Note: Descriptions are shown in the official language in which they were submitted.
CA 02546538 2006-05-10
,
COMPOSITION PARTICLE ANIMAL LITTER AND METHOD THEREOF
FIELD OF THE INVENTION
[0001] The present invention relates to composite particles useful as
animal litter
having improved clumping and odor-inhibiting properties.
RELATED ART
[0002] Clay has long been used as a liquid absorbent, and has found
particular
usefulness as an animal litter. 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)
(20-8 mesh) into the litter. US Patent 5,860,391 to Maxwell et al. discloses
the use of
activated carbon in cat litter.
[0003] 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
are reduced. What is needed is an absorbent material with improved odor-
controlling
properties, and that maintains such properties for longer periods of time.
SUMMARY OF THE INVENTION
[0004] An aspect of the invention includes a composite particle
comprising:
an agglomerated mixture of (1) a plurality of particles of at least one
absorbent clay
material and (2) a plurality of particles of at least one light-weighting
material, said
agglomerated mixture suitable for use as an animal litter; and optionally a
plurality of
particles of at least one performance-enhancing active incorporated into said
agglomerated mixture.
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[0004A] In a preferred aspect, the light-weighing material is selected
from the group
consisting of perlite, expanded perlite, volcanic ash, vermiculite, expanded
vermiculite,
silica gels, opaline silica, tuff, lightweight agricultural byproducts and
mixtures thereof.
More preferably, the light-weighing material is expanded perlite, expanded
vermiculite or a
mixture thereof, and has a bulk density of between 5-20 lb/ft3.
[0005] Another aspect of the invention includes an animal litter
comprising: the
aforementioned composite particle and a plurality of particles selected from
the group
consisting of a plurality of composite particles formed by agglomerating at
least one
absorbent clay material, a plurality of non-agglomerated particles of at least
one absorbent
clay material, or a mixture thereof.
[0006] A further aspect of the invention includes a method of forming a
composite
particle comprising: providing a plurality of particles of an absorbent clay
material; providing
a plurality of particles of a light-weighting material; agglomerating said
particles of absorbent
clay material together with said particles of light-weighting material to form
a plurality of
composite particles; and sieving said composite particles to meet a
predetermined particle
size distribution.
[0007] Another aspect of the invention includes a composite particle
comprising: an
agglomerated mixture of a plurality of particles of bentonite and a plurality
of particles
selected from the group consisting of expanded vermiculite, expanded perlite,
or a mixture
thereof, said agglomerated mixture suitable for use as an animal litter; and
optionally a
plurality of particles of at least one performance-enhancing active
incorporated into said
agglomerated mixture.
[0008] Another aspect of the invention includes a composite particle
comprising: an
agglomerated mixture of a plurality of particles of bentonite and a plurality
of particles
selected from the group consisting of expanded vermiculite, expanded perlite,
or a mixture
thereof, said agglomerated mixture suitable for use as an animal litter; and a
plurality of
particles of activated carbon incorporated into said composite particle.
[0009] A further aspect of the invention includes a composite particle
comprising: an
agglomerated mixture of (1) a plurality of particles of at least one absorbent
clay material and
(2) a plurality of particles of at least one light-weighting material, said
agglomerated mixture
suitable for use as an animal litter; and a plurality of particles of
activated carbon
incorporated into said composite particle.
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[0009A] Accordingly, in another aspect, the invention provides a plurality
of animal
litter composite particles comprising: a homogeneously agglomerated mixture of
(1) a
plurality of particles of naturally occurring sodium bentonite; (2) a
plurality of particles of at
least one light-weighting material, said agglomerated mixture suitable for use
as an animal
litter; and (3) a plurality of particles of powdered activated carbon (PAC)
incorporated into
said agglomerated mixture, wherein said agglomerated mixture is agglomerated
via a
tumble/growth pan agglomeration process and a secondary tumble/growth
agglomeration
process used in combination with the pan agglomeration process wherein the
secondary
tumble/growth agglomeration process is selected from the group consisting of a
pin mixer
process, a mix muller process, a rotary drum process, a batch tumble blending
mixer process,
a fluid bed process and combinations thereof; wherein the tumble/growth
agglomeration
processes form composite particles having a porous structure wherein at least
a portion of the
PAC is dispersed throughout the composite particle.
[0009B] More preferably, the particles of sodium bentonite range from 1 to
100
microns.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a fuller understanding of the nature and advantages of the
present
invention, reference should be made to the following detailed description read
in conjunction
with the accompanying drawings.
[0011] Figure 1 illustrates several configurations of agglomerated
composites
according to various embodiments of the present invention.
