An ultraviolet absorbing and optically transparent packaging material

Abstract: A transparent packaging laminate (10) for use in a container (15) for protecting medical products (18) from oxidation and deterioration as a result of exposure to ultraviolet light. The laminate includes a first transparent film (11) of a polyethylene material laminated with a polyester adhesive (13) to a second transparent film (12) of a polyester material. The transparent polyethylene material has a water vapor transmission rate of less than 20 grams/m²/24 hours. The transparent polyester material absorbs ultraviolet light having a wavelength in a range of from 285 to 358 nanometers and has a water vapor transmission rate greater than 20 grams/m²/24 hours, whereby the resulting laminate is unexpectedly wrinkle-free after ethylene oxide sterilization. The container comprises the ultraviolet light absorbing laminate and a sheet of spun-bonded olefin material attached to the laminate, which is opaque to ultraviolet light and forms a cavity (17) therebetween with the laminate for containing a medical product therein.

Description: This invention relates generally to optically transparent, ultraviolet radiation absorbing packaging material. Medical products, such as plastic material catheters and the like are vulnerable to ultraviolet oxidation and deterioration. One approach to combatting the effects of ultraviolet light on medical products is to include antioxidant and/or inhibitor additives in, for example, the material used to form plastic catheters. The antioxidants and/or inhibitors serve to extend the shelf life of ultraviolet sensitive medical products. A problem with the use of antioxidants and/or inhibitors in catheter materials is that the resulting catheters exhibit undesirable characteristics, such as increased durometer and stiffness. Furthermore, a high concentration of antioxidants and/or inhibitors negatively affects the bonding properties of constituent materials. Poor bonding of constituent materials can result in medical product failure, which impacts safety and efficacy for the patient. Another approach to combating the effects of ultraviolet on medical products is to package a medical product in a container that is impervious to ultraviolet radiation, as well as visible light. Medical products are typically packaged in a pathogen-free environment or sterilized after packaging. A disadvantage of packaging medical products in a light-impervious container is that medical personnel are unable to visually identify the medical product before opening the container. As a result, medical products can be unnecessarily opened and exposed to an infectious environment. US 3,926,311, EP 0 307 173 and JP 59-18253 all disclose a sealed container (package) for medical use, comprising a layer of spun-bonded olefin or other suitable porous material heat sealed to a transparent thermoplastic laminate. In each citation, the polyethylene layer of the laminate is apposed to the porous layer of the package to enable heat-sealing of the package. US 3,926,311 discloses an inventive peel-seal between a spun-bonded olefin and a laminate (constituted by a layer of polyester and a layer of polyethylene), which allows the package to be peeled open without tearing of the spun-bonded olefin. In EP 0 307 173, the invention is aimed at minimising the loosening of fibres of a porous material from the package after sterilisation, because the loosened fibres may contaminate the packed medical device. A layer of polyester and a layer of polypropylene or polyethylene constitute the laminate that is sealed to the porous material. JP 59-18253 discloses an inventive seal between a spun-bonded olefin and a laminate, which allows detecting a breakage in heat-sealed parts of a sterilised package. A layer of polyester and a layer of polyethylene constitute the laminate used in this invention. In JPI Journal 28:(3), 290-300(1990), many characteristics of PET films as basic packaging materials are reviewed. In this review, it is disclosed that a PET film absorbs only a fraction of the ultraviolet spectrum, i.e. wavelengths of less than 310 nm, but transmits 85% to 90% of visible radiation. Shrinking of a PET film occurs both in the longitudinal and transversal directions when heated. It is also disclosed that on normal usage conditions, moisture absorption problems of a PET film are negligible. None of the prior art cited above discloses any wrinkling effect on the laminates during and after exposure to a high water vapour environment, as for example in a conventional sterilisation process with ethylene oxide. Moreover, none of the prior art citations mentioned above discloses a laminate constituted by two films of a different thickness having different WVTR requirements. According to the present invention, there is provided a laminate as defined in claim 1, or a container as defined in claim 2, or a method as defined in claim 9. The transparent laminate and container are advantageously suited for sterilizing a medical product contained therein with a commonly used sterilant such as ethylene oxide. The laminate and container along with the medical product therein also advantageously exhibit residuals of ethylene oxide less than 250 parts per million after ethylene oxide sterilization. Unexpectedly, the laminate with a constituent film having a high water vapor