Note: Descriptions are shown in the official language in which they were submitted.
~ 33~i43
MULT I LAYERED F I LM
The present invention relates to a multilayered
film having a base layer and at least one surface layer,
to a process of producing the multilayered film and to
the use of the multilayered film for wrapping food.
Backqround of the Invention
Films which are used for wrapping food such as
vegetables, meat or fish have to meet a number of
requirements, among others a good puncture resistance
and a good ela,tic recovery. Polyvinylchloride (PVC)
films meet these requirements and have been used in the
past to a great extent for wrapping food. However, due
to the increasing environmental concerns about the
extended use of PVC films the skilled artisans have
tried to replace PVC films, with other films having
similar properties but causing less environmental
2~ concerns. Much research effort has been spent on
ethylene homo- or copolymers or mixtures of these
polymers with other polymers.
2 133~43
The abstract of Japanese patent application
61200142 discloses a composition which is composed of 80
to 99.9 weight percent of polyolefin resin containing
ethylene/ acrylic copolymer as essential component and
20 to 0.1 weight percent of a water-absorbable resin of
polyacrylic acids. The polyolefin is for example
polyethylene, an ethylene/vinyl acetate copolymer, an
ethylene/acrylic acid copolymer or polypropylene. The
ethylene/acrylic copolymer is for example an
ethylene/acrylic acid copolymer or an ionic copolymer
thereof. Evidently a monolayered film is made from this
resin composition of which the essential property is
said to be its excellent water-adsorbability.
The abstract of Japanese patent application
61083038 discloses a multilayered bag which has an inner
layer of a polyolefinic resin and an anti-fogging agent.
It is disclosed that each layer can be produced of a
polyolefin resin such as polyethylene, polypropylene, an
ethylene/vinyl acetate polymer, an ethylene/acrylic acid
copolymer etc. Unfortunately, the disclosed teaching is
so broad and unspecific with respect to the polymers in
the multilayered film that the skilled artisan does not
learn what type of polymer are to be selected in order
to produce a film having the desired properties.
US patent 4,277,578 relates to heat shrinkable
packaging films from polyolefin blends. The blends
consist of an ethylene/alpha-olefin copolymer with a
density of up to 0.91 g/cm3 with a polymer (a) and/or
(c). Polymer (a) is a low density polyethylene and/or a
3 1339~3
copolymer of ethylene with a vinylester, with an
unsaturated aliphatic monocarboxylic acid such as
acrylic acid or with its alkyl ester and polymer (c) is
a crystalline polypropylene, a high density polyethylene
and/or crystalline polybutene-l. US patent 4,277,578
teaches that a film of poor dimensional stability is
obtained when the amount of polymers (c) is below a cer-
tain level and that such a film ~ends to undergo
deterioration by aging.
US patent 4,619,859 discloses a multilayered
oriented film of good sealability and stretchability
having at least three layers, preferably five layers. It
contains a base layer which consists of a mixture of an
ethylene type polymer and a soft elastomer, a core layer
produced of polypropylene and polybutene-l and a surface
layer containing an ethylene type polymer, a soft
elastomer, crystalline 1,2-polybutadiene and/or a soft
ionomer resin from an ethylenic copolymer. The ethylene
type polymer is selected from a low density
polyethylene, a copolymer of ethylene with a vinyl ester
monomer, an aliphatic unsaturated monocarboxylic acid or
with an alkyl ester of that monocarboxylic acid. Instead
or in addition to the ethylene type polymer the base
layer may contain a crystalline polypropylene or a
crystalline polybutene-l for improving the strength and
the workability of the film. Unfortunately, the
production of the multilayered oriented film which
contains at least three different layers and wherein at
least one of the layers contains a mixture of various
types of polymers is labour intensive and the film
structure is complicated. For example, the preparation
of the mixtures by kneading and extrusion requires
expensive machines.
4 ~3~i3
European patent application 0 243 965 discloses
a multilayered film useful for packaging vegetables and
fruits. The film has a base layer A and at least one
surface layer B containing an anti-fogging agent. The
base layer A is a mixture of l) one or more copolymers
of alpha-olefins having 2 to lO carbon atoms and 2) one
or more copolymers containing monomer units selected
from vinyl acetate, acrylic acid and styrene and other
copolymerisable monomer units such as ethylene,
propylene, acrylates, butadiene and the like. Random or
block copolymers of 2 or more alpha-olefins having 2 to
lO carbon atoms are preferred for producing the surface
layer(s) B). This film is designed for producing bags.
