Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02607676 2007-10-25
DRY BED AGGLOMERATION PROCESS AND
PRODUCT FORMED THEREBY
BY INVENTOR: DElvlvis JENKiNs
CROSS REFERENCE To RELATED APPLICATIONS
[0001 ] This application is a continuation-in-part of Application No.
10/618,401; filed
July 11, 2003, which is hereby incorporated by reference in its entirety. This
application claims the benefit of US Provisional Application No. 60/863,910,
filed
November 1, 2006, which is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and systems for forming
agglomerated
particles, and more particularly, this invention relates to a methods and
systems for
forming agglomerated particles on a dry bed.
BACKGROUND OF THE INVENTION
[0003] Clay has long been used as a liquid absorbent, and has found particular
usefulness as an animal litter.
[0004] Because of the growing number of domestic animals used as house pets,
there
is a need for litters so that animals may micturate, void or otherwise
eliminate liquid
or solid waste indoors in a controlled location. Many cat litters use clay as
an
absorbent. Typically, the clay is mined, dried, and crushed to the desired
particle size.
[0005] Some clay litters have the ability to clump upon wetting. For example,
sodium bentonite is a water-swellable clay which, upon contact with moist
animal
waste, is able to agglomerate with other moistened sodium bentonite clay
par~ticles.
The moist animal waste is contained by the agglomeration of the moist clay
particles
into an isolatable clump, which can be removed from the container (e.g.,
litterbox)
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CA 02607676 2007-10-25
housing the litter. However, the clump strength of clay litters described
above is
typically not strong enough to hold the clump shape upon scooping, and
inevitably,
pieces of the litter break off of the clump and remain in the litter box,
allowing waste
therein to form malodors. The breakage problem is compounded when the size of
the
clump is large.
[0006] Further, raw clay typically has a high clump aspect ratio when urinated
in.
The result is that the wetted portion of clay will often extend to the
container
containing it and stick to the side or bottom of the container. This in turn
often results
in wetted litter remaining in the container after removal of the clump. The
wetted
litter that remains is often a source of strong malodors, and is also often
difficult to
remove from the container once dried. High clump aspect ratios also require
removal
of large quantities of soiled litter from the container.
[0007] Another problem inherent in typical litters is the inability to
effectively control
malodors. Clay has very poor odor-controlling qualities, and inevitably waste
build-
up leads to severe malodor production. One attempted solution to the malodor
problem has been the introduction of granular activated carbon (GAC) into the
litter.
However, the GAC is usually dry blended with the litter, making the litter
undesirably
dusty. Also, the GAC concentration must typically be 1% by weight or higher to
be
effective. Activated carbon is very expensive, and the need for such high
concentrations greatly increases production costs. Further, because the clay
and GAC
particles are merely mixed, the litter will have GAC concentrated in some
areas, and
particles with no GAC in other areas.
[0008] The human objection to odor is not the only reason that it is desirable
to
reduce odors. Studies have shown that cats are territorial animals and will
often
"mark" litter that has little or no smell with their personal odor, such as by
urinating.
When cats return to the litterbox and don't sense their. odor, they will try
to mark their
territory again. The net effect is that cats will return to use a litter box
more often if
the odor of their markings are reduced. Thus, a litter that is effective at
eliminating or
hiding a cat's personal odor can encourage the animal to use a litter box
rather than
depositing waste outside the box.
[0009] What is needed is an absorbent article of manufacture that is suitable
for use
as a cat litter/liquid absorbent with at least one of the following
properties: better
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CA 02607676 2007-10-25
clumping characteristics, e.g., aspect ratio and/or clump strength, than
absorbent
materials heretofore known; improved odor-controlling properties, and that
maintains
such properties for longer periods of time and/or requiring much lower
concentrations
of odor controlling actives; a lower bulk density while maintaining a high
absorbency
rate comparable to or exceeding heretofore known materials; and which
encourages
animals to micturate and void on the absorbent material.
[0010] What is also needed are ways to form these and other types of
particles.
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CA 02607676 2007-10-25
SUMMARY OF THE INVENTION
[0011 ] A method for creating a particle from a powder according to one
embodiment
includes applying a droplet of a liquid to a bed of powder, wherein a particle
is
formed at about a point of contact of the droplet with the bed.
[0012] A size of the particle may be determined primarily by a volume of
liquid in the
droplet fomiing the particle.
[0013] The liquid may include water, a binding agent, etc.
[0014] The powder may include a liquid-activated binding agent, a liquid-
activated
gas forming agent, etc.
[0015] In one embodiment, at least one processing condition is selected for
creating a
generally spherical particle, the processing condition being selected from a
group
consisting of a droplet size, a force in which the droplet hits the bed, a
density of the
bed, a thickness of the bed, absorptive properties of the powder, and
hydrophilicity or
hydrophobicity of the powder.
[0016] In another embodiment, at least one processing condition is selected
for
creating a generally bagel-shaped particle, the processing condition being
selected
from a group consisting of a droplet size, a force in which the droplet hits
the bed, a
density of the bed, a thickness of the bed, absorptive properties of the
powder, and
hydrophilicity or hydrophobicity of the powder.
[0017] In a further embodiment, at least one processing condition is selected
for
creating a generally cupped particle, the processing condition being selected
from a
group consisting of a droplet size, a force in which the droplet hits the bed,
a density
of the bed, a thickness of the bed, absorptive properties of the powder, and
hydrophilicity or hydrophobicity of the powder.
[0018] In a yet further embodiment, at least one processing condition is
selected for
creating a hollow particle, the processing condition being selected from a
group
consisting of a droplet size, a force in which the droplet hits the bed, a
density of the
bed, a thickness of the bed, absorptive properties of the powder, and
hydrophilicity or
hydrophobicity of the powder.
[0019] Powder may be applied to the formed particle. The particle may be
rolled.
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[0020] The process may also include removing the particle from the bed and
drying
the particle.
[0021 ] The powder may have a multitude of compositions. One illustrative
powder
comprises a mineral and a performance-enhancing active selected from a group
consisting of an antimicrobial, an odor reducing material, a binder, a
fragrance, a
health indicating material, a color altering agent, a dust reducing agent, a
nonstick
release agent, a superabsorbent material, cyclodextrin, zeolite, activated
carbon, a pH
altering agent, a salt forming material, a ricinoleate, silica gel,
crystalline silica,
activated alumina, a clump enhancing agent, and mixtures thereof.
[0022] A method for creating multiple particles from a powder according to one
embodiment includes applying a first series of droplets of a liquid to a bed
of powder
for forming a particle, and applying a second series of droplets of a liquid
to the bed
of powder for forming a particle, where the second series of droplets have a
different
composition than the first series of droplets.
[0023] The first and second series of droplets may be applied to the bed of
powder
concurrently, consecutively, etc.
[0024] A method for creating an absorbent particle suitable for use as an
animal litter
according to yet another embodiment includes dropping a droplet of a liquid
onto a
bed of powder for forming a particle, the liquid comprising water, the powder
comprising a liquid-absorbing material selected from a group consisting of: a
mineral
(e.g., sodium bentonite clay), fly ash, absorbing pelletized material,
perlite, silica,
organic materials, and mixtures thereof. Again, the powder may include a
performance-enhancing active.
[0025] A composite particle according to one embodiment includes a liquid-
absorbing material selected from a group consisting of: a mineral, fly ash,
absorbing
pelletized material, perlite, silica, organic materials, and mixtures thereof;
and a
liquid-induced binding agent substantially homogeneously dispersed in the
particle.
[0026] The particle may be generally spherical, cupped, generally bagel
shaped,
hollow, etc. Again, the particle may include a performance-enhancing active
[0027] A composite particle according to yet another embodiment includes a
liquid-
absorbing material selected from a group consisting of: a mineral, fly ash,
absorbing
pelletized material, perlite, silica, organic materials, and mixtures thereof;
and a
CA 02607676 2007-10-25
byproduct of a liquid-induced gas forming agent substantially homogeneously
dispersed in the particle.
[0028] The particle may be generally spherical, cupped, generally bagel
shaped,
hollow, etc. Again, the particle may include a performance-enhancing active
[0029] A composite particle suitable for use as an animal litter according to
an
embodiment includes a liquid-absorbing material selected from a group
consisting of:
a mineral, fly ash, absorbing pelletized material, perlite, silica, organic
materials, and
mixtures thereof; where the particle has at least one of the following
properties:
hollow, cupped, and generally bagel shaped.
[0030] A composite particle in yet another embodiment includes a material
formed in
a shape substantially defined by a droplet of liquid.
[0031 ] Other aspects and advantages of the present invention will become
apparent
from the following detailed description, which, when taken in conjunction with
the
drawings, illustrate by way of example the principles of the invention.
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CA 02607676 2007-10-25
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] For a fuller understanding of the nature and advantages of the present
invention,
as well as the preferred mode of use, reference should be made to the
following detailed
description read in conjunction with the accompanying drawings.
[0033] Fig. 1 illustrates several configurations of absorbent composite
particles
according to various embodiments of the present invention.
[0034] Fig. 2A is a plot of bulk density reduction vs. fiber content in an
absorbent
particle.
[0035] Fig. 2B is a photograph of composite particles containing sodium
bentonite
and 15% paper fluff fibers
[0036] Fig. 3A is a cross sectional view of a hollow SAP particle.
[0037] Fig. 3B is a cross sectional view of an SAP-containing particle with a
permeable skin surrounding an SAP core.
[0038] Fig. 3C is a cross sectional view of an SAP-containing particle with a
fast
absorbing layer surrounding an SAP core.
[0039] Fig. 3D is a cross sectional view of an absorbent particle according to
one
embodiment.
[0040] Figs. 3E-H illustrate the progression of the formation of pores in a
structure of
absorbent material, structure directing agent and solvent.
[0041] Fig. 4A is a process diagram illustrating a pan agglomeration process
according to a preferred embodiment.
[0042] Fig. 4B depicts the structure of an illustrative agglomerated composite
particle
formed by the process of Fig. 2.
[0043] Fig. 4C is a process diagram illustrating another exemplary pan
agglomeration
process with a recycle subsystem.
[0044] Fig. 5 is a process diagram illustrating an exemplary pin mixer process
for
forming composite absorbent particles.
[0045] Fig. 6 is a process diagram illustrating an exemplary mix muller
process for
forming composite absorbent particles.
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CA 02607676 2007-10-25
[0046] Fig. 7 is a process diagram illustrating recovery of raw material from
a first
process and use thereof in a second process.
[0047] Fig. 8 is a flow diagram depicting a general method for dry bed
agglomeration
according to one embodiment of the present invention.
[0048] Fig. 9 is a process diagram of an illustrative system for creating
composite
particles by dry bed agglomeration.
[0049] Fig. 10 illustrates perspective views of several potential shapes for
absorbent
particles.
[0050] Fig. 11 is a process diagram illustrating a method of using absorbent
particles.
[0051] Fig. 12 is a process diagram illustrating a method for orienting
particles.
[0052] Fig. 13 depicts the clumping action of composite absorbent particles
according
to a preferred embodiment.
[0053] Fig. 14 depicts disintegration of a composite absorbent particle
according to a
preferred embodiment.
[0054] Fig. 15 is a graph depicting malodor ratings.
[0055] Fig. 16 is an interval plot of mass transferred (g) to the dropped
filter paper vs.
sample (surface stickiness) for experimental results.
[0056] Fig. 17 is an interval plot of clump mass (g) vs. sample for
experimental
results.
[0057] Fig. 18 is an interval plot of clump depth (cm) vs. sample for
experimental
results.
[0058] Fig. 19 is an interval plot of liquid absorption (g/g) vs. sample for
experimental results.
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CA 02607676 2007-10-25
BEST MODES FOR CARRYING OUT THE INVENTION
[0059] The following description includes the best embodiments presently
contemplated for carrying out the present invention. This description is made
for the
purpose of illustrating the general principles of the present invention and is
not meant
to limit the inventive concepts claimed herein.
[0060] The present invention relates generally to composite absorbent
particles with
improved physical and chemical properties comprising an absorbent material and
optional performance-enhancing actives. By using various processes described
herein, such particles can be "engineered" to preferentially exhibit specific
characteristics including but not limited to improved odor control, lower
density,
easier scooping, better particle/active consistency, higher clump strength,
etc. One of
the many benefits of this technology is that the performance-enhancing actives
may
be positioned to optimally react with target molecules such as but not limited
to odor
causing volatile substances, resulting in surprising odor control with very
low levels
of active ingredient.
[0061 ] A preferred use for the absorbent particles is as a cat litter, and
therefore much
of the discussion herein will refer to cat litter applications. However, it
should be
kept in mind that the absorbent particles have a multitude of applications,
such as air
and water filtration, fertilizer, waste remediation, etc., and should not be
limited to the
context of a cat litter.
[0062] One preferred method of forming the absorbent particles is by
agglomerating
granules of an absorbent material in a pan agglomerator. A preferred pan
agglomeration process is set forth in more detail below, but is described
generally
here to aid the reader. Generally, the granules of absorbent material are
added to an
angled, rotating pan. A fluid or binder is added to the granules in the pan to
cause
binding of the granules. As the pan rotates, the granules combine or
agglomerate to
form particles. Depending on pan angle and pan speed among other factors, the
particles tumble out of the agglomerator when they reach a certain size. The
particles
are then dried and collected.
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[0063] One or more performance-enhancing actives are preferably added to the
particles in an amount effective to perform the desired functionality or
provide the
desired benefit. For example, these actives can be added during the
agglomeration
process so that the actives are incorporated into the particle itself, or can
be added
during a later processing step.
[0064] Fig. 1 shows several embodiments of the absorbent particles of the
present
invention. These particles have actives incorporated:
1. In a layer on the surface of a particle (102)
2. Evenly (homogeneously) throughout a composite litter particle (104)
3. In a concentric layer(s) throughout the particle and/or around a core
(106)
4. In pockets or pores in and/or around a particle (108)
5. In a particle with single or multiple cores (110)
6. Utilizing non-absorbent cores (112)
7. No actives (114)
8. No actives, but with single or multiple cores (116)
9. In any combination of the above
[0065] As previously recited hereinabove, other particle-forming processes may
be
used to form the inventive particles of the present invention. For example,
without
limitation, extrusion and fluid bed processes appear appropriate. Extrusion
process
typically involves introducing a solid and a liquid to fonn a paste or doughy
mass,
then forcing through a die plate or other sizing means. Because the forcing of
a mass
through a die can adiabatically produce heat, a cooling jacket or other means
of
temperature regulation may be necessary. The chemical engineering literature
has
many examples of extrusion techniques, equipment and materials, such as
"Outline of
Particle Technology," pp. 1-6 (1999), "Know-How in Extrusion of Plastics
(Clays) or
NonPlastics (Ceramic Oxides) Raw Materials, pp. 1-2, "Putting Crossflow
Filtration
to the Test," Chemical En 'n~ eerin~, pp. 1-5 (2002), and Brodbeck et al.,
U.S. Patent
5,269,962, especially col. 18, lines 30-61 thereof, all of which is
incorporated herein
by reference thereto. Fluid bed process is depicted in Coyne et al., U.S.
Patent
5,093,021, especially col. 8, line 65 to col. 9, line 40, incorporated herein
by
reference.
CA 02607676 2007-10-25
Materials
[0066] Many liquid-absorbing materials may be used without departing from the
spirit and scope of the present invention. Illustrative absorbent materials
include but
are not limited to minerals, fly ash, absorbing pelletized materials, perlite,
silicas,
other absorbent materials and mixtures thereof. Preferred minerals include:
bentonites, zeolites, fullers earth, attapulgite, montmorillonite diatomaceous
earth,
opaline silica, crystalline silica, silica gel, alumina, Georgia White clay,
sepiolite,
calcite, dolomite, slate, pumice, tobermite, marls, attapulgite, kaolinite,
halloysite,
smectite, vermiculite, hectorite, Fuller's earth, fossilized plant materials,
expanded
perlites, gypsum and other similar minerals and mixtures thereof. One
preferred
absorbent material is sodium bentonite having a mean particle diameter of
about 5000
microns or less, preferably about 3000 microns or less, and ideally in the
range of
about 25 to about 150 microns.
[0067] Because minerals, and particularly clay, are heavy, it may be desirable
to
reduce the weight of the composite absorbent particles to reduce shipping
costs,
reduce the amount of material needed to need to fill the same relative volume
of the
litter box, and to make the material easier for customers to carry. To lower
the weight
of each particle, a lightweight core material, or "core," may be incorporated
into each
particle. The core can be positioned towards the center of the particle with a
layer or
layers of absorbent and/or active surrounding the core in the form of a shell.
This
configuration increases the active concentration towards the outside of the
particles,
making the active more effective. The shell can be of any desirable thickness.
In one
embodiment with a thin shell, the shell has an average thickness of less than
about %2
that of the average diameter of the particle, and preferably the shell has an
average
thickness of not less than about 1/16 that of the average diameter of the
particle.
More preferably, the shell has an average thickness of between about 7/16 and
1/8
that of the average diameter of the particle, even more preferably less than
about 1/2
that of the average diameter of the particle, and ideally between about 3/8
and 1/8 that
of the average diameter of the particle. Note that these ranges are preferred
but not
limiting.
