U.S. patent application number 11/145850 was filed with the patent office on 2005-10-13 for adhesive composite having distinct phases.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Bisbee, Karen M., Heinecke, Steven B., Menzies, Robert H., Norquist, Scott G..
Application Number | 20050228352 11/145850 |
Document ID | / |
Family ID | 32594981 |
Filed Date | 2005-10-13 |
United States Patent
Application |
20050228352 |
Kind Code |
A1 |
Heinecke, Steven B. ; et
al. |
October 13, 2005 |
Adhesive composite having distinct phases
Abstract
A conformable adhesive article for use as a sterile medical
dressing is described. The article includes a breathable polymeric
matrix, a plurality of phases, and an adhesive composition
positioned on the polymeric matrix. The plurality of phases
preferably provide reinforcement and stiffness to the article. The
article permits transport of moisture across the breathable
polymeric matrix, preferably at an Inverted water moisture vapor
transmission rate of at least 300 g/m.sup.2/24 hours.
Inventors: |
Heinecke, Steven B.; (New
Richmond, WI) ; Menzies, Robert H.; (Hudson, WI)
; Bisbee, Karen M.; (Maplewood, MN) ; Norquist,
Scott G.; (St. Paul, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
32594981 |
Appl. No.: |
11/145850 |
Filed: |
June 6, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11145850 |
Jun 6, 2005 |
|
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09364506 |
Jul 30, 1999 |
|
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6927315 |
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Current U.S.
Class: |
604/383 |
Current CPC
Class: |
A61F 13/0223 20130101;
A61F 13/0226 20130101; A61F 2013/00855 20130101; A61F 2013/00608
20130101 |
Class at
Publication: |
604/383 |
International
Class: |
A61F 013/15 |
Claims
We claim:
1. A conformable adhesive article for use as a sterile medical
dressing, the article comprising: a substantially continuous
breathable polymeric matrix comprising an elastic material, and
having a first surface and a second surface; a plurality of phases
retained proximate the polymeric matrix, the plurality of phases
substantially discontinuous in a first direction and substantially
continuous in a second direction; and an adhesive composition
positioned on at least a portion of the first surface of the
polymeric matrix; wherein the plurality of phases are retained on
the second surface of the polymer matrix.
2. The conformable adhesive article according to claim 1, wherein
the breathable polymeric matrix comprises at least a first layer
and a second layer.
3. The conformable adhesive article according to claim 2, wherein
the first layer and second layer comprise different
compositions.
4. The conformable adhesive article according to claim 1, wherein
the plurality of phases comprise a substantially non-elastic
material.
5. The conformable adhesive article according to claim 1, wherein
the plurality of phases are heat laminated between a polymeric
matrix having at least two layers.
6. The conformable adhesive article according to claim 1, wherein
the polymeric matrix is extruded in two stages.
7. The conformable adhesive article according to claim 1, wherein
the polymeric matrix material is solvent cast onto a release
sheet.
8. The conformable adhesive article according to claim 1, wherein
the article comprises a roll good.
9. The conformable adhesive article according to claim 8, wherein
the roll good is perforated to form individual lengths of sterile
medical dressings.
10. A conformable adhesive article for use as a sterile medical
dressing, the article comprising: a breathable polymeric matrix
having a first surface and a second surface; a plurality of phases
proximate the polymeric matrix; and an adhesive composition
positioned on at least a portion of the first surface of the
polymeric matrix; wherein the adhesive article has a conformability
of greater than 2 and less than 10 in a direction parallel to the
plurality of phases.
11. The conformable adhesive article according to claim 10, wherein
the article has an inverted moisture vapor transmission rate of at
least about 1500 g/m.sup.2/24 hrs.
12. The conformable adhesive article according to claim 10, wherein
the plurality of phases retained proximate the polymeric matrix are
retained within the polymeric matrix.
13. The conformable adhesive article according to claim 10, wherein
the plurality of phases substantially surrounded by the polymeric
matrix are incompatible with the polymeric matrix.
14. The conformable adhesive article according to claim 10, wherein
the plurality of phases are retained on the second surface of the
polymer matrix.
15. The conformable adhesive article according to claim 14, wherein
the plurality of phases are retained intermediate the adhesive
composition and the first surface of the polymeric matrix.
16. The conformable adhesive article according to claim 10 wherein
the breathable polymeric matrix comprises an elastomeric material
and the plurality of phases comprise a substantially non-elastic
material.
17. A conformable adhesive roll good for use as a sterile medical
dressing, the roll good comprising: a breathable polymeric matrix
having a first surface and a second surface; a plurality of
substantially continuous phases retained proximate the polymeric
matrix; an adhesive composition positioned on at least a portion of
the first surface of the polymeric matrix.
18. The conformable adhesive roll good according to claim 17,
wherein the roll good comprises perforations to form individual
lengths.
19. The conformable adhesive roll good according to claim 18,
wherein the plurality of substantially continuous phases are
discontinuous at the perforations.
20. The conformable adhesive article according to claim 17, wherein
the article has an inverted moisture vapor transmission rate of at
least 1,500 g/m.sup.2/24 hours.
21. A conformable adhesive article for use as a sterile medical
dressing, the article comprising: a substantially continuous
breathable polymeric matrix comprising an elastic material, and
having a first surface and a second surface; a plurality of phases
retained proximate the polymeric matrix, the plurality of phases
substantially discontinuous in a first direction and substantially
continuous in a second direction; and an adhesive composition
positioned on at least a portion of the first surface of the
polymeric matrix; and wherein the plurality of phases are retained
on the first surface of the polymeric matrix.
22. The conformable adhesive article according to claim 21, wherein
the plurality of phases are retained intermediate the adhesive
composition and the first surface of the polymeric matrix.
23. The conformable adhesive article according to claim 21, wherein
the breathable polymeric matrix comprises at least a first layer
and a second layer.
24. The conformable adhesive article according to claim 23, wherein
the first layer and second layer comprise different
compositions.
25. The conformable adhesive article according to claim 21, wherein
the breathable polymeric matrix comprises an elastomeric material,
and the plurality of phases comprise a substantially non-elastic
material.
26. The conformable adhesive article according to claim 21, wherein
the breathable polymeric matrix and the plurality of phases
comprise elastomeric materials.
27. The conformable adhesive article according to claim 21, wherein
the plurality of phases are heat laminated between a polymeric
matrix having at least two layers.
28. The conformable adhesive article according to claim 21, wherein
the polymeric matrix is extruded in two stages.
29. The conformable adhesive article according to claim 21, wherein
the polymeric matrix material is solvent cast onto a release
sheet.
30. The conformable adhesive article according to claim 21, wherein
the article comprises a roll good.
31. The conformable adhesive article according to claim 30, wherein
the roll good is perforated to form individual lengths of sterile
medical dressings.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. patent application
Ser. No. 09/364,506, filed Jul. 30, 1999, now allowed.
FIELD OF THE INVENTION
[0002] The present invention is directed to conformable adhesive
articles, including adhesive articles for use as sterile medical
dressings. The invention is particularly directed to adhesive
coated polymeric articles having high moisture vapor transmission
rates. The articles of the present invention can be used for
medical tapes, dressings, skin closures, drapes, and for other uses
where a breathable conformable film is desired.
BACKGROUND OF THE INVENTION
[0003] Breathable films are widely used as protective layers over
wounds, including dressings and surgical drapes. These films
facilitate healing in a moist environment, act as a barrier to
contamination from microorganisms, and allow for exchange of
moisture to prevent excessive fluid buildup. Breathable films are
preferably thin and flexible in order to permit high moisture
transmission rates and to conform well to various irregular
surfaces of a patient's body. Films fitting this description are
available under a number of trade names, including TEGADERM.TM.
produced by Minnesota Mining and Manufacturing Company of St. Paul,
Minn.; BIOCLUSIVE.TM. produced by Johnson & Johnson Company of
New Brunswick, N.J.; and OP-SITE.TM. produced by T. J. Smith &
Nephew of Hull, England.
[0004] Unfortunately, the thin and flexible nature of breathable
films can result in challenges when applying them to patients.
These challenges often arise because dressings formed of adhesive
coated film tend to wrinkle and adhere to themselves, interfering
with smooth, aseptic application to a patient's skin. Various
delivery systems have been proposed to address this challenge. One
such delivery system is described in U.S. Pat. No. 5,531,855, which
is directed to a releasable protective liner that covers the
adhesive coated surface of the film. Unfortunately, when the liner
is removed, the adhesive coated film often still wrinkles and
adheres to itself.
[0005] An alternative delivery system includes a thin disposable
frame on which the breathable film is releasably secured, such as
the frames described in U.S. Pat. No. 5,520,629. As the film is
applied to a wound on a patient, the frame is lifted away, leaving
the film adhered to the patient. In such implementations, the film
adheres more strongly to the patient than it does to the frame,
thereby allowing for the release of the film from the frame.
Although this method can work well, it poses some difficulty in
making large breathable films, and can be difficult to produce.