F~rthermore, the disclosed teaching is so broad and un-
specific with respect to the polymers in themultilayered film that the skilled artisan does not
learn what type of polymer are to be selected in order
to produce a film which is useful for wrapping food
instead of producing bags.
Accordingly, it would be desirable to provide
new multilayered films which are useful for packaging
food products, in particular fresh food such as meat,
fish, cheese, vegetables and fruit. In particular, it
would be desirable to provide such films which do not
require expensive blending techniques or equipment when
manufacturing them.
It would also be desirable to provide films
which can be wrapped around the food in automotive
packaging machines in particular in high speed packaging
machines. Furthermore, it would be desirable to provide
films with good puncture resistance and
1339~3
deformation recovery properties. A high puncture
resistance is for example important when packaging meat
with bones. Good deformation recovery properties are
very important for films which will be used as a
packaging material for food. Typically the food is sold
in self- service shops where many customers touch the
packages. By touching the film it is deformed at several
spots. When the food is wrapped in films having
insufficient deformation recovery properties the
packaged food looks unfresh after a short time and often
cannot be aOld anymore.
Summary of the Invention
One aspect of the invention is a multilayered
film having a base layer (A) of which the film-forming
component is at least one copolymer of Al) ethylene and
A2) an ethylenically unsaturated carboxylic acid or an
ionomer thereof and
at least one surface layer (B) of which the
film-forming component is an ethylene homopolymer or a
copolymer of ethylene and at least one alpha-olefin
having from 3 to 12 carbon atoms or a blend of said
polymers,
the weight of the base layer (A) being from 25
to 75 percent by the total weight of (A) and IB).
A further aspect of the present invention is a
process for producing the multilayered film by
coextruding or in-line laminating the base layer (A) and
at least one surface layer (B).
6 1~39~43
Yet another aspect of the present invention is
the use of the multilayered film for wrapping food.
Yet another aspect of the present invention is
a method of packaging food with the multilayered film of
the present invention wherein the film is wrapped around
the food and then sealed, preferably by heat.
Detailed description of the Invention
The multilayered film has a base layer (A) and
at least one surface layer (B). The weight of the base
layer (A) is from 25 to 75 percent, preferably from 30
to 70 percent and more preferably from 40 to 60 percent
of the total weight of (A) and (B). If the multilayered
film has more than one surface layer (B), the total
weight of the surface layers has to be chosen in such a
manner that the above mentioned weight ratios are met.
Most preferably, the multilayered film has two surface
layers (B) which cover both surfaces of base layer (A).
The film-forming component of base layer (A) is
at least one copolymer of Al) ethylene and A2) an
ethylenically unsaturated carboxylic acid or an ionomer
thereof. By "film- forming component" is meant that the
base laye- may contain known additives such as slip or
anti-block agents or tackifiers, however, that the
copolymer of ethylene and an ethylenically unsaturated
carboxylic acid is not mixed with substantial amounts of
other polymers such as polyethylene. By "substantial
7 ~339~ i3
amounts" are meant amounts which can influence the
properties of the film. The mentioned known additives
may be useful for facilitating the production of the
multilayered film. When the multilayered film of the
present invention only contains one surface layer (B),
it may be useful to include a known anti-fogging agent
into the base layer (A). In general, the copolymer of
Al) and A2) is not mixed with any amounts of other types
of polymers. The copolymer in base layer (A) preferably
contains in copolymerised form from 75 to 98 percent,
more preferably from 85 to 97 percent and most
preferably from 90 to 95 percent of a Al) ethylene and
preferably from 2 to 25 percent, more preferably from 3
to 15 percent and most preferably from 5 to 10 percent
of A2) an ethylenically unsaturated carboxylic acid or
an ionomer thereof, based on the total weight of Al) and
A2). Ethylenically unsaturated monocarboxylic acids are
preferred of which acrylic acid and methacrylic acid are
particularly preferred. Acrylic acid is the most
~ preferred comonomer in base layer (A). A portion or all
of the ethylenically unsaturated carboxylic acid may
have been converted into an ionomer thereof by treatment
with a basic material. Preferred ionomers are alkali
metal ionomers such as sodium ionomer, alkaline earth
metal ionomers such as magnesium and the zinc ionomers.
