Note: Descriptions are shown in the official language in which they were submitted.
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WO 2014/072066 Al -1-
FOODSTUFFS PACKAGING CONTAINING A FILM WITH PROPERTIES
PROVIDING A BARRIER TO MINERAL OILS
The present invention relates to a foodstuffs packaging
containing a polyolefin-based film with properties
providing a barrier to mineral oils.
Polyolefin-based films, in particular biaxially oriented
propylene (boPP) films, are nowadays used as packaging
films in a wide range of applications. Polypropylene films
are characterised by many advantageous use properties, such
as high transparency, gloss, barrier to water vapour, good
printability, rigidity, penetration strength, etc. The
polypropylene films can be used both as transparent films
and as opaque films.
The above films are often also used in combination with
other packaging materials, in particular in the field of
foodstuffs.
For foodstuffs packaging, cardboard packaging is often used
that, due to its availability, is often present in the form
of recycled cardboard. This results in problems, since
recycled cardboards typically contain 300-1000 mg/kg
mineral oil with a relatively low molar mass (primarily n-
C18 to n-C22) and a content of aromatic components between
15-20 % (opinion no. 008/2010 of the Federal Institute for
Risk Assessment "BfR" of 09.12.2009).
The mineral oil mixtures detected in recycled cardboard are
paraffin-like (open-chained, usually branched) and
naphthene-like (cyclical) hydrocarbons that are referred to
as "mineral oil saturated hydrocarbons" (MOSH), and also
aromatic hydrocarbons, or "mineral oil aromatic
hydrocarbons" (NOAH), which consist primarily of highly
alkylated systems (see Biedermann M, Fiselier K, Grob K,
2009, "Aromatic hydrocarbons of mineral oil origin in
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foods: Method for determining the total concentration and
first results. Journal of Agricultural and Food Chemistry
57: 8711-8721).
Insofar as no suitable precautionary measures are taken,
for example by metallisation of the cardboard, there is
= thus the risk that the above-specified mineral oil mixtures
will contaminate the foodstuffs to be packaged or already
= packaged.
First approaches for using films based on polyolefin films,
in particular biaxially oriented polypropylene (boPP)
films, as barrier to the above-specified mineral oil
mixtures show that the polyolefin films alone do not
effectively prevent the migration. The films thus require
an additional finishing in order to act as a barrier to the
above-specified mineral oil mixtures.
By way of example, films that have a metallisation with
sufficient optical density are suitable. This metal layer
forms an effective barrier against the mineral oils. For
some applications, however, such metal layers are
undesirable for aesthetic reasons or for cost reasons. In
particular, these metal layers cannot be used when the film
packaging is to be transparent. Furthermore, the efficacy
as a barrier is also dependent on the quality of the
coating, such that only a high-quality costly metallisation
serves this purpose.
The object of the present invention was to provide a
polyolefin-based film, in particular a film based on
biaxially oriented polypropylene (boPP) films, for
foodstuffs packaging formed from recycled cardboard, which
film has a sufficient barrier to mineral oil mixtures and
at the same time retains the good application properties,
such that a contamination of the foodstuff to be packaged
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or already packaged by the mineral oil mixture in the
recycled cardboard is avoided.
The present invention thus relates to a foodstuffs
packaging comprising:
a) a foodstuff,
= b) a polyolefin-based film, in particular a film based on
biaxially oriented polypropylene (boPP) films, which
film encases the foodstuff,
c) a cardboard based on recycled cardboard, which encases
the polyolefin-based film, in particular the film
based on biaxially oriented polypropylene (boPP)
films, containing the foodstuff,
characterised in that the polyolefin-based film, in
particular the film based on biaxially oriented
polypropylene (boPP) films, comprises at least one
coating comprising (i) acrylate polymer and/or (ii)
halogen-containing vinyl polymers and/or vinylidene
polymers and/or (iii) polymers based on vinyl alcohol
(VOH), and this coating is present on the side of the
film facing towards the cardboard based on recycled
cardboard.
The foodstuffs packaging according to the invention does
not require any barrier layers produced by metallisation of
surfaces and can thus be produced more economically than a
metallised cardboard or a metallised film, for example. In
addition, with use of transparent embodiments, the
invention enables new types of packaging that previously
were not possible on account of the metallisation.
The invention can be provided by differently designed
foodstuffs packagings. In one embodiment bag packaging or
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wrap packaging is produced with technology known per se and
contains the foodstuff. The filled bag or wrap packaging is
then packaged in a further encasing cardboard packaging.
The coating on the outer side of the bag or wrap packaging
=
prevents the migration of the mineral oils from the
cardboard into the foodstuff. In a further embodiment the
= cardboard can be laminated or lined with the coated film. A
packaging that contains the foodstuff is then produced from
= the coated cardboard. This variant is advantageous for
packaging in which the foodstuff would otherwise come into
direct contact with the cardboard.
FILM:
The polyolefin-based films used within the scope of the
present invention are in particular films based on
biaxially oriented polypropylene (boPP) films. These films
can be constructed in a monolayer or multi-layer manner and
have a coating comprising (i) acrylate polymer and/or (ii)
halogen-containing vinyl polymers and/or vinylidene
polymers and/or (iii) polymers based on vinyl alcohol
(VOH).
