Substrate-coated hardening animal litter, self-hardening substrate-coated animal litter granules, and manufacturing method thereof

Abstract

The self-clumping coated substrate animal litter comprises self-clumping coated substrate animal litter granules having an outer coating of modified starch flocculant formed by agglomerating particulate modified starch flocculant around an inner substrate. The coating has an inner self-adhering region attached to the substrate and an outer region of the flocculant surrounding the inner region, defining the outer surface of each granule. The outer surface is formed with fine raised protrusions including microcracks and spikes for enhanced absorbency. The coating has a first moisture-activated, moisture-curing adhesive and a second moisture-reactivated, moisture-resetting adhesive formed by modifying the starch during ultra-high-pressure extrusion using a single-screw extruder. A preferred agglomeration method for manufacturing includes wetting substrate particles with water, applying powdered flocculant, and tumbling the wet mixture until rounded, low-tracking clumping animal litter granules are obtained. Another suitable clumping method involves applying a clumping agent slurry to rolling substrate particles until rounded, low-tracking clumped animal litter granules are obtained.

Description

[Technical Field]

[0001] The present invention relates generally to absorbent materials, particularly to animal litter, and more particularly to a setting or self-setting animal litter that sets when wet. More particularly, the present invention relates to a self-setting animal litter comprising litter granules formed from a substrate at least partially coated with an absorbent solidifying material comprising a cold water-swellable, water-absorbent starch and a cold water-soluble binder, the litter granules self-setting when wet, and a method for making the same. [Background technology]

[0002] Numerous attempts have been made by others to develop low-cost cat litter using non-self-solidifying granular or particulate materials. The first non-solidifying litters were products like Playbox litter, because the litter was inexpensive and readily available. Next came calcium bentonite litter, which absorbed urine when a cat urinated but did not solidify. When a cat soiled such non-solidifying litters, the soiled litter was often simply covered over or covered with additional non-solidifying litter. These types of non-solidifying litters were not only inefficient, but also tended to be actually expensive to use. This was because it was not uncommon for the entire litter to become contaminated, foul-smelling, and unusable after just one day of use by a single cat, sometimes even after just one use by a cat.

[0003] This resulted in the development of sodium bentonite clumping litter that absorbs urine and liquid feces. When soiled by cats, sodium bentonite litter exhibits excellent clumping properties, allowing for easy removal of soiled clumps from clean litter by simply scooping the clumps with a perforated handle. While sodium bentonite clumping litter has been the gold standard for several years due to its clumping capabilities, improvements in clumping litter have led to the development of litter with improved clump retention. Clump retention measures how well clumps in litter retain their cohesion in a drop test from a predetermined height, typically about 12 to 18 inches. It is used to measure how well the original clumps retain their cohesion when removing soiled clumps from clean litter in an animal litter tray. Animal litter with a clump retention rate of greater than 90%, meaning that at least 90% of the clumps remain together after being dropped from a given drop test height, is considered good animal litter, animal litter with a clump retention rate of at least 96% is considered excellent animal litter, and there are particularly excellent sodium bentonite animal litter with a clump retention rate of at least 99%, with this 99% or higher retention rate now being the gold standard for all types of animal litter. Summary of the Invention [Problem to be solved by the invention]

[0004] Unfortunately, sodium bentonite is very dusty, which can increase the amount of cleaning required in and around the animal litter tray when sodium bentonite animal litter is used. After mining, the sodium bentonite used in clumping animal litter is typically little processed other than being crushed into relatively small granules to enhance clumping. Depending on the mining site, sodium bentonite is a brittle material containing many impurities, including sand, limestone, sodium chloride, calcium chloride, magnesium chloride, potassium chloride, ammonium chloride, calcium carbonate, magnesium carbonate, calcium sulfate, sodium sulfate, sodium nitrate, ferrous sulfate, and other organic and inorganic contaminants, resulting in dusty animal litter particles. Due to its brittleness, sodium bentonite animal litter particles rub against each other during packaging, transportation to, and handling by, retailers, creating fine, powdery dust particles. Unfortunately, consumers and cats are exposed to airborne dust when pouring the animal litter into the animal litter tray or when scooping the clumps out of the animal litter tray. Sodium bentonite dust not only adheres to the litter tray, floors, and surrounding walls, but also to the fur of cats using the litter tray, requiring more frequent grooming to remove the dust.

[0005] Commercially available sodium bentonite is very heavy, with bulk densities typically ranging from 54 to 72 pounds per cubic foot. This weight makes it costly to transport sodium bentonite from mines to animal litter manufacturing plants, where it is crushed into smaller animal litter particles and packaged in bags, jugs, and other types of containers for consumer use. Due to its considerable weight, it is also costly to transport sodium bentonite animal litter to stores and consumer homes across the country. Its weight also makes it difficult for consumers to lift the animal litter containers from the store and into their homes, and it is also cumbersome to lift to pour into animal litter trays for use.

[0006] To reduce both the weight and cost of animal litter, animal litter manufacturers have introduced multi-component animal litter blends that combine sodium bentonite animal litter particles with one or more other animal litter particles that are lighter, less expensive to ship, and less expensive to source as raw materials. Examples of such hybrid multi-component sodium bentonite animal litter include animal litter containing sodium bentonite and calcium bentonite particles, animal litter containing crushed or crushed perlite particles, animal litter containing pellets or particles of compressed, crushed, ground, or milled organic material, usually with a high cellulose content, and even multi-component sodium bentonite animal litter blends that combine sodium bentonite particles with particles, pellets, or particles of two or three other animal litter ingredients other than sodium bentonite. However, virtually all of these multi-component animal litter made with sodium bentonite suffer from many or most of the same drawbacks as animal litter made solely with sodium bentonite, and often exhibit poor clumping properties.

[0007] Newer, lighter weight products are now replacing sodium bentonite-based animal litters in the retail market. Natural animal litters derived from distillers grains were early products but had difficulty meeting even the 90% clump retention standard. Applicant's newer extruded grain-based animal litters have better clumping performance than the best clumping sodium bentonite-based animal litters and have therefore achieved considerable commercial success in the marketplace; nevertheless, improvements in clumping animal litters remain desirable.

[0008] For example, what is needed is an animal litter that complements extruded grain granule animal litter, which not only hardens when wet, and is superior to many of the bentonite-based and bentonite multi-component animal litter still prevalent on the market, but which also possesses, and preferably further improves upon, one or more of the desirable properties and characteristics of Applicant's own commercially successful extruded grain granule animal litter.

[0009] Tracking is also a concern in modern cat litter boxes. This is because it is desirable not only to prevent litter from escaping the litter box, but also to prevent litter from adhering to or accumulating on the cat's paws in the first place. Tracking depends on the wetness of the cat's paws and the wetness of the litter in the litter box. It is also related to the shape of the litter particles and pellets. Because cats have hair and sweat glands between their paw pads, litter particles and pellets can become entangled in the fur between their paw pads. The hair acts like a spring, pushing small particles back after they penetrate between the pads, often causing them to become trapped in the fur. Small dust-like particles can become entangled in the fur between a cat's paw pads, especially when the cat is sweating. If the accumulation of litter particles in the fur between the pads of a cat's paws becomes too great or deeply embedded, it can cause pain when the cat walks, and a veterinarian may (and often does) need to remove the entangled litter particles.

[0010] What is also needed is an animal litter that has anti-stick properties that prevent litter from sticking to a cat's paws while using the litter box. [Means for solving the problem]

[0011] The present invention relates to a self-clumping, absorbent granular animal litter and a method for manufacturing the same, wherein the self-clumping, absorbent granular animal litter is comprised of self-clumping, absorbent animal litter particles comprising a generally rounded self-clumping absorbent coated on a base animal litter particle. Each of the generally rounded, self-clumping, absorbent-coated base animal litter particles comprises a coating having a generally rounded outer surface, the outer surface of which is at least partially, and preferably substantially completely, formed with microscopic water absorption-enhancing protrusions (e.g., spikes), which are formed by protrusions raised from the outer surface of the particle during the agglomeration process. The outer surface of the coating of each of the generally rounded, self-clumping, absorbent-coated base animal litter particles is also configured to comprise numerous water absorption-enhancing microcracks that are formed on the outer surface during post-agglomeration curing and post-agglomeration drying.

[0012] Each coated substrate litter particle is formed from an inner substrate in the form of a litter particle nucleating substrate particle and an outer modified starch water-absorbent clumping agent configured to absorb water or urine during litter use, clump, and self-clump into a removable, scoopable clump of wetted litter particles, said clumps comprising at least a plurality of pairs of coated substrate litter particles, scoopable using a perforated litter scoop with a handle, having a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, and having a clump crush strength when dry of at least 40 pounds per square inch (PSI), preferably at least 60 PSI, more preferably 80 PSI, and even more preferably 100 PSI. In a preferred self-clumping absorbent coated substrate litter particle embodiment, each coated substrate litter particle of the present invention has an outer coating of modified starch water-absorbent clumping agent adhesively self-adhered to the outer surface of the inner substrate particle by inner self-adhesive regions using the clumping method of the present invention, which is described in more detail below.

[0013] In one preferred embodiment, the self-clumping animal litter of the present invention is at least 20%, preferably at least 30%, and more preferably at least a majority, i.e., at least 50%, (by weight of the animal litter) made up of self-clumping absorbent coated substrate animal litter particles of the present invention, forming a multi-component animal litter, the remainder of which may be made up of one or more other types of granular components, such as non-clumping calcium bentonite particles and / or non-clumping organic particles, which still form removable, scoopable clumps when wetted with water or urine, have a clump retention of at least 95%, preferably at least 97%, and more preferably at least 99%, and have a dry clump compressive strength of at least 40 PSI, preferably 60 PSI, more preferably 80 PSI, and even more preferably 100 PSI. Such self-clumping absorbent granular animal litter can be a multi-component animal litter containing in the range of 20% to 100% of the self-clumping absorbent coated substrate animal litter particles of the present invention, and advantageously improves upon one or more of the properties and / or characteristics of past and current sodium bentonite animal litter and sodium bentonite-based animal litter, by producing lighter weight, cheaper to manufacture and ship, easier to handle during transport, easier for users to lift, carry and pour, less dusty, preferably dust-free or dust-suppressing, and rounded coated substrate animal litter particles that do not easily adhere to a cat's paws, thereby advantageously reducing carry-out from the litter box.

[0014] During the manufacture of coated substrate animal litter particles, a coating of modified starch-based water-absorbent flocculant is applied to the outer surface of the substrate particle, preferably by wet flocculation. At this time, some (but not all) of the modified starch-based water-absorbent flocculant is used to form an inner self-adhering region of the coating that adheres directly to the outer surface of the substrate particle. The inner self-adhering region of the coating is applied directly to the outer surface of the substrate particle by wetting at least one of the outer surface and the modified starch-based water-absorbent flocculant material applied to the outer surface. This leaves the remaining modified starch-based water-absorbent flocculant in the outer region of the coating surrounding the inner self-adhering region, substantially unmodified and unchanged, and capable of absorbing water and promoting flocculation when wetted with water or urine during use of the animal litter or absorbent material. The inner adhesive region is self-adhering because it is formed from the same modified starch-based water-absorbent flocculant as the outer region, but some of its adhesive properties are activated to adhere the inner adhesive region directly to the outer surface of the substrate particle. In addition to the water-absorbing nature of at least one component of the modified starch-based water-absorbing flocculant in the coating of each coated substrate, the modified starch-based water-absorbing flocculant also has, as at least one other component of the coating of each coated substrate, a water-activated adhesive (preferably a moisture-curing water-activated adhesive) that is activated when wetted with an aqueous wetting liquid, such as water or urine, and becomes at least tacky and preferably also flowable, forming a flowable adhesive, and that can also gel (i.e., thicken) during or after flow.

[0015] In a preferred embodiment, the modified starch-based water-absorbing flocculant comprises a first adhesive component and a second adhesive component. The first adhesive component is an at least partially water-soluble adhesive that can be water-activated and water-cured once, and the second adhesive component is an at least partially water-soluble adhesive that can be water-reactivated and water-cured. The second adhesive component can be water-reactivated and water-cured at least multiple times, more preferably at least three times. In a preferred embodiment, the first adhesive component is a starch that has been at least physically modified during extrusion, i.e., a physically modified starch, preferably a dextrinized starch, which may contain dextrin, but is not necessarily dextrin. In such a preferred embodiment, the second adhesive component is a starch that has been modified to form a starch pregel or pregelatinized starch during extrusion and has adhesive properties.

[0016] The coating applied to the substrate granules or particles includes both a first adhesive component and a second adhesive component. In a preferred embodiment, the coating applied to the substrate granules or particles includes a first adhesive component, a second adhesive component, and a third water-absorbent component configured to absorb room temperature water or cat urine. In one embodiment, at least one of the first, second, and third components includes or consists of a cold-water soluble starch capable of absorbing water and urine and at least partially solubilized in room temperature water and cat urine. In another embodiment, at least both the first and second components include or consist of both a water-absorbent starch that absorbs water and urine and a modified starch that at least partially solubilizes in room temperature water and cat urine.

[0017] During the production of substrate-coated litter particles, preferably by flocculation, the modified starch water-absorbing flocculant and / or the outer surface of the substrate particle are wetted with an aqueous dampening fluid, preferably water, to ultimately wet at least a portion of the modified starch water-absorbing flocculant and activate some (if not all) of the water-activated adhesive in the modified starch water-absorbing flocculant in forming the internal self-adhesive domains. In at least one preferred embodiment of the modified starch water-absorbing flocculant, at least a portion of the adhesive activated by the aqueous dampening fluid becomes at least somewhat tacky, preferably tacky, such that at least a portion of the modified starch water-absorbing flocculant adheres to and bonds with the outer surface of the substrate particle. In at least another preferred embodiment of the modified starch water-absorbing flocculant, at least a portion of the adhesive activated by the aqueous dampening fluid gelates, such that at least a portion of the modified starch water-absorbing flocculant adheres to and bonds with the outer surface of the substrate particle in forming the internal self-adhesive domains. In at least another preferred embodiment of the modified starch water-absorbing flocculant, at least a portion of the adhesive activated by the aqueous dampening fluid becomes flowable, preferably forming a flowable adhesive, and at least a portion of the modified starch water-absorbing flocculant adheres to and bonds with the outer surface of the substrate particle, forming an inner self-adhesive region. In at least one preferred embodiment of the modified starch water-absorbing flocculant, at least a portion of the adhesive activated by the aqueous dampening fluid wetting the modified starch water-absorbing flocculant becomes tacky, at least a portion of the adhesive activated by the aqueous dampening fluid wetting the modified starch water-absorbing flocculant gels, and / or at least a portion of the adhesive activated by the aqueous dampening fluid wetting the modified starch water-absorbing flocculant forms a flowable water-activated adhesive, whereby at least a portion of the modified starch water-absorbing flocculant adheres to and bonds with the outer surface of the substrate particle, forming an inner self-adhesive region.

[0018] This adhesiveness, combined with the rolling action of the substrate particles, such as in a rotating drum, during aggregation, results in the coated substrate animal litter particles of the present invention having an outer surface with a substantial number of raised protrusions (preferably including spikes) across their entire outer surface. These microscopic protrusions (including spikes) are microscopic in size, extending outward from the surface of the coated substrate animal litter particle by no more than 5 microns, preferably no more than 2 microns, and more preferably no more than about 1 micron (1 micron ± 0.25 microns). Preferably, these microscopic protrusions (including spikes) are nano-sized or nano-sized, each extending no more than 1 micron from the outer surface. This rolling action (as occurs in a rotating drum) can cause the coated substrate animal litter particles of the present invention to have a rounded shape, making them substantially round, minimizing the likelihood of them adhering to a cat's paws during use and minimizing tracking. Because these protrusions (including spikes) are microscopic in size, when water or urine wets the protrusions (including spikes), it spreads substantially along the entire outer surface of the coated substrate animal litter particle by capillary action, accelerating absorption and thereby advantageously improving absorption while maintaining the generally rounded configuration or shape of the coated substrate animal litter particle, which minimizes tracking.

[0019] Upon curing, the spike-containing projections become substantially hard, forming absorption-promoting microcracks on the outer surface. These microcracks continue to form and propagate after curing, during drying, and even during storage of the coated substrate litter particles after packaging and before use. The length of these microcracks can range from nanoscale or nano-sized, i.e., less than 1 micron, to the same length as the multi-micron thickness of the flocculant coating at least partially covering the substrate particle or substrate granule. In preferred embodiments, the size of these microcracks ranges from a base thickness of about 1 micron or less and a length of about 50 microns (50 microns ± 5 microns) or less to a base thickness of about 5 nanometers (5 nanometers ± 3 nanometers) and a length of about 5 nanometers. For example, the base thickness is between about 5 nanometers and about 1 micron, and a length of about 5 nanometers and about 50 microns. These microcracks further promote absorption by capillary action (or wicking). When moistened with water or urine, openings form in the outer portion of the coated substrate litter particle coating, thereby rapidly increasing the amount of surface area in contact with the water or urine and allowing the water or urine to be absorbed. The spike-containing protrusions, working in concert with the microcracks, not only promote absorption by increasing the rate of absorption, but also accelerate the flow of fluid adhesive from each moist coated substrate litter particle, thereby promoting cohesion.

[0020] In preferred methods and embodiments, at least a portion of the adhesive of the first adhesive component of the modified starch water-absorbing flocculant is activated and hardens, thereby helping to bond the self-adhesive regions to the outer surface of the substrate particle, and at least a portion of the adhesive of the second adhesive component is also activated and hardens, thereby also helping to bond the self-adhesive regions to the outer surface of the substrate particle.

[0021] A preferred self-clumping animal litter of the present invention comprises substrate animal litter particles coated with a self-clumping absorbent, each coated substrate animal litter particle having a coating weight of modified starch-based water-absorbent clumping agent ranging from about 5% to about 35%, preferably from about 5% to 50%, more preferably from about 5% to 85%, based on the particle weight, producing a self-clumping coated substrate animal litter particle that absorbs at least two, preferably at least three, more preferably at least four, and most preferably at least six times its coating weight of water or urine, such as water at room temperature, preferably 68°-72° Fahrenheit, or urine at about cat body temperature, from about 100° Fahrenheit to about 104° Fahrenheit. Upon absorption, the wetted coated substrate animal litter particles self-clump with adjacent water- or urine-wetted animal litter particles to form clumps that can be scooped away from other unwetted or uncontaminated animal litter particles using a perforated animal litter scoop with a handle. The self-coalescing absorbent coated substrate animal litter particles of the present invention absorb at least one coating weight of water, preferably room temperature water, or urine, preferably cat urine, within 1 minute, i.e., 60 seconds, preferably 30 seconds, more preferably 20 seconds, of being wetted when they agglomerate with other wetted animal litter particles to form a mass consisting of at least pairs of said coated substrate animal litter particles. In such a preferred embodiment, each coated substrate animal litter particle is composed of about 5% to about 35%, preferably about 5% to 50%, more preferably about 5% to 85% of said modified starch-based water-absorbent flocculant by particle weight. In one preferred embodiment and method of manufacturing the coated substrate animal litter particles of the present invention, a modified starch-based water-absorbing flocculant is applied to each substrate particle until the coating weight of the flocculant relative to the weight of the substrate particle is 5% to 35%, preferably about 5% to 50%, more preferably about 5% to 85%, so that each finished coated substrate animal litter particle contains 5% to 35%, preferably about 5% to 50%, more preferably about 5% to 85% of the modified starch-based water-absorbing flocculant relative to the particle weight.

[0022] In preferred self-cohering, absorbent-coated substrate animal litter particles of the present invention, the particle coating weight of the external modified starch-based water-absorbent flocculant on the internal substrate particle ranges from about 5% to about 35%, preferably from about 5% to 50%, and more preferably from about 5% to 85% by particle weight. This particle coating weight is sufficient to form a coating on the self-cohering, coated substrate animal litter particle such that each particle absorbs at least one time the coating weight of the coated substrate animal litter particle in water or urine, and swells in volume upon absorption of water or urine by at least 25%, preferably at least 35%, more preferably at least 50%, and most preferably at least 80% compared to the volume of the animal litter particle before wetting. In a preferred embodiment, each self-cohering, absorbent-coated substrate animal litter particle of the present invention has a particle coating weight of the external modified starch-based water-absorbent flocculant on the internal substrate particle ranges from about 5% to about 35%, preferably from about 5% to 50%, and more preferably from about 5% to 85% by particle weight. The particle coating weight is sufficient to form a coating on the self-cohering coated substrate animal litter particles such that each particle absorbs at least twice the coating weight of the coated substrate animal litter particle in water or urine, and upon absorption of water or urine, swells in volume by at least 25%, preferably at least 35%, more preferably at least 50%, and most preferably at least 80% compared to the volume of the animal litter particle before wetting.

[0023] The self-clumping, absorbent coated substrate litter particles of the present invention are preferably swelling and gelling self-clumping, absorbent coated substrate litter particles, wherein the outer region of the modified starch-based water-absorbent flocculant outer coating swells upon absorption of water or urine, preferably room temperature water or cat body temperature urine, wetting the particle and substantially simultaneously forming a gel on and along the outer surface of the coated substrate litter particle and in a depth direction below the surface, the gel preferably being tacky when wet and can, or preferably containing, a water-activated, moisture-curing adhesive, which promotes cohesion with other contacting litter particles by its tackiness or adhesive properties and adhesively bonds contacting particles into the aggregate by moisture-curing as the water evaporates from the aggregate as the aggregate dries. In one embodiment of the coated substrate litter particles of the present invention, the modified starch water-absorbent flocculant outer coating of each wetted coated substrate litter particle at least partially solubilizes in water or urine, preferably in water at room temperature or urine at cat body temperature, to form a flowable, water-activated, moisture-curing adhesive whose viscosity remains sufficiently low, preferably 15,000 centipoise or less, more preferably 10,000 centipoise or less, even more preferably about 5,000 centipoise or less, for a sufficiently long period of time, preferably at least 1 second, more preferably at least 4 seconds, after wetting, to enable the modified starch water-absorbent flocculant of the litter particle, wetted with water or urine, to flow along and between contacting and adjacent particles, and thereafter increase in viscosity to reform into a cohesive, semi-solid gel having a viscosity of at least about 30,000 centipoise, preferably at least 50,000 centipoise, more preferably at least 80,000 centipoise, within 20 seconds after wetting, preferably within 10 seconds after wetting, more preferably within 5 seconds after wetting. As the viscosity of the flowable adhesive increases, the adhesive gels (but remains at least somewhat tacky) and the moisture in the formed mass hardens during drying, hardening into a glassy material that has a glassy state at room temperature, thereby bonding the agglomerated particles together, these bonds including at least one of hydrogen bonds and covalent bonds, preferably covalent bonds.In any event, the resulting mass formed will be sufficiently hard to have a mass retention of at least 95%, preferably at least 97%, more preferably at least 99%, and a mass crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably 80 PSI, and even more preferably at least 100 PSI when the mass is dried to a moisture content of about 12% (12%±1.5%) by mass weight.

[0024] Preferably, at least a portion of the modified starch-based water-absorbing flocculant in each animal litter particle of the present invention is at least partially solubilized by room temperature water or cat urine that contacts the particle, forming a flowable adhesive. The flowable adhesive is preferably a water-activated flowable adhesive and is moisture-curable, flowing outward from the wetted particle and between adjacent contacting animal litter particles. The flowable adhesive initially has a flowable viscosity higher than that of water, and increases in viscosity over time to solidify into an adhesive gel. This gel initially bonds contacting animal litter particles together through surface tension, capillary action, liquid adhesive forces, and / or intermolecular forces (e.g., van der Waals forces), and upon drying and moisture-curing, transforms into a more viscous, cohesive gel that more firmly bonds contacting animal litter particles together, preferably through at least hydrogen bonds and / or preferably at least some covalent bonds. The initially flowable adhesive transitions over time into an adhesive gel, then a cohesive gel, and as the moisture cure continues until the moisture content dries to less than 15% by weight, preferably 12% or less, to form a substantially fully cured solid adhesive that becomes a glassy solid adhesive that adhesively bonds contacting animal litter particles by at least hydrogen bonds, i.e., hydrogen bonding, and / or preferably covalent bonds, i.e., covalent bonds. At least pairs of animal litter particles of the present invention, i.e., at least three animal litter particles, are wetted with water or urine and are adhesively bonded by the solid adhesive formed from the initially flowable adhesive by hydrogen bonds, covalent bonds, or a combination of hydrogen and covalent bonds, to form a substantially fully moisture cured, rock-hard mass, the mass having a moisture content of about 12% by mass, a mass crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably at least 100 PSI, and a mass retention of at least 95%, preferably at least 97%, and more preferably at least about 99%. In a preferred embodiment of the modified starch-based water-absorbing flocculant in each coated substrate animal litter particle of the animal litter of the present invention, the modified starch-based water-absorbing flocculant is composed of the following (1) and (2): (1) a water-swellable modified starch (preferably a cold-water-swellable modified starch) that has water absorption properties, swells upon absorbing water, and absorbs at least 4.5 times, preferably at least 6 times, the weight of the animal litter particle in water at room temperature or urine at cat body temperature, and (2) a water-soluble modified starch binder (preferably a cold-water-soluble modified starch binder) that is at least partially cold-water soluble in water at room temperature. the modified starch-based water-absorbent flocculant is at least partially soluble in cat urine at body temperature, is flowable upon at least partial solubilization and flows out of the moistened animal litter particles, increases in viscosity during moisture cure to form a tacky adhesive gel, adhering particles together by at least one of liquid adhesion, hydrogen bonding, and / or other intermolecular forces, increases in viscosity during further moisture cure to form a cohesive gel, adhering particles together by at least one of hydrogen bonding and covalent bonding, and upon substantially complete moisture cure to a moisture content of less than 15%, preferably 12% by weight or less, becomes a substantially solid adhesive that is a glassy material having a glassy material state. The water-swellable modified starch (preferably cold water-swellable modified starch) of the modified starch-based water-absorbent flocculant in each animal litter particle is composed of natural starch. The native starch is derived from one or more grains, such as corn, rice, wheat, rye, barley, millet, triticale, oats, fonio, and sorghum, and / or one or more legumes, such as beans, soybeans, peas, chickpeas, peanuts, lentils, lupin, mesquite, carob, tamarind, alfalfa, and / or clover.The native starch is preferably physically modified by a starch modification method or process to degrade starch granules and / or reduce the molecular weight of one or both of the amylose and / or amylopectin molecules of the native starch.The starch modification method or process is, for example, extrusion molding, and the native starch is processed in a starch modification machine, such as an extruder, preferably a single-screw extruder.The native starch is modified to a water-swellable, water-absorbent modified starch, preferably a cold-water-swellable, cold-water-absorbent modified starch, by subjecting it to an ultra-high extrusion pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI in an extruder, and an extrusion temperature of at least 100° F. The at least partially soluble, preferably at least partially cold-water soluble, modified starch binder of each animal litter particle of the modified starch-based water-absorbent flocculant is also composed of native starch. The native starch is derived from one or more grains, such as corn, rice, wheat, rye, barley, millet, triticale, oats, fonio, and sorghum, and / or one or more legumes, such as beans, soybeans, peas, chickpeas, peanuts, lentils, lupin, mesquite, carob, tamarind, alfalfa, and / or clover.The native starch is preferably physically modified by a starch modification method or process to degrade starch granules and / or reduce the molecular weight of one or both of the amylose and / or amylopectin molecules of starch.The starch modification method or process is, for example, extrusion molding, and the native starch is processed in a starch modification machine, such as an extruder, preferably a single-screw extruder. The native starch is modified in an extruder under ultra-high extrusion pressures of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI, at an extrusion temperature of at least 100° F. to form an at least partially water soluble modified starch, preferably at least partially cold water soluble modified starch, which comprises a water-activated moisture-setting binder that is activated with room temperature water and / or cat urine to form a flowable adhesive having the properties and characteristics described above.

[0025] In producing the coated substrate litter particles of the present invention, a pulverized form of the modified starch-based water-absorbing flocculant, preferably a milled form obtained by milling, is used. The form has a relatively small particle size smaller than the smallest substrate particle, preferably in the size range of flour or powder. Specifically, it passes through a 40-mesh screen, preferably a 60-mesh screen, more preferably a 40-60-mesh screen, and is retained on a smaller mesh screen, such as an 80-mesh screen. In this process, extruded pellets produced using the extrusion method described above and / or methods disclosed elsewhere herein are milled using a mill to produce powder or flour having the mesh size described above in this paragraph.

[0026] In preferred embodiments and practice of the method for producing substrate-coated litter particles, freshly extruded pellets produced according to at least one modified starch water-absorbing flocculant extrusion method disclosed herein can be used as a modified starch water-absorbing flocculant to be agglomerated with substrate particles or particles to produce coated substrate litter in accordance with the present invention. In practice of such preferred embodiments and methods, the freshly extruded pellets can be mixed with water to form a slurry, which can be applied to the substrate particles or substrate particles in a manner described in more detail below. In practice of another such preferred embodiment and method, water can be applied to the substrate particles or substrate pellets in an agglomerator or coater, preferably a rotary or tumbling agglomerator or coater, after which the freshly extruded pellets can be mixed and the substrate particles or substrate particles can be agglomerated into the coated substrate litter particles of the present invention in a manner described in more detail below.

