Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF MANUFACTURE OF A WINDOWLESS FRAME DELIVERED
DRESSING
This is a divisional application of Canadian
Patent Application No. 2,157,040 filed February 8, 1994.
Field of the Invention
The present invention relates to pressure
sensitive adhesive composite dressings comprising thin film
backings coated on one side with a pressure sensitive
adhesive, that are delivered by a removable frame. The
present invention also relates to methods of manufacturing
such pressure sensitive adhesive composite dressings.
The subject matter of this divisional application
is directed to a method of manufacturing an adhesive
composite dressing.
The subject matter of the parent application was
restricted to an adhesive composite dressing. However, it
should be understood that the expression "the invention" and
the like when used herein encompasses the subject matter of
both the parent and this divisional application.
Background of the Invention
Transparent film dressings are widely used as
protective layers over wounds because they facilitate
healing in a moist environment while acting as a barrier to
contaminating liquids and bacteria. The films are also used
as surgical drapes because of their barrier properties.
Dressings and drapes fitting the above description are
available under a number of trade names such as TEGADERMTM
(3M Company, St. Paul, MN), BIOCLUSIVETM (Johnson & Johnson
Company, New Brunswick, NJ), OP-SITETM (T.J. Smith & Nephew,
Hull, England), and UNIFLEXTM (How Medica, Largo, FL).
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The polymeric films used in those dressings and
drapes, referred to as dressings below, are conformable,
i.e., the films are extremely thin, flexible and supple.
They are typically supplied with a releasable protective
liner covering the adhesive coated surface of the film.
When the liner is removed, the adhesive coated film tends to
wrinkle and adhere to itself, interfering with the smooth,
aseptic application of the dressing to a patient's skin.
Various delivery systems have been proposed to address this
problem.
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One known delivery system is described in U.S.
Patent No. 4,485,809 in which a dressing is attached
to a release liner by the use of adhesive between the
dressing and the liner. The liner material functions
as a frame to provide support during placement of the
dressing after a center section of the release liner
has been removed. After the dressing has been
affixed, the frame is removed from the dressing by
tearing the film along perforations provided around
the center section. Because the center section
functions as a liner, however, it cannot be removed
until immediately before the dressing is placed on a
patient. Furthermore, because the frame must be torn
from the perimeter of the dressing, the adhesive bond
between the skin and the dressing is often disturbed,
which can then lead to premature failure and removal
of the dressing by bed linens and other means.
U.S. Patent No. 4,600,001 also describes a
delivery system which includes a pair of opposed
strips and a delivery layer which is heat laminated to
the film. In use, a release liner is removed from a
dressing, the dressing is placed on a patient, the
delivery means layer is then removed from attachment
with the film. After the film is secured on a
patient, the opposed strips and film attached to them
are removed using perforations in the film. In this
device, the delivery means layer is preferably
transparent or translucent to allow viewing through
the dressing during placement. Like the dressing
described above, the tearing of the film to remove the
opposed strips can disturb the adhesive bond between
the skin and the dressing, again leading to premature
failure.
Frame-type delivery systems offer an alternative
delivery system for use with conformable thin films.
The use of a removable frame, which does not require
tearing of the filn after it has been placed on the
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patient, avoids the problems described above.
Furthermore, the ability to view the attachment site
on a patient through the film exposed within the frame
aids in accurate placement of the dressing on a
patient.
EPO Publication No. 0 051 935 describes a
removable frame delivery system for thin polymeric
film dressings. In that delivery system, the bond
between the frame material and the film is mechanical
in nature and is formed when the film is extruded onto
the frame material. Dressings according to this
reference are manufactured with a central window which
is control depth die cut in the frame material. In
use, the die cut window is first removed from the
center of the frame, after which the release liner is
removed from the adhesive layer and the dressing is
placed on a patient. The frame is then removed from
the film leaving the dressing in place on the patient.
One drawback associated with dressings
manufactured according to EPO Publication No. 0 051
935 is the additional step of removing the window
prior to placing the dressing on a patient. Although
the window does not have to be removed before the
dressing is placed on a patient, it is advantageous to
do so as removal allows the person applying the
dressing to view the area to which it is applied.
Removal of the window before packaging such dressings
has been attempted. The bond between the window
material and the backing was broken by running the
dressing over a sharp object and pulling the window
off as it released from the backing. That process,
however, resulted in two additional problems. First,
the maximum speed at which the process could be
effectively accomplished was too slow. Second, the
bond of the frame to the dressing was compromised and
led to the failure of the frame delivery system.
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U.S. Pat. No. Re 33,727 also describes a frame
type delivery system including a composite with a thin
polymeric film and a pressure-sensitive adhesive
coated on one surface of the polymeric film. A
release liner is attached to the adhesive coated
surface of the film and a frame is attached to the
exposed surface of the film opposite the surface to
which the adhesive has been applied. When applied,
the release liner is first removed from the adhesive
coated surface, the film and frame are then placed on
a patient and the frame is then removed from the film,
which is left on the skin. '
U.S. Pat. No. Re 33,727 does not discuss the
mechanism by which the frame is bonded to the film,
nor does it discuss the problems associated with
removing the central window without disturbing the
bond between the frame and the film. The patentee in
Re 33,727, however, relied on label construction for
enablement which used either pressure sensitive
adhesives or a radiation-curable film to bond layers
of a composite together. In this regard, such frame
delivered dressings according to the above references
contemplate the extrusion or radiation curing of the
thin film directly on the carrier material.