transmission rate exhibits a substantially wrinkle-free texture while maintaining its transparent property. The laminate also absorbs ultraviolet light having a wavelength in a given range of, for example, from 285 to 358 nanometers, which causes oxidation and deterioration of most medical products such as plastic material catheters. Furthermore, medical products, such as pharmaceuticals, are also advantageously protected from deterioration due to harmful ultraviolet light in this wavelength spectrum. The high water vapor transmission rate of the polyester material would suggest wrinkling thereof during the high humidity ethylene oxide sterilization process. However, the laminating of the transparent films unexpectedly results in laminate that is substantially wrinkle-free after ethylene oxide sterilization. In addition, the resulting laminate advantageously exhibits residuals of ethylene oxide below 250 ppm as required by the Federal Food and Drug Administration. The synthetic polymer material is selected from a group of transparent polymeric materials which includes polyvinylidene chloride, styrene polymer, polyamides, polyether block amides, polyesters, and polyolefins. The styrene polymer includes a butadiene-styrene copolymer. The polyamides and polyether block amides include an ionomer film laminated thereto and formed from ethylene copolymers with methacrylic acid. The polyester polymeric material includes at least one of polyester terephthalate and polyester terephthalate glycol modified. The polyolefins include at least one of polyethylene and ethylene vinyl acetate copolymer. The ultraviolet light absorbing medical product container comprises the ultraviolet light absorbing laminate and a sheet of spun-bonded olefin material attached to the laminate. The sheet of spun-bonded olefin material is opaque to ultraviolet light and forms a cavity between the transparent laminate for containing the medical product therein. The sheet of spun-bonded olefin readily transmits ethylene oxide gas and water vapor therethrough during the sterilization process, but blocks the transmission of harmful particulate such as bacteria and spores. Further according to the invention, a method for packaging a medical device which is adversely affected by a given range of wavelengths of ultraviolet light comprises the steps of placing a medical device between a pair of thermoplastic sheets, at least one of which has a transparent portion which is capable of absorbing ultraviolet light at least in the given range of wavelengths and the remainder of the thermoplastic sheets is opaque at least to ultraviolet light in the given range of wavelengths. At least one of the thermoplastic sheets has at least a portion which is permeable to ethylene oxide gas and water vapor and is characterized by a residual ethylene oxide content of less than 250 ppm after sterilization. The thermoplastic sheets are sealed around the entire medical device, the transparent portion and the permeable portion encapsulating the medical device between the pair of thermoplastic sheets to thereby form a package with the medical device visible through the transparent portion. Ethylene oxide and water vapor are then passed through the permeable portion to sterilize the medical device within the package and to sterilize the interior of the package. The ethylene oxide gas is subsequently removed from the package. One of the thermoplastic sheets comprises a first transparent thermoplastic film which has a water vapor transmission rate of less than 20 g /m 2 /24 h and a second transparent thermoplastic film which is laminated to the first transparent film and is formed of an ultraviolet light absorbing material, preferably a polyester, having a water vapor transmission rate greater than 20 g /m 2 /24 h. In accordance with a preferred embodiment of the invention, the other of the thermoplastic sheets is a spun-bonded olefin and the permeable portion comprises the spun-bonded olefin sheet. An alternative to the spun bonded olefin is shredded cellulose paper. Brief Description of the Drawing FIG. 1 depicts an illustrative embodiment of an ultraviolet radiation absorbing container of the present invention for containing medical products; FIG. 2 depicts a partially enlarged cross-sectional view of the container of FIG. 1 taken along the line 2-2; FIG. 3 depicts an exploded and enlarged cross-sectional view of the container of FIG. 2; and FIG. 4 depicts a transparent layer of dyed polyester material of FIG. 3 with dye contained therein. Detailed Description FIG. 1 depicts an illustrative, preferred embodiment of ultraviolet light absorbing package or container (15) for containing sterile medical products such as guiding catheter (18) and for protecting the catheter from harmful ultraviolet radiation. Sterile medical products include any medical product that is injected, inserted, or introduced into a human or animal body or eye. Other medical products such as pharmaceuticals and the like that are subjected to less stringent pathogen-free or aseptic packaging requirements are also contemplated. Many sterile medical products such as guiding catheter (18) and other intravascular products are formed from and include a plastic or polymer material that is subject to oxidation and consequential deterioration when exposed to harmful ultraviolet. Although the complete spectrum