[0027] In other preferred embodiments and method practices, the as-extruded pellets are broken down into smaller particles of the modified starch-based water-absorbing flocculant using a high-speed, high-shear mixer, such as a batch, in-line, or granulator-type high-speed, high-shear mixer. In one such preferred embodiment and method practice, the as-extruded pellets are broken down with water in such a high-shear mixer to form a substantially homogeneous slurry of smaller pellet particles of the modified starch-based water-absorbing flocculant, which is then coated as a slurry onto substrate granules or particles that are preferably tumbled and agitated in a rotary granulator or coater in a manner described in more detail below.

[0028] In yet another preferred embodiment and method practice, the modified starch-based water-absorbing flocculant is formed from a combination of a powder or flour having the mesh size defined above and extruded pellets produced according to at least one of the modified starch-based water-absorbing flocculant extrusion methods disclosed herein. In one such preferred embodiment and method practice, the mixture of the powdered or floured modified starch-based water-absorbing flocculant and the extruded pellets is homogenized into a water-containing slurry using a high-speed, high-shear mixer in the manner described above.

[0029] Optionally, the modified starch-based water-absorbing flocculant can be in the form of grain-based animal litter particles classified as too small for use in any of the extrusion-type animal litter disclosed in one or more of commonly owned U.S. Patent Nos. 9,491,926, 10,028,481, 10,098,317, 10,882,238, 11,013,211, and / or 11,083,168, each of which is expressly incorporated by reference in its entirety. Optionally, particles of modified starch-based water-absorbing flocculant obtained from rejected particles of extrusion-type animal litter made in accordance with one or more of the foregoing patents can be further reduced in size, for example, by grinding, e.g., hammer mill grinding, use of other particle size reduction machinery, and / or use of other particle size reduction or particle grinding methods, such as the particle size reduction systems, apparatus, and methods disclosed in commonly owned U.S. Patent No. 11,013,211, which is expressly incorporated by reference in its entirety.

[0030] In a method for manufacturing self-clumping absorbent animal litter particles for a preferred animal litter according to the present invention, as will be described in more detail below, these powdered or pulverulent relatively small modified starch-based water-absorbent flocculant particles are wetted with an aqueous wetting liquid such as water, thereby activating some (but not all) of the at least partially water-soluble binder in at least some of the modified starch-based water-absorbent flocculant particles, causing some (but not all) of the modified starch-based water-absorbent flocculant particles to adhere in a wet state to the outer surface of each base particle, and then, when substantially completely moisture-cured and dried, to be adhesively bonded to the outer surface of each base particle, forming an internal adhesion region between the internal base particle and the outer modified starch-based water-absorbent flocculant region of each animal litter particle. Upon wetting substantially all of the modified starch-based water-absorbent flocculant particles with an aqueous wetting solution, some (but not all) of the at least partially water-soluble binder of the remaining unattached wet modified starch-based water-absorbent flocculant particles is activated, such that some (but not all) of the modified starch-based water-absorbent flocculant particles that contact the internal attachment region adhere to the internal attachment region in a wet state, and then, upon substantially complete moisture curing and drying, become adhesively bonded thereto, forming one or more additional modified starch-based water-absorbent flocculant regions in each animal litter particle being manufactured.

[0031] In one preferred method of making animal litter granules, the modified starch-based water-absorbent flocculant particles are wetted by mixing the powdered or pulverulent modified starch-based water-absorbent flocculant particles with an aqueous wetting liquid (preferably water) to form a slurry and applying the slurry to the substrate particles, preferably while substantially simultaneously mixing the slurry with the substrate particles by tumbling, stirring, or other methods such as using a mixer, coater, blender, or other mixing device or arrangement, thereby forming an inner adhesive region on the outer surface of each substrate particle before forming the outer region of the modified starch-based water-absorbent flocculant. In another preferred method for manufacturing animal litter granules, the modified starch-based water-absorbing flocculant particles are moistened by an indirect method in which an aqueous liquid (preferably water) is applied to the base particles to moisten them, and then dry particles of the modified starch-based water-absorbing flocculant in powder or pulverulent size are applied to the moistened base particles, preferably while the moistened base particles and the applied modified starch-based water-absorbing flocculant particles are rolled, stirred, or otherwise mixed, so that the moisture on the surface of the base particles moistens the modified starch-based water-absorbing flocculant particles that come into contact with them, thereby forming internal adhesive regions on the outer surface of each base particle. Preferably, one or more wetting cycles and application cycles are performed, with each wetting cycle applying additional aqueous wetting liquid onto the at least partially coated substrate particles substantially simultaneously with or substantially immediately after another application cycle applying additional powder-sized or pulverulent-sized modified starch-based water-absorbing flocculant particles onto the wetted, at least partially coated substrate particles, all of which are performed while tumbling, stirring or otherwise mixing the wetted, at least partially coated substrate particles until one or more additional outer regions are added onto the inner adhesive region of each formed animal litter particle.

[0032] An aqueous wetting liquid, preferably water, is applied to the substrate particles and the at least partially formed animal litter particles until a desired thickness of coating of modified starch-based water-absorbent flocculant particles is accumulated on each substrate particle, thereby forming a finished animal litter particle, such that the modified starch-based water-absorbent flocculant particles applied to each substrate particle are wetted, causing the modified starch-based water-absorbent flocculant particles in the outer region of each animal litter particle surrounding its inner substrate particle to coalesce into a region of amorphous, substantially homogeneous modified starch-based water-absorbent flocculant material that is adhesively bonded to its inner substrate particle when substantially fully moisture-cured. Preferred self-cohering absorbent particles of the present invention produced by the manufacturing method disclosed herein have an outer region of the modified starch-based water-absorbent flocculant having a thickness of 1 mm or less, preferably 0.8 mm or less, more preferably about 0.5 mm or less, and even more preferably about 0.3 mm or less, and at least 50%, preferably at least 80%, more preferably at least 95%, and even more preferably substantially the entire outer surface of each substrate particle of each animal litter particle is coated with the modified starch-based water-absorbent flocculant material. One preferred self-cohering absorbent particle of the present invention produced by the manufacturing method disclosed herein has an outer modified starch-based water-absorbent flocculant region having a thickness of 20 microns (i.e., 0.02 mm) to 1000 microns (i.e., 1 mm), preferably 20 microns (i.e., 0.02 mm) to 800 microns (i.e., 0.8 mm), more preferably 20 microns (i.e., 0.02 mm) to 500 microns (i.e., 0.5 mm), and even more preferably 20 microns (i.e., 0.02 mm) to 300 microns (i.e., 0.3 mm), wherein at least 50%, preferably at least 80%, more preferably at least 95%, and even more preferably substantially the entire outer surface of each substrate particle of each animal litter particle is coated with said modified starch-based water-absorbent flocculant material.

[0033] In a preferred embodiment, the rounded coated substrate animal litter particles are advantageously sized to minimize removal of the animal litter from the animal litter box during use and operation of the coated substrate animal litter of the present invention. The roundness of the coated substrate animal litter particles is advantageous in preventing the coated substrate animal litter particles from becoming entangled in a cat's paws during use of the animal litter box. Furthermore, the coated substrate animal litter particles are sized to also help prevent removal of the animal litter box by a cat during use of the animal litter box. In a preferred embodiment, the coated substrate animal litter particles should be sized larger than a 25-mesh sieve (i.e., larger than 25 mesh) and not larger than a 10-mesh sieve (i.e., not larger than 10 mesh). At least 80% of the coated substrate animal litter particles should be sized smaller than 10 mesh and larger than 25 mesh (10 / 25). For example, in one embodiment, between 60% and 95%, preferably about 80% (80%±15%) of the particles pass through a 12 mesh sieve but larger than a 25 mesh sieve. The remaining coated substrate animal litter particles are larger than 10 mesh. Rounded coated substrate animal litter particles having a particle size distribution between 12 mesh and 20 mesh (12 / 20) provide an optimal feel on a cat's paws.

[0034] Thus, in one preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have raised protrusions including spikes, and have a particle size distribution between 12 mesh and 20 mesh (12 / 20), thereby producing a preferred embodiment of a low-tracking litter that minimizes tracking by cats out of the litter box. In another preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have raised protrusions including spikes, and have a particle size distribution between 10 mesh and 25 mesh (10 / 25), thereby producing another preferred embodiment of a low-tracking litter that minimizes tracking by cats out of the litter box.

[0035] In a method for applying a modified starch-based water-absorbent flocculant to a base particle to produce the self-cohesive, absorbent coated base granules of the present invention, a slurry containing a predetermined amount (e.g., a predetermined weight or mass) of modified starch-based water-absorbent flocculant particles is applied to a predetermined amount (e.g., a predetermined weight or mass) of base particle depending on the type and size of the base particle, with each predetermined amount of modified starch-based water-absorbent flocculant being slurried in water selected based on the size or size range and predetermined amount of base particle to be coated to form the self-cohesive, absorbent granules of the present invention. In a preferred method for producing the self-cohering absorbent granules of the present invention using a slurry of water and modified starch-based water-absorbing flocculant particles, the slurry is applied to base granules or base particles tumbling within the rotating barrel or drum of a drum mixer, cement mixer, drum coater or similar equipment using one or more spaced spray heads, nozzles, misters, or other types of slurry applicators or distributors configured or operated to controllably discharge the slurry onto the base particles within the rotating mixer or coater barrel when producing the self-cohering absorbent granules of the present invention. In another preferred method for applying the modified starch-based water-absorbing flocculant to a base granule or substrate particle to produce the self-cohering, absorbent, coated substrate granules of the present invention, the base particle is wetted with an aqueous wetting liquid such as water, and the dried particles of the modified starch-based water-absorbing flocculant are applied to the base particle, modified starch-based water-absorbing flocculant particles, and aqueous wetting liquid (preferably water), first to the base particle alone, and then to the base particle, modified starch-based water-absorbing flocculant particles, and aqueous wetting liquid (preferably water), while they are all mixed together, preferably tumbling or otherwise agitated in a rotating barrel such as a drum mixer, cement mixer, drum coater, etc. This cycle of wetting the at least partially coated base particle with aqueous wetting liquid (preferably water) and then applying the modified starch-based water-absorbing flocculant particles is repeated one or more times as necessary until each base particle achieves the desired granule coating weight (e.g., coverage) and / or outer layer thickness of the modified starch-based water-absorbing flocculant, thereby producing the finished self-cohering, absorbent granules of the present invention.The at least partially moistened, finished self-cohering absorbent granules are then subjected to a moisture curing step, preferably a moisture removal step, such as by drying the at least partially moistened, finished granules using convective drying with flowing air, preferably turbulent air, directed at the granules, by drying in a heated oven using one or more of radiant heat, convective drying with heated air, or other types of heated drying methods, until moisture curing is complete or substantially complete in each granule when each granule has been dried to a moisture content of 12% or less, preferably greater than 10%, and more preferably 8% or less, by weight of the granule.

[0036] When a slurry is used in producing the self-clumping, absorbent-coated substrate animal litter particles of the present invention, the slurry is a mixture of water and relatively small particles of modified starch-based water-absorbent flocculant, preferably powder or dust-sized, mixed with water until a substantially uniform mixture or slurry is formed. As described above, mixing can be performed using a high-speed, high-shear mixer. In a preferred slurry, when water is used as the aqueous wetting liquid, the ratio of the amount of modified starch-based water-absorbent flocculant to water is about 1:1±10% by weight. The slurry is applied to the substrate particles while the substrate particles are being stirred, tumbled, or otherwise mixed in a rotating barrel, drum, or chamber of a mixer, coater, or blender, thereby forming regions of the modified starch-based water-absorbent flocculant on each of the substrate particles until the desired area thickness or desired particle coating weight of the modified starch-based water-absorbent flocculant on the substrate particles is reached. Tumbling in a rotating barrel or drum-type mixer or coater is preferred. This is because the above-described method also ensures that rounded coated substrate animal litter particles are produced to minimize spillage from the cat litter box. The water in the slurry activates at least some, but not all, of the water-soluble modified starch binder (preferably a cold-water soluble modified starch binder) in the modified starch-based water-absorbent flocculant particles in the slurry. This creates a sticky gel and flowable adhesive that adheres the modified starch-based water-absorbent flocculant particles to the substrate particles to which the slurry is applied. This adhesion ensures that protrusions (including spikes) are formed on the outer surfaces of the coated substrate particles, thereby improving the amount and speed of water absorption during use of the animal litter. The slurry is applied to the substrate particles while the substrate particles are being stirred, tumbling, or mixed. This not only promotes uniform adhesion of the modified starch-based water-absorbent flocculant particles to each substrate particle, but also helps prevent agglomeration of the at least partially coated substrate particles during the production of slurry-based self-clumping, absorbent animal litter particles.The slurry is applied onto the substrate particles while the substrate particles are tumbling, stirring, and / or mixing until a desired thickness or particle coverage weight of the modified starch-based water-absorbent flocculant particles on the substrate particles is reached. In a preferred method embodiment, the initial application of the slurry onto the substrate particles causes each substrate particle to act as a nucleator for the animal litter particles, with the modified starch-based water-absorbent flocculant in the slurry adhering to the outer surface of each substrate particle to form an internal adhering region, whose moisture wettability promotes more rapid adhesion of another external region of the modified starch-based water-absorbent flocculant.

[0037] In a preferred method of slurry application, a slurry containing a predetermined amount (e.g., a predetermined weight or mass) of modified starch-based water-absorbent flocculant particles is applied to a predetermined amount (e.g., a predetermined weight or mass) of substrate particles, depending on the type and size of the substrate particles. This slurry is prepared by dissolving a corresponding predetermined amount of modified starch-based water-absorbent flocculant in water selected based on the size or size range and predetermined amount of substrate particles to be coated into the self-cohesive, absorbent granules of the present invention. In a preferred method of producing the self-cohesive, absorbent animal litter granules of the present invention using a slurry of water and modified starch-based water-absorbent flocculant particles, the slurry is applied to the substrate particles tumbling within the rotating barrel or drum of a drum mixer, cement mixer, drum coater, or similar device using one or more spaced spray heads, nozzles, misters, or other type of slurry application or distribution device configured or operated to controllably discharge the slurry onto the substrate particles within the rotating mixer or coater barrel to produce the self-cohesive, absorbent animal litter granules of the present invention.

[0038] In a preferred embodiment of the slurry application method, the amount of slurry applied to the substrate particles, and preferably the application rate, such as volumetric flow rate or metering, is varied in real time as the slurry is applied to the substrate particles, thereby (a) controlling the granular coating weight and / or thickness of the modified starch-based water-absorbing flocculant that forms an outer layer around each substrate particle, and (b) preventing the substrate particles, at least partially coated with a layer of modified starch-based water-absorbing flocculant, from agglomerating during tumbling, stirring, or other mixing. The ratio of modified starch-based water-absorbent flocculant to water can also be controlled or varied in real time during application of the slurry to the substrate particles, for example, within a range of 1:1 to +25%, or 1:1 to -25%, up to ±25%, thereby controlling: (a) activation of the at least partially soluble modified starch binder by water; (b) the deposition / coating rate of the granular coating weight of the modified starch-based water-absorbent flocculant attached to and / or coating each of the substrate particles; (c) the granular coating weight of the modified starch-based water-absorbent flocculant attached to and / or coating each of the substrate particles; (d) the thickness of the outer layer of the modified starch-based water-absorbent flocculant attached to and / or coating each of the substrate particles during production of the animal litter particles of the present invention; (e) the viscosity of the slurry; and / or (f) prevention of agglomeration of partially coated or partially formed animal litter particles during tumbling, stirring, or other mixing.

[0039] In one preferred embodiment of the method, the formed slurry can be, and preferably is, in the following form: (a) a suspension obtained by mixing an aqueous wetting liquid (preferably water) with dry particles of the modified starch-based water-absorbing flocculant using a high shear mixer, other suitable type of blender, or other suitable type of mixer until a suspension is formed, or (b) an emulsion obtained by mixing an aqueous wetting liquid (preferably water) with dry particles of the modified starch-based water-absorbing flocculant using a high shear mixer, other suitable type of blender, or other suitable type of mixer until an emulsion is formed. When using such a slurry in the form of a suspension, the suspension may contain one or more surfactants (including one or more super surfactants) to promote the suspension of the powder-sized or powder-like dry particles of the modified starch-based water-absorbing flocculant in the aqueous wetting liquid (preferably water) during the slurry-suspension mixing step when all components of the suspension are mixed. When such a slurry in the form of an emulsion is used, the emulsion may contain (1) one or more surfactants (including one or more supersurfactants), and / or (2) one or more emulsifiers for emulsifying or promoting the emulsification of all the dry powder or powdery particles of the modified starch-based water-absorbent flocculant in the aqueous wetting liquid (preferably water) when all the components of the emulsion are mixed in the slurry-emulsion mixing step. During application of the slurry to the substrate particles, the ratio of the modified starch-based water-absorbent flocculant to water in the slurry suspension or emulsion can be controlled, preferably in real time, during application of the slurry suspension or emulsion to the substrate particles to control at least one of the viscosity, the rate of increase in coating thickness of the modified starch-based water-absorbent flocculant, the amount of coating thickness of the modified starch-based water-absorbent flocculant, and / or the granular coating weight of the modified starch-based water-absorbent flocculant on each substrate particle.Such a slurry suspension or emulsion is preferably a substantially homogeneous suspension or emulsion of modified starch-based water-absorbent flocculant particles suspended or emulsified in water, and is applied onto the substrate particles while the substrate particles are being stirred, tumbling, or otherwise mixed, whereby a region of modified starch-based water-absorbent flocculant is formed on the outer surface of each substrate particle until a desired region thickness or desired granular coating weight is reached. The water in the slurry activates at least a portion, but not all, of the water-soluble modified starch binder (preferably a cold-water soluble modified starch binder) in the modified starch-based water-absorbent flocculant particles in the slurry to form a tacky gel and flowable adhesive, which causes the modified starch-based water-absorbent flocculant in the suspension or emulsion to adhere to the substrate particles to which the slurry suspension or emulsion is applied. The slurry suspension or emulsion is applied onto the substrate particles while they are being stirred, rolled or mixed, which not only promotes more uniform adhesion of the modified starch-based water-absorbing flocculant to each substrate particle, but also helps prevent the at least partially coated substrate particles / partially finished animal litter particles from clumping together while being rolled, stirred or otherwise mixed during application of the slurry suspension or emulsion during the manufacture of the slurry-based self-clumping absorbent animal litter particles.

[0040] The slurry, slurry suspension, or slurry emulsion is applied to the substrate particles while the substrate particles are being tumbled, stirred, and / or mixed until a desired thickness or granular coating weight of modified starch-based water-absorbent flocculant particles is formed on the substrate particles, thereby producing the self-cohesive, absorbent animal litter particles of the present invention. The moisture content of the finished animal litter particles is then reduced to moisture cure the at least partially soluble modified starch binder, which was activated during the slurry application and formed a flowable adhesive and gel to adhere one or more outer regions of the modified starch-based water-absorbent flocculant to each substrate particle. The moisture content of the finished animal litter particles is reduced to a moisture content of 12% or less, preferably 10% or less, and more preferably about 8% or less, by weight of the finished animal litter particle, to substantially completely moisture cure the water-activated at least partially soluble modified starch binder, flowable adhesive, and gel to a solid adhesive in a glassy state that adhesively bonds the outer regions of the modified starch-based water-absorbent flocculant to each internal substrate particle. In at least a portion of the outer region of the modified starch-based water-absorbent flocculant in each of the finished self-clumping absorbent animal litter particles of the present invention, the at least partially soluble modified starch binder remains in an unactivated and / or unhardened state, thereby being capable of being wetted with moisture such as room temperature water or cat urine at about body temperature, and at least partially solubilizing as a flowable adhesive that flows out of the wetted animal litter particle and between contacting and adjacent animal litter particles, increasing in viscosity to form an adhesive or sticky gel during initial moisture cure, changing into a binding gel as further moisture cures, and finally changing into a glassy starch-like solid adhesive that binds contacting and adjacent animal litter particles together to form a substantially rock-hardened mass upon moisture cure due to evaporation of the moisture.Moisture curing of the mass is preferably completed when the moisture content of the mass is about 12% or less by mass weight, due to evaporation of water from the mass, such as by air drying the mass in a cat litter box, and produces a substantially rock hard mass when fully moisture cured, having a mass retention of at least 95%, preferably at least 97%, more preferably at least 99%, and / or a mass cross-section strength of at least 40 PSI, preferably 60 PSI, more preferably 80 PSI, and even more preferably 100 PSI.

[0041] The substrate particles or granules may be organic, inorganic, smooth, rough, round, cylindrical, irregularly shaped, porous, non-porous, absorbent, water-repellent, smooth, and / or rough, and are preferably non-cohesive, i.e., comprised of a material that does not form clumps when wetted with water. Preferred substrate materials include nut shells or hulls, wood, paper, sand, perlite, and bentonite, which are crushed, ground, milled, or otherwise comminuted to form relatively small-sized substrate particles, which are then at least partially coated with a modified starch water-absorbent flocculant, preferably in the form of a starch-based water-absorbent flocculating promoter, to form the self-clumping animal litter particles of the present invention, wherein an outer layer of the modified starch water-absorbent flocculant at least partially coats, and preferably substantially completely surrounds, each of the substrate particles. The modified starch water-absorbing flocculant is preferably in the form of a starch-based water-absorbing flocculating promoter, more preferably a swelling and gelling material made of modified starch configured by starch modification, which is configured to rapidly swell and absorb water, gelling in the process, preferably by extrusion molding, more preferably by ultra-high pressure extrusion molding using a single-screw extruder, and preferably also contains at least a portion of the original unmodified starch modified into an at least partially water-soluble binder that is at least partially solubilized and flows when wetted with water, forming a flowable adhesive that adheres the swelling and gelling material to the substrate particles during the production of animal litter particles. The preferred modified starch water-absorbing flocculant is preferably in the form of a starch-based water-absorbing flocculation promoter, more preferably a starch-based absorbent swellable biopolymer gelling agent, e.g., comprising a gelling biopolymer or biopolymer that gels, preferably forms a gel, when wet, and is composed of a cold water soluble extrusion-modified starch binder and a cold water swellable extrusion-modified absorbent starch, the cold water swellable extrusion-modified absorbent starch preferably being or comprising cold water swellable extrusion-modified cold water absorbent starch that has been milled or otherwise reduced in particle size to form a powder or dust that coats the substrate particles when wet.Optionally, such modified starch water-absorbing flocculant powders or dust particles are rejected or unused pellets or particles of extruded grain-based animal litter classified as too small for use in one or more animal litter disclosed in one or more of commonly owned U.S. Patent Nos. 9,491,926, 10,028,481, 10,098,317, 10,882,238, 11,013,211, and / or 11,083,168, the disclosures of each of which are expressly incorporated herein by reference. The resulting animal litter particles form the removable clumping animal litter of the present invention, each particle having an outer self-cohesive, water-absorbing region surrounding an inner substrate particle, said outer region rapidly absorbing and swelling upon contact with water, at least a portion of said outer region at least partially solubilizing to form a flowable adhesive that flows along and between contacting and adjacent animal litter particles, and gelling as the wetted animal litter particles clump together to form a clump that can be scooped from the animal litter.

[0042] In a method of making the self-cohesive coated substrate litter particles of the present invention, a desired or predetermined amount of substrate particles having particle sizes within a desired particle size range or particle size distribution is (a) (1) wetted with water while stirring, and (2) mixed with a modified starch water-absorbent flocculating agent, preferably in the form of a starch-based water-absorbent flocculating powder or powder, and stirring is continued while the water wets the exterior surfaces of the substrate particles, whereby (i) some, but not all, of the water-soluble binder is at least partially solubilized to form a flowable adhesive and the starch-based water-absorbent flocculating powder or powder adheres to the substrate particles. and (ii) some, but not all, of at least a plurality, preferably at least a plurality of pairs, i.e., at least three different types of modified starches contained in the starch-based water-absorbent, cohesion-promoting powder or powder gelatinize, thereby causing the wetted powder particles to agglomerate and form an amorphous, substantially homogeneous mass of starch-based water-absorbent, cohesion-promoting material around each of the substrate particles and forming an outer region thereof to produce the finished litter particles of the present invention, which are then dried, such as by turbulent air, heated air, and / or radiant heat directed and / or impinged on the finished litter particles. Drying is conducted to reduce the moisture content of the still-wet finished litter particles until each litter particle has a moisture content of less than 12%, preferably less than 10%, and more preferably 8% or less by weight of the particle. The moisture reduction is carried out to moisture cure the water-soluble adhesive into a solid adhesive, adhesively bonding the outer region starch-based, water-absorbent, cohesion-promoting material to the outer surface of each inner substrate particle, and to prevent water activation and / or further moisture curing of at least a portion of the at least partially soluble binder in each finished litter particle, preferably preventing the reverse thereof, so that at least a portion of the water-activatable, at least partially soluble binder in each particle remains available to cohere the particles when wetted with water or urine.

[0043] The moisture removal step (preferably a drying step) can be, and preferably is, carried out while the newly finished, still-wet granules continue to be mixed (e.g., stirred). This allows the binder that adhesively attaches the outer, self-coherent, water-absorbing regions to the inner substrate particles to harden, while simultaneously preventing water activation of the binder in the outer regions of the starch-based, water-absorbing, cohesion-promoting material that do not adhesively bond the outer regions to the outer surface of each substrate particle. The moisture removal step (preferably a drying step) can be, and preferably is, carried out while the partially coated granules (e.g., partially finished granules) are being wetted and / or rewetted. This can also include adding additional dry starch-based, water-absorbing, cohesion-promoting powder or powder material while everything is being mixed (e.g., activated), such as in the barrel or drum of a mixer. The moisture removal step (e.g., drying step) can be carried out while the substrate particles are being coated with the starch-based water-absorbing clumping promoting powder or powder material and water slurry (including while all are being mixed together), but is preferably carried out after the slurry application step is complete.

[0044] In preferred coated substrate animal litter and coated substrate animal litter particle embodiments, the modified starch-based water-absorbent flocculant is in the form of a starch-based water-absorbent flocculating powder or powder and comprises at least a plurality of types, preferably at least a plurality of pairs (i.e., at least three types), of different modified starches, each different type of modified starch having a different, preferably lower, molecular weight than the unmodified or native starch from which the corresponding modified starch is formed. Each of the different types of modified starches is formed from unmodified or native starches, preferably unmodified amylose starch and amylopectin starch, contained in one or more grains and / or pulses in a mixture containing grains and / or pulses, and the unmodified or native starches in the mixture are modified during extrusion using a single screw extruder at an ultra-high extrusion pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI, thereby modifying the unmodified or native starches to produce modified starch-based water-absorbent flocculants in the form of extrudates of starch-based water-absorbent clumping-promoting material, which are used in powder or dust form in the manufacture of the self-clumping, absorbent animal litter particles of the animal litter of the present invention.

[0045] The substrate moisture application method in the production of coated substrate animal litter particles of the present invention includes wetting the substrate particles before applying a modified starch-based water-absorbing flocculant (preferably in the form of a starch-based water-absorbing flocculation promoting powder or powder), and the amount of water used is greater than the amount of the modified starch-based water-absorbing flocculant powder or powder (preferably the starch-based water-absorbing flocculation promoting powder or powder) used. Before adding the modified starch-based water-absorbing flocculant (whether it is in the form of a powder or powder, extruded pellets, or crushed extruded pellets (e.g., crushed using a high-speed high-shear mixer)), water is added until the substrate particles or substrate particles begin to self-agglomerate to achieve adequate wetting.

[0046] In one embodiment of the method, in the coating step of coating the base granules or base particles with a modified starch-based water-absorbent flocculant powder or powder, preferably a starch-based water-absorbent flocculation-promoting powder or powder, the ratio of water to the modified starch-based water-absorbent flocculant powder or powder, preferably a starch-based water-absorbent flocculation-promoting powder or powder, is between 6:1 and 10:1, preferably between 7:1 and 9:1, more preferably about 8:1. In carrying out the method of wetting the substrate with water, the substrate is wetted, each wet substrate particle is coated with a dry modified starch-based water-absorbent flocculant powder or powder, preferably a dry starch-based water-absorbent cohesion-promoting powder or powder, the mixture is wetted or rewetted with additional water, and the at least partially coated wet substrate granules or substrate particles are coated with further dry modified starch-based water-absorbent flocculant powder or powder, preferably a dry starch-based water-absorbent cohesion-promoting powder or powder, in multiple cycles, while the substrate granules or substrate particles and the modified starch-based water-absorbent flocculant powder or powder, preferably a starch-based water-absorbent cohesion-promoting powder or powder, are mixed in a rotating barrel or drum of a drum coater, cement mixer, drum mixer, mixing blender, etc., preferably continuously tumbling, rotating, or other form of agitation.