[0006] Accordingly, a need exists for a thin, breathable film that
can be applied to a wound in an easy and efficient manner. The film
should allow for escape of moisture while protecting the wound from
contamination. Such film should preferably be efficient and cost
effective to produce, as well as easy to apply.
SUMMARY OF THE INVENTION
[0007] The invention is directed to a conformable adhesive article.
The article is suitable for use as a sterile medical dressing, and
includes a breathable polymeric matrix, a plurality of phases, and
an adhesive composition positioned on or within at least a portion
of the polymeric matrix. The breathable polymeric matrix allows for
the escape of moisture across the adhesive article. The plurality
of phases reinforce the polymeric matrix, thereby making a stronger
matrix and permitting the matrix thickness to be minimized. The
reinforcing phases can increase the stiffness of the article as
measured by hand conformability and F.sub.10 modulus
conformability. The phases can also provide an increase in tensile
strength of the article in order to make it less fragile during
application and more durable after application.
[0008] A preferred use of the article is as an adhesive dressing
applied over wounds. The dressing aids in the regulation of the
amount of moisture in contact with the wound. In certain
embodiments, the article maintains a sufficiently moist environment
to prevent the underlying wound from dehydrating, without creating
pools of liquid that can cause adhesive failure. The article
preferably exhibits a satisfactory moisture vapor transmission rate
while retaining its structural integrity in moist environments.
This combination of breathability and strength allows for a
superior breathable film that promotes the quick recovery of
injuries, such as burns to a patient's skin.
[0009] The article preferably has enough modulus or stiffness to
allow easy application to a patient, but is conformable enough to
readily adapt to the shape of the covered area. In certain
implementations, the article can be readily applied without the use
of a release film, a retainer frame surrounding the article, or
retainer handles at the ends of the article. However, the article
can alternatively be used with these devices to aid in application
to a patient.
[0010] The modulus of the article is preferably sufficient to aid
in application, but not so great as to interfere with
conformability to the patient. The article preferably exhibits
increased modulus and tensile strength relative to existing
breathable films suitable as wound dressings. The article typically
has a conformability (Hand) of at least about 2 and less than about
10 in the direction parallel to the phases (in the cross-web
direction when the phases are co-extruded in a down-web machine
direction) and at least about 2 and less than 25 in the direction
perpendicular to the phases (in the machine direction when the
phases are co-extruded in a down-web machine direction).
[0011] In implementations where the film will be applied to
generally flat surfaces, the film can have greater modulus than a
film that would be applied to an irregular surface. Similarly, in
implementations where the film will be applied to irregular
surfaces or curved surfaces, then the film is preferably more
flexible. However, even when the film has greater flexibility, such
modulus is still preferably great enough to limit the amount of
contact of the filming adhesive surface with itself.
[0012] The article should also typically have sufficient tensile
strength to function as a satisfactory wound drape or dressing. In
certain implementations the article has a tensile strength of at
least about 8 N/cm width in the direction perpendicular to the
phases (cross-web direction); and at least about 8 N/cm width, and
preferably at least about 16 N/cm width in the direction parallel
to the phases (machine direction). The tensile strength can vary
depending upon the direction of the phases. The tensile strength is
preferably more than 50 percent greater in the machine direction
than a breathable polymeric matrix of the same thickness that does
not contain a plurality of phases.
[0013] In order to allow transport of moisture away from a wound,
the article typically has an inverted water moisture vapor
transmission rate of at least about 300 g/m.sup.2/24 hours,
preferably an inverted water moisture vapor transmission rate of at
least about 1500 g/m.sup.2/24 hours, and more preferably an
inverted water moisture vapor transmission rate of at least about
4000 g/m.sup.2124 hours. The article typically has an upright water
moisture vapor transmission rate of at least about 300 g/m.sup.2/24
hours, preferably an upright water moisture vapor transmission rate
of at least about 600 g/m.sup.2/24 hours, and more preferably an
upright water moisture vapor transmission rate of at least about
1000 g/m.sup.2/24 hours.
[0014] The breathable polymeric matrix can be formed of various
materials. The matrix may include an elastomeric material and the
plurality of phases can include a substantially non-elastic
material. Alternatively, the breathable polymeric matrix and the
plurality of phases can be formed of elastomeric materials,
including a polymeric matrix comprising a thermoplastic
polyurethane. The matrix can contain one layer or more than one
layer, and the layers can comprise different materials or the same
material. In specific implementations, the plurality of phases
includes phases that are continuous in one direction, but
discontinuous in another direction. The phases can be formed of a
polymeric material different from the material used to form the
polymeric matrix. The phases can have a significantly greater
stiffness than the polymeric matrix and impart overall stiffness to
the article by reinforcing the polymeric matrix. The phases
preferably provide support and stiffness to the matrix without
significantly reducing the conformability of the article.
[0015] In a specific implementation of the invention, the article
comprises an extruded web containing a plurality of uniform,
distinct phases positioned proximate the web. The phases are
discontinuous in a cross-web direction. The phases positioned
proximate the web may be entirely within the web, partially within
the web, or adhered to the exterior of the web. The embedded phases
preferably have a width uniform to within a coefficient of
variation of less than 8 percent for three consecutive
discontinuous phases. The width of these phases is measured in a
cross-section of the web cut transverse (i.e., cross-web) to the
machine direction (i.e., down-web) and is the largest dimension of
the cross-section of the phases in the cross-web direction.
[0016] In certain implementations, the article is made into a roll
good that facilitates easy dispensing of the breathable film. The
roll good includes a breathable polymeric matrix having a first
surface and a second surface, a plurality of substantially
continuous phases retained proximate the polymeric matrix, and an
adhesive composition positioned on at least a portion of the first
surface of the polymeric matrix. The roll good can include
perforations to form individual lengths of sterile medical
dressings. These perforations provide tear lines that facilitate
tearing of the roll good into shorter lengths.
[0017] The phases can be formed of a material compatible with the
matrix to form a substantially integrated product with a strong
interface between the matrix and the phases. Alternatively,
incompatible materials can be co-extruded to form the article. In
such implementations, the phases are preferably encapsulated within
the matrix in order to secure the phases in place. As used herein,
"compatible" refers to the property of forming a strong interface
between the two materials, while "incompatible" materials form a
weak interface. Thus, one implementation of the invention provides
for a plurality of phases substantially surrounded by the polymeric
matrix and compatible with the matrix, and a second implementation
provides for phases substantially surrounded by the polymeric
matrix and not substantially compatible with the polymeric
matrix.
[0018] Numerous alternative processes can be used to form the
articles of the invention. These processes can alter the properties
of the finished article, as well as the structure of the article.
For example, the plurality of phases can be retained on the same
surface of the polymer matrix as the adhesive composition, or can
be retained on an opposite surface from the adhesive composition.
When the plurality of phases are retained on the same surface as
the adhesive composition, the phases can be intermediate the
adhesive composition and the surface of the polymeric matrix or can
be placed on top of the adhesive composition. The plurality of
phases can be heat laminated between a polymeric matrix having at
least two layers, extruded in two stages, solvent cast onto a
release sheet, etc. A specific process suitable for forming the
breathable article includes providing an extrudable material and an
extrusion die, as described in United States patent application
Attorney Docket No. 54324USA4A entitled "Polymeric Articles Having
Embedded Phases, filed on Jul. 30, 1999.
[0019] Other features and advantages of the invention will be
apparent from the following description of the preferred
embodiments thereof, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1A is a perspective view of a medical dressing
containing a breathable film constructed and arranged in accordance
with the invention.
[0021] FIG. 1B is a fractional cross-sectional view of the medical
dressing shown in FIG. 1A taken along plane A-A'.
[0022] FIG. 2A is a fractional cross-sectional view of a
conformable adhesive article constructed and arranged in accordance
with the invention, showing a polymeric matrix surrounding a
plurality of phases.
[0023] FIG. 2B is a fractional cross-sectional view of a
conformable adhesive article constructed and arranged in accordance
with the invention, showing a polymeric matrix with a plurality of
phases adhered to a surface of the matrix.
[0024] FIG. 2C is a fractional cross-sectional view of a
conformable adhesive article constructed and arranged in accordance
with the invention, showing an alternate implementation of a
polymeric matrix with a plurality of phases adhered to a surface of
the matrix.
[0025] FIG. 2D is a fractional cross-sectional view of a
conformable adhesive article constructed and arranged in accordance
with the invention, showing a matrix having two layers.
[0026] FIG. 3A is a perspective view of an extrusion die
constructed in accordance with an embodiment of the invention.
[0027] FIG. 3B is a perspective view of an extrusion die vane
constructed in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The invention is directed to a conformable adhesive article
for use as a sterile medical dressing. The article includes a
breathable polymeric matrix, a plurality of phases proximate the
matrix, and an adhesive composition positioned on at least a
portion the polymeric matrix. The breathable polymeric matrix
allows for escape of moisture across the adhesive article. This
escape of moisture is particularly advantageous when the article is
used as a medical dressing, drape, or other breathable article.
