U.S. patent application number 12/684261 was filed with the patent office on 2010-06-10 for carbon black pellets and method of forming same.
Invention is credited to Chang H. Lee.
Application Number | 20100143585 12/684261 |
Document ID | / |
Family ID | 39668341 |
Filed Date | 2010-06-10 |
United States Patent
Application |
20100143585 |
Kind Code |
A1 |
Lee; Chang H. |
June 10, 2010 |
CARBON BLACK PELLETS AND METHOD OF FORMING SAME
Abstract
A carbon black pellet comprising an inner core of de-aerated
carbon black and an outer surrounding shell of an encapsulating
material, the shell of the encapsulating material having an average
thickness of from about 1% to about 10% of the average thickness of
the pellet.
Inventors: |
Lee; Chang H.; (Houston,
TX) |
Correspondence
Address: |
C. JAMES BUSHMAN
5851 San Felipe, SUITE 975
HOUSTON
TX
77057
US
|
Family ID: |
39668341 |
Appl. No.: |
12/684261 |
Filed: |
January 8, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11700794 |
Jan 31, 2007 |
7651772 |
|
|
12684261 |
|
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Current U.S.
Class: |
427/221 ;
427/215; 427/220 |
Current CPC
Class: |
C08K 9/10 20130101; C08L
21/00 20130101; Y10T 428/2991 20150115; C08L 21/00 20130101; Y10T
428/2998 20150115; Y10T 428/30 20150115; C08K 9/10 20130101 |
Class at
Publication: |
427/221 ;
427/215; 427/220 |
International
Class: |
C08K 3/04 20060101
C08K003/04; B05D 7/00 20060101 B05D007/00 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. A method of forming carbon black pellets comprising:
de-aerating carbon black aggregates to form de-aerated carbon
black; introducing said de-aerated carbon black into a fluid-solids
contactor; introducing a particulate encapsulating material into
said contactor; and contacting said de-aerated carbon black with
said encapsulating material for a period of time sufficient to form
encapsulated carbon black pellets comprising an inner core of
de-aerated carbon black and an outer surrounding shell of
encapsulating material, wherein said shell has an average thickness
of about 1% to about 10% of the average thickness of said
pellet.
12. The method of claim 11, wherein said contactor comprises a
moving-bed system.
13. The method of claim 12, wherein said moving-bed system
comprises a rotary drum mixer.
14. The method of claim 11, wherein said contactor comprises a
fluidized bed system.
15. The method of claim 11, wherein said particulate encapsulating
material is introduced into said contactor in the form of a
mist.
16. The method of claim 11, wherein said encapsulating material
comprises a single encapsulating agent.
17. The method of claim 11, wherein said encapsulating material
comprises multiple encapsulating agents.
18. The method of claim 11, wherein said encapsulated carbon black
pellets are removed from said contactor and cooled.
19. The method of claim 11, wherein said carbon black pellets are
generally spherical.
20. The method of claim 19, wherein said spherical pellets have a
diameter of from 125 to 2000 .mu.m.
21. The method of claim 11, wherein said carbon black aggregates
are selected from the carbon black group consisting of I.sub.2N0
(ASTM D1510) in the 20 g/Kg to 1000 g/Kg range and OAN (ASTM D2414)
in the 45 ml/100 g to 500 ml/100 g range.
22. The method of claim 11, wherein said encapsulating material is
selected from the group consisting of carbohydrates, lignin oxides,
cellulose by-products, natural rubbers, synthetic rubbers,
synthetic polymers, waxes, resins, rosins, and mixtures
thereof.
23. The method of claim 11, wherein said encapsulating material is
present in said pellet at a maximum amount of 10 wt. % based on the
total carbon black present in said pellet.
24. The method of claim 11, wherein said encapsulating material in
said shell comprises at least 30 wt. % of the total encapsulating
material present in said pellet.
