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MULTILAYER FILM
The present invention relates to a multilayer film.
Single layer plastics films are well known in the art. These films are used for a wide
range of purposes such as plastic shopping bags and food packaging. While the known
single layer films function satisfactorily in some applications there is a need for plastic
films exhibiting properties not found in current allowable single layer films. Examples
of some well known single layer films include High Density Polyethylene (HDPE),
Linear Low Density Polyethylene (LLDPE), Low Density Polyethylene (LDPE) and
Styrene Butadene Copolymers (SBC).
HDPE films are approved for use in the food industry. They have good mechanical
property and exhibit some degree of toughness. In addition, products made of HDPE
are recyclable and are economically viable.
LLDPE films also meet the criteria for approval for use in the food industry. They also
have good mechanical property, are recyclable and are economically viable. In addition,
they may be heat shrunk, that is they may be subjected to a heat source to shrink the film
around a product for improved packaging.
LDPE is not approved for food use, however, it exhibits other properties not found in
HDPE or LLDPE. LDPE films exhibit easy manual tear, are heat shrinkable and are
recyclable. In addition, layers of the film are capable of bonding with each other upon
heat exposure, without binding to any packaged contents. The films also exhibit good
clarity which is a desirable feature in certain applications.
SBC films are also able to bind between themselves on exposure to heat without binding
to the contents. In addition, they exhibit easy manual tear, are heat shrinkable,
recyclable and have excellent clarity.

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There is a need for a film which combines all of the features described in relation to the
known single layer films. Further additional features are also desirable. Unfortunately,
it has not proved possible to blend together known materials to achieve a suitable film.
Blending the known plastics materials together results in a loss of the desired features,
rather than combining them. For example, the polyolefms (HDPE, LLDPE and LDPE)
can be mixed from a processing point of view but the resulting film does not exhibit
improved features. It has not proved possible to blend the polyolefms with SBC. The
resulting film becomes brittle, hazy and unable to perform satisfactorily.
There is a need to produce a film which combines a variety of features not currently
available in a single layer plastics film. The characteristics required for the film are:
i) the film should meet the standards for use in the food industry i.e.
must be non-toxic with no heavy metal content;
ii) it should have good mechanical property and some degree of
toughness;
iii) it should have some degree of easy manual tear-ability and heat
shrink-ability;
iv) it should have some degree of low slip on the outside and higher slip
in the inside;
v) it should be able to maintain the pack integrity for use as transit
packaging and/or display packaging;
vi) it should be recyclable;
vii) it should be able to bond between its own films and must not stick to
the content;
viii) it should be affordable and offer better economics than corrugated
carton;
ix) it should be able to be combined with different features such as UV
resistance, flame retardance, anti-static (permanent or not) and/or
conductivity; and
x) it should offer reasonable clarity/haze to enable the content to be seen.

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One particular area where such a film would be desirable is as a flexible enclosure for
use in the vacuum packaging of products. In particular, a film with the properties listed
above would be particularly suitable for use with the vacuum packaging apparatus
described in WO 02/083505, the contents of which are incorporated herein by reference.
The vacuum packaging apparatus disclosed in WO 02/083505 comprises means for
evacuating air from within a flexible enclosure, means for compressing the enclosure
prior to evacuation of the air and means for sealing sealable meeting portions of the
unsealed enclosure, wherein the means for compressing the enclosure comprises a
pressure plate mounted in a plane parallel to the plane of an opposed surface upon which
the unsealed enclosure is disposed in use. The apparatus functions very well and results
in the production of a neatly vacuum packed product. However, to a certain extent, the
quality of the vacuum packed product is determined by the characteristics of the film
which the enclosure is made of. The flexible enclosure must be capable of providing
an airtight enclosure which is capable of being readily sealed e.g. by heat sealing. The
enclosure is provided as a pre-formed pocket, preferably closed along a portion of the
periphery to leave an open mouth for access to the interior and sealing.
When the air has been extracted from within the enclosure the open mouth is sealed and
the package is complete, generally, this leaves a protruding flap of the enclosure material
at the mouth of the bag. If this flap of material is punctured it will allow air to enter the
enclosure thus destroying the integrity of the vacuum package product. Similarly, if the
film is punctured at any other point it will allow air to enter the package, causing the
package to expand and lose its vacuum packed shape.
It is the object of the present invention to overcome the problems of the prior art or at
least to provide an alternative to currently sealable films.
According to the present invention there is provided a multilayer film which loses its
memory when subjected to heat shrinking comprising at least three layers, wherein at
least one of the layers comprises a styrene-butadiene copolymer and the other layers

