Adhesion in Extrusion Coating & Laminating

AdhesionAdhesion inin ExtrusionExtrusion CoatingCoating && LaminatingLaminating -- thethe ImportanceImportance ofof MachineMachine VariablesVariables

BruceBruce FosterFoster MicaMica CorporationCorporation OutlineOutline

•• IdentifyIdentify keykey factorsfactors thatthat affectaffect adhesionadhesion

•• ExamineExamine MachineMachine VariablesVariables thatthat affectaffect thesethese factorsfactors TheThe ExtrusionExtrusion CoatingCoating System:System:

Secondary substrate (if extrusion lamination)

++++++++++++++++++++++++++++++++++++++++++ Surface Extrudate (LDPE, copolymer, ionomer = adhesive) modifier ++++++++++++++++++++++++++++++++++++++++++ (corona, flame, chemical primer) Primary Substrate (paper, film, foil, fabric, etc) TwoTwo KeyKey ComponentsComponents forfor AdhesionAdhesion

1.1. IntimateIntimate contactcontact between adhesive & substrate, which permits:

2.2. ChemicalChemical bondingbonding between adhesive & substrate FactorsFactors InfluencingInfluencing IntimateIntimate ContactContact

•• AdhesiveAdhesive ThicknessThickness (thicker(thicker == moremore easilyeasily deformed,deformed, longerlonger solidificationsolidification time)time) •• AdhesiveAdhesive mobility/mobility/ deformabilitydeformability (viscosity,(viscosity, modulus,modulus, solidificationsolidification temp.,temp., wetwet--out)out) •• SubstrateSubstrate morphologymorphology (rough(rough surfacesurface == lessless intimateintimate contact)contact) •• SubstrateSubstrate wettabilitywettability (poor(poor wettingwetting == lessless intimateintimate contact)contact MachineMachine FactorsFactors ThatThat CanCan ImproveImprove IntimateIntimate ContactContact

•• ExtrudateExtrudate thicknessthickness •• NipNip conditionsconditions (pressure(pressure && length)length) •• MeltMelt temperaturetemperature FactorsFactors InfluencingInfluencing ChemicalChemical BondingBonding

•• DegreeDegree ofof intimateintimate contactcontact •• SubstrateSubstrate surfacesurface chemistrychemistry •• AdhesiveAdhesive surfacesurface chemistrychemistry •• MigratoryMigratory chemicalschemicals (in(in adhesiveadhesive oror substrate)substrate) •• EnvironmentalEnvironmental stressesstresses MachineMachine FactorsFactors ThatThat CanCan ImproveImprove ChemicalChemical BondingBonding

•• SubstrateSubstrate treatmenttreatment conditionsconditions (corona(corona oror flameflame powerpower level,level, oror primerprimer applicationapplication variables)variables) •• ChoiceChoice ofof extrudateextrudate typetype •• ExtrudateExtrudate thicknessthickness •• AirAir--gapgap distancedistance •• MeltMelt temperaturetemperature ofof extrudateextrudate •• ExtruderExtruder backback--pressurepressure •• OzoneOzone assistassist IntimateIntimate contactcontact ++ ChemicalChemical bondingbonding == DurableDurable AdhesionAdhesion Now,Now, ExamineExamine EachEach MachineMachine FactorFactor inin MoreMore DetailDetail…… MachineMachine FactorsFactors ThatThat CanCan ImproveImprove IntimateIntimate ContactContact

1.1. ExtrudateExtrudate thicknessthickness 2.2. NipNip conditionsconditions (pressure(pressure && length)length) 3.3. MeltMelt temperaturetemperature ExtrudateExtrudate ThicknessThickness

SingleSingle mostmost importantimportant variablevariable inin achievingachieving goodgood adhesion*adhesion*

ThickerThicker isis almostalmost alwaysalways betterbetter

*(Assumption: Other extrusion conditions are in “normal” ranges) 500Fig.Fig. 11 -- TypicalTypical AdhesionAdhesion ResponseResponse 450 toto CoatingCoating ThicknessThickness 400

