Note: Descriptions are shown in the official language in which they were submitted.
WO 91/16464 PCT/US91/02593
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TREATMENT OF PARTICULATE MATERIALS
WITH RETICULATED CELLULOSE
BACKGROUND OF THE INVENTION
This invention relates to methods for
agglomerating or binding fine materials or particles
and to methods for producing particulate materials
with high liquid absorbencies. "Agglomerating" or
"Agglomeration" means consolidating fine materials
and substantially changing the size distribution of
particles from very fine to coarse, thereby
providing larger particles having a high degree of
structural integrity, Through the process of
agglomeration, increases in the liquid absorbency of
the material may be achieved, and material's utility
or desirable qualities are significantly increased.
It would be beneficial if there was some method
of agglomerating or binding the fine particles to
provide a useful product. Particularly helpful
would be a method to provide an agglomerated product
that has properties similar to the commodity granule
products from which the fines were separated.
In the manufacture of granular commodity
materials, such as clay animal litter and flour,
"dusts" or "fines" are created as an undesired
byproduct. These "dusts" or "fines" also include
various materials such as metal, metal ore particles
WO 91/16464 PCT/US91/02593
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cZ ~ ~ ~ ~ Q ~ and fly ash. When handling such materials in bulk,
their dusts can become sources of airborne pollution
as well as creating problems in the production of a
saleable product. Therefore,'these fines create
handling problems as well as waste products which
cannot be adapted for granular commodity materials.
In addition, combustible dusts, such as flour, can
be explosive when suspended in a confined air space;
and, it may be necessary to continuously filter or
scrub the air to prevent combustion.
The grinding of clay ore, to make clay animal .
litter of a useful particle size distribution, can
result in the generation of significant amounts
(e.g. 5 wt. percent) of very fine material. The
presence of such dust particles annoys consumers, so
the dust must be removed in order to make a
commercially acceptable product. Typically, the
separated clay dust has no commercial value and must
be disposed of in a landfill or otherwise.
To be useful as animal litter, particles of
agglomerated clay dust would need to have a high
degree of liquid absorbency. other properties, such
as wet strength,.should equal or exceed those of
standard clay litter particles. To date, there has
been no successful method of agglomerating clay dust
or other particulate materials to form larger
particles having a high degree of structural
integrity, high wet strength, and an enhanced
capacity to absorb liquids. .
Ceramics require binders, which are green
strength organic materials, to form the ceramic
products. These green strength materials aid in
process handling, including maintaining the shape or
structure of the ceramics before firing.
It would also be useful to have a method for
increasing the liquid absorbency of existing
WO 91/16464 PCT/US91102593
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particulate materials. Highly liquid absorbent
particles are useful in cleaning up spilled liquids
such as petroleum products and hazardous substances.
The absorbent particles should have the ability to
absorb the liquids and still maintain their
integrity.
Also, it has been known for many years that
cellulose can be synthesized by certain bacteria,
particularly those of the genus Acetobacter. But,
neither this type of cellulose, nor any other, has
been recognized as serving a role in agglomerating .
fine particles or in increasing the liquid
absorbency of existing particulate materials.
It has, been known for many years that cellulose
can be synthesized by certain bacteria, particularly
those of the genus Acetobacter. However,
taxonomists have been unable to agree upon a
consistent classification of the cellulose producing
species of Acetobacter. For example, the cellulose
producing microorganisms listed in the 15th Edition
of the Catalog of the American Type Culture
Collection under accession numbers 10245, 10821 and
23769 are classified both as Acetobacter aceti
subsp. xylinum and as Acetobacter nasteurianus. For
the purposes of the present invention any species or
variety of bacterium within the genus Acetobacter
that will produce cellulose under agitated
conditions should be regarded as a suitable
cellulose producer. ,
The cellulose fibrils produced by ~cetobacter,
although chemically resembling, in many aspects,
cellulose produced from wood pulp, are different in
a number of respects. Chief among the differences
is the cross sectional width of these fibrils. The
cellulose fibrils produced by Acetobacter are
greater than two orders of magnitude narrower than
CA 02080701 2000-OS-OS
75149-18
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the cellulose fibers typically produced by pulping birch or
pine wood. The small cross sectional size of these
Acetobacter-produced fibrils, together with the concomitantly
greater surface area than conventional wood-pulp cellulose and
the inherent hydrophilicity of cellulose, leads to a cellulose
product having unusually great capacity for absorbing aqueous
solutions.