The monolayer film or the base layer of the multilayer film
contains polyolefin, preferably a propylene polymer and
optionally further conventional additives in effective
quantities in each case. The base layer generally contains
at least 70 to <100 % by weight, preferably 75 to 98 % by
weight, in particular 85 to 95 % by weight, of the
polyolefin, in each case in relation to the weight of the
layer.
Propylene polymers are preferred as polyolefins of the base
layer or as material for monolayer films. These propylene
polymers contain 90 to 100 % by weight, preferably 95 to
100 % by weight, in particular 98 to 100 % by weight, of
propylene units and have a melting point of 120 C or
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above, preferably 150 to 170 C, and generally a melt flow
index from 1 to 10 g/10 min, preferably 2 to 8 g/10 min, at
230 C and a force of 21.6 N (DIN 53735). Isotactic
propylene homopolymer with an atactic proportion of 15 % by
=
weight and below, copolymers of ethylene and propylene with
an ethylene content of 5 % by weight or below, copolymers
of propylene with C4-C8 olefins with an olefin content of
% by weight or below, and terpolymers of propylene,
ethylene and butylene with an ethylene content of 10 % by
weight or below and with a butylene content of 15 % by
weight or below are preferred propylene polymers for the
base layer, wherein isotactic propylene homopolymer is
particularly preferred. The specified percentages by weight
relate in each case to the respective polymers.
Furthermore, a mixture of the specified propylene
homopolymers and/or copolymers and/or terpolymers and other
polyolefins, in particular of monomers with 2 to 6 C atoms,
is suitable, wherein the mixture contains at least 50 % by
weight, in particular at least 75 % by weight, of propylene
polymer. Suitable other polyolefins in the polymer mixture
are polyethylenes, in particular HDPE, MDPE, LDPE, VLDPE
and LLDPE, wherein the proportion of each of these
polyolefins does not exceed 15 % by weight in relation to
the polymer mixture.
In an opaque embodiment the base layer of the film or the
monolayer film contains vacuole-initiating fillers in a
quantity of at most 30 % by weight, preferably 5 to 25 % by
weight, in relation to the weight of the opaque base layer.
Vacuole-initiating fillers are solid particles that are
incompatible with the polymer matrix and, as the films are
stretched, lead to the formation of vacuole-like cavities.
The vacuole-initiating fillers generally have a minimum
size of 1 pm in order to lead to an effective, i.e. opaque-
making, quantity of vacuoles. The mean particle diameter of
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the particles is generally 1 to 6 pm, preferably 1.5 to
pm. The chemical nature of the particles plays a
subordinate role.
Conventional vacuole-initiating fillers are inorganic
and/or organic materials incompatible with polypropylene,
such as aluminium oxide, aluminium sulphate, barium
sulphate, calcium carbonate, magnesium carbonate, silicates
= such as aluminium silicate (kaolin clay) and magnesium
silicate (talc) and silicon dioxide, from which calcium
carbonate and silicon dioxide are preferably used. The
conventionally used polymers incompatible with the polymers
of the base layer are considered as organic fillers, in
particular copolymers of cyclic olefins (COC) as described
in EP-A-0 623 463, polyesters, polystyrenes, polyamides,
halogenated organic polymers, wherein polyesters such as
polybutylene terephthalates and cycloolefin copolymers are
preferred. Incompatible materials or incompatible polymers
in the sense of the present invention means that the
material or the polymer is present in the film in the form
of separate particles or in the form of a separate phase.
In a further opaque embodiment the base layer or the
monolayer films, additionally or alternatively to the
vacuole-initiating fillers, contain pigments, for example
in a quantity from 0.5 to 10 % by weight, preferably 1 to
8 % by weight, in particular 1 to 5 % by weight. The
specified quantities relate to the weight of the layer.
Pigments in the sense of the present invention are
incompatible particles that essentially do not lead to
vacuole formation as the film is stretched. The, for
example, colouring effect of the pigments is caused by the
particles themselves. Pigments are both what are known as
"white pigments" which colour the films white, and
"coloured pigments" which provide the film with a bright or
black colour. Generally the mean particle diameter of the
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pigments lies in the range from 0.01 to 1 pm, preferably
0.01 to 0.7 pm, in particular 0.01 to 0.4 pm.
Conventional pigments are materials such as aluminium
=
oxide, aluminium sulphate, barium sulphate, calcium
carbonate, magnesium carbonate, silicates such as aluminium
silicate (kaolin clay) and magnesium silicate (talc),
silicon dioxide and titanium dioxide, from which white
= pigments such as calcium carbonate, silicon dioxide,
titanium dioxide and barium sulphate are preferably used.
Titanium dioxide is particularly preferred. Various
modifications and coatings of TiO2 are known per se in the
prior art.
The density of the film is determined essentially by the
density of the base layer. The density of the base layer
generally lies in a range from 0.45-0.95 g/cm3. The
vacuoles reduce the density of the base layer, and pigments
increase the density of the base layer compared with the
density of polypropylene (-0.9 g/cm3).