[0029] The plurality of phases reinforce the polymeric matrix,
thereby strengthening the matrix and permitting the thickness of
the matrix to be reduced. The reinforcement can also increase the
modulus of the article so as to make it easier to apply to a
patient, with reduced problems associated with adhesion of the
article to itself. The phases can also provide an increase in
tensile strength of the article in order to make it more durable.
The modulus of the article is preferably not so great as to
interfere with conformability to the patient. The article typically
has a conformability (Hand) of at least about 2, and less than 10
in the direction parallel to the phases (measured such that the bar
is parallel to the phases) and at least about 2 and less than 25
the direction perpendicular to the phases (measured such that the
bar is perpendicular to the phases). The article preferably has a
conformability (hand) of less than 5 in the direction parallel to
the phases and less than 10 in the direction perpendicular to the
phases.
[0030] A preferred use of the article is as an adhesive dressing
for application over wounds. The dressing effectively regulates the
amount of moisture in contact with the wound underlying the
dressing. In certain embodiments, the article maintains a
sufficiently moist environment to prevent the underlying wound from
dehydrating, without creating pools of liquid that can cause
adhesive failure. The article exhibits a high moisture vapor
transmission rate while retaining its structural integrity in moist
environments. The existence of phases of a second material within
the matrix can promote formation of a stronger article than would
otherwise be obtained without use of phases. In addition, the
phases are preferably constructed and arranged such that moisture
transport through the matrix is not greatly reduced.
[0031] In a preferred implementation, the article is stiff enough
to allow easy application to a patient, but conformable enough to
readily adapt to the shape of the covered area. The article can be
readily applied to a patient without the use of a release film, a
retainer frame surrounding the article, or retainer handles at the
ends of the article.
[0032] The article should have sufficient tensile strength to
function as a satisfactory wound drape or dressing. In certain
implementations the article has a tensile strength of at least
about 8 N/cm width in the direction perpendicular to the phases
(cross-web direction when the matrix and phases are co-extruded);
and at least about 8 N/cm width, and preferably at least about 16
N/cm width in the direction parallel to the phases (machine
direction when the matrix and phases are co-extruded). The tensile
strength can vary depending upon the direction of the phases, and
the tensile strength is preferably more than 50 percent greater
than a breathable polymeric matrix of the same thickness that does
not contain a plurality of phases.
[0033] In order to allow transport of moisture away from a wound,
the article typically has an inverted water moisture vapor
transmission rate of at least about 300 g/m.sup.2/24 hours,
preferably an inverted water moisture vapor transmission rate of at
least about 1500 g/m.sup.2/24 hours, more preferably an inverted
water moisture vapor transmission rate of at least about 4000
g/m.sup.2/24 hours. The article typically has an upright water
moisture vapor transmission rate of at least about 300 g/m.sup.2/24
hours, preferably an upright water moisture vapor transmission rate
of at least about 600 g/m.sup.2/24 hours, more preferably an
upright water moisture vapor transmission rate of at least about
1000 g/m.sup.2/24 hours.
[0034] The article is preferably conformable to anatomical surfaces
so that when the article is applied to a human or animal anatomical
surface it conforms to the surface even when the surface is moved.
Preferred articles are also conformable to animal or human
anatomical joints. When the joint is flexed and then returned to
its unflexed position, the article stretches to accommodate the
flexing of the joint but is resilient enough to continue to conform
to the joint when the joint is returned to its unflexed position.
Generally the films are from 12 to 25 microns thick. Conformability
is somewhat dependent upon thickness, thus the thinner the film the
more conformable it is.
[0035] A measure of conformability is the F.sub.10 modulus. The
F.sub.10 modulus should preferably be greater than about 1.8 N/cm
and more preferably greater than about 1.4 N/cm. In preferred
embodiments the wound dressings and drapes, films having an
F.sub.10 modulus upwards of 4.4 N/cm may be used. The F.sub.10
modulus increases the conformability decreases and the ability of
the film to perform comfortably as medical dressings decreases.
[0036] In reference now to the figures, an example breathable
polymeric wound dressing 10 constructed in accordance with the
invention is shown in perspective view in FIG. 1A. Wound dressing
10 includes a top surface 12, a bottom surface 14, first and second
ends 16, 18, and edges 20, 22. Wound dressing 10 is constructed of
a thin polymeric matrix that allows for release of moisture from
bottom surface 14 to top surface 12. An adhesive 23 is positioned
on the bottom surface 14, and also allows for release of moisture
through the dressing 10.
[0037] In the implementation shown the adhesive is placed over only
a portion of bottom surface 14, such as by the method taught in
U.S. Pat. No. 4,798,201. In other implementations (shown later in
FIG. 2A-2D), the adhesive covers all or substantially all of bottom
surface 14. When the adhesive covers substantially all of the
bottom surface, then the adhesive itself should be breathable.
However, when the adhesive covers significantly less than all of
bottom surface 14, then the adhesive is optionally either
breathable or not breathable.
[0038] A cross-sectional fragment 24 of wound dressing 10, taken
along plane A-A', is depicted in FIG. 1B. Fragment 24 of dressing
10 includes a plurality of phases 26 positioned within matrix 28.
In the embodiment shown, matrix 28 contains a single layer into
which the plurality of phases 26 are positioned. Phases 26 can be
formed within matrix 28 by, for example, coextruding the phases 26
and matrix 28 at the same time. In the embodiment depicted in FIGS.
1A and 1B, the phases are continuous between the ends 16 and 18 of
the dressing 10, but are discontinuous from edge 20 to edge 22.
[0039] FIGS. 2A through 2D show additional cross-sectional
fragments of articles constructed in accordance with the invention.
In FIG. 2A, fragment 30 includes a plurality of phases 32 entirely
surrounded by matrix 34. An adhesive 36 is applied to the bottom
surface 38 of fragment 30. In contrast, FIG. 2B shows fragment 40
with a plurality of phases 42 secured to an upper surface 44 of the
matrix 46. An adhesive 48 is positioned on the bottom surface 50 of
fragment 40. Yet another embodiment is shown in FIG. 2C, which
depicts a fragment 52 with a plurality of phases 54 secured to the
bottom surface 56 of the matrix 58 by adhesive 60. A further
embodiment is shown in FIG. 2D, depicting fragment 62 with a matrix
having an upper layer 64 and a lower layer 66. The phases 68 are
positioned within the matrix between layers 64, 66.
[0040] In a specific implementation of the invention, the article
includes an extruded breathable film and a plurality of distinct,
co-extruded phases positioned proximate the film. The article is
extruded as a continuous or substantially continuous web, with the
phases discontinuous in a cross-web direction. The phases
positioned proximate the film may be entirely within the film,
partially within the film, or adhered to the exterior of the film.
The extruded phases preferably have a width uniform to within a
coefficient of variation of less than 8 percent for three
consecutive discontinuous phases. The width of these extruded
phases is measured in a cross-section of the film cut transverse
(i.e., cross-web) to the machine direction (i.e., down-web) and is
the largest dimension of the cross-section of the phases in the
cross-web direction. In one embodiment, the phases are spaced at
substantially uniform intervals in the cross-web direction.
[0041] The article can be made into a roll good that facilitates
easy dispensing. The roll good includes a breathable polymeric
matrix having a first surface and a second surface, a plurality of
substantially continuous phases retained proximate the polymeric
matrix, and an adhesive composition positioned on at least a
portion of the first surface of the polymeric matrix. The roll good
can include perforations to form individual lengths of sterile
medical dressings.
[0042] The invention is further directed to processes for making a
breathable polymeric co-extruded article. The phases can be
co-extruded with the polymeric matrix, thereby forming a
substantially integrated product with a strong interface between
the matrix and the phases. Alternatively, incompatible materials
can be co-extruded to form the article. In such implementations,
the phases are preferably encapsulated within the matrix in order
to secure the phases in place. Thus, the plurality of phases can be
substantially surrounded by the polymeric matrix and have a strong
interface with the matrix, or can be substantially surrounded by
the polymeric matrix and not have a strong interface with the
polymeric matrix.
[0043] Numerous alternative processes can be used for forming the
articles of the invention. These processes can alter the properties
of the finished product, as well as the structure of the product.
For example, the plurality of phases can be retained on the same
surface of the polymer matrix as the adhesive composition, or can
be retained on an opposite surface. When the plurality of phases
are retained on the same surface as the adhesive composition, the
phases can be intermediate the adhesive composition and the surface
of the polymeric matrix. The plurality of phases can be heat
laminated between a polymeric matrix having at least two layers,
extruded in two stages, solvent cast onto a release sheet, etc.
[0044] When the breathable polymeric article is made by
co-extrusion in other implementations, two extruders provide molten
streams of first and second extrudable materials. The extrudable
materials are extruded from the die such that the first extrudable
material substantially surrounds or forms a matrix around the
second extrudable material, which becomes phases embedded within
the matrix. Alternatively, a third extruder may be used to feed a
third material into the die to form a matrix having a different
material for each matrix layer.
