Note: Descriptions are shown in the official language in which they were submitted.
CA 02484254 2004-10-06
1. Related ~bx~~icmtions
This application claims the benefit of a provisional application having United
States Serial No. 60/505,371, filed on Octobex 2, 2003, which hexeby is
incorporated by
reference in its entirety.
2. Field of the invention
(ooOl] The presezzt invention relates to multilayer films,
specificallyrnultilayer films tlxat
also can be used as packaging films. More spECifically, the present invention
is directed
to multilayer films having relatively low haze and high ,gloss properties and
associated
methods of forming and using same.
I3A.C~OROUND OF THE INVENTION
3. JDescritption of Related Art
[000] Multilayered films are used in many industries to package alI Types of
consumer
goods, such as food, bottles, canned items, cleaning supplies, compact discs,
and many
more items. Numerous attempts have been made to manufacture packaging films
that
provide suffioient claxnty and strength to allow consumers to clearly see the
product
through the packaging and also protect the product from. the atmosphere or
protECt the
atxx~osphere ~rorn the product.
(0003] palms can be used to wrap products directly or can be used to fbrin
bags that
contain consumer products. pre~rious attempts have been ro.ade to use falnzs
that can be
used to package consumer products that nccd transparent packaging, such as
produce.
Some of these films have 'been manufactured with an outer heat-resistant layer
of
elastomer, such as a styrene~butadzene copo]yxnex, with, an oulex sealant
layer of a
metallocene-catalyzed ethylene/alpha-olefin copolymer. Films with these types
of
1
CA 02484254 2004-10-06
nxaterials have generally been fond to curl, making them very difficult to
process
through traditional filxxt xxaanufacturing machinery.
[0004) Another example film with an elastomer on an outer layer with
polyolefins
disposed on a second and third layer can be found in U.S. Patent No, Sy~23,136
by
Fischer et al. titled PacTraging Filrra, Packager, a~ad Methods of tlsar~g
Them (hereinafter
"Fischer '136 latent"). The Fischer '136 Patent describes a multilayer filtxo,
with an
elastoxner on a f rst outermost layer with an ethyletxe layer as the central
layer azxd as
another outexxuost Iayer. Because the films described in the p'ischer '136
Patent are not
symmetrical in structure, the films also tend to curl, which makes them very
difficult to
machine.
[0005 To combat problems with curling, more structttxally symmetrical films
have been
developed. An example of such a structurally symmetrical film can be found in
U.S.
Patent No. 6,294,210 by Kuo titled Oxygen PerrraeableMultilayer.Filnz
(hereinafter "Kuo
'210 Patent"), The Kuo '210 latent describes a film that has a first layer of
a
homogeneous ethyletxe/a-oleiC'tn copolymer, a secoyxd layer of a polyoiefin,
and a filxzxd
layer of the homogeneous ethylene/a-olefin copolymer that can be usEd to
package
produce and the like. Additional layers can be added as well. Because a
tl~cl~ex :Clm
must be used in some applications to provide the needed fYhxx strength, fzlx~s
made
prirxxazily of polyolEfin tend to be hazy t~he~x they are produced with
thicker film gauges,
[0006] To atterr~pt to nxake stranger films, others lxave attempted to make
packaging
films with varying chemical coxtapounds that ar a known fox providing
st~engtlz. An
example packaging filth that 'uses a chezxa,ical compound fihat is kxtown to
increase
strength can be found in U.S. Patent No, 6,060,136 by Patrick et al. titled
High Modulus
Oxygen-Permeable MultiCayerFilm (lt.ereinafZer "'Patrick '236 Patezit"). The
Patrick '136
Patent describes a stxtrctural.]y symmetrical multilayer hlm including a first
layer of a
homogeneous ethylene/alpha-ole:~xx copolymer, a second layer of a
thermoplastic
elastomer, and a third Iayex oI° the homogeneous ethylexae/alpha-olefin
copolynxer.
Adda.txvz~al layers can be added. 'fhemnop)astic elastomers are known. to
increase stren~h
in films. The film of the Patrick '136 latent is used fox packaging food at~d
xequir~s a
high oxygen tr anstxzissiozx rate to cnsua~e that the produce contained within
the film
z
CA 02484254 2004-10-06
receives enough oxygen to xen~aain fresh. The core layer of the thermoplastic
elastomer of
a xa~.ultilayer film is gexaexally the center layer of the film, vvhxeh is
also generally the
thickest layer. Because the therz~~oplastic elastomer rx~atc~rial used iii the
center layer is
relatively expensive, tl~e cost of producing a ~lmz in accordance with the
Patricl~ '136
Patent can be expensive, p'ilzns made vt~ith tlaerxnoplastic elastoro.ez~s
also lack optical
properties that may be important in other applications.
[0007] A need e:~ists for a packaging fxlrn that is econotxtxcal to produce
and can be
manufactured on existing equipment, without having to modify the equipz~mnt.
There
also is a contiu~.ued need for a packaging film that is relatively thin, has
good optical
properties to allow a product to be seen easily through tlxe packaging ftlxn,
and has good
mechanical properties to allow the packaging filna to withstand outward forces
being
applied to the packaging vaithout punctuizng easily,
S~C7M11ZARX U~ TtTI~ T1~IVEhTT~Ol~T
[0008] In view ofthe foregoing, mnbodime~~.ts of the present invention
advantageously
provide a packaging film that is relatively thin, and has enhanced optical and
xxxechanical
properties. The eanced optical and xnechaa~ical properties allow a product
when
substantially surrounded by the film to be seen clearly thxon.gh the packaging
film and
also allow the packaging film to resist from being punctured easily when an
outside force
is aplalied to the packaging f~Jlx~. Embodimezxts of the present invention
also
advantageously provide a packaging film that is relatively inexpensive to
produce and
can be produced using known film manufacturing equipment.
