Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ WO9S/~368 2 1 61 5 3 6 PCT~ ~4/02381
-- 1 --
Pressure sens~t~Ye adheslve f~l~
This invention relates to an adhesive film; more
particularly, this invention relates to a pressure sensitive
adhesive film, preferably in tape form.
Adhesive films generally comprise a support provided on one
surface with a pressure sensitive adhesive coating, and provided
on the other surface with a release coating. The purpose of the
release coating is to prevent the film from sticking too
strongly to itself when it has been wound on a roll, so that it
can be readily unwound from the roll. Without a release coating
it can be difficult or impossible to unwind the film from the
roll; and during unwinding the adhesive tends to transfer from
one surface of the film to the other. Finally, the unwinding
process in films of the prior art can be quite noisy.
US 4673611 discloses an adhesive tape which can be drawn
from a roll which comprises a coextruded, biaxially oriented,
multilayer polypropylene support film and an adhesive layer. The
support comprises at least two polypropylene layers having
different compositions; the second layer of the support, which
faces away from the adhesive coating, has a thickness of less
than one third of the total thickness of the adhesive tape and
contains an anti-adhesive substance (for example from 0.2 wt%
to about 3.0% wt% of a polydiorganosiloxane). This structure has
the advantage that a release coating is not needed on the
support. However, it is necessary to incorporate an additive
into the support. Moreover, the additive is transferred to the
adhesive, when the film is wound on a roll, and this causes loss
of tackiness in the adhesive.
According to a first aspect of the present invention, there
is provided a thermoplastic polymeric film structure comprising
a support which is coated with a pressure sensitive adhesive on
a first surface thereof, wherein a second surface of the
support, opposite to the first surface, comprises high density
polyethylene (HDPE).
It has been found that the presence of HDPE in the surface
of the support opposite from the adhesive gives the surface
CONFIRMATION COPY
W095/03368 2 1 ~ ~ ~ 6 PCT~4/02381 ~
excellent release properties, so that after the film has been
wound on a roll it can readily be unwound again without any
significant tranfer of adhesive onto the second surface of the
support. In addition, it has been found that during unwinding
there is less noise than with the pressure sensitive tapes of
the prior art.
The support may comprise a single layer or a plurality of
layers.
The HDPE should desirably have a density from 0.930 to
0.965, preferably from 0.945 to 0.955, most preferably 0.950.
In a first preferred embodiment the support comprises a
single layer of HDPE.
Advantageously the second surface of the support has not
been subjected to any form of surface treatment. However, it is
preferred that the first surface of the support has been
subjected to surface treatment.
In the first embodiment the support preferably contains
from 50 to 100 wt% HDPE, more preferably from 80 to 100 wt%
HDPE. When the support contains less than 100 wt~ HDPE it is
preferred that it comprises a blend of HDPE with at least one
other olefin polymer. The other olefin polymer may be, for
example: a polyethylene of lower density such as linear low
density polyethylene (LLDPE); low density (high pressure)
polyethylene (LDPE); medium density polyethylene (MDPE); or a
copolymer or terpolymer of propylene.
The copolymer or terpolymer of propylene is suitably a
random or block copolymer of ethylene and propylene or of
butylene and propylene; or a random or block terpolymer of
ethylene, propylene and butene-1.
The preferred copolymers of ethylene and propylene contain
from 1 to 30 wt%, preferably from 2 to 7 wt%, more preferably
3 to 5 wt%, ethylene. Also, the preferred copolymers have a melt
flow rate at 230C from 2 to 15, more pre~erably 3 to 8; a
crystalline melting point from 125 to 150C; a number average
molecular weight from 25000 to 100000; and a density from 0.89
to 0.90.
The preferred copolymers of butylene and propylene contain
~WO 9S/03368 2 1 61 5 3 ~ PCT~ ~4/02381
up to 30 wt% butylene.
The preferred terpolymers of propylene contain from l to
lO, preferably from 2 to 6, wt% ethylene, from 80 to 97,
preferably from 88 to 95, wt% propylene, and from l to 20,
preferably from 2 to lS, wt% butene-l.
