Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Description
Assembly adhesive tape and use of the assembly adhesive
tape for the printing industry
The invention relates to an adhesive assembly tape and
to its use for the printing industry.
In nowadays customary printing processes, such as for
newspaper or book printing, replaceable printing plates
are in use. The printing plates can be applied to flat
supports or else, in the case of flexible printing
plates, to printing rolls. For the printing operation,
the printing plate is inked and lastly is contacted with
the material to be printed. The application and fixing
of the replaceable printing plates necessitate adhesive
assembly tapes.
For this purpose it is customary to make use of adhesive
assembly tapes which feature a foam layer reinforced with
a film.
Polyethylene films are often employed here as reinforcing
film. While polyethylene (PE)-based films do permit a
good printed image, they cannot usually, however, be
detached without destruction from the substrate after
use. For example, there may be problems during detachment
from printing rolls. Besides PE-based films, polyester-
based films (PET) are also employed. It is possible, for
example, for oriented polyester films (o-PET) to be used,
with "oriented" meaning that the films have been drawn.
Such films are generally easier to detach from the
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printing roll, but do not have satisfactory printing
properties, a failing which is manifested in the printed
image. Behavior similar to that of 0-PET is observed for
oriented polypropylene films as well.
It is therefore an object of the invention to provide an
adhesive assembly tape for the printing industry that is
improved in relation to the disadvantages identified
above.
This object is achieved by means of an adhesive tape
according to main claim 1. Further embodiments of the
adhesive assembly tape, and also the use of the adhesive
tape for the printing industry, are subjects of further
claims.
The invention relates to an adhesive assembly tape for
the printing industry, said adhesive tape comprising
- a foam layer,
a reinforcing carrier layer disposed on the
foam layer, and
- a first adhesive layer disposed on the carrier
layer,
where the carrier layer has a tensile value of a force
of at least 1 N at 1% elongation in the machine direction,
and
where the carrier layer also has a tear resistance of
more than 0.2 N in the machine and/or cross direction.
The adhesive assembly tape may be used, for example, for
applying a flat printing plate to a flat substrate.
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Alternatively, for example, it may be used for applying
a flexible printing plate to a printing roll.
The carrier layer may for example be a multi-ply carrier
layer.
The term "on" here and below, may in each case mean
"directly on"; i.e., in that case the layers have a common
interface. Alternatively, "on" may mean that there are
one or more interposed layers.
The term "machine direction" is the term customary within
the art for "longitudinal direction" and is abbreviated
to "MD". It refers to the running direction in the
machine, in general, in connection with the processing
of films or other layers of material (such as, for
instance, layers of woven fabric, nonwoven web, polymer
or laminate) which are guided over rollers in machines.
Winding or unwinding also takes place along this
direction.
The direction perpendicular to the "machine direction"
is referred to, conversely, as the "cross direction". The
term "cross direction" corresponds to the "transverse
direction" and is abbreviated "CD". Materials of film or
layer type may have different properties in machine and
cross directions. In the text below, therefore,
directionally dependent physical properties are in each
case expressed relative to the machine or cross
direction.
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The term "elongation" refers to the ratio between change
in length (Ln = L - Lo) due to an extent tensile force to
the original length (Lo) of the carrier layer without a
tensile force.
The tensile values provide information on the tensile
properties of the carrier layer. They indicate the size
of the force that must be expended in order to bring
about a particular elongation of the carrier layer. The
higher the tensile values, therefore, the higher the
strength of the material. Materials having low tensile
values are subject to greater elongation.
In the case of the present invention, the tensile
properties were determined in accordance with the
measurement provisions of DIN EN ISO 527-3 (July 2003
version). Accordingly, measurements for determining the
tensile value (in N) were carried out with a sample width
of 15 mm, a measuring velocity of 500 mm/min, and a
pretensioning force of 0.1 N.
The tear resistance or notch strength is the capacity of
a substance to resist further tearing even when a notch
is present. The tear resistance therefore indicates the
force which is sufficient to continue the tearing - that
is to enlarge - a notch or a tear.
The tear resistance was determined according to the
measurement provisions of DIN 53356 (August 1982
version). Accordingly, measurements were performed with
a carrier layer having a width of 50 mm and a length of
100 mm at a measuring velocity of 300 ram/min.
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The inventors of the present invention have found that
adhesive tapes of the invention having a carrier layer
which has a tensile value of a force of at least 1 N at
1% elongation in the machine direction and also has a
tear resistance of more than 0.2 N in the machine and/or
cross direction likewise permit a good printed image and
improved detachment.
The inventors have recognized that a sufficient softness
or elasticity of the carrier layer is necessary in order
to obtain a good printed image. This is a result of the
necessity, for a good printed image, that the carrier
layer during the printing operation is not to distribute
the pressure acting locally on it to the entire area of
the foam layer, but instead is to deform only at the
location at which the pressure acts on the adhesive
assembly tape. Soft or elastic carrier layers therefore
result in good printing quality. This explains the good
printing properties when using conventional adhesive
tapes with PE films as carrier layers.
The inventors have determined, however, that the use of
excessively soft carrier layers, such as a PE film, for
instance, does not allow undestructive and hence user-
friendly detachment, since their strength is too low. The
inventors have determined that adhesive assembly tapes
of the invention having a tensile value of a force of at
least 1 N at 1% elongation in the machine direction are
indeed still sufficiently soft and elastic to enable a
printed image of very good quality, but at the same time
such tapes already have a strength which allows easier
detachment of the adhesive tape after use. For example,
. ,
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adhesive assembly tapes of the invention permit more easy
detachment from printing rolls after use. Conversely,
carrier layers having a tensile value of a force of less
than 1 N at 1% elongation in the machine direction have
proven to be too soft and, while they do allow a good
printed image, they do not allow favorable properties on
removal of the adhesive tape after printing.