[0009] More specifically, ali embodiment of the present invention provides a
combination product and shrink wrap packaging filnx that preferably includes a
product
that is substax~tially sm~-ounded by the packaging fxhrt. The packaging film
preferably
contacts and substantially surrounds the product so that when the packaging
~lTn is
heated to shrink the packaging film around the product, the packaging ~ltx'~
encases the
product so that the product is securely restrained by the packaging frlm. This
type of film
is commonly referred to as shrink-wrap film. The packaging film preferably
includes a
first outemraost layer of elaston~ez°, a second layer of polyolefu, and
a fihird outemnost ,
layer of elastomer, 'the second layer of polyolefn preferably overlies and
abuttmgly
CA 02484254 2004-10-06
contacts the first outermost layer of elastomer. T'he third outermost layer of
elastomer.
preferably overlies and abuttingly contacts the second Iayer of the
polyolefixx so that the
second layer of polyolefin is preferably positioned betrxreen the first azzd
the third
outermost layers of elastozzxer. The packaging film advantageously has
enhanced optical
and mechanical properties for a selECted overall packaging elm gauge
lhielrness that
allow the product to be seen more clearly thmug~t the packagirxg film and that
increase
modulus for the packaging film so that the packaging ~ilm is readily usable
with
packaging n xaelu~.eryr, i.e., macb~.nable, at relatx~vely high speeds and
provides packaging
film having preselected optical and mechanical properties related to
appearance, strenbtlx,
and shrink. Conventiozxal packaging rnaclxinery can be used, as understood by
those of
ordinary skill iza the art.
1~010] Embodiments ofthe present invention also advantageously provide a
packaging
~Im that has ez'fzarreed optical atxd mechanical properties. The packaging
fthxxt preferably
includes a first layer of a sheet of elastomer, a second layer of polyolefin,
and a third
layer of a sheet of elastomer. The second layer ofpolyolefmpxeferablyhas a
first surface
that abuttingly contacts a fzrst surface of the first layer of the sheet of
elastomex. 'The
third layer of the sheet of elastotner preferably abuttingly contacts a second
surface of the
second layer of polyolefz~. The second layer of polyolefin is preferably
positioned
betv~ree~n. the first and third layers ofthe sheets of elastomer.
[0011] The packaging film advantageously has enhanced optical properties and
enhatxced
mechanical propezfii,es for a selected overall packaging tiim gauge thiclauess
so that a
product surx'ounded by the packaginb filzxz can be seen more clearly through
the
packaging fzlm without the necessity of renxoving the pacl~aging filmy and the
packaging
fzlzn is not easily punctured vc~hex~ an outside force is applied thereto. The
packaging film
of the present invention is advantageously cap able of being readily usable
with packaging
machinery, i.e., machiz~able, at relatively high speeds and provides packaging
film having
preselected optical axx,d mechanical properties related to appearax'zce,
sh~ength, and shrink
pTOpertl~s. FoT exatllple, t]1e packaging filth of the presexlt invention caxr
have a 45° gloss
in a raxzge of about 7Q% to about 110%.
CA 02484254 2004-10-06
[0012] Methods of farrzaizig the packaging filna with enhaaaced optical and
mechanical
properties are also advantageously provided. Txa one embodiment, the method of
forming
a packaging film having enhanced optical and mechanical properties
advantageously
includes positioning a first e~.truded layer of elastonaez°, a second
layer ofpolyolefnland a
third extruded Iayer of elastomer so that the ~~rst and tlaizd extruded layers
of elastomer
are the outerzaiost layers o~'the packaging falm. The packaging film can be
produced by a
blow film process, as understood by those ofordinary skill ixt the a~.~t
ofpackaging films.
As a step of the blown ~ lm pzocess, the layered laminar structuze is
stretched and air is
supplied to the layered laminar structure to produce a bubble. ~'he bubble is
then
collapsed, typically by rollers, to fozxz~. the packaging fihxa. The packaging
tilin
preferably has a second layer of polyole~x~ positioiaed between, first and
third outerzaaost
layers of elastomer. The packaging film advazatageously has enhanced optical
and
mechanical properties for a selected overall packaging film gauge'diickness
that allovtr a
product surrounded by the packaging fihu to be seen more clearly through the
packaging
film and that increase modulus for the packaging fZlm so that the packaging is
readily
usable with packaging maclain.ery, i.e., machinable, at relativelyhigh speeds
and provides
pacl~aging filzaa having preselected optical and mechanical properties for
tlae packaging
film related to appeara~ace, strength, and slarink properties.
~oox3] Another embodiment of a naetlood of fox~ning a paclcaging ~hn havi~ag
enhanced
optical and zxiechanioal properties so that a product surrounded by the
packaging ~lrn can
be seen more clearly through the packaging film and the packaging filaa is not
ptuictured
easily when an outside force is applied thereto. Xn this ezazbodimeztt, the
za~ethod
preferably includes the step of positionibg a first extruded Iayer of
elastomer, a second
ex'I~udEd layer of polyolefm, and a thia~d e~ctruded Iayer of elastoaner to
form the
packaging ~hn. The paclta~ing fihb, is preferably formed by using a cast elm
process, as
understood by those of ordinary skill ixa the art of packaging ~lrn
production, As a step
of the cast filxu process, tlae layered structure of the layers of extruded
materials is rolled
to fozm a packaging elm. In the packaging film, the secozad layer of polyole~n
is
preferably positioned between the fast and tae bird ]ayeks of a]aS'hOtYler.
