Note: Descriptions are shown in the official language in which they were submitted.
~'VO 95/15136 PCT/US9~/12653
PROCESS FOR APPLYING A FOAMED COATING TO A
MEDICAL ADIiESIVE TAPE
BACKGROUND
This invention generally relates to a process for applying a foamed
coating to a web and particularly relates to a process for applying a foamed
release
coating to a porous, pressure sensitive adhesive medical tape backing.
Pressure sensitive adhesive tapes for medical purposes place special
demands on the components used to make these tapes. In particular, the
components making up the tape must be accommodated by the user, i.e.,
biocompatible. Furthermore, the adhesives and coatings must not be undesirably
transferred to the user during use. Briefly put, when pressure sensitive tapes
are
adapted for medical use, stringent demands are placed on the materials and
processes used to make such tapes.
Pressure sensitive adhesive tapes are typically made from polymeric
films, paper, woven fabrics or nonwoven tape backings coated with a pressure
sensitive adhesive on one side or surface of the backing and with a release
coating
on the other side of the backing. The release coating allows the coated tape
backing to be rolled onto itself and prevents the transfer of the adhesive on
the
tape from one layer of tape in the roll to an adjacent layer.
A variety of release coatings have been used for this particular
purpose. Until recently, typical release coatings were dissolved in a volatile
organic solvent to give a mixture or solution that was then applied to one
side or
surface of a tape backing using a variety of methods. For example, mixtures or
solutions of release coatings and volatile solvents have been applied to tape
backings using rollers, dips, knife coaters or other common application
apparatus.
WO 95/15136 PCT/US94/12653 t
The problems caused by using mixtures or solutions of release
coatings and volatile organic solvents has prompted the development of
water-based release coatings.
Various methods of applying water-based release coatings have been
reported. For example, U.S. Patent 4,973,513 reports that a water-based
release v
coating may be applied to a pressure sensitive adhesive tape using
conventional
coating processes such as wire-wound rod, reverse roll, air knife, direct and
offset
gravure trailing blade, print bond or spray coating.
U.S. Patent 5,089,296 reports that release coatings may be foamed
and then applied to paper and other substrates. In this patent, the foams are
slow
breaking and require an external force such a mechanical compression or vacuum
to collapse. It is also reported that control of the collapse of the foam is
important
because the foams rapidly penetrate and impregnate surfaces after the foam has
collapsed. When a release coating is applied according to the reported
process,
the release coating composition must not be fast wetting in order to insure
that the
release coating remains on the surface of the substrate. This patent indicates
that
fast breaking foams are not acceptable for coating processes because migration
of
the release coating into a tape backing would be expected.
In spite of the many different ways a release coating may be applied
to a pressure sensitive adhesive, there is no single process which is believed
to be
preferred in any specific application. Further, there is no report that a
particular
process would provide the superior properties required of a medical adhesive
tape.
Thus, those of ordinary skill in the art are confronted with a plurality of
methods
or processes which might be used to manufacture a medical adhesive tape but
are
not provided with a process which is known to provide the tape with the
required
superior properties. In short, a need exists for a process to apply a release
coating
to a medical adhesive tape which will both reliably and predictably provide a
superior medical pressure sensitive adhesive tape.
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~WO 95/15136 PCTlUS94/12653
~:~~~~~U
SUMMARY OF THE INVENTION
The present invention provides a process for applying a foamed
coating to a medical pressure sensitive adhesive tape. The present process may
be
used to apply a thin, uniform coating, such as a release coating or a low
adhesion
backsize, to a porous, pressure sensitive tape backing and includes the steps
of i)
forming a porous tape backing having a least one surface from polymeric
fibers,
ii) forming a foam of an aqueous emulsion to give a foamed emulsion, wherein
the foamed emulsion is prepared by mixing water, an aqueous emulsion, and a
surfactant to give a foam that collapses immediately when the foamed emulsion
is
applied to the tape backing, iii) applying the foamed emulsion to at least one
surface of the tape backing to give a coated tape backing, and iv) coating the
tape
backing with a pressure sensitive adhesive. Suitable tape backings include
both
woven and nonwoven fabrics, webs containing elastomeric fibers or yarns, and
laminated or composite porous backings.