[0045] A specific process suitable for forming the breathable
article includes providing an extrudable material and an extrusion
die, as described in U.S. Pat. No. 6,447,875. In a specific
embodiment, the die contains two chambers and an adjustable vane
between the chambers. The vane contains a cavity having at least
one input orifice positioned to receive extrudable material and at
least one exit orifice. The cavity is designed so that the
difference in pressure of molten polymer from one end to the other
is sufficiently small to yield embedded phases of good uniformity
extruded from the exit orifices. A matrix material is extruded
through the chambers of the die, and a phase material is extruded
through the exit orifice in the vane to produce a co-extruded web
containing the matrix and phase materials. The phase material is
embedded between the two layers of the first material.
[0046] In reference now to FIG. 3A, a perspective view of an
extrusion die 70 is depicted showing an exemplary apparatus that
can be used to form a breathable polymeric article in accordance
with the invention. The die 70 depicted in FIG. 3A is one apparatus
suitable for formation of the article of the invention, and other
apparatuses are also appropriate for various implementations. Die
70 includes a body 72 that has at least first and second orifices
74 and 76. Orifice 74 provides entry for a first extrudable
material, while orifice 76 provides entry for a second extrudable
material. Extrusion die 70 also includes an exit port 78. The width
of port 78 (also called the die gap) is typically 1000 .mu.m or
less. Extrudable materials enter die 70 at orifices 74 and 76,
respectively, flow through die 70, and then leave die 70 at exit
port 78 as a co-extruded web.
[0047] Within extrusion die 70 is an adjustable vane 80, shown in
FIG. 3B. Adjustable vane 80 includes at least two orifices 82 and
84. Entrance orifice or orifices 82 allow entry of polymeric
material for the interior of vane 80, and outlet orifices 84 permit
the exit of polymeric material from the interior of vane 80. The
shape and position of outlet orifices 84 define the shape and
position of the plurality of distinct embedded phases in the
polymeric web. Advantageously, tip 86 of vane 80 may be removable
and replaceable to allow placement of different tips having
different configurations of orifices 84 to form different web
configurations. Vane 80 is thus adjustable in at least one of two
modes. The vane can be pivoted so the tip can be moved closer to
the exit of one die chamber or the other causing a difference in
die gap for the exits of each of the two matrix layers. This can
result in a different matrix layer thickness if each layer is made
with matrix material having a similar melt viscosity.
Alternatively, different exit gaps can result in a similar matrix
layer thickness if each layer is made with matrix material having a
different melt viscosity. The vane can also be adjusted by
replacement of tip 86 with one having orifices of different shapes
and spacing.
[0048] This implementation is advantageous in that materials are
co-extruded in a controlled manner. The materials are brought
together in the melt state, thereby allowing for improved adhesion
to one another. In addition, even when the materials are not
compatible, they may still be co-extruded in order to produce a
breathable polymeric article.
[0049] If one matrix material is less viscous than the other, it is
possible to narrow the gap through which the less viscous matrix
material flows in order to maintain uniformity of the thickness of
each of the two matrix layers. The gap can be altered during
processing in order to account for variations in processing
conditions, such as changes in the temperature, pressure, flow
rate, or viscosity over time. Thus, if die 70 has a warmer upper
portion than lower portion resulting in lower viscosity of
materials flowing through the upper gap, then the gap can be
adjusted to account for this change in viscosity. In addition, the
gap can be altered to achieve a different thickness in each matrix
layer. This is particularly useful when each matrix layer is of a
different material, e.g., a thermoplastic elastomer and a
pressure-sensitive adhesive, where different properties are desired
from each layer of the matrix.
[0050] The co-extrusion process of the invention is able to
reproduce in the phases the relative dimensions of the orifices in
the tip to a degree that has not previously been known. In one
aspect, where the orifices have substantially the same dimensions,
the width of the discontinuous embedded phases are relatively
uniform. The coefficient of variation (COV) of the width of any
three consecutive discontinuous phases is less than 8, preferably
less than 5 and more preferably less than 3 percent when three or
more similarly sized orifices are used.
[0051] Another way of modifying the properties of the webs of the
invention is to use specific materials having desired properties
for the layers of the matrix and the embedded phases. Suitable
polymeric materials for forming the matrix layers and embedded
phases of the inventive coextruded web include pressure sensitive
adhesives, thermoplastic materials, elastomeric materials, polymer
foams, high viscosity liquids, etc.
[0052] "Pressure-sensitive adhesives" (PSAs) include adhesives that
display permanent and aggressive tackiness to a wide variety of
substrates after applying only light pressure. PSAs have a
four-fold balance of adhesion, cohesion, stretchiness, and
elasticity, and are normally tacky at use temperatures, which is
typically room temperature (i.e., about 20.degree. C. to about
30.degree. C.). PSAs also typically have an open time tack (i.e.,
period of time during which the adhesive is tacky at room
temperature) on the order of days and often months or years. An
accepted quantitative description of pressure-sensitive adhesives
is given by the Dahlquist criterion line (as described in Handbook
of Pressure-Sensitive Adhesive Technology, Second Edition, D.
Satas, ed., Van Nostrand Reinhold, New York, N.Y., 1989, pages
171-176), which indicates that materials having a storage modulus
(G') of less than about 3.times.10.sup.5 Pascal (measured at 10
radians/second at a temperature of about 20.degree. C. to about
22.degree. C.) have pressure-sensitive adhesive properties, but
materials having a G' in excess of this value do not.
[0053] "Nonpressure-sensitive adhesives" include nontacky polymeric
materials as well as tacky polymeric materials that, when in the
melt state, do not display pressure sensitive properties, or other
materials that have adhesive properties at room temperature but do
not meet the Dahlquist criterion as described above. Such materials
have a storage modulus (G') of at least about 3.times.10.sup.5
Pascal (measured at 10 radians/second at a room temperature of
about 20.degree. C. to about 22.degree. C.). These materials can be
nontacky thermoplastic materials, which can be elastomeric or
non-elastomeric. Alternatively, they can be nontacky
elastomers.
[0054] Preferred materials for use in preparing the articles of the
present invention, whether they include pressure-sensitive
adhesives or nonpressure-sensitive adhesives, are melt processable.
That is, they are fluid or pumpable at the temperatures used to
melt process the webs (e.g., about 50.degree. C. to about
300.degree. C.), and they form films. Furthermore, preferred
materials do not significantly degrade or gel at the temperatures
employed during melt processing (e.g., extruding or compounding).
Preferably, such materials have a melt viscosity of about 10 poise
to about 1,000,000 poise, as measured by capillary melt rheometry
at the processing temperatures and shear rates employed in
extrusion. Typically, suitable materials possess a melt viscosity
within this range at a temperature of about 175.degree. C. and a
shear rate of about 100 seconds.sup.-1.
[0055] Pressure-sensitive adhesives useful in articles of the
present invention can be any material that has pressure-sensitive
adhesive properties as described above at use temperatures, which
are typically about room temperature (i.e., about 20.degree. C. to
about 30.degree. C.). Generally, although not necessarily,
particularly useful pressure-sensitive adhesives are amorphous with
a glass transition temperature (Tg) of less than about 20.degree.
C.
[0056] The pressure-sensitive adhesive material can include a
single pressure-sensitive adhesive, a mixture (e.g., blend) of
several pressure-sensitive adhesives, or a mixture (e.g., blend) of
a pressure-sensitive adhesive and a material that is a
nonpressure-sensitive adhesive (e.g., a nontacky thermoplastic
material, which may or may not be elastomeric), as long as the
layer has pressure-sensitive adhesive properties. Examples of some
pressure-sensitive adhesive blends are described in PCT Publication
Nos. WO 97/23577, 97/23249, and 96/25469. Similarly, a suitable
nonpressure-sensitive adhesive matrix layer can include a single
material that is a nonpressure-sensitive adhesive, a mixture of
several such materials, or a mixture of a material that is not a
pressure-sensitive adhesive with a pressure-sensitive adhesive, as
long as the layer does not have pressure-sensitive adhesive
properties.
[0057] Pressure-sensitive adhesives useful in the present invention
can be self-tacky or require the addition of a tackifier. Such
materials include, but are not limited to, tackified natural
rubbers, tackified synthetic rubbers, tackified styrene block
copolymers, self-tacky or tackified acrylate or methacrylate
copolymers, self-tacky or tackified poly-.alpha.-olefins, and
self-tacky or tackified silicones. Examples of suitable
pressure-sensitive adhesives are described in U.S. Pat. No. Re
24,906 (Ulrich), U.S. Pat. No. 4,833,179 (Young et al.), U.S. Pat.
No. 5,209,971 (Babu et al.), U.S. Pat. No. 2,736,721 (Dexter), and
U.S. Pat. No. 5,461,134 (Leir et al.), for example. Others are
described in the Encyclopedia of Polymer Science and Engineering,
vol. 13, Wiley-Interscience Publishers, New York, 1988, and the
Encyclopedia of Polymer Science and Technology, vol. 1,
Interscience Publishers, New York, 1964.
