Note: Descriptions are shown in the official language in which they were submitted.
CA 02588492 2007-05-10
CLUMPING ANIMAL LITTER
BY INVENTORS: Kimberly A. Petska, Charles F. Fritter, Bradley L. Kirsch, Marc
P.
Privitera, Roger V. Lee and Christina M. Borgese.
Related Application
This application claims priority to U.S. Provisional Application No.
60/805,007, filed on June 16, 2006.
Field of the Invention
[0001] This invention relates generally to clumping animal litter, and, more
specifically, to clumping animal litter containing reinforcing fibers.
[0002] The invention is directed generally to the addition of reinforcing
fibers to
animal litter and, more specifically, to the addition of reinforcing fibers to
individual
composite particles of absorbent animal litter materials and methods of
forming the
same.
Description of the Related Art
[0003] Because of the growing number of domestic animals used as household
pets,
there is a need for litters so that animals may void, or otherwise eliminate
liquid or
solid waste indoors in a controlled location. However, waste buildup
eventually leads
to malodor production. In order to reduce or eliminate these odors, pet owners
may
periodically remove soiled material from the litter. The physical removal of
the fecal
matter does not eliminate all odors since bacteria can decompose urine that is
left
behind and produce foul odors. Litters have subsequently been developed that
allow
the user to scoop portions of litter that have absorbed the urine, thus
removing one of
the primary sources of odor. However, clumping litters that break,
disintegrate, create
dust, or crumble, are consumer dissatisfiers.
[0004] Clumping aids and other litter additives primarily geared towards
improving
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odor control, have been disclosed. Although it is desired that these additives
enhance
the animal litter, they have a number of drawbacks including, stickiness,
segregation,
dust, density, and costliness.
[0005] Accordingly, there is a need for improved processes and materials for
adding
additional benefits to animal litter materials such as increased odor control
without
introducing the aforementioned drawbacks.
Summary of the Invention
[0006] In accordance with one aspect of the present invention a clumping
animal litter
comprising a plurality of composite particles is provided. Each composite
particle
contains a percentage of an absorbent material suitable for use as an animal
litter and
a percentage of a reinforcing fiber material. Optionally, a clumping agent may
be
added dependent upon the absorbent material chosen.
100071 Exemplary fibers include natural materials, e.g., wool, cotton, hemp,
rayon,
paper, paper fluff, cellulose (including hardwood fibers, softwood fibers,
processed
pulp fibers, rice straw fibers, corn stover fibers, gyouli stick fibers, wheat
straw fibers,
starch fibers including various modified and extracted starch fibers), carbon,
avian
feathers, activated carbon and synthetic materials, e.g., polyester, nylon,
plastics,
polymers, copolymers, polypropylene, polyethylene, sodium polyacrylate,
polyvinyl
acetate. Combination fibers such as SAP (super absorbent polymer)/pulp fiber
(about
400 m) or SAP charged non-woven fibers can also be incorporated into the
composite particles.
[0008] Reinforcing fiber attributes include the size, shape and activity of
the fibers.
Examples of fibers having beneficial shapes include bicomponent sheath core,
bicomponent side by side, crimped fibers, bicomponent islands in the sea
fibers.
Examples of bicomponent fibers include fibers made of both polyethylene and
polyester, or polyethylene and polypropylene. Nanofibers (i.e., fibers having
at least
one dimension in the nanometer size range) include those made through
electrospinning techniques and bicomponent spitting techniques. Examples of
active
fibers include those with antimicrobial efficacy, water absorbing or (mass
binding)
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and absorption rate efficacy, fragran ce control release efficacy, and odor
absorbing
efficacy.
[0009] In accordance with a further aspect of the present invention a clumping
animal
litter comprising a plurality of composite particles is provided. Each
composite
particle contains a percentage of an absorbent material suitable for use as a
clumping
animal litter, a percentage of reinforcing fiber material and a percentage of
performance-enhancing active. Exemplary actives include antimicrobials, odor
absorbers/inhibitors, light-weighting agents, binders (liquid/solid, silicate,
ligninsulfonate, etc.), fragrances, health indicating materials, nonstick
release agents,
clumping agents, low cost filler material and combinations thereof.
[0010] In accordance with another aspect of the present invention a method of
forming a plurality of composite particles suitable for use as an animal
litter is
provided. An agglomeration process is employed to form a plurality of
composite
particles such that each composite particle contains a percentage of an
absorbent
material suitable for use as an animal litter, a percentage of a reinforcing
fiber
material and optionally a percentage of a performance-enhancing active.
Additionally
the method can further comprise the step of screening the composite particles
to a
specific particle size range.
[0011] Further features and advantages of the present invention will become
apparent
to those of ordinary skill in the art in view of the detailed description of
preferred
embodiments below, when considered together with the claims.
Brief Description of the Drawin2s
[0012] Figure 1 is a plot of the values listed in Table IV.
[0013] Figure 2 is a photograph (18x magnification) of an agglomerated
composite
particle containing sodium bentonite clay and 15% paper fluff fiber.
[0014] Figure 3 is an illustration of composite particle having a core.
[0015] Figures 4a and 4b are illustrations of composite particles.
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Detailed Description
[0016] 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 and
is not
intended to limit the scope of the invention.