The thickness of the film lies generally in a range from 20
to 100 pm, preferably 25 to 60 pm, in particular 30 to
50 pm. Insofar as the films have a multi-layered structure,
the thickness of the base layer is between 10 and 60 pm,
preferably between 10 and 40 pm. The above-mentioned
thicknesses are to be understood without the coating
comprising (i) acrylate polymer and/or (ii) halogen-
containing vinyl and/or vinylidene polymers and/or (iii)
polymers based on vinyl alcohol (VOH).
Insofar as the film is multi-layered, the films also
comprise, besides the specified base layer, further layers
that are applied at least to one side or to both opposite
sides of the base layer. A three-layered structure of the
film thus results in the case of two cover layers.
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The thickness of the cover layer is generally 0.5-3 pm. In
a further embodiment of the invention intermediate layers
are also located on one or both sides between the cover
layer and the base layer, the thickness of said
intermediate layers lying in the range from 1 to 8 pm. With
a combination of intermediate layer and cover layer, these
together preferably have a total thickness from 2 to 8 pm.
= The cover layers can be formed as a sealable layer, wherein
this is understood to mean both heat-sealable and cold-
sealable layers. Cold seal coatings can be applied directly
to the surface of a monolayer film. However, it is
generally preferred to cover the base layer first with a
coextruded polymer layer and to apply the cold seal coating
to this polymer cover layer. Suitable materials for the
hot-sealable cover layer are the homopolymers, copolymers
and terpolymers specified hereinafter.
To improve the adhesion, the surface of the film is
subjected, prior to the coating in a manner known per se by
means of corona, flame or plasma, to a method in order to
increase the surface tension. The surface tension of the
layer thus treated then lies typically in a range from 35
to 45 mN/m. This surface treatment can be performed on one
or both surfaces of the film.
The above-described cover and intermediate layer generally
contain at least 80 % by weight, preferably 90 to <100 % by
weight of olefin polymers or mixtures thereof, and
optionally also conventional additives, in each case in
effective quantities. Suitable polyolefins are, for
example, polyethylenes, propylene copolymers and/or
propylene terpolymers, and also the propylene homopolymers
already described in conjunction with the base layer.
Suitable propylene copolymers or terpolymers are generally
constructed from at least 50 % by weight of propylene units
= CA 02891169 2015-05-11
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and ethylene units and/or butylene units as comonomer.
Preferred mixed polymers are static ethylene-propylene
copolymers with an ethylene content from 2 to 10 % by
= weight, preferably 5 to 8 % by weight, or static propylene-
butylene-1 copolymers with a butylene content from 4 to
25 % by weight, preferably 10 to 20 % by weight, in each
case in relation to the total weight of the copolymer, or
static ethylene-propylene-butylene-1 terpolymers with an
= ethylene content from 1 to 10 % by weight, preferably 2 to
6 % by weight, and a butylene-1 content from 3 to 20 % by
weight, preferably 8 to 10 % by weight, in each case in
relation to the total weight of the terpolymer. These co-
and terpolymers generally have a melt flow index from 3 to
15 g/10 min, preferably 3 to 9 g/10 min (230 C, 21.6 N DIN
53735) and a melting point from 70 to 145 C, preferably 90
to 140 C (DSC).
Suitable polyethylenes are, for example, HDPE, MDPE, LDPE,
LLDPE and VLDPE, from which HDPE and MDPE types are
particularly preferred. The HDPE generally has an MFI (50
N/190 C) of greater than 0.1 to 50 g/10 min, preferably
0.6 to 20 g/10 min, measured in accordance with DIN 53 735,
and a viscosity number, measured in accordance with DIN 53
728, part 4, or ISO 1191, in the range from 100 to
450 cm3/g, preferably 120 to 280 cm3/g. The crystallinity
is 35 to 20 %, preferably 50 to 80 %. The density, measured
at 23 C in accordance with DIN 53 479, method A, or ISO
1183, lies in the range from >0.94 to 0.96 g/cm3. The
melting point, measured with DSC (maximum of the melt
curve, heating rate 20 C/min), lies between 120 and
140 C. Suitable MDPE generally has an MFI (50 N/190 C) of
greater than 0.1 to 50 g/10 min, preferably 0.6 to
20 g/10 min, measured in accordance with DIN 53 735. The
density, measured at 23 C in accordance with DIN 53 479,
method A, or ISO 1183, lies in the range from >0.925 to
0.94 g/cm3. The melting point, measured with DSC (maximum
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of the melt curve, heating rate 20 C/min), lies between
115 and 130 C.
The film generally contains, in the respective layers,
conventional stabilisers and neutralising agents in
conventional quantities, and optionally antiblocking agents
in the cover layer(s). Only additives or quantities of
additives that do not impair the coatings are added as
lubricants and antistatic agents to the layers.
The conventional compounds having a stabilising effect for
ethylene, propylene and other olefin polymers can be used
as stabilisers. The added quantity of said compounds lies
between 0.05 and 2 % by weight. Phenolic stabilisers,
alkali/alkaline earth stearates and/or alkali/alkaline
earth carbonates are particularly suitable. Phenolic
stabilisers are preferred in a quantity from 0.1 to 0.6 %
by weight, in particular 0.15 to 0.3 % by weight, and with
a molar mass of more than 500 g/mol. Pentaerythrityl
tetrakis-3-(3,5-di-tertiary buty1-4-
hydroxyphenyl)propionate or 1,3,5-trimethy1-2,4,6-tris(3,5-
di-tertiary butyl-4-hydroxybenzyl)benzene are particularly
advantageous.