This capacity for high absorbency has been
demonstrated to be useful in the manufacture of dressings which
may be used in the treatment of burns or as surgical dressings
to prevent exposed organs from surface drying during extended
surgical procedures. Such uses and a variety of medicament
impregnated pads made by treatment of Acetobacter-produced
intact pellicles are disclosed in U.S. Patent No. 4,788,146.
The pellicles of U.S. Patent No. 4,788,146 are
produced by growing Acetobacter in a culture medium tray which
remains motionless. Acetobacter is normally cultured under
such static conditions with the cellulose microfibrils being
produced at the air medium interface. Most bacteria of this
genus are very poor cellulose producers when grown in agitated
culture. One reason proposed for such poor production is that
an agitated culture induces a tendency for reversion to
noncellulose producing strains.
However, certain Acetobacter strains are
characterized by an ability to produce large amounts of a
reticulated bacterial cellulose in agitated culture without
manifesting instability leading to loss of cellulose production
in culture. European Patent No. 228 779 and U.S. Patent No.
4,863,565 disclose Acetobacter varieties which are vigorous
cellulose producers under agitated
WO 91!16464 PCT/US91/02593
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culture conditions. The reticulated cellulose
produced by the disclosed microorganisms and culture
conditions appears to be a unique type, physically
quite different from other known bacterial
cellulose. It has a highly branched, three
dimensional, reticulated structure. A normal
cellulose pellicle tends to have a lamellar
structure with significantly less branching.
SUMMARY OF THE INVENTION
It has now been discovered that fine particles,
such as the dust produced when grinding clay ore,
can be mixed with reticulated bacterial cellulose
(also referred to as "BAC"), which serves as an
agglomerator to form particles of a commercially
useful size. This agglomeration method produces
particles which have a high degree of structural
integrity and significant wet and dry strength.
Fines of various commodity materials can be
agglomerated, and particulate materials can be made
more liquid absorbent according to the processes of
the present invention.
Commodity materials include any inorganic or
organic materials that exist in powdered or granular
form and that would benefit from agglomeration to
produce particles of an increased size or from an
enhancement in liquid absorbency. An example of
such materials are clay ore, particles used in
ceramics manufacture, metal and metal ore particles,
coal dust,.fly ash, carbon particles, and
ingredients for pharmaceutical tablets.
An. additional example is the use of reticulated
bacterial cellulose in the food industry to increase
the integrity of certain food products that may
suffer from undesirable degradation or failure to
WO 91/16464
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hold its shape in storage, handling or cooking, such
as packaged pasta products.
A further example is the use of reticulated
bacterial cellulose in the mineral processing
industry as a means of agglomerating fine particles
for heap leaching. The cellulose helps preserve the
integrity of the agglomerated fine material during
the heap leaching process. The cellulose is clearly
superior over the use of cement as an agglomerate in
l0 acid heap leaching.
Only a small amount of reticulated cellulose
need be used so that particles of the agglomerated
dust or fines have physical characteristics that are
comparable to the characteristics of similarly sized
or larger nonagglomerated particles of the same
commodity. And, in some instances, the agglomerated
particles have improved characteristics.
It has also been found that existing
particulate materials, such as commercially
available clay particles, can be treated with
reticulated cellulose to obtain particles of
enhanced liquid absorbency.
In some embodiments, it is an object of this
invention to agglomerate fine particles so as to
avoid dusting problems or to produce a useable
product from the fine particles. And, in some
embodiments, it is an object to produce a
particulate material with improved liquid
absorbency.
These and other objects and features of the
invention will be understood from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a graph showing the particle size
distribution for untreated clay fines and for clay
WO 91/16464 PGT/US91/02593
fines treated with water only or treated with
reticulated cellulose.
Figure 2 is a graph showing the particle size
distribution of flyash treated'with three levels of
BAC versus untreated flyash.
Figure 3 is a graph showing the particle size
distribution of carbon black treated with three
levels of BAC as compared to untreated carbon black.
Figure 4 is a graph showing the use of BAC
dried with either carboxymethyl cellulose or sucrose
in agglomerating clay fines.
Figure 5 is a graph showing the fluid
absorbencies of untreated clay particles and of
comparable clay particles that had been treated with
water only or treated with BAC.
DETAILED DESCRIPTION
Preferred methods for agglomerating or
increasing the absorbency of materials are explained
in this detailed description.
