PACKAGING LAMINATE AND METHOD OF USING THE SAME

STRATIFIE D'EMBALLAGE ET SON PROCEDE D'UTILISATION

English Abstract

A laminate for manufacturing of packaging containers comprises a
thermoformable base layer, a barrier layer and a laminate layer
adjacent the barrier layer and directed towards the inside of the container
contemplated. The base layer consists of polypropylene, foamed
polypropylene, filled polypropylene, polyethylene terephtalate, filled
polyethylene terephtalate, amorphous polyethylene terephtalate or filled
amorphous polyethylene terephtalate, the barrier layer consists of aluminium,
and an aluminium oxide coating, a silica coating, ethylene/vinyl
alcohol, polyvinyl alcohol, metalized oriented polyethylene terephtalate or
metalized oriented polypropylene, and the laminate layer consists
of polypropylene, high density polyethylene, linear low density polyethylene,
polyethylene terephtalate, amorphous polyethylene terephtalate,
an adhesive plastic, a heat sealable plastic, a primer or a lacquer.
Furthermore, the invention relates to a method for the manufacturing
of packaging containers by means of folding of a laminate according to the
invention, the laminate being subjected to autoclaving or hot
filling.

French Abstract

L'invention se rapporte à un stratifié pour la fabrication de récipient d'emballages, qui comprend une couche de base thermoformable, une couche d'arrêt et une couche stratifiée adjacente à la couche d'arrêt et orientée vers l'intérieur du récipient considéré. La couche de base est en polypropylène, en polypropylène expansé, en polypropylène injecté, en polyéthylène téréphtalate, en polyéthylène téréphtalate injecté, en polyéthylène téréphtalate amorphe ou en polyéthylène téréphtalate amorphe injecté. La couche d'arrêt comprend de l'aluminium, un revêtement d'oxide d'aluminium, un revêtement de silice, de l'alcool éthylénique/vinylique, de l'alcool polyvinylique, du polyéthylène téréphtalate métallisé ou du polypropylène métallisé. La couche stratifiée comprend du polypropylène, du polyéthylène haute densité, du polyéthylène linéaire basse densité, du polyéthylène téréphtalate, du polyéthylène téréphtalate amorphe, une matière plastique adhésive, une matière plastique thermosoudable, une couche primaire d'apprêt ou une laque. On décrit par ailleurs un procédé relatif à la fabrication des récipients d'emballages visés dans l'invention, qui consiste à plier un stratifié conformément aux indications fournies, ledit stratifié étant soumis à un autoclavage ou à une injection à chaud.

Claims

9
CLAIMS:
1. Method for manufacturing a dimensional stable and
impermeable packaging container from a laminate, wherein the
laminate, which comprises at least a thermoformable base
layer, a barrier layer and adjacent to the barrier layer a
lamination layer directed towards the inside of the
container, the base layer consisting of a material selected
from the group including filled polypropylene and filled
polyethylene terephthalate, the barrier layer being selected
from the group including aluminium and a silica coating, and
the lamination layer being selected from the group including
polypropylene and polyethylene terephthalate, by means of
folding is given its desired shape during the manufacturing
of the packaging container, the laminate then being
subjected to autoclaving or hot filling in order to endow
the container its desired mechanical rigidity.
2. Method as claimed in claim 1, wherein the
packaging container manufactured from the laminate is
allowed to cool in a liquid bath.

Description

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PACKAGING LAMINATE AND METHOD OF USING THE SAME
The present invention relates to a packaging laminate
and a method of its use. More specifically the invention
relates to a laminate for the manufacturing of packaging
containers as well as a method for the manufacturing of a
dimensional stable and impermeable packaging container by
means of folding of the laminate.
The demand on a container intended for foods is that
it should be easy to manufacture and handle as well as be
designed and constructed in such a way that it gives the
best protection possible to the products which are to be
filled and transported in the container. A good product
protection implies among other things that the container
should be sufficiently mechanically strong and dimensional
stable in order to withstand the outer influences which the
container is exposed to during normal handling without the
container being deformed or destroyed. Furthermore, the
container should be sufficiently physically andchemically
impermeable in order to prevent transport of liquid and/or
gases through the walls of the container.
Several plastic materials have been extensively used
as package material for foods, among other things due to
their strength and since they have different permeabilities
for water vapour, oxygen gas, flavouring agents, etc.
However, containers manufactured of only one material
seldomly have all the desired properties for a specific
application. Consequently, containers of the laminate type
have been more or less tailored, the different layers of
the laminate being adapted to the application in question.
In this connection a laminate means a material which is
constructed of more than two layers joined together, the
laminate - by a combination of materials with different
properties - obtaining a condition which would not be
achieved with one material only.