350

300

250

200

150 Max Peel,Max g/25mm

100

0 5 10152025303540 Coating Weight, gsm

Ref. 1 - Foster, Bruce ; Baker, Mike, Effect of Extrusion Parameters on Adhesion of Polyester – A Line Study, 2001 TAPPI Polymers, Laminations, Coatings Conference Proceedings, TAPPI PRESS, Atlanta, paper 17-2 WhyWhy ThicknessThickness isis ImportantImportant

•• TransferTransfer ofof thermalthermal massmass toto insureinsure intimateintimate contactcontact •• ThermalThermal massmass aidsaids inin surfacesurface oxidationoxidation ofof thethe extrudateextrudate •• ThickerThicker == moremore compressible,compressible, importantimportant forfor nonnon--smoothsmooth substratessubstrates WhyWhy ThicknessThickness isis ImportantImportant

die Extrudate

Substrate >>> Air gap Nip Chill Roll

Objective: Transfer thermal energy from die to nip Fig.Fig. 22 -- TransferTransfer ofof ThermalThermal EnergyEnergy

Nip Roll apex Position in Nip

Nip impression 0 Chill Roll (deformation of Nip pressure max rubber)

60 x Nip length, mm Time in Nip, msec = Line speed, mpm TransferTransfer ofof ThermalThermal EnergyEnergy

SolidificationSolidification ModelModel GivesGives InsightInsight…….. 1-dimensional unsteady-state heat conduction equation:*

ModelModel predictspredicts solidificationsolidification ofof polymerpolymer inin thethe nipnip

*Ref. 2 - Trouilhet, Yves; Morris, Barry A, Prediction of Temperature Profiles Across Coating and Substrate in the Nip, 1999 TAPPI Polymers, Laminations, Coatings Conference Proceedings, TAPPI PRESS, Atlanta, p. 457. Fig.Fig.5 33 –– ModelingModeling PolymerPolymer SolidificationSolidification

4.5 TimeTime vs.vs. ThicknessThickness

3.5

c 3 Ts = 80oC 2.5 2 - Assumed Solidification Temperatures (Ts): 2

1.5 Solidification Time, mse Time, Solidification 1 Ts = 100oC

0.5

0 0 5 10 15 20 25 Chill-rollChill-Roll sideThickness, um Substrate side Fig.Fig. 44 –– SolidificationSolidification TimeTime vs.vs. MeltMelt TemperatureTemperature

5 4.5 4 3.5 3 2.5 2 1.5 msec to Solidify to msec 1 0.5 0 300 305 310 315 320 325 330 Melt Temperature, deg C Fig.Fig. 55 –– SolidificationSolidification TimeTime vs.vs. ChillChill RollRoll TemperatureTemperature

5 4.5 4 3.5 3 2.5 2 1.5 msec to Solidify to msec 1 0.5 0 25 35 45 55 65 75 85 Chill Roll Temperature, deg C MachineMachine FactorsFactors ThatThat CanCan ImproveImprove IntimateIntimate ContactContact

1.1. ExtrudateExtrudate thicknessthickness 2.2. NipNip conditionsconditions (pressure(pressure && length)length) 3.3. MeltMelt temperaturetemperature Fig.Fig. 66 –– NipNip ConditionsConditions

Nip Roll apex Position in Nip

Nip impression 0 Chill Roll (deformation of Nip pressure max rubber)

60 x Nip length, mm Time in Nip, msec = Line speed, mpm Fig.Fig. 77 EffectEffect ofof NipNip LengthLength && LineLine SpeedSpeed

12 Nip Impression, mm: 20 10 10 8 5 6

4 Nip Time, msec Time, Nip 2

0 100 150 200 250 300 Line Speed, mpm Fig.Fig. 33 5

4.5 SolidificationSolidification TimeTime vs.vs. ThicknessThickness

3.5

c 3 Ts = 80oC 2.5 2 - Assumed Solidification Temperatures (Ts): 2

1.5 Solidification Time, mse Time, Solidification 1 Ts = 100oC

0.5

0 0 5 10 15 20 25 Chill-rollChill-Roll sideThickness, um Substrate side GuidelinesGuidelines forfor NipNip LengthLength && PressurePressure •• SofterSofter PolymersPolymers (e.g.:(e.g.: LDPE,LDPE, EVA,EVA, EMA)EMA) –– LongerLonger impression,impression, lowerlower pressurepressure (softer(softer nipnip roll)roll)