Example 1
Production of Reticulated Bacterial Cellulose
For the purpose of this disclosure,
"reticulated cellulose" refers to any cellulose
material that has similar characteristics to
cellulose produced by growing the Acetobacter strain
of ATCC Accession No. 53263 or No. 53524 by the
method described below. Such reticulated cellulose
is characterized by a three-dimensional, multiple
branching fiber structure such that the fibers do
not have recognizable "ends". In particular, the
structure has strands of cellulose that interconnect
forming a grid-like pattern extending in three
dimensions. Unlike some bacterial cellulose which
- has overlapping adjacent strands of cellulose that
WO 91/16464 PCT/US91l02593
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are oriented predominantly with the long axis of the
strand in parallel but disorganized planes
(thereinafter described as "non-reticulated
cellulose"), the structure of'reticulated cellulose
has interconnecting, rather than overlapping,
strands of cellulose. These interconnecting strands
have both roughly perpendicular, as well as roughly
parallel, orientations. As a result, the
reticulated cellulose product has a more generally
fenestrated appearance in scanning electron
micrographs, whereas non-reticulated cellulose has
an appearance in scanning electron micrographs of
strands piled on top of one another in a criss-
crossing fashion, but frequently parallel in any
given layer. The fibrils of non-reticulated
cellulose, as compared to the fibrils of the
reticulated product, appear to branch and
interconnect less frequently. Although the
non-reticulated cellulose product appears to have
many fibrils that contact one another, the fibrils
overlay one another rather than interconnect. By
contrast, fibrils of reticulated cellulose have a
large proportion of fibers that interconnect to form
~a substantially continuous network of
interconnecting fibers.
Bacterial cellulose for the present invention
was produced in agitated culture by a strain of
Acetobacter aceti var. LCy inum grown as a subculture
of ATCC Accession No. 53263, deposited September 13,
1985 or ATCC Accession No. 53524, deposited~on
July 25, 1986 under the terms of the. Budapest
Treaty.
The following base medium was used for all
cultures. This will be referred to henceforth as
CSL medium.
WO 91/16464 PCT/US91/02593
Ingredient Final Conc.(mM)
(NH4)2504 25
KH2P04 ~ 7.3
MgS04 1.0
FeS04 0.013
CaCl2 0.10
Na2Mo04 0.001
ZnS04 0.006
10MnS04 0.006
CuS04 0.0002
Vitamin mix 10 mL/L
Carbon source As later specified
(usually glucose 2
or 4% w/v)
Corn Steep liquor As later specified
(usually 5%, v/v)
(supernatant fraction
after centrifugation)
20Antifoam 0.01 percent (v/v)
The final pH of the medium was
5.0 0.2.
The vitamin mix was formulated follows:
as
Ingredient Conc. ma/L
Inositol 200
Niacin 40
30Pyridoxine HC1 40
Thiamine HC1 40
Ca Pantothenate 40
Riboflavin 20
p-Aminobenzoic acid 20
35Folic acid 0.2
Biotin 0.2
Corn steep liquor (CSL) varies
in composition
depending on the supplier and mode
of treatment. A
40product obtained as Lot E804 from Corn Products
Unit, CPC North America, Stockton,California may be
considered typical and is described
as follows:
WO 91/16464 PCT/US91/02593
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Maior Component Percent
Solids 43.8
Crude protein . 18.4
Fat 0.5
Crude fiber 0:1
Ash 6.9
Calcium 0.02
Phosphorus 1.3
Nitrogen-free extract 17.8
Non-protein nitrogen 1.4
NaCl 0.5
Potassium 1.8
Reducing sugars
(as dextrose) 2.9
Starch ~ 1.6
The pH of the above is about 4.5.
The bacteria were first multiplied as a
pre-seed culture using CSL medium with 4 percent ,
(w/v) glucose as the carbon source and 5 percent
(w/v) CSL. Cultures were grown in 100 mL of the
medium in a 750 mL Falcon No. 3028 tissue culture
flask at 30oC for 48 hours. The entire contents of
the culture flask was blended and used to make a
5 percent (v/v) inoculum of the seed culture.
Preseeds were streaked on culture plates to check
for homogeneity and possible contamination.