[0058] Useful natural rubber pressure-sensitive adhesives generally
contain masticated natural rubber, one or more tackifying resins,
and one or more antioxidants. Useful synthetic rubber adhesives are
generally rubbery elastomers, which are either inherently tacky or
nontacky and require tackifiers. Inherently tacky (i.e.,
self-tacky) synthetic rubber pressure-sensitive adhesives include
for example, butyl rubber, a copolymer of isobutylene with less
than 3 percent isoprene, polyisobutylene, homopolymers of isoprene,
polybutadiene, or styrene/butadiene rubber.
[0059] Styrene block copolymer pressure-sensitive adhesives
generally comprise elastomers of the A-B or A-B-A type, wherein, in
this context, A represents a thermoplastic polystyrene block and B
represents a rubbery block of polyisoprene, polybutadiene, or
poly(ethylene/butylene), and tackifying resins. Examples of the
various block copolymers useful in block copolymer
pressure-sensitive adhesives include linear, radial, star, and
tapered block copolymers. Specific examples include copolymers such
as those available under the trade designations Kraton from Shell
Chemical Co., Houston, Tex., and Europrene Sol from EniChem
Elastomers Americas, Inc., Houston, Tex. Examples of tackifying
resins for use with such styrene block copolymers include aliphatic
olefin-derived resins, rosin esters, hydrogenated hydrocarbons,
polyterpenes, terpene phenolic resins derived from petroleum or
turpentine sources, polyaromatics, coumarone-indene resins, and
other resins derived from coal tar or petroleum and having
softening points above about 85.degree. C.
[0060] (Meth)acrylate (i.e., acrylate and methacrylate or
"acrylic") pressure-sensitive adhesives generally have a glass
transition temperature of about -20.degree. C. or less and
typically include an alkyl ester component such as, for example,
isooctyl acrylate, 2-ethyl-hexyl acrylate, and n-butyl acrylate,
and a polar component such as, for example, acrylic acid,
methacrylic acid, ethylene vinyl acetate, and N-vinyl pyrrolidone.
Preferably, acrylic pressure-sensitive adhesives comprise about 80
wt-% to about 100 wt-% isooctyl acrylate and up to about 20 wt-%
acrylic acid. The acrylic pressure-sensitive adhesives may be
inherently tacky or tackified using a tackifier such as a rosin
ester, an aliphatic resin, or a terpene resin.
[0061] Poly-.alpha.-olefin pressure-sensitive adhesives, also
called poly(1-alkene) pressure-sensitive adhesives, generally
comprise either a substantially uncrosslinked polymer or an
uncrosslinked polymer that may have radiation activatable
functional groups grafted thereon as described in U.S. Pat. No.
5,209,971 (Babu et al.). Useful poly-.alpha.-olefin polymers
include, for example, C.sub.3-C.sub.18 poly(1-alkene) polymers. The
poly-.alpha.-olefin polymer may be inherently tacky and/or include
one or more tackifying materials such as resins derived by
polymerization of C.sub.5-C.sub.9 unsaturated hydrocarbon monomers,
polyterpenes, synthetic polyterpenes, and the like.
[0062] Silicone pressure-sensitive adhesives comprise two major
components, a polymer or gum and a tackifying resin. The polymer is
typically a high molecular weight polydimethylsiloxane or
polydimethyldiphenylsiloxane that contains residual silanol
functionality (SiOH) on the ends of the polymer chain, or a block
copolymer comprising polydiorganosiloxane soft segments and urea
terminated hard segments. The tackifying resin is generally a
three-dimensional silicate structure that is endcapped with
trimethylsiloxy groups (OSiMe.sub.3) and also contains some
residual silanol functionality. Silicone pressure-sensitive
adhesives are described in U.S. Pat. No. 2,736,721 (Dexter).
Silicone urea block copolymer pressure-sensitive adhesive are
described in U.S. Pat. No. 5,461,134 (Leir et al.), and PCT
Publication Nos. WO 96/34029 and 96/35458.
[0063] Nonpressure-sensitive adhesive polymeric materials used in
the articles of the present invention include one or more
thermoplastic materials, which may or may not be elastomeric
materials, and elastomers. These may be adhesive (i.e., tacky) when
in the melt state or nonadhesive (i.e., nontacky) materials, as
long as the adhesive materials are not pressure sensitive, as
defined above.
[0064] Thermoplastic materials are generally materials that flow
when heated sufficiently above their glass transition temperature
and become solid when cooled. They may be elastomeric or
non-elastomeric. Thermoplastic materials useful in the present
invention that are generally considered non-elastomeric include,
for example, polyolefins such as isotactic polypropylene, low
density polyethylene, linear low density polyethylene, very low
density polyethylene, medium density polyethylene, high density
polyethylene, polybutylene, non-elastomeric polyolefin copolymers
or terpolymers such as ethylene/propylene copolymer and blends
thereof; ethylene-vinyl acetate copolymers such as those available
under the trade designation Elvax from E.I. DuPont de Nemours,
Inc., Wilmington, Del.; ethylene acrylic acid copolymers; ethylene
methacrylic acid copolymers such as those available under the trade
designation Surlyn 1702 from E.I. DuPont de Nemours, Inc.;
polymethylmethacrylate; polystyrene; ethylene vinyl alcohol;
polyesters including amorphous polyester; polyamides; fluorinated
thermoplastics such as polyvinylidene fluoride and fluorinated
ethylene/propylene copolymers; halogenated thermoplastics such as
chlorinated polyethylene; polyether-block-amides such as those
available under the trade designation Pebax 5533 from Elf-Atochem
North America, Inc. Philadelphia, Pa.
[0065] Thermoplastic materials that have elastomeric properties are
typically called thermoplastic elastomeric materials. Thermoplastic
elastomeric materials are generally defined as materials that
exhibit high resilience and low creep as though they were
covalently crosslinked at ambient temperatures, yet process like
thermoplastic non-elastomers and flow when heated above their
softening point. Thermoplastic elastomeric materials useful in the
articles of the present invention include, for example, linear,
radial, star, and tapered block copolymers such as those listed
above with respect to pressure-sensitive adhesives (e.g.,
styrene-isoprene block copolymers, styrene-(ethylene-butylene)
block copolymers, styrene-(ethylene-propylene) block copolymers,
and styrene-butadiene block copolymers); polyetheresters such as
that available under the trade designation Hytrel G3548 from E.I.
DuPont de Nemours, Inc.; polyether block amides such as Pebax
available from Atochem, Philadelphia, Pa.; ethylene copolymers such
as ethylene vinyl acetates, ethylene/propylene copolymer elastomers
or ethylene/propylene/diene terpolymer elastomers and metallocene
polyolefins such as polyethylene, poly (1-hexene), copolymers of
ethylene and 1-hexene, and poly(1-octene); thermoplastic
elastomeric polyurethanes such as that available under the trade
designation Morthane PE44-203 polyurethane from Morton
International, Inc., Chicago, Ill. and the trade designation Estane
58237 polyurethane from B. F. Goodrich Company, Cleveland, Ohio;
polyvinylethers; poly-.alpha.-olefin-based thermoplastic
elastomeric materials such as those represented by the formula
--(CH.sub.2CHR).sub.x where R is an alkyl group containing 2 to 10
carbon atoms, and poly-.alpha.-olefins based on metallocene
catalysis such as Engage EG8200, ethylene/poly-.alpha.-olefin
copolymer available from Dow Plastics Co., Midland, Mich.
[0066] Elastomers, as used herein, are distinct from thermoplastic
elastomeric materials in that the elastomers require crosslinking
via chemical reaction or irradiation to provide a crosslinked
network, which imparts modulus, tensile strength, and elastic
recovery. Elastomers useful in the present invention include, for
example, natural rubbers such as CV-60, a controlled viscosity
grade of rubber, and SMR-5, a ribbed smoked sheet rubber; butyl
rubbers, such as Exxon Butyl 268 available from Exxon Chemical Co.,
Houston, Tex.; synthetic polyisoprenes such as Cariflex, available
from Shell Oil Co., Houston, Tex., and Natsyn 2210, available from
Goodyear Tire and Rubber Co., Akron, Ohio; ethylene-propylenes;
polybutadienes; polybutylenes; polyisobutylenes such as Vistanex MM
L-80, available from Exxon Chemical Co.; and styrene-butadiene
random copolymer rubbers such as Ameripol Synpol 1011A, available
from American Synpol Co., Port Neches, Tx.
[0067] Foams are those materials made by combining the above
polymeric materials with blowing agents. The resulting mixtures are
then subjected to various changes known in the art to activate the
blowing agent used to form a multiplicity of cells within the
polymer. Additional crosslinking may occur to cause resulting foams
to be more stable. A particularly useful foam, when an elastic foam
matrix is desired, is that disclosed in Ser. No. 09/325,963,
Attorney Docket No. 54664USA4A, "Breathable Polymer Foams" filed
Jun. 4, 1999 and incorporated herein by reference. High viscosity
liquids are any that do not diffuse through the matrix material and
prematurely escape the article of the invention. These include, for
example, various silicone oils, mineral oils and specialty
materials having a sharp melting temperatures below room
temperature.