Preferably, the support contains an anti-blocking agent,
or other additives. Such additives are not essential - HDPE has
very good release properties without them - but certain
additives can produce further improvements to the release
properties, and to other desirable properties. Particularly good
results have been obtained with silicone oil, EBS (ethylene bis
stearamide), GMS (glycero mono stearate) and montan wax. A
preferred silicone oil is a polydialkyl-siloxane.
When silicone oil is used there is some transfer of the
silicone oil to the surface of the adhesive after the film has
been wound onto a roll. However, despite this transfer, good
adhesion by the pressure sensitive adhesive coated surface was
manifest.
In a second preferred embodiment the support has three
layers in a structure comprising a core layer, sandwiched
between two other layers. A first of said other layers is
provided with the adhesive coating on the external surface
thereof. A second of said other layers comprises HDPE; the
external surface of the second layer faces away from the
adhesive coating.
Advantageously the external surface of the second layer has
not been subjected to any form of surface treatment. However,
it is preferred that the external surface of the first layer has
been subjected to surface treatment prior to the application of
the adhesive.
In the second embodiment the second layer preferably
contains from 50 to lO0 wt% HDPE, more preferably from 80 to lO0
wt% HDPEo When the second layer contains less than lO0 wt% HDPE
it is preferred that it comprises a blend of HDPE with at least
one other olefin polymer. The other olefin polymer may be, for
example: a polyethylene of lower density such as linear low
density polyethylene (LLDPE); low density (high pressure)
W095/03368 2 1 61 5 3 ~ PCT~ ~4/02381 ~
polyethylene (LDPE); medium density polyethylene (MDPE); or a
copolymer or terpolymer of propylene.
The copolymer or terpolymer of propylene is suitably a
random or block copolymer of ethylene and propylene or of
butylene and propylene; or a random or block terpolymer of
ethylene, propylene and butene-1.
The preferred copolymers of ethylene and propylene contain
from 1 to 30 wt%, preferably from 2 to 7 wt%, more preferably
3 to 5 wt%, ethylene. Also, the preferred copolymers have a melt
flow rate at 230C from 2 to 15, more preferably 3 to 8; a
crystalline melting point from 125 to 150C; a number average
molecular weight from 25000 to 100000; and a density from 0.89
to 0.90.
The preferred copolymers of butylene and propylene contain
up to 30 wt% butylene.
The preferred terpolymers of propylene contain from 1 to
10, preferably from 2 to 6, wt% ethylene, from 80 to 97,
preferably from 88 to 95, wt% propylene, and from 1 to 20,
preferably from 2 to 15, wt% butene-l.
Preferably, the second layer contains an anti-blocking
agent, or other additives. As noted above, such additives are
not essential. Particularly good results have been obtained with
silicone oil, EBS, GMS and montan wax. A preferred silicone oil
is a polydialkylsiloxane.
When silicone oil is used there is some transfer of the
silicone oil to the surface of the adhesive after the film has
been wound onto a roll. However, despite this transfer, good
adhesion by the pressure sensitive adhesive coated surface was
manifest.
Preferably the core layer comprises an oriented olefin
polymer. The core layer desirably comprises a polymer of
propylene, suitably homopolymeric polypropylene and preferably
isotactic polypropylene.
The core layer may be provided with voids: more
specifically, the core layer may be cavitated, for example, as
disclosed in EP-A-0083495. A preferred cavitating agent is
polybutylene terephthalate, especially as spherical particles.
~ wo 95~03368 2 l 61 5 3 6 PCT~ ~4/02381
The first layer may comprise any olefin polymer useful in
the manufacture of an adhesive liner, or a mixture thereof, and
is suitably a polymer of propylene, such as polypropylene. The
first layer may comprise any of the materials described above
with reference to the second layer. If desired, the first layer
may be the same material as the second layer.
In a particularly advantageous construction the first layer
comprises HDPE, the external surface of which has been treated
to alter its surface properties.
The surface treatments discussed above may be achieved, for
example, by subjecting the surface to corona discharge, to a
flame or to oxidising chemicals; a flame treatment is preferred.
Preferably, the surface is treated to a surface activity of at
least 36 dynes/cm (36 mN/m), more preferably to at least 40
dynes/cm (40 mN/m).
