Abstract:
An economical process that combines bentonite, or similar clays, that form a clump when in contact with cat urine, with waste cellulosic fibrous materials, preferably paper mill sludge, to form a light weight scoopable (clumping) cat litter product. In the process, paper mill cellulose waste is combined with bentonite clay (preferably sodium bentonite) in a mixing auger in varying percentages depending upon the desired end weight of the finished product, transferred to a secondary rotating drum mixer, then to a rotating drum dryer, and from the dryer to a screening process. The finished product is a granule weighing between 20 lbs./cubic foot and 50 lbs./cubic foot. The granule is highly absorbent and capable of forming a distinct clump that can be separated from the surrounding granules without falling apart. A unique characteristic of the process is the combination of heavy clay particles with light weight cellulose particles to form a new composite particle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to processes for manufacturing cat litter products. 
     2. Background of the Invention 
     Materials traditionally used as cat litter due to their moisture absorbent characteristics include bentonite (montmorillonite) clays. Such bentonite clays include sodium bentonite, calcium bentonite, potassium bentonite, lithium bentonite, magnesium bentonite, or some combination of those clays. However, the moisture characteristics of those clays are not equal. Sodium bentonite is known to have better moisture absorbing properties than the other clays. 
     It is also known that sodium bentonite particles, upon absorbing moisture, swell and bind together as a mass (agglomerate). This is particularly desirable because the mass, including the liquid waste contained therein, can be easily and integrally removed and discarded. Thus, the source of odor in a litter box can be conveniently removed without the necessity of changing out the entire box. The result of this, however, is to place a premium on sodium bentonite for cat litter purposes. A need, therefore, exists for a process that combines clumping cat litter, such as sodium bentonite with other materials of lesser value, which can result in a final product which still provides for the clumping properties of the bentonite clay. 
     It is well known that waste cellulosic fiber and paper mill sludge, which are produced in large quantities in most industrial nations of the world today, due to the large usage of paper, constitute a substantial environmental problem. Paper mill sludge has substantially little usage as a material that can be employed in other industrial applications. Because of this non-utility, the paper mill sludge is merely discarded, along with other waste cellulosic fiber. This creates a tremendous disposal problem. A need, therefore, exists for an integral process from which a single source of paper mill sludge can be utilized in an economical continuous flow procedure to output usable product. 
     A particular known problem with all clay cat litter products and particularly clumping cat litter products is their weight/volume ratio. A significant amount of cat litter product is necessary to fill a litter box. It is known that such cat litter boxes are changed every 5-10 days, depending on the number of animals, to avoid odor problems. As a result, it is necessary to purchase a sufficient volume of cat litter in order to avoid frequent trips to the pet store or pet aisle of a grocery store. Moreover, as with most products, there are certain economics to be gained through the purchase of larger volumes. The problem is that the container for a sufficient volume and economy of clumping cat litter product is generally heavy, approximately 60 lbs./cubic foot or more for an all clay product. Such weights are awkward, and in some cases, impossible for some people to handle. A need, therefore, exists for an effective cat litter product with a reduced weight/volume ratio. 
     SUMMARY OF THE INVENTION 
     The present invention is an economical process that combines bentonite, or similar clays, that form a clump when in contact with cat urine, with cellulosic materials, preferably paper mill sludge and waste cellulosic fibrous material, to form a lighter weight scoopable cat litter. The process includes: (1) component introduction; (2) combining the component paper mill sludge including waste cellulosic fibrous material with bentonite clay (preferably sodium bentonite) in a mixing auger in varying percentages depending upon the desired end weight of the finished product; (3) transferring the mixture to a secondary rotating drum mixer for particle shaping; (4) drying the mixed and shaped particles; and (5) particle size separation (screening). 
     The finished product is a granule weighing between 20 lbs./cubic foot and 50 lbs./cubic foot. The granule is highly absorbent and forms a distinct clump that can be separated from the surrounding granules without falling apart. Unique characteristics of the process are the combination of heavy clay particles with light weight cellulose particles to form a new composite particle. 