[0017] All publications, patents and patent applications cited herein, whether
supra or
infra, are hereby incorporated by reference in their entirety to the same
extent as if
each individual publication, patent or patent application was specifically and
individually indicated to be incorporated by reference.
[0018] 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 an "odor controlling
agent"
includes two or more such agents.
[0019] 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.
[0020] 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.
Definitions
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[0021] As is generally accepted by those of ordinary skill in the animal
litter art, the
following terms have the following meanings.
[0022] As used herein particle size refers to sieve screen analysis by
standard ASTM
methodology (ASTM method D6913-04e1).
[0023] As used herein, the terms "scoopable" and "clumping litter" refer to a
litter
that agglomerates upon wetting such that the soiled portion can be removed
from the
litter box leaving the unsoiled portion available for reuse.
[0024] The terms "non-clumping" or "poorly clumping" as used herein refers to
a
litter material that doesn't agglomerate upon wetting to the extent that the
soiled
portion could be easily removed from the litter box. As will be discussed in
further
detail below, additives may be added to a non-clumping or poorly clumping
litter
substrate to create clumping behavior that is satisfactory to the end user.
[0025] As used herein the term "composite particle" means a particle formed by
combining smaller discrete particles of either the same composition or
different
compositions such that the resulting particle, i.e., the "composite particle",
is a
particle having structural integrity that is of a particle size bigger than
that of its
component parts. The composite particles useful for animal litter can range in
particle
size between about 150 m and about 5mm and are typically between about 350 m
and about 3 mm.
[0026] As used herein the term "composite blend" refers to a dry mixing of the
composite particles of the present invention and one or more additional
absorbent
litter materials and/or other litter additives or the dry mixing of composite
particles
having different compositions, and/or combinations thereof.
[0027] As used herein the terms "litter additives" or "other materials
suitable for use
as litter additives" refer to performance-enhancing actives as described
herein as well
as other additives known to be used in litter compositions by those having
ordinary
skill in the art.
[0028] As used herein the term "absorbent material suitable for use as an
animal
CA 02588492 2007-05-10
litter" refers to the many liquid-absorbing materials and combinations thereof
disclosed herein as well as any other liquid-absorbing materials or
combinations
thereof known to those having ordinary skill in the art. The absorbent
particles may
range in particle size from about 150 m to about 5mm (4-100 mesh). Absorbent
particles 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.
[0029] As used herein the term "absorbent material suitable for use as a
clumping
animal litter" refers to a liquid-absorbing material having an inherent
ability to clump
(i.e., form an agglomerate, such as sodium bentonite) when wetted or to a
liquid-
absorbing material having little to no inherent ability to clump that has been
combined
with a clumping agent.
[0030] As used herein the term "clumping agent" refers to additives, such as
starch or
sugar based binders that can be added to inherently non-clumping or poorly-
clumping
absorbent materials to create a litter material that behaves like a clumping
absorbent
material (i.e., upon contact with liquid, readily agglomerates with other
moistened
clay particles). For example, US Patent 5,359,961 discloses a clumping, non-
swelling
clay based litter and is hereby incorporated by reference in its entirety.
Clumping
agents as used herein are one form of performance-enhancing active.
[0031] As used herein the term "aspect ratio" when referring to a litter clump
means
the square root of (the square of the longest clump length plus the square of
the
shortest clump length) divided by the clump height. The term "aspect ratio"
when
referring to the reinforcing fiber materials means the length of the fiber
divided by the
width of the fiber.
[0032] As used herein the term "reinforcing fiber material(s)" (hereinafter
"fiber(s)")
means 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
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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).
[0033] The fibers may be incorporated in the composite particles in a variety
of
configurations such as in a layer on the surface of a particle, evenly
(homogeneously)
throughout the particle, in a concentric layer(s) throughout the particle
and/or around
a core, in pockets or pores in and/or around a particle, in a particle with
single or
multiple cores. A plurality of composite particles in any combination of the
above
configurations may be combined to form a litter material. Processes and
embodiments describing the incorporation of performance-enhancing actives into
a
composite absorbent particle that are described in pending US Patent
Application
Serial No. 10/618,401 filed July 11, 2003, which is hereby incorporated by
reference
in its entirety, can be employed for the incorporation of fibers into the
composite
particle of the present invention.
[0034] As used herein the term "performance-enhancing active" refers to a
material
that when present causes the litter composition to exhibit specific
characteristics
including but not limited to improved odor control, lower density (light-
weighting
agents), easier scooping, better particle/active consistency, higher clump
strength,
lower cost, etc. Illustrative materials for the performance-enhancing
active(s) include
but are not limited to antimicrobials, odor absorbers, odor inhibitors,
binders,
fragrances, health indicating materials, nonstick release agents,
superabsorbent
materials, light-weighting minerals, filler materials and combinations
thereof.
Performance-enhancing actives may comprise between 0-50% of the litter
composition. In some cases where the performance-enhancing active is a
particularly
strong substance, it may be present in only about 0.001 %
[0035] As used herein the term "activated carbon" means absorbent carbon-based
materials, including activated and reactivated carbon-based absorbents.