A low adhesion coating on the top face of the
dressing provides the ability to apply and remove
tapes and other devices over the dressing, thereby
enabling the dressing to be used as a platform for
those tapes and other devices. The low adhesion
coating allows the tapes and other devices to be
removed without also removing or disturbing the
underlying dressing and allowing additional
contamination to reach the wound. An. example of such
a dressing is TEGADERM' No. 1620 dressing available
from 3M Company, St. Paul, MN.
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Summarv of the Invention
The adhesive composite of the present invention
(and methods of manufacturing the same) address the
above-noted problems by providing a windowless frame
delivered dressing having a conformable backing with a
pressure sensitive adhesive coated on a bottom face
and an optional low adhesion coating on a top face,
and which is supported by a removable frame attached
to the top face of the backing. In particular, the
present invention overcomes the problems discussed
above by heat sealing the frame to the backing, and if
need be, over a heat seai compatible low adhesion
coating on the top -face of the backing. Furthermore,
the method and apparatus of the present invention
provide such a frame delivered dressing in which the
window is removed prior to use by the consumer,
thereby minimizing the steps necessary to apply the
dressings and reducing the waste stream at the
consumer level.
In one preferred method, the present invention
also offers the advantage of a reduced number of
processing steps which, in turn, further reduces the
costs associated with producing dressings according to
the present invention. Furthermore, the application
of a low adhesion coating on the backing which is
compatible with the heat seal bond between the frame
and the backing provides a product, which in use
displays reduced friction between the dressing and bed
linens or other surfaces which can lead to the
accidental removal of the dressings, resulting in
contamination of the wound and necessitating
replacement of the dressing.
In particular, the present invention provides an
adhesive composite dressing comprising: (a) a
conformable backing having top and bottom faces; (b)
a pressure sensitive adhesive coated on at least
a portion of the bottom face of the backing; (c) a
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liner releasably adhered to the pressure sensitive adhesive
opposite the backing; and (d) a frame releasably attached to
and covering a portion of the top face of the low adhesion
coating and backing, the frame being heat-sealed to the low
adhesion coating and backing and substantially defining a
window proximate a center of the backing exposing a portion
of the top face of the backing, the frame further being
formed of material substantially more rigid than the backing
to provide rigidity to the adhesive composite. The
composite dressing may also include an optional low adhesion
coating on the top face of the backing, in between the frame
and the top face of the backing.
The present invention also provides a method of
manufacturing an adhesive composite dressing comprising the
steps of: (a) providing a conformable backing have top and
bottom faces, a pressure sensitive adhesive on at least a
portion of the bottom face of the backing and a liner on the
pressure sensitive adhesive; (b) heat sealing a carrier to
the top face of the backing, the bond between the carrier
and top face of the backing being greater than the bond
between the liner and the pressure sensitive adhesive; and
(c) removing a portion of the carrier from the top face of
the backing, thereby providing a frame formed of the carrier
on the top face of the backing.
According to one aspect of the invention of the
parent application, there is provided an adhesive composite
dressing comprising: (a) a conformable backing having top
and bottom faces; (b) a pressure sensitive adhesive coated
on at least a portion of the bottom face of the backing; (c)
a liner releasably adhered to the pressure sensitive
adhesive opposite the backing; and (d) a carrier releasably
attached to and covering the top face of the backing, a cut
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in the carrier substantially defining a window proximate a
center of the backing exposing a portion of a top face of
the backing when the window is removed, the carrier further
being formed of material substantially more rigid than the
backing to provide rigidity to the adhesive composite,
wherein the carrier provides a frame about a substantial
portion of the periphery of the backing the frame being
releasably heat-sealed to the backing.
According to one aspect of the invention of the
present divisional application, there is provided a method
of manufacturing an adhesive composite dressing comprising
the steps of: (a) providing a conformable backing having top
and bottom faces, a pressure sensitive adhesive on at least
a portion of the bottom face of the backing and a liner on
the pressure sensitive adhesive; (b) attaching a carrier to
the top face of the backing, the carrier having a cut
defining a window proximate a center of the backing, wherein
the carrier provides a frame about a substantial portion of
the periphery of the backing the frame being releasably heat
sealed to the top face of the backing to form a bond between
the carrier and the top face of the backing that is greater
than the bond between the liner and the pressure sensitive
adhesive.
These and various other advantages and features of
novelty which characterize the invention are pointed out
with particularity in the claims annexed hereto and forming
a part hereof. However, for a better understanding of the
invention, its advantages, and objects obtained by its use,
reference should be had to the accompanying drawings and
descriptive matter, in which there is illustrated and
described preferred embodiments of the invention.
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Brief Description of the Drawings
The invention may be further illustrated by
reference to the accompanying drawings wherein:
FIGURE 1 is a top perspective view of one
preferred embodiment of a dressing according to the
present invention;
FIGURE 2A is a top perspective view of an
alternate preferred embodiment of a dressing according
to the present invention;
FIGURE 2B is a bottom perspective view of the
dressing of Fig. 2A with the liner removed;
FIGURE 3 is a top perspective view in partial
cross-section of an alternate preferred embodiment of
a dressing manufactured according to the present
invention;
FIGURE 4 is a flow chart of one preferred method
of manufacturing dressings according to the present
invention;
FIGURES 5A & 5B are flow charts of alternate
preferred methods of providing backing/pressure
sensitive adhesive/liner composites during a preferred
manufacturing process according to the present
invention;
FIGURE 6 is a schematic diagram in perspective of
one preferred method of manufacturing dressings
according to the present invention;
FIGURE 7 is a schematic diagram in,perspective of
an alternate preferred method of manufacturing
dressings acccrding to the present invention; and
FIGURE 8 is a schematic diagram in perspective of
an alternate preferred method of manufacturing
dressings according to the present invention.