Seed cultures were grown in 400 mL of the
above-described medium in 2 L baffled flasks in a
reciprocal shaker at 125 rpm at 30°C for two days.
r Seed cultures were blended and streaked as before to
check for contamination before further use. ,
Bacterial cellulose was initially made in a
continuously stirred 14 L Chemap fermenter using a ,
12 L culture volume inoculated with 5 percent (v/v)
of the seed cwltures. An initial glucose
concentration of 32 g/L in the medium was
supplemented during the 72-hour fermenter run with
an additional 143 g/L added intermittently during
the run. In similar fashion, the initial 2 percent
WO 9t/t6464 PCT/US91/02593
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(v/v) CSL concentration was augmented by th (ale
addition of an amount equivalent to 2 percent by
volume of the initial volume at 32 hours .and
59 hours. Cellulose concentration reached about
12.7 g/L during the fermentation. Throughout the
fermentation, dissolved oxygen was maintained at
about 30 percent air saturation.
Following fermentation,.the cellulose was
allowed to settle and the supernatant liquid poured
off. The remaining cellulose was washed with
deionized water and then extracted with 0.5 M NaOFi
solution at 60°C for two hours. After extraction,
the cellulose was again washed with deionized water
to remove residual alkali and bacterial cells. More
recent work has shown that 0.1 M NaOH solution is
entirely adequate for the extraction step. The
purified cellulose was maintained in wet condition
for further use. This material was readily
dispersible in water to form a uniform slurry.
Bacterial cellulose for the later examples was
made in 250 L and 6000 L fermenters.
The bacterial cellulose produced under stirred
or agitated conditions, as described above, has a
microstructure quite different from that produced in
conventional static cultures. It is a reticulated
product formed~by a substantially continuous network
of branching interconnected cellulose fibers.
The bacterial cellulose prepared as above by
the agitated fermentation has filament widths much
smaller than softwood pulp fibers or cotton fiber.
Typically these filaments will be about o.l to
' 0.2 microns in width with indefinite length due to
the continuous network structure. A softwood fiber
averages about 30 microns in width and 2 to 5 mm in
length while a cotton fiber is about 15 microns in
width and about 25 mm long.
WO 91/16464 PCT/US91/02593
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Example 2
Agglomeration of Clay With BAC
In the manufacturing of clay animal litter,
calcined clay ore is ground into particles of a
suitable average size. The particles.should be
sufficiently small as to provide the surface area
needed for rapid absorption of liquids.
Additionally, the particles should not be so small
that they constitute an irritating dust.
Present clay grinding techniques are imprecise,
however, so a substantial amount of fine particles
(generally particles that pass through 250 mesh
screen) are almost always formed as an undesired
byproduct. In particular,' the degree of grinding
needed to obtain litter particles of sufficient
surface area also produces a significant fraction of
particles which are smaller than desirable. Before
a clay litter product is sold, the undersize
particles or "fines" are screened out and must be
disposed of in an environmentally acceptable manner.
Such clay fines can be agglomerated into
usefully-sized litter particles by combining the
fines with reticulated cellulose of the type
described in Example 1. Typically, the clay fines
will be mixed with an aqueous slurry of reticulated
cellulose, there being sufficient water to
facilitate mixing. Reticulated cellulose should be
allowed to retain sufficient water, at least 50 wt.
percent, so that it can be mixed directly with clay
fines in most instances. Make-up water can be added
as needed to form a blendable slurry. The
reticulated cellulose can comprise as little as 0.5
wt. percent of the.total solids in the slurry. The
mixing may be low shear (e. g. hand mixing) or high
shear to blend the mixture.
WO 9t/16464 PCT/US91/02593
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After mixing, water is removed from the slurry.
Preferably, water is first removed with a screw
press or other mechanical dewatering apparatus.
Drying then can be completed in an oven at elevated
temperature.
After drying, the agglomerated product is
ground in a mechanical mill and thereafter screened
to separate any residual fines. The separated fines
can be recycled to the slurry-forming stage of the
agglomeration process.
Calcined clay dust was obtained from Edward
Lowe Industries, Inc. of Maricopa, California. The
dust, which is a waste product of animal litter
manufacturing, was combined with aqueous reticulated
cellulose. The combined materials were mixed for 5
minutes, and the resulting mixture filtered through
sharkskin filter paper to remove a portion of the
water, if necessary. The remaining solid material
was removed from the filter, pressed at 3000 psi
between blotter boards to further dewater the
sample, and oven dried for 12 hours at 105oC until
substantially dry. The dried material was broken up
in a Wiley mill fitted with a 6 mm screen to provide
particles of a size suitable for use as litter
material.