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.In order to be able to use the packaging laminate in
containers for e.g. light sensitive products the laminate
has to be supplemented with at least one additional layer
of a material with barrier properties. In this connection
such a barrier layer means a laminate layer with good
barrier properties against light, gases and/or flavouring
agents.
Known packa5ing laminates comprise a base layer of
paper or cardboard, which gives the container strength and
lo dimensional stability, and an outer layer of plastic,
preferably polyethylene, which gives the container the
necessary impermeability properties against liquid and
furthermore makes the packaging laminate heat sealable in
such a way that thermoplastic layers facing each other
easily can be sealed by means of surface fusion with each
other during the manufacturing of containers in order to
form mechanically strong and liquid impermeable sealing
joints.
However, the known package material has several
serious drawbacks which to a large extent and sometimes
completely depend on the material used as barrier layer,
i.e. a material which is completely impermeable to oxygen
and which also has other barrier properties valuable for
the filled product, e.g. light impermeability. Such a
common barrier material is a metal foil, usually a foil of
aluminium (Al foil).
When containers of the type described above are
manufactured the package material is often subjected to
stresses which become especially great when the material is
folded. This is due to the fact that the folding of a base
layer having a comparatively large thickness results in
that the other layers in the laminate become substantially
stretched or to a corresponding extent compressed along the
folding line.

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When an Al foil is folded the foil can crack when
very great tensile stresses are applied. The risk that this
will take place during folding increases since an Al foil
applied against the inside of the laminate must be covered
with one or several plastic layers, usually polyethylene, in
order to prevent contact between the Al foil and the latter
on filled foodstuff.
The known package material also has drawbacks
caused by the soaking paper or cardboard layers which
rapidly lose their mechanical strength properties and make
the container flabby and cumbersome when it is exposed to
liquid or moisture. Furthermore, the paper or cardboard
layer must be made relatively thick in order to give the
container a necessary dimensional rigidity, which
contributes to increasing the material load and thus the
risk of crack formation in the Al foil during the
manufacturing of containers.
The purpose of the present invention is thus to
eliminate the above mentioned drawbacks which arise when
previously known packaging laminates are folded.
According to an aspect of the invention, there is
provided method for manufacturing a dimensional stable and
impermeable packaging container from a laminate, wherein the
laminate, which comprises at least a thermoformable base
layer, a barrier layer and adjacent to the barrier layer a
lamination layer directed towards the inside of the
container, the base layer consisting of a material selected
from the group including filled polypropylene and filled
polyethylene terephthalate, the barrier layer being selected
from the group including aluminium and a silica coating, and

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the lamination layer being selected from the group including
polypropylene and polyethylene terephthalate, by means of
folding is given its desired shape during the manufacturing
of the packaging container, the laminate then being
subjected to autoclaving or hot filling in order to endow
the container its desired mechanical rigidity.
The packaging laminate according to the invention
comprises at least one thermoformable base layer, and a
laminate layer arranged adjacent to the same, which laminate
layer is directed towards the inside of the container
contemplated.
According to the invention the packaging laminate
is not composed of a usual package material of the laminate
type of cardboard or paper but of a plastic material. In
such a package material with a strengthening base layer of

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plastic a filler can be intermixed with the plastic. Such a
filler can for example consist of finely ground chalk or
kaolin. Thus, the base layer can consist of polypropylene,
foamed polypropylene, filled polypropylene, polyethylene
terephtalate, filled polyethylene terephtalate, amorphous
polyethylene terephtalate or filled amorphous polyethylene
terephtalate.
The barrier layer can also consist of aluminium, an
aluminium oxide coating, a silica coating, ethylene/vinyl
alcohol, polyvinyl alcohol, metalized oriented polyethylene
terephtalate or metalized oriented polypropylene.
The laminate layer can consist of polypropylene, high
density polyethylene, linear low density polyethylene,
polyethylene terephtalate, amorphous polyethylene
is terephtalate, an adhesive plastic, a heat sealable plastic,
a primer or a lacquer.
Normally, the adhesion between the layers included in
a laminate is not affected after the manufacturing of a
container. On the contrary, the properties of the laminate
are deteriorated during a subsequent treatment of the
packaging laminate, which impairs its rigidity properties.
It has thus surprisingly become apparent that in contrast
to the corresponding packaging laminate according to known
technique containers of a laminate according to the
invention, which is folded in a first step and then is
endowed its desired mechanically rigidity in a subsequent
step, obtained considerably improved rigidity properties. A
container manufactured from such a packaging laminate is
thus due to the utilization of the total barrier optimized
with reference to the barrier properties.
When converted to dimensional stable containers the
packaging laminate according to the invention is subjected
to folding. For this purpose the laminate as a package
material in the form of a sheet or a web is folded in the
same way as package materials which are constructed around