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Detailed Description of
Embodiments of the Invention
Figs. 1-3 depict preferred embodiments of
dressings manufactured according to the present
invention. The adhesive composite configuration of
the present invention is useful in connection with any
conformable backing having a pressure-sensitive
adhesive coating onto it. Representative backings
include nonwoven fibrous webs, woven fibrous webs,
knits, and other familiar backing materials. The
preferred backing materials are'translucent or
transparent polymeric films.
The invention is particularly useful in the field
of pressure sensitive adhesive composites having high
moisture vapor permeable film backings. Issued U.S.
Patent Nos. 3,645,835 and 4,595,001, describe methods
of making such films and methods for testing their
permeability. Preferably, the film/adhesive composite
should transmit moisture vapor at a rate equal to or
greater than human skin. Preferably, the adhesive
coated film transmits moisture vapor at a rate of at
least 300 g/m2/24 hrs/37 C/100-10% RH, more preferably
at least 700 g/mZ/24 hrs/37 C/100-10% RH, and most
preferably at least 2000 g/mZ/24 hrs/37 C/100-10% RH
using the inverted cup method as described in U.S.
Patent No. 4,595,001.
The backing is preferably conformable to
anatomical surfaces. As such, when the backing is
applied to an animal's anatomical surface, it conforms
to the surface even when the surface is moved. The
preferred backing is also conformable to animal
anatomical joints. When the joint is flexed and then
returned to its unflexed position, the backing
stretches to accommodate the flexion of the joint, but
is resilient enough to continue to conform to the
joint when the joint is returned to its unflexed condition.
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A description of this characteristic of backings
preferred for use with the present invention can be
found in issued U.S. Patent Nos. 5,088,483 and
5,160,315. As discussed, particularly preferred
backings are elastomeric polyurethane, polyester, or
polyether block amide films. These films combine the
desirable properties of resiliency, high moisture
vapor permeability, and transparency found in
preferred backings.
The preferred pressure sensitive adhesives which
can be used in the adhesive composites of the present
invention are the normal adhesives which are applied
to the skin such as the acrylate copolymers described
in U.S. Patent No: RE 24,906, particularly a 97:3 iso-
octyl acrylate:acrylamide copolymer. Also preferred
is an 70:15:15 isooctyl acrylate: ethyleneoctyl
acrylate:acrylic acid terpolymer, as described in U.S.
Patent No. 4,737,410 (Example 31). Other useful
adhesives are described in U.S. Pat. Nos. 3,389,827,
4,112,213, 4,310,509, and 4,323,557. Inclusion of
medicaments or antimicrobial agents in the adhesive is
also contemplated, as described in U.S. Patent Nos.
4,310,509 and 4,323,557.
The preferred pressure sensitive adhesives
described above preferably transmit moisture vapor at
a rate greater to or equal to that of human skin.
While such a characteristic can be achieved through
the selection of an appropriate adhesive, it is also
contemplated in the present invention that other
methods of achieving a high relative rate of moisture
vapor transmission, such as pattern coating the
adhesive on the backing, as described in U.S. Patent
No. 4,595,001.
Liners which are suitable for use in the adhesive
composites of the present invention can be made of
kraft papers, polyethylene, polypropylene, polyester
or composites of any of these materials. The liners
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are preferably coated with release agents such as
fluorochemicals or silicones. For example, U.S.
Patent No. 4,472,480, describes low surface energy
perfluorochemical liners. The preferred liners are
papers, polyolefin films, or polyester films coated
with silicone release materials. Examples of
commercially available silicone coated release papers
are POLYSLIKTM silicone release papers available from
James River Co., H.P. Smith Division (Bedford Park,
Ill.) and silicone release papers supplied by Daubert
Chemical Co. (Dixon, Ill.). The most preferred liner
is 1-60BKG-157 paper liner available from Daubert,
which is a super calandered Kraft paper with a water-
based silicone release surface.
Other combinations of adhesives and liners are
contemplated for use with embodiments according to the
present invention. Those skilled in the art will be
familiar with the processes of testing a new adhesive
against different liners or a new liner against
different adhesives to arrive at the combination of
qualities desired in a final product. The
considerations pertinent to the selection of a
silicone release liner can be found in Chapter 18 of
the Handbook of Pressure Sensitive Adhesive
Technology, Van Nostrand-Reinhold, 1982, pp. 384-403.
U.S. Pat. No. 4,472,480 also describes considerations
pertinent to the selection of a perfluoropolyether
release liner.
In the preferred embodiments according to the
present invention, the choice of adhesives is limited
to those that are safe to use on human skin, and
preferably to those that are of the class known as
"hypoallergenic". The preferred acrylate c0polymers
are adhesives of this class. Liners are available
from a variety of manufacturers in a wide variety of
proprietary formulations. Those skilled in the art
will normally test those liners in simulated use
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conditions against an adhesive of choice to arrive at
a product with ttie desired release characteristics.