[0047] The slurry method uses significantly less water relative to the granular modified starch-based water-absorbing flocculant (preferably in the form of a powder or dust of the starch-based water-absorbing flocculant). The ratio of water to the granular modified starch-based water-absorbing flocculant (preferably in the form of a powder or dust of the starch-based water-absorbing flocculant) is preferably in the range of 0.5:1 to 2:1, more preferably about 1:1. These are mixed before applying the slurry to the substrate particles, and preferably all components are mixed together. Mixing is preferably carried out by tumbling in a mixer such as a pin mixer, drum coater, cement mixer, blender (e.g., ribbon blender), or using other types of mixing or blending equipment. In a preferred method embodiment, a continuous slurry process, preferably a continuous flow application process, is employed in which water and granular modified starch-based water-absorbing flocculant (preferably in the form of a starch-based water-absorbing flocculant powder or dust) are mixed and stored in a tank, vessel, or other container, from which the slurry is substantially continuously pumped to one or more mist atomizers, sprayers, nozzles, dispensers, or other application devices, and the slurry is dispensed onto the substrate particles while they are in a rotating drum or barrel, or while they are being transported on a conveyor while passing under the mist atomizers, sprayers, nozzles, dispensers, or application devices. In another preferred method embodiment, the slurry can be applied using a mister, sprayer, nozzle, dispenser, or other application device to substrate particles that are being stirred, tumbled, or otherwise mixed in a drum coater, drum mixer, concrete mixer, pin mixer, ribbon blender, or other suitable blender or mixer, thereby more uniformly coating the particles with the modified starch-based water-absorbent flocculant, preferably starch-based water-absorbent flocculant powder or dust, advantageously producing self-clumping absorbent litter particles of the present invention in or from the slurry, the litter particles having a substantially uniform outer layer of modified starch-based water-absorbent flocculant, preferably starch-based water-absorbent flocculant material, the outer layer having substantially the same thickness from one litter particle to the next and substantially completely encapsulating each substrate particle.In the application process of the modified starch-based water-absorbent flocculant, preferably a starch-based water-absorbent flocculant material, the particles are tumbled, rolled, or otherwise agitated, preferably in a rotating, generally cylindrical, barrel, or drum-shaped coater, mixer, or similar device, to form an outer layer of the modified starch-based water-absorbent flocculant, preferably a starch-based water-absorbent flocculant material. This outer layer fills any recesses or voids in the outer surface of the substrate particles and smooths out any other surface irregularities of the substrate particles. This produces animal litter particles with a substantially smooth, rounded outer surface that will not scratch the paws of a declawed cat and is non-trackable because the smooth, rounded particles do not easily adhere to cat paws and are not carried away to the floor outside the animal litter box. When the substrate particles are generally round, for example when substrate particles such as paper, i.e., paper spheres, are used, the self-clumping absorbent animal litter particles produced by the present invention have a substantially smooth, rounded outer layer of modified starch-based water-absorbent clumping agent, preferably a starch-based water-absorbent clumping agent material, preferably producing substantially round and / or generally spherical animal litter particles (e.g., the self-clumping absorbent litter particle spheres of the present invention).

[0048] As previously mentioned, the rounded animal litter particles of the coated substrate are advantageously sized to minimize animal litter removal from the animal litter box during use and handling of the animal litter. The roundness of the animal litter particles of the coated substrate is advantageous for preventing the animal litter particles of the coated substrate from adhering to a cat's paws during use of the animal litter box. Furthermore, the animal litter particles of the coated substrate are sized to help prevent removal by a cat during use of the animal litter box. In a preferred embodiment, the animal litter particles of the coated substrate should have a size larger than a 25-mesh sieve (i.e., larger than 25 mesh) and not larger than a 10-mesh sieve (i.e., not larger than 10 mesh). At least 80% of the animal litter particles of the coated substrate should be larger than 25 mesh and smaller than 10 mesh (10 / 25). For example, in one embodiment, between 60% and 95%, preferably about 80% (80%±15%) of the particles pass through a 12 mesh sieve but larger than a 25 mesh sieve. The remaining coated substrate animal litter particles are larger than 10 mesh. Rounded coated substrate animal litter particles having a particle size distribution between 12 mesh and 20 mesh (12 / 20) provide an optimal feel for a cat's paws.

[0049] Thus, in one preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have protrusions (including spikes), and have a particle size distribution between 12 mesh and 20 mesh (12 / 20), resulting in a preferred embodiment of a low-tracking litter that minimizes tracking by cats out of the litter box in accordance with the present invention. In another preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have protrusions (including spikes), and have a particle size distribution between 10 mesh and 25 mesh (10 / 25), resulting in another preferred embodiment of a low-tracking litter that minimizes tracking by cats out of the litter box in accordance with the present invention.

[0050] In a method for producing a self-cohering absorbent according to the present invention, at least a plurality of different substrate particles, preferably at least a plurality of pairs, i.e., at least three different substrate particles, are substantially simultaneously coated with outer regions of a modified starch-based water-absorbent flocculant when producing a batch of self-cohering absorbent particles according to the present invention comprising at least a plurality of different substrate particles, preferably at least a plurality of pairs, i.e., at least three different substrate particles. In one example of such a method, at least one type of substrate particle is an organic substrate particle, preferably a functional substrate particle, having a lower density than the other type of inorganic substrate particle. Both types of substrate particles are thereby substantially simultaneously coated with the granular modified starch-based water-absorbent flocculant using either a slurry method or an aqueous wetting and rewetting absorbent particle production method.

[0051] In a preferred embodiment, the modified starch-based water-absorbing flocculant is preferably a starch-based water-absorbing, clumping-promoting material, which is produced by extruding a starch-based mixture, such as the aforementioned mixture containing one or more grains and / or one or more legumes, at a relatively low moisture content of 25% or less by weight through an extruder at an ultra-high extrusion pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably 5000 PSI. Thus, the modified starch-based water-absorbing flocculant is preferably extruded in the form of a starch-based water-absorbing, clumping-promoting material, and more preferably is or contains a starch-based absorbent, swellable biopolymer gelling agent, including modified starch modified in an extruder at an ultra-high extrusion pressure. This gelling agent swells and gels upon sorption, including the absorption of a liquid, such as water at room temperature, or an aqueous solution such as cat urine at body temperature. The gelling agent preferably comprises at least a portion of the starch in the mixture that has been modified by ultra-high pressure extrusion to a cold water soluble binder, and at least a portion of the other starch in the mixture that has been modified by ultra-high pressure extrusion to a cold water swelling, water-absorbent modified starch. In preferred animal litter particle embodiments and methods for making animal litter particles, waste fines from the process of making absorbent starch-based animal litter, such as the extruded grain-based animal litter disclosed in commonly owned U.S. Pat. Nos. 9,491,926, 10,028,481, 10,098,317, 10,882,238, 11,013,211, and / or 11,083,168 (the entireties of which are expressly incorporated herein by reference), are used either: (1) as a granular modified starch-based water-absorbent clumping agent, preferably a granular water-absorbent clumping-promoting material, applied directly or as a slurry to substrate particles, or (2) ground, milled, crushed, or otherwise reduced in particle size to smaller powder-sized particles having mesh sizes and / or mesh size ranges described elsewhere herein and applied to or slurried into substrate particles.When the granular modified starch-based water-absorbent flocculant (preferably in the form of a starch-based water-absorbent, cohesion-promoting granular material, more preferably containing a starch-based absorbent, swellable biopolymer gelling agent) is used in powder-sized granular form, the powder-sized particles preferably have a particle size of less than 1,000 μm, and preferably comprise particles in the size range of 100 μm to 400 μm. When the granular modified starch-based water-absorbent flocculant is preferably in the form of a starch-based water-absorbent, cohesion-promoting granular material, more preferably containing a starch-based absorbent, swellable biopolymer gelling agent, and is used in flour-sized granular form, the flour-sized particles preferably have a particle size that passes through a 40-mesh screen, more preferably a 60-mesh screen, and even more preferably a 40-60-mesh screen and is retained on an 80-mesh screen. Such extremely small particle sizes allow for rapid wetting and activation of the water-soluble binder in some of the particles, but not all of the water-soluble binder in the particles that are applied in contact with larger substrate particles is activated.

[0052] The end result is animal litter particles that have the following properties: they are instantly self-clumping, absorb water, resist crumbling, minimize dust generation during storage, packaging, shipping, and actual use, preferably reducing dust by attracting and adhering to dust particles, have a rounded particle shape that minimizes particle removal from the litter box, have a smooth, rounded appearance that does not scratch the paws of declawed cats, and form clumps with at least 95%, preferably at least 97%, and more preferably at least 99% clump retention, meaning that a clump formed from animal litter particles moistened with 10 milliliters of water or urine and dried to a moisture content of about 12% by clump weight retains at least 95%, preferably at least 97%, and more preferably at least 99% of its weight or mass when dropped onto a perforated mesh screen from a height of about 10 inches. In another preferred embodiment, each clump has a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, meaning that when a clump formed from animal litter particles moistened with 15 milliliters of water or urine and dried to a moisture content of about 12%, the clump retains at least 95%, preferably at least 97%, more preferably at least 99% of its weight or mass when dropped onto a mesh screen from a height of about 10 inches. In another preferred embodiment, each clump has a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, meaning that when a clump formed from animal litter particles moistened with 10 milliliters of water or urine and dried to a moisture content of about 12%, the clump retains at least 95%, preferably at least 97%, more preferably at least 99% of its weight or mass when drop tested onto a mesh screen from a height of about 12 inches.In yet another preferred embodiment, each clump has a clump retention of at least 95%, preferably at least 97%, and more preferably at least 99%, meaning that a clump formed from animal litter particles moistened with 15 milliliters of water or urine and dried to a moisture content of about 12% retains at least 95%, preferably at least 97%, and more preferably at least 99% of its weight or mass when drop tested onto a mesh screen from a height of about 12 inches. Each clump dried to a moisture content of about 12% also has a clump crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably 80 PSI, and even more preferably 100 PSI.

[0053] In other preferred animal litter granule embodiments and methods of manufacture, the outer region of each animal litter granule surrounding the inner substrate particles is formed during or by ultra-high pressure extrusion, as described elsewhere herein, and is composed of a modified starch-based water-absorbing flocculant comprising at least one of the following: (a) an at least partially water-soluble, water-activated, moisture-setting modified starch binder, which is or comprises a thermoplastic modified starch component that retains its water-soluble binder and / or water-activated, moisture-setting adhesive properties even when repeatedly wetted and dried; and (b) a one-time, at least partially water-soluble, water-activated, moisture-setting modified starch binder (which is or includes a thermosetting modified starch component or a thermosetting modified starch component, the adhesive (such as a gel or flowable adhesive) being water-activated once when wetted with water or urine, moisture-setting once, and moisture-setting irreversibly as it dries, such that when the animal litter granules of the present invention are formed and dried, they have a moisture content of 15% or less by weight, preferably about 12% by weight (preferably based on the weight of the mass) of the mass). During ultra-high pressure extrusion, the extrusion temperature, ultra-high pressure, and shear forces applied during extrusion cause one or more proteins in the starch-containing mixture to change their original folding structure, such that the refolded proteins crosslink with a portion of the extrusion-modified starch (e.g., extrusion-modified amylopectin and / or extrusion-modified amylose), thereby forming an at least partially water-soluble, water-activated, moisture-hardening thermoplastic binder that is reversible in that it can be repeatedly, preferably indefinitely, rewetted, resolubilized, formed into a flowable adhesive, gelled, and moisture-hardened by drying.

[0054] The end result is absorbent animal litter particles that self-cohere substantially instantly, are not brittle, and thus minimize dust generation during storage, packaging, shipping, and actual use; preferably reduce dust by attracting and adhering to dust particles; have a rounded particle shape that minimizes cats from removing the animal litter from the litter box; have a smooth, rounded outer surface that does not scratch the paws of declawed cats; and form clumps with at least 95%, preferably at least 97%, and more preferably at least 99% clump retention. In preferred embodiments, each clump has at least 95%, preferably at least 97%, and more preferably at least 99% clump retention, meaning that a clump of animal litter particles moistened with 10 milliliters of water or urine and dried to a moisture content of about 12% by weight of the clump retains at least 95%, preferably at least 97%, and more preferably at least 99% of its weight or mass when dropped onto a perforated mesh screen from a height of about 10 inches. In another preferred embodiment, each clump has a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, meaning that a clump of animal litter particles moistened with 15 milliliters of water or urine and dried to about 12% moisture content retains at least 95%, preferably at least 97%, more preferably at least 99% of its weight or mass when dropped onto a mesh screen from a height of about 10 inches. In another preferred embodiment, each clump has a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, meaning that a clump of animal litter particles moistened with 10 milliliters of water or urine and dried to about 12% moisture content retains at least 95%, preferably at least 97%, more preferably at least 99% of its weight or mass when dropped onto a mesh screen from a height of about 12 inches.In yet another preferred embodiment, each clump has a clamp retention of at least 95%, preferably at least 97%, and more preferably at least 99%, meaning that a clump of animal litter particles moistened with 15 milliliters of water or urine and dried to about 12% moisture content retains at least 95%, preferably at least 97%, and more preferably at least 99% of its weight or mass when drop tested onto a mesh screen from a height of about 12 inches. Each such clump dried to about 12% moisture content also has a clump crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably 80 PSI, and even more preferably 100 PSI.

[0055] The present invention also relates to a self-cohering absorbent granular litter comprising self-cohering, cold-water-swellable, water-absorbent starch-containing absorbent litter particles comprising an at least partially cold-water-soluble, water-activated, moisture-setting binder, the litter particles having an internal substrate such as a non-cohering material, preferably a coated nucleated substrate particle whose outer surface has been wetted with an aqueous liquid such as water or treated with a slurry of water and a granular modified starch-based water-absorbent flocculant, thereby rendering the substrate particle a nucleating material having attached to its outer region a modified starch-based water-absorbent, water-activated flocculant, preferably a self-cohering modified starch-containing material, and more preferably an extruded material comprising a self-cohering, cold-water-swellable, water-absorbent modified starch-containing material comprising an at least partially cold-water-soluble, water-activated, moisture-setting binder. The granular material preferably has powder or powder-sized particles and is applied wet and adheres to the outer surface of the substrate particle by hydrogen and / or preferably covalent bonds when the finished wet litter particle is dried and moisture hardened.The self-cohering, cold water swelling, water-absorbent modified starch-containing granular material containing an at least partially cold water soluble, water-activated, moisture-curable binder can be prepared by extruding a starch-containing mixture having a relatively low moisture content of about 25% or less by weight of the mixture in a single screw extruder at a pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI. and a third amount of the starch mixture is formed by extruding the starch mixture under an ultra-high extrusion pressure of 100 psi, wherein a first amount of starch in the mixture is gelatinized in the extruder during the ultra-high extrusion pressure; a second amount of the starch mixture is modified, e.g., thermally and / or mechanically, by exposure to the ultra-high extrusion pressure in the extruder during extrusion, to form at least 5% by weight of an at least partially cold water soluble, ultra-high extrusion pressure water-activated, moisture-setting modified starch binder in the extrudate exiting the extruder, preferably at least 7.5%, more preferably at least 10%, by weight of the extrudate; and a third amount of the starch mixture is modified, e.g., thermally and / or mechanically, in the extruder during the ultra-high extrusion pressure, to form at least 5% by weight of an at least partially cold water soluble, ultra-high extrusion pressure water-activated, moisture-setting modified starch binder in the extrudate exiting the extruder, preferably at least 10% by weight of the extrudate, more preferably at least 20% by weight of the extrudate.

[0056] The present invention also relates to a method for producing moisture-absorbent, self-clumping, granular animal litter, the animal litter comprising moisture-absorbent animal litter particles that self-clump when wetted, the particles comprising a granular substrate and an outer layer of absorbent clumping material extruded from a starch-containing material under extrusion conditions to form a cold-water-swellable, extrusion-modified, moisture-absorbent starch, the starch preferably being or comprising a cold-water-swellable, extrusion-modified, moisture-absorbent starch, and including an at least partially cold-water-soluble, extrusion-modified, moisture-activated, moisture-setting starch binder. In preferred self-clumping granular animal litter of the present invention, each self-clumping, absorbent animal litter particle is formed from a small inner particle of a substrate made from a non-cohesive material, which substrate may be a non-absorbent, or even non-adsorbent, material, to which even smaller particles of extruded self-clumping, absorbent material (e.g., powder or dust of extruded self-clumping, absorbent material) are attached and adhered. The extruded self-cohering absorbent material of each animal litter particle coats or surrounds at least half of the outer surface of the inner substrate particle of each particle, preferably coats or surrounds at least 65% of the outer surface of the inner substrate particle of each particle, and more preferably coats or surrounds at least 75% of the outer surface of the inner substrate particle of each coated animal litter substrate particle. Each animal litter particle is comprised of 2% to 30% by volume of extruded self-cohering absorbent material, preferably 3% to 27% by volume, and more preferably 5% to 25% by volume. Each animal litter particle of the present invention is comprised of 2% to 30% by weight of extruded self-cohering absorbent material, preferably 3% to 27% by weight, and more preferably 5% to 25% by weight.

[0057] The self-cohering sorbent material comprising an extruded, at least partially water-soluble, water-activated, moisture-setting modified starch binder contained in each of the self-cohering, absorbent coated substrate animal litter particles comprises a cold water-swellable, extruded, modified, water-sorbent starch, preferably a cold water-swellable, extruded, modified, water-absorbing starch, which absorbs at least two times its weight in water, preferably at least three times its weight in water, more preferably at least four times its weight in water, and even more preferably at least six times its weight in water. The self-cohering sorbent material comprising an extruded, at least partially water-soluble, water-activated, moisture-setting modified starch binder contained in each of the self-cohering, absorbent coated substrate animal litter particles comprises a cold-water-swellable, extruded, water-sorbent modified starch, preferably a cold-water-swellable, extruded, water-absorbent modified starch, in an amount sufficient for the coating on the substrate of each coated substrate animal litter particle to sorb and preferably absorb at least a multiple of the weight of the substrate coating in water, urine, or synthetic urine, i.e., at least 3 times, preferably at least 4 times, more preferably at least 5 times, and even more preferably at least 6 times its weight. This performance is achieved, including when these animal litter particles are actually used in the self-cohering animal litter of the present invention (wherein at least 60%, preferably at least 75%, and more preferably at least 85% of the animal litter weight is composed of the coated substrate animal litter particles of the present invention). In at least one preferred embodiment, the extruded self-cohering sorbent material of each coated substrate animal litter particle comprises cold water swellable, extruded modified, water sorbent starch, preferably cold water swellable, extruded modified, water-absorbing starch, in an amount sufficient for the coating of each coated substrate animal litter particle to sorb and preferably absorb at least a multiple of the weight of the substrate coating, i.e., at least 3 times, preferably at least 4 times, more preferably at least 5 times, and even more preferably at least 6 times the weight of water, urine, or synthetic urine, upon wetting the granules with water, urine, or synthetic urine.

[0058] The extruded self-cohering absorbent material of each coated substrate sand grain comprises cold-water-swellable, extruded, water-absorbent starch, preferably cold-water-swellable, extruded, water-absorbent starch, in an amount sufficient for the outer coating of each coated substrate sand grain to absorb (preferably absorb) at least multiple times (i.e., at least three times) its weight in water, urine, or synthetic urine, preferably at least four times its weight in water, urine, or synthetic urine, more preferably at least five times its weight in water, urine, or synthetic urine, and even more preferably at least six times its weight in water, urine, or synthetic urine. This includes when the coated substrate sand grains are wetted with water, urine, or synthetic urine, and during actual use of the self-cohering sand of the present invention, which comprises at least 60%, preferably at least 75%, and more preferably at least 85% of the total weight of the sand comprise coated substrate sand grains of the present invention. In a preferred embodiment, the extruded self-cohering absorbent material of each coated substrate sand grain comprises cold-water-swellable, extruded, water-absorbent starch, preferably cold-water-swellable, extruded, water-absorbent starch, in an amount sufficient to cause the coating layer of each coated substrate sand grain to absorb (preferably absorb) at least multiple times (i.e., at least three times) its weight in water, urine, or synthetic urine, preferably at least four times its weight in water, urine, or synthetic urine, more preferably at least five times its weight in water, urine, or synthetic urine, and even more preferably at least six times its weight in water, urine, or synthetic urine. This includes when the sand grains are wetted with water, urine, or synthetic urine, and also during actual use of the self-clumping sand of the present invention, which contains at least 60% and no more than 75% (i.e., 60%-75%), preferably at least 75% and no more than 90% (i.e., 75%-90%), and more preferably at least 90% and up to 100% (i.e., 90%-100%) of the coated substrate sand grains of the present invention based on the total weight of the sand.The extruded self-cohering absorbent material of each coated substrate litter grain is preferably comprised of at least 5%, preferably at least 7.5%, more preferably at least 10%, and even more preferably at least 15% cold water swelling extruded modified water-absorbent starch, which preferably is or comprises at least a portion of the cold water swelling extruded modified water-absorbent starch, based on the weight of the extruded self-cohering absorbent material. In a preferred animal litter particle embodiment, the extruded self-cohering coated substrate particle comprises preferably at least 5%, preferably at least 7.5%, more preferably at least 10%, and even more preferably at least 15% cold water swelling extruded modified water-absorbent starch, based on the weight of the extruded self-cohering absorbent material.

[0059] To produce such self-clumping litter comprised of at least 60% but not more than 75% (i.e., 60%-75%), preferably at least 75% but not more than 90% (i.e., 75%-90%), and more preferably at least 90% but not more than 100% (i.e., 90%-100%), by weight of the litter, self-clumping, absorbent coated substrate litter particles that form a scoopable clump when wetted with water, urine, or synthetic urine, the extruded self-clumping absorbent material of each self-clumping, absorbent coated substrate litter particle contains a sufficient amount of binder such that, when wetted with water, urine, or synthetic urine, at least a portion of the at least partially cold water soluble, extruded, modified, water-activated, moisture-setting starch binder is at least partially or completely solubilized to form a flowable adhesive therefrom. The flowable adhesive flows from the wetted self-cohering absorbent coated substrate litter particle along and between at least a plurality of contacting litter particles and / or at least a plurality of adjacent litter particles (preferably similarly wetted with said water, urine, or synthetic urine) to form a clump that can be scooped from the litter using a handled litter scoop. In such a preferred self-cohering litter embodiment, the extruded self-cohering absorbent material of each self-cohering absorbent coated substrate litter particle contains at least 3%, preferably at least 5%, and more preferably at least 7.5%, by weight of the extruded self-cohering absorbent material in each particle, of an at least partially cold water soluble, water-activated, moisture-curing, extruded modified starch binder. This is a sufficient amount of cold water soluble extrusion-modified starch binder in each coated substrate litter particle that, when wetted with water, urine, or synthetic urine, at least partially solubilizes and forms a flowable adhesive that flows along at least a plurality of contacting wet particles and between at least a plurality of adjacent wet particles, causing them to self-cohere and form a clump that can be scooped from the litter particle with one hand using a conventional handled litter scoop (e.g., a perforated litter scoop) within 30 seconds of being wetted with the water, urine, or synthetic urine.

[0060] The animal litter of the present invention, even if composed of less than 100% self-clumping, absorbent-coated substrate animal litter particles of the present invention, will self-clump when wetted with water, urine, or synthetic urine, forming clumps of animal litter particles that can be scooped with a conventional perforated handled animal litter scoop. Such animal litter of the present invention, even if 75% or less of its particulate matter is composed of self-clumping, absorbent-coated substrate animal litter particles of the present invention, and preferably 60% to 75% of its particulate matter is composed of self-clumping, absorbent-coated substrate animal litter particles of the present invention, is still self-clumping animal litter that, when wetted with water, urine, or synthetic urine, forms clumps that can be scooped with a conventional perforated handled animal litter scoop. In another preferred embodiment of the self-clumping animal litter of the present invention, the animal litter has up to 85% of its particulate matter comprised of self-clumping absorbent coated substrate animal litter particles of the present invention, preferably 70% to 85% of its particulate matter comprised of self-clumping absorbent coated substrate animal litter particles of the present invention, yet still forms a clump that can be scooped with a conventional perforated handled animal litter scoop when wetted with water, urine, or synthetic urine. In a further preferred embodiment of the self-clumping animal litter of the present invention, the animal litter has up to 90% of its particulate matter comprised of self-clumping absorbent coated substrate animal litter particles of the present invention, preferably 75% to 90% of its particulate matter comprised of self-clumping absorbent coated substrate animal litter particles of the present invention, and still forms a clump that can be scooped with a conventional perforated handled animal litter scoop when wetted with water, urine, or synthetic urine.

[0061] If the animal litter of the present invention contains less than 100% of the animal litter particles of the self-clumping absorbent coated substrate of the present invention, the remainder of the animal litter can be made up of one or more particles or pellets that do not contain the extruded self-clumping absorbent, and these particles or pellets can be non-absorbent and / or non-clumping particles or pellets, particles or pellets of filler material, and / or functional particles or pellets that contain or consist of one or more of the following: scents, fragrances, deodorizers, urea inhibitors, preservatives, desiccants, The composition may comprise a moisturizer, activated charcoal and / or activated carbon, carbon black, an odor mask, a scent mask, an odor blocker or odor blocker, a scent blocker or scent blocker, a urine odor mask or urine odor mask, a urine odor blocker or blocker, a feces odor mask or feces odor mask, a dye such as a urine reactive dye or feces reactive dye, a reagent such as a urine reactive reagent or feces reactive reagent, a catalyst such as a urine reactive or responsive catalyst and / or a feces reactive or responsive catalyst, or other types of functional chemicals, molecules and / or components.

[0062] The extruded sorptive clumping material on the exterior of each of the self-clumping animal litter particles of the present invention comprises a cold water swellable extrusion modified water sorbent starch (preferably a cold water swellable extrusion modified water absorbing starch) in an amount sufficient to cause each animal litter particle to sorb (preferably absorb) at least multiple times (i.e., at least three times) the weight of the animal litter particle in water, urine, or synthetic urine, thereby preferably sorbing (preferably absorbing) at least four times the weight of the animal litter particle in water, urine, or synthetic urine, and more preferably sorbing at least four times the weight of the animal litter particle in water, urine, or synthetic urine. sorbs (preferably absorbs) at least 5 times its particle weight in synthetic urine, more preferably sorbs (preferably absorbs) at least 6 times its particle weight in water, urine, or synthetic urine, and even more preferably sorbs (preferably absorbs) at least 6 times its particle weight in water, urine, or synthetic urine when the particles are wetted with water, urine, or synthetic urine, for example, during actual use of an animal litter of the present invention comprising at least 60% (preferably at least 75%, more preferably at least 85%) of the animal litter weight of the animal litter.

[0063] In preferred animal litter particle embodiments, the extruded absorbent aggregate material surrounding at least a majority, preferably at least 65%, more preferably at least 75%, of the outer surface of each inner substrate particle is composed of at least 10%, preferably at least 15%, more preferably at least 20% cold water swellable, extruded modified water absorbent starch by weight of the extruded absorbent aggregate material in each animal litter particle. In one particularly preferred animal litter particle embodiment, the exterior of the extruded absorbent aggregate material of each animal litter particle is composed of at least 10%, preferably at least 15%, more preferably at least 20% cold water swellable, extruded modified water absorbent starch by weight of the extruded absorbent aggregate material of each animal litter particle.

[0064] The extruded self-clumping absorbent material of each animal litter particle contains cold water swellable extrusion modified water-absorbent starch, preferably cold water swellable extrusion modified water-absorbent starch, in an amount sufficient to absorb at least multiple times (i.e., at least 3 times), preferably at least 4 times, more preferably at least 5 times, and even more preferably at least 6 times the weight of the animal litter particle in water, urine, or synthetic urine when each animal litter particle is wetted with water, urine, or synthetic urine, including during actual use of the self-clumping animal litter of the present invention, which contains at least 60%, preferably at least 75%, and more preferably at least 85% of the animal litter weight of the animal litter particles of the present invention.

[0065] In one preferred embodiment, the extruded self-cohering absorbent material of each coated substrate sand grain contains cold water-swellable extruded modified water-absorbent starch, preferably cold water-swellable extruded modified water-absorbent starch, in an amount sufficient for the coating of each sand grain to absorb, preferably absorb, at least multiple times the weight of the sand grain, i.e., at least 3 times the weight of the water, urine, or synthetic urine, more preferably at least 4 times the weight of the sand grain, more preferably at least 5 times the weight of the water, urine, or synthetic urine, and even more preferably at least 6 times the weight of the sand grain, including during actual use of the self-cohering sand of the present invention, which self-cohering sand contains at least 60% and not more than 75%, i.e., between 60%-75%, preferably at least 75% and not more than 90%, i.e., between 75%-90%, and more preferably at least 90% and up to 100%, i.e., between 90%-100%, of the sand grain by weight. Each pellet of litter preferably contains at least 5%, more preferably at least 7%, of the extruded self-cohering absorbent material. The cold water swelling, extrusion-modified, water-absorbing starch is preferably at least 5%, more preferably at least 10%, even more preferably at least 15%, by weight of the extruded self-cohering absorbent material, and preferably comprises or consists of at least a portion of the cold water swelling, extrusion-modified, water-absorbing starch. In a preferred animal litter particle embodiment, the extruded self-cohering particles preferably comprise at least 5%, preferably at least 7.5%, more preferably at least 10%, even more preferably at least 15%, of the cold water swelling, extrusion-modified, water-absorbing starch, by weight of the extruded self-cohering absorbent material of each pellet.

[0066] The at least partially cold-water soluble extrusion-modified starch water-activated moisture-setting binder contained in the extruded clump material exterior to each animal litter particle is at least partially solubilized upon wetting with water, urine, or synthetic urine, and at least a portion of the solubilized binder forms a flowable adhesive that flows from the wetted animal litter particle between and around contacting or adjacent animal litter particles, causing at least a plurality of pairs of animal litter particles, i.e., at least 3, preferably at least 5, more preferably at least 10, and even more preferably at least 20, to self-cohere and form clumps. Such clumps, when air-dried at room temperature to a moisture content of about 12% by weight of the clump, have a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, and a clump crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and most preferably at least 100 PSI. This allows the animal litter of the present invention to harden more efficiently than animal litter composed substantially entirely (eg, 95%±5%) of sodium bentonite.