25. The method of claim 11, wherein said encapsulating material in
said shell comprises at least 90 wt. % of the total encapsulating
material present in said pellet.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This Application is a divisional of U.S. patent application
Ser. No. 11/700,794, filed Jan. 31, 2007 for CARBON BLACK PELLETS
AND METHOD OF FORMING SAME, the disclosure of which is incorporated
herein in their entirety for all purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to carbon black pellets and,
more particularly, to carbon black pellets having good
dispersibility, good bulk handling characteristics and good
attrition resistance, and to a method of manufacturing such
pellets.
[0004] 2. Description of Prior Art
[0005] Carbon black finds wide industrial use. Carbon black is used
as a reinforcing agent in rubber products such as tires, tubes,
conveyor belts, cables and other mechanical rubber goods; as a
black pigment in printing, lithographic, letter press, carbon paper
and typewriter ribbon inks, paints, coatings, lacquers, plastics,
fibers, ceramics, enamels, paper, record discs and photocopier
toner; in leather finishes; in the manufacture of dry-cell
batteries, electrodes and carbon brushes; in electrical conductors;
in conductive and anti-static rubber and plastic products; for
electromagnetic interference shielding; video discs and tapes; for
UV stabilization of polyolefins; as a high temperature insulating
material; etc.
[0006] As produced, carbon black particles have a fractal
morphology. They are composed of primary particles about 10 to 500
nm in diameter which irreversibly fuse during the
furnace/combustion process used and produce primary aggregates
having a diameter of from 50 to 20,000 nm. Carbon black cannot be
practically used in its produced form because of its light and
dusty form making its handling, shipment and end use not only
difficult but environmentally unacceptable. To improve these
handling, shipping and use problems, the produced, fluffy carbon
black is densified. It is well known in the art that for a given
grade of carbon black, handling properties improve with increasing
degree of densification. However, dispersibility of the densified
carbon black is progressively degraded as the extent of
densification is increased. Thus, there is a trade off between
improvements in bulk handling properties and degradation in
dispersibility.
[0007] In general, currently the industry uses three basic methods
to obtain densification. These, in order of providing increased
levels of densification are: agitation or vacuum treatment of the
fluffy produced product, dry pelletization and wet pelletization.
All of these methods are well documented in the art as disclosed,
for example, in U.S. Pat. Nos. 2,850,403; 3,011,902; 4,569,834;
5,168,012; 5,589,531; and 5,654,357, all of which are incorporated
herein by reference for all purposes. The densification processes
mentioned above, all suffer from disadvantages, e.g., product that
has poor properties in bulk handling, the formation of pellets
which are relatively weak and have poor attrition resistance or
relatively dense, hard and attrition resistant pellets which
possess good bulk handling properties but are difficult to
disperse.
[0008] Thus there still remains a need for a densified carbon black
which exhibits good bulk handling properties, has good attrition
resistance and is readily dispersible.
SUMMARY OF THE INVENTION
[0009] In one aspect the present invention provides a carbon black
pellet comprising an inner core of de-aerated carbon black and an
outer, surrounding shell of an encapsulating material, the shell of
encapsulating material having an average thickness of from about 1%
to about 10% of the average thickness of the pellet.
[0010] In another aspect of the present invention, there is
provided a method for producing encapsulated carbon black pellets
wherein de-aerated carbon black is contacted with a fluidized
encapsulating material in a fluid-solids contactor for a period of
time sufficient to form a carbon black pellet as described
above.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0011] Virtually any carbon black can be used in the process of the
present invention. Thus, carbon blacks produced by various
industrial processes including acetylene black, channel black,
furnace black, lamp black and thermal black can be employed.
Preferred carbon blacks used in forming the pellets of the present
invention, include carbon black in the I.sub.2N0 (ASTM D1510) range
of 20 g/Kg to 1000 g/Kg and OAN(ASTM D2414) range of 45 ml/100 g to
500 ml/100 g.
