Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-09-07
2003-10-07
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C128S897000, C602S904000, C604S264000, C604S404000, C604S408000, C604S910000, C604S915000, C428S036800, C428S036900, C428S036920
Reexamination Certificate
active
06630215
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a medical material comprising an aromatic vinyl compound/&agr;-olefin random copolymer and a medical device formed therefrom. More particularly, the present invention relates to a medical material which has not only radiation resistance but also biocompatibility, particularly blood compatibility and is excellent in the mechanical properties and transparency and which contains substantially no chlorine, and a medical device made thereof.
BACKGROUND ART
Medical devices such as tubes to be used for intravenous drip injection, catheters, circuits and bags or containers for bloods, infusion solutions and dialysis, are usually required to be excellent in not only flexibility, elasticity and transparency but also radiation resistance and biocompatibility, particularly blood compatibility. Further, sufficient strength durable for operations is also required. Especially, tubes are required to have proper elastic elongation and touchiness and to have so-called resilience. Heretofore, they have been produced in many cases from a soft vinyl chloride which is a base material having these properties. Further, in recent years, disposability of the medical devices has been advanced, and they are in many cases disposed by incineration treatment to prevent biohazard. With respect to medical devices wherein soft polyvinyl chloride is used, the load to the environment due to e.g. incineration is considered to be problematic, and a study is being made to substitute other materials for the soft polyvinyl chloride as the base material for medical devices.
As films and tubes containing no chlorine, those made of a linear low density ethylene/&agr;-olefin type copolymer, have been known, but there has been no medical material which fully satisfies the above conditions as a medical material. As a resin composition which is excellent in flexibility and which presents a formed product suitable for medical use, JP-A-4-159344 proposes a resin composition comprising an olefin type resin, a hydrogenation product of styrene/butadiene block copolymer and a hydrogenation product of styrene/isoprene block copolymer. This resin composition presents a formed product which is excellent in flexibility and has a feature that even if the formed product is incinerated, no toxic gas will be formed. However, the formed product obtained by such a resin composition is not yet adequate in another property i.e. transparency required for medical devices and still has a room for improvement in this respect.
Further, JP-A-3-202298 discloses that a non-soft vinyl chloride resin, specifically a composition comprising a styrene type elastomer, polypropylene, etc. or a composition of a citric acid ester, has an activity to inhibit hemolysis, and JP-A-6-319785 discloses a thermoplastic polyester type composition. However, either one is not adequate as compared with the hemolysis inhibitory action of a plasticizer in the soft vinyl chloride resin and is poor in the practical applicability.
Further, among catheters, a balloon catheter of a type whereby a balloon is expanded in a blood vessel and then shrinked to be retained for a few days, has a problem such that if the surface loosens, a blood clot is likely to result due to slackening of blood flow. A gastrointestinal catheter is repeatedly pulled by a peristaltic motion of the gastrointestinal tract. Accordingly, in such an application, it is required to be excellent in strain recovery. Thermoplastic polyurethane used for conventional catheters is excellent in mechanical properties, but has a drawback that it is poor in strain recovery.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a medical product which is excellent not only in flexibility, elasticity and transparency required for medical use but also in radiation resistance and biocompatibility including blood compatibility and which is free from generation a toxic gas at the time of incineration, and a medical device made thereof.
The present inventors have conducted an extensive study to solve the above problem and as a result, have found that an aromatic vinyl/&agr;-olefin random copolymer or a resin composition having a plasticizer blended to such a copolymer in a certain amount, is suitable as a medical material or a material for a medical device, and have finally completed the present invention.
Namely, the present invention is a medical material and a medical device comprising an aromatic vinyl compound/&agr;-olefin random copolymer, preferably a medical material and a medical device, obtained by processing a resin composition (C) comprising 100 parts by weight of a resin component (A) containing at least 50 wt % of an aromatic vinyl compound/&agr;-olefin random copolymer and from 0.1 to 200 parts by weight, preferably from 0.5 to 100 parts by weight, more preferably from 1 to 50 parts by weight, of a plasticizer (B).
The medical material and the medical device of the present invention are excellent in flexibility, elasticity, transparency, radiation resistance and biocompatibility. In the present invention, a medical device is meant for a medical device to which sterilization treatment has been applied and which is to be used for medical application. A medical material is meant for a material for a medical device and is meant for e.g. a sheet (including a film and a plate) obtained by processing an aromatic vinyl compound/&agr;-olefin random copolymer or its composition (C) by e.g. extrusion stretch forming.
The aromatic vinyl compound/&agr;-olefin random copolymer to be used in the present invention, is basically a copolymer made of an aromatic vinyl compound monomer and an &agr;-olefin monomer. The structure is not particularly limited. However, for example, an aromatic vinyl compound/&agr;-olefin random copolymer obtainable by means of a metallocene catalyst of the chemical formula 1 which will be described hereinafter, has high stereo regularity and a head-to-tail chain structure of at least two aromatic vinyl compound units, whereby it is excellent in initial tensile modulus of elasticity, breaking strength, elongation, transparency and chemical resistance.
As the aromatic vinyl/&agr;-olefin random copolymer to be used in the present invention, one having a weight average molecular weight of at least 30,000, is practical.
The upper limit for the weight average molecular weight is not particularly limited, but it is preferably at most 3,000,000, more preferably at most 1,000,000. If the molecular weight exceeds 3,000,000, the melt viscosity tends to increase, whereby molding by a common molding method such as injection molding or extrusion molding tends to be difficult.
Here, the weight average molecular weight (Mw) is a molecular weight calculated as polystyrene, obtained by GPC using standard polystyrene.
Further, the molecular weight distribution (Mw/Mn) is at most 6, preferably at most 4, particularly preferably at most 3. The molecular weight distribution being small or the uniformity of the resin being high consequently contributes to good transparency of the resin.
Mn represents a number average molecular weight and can likewise be measured by a GPC method.
With the aromatic vinyl compound/&agr;-olefin random copolymer to be used in the present invention, the glass transition point (Tg) can be changed within a wide range depending upon the content of the aromatic vinyl compound. For example, with the styrene-ethylene random copolymer, Tg becomes to be close to 30° C. at a styrene content of 50% by molar ratio. Further, by using it in combination with a thermoplastic resin having Tg of at least 30° C, Tg as the composition can be set within a wide range, whereby the temperature dependency of viscoelasticity such as storage modulus or loss tangent (tan&dgr;) can be controlled. Accordingly, in the present invention, Tg can be increased to a level close to normal temperature, if desired, by mixing a petroleum resin, a terpene resin, a cumarone-indene resin, a rosin type resin or hydrogenation derivatives thereof, having high Tg, to th
Arai Toru
Nishitoba Yukiko
Oda Takeshi
Okamoto Akio
Otsu Toshiaki
Denki Kagaku Kogyo Kabushiki Kaisha
Nolan Sandra M.
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