U.S. patent application number 12/032450 was filed with the patent office on 2008-08-07 for composite absorbent particles.
This patent application is currently assigned to THE CLOROX COMPANY. Invention is credited to Charles Fritter, Ananth N. Shenoy.
Application Number | 20080184939 12/032450 |
Document ID | / |
Family ID | 35503611 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080184939 |
Kind Code |
A1 |
Fritter; Charles ; et
al. |
August 7, 2008 |
Composite Absorbent Particles
Abstract
Composite particles and methods for making the same. An
absorbent material is formed into a particle. An optional
performance-enhancing active is coupled to the absorbent material
before, during, or after the particle-forming process,
homogeneously and/or in layers. Additionally, the composite
absorbent particle may include a core material. Preferred methods
for creating the absorbent particles include 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 a fluid bed process.
Inventors: |
Fritter; Charles; (Oakland,
CA) ; Shenoy; Ananth N.; (Oakland, CA) |
Correspondence
Address: |
MICHAEL J. MAZZA, ESQ.;THE CLOROX COMPANY
P.O. BOX 24305
OAKLAND
CA
94623-1305
US
|
Assignee: |
THE CLOROX COMPANY
|
Family ID: |
35503611 |
Appl. No.: |
12/032450 |
Filed: |
February 15, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10861044 |
Jun 4, 2004 |
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12032450 |
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10618401 |
Jul 11, 2003 |
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10861044 |
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10773585 |
Feb 6, 2004 |
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10618401 |
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Current U.S.
Class: |
119/173 |
Current CPC
Class: |
B01J 20/12 20130101;
B01J 20/28016 20130101; A01K 1/0152 20130101; A01K 1/0155 20130101;
B01J 20/3295 20130101; A01K 1/0154 20130101; B01J 20/2803 20130101;
B01J 20/324 20130101; B01J 20/3204 20130101; B01J 20/28023
20130101; B01J 20/20 20130101; B01J 20/28004 20130101 |
Class at
Publication: |
119/173 |
International
Class: |
A01K 29/00 20060101
A01K029/00 |
Claims
1. A plurality of porous composite particles suitable for use as an
animal litter formed by: the process comprising: agglomerating
bentonite and powder activated carbon (PAC) into a plurality of
bentonite-based porous composite particles suitable for use as an
animal litter, wherein the PAC is present in 0.1-1%, at least a
portion of the PAC is encapsulated within the pores of the
composite particle, and the agglomeration is accomplished using a
pan agglomerator, a pin mixer or a Pelligrini mixer/Muller
agglomerator.
2. The plurality of porous composite particles formed by the
process recited in claim 1, wherein the PAC is present in 0.5%.
3. The plurality of porous composite particles formed by the
process recited in claim 1 having a malodor rating less than 15 as
determined by the Malodor Sensory Method.
4. The plurality of porous composite particles formed by the
process recited in claim 1 having a malodor rating between 10 and
15 as determined by the Malodor Sensory Method.
5. The plurality of porous composite particles formed by the
process recited in claim 1 having a hydraulic conductivity value of
0.25 cm/s or less.
6. The plurality of porous composite particles formed by the
process recited in claim 1, wherein the composite particles have a
dusting attrition value of at most about 15% as measured by ASTM
method E-728 Standard Test Method for Resistance to Attrition of
Granular Carriers and Granular Pesticides.
7. The plurality of porous composite particles formed by the
process recited in claim 1, wherein the clump strength, an
indication of the percentage of particles retained in a clump after
six hours upon addition of animal urine, is greater than 90%.
8. The plurality of porous composite particles formed by the
process recited in claim 1 wherein the bentonite is sodium
bentonite.
9. The plurality of porous composite particles formed by the
process recited in claim 1 wherein the bentonite has a mean
particle diameter of about 25-150 .mu.m.
10. An improved animal litter comprising: an absorbent material
suitable for use as an animal litter; and a plurality of porous
composite particles formed by the process recited in claim 1.
11. The improved animal litter recited in claim 10 having a malodor
rating less than 15 as determined by the Malodor Sensory
Method.
12. The improved animal litter recited in claim 10 having a malodor
rating between 10 and 15 as determined by the Malodor Sensory
Method.
13. The improved animal litter recited in claim 10 having a
hydraulic conductivity value of 0.25 cm/s or less.
14. The improved animal litter recited in claim 10, wherein the
animal litter has a dusting attrition value of at most about 15% as
measured by ASTM method E-728 Standard Test Method for Resistance
to Attrition of Granular Carriers and Granular Pesticides.
15. The improved animal litter recited in claim 10 having a clump
strength greater than 95%.
16. The improved animal litter recited in claim 10, wherein the
clump strength, an indication of the percentage of particles
retained in a clump after six hours upon addition of animal urine,
is greater than 90%.
17. The improved animal litter recited in claim 10 having a
Multiple Cat Usage Index of at least 8.
18. The improved animal litter recited in claim 10 wherein the
bentonite is sodium bentonite.
19. The improved animal litter recited in claim 10 wherein the
bentonite has a mean particle diameter of about 25-150 .mu.m.
20. The improved animal litter recited in claim 10 wherein the
absorbent material suitable for use as an animal litter is
bentonite.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application entitled "Composite Absorbent Particles" and having
Ser. No. 10/618,401 filed Jul. 11, 2003, which is herein
incorporated by reference. This application is also a
continuation-in-part of U.S. patent application entitled "Absorbent
Composition with Improved Odor Control" and having Ser. No.
10/773,585 filed Feb. 6, 2004 and which is also herein incorporated
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to composite absorbent
particles, and more particularly, this invention relates to a
composite absorbent particle having improved clumping and
odor-inhibiting properties.
BACKGROUND OF THE INVENTION
[0003] Clay has long been used as a liquid absorbent, and has found
particular usefulness as an animal litter.
[0004] Because of the growing number of domestic animals used as
house pets, there is a need for litters so that animals may
micturate, void or otherwise eliminate liquid or solid waste
indoors in a controlled location. Many cat litters use clay as an
absorbent. Typically, the clay is mined, dried, and crushed to the
desired particle size.
[0005] Some clay litters have the ability to clump upon wetting.
For example, sodium bentonite is a water-swellable clay which, upon
contact with moist animal waste, is able to agglomerate with other
moistened sodium bentonite clay particles. The moist animal waste
is contained by the agglomeration of the moist clay particles into
an isolatable clump, which can be removed from the container (e.g.,
litterbox) housing the litter. However, the clump strength of clay
litters described above is typically not strong enough to hold the
clump shape upon scooping, and inevitably, pieces of the litter
break off of the clump and remain in the litter box, allowing waste
therein to create malodors. Further, raw clay typically has a high
clump aspect ratio when urinated in. The result is that the wetted
portion of clay will often extend to the container containing it
and stick to the side or bottom of the container.
[0006] What is needed is an absorbent material suitable for use as
a cat litter/liquid absorbent that has better clumping
characteristics, i.e., clump strength and aspect ratio, than
absorbent materials heretofore known.
[0007] Another problem inherent in typical litters is the inability
to effectively control malodors. Clay has very poor
odor-controlling qualities, and inevitably waste build-up leads to
severe malodor production. One attempted solution to the malodor
problem has been the introduction of granular activated carbon
(GAC) into the litter. However, the GAC is usually dry blended with
the litter, making the litter undesirably dusty. Also, the GAC
concentration must typically be 1% by weight or higher to be
effective. Activated carbon is very expensive, and the need for
such high concentrations greatly increases production costs.
Further, because the clay and GAC particles are merely mixed, the
litter will have GAC concentrated in some areas, and particles with
no GAC in other areas.
[0008] The human objection to odor is not the only reason that it
is desirable to reduce odors. Studies have shown that cats are
territorial animals and will often "mark" litter that has little or
no smell with their personal odor, such as by urinating. When cats
return to the litterbox and don't sense their odor, they will try
to mark their territory again. The net effect is that cats will
return to use a litter box more often if the odor of their markings
are reduced. Thus, a litter that is effective at eliminating or
hiding a cat's personal odor can encourage the animal to use a
litter box rather than depositing waste outside the box.
[0009] What is needed is an absorbent material with improved
odor-controlling properties, and that maintains such properties for
longer periods of time.
[0010] What is further needed is an absorbent material with
improved odor-control, yet requiring much lower concentrations of
odor controlling actives.
[0011] What is still further needed is an absorbent material with a
lower bulk density while maintaining a high absorbency rate
comparable to or exceeding heretofore known materials.
