Note: Descriptions are shown in the official language in which they were submitted.
CA 02510890 2005-06-27
Process for Manufacturing a Packaging Material
The invention relates to a process for manufacturing a packaging material
having at least two films or foils bonded together into a multilayer laminate
by
means of at least one layer of adhesive, whereby the adhesive layer/layers
is/are cure-hardened. Also within the scope of the invention is a self-
standing
pouch made from the laminate.
Laminates for manufacturing self standing pouches for drinks are manufactured
today in two steps using solvent-free adhesives and in one step using solvent-
based adhesives.
The solvent-free process is environmentally friendly, however, requires two
production steps. In a first step an aluminium foil is bonded to a printed
polyethyleneterephthalate (PET) ~Im which is coated with a solvent-free poly-
urethane (PUR) adhesive. After a curing time of several hours this pre-
laminate
can be bonded to a polyolefin-film using a solvent-based or solvent-free PUR
adhesive. The final structure is: PET-film / adhesive layer / aluminium foil /
adhesive layer / polyolefin film. After the final curing over a period of
several
days, the final laminate can be cut to size and dispatched to the customer.
The
throughput time from receipt of order to dispatch of the finished product
depends essentially on the time required for curing the PUR-adhesive
The object of the invention is to provide a process of the kind described at
the
start by means of which the time required for curing the adhesive needed for
the
laminate - and with that the throughput time can be reduced in comparison with
the adhesive curing time in conventional laminate manufacture.
That objective is achieved by way of the invention in that at least one
adhesive
layer is of an adhesive that can be cured using an electron beam and the
laminate is radiated with electrons for the purpose of curing the adhesive.
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The application of an electron beam curable adhesive results in an increase of
the initial adhesion, the so called greentack, which could not be expected at
once. Furthermore the application of an electron beam curable adhesive results
not only in an excellent adhesion against plastic films but also against
aluminium foils. In addition, an aluminium foil forms a functional barrier for
electron beam curable adhesives, which is important with packaging for food,
in
particular beverages.
The radiation curing of plastics that can be cured with an electron beam takes
place in a fraction of a second on passing through a radiation station,
whereby
the final bond strength has already been essentially achieved without an
additional curing time when the laminate emerges from the radiation station
and
is coiled.
The advantage of manufacturing laminate using adhesives that can be cured by
means of electron beam radiation is not only the much reduced throughput time,
but also in the reduction of solvent emissions is solvent based adhesives can
be
replaced by adhesives that can be cured using an electron beam.
A preferred laminate exhibits three films or foils and two adhesive layers,
whereby one of the adhesive layers or both adhesive layers is/are of the
electron beam curing type of adhesive.
If only one of the adhesive layers is curable with an electron beam, a solvent
based or solvent-free PUR-adhesive is used by way of preference for the
second adhesive layer.
A preferred laminate exhibits the following structure: PET film / first
adhesive
layer of electron beam curable adhesive / aluminium foil / second adhesive
layer of an electron beam curable adhesive / polyolefin film.
If only one of the two adhesive layers is of an electron beam curable
adhesive,
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a further preferred laminate exhibits the following structure: PET film /
first
adhesive layer of electron beam curable adhesive / aluminium foil / second
adhesive layer of a solvent based or solvent-free PUR adhesive / polyolefin
film
or PET film / first adhesive layer of a solvent based or solvent-free PUR
adhesive / aluminium foil / second adhesive layer of an electron beam curable
adhesive / polyolefin film
Preferred polyolefin films are sealable films of polyethylene (PE) or
polypropylene (PP). For applications involving sterilisation or high
temperature
cooking, PP is preferable because of its ability to withstand high thermal
loads.
The PET film may exhibit printing on it. The printing is preferably provided
as
counterprint on the side coated with adhesive.
The electron beam curable adhesive is preferably an adhesive on an acrylate
basis.
The adhesive on an acrylate basis may contain monomers, oligomers or
mixtures of monomers and oligimers as the basis. Examples of monomers are
mono, di- and multifunctional acrylates such as phosphoric acid ester
acrylates,
hydroxy-acrylates, carboxy-acrylates, amino-acrylates, acrylic acid and
acrylamide. Examples of oligomers are epoxy-acrylates, urethane-acrylates,
polyester-acrylates and silicon-acrylates. The monomers and oligomers
mentioned are either available commercially or can be manufactured by routine
methods. The term "acrylate"(or "acryl") used here also includes
"methacrylate"(or "methacryl", whereby the acrylates are preferred.
The laminate manufactured according to the invention is particularly suitable
for
manufacturing self-standing pouches, in particular such for drinks. Preferred
is
at least for the film of the laminate forming the outside of the pouch to be
laminated using an adhesive layer that can be cured using an electron beam.
..
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Further advantages, features and details of the invention are revealed in the
following description of preferred exemplified embodiments and with the aid of
the drawing which shows schematically in
Fig. 1 cross-section through a laminated packaging film;
Fig. 2 manufacture of a pre-laminated partial film of the packaging film
shown in Fig. 1;
Fig. 3 manufacture of the packaging film in Fig. 1 from the pre-laminated
partial film in Fig. 2;
Fig. 4 manufacture of the packaging film in Fig. 1 by triple lamination;
Fig. 5 another embodiment of the manufacture of the packaging film.
Fig. 1 shows a packaging film 10 for manufacturing self-standing pouches for
drinks featuring a printed PET film 12 representing the outer side, an
aluminium
foil 14 as barrier layer and a sealable PE or PP film 16 representing the
inner
side. The PET film 12 is permanently bonded to the aluminium foil 14 by way of
a first adhesive layer 13 and the aluminium foil 14 to the sealing film 16 by
way
of a second adhesive layer 15. In a typical packaging film 10 the thickness of
the PET film is e.g. 12 Nm, the thickness of the aluminium foil 8 - 10 Irm and
the
thickness of the sealing layer 90 - 100 pm.