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comprise at least one material selected from the group consisting of HDPE, LLDPE and
LDPE.
The term " loses its memory", as used herein, refers to the fact that the multilayer film
does not return to its original shape once it has been subjected to heat shrinking. In
effect, the film loses the memory of its original shape and maintains its new shape. Heat
shrinking involves subjecting the film to a heat source in a shrink tunnel. The film
shrinks around the contours of the packaged goods. This is an important features of the
present invention, particularly with respect to the use of the film in vacuum packing.
Vacuum packing of products has two main benefits: i) it prolongs the life of food
products by providing a barrier, ii) it reduces transportation costs of compressible
products. It is in relation to the second of these benefits that the multilayer film
according to the present invention is particularly useful.
Compressible products can be defined as any product the size of which may be reduced
by the application of a compression force. When the product is compressed air is forced
out. In conventional vacuum packing the air is evacuated from the enclosure using a
vacuum pump and the enclosure is then sealed, usually by means of a heat seal. This
enables the product to be transported in its compressed form. If the enclosure is
punctured air will be able to enter the enclosure and the vacuum packed product will
expand to the maximum size permitted by the enclosure. However, if the enclosure is
manufactured from a multilayer film according to the present invention and the vacuum
packed product is subjected to heat shrinking after compression, air extraction and
sealing of the enclosure then the vacuum packed product will not expand if the enclosure
is punctured. This is because the multilayer film loses its memory when subjected to
heat shrinking. Consequently, it does not attempt to return to its original shape when
air enters the enclosure. The result is only a minimal increase in package size.
Preferably, an inner surface of the multilayer film adheres to a corresponding surface of
film when heated. The two layers of film preferably adhere to one another without
actually becoming sticky themselves. Consequently, the two layers of film will stick to
one another, but not to other surfaces, such as goods which are being packed. This is

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particularly useful when the multilayer film is used to make an enclosure for vacuum
packing goods. As described above, the product is compressed, air is evacuated from
within the enclosure and the enclosure is heat sealed. Next the vacuum packed product
is subjected to heat shrinking. This causes the enclosure to shrink around the product
to form a neat package. Layers of multilayer film which come into contact stick together
but the film does not stick to the product. A periphery of film is provided around the
product as a result of its compression. In a conventional enclosure if the enclosure was
punctured in the peripheral region air would get in and destroy the integrity of the
package. However, if the enclosure is manufactured with a multilayer film according
to the present invention then the layers of film in the peripheral region will adhere
together. Thus, if the enclosure is punctured in the peripheral region, no air can enter
the enclosure.
The multilayer film may comprise a layer comprising SBC sandwiched between an inner
layer comprising LLDPE and an outer layer comprising LLDPE. Preferably, the film
is a three layer film. The LLDPE may conveniently comprise a mixture of high-slip
LLDPE and non-slip LLDPE or, alternatively, it may comprise only high-slip LLDPE.
It is preferred that the LLDPE layers are provided with one or more additives. The
additives may be selected from the group consisting of processing aids and anti-oxidants
in an amount up to 1%.
Alternatively, the multilayer film may comprise an inner layer comprising SBC, a
middle layer comprising LLDPE and an outer layer comprising HDPE. The LLDPE
layer may conveniently comprise a mixture of high-slip LLDPE and non-slip LLDPE.
The SBC layer may conveniently comprise high impact polystyrene. The high impact
polystyrene may be present in an amount up to 5%.
As a further alternative, the multilayer film may comprise an inner layer comprising
HDPE, a middle layer comprising LLDPE and an outer layer comprising SBC. The
LLDPE layer may conveniently comprise a mixture of high-slip and non-slip LLDPE.

