Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-08-02
2002-09-24
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06455620
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polymers containing compounds capable of removing oxygen from the materials with which the polymer comes in contact.
BACKGROUND OF THE INVENTION
There are many products, particularly foods and beverages, which are sensitive to oxygen and suffer significant deterioration upon exposure to very low levels of oxygen. To extend the lifetime of oxygen sensitive products such as beer and fruit drinks there are many commercial containers that incorporate oxygen barriers and/or oxygen absorbers (scavengers). In these designs, an oxygen barrier is used to effectively reduce the permeation of oxygen into the package. For extremely sensitive products an oxygen absorber is used to chemically react with any oxygen permeating into the package or any oxygen trapped in the headspace during filling. Through careful design, the use of oxygen barrier and/or scavenger materials results in the creation and maintenance of extremely low oxygen levels within the container.
A polymeric material that is commonly used in packaging applications is polyethylene terephthalate or PET. This material has a number of valuable properties for packaging but lacks sufficient gas barrier for some applications. For example, although PET has adequate oxygen barrier properties for products which are relatively oxygen-insensitive such as carbonated soft drinks, its oxygen permeability limits its use in packaging for beer, fruit juices, other citrus products, tomato based products and aseptically packed meat. Multilayer structures have been proposed to improve PET's gas barrier. Polymers that have excellent oxygen barrier (passive barrier) or scavenging properties (active barrier) are combined with PET to produce a layered structure consisting of the individual polymers. The methods disclosed for producing multilayer structures include co-injection, co-extrusion, lamination, and coating. Polymers which have been used to provide oxygen barrier include EVOH, PVOH, PVDC and polyamides such as m-xylylene diamine adipate. Blends of barrier polymers with PET have also been taught as a method to improve the oxygen barrier of packages. Some examples of polymers that have been blended with PET are PEN, EVOH, m-xylylene diamine adipate, liquid crystal polymers, and Mitsui's B010.
Oxygen scavengers which have been disclosed to be useful include polymers capable of undergoing metal catalyzed oxidation such as m-xylylene diamine adipate or polybutadiene, oxidizable metals such as iron, or reduced anthraquinones. Oxygen absorbers that have been blended into PET include m-xylylene diamine adipate with a cobalt catalyst as well as modified polybutadienes incorporated through a reactive extruder.
Examples of scavengers incorporated into polyesters are known. For example, WO 98/12127 and WO 98/12244 disclose blends of PET containing either oxidizable metals or modified polybutadienes. However, these materials have no passive barrier and are hazy. Further, these blends introduce undesirable contaminants into existing PET recycle streams.
U.S. Pat. No. 5,2736,616 disclose oxygen scavengers containing certain pendant ether moieties. However the general class of polyether compounds of the present invention are not disclosed.
Neiman and Goglev (Vysokomol. Soyed. A9, No. 10, pp.2083-2093, 1967; as translated in Polymer Science U.S.S.R., vol. 9, pp.2351-2363, 1967, pub. 1968) disclose that oxygen is taken up during the thermal degradation of poly(propylene glycol) and poly(ethylene glycol) above their melting point. However, they do not disclose oxygen up-take in blends or copolymers of polyethers with other polymers. Furthermore, they do not disclose scavenging in the solid state or at room temperature. They are also silent on the use of transition metal catalyst or photoinitiators.
WO 99/48963 discloses oxygen scavenging compounds which include a polymer or oligomer having at least one cyclohexene group or functionality and a transition metal compound as a catalyst. Other oxygen scavenging compounds are not disclosed.
WO 99/15433 discloses oxygen scavenging polymeric substances which contain compounds which are devoid of ethylenic unsaturation and specifically a polyether oligomer (specifically polypropylene oxide) and a transition metal catalyst. Other polyethers are not disclosed to be effective scavengers when incorporated into a polymer with a catalyst.
Thus, there are several oxygen barrier and scavenging technologies known in the art, but none fully address the needs for an optimum package.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to oxygen scavenging systems comprising an oxidation catalyst and at least one polyether selected from the group consisting of poly(alkylene glycol)s, copolymers of poly(alkylene glycol)s and blends containing poly(alkylene glycol)s. The oxygen scavenging systems of the present invention are suitable for incorporating into articles containing oxygen-sensitive products. The present invention further relates to novel compositions comprising: a poly(alkylene glycol), an oxidation catalyst and a thermoplastic polymer.
DETAILED DESCRIPTION
The present invention relates to oxygen scavenging systems comprising an oxidation catalyst and at least one polyether selected from the group consisting of unsubstituted poly(alkylene glycol)s having alkylene chains of 1 to 3 carbon atoms, substituted or unsubstituted poly(alkylene glycol)s having alkylene chains of at least 4 carbon atoms, copolymers of poly(alkylene glycol)s and blends containing poly(alkylene glycol)s. The oxygen scavenging systems of the present invention can be incorporated into a variety of polymers. The oxygen scavenging systems of the present invention act as an active oxygen barrier by scavenging oxygen from whatever is in contact with the article containing the oxygen scavenging system.
Polymers comprising the oxygen scavenging systems of the present invention can be used as layers in rigid containers, flexible film and in thermoformed, foamed, shaped or extruded articles and the like for packaging oxygen-sensitive products or use in oxygen sensitive environments. The articles containing the composition limit oxygen exposure by acting as an active oxygen barrier and/or a means for scavenging oxygen from within the article.
Suitable articles include, but are not limited to, film, sheet, tubing, profiles, pipes, fiber, container preforms, blow molded articles such as rigid containers, thermoformed articles, flexible bags and the like and combinations thereof Typical rigid or semi-rigid articles can be formed from plastic, paper or cardboard cartons or bottles such as juice containers, soft drink containers, beer containers, soup containers, milk containers, thermoformed trays or cups. In addition, the walls of such articles often comprise multiple layers of materials. This invention can be used in one, some, or all of those layers.
The first component of the oxygen scavenging systems of the present invention is at least one polyether. Suitable polyethers include unsubstituted poly(alkylene glycol)s having alkylene chains of 1 to 3 carbon atoms, substituted or unsubstituted poly(alkylene glycol)s having alkylene chains of at least 4 carbon atoms and preferably less than 10 carbon atoms. The poly(alkylene glycol)s can be obtained by methods well known in the art. Examples of poly(alkylene glycol)s include poly(ethylene glycol), poly(trimethylene glycol), poly(tetramethylene glycol), poly(pentamethylene glycol), poly(hexamethylene glycol), poly(heptamethylene glycol), and poly(octamethylene glycol). Preferred poly(alkylene glycols) include poly(ethylene glycol) and poly(tetramethylene glycol). Almost any number of repeating units may be used, however, for ease of handling and mixing poly(alkylene glycols) having number average molecular weights in the range of about 500 to about 5,000 are preferred. Suitable poly(alkylene glycol)s may have a variety of suitable end groups, including, but not limited to hydroxyl, epoxy, methyl and the like. Preferred end groups include meth
Clauberg Horst
Cyr Michael John
Falling Stephen Neal
Rogers Martin Emerson
Stewart Mark Edward
Carrier, Esq. Michael K.
Eastman Chemical Company
Graves, Jr. Esq. Bernard J.
Michl Paul R.
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