The inventors have observed, moreover, that a tear
resistance of more than 0.2 N in the machine and/or cross
directions is necessary in order to permit both good
detachment behavior and a good printed image. A carrier
layer which has a high tear resistance is therefore a
carrier layer which prevents high resistance to tear
propagation even in the case of an incision. The
inventors have determined that tear resistances of more
than 0.2 N are necessary for good detachment behavior.
For the behavior of the carrier layer, the interplay of
tensile value and tear resistance is critical. Only if
the tensile value is at least 1 N at 1% elongation and
also the tear resistance is more than 0.2 N does the
material have the requisite mechanical properties.
According to one development of the invention, the
carrier layer, which may also be a multi-ply or
multilayer layer, has a basis weight overall of 20 to
100 g/m2, preferably 20 to 50 g/m2, more preferably 20 to
g/m2, most preferably 22 to 28 g/m2.
The inventors of the present invention have determined
that carrier layers which, in addition to the above-
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described tensile strengths and tear resistances, have a
basis weight of at least 20 g/m2 possess particularly
good strength and can therefore be detached particularly
easily again from, for instance, a printing roll. Basis
weights of less than 100 g/m2, as well as the associated
saving in mate2:ial, have positive effects on the printed
image.
In another embcdiment, the thickness of the carrier layer
is between 10 and 400 pm, preferably between 20 and
250 pm, more preferably between 30 and 150 pm, more
preferably stiLl between 40 and 100 pm, most preferably
between 50 and 80 pm. These thickness ranges have proven
to be particularly favorable for the carrier layer and
its mechanical properties. Measurement provisions for the
determination of thicknesses are found in DIN 53370
(November 2006 version). An estimation of the thickness
with high reliability is possible via the basis weight,
furthermore.
One embodiment of the invention relates to the adhesive
assembly tape of the invention where the carrier layer
has a tensile value of a force of at most 15 N, preferably
at most 10 N, more preferably at most 8 N, especially
preferably at nost 4 N at 1% elongation in the machine
direction.
One development of the invention relates to the adhesive
assembly tape of the invention where the carrier layer
has a tensile value of a force of 1.5 N at 1% elongation
in the machine direction. Carrier layers of this kind
possess even higher strength, with further beneficial
. .
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consequences for detachment behavior. At the same time,
however, such materials are still soft and elastic enough
for good printing properties.
A further embodiment of the adhesive assembly tape of the
invention has a carrier layer which has a tear resistance
of more than 0.5 N, preferably greater than 1 N, more
preferably greater than 2 N, and most preferably greater
than 3 N in the machine direction and/or cross direction.
Another development of the invention relates to the
adhesive assembly tape of the invention where the carrier
layer has a tear resistance of at most 15 N, preferably
at most 10 N, more preferably at most 7 N in the machine
direction and/or cross direction.
Carrier layers of these kinds ensure particularly
effective reinforcement of the foam layer and
significantly better detachment in combination with the
good tensile values of the carrier layer of the adhesive
tape of the invention.
Particularly preferred in this context are carrier layers
which have the stated values for the tear resistances in
each case both for the machine direction and for the
cross direction.
In another development of the invention, the carrier
layer has a tensile value of a force of 5 N to 19 N,
preferably of 6 N to 18 N, more preferably of 7 to 17 N
at 10% elongation in the machine direction. The inventors
have recognized that in the case of the tensile
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properties specifically, the best mechanical properties
can be achieved both for printing quality and for the
detachment process in the ranges specified for the
tensile value. Tensile values that are too low lead to
carrier layers which are too easily stretchable and
therefore less effectively detachable. Tensile values
that are too high suggest a lower elasticity.
Another embodiment of the adhesive tape of the invention
has a carrier layer where the carrier layer has a tensile
value of a force of at least 8 N, preferably at least
9 N, more preferably at least 10 N at 25% elongation in
the machine direction. Tensile values of at least 8 N or
higher at 25% elongation in the machine direction show
particularly favorable mechanical properties and
resistances.
A further embodiment of the adhesive assembly tape of the
invention has a carrier layer where the carrier layer has
an elongation at break of less than 1000%, preferably
less than 600%, more preferably less than 300% in machine
and cross directions.
Elongations at break of less than 80% are possible as
well. Conversely, for example, conventional adhesive
tapes with a o-PET carrier layer often have significantly
higher elongations at break. The determination of the
elongation at break, as a further key tensile property
in addition to the tensile value, took place in the case
of the present invention, in just the same way as for the
tensile value, in accordance with the measurement
provisions of DIN EN ISO 527-3 (July 2003 version).
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The elongation at break is a physical characteristic
which indicates the remaining lengthening of the sample
up to fracture, based on the initial measured length.
It therefore also provides information on the stretch and
elasticity and also stability behavior of the sample.
The inventors of the present invention have determined
that an elongation at break of less than 1000% or even
lower is particularly advantageous.
In a further embodiment, the material of the carrier
layer of the inventive adhesive tape has a modulus of
elasticity in machine and cross directions of less than
4000 N/mm2, more preferably less than 1000 N/mm2, most
preferably less than 200 N/mm2. Moreover, the carrier
layer preferably has a modulus of elasticity of at least
N/mm2, preferably at least 30 N/mm2.
The modulus of elasticity was computed from the tensile
property data, in other words from the tensile value and
the cross-sectional area of material.
The modulus of elasticity provides information on the
elongation as a function of the tensile stress applied.
It makes a statement on the elasticity of the carrier
layer material used. It has emerged that materials with
the stated values for the modulus of elasticity are
particularly elastic and therefore allow particularly
good printing quality.
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According to another preferred embodiment, the tear force
of the carrier layer in the machine direction is less
than 30 N, more preferably less than 20 N.
The tear force is the tensile force at which the carrier
layer tears. Materials having particularly high tear
forces usually lack sufficient flexibility to allow a
good printed image.
In one preferred embodiment of the adhesive assembly tape
of the invention, the carrier layer comprises a woven-
fabric or nonwoven layer or a laminate comprising the
woven-fabric or nonwoven layer. This may in particular
be a continuous, all-through woven-fabric or nonwoven
layer, or a laminate comprising a continuous woven-fabric
or nonwoven layer. A "continuous layer" here may in
particular be an all-through woven-fabric or nonwoven
layer which has no passages and is therefore particularly
stable mechanically.