Activated
carbon, including the material commonly called activated charcoal, is an
amorphous
fonm of carbon characterized by high adsorptivity for many gases, vapors and
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colloidal solids. Carbon is generally obtained by the destructive distillation
of coal,
wood, nut-shells, animal bones or other carbonaceous materials, including
coconuts.
The carbon is typically "activated" or reactivated by heating to about 800-900
C,
with steam or carbon dioxide, which results in a porous internal structure.
The internal
surfaces of activated carbon typically average about 10,000 square feet per
gram.
Surface area in absorptive carbons is typically measured by a test called BET-
Nitrogen, and measures the extent of the pore surfaces within the matrix of
the
activated carbon. BET- Nitrogen is used as a primary indicator of the activity
level of
the carbon, based on the principle that the greater the surface area, the
higher the
number of adsorptive sites available. It is believed that carbons having a BET
number
greater than 500 will provide odor control equivalent to PAC at concentration
levels
equal to or less than those disclosed herein as effective for PAC.
[0036] As used herein the term "filler materials" refer 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.
[0037] The following description includes 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.
[0038] The present invention relates generally to composite particles with
improved
physical and chemical properties. The composite particles of the present
invention
comprise an absorbent material suitable for use as an animal litter, a
reinforcing fiber
material and optionally a performance-enhancing active. One of the many
benefits of
this technology is that the composite particles of the present invention can
exhibit the
beneficial properties of one or more performance-enhancing actives while
surprisingly retaining the clump strength and absorption properties of the
underlying
absorbent material.
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[0039] Methods for creating the composite particles of absorbent material,
fibers and
optional performance-enhancing active 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 rotary drum
agglomeration process having an O'Brien Cage installed, 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. Suitable
agglomeration
techniques are discussed in pending US Patent Application Serial No.
10/618,401
filed July 11, 2003 and Serial No. 11/119204 filed April 29, 2005, which are
hereby
incorporated by reference in their entirety.
[0040] The term "non-compaction" agglomeration process refers to agglomeration
that takes place under ambient or substantially ambient conditions. Examples
of non-
compaction agglomeration processes include a pan agglomeration process, a
rotary
drum agglomeration process, a rotary drum agglomeration process having an
OBrien
Cage installed, a mix muller process, a pin mixer process, a batch tumble
blending
mixer process, and fluid bed processes.
[0041] Composite particles prepared using a non-compaction agglomeration
process
show a reduction in bulk density of at least about 10%. This reduction is
attributed
simply to the agglomeration process itself. For example, the bulk density of
raw
sodium bentonite is approximately 64-671b/ft3. The reduction in bulk density
of
sodium bentonite agglomerated using a pan agglomerator, a pin mixer or a
rotary
drum agglomeration process (including a rotary drum agglomeration process
having
an O'Brien Cage installed) ranges from about 8-17% (i.e., approximately 53-61
lb/ft). It has been observed that pores, cavities and/or air pockets are
created in each
composite particle that is created through the use of the non-compaction
agglomeration process.
[0042] One great advantage of the animal litter of the present invention is
that a
variety of performance-enhancing actives can be added without sacrificing the
clump
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strength or absorptive ability of the resulting litter composition. One reason
for this
benefit is that composite particles are made such that substantially every
composite
particle contains fibers, or in the case of a composite blend, the fibers are
substantially
distributed throughout the litter composition. 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.
[0043] The fibers can be added to the absorbent material matrix to impart a
variety of
benefits to the resulting composite animal litter material. For example, the
addition of
fibers increase the absorptivity and/or the structural integrity of the clumps
formed
when the material is wetted. By analogy, and without being bound by any
particular
theory, it is believed that the fibers behave in a manner similar to the
reinforcing bars
(i.e., rebar) used in a concrete matrix to form reinforced concrete.
[0044] Another theory is that fractions of the fibers actually protrude
through the
surface of the composite particles. These fractions may effect the chemical
and/or
physical interactions of the composite particles with each other. Without
being bound
by any particular theory, it is postulated that the fiber fractions may
intertwine with
each other in a manner that enhances clumping. By analogy, the intertwining of
the
fiber fractions at the composite particle surfaces appears to have an effect
similar to
that of Velcro balls.
[0045] A further observed benefit of having fibers in the composite particles
is that
the light-weight fiber materials actually decrease the bulk density of the
final product
to a degree greater than what was expected. For example, agglomerating 10%
paper
fluff fibers with sodium bentonite clay was found to reduce the bulk density
by 57%.
[0046] Another observed benefit of having fibers in the composite particles is
their
effect on clump appearance. The clumps formed with composite particles
containing
CA 02588492 2007-05-10
fibers appear smoother, drier and closer in color to unwetted portions of the
litter
material. This attribute is important to the end user because a smoother,
drier clump
will be: (1) less apt to break apart during the removal process, (2) less apt
to stick to
the scoop, the box, or the animal; (3) more apt to lock in odors; (4) less apt
to hurt
paws or be tracked out of the litter box; (5) more apt to give the end user a
better
visual indication of when the clump is structurally ready for removal. Wet
clumps
tend to break apart so dry clumps that look wet do not give a good indication
of
readiness. In contrast, dry clumps that also appear dry, provide a visual que
to the end
user.
[0047] Composite particles containing fibers tend to have less attrition (the
tendency
to disintegrate, particularly during transport/shipment) and form more
hemispherical
(round in shape) waste clumps compared to composite particles without fibers.