~'~L pa.Ckab~ng
film, advantageously has ezahanced optical and mechanical properties for a
selected
overate packaging film gauge thickness.
5
CA 02484254 2004-10-06
j0014] The enhanced 8ptical and mechanical properties advantageously allow a
product
surrounded by the packaging film to be seen more clearly through the packaging
film.
The exxlxanced properties also increase modules in the packaging film so that
the
packaging film is readily usable with packaging machinery, i.e., maclxinable,
at relatively
high speeds and providespackaging Ii1m11avingpreselected optical and
nc~echanical
properties related to appearance, strength, and shxink properties.
{001.5] The packaging fihx~ of the present invezttion has very lo'tw ha.~e and
high gloss
properties that allow indicia on a product to be seen easily through the
packaging film
without having to remove the packaging film from the product. The packaging
film also
has high. gloss values that make the combination pmduct and film packaging
more
aestheticahy appealing to consumers.
lBItICaJIE' IDESCRXI'TIO~ OF TAE I?R~,~Vrl~t~S
[001G] Sorne of the obj ects and advantages of the present invention having
been stated,
others~vill become apparent as the descx~ption proceeds '4vhen taken in
conjunction with
the accompanying drawings, in which:
[0017] JFIG. 1 is a perspective view of a roll of a packaging film in
accordance wiih an
embodizx~ent of the preset~at invention.;
[0018] FIG. 2 is a ~fraginentary sectional view of the packaging fihn of FIG,
I taken
along tl~e line 2-2 in accordance with an embodiment of the present invention;
[0019] FIG. 3 is a perspective view of a packaging filni~. being placed to
substantially
surround a product in accordance with an embodixx~.ent of tlxe present
invention;
[OOZO) FIG. 4,P~ is a perspective of a combination product and packaging film
with the
packaging film substantially surmuziding tb~e product so that the product is
securely
restrained by the packaging film ixx accordance with prior art packaging
films;
[0021] FAG. 4B is a perspee~.ve of a combination ~rot~'~ct anal packaging film
witk~ the
paclzaging ~iltn substantially s'W roundi~ the product so that the prodLxct is
securely
restrained by the packaging film, the pach:aging film having enhanced optical
properties
6
CA 02484254 2004-10-06
so that the product can be seewmore clearly through the packaging film, in
accordance
sixth an embodiment of the present invention;
[0022] FZG. SA is a bar graph illustratiy the percetxtage ofhaze for a
plurality of tested
film samples that were eaclx formed in accordance With an embodiment of the
presexJt
invention;
[0423] FTG. 5B is a graph illustrating tlac percentabe ofhaze fox a plurality
of tested hlm
samples that were formed in accordance with ata embodiment of the present
invention
grouped according to the percentage of elastomer contained in a first outer
layer of the
packaging film;
[00241 FIG. 6A is a bar graph illustrating the percentage of formfive dEgrae
(4S°) gloss
for a plurality o~ tested film samples that were each formed in accordance
with an
embodiment of the pxESent inv~t~tion9
(0025] FTG. 6B is a graph illustrating the perce~~,tage of forty-hve degree
(45°) gloss for a
plurality oftested flm satxaples that were each formed in accordance with an
embodituent
of the present invention gzouped according to the per~cent~ge of elastomer
contained in a
fist outer layer of the packaging f hn;
[0026] FTG. 7A is a graph illustrating the one percent (1 %) secant xnodulus
in a machine
direction measured in pounds per sdu.are inch ("psi") fox apluxality of tested
film samples
that were each formed in accordance with a~. embodiment of the present
invention;
[OU271 FIG. 713 is a graph illustrating the one percent ( 1 %j secant modtilus
in a machine
direction txic:asuxad in pounds per square inch ("psi") for of a plurality of
tested filnn
sarcaples that were each foz7med in accordance vcrith an embodiment o~ the
present
izwantion grouped according to the percentage of elastomer contained in a
first outer
layer of the packaging filib;
[0028) FIG, 8A is a graph illustrating the one percent (1%) secant modules in
a
transvezse direction measured ui psi for a plurality of tested film samples
that were each
fomned in accordance with an embodiment of the present invention;
7
CA 02484254 2004-10-06
[0029] FrG. 8B is a graph illustratzn; the one percent (1%) secant madulus in
a
transverse direction measured in psi for a plurality of tested film samples
that were each
fomoed in accordance with an er7abodizn.ent of the present iawention grouped
according to
the percentage of alastomer contained in a first outer layer of the packaging
fihza;
[0030] FIG. 9A is a graph illustrating tb,e tensile at yield W a. machine
direction ~neasmed
in psi fox each sample that was tested in aocordan.ce witJh an eznbodixnent
o:Ethe present
invention;
[0031] FXG. 9B is a graph illustrating the tensile at yield in a x~aaohine
direction xneasuxed
inn psi for each sample that was tested in accordance with ail embodiment of
the present
invention grouped according to the percentage of elastomer cantaixied ins a
first outer
layer of the pacl~aging ixlin;
[0032] FIG. l0A is a graph illustrating tb.e tensile at yield test results in
a transverse
direction measured in psi for a plurality of tested film. samples that were
each. formed in
accordance with an enabodit~ent of the present inve~ation,
[0033] FrG. 108 is a graph illustratixzg the tensile at yield test results in
a transverse
direction measured in psi for a plurality of tested film samples that were
each fozxned in
accordance with an e~.bodiment of the present invention grouped according to
the