[0012] What is also needed is an absorbent material suitable for an
animal litter which encourages animals to micturate and void on the
absorbent material.
SUMMARY OF THE INVENTION
[0013] The present invention provides composite absorbent particles
and methods for making the same. An absorbent material is formed
into a particle, preferably, by an agglomeration process. An
optional performance-enhancing active is coupled to the absorbent
material during the agglomeration process, homogeneously and/or in
layers. Exemplary actives include antimicrobials, odor
absorbers/inhibitors, binders (liquid/solid, silicate,
ligninsulfonate, etc.), fragrances, health indicating materials,
nonstick release agents, and mixtures thereof. Additionally, the
composite absorbent particle may include a core material.
[0014] Methods disclosed for creating the absorbent particles
include 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, and an extrusion process. Fluid bed process
may also represent a technique for forming the inventive
particles.
[0015] The processing technology disclosed herein allows the
"engineering" of the individual composite particles so that the
characteristics of the final product can be predetermined. The
composite particles are particularly useful as an animal litter.
Favorable characteristics for a litter product such as odor
control, active optimization, low density, low tracking, low dust,
strong clumping, etc. can be optimized to give the specific
performance required. Another aspect of the invention is the use of
encapsulated actives, i.e., formed into the particle itself and
accessible via pores or discontinuities in the particles.
Encapsulation of actives provides a slow release mechanism such
that the actives are in a useful form for a longer period of time.
A further aspect of the invention provides control over granule
strength, and therefore, degradation and/or disintegration
properties. Controlling the rate at which granules degrade, for
example when the granules disintegrate due to urine deposition,
provides another mechanism to slowly release actives from the
granule's interior and surface, and in so doing, optimize
performance. Thus, the present invention's engineered composite
particle optimizing the performance enhancing actives is novel in
light of the prior art.
[0016] Other aspects and advantages of the present invention will
become apparent from the following detailed description, which,
when taken in conjunction with the drawings, illustrate by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] For a fuller understanding of the nature and advantages of
the present invention, as well as the preferred mode of use,
reference should be made to the following detailed description read
in conjunction with the accompanying drawings.
[0018] FIG. 1 illustrates several configurations of absorbent
composite particles according to various embodiments of the present
invention.
[0019] FIG. 2 is a process diagram illustrating a pan agglomeration
process according to a preferred embodiment.
[0020] FIG. 3 depicts the structure of an illustrative agglomerated
composite particle formed by the process of FIG. 2.
[0021] FIG. 4 is a process diagram illustrating another exemplary
pan agglomeration process with a recycle subsystem.
[0022] FIG. 5 is a process diagram illustrating an exemplary pin
mixer process for forming composite absorbent particles.
[0023] FIG. 6 is a process diagram illustrating an exemplary mix
muller process for forming composite absorbent particles.
[0024] FIG. 7 is a graph depicting malodor ratings.
[0025] FIG. 8 depicts the clumping action of composite absorbent
particles according to a preferred embodiment.
[0026] FIG. 9 depicts disintegration of a composite absorbent
particle according to a preferred embodiment.
BEST MODES FOR CARRYING OUT THE INVENTION
[0027] The following description includes the best embodiments
presently contemplated for carrying out the present invention. This
description is made for the purpose of illustrating the general
principles of the present invention and is not meant to limit the
inventive concepts claimed herein.
[0028] The present invention relates generally to composite
absorbent particles with improved physical and chemical properties
comprising an absorbent material and optional performance-enhancing
actives. By using various processes described herein, such
particles can be "engineered" to preferentially exhibit specific
characteristics including but not limited to improved odor control,
lower density, easier scooping, better particle/active consistency,
higher clump strength, etc. One of the many benefits of this
technology is that the performance-enhancing actives may be
positioned to optimally react with target molecules such as but not
limited to odor causing volatile substances, resulting in
surprising odor control with very low levels of active
ingredient.
[0029] A preferred use for the absorbent particles is as a cat
litter, and therefore much of the discussion herein will refer to
cat litter applications. However, it should be kept in mind that
the absorbent particles have a multitude of applications, such as
air and water filtration, fertilizer, waste remediation, etc., and
should not be limited to the context of a cat litter.
[0030] One preferred method of forming the absorbent particles is
by agglomerating granules of an absorbent material in a pan
agglomerator. A preferred pan agglomeration process is set forth in
more detail below, but is described generally here to aid the
reader. Generally, the granules of absorbent material are added to
an angled, rotating pan. A fluid or binder is added to the granules
in the pan to cause binding of the granules. As the pan rotates,
the granules combine or agglomerate to form particles. Depending on
pan angle and pan speed among other factors, the particles tumble
out of the agglomerator when they reach a certain size. The
particles are then dried and collected.
[0031] One or more performance-enhancing actives are preferably
added to the particles in an amount effective to perform the
desired functionality or provide the desired benefit. For example,
these actives can be added during the agglomeration process so that
the actives are incorporated into the particle itself, or can be
added during a later processing step.
[0032] FIG. 1 shows several embodiments of the absorbent particles
of the present invention. These particles have actives
incorporated: [0033] 1. In a layer on the surface of a particle
(102) [0034] 2. Evenly (homogeneously) throughout a composite
litter particle (104) [0035] 3. In a concentric layer(s) throughout
the particle and/or around a core (106) [0036] 4. In pockets or
pores in and/or around a particle (108) [0037] 5. In a particle
with single or multiple cores (110) [0038] 6. Utilizing
non-absorbent cores (112) [0039] 7. No actives (114) [0040] 8. No
actives, but with single or multiple cores (116) [0041] 9. In any
combination of the above
[0042] As previously recited hereinabove, other particle-forming
processes may be used to form the inventive particles of the
present invention. For example, without limitation, extrusion and
fluid bed processes appear appropriate. Extrusion process typically
involves introducing a solid and a liquid to 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.
Pat. No. 5,269,962, especially col. 18, lines 30-61 thereof, all of
which is incorporated herein by reference thereto. Fluid bed
process is depicted in Coyne et al., U.S. Pat. No. 5,093,021,
especially col. 8, line 65 to col. 9, line 40, incorporated herein
by reference.
[0043] Materials
[0044] Many liquid-absorbing materials may be used without
departing from the spirit and scope of the present invention.
Illustrative absorbent materials include but are not limited to
minerals, fly ash, absorbing pelletized materials, perlite,
silicas, other absorbent materials and mixtures thereof. Preferred
minerals include: bentonites, zeolites, fullers earth, attapulgite,
montmorillonite diatomaceous earth, opaline silica, crystalline
silica, silica gel, alumina, Georgia White clay, sepiolite,
calcite, dolomite, slate, pumice, tobermite, marls, attapulgite,
kaolinite, halloysite, smectite, vermiculite, hectorite, Fuller's
earth, fossilized plant materials, expanded perlites, gypsum and
other similar minerals and mixtures thereof. The preferred
absorbent material is sodium bentonite having a mean particle
diameter of about 5000 microns or less, preferably about 3000
microns or less, and ideally in the range of about 25 to about 150
microns.
[0045] Because minerals, and particularly clay, are heavy, it is
may be desirable to reduce the weight of the composite absorbent
particles to reduce shipping costs, reduce the amount of material
needed to need to fill the same relative volume of the litter box,
and to make the material easier for customers to carry. To lower
the weight of each particle, a lightweight core material, or
"core," may be incorporated into each particle. The core can be
positioned towards the center of the particle with a layer or
layers of absorbent and/or active surrounding the core in the form
of a shell. This configuration increases the active concentration
towards the outside of the particles, making the active more
effective. The shell can be of any desirable thickness. In one
embodiment with a thin shell, the shell has an average thickness of
less than about 1/2 that of the average diameter of the particle,
and preferably the shell has an average thickness of not less than
about 1/16 that of the average diameter of the particle. More
preferably, the shell has an average thickness of between about
7/16 and 1/8 that of the average diameter of the particle, even
more preferably less than about 1/2 that of the average diameter of
the particle, and ideally between about 3/8 and 1/8 that of the
average diameter of the particle. Note that these ranges are
preferred but not limiting.
[0046] According to another embodiment comprising a core and
absorbent material surrounding the core in the form of a shell, an
average thickness of the shell is at least about four times an
average diameter of the core. In another embodiment, an average
thickness of the shell is between about 1 and about 4 times an
average diameter of the core. In yet another embodiment, an average
thickness of the shell is less than an average diameter of the
core. In a further embodiment, an average thickness of the shell is
less than about one-half an average diameter of the core.