The
hemispherical clumps tend to be stronger and better at encapsulating odor.
Materials
Absorbent
[0048] Illustrative absorbent materials suitable for use as an animal litter
that have an
inherent ability to clump when wetted include but are not limited to
"swelling" clays
such as sodium smectite, sodium montmorillonite (aka sodium bentonite or
Wyoming
bentonite), beidellite, and hectorite.
[0049] Absorbent materials having little to no inherent ability to clump
generally
require the aid of a clumping agent to form a clumping litter material.
Illustrative
examples include non-swelling or poorly-swelling clays such as calcium
smectite,
calcium montmorillonite (aka calcium bentonite or Georgia White Clay),
attapulgite
(aka palygorskite), sepiolite, natural zeolite, synthetic zeolite, kaolinite,
tobermorite,
vermiculite, halloysite, illite, and mica; absorbent rocks such as perlite,
volcanic ash,
expanded perlite, pumice, diatomite (aka diatomaceous earth), tuff, opaline
silica,
slate, marls, and fossilized plant material; natural minerals such as opal
(aka
amorphous silica), silica, quartz (aka sand), calcite, dolomite, gypsum,
bassenite (aka
plaster of Paris), aragonite, and feldspar; synthetic minerals such as
dicalcium silicate
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and amorphous silicas (e.g., silica gel, precipitated silica, fumed silica,
silica aerogel)
and aluminas (e.g., amorphous alumina, activated alumina, activated bauxite,
gibbsite,
bauxite, boehmite, pseudoboehmite). As used herein the terms "non swelling
clays"
and "poorly swelling clays" are synonymous.
[0050] Other absorbent materials having little to no inherent ability to clump
include
straw, sawdust, wood chips, wood shavings, porous polymeric beads, shredded
paper,
bark, cloth, ground corn husks, cellulose, water-insoluble inorganic salts,
such as
calcium sulfate, and sand.
Fibers
[0051] 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
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).
[0052] 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 or synthetic materials,
e.g., polyester,
nylon, plastics, polymers (including super absorbent polymers (SAPs) and
copolymers). 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.
[0053] 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
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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) could be combined with an absorbent clay
to
form composite particles having increased absorptivity. The resulting litter
compositions would have the advantage of controlling odors and moisture as
strong
clumps are formed.
[0054] Benefits imparted by the fibers (either alone or in combination with
performance-enhancing actives) may include without limitation, structural
integrity,
clump strength, increased liquid absorption, abrasion resistance, animal
attractant/repellant, visual aesthetics, tactile aesthetics 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.
[0055] 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 it's 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.
[0056] 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
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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.
[0057] 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.
[0058] 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
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).
[0059] 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.
[0060] 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
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interlocking with the barbules of an adjacent barb to link the barbs into a
continuous
vane.
[0061] 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.
[0062] 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.
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.
[0063] 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.
[0064] 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.
[0065] Processing conditions also contribute to fiber length. When made from
the
CA 02588492 2007-05-10
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.
[0066] Illustrative performance-enhancing actives include but are not limited
to
antimicrobials, odor absorbers/inhibitors, binding agents (aka clumping
agents),
fixing agents, fragrances, health indicating materials, nonstick release
agents, super
absorbent materials (e.g., super absorbent polymers), and combinations
thereof. The
composite particles of the present invention can be formed such that
substantially
every composite particle contains a percentage of performance-enhancing
active. In
the case of a composite blend, the performance-enhancing actives are
substantially
distributed throughout the resulting litter composition.
Antimicrobial
[0067] Antimicrobials and/or urease inhibitors are performance-enhancing
actives
that act as odor control agents by preventing the causes of the odor, such as
inhibiting
the bacteria that create the odors. One class of anti-bacterial or odor
control agents is
water soluble transition metal ions and their soluble salts such as silver,
copper, zinc,
iron, and aluminum salts and mixtures thereof. Examples of metallic salts
include zinc
chloride, zinc gluconate, zinc lactate, zinc maleate, zinc salicylate, zinc
sulfate, zinc
ricinoleate, copper chloride, copper gluconate, and combinations thereof.
Preferred
transition metals include silver, copper, zinc, ferric and aluminum salts.
[0068] Other odor control anti-bacterial agents include sulfuric acid,
phosphoric acid,
hydroxamic acid, thiourea, iodophores, 3-isothiazolones, salts of phytic acid,
plant
extracts, pine oil, naturally occurring acids and antimicrobials, such as
quatemary
ammonium compounds, organic sulfur compounds, halogenated phenols,
hexachlorophene, 2,4,4'-trichloro-2'-hydroxydiphenyl ether,
trichiorocarbanalide,
2,4-dichloro-meta-xylenol, 3,4,5- tribromosalicylanalide, 3,5,3', 4'-
tetrachlorosalicylanalide, and combinations thereof. Some of these odor
control anti-
16
CA 02588492 2007-05-10
bacterial agents can be added to litters to function as bacteriostats, ie.,
they are present
in relatively low amounts to ensure lack of or minimalodor by transiently
present
bacteria which may act on the unused litter ingredients to produce off-odors
or signal
to the consumer that the product is "not fresh." Some of the preferred
bacteriostats
include a number of materials produced by Rohm and Haas under the brand name
Kathon.