In the second embodiment the core layer is preferably
coextruded or extrusion coated with the first and second layers,
and then the whole support is desirably biaxially oriented. The
polymers can be brought to the molten state and coextruded from
a conventional extruder through a flat sheet die, the melt
streams being combined in an adapter prior to being extruded
from the die. After leaving the die orifice, the thermoplastic
polymeric film structure is chilled and the quenched sheet is
then preferably reheated and oriented by stretching (for
example, from 4 to 6 times in the machine direction at about
253F (123C) and, subsequently, from 8 to 10 times in the
transverse direction, at about 310F (154C)).
According to a second aspect of the present invention there
is provided a thermoplastic polymeric film structure which
comprises:
(a) a support which is coated with a pressure sensitive
adhesive on a first surface thereof, said surface
comprising HDPE and having been surface treated prior
to the application of said adhesive; and
(b) an anti-adhesive material incorporated in or coated
on a second surface of the support opposite to the
adhesive coating.
wo 9~,03368 ~ ~ 61 ~ 3 6 PCT~ ~4/02381 ~
-- 6 --
This aspect of the invention is predicated on the
unexpected discovery that adhesive provided on surface treated
HDPE has remarkably good adhesive properties. These adhesive
properties are most remarkable when the adhesive is a hot melt
adhesive. However, good results can be obtained with other
adhesives, including solvent based adhesives.
The support may comprise a single layer or a plurality of
layers.
The HDPE should desirably have a density from 0.930 to
0.965, preferably from 0.945 to 0.955, most preferably 0.950.
The anti-adhesive material may be any anti-adhesive
material known from the prior art, which is coated upon the
second surface of the support. Alternatively the anti-adhesive
material may be incorporated into the second surface of the
support.
It is preferred that the anti-adhesive material comprises
HDPE, incorporated into the second surface of the support.
In a first preferred embodiment of the second aspect of the
invention the support comprises a single layer of HDPE.
Advantageously the second surface of the support has not
been subjected to any form of surface treatment.
In the first embodiment the support preferably contains
from 50 to lO0 wt% HDPE, more preferably from 80 to lO0 wt%
HDPE. When the support contains less than lO0 wt% HDPE it is
preferred that it comprises a blend of HDPE with at least one
other olefin polymer. The other olefin polymer may be, for
example: a polyethylene of lower density such as linear low
density polyethylene (LLDPE); low density (high pressure)
polyethylene (LDPE); medium density polyethylene (MDPE); or a
copolymer or terpolymer of propylene.
The copolymer or terpolymer of propylene is suitably a
random or block copolymer of ethylene and propylene or of
butylene and propylene; or a random or block terpolymer of
ethylene, propylene and butene-l.
The preferred copolymers of ethylene and propylene contain
from l to 30 wt%, preferably from 2 to 7 wt%, more preferably
3 to 5 wt%, ethylene. Also, the preferred copolymers nave a melt
~ W095t03368 2 1 61 5 3 6 PCT~ ~4/02381
- 7 -
flow rate at 230C from 2 to 15, more preferably 3 to 8; a
crystalline melting point from 125 to 150C; a number average
molecular weight from 25000 to 100000; and a density from 0.89
to o.go.
The preferred copolymers of butylene and propylene contain
up to 30 wt% butylene.
The preferred terpolymers of propylene contain from 1 to
10, preferably from 2 to 6, wt% ethylene, from 80 to 97,
preferably from 88 to 95, wt% propylene, and from 1 to 20,
preferably from 2 to 15, wt% butene-1.
Preferably, the support contains an anti-blocking agent,
or other additives. Such additives are not essential - HDPE has
very good release properties without them - but certain
additives can produce further improvements to the release
properties, and to other desirable properties. Particularly good
results have been obtained with silicone oil, EBS, GMS and
montan wax. A preferred silicone oil is a polydialkyl-siloxane.
When silicone oil is used there is some transfer of the
silicone oil to the surface of the adhesive after the film has
been wound onto a roll. However, despite this transfer good
adhesion by the pressure sensitive adhesive coated surface was
manifest.
