Adhesives and Key Essentials for Laminating Biopolymer

Transcription

Adhesives and Key
Essentials for Laminating
Biopolymer Films into
Flexible Packaging
Lowell Lindquist
Wayne Eklund
© 2012 H.B. Fuller Company
H.B. Fuller Company
 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)
Organization
H.B. Fuller Company is organized
geographically:
• North America • Europe
• Latin America
• Asia Pacific
Focus Market Areas
 Packaging
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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
Outline
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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
Flexible Packaging Structure
 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
Flexible Packaging Film Cross Section
Outer layer
Printing ink
Adhesive
Inner layers / Sealant film, barriers,..
Adhesive
Printing Ink
Printing Ink
Flexible Packaging Structure
 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
Scanning Electron Microscopy (SEM)
 Thickness 1-5µm
 ~2-6% of a lamination volume is
adhesive
Typical Package Construction
 Outer Layers
 Reverse printed via flexo or
gravure
 Provide barrier properties
 Carry brand image
 Typical films
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Cellophane
PLA
Paper
Aliphatic-Aromatic Polyesters
Blends of bio-esters
Polypropylene (OPP) and Metalized
Oriented Polypropylene (MOPP)
Aclar
Polyester (PET) and Metalized
Polyester (METPET)
Nylon
Foil
 Inner Layers
 Primary purpose is to seal
package
 Direct contact with fill goods
 Typical Films
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Bio - Polyethylene (PE)
PLA
PHA
Starch Based TPU’s
Aliphatic-Aromatic Polyesters
PGA
Blends of bio-esters
Polypropylene (CPP or OPP)
Polyethylene (LDPE, LLDPE,
metallocene, EVA, etc.)
9
Flexible Packaging Market Adhesives Perspective
High Performance (Foil)
Retort
Difficult Foil
Mid Performance (Film)
Barrier to Barrier
Chemical Resistance
Heat Resistance
Cellophane with Barrier
General Purpose (Film)
Dry Goods
Confectionery Snack
Lid Stock
Biodegradable Polyesters (PLA,PHA,etc.)
Solvent Free
Water-based
Solvent-based
Market Volume
Potential Applications-Bio-Films
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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
Application of Adhesives
Comparison of Lamination Processes
Dry Bond
Solvent Free
Flexible Packaging Adhesives
Dry Bond Laminating Process
Laminate
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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
Dry Bond Laminator
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
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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
Solvent Free Laminating Process
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
Typical Solvent Free Laminator
Secondary film
introduced
Adhesive applied
to the primary film
Primary film
nipped to the
secondary film
Primary film introduced
Lamination wound
onto a core
Adhesive pumped
into the machine
Typical Solvent Free Meter-Mix
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
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)
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Corona
Plasma
Chemical / Primers
Coatings
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PVdC
Acrylic
PVOH
Urethane
 Vapor Deposition
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Metallization
Ceramic
 Why do we treat the films?
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Remove contamination
Modify the polarity of film surface
Increase the surface roughness on film
Add or enhance chemical functionality of film surface
23
Corona Treatment vs. Adhesion
700
Corona Treatment Study
B 600
o
n
d 500
Printed Cello - Clear high slip LDPE
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
Corona Treatment:
 Adds polarity to film increasing adhesion
 Removes contaminants
 Increases surface roughness
Lamination Adhesives
Solvent Free Composition- Typical Example
Isocyanate Functional Prepolymer
Polyol Curative
40%
60%
 No Solvent
 Reactive chemistry
 Two-components
Solvent Free Naming and Composition
Common Names Chemical Representation
OH
OH
Polyol
B-side
Curative
Hydroxyl
OH
Isocyanate
A-Side
NCO
Adhesive
Prepolymer
Laminate
Slit
Pouch
Fill
OH
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
OH
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
OH
 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