The carrier material used to supply the frames
for dressings manufactured according to the present
invention is preferably substantially more rigid than
the backing to prevent the backing from wrinkling
during application. The carrier material must also be
heat-sealable to the backing, with or without the low
adhesion coating described below, for the purpose of
manufacturing the preferred dressings. In general,
the preferred carrier materials can include, but are
not limited to, polyethylene/vinyl acetate copolymer-
coated papers and polyester films. One example of a
preferred carrier material is a polyethylene/vinyl
acetate copolymer-coated super calandered Kraft paper
(1-80BKG-157 PE; Daubert Chemical Co.).
The adhesive composites of the present invention
preferably include a low adhesion coating on a top
face of the backing, which is coated as a solution of
polyvinyl N-octadecyl carbamate and a blend of
silicone resins, further described in conjunction with
Example 1 below. The preferred low adhesion coating
is compatible with the heat seal bond between the
frame and the backing and also retains its low
adhesion characteristics after heat sealing. While it
is preferred that the top face of the adhesive
composites of the present invention include a low
adhesion coating, adhesive composites without such a'
coating with a framed carrier material heat sealed
thereto are also considered to be within the present
invention.
The preferred low adhesion coating, polyvinyl
N-octadecyl carbamate, is disclosed in detail in U.S.
Patent No. 2,532,011. As described in that reference,
the polyvinyl carbamate polymers which exhibit
properties useful for the present invention have
carbamate side chains terminating with an alkyl group
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more than five carbon atoms in length. They can be
made by reacting polyvinyl alcohol and an appropriate
isocyanate having a terminal alkyl group. In this
regard, the preferred polyvinyl N-octadecyl carbamate
is made by reacting polyvinyl alcohol and octadecyl
isocyanate, which has 18 carbon atoms in the nitrogen-
bonded side chain alkyl groups. As used here, the
term "isocyanate" refers to monofunctional compounds
containing a single -N=C=O group, and does not include
di-isocyanates.
It will also be understood that other coatings
providing the low adhesion characteristics of the
preferred coating could be substituted. The primary
considerations in choosing any low adhesion coatings
according to the present invention are their release
characteristics and their compatibility with the heat
seal bond between the frame and the backing.
Because the low adhesion coating on the backing
is very thin, the heat seal bond incorporates
materials from all three layers of the carrier
material, the low adhesion coating and the backing.
As a result, the selection of the carrier material,
low adhesion coating and backing must be made as a
combination which provides suitable heat sealing
characteristics. Examples of combinations providing
suitable heat seal bonding are presented in the
examples below, but it is contemplated that many other
combinations will also satisfy the requirements for
the apparatus and method according to the present
invention.
Preferred Dressings
Turning to Fig. 1, one preferred embodiment of an
adhesive composite dressing 10 comprises a backing 14
which is preferably conformable as described above; a
low adhesion coating 13 on a top face of the backing
14; a frame 12 attached to the top face of the backing
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14 over the low adhesion coating 13; a
pressure-sensitive adhesive 16 on a bottom face of the
backing 14; and a liner 18 attached to the exposed
surface of pressure-sensitive adhesive 16.
In the preferred embodiment, the frame 12 is
attached to backing 14 (over low adhesion coating 13)
with,a heat seal bond. Frame 12 provides rigidity to
the backing 14 after liner 18 is removed and
preferably has an opening proximate its center forming
a window 15 which exposes a portion of the top face of
backing 14. As described above, low adhesion coating
13 is compatible with the heat seal bond between the
frame 12 and backing 14.
Liner 18 and frame 12 both preferably include
tabs 17 and 19 which extend beyond the perimeter of
backing 14 to provide a means of applying the
backing/frame/adhesive composite without contacting
the adhesive 16.
In the preferred embodiment, the heat seal bond
between the frame 12 and the backing 14 is stronger
than the bond between the adhesive 16 and the liner
18. That difference ensures that the backing 14
remains attached to the frame 12 when liner 18 is
removed from the adhesive composite dressing 10.
The dressing 10 is shown as having a frame 12
which includes an opening 20 such that the frame 12
does not extend ccmpletely around the perimeter of the
backing 14. That feature allows the dressing 10 to be
placed over catheters or other devices while still
attached to the frame 12 to increase the ease of
handling of backing 14.
In use, liner 18 is first removed from the
adhesive composite dressing 10 leaving the frame
12/backing 14/pressure-sensitive adhesive 16 intact.
The user can then manipulate the adhesive composite
dressing 10 using tabs 17 on the frame 12 while
viewing the area to which the dressing 10 will be
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attached through window 15, as the preferred backing
14 is transparent or translucent.
The removal of the carrier material which would
normally cover window 15 during manufacturing provides
important advantages to dressings 10 manufactured
according to the present invention. It eliminates one
step in the delivery process for previously known
window style dressings (i.e., the step of removing the
carrier material from the window 15 prior to removing
the liner 18 from the remainder of the dressing 10)
and also reduces the waste stream at the consumer
level.