Neutralising agents are preferably calcium carbonate and/or
dihydrotalcite (DHT) of a mean particle size of at most
0.7 pm, an absolute particle size of less than 10 pm, and a
specific surface area of at least 40 m2/g. Neutralising
agents in a quantity from 50 to 1000 ppm, in relation to
the layer, are generally used.
Suitable antiblocking agents are inorganic additives such
as silicon dioxide, calcium carbonate, magnesium silicate,
aluminium silicate, calcium phosphate and the like and/or
incompatible polymers, such as polymethyl methacrylate
(PMMA) polyamides, polyesters, polycarbonates and the like,
preferably polymethyl methacrylate (PMMA), silicon dioxide
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and calcium carbonate. The effective quantity of
antiblocking agent lies in the range from 0.1 to 2 % by
weight, preferably 0.1 to 0.5 % by weight, in relation to
the respective cover layer. The mean particle size lies
=
between 1 and 6 pm, in particular 2 and 5 pm, wherein
particles with a spherical form, as described in EP-A-0 236
= 945 and DE-A-38 01 535, are particularly suitable.
= The film provided in the packaging according to the
invention is produced by means of processes and methods
known per se.
In respect of the subsequent coating, the film should
generally have no migrating additives in any layer, for
example should comprise no lubricants or antistatic agents,
since these may lead to problems with regard to the
adhesion of the coating.
COATING:
The polyolefin-based films used within the scope of the
present invention, in particular the films based on
biaxially oriented polypropylene (boPP) films, have a
coating comprising (i) acrylate polymer and/or (ii)
halogen-containing vinyl and/or vinylidene polymers and/or
(iii) polymers based on vinyl alcohol (VOH). The coating
may be present on one or both sides of the film.
The total thickness of the coating per side of the film is
generally between 0.1-5 pm, preferably between 0.5-3 pm. "
The coating may be applied in a multiple layers, wherein
combinations of different materials/polymers, for example
acrylate polymer and polyvinylidene dichloride (PVDC), are
also used. In the present case, multiple layers means that,
per layer, one of the specified materials selected from the
group acrylate polymer, polyvinylidene dichloride (PVDC) or
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=
polymers based on vinyl alcohol (VOH) is present as primary
component.
The film is generally treated initially on the side to be
=
coated so as to increase the surface tension. Once the
surface tension has been increased, an adhesion promoter is
- usually applied to the surface to be coated. Such adhesion
promoters are known per se and are based for example on
. polyurethane, acrylate polymers or polyethylene imines. The
adhesion promoters can also be applied in multiple layers
(secondary adhesion promoter layer), wherein combinations
of different adhesion promoters are also possible. In the
present case, multiple layers means that, per layer, one of
the above-mentioned adhesion promoters is present as
primary component. If aqueous polyethylene imine solution
is applied as adhesion promoter, this usually contains 1 %
by weight of polyethylene imine. Polyethylene imine
solution promotes the subsequent coating, as described in
EP-A-0255870.
The coating materials according to the invention are (i)
acrylate polymer and/or (ii) halogen-containing vinyl
polymers and/or vinylidene polymers and/or (iii) polymers
based on vinyl alcohol (VOH). These are in each case
arranged as a specific layer. Specific layers are
homogeneous layers made of a defined coating material.
Here, mixtures of the above-specified materials/polymers
are not desirable for the respective coating material, but
are not ruled out in the form of copolymers.
Besides the above-specified materials, the coatings
possibly also contain further components, for example as
lubricants, preferably non-migrating lubricants, such as
waxes and/or antiblocking agents.
The coating materials according to the invention are
applied as dispersions, in particular aqueous dispersions,
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of which the solids content is between 10 to 70 % by
weight, preferably 20-60 % by weight.
The acrylate polymers used in accordance with the invention
=
are preferably acrylate homopolymers and/or acrylate
copolymers based on, for example, alkyl acrylates, such as
methyl methacrylate and/or ethyl acrylate, or further
comonomers, such as unsaturated carboxylic acids or
= substituted vinyl compounds. An acrylate copolymer can be
constructed from 2 or more different monomers. Furthermore,
mixtures of the respective acrylate homopolymers and/or
acrylate copolymers are possible. Materials of this type
are obtainable on the market for example under the name
NeoCryl BT-36 and NeoCryl FL-711 from the company DSM
NeoResins (Netherlands) or under another name from the
company BASF. Preferred aqueous coating dispersions based
on acrylate polymer comprise at least 80 % by weight
acrylate dispersion, at least 10 % by weight wax
dispersion, at least 12 % by weight dispersion of a
colloidal silica, and at least 7 % by weight of
antiblocking agent dispersion. The differences to make up
100 % by weight consist of water. The quantity of acrylate
coating per side of the film after drying is generally
between 0.1 and 1.5 g/m2. The thickness of this acrylate
layer is <2.0 pm, inclusive of the layer of the adhesion
promoter.