Depending on the particular type of pressure sensitive adhesive tape
desired, the present invention also includes a process in which the pressure
sensitive adhesive is applied to the tape backing before the application of
the
release coating. In one example of this embodiment, the process would include
the steps of i) forming a porous tape backing having at least one surface from
polymeric fibers, ii) coating at least one surface of the tape backing with a
pressure sensitive adhesive, iii) forming a foam of a release coating to give
a
foamed composition, wherein the foam is prepared by mixing water, the release
coating, and a surfactant to give a fast breaking foam composition that
collapses
immediately when the foam composition is applied to the porous tape backing,
and
iv) applying the foamed emulsion to one surface of the porous tape backing
containing the pressure sensitive adhesive to give a coated pressure sensitive
adhesive tape.
Advantageously, when a release coating or low adhesion backsize
are applied to a tape backing using the present process, there is no need to
use any
external force to break the foamed coating. It has also been found that the
use of
a fast breaking foam does not cause undue migration of a coating into the
porous
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WO 95/15136 PCT/US94/12653
tape backing. Control of excessive migration is especially important in a
medical
tape because it is believed that migration of the coating may lead to
inadequate
attachment of the adhesive to the tape backing. If the adhesive attachment is
,
insufficient, adhesive residue may be left on a patient. The present
process therefore may be reliably performed with much simpler apparatus than
previously reported which avoids critical or complicated foam application,
spreading or breaking equipment, reduces the amount of release coating which
must be applied to the backing, removes potential for mechanical failure,
allows
high tape backing throughput and ensures proper adhesive attachment to the
tape
backing. In addition, the present process may be used to produce pressure
sensitive adhesive tapes which are capable of passing the stringent
requirements
associated with medical pressure sensitive adhesive tapes. In particular, the
present process provides pressure sensitive adhesive tapes which may be used
in
a variety of medical applications.
' 15 In another embodiment of the present process, a fast breaking foam
of a natural rubber latex may be used to apply a thin, uniform coating of an
aqueous natural rubber latex emulsion to a woven or nonwoven elastomeric
backing. This process is essentially the same as the process for applying a
release
coating to a tape backing except that a porous elastomeric material is used as
the
backing. This process includes the steps of i) forming a porous, elastomeric
backing having a least one surface, ii) forming a foam of an aqueous natural
rubber latex emulsion to give a foamed emulsion, wherein the foamed emulsion
is prepared by mixing water, natural rubber latex, and a surfactant to give a
foam
that collapses immediately when the foam is applied to the porous, elastomeric
backing, iii) applying the foamed emulsion to both surfaces of the elastomeric
backing to give a coated backing, and iv) drying the coated backing.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic representation of a tape coating process in
which a fast breaking foam is applied to a tape backing. No mechanical
apparatus
or externally applied force is used to break the fast breaking foam. Figure 2
is a
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-WO 95/15136 PCT/US94/12653
schematic representation of a tape coating process in which a slow breaking
foam
is applied to a tape backing and the applied foam is then mechanically broken
on
the surface of the backing. Figure 3 is a schematic representation of a tape
coating
process which applies a foamed natural rubber latex to an elastomeric backing.
Figure 4 is a schematic representation of a tape coating process which applies
a
foamed release coating and a transfer adhesive to a tape (with removal of the
liner
after application of the transfer adhesive).
DETAILED DESCRIPTION
The process of this invention is readily adapted to typical processes
used to make pressure sensitive adhesive tape. Some typical processes
currently
used to make pressure sensitive adhesive tapes include forming a web from a
fibrous material and then adhering the fibers of the web together with a wet
binder. The wet web is then dried at elevated temperatures to give a tape
backing.
A release agent is then applied to one surface of the tape backing and the
coated
backing is again dried. Finally, a pressure sensitive adhesive is applied to
the
surface of the tape backing which is not coated with the release agent, the
tape
backing is again dried and then the tape is wound into rolls.
Apparatus to perform coating processes are illustrated in Figs. 1-4.
Figure 1 is a schematic illustration of a tape coating process of the present
invention in which a fast breaking foam of a low adhesion backsize emulsion is
applied to a binder wet web tape backing. A backing 10 is led from a nonwoven
maker (not shown) and passes between binder application rollers 12 and 14.