Fig. 2 shows the manufacture of a partial film A comprising PET film 12,
adhesive layer 13 and aluminium foil 14. The printed PET film 12 is uncoiled
from a first spool 18 in strip form an continuously coated with adhesive 13.
The
aluminium foil 14 is uncoiled in strip form from a second spool 20 and fed to
the
PET film 12 coated with adhesive 13 and laminated to this to a partial film A.
The partial film A is passed through a radiation station 22 in which the
adhesive
layer 13 is cured by electron beam radiation within a fraction of a second.
After
leaving the radiation station 22, the partial film A is coiled onto a third
spool 24.
In a further production step, shown in Fig. 3, the sealing film 16 is uncoiled
from
CA 02510890 2005-06-27
a fourth spool 26 and continuously coated with adhesive 15. The partial film A
is fed from the third spool in strip form and fed to the sealing film 16
coated with
adhesive 15 and laminated continuously to this to yield the packaging film 10.
The packaging film passes through a radiation station 28 in which the adhesive
5 layer 15 is cured by electron beam radiation within a fraction of a second.
On
leaving the radiation station 22 the packaging film 10 is coiled onto a fifth
spool
30.
The second adhesive layer 15 does not necessarily have to be an electron
beam curing adhesive. Instead, it may e.g. be a conventional PUR adhesive. In
that case the curing station 28 is omitted. The longer curing time required
for
the PUR adhesive has no influence on the process for producing the composite
film 10 and simply requires a minimum storage time until it is processed
further.
Another version of the manufacturing process - not shown in the drawing - is
such that first a partial film B comprising sealing film 16, adhesive layer 15
and
aluminium foil 14 is produced. The sealing film 16 is uncoiled from a first
spool
and continuously coated with adhesive 15. The aluminium foil is fed to the
sealing film 16 which is coated with adhesive 15 and laminated to this to give
a
partial film B. The partial film B passes through a radiation station in which
the
adhesive a layer 15 is cured within a fraction of a second. After leaving the
radiation station, the partial film is coiled onto a third spool.
In a further step the printed PET film 12 is uncoiled from a fourth spool and
coated continuously with adhesive 13. The partial film B is fed from the third
spool to the PET film 12 coated with adhesive 13 and laminated in a continuous
manner to yield the packaging film 10. The packaging film 10 passes through a
radiation station in which the adhesive layer 12 is cured by electron beam
curing within a fraction of a second. On leaving the radiation station the
packaging film 10 is coiled onto a fifth spool.
The first adhesive layer 13 does not necessarily have to be an electron beam
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curing adhesive. Instead, it may e.g. be a conventional PUR adhesive. In that
case of course the radiation station is omitted. The longer curing time
required
by the PUR adhesive has no influence on the process for manufacturing the
composite film 10 and requires simply a minimum storage time to be observed
until further processing.
In a first way of manufacturing the threefold lamination shown in Fig. 4, the
production of the packaging film 10 takes place by bringing together the PET
film 12, the aluminium foil 14 and the sealing film 16 and adhesively bonding
via
the two adhesive layers 13, 15 in one single pass. The printed PET film 12 is
uncoiled from a first spool 32 and coated continuously with adhesive 13. The
aluminium foil 14 is fed in strip form from a second spool 34 to the PET film
12
coated with adhesive 13and laminated continuously to this to yield partial
film A.
The sealing film 16 is uncoiled from a third spool 36 and coated continuously
with adhesive 15, fed in strip form to the partial film A and laminated to it
in a
continuous manner yielding the packaging film 10. The sealing film 16 is
uncoiled from a third spool 36 and coated with adhesive 15, fed in strip form
to
the partial film A and laminated to it in a continuous manner yielding the
packaging film 10. The packaging film 10 passes through a radiation station 38
with adequate capacity enabling both adhesive layers 13, 15 to be cured by
electron beam radiation within a fraction of a second in one single pass. On
leaving the radiation station 38 the packaging film 10 is coiled onto a fourth
spool 40.
In a second way of manufacturing the threefold lamination shown in Fig. 5, the
production of the packaging film 10 takes place the same way as the production
shown in Fig. 4 by bringing together the PET film 12, the aluminium foil 14
and
the sealing film 16 and adhesiveiy bonding via the two adhesive layers 13, 15
in
one single pass. The aluminium foil 14 is uncoiled from a first spool 42 and
coated continuously with adhesive 15 at a first adhesive application station
17.
The sealing film 16 is fed in strip form from a second spool 44 to the
aluminium
foil 14 coated with adhesive 15 and laminated continuously to this to yield
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partial film B. The partial film B passes through a first radiation station 50
with
adequate capacity enabling the adhesive layer 15 to be cured by electron beam
radiation within a fraction of a second. The PET film 12 is uncoiled from a
third
spool 46 and coated continuously with adhesive 13 at a second adhesive
application station 19, fed in strip form to the partial film B on leaving the
first
radiation station 50 and laminated to it in a continuous manner yielding the
packaging film 10. The packaging film 10 passes through a second radiation
station 52 with adequate capacity enabling also the adhesive layer 13 to be
cured by electron beam radiation within a fraction of a second. On leaving the
radiation station 52 the packaging film 10 is coiled onto a fourth spool 48.
Immediately after coiling onto the spool 40, 48 the packaging film 10 with
fully
cured adhesive layers 13, 15 is divided on a slitting line into commercially
required breadths ready for dispatch.
It is self evident that, on bonding the films or foils in the above laminating
processes, the adhesive may also be deposited on the other films or foils
mentioned in the examples.
