Liquid purification or separation – Processes – Treatment by living organism
Reexamination Certificate
2002-02-27
2003-09-23
Smith, Duane (Department: 1724)
Liquid purification or separation
Processes
Treatment by living organism
C210S758000, C210S759000, C210S763000, C210S908000, C588S001000, C525S061000, C528S480000
Reexamination Certificate
active
06623643
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a process for treating an aqueous environment comprising a polymer or a material comprising at least one polymer. In particular, the invention provides a process that is capable of accelerating the degradation of solubilized polymer into environmentally benign products and also substantially prevents the subsequent precipitation and solidification of solubilized polymer from an aqueous environment.
BACKGROUND OF THE INVENTION
During the twentieth century, international treaties, congressional acts, and executive orders have resulted in a number of regulations controlling all aspects of the environment and health and safety practices in the workplace. In particular, the disposal of industrial waste has been heavily regulated. Landfills nationwide have been closed and industry has been forced to turn to using alternatives such as conservation, recycling, fuel blending, deep-well injection and incineration.
A representative example is the medical industry which generates millions of pounds of waste each year. Much of that waste is related to the use of disposable materials, such as personal protective clothing, equipment, and accessories necessary for patient care that become contaminated with bloodborne pathogens and are therefore unsafe for reuse. To prevent the spread of disease, it is imperative, and required by law, that these materials be discarded and not reused.
In addition, the nuclear industry also generates millions of pounds of waste each year. In the nuclear industry, much of the waste is similarly related to the use of disposable materials such as personal protective clothing, bags, mop heads, rags, and other accessories that become contaminated by radioactive material, and are unsafe or impractical for reuse. The waste disposal and landfilling practices of the nuclear industry are highly regulated, and nuclear burial ground space is limited.
Various other industries also generate waste streams with similar characteristics. In seeking alternatives to landfilling and incineration, products have been developed that are water-soluble. Accordingly, these products present a convenient and cost effective alternative to conventional waste disposal means.
A readily available water-soluble polymer is polyvinyl alcohol (PVA). PVA is a tough, whitish polymer that can be formed into strong fabrics, films, tubes, fibers and other molded or extruded articles that are highly resistant to hydrocarbon solvents. While PVA is inherently water-soluble, the degree of solubility can be altered by various means known in the art. PVA is commonly used to make disposable personal equipment, such as garments, apparel, linens, drapes, towels, sponges, gauze, utensils, rags, mops and other useful articles. These articles are often produced from non-woven, woven, knitted or otherwise formed thermoplastic polyvinyl alcohol polymer films, fabrics, and fibers that are water-soluble. However, in addition to the development of PVA, other water-soluble polymer products have recently been developed as well. These materials have physical properties and characteristics very similar to that of PVA and, like PVA, these materials can also be used for manufacturing disposable personal equipment, such as garments, apparel, linens, drapes, towels, sponges, gauze, utensils, rags, mops and other useful articles.
Since the introduction of PVA materials, the practice in industry for disposing of these articles has been simply to solubilize them in hot water and discharge the resulting solution into sanitary sewers and drainage systems. As such, historical practice has involved placing garments, utensils, and other clothing accessories and equipment made of PVA film, fabric or fiber, into large hot water wash tanks in which the material is solubilized and then discharged to sanitary sewers or tank farms for further treatment of other contaminants.
It has recently been discovered that solubilized PVA material does not invariably remain in solution, as was once believed. Instead, the introduction of air or oxygen often present in turbulent fluid transport can initiate the precipitation and resolidification of the solubilized PVA material. The precipitated PVA material thus forms a hardened gelled like substance. This gelled substance can further dehydrate to form insoluble plastic plugs that can aggregate in pipes and drainage systems in close proximity to where the solutions were discharged. As a result, costly remediation actions have been, and may continue to be required in order to restore damaged piping, sewer lines, ditches and other means of waste stream conveyance.
It is unknown exactly how much precipitated PVA material may have been delivered to sanitary treatment facilities worldwide. However, under certain circumstances it is hypothesized that this resolidification phenomenon could potentially have a negative impact on many of the industries that relied upon the use of water-soluble PVA products. The failure to devise a viable treatment option could force numerous industries to once again rely on costly landfill and incineration alternatives. Therefore, the need exists to develop a process and system for treating solid waste comprising PVA or other water-soluble polymer materials that eliminates subsequent downstream precipitation of the polymer material from the liquid waste stream.
SUMMARY OF THE INVENTION
Among other aspects, the present invention is based on the surprising discovery that the use of a degradation-enhancing reactant or a precursor thereof, e.g., an oxidizing agent, can effectively increase the rate of reaction for the degradation of polymers in an aqueous environment. To this end, the present invention provides a process, which comprises contacting a polymer and a degradation-enhancing reactant in an aqueous environment under conditions effective to provide one or more degradation products. Preferably, at least one degradation product is a unique and different compound from the polymer and will therefore exhibit different physical and chemical characteristics such that it is no longer susceptible to precipitation from an aqueous environment.
Moreover, the present invention relates to a chemical process for reacting, degrading or otherwise breaking down a polymer in an aqueous environment such that it advantageously prevents, or at least substantially reduces, the subsequent precipitation of the solubilized polymer from an aqueous environment. For example, the process includes contacting a solubilized polymer and a degradation-enhancing reactant, within an aqueous environment, and subsequently reacting the polymer under conditions that are effective to provide at least one degradation product from the polymer.
In a first aspect, the present invention provides a process for treating a material comprising at least one polymer wherein a degradation-enhancing reactant and the material are introduced into an aqueous environment. The polymer is then reacted under conditions effective to provide one or more degradation products.
In another aspect, the present invention further provides a process for treating an otherwise provided aqueous environment comprising a material comprising at least one polymer wherein a degradation-enhancing reactant is introduced into the otherwise provided aqueous environment. The polymer is then reacted under conditions effective to provide one or more degradation products.
In still another aspect, the invention provides a process for treating an otherwise provided aqueous environment comprising both a degradation-enhancing reactant and material comprising at least one polymer. Once again, the polymer is reacted under conditions effective to provide at least one degradation product.
In an alternative aspect, the present invention also provides a process for treating an otherwise provided aqueous environment comprising at least one polymer wherein a degradation-enhancing reactant is introduced into the aqueous environment. The polymer is then reacted under conditions effective to provide at least one degrada
Beck Debrah A.
Chisholm Robert D.
Johnston Jordan M.
Lee Baosheng
Steward John B.
Lawrence Frank M.
Merchant & Gould LLC
Microtek Medical Holdings, Inc.
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