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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
SF Lamination Adhesives
Bio-Film Interactions
 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
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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
BOPP/BOPP (Reference Laminations)
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
OPLA / OPLA
1000
900
800
700
600
500
400
300
200
SF Adhesive A
100
0
SF Adhesive B
1 day 2 day
SF Adhesive C
5 day 7 day
 Not all the Solvent Free Adhesives were successful on these films
OPLA / High Slip LDPE
1000
900
800
700
600
500
400
300
200
SF Adhesive A
100
0
SF Adhesive B
1 day 2 day
SF Adhesive C
5 day 7 day
 Not all Solvent Free Adhesives were successful on these films
OPLA / LDPE and OPLA / OPLA for Snack Food
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
Example Set #2
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OPLA / Cellophane
OPLA-PHA blend / Cellophane
OPLA / Met PLA
OPLA / Met PLA-PHA blend
Bio-Film Constructions –Solvent Free
Bond Strength
700
600
500
400
Adhesive 1
Adhesive 2
Adhesive 3
300
200
100
0
Sample Set #2-Conclusions
Lamination
Notes
OPLA / Cellophane
Adhesive selection is critical, can achieve
excellent bonding.
PHA / Cellophane
excellent bonding.
OPLA / Met PLA
These films had metal transfer to adhesive,
need to run primer study
OPLA / PHA
excellent bonding.
Solvent Based Composition – Typical Example
35%
60%
5%
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Prepolymer
Curative
Solvent
Long pot life
Very low viscosity at application station
Very high viscosity at nipping station
Solvent must be removed in application process
Solvent Based Naming and Composition
Common Names Chemical Representation
Polyol
OH
OH
OH
B-side
Curative
Hydroxyl
Isocyanate
A-Side
NCO
Adhesive
Solvent
Ethyl Acetate
Solvent
Solvent Based Dry Bond Laminating
Application
Drying
Nipping
OH
OH
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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
Application
Drying
Nipping
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
Application
Drying
Nipping
OH
OH
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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
Solvent Based Dry Bond
OH
Slit
Pouch
Fill
OH
Laminate
OH
 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
OH
 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
SB Lamination Adhesives
Bio-Film Interactions
 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)
Water Based Composition – Typical Example
2%
40%
58%
WB Polymer
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
Water Based Dry Bond
Laminate
Slit
Pouch
Primary Film
Coalesced Adhesive
Primary Film
Secondary Film
Coalesced Adhesive
Primary Film
Fill
WB Adhesive is
gravure applied to
the film.
Water is evaporated
in the oven, film of
adhesive is formed.
Second film is dry
bonded to adhesive.
Water Based Dry Bond
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.
Bio-Film Construction –Dry Bond WB
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
PLA / PLA Bond Strength
Dry Bond - WB
Green peel
800
24 hr peel
700
2 week peel
600
500
400
300
200
100
0
Acrylic /
CR1
Acrylic /
CR2
Hybrid A / Hybrid A / Hybrid B / Hybrid B / Urethane Urethane Urethane Urethane Urethane Urethane
CR1
CR2
CR1
CR2
A / CR1
A / CR2
B / CR1
B / CR2
C / CR1 C / CR2
OPLA / OPLA for Lidstock
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
bio-film projects
Cellophane / Ecoflex+PLA blend for Compostable Pouches
 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.
bio-film projects
Adhesive Comparison
Solvent
Based
Solvent Free
Water Based
Coat Weight
(#/Ream)
1.5-3.5
1.0-1.8
1.0-2.0
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
Oven limit
1500
Oven limit
Time to Slit
2 hours
12 hours
1 hour
Fire Hazard
Yes
No
No
Cost (adhesive +
energy)
3.5X
X
2.7X
Lamination speed
Last Example
Laminate
Slit
Pouch
Fill
 PLA / MetPLA snack food application
Last Example
Laminate
Slit
Pouch
Fill
 Correct adhesive gives high bond
strength
 Correct adhesive gives sound
reduction
 Working together accelerates
success
ITR Workshop Support
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
Thank You
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.

Adhesives and Key Essentials for Laminating Biopolymer

Transcription

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