Note: Descriptions are shown in the official language in which they were submitted.
~:3~7$9
-- 1 --
MULTILAYER FOOD WRAP ~ITH CLI~G
Field of the Invention
This invention relates to multilayer food
wrap films having ~ood cling properties and high
resistance to heat, making them ~uitable for use in
direct food contact cooking. The cling propertiefi
of the films enable them to cling to ~hemselves, or
to ensure a tight seal when the films are used as a
food wrap or a cover for containers.
Backaround of the Invention
Thermoplastic ~esin films are popularly
used as household wraps and bag~ to contain food and
other items. A necessary characteristic of such
wrap films is the ability to "cling", that is, to
adhere to itfielf or to form a tight seal with other
surfaces, as when the film is used as a cover for
containers. The clingabili~y of the film preserves
the freshness and moisture con~ent of wrapped food
items and al~o prevents the migration of food odors.
Thermoplastic resin films do not generally
possess inherent cling characteristics sufficient to
satisfactorily adheLe to themselves and other
surfaces. The cling charac~eristic of thermoplastic
films is generally obtained through the use of
so-called cling agent6. Cling agent6 are chosen for
their ability to produce a surface on a
thermoplastic film that can be sealed, opened and
resealed, and are selected with due care in
consideration of the use of thermoplastic films in
food contact applications.
D-14004
123~ 9
With the increa6ed u~e of microwave ovens,
it has become desirable for food cling wraps to he
used in microwave cooking. Currently, commercial
food wrap~ such as Saran ~rap , Handi-Wrap ,
and Glad Wrap are produced as a 6ingle layer
film 6tructure that i6 modified with addi~ives to
provide the desired "cling" property. These
commercial cling wraps are useful in microwave
cooking as a cover for microwave cooking utensil~
and, as such, are not in contact with the food with
which they are to be used. Functionally, it would
be desirable to have a food wrap ~hich withstands
higher temperatures so that it could be used in
direct food contact, and in es~ence, serve the
purpo6e of a microwave cooking utensil. That is,
food would be wrapped in the food wrap, frozen, and
when needed the food could be cooked in a microwave
oven in the original food wrap.
Commercial food cling wraps may be produced
from various polymers such as low density
polyethylene, polyvinylidene chloride copolymers,
and polyvinyl chloride copolymers. Currently, only
polyvinylidene chloride and polyvinyl chloride type
food cling wraps are able to with6tand ~omewhat
higher microwave oven cooking temperatures, that i~,
on the order of up to about 335F. Howevee, at
these temperatures, the polyvinylidene chloride and
polyvinyl chloride type food wraps have limited use
for direct food contact m;crowave cooking since many
fatty foods and foods high in sugar content require
higher cooking temperatures than such food wraps can
withstand without degrada~ion.
~- l40n4
~30~7~9
- 3 -
In addition, in the production of plastic
films for use as food wraps, a balance must be
attained between the film's "cling" and
"handleability" characteristics. "Handleability" is
the characteristic of the film to resist the
tangling that results from the film clinging to
itself during use. While cling agents impart good
cling properties to the film, it has been found that
an increase in the amount of cling agent that is
incorporated into the film corresponds to a decrease
in the handleability of the film. With increased
cling agent, the tendency of the film to adhere to
itself and tangle increases.
It is known that handleability is improved
through the use of "antiblocking" agents.
"Antiblocking" agents prevent thin plastic films
from sticking to one another. Antiblocking agents
suitable for use in plastic films include, but are
not limited to, diatomaceous silica, such as those
commercially available under the tradenames
"SUPERFLOSS", "SILVERFROST"*, and "CELITE"* which
are silica products of the Johns-Manville Company~
The concentration of the antiblocking agent
incorporated into the film generally ranges from
about 100 to about 10,000 parts per million, and
usually from about 3,000 to about 7,000 parts per
million. As disclosed in U.S. Patent 3,028,355, the
diatomaceous silica, referred to as diatomaceous
earth in the patent, should generally have an
average particle size of between about 2 to about 6
microns. Other antiblocking agents selected by
those skilled in the art can also be suitably used.