[0069] A particularly effective class of bacteriostats are boron compounds,
including
borax pentahydrate, borax decahydrate and boric acid. Polyborate, tetraboric
acid,
sodium metaborate and other forms of boron are also appropriate alternative
materials. Other boron-based compounds potentially suitable for use are
disclosed in
Kirk-Othmer, Encyclopedia of Chemical Technology, 3ra Ed., Vol. 4, pp. 67-109
(1978), which is incorporated by reference herein. Effective borax compounds
are
disclosed in US Patent 5,992,351, which is incorporated herein by reference in
its
entirety.
[0070] Applicants have found that borax provides multiple benefits in odor
control
by: (1) acting as a urease inhibitor, which controls odors by preventing
enzymatic
breakdown of urea; and (2) exhibiting bacteriostatic properties, which appear
to help
control odor by controlling the growth of bacteria which are responsible for
production of the urease enzymes. Applicants have further found that an odor
controlling effective amount comprises at least about 0.02% equivalent boron.
Greater
than 0.03% equivalent boron is preferred.
100711 In some embodiments, the anti-bacterial agent comprises approximately
0.02% - 1%, by weight, of the litter composition and typically the anti-
bacterial agent
comprises approximately 0.02% - 0.15%, by weight, of the litter composition.
As will
be appreciated by one skilled in the art, the compositional levels can be
adjusted to
ensure effective odor control and cost effectiveness.
Light Weighting
[0072] Exemplary light-weighting materials include but are not limited to
perlite,
expanded perlite, volcanic glassy materials having high porosities and low
densities,
17
CA 02588492 2007-05-10
vermiculite, expanded vermiculite, pumice, silica gels, opaline silica, tuff,
and
lightweight agricultural byproducts. As used herein the term "expanded
perlite" is
synonymous with the term "volcanic ash". 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. Light-weighting actives can be incorporated
within the
composite particles of the present invention or they may be dry blended with
the
composite particles of the present invention. Incorporation of light-weighting
actives
into composite particles is extensively described in US Patent Application
Serial
Number 11/119,204 filed Apri129, 2005, which is hereby incorporated by
reference
in its entirety.
Odor Absorber
[0073] The performance-enhancing active may be one or more odor controlling
agents in the form of odor absorbing agents, such as activated carbon, which
provide
an odor control benefit by preventing the odors from being detected, such as
absorbing, encasing, or neutralizing the odor. Compounds that absorb primary
amines
are particularly desirable. Other odor control actives include nanoparticles
that may
be composed of many different materials such as carbon, metals, metal halides
or
oxides, or other materials. Additional types of odor absorbing/inhibiting
actives
include fragrant oils, carbonates, bicarbonates, kieselguhr, chelating agents,
chitin and
pH buffered materials, such as carboxylic acids and the like, cyclodextrin,
zeolites,
silicas, acidic salt-forming materials, and mixtures thereof. Activated
alumina (A12O3)
has been found to provide odor control comparable and even superior to other
odor
control additives. Alumina is a white granular material, and is properly
called
aluminum oxide.
[0074] Powdered Activated Carbon (PAC) and Granular Activated Carbon (GAC) are
effective odor absorbing materials. 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
18
CA 02588492 2007-05-10
to segregate out of the litter during shipping, thereby creating excessive
dust (also
known as "sifting"). By agglomerating PAC into the composite particles of the
present invention (or adding the PAC to the composite particles 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 particles (or adding it to the composite particles 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
composite particles 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
(-100 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. 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. However, PAC may be present in
concentrations ranging from 0-50%, but typically would not be expected to
exceed
20%. The incorporation of PAC into composite particles is described in
previously
cited US Patent Application Serial Number 11/119,204 filed April 29, 2005.
Fragrance
[0075] The performance-enhancing active may comprise one or more fragrances to
provide a freshness or deodorizing impression to humans or serve as an
attractant.
fragrance to animals. Although some "free" fragrance can be present, it is
preferable
that at least a major part of the fragrance (or perfume) be contained or
encapsulated in
a carrier to prevent premature loss to the atmosphere, as well as to avoid a
strong
fragrance odor which can be uncomfortable to the animals. The encapsulation
can be
in the form of molecular encapsulation, such as the inclusion complex with
cyclodextrin, coacevate microencapsulation wherein the fragrance droplet is
enclosed
in a solid wall material, or "cellular matrix" encapsulation wherein solid
particles
containing perfume droplets are stably held in the cells. Incorporating the
fragrance
in the composite particle is one method of encapsulation. The fragrance can
also be
19
CA 02588492 2007-05-10
more crudely embedded in a matrix, such as a starch or sugar matrix.
[0076] The encapsulated fragrance can be released either by a moisture
activation
and/or a pressure activation mechanism. Moisture-activated microcapsules
release
fragrance upon being wetted, e.g., by the animal urine. Pressure-activated
microcapsules release fragrance when the shell wall is broken, e.g., by the
scratching
or stepping of the animals on the litter. Some microcapsules can be activated
both by
moisture and pressure.
100771 Alternatively, the fragrance can be a pro-fragrance. A pro-fragrance is
a
normally nonvolatile molecule which consists of a volatile fragrance
ingredient
covalently bonded to another moiety by a labile covalent bond. In use, the pro-
fragrance is decomposed to release the volatile fragrance ingredient.
