Clumping animal litter and method of making same

Details Clumping animal litter and method of making same Clumping animal litter and method of making same

2002-10-29

2004-06-08

Poon, Peter M. (Department: 3643)

Animal husbandry

Material for absorbing moisture from waste product

Having paper-related component

C119S171000, C119S173000

Reexamination Certificate

active

06745720

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to cellulose-based animal litter products, and in particular to clumping-type animal litters comprising cellulose-based core particles that are covered with specially designed water-permeable coatings.
BACKGROUND OF THE INVENTION
American families increasingly prefer cats, with their independent natures and reduced need for care, as compared with dogs. Domesticated animals such as cats are provided in homes with litter boxes, where they dispose of their biological waste. The performance of the litter product in the litter box can vary greatly, depending upon the precise nature of the product. Key attributes of a litter product that are of importance to cat owners are odor control and litter care convenience (that is, supply and removal).
Originally litter products were relatively unsophisticated, and of the type known today as “non-clumping”. More recently, clumping type cat litters have been introduced. Both types are essentially equivalent with respect to the removal of solids. With both types, solid excretions are scooped out of the litter box daily or at least frequently. However, clumping litters provide great advantages with respect to the way in which urine excretion is handled. Non-clumping litters absorb the urine and hold it until ammonia-type malodors develops, at which time the entire content of the litter box is removed and replaced. Clumping litters, however, are designed to gel when wetted by urine, and the urine soaked granules agglomerate into clumps whose mechanical strength facilitates their removal in the same manner as solid waste is removed, leaving the remaining litter fresh and urine-free.
Litter products have been made with natural substrates or artificial substrates. Natural substrates that have been used include minerals, usually types of clay, or organic matter, usually agricultural byproducts or paper derivatives. Artificial litter particles have generally comprised granules combining several materials of an absorbent nature, aggregated together with a binder to form a granule. These prior art aggregated granules are of a single component nature—that is, all their ingredients are mixed together into one more or less homogeneous entity.
Clumping litters made from bentonite were introduced in 1989, providing better and longer lasting odor control than did traditional litters. Bentonite is a swelling mineral of the clay category, with a unique ability to gel and agglomerate when wetted, creating scoopable clumps. However, mineral based clumping litter are heavy and dusty. While their innate absorption, clumping, and odor control attributes are good, further performance improvement by solid and/or liquid additives is limited.
Organic based clumping litters, on the other hand, make use of the improved absorption capabilities of cellulose fibers. Unfortunately, they have minimal innate clumping properties, and require the addition of clumping agents such as starches and/or polymers. These clumping additives produce litters with much less clumping effectiveness than that of the mineral variety. This lesser clumping performance is apparent from their reduced speed of effective agglomeration, their reduced mechanical strength of the clump, and their duration of cohesion forces in the clumped matter. However, organic clumping litters are lighter in weight, are less dusty, and are flushable, which makes their use more convenient.
U.S. Pat. Nos. 4,949,672; 5,129,365; 5,329,880; 5,361,719; 5,469,809; 5,609,123; and 6,089,189 are typical of patents relating to clumping litters.
U.S. Pat. No. 4,949,672 relates to the use of boron-containing compounds (especially, boric acid) as a urease inhibitor in clumping cat litter. The boric acid is used as a superficial liquid additive, rather than being built into the substrate. The patent claims a method of controlling odor formation in animal litters comprising applying a liquid carrier to particles of absorbent litter substrate, said liquid carrier containing an odor-controlling-effective amount of a boron containing material having an equal boron level of at least about 0.06%.
U.S. Pat. No. 5,129,365 discloses a bentonite-based clumping litter. The odor control performance of such a litter is derived from its natural properties or by commingling odor-control particles with it or by spraying it superficially with odor-control liquids. One disclosed embodiment comprises discrete particles of a combination of non-compacted water-swellable sodium bentonite clay and calcium bentonite clay that effectively absorbs animal dross and simultaneously agglomerates into a water-dispersible but physically stable mass, thereby permitting physical separation of the soiled and wetted bentonite clay particles from discrete particles of the unsoiled and unwetted water-swellable bentonite clay. All ingredient particles in this invention are relatively large, and thus “mixing” means between the granules themselves and not within a granule. The mixing of calcium bentonite with sodium bentonite weakens the clump but enables it to be flushable.
U.S. Pat. No. 5,329,880 describes a litter in which a mixture of hydrophilic shale may contain up to 10% clumping agent selected from water absorbent polymers, corn starch, gelatin, gluten, and dried plants of the Plantago family. It is further disclosed that, in addition, 5-25% ammonia-absorbing zeolite may be added for odor control. All ingredient particles in this invention are relatively large, and thus “mixing” means between the granules themselves and not within a granule.
U.S. Pat. No. 5,361,719 disclosed a hydrating cat litter which solidifies upon contact with liquids to encapsulate pet waste matter. The litter comprises a mixture of a granulated, organic base material (preferably coarse ground agricultural grains, pulse crops, and/or agricultural byproducts, which support in suspension a quantity of semolina), a gluten-containing material, and optionally a fragrance carrier.
U.S. Pat. No. 5,469,809 describes a single-component granule that combines bentonite and other minerals into an artificial substrate (which contains no fibers). The patent teaches a process that comprises forming a mixture of opal clay with one or more of sodium bentonite, calcium lignosulfonate, and binder, and subsequently pelletizing the mixture.
U.S. Pat. No. 5,609,123 uses superabsorbing polymer as an agglomeration agent on a natural clay substrate. The superabsorbent polymer is sprayed externally and not incorporated as part of a coating complex. The patent claims a method that comprising spraying particulate substrate with a surface-bonding, non-aggregating, amount of moisture, allowing the sprayed moisture to be absorbed onto the surface of the substrate, and mixing the substrate with superabsorbent particles and with clumping particles.
U.S. Pat. No. 6,089,189 discloses cellulose-based clumpable animal litter products that comprise a mixture of adhesive-bearing cellulosic granules and a particulate polymeric clumping agent. The patent claims a process that comprises de-dusting cellulosic granules, contacting the de-dusted granules with water-soluble adhesive, drying the adhesive-bearing granules to a free-flowing state, and combining the dried granules with a particulate polymeric clumping agent to form a uniform admixture. None of these granules has a designed structure, and all ingredient particles in this invention are relatively large, so that “mixing” means between the granules themselves and not within a granule.
Applicants are unaware of any prior art that teaches animal litter granules comprising a multi-component functional core coated with a multi-component coating having different functional attributes, as described hereinbelow.
SUMMARY OF THE INVENTION
The animal litter of the present invention comprises plural discrete particles which are dual component granules. That is, in accordance with this invention, an absorbent granule is made up of an inner core and an external coating complex. Both the core and the coating comprise aggregates of (different) dry

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