The halogen-containing vinyl polymers and/or vinylidene
polymers used in accordance with the invention are
preferably polymers based on vinyl chloride homopolymers
and/or vinylidene chloride homopolymers and/or copolymers,
wherein the comonomer originates from the group of vinyl
acetates, vinyl halides or acrylates. The individual
monomers can be present in different weighting in the
copolymer. Such materials are obtainable on the market for
example under the name Diofan A 297, Diofan A 114 and
Diofan B 200 from the company SolVin.S.A. (Belgium).
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Preferred aqueous coating dispersions based on halogen-
containing vinyl polymers and/or vinylidene polymers, in
particular polyvinylidene dichloride (PVDC), comprise at
least 95 % by weight of PVDC acrylate copolymer dispersion,
at least 10 % by weight of wax dispersion, at least 7 % by
weight of antiblock dispersion. The differences to make up
100 % by weight consist of water. The quantity of coating
per side of the film after drying is generally between 2.5
= and 4 g/m2. The thickness of this layer is <4.5 pm,
inclusive of the layer of the adhesion promoter.
The polymers based on vinyl alcohol (VOH) used in
accordance with the invention are vinyl polymers that are
known per se. Preferred aqueous coating materials based on
vinyl alcohol (VOH) are ethylene vinyl alcohol (EVOH) and
comprise 5-15 % by weight of a mixture of ethylene vinyl
alcohol and polyvinyl alcohol, preferably in the ratio 0.8-
1.2 to 1.2-0.8, in particular 1:1 ratios by weight. The
quantity of coating per side of the film after drying is
generally between 0.5 and 1.0 g/m2 for coating materials
based on vinyl alcohol (VOH). The thickness of this layer
is <2.0 pm, inclusive of the layer of the adhesion
promoter.
The coating materials according to the invention are
applied preferably after the increase of the surface
tension, for example by corona treatment, whereby the
adhesion is improved. As already mentioned, an adhesion
promoter is usually applied to the side to be coated
following the surface treatment and is dried. Insofar as a
secondary adhesion promoter (second adhesion promoter
layer) is advantageous, this is also applied. The adhesion
promoter and the coating materials are applied in
accordance with methods known per se, such as roller
coating (roll application systems, for example with
engraved rolls), curtain coating, spray coating. The
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- 15 -
applied coating is then dried using conventional drying
methods (for example hot air).
The coated films are used in accordance with the invention
=
such that the coated side of the film faces towards the
loaded cardboard. Surprisingly, the coating in direct
- contact with the loaded cardboard constitutes an effective
migration barrier. Thus, the alternative metallisation of
' the film or of the cardboard can be omitted. The packaging
according to the invention is therefore preferably free
from an additional metal layer. This, however, does not
rule out metallic prints or similar metallic decorations.
Cost-efficient packaging made of loaded cardboard packaging
can thus be produced, with which no considerable quantities
or even no quantity of mineral oils migrate into the
foodstuff.
DEFINITION OF RECYCLED CARDBOARD:
The cardboard based on recycled cardboard used within the
scope of the present invention is constituted by cardboard
packaging that comprises significant quantities of mineral
oils and is thus subject to the provisions of COMMISSION
REGULATION (EC) no. 1935/2004 of 27 October 2004 (also
referred to hereinafter or below as loaded cardboard
packaging).
Cardboard packaging of this type based on recycled
cardboard typically contains at least 300-1000 mg/kg
mineral oil. These mineral oils are referred to as "mineral
oil saturated hydrocarbons" (MOSH) or as "mineral oil
aromatic hydrocarbons" (MOAN). The MOSH and NOAH mineral
oils are often also specified in terms of their carbon
chains, for example as MOSH 14-24, MOSH 24-35, NOAH 14-24
and NOAH 24-35, wherein the numerical value reflects the
number of carbon atoms. The exact composition of the MOSH
and NOAH mineral oils is dependent on the type of recycled
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cardboard, i.e. the fractions of MOSH 14-24, MOSH 24-35,
NOAH 14-24 and NOAH 24-35 are different.
The film provided in the foodstuffs packaging according to
the invention has good barrier properties with respect to
MOSH and NOAH mineral oils, in particular with respect to
MOSH 14-24, MOSH 24-35, NOAH 14-24 and NOAH 24-35.
-
.
The film provided in the foodstuffs packaging according to
the invention preferably has a good barrier to MOSH and
NOAH mineral oils, such that it may come into contact with
foodstuffs in accordance with COMMISSION REGULATION (EC)
no. 1935/2004 of 27 October 2004. A foodstuff simulant,
i.e. a test medium, that mimics dry foodstuffs pursuant to
COMMISSION REGULATION (EC) no. 10/2011 of 14 January 2011
is understood to be a foodstuff. The behaviour of this
foodstuff simulant mimics the migration from foodstuff
contact materials.
With the use according to the invention of the coated film
in the foodstuffs packaging according to the invention,
merely at most 1 %, in particular at most 0.5 %, of the
MOSH 14-24 fraction present in the recycled cardboard
preferably migrates into a foodstuff simulant pursuant to
COMMISSION REGULATION (EC) no. 10/2011 of 14 January 2011
(Tenax obtainable from the company Buchem B.V, poly(2,6-
diphenyl-p-phenylene oxide), particle size 60-80 mesh, pore
size 200 nm), when the recycled cardboard comprises at
least 300-1000 mg/kg mineral oil (sum of MOSH 14-24, MOSH
24-35, NOAH 14-24 and NOAH 24-35) and the proportion of the
fraction MOSH 14-24 in the mineral oil is at least 30 % by
weight. The above migration measurement is taken at 40 C
and for the duration of 10 days.
