Chemistry: fertilizers – Processes and products – Inorganic material
Reexamination Certificate
1999-12-30
2001-03-27
Straub, Gary P. (Department: 1757)
Chemistry: fertilizers
Processes and products
Inorganic material
C119S171000, C119S173000, C252S184000, C502S400000
Reexamination Certificate
active
06206947
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to animal litter absorbent compositions and to processes for making the litter compositions. More particularly, the present invention relates to an animal litter absorbent composition based on calcium sulfate that may be used for both indoor pets and outdoor farm animals.
2. The Prior Art
Animal litters are useful for absorbing animal urine and to encapsulate animal feces until the litter is either cleaned-up or otherwise disposed of. The most commonly used absorbent materials are clays that are safe and non-irritating to the animal and that absorb relatively large amounts of liquids. Animal urine forms ammonia which has an unpleasant odor. The clay materials only absorb and hold urine resulting in a source of odor requiring frequent replacement and disposal of the litter.
Efforts have been made to develop a litter capable of disposing of both solid wastes and liquid wastes. This led to the development of clumping litters in the form of finely ground particles of certain clays, sometimes augmented by binders or additives to form discernable clumps when contacted by animal waste. These particles clump in the presence of liquid wastes, which is scooped up and removed with the solid wastes. Although the clumping litters enable a cat owner to remove waste without disposing of the entire contents of the litter box, these clumping litters are frequently dusty and the odor problem remains. Animal litters sometimes contain other absorbents such as wood chips, sawdust or sand but most of the cat litter products currently in commerce are manufactured from ground clay. These products are not water-soluble and thus are difficult to dispose of properly.
In addition to cat litter, problems exist with the growing environmental demand to ban waste water lagoons in mass production hog farms. The existing flush water systems currently in use by the swine industry are inadequate to control odor and pose other environmental risks by dangerous proximity to water tables.
A material useful as cat litter is described in U.S. Pat. No. 4,459,368 to Jaffe et al., which discloses a mixture of fuller's earth, preferably in the form of calcium bentonite, mixed with calcium sulfate dihydrate at a weight ratio of 1:9 to about 3:7. In addition, the particle size of the clay and the calcium sulfate dihydrate are such that no more than about 60 weight % of clay and about 20 weight % of calcium sulfate particle are retained on a 6 mesh sieve screen. The manner of mixing is not important as the clay and calcium sulfate dihydrate are simply mixed to form the cat litter. The patent states that the ratio of the weight of clay particles to the weight of calcium sulfate is important in order to maximize the liquid absorbing effect.
Another cat litter product is described in U.S. Pat. No. 5,469,809 to Coleman, wherein there is disclosed a litter having clumping characteristics. The litter comprises a mixture of opal clay and sodium bentonite formed into smooth round balls to eliminate dusting. There is also disclosed a cat litter having up to ten percent of a lignosulfonate. The lignosulfonate is said to help form and maintain a smooth round shape for the resulting litter granules. The litter is formed by mixing the opal clay and sodium bentonite, pelletizing in a disc pelletizer to form the spherical pellets and then screening to the desired size.
An animal litter that is said to form clumps is disclosed in the Elazier-Davis et al. patent, U.S. Pat. No. 5,452,684, directed to a method of agglomerating a smectite clay litter. Therein the clay is sheared in an extruder to align the clay platelets to produce a litter having stronger clumps. The smectite clay may be mixed with a small amount of water-soluble adhesive such as carboxymethylcellulose, alginate, starches, gums and the like to form the coherent clumps. The preferred clay is sodium bentonite which absorbs liquids such as urine and interacts with nearby clay particles to form strong clumps through physical reaction. However, this product simply holds the urine and does not reduce or eliminate the odor.
In addition to the above-disclosed litter products, it is also known that calcium sulfate may be mixed with soluble salts including urea to form a granulated soil additive product such as disclosed in U.S. Pat. No. 3,660,068 to Wilson. Along these same lines, U.S. Pat. No. 3,976,467 and 2,154,541, both to fertilizer-type products, also combine calcium sulfate or gypsum with urea.
Thus, there continues to be a need for an animal litter which is easily disposable. In addition there is need for an animal litter which has a high density to prevent tracking and in which the pungent ammonia odor of the animal urine is reduced.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an animal litter that absorbs large amounts of animal urine, has good clumping and tracking characteristics, and is substantially dust free, environmentally safe.
In accordance with the present invention there is provided an animal litter which has been developed in response to growing environmental concerns and consumer trends to premium grade litter products that clump on contact with animal waste.
In its broadest aspects, the present invention provides a calcined calcium sulfate absorbent as an animal litter which is made by compacting the calcium sulfate to increase the density or by adding a binder to the calcium sulfate powder and agglomerating or compacting. The materials which are primarily used to make the animal litter of the present invention include gypsum, waste gypsum separated from wallboard, synthetic gypsum, and combinations of these materials.
In the embodiment wherein the calcium sulfate is compacted, it is passed through an extruder to increase the density to produce a litter having the desired properties. The compacted calcium sulfate is then screened to a particle size range between a 4 mesh and about 100 mesh, U.S. sieve series, and dried until calcined. Depending upon the end use of the litter, the most typical particle size is between 8 mesh and 40 mesh.
In another embodiment of the product of the present invention it has been found that an animal litter having the desired properties may be made by adding to calcium sulfate an effective amount of a binder to agglomerate, thus forming pellets, pelletizing and calcining. Preferred binders include certain clays, especially bentonite clay, lignins and starches. The effective amount of binder will depend upon the binder selected. For example, when bentonite clay is the binding agent, it may be present in an amount up to about 5.0%. Other binders will generally range in amounts from about 0.25% to about 10.0% by weight of the total composition, preferably from about 0.5% to about 2.0% by weight. Optionally, trace additives such as sodium bicarbonate,
Yucca schidigera
and other olfactory agents may be added in amounts up to about 5.0 by total weight, preferably 1.5% to 4.0% by weight, for ammonia and odor control.
Another aspect of the present invention is to provide a process for producing animal litter. In one of the processes of this invention, calcium sulfate is crushed and screened to a powder. A paste of powdered calcium sulfate is prepared and the paste is compacted by passing the paste through an extrusion mill at a pressure up to 1000 p.s.i., typically from about 300 p.s.i. to about 500 p.s.i., to form noodles which are broken into pellets. The compacted pellets are screened to the desired size to remove fines and oversized particles. The pellets are then heated at a temperature from about 50° C. to about 430° C. until the calcium sulfate is calcined. Litter made according to this process does not require a binder because the compaction of the extrusion and the heating provide a calcined, hard product. However, when it is desirable to add a binder, such as when lower temperatures are used, the binder may be added when the paste is formed.
Alternatively, it has been found that the animal litter may be made
Evans Donald Frederick
Steele Richard Binion
Sumner Malcolm Edward
Alston & Bird LLP
Straub Gary P.
Waste Reduction Products Corp.
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