The density of the copolymer(s) in base layer (A)
generally is from 0.91 g/cm3 to 0.95 g/cm3, preferably
from 0.92 g/cm3 to to 0.94 g/cm3, measured according to
ASTM method D-792. The melt index preferably is from 0.1
g/10 min. to 30 g/10 min., more preferably from 1 g/10
min. to 20 g/10 min., measured according to ASTM method
D-1238, condition (E). The base layer (A) may contain
more than one type of copolymers of Al) ethylene and A2)
an ethylenically
- 8 1~39S4~
unsaturated carboxylic acid or an ionomer thereof.
However, when using a blend of such copolymers it is
recommended that all copolymers contain the same copoly-
merised monomer A2). Blending such polymers is not
difficult and does not require expensive blending
equipment. Most preferably, base layer (A) contains only
one type of film- forming polymer. A blending step can
be avoided and the films having a base layer (A) which
contains only one type of film-forming polymers have
surprisingly good deformation recovery properties.
The copolymer(s) in base layer (A) can be
prepared by methods well ~nown in the art. Typically it
is produced by a gas phase polymerisation process in a
high pressure autoclave. The base layer (A) may contain
a mixture of different copolymers of Al) and A2).
Exemplary of ethylene homopolymers which are
useful in the surface layer(s) (B) are the known high,
medium and low density homopolymers of ethylene. Useful
ethylene copolymers preferably contain ethylene in a
predominant amount, more preferably 80 percent or more,
most preferably from 80 to 95 percent and preferably a
minor amount, more preferably up to 20 percent, most
preferably 5 to 20 percent, of at least one alpha-olefin
having from 3 to 12, preferably from 4 to 8, carbon
atoms per alpha-olefin molecule. Mixtures of different
ethylene homopolymers and copolymers of ethylene and at
least one alpha-olefin are also useful. Using mixtures
requires an additional blending step which is preferably
avoided although it does not create major problems.
These polymers in surface layer(s) (B) preferably have
melt indexes, as determined by ASTM method D-1238
(190~C/2.16 kg) in the range of from 0.1
9 1339~43
g/10 min. to 50 g/10 min. and densities, as determined
by ASTM method D-792, in the range of from 0.880 g/cm3
to 0.990 g/cm3. Methods for the preparation of such
polymers are well known in the art, for example as
taught by Schildknecht, Polymer Processes Vol. X (1956)
or in Chem. Eng. News, 5 December 1977.
Preferred polymers in the surface layer(s) (B)
are linear low density polyethylenes.
By "linear low density polyethylene" (LLDPE) is
meant normally solid ethylene polymers suitable for
extrusion, casting, moulding or similar fabrication
produced by polymerization of ethylene with up to 25
percent by weight of the polymer of at least one alpha-
olefin having from 3 to 12, preferably 4 to 8, carbonatoms per olefin molecule.
The LLDPE copolymers preferably used in the
surface layer(s) (B) are those which are for example
prepared using coordination catalysts, e.g., the well
known Ziegler, Natta or Phillips catalysts. This
includes those made at low, intermediate or high
pressures. These ethylene polymers contain up to 25
percent, preferably from 5 to 15 percent, more
preferably from 5 to 10 percent, by weight of at least
one alpha-olefin comonomer which is preferably selected
from the group consisting of propylene, l-butene, 1-
isobutene, 4-methyl-1-pentene, l-pentene, l-isopentene,
l-hexene, l-isohexene, l-heptene, l-isoheptene, 1-
octene, l-isooctene, l-nonene, l-isononene, l-decene and
l-isodecene. l-Hexene, 4-methyl-1-pentene, l-butene,
propylene and in particular l-octene are the most
preferred comonomers. The amount of comonomers used
should generally be enough to result in polymer
1~9543
densitles in the low range of 0.880 to 0.935
gfcm3, preferably from 0.890 to 0.920 g/cm3. The copolymers
generally have a high molecular welght and have a melt lndex
(melt flow) ln the range of 0.1 to 30 dg/mln, preferably of
from 0.1 to 20 dgtmln. as measured by ASTM-D-1238 condltlon
(E). These LLDPE polymers are recognised ln the art as
havlng excellent strength, reslstance to tear propagatlon and
exhlblt good reslstance to tearlng or puncturlng. Thls
performance of the LLDPE polymers ls especlally important ln
food packaglng appllcatlons and most especlally ln packaglng
of meat.