[0067] In preparation for carrying out the method for producing animal litter in accordance with the present invention, desired substrate particles that do not compact when wetted with water, urine, or synthetic urine can be, and preferably are, classified in a size classification step, such as by sieving or screening. This is done to remove undesirable oversized particles and undesirable undersized particles. In one preferred size classification step, a first or initial quantity of unclassified substrate particles is sized using a plurality of differently sized screens or sieves. The mesh or sieve sizes of the screens or sieves are selected to obtain a second desired quantity of sized particles having at least a plurality of pairs, i.e., at least three different particle sizes, that fall within a desired upper and lower particle size range, i.e., within a desired substrate particle size distribution range. The range is defined by at least one screen or sieve having a first mesh, screen, or sieve size configured to define an upper or large particle size cutoff, and at least one other screen having a second mesh, screen, or sieve size configured to define a lower or small particle size cutoff, respectively.

[0068] In a preferred substrate particle classification step, a plurality of classification screens are selected to classify a first or initial quantity of unclassified substrate particles to obtain a desired second quantity of classified substrate particles, wherein at least 80%, preferably at least 90%, and more preferably at least about 95% of the substrate particles have particle sizes within the following ranges, e.g., particle size distribution ranges: (a) between 0.0165 inches or 0.42 mm (#40 sieve / screen or 35 mesh screen) and 0.0937 inches or 2.38 mm (#8 sieve / screen or 8 mesh screen), (b) preferably between 0.0234 inches or 0.595 mm (#30 sieve / screen) and 0.0937 inches or 2.38 mm (#8 sieve / screen or 8 mesh screen), (c) preferably between 0.0234 inches or 0.595 mm (#30 sieve / screen) and 0.0937 inches or 2.38 mm (#8 sieve / screen or 8 mesh screen), (d) preferably between 0.0234 inches or 0.595 mm (#30 sieve / screen) and 0.0937 inches or 2.38 mm (#8 sieve / screen or 8 mesh screen), (e) preferably between 0.0234 inches or 0.595 mm (#30 sieve / screen) and 0.0937 inches or 2.38 mm (#8 sieve / screen or 8 mesh screen), (f) preferably between 0.0234 inches or 0.595 mm (#30 sieve / screen) and 0.0937 inches or 2.38 mm (#8 sieve / screen or 8 mesh screen), (g) preferably between 0.0234 inches or 0.595 mm (#30 sieve / screen) and 0.0937 (c) more preferably between 0.0278 inches or 0.707 mm (a No. 25 sieve / screen or a 24 mesh screen) and 0.0661 inches or 1.68 mm (a No. 12 sieve / screen or a 10 mesh screen); and (d) even more preferably between 0.0331 inches or 0.841 mm (a No. 20 sieve / screen or a 20 mesh screen) and 0.0661 inches or 1.68 mm (a No. 12 sieve / screen or a 10 mesh screen).

[0069] In practicing the preferred animal litter particle embodiments and methods of making the particles of the present invention, one preferred substrate particle used as a nucleating material for the animal litter particles is a generally non-compressible or pressure-resistant inorganic granular substrate, preferably perlite, which is non-agglomerated, preferably porous, e.g., microporous, and preferably at least slightly water-absorbent, and is crushed, ground, or otherwise comminuted into substrate particles having the following particle size ranges: (a) between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen).

[0070] In another preferred embodiment of the animal litter granules of the present invention and the method for producing the same, a preferred type of substrate particle used as an animal litter granule nucleating agent for producing the animal litter granules is a shatter-resistant inorganic particulate substrate, preferably sand granules, such as non-porous and non-water-absorbent silica sand granules. These substrate particles, i.e., sand granules, have been classified to have particle sizes or diameters within the following ranges: (a) between 0.0165 inches or 0.42 mm (No. 40 sieve / screen or 35 mesh screen) and 0.0937 inches or 2.38 mm (No. 8 sieve / screen or 8 mesh screen), and / or (b) between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen).

[0071] In practicing yet another preferred animal litter granule embodiment of the present invention and its manufacturing method, a preferred type of substrate particle used as a nucleating material for the animal litter granules is a water-absorbent granular smectite clay, preferably bentonite or bentonite clay, which is relatively soft, friable and / or brittle and can be (preferably is) porous, and is at least partially composed of montmorillonite, preferably having a particle size distribution range of between 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), but can also have a particle size distribution range of between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen). In one such preferred granular substrate material, the substrate particles are each composed of a relatively soft, non-agglomerating, water-absorbent smectite clay, preferably calcium bentonite, having a particle size distribution range between 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), or between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen). In another such preferred granular substrate material having a particle size distribution range similar to or substantially the same as one of the particle size distribution ranges described above in this paragraph, the substrate particles are each composed of another type of smectite, such as attapulgite, fuller's earth, sepiolite, and / or kaolinite.

[0072] The self-cohering absorbent animal litter of the present invention can also be produced from self-cohering absorbent animal litter particles produced according to the animal litter particle production method of the present invention using a mixture or blend of multiple or pairs of different types of smectite clay nucleating materials, including combinations of multiple or pairs of calcium bentonite substrate particles, sodium bentonite substrate particles, and / or attapulgite substrate particles, fuller's earth substrate particles, sepiolite substrate particles, and / or kaolinite substrate particles, all of which are mixed or blended in a mixing step which can occur during the wetting step, but which preferably occurs prior to the addition of the extruded self-cohering absorbent particles. In such a mixture of different types of substrate particles, the combined substrate particle mixture can have a particle size distribution range between (a) 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and (b) 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen).

[0073] Another preferred substrate for use in granular form as a nucleating material for the litter particles in the other preferred self-clumping absorbent litter particles and method of making same of the present invention is comprised of organic material, is substantially entirely organic, and is in the form of substrate particles comprised substantially entirely of paper, wood fibers (e.g., wood or sawdust pellets, wood chips, bark, etc.), and has a substrate particle size distribution range of (a) between 0.0331 inch or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inch or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) between 0.0278 inch or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inch or 1.68 mm (No. 12 sieve / screen or 10 mesh screen). In preferred paper substrate particle embodiments, the paper substrate particles are preferably generally rounded, preferably substantially round or substantially spherical in shape, with particle sizes ranging from (a) 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) to 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) to 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen).

[0074] In further preferred embodiments of the self-clumping absorbent animal litter particles of the present invention and methods for making same, another suitable organic substrate material for use in granular form as an animal litter particle nucleating material for making the animal litter particles of the present invention is a granular nut shell material, preferably porous, e.g., microporous, absorbent walnut shells that have been crushed, pulverized, or otherwise comminuted into relatively small substrate particles having a particle size ranging from 0.0331 inch or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) to 0.0661 inch or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), but which can be classified to a particle size ranging from 0.0278 inch or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) to 0.0661 inch or 1.68 mm (No. 12 sieve / screen or 10 mesh screen). In yet another preferred embodiment of the self-clumping absorbent animal litter particles of the present invention and the method of making the same, another suitable organic nut shell substrate material used in granular form as an animal litter particle nucleating material for making the animal litter particles of the present invention is granular hazelnut shell material, preferably porous, e.g., microporous, absorbent hazelnut shells that have been crushed, pulverized, or otherwise comminuted into relatively small substrate particles, the particle size of the particles being in the range of (a) between 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen).In another preferred self-clumping absorbent animal litter particle and method of making said self-clumping absorbent animal litter particle of the present invention, another preferred organic nut shell substrate to be used in granular form as an animal litter particle nucleating material for making the animal litter particles of the present invention is granular cashew nut shell material, preferably porous, e.g., microporous, absorbent cashew nut shells that have been crushed, pulverized, or otherwise finely ground into relatively small substrate particles having the following particle sizes: (a) in the range between 0.0331 inch or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inch or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) in the range between 0.0278 inch or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inch or 1.68 mm (No. 12 sieve / screen or 10 mesh screen). In yet another preferred self-clumping absorbent animal litter particle and method of making said self-clumping absorbent animal litter particle of the present invention, another preferred organic nut shell substrate to be used in granular form as an animal litter particle nucleating material for making the animal litter particles of the present invention is granular almond shell material, preferably porous, e.g., microporous, absorbent almond shells that have been crushed, pulverized, or otherwise finely ground into relatively small substrate particles having the following particle sizes: (a) between 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen).Other types of nut shells, such as macadamia nut shells or husks (macadamia nut shells), peanut shells or husks (peanut shells or peanut husks), Brazil nut shells or husks (Brazil nut shells), pine nut shells or husks (pine nut shells), and pecan shells or husks (pecan shells), can also be obtained or otherwise finely ground to form particles for use as animal litter particle nucleating materials in producing the animal litter particles of the present invention, and the ground or finely ground particles can be used to form particles for use as animal litter particle nucleating materials in producing the animal litter particles of the present invention. The crushed shell substrate particles have the following particle sizes: (a) between 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen).

[0075] It is also contemplated that other types of materials, such as plastic, rubber (e.g., scrap tires), glass, wood pellets, sawdust pellets, wood chips, bark, and other non-cohesive materials, may be crushed, crushed, or otherwise reduced in size to particles that are sieved, sieved, or otherwise sized to have a particle size range or particle size distribution range that falls within at least one of the following preferred particle size ranges: (a) between 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), and / or (b) between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen). In preferred paper substrate particle embodiments, the paper substrate particles preferably have a generally rounded, preferably substantially round or substantially spherical shape, and particle sizes ranging from (a) 0.0331 inches or 0.841 mm (#20 sieve / screen or 20 mesh screen) to 0.0661 inches or 1.68 mm (#12 sieve / screen or 10 mesh screen), and / or (b) 0.0278 inches or 0.707 mm (#25 sieve / screen or 24 mesh screen) to 0.0661 inches or 1.68 mm (#12 sieve / screen or 10 mesh screen).

[0076] The present invention relates to a self-clumping absorbent litter comprising self-clumping absorbent litter particles made from at least a plurality, preferably at least a plurality of pairs (i.e., at least three) of different types of substrate particles. These different types of substrate particles are mixed or blended before or during a wetting, activation, and / or nucleation step (and optional drying step) in which an aqueous liquid (preferably water) is applied to wet the substrate particles. Each wetted substrate particle acts as a nucleator to which extruded self-clumping absorbent particles adhere and adhesively attach. This occurs as a result of the water on the contacting wetted substrate particles at least partially solubilizing some (but not all) of the water-soluble binder in the adhering extruded self-clumping absorbent particles, thereby activating and becoming tacky. In one preferred embodiment of the method for producing litter and litter particles, at least a plurality, preferably at least a plurality of pairs (i.e., at least three) of different types of crushed nut shell particles, for example, a plurality, preferably at least a plurality of pairs of walnut shell particles, hazelnut shell particles, cashew nut shell particles, pecan nut shell particles, peanut shell particles, macadamia nut shell particles, pine nut shell particles, almond shell particles and / or Brazil nut shell particles, are blended together and wetted together, and smaller extruded self-cohering absorbent particles are added to the mixture or blend of wetted nut shell particles, and an activation step, a nucleation step, and an optional drying step can be carried out together.

[0077] In one preferred embodiment of the present invention, a method for producing cat litter and cat litter granules is provided. In this method, at least one substrate, such as the aforementioned nutshell substrate particles, is mixed or blended with at least one other substrate, such as one or more smectite clays, perlite, paper, pellets, or other types of materials suitable as nucleating substrate particles for extruded self-cohering adsorbent materials. This mixing is carried out in a bonded substrate particle mixing step, before or during wetting of the mixture or blend of substrate particles, and before or during the application and / or nucleation step of the extruded self-cohering adsorbent particles. In another preferred embodiment, a method for producing cat litter and cat litter granules is provided. In this method, substrate particles of at least one smectite clay, preferably calcium bentonite, are mixed or blended with substrate particles of an organic substrate material, such as paper and / or nutshells (preferably walnut shells). The mixing is carried out in a combined substrate particle mixing step in which different types of substrate particles are mixed or blended, preferably substantially simultaneously, and this step can be carried out before or during wetting of the mixture or blend of calcium bentonite substrate particles, paper substrate particles, and / or nutshell substrate particles (preferably walnut shell substrate particles), and before or during application of the extruded self-cohering adsorbent particles. In yet another preferred embodiment, there is provided a method for producing cat litter and cat litter granules, in which substrate particles of at least one smectite clay, preferably calcium bentonite, are mixed or blended with substrate particles of another substrate material, preferably perlite. The mixing is carried out in a bonded substrate particle mixing step, which can be carried out before or during wetting of the mixture or blend of calcium bentonite and perlite substrate particles, and which is carried out before or during application of the extruded self-cohering adsorbent particles in carrying out a preferred embodiment of the cat litter production method of the present invention. In yet another preferred embodiment, there is provided a method for producing cat litter and cat litter granules, in which substrate particles of at least one smectite clay, preferably calcium bentonite, are mixed or blended with substrate particles of another substrate material, preferably sand. The mixing is carried out in a bonded substrate particle mixing step which can be carried out before or during wetting of the mixture or blend of calcium bentonite and sand substrate particles, which step is carried out at the time of application of the extruded self-cohering adsorbent particles in carrying out an embodiment of the cat litter manufacturing method of the present invention. In yet another preferred embodiment, a method for producing cat litter and cat litter granules is provided. In this method, substrate particles of at least one type of organic material, such as paper, wood pellets, wood chips, or bark, are mixed or blended with substrate particles of another type of substrate material, such as sand. The mixing is carried out in a bonded substrate particle mixing step, which can be carried out before or during wetting of the mixture or blend of substrate particles of at least one organic material and sand, and this step is carried out during application of the extruded self-cohering adsorbent particles in the production of the self-cohering cat litter granules of the present invention. In yet another preferred embodiment, a method for producing cat litter and cat litter granules is provided. In this method, substrate particles of at least one organic material, such as paper, wood pellets, wood chips, or bark, are mixed or blended with substrate particles of another type of substrate material, such as perlite. The mixing is carried out in a bonded substrate particle mixing step, which can be carried out before or during wetting of the mixture or blend of substrate particles of at least one organic material and perlite. In yet another preferred embodiment, a method for producing cat litter and cat litter granules is provided. In this method, substrate particles of at least one type of organic material, such as paper, wood pellets, wood chips, bark, etc., are mixed or blended with substrate particles of another type of organic substrate material, such as nut shells, particularly walnut shells, in a combined substrate particle mixing step that can be carried out before or during wetting of the substrate particles of at least one organic material with the other type of organic material, and that is carried out at the time of application of the extruded self-cohering absorbent particles in carrying out a preferred embodiment of the cat litter manufacturing method of the present invention.

[0078] In one clumping sand animal litter consisting of self-clumping absorbent animal litter particles composed of sand grains as substrate particles coated with a modified starch absorbent clumping material or clumping agent of the present invention, only 10% by weight of the animal litter is composed of extruded fine powder / flour / powder of the modified starch absorbent clumping material or clumping agent, and the remaining 90% is composed of the sand grains, and the sand grains clump to produce dry clumps having a clump retention of at least 95% and a clump crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably 100 PSI when dried to a moisture content of about 12% by clump weight.

[0079] When the litter is a non-cohesive substrate, the coating thickness is less than 0.5 mm, and the coating, 0.25 mm to 0.5 mm thick, comprises: (a) a water-soluble binder comprising (i) an irreversibly aged water-soluble binder portion, and (ii) a resolubilizing water-soluble binder portion; and (b) a granular non-cohesive substrate, wherein not more than 35% by weight of the clumping animal litter is comprised of a water-soluble binder and extruded fines and powders comprised of an extruded modified starch absorbent clumping agent or material.

[0080] In one embodiment of the preferred animal litter and animal litter particle manufacturing method, substrate particles of at least one type of smectite clay, preferably calcium bentonite, are mixed or blended with substrate particles of at least one other type of smectite clay, preferably sodium bentonite, in a combined substrate particle mixing step that can be carried out before or during wetting of the mixture or blend of calcium bentonite and sodium bentonite substrate particles, before or during application of the extruded self-cohering absorbent material particles, when carrying out a preferred embodiment of the animal litter manufacturing method of the present invention. In another preferred embodiment of the animal litter and method for producing animal litter particles, a first batch of self-clumping animal litter particles of the present invention is produced using particles of a first type of smectite clay, preferably calcium bentonite or Ca-montmorillonite, as substrate particles which, when wet, also function as nucleating material to which smaller particles of the extruded self-clumping absorbent material adhere, and another batch of self-clumping animal litter particles of the present invention is produced using particles of a second type of smectite clay, preferably sodium bentonite or Na-montmorillonite, as substrate particles which, when wet, also function as nucleating material to which smaller particles of the extruded self-clumping absorbent material adhere, and both batches of the resulting self-clumping absorbent animal litter particles of the present invention are combined by mixing or blending in a drum mixer or drum-type mixer, pin mixer, or other type of commercial mixer or blender.

[0081] In one embodiment of the preferred method for producing animal litter and animal litter particles, at least a plurality, preferably at least a plurality of pairs, i.e., at least three different types of crushed nut shell particles, for example, a plurality, preferably at least a plurality of pairs of walnut shell particles, hazelnut shell particles, cashew nut shell particles, pecan nut shell particles, peanut shell particles, macadamia nut shell particles, pine nut shell particles, almond shell particles and / or Brazil nut shell particles, are mixed and moistened together, and smaller extruded self-cohering substrate particles are added to the mixture or blend of moistened nut shell particles, thereby allowing the activation, nucleation and optional drying steps to be carried out together.

[0082] The resulting self-cohering adsorbent cat litter granules produced using substrate particles having the preferred particle size ranges disclosed above will have a similar range or distribution of particle size ranges, but will be 1% to 8% larger in size than the substrate particles, depending on the thickness of the extruded self-cohering adsorbent applied when performing one of the embodiments of the method for making self-cohering cat litter granules disclosed above. For example, if substrate particles are used having a particle size range or particle size distribution range between 0.0165 inches or 0.40 mm (No. 40 sieve / screen or 35 mesh screen) and 0.0937 inches or 2.38 mm (No. 8 sieve / screen or 8 mesh screen), the resulting self-cohering cat litter grains formed from substrate particles in this size range will be slightly larger, having particle sizes ranging from about 0.018 inches or about 0.45 mm to about 0.0985 inches or about 2.5 mm. For example, if substrate particles are used having a particle size range between 0.0234 inches or 0.595 mm (No. 30 sieve / screen or 28 mesh screen) and 0.0787 inches or 2.00 mm (No. 10 sieve / screen or 9 mesh screen), the resulting self-cohering cat litter grains formed from substrate particles of this size range will have particle sizes ranging from about 0.025 inches or about 0.635 mm to about 0.085 inches or about 2.16 mm. When substrate particles are used having a particle size range or particle size distribution range between 0.0278 inches or 0.707 mm (No. 25 sieve / screen or 24 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), the resulting self-cohering cat litter grains formed from substrate particles in this size range will be slightly larger, having particle sizes ranging from about 0.0290 inches or about 0.736 mm to about 0.075 inches or about 1.90 mm. Finally, when substrate particles are used having a particle size range or particle size distribution range between 0.0331 inches or 0.841 mm (No. 20 sieve / screen or 20 mesh screen) and 0.0661 inches or 1.68 mm (No. 12 sieve / screen or 10 mesh screen), the resulting self-cohering cat litter granules formed from substrate particles in this size range will also be slightly larger, having particle sizes ranging from about 0.0365 inches or about 0.927 mm to about 0.075 inches or about 1.90 mm.The preferred substrate particle size ranges described above therefore advantageously produce self-cohering adsorbent cat litter according to the present invention, i.e. after applying a desired amount, e.g. a desired mass, weight or volume, of extruded self-cohering adsorbent particles to a desired amount of substrate particles of the type described above, having a particle size, particle size range or particle size distribution within one of the particle size ranges disclosed above, the resulting self-cohering adsorbent cat litter granules of the present invention have a particle size that falls within a similar particle size range of the substrate particles used to make the cat litter granules, and are 1% to 5% larger in size than the size of the substrate particles used to make the cat litter granules.

[0083] The self-solidifying absorbent animal litter particles of the present invention, produced using substrate particles as the nucleating material for the animal litter particles, can be coated with an outer layer of extruded self-solidifying absorbent material to produce finished animal litter particles in which the particle coating weight of the extruded self-solidifying absorbent material on each substrate particle is in the range of 5% to 45% of the weight of the animal litter particle, preferably 10% to 40% of the weight of the extruded self-solidifying absorbent material on each substrate particle, and more preferably 15% to 35% of the weight of the extruded self-solidifying absorbent material on each substrate particle. When the self-solidifying absorbent animal litter particles are produced using sand as the substrate particle and particle nucleating material, the coating rate of the extruded self-solidifying absorbent material on each sand particle is in the range of 5% to 20% of the weight of the animal litter particle, preferably 10% to 20% of the weight of the animal litter particle, and more preferably 5% to 15% of the weight of the animal litter particle. When the self-solidifying absorbent animal litter particles are produced using calcium bentonite as the substrate particle and particle nucleating material, the application rate of the extruded self-solidifying absorbent material on each calcium bentonite particle is in the range of 10% to 40% by weight of the animal litter particle, preferably 15% to 30% by weight of the animal litter particle, and more preferably 20% to 25% by weight of the animal litter particle.

[0084] It has been found that the larger the substrate particle, the greater the granular coating weight of the modified starch-based water-absorbent flocculant, preferably the extruded self-cohesive absorbent material, that needs to be applied to each substrate particle during the manufacture of the animal litter particles. This is to ensure that each finished animal litter particle contains a sufficient amount of the modified starch-based water-absorbent flocculant, preferably the extruded self-cohesive absorbent material, that constitutes the outer layer region of each animal litter particle to ensure good cohesion when wetted with water or urine. In other words, it has been found that the larger the size of the substrate particle used to manufacture the animal litter particles, the greater the coating weight of the granular modified starch-based water-absorbent flocculant, preferably the extruded self-cohesive absorbent material, that needs to be attached to the substrate particle of each animal litter particle. This is to ensure that each finished animal litter particle contains sufficient extruded self-cohering absorbent material that constitutes the absorbent water-soluble binder release region in its outer layer so that when animal litter made from said animal litter particles is wetted with water or urine, a rapidly removable, scoping clump of wet animal litter particles is formed having a clump retention of at least 97%, preferably at least 99%.

[0085] The self-clumping absorbent litter particles of the present invention produced according to the method of the present invention have substrate particles at least partially coated or encapsulated by extruded absorbent clumping material, wherein the modified starch-based water-absorbing clumping agent, preferably in the form of extruded absorbent clumping material, accounts for 2% to 40%, preferably 5% to 35%, more preferably 5% to 25% of the weight of each particle, and absorbs at least multiple times its weight in water or urine, i.e., at least 3 times its weight in water or urine, preferably at least 4 times its weight in water or urine, more preferably at least 5 times its weight in water or urine, and even more preferably at least 6 times its weight in water or urine, and the particles, when wetted with water or urine, self-clump into a clump that, when air-dried at room temperature to a moisture content of about 12% of the clump weight, has a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, and a clump crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably at least 100 PSI.

[0086] In a preferred embodiment of the method for producing the self-clumping absorbent litter particles of the present invention, substrate particles, which may be non-clumping, preferably non-clumping, e.g., comprised of a non-clumping material, and which may be non-absorbent, e.g., comprised of a material that does not absorb water, are subjected to a wetting step in which they are wetted with an aqueous liquid, preferably water only, to prepare the substrate particles for attachment of smaller particles of modified starch-based water-absorbent flocculant, preferably extruded absorbent aggregate, while the substrate particles are wet. In this step, the particles are prepared by wetting the outer surfaces of the substrate particles with an aqueous liquid, preferably water, so that smaller particles of modified starch-based water-absorbent flocculant, preferably extruded absorbent aggregate, can be attached thereto and adhered thereto during the subsequent steps of the method for producing the self-clumping absorbent litter particles of the present invention as a finished product. Wetting the substrate particles with an aqueous liquid such as water ensures that at least some water, preferably a sufficient amount of water, is present on the outer surface of the substrate particle to at least partially, if not completely, solubilize a portion of the cold water soluble extrusion-modified starch binder contained in the smaller modified starch-based water-absorbent flocculant particles, preferably extruded absorbent aggregate, that contact the surface of the wetted substrate particle. When these smaller sized particles of modified starch-based water-absorbent flocculant, preferably extruded absorbent aggregate, contact the outer surface of the water-wetted substrate particle, at least some, but not all, of the smaller modified starch-based water-absorbent flocculant particles, preferably extruded absorbent aggregate, form a flowable adhesive that initially promotes or further promotes adhesion to the outer surface of the substrate particle before hardening as the water in the flowable adhesive dries and becoming substantially immovably bonded.During this process, the water-soluble binder that has been at least partially solubilized from the wetted extruded absorbent aggregate particles forms a flowable adhesive that initially adhesively bonds to a portion of the outer surface of a corresponding one of the wetted substrate particles through intermolecular attractive forces, and then, as the water in the flowable adhesive cures and hardens into a hard, solid glassy material in a glassy material state, becomes substantially immovably bonded or fixed to the same portion of the outer surface of a corresponding one of the wetted substrate particles through intramolecular attractive forces. This occurs when the resulting finished, wet-formed self-cohesive litter particles dry, preferably to a moisture content of 12% by weight or less, more preferably 10% by weight or less, and even more preferably about 8% by weight or less, to ensure adequate moisture-setting, hardening, and adhesive bonding of the outer region of each finished litter particle to each substrate particle.

[0087] In a preferred embodiment of the method for producing animal litter particles, at least a portion (but not all) of the cold water soluble extrusion-modified starch water-activated moisture-setting binder is at least partially solubilized such that at least 5% and no more than 65% (i.e., between 5% and 65%), preferably at least 10% and no more than 50% (i.e., between 10% and 50%), and more preferably at least 15% and no more than 45% (i.e., between 15% and 45%) by weight of the cold water soluble extrusion-modified starch water-activated moisture-setting binder in the wetted small particles of extruded self-cohering absorbent material is at least partially solubilized during the coating step and / or nucleation substep. In another method embodiment, for an amount of 5% to 65% (preferably 10% to 50%, more preferably 15% to 45%) by weight of the cold water soluble extrusion modified starch moisture-setting binder that is at least partially solubilized during one or more of the wetting step, the coating step, and / or the nucleation sub-step, at least a portion (but not all) of the at least partially solubilized cold water soluble extrusion modified water-activated moisture-setting starch binder contained in the granular modified starch water-absorbing flocculant applied to the substrate particles is substantially completely solubilized by the water of the aqueous wetting liquid that wets the substrate particles during the wetting step, the coating step, and / or the nucleation sub-step.

[0088] In a further preferred method embodiment, at least a portion (but not all) of the cold water soluble extruded modified starch water-activated moisture-setting binder of the modified starch-based water-absorbent flocculant is at least partially solubilized, such that during the wetting, applying, and nucleating substeps, at least 5% and no more than 65% (i.e., 5% to 65%), preferably at least 10% and no more than 50% (i.e., 10% to 50%), and more preferably at least 15% and no more than 45% (i.e., 15% to 45%) of the cold water soluble extruded modified starch binder by weight in the small particles of wetted extruded self-cohered absorbent material is at least partially solubilized. In a further method embodiment, of the 5% to 65% (preferably 10% to 50%, more preferably 15% to 45%) by weight of cold water soluble extrusion modified starch binder that is at least partially solubilized during one or more of the wetting step, the coating step, and / or the nucleation sub-step, at least a portion of the at least partially solubilized cold water soluble extrusion modified starch binder is substantially completely solubilized by the water providing wetting during said wetting step, said coating step, and / or said nucleation sub-step.

[0089] In another preferred method embodiment, at least a portion (but not all) of the cold water soluble extrusion-modified starch water-activated moisture-setting binder is preferably substantially completely solubilized in or by the wetting water, such that at least 5% and not more than 65% (i.e., 5% to 65%), preferably at least 10% and not more than 50% (i.e., 10% to 50%), and more preferably at least 15% and not more than 45% (i.e., 15% to 45%) of the weight of the cold water soluble extrusion-modified starch binder in the wetted small particles of extruded self-cohered absorbent material is solubilized during the coating step and nucleation substep. In further preferred process embodiments, at least a portion (but not all) of the cold water soluble extrusion modified starch binder is preferably substantially completely solubilized in or by the wetting water, such that at least 5% but not more than 65% (i.e., 5% to 65%), preferably at least 10% but not more than 50% (i.e., 10% to 50%), and more preferably at least 15% but not more than 45% (i.e., 15% to 45%) of the weight of the cold water soluble extrusion modified starch binder in the wetted small particles of extruded self-cohered absorbent material is solubilized during the wetting, coating, and nucleation sub-steps that occur during the depositing steps.

[0090] During this time, at least partial dissolution of the cold water-soluble binder and any cold water-soluble starches of the extruded self-cohered adsorbent particles adhered to the corresponding wetted outer surfaces of the animal litter particle nucleating substrate particles forms a flowable adhesive that allows the wetted extruded self-cohered adsorbent to flow, and the cold water-soluble binder and other cold water-soluble starches of each of the adhered extruded self-cohered adsorbent particles flow together, thereby fusing the adhered extruded self-cohered adsorbent particles into a substantially homogeneous and uniform outer region of extruded self-cohered adsorbent that at least partially, and preferably substantially completely, surrounds or encapsulates the wetted outer substrate particle surface. The flowable adhesive dries, ages, and adhesively bonds the substantially homogeneously fused outer region of the extruded self-cohered adsorbent to that substrate surface.