* Trademark
D-14004-C
~lLZ30~
In addition to having good "cling~ and
"handleability~ characteristics", as well a~ having
a resi6tance to heat for use in direct food contact
microwave cooking, the food wrap ~hould have good
barrier properties such as oxygen, moisture, and
food odor ~mpermeability. Further, the food wrap
~hould po se~s a deqree of toughness. All of these
properties cannot be found in a single layer film
food wrap. It iB only by providing a multilayer
film that all of the aforementioned desirable
properties and characteristics may be attained in a
food wrap. Mul~ilayer films consist of two or more
layers, each imparting specific desired
characteristics to the multilayer film.
SummarY of the Invention
The present invention relates to a
multilayer film suitable for use in the manufacture
of food wraps. In general, the multilayer film of
this invention comprises at least outer layers of a
polyolefin resin including a cling agent, and a core
layer of a thermoplastic resin having a high melting
point, resistance to heat for use in direct food
contact microwave cooking, low permeability to
oxygen, moisture and food odor, and film toughness.
In one embodiment of this invention, the
multilayer film comprise6 a three-layer film having
outer layers of a polyolefin resin containing a
cling agent and a core layer having the
aforedescribed charact.eristics and properties. In a
preferred mode of this embodiment., the multilayer
film comprises two outer layers of a polyolefin
cont.aining a cling agent and a core layer of a
D-14004
3~719
polyamide~ The optimum composition of the
multilayer film of this embodiment co~prises two
outer layers of polypropylene containinq a cling
agent, and a core layer of a polyamide such as
Nylon, and preferably Nylon-6.
In another embodiment of this invention,
the multilayer film comprises a five-layer film
having outer layers of a polyolefin resin containing
a cling agent, a core layer of a resin having a high
melting point, resistance to heat, low permeability
to oxygen, moisture and food odor, and film
toughness, and a bonding layer between the core
layer and each of the outer layers. In a preferred
mode of this embodiment, the multilayer film
comprises two outer layer6 of a polyolefin
containing a cling agent, a core layer of a
polyamide, and a bonding layer between the core
layer and each of the outer layers. The optimum
composition of ~he five-layer film of this
embodiment comprises two outer layers of
polypropylene containing a cling agenl, a core layer
of a polyamide such as Nylon-6, and a bonding layer
between the core layer and each of the outer layers.
Any suitable thermoplastic resin or
copolymer, or mixtures thereof, may be used for the
outer layers of the multilayer films of this
invention. Typical thermoplastic resins include
polyolefins such as low and high density
polyethylene, polypropylene, and polybutylene.
However, of the polyolefin resins, polypropylene is
preferred for the outer film layers because of its
higher melting point and better resistance to heat.
D-14004
~L23~7~L9
-- 6
The outer polyolefin layers, preferably comprising
polypropylene, contain a cling agent which makes the
film functional as a food wrap. Further, it has
been found that not all polypropylene resin types
are optimally suitable for the addition of cling
agents thereto. More specifically, optimum results
are obtained when the outer film layers comprise a
polypropylene random copolymer having a melt flow
index of between about 2 and about 25 decigrams per
minute.
Any suitable cling agent may be present in
the outer layers of the multilayer films of this
invention. Typical cling agents include glycerol
monooleate, sorbitan monooleate, sorbitan trioleate,
glycerol dioleate, mono- and diglycerides, vegetable
oils, epoxidized soybean oil, fatty esters,
polyisobutylene polymers, polybutene polymers,
ethoxylated nonylphenols, mineral oil, saturated
aliphatic and alicyclic hydrocarbons, polyalkylene
ether diols, such as polyepichlorohydrin, trihydric
and higher polyhydric alcohols, the liquid esters of
the higher molecular weight fatty acids, and
polyethers, and surfactants. Preferably, the cling
agent present in the outer layers of the multilayer
film is glycerol monooleate.