[0068] Viscosity reducing polymers and plasticizers can also be
blended with the elastomers. These viscosity reducing polymers
include thermoplastic synthetic resins such as polystyrene, low
molecular weight polyethylene and polypropylene polymers and
copolymers, or tackifying resins such as Wingtack.TM. resin from
Goodyear Tire & Rubber Company, Akron, Ohio. Examples of
tackifiers include aliphatic or aromatic liquid tackifiers,
aliphatic hydrocarbon resins, polyterpene resin tackifiers, and
hydrogenated tackifying resins. Additives such as dyes, pigments,
antioxidants, antistatic agents, bonding aids, antiblocking agents,
slip agents, heat stabilizers, photostabilizers, foaming agents,
glass bubbles, starch and metal salts for degradability or
microfibers can also be used in the elastomeric phase. Suitable
antistatic aids include ethoxylated amines or quaternary amines
such as those described, for example, in U.S. Pat. No. 4,386,125
(Shiraki), which also describes suitable antiblocking agents, slip
agents and lubricants. Softening agents, tackifiers or lubricants
are described, for example, in U.S. Pat. No. 4,813,947 (Korpman)
and include coumarone-indene resins, terpene resins, hydrocarbon
resins and the like. These agents can also function as viscosity
reducing aids. Conventional heat stabilizers include organic
phosphates, trihydroxy butyrophenone or zinc salts of alkyl
dithiocarbonate.
[0069] Various additives may be incorporated into the phase(s)
and/or the matrix to modify the properties of the finished article.
For example, additives may be incorporated to improve the adhesion
of the phases and the matrix to one another. The article may also
be laminated to a fibrous web. Preferably, the fibrous web is a
nonwoven web such as a consolidated or bonded carded web, a
meltblown web, a spunbond web, or the like. The fibrous web
alternatively is bonded or laminated to the matrix by adhesives,
thermal bonding, extrusion, ultrasonic welding or the like.
Preferably, a co-extruded web can be directly extruded onto one or
more fibrous webs.
[0070] Short fibers or microfibers can be used to reinforce the
distinct phases or matrix layers for certain applications. These
fibers include polymeric fibers, mineral wool, glass fibers, carbon
fibers, silicate fibers and the like. Further, certain particles
can be used, including carbon and pigments. Glass bubbles or
foaming agents may be used to lower the density of the matrix layer
or embedded phases and can be used to reduce cost by decreasing the
content of an expensive material or the overall weight of a
specific article. Suitable glass bubbles are described in U.S. Pat.
Nos. 4,767,726 and 3,365,315. Blowing agents used to generate foams
in melt processable materials are known in the art and include
azodicarbonamides such as SAFOAM RIC-50 sodium bicarbonate-based
chemical blowing agent. Fillers can also be used to some extent to
reduce costs. Fillers, which can also function as antiblocking
agents, include titanium dioxide and calcium carbonate.
[0071] A number of additional steps can optionally be performed.
For example, the article may be uniaxially or biaxially oriented,
either sequentially or simultaneously, can be cured (such as
through heat, electromagnetic radiation, etc.), can be embossed,
laminated, or can be dusted with various tack-reducing agents.
[0072] Articles of the invention are suitable for use in various
medical articles, such as wound dressings and tapes, surgical
drapes, and wound closure systems. In certain embodiments, distinct
phases are formed in the polymeric matrix in order to provide
increased strength and improved handling without affecting the
overall conformability, transparency or breathability of the
polymeric material. Preferred matrix materials for use in
constructing such medical articles include breathable polymers such
as polyurethanes, polyesters (e.g., Hytrel.TM. 4056 resin from
Dupont, Wilmington, Del.), and polyether block amides (e.g., made
from Pebax.TM. 3533, Pebax.TM. MX-1657, and Pebax.TM.MX-1074, all
available from Elf Atochem, Philadelphia, Pa.). Also preferred are
polyolefins, e.g., polyethylene and polypropylene, when constructed
in a manner to allow breathability, such as when co-extruded with
oil to form a porous film. Combinations of these two types of
preferred matrix materials could also be used. Preferred phase
materials for use in constructing such medical articles include
polyamides, polyethylene, polypropylene, polyesters and styrene
block copolymers, such as Kraton.TM. block copolymers.
[0073] In one preferred embodiment, distinct phases of polyester
(e.g., Eastar.TM. 6763 from Eastman Chemical Company, Kingsport,
Tenn.) are formed in a breathable polyurethane web matrix (e.g.,
Estane.TM. 58237 from B. F. Goodrich Company, Cleveland, Ohio) to
increase strength and aid in the ability to handle and position the
article in final sheet or tape form. This represents a significant
improvement over current surgical dressings formed of polyurethane
that are difficult to handle because they are too flexible and thus
do not easily maintain a shape. The addition of phases to the
polyurethane matrix allows for retention of breathability (at least
about 300 grams/square meter/24 hours, and preferably at least
about 600 grams/square meter/24 hours by Moisture Vapor
Transmission Rate--Upright Method) while increasing tensile
strength and web handling characteristics. The down-web tensile
strength of the resulting webs typically is increased at least 50
percent over comparable webs not having discontinuous phases and
preferably is increased at least 100 percent.
[0074] Alternate methods of making the above breathable article are
lamination and other extrusion methods. One method of making the
article by lamination involves placing a plurality of synthetic or
natural fibers in a parallel direction between two sheets of
breathable elastic material. The resulting sandwich can be pressed
together under heat by means of a platten press of a hot nip. An
alternate extrusion method is that disclosed in Krueger et al, U.S.
Pat. No. 5,429,856, except the two matrix layers are of an elastic
breathable material and the discontinuous phases include preferably
inelastic thermoplastic materials.
[0075] The precise extruders employed in the inventive process are
not critical as any device able to convey melt streams to a die of
the invention is satisfactory. However, it is understood that the
design of the extruder screw will influence the capacity of the
extruder to provide good polymer melt quality, temperature
uniformity, and throughput. A number of useful extruders are known
and include single and twin screw extruders. These extruders are
available from a variety of vendors including Davis-Standard
Extruders, Inc. (Pawcatuck, Conn.), Black Clawson Co. (Fulton,
N.Y.), Berstorff Corp (North Carolina), Farrel Corp. (Conn.),
Moriyama Mfg. Works, Ltd. (Osaka, Japan). Other apparatus capable
of pumping organic melts may be employed instead of extruders to
deliver the molten streams to the forming die of the invention.
They include drum unloaders, bulk melters and gear pumps. These are
available from a variety of vendors, including Graco LTI (Monterey,
Calif.), Nordson (Westlake, Calif.), Industrial Machine
Manufacturing (Richmond, Va.), Zenith Pumps Div., Parker Hannifin
Corp., (North Carolina).
[0076] Once the molten streams have exited the pump, they are
typically transported to the die through transfer tubing and/or
hoses. It is preferable to minimize the residence time in the
tubing to avoid problems of, for example, melt temperature
variation. This can be accomplished by a variety of techniques,
including minimizing the length of the tubing, providing
appropriate temperature control of the tubing, and utilizing static
mixers in the tubing to maintain a homogeneous temperature in the
tubing. Patterned tools which contact the web can provide surface
texture or structure to improve the ability to tear the web in the
cross web or transverse direction without affecting the overall
tensile strength or other physical properties of the product.
EXAMPLES
[0077] The invention is further illustrated by the following
examples, which are not intended to limit the scope of the
invention. In the examples, all parts, ratios and percentages are
by weight unless otherwise indicated. The following test methods
were used to characterize the articles in the following
examples:
[0078] Test Methods
[0079] Tensile Strength and Elongation
[0080] Tensile strength and elongation in the down-web direction of
co-extruded articles were determined in the following manner. A
10.2 cm long by 2.5 cm wide sample was placed between the jaws of
an Instron.TM. Tensile Tester to expose a 5.1 cm gauge length. The
crosshead and chart speeds were set at 25.4 cm/min. The jaws were
drawn apart at 25.4 cm/min until the machine detected a break.
Tensile strength and percent elongation were calculated by the
Instron.TM. software. Tensile strength measurements (each with 3
replications) were taken on samples oriented in the cross web
direction (with force of pull perpendicular to the orientation of
the phases) and in the machine direction (with machine force of
pull parallel to the orientation of the phases).
[0081] Moisture Vapor Transmission Rate (MVTR)
[0082] Moisture vapor transmission rates of the samples were tested
using either the upright method (A) or inverted method (B) as
described below.