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The SBC preferably has a density in the range from 0.98 to 1.20 g/cm3. The SBC
preferably has a melt flow rate in the range from 5.0 to 10.0 g/l0min.
The HDPE preferably has a density in the range from 0.945 to 0.960 g/cm3. The HDPE
preferably has a melt flow rate in the range from 0.02 to 0.10 g/10 min.
The LLDPE has a density in the range from 0.916 to 0.930 g/cm3 and a melt flow rate
of0.03 to 3.00 g/10min.
The LDPE has a density in the range from 0.916 to 0.930 g/cm3 and a melt flow rate in
the range 0.03 to 8.00 g/lOmin.
The outer layer of the film preferably comprises from 10-45% of the total thickness of
the film, the middle layer preferably comprises 10-80% of the total thickness of the film
and the inner layer preferably comprises from 10-45% of the total thickness of the film.
The film is preferably a three layer structure. The structure may be symmetrical about
the middle layer, i.e. the inner and outer layers being the same width. Alternatively, the
structure may be non-symmetrical, i.e. the inner and outer layers being of different
thicknesses.
The multilayer film may also be a five layer structure. As with the three layer structure,
the structure may be symmetrical or non-symmetrical about the middle layer.
According to a second aspect of the present invention there is also provided a method
of vacuum packing a product in an enclosure comprising the following steps, in any
suitable order:
i) placing the product within the enclosure;
ii) compressing the enclosure with the product inside;
ii) evacuating air from within the enclosure;

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iv) sealing the open mouth of the enclosure with the product inside; and
v) subjecting the enclosure and product to heat treatment in a shrink tunnel.
The invention will now be described, by way of example, with reference to the following
examples. The films are coextruded multilayer films and are manufactured using a
conventional co-extrusion blown film production line such as the one manufactured by
Reifenhauser GmbH & Co. KG Macbinenfabrik. The films were formed into
enclosures of the type used in vacuum packing and were tested for their suitability as
such.
Example 1
A three layer film was produced by the blown film coextrusion method. The film
comprised an outer layer of LLDPE, a middle layer of SBC and an inner layer of
LLDPE. The inner and outer layers of LLDPE comprised 75% of Nova 9022D, a high-
slip LLDPE manufactured by Nova Chemicals, and 25% of Nova 9022C, a non-slip
LLDPE manufactured by Nova Chemicals. The SBC was K Resin KR05.
The first extruder, which forms the outer layer of the film was operated at 180°C and at
a screw pressure of 480 bar. The screw operated at 41 RPM.
The second extruder, which forms the middle layer of the film was operated at 190°C
and at a screw pressure of 300 bar. The screw operated at 57 RPM.
The third extruder, which forms the inner layer of the film was operated at 180°C and
at a screw pressure of 380 bar. The screw operated at 50 RPM. The speed of the nip
roll was 28 m/min and the bubble neck was 80 cm.
The resulting film was a symmetrical film with a total thickness of 50 |im. The inner
and outer layers were both 15mm thick and the middle layer was 20 |im thick. The film
was stable, exhibited some melt fracture and did not have good optical properties.

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However, the film lost its memory when subjected to heat shrinking in a shrink tunnel
and layers of the film were capable of bonding to each other without bonding to any
packaged goods within the enclosure.
Example 2
A three layer film was produced by the blown film coextrusion method. The film
comprised an outer layer of LLDPE, a middle layer of SBC and an inner layer of
LLDPE. The inner and outer layers comprised 74% ofNova 9022D, a high slip LLDPE,
25% of Nova 9022C, a non-slip LLDPE, and 1% of a processing aid and anti-oxidant.
The SBC copolymer was K Resin KR05.
The first extruder, which forms the outer layer of the film, was operated at 200°C and
at a screw pressure of 480 bar. The screw operated at 41 RPM.
The second extruder, which form the middle layer of the film, was operated at 190°C
and at a screw pressure of 300 bar. The screw operated at 57 RPM.
The third extruder, which forms the inner layer of the film, was operated at 200°C and
at a screw pressure of 380 bar. The screw operated at 50 RPM. The speed of the nip
roll was 25 m/min and the bubble neck was 80 cm.
The resulting film was a symmetrical film with a total thickness of 50 p,m. The inner
and outer layers were both 15 |im thick and the middle layer was 20 mm thick. The melt
fractures present in the film of Example 1 were reduced. However, the film exhibited
a tendency to stick together during manufacture which leads to production difficulties.
It is believed the high loading of non-slip LLDPE causes the melt not to go out
smoothly. It is believed that some amount of non-slip LLDPE is required to provide a
film with non-slip properties. However, it appears that too much may be undesirable
and the level will need to be determined on a case-by-case basis. When tested the film
lost its memory when subjected to heat shrinking in a shrink tunnel and layers of the

