Adhesives and Key Essentials for Laminating Biopolymer Films Into Flexible Packaging

Adhesives and Key Essentials for Laminating Biopolymer Films into Flexible Packaging

Lowell Lindquist Wayne Eklund

 125 years of success as a manufacturer of specialty chemical products

 Headquartered in St. Paul , Minnesota

 Recognized for quality adhesives, sealants, coatings, and paints

 Global with direct presence in 36 countries, 3300 employees, and customers in more than 100 nations

 2010 sales of $1.4 billion

 Public company listed on NYSE (FUL)

 Component stock of the Standard & Poor’s Small Cap Index (S&P 600)

H.B. Fuller Company is organized geographically:

• North America • Europe

• Latin America • Asia Pacific

 Packaging  Case and Carton  Container Labeling  Flexible Packaging  Packaging Reinforcement  General Assemble  Building and Construction  Personal Hygiene and Nonwovens  Paper Converting  Consumer Product Adhesives  Paper Converting  Polymers  Woodworking

 Flexible Packaging Review  Bio-Films that can be Laminated  Flexible Packaging Applications for Bio-Films  Lamination Processes  Dry Bond  Solvent Free  Bio-Film Surface Treatments  Adhesive Chemistry and Interactions with Bio-Films  Solvent Free  Solvent Based  Water Based  Examples of Bio-Film Laminations

 Complete adhesive coverage across entire film  Bonding a combination of films, foils, or paper  Often reverse printed ink between layers  Adhesive thickness ~ 1 lb/ream

Outer layer Printing ink Adhesive

Inner layers / Sealant film, barriers,..

Adhesive

Printing Ink Printing Ink

 Substrate Surface  Not perfectly regular  Gaps and irregularities in ink  Adhesive  Must overcome surface irregularity  Typical coat weight 1.0 pounds / ream  Range coat weight 0.8-4.0 pounds / ream  Thickness 1-5µm Scanning Electron Microscopy (SEM)  ~2-6% of a lamination volume is adhesive

© 2012 H.B. Fuller Company Typical Package Construction  Outer Layers  Inner Layers  Reverse printed via flexo or  Primary purpose is to seal gravure package  Provide barrier properties  Direct contact with fill goods  Carry brand image  Typical Films  Typical films  Bio - Polyethylene (PE)  Cellophane  PLA  PLA  PHA  Paper  Starch Based TPU’s  Aliphatic-Aromatic Polyesters  Aliphatic-Aromatic Polyesters  Blends of bio-esters  PGA  Polypropylene (OPP) and Metalized  Blends of bio-esters Oriented Polypropylene (MOPP)  Polypropylene (CPP or OPP)  Aclar  Polyethylene (LDPE, LLDPE,  Polyester (PET) and Metalized metallocene, EVA, etc.) Polyester (METPET)

 Nylon  Foil

High Performance (Foil) Retort Difficult Foil

Mid Performance (Film) Barrier to Barrier Chemical Resistance Cellophane with Barrier Heat Resistance

General Purpose (Film) Dry Goods Confectionery Snack Lid Stock Biodegradable Polyesters (PLA,PHA,etc.)

Solvent Free Water-based Solvent-based

Market Volume

 Frozen Foods

 Fresh Cut Produce  Room Temp Confectionary  Snack  Hot Fill  Condiment  Lid Stock  Overwraps  Pasta Package  Some industrial and consumer  Not currently used above hot fill temperature

Dry Bond

Solvent Free

Laminate Slit Pouch Fill

 In-line corona treatment  Coat weight controlled by gravure  Coat weights of 0.8 -3.0 pound/ream  Line speed limited by drying process  Liquid carrier must be removed for health and adhesive quality  Nip temperature and pressure as high as possible – limited by film properties  Typical pot life is 8 hours  Smoothing bar is required for WBA  Drying related to temperature, air flow, and inlet humidity