[0091] Because only a portion, but not all, of the cold water soluble extruded modified starch water-activated moisture-setting binder of the at least partially wetted extruded absorbent agglomerate particles is partially or completely solubilized during at least one of the activation, deposition, and / or nucleation steps (and during the wetting step if the extruded self-cohering absorbent particulates are added during the wetting step), at least another portion, but not all, of the cold water soluble extruded modified starch binder of the at least partially wetted extruded absorbent agglomerate particles is not partially or completely solubilized, thereby leaving the self-cohering absorbent animal litter particles formed therefrom in a state that can be at least partially or completely solubilized when wetted with water, urine, or synthetic urine.

[0092] In at least one preferred embodiment of the method for producing self-cohering absorbent litter particles from the substrate particles, a drying step can be, and preferably is, performed during or after the completion of the coating, deposition, and / or nucleation steps. The drying step (a) removes excess moisture from each newly formed litter particle from a region of extruded self-cohering absorbent material that at least partially, and preferably substantially completely, surrounds the outer surface of each substrate particle that forms the particle's nucleus, and (b) cures, or at least accelerates, the at least partially solubilized, water-soluble, water-activated, moisture-curable binder contained in the extruded self-cohering absorbent material, thereby adhering or bonding the extruded self-cohering absorbent material region to the substrate particle that forms the particle's nucleus. In one preferred drying step, a turbulent heated air stream at a temperature of at least 100°F, preferably at least 125°F, and more preferably at least 150°F, is introduced into a drum and flows through the drum against the newly formed litter particles, thereby reducing the moisture content of the outer region of the extruded self-cohering absorbent material of each litter particle and drying each litter particle. As the outer regions of each extruded self-cohering absorbent particle are dried by heated air, the starch contained in the water-soluble binder, which was previously at least partially solubilized by the water wetting the substrate particle to form a flowable adhesive, rapidly reverses, solidifies, and moisture-sets or hardens, thereby firmly and adhesively bonding the outer regions of the extruded self-cohering absorbent to the substrate particle. In one such preferred drying process, a sufficiently high flow rate of heated air is introduced into the drum, causing the heated air to turbulently flow and circulate within the drum, impinging on the newly formed litter particles and accelerating their reversal and drying. During this time, the drum preferably continues to rotate, thereby agitating the litter particles. In such a preferred drying process, the temperature of the flowing heated air is raised to a temperature sufficient to rapidly reverse the previously water-soluble starch in the flowable adhesive within at least 3 to 5 minutes, preferably within 1 to 3 minutes, and more preferably within 30 seconds to 1 minute, after the start of the drying process.Rapid reversal of the previously at least partially solubilized starch contained in the water-soluble, water-activated, moisture-curing binder is desirably induced while the drum rotates to substantially simultaneously agitate the self-cohering absorbent litter particles of the present invention during drying. This ensures that adjacent self-cohering absorbent litter particles within the drum do not form clumps when they come into contact with each other. Furthermore, the rapid reversal induced by this drying process also serves to rapidly remove any tackiness that may be present on the outer surfaces of the finished self-cohering absorbent litter particles, thereby helping to prevent the particles from adhering to each other and forming clumps.

[0093] When wetted with water, urine, or synthetic urine, for example, during use in an animal litter box, the non-solubilized, cold-water-soluble, extrusion-modified starch water-activated, moisture-setting binder at least partially or completely solubilizes and forms a flowable adhesive that flows between contacting and adjacent wet animal litter particles, causing at least pairs, i.e., at least three, of wet animal litter particles to self-cohere and form scoopable clumps. The formed scoopable clumps have a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, and a clump crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably 100 PSI when the clumps are dried, preferably air-dried, at room temperature to a moisture content of about 12% by weight of the clump.

[0094] In a preferred embodiment of the method for producing animal litter particles, in the wetting step, the substrate particles are substantially simultaneously collectively wetted by application of an aqueous liquid. The aqueous liquid may be an aqueous solution, but is preferably water. In one preferred wetting stage or step, the aqueous liquid (preferably water) is sprayed in a mist onto the substrate particles while the substrate particles are being agitated. This agitation is achieved by shaking or rotating in a drum or rotary drum mixer (e.g., a rotary drum cement mixer), thereby distributing the aqueous liquid (preferably water) more uniformly along substantially the entire outer surface of each particle, thereby substantially uniformly wetting each particle with the aqueous liquid (preferably water) in its region. In another preferred embodiment of the wetting step, one or more streams of aqueous liquid (preferably water) are sprayed onto the substrate particles from a sprayer while the substrate particles are being agitated. This agitation is achieved by shaking or rotating in a drum or rotary drum mixer, thereby more uniformly distributing the aqueous liquid (preferably water) along substantially the entire outer surface of each particle, thereby substantially uniformly wetting each particle with the aqueous liquid (preferably water) in its region.

[0095] In the wetting step, the amount of aqueous liquid (preferably water) supplied is controlled or adjusted to ensure that sufficient aqueous liquid (preferably water) is supplied to wet substantially all of the outer surface of each substrate particle in the wetting chamber. The wetting chamber is preferably the drum of a rotary drum mixer, such as a rotary drum cement mixer, which rotates to agitate the substrate particles while introducing the aqueous liquid (preferably water) into the drum, thereby more uniformly wetting the outer surfaces of the substrate particles with the aqueous liquid (preferably water). In the wetting step, the rotary drum is oriented so that it is tilted upward, generally about the central axis of the drum rotation, at an acute angle of between 5° and 60°, preferably between 7.5° and 50°, and more preferably between 10° and 45°, relative to the horizontal. This not only promotes wetting of the outer surfaces of the substrate particles, but also helps promote mixing and adhesion between the extruded self-cohering absorbent particles and the wet substrate particles in a subsequent step. In carrying out the method for producing self-cohering absorbent litter granules of the present invention, the orientation angle of the drum relative to the horizontal, the rotational speed of the drum, and the amount and / or rate at which aqueous liquid (preferably water) is introduced into the drum, such as by misting or spraying, are all adjusted in real time during the wetting step, the application step in which extruded self-cohering absorbent particles are introduced into the drum, and the nucleation step in which the wet substrate particles act as nucleators to which the extruded self-cohering absorbent particles adhere, forming at least a partial region or coating of extruded self-cohering absorbent on each substrate particle.

[0096] The amount of aqueous solution, preferably water, used in the wetting step is sufficient to substantially completely wet the exterior surface of each substrate particle prior to applying the smaller particles of extruded adsorbent agglomerate material to the substrate particles in the application step disclosed in more detail below, and includes at least an additional 2%, preferably an additional 5%, of aqueous liquid, preferably water, to ensure that there is excess water beyond the amount necessary to wet substantially all of the exterior surface area of ​​all of the substrate particles. Applying an amount of aqueous solution, preferably water, in excess of the amount necessary to wet substantially all of the exterior surface area of ​​the total amount of substrate particles used to make a batch of self-clumping adsorbent animal litter of the present invention ensures that there is sufficient water to at least partially solubilize some, if not all, of the cold water soluble extruded modified starch water-activated moisture-setting binder of the smaller particles of extruded adsorbent agglomerate material that contact the exterior surfaces of the wetted substrate particles. This not only promotes adhesion of the smaller particles of extruded adsorbent agglomerate material that contact the wetted outer surface of each larger substrate particle during the application process, but also ensures that the extruded adsorbent agglomerate material particles are adhesively bonded to the substrate particle by partial solubilization of at least some, if not all, of the cold water soluble extrusion-modified starch binder of the contacting extruded adsorbent agglomerate material particles.

[0097] In a further preferred method embodiment, an aqueous liquid, preferably water, is added to a mixture of substrate particles and small particles of extruded self-cohering absorbent material that is being agitated, such as by shaking or rolling, in an amount sufficient to form a slurry of aqueous liquid (e.g., water), substrate particles, and extruded self-cohering absorbent particles. By continuing to agitate, shake, or roll the slurry of the substrate and extruded self-cohering absorbent particle mixture, the substrate particles become nucleation points to which the extruded self-cohering absorbent particles begin to adhere.

[0098] After the wetting step is completed, or even while the wetting step is being carried out, smaller particles of extruded adsorbent aggregate material are added in a coating step so that each of the wetted substrate particles is at least partially covered, at least partially coated, and / or at least partially encapsulated by at least a portion of the added extruded adsorbent aggregate material particles, preferably mixed using stirring, shaking, mechanical mixing, or other mixing methods and / or means. In the step of adding smaller particles of extruded adsorbent agglomerate material during or after the step of wetting the substrate particles with an aqueous solution, preferably water, the wetted substrate particles become nuclei of the cohesive adsorbent agglomerate material during the nucleation sub-step, in which the smaller particles of extruded adsorbent agglomerate material are attracted to and even come into contact with the corresponding wetted substrate particles, which are caused by at least one of the following: surface tension forces acting between the water wetting the outer surface of the substrate particles and the nearby extruded adsorbent agglomerate particles, capillary adhesion acting between molecules of each substrate particle and molecules of extruded adsorbent agglomerate particles that are in sufficient proximity and / or contact, and / or intermolecular forces, preferably van der Waals forces and / or intermolecular adhesive forces, acting between molecules of water wetting the outer surface of each substrate particle and / or molecules of the outer surface of each substrate particle and molecules of extruded adsorbent agglomerate particles that are in close proximity and / or contact. In this nucleation stage or sub-stage of the extruded adsorbent aggregate material application process, the initial regions of particles of extruded adsorbent aggregate material are attracted to and contact the aqueous liquid, preferably water, on the outer surface of each substrate particle wetted with water, until at least a portion of the water wetting the outer surface of said substrate particles wets at least a portion of said extruded adsorbent aggregate material particles that are in sufficient proximity and / or contact.

[0099] If the nucleation step overlaps with the wetting step, it overlaps only partially with the wetting step and is initiated after at least half of the wetting step has taken place, preferably after at least three-quarters of the wetting step has taken place, and more preferably after about 90% to 95% of the wetting step has taken place. An advantage of initiating the nucleation step during the wetting step is that the amount of water required to complete the wetting step can be adjusted to add excess water beyond that required just to wet the substrate particles, thereby ensuring that the nucleation step has reached a stage where the extruded adsorbent aggregate material particles are attached to at least 50%, preferably at least 65%, and more preferably at least 75% of the outer surface of the substrate particles by the time the wetting step is completed and water addition is stopped.

[0100] The mixing or agitation step continues after the wetting step is completed and water addition is stopped, followed by a nucleation sub-step in which unattached extruded sorbent aggregate particles attach to (i) portions of the outer surface of the substrate particles that did not previously have extruded sorbent aggregate particles attached thereto, and / or (ii) other portions of the outer surface of the substrate particles that already have extruded sorbent aggregate particles attached thereto, thereby increasing the thickness of the attached layer of extruded sorbent aggregate particles. As the mixing or agitation step continues, more of the previously unattached extruded sorbent aggregate particles attach to (i) surface areas of the substrate particles that were previously unattached, and / or (ii) surface areas of the substrate particles that already had extruded sorbent aggregate particles attached thereto, thereby further increasing the thickness of the attached layer of extruded sorbent aggregate particles.

[0101] In a preferred method for producing self-clumping litter comprising self-clumping absorbent litter particles having adhered to a non-clumping substrate particle a water-activated moisture-setting binder of cold water soluble extruded modified starch and small particles in the form of an extruded self-clumping absorbent powder or dust comprised of cold water swellable extruded modified starch (preferably in the form of a cold water swellable extruded modified starch pregel), the following steps are carried out: The rotary drum mixer is turned on and the substrate particles to be coated with the extruded self-cohering absorbent powder or powder-like particles are added, and the weight of the substrate entering the rotating drum of the rotary mixer is recorded.

[0102] The angle of the drum barrel is changed to maximize the tumbling or rolling action of the base particles to be coated induced by the rotation of the drum of the mixer. By changing the angle, we mean changing the acute angle formed by the central axis of rotation of the drum with respect to the generally horizontal ground on which the rotary mixer is supported, so as to maximize or optimize the agitation or rolling of the base particles within the rotating barrel and to uniformly wet the base particles with water when water is supplied into the drum during the wetting step.

[0103] The wetting process is initiated by adding water into the barrel of the rotary mixer drum while the drum is rotating, in an amount sufficient to completely wet the outer surface of the substrate particles. The water is mixed with the substrate particles and allowed to wet for up to 4 minutes, preferably about 3 minutes or less, more preferably 1 to 3 minutes, and then checked for the presence of free water. The substrate particles should be sufficiently wet, but not so wet that the water drains off and accumulates at the bottom of the mixer drum barrel. A sample of the wet substrate particles is removed from the rotating barrel, held in your hand, and an attempt is made to roll the sample while continuously holding and squeezing it with your hand. The ball formed when you release your hand should only slightly or loosely retain its shape, e.g., only slightly. Inorganic substrate particles, such as sand, perlite, rubber, glass, and sand, require only a few seconds, preferably less than 5 seconds, to stabilize water adsorption and thereby ensure sufficient wetting with water. Organic substrate particles, such as paper, wood fiber, wood pellets, and nut shells, require a two-stage wetting process in which enough water is added to completely coat the organic substrate particles while the mixer drum continues to rotate for approximately five minutes. This allows sufficient time for the organic substrate particles to fully wet and, preferably, to begin absorbing water by drawing at least some of the water into the fibers of the organic substrate particles. While the fibers on the outer surface of the organic substrate particles are instantly wetted, it takes time for some of the water to penetrate the outer fibers and wet the interior fibers of the organic substrate particles. In organic substrate particles, additional time is required for the water to traverse or migrate through the outer fibers of each particle and begin wetting additional areas below the outer particle surface. If this second step is not performed to ensure that wetting extends to the surface fibers of each particle, preferably to the fibers in the area below the outer surface, the actual area of ​​water wetting on the outer fiber surface of each organic substrate particle will lack consistency or uniformity. In other words, without this additional water wetting step or substep, the water wetting the exterior of each organic substrate particle will not form a consistent or uniform coating of water on the fibrous exterior of each organic substrate particle. The roughness of the exterior surface of the organic substrate particle also affects this water rewetting substep.This is because, for substrate particles with rougher outer surfaces, additional rewetting cycles may be required to ensure that enough water penetrates the outer surface of each particle to coat the exterior of the coarse substrate particle with a uniform water film. Therefore, depending on the roughness of the fibrous surface of the substrate particle, at least multiple, and possibly at least multiple, pairs of rewetting and addition of additional water may be required. By performing multiple rewetting cycles, with additional water added to the drum during each rewetting cycle, the outer surface of each organic substrate particle can be saturated with water without excessive wetting or oversaturation, which would result in pooling of water at the bottom of the organic substrate particle mixture at the bottom of the rotating drum. The total amount of water used throughout the wetting step, including the additional water used during the rewetting substep, is recorded.

[0104] In the coating step, the extruded self-aggregating adsorbent substrate coating powder or powdery particles are added to a rotating drum during the wetting step, or more preferably after the wetting step is completed. The powder or powdery particles are controllably and gradually introduced into the drum, for example, preferably by sieving into the drum, to ensure that the wetted outer surface of the substrate particles is preferably substantially completely, e.g., entirely, coated with the powder or powdery particles.

[0105] During the coating process, additional powder or powder particles of the extruded self-cohering absorbent material are continuously added to the drum onto the wetted substrate particles. This is continued until the outer coating surface formed on the nucleated substrate particles gradually loses its tackiness, and the area formed on the substrate particles becomes substantially, preferably completely, tack-free. The powder or powder particles must be added gradually and controllably while the drum is rotating. This agitates or tumbles the at least partially coated substrate particles, preventing the gel formed from the cold-water-soluble, water-activated, moisture-setting binder and the cold-water-swellable starch from adhering and clumping adjacent coated substrate particles that come into contact with each other during agitation by the rotating drum. It is important to remove agglomerates formed by this gel agglomeration phenomenon by sieving during drum rotation or after the finished self-cohering absorbent litter particles of the present invention are removed from the drum mixer. Small agglomerates resulting from gel agglomeration, e.g., agglomerates of two or three pellets, are broken down and sized in a subsequent particle size reduction step using a particle size reducer, e.g., a counter-rotating roll particle size reducer or other type of particle size reducer such as a hammer mill.

[0106] The extruded self-cohering absorbent powder or dust is an instant starch powder or dust comprised of an ultra-high pressure extrusion modified starch pregel, preferably comprising a cold water swellable, extrusion modified starch, and a sufficient amount of cold water soluble, water activated, moisture curing binder such that there is at least some water soluble binder that not only dissolves and adheres to the surface of a wetted outer substrate particle upon application of the powder or dust, but also some remains in the finished self-cohering absorbent animal litter particles of the invention to form a flowable adhesive when the animal litter particles are wetted with water, urine, or synthetic urine during actual animal litter use. It is important to maximize the degree of starch damage in the extruded mixture, and preferably the degree of protein damage in the extruded starch mixture, through configuration of the single screw extruder, which includes operating the extruder at an ultra-high extrusion pressure measured at the extruder die of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI, whereby a self-cohering absorbent powder or flour comprising at least a portion of instant starch and at least a portion of ultra-high pressure extrusion-modified cold water swelling water-absorbent starch is extruded.

[0107] In preferred methods and embodiments for extruding self-cohering adsorbent powders or dusts, it is important that the barrel of the single screw extruder be longer than 12 inches, preferably longer than 14 inches. This is because the longer extruder barrel increases the residence time of the starch in the extruder, thereby ensuring that a sufficient amount of the starch is thermally modified into instantized starch during ultra-high pressure extrusion. The instantized starch is preferably a cold-water-swellable, water-absorbing, extrusion-modified starch, more preferably a cold-water-swellable, water-absorbing, extrusion-modified pregelatinized starch or a cold-water-swellable, water-absorbing, extrusion-modified starch pregel. By using a longer extruder barrel in a single screw extruder, even if some of the starch is mechanically damaged during extrusion and is not instantized and / or pregelatinized, the longer barrel ensures sufficient residence or dwell time of the starch in the extruder barrel to ensure that a sufficient amount of the starch is modified during or by extrusion, preferably thermally modified during extrusion, to form instantized starch. The instantized starch is preferably a cold water-swellable pregel, which maximizes the amount and number of starches that gel when wetted in contact with the water-wet outer surface of the substrate particle, coating the water-wet outer substrate particle surface and thereby firmly adhering, preferably via hydrogen bonding, as the wet gel dries.

[0108] In a finishing step for the self-cohering absorbent animal litter particles, which is carried out after the coating step is completed, an additional amount of extruded self-cohering absorbent powder or powder is applied, for example, as a dusting or powder, to the outer surface of the coated substrate particle, i.e., the outer surface of the self-cohering absorbent animal litter particle of the present invention. This ensures that a thin outer layer region of extruded self-cohering absorbent powder or powder remains without ever being wetted, and that substantially all of the cold-water-soluble, extrusion-modified starch water-activated, moisture-setting binder in this outer layer region is contributed when the finished animal litter particle is wetted with water, urine, or artificial urine during use in a cat litter box. The finishing step for the self-cohering absorbent animal litter particles after coating can be, and preferably is, carried out while the outer surface of the self-cohering absorbent animal litter particle is still wet or sticky, which promotes adhesion of the dried extruded self-cohering absorbent powder or powder region to the self-cohering absorbent animal litter particle. The finishing step of the self-cohering absorbent animal litter particles after coating can be, and preferably is, carried out while the mixer drum is rotating to continue agitating the self-cohering absorbent animal litter particles of the present invention. This ensures a more consistent and uniform distribution of the dry powder or powder particles, resulting in an outer region having a more consistent and uniform thickness. In a preferred embodiment of the method for making self-cohering absorbent animal litter particles of the present invention, the dry extruded self-cohering absorbent powder or powder region is applied while at least a portion, and preferably substantially all, of the outer surface of the self-cohering absorbent animal litter particles is a starch gel formed from at least a portion of the starch that has been modified, preferably thermally modified, during extrusion in the barrel of the extruder.In a preferred embodiment of the method for making self-cohering absorbent animal litter particles of the present invention, the dry extruded self-cohering absorbent powder or powder region is applied to at least a portion, preferably substantially all, of the outer surface of the self-cohering absorbent animal litter particle while it is a starch gel in a gelled state, and preferably before the gel has completely changed from a semi-solid to a solid, such as by retrogradation of the starch that forms the gel.

[0109] In a preferred embodiment of the method for producing self-clumping absorbent litter particles of the present invention, a dry granular modified starch-based water-absorbent flocculant (preferably in the form of an extruded self-clumping absorbent powder or powder) is applied to at least a portion, preferably substantially all, of the outer surface of the self-clumping absorbent litter particles while the outer surface is still composed of a wet and / or sticky starch gel. In this way, not only does the still wet and / or sticky outer gel surface promote adhesion of the dry particles of extruded self-clumping absorbent powder or powder, but the application of the dry particles of extruded self-clumping absorbent powder or powder also absorbs at least a portion of the moisture from the outer surface, removing the stickiness of the outer gel surface and forming self-clumping absorbent litter particles of the present invention having a dry, wettable self-clumping absorbent exterior. Furthermore, the starch in the dried extruded self-cohering absorbent powder or powders comprising a cold water soluble extruded modified starch-based water-activated, moisture-setting binder and a cold water swellable, water-absorbent extruded modified starch advantageously does not retrograde when heated air is applied during the drying process of the self-cohering absorbent litter particles. The finished self-cohering absorbent litter particles are preferably dried to a moisture content of 8% or less, more preferably less than 8%, by weight of the particle, to ensure that residual moisture or water is not in an amount sufficient to plasticize the starch in the outer regions of the extruded self-cohering absorbent of the litter particle and cause further retrogradation of the starch in the outer regions of the particle.

[0110] When a self-cohering absorbent animal litter particle is formed by adhering a coating or region of extruded self-cohering, water-absorbent powder or powder to a water-moistened nutshell substrate particle, the coating or region forming an outer region containing a gel that promotes adhesive adhesion to the substrate particle, applying a region of dry extruded self-cohering, absorbent powder or powder to the outer self-cohering, water-absorbent animal litter particle region while it is still wet and contains gel in a gelled state promotes adhesion of the dry powder or powder particles to form a dry shell on the outer gel region, which is well adhered to the outer gel region, preferably by adhesive attachment via hydrogen bonding between the outer gel region and the outer surface of the substrate particle.

[0111] In the drying step, heated air introduced into the drum during or after the completion of the post-coated self-clumping absorbent animal litter particle finishing step to dry the self-clumping water-absorbent animal litter particles of the present invention not only promotes drying of the wet gelatinized starch adhered to the outer surface of the substrate particle, but also retrogrades the water-wet starch (including starch gel) on the outer surface of the substrate particle, hardening the inner region that is adhered to, and preferably adhesively bonded to, the outer surface of the substrate particle and that is located between the outer surface of the substrate particle and the outer region of the dried extruded self-clumping water-absorbent powder or powder adhered to, and preferably adhesively bonded to, said inner region, to form the finished self-clumping water-absorbent animal litter particles of the present invention.

[0112] These and various other features, aspects and advantages of the present invention will become apparent from the following description of the drawings.

[0113] One or more preferred embodiments of the present invention are illustrated in the accompanying drawings, in which like parts are designated with the same reference numerals throughout. [Brief explanation of the drawings]