Carrier layers comprising a nonwoven layer or a laminate
comprising a nonwoven layer are particularly preferred.
Nonwoven layers have fibers which may for example be
polymer fibers, which unlike the fibers in a woven fabric
are not woven (hence the name) but instead are laid
arbitrarily without being woven into one another. These
layers therefore have a different structure from woven-
fabric layers, which have a regular weave structure.
Nonwovens not only are inexpensive and simple to produce
but also have significantly higher tensile strengths by
comparison with conventional films based on polyolefin
layers that are not nonwovens.
. .
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For woven-fabric and nonwoven layers, in the case of the
present invention, a large number of different polymers
and polymer fibers can be used. Use may be made, for
example, of polyolefins, polyamides or polyesters such
as, for example, polyethylene terephthalate or
polybutylene terephthalate.
It is, however, particularly preferred if the woven-
fabric or nonwoven layer has fibers comprising a
polyolefin. The inventors of the present invention have
observed that woven-fabric and nonwoven layers based on
polyolefins, more particularly based on polyethylene,
polypropylene, polybutylene, and polyisobutylene, are
particularly suitable for obtaining optimum elasticity
and tensile properties on the part of the carrier layer,
with polyethylene and polypropylene being the most
preferred.
According to another development, the woven-fabric or
nonwoven layer may have a basis weight of 10 to 50 g/m2,
preferably of 11 to 25 g/m2, more preferably of 12 to
20 g/m2. Woven-fabric or nonwoven layers having the
stated basis weights enable the desired mechanical
properties to be achieved and, moreover, have a thickness
especially suitable for the applications of adhesive
tapes of the invention in the context of the printing
operation.
One particularly preferred embodiment of the invention
relates to the adhesive tape of the invention having a
carrier layer which comprises a laminate that as well as
the woven-fabric or nonwoven layer has a polymer layer.
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The polymer layer of such a laminate may preferably be a
continuous polymer layer configured as a polymer film.
For example, both the woven-fabric or nonwoven layer and
the polymer layer may be continuous layers which are in
direct contact with one another.
The inventors of the present invention have determined
that a laminate comprising both a woven-fabric or
nonwoven layer and a polymer layer allows especially
favorable mechanical properties for carrier layers of
adhesive assembly tapes. As a result of the combination
it is also possible to achieve outstanding elasticity,
of the kind vital for a good printed image. At the same
time, it is also possible to attain a strength which
satisfies exacting requirements in relation to detachment
from the printing roll after the printing operation.
Adhesive assembly tapes having a carrier layer which
comprises or consists of the stated laminate allow
significantly improved detachment from the printing roll
and also good quality on the part of the printed image.
The mechanical characteristics, in relation for instance
to the tensile values and the tear resistance, are
particularly suitable for this type of carrier layers.
The inventors have determined that in this way,
surprisingly, the advantages of conventional adhesive
tapes wherein a foam layer is reinforced with PE films
(good printed image), and of adhesive tapes where the
foam layer is reinforced with 0-PET films (nondestructive
detachment from the printing roll), can be combined with
one another without giving rise to the respective
disadvantages.
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The laminate may comprise or consist of the woven-fabric
or nonwoven layer and the polymer layer. The laminate may
be produced, for example, by extrusion of the polymer
layer onto the woven or nonwoven layer. The laminate may
be disposed within the adhesive tape in such a way that
the woven-fabric or nonwoven layer is located on the side
of the foam layer, while the polymer layer of the laminate
is located on the side of the first adhesive layer of the
adhesive tape. This arrangement is particularly suitable,
since in this way a comparatively smooth surface on the
side of the first adhesive layer is achieved. However,
the opposite arrangement, in which the polymer layer lies
on the side of the foam layer and the woven-fabric or
nonwoven layer lies on the side of the first layer of
adhesive is equally suitable as well.
According to another preferred development, the polymer
layer of the laminate comprises a polyolefin, more
particularly polyethylene or polypropylene or copolymers
thereof. These materials are not only inexpensive but
also preferable in relation to their mechanical
properties.
With further preference, in the case of the laminate, not
only the fibers of the woven-fabric or nonwoven layer,
but also the polymer layer, in each case independently
of one another, contain a polyolefin, which may in each
case be, for example, polyethylene and/or polypropylene.
The most preferable is for the laminate to have a nonwoven
layer comprising or consisting of PE or PP and for the
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laminate also to comprise a polymer layer which contains
or consists of PE or PP. In this way, the layers can be
easily joined to one another, durably and robustly.
This is possible, for example, by means of an extrusion
coating operation in which the polymer layer is extruded
onto the nonwoven layer. An intimate join between the
layers may be achieved in particular by the melting of
the polymer layer onto the nonwoven layer.
A further embodiment of the present invention relates to
the adhesive assembly tape of the invention for the
printing industry, where the carrier layer contains at
least a first copolymer, more particularly a copolymer
selected from the group of polyolefin copolymers. By way
of example these are polypropylene copolymers,
polyethylene copolymers, or mixtures thereof.
The inventors of the present invention have determined
that through the use of copolymers it is possible to
adapt the desired mechanical properties in terms of
tensile properties and tear resistance particularly well
to the requirements for the printing industry.
Homopolymers such as oriented polypropylene, for example,
are conversely often too stiff for a good printed image
to be obtained. In addition, their tear resistance is
frequently inadequate, as can likewise be seen from the
example of oriented polypropylene.
The use of copolymers, on the other hand, allows
nondestructive detachment and a good printed image to be
realized at the same time.
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According to one preferred embodiment, the copolymer is
a polyolefin copolymer comprising or consisting of at
least two olefins of different kinds. The olefin
copolymer is obtained by copolymerizing the at least two
or exactly two olefins of different kinds. Polyolefin
copolymers permit excellent setting of the mechanical
properties for printing applications.