[0047] Other ranges can be used, but the thickness of the shell of
absorbent material/active surrounding a non-clumping core should be
balanced to ensure that good clumping properties are
maintained.
[0048] In another embodiment, the absorbent material "surrounds" a
core (e.g., powder, granules, clumps, etc.) that is dispersed
homogeneously throughout the particle or in concentric layers. For
example, a lightweight or heavyweight core material can be
agglomerated homogeneously into the particle in the same way as the
active. The core can be solid, hollow, absorbent, nonabsorbent, and
combinations of these.
[0049] Exemplary lightweight core materials include but are not
limited to calcium bentonite clay, Attapulgite clay, Perlite,
Silica, non-absorbent silicious materials, sand, plant seeds,
glass, polymeric materials, and mixtures thereof. A preferred
material is a calcium bentonite-containing clay which can weigh
about half as much as bentonite clay. Calcium bentonite clay is
non-clumping so it doesn't stick together in the presence of water,
but rather acts as a seed or core. Granules of absorbent material
and active stick to these seed particles during the agglomeration
process, forming a shell around the seed.
[0050] Using the above lightweight materials, a bulk density
reduction of .gtoreq.10%, .gtoreq.20%, preferably .gtoreq.30%, more
preferably .gtoreq.40%, and ideally .gtoreq.50% can be achieved
relative to generally solid particles of the absorbent material
(e.g., as mined) and/or particles without the core material(s). For
example, in a particle in which sodium bentonite is the absorbent
material, using about 50% of lightweight core of calcium bentonite
clay results in about a 42% bulk density reduction.
[0051] Heavyweight cores may be used when it is desirable to have
heavier particles. Heavy particles may be useful, for example, when
the particles are used in an outdoor application in which high
winds could blow the particles away from the target zone. Heavier
particles also produce an animal litter that is less likely to be
tracked out of a litter box. Illustrative heavyweight core
materials include but are not limited to sand, iron filings,
etc.
[0052] Note that the bulk density of the particles can also be
adjusted (without use of core material) by manipulating the
agglomeration process to increase or decrease pore size, pore
volume and surface area of the particle.
[0053] Note that active may be added to the core material if
desired. Further, the core can be selected to make the litter
flushable. One such core material is wood pulp.
[0054] 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 absorbent particle
contains active.
[0055] Preferred antimicrobial actives are boron containing
compounds such as borax pentahydrate, borax decahydrate, boric
acid, polyborate, tetraboric acid, sodium metaborate, anhydrous,
boron components of polymers, and mixtures thereof.
[0056] One type of odor absorbing/inhibiting active inhibits the
formation of odors. An illustrative material is a water soluble
metal salt such as silver, copper, zinc, iron, and aluminum salts
and mixtures thereof. Preferred metallic salts are zinc chloride,
zinc gluconate, zinc lactate, zinc maleate, zinc salicylate, zinc
sulfate, zinc ricinoleate, copper chloride, copper gluconate, and
mixtures thereof. Other odor control actives include nanoparticles
that may be composed of many different materials such as carbon,
metals, metal halides or oxides, or other materials. Additional
types of odor absorbing/inhibiting actives include cyclodextrin,
zeolites, silicas, activated carbon (also known as activated
charcoal), acidic, salt-forming materials, and mixtures thereof.
Activated alumina (Al.sub.2O.sub.3) has been found to provide odor
control comparable and even superior to other odor control
additives such as activated carbon, zeolites, and silica gel.
Alumina is a white granular material, and is properly called
aluminum oxide.
[0057] The preferred odor absorbing/inhibiting active is Powdered
Activated Carbon (PAC), though Granular Activated Carbon (GAC) can
also be used. PAC gives much greater surface area than GAC (GAC is
something larger than powder (e.g., .gtoreq.80 mesh U.S. Standard
Sieve (U.S.S.S.))), and thus has more sites with which to trap
odor-causing materials and is therefore more effective. PAC has
only rarely been used in absorbent particles, and particularly
animal litter, as it tends to segregate out of the litter during
shipping, thereby creating excessive dust (also known as
"sifting"). By agglomerating PAC into particles, the present
invention overcomes the problems with carbon settling out during
shipping. Generally, the preferred mean particle diameter of the
carbon particles used is less than about 500 microns, but can be
larger. The particle size can also be much smaller (less than 100
nanometers) as in the case of carbon nanoparticles. The preferred
particle size of the PAC is about 150 microns (.about.100 mesh
U.S.S.S.) or less, and ideally in the range of about 25 to 150
microns, with a mean diameter of about 50 microns (.about.325 mesh
U.S.S.S.) or less.
[0058] An active may be added to reduce or even prevent sticking of
the litter to the litter box. Useful anti-stick agents include, but
are not limited to, hydrophobic materials such as activated carbon,
carbon black, Teflon.RTM., hydrophobic polymers and co-polymers,
for example poly(propylene oxide).
[0059] 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 150 cc 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.
[0060] The data in the table below refer to the following formulas.
Formula P is composed of composite particles of the present
invention that contain 0.5% PAC as an anti-stick agent. Formula S
is a commercially available granular clay litter with no added
anti-stick agents.
[0061] The data in the table below show that a urine clump formed
from the formula composed of composite particles containing 0.5%
PAC as an anti-stick agent requires less force for removal from the
bottom of a cat box than a urine clump formed from a commercially
available granular clay litter containing no anti-stick agents.
TABLE-US-00001 TABLE 1 Formula S Litter height Formula P Removal
Force in Inches Removal Force in pounds pounds 0.5 0.17 0.63 0.25
0.46 0.81
[0062] Generally, PAC is effective to reduce sticking when present
in the composite particles in an amount of 0.1% or more, preferably
in the range of about 0.1 to about 1.0%, when compared to composite
particles not having the PAC present.
[0063] The active may also include a binder such as water, lignin
sulfonate (solid), polymeric binders, fibrillated Teflon.RTM.
(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.
[0064] Another active that can be added to the composite particles
is a clump enhancing agent that is activated by contact with a
liquid to strengthen clumps, thereby assisting in the isolation and
encapsulation of the offensive material. Clump enhancing agents are
particularly useful when the composite particles are formed of
materials that do not have strong inherent clumping capabilities,
and where other non-clumping performance enhancing actives are
formed on an outer surface of the particles. Preferred clump
enhancing agents include binders, gums, starches, and adhesive
polymers. The clump enhancing agent is preferably added to outer
surfaces of the particles by spraying or by addition during the
final stages of agglomeration. Clump enhancing agents can also be
bulk-added to the composite particles.
[0065] Dedusting agents can also be added to the particles in order
to reduce the dust level in the final product. All of the clump
enhancing agents listed above are effective dedusting agents when
applied to the outer surface of the composite absorbent particles.
Other dedusting agents include but are not limited to fibrillated
Teflon, resins, water, and other liquid or liquefiable
materials.
[0066] A color altering agent such as a dye, pigmented polymer,
metallic paint, bleach, lightener, etc. may be added to vary the
color of absorbent particles, such as to darken or lighten the
color of all or parts of the litter so it is more appealing.
Preferably, the color altering agent comprises up to approximately
20% of the absorbent composition, more preferably, 0.001%-5% of the
composition. Even more preferably, the color altering agent
comprises approximately 0.001%-0.1% of the composition.
[0067] Preferred carriers for the color altering agent are
zeolites, carbon, charcoal, etc. These substrates can be dyed,
painted, coated with powdered colorant, etc.
[0068] Activated alumina and activated carbon may include an
embedded coloring agent that has been added during the fabrication
of the activated alumina or activated carbon particles to form a
colored speckle. The inventors have found that the odor absorbing
properties of activated alumina and activated carbon are not
significantly reduced due to the application of color altering
agents thereto.
[0069] Additionally, activated alumina's natural white coloring
makes it a desirable choice as a white, painted or dyed "speckle"
in litters. In composite and other particles, the activated alumina
can also be added in an amount sufficient to lighten or otherwise
alter the overall color of the particle or the overall color of the
entire composition.
[0070] Compositions may also contain colored speckles for visual
appeal. Other examples of speckle material are salt crystals or
gypsum crystals.
[0071] Large particles of carbon, e.g., activated carbon or
charcoal, can also be used as a dark speckle. Such particles are
preferably within a particle diameter size range of about 0.01 to
10 times the mean diameter of the other particles in the
mixture.
[0072] Suitable superabsorbent materials include superabsorbent
polymers such as AN905SH, FA920SH, and FO4490SH, 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.
