei uti02ed In the ~ ... . ~ reaction was netural gr~. having e meth~ ne eontent ot 95.'4%
and a wot heating value o~ 925 FiTU/SCF.
201262~
- As will be generally understood by those of ordinary skill
in the art, the process variables set forth in the Table
represent the variable at one point in the reactor and are
determined in the manner generally known. Each set of carbon
black runs was made in a carbon black reactor similar to the
reactor disclosed in Example 1 of U.S. Patent No. 3,922,335
with the exceptions as noted in the Table.
In the Table, Q refers to Quench. 1st Q ft. refers to L-l,
the distance from the furthest downstream point of injection
of feedstock to the first quench. Temperature Before 1st
Quench (Temp. Bef. 1st Q) refers to the temperature of the
effluent before the 1st quench, and Temperature After 1st
Quench (Temp. Aft. 1st Q) and Temperature After 2nd Quench
(Temp. Aft. 2nd Q) refer to the temperature of the effluent
after the 1st quench, and the temperature of the mixture of
feedstock and combustion gases after the 2nd quench,
respectively. All temperatures relatinq to quenching are
calculated by con~entional, well known, thermodynamic
techniques. Residence Time (Res. Time), in the Table , refers
to the amount of time after furthest downstream point of
in3ection of feedstock, which elapsed before the temperature
1 9
2012627
of the effluent was initially lowered. 2nd Q ft.,
refers to L-2 and was empirically determined using
the toluene extract level. After each run the carbon
blacks produced were collected and analyzed to
determine CTAB, tint, Dst(median Stokes diameter),
CDBP, Fluffy DBP and Toluene Discoloration. The
results for each run, are shown in the Table.
CTAB was determined according to ASTM Test
Procedure D3765-85. Tint was determined according to
ASTM Test Procedure D3265-85a. DBP of the fluffy
blacks was determined according to the procedure set
forth in ASTM D2414-86. CDBP was determined accord-
ing to the procedure set forth in ASTM D3493-86.
Toluene Discoloration was determined according to
ASTM Test Procedure D1618-83.
Dst(median Stokes Diameter) was determined
with disc centrifuge photosedimentometry according
to the following description. The following
procedure is a modification of the procedure
described in the Instruction Manual for the Joyce-
Loebl Disc Centrifuge, File Ref. DCFA.008, published
1 Feb. 1985, available from Joyce-Loebl Company,
(Maquisway, Team Valley, Gateshead, Tyne & Wear,
England). The procedure is
- 20 -
.,
2012627
-
as follows. 10 mg (milligrams) of a carbon black sample are
weighed in a weighing vessel, then added to 50 cc of a solution
of 10% absolute ethanol, 90% distilled water which is made
0.05% NONIDET P-40 surfactant (NONIDET P-40 is a registered
trademark for a surfactant manufactured and sold by Shell
Chemical Co.). The suspension is dispersed by means of
ultrasonic energy for 15 minutes using Sonifier Model No. W
385, manufactured and sold by Heat Systems Ultrasonics Inc.,
Farmingdale, New York. Prior to the disc centrifuge run the
following data are entered into the computer which records
the data from the disc centrifuge:
1. The specific gravity of carbon black, taken as 1.86
g/cc:
2. The volume of the solution of the carbon black
dispersed in a solution of water and ethanol, which in this
instance is 0.5 cc.;
3. The ~olume of spin fluid, which in this instance is 10
cc of water:
4. The viscosity of the spin fluid, which in this instance
is taken as 0.933 centipoise at 23 degrees C;
5. The density of the spin fluid, which in this instance is
~2~27
0.9975 g/cc at 23 degrees C;
6. The disc speed, which in this instance is 8000 rpm;
7. The data sampling interval, which in this instance is
1 second.
The disc centrifuge is operated at 8000 rpm while the
stroboscope is operating. 10 cc of distilled water are injected
into the spinning disc as the spin fluid. The turbidity level is
set to 0; and 1 cc of the solution of 10% absolute ethanol and
90% distilled water is injected as a buffer liquid. The cut and
boost buttons of the disc centrifuge are then operated to
produce a smooth concentration gradient between the spin
fluid and the buffer liquid and the gradient is monitored
visually. When the gradient becomes smooth such that there is
no distinguishable boundary between the two fluids, 0.5 cc of
the dispersed carbon black in aqueous ethanol solution is
injected into the spinning disc and data collection is started
immediately. If streaming occurs the run is aborted. The disc
is spun for 20 minutes following the injection of the dispersed
carbon black in aqueous ethanol solution. Following the 20
m,inutes of spinning, the disc is stopped, the temperature of
the spin fluid is measured, and the average of the temperature
- 2012627
of the spin fluid measured at the beginning of the run and the
temperature of the spin fluid measured at the end of the run is
entered into the computer which records the data from the
disc centrifuge. The data is analyzed according to the standard
Stokes equation and is presented using the following
definitions:
Carbon black aggregate - a discrete, rigid colloidal
entity that is the smallest dispersible unit: it is composed of
extensively coalesced particles;
Stokes diameter - the diameter of a sphere which
sediments in a viscous medium in a centrifugal or
gravitational field according to the Stokes equation. A non-
spherical object, such as a carbon black aggregate, may also be
represented in terms of the Stokes diameter if it is considered
as behaving as a smooth, rigid sphere of the same density, and
rate of sedimentation as the object. The customary units are
expressed as nm diameters.
Median Stokes diameter (~tfor reporting purposes) - the
point on the distribution curve of Stokes diameter where 50%
by weight of the sample is either larger or smaller. It
therefore represents the median value of the determination.
ZOlZ627
- As shown in the Table the present invention allowed
production of carbon blacks with increased CDBP's, fluffy
DBP's and ~'s and decreased tints as compared to the carbon
blacks produced by the control carbon black process runs, 1 and
4, utilizing a single quench. This indicates that carbon blacks
of the present invention are characterized by increased
aggregate size and structure. Further, as shown by the results
for Set II, the present invention allowed for the production of
carbon blacks having increased CDBP~s, fluffy DBP's and ~t's
and decreased tints for a relatively constant CTAB. This
indicates that the present invention produced carbon blacks
with increased aggregate size and structure for a given CTAB.
As shown by the results for Set I, the present invention
produced carbon blacks with increased CDBP's, fluffy DBP's and
~'s and decreased tints as compared to the carbon blacks
produced by the control car~on black process run 1 at differing
residence times at which the temperature of the effluent was
initially lowered by the same amount.
Since the present invention relates to a process for
controlling the aggregate size and structure of carbon blacks,
nu~erous variations and modifications may obviously be made
24
2012627
in the above described carbon black production runs
without departing from the present invention.
Accordingly, it should be clearly understood that the
forms of the present invention herein described, and
shown in the figure, are illustrative only and are not
intended to limit the scope of the invention. The
present invention includes all modifications falling
within the scope of the following claims.