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[0068] According to another embodiment comprising a core and absorbent
material
surrounding the core in the form of a shell, an average thickness of the shell
is at least
about four times an average diameter of the core. In another embodiment, an
average
thickness of the shell is between about 1 and about 4 times an average
diameter of the
core. In yet another embodiment, an average thickness of the shell is less
than an
average diameter of the core. In a further embodiment, an average thickness of
the
shell is less than about one-half an average diameter of the core.
[0069] Other ranges can be used, but the thickness of the shell of absorbent
material/active surrounding a non-clumping core should be balanced to ensure
that
good clumping properties are maintained.
[0070] In another embodiment, the absorbent material "surrounds" a core (e.g.,
powder, granules, clumps, etc.) that is dispersed homogeneously throughout the
particle or in concentric layers. For example, a lightweight or heavyweight
core
material can be agglomerated homogeneously into the particle in the same way
as the
active. The core can be solid, hollow, absorbent, nonabsorbent, and
combinations of
these.
[0071] Exemplary lightweight core materials include but are not limited to
calcium
bentonite clay, Attapulgite clay, Perlite, Silica, non-absorbent silicious
materials,
sand, plant seeds, glass, polymeric materials, and mixtures thereof. A
preferred
material is a calcium bentonite-containing clay which can weigh about half as
much
as bentonite clay. Calcium bentonite clay is non-clumping so it doesn't stick
together
in the presence of water, but rather acts as a seed or core. Granules of
absorbent
material and active stick to these seed particles during the agglomeration
process,
forming a shell around the seed.
[0072] Using the above lightweight materials, a bulk density reduction of
>I0%,
>20%, preferably >30%, more preferably >40%, and ideally 2:50% can be achieved
relative to generally solid particles of the absorbent material (e.g., as
mined) and/or
particles without the core material(s). For example, in a particle in which
sodium
bentonite is the absorbent material, using about 50% of lightweight core of
calcium
bentonite clay results in about a 42% bulk density reduction.
[0073] Heavyweight cores may be used when it is desirable to have heavier
particles.
Heavy particles may be useful, for example, when the particles are used in an
outdoor
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CA 02607676 2007-10-25
application in which high winds could blow the particles away from the target
zone.
Heavier particles also produce an animal litter that is less likely to be
tracked out of a
litter box. Illustrative heavyweight core materials include but are not
limited to sand,
iron filings, etc.
[0074] Note that the bulk density of the particles can also be adjusted
(without use of
core material) by manipulating the agglomeration process to increase or
decrease pore
size, pore volume and surface area of the particle.
[0075] Note that active may be added to the core material if desired. Further,
the core
can be selected to make the litter flushable. One such core material is wood
pulp.
[0076] In some embodiments, the absorbent materials or composite particles
containing absorbent materials may be blended with litter filler materials or
other
additives suitable for use in animal litter. As used herein the term "litter
filler
materials" refers to materials that can be used as the absorbent material, but
are
generally ineffective at liquid absorption if used alone. Therefore these
materials are
generally used in combination with other absorbent materials to reduce the
cost of the
final litter product. Illustrative examples of filler materials include
limestone, sand,
calcite, dolomite, recycled waste materials, zeolites, and gypsum.
[0077] Illustrative materials for the performance-enhancing active(s) include
but are
not limited to antimicrobials, odor absorbers/inhibitors, binders, fragrances,
health
indicating materials, nonstick release agents, superabsorbent materials, and
mixtures
thereof. In some embodiments reinforcing fiber materials can be added.
Absorbent
fibers may be added to some embodiments. One great advantage of the particles
of the
present invention is that substantially every absorbent particle may contain
an active.
[0078] Preferred antimicrobial actives are boron containing compounds such as
borax
pentahydrate, borax decahydrate, boric acid, polyborate, tetraboric acid,
sodium
metaborate, anhydrous, boron components of polymers, and mixtures thereof.
[0079] One type of odor absorbing/inhibiting active inhibits the formation of
odors.
An illustrative material is a water soluble metal salt such as silver, copper,
zinc, iron,
and aluminum salts and mixtures thereof. Preferred metallic salts are zinc
chloride,
zinc gluconate, zinc lactate, zinc maleate, zinc salicylate, zinc sulfate,
zinc ricinoleate,
copper chloride, copper gluconate, and mixtures thereof. Other odor control
actives
include nanoparticles that may be composed of many different materials such as
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CA 02607676 2007-10-25
carbon, metals, metal halides.or oxides, or other materials. Additional types
of odor
absorbing/inhibiting actives include cyclodextrin, zeolites, silicas,
activated carbon
(also known as activated charcoal), acidic, salt-forming materials, and
mixtures
thereof. Activated alumina (A1203) has been found to provide odor control
comparable and even superior to other odor control additives such as activated
carbon, zeolites, and silica gel. Alumina is a white granular material, and is
properly
called aluminum oxide.
[0080] The preferred odor absorbing/inhibiting active is Powdered Activated
Carbon
(PAC), though Granular Activated Carbon (GAC) can also be used. PAC gives much
greater surface area than GAC (GAC is something larger than powder (e.g., > 80
mesh U.S. Standard Sieve (U.S.S.S.))), and thus has more sites with which to
trap
odor-causing materials and is therefore more effective. PAC has only rarely
been
used in absorbent particles, and particularly animal litter, as it tends to
segregate out
of the litter during shipping, thereby creating excessive dust (also known as
"sifting").
By agglomerating PAC into particles, the present invention overcomes the
problems
with carbon settling out during shipping. Generally, the preferred mean
particle
diameter of the carbon particles used is less than about 500 microns, but can
be larger.
The particle size can also be much smaller (less than 100 nanometers) as in
the case of
carbon nanoparticles. The preferred particle size of the PAC is about 150
microns
(-100 mesh U.S.S.S.) or less, and ideally in the range of about 25 to 150
microns,
with a mean diameter of about 50 microns (-325 mesh U.S.S.S.) or less.
[0081 ] An active may be added to reduce or even prevent sticking of the
litter to the
litter box. Useful anti-stick agents include, but are not limited to,
hydrophobic
materials such as activated carbon, carbon black, Teflon , hydrophobic
polymers and
co-polymers, for example poly(propylene oxide). Other nonstick additives may
include surfactants, polymers, polytetrafluoroethylene, starches, silicones,
Georgia
white clay, sand, limestone. Generally, any mineral material that does not
dissolve or
swell in the presence of water will act as an inert spacer between the sodium
bentonite
clay and the litter box, providing some reduction in sticking. The effect is
greater
when the spacer is a particle size that is finer than the clay.
[0082] How tightly swelled litter sticks to a litter box can be measured as a
function
of the force necessary to remove the 'clump'. One method of measuring this
force
14
CA 02607676 2007-10-25
uses 150cc of litter and 20 cc of pooled cat urine (from several cats so it is
not
specific) to form a clump on the bottom of a cat box. The urine causes the
litter to
clump, and in so doing, the swelled litter adheres to the litter box. The
relative amount
of force (in pounds) necessary to remove the adhered clump is measured using
an
Instron tensile tester and a modified scooper.
[0083] The data in the table below refer to the following formulas. Formula P
is
composed of composite particles of the present invention that contain 0.5% PAC
as an
anti-stick agent. Formula S is a commercially available granular clay litter
with no
added anti-stick agents.
[0084] The data in the table below show that a urine clump formed from the
formula
composed of composite particles containing 0.5% PAC as an anti-stick agent
requires
less force for removal from the bottom of a cat box than a urine clump formed
from a
commercially available granular clay litter containing no anti-stick agents.
Table 1
Lifter height Formula P - Removal Formula S - Removal
(Inches) Force in pounds Force in pounds
0.5 0.17 0.63
0.25 0.46 0.81
[0085] Generally, PAC is effective to reduce sticking when present in the
composite
particles in an amount of 0.1 % or more, preferably in the range of about 0.1
to about
1.0%, when compared to composite particles not having the PAC present.
[0086] The active may also include a binder such as water, lignin sulfonate
(solid),
polymeric binders, fibrillated Teflon (polytetrafluoroethylene or PTFE), and
combinations thereof. Useful organic polymerizable binders include, but are
not
limited to, carboxymethylcellulose (CMC) and its derivatives and its metal
salts, guar
gum cellulose, xanthan gum, starch, lignin, polyvinyl alcohol, polyacrylic
acid,
styrene butadiene resins (SBR), and polystyrene acrylic acid resins. Water
stable
particles can also be made with crosslinked polyester network, including but
not
limited to those resulting from the reactions of polyacrylic acid or citric
acid with
CA 02607676 2007-10-25
different polyols such as glycerin, polyvinyl alcohol, lignin, and
hydroxyethylcellulose.
[0087] Another active that can be added to the composite particles is a clump
enhancing agent that is activated by contact with a liquid to strengthen
clumps,
thereby assisting in the isolation and encapsulation of the offensive
material. Clump
enhancing agents are particularly useful when the composite particles are
formed of
materials that do not have strong inherent clumping capabilities, and where
other non-
clumping performance enhancing actives are formed on an outer surface of the
particles. Preferred clump enhancing agents include binders, gums, starches,
and
adhesive polymers.. The clump enhancing agent is preferably added to outer
surfaces
of the particles by spraying or by addition during the final stages of
agglomeration.
Clump enhancing agents can also be bulk-added to the composite particles.
[0088] Dedusting agents can also be added to the particles in order to reduce
the dust
level in the final product. All of the clump enhancing agents listed above are
effective
dedusting agents when applied to the outer surface of the composite absorbent
particles. Other dedusting agents include but are not limited to fibrillated
Teflon,
resins, water, and other liquid or liquefiable materials.
[0089] A color altering agent such as a dye, pigrnented polymer, metallic
paint,
bleach, lightener, etc. may be added to vary the color of absorbent particles,
such as to
darken or lighten the color of all or parts of the litter so it is more
appealing.
Preferably, the color altering agent comprises up to approximately 20% of the
absorbent composition, more preferably, 0.001 %- 5% of the composition. Even
more
preferably, the color altering agent comprises approximately 0.001 %- 0.1 % of
the
composition.
[0090] Preferred carriers for the color altering agent are zeolites, carbon,
charcoal,
etc. These substrates can be dyed, painted, coated with powdered colorant,
etc.
[0091 ] Activated alumina and activated carbon may include an embedded
coloring
agent that has been added during the fabrication of the activated alumina or
activated
carbon particles to form a colored speckle. The inventors have found that the
odor
absorbing properties of activated alumina and activated carbon are not
significantly
reduced due to the application of color altering agents thereto.
16
CA 02607676 2007-10-25
[0092) The color altering agent can be the absorbent material, e.g., a
bentonite clay,
particularly if the absorbent material contains some dust-sized particles. It
has been
observed that dust-sized particles actually coat the activated carbon therebyt
lightening the black color.
[0093] Additionally, activated alumina's natural white coloring makes it a
desirable
choice as a white, painted or dyed "speckle" in litters. In composite and
other
particles, the activated alumina can also be added in an amount sufficient to
lighten or
otherwise alter the overall color of the particle or the overall color of the
entire
composition.
[0094] Compositions may also contain colored speckles for visual appeal. Other
examples of speckle material are salt crystals or gypsum crystals.
[0095] Large particles of carbon, e.g., activated carbon or charcoal, can also
be used
as a dark speckle. Such particles are preferably within a particle diameter
size range
of about 0.01 to 10 times the mean diameter of the other particles in the
mixture.
[0096] Carbon-coated particles of absorbent material (particularly absorbent
materials
coated with PAC) can also be used as dark speckles. In this case, the particle
size of
the dark speckles would be virtually the same as uncoated particles of
absorbent
particles.
Reinforcing Fiber Materials
[0097) Reinforcing fiber material(s) (hereinafter "fiber(s)") may be added to
increase
clump strength and/or reduce the overall bulk density of the litter material.
Fibers are
any solid material having a mean cylindrical shape and a length to diameter
aspect
ratio greater than one that helps to maintain the structural integrity of
litter clumps
once formed. The fibers may range in particle size from about lnm to about
5mm.
The fibers are typically in the size range of about lnm to about 5mm prior to
agglomeration, but could be up to 6 inches depending on whether the process
used
first breaks down the material into a smaller size prior to forming composite
particles.
The fibers may comprise between 0.1 and 50% of the composite particle, but
typically
are present in an amount less than 20% (i.e., 19% or less).
[0098] Preferred fibers include any solid material that demonstrates a mean
cylindrical shape with a large length to diameter aspect ratio (e.g, 2 to 1 or
greater)
and the following two properties. First, a built tensile strength that is due
to
17
CA 02607676 2007-10-25
molecular orientation induced by the formation of the fiber whether natural or
synthetically produced. Second, a surface morphology that creates bonding
sites that
allow the fiber to reinforce the overall structure of the particle. The
bonding sites may
be created either by allowing association with other chemical elements and
structures
(e.g., hydrogen bonding as present in polyester) or by a physical interlocking
of
surface morphologies (e.g., puzzle pieces).
[0099] Fibers may be made of materials such as, but not limited to natural
materials,
e.g., wool, cotton, hemp, rayon, lyocell, paper, paper fluff, cellulose,
regenerated
cellulose, bird feathers, carbon, activated carbon, as well as synthetic
materials, e.g.,
polyester, nylon, plastics, polymers (including super absorbent polymers
(SAPs) and
copolymers). Combinations of these materials are also possible, as in the
multi-
component fibers discussed below. Illustrative reinforcing fibers include
paper fluff,
DuPont's Kevlar (poly-paraphenylene terephthalamide) yarn, PET (polyethylene
terephthalate), Tencel cellulose fiber, rayon, cotton, poultry feather parts,
cellulose,
and combinations thereof. Reclaim, i.e., a recycled mixture incorporating some
or all
of the synthetic materials listed above, could also be used.
[00100] In addition, fibers recovered as a byproduct or waste product from
another process can also be incorporated in the absorbent particles. For
example, the
fibrous waste from a paper or tissue manufacturing process can be used. The
size of
the fibers is not critical, and can range from small particles captured by a
dust
collection process to relatively larger particles.
[00101] Other performance-enhancing actives may be embedded within the
fibers or attached to the surface of the fibers to augment a specific consumer-
benefiting feature, such as odor control or enhanced absorptivity or both.
Cotton
fibers embedded with activated carbon could be combined with an absorbent clay
to
form composite particles suitable for use as an animal litter having increased
odor
control. Non-woven fibers charged with SAPs (e.g., BASF luquafleece IS) can be
combined with an absorbent clay to form composite particles having increased
absorptivity. The resulting litter compositions have the advantage of
controlling
odors and moisture as strong clumps are formed.
[00102] Benefits imparted by the fibers (either alone or in combination with
other performance-enhancing actives) may include without limitation, increased
18
CA 02607676 2007-10-25
structural integrity (e.g., less breakage and dust), increased clump strength,
increased
liquid absorption, abrasion resistance, animal attractant/repellant, visual
aesthetics,
tactile aesthetics, lower overall bulk weight, and increased odor control
(e.g.,
activated carbon fibers). Clump strength is a measure of the mechanisms that
aid in
the formation of agglomerates (moist litter particles that stick together) in
the litter
box. Crimped fibers (helical and saw-tooth) may provide higher clumping
strength or
reduced attrition in processing and handling.
[00103] Bicomponent and/or multi-component fibers may provide additional
benefits. For example, one component of the fiber may melt and act as an
adhesive
during the agglomeration drying process to further enhance the strength of the
composite particles, while the other component may retain its length/integrity
in order
to provide a reinforcing benefit and increase clump strength. When the fiber
is
subjected to the melt temp of the lower meting component, the lower melting
component acts as the adhesive, while the higher melting component retains the
shape
and a portion of the integrity of the fiber. Some examples include fibers made
of both
polyethylene and polyester, or polyethylene and polypropylene in a side by
side or a
sheath /core configuration.
[00104] Additional attributes may be present if the fibers are porous. Fiber
porosity could lead to a three-fold benefit: (1) light-weighting (i.e., a
decrease in the
bulk density of the litter composition), (2) increased odor and/or moisture
absorption
(i.e., within the pores due to an increase in surface area), and (3)
encapsulation/carrier
vehicle for performance-enhancing actives, such as odor absorbers, moisture
absorbers, antimicrobials, fragrances, clumping agents, etc. These benefits
combined
with the aforementioned additional clump strength and clump integrity are
unexpected. Generally lower density, higher porosity litter materials with
litter
additives work to decrease clump strength. This common drawback is overcome by
the composite particles disclosed herein.
[00105] When only 2% paper fluff fibers are added to a primarily sodium
bentonite composition via a pilot plant scale pin mixer equipped with a rotary
drier, a
13% reduction in bulk density is observed.
[00106] The clump aspect ratio, which is defined as Square root ((longest
clump length)2 + (shortest clump length) 2)/clump height may be affected by
the
19
CA 02607676 2007-10-25
addition of fibers to the composite particles. In general, it is desirable to
have a round
clump, which translates to an aspect ratio of about 0.5. Higher aspect ratios
are
indicative of less round, more "pancake-shaped" clumps, which may be
acceptable, if
other benefits are gained (e.g., an increase in liquid absorption or a
decrease in clumps
sticking to the box).
[00107] The fibers can range in particle size from about lnm to about 6 inches
(typically ranging between lnm and 5mm) and generally are present in 0.1-50%
by
weight of the composite particles. The size and shape of the fibers chosen may
aid in
controlling the particle size and shape of the resulting composite particles.
For
example, it is expected that longer fibers will yield larger agglomerate
particles and a
blend of fiber lengths will yield composite particles of varying particle
sizes.