[0073] The core mentioned above can also be considered an active,
for example including a lightweight material dispersed throughout
the particle to reduce the weight of the particle, a core made of
pH-altering material, etc. A preferred embodiment is to bind
actives directly to the surface of composite absorbent particles.
The use of extremely low levels of actives bound only to the
surface of absorbent particles leads to the following benefits:
[0074] 1. the use of extremely small particle size of the active
material results in a very high surface area of active while using
a very small amount of active, [0075] 2. with actives present only
on the surface of the substrate, the waste of expensive actives
that would be found with `homogeneous` composite particles [where
actives are found throughout the substrate particles] is
eliminated, [0076] 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, [0077] 4. by using very low
levels of expensive actives, the cost of the product is greatly
reduced, [0078] 5. binding of small particle size actives directly
to the substrate surface results in lower dust levels than in bulk
added product.
[0079] Surprisingly, low levels of PAC 0.2-0.3% have been found to
provide excellent odor control in cat litter when they are bound to
the surface of a material such as sodium bentonite clay. For
example, binding of small amounts of PAC particles to sodium
bentonite substrate particles using xanthan gum or fibrillatable
PTFE as binder results in litter materials with superior odor
adsorbing performance. In this example, the PAC is highly effective
at capturing malodorous volatile organic compounds as they escape
from solid and liquid wastes due to the high surface area of the
PAC, and its preferred location on the surface of the sodium
bentonite particles.
[0080] Another aspect of the invention is the use of Encapsulated
Actives, where the actives are positioned inside the particle,
homogeneously and/or in layers. Because of the porous structure of
the particles, even actives positioned towards the center of the
particle are available to provide their particular functionality.
In addition, as previously mentioned, controlled degradation of the
composite particles can result in controlled release of
encapsulated actives. Encapsulation of actives provides a slow
release mechanism such that the actives are in a useful form for a
longer period of time. This is particularly so where the active is
used to reduce malodors, control or kill germs, reduce sticking to
the box, enhance clump strength, or as an indicator of health.
[0081] Pan Agglomeration and Other Particle Creation Processes
[0082] The agglomeration process in combination with the unique
materials used allows the manufacturer to control the physical
properties of particles, such as bulk density, dust, strength, as
well as PSD (particle size distribution) without changing the
fundamental composition and properties of absorbent particles.
[0083] One benefit of the pan agglomeration process of the present
invention is targeted active delivery, i.e., the position of the
active can be "targeted" to specific areas in, on, and/or
throughout the particles. Another benefit is that because the way
the absorbent particles are formed is controllable, additional
benefits can be "engineered" into the absorbent particles, as set
forth in more detail below.
[0084] FIG. 2 is a process diagram illustrating a pan agglomeration
process 200 according to a preferred embodiment. In this example,
the absorbent granules are bentonite clay and the active is PAC.
Cores of a suitable material, here calcium bentonite clay, are also
added. The absorbent particles (e.g., bentonite powder) is mixed
with the active (e.g., PAC) to form a dry mixture, which is stored
in a hopper 202 from which the mixture is fed into the agglomerator
206. Alternatively, the absorbent granules and active(s) may be fed
to the agglomerator individually. For example, liquid actives can
be added by a sprayer. The cores are preferably stored in another
hopper 204, from which they are fed into the agglomerator. A feed
curtain can be used to feed the various materials to the
agglomerator.
[0085] In this example, the agglomerator is a pan agglomerator. The
pan agglomerator rotates at a set or variable speed about an axis
that is angled from the vertical. Water and/or binder is sprayed
onto the granules in the agglomerator via sprayers 208 to
raise/maintain the moisture content of the particles at a desired
level so that they stick together. Bentonite acts as its own binder
when wetted, causing it to clump, and so additional binder is not
be necessary. The pan agglomeration process gently forms composite
particles through a snowballing effect broadly classified by
experts as natural or tumble growth agglomeration. FIG. 3 depicts
the structure of an illustrative agglomerated composite particle
300 formed during the process of FIG. 2. As shown, the particle
includes granules of absorbent material 302 and active 304 with
moisture 306 or binder positioned interstitially between the
granules.
[0086] Depending on the pan angle and pan speed, the particles
tumble off upon reaching a certain size. Thus, the pan angle and
speed controls how big the particles get. The particles are
captured as they tumble from the agglomerator. The particles are
then dried to a desired moisture level by any suitable mechanism,
such as a rotary or fluid bed. In this example, a forced air rotary
dryer 210 is used to lower the high moisture content of the
particles to less than about 15% by weight and ideally about 8-13%
by weight. At the outlet of the rotary dryer, the particles are
screened with sieves 212 or other suitable mechanism to separate
out the particles of the desired size range. Tests have shown that
about 80% or more of the particles produced by pan agglomeration
will be in the desired particle size range. Preferably, the yield
of particles in the desired size range is 85% or above, and ideally
90% or higher. The selected particle size range can be in the range
of about 10 mm to about 100 microns, and preferably about 2.5 mm or
less. An illustrative desired particle size range is 12.times.40
mesh (1650-400 microns).
[0087] The exhaust from the dryer is sent to a baghouse for dust
collection. Additional actives such as borax and fragrance can be
added to the particles at any point in the process before, during
and/or after agglomeration. Also, additional/different actives can
be dry blended with the particles.
[0088] Illustrative composite absorbent particles after drying have
a specific weight of from about 0.15 to about 1.2 kilograms per
liter and a liquid absorbing capability of from about 0.6 to about
2.5 liters of water per kilogram of particles. Preferably, the
particles absorb about 50% or more of their weight in moisture,
more preferably about 75% or more of their weight in moisture, even
more preferably greater than approximately 80% and ideally about
90% or more of their weight in moisture.
[0089] Specific examples of compositions that can be fed to the
agglomerator using the process of FIG. 2 include (in addition to
effective amounts of active): [0090] 100% Bentonite Powder [0091]
67% Calcium Bentonite Clay (core) & 33% Bentonite Powder [0092]
50% Calcium Bentonite Clay (core) & 50% Bentonite Powder [0093]
Perlite (core) & Bentonite Powder [0094] Sand (core) &
Bentonite Powder
[0095] The following table lists illustrative properties for
various compositions of particles created by a 20'' pan
agglomerator at pan angles of 40-60 degrees and pan speeds of 20-50
RPM. The total solids flow rates into the pan were 0.2-1.0
kg/min.
TABLE-US-00002 TABLE 2 Bulk Bentonite Final Density Clump Core
Water to Core Ratio Moisture (kg/l) Strength None 15-23% 100:0
1.0-1.4% 0.70-0.78 95-97 Calcium 15-23 50:50 3.4 0.60-0.66 95-97
bentonite Calcium 15-18 33:67 4.3-4.4 0.57-0.60 93-95 bentonite
Sand 10-12 50:50 2.0 0.81-0.85 97-98 Sand 6-8 33:67 1.6-2.4 0.92 97
Perlite 15-19% 84:16 0.36-0.39 97% Perlite 16-23% 76:24 0.27-0.28
95-97%
[0096] 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 1/2'' screen
after a predetermined amount of time (e.g., 6 hours) has passed
since the particles were wetted. The screen is agitated for 5
seconds with the arm up using a Ro-Tap Mechanical Sieve Shaker made
by W.S. Tyler, Inc. The percentage of particles retained in the
clump is calculated by dividing the weight of the clump after
agitation by the weight of the clump before agitation. Referring
again to the table above, note that the clump strength indicates
the percentage of particles retained in the clump after 6 hours. As
shown, >90%, and more ideally, >95% of the particles are
retained in a clump after 6 hours upon addition of an aqueous
solution, such as deionized water or animal urine. Note that
.gtoreq. about 80% particle retention in the clump is preferred.
Also, note the reduction in bulk density when a core of calcium
bentonite clay or perlite is used.
[0097] FIG. 4 is a process diagram illustrating another exemplary
pan agglomeration process 400 with a recycle subsystem 402. Save
for the recycle subsystem, the system of FIG. 4 functions
substantially the same as described above with respect to FIG. 2.
As shown in FIG. 4, particles under the desired size are sent back
to the agglomerator. Particles over the desired size are crushed in
a crusher 404 and returned to the agglomerator.
[0098] The diverse types of clays and mediums that can be utilized
to create absorbent particles should not be limited to those cited
above. Further, unit operations used to develop these particles
include but should not be limited to: high shear agglomeration
processes, low shear agglomeration processes, high pressure
agglomeration processes, low pressure agglomeration processes, mix
mullers, roll press compacters, pin mixers, batch tumble blending
mixers (with or without liquid addition), and rotary drum
agglomerators. For simplicity, however, the larger portion of this
description shall refer to the pan agglomeration process, it being
understood that other processes could potentially be utilized with
similar results.