Laminate Slit Pouch Fill

Bio-Film Considerations During Dry Bond Lamination

 Treatment level of films

 Adsorbed water on films due to hydroscopic nature may affect adhesion  Speed ramp-up-rate is a critical due to tear propagation, many bio-films do not like mechanical shock  Conventional coat weights (0.8 to 3.0 lbs/ream)  Smoothing bar critical for optimum appearance – water-base only  Oven temperature limitations due to yield and shrink of some bio-films- (may limit line speed due to slower drying at low temp)

Laminate Slit Pouch Fill

Bio-Film Considerations During Dry Bond Lamination

 High nip temperature is desirable – limited by film stability

 High nip pressure is desirable – limited by film stability  Rewind tensions less critical due to high green strength  Must be aware of film relaxation (elasticity will cause corrugation and crushed cores)  Sensitive to roll damage like nicks and bruises  Potential for film solvent sensitivity  Modified coat weight testing

Laminate Slit Pouch Fill

 In-line corona treatment  Two part reactive system (meter-mix accuracy is critical)  Pot life 30 to 60 minutes  Typical line speed > 1000 fpm  Typical coat weight 1.0 lbs/ream  Heat used to adjust viscosity  Very little green strength  Rewind tension is critical due to lack of green strength

Secondary film introduced

Adhesive applied to the primary film Primary film nipped to the secondary film

Lamination wound onto a core Primary film introduced Adhesive pumped into the machine

Laminate Slit Pouch Fill

Bio-Film Considerations During Solventfree Lamination  Check film dyne level treatment level of films (no solvent to help clean film surface)  Adsorbed water on films due to hydroscopic nature may affect adhesion  Controlled speed ramp-up-rate is critical due to tear propagation, many bio-films do not like mechanical shock  Rewind tensions critical due to low adhesive green strength  Less aggressive nip but air must be excluded

Laminate Slit Pouch Fill

Bio -Film Considerations During Solvent Free Lamination  Must be aware of film relaxation (elasticity will cause corrugation, crushed cores, curl, ink smearing, and telescoping)  Sensitive to roll damage like nicks and bruises  Potential isocyanate reaction with film and ink components (glycol)  Conventional coat-weights (0.8-1.5 pounds / ream)  Yield and elasticity of some bio-films can create web handling challenges

© 2012 H.B. Fuller Company Comparison of Lamination Processes Shift toward Solvent Free Adhesives Dry Bond  High Green Tack  High Strength Adhesives - High Energy Demand - Emissions - Footprint - Speed Limited by Oven Size

Solvent Free

 High Speed  No Emissions  Low Energy Demand  Small Footprint - Need for accurate metering - Little Green Tack

Bio-Film Surface Modification  Surface treatments- (Initial treatment critical followed with in-line treatment)  Corona  Plasma  Chemical / Primers  Coatings  PVdC  Acrylic  PVOH  Urethane  Vapor Deposition  Metallization  Ceramic  Why do we treat the films?  Remove contamination  Modify the polarity of film surface  Increase the surface roughness on film  Add or enhance chemical functionality of film surface

700 Corona Treatment Study B 600 Printed Cello - Clear high slip LDPE o n d 500

S 400 t r e 300 n g t 200 h W-minutes/sq.ft. 100 0 0.5 1 1.5 2

Corona Treatment:  Adds polarity to film increasing adhesion  Removes contaminants  Increases surface roughness

Isocyanate Functional Prepolymer Polyol Curative 40% 60%

 No Solvent  Reactive chemistry  Two-components

Common Names Chemical Representation

Polyol OH

B-side OH Curative OH Hydroxyl

Isocyanate A-Side NCO Adhesive Prepolymer

Laminate Slit Pouch Fill

OH OH

 The two components are mixed and applied to the film but have not reacted  The ratio of the two components is important for polymer creation  Low viscosity to allow application to film  Very little green strength to hold films together  Water is supplied from the environment and films

Laminate Slit Pouch Fill

OH OH

 Partial polymerization after 3-12 hours creates enough adhesive strength to allow film slitting  Curative and water are reacting to begin formation of ideal polymer structure  Heat will accelerate polymer formation time and decrease time-to-slit.