With the use according to the invention of the coated film
in the foodstuffs packaging according to the invention,
merely at most 1.6 %, in particular at most 1.4 %, of the
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..
MOSH 24-35 fraction present in the recycled cardboard
preferably migrate into a foodstuff simulant pursuant to
COMMISSION REGULATION (EC) no. 10/2011 of 14 January 2011
(Tenax obtainable from the company Buchem B.V, poly(2,6-
-
diphenyl-p-phenylene oxide), particle size 60-80 mesh, pore
size 200 nm), when the recycled cardboard comprises at
= least 300-1000 mg/kg mineral oil (sum of MOSH 14-24, MOSH
24-35, NOAH 14-24 and NOAH 24-35) and the proportion of the
. fraction MOSH 24-35 in the mineral oil is at least 10 % by
weight. The above migration measurement is taken at 40 C
and for the duration of 10 days.
With the use according to the invention of the coated film
in the foodstuffs packaging according to the invention,
merely at most 0.5 %, in particular at most 0.3 %, of the
NOAH 14-24 fraction present in the recycled cardboard
preferably migrates into a foodstuff simulant pursuant to
COMMISSION REGULATION (EC) no. 10/2011 of 14 January 2011
(Tenax obtainable from the company Buchem B.V, poly(2,6-
diphenyl-p-phenylene oxide), particle size 60-80 mesh, pore
size 200 nm), when the recycled cardboard comprises at
least 300-1000 mg/kg mineral oil (sum of MOSH 14-24, MOSH
24-35, NOAH 14-24 and NOAH 24-35) and the proportion of the
fraction MOAH 14-24 in the mineral oil is at least 10 % by
weight. The above migration measurement is taken at 40 C
and for the duration of 10 days.
With the use according to the invention of the coated film
in the foodstuffs packaging according to the invention,
merely at most 3.5 %, in particular at most 2.0 %,
particularly preferably at most 1.0 %, of the NOAH 24-35
fraction present in the recycled cardboard preferably
migrate into a foodstuff simulant pursuant to COMMISSION
REGULATION (EC) no. 10/2011 of 14 January 2011 (Tenax
obtainable from the company Buchem B.V, poly(2,6-diphenyl-
p-phenylene oxide), particle size 60-80 mesh, pore size 200
nm), when the recycled cardboard comprises at least 300-
CA 02891169 2015-05-11
. - 18 -
1000 mg/kg mineral oil (sum of NOSH 14-24, MOSH 24-35, NOAH
14-24 and NOAH 24-35) and the proportion of the fraction
NOAH 24-35 in the mineral oil is at least 1 % by weight.
The above migration measurement is taken at 40 C and for
the duration of 10 days.
= The present invention also relates to the use of the film
described in the introduction for the production of
foodstuffs packaging comprising recycled cardboard.
The film contained in the foodstuffs packaging according to
the invention is produced by means of extrusion or
coextrusion methods known per se, wherein the stenter
method is preferred in particular.
To this end, the melts corresponding to the individual
layers of the film are coextruded through a flat film die,
the film thus obtained is removed for solidification on one
or more roll(s), the film is then stretched (oriented), the
stretched film is then heat set and optionally plasma-,
corona- or flame-treated at the surface layer intended for
treatment.
More specifically, as in the extrusion method, the polymers
or the polymer mixture of the individual layers is/are
compressed here in an extruder and liquefied, wherein
optionally added additives may already be contained in the
polymer or in the polymer mixture. Alternatively, these
additives can also be incorporated via a master batch.
The melts are then optionally pressed jointly and
simultaneously through a flat film die (slit die), and the
pressed multilayer film is removed on one or more take-off
rolls at a temperature from 5 to 100 C, preferably 10 to
50 C, wherein said film cools and solidifies.
= CA 02891169 2015-05-11
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The film thus obtained is then stretched longitudinally and
= transversely to the extrusion direction, which leads to an
orientation of the molecule chains. The longitudinal
= stretching is preferably performed at a temperature from 80
to 150 C, expediently with the aid of two rolls running at
different speeds in accordance with the sought draw ratio,
= and the transverse stretching is preferably performed at a
temperature from 120 to 170 C with the aid of an
= appropriate clip frame. The longitudinal draw ratios lie in
the range from 4 to 8, preferably 4.5 to 6. The transverse
draw ratios lie in the range from 5 to 10, preferably 7 to
9.
The stretching of the film is followed by the heat setting
of said film (heat treatment), wherein the film is held for
approximately 0.1 to 10 s long at a temperature from 100 to
160 C. The film is then usually rolled up using a winding
device.
Following the biaxial stretching, one or both surface/s of
the film is/are preferably plasma-, corona- or flame-
treated in accordance with one of the known methods. The
treatment intensity generally lies in the range from 35 to
45 mN/m, preferably 37 to 45 mN/m, in particular 38 to
41 mN/m.