•• HarderHarder PolymersPolymers (e.g.:(e.g.: HDPE,HDPE, PP,PP, PET)PET) –– ShorterShorter impression,impression, higherhigher pressurepressure (harder(harder nipnip roll)roll) MachineMachine FactorsFactors ThatThat CanCan ImproveImprove IntimateIntimate ContactContact

1.1. ExtrudateExtrudate thicknessthickness 2.2. NipNip conditionsconditions (pressure(pressure && length)length) 3.3. MeltMelt temperaturetemperature MeltMelt TemperatureTemperature (T)(T) && IntimateIntimate ContactContact

TT LowerLower ViscosityViscosity …….Yes!.Yes!

TT ImproveImprove intimateintimate ….No! contact?contact? ….No!

WellWell………… maybemaybe……………… Fig.Fig. 44 –– SolidificationSolidification TimeTime vs.vs. MeltMelt TemperatureTemperature

5 4.5 4 3.5 3 2.5 2 1.5 msec to Solidify to msec 1 0.5 0 300 305 310 315 320 325 330 Melt Temperature, deg C MeltMelt TemperatureTemperature (T)(T) && IntimateIntimate ContactContact

TT MoreMore surfacesurface oxidationoxidation

SurfaceSurface oxidationoxidation BetterBetter wettingwetting ofof substratesubstrate MachineMachine FactorsFactors ThatThat CanCan ImproveImprove IntimateIntimate ContactContact

1.1. ExtrudateExtrudate thicknessthickness 2.2. NipNip conditionsconditions (pressure(pressure && length)length) 3.3. MeltMelt temperaturetemperature IntimateIntimate contactcontact ++ ChemicalChemical bondingbonding == DurableDurable AdhesionAdhesion MachineMachine FactorsFactors ThatThat CanCan ImproveImprove ChemicalChemical BondingBonding

•• TreatmentTreatment addsadds reactivereactive sitessites toto substratesubstrate

•• ConsultConsult thethe suppliersupplier forfor PROPERPROPER treatmenttreatment levelslevels forfor youryour substratessubstrates

•• AvoidAvoid overover--treatmenttreatment SubstrateSubstrate TreatmentTreatment

++++++++++++++++++++++++++++++++++++++++++

Substrate (after proper treatment)

Reactive sites Corona, flame, plasma, priming

+ + + + + + + + + +

Substrate (as received) AvoidAvoid OverOver--Treatment!Treatment! Substrate fracture +++++++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + Substrate (after over-treatment)

Reactive sites Excess Corona, flame, plasma, priming

+ + + + + + + + + +

Substrate (as received) CoronaCorona TreatmentTreatment ofof FilmsFilms UseUse ProperProper WattWatt--DensityDensity

Watt-Density = Power / area / time

Metric Units: W/m2/minute

[KW setting x1000] / [Line Speed (m/min) x width (m)]

Example: Treater is 3.0kW, line speed is 130mpm, and the treater width is 1400mm (1.4m), then the watt-density is:

(3.0 x 1000) / (130 x 1.4) = 16.5 W/m2/min

Important: You must determine optimum watt-density for each film and each set of running conditions. Some starting suggestions: BOPP films: 30 – 40 WD OPET films: 15 – 20 WD BON films: 5 – 15 WD OtherOther TreatmentTreatment MethodsMethods

•• FlameFlame –– properproper air/gasair/gas ratioratio && manifoldmanifold positionposition

•• ChemicalChemical primingpriming –– primerprimer choice,choice, properproper amountamount && completecomplete dryingdrying

•• PlasmaPlasma –– askask thethe experts!experts! MachineMachine FactorsFactors ThatThat CanCan ImproveImprove ChemicalChemical BondingBonding

•• SubstrateSubstrate treatmenttreatment conditionsconditions (corona(corona oror flameflame powerpower level,level, oror primerprimer applicationapplication variables)variables) •• ChoiceChoice ofof extrudateextrudate typetype •• ExtrudateExtrudate thicknessthickness •• AirAir--gapgap distancedistance •• MeltMelt temperaturetemperature ofof extrudateextrudate •• ExtruderExtruder backback--pressurepressure •• OzoneOzone assistassist ChoiceChoice ofof ExtrudateExtrudate ((GeneralGeneral ““RulesRules ofof ThumbThumb””))