[00108] U.S. Patent No. 5,705,030 assigned to the United States Department of
Agriculture, which is hereby incorporated by reference in its entirety,
describes a
process for converting chicken feathers into fibers. According to U.S. Patent
No.
5,705,030, feathers from all avian sources have the characteristics which are
necessary for the production of useful fibers, therefore feathers from any
avian
species may be utilized. Feathers are made up of many slender, closely
arranged
parallel barbs forming a vane on either side of a tapering hollow shaft. The
barbs have
bare barbules which in turn bare barbicels commonly ending in hooked hamuli
and
interlocking with the barbules of an adjacent barb to link the barbs into a
continuous
vane.
[00109] Structurally, chicken feather fibers have naturally-occurring nodes
approximately 50 microns apart. These nodes are potential cleavage sites for
producing fibers of uniform 40-50 m lengths. In addition, feathers from
different
species vary in length: poultry feather fibers are approximately 2 cm in
length while
those derived from exotic birds such as peacocks or ostriches are 4 to 5 cm or
longer.
Feather fibers are also thinner than other natural fibers resulting in
products having a
smooth, fine surface.
[00110] The composition of wood pulp fiber is generally about 50% cellulose
with the remainder being lignin and hemicelluloses. Hardwood trees have broad
leaves and softwood trees have needle-like or scale-like leaves. Hardwood
trees have
shorter fibers compared to softwood trees. All freshly cut wood contains
moisture.
CA 02607676 2007-10-25
Wood pulp has a tendency to be at "equilibrium density", i.e., the density at
which the
addition of more water does not swell or flatten the wood. If the wood pulp
sheet is
low density and water is added, it flattens out to equilibrium density. If the
wood pulp
sheet is high density, it swells to the equilibrium density.
[00111] Equilibrium density plays a significant role when agglomerated with
an absorbent material suitable for use as a cat litter. While in an air
stream, if the
density of the wood pulp fiber is close to the density of the composite
particles
formed, a homogenous blend of fibers within the composite particles may be
obtained. If there is a significant difference between the density of the wood
pulp and
the density of the composite particles formed, there is the possibility of
fiber
aggregation.
[00112] Wood pulp strength is directly proportional to fiber length and
dictates
its final use. A long fiber pulp is good to blend with short fiber pulp to
optimize on
fiber cost, strength and formation of paper. In general, pulp made from
softwood
trees or wood grown in colder climates have longer fibers compared to pulp
made
from hardwood trees or wood grown in warmer climates.
[00113] Processing conditions also contribute to fiber length. When made from
the same wood, chemical pulps tend to have longer fibers compared to semi-
chemical
pulp and mechanical pulp. Examples of long fiber pulp (>10mm) are cotton,
hemp,
flax and Jute. Examples of medium fiber pulp (2-10mm) are Northern softwoods
and
hardwoods. Examples of short fiber pulp (<2mm) are tropical hardwoods, straws
and
grasses.
[00114] Cellulose fibers in the form of paper fluff were obtained from FEECO,
Green Bay, WI. Sodium bentonite clay was obtained from Black Hills Bentonite,
Casper, WY. Activated carbon was obtained from Calgon Carbon Corporation,
Pittsburgh, PA. Expanded perlite (bulk density 5 lb/ft) was obtained from
Kansas
Minerals, Mancato, KS.
[00115] Fibers were added to a sodium bentonite clay litter material to assess
what effect the addition of the fibers had on the litter composition's
properties such as
absorptivity, clump strength and odor control. The fibers were added in a
manner
such that a homogeneous mixture of fibers and absorbent material resulted.
[00116] Cat urine was obtained from several cats so it is not cat specific.
21
CA 02607676 2007-10-25
Experiment 1
[00117] Cellulose fibers (-2-3 mm) were added to sodium bentonite clay
(about 100-500 mesh) in a pilot plant scale pin mixer equipped with a rotary
drier to
form composite particles. The particles were then sieve-screened to
approximately 12
x 40 mesh and 6 x 40 mesh in size. The cellulose fibers were added at 0%, 4%,
and
6% levels. Each sample depicted in the tables below represents six clumps.
Three of
the six clumps were formed by dosing the litter composition with 10 ml of cat
urine
and waiting 2 hours. The remaining three of the six clumps were formed by
dosing
the litter compositions with 10 ml of cat urine, waiting 1 hour, then redosing
with an
additional 10 ml of cat urine and waiting an additional 1 hour. All six clumps
were
then shaken lightly for 5 seconds. The clumps were pancake-shaped and sticky
to the
scoop and to the touch.
[00118] Table 2 summarizes the average size, shape and strength of the clumps.
Table 2
Sample Avg. Avg. Avg. Aspect Avg.
Longest Shortest Height Ratio Clump
Length Length (mm) Strength
(mm) (mm) (%
retained)
0% fibers (12 x 40 67.14 63.26 11.65 7.9 97.6%
0% fibers (6 x 40 68.33 61.23 15.55 5.9 97.8%
4% fibers (12 x 40) 63.34 59.74 12.13 7.2 96.3%
% fibers (6 x 40) 66.81 58.82 18.44 4.8 96.8%
6% fibers (12 x 40) 64 61.33 11.35 7.8 95.8%
6% fibers (6 x 40) 68.46 54.75 15.25 5.7 97.7%
22
CA 02607676 2007-10-25
Table 3
Sample Avg. Avg. Avg. Aspect Avg. Clump
Longes Shortest Height Ratio Strength
Length Length (mm) (% retained)
mm mm
0% fibers (12 x 40) single dose 48.33 46.67 17.67 3.8 95.10%
0% fibers (12 x 40) double dose 73.33 64.33 17.67 5.5
0% fibers 6 x 40) single dose 43.67 43.33 19.33 3.2 94.40%
0% fibers (6 x 40) double dose 70.67 61.67 20 4.7
4% fibers (12 x 40) single dose 44.5 44 17 3.7 94.50%
4% fibers (12 x 40) double dose 49 45 19 3.5
% fibers 6 x 40) single dose 4 44.33 20 3.2 94.10%
4% fibers 6 x 40) double dose 69.33 56 22 4.1
6% fibers (12 x 40) single dose 59.33 54.68 16.67 4.8 94.30%
6% fibers (12 x 40) double dose 68.33 67 16 6
6% fibers 6 x 40) single dose 54.67 49 13 5.6 94.70%
ExReriment 2
[00119] Cellulose fibers were added to sodium bentonite clay in a pilot plant
scale pin mixer equipped with a rotary drier to form composite particles. The
cellulose fibers were added at 0%, 4%, and 6% levels. The composite particles
were
then blended with non-agglomerated bentonite clay and sieve-screened to 12 x
40
mesh to form a litter composition comprised of a composite blend (i.e., about
35%
composite particles: about 65% bentonite clay). Each sample represents the
average
of three clumps formed by dosing the litter compositions with 10 ml of cat
urine and
waiting 2 hours (single dose) or the average of three clumps formed by dosing
the
litter compositions with 10 ml of cat urine, waiting 1 hour, redosing the
clumps with
an additional 10 ml of cat urine and waiting an additional 1 hour. Longest
length,
shortest length and height measurements were taken without disturbing the
clumps in
the box.
[00120] In addition to the clump size, the clump strength was also measured,
i.e., the ability of a scoopable litter composition to form strong urine
clumps which
remain intact when removed from a litter box. After being measured, the clumps
were allowed to sit in the box for about six hours. The clumps were then
removed,
placed on a wide (about %2 inch) mesh screen, shaken on a machine using
lateral
rotating action (about 5 lateral revolutions per second) for about_ 5 seconds
and
23
CA 02607676 2007-10-25
weighed. The clump strength is reported as Percent Retained, i.e., final
weight / g
initial wei ht
x 100%. The higher the number, the better the clump strength. The clumps were
pancake-shaped and sticky to the scoop and to the touch.
[00121] Table 3 summarizes the average size and shape of the clumps and the
clump strength at the two different dosing levels and the three different
fiber levels.
Experiment 3
[00122] Cellulose fibers were added to sodium bentonite clay (about 100-500
mesh) and powder activated carbon (about 25-150 pm) in a pilot plant scale
drum
mixer equipped with a rotary drier to form composite particles. The composite
particles were sieve-screened to about 4 x 60 mesh. The cellulose fibers were
added
at 0%, 5%, and 15% levels. Each sample represents three clumps formed by
dosing
the litter compositions with 10 ml of cat urine and waiting 2 hours (single
dose) or
three clumps formed by dosing the litter compositions with 10 ml of cat urine,
waiting
1 hour, redosing the clumps with an additional 10 ml of cat urine and waiting
an
additional 1 hour. In addition to the clump size, the clump strength was also
measured using the method outlined in Experiment 2 above. Absorbent capacity
was
calculated by determining the weight of litter needed to absorb 10 ml or cat
urine.
Absorbency is reported as the grams of urine absorbed per 1 gram of litter
composition.
[00123] Table 4 summarizes the average size, shape, strength and absorbency
of the three clumps at different fiber and different active levels. In
addition, a
comparison of cellulose fiber composite particles and expanded perlite
composite
particles is shown.
[00124] About ten percent cellulose fibers (about 2-3mm paper fluff) were
blended with about 90% bentonite (about 100-500 m) in a drum agglomerator.
The
average bulk density of three different runs was calculated to be 0.46 g/cc or
28.7
lb/ft3. The average bulk density of agglomerated bentonite alone is
approximately 55
lb/ft3. Thus, the addition of cellulose fibers into the composite particle
provides a
beneficial light-weighting effect. Table 5 lists the bulk density reduction
observed
with the addition of 2, 5, 10 and 15 percent paper fluff fibers. Fig. 2A is a
plot 140 of
the values listed in Table 5. Fig. 2B is a photograph 160 at 18 times
magnification of
composite particles containing sodium bentonite and 15% paper fluff fibers.
24
CA 02607676 2007-10-25
Table 4
Sample (balance is Dose Avg. Avg. Avg. Avg. Avg. Avg.
bentonite) Type 4onges Shortes Height Aspect Clump Clump
Length Length (inches) Ratio Absorbenc Strength
% % % (inches) (inches) (%Retained)
Paper PAC xpanded
fluff Perlite
15 0.5 0 Sin 1 1.4 1.4 1.2 1.7 1.29 86%
15 0.5 0 Doubl 1.8 1.9 1.2 2.2 1.48
0.5 0 Sin 1 1. 1.4 1 2.1 0.8 96.40%
5 0.5 Doubl 2.3 2.3 0.9 3. 0.8
0 0.5 4 Singl 2.3 1.7 0.5 5.7 1.56 98.50%
0 0.5 4 Double 2.9 1.8 0.5 6.8 1.48
Table 5
% Paper Bulk Bulk
fluff Density Density
fibers (lb/ft3) Reduction
2 3 35%
5 2 47%
2 53%
1 67%
Table 6
Sample Dose Avg. Avg. Avg. Avg. Avg. Avg. Cli
Type Longest Shortest Height Aspect Clump Streng
Length Length (inches) Ratio bsorbenc (%
(inches) (inches) Retaini
Raw bentonite Single 44.6 43.2 25.8 2.41 0.44 94.1
w bentonite oubl 70.5 54.3 26.6 3.35 0.44
Composite Particles, Single 47 41.3 21.5 2.91 0.97 96.7
100% bentonite
Composite Particles, oubl 67.8 55.7 18.9 4.65 0.9
100% bentonite
omposite Particles, Single 53.1 36.6 15.9 4.06 1.5 97.6
98% bentonite,
2% paper fluff
Composite Particles, oubl 65.5 48.5 16.3 5.01 1.5
98% bentonite,
% a er fluff
CA 02607676 2007-10-25
Experiment 4
[00125] The absorption capacity and clumping characteristics of raw sodium
bentonite, agglomerated sodium bentonite, and sodium bentonite agglomerated
along
with 2% paper fluff were compared. The agglomeration was performed in a pilot
plant scale pin mixer and drum agglomerator equipped with a rotary drier.
Composite
particles as defined above were formed. Absorbency was calculated by
determining
the weight of litter needed to absorb 10 ml of cat urine. Absorbency is
reported as the
grams of urine absorbed per 1 gram of litter composition. The clumps were
formed
using the following method. Each sample represents three clumps formed by
dosing
the litter compositions with 10 ml of cat urine and waiting 2 hours (single
dose) or
three clumps formed by dosing the litter compositions with 10 ml of cat urine,
waiting
1 hour, redosing the clumps with an additional 10 ml of cat urine and waiting
an
additional 1 hour (double dosed). Table 6 summarizes the average size, shape,
strength and absorbency of the three samples.
[00126] Without being bound by any particular theory, it is believed that the
clumping benefit results from the fibers in one composite particle grabbing
onto the
fibers in another composite particle providing a loading effect. It is
believed that the
absorption benefit results from the fact that wetting plus absorption occurs
faster in
fiber/clay composites than in clay-only composites or raw clay alone. Although
paper
fluff was used in the above experiments, incorporation of any one or more of
the other
types of fibers described herein into the bentonite composite particles is
expected to
result in a litter composition that exhibits similar clumping and absorption
benefits.
Similarly, although sodium bentonite was used in the above experiments,
composite
particles containing any one or more of the other types of absorbents
described herein
together with any one or more fibers is expected to result in a litter
composition that
exhibits enhanced clumping and absorption benefits.
[00127] If, for example, poultry feathers (such as from a chicken) are the
reinforcing fiber material incorporated into the composite particle, the
branched
nature microstructure of the feathers will enhance the number and efficiency
of
connection bond points within the composite particle. This increase in
connection
bond points induces physical crosslinks and entanglements through feather-
feather
interdigitation that allow structural loads in the composite particle to be
carried along
26
CA 02607676 2007-10-25
the fiber, thus allowing strength in tension.
[00128] Samples having a bentonite to chicken feather ratio ranging from 100:0
to 50:50 were prepared and evaluated. The diameters of the fibers used were
less than
the mean diameter of the composite particles formed. At about 20% by weight of
chicken feathers, the excess feathers began to extend from the composite
particle
surface. As the fiber length increased, the less the chicken feather mass was
completely incorporated into the composite particles.
[00129] Poultry feathers incorporated into the composite particles described
herein generally range in size from about 0.1-5mm in length for single strand
cuts and
from about 0.1-5 mm in mean diameter and about 80 m in mean length for planer
cut
shapes (inclusive of tendrils extending from the core, vanes and/or barbs).
The
average bulk density of the fibers is approximately 9 lb/ft3. Thus, in
addition to
absorptive and clumping benefits, poultry feathers can also add a
lightweighting
benefit to the resulting litter composition.
Odor Controllin2 Fibers
[00130] Odor controlling fibers may also be implemented in any of the various
embodiments of the present invention. Odor controlling fibers generally refer
to fibers
treated with a substance that helps control odors in the vicinity of the
fibers, with or
without requiring contact with the source of the odors.
[00131] In one embodiment, a fibrous material, which can be an absorbent
material, includes a plurality of natural fibers treated with an odor control
agent,
which are preferably able to withstand insults with an aqueous liquid without
dissolving the odor control agent. The odor control agent may be bound to the
natural
fibers by a binder. The binder can be water-insoluble, and can form a highly
gas
permeable coating. The binder may also be highly porous, so as to expose the
odor
control agent to ammonia and other odoriferous gases which it is intended to
control.
[00132] Cellulose fibers include fibers from wood, paper, woody plants, and
certain non-woody plants. Woody plants include, for example, deciduous and
coniferous trees. Non-woody plants include, for instance, cotton, flax,
esparto grass,
milkweed, straw, jute hemp, and bagasse. Natural fibers include cellulose
fibers,
carbon fibers, and other fibers existing in nature, as well as modifications
of such
fibers (for instance, treated cellulose fibers, activated carbon fibers, and
the like).
27
CA 02607676 2007-10-25
[00133] In one embodiment, natural fibers such as cellulose, activated carbon
or the like, are treated with a combination of odor control system and binder.
An
"odor control system" refers collectively to individual odor control agents,
and
combinations (by chemical reaction and/or blending) of two or more odor
control
agents.
[00134] In some embodiments, the odor control system includes a carboxylic
acid odor control agent and the binder includes a silicone polymer, e.g.,
polyorganosiloxane. Silicone polymers serve as excellent binders between
carboxylic
odor control agents (and systems containing them) and the natural fibers.
[00135] Preferred silicon polymers are siloxane polymers based on a structure
of alternating silicon and oxygen atoms with various organic radicals attached
to the
silicon:
6 I f
--- ---~~--~r ~-s~--
! I ~
[00136] The silicone polymers have a unique ability to protect the acidic odor
control agents from being dissolved or otherwise passed into solution by
aqueous
liquids, while at the same time permitting odoriferous gases such as ammonia
to reach
the odor control agents. Put another way, the silicone polymers are water
insoluble,
and at the same time are highly porous.
[00137] Carboxylic acid-based odor control agents include odor control agents
based on carboxylic acids and/or their partially neutralized salts. Multi-
carboxylic
acid-based odor control agents include odor control agents based on
dicarboxylic
acids, tricarboxylic acids, polycarboxylic acids, etc., having two or more
carboxylic
acid groups, and/or their partially neutralized salts. Polymeric
polycarboxylic acids
refer to polymers having multiple carboxylic acid groups in its repeating
units.
Examples include polyacrylic acid polymers, polymaleic acid polymers,
copolymers
of acrylic acid, copolymers of maleric acid, and combinations thereof. Other
examples
are disclosed in U.S. Patent No. 5,998,511, which is incorporated by reference
in its
entirety.
