Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2002-12-27
2004-09-28
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S213000
Reexamination Certificate
active
06797398
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a plastic film for medical liquid containers and more particularly to a plastic film suitable for use as a material from which to form medical liquid containers such as bags for transfusions, drug solutions, and blood.
BACKGROUND ART
There have been proposed a variety of materials from which to form medical liquid containers to hold transfusions, drug solutions, and the like. For example, there is disclosed in Japanese Patent Laid-open No. Hei 8-252298, a plastic film for medical liquid containers which is composed of an oriented plastic surface layer, an adhesive resin layer, an oriented polyethylene or polypropylene layer, and a sealant layer directly fusion-bonded to the oriented polyethylene or polypropylene layer. The layers are directly laminated to each other without any anchoring agent and adhesives interposed between them. There is also disclosed in Japanese Patent Laid-open No. Hei 9-75444, a base material for medical use in which the layers contain a block copolymer composed of a random copolymer composed mainly of propylene and a polymer composed mainly of &agr;-olefin other than propylene. There is disclosed in Japanese Patent Laid-open No. Hei 9-85913 a plastic film for liquid containers which is composed of a transparent base film and a polypropylene-based film laminated on at least one side of the transparent base film, the latter being incorporated with syndiotactic polypropylene, isotactic polypropylene copolymerized with ethylene, and/or olefin-based elastomer.
Moreover, there is disclosed in Japanese Patent Laid-open No. Hei 9-308682, a plastic film for medical liquid containers which has a sealant layer composed of at least two layers of mixed film directly laminated to each other without any adhesives interposed between them. The films are formed from a mixture of high-density polyethylene having a density no lower than 941 kg/m
3
and linear low-density polyethylene having a density of 900-940 kg/m
3
in varied mixing ratios. There is also disclosed in Japanese Patent Laid-open No. Hei 9-308683 a plastic film for medical liquid containers which has a sealant layer composed of at least two layers of mixed film directly laminated to each other without any adhesives interposed between them. The films are formed from a mixture of high-density polyethylene having a density no lower than 941 kg/m
3
and linear low-density polyethylene having a density of 900-940 kg/m
3
in varied mixing ratios. The sealant layer is laminated to the upper and lower sides of a transparent film, with adhesives interposed between them, such that the transparent film is bonded to the mixed film layer in which the mixing ratio of the high-density polyethylene is lower.
In addition, there is disclosed in Japanese Patent Laid-open No. Hei 10-323381 a medical container formed from a multi-layered film constructed of an intermediate layer and an inner layer directly adjacent to the inside thereof. The intermediate layer is formed from a mixture of ethylene-vinyl alcohol copolymer and styrene resin. The inner layer is formed from any of a resin composed mainly of modified polyolefin, a first mixed resin composed mainly of modified polyolefin and styrene resin, and a second mixed resin composed mainly of polypropylene resin and styrene resin. There is also disclosed in Japanese Patent Laid-open No. Hei 11-290422 a transfusion container formed from a multilayered sheet composed of an outer layer and an inner layer. The outer layer contains a polymer composition of polypropylene block copolymer and hydrogenated butadiene-styrene polymer. The inner layer contains any of (a) polypropylene block copolymer, (b) polypropylene random copolymer, and (c) polymer composition of the polypropylene block copolymer or polypropylene random copolymer and hydrogenated butadiene-styrene polymer. The melting point of the outer layer is higher than the melting point of the inner layer by 10° C. or more.
Moreover, there is disclosed in Japanese Patent Laid-open No. 2000-14747 a medical container having a triple-layered wall which is constituted such that the inner and outer layers are composed mainly of high-density polyethylene (HOPE) and the intermediate layer is composed mainly of linear low-density polyethylene (LLDPE), with the total thickness of the inner and outer layers being no larger than 80 &mgr;m and no smaller than 10 &mgr;m. The HOPE has a density no lower than 945 kg/m
3
and a peak temperature no lower than 125° C. (measured by a differential scanning calorimeter). The LLDPE is obtained by means of metallocene catalyst having a density of no lower than 925 kg/m
3
and no higher than 935 kg/m
3
. There is disclosed in Japanese Patent Laid-open No. 2000-33674, a medical container of multi-layered laminate film at least composed of a first layer (as the inner most layer), second layer (as a bonding layer), and third layer. The first layer is formed from a mixture of polypropylene and/or polyethylene resin and styrene resin. The second layer is formed from modified polyolefin, and a third layer is formed from ethylene-vinyl alcohol copolymer on the outer side of the first layer.
None of the disclosed plastic films for medical liquid containers, however, do not meet all the requirements for heat resistance, transparency, haze, heat-sealability, drop strength, impact strength, and flexibility. The laminate film having a bonding layer such as adhesives and adhesive resin tends to permit organic matters to dissolve in the content liquid. The plastic film of propylene block copolymer is hazy (or poor in transparency) although it is improved in drop strength and impact strength. High haze prevents the inspection of the content liquid.
The disadvantage of the film incorporated with a thermoplastic elastomer for improvement in film flexibility is that the thermoplastic elastomer presented on the surface layer causes sticking and hampers handling. Moreover, such thermoplastic elastomer whitens immediately after sterilization with high-pressure steam, thereby preventing the inspection of the content liquid. Moreover, the thermoplastic elastomer (excluding propylene-based elastomer) contained in the innermost layer (in contact with liquid) causes not only whitening and sticking but also tends to permit organic matters to dissolve in the content liquid. This is undesirable for medical containers. The container with an intermediate layer containing elastomer, such as mixed layer with ethylene-vinyl alcohol copolymer, has improved gas barrier properties for existence of ethylene-vinyl alcohol copolymer but is subject to whitening upon sterilization with high-pressure steam. Whitening prevents the inspection of content liquid.
Moreover, the container with an intermediate layer formed from elastomer alone is subject to whitening as well as dissolution in the content liquid and it is high in production cost. The plastic film for medical liquid containers should preferably be capable of high-frequency fusion cutting and sealing from the standpoint of efficient operation if it is to be fabricated into containers by using the existing bag-making machines for polyvinyl chloride materials.
DISCLOSURE OF INVENTION
The present invention was completed in view of the foregoing. It is an object of the present invention to provide a plastic film for medical liquid containers which is characterized by such properties as weak tendency toward whitening by sterilization with high-pressure steam, ability to permit the inspection of content liquid immediately after sterilization with high-pressure steam, freedom from sticking (which leads to easy handling of the resulting containers), good flexibility, high drop strength and impact strength, insolubility in the content liquid upon sterilization with high-pressure steam at 121° C., nontoxicity, ability to be fabricated into safe medical liquid containers, and capability of heat-sealing as well as high-frequency fusion-sealing (which permits fabrication by the existing bag-making machine for polyvinyl chloride materials). These proper
Miura Koichi
Suzuki Tokoaki
Fujimori Kogyo Co. Ltd.
Tarazano D. Lawrence
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