Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MULTI-LAYER LAMINATE FOR TUBES WITH AN EMBEDDED BARRIER
LAYER AND TUBE PRODUCED THEREFROM AND USE OF SUCH A
LAMINATE
Description
The present application generally relates to a multilayer
laminate for tubes, a tube produced therefrom and use of
such a laminate.
Multilayer laminates are needed in the packaging industry
sector, in particular also for the production of tubes.
Depending on the thickness of the laminate, they have
flexible to relatively dimensionally stable properties and
are used inter alia for the production of tubes, bags and
other packaging. In particular, multilayer laminates which
have an embedded barrier layer, for example in the form of
an aluminum foil, are suitable for packaging aroma-
containing substances. This is based on the fact that a
barrier layer present in the laminate, such as an aluminum
foil, acts as a barrier layer for many, mainly volatile,
substances. However, it has been found to be a problem
here that the barrier layer itself, and here in particular
an aluminum layer, is attacked by aggressive substances
such as for example acids and aggressive organic
substances, so that shielding of the barrier layer or
aluminum layer against the contents of the tube is
necessary. This was hitherto achieved by the layers
encasing the barrier layer being of great material
strengths and thus great thickness, so that the particular
aggressive substances attacking the aluminum layer had to
surmount a longer diffusion path. In addition, an aluminum
layer was if necessary shielded against the packaging
content by an additional barrier layer, e.g. of ethylene
vinyl alcohol copolymer (EVOH).
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However, the need for the use of such thick laminate
layers has the result that the multilayer laminate as a
whole becomes very thick, stiff and difficult to handle
and not least becomes expensive because of the large
quantity of material to be used.
Thus the thicknesses of the laminates used, for example in
the toothpaste tube sector, vary in the order of magnitude
of a quarter of a millimeter, which in lap or fin seal
regions leads to material thicknesses of half a millimeter
and more. This great material thickness has adverse
effects both esthetically and as regards process
technology in all regions of a tube in which overlapping
of the laminate is necessary. Such overlapping is for
example necessary in the production of a tubular lap seal
article from a flat laminate blank.
A further disadvantage of such thick laminates also
consists inter alia in that with use of such laminates it
is difficult to impossible to produce a uniformly shaped
tube body. This difficulty arises firstly from the greatly
decreased flexibility and stiffness of seal regions which
are necessary for the production of a tube body by lap
sealing. In addition, with laminates known from the state
of the art, stretched or orientated film material is often
used. However, particularly during sealing, such oriented
film material has the disadvantage that during heating
during the sealing process the film material at least
partly loses its orientation and as a result at least
partly shrinks. This effect is a particular problem in the
production of tubes, since here because of the great layer
thickness in the sealing region a sealing temperature is
not constant over the cross-section of the laminate
thickness to be sealed, which has the result that any
shrinkage of an oriented film is not constant over a
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cross-section of the laminate, but instead takes place
unevenly. Thus, with such a laminate, particularly if as
aforesaid this necessitates a large laminate thickness,
practically no actually round, but instead in all cases an
oval tube shape is produced, which is not only visually
ugly, since the tube has a very thick lap seal weld, which
is unsatisfactory visually and also to the touch, since
this weld can be seen and felt as a linear thickening.
A further disadvantage which results from the use of such
thick laminates known from the state of the art further
consists in that during the tube production it is in
practice impossible to produce a round tube body into
which a tube head is then sealed, since the stiffness of
previous laminates, particularly in the region of the lap
seal weld of a tube, has the result that the radius of
curvature in the region of the lap seal weld is greater
than in the remaining extent of the tube. Since the tube
head is usually designed essentially completely round,
difficulties thus arise in inserting this round tube head
into a non-round tube body, so that according to the
current state of the art additional measures and auxiliary
devices are necessary for this, which entail additional
work processes and slowing of tube production.
A further disadvantage of previous laminates also consists
in the risk of delamination, which is naturally all the
greater the thicker the laminate-forming layers since
during rolling of the laminate the individual laminate
layers are exposed to a greater shear stress the thicker
the individual layers. Here, the risk of delamination
further intensifies with the sensitivity of the materials
used to the particular contents of the tube.
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Further, the haptic properties are also unsatisfactory
with previously known laminates, which is essentially also
attributable to the necessary high layer thicknesses of
previously known laminates since owing to the material
thickness in the region of the lap seal weld these always
entail a certain stiffness and ovality and a ridge along
the lap seal weld as a result of this.
The purpose of the invention is to provide a multilayer
laminate with an embedded barrier layer and packaging
produced therefrom which enables improved barrier
properties simultaneously with thinner layer thicknesses
of the individual laminate layers and simple, rapid and
inexpensive process technology for production of round
laminate pipes, in particular tubes, wherein the laminate
can be inexpensively produced and individually better
printed and furthermore articles produced therefrom
provide improved haptic properties and improved
environmental compatibility.
This problem may be solved by one or more embodiments
according to the present disclosure.
According to an aspect, the present disclosure provides a
multilayer laminate for tubes with an embedded barrier
layer, wherein the laminate has an outer cover layer
bordering the laminate on one side and an inner cover
layer bordering the laminate on the other side, with the
barrier layer being arranged between them, wherein the
laminate has an asymmetrical structure with respect to the
barrier layer and with respect to the cover layers, and
the molecular orientation of the inner cover layer is
different from the molecular orientation of the outer
cover layer, each based on the elongation or drawing in
the machine direction (MD) as well as crosswise to the
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machine direction (CD), and wherein the outer cover layer
has a biaxial orientation with 200% to 800% drawing in the
machine direction (MD), as well as 500% to .1300% crosswise
to the machine direction (CD), and the inner cover layer
has a monoaxial orientation or none at all.