Preferred pro-
fragrances include complexes of bisulfite, with fragrance ingredients having
aldehyde
or ketone functional groups, and esters of phosphoric acids, and sulfuric
acids with
fragrance ingredients having a hydroxyl group.
[0078] The fragrance may comprise approximately 0.001% - 1%, by weight, of the
litter composition, and typically comprises approximately approximately 0.01
1% -
0.2%by weight, of the litter composition.
Binding Agent
[0079] Illustrative examples of binder agents which can be incorporated in the
composite particles or added to the litter composition are 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 and
combinations
thereof. 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. The binding agents can function as clumping agents as
CA 02588492 2007-05-10
described in US5,359,961 cited above and U.S. Patent Application Publication
Number US 2004/0025798 filed August 7, 2002, which is hereby incorporated by
reference in its entirety.
FixingAgent
[0080] A fixing agent or combination of fixing agents may be used in
conjunction
with a binding agent to keep the binding agent adhered to the composite
particles or
particles in a composite blend. Fixing agents help eliminate segregation
(which can
decrease clump strength) during agitation such as when the litter composition
is
shipped from one location to another. Suitable agents include (i) natural
polymers
and synthetic derivatives thereof, including, but not limited to, lignins,
gums, starches
and polysaccharides, such as lignin sulfonate, carboxymethylcellulose,
hydroxyethylcellulose, hydroxypropylcellulose, ethylhydroxyethyl cellulose,
methylhydroxypropylcellulose, guar gum, alginates, starch, xanthan gum, gum
acacia,
and gum Arabic, (ii) synthetic polymers, including, but not limited to,
polyvinylpyrrolidone, polyethylene glycol, polyethyleneoxide, acrylate
polymers and
copolymers, acrylic emulsions, polyvinyl alcohol, polyvinyl acetate, polyvinyl
pyrrolidine, polyacrylic acid, latexes (e.g., neoprene latex), superabsorbent
polymers
(e.g., cross-linked polyacrylates), flocculating agents (e.g.,
polycarboxylates), and
fluori nated polymers (e.g., polytetrafluoroethylene), fibrillated Teflon, and
(iii)
inorganic agglomerating agents, including, but not limited to, soluble
silicates and
phosphates, including pyrophosphates and aluminates. Acrylic polymers or co-
polymers from Rhodia, BASF and other emulsion polymer vendors may be used.
[0081] The amount of the fixing agent present in the litter composition
varies. The
fixing agent is water-soluble and generally comprises up to approximately 6%,
by
weight, of the litter composition. Typically, the fixing agent comprises less
than
approximately 2%, by weight, of the litter composition.
[0082] Suitable fixing agents which also serve to control dust include, but
are not
limited to fluorinated polymers such as Teflon and tacky acrylic polymers such
as
those sold as Rhodopas or Rhoplex .
21
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Non-Stick
[0083] Suitable nonstick additives include surfactants, polymers, Teflon,
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 primary absorbent material 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
primary absorbent material.
Health Indicating
[0084] Suitable health indicating actives may also be added to the litter
compositions
disclosed herein. One such additive is a pH indicator that changes color when
urinated upon, thereby indicating a health issue with the animal. US Patent
No.
6,308,658, incorporated herein by reference in its entirety, describes a
litmus agent
that visually indicates the presence of a urinary infection in animals.
Another
additive, disclosed in US Patent Application Serial No. 11/140,795, filed May
31,
2005 detects the presence of protein in urine which is indicative of a health
problem
in the animal.
Moisture Absorbing Polymers
[0085] 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.
Colorant
[0086] A dye or pigment such as a dye, bleach, lightener, etc. may be added to
vary
the color of composite particles, such as to lighten the color of the litter
composition
so it is more appealing to the end user.
Filler
22
CA 02588492 2007-05-10
[0087] Filler materials can be combined with the composite particles to reduce
the
cost of the animal litter composition without significantly decreasing the
material's
performance as a litter. Filler materials are one form of performance-
enhancing
active as they tend to reduce the cost of the litter composition. Illustrative
filler
materials include limestone, sand, calcite, dolomite, recycled waste
materials,
zeolites, perlite, expanded perlite, vermiculite, expanded vermiculite,
diatomaceous
earth, gypsum and combinations thereof. Although these materials could be
included as part of the composite particles themselves, they are typically
incorporated
into the animal litter by dry blending with the composite particles to form a
composite
blend. Filler materials may comprise anywhere from 1-50% of the litter
composition.
Examples
[0088] 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.
[0089] Fibers were added to a sodium bentonite clay litter material to access
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.
[0090] Cat urine was obtained from several cats so it is not cat specific.
Experiment 1
[0091] 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
23
CA 02588492 2007-05-10
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.
[0092] Table I summarizes the average size, shape and strength of the clumps.