Binder is applied from station 13 by doctor blade 11. The backing proceeds to
a
foam coating station at which a fast breaking foam 16 is applied from a foam
die 18. The applied foam coating 16 is dried by oven 20.
Figure 2 is a schematic illustration of a known tape coating process
in which a slow breaking foam of a low adhesion backsize emulsion is applied
to
a thermal bonded binder wet tape backing and the applied foam is then
mechanically broken on the surface of the backing. A backing 22 is led from a
nonwoven maker (not shown) between binder application rollers 24 and 26.
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WO 95/15136 PCT/US94/12653
Binder is applied from station 25 by doctor blade 27. The backing proceeds to
a
coating station at which a slow breaking foam 28 is applied from a foam die 29
and the foam is broken as the coated backing passes under a plastic knife edge
spreader 21. The applied coating 28 is dried by oven 20.
Figure 3 is a schematic illustration of a tape coating process of the
present invention in which a foamed natural rubber latex is applied to an
elastomeric backing. Elastic yarns 36 are led from supply spools 34 through
combs 35 and then between pressure rollers 38 and 40 so that the elastic yarns
will
be placed between two layers of nonwoven backing 32 which are unrolled from
supply rollers 30A and 30B. The layered construction is carried between roller
42, which applies a noncohesive elastomer binder from coater 44, and roller 46
to foam dies 48 and 50 which apply natural rubber latex foam and then through
oven 52 to dry the composite web 53. The dried web 53 is then directed through
a pair of nip rollers 54 and 56 and through an oven 58 which is sufficiently
hot to
effect shirring and heat-setting as described in U.S. Patent 3,575,782
(Hansen) and
then through a pair of nip rollers 60 and 62 and wound into a roll with the
aid of
a winder roller 72.
Figure 4 is a schematic illustration of a tape coating process in
which the process illustrated in Figure 3 applies a foamed low adhesion
backsize
emulsion from foam die 50 and is expanded by applying a transfer adhesive to
the
web 53 after it has exited oven 52, with subsequent removal of the transfer
tape
liner. The transfer adhesive on a liner 66 is supplied from roller 64 and the
resulting laminate 67 is carried between nip rolls 54 and 56 with removal of
liner 70 to roll 68 while web 59 is carried through oven 58 and wound into a
roll.
Nonwoven webs for use in preparation of porous tape backings are
made in accordance with conventional methods known in the art, including wet
laid methods, dry laid methods such as air layering and carding, and direct
laid
methods such as spunbonding and meltblowing. Examples of such methods are
disclosed in U.S. Patent 3,121,021 (Copeland) and U.S. Patent 3,575,782
(Hansen). Conventional woven webs and other porous webs may also be used in
the process of this invention.
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~O 95/15136 PCT/US94/12653
The nonwoven web is formed from synthetic or natural fibers
selected according to the desired properties of the resulting web. Examples of
textile fibers appropriate for use in the backing webs include polyester,
polyolefin,
polyamide, rayon, cotton, or the like. The nonwoven web may also incorporate
reinforcing filaments, such as polyester, or shirring fibers such as LYCRA
spandex yarns.
The fibers are preferably coated with a water-based binder to give
a suitable tape backing. Examples of such binders include latexes
incorporating
acrylics, styrene/butadiene rubbers, vinyl acetate/ethylenes, vinyl
acetate/acrylates,
polyvinyl chloride, polyvinyl alcohols, polyurethanes and vinyl acetates. Such
binders are typically applied to the fibers at 25-35 weight percent solids by
any
suitable coating method, including wire-wound rod, reverse roll, air knife,
direct
and offset gravure, trailing blade, print bond and spray coating methods. The
binder is applied in amounts sufficient to provide the desired properties to
the
backing, typical amounts for different types of backings would be readily
apparent
to the skilled artisan in the nonwoven manufacturing field. For example, more
binder may be applied to produce a stronger material, which is usually
stiffer, of
a similar construction.
After the binder has been applied, and either before the tape backing
is dry or after the tape backing has been dried, a water-based release coating
is
applied using the process of the present invention. The water-based release
coating materials include polyethylenes, fluorochemicals, acrylates,
silicones, vinyl
copolymers and combinations of these polymers with other polymers. Preferably,
the release coating is a low adhesion backsize comprising poly(dimethyl
siloxane)
and acrylate polymers. Acceptable low adhesion backsizes are disclosed, for
example, in U.S. Patent 4,728,571 (Clemens, et al.).
