Patent Application
20060016708
The invention relates to a sterilization bag for medical applications, and to a composite film laminate suitable for producing such a bag.
Many healthcare products, including medical devices and pharmaceutical solutions, are stored until ready for use inside of sealed sterilization bags. Typically, the bags are in the form of a pouch, open along one side for receiving the medical instrument or other medical supply. The bag is then sealed and subjected to sterilization by exposure to gamma irradiation, electron beam, ultraviolet radiation, ethylene oxide, autoclaving, or other sterilization procedures.
In order to withstand the severe conditions of sterilization while providing high moisture barrier properties and long shelf life, sterilization bags this type have traditionally used composite laminate films with a barrier layer of either a metal foil or a metallized film. A disadvantage this type of laminate structure is that the bag is not transparent and therefore does not reveal the contents of the bag. To address this problem, some sterilization bags have provided a small window formed of a transparent barrier material. However, in order to maintain high barrier properties for the bag, the transparent window is kept relatively small in size. It would be desirable for a sterilization bag to have at least one transparent side to more clearly reveal the contents of the bag.
The present invention provides a transparent high barrier laminate material that can be suitably fabricated into sterilization bags, providing the ability to see the contents of the bag. The high barrier properties are achieved by using as the barrier layer a molecularly oriented polychlorotrifluoroethylene (PCTFE) film layer.
The autoclavable sterilization bag of the present invention comprises first and second composite film laminates positioned in opposing relation and sealed to one another to form a pouch. At least the first laminate comprises a heat sealable transparent thermoplastic polymer inner layer forming an inner surface of the laminate and a transparent polymer film outer layer. A transparent barrier layer is located between the inner and outer layers and formed of molecularly oriented polychlorotrifluoroethylene (PCTFE). In advantageous specific embodiments of the invention, the heat sealable transparent thermoplastic polymer inner layer is a polyolefin film, polyolefin copolymer, or coextrusions of either, and the transparent polymer outer layer is a film selected from the group consisting of polyethylene terephthalate, nylon, polypropylene, polyethylene and cellophane.
Polychlorotrifluoroethylene (PCTFE) fluoropolymer films are manufactured and sold by Honeywell Inc. under the trademark Aclar®. Non-oriented PCTFE films are used extensively by pharmaceutical companies in manufacturing transparent vacuum-formed blister packages for pharmaceuticals and for other healthcare packaging. However, PCTFE films have seen limited success in non-forming barrier applications in the flexible packaging industry.
The present invention is based upon the discovery that molecularly oriented PCTFE films provide a clear structure with sufficient barrier properties to replace metal foil in even the most demanding barrier applications utilizing ethylene oxide, gamma sterilization, e-beam sterilization, and autoclave sterilization techniques, as well as in non-sterilized applications. Molecularly orienting the PCTFE film decreases the moisture permeation rate significantly as compared to standard non-oriented PCTFE film and provides a very durable barrier layer with superior flex crack resistance.
For most polymer films, the process of molecularly orienting the film results in the film having poor dimensional stability at elevated temperature. When the film is reheated, the molecular chains tend to try to revert to their original non-oriented state, resulting in a dimensional change in the film. When the film is a component of a composite laminate, the dimensional change can result in warping, curling or other unsightly and undesirable changes in the product. Molecularly oriented PCTFE film has surprisingly good thermal dimensional stability, and thus is well suited for use in applications involving exposure to high temperatures, such as in an autoclave sterilization process.
The present invention also provides a dimensionally stable autoclavable composite film laminate that can be used in the fabrication of sterilization bags or other articles. The laminate comprises a heat sealable transparent thermoplastic polymer inner layer forming an inner surface of the laminate, a transparent polymer film outer layer, and a transparent barrier layer between the inner and outer layers and formed of molecularly oriented polychlorotrifluoroethylene (PCTFE). In advantageous embodiments of the invention, the heat sealable transparent thermoplastic polymer inner layer is a film or coating of a polyolefin, polyolefin copolymers, or coextrusions of either, and the transparent polymer outer layer is a film selected from the group consisting of polyethylene terephthalate, nylon, polypropylene, polyethylene and cellophane. The laminate may suitably include a layer of adhesive adhering the polyolefin film inner layer to the transparent barrier layer. The laminate may further include a layer of adhesive adhering the transparent polymer outer film layer to the barrier layer. In one specific embodiment, the dimensionally stable autoclavable composite film laminate comprises a heat sealable transparent polypropylene inner layer forming an inner surface of the laminate, a transparent biaxially oriented polyethylene terephthalate film outer layer, and a transparent barrier layer between the inner and outer layers and formed of molecularly oriented polychlorotrifluoroethylene (PCTFE).