In a second preferred embodiment of the second aspect of
the invention the support has three layers in a structure
comprising a core layer, sandwiched between two other layers.
A first of said other layers is provided with the adhesive
coating on the external surface thereof. A second of said other
layers comprises HDPE; the external surface of the second layer
faces away from the adhesive coating.
Advantageously the external surface of the second layer has
not been subjected to any form of surface treatment.
In the second embodiment the second layer preferably
contains from 50 to 100 wt% HDPE, more preferably from 80 to 100
wt% HDPE~ When the second layer contains less than 100 wt~ HDPE
it is preferred that it comprises a blend of HDPE with at least
one other olefin polymer. The other olefin polymer may be, for
example: a polyethylene of lower density such as linear low
wo 9~,~368 2 1 61 5 3 6 PCT~ ~4/02381 ~
density polyethylene (LLDPE); low density (high pressure)
polyethylene (LDPE); medium density polyethylene (MDPE); or a
copolymer or terpolymer of propylene.
The copolymer or terpolymer of propylene is suitably a
random or block copolymer of ethylene and propylene or of
butylene and propylene; or a random or block terpolymer of
ethylene, propylene and butene-1.
The preferred copolymers of ethylene and propylene contain
from 1 to 30 wt%, preferably from 2 to 7 wt%, more preferably
3 to 5 wt%, ethylene. Also, the preferred copolymers have a melt
flow rate at 230C from 2 to 15, more preferably 3 to 8; a
crystalline melting point from 125 to 150C; a number average
molecular weight from 25000 to 100000; and a density from 0.89
to 0.90.
The preferred copolymers of butylene and propylene contain
up to 30 wt% butylene.
The preferred terpolymers of propylene contain from 1 to
10, preferably from 2 to 6, wt% ethylene, from 80 to 97,
preferably from 88 to 95, wt% propylene, and from 1 to 20,
preferably from 2 to 15, wt% butene-1.
Preferably, the second layer contains an anti-blocking
agent, or other additives. As noted above, such additives are
not essential. Particularly good results have been obtained with
silicone oil, EBS, GMS and montan wax. A preferred silicone oil
is a polydialkylsiloxane.
When silicone oil is used there is some transfer of the
silicone oil to the surface of the adhesive after the film has
been wound onto a roll. However, despite this transfer good
adhesion by the pressure sensitive adhesive coated surface was
manifest.
Preferably the core layer comprises an oriented olefin
polymer. The core layer desirably comprises a polymer of
propylene, suitably homopolymeric polypropylene and preferably
isotactic polypropylene.
The core layer may be provided with voids: more
specifically, the core layer may be cavitated, for example, as
disclosed in EP-A-0083495. A preferred cavitating agent is
~ W095/~36~ 2 ~ bl 5 3 6 PCT~ ~4/02381
g
polybutylene terephthalate, especially as spherical particles.
The first layer comprises HDPE which has been treated to
alter its surface properties. The first layer may comprise any
of the materials described above with reference to the second
layer. If desired, the first layer may be the same material as
the second layer.
The surface treatments discussed above, with reference to
the second aspect of the invention, may be achieved, for
example, by subjecting the surface to corona discharge, to a
flame or to oxidising chemicals; a flame treatment is preferred.
Preferably, the surface is treated to a surface activity of at
least 36 dynes/cm (36 mN/m), more preferably to at least 40
dynes/cm (40 mN/m).
In the second embodiment the core layer is preferably
coextruded or extrusion coated with the first and second layers,
and then the whole support is desirably biaxially oriented. The
polymers can be brought to the molten state and coextruded from
a conventional extruder through a flat sheet die, the melt
streams being combined in an adapter prior to being extruded
from the die. After leaving the die orifice, the thermoplastic
polymeric film structure is chilled and the quenched sheet is
then preferably reheated and oriented by stretching; for
example, from 4 to 6 times in the machine direction at about
253F (123C) and, subsequently, from 8 to 10 times in the
transverse direction, at about 310F (154C).