Laminate Slit Pouch Fill

 Significant polymerization in 12-48 hours to provide heat resistance for seal making  Bond strength is very high  Water is used in reaction to increase stiffness of polymer by creating a urea group

Laminate Slit Pouch Fill

 Polymerization complete, food can be safely added  Full adhesive strength is produced  Product resistance is developed  This polymer is significantly different from the starting materials

 Hydroscopic films may provide excessive water which will alter the polymer that is formed  More polyurea (harder, more heat and chemical resistance)  Excessive water can cause CO2 generation (gassing)  Plasticizers can be difficult for SF adhesives to displace for optimum adhesive strength  Glycols and other reactive film components will likely react into the adhesive which will alter the polymer that is formed  Because of the low molecular weight starting materials SF adhesives can smear ink when film tensions are not matched. A film that is over stretched during laminating will relax in the roll with a potential to smear ink.  Covalent bonds to film moiety (specifically reaction with OH or COOH groups)

Bio-Film Construction –Solvent Free OPLA / LDPE and OPLA / OPLA for Snack Food

 Goal – Lamination of renewable films with maximum adhesion  Use 1 mil OPLA and 1mil LDPE  Unprinted films laminated with 1.0 pounds / ream of SF adhesive  Screened three adhesive systems

SF Adhesive A SF Adhesive B SF Adhesive C

1 Day 2 Day 5 Day 7 Day  All three Solvent Free Adhesives have destruct bond level on BOPP

1000 900 800 700 600 500 400 300 200 100 SF Adhesive A 0 SF Adhesive B SF Adhesive C 1 day 2 day 5 day 7 day  Not all the Solvent Free Adhesives were successful on these films

1000 900 800 700 600 500 400 300 200 100 SF Adhesive A 0 SF Adhesive B SF Adhesive C 1 day 2 day 5 day 7 day  Not all Solvent Free Adhesives were successful on these films

Conclusions  Goal was reached by careful selection of SF adhesive system  Not all SF adhesives give high bond strength on OPLA / OPLA or OPLA / LDPE.  Recommendation: Involve the adhesive supplier early in bio-film projects

 OPLA / Cellophane  OPLA-PHA blend / Cellophane  OPLA / Met PLA  OPLA / Met PLA-PHA blend

600

500 Adhesive 1 Adhesive 2 400 Adhesive 3 300

200

100

Lamination Notes OPLA / Cellophane Adhesive selection is critical, can achieve excellent bonding. PHA / Cellophane Adhesive selection is critical, can achieve excellent bonding. OPLA / Met PLA These films had metal transfer to adhesive, need to run primer study OPLA / PHA Adhesive selection is critical, can achieve excellent bonding.

35%

Prepolymer 60% Curative 5% Solvent

 Long pot life  Very low viscosity at application station  Very high viscosity at nipping station  Solvent must be removed in application process

Common Names Chemical Representation

Polyol OH

B-side OH Curative OH Hydroxyl Isocyanate A-Side NCO Adhesive Solvent Ethyl Acetate Solvent

OH OH

 The three components are in solution  Very low viscosity due to solvent  Water is supplied from the environment or films  Solvent is a carrier to get the adhesive to the film

OH OH

 An in-line oven is used to evaporate the solvent  The chemical reaction is the same as for a solvent free adhesive but the starting molecules are much larger  Reaction is not completed

OH OH

 The solvent is evaporated before nipping (dry bond)  Very high viscosity due to loss of solvent = high green strength  Oven air flow and temperature adjusted to evaporate all the solvent  Chemical reaction is not complete

Laminate Slit Pouch Fill

 High starting molecular weight allows for slitting in as quick as one hour.  Curative and water react to form ideal polymer structure  Heat will accelerate polymer formation time and decrease time-to-slit.