[0012] The carbon black pellets of the present invention are
characterized by a soft or fluffy carbon black inner core and an
outer, surrounding shell of an encapsulating material which forms a
rigid to semi-rigid coating which resists attrition and physical
impact to thereby render the pellets more dust free. While the
pellets produced according to the present invention can vary in
shape and size, generally speaking for the most part the pellets
are of a spherical or spherical-like shape and have a diameter of
from 125 to 2000 .mu.m. However, as noted, the pellets may not
necessarily be spherical and the size range can vary substantially
over that noted above. The outer, encapsulating shell, whether it
be termed a crust, film, layer or the like, will generally have an
average thickness of from about 1% to about 10% of the average
thickness of the carbon black pellet. It will be understood that in
cases where the pellets are asymmetric, e.g., not spherical or
generally spherical, that this average thickness of the outer
surrounding layer will still hold true. In this regard, the volume
of the inner core of the pellet relative to the volume of the
encapsulating layer will be such that if the pellet, albeit
irregular in shape were spherical in nature, the combined volumes
of the inner core and the encapsulating layer, viewed as a
generally spherical body would be such that the above relationship
held true, i.e., the average thickness of the encapsulating layer
is from about 1% to about 10% of the thickness, e.g., diameter, of
the overall pellet.
[0013] From a compositional perspective, it is desired that the
encapsulating shell be as thin as possible consistent with the
pellets having adequate bulk handling properties. In general, the
shell of the pellets of the present invention will contain a
maximum amount of 10 wt. % of encapsulating material based on the
total weight of the carbon black present in the pellet. In cases
where the encapsulating material comprises a single encapsulating
agent, the weight of the encapsulating agent will generally be from
about 1 to about 3 wt. % based on the total carbon black present in
the pellet while in cases where multiple encapsulating agents are
employed, the weight of the encapsulating material will be from
about 5 to about 7 wt. % based on the total carbon black present in
the pellet. While some of the encapsulating material will be
present in the core of the pellet, at least 30 wt. %, preferably
more than 50 wt. %, and more preferably 90 wt. % or more of the
total encapsulating material employed will be present in the outer,
surrounding shell of the pellet. Because of the unique construction
of the pellet of the present invention, i.e., a soft, fluffy inner
core of carbon black and an outer more rigid shell, crust or layer
of encapsulating material, relatively small amounts of
encapsulating material(s), can be employed, since the encapsulating
material is concentrated in the outer surrounding shell of the
pellet.
[0014] The encapsulating material used in the process of the
present invention, as noted above, can comprise a single
encapsulating agent or multiple encapsulating agents. Encapsulating
agents are well known to those skilled in the art and include
numerous materials. Thus, non-limiting examples of encapsulating
materials include carbohydrates, lignin oxides, cellulose
by-products, natural rubbers, synthetic rubbers, synthetic
polymers, natural and synthetic waxes, resins, rosins, and mixtures
thereof. The encapsulating material whether it be one encapsulating
agent or multiple encapsulating agents will be in particulate form.
In certain cases, this can be accomplished by melting the
encapsulating material and forming it into a mist, spray, aerosol
or other particulate form. In still other cases, the encapsulating
material can be dissolved in a suitable carrier which can then be
formed into a mist, spray, aerosol or the like. The term carrier as
used herein is intended to mean any fluid, e.g., a liquid, in which
the encapsulating agent or agents can be dissolved, dispersed or
otherwise formed into a particulate form such that it can be
introduced into a fluid-solids contactor in the form of an aerosol,
mist, spray or other particulate form. Non-limiting examples of
liquid carriers include mineral oils, animal oil, plant oils,
alcohols, and acids. In certain cases, the encapsulating material
can be in the form of an aerosol of finely divided solid particles,
which at the temperature of the encapsulating step will coalesce to
form the shell. In this case, the finely divided solid particles
would simply be introduced into the encapsulated step by being
carried in a gaseous stream, e.g., air or an inert gas, if desired.
In any event, the encapsulating agent will be of a type which can
form a crust, coating, film, covering, etc., on the carbon black to
form the encapsulating shell.
[0015] While the shell has been described as "surrounding the core
of the pellet," it is to be understood that there could be minor
fissures or discontinuities in the shell such that the inner core
was exposed, albeit slight. However, any such fissures or
discontinuities in the encapsulating shell will be of such a
dimension that there is no substantial escape of the core material
from the pellet.