As shown in Table I, the use of reticulated
cellulose increased the size of particles through
agglomeration.
WO 91/16464 PCT/US91/02593
Table I
Cla~r Treatment and Resultincr Properties
Reticulated
Cellulose Water ~ Fraction
Run >250 Hardness
(dry hem
wt.
(g/g
Blending
No. percent)1 Clay) Method (percent)(lbf) '
1 -0- -0- None 32.4 0~
2 -0- 17.6 Hand mix2 55.3 8.6
3 -0- 10.0 Waring3 59.4 8.0
4 0.1 0.66 Hand mix 55.1 PID6
5 0.1 1.3 blaring 54.1 ND
6 0.5 0.73 Hand mix 57.3 ND
7 0.5 6.0 blaring 68.1 ND
8 0.5 4.9 Low4 58.0 ND
9 1.0 0.82 Hand mix 61.1 8.9
10 1.2 2,7 blaring 73.3 9.2
11 5.0 0.89 Hand mix 66.6 ND
12 5.0 10.0 blaring 73.2 9.6
13 Low 74.3 ND
5.0 10.5
14 _ 79.6 ND
5.6 11.8 blaring
15 10.0 1.9 Hand mix 75.8 Deformed
16 10.5 18.7 blaring 83.5 9.6
T7 15.0 17.7 Hand mix 82.2 Deformed
18 15.0 28.1 blaring 82.4 9.4
19 15.0 35.1 Low 82.8 ND
1 Dry weight percent based the amount
on ratio to of clay.
3 Stirred with spatula for
5 minutes.
Medium speed on 3-speed blaring
blender.
4 Propeller mixer.
5 Tablet could not be formed.
6 ND - Not Determined.
Uncomminuted particles of ay had ardness,
cl a h
as measured by a tablet hardnesstester izer
(Pf
Tablet nc. - ical
Hardness Chem
Tester,
Pfizer,
I
Division, Machines,Inc.,
manufactured
by
Testing
Amityville s force).As shown
NY)
of
10.6
lbf
(pound
in Run 1, clay fines alone werencapablef forming
i o
tablets. of up 9.6 lbf
In to
contrast,
hardnesses
were llulose s used as
achieved wa
when
reticulated
ce
an agglomerate of the slay fines.But, seen in
as
Run particles
3,
the
hardness
achieved
for
agglomerated less with the
with than
water
alone
was
use
of
reticulated
cellulose.
WO 91!16464 PCT/US91/02593
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200701
Hardness of the agglomerated product was
greatest when using a Waning blender to blend an
aqueous mixture of clay and reticulated cellulose.
The hardness measure indicates that particles
agglomerated with reticulated cellulose had
comparable integrity as uncomminuted particles of
clay.
Table I also shows that, for a given method of
mixing, the proportion of dust-sized particles was
decreased when as little as 0.5 wt. percent of
reticulated cellulose was added. At 15.0 wt.
percent reticulated cellulose, similar particle
distributions were achieved regardless of the mixing
method used. But, at lower reticulated cellulose
- 15 levels, more of the desired large sized particles
were obtained when a Waning blender was used. The
improvement in particle size distribution can also
be seen in Figure 1. This figure illustrates that
when clay particles are agglomerated with
reticulated cellulose, there are far fewer
undersized particles than in batches of untreated
clay particles or those treated with water alone.
Example 3
~'omparat~ve Aq"alomeration of Clav
The effectiveness of unbleached kraft pulp and
BAC were compared in agglomerating calcined clay
fines. Wood pulp and BAC were tested under
substantially parallel conditions at a level of 15%.
Additionally, a control sample was prepared without
using an agglomerating agent.
For the Kraft pulp sample, 24.31 gm (5.25 gm.
dry wt.) unbleached kraft pulp was slurried into 500
gm water and stirred for 20 minutes to disperse the
~ pulp. Calcined clay dust having a size distribution
similar to that shown in Fig. 1 was obtained from
WO 91/16464 PCT/US91/02593
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_16_
Edward Lowe Industries of Maricopa, California, and
29.75 gm calcined clay dust was added to the wood
pulp slurry and mixed. The blend was then filtered
using Buchner funnel. The filter cake was placed
between blotter paper and further dewatered using a
hand platen press. The pressed filter cake was over
dried at 120° for 4 hours or air dried. The dried
filter cake was ground with a Wiley mill equipped
with a 6mm screen. The size distribution of the
particulates was measured on standard Tyler screens
and is shown below in Table II.
