Technology on heat sealing and peeling multilayer film preparation.

1. Heat Sealable and Easy Peelable Films for food packaging
trays or containers
Nowa days plasticcontainershave been widely usedinpackagingapplications forexample ready-
preparedovenablemealswhichare warmedeitherinamicrowave ovenorina conventional oven.
Polyesterfilmsare commonlyusedasliddingfilmsforovenable containers.Packagingsystems
comprisingarigidheat-stable containerhavingathinflexible thermoplasticfilmsealedontoitare
commonlyusedforthe packagingof so-called"ready-meals",thatisfoodproductswhichonlyrequire
heatingtobe readyforconsumption.Heatingcanbe carriedout ina microwave or ina conventional
oven.Due to the temperaturesinvolvedinthe heatingsteponlyfew materialscanbe usedforthe
container,suchas aluminium, polyester-coatedcardboardorpoly(ethyleneterephthalate)(PET).
Crystalline PET(CPET) containersare especiallysuitable forthisapplication.Toimprove the heat-
sealabilityof these containerswiththe liddingfilmsoftenthe containercomprisesalayerof amorphous
PET (APET) as the foodcontact layer.
General heatresistantPlasticcontainerisa APET/CPETtray (acomposite material havinganamorphous
polyethylene terephthalate layerontopof a crystalline polyethylene terephthalatelayer).
To improve the heat-sealabilityof the PETliddingfilmtothe containeraheat-sealablelayerof alower
meltingmaterial isusuallyprovidedonthe film.The heat-sealable layermaybe coextrudedwiththe PET
base layer,thatis extrudedsimultaneouslythroughasingle die.
Low melt Compositionsgenerallyusedforsealantsfor liddingappications
Polypropylene
Polyethylene
Ethylene vinylacetate copolymers(EVA)
Ethylene/(meth)acrylate copolymers
Amorphouspolyester
sealantcomposition canalsocontainfillersoradditivesforachievinganeasypeel characteristic.Many
compositionscomprisingpolyolefinsare currentlyusedforpeelableheatsealsinpackagingapplications
because of theirgoodprocessability,low cost,andadequate adhesionformanyapplications.
PP,PE, EVA compositionsare notsufficientlyrobustforall applications.Forexample,manypackages
are refrigeratedorfrozentohelppreservethe product therein,anditisdesirable toretainseal strength
incold temperatures.Also,polyolefincompositions(forexample,thosethatcontainEVA) have limited
heatresistance thatrestrictstheirabilitytobe processedathightemperatures.

2. The use of plasticcontainershasledtoa requirementforlidswhichcanbothseal the container,inorder
to preventleakage anddryingoutof the packagedcontentsduringstorage,andalsobe easilypeeled
fromthe containeronopening.The lidsshouldalsonotstick to the packagedcontentsandshouldbe
able to withstandthe heatgeneratedinthe oven.
Prior –art technologies forEasy peelable liddingfilms:
1) Off-line process
In the filmindustryfirsttime peelablefilmwasdevelopedbyusingoff-line coatingmethod.
Organicsolventwasusedinthe off-linecoatingfordissolvingthe polymerin orderto make polymer
solution. Thispolymersolutionwasusedascoatinglayeron base filmatany stage of filmprocesssuch
as before,duringorbetweenanystretchingprocesses.
Remarks/Disadvantage:
 Organicsolventscancause stickingor blockingof the filmduringthe windingprocess
 Solventsmaybe harmful,hazardousinuse ortoxicto the environment
 Filmmade inthisway oftencontainsaresidual amountof solventso maynotsuitable foruse in
applicationswheretheycome intocontact withfoodproduct.
 The off-line processiscostlyandtime consumed
2) In-line process
Sealingfilmproducedbyin-line processwhichavoidsthe use of substantialamountof organic solvent.
The filmcomprisesasubstrate andcoatinglayer.
The coating layerisapplied asan aqueousdispersionorsolution,usuallywithminoramountof organic
solvent.
Remarks/Disadvantage:
 Limitedtocertaintype of coatingcompositioni.e those that are soluble ordispersable inwater
 In addition,thisprocessislimitedinrespectof the achievablelayerthicknessbecausestenter
ovenscan remove onlyacertainamountof aqueoussolvent;
3) In line –extrusioncoating process.
Example forInline –extrusioncoatingprocess
Polyolefinicmaterialontoapolyolefinicsubstrate usinganextrusion-coatingtechnique betweenthe
longitudinalandtransverse stretchingoperations("inter-draw"coating)
Inter-drawextrusioncoatingof anethylene-vinyl acetate (EVA) copolymerontoa polypropylene
substrate toprovide a heat-sealablepeelable film

3. 4) Melt-coatingor hot melt-coatingor slot-coating:
Anothertechnique thatallowspolymers,typicallyanEVA or modified-EVA meltadhesive,tobe applied
to a varietyof substratessuchas paperor polymericfilm.
Thisprocessusedinthe manufacture of commercially-available pressure-sensitiveadhesivetape
In the traditional melt-coatingprocess,the substrate webispressedupagainstthe die bya rollersuch
that there isno air gap betweenthe die andsubstrate.The rollerisgenerallyarubber-backingroller
whichprovidessufficientback-pressure tothe die toprovide anevencoatinglayer
Remarks/disadvantages:
The use of a melt-coatingtechnique isrestrictedtopolymerswhichhave asuitablylow viscosityatthe
temperature of the coatingoperation.Ingeneral,melt-coatingprocesseshave previouslybeenusedfor
applyingpolymericadhesivecompositions,andnotforpolymerswhichcanprovide the requiredheat-
seal and peelingpropertiessuitableforfilmsforcontainerlids.Inaddition,melt-coatinghasgenerally
onlybeenusedformaterialswhichmustbe coated"off-line"inordertoavoidstickingandhandling
problemsduringsubsequentprocessingandwind-up.
5) RecentCo-ExtrusionTechnology
Presentmanycompaniesare usingCo-extrusiontechnologytomake multi-layeredheatsealableand
peelablefilmsforfoodpackaging applications