In the preferred embodiments, the low adhesion
coating 13 on the backing 14 also reduces dressing
changes due to unwanted dressing removal when other
tapes or devices are placed on the dressing 10 and
removed. The low adhesion coating 13 also reduces the
surface friction of the dressing 10 on linen or other
fabrics, thereby offering additional protection
against the accidental removal of dressings 10. In
this regard, it will be appreciated that the unique
features provided by a low.adhesive coating on the
backing 14, heat sealed under frame 12 of the carrier
material, does not necessitate the removal of the
carrier material from window 15 prior to use by the
end user. However, the removal of such carrier
material to expose window 15 during manufacture is the
preferred means of making the adhesive composite
dressings of the present invention.
Turning to Figs. 2A and 2B, an alternate
embodiment of a dressing 21 according to the present
invention is depicted. As shown, the dressing 21 is
an adhesive composite comprising a frame 22, a backing
24, adhesive 26 and a liner 28. Liner 28 preferably
has opposing tabs 29 for handling, and frame 22 also
includes tabs 27 for handling.
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As with dressing 10 in Fig. 1, dressing 21 also
includes an open area or window 25 in frame 22 which
exposes a portion of the top surface of backing 24.
Frame 22 preferably extends around the entire
perimeter of backing 24 and preferably includes a
control depth die,cut 23 to facilitate removal of
frame 22 from backing 24 after the dressing 21 has
been applied to a patient.
Fig. 2B is a bottom view of dressing 21 with
liner 28 removed to expose the adhesive layer 26 and
absorbent pad 29 disposed proximate the center of the
dressing 21. Absorbent pad 29'can be manufactured of
a riumber of materials including; but not limited to,
woven or knit cotton or rayon, hydrocolloids, foams,
15' and nonwoven pads. Absorbent pad 29 is useful for
containing a number of substances,, including
antimicrobial agents, drugs for transdermal drug
delivery, chemical indicators to.monitor hormones or
other substances.in a patient, etc. Furthermore,
although absorbent pad 29 is shown as centered on,
dressing 21, it can take any appropriate shape and/or
can be located off-center on the dressing 21 as
desired.
It should be noted that the removal of the frame
material 22 from the window area 25 of dressing 21 is
especially advantageous with this embodiment of the
present invention as the pad 29 tends to deform the
backing 24 and cause delamination between the frame,
material 22 in window 25 if that material were still
present when pad 29 were placed on dressing 21.
Turning to Fig. 3, another alternate preferred
embodiment of a dressing 30 is depicted as
manufactured according to the present invention. As
shown there, the dressing 30 includes a frame 32,
backing material 34, adhesive 36 and liner 38. As
with the embodiments described above, the frame 32 is
located around the perimeter of the backing 34 and is
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removed from the center 35 of the dressing 30 to
provide a window, exposing a portion of the top
surface of backing 34 of the dressing 30.
This particular embodiment of the present
invention is particularly useful for allergy testing
as a patch testing system with the holes 37 used for
the placement of allergens on a patient's skin for
monitoring to determine whether an allergic reaction
to that particular allergen occurs.
With larger dressings, such as those depicted in
Fig. 3, multiple windows with supporting areas of
carrier material in between each window (not shown)
may be utilized to provide a more secure (e.g., rigid)
means of delivery to a patient's skin. These
supporting areas of carrier material help to insure
that the dressings do not fold in and adhere to
themselves during delivery. In addition, it will also
be appreciated that any of the dressings of the
present invention may include additional tape strips
or other structures useful for securing devices (e.g.,
tubes, catheters) to a patient, as described in U.S.
Patent No. 5,160,315. The incorporation of these
secural strips will be particularly useful in
conjunction with a dressing including a low adhesion
coating according to the present invention. In
particular, a low adhesion coating on the top face of
the backing will allow for the placement and
replacement of such strips, thus obviating the need to
replace the dressing when another secural
configuration is desired.
Preferred Methods of Manufacture
Turning now to the preferred and alternate
methods of manufacturing dressings according to the
present invention, the preferred basic method is
depicted in the flowchart of Fig. 4. As shown there,
step 40 preferably comprises providing an adhesive
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composite formed of a backing/backing (pressure
sensitive) adhesive/liner. The preferred materials
for each component in that composite are described
above.
Step 42 in the preferred method comprises
providing a low adhesion coating on the top face of
the backing to provide the tape-over feature, as well
as to minimize surface friction due to linen which
also reduces unwanted removal of the dressings.
In the preferred method, the carrier material i.s
die cut 44 to form the windows which lie in the center
of the frames on the preferred dressings. In the
preferred embodiments, the die cutting is accomplished
using rotary die cutting equipment which is well known
to those skilled in the art. After the windows have
been die cut in the carrier material, they are removed
in step 46. Removal of the windows defines the inner
edge of the frame of carrier material which is located
around the perimeter of each of the preferred
dressings.
The windows die cut into the carrier material can
be removed using a number of methods known to those
skilled in the art. Those methods could include the
use of vacuum, air pressure, gravity, and nip rolls
having a small diameter which cause the windows to be
removed from the framed carrier material.
As discussed above, the carrier material forming
the window (which is removed) is preferably not heat
sealed to the backing as is the remainder of the
carrier material making up the frame of each dressing.
After the low adhesion coating step 42 and the
die cutting 44 and window removal steps 46 are
completed, the carrier material (with windows removed)
is heat sealed 48 to the top face of the backing, over
the low adhesion coating.
It will be understood that although steps 42, 44
and 46 are depicted sequentialll~ in Figure 4, they
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could be performed simultaneously and are shown
sequentially only for convenience.