[0012] Figure 2 is a process diagram illustrating an exemplary pan
agglomeration
process for forming composites.
[0013] Figure 3 is a process diagram illustrating an exemplary
combination pin-
mixer/pan agglomeration process for forming composites.
[0014] Figure 4 is a process diagram illustrating an exemplary roll press
agglomeration process for forming composites.
[0015] Figure 5 is a process diagram illustrating an exemplary pin mixer
process for
forming composites.
[0016] Figure 6 is a process diagram illustrating an exemplary mix muller
process for
forming composites.
[0017] Figure 7 is an exemplary drawing of an embodiment of a composite
particle.
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[0018] Figure 8 is a graph illustrating the malodor ratings of
embodiments of the
present invention.
[0019] Figure 9 depicts disintegration of a composite absorbent particle
according to
an embodiment of the present invention.
[0020] DETAILED DESCRIPTION
[0021] Before describing the present invention in detail, it is to be
understood
that this invention is not limited to particularly exemplified systems or
process parameters
as such may, of course, vary. It is also to be understood that the terminology
used herein is
for the purpose of describing particular embodiments of the invention only,
and is not
intended to limit the scope of the invention in any manner.
[0022] It must be noted that, as used in this specification and the
appended claims, the
singular forms "a", "an" and "the" include plural referents unless the content
clearly dictates
otherwise. Thus, for example, reference to a "colorant agent" includes two or
more such
agents.
[0023] Unless defined otherwise, all technical and scientific terms used
herein
have the same meaning as commonly understood by one of ordinary skill in the
art to which
the invention pertains. Although a number of methods and materials similar or
equivalent to
those described herein can be used in the practice of the present invention,
the preferred
materials and methods are described herein.
[0024] All numbers expressing quantities of ingredients, constituents,
reaction
conditions, and so forth used in the specification and claims are to be
understood as being
modified in all instances by the term "about". Notwithstanding that the
numerical ranges
and parameters setting forth the broad scope of the subject matter presented
herein are
approximations, the numerical values set forth in the specific examples are
reported as
precisely as possible. All numerical values, however, inherently contain
certain errors
necessarily resulting from the standard deviation found in their respective
testing
measurements.
[0025] The following description includes embodiments presently
contemplated for carrying out the present invention. This description is made
for the
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CA 02546538 2006-05-10
,
o
purpose of illustrating the general principles of the present invention and is
not meant
to limit the inventive concepts claimed herein.
[0026] The present invention relates generally to composite particles,
hereinafter referred to as composites, with improved physical and chemical
properties
that are useful as an animal litter. The composites of the present invention
comprise a
mixture of particles of an absorbent material(s), preferably an absorbent clay
material(s), and particles of a light-weighting material(s). Light-weighting
as defined
herein means a material that causes a reduction in bulk density when compared
to the
bulk density of a comparably produced clay only material. Light-weighting
materials
may have other beneficial attributes in addition to providing for a decrease
in bulk
density. For example, as will be discussed in greater detail, composites
containing
expanded perlite stick less to the litter box when compared to their clay-only
counterparts. Optionally, performance-enhancing active(s) may be added to the
mixture. Performance-enhancing actives as defined herein mean any component
that
enhances the composite materials performance as an animal litter. Thus, light-
weighting materials are one form of performance-enhancing active.
[0027] By using various processes described herein, such composites 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, lower cost, etc. One of the many benefits
of the
technology disclosed herein is that the light-weighting material and/or the
performance-enhancing actives may be positioned throughout the animal litter
to
optimally react with target molecules. For example, an odor-controlling active
distributed correctly may react with odor-causing volatile substances such
that the
resulting odor control is achieved using surprisingly low levels of active
ingredient.
[0028] One method of forming an embodiment of the animal litter of the
present invention involves forming composites by agglomerating particles of an
absorbent material(s) along with particles of a light-weighting material(s)
and
optionally a performance enhancing active(s). A second method involves forming
two sets of composites by (1) agglomerating particles of an absorbent
material(s)
along with particles of a performance enhancing active(s) or by adding
particles of a
performance-enhancing active to the agglomerated absorbent material composites
and
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(2) agglomerating particles of an absorbent material(s) along with particles
of a light-
weighting material(s) and optionally a different performance enhancing
active(s) and
then blending the two composites to form a blended composite animal litter. A
third
method involves forming composites by agglomerating particles of an absorbent
material and a light-weighting material(s) and optionally a performance
enhancing
active(s) and blending the composites with either composites of an
agglomerated
absorbent material or blending the composites with a non-agglomerated
absorbent
material. The term "composite blend" will be used hereinafter to refer to
embodiments created using the above-mentioned second and third methods.