Methods of foaming a release coating are also known in the art. In
the practice of the present invention, a release coating is preferably mixed
with
more than about 0.5 weight percent of an anionic or nonionic surfactant. A
preferred surfactant is an anionic surfactant such as TRITON GR-SM or a
nonionic
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WO 95/15136 PCT/US94/12653
w~~~~~~
surfactant such as TRITON X-100 (both surfactants are available from Rohm and
Haas Company, Philadelphia, PA). Typical blowing ratios for the foamed release
coatings are from about 4 to 30. Preferred blow ratios for foaming a release
coating are 20 to 30. Preferred blow ratios for foaming a natural rubber latex
are
8 to 12.
Suitable foams for use in the present invention may be prepared
using conventional methods and apparatus. For example, a foamed release
coating
or a foamed natural rubber latex may be prepared in a commercially available
foamer such as a LESS SUPERFOAMER foaming apparatus (Latex Equipment
Sales and Surface, Palton, GA). The SUPERFOAMER apparatus is particularly
convenient because it is equipped to pump the foamed material under pressure
directly to a foam die. The foam die provides a back pressure and an
appropriate
delivery rate of the foam.
After the release coating or rubber latex is foamed, the foamed
material is pumped to a foam die and then applied to the tape backing by the
die.
The amount of material which is coated onto the tape backing is controlled by
the
rate the material is pumped through the die. In the present process the rate
is set
to deliver a thin coating at a rate of less than about 4.0 g/m2 of a dry
release
coating to the tape backing (measured as difference of the dry tape backing
from
the dry coated tape backing). Preferably, the rate of delivery is about
0.5-1.5 g/m2. The rate of delivery for applying a thin coating of a dry rubber
latex to a tape backing is about 5 to 7 g/m2 per side.
In addition to delivering the foam to the tape backing, the foam die
also controls the uniformity of the foam applied across the width of the tape
backing. A foam die which particularly applies a uniform coating from the die
uses the foam emission nozzle described in U.S. Patent 4,655,056 (Zeiffer).
This
type of die is properly shaped to deliver a uniform flow of foam across the
width
of the tape backing and provides an edge-center-edge weight percent
distribution
of less than about plus or minus 8 weight percent. Other types of foam dies
which
are capable of delivering foam to a tape backing in such a controlled manner
may
be used in the present process.
_g_
~O 95/15136 PCT/US94/12653
After the release coating has been applied, the coated tape backing
is dried using any appropriate drying means. For example, drying means that
are
conventional in the nonwoven textile arts include contact drying, circulating
air
ovens, impingement ovens and through-air ovens. Preferably, the tape backing
is
dried in a circulating air oven at about 145-155°C for about one
minute. The heat
source is preferably located on the same side of the tape backing in the oven
as the
release coating, so that wicking of the release coating through the web is not
encouraged by uneven drying. It is envisioned that on production scale
equipment,
the wet release coated tape backing will be conveyed to the drying oven about
0.5-10 seconds after application of the release coating.
At this point, the coated tape backing may be wound in a roll for
transportation for later application of an adhesive, or it may be conveyed
directly
to an adhesive coater, followed by slitting into individual tape rolls.
Alternatively,
adhesive may be applied as a transfer adhesive from a liner.
The pressure sensitive adhesive that is applied to the nonwoven tape
backing may be solvent-based, water based, or a hot melt adhesive. Suitable
adhesives such as phenolic cured rubber based adhesives are disclosed in U.S.
Patent 2,708,192 (Joesting et al.). Both water-based and solvent-based
adhesives
are disclosed in U.S. Patent RE 24,906 (IJlrich). Hot melt adhesives are
disclosed, for example, in U.S. Patent 4,833,179 (Young et al.).
Surprisingly, it has been observed that there is minimal migration
of the release coating into the tape backing except adjacent to the area of
application. In other words, the release coating does not diffuse through the
tape
backing as would be expected of a fast breaking foam applied to a porous
material.
Minimal migration of the release coating into the tape backing is
demonstrated by measurement of adhesive residue left on a surface after the
tape
has been applied. A suitable residue test is described in U.S. Patent
4,693,776
(Krampe et al. ) .