A satisfactory concentration of the cling
agent in each of the outer layers of the multilayer
film into which it is incorporated is one in the
range of from about 0.5 to about 2.0 weight percent,
preferably about 0.8 weight percent, based on the
weight of each outer film layer. The optimum
concentration of cling agent in a thermoplastic
D-14004
~23~7~9
-- 7 --
resin layer is usually dependent on the particular
resin system employed.
Any suitable thermoplastic resin or
copolymer, or mixtures thereof, may be employed for
~he core layer of the multilayer films of this
invention. Typical thermoplastic resins having a
high melting point, resistance to heat, low
permeability to oxygen, moisture and food odor, and
film toughness include the polyamides such as
Nylon-6, Nylon-6.6, and Nylon-12; polybutylene
terephthalate, polyethylene terephthalate,
ethylene-vinyl alcohol, and mixtures thereof.
However, it is preferred that the core layer
comprise a polyamide, and more preferably, that the
polyamide comprise Nylon-6, which is commercially
available under the tradename Capron-8207* from the
Allied Chemical Company.
When the multilayer film of this invention
comprises a five-layer film having a bonding layer
between the core layer and each of the outer layers,
the bonding layer should be sufficient to provide a
bonding strength between said core layer and said
outer layers of at least about 200 grams~inch of
film.
Any suitable bonding material, or mixtures
thereof, that exhibit strong adhesion to polar
resins may be employed as the bonding layer between
the core layer and each of the outer layers in the
multilayer film of this invention. Typical bonding
materials include adhesive resins such as ionomer
copolymers, chemically modified polyolefins,
ethylene-vinyl acetate copolymers, ethylene-acrylic
* Trademark
D-14004-C
1~3~7~ ~
acid copolymers, polyolefins grafted with acrylic
acid, and other multi-polymer compo~itions. The
chemically modified polyolefin may be obtained f rom
a number of polyolefin resin~, such as high, medium
and low density polyethylenes, polypropylenes,
ethylene ~inyl acetate copolymers, and
ethylene-acrylic acid copolymers, which are modified
by the provision of functional groups to the
polymer, which have a strong affinity for the nylon
molecule, and which will form strong bonds to nylon
under the heat and pressure involved in the
coextrusion proce6s. These bonding materials are
generally commercially available. For example,
ionomer copolymer6 may be obtained from E. I. DuPont
de Nemour~ and Co. under the tradename Surlyn
resin. Likewise, the modified polyolefins are
available from Chemplex Company of Rolling Meadows,
Illinois, uncler the tradename Plexar re~ins,
such as Plexar-3, which is a modified ethylene-vinyl
acetate copolymer adapted for cast film
coextrusion. The preferred bonding materials are
selected from modified polyolefins such as Plexar-3,
and other multipolymer compositions 6uch as CXA-3101
available from E. I. DuPont de Nemours and Co. The
bonding layer between the core layer and each of the
outer layers may have a thickness of from about 0.03
mil to about 0.60 mil, preferably from about 0.05
mil to about 0.15 mil. When present, the thickness
of the bonding layers may range from about 10
percent to about 20 percent of the total thickness
of the multilayer films of this invention.
D-14004
~23071g
- 9
The total thickness of the multilayer films
of this invention may range from about 0.3 mil to
about 3 mil6, preferably from about 0.5 mil to about
1.0 mil, and more preferably, about 0.75 mil. The
thickness of each of the outer layers of the
multilayer films of this invention may range from
about 0.1 mil to about 1.0 mil, preferably from
about 0.2 mil to about 0.4 mil, and more preferably,
about 0.32 mil. The thickness of the core layer of
the multilayer films of this invention may range
from about 0.05 mil to about 1.0 mil, preferably
from about 0.08 mil to abou~ 0.5 mil, and more
preferably, about 0.11 mil.
The multilayer film of this inventior. may
have an outer layer to core layer to outer layer
thickness ratio of from about 1:1:1 to about 4:1:~,
but the preferred layer thickness ratio i8 about
3:1:3. When an adhesive layer is present, the
thickness of the adhesive layer is included in the
outer layer thickness ratio values.