[0016] In forming the carbon black pellets of the present
invention, two main steps are employed--de-aerating and
encapsulating. As is well known, produced carbon black is extremely
fluffy with a low apparent density. The fluffiness of the produced
carbon black can be to some extent reduced and the apparent density
increased by de-aerating the produced carbon black per methods well
known to those skilled in the art. For example, carbon black
de-aeration can be accomplished by using equipment such as vacuum
filtration and/or compactors all of which are commercially
available and commonly used for the purpose of removing air from
produced, fluffy carbon black.
[0017] The terms fluid, fluids and derivatives thereof, as used
herein with respect to the fluid/solids contactor means a physical
form such as a spray, aerosol, mist, dust or the like, wherein
particulate matter, whether in solid or liquid form, is suspended
in a generally gaseous environment. The de-aerated carbon black is
introduced into a fluid-solids contactor. The fluid-solids
contactor can comprise a moving bed system such as a rotary drum,
with or without pins, or a fluidized bed system or for that matter
any type of equipment wherein solid particles, e.g., the de-aerated
carbon black can be contacted with a fluid, as defined above, of
the encapsulating material such that the fluid ultimately forms a
shell around an agglomeration of the carbon black to thereby form
the carbon black pellets of the present invention. The contacting
between the de-aerated carbon black and the fluidized particulate
encapsulating material is conducted for a period of time sufficient
to accomplish the pelletizing process, i.e., to form an inner core
of carbon black and an outer shell or crust of encapsulating
material. It will be understood that the time for forming the
pellets can vary over wide limits depending upon the nature of the
carbon black, the nature of the encapsulating material, etc.
[0018] The encapsulation process can be carried out at ambient or
elevated temperatures of from 10 to 200.degree. C. depending on the
nature of the encapsulating material. For example, in cases where
the encapsulating material is in the form of a wax which can be
melted to form a mist, dispersion or other particulate form of the
wax, the temperature may range from 60 to 160.degree. C. depending
upon the particular wax employed. It needs to be understood that
the wax as contemplated herein can be either natural or synthetic.
In cases where the encapsulating material is dissolved in a
carrier, temperatures can be considerably lower than would be
employed in the case of a relatively high temperature melting wax
and need only be high enough to evaporate the carrier leaving the
encapsulating material to form the shell on the carbon black
core.
[0019] Once the encapsulation process has been finished and the
pellets formed, they are removed from the contactor and cooled if
necessary. In certain cases, again depending upon the nature of the
encapsulating material, the cooling step is not required. However,
in cases where relatively high temperatures are employed in the
encapsulation process, it may be necessary to remove the pellets
and cool them by methods well known to those skilled in the art. A
feature of the present invention is that because a relatively small
amount of the encapsulating material is employed, the encapsulating
material tends to solidify or harden very quickly to form the shell
minimizing the need for cooling in many cases.
[0020] To more fully illustrate the present invention, the
following non-limiting examples are presented.
Example 1
[0021] A 6000 pound charge of de-aerated N650 (ASTM D1765) carbon
black was wet pelletized with 6000 pounds of water and 0.5 wt. %
molasses binder based on the total weight of carbon black, in a
commercial pin mixer at 100.degree. C. for 10 minutes, to form
control sample pellets.
Example 2
[0022] De-aerated carbon black from fluffy N650 (ASTM D1765) was
wet pelletized with water but without any binder. Thus, the pellets
produced were as per Example 1 but without any molasses binder.
Fifty pounds of the pellets were introduced into a Munson Rotary
Batch Mixer which had a bladed interior to keep the pellets in
motion. Polyethylene wax was heated to a temperature of around
90.degree. C., i.e., to the melting point, and sprayed into the
rotating drum, the interior of the drum being substantially at
ambient temperature. The amount of polyethylene wax employed was
1.7 wt. % based on the weight of the carbon black charged to the
drum. The encapsulation process was continued for a period of
approximately 2 minutes at which point the pellets were
removed.