In another embodiment of the present invention, a foamed natural
rubber latex is applied to an elastomeric tape backing. Processes to prepare a
porous, elastomeric backing are known in the art. For example, an elastomeric
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WO 95/15136 PCT/US94/12653
self adhering bandage is described in U.S. Patents 3,575,782 (Hansen) and
4,984,584 (Hansen et al.). Briefly, elastic yarns are bonded between two
layers
of a nonwoven web with a natural rubber latex to provide a backing having good
compression characteristics and cohesiveness or the ability to self adhere.
The following examples are provided to further illustrate the practice
of the present invention. The examples should not be construed to limit the
invention which is defined in the appended claims.
EXAMPLES
Example 1 Processes Using Mechanical Breaking of an Applied Foam
Using an apparatus illustrated schematically in Figure 2, 30 yards
(27.4 m) by 20 inches (50.8 cm) in width and 3.5 mils (0.0889 cm) in thickness
of 80:20 polyethylene terephthalate: a nonwoven web was prepared from a blend
of 80 parts T-121 staple polyester fiber, 1.2 denier 38 mm polyethylene
terephthalate available from Hoechst Celanese Corp., Charlotte, NC and 20
parts
of 2 denier 38 mm type K-54 MELTY type binder fiber (a core-sheath fiber
containing an oriented polyester core and a meltable polyester sheath also
available
from Hoechst Celanese Corp., Charlotte, NC) were processed in a Hergeth
Random-Card machine (available from Hergeth Hollingsworth GMBH, Dulman,
West Germany) utilizing conventional nonwoven web formation techniques to
produce an approximately 35 g/m2 basis weight nonwoven web. The nonwoven
web was embossed using a heated calender and then was wet with 25 wt. % solids
acrylic/vinyl acetate copolymer latex binder (available from National Starch
Company, Bridgewater, NJ as 78-6283) to give nonwoven tape backing. The wet
tape backing was treated with a foamed release agent. The foam was made by a
LESS foaming apparatus (available from Latex Equipment Sales and Service,
Palton, GA, as SUPERF~AMER model) from a 2 wt. % aqueous solution of
water-based low adhesion vinyl silicone copolymer backsize (prepared as
described
in U.S. Patent 5,032,460 (Kantner et al.)) of 20/50/10/30 methyl
acrylate/methyl
methacrylate/methacrylic acid/mercapto dimethyl siloxane. The foam was applied
using a knife edge type system of a straight edge of hard plastic sheeting 100
mils
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~WO 95/15136
PCT/US94/12653
(2.54 mm) thick by 4 inches (10.2 cm) wide by 36 inches (91.4 cm) long. The
foam covered backing was carried at 15 feet per minute (4.57 m/min) into and
through an oven at 325-350°F (163-177°C) and the dried backing
web was wound
onto a 3 inch (7.6 cm) core.
S The coated backing was then coated full width at 6.5 grains/24 inZ
(27 g/m2) using a semi-wet lamination process generally described in U.S.
Patent
3,121,021 (Copeland) with a water based 40 to 44 wt. % 95:5 isooctyl
acrylate:acrylic acid polymer adhesive prepared as described in U.S. Patent
Re 24,905 (Ulrich) to provide a medical adhesive tape. The tape was then slit
into
one inch (2.54 cm) wide by 10 yards (9.1 m) long rolls.
The rolls were found to unroll readily after aging for 2 days at
120°F (49°C) at 90% relative humidity. However, the adhesive
attachment to the
coated backing was not adequate because an adhesive residue was left on the
skin
when the medical tape was used. Specifically, the amount of adhesive residue
was
more than about two times the adhesive residue when compared to a similar tape
prepared by spraying the low adhesion backsize onto the backing as generally
described in U.S. Patent 4,973,513 (Riedel et al.). The decrease in adhesive
attachment to the backing is a result of low adhesion backsize penetration
into the
backing when the foam was mechanically broken on the backing surfacing using
the plastic knife edge.
Another tape backing was prepared from standard viscose processed
rayon staple fibers (1.5 denier, 40 mm length, available from Courtaulds North
America, Inc., New York, N.Y.) in a Hergeth Random-Card machine to produce
an approximately 22 g/m2 basis weight nonwoven backing.