According to an aspect, the present disclosure provides a
tube produced from a laminate according to the present
disclosure.
According to an aspect, the present disclosure provides a
use of a laminate according to the present disclosure for
producing a package.
According to an aspect, the present disclosure provides a
multilayer laminate for tubes with an embedded barrier
layer, wherein the laminate has an outer covering layer
bounding the laminate on one side and an inner covering
layer bounding the laminate on the other side, between
which the barrier layer is positioned, wherein the
laminate has an asymmetric structure relative to the
barrier layer, particularly with regard to the covering
layers, namely the outer and the inner covering layer,
wherein in particular a molecular orientation of the inner
covering layer differs from a molecular orientation of the
outer covering layer, each in relation to elongation or
stretching in the machine direction (MD) and transverse to
the machine direction (CD). This means that the outer
covering layer has an orientation, while the inner
covering layer has no orientation, or that an orientation
of the outer covering layer is other, in particular
greater, than an orientation of the inner covering layer.
A concept according to the present disclosure, in at least
one embodiment, consists in that it was discovered that
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the effect of shrinkage of an oriented covering layer in
the course of production of a lap seal for production of a
tubular pipe can be influenced astonishingly simply in
that the two covering layers bounding a multilayer
laminate for tubes towards the exterior are implemented
differently, wherein a stretching or elongation of an
outer covering layer is other, in particular greater, than
the stretching or elongation of an inner covering layer.
Here according to the invention it was further found
advantageous if the outer covering layer is biaxially
oriented or biaxially stretched, while the inner covering
layer is elongated or stretched monoaxially or not at all.
Hence according to the invention the outer covering layer
has a biaxial orientation with stretching in the machine
direction (MD) of 200% to 800%, preferably of 400% to 600%
and particularly preferably of essentially 500% and
transverse to the machine direction (CD) of 500% to 1300%,
preferably of 700% to 900% and particularly preferably of
essentially 800%, while the inner covering layer has a
monoaxial orientation or none.
In this manner, it is possible to prevent the inner
covering layer from shrinking or alternatively to
establish a specific shrinkage of the inner covering layer
in the course of a sealing process, so that as a result an
optimized round laminate tube closed by lap seal for
production of tubes can be created.
As regards the material of the embedded barrier layer,
according to the invention the barrier material aluminum
can be used. It is however also possible to use polyamide,
in particular amorphous and/or aromatic and/or partly
aromatic polyamide, ethylene vinyl alcohol copolymer
(EVOH), polyacrylonitrile (PAN), polyethylene
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terephthalate (PET) or SiOx or aluminum oxide as barrier
layer material. The choice of the particular barrier
material here depends on the particular contents of the
tube produced or on the aggressive materials which have to
be retained.
The invention is now explained below on the basis of a
multilayer laminate for tubes with an embedded aluminum
layer, however it should be noted that a barrier layer of
ethylene vinyl alcohol copolymer, optionally in
combination with polyamide, can also excellently be used
in the multilayer laminate according to the invention.
Further, it should be noted that the barrier layer used in
the laminate according to the invention can itself also be
multilayer, for which recourse can preferably be had to
prefabricated, for example coextruded, foil
configurations.
Here for example an ethylene vinyl alcohol copolymer layer
which is embedded between two polyolefin layers, such as
for example polyethylene layers, by means of a bonding
agent has proved effective. A composite of polyamide-
ethylene vinyl alcohol copolymer-polyamide, i.e. an
ethylene vinyl alcohol copolymer layer embedded between
two polyamide layers, has also proved effective, where in
this case both the externally lying polyamide layers each
can be bonded to a respective polyolefin layer, such as a
polyethylene layer, by means of a bonding agent. These
aforesaid structures can be prefabricated and be
integrated into the multilayer laminate according to the
invention. Alternatively, simultaneous extrusion of the
individual layers of the multilayer laminate according to
the invention is also possible, if the particular
individual layers are extrudable.
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As aforesaid, the problem of the invention is thus solved
by a multilayer laminate for tubes with an embedded
aluminum layer, wherein the laminate has an outer, in
particular biaxially, oriented coextruded covering layer
bounding the laminate on the outside and an inner covering
layer, not oriented or less so than the outer covering
layer, bounding the laminate on the inside, wherein the
outer covering layer is bonded to the barrier layer or
aluminum layer, via an outer intermediate layer material
and the inner covering layer according to one embodiment
is bonded to the optionally multilayer barrier layer, in
this case with the aluminum layer, via an inner
intermediate layer material.
According to a further embodiment of the invention, the
inner covering layer can also be bonded directly with the
barrier or aluminum layer, where in this case the inner
covering layer has a shell layer which can be designed as
a skin layer, which preferably consists of a polyolefin,
preferably of a polyethylene, and which bounds the barrier
or aluminum layer, if necessary via a bonding agent.
A further important concept of the invention consists in
that the barrier layer, namely here the aluminum layer, is
surrounded on one or both sides and preferably directly by
an intermediate layer material, namely an outer
intermediate layer material facing an oriented coextruded
outer covering layer on one side and an inner intermediate
layer material facing a non- or monoaxially oriented inner
covering layer on the other side, or alternatively the
barrier layer is surrounded directly on the inside by the
non- or monoaxially oriented covering layer, wherein the
inner covering layer is in every case less oriented than
the outer covering layer or not oriented.
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A further important aspect of the invention also consists
in that the laminate according to the invention is on the
one side bounded on the outside by an oriented coextruded
covering layer and on the other side, i.e. on the side of
the laminate not lying opposite the oriented coextruded
covering layer, is bounded by a covering layer not or less
than the outer covering layer or by a monoaxially oriented
covering layer.
