Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-11-03
2002-10-08
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, C528S483000
Reexamination Certificate
active
06462142
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
The present invention relates to a process and an apparatus for improving the surface properties of polymers, such as improving adhesion or improving wicking, i.e., conveying liquid by capillary action.
Existing technologies for surface treating polymers include abrasive buffing, etching, solvent washing, chlorinated polyolefin (CPO) treatment, exposure to corona or glow discharge treatments, and plasma or flame treatments. Fluorination and oxyfluorination technologies also exist. Each of these technologies has its own shortcomings.
Subjecting a polymer surface to abrasive buffing and etching (solvent or otherwise) makes it difficult to obtain a smooth and lustrous paint coating on the polymer surface thereafter. Solvent washing and CPO treatments generate large volumes of waste by-products and use solvents which contribute to volatile organic compound emissions if not captured and destroyed. Corona and glow discharge treatments tend to age and become ineffective with time. Plasma and flame treatments do not provide a homogeneous surface modification on a convoluted part.
The disadvantages of present fluorination and oxyfluorination processes having surface modification as an objective are manifest. Some of these processes need substantial apparatus because they entail moving the fluorine gas from a holding chamber to a reaction chamber and back again. Substantial apparatus may also be required because these processes use very high concentrations of fluorine or relatively long treatment cycles during which pressure is increased gradually. As more apparatus is required, costs increase. Processes utilizing fluorine pose a threat to safety because fluorine is a highly toxic, highly corrosive, irritating gas. Any process that uses relatively high temperatures, pressure, concentrations and/or volumes of fluorine is hazardous due to an increased possibility of fire or leakage. Finally, these processes raise the pollution factor because of the amount of fluorine and/or fluorine by-products, such as hydrogen fluoride, which must be disposed of after the completion of the fluorination process.
Numerous attempts have been made to improve the surface properties of polymers. For example, U.S. Pat. No. 5,654,378 (Dehennau et al) discloses articles including polyolefins which are surface treated and printed with inks, such as PVC inks. The article surface includes fluorine and oxygen in concentrations such that the oxygen/carbon atom ratio at a depth of 1.5 nm is at least 0.08 and the fluorine/carbon atom ratio is at least 90% but not more than 290% of the oxygen/carbon atom ratio.
U.S. Pat. No. 5,654,378 also relates to a process for the manufacture of such articles that involves an oxidation stage and a fluorination stage. By example, the patent shows that an ambient temperature, sub-ambient pressure fluorination or fluoroxidation process which exposes a polymer to approximately 20 millibars of F
2
for approximately seven minutes by gradually raising the gas pressure over approximately 5 minutes from 200 millibars to 400 millibars at a rate of 40 millibars per minute for a total fluorine exposure time of approximately fifteen minutes can provide an ink-receptive surface, particularly when the oxygen content on the surface is high.
European Patent Application Publication No. 0-502-303-A1 teaches a process for the treatment of objects with a gas containing fluorine as well as an arrangement for carrying out the process. In particular, the publication teaches the design of fluorination equipment that is arranged to be operated always in a sub-ambient pressure mode with fluorine being recycled. It is silent on the rate of pressurization.
U.S. Pat. No. 4,752,428 (Williams et al) teaches a process for making shaped articles by injecting a thermoplastic or thermoset polymer into a mold cavity in which a concentration of fluorine and oxygen is contained at atmospheric pressure while the polymer is being injected into the mold. The process results in shaped articles having altered physical and chemical characteristics, including improved surface adhesion.
U.S. Pat. No. 4,764,405 (Bauman et al) discloses a method for improving the barrier properties of thermoplastic substrates. A surface of the thermoplastic substrate is contacted with a reactive gas stream having a particular concentration of fluorine and oxygen.
U.S. Pat. No. 4,743,419 (Bierschenk) teaches an on-line film fluorination apparatus cooperative with a continuous polymer film extruding apparatus. In one embodiment, a continuous feed film is introduced into a closed cabinet having guide rollers for directing the film into a housing. The film passes around a roller formed of sintered nickel to enable gaseous impregnation of a surface of the film with a gas flow including fluorine. The gas acts on the exposed face of the film, changing the surface of the polymer film, thereby providing a relatively thick surface upgrading of the film. After exposure to the fluorine, the film passes a closed vacuum container having an open face for drawing off unreacted fluorine for recapture and recycling. The film emerges from the closed cabinet having a modified surface and the cabinet is evacuated with a slight negative pressure.
U.S. Pat. No. 4,484,954 (Tarancon) teaches a process for the halogenation of solid polymeric or metallic material. A halogen is introduced into an evacuated chamber and is recirculated.
U.S. Pat. No. 4,404,256 (Anand et al) relates to low energy fluorinated polyolefin surfaces and to fluorinated polymers produced therewith. This patent teaches plasma fluorinations of surfaces to obtain lightly fluorinated oxygen-free surfaces of less than 200 Angstroms.
U.S. Pat. Nos. 4,296,151 and 4,237,156 (Boultinghouse) each teach treating the surface of a solid article made from a polymer, such as polyolefin or polystyrene, with a fluorine-containing gas to render the article receptive to adhesion.
U.S. Pat. No. 4,142,032 (D'Angelo) teaches a process for achieving significant improvements in the barrier properties of polymeric articles such as films and containers by surface treatment with both fluorine and bromine.
U.S. Pat. No. 4,081 574 (Hawkins et al) discloses an apparatus and process for exposure of articles to reactive gaseous fluids to alter their surface characteristics. The articles are exposed to one or more fluids which are transferred back and forth from a reaction chamber to a holding chamber. As the fluids are transferred, they pass through a trap designed to remove reaction by-products without affecting valuable reactant fluids.. Since the fluids can be transferred under vacuum and the overall reaction can take place at relatively low temperature, the process provides a convenient and safe method for handling reactive fluids. The process is particularly useful for the fluorination of a variety of articles such as plastic containers, aerosol bottles and films to improve their barrier resistance to solvents and gases.
U.S. Pat. No. 4,020,223 (Dixon et al) teaches surface modification of polyolefin and polyacrylonitrile fibers using elemental fluorine and low oxygen blends for improved oil release and moisture transport characteristics.
U.S. Pat. No. 4,009,304 (Dixon et al) teaches a process for improving adhesion of polyester yarn, tire cord or fabric and polyester reinforced rubber goods such as tires. Improved adhesion is achieved by fluorinating the polyester yarn, tire cord or fabric prior to incorporation into the tire or rubber goods.
U.S. Pat. No. 3,988,491 (Dixon et al) discloses a process for improving dye receptivity and soil and stain release properties of fiber-formed materials, such as polyesters and polyamides. The improved properties are achieved by subjecting the fibers to fluorine treatment in the presence of little or no oxygen for brief periods of time.
U.S. Pat. No. 3,413,266 (Saines et al) teaches fluorination of polycarbonate films usi
Henderson Philip Bruce
Hobbs John Peter
Air Products and Chemicals Inc.
Chase Geoffrey L.
Lipman Bernard
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