percentage of elastomer cantaizled in a fimt outer layer of tl~e paclcagin.g
film;
[0034] F1G. 11.~ is~ a graph illustrating the tear test results in a machine
direction
measured in psi for a plurality of tested film samples that were each formed
in
accordance with an embodiment of the present invention,
[0035] FIG. I1B is a ~aph illustratix~.g the tear test results in a machine
direction
measured in psi for a plurality of tested film samples tb,at werE each formed
in
accordance with an embodiment of tlxe present invention grouped. according to
the
percentage of elastoxner contained ui a first outer layer of the packaging
film;
[oo3G) FXG. 12A is a, graph illustrating the tear test results xn a transverse
direction
rneaszu-ed i~~ psi fox a plurality oftested filzza samples that were each
tested u~ accordance
with an enabodi~;ent of the present invention;
8
CA 02484254 2004-10-06
[00371 FIG. 12B is a graph illustrating the tear test results in a transverse
direction
measured in psi for a plurality of tested film samples that wez~e each tested
in accordance
with ari. embodiment of the present invention pr'ouped according to the
percentage of
elastoxner contained in. a first outer layer of the pact.{agung flm,
[0038] FZG.13,A is a graph illustrating the dart impact test results
m.easiured in brains for
a plurality of tested elm samples that were each foiTned in accordance with an
el~,lbodi~nent of the present invention;
[0~39j FIGr.13f3 is a graph illustrating the dart impact test results measured
in grams fox
a plurality of tested f~lm samples that were each formed in accordance with an
en.~bodixnent of the present invention grouped according to the percentage of
elastomer
contained in a first outer layer of the packagixxg fih~.~.;
[OD40] FIG, lA~ is a perspective view of an example of a blown film apparatus
and
process used to rnanufactnre a packaging film in accordance with an
enabodin~ent of the
present invention; and
j00471] FIG. 1,5 is perspective view of an example of a cast film apparatus
and process
used to manufacture a packaging film in accordance with an embodiment of the
present
invention.
DETAILED AESGRIPT~ON
[OOA2] The present invention xlow will be described xsrore
fullyhereirxafterwith reference
to the accompanying drawings in which illustrated embodiments of the invention
are
shown. This invention rnay, however, be embodied itn max~,y different forms
and should
not be construed as limited to the embodiments set forth herein; rather,
tk~ese
emboditxtents are provided so that this disclosure will be'thoroufh and
compXete, and will
full convey the scope of the invention to those skilled in the art. Like
numbers refer to
like elements throu.~ouC, and prime notation, if used, indicates siiuilar
elements in
alteratative embodiments.
9
CA 02484254 2004-10-06
[043] As illustrated W FTCrS_ 1 - 3 and 4B, embodiments of the present
invention,
advantageously prov~i~de a combination product f and packaging film 20 that
has
enhanced optical and mechanical properties. The exzhanced optical anal
mechanical
properties allow the product P and indicia x on the product P to be seen
clearly through
the packaging f lm 20 and also allow the packaging flm 20 to resist from being
punctured easily vthexi an outside force is applied to tlae film 20. The
combination
preferably includes a product P and a shrink-wrap packaging film 20. The
shrink-wrap
packaging film 20 preferably contacts and substantially surrounds the product
P and is
shrunk thereon. As shown in FIG. 2, the shtznk~wrap packabing fihxi 20
preferably
includes a ~-st outermost layer of elastozxmr 21, a second inner layer of
polyolefin 23,
arid a third outermost layer of elastomer 25. The second inner layer of
polyolefan 23
preferably ov~erl.ies and abuttingly co~aaats the first outernaost layer of
elastomer 21..
Third outermost layer of elastoxner 25 preferably overlies axed abuttingly
contacts the
second inner layer of the potyolefin 23. Second inner layer of polyole~n 23 is
prefer ably
positioned between the first and the third outermost layers of elastomer 21,
25.
[0044] T.n embodiments of the present invention, the shrink-wrap packaging
film 20
advantageously provides enhanced opticai and znechaixical properties for a
selected
overall packaging fihn gauge thiclrness, The ezihanced optical andxnechanical
properties
allow the product P to be seen more clearly through the packaging film 20 and
increase
modulus for the packaging filxxz 20 that allow the packaging film 20 to be
readily usable
through packagiazg machinery, i..e., maehinable, at relatively high speeds and
provides
packaging film having preselected optical and mechanical properties related to
appearance, strengCla, and shrink properties. Conventional packaging machinery
can be
used, as understood by those ofordrnary skill in the art of packa~ag f lxzr
manufacturing.
[0045] It1 all embodi2nents ofthepresent ixwen tian, thhepackaging ~lrn 20 is
cuffciently
durable to be useful as a packagirxg film 20. The packaging flm 20 can
withstand forces
being applied thereto, such as puncture sources, chime cuts, i.e, firom
products rubbing
to~et~.er, users lifting vhe combination product P and packaging film ~o by
tie pa~ka~i~ag
film 20, arrd the like,
10
CA 02484254 2004-10-06
(004G] FIG. 4A illustrates a prior ~u.~t. pacha$ing ~lnnurith a product having
shrink-'wrap
packaging film sluunk thereon. With the prior art film, the indicia r otx the
product P
cannot be seen as easily through the film, In the present invention, the
indicia I oz~ the
product P can he seen clearly through the pacl~aging fihn 20, as shown in FIG
4B, due to
tha enhanced optical properties of the present itxvention at a comparable film
gauge
thickness.