•• LDPELDPE –– forfor paper,paper, primedprimed plasticsplastics && primedprimed foilsfoils •• AcidAcid copolymerscopolymers –– forfor metalmetal substratessubstrates && primedprimed filmsfilms •• IonomersIonomers –– forfor metalmetal && primedprimed substratessubstrates •• AcrylateAcrylate copolymerscopolymers –– forfor PPPP && PETPET films,films, && primedprimed surfacessurfaces MachineMachine FactorsFactors ThatThat CanCan ImproveImprove ChemicalChemical BondingBonding

die Extrudate

Substrate >>> Air gap Nip Chill Roll 44 –– References:References:

Ref. 3 - W.J. Ristey and R.N. Schroff; The Degradation and Surface Oxidation of Polyethylene During the Extrusion Coating Process, 1978 TAPPI Paper Synthetics Proceedings, TAPPI PRESS, Atlanta, p.267

Ref. 4 - V. Antonov and A.M. Soutar; Foil Adhesion With Copolymers: Time in the Air Gap, 1991 TAPPI Polymers, Laminations, and Coatings Conference Proceedings, TAPPI PRESS, Atlanta, p.553

Ref. 5 - B.A. Morris & N. Suzuki; The Case Against Oxidation as a Primary Factor for Bonding Acid Copolymers to Aluminum Foil, 2000 TAPPI Polymers, Laminations, and Coatings Conference Proceedings, TAPPI PRESS, Atlanta

Ref. 6 – B. Foster; Effect of Extrusion Coating Parameters on Activation of a Primed Film, 2002 TAPPI PLACE Proceedings, TAPPI PRESS, Atlanta Paper 14-2. RisteyRistey && SchroffSchroff -- 19781978

•• StudiedStudied EffectsEffects of:of: –– AirAir--GapGap –– MeltMelt TemperatureTemperature –– ThicknessThickness •• OnOn TheseThese Properties:Properties: –– MolecularMolecular WeightWeight ChangesChanges –– SurfaceSurface OxidationOxidation RisteyRistey && SchroffSchroff -- 19781978

•• MostMost SignificantSignificant Conclusion:Conclusion:

25mm25mm ↑↑airair--gapgap == 5.55.5oCC ↑↑meltmelt temptemp

For LDPE surface oxidation between 321 – 338oC 44 –– References:References:

Ref. 3 - W.J. Ristey and R.N. Schroff; The Degradation and Surface Oxidation of Polyethylene During the Extrusion Coating Process, 1978 TAPPI Paper Synthetics Proceedings, TAPPI PRESS, Atlanta, p.267

Ref. 4 - V. Antonov and A.M. Soutar; Foil Adhesion With Copolymers: Time in the Air Gap, 1991 TAPPI Polymers, Laminations, and Coatings Conference Proceedings, TAPPI PRESS, Atlanta, p.553

Ref. 6 – B. Foster; Effect of Extrusion Coating Parameters on Activation of a Primed Film, 2002 TAPPI PLACE Proceedings, TAPPI PRESS, Atlanta Paper 14-2. AntonovAntonov && SoutarSoutar -- 19911991

Introduced the concept of:

TimeTime InIn thethe AirAir--GapGap (TIAG)(TIAG)

Simplifying Assumption: Extrudate Speed = Line Speed

AirAir--GapGap (mm)(mm) xx 6060 ~~ Then,Then, TIAGTIAG (msec)(msec) == LineLine SpeedSpeed (mpm)(mpm) AntonovAntonov && SoutarSoutar -- 19911991

•• MostMost SignificantSignificant Conclusion:Conclusion: AirAir--gapgap timetime ofof ca.ca. 8080 –– 120120 msecmsec

ToTo allowallow oxidationoxidation ofof EAAEAA && therebythereby getget goodgood adhesionadhesion toto aluminiumaluminium foilfoil

SubsequentlySubsequently foundfound toto bebe aa goodgood ““rulerule ofof thumbthumb”” forfor LDPELDPE resinsresins TimeTime InIn thethe AirAir--GapGap