An alternate preferred method involves performing
the heat sealing step 48 before the die cutting and
window removal steps 44 and 46. In that method, the
heat sealed areas preferably do not extend over the
window areas on the backing to avoid heat sealing the
window material to the backing, thereby making removal
of the windows difficult. In addition, the die
cutting step 44 now involves control depth die cutting
to avoid cutting through the backing when the windows
are cut out of the carrier material.
Control over the heat sealing process can be
accomplished a number of ways. It can include
cavities in the heated rolls used in heat sealing or
other means, such as texturing the nip rolls which
compress the adhesive composite web against the heated
roll during processing. Those methods are described
in greater detail below.
After the windows have been removed in steps 44
and 46 and the heat sealing step 48 has been
performed, the only remaining step 50 is to convert
the adhesive composite web into finished product. In
the preferred methods, the web now consists of the
frame material heat sealed to the backing which has an
adhesive and liner on its opposing side. In addition,
the windows defining the center of each dressing have
been removed from the carrier material. That web is
preferably directed into a rotary die sheeting station
which cuts the dressings out of the web and pulls the
weed or waste material away for disposal. Preferably,
the individual dressings are fed directly into a
packaging station which packages the dressings for
sterilization and delivery to customers.
Figs. 5A and 5B depict two alternate preferred
methods of accomplishing step 40, i.e., providing the
backing/backing (pressure sensitive) adhesive/liner
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composite used in step 40 described above. Fig. 5A
depicts one method including step 52 which comprises
the extrusion or coating of the backing on a waste
carrier material. Step 54 comprises the coating of
the backing adhesive on the liner to form a backing
adhesive/liner composite. The backing adhesive/liner
.composite is laminated to the backing/waste carrier
composite in step 56-to form a waste
carrier/backing/backing adhesive/liner composite.
Finally, the waste carrier is removed from the backing in
step 58 to provide a composite comprising the
9 ,
backing/backing (pressure sensitive) adhesive/liner
composite,material which can then be processed as described
in the method of Fig. 4.
Turning to Fig. 5B, in an alternative embodiment,
the backing adhesive is coated on the liner in step 60
and in step 62 the backing material is extruded or
coated directly onto the pressure sensitive adhesive
to provide a backing/backing (pressure sensitive)
adhesive/liner composite material. The method
described in Fig. 5B is somewhat advantageous over
that described in Fig. 5A as it avoids the use of a
waste carrier to reduce product costs and processing
steps. Both methods are, however, contemplated for
use in the methods according to the present invention.
Figs. 6-8 depict various schematic diagrams of
web fed rotary processing equipment for producing
dressings according to the preferred methods of the
present invention. The details of designing such
equipment will be well known to those skilled in the
art. Commercially available rotary web processing
equipment including control depth die cut systems
useful for practicing the method of the present
invention can be obtained from, for example, the Mark
Andy Company (St. Louis, MO) and Bernal Rotary Systems
(Troy, MI).
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Turning to Fig. 6, roll 72 preferably comprises a
heat sealable carrier material (also designated 72) as
described above with the heat seal side 73 threaded as
shown. The carrier material 72 is wrapped around a
heated roll 82 as shown. The second input roll 70
comprises the low adhesion coating/backing/backing
(pressure sensitive) adhesive/liner composite (also
70) according to the present invention. The low
adhesion coating/backing portion 74 is wound in and
the liner 78 is wound out as shown. The web from
input roll 70 is threaded between the nip 81 formed
between nip roll 80 and heated roll 82. In the
preferred embodiment as shown, heated roll 82 includes
cavities 83 disposed around its perimeter which are
provided to avoid heat sealing areas 84 in the web as
it exits the heated roll nip 81.
Downstream, die cut roll 86 and anvil roll 87
control depth die cut the carrier material 72 to form
windows in the web. The windows 88 are then removed
using a variety of means as discussed above. Pull
rolls 90 establish a constant tension zone and
sheeting rolls 92 remove the finished product 10 from
the web. Weed 94 is wound on roll 96 and is then
disposed.
In an alternative embodiment illustrated in Fig.
7, the carrier material roll 102 is provided with its
heat sealable side 103 wound out. The carrier
material (also 102) is threaded through a nip 105
formed between a die cut roll 116 and anvil roll 114.
At that station the windows 118 are cut from and
removed from the web of carrier material 102.
Carrier material 102 is threaded through the
lamination nip ill formed by heated roll 112 and nip
roll 110 as shown. Also threaded into that lamination
station is the low adhesion coating/backing/backing
(pressure sensitive) adhesive/liner composite of the
present invention off of feed roll 100 with the low
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adhesion coating/backing portion 104 wound out and the
liner 108 wound in as shown. In the embodiment
pictured in Fig. 7, heated roll 112 does not need
cavities as described with respect to heated roll 82
in Fig. 6 because the window material in carrier 102
is removed prior to the heat laminating step. Pull
rolls 120 establish a constant tension zone for
sheeting dies 122 which produce dressings 10 and weed
124 which is wound on roll 126.
Turning to Fig. 8, which illustrates another
alternative method, the carrier material 132 is
supplied with the heat sealable side 133 threaded in
as shown. In this process, the control depth die
cutting is performed at the same station as the heat
lamination. Roll 142 is the heated roll and 146 is
the die cut roll which produces the window materials
148 which are removed from the carrier material 132.
