20~47 TITLE: MEDICAL ADHESIVE PRODUCT
BACKGROUND OF THE INVENTION
In wound treatment, it is heretofore known to utilize oxygen- and moisturc vapor-pcrmcable drcssings consisting of a thin polymer ~ilm coated with a hypoallcrgenic or "medical grade" adhesive. As an example of such a dressing, mention may be made of "POLYSKIN" (trademark of The Kendall Company, assignee of the present invention), a transpaxent dressing of the foregoing general description intended primarily for use as a dressing for peripheral and central IV catheters as well as a wound dressing on minor abrasions and superficial decubitus ulcers.
With such dressings, it is of course most desirable that the dressing maintain its adherence to the skin so that it is retained in place until the clinician chooses to remove or replaces it.
However, i~ is known that skin moisture and/or wound fluid undermines the adhesive, so that the dressing does not properly adhere to the skin.
Stated simply, the task of this invention is to provide medical adhesive products such as dressings of the foregoing description having an adhesive layer or coating that obviates the problem of undermining by fluid while at the same time permitting transpiration of vapor through the vapor-permeable dressing carrying the adhesive coating.
patO4118 2 S~47 BRIEF DESCRIPTION OF TE~E LNVENTION
In accordance with the present invention this task is solved in an elegant manner by applying the adhesive as a discontinuous coating of thick intersecting deposits defining islands or isolated areas of the dressing which are characterized as being substantially or effectively free of adhesive, the thickness of the adhesive deposits being such that fluid becomes ~trapped~ in the respective islands defined by the adhesive deposits so that it cannot diffuse laterally whereby to undermine the adhesiveness.
In the preferred embodiment, the intersecting deposits defining the individual islands may be termed a "grid pattern" wherein the intersecting deposits of adhesive are lines defining substantially rectangular non-adhesive islands, as illustrated in the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
The Figure is a fragmented perspective view of the preferred embodiment of the invention, with the dimensions exaggerated for purposes of illustration.
patO4118 3 ~0~5Z~7 DETAILED DESCRIPTION OF THE INVENTION
l~s heretofore mentioned, the present invention is directed to medical products consisting of a thin vapor-permeable film having an adhesive on one surface thereof for adhering the dressing to the skin, the task of the invention being to provide the adhesive in such a manner that it ef~ectively resists undermining of its adhesiveness by skin moisture andtor wound fluid while at the same time retaining the ability of the vapor~permeable backing to permit transpiration of skin moisture therethrough.
Applicant's U.S. Patent 4,935,087 issued June 19, 1990 discloses wound dressings, a feature of which (Col. 1) is that fluids from the wound are dissipated into an absorbent layer and do not undermine the adhesive of the dressing surrounding the wound. As is described thexein, the dressing comprises an absorbent layer sandwiched between a transparent backing sheet having a relatively high water vapor permeability and a front sheet such as POLYS~IN (bottom of Col. 3) which is an adhesive coated elastomer film highly permeable to water vapor.
At the top of Col. 4 it is stated that apertures are punched in both the front sheet and the adhesive with a 1/8 inch circular punch with the apertures being on a one inch square grid pattern.
Apart from being directed to medical products of a different structure, the present invent~on has as its task to provide dressings and medical tapes which have markedly superior ability to prevent fluid undermining than that obtainable by the perforated adhesive-coated polymeric film described in the patent.
The objects of the invention are accomplished by providing intersecting thick adhesive deposits deEining individual islands or isolated areas effectivel~ adhesive-free and from which fluid which can induce undermining cannot escape.
Since trace amounts of adhesive may be detected in patO4118 4 ~ o~x~
~le island areas by electron photomicroscopy or other analytical means, it cannot be said with a certai~tY that these areas are completely or totally free of adhesive. Accordingly, as used herein and in the appended claims, the term "effectively~ adhesive free connotes areas which at most contain inconsequential amounts of adhesive material and which present no significant barrier to transpiration o~ skin moisture through the overlying film.
The nature and objects of the invention will be more readily apparent by reference to the accompanying drawing taken in conjunction with the following detailed description.
As shown in the illustrative drawing, a medical adhesive product of this invention 10 consists of a thin film 12 carrying a discontinuous coating of thick intersecting deposits of a pressure-sensitive adhesive 14 defining islands or isolated areas 16 wherein fluid becomes trapped so that it cannot diffuse laterally whereby to undermine the ability of the product to adhere to the skin and thus be retained in place until removal or replacement is contemplated.
As heretofore alluded to, film lZ may be any of the thin vapor-permeable films previously known in the art.
Typically, such films may be on the order of about 1 mil thick and possess a vapor transmission rate of at least 50 gms/m2t24 hrs @ 37c, 50% RH. Preferably, the amount transmitted under the aforementioned conditions will be at least 500 grams.
Adhesive 14 may comprise any of the per se known acrylic or rubber-based hypoallergenic pressure-sensitive adhesives commonly referred to in the adhesive industry as "medical grade" adhesives. Their selection per se comprises no part of this invention and will be a matter of individual choice within the expected judgement of the skilled worker.
