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Oxygen-scavenging containers having low hazeRelated Patent Categories: Synthetic Resins Or Natural Rubbers -- Part Of The Class 520 Series, Involving Inert Gas, Steam, Nitrogen Gas, Or Carbon Dioxide, Processes Of Preparing A Desired Or Intentional Composition Of At Least One Nonreactant Material And At Least One Solid Polymer Or Specified Intermediate Condensation Product, Or Product Thereof, Adding A Nrm To A Preformed Solid Polymer Or Preformed Specified Intermediate Condensation Product, Composition Thereof; Or Process Of Treating Or Composition Thereof, Dnrm Which Is Other Than Silicon Dioxide, Glass, Titanium Dioxide, Water, Halohydrocarbon, Hydrocarbon, Or Elemental Carbon, Inorganic Compound Devoid Of A Silicon Atom Dnrm, Heavy Metal Atom DnrmOxygen-scavenging containers having low haze description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070100050, Oxygen-scavenging containers having low haze. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE [0001] This application is a continuation of pending application Ser. No. 10/195,385 filed Jul. 16, 2002 which is a continuation in part of Ser. No. 09/916,671, filed on Jul. 26, 2001 which is now U.S. Pat. No. 6,780,916 all of which are incorporated by reference in their entirety. BACKGROUND OF THE INVENTION [0002] Thermoplastic resins such as polyethylene terephthalate (PET) are commonly used to manufacture packaging materials. PET processed under the right conditions produces high strength articles with excellent gas barrier properties. Foods, beverages, and medicines can deteriorate or spoil if exposed to oxygen. To improve shelf life and flavor retention of products such as foods, beverages, and medicines, therefore, the barrier protection provided by PET is often supplemented with additional layers of packaging material or with the addition of oxygen scavengers. [0003] Adding a layer of gas barrier film is known as passive-barrier packaging. Ethylvinyl alcohol (EVOH), Polyvinylidene dichloride (PVDC), and Nylon MXD6, are examples of films commonly used for this purpose due to their excellent oxygen barrier properties. Using distinct layers of differing materials is not preferred, however, because it adds cost to packaging construction and does not reduce the levels of oxygen already present in the package. [0004] Adding oxygen scavengers to the PET resin is known as active-barrier packaging. This approach to protecting oxygen-sensitive products is two-fold; the packaging prevents oxygen from reaching the product from the outside, and also absorbs some of the oxygen present in the container and from within the polymer matrix. In some applications, small packets or sachets containing oxygen scavengers are added to the packaging container and lie next to the food. Sachets are generally limited to solid foods, where the sachet can be readily removed from the foodstuff and not accidentally ingested. Construction of the sachets and the cumbersome nature of their introduction into the package result in increased costs. [0005] One way to overcome the disadvantages of sachets is to incorporate the scavenger directly into the wall of the food package. This can be done by placing the scavenger throughout the scavenger wall or placing the scavenger in a unique layer between many layers of the container sidewall. It should be appreciated that references to the sidewall and wall include the lid and bottom sides of the container. At present the incorporation of the scavenger throughout the container wall is found in non-transparent trays or packaging films where the scavenger is not visible. Virtually any scavenger can be used in this application because the scavenger is not visible. However, containers requiring clarity have heretofore been limited to organic type scavengers that maintain their clarity when placed in a separate layer in the wall of the container. The use of the organic scavenger in a mono-layer or single-layer construction is limited by cost and regulatory constraints due to the nature of the organic scavenger or the by-products of the scavenging reaction. [0006] Contributing to the cost is the logistical problems encountered with the use of organic type scavengers. In most embodiments, a transition metal catalyst is used to activate an oxidizable polymer. A disadvantage of this technique is that the polymer begins reacting with oxygen as soon as the package is made. Consequently, the bottles must be filled immediately. Higher amounts of scavenger are used to compensate for the scavenging capacity lost between the time the bottle is made and when the bottle is filled. [0007] In another technique, UV radiation is used to activate the oxidizable polymer. However, UV activation techniques are relatively expensive, and the initiators are often not regulated for use in food packaging. Packages designed for beers and juices are specifically designed to prevent UV penetration, hence UV activation would not be practical for these containers which block UV. [0008] An alternative to a visually acceptable organic material is to use discrete scavenging particles in the container sidewall, such as reduced metal powders. Reduced iron powder is commonly used for oxygen scavenging in food packages. Iron reacts with the oxygen and forms iron oxide. Most applications also utilize a salt and a moisture absorber as reaction-enhancing agents to increase the effectiveness of the iron powder. Because the reaction usually requires water, the iron scavenging composition remains inactive until the package is filled and the reaction is activated by the water of the packaged contents which migrates into the polymer and contacts the scavenging composition. [0009] The use of scavenging powders in clear packages has previously been limited by aesthetics, particularly haze and color. High loadings of iron powder, on the order of 500-5000 parts per million, are typically required to obtain sufficient oxygen absorption. Conventional wisdom and prior art teaches the practitioner to use the highest amount of scavenging surface area possible so that the efficiency and capacity is increased and the amount of iron added is minimized. In practice, this means a large number of small particles. Unfortunately, previous attempts at preparing resin compositions comprising high levels of small particles of iron for use in clear packages have resulted in packages with poor optical properties. This is particularly true when the resin composition is stretched or oriented to any degree in forming the final article, such as in polyester bottles. Typically, bottles prepared from such resin