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film were capable of bonding to each other without bonding to any packaged goods
within the enclosure.
Example 3
A three layer film was produced by the blown film coextrusion method. The film
comprised an outer layer of LLDPE, a middle layer of SBC and an inner layer of
LLDPE. The inner and outer layers comprised 89% ofNova 9022D, a high-slip LLDPE,
10% of Nova 9022C, a non-slip LLDPE and 1 % of a processing aid and an anti-oxidant.
The SBC was K Resin KR05.
The first extruder, which forms the outer layer of the film, was operated at 195°C and
at a screw pressure of 453 bar. The screw operated at 41 RPM.
The second extruder, which forms the middle layer of the film, was operated at 190°C
and at a screw pressure of 236 bar. The screw operated at 40 RPM.
The third extruder, which forms the inner layer of the film, was operated at 195°C and
at a screw pressure of 405 bar. The screw operated at 40 RPM. The speed of the nip
roll was 23 m/min and the bubble neck was 80 cm.
The resulting film was a symmetrical film with a total thickness of 50mm. The inner and
outer layers were both 15mm thick and the middle layer was 20mm thick. The film
exhibited no melt fractures, but was still prone to sticking during manufacture. When
tested, the film lost its memory when subjected to heat shrinking in a shrink tunnel and
layers of the film were capable of bonding to each other without bonding to any
packaged goods within the enclosure.
Example 4
In order to determine the effect of removing the non-slip LLDPE, a further three layer
film was produced by the blown film co-extrusion method. The film comprised an outer

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layer of LLDPE, a middle layer of SBC and an inner layer of LLDPE. The inner and
outer layers comprised 99% of Nova 9022D, ahigh-slip LLDPE and 1% of aprocessing
aid and anti-oxidant. The SBC was K Resin KR05.
The first extruder, which forms the outer layer of the film, was operated at 195°C and
at a screw pressure of 453 bar. The screw operated at 41 RPM.
The second extruder which forms the middle layer of the film, was operated at 190°C
and a screw pressure of 236 bar. The screw was operated at 40 RPM.
The third extruder, which forms the inner layer of the film, was operated at 195°C and
a screw pressure of 405 bar. The screw was operated at 40 RPM. The speed of the nip
roll was 23 m/min and the bubble neck was 80 cm.
The resultant film was a symmetrical film with a total thickness of 50mm. The inner
and outer layers were both 15|mm thick and the middle layer was 20 mm thick. The film
exhibited no melt fractures and did not stick together during manufacture. In addition,
the film was relatively soft and had good clarity. When subjected to heat in a shrink
tunnel the film loses its memory and layers of film will adhere to each other without
sticking to the goods which they surround.
Example 5
A three layer film was produced using the blown film co-extrusion method. The film
comprised an outer layer of HDPE, a middle layer of LLDPE and an inner layer of SBC.
The outer layer comprised 100% of the high molecular weight polyethylene El-ene F15,
manufactured by Cementhai Chemicals. The middle layer comprised a mixture of 50%
of the high-slip Nova 9022D and 50% of the non-slip Nova 9022C. The inner layer
comprised 98% of K Resin KR05 and 2% of the high impact polystyrene Idemitsu
HH30, manufactured by Idemitsu Petrochemical.

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The first extruder, which forms the outer layer of the film, was operated at 205°C and
at a screw pressure of 478 bar. The screw operated at 20.1 RPM.
The second extruder, which forms the middle layer of the film, was operated at 195°C
and at a screw pressure of 408 bar. The screw operated at 68.6 RPM.
The third extruder, which forms the inner layer of the film, was operated at 190°C and
at a screw pressure of 213 bar. The screw operated at 23.9 RPM. The speed of the nip
roll was 25 m/min and the bubble neck was 110 cm.
The resultant film was a symmetrical film with atotal thickness of 50[im. The inner and
outer layers were both 10mm thick and the middle layer was 30mm thick. The bubble
was stable and the film had good clarity. However, there was a tendency for the film to
stick together during manufacture. When subjected to heat in a shrink tunnel the film
loses its memory and layers of the film will adhere to one another without sticking to the
goods being packaged.
Example 6
A three layer film was prepared according to the operating parameters of Example 5.
The composition of the film was identical to that of Example 5 with the exception that
the high impact polystyrene content in the inner layer was increased to 3%.
The bubble was stable, the film was less prone to sticking during manufacture and it had
reasonable clarity. It appears as though the increased high impact polystyrene content
aids the processability of the film. The film lost its memory when heated in a shrink
tunnel and it was able to adhere to itself but not to the goods when used as a vacuum
packing enclosure.