of ultraviolet is contemplated, of major concern is ultraviolet that has a wavelength in a range of from 285 to 358 nanometers. Oxidation and deterioration of the medical product results from the product being stored for extended periods of time, particularly when exposed to ultraviolet emitted from the sun or fluorescent illumination. Such deterioration over extended periods of, for example, six months or more can render the medical product unsafe for use, particularly when inserted in the body of a human or animal patient. Ultraviolet absorbing container (15) includes an ultraviolet radiation absorbing transparent laminate (10) attached through heat sealing or other suitable form of encapsulation to sheet (16) of spun-bonded olefin material which forms a cavity (17) therebetween for inserting the medical product therein. The cavity is defined by a heat seal (23) or other suitable form of encapsulation and extends around the entire periphery of the laminate (10) and the sheet (16) to. encapsulate the cavity (17) and a medical product (18). The medical product (18) is inserted in the cavity and the package sealed for subsequent use. Commonly, the attached transparent laminate and sheet of spun-bonded olefin material are then subjected to a well-known sterilization process using for example, an ethylene oxide gas sterilant. The ethylene oxide sterilant passes through the olefin material sheet of the container and sterilizes the medical product, as well as the inside of the container, from harmful microorganisms and particulates, such as bacteria and spores. Transparent packaging laminate (10) most effectively absorbs harmful ultraviolet radiation having a wavelength in a range of from 285 to 358 nanometers and protects the contained medical product from exposure to this harmful ultraviolet radiation and subsequent deterioration of the product. Samples of the laminate indicate that all but approximately 6-7% of the ultraviolet light in the given range is absorbed. The transparent packaging laminate (10) allows the user easy visualization of the product and protects the product for periods of up to five or more years without harmful deterioration. A transparent material is one in which light of a given spectrum can pass therethrough so that distinct objects or images can still be perceived by the human eye. A translucent material is one in which light of a given spectrum can pass therethrough so that distinct objects or images can no longer be perceived by the human eye. Sheet (16) of the spun-bonded olefin material is a well-known and commercially available ultraviolet opaque material such as "TYVEK" (R.T.M.) material, which is commercially available from E.I. DuPont de Nemours and Company. Other material or materials which readily transmit ethylene oxide gas and water vapor therethrough for sterilization of medical product (18) may alternatively be used. The material should, however, provide an effective barrier to microorganisms, such as bacteria. FIG. 2 depicts a partially enlarged, cross-sectional view of container (15) and guiding catheter (18) of FIG. 1 taken along the line 2-2. This cross-sectional end view depicts guiding catheter (18) in cavity (17) of container (15) between ultraviolet radiation absorbing transparent laminate (10) and sheet (16) of spun-bonded olefin material Ultraviolet radiation (19) incident on transparent packaging laminate (10) is absorbed by the laminate with the remaining spectrum of light (22) being transmitted therethrough for incidence on the medical product and sheet (16) of olefin material. Transparent packaging laminate (10) includes first optically transparent film (11) of a flexible carrier material, such as, for example, a synthetic polymer layer laminated to second optically transparent film (12) of an ultraviolet radiation absrobing material, such as a polymer material, for example, a polyester. FIG. 3 depicts a further enlarged cross-sectional view of container (15) and catheter (18) of FIG. 2. The view of the ultraviolet radiation absorbing, optically transparent packaging laminate has been exploded to further depict optically transparent films (11) and (12) thereof with adhesive (13) for laminating the two optically transparent films together. Adhesive (13) is a commercially available polyester adhesive for bonding or laminating the polymeric material to the ultraviolet absorbing polyester materials. The use of the laminate adhesive is preferred but not essential. First optically transparent film (11) of a flexible carrier material has a thickness (20) of approximately .038 mm and a water vapor transmission rate of less than 20 g /m 2 /24 b . The water vapor transmission rates of the films utilized herein were determined per the American Society of Testing and Materials (ASTM) test method and practice F1249 on commercially available Mocon Permatran test equipment. Preferably, polymeric material of the first transparent film (11) comprises a commercially available, flexible transparent polyethylene packaging material. This flexible polyethylene material is preferred not only for its low water vapor transmission rate of, for example, 12.4 to 13.95 g /m 2 /24 h , but it also exhibits residuals of ethylene oxide less than 250 ppm after ethylene oxide sterilization. Residuals of ethylene oxide less than 250 ppm are required to meet Federal Food and Drug Administration