According to one preferred embodiment, the copolymer is
a copolymer from the group of polypropylene copolymers,
polyethylene copolymers, and mixtures thereof. These
copolymers combine good tensile strengths with an
unexpectedly high tear resistance.
By copolymerizing propylene with other, different
monomers it is possible, for example, to improve the tear
resistance relative to conventional polypropylene. The
monomer other than propylene may be an olefin other than
propylene. In a similar way, by copolymerizing ethylene
with a monomer different from it, the tensile strength
can be improved significantly relative to conventional
polyethylene. In this case the monomer different from
ethylene may likewise be an olefin.
According to one preferred embodiment, the first
copolymer is a heterophasic copolymer. Such copolymers
generally have a high impact strength.
With further preference, the heterophasic copolymer may
be a heterophasic polypropylene copolymer.
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In particular, the polymer in each case may be a
heterophasic block copolymer. The heterophasic block
copolymer consists preferably of two phases.
According to one preferred embodiment, the copolymer is
what is called a pure-heterophasic block copolymer.
For example, the block copolymer may have a polypropylene
block and a polyethylene block. In particular it may be
a diphasic block copolymer, with both the polypropylene
block and the polyethylene block each forming one phase.
Block copolymers of the types stated have proven to be
especially suitable in terms of their mechanical
properties. They allow good tensile values and sufficient
tear resistances for use in the printing industry.
According to a further-preferred embodiment of the
adhesive assembly tape of the invention, the reinforcing
carrier layer contains a first copolymer which is an
ethylene-propylene copolymer. The ethylene-propylene
copolymer may consist of ethylene and propylene. That is,
it is formed by polymerization of ethylene and propylene
and is free from further monomers different from ethylene
and propylene. Carrier layers comprising ethylene-
propylene copolymers combine suitable tear resistances
with very good tensile values and produce adhesive
assembly tapes which are easy to detach and satisfy high
standards in terms of printing quality.
Based on the ethylene-propylene copolymer, the fraction
of ethylene may be between 4 and 20 weight percent and
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the fraction of propylene between 80 and 96 weight
percent, for example. Preferably the fraction of ethylene
is between 5 and 15 weight percent and the fraction of
propylene is between 85 and 95 weight percent. These
ranges have proven to be particularly suitable and enable
excellent mechanical properties for the sector of the
printing industry.
One preferred development of the invention relates to the
adhesive assembly tape of the invention where the carrier
layer additionally has a second copolymer, different from
the first copolymer. The inventors have observed that the
presence of a second copolymer makes the carrier layer
softer, leading to a further improvement in the tear
resistance and therefore supporting nondestructive
detachment of the adhesive assembly tape.
One preferred embodiment of the development of the
invention just mentioned relates to an adhesive assembly
tape where the second copolymer has a melting point (Tm)
of less than 140 C, preferably less than or equal to
120 C, and more preferably less than or equal to 100 C.
The use of copolymers having low melting points at this
level enables the softness and stretchability of the
carrier layer to be improved, with beneficial
consequences for the tear resistance. For example, the
second copolymer may comprise ethylene-vinyl acetate
copolymers (EVA) or acrylate-based copolymers.
One particularly preferred embodiment of the adhesive
assembly tape of the invention has as its second
copolymer an acrylate-based copolymer, more particularly
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a polyolefin-acrylate-based copolymer, i.e., a copolymer
obtained by copolymerization of acrylate monomers and of
olefin monomers different therefrom. With particular
preference the acrylate-based copolymer may be an
ethylene-butyl acrylate copolymer (EBA). For example, the
acrylate-based copolymer may also be a methyl acrylate-
butyl acrylate copolymer. Acrylate-based copolymers make
the carrier layer softer and more stretchable and
therefore increase its tear resistance.
One development of the embodiment just stated has as its
second copolymer an ethylene-butylene acrylate copolymer
(ERA), where the fraction of ethylene is preferably
between 65 and 95 weight percent and the fraction of
butyl acrylate is between 5 and 35 weight percent, based
in each case on the ethylene-butyl acrylate copolymer.
With further preference, the ethylene-butyl acrylate
copolymer has an ethylene fraction of between 75 and 90
weight percent and a butyl acrylate fraction of between
10 and 25 weight percent, especially preferably an
ethylene fraction of between 82 and 88 weight percent and
a butyl acrylate fraction of between 12 and 18 weight
percent. With the fraction of the butyl acrylate relative
to the ethylene-butyl acrylate copolymer it is possible
to adjust the softness of the ethylene-butyl acrylate
copolymer. The stated ranges permit optimum mechanical
properties for the carrier layers comprising the second
copolymer. A composition within this range is beneficial
in particular for the printing quality.
A further embodiment relates to the adhesive assembly
tape of the invention where the fraction of the first
copolymer in the carrier layer is at least 40 weight
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percent based on the carrier layer, preferably at least
55 weight percent. For example, the fraction of the first
copolymer, based on the carrier layer, may be between 40
and 100 weight percent, preferably between 55 and
90 weight percent, more preferably between 55 and
75 weight percent. The inventors of the present invention
have recognized that a fraction of the first copolymer
in these ranges generally allows good tensile values.
A further embodiment relates to the adhesive assembly
tape of the invention where the fraction of the second
copolymer in the carrier layer is at least 10 weight
percent based on the carrier layer, preferably at least
weight percent. For example, the fraction of the
15 second copolymer in the carrier layer may be between 10
and 60, preferably between 20 and 50, more preferably
between 20 and 40 weight percent. The inventors of the
present invention have recognized that carrier layers
with a fraction of at least 10 weight percent of the
20 second copolymer have particularly favorable tear
resistances. A further increase in the fraction of the
second copolymer beyond 20 weight percent usually leads
to a further improvement in the tear resistance.
Another embodiment of the invention relates to an
adhesive assembly tape of the invention where the carrier
layer is a multilayer film which comprises
- a first layer,
- a second layer, disposed on the first layer, and
- a third layer, disposed on the second layer.