It should at this point be noted that the feature that
"the inner covering layer is less oriented than the outer
covering layer" in the context of this invention means
that the inner covering layer is not oriented, while the
outer covering layer is oriented, or that the inner
covering layer is oriented in one direction, while the
outer covering layer is oriented in more than one
direction or that a degree to which the inner covering
layer is oriented is less than a degree to which the outer
covering layer is oriented, or that the inner covering
layer is oriented in more than one direction, while the
outer covering layer is also oriented in more than one
direction and furthermore with a higher stretch or blow-up
ratio than the inner covering layer.
In the production of a tube from the laminate according to
the invention, the outer side of the tube is by definition
formed from the oriented coextruded covering layer, while
the inner side of the tube is formed by the non-oriented
layer. Based on this arrangement, the oriented coextruded
covering layer is therefore described in the context of
this invention as the outer covering layer, while the non-
or slightly oriented covering layer facing the interior of
the tube is described as the inner covering layer.
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Both the outer covering layer and also the inner covering
layer are respective layers bounding the laminate on the
outside and the inside, which however, if necessary, can
have print and optionally a protective layer covering the
print.
A further important aspect of the invention also consists
in that the laminate according to the invention is
asymmetrically structured at least as regards its inner
and outer covering layer, wherein the outer covering layer
in every case is an oriented coextruded covering layer,
which is stretched either monoaxially, or, preferably,
biaxially, i.e. in the machine direction and also
transverse to the machine direction, while the inner
covering layer has no or a lesser orientation and/or
stretching than the outer covering layer, or alternatively
has a monoaxial stretching or a lesser orientation ratio
than the outer covering layer.
Concerning this, it should be noted that a monoaxial outer
covering layer is not preferred, but under some
circumstances can be combined with a non-oriented inner
covering layer.
In contrast, a preferred embodiment of the invention
consists in the use of a biaxially oriented outer covering
layer in combination with a non- or monoaxially oriented
inner covering layer. Here the inner covering layer is
either formed as stretched film or, preferred according to
the invention, as blown film, wherein the blow-up ratio in
machine direction (MD) to transverse direction (CD) is in
the range from 1:1 to 1:2.5, preferably in the range from
1:1.05 to 1:1.75 and particularly preferably in the range
from 1:1.2 to 1:1.9. Here the ratio information should in
each case be understood to mean that a stretching or
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elongation of the inner covering layer is always effected
only in one direction, i.e. either in machine direction or
transverse thereto, so that in every case an unstretched
or an only monoaxially stretched or elongated film is
present within the stated limits.
It has been found according to the invention that with a
laminate which has such an asymmetrical structure it is
possible to manufacture tubular articles which have
exceptionally good roundness, which has been found
particularly advantageous in particular in the tube
manufacturing process, wherein the laminate has high
stability, improved haptic properties compared to the
state of the art and moreover very good barrier
properties, also in particular as regards protection of an
aluminum layer or film.
Thus the embedded barrier layer is protected both by the
outer intermediate layer material and also by the oriented
' 20 coextruded outer covering layer on the one hand and also
optionally by the inner intermediate layer material and in
every case by the inner covering layer on the other hand
both in the mechanical sense and also with regard to
diffusible substances, since these must firstly diffuse
from a side of the laminate facing the inside of a tube
through the inner non-oriented covering layer and then
through the intermediate layer material or alternatively
only through the inner covering layer, if this itself has
a barrier layer protecting the embedded barrier layer, in
particular aluminum layer, in order to reach the embedded
barrier layer, for example aluminum layer.
The oriented coextruded outer covering layer is, exactly
like the outer intermediate layer material, present
outside the embedded barrier layer, so that protection of
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the barrier layer against aggressive substances is also
optimized from a tube exterior.
According to the invention, the coextruded oriented outer
covering layer is designed at least two-layer and
comprises at least one oriented polymer layer and at least
one, optionally two or more, shell layers. The shell
layers, which are also described as skin layers, surround
the polymer layer and are themselves printable on their
side facing the polymer layer.
According to the invention and preferably, these skin
layers are designed very thin and have a layer thickness
in the range from 0.2 pm to 10 pm, preferably in the range
from 0.8 pm to 6 pm and particularly preferably in the
range from 1 pm to 2.5 pm and thus form a kind of skin
surrounding the polymer layer.
Further, these skin layers are designed sealable, so that
a lap seal or a fin seal sealing of such laminates is
easily possible. Here a preferred embodiment of the outer
covering layer consists in that a polymer layer, for
example of polypropylene, is surrounded on both sides by a
skin layer, where the skin layers positioned on both sides
are similar or identical as regards thickness and
material. The thickness of the polymer layer here
according to the invention is 6 to 100 times, preferably
14 to 81 times and particularly preferably 50 to 70 times
or for example 10 to 30 times the thickness of the skin
layer. This means that the skin layers are designed very
thin relative to the polymer layer, so that as a result a
thin outer covering layer is produced, which according to
a preferred embodiment of the invention has a thickness in
the range from ca. 40 to ca. 70 pm.
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According to the invention, the outer covering layer is
coextruded, wherein the polymer layer and the skin layer
or layers are extruded and bonded in one operation. After
application of the skin layer or layers, the coextruded
covering layer is stretched, in particular biaxially, so
that after the stretching process the whole covering layer
is oriented. This also relates in particular to the skin
layer.
As aforesaid, the inner covering layer of the laminate
according to the invention in every case consists of a
material which according to the above definition according
to the invention is less oriented than the outer covering
layer.
