Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-09-02
2004-01-27
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S034100, C428S034300, C428S035200, C428S036910
Reexamination Certificate
active
06682793
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to multi-layered structures that may be autoclavable and are particularly suitable for use as medical packaging. More particularly, structures such as the multi-layered films or sheets include a layer comprising an ethylene copolymer having a density of less than 0.916 g/cc and a melting peak temperature greater than 118° C.
BACKGROUND OF THE INVENTION
Multi-layered structures are useful in forming packages, containers, or other articles for use in the medical and pharmaceutical industries. The structures may be in the form of films, sheets, tubing, profiles of different geometry, and the like, and are typically formed by coextrusion. Certain properties are desirable for such structures including clarity, toughness over a wide temperature range, retention of properties after autoclave sterilization, resistance to chemicals, and low water vapor transmission rates. Additionally, structures having flexibility and low seal initiation temperatures are particularly useful in producing packages and containers for parenteral solutions, plasma, drugs, nutrition products, and other medical and pharmaceutical products. Reference to such multi-layered structures is found in many patents, such as, for example, U.S. Pat. Nos. 4,643,926; 4,803,102; 4,939,009; 4,910,085; 4,948,643; 4,978,579; 5,484,654; 5,486,387; 5,532,053; 5,681,627; 5,686,527; 5,695,840; and others.
SUMMARY OF THE INVENTION
There are provided improved, multi-layered structures that may be autoclavable as defined by the test procedure herein, and are useful, particularly, for packaging, specifically medical packaging. The multi-layered structures comprise at least two (2) layers, one of which layers must be a first layer comprising an ethylene/alpha-olefin copolymer, as defined hereinafter in more detail, characterized by having a density of less than 0.916 g/cc and a melting peak temperature greater than 118° C. In the multi-layered structures of the present invention, the second layer comprises a polyolefin, particularly a propylene homopolymer or a propylene/alpha-olefin copolymer. When utilizing the multi-layered structures of the present invention, the necessity for using an adhesive layer or tie layer is eliminated.
DETAILED DESCRIPTION OF THE INVENTION
There are provided improved, multi-layered structures that may be autoclavable as defined by the test procedure herein, and are useful, particularly, for packaging, specifically medical packaging. The multi-layered structures comprise at least two (2) layers, one of which layers must be a first layer comprising an ethylene/alpha-olefin copolymer, as defined hereinafter in more detail, characterized by having a density of less than 0.916 g/cc and a melting point greater than 118° C. In the multi-layered structure of the present invention, the second layer comprises a polyolefin, preferably a propylene homopolymer or a propylene/alpha-olefin copolymer that is autoclavable as defined by the test procedure described herein.
Where the structure is a film or sheet, the multi-layered film or sheet of the invention can have a total thickness ranging from about 2 mils to about 50 mils. The preferred thickness of the film or sheet ranges from about 2 mils to about 20 mils, for packaging materials. The thickness of each of the layers of the multi-layered film or sheet can vary depending on the desired properties of the film or sheet. Where it is desired that the multi-layered structure of the present invention be autoclavable as determined by the test procedure herein, it is preferred that the second polyolefin layer have a thickness of at least about 1 mil.
The multi-layered films of the present invention comprise a first layer that comprises an ethylene/alpha-olefin copolymer having a density of less than 0.916 g/cc and a melting point greater than 118° C. It is preferred that the density of the ethylene/alpha-olefin copolymer range from about 0.86 to less than 0.916 g/cc. Moreover, it is preferred that the melting peak temperature of the ethylene/alpha-olefin copolymer range from greater than 118° C. to about 130° C., more preferably from about 121° C. to about 124° C.
The ethylene/alpha-olefin copolymer of the first layer may be any interpolymer of ethylene, including copolymers, terpolymers, and the like, of ethylene and at least one or more other alpha-olefins wherein the ethylene content is at least about 50% by weight of the total monomers involved. The alpha-olefins, for example, may contain from 3 to 16 carbon atoms. Exemplary alpha-olefins that may be utilized herein are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene and the like. Also utilizable herein are polyenes such as 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene, 5-vinyl-2-norbomene. In a preferred embodiment, the ethylene/alpha-olefin copolymer comprises from about 8 to about 30 weight percent of alpha-olefin, and, more preferably, from about 10 to about 15 weight percent of alpha-olefin based on the copolymer. Further, in a preferred embodiment, the alpha-olefin of the ethylene/alpha-olefin copolymer has from 3 to about 12 carbon atoms.
The multi-layered film of the present invention comprises a second layer. The second layer comprises a polyolefin, preferably propylene homopolymer or a propylene/alpha-olefin copolymer. The propylene/alpha-olefin copolymer comprises preferably from about 70 to about 99.5 weight percent propylene and from about 0.5 to about 30 weight percent alpha-olefin. More preferably, the propylene/alpha-olefin copolymer comprises from about 0.5 to about 10 weight percent alpha-olefin, and more preferably, from about 0.5 to about 6 weight percent alpha-olefin, based on the copolymer. Suitable for use in the propylene/alpha-olefin copolymers herein are alpha-olefins having from 2 to about 12 carbon atoms, preferably from 2 to about 6 carbon atoms. Exemplary alpha-olefins that may be utilized herein are ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene and the like. Preferred for use as a copolymer for the second layer is a propylene/ethylene copolymer.
Further exemplary of polyolefins suitable for use herein are:
1. Ethylene-based Polymers Such as:
A) Ethylene homopolymers including high density polyethylene (HDPE) and low density polyethylene (LDPE)
B) Ethylene interpolymers including copolymers, terpolymers, and the like, of ethylene and at least one or more other olefins wherein the ethylene content is at least about 50% by weight of the total monomers involved. Preferably the olefins are alpha-olefins. The olefins, for example, may contain from 3 to 16 carbon atoms. Exemplary olefins that may be utilized herein are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene and the like. Also utilizable herein are polyenes such as 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene, 5-vinyl-2-norbornene, and olefins formed in situ in the polymerization medium. When olefins are formed in situ in the polymerization medium, the formation of ethylene/olefin interpolymers containing long chain branching may occur.
C) Ethylene-vinyl aromatic interpolymers
Including ethylene-styrene interpolymers
D) Copolymers of ethylene with vinyl acetate, methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacryclate, carbon monoxide.
2. Isotactic Propylene-based Polymers:
A) Polypropylene homopolymer
B) Propylene-based interpolymers including copolymers, terpolymers, and the like, of propylene and at least one or more other olefins wherein the propylene content is at least about 50% by weight of the total monomers involved. Preferably the olefins are alpha-olefins. The olefins, for example, may contain from 2 to 16 carbon atoms. Exemplary olefins that may be utilized herein are ethylene, 1-butene
Greer Kathleen Diane
Rhein James Edward
Small, Jr. James Douglas
Vanderbilt Jeffrey James
Boshears B. L.
Eastman Chemical Company
Graves Bernie
Patterson Marc
Pyon Harold
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