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The carrier layer may for example have exactly three
layers.
The use of at least three layers leads to an improvement
in the stability of the carrier layer, which facilitates
nondestructive handling of the adhesive assembly tape in
the printing industry, and may also be useful for
producing particularly low levels of scrap in
manufacture.
Another embodiment relates to the adhesive assembly tape
of the invention where the carrier layer is a multilayer
film, as for example a multilayer blown film, which
comprises
- a first layer, and
- a second layer, disposed on the first layer,
where at least one of the two layers comprises the
first and the second copolymers, while the other of
the two layers is free of the second copolymer.
The inventors have recognized that layers which comprise
the first copolymer but are free of the second copolymer
allow particularly good tensile values. In contrast,
layers which comprise the first and second copolymers
permit the attainment of particularly good tear
resistances. The inventors of the present invention have
determined that multilayer films which comprise layers
of both kinds produce carrier layers which combine
particularly good tensile values and tear resistances
with one another.
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One preferred embodiment relates to the adhesive assembly
tape of the invention where the carrier layer is a
multilayer film, as for example a multilayer blown film,
which comprises
- a first layer,
- a second layer, disposed on the first layer, and
- a third layer, disposed on the second layer,
where the first, second, and third layers each
comprise the first copolymer.
If the carrier layer has three layers comprising the
first copolymer, this is beneficial to the stability and
tensile strength of the arrangement as a whole. Moreover,
sufficient tear resistances are possible accordingly.
One particularly preferred embodiment relates to the
adhesive assembly tape of the invention where the carrier
layer is a multilayer film which comprises
- a first layer,
- a second layer, disposed on the first layer, and
- a third layer, disposed on the second layer,
where the first, second, and third layers each
comprise the first copolymer,
and where
- either the first and third layers additionally
comprise the second copolymer while the second layer
is free of the second copolymer,
- or the second layer additionally comprises the
second copolymer while the first and third layers
are free of the second copolymer.
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For the arrangement in which the first and third layers
each have the first copolymer but are free of the second
copolymer, while the second layer comprises the first and
second copolymers, carrier layers are obtained which have
particularly good processing properties and stability.
The second copolymer (e.g., acrylate-based copolymers
such as EBA or other copolymers such as EVA) usually has
a lower melting point than the first copolymer. A layer
comprising the first and second copolymers therefore has
a lower thermal resistance than layers which have the
first but not the second copolymer. For this reason an
arrangement in which the second layer, in other words the
middle layer, has the second copolymer while the outer
layers (first and second layers) are free of the second
copolymer is more temperature-stable. The less
temperature-stable middle layer is protected by the
outer, more temperature-resistant layers. A carrier layer
of this kind may therefore be exposed to relatively high
temperatures during the manufacturing procedure as well.
If the first and third layers each have the first and
second copolymers, while the second layer has the first
copolymer but is free of the second copolymer, this leads
to an arrangement which is particularly preferred for the
purpose of achieving high tear resistances. The inventors
of the present invention have recognized that it is
beneficial to the tear resistance of the overall
multilayer film if the outer layers (first and third
layers) are softer than the middle layer (second layer).
Since layers comprising the first and second copolymers
are softer than layers comprising the first but not the
second copolymer, the stated arrangement allows a further
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improvement to be achieved in the tear resistance of the
carrier layer as a whole.
According to one development of the embodiment just
described, the fraction of the first copolymer in the
first and third layers is in each case independently of
one another between 20 and 70 weight percent, preferably
between 40 and 60 weight percent, more preferably between
45 and 55 weight percent.
According to another development of the embodiment just
described, the fraction of the second copolymer in the
first and third layers in each case independently of one
another is between 20 and 70 weight percent, preferably
between 40 and 60 weight percent, more preferably between
45 and 55 weight percent. For example, the first and
third layers may each comprise the first copolymer with
a fraction of 40 to 55 weight percent and the second
copolymer likewise with a fraction of 40 to 55 weight
percent, based on the respective layer.
According to one preferred embodiment, the first and
third layers of the multilayer film are identical. This
makes production easier.
According to another embodiment, there are no further
polymers or copolymers present in the carrier layer apart
from the first and second copolymers.
According to a further embodiment, the first and third
layers of the multilayer film may in each case
independently of one another comprise processing
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auxiliaries, such as antiblocking auxiliaries, for
example.
According to a further embodiment, the second layer may
have a fraction of the first copolymer of at least
60 weight percent, preferably at least 75 weight percent,
while being free of the second copolymer. For example,
the second layer may include a fraction of 75 to 90 weight
percent of the first copolymer.
According to one development, the second layer of the
multilayer film may comprise dyes, as for example dye
particles. Effective coloring of the carrier layer is
possible accordingly.
According to one preferred embodiment, the thickness of
the first and third layers of the multilayer film
independently of one another is in each case between 3
and 100 pm, preferably between 5 and 25 pm, more
preferably between 7 and 10 pm.
According to a further embodiment, the thickness of the
second layer of the multilayer film is between 4 and
200 pm, preferably between 7 and 40 pm, more preferably
between 10 and 16 pm.
These thicknesses have proven highly suitable in each
case for the printing method.
According to one particularly preferred embodiment, the
multilayer film is a multilayer blown film. Carrier
layers of this kind can be produced easily and without
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great technical effort and complexity, and allow
properties of the respective individual layers to be
combined. Blown films exhibit a high holding force,
puncture resistance and tear resistance, and are
therefore highly suitable, as recognized by the
inventors, for use in the sector of the printing
industry.
A further embodiment of the present invention relates to
the adhesive assembly tape of the invention where the
foam layer comprises a polymer. In principle it is
possible here to use all common foam polymers, of the
kind also employed in conventional adhesive tapes in the
printing industry. Particularly suitable, however, are
foam layers comprising foams based on polyacrylate,
polyurethane, polyethylene, polypropylene, or copolymers
based on ethylene and propylene. Also possible, in
addition, are foams based on synthetic rubber, or
silicone-based foams.