4. Technology on heat sealing and peeling multilayer film preparation
MitsubishiTechnology:(Commercial grade is Hostaphan RPSE/RPSM)
Mitsubishi ismaking3layeredco-extrudedfilmforsealingapplication(ABCType)
CompositionusedinABCtri-layerfilm:
Layer A composition
a) 20 wt%of polyestercomprising22mol% IPA and 6 wt% Sylysia-430
(SiO2d50 3 micron)
b) 80 wt%polyesterpreparedbyusing40mol% azealicacidand 10
mole%IPA (Tgisabout 0 Deg C)
Layer B composition 100% homoPET
Layer C composition
a) 85 wt%homoPET
b) 15 wt%of masterbatch of 99% homoPETand 1 wt%of Sylobloc44H
d50 2.5 micron
http://www.m-petfilm.com/Europe/peelable%20film.htm
Sealingtemp:120 to 200 degC
SealingPressure:4bar
SealingTime:0.5seconds

5. Terphane Inc Technology:(commercial Grade is SEALPHANE)
Terphane isalsomaking3 layersealable/peelablefilm film
CompositionusedinABCtri-layerfilm:
Layer A composition
Blendingof 75 wt% of homoPETand 25 wt%of homoPETcontaining
5000 ppm of silica(2 micron)
Layer B composition 65 wt%Virgin PET and35 wt%of filmregrindPET
Layer C composition
100 wt%Low meltPET,1 wt%2 micronsilica,1%stearyl erucamideand1
wt%Behenamide
SealingTemp:110 to 230
Sealingpressure: 25 Psi
SealingTime:2seconds
Terphane has developed SEALPHANEheatsealable PETforlidding(peelable/sealable) andpermanent
seal applications

6. Eastman Chemical Co.Technology:
Heat Man has developedco-extrusiontechnologyforheatsealingfilmforPETtrays by usingthe
followingcomposition:
Layer A composition
95 wt%copolyestercontaining31 mol% CHDMand 5 wt%of random
ethylene/methyl acrylate/glycidyl methacrylateterpolymer(Lotader
AX8900)
Layer B composition 100% PET copolymercontaining3.5mol% CHDM
SealingTemp:120 -140 degC
SealingTime:2- 5 seconds
Dupont Technology-1(off-line coating)
Duponthas developdheatseal filmsforliddingapplication,Inthisprocessbase filmwascoatedwith
polymerof 65 mole %methyl methacrylate,33mole % ethyl acrylate and2 mole % acrylic acidto
interfacial layer(ADCOTEX5-183A.) and appliedheatseal layeroninterfacial layer;
Base Layer 100 wt%of biaxiallyorientedpolyethyleneterephthalate
interfacial layer
95wt% of polymerof 65 mole % methyl methacrylate,33mole % ethyl
acrylate and 2 mole % acrylicacid
5 wt%of melamine formaldehyde
Heat Seal Layer
(control film)
a) 50 wt% copolyestercontaining45mol% azealaicacid
b) 50 wt% copolyestercontaining45mol% IPA
Heat Seal filmpreparation throughin-line process:
The Supportlayerwas solutioncoatedwiththe Interface Material inanamountof about0.1 to 0.5
grams Interface Material persquare meterof SupportLayer;thereafterthe interface coatingwas
solutioncoatedwiththe copolyestermaterial usedinthe Control inanamountof 1 gram copolyester
persquare meter.
SealingTemp:120 deg C
SealingTime:0.2minutes
Peel strengthsinthe range of about50-100 g/inch.

7. Toray Technology:
Toray has developedhigh beneficial feature of liddingfilms(peelable films);The filmcontain4layers
Base Layer Polypropylene
BarrierLayer
Blendof ethylenevinyl alcohol andapolyvinyl alcohol aqueoussolution
and crosslinkinganddefoamingagents,
Adhesive Layer Polyethylene
Heat Seal Layer
Ethylene vinylacetate copolymer(EVA copolymer) andblendsof EVA
copolymerwithpolyethylene
Seal Temperature:140 degC
Sealingpressure:30 Psi
SealingTime:0.5seconds
Presto Products,Incorporated:
Thiscompanyhas developed2layersealable films
Base Layer (B) PolyesterorcopolyesterLayer
Sealinglayer(A) AmorphousCo-polyestercontainingCHDMand /or IPA
SealingTemp:120 to 232
Sealingpressure:40 Psi
SealingTime:0.5seconds
Dupont Technology-2(co-extrusion) –Commercial Grade-Malor-OL
Heat-sealable,coextrudedcomposite polymericfilm wdevelopedbyDupont
Substrate copolyesterof azelaicacid/terephthalicacid/ethylene glycol (6/94/100)
Heat-sealable
layer
copolyesterof azelaicacid/terephthalicacid/ethylene glycol (45/55/100) and1.5%
by weight(relativetothe total compositionof the layer) of anN,N'-ethylene
bis(oleamide) wax (EBO;obtainedasCrodamide EBOfromCroda),and3% by weight
(relative tothe total compositionof the layer) of silicafillerparticleswithan
average particle size of 1 .mu.m.
SealingTemp:110 to 150
Sealingpressure:1N/mm2
Sealingtime: 0.5 sec