For the alternative corona treatment the film is passed
through between two conductor elements serving as
electrodes, wherein a sufficiently high voltage, usually an
AC voltage (approximately 10,000 V and 10,000 Hz), is
applied between the electrodes so that spray or corona
discharges can take place. Due to the spray or corona
discharge, the air above the film surface is ionised and
reacts with the molecules of the film surface, such that
polar deposits in the essentially unipolar polymer matrix
are produced. The treatment intensities lie within the
conventional scope, wherein 37 to 45 mN/m are preferred.
CA 02891169 2015-05-11
=
- 20
The coextruded multi-layer film is then provided on one or
both sides on one or both outer surface(s) with the above-
described coatings in accordance with the methods known per
se.
= To characterise the raw materials and the films, the
following measurement methods were used:
MELT FLOW INDEX
The melt flow index was measured in accordance with DIN 53
735 and 21.6 N load and 230 C.
DETERMINATION OF THE ETHYLENE CONTENT
The ethylene content of the polyolefin copolymers was
determined by means of 13C-NMR spectroscopy. The
measurements were taken using a nuclear magnetic resonance
spectrometer from the company Bruker Avance 360. The
copolymer to be characterised was dissolved in
tetrachloroethane, such that a 10 % mixture was produced.
Octamethyltetrasiloxane (OTMS) was added as reference
standard. The nuclear magnetic resonance spectrum was
measured at 120 C. The spectra were evaluated as described
in J.C. Randall Polymer Sequence Distribution (Academic
Press, New York, 1977).
MELTING POINT AND MELT ENTHALPY
The melting point and the melt enthalpy were determined by
means of a DSC (differential scanning calometry)
measurement (DIN 51 007 and DIN 53 765). A few milligrams
(3 to 5 mg) of the raw material to be characterised were
heated in a differential calorimeter with a heating rate of
20 C per minute. The heat flow rate was plotted against
the temperature and the melting point was determined as
CA 02891169 2015-05-11
- 21 -
maximum of the melt curve, and the melt enthalpy was
determined as the area of the respective melt peak.
DENSITY
The density was determined in accordance with DIN 53 479,
method A.
* SURFACE TENSION
The surface tension was determined by means of ink methods
in accordance with DIN 53 364.
FRICTION
The friction was measured in accordance with DIN 533375.
MIGRATION MEASUREMENT
The migration of the NOSH and NOAH mineral oils was
measured in accordance with the method developed by the BfR
(Federal Institute for Risk Assessment) in collaboration
with the Kantonalen Labor, Zurich. It was based on an
analysis by means of gas chromatography of the mineral oils
following manual pre-separation by column chromatography
("determination of hydrocarbons from mineral oil (NOSE and
NOAH) or plastics (POAH, PAO) in packaging materials and
dry foodstuffs by means of solid phase extraction and GC-
FID"). The method was presented at the conference "Mineral
oils in Foodstuffs Packaging - Development and Solution
Approaches", which took place on 22 and 23 September 2011
in Berlin. A test substance Tenax0 obtainable from the
company Buchem B.V (poly(2,6-diphenyl-p-phenylene oxide),
particle size 60-80 mesh, pore size 200 nm) was used as
foodstuff simulant.
CA 02891169 2015-05-11
- 22 -
Test structure (Figure 1): A cardboard saturated with a
defined quantity of mineral oil was covered with the sample
to be measured, Tenaxe was distributed thereon, and the
= entire assembly was stored in a closed system made of
aluminium (temperature 40 C, time 10 days).
= Following the storage time, the Tenax0 was extracted with
hexane and suitable internal standards were added (solid
. phase extraction), then a separation was performed by means
of liquid chromatography (LC) with a stationary phase made
of silica gel doped with 0.3 % silver nitrate and a mobile
phase initially of hexane, then a mixture of hexane,
dichloromethane and toluene. The eluate was separated in a
third step by means of gas chromatography, and detection
was performed in a manner deviating from the above-cited
BfR method by means of GC-MS/FID.
The invention will now be explained by the following
examples.
PRODUCTION OF THE UNCOATED FILMS:
The films type 1 to 3 were produced in accordance with the
known coextrusion method. Here, a transparent three-layered
film with cover layers on either side and with a total
thickness of 25 pm was produced by coextrusion and
subsequent stepwise orientation in the longitudinal and
transverse direction. The cover layers each had a thickness
of 0.9 pm.
FILM TYPE 1:
Base layer:
Approx. 100 % by weight isotactic propylene homopolymer
with a melting point of 163 C and
a melt flow index of 3.2 g/10 min.
CA 02891169 2015-05-11
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,
Cover layers:
Approx. 100 % by weight static ethylene-propylene-butylene
terpolymer with an ethylene
= content of 3 % by weight and a
butylene content of 6 % by weight
(rest propylene).
0.1 % by weight Si02 as antiblocking agent with a
= mean particle size d50 of 5 pm
The production conditions in the individual method steps
were:
Extrusion: Temperatures Base layer: 260 C
Cover layers: 240 C
Temperature of the
take-off roll: 30 C
Longitudinal
stretching: Temperature: 120 C
Longitudinal draw ratio: 5.5
Transverse
stretching: Temperature: 160 C
Transverse draw ratio: 9
Fixing: Temperature: 130 C
Convergence 20 %
All layers of the film contained neutralising agents and
stabilisers in the conventional quantities. Both surfaces
were pre-treated by means of corona in order to increase
the surface tension.
