Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-12-08
2004-04-13
Ahmad, Nasser (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S349000, C428S212000, C428S219000, C428S516000, C428S035400, C428S036910, C428S520000, C428S036600, C428S036700
Reexamination Certificate
active
06720045
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to films showing excellent easy peelability when the films are sealed to each other and medical packaging containers using the films as an inner layer.
Herein, the term “easy peelability” means that the following two portions can be formed selectively from one material. They are a strongly heat welded portion that can be sealed by heating two members of one material at a relatively high temperature and cannot be substantially peeled, and a weakly heat welded portion that can be sealed by heating the members of the material at a relatively low temperature (hereinafter referred to as low temperature welding) and can be easily peeled.
BACKGROUND OF THE INVENTION
Hitherto, there have been known lid materials and packaging materials provided with an adhesive surface that can be easily peeled to facilitate unsealing as well as medical multi-chamber containers partitioned with easily peelable partition walls.
Medical multi-chamber containers are used for applications such as the aseptical mixing, immediately before use, of drugs or chemical solutions that tend to be denatured or to have decreased preservative qualities when they are in a mixed state. That is, the contents are preserved in a container separately in a plurality of chambers partitioned by partition walls that can be easily peeled. The container is compressed by hand immediately before use so as to have the chambers communicate with each other and have the contents aseptically mix.
The multi-chamber container is usually formed of a single layer film having easy peelability mentioned above or formed of a multi-layer film obtained by laminating the film having easy peelability as an inner layer. First, a peripheral portion of superposed films is heat welded at a relatively high temperature to form a container. Then, an intermediate portion of the formed container is heat welded at a relatively low temperature from outside of the container using a heating mold in order to form easily peelable partition walls and partition the container into a plurality of chambers. Where the multi-chamber container is formed of a resin that does not show easy peelability, the partition walls in the multi-chamber container can be formed by inserting an easily peelable film (usually, a film made of a mixture of the resin used for the film for forming the container and a resin incompatible therewith) between partition wall portions and heat welding the partition wall portions together.
The easily peelable film used for the medical container must satisfy heat resistance, transparency, flexibility and impact resistance requirements as well as medical safety requirements and disposability and thus far many proposals have been made.
For example, there have been known easily peelable films made of mixtures of polypropylene type polymers and ethylene/&agr;-olefin type elastomers (JP-A-Hei 7-136234 and JP-A-Hei 8-131515) and films made of mixtures of polypropylene type polymers or polyethylene type polymers as a major component and styrene type elastomers (JP-A-Hei 8-229099 and JP-A-Hei 8-229100). However, these films contain a large content of the &agr;-olefin or the elastomer so that they have poor heat resistance and an increased change or fluctuation in peel strength of the formed partition walls, allowing high pressure steam sterilization to be performed only at 115° C. or less.
On the other hand, easily peelable films made of resin compositions containing polyolefin type resins and incompatible resins such as polymethylpentene type resins having excellent heat resistance (JP-B-Hei 7-96283) have blended therein a significant amount of incompatible resins so that they are poor in transparency and flexibility, and are unsuitable as medical containers.
Furthermore, a bag using a copolymer comprising an homogeneous phase of propylene for internal partition walls is also known (JP-A-Hei 10-314275). The copolymer comprising an homogeneous phase of propylene preferably has a melting point of 150-160° C. and contains about 3% by weight of an ethylene component. However, although a bag made of the copolymer is excellent in heat resistance, a temperature range for low temperature welding at which peelable partition walls can be formed is as narrow as 137.5°±1° C., so that it is difficult to form partition walls.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances and an object of the present invention is to provide an easily peelable film that has excellent heat resistance, flexibility, and transparency and further has a broad temperature range for low temperature welding at which peelable partition walls can be formed, and a medical packaging container using the above-mentioned film.
The present inventors have made intensive research to achieve the above object and have discovered that use of a mixture of two or more propylene polymers having different melting points can attain the above object, thus achieving the present invention.
That is, the present invention relates to an easily peelable film comprising a mixture of a propylene/&agr;-olefin copolymer (A) and a propylene/&agr;-olefin copolymer (B) having an &agr;-olefin content different from that of the copolymer (A), and/or a propylene homopolymer (C).
Also, the present invention relates to an easily peelable laminated film using the above-mentioned film as a surface layer film.
Furthermore, the present invention relates to a medical packaging container using the easily peelable film or easily peelable laminated film.
The propylene/&agr;-olefin copolymer (A) according to the present invention has a melting point of 110-130° C., preferably 115-125° C. On the other hand, the propylene/&agr;-olefin copolymer (B) according to the present invention has a melting point of 130-170° C., preferably 135-155° C. The propylene homopolymer (C) according to the present invention has a melting point of 130-170° C., preferably 161-170° C. Where the melting point of (A) is lower than 110° C. or the melting point of (B) or (C) is lower than 130° C., the film or packaging container after molding has poor heat resistance, so that there is a possibility that a decrease in transparency or a deformation of the container after high pressure steam sterilization can occur. Where the melting point of (A) is higher than 130° C., the difference from the melting point of (B) or (C) is small, so that it is difficult to form easily peelable partition walls.
Furthermore, a difference between the melting point of (A) and the melting point of (B) or (C) is preferably at least 5° C. and, more preferably, 7° C. or more. If the difference in melting point is smaller than 5° C., it is difficult to selectively form a strong heat welded portion or a weak heat welded portion.
The melting point referred to herein means a temperature at which a DSC (differential scanning calorimetry) measurement of the copolymer or homopolymer pellets gives a maximum endothermic peak by melting.
The &agr;-olefin content of the propylene/&agr;-olefin copolymer (A) is 5-20 mol % and, preferably 7-15 mol %. The &agr;-olefin content of the propylene/&agr;-olefin copolymer (B) is 8 mol % or less and, preferably, 7 mol % or less. If the &agr;-olefin content of the propylene/&agr;-olefin copolymer (A) is higher than 20 mol %, not only are the heat resistance and transparency decreased but also, the peel strength increases when easily peelable partition walls are prepared, so that it is difficult to release the partition walls by hand.
The mixture that forms the easily peelable film according to the present invention may be a mixture of three components, i.e., the propylene/&agr;-olefin copolymer (A), propylene/&agr;-olefin copolymer (B), and the propylene homopolymer (C) or a mixture of two components, i.e., (A) and (B) or (A) and (C). Copolymer (A) may be two or more propylene/&agr;-olefin copolymers having a melting point of 110-130° C. Copolymer (B) may be two or more propylene/&agr;-olefin copolymers having a melting point of 130-170° C. and propylene homopo
Fukushima Hiroshi
Kawamura Shin'ichi
Ahmad Nasser
Kubovcik & Kubovcik
Nipro Corporation
Rhee Jane J
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