The BAC sample was similarly prepared and ,
tested. Reticulated bacterial cellulose prepared
substantially as described in Example 1 was added in
an amount of 91.3 gm (5.25 gm dry wt.) to 1.1 kg
water having 29.75 gm calcined clay dust mixed
therein, and the blend was stirred for 15 minutes.
Filtration, dewatering, drying, grinding and sizing
were performed as described above for the wood pulp
sample.
A control was provided by mixing 29.75 gm.
calcined clay dust in 500 ml of water and filtering
with a Buchner funnel. The filter cake was air
dried and ground as described above. The size
distribution of particles was measured using
standard Tyler screens.
Table II
Size Distribution of Aaalomerates
Screen Size Particle Size Distribution (%)
j~m1 15% BAC 15% Wood Puln Clay Only
>500 62.8 35.0 6.7
250 13.5 17.9 25.7
150 9.2 15.9 23.2
106 3.5 9.0 17.8
75 4.2 10.8 17.7
3.5 8.4 8.0
<45 . 3.5 3.1 0.9
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The results shown in Table 3 demonstrate that
agglomeration of clay fines using 15% BAC results in
a significant increase in the number of large
particles (>500 Vim) compared to agglomeration using
wood pulp. Moreover, although there is some
indication that the distribution of fines treated
with wood pulp shifted to a larger particle size,
qualitative observations indicated that.the majority
of the pulp/clay material that did not pass through
the 500 ~.m screen was not "particulate." The wood
pulp and clay material formed fluffy, fibrous
aggregations of wood pulp fibers dusted with fines.
The wood pulp and clay fines were not. well
integrated clay/pulp particulates. Qualitative
observations therefore confirmed that wood pulp is
not effective to agglomerate clay fines into
particles that have structural or'physical
integrity. In contrast, BAC effectively agglomer-
ated,clay fines into particulates having a
satisfactory particle size (>500 ~,m) and a high
degree of structural integrity.
Example 4
Aaalomeration of Flvash
This example demonstrates the ability of BAC to
agglomerate flyash material into a form that can be
easily handled. Flyash is a combustion by-product
from burning wood debris (source - Weyerhaeuser's
Klamath Falls, Oregon facility). The flyash was
mixed with 1, 5; 10% BAC on a dry basis based on
flyash dry weight. In addition to the water
contained in the BAC, an additional amount of water
was added equal to twice the flyash weight. The BAC
in original form was from 0.5 to 2.0% solids. The
material was mixed either with a blaring blender far
5 minutes or with hand mixing until thoroughly
WO 91/16464 PGT/US91/02593
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mixed. The resultant material was dewatered by
filtering under low vacuum, and the cake dried for
12-18 hours at 105°C. A control. sample of flyash
was treated in a similar fashion with water only.
5. The dried cake was ground in a Wiley mill using
a 4 mm screen. The samples were sized using
standard testing sieves from 10 to 120 screen mesh. ,
The results, shown in Figure 2, indicate a greater
number of larger sized particles in the BAC
containing samples. The untreated flyash did not
contain any appreciable amount of particles greater
than 100 mesh.
Example 5
Comparative Agglomeration of Flyash
The effectiveness of unbleached kraft pulp and
BAC were compared in agglomerating fly ash. Fly ash
was obtained from Weyerhaeuser's Klamath Falls,
Oregon facility, as described in Example 4. For the
wood pulp sample, unbleached kraft pulp was refined
in a Valley Beater until the Canadian Standard
Freeness was 132. Samples were prepared by
slurrying 1 and 10 grams dry weight pulp or BAC with
sufficient fly ash to achieve a total dry solids
weight of 100 grams (1% and 10% pulp and 10% BAC) in
40O grams water. A control sample was also prepared
by blending 100 gm fly ash in water. The slurry was
mixed for five minutes in a blender, and filtered
through shark skin paper in a Buchner funnel. The
filter cake Was oven dried at 105°C for 12 hours.
The dried filter cake was ground with a Wiley mill
equipped with a 4 mm screen. The size distribution
was determined using standard Tyler screens.