Adhesive 14 should be of sufficient thickness to provide an effective barrier against lateral diffusion of fluid within the islands defined by the intersecting adhesive lines.
patO4118 5 ~0~5;~ 7 ickness of at least two mils will provide a barxier to inhibit lateral diffusion. However thickness of on the order of at least 5 mils are preferred, most preferably on the order of 10 mils.
The width of the adhesive deposits should be such that transpiration, which can only occur through islands 16, is not significantly inhibited. While Applicant has not conducted tests to ascertain the minimum percentage of surface area for islands 16 which is acceptable, such determination will be a matter of routine experimentation within the judgment of the skilled worker, depending upon the rate of transpiration desired for a particular product.
By way of illustration, Applicant has determined that an island surface area of 25% of the total surface area (an adhesive:island ration of 4:1) is quite satisfactory, with 50%
or a l:l ration of surface area being preferred.
As seen from the drawing, the intersecting lines of adhesive are preferably (for ease of manufacture3 in the form of a first set of parallel lines arranged substantially perpendicular to a second set oE parallel lines to provide a grid pattern wherein the lslands 16 are substarl~ially rectangular in configuration. However, it will be appreciated that the invention is not restricted to any particular configuration and the islands 16 may, for example, be diamond-shaped or even of an irregular configuration, provided, of course, that the ratio of adhesive to islands is no greatex than 4:1, as heretofore mentioned.
The particular method of preparing the novel adhesive products of this invention is not critical and various devices for doing so may be readily suggested to the skilled worker.
For example, one may utilize a plate of a heat-conductive material such as steel which has been etched or engraved to provide an intaglio mold having grooves to receive adhesive in the requisite pattern and thickness. As will be understood, the grooves should have a surface, e.g. by surface treating, which possesses release properties so the adhesive contained therein is non-adherent. I a "sandwich" is then made of the plate, a suitable adhesive 14 such as a hot melt adhesive and the polymer film 12 and the resulting sandwich is then placed in a hot press for the requisite time, e.g. several minutes, the desired adhesive product 10 will be formed.
patO4118 6 ~O~Z~7 The following example illustrates the preparation of a medical adhesive product in accordanae with this invention.
In the surface of a block of steel approximately 5" by 5" a grid pattern was cut using fine saw blades. To do so, a first set of parallel lines was cut, the lines being approximately 0.010" deep, 0.012" wide and spaced approximately 0.025" apart. A substantially identical second set of grid lines was then cut perpendicular to the first set. The resulting grid embossing tool was then surf ace-treated with a Nickel-Teflon release coating for adhesive. A sandwlch was made of the surface-treated grid tool, an acrylic hot melt pressure-sensitive adhesive and an elastomeric film approximately 1.0 mil thick comprising a block copolymer of polyethylene terephthalate and a polyalkylene glycol. The resulting sandwich was placed in a hot press for several minutes. It was then removed (the adhesive separated cleanly from the mold) to provide the desired elastomer film coated with an adhesive pattern that looked like a screen.
In the foregoing illustrative example, the ratio of adhesive to non-adhesive surface area was approximately 1:1.
Although the adhesive areas were thick to provide a good skin seal and fluid barrier, the product nevertheless possessed the vapor permeability of a conventional dressing having a one mil continuous coating. In other words, the islands 16 with no adhesive compensated for the thick adhesive 14 to provide a total water vapor permeability comparable to a conventional dressing.
Throughout the foregoing discussion, reference has been made to medical adhesive products broadly.
The pre~erred such products are thin dressings for uses such as those to which the commercially available "POLYSKIN"~are employed. However, the invention is not limited thereto.
The invention is also applicable to other types of dressings such as dressings having one of more vents or patO4118 7 .
~S247 ~penings for wound fluids to diffuse.
Further, the invention finds use in thin, hiyhly conformable medical grade adhesive tapes or strips for securing dressings in place. Due to their ~breathability" and the presence of non-adhesive areas, it is postulated that such tapes would minimize s~in problems such as maceration.
Other possible uses will be readily apparent to the skilled worker in the light of the foregoing descriptlon.
In the preferred embodiments, the elastomer will be transparent for purposes of observation while the tape is applied. However, it need not be.
In addition, certain elements performing specific desired functions may be included as component parts of the product.
For example, a conventional release sheet may and preferably will be provided over the adhesive pattern.
Additionally, because of the thin nature of the product, a support sheet may and preferably will be provided on the outer surface of the elastomer (i.e. the surface opposed from the surface carrying `the adhesive) in order to ~acilitate handling and application without wrinkling or tearing. The support sheet will then be removed following application, similar to the manner of applying "POLYSKIN".
Since certain changes may be made without departing from the scope of the invention herein contemplated, it is intended that all matter contained in the ~oregoing description, including the Example and accompanying drawing, shall be taken as illustrative and not in a limiting sense.