[0099] FIG. 5 is a process diagram illustrating an exemplary pin
mixer process 500 for forming composite absorbent particles. As
shown, absorbent particles and active are fed to a pin mixer 502.
Water is also sprayed into the mixer. The agglomerated particles
are then dried in a dryer 504 and sorted by size in a sieve screen
system 506. The following table lists illustrative properties for
various compositions of particles created, by pin mixing.
TABLE-US-00003 TABLE 3 Bentonite to Water Bulk Clump Strength -
Lightweight Clay Ratio Addition Density 6 hours Clay (wt %) (wt %)
(lb/ft.sup.3) (% Retained) Zeolite 50:50 20 59 91 (39 lb/ft.sup.3)
Bentonite 100:0 20 67 95 (64 lb/ft.sup.3)
[0100] FIG. 6 is a process diagram illustrating an exemplary mix
muller process 600 for forming composite absorbent particles. As
shown, the various components and water and/or binder are added to
a pellegrini mixer 602. The damp mixture is sent to a muller
agglomerator 604 where the mixture is agglomerated. The
agglomerated particles are dried in a dryer 606, processed in a
flake breaker 608, and then sorted by size in a sieve screen system
610.
[0101] The following table lists illustrative properties for
various compositions of particles created by a muller process. Note
that the moisture content of samples after drying is 2-6 weight
percent.
TABLE-US-00004 TABLE 4 Clump Calculated Actual Strength - 6 Water
Bulk Bulk hours Bentonite:Clay Addition Density Density (% Clay (wt
%) (wt %) (lb/ft.sup.3) (lb/ft.sup.3) Retained) Dust (mg) GWC 50:50
33 43 45 83 39 (32 lb/ft.sup.3) GWC 50:50 47 43 42 56 34 (32
lb/ft.sup.3) Taft DE 50:50 29 33 46 86 38 (22 lb/ft.sup.3) Taft DE
50:50 41 33 43 76 35 (22 lb/ft.sup.3)
[0102] The composite absorbent particle can be formed into any
desired shape. For example, the particles are substantially
spherical in shape when they leave the agglomeration pan. At this
point, i.e., prior to drying, the particles have a high enough
moisture content that they are malleable. By molding, compaction,
or other processes known in the art, the composite absorbent
particle can be made into non-spherical shapes such as, for
example, ovals, flattened spheres, hexagons, triangles, squares,
etc. and combinations thereof.
EXAMPLE 1
[0103] Referring again to FIG. 1, a method for making particles 102
is generally performed using a pan agglomeration process in which
clay particles of .ltoreq.200 mesh (.ltoreq.74 microns), preferably
.ltoreq.325 mesh (.ltoreq.43 microns) particle size premixed with
particles of active, are agglomerated in the presence of an aqueous
solution to form particles in the size range of about 12.times.40
mesh (about 1650-250 microns). Alternatively, the particles are
first formed with clay alone, then reintroduced into the pan or
tumbler, and the active is added to the pan or tumbler, and a batch
run is performed in the presence of water or a binder to adhere the
active to the surface of the particles. Alternatively, the active
can be sprayed onto the particles.
EXAMPLE 2
[0104] A method for making particles 104 is generally performed
using the process described with relation to FIG. 2, except no core
material is added.
EXAMPLE 3
[0105] A method for making particles 106 is generally performed
using the process described with relation to FIG. 2, except that
introduction of the absorbent granules and the active into the
agglomerator are alternated to form layers of each.
EXAMPLE 4
[0106] A method for making particles 108 is generally performed
using the process described with relation to FIG. 2, except that
the active has been pre-clumped using a binder, and the clumps of
active are added. Alternatively, particles of absorbent material
can be created by agglomeration and spotted with a binder such that
upon tumbling with an active, the active sticks to the spots of
binder thereby forming concentrated areas. Yet another alternative
includes the process of pressing clumps of active into the
absorptive material.
EXAMPLE 5
[0107] A method for making particles 110 is generally performed
using the process described with relation to FIG. 2.
EXAMPLE 6
[0108] A method for making particles 112 is generally performed
using the process described with relation to FIG. 2.
EXAMPLE 7 & 8
[0109] A method for making particles 114 and 116 are generally
performed using the process described with relation to FIG. 2,
except no active is added.
[0110] In addition, the performance-enhancing active can be
physically dispersed along pores of the particle by suspending an
insoluble active in a slurry and spraying the slurry onto the
particles. The suspension travels into the pores and
discontinuities, depositing the active therein.
[0111] Control over Particle Properties
[0112] Strategically controlling process and formulation variables
along with agglomerate particle size distribution allows for the
development of various composite particles engineered specifically
to enable attribute improvements as needed. Pan agglomeration
process variables include but are not limited to raw material and
ingredient delivery methods, solid to process water mass ratio, pan
speed, pan angle, scraper type and configuration, pan dimensions,
throughput, and equipment selection. Formulation variables include
but are not limited to raw material specifications, raw material or
ingredient selection (actives, binders, clays and other solids
media, and liquids), formulation of liquid solution used by the
agglomeration process, and levels of these ingredients.
[0113] 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.
[0114] As mentioned above, the agglomeration process can be
manipulated to control process and formulation variables. This
manipulation can be used, for example, to increase or decrease pore
size, pore volume and surface area which can then result in control
of bulk properties such as the bulk density of the particles (with
or without use of core material), the overall liquid absorption
capacity by the particles, and the rate of degradation of formed
granules under swelling conditions. The pore size, pore volume,
surface area and resulting bulk properties depend primarily on the
pan angle and the pan speed, which together create an effective
pressure on the particles being agglomerated into composite
particles. By increasing the pan speed, the centrifugal force
exerted on the particles is increased, thereby reducing the
internal pore size of the resulting composite particles. Similarly,
as the pan angle is increased from the horizontal, the particles
will tumble more violently towards the bottom of the pan, again
reducing the internal pore size of the resulting composite
particles.
[0115] A larger pore size results in a lower overall bulk density
of the composite particles. A larger pore size also allows
odoriferous molecules to more readily reach actives embedded within
the composite particles. The pore size also affects hydraulic
conductivity.
[0116] By knowledge of interactions between pan, dryer, and
formulation parameters one could further optimize process control
or formulation/processing cost. For example, it was noted that by
addition of a minor content of a less absorptive clay, we enabled
easier process control of particle size. For example, by addition
of calcium bentonite clay the process became much less sensitive to
process upsets and maintains consistent yields in particle size
throughout normal moisture variation. Addition of calcium bentonite
clay also helped reduce particle size even when higher moisture
levels were used to improve granule strength. This is of clear
benefit as one looks at enhancing yields and having greater control
over particle size minimizing need for costly control equipment or
monitoring tools.
[0117] For those practicing the invention, pan agglomeration
manipulation and scale-up can be achieved through an empirical
relationship describing the particle's path in the pan. Process
factors that impact the path the particle travels in the pan
include but are not limited to pan dimensions, pan speed, pan
angle, input feed rate, solids to process liquid mass ratio, spray
pattern of process liquid spray, position of scrapers, properties
of solids being processed, and equipment selection. Additional
factors that may be considered when using pan agglomerators include
particle to particle interactions in the pan, gravity effects, and
the following properties of the particles in the pan: distance
traveled, shape of the path traveled, momentum, rotational spin
about axis, shape, surface properties, and heat and mass transfer
properties.
[0118] The composite particles provide meaningful benefits,
particularly when used as a cat litter, that include but are not
limited to improvements in final product attributes such as odor
control, litter box maintenance benefits, reduced dusting or
sifting, and consumer convenience. As such, the following
paragraphs shall discuss the composite absorbent particles in the
context of animal litter, it being understood that the concepts
described therein apply to all embodiments of the absorbent
particles.
[0119] Significant odor control improvements over current
commercial litter formulas have been identified for, but are not
limited to, the following areas: [0120] Fecal odor control (malodor
source: feline feces) [0121] Ammonia odor control (malodor source:
feline urine) [0122] Non-ammonia odor control (malodor source:
feline urine) Odor control actives that can be utilized to achieve
these benefits include but are not limited to powdered activated
carbon, silica powder (Type C), borax pentahydrate, and bentonite
powder. The odor control actives are preferably distributed within
and throughout the agglomerates by preblending the actives in a
batch mixer with clay bases and other media prior to the
agglomeration step. The pan agglomeration process, in conjunction
with other unit operations described here, allows for the targeted
delivery of actives within and throughout the agglomerate, in the
outer volume of the agglomerate with a rigid core, on the exterior
of the agglomerate, etc. These or any targeted active delivery
options could also be performed in the pan agglomeration process
exclusively through novel approaches that include, but should not
be limited to, strategic feed and water spray locations, time
delayed feeders and spray systems, raw material selection and their
corresponding levels in the product's formula (actives, binders,
clays, and other medium), and critical pan agglomeration process
variables described herein.