Using the apparatus of Figure 2 about 50 yards (45.7 m) of the
rayon backing was either wet treated with various binders at 28 wt. % aqueous
solids loading or treated with the binders at 28 wt. % aqueous solids and
dried, and
then was froth coated according to the procedure described above with a 2 wt.
solution of the low adhesion backsize containing a surfactant added (0.5 wt. %
TRITON GR-SM, available from Rohm and Haas Company, Philadelphia, PA).
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WO 95/15136 PCT/US94/12653
The line speed was 15 feet/minute (4.57 mlmin) and the oven temperature was
340°F (I71 °C). Spreading was done by an idler arm or a wipe
blade.
Specific processing conditions are listed in Table 1 below. After the
listed tapes were coated and dried, they were aged for 2 days at 120°F
(49°C) at
90 % relative humidity. Roll unwind of the aged tapes was determined according
to ASTM D-1000. The roll unwind was 450 g/2.54 cm and found to be
unsatisfactory. In addition, the adhesive attachment was determined for the
listed
tapes and it was found that the adhesive residue was above acceptable levels
for
a medical adhesive tape.
-12-
~WO 95/15136
PCT/US94/12653
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-13-
WO 95/15136 . . PCT/US94/12653
Example 2 ~czam Release Coating Process
Medical adhesive tapes were prepared according to the process
generally described in Example 1 above except that no mechanical means were
used to break or spread the foam after it was applied to a tape backing as
illustrated schematically in Figure 1. More specifically, a rayon backing was
prepared from 1.5 denier and 1-9/16 inch (3.97 cm) long fibers using the
process
described in Example 1. The web had a basis weight of 20 g/m2 and was about
12 to 14 inches (30.5 to 35.6 cm) wide and was trimmed to 12 inches (30.5 cm)
wide. It was coated at a speed of about 30 to 35 feet/minute (9.1 to 10.7
m/min)
with a variety of binders as shown in Table 2 to a ratio of about 1 g of
binder to
1 g of web fiber using suspensions of 26 wt. % binder solids at pH 7.5 to 8.5.
After the binder was coated on, the low adhesion backsize used in Example 1
was
coated as a foam using the foamer described in Example l and a Gaston County
0.25 inch (0.635 cm) oriface parabolic die. The low adhesion backsize included
1.25 wt. % GR-SM surfactant and was applied at a 22:1 blow ratio.
Specific processing conditions are listed in Table 2 below. After the
listed tapes were coated and dried, they were aged for 2 days at 120°F
(49°C) at
90 % relative humidity. Roll unwind of the aged tapes was determined according
to ASTM D-1000. The roll unwind was less than 350 g/2.54 cm. In addition, the
adhesive attachment was determined for the listed tapes and it was found that
the
adhesive residue as determined according to the procedure listed in U.S.
Patent
4,693,776 (Krampe et al.) was below a value of 2.5. These data indicate that
the
medical adhesive tape prepared according the process listed in the present
example
are acceptable for its intended use. The backings listed in Table 2 which are
odd-numbered were coated with a pressure sensitive adhesive using the process
described in U.S. Patent 3,121,021 (Copeland) before a low adhesion backsize
was
applied to the backing using the present process.
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~'VO 95/15136 ~ _ PCT/US9.~/12653
TABLE 2
Sample Binder LAB Primer Yardage
I,
1 4402 - - 50
2 4402 X - 100
3 V-43 - - 50
4 V-43 X - 100
6283 - - 50
6 6283 X - 100
7 4260 - - 50
8 4260 X - 100
9 HP-2931 - - 50
HP-2931 X - 100
11 2833 - - 50
12 2833 X - 100
13 1715 - - 50
14 1715 X - 100
1845 - - 50
16 1845 X - 100
17 B15 - - 50
18 B15 X - 150
19 B15 - X 50
Backing Primed side not X 50
#18 coated
LAB: low adhesion backsize
Binders: 4402 Rohm and Hass SBR
4402
V-43: B.F. Goodrich
6283: National Starch 78-6283
4260: National Starch 25-4260
HP-2931: Rohm and Haas
2833: National Starch 25-2833
1715: Rohm and Haas
1845: Rohm and Haas
B15: Rohm and Haas
Primer: Mica G 1147 Mica Corp. at 1 wt. f solids with 0.25 wt.
