Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-09-02
2002-11-12
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S476100, C428S475800, C428S483000
Reexamination Certificate
active
06479116
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 an exterior 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 three (3) layers, one of which layers must be a first exterior 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, another of the requisite three layers must be a second exterior layer comprising a polyester or copolyester, a polyamide, or a polyolefin. The second exterior layer must be autoclavable as defined by the test procedure described herein. The multi-layered structures of the present invention further comprise at least one intermediate tie layer positioned between the first and/or second exterior layers and that provides adequate adhesion to prevent delamination or separation of the layers of the multi-layered structure. The tie layer comprises preferably an alpha-olefin/unsaturated monomer copolymer. More preferably, the alpha-olefin/unsaturated monomer copolymer has a melt flow rate greater than 0.25 g/10 min, more preferably 1.0-10 g/10 min and a melting peak temperature of at least 65° C., more preferably 65-150° C.
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 three (3) layers, one of which layers must be a first exterior 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, another of the requisite three layers must be a second exterior layer comprising a polyester or copolyester, a polyamide, or a polyolefin. The second exterior layer must be autoclavable as defined by the test procedure described herein. The multi-layered structures of the present invention further comprise at least one intermediate tie layer positioned between the first and/or second exterior layers and that provides adequate adhesion to prevent delamination or separation of the layers of the multi-layered structures. The tie layer comprises preferably an alpha-olefin/unsaturated monomer copolymer preferably having a melt flow rate greater than 0.25 g/10 min, more preferably 1.0-10 g/10 min and a melting peak temperature of at least 65° C., more preferably 65°-150° C.
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 3 mils to about 20 mils, for packaging materials. The thickness of each of the layers of the multi-layer film or sheet can vary depending on the desired properties of the film or sheet.
Where it is desired that the multi-layered structures of the present invention be autoclavable, as determined by the test procedure herein, it is preferred that the second exterior layer comprising of a polyester or copolyester, polyamide, or polyolefin have a thickness of at least about 1 mil. In a further preferred embodiment, the second exterior layer comprises a copolyester having a thickness of at least about 1 mil.
The multi-layered structures of the present invention comprise a first exterior layer that comprises an ethylene/alpha-olefin copolymer having a density of less than 0.916 g/cc and a melting peak temperature 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 exterior 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, and 5-vinyl-2-norbornene. 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 at least one or more intermediate tie layer(s) of the multi-layered structures is positioned between, and adheres to, the first exterior layer and/or the second exterior layer. The tie layer(s) provides adequate adhesion to prevent delamination or separation of the layers of the multi-layered structures, especially during autoclaving conditions. In addition, certain of the intermediate layers may provide enhanced gas or moisture barrier properties. The tie layer(s) is preferably an alpha-olefin/unsaturated monomer copolymer having a melt flow rate of greater than 0.25 g/10 min, preferably 1.0 to 10 g/10 min, and a melting peak temperature of at least 65° C. preferably 65-150° C. In a preferred embodiment, the alpha-olefin/unsaturated monomer copolymer comprises from about 0.1 to about 30 weight percent of at least one, or more, unsaturated monomer(s), based upon the weight of the copolymer, that is copolymerizable with the alpha-olefin component of the copolymer. Any alpha-olefin and/or any unsaturated monomer copolymerizable therewith may be used in preparing the copolymer to be used as the tie layer. Also suitable for use herein as a tie layer is an ethylene-vinyl alcohol copolymer and/or an ethylene-vinyl alcohol interpolymer.
Suitable for use in preparing the alpha-olefin/unsaturated monomer copolymer to be used as a tie layer herein are alpha-olef
Greer Kathleen Diane
Rhein James Edward
Small, Jr. James Douglas
Vanderbilt Jeffrey James
Eastman Chemical Company
Graves, Jr. Bernard J.
Nolan Sandra M.
Tubach Cheryl J.
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