Animal husbandry – Material for absorbing moisture from waste product – Having paper-related component
Reexamination Certificate
1996-01-24
2001-07-17
Colilla, Daniel J. (Department: 2854)
Animal husbandry
Material for absorbing moisture from waste product
Having paper-related component
C119S171000
Reexamination Certificate
active
06260511
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to processes for the preparation of absorbent materials. More particularly, the present invention relates to processes for the preparation of absorbent materials from recycled fiber sludge.
BACKGROUND OF THE INVENTION
Absorbent materials, especially granular absorbent materials, are used for a variety of industrial and household purposes. Typical uses include the absorption of liquids, such as water, oil, grease and solvents, spilled on floors and other surfaces, and as animal litters, such as cat litter.
Conventional granular liquid absorbents usually comprise naturally-occurring organic or inorganic absorbent materials, such as clay, sand, wood chips, sawdust, peanut shells, rice hulls and shredded paper, cardboard and newsprint. Animal litters comprise a special class of granular liquid absorbents and are used to collect animal waste products in households having pets, especially cats. Conventional animal litters typically comprise inert, high surface area materials, such as clay, bentonites and cellulose. Fragrances and odor-controlling agents can be added to some of these materials to improve and/or mask odors.
Conventional absorbent materials, including industrial-grade waste liquid absorbents and animal litters, are disadvantageous in that they generally have low absorbency, and suffer from dusting and disposal problems. Typical prior art absorbent materials can absorb an amount of liquid equal to or less than their own weight. Accordingly, these materials become saturated quickly and must be discarded and replaced frequently. This increases the costs associated with using industrial-grade waste liquid absorbents and animal litters. With particular reference to animal litters, there are also disposal problems since the saturated litters often cling to litter trays and pans. Conventional absorbents also possess high bulk densities, generally from about 36 to about 50 lbs/ft
3
, which creates handling problems for consumers. Conventional litters also tend to adhere to the feet of domestic pets, resulting in the litter being scattered out of the litter box. This creates housekeeping problems. Inorganic absorbents, such as clay absorbents, are also abrasive, and can cause damage to nearby flooring.
There is an increasing need for methods of disposal of fibrous sludge from paper processing plants. In a conventional paper deinking plant, 100 dry tons of waste paper can be processed into about 65 to about 80 dry tons of recycled (reusable) fiber. The remaining 20 to 35 tons of waste paper is unusable, and becomes part of the sludge produced by the deinking plant. This unusable sludge typically contains about 50 to about 70 percent water. Thus, 100 dry tons of waste paper can produce from about 70 to about 120 wet tons of sludge requiring disposal.
Conventional methods for disposing sludge include landfill disposal, land spreading, composting and incineration. Landfill and land spreading sites are being depleted at an alarming rate, and the establishment of new sites is difficult due to environmental concerns. Composting and incineration of sludge also raises environmental concerns. Some innovative sludge disposal techniques include processing the sludge into pellets for fuel or into lightweight aggregates for construction, pyrolysis, gasification, and incorporation into cements. However, these techniques generally require the use of complex methods and expensive equipment.
The incorporation of fiber sludge into animal litters has also been reported. For example, Lowe et al., U.S. Pat. No. 4,721,059 describes animal fillers produced from the waste material obtained during paper manufacture. The methods for making the animal fillers of Lowe et al. suffer from drawbacks in that they require that dewatered fibers be broken down or shredded with a delumper, reduction mill or shredder to a fiber length of 1 to 10 mm, with a fiber length of 1 to 4 mm being preferred. Breaking down or shredding the fibers to a specific fiber length requires additional manufacturing steps and, therefore, increased manufacturing costs.
Cortigene et al., U.S. Pat. No. 4,203,388 describes an animal litter comprising pelleted and dried rejects of a secondary fiber plant. The methods for making animal litters of Cortigene et al. suffer from drawbacks in that they require that the sludge be dewatered to a water content between about 32 and 40%. Dewatering sludge to a water content of 40% and below can be difficult. Moreover, the methods disclosed in the Cortigene et al. patent require that the dewatered sludge cake be cut into small pieces, prior to pelletizing. Dewatering the sludge to a water content of 40% or less and cutting the sludge cake into small pieces requires additional manufacturing steps and, therefore, increased manufacturing costs.
Although processes have been developed for recycling fiber sludge into recycled paper products, these processes have not been widely accepted because of the difficulty associated with controlling the quality of the resulting recycled paper products.
Accordingly, new and/or better absorbent materials, including absorbent materials for use as industrial-grade waste liquid absorbents and household absorbents, such as animal litters, are needed. In addition, new and/or better methods for the use or disposal of fibrous sludge are needed. The present invention is directed to these, as well as other important ends.
SUMMARY OF THE INVENTION
The present invention is directed in part to methods for preparing absorbent materials and the absorbent materials themselves. In one embodiment, there are provided methods for preparing absorbent material which comprise providing non-broken down and uncut recycled fiber sludge having a moisture content of greater than about 40%. The sludge is pelletized to form wet pellets which are subsequently dried.
Another aspect of the present invention relates to methods for preparing absorbent material which comprise providing recycled fiber sludge having a moisture content of greater than about 50% to less than about 70%. The sludge is pelletized to form wet pellets which are subsequently dried.
Yet another aspect of the present invention relates to absorbent material which is prepared by a process comprising providing non-broken down and uncut recycled fiber sludge having a moisture content of greater than about 40%. The sludge is pelletized to form wet pellets which are subsequently dried.
Still another aspect of the present invention relates to absorbent material prepared from recycled fiber sludge. The absorbent material comprises a bulk density of less than about 36 lb/ft
3
and a liquid absorbing capacity of at least about 1.1.
Another aspect of the invention relates to methods of absorbing a liquid which comprise contacting the liquid with an absorbent material. The absorbent material is prepared by a process comprising providing non-broken down and uncut recycled fiber sludge having a moisture content of greater than about 40%. The sludge is pelletized to form wet pellets and the wet pellets are dried.
Highly desirable and unexpected benefits are achieved with embodiments of the present invention. In this connection, the absorbent materials of the present invention possess desirable liquid absorbing capacities. Accordingly, small quantities of the absorbent materials can be used to absorb large volumes of liquid. The desirable liquid absorbing capacity increases the cost-effectiveness of the present absorbent materials. They also do not need to be discarded and substituted with fresh absorbent materials as frequently as conventional absorbent materials. This lessens environmental concerns. In addition, the present invention utilizes recycled fiber sludge as a raw material, the disposal of which is generally included in the overhead costs of the producer. Thus, embodiments of the present invention can be employed to significantly reduce the production costs for absorbent materials.
The present absorbent materials possess low bulk densities, which permits easy handling by consumers. Th
Colilla Daniel J.
Garrison Scott B.
Kimberly--Clark Worldwide, Inc.
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