[0123] Additionally, the pan agglomeration process allows for the
incorporation of actives inside each agglomerate or granule by
methods including but not limited to dissolving, dispersing, or
suspending the active in the liquid solution used in the
agglomeration process. As the pan agglomeration process builds the
granules from the inside out, the actives in the process's liquid
solution become encapsulated inside each and every granule. This
approach delivers benefits that include but should not be limited
to reduced or eliminated segregation of actives from base during
shipping or handling (versus current processes that simply dry
tumble blend solid actives with solid clays and medium), reduced
variability in product performance due to less segregation of
actives, more uniform active dispersion across final product,
improved active performance, and more efficient use of actives.
This more effective use of actives reduces the concentration of
active required for the active to be effective, which in turn
allows addition of costly ingredients that would have been
impractical under prior methods. For example, dye or pigment can be
added to vary the color of the litter, lighten the color of the
litter, etc. Disinfectant can also be added to kill germs. For
example, this novel approach can be utilized by dissolving borax
pentahydrate in water. This allows the urease inhibitor (boron) to
be located within each granule to provide ammonia odor control and
other benefits described here. One can strategically select the
proper actives and their concentrations in the liquid solution used
in the process to control the final amount of active available in
each granule of the product or in the product on a bulk basis to
deliver the benefits desired.
[0124] Targeted active delivery methods should not be limited to
the targeted active delivery options described here or to odor
control actives exclusively. For example, another class of active
that could utilize this technology is animal health indicating
actives such as a pH indicator that changes color when urinated
upon, thereby indicating a health issue with the animal. This
technology should not be limited to cat litter applications. Other
potential industrial applications of this technology include but
should not be limited to laundry, home care, water filtration,
fertilizer, iron ore pelletizing, pharmaceutical, agriculture,
waste and landfill remediation, and insecticide applications. Such
applications can utilize the aforementioned unit operations like
pan agglomeration and the novel process technologies described here
to deliver smart time-releasing actives or other types of actives
and ingredients in a strategic manner. The targeted active delivery
approach delivers benefits that include but should not be limited
to the cost efficient use of actives, improvements in active
performance, timely activation of actives where needed, and
improvements in the consumer perceivable color of the active in the
final product. One can strategically choose combinations of
ingredients and targeted active delivery methods to maximize the
performance of actives in final products such as those described
here.
[0125] Litter box maintenance improvements can be attributed to
proper control of the product's physical characteristics such as
bulk density, clump strength, attrition or durability (granule
strength), clump height (reduction in clump height has been found
to correlate to reduced sticking of litter to the bottom of litter
box), airborne and visual dust, lightweight, absorption (higher
absorption correlates to less sticking to litter box--bottom,
sides, and corners), adsorption, ease of scooping, ease of carrying
and handling product, and similar attributes. Strategically
controlling process and formulation variables along with
agglomerate particle size distribution allows for the development
of various cat litter particles engineered specifically to "dial
in" attribute improvements as needed. Pan agglomeration process
variables include but are not limited to raw material and
ingredient delivery methods, solid to process water mass ratio, pan
speed, pan angle, scraper type and configuration, pan dimensions,
throughput, and equipment selection.
[0126] Formulation variables include but are not limited to raw
material specifications, raw material or ingredient selection
(actives, binders, clays and other solids medium, and liquids),
formulation of liquid solution used by the agglomeration process,
and levels of these ingredients. For example, calcium bentonite can
be added to reduce sticking to the box.
[0127] Improvements in consumer convenience attributes include but
are not limited to those described here and have been linked to
physical characteristics of the product such as bulk density or
light weight. Because the absorbent particles are made from small
granules, the pan agglomeration process creates agglomerated
particles having a porous structure that causes the bulk density of
the agglomerates to be lower than its initial particulate form.
Further, by adjusting the rotation speed of the pan, porosity can
be adjusted. In particular, a faster pan rotation speed reduces the
porosity by compressing the particles. Since consumers use products
like cat litter on a volume basis, the pan agglomeration process
allows the manufacturer to deliver bentonite based cat litters at
lower package weights but with equivalent volumes to current
commercial litters that use heavier clays that are simply mined,
dried, and sized. The agglomerates' reduced bulk density also
contributes to business improvements previously described such as
cost savings, improved logistics, raw material conservation, and
other efficiencies. Lightweight benefits can also be enhanced by
incorporating cores that are lightweight. A preferred bulk density
of a lightweight litter according to the present invention is less
than about 1.5 grams per cubic centimeter and more preferably less
than about 0.85 g/cc. Even more preferably, the bulk density of a
lightweight litter according to the present invention is between
about 0.25 and 0.85 g/cc, and ideally for an animal litter 0.35 and
0.50 g/cc.
[0128] The porous structure of the particles also provides other
benefits. The voids and pores in the particle allow access to
active positioned towards the center of the particle. This
increased availability of active significantly reduces the amount
of active required to be effective. For example, in particles in
which carbon is incorporated in layers or heterogeneously
throughout the particle, the porous structure of the absorbent
particles makes the carbon in the center of the particle available
to control odors. Many odors are typically in the gas phase, so
odorous molecules will travel into the pores, where they are
adsorbed onto the carbon. By mixing carbon throughout the
particles, the odor-absorbing life of the particles is also
increased. This is due to the fact that the agglomeration process
allows the manufacturer to control the porosity of particle, making
active towards the center of the particle available.
[0129] Because of the unique processing of the absorbent particles
of the present invention, substantially every absorbent particle
contains carbon. As discussed above, other methods merely mix GAC
with clay, and compress the mixture into particles, resulting in
aggregation and some particles without any carbon. Thus, more
carbon must be added. Again, because of the way the particles are
formed and the materials used (small clay granules and PAC), lower
levels of carbon are required to effectively control odors. In
general, the carbon is present in the amount of 5% or less based on
the weight of the particle. In illustrative embodiments, the carbon
is present in the amount of 1.0% or less, 0.5% or less, and 0.3% or
less, based on the weight of the particle. In other embodiments,
activated alumina is present in the amount of 1.0% or less, 0.5% or
less, and 0.3% or less, based on the weight of the particle. This
lower amount of carbon or other odor controlling additive
significantly lowers the cost for the particles, as these additives
are very expensive compared to clay. The amount of carbon or other
odor controlling additive required to be effective is further
reduced because the agglomeration process incorporates the carbon
into each particle, using it more effectively. As shown in the
graph 700 of FIG. 7, the composite absorbent particles according to
a preferred embodiment have a malodor rating below about 15,
whereas the non-agglomerated control has a rating of about 40, as
determined by a Malodor Sensory Method.
[0130] Description of Malodor Sensory Method: [0131] 1. Cat boxes
are filled with 2,500 cc of test litter. [0132] 2. Boxes are dosed
each morning for four days with 30 g of pooled feces. [0133] 3. On
the fourth day the center of each box is dosed with 20 ml pooled
urine. [0134] 4. The boxes are placed into sensory evaluation
booths. [0135] 5. The boxes are allowed to equilibrate in the
closed booths for 30-45 minutes before panelist evaluation. [0136]
6. The samples are then rated on a 60 point line scale by trained
panelists.
[0137] Preferably, the agglomerated particles exhibit noticeably
less odor after four days from contamination with animal waste as
compared to a generally solid particle of the absorbent material
alone under substantially similar conditions.
[0138] As mentioned above, the human objection to odor is not the
only reason that it is desirable to reduce odors. Studies have
shown that cats prefer litter with little or no smell. One theory
is that cats like to mark their territory by urinating. When cats
return to the litterbox and don't sense their odor, they will try
to mark their territory again. The net effect is that cats return
to use the litter box more often if the odor of their markings is
reduced.
[0139] Accordingly, the composite particles induce a cat to use the
litter, and thus provide a mechanism to defeat a cat's instinct to
mark its territory in areas other than the litter box.
[0140] A preferred embodiment of the present invention has a feline
inducement to use index of at least 8, and ideally at least 9, as
measured by the following test.