     The process can be accomplished by using paper mill sludge or any such cellulosic material. As used herein the term “paper mill sludge” encompasses bi-products of the production of paper as described above, mixtures of said bi-products and waste cellulosic fibrous materials, slurried waste cellulosic fibrous materials and slurried plant fibrous materials. Paper mill sludge for this process contains approximately 55-75% H 2 O by weight and clay that is 15% or less H 2 O. The H 2 O in the cellulose creates an environment conducive to blending the two materials in an agglomeration/swelling action that is characteristic of bentonite clay. When this agglomeration is dried, the particle decreases in size thus binding the two materials tightly to create a low dust, absorbent particle that has a lower weight/volume ratio than an all clay particle, that swells and forms a scoopable clump. Thus, the swelling/clumping properties of the bentonite clay are retained. The lighter weight/volume ratio is desirable for a variety of reasons: (1) less weight for the consumer to carry in the same volume; (2) less cost to ship from manufacture to retailer; and (3) a higher cost per pound for the manufacturer yet still providing the retailer the ability to sell the same volume for the same price as heavier scoopable cat litter products. 
     In an alternate embodiment of the process of the present invention, the paper mill sludge may be first dried and then run through a hammer mill in order to create a dry, small particle size cellulosic material. These small, dried particles are then dry blended with the bentonite clay. Moisture is then added to aggregate the cellulosic material and the bentonite clay. The resulting aggregate particles may then be shaped, dried and separated as in the process described above. 
     Odor control agents could also be added to the process during the component introduction step. Such odor control agents could include activated carbon, chabazite (zeolite) or any other known suitable material. When the particles are agglomerated according to the present process and then dried, the odor control agent is then trapped inside the particle. As a result, the odor control agent forms an integral part of the particle itself as opposed to added separately or sprayed onto the particles. 
     It is therefore an object of the present invention to provide an integral system for reclaiming paper mill sludge and waste cellulosic fibrous material into an environmentally acceptable product. 
     It is a further object of the present invention to utilize paper mill sludge and waste cellulosic fibrous material in the manufacture of a clumping cat litter. 
     It is still a further object of the present invention to combine bentonite clay with paper mill sludge and waste cellulosic fibrous material in the manufacture of a cat litter. 
     It is an additional object of the present invention to combine bentonite clay with paper mill sludge and waste cellulosic fibrous material in the manufacture of a clumping cat litter. 
     It is yet a further object of the present invention to combine bentonite clay with paper mill sludge and waste cellulosic fibrous material in the manufacture of a cat litter product with a lower weight/volume ratio that an all clay product. 
     It is still another object of the present invention to form a composite cat litter product containing an odor control agent(s) which are contained within the composite agglomerated particles. 
     A better understanding of the invention and its objects and advantages as well as further objects will become apparent to those skilled in this art from the following detailed description, taken in conjunction with the attached drawings, whether is shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of modifications and various obvious respects, all without departing from the scope of the invention. Accordingly, the description should be regarded as illustrative in nature and not as restrictive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an overall process sketch of the method of manufacture of an absorbent particle of the present invention identified with its component substeps. 
     FIG. 2A depicts the component introduction substep  2 A of FIG.  1 . 
     FIG. 2B depicts the component mixing substep  2 B of FIG.  1 . 
     FIG. 2C shows the particle shaping substep  2 C of FIG.  1 . 
     FIG. 2D depicts the particle drying substep  2 D of FIG.  1 . 
     FIG. 2E shows the particle separation substep  2 E of FIG.  1 . 
     FIG. 3 is a view taken along line  3 — 3  of FIG.  2 A. 
     FIG. 4 is a detail view of the double ribbon flighting of FIG.  2 B. 
     FIG. 5 is a detail view of the cut and fold auger flighting of FIG.  2 B. 
     FIG. 6 is a cross sectional view taken along line  6 — 6  of FIG. 4 showing the cross section of the double ribbon auger flighting of the present invention. 
     FIG. 7 is a cross section view taken along line  7 — 7  of FIG. 5 depicting the cut and fold auger flighting of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The process of this invention includes combining of bentonite, or similar clay, that forms a clump when in contact with cat urine, with cellulose materials, preferably paper mill waste, to form a light-weight, scoopable, clumping cat litter. With reference to FIG. 1, the process can be broken down for the purpose of illustration into five main substeps: (1) Reactant stream introduction ( 2 A); (2) component mixing ( 2 B); (3) particle shaping ( 2 C); (4) drying ( 2 D); and, (5) separation ( 2 E). This general description is for the purpose of illustration herein and shall not be considered limiting. According to this process, a bentonite clay, preferably sodium bentonite, is combined with paper mill sludge including waste cellulosic fibrous material in the manufacture of a cat litter product which retains the moisture swellable and clumping properties of the bentonite clay but has a lower weight/volume ratio than does an all clay product. 