GR-5M surfactant
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WO 95/15136 PCT/US94/12653
Example 3 Elastomeric Tape Backings Treated with Foamed Compositions
Using an apparatus shown diagrammatically in Figure 3, a web of
12 g/m~ thermally bonded polyethylene terephthalate fibers of web width 16 in
(40.64 cm) was prepared according to the method described in Example 1 above.
A noncohesive elastomer, Hystretch V-43 (available from B.F. Goodrich
Company, Akron, OH) was applied to two layers of the backing sandwiching a
spandex elastomeric yarn to give an elastomeric tape backing as shown in
Figure 3. Cohesive elastomer natural rubber latex (available from Goodyear
Rubber Plantations Company, Akron, OH) was applied as a foam to both sides of
the wet elastomeric tape backing at a blow ratio of 10:1 and dried. The coated
tape backing was subsequently slit using a conventional slitting apparatus
into self
wound rolls. The product exhibited a light cohesion to itself after foam
coating
of the natural rubber latex.
A similar elastomeric adhesive tape was also prepared according to
the following procedure. A coating of a low adhesion backsize was applied to
one
side of the noncohesive polyethylene terephthalate elastomeric tape backing
described above using the process of the present invention from the LESS
foaming
apparatus of Example 1. The low adhesion backsize used was that used in
Example 1 which had been foamed at a blender speed of 153 rpm, pump speed
15 rpm, air flow setting 20, air inlet setting 40 psi and back pressure 7 psi
at a
blow ratio of 22:1.
The release coating process was carried out at 12 ft/min
(3.66 m/min) line speed, the low adhesion backsize was applied at 2.0 gl m2 at
an
application rate of about 140 g/min of low adhesion backsize emulsion (2 ~
solids
in water). Then, an acrylic acid-isooctyl acrylate (4:96 molar ratio)
copolymeric
transfer adhesive (as described in U.S. Patent RE 24,906) coated at 60 g/m2 on
a
differential release liner (liner 2-80 BKG 157/99 AM available from Daubert
Coated Products, Dixon, IL) was dry laminated from the coated liner onto the
uncoated side of the elastomeric backing using conventional procedures.
The resulting elastomeric adhesive tape had no cohesion to the
nonfoam coated web. The rolls were tested for roll unwind according to ASTM
D-1000 and found to have acceptable unwind of less than 350 g/2.54 cm. The
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~O 95/15136 PCT/US94/12653
rolls were also tested for adhesive anchorage according to residue left as
described
above and found to be satisfactory.
Example 4 Cloth Backing Treated with Foamed Low Adhesion Backsize
An acetate cloth fabric pressure sensitive adhesive tape was prepared
according to the following procedure. A 25 m in length by 20 cm in width of
the
acetate fabric (style 180 x 48 plain weave available from Milliken & Company,
LaGrange, Georgia) was coated on one side with an acrylic acid-isooctyl
acrylate
(4:96 molar ratio) copolymer adhesive in ethyl acetate solvent prepared as
described in U.S. Patent RE 24906 (LTlrich) at a rate of 60 g/m2 and dried in
an
air circulating oven. Before entering the final oven drying stages a coating
of low
adhesion backsize was applied to the non-adhesive coated side of this backing
using the process of the present invention from the LESS foaming apparatus of
Example 1.
The low adhesion backsize used was the vinyl silicone copolymer
that was used in Example 1 which had been foamed at a blender speed of 153
rpm,
pump speed of 15 rpm, air flow setting of 20, air flow setting of 40 psi and a
back
pressure of 7 psi and a blow ratio of 22:1. The coating process was carried
out
at 12 ft/min (3.66 meters) line speed, the low adhesion backsize was applied
at a
rate of 2.1 g/m2 from about 140 g/min of low adhesion backsize emulsion (2
solids in water).
The resulting adhesive tape rolls were tested for roll unwind
according to ASTM D-1000 and found to have acceptable unwind of less than
350 g/2.54 cm. The rolls were also tested for adhesive anchorage according to
residue left as described above in Example 2 and found to be satisfactory,
i.e., to
have a value below 2.5.
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