[00138] Another type of odor control agent includes metal ions coupled to the
fiber. Examples of fibers incorporating metal ions is found in U.S. Patent No.
28
CA 02607676 2007-10-25
6,869,537, which is herein incorporated by reference in its entirety. In one
embodiment, the fiber is characterized in that at least one metal chelate-
forming
compound such as aminocarboxylic acid, aminocarboxylic acid, thiocarboxylic
acid
and phosphoric acid, which are reactive with a glycidyl group, is bonded to a
molecule of a synthetic fiber through a crosslinkable compound having a
reactive
double bond and a glycidyl group in its molecule. The chelate-forming fiber is
excellent in capturing harmful heavy metal ions and can be easily produced in
a
simple and safe way at a low cost. When the fibrous powdery chelate-capturing
material obtained in the above manner is allowed to capture copper, silver,
zinc or
another metal having microbicidal activities, the resulting metal chelate
fiber can
impart odor-removing, deodorizing, boiocidal, antimicrobial, microbicide
activity.
[00139] In one embodiment of the invention, the odor control system and
silicone polymer are combined together, with the silicone polymer being in a
molten
form or dissolved or suspended in a solvent. The combination of odor control
system
and silicone polymer are applied to the natural fibers, desirably absorbent
fibers such
as cellulose, by spray coating, brushing, printing, dipping, extrusion, or the
like.
[00140] In another embodiment of the invention, the odor control system is
first
applied to the natural fibers using spray coating, brushing, printing,
dipping,
extrusion, or the like. The silicone polymer is then applied to the natural
fibers over
the odor control agent using spray coating, brushing, printing, dipping,
extrusion, or
the like.
[00141] In one embodiment of the invention, the odor control system includes
activated carbon fibers in addition to the carboxylic acid odor control agent.
The
silicone polymer, other natural fibers (e.g., cellulose fibers) and carbon
fibers can be
combined using any foregoing technique. The silicone polymer binds to the
activated
carbon fibers as well as to the cellulose or other natural fibers to form an
integrated
odor control/binder system.
[00142] In another embodiment of the invention, the odor control system
includes a multi-carboxylic acid-modified chitin or chitosan complex odor
control
agent. The carboxyl sites facilitate absorption of ammonia and amine-based
odors.
The amino groups on the chitin or chitosan facilitate absorption of acid-based
odor
compounds, and suppress the enzymatic decomposition of urine and menses,
thereby
29
CA 02607676 2007-10-25
inhibiting odor generation. This odor control system can also be combined with
activated carbon to provide additional control of amino, sulfuric and acidic
odors.
[00143] Illustrative odor controlling fibers are described in U.S. Patent No.
6,767,553 to Sun et al, which is herein incorporated by reference in its
entirety.
Structure Directing Agent to Increase Porosity of Particles
[00144] One of the great benefits of the composite absorbent particles
described herein is that the particles have a lower bulk density compared to
standard
granular bentonite clay litters. A typical particle is shown in Fig. 4B. To
further
decrease the bulk density of absorbent particles, the particles may be made
more
porous. Particularly, composite absorbent particles according to one
embodiment
include an absorbent material, e.g., bentonite, that forms around surfactant
micelles.
For example, as shown in Fig. 3D, composite particles 3000 are formed of an
absorbent material 3002 having pores 3004 where a structure directing agent
once
resided.
[00145] In one illustrative method of fabrication, an absorptive material such
as
powdered bentonite, silica, etc. is added to an aqueous solution containing
the
structure directing agent, e.g., a cationic surfactant, a nonionic surfactant,
an anionic
surfactant, etc. to create a slurry. The absorptive material interacts with
the structure
directing agent in the slurry, surrounding it and precipitating out. Dry and
non-slurry
methods are also contemplated. At least one additional method of fabrication
for
surfactant includes dry bed agglomeration, discussed in detail below.
[00146] In one exemplary embodiment, negatively charged bentonite materials
are attracted to micelles of a cationic/nonionic surfactant to form a
precipitate of
bentonite surrounding the micelles. An illustrative weight percent of
surfactant in the
solution may be between about 1% and about 30 %, but may be higher or lower.
The
precipitate may then be heat-treated to remove some or all of the surfactant,
and
optionally mixed, ground or crushed, thereby forming composite particles that
are
highly porous and with a low bulk density.
[00147] Figs. 3E-H illustrate the progression of the formation of pores in a
structure of absorbent material (e.g., clay), structure directing agent (e.g.,
surfactant)
and solvent (e.g., water). Fig. 3E illustrates a particle 3100 prior to
drying, with the
stgructure directing agent 3102 present. As the solvent evaporates, the
surfactant
CA 02607676 2007-10-25
becomes more and more concentrated until it forms micelles 3104, as shown in
Fig.
3F. Upon further evaporation, the micelles self-organize into periodic or
quasi-
periodic structures, as shown in Fig. 3G. Fig. 3H depicts the particle 3100
upon
complete drying, and consequent forrnation of voids.
[00148] In various embodiments, the structure directing agent may interact
with
the absorbent material via one or more of electrostatics, hydrogen bonding,
dispersion
forces, etc.
[00149] The particles formed by these processes yield very high surface area
material that are excellent for odor and liquid absorption. Further, the pore
sizes can
be tuned by selecting structure directing agents having desired properties.
For
example, small surfactants such as cetyl trimethyl ammonium bromide (CTAB)
provide a pore size on the 2-5 nm length scale. Larger surfactants such as
Pluronic
P123 from BASF provide a pore size on the 5-10 nm length scale. These pores
can
then be opened to absorption by removing the structure directing agents, e.g.,
heating
and oxidizing the organic species, to produce empty channels throughout the
particle.
Accordingly, absorbent particles can be created with virtually any desired
porosity.
Super Absorbine Materials
[00150] The active may also be a superabsorbent material (SAM). Preferably,
the superabsorbent material can absorb at least 5 times its weight of water,
and ideally
more than 10 times its weight of water. While any SAM known in the art can
potentially be used, superabsorbent polymers (SAPs) are preferred. For
simplicity and
to place the following embodiments in a context, much of the following
discussion
will refer to SAPs, it being kept in mind that other SAMs can be used
interchangeably
with SAP.
[00151] Because of their large absorption capacities, SAP materials are
commonly used in diapers and pads to sequester excess moisture, including
urine
waste. However, previous dry blending of SAP particles into granular animal
litters
has not shown significant absorption benefits. With the introduction of the
herein-
disclosed agglomeration technology into cat litter products, SAP can be
incorporated
into most if not every granule to ensure relatively even distribution
throughout the
litter box. Due to this uniform distribution, preliminary experiments with SAP
in
agglomerates show promising absorption benefits.
31
CA 02607676 2007-10-25
[00152] Illustrative superabsorbent materials include superabsorbent polymers
(SAPs) include polyacrylates such as sodium polyacrylate. SAP products include
AN905SH, FA920SH, and F04490SH, all from Floerger. Another group of
illustrative superabsorbent polymers is the SNF Flocare series of products
from SNF
FLOERGER, ZAC de Milieux, 42163 Andrezieux Cedex, FRANCE.
[00153] In one illustrative embodiment, particles of an SAP material have been
formed into a composite particle with a primary absorbent material, such as
powdered
bentonite clay, to produce composite particles containing SAP in all or most
(>50%)
of the absorbent particles. The SAP material absorbs urine or other liquid in
competition with the primary absorbent material component, and as a result the
absorption kinetics of these two individual components are determining factors
for the
overall liquid absorption performance. Because the SAP has a large effective
absorption capacity relative to sodium bentonite clay, for example, it is
preferred that
the SAP absorb urine at least as quickly as the clay (or other absorbent
material), and
preferably faster, in order to maximize utilization of the larger capacity of
the SAP.
One observation was when the absorbent material absorbs urine faster than the
SAP,
the urine tends to flow down in the litter box and is no longer accessible to
a given
SAP particle. Another observation was that absorbed liquid in a clump tends to
transfer from the clumped absorbent particles to SAP particles which causes
the
clump to break apart. Experiments have shown that urine is generally absorbed
by
clay within 3-8 seconds, and so preferred SAPs should show similar or better
rates of
absorption.
[00154] The ratio of SAP absorption rate to primary absorbent material
absorption rate can be used to control the size of the urine clump and thus
the amount
of composite material required to absorb a given volume of urine. In preferred
embodiments, this ratio of absorption rates for water and/or cat urine is
equal to or
greater than 1:1, where the rate of absorption may be defined as weight of
liquid
absorbed by a given mass of material in a given time period starting with
initial
contact with the liquid. Without wishing to be bound by any theory, the
inventors
believe that a ratio of absorption rates of SAP vs. sodium bentonite equal to
1:1 will
reduce clump size because the SAP holds more liquid per unit volume than
sodium
32
CA 02607676 2007-10-25
bentonite. The inventors believe that ratios higher than 1:1 will lead to even
more
effective absorption and absorption-related improvements.
[00155] Where the composite particles are used as a litter, for example,
control
over the litter clumping and absorption behavior makes it easier for consumers
to
remove urine clumps because of the formation of smaller clumps compared to
standard granular litters and litters with no SAP. Control over the litter
clumping and
absorption behavior also makes it easier for consumers to perform a complete
box
change because the urine penetration can be controlled to eliminate urine
pooling and
forming clumps at the bottom of the box that can stick to the container.
Further,
control over the litter clumping and absorption behavior makes it easier for
consumers
to refresh the box with new litter because removing smaller urine clumps means
adding less new litter to refill the container to the desired volume.
[00156] Preferred SAPs may exhibit a greater Jenkins osmotic potential to
water, urine, oils, and/or other liquids than the primary absorbent material
in the
particle. The Jenkins osmotic potential refers to the aggressiveness of a
first material
to attract a liquid to it relative to a second material in physical contact
with the first
material. The test for determining the relative Jenkins osmotic potential of
two
materials is as follows.
1. Place equal masses of first and second materials in physical contact
with each other. The first and second materials should have about the same
initial water content by weight, and not exceeding 25% of the total weight
of the material.
2. Drop 1 ml of liquid per 10 grams of materials (combined) onto the
interface of the first and second materials.
3. Wait 30 seconds.
4. Separate first and second materials.
5. Weigh first and second materials to determine a weight of liquid
gained by each of the materials.
6. Calculate the ratio of weight gained by the first material vs. the weight
gained by the second material.
33
CA 02607676 2007-10-25
[00157] Materials having an equal Jenkins osmotic potential will gain about
the
same amount of weight, and so will have a relative Jenkins osmotic potential
of about
1:1.
[00158] In addition to the ratio of absorption rates, the particle size
distribution
and the overall SAP content of the absorbent particles can also be adjusted to
affect
the clumping and urine absorption behavior of the absorbent particles. While
not
wishing to be bound by any theory, the inventors believe that a smaller
particle size of
the SAP relative to a larger particle size of the primary absorbent material
improves
absorption performance due to a larger available surface area of the SAP that
may be
exposed to the liquid, as opposed to the case where the particle sizes of the
SAP and
primary absorbent material are about the same. Accordingly, it is preferred
that the
mean or average particle size of the SAP is smaller than the mean or average
particle
size of the primary absorbent material, thereby maximizing the ratio of SAP
surface
area to the surface area of the primary absorbent material. An illustrative
ratio of
average or mean primary absorbent material diameter to average or mean SAP
particle diameter is greater than about 1:1, and preferably greater than about
4:1.
[00159] In illustrative embodiments containing bentonite clay and SAP, the
particle size of the clay may be in a range of about 1 m to about 1 cm. The
particle
size of the SAP may be in the range of about 10 m to about 1 cm. The SAP is
preferably present in about 0.5% - 15% of the composition. Note that the
ranges
presented herein are merely for illustration of preferred embodiments, and are
not
meant to be limiting. Accordingly, the values may be higher or lower.
[00160] The inventors have also observed that when wet clumps of SAP- and
sodium bentonite-containing particles dry out, the resulting clump is
significantly
harder than a comparable clump of particles not containing the SAP. This means
that
the clump is more apt to maintain its integrity and be removed from a
container
substantially in whole.
[00161] Additives may be added to the SAP particles to enhance their liquid
absorption rates and/or osmotic potentials. One class of additive includes
humectants
such as sorbitol, glycerin, glycerin, polyethylene glycol, polypropylene
glycol, etc.
Humectants rapidly attract water, thereby drawing liquid to the SAP particle
potentially faster than it is drawn to other materials in the composite
particle. Another
34
CA 02607676 2007-10-25
class of additive includes desiccants such as silica gel, calcium sulfate,
montmorillonite clay, etc. A further class of additive includes deliquescents
such as
calcium chloride, magnesium chloride, zinc chloride, sodium hydroxide, etc.
Because
the liquid is preferentially attracted to the SAP particle with additive, the
SAP has a
greater opportunity to absorb the liquid. Such additives can be present on the
surface
of the SAP particles (preferred), incorporated into the SAP particles, etc.
[00162] The SAP materials used in the various embodiments may or may not
include a surfactant. Surfactant-treated SAPs tend to have a faster liquid
absorption
rate because the contact angle at the liquid/surface interface is reduced.
However,
some surfactants may have a detrimental effect on clump strength.
[00163] The SAP could be incorporated using a "Differential Absorbance
Model". The "Differential Absorbance Model" proposes that a high kinetic
rate/low
capacity absorbent is combined with a low kinetic rate /high capacity
absorbent. The
first absorbent (i.e., the high kinetic rate/low capacity absorbent) would
direct or
funnel urine into the second absorbent (i.e., the low kinetic rate /high
capacity
absorbent) that would behave like a "sink". It would be particularly
advantageous if
the first absorbent is able to utilize "capillary wicking forces" to achieve a
greater rate
of fluid transfer than the diffusion alone by channeling urine through a fast
rate/low
capacity region that had capillary pores or channels to a low rate/high
capacity region.
[00164] One possible structure to incorporate the "Differential Absorbance
Model" include hollow SAP particles 180 (Fig. 3A), e.g., spherical particles,
that
allows fast flow to the hollow portion in the center, e.g., via apertures 181,
then
slower absorption in the SAP layer. Note that the hollow portion need not be
in the
center of the particle as shown. Rather, those skilled in the art will
appreciate that the
particle may have a hollow portion that is not nearly completely encircled.
Such
particles may include cylindrical particles, cup shaped particles, etc. having
a hollow
portion where the liquid can accumulate, or even be wicked in.
[00165] Fig. 3B illustrates another possible structure 190 that includes an
SAP
core 192 (i.e., low kinetic rate /high capacity absorbent sink) having a
permeable skin
194 that is cross-linked to resist excessive expansion but allowing expansion
within a
defined volume. By controlling expansion, the propensity of litter clumps
breaking is
reduced. In another embodiment 196, shown in Fig. 3C, an SAP core 192 is
coated
CA 02607676 2007-10-25
with a fast absorbing layer 198 having a porous outer surface 199. The fast
absorbing
layer 198 may absorb liquid more quickly than the SAP core 192, then allow the
liquid to be absorbed by the SAP core. The SAP core 192 may have a permeable
skin
194 that is cross-linked to resist excessive expansion but allowing expansion
within a
defined volume.
[00166] Any of the embodiments above may be agglomerated with an
absorbent material. As alluded to above, these structures avoid the problem of
excessive expansion which has been observed to lead to clump breakage.
[00167] Any of the cores mentioned herein can also be considered an active,
for example including a lightweight material dispersed throughout the particle
to
reduce the weight of the particle, a core made of pH-altering material, a core
made of
SAP, etc.
[00168] One preferred embodiment includes actives bound directly to the
surface of composite absorbent particles. The use of extremely low levels of
actives
bound only to the surface of absorbent particles leads to the following
benefits:
1. the use of extremely small particle size of the active material results
in a very high surface area of active while using a very small amount
of active,
2. with actives present only on the surface of the substrate, the waste of
expensive actives that would be found with 'homogeneous'
composite particles [where actives are found throughout the
substrate particles] is eliminated,
3. segregation of actives from substrates is eliminated; thus, the actives
remain dispersed and do not end up on the bottom of the litter
container,
4. by using very low levels of expensive actives, the cost of the product
is greatly reduced,
5. binding of small particle size actives directly to the substrate surface
results in lower dust levels than in bulk added product.
[00169] Surprisingly, low levels of PAC [0.2-0.3%] have been found to provide
excellent odor control in cat litter when they are bound to the surface of a
material
such as sodium bentonite clay. For example, binding of small amounts of PAC
36
CA 02607676 2007-10-25
particles to sodium bentonite substrate particles using xanthan gum or
fibrillatable
PTFE as binder results in litter materials with superior odor adsorbing
performance.
In this example, the PAC is highly effective at capturing malodorous volatile
organic
compounds as they escape from solid and liquid wastes due to the high surface
area of
the PAC, and its preferred location on the surface of the sodium bentonite
particles.
[00170] PAC bound to particles of any absorbent material suitable for use as
an
animal litter will provide excellent odor control.
[00171] Another aspect of the invention is the use of Encapsulated Actives,
where the actives are positioned inside the particle, homogeneously and/or in
layers.
Because of the porous structure of the particles, even actives positioned
towards the
center of the particle are available to provide their particular
functionality. In
addition, as previously mentioned, controlled degradation of the composite
particles
can result in controlled release of encapsulated actives. Encapsulation of
actives
provides a slow release mechanism such that the actives are in a useful form
for a
longer period of time. This is particularly so where the active is used to
reduce
malodors, control or kill germs, reduce sticking to the box, enhance clump
strength, or
as an indicator of health.