The inner covering layer of the laminate according to the
invention can be designed as monofilm or as two- or three-
layer multilayer film.
In the case where the inner covering layer is designed as
monofilm, this essentially consists of sealable materials,
such as for example polyolefins, such as polyethylene
(PE), in particular polyethylene with weakly branched
polymer chains and hence high density (HDPE), polyethylene
with strongly branched polymer chains and hence low
density (LDPE) or linear polyethylene of low density
(LLDPE) and/or polypropylene (PP), since these materials
are particularly suitable for the production of a fin or
preferably lap seal, with which a tubular article can be
shaped into a pipe and then further processed.
In the case where the inner covering layer is designed as
two- or three-layer multilayer film, the inner covering
layer is essentially composed of one or two skin layer(s)
and/or a polymer layer and/or an inner barrier layer.
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Here according to the invention the skin layer or layers
are based on sealable materials such as for example
polyolefins, such as in particular and preferably
polyethylene, since this/these material(s) is/are
particularly suitable for the production of a fin or
preferably lap seal, with which a tubular article can be
shaped into a pipe and then further processed. Further,
the polyolefins usable for a skin layer can be the
sealable materials HDPE, LDPE or LLDPE and/or
polypropylene (PP).
The individual layers of an inner covering layer designed
as a two- or three-layer multilayer film can be the same
or different polyolefins, such as for example polyethylene
or polypropylene, which are bonded together. Such bonding
of different layers to form the inner covering layer can
according to the invention for example be effected by
coextrusion, wherein the individual layers can for example
consist of high density polyethylene (HDPE) or of low
density polyethylene (LDPE) or of linear low density
polyethylene (LLDPE). In this regard, for example a. core
layer of polypropylene with respective skin layers of
polyethylene, which can for example be structured
analogously to the outer covering layer is also
conceivable.
In this, it is particularly advantageous if, for forming a
lap seal bond for forming the tube body, identical
materials are used for the outer oriented coextruded
covering layer and for the inner non-oriented covering
layer which are sealed together. This means that for the
outer oriented covering layer and the inner non-, or
slightly oriented covering layer either similar skin
layers made of polyethylene or polypropylene are used or
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else a respective monofilm designed as the inner covering
layer consists of the same material as the layer of the
outer covering layer with which the monofilm is sealed in
a lap sealing operation.
Thus in a multilayer embodiment the inner covering layer
comprises a polymer layer which at least on one side,
preferably on both sides, comprises one or more, in
particular essentially identical, shell layer(s) in the
form of respective skin layers, which are preferably
positioned symmetrically relative to the polymer layer.
The skin layers are designed thick, preferably each
equally thick, relative to the polymer layer, and bonded
to the polymer layer by coextrusion.
Alternatively, in a multilayer embodiment, the inner
covering layer can have a, preferably central, inner
barrier layer which is surrounded on each side, and
preferably symmetrically relative to the inner barrier
layer by an, in particular essentially identical, shell
layer, for example in the form of a skin layer, wherein
between the inner barrier layer and the respective skin
layer a bonding agent or adhesive, particularly a
laminating adhesive, is optionally, in particular
preferably, provided.
As materials of the inner barrier layer according to the
invention, polyamide, in particular amorphous and/or
aromatic and/or partly aromatic polyamide, ethylene-vinyl
alcohol copolymer (EVOH), polyacrylonitrile (PAN),
polyethylene terephthalate (PET), aluminum, Si0õ, AlOx and
mixtures and/or combinations of the aforesaid materials
are possible, wherein it should be noted that an inner
barrier layer layer sequence of polyamide-EVOH-polyamide
is a particularly effective protective barrier against
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gaseous and/or diffusible substances, as has been found
according to the invention. If a multilayer inner barrier
layer is used, the respective layers of the inner barrier
layer can as required be bonded to a laminating adhesive.
The same applies for bonding of the inner barrier layer to
respective adjacent layers.
According to the invention, the outer intermediate layer
material facing the tube exterior is designed at least
single-layer, but preferably multilayer, in particular
one- to three-layer and particularly preferably two-layer
and comprises a first and/or a second and/or a third
bonding layer.
The inner intermediate layer material facing the tube
interior is at least single-layer, preferably multilayer,
in particular one- to five-layer, wherein one to three
layers thereof have the material of the first and/or the
second and/or the third bonding layer. A particularly
preferred embodiment of the inner intermediate layer is
made two-layer of different polymers.
Further, according to one embodiment, the inner
intermediate layer material facing the tube interior
comprises at least one additional barrier layer which
optionally has a bonding layer, in particular an adhesive
layer, a bonding agent or a laminating adhesive on at
least one side. This bonding layer ensures that the
additional barrier layer is optimally integrated into the
inner intermediate layer material and has optimal bonding
with the layers surrounding the additional barrier layer.
This additional barrier layer can also itself be made
multilayer and form a composite of the aforesaid organic
barrier layer materials, where again already prefabricated
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barrier layer composites, which optionally comprise skin
layers, can also be used.
Further, it should be noted that an inner intermediate
layer material which has an additional barrier layer can
be replaced by an inner covering layer with an inner
barrier layer.