     Throughout the specification, the preferred equipment is referenced. It should be understood, however, that this equipment is provided to illustrate the best mode known at the time for carrying out the invention. The use of equivalent equipment or equipment of different dimensions should be understood to fall within the scope of this invention. 
     Reference will now be made to FIGS. 2A and 3 in the preferred process of manufacturing a composite clumping cat litter. In the preferred process, sodium bentonite clay of a particle size capable of passing through a 20 mesh sieve and is deposited and stored in a dump hopper  10 . At the bottom of dump hopper  10 , there is an auger  12  for conveying the sodium bentonite clay to the upstream end of a mix-auger  14 . By varying the size or speed of rotation of auger  12 , the amount of clay processed into mix-auger  14  can be controlled. A predetermined amount of sodium bentonite is delivered by auger  12  into the mix-auger  14 . 
     Mix-auger  14  functions to mix the sodium bentonite clay with cellulosic fibrous material, preferably derived from paper mill waste. The waste cellulosic fibrous material is introduced into mix-auger  14  through sludge storage reservoir  18  to mix with the sodium bentonite clay to form a reactant stream. The cellulosic fibrous material is discharged into the bentonite clay by a metering conveyor  20  thus allowing control of material ratios. 
     In the alternate embodiment of the present invention, the cellulosic paper mill sludge is dried through the drier and then processed through a hammer mill in order to reduce the size of the particles. Once dried and sized, the small dry particles of paper (cellulosic material) are dry blended (mixed) with the bentonite clay in mix auger  14 . Once dry mixed, water is added to the paper/bentonite clay dry mix to form agglomerated particle which are further processed in the same manner as described below. 
     Paper mill sludge is a by-product of the production of paper and typically is an environmental contaminant. The disposal of paper mill sludge has been an ecological problem throughout the world. Heretofore utilized methods of disposing of paper mill sludge typically include burning or burial. Burning of the paper mill sludge is an expensive method of disposal, since before the paper mill waste can be burned, it must be dried. Burial of the material takes up large volumes of land fills and only conceals the waste which takes a long period of time to decay. Under the principals of this invention, paper mill sludge is moved directly from the paper manufacturing process into sludge storage reservoir  18  from which it is continuously fed into an integrated process for its reclamation thereby eliminating the waste and forming a commercially useful product. 
     The composition of paper mill sludge varies slightly depending upon the particular manufacturer from which it is obtained. Paper mill sludge generally comprises cellulosic fibrous materials, water, and fillers, in addition to contaminants. Normal paper mill sludge has a solids content of 40-90 weight percent fiber (the fibers are typically 500-1000 microns in length) and 10-60 weight percent filler. Fillers include such materials as kaolin clay, barytes, titanium dioxide and other plant fibers. Clay is the most important of the filler components. Some paper mill sludges might have a negligible or very low (3%) clay content by weight, while others might have up to a 40% clay content by weight. Raw paper mill sludge has a usual water content ranging from 60-90 weight percent. In the preferred combination, the cellulosic fibrous material has an H 2 O content of between 55% and 75% by weight while the H 2 O content of the bentonite clay is 15% or less. The water content in the paper mill sludge facilitates agglomeration of the composite particles. 
     Odor control agents may be added during the reactant introduction step through an additional silo and metering conveyor (similar to silo  18  and metering conveyor  20  of FIG. 2A) into the reactant stream. In the preferred embodiment, chabazite, having a particle size of 0 to 5 Å is added in an amount so as to provide an end product that is 1-15% by weight chabazite. Chabazite is a naturally hydrated calcium ammonium silicate zeolite (CaAl 2 Si 4 O 12 6H 2 O) available commercially. Chabazite is frequently used in water treatment and particularly water softening by providing cationic exchange of the sodium of the zeolite of the calcium or magnesium contained hard water. In the present process, however, the chabazite is introduced to provide its known odor elimination properties of the final product. Another additive contemplated in the present process is activated carbon added in powder form of approximately 5-15 Å particle sizes also for the purpose of odor control/elimination. The powder activated carbon and the chabazite are sealed within the composite particle as the particles are agglomerated according to the present process and function to absorb (trap) gas molecules in the final product. 