Pan Aeglomeration and Other Particle Creation Processes
[00172] The agglomeration process in combination with the unique materials
used allows the manufacturer to control the physical properties of particles,
such as
bulk density, dust, strength, as well as PSD (particle size distribution)
without
changing the fundamental composition and properties of absorbent particles.
[00173] One benefit of the pan agglomeration process of the present invention
is targeted active delivery, i.e., the position of the active can be
"targeted" to specific
areas in, on, and/or throughout the particles. Another benefit is that because
the way
the absorbent particles are formed is controllable, additional benefits can be
"engineered" into the absorbent particles, as set forth in more detail below.
[00174] Fig. 4A is a process diagram illustrating a pan agglomeration process
200 according to a preferred embodiment. In this example, the absorbent
granules are
bentonite clay and the active is PAC. Cores of a suitable material, here
calcium
bentonite clay, are also added. The absorbent particles (e.g., bentonite
powder) is
mixed with the active (e.g., PAC) to form a dry mixture, which is stored in a
hopper
37
CA 02607676 2007-10-25
202 from which the mixture is fed into the agglomerator 206. Alternatively,
the
absorbent granules and active(s) may be fed to the agglomerator individually.
For
example, liquid actives can be added by a sprayer. The cores are preferably
stored in
another hopper 204, from which they are fed into the agglomerator. A feed
curtain
can be used to feed the various materials to the agglomerator.
[00175] In this example, the agglomerator is a pan agglomerator. The pan
agglomerator rotates at a set or variable speed about an axis that is angled
from the
vertical. Water and/or binder is sprayed onto the granules in the agglomerator
via
sprayers 208 to raise/maintain the moisture content of the particles at a
desired level
so that they stick together. Bentonite acts as its own binder when wetted,
causing it to
clump, and so additional binder is not be necessary. The pan agglomeration
process
gently forms composite particles through a snowballing effect broadly
classified by
experts as natural or tumble growth agglomeration. Fig. 4B depicts the
structure of an
illustrative agglomerated composite particle 300 formed during the process of
Fig.
4A. As shown, the particle includes granules of absorbent material 302 and
active
304 with moisture 306 or binder positioned interstitially between the
granules.
[00176] Depending on the pan angle and pan speed, the particles tumble off
upon reaching a certain size. Thus, the pan angle and speed controls how big
the
particles get. The particles are captured as they tumble from the
agglomerator. The
particles are then dried to a desired moisture level by any suitable
mechanism, such as
a rotary or fluid bed. In this example, a forced air rotary dryer 210 is used
to lower
the high moisture content of the particles to less than about 15% by weight
and ideally
about 8-13% by weight. At the outlet of the rotary dryer, the particles are
screened
with sieves 212 or other suitable mechanism to separate out the particles of
the
desired size range. Tests have shown that about 80% or more of the particles
produced by pan agglomeration will be in the desired particle size range.
Preferably,
the yield of particles in the desired size range is 85% or above, and ideally
90% or
higher. The selected particle size range can be in the range of about 10 mm to
about
100 microns, and preferably about 2.5 mm or less. An illustrative desired
particle size
range is 12x40 mesh (1650-400 microns).
[00177] The exhaust from the dryer is sent to a baghouse for dust collection.
Additional actives such as borax and fragrance can be added to the particles
at any
38
CA 02607676 2007-10-25
point in the process before, during and/or after agglomeration. Also,
additional/different actives can be dry blended with the particles.
[00178] Illustrative composite absorbent particles after drying have a
specific
weight of from about 0.15 to about 1.2 kilograms per liter and a liquid
absorbing
capability of from about 0.6 to about 2.5 liters of water per kilogram of
particles.
Preferably, the particles absorb about 50% or more of their weight in
moisture, more
preferably about 75% or more of their weight in moisture, even more preferably
greater than approximately 80% and ideally about 90% or more of their weight
in
moisture.
[00179] Specific examples of compositions that can be fed to the agglomerator
using the process of Fig. 4A include (in addition to effective amounts of
active):
= 100% Bentonite Powder
= 67% Calcium Bentonite Clay (core) & 33% Bentonite Powder
= 50% Calcium Bentonite Clay (core) & 50% Bentonite Powder
= Perlite (core) & Bentonite Powder
= Sand (core) & Bentonite Powder
[00180] The following table lists illustrative properties for various
compositions of particles created by a 20" pan agglomerator at pan angles of
40-60
degrees and pan speeds of 20-50RPM. The total solids flow rates into the pan
were
0.2-1.0 kg/min.
39
CA 02607676 2007-10-25
Table 7
Bentonite to Final Bulk Density Clump
Core Water Core Ratio Moisture (kg/l) Strengtl
None 15-23% 100:0 1.0-1.4% 0.70-0.78 95-97
Calcium
bentonite 15-23 50:50 3.4 0.60-0.66 95-97
Calcium
bentonite 15-18 33:67 4.3-4.4 0.57-0.60 93-95
Sand 10-12 50:50 2.0 0.81-0.85 97-98
Sand 6-8 33:67 1.6-2.4 0.92 97
Perlite 15-19% 84:16 0.36-0.39 97%
Perlite 16-23% 76:24 0.27-0.28 95-970%
[00181] Clump Strength Test. Clump strength is measured by first generating a
clump by pouring 10 ml of pooled cat urine (from several cats so it is not cat
specific)
onto a 2 inch thick layer of litter. The urine causes the litter to clump. The
clump is
then placed on a'/z" screen after a predetermined amount of time (e.g., 6
hours) has
passed since the particles were wetted. The screen is agitated for 5 seconds
with the
arm up using a Ro-Tap Mechanical Sieve Shaker made by W.S. Tyler, Inc. The
percentage of particles retained in the clump is calculated by dividing the
weight of
the clump after agitation by the weight of the clump before agitation.
Referring again
to the table above, note that the clump strength indicates the percentage of
particles
retained in the clump after 6 hours. As shown, >90%, and more ideally, >95% of
the
particles are retained in a clump after 6 hours upon addition of an aqueous
solution,
such as deionized water or animal urine. Note that > about 80% particle
retention in
the clump is preferred. Also, note the reduction in bulk density when a core
of
calcium bentonite clay or perlite is used.
[00182] Fig. 4C is a process diagram illustrating another exemplary pan
agglomeration process 400 with a recycle subsystem 402. Save for the recycle
subsystem, the system of Fig. 4C functions substantially the same as described
above
with respect to Fig. 4A. As shown in Fig. 4C, particles under the desired size
are sent
back to the agglomerator. Particles over the desired size are crushed in a
crusher 404
and returned to the agglomerator.
CA 02607676 2007-10-25
[00183] The diverse types of clays and mediums that can be utilized to create
absorbent particles should not be limited to those cited above. Further, unit
operations used to develop these particles include but should not be limited
to: high
shear agglomeration processes, low shear agglomeration processes, high
pressure
agglomeration processes, low pressure agglomeration processes, mix mullers,
roll
press compacters, pin mixers, batch tumble blending mixers (with or without
liquid
addition), and rotary drum agglomerators. For simplicity, however, the larger
portion
of this description shall refer to the pan agglomeration process, it being
understood
that other processes could potentially be utilized with similar results.
[00184] Fig. 5 is a process diagram illustrating an exemplary pin mixer
process
500 for forming composite absorbent particles. As shown, absorbent particles
and
active are fed to a pin mixer 502. Water is also sprayed into the mixer. The
agglomerated particles are then dried in a dryer 504 and sorted by size in a
sieve
screen system 506. The following table lists illustrative properties for
various
compositions of particles created by pin mixing.
Table 8
Bentonite to Water Bulk Clump Strength
Lightweight Clay Ratio Addition Density - 6 hours
Clay (wt%) (wt%) (Ib/ft) (% Retained)
Zeolite (39 Ib/ft) 50:50 20 59 91
Bentonite (64
!b/ft) 100:0 20 67 95
[00185] Fig. 6 is a process diagram illustrating an exemplary mix muller
process 600 for forming composite absorbent particles. As shown, the various
components and water and/or binder are added to a pellegrini mixer 602. The
damp
mixture is sent to a muller agglomerator 604 where the mixture is
agglomerated. The
agglomerated particles are dried in a dryer 606, processed in a flake breaker
608, and
then sorted by size in a sieve screen system 610.
41
CA 02607676 2007-10-25
[00186] The following table lists illustrative properties for various
compositions of particles created by a muller process. Note that the moisture
content
of samples after drying is 2-6 weight percent.
Table 9
Clump
Calculated Actual Strength - 6
Bentonite: Water Bulk Bulk hours
Clay Addition Density Density (% Dust
Clay (wt%) (wt%) (ib/ftg) (ib/ft3) Retained) (mg)
GWC
(321b/ft3) 50:50 33 43 45 83 39
GWC
(321b/ft) 50:50 47 43 42 56 34
Taft DE
(22 fb/ft3) 50:50 29 33 46 86 38
Taft DE
(221b/ft) 50:50 41 33 43 76 35
Recovery of Materials From Other Processes for Incorporation In Composite
Particles
[00187] Raw materials for the particles described herein may be captured from
waste streams or by-product streams of other processes. The current
disposition of
much of this material is disposal thereof as a solid waste stream. The ability
to use
this material to enhance the functionality of an engineered absorbent system
would
allow the material to be recycled in a value added product.
[00188] Fig. 7 illustrates how one or more materials can be recovered from
another unrelated process and implemented in conjunction with various
embodiments
of the present invention. In this example, assume products containing pulp
(e.g., wood
pulp), nonwoven materials and SAMs are being produced in an airlaid nonwoven
process. Examples of these include diapers, absorbent sheets for medical and
other
applications, etc. As shown, fiber 702, pulp, 704, and SAP 706 are applied to
a
rollstock 708. Pulp and SAP dust from the process is collected and sent to a
bag
42
CA 02607676 2007-10-25
house 710, where larger fines may be collected and bagged. The captured dust
is
formed into a briquette by a press 711. For example, briquettes may be
transported to
another facility (if necessary), ground in a grinder 712, and agglomerated
with an
absorbent material, e.g., sodium bentonite, in an agglomerator 714 or other
processor
to form a composite particle. The collection on the baghouse sock subjects the
fine
particles to a random layering that yields a more uniform presentation of each
type of
particle to the other allowing for a coupling type of functionality. The
briquetting and
regrinding of the mixed material uniquely distributes the two components, as
well as
allows their transport. Note also that pulp and SAM fines in the briquetted
bag house
waste can also be captured and used in the composite particles. The composite
particle should have super absorbing, fibrous strength, and surface tack
properties for
use in product articles.
[00189] The pulp absorbs water more quickly than the SAM, and so is able to
quickly immobilize the water to make it available for transfer to the SAM.
Some
SAMs prefer the water to be first immobilized for its maximum absorption.
Dry Bed Malomeration Process and Illustrative Eguipment
[00190] The techniques for agglomerating powders into granular material
described above involve the mixing of water, powder, and (optionally) some
binder
together, along with the application of some kind of mechanical force to form
discrete
particles.
[00191] One embodiment of the present invention is a novel process for
agglomerating powders into particles. By using the inherent sphericity and
uniformity
of liquid drops, this process creates substantially uniform-sized, spherical
or
controlled-shaped agglomerated particles. The process is robust and stable,
and
avoids many of the drawbacks of standard mechanical agglomeration methods.
Although described below primarily in terms of creating absorbent particles,
e.g.,
litter, this agglomeration technique could be used for any powder
agglomeration
application.
[00192] Fig. 8 illustrates a general method 800 for dry bed agglomeration
according to one embodiment of the present invention. In step 802, a powder is
acquired, and if necessary, prepared. For example, if the powder contains
multiple
components, the components are dry mixed. In step 804, the powder is placed on
a
43
CA 02607676 2007-10-25
substrate or in a chamber to form a bed. In step 806, droplets of a liquid are
formed
and applied to (e.g., dropped on) the bed. In step 808, the newly formed
particles are
separated from the dry powder, e.g., by screening. In step 810, the particles
are dried.
[00193] One of the advantages of this invention is that processing can be done
using simple off-the-shelf equipment. All of the processing described should
be
possible with a gentle powder mixer, a conveyor belt, simple tubing to create
the
droplets, and a screener. The process can include additional treatment after
formation
such as a tumbler to increase roundness and/or attrition, rollers to flatten
the particles,
etc.
[00194] With reference to step 802 of Fig. 8, the powder can be any
composition, and most if not all of the materials listed herein may be used.
Preferably,
the powder includes at least one component that creates a binding mechanism
when
dry. Sodium bentonite inherently has this property. Any of the materials
described
herein may be used in the process. One preferred absorbent material is sodium
bentonite having a mean particle diameter of about 5000 microns or less,
preferably
about 3000 microns or less, and ideally in the range of about 25 to about 150
microns.
[00195] An advantage of this process is that moisture-triggered additives can
be
used that might in other processes build up on the surfaces of the equipment.
In this
process, only the agglomerates themselves receive the moisture; the rest of
the dry
powder is unaffected. For this reason, the powder composition can also contain
an
additional liquid-activated agent that would be impractical in other moist-bed
processing systems. Thus, a binder can be mixed into the powder, and will only
activate in the newly formed particle. Similarly, a gas forming agent can be
used to
create foamed particles. For example, plaster of paris can be used for binding
or
bicarbonate/citric acid can be used as a gas forming agent for foamed litter.
[00196] Other binders such as natural, modified and synthetic polymers, water
soluble film and gel formers, may be used for agglomerate-binding or improved
product clumping. Fibrous materials (cellulose, plastic, etc.) can be added to
increase
the particle strength or product clump strength.
[00197] For lightweight litter, one illustrative composition for the powder
would be bentonite (creates binding), a lightweight additive (such as perlite,
sawdust,
44
CA 02607676 2007-10-25
or other material weighing less than the bentonite), carbon powder, and
optional
additives, but could be a simple as pure bentonite.
[00198] It should be kept in mind that this aspect of the present invention is
not
limited to litter particles, but could be used to create agglomerates using
any powder,
for any application. The bed properties can be controlled by the composition
of the
powders (lightweight materials such as perlite to decrease density), the depth
of the
bed, the amount of vibration, air from below to lighten the bed, and the angle
of the
bed.
[00199] With reference to step 804 of Fig. 8, the dry bed of powder can be
created on or in the form of a moving substrate such as a conveyor belt, a
vibratory
bed, a fluid bed, a stationary substrate, etc. The bed is preferably created
and
maintained at a relatively consistent composition and density.
[00200] With reference to step 806 of Fig. 8, to create the agglomerates, a
liquid is emitted from an orifice to create individual drops. The liquid may
include
water, a solution of water and additives, or nonaqueous components.
Illustrative
additives in the solution used to form the drops include antimicrobials,
binders,
colors, etc., which advantageously may be delivered uniformly to each
particle, or
selectively to some particles and not others. Surfactants may be added to
control the
size of the droplets.
[00201] The drops can be formed naturally, growing, terminating, and dropping
due to the interplay of surface tension, gravity and the surface properties of
the
orifice. Or, they can be formed by mechanical means by a pulsing sprayer,
peristaltic
pump, etc. If developed naturally, the weight of the drops are approximated by
the
formula
mg=2naX cos a
where a is the tube radius, k is the surface tension of the liquid and a is
the angle of
contact with the tube. Accordingly, the size of the drops can be controlled by
the tube
size and other factors, or be controlled by mechanical means.
[00202] Once emitted, the drop naturally takes on a spherical shape due to the
need to reduce surface energy. The drop is allowed to fall onto a dry bed of
powder
CA 02607676 2007-10-25
and absorb the powder it comes in contact with to form a generally spherical
or sub-
spherical particle. The size and shape of the particle is determined by one or
more
processing conditions including droplet size, force in which the droplet hits
the bed,
the density of the bed, the thickness of the bed, the absorptive properties
and
hydrophilicity/phobicity of the powder, and the post treatment. For instance,
the
fundamental size of the droplet is the primary determining factor for the
final particle
size. Unlike other agglomeration methods whose particle size and distribution
output
depends on a dynamic balance of mechanical factors and can fluctuate easily,
the size,
shape and density of the particles in this novel process are relatively fixed
by the
initial conditions.
[00203] Thus, the agglomerated particle size and particle size distribution
can
be accurately engineered directly from the initial water drop size. This in
turn makes
the process very stable and predictable, since it is dependent on physical
parameters
and not significantly dependent on an equilibrium of mechanical forces.
[00204] The particles can be designed to be any size. Ain illustrative,
nonlimiting average particle diameter range for particles primarily of sodium
bentonite formed with water droplets is from about 0.1 mm to about 1 cm.
[00205] Further, the process is very scalable, as the particle size and
particle
size distribution can be consistently delivered even as the process is scaled
up, since
the process is not significantly dependent upon equipment or a dynamic
equilibrium
that is scale-dependent.
[00206] The inventor has surprisingly found that compositions that are
predominantly bentonite can be processed to form hollow particles, which also
results
in a low bulk density of the particles. Without wishing to be bound by any
theory, it is
believed that the powder adheres to the outer surface of the droplet. As water
is
absorbed by this outer shell, it is drawn out of the center of the particle,
thereby
leaving a hollow center.