The n~ultilayer films of this invention may
be produced by any of several well-known methods.
Preferably, the film may be produced by what is
commonly known as the slot cast extrusion method.
The film may also be produced by what is commonly
known as the air blown film tubular exteusion
method, but this latter method is le~s preferred.
The slot cast method produces a film of better
clarity than the other methods known to the art.
Various cling enhancing agents and/or antiblocking
agents, as the case may be, can be incorporated into
D-14004
.
~L2307~L9
-- 10 --
the outer layers of the multilayer films of this
invention by mixing the agents with the resin,
preferably prior to extrusion thereof. For better
control, it is preferred to mix the cling agent
and/or the antiblocking agent with all of the resin
of a particular layer to a final concentration,
rather than master batching the additive to the
resin, that is, adding a high concentration of the
additive to a small amount of the resin and then
adding that mixture to the total resin. The
multilayer film may be slot cast on conventional
extrusion equipment using a conventional slot cast
multilayer die or a multilayer adapter for a single
layer slot cast die.
The multilayer films of this invention can
be slit to a preferred width, for example about 12
inches to about 18 inches, wound on cardboard coLes,
and packaged in dispensing cartons having the
typical metal sawtooth edge cutter bar.
The invention will become more apparent
when considered together with the following
examples, which are set forth as being merely
illustrative of the invention and which are not
intended, in any manner, to be limitative thereof.
Unless otherwise indicated, all par~s and
percentages are by weight.
The Cling-to-Glass test used in the
examples i6 designed to measure relative values of
cling and employs an Instron testing
instrument, such as an Instron Model TM or its
equivalent. The apparatus consists of a glass
plate, a clamp which holds one end of a film
specimen, about 2.5q cm wide, a string which
D-14004
3L~307~9
-- 11 --
connects the clamp at one end and a 30 gram weigbt
at the other, a metal or gla~6 rod over which the
6tring slides, a rin~6tand to hold the rod parallel
~o the Instron crosshead, and a metal plate which
allows the glass plate to be attached to ehe Instron
cro~shead.
The sample, about 22.86 cm long by about
2.54 cm wide, is prepared by placing the film wrap
between two pieces of paper and cutting on a paper
cutter.
About 20.32 cm of the 2~.B6 cm sample is
placed on the gl~ss plate. The film is firmly
folded flat onto the plate with a rubber roller.
The additional 2.54 cm of the sample is clamped in
the small ~teel clamp. ~he glass plate is mounted
horizontally on the Instron crosshead. A glass or
metal rod i6 held parallel to the p~ate edge and to
the crosshead, about 12.7 cm from the ed~e- of the
pla~e. The string attached to the clamp holding the
sample is hung over the rod. A 30 gram mass is
attached to the end of the string. In this position
the mass is exerting a force which tries to slide
the film specimen over the glass plate. Generally,
the coefficient of friction is 60 great that the
film will not slide. Initially, the plate and
cros6head are 6.35 cm above the rod, The cros~head
is lowered at a rate of 50,8 cm per minute and as
the plate drops below the level of the rod, the film
begins to peel from the plate. When the film
releases completely from the plate, the crosshead is
stopped. The distance the plate has dropped below
the rod is related to the magnitude of adhesive
force or cling between the film and the plate.
D-14004
~3~)~19
Cling-to-Glass is ~eported as centimeters of plate
travel for the film sample.
Exam~le I
A three-iayer-film was manufactured usin~
the slot cast extrusion method. Polypropylene
having a melt flow index of about 6 decigrams per
minute, and a cling agent comprising glycerol
monooleate, were mixed in a Banbury mixer. The
cling agent was pre~ent at a concentration of about
0.8% by weight of the mixture. The resulting
mixture was fed to an extruder connected to a
multiple orifice slot cast extrusion die and the
molten mixture was extruded through the two outer
orifices of the die forming the outer layers of the
three-layer film. Nylon-6 having an approximate
melting point of 425F and a density of 1.13 g./cc
was extruded through the center crifice of the die
forming the core layer. The mult,ilayer film had a
total thickness of about 0.75 mil, and a layer to
layer to layer thick~ess ratio of about 3:1:3.