[0141] Description of Feline Inducement to Use Index Test: [0142]
1. Cat boxes are filled with 2,500 cc of test litter of >95%
bentonite, .about.1% activated carbon, and may include other
optional actives. The cat boxes are each placed in an individual
cage having a floor area of 12 square feet. [0143] 2. One cat is
placed in each cage and kept there for seven days. The excrement
and urine are not removed from the litter. [0144] 3. On the seventh
day the cage is examined for urine and excrement in areas other
than the box. [0145] 4. The number of soiled areas of the cage
other than the box are enumerated and subtracted from a base number
of 10 to produce individual indices. The individual indices are
averaged by the total number of cat boxes in the test to determine
the feline inducement to use index.
[0146] Additionally, in households with multiple cats, one or both
cats may object to sharing the litterbox upon sensing the odor of
the other cat's waste. However, the superior odor control
properties of the composite particles described herein have been
found to sufficiently control odors that multiple cats use litter
even after an extended period of time.
[0147] A preferred embodiment of the present invention has a
multiple cat usage index of at least 8, and ideally at least 9, as
measured by the following test.
[0148] Description of Multiple Cat Usage Index Test: [0149] 1. Cat
boxes are filled with 2,500 cc of test litter of >95% bentonite,
.about.1% activated carbon, .about.1% of a boron compound sprayed
onto the particles, and optionally additional actives. The cat
boxes are each placed in an individual cage having a floor area of
12 square feet. [0150] 2. Two cats are placed in each cage and kept
there for seven days. The excrement and urine are not removed from
the litter. [0151] 3. On the seventh day the cage is examined for
urine and excrement in areas other than the box. [0152] 4. The
number of soiled areas of the cage other than the box are
enumerated and subtracted from a base number of 10 to produce
individual indices. The individual indices are averaged by the
total number of cat boxes in the test to determine the multiple cat
usage index.
[0153] The composite absorbent particles of the present invention
exhibit surprising additional features heretofore unknown. The
agglomerated composite particles allow specific engineering of the
particle size distribution and density, and thereby the clump
aspect ratio. Thus, hydraulic conductivity (K) values of
.ltoreq.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.
[0154] Method for Measuring Hydraulic Conductivity
[0155] Materials: [0156] 1. Water-tight gas drying tube with 7.5
centimeter diameter [0157] 2. Manometer [0158] 3. Stop watch [0159]
4. 250 ml graduated cylinder
[0160] Procedure: [0161] 1. Mix and weigh sample [0162] 2. Pour the
sample into the Drying tube until the total height of the sample is
14.6 centimeters. [0163] 3. Close the cell. [0164] 4. Use vacuum to
pull air through and dry the sample for at least 3 minutes. [0165]
5. When the sample is dry, saturate the sample slowly with water by
opening the inlet valve. [0166] 6. Allow the water exiting the
drying tube to fill the graduated cylinder. [0167] 7. Deair the
system using vacuum, allowing the system to stabilize for 10
minutes. [0168] 8. After 10 minutes, record the differential
pressure as displayed by the manometer. [0169] 9. Record at least 4
differential pressure measurements, waiting 3 minutes between each
measurement. [0170] 10. Record the flow rate of the water entering
the graduated cylinder. [0171] 11. Calculate the Hydraulic
Conductivity, K, using Darcy's Law
[0171] Q=-KA(ha-hb)/L [0172] Q=Flow Rate [0173] K=Hydraulic
Conductivity [0174] A=Cross Sectional Area [0175] L=Bed Length
[0176] Ha-Hb=Differential Pressure
[0177] One of the distinguishing characteristics of the optimum K
value is a litter clump with a very low height to length ratio
(flat). By controlling the particle size of the litter, clump
strength and clump profile can be controlled. This is important
because the smaller the clumps are, the less likely they are to
stick to something like the animal or litterbox. For instance, with
prior art compacted litter, if a cat urinates 1 inch from the side
of the box, the urine will penetrate to the side of box and the
clay will stick to the box. However, the present invention allows
the litter particles to be engineered so urine only penetrates
about 1/2 inch into a mass of the particles.
[0178] Agglomerated composite particles according to the present
invention also exhibit interesting clumping action not previously
seen in the literature. Particularly, the particles exhibit
extraordinary clump strength with less sticking to the box,
especially in composite particles containing bentonite and PAC. PAC
is believed to act as a release agent to reduce sticking to the
box. However, intuitively this should also lead to reduced clump
strength, not increased clump strength. The combination of stronger
clumps yet exhibiting less sticking to the box is both surprising
and counter-intuitive. The result is a litter with multiple
consumer benefits including strong clumps, low urine seepage, and
little sticking to the box.
[0179] While not wishing to be bound by any particular theory, the
increased clump strength is believed to be due to at least some of
the PAC-containing granules "falling apart" and releasing their
bentonite particles to reorder themselves, and this `reordering`
produces a stronger clump. As shown in FIGS. 8 and 9, this can best
be described as a disintegration of more-water-soluble pieces of
the agglomerated composite particles 800 when in contact with
moisture 802, allowing the pieces 804 of the particles to attach to
surrounding particles. This "reordering" produces a stronger clump.
In testing, the visual appearance of the cores is a signal that at
least some of the granules decompose to smaller particles, and
these particles are "suspending" in the urine and are free to
occupy interstitial spaces between particles, forming a stronger
clump. This creates a network of softened agglomerated particles
where broken particle pieces are attaching to others and creating a
web of clumped material. Note however that the particles described
herein should not be limited to clumping or scoopable
particles.
[0180] As mentioned above, the composite absorbent particles have
particular application for use as an animal litter. The litter
would then be added to a receptacle (e.g., litterbox) with a closed
bottom, a plurality of interconnected generally upright side walls
forming an open top and defining an inside surface. However, the
particles should not be limited to pet litters, but rather could be
applied to a number of other applications such as: [0181] Litter
Additives--Formulated product can be pre-blended with standard
clumping or non-clumping clays to create a less expensive product
with some of the benefits described herein. A post-additive product
could also be sprinkled over or as an amendment to the litter box.
[0182] Filters--Air or water filters could be improved by either
optimizing the position of actives into areas of likely contact,
such as the outer perimeter of a filter particle. Composite
particles with each subcomponent adding a benefit could also be
used to create multi-functional composites that work to eliminate a
wider range of contaminants. [0183] 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. [0184]
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. [0185] 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. [0186] Mixtures of
Different Particles--The composite particles can be dry mixed with
other types of particles, including but not limited to other types
of composite particles, extruded particles, particles formed by
crushing a source material, etc. Mixing composite particles with
other types of particles provides the benefits provided by the
composite particles while allowing use of lower cost materials,
such as crushed or extruded bentonite. Illustrative ratios of
composite particles to other particles can be 75/25, 50/50, 25/75,
or any other ratio desired. For example, in an animal litter
created by mixing composite particles with extruded bentonite, a
ratio of 50/50 will provide enhanced odor control, clumping and
reduced sticking, while reducing the weight of the litter and
lowering the overall cost of manufacturing the litter. [0187]
Mixtures of Composite Particles with Actives--The composite
particles can be dry mixed with actives, including but not limited
to particles of activated carbon.
ADDITIONAL EXAMPLES
[0188] Note that all percentages are in weight percent in the
following examples.