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
In
As shown in greater detail in
The transparent outer film layer 22 imparts strength, puncture resistance, dimensional stability and durability to the film laminate. The film layer 22 also assists in giving the laminate resistance to shrinkage when heated to elevated temperature. Suitable materials for the outer film 22 include polyethylene terephthalate (PET), nylon, polypropylene, polyethylene and cellophane. Particularly preferred are biaxially oriented films such as biaxially oriented PET and biaxially oriented nylon. The outer film layer 22 may have a thickness of from about 0.36 to 2.0 mils, more preferably from about 0.48 to 1.0 mils, and most preferably about 0.48 mils (48 ga).
The transparent barrier layer 23 imparts moisture barrier properties to the laminate. Barrier layer 23 is a molecularly oriented polychlorotrifluoroethylene (PCTFE) fluoropolymer film. The PCTFE film is transparent, biochemically inert, chemical resistant and free from plasticizers and stabilizers. Preferably the molecularly oriented PCTFE film is a monoaxially oriented film. The film may suitably have a thickness of from about 0.60 to 3 mils, more preferably from about 1 to 2 mils, and most preferably a thickness of about 1.5 mils. PCTFE fluoropolymer films are sold by Honeywell, Inc. under the Aclar® trademark.
The sealable inner film layer 21 may be laminated to the barrier layer 23 with an adhesive, using conventional lamination techniques. The adhesive may be applied using known processes such as spraying, roll coating, knife over roll coating, wire rod coating, or gravure coating. Suitable adhesives include solvent based, water based or solventless adhesives including acrylic adhesives, epoxy cured polyester urethanes, moisture cured polyester urethanes and isocyanate terminated polyester adhesives. Alternatively, the inner layer 21 can be formed directly on the barrier layer 23 by extrusion coating. The transparent outer layer 22 can be laminated directly to the barrier layer 23 using known adhesives and techniques as described above. If desired, the inner surface of the transparent outer layer 22 may be reverse printed prior to laminating to provide a layer of printing with graphics or other information. The outer layer may also be surface printed prior to or post lamination.
The film laminate 12 in the embodiment shown in
In the embodiment shown and described, the autoclavable bag 10 has a transparent composite film laminate 11 on one side and an opaque metal layer-containing laminate 12 on the opposite side. The article contained within the bag is readily visible through the transparent film laminate 11. However, bags in accordance with the present invention can also be produced using the transparent composites film laminate 11 for both the front and back side of the bag.
A dimensionally stable composite film laminate was manufactured by first laminating a 0.48 mil biaxially oriented transparent polyethylene terephthalate (PET) film to a 1.5 mil thick monoaxially oriented transparent Aclar® polychlorotrifluoroethylene (PCTFE) film to form a two-layer composite. Rolls of the PET film and the Aclarg film were each mounted on unroll stands. The PET film was unrolled and directed across a gravure coating apparatus and a 1.5 lb/ream layer of urethane adhesive was applied to one surface. The Aclar® film was unrolled and then brought into contact with the adhesive-coated surface of the PET film, and the films were directed through a nip formed between two smooth surface rolls. A 2.0 mil polypropylene transparent film made using a cast film extrusion process was then laminated to the exposed surface of the Aclar® film by a similar laminating procedure. The resulting composite laminate exhibited high moisture barrier properties and excellent dimensional stability at elevated temperature. The 1.5 mil machine direction oriented Aclar® layer provided a moisture barrier of 0.0077 g/100 in2/24 hours at 100° F. and 100% relative humidity.
A laminating procedure similar to that described in
A metal laminate of the following structure can be produced by a procedure similar to example 2: 0.48 mil biaxially oriented transparent PET film with a coating of aluminum deposited on one surface by vacuum metallization to an optical density of 2.8/adhesive/2.0 mil cast polypropylene. A pouch is fabricated from this laminate and the laminate of Example 1.
A pouch is produced by the procedure generally described Example 2, except that the following transparent laminate structure is substituted for the transparent laminate of example 1: 48 gauge biaxially oriented PET/adhesive/1.5 mil oriented Aclar® PCTFE film/adhesive/0.6 mil biaxially oriented nylon film/adhesive/2.0 mil cast polypropylene.
A pouch is produced by the procedure generally described example 2, except that the following transparent laminate structure is substituted for the transparent laminate of Example 1: 48 gauge biaxially oriented PET/adhesive/1.5 mil oriented Aclar® PCTFE film/adhesive/0.48 mil biaxially oriented PET film/adhesive/2.0 mil cast polypropylene.
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