[00207] The composition and/or processing conditions can be used to control
the shape of the particles also. For example, the inventor has surprisingly
found that
compositions that are predominantly bentonite can be processed to form a
generally
bagel-shaped or generally cupped-shape particle. Without wishing to be bound
by any
theory, it is believed that in some cases, the cupping or bagel shape is a
result of the
46
CA 02607676 2007-10-25
particles collapsing into the hollow core. In other cases, it is believed that
deformation
of the droplet upon impact is responsible for the shape. In yet other cases, a
combination of the two phenomenon may be responsible. Regardless of how the
shapes are formed, the cupped or bagel shaped particles can have advantages in
creating more permeability and air space in the particle packing and lowering
the bulk
density of the particles.
[00208] These findings were unexpected. The inventor believes that similar
results may be obtained with other materials as well.
[00209] The same or a different powder can be added to the particle to further
increase its size, make it less tacky for later separation from the bed,
prevent the
particles from ticking together, etc. For example, the bed can include a
dusting or
sprinkling mechanism from the top to fully cover the agglomerates in dry
powder, or
have some other means of modifying or plowing the bed. The particles can also
be
rolled. Again, a plow can be used. Testing showed that creating a tumbler or
drum for
the particles was possible, but provided opportunity for overlapping drops and
multiple particles to become fused together.
[00210] In another variation, drops of differing volume are applied to the bed
of powder to create particles of two different sizes.
[00211] Particle shape can be controlled directly by drop force, droplet
pattern,
and/or composition, and/or can be created by secondary shapers such as rollers
(a dry
powder coating on the particles makes this feasible).
[00212] With reference to steps 808 and 810 of Fig. 8, after the particles are
formed, they are easily screened from the dry powder and sent for drying. The
dry
powder may be recycled back to be part of the dry bed. The screening is of
mostly
dry material, but it may be desirable to use a heated screen, or a screen that
has some
self cleaning ability, since some particles may adhere to the screen at times.
An
optional polishing screener may be positioned after the dryer. An angled
screen may
be helpful in providing both screening of the powder and conveyance of the
particles
to the dryer.
[00213] Illustrative drying processes include air drying with ambient air, air
drying with heated air, radiant heat drying, tumbling in combination with air
drying,
cycloning, etc.
47
CA 02607676 2007-10-25
[00214] A benefit of this process is that the separation of the particles from
the
bed may be performed prior to drying. The only material that is dried is of
the desired
size, so there is a very high yield from the dryer, and the only drying energy
needed is
of water inside the sized particles.
[00215] The dry bed processes described herein may be used in a plethora of
applications. One such application is creation of an animal litter having, for
example,
one or more of the following properties or ingredients: borate ammonia
control,
activated carbon, lightweight ingredients, addition of binders, functional
speckles,
solid waste encapsulation, super absorbent polymers, particle size
modifications, non-
stick litter, and use of different minerals (e.g., zeolite). Other binders
that could be
used for agglomerate-binding or improved product clumping, in addition to
those
already listed herein, are natural polymers such as galactomannan or
polysaccharide.
gums and starches (guar gum, alginate, chitosan, xanthan, carrageenan)),
synthetic
water-reactive polymers such as modified starches, modified cellulose
(CMC),water
soluble film and gel formers such as PVP, PEG, PVA, acrylates or similar
materials.
Fibrous materials (cellulose, plastic, etc.) can be added to increase the
particle
strength or product clump strength.
[00216] Fig. 9 illustrates an illustrative system 900 for creating composite
particles by dry bed agglomeration. As shown, powder 902 is held in a hopper
904,
and applied to a conveyor belt 906. The powder can be applied in a relatively
uniform thickness, or a distributor bar (not shown) can grade the powder to
the
desired bed height.
[00217] Liquid droplets 908 are formed by a droplet forming mechanism 910
that includes emitter tubes having an orifice shape, size and angle to produce
drops of
a predetermined size at a selected flow rate. The system can be in the form of
a
spinning disk sprayer to allow for rapid flow through of agglomerate
production.
[00218] A prototype system used a series of syringes create the droplets.
Also,
the height of the droplet forming mechanism 910 may be adjusted to set the
distance
that the droplets fall to the bed. At this point, the particles begin to form
at about the
point of contact of each droplet with the bed. Note that the point of contact
is relative
to the bed, and so will move with the bed, e.g., along the conveyor belt.
48
CA 02607676 2007-10-25
[00219] A second powder distributing mechanism 912 may provide a layer of
powder over the forming particles as they pass thereby. A plow 914 may also or
alternatively disrupt the bed to apply additional powder to the particles.
Vibrating the
bed may also be employed.
[00220] The particles and powder fall off the end of the conveyor belt into a
vibrating screen 916, which separates the particles from the powder. The
particles are
sent to a dryer 918. The powder is sent to the hopper 904 via a recycle line
920.
Oversize and undersized particles may also be recycled.
[00221] As mentioned above, a structure directing agent may be used during
fabrication of the various particles found herein to increase the porosity of
the
resultant particle. In a dry bed agglomeration process, a structure directing
agent can
be used to create nanoscopic pores. For instance, where particles formed by
the dry
bed agglomeration process have an average pore diameter of 10-500 microns, the
inclusion of a structure directing agent in the process may create pores on
the order of
1 nanometer to a few microns in diameter.
[00222] In one illustrative embodiment, a surfactant is included in the
droplets
that form the particles. Suitable surfactants include cetyl trimethyl ammonium
bromide (CTAB), Pluronic P123 from BASF, etc. As the solvent evaporates, the
droplet will concentrate the surfactant until it forms micelles, which can
self-organize
into periodic or quasi-periodic structures.
[00223] In various embodiments, the structure directing agent may interact
with
the absorbent material via one or more of electrostatics, hydrogen bonding,
dispersion
forces, etc.
Shaped Particles
[00224] As alluded to above, cat litters are commonly used to sequester cat
waste into a central location that is relatively easy to maintain and clean.
An effective
clumping cat litter controls odors, readily absorbs urine waste to produce
strong urine
clumps, and minimizes litter tracking outside the box. One mechanism that may
be
used to control these attributes is optimizing the shape of the litter
particles. A shaped
litter formulation can improve upon existing urine absorption, urine clumping,
and
tracking behaviors using the proper granule shape(s). The exact shape(s)
depends on
the behavior desired, and embodiments may also include different amounts of
49
CA 02607676 2007-10-25
different shapes to control void space, surface area, and propensity to stick
to cats'
paws.
[00225] Absorbent materials with shaped granules may provide multiple
benefits over products without shaped granules, including enhanced urine
absorption,
decreased urine penetration toward the bottom of the litter box, stronger
waste
clumps, less sticking, and decreased tracking of litter out of the litter box
into the
surrounding environment. The clay minerals, cellulosic materials, and other
materials
listed herein can potentially be formed into virtually any shape. While many
materials listed herein are commonly found in animal litters, the creation and
use of
shaped granules as described herein is generally applicable to any absorbent
material.
Further, the particles may be composite particles, particles of a single
material, or
combinations thereof.
[00226] The particles can be formed into any desired shape, and many
illustrative shapes have been contemplated for the absorbent particles. It
should be
kept in mind that the following list of shapes is nonexhaustive. It should
also be kept
in mind that portions of the various particles can be combined with portions
of other
particles to form a nearly unlimited combination of features in a single
particle. Fig.
illustrates several potential shapes. As shown, particle 1000 has a flat form,
disc-
like profile. Particle 1002 is generally square shaped and has a flat form,
i.e., low
profile, while particle 1004 is generally rectangular shaped and has a flat
form. Flat
form particles such as these inhibit penetration, and enhance clumping because
the
particles tend to overlap in the container. Flat forms also lower tracking as
flat forms
are less apt to stick to animal fur.
[00227] Particle 1006 is a generally rectangular particle, and has a generally
square profile when looking at its ends. Particle 1008 is diamond shaped.
Particle
1010 is generally star shaped. Particle 1012 is generally shaped like a
tetrahedron or
pyramid. Particles with flat sides exhibit less tracking than spherical
particles, as the
flatness of the particles tends to make it less likely to become bound up in
an animal's
fur, between toes, etc. Particles with flat sides also tend to exhibit better
clumping, as
the abutting surface area of the particles is maximized. Additionally, for
spill cleanup,
flat sides allow particles to lie flat against a surface, maximizing the
surface area in
contact with the spill.
CA 02607676 2007-10-25
[00228] Particle 1014 is cupped. The cupped shape beneficially decreases the
overall bulk density of the material, while liquids are caught in the cups,
thereby
reducing penetration.
[00229] Particle 1016 is generally bagel shaped. Particle 1018 is mesh shaped.
Particle 1020 is generally cone shaped. Particle 1022 has a combination of
cone and
hemisphere shapes.
[00230] Particle 1024 is generally cylindrical. This particle 1024 also
exhibits
how grooves 1026 may be added to a particle to increase its surface area and
reduce
bulk density.
(00231] Particle 1028 exhibits how a particle may be scored to increase its
surface area, as well as provide resistance to liquid flow therearound.
[00232] Particle 1030 is a generally spherical particle illustrating how
dimples
may be added to a particle to increase its surface area.
[00233] Particles 1032 have angled portions along one side thereof. Particles
1034 have angled portions along more than one side thereof. In some
embodiments,
the angled portions may allow the particles to exhibit some type of
interlocking.
Particles that provide some type of interlocking increases clump strength due
to the
interlocking of the particles. Interlocking particles may also contain
features that
cause water to collect thereon, thereby reducing liquid penetration.
[00234] Particle 1036 has a crescent shape.
[00235] In general, an illustrative lower end of average particle length or
diameter is about 1 mm, as sizes smaller than about 1 mm tend to lose benefits
associated with particular particle orientations (how particles tend to align
with
respect to each other). The upper end of average particle length or diameter
is
virtually unlimited. For animal litters, a preferred upper end of average
particle length
or diameter is less than about 1/2 inch.
[00236] Illustrative aspect ratios of the particles, presented by way of
example
only, may be any value meeting length:height > 2:1, length:diameter > 2:1, and
diameter:height > 2:1.
[00237] The shaped particles can be formed using many processes, including
but not limited to extrusion, agglomeration, pressing including roll pressing,
stamping, dry bed agglomeration, punch roller processing, hammer mill
processing,
51
CA 02607676 2007-10-25
molding, flash drying (e.g., spray slurry onto hot roller), etc. For example,
composite
absorbent particles formed in the pan agglomeration process described above
are
substantially spherical in shape when they leave the agglomeration pan. At
this point,
i.e., prior to drying, the particles typically have a high enough moisture
content that
they are malleable. By molding, compaction, or other process, the composite
absorbent particle can be made into non-spherical shapes such as, for example,
ovals,
flattened spheres, hexagons, triangles, squares, etc. and combinations
thereof.
Variations on spherical shapes can also be provided. The shaped particles may
be
executed in both clumping and non-clumping litters.
[00238] Embodiments of the present invention also include combinations of
various shapes to create consumer products that provide enhanced benefits over
absorbent materials currently on the market. For example, smaller particles
may be
mixed with larger particles. The smaller particles fit into voids,
depressions, etc. in or
between the larger particles, thereby minimizing liquid penetration.
[00239] The fact that particles in a container tend to shift during movement,
e.g., when an animal steps and digs in the litter, as the litter is
transported, etc. can
also provide advantages in terms of targeted segregation. In other words, one
can take
advantage of the known segregational behaviors of various particles to provide
targeted benefits. For example, large flat particles will tend to rise to the
surface of the
litterbox, while smaller particles will aggregate towards the bottom. Thus,
for
example, smaller particles exhibiting low liquid penetration and/or greater
liquid
absorption can be combined with larger particles exhibiting greater odor
control. In
one embodiment, a smaller particle containing SAP can be admixed with larger
particles containing activated carbon. The smaller particles have less void
space
therebetween and/or will absorb more liquid, thereby limiting penetration. The
larger
particles control odors. A variation may use identically-shaped particles,
where the
odor-controlling particles have a lower bulk density, e.g., due to lightweight
additives,
lightweight core, etc.
[00240] A further variation has larger particles that segregate towards the
bottom of the pan, while smaller particles aggregate at the top of the box.
Here, the
larger particles may have a greater bulk density than the smaller particles to
induce
52
CA 02607676 2007-10-25
such segregation. An example of this may include larger cylindrical particles
(e.g.,
particle 1024) with smaller hollow spherical particles.
[00241] In a similar way, the way litter segregates in the bag during shipment
can be taken advantage of to provide, for example, a litter having particles
with
particular properties segregated in a predefined way. Then, for instance, when
the
consumer pours the litter into the litter box, the predefined particle
distribution will be
inversely transferred to the litter box. Going further, the particles
initially positioned
or tending to settle to the bottom of the bag during shipment, now out of the
bag and
on top of the container, will segregate down to the bottom with use. This may
allow
particles with odor controlling properties to move downward towards the bottom
of
the pan as their effectiveness is consumed. Likewise, relatively unaffected
particles
initially positioned towards the bottom of the pan migrate towards the top
over time,
thereby providing long term odor control benefits.
[00242] In other embodiments, absorbent particles having the same shape but
different properties may be provided, and have about the same size or
different sizes.
In further embodiments, particles having different shapes but about the same
size can
be provided.
[00243] Accordingly, shaped particles having certain desirable benefits can be
combined with particles of other shapes and complementary benefits to provide
a
plethora of desirable results.
[00244] Fig. 11 depicts a method 1100 of using absorbent particles. In step
1102, the user pours first and second absorbent particles having different
shapes into a
container such as a litterbox. In step 1104, the user agitates the particles
to induce
targeted segregation. The particles may be agitated by physically contacting
the
particles, e.g., by stirring, scratching, etc. The particles may also be
agitated by
shaking the container.
[00245] Fig. 12 depicts a method 1200 for orienting particles. In step 1202,
the
user pours absorbent particles, which may or may not have different shapes,
into a
container. In step 1204, the user agitates the particles to induce a targeted
orientation.
Again, the particles may be agitated by physically contacting the particles,
by shaking
the container, enabling an electronic device such as an automatic litterbox
with a
moving rake to contact the particles, etc.
53
CA 02607676 2007-10-25
[00246] A targeted orientation may be virtually any orientation that may be
provided by agitating the particles. For example, flat form particles can be
agitated so
that many of them lie generally coplanar with the bottom of the container.
This in turn
maximizes the surface encountered by a liquid entering the container, thus
minimizing
penetration. Another example includes agitating the particles to orient
smaller
particles in voids created between larger particles. Yet another example
includes
orienting the particles so that flat surfaces of some particles abut with flat
surface of
other particles, thereby creating a more tortuous path for liquids passing
from the top
of the container downward. Yet another example includes agitating interlocking
particles to induce the interlocking. Those skilled in the art will appreciate
that the
number and ways of orienting the various possible combinations of types of
particles
is nearly infinite.
[00247] Particles may also be shaped in various combinations to minimize
penetration in automatic litterboxes. One of the predominant issues in
automatic
litterboxes is liquid penetrating to the bottom, causing litter to stick to
the bottom.
[00248] Further embodiments vary combinations of the particle shape(s), ratio
of combinations of particle shapes, particle size, and addition levels to
further
optimize the litter performance.
[00249] Accordingly, using particles of a particular shape or shapes may make
it easier for consumers to:
1. Scoop waste clumps from the litter box because they may form
smaller, stronger clumps compared to standard litters. The clumps may be
smaller and stronger because the granule size and shape can be optimized to
increase the absorption and wet contact area between neighboring particles.
2. Completely change out the used litter because decreased urine
penetration decreases the occurrence of litter sticking to the box. Urine
penetration can be decreased by controlling the granule size and/or shape to
eliminate void space that can serve as channels for urine flow in the litter
box.
3. Reduce odor permeability. The same mechanism that inhibits liquid
penetration into the box also inhibits vapor penetration out of the box.
4. Avoid litter being tracked out of the litter box because the shape can
be optimized to minimize litter sticking to the cat's paws.
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CA 02607676 2007-10-25
5. Absorb spills from a flat surface, e.g., oil on a floor. Flat sides allow
particles to lie flat against the surface, maximizing the surface area in
contact
with the spill.
[00250] Several additional uses for the shaped particles are also anticipated,
and accordingly the various aspects of the invention are not to be limited to
animal
litter. For example, interlocking particles may be used as a soil amendment to
reduce
erosion.
Examples
Example 1
[00251] Referring again to Fig. 1, a method for making particles 102 is
generally performed using a pan agglomeration process in which clay particles
of
<200 mesh (<74 microns), preferably <325 mesh (<43 microns) particle size
premixed with particles of active, are agglomerated in the presence of an
aqueous
solution to form particles in the size range of about 12x40 mesh (about 1650-
250
microns). Alternatively, the particles are first formed with clay alone, then
reintroduced into the pan or tumbler, and the active is added to the pan or
tumbler,
and a batch run is performed in the presence of water or a binder to adhere
the active
to the surface of the particles. Alternatively, the active can be sprayed onto
the
particles.
Example 2
[00252] A method for making particles 104 is generally performed using the
process described with relation to Fig. 2, except no core material is added.
Example 3
[00253] A method for making particles 106 is generally performed using the
process described with relation to Fig. 2, except that introduction of the
absorbent
granules and the active into the agglomerator are alternated to form layers of
each.