By "llnear low denslty polyethylene" are also meant
terpolymers of ethylene, an alpha-olefln havlng 3 or 4 carbon
atoms and an alpha-olefln havlng 5 to 12 carbon atoms per
molecule whlch terpolymers are dlsclosed ln EP-A-010428. The
alpha-olefln having 3 or 4 carbon atoms to be terpolymerized
with ethylene ls propylene or butene-l. Examples of the
alpha-olefln havlng 5 to 12 carbon atoms lnclude l-pentene,
l-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, l-heptene,
l-octene, l-decene and l-dodecene of whlch l-octene is
preferred. The terpolymer ls preferably produced of 90 to
99.5 mol percent, more preferably 92 to 99 mol percent, of
ethylene, 0.2 to 9.8 mol percent, more preferably 0.3 to 7
mol percent, of the alpha-olefln having 3 or 4 carbon atoms,
and 0.2 to 9.8 mol percent, more preferably 0.3 to 7 mol
percent, of the alpha-olefln having 5 to 12 carbon atoms.
The llnear ethylene polymers havlng polymer densitles in the
range of 0.880 g/cm3 to 0.920 g/cm3
11 1~3~) i3
are usually referred to as linear very low density
polyethylene (VLLDPE). The density of the polymer can be
chosen according to the preferred properties of the
multilayered film. Generally at higher densities the
mechanical strength increases and at lower densities the
elastic recovery increases. The surface layer(s) (B) can
have more than one type of the described polymers,
however, preferably each surface layer only contains one
type of the described polymers. If the multilayered film
contains more than one surface layer (B), the polymer
need not be the same in all the surface layers (B). For
example, the multilayered film may consist of three
layers, of which the first surface layer (B) contains a
linear very low density polyethylene having a density
between 0.880 g/cm3 and 0.920 g/cm3 which results in
good mechanical properties such as elastic recovery and
tear resistance, the base layer (A) contains the above
described polymers and the second surface layer (B)
contains a linear low density polyethylene having a
density between 0.920 g/cm3 and 0.935 g/cm3 which
provides the film with the desired stiffness. The
surface layer(s) (B) may also contain a mixture of one
or more linear (very) low density polyethylenes and a
known low density polyethylene for improving the
tearability of the multilayered film.
The expression " film-forming component"
referring to surface layer (B) is defined in the same
way as said expression referring to the base layer (A).
In addition to the film-forming component the surface
layer(s) (B) may contain optional additives such as
stabilisers, anti-oxidants or lubricants. In some cases
it may be useful to incorporate an anti-fogging agent
12 1~3!~43
in one or all surface layers (B). Addition of an anti-
fogging agent is particularly recommended when the
multilayered film will be used for packaging material of
a high water content such as fruits or meat in order to
prevent a condensate of small water droplets on the sur-
face of the film which faces the packaged food. Usefulanti-fogging agents are known. Preferred types of anti-
fogging agents are compounds of Formula I
cpH(2p+l) ~ O(CH2CH2O)nH (I)
wherein n is an average number of 3 to 8 and p is 9 or
lO. The surface layer (B) generally contains from 0.8 to
5 percent by weight of the anti-fogging agent. When a
compound of Formula I is used, an amount of from 0.1 to
l.0 percent, preferably of from 0.4 to 0.8 percent by
weight of the surface layer (B) is usually sufficient.
It may also be useful to include a cling
additive such as a fatty acid ester or a polyisobutylene
or another known cling additive in the surface layer
(B), generally in an amount of 0.1 to 5 percent by
weight of the surface layer (B).
The overall thickness of the multilayered film
generally is from 5 to 40 micrometers, preferably from
13 1339~4~
10 to 20 micrometers, more preferably from 13 to 17
micrometers. Preferably the ratio of the thickness of
the base layer (A) to the total thickness of the surface
layer(s) (B) is from 0.5:1 to 2:1, more preferably from
0.75:1 to 1.3:1. Although there is no limitation of
thickness of each layer, it is preferred that the
thickness of the base layer (A) is from 5 to 10
micrometers, more preferably from 6 to 9 micrometers and
the thickness of each surface layer (B) is from 2 to 6
micrometers, more preferably from 3.0 to 4.5
micrometers.