The materials used according to the invention are listed
in the following table and can each be present in the
respective layer alone or in combination:
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Layer Material(s)
outer shell polyolefin(s), such as
covering layer
polyethylene (PE), in particular
layer (10o) or HDPE, LOPE or
LLDPE and/or
(30a) skin
layer polypropylene (PP), polyethylene
terephthalate (PETP),
polyethylene terephthalate glycol
(PETG), mixtures of aforesaid
materials
oriented polyolefin(s), such as
polymer
polyethylene (PE), in particular
layer HOPE,
LOPE or LLDPE and/or
(20o)
polypropylene (PP), polyethylene
terephthalate (PET), polyamide
(PA).
inner shell polyolefin(s), such as
covering layer
polyethylene (PE), in particular
layer (10n) or HOPE, LOPE or
LLDPE and/or
(301) skin
layer polypropylene (PP), polyethylene
terephthalate (PETP),
polyethylene terephthalate glycol
(PETG), mixtures of aforesaid
materials
polymer polyolefin(s), such as
layer
polyethylene (PE), in particular
(20n) HOPE,
LOPE or LLDPE and/or
polypropylene (PP), polyethylene
terephthalate (PET), polyamide
(PA).
inner polyamide, in
particular
barrier amorphous
and/or aromatic and/or
layer (55) partly aromatic
polyamide,
ethylene vinyl alcohol copolymer
(EVOH), polyacrylonitrile (PAN),
polyethylene terephthalate (PET),
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mixtures and combinations of
aforesaid materials
first bonding layer maleic anhydride (MA), ethylene
(43) methacrylate (EMA), ethylene-
acrylic acid copolymers (EAA),
ionomers, terpolymers (ethylene-
acrylic acid-maleic anhydride),
ethylene-vinyl acetates (EVA),
modified olefins, mixtures of
aforesaid materials
second bonding layer maleic anhydride (MA), ethylene
(45) methacrylate (EMA), ethylene-
acrylic acid copolymers (EAA),
ionomers, terpolymers (ethylene-
acrylic acid-maleic anhydride),
ethylene-vinyl acetates (EVA),
polyolefins, in particular
polyethylene (PE), polypropylene
(PP), modified olefins, mixtures
of aforesaid materials
third bonding layer maleic anhydride (MA), ethylene
(47) methacrylate (EMA), ethylene-
acrylic acid copolymers (EAA),
ionomers, terpolymers (ethylene-
acrylic acid-maleic anhydride),
ethylene-vinyl acetates (EVA),
polyolefins, in particular
polyethylene (PE), polypropylene
(PP), modified olefins, mixtures
of aforesaid materials
bonding layer (60) maleic anhydride (MA), ethylene
methacrylate (EMA), ethylene-
acrylic acid copolymers (EAA),
ionomers, terpolymers (ethylene-
acrylic acid-maleic anhydride),
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ethylene-vinyl acetates (EVA),
modified olefins, mixtures of
aforesaid materials
barrier layer (50) polyamide, in
particular
amorphous and/or aromatic and/or
partly aromatic
polyamide,
ethylene vinyl alcohol copolymer
(EVOH), polyacrylonitrile (PAN),
polyethylene terephthalate (PET),
in particular oriented
polyethylene
terephthalate
(OPET), aluminum, SiO., A10.,
mixtures and combinations of
aforesaid materials
additional barrier polyamide, in
particular
layer (70) amorphous and/or aromatic and/or
partly aromatic
polyamide,
ethylene vinyl alcohol copolymer
(EVOH), polyacrylonitrile (PAN),
polyethylene terephthalate (PET),
in particular oriented
polyethylene
terephthalate
(OPET), mixtures and combinations
of aforesaid materials
The respective layer thicknesses of the individual layers
can be seen from the following table:
Layer Layer Preferred layer Particularly
thickness thickness preferred layer
thickness
shell layer (10) or skin 0.2 pm - 10 0.8 pm - 6 pm 1 pm - 2.5 pm
layer pm
oriented polymer layer 10 pm - 100 15 pm - 80 pm 30 pm - 50 pm
(20) pm
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f irst bonding layer (43) 5 pm - 140 8 pm - 95 pm
10 pm - 50 pm
pm
second bonding layer (45) 5 pm - 140 8 pm - 95 pm 10 pm - 50 pm
pm
third bonding layer (47) 5 pm - 140 8 pm - 95 pm 10 pm - 50 pm
pm
bonding layer (60) 1.5 pm - 25 3 pm - 18 pm 4.5 pm - 12 pm
pm
barrier layer (50) or 3 pm - 60 pm 3.8 pm - 40 pm
4 pm - 28 pm
additional barrier layer
(70) or inner barrier
layer (55)
(not in case of an
aluminum foil, 3i0. or
AlC)
barrier layer (50) in case 3 pm - 70 pm 5 pm - 40 pm 8 pm - 15
pm
of an aluminum foil
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Further, the thickness of the barrier layer materials SiOx
and A10. usually lies in the region of 1 Angstrom. These
barrier layer materials are usually vapor deposited and
thus advantageously have only a very small layer
thickness.
Furthermore, at this point it should once again be noted
that the shell layer must be differentiated, namely in
that an outer shell layer is present oriented and an inner
shell layer not or only slightly oriented.
Through the multilayer design of the intermediate layer
material, both for the side facing the tube interior and
the side facing the tube exterior, materials can be
combined whose properties in an unforeseeable manner
interact advantageously at small layer thicknesses and in
this way afford an intermediate layer material which has
high mechanical and also high chemical stability. In
particular, in this regard a high ductility with at the
same time high tear and pierce resistance and high
resistance to diffusion may be mentioned.
As regards the material thickness of the first, second and
third bonding layer, it has according to the invention
been found particularly advantageous if the layer material
provided in these layers is available with sufficiently
high layer thickness and thermoplastic consistency, so
that the layer material which forms the outer intermediate
layer and in particular also the inner intermediate layer
are pressed out from the respective intermediate layer
under the action of pressure and heat in the course of a
sealing operation and in this manner can overflow and
cover an adjacent, in particular exposed, cut edge of an
aluminum layer so that the aluminum cut edge is
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effectively protected against attack by any aggressive
substances, in particular from the tube interior.