Example 4
[00254] A method for making particles 108 is generally performed using the
process described with relation to Fig. 2, except that the active has-been pre-
clumped
CA 02607676 2007-10-25
using a binder, and the clumps of active are added. Alternatively, particles
of
absorbent material can be created by agglomeration and spotted with a binder
such
that upon tumbling with an active, the active sticks to the spots of binder
thereby
forming concentrated areas. Yet another alternative includes the process of
pressing
clumps of active into the absorptive material.
Example 5
[00255] A method for making particles 110 is generally performed using the
process described with relation to Fig. 2.
Example 6
[00256] A method for making particles 112 is generally performed using the
process described with relation to Fig. 2.
Example 7 & 8
[00257] A method for making particles 114 and 116 are generally performed
using the process described with relation to Fig. 2, except no active is
added.
[00258] In addition, the performance-enhancing active can be physically
dispersed along pores of the particle by suspending an insoluble active in a
slurry and
spraying the slurry onto the particles. The suspension travels into the pores
and
discontinuities, depositing the active therein.
Control Over Particle Prouerties
[00259] Strategically controlling process and formulation variables along with
agglomerate particle size distribution allows for the development of various
composite particles engineered specifically to enable attribute improvements
as
needed. Pan agglomeration process variables include but are not limited to raw
material and ingredient delivery methods, solid to process water mass ratio,
pan
speed, pan angle, scraper type and configuration, pan dimensions, throughput,
and
equipment selection. Formulation variables include but are not limited to raw
material specifications, raw material or ingredient selection (actives,
binders, clays
56
CA 02607676 2007-10-25
and other solids media, and liquids), formulation of liquid solution used by
the
agglomeration process, and levels of these ingredients.
[00260] The pan agglomeration process intrinsically produces agglomerates
with a narrow particle size distribution (PSD). The PSD of the agglomerates
can be
broadened by utilizing a pan agglomerator that continuously changes angle
(pivots
back and forth) during the agglomeration process. For instance, during the
process,
the pan could continuously switch from one angle, to a shallower angle, and
back to
the initial angle or from one angle, to a steeper angle, and back to the
initial angle.
This variable angle process would then repeat in a continuous fashion. The
angles
and rate at which the pan continuously varies can be specified to meet the
operator's
desired PSD and other desired attributes of the agglomerates.
[00261] As mentioned above, the agglomeration process can be manipulated to
control process and formulation variables. This manipulation can be used, for
example, to increase or decrease pore size, pore volume and surface area which
can
then result in control of bulk properties such as the bulk density of the
particles (with
or without use of core material),the overall liquid absorption capacity by the
particles,
and the rate of degradation of formed granules under swelling conditions. The
pore
size, pore volume, surface area and resulting bulk properties depend primarily
on the
pan angle and the pan speed, which together create an effective pressure on
the
particles being agglomerated into composite particles. By increasing the pan
speed,
the centrifugal force exerted on the particles is increased, thereby reducing
the
internal pore size of the resulting composite particles. Similarly, as the pan
angle is
increased from the horizontal, the particles will tumble more violently
towards the
bottom of the pan, again reducing the internal pore size of the resulting
composite
particles.
[00262] A larger pore size results in a lower overall bulk density of the
composite particles. A larger pore size also allows odoriferous molecules to
more
readily reach actives embedded within the composite particles. The pore size
also
affects hydraulic conductivity.
[00263] By knowledge of interactions between pan, dryer, and formulation
parameters one could further optimize process control or
formulation/processing cost.
For example, it was noted that by addition of a minor content of a less
absorptive clay,
57
CA 02607676 2007-10-25
we enabled easier process control of particle size. For example, by addition
of
calcium bentonite clay the process became much less sensitive to process
upsets and
maintains consistent yields in particle size throughout normal moisture
variation.
Addition of calcium bentonite clay also helped reduce particle size even when
higher
moisture levels were used to improve granule strength. This is of clear
benefit as one
looks at enhancing yields and having greater control over particle size
minimizing
need for costly control equipment or monitoring tools.
[00264] For those practicing the invention, pan agglomeration manipulation
and scale-up can be achieved through an empirical relationship describing the
particle's path in the pan. Process factors that impact the path the particle
travels in
the pan include but are not limited to pan dimensions, pan speed, pan angle,
input feed
rate, solids to process liquid mass ratio, spray pattern of process liquid
spray, position
of scrapers, properties of solids being processed, and equipment selection.
Additional
factors that may be considered when using pan agglomerators include particle
to
particle interactions in the pan, gravity effects, and the following
properties of the
particles in the pan: distance traveled, shape of the path traveled, momentum,
rotational spin about axis, shape, surface properties, and heat and mass
transfer
properties.
[00265] The composite particles provide meaningful benefits, particularly when
used as a cat litter, that include but are not limited to improvements in
final product
attributes such as odor control, litter box maintenance benefits, reduced
dusting or
sifting, and consumer convenience. As such, the following paragraphs shall
discuss
the composite absorbent particles in the context of animal litter, it being
understood
that the concepts described therein apply to all embodiments of the absorbent
particles.
[00266] Significant odor control improvements over current commercial litter
formulas have been identified for, but are not limited to, the following
areas:
= Fecal odor control (malodor source: feline feces)
= Ammonia odor control (malodor source: feline urine)
= Non-ammonia odor control (malodor source: feline urine)
[00267] Odor control actives that can be utilized to achieve these benefits
include but are not limited to powdered activated carbon, silica powder (Type
C),
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CA 02607676 2007-10-25
borax pentahydrate, and bentonite powder. The odor control actives are
preferably
distributed within and throughout the agglomerates by preblending the actives
in a
batch mixer with clay bases and other media prior to the agglomeration step.
The pan
agglomeration process, in conjunction with other unit operations described
here,
allows for the targeted delivery of actives within and throughout the
agglomerate, in
the outer volume of the agglomerate with a rigid core, on the exterior of the
agglomerate, etc. These or any targeted active delivery options could also be
performed in the pan agglomeration process exclusively through novel
approaches
that include, but should not be limited to, strategic feed and water spray
locations,
time delayed feeders and spray systems, raw material selection and their
corresponding levels in the product's formula (actives, binders, clays, and
other
medium), and critical pan agglomeration process variables described herein.
[00268] Additionally, the pan agglomeration process allows for the
incorporation of actives inside each agglomerate or granule by methods
including but
not limited to dissolving, dispersing, or suspending the active in the liquid
solution
used in the agglomeration process. As the pan agglomeration process builds the
granules from the inside out, the actives in the process's liquid solution
become
encapsulated inside each and every granule. This approach delivers benefits
that
include but should not be limited to reduced or eliminated segregation of
actives from
base during shipping or handling (versus current processes that simply dry
tumble
blend solid actives with solid clays and medium), reduced variability in
product
performance due to less segregation of actives, more uniform active dispersion
across
final product, improved active performance, and more efficient use of actives.
This
more effective use of actives reduces the concentration of active required for
the
active to be effective, which in turn allows addition of costly ingredients
that would
have been impractical under prior methods. For example, dye or pigment can be
added to vary the color of the litter, lighten the color of the litter, etc.
Disinfectant can
also be added to kill germs. For example, this novel approach can be utilized
by
dissolving borax pentahydrate in water. This allows the urease inhibitor
(boron) to be
located within each granule to provide ammonia odor control and other benefits
described here. One can strategically select the proper actives and their
concentrations in the liquid solution used in the process to control the final
amount of
59
CA 02607676 2007-10-25
active available in each granule of the product or in the product on a bulk
basis to
deliver the benefits desired.
[00269] Targeted active delivery methods should not be limited to the targeted
active delivery options described here or to odor control actives exclusively.
For
example, another class of active that could utilize this technology is animal
health
indicating actives such as a pH indicator that changes color when urinated
upon,
thereby indicating a health issue with the animal. This technology should not
be
limited to cat litter applications. Other potential industrial applications of
this
technology include but should not be limited to laundry, home care, water
filtration,
fertilizer, iron ore pelletizing, pharmaceutical, agriculture, waste and
landfill
remediation, and insecticide applications. Such applications can utilize the
aforementioned unit operations like pan agglomeration and the novel process
technologies described here to deliver smart time-releasing actives or other
types of
actives and ingredients in a strategic manner. The targeted active delivery
approach
delivers benefits that include but should not be limited to the cost efficient
use of
actives, improvements in active performance, timely activation of actives
where
needed, and improvements in the consumer perceivable color of the active in
the final
product. One can strategically choose combinations of ingredients and targeted
active
delivery methods to maximize the performance of actives in final products such
as
those described here.
[00270] Litter box maintenance improvements can be attributed to proper
control of the product's physical characteristics such as bulk density, clump
strength,
attrition or durability (granule strength), clump height (reduction in clump
height has
been found to correlate to reduced sticking of litter to the bottom of litter
box),
airborne and visual dust, lightweight, absorption (higher absorption
correlates to less
sticking to litter box - bottom, sides, and corners), adsorption, ease of
scooping, ease
of carrying and handling product, and similar attributes. Strategically
controlling
process and formulation variables along with agglomerate particle size
distribution
allows for the development of various cat litter particles engineered
specifically to
"dial in" attribute improvements as needed. Pan agglomeration process
variables
include but are not limited to raw material and ingredient delivery methods,
solid to
process water mass ratio, pan speed, pan angle, scraper type and
configuration, pan
CA 02607676 2007-10-25
dimensions, throughput, and equipment selection. Formulation variables include
but
are not limited to raw material specifications, raw material or ingredient
selection
(actives, binders, clays and other solids medium, and liquids), formulation of
liquid
solution used by the agglomeration process, and levels of these ingredients.
For
example, calcium bentonite can be added to reduce sticking to the box.
[00271] Improvements in consumer convenience attributes include but are not
limited to those described here and have been linked to physical
characteristics of the
product such as bulk density or light weight. Because the absorbent particles
are
made from small granules, the pan agglomeration process creates agglomerated
particles having a porous structure that causes the bulk density of the
agglomerates to
be lower than its initial particulate form. Further, by adjusting the rotation
speed of
the pan, porosity can be adjusted. In particular, a faster pan rotation speed
reduces the
porosity by compressing the particles. Since consumers use products like cat
litter on
a volume basis, the pan agglomeration process allows the manufacturer to
deliver
bentonite based cat litters at lower package weights but with equivalent
volumes to
current commercial litters that use heavier clays that are simply mined,
dried, and
sized. The agglomerates' reduced bulk density also contributes to business
improvements previously described such as cost savings, improved logistics,
raw
material conservation, and other efficiencies. Lightweight benefits can also
be
enhanced by incorporating cores that are lightweight. A preferred bulk density
of a
lightweight litter according to the present invention is less than about 1.5
grams per
cubic centimeter and more preferably less than about 0.85 g/cc. Even more
preferably, the bulk density of a lightweight litter according to the present
invention is
between about 0.25 and 0.85 g/cc, and ideally for an animal litter 0.35 and
0.50 g/cc.
[00272] The porous structure of the particles also provides other benefits.
The
voids and pores in the particle allow access to active positioned towards the
center of
the particle. This increased availability of active significantly reduces the
amount of
active required to be effective. For example, in particles in which carbon is
incorporated in layers or heterogeneously throughout the particle, the porous
structure
of the absorbent particles makes the carbon in the center of the particle
available to
control odors. Many odors are typically in the gas phase, so odorous molecules
will
travel into the pores, where they are adsorbed onto the carbon. By mixing
carbon
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CA 02607676 2007-10-25
throughout the particles, the odor-absorbing life of the particles is also
increased.
This is due to the fact that the agglomeration process allows the manufacturer
to
control the porosity of particle, making active towards the center of the
particle
available.
[00273] Because of the unique processing of the absorbent particles of the
present invention, substantially every absorbent particle contains carbon. As
discussed above, other methods merely mix GAC with clay, and compress the
mixture
into particles, resulting in aggregation and some particles without any
carbon. Thus,
more carbon must be added. Again, because of the way the particles are formed
and
the materials used (small clay granules and PAC), lower levels of carbon are
required
to effectively control odors. In general, the carbon is present in the amount
of 5% or
less based on the weight of the particle. In illustrative embodiments, the
carbon is
present in the amount of 1.0% or less, 0.5% or less, and 0.3% or less, based
on the
weight of the particle. In other embodiments, activated alumina is present in
the
amount of 1.0% or less, 0.5% or less, and 0.3% or less, based on the weight of
the
particle. This lower amount of carbon or other odor controlling additive
significantly
lowers the cost for the particles, as these additives are very expensive
compared to
clay. The amount of carbon or other odor controlling additive required to be
effective
is further reduced because the agglomeration process incorporates the carbon
into
each particle, using it more effectively. As shown in the graph 1500 of Fig.
15, the
composite absorbent particles according to a preferred embodiment have a
malodor
rating below about 15, whereas the non-agglomerated control has a rating of
about 40,
as determined by a Malodor Sensory Method.
Description of Malodor Sensory Method:
1. Cat boxes are filled with 2,500 cc of test litter.
2. Boxes are dosed each morning for four days with 30g of pooled feces.
3. On the fourth day the center of each box is dosed with 20 ml pooled urine.
4. The boxes are placed into sensory evaluation booths.
5. The boxes are allowed to equilibrate in the closed booths for 30 - 45
minutes before panelist evaluation.
6. The samples are then rated on a 60 point line scale by trained panelists.
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CA 02607676 2007-10-25
[00274] Preferably, the agglomerated particles exhibit noticeably less odor
after
four days from contamination with animal waste as compared to a generally
solid
particle of the absorbent material alone under substantially similar
conditions.
[00275] As mentioned above, the human objection to odor is not the only
reason that it is desirable to reduce odors. Studies have shown that cats
prefer litter
with little or no smell. One theory is that cats like to mark their territory
by urinating.
When cats return to the litterbox and don't sense their odor, they will try to
mark their
territory again. The net effect is that cats return to use the litter box more
often if the
odor of their markings is reduced.
[00276] Accordingly, the composite particles induce a cat to use the litter,
and
thus provide a mechanism to defeat a cat's instinct to mark its territory in
areas other
than the litter box.
[00277] A preferred embodiment of the present invention has a feline
inducement to use index of at least 8, and ideally at least 9, as measured by
the
following test.
Description of Feline Inducement to Use Index Test:
1. Cat boxes are filled with 2,500 cc of test litter of >95% bentonite, -l %
activated carbon, and may include other optional actives. The cat boxes
are each placed in an individual cage having a floor area of 12 square
feet.
2. One cat is placed in each cage and kept there for seven days. The
excrement and urine are not removed from the litter.
3. On the seventh day the cage is examined for urine and excrement in
areas other than the box.
4. The number of soiled areas of the cage other than the box are
enumerated and subtracted from a base number of 10 to produce
individual indices. The individual indices are averaged by the total
number of cat boxes in the test to determine the feline inducement to
use index.
[00278] Additionally, in households with multiple cats, one or both cats may
object to sharing the litterbox upon sensing the odor of the other cat's
waste.
However, the superior odor control properties of the composite particles
described
63
CA 02607676 2007-10-25
herein have been found to sufficiently control odors that multiple cats use
litter even
after an extended period of time.
[00279] A preferred embodiment of the present invention has a multiple cat
usage index of at least 8, and ideally at least 9, as measured by the
following test.
Description of Multiple Cat Usage Index Test:
1. Cat boxes are filled with 2,500 cc of test litter of >95% bentonite, -1%
activated carbon, -1 % of a boron compound sprayed onto the particles,
and optionally additional actives. The cat boxes are each placed in an
individual cage having a floor area of 12 square feet.
2. Two cats are placed in each cage and kept there for seven days. The
excrement and urine are not removed from the litter.
3. On the seventh day the cage is examined for urine and excrement in
areas other than the box.
4. The number of soiled areas of the cage other than the box are
enumerated and subtracted from a base number of 10 to produce individual
indices. The individual indices are averaged by the total number of cat
boxes in the test to determine the multiple cat usage index.
[00280] The composite absorbent particles of the present invention exhibit
surprising additional features heretofore unknown. The agglomerated composite
particles allow specific engineering of the particle size distribution and
density, and
thereby the clump aspect ratio. Thus, hydraulic conductivity (K) values of <
0.25
cm/s as measured by the following method can be predicted using the technology
disclosed herein, resulting in a litter that prevents seepage of urine to the
bottom of
the box when sufficient litter is present in the box.
Method for measuring Hydraulic Conductivity
Materials:
1. Water-tight gas drying tube with 7.5 centimeter diameter
2. Manometer
3. Stop watch
4. 250ml graduated cylinder
64
CA 02607676 2007-10-25
Procedure:
1. Mix and weigh sample
2. Pour the sample into the Drying tube until the total height of the
sample is 14.6 centimeters.
3. Close the cell.
4. Use vacuum to pull air through and dry the sample for at least 3
minutes.
5. When the sample is dry, saturate the sample slowly with water by
opening the inlet valve.
6. Allow the water exiting the drying tube to fill the graduated cylinder.
7. Deair the system using vacuum, allowing the system to stabilize for 10
minutes.
8. After 10 minutes, record the differential pressure as displayed by the
manometer.
9. Record at least 4 differential pressure measurements, waiting 3 minutes
between each measurement.