Example 3
[0023] The procedure of Example 2 was followed with the exception
that the encapsulating agent comprised a phenolic resin which had
been melted and dispersed or suspended in paraffinic mineral oil as
a carrier. The phenolic resin was present in an amount of 1.5 wt. %
based on the carbon black charge while the paraffinic mineral oil
was present in an amount of 4.8 wt. % based on the carbon black
charge.
[0024] The pellets made per Examples 1, 2 and 3, were subjected to
various tests to determine dust generation, attrition resistance
and dispersibility. To determine dust generation, two methods were
employed--visual inspection and a modified ASTM D1508 test (Test
time increased from 20 minutes to 60 minutes). The visual
inspection method involved placing a half gallon of the carbon
pellets in a container, agitating the pellets in the container with
gloved hands 10 times and determining visually the amount of carbon
black on the gloves. In the modified ASTM D1508 method, the pellets
were subjected to a 60 minute test to simulate long distance
shipment of the pellets to determine attrition resistance and dust
generation.
[0025] Table 1 shows the results of the two dust
generation/attrition tests as well as individual pellet crush
strength (ASTM D3313). In the results in Table 1 below, the pellet
of Example 1 is arbitrarily assigned a value of 100 for the
modified ASTM D1508 test and the ASTM D3313 test. With respect to
the visual inspection method of determining dust generation by the
pellets, an arbitrary scale of 1-5 was employed with 5 being worst
and 1 being best. The results are shown in Table 1 below. As can be
seen from Table 1, the pellets made by the process of the present
invention Examples 2 and 3 (Ex 2, Ex. 3) generated much less dust
albeit that they had less pellet rigidity or crush strength versus
the prior art pellet, e.g., the pellet made per Example 1 (Ex.
1).
TABLE-US-00001 TABLE 1 Test Ex 1 Ex 2 Ex 3 Modified ASTM D1508
(Attrition) 100 60 17 % Improvement, % vs. Ex 1 40 83 Visual
Inspection (Dustiness) 5 3 1 % Improvement, % vs. Ex 1 40 80 ASTM
D3313 (Pellet strength) 100 49 72
[0026] The pellets of Examples 1-3 were compounded in a 1.5 liter
internal mixer with various amounts of rubber components and other
additives for purposes of conducting dispersibility testing. For
further comparison purposes, two additional formulations, Compound
2 and Compound 3, were also used. Compounds 2 and 3 have the same
type and amount of encapsulating materials that were used to form
the pellets of the Ex. 2 and 3. However, the pellets of Compounds 2
and 3 were made the same as Ex1. The compound of Examples 1-3 and
Compounds 2 and 3 were then formed into rubber-containing
compositions for determination of dispersibility. The compositions
of the pellet-rubber formulations are shown in Table 2 below
wherein all components are parts-per-hundred of rubber (PHR).
TABLE-US-00002 TABLE 2 Test Ex 1 Ex 2 Ex 3 Compound 2 Compound 3
Molasses Binder Yes No No Yes Yes 1.sup.st Stage, 1.5L Banbury
Mixer SBR.sup.1 75.00 75.00 75.00 75.00 75.00 BR.sup.2 25.00 25.00
25.00 25.00 25.00 Ex 1 Wet Pellet N650 72.00 72.00 72.00 Ex 2
Encapsulated N650 73.25 Ex 3 Encapsulated N650 76.52 PE wax 1.25
Phenolic resin 1.07 Paraffinic oil 3.45 Additives 1* 38.00 38.00
38.00 38.00 38.00 2.sup.nd Stage, 2-roll mill 1.sup.st stage lump
210.00 211.25 214.52 211.25 214.52 Additives 2** 3.50 3.50 3.50
3.50 3.50 Total 213.50 214.75 218.02 214.75 218.02
.sup.1Styrene-Butadiene rubber sold under the name SOLFLEX .RTM.
.sup.2Butadiene rubber sold under the name BUDENE .RTM. *"Additives
1" comprises plasticizers, antioxidants, and antiozonants
**"Additives 2" comprise curing agents
[0027] The dispersibility of the pellets of Examples 1-3 and
Compounds 2 and 3 were evaluated by two methods--optical inspection
for micro-dispersion and extrusion tests for macro-dispersion. In
the optical evaluation, no significant differences were observed.