     Yet another additive contemplated is a desiccant pellet dust to provide increased moisture absorbency to the composite. The addition of the desiccant is also intended to absorb ammonia from cat urine thereby trapping/neutralizing odor. Known desiccants include activated alumina, calcium chloride, silica gel, or zinc chloride. 
     Clumping of the product produced by the process of the present invention is desirous so as to facilitate removal of the animal waste from the litter box. If the product clumps when subjected to the moisture in the animal waste, the clump, including the waste and the odor associated therewith, can be easily removed. The clumping properties of the product can be improved by the addition of agents such as natural resins and plant gums. 
     Once the reaction components are introduced into mix-auger  14 , the reactant stream is conveyed by mix-auger  14  and deposited into reaction mixer unit  16 . It is within reaction mixer unit  16  that intimate mixing takes place between the components in the manufacture of a composite particle. 
     Reference is next made to FIG. 2B for a discussion of reaction mixer unit  16 . Reaction mixer unit  16  is a 60′ long reaction chamber in the preferred embodiment. The length of reaction mixer unit  16  is divided into two major phases. The first phase includes subjecting the reactant stream to a thorough mixing/agitation process, and the second phase includes intimate mixing/agitation/shear of the component particles comprising the reactant stream. 
     The length of the reaction mixer unit  16  is set at a 10° incline and powered by motor  17 . The total 60′ length is divided into auger flighting, each flight being 12′ in length. The mixing/agitation phase within reaction mixer unit  16  is accomplished by a 12′ double ribbon auger flighting  22 . The intimate mixing/agitation/shear phase is carried out by cut and fold auger flighting  24 . In the preferred embodiment there are four (4) cut and fold auger flighting segments, each 12′ in length. Reaction mixer unit  16  comprised of its two phases operates at a speed of 60 rpm in order to convey a desired discharge of 19 cubic tons per hour, weighing between 20 pounds per cubic foot and 50 pounds per cubic foot. 
     FIG. 4 is a detailed view of double ribbon auger flighting  22  of FIG.  2 B. As can be seen, double ribbon auger flighting  22  includes an outer ribbon  28  and an inner ribbon  30 . The double ribbon auger flighting  22  acts to convey the reactant stream while providing thorough mixing and agitation of the component particles conveyed there through. 
     Outer ribbon  28  includes a 2″ wide blade with a 12″ inner diameter, while inner ribbon  30  includes a 1″ blade and 9″ outer diameter in the preferred embodiment. Such double ribbon auger configurations are available commercially. Outer ribbon  26  and inner ribbon  28  are mounted on and supported from a 5″ diameter central pipe 32. 
     FIG. 6 depicts double ribbon auger flighting  22  from a cross-section showing outer ribbon  28  and inner ribbon  30  supported from central pipe  32 . The support structure for outer ribbon  28  and inner ribbon  30  are depicted in FIG.  6 . 
     Referring back to FIG. 2B, cut and fold auger flighting  24  provides intimate mixing, shearing, and agitation of the component particles of the reactant stream. The water contained within the cellulose creates an environment to blend the two components along with the sticking/swelling action that is characteristic of sodium bentonite in a process to form an agglomerated particle. 
     FIG. 5 is a detail of cut and fold auger flighting  24  of FIG.  2 B. Cut and fold auger flighting is known commercially to provide intimate mixing, agitation, and particle shear. Cut and fold auger flighting  24  includes a blade  38  on a 5′ center shaft  40 . Screw blade  38  is 16″ in diameter and is notched along its outer circumference. The reactant stream covers a 45% area of screw blade  38  such that 70% of the reactant stream is conveyed and 30% is dropped so as to be worked back into the reactant stream thereby providing the intimate mixing/agitation/shear described herein. The mixing/agitation/shear in the presence of the water contained in the cellulose acts to bind the two component materials as described above. Sodium bentonite is known to swell when absorbing moisture. The water in the cellulose serves the purposes of a transport means to infuse the fibrous material into the porous sodium bentonite particle to provide mechanical cohesion and serves an agglomeration and lubricity function by cementing the particles together. In the event that the volume of water in the cellulose is insufficient to facilitate particle agglomeration, water may be added via water conduit  34  and spray nozzles  36  to provide for sufficient agglomeration. 