HasHas beenbeen && continuescontinues toto bebe aa usefuluseful tooltool forfor troubleshootingtroubleshooting adhesionadhesion problemsproblems inin extrusionextrusion coatingcoating && laminatinglaminating processesprocesses

But....But.... 44 –– References:References:

Ref. 3 - W.J. Ristey and R.N. Schroff; The Degradation and Surface Oxidation of Polyethylene During the Extrusion Coating Process, 1978 TAPPI Paper Synthetics Proceedings, TAPPI PRESS, Atlanta, p.267

Ref. 4 - V. Antonov and A.M. Soutar; Foil Adhesion With Copolymers: Time in the Air Gap, 1991 TAPPI Polymers, Laminations, and Coatings Conference Proceedings, TAPPI PRESS, Atlanta, p.553

Ref. 6 – B. Foster; Effect of Extrusion Coating Parameters on Activation of a Primed Film, 2002 TAPPI PLACE Proceedings, TAPPI PRESS, Atlanta Paper 14-2. MorrisMorris && SuzukiSuzuki -- 20002000

MostMost significantsignificant conclusion:conclusion:

OxidationOxidation isis notnot thethe mechanismmechanism forfor EAA*EAA* adhesionadhesion toto aluminiumaluminium foil,foil, butbut

TimeTime inin thethe airair--gapgap doesdoes influenceinfluence thethe adhesionadhesion

** ForFor NucrelNucrel gradesgrades ofof 9%9% && 12%12% acidacid MorrisMorris && SuzukiSuzuki -- 20002000

AnotherAnother conclusion:conclusion:

ForFor LDPELDPE && lowlow--acidacid EAAEAA copolymers,copolymers, OxidationOxidation isis aa keykey mechanismmechanism forfor adhesionadhesion 44 –– References:References:

Ref. 3 - W.J. Ristey and R.N. Schroff; The Degradation and Surface Oxidation of Polyethylene During the Extrusion Coating Process, 1978 TAPPI Paper Synthetics Proceedings, TAPPI PRESS, Atlanta, p.267

Ref. 4 - V. Antonov and A.M. Soutar; Foil Adhesion With Copolymers: Time in the Air Gap, 1991 TAPPI Polymers, Laminations, and Coatings Conference Proceedings, TAPPI PRESS, Atlanta, p.553

Ref. 6 – B. Foster; Effect of Extrusion Coating Parameters on Activation of a Primed Film, 2002 TAPPI PLACE Proceedings, TAPPI PRESS, Atlanta Paper 14-2. ExperimentExperiment SetSet #1#1 –– FebFeb ‘‘0202 Experimental Design - Modified Box-Benkin (center and edge-centers) Variables: Melt temp, Acid#, Coat Wt, Offset Fixed Line-Speed @26mpm (85fpm) & Air-Gap at 44mm (100msec) Point # Melt Temp Acid # Coat Wt Offset Adhesion Comments deg C (deg F) gsm (#/rm) (0, -0.5) (g/25mm) 1 271 (520) 0 20 (12) 0 & -0.5 0 2 271 (520) 3 10 (6) -0.5 FT @300 3 271 (520) 3 30 (18) - 4 271 (520) 9 20 (12) 0 FT @2000 5 293 (560) 0 10 (6) 0 & -0.5 FT @300 6 293 (560) 0 30 (18) 0 & -0.5 FT @900 7 293 (560) 3 20 (12) - 8 293 (560) 9 10 (6) - Degraded melt 9 293 (560) 9 30 (18) - 10 315 (600) 0 20 (12) - 11 315 (600) 3 10 (6) - 12 315 (600) 3 30 (18) - 13 315 (600) 9 20 (12)- not - tested Max T= 302 (575) ExperimentExperiment Set#2Set#2 –– MayMay ‘‘0202 Following are designed to vary air-gap distance & TIAG, all with LDPE only: (and the primed stock is now 4 months old!) Pt. # Melt Temp Line Speed Coat Wt Air-Gap Air Gap, Adhesion Failure deg C (F)mpm(fpm) gs m (#/rm) mm (inch) mse c (g/25mm) M ode 1 293 (560) 15 (50) 10 (6) 25 (1.0) 100 40 2 293 (560) 26 (85) 10 (6) 44 (1.7) 103 35 3 293 (560) 15 (50) 10 (6) 89 (3.5) 350 300 FT 4 293 (560) 15 (50) 20 (12) 25 (1.0) 100 50 5 293 (560) 26 (85) 20 (12) 44 (1.7) 103 500 FT 6 293 (560) 26 (85) 20 (12) 64 (2.5) 147 500 FT 7 293 (560) 26 (85) 20 (12) 89 (3.5) 206 500 FT 8 293 (560) 15 (50) 20 (12) 89 (3.5) 350 500 FT