Table I
Sample Avg. Longest Avg. Shortest Avg. Height Aspect Ratio Avg. Clump
Length (mm) Length (mm) (mm) Strength
(% retained)
k fibers (12 x 40) 67.1 63.2 11.65 7. 97.60A
% fibers (6 x 40) 68.33 61.23 15.55 5. 97.8 /
% fibers (12 x 40) 63.34 59.7 12.13 7_ 96.30
% fibers (6 x 40) 66.81 58.8 18.44 4. 96.80
6% fibers (12 x 40) 64 61.33 11.35 7. 95.8 /
6% fibers (6 x 40) 68.4 54.75 15.25 5.7 97.79
Table II
Sample Avg. Longest Avg. Shortest Avg. Height Aspect Ratio Avg. Clump
Length (mm) Length (mm) (mm) Strength
(% retained)
0% fibers (12 x 40) single dose 48.33 46.67 17.67 3.8 95.10 /
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
% fibers (12 x 40) single dose 44.5 44 17 3.7 94.50 /
% fibers (12 x 40) double dose 4 45 19 3.5
% fibers (6 x 40) single dose 46 44.33 20 3.2 94.10 /
% fibers (6 x 40) double dose 69.33 5 22 4.1
% fibers (12 x 40) single dose 59.33 54.68 16.67 4.8 94.300
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%
Experiment 2
[00931 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
24
CA 02588492 2007-05-10
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.
[0094] 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 t/Z inch) mesh screen, shaken on a machine using lateral
rotating
action (about 5 lateral revolutions per second) for about 5 seconds and
weighed. The
clump strength y, is reported as Percent Retained, i.e., final weight /
initial weight 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.
[0095] Table II 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
[0096] Cellulose fibers were added to sodium bentonite clay (about 100-500
mesh)
and powder activated carbon (about 25-150 m) 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
CA 02588492 2007-05-10
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.
[0097] Table III 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.
[0098] 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
551b/ft3.
Thus, the addition of cellulose fibers into the composite particle provides a
beneficial
light-weighting effect. Table IV lists the bulk density reduction observed
with the
addition of 2, 5, 10 and 15 percent paper fluff fibers. Figure 1 is a plot of
the values
listed in Table IV. Figure 2 is a photograph at 18 times magnification of
composite
particles containing sodium bentonite and 15% paper fluff fibers.
Table III
Sample (balance is bentonite) Dose Type Avg. Avg. vg. Heigh Avg. Avg. Avg.
Longest Shortest (inches) Aspect Clump Clump
Length Length Ratio Absorben Strength
(inches) (inches)
% Paper % PAC % Expanded (%Retained)
fluff Perlite
15 0.5 Singl 1.4 1.4 1.2 1.7 1.2 86 /
15 0.5 Doubl 1.8 1. 1.2 2.2 1.48
0.5 Singl 1.6 1. 1 2.1 0.87 96.40 /
5 0.5 Doubl 2.3 2.3 0. 3. 0.8
0.5 4 Singl 2.3 1.7 0.5 5.7 1.56 98.50 /
0.5 4 Doubl 2. 1.8 0.5 6.8 1.48
26
CA 02588492 2007-05-10
Table IV
% Paper Bulk Bulk
fluff fibers Density Density
(lb/ft3) Reduction
2 3 35%
2 47%
2 53%
1 67%
Table V
Sample Dose Avg. Avg. Shortest Avg. Height Avg. Aspect Avg. Clump Avg. Clump
Type Longest Length (inches) Ratio Absorbency Strength
Length (inches) (% Retained)
(inches)
Raw bentonite Single 44.6 43.2 25.8 2.41 0.44 94.1
Raw bentonite Double 70.5 54.3 26.6 3.35 0.44
omposite Particles, Single 47 41.3 21.5 2.91 0.97 96.7
100% bentonite
omposite Particles, Double 67.8 55.7 18.9 4.65 0.9
100% bentonite
oniposite Particles, Single 53.1 36.6 15.9 4.06 1.5 97.6
98% bentonite,
% paper fluff
omposite Particles, Double 65.5 48.5 16.3 5.01 1.5
98% bentonite,
2% a er fluff
Experiment 4
[0099] 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
27
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additional 1 hour (double dosed). Table V summarizes the average size, shape,
strength and absorbency of the three samples.
[00100] 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.
[00101] 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
the fiber, thus allowing strength in tension.
[00102] 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.
[00103] 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
28
CA 02588492 2007-05-10
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.
Agglomerated litter with a swelling core
[00104] A plurality of agglomerated animal litter particles comprising a
swelling core and clumping agent coating surface is described. Fibers as
described
above can be used as the cores. The core:coating ratio might range between 0.5
and
2. Referring to Figure 3, the core 32 of the agglomerate particle 30 comprises
primarily a swelling material (at least 60%) such as fibers preferably paper
and or
wood fibers, Na-bentonite, organic compounds like corn, rice, hay, straw, char
etc...
Core 32, with a particle size distribution that can range from 0.05 to 3 mm,
might
contain, in addition to swelling materials, a filling mineral and or a binder.
The
coating surface 34 comprises primarily a clumping bentonite, e.g., Na-
bentonite. In
addition, other minerals (e.g., kaolinite, zeolite etc...), binders along with
activated
carbon and boron compounds and coloring agents can be added to the coating.
[00105] A plurality of light weight particles suitable for use as an animal
litter
comprising a core and a coating are formed. The coating process is intended to
encapsulate granulated or particulated materials in order to improve the
quality of the
litter. The process can be any suitable process, however, processes already
familiar to
those of ordinary skill in the animal litter manufacturing art are
particularly suitable.
