Restoration of contaminated polymer articles

Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...

Reexamination Certificate

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C134S010000, C134S013000, C134S019000, C134S026000, C134S034000, C134S035000, C134S036000, C134S030000, C134S040000, C134S042000

Reexamination Certificate

active

06682604

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods of restoring a contaminated polymer article.
BACKGROUND OF THE INVENTION
Polymer articles are used in numerous applications, including engineering applications. Such engineering applications include, for example, automotive parts, tools, and aircraft parts. Most of the polymer articles used in engineering applications have polar groups. Examples of such engineering polymers include nylons, polyaryletherketones, polyetherimides, and polycarbonates. Due to the presence of the polar groups, polar solvents, such as water, affect the polymer articles. For example, the polymer articles form hydrogen bonds with water, due to which absorption of water takes place. Absorption of water causes numerous effects including: (1) temporary loss of physical properties, such as tensile strength and chemical resistance; (2) dimensional change or swelling of chains; (3) fading and discoloration; and (4) cracking of the polymer article.
Such polymer articles are typically cleaned in a barrel tumbler with steel media and a detergent in water. However, such cleaning methods are unable to restore the color of the faded polymer articles and, in fact, exacerbate the above-mentioned problems, e.g., leading to further fading, discoloration, and degradation of physical properties. As a result, remanufacture and recycling of the polymer articles is limited due to improperly cleaned parts.
SUMMARY OF THE INVENTION
The present invention relates to a method of restoring a contaminated polymer article. This method involves contacting a contaminated polymer article with an oil which is not a plasticizer under conditions effective to remove substantially all contaminants present on the polymer article to produce a restored polymer article.
The present invention also relates to a method of restoring a contaminated polymer article including contacting a contaminated polymer article with an oil which is not a plasticizer under conditions effective to remove substantially all contaminants present on the polymer article to produce a restored polymer article, wherein the oil which is not a plasticizer is heated to from about 10° C. to about 5° C. below the maximum service temperature of the polymer article.
Another aspect of the present invention is a method of restoring a contaminated polymer article including contacting a contaminated polymer article with a soybean oil which is not a plasticizer under conditions effective to remove substantially all contaminants present on the polymer article to produce a restored polymer article.
The use of an oil to restore a contaminated polymer article in the method of the present invention allows the elimination of contaminants on the article, in particular, polar polymer articles, without fading, discoloration, or adversely affecting the physical properties of the polymer article. More specifically, by using an oil which is not a plasticizer in the method of the present invention, any grime or grease on the polymer article will be dissolved by the oil, without dissolving the polymer article itself. In addition, the oil may be rinsed from the polymer article surface, leaving a clean, non-tacky surface.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method of restoring a contaminated polymer article. This method involves contacting a contaminated polymer article with an oil which is not a plasticizer under conditions effective to remove substantially all contaminants present on the polymer article to produce a restored polymer article.
In accordance with the present invention, the polymer article may be polar or non-polar. In one embodiment of the invention, the polymer article is polar. Suitable polymer articles in accordance with the present invention include a polyamide article, a polyimide article, an acetal article, a polycarbonate article, an acrylic article, a fluoropolymer article, a polystyrene article, an acrylonitrilebutadienestyrene article, a polysulfone article, a polyaryletherketone article, and a thermoset polymer article.
There are different types of polyamides or nylons which are suitable polymer articles in accordance with the present invention, such as PA-66, PA-9, PA-11, and PA-12. The maximum service temperature for such nylons is about 75° C. They have excellent flexibility and impact resistance, but water absorption is a problem. They can be used for making gears, clothes, fuel nozzles, and automotive parts. Some of the nylons can work at high temperature.
Suitable polyimide articles include polyetherimide and polyimide.
Suitable acetal articles include polyoxomethyl and polyphenyloxide. Acetal articles exhibit excellent strength, stiffness, surface hardness, barrier properties, and solvent resistance due to high levels of crystallinity. The maximum service temperature for such acetal articles is about 100° C.
Suitable polycarbonate articles include polycarbonates and polycarbonate acrylonitrilebutadienestyrene alloys. Polycarbonates are known for their excellent clarity. They have excellent mechanical properties, but absorb water at high temperatures. They are sensitive to aromatic, chlorinated solvents and have poor resistance to alkali solutions.
Suitable acrylic articles include polymethylmethacrylate (PMMA). PMMA has good coloring properties and its UV stability is good. In repeated hot water washes PMMA tends to craze.
Suitable fluoropolymers include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF). Fluoropolymers have very good chemical properties and are used in many engineering applications, such as gears and high value electrical goods.
Suitable polystyrene articles include polystyrene, high impact polystyrene, acrylonitrilebutadienestyrene, acrylic-styrene acrylonitrile, styrene butadiene copolymers, and olefin-modified styrene acrylonitrile resins.
Suitable polysulfone articles include polyethersulfone and polysulfone. Suitable polyaryletherketone articles include polyetheretherketone and polyetherketone. These polymers are very stable and used in the aerospace industry. These materials have excellent impact and chemical resistance and they are used extensively as a resin in carbon fiber reinforced composites for challenging applications.
Suitable thermoset polymer articles include phenol formaldehyde, melamine, epoxy resins, and polyurea. The main difference between thermoplastic and thermnoset polymers is that a thermoset polymer cannot be melted again—i.e., it is a one time use.
Other suitable polymer articles include, but are not limited to, bismaleimides, cellulocs, fluoroplastics, ketone based polymers, melamine formaldehyde, phenolics, polyamide-imides, polyarylate, polybenzimidazole, polybutylene, polyester thermoplastics, such as liquid crystal polymers, polybutylene terephthalate, polycyclohexylenedimethylene terephthalate, and polyethylene terephthalate, polyester thermosets, polyethylene, polymethylpentene, polyphenylenes, such as polyphenylene oxide and polyphenylene sulfide, polyphthalamide, polypropylene, polyurethanes, silicon, thermoplastic elastomers, and vinyl based resins, such as polyvinylchloride, chlorinated polyvinylchloride, and vinylidene chloride.
As used herein, a contaminated polymer article is a polymer article as described above including one or more contaminants on at least a portion of its surface. Such contaminants include grease, petroleum, and dirt.
In accordance with the present invention, the contaminated polymer article is contacted with an oil which is not a plasticizer under conditions effective to remove substantially all contaminants present on the polymer article to produce a restored polymer article. As used herein, a plasticizer is a chemical solvent that is capable of dissolving the polymer article to some extent. Thus, as used herein, an oil which is not a plasticizer will not dissolve the polymer article, however the oil will dissolve contaminants present on the polymer article. The oil which is not a plasticizer is typically non-polar, however, the oil may also be polar. Suitable oils inc

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