[0047] In all embodiments o:fthe present invention, the elastomexpreferably
includes a
styrene butadiene copolymer, Suitable butadiene st~rrene copolymers for use in
the
present invention include those con;imercially identified as the I~.-l~esin~
SEries from
Chevroxl Phillips Chemical Company LP of 10001 Sip Pines x?riwe, The
Woodlands, T~
773 s0. The butadiene styrene copolymer known cozxrrraercially as DI~11 in the
K Resia~~
Series performed exceptionally well in initial tests, Another exemplary
e~canaple
butadiene styrene copolymer is known coxmnercially as DK13, also in the ~-
Resin~
Series. Other suitable eiastomez's can include polymethylpentexre;
polybutylene,
polyisobutylene, ethyle~ae propylene dime monomer terpolytner, styrene
butadiene
styrene copolymer, styrene ethylene butylene copolymer, styrene isoprene
styrene
copolymer, polybutene-1, isob~xtyleue rubber, methyl acrylate butadietxe
styrene
copolymer, acrylonitizle butadien,E styrene copolymer, aczylonitrile
alkylacrylate
butadiene styrene copolymer, methyl n~ethacrylate alkyl acxylate styrene
copolymer,
methyl methaerylate allzyl aerylate butadiene styrene copolymer, and. the
like.
~,lastomers having good optical characteristics, such as high clarity, are
preferred. OtbEr
suitable elastomer m~atei~als will be known to those of ordinary skill in the
art and are to
be considered within the scope of th.e present invention.
j004$] In all exnbodizxxents of the present invention, the polyolefin
preferably includes
such polyale~.ns as polyethylene honrxopvlymer, polypropylene hazxxopolymer,
ethylene/ olefin copolymer, propylene/ethylene copolymer, or
ethylene/unsatttrated
ester copolymer. A particularly effective polyolefu~ is a linear low density
polyolefin.
Other suitable polyole~.n materials will be known to those of ordinary skill
in the au and
arE to be coxtsidered within the scope of the present inwentioxx.
11
CA 02484254 2004-10-06
[OOa9) Although other tlucknesses of film can. be ztsed as tmderstood by those
skilled ixz
the art, the overall packaging fihLt gauge thickness of pacltaging fihzr 20
accordx~ng to
embodiments of the present ipvention. prefErably is ia5. a rau.ge of about 0.5
to about 3 mil
so that the packaging film 20 is rz~ore eeonor~ical to manufacture without a
reduction in
clarity or strength of the packaging fzhn 20.
[0050] In embodiments oftlie f lm 20 of the present invez~tioin, the first
Layer ofelastomer
is preferably in a range of about 10°!o to about 25% of the overall
shrink-wrap packaging
him gauge thickness ~1, the second irxner layer ofpolyolefin is preferably in
a range of
about 50% to about 80% o~the overall shrink-~wr~tp packaging ~.lm gauge
thicltness X'I,
and tl~.e third outermost layer o~'elastbrrzer is preferably in a range of
about 10% to about
25% of the overall shrink-wrap packaging elm gauge thickness :~2, as sho-vvxi
in FIG. 2.
The f~hn 20 made in accordance'v4 zth embodiro.ents ofthe pxeseztt inventiota
has ezihanced
optical and mechanical properties that are particularly advantageous when used
as a film
20 and, more specifically; as a shrink elm 20. The optical and mechanical
properties that
are enhanced as a result of the present invention include haze, gloss,
modulus, tensile
strength, a measure o~ shiii~k, and a dart impact strength.
[0051) In embodiments of the film 20 of the present irmentiton, the fihx~. 20
preferably has
a haze, which is one of the enhanced optical properties, in a range o~ abo'at
1 % to about
10%, as shown in l~ IGS. 51~, azld 5B. The lower the haze, the better for a
packaging ~lxn.
20. :Gaze is a measurement of the cloudiness of the fih~.a 20, A haze value in
a range of
about 1 % to about 10°/a indicates that the packaging ~J.m 2a is clear
az~d the product I',
which is substantially surrounded by the packaging elm 20 vv~lzen shrunk
thereon,
optionally having indicia I thereon can be seen easily through the packaginb
i~lm 20. As
shown in FIGS. 6A and 6B, the enhanced optical properties can also includE a
45° gloss
in a range of about 70% to about 110%, and more preferably in a range of about
70% to
about 1 IO%, so that the packaging film 20 is slung and the product P cax~ be
seen easily
through l5ackagiz~g filrxt 20 once the packaging filixz 20 is heated to
secrtrely restrain the
product P within packagi~.g filixz 20, Gloss is important for packaging film
20 since the
packaging has a more appealing look and presence 'when displayed upon a shelf.
Packaging with shitxy surfaces is generally more desirable to consumers than
packaging
having dull surfaces.
12
CA 02484254 2004-10-06
[005] In all. embodiments of the present invention, packaging film 20 can
include
indicia I on the packaging elm 20. This indicia z can xnake the combination
product P
and shrinJ.~-wrap paclZa~;ing ~.lm 20 more aesthetically pleasing to
consumers.
