Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1996-10-07
2002-11-12
Webman, Edward J. (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C424S484000, C424S443000, C428S327000
Reexamination Certificate
active
06479073
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to adhering a substrate to a surface such as skin using a pressure sensitive adhesive.
Pressure Sensitive Adhesives (PSAs) are normally tacky at room temperature and typically can form a bond to a surface by, at most, light finger pressure. Pressure sensitive adhesive tapes have been used for a variety of marking, holding, protecting, sealing and masking purposes. PSA tapes have many uses in medical applications as well. Such applications typically involve adhering the tape to skin. The irregular and complex surface of the skin presents obstacles in itself, and the wide variation in the skin surface from individual to individual and from one position on the individual to another position compounds these obstacles.
SUMMARY OF THE INVENTION
In a first aspect, the invention features an article that includes a substrate having a surface, at least a portion of which is provided with a pressure sensitive adhesive composition that includes a blend of discrete, crosslinked polymer microspheres and a polymer matrix. The adhesive composition has a substantially smooth, exposed surface available for adhesion.
The microspheres can be tacky microspheres, solid microspheres, hollow microspheres, tack-free microspheres or plastic microspheres. Preferred microspheres comprise tacky, hollow microspheres. In a preferred embodiment, the adhesive composition includes between about 1% and about 75% percent by volume of the microspheres.
The microspheres preferably have an average diameter between about 1 micrometer and about 300 micrometers. A preferred matrix polymer includes an acrylic polymer.
In a preferred embodiment, the thickness of the adhesive composition on the substrate is between about 10 micrometers and about 300 micrometers. The article is preferably substantially transparent upon observation by the naked eye. For example, the article is sufficiently transparent such that a health care worker can observe the skin underlying the article.
The adhesive composition can be in the form of a substantially continuous coating on the surface of the substrate or a discontinuous coating on the surface of the substrate. The microspheres preferably include the reaction product of iso-octylacrylate, acrylic acid, and poly(ethylene oxide)acrylate.
In another aspect, the invention features an article adapted for adhesion to the skin of a patient that includes a substrate having a surface, at least a portion of which is provided with a pressure sensitive adhesive composition that includes a blend of discrete, crosslinked polymer microspheres and a polymer matrix. The adhesive composition has a substantially smooth, exposed surface available for adhesion. The article may be provided, e.g., in the form of a skin patch, wound dressing, adhesive bandage, or island dressing.
In a third aspect, the invention features a method of making an article including the steps of:
(a) preparing a pressure sensitive adhesive composition including a blend of discrete, crosslinked polymer microspheres and a polymer matrix; and
(b) depositing the blend on at least a portion of a substrate in the form of a coating,
the average microsphere diameter, the volume fraction of the microspheres in the composition and the thickness of the coating being selected such that the coating has a substantially smooth, exposed surface available for adhesion.
The smooth surface of the adhesives of the present invention provides for more extensive contact with an opposing surface than corresponding adhesives with protruding microspheres. As a result, the initial peel adhesion of the adhesive composition generally is relatively high. Also, the adhesive composition does not exhibit unacceptably high adhesion build-up over time when adhered to an opposing surface. The refractive indices of the polymer microspheres and matrix are generally substantially the same, making it possible to prepare a substantially transparent article. Such articles, in turn, permit observation of the substrate to which the article is adhered. This feature is particularly useful in medical applications because it enables examination of the underlying skin.
Other advantages and features of the invention will be apparent from the detailed description and from the claims.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention is directed to articles featuring a substrate coated with a pressure sensitive adhesive composition that includes a polymer matrix blended with discrete, crosslinked polymer microspheres. The average microsphere diameter, volume fraction of microspheres and coating thickness are selected such that when the adhesive composition is applied to the substrate, the adhesive composition forms an exposed surface available for adhesion that is substantially smooth on a scale on the order of the size of the microspheres.
Smoothness of the exposed surface on this order indicates that the microspheres are not protruding from the plane of the surface. This is in contrast to adhesives where protrusion of polymer microspheres, whether or not covered by polymer matrix, provides for positionability. Positionability of adhesives with protruding microspheres is due, at least partly, to more limited point contact with the protruding regions during adhesion to an opposing surface.
The substrate generally can be made from any material suitable for the particular application envisioned for the article. Preferred substrates exhibit a desired combination of properties such as moisture vapor permeability, texture, conformability, yield modulus, appearance, processability, and strength. A substrate can have structure on its surface as long as the structure does not interfere with the formation of a smooth layer of adhesive at an appropriate adhesive thickness. For certain applications (e.g., transparent dressings), it is preferred for the substrates to be substantially transparent upon observation by the naked eye of an observer.
Suitable materials for flexible substrates include paper, latex saturated paper, polymeric film, metallic foil, and ceramic sheeting. Appropriate materials for polymeric films include cellulose acetate film, ethyl cellulose film, polyolefins (such as polyethylene and polypropylene, including isotactic polypropylene), polystyrene, polyvinyl alcohol, polyester (e.g., poly(ethylene terephthalate) or poly(butylene terephthalate)), poly(caprolactam), poly(vinylidene fluoride), and the like. Suitable substrates also include commercially available fabrics such as non-woven, woven or knitted fabrics. Such fabrics may be constructed from a wide range of synthetic or natural fibers, used singly or in blends. Examples of suitable non-woven fabrics include carded, spun-bonded, spun-laced, air-laid, blown microfibrous constructions, and stitch-bonded fabrics.
Suitable commercially available substrate materials include kraft paper (available from Monadnock Paper, Inc.); cellophane (available from Flexel Corp.); spun-bond poly(ethylene) and polypropylene, such as Tyvek™ and Typar™ (available from DuPont, Inc.); and porous films obtained from polyethylene and poly(propylene), such as Teslin™ (available from PPG Industries, Inc.), and Cellguard™ (available from Hoechst-Celanese).
Release coated substrates can also be used. Such substrates are typically employed when an adhesive transfer tape is provided. Examples of release coated substrates include silicone coated kraft paper and the like. Tapes of the invention may also incorporate a low adhesion backsize (LAB). The LAB typically is applied to the substrate surface that is opposite the surface bearing the pressure sensitive adhesive.
The adhesive compositions of the present invention are particularly suitable for the production of medical articles intended for adhesion to skin. Examples include tapes, skin patches, strips, wound dressings, monitoring or neuro-stimulating electrodes, transparent adhesive dressings, island dressings (with absorbent polymeric or fabric islands), consumer first aid dressings, drapes, and the like. Suitable substrates for these applicati
Goetz Richard J.
Lucast Donald H.
3M Innovative Properties Company
Burtis John A.
Webman Edward J.
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