This effect is particularly advantageous against
aggressive contents of the tube produced according to the
invention. It is however also possible in this manner to
protect the aluminum layer against substances which lie
outside the tube. Through such overmelting of a cut edge
of the laminate according to the invention it is moreover
possible to protect all layers bounding the cut edge,
except for the melt layer itself, against outside
influences and influences of the tube contents.
In this connection, it should further be mentioned that
according to the invention the inner intermediate layer
material is made at least as thick and/or at least as
multi-layered as the respective outer intermediate layer
material used or can comprise more and/or thicker layers.
Here, a two-layer outer intermediate layer material and a
two- to three-layer inner intermediate layer material has
proved especially effective. In this manner, in the course
of a sealing operation to create a lap seal for forming a
round tubular article, melting of the inner intermediate
layer material and the outer intermediate layer material
and overmelting of a cut edge with this melted
intermediate layer material both from inside and also from
outside the aluminum layer of the laminate according to
the invention is possible.
Furthermore, through the provision of the oriented
coextruded outer covering layer according to the invention
and the non-, or less than the outer covering layer or
monoaxially, oriented inner covering layer each of
sealable material or with at least one sealable skin
layer, good external stability of the laminate according
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to the invention with at the same time good sealability
and, resulting therefrom, high stability of the seals and
hence of the tube produced therefrom is obtained.
According to the invention, printing can be effected both
on an outer skin layer facing the tube exterior. In
addition, it is possible to print the inner shell layer or
the corresponding skin layer facing the tube exterior or
the tube interior on its side facing the outer
intermediate layer material by means of a so-called
"reverse print". This is possible since according to the
invention the polymer layer positioned between the skin
layers can be designed transparent.
For the case that the use of a "reverse print" is desired,
a further bonding layer is preferably provided between the
color layer positioned on the inner shell layer or the
corresponding skin layer and the outer intermediate layer
material, =order to ensure good adhesion of the color
layer to the intermediate layer material.
Through the use of the materials according to the
invention and in particular the layer sequence described,
it is possible to create layer thicknesses in the stated
thickness ranges and in this manner to achieve a
considerably thinner laminate thickness compared to the
state of the art, while the multilayer laminate at the
same time has improved barrier properties and optimized
mechanical and chemical properties and is particularly
suitable for the production of round tubular articles with
no significant tendency to ovality.
The production of the intermediate layer material
according to the invention is effected by joint extrusion
of the layers forming the intermediate layer material,
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whereby the laminate can be produced in the course of a.
tandem extrusion, wherein in a first extrusion step one
side of the barrier layer is coated and in a second
extrusion step the other side of the barrier layer. These
extrusion steps can be performed as coextrusion steps,
wherein a multilayer composite of layers is extruded
simultaneously. Provided that the barrier layer is
extrudable, such as for example EVOH, this can also be
extruded jointly with the intermediate layer material.
Further, the invention also comprises a method for
production of a multilayer laminate for tubes with an
embedded aluminum layer, wherein the aluminum layer is
coated on both sides with intermediate layer material and
with an outer oriented coextruded covering layer on one
side and on the other side with a non-, less than the
outer covering layer or monoaxially, oriented inner
covering layer. The oriented coextruded outer covering
layer is itself produced by at least one-sided coating, in
particular coextrusion, of the polymer layer with a skin
layer. Preferably the polymer layer is coated on both
sides with a, preferably identical, skin layer. After a
coating of the polymer layer with the particular assigned
skin layer, the outer covering layer resulting from this
is stretched, in particular biaxially. The non-oriented
inner covering layer can also be produced by coextrusion,
if this is to be made multilayered. Further, production of
the inner covering layer as blown film is possible, where
an essentially monoaxial elongation of the film occurs in
the course of the blowing.
Further, the layers forming the intermediate layer
material are coextruded and extruded essentially
simultaneously or directly consecutively with formation of
the laminate.
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In summary, a concept according to the present disclosure,
in at least some embodiments, is based on the fact that
the inventors surprisingly discovered that a laminate can
be molded particularly well into a round film article if
an outer covering layer bounding the laminate on one side
is oriented, in particular biaxially oriented, and
consists of a central layer which can be a polymer layer
and preferably two skin layers which surround the central
polymer layer, wherein the polymer layer together with the
skin layers applied onto this on both sides is oriented,
i.e. stretched.
In at least some embodiments, this oriented polymer layer
together with the oriented skin layers here is the outer
covering layer, which in combined action with a further
non-, less than the outer covering layer or monoaxially
oriented inner covering layer bounding the laminate on the
other side results in the manifestation of the
advantageous properties here, which make it possible to
produce a tubular article which is designed round, and not
oval as previously in the state of the art, since through
the use of the inner non-oriented covering layer according
to the invention extremely advantageously a shrinkage
process can be avoided or, decided by the degree and/or
direction of stretching or orientation "adjusted", which
occurred uncontrolled or to an undesirably high extent in
films according to the state of the art in the course of
lap sealing of previous laminates, when these previous
laminates were shaped into a tubular article.
Moreover, the problem according to the invention is also
solved by a tube which is produced from a laminate
according to the present explanations, and further through
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the use of an above-described laminate for production of
packaging with tubular articles, namely a tube.