[0029] Specific embodiments of agglomeration processes will be set forth
in
more detail below. Generally, agglomeration processes involve adding particles
of
absorbent material(s) and particles of light-weighting material(s) and/or
performance-
enhancing actives to an agglomerator. A fluid, e.g., water, or binder is
usually added
to the particles in the agglomerator. During the agglomeration process, the
particles
combine or coalesce to form composites. Controlled, predetermined
agglomeration
parameters are used to manipulate physical properties of the composites such
as
particle size, porosity, etc. The composites are then dried (if necessary) and
collected.
[0030] Particles of one or more performance-enhancing active(s) may be
added to the composites or a portion of the composites in an amount effective
to
perform the desired functionality or provide the desired benefit. These
particles of
active(s) can be added during the agglomeration process so that the actives
are
incorporated by agglomeration into the composite itself, or can be added
during a later
processing step.
[0031] As absorbent clay(s) is a preferred absorbent material, much of
the
discussion will involve the use of absorbent clay(s). However, it should be
kept in
mind that other absorbent materials suitable for use as animal litter may be
used in
place of the absorbent clay(s) discussed herein.
[0032] Figure 1 shows several embodiments of the composites disclosed
herein. Note that in all embodiments illustrated the performance enhancing
active
component is optional. Referring to Figure 1:
[0033] 102 shows clay particles, light-weighting particles and
performance-
enhancing actives homogeneously dispersed throughout the composite.
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[0034] 104 shows clay particles and light-weighting particles
homogeneously
dispersed throughout the composite with performance-enhancing active particles
located on the outer edges or exposed surfaces of the composite.
[0035] 106 shows light-weighting particles concentrated in the center of
the
composite forming a "core" with clay particles and performance-enhancing
active
particles homogeneously dispersed throughout the rest of the composite
surrounding
the light-weighting particle cores.
[0036] 108 shows light-weighting particles concentrated in "cores"
throughout
the composite with clay particles and performance-enhancing active particles
homogeneously dispersed throughout the rest of the composite.
[0037] 110 shows light-weighting particles concentrated in the center of
the
composite forming a "core" with clay particles dispersed in a layer
surrounding the
light-weighting particle core and performance-enhancing active particles
located on
the outer edges of the composite.
[0038] 112 shows light-weighting particles concentrated in "cores"
throughout
the composite with clay particles dispersed throughout the rest of the
composite
surrounding the light-weighting "cores" and performance-enhancing active
particles
located on the outer edges of the composite.
[0039] 114 shows a blend of light-weighting particle/absorbent clay
particle
composites and performance-enhancing active particle/absorbent clay particle
composites.
[0040] Further embodiments (not shown) comprise any one or more of the
above-depicted composite embodiments blended with non-agglomerated absorbent
materials, preferably clay(s).
MATERIALS
[0041] As used herein particle size refers to sieve screen analysis by
standard
ASTM methodology (ASTM method D6913-04e1).
[0042] Many liquid-absorbing clay materials may be used without departing
from the scope of the present invention. Illustrative absorbent clay
materials include but are not limited to bentonites, attapulgite,
montmorillonite
diatomaceous earth, Georgia White clay, sepiolite, slate, pumice, tobermite,
marls,
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kaolinite, halloysite, smectite, hectorite, Fuller's earth, zeolites and
mixtures thereof.
Various embodiments of the present invention utilize clay materials having the
following mean particle diameters: about 5000 microns or less; about 3000
microns or
less; ranging from about 25 to about 150 microns.
[0043] In addition to liquid-absorbing clay materials, filler materials
such as
limestone, sand, calcite, dolomite, recycled waste materials, zeolites, and
gypsum can
also be incorporated with the clay materials to reduce the cost of the litter
without
significantly decreasing the material's performance as a litter.
[0044] Because clays are heavy, it may be desirable to reduce the weight
of
the composites to reduce shipping costs, reduce the amount of material needed
to fill
the same relative volume of the litter box, and to make the material easier
for
customers to carry. Exemplary light-weighting materials include but are not
limited
to perlite, expanded perlite, volcanic glassy materials having high porosities
and low
densities, vermiculite, expanded vermiculite, pumice, silica gels, opaline
silica, tuff,
and lightweight agricultural byproducts. When selecting a light-weighting
material,
the effect the light-weighting material will have on the litter's performance
is an
important consideration. Factors to evaluate include how the light-weighting
material
will effect cost, ease of manufacture, clumping, tracking, absorbency, odor
control,
sticking to the box, dust, etc. In some cases, the light-weighting materials
may also
be performance-enhancing.