Example II
A three-layer film was prepared as in
Example I except that the multilayer film had a
total thickness of about 0.75 mil and a laye~ to
layer to layer thicknes& eatio of about 2:1:2.
Exam~le III
A three-laye~ film was prepared as in
Example I except that the multilayer film had a
total thickness of about 0.50 mil and a layer to
layer to layer thicknes6 ratio of about 3:1:3.
D-14004
~23~9
- 13 -
Example IV
A three-layer film was prepared a6 in
Example I except that the multilayer film had a
total thicknes~ of about 0.~0 mil and a layer to
layer to layer thickness ratio of about 2:1:2.
In Table 1, the effectiveness of the
multilayer films of Examples I through IV was
compared with a commercial single layer
polyvinylidene chloride food wrap, and also with a
commercial 6ingle layer polyethylene food wrap in a
microwave oven cooking test. The microwave oven was
a commercial Amana range set on high for a
cooking time of about 6 minutes. The food ~amples
comprised (A) about 200 grams of beef patty
consisting of about 70~ lean ground beef, and (B)
about 150 grams of pork sausage made into a patty.
During the microwave cooking test, one each of the
food samples was individually wrapped with the
multilayer film food wraps of Examples I through IV,
the commercial polyvinylidene chloride food wrap,
and the commercial polyethylene food wrap, and the
twelve wrapped food samples were placed in the oven,
thr~ee samples at one time. Failure of the food wrap
was defined as any rupture of the film to permit
leakage of grease or juices accumulated from the
food 6amples. Table 1 summarizes these test results.
D-1400g
1~3~7~
- 14 -
Table 1
Miorowave Oven Test Performance
Food Wrap Film Beef Pattv Pork Patty
Example I no failure no failure
Example II no failure no failure
Example III failed failed
Example IV failed failed
Polyvinylidene chloride failed failed
Polyethylene failed failed
From the above results, it was determined
that the high melting point Nylon-6 in the core
layer of Examples I and II serve6 as a high
temperature supportinq layer in the multilayer film
structure. It was also ~ound that total film
thickne6~ and layer ratios are important factors
~ince the multilayer films of Examples III and IV
permitted some leakage of food juices.
ExamPles V - VIII
Example V through Example VIII demonstrate
that not all polypropylenes in combination with
nylon are suitable for food wraps containing a cling
agent. It was found that when employing a high melt
flow polypropylene and some low melt flow
polyallomers, a lo~s of cling properties was
experienced after extrusion. Polyallomers are
crystalline polyolefins made from two or more
,polymers such as ethylene-propylene block
copolymers. Example V comprised a slot cast
D-14004
~230~
- 15 -
extruded three-layer film consi6ting of outer layers
of a polypropylene copolymer having a melt flow
index of about 7 decigrams per minute. Example VI
was a ~lot cast extcudea three-layer film compri~ing
outer layers of a polypropylene homopolymer havinq a
melt flow index of about 12 decigram~ per minute.
Example VII and Example VIII were slot cast extruded
three-layer film~ having outer layer~ of a
polyallomer having a melt flow index of about 2
decigram~ per minute, and about 6 decigrams per
minute, respectively. The three-layer films of
Examples V through VIII each had a core layer of
Nylon-6, and each of the film composition6 contained
about one percent by weight of glycerol monooleate
as the cling agent in each of the outer layers. The
multilayer films of Examples V through VIII had a
t~tal film thickness of about 0.75 mil, and a layer
to layer to layer thickness ratio of about 3:1:3.
Table 2 summarizes the results of cling tests
performed on these film compositions.
Table 2
Clinq ProPerties Of Various PolYProPYlene TYPes
.