[00106] In one embodiment, the core comprises at least 60% the composite
particle and may include, fibers, Na-bentonite, hay, straw, corn, wood, rice,
starch,
super absorbent polymers, char etc. The coating is a Na-bentonite clay or
other
suitable clumping clay-based material, e.g., Ca-bentonite and a clumping
agent.
Optionally, activated carbon, boron compounds, binders, colorants and other
minerals
such as zeolite, kaolinite and Ca-carbonate might be added to the coating as
well as to
the core.
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CA 02588492 2007-05-10
[00107] Benefits of this light weight composite particle include bulk density
reduction (BDR), clump shape and strength, granules shape, attrition and
particle size
homogeneity. Specifically, the composite particles could provide from 30 to
60%
BDR, which would drastically reduce shipping costs and make transportation of
the
litter product easier for consumers.
[00108] In addition, utilizing composite particles allows a more convenient
way
to incorporate other additives and provides a more homogeneous distribution of
such
additives (e.g., carbon and boron compounds). Thereby, maximizing the
efficiency of
the performance-enhancing actives' performance while minimizing the quantity
of
performance-enhancing active necessary.
Conglomerated Ca/Na Bentonite
[00109] A two-part agglomerated clay particle is described: a granular light
weight non-swelling material and a cementing/clumping agent such as Na-
bentonite.
The non-swelling particles (e.g., Ca-bentonite) are aggregated in the form of
agglomerates by mixing with a clumping agent such as powdered Na-bentonite.
The
particle size distribution for the non-swelling granules ranges from about 25
to 40
mesh, whereas that of the cementing clumping agent ranges between about 200 to
325
mesh. Light weight granules would decrease the bulk density of the
agglomerated
particles while the Na-bentonite would give the particles a clumping behavior.
The
light weight granules serve as a skeleton to the newly formed composite
particles
while the clumping agent serves as cement. The amount of the non-swelling
particles
can range from 0 to 75%, while the clumping agent can vary from 20 to 80%.
Optionally, a clumping agent such as starch, polyvinyl acetates, polyacrylates
can be
added to reinforce the cementing bentonite.
[00110] Sodium bentonite expands when wet and absorbs several times its dry
weight in water. The property of swelling makes sodium bentonite an excellent
clumping agent. On the other hand, Ca-bentonite is a non-swelling clay unless
other
additives or chemicals are added. The ionic surface of bentonite has a useful
property
in making a sticky coating on minerals (e.g., sand) or other hard grains. For
example,
CA 02588492 2007-05-10
when a small proportion of finely ground bentonite clay is added to hard sand
particles and wetted, the clay binds these particles into a moldable aggregate
known
as "green sand" which is used for making molds in sand casting. Some river
deltas
naturally deposit "green sand".
[00111] Referring to Figure 4a, small cementing particles 40, e.g., Na-
bentonite
powder, can stick larger absorbent particles 42, e.g., Ca-bentonite,
diatomites, lignite,
shale, etc. to each other and generate a plurality of multi-particle
agglomerates 44
(Figure 4b) made up with several Ca-bentonite granules cemented to each other
with
Na-bentonite. Na-bentonite and Ca-bentonite have similar properties as they
belong to
the smectites group, plus the roughness of the Ca-bentonite provides a good
substrate
for Na-bentonite to stick to. It should be understood that present invention
is not
limited to Ca-bentonite but encompasses any material that can stick to the Na-
bentonite and provide light weight liquid-absorbing particles, including
kaolinite,
volcanic ash, perlite, zeolite, silica gels, lignite, shale, diatomites and
organic
materials.
[00112] Pre-wetting of Ca-bentonite or other non-swelling absorbent material
prior to blending with Na-bentonite would increase its volume and therefore
decrease
the density of the resulting composite particle even more.
[00113] In one embodiment, a pin mixer is used to agglomerate both the Ca-
bentonite and Na-bentonite at the same time. This allows one or more
performance -
enhancing actives such as PAC and borax to be concentrated ate the on the
surface of
the resulting composite particle where they are expected to produce optimal
odor
control.
[00114] In another embodiment, a pin mixer is used to make a clay/paper-based
litter. Recycled paper granules (50%) were coated with a mixture of bentonite
powder (40-47%), kaolinite powder (2-5%), activated carbon (0-1%) and boric
acid
(0-1%). The bulk density ranges from about 0.60-0.70 g/cc, which is about a 30-
40%
reduction from traditional clay-based clumping animal litter. The mass of the
coating
is about one times the weight of the core.
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CA 02588492 2007-05-10
[00115] In another embodiment, wood flour, e.g., that obtained form American
Wood Fibers, Schofield, Wisconsin, can be combined with the bentonite powder
during the agglomeration. The wood flour would both lighten the particles and
provide a natural means of ammonia control. Wood flour contains natural pine
oil
anti-microbials which help control anunonia. Wood flour is also a source of
natural
fragrance.
[00116] Without departing from the spirit and scope of this invention, one of
ordinary skill can make various changes and modifications to the invention to
adapt it
to various usages and conditions. As such, these changes and modifications are
properly, equitably, and intended to be, within the full range of equivalence
of the
following claims.
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