Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1991-04-17
1992-08-11
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
523122, C08K 320
Patent
active
051379570
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method preparing an antibacterial polymer and its application, and particularly to an antibacterial packing material using the same polymer.
BACKGROUND ART
It has long been known that compounds of silver exhibit antibacterial property. For instance, calcium carbonate to which silver is added has been extensively used for the sterilization of the dechlorinated tap water.
It has also been known that antibacterial property is exhibited by a polymer that contains silver acrylate and/or silver methacrylate as a structural unit. Japanese Patent Publication No. 43123/1983 discloses an antibacterial semi-permeable composed of the above polymer and a cellulose ester.
Furthermore, Japanese Laid-Open Patent Publication No. 154746/1988 discloses an antibacterial film composed of a synthetic resin which contains dispersed therein a hygroscopic agent and zeolite-type solid particles that hold metal ions such as silver ions that exhibit antibacterial action by the exchange of ions, the zeolite-type solid particles having a specific surface area of greater than 150 m.sup.2 /g and an SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio of smaller than 14.
According to the method of producing the antibacterial polymer of the former publication, the silver acrylate and/or the silver methacylate is polymerized, or silver nitrate is reacted with polyacrylic acid, polymethacrylic acid or a copolymer thereof. However, the antibacterial polymer that is obtained lacks thermal stability under dry heated conditions, and does not apparently lend itself for such applications as forming films by the heat treatment or forming containers through the heat-molding.
According to the method of blending the silver ion-exchanged zeolite in the resin disclosed in the latter publication, there remain problems in regard to producing the silver ion-exchanged zeolite and in regard to that the sterilizing power decreases if there exist silver oxides in the zeolite, though there is problem with regard to heat resistance. There still exists a problem in that the silver ion-exchanged zeolite is alkaline just as the zeolite is in general, and hence tends to hydrolyze the resin that is blended.
DISCLOSURE OF THE INVENTION
The present inventors have discovered the fact that a polymer having antibacterial property is obtained when a silver oxide and a thermoplastic copolymer that contains a unit consisting of ethylenically unsaturated carboxylic acid or an anhydride thereof and that can be melted upon heating, are melted and kneaded together, and that the polymer can be heat-treated or heat-molded making it possible to obtain a container having antibacterial property if the innermost layer of the container is formed by using this polymer.
That is, the object of the present invention is to provide an antibacterial polymer that has a combination of excellent antibacterial property and heat-moldability or heat-processability, and that can be produced cheaply and easily, as well as a method of preparing the same polymer.
Another object of the present invention is to provide an antibacterial packing material that is free from the above-mentioned defects inherent in the prior art, that exhibits excellent antibacterial action as well as excellent flavor retentivity for the contents.
According to the present invention, there is provided a method of preparing an antibacterial polymer comprising mixing a silver oxide and a thermoplastic copolymer that contains a unit consisting of ethylenically unsaturated carboxylic acid or an anhydride thereof and that can be melted upon heating, and then melting and kneading the mixture.
According to the present invention, furthermore, there is provided an antibacterial packing material wherein at least the inner surface layer of the packing material contains an antibacterial polymer that a formed by kneading a silver oxide and a thermoplastic copolymer that contains a unit consisting of ethylenically unsaturated carboxylic acid or an anhydride thereof and that can be melting upon heat
REFERENCES:
patent: 5049592 (1991-09-01), Kronstein
Asai Tamio
Maruhashi Yoshitsugu
Michl Paul R.
Toyo Seikan Kaisha Ltd.
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