The multilayered films of the present invention
can be prepared in a known way by coextruding or in-line
laminating the base layer (A) and at least one surface
layer (B). The production of blown and cast films is
generally known. When producing the multilayered films
by in-line laminating the base layer (A) and at least
one surface layer (B) it may be useful to include an
adhesive layer between the base layer (A) and the
surface layer(s) (B). Useful components for adhesive
layers are known. In general, the multilayered films of
the present invention do not contain an adhesive layer.
Preferably, cast films are produced by coextruding
layers (A) and (B) through a flat dye. Most preferably,
the produced multilayered film has a sequence of layers
B / A / B. Further preferred multilayered films have the
sequence B/A/B/A, B/A/B/A/B, B/A/B/A/B/A or
B/A//B/A/B/A/B and so on. Typically the multilayered
film is coextruded at a temperature of fro~ 180~C to
280~C, preferably of from 240~C to 260~C.
' 14 133~-4~
The multilayered films of the present invention
have a high puncture resistance and good deformation
recovery properties.
A further aspect of the present invention is
the use of the multilayered film of the present
invention for wrapping food. According to one method the
food may be wrapped by hand with the multilayered film
of the present invention. Preferably, the method of
wrapping food with the multilayered film is carried out
automatically. According to this method the food is
placed in a container or on a tray, the film of the
present invention is automatically wrapped around the
container or the tray and is sealed, for example by
applying heat. According to a preferred embodiment of
this method the packaging machine is equipped with a
roll of the multilayered film of the present invention.
A portion of the film is unrolled and cut while being
held by a spreading device. The container or tray having
the food is then brought into contact with the film;
preferably it is pushed upwards from beneath towards the
film. The film is then wrapped around the container or
the tray, preferably in such a way that the ends of the
film piece contact each other below the container or
tray. The ends of the film piece are then sealed
together, for example by heat sealing. Heat sealing can
be carried out by contacting the bottom of the container
or of the tray with a heated plate.
For sealing the films of the present invention
the films preferably are heated to a temperature between
80~C and 180~C, more preferably between 140~C and 160~C.
1~39~3
The multilayered film of the present invention
is useful for automatic packaging. Trials to
automatically package food with a film produced of an
ethylene homopolymer or a copolymer of ethylene and an
alpha-olefin only have not shown satisfactory results.
The use of the film of the present invention in a
process for automatically wrapping food is very
advantageous since the wrapping machine can be run at a
high speed. Generally the machine can be run at such a
speed that from 25 to 180, preferably from 80 to 120
containers or trays can be wrapped with the f lm per
~inute.
The invention is further illustrated by the
following Examples which should not be construed to
limit the scope of the invention. All parts and
percentages are by weight unless otherwise mentioned.
The following polymers and additives are used
for producing the multilayered films:
an ethylene/acrylic acid copolymer (EAA-l)
containing 9 weight percent copolymerised acrylic
acid and having a melt index of 1.5 g/10 min. and a
density of 0.938 g/cm3;
- an ethylene/acrylic acid copolymer (EAA-2)
containing 9 weight percent copolymerised acrylic
acid and having a melt index of 3.0 g/10 min. and a
density of 0.938 g/cm3;
- an ethylene/acrylic acid copolymer (EAA-3)
containing 9 weight percent copolymerised acrylic
16 13~9~13
acid and having a melt index of 5.0 9/lO min. and a
density of 0.938 g/cm3;
- a linear low density polyethylene (LLDPE-l) having a
nominal content of copolymerised l-octene of 7 - 8
weight percent, a melt index of 3.3 g/lO min. and a
density of 0.917 g/cm3;
- a linear low density polyethylene (LLDPE-2) having a
nominal content of copolymerised l-octene of 7 - 8
weight percent, a ~elt index of 2.3 g/10 min. and a
density of 0.917 g/cm3;
- a linear low density polyethylene (LLDPE-3) having a
nominal content of copolymerised l-octene of 6 - 7
weight percent, a melt index of 6.0 9/lO min. and a
density of 0.919 g/cm3;
- a linear very low density polyethylene (VLLDPE-l)
having a nominal conten~ of copolymerised l-octene
of lO - ll weight percent, a melt index of 2.0 g/lO
min. and a density of 0.912 g/cm3;
- a linear very low density polyethylene (VLLDPE-2)
having a nominal content of copolymerised l-octene
of ll - 12 weight percent, a melt index of 7.0 g/lO
min. and a density of 0.910 g/cm3;
The octene content in LLDPE-l, LLDPE-2, LLDPE-
3, VLLDPE-l and VLLDPE-2 is determined accordinc to ASTM
D-2238, Method B.