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Example 7
A three layer film was prepared according to the operating parameters of Example 5.
The composition of the film was identical to that of Example 5 with the exception that
the high impact polystyrene content in the inner layer was increased to 4%.
The bubble was stable. The resultant film was less prone to sticking than the films of
Examples 5 and 6. The clarity of the film was less than that of those of Examples 5 and
6, although it was still reasonably see-through. The film lost its memory when subjected
to heat in a shrink tunnel and it was able to adhere to itself but not to any goods which
it was surrounding.
Example 8
A three layer film was prepared according to the general structure of Examples 5,6 and
7. However, the high impact polystyrene content of the inner layer was increased to 5%.
The first extruder, which forms the outer layer of the film, was operated at 205°C and
at a screw pressure of 513 bar. The screw operated at 24 RPM.
The second extruder, which forms the middle layer of the film, was operated at 195°C
and at a screw pressure of 417 bar. The screw operated at 70.4 RPM.
The third extruder, which forms the inner layer of the film, was operated at 185°C and
at a screw pressure of 262 bar. The screw operated at 36.5 RPM. The speed of the nip
roll was 20 m/min and the bubble neck was 110 cm.
The resultant film had a stable bubble, was less prone to sticking during manufacture but
the clarity was not as good as the films of Examples 5-7. It appears as though high
impact polystyrene improves the processability of the film at the expense of the
appearance. Thus, the composition of the film must be selected based on consideration
about its end use. For example, if it is to be used to package goods which must be seen

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in the package then the amount of high impact polystyrene must be limited.
Alternatively, if the packaging is merely for transportation then higher levels of high
impact polystyrene may be used. As with the films of Examples 5 - 7, the film loses its
memory when subjected to heat in a shrink tunnel and it will stick to itself but not to the
goods which it surrounds.
Example 9
A three layer film was prepared using the blown film co-extrusion method. The film
comprised an outer layer of SBC, a middle layer of LLDPE and an inner layer of HDPE.
The outer layer comprised 100% of K Resin KR10. The middle layer comprised a
mixture of 5 0% of the high-slip LLDPE made by Exxon Mobil and soldaslOOl XV and
50% of the non-slip LLDPE made by Exxon Mobil and sold as 1001KW. The inner
layer comprised 100% of the HDPE sold under the brand Hizex 7000F.
The first extruder, which forms the outer layer of the film, was operated at 200°C and
at a screw pressure of 342 bar. The screw operated at 30 RPM.
The second extruder, which forms the middle layer of the film, was operated at 200°C
and at a screw pressure of 349 bar. The screw operated at 53 RPM.
The third extruder, which forms the middle layer of the film, was operated at 200°C and
at a screw pressure of 571 bar. The screw operated at 54 RPM. The speed of the nip
roll was 41 m/min and the bubble neck as 100 cm.
The resultant film was a non-symmetrical film with a total thickness of 50mm. The
outer layer and middle layer were 17mm thick and the inner layer was 16mm thick. The
bubble was stable and the film exhibited some curling in the direction of the SBC layer.
When subjected to heat in a shrink tunnel the film loses its memory and layers of the
film were able to adhere to one another without sticking to the goods being packed.

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Examples 10 -11
In order to demonstrate the effect that the manufacturing parameters had on the film two
further examples were prepared using the film composition of Example 9 with different
manufacturing parameters.
In Example 10 the first extruder was operated at 200°C with a screw pressure of 286 bar
and a screw speed of 30 RPM. The second extruder was operated at 205°C with a screw
pressure of 237 bar and a screw speed of 40 RPM. The third extruder was operated at
205°C with a screw pressure of 479 bar and a screw speed of 50 RPM. The speed of the
nip roll was 27 m/min and the bubble neck was 100 cm.
The resultant film had a stable bubble and exhibited less curling than that of Example
9.
In Example 11 the first extruder was operated at 200°C with a screw pressure of 237 bar
and a screw speed of 30 RPM. The second extruder was operated at 205°C with a screw
pressure of 105°C and a screw speed of 35 RPM. The third extruder was operated at
205°C with a screw pressure of 240 bar and a screw speed of 50 RPM. The speed of the
nip roll was 27 m/min and the bubble neck was 100 cm.
The resultant film had a stable bubble and did not curl towards the SBC layer.
All of the multilayer films in Examples 1 - 11 are suitable for use in food related
applications. In addition, they are particularly suited for use as enclosures for vacuum
packing. During manufacture of the film the bubble is flattened to create a tube of film.
The tube may be slit down one side to produce a sheet of film or it may be sealed across
the width of the film to make individual enclosures which may be used as bags or
vacuum packing pouches.
The layers of the film may be treated during production to impart a range of potentially
desirable characteristics to it, depending on the intended use. Such characteristics can

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include low slip, opacity, resistance to ultra-violet light, water resistance, air moisture
resistance, biodegradability, pest repellency (including dog and bird repelling),
fragrancing and colour change after a certain age (to indicate expiry of shelf life of the
packed product).

