Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-03-30
2002-11-19
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S125000, C523S126000, C523S128000
Reexamination Certificate
active
06482872
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for preparing a polymer component that contain one or more degradants to facilitate degradation of the polymer component.
BACKGROUND ART
The use of plastics has given rise to improved methods of packaging goods. For example, polyethylene and polypropylene plastic films, bags, bottles, Styrofoam cups, blister packages, and the like provide stable, relatively unbreakable, chemically resistant light weight packaging. Conventional plastics used for packaging include, for example, polyethylene, polypropylene, polystyrene, polyethylene terphthalate, and polyvinyl chloride. Plastics have also found wide spread use in other disposable products such as, for example, disposable personal care products such as diapers, disposable work garments, and other disposable garments. The many advantages of plastics has lead to their increased usage in a variety of products. This increased usage, however, has created a serious environmental problem, since the plastic must be disposed of after it is used. As a result of the stability and durability of plastics, however, they tend to remain in our environment without decomposing after disposal. It has been estimated that over 50 percent of the annual tonnage of all manufactured synthetic polymers are applied as packaging materials and that 90 percent of this ends up as a component of urban garbage. It has also been estimated that recalcitrant plastic accumulates in our environment at a rate of 25 million tons per year.
Burning of plastics is an unsatisfactory disposal solution, since this tends to damage incinerators due to the large quantity of heat generated during combustion and the adverse effects from the discharged smoke that adds to air pollution and destruction of the ozone layer. Similarly plastics, unlike paper and cardboard, are not readily destroyed by natural means, such as degradation by micro-organisms, which degrade most other forms of organic matter and return such matter to the biological life cycle. Thus, burial in a waste site is also not an effective means of disposal. The resulting accumulation of plastics in our environment has tended to result in landfills becoming filled to capacity; unsightly litter destroying the scenery and landscape; and destruction of the living environment for marine life and other forms of life.
In an effort to resolve the environmental problem, additives have been combined in certain ways with the polymeric compositions used to make plastics to increase the rate at which the plastic is degraded to environmentally friendly compounds. These additives, commonly called degradants, increase the rate of degradation of the plastic by increasing the rate of photodegradation, biological degradation, and/or chemical degradation.
Photodegradation involves the natural tendency for most polymers to undergo gradual reaction with atmospheric oxygen, particularly in the presence of light. Typically, a photosensitizing agent is employed in order to accelerate this natural tendency. The photosensitizing additive absorbs ultraviolet light (e.g., from sunlight) and the additive, in the photo-excited state, then undergoes a chemical reaction that leads to the generation of free radicals, which leads to an auto-oxidation and eventual disintegration of the plastic. Photodegradation has generally involved two technological approaches: (a) introduction of photosensitive functional group into the polymer; or (b) adding of photosensitive reagents to the polymer. A copolymer of ethylene and carbon monoxide, such as those commercially available from Dow Chemical Co., DuPont Co., Union Carbide Co., and Bayer Co., or the vinyl ketone copolymer commercially available from Ecoplastics Co. are examples of introducing a photosensitive functional group into the polymer. The approach of adding photosensitive reagents is exemplified by the commercially available polymers of Ampacet Co. and Ideamasters Co. that contain an added metal complex, such as that developed by Scott-Gilead Co. as disclosed in U.S. Pat. No. 4,360,606. The thermal oxidation that follows the initial photochemical initiation step may be accelerated by the addition of auto-oxidizable substances. The auto-oxidizable substances may also increase the rate or efficiency of the photochemical step.
Biodegradable plastics developed so far include, as the degradable material, polymeric products of microorganisms such as poly-&bgr;-hydroxybutylate, polymers synthesized from biochemicals produced by microorganisms, chemically synthesized aliphatic polyesters, or naturally synthesized polymers, such as starch or chitin.
U.S. Pat. No. 3,840,512 discloses thermoplastic compositions containing a metal salt of a fatty acid and a free carboxylic acid. Compression molded films which included both the metal salt of a fatty acid and a free carboxylic acid exhibited shorter times before the film became embrittled when exposed to light than films containing only the metal prodegradant.
U.S. Pat. No. 3,941,759 discloses a degradable plastic containing an organic photosensitizer and at least one organic derivative of a transition metal. Degradation is initiated by a photo-oxidative reaction of the photosensitizer and is sustained by the organic derivative of a transition metal. The plastic will continue to oxidize in the dark after an initial exposure to ultraviolet light.
U.S. Pat. No. 3,994,855 discloses thermoplastic polymers or copolymers of &agr;-olefins containing one or more transition metals. The polymer compositions are degraded under the action of sunlight and/or ultraviolet light and may also be subject to thermal degradation.
U.S. Pat. No. 4,101,720 discloses a degradable plastic composition that includes an organic polymeric material having dispersed therein at least one organic derivative of a transition metal and at least one readily autoxidizable organic material.
U.S. Pat. No. 4,156,666 discloses a degradable polyolefin resin comprising a polyolefin, a fatty acid or ester of a fatty acid and a monohydric aliphatic alcohol, and optionally an inorganic filler. The resins are molding resins and degrade when subjected to sunlight.
U.S. Pat. No. 4,256,851 discloses a degradable plastic composition comprising an organic polymeric material having dispersed therein at least one ethylenically unsaturated alcohol or ethylenically unsaturated ester derived therefrom as a readily autoxidizable substance.
U.S. Pat. No. 4,360,606 discloses a plastic composition containing an organic photosensitizer and at least one readily autoxidizable organic substance. Exposure of the polymeric material to an artificial source of light or sunlight initiates a chemical degradation process. The initial photochemical reaction is followed by susbequent reactions that are essentially thermal (i.e., non-photochemical). The readily autoxidizable substance accelerates the thermal autoxidation step that follows the initial photochemical step.
U.S. Pat. No. 4,461,853 discloses a controllably degradable vinyl polymer composition that contains a complex of two different metals. A combination of iron and nickel compounds provides enhanced photodegradation of the polymer composition.
U.S. Pat. No. 4,476,255 discloses a plastic composition containing a photosensitizer. Exposure of the plastic composition to natural sunlight or artificial sources of ultraviolet light initiates degradation of the composition.
U.S. Pat. No. 4,517,318 discloses a photodegradable styrene resin that comprises a styrene resin and at least one photodegradable agent selected from benzophenone, anthroquinone, fluorene, xanthone, phenylalkyl ketones, phenacyl halides, and derivatives of these compounds and optionally at least one photodegradable accelerator.
U.S. Pat. No. 4,931,488 discloses thermoplastic polymer compositions that include a biodegradable substance, such as starch; a transition metal compound; and a fatty acid or ester of a fatty acid. The compositions may further include one or more other transition metal compounds to catalyze degradation of the polymer. The polymer com
Barkume Anthony R
Programmable Materials, Inc.
Szekely Peter
LandOfFree
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