[0045] One embodiment disclosed herein utilizes expanded perlite having a
bulk density of 5 lb/ft3. Expanded perlites having bulk densities greater than
5 lb/ft3
may also be used. Perlite is a generic term for a naturally occurring
siliceous rock.
The distinguishing feature which sets perlite apart from other volcanic
glasses is that
when heated to a suitable point in its softening range, it expands from four
to twenty
times its original volume. This expansion is due to the presence of two to six
percent
combined water in the crude perlite rock. Firing, i.e., quickly heating to
above 1600 F
(871 C), causes the crude rock to pop in a manner similar to popcorn yielding
a very
open, highly porous structure referred to as expanded perlite. Once the
perlite is
expanded, it can then be gently crushed to form materials having varying
structural
properties. The perlite can be obtained either expanded or unexpanded and the
firing
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step can be performed on site prior to agglomeration. Significant cost savings
in
shipping can result from expanding the perlite on site.
[0046] A particular source of perlite is Kansas Minerals. Perlite
obtained
from Kansas Minerals is believed to be somewhat physically unique after being
popped. It is expected that hollow spheres are formed during the firing
process,
however, when the Kansas Minerals material is examined under a microscope, it
appears as though only a portion of the material comprises hollow spheres. The
other
portion comprises broken spheres. Without being bound by any particular
theory, it is
possible that the wall thickness of the expanded perlite spheres initially
formed
through the firing process are very thin and thus, tend to break apart.
Whatever the
cause of this physical property, it is believed to result in a material that
is particularly
well suited for use in the agglomeration processes of the present invention.
The
combination of approximately 50/50 hollow spheres to broken spheres has been
observed to perform particularly well.
[0047] Another suitable, expandable mineral similar to perlite is
vermiculite.
In all examples containing expanded perlite, expanded vermiculite could be
substituted for the perlite with similar results expected.
[0048] Various embodiments of the present invention utilize light-
weighting
materials having the following mean particle diameters: about 1500 microns or
less;
about 500 microns or less; ranging from about 1 to about 100 microns.
[0049] Using the above lightweight materials, a bulk density reduction of
10-
50% can be achieved relative to generally solid particles of the absorbent
clay
material (e.g., as mined). For example, composites in which sodium bentonite
(Black
Hills Bentonite, Mills, Wyoming) is the absorbent clay material (bulk density
67
lb/ft3), using about 17% of expanded perlite, e.g., Kamco 5, (Kansas Minerals,
Mancato, Kansas) having a bulk density of 5 lb/ft3 results in up to a 53% bulk
density
reduction. Using roughlyl 3% of the 51b/ft3 expanded perlite results in about
a 43%
reduction in bulk density. Using roughly 5% of the 51b/ft3 expanded perlite
results in
about a 37% reduction in bulk density.
[0050] In addition to the light-weighting material chosen, the bulk
density of
the composites can be adjusted by manipulating the agglomeration process to
increase
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or decrease pore size within the particle. Agglomeration parameters will be
discussed
in more detail below.
[0051] Heavyweight materials may be added to the light-weighted composite
when it is desirable to have heavier particles. Heavy particles may be useful,
for
example, when the particles are used in an outdoor 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
materials include but are not limited to sand, iron filings, etc.
[0052] 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. One great advantage of the particles of the present
invention is that
substantially every composite particle contains active, or in the case of a
composite
blend, the actives are substantially distributed throughout the final product.
[0053] Antimicrobial actives include boron containing compounds such as
borax pentahydrate, borax decahydrate, boric acid, polyborate, tetraboric
acid, sodium
metaborate anhydrous, boron components of polymers, and mixtures thereof.
[0054] 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. Zinc chloride, zinc
gluconate,
zinc lactate, zinc maleate, zinc salicylate, zinc sulfate, zinc ricinoleate,
copper
chloride, copper gluconate, and mixtures thereof are particularly effective.
Other odor
control actives include metal oxide nanoparticles. Additional types of odor
absorbing/inhibiting actives include cyclodextrin, zeolites, activated carbon,
acidic,
salt-forming materials, and mixtures thereof.