For example, the foam layer may comprise a foam material
having a density of between 0.03 and 0.8 g/cm3, preferably
between 0.06 and 0.7 g/cm3, more preferably between 0.09
and 0.3 g/cm3.
According to another embodiment, the thickness of the
foam layer is at least 0.1 mm, preferably at least 0.2 mm,
more preferably at least 0.5 mm.
According to a further embodiment, the thickness of the
foam layer is at most 25 mm, preferably less than 10 mm,
more preferably less than 5 mm, more preferably less than
2 mm. The thickness may also, however, be less than 1 mm.
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According to another development, the adhesive tape of
the invention has a second adhesive layer on that side
of the foam layer that is remote from the carrier layer.
An adhesive assembly tape of this kind therefore has at
least two adhesive layers. The first adhesive layer,
disposed on the carrier layer, and the second adhesive
layer, disposed on the foam layer, and specifically on
that side of the foam layer that is remote from the
carrier layer. In this case it is possible, for example,
for the first adhesive layer to be disposed directly on
the carrier layer, and the second adhesive layer directly
on the foam layer.
An adhesive tape having two adhesive layers may be
adhered by one of the adhesive layers to the substrate
for printing, more particularly to a printing roll. The
second adhesive layer may then be used to mount the
printing plate, in particular a flexible printing plate,
on the printing roll. These adhesive layers may have
different adhesives, for example. The adhesive tape of
the invention is affixed preferably via the second
adhesive layer to the printing roll - which frequently
has a metal or steel surface - whereas the first adhesive
layer serves for the attachment and fixing of the
printing plate.
In another embodiment of the adhesive tape of the
invention, the foam layer and the carrier layer are
joined to one another via an adhesion promoter layer,
which is likewise an adhesive layer.
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In an embodiment different from this, the foam layer and
the carrier layer are joined directly to one another via
a common interface. In this case, the application of the
two layers to one another may take place thermally during
manufacture of the adhesive tape. The two layers are in
this case heated, contacted in the heated state, and so
joined durably to one another.
Adhesives for the layers of adhesive in the adhesive
assembly tape are suitably, in each case independently
of one another, adhesive materials, more particularly
pressure-sensitive adhesive materials, based for example
on acrylic, vinyl ether, natural or synthetic rubber-
based materials, poly(alpha-olefins) and silicones.
One preferred embodiment of the adhesive tape of the
invention relates to an adhesive tape where the first
adhesive layer has a regular or irregular structure, more
particularly grooves or fins.
By structuring the adhesive layer it is possible to steer
air, which is included in the adhesive tape between, for
example, the adhesive layer and further layers, in such
a way that it is able to escape without problems during
the printing process. This is an advantage in order to
prevent unwanted air inclusions which may cause
disruption during printing.
It is possible, furthermore, if the adhesive tape has a
second adhesive layer, for that layer as well to have a
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regular or irregular structure, more particularly grooves
or fins.
According to another preferred embodiment of the adhesive
assembly tape of the invention, a top layer may be
disposed on the first adhesive layer. This top layer can
be removed prior to use. It allows the adhesive tape of
the invention to be covered and hence allows the first
adhesive layer to be protected (release liner). A top
layer of this kind makes it possible in particular for
the adhesive tape to be wound and hence more easily stored
and transported.
It is possible, for example, for the top layer to have a
structure, on the side facing the first adhesive layer.
For example, it is possible to achieve structuring of the
adhesive layer by way of the structure of the top layer.
The invention relates, moreover, to the use of the
adhesive assembly tape of the invention for the printing
industry. The adhesive tapes of the invention are
suitable for printing operations, since they are suitable
for achieving images of high printing quality.
Furthermore, the use of the adhesive assembly tape of the
invention for applying a flexible printing plate to a
printing roll is particularly preferred.
The printing plate may for example comprise what are
called clichés, of the kind employed customarily in the
letterpress technology. For example, the printing plate
may consist of or comprise a photopolymer or rubber. The
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printing roll may have, for example, a surface comprising
a metal. For example, the printing roll may have a steel
surface.
Particular preference is given to the use of the adhesive
assembly tape of the invention for the process known as
flexographic printing. The adhesive tapes of the
invention can be used, for example, for applying and
fixing flexographic printing plates, and in the context
of the flexographic printing process they allow the
fulfilment of high yardsticks in terms of printing
quality, and user-friendly mounting before printing, and
also the easy removal of the adhesive tape after
printing.
The invention is elucidated in more detail below with
reference to working examples and figures. Preferred
embodiments of the invention are represented in the
figures and are explained in more detail below.
Figure 1 shows a schematic representation of an adhesive
tape (10) of the invention for the application and fixing
of a printing plate. The adhesive tape has at least one
foam layer (1). Disposed on the foam layer (1) is a
carrier layer (2), which reinforces the foam layer (1)
and so increases the stability of the adhesive tape. For
example, the carrier layer (2) may be disposed directly
on the foam layer.
Lastly, the adhesive tape has at least one adhesive layer
(3). This first adhesive layer (3) is disposed on the
carrier layer (2). It may for example be disposed
directly on the carrier layer (2). The carrier layer (2)
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is required to have defined mechanical properties. It is
distinguished by a tensile value of a force of at least
1 N at 1% elongation in the machine direction, and at the
same time possesses a tear resistance of more than 0.2 N
in the machine and/or cross directions.
Figures 2A and 23 show schematic representations of two
further embodiments of the adhesive assembly tape (10)
of the invention, comprising a foam layer (1), a carrier
layer, and at least one first adhesive layer (3), the
carrier layer (2) in both cases comprising a laminate
(2a, 2b) or consisting of a laminate (2a, 2b). The
laminate in each case has a woven-fabric or nonwoven
layer (2a) with nonwoven layers being especially suitable
on account of their favorable mechanical properties. The
laminate moreover, in each case has a polymer layer (2b).