Clinq (inches~ Blocking
ExamPle Glas~ Self Clinq (qrams)
V 8.6 9.7 40
VI 5.2 4.9 10
VII 5 5 4,3 9
VIII 6.0 1.0 9
In Table 2, it should be noted that the
higher the cling ~alue, the better is the clinging
D-14004
~L23~
- 16 -
property of the film composition. It can be ~een
from the results that a multilayer film containing
the polypropylene copolymer of Example V provide6
the ~ost de~icable cling propertie~
ExamDle~ IX - ~IV
Example IX through Example ~IV illustrate
the barrier properties of various food wrap
compositions with respect to moi~ture vapor
transmission, oxygen permeability, and onion odor
permeability. Example I~ throuqh Example XII
comprised three-layer films manufac~ured by slot
cast extrusion wherein the outer layers were made
from polypeopylene having a melt flow index of about
7 decigrams per minute and a density of about 0.897
g/ml., and each outer layer contained about 0.8
percent by weight of glycerol monooleate. The core
layer comprised Nylon-6. The film w~ap of Example
IX h~ a total film thickness of about 0.43 mil, and
a layer to layer to layer thickness ratio of about
2;1:2. The film wrap of Example X had a total film
thickness of about 0.71 mil. and a layer to layer to
layer thickness ratio of about 2:1:2. The film wrap
of Example XI had a total film thickness of about
0.42 mil, and a layer to layer to layer thickness
ratio of about 3:1:3. The film wrap of Example XII
had a total film thickness of about 0.64 mil, and a
layer to layer to layer thickne~s ratio of about
3:1:3. The film wrap of Example XIII was a single
layer commercial polyethylene product having a film
thickness of about 0.45 mil. The film wrap of
Example XIV was a single layer commercial
D-14004
~23~
poiyvinylidene chloride product having a film
~hickne~s o~ abou~ 0.46 mil.
The barrier properties of the film wcap
compositions of Examples IX though XIV are
summarized in Table 3. In Table 3, the values shown
for the moisture vapor transmission are reported as
grams per 100 squace inches of film wrap per 24
hours. The oxygen permeability values are reported
as cubic centimeters per 100 square inches of film
wrap per 24 hour~. For the onion odor pecmeability
results reported, sliced raw onions were placed in
separate beakers which were covered with the film
wrap of Examples IX through XIV~ respectively. A
panel of five persons rated the sample beakers for
odor detection. The panel was in 100% agreement for
the odor detection evaluation.
Table 3
Barrier Pro~ertles
Moisture Vapor Oxygen Onion Odor
Example Tran6mission PermeabilitY Permeability
IX 2.5 21.6 yes
X 2.3 9.~ no
XI 2.9 81.1 yes
~II 2.1 17.0 no
XIII 1.8 960 yes
XIV 0.5 1~8 no
From the above ce6ult~, it can be seen that
polyvinylidene chlocide film wrap has excellent
bacrier properties~ whereas polyethylene has very
poor oxygen barrier properties. It can also be seen
that of the three-layer film wraps, the compositions
of Example X and Example XII provide the most
satisfactocy barcier pcopecties.
~-14004
~L2~7~9
- 18 -
The film wrap compositions of Example IX
through Example XIV were also evaluated for strength
and toughness properties. Table 4 summarizes the
various physical pLoperties evaluated on these film
wrap compositions.
The values for the physical properties
reported in Table 4 were obtained pursuant to the
ASTM test methods indicated in Table 4 with the
exception of the melting point values and the
puncture toughness values. The melting point values
given in Table 4 were obtained with a dif~erential
scanning calorimeter. The composition of polymer
blends wherein the parent polymers have sufficiently
different polymer crystallinity melt temperatures
can be determined u6ing differential scanning
calocimetcy. The method i8 based on the
measurements of the heat of fusion for the
respective pa~ent polymers. The amount of polymer
crystallinity, upon which this heat of fusion is
based, i6 sensitive to thermal histo~y. Known
standards upon which a calibration curve is based,
and samples, are p~etreated in the same manne~ to
obtain valid correlation~.