The results of this experiment demonstrate an
apparent shift to larger particle sizes for fly ash
agglomerated with both wood pulp and BAC. Visual
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inspection of the agglomerated material, however,
revealed that the fly ash agglomerated with wood
pulp was in the form of fluffy, fibrous material
resembling small cotton balls: The fly ash was
dispersed throughout the fibrous pulp, but
particulates having structural and physical
integrity were not formed. In contrast,
agglomeration of fly ash using BAC resulted in the
formation of hard particles throughout the size
distribution range.
Example 6
P~y,_alomeration of Carbon Black
This example demonstrates the use of BAC to
agglomerate carbon black (Monarch 1400, Cabot
Corporation) into a form that can be more easily
handled. The agglomeration of carbon black with BAC
eliminates the handling problem of airborne carbon
black~dust when mixing the carbon black with other
materials.
Twenty (20) grams of carbon black were mixed
with BAC in 200 to 4'00 mL of water containing 1 mL
surfactant (Tetronic 304, BASF Corporation) at 1, 5
and 10% BAC based on carbon black weight. The
original BAC was from 0.5 to 4.0% solids. The
. carbon/BAC material was mixed with a paddle stirrer
for 5 minutes. The resultant material was dewatered
by filtering under low vacuum, and the cake dried
for 18-24 hours at 105°C. A control sample of
carbon black was treated in a similar fashion with
. water only.
The dried cake was ground in a Wiley mill using
a 6 mm screen. The samples were sized using
standard testing sieves from 6 to 325 screen mesh.
The results are shown in Figure 3, and in the
following Table III. They indicate that the
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PCT/US91/02593
it
rb
major
y of the ca
on black with BAC has been bound
into considerably larger particles than samples
without BAC, with very little material left at the
original particle size of -100' mesh.
Table III
Particle Size Distribution - Carbon Black
Size 10% BAC 5% BAC 1% BAC Control
6 0.1 0.1 0.0 0.0
10 8.8 7.2 2.8 0.0
18 41.0 35.3 12.1 0.0
35 31.0 29.3 25.3 0.0
50 8.1 9.6 20.7 0.0
70 3.9 4.6 19.1 0.0
100 2.6 3.6 8.1 0.0
I20 2.6 5.3 6.1 87.4
200 1.5 3.9 4.1 8.3
325 0.4 1.0 1.3 3.8
<325 0.6 0.1 0.4 0.5
1 Percent particle size at respective BAC
concentrations and control.
Example 7
Use of Dried BAC to Bind Clay Fines
One of the conditions of using BAC in most
cases, as an agglomeration agent, is that the BAC
must be used in a wet form. This can present
problems in some processes because of the need to
have a dry agglomerating material in the initial
mixing step. In this example, BAC was dried before
use as a binder. BAC was dried by two different
methods. In the first, wet BAC was slurried with
carboxymethyl cellulose (CMC) from Hercules, grade
CMC 7L in the ratio of 80% BAC, 20% CMC. The second
method involved slurrying BAC with sucrose in a 1 to
1 ratio. In both, processes the materials were dried
as a sheet at 85C for 18 to 24 hours. The
resultant dried sheet was then ground using a Wiley
mill with a 0.5 mm screen.
WO 91/16464 PCT/US91/02593
In the agglomeration process, the dried
was mixed with clay fines from Maricopa, California,
using a Hobart mixer and a wire whip spindle to
yield a composite containing 3'% BAC. In a blaring
blender, 25 g of the composite were mixed with 400
mL water at a high setting for 2 minutes. This was
filtered to remove excess water, pressed into a cake
and dried in an oven for 12 hrs at 105oC. The dried
material was.ground in a Wiley mill using a 6 mm
screen, and the particle size distribution
determined using standard testing sieves of 6 to
325 screen mesh. The results are shown in Figure 4.
The control material was made using undried SAC. As
can be seen, the dried BAC produced about the same
degree of agglomeration as the undried BAC.
Example 8
Liauid Absorbency
It has been found that particles of a variety
of sizes can be treated with reticulated cellulose
to increase liquid absorbency. This applies not
only to fine particles which are agglomerated with
reticulated cellulose, but also to larger,
nonagglomerated particles. Particles agglomerated
or treated with BAC exhibit exceptionally good
absorbency properties for non-aqueous liquids.
Figure 5 illustrates that substantial increases
in absorbency can be achieved if sufficient
reticulated cellulose is used to treat clay
particles. This is significant since clay animal
Titter must have a liquid absorption capacity for
its intended function and is frequently used in the
clean up of automotive oil spills and other fluid
spills. .