9 282 (540) 15 (50) 10 (6) 25 (1.0) 100 6 10 282 (540) 26 (85) 10 (6) 44 (1.7) 100 7 11 282 (540) 26 (85) 10 (6) 89 (3.5) 206 70 12 282 (540) 15 (50) 10 (6) 89 (3.5) 350 70 13 282 (540) 15 (50) 20 (12) 25 (1.0) 100 6 14 282 (540) 26 (85) 20 (12) 44 (1.7) 100 9 15 282 (540) 26 (85) 20 (12) 89 (3.5) 206 500 FT 16 282 (540) 15 (50) 20 (12) 89 (3.5) 350 500 FT 17 282 (540) 26 (85) 30 (18) 44 (1.7) 100 12 Oxidation -vs- Air Gap Time 1978 Data of Ristey & Schroff

1.9016

2 321 C (610 F) R = 0.965

329 C (625 F) y = 0.0001x 338 C (640 F) 1.4 Power (321 C (610 F)) 1.2 Power (329 C (625 F))

1 Power (338 C (640 F)) l Absorbance l y 0.8 1.6735 1.7915 y = 0.0002x y = 9E-05x 2 2 0.6 R = 0.9107 R = 0.9649 Carbon

0.4

0.2

0 20 40 60 80 100 120 140

Air Gap, msec FosterFoster --20022002

•• MostMost SignificantSignificant Conclusion:Conclusion:

(For(For oxidationoxidation ofof LDPELDPE inin airair gap):gap):

–– AirAir--gapgap timetime >> thicknessthickness >> meltmelt temptemp ScaleScale--UpUp Differences..Differences..

“Typical” Production Parameter Pilot-Line Conditions Conditions

100-400m/min Line speed: 26m/min (85ft/min) (~300-1300ft/min)

Air-gap: 44mm (1.75 inches) 150-300mm (6- 12 inches)

Die shear rate: 190sec-1 500-2500sec-1 FosterFoster –– 20022002

QQ –– IsIs diedie shearshear raterate anan importantimportant factor?factor? RecentRecent ExperimentExperiment –– JanJan ‘‘0505

Surface Oxidation -vs- Die Shear Rate

0.018

0.016

0.014

0.012 Carbonyl AbsorbanceCarbonyl

0.01

0.008

0.006 600 800 1000 1200 1400 1600 1800 Die Shear Rate, 1/s QQ –– IsIs diedie shearshear raterate anan importantimportant factor?factor?

AA –– Maybe!Maybe! MoreMore workwork neededneeded…… MachineMachine FactorsFactors ThatThat CanCan ImproveImprove ChemicalChemical BondingBonding

BackBack Pressure:Pressure: •• CreatesCreates moremore shearshear •• MoreMore polymerpolymer chainchain endsends •• MoreMore oxidationoxidation

•• MoreMore degradation!degradation! (possible(possible heatheat--sealseal && bondbond agingaging problems)problems) MachineMachine FactorsFactors ThatThat CanCan ImproveImprove ChemicalChemical BondingBonding

die Ozone

Substrate >>> Air gap Nip Chill Roll OzoneOzone AssistAssist

•• AidsAids surfacesurface oxidationoxidation •• LowerLower meltmelt tempstemps and/orand/or thinnerthinner coatcoat weightsweights maymay bebe possiblepossible

•• ManyMany ReferencesReferences availableavailable ConclusionsConclusions

•• ManyMany factorsfactors affectaffect adhesionadhesion

•• MoreMore researchresearch neededneeded toto betterbetter understandunderstand thethe oxidationoxidation // mechanicalmechanical processprocess inin thethe airair--gap.gap.