[0114] [Figure 1]1 is an enlarged cross-sectional view of an absorbent particle that is a self-clumping absorbent litter particle, the absorbent particle being comprised of an inner substrate particle that is at least partially, preferably substantially completely, coated with a modified starch absorbent clumping material, preferably a modified starch absorbent clumping agent. [Figure 2A] 1 is a magnified photomicrograph of calcium bentonite particles used as a non-agglomerating granular substrate in one embodiment of the present invention. [Figure 2B] 1 is an exemplary enlarged micrograph of sand particles used as a non-cohesive granular substrate in a second embodiment of the present invention. [Figure 2C] 1 is a magnified photomicrograph of additional exemplary sand grains used as a non-cohesive granular substrate in a second alternative embodiment of the present invention. [Figure 2D] 1 is a photomicrograph of particles of ground walnut shells used as a non-agglomerating granular substrate in a third embodiment of the present invention. [Figure 2E] 1 is a photomicrograph of particles of a cellulosic material, preferably paper or including paper, used as a non-agglomerated granular substrate in a fourth embodiment of the present invention. [Figure 2F] 1 is an enlarged microscope photograph of perlite particles used as a non-agglomerating granular substrate in a sixth embodiment of the present invention. [Figure 2G] 1 is a magnified micrograph of wood particles used as a non-agglomerated granular substrate in a fifth embodiment of the present invention. [Figure 3] 1 is a magnified photomicrograph of pairs of calcium bentonite substrate particles coated with an outer layer of extrusion-modified starch-based water-absorbing flocculant. [Figure 4] 1 is a magnified photomicrograph of pairs of calcium bentonite substrate particles coated with an outer layer of extrusion-modified starch-based water-absorbing flocculant. [Figure 5] 1 is a magnified photomicrograph of pairs of calcium bentonite substrate particles coated with an outer layer of extrusion-modified starch-based water-absorbing flocculant. [Figure 6]1 is a first video frame image of a plurality of self-clumping absorbent animal litter particles prior to wetting with water, showing that each animal litter particle is comprised of an outer layer region of extruded modified starch-based water-absorbent clumping agent coating a calcium bentonite substrate particle. [Figure 7] is a second video frame image taken at least several seconds after the first video frame image of Figure 6, showing the animal litter particles of Figure 6 being initially wetted with water, and showing that in at least a portion of the water-wetted particles, the outer layer of the extrusion-modified starch-based water-absorbing flocculant is at least partially solubilized in the water, flows out of the wetted particle into the water, and forms a flowable adhesive that flows toward adjacent animal litter particles with which it comes into contact. [Figure 8]8 is a third video frame image taken at least several seconds after the second video frame image of FIG. 7 , showing further adhesion of water to the animal litter particles of FIG. 7 . This causes a portion of the outer layer of the extruded modified starch-based water-absorbent flocculant of the water-wetted particle to absorb and swell, while another portion of the outer layer of the extruded modified starch-based water-absorbent flocculant of the same wetted particle at least partially solubilizes in the water, forming a flowable adhesive. This flowable adhesive flows from the wetted particle through the water and migrates toward adjacent contacting animal litter particles, increasing in viscosity over time and transforming into an adhesive gel, which begins to cohere the wetted contacting and adjacent particles into a clump. FIG. 8 also shows a further increase in viscosity of at least a portion of the adhesive gel, consisting of the water-soluble binder, which formed earliest, thereby thickening the binding gel that bonds the wetted particles and adjacent particles together. This adhesion is preferably achieved through the use of intermolecular forces such as liquid adhesive forces, surface tension, van der Waals forces, and even hydrogen bonding, which act during the initial stages of contacting and clumping adjacent animal litter particles upon wetting. Figure 8 also shows how the partially solubilized binder transforms into a flowable adhesive that flows from the wetted particles along and between contacting and adjacent particles, increasing in viscosity over time and thickening into an adhesive gel, promoting adhesion of contacting and adjacent particles during the initial stages of animal litter clump formation. [Figure 9] is a fourth video frame image taken at least a few seconds after the third video frame image of Figure 9, showing: (a) further wetting of the animal litter particles of Figure 8 with water; (b) wetting of at least a partially soluble binder in the outer layer portion of the extruded modified starch-based water-absorbent flocculant of each wet particle to produce more fluid adhesive; (c) further swelling and gelling of the water-swellable, water-absorbent extruded modified starch in the outer layer portion of the extruded modified starch-based water-absorbent flocculant of each wet particle; (d) transformation of more of the fluid adhesive into a viscous, low-fluidity adhesive gel; and (e) transformation of at least a portion, preferably a greater portion, of the adhesive gel into a stable, firm, binding gel with little or no flow. [Figure 10]is a fifth video frame image taken at least several seconds after the fourth video frame image in Figure 9, showing solubilization of at least a portion of the water-soluble binder present in at least the outer region of the extruded modified starch-based water-absorbing flocculant of each moistened particle, and swelling and gelling upon water absorption by at least a portion of the cold water-swellable, cold water-absorbent extruded modified starch also present in at least the outer region of the extruded modified starch-based water-absorbing flocculant of each moistened particle. [Figure 11] is a sixth video frame image taken at least a few seconds after the fifth video frame image in Figure 10, showing extensive solubilization of the water-soluble binder into a flowable adhesive in water wetting the outer layer of the extruded modified starch-based water-absorbing flocculant of all the granules, and extensive swelling and gelation due to volume expansion of the cold water-swellable and cold water-absorbent extruded modified starch in the outer layer of the extruded modified starch-based water-absorbing flocculant of all the granules, and showing how the boundaries of the wetted granules become increasingly unclear as substantially all of the granules are wetted and coalesce into an amorphous gel-like mass. [Figure 12]shows further progression of the water-wetted, self-cohesive, water-absorbent animal litter particles of the present invention, where further gelation and swelling occurs. This occurs as a highly fluid adhesive, formed at least in part from a water-soluble binder, flows from, around, along, and between the animal litter particles, not only from the particle from which it was released, but also from contacting and adjacent particles. The adhesive thickens over time to form an adhesive gel, promoting the cohesion of contacting and adjacent animal litter particles. The gel further thickens over time to form a binding gel, adhesively bonding contacting and adjacent animal litter particles. All of this proceeds with continued moisture curing and hardening, ultimately forming an in-situ mass of animal litter particles within 120 seconds. In this mass, at least the binding gel hardens to a substantially hard adhesive in the form of a glass-like material, creating a substantially rock-hard mass. The loaf has a moisture retention of at least 95%, preferably at least 97%, and more preferably at least 99%, and when dried to a moisture content of about 12% by weight of the loaf, has a loaf crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably at least 100 PSI. [Figure 13] 1 illustrates further development of the water-wetted self-clumping absorbent animal litter particles of the present invention. [Figure 14] 1 illustrates further development of the water-wetted self-clumping absorbent animal litter particles of the present invention. [Figure 15] 1 illustrates further development of the water-wetted self-clumping absorbent animal litter particles of the present invention. [Figure 16]FIG. 1 is a magnified micrograph of the top surface of a mass of at least two pairs of self-clumping animal litter particles, each of which comprises an inner substrate particle of sand grains coated with and attached to an outer region of ultra-high-pressure modified starch extrudate. This outer region comprises a modified starch-based water-absorbing flocculant. FIG. 5 shows a top view of the extrudate-coated sand mass after drying, particularly showing the abundant presence of ultra-high-pressure extrusion-modified starch spherules. Ultra-high-pressure extrusion-modified starch partially solubilized gel spherules are preferred, more preferably ultra-high-pressure extrusion-modified starch water-insoluble and / or partially water-soluble pre-gelatinized starch spherules, and even more preferably ultra-high-pressure extrusion-modified starch water-insoluble pre-gelatinized starch gel spherules. After wetting with water or urine during agglomeration, these starch spherules rise to the top of the mass, exposing at least a portion of the outer surface of the inner sand grains. [Figure 17] 17 is a close-up photomicrograph of the bottom of the clamp of FIG. 16, the clump being formed from multiple pairs or more of self-clumping animal litter particles that have been wetted with water or urine, each particle having an outer region of ultra-high pressure modified starch extrudate consisting of a modified starch-based water-absorbing flocculant coated on and attached to an inner substrate particle that is a sand grain - in the bottom view of the extrudate-coated sand particles, no free starch is shown, e.g. - note the absence of free starch - only extruded modified starch spheres attached to the sand grain are shown. [Figure 18] is a micrograph of an enlarged side view of the agglomerate shown in Figures 16 and 17, the agglomerate being formed from at least a plurality of pairs of self-cohesive animal litter particles, each particle having an outer region of ultra-high pressure modified starch extrudate comprised of modified starch water-absorbent flocculant coated onto and adhered to an inner substrate sand grain or particles, the side view of the extrudate-coated sand particle agglomerate also showing extruded modified starch spheres floating to the top of the agglomerate. [Figure 19]is a series of video images showing the water reactivation of an at least partially water-soluble modified starch binder, including the production of a water-reactivated, moisture-resetting flowable adhesive from pre-wetted, self-clumping, absorbent animal litter grains of the present invention, including sand grains as substrate particles coated on their outer layers with a modified starch water-absorbent flocculating material or flocculant, upon rewetting with water. The series of images shows the progression of the flowable adhesive flowing from the rewetted grains, which gels as water is absorbed by the outer layer of modified starch water-absorbent flocculating material or flocculant remaining on the sand grain substrate particle and its volume swells. After rewetting and drying, the flowable adhesive, and at least a portion of the adhesive remaining in the old areas of the modified starch water-absorbent flocculating material or flocculant that did not dissolve in the rewet water, rehardens upon moisture resetting and hardens into a substantially hard mass or agglomerate, transitioning to a solid, glassy state. This results in the clumps or agglomerates, when dried to a moisture content of about 12% by weight, having a cohesion retention of at least 95%, preferably at least 97%, more preferably at least 99%, and a crushing or compressive strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably at least 100 PSI. [Figure 20] 1 is a series of video images showing the reactivation of an at least partially water-soluble modified starch binder with water. [Figure 21] 1 is a series of video images showing the reactivation of an at least partially water-soluble modified starch binder with water. [Figure 22] 1 is a series of video images showing the reactivation of an at least partially water-soluble modified starch binder with water. [Figure 23] 1 is a series of video images showing the reactivation of an at least partially water-soluble modified starch binder with water. [Figure 24] 1 is a series of video images showing the reactivation of an at least partially water-soluble modified starch binder with water. [Figure 25]1 is a series of video images showing the reactivation of an at least partially water-soluble modified starch binder with water. [Figure 26] 1 is a series of video images showing the reactivation of an at least partially water-soluble modified starch binder with water. [Figure 27] 1 is a magnified photomicrograph of particles of crushed walnut shells before they are coated with an ultra-high pressure extrudate containing water-absorbing cohesive starch modified by extrusion. [Figure 28] is a magnified micrograph of crushed walnut shell particles coated with an ultra-high pressure extrudate, which is or contains a starch-based water-absorbing flocculant modified by extrusion to form a thin outer coating adhered to the outer surface of each walnut shell substrate particle, forming the self-cohering absorbent and self-cohering absorbent particles of the present invention. [Figure 29] 1 is another enlarged photomicrograph of ground walnut shell particles coated with an ultra-high pressure extrudate that forms the self-cohering absorbent and self-cohering absorbent particles of the present invention, the ultra-high pressure extrudate being or including a starch-based water-absorbing flocculant that has been modified by extrusion processing to form a thin outer coating adhered to the outer surface of each ground walnut shell substrate particle. [Figure 30] 1 is a magnified micrograph of crushed walnut shell particles, each coated with an ultra-high-pressure extrudate. The ultra-high-pressure extrudate is or includes an extrusion-modified starch-based water-absorbent flocculant, forming a thin outer coating adhered to the outer surface of each walnut shell substrate particle to form a self-cohesive animal litter particle. Ten grams of the self-cohesive animal litter particles are shown after being washed for 20 seconds and then dried. This treatment reduces the particle coating weight of the thin outer coating of ultra-high-pressure extrudate (which is or includes an extrusion-modified starch-based water-absorbent flocculant) from approximately 15% to 16% (by weight of the animal litter particle) to approximately 4.5% (by weight of the animal litter particle). Even after this reduction, each animal litter particle still has sufficient coating to absorb water or urine and form at least weak cohesion when wet, and preferably form clumps when wet. [Figure 31] 1 is a magnified micrograph of crushed walnut shell particles. Each particle is coated with an ultra-high-pressure extrudate that is or includes an extrusion-modified starch water-absorbent flocculant, forming a thin outer coating adhered to the outer surface of each crushed walnut shell substrate particle, thereby forming a self-cohesive animal litter particle. 20 grams of these self-cohesive animal litter particles were washed for 20 seconds and then dried, resulting in a particle coating weight reduction of the thin outer coating of the ultra-high-pressure extrudate that is or includes an extrusion-modified starch water-absorbent flocculant on each animal litter particle from about 15%-16% to about 5% by weight of the animal litter particle. As a result, each animal litter particle still has sufficient coating to absorb water or urine when wet to form at least weak cohesion, and preferably form clumps when wet. DETAILED DESCRIPTION OF THE INVENTION

[0115] Although preferred embodiments of the method for making self-clumping animal litter using granular non-clumping substrates in accordance with the present invention have worked with many types of granular non-clumping substrates that have been attempted, it is envisioned that the animal litter making method of the present invention will also work with many other types of substrate particles, including both non-clumping and clumping substrate particles.

[0116] Before describing one or more embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. [Definition] Before describing one or more embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0117] Before the materials, products, and methods of the present invention are described below, it is to be further understood that this invention is not limited to the particular methodology, protocols, materials, and reagents described, as these may vary. Also, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments, and is not intended to limit the scope of the present invention, which is limited only by the appended claims.

[0118] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Also, the terms "a" (or "an"), "one or more," and "at least one" can be used interchangeably herein. It should further be noted that the terms "comprising," "including," and "having" can be used interchangeably.

[0119] In the present invention, terms indicating directions, such as "upper," "lower," "top," "lower," "upper," "lower," "left," "right," "horizontal," "vertical," "upward," "downward," and other terms indicating positions and orientations, are used merely for convenience in describing various embodiments of the present invention. Embodiments of the present invention may also be oriented in various ways. For example, diagrams, devices, etc. shown in the drawings may be flipped upside down, rotated 90 degrees in any direction, inverted, or mirrored.

[0120] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described below. All publications and patents specifically mentioned herein are incorporated by reference for all purposes to describe and disclose components, reagents, chemicals, equipment, articles of manufacture, statistical analyses and methodologies that might be used in connection with the present invention. All references cited herein are to be construed as indicative of the state of the art. Nothing herein should be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.

[0121] Where the definitions of the following terms deviate from the commonly used meaning of such terms, applicants intend to use the definitions set forth below unless otherwise indicated.

[0122] For purposes of this invention, a value or characteristic is "based on" a particular value, characteristic, satisfaction of a condition, or other factor means that it is derived by performing a mathematical calculation or logical judgment using the value, characteristic, or other factor.

[0123] As used herein, the term "blend" refers to a homogeneous or substantially homogeneous mixture of two or more solid materials, one or more of which may be coated.

[0124] For purposes of the present invention, the term "substantially homogeneous" refers to a mixture having substantially the same density throughout the mixture.

[0125] As used herein, the term "homogeneous" refers to a mixture of two or more solid materials, wherein the density of the composition measured on at least 10 samples of the mixture has a standard deviation throughout the mixture of 2.0 pounds per cubic foot or less, and one or more of the solid materials may be coated.

[0126] In the present invention, the term "homogeneous blend" refers to a blend that is homogeneous.

[0127] In the present invention, the term "homogeneous mixture" refers to a mixture that is uniform.

[0128] In the present invention, the term "wetting agent" or "wetting liquid" refers to a liquid that wets sorbent particles, such as animal litter particles. Examples of wetting agents or liquids include liquids such as water, aqueous solutions, urine, and artificial urine.

[0129] In the present invention, the term "cellulose-containing material" refers to a material in which at least 10% of the material is composed of cellulose. Examples of cellulose-containing materials include paper, wood fiber, sawdust, fiber, and husk.

[0130] In the present invention, the term "flocculating additive" refers to a flocculating agent other than sodium bentonite.

[0131] In the present invention, the term "flocculant" refers to a material in which particles containing the flocculant, when wetted with a wetting agent, flocculate to form a bonded mass of at least multiple pairs of wetted particles, i.e., at least three, which substantially hardens when dried to a moisture content of 15% or less by weight of the hardened mass.

[0132] For purposes of this invention, the term "clump strength" refers to the average compressive strength, expressed in pounds per square inch (PSI), of clumps dried to a moisture content of about 12% and crushed while measuring their compressive or crushing strength.

[0133] In the present invention, the terms "filler" and "filling material" refer to materials in an animal litter product other than the clumping agent, i.e., sodium bentonite or clumping additive. In one embodiment of the present invention, the filler material may be calcium bentonite. In another embodiment of the present invention, the filler material may be sand. In a further embodiment of the present invention, the filler material may be a cellulose-containing material.

[0134] For purposes of this invention, the term "fines" generally refers to particles smaller than 1 / 32 inch (800 microns) and larger than 2 / 125 inch (400 microns), which particles will pass through a No. 20 U.S. mesh screen or sieve and be retained on a No. 40 U.S. mesh screen or sieve.

[0135] For purposes of this invention, the term "dust" refers to particles smaller than fines that will pass through a No. 40 US mesh screen or sieve.

[0136] In the present invention, the term "fragrance" refers to a compound that emits an odor perceived as a pleasant scent and / or a compound in the form of a masking fragrance or the like that neutralizes or masks an unpleasant or objectionable odor. The term "fragrance" can refer to a coating that contains a fragrance, either by being added to the coating or by the fragrance itself being the coating. The fragrance coating may also contain one or more other ingredients or components.

[0137] In the present invention, the term "granular" refers to a solid material having a particle size of less than mesh 2. The solid material used in the mixture of the present invention may be ground to form a granular material.

[0138] In the present invention, the terms "particulate filler" and "particulate filler material" refer to a filler that is in particulate form.

[0139] In the present invention, the term "heterogeneous mixture" refers to a composition in which the components of the mixture are readily separable from one another.

[0140] In the present invention, the term "homogeneous mixture" refers to a uniform composition.

[0141] In the present invention, the term "mixture" refers to a composition containing two or more different components that are not chemically bonded. Individual components of a heterogeneous mixture can contain two or more chemically bonded substances, such as, for example, a substrate that is a filler material coated with the water-swelling and gelling starch-containing biopolymer flocculant of the present invention.

[0142] In the present invention, the term "non-calcium bentonite clay" refers to clays other than calcium bentonite. The filler material must not be sodium bentonite, and therefore the "non-calcium bentonite clay" must not be sodium bentonite.

[0143] In the present invention, the term "removable clump-forming" refers to animal litter that, when exposed to a wetting agent or liquid, forms a clump consisting of at least a plurality of pairs of animal litter particles, the clump having sufficient structural integrity and hardness to be mechanically separated from the unwetted animal litter for disposal, and has a clump retention rate of at least 98%, preferably at least 99%, when the clump of animal litter particles is drop tested according to the Standard Animal Litter Drop Test defined below. [Introduction] The present invention relates to a granular swelling and gelling absorbent comprising particles of an inorganic or organic substrate, either a non-absorbent substrate or a minimally absorbent substrate, and an absorbent particle-forming nucleating material having attached thereto an exteriorly disposed modified starch-based water-absorbent flocculant, preferably an absorbent swellable biopolymer gelling agent based on modified starch. The resulting swelling and gelling absorbent particles are preferably self-cohering absorbent granules, each having an exterior coating layer or region that at least partially coats and can substantially completely encapsulate the interior non-absorbent or minimally absorbent substrate particle. During use of the absorbent, upon contact with a liquid, preferably an aqueous liquid, the exterior region of the modified starch-based water-absorbent flocculant, preferably comprising the absorbent swellable biopolymer gelling agent, of each swelling and gelling absorbent particle absorbs at least a portion of the liquid, swells in size and volume, and simultaneously substantially gels. The gel of the fluid-imbibed gelling agent swells and expands in each of the wetted swollen and gelling absorbent particles as a result of fluid absorption, combining with the gel of the fluid-imbibed gelling agent of adjacent wetted swollen and gelling absorbent particles to form an agglomerate or coagulated mass of wetted swelled and gelling absorbent particles. The wetted absorbent-swellable biopolymer gelling agent of each of the swollen and gelling absorbent particles not only swells as it absorbs fluid, preferably an aqueous fluid such as water, urine, or an aqueous solution, to form a water-activated, moisture-curing adhesive gel, but also increases in size and volume during absorption and gelling, and moisture-cures into a substantially hard adhesive that binds the wetted particles together as they dry to form a substantially rock-hard mass. Such loaves, when moisture cured by drying to a moisture content of about 12% by weight of the loaves, have a loave retention of at least 95%, preferably at least 97%, or preferably at least 99%, while having a loave crush strength or loave compression strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably at least 100 PSI.

[0144] In a preferred embodiment, the wetted adsorbent-swellable biopolymer gelling agent not only forms an adhesive gel when wet, but also forms a water-activated, moisture-curable modified starch flowable adhesive that flows from the particles, around contacting particles, and between adjacent particles, flocculating or coagulating the particles and causing them to agglomerate. Such agglomerates, when moisture-cured by drying to a moisture content of about 12% by weight of the agglomerate, have a mass retention of at least 95%, preferably at least 97%, and more preferably at least 99%, while also having a mass crush strength or mass compression strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably at least 100 PSI.

[0145] The present invention also relates to a self-clumping animal litter, most preferably comprising self-clumping animal litter particles, each of which is formed by attaching to a non-clumping substrate particle a flocculant comprising a water-activated, moisture-curing, water-swelling gelling polymer or biopolymer, the flocculant containing at least 5% water-soluble binder which not only imparts cohesive properties to the non-clumping substrate particles but also causes pairs of wetted self-clumping animal litter particles to form substantially hard, i.e., rock-hard, clumps when dry.

[0146] The present invention also relates to a method for making a granular adsorbent comprising water-absorbent, gelling, and swelling adsorbent particles on a non-absorbent or minimally absorbent substrate bearing an outer layer (comprising a starch-based, water-absorbent gelling agent that is water-activated and includes a modified starch-based, aqueous polymer binder that moisture-cures as a solid adhesive when the starch is in its glassy state upon drying). Most preferably, the present invention relates to a method for making self-clumping animal litter comprising self-clumping animal litter particles having a water-activated, moisture-cured, water-absorbent, swelling and gelling polymer or biopolymer flocculant attached to a non-clumping substrate particle.

[0147] In one embodiment of the method for producing water-gelling and swelling adsorbent particles, non-absorbent or minimally absorbent substrate particles are wetted with a wetting liquid, preferably water or an aqueous solution, in a wetting step to prepare the outer surface of each substrate particle for attachment of a powdered starch-based water-absorbent gelling agent (comprising a modified starch-water-soluble polymer binder) applied during a coating step. During the coating step, the powdered starch-based water-absorbent gelling agent (comprising a modified starch-water-soluble polymer binder) and the wetted substrate particles are mixed such that an outer layer of the powdered starch-based water-absorbent modified starch-water-soluble polymer binder-containing gelling agent adheres to each of the wetted substrate particles to produce the water-gelling and swelling adsorbent particles of the present invention. Preferably, each of the wetted substrate particles is at least partially, preferably substantially completely, encapsulated by an outer layer of the powdered starch-based water-absorbent modified starch-water-soluble polymer binder-containing gelling agent. In the coating step, at least a portion of the modified starch water-soluble polymer binder in the starch-based water-absorbing gelling powder is solubilized by the wetting liquid, preferably water or an aqueous solution, when it comes into contact with each of the wetted substrate particles, thereby adhering partially wetted and unwetted water-absorbing gelling powder particles to each of the substrate particles. After the coating step is completed, a moisture curing step is carried out, preferably by drying, to remove moisture, thereby curing the solubilized water-soluble polymer binder that has adhered the partially wetted and unwetted water-absorbing gelling powder particles to each of the wetted substrate particles, and adhesively fixing the regions of the water-absorbing gelling powder particles to each of the substrate particles.

[0148] The present invention also relates to a self-clumping, absorbent granular animal litter and a method for producing the same, wherein the self-clumping, absorbent granular animal litter is composed of self-clumping, absorbent animal litter particles including generally rounded, self-clumping, absorbent-coated base animal litter particles. Each of the generally rounded, self-clumping, absorbent-coated base animal litter particles has a coating with a generally rounded outer surface that is at least partially, and preferably substantially completely, filled with minute moisture absorption-promoting protrusions (e.g., spikes) formed during granulation and protruding from the particle outer surface. The outer surface of the coating of each of the generally rounded, self-clumping, absorbent-coated base animal litter particles is also configured to have numerous moisture absorption-promoting microcracks formed on the outer surface during hardening after granulation and drying after hardening after granulation.

[0149] Each of the coated substrate animal litter particles is formed from an inner substrate having the form of a nucleating substrate particle for the animal litter particle, and an outer modified starch water-absorbing clumping agent configured to absorb water or urine, clump, and self-aggregate during use of the animal litter into a removable, scoopable clump of wet animal litter particles, the clump comprising at least a plurality of pairs of the coated substrate animal litter particles, which can be scooped using a perforated animal litter scoop with a handle, has a clump retention of at least 95%, preferably at least 97%, more preferably at least 99%, and has a dry clump crush strength of at least 40 pounds per square inch (PSI), preferably at least 60 PSI, more preferably 80 PSI, and even more preferably 100 PSI. In a preferred embodiment of the self-clumping absorbent coated substrate animal litter particle, each of the coated substrate animal litter particles of the present invention has an outer coating of modified starch water-absorbing clumping agent adhesively self-bonded to the outer surface of the inner substrate particle by internal self-adhesive regions using the clumping method of the present invention described in more detail below. In a preferred embodiment, the self-clumping animal litter of the present invention is a composite animal litter comprising at least 20%, preferably at least 30%, and more preferably at least a majority, i.e., at least 50%, of its weight comprised of self-clumping, absorbent-coated substrate animal litter particles of the present invention, with the remainder being comprised of other types of granular components, such as non-clumping calcium bentonite particles and / or non-clumping organic particles. The animal litter forms a removable, scoopable clump when moistened with water or urine. The clump has a clump retention of at least 95%, preferably at least 97%, and more preferably at least 99%, and a clump compression strength of at least 40 PSI, preferably 60 PSI, more preferably 80 PSI, and especially preferably 100 PSI, when dry. Such self-clumping absorbent granular animal litter (which may be composite animal litter) comprising 20% ​​to 100% of the self-clumping absorbent coated substrate animal litter particles of the present invention advantageously improves upon one or more of the properties and / or characteristics of past and current sodium bentonite animal litter and sodium bentonite-based animal litter, producing rounded coated substrate animal litter particles that are lighter in weight, less expensive to manufacture and transport, easier to handle during transport, easier for users to lift, carry and pour, less dusty, preferably dust-free or dust-inhibiting, and less likely to stick to a cat's paws, thereby advantageously reducing shedding from the animal litter box.

[0150] During the manufacture of substrate-coated litter particles, a coating of modified starch-based water-absorbing flocculant is applied to the outer surface of the substrate particle by flocculation, preferably wet flocculation. In this process, some (but not all) of the modified starch-based water-absorbing flocculant is used to directly adhere to the outer surface of the substrate particle, forming an inner self-adhering region of the coating. The inner self-adhering region of the coating is directly applied to the outer surface of the substrate particle by wetting at least one of the outer surface and the modified starch-based water-absorbing flocculant material applied to the outer surface. This leaves the remaining portion of the modified starch-based water-absorbing flocculant substantially unmodified and unchanged in the outer region of the coating surrounding the inner self-adhering region of the coating, allowing it to absorb water and promote flocculation when wetted with water or urine during use as litter or absorbent material. The inner self-adhering region is formed of the same modified starch-based water-absorbing flocculant as the outer region, but has some of its adhesive properties activated to adhere directly to the outer surface of the substrate particle, thereby providing self-adherence. In addition to at least one component of the modified starch-based water-absorbing flocculant in the coating of each coated substrate having water-absorbing properties, the modified starch-based water-absorbing flocculant has a water-activated adhesive (preferably a moisture-curing water-activated adhesive) as at least one other component of the coating of each coated substrate, which is activated when wetted with an aqueous wetting liquid such as water or urine, and becomes at least tacky, preferably also fluid, to form a fluid adhesive, and can also gel (i.e., thicken) during or after flowing.

[0151] In a preferred embodiment, the modified starch-based water-absorbing flocculant comprises a first adhesive component and a second adhesive component. The first adhesive component is an at least partially water-soluble adhesive capable of one water activation and one water cure, and the second adhesive component is an at least partially water-soluble adhesive capable of water reactivation and water re-hardening. The second adhesive component is preferably capable of water reactivation and water re-hardening multiple times, more preferably at least multiple times (i.e., at least three times). In a preferred embodiment, the first adhesive component is a starch that is at least physically modified during extrusion, i.e., a physically modified starch, preferably a dextrinized starch that can include dextrin, but not necessarily dextrin. In such a preferred embodiment, the second adhesive component is a starch that is modified during extrusion to form a starch pregel or a gelatinized starch with adhesive properties.

[0152] The coating applied to the substrate particle or substrate granule contains both a first adhesive component and a second adhesive component. In a preferred embodiment, the coating applied to the substrate particle or substrate granule contains a first adhesive component, a second adhesive component, and a third water-absorbing component configured to absorb water at room temperature or urine at cat body temperature. In one embodiment, at least one of the first component, the second component, and the third component comprises or consists of a cold-water-soluble starch capable of absorbing water and urine and at least partially solubilized in water at room temperature and urine at cat body temperature. In another embodiment, at least both the first component and the second component comprise or consist of a water-absorbing starch that absorbs water and urine, and a modified starch that at least partially solubilizes in water at room temperature and urine at cat body temperature.

[0153] To produce coated substrate granules, preferably by flocculation, one or both of the modified starch-based water-absorbing flocculant and the outer surface of the substrate particle are wetted with an aqueous wetting liquid, preferably water. This ultimately wets at least a portion of the modified starch-based water-absorbing flocculant and activates some (but not all) of the water-activated adhesive in the modified starch-based water-absorbing flocculant, forming internal self-adhesive regions. In at least one preferred embodiment of the modified starch-based water-absorbing flocculant, at least a portion of the adhesive activated by the aqueous wetting liquid becomes at least somewhat tacky, preferably tacky. This causes at least a portion of the modified starch-based water-absorbing flocculant to adhere to and bond with the outer surface of the substrate particle. In at least another preferred embodiment of the modified starch-based water-absorbing flocculant, at least a portion of the adhesive activated by the aqueous wetting liquid gelates. This causes at least a portion of the modified starch-based water-absorbing flocculant to adhere to and bond with the outer surface of the substrate particle, forming internal self-adhesive regions. In at least a further preferred embodiment, at least a portion of the adhesive activated by the aqueous wetting liquid becomes flowable, preferably forming a flowable adhesive. This causes at least a portion of the modified starch-based water-absorbing flocculant to adhere to and bond with the outer surface of the substrate particle, forming an internal self-adhesive region. In at least one preferred embodiment of the modified starch-based water-absorbing flocculant, at least a portion of the adhesive activated by the aqueous dampening liquid wetting the modified starch-based water-absorbing flocculant becomes tacky, at least a portion gels, and / or at least a portion forms a flowable water-activated adhesive. This causes at least a portion of the modified starch-based water-absorbing flocculant to adhere to and bond with the outer surface of the substrate particle, forming an internal self-adhesive region.

[0154] This stickiness, combined with the rolling action of the substrate particles within the rotating drum, results in the formation of the coated substrate animal litter particles of the present invention, which have numerous raised protrusions (preferably including spikes) across their entire outer surface. These microscopic protrusions (including spikes) have a microscopic size that extends outward from the surface of the coated substrate animal litter particle by a distance of 5 microns or less, preferably 2 microns or less, and more preferably about 1 micron (1 micron ± 0.25 microns) or less. Preferably, these microscopic protrusions (including spikes) are nanoscale or nano-sized, extending no more than 1 micron from the outer surface. This rolling action, as occurs within the rotating drum, also causes the coated substrate animal litter particles of the present invention to be rounded, substantially round, thereby minimizing the likelihood of being picked up by a cat's paws during use and thereby minimizing tracking. These protrusions (including spikes) are so small as to be microscopic in size that they advantageously promote absorption by spreading water or urine that wets the protrusions (including spikes) more rapidly along substantially the entire outer surface of the coated substrate animal litter particle by wicking or capillary action, while at the same time maintaining the overall rounded configuration or shape of the coated substrate animal litter particle which minimizes tracking.

[0155] The spike-containing protrusions are then cured, substantially hardening them and forming absorption-enhancing microcracks on their outer surface. These microcracks continue to form and propagate after curing, during drying, and even during storage of the coated substrate litter particles after packaging and prior to use. The lengths of these microcracks can range from nanoscale or nano-sized (i.e., less than 1 micron) to several microns thick in the flocculant coating at least partially coating the substrate particle or substrate granule. In preferred embodiments, the sizes of these microcracks range from a base thickness of about 1 micron or less and a length of about 50 microns (50 microns ± 5 microns) or less to a base thickness of about 5 nanometers (5 nanometers ± 3 nanometers) or so and a length of about 5 nanometers, e.g., a base thickness of between about 5 nanometers and about 1 micron and a length of between about 5 nanometers and about 50 microns. These microcracks further enhance absorption through capillary or wicking action, opening up portions of the outer coating of the coated substrate litter particle upon wetting with water or urine, thereby rapidly increasing the amount of surface area in contact with the water or urine that can absorb the water or urine. The protrusions, including spikes, cooperate with the microcracks to not only enhance absorption by facilitating absorption, but also enhance cohesion by facilitating the flow of flowable adhesive from each wetted coated substrate litter particle.

[0156] In preferred methods and embodiments, at least a portion of the adhesive of the first adhesive component of the modified starch-based water-absorbing flocculant is activated and hardened to aid in bonding the self-adhesive regions to the outer surface of the substrate particle, and at least a portion of the adhesive of the second adhesive component is also activated and hardened to further aid in bonding the self-adhesive regions to the outer surface of the substrate particle.

[0157] A preferred self-clumping animal litter of the present invention comprises substrate animal litter particles coated with a self-clumping absorbent, each coated substrate animal litter particle containing about 5% to about 35%, preferably about 5% to 50%, more preferably about 5% to 85%, by particle weight, of a modified starch-based water-absorbent clumping agent, and the coated substrate self-clumping animal litter particles of the present invention absorb at least two, preferably at least three, more preferably at least four, and most preferably at least six times their coating weight in water, e.g., preferably room temperature water at 68°-72° F. or cat urine at about 100° F. to about 104° F. The wetted coated substrate animal litter particles clump together with adjacent water- or urine-wetted animal litter particles to form self-clumping clumps that can be scooped away from other non-wetted or non-contaminated animal litter particles using a perforated animal litter scoop with a handle. The self-cohering, absorbent-coated substrate animal litter particles of the present invention absorb at least one coating weight of water, preferably room temperature water, or urine, preferably cat urine, within one minute. Within 60 seconds, preferably within 30 seconds, and more preferably within 20 seconds, of being wetted with water or urine, they cohere with other wetted animal litter particles to form clumps consisting of at least a plurality of pairs of the coated substrate animal litter particles. In such a preferred embodiment, each coated substrate animal litter particle contains about 5% to about 35%, preferably about 5% to 50%, and more preferably about 5% to 85% of the modified starch-based water-absorbent flocculant by particle weight. In one preferred embodiment and manufacturing method of the coated substrate animal litter particles of the present invention, the modified starch-based water-absorbent flocculant is applied to each substrate particle until the coating weight of the modified starch-based water-absorbent flocculant is 5% to 35%, preferably about 5% to 50%, more preferably about 5% to 85%, based on the weight of each finished coated substrate animal litter particle, so that each finished coated substrate animal litter particle contains 5% to 35%, preferably about 5% to 50%, more preferably about 5% to 85% of the modified starch-based water-absorbent flocculant based on the particle weight.