[0083] A--Upright Method: Glass bottles were filled with
approximately 50 ml of water. Three test samples and three control
samples were cut into 3.8 cm diameter samples using a round die
cutter. The samples were placed between two foil rings that had
holes cut in the centers. A rubber gasket was placed between the
bottom of the foil and the glass container. A screw cap with a 3.8
cm diameter hole was attached to the glass jar enclosing the
foil-sample sandwich and gasket to the glass. The samples were
conditioned for four hours at 40.degree. C. at 20% relative
humidity in a control chamber. The cap was then tightly secured to
the jar and the jar was removed from the chamber and weighed on an
analytical balance to the nearest 0.01 gram. The jars were returned
to the chamber for at least 18 hrs. (at the conditions listed
above). The bottles were then removed and weighed immediately to
the nearest 0.01 gram. Moisture vapor rates were calculated by the
change in weight multiplied by the exposed area divided by the time
they were exposed. Rates are reported in grams per square meter in
24 hours.
[0084] B--Inverted Method: The same procedure was followed as
outlined above. However, after the samples were conditioned and
weighed, they were returned to the chamber and the bottles were
inverted so that the water contacted the test surface. The bottles
were left undisturbed for at least 18 hrs. The bottles were then
removed and weighed, and the moisture vapor transmission rate was
calculated as above.
[0085] Conformability (Hand)
[0086] The total Hand conformability in grams of example sheet
materials or tapes provides a measure of the drape/conformability
of these materials. Those materials with a relatively high Hand
value are stiff and nonconformable. Conversely, relatively low Hand
values reflect soft, conformable materials. The Hand values
reported for the following examples were obtained on a
Thwing-Albert Handle-O-Meter Model No. 211-300 (Thwing-Albert
Instrument Co., Philadelphia, Pa.), according to the procedures
outlined in the instruction manual included with Model No. 211-300.
All of the Hand measurements were performed on about 10 cm square
sheet materials that were powdered with talc to reduce friction.
Hand measurements (each with 3 replications) were taken on samples
oriented in the cross-web direction (with machine bar parallel to
the orientation of the phases) and in the machine direction (with
machine bar perpendicular to the orientation of the distinct
phases).
[0087] Conformability (Modulus)
[0088] F.sub.10 modulus as referred to herein is a measure of the
force to elongate a sample 10 percent and is effectively determined
using an Instron Unit Model 1102 from Instron Corp., 2500
Washington Street, Canton, Mass. The cross-head speed of the
Instron was set at ten inches per minute and the chart speed is set
at ten inches (25.4 cm) per minute. The gauge length is set at two
inches (5 cm) with the test sample cut to test a one-inch width
(2.54 cm).
[0089] Modulus measurements (each with 3 replications) were taken
on samples oriented in the cross-web direction (with machine bar
parallel to the orientation of the phases) and in the machine
direction (with machine bar perpendicular to the orientation of the
distinct phases).
Examples 1 and 2
[0090] Examples 1 and 2 describe the preparation of extruded
articles having an elastic continuous polyurethane matrix and a
plurality of distinct inelastic phases. The inelastic phases
comprised either modified polyester (Example 1) or polyethylene
(Example 2).
[0091] For Example 1, a continuous extrusion was carried out using
a 45 cm (18 in) wide Cloeren.TM. two-layer multi-manifold die
(available as Model 96-1502 from Cloeren Co., Orange, Tex.) that
had been modified as described in U.S. Pat. No. 6,447,875. A vane
tip containing 95 orifices was mounted to the vane manifold with
socket head bolts. The vane tip had circular orifices each having a
diameter of 508 microns (20 mils) and separated by a space of 4.1
mm (0.160 in) and extended from the vane tip 2.5 mm (0.100 in) into
the matrix flow.
[0092] The continuous matrix material was an elastic material,
Estane.TM. 58237 polyurethane (B.F. Goodrich, Cleveland, Ohio). It
was fed with a 51 mm (2.0-inch) Berlyn.TM. single screw extruder
that was operated at a temperature profile of zone 1--149.degree.
C. (300.degree. F.), zone 2--171.degree. C. (340.degree. F.) and
zones 3 to 7--204.degree. C. (400.degree. F.). The 51 mm extruder
was run at 25 rpm with a head pressure of 31.1 MPa (4500 psi) to
feed continuous matrix material. The discontinuous phase material
was an inelastic thermoplastic polymer, Eastar.TM. 6763 glycol
modified polyester (Eastman Chemical Co., Kingsport, Tenn.). It was
fed with a 32 mm (1.25-inch) Killion.TM. single screw extruder
(available from Davis-Standard Killion Systems, Cedar Grove, N.J.)
that was operated with a temperature profile of zone 1--188.degree.
C. (370.degree. F.), zone 2--227.degree. C. (440.degree. F.) and
zones 3 and 4--243.degree. C. (470.degree. F.). The 32 mm extruder
was run at 6 rpm with a head pressure of 15.9 MPa (2300 psi) to
feed discontinuous phase material through the modified vane in the
die. The die was operated at 218.degree. C. (425.degree. F.). The
extrudate comprising a two-layer polymer matrix containing embedded
discontinuous phases running down-web was extruded into a nip
formed by a chrome casting wheel, at 7.2.degree. C. (45.degree. F.)
and a silicone coated nip roll, at 7.2.degree. C. (45.degree. F.).
The web take-away speed was 11.3 m/min (37 fpm) resulting in an
overall thickness of 43 microns (1.7 mils). The cast web was not
oriented.
[0093] Example 2 was made as Example 1 except the discontinuous
phase material was different and some conditions were changed. The
temperature profile for the extruder that fed the continuous matrix
material was zone 1--149.degree. C. (300.degree. F.), zone
2--166.degree. C. (330.degree. F.) and zones 3 to 7--199.degree. C.
(390.degree. F.). The 51 mm extruder was run at 10 rpm with a head
pressure of 13.8 MPa (2000 psi) to feed continuous matrix material.
The discontinuous phase material was an inelastic thermoplastic
polymer, Dowlex.TM. 10462N polyethylene. The temperature profile of
the extruder that fed this material was zone 1--182.degree. C.
(360.degree. F.), zone 2--241.degree. C. (465.degree. F.) and zones
3 and 4--249.degree. C. (480.degree. F.). The 32 mm extruder was
operated at 12 rpm with a head pressure of 3.5 MPa (500 psi) to
feed discontinuous phase material. The temperature of the nip rolls
was approximately 16.degree. C. (60.degree. F.). The material
take-away speed was 5.2 m/min (17 fpm) resulting in an overall
thickness of 79 microns (3.1 mils).
Example 3
[0094] Example 3 describes the preparation of an extruded adhesive
article having two layers of different materials (polyacrylate PSA
and polyurethane) that comprise an elastic continuous polymeric
matrix and a plurality of distinct inelastic phases comprised of
modified polyester.
[0095] An acrylic PSA (96 weight percent isooctyl acrylate/4 weight
percent methacrylic acid, water suspension polymerized), prepared
according to U.S. Pat. No. 4,833,179 (Young) was dried to about 90
weight percent and melt blended with Floral.TM. 85 (a tackifying
resin available from Hercules Inc., Wilmington, Del.) in a weight
ratio of acrylate to Foral.TM. of 80:20. The PSA was designated as
PSA A.
[0096] Example 3 was made in a manner similar to Example 1 except
that the two layers of continuous matrix material were made of
different materials and an additional extruder was used. The first
layer of continuous matrix material was made of a tacky elastomeric
material, PSA A, and the second layer was made of the elastic
thermoplastic polymer, Estane.TM. 58237 polyurethane. The first
continuous matrix material was fed with a first extruder, a 34 mm
fully intermeshing, co-rotating Leistritz.TM. twin screw extruder
that used an increasing temperature profile reaching a peak
temperature of 193.degree. C. (380.degree. F.). The 34 mm extruder
was run at 180 rpm with gear pump speed of 4.7 rpm and a head
pressure of 4.2 MPa (610 psi) to feed continuous matrix material
into the first feed orifice of the die. The second material was fed
with the 51 mm extruder into the second feed orifice of the
die.
[0097] The resulting construction, which comprised an article
having a PSA on one side, a polyurethane on the opposite side, and
a distinct phase of polyester embedded strands, provides an example
of a polymeric matrix composed of two different materials.
Example 4
[0098] Example 4 describes the preparation of a laminated adhesive
article comprising a first layer of extruded elastic polyurethane
film, a plurality of nylon monofilaments, a second layer of
extruded elastic polyurethane film, and a polyacrylate PSA
layer.
[0099] 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 80 pound (36 kg) bleached release
liner, one side coated, silicone paper (1-80BKG-157) (DCP-Loyha,
Willowbrook, Ill.) using a standard horizontal knife coater.
[0100] A 0.6 mil (14 micron) film of ESTANE 58309 polyurethane
resin (B. F. Goodrich, Cleveland, Ohio) was extruded using
conventional methods. A silicone liner was placed on the bed of a
fixture with a first layer of film. A 4 pound (1.8 kg) test Nylon
Monofilament fishing line (Berkley & Co. Inc., Spirit Lake,
Iowa) was threaded in a parallel manner over the first layer of
film (2 mm apart) using the ends of the fixture and a second layer
of film was place over the monofilaments with a second release
liner placed over the sandwich laminate. The laminate was then
placed in a heated press at 190.degree. C. and 2 tons (1800 kg) of
pressure. The laminate was then laminated to the adhesive surface
to form an adhesive article of the present invention.