[0053] As shown in FIGS. 9A, 9B, 10A, and 3.OB, enhancedmlechauical properties
ofthe
~.Izn 20 can include a tensile strength in a range of about 2000 psi to about
3500 psi so
that 'lhe packagixtg hhn 20 is not easily puzlctured once slu~unk onto a
product p to
securely restrain the product p w~itlaizW.e packagiza,g filtxx 20. As
illustrated in FIGS . 7A,
7B, 8A, and 8B, the enhanced mechanical properties also can include a tensile
niodulus
in a ra~~ge of about 50,000 psi to aiaout 120,000 psi so fat the packabixig
film 20 is
sufficiently durable once heated to secwely restrain the product P withi;a the
packaging
elm 20. The increased tensile modules advat~.tageously enables packaging film
20 to be
processed through packaging machinezy at relatively high. speeds, The enhanced
mechanical properties further can iz~elude a mea~uuement of shrink in. a
transverse
direction in a range of about 0% to about 60% and in a ~nacbina direction in a
ra.;age of
about 60% to about 90% so that the pac~.aging film 20 shrinks sufficiently to
securely
restrain the product 1? within the packaging elm 20. p'ilms having low
transverse
direction shri~ak perform exceptionally well in "bulls eye" shriyzk-wrap
packaging
applications, as understood by those of ordinary skill in the art of shrirxk
wrap films.
[0054] Another mechanical property that is measured for embodiments of
paekaginb
films 20 of the present invention is the dax't impact strength. The dart
in~.pact strength in
all embodiments of the laxesent invention is preferably i;ct a ra:~.ge of
about 300 grams to
about 1000 grams so that the packaginb film 20 vvih not puncture easily when
an outside
force is applied thereto, as shown in FTGS, 13A anal 13B. A dart impact test,
which has
been sta~.dardzzed in ASTM D 3763, for e~cample, measures the amount of enerby
necessary for a high~speed, round-tipped dan to puncture a 3.2 mm tlaiclc film
20. This
test is an important ix~dioator of impact strength for falms 20.
[OOSSJ In an en~badiment of the present inventioxx, the present invention also
advantageously provides a paelcagnng elm 24 laavitlg eri~laIlCCf]. O~ilCa~
~,i1(~ llleC~lanICal
properties. The enhanced optical and mechanical properties enable a product P
sunrotznded by packaging ~lrr~ 20 to ire seen more clearly through paeka.~ing
film 20,
13
CA 02484254 2004-10-06
without the xaeed. to remove packaging film 20. The enlaarxced pzopexties also
prevent tlxe
paclcagirag filin 20 from being punctured easily when an outside force is
applied thereto.
Packaging film 20 pre~exably includes a first layer of a sheet of elastomer
21, a second
layer of poIyalefin 23, and a fb~ird Layer of a sheet of elastorrxer 25. The
second sheet of
polyolefin 23 advantageously has a first surface abuttixxgly contacting a ~xst
surface of
the first layer of the sheet of elastomer 21. The thud layer of the sheet of
elastomer 25
abuttingly contacts a second suzface of the second Layer of polyolefixs 23 so
that the
second layer of polyolefin 23 is preferably positioned betweexi the first and
third layexs of
elastomer 21, 25. Packaging film 20 preferably has a 45° gloss in a
range of about 70%
to about 1 I0%.
[0(fS6J Several methods of foi~li~g the packaging fahn 20 with enhanced
optical and
mechanical properties also are provided accordixig to the present inventioxi.
The
packaging filnx 20 of the present iz~ventron can be manufactured using typical
bubble
blown film processes and machines 30 arid cast film processes and machines 30'
without
having to modify the rnachi:ne or equipment, as caa be seen in FIGrS. 14 and
15.
(OQS7] In one embodiment illustrated in 1~IG. 14, the method. of fort~inb
apaekabing film
20 havinb enhanced optical and xncchanical pxopet~tias advantageously includes
positioning a first extruded layer of elasto:tner Z1, a-second extntded layex
of polyolefixz
23, and a'third extruded Layer of elastoxner 25 so that the first and third
extxuuded layers of
elastoxner 21, 25 are the outexnlost layers of pacZcagin,g fixm 20. The
extruder 32 used to
form the layexs for use in packaging film 20 eaxz be a series oi:'individual
extruders 32 for
each material to foi-rn a separate layer havi~ag its own extruder 32.
Alternatively, a
coextrudex 32 that can extrude two or more materials through a single die with
two or
more axifices arranged so that the extruded materials merge into a laminar
stxucture can
also be used. The elastomer and polyolehn materials are melted i~z the
extxudex' 32 to
produce a molten material, each of ~hieh zs then, forced through a die to
produce a
layexed laminar structure. The layered laminar,stnzcture is then formed into
packaging
film 20 by coxiventional blown film pzocesses, as ur~,denstood by those of
oxdinaxy shill ixz
the art ofpackaging f lm xnanufacttu~ing. Fox e~cample, the layered laminar
struCti~re cats
be stretched and e:~posed to air that is supplied to the layered laminar
structure to produce
a bubble 34. The bubble 3~~ is then collapsed, typicallybyrollers 36, to fozxn
apackagizas
14
CA 02484254 2004-10-06
film 20, as understood by those of ordinary skill in the art. , The packaging
f lII7 20
preferably has arA inner second layer of polyolefxn 23 positioned betweeix
first and third
outermost layers of elastomer 21= 25. The packaging film 20 advantageously has
enha~xeed optical and mechanical properties for a selected overall packaging
film gauge
thickt~css that allow a product P surrounded by packaginb film 20 to be seen
more clearly
though packaging til2n 20 without having to xemove packaging film 20. The
enhanced
optical and mechanical properties also increase xnodulus fox packaging film 20
so that
pacl~aging film 20 is readily usable with, pacl~aging machinery, i.e.,
maclxinable, at
relatively high speeds. The elastomer is preferably a styrene btztadiez~e
copolymer or any
other suitable elastomer, as described herein, and the polyolefin is selected
from the
group cotasisting of polyethylene at~d polypropylene or any other suitable
polyolefin, as
described herein.
[0058] It is understood that ixx the blown filrtz manufacturing process, as
shown, in FIG.