The data for Figure 5 was obtained from two
clay/reticulated cellulose mixtures. One contained
WO 9t/16464 PCT/US91/02593
,
,
-22-
l0 wt. percent reticulated cellulose, the other 20%.
The clay (15o g oven dry basis), calcined clay from
Edward Lowe Industries, Inc. of Paris, Tennessee,
was slurried with reticulatedvcellulose (15 g or
30 g oven dry basis) in two liters of water. A
third sample, used as a control, was prepared. by
slurrying only clay, i.e., no reticulated cellulose
was added.
Each slurry was mixed for 1.5 hours and
filtered. The filter cakes were dried at 105C
overnight and then broken into small pieces. These
three samples and a fourth sample of the clay (used
as received) were conditioned at 50% relative
humidity for 5-8 days. After conditioning, each
X15 sample was screened with a 10 mesh screen. The
material which did not pass through the screen was
reduced in a Wiley mill fitted with a 6 mm screen.
The fractions were recombined for the absorbency
tests.
The absorbency tests were conducted with 15 g
samples suspended in screen baskets (60 mesh sides,
200 mesh bottoms). Tests with each of four fluids
were conducted: kerosene, corn oil, diesel fuel, and
ethyl acetate. The samples were immersed in the
fluid for ten minutes, removed and allowed to drain,
and then weighed. Drainage time for the kerosene,
corn oil,'and diesel fuel was ten minutes and two
minutes for the ethyl acetate. The calculation of
absorption was based on conditioned weight of the
sample..
Results of the tests are listed in Table IV.
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Table IV
Reticulated Cellulose Function As Absorbent
Clay/
Reticulated
Clay Cellulose Clay
(as is) f90 10) j80 20) Lslurried)
Solids Content
(wt. percent) --- 97.7 97.3 97.8
Absorption
(wt. percent,
as is)
Diesel Fuel 73.0 111.1 114.3 62.9
Corn Oil 64.8 131.7 122.0 70.9
Ethyl Acetate 81.7 106.4 119.5 58.6
Kerosene 65.0 108.6 98.9 58.8
Table IV shows that substantial increases in
non-aqueous liquid absorbency are achieved when
particles of a solid material are treated with
reticulated cellulose.
Example 9
Bindina of Aluminum Oxide Bv BAC
This example demonstrates the use of BAC as a
green strength binder for ceramic materials. A test
ceramic material was made by making a slurry of 50%
alumina (Alcoa A16 SG), 50% distilled water, and
1.5% Darvan C (as dispersant based on alumina).
This alumina slurry was stirred for one hour. For
the control samples, a 40% solution of Carbowax 20M,
as a binder, was added in sufficient quantity to the
alumina slurry to yield 4% binder based on the
alumina content. For the BAC containing samples,
sufficient BAC at 12% solids was added to the
alumina slurry to yield binder levels of 0.5, 1.0,
2.0 arid 4.0% based on the alumina content. All
samples were air-dried for 24 hours at room
temperature. The dried materials were ground with a
mortar and pestle, and then screened through a
WO 91 / 16464 PGTI US91 /02593
f
48 mesh sieve. Test slugs. on each sample were made
2 0 8 0'~ 01 ~ -24-
by pressing the powder in a die at 10,000 psi to
give a disc that was 0.3 inches thick and an area of
one square inch.
The samples were tested for strength by loading
the discs biaxially in an Instron Universal Tester
for diametral compression testing. The loading rate
was 0.5 inch/min. The modulus of rupture (MOR) was
calculated by the formula:
2P
MOR = ~Dt
Where, P = breaking load (pounds)
D = sample diameter (inches)
t = sample thickness (inches)
The results shown in the following Table V
indicate a comparable strength at 0.5 to 1.0% BAC to
the 4.0% Carbowax. Furthermore, higher levels of
BAC yielded even greater green strength.
Table V
ceramic Disc Diametral Compression Test
Breaking Load Modulus of Rupture
Binder llbs) (usi)
4% Carbowax
(Control)
17.3 31.5
0.5% BAC 17.0 28.6
1.0% BAC 21.0 34.9
2.0% BAC 28.2 46.4
4.0% BAC 41.7 66.6
Having illustrated and described preferred
embodiments of our invention, it should be apparent
' to those skilled in the art that the invention
permits modification in arrangement and detail. We
claim as our invention all such modifications as
come within the true spirit and scope of the
following claims.