The invention is described below on the basis of practical
examples which are explained in more detail on the basis
of the diagrams. These show:
Fig.1 a schematic diagram of a first embodiment
of a laminate according to the invention;
Fig.2 a schematic diagram of a second embodiment
of a laminate according to the invention;
Fig.3 a schematic diagram of a third embodiment
of a laminate according to the invention;
Fig.4 a schematic diagram of a further embodiment
of a laminate according to the invention;
Figs.5-7 schematic diagrams of further embodiments
of laminates according to the invention on
the basis of the embodiments according to
Fig.1, Fig.2 and Fig.4, but with additional
barrier layer;
Figs.8 & 9 schematic diagrams of further embodiments
of laminates according to the invention;
and
Figs.10-12 schematic diagrams of different barrier
layer composites which can be used
according to the invention as an embedded
barrier layer and/or additional barrier
layer and/or inner barrier layer.
In the description below, the same reference numerals are
used for identical and identically acting parts.
Fig.1 shows a schematic diagram of the simplest form of a
laminate according to the invention, wherein an aluminum
layer 50 is coated in the direction of an, in the case of
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intended formation of a tube, outer side of such a tube
with an outer intermediate material layer 40a onto which a
coextruded covering layer 30a is attached, which itself
consists of a central oriented polymer layer 20o, which is
covered on both sides with also oriented skin layers 10o.
In the direction of an imaginary tube interior, an inner
intermediate layer material 40i is attached to the
aluminum layer 50, which in turn bounds a non-oriented
skin layer 10n, which is itself positioned adjacent to a
non-oriented polymer layer 20n. As a layer bounding this
polymer layer 20n, a non-oriented skin layer 10n is in
turn provided. Thus this laminate according to the
invention relative to the aluminum layer 50 is
asymmetrically structured as regards the molecular
orientation of the respective outer and inner covering
layer. According to this embodiment, the aluminum layer
has a layer thickness of 12 pm, while the outer
intermediate layer material 40a has a layer thickness of
40 pm. The inner intermediate layer material 40i has a
thickness of 50 pm. The coextruded covering layer 30a
lying outside and the inner covering layer 30i each have a
layer thickness of 30 pm, wherein the oriented and non-
oriented polymer layers 200 and 20n are allotted 22 pm and
the respective skin layers 10o and 10n 2 to 4 pm each.
According to a further embodiment of the invention, in the
laminate according to the invention according to Fig.1,
the inner covering layer 30i alternatively to the above-
described embodiment according to Fig.1 can also be
structured according to the diagrams 10 or 12 described
below, where in these cases also the inner covering layer
is not or not significantly oriented.
Fig.2 differs from Fig.1 in that the outer and the inner
intermediate layer materials 40a and 40i consist not only
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of a first bonding layer 43, but both the outer
intermediate layer material 40a and also the inner
intermediate layer material 40i consist of a first bonding
layer 43 and a second bonding layer 45. Here each second
bonding layer 45 has 34 pm layer thickness, while the two
first bonding layers 43 each have a layer thickness of 14
pm. In this case also, the inner covering layer 30i can
alternatively to the above-described embodiment according
to Fig.2 also be structured according to Figures 10 or 12
described below, wherein the inner covering layer in these
cases is also not or not significantly oriented.
According to Fig.3, the inner intermediate layer material
40i is again subdivided into a first bonding layer 43 with
a layer thickness of 14 pm, a second bonding layer 45 with
a layer thickness of 17 pm and a third bonding layer 47
with a layer thickness of 30 pm. Thus there results for
the inner intermediate layer material 40i a total layer
thickness of only 65 pm, which contributes to markedly
greater flexibility of the laminate according to the
invention and also to better sealability with at the same
time a very high barrier property. In this case also, the
inner covering layer 30i can alternatively to the above-
described embodiment according to Fig.3 also be structured
according to Figures 10 or 12 described below, wherein the
inner covering layer in these cases is also not or not
significantly oriented.
The embodiment according to Fig.4 essentially corresponds
to the embodiment according to Fig.3, with the difference
that the outer intermediate material layer 40a is made
three-layer, from a first bonding layer 43, a second
bonding layer 45 and a third bonding layer 47. In this
case also, the inner covering layer 30i can alternatively
to the above-described embodiment according to Fig.4 also
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be structured according to Figures 10 or 12 described
below, wherein the inner covering layer in these cases is
also not or not significantly oriented.
Figs.5, 6 and 7 as regards their outer structure in
relation to the aluminum layer 50 correspond to the
embodiments according to Figs.1, 2 and 4. The inner
structure of the laminate is modified in that an
additional barrier layer 70 which is surrounded on both
sides by a bonding layer 60 is integrated into a first or
second bonding layer 43, 45 forming the inner intermediate
layer material 40i.
With a laminate structure according to Figures 5 to 7,
according to the invention it is possible that the inner
intermediate layer material 40i forms the inner covering
layer 30i, so that in this case the inner covering layer
30i bounds the embedded barrier layer 50 directly or
optionally via a bonding agent or laminating adhesive.
Further, also in the case of a laminate structure
according to Figures 5 to 7 it is possible that the inner
covering layer 30i can alternatively to the above-
described embodiment according to Figures 5 to 7 also be
structured according to Figures 10 or 12 described below,
wherein the inner covering layer in these cases is also
not or not significantly oriented.
Moreover, it should be noted that although the embedded
barrier layer 50 according to Figures 1 to 7 was by way of
example described as an aluminum layer, the embedded
barrier layer 50 can however as required, for example for
creating a transparent laminate, also consist of one or
more plastic material(s) according to the above
explanations. In this case, the embedded barrier layer 50
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has a layer thickness in the range from 3.8 pm to 40 pm,
preferably in the range from 4 pm to 28 pm. In the case of
the use of aluminum as the barrier layer material for the
embedded barrier layer 50, a nontransparent laminate
according to the invention is obtained.