Example 5
[0101] Example 5 describes the preparation of an extruded article
(from Example 1) coated with a microsphere-containing polyacrylate
PSA.
[0102] A pressure sensitive adhesive matrix blended with polymeric
microspheres was prepared and coated on one surface of the Example
1 extruded article according to the procedure described in Example
1 of Heinecke et al., U.S. Pat. No. 5,849,325 to provide an
adhesive article of the present invention.
Example 6
[0103] Example 6 describes the preparation of an extruded article
(from Example 1) pattern coated with a polyacrylate PSA.
[0104] The polyacrylate PSA described in Example 4 was pattern
coated on one surface of the Example 1 extruded article to form a
25 percent void area grid according to the procedure described by
Rawlings in U.S. Pat. No. 4,798,201.
Example 7
[0105] Example 7 describes the preparation of an extruded article
having an elastic continuous polyurethane matrix and a plurality of
distinct elastic phases comprised of ultra low density
polyethylene.
[0106] The continuous extrusion was carried out using a 45 cm wide
Cloeren.TM. three-layer multi-manifold die that had been modified
as described in U.S. Pat. No. 5,429,856 (Krueger). A "comb" insert
was bolted to the internal surface of one of the two unmodified
vanes and snugly engaged with the second vane to allow the vanes to
rotate in unison. The "comb" insert had orifices of 1.6 mm in
length and a separation distance of 3.2 mm.
[0107] The continuous matrix material was an elastic material,
Estane.TM. 58309 polyurethane. The matrix material was fed with a
63.5 mm Davis Standard.TM. single screw (available from
Davis-Standard Corp., Pawcatuck, Conn.) that operated at a
temperature profile of zone 1--149.degree. C. (300.degree. F.),
zone 2--149.degree. C. (300.degree. F.), zone 3--177.degree. C.
(350.degree. F.), zone 4--182.degree. C. (360.degree. F.), zone
5-6--188.degree. C. (370.degree. F.). The 63.5 mm extruder was run
at 12 rpm to feed the continuous matrix material. The discontinuous
phase material was an elastic thermoplastic polymer, Engage.TM.
8200 (ultra low density polyethylene, Dupont, Wilmongton, Del.). It
was fed with 19 mm Killion.TM. single screw extruder (available
from Davis-Standard Killion Systems, Cedar Grove, N.J.) that was
operated with a temperature profile of zone 1--155.degree. C.
(311.degree. F.), zone 2--180.degree. C. (356.degree. F.), zones
3-4--200.degree. C. (392.degree. F.), and zone 5--210.degree. C.
(410.degree. F.). The 19 mm extruder was run at 87.5 rpm to feed
the discontinuous phase material through the modified vane and
cutouts in the die. The die was operated at 204.degree. C.
(400.degree. F.). The extrudate comprising a two-layer polymer
matrix containing embedded discontinuous phases running down-web
was extruded into a nip formed by a chrome casting wheel and a
silicone coated nip roll. The material take-away speed was 15.2
m/min (50 fpm) resulting in an overall basis weight of 3.0
g/cm.sup.2.
Example 8
[0108] Example 8 describes the preparation of a laminated adhesive
article comprising a layer of polyacrylate PSA, a layer of extruded
elastic polyether block amide matrix and a plurality of distinct
elastic phases comprised of polyether block amide blended with
linear low density polyethylene and a white pigment.
[0109] A 13 micron (0.5 mil) film of Pebax 3533 polyether block
amide resin (Elf Atochem, Philadelphia, Pa.) was extruded using a
19 mm Rheocord.TM. System 40 single screw extruded (Haake Buechler,
Saddle Brook, N.J.) that was equipped with an Ultraflex 40 flex lip
die (Extrusion Die Inc., Chippewa Falls, Wis.). The extruder was
operated with a temperature profile of zone 1--177.degree. C.
(350.degree. F.), zone 2--182.degree. C. (360.degree. F.), zone
3--193.degree. C. (380.degree. F.), and a die temperature of
204.degree. C. (400.degree. F.). The extruder was run at 35 rpm.
The extruded film was laminated to a layer of the polyacrylate PSA
(on silicone release liner) described in Example 4 using
conventional laboratory lamination conditions.
[0110] The Ultraflex.TM. 40 die used above was then shimmed with 10
mil brass shim stock cut into 10 mm lengths to form a series of 5
apertures spaced 15 mm apart. A blended thermoplastic polymer was
prepared by combining 50% Pebax.TM. 3533 and 50% LLDPE 7047 (Union
Carbide), and then adding 3% white pigment concentrate CBE 101 E
White (Charles B. Edwards & Co., Inc.). The blended polymer was
fed into the shimmed Ultraflex 40 die using the 19 mm Rheocord
System 40 extruder described above that was operated with a
temperature profile of zone 1--177.degree. C. (350.degree. F.),
zone 2--188.degree. C. (370.degree. F.), and zones 3-4--199.degree.
C. (390.degree. F.). The extruder was run at 10 rpm. The extruded
discontinuous phase material was laminated to the Pebax.TM. film
layer of the above laminate using the same conventional laboratory
lamination conditions.
Example 9
[0111] Example 9 describes the preparation of an adhesive article
having an extruded elastic continuous matrix comprised of porous
polypropylene and a plurality of distinct inelastic polypropylene
phases, and a layer of polyacrylate PSA.
[0112] Example 9 was made in a manner similar to Example 1 except
the continuous matrix material was made of a melt blend of 40% by
weight mineral oil and 60% by weight thermoplastic polymer, a dry
blend of 95% SD45 polypropylene (Union Carbide, Danbury, Conn.) and
5% of a 2% Millad 3905 (Milliken Chemical, Inman, S.C.) nucleating
agent concentrate. The Millad 3905 amounted to 0.1% of the total
continuous matrix. The continuous matrix material was fed with a 34
mm fully intermeshing, co-rotating Leistritz.TM. twin screw
extruder that used an increasing temperature profile reaching a
peak temperature of 232.degree. C. (450.degree. F.). The
discontinuous phase material was an inelastic thermoplastic
polymer, PP 3374 polypropylene (Fina Oil & Chemical Co.,
Dallas, Tex.). A 32 mm (1.25-inch) Killion.TM. single screw
extruder was operated with a temperature profile of zone
1--182.degree. C. (360.degree. F.), zone 2--221.degree. C.
(430.degree. F.), and zones 3 and 4--243.degree. C. (470.degree.
F.). The 32 mm extruder was run at 20 rpm with a head pressure of
15.9 mPa (2300 psi). The construction was then length oriented and
tentered by a factor of 2.0 in both directions to provide porosity.
The oriented temperature was 65.degree. C. A detailed description
of preparing porous films can be found in Shipman, U.S. Pat. No.
4,536,256.
[0113] The extruded film was laminated to a layer of polyacrylate
PSA (on a silicone release liner) described in Example 4 using
conventional laboratory lamination conditions.
[0114] Evaluations
[0115] Samples of articles from Examples 1, 3 and 9 were evaluated
for stiffness (Hand and F.sub.10 modulus measurements), tensile
strength at break, percent elongation at break, and MVTR (upright
method). The results are provided in Table 1 and are compared with
comparative data from the commercial adhesive dressings
TEGADERM.TM. HP (3M Company) and OP-SITE.TM. IV (Smith &
Nephew)
1 TABLE 1 Modulus Tension at Elongation MVTR Modulus (F.sub.10)
Break at Break gm/m.sup.2/24 hr (Hand) (N/cm) (N/cm) (%) Upright MD
CD MD CD MD CD MD CD Method Example 1 5 4 3.06 2.31 17.5 12.25 480
408 8900 Example 3 7 4 3.12 2.19 26.25 11.38 640 380 500 Example 9
18 6 5.6 4.03 13.1 8.93 92 91 NA TEGADERM 2 2 0.46 0.46 4.73 4.38
360 340 4000 HP.sup.1 OP-SITE IU.sup.2 1 1 0.72 0.72 9.98 9.45 545
555 1540 .sup.1TAGADERM .TM. HP #9536HP, transparent dressing with
label; 10 .times. 12 cm; Lot #2001-07 HD .sup.2OP-SITE .TM. IV3000
moisture responsive cannula dressing; 10 .times. 14 cm; Lot
#9243
[0116] As seen from Table 1, the presence of distinct phases in
Example 3 provided an adhesive article with significantly increased
stiffness (higher Hand and F.sub.10 Modulus values), significantly
increased tensile strength and a high degree of breathability (MVTR
greater than 300 gm/m.sup.2/24 hr) as compared to the two
commercial adhesive dressings that do not contain phases.
[0117] All patents, patent documents, and publications cited herein
are incorporated by reference. The foregoing detailed description
and examples have been given for clarity of understanding only. No
unnecessary limitations are to be understood therefrom. The
invention is not limited to the exact details shown and described,
for variations obvious to one skilled in the art will be included
within the invention defined by the claims.
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