[0055] Embodiments where the odor absorbing/inhibiting active is Powdered
Activated Carbon (PAC), though Granular Activated Carbon (GAC) can also be
used,
are disclosed herein. PAC gives more exposed surface than GAC (e.g., > 80 mesh
U.S. Standard Sieve (U.S.S.S.)), and thus has more exposed sites with which to
trap
odor-causing materials and is therefore more effective. PAC will tend to
segregate
out of the litter during shipping, thereby creating excessive dust (also known
as
"sifting"). By agglomerating PAC into the composites (or adding the PAC to the
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_ mmt, 1 4. 41,4H446.4181.11*
=
CA 02546538 2006-05-10
, = ,
=
composites by a later processing step), the problems with carbon settling out
during
shipping is overcome. Additionally, carbon is black in color. Agglomerating
the
PAC (and/or GAC) into the composite (or adding it to the composites by a later
processing step) aids in diluting the black color of the carbon, a factor
known to be
disliked by cat litter consumers. The above-mentioned benefits of
incorporating
carbon into the composites are true for composite blends, as well. Generally,
the
mean particle diameter of the carbon particles used is less than about 500
microns, but
can be larger. One embodiment utilizes PAC having a particle size about 150
microns
(-400 mesh U.S.S.S.) or less. Another embodiment utilizes PAC having a
particle
size 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.
[0056] The active may be calcium bentonite added to reduce
sticking to a litter
box.
[0057] 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
different polyols such as glycerin, polyvinyl alcohol, lignin, and
hydroxyethylcellulose.
[0058] Dedusting agents can also be added to the particles
in order to reduce
the dust level. Many of the binders 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 gums, resins, water, and other liquid or
liquefiable materials.
[0059] A dye or pigment such as a dye, bleach, lightener,
etc. may be added to
vary the color of absorbent particles, such as to lighten the color of litter
so it is more
appealing.
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,
[0060] Superabsorbent materials can be used as a performance-enhancing
active. Suitable superabsorbent materials include superabsorbent polymers such
as
AN905SH, FA920SH, and F04490SH, all from Floerger. Preferably, the
superabsorbent material can absorb at least 5 times its weight of water, and
ideally
more than 10 times its weight of water.
[0061] The binding of actives directly to the surface of the pores of the
composites, even in extremely low levels, leads to the following benefits:
1. the use of extremely small particle sizes (e.g., for example ranging
from nanoparticles to 200 microns) of the active material results in a
very high surface area of active while using a very small amount of
active,
2. encapsulation of actives prior to attachment to the porous surfaces of
the composites can provide a slow release mechanism such that the
actives are in a useful form for a longer period of time,
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.
[0062] Granular activated carbon (GAC) (20-8 mesh) has been introduced
into
litter materials. However, the GAC is usually dry blended with the litter,
making the
litter undesirably dusty. Other methods mix GAC and clay and compress the
mixture
into particles. In either case, the GAC concentration must typically be 1% by
weight
or higher to show discernable effects. GAC 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 absent in others.
[0063] Surprisingly, low levels of PAC (0.05-5%) have been found to
provide
excellent odor control in cat litter when they are bound to the porous
surfaces of a
sodium bentonite clay/expanded perlite composite material. For example,
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agglomerating small amounts of PAC particles to sodium bentonite/expanded
perlite
composites using water as binder results in litter materials with superior
odor
adsorbing performance. In this configuration, 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 within the
porous
surfaces of the composites. Alternatively, xanthan gum, acrylic polymer,
natural and
synthetic polymers, fibrillatable PTFE, or other binders known to those in the
art
could be used in place of water as the binder.
METHODS OF CREATING COMPOSITES AND COMPOSITE BLENDS
[0064] Methods for creating the composites and composite blends disclosed
herein include, without limitation, a pan agglomeration process, a high shear
agglomeration process, a low shear agglomeration process, a high pressure
agglomeration process, a low pressure agglomeration process, a rotary drum
agglomeration process, a mix muller process, a roll press compaction process,
a pin
mixer process, a batch tumble blending mixer process, an extrusion process and
fluid
bed processes. All of these are within the definition of "agglomeration"
according to
the invention.
[0065] Extrusion processes typically involve introducing a solid and a
liquid
to form 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
Engineering,
pp. 1-5 (2002), and Brodbeck et al., U.S. Patent 5,269,962, especially col.
18, lines
30-61 thereof. 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.
[0066] The agglomeration process in combination with the materials used
allows the manufacturer to control the physical properties of particles, such
as bulk
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density, dust, strength, as well as particle size distribution (PSD) without
changing the
fundamental composition and properties of the component particles.
[0067] Generally, clay particles (e.g., bentonite powder) are mixed with
the
light-weighting particles (e.g., expanded perlite) to form a dry mixture,
which is
stored in a hopper or feeder. The mixture is fed with optional wetting from
the
hopper into an agglomerating apparatus. Alternatively, the clay particles and
light-
weighting particles may be fed individually from separate hoppers. The
particles of
active (e.g., PAC) may optionally be dry blended with either the clay or light-
weighting particles or added to the mixture at this time. Alternatively, the
particles of
active can be stored in another hopper, from which they are fed into the
agglomerator.