The low adhesion coating/backing/backing
(pressure sensitive) adhesive/liner composite 130 is
wound into the nip 141 formed between roll 140 and
heated roll 142. Composite 130 is preferably wound
with the low adhesion coating/backing portion 134 out
and the liner 138 wound in. After the carrier 132 and
composite 130 have been laminated together they are
fed into pull rolls 150 which provide a constant
tension zone for sheeting dies 152 which produce
dressings 10 and waste or weed 154 which is wound on
roll 156.
It will be understood by those skilled in the art
that the schematic diagrams contained in Figs. 6-8
represent possible equipment configurations only and
should not be construed as limiting the method of the
present invention.
The heat seal portion of the methods according to
the present invention must be carefully controlled
because of the importance of the relative strength of
the heat seal bond between the backing and the frame
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material (over the low adhesion coating) as compared
to the bond between a patient's skin and the backing
adhesive. As discussed above, the heat seal bond
between the frame and backing must be stronger than
the bond between the backing adhesive and the liner.
That relationship prevents delamination of the frame
from the backing when the liner is removed before
applying the dressing to a patient.
Also, it is preferred that the carrier material
in the window, which must be removed at some point in
the process, is not heat sealed to the backing because
of the difficulty associated with removing the window
if it is heat sealed to the backing. Alternatively,
if the window material is heat sealed to the backing,
it is preferred that the strength of that heat seal
bond is less than the strength of the heat seal bond
between the frame and backing to facilitate removal of
the windows without adversely affecting the bond
between the frame and backing.
It will be understood that control over the bonds
produced during the heat seal portion of the
manufacturing is affected by a number of variables
including the materials heat sealed, the temperature
of the heated roll, the speed of the web and pressure
between the heated roll and a nip roll.
Furthermore, it will be understood that
sterilization of the resulting products can also
affect the bond strength. In particular, it is known
that the strength of the bond between the preferred
backing adhesive and a patient's skin is affected by
gamma sterilization. Gamma sterilization also has
been found to have some effect in strengthening heat
seal bonds produced using the present invention, but
the effect is much less pronounced than the effect on
the backing adhesive/skin bond strength.
Variations in the heated roll to control the
areas bonded by the heat seal process described above
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include the formation of cavities in the heated roll,
or alternatively the nip roll, to produce areas in
which little or no heat seal bond is produced (See
e.g., Figure 6, roll 82 with cavity 83 and unbonded
area 84 in the web). Figures 7 and 8 depict processes
in which the window materials are removed before heat
sealing to avoid the problem of controlling the heat
sealing in the window area (see Figure 7, windows 118
and Figure 8, windows 148).
Another method to control heat sealing of the
frames to the backing is the use of a textured nip
roll in conjunction with the heated rolls as described
above. The texturing can be useful to control the
area under compression between the nip roll and the
heated roll, as well as having an effect on the
overall compressive force between the rolls. The
texturing could cover the entire surface of the roll,
or be limited to areas on the roll which correspond to
areas on the web in which the bond strength is
preferred to be stronger or weaker.
The texturing could take many forms, including,
but not limited to, as parallel or intersecting
grooves at any suitable angle with respect to the
centerline of the web or a knurled pattern-formed in
the roll. The primary consideration is to reduce or
control the area of contact between the nip roll and
the heated roll, thereby controlling the bond
strength.
The preferred textured nip roll has a pattern of
intersecting grooves milled in a silicone coated roll
with a durometer of about 85 Shore A hardness. The
grcoves are set at angles of approximately 45 degrees
from the machine direction.along the face of the roll.
When not compressed, the grooves reduce the contact
surface of the nip roll by about 50%.
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Alternatively, it will be understood that the
heated roll could be textured to provide additional
control over the heat sealing process.
Another variation to provide control over the
heat seal bonds is the use of elastomeric nip rolls
formed of materials with varying durometers to provide
different compression ratios across the nip area,
thereby affecting the heat seal bond strength. This
particular variation relies on varying the compressive
forces to control bond strength and, in some
instances, could be used in conjunction with
texturing.
The following non-limiting examples will further
illustrate the articles and methods of the present
invention. All parts and percentages are expressed as
parts by weight unless otherwise indicated.
Example 1
Twenty-five grams per square meter of a pressure
sensitive adhesive prepared in accordance with U.S.
Pat. No. Re. 24,906, comprising a copolymer of 96%
units of isooctyl acrylate and 4% units acrylamide was
applied to a 78 pound bleached release liner, one side
coated, polyethylene and silicone paper (POLYSLIK S-
8053, H.P. Smith, Chicago, IL) using a standard
horizontal knife coater.
A 1.1 mil (28 micron) film of ESTANE 58309NAT022
polyurethane resin (B.F. Goodrich, Cleveland, OH) was
laminated to the adhesive surface to form the backing
for the dressings. At that point, the backing/backing
(pressure sensitive) adhesive/liner composite was
completed.
The next step was to coat a low adhesion layer on
the backing to provide the tape-over feature of the
present invention. Using a Gravure station, a 6%
solids solution (20 parts silicone and 80 parts
polyvinyl N-octadecyl carbamate) was coated on the
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polyurethane (non-adhesive) side of the composite
using a 200 line pyramid knurl and dried. The
solution comprised:
1) a silicone resin blend of SS4300 at 95%
units and SR-0545 at 5% units, both from General
Electric (Waterford, NY) provided in 90% toluene
(by weight); and
2) a backsizing solution in accordance with
U.S. Pat. No. 2,532,011, comprising polyvinyl N-
octadecyl carbamate 5% solids in xylene-toluene
(22%-78% by weight).