Laminate Slit Pouch Fill

 Significant polymerization to provide heat resistance for seal making  Less time to get to high polymer formation because of high molecular weight starting material  Bond strength is very high  Water is used in reaction to increase stiffness of polymer

Laminate Slit Pouch Fill

 Polymerization complete, food can be safely added  Full adhesive strength allows for freezing, boiling, microwaving, etc.  Thermal resistance dependant on films and adhesive  Product resistance is developed  Chemical resistance is one of the last properties to develop

 Ethyl acetate in adhesive may soften bio-film resulting in poor web handling, frosting, shrinking  Hydroscopic films may provide excessive water which will alter the polymer that is formed  More polyurea (harder, more heat and chemical resistance)  Excessive water can cause CO2 generation (gassing)  Glycols and other reactive film components will likely react into the adhesive which will alter the polymer that is formed  Covalent bonds to film moiety (specifically reaction with OH or COOH groups)

40% WB Polymer

58% water

Crosslinker - optional

 Long pot life  Can add cross-linker for added performance  Very low application viscosity  Water has to be removed in application process

Laminate Slit Pouch Fill

WB Adhesive is gravure applied to the film. Primary Film

Coalesced Adhesive Water is evaporated in the oven, film of Primary Film adhesive is formed.

Secondary Film Second film is dry Coalesced Adhesive bonded to adhesive. Primary Film

Laminate Slit Pouch Fill

Secondary Film Coalesced Adhesive Primary Film

 The polymer cures, flows, crystallizes over a short time period and has enough bond strength to be slit  Drying conditions should be ramped to avoid skinning or bubbling  Aggressive nip to increase bond strength and improve appearance  Nip conditions specifically set to match Tg of adhesive without exceeding film handling limits  Pouching is possible when the polymer is near full cure and has enough heat resistance to make heat seals.

OPLA / OPLA for Lidstock  Goal – lightly printed biodegradable lid for biodegradable tray with superior film-to-film adhesion  Use matched 1 mil oriented multilayer films for best web handling  Reverse printed with light ink coverage  Screened six adhesives and two co-reactants  Both adhesive and co-reactant impact adhesion values

600

500

400

300

200

100

0 Acrylic / Acrylic / Hybrid A / Hybrid A / Hybrid B / Hybrid B / Urethane Urethane Urethane Urethane Urethane Urethane CR1 CR2 CR1 CR2 CR1 CR2 A / CR1 A / CR2 B / CR1 B / CR2 C / CR1 C / CR2

Conclusions  Goal was reached  Acrylic performance is greatly influenced by co-reactant selection  Acrylic performance often approached urethane performance based on selection  Not all urethanes are better than acrylics, selection of urethane adhesive is important  Match the chemistry  Recommendation: Involve the adhesive supplier early in bio-film projects

 Goal –printed biodegradable lid for biodegradable tray with superior adhesion  Use matched 1 mil oriented multilayer films for best web handling  Reverse printed with light ink coverage  Choice of WB dry bond dictated by existing assets

grams / inch 600

500

400

300

200

100

0 Cellophane / LDPE Cellophane / Ecoflex+PLA

Conclusions  Goal was reached  The compostable sealant had web handling like a conventional sealant  The compostable sealant had superior adhesion properties to LDPE with this adhesive.  Recommendation: Involve the adhesive supplier early in bio-film projects

© 2012 H.B. Fuller Company Adhesive Comparison Solvent Solvent Free Water Based Based Coat Weight 1.5-3.5 1.0-1.8 1.0-2.0 (#/Ream) Initial Bonds 300 grams 20 grams 300 grams Viscosity Low High Low Pot Life 8 hours 30 minutes 8 hours Retained Solvent Possible No Amine possible Emissions Yes No No Energy used High Low High Lamination speed Oven limit 1500 Oven limit Time to Slit 2 hours 12 hours 1 hour Fire Hazard Yes No No Cost (adhesive + 3.5X X 2.7X energy)

Laminate Slit Pouch Fill

 PLA / MetPLA snack food application

Laminate Slit Pouch Fill

 Correct adhesive gives high bond strength  Correct adhesive gives sound reduction  Working together accelerates success

HB Fuller would like to thank the following supporters for their contributions to this workshop! Taghleef Industries Innovia Metabolix BioBag Heritage Plastics/Plastimin Imaflex Sierra Converting

This presentation is for informational purposes only and does not constitute an offer by H.B. Fuller to sell or a warranty of any kind.