10. Record the flow rate of the water entering the graduated cylinder.
11. Calculate the Hydraulic Conductivity, K, using Darcy's Law
Q= -KA (ha-hb)/L
Q= Flow Rate
K= Hydraulic Conductivity
A= Cross Sectional Area
L= Bed Length
Ha-Hb= Differential Pressure
[00281] One of the distinguishing characteristics of the optimum K value is a
litter clump with a very low height to length ratio (flat). By controlling the
particle
size of the litter, clump strength and clump profile can be controlled. This
is
important because the smaller the clumps are, the less likely they are to
stick to
something like the animal or litterbox. For instance, with prior art compacted
litter, if
a cat urinates 1 inch from the side of the box, the urine will penetrate to
the side of
box and the clay will stick to the box. However, the present invention allows
the litter
CA 02607676 2007-10-25
particles to be engineered so urine only penetrates about '/2 inch into a mass
of the
particles.
[00282] Agglomerated composite particles according to the present invention
also exhibit interesting clumping action not previously seen in the
literature.
Particularly, the particles exhibit extraordinary clump strength with less
sticking to the
box, especially in composite particles containing bentonite and PAC. PAC is
believed
to act as a release agent to reduce sticking to the box. However, intuitively
this
should also lead to reduced clump strength, not increased clump strength. The
combination of stronger clumps yet exhibiting less sticking to the box is both
surprising and counter-intuitive. The result is a litter with multiple
consumer benefits
including strong clumps, low urine seepage, and little sticking to the box.
[00283] While not wishing to be bound by any particular theory, the increased
clump strength is believed to be due to at least some of the PAC-containing
granules
"falling apart" and releasing their bentonite particles to reorder themselves,
and this
'reordering' produces a stronger clump. As shown in Figs. 13 and 14, this can
best be
described as a disintegration of more-water-soluble pieces of the agglomerated
composite particles 1300 when in contact with moisture 1302, allowing the
pieces
1304 of the particles to attach to surrounding particles. This "reordering"
produces a
stronger clump. In testing, the visual appearance of the cores is a signal
that at least
some of the granules decompose to smaller particles, and these particles are
"suspending" in the urine and are free to occupy interstitial spaces between
particles,
forming a stronger clump. This creates a network of softened agglomerated
particles
where broken particle pieces are attaching to others and creating a web of
clumped
material. Note however that the particles described herein should not be
limited to
clumping or scoopable particles.
[00284] As mentioned above, the composite absorbent particles have particular
application for use as an animal litter. The litter would then be added to a
receptacle
(e.g., litterbox) with a closed bottom, a plurality of interconnected
generally upright
side walls forming an open top and defining an inside surface. However, the
particles
e
should not be limited to pet litters, but rather could be applied to a number
of other
applications such as:
66
CA 02607676 2007-10-25
= Litter Additives - Formulated product can be pre-blended with standard
clumping or non-clumping clays to create a less expensive product with some
of the benefits described herein. A post-additive product could also be
sprinkled over or as an amendment to the litter box.
= Filters - Air or water filters could be improved by either optimizing the
position of actives into areas of likely contact, such as the outer perimeter
of a
filter particle. Composite particles with each subcomponent adding a benefit
could also be used to create multi-functional composites that work to
eliminate
a wider range of contaminants.
= Bioremediation / Hazardous / Spill Cleanup - Absorbents with actives
specifically chosen to attack a particular waste material could be engineered
using the technology described herein. Exemplary waste materials include
toxic waste, organic waste, hazardous waste, and non-toxic waste.
= Pharma / Ag - Medications, skin patches, fertilizers, herbicides,
insecticides,
all typically use carriers blended with actives. Utilization of the technology
described herein reduce the amount of active used (and the cost) while
increasing efficacy.
= Soaps, Detergents, and other Dry Products - Most dry household products
could be engineered to be lighter, stronger, longer lasting, or cheaper using
the
technology as discussed above.
= Mixtures of Different Particles - The composite particles can be dry mixed
with other types of particles, including but not limited to other types of
composite particles, extruded particles, particles formed by crushing a source
material, etc. Mixing composite particles with other types of particles
provides the benefits provided by the composite particles while allowing use
of lower cost materials, such as crushed or extruded bentonite. Illustrative
ratios of composite particles to other particles can be 75/25, 50/50, 25/75,
or
any other ratio desired. For example, in an animal litter created by mixing
composite particles with extruded bentonite, a ratio of 50/50 will provide
enhanced odor control, clumping and reduced sticking, while reducing the
weight of the litter and lowering the overall cost of manufacturing the
litter.
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CA 02607676 2007-10-25
= Mixtures of Composite Particles with Actives- The composite particles can be
dry mixed with actives, including but not limited to particles of activated
carbon.
Additional Examples
[00285] Note that all percentages are in weight percent in the following
examples.
Example 9
[00286] A composite particle includes:
about 90-99.5% sodium bentonite as the primary absorbent material
about 0.1-10% activated carbon added to the sodium bentonite as in
particles 102-108 and 114 of Fig. 1
about 0-9.9% additional active
Example 10
[00287] A composite particle includes:
about 90-99.5% sodium bentonite as the primary absorbent material
about 0.1-10% zeolite, crystalline silica, silica gel, activated alumina,
activated carbon, a superabsorbent polymer, and mixtures thereof added to the
sodium bentonite as in particles 102-108 and 114 of Fig. 1
about 0-9.9% additional active
Example 11
[00288] A composite particle includes:
about 10-70% core material selected from zeolite, crystalline silica,
silica gel, activated alumina, activated carbon, a superabsorbent
polymer, and mixtures thereof
about 30-90% sodium bentonite surrounding the core
about 0.1-10% activated carbon added to the sodium bentonite as in
particles 110-112 and 116 of Fig. 1
about 0-10% additional active
68
CA 02607676 2007-10-25
Example 12
[00289] A composite particle includes:
about 10-70% core material selected from zeolite, crystalline silica,
silica gel, activated alumina, activated carbon, a superabsorbent
polymer, and mixtures thereof
about 30-90% sodium bentonite surrounding the core
about 0.1-25% zeolite, crystalline silica, silica gel, activated alumina, a
superabsorbent polymer, and mixtures thereof added to the
sodium bentonite as in particles 110-112 and 116 of Fig. 1
about 0-10% additional active
Exam lpe13
[00290] A composite particle includes:
about 10-70% core formed from agglomerated particles
about 30-90% sodium bentonite surrounding the core
about 0.1-25% zeolite, crystalline silica, silica gel, activated alumina, a
superabsorbent polymer, and mixtures thereof added to the
sodium bentonite as in particles 110-112 and 116 of Fig. 1
about 0-10% additional active
Example 14
[00291] An absorbent composition of multiple composite particles, each
composite particle including:
optional 10-70% core
about 30-100% agglomerated absorbent material
about 0.1-10% active added to the absorbent material as in particles
102-116 of Fig. 1
about 0-10% additional active selected from an antimicrobial, an odor
reducing material, a binder, a fragrance, a health indicating
material, a color altering agent, a dust reducing agent, a
nonstick release agent, a superabsorbent material, cyclodextrin,
69
CA 02607676 2007-10-25
zeolite, activated carbon, a pH altering agent, a salt forming
material, a ricinoleate, silica gel, crystalline silica, and mixtures
thereof
where about 1-25% of the composite particles are colored for creating
"speckles" in the litter
Example 15
[00292] An absorbent composition of multiple composite particles admixed
with particles of sodium bentonite, including:
about 10-90% particles of swellable sodium bentonite clay particles,
-1.4mm-0.3mm (14x50 mesh), dried and crushed
about 10-90% composite particles, each composite particle including:
optional 10-70% core
about 30-100% agglomerated absorbent material
about 0.1-10% active added to the absorbent material as in
particles 102-116 of Fig. 1
about 0-10% additional active selected from an antimicrobial,
an odor reducing material, a binder, a fragrance, a
health indicating material, a color altering agent, a dust
reducing agent, a nonstick release agent, a
superabsorbent material, cyclodextrin, zeolite, activated
carbon, a pH altering agent, a salt forming material, a
ricinoleate, silica gel, crystalline silica, and mixtures
thereof
about 0-25% colored or white "speckles" in the litter (can be activated
alumina, colored composite particles, etc.)
[00293] The activated alumina itself may include an embedded coloring agent
that has been added during the fabrication of the activated alumina particles.
The
inventors have found that the odor absorbing properties of activated alumina
are not
significantly reduced due to the application of color altering agents thereto.
CA 02607676 2007-10-25
[00294] Additionally, activated alumina's natural white coloring makes it a
desirable choice as a white, painted or dyed "speckle" in litters. In
composite and
other particles, the activated alumina can also be added in an amount
sufficient to
lighten or otherwise alter the overall color of the particle or the overall
color of the
entire composition.
[00295] Compositions may also contain visible but ineffective colored speckles
for visual appeal. Examples of speckle material are salt crystals or gypsum
crystals.
Example 16
[00296] An absorbent composition of multiple composite particles admixed
with particles of sodium bentonite, including:
about 10-90% composite particles, each composite particle including:
optional 10-70% core
about 30-99.9% agglomerated absorbent material
about 0.1-10 /a active added to the absorbent material as in
particles 102-116 of Fig. 1
about 0-10 /a additional active selected from an antimicrobial,
an odor reducing material, a binder, a fragrance, a
health indicating material, a color altering agent, a dust
reducing agent, a nonstick release agent, a
superabsorbent material, cyclodextrin, zeolite, activated
carbon, a pH altering agent, a salt forming material, a
ricinoleate, silica gel, crystalline silica, and mixtures
thereof
about 0.01-50% particles of activated alumina dry mixed with the
composite particles. Preferably, the activated alumina is present
in the composition in an amount of about 0.01% to about 50%
of the composition by weight based on the total weight of the
absorbent composition. More preferably, the activated alumina
is present in the composition in an amount of about 0.1 % to
about 25% by weight.
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Example 17
[00297] An absorbent composition (clumpable or nonclumpable) with
improved odor control includes:
about 0.1-25.0% activated alumina and/or zeolite and/or silica particles
about 0-75% additives
to 100% composite particles as in particles 102-116 of Fig. 1
Example 18
[00298] An absorbent composition with antimicrobial benefit includes:
about 0.5-5.0% activated alumina and/or zeolite and/or silica particles
[odor control]
about 0.001-1.0% borax pentahydrate [antimicrobial]
about 0.001-10% fragrance
about 0-25% additional additives
to 100% composite particles as in particles 102-116 of Fig. 1
Example 19
[00299] A clumping absorbent composition with antimicrobial benefit includes:
about 2% colored activated alumina and/or zeolite and/or silica
particles, 1-2 mm (10x 18 mesh)
about 0.5% borax pentahydrate [antimicrobial]
about 0.71 % spray-dried fragrance - sprayed onto starch beads and
mixed in
about 96.79% composite particles as in particles 102-116 of Fig. 1,
-1.4mm-0.3mm (14x50 mesh), dried and crushed
Example 20
[00300] The following composition provides the benefit of improved odor
control throughout the litter due to the varying densities of zeolite,
activated, alumina,
and silica gel.
[00301] An absorbent composition that is either clumpable or nonclumpable
includes:
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about 0.001-25.0% zeolite particles
about 0.001-25.0% activated alumina particles
about 0.001-25.0% silica gel particles
about 0-50% additives
to 100% composite particles including sodium bentonite clay as in
particles 102-116 of Fig. 1
[00302] The zeolite is the heaviest of the three odor-absorbing materials,
alumina is in the middle, and silica gel is the lightest. Because of the
tendency of the
materials to segregate upon agitation such as a cat digging in the litterbox,
the zeolite,
being heavier, will tend to move towards the bottom of the litter, while the
lighter
silica gel will tend to migrate towards the top of the litter. Thus, the
litter will contain
odor controlling actives throughout. An additional benefit is that the silica
gel tends to
repel liquid running across it, malcing it the ideal material for the upper
layer of litter,
as it will not immediately become saturated by animal urine but will retain
its odor
absorbing properties.
[00303] Also, by adding a lighter material such silica (251bs/ft) or zeolite
(about 501bs/fft3), the overall weight per volume unit of the mixture is
reduced.
[00304] For clumping litter not relying on binders for clump strength, the
total
content of zeolite, activated alumina, and silica gel particles is preferably
less than
about 25% so that the clay provides satisfactory clumping performance.
Example 21
[00305] In a variation of Example 20:
An absorbent composition that is either clumpable or nonclumpable includes:
about 0.001-25.0% activated alumina particles
about 0.001-25.0% zeolite particles
about 0-50% additives
to 100% composite particles as in particles 102-116 of Fig. 1
Example 22
[00306] In a variation of Example 20:
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An absorbent composition that is either clumpable or nonclumpable includes:
about 0.001-25.0% zeolite particles
about 0.001-25.0% silica gel particles
about 0-50% additives
to 100% composite particles as in particles 102-116 of Fig. 1
Example 23
[00307] In a variation of Example 20:
An absorbent composition that is either clumpable or nonclumpable includes:
about 0.001-25.0% activated alumina particles
about 0.001-25.0% silica gel particles
about 0-50% additives
to 100% composite particles as in particles 102-116 of Fig. 1
Example 24
[00308] A flushable and clumping absorbent composition with improved odor
control includes:
about 0.1-25.0% activated alumina and/or zeolite and/or silica particles
about 0-75% additives
less than about 1% of a water soluble binding agent
to 100% composite particles as in particles 102-116 of Fig. 1
Example 25
[00309] A clumping absorbent composition with liquid retention and smaller
clump aspect ratio includes:
about 90-99.5% sodium bentonite having a mean particle size in the
range of about -100 to +200 mesh
about 0.5-10% SAP
about 0-75% additives
to 100% composite particles as in particles 102-116 of Fig. 1
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Example 26 - Experimental data of composite particles with SAP
[00310] In one set of experiments aimed at studying the surface stiffness and
clump characteristics of blends of SAP with sodium bentonite clay, SAP
agglomerated with sodium bentonite was compared to pure agglomerated sodium
bentonite and raw bentonite (not agglomerated).
[00311] During the procedure, synthetic urine ( l Oml of 1 M NH4C1) as liquid
was added to the agglomerate containing SAP (2% Hysorb 8400 SAP from BASF
Corporation, 98% sodium bentonite), agglomerated sodium bentonite, and plain
bentonite. In more detail, the procedure was as follows: 1) add lOm ml NH4CL
to the
litter and wait 30 seconds, 2) tare a 9 inch diam. circle of Whitman No. 1
filter paper
and drop the paper onto the wetted litter, 3) allow the filter paper to sit on
the litter for
30 seconds, then remove and weigh to calculate the amount of material
transferred to
the filter paper (stickiness), and 4) after 1 hour of setting time, measure
the clump
mass, clump depth, and calculate absorption as (mass liquid) /[(clump mass -
mass
liquid)].
[00312] Fig. 16 illustrates an interval plot 1600 of mass transferred (g) to
the
dropped filter paper vs. sample (surface stickiness). As shown, the sample
with SAP
clearly had more surface stickiness. The surface stickiness improves clump
strength.
Note that the SAP in the agglomerated particles had a smaller particle size
than the
agglomerate alone. Accordingly, some of the stickiness could be attributable
to the
smaller particulate size, as well as the SAP.
[00313] Fig. 17 illustrates an interval plot 1700 of clump mass (g) vs.
sample.
As shown, the clump mass of the SAP-containing particles was much less than
raw
bentonite or the agglomerated bentonite. This is believed to reflect less
material in the
clump, as well as lighter overall particles.
[00314] Fig. 18 illustrates an interval plot 1800 of clump depth (cm) vs.
sample. As shown, both agglomerates inhibit penetration, but the SAP-
containing
particle showed greater inhibition.
[00315] Fig. 19 illustrates an interval plot 1900 of liquid absorption (g/g)
vs.
sample as calculated by the formula above. As shown, the agglomerated
bentonite
sample absorbed about twice as much liquid as the plain bentonite sample,
while the
CA 02607676 2007-10-25
SAP-containing particle absorbed about three times as much liquid as the plain
bentonite sample.
Example 27
[00316] In a variation of particles from any example above, and/or formed of a
single material:
An absorbent composition that is either clumpable or nonclumpable includes:
about 5-95% first absorbent particles as in particles 1000-1034 of Fig.
10, and
about 5-95% second absorbent particles as in particles 1000-1034 of
Fig. 10, but having a different shape than the first absorbent particles.
Example 28
[00317] In a variation of Example 27:
An absorbent composition that is either clumpable or nonclumpable includes:
about 5-95% first absorbent particles as in particles 1000-1034 of Fig.
10, and
about 5-95% second absorbent particles as in particles 1000-1034 of
Fig. 10, having about the same shape as, or different shape than, the
first absorbent particles but a different bulk density.
Example 29
[00318] In a variation of Example 27:
An absorbent composition that is either clumpable or nonclumpable includes:
about 5-95% first absorbent particles as in particles 1000-1034 of Fig.
10, and
about 5-95% second absorbent particles as in particles 1000-1034 of
Fig. 10, having about the same shape as, or different shape than, the
first absorbent particles but a different maximum distal dimension
(e.g., length, diameter, width, height, etc.).
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Example 30
[00319] In a variation of Example 27:
An absorbent composition that is either clumpable or nonclumpable includes:
about 5-95% first absorbent particles as in particles 102-116 of Fig. 1,
and
about 5-95% second absorbent particles as in particles 1000-1034 of
Fig. 10.
[00320] While various embodiments have been described above, it should be
understood that they have been presented by way of example only, and not
limitation.
Thus, the breadth and scope of a preferred embodiment should not be limited by
any
of the above-described exemplary embodiments, but should be defined only in
accordance with the following claims and their equivalents.
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