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CLAIMS
1. A multilayer film which loses its memory when subjected to heat shrinking
comprising at least three layers, wherein at least one of the layers comprises
a styrene-butadiene copolymer and the other layers comprise at least one
material selected from the group consisting of HDPE, LLDPE and LDPE.
2. A multilayer film according to claim 1, wherein an inner surface of the film
adheres to a corresponding surface of film when heated.
3. A multilayer film according to claim 1 or claim 2, wherein the film comprises
a layer comprising SBC sandwiched between an inner layer comprising
LLDPE and an outer layer comprising LLDPE.
4. A multilayer film according to claim 3, wherein the LLDPE comprises a
mixture of high slip LLDPE and non-slip LLDPE.
5. A multilayer film according to claim 3, wherein the LLDPE comprises only
high slip LLDPE.
6. A multilayer film according to claim 4 or claim 5, wherein the inner layer and
the outer layer comprise one or more additives.
7. A multilayer film according to claim 6, wherein the or each additive is
selected from the group consisting of processing aids and antioxidants.
8. A multilayer film according to claim 6 or claim 7, wherein the or each
additive is present in an amount up to 1%.
9. A multilayer film according to claim 1 or claim 2, wherein the film comprises
an inner layer comprising SBC, a middle layer comprising LLDPE and an
outer layer comprising HDPE.

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10. A multilayer film according to claim 9, wherein the middle layer comprises
a mixture of high-slip LLDPE and non-slip LLDPE.
11. A multilayer film according to claim 9 or claim 10, wherein the inner layer
comprises high impact polystyrene.
12. A multilayer film according to claim 11, wherein the high impact polystyrene
is present in an amount up to 5%.
13. A multilayer film according to claim 1 or claim 2, wherein the film comprises
an inner layer comprising HDPE, a middle layer comprising LLDPE and an
outer layer comprising SBC.
14. A multilayer film according to claim 13, wherein the middle layer comprises
a mixture of high slip LLDPE and non-slip LLDPE.
15. A multilayer film according to any preceding claim, wherein the SBC has a
density in the range from 0.980 to 1.20 g/cm3.
16. A multilayer film according to any preceding claim, wherein the SBC has a
melt flow rate in the range from 5.0 to 10.0 g/l0min.
17. A multilayer film according to any preceding claim, wherein the HDPE has
a density in the range from 0.945 to 0.960 g/cm3
18. A multilayer film according to any preceding claim, wherein the HDPE has
a melt flow rate in the range from 0.02 to 0.10 g/10 min.
19. A multilayer film according to any preceding claim, wherein the LLDPE has
a density in the range from 0.916 to 0.930 g/cm3.

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20. A multilayer film according to any preceding claim, wherein the LLDPE has
a melt flow rate of 0.03 to 3.00 g/l0min.
21. A multilayer film according to any preceding claim, wherein the LDPE has a
density in the range from 0.916 to 0.930 g/cm3.
22. A multilayer film according to any preceding claim, wherein the LDPE has a
■ melt flow rate in the range 0.03 to 8.00 g/10min.
23. A multilayer film according to any preceding claim,wherein the outer layer
comprises from 10 - 43% of the total thickness of the film, the middle layer
comprises from 10 - 80% of the total thickness of the film and the inner layer
comprises from 10 - 45% of the total thickness of the film.
24. An enclosure in the form of a preformed pocket having an open mouth and
closed sides, the enclosure being formed from a multilayer film according to
any preceding claim.
A method of vacuum packing a product in an enclosure according to claim 24
comprising the following steps, in any suitable order:
i) placing the product within the enclosure;
ii) compressing the enclosure with the product inside;
ii) evacuating air from within the enclosure;
iv) sealing the open mouth of the enclosure with the product inside; and
v) subjecting the enclosure and product to heat treatment in a shrink tunnel.

A multilayer film which loses its memory when subjected to heat shrinking comprising at least three layers, wherein
at least one of the layers comprises a styrene-butadiene copolymer and the other layers comprise at least one material selected from
the group consisting of HDPE, LLDPE and LDPE.