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a base layer of paper or cardboard to give the container
necessary strength and dimensional stability. This folding
is accomplished by means of conventional packaging machines
intended for such a purpose. Thus, by the base layer being
5 plastic a folded stackable container is obtained.
After the packaging laminate has obtained its desired
form by means of folding in a first step it is then in a
subsequent step endowed its desired mechanical rigidity.
The adhesion between the layers in the packaging laminate
is thus altered during the procedure for manufacturing of
the completed container. In this way a container is
achieved which is impermeable to liquid and gas, i.e. it
possesses good barrier properties.
The adherence can for example be accomplished by
means of heat lamination of the laminate layers in the form
of a premanufactured film. The adherence can also be
accomplished by means of pasting or extrusion. When pasting
is used the paste (dissolved in water or an organic
solvent) is applied on one of the layers which then is
dryad and pressed against the other layer. The laminate
layer can also be supplied as a film or paste in the form
of the above mentioned macromolecules dissolved or
dispersed in a solvent, and the solvent or the dispersing
agent, respectively, is then evaporated. By the choice of
material in the laminate layer and the solvent or
dispersing agent, the adherence can be adapted in such a
way that it becomes sufficient for the further forming of
the packaging laminate to a more or less completed
container. The adherence by means of pasting is preferably
controlled by means of varying the velocity of the laminate
web through a drying oven.
J -An altered adhesion between the two layers in the
laminate can also be accomplished by means of extrusion,
i.e. one of the layers is extruded while still being melt,
if necessary by means of co-extrusion, i.e. the layers are

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extruded at the same time. The procedure is well known to
the skilled man in the art. In this respect the adhesion is
also controlled by means of the velocity of the laminate
web.
After the processing of the packaging laminate to the
desired shape it is endowed its desired mechanical rigidity
in a subsequent step by means of exposure to heat and/or
pressure. The heat treatment can be accomplished by means
of moist as well as dry heat. When the adherence is
performed by means of pasting dry heat is preferred, and
when the adherence is performed by means of extrusion moist
heat is preferred, preferably by autoclaving.
It is an advantage to form and fold a container with
the desired impermeability properties for the product in
question while the adherence to the laminate with a
disposition to crack is low since the risk of crack
formation in the packaging laminate, principally in its
barrier layer, increases with increased adhesion to the
laminate layer. During the subsequent step the container is
locked in its final form.
When an extrusion by means of known technique is used
the procedure is adapted in such a way that the laminate
layer does not reach a certain temperature which depends on
the extruded component in the layer in question. This can
be accomplished by means of changing the extrusion velocity
and/or the extrusion temperature. The laminate layer is
thus applied as a hot melted paste with rapidly binds when
the layers are cold.
When for example an adhesion plastic in the form of
modified polypropylene as a laminate layer is extruded on a
barrier layer of aluminium foil the extrusion is adapted in
such a way that the plastic melts, only adherence being
achieved. The fastening is then completed by means of
raising the temperature for a varying period. At the same
time a pressure can be applied on the package material, but

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t this is not always necessary. In this connection an
autoclave is preferably used, but an oven can also be
applicable.
The mechanical rigidity of the container can also be
achieved in the subsequent step by an initiator integrated
in one or several of the layers in the packaging laminate,
preferably the base layer, the initiator being brought to
initiate that chemical chain reaction which hardens the
layers. Such a hardening reaction can thus be achieved by a
radical initiator being present in one or several of the
laminate layers. Usually, such initiators can be used
without an activator or in the presence of a reduction
agent. The hardening can be performed at any temperature
within the interval of 0 C to 100 C . However, the
interval 40 C to 90 C is adequate and preferred.
The use of the packaging laminate according to the
invention gives extraordinary advantages. The laminate can
by means of folding be used for the manufacturing of
dimensional stable impermeable packaging containers which
are very suitable foruse at highly extreme conditions in a
humid environment including heat treatment with moist heat
at a pressure above the atmospheric. Such harsh
environments comprise autoclaving at temperatures and
periods customary for foodstuff. This means that the
laminate is also extremely suitable to be used for the
manufacturing of a container which is intended to be filled
with a product under aseptic conditions. In this connection
the product is sterilized and filled under almost sterile
conditions in a likewise sterilized container which after
fillig is sealed in such a way that the filled product
before it is consumed is not reinfected by micro-organisms
during storage.
When such a packaging procedure, a so called hotfill,
is used the filling material is thus packed according to
known technology while still being hot in sterilized,

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preferably heat sterilized containers. Such a treatment
results in that the container is exposed to moist heat at a
temperature of 85 C or more.
During a subsequent cooling phase containers exposed
to the above mentioned example of heat treatment will also
be subjected to environments in which good sealing
properties of the container are required against moisture
and liquid. During the cooling phase the filling material
is allowed to cool_in the container manufactured from a
laminate. This cooling can for example take place in a
fluid bath and.also by means of spraying with cool water,
if necessary with an accompanying cooling with CO2 or N2 in
order to rapidly_be able to achieve a sufficiently low
temperature, such as 4 C.