In determining macro-dispersion, a lab extruder (single screw of
0.75 inch O.D., 10:1 L/D ratio, and 0.75 inch channel depth) with
screen packs of U.S. No. 325 and No. 60 at the end of the screw
barrel was employed. Operating conditions were 45 rpm screw speed,
110.degree. C. die temperature and 70.degree. C. barrel
temperature. The results are shown in Table 3 using two indices (1)
the average pressure buildup in the extruder barrel per unit volume
of compound extruded and (2) elapsed time for the pressure build-up
in the extruder barrel to reach a given pressure of 5200 PSI.
Example 1 was assigned an arbitrary value of 100. The results are
shown in Table 3.
TABLE-US-00003 TABLE 3 Test Ex 1 Ex 2 Ex 3 Compound 2 Compound 3
Pressure build-up 100 58 64 94 92 % Improvement, 42 36 6 8 % vs. Ex
1 Elapsed time 100 490 450 100 110 % Improvement, 390 350 0 10 %
vs. Ex 1
[0028] As can be seen from the results in Table 3, there was much
less pressure build-up in the encapsulated pellets according to the
present invention (Examples 2 and 3) as compared with the control
(Example 1) and Compounds 2 and 3. As can also be seen, the elapsed
time to reach the 5200 PSI pressure build-up in the extruder barrel
was much greater for the encapsulated pellets of the present
invention (Examples 2 and 3) as compared to the control (Example 1)
or Compounds 2 and 3. Thus it can be seen from the data in Table 3
that the encapsulated pellets of the present invention are more
readily dispersible than a prior art wet pelletized carbon black
pellet using a carbohydrate (molasses) binder or prior art pellets
such as Compounds 2 and 3. It is well known that the dispersibility
of carbon black pellets in a polymeric matrix such as that employed
in Examples 1-3 and Compounds 2 and 3, is reflected by the two
indices evaluated, i.e., pressure build-up and elapsed time for
pressure build-up in the extruder barrel. In this regard, the
former represents extrusion rate while the latter represents
extrusion energy. As can be seen from Table 3, the extrusion rate
was higher for the encapsulated pellets of the present invention
and extrusion energy was lower for the encapsulated pellets of the
present invention.
Example 4
[0029] The procedure of Example 1 was followed to form wet
pelletized pellets of carbon black, N650 using molasses as a
binder.
Example 5
[0030] This example demonstrates production of the encapsulated
pellets of the present invention in a continuous process. Pellets
produced per Example 4 but without any binder were introduced at a
rate of 1000 PPH (pounds per hour) into a Munson Rotary Continuous
Blender. An encapsulating material comprising 1.2 wt. % phenolic
resin suspended in 3.6 wt. % paraffinic mineral oil, both based on
the carbon black weight, was introduced into the Munson Rotary
Continuous Blender by spraying. The temperature in the Munson
Rotary Continuous Blender was 35.degree. C.
Example 6
[0031] The procedure of Example 1 was followed with the exception
that the carbon black employed was N339 (ASTM D1765) and the binder
was lignin oxide.
Example 7
[0032] The procedure of Example 5 was followed with the exception
that the pellets employed were those produced per Example 6 but
without any binder and the encapsulating material comprised 2.6 wt.
% polyethylene wax dispersed in 2.3 wt. % paraffinic mineral oil,
both based on the carbon black weight. The encapsulating material,
i.e., the mixture of polyethylene wax suspended in the paraffinic
mineral oil, was introduced as a mist into the Munson Rotary
Continuous Blender at a temperature of 35.degree. C.