In all Examples and in Comparative Examples A
and B a three layer film is produced by flat dye
extrusion at a melt temperature between 240~C to 280~C
and at a line speed of 150 m/min. The thickness of the
1339543
17
film in all Examples and in Comparative Examples A and B
is between 14 and 16 micrometers. The thickness of the
base layer (A) iS about 7 to 8 micrometers and the
thickness of each surface layers ~B) is about 4
micrometers. In each Example and in Comparative Examples
5 A and B a film structure / A / B / A / iS produced
wherein the weight percentage of the layers is 25 / 50
/ 25.
In Comparative Example C a commercially
available monolayered polyvinylchloride film having a
thickness of 14 micrometers is used.
The physical properties of the produced films
15 listed in the following tables are measured as follows:
- dart drop impact (g): ASTM D-1709
- Elmendorf tear strength (g): ASTM D-1922
"MD" means: machine direction
"CD" means: cross direction.
The recovery (~) and the puncture energy (J)
are measured as described below:
a) Recovery
A tensile test machine JJ Type T 500 is used which is
equipped with a probe of 12.5 mm diameter having a
hemispherical tip of polytetrafluoroethylene. A film
sample is changed with a clamping ring having an inner
diameter of 125 mm. The probe is lowered until it just
touches the film samples (starting position). The probe
is then further lowered to a depth of 25 mm at a rate
18 133~ 3
of 100 mm/min. whereby the film sample is deformed. A
force/deflection curve is recorded. The deflection is
recorded on the x-axis.
The probe is then withdrawn from the film
sample at a rate of 100 mm/min. until it reaches its
starting position. One minute after the withdrawal of
the probe has commenced, the probe is relowered at the
same rate to the same depth and a second
force/deflection curve is recorded. The separation of
the first and the second curve on the x-axis is due to
the additional movement of the probe to contact the sur-
face of the film that has not entirely recovered after
the first deflection of 25 mm. The distance x between
the two curves is always measured at a force of 1
Newton. From the distance x between the two curves the
actual difference between the movement of the probe in
the second run and in the first run is determined and
the recovery in percent is calculated, based on this
difference and on the total deflection (25 mm).
b) Puncture resistance (puncture enerqy)
The same clamping system is used but an aluminium probe
having a diameter of 12.5 mm and a hemispherical tip
having a radius of 6.25 mm is used. The probe is lowered
at a rate of 500 mm/min. whereby the film sample is
deformed.
The puncture energy in Joules to break the film is
recorded.
O ~ O ~n O
Examples 1 to 3 an Comparative Example A
Film structureExample 1 Example 2 Example 3 Comp. Example A
LLDPE-1/EAA-2/LLDPE-1 LLDPE-1/EAA-1/LDPE-1 LLDPE-1/EAA-3/LLDPE-1 LLDPE-1NLLDPE-1/LLDPE-1
Dart drop 108 93 143
impact (g)
Elmendorf tear MD CD MD CD MD CD MD CD
resistance (g) 224 40 243 26 201 82 185 293
Puncture 074 0 65 0.60 0 89
"energy (J)
Recovery (~/~) 91 91 94 84 ~~
Table I
~3
13~9~3
Table I illustrates that a multilayered film
wherein a copolymer of ethylene and at least one alpha-
olefin having from 3 to 12 carbon atoms is used as a
film-forming component of the base layer (A) has a
considerably lower recovery than the films of the
present invention which have the same surface layers (B)
but which contain a copolymer of Al) ethylene and A2) an
ethylenically unsaturated carboxylic acid as a film-
forming component of the base layer (A).
The films of Examples 1 to 3 were subjected to
packaging trials with commercially available packaging
machines. The used packaging machines and the results of
the trials are listed in Table II:
Example Used machine/results
An Automac 44 machine; 40 packages
1 were wrapped. The film could easily
be cut in CD, sealed well and showed
an excellent recovery.
A Chick machine; trays having 3 or 4
apples were packed. The film could
2 easily be cut in CD, sealed well and
showed an excellent recovery.
An Automac 44 machine; 300 trays
having 4 or 5 apples were packed.
3 The film could easily be cut in CD,
sealed well and showed an excellent
recovery and strength.
An Automac 44 machine; trays having
4 or 5 apples were packed. The film
Comparative could easily be cut in CD, sealed
Example A well and showed a good film
strength. However, the recovery of
the film was insufficient.