[0158] The self-clumping, absorbent-coated substrate animal litter particles in the preferred self-clumping animal litter of the present invention have a particle coating weight of the external modified starch-based water-absorbent flocculant on the internal substrate particle of about 5% to about 35%, preferably about 5% to 50%, and more preferably about 5% to 85% by particle weight. This particle coating weight is sufficient to form a coating on the self-clumping, coated substrate animal litter particles such that each of the self-clumping, coated substrate animal litter particles absorbs at least one time the coating weight of the coated substrate animal litter particle and swells in volume by at least 25% (preferably at least 35%, more preferably at least 50%, and most preferably at least 80%) relative to the volume of the animal litter particle before wetting. In a preferred embodiment, the self-clumping, absorbent-coated substrate animal litter particles of the present invention each have a particle coating weight of the external modified starch-based water-absorbent flocculant on the internal substrate particle of about 5% to about 35%, preferably about 5% to 50%, and more preferably about 5% to 85% by particle weight. This is a particle coating weight sufficient to form a coating on the self-cohering coated substrate animal litter particles, each of which absorbs at least twice the coating weight of the coated substrate animal litter particles, and which swells in volume upon absorption of water or urine by at least 25% (preferably at least 35%, more preferably at least 50%, and most preferably at least 80%) compared to the volume of the animal litter particles before wetting.

[0159] Each animal litter particle of the self-cohering absorbent coated substrate of the present invention is preferably a swelling and gelling self-cohering absorbent coated substrate animal litter particle, wherein the outer region of the modified starch-based water-absorbing flocculant outer coating swells upon absorption of water or urine, preferably room temperature water or cat body temperature urine, wetting the particle and substantially simultaneously forming a gel on and along the outer surface of the coated substrate animal litter particle and in a depth direction below the surface, said gel being preferably tacky when wet and may, or preferably contains, a water-activated moisture-curing adhesive which promotes cohesion with other contacting animal litter particles through its tackiness or adhesive properties and adhesively bonds the contacting particles into the aggregate through moisture-curing caused by evaporation of water from the aggregate as the aggregate dries. In one embodiment of the coated substrate litter particles of the present invention, the modified starch-based water-absorbent flocculant outer coating of each wetted coated substrate litter particle is at least partially solubilized in water or urine, preferably in water at room temperature or urine at cat body temperature, to form a flowable, water-activated, moisture-curing adhesive whose viscosity remains sufficiently low, preferably 15,000 centipoise or less, more preferably 10,000 centipoise or less, and even more preferably about 5,000 centipoise or less, for a sufficiently long period of time, preferably at least 1 second, more preferably at least 4 seconds, after wetting. The viscosity of the modified starch-based water-absorbent clumping agent is maintained at or below 1 / 2 centipoise, thereby allowing it to flow from the water- or urine-wetted portion of the litter particles along and between contacting and adjacent particles, whereupon it increases in viscosity and reforms into a viscous, semi-solid gel having a viscosity of at least about 30,000 centipoise, preferably at least 50,000 centipoise, and more preferably at least 80,000 centipoise within 20 seconds after wetting, preferably within 10 seconds after wetting, and more preferably within 5 seconds after wetting. As the viscosity of the flowable adhesive increases, the adhesive gels (but maintains at least some tackiness), and the moisture in the formed mass hardens during drying, hardening into a glassy material that has a glassy state at room temperature, thereby binding the agglomerated particles together.These bonds include at least one of hydrogen bonds and covalent bonds, preferably covalent bonds. In any event, the resulting mass formed hardens to have a mass retention of at least 95%, preferably at least 97%, more preferably at least 99%, and a mass crush strength of at least 40 PSI, preferably at least 60 PSI, more preferably 80 PSI, and even more preferably at least 100 PSI when the mass is dried to a moisture content of about 12% (12%±1.5%) by mass weight.

[0160] Preferably, at least a portion of the modified starch-based water-absorbing flocculant in each animal litter particle of the present invention is at least partially solubilized by room temperature water or cat urine that contacts the particle, forming a flowable adhesive. The flowable adhesive is preferably a water-activated flowable adhesive and is moisture-curable, flowing outward from the wetted particle and between and around adjacent contacting animal litter particles. The flowable adhesive initially has a flowable viscosity higher than that of water, and increases in viscosity over time to solidify into an adhesive gel. This gel initially adheres contacting pellets to each other through surface tension, capillary action, liquid adhesive forces, and / or intermolecular forces (e.g., van der Waals forces), and then dries and moisture-cures to form a more viscous, cohesive gel that more firmly adheres contacting pellets to each other, preferably through at least hydrogen bonding and / or preferably at least some covalent bonding. The initially flowable adhesive transitions over time into an adhesive gel, then a cohesive gel, and as the moisture cure proceeds until the moisture content dries to less than 15% by weight, preferably 12% or less, to form a substantially fully cured solid adhesive, which becomes a glassy substance that adhesively bonds contacting animal litter particles by at least hydrogen bonds, i.e., hydrogen bonding, and / or preferably covalent bonds, i.e., covalent bonds. At least pairs of animal litter particles of the present invention, i.e., at least three animal litter particles, are wetted with water or urine and adhesively bonded by the solid adhesive formed from the initially flowable adhesive by hydrogen bonds, covalent bonds, or a combination of hydrogen and covalent bonds, and substantially fully moisture cure to form a rock-hard mass having a mass moisture content of about 12% by mass, the mass having a mass compressive strength of at least 40 PSI, preferably at least 60 PSI, more preferably at least 80 PSI, and even more preferably at least 100 PSI, and a mass retention of at least 95%, preferably at least 97%, and more preferably at least about 99%.

[0161] In a preferred embodiment of the modified starch-based water-absorbing flocculant in each coated substrate animal litter particle of the animal litter of the present invention, the modified starch-based water-absorbing flocculant is composed of the following (1) and (2): (1) a water-swellable modified starch (preferably a cold-water-swellable modified starch) that has water absorption properties, swells upon absorbing water, and absorbs at least 4.5 times, preferably at least 6 times, the weight of the animal litter particle in water at room temperature or urine at cat body temperature, and (2) a water-soluble modified starch binder (preferably a cold-water-soluble modified starch binder) that is at least partially cold-water soluble in water at room temperature. , which is at least partially soluble in urine at body temperature of a cat, and upon at least partial solubilization forms a fluid that flows from the moistened animal litter particles, and upon moisture setting increases in viscosity to form a tacky adhesive gel that bonds the particles together by at least one of liquid adhesion, hydrogen bonding, and / or other intermolecular forces, and upon further moisture setting increases in viscosity to form a cohesive gel that bonds the particles together by at least one of hydrogen bonding and covalent bonding, and upon substantially complete moisture setting to a moisture content of less than 15%, preferably 12% by weight or less, becomes a substantially solid adhesive that is a glassy material having a glassy material state. The water-swellable modified starch (preferably cold water-swellable modified starch) in the modified starch-based water-absorbent flocculant in each animal litter particle is composed of native starch. The native starch may be derived from one or more grains, such as corn, rice, wheat, rye, barley, millet, triticale, oat, fonio, and sorghum, and / or one or more legumes, such as beans, soybeans, peas, chickpeas, peanuts, lentils, lupin, mesquite, carob, tamarind, alfalfa, and / or clover. The native starch is preferably physically modified to break down the starch granules and / or reduce the molecular weight of one or both of the amylose and / or amylopectin molecules of the native starch. Starch modification methods or processes include, for example, extrusion, in which the native starch is processed in a starch modification machine, such as an extruder, preferably a single-screw extruder.In the extruder, the native starch is subjected to an ultra-high extrusion pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI at an extrusion temperature of at least 100° F., thereby modifying the native starch into a water-swellable, water-absorbing modified starch, preferably a cold-water-swellable, cold-water-absorbing modified starch. The at least partially soluble, preferably at least partially cold-water soluble, modified starch binder in each animal litter particle of the modified starch-based water-absorbing flocculant is also composed of native starch. The native starch may be derived from one or more grains, such as corn, rice, wheat, rye, barley, millet, triticale, oat, fonio, and sorghum, and / or one or more legumes, such as beans, soybeans, peas, chickpeas, peanuts, lentils, lupin, mesquite, carob, tamarind, alfalfa, and / or clover. The native starch is preferably physically modified to break down the starch granules and / or reduce the molecular weight of one or both of the amylose and / or amylopectin molecules of the starch. Starch modification methods or processes include, for example, extrusion, in which the native starch is processed in a starch modification machine, such as an extruder, preferably a single-screw extruder. By subjecting the native starch to an ultra-high extrusion pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI in an extruder at an extrusion temperature of at least 100° Fahrenheit, the native starch is converted into a modified starch, which is an at least partially water soluble modified starch, preferably at least partially cold water soluble modified starch, and which is comprised of a water-activated moisture-curing binder that is activated with room temperature water and / or cat urine to form a flowable adhesive having the properties and characteristics described hereinabove.

[0162] In the production of coated substrate litter particles of the present invention, a pulverized form of the modified starch-based water-absorbing flocculant is used, preferably a form produced by pulverization, i.e., grinding. This form has a relatively small particle size, even smaller than the smallest substrate particle, and preferably has a particle size in the size range of flour or powder. For example, it is sized to pass through a 40-mesh screen, preferably a 60-mesh screen, and more preferably a 40-60 mesh screen, and be retained on a smaller mesh screen, such as an 80-mesh screen. In this process, extruded pellets produced using the extrusion method described above and / or methods disclosed elsewhere herein are ground into a powder or flour having the mesh size described above in this paragraph using a grinder.

[0163] In one preferred embodiment and practice of the method for producing coated substrate litter granules, freshly extruded pellets produced according to at least one modified starch water-absorbing flocculant extrusion method disclosed herein can be used as a modified starch water-absorbing flocculant used to agglomerate substrate granules or particles to produce coated substrate litter in accordance with the present invention. In one such preferred embodiment and practice of the method, the freshly extruded pellets are mixed with water to form a slurry, which can be applied onto the substrate granules or particles in a manner described in more detail below. In another such preferred embodiment and practice of the method, water is applied onto the substrate granules or substrate pellets in an agglomerator or coater, preferably a rotary or tumbling agglomerator or coater, after which the freshly extruded pellets are mixed and the substrate granules or particles can be agglomerated into coated substrate litter granules of the present invention in a manner described in more detail below.

[0164] In other preferred embodiments and method practices, the as-extruded pellets are broken down into smaller particles of the modified starch-based water-absorbing flocculant using a high-speed, high-shear mixer, such as a batch, in-line, or granulator-type high-speed, high-shear mixer. In one such preferred embodiment and method practice, the as-extruded pellets are broken down with water in such a high-shear mixer to form a substantially homogeneous slurry of smaller pellet particles of the modified starch-based water-absorbing flocculant, which is then coated as a slurry onto agitated, preferably tumbled, substrate granules or particles in a rotary granulator or coater in a manner described in more detail below.

[0165] In yet another preferred embodiment and method practice, the modified starch-based water-absorbing flocculant is formed from a combination of a powder or flour having the mesh size defined above and extruded pellets produced according to at least one of the modified starch-based water-absorbing flocculant extrusion methods disclosed herein. In one such preferred embodiment and method practice, the mixture of the powdered or floured modified starch-based water-absorbing flocculant and extruded pellets is homogenized into a water-containing slurry using a high-speed, high-shear mixer in the manner described above.

[0166] Optionally, the modified starch-based water-absorbing flocculant can be in the form of grain-based animal litter particles classified as too small for use in any of the extrusion-type animal litter disclosed in one or more of commonly owned U.S. Patent Nos. 9,491,926, 10,028,481, 10,098,317, 10,882,238, 11,013,211, and / or 11,083,168 (each of which is expressly incorporated by reference in its entirety). Optionally, particles of modified starch-based water-absorbing flocculant obtained from rejected particles of extrusion-type animal litter made in accordance with one or more of the foregoing patents can be further reduced in size by, for example, grinding (e.g., hammer mill grinding), use of other particle size reduction machinery, and / or use of other particle size reduction or particle comminution methods, such as the particle size reduction systems, apparatus, and methods disclosed in commonly owned U.S. Patent No. 11,013,211 (which is expressly incorporated by reference in its entirety).

[0167] In more detail, in the method for manufacturing the self-clumping absorbent animal litter grains of the preferred animal litter of the present invention, these powdered or powdery relatively small modified starch-based water-absorbent flocculant particles are wetted with an aqueous wetting liquid such as water, thereby activating some (if not all) of the at least partially water-soluble binder in at least some of the modified starch-based water-absorbent flocculant particles, and some (if not all) of the modified starch-based water-absorbent flocculant particles adhere to the outer surface of each base particle in a wet state, and then, when substantially completely moisture-cured and dried, they are adhesively bonded to the outer surface of each base particle, forming an internal adhesion region between the internal base particle and the external modified starch-based water-absorbent flocculant region of each animal litter grain. By wetting substantially all of the modified starch-based water-absorbent flocculant particles with an aqueous wetting solution, some (if not all) of the at least partially water-soluble binder of the remaining unattached, wetted modified starch-based water-absorbent flocculant particles is activated, and some (if not all) of the modified starch-based water-absorbent flocculant particles that contact the internal attachment region adhere to the internal attachment region in a wet state, and then, upon substantially complete moisture curing and drying, become adhesively bonded thereto, forming one or more additional modified starch-based water-absorbent flocculant regions in each animal litter grain produced.

[0168] In one preferred method of making animal litter particles, the modified starch-based water-absorbent flocculant particles are wetted by mixing dry, powder-sized or flour-sized modified starch-based water-absorbent flocculant particles with an aqueous wetting liquid (preferably water) to form a slurry and applying the slurry to the substrate particles, preferably while substantially simultaneously mixing the slurry with the substrate particles by tumbling, stirring, or other methods, such as using a mixer, coater, blender, or other mixing device or arrangement, thereby forming an inner adhesive region on the outer surface of each substrate particle before forming an outer region of the modified starch-based water-absorbent flocculant thereon. In another preferred method for manufacturing animal litter particles, the modified starch-based water-absorbing flocculant particles are wetted in an indirect manner by wetting the base particles with an aqueous liquid (preferably water), and then applying dry particles of the modified starch-based water-absorbing flocculant in powder or pulverulent size to the wetted base particles, preferably while rolling, stirring, or otherwise mixing the wetted base particles and the applied modified starch-based water-absorbing flocculant particles, thereby wetting the modified starch-based water-absorbing flocculant particles that come into contact with the moisture on the surface of the base particles, thereby forming internal adhesive regions on the outer surface of each base particle. Preferably, one or more rewetting and application cycles are performed, with each rewetting cycle applying additional aqueous wetting liquid onto the at least partially coated substrate particles substantially simultaneously with or substantially immediately after another application cycle applying additional powder-sized or pulverulent-sized modified starch-based water-absorbing flocculant particles onto the wetted, at least partially coated substrate particles, all of which are performed while tumbling, stirring or otherwise mixing the wetted, at least partially coated substrate particles until one or more additional outer regions are added onto the inner adhesive region of each formed animal litter particle.

[0169] The at least partially formed animal litter particles are coated with an aqueous wetting liquid, preferably water, until a desired thickness of coating of modified starch-based water-absorbent flocculant particles accumulates on each substrate particle to form a finished animal litter particle. Wetting the modified starch-based water-absorbent flocculant particles coated on each substrate particle causes the modified starch-based water-absorbent flocculant particles in an outer region surrounding the inner substrate particle of each animal litter particle to agglomerate into a region of amorphous, substantially homogeneous modified starch-based water-absorbent flocculant material adhesively bonded to the inner substrate particle upon substantially complete moisture cure. In the present invention, preferred self-cohering absorbent particles produced by the manufacturing method disclosed herein have an outer region of the modified starch-based water-absorbent flocculant having a thickness of 1 mm or less, preferably 0.8 mm or less, more preferably about 0.5 mm or less, and even more preferably about 0.3 mm or less, and at least 50%, preferably at least 80%, more preferably at least 95%, and even more preferably substantially the entire outer surface of each substrate particle of each animal litter particle is coated with the modified starch-based water-absorbent flocculant material. In the present invention, the preferred self-cohering absorbent particles produced by the manufacturing method disclosed herein have an outer modified starch-based water-absorbent flocculant region having a thickness of between 20 microns (i.e., 0.02 mm) and 1000 microns (i.e., 1 mm), preferably between 20 microns (i.e., 0.02 mm) and 800 microns (i.e., 0.8 mm), more preferably between 20 microns (i.e., 0.02 mm) and 500 microns (i.e., 0.5 mm), and even more preferably between 20 microns (i.e., 0.02 mm) and 300 microns (i.e., 0.3 mm), and at least 50%, preferably at least 80%, more preferably at least 95%, and even more preferably substantially the entire outer surface of each substrate particle of each animal litter particle is coated with said modified starch-based water-absorbent flocculant material.

[0170] In a preferred embodiment, the rounded coated substrate animal litter particles are advantageously sized to minimize removal of the animal litter from the animal litter box during use and operation of the coated substrate animal litter of the present invention. The roundness of the coated substrate animal litter particles is advantageous in preventing the coated substrate animal litter particles from becoming trapped between a cat's paws during use of the animal litter box. Furthermore, the coated substrate animal litter particles are sized to help prevent removal of the animal litter box by a cat during use of the animal litter box. In a preferred embodiment, the coated substrate animal litter particles should have a size larger than a 25-mesh sieve, i.e., larger than 25 mesh, and not larger than a 10-mesh sieve, i.e., not larger than 10 mesh. At least 80% of the coated substrate animal litter particles should be smaller than 10 mesh and larger than 25 mesh (10 / 25). For example, in one embodiment, between 60% and 95%, preferably about 80% (80%±15%) of the particles pass through a 12 mesh sieve but larger than a 25 mesh sieve. The remaining coated substrate animal litter particles are larger than 10 mesh. Rounded coated substrate animal litter particles having a particle size distribution between 12 mesh and 20 mesh (12 / 20) provide an optimal feel against a cat's paws.

[0171] Thus, in one preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have protrusions (including spikes), and have a particle size distribution between 12 mesh and 20 mesh (12 / 20), thereby forming a preferred embodiment of a low-tracking litter that minimizes tracking carried out by cats from the litter box in accordance with the present invention. In another preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have protrusions (including spikes), and have a particle size distribution between 10 mesh and 25 mesh (10 / 25), thereby forming another preferred embodiment of a low-tracking litter that minimizes tracking carried out by cats from the litter box in accordance with the present invention.

[0172] In a method for applying a modified starch-based water-absorbing flocculant to substrate particles to produce the self-cohering, absorbent-coated substrate granules of the present invention, a predetermined amount (e.g., a predetermined weight or mass) of substrate particles, depending on the type and size of the substrate particles, is applied with a slurry comprising a predetermined amount (e.g., a predetermined weight or mass) of particles of the modified starch-based water-absorbing flocculant slurried in water selected based on the size or size range and predetermined amount of the substrate particles to be coated and processed into the self-cohering absorbent granules of the present invention. In a preferred method for producing the self-cohering absorbent granules of the present invention, a slurry consisting of water and particles of the modified starch-based water-absorbing flocculant is used, and the slurry is applied to the substrate granules or substrate particles tumbling within the rotating barrel or drum of a drum mixer, cement mixer, drum coater, or similar equipment using one or more spaced spray heads, nozzles, misters, or other types of slurry applicators or distributors configured or operated to controllably discharge the slurry onto the substrate particles within the rotating mixer or coater barrel in producing the self-cohering absorbent granules of the present invention. In another preferred method for applying the modified starch-based water-absorbing flocculant to a substrate particle or substrate granule to produce the self-cohering, absorbent-coated substrate granules of the present invention, the substrate particle is wetted with an aqueous wetting liquid, such as water, and then coated with dry particles of the modified starch-based water-absorbing flocculant. This is done first with the substrate particle, and then with the substrate particle, modified starch-based water-absorbing flocculant particles, and aqueous wetting liquid (preferably water), preferably in the rotating barrel of a drum mixer, cement mixer, drum coater, or similar device, while tumbling or stirring to mix everything together. The wetting of the at least partially coated substrate particle with the aqueous wetting liquid, preferably water, and the coating of the modified starch-based water-absorbing flocculant particles are repeated one or more times as necessary until each substrate particle achieves the desired granular coating weight (e.g., degree of coating) and / or outer layer thickness of the modified starch-based water-absorbing flocculant, producing the finished self-cohering absorbent granules of the present invention. The at least partially moistened finished self-clumping absorbent animal litter particles are then subjected to a moisture curing step, which is preferably a moisture removal step.This moisture curing step is carried out by drying each particle, such as by convection drying with flowing air (preferably turbulent air) directed at the animal litter particles, drying in a heated oven using one or more of radiant heat, convection drying with heated air, or other types of heat drying methods, until the moisture content of each particle is 12% or less, preferably greater than 10%, and more preferably 8% or less, by weight, until moisture curing is complete or substantially complete in each animal litter particle.

[0173] When a slurry is used in producing the self-clumping, absorbent-coated substrate animal litter granules of the present invention, the slurry is a slurry of water and relatively fine modified starch-based water-absorbent flocculant particles, preferably powder or dust-sized, mixed with water until a substantially uniform mixture or slurry is formed. As described above, mixing can be performed using a high-speed, high-shear mixer. In a preferred slurry, when water is used as the aqueous wetting liquid, the ratio of the amount of modified starch-based water-absorbent flocculant to water is about 1:1 ± 10% by weight. The slurry is applied to the substrate particles while the substrate particles are being stirred, tumbled, or otherwise mixed in a rotating barrel, drum, or chamber of a mixer, coater, or blender, thereby forming regions of the modified starch-based water-absorbent flocculant on each of the substrate particles until the desired area thickness or desired granule coating weight of the modified starch-based water-absorbent flocculant on the substrate particles is reached. Tumbling in a rotating barrel or drum-type mixer or coater is preferred. This is to ensure that the above-described method also produces rounded coated substrate animal litter granules to minimize tracking from the cat litter box. The water in the slurry activates at least some, but not all, of the water-soluble modified starch binder (preferably a cold-water-soluble modified starch binder) contained in the modified starch-based water-absorbent flocculant particles in the slurry. This activation creates a sticky gel and flowable adhesive that adheres the modified starch-based water-absorbent flocculant particles to the substrate particles to which the slurry is applied. This stickiness aids in the formation of protrusions (including spikes) on the outer surface of the coated substrate particles, thereby improving the amount and speed of water absorption during use of the animal litter. The slurry is applied onto the substrate particles while they are being stirred, rolled, or mixed, which not only promotes more uniform adhesion of the modified starch-based water-absorbent flocculant particles to each substrate particle, but also helps prevent the at least partially coated substrate particles from clumping together during the production of the slurry-based self-clumping absorbent animal litter granules.The slurry is applied while the substrate particles are being tumbled, stirred, and / or mixed until a desired thickness or granule coverage weight of the modified starch-based water-absorbent flocculant particles on the substrate particles is reached. In a preferred method embodiment, the initial application of the slurry onto the substrate particles causes each substrate particle to act as a nucleator for the animal litter granules, with the modified starch-based water-absorbent flocculant in the slurry adhering to the outer surface of each substrate particle to form an internal adherent region, whose aqueous wettability promotes more rapid adhesion of another external region of the modified starch-based water-absorbent flocculant.

[0174] In a preferred method of slurry application, a predetermined amount (e.g., a predetermined weight or mass) of modified starch-based water-absorbent flocculant particles is applied to a predetermined amount (e.g., a predetermined weight or mass) of base particles, depending on the type and size of the base particles. In this case, the predetermined amount of modified starch-based water-absorbent flocculant is applied as a slurry in water selected based on the size or size range and the predetermined amount of base particles to be coated into the self-cohering absorbent granules of the present invention. In a preferred method of producing the self-clumping, absorbent animal litter granules of the present invention using a slurry comprising water and particles of a modified starch-based water-absorbing flocculant, the slurry is applied to substrate particles tumbling within the rotating barrel or drum of a drum mixer, cement mixer, drum coater, or similar equipment using one or more spaced spray heads, nozzles, misters, or other types of slurry applicators or distributors configured or operated to controllably discharge the slurry onto the substrate particles within the rotating mixer or coater barrel in producing the self-clumping, absorbent animal litter granules of the present invention.

[0175] In a preferred embodiment of the slurry application method, the amount of slurry applied to the substrate particles, and preferably the application speed, such as volumetric flow rate or metering, is varied in real time during slurry application to (a) control the particle coating weight and / or thickness of the modified starch-based water-absorbing flocculant that forms an outer layer around each substrate particle, and (b) prevent the substrate particles, at least partially coated with a layer of modified starch-based water-absorbing flocculant, from agglomerating during tumbling, stirring, or other mixing. The ratio of modified starch-based water-absorbing flocculant to water can also be controlled or varied in real time during application of the slurry to the substrate particles, for example, within a range of ±25%, such as up to +25% from a 1:1 basis or up to -25% from a 1:1 basis, to control: (a) the activation of the at least partially soluble modified starch binder by water; (b) the rate of particle coating weight of modified starch-based water-absorbing flocculant attached to and / or coating each substrate particle; (c) the particle coating weight of modified starch-based water-absorbing flocculant attached to and / or coating each substrate particle; (d) the thickness of the outer layer of modified starch-based water-absorbing flocculant attached to and / or coating each substrate particle during production of the animal litter particles of the present invention; (e) the viscosity of the slurry; and / or (f) the prevention of agglomeration of partially coated or partially formed animal litter particles during tumbling, stirring, or other mixing.

[0176] In one preferred embodiment of the method, the formed slurry can be, and preferably is, in the following form: (a) a suspension obtained by mixing an aqueous wetting liquid (preferably water) with dry particles of the modified starch-based water-absorbing flocculant using a high-shear mixer, other suitable type of blender, or other suitable type of mixer until a suspension is formed, or (b) an emulsion obtained by mixing an aqueous wetting liquid (preferably water) with dry particles of the modified starch-based water-absorbing flocculant using a high-shear mixer, other suitable type of blender, or other suitable type of mixer until an emulsion is formed. When using such a slurry in the form of a suspension, the suspension may contain one or more surfactants (including one or more super surfactants) to promote the suspension of the powder-sized or flour-sized dry particles of the modified starch-based water-absorbing flocculant in the aqueous wetting liquid (preferably water) when all components of the suspension are mixed in the slurry-suspension mixing step. When such a slurry in the form of an emulsion is used, the emulsion may contain (1) one or more surfactants (including one or more supersurfactants) and / or (2) one or more emulsifiers to emulsify or promote emulsification of all powder- or flour-sized particles of the modified starch-based water-absorbent flocculant in the aqueous wetting liquid (preferably water) when all components of the emulsion are mixed in the slurry-emulsion mixing step. During application of the slurry to the substrate particles, the ratio of the modified starch-based water-absorbent flocculant to water in the slurry suspension or emulsion can be controlled, preferably in real time, to control at least one of the viscosity, the rate of build-up of the coating thickness of the modified starch-based water-absorbent flocculant, the coating thickness of the modified starch-based water-absorbent flocculant, and / or the granular coating weight of the modified starch-based water-absorbent flocculant on each substrate particle.Such a slurry suspension or emulsion is preferably a substantially homogeneous suspension or emulsion of modified starch-based water-absorbing flocculant particles suspended or emulsified in water, and is applied to the substrate particles while the substrate particles are being stirred, tumbled, or otherwise mixed, thereby forming a layer of modified starch-based water-absorbing flocculant on the outer surface of each substrate particle until a desired areal thickness or desired granular coating weight is reached. The water in the slurry activates at least a portion (but not all) of the water-soluble modified starch binder (preferably a cold-water-soluble modified starch binder) in the modified starch-based water-absorbing flocculant particles in the slurry to form a sticky gel and flowable adhesive. The resulting sticky gel and flowable adhesive adheres the modified starch-based water-absorbing flocculant in the suspension or emulsion to the substrate particles to which the slurry is applied. The slurry suspension or emulsion is applied to the substrate particles while the substrate particles are being stirred, tumbled, or otherwise mixed. This not only promotes uniform adhesion of the modified starch-based water-absorbing flocculant to each substrate particle, but also helps prevent clumping of the at least partially coated substrate particles / partially finished animal litter granules while they are being tumbled, stirred or otherwise mixed during application of the slurry suspension or emulsion in the manufacture of slurry-based self-clumping absorbent animal litter granules.