EXAMPLE 9
[0189] A composite particle includes: [0190] about 90-99.5% sodium
bentonite as the primary absorbent material [0191] about 0.1-10%
activated carbon added to the sodium bentonite as in particles
102-108 and 114 of FIG. 1 [0192] about 0-9.9% additional active
EXAMPLE 10
[0193] A composite particle includes: [0194] about 90-99.5% sodium
bentonite as the primary absorbent material [0195] about 0.1-10%
zeolite, crystalline silica, silica gel, activated alumina,
activated carbon, a superabsorbent polymer, and mixtures thereof
added to the sodium bentonite as in particles 102-108 and 114 of
FIG. 1 [0196] about 0-9.9% additional active
EXAMPLE 11
[0197] A composite particle includes: [0198] about 10-70% core
material selected from zeolite, crystalline silica, silica gel,
activated alumina, activated carbon, a superabsorbent polymer, and
mixtures thereof [0199] about 30-90% sodium bentonite surrounding
the core [0200] about 0.1-10% activated carbon added to the sodium
bentonite as in particles 110-112 and 116 of FIG. 1 [0201] about
0-10% additional active
EXAMPLE 12
[0202] A composite particle includes: [0203] about 10-70% core
material selected from zeolite, crystalline silica, silica gel,
activated alumina, activated carbon, a superabsorbent polymer, and
mixtures thereof [0204] about 30-90% sodium bentonite surrounding
the core [0205] about 0.1-25% zeolite, crystalline silica, silica
gel, activated alumina, a superabsorbent polymer, and mixtures
thereof added to the sodium bentonite as in particles 110-112 and
116 of FIG. 1 [0206] about 0-10% additional active
EXAMPLE 13
[0207] A composite particle includes: [0208] about 10-70% core
formed from agglomerated particles [0209] about 30-90% sodium
bentonite surrounding the core [0210] about 0.1-25% zeolite,
crystalline silica, silica gel, activated alumina, a superabsorbent
polymer, and mixtures thereof added to the sodium bentonite as in
particles 110-112 and 116 of FIG. 1 [0211] about 0-10% additional
active
EXAMPLE 14
[0212] An absorbent composition of multiple composite particles,
each composite particle including: [0213] optional 10-70% core
[0214] about 30-100% agglomerated absorbent material [0215] about
0.1-10% active added to the absorbent material as in particles
102-116 of FIG. 1 [0216] about 0-10% additional active selected
from an antimicrobial, an odor reducing material, a binder, a
fragrance, a health indicating material, a color altering agent, a
dust reducing agent, a nonstick release agent, a superabsorbent
material, cyclodextrin, zeolite, activated carbon, a pH altering
agent, a salt forming material, a ricinoleate, silica gel,
crystalline silica, and mixtures thereof [0217] where about 1-25%
of the composite particles are colored for creating "speckles" in
the litter
EXAMPLE 15
[0218] An absorbent composition of multiple composite particles
admixed with particles of sodium bentonite, including: [0219] about
10-90% particles of swellable sodium bentonite clay particles,
.about.1.4 mm-0.3 mm (14.times.50 mesh), dried and crushed [0220]
about 10-90% composite particles, each composite particle
including: [0221] optional 10-70% core [0222] about 30-100%
agglomerated absorbent material [0223] about 0.1-10% active added
to the absorbent material as in particles 102-116 of FIG. 1 [0224]
about 0-10% additional active selected from an antimicrobial, an
odor reducing material, a binder, a fragrance, a health indicating
material, a color altering agent, a dust reducing agent, a nonstick
release agent, a superabsorbent material, cyclodextrin, zeolite,
activated carbon, a pH altering agent, a salt forming material, a
ricinoleate, silica gel, crystalline silica, and mixtures thereof
[0225] about 0-25% colored or white "speckles" in the litter (can
be activated alumina, colored composite particles, etc.)
[0226] The activated alumina itself may include an embedded
coloring agent that has been added during the fabrication of the
activated alumina particles. The inventors have found that the odor
absorbing properties of activated alumina are not significantly
reduced due to the application of color altering agents
thereto.
[0227] Additionally, activated alumina's natural white coloring
makes it a desirable choice as a white, painted or dyed "speckle"
in litters. In composite and other particles, the activated alumina
can also be added in an amount sufficient to lighten or otherwise
alter the overall color of the particle or the overall color of the
entire composition.
[0228] Compositions may also contain visible but ineffective
colored speckles for visual appeal. Examples of speckle material
are salt crystals or gypsum crystals.
EXAMPLE 16
[0229] An absorbent composition of multiple composite particles
admixed with particles of sodium bentonite, including: [0230] about
10-90% composite particles, each composite particle including:
[0231] optional 10-70% core [0232] about 30-99.9% agglomerated
absorbent material [0233] about 0.1-10% active added to the
absorbent material as in particles 102-116 of FIG. 1 [0234] about
0-10% additional active selected from an antimicrobial, an odor
reducing material, a binder, a fragrance, a health indicating
material, a color altering agent, a dust reducing agent, a nonstick
release agent, a superabsorbent material, cyclodextrin, zeolite,
activated carbon, a pH altering agent, a salt forming material, a
ricinoleate, silica gel, crystalline silica, and mixtures thereof
[0235] about 0.01-50% particles of activated alumina dry mixed with
the composite particles. Preferably, the activated alumina is
present in the composition in an amount of about 0.01% to about 50%
of the composition by weight based on the total weight of the
absorbent composition. More preferably, the activated alumina is
present in the composition in an amount of about 0.1% to about 25%
by weight.
EXAMPLE 17
[0236] An absorbent composition (clumpable or nonclumpable) with
improved odor control includes: [0237] about 0.1-25.0% activated
alumina and/or zeolite and/or silica particles [0238] about 0-75%
additives [0239] to 100% composite particles as in particles
102-116 of FIG. 1
EXAMPLE 18
[0240] An absorbent composition with antimicrobial benefit
includes: [0241] about 0.5-5.0% activated alumina and/or zeolite
and/or silica particles [0242] [odor control] [0243] about
0.001-1.0% borax pentahydrate [antimicrobial] [0244] about
0.001-10% fragrance [0245] about 0-25% additional additives [0246]
to 100% composite particles as in particles 102-116 of FIG. 1
EXAMPLE 19
[0247] A clumping absorbent composition with antimicrobial benefit
includes: [0248] about 2% colored activated alumina and/or zeolite
and/or silica particles, 1-2 mm (10.times.18 mesh) [0249] about
0.5% borax pentahydrate [antimicrobial] [0250] about 0.71%
spray-dried fragrance--sprayed onto starch beads and mixed in
[0251] about 96.79% composite particles as in particles 102-116 of
FIG. 1, [0252] .about.1.4 mm-0.3 mm (14.times.50 mesh), dried and
crushed
EXAMPLE 20
[0253] The following composition provides the benefit of improved
odor control throughout the litter due to the varying densities of
zeolite, activated, alumina, and silica gel.
[0254] An absorbent composition that is either clumpable or
nonclumpable includes: [0255] about 0.001-25.0% zeolite particles
[0256] about 0.001-25.0% activated alumina particles [0257] about
0.001-25.0% silica gel particles [0258] about 0-50% additives
[0259] to 100% composite particles including sodium bentonite clay
as in particles 102-116 of FIG. 1
[0260] The zeolite is the heaviest of the three odor-absorbing
materials, alumina is in the middle, and silica gel is the
lightest. Because of the tendency of the materials to segregate
upon agitation such as a cat digging in the litterbox, the zeolite,
being heavier, will tend to move towards the bottom of the litter,
while the lighter silica gel will tend to migrate towards the top
of the litter. Thus, the litter will contain odor controlling
actives throughout. An additional benefit is that the silica gel
tends to repel liquid running across it, making it the ideal
material for the upper layer of litter, as it will not immediately
become saturated by animal urine but will retain its odor absorbing
properties.
[0261] Also, by adding a lighter material such silica (25
lbs/ft.sup.3) or zeolite (about 50 lbs/ft.sup.3), the overall
weight per volume unit of the mixture is reduced.
[0262] For clumping litter not relying on binders for clump
strength, the total content of zeolite, activated alumina, and
silica gel particles is preferably less than about 25% so that the
clay provides satisfactory clumping performance.
EXAMPLE 21
[0263] In a variation of Example 20:
[0264] An absorbent composition that is either clumpable or
nonclumpable includes: [0265] about 0.001-25.0% activated alumina
particles [0266] about 0.001-25.0% zeolite particles [0267] about
0-50% additives [0268] to 100% composite particles as in particles
102-116 of FIG. 1
EXAMPLE 22
[0269] In a variation of Example 20:
[0270] An absorbent composition that is either clumpable or
nonclumpable includes: [0271] about 0.001-25.0% zeolite particles
[0272] about 0.001-25.0% silica gel particles [0273] about 0-50%
additives [0274] to 100% composite particles as in particles
102-116 of FIG. 1
EXAMPLE 23
[0275] In a variation of Example 20:
[0276] An absorbent composition that is either clumpable or
nonclumpable includes: [0277] about 0.001-25.0% activated alumina
particles [0278] about 0.001-25.0% silica gel particles [0279]
about 0-50% additives [0280] to 100% composite particles as in
particles 102-116 of FIG. 1
EXAMPLE 24
[0281] A flushable and clumping absorbent composition with improved
odor control includes: [0282] about 0.1-25.0% activated alumina
and/or zeolite and/or silica particles [0283] about 0-75% additives
[0284] less than about 1% of a water soluble binding agent [0285]
to 100% composite particles as in particles 102-116 of FIG. 1
[0286] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only, and not limitation. Thus, the breadth and scope of a
preferred embodiment should not be limited by any of the
above-described exemplary embodiments, but should be defined only
in accordance with the following claims and their equivalents.
* * * * *