Table II
21 1~39~43
The results of the packaging trials listed in
Table II confirm the measurements of the physical
properties listed in Table I.
O ~n O ~ O
Examples 4 and 5 and Comparative Examples B and C
Film structureExample 4 Example 5 Comp. Example B Comp. Example C
LLDPE-3/EAA-1/LLDPE-3 LLDPE-3/EAA-3/LLDPE-3 LLDPE-3/VLLDPE-2/LLDPE-3 PVC
Dart drop 86 105 85 252
impact (g)
Elmendorf tear MD CD MD CD MD CD MD CD
resistance (g) 138 45 163 151 261 469 26 46
Puncture 047 0 71 0 81 0.33
energy (J) ~,
Recovery (%) 93 93 91 95
Table 111
C5~
~-t
23 1~ 3g ~43
The puncture resistance (punture energy) of the
films of all Examples is considerably higher than the
puncture resistance of the PVC film of Comparative
Example C.
Besides the physical properties of the films
their behaviour in wrapping trials on a high speed
machine Automac 44 was evaluated. Trays with 4 or 5
apples were wrapped with the film. The films of Examples
4 and 5 and Comparative Example B could easily be cut in
CD and sealed well.
The film of Example 4 exhibited excellent
recovery and strength.
The film of Example 5 exhibited excellent
recovery but split in the machine direction in numerous
cases.
The film of Comparative Example B exhibited
insufficient recovery.
The comparison between Examples 4 and 5 shows
that the evaluation of the Elmendorf tear resistance is
not necessarily sufficient for predicting which film is
the most useful one for automatic food wrapping on a
given machine under given condi~ions such as machine
speed and force of the spreading device. Although the
film of Example 5 has a higher Elmendorf tear resistance
than the film of Example 4, the film of Example 4 showed
a higher strength in the food wrapping trial than the
film of Example 5. This difference is believed to be due
to the different testing conditions, i.e. a testing of a
substantially motionless film versus a testing of a film
running at a high speed on a packaging machine.
24 1339~43
Example 6
Film structure LLDPE-3/EAA-2/LLDPE-3
Dart drop impact (g) 170
Elmdendorf tear MD CD
resistance ~g) 181 51
10 Puncture energy (J) 0.80
Recovery (%) 88.0
Two different film samples having the structure
of the film of Example 6 were tested on a an Automac 44
machine as described in Example 1. The film samples
could easily be cut in cross direction, sealed well and
showed a good recovery and strength.
Examples 7 to 9
The same film structures as those in Example 1,
2 and 6 are prepared, their physical properties are
measured and their usefulness for automatic food
wrapping is determined as in Examples 1, 2 and 6.
However, the time period between the production and the
measurements of the films having the same structure
(Examples 1/7, Examples 2/8 and Examples 6/9) is several
months. Because of slightly different production and
test conditions, such as different temperatures,
different resin batches and so on, the results of the
physical properties are not the same
~ ~ 3g 5 i3
when measuring above mentioned individual films having
the same structure. However, Examples 7 to 9 also
confirm the superior recovery properties of the films of
the present invention compared with the film of
Comparative Example A (see Table IV) and the usefulness
of the films of the present invention for automatic food
wrapping (see Table V).
Examples 7 to 9
Fllm Structure Example 7 Example 8 Example 9
LLDPE-l~EAA-2/LLDPE-1 LLDPE-1/EAA-1/LLDPE-1 LLDPE-3/EAA-2/LLDPE-3
Dart drop 157 174 185
lmpact (g)
Elmendorf tear MD CD MD CD MD CD
resistance (g) 149 26 240 28 70 35
Puncture 0.75 0.66 0.75
energy (~)
Recovery (%) 95.1 g4.0 88.5
Table IV
N
1339S~13
27
Example Used machlne~results
_
7 Chlck machlne; trays havlng 3
or 4 apples were packed. The
film could easlly be cut ln
CD, sealed well and showed an
excellent recovery.
8 An Automac 44 machlne; trays
havlng 4 or 5 apples were
packed. The fllm could easlly
be cut ln CD, sealed well and
showed an excellent recovery
and strength.
9 Chlck machlne; trays having 3
or 4 apples were packed. The
fllm could easlly be cut ln
CD, sealed well and showed a
good recovery and strength.
Table V
,
. .