FILM TYPE 2
A film was produced in accordance with film type 1. In
contrast to film type 1, both cover layers contained a
static ethylene-propylene copolymer with an ethylene
CA 02891169 2015-05-11
- 24 -
content of approx. 4.5 % by weight and a softening point of
approx. 130 C.
FILM TYPE 3 (COMPARATIVE EXAMPLE)
A film was produced in accordance with film type 1. In
contrast to film type 1, the base layer additionally
contained erucic acid amide as lubricant in a quantity of
0.05 % by weight and a bis-ethoxylated amine in a quantity
of 0.09 % by weight.
COATING:
A polyethylene imine adhesion promoter was first applied to
the above-described uncoated film and then dried. Different
coatings made of acrylate polymer, PVDC or vinyl alcohol
polymer were then applied by means of engraving rolls.
EXAMPLE 1:
A 1 % by weight polyethylene imine dispersion was applied
on either side to film type 1 and was dried. An acrylate
polymer dispersion from the company NeoResins with trade
name BT36 with a solids content of 20 % by weight was then
applied likewise on either side and was dried. Besides the
acrylate polymer dispersion, additives such as Carnauba wax
and antiblocking agent were used. The quantity was selected
such that sufficient antiblock effect for unwinding the
film roll and also a frictional value of approximately 0.3
were achieved.
The thickness of the acrylate polymer layer was 0.8 pm,
which corresponded to a coating weight of 0.8 g/m2.
EXAMPLE 2:
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=
- 25 -
,
*
A film as described in Example 1 was produced. In contrast
= to Example 1, however, only side 1 of film type 1 was
coated with the acrylate polymer dispersion. Side 2 was
= coated on the adhesion promoter layer with a polyvinyl
chloride dispersion from the company Solvin with the trade
name Diofan A114 having a solids content of 50 % by weight.
- Similarly to Example 1, additives (Carnauba wax and
antiblock) were also added here to both sides. The
' thickness of the polyvinyl chloride layer was 2.0 pm, which
corresponded to a coating weight of 3.5 g/m2.
EXAMPLE 3:
A 1 % by weight polyethylene imine dispersion was applied
to film type 2 on side 1 and was dried. A vinyl alcohol
dispersion from the company Kurary with the trade name
Mowiol 3-98 and Exceval AQ-4005 (in the ratio 1:1) having a
solids content of, on the whole, 10 % by weight was applied
thereto and dried.
The thickness of the coating layer was 0.8 pm, which
corresponded to a coating weight of 0.8 g/m2. In addition,
additives such as Carnauba wax and antiblocking agent were
used. The quantity was selected such that sufficient
antiblock effect for unwinding the film roll and also a
frictional value of approximately 0.3 were achieved.
EXAMPLE 4:
A film was produced in accordance with Example 3. In
contrast to Example 3, a 1 % by weight polyethylene imine
dispersion was additionally applied to side 2 and was
dried. An acrylate polymer dispersion from the company
NeoResins with the trade name BT36, having a solids content
of 20 % by weight was applied to this adhesion promoter
layer and dried. Besides the acrylate polymer dispersion,
additives such as Carnauba wax and antiblocking agent were
CA 02891169 2015-05-11
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used. The quantity was selected such that sufficient
antiblock effect for unwinding the film roll and also a
frictional value of approximately 0.3 were achieved. The
thickness of the acrylate polymer layer was 0.8 pm, which
corresponded to a coating weight of 0.8 g/m2.
COMPARATIVE EXAMPLE:
= Film type 3 was used without coating.
The above coating was varied in accordance with the
invention and is summarised in Table 1:
Coating Coating Mineral oil
barrier
Front side-side 1 Rear side-side 2 +++ very good
(facing towards ++ good
the cardboard) + satisfactory
- no barrier
Example 1 Acrylate polymer Acrylate polymer MOSH 14-24 +++
(film type 1: 0.8 pm coating 0.8 pm coating MOSH 24-35 ++
terpo-homo- layer thickness layer thickness NOAH 14-24 +++
terpo) NOAH 24-35 +++
Example 2 Acrylate polymer PVDC MOSH 14-24 ++
(film type 1: 0.8 pm coating 2.0 pm coating MOSH 24-35 ++
terpo-homo- layer thickness layer thickness NOAH 14-24 +++
terpo) NOAH 24-35 +++
Example 3 Vinyl alcohol none MOSH 14-24 ++
(film type 2: polymer (EVOH) MOSH 24-35 +
Copo-homo- 0.8 pm coating NOAH 14-24 +++
Copo) layer thickness NOAH 24-35 +/-
Example 4 Vinyl alcohol Acrylate polymer MOSH 14-24 +++
(film type 2: polymer (EVOH) 0.8 pm coating MOSH 24-35 ++
Copo-homo- 0.8 pm coating layer thickness NOAH 14-24 +++
Copo) layer thickness NOAH 24-35 ++
Comparative none none MOSH 14-24 -
example 1 MOSH 24-35 -
i CA 02891169 2015-05-11
= - 27 -
,
,
( f ilm type 3)
MOAH 14-24 -
MOAH 24-35 -
,