The pressure sensitive adhesive referred to above may be
a hot melt adhesive, a solvent based adhesive or a water based
adhesiveO The invention may be used with any pressure sensitive
adhesive used in the adhesive tapes of the prior art. Particular
adhesives that may be used include rubber and acrylic based
adhesives, which are described in detail in the prior art.
The following Examples illustrate the invention.
.
ExamPle
Polypropylene homopolymer was fed into the feed hopper of
a rotating screw extruder having a 2.5 inch (6.4 cm) diameter
and an L D ratio of 24:1. HDPE (density 0.952) was also fed
.
WO95/03368 2 1 61 5 3 6 PCT~4102381 ~
-- 10 --
into a satellite extruder having a 1.5 inch (3.8 cm) diameter
and an L:D ratio of 20:1. The molten polyethylene was fed into
the slot die fixed to the first extruder through an adaptor
designed to ensure that the molten polyethylene stream covered
both sides of the molten polypropylene stream. The multi-layer
structure was then quenched onto a chill roll to form a cast
film which was immediately quenched in a cold water bath and
sequentially biaxially oriented on conventional e~uipment.
During the orientation the quenched film was first reheated to
about 253F (123C) and stretched 5 times the machine direction
between differential speed rollers, and was then fed to a
transverse orientor where it was heated to about 310F (154C)
and stretched 8 times.
The film, comprising 0.6 ~m HDPE skin, on both sides, was
next cooled; and trimmed. Thereafter it was flame treated to
> 48 dynes/cm on one side; and wound on a roll. Finally the film
was tested, using the following procedure, to demonstrate
release effect.
PROCEDURE :
A standard adhesive tape, containing a pressure sensitive
adhesive was applied to the treated, or the untreated, side of
the prepared film in the MD direction. This provides an adhesive
coating on the prepared film, and gives the film a structure in
accordance with the invention.
The samples were, or were not, stored 24 hours at 50C. The
peel force necessary to separate both the standard tape and the
test film was measured at 300 mm/min with the film test and
adhesive at 90 angle.
The transfer of adhesive was observed when peeling the
samples at different angles (90 and 180).
The measurements were performed 3 times, and the mean was
taken. The results are shown in Table 1.
This test simulates what happens during unwinding a reel
of tape composed of a support layer and a pressure sensitive
adhesive applied to a treated surface of the support layer.
~ W095t~368 2 1 ~ 5 3 ~ PCT~ ~4/0~81
Example 2
A film A was prepared using HDPE as the first layer;
polypropylene as the core; and HDPE as the second layer. This
film was produced by the same method as the film of example l.
ExamPle 3
A film B was prepared by the same method as in Example l,
but the second layer incorporated 12000 ppm of silicone oil.
ExamPle 4
A film C was prepared by the same method as in Example l,
but the second layer incorporated 2000 ppm EBS.
ExamPle 5
A film D was prepared by the same method as in Example l,
but the second layer incorporated 2000 ppm GMS.
Example 6
A film E was prepared by the same method as in Example l,
but the second layer incorporated 2000 ppm montan wax.
Example 7
The Films A to E were tested using a similar procedure to
example l: a standard adhesive tape was applied uniformly to the
untreated side of each film A to E, and the release force was
measured on the untreated side at 300 mm/min and with the test
tape at 90, 135 and 180 angles. The percentage transfer of
adhesive when peeling the samples was also observed.
The following films were also tested :
Film F - Reference tape 35 ~m
Film G - PP terpolymer
Film H - PP terpolymer + 20000 ppm EBS
Film I - PP terpolymer + 2000 ppm GMS
Film J - PP terpolymer + 2000 ppm montan wax
The release forces were measured 5 times, and the mean was
taken. The results are shown in table 2.
WO 95/03368 2 1 ~t 5 3 ~ PCT/EP94/02381 ~
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wo 95/03368 2 1 61 5 3 6 PCTIEP94102381
--13--
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W095/03368 2 1 61 5 3 6 PCT~ ~4/02381 ~
The results in Table 2 show that the film structure according
to the invention can be readily unwound from the roll, even
without a release film; and that it is more readily unwound,
with less adhesive transfer, than film structures of the prior
art. It was also noted that the film structure of the present
invention can be unwound with less raise than the film
structures of the prior art.