[0177] The slurry, slurry suspension, or slurry emulsion is applied to the substrate particles while the substrate particles are being tumbled, stirred, and / or mixed until a desired thickness or granular coating weight of the modified starch-based water-absorbent flocculant particles is achieved, thereby producing the self-cohesive, absorbent animal litter particles of the present invention. The moisture content of the finished animal litter particles is then reduced to moisture-cure the at least partially soluble modified starch binder, which was activated during the slurry application and formed a flowable adhesive and gel to adhere one or more outer regions of the modified starch-based water-absorbent flocculant to each substrate particle. The moisture content of the finished animal litter particles is reduced to a moisture content of 12% or less, preferably 10% or less, and more preferably about 8% or less, by weight of the finished animal litter particle, to substantially completely moisture-cure the water-activated at least partially soluble modified starch binder, flowable adhesive, and gel into a solid adhesive in a glassy state that adhesively bonds the outer regions of the modified starch-based water-absorbent flocculant to each internal substrate particle. In at least a portion of the exterior region of the modified starch-based water-absorbent flocculant in each of the finished self-clumping absorbent animal litter particles of the present invention, the at least partially soluble modified starch binder remains in an unactivated and / or unhardened state, thereby allowing it to be wetted with moisture, such as room temperature water or cat urine at body temperature, and at least partially solubilizes as a flowable adhesive that flows out of the wetted animal litter particle and between the contacting animal litter particle and its adjacent animal litter particle, increasing in viscosity during initial moisture cure to form an adhesive or sticky gel, changing into a binding gel as further moisture cure proceeds, and finally, upon completion of moisture cure by evaporation of the water, becoming a solid adhesive in a glassy starch state that bonds the contacting animal litter particle and adjacent animal litter particle into a substantially rock-hard mass.Moisture curing of the mass is preferably completed when the moisture content of the mass is about 12% or less by mass weight, due to evaporation of water from the mass, such as by air drying the mass in a cat litter box, and produces a substantially rock hard mass when fully moisture cured, having a mass retention of at least 95%, preferably at least 97%, more preferably at least 99%, and / or a mass cross-section strength of at least 40 PSI, preferably 60 PSI, more preferably 80 PSI, and even more preferably 100 PSI.

[0178] The substrate particles may be organic, inorganic, smooth, rough, round, cylindrical, irregularly shaped, porous, non-porous, absorbent, impermeable, smooth, and / or rough, and preferably comprise a material that is non-cohesive, i.e., the particles do not clump together when wetted with water. Preferred substrate materials include nut shells or hulls, wood, paper, sand, perlite, and bentonite, which are crushed, ground, milled, or otherwise comminuted to form relatively small substrate particles, which are then at least partially coated with a modified starch water-absorbing clumping agent, preferably in the form of a starch-based water-absorbing clumping promoter, to form the self-clumping animal litter particles of the present invention. The animal litter particles have an outer region of the modified starch water-absorbing clumping agent at least partially coating, and preferably substantially completely surrounding, each of the substrate particles. The modified starch water-absorbing flocculant is preferably in the form of a starch-based water-absorbing and clumping-promoting material, more preferably a swelling and gelling material consisting of modified starch formed by starch modification, preferably by extrusion, more preferably by ultra-high pressure extrusion using a single-screw extruder, so as to rapidly swell, absorb water, and gel, and preferably also contains at least a portion of the original native or unmodified starch modified into an at least partially water-soluble binder that is at least partially solubilized and flows when wetted with water to form a flowable adhesive that adheres the swelling and gelling material to the substrate particles during the manufacture of litter particles. The preferred modified starch water-absorbing flocculant is preferably in the form of a starch-based water-absorbing and clumping-promoting material, more preferably a starch-based absorbent, swellable biopolymer gelling agent, such as a gelling biopolymer or biopolymer that gels, preferably forms a gel, when wetted, and is composed of a cold-water soluble extrusion-modified starch binder and a cold-water swellable, extrusion-modified absorbent starch. The cold water swelling, extruded, modified absorbent starch preferably is or comprises a cold water swelling, extruded, modified absorbent starch that has been milled or otherwise reduced in particle size to a powder or flour form that coats the substrate particles when wet.Optionally, such modified starch water-absorbent flocculant powder or dust particles are rejected or unused pellets or particles of extruded grain animal litter classified as too small for use in one or more animal litters as disclosed in one or more of commonly owned U.S. Patent Nos. 9,491,926, 10,028,481, 10,098,317, 10,882,238, 11,013,211, and / or 11,083,168, the disclosures of each of which are expressly incorporated herein by reference. The resulting animal litter particles form the removable clumping animal litter of the present invention, each particle having an outer self-cohesive, water-absorbing region surrounding an inner substrate particle, said outer region rapidly absorbing and swelling upon contact with water, at least a portion of said outer region at least partially solubilizing and forming a flowable adhesive therefrom that flows along and between contacting and adjacent animal litter particles, and gelling as the wetted animal litter particles clump into a scoopable mass from the animal litter.

[0179] In a method of making the self-cohesive coated substrate litter particles of the present invention, a desired or predetermined amount of substrate particles having particle sizes within a desired particle size range or particle size distribution is (a) (1) wetted with water while stirring, and (2) mixed with a modified starch water-absorbing flocculant, preferably in the form of a starch-based water-absorbing flocculating powder, and stirring is continued while the water wets the exterior surfaces of the substrate particles, whereby (i) some, but not all, of the water-soluble binder is at least partially solubilized to form a flowable adhesive and the starch-based water-absorbing flocculating powder adheres to the surfaces of the substrate particles. and (ii) at least some, but not all, of at least some, preferably at least some pairs, i.e., at least three different types of modified starches in the starch-based, water-absorbent, cohesion-promoting powder gelatinize, causing the wetted powder particles to clump together and form an outer layer around each of the substrate particles, a substantially homogeneous, amorphous mass of starch-based, water-absorbent, cohesion-promoting material, to form the outer layer, producing the finished litter particles of the present invention, which are then dried, such as by turbulent air, heated air, and / or radiant heat directed at and / or impinged on the finished litter particles. Drying is carried out until the moisture content of the still-wet finished litter particles is reduced to less than 12%, preferably less than 10%, and more preferably 8% or less by weight of each litter particle. The moisture reduction is carried out to moisture cure the water-soluble adhesive into a solid adhesive, adhesively bond an outer layer of the starch-based, water-absorbent, cohesion-promoting material to the outer surface of each inner substrate particle, and to prevent at least a portion of the at least partially soluble binder in each finished litter particle from moisture activation and / or further moisture hardening (preferably by preventing its aging), so that at least a portion of the moisture-activatable, at least partially soluble binder in each particle remains available to cohere the particles together when wetted with water or urine.

[0180] The moisture removal step (preferably a drying step) can be, and preferably is, carried out while the newly finished, still-wet granules continue to be mixed (e.g., stirred). This allows the binder that adhesively attaches the outer, self-coherent, water-absorbing regions to the inner substrate particles to harden, while simultaneously preventing water activation of the binder contained in that portion of the outer region of the starch-based, water-absorbent, clumping-promoting material that does not adhesively bond the outer region to the outer surface of each substrate particle. The moisture removal step (preferably a drying step) can be, and preferably is, carried out while the partially coated animal litter granules (e.g., partially finished animal litter granules) are being wetted and / or rewetted. This can include adding additional dry starch-based, water-absorbent, clumping-promoting powder or powder material while everything is being mixed (e.g., stirred), such as in a mixer barrel or drum. The water removal step (e.g., drying step) can be carried out while the substrate particles are being coated with the starch-based water-absorbing clumping promoting powder or powder and water slurry (including while they are all being mixed together), but is preferably carried out after the slurry application step is complete.

[0181] In preferred embodiments of the coated substrate animal litter and coated substrate animal litter particles, the modified starch-based water-absorbing flocculant is in the form of a starch-based water-absorbing flocculation promoting powder or dust, and comprises at least a plurality, preferably at least a plurality of pairs, i.e., at least three different types of modified starches, each having a different, preferably smaller, molecular weight than the unmodified or native starch from which the corresponding modified starch is formed. Each of the different types of modified starches is formed from unmodified or native starches, preferably unmodified amylose starch and amylopectin starch, contained in one or more grains and / or pulses in the grain and / or pulse-containing mixture. The unmodified or native starch in the mixture is modified during extrusion using a single screw extruder at an ultra-high extrusion pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably at least 5000 PSI, thereby modifying the unmodified or native starch to produce a modified starch-based water-absorbent flocculating agent in the form of an extrudate of the starch-based water-absorbent flocculation-promoting material, which is used in powder or dust form in the manufacture of the self-clumping, absorbent animal litter particles of the animal litter of the present invention.

[0182] The substrate moistening method for producing the coated substrate litter particles of the present invention includes moistening the substrate particles before applying a modified starch-based water-absorbent flocculant (preferably in the form of a starch-based water-absorbent flocculating powder or powder), and the amount of water used is greater than the amount of the modified starch-based water-absorbent flocculant powder or powder (preferably the starch-based water-absorbent flocculating powder or powder) used. Before adding the modified starch-based water-absorbent flocculant, water is added until the substrate particles begin to self-agglomerate to achieve appropriate moistening, and then the modified starch-based water-absorbent flocculant is added in the form of a powder or powder, extruded pellets, or crushed extruded pellets (e.g., crushed using a high-speed high-shear mixer).

[0183] In one embodiment of the method, in the application step of coating the substrate particles with a modified starch-based water-absorbent flocculant powder or powder, preferably a starch-based water-absorbent cohesion-promoting powder or powder, the ratio of water to the modified starch-based water-absorbent flocculant powder or powder, preferably a starch-based water-absorbent cohesion-promoting powder or powder, is between 6:1 and 10:1, preferably between 7:1 and 9:1, and more preferably about 8:1. When performing the substrate water wetting method, multiple cycles are performed in which the substrate is wetted, dry modified starch-based water-absorbent flocculant powder or powder, preferably dry starch-based water-absorbent cohesion-promoting powder or powder is applied to each wet substrate particle, the mixture is wetted or rewetted with additional water, and additional dry modified starch-based water-absorbent flocculant powder or powder is applied to the at least partially coated wet substrate particles. During this time, the substrate particles and the modified starch-based water-absorbing flocculant powder or powder, preferably the starch-based water-absorbing flocculation promoting powder or powder, are mixed in a rotating barrel or rotating drum of a drum coater, cement mixer, drum mixer, mixing blender, etc., preferably by continuous tumbling, rotation, or other form of agitation.

[0184] The slurry method uses significantly less water relative to the granular modified starch-based water-absorbing flocculant (preferably in the form of a powder or dust of the starch-based water-absorbing flocculant), preferably in a ratio of water to granular modified starch-based water-absorbing flocculant (preferably a starch-based water-absorbing flocculation promoting powder or dust) of 0.5:1 to 2:1, more preferably about 1:1, and mixes them together before applying the slurry to the substrate particles, preferably all of which are mixed together. Mixing is preferably carried out by tumbling in a mixer such as a pin mixer, drum coater, cement mixer, blender (e.g., ribbon blender), or using other types of mixing or blending equipment. In a preferred method embodiment, a continuous slurry process is employed in which water and granular modified starch-based water-absorbing flocculant (preferably in the form of a starch-based water-absorbing flocculation-promoting powder or dust) are mixed and stored in a tank, vat, or other container, from which the slurry is substantially continuously pumped to one or more mister atomizers, sprayers, nozzles, dispensers, or other application devices. These application devices dispense the slurry onto the substrate particles while they are in a rotating drum or barrel, or while they are conveyed on a conveyor and passing underneath the application device. This is a continuous application process, preferably a continuous-flow application process. In another preferred method embodiment, the slurry can be applied using a mister, sprayer, nozzle, dispenser, or other application device to substrate particles that are being stirred, tumbled, or otherwise mixed. Mixing can be performed in a drum coater, drum mixer, concrete mixer, pin mixer, ribbon blender, or other suitable blender or mixer. This allows the granular modified starch-based water-absorbent flocculant (preferably a starch-based water-absorbent clumping promoting powder or fine powder) to be more uniformly coated onto the particles in or from the slurry, advantageously producing self-clumping absorbent litter particles of the present invention having a substantially uniform outer layer of modified starch-based water-absorbent flocculant (preferably a starch-based water-absorbent clumping promoting material), which outer layer has substantially the same thickness from one litter particle to the next and which substantially completely encapsulates each substrate particle.During the application process, the particles are tumbled, rolled, or otherwise agitated in a preferably rotating, generally cylindrical, barrel, or drum-shaped coater, mixer, or similar device to form an outer layer of the modified starch-based water-absorbent flocculant (preferably, a starch-based water-absorbent flocculation-promoting material). This outer layer fills any recesses or voids in the outer surface of the substrate particles and smooths out any other surface irregularities of the substrate particles. This advantageously produces litter particles with a substantially smooth, rounded outer surface. The litter particles do not scratch the paw pads of declawed cats and are non-tracking. Non-tracking occurs because the smooth, rounded particles do not easily adhere to cat paws and are not carried to the floor outside the litter box. When the substrate particles are generally round, for example when substrate particles of paper (i.e. paper spheres) are used, the self-clumping absorbent litter particles of the present invention produced each have a substantially smooth, rounded outer layer of modified starch-based water-absorbent clumping agent (preferably starch-based water-absorbent clumping promoter), preferably producing substantially round and / or generally spherical litter particles, for example the self-clumping absorbent litter particle spheres of the present invention.

[0185] As previously mentioned, the rounded animal litter particles of the coated substrate are advantageously sized to minimize removal of the animal litter from the animal litter box during use and handling of the animal litter. The roundness of the animal litter particles of the coated substrate is advantageous for preventing the animal litter particles of the coated substrate from becoming trapped between a cat's paws during use of the animal litter box. Furthermore, the animal litter particles of the coated substrate are sized to help prevent removal by a cat during use of the animal litter box. In a preferred embodiment, the animal litter particles of the coated substrate should have a size larger than a 25-mesh sieve (i.e., larger than 25 mesh) and not larger than a 10-mesh sieve (i.e., not larger than 10 mesh). At least 80% of the animal litter particles of the coated substrate should be smaller than 10 mesh and larger than 25 mesh (10 / 25). For example, in one embodiment, between 60% and 95%, preferably about 80% (80%±15%) of the particles pass through a 12 mesh sieve but larger than a 25 mesh sieve. The remaining coated substrate animal litter particles are larger than 10 mesh. Rounded coated substrate animal litter particles having a particle size distribution between 12 mesh and 20 mesh (12 / 20) provide an optimal feel for a cat's paws.

[0186] Thus, in one preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have raised protrusions including spikes, and have a particle size distribution between 12 mesh and 20 mesh (12 / 20), thereby producing a preferred embodiment of a low-tracking litter that minimizes tracking by cats out of the litter box. In another preferred coated substrate cat litter embodiment, the coated substrate litter particles are generally rounded, have raised protrusions including spikes, and have a particle size distribution between 10 mesh and 25 mesh (10 / 25), thereby producing another preferred embodiment of a low-tracking litter that minimizes tracking by cats out of the litter box.

[0187] In a method for producing a self-cohesive absorbent material according to the present invention, at least a plurality of different types, preferably at least a plurality of pairs, i.e., at least three different types of substrate particles are coated substantially simultaneously with outer regions of a modified starch-based water-absorbent flocculant when producing a batch of animal litter of the present invention comprising self-cohesive animal litter particles of the present invention comprising at least a plurality of different types, preferably at least a plurality of pairs, i.e., at least three different types of substrate particles. In one example of such a method, at least one type of substrate particle is an organic substrate particle having a lower density than the other type of inorganic substrate particle, preferably the functional substrate particle, such that both types of substrate particles are coated substantially simultaneously with the granular modified starch-based water-absorbent flocculant using either a slurry method or an animal litter particle production method using wetting and rewetting with an aqueous wetting liquid.

[0188] In a preferred embodiment, the modified starch-based water-absorbing flocculant is preferably a starch-based water-absorbing, clumping-promoting material produced by extruding a starch-based mixture, such as the aforementioned mixture containing one or more grains and / or one or more legumes, at a relatively low moisture content of about 25% or less by weight through an extruder at an ultra-high extrusion pressure of at least 2500 PSI, preferably at least 3000 PSI, more preferably at least 4000 PSI, and even more preferably 5000 PSI. Thus, the modified starch-based water-absorbing flocculant is preferably extruded in the form of a starch-based water-absorbing, clumping-promoting material, and more preferably is or contains a starch-based absorbent, swellable biopolymer gelling agent, including modified starch modified in an extruder at an ultra-high extrusion pressure. This gelling agent swells and gels upon sorption, including the absorption of liquids such as water at room temperature or aqueous liquids, such as cat urine at body temperature. The gelling agent preferably comprises at least a portion of the starch in the mixture that has been modified by ultra-high pressure extrusion to a cold water soluble binder, and at least a portion of the other starch in the mixture that has been modified by ultra-high pressure extrusion to a cold water swelling, water-absorbent modified starch. In preferred animal litter particle embodiments and methods for manufacturing animal litter particles, waste fines from the process of manufacturing absorbent starch-based animal litter (e.g., the extruded grain-based animal litter disclosed in commonly owned U.S. Patent Nos. 9,491,926, 10,028,481, 10,098,317, 10,882,238, 11,013,211, and / or 11,083,168, which are expressly incorporated herein by reference in their entireties) are used as a starch-based granular modified starch-based water-absorbent flocculant, preferably a granular water-absorbent flocculation-promoting material, and are applied directly or as a slurry to the substrate particles, or are ground, milled, pulverized, or otherwise reduced in particle size to smaller powder-like particles having mesh sizes and / or mesh size ranges described elsewhere herein and applied or slurried to the substrate particles.When the granular modified starch-based water-absorbing flocculant (preferably in the form of a starch-based water-absorbing, cohesion-promoting granular material, more preferably containing a starch-based absorbent, swellable biopolymer gelling agent) is used in powdered particle form, the powdered particles preferably have a particle size of less than 1,000 μm, and preferably comprise particles in the size range of 100 μm to 400 μm. When the granular modified starch-based water-absorbing flocculant is preferably in the form of a starch-based water-absorbing, cohesion-promoting granular material, more preferably containing a starch-based absorbent...

Claims

1. 1. Self-clumping, absorbent granular animal litter comprising a plurality of absorbent animal litter particles that self-clump when wet, wherein each self-clumping, absorbent animal litter particle comprises: (a) an inner substrate particle; and (b) a modified starch flocculant adhesively self-attached to said inner substrate particle; A self-clumping, adsorbent granular animal litter comprising:

2. 2. The self-clumping, adsorptive granular animal litter of claim 1, wherein the modified starch flocculating agent is adhesively self-adhered to the substrate particles by an inner self-adhering region comprising a modified starch water-absorbing flocculating agent.

3. 3. The self-clumping, absorbent granular animal litter of claim 2, wherein the modified starch flocculating agent includes an outer region that encompasses the inner self-adhering region and defines the outer surface of each absorbent animal litter particle.

4. 4. The self-clumping, absorbent granular animal litter of claim 3, wherein the outer surface includes at least a plurality of pairs of raised protrusions each protruding from the outer surface, the raised protrusions being configured to improve water and urine absorption of the absorbent animal litter particles.

5. 5. The self-clumping, adsorptive granular animal litter of claim 4, wherein each of said raised projections is microscopic in size.

6. 6. The self-clumping, adsorptive granular animal litter of claim 5, wherein each of said raised protrusions is nano-sized or nano-scale.

7. 4. The self-clumping, absorbent granular animal litter of claim 3, wherein the outer surface includes at least a plurality of pairs of cracks formed on the outer surface, the cracks being configured to improve water and urine absorption of the absorbent animal litter particles.

8. 8. The self-clumping, adsorptive granular animal litter of claim 7, wherein each of said cracks is a microcrack.

9. 4. The self-clumping, adsorbent granular animal litter of claim 3, wherein the modified starch flocculating agent defines an outer surface of each adsorbent particle, the outer surface of each adsorbent particle including at least a plurality of pairs of raised protrusions formed on the outer surface, each of the raised protrusions protruding from the outer surface, and the raised protrusions are configured to improve water and urine absorption of the adsorbent animal litter particles.

10. 10. Self-clumping, adsorbent granular animal litter according to claim 9, wherein substantially the entire outer surface of each adsorbent particle comprises said raised projections.

11. 11. The self-clumping, adsorptive granular animal litter of claim 10, wherein each of said raised projections is microscopic in size.

12. 4. The self-clumping, adsorbent granular animal litter of claim 3, wherein the modified starch flocculating agent defines the outer surface of each adsorbent particle, the outer surface of each adsorbent particle including at least a plurality of pairs of microcracks formed in the outer surface, the microcracks being configured to improve water and urine absorption of the adsorbent animal litter particles.

13. 4. The self-clumping, adsorbent granular animal litter of claim 3, wherein the modified starch flocculating agent defines an outer surface of each adsorbent particle, the outer surface of each adsorbent particle including (i) at least a plurality of pairs of microscopic raised protrusions formed on the outer surface and each protruding therefrom, and (ii) at least a plurality of pairs of microscopic cracks formed on the outer surface, the microscopic raised protrusions and the microcracks configured to improve water and urine absorption of the adsorbent animal litter particles.

14. 2. The self-clumping, absorbent granular animal litter of claim 1, wherein the clumping agent comprises: (a) a first component comprising a one-time moisture-activated, one-time moisture-curing binder; and (b) a second component comprising a moisture-reactivated, moisture-recuring binder configured for multiple moisture activations and moisture curing.

15. 15. The self-clumping, adsorptive granular animal litter of claim 14, wherein said clumping agent further comprises a third component comprising a water-absorbing agent.

16. 15. The self-clumping, adsorptive granular animal litter of claim 14, wherein said first component comprises a cold water soluble starch that is at least partially water soluble at room temperature of 68°F to 72°F.

17. 17. The self-clumping, adsorptive granular animal litter of claim 16, wherein the first component comprises an extrusion-modified starch comprising starch mixed during extrusion.

18. 18. The self-clumping, adsorptive granular animal litter of claim 17, wherein said first component comprises dextrinized starch.

19. 15. The self-clumping, adsorptive granular animal litter of claim 14, wherein said second component comprises a cold water soluble starch that is at least partially water soluble at room temperature of 68°F to 72°F.

20. 20. The self-clumping, adsorptive granular animal litter of claim 19, wherein the second component comprises an extrusion-modified starch comprising starch mixed during extrusion.

21. 21. The self-clumping, adsorptive granular animal litter of claim 20, wherein the second component comprises pregelatinized starch or starch pregel.

22. 15. The self-clumping, adsorptive granular animal litter of claim 14, wherein the first component comprises dextrinized starch and the second component comprises pregelatinized starch or starch pregel.

23. 2. The self-clumping, adsorptive granular animal litter of claim 1, wherein the modified starch water-absorbing flocculant is adhesively self-adhered to the substrate particles by internal self-adhering regions comprising the modified starch water-absorbing flocculant.

24. 24. The self-clumping, adsorptive granular animal litter of claim 23, wherein the modified starch water-absorbing clumping agent comprises: (a) a first type of starch that has been modified into a water-swellable modified starch that is also water-absorbent; and (b) a second type of starch that has been modified into a binder that is at least partially water-soluble and becomes a water-activated adhesive when wetted with an aqueous liquid.

25. 25. The self-clumping, absorbent granular animal litter of claim 24, wherein said water-activated adhesive comprises a moisture-curing water-activated adhesive.

26. 26. The self-clumping, absorbent granular animal litter of claim 25, wherein the room temperature moisture curing, water-activated adhesive comprises one of a room temperature moisture curing, water-activated thermosetting adhesive and a room temperature moisture curing, water-activated thermoplastic adhesive.

27. 2. The self-clumping, absorbent granular animal litter of claim 1, wherein the inner substrate particle has an outer surface, and at least a portion of the outer region of the modified starch water-absorbing flocculant adhesively self-adheres the outer region of the modified starch water-absorbing flocculant to the outer surface of the inner substrate particle.

28. 28. The self-clumping, absorbent granular animal litter of claim 27, wherein the outer region of the modified starch water-absorbing flocculant comprises (1) a cold-water-swellable, water-absorbing modified starch, and (2) a cold-water-soluble modified starch binder that, when wetted with an aqueous liquid or solution containing water, forms an at least partially water-soluble, flowable adhesive, at least a portion of which adhesively self-adheres the outer region of the modified starch water-absorbing flocculant to the outer surface of the internal substrate particle.

29. 28. The self-clumping, absorbent granular animal litter of claim 27, wherein the outer region of the modified starch water-absorbing flocculant comprises (a) a cold-water-swellable, water-absorbent modified starch, and (b) a cold-water-soluble modified starch binder that forms an at least partially water-soluble flowable adhesive when wetted with an aqueous liquid or solution containing water, at least a portion of which comprises an inner self-adhesive region that is a solidified, hardened adhesive in a glassy state when (1) either (i) the modified starch water-absorbing flocculant, and (ii) the inner substrate particles are wetted with an aqueous wetting liquid containing water, (2) the wetted modified starch water-absorbing flocculant contacts the wetted outer surface of the inner substrate particles, and (3) the flowable adhesive subsequently moisture-cures or solidifies to bond the outer region of the modified starch water-absorbing flocculant to the outer surface of the inner substrate particles.

30. 30. The self-clumping, absorbent granular animal litter of claim 29, wherein the flowable adhesive of said inner adhesive region cures or hardens to become a solid and hardened material.

31. 31. The self-clumping, absorbent granular animal litter of claim 30, wherein the moisture content of the self-clumping, absorbent granules is reduced to cause the flowable adhesive of the inner adhesive region to transform into a solid glassy material.

32. 32. The self-clumping, absorbent granular animal litter of claim 31, wherein the moisture content of the self-clumping, absorbent granules is reduced until the flowable adhesive in the internal adhesive region transitions from either a flowable liquid or a gel to a solid glassy material.

33. 32. The self-clumping, absorbent granular animal litter of claim 31, wherein the moisture content of the self-clumping, absorbent granules is reduced until the flowable adhesive of the internal adhesive region transitions from either a flowable liquid or a gel to a solid, glassy material that is hard to the touch.

34. 34. The self-clumping, absorbent granular animal litter of claim 33, wherein the moisture content of the self-clumping, absorbent granules is reduced to about 8% or less by weight of the animal litter granules, and the flowable adhesive in the interior region hardens or solidifies, causing the flowable adhesive to transition from either a viscous liquid and a semi-solid gel to a solid, glassy material that is hard to the touch.

35. 1. A method of making self-clumping, absorbent granular animal litter comprising a plurality of absorbent animal litter granules that self-clump together when wet, the method comprising the steps of: (a) providing a substrate particle and a modified starch flocculating agent; (b) applying the modified starch flocculant to the base particles to form self-cohesive, adsorptive animal litter granules comprising the base particles and the modified starch flocculant adhesively self-adhering to the base particles.

36. 36. The method of claim 35, wherein the modified starch flocculant adhesively self-adheres to the substrate particle by internal self-adhering regions comprised of the modified starch water-absorbing flocculant.

37. 37. The method of claim 36, wherein the modified starch flocculating agent comprises an exterior region that encompasses the interior self-adhesive region and defines the outer surface of each absorbent animal litter granule.

38. 38. The method of claim 37, wherein the outer surface includes at least a plurality of pairs of raised protrusions extending therefrom, the raised protrusions being configured to improve water and urine absorption of the absorbent animal litter granules.

39. 39. The method of claim 38, wherein each of the raised protrusions is microscopic in size.

40. 40. The method of claim 39, wherein each of the raised protrusions is nano-sized or nanoscale sized.

41. 38. The method of claim 37, wherein the outer surface includes at least a plurality of pairs of cracks formed in the outer surface, the cracks configured to improve water and urine absorption of the absorbent animal litter granules.

42. 42. The method of claim 41, wherein each of the cracks is a microcrack.

43. 38. The method of claim 37, wherein the modified starch flocculant defines an outer surface of each adsorbent granule, the outer surface of each adsorbent granule including at least a plurality of pairs of raised protrusions formed on the outer surface and each protruding from the outer surface, the raised protrusions being configured to improve water and urine absorption of the adsorbent animal litter granules.

44. 44. The method of claim 43, wherein substantially the entire outer surface of each adsorbent granule is made up of said raised protrusions.

45. 45. The method of claim 44, wherein each of the raised protrusions is microscopic in size.

46. 38. The method of claim 37, wherein the modified starch flocculant defines an outer surface of each adsorbent granule, the outer surface of each adsorbent granule including at least a plurality of pairs of microcracks formed in the outer surface, the microcracks configured to improve water and urine absorption of the adsorbent animal litter granules.

47. 38. The method of claim 37, wherein the modified starch flocculant defines an outer surface of each adsorbent granule, the outer surface of each adsorbent granule including at least (i) a plurality of pairs of microscopic raised protrusions formed on the outer surface, each protruding from the outer surface, and (ii) a plurality of pairs of microcracks formed on the outer surface, the microscopic raised protrusions and the microcracks configured to improve water and urine absorption of the adsorbent animal litter granules.

48. 36. The method of claim 35, wherein the coagulant comprises: (a) a first component comprising a one-time moisture-activated, one-time moisture-cure binder; and (b) a second component comprising a moisture-reactivated, moisture-re-cure binder configured for multiple moisture activation and moisture curing.

49. 49. The method of claim 48, wherein the flocculant further comprises a third component comprising a water-absorbing agent.

50. 49. The method of claim 48, wherein the first component comprises a cold water soluble starch that is at least partially water soluble at room temperature between 68 and 72 degrees Fahrenheit.

51. 51. The method of claim 50, wherein the first component comprises an extrusion-modified starch comprising starch mixed during extrusion.

52. 52. The method of claim 51, wherein the first component comprises a dextrinized starch.

53. 49. The method of claim 48, wherein the second component comprises a cold water soluble starch that is at least partially water soluble at room temperature between 68 and 72 degrees Fahrenheit.

54. 54. The method of claim 53, wherein the second component comprises an extrusion-modified starch comprising starch mixed during extrusion.

55. 55. The method of claim 54, wherein the second component comprises pregelatinized starch or starch pregel.

56. 49. The method of claim 48, wherein the first component comprises a dextrinized starch and the second component comprises a pregelatinized starch or a starch pregel.

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