Medical multilayer film structure

Details Medical multilayer film structure Medical multilayer film structure

2002-06-12

2004-04-20

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Hollow or container type article

Nonself-supporting tubular film or bag

C428S035700, C428S036800, C428S516000, C428S517000, C428S521000

Reexamination Certificate

active

06723399

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a coextruded multilayer thermoplastic film structure for use in forming medical fluid containers.
2. Description of Related Art
Medical fluid containers (e.g., IV bags) are used to collect, process, store, transport, and ultimately deliver (typically via medical tubing) medical fluids (e.g., saline solutions and lactated Ringers solutions) to patients. The material used to fabricate medical containers of this type must possess a unique combination of properties. For example, to facilitate visual inspection for contaminants, the material used to fabricate the container must be optically transparent (i.e., see through) or exhibit contact clarity (i.e., visual inspection of the contents can be made when the container is laid on a surface). The material must be also be sufficiently flexible to permit the container walls to be fully collapsed prior to filling to prevent the introduction of air into the container during filling, but also sufficiently strong to resist rupture and/or puncture. It is also important that the material be able to retain its flexibility and strength over a wide range of temperatures. Filled medical fluid containers are frequently transported in the cargo bays of non-pressurized aircraft at high altitudes where temperatures of −40° C. or lower and low atmospheric pressures are often encountered. Moreover, some premixed drug solutions are stored and transported in medical fluid containers at temperatures as low as 40° C. to minimize drug degradation. In addition, the material must also be able to withstand various sterilization processes including, for example, high temperature (e.g., 121° C.) steam sterilization treatment, gamma radiation treatment, and/or ethylene oxide treatment.
The material used to fabricate medical fluid containers must also be environmentally friendly. In other words, the material should not leach out low molecular weight components when disposed of in landfills. Furthermore, the material should minimize the formation of acids upon incineration.
It is believed that it may be desirable in some applications for the material be free from or have a low content of additives such as plasticizers, stabilizers and the like that could possibly be released into the medications or biological fluids or tissues thereby possibly causing danger to patients using such devices or are contaminating the substances being stored or processed in such devices. For containers which hold solutions for intravenous transfusion, such contamination could make its way into the transfusion pathway and into the patient possibly causing injury to the patient.
Flexible polyvinyl chloride (“PVC”) is one of the most cost effective materials for constructing devices, which meet some of the above requirements. However, concerns have been raised in recent years that flexible PVC may generate objectionable amounts of hydrogen chloride (or hydrochloric acid when contacted with water) upon incineration, which can cause corrosion of the incinerator. Efforts have been undertaken in recent years to develop PVC-free materials for constructing medical containers.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a PVC-free coextruded multilayer thermoplastic film structure for use in forming a medical fluid container such as an IV bag. A multilayer thermoplastic film structure according to the invention comprises at least three layers. The first layer (A), which is the inner layer that contacts the medical fluid, comprises a mixture of a major part of a homopolymer or copolymer of polypropylene and a minor part of a block polymer of a vinyl aromatic comonomer and a conjugated diene, a partially hydrogenated derivative thereof, or a selectively hydrogenated derivative thereof to which has been grafted an unsaturated carboxylic reagent. The second layer (B), which is melt bonded to the first layer (A), comprises a block polymer of a vinyl aromatic comonomer and a conjugated diene, a partially hydrogenated derivative thereof, or a selectively hydrogenated derivative thereof to which has been grafted a unsaturated carboxylic reagent. The third layer (C), which is melt bonded to the second layer (B), comprises a homopolymer or a copolymer of polypropylene.
In a preferred embodiment of the invention, the multilayer thermoplastic film structure according to the invention is formed as a coextruded blown film. The first layer (A) comprises a mixture comprising a major amount of a propylene-ethylene random copolymer, a minor amount of a styrene-ethylene/butylene-styrene block copolymer, and optionally a hindered phenolic primary antioxidant and an anti-blocking agent. The second layer (B) consists essentially of a styrene-ethylene/butylene-styrene block copolymer and optionally a hindered phenolic primary antioxidant. And, the third layer (C) consists essentially of a propylene-ethylene random copolymer and optionally a hindered phenolic primary antioxidant.
The multilayer thermoplastic film structure according to the invention can be formed into medical containers such as IV bags by heat sealing a first layer (A) to another first layer (A), such as when a coextruded bubble of film is collapsed on itself. Medical containers formed from the coextruded multilayer thermoplastic film structure according to the invention exhibit excellent optical clarity and/or contact clarity both before and after steam sterilization, a lower heat sealing temperature, excellent gas and liquid permeability barrier properties, and remain flexible, tough, and tear resistant over a wide range of service temperatures. The coextruded multilayer thermoplastic film structure is environmentally friendly.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a plasticized PVC-free coextruded multilayer thermoplastic film structure for use in forming a medical fluid container such as an IV bag. The term “plasticized PVC-free” means that the thermoplastic film structure does not contain any PVC and/or PVC plasticizers. A coextruded multilayer thermoplastic film structure according to the invention comprises at least three layers. The first layer (A) is the inner layer that contacts medical fluids such as, for example, saline solutions, lactated Ringers solutions, and the like. The first layer (A) can be melt bonded to another first layer (A) using conventional heat sealing technology. The second layer (B) is melt bonded to the first layer (A). The third layer (C) is melt bonded to the second layer (B). In the preferred embodiment of the invention, all three layers (A), (B), and (C) are coextruded simultaneously and formed into a multilayer thermoplastic film structure by blowing a bubble (upwardly or downwardly) without the use of any glues or adhesives. The coextruded multilayer thermoplastic film structure can also be coextruded as a flat sheet.
First Layer (A)
The first layer (A) of the multilayer thermoplastic film structure according to the invention comprises a mixture of a major part of a homopolymer or copolymer of polypropylene, a minor part of a block polymer, and optionally a hindered phenolic primary antioxidant stabilizer. Throughout the instant specification and in the appended claims, the term “major amount” means an amount equal to or greater than 50% by weight, and the term “minor amount” means an amount less than about 50% by weight. The mixture preferably comprises, by weight, from about 60% to about 95%, more preferably from about 70% to about 90%, and most preferably about 80%, of one or more homopolymers or copolymers of polypropylene and optionally a hindered phenolic primary antioxidant stabilizer.
The homopolymers or copolymer

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