Water and/or binder is sprayed onto the particles in the agglomerating
apparatus via
sprayers to raise/maintain the moisture content of the particles at a desired
level so
that they stick together. Some clays, e.g., bentonite, act as its own binder
when
wetted, causing it to coalesce, so additional binder may not be necessary if
the
percentage of bentonite used is high enough. Liquid actives or solid actives
physically suspended in a slurry can be added by a sprayer.
[0068] Depending on the agglomeration parameters chosen, the composites
tumble off upon reaching a certain size. At this point, i.e., prior to drying,
if a drying
step is employed, the particles typically have a high enough moisture content
that they
are malleable and can be formed into any desired shape. If the composites are
substantially spherical in shape when they leave the agglomerator, such as
with pan
agglomeration, molding, compaction, or other processes known in the art, can
transform them into non-spherical shapes such as, for example, ovals,
flattened
spheres, hexagons, triangles, squares, etc. and combinations thereof. The
composites
are then dried, if necessary, to a desired moisture level by any suitable
mechanism,
such as a rotary or fluid bed drier.
[0069] In one embodiment, the moisture content of the composites is less
than
about 15% by weight, generally in the range of 8-13% by weight. At the outlet
of the
dryer, the particles are screened with sieves or other suitable mechanism to
separate
out the particles of the desired size range. In another embodiment, e.g., roll
pressing,
no drying is necessary, but the agglomerates are fed into a grinder after the
agglomerator to form composites of suitable size which are then screened as
described
Docket No.: 430.202 The
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,
above. In one embodiment, the selected particle size range is about 10 mm to
about
100 microns. In another embodiment, the size range is about 2.5 mm to about
100
microns. Preferred particle sizes for use as animal litter are in 12 x 40 mesh
(1650-
400 microns) range. The exhaust from the dryer is sent to a baghouse for dust
collection.
[0070] Alternatively, the performance-enhancing active can be physically
dispersed along pores of an agglomerated composite 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.
[0071] Additional actives such as borax and fragrance can be added to the
particles at any point in the process before, during and/or after
agglomeration. Also,
additional/different actives can be dry blended with the particles.
Pan Agglomeration
[0072] 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.
[0073] 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 agglomeration 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. A more detailed description
of the
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benefits of the pan agglomeration process is contained in pending US
Application
Serial No. 10/618,401 filed July 11, 2003 and owned by the same assignee.
[0074] Figure 2 is a process diagram illustrating an exemplary pan
agglomeration process 200 for forming composites. As shown, clay particles,
optionally active particles, light-weighting particles 204 are fed to a pan
agglomerator
206. Water is sprayed onto the particles via a sprayer 208 in the
agglomerator. The
agglomerated composites are then dried in a dryer 210 and sorted by size in a
sieve
screen system 212. One draw back to the pan agglomeration, is that the light-
weighting material tends to blow away when first added to the pan resulting in
a need
to use more starting material than theoretically calculated. One way of
alleviating this
problem is to "protect" the light-weighting material by first blending it with
a small
amount of heavier clay material. This can be accomplished in a variety of ways
including any kind of mixing apparatus, e.g., a pin mixer.
Pin/pan agglomeration
[0075] Figure 3 is a process diagram illustrating a combination pin/pan
agglomeration process 300 for forming composites. Clay particles, light-
weighting
particles and active are fed to a pin mixer 302. The pin/pan process enables
the light-
weighting material to first be blended with the absorbent clay material in
order to
"weigh down" the light-weighting material by forming small "dedusted particle
mixtures" which are then fed into a pan agglomerator 304 where they are
agglomerated and dried in a dryer 306. It should be noted that almost any kind
of
mixing apparatus could be used in place of the pin mixer. The dry unsieved
agglomerates are sorted in a screener 308 to produce composites in the desired
size
range. The pin mixer upstream from the pan minimizes dust issues that are
often
encountered when feeding dry powders to a pan agglomerator exclusively. The
pin/pan agglomeration process creates composites that are highly porous and
have a
relatively narrow particle size distribution. The process has a large capacity
per unit
operation and is relatively easy to scale up.
Roll-press
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CA 02546538 2006-05-10
=
[0076] Figure 4 is a process diagram illustrating an exemplary roll press
process 400 for forming composites. Clay particles, light-weighting particles
and
optionally active(s) are fed to a roll press 402 and agglomerated through
applied
external forces in dies. The agglomerated composites travel through a flake
breaker
404 which grinds them to form smaller-sized composites. The composites are
then
sized with a sieve screen 406. The roll-press requires little to no water
addition and
therefore no drying is necessary which significantly reduces operating costs.
The
process is stable, robust and can be automated.