compositions are translucent. Haze values for these bottles are generally high, and clarity is lacking. [0010] Thus, there remains a need for packaging materials having acceptable visual aspects and comprising activatable oxygen scavenging resin compositions. BRIEF SUMMARY OF THE INVENTION [0011] In general the present invention provides a container comprising an effective amount of oxygen-scavenging particles and having low haze. More specifically, the present invention includes a container having at least one wall, wherein the wall comprises a populated area, and wherein the populated area comprises a film-forming polymer; and a population of particles comprising an effective amount of oxygen-scavenging particles, wherein the number of particles of said population does not exceed a concentration of about [0012] (6.times.10.sup.7 particles/T) per cubic centimeter of polymer wherein T is the thickness of the populated area in mils; and wherein the wall has a transmission Hunter haze of up to about 1 percent per mil of the container wall. [0013] The iron or other oxygen scavenger is present in an amount sufficient to effectively scavenge oxygen and provide longer shelf life for oxygen-sensitive materials. The particle size of the particle population is optimized to provide effective scavenging activity, while reducing haze. DETAILED DESCRIPTION OF THE INVENTION [0014] The present invention is directed to a container and a container wall. The wall includes a populated area comprising a film-forming polymer. Suitable thermoplastic polymers for use in the present invention include any thermoplastic homopolymer or copolymer. Examples of thermoplastic polymers include polyamides, such as nylon 6, nylon 66 and nylon 612, linear polyesters, such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate, branched polyesters, polystyrenes, polycarbonate, polyvinyl chloride, polyvinylidene dichloride, polyacrylamide, polyacrylonitrile, polyvinyl acetate, polyacrylic acid, polyvinyl methyl ether, ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, polyethylene, polypropylene, ethylene-propylene copolymers, poly(1-hexene), poly(4-methyl-1-pentene), poly(1-butene), poly(3-methyl-1-butene), poly(3-phenyl-1-propene) and poly(vinylcyclohexane). Preferably, the thermoplastic polymer used in the present invention comprises a polyester polymer or copolymer. [0015] It will be understood that a film-forming polymer is one that is capable of being made into a film or sheet. The present invention is not, however, limited to films and sheets. The container of the present invention also includes bottle walls, trays, container bases, or lids. The walls of containers such as blown bottles and thermoformed trays can be considered films or sheets that have been formed into the shape of the container, and are therefore also within the scope of the invention. Bases and lids of containers are also considered walls of a container. [0016] Polymers employed in the present invention can be prepared by conventional polymerization procedures well known in the art. The polyester polymers and copolymers may be prepared by melt phase polymerization involving the reaction of a diol with a dicarboxylic acid, or its corresponding diester. Various copolymers resulting from use of multiple diols and diacids may also be used. Polymers containing repeating units of only one chemical composition are homopolymers. Polymers with two or more chemically different repeat units in the same macromolecule are termed copolymers. The diversity of the repeat units depends on the number of different types of monomers present in the initial polymerization reaction. In the case of polyesters, copolymers include reacting one or more diols with a diacid or multiple diacids, and are sometimes referred to as terpolymers. [0017] Suitable dicarboxylic acids include those comprising from about 6 to about 40 carbon atoms. Specific dicarboxylic acids include, but are not limited to, terephthalic acid, isophthalic acid, naphthalene 2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4'-dicarboxylic acid, 1,3-phenylenedioxydiacetic acid, 1,2-phenylenedioxydiacetic acid, 1,4-phenylenedioxydiacetic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and the like. Specific esters include, but are not limited to, phthalic esters and naphthalic diesters. [0018] These acids or esters may be reacted with an aliphatic diol having from about 2 to about 10 carbon atoms, a cycloaliphatic diol having from about 7 to about 14 carbon atoms, an aromatic diol having from about 6 to about 15 carbon atoms, or a glycol ether having from 4 to 10 carbon atoms. Suitable diols include, but are not limited to, 1,4-butenediol, trimethylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, resorcinol, and hydroquinone. [0019] Polyfunctional comonomers can also be used, typically in amounts of from about 0.1 to about 3 mole percent. Suitable comonomers include, but are not limited to, trimellitic anhydride, trimethylopropane, pyromellitic dianhydride (PMDA), and pentaerythritol. Polyester-forming polyacids or polyols can also be used. [0020] One preferred polyester is polyethylene terephthalate (PET) formed from the approximate 1:1 stoichiometric reaction of terephthalic acid, or its ester, with ethylene glycol. Another preferred polyester is polyethylene naphthalate (PEN) formed from the approximate 1:1 to 1:1.6 stoichiometric reaction of naphthalene dicarboxylic acid, or its ester, with ethylene glycol. Yet another preferred polyester is polybutylene terephthalate (PBT). Copolymers of PET, copolymers of PEN, and copolymers of PBT are also preferred. Specific co and terpolymers of interest are PET with combinations of isophthalic acid or its diester, 2,6 naphthalic acid or its diester, and/or cyclohexane dimethanol. [0021] The esterification or polycondensation reaction of the carboxylic acid or ester with glycol typically takes place in the presence of a catalyst. Suitable catalysts include, but are not limited to, antimony oxide, antimony triacetate, antimony ethylene glycolate, organomagnesium, tin oxide, titanium alkoxides, dibutyl tin dilaurate, and germanium oxide. These catalysts may be used in combination with zinc, manganese, or magnesium acetates or benzoates. Catalysts comprising antimony are preferred. Continue reading about Oxygen-scavenging containers having low haze... Full patent description for Oxygen-scavenging containers having low haze Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Oxygen-scavenging containers having low haze patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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