[0033] The pellets of Examples 4 and 5 were compared to determine
the effect of sieve residue on dispersibility. For example, as can
be seen from Table 4 below, the encapsulated pellets according to
the present invention (Example 5) had 8 times more sieve residue as
the prior art pellets (Example 4). It can be speculated that
pellets of lower sieve residue (U.S. No. 325 screen) would cause
less average pressure build-up in the barrel of an extruder using a
U.S. No. 325 screen. The results are shown in Table 4. Also shown
in Table 4, as to the pellets of Examples 4 and 5, is a dust
generator test which was performed in two ways--visual inspection
and a modified ASTM D1508 as described above with respect to
Examples 1-3. Table 4 shows the results of the dust generation test
as well as indices pellet crush strength (ASTM D3313), pellet size
distribution (ASTM D1511) and sieve residue (ASTM D1514-U.S. No.
325 screen).
TABLE-US-00004 TABLE 4 Test Ex 4 Ex 5 Modified ASTM D1508
(Attrition) 100 17 % Improvement, % vs. Ex 4 83 Visual Inspection
(Dustiness) 5 1 % Improvement, % vs. Ex 4 80 ASTM D3313 (Pellet
Strength) 100 77 Sieve residue #325 100 843 Pellet Size
Distribution, % #10 2.2 1.8 #18 31.7 44.0 #35 47.9 41.5 #60 14.2
10.5 #120 2.8 2.0 Pan 1.2 0.2
[0034] The pellets produced per Examples 4-7 were subjected to the
procedure set forth with respect to Examples 1-3 and as set forth
in Table 2. The same styrene butadiene rubber and butadiene rubber
were employed in the formations using the pellets of Examples 4-7.
Examples 4-1 and 6-1 are the pellets produced per Examples 4 and 6
but blended with the binders used to produce the pellets of
Examples 5 and 7, respectively, to form generally homogeneous
pellets wherein the binder was dispersed throughout the pellet
rather than forming encapsulating pellets as per Examples 5 and 7.
The rubber formulations are shown in Table 5 below.
TABLE-US-00005 TABLE 5 Test Ex 4-1 Ex 5 Ex 6-1 Ex 7 Molasses Binder
Yes No No No Lignin Oxide Binder No No Yes No 1.sup.st Stage, 1.5L
Mixer SBR 75.00 75.00 75.00 75.00 BR 25.00 25.00 25.00 25.00 Ex 4
Wet-pellet N650 72.00 Ex 6 Wet-pellet N339 72.00 Ex 5 Encapsulated
N650 75.48 Ex 7 Encapsulated N339 75.52 PE wax 1.87 Phenolic resin
0.88 Paraffinic oil 2.60 1.65 Additives 1* 39.50 39.50 39.50 38.00
2.sup.nd Stage, 2-roll mill 1.sup.st stage lump 214.98 214.98
215.02 215.02 Additives 2** 3.50 3.50 3.50 3.50 Total 218.48 218.48
218.52 218.52 *"Additives 1" comprises plasticizers, antioxidants,
and antiozonants **"Additives 2" comprise curing agents
[0035] Dispersibility of the pellets of Examples 4-1, 5, 6-1 and 7,
was evaluated by an extrusion test. The pellets were extruded in a
Haake.RTM. lab extruder (single screw of 0.75 inch O.D., 10:1 L/D
ratio, and 0.75 inch channel depth) with the screen packs of U.S.
No. 325 and No. 6-0 at the end of the screw barrel. Operating
conditions were 45 rpm screw speed, 110.degree. C. die temperature
and 70.degree. C. barrel temperature. Dispersibility was described
in terms of the average pressure build-up in the extruder barrel
per unit volume of compound extruded and elapsed time for the
pressure build-up in the extruder barrel to reach a given pressure,
in this case 5200 PSI for the pellets of Examples 4-1 and 5 and
4000 PSI for the pellets of Examples 6-1 and 7. The results for
Examples 4 and 5 are shown in Table 6.
