Surgery: splint – brace – or bandage – Bandage structure
Reexamination Certificate
1999-09-21
2001-06-12
Brown, Michael A. (Department: 3764)
Surgery: splint, brace, or bandage
Bandage structure
C602S042000, C602S043000, C602S044000, C602S045000, C602S046000
Reexamination Certificate
active
06245959
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a substrate for an adhesive dressing used for application to the skin in medical sanitary field or the like, a medical adhesive dressing and an adhesive tape (also termed as “adhesive plaster” or “bandage”),e.g.,a first-aid adhesive tape, using the same. More particularly, the present invention relates to a substrate for an adhesive dressing having excellent feeling and mechanical strength, which is used in an adhesive tape, a large-sized adhesive tape, a dressing material, a drape material or the like, and can be utilized in a medical adhesive dressing and an adhesive tape.
BACKGROUND ART
A medical adhesive dressing generally comprises a substrate film and a pressure-sensitive adhesive layer formed on one side of the substrate film and is adhered to a skin surface to be applied through the pressure-sensitive adhesive layer upon use.
Most substrates conventionally employed in adhesive dressings for such a medical use comprise a soft polyvinyl chloride as a main component in view of a skin follow-up property (flexibility), a stretchability, hand and drape or the like while they are adhered.
However, soft polyvinyl chlorides generally contain one or more plasticizers such as dioctyl phthalate in large amounts in order to impart flexibility to a film that is formed. Many problems have been pointed out that migration of the plasticizer(s) into a pressure-sensitive adhesive layer decreases the cohesive force of a pressure-sensitive adhesive layer, which causes a phenomenon that an adhesive remains on the skin or decreases the adhesion strength of the pressure-sensitive adhesive layer. On the other hand, in recent years, importance has been increasingly attached to environmental problems and from this standpoint, various attempts have been made in every field to use less amounts of polyvinyl chloride resins, which contain chlorine atoms, i.e., species of halogen.
Further, in the case where it is attempted to use an adhesive tape with a film substrate comprising a polyvinyl chloride resin by winding it around a site that is in a brisk motion, such as a joint portion of fingers, the adhesive tape elongates in a proper degree when it is affixed so that it can be wound around the site fittingly. However, since the adhesive tape has a low shrinkage rate and is susceptible to a stress relaxation, a gap is gradually caused between the adhered surface and the adhesive tape after the affixing. As a result, the adhesive tape may fall out from the finger or the like site, or the position of the adhesive tape may shift. Further, since the polyvinyl chloride resin has a high temperature-sensitivity, the film substrate becomes harder in the winter seasons, so that it may happen that the face of a user is injured while he or she washes his or her face.
Therefore, a substrate film for an adhesive dressing with a polyolefin-based resin as a substitute resin for polyvinyl chloride has come to be examined.
In order to obtain a flexibility equal to that of the polyvinyl chloride resin film in the substrate film comprising the above-mentioned substitute resin, various attempts have been made such as reduction in the thickness of the substrate film or mixing an elastomer component to impart stretchability. However, the resulting substrate film is insufficient in mechanical strength, and it cannot be peeled off cleanly when it is peeled after it is affixed and used. As a result, the substrate film may be torn off.
In order to improve such a poor mechanical strength, it has been attempted to provide a substrate film of multilayer structure and form a resin layer having a relatively high strength as an inner layer thereof. However, the problem may arise that the substrate film curls or the substrate film is difficult to affix since it easily curls by the stress when removing a release paper.
As a result of extensive investigations with view to solving the problem on the conventional substrate film comprising polyvinyl chloride and the problem on the substrate film comprising a polyolefin-based resin as a substitute therefor, the present inventors have found that use of an ethylene/vinyl acetate copolymer having specified properties as a film substrate can provide a medical adhesive dressing or an adhesive tape that satisfies the desired characteristics such as flexibility, stretchability, mechanical strength, curl prevention property and the like, thus having completed the present invention.
DISCLOSURE OF THE INVENTION
Accordingly, the present invention is to provide a substrate for an adhesive dressing, characterized by comprising an ethylene/vinyl acetate copolymer having a weight average molecular weight (Mw) of 1×10
4
to 1×10
5
, a molecular weight distribution (Mw/Mn) of 4.0 or less, a melt flow rate (MFR) of 3.0 g/10 minutes or less, and a vinyl acetate content of 15 to 28% by weight.
Further, the present invention is to provide a medical adhesive dressing comprising the above-mentioned substrate for an adhesive dressing and a pressure-sensitive adhesive layer formed on one side of the substrate and also an adhesive tape having a pad for protecting a wounded portion arranged on a part of the surface of the pressure-sensitive adhesive layer.
BEST MODE FOR CARRYING OUT THE INVENTION
The substrate for an adhesive dressing of the present invention is obtained by molding an ethylene/vinyl acetate copolymer having a weight average molecular weight (Mw) of 1×10
4
to 1×10
5
, a molecular weight distribution (Mw/Mn) of 4.0 or less, a melt flow rate (MFR) of 3.0 g/10 minutes or less, and a vinyl acetate content of 15 to 28% by weight into a sheet form by a calendering method, an inflation method, an extrusion method or the like. As the sheet formation method, it is preferable to use a calendering method from the viewpoints of ease of molding a resin having a poor flowability (MFR≦3.0 g/10 minutes) as in the present invention into a sheet form and of ease of processing when subjecting the molded sheet to embossing finish.
In the present invention, adjustment of vinyl acetate content in the ethylene/vinyl acetate copolymer to 15 to 28% by weight, preferably 20 to 25% by weight, can inhibit crystallization of the copolymer resin, so that a substrate having moderate elasticity and flexibility imparted thereto can be obtained. If the vinyl acetate content is less than 15% by weight, the copolymer has properties like those of a soft polyethylene, and thus has poor flexibility. On the other hand, if the vinyl acetate content exceeds 28% by weight, flexibility is improved, but the substrate obtained tends to exhibit pressure-sensitive properties. As a result, the phenomenon of blocking among substrates occurs during the production process or use feeling becomes poor, which is unpreferable. Further, the mechanical strength is gradually decreased, and this is also unpreferable.
Further, the ethylene/vinyl acetate copolymer used in the present invention has the greatest characteristics that the weight average molecular weight (Mw) is 1×10
4
to 1×10
5
, preferably 4.5×10
4
to 9.5×10
4
, and the molecular weight distribution (Mw/Mn) is a relatively narrow molecular weight distribution of 4.0 or less, preferably 3.5 or less. In the present invention, the tendency is observed that if Mw exceeds the above upper limit, the flexibility decreases, and if Mw is below the lower limit, the mechanical strength becomes insufficient, which are unpreferable. Further, if Mw/Mn exceeds 4.0, it is insufficient in mechanical strength. In many cases, the ethylene/vinyl acetate copolymers generally used have a molecular weight distribution exceeding 4.3.
The ethylene/vinyl acetate copolymer used in the present invention is characterized by not only satisfying the above-mentioned characteristics, but also having a poor flowability of 3.0 g/10 minutes or less in melt flow rate (MFR). MFR has a relatively high correlation with the tensile strength of a resultant film and also with the above-mentioned Mw. Generally, if MFR is 3.0 g/10 minutes
Kinoshita Takashi
Kousaka Takahiro
Ohira Osamu
Sasaki Yasuyuki
Brown Michael A.
Hamilton Lalita M.
Nitto Denko Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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