The punctu~e toughness values were obtained
using an Instron Tensile-Compre~sion Tester. The
tensile tester used was Instron Model TM, and the
compcession teste~ was Model G-03-2 having a full
scale range of 0-1 to 0-50 pounds employed with
compression cell CC. The test is similar to ASTM
method D-1709 which employs f~ee falling darts and
E-154 which employs a slowly moving plunger to
measure the puncture resi6tance of films used as
D-14004
~23~73L9
- 19 _
vapor bar~iers. The puncture resistance is a
measure of the force required to rupture a ~est
~pecimen, and the energy ab~orbed by the film during
rupture.
D-14004
123~)71~
- 20 -
O O ~ D O er
~ ~ D ~ O U~
X _/ a:) 1~') 11~ N
H I ~ ~ ~0 Ct) ~D
X ~ ~ ~ O ~ ~ ~ ~ ~ ~ <~I
O~ ~
H ~ ~I Cl~ ~ CO U~ O r-- ~D
i-l I~ U~ ~D~ ~) ~D 1-` 0 0 ~`I
X
~D ~
H O ~ O 11~O ~-- O O ~`J
a)l
E ~ ~ ~ o t` ~D
~: O Cl~ . ~ ~ er CO ~ ~ ~ u~ o ~
Xl -1 ~1 ~ ~ ~ ~ D ~ ~` ~ ~1 ~ er
~ .
X ~r ~ u~ 1--~ ~ o o o
a
q) O
~ . ~ O~
E~ ~ ~ ~ ~ o
Cl~
E~ 0 co OD ~
cC G a a a a
^ C
.
C U~
C C C C
--o o o o
O C v C V C J~ C J~
_I o o o ~ o o O ~
u~ 8 ~ v ~ ~ ~I v ~ v ~ ~4
J ~--I S ~ ~ O
c
'
:: C .r~ a) oP ~ a~ ~~ ~ ra ~ a) E ~
o~ u, ~ a) ~ u~ ~ u) _I~ u) a) ~ u~ ~ c
O ~ ~ ~ ~ ~ V ~ L~
v a) a~ c a~ GJ ~ O
~ ~ U~ O C ~ O O C
E ~ ~ u) ~ E~ o
C C ~ C C S C O ~ C
O3 (~] a _I O ra ~ O 11~ V X ~
.~,v o r~ c ~ ~ c e ~ ~ o ~
rn r~ e ~ c E~ v ~ v v
~ c C O r~ u~ e ~
D - 14004
3~ g
- 21 -
From the values obtained for the film
compositions of Examples I~, X, XI and XII, it can
be seen that these compositions possess puncture
toughness and tensile strength load proper~ies which
are superior to those of the single layer commercial
polyethylene product of Example XIII. Further, the
film compositions of Examples IX, X, XI and XII
possess puncture toughness energy properties which
are superior to thofie of both the single layer
0 commercial polyethylene product of Example XIII and
the single layer commercial polyvinylidene chloride
product of Example XIV. In addition, the tear
strength properties of the film compositions of
Examples IX, X, XI and XII are substantially greater
than those of the polyvinylidene chloride product of
Example XIV. It can also be seen that the film
compositions of Examples IX, X, XI and XII have a
high melting point, i.e., substantially higher than
the single layer polyethylene film of Example XIII,
thus enabling their use in micro-wave cooking
applications.
The multilayer film wrap compositions of
this invention al60 possess clinging properties
enabling the film wrap to seal to itself when used
for wrapping foods, storing the wrapped food in a
freezer, and cooking the food in the film wrap such
as in a microwave oven. The multilayer film wraps
are also well-suited for use as a cover for
containers, and can also be used to protect
sandwiches and other foods.
Although the present invention has been
described and set forth in some detail, it should be
D-14004
~2~)7~L~
- 22 -
further under6tood that the same is su~ceptible to
change~, ~odifications and variation~ without
depa~ting from the scope and spirit of the invention
a~ 6et forth in the appended claims. Such changes,
modifications and variations are within the scope of
this in~ention.
D-14004