     FIG. 7 depicts cut and fold auger flighting  24  in cross-section. Notches  46  and blade  42  allow material in the reactant stream to be dropped and folded back into the reactant stream. The aggressive shape of the cut and fold blades provide for the particle shear. 
     Once the composite particles are manufactured, the reactant stream is conveyed for further processing. A belt conveyor  48  transports the reactant stream to a shaper/mixer  50 . The shaper/mixer  50  shapes the composite particles into generally spheroidal granules. Shaper/mixer  50  is comprised of a truck-mixer, such as a standard cement mixer, mounted on a skid and capable of rotation by rollers  52 . Once the reactant stream reaches the shaper/mixer  50 , the process becomes a batch process in that a batch of composite particles is supplied to shaper/mixer and then rolled therein. Once the step of shaping/mixing is completed, the batch reactant stream is transferred from shaper/mixer  50  through a transfer point  54  and supplied to a conveyor  56  such that the shaped composite particle may be conveyed to surge hopper  58 . Surge hopper  58  acts to shake the agglomerated particles thereby separating adjacent particles to form a granulated mixture of individual composite particles. Surge hopper  58  also acts to control the volume of granulated mixture process through the dryer as shall be next described. As a result, the moisture content of the manufactured composite product is controlled. 
     From surge hopper  58 , the granulated mixture is transferred via a conveyor  60  to a dryer  62 . Reference is next made to FIG.  2 D. Dryer  62  is in a declined orientation so as to assist the flow of the granulated mixture along its length. Dryer  62  may be a rotating dryer, a fluid bed dryer, or a straight air dryer. The dryer  62  illustrated in the drawings for the purpose of exemplification is a rotating dryer having a firing cone  64  at which the temperature is approximately 1600° F.-1700° F. Dryer  62  is rotated by a plurality of rollers, collectively  66 . 
     The granulated mixture is conveyed through dryer  62  and has a residency time of approximately 8 minutes. The exit temperature of the composite mixture is approximately 250° F. The rolling and heating action of dryer  62  accomplishes the purpose of removing moisture from the manufactured particles comprising the granulated mixture. When the composite particles are dried, the particle decreases in size, thus binding tighter the two component materials to create a low dust, absorbent particle that is lighter in weight than an all clay particle of the same volume. 
     Fresh air is then put into dryer  62  through several air intake  68 . An air pump  70  is ducted to a heat exchanger  72  to provide fresh air and evacuate dead air. The dead air is taken off through a heat exchanger/steam vent  74  which is exhausted into an emissions control device (not shown) such as a cyclone for the recovery of aerosolized materials. Thus, all emissions, including vaporized water and any contaminants released therewith are recovered. Heat exchanger  72  is also ducted to fresh air ducts via conduit  76 . A dry granule mixture  78  is thus output from dryer  6  and deposited on a conveyor  80 . 
     Reference is next made to FIG. 2E wherein the dry granule mixture  78  is conveyed by conveyor  80  onto a shaking conveyor  82 . The shaking conveyor  82  functions as a separator for receiving the dry composite particles of the granulized mixture  78  for separation based upon particle size to form piles of segregated product particles. The dry granule mixture is passed over screens of various mesh sizes to segregate the product which is then dispensed into piles through chutes  84 ,  86 ,  88 , and  90 . 
     Referring back to FIG. 2E, particles larger than approximately ½″ are removed from shaking conveyor  82  and deposited in bin  92  through chute  90 . These large particles are transported and recirculated through the process. In the process of the alternative embodiment, the larger particles are again processed through the hammer mill and processed as described above. 
     The particles exiting through chutes  84  pass through a 20 mesh sieve screen and are collected in a first bin  104 . These particles are usually considered too fine and are also efficiently reprocessed and thereby re-manufactured into a useable particle size. Thus, substantially all raw material becomes useful. 
     The remaining particles are preferably divided into two or more groups. The screen sizes utilized to divide these particles may vary, but are generally between 40 mesh, up to 6 mesh. As an example, particles passing through a 12 mesh sieve screen, may be exited through chute  88  into a bin  106 . Larger particles may be passed through an 8 mesh sieve screen and exited through chute  86  into a bin  108 . The particles processed into the bins may then be bagged and shipped for use as a cat litter product. 
     While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiment set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.