requirements. The low water vapor transmission rate of the polyethylene material resists water vapor penetration. Significant water vapor penetration of a packaging material can wrinkle the smooth transparent surfaces of the material and distort and alter the image of a medical product contained thereunder. However, sheet (16) of the spun-bonded olefin material on the other side of the container has a significantly greater water vapor transmission rate for readily transmitting water vapor therethrough, which is needed in the ethylene oxide sterilization process. Since the spun-bonded olefin material is opaque to ultraviolet radiation, the wrinkling of the material and the distortion of visual images therethrough is not of major concern. As also previously suggested, the spun-bonded olefin material has a thickness in a range of .18 to .25 mm and readily transmits ethylene oxide gas and water vapor therethrough for the ethylene oxide sterilization process. Flexible, optically transparent polymeric materials other than polyethylene are available with a water vapor transmission rate of less than 20 g /m 2 /24 h for use as first transparent film. Suitable polymeric carrier materials include commercially available polyvinylidene chloride, styrene polymer, polyamides, polyether block amides, polyesters, and polyolefins. The styrene polymer includes a butadiene-styrene copolymer. The polyamides and the polyether block amides also include an ionomer film laminated thereto and formed from ethylene copolymers with methacrylic acid. The polyesters include polyester terephthalate and polyester terephthalate glycol modified. Polyethylene along with ethylene vinyl acetate copolymer is part of the group of polyolefins. Classically, polymeric carrier materials such as polyethylene do not absorb or reflect harmful ultraviolet radiation, which can readily oxidize and deteriorate medical products, such as guiding catheter (18). As a result, the second transparent film (12) of ultraviolet radiation absorbing or U.V.-reflecting polyester material is laminated to first transparent film (11). The ultraviolet radiation absorbing material is preferably a polyester material and can be commercially available as "Courtgard" (R.T.M.), a dyed polyester film from Courtaulds Performance Films, Inc., Martinsville, Virginia. This dyed polyester film absorbs all but approximately 6 to 7% of ultraviolet light having a wavelength in the range of from 285 to 358 nanometers, which is incident on the film. FIG. 4 depicts layer (12) of ultraviolet radiation absorbing optically transparent polyester material of FIG. 3 with ultraviolet absorbing material (14) in a matrix of polyester material. Ultraviolet light absorbing material (14) is from the chemical family of benzophenones. A preferred ultraviolet radiation absorbing material is methanone, bis (2-hydroxy-4-methoxyphenyl) of the chemical formula C 15 H 14 O 5 . Another ultraviolet light absorbing material is 2.2'-dihydroxy-4.4'-dimethoxy-benzophenone. This preferred UV light absorbing material is also commercially available as "UVINUL" (R.T.M.) D-49 absorbing material from the BASF Corp., Parsippany, New Jersey. There are many different forms of U.V. radiation absorbing materials available, such materials also being optically transparent. As depicted in FIGs. 3 and 4, optically transparent film (12) absorbs ultraviolet radiation having a wavelength in a range of from 285 to 358 nanometers and has thickness (21) of approximately .013 mm. The dyed polyester film has a water vapor transmission rate greater than 20 g /m 2 /24 h. The ultraviolet radiation absorbing film (12) transmits and absorbs water vapor and has a tendency to wrinkle. However, the lamination of this ultraviolet light absorbing transparent film (12) to the polymeric transparent film (11) with adhesive (13) unexpectedly produces a laminate which is substantially wrinkle free after ethylene oxide sterilization which requires various levels of humidity. A water vapor transmission rate of approximately 11.11 g /m 2 /24 h was obtained for the laminate at 37.7°C (100°F) and 90% relative humidity with the adhesive sealant towards or away from the moisture, respectively. In addition, the dyed polyester material exhibits residuals of ethylene oxide below 250 ppm after ethylene oxide sterilization. Furthermore, laminate (10) exhibits residuals of ethylene oxide less than 250 ppm after ethylene oxide sterilization. In summary, the ultraviolet absorbing, optically transparent packaging laminate of the present invention represents a significant breakthrough in packaging material for protecting sterile medical products which are subject to ultraviolet oxidation and resulting deterioration. The water vapor transmission rate and ultraviolet absorbing properties of the laminate make this packaging material particularly suited for ethylene oxide sterilization in which high levels of humidity are encountered. Furthermore, the high water vapor transmission rate of the ultraviolet absorbing, polyester film would suggest that the laminate would wrinkle and distort the visual appearance of the contained medical product. Unexpectedly, the laminate of the present invention is substantially wrinkle-free and presents a smooth surface for substantially distortion-free viewing of the product while still offering a high degree of ultraviolet absorption. This