TABLE-US-00006 TABLE 6 Test Ex 4-1 Ex 5 Pressure build-up 100 86 %
Improvement, % vs. Ex 4-1 14 Elapsed time 100 154 % Improvement, %
vs. Ex 4-1 54
[0036] Although the pellets of Example 5 contain 8 times more sieve
residue (No. 325 mesh) than the pellets of Examples 4-1,
nonetheless, as can be seen from the data in Table 6, the
encapsulated pellets of Example 5 showed much slower pressure
build-up in the extrusion test. These results demonstrate that
macro-dispersion is independent of sieve residue amount to a
certain extent and that the encapsulated pellets of Example 5
disperse more quickly and to smaller sizes which ultimately
contributes to an improvement in extrusion productivity and reduces
manufacturing costs. Similar results were exhibited with the
pellets of Examples 6-1 and 7 as shown in Table 7 below.
TABLE-US-00007 TABLE 7 Test Ex 6-1 Ex 7 Pressure build-up 100 71 %
Improvement, % vs. Ex 6-1 29 Elapsed time 100 144 % Improvement, %
vs. Ex 6-1 44
[0037] Table 7 also demonstrates that the enhanced benefits of the
encapsulated pellets are not dependent upon a specific grade of
carbon black since the pellets of Examples 6-1 and 7 were made from
a different carbon black than the pellets of Examples 4-1 and
5.
[0038] Pellets of Examples 6-1 and Example 7 were also tested in
silica blend formulations to determine if the encapsulated pellets
(Example 7) could reduce manufacturing costs or increased
dispersibility in a multiple mixing system as well as in a single
mixing system as per the results obtained and shown in Table 7. In
this respect, it is well known that silica is difficult to disperse
compared to carbon black. Accordingly, multiple pass mixing or
dynamic mixing methods are imperative to obtain a satisfactory
dispersion of the silica which increases manufacturing costs and
reduces productivity. The formulations are shown in Table 8 below.
In Table 8, all amounts are in PHR unless other indicated.
TABLE-US-00008 TABLE 8 Test Ex 6-2 Ex 7-1 Lignin Oxide Binder Yes
No 1.sup.st to 3.sup.rd Stage, 1.5L Mixer SBR 103.12 103.12 BR
25.00 25.00 Ex 6 Wet-pellet N339 36.00 Ex 7 Encapsulated N339 38.00
PE wax 1.5 0.5 Aromatic oil 4.38 3.38 Micro-pearl Silica 40.00
40.00 Additives 1* 11.90 11.90 Final Stage, 1.5L mixer 3.sup.rd
stage lump 221.90 221.90 Additives 2** 5.30 5.30 Total 227.2 227.2
*"Additives 1" comprise plasticizers, silica coupling agents,
antioxidants, and antiozonants. **"Additives 2" comprise curing
agents
Example 8
[0039] The dispersibility was evaluated through extrusion tests.
Formulations from Table 8 were extruded in the lab extruder (single
screw of 0.75 inch O.D., 10:1 L/D ratio, and 0.75 inch channel
depth) with the screen packs of U.S. No. 200 and No. 35 at the end
of the screw barrel under operating conditions of 45 RPM screw
speed, 70.degree. C. die temperature and 70.degree. C. barrel
temperature. Dispersibility was determined by average pressure
build-up in the extruder barrel per unit volume of compound
extruded and elapsed time for pressure build-up in the extruder
barrel to reach a given pressure (5200 PSI). The results are shown
in Table 9 below.
TABLE-US-00009 TABLE 9 Test Ex 6-2 Ex 7-1 Pressure build-up 100 86
% Improvement, % vs. Ex 6-2 14 Elapsed time 100 131 % Improvement,
% vs. Ex 6-2 31
[0040] As can be seen from Table 9, the encapsulated pellets
(Example 7), showed significant improvement over dispersibility in
a multiple pass mixing of a silica blend formulation as compared
with pellets of Example 6-1 wherein the binders were generally
homogeneously mixed throughout the pellets.
[0041] The data above demonstrates that the encapsulated pellets of
the present invention show reduced attrition (less dusting) and
better dispersibility as compared with prior art pellets made by a
wet pelletizing method regardless of binder types employed and
amounts, carbon black types or grades, and formulations and/or
methods of mixing.
[0042] The foregoing description and examples illustrate selected
embodiments of the present invention. In light thereof, variations
and modifications will be suggested to one skilled in the art, all
of which are in the spirit and purview of this invention.
* * * * *