The low adhesion coating/backing/backing
(pressure sensitive) adhesive/liner composite web was
then slit to proper width to make the size dressing
desired.
A carrier material (1-80BKG-157 & PE; Daubert
Chemical Co.) was then die cut, to form windows which
were then removed.
The PE side of the carrier material was heat
laminated to the backing (over the low adhesion
coating) of the above composite. The POLYSLIK S-8053
was removed and replaced with a wider liner (2-60BKG-
157-99AM; Daubert Chemical Co.) sheeted to the proper
dressing size using rotary equipment similar to die-
cutting/printing machines manufactured by Mark Andy
(St. Louis, MO). The station modified for heat
sealing used a heated roll manufactured by Tokuden
Ltd. (Kyoto, Japan).
Example 2
The procedure of Example 1 was followed except
that the carrier material (1-80BKG-157 and PE) was die
cut with a window and then the slug removed after heat
sealing and liner swap. In this case the Tokuden
heated roll was milled to form cavities that would not
seal in the window portion.
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Example 3
The procedure of Example 1 was followed except
that the low adhesion coating was left off the
backing, thereby illustrating that the adhesive
composites of the present invention can be made
without a low adhesion coating on the top of the
backing. In this regard, the peel force of the bond
between the carrier material and the film backing was
compared between the low adhesion coated composite of
Example 1 and the uncoated composite of Example 3
using the following procedure.
The peel force of each composite was measured
using a 90 degree rotary peel adhesion test on an
Instron testing machine (Model No. 1122; Instron
Corp., Canton, MA). A 2.54cm wide double coated tape
was adhered to the full circumference of a rotatable
metal wheel which was mounted on the lower jaw of the
Instron machine. A 2.54cm wide polyester silicone
adhesive tape (No. 8402 tape, 3M Company, St. Paul,
MN) was adhered to the double coated tape, adhesive
side out. The sample composite dressings were die cut
into 2.54cm x 10.2cm strips, each of which was placed
on the silicone tape covering the wheel with the
carrier material facing against the wheel and the
pressure sensitive adhesive surface facing the
operator. Prior to testing, one end of the
film/adhesive portion of the sample strip was lifted
away from the carrier to form a tab, which was clamped
onto the upper jaw of the Instron machine. The
film/adhesive composite was then peeled off the
carrier material at a 90 degree angle and crosshead
speed of 300mm/min. The peel force was recorded in
grams force per 2.54cm width.
Samples of both Example 1 and Example 3
composites were tested using the procedure described
above. One skilled in the art would recognize that
line speed, nip temperature and materials selections
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are the three main variables to consider when
laminating materials together. Other variables
investigated include web tension, nip pressure, and
the durometer of the rubber roll used at the heated
lamination station. The effect of these variables
proved to be significant. In this regard, the affect
of ma"nufacturing line speed (meters/min) and heat seal
temperature ( C) on the peel force (g/2.54cm width)
between the carrier material and film backings of the
dressing composites of Examples 1 and 3 are shown
below in Table 1.
TABLE 1
Affect of manufacturing line speed and heat
seal temperature on the peel force between the
carrier material and film backings of the
dressing composites of Examples 1 and 3.
line heat seal peel force
Example speed temperature (g/2.54cm
Number (m/min) ( C) width)
1 1.5 93 65
1 1.5 116 113
1 10.7 93 29
1 10.7 116 48
3 1.5 93 76
3 1.5 116 142
3 10.7 93 10
3 10.7 116 46
Suprisingly, the heat seal bond force between the
carrier material and film backing of the composite
dressings of Example 1 was comparable with bond force
for the composites of Example 3, despite the fact that
the backing of the Example 1 composites were coated
with a low adhesion coating prior to heat sealing. In
fact, at high line speeds and lower heat seal
temperatures, these low adhesion containing
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composities exhibited superior bond force to the
composites of Example 3, which did not contain a low
adhesion coating in between the backing and carrier
material.
Example 4
The procedure of Example 1 was followed except a
PE-44 polyurethane resin (Morten International,
Seabrook, NH) was extruded with a thickness of 1.1 mil
(28 micron) directly to the pressure sensitive
adhesive coated on the high release side (i.e. side
99AM) of the preferred liner (2-60BKG-157-99AM;
Daubert Chemical Co.). The coating solution was
comprised of a copolymer of 70% monomeric units of
isooctyl acrylate, 15% monomeric units of
ethyleneoctyl acrylate and 15% monomeric units of
acrylic acid and was coated at a coating weight of
thirty grams per square meter.
Example 5
The film backing and adhesive construction of
Example 4 were used in conjunction with a carrier
material SCOTCHPAK 1220 film -- a clear, heat-
sealable polyester film laminate (3M Company, St.
Paul, MN), and was formed using the same procedures
and equipment as used in Example 1 herein.
In view of the foregoing description, it will be
apparent that the methods and composite dressings of
the invention are not limited to the specific details
set forth herein for purposes of illustration, and
that various other modifications are equivalent for
the stated and illustrated functions without departing
from the spirit of the invention and the scope thereof
as defined in the appended claims.