It is preferred for the polymer layer (2b), which may for
example have a smooth surface, to form the outer layer,
on which the first adhesive layer (3) is located (figure
2A). However, the opposite arrangement (figure 2B) is
equally suitable as well.
Figures 3A and 33 show schematic representations of two
further embodiments of the adhesive tape (10) of the
invention. Figure aA shows an adhesive tape of the
invention as in figure 1, but additionally having a
second adhesive layer (4) which is disposed on that side
of the foam layer (1) that is remote from the carrier
layer (2). For example, the second adhesive layer (4) may
have a common interface to the foam layer (1). This
arrangement makes it possible to apply and fix a printing
plate without using further adhesive materials. The
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carrier layer (2) of the arrangement shown in figure 3A
may, according to a further-preferred variant, possess
in turn a laminate (as shown in figures 2A or 2B). The
adhesive tape (10) of the invention, however, in addition
to first and second adhesive layers (3, 4) may also have
further adhesive layers. In particular it is possible -
as shown in figure 3B - for individual layers of the
adhesive tape to be joined to one another by a layer of
adhesion promoter. In particular, an adhesion promoter
layer (5) may be disposed between the foam layer (1) and
the carrier layer (2). In this case as well, the carrier
layer may comprise a laminate or consist of a laminate
(as shown in figures 2A or 2B).
Figure 4 shows schematically a detail of a printing
apparatus of the kind used in the printing industry for
the purpose, for instance, of printing books or
newspapers. The printing operation may take place, for
example, by means of a printing roll (12) which is also
referred to as a printing-forme cylinder. The printing
plate (11) is applied to and fixed on the printing roll
(12). This is made possible by the adhesive tape (10) of
the invention. For example, by contact with a further
roll (e.g., a so-called halftone roll; not shown), the
printing plates (11) may be provided with a dye. The
printing operation may take place in interplay with a
further roll (13), also referred to as an impression
cylinder. The initially unprinted material (14a) is
guided over the roll (13), where it comes into contact
with the printing plate (11) mounted on the printing roll
(12) and inked, and can then be passed on in the printed
state (14b) and worked on. From the arrangement it can
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be seen that the adhesive tape (10) plays a significant
part during the printing operation, by virtue of its
arrangement, and exerts an influence on the printed
image. The adhesive tape (10) of the invention not only
allows easy mounting and good printing quality, but also
facilitates the replacement of the printing plates (11),
on the basis of its easy detachability.
Figure 5 compares measurements of the tensile properties
carried out on different reinforcing carrier layers, the
tensile value in N being placed in relation to the
elongation in %. The measurements relate in each case to
the properties in the machine direction.
The measurements shown in figure 5 relate to conventional
materials for the carrier layer such as PE films
(reference example 1), 0-PET films (reference example 2a)
and 0-PP films (reference example 3), and also to carrier
layers of the invention comprising a laminate ("nonwoven-
PE laminate I" - example I and "nonwoven-PE laminate
II" - example 2) and also to carrier layers of the
invention comprising a copolymer ("PP copolymer
(multilayer blown film)" - example 3).
The measurements were carried out in each case on the
films or laminates which form the carrier layers in an
adhesive tape - without the other constituents of the
adhesive tape (foam layer, adhesive layers, etc.) - in
order to enable better comparability and reproducibility.
The properties of the reinforcing carrier layers have
proved to be key to the quality of printed image and to
the detachment behavior of the adhesive assembly tapes.
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Adhesive assembly tapes of the invention have reinforcing
carrier layers whose tensile properties are depicted in
a wide range (black line) limited by the outlined
schematically in fig. 5. For example, the range may cover
tensile properties of at least 1 N at 1% elongation up
to a force of 18 N at 25% elongation in the machine
direction (MD).
The physical properties of reference examples 1, 2a and
3, and the carrier layers of the invention, i.e., the
laminates of the invention (examples 1 and 2), and also
the carrier layers of the invention comprising at least
one first copolymer (example 3) are summarized in
table 1.
The measurement data from figure 5 demonstrates that PE
films undergo high elongation in the machine direction
even under a very low applied force. PE films are very
elastic and soft and therefore, while exhibiting good
properties during printing, do not exhibit such
properties when under high tensile loading during their
removal from the printing roll after use. Standing in
contrast with these films are o-PET films, i.e., oriented
polyester films, which undergo deformation only when high
tensile forces are applied. Their high strength allows
easier detachment from the printing roll, but is also the
reason for a reduced quality of the printed image.
Additionally, o-PET films offer very low tear resistance
for the high tensile strength.
Relative to this, the inventors of the present invention
have recognized that tensile properties lying between
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those of PE films and o-PET films offer the best
mechanical properties for adhesive tapes in the context
of printing operations. In this way, surprisingly, the
advantages of different conventional systems can be
combined. The range with the most suitable mechanical
characteristics is drawn in schematically in the graph
of figure 5. Surprisingly, precisely those tensile values
in the range between the tensile values for the
conventionally employed PE films and o-PET films are
particularly suitable, the outlining in the graph serving
here to illustrate this principle. The tensile properties
of two examples for carrier layers of the invention which
are laminates are shown in figure 5: "nonwoven-PE
laminate I" (example 1) and "nonwoven PE laminate II"
(example 2). In both cases the laminate is one having in
each case a nonwoven polypropylene web with a basis
weight of 12 g/m2, and also a polymer layer applied
thereto by extrusion and comprising polyethylene, with a
basis weight of 12 g/m2. The carrier layers each possess
a total basis weight of 24 g/m2. Both carrier layers are
notable for tensile behavior which lies between that of
the conventional carrier films PE and o-PET. The
inventors have determined that these tensile properties,
in combination with the good tear resistances obtained
(see table 2 in figure 6), allow optimum mechanical
properties to be obtained for the printing operation and
the handling of the adhesive tape.