Pin-mixer
[0077] Figure 5 is a process diagram illustrating an exemplary pin mixer
process 500 for forming composites. Clay particles, light-weighting particles
and
optionally active(s) are fed to a pin mixer 502. Water and optional binders
are also
sprayed into the mixer; the random particle dynamics in the mixer allow for
both
mixing and agglomeration of the particles into composites. The agglomerated
composites are then dried in a dryer 504 and sorted by size in a sieve screen
system
506. The pin-mixer uses less moisture that the pan or pin/pan combination, has
a
large capacity per unit of operation, and automated control is possible.
Mix-muller
[0078] Figure 6 is a process diagram illustrating an exemplary mix muller
process 600 for forming composites. The various components including clay
particles, light-weighting particles and optionally active(s) 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 with some pressure applied
but
typically not as much as with a roll press. 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.
MATERIAL PROPERTIES AND TESTING METHODS
[0079] Figure 7 depicts the structure of an illustrative agglomerated
composite
particle 700 formed during the process of Figure 2. As shown, the particle
includes
clay material(s) 702, light-weighting material(s) 704 and performance-
enhancing
active 706. Illustrative composites after drying have a specific weight of
from about
Docket No.: 430.202 The
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,
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. In one embodiment
of the
present invention, the composites absorb about 50% or more of their weight in
moisture. In another embodiment of the present invention, the composites
absorb
about 75% or more of their weight in moisture. In a further embodiment of the
present invention, the composites absorb greater than approximately 80% of
their
weight in moisture. In another embodiment of the present invention, the
composites
absorb about 90% or more of their weight in moisture.
[0080] Examples of materials that can be fed to the agglomerator using
the
processes of Figures 2-6 include:
= 0-100% Bentonite Powder & 0-5% PAC
= 85-99% Bentonite Powder, 1-15% Expanded Perlite, & 0-5% PAC
= 45-90% Bentonite Powder, 10-55% Mounds Clay, & 0-5% PAC
= 75-90% Bentonite Powder, 10-25% Georgia White Clay (GWC), &
0-5% PAC
= 60-70% Bentonite Powder, 30-40% Sand, & 0-5% PAC
= 70-80% Bentonite Powder, 20-30% Zeolite, & 0-5% PAC
[0081] Table 1 lists illustrative properties for various compositions of
bentonite-based agglomerated composites. In all cases the balance of material
is
bentonite clay.
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kµ ,,
Tablel
Percentage Percentage Moisture Agglomeration Bulk % Bulk
Expanded PAC Addition Process Density Density
Perlite to Feed (1b/ft3) Reduction
(wt%)
0 0.54 0 Roll Press 61 10
2000 psi
0 0.54 10 High shear 47 31
mixer
0.51 15 High shear 37 46
mixer
' 14 0.51 15 High shear 31 54
mixer
14 0.46 10 Roll Press 57 16
300 psi
28 0.39 9 Roll Press 50 26
200 psi
42 0.31 13 Roll Press 43 37
100 psi
14.4 0.54 45 Pin/Pan 31 54
combination
17.1 0.54 50 Pin/Pan 32 53
combination
13.4 0.54 40 Pin/Pan 41 40
combination
13.4 0.54 40 Pin/Pan 39 43
combination
13.4 0.54 40 Pin/Pan 41 40
combination
13.4 0.54 33 Pin/Pan 35 49
combination
13.4 0.1 35 Pin/Pan 38 44
combination
13.4 0.1 35 Pin/Pan 37 46
combination
13.4 None 40 Pin/Pan 39 43
combination
Clump Strength
[0082] 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 Y2"
screen after a predetermined amount of time (e.g., 6 hours) has passed since
the
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a
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 weigh 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.
Malodor Rating
[0083] The composites disclosed herein provide meaningful benefits,
particularly when used as an animal 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 composites in the context of animal
litter, it
being understood that the concepts described therein apply to all embodiments
of the
composites.
[0084] 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)
[0085] Odor control actives that can be utilized to achieve these
benefits
include but are not limited to powdered activated carbon, granular activated
carbon,
silica powder (Type C), borax pentahydrate, and bentonite powder.
[0086] Because of the unique processing of the composites of the present
invention, lower levels of active are required to effectively control odors.
In the case
of carbon, the effective amount present is 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.
This lower
amount of carbon significantly lowers the cost for the particles, as carbon is
very
expensive compared to clay. The amount of carbon required to be effective is
further
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,
reduced because the agglomeration process incorporates the carbon into each
particle,
using it more effectively. In the case of composite blends, carbon is present
in
substantially every other particle or every third particle (depending on the
composition of the blend). Figure 8 illustrates the malodor ratings for the
animal litter
compositions contained in Table 2 below. Two separate sessions were conducted
to
evaluate each sample. The sessions were averaged and the results plotted
graphically
in Figure 8. The percent attrition is a measure of granule strength. It is
directionally
indicative of porosity, whereby the higher the percent attrition, the higher
the porosity
and the lower the percent attrition, the lower the porosity. All samples
comprise pan
agglomerated sodium bentonite.