14, the step of collapsing the babble 3~ catl be perfozxr~ed in ~rarious
manners. Bubble 34
caz~ be collapsed quial~ly, which alloyvs the innex layers of the bubble 34 to
fuse together,
effeotually lx~aki~, a flat sheet. if this technique is used with 'the
packaginb fxlix~ 20 of the
present invention, then a five layer packaging film 20 lvould be nxanufact~red
with the
structure being a layer of eiastomex / a layer of polyolefiix / a layer of
elastoxn.er / a layer
of polyolefin / a layer of elastom.er. Alternatively, the bubble 34 could be
sr~fficiently
quenched unto a solid farm prior to collapsing the bubble. If this method is
used,
essentially a flattened tube itx fonxxed in wlxich the inside surfaces of the
flattelxed tube
will riot adhere to one another. Both of the methods of collapsitxg the bubble
34 in the
blown. fzlm pxocessES are consideredwithin the scope ofthe present invention,
along witlx
the resulting five layer pacl~aging filth ernbodiznents and the flattened tube
nxaterial.
[0059] If a flattened tube material is formed, the flattened tube material
cazi then be
converted to a roll stock ofpackaging fillx~ far sale to consutxiers, as shown
in FIG. 1, by
three methods, The first metT.sod xs to toll up the flattened tube material on
a winder
res'ulfirig in a hibular roll that can then be sold, This method is typically
tried for some
form-fill-seal xiiacl~.n:es that form bags by placing a horizontal seal on the
tube to form a
bottom of the bag, filli.~zg the tube with product P, and then placi?~g
another hoxlzonaal
seal across the top of the tube to form a top oftha bag that is sealed, 'The
second metlxod.
15
CA 02484254 2004-10-06
of converting the flattened tube material to a roll stock is to cut the
flattened tube material
with a single slitting Glade at one location orx the web, which makes what is
lrno~vn as V
sheeting, V sheeting can be used by end users to insert products, such as
compact discs,
bet-~veen tl~e sheets and heat seal both ends and the side of the sheets that
has been cut
open. The third method of converting the flattened tube anafierial to a roll
stock is to cttt
the flattened tube material with slitting blades at both ends, and optionally
bet~sveen the
ezlds, to fonx~ what is known as sheeting, ox single wound rolls. Packaging
~"ilm sheeting
is then formed by the end users ox~ their own machinery to enclose the product
within. the
packaging filmy sheeting. The methods for converting the flattened tube
material to roll
stock are also considered within the scope ofthe present inventicn.
[0060] The overall packaging filmy gauge thicltness preferably is in, a range
o~ about 0.5
to about 3 mil, and the method can further include the step of printin;
indicia I on the
packaging film 20 after the packaging elm 20 has been forrrzed, as shown ix~
FIG. 3. As
understood by those skilled in the art, when indicia I is printed an the
paclraging film ZO
of the presexzt invention, the indicia i is reverse printed on a sturface of
the paokaging hhn
20 that contacts the product f so that the izzdicia I caxr be seen, clearly
through the
packaging film 20_ The indicia I is located ox, a surface .of the packa~g film
20 that
contacts the product P when the packaging fllrn 20 is shrunk thereon. The
packagitz~g~
film 20 functions as a physical protective coatinb for the ixzdicia r.
Chenucal coaYixlgs
that are fiypically used in printing processes to protect the indicia I are
not required.
(OOGi] Another embodinxent o~ a method of ~ormi.ng a packaging film 20 having
enhanced optical axrd mechanical properii.es 30' so that fox a selected
o~rexall packaging
flm gauge thickness, as showzt in FICr. 15. In this embodiment, the method
preferably
includes the step ofpositioning a first extruded layer o~elastomer 21, a
second extruded
layer of polyolefm 23, and a third extzuded layer of elastomer 25 to form
packaging f lm
20. Ta produce the e.~ctrudecl layers, in the extruder 32°, the
elastomer and polyolefm are
melted. to produce a molten material, wluch is then forced through a die to
produce a
layered iarninar structure. As previously indicated, a coextruder witli a
single die with
two or more orifices can also be used, The layered laminar' stc-ucture is then
formed izrto
packa5ing film 20 by conventional cast flhn processes, as shown in FIG. 15 and
as
understood by those of ordinary skill in the art of packa~ix~g film
manufacturing. for
16
CA 02484254 2004-10-06
e~;ata~ple, the extzv.ded layez-s can be rolled with rollers 36' to form ~
packaging film 20, as
shown in FIG. 15. Tn the layered laminar structure of the packaging film. 20,
the second
layer preferably is polyolefixx 23 positioned bet<veeri first and tb_ird
layers of elastomer 21,
25. 'Tile packaging film 20 advantageously has enhanced optical. and
mechanical
properties fox a selected overall packaging elm gaube thickness. For e~tampXe,
a thinner
f lm 20 can be produced that still enables users to clearly see the product P
through the
packagixig film 20 and that resists puncturing when an outside force is
applied thereto.
[0062] The elasta~mer provided is preferably a styrene butadiexse copolymer
and the
polyolefiin is preferably selected from the group consisting of polyethylene
and
polypropylene. Other sttxta~6le elastomers axzd polyolefins are described
k~erein and can
also be used in the emboditn.ents of forming a packaging elm 20 in accordat~ee
with the
present invention. The overall packaging film gauge thicl~ness preferably is
in arange of
about 0.5 to about 3 xz~il, arzd the method further inchides the step of
printing indicia I on
the packaging fiJ,zn 20 after the packaging film 20 has been formed, as
indicated herein.