ultraviolet absorption protects medical products subject to U.V. oxidation and deterioration and extends its shelf life substantially. Prior to this, medical products such as guiding catheters and the like included large amounts of antioxidants and the like to combat the effects of ultraviolet radiation. However, the inclusion of these antioxidants significantly alter the properties of the catheter such as significantly and undesirably increasing the durometer and stiffness of the catheter. Furthermore, high concentration of these antioxidants also seriously affect the bonding property of the constituent materials which affect the safety and efficacy of the device. The medical device (18) is packaged by placing the medical device (18) between the transparent laminate (10) and the spun-bonded olefin sheet (16). The two sheets are then preferably sealed together through heat sealing around the entire periphery of the two sheets to define a cavity (17) with the medical device (18) positioned therein. The heat-sealing operation seals the medical device (18) within the cavity (17). After the package has been thus formed, the package is treated in an ethylene oxide and water vapor atmosphere process to sterilize the cavity (17) and the medical device (18) therein. The ethylene oxide passes through the sheet (16) of spun-bonded olefin or equivalent material and into the cavity (17) to sterilize the medical device (18). After the appropriate length of time, the ethylene oxide and water vapor atmosphere is removed and the package is then withdrawn from the ethylene oxide atmosphere. The ethylene oxide can then pass back through the sheet (16) to a point where the package contains less than 250 ppm of ethylene oxide.

Claims: Ultraviolet radiation absorbing packaging laminate (10) comprising first (11) and second (12) films, characterised in that the first film is optically transparent to visible light and has a first thickness (20) and a water vapour transmission rate of less than 20 g/m 2 /24 h; and the second film is: a light transparent, ultraviolet radiation absorbing film having a second thickness (21) less than said first thickness and a water vapour transmission rate greater than 20 g/m 2 /24 h, said films constituting a laminate substantially wrinkle free after sterilization with gas. An ultraviolet radiation absorbing medical product container (15) characterised by the laminate according to claim 1, further comprising: a sheet (16) of ultraviolet opaque material attached to said laminate and forming a cavity (17) therebetween for containing a medical product (18) in the cavity, said sheet of material being capable of receiving a sterilizing gas therethrough and of inhibiting reception of microorganisms therethrough, wherein the container has residuals of sterilising gas, for example ethylene oxide, less than 250 ppm after the sterilization. The laminate of claim 1, or the container of claim 2, comprising an adhesive (13) for bonding said first film and said second film together. The laminate of claim 1, or the container of claim 2, wherein said ultraviolet radiation absorbing material includes a benzophenone (14). The laminate of claim 1, or the container of claim 2, wherein said first film comprises polymeric material selected from polyvinylidene chloride, styrene polymer, butadiene-styrene copolymer, polyamides, polyether block amides, polyesters, and polyolefins, such as polyethylene and ethylene vinyl acetate copolymer. The laminate or container of claim 5, wherein at least one of said polyamides and said polyether block amides includes an ionomer film laminated thereto and formed from ethylene copolymers with methacrylic acid. The laminate or container of claim 5, wherein the ultraviolet absorbing material includes polyester terephthalate or polyester terephthalate glycol modified. The container according to claim 2 or any claim appendant thereto, wherein the first film is of flexible polyethylene material, and the second film is of polyester material. A method for packaging a medical device requiring protection from ultraviolet light radiation, said method characterised by the steps of placing the medical device between the laminate (10) and the sheet (16) of claim 2; sealing said one sheet and the laminate around the entire medical device, to encapsulate the medical device and thereby form a package with the medical device visible through the transparent laminate; passing sterilising gas and water vapour through said one sheet to sterilise the medical device within the package and to sterilize the interior of the package; and subsequently removing the gas from the interior of the package, wherein the package has a residual sterilizing gas content of less than 250 ppm. The method of claim 9, wherein the said one sheet is a spun bonded polyolefin. The method of claim 10, wherein the first transparent film is selected from polyvinylidene chloride, styrene polymer, polyamide, polyether block amides, polyesters and polyolefins; and/or wherein the second transparent film is an ultraviolet light in polyester material selected from polyester terephthalate and polyester terephthalate glycol modified.

Inventors: BAKER BRETT O, BAKER, BRETT O.
Applicants: SABIN CORP, SABIN CORPORATION
Application year: 1995
Main classification: B32B27
IPC codes: B32B27, A61F2, A61B19, A61M25, B65D81, A61L2, B65D65, A61L31, B32B7