Table 2
Sample PAC Attrition Bulk Density Moisture
(wt.%) (wt.%) (g/cc) Content
(wt.%)
A 0 27.8 0.79 10.6
0 4.8 0.86 10.7
IC 0.15 26.8 0.79 10.6
ID 0.15 4.5 0.86 10.9
0.3 25.0 0.80 10.8
IF 0.3 4.36 0.87 10.5
20 0.15 4.8 0.86 10.7
21.1 0.3 4.8 0.86 10.7
'PAC dispersed throughout the composite
2PAC located on outer perimeter of composite
[0087] In summary, composites containing PAC have a malodor rating
ranging from 11-27, whereas the control that does not contain carbon has a
rating of
ranging from about 40-45, as determined by a Malodor Sensory Method.
[0088] Figure 9 illustrates that even the addition of small
percentages of PAC
have a profound effect on odor control. Table 3 lists the litter compositions
plotted in
Figure 9(2 reps of each sample were evaluated and averaged).
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Table 3
Sample Composition Notes
Bulk Density Expanded Perlite PAC
(1b/ft3) (wt.%) (wt.%)
A 67 0 0 50%
agglomerated bentonite
blended with 50% non-
agglomerate bentonite
48 4 0.5 pan agglomerated
composite
59 1.28 0.2 32% Sample B blended with
68% Sample A
63 0.6 0.1 15% Sample B blended with
68% Sample A
[0089] 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 positioned 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.
[0090] The agglomerated mixture of clay plus a light-weighting material
containing activated carbon exhibit noticeably less odor after four days from
contamination with animal waste as compared to agglomerated particles of clay
alone
or blends of agglomerated particles of clay and non-agglomerated particles of
clay
under substantially similar conditions.
Sticking Data
[0091] An active may be added to reduce or even prevent sticking of the
litter
to the litter box. Table 4 shows that samples light-weighted with expanded
perlite
exhibit less sticking than comparably prepared samples of bentonite clay or
bentonite/Georgia White clay combinations. Expanded vermiculite is expected to
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have a similar anti-sticking effect to expanded perlite. Other 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).
[0092] 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 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.
Table 4
Sample Removal Composition
Force
Bentonite GWC Ex. Perlite
(units)
(wt.%) (wt.%) (wt.%)
A 2.32 100 0 0
0.91 78 22 0
0.86 95 0 5
0.48 87 0 13
0.52 83 0 17
Hydraulic Conductivity
[0093] The agglomerated composites 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
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2. Manometer
3. Stop watch
4. 250m1 graduated cylinder
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
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
Flow Rate
K= Hydraulic Conductivity
A= Cross Sectional Area
L= Bed Length
Ha-Hb= Differential Pressure
[0094] 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
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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 materials and processes
disclosed
herein allows litter particles to be engineered so urine only penetrates about
1/2 inch
into a mass of the particles.
[0095] Agglomerated composites according to the present invention also
exhibit interesting clumping action. The composites exhibit extraordinary
clump
strength with less sticking to the box, especially in composites containing
bentonite,
perlite 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.
[0096] 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
composites "falling apart" and releasing their bentonite particles to reorder
themselves, and this 'reordering' produces a stronger clump. This "reordering"
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
composites described herein should not be limited to clumping or scoopable
particles
as those properties tend to depend on the type of absorbent clay particles
chosen.
[0097] As mentioned above, the composites have particular application for
use
as an animal litter. The litter would then be added to a receptacle (e.g.,
lifterbox) with
a closed bottom, a plurality of interconnected generally upright side walls
forming an
open top and defining an inside surface. However, the particles should not be
limited
to animal litters, but rather could be applied to a number of other
applications such as:
= 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
sprinlded over or as an amendment to the litter box.
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,
= 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. Composites 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 composites can be dry mixed with
other
types of particles, including but not limited to other types of composites,
extruded particles, particles formed by crushing a source material, etc.
Mixing
composites with other types of particles provides the benefits provided by the
composites while allowing use of lower cost materials, such as crushed or
extruded bentonite. Illustrative ratios of composites 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 composites 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.
= Mixtures of Composites with Actives¨ The composites can be dry mixed with
actives, including but not limited to particles of activated carbon.
[0098] While various embodiments have been described above, it should be
understood that they have been presented by way of example only, and not
limitation.
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=
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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