[0063) The film 20 produced in accordance with the present invention
advantageously
can be produced with a lower gauge, which allows manufacturers to use less
material
when manufacturing the film 20, thereby lowerixag rr~anufacturing costs. films
20
typically have a gauge of about 2 to about 3.5 mil thicl~. 'the film 20 of the
present
invention advantageously leas a film gauge thickness is iii a range of about
0. S to about 3
mil, A zx~il is defined herein as am;easuxeme~.t ofthickuess. One xnil is one
thousandth of
ran inch. Fox example, a 0, SO stretch wrap is 0, S thousandths of ao inch
thick. 80 gauge
is the equivalent as 0.80 mil. 80 gauge or 0.80 mil thick stretch wrap is
pexforxns well for
nanny applicatiozts requiring packaging elm 20.
[0064] To form the combination product P and fllxxi 20 embodiments of the
present
invention, the filin 20 is first stretched out. Burin~g this stretched out
orientation, the
rxsolecules with the elastotners at~d polyolefins are locked, or frozen, into
their elongated
state. A product P is then planed on the film 20 and the filter 20 is then
essentially
wrapped around the product P. 'i~Vhen heat is app~ed to the film 20 With th2
pT0d11Gt P
placed within the film 20, excess energy increases molecular motion 'within
the chemical
compounds that form the layers of the ~ hn 20. The elangated chcrnxcal
molecules recoil,
17
CA 02484254 2004-10-06
ox slar:izuk, back to their preferred random and ciasordered oriEntation. The
result is a
product lP with the shrink-wrap packaging film 20 shrunk thereon. Tlae film 20
securely
restrains the product P within the film 20.
g0aG5) Tests were ,performed on twelve different samples of packaging film. 20
manufactured in accordance 'with the present invention. Deseyptions of the
ttwelve
samples can be found in Table 1 herein below. For floe elastomex, a butadiene
styrene
copolymer kno~cen commercially as DKl l in the K-IZ.esin~ Series
ixaanufactured by
Chevron Phillips Chemical Coznpai~.y was used in the test, A 3 % antiblock
additive was
used in the elastomer layers to prevent the outer layers From sticl~ing
to,getlaer once the
finish packabing film 20 was made and formed into rolls. For the polyolefin, a
low-
density polyethylene was used. The layer percentages relate to the thickness
of each
layer used in the total film gauge thickness, For example, Sample A was a 1.0
~onil thick
packaging film 20 that vvas created with a 0.25 mil thiclt layer of butadiene
styrene
copolymer, a .50 mail thick layer of polyolefin., and a 0.25 mil thick layer
of butadiene
styrene copolymer. The test aresults are showxi in the graphs shovtrn in FrGS.
5A -13B.
The sample designations listed in Table 1 correspond to tl~e samples listed on
the ~-axis
of the ;xaphs in FIGS. 5.la -1.313,
Table 1
SAMJ~SLE
D~~SC~PTION~
Tntal Film Layer Percentages
ba'age 2/50125 20/60/20 ISI70/15 10/80/10
tluickness
(mils)
1.0 .A B G D
2.0 E F G H
3.0 I J K f,
[006b] Depending upon the desired characteristics of the packa~g film 20 izi
accordaarce with an embodiment of the pi°esent il~.vention, the optical
and mechanical
properties can be customized by increasing the x~xiount of elastolxler ox
polyole~tn within
the pacl~aging film ~Ø For e:~asnple, mechat~.ieal properties related to
strength, such as
tensile at yield, naodulus, and ultimate tensile are generally higher for the
pachagir~.g films
18
CA 02484254 2004-10-06
20 containing a higher a~,~~ount of the elastoiner and Iower fox those
conta3ni~~g a hiyer
amount of palyolef n, as shown in FrGS, 7A, 7B, 8A, B:B, ~A, ~B, 10A, 10B,
13,t-i, and
13B. Similarly, optical properties, such. as haze and gloss, axe generally
liigher for the
packaging ~lxz~s 20 containing a higher amount of the elastomer and lower for
those
containing a higher amount of polyolefm, as shown in FrGS, SA, SB, bA, and 6B.
Conversely, tear resistance is higher for structures containing higher amounts
of
polyolefin and Iower for structures containing higher amounts of elastoxner,
as shown in
FIGS. IIA, lIB, 12A, and 128, The ability to change the arnouxzt of elastomer
or
polyolefin allows the packaging fihn 20 to be a~nanttfactu~Cetl, or
customized, to enhance
speci~xc characteristics related to the packaging ~a,hn. 20.
[0067] As an advantage of the present invention, the shrink-wrap or other
packaging
films 20 made in accordance with the present invention axe more eeonon~ical to
manufacture. The use of the elastotner in the firm imiproves the physical
properties of the
hlrn 20, so that a thinner packaging film 20 can be made. The perfoxmaarce
properties of
tk~e paekabirag filix~ 20 remains the same ox are increased with a 'thinner
gauged ~tlm 20.
Because less material is needed to znant~facture the fzlzn ZO and conventional
equipment
can he used, mataufacturing costs are lowered.
[0068) As another advantage of the present invention, the f lrxas 20 provide
evidence of
tampe~.7.ng if someone attempts to re~uove the $lrn 20 that has been heat
sealed to a
product P. The clarity of the fihxu: 20 allows users to easily determine if
tamperurg has
occurred.
[OOl9] In the drawings azxd specification, there have been disclosed various
illustrated
embodimenfis afthe invention and, although specific teams axe employed, they
are used in
a generic and descriptive sense only and not foz the purpose of limitation,
the scope of the
invention being set forth in the following claims.
19