Moreover, the inventors have observed that even carrier
layers which comprise at least a first copolymer enable
outstanding tensile values and tear resistances, which
likewise fall within the outlined range shown in figure
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5. Carrier layers made of homopolymers such as, for
instance, the o-PP film shown in figure 5 (a cast film
consisting 100% of oriented polypropylene), generally
have good tensile values, but are not soft enough to
permit a good printed image. Conversely, carrier layers
with at least one first copolymer exhibit the mechanical
properties desired for printing and for detachment.
The carrier films investigated are described in table 1.
Table 1: Films for carrier layers in adhesive tapes
Designation Description Thickness
Density
[pm] [g/cm3]
Reference example 1: Blown film of 30% LLDPE (Sabic LLDPE 118
PE film NE from SABIC) and 70% LOPE (Lupolen 25 0.922
2420F from Lyondellbasell)
Reference example
2a: Oriented
polyester film from Mitsubishi 12 1.4
"o-PET film l"
Reference example
2b: Oriented
polyester film from Mitsubishi 23 1.4
"o-PET film II"
Oriented cast film (biaxially drawn) consisting
Reference example 3: of 100% polypropylene (polypropylene 30 0.9
"0-PP film" homopolymer from !nos; melting point =
163 C; type designation: Amoco 100-GA03)
Example 1: 12 g/m2 nonwoven polypropylene web with 12
"nonwoven-PE g/m2 extruded-on polyethylene layer from 70 n.a.
laminate l" lnfiana
Example 2: 12 g/m2 nonwoven polypropylene web with 12
"nonwoven-PE g/m2 extruded-on polyethylene layer from 70 n.a.
laminate II" Infiana
Three-layer blown film consisting of:
- about 63 wt% heterophasic ethylene-
propylene copolymer (ethylene fraction about
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9 wt%) (PP copolymer: melting point = 164 C;
density 0.9 g/cm3; manufacturer: Braskem;
Example 3: type designation: Inspire 137) 30 0.955
"PP copolymer - about 27 wt% ethylene-butyl acrylate
(multilayer blown filmy' copolymer (butyl acrylate fraction about
16 wt%) (EBA copolymer: melting point = 96 C;
density 0.924 g/cm3; manufacturer: Lucobit;
type designation: Lucofin 1400)
- about 7 wt% color masterbatch and
- about 3 wt% processing assistant
*The detailed construction of the multilayer blown film
of example 3 is elucidated further in table 2.
Example 3 presents a carrier layer which is a multilayer
blown film, consisting in this specific case of three
layers. The outer layers (first and third layers) are
each identical and comprise an ethylene-propylene
copolymer as first copolymer and an ethylene-butyl
acrylate copolymer (EBA) as second copolymer. The
ethylene-propylene copolymer itself enables good tensile
values and sufficient tear resistances. The tear
resistance is improved still further by the presence of
EBA as a second copolymer.
The second layer has a high fraction of the ethylene-
propylene copolymer and is free of EBA. This layer is
beneficial for the acquisition of excellent tensile
values.
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Table 2: Multilayer film construction of a carrier layer
in accordance with example 3
Layer 1 2 3
Example 3: 47.5% 813% 47.5%
"PP copolymer heterophasic heterophasic heterophasic
(multilayer blown ethylene-propylene ethylene-propylene
ethylene-propylene
film)" copolymer (ethylene copolymer (ethylene
copolymer (ethylene
fraction about 9%) fraction about 9%) fraction about 9%)
47.5% 16.7% color 47.5%
ethylene-butyl masterbatch ethylene-butyl
acrylate copolymer acrylate copolymer
(butyl acrylate fraction (butyl
acrylate fraction
about 16%) about 16%)
5% 5%
processing auxiliary processing auxiliary
(antiblocking) (antiblocking)
Layer thickness in pm 8.5 13 8.5
A comprehensive comparison of the mechanical properties
of examples 1 and 2 and also of reference examples 1, 2a
and 2b, both for the machine direction "MD" and for the
cross direction "CD" is summarized in table 3, which is
shown in figure 6. The mechanical properties of the
laminates of the invention (examples 1 and 2) lie between
the properties of the PE film (reference example 1) and
of the o-PET films (reference examples 2a and 2b).
A similar comparison can be seen in table 4 which is
shown in figure 7. Reference example 3 is a homopolymer
(o-PP film), while example 3 relates to a carrier layer
comprising a polypropylene copolymer. In terms of the
mechanical properties, the copolymer ("PP copolymer,
multilayer blown film") is situated between reference
example 3 (o-PP film) and reference example 1 (PE film).
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Adhesive assembly tapes of the invention can be produced,
for example, as follows. First of all, the foam layer
(e.g. a PE or PP foam layer as may be obtained
commercially) and the carrier layer are provided.
The carrier layer may as described be a laminate.
Laminates of the invention are produced by providing a
woven-fabric or nonwoven layer, to which a polymer layer
is applied and fixed. In the case of examples 1 and 2, a
nonwoven layer of polypropylene was used in each case.
Nonwoven layers of this kind can be produced by
conventional methods or acquired commercially. Applied
to the woven-fabric or nonwoven layer is then the polymer
layer, application taking place by means for example of
extrusion coating. A good, durable connection can be
achieved through melting. In the case of examples 1 and
2, a PE polymer layer was extruded onto the PP nonwoven
layer in each case, and was subsequently melted on.
Alternatively, the carrier layer, as described, may also
be a layer comprising a copolymer. It may for example as
described be a multilayer blown film comprising the PP
copolymer. A multilayer blown film of this kind may be
manufactured in accordance with the customary extrusion
and blowing methods for films.
The resulting carrier layer may subsequently either be
adhered to the foam layer or joined to it thermally by
melting. In the case of adhering, an adhesion promoter
layer is first applied either to the carrier layer or the
foam layer, and then the layers are joined. Lastly, the
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first adhesive layer is applied to the carrier layer. The
second adhesive layer can be applied analogously on the
foam layer.
The invention is not confined by the description in
relation to the working examples. Instead, the invention
encompasses every new feature and also every combination
of features, including in particular each combination of
features in the claims, even if that feature or that
combination is not itself explicitly set out in the
claims or working examples.