In addition it should be mentioned that the embedded
barrier layer 50, and also the additional barrier layer
70, and also the inner barrier layer 55 can be formed by
barrier layer composites according to Figures 10 to 12.
= Fig.8 shows a further schematic diagram of a multilayer
laminate according to the invention for tubes with an
embedded aluminum layer 50. According to Fig.8, the
aluminum layer 50 is surrounded on both sides by a second
bonding layer 45 of a copolymer. The copolymer of the
second bonding layer 45 in the direction of the coextruded
oriented outer covering layer 30a together with a first
bonding layer 43 forms an outer intermediate layer
material 40a, via which the aluminum layer 50 is bonded to
the coextruded oriented outer covering layer 30a. The
coextruded oriented outer covering layer 30a is in turn
composed of a central oriented polymer layer 20o and
oriented skin layers 100 bonded to this oriented polymer
layer 20o on both sides. The coextruded oriented outer
covering layer here is produced by coextrusion of the
oriented polymer layer 200 and the two oriented skin
layers 10o, wherein the oriented polymer layer 20o
consists of a transparent biaxially oriented polypropylene
with a layer thickness of 50 pm.
On the side of the aluminum layer 50 facing the coextruded
oriented outer covering layer 30a, an inner intermediate
layer material 40i is attached to this, which, as
aforesaid, consists of a second bonding layer 45 of a
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copolymer and a third bonding layer 47 of a polymer. The
aluminum layer 50 itself is bonded to a non-oriented inner
covering layer 30i via the inner intermediate layer
material 40i. This non-oriented inner covering layer 301
is formed by a transparent monofilm in the form of a
polyethylene film with a layer thickness of 50 pm. This
polyethylene film is designated with the reference symbol
20n. The two bonding layers which form the outer
intermediate layer material 40a are a white polyethylene
with a layer thickness of 20 pm. This white polyethylene
film is the first bonding layer 43. The copolymer forming
the second bonding layer 45 adjoining this first bonding
layer is also made white, i.e. nontransparent and has a
layer thickness of 15 pm. The aluminum layer 50 has a
layer thickness of 12 pm, while the copolymer forming the
second bonding layer 45 of the inner intermediate layer
material 40i has a layer thickness of 17 pm. This
copolymer is designed transparent. The third bonding layer
47 adjacent to the copolymer of the second bonding layer
45 is a polyethylene copolymer which is transparent and
has a layer thickness of 20 pm.
Fig.9 also shows a schematic diagram of a further
embodiment of a multilayer laminate according to the
invention for tubes with an embedded aluminum layer 50.
The layer structure of the laminate shown in Fig.9
essentially corresponds to that in Fig.8, with the
difference that the oriented polymer layer 20o of the
coextruded oriented outer covering layer 30a according to
Fig.9 only has a layer thickness of 30 pm. Also the
bounding layer of white polyethylene which forms the first
bonding layer 43 of the outer intermediate layer material
40a has a layer thickness of 18 pm. The layer thickness of
the adjacent copolymer which forms the second bonding
layer 45 is about 15 pm. The layer thickness of the
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aluminum sheet 50 lies in the region of 9 pm. The polymer
layer which forms the third bonding layer 47 of the inner
intermediate layer material 40i is again a polyethylene
copolymer which like the bounding copolymer is designed
transparent. The polyethylene copolymer layer has a layer
thickness of 23 pm.
The further Figures 10 to 12 show further different
structures for an embedded barrier layer 50, an additional
barrier layer 70 or an inner barrier layer 55. It should
be explicitly noted here that the aforesaid examples each
mentioned an aluminum layer as barrier layer material for
the embedded barrier layer 50. However, this barrier layer
can be replaced by a layer of ethylene-vinyl alcohol
copolymer (EVOH) or another organic barrier layer and a
combination of the plastic barrier layer materials
discussed in each case. Further, these plastic barrier
layer materials can also be used for the additional
barrier layer 70 and/or the inner barrier layer 55.
Furthermore, for example alternatively to a monolayer of
EVOH, the barrier layer composites shown in Figs.10 to 12
can also be used. These are advantageously already
obtainable as finished composite and can in this manner
extremely simply be integrated into the multilayer
laminate according to the invention. In this context, it
should further be noted that the composites shown can also
be combined with the barrier layer materials, such as for
example polyethylene terephthalate, polyacrylonitrile or
silicon oxide or aluminum oxide, if this is desired or
necessary.
As regards the choice of the particular barrier layer
material, it should be mentioned that a barrier layer of
aluminum is preferably used when a nontransparent
multilayer laminate is to be created or is desired. In
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contrast to this, as shown in Figs.10 to 12,the barrier
layers based on polymers are preferably used for
multilayer laminates which are to be transparent, for
example when it is desired that the filling of a tube be
visible from outside.
Thus the multilayer laminate according to the invention
and a tube produced therefrom is usable in very many ways
and displays substantial advantages and improvements
compared to previous laminates for tubes, particularly as
regards manufacturing technology possibilities and also as
regards barrier properties.
As materials for the stated layers, the aforesaid
materials are possible, but it should be emphasized that
adjacent layers are preferably different in nature.
Modifications of all parts described above seen in
themselves alone and in any combination, in particular the
details shown in the diagrams are familiar to those
skilled in the art.
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List of Reference Symbols
10o oriented skin layer
10n non-oriented skin layer
20o oriented polymer layer
20n non-oriented polymer layer
30a coextruded oriented outer covering layer
30i non-oriented inner covering layer
40a outer intermediate layer material
40i inner intermediate layer material
43 1st bonding layer
45 2nd bonding layer
47 3rd bonding layer
50 embedded barrier layer
55 inner barrier layer
60 bonding layer
70 additional barrier layer
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