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Gas Barrier Coatings For Flexible Packaging
AIMCAL EUROPE WEB COATING CONFERENCE 2012
12th June Prague
Mike Leonard
Manager Functional Coatings Research
2
Gas barrier Coatings Definition & Background Market Information
Nanocomposite Gas Barrier Coatings Exfoliated Clay Composites Analysis of Clay Composite Coatings
Performance in Packaging Applications Environmentally Friendlier Packaging Coating Applications
Conclusions
Outline
3
Barrier Coatings: Definition
Prevent the penetration (or loss) of specific gases, light or aroma/odour which could compromise the integrity of the packaged product.
Typical Barrier Coatings: • Oxygen Barrier • Moisture Vapour Barrier • CO2 Barrier • UV Barrier • Aroma Barrier
4
History/Evolution Of Gas Barriers in Packaging
Glass & Tin Plastics First coatings
on plastics
Extrusion
Lamination
Excellent barriers
but heavy
Poor barriers, but light weight
Reasonable barriers
Especially PVdC and Al
metallisation
also
lightweight
EVOH-Excellent
O2 Barrier at medium
%RH
Thick laminates
SiOx & AlOx Ceramics
Emerging
Technologies
Excellent moisture
vapour and O2 barriers,
transparent but brittle
Organic polymer structures and
nanocomposites
All of these materials are in present use today
There is no one barrier technology that meets all requirements
Al Foil
5
Oxygen Transmission Rates of Typical Flexible Packaging Materials
0
2
4
6
8
10
12
14
16
18
20
Al Foil PET-Al PET-SiOx/AlOx
PET-PVDC PET-EVOH Nylon PET PP/PE
OTR
(cm
3 /m2 /d
ay; @
23o
C&
50%
RH
)
c. 100 >1000
Printable Oxygen Barrier Coatings will offer an alternative to existing High Barrier Options
(Sun Chemical Measurements)
6
Gas Barrier Coatings:
Market information
7
Market Overview - Barrier Materials for Food Packaging
Conversion from current barrier technology/ film is a multi $ million coating opportunity
Aluminum Foil (535)
MET-Films (205)
EVOH Resins (55)
Glass Oxides (34)
PVDC Resins (164)
Global Addressable (Printable) Market for Barrier Coatings potential –2,074,000tonnes
2008
Fresh Meat, 59% Processed Meat, 7%
Cheese & Dairy, 9%
Prepared Food, 2%
Snack Foods, 17%
Confectionery, 2% Dry Mixes, 2%
Coffee, 4%
Market Segmentation by Application
Source: ADC/Kline
8
Packaging market overview (barriers)
Coating Applications
PVdC EVOH Nylon Speciality Oxides Metallised Co-extrusions
Bags Lidding Stand Up Pouches Forming Webs Wraps
Chilled Food Dry Food Liquid Packaging
Market / Applications Package structure Barrier technology
Temperature & Relative Humidity are Important Considerations
9
Printable Oxygen Barrier Coatings A gap exists in the market for transparent barrier coatings;
free from halogenated compounds, converter applied, which afford high barrier performance.
10
Nanocomposite Gas Barrier Coatings Description, Preparation, Function & Analysis
11
Emerging Technologies
Nanocomposites – Highly dispersed/exfoliated silicates/clays
Sol-Gel Coatings – Inorganic/Organic composites formed in-situ
– e.g. Si(EtOH)4 Si(OH)4 ‘SiOx’ – Organically modified ceramic lacquers.
– vapor and barrier layer strategy
Epoxy Based Coatings
PAA & PGA-based coatings
Hydrolysis Condensation
12
Sun Chemical’s Nanocomposite Barrier Coatings
• Finely dispersed nanoparticulate (intercalated/ exfoliated) silicate mineral in a polymer solution/ dispersion
• The dispersion is applied using traditional printing and drying techniques
• The dried polymer coating on a film enhances the oxygen barrier performance of the substrate
Functional oxygen barrier of less than 1.0 cm3/m2/24h at 23oC & 75%RH
13
The influence of Exfoliated Minerals on Barrier Improvement
The generally accepted theory for barrier improvement is that dispersed/exfoliated ‘platy’ minerals increase the diffusion path length through a coating; ‘TORTUOUS PATH’.
+
Polymer Matrix Layered Silicate
Mineral Dispersion
Exfoliated Nanocomposite
d1 d2
d2 > d1
O2 O2
14
Analysis of Nanocomposites: XRD
Cloisite Na+ - File: E-REQ09-4163-Cloisite-Na-EXFO-9-4-2009.raw - Type: Locked Coupled - Start: 2.250 ° - End
Inte
nsity
0
20
40
60
80
100
120
140
160
180
200
d - Scale
6102030
X-Ray Diffraction shows the increase in d-spacing (001) when the clay is successfully exfoliated.
Clay Nanocomposite;
<10% (w/w) Clay
30 20 10 6
d Spacing (Å)
d001=12.1 Å
Sample # 3 - File: E-REQ09-4163-Sapmle3-EXFO-9-4-2009.raw - Type: Locked Coupled - Start: 2.250 ° - End: 15.00
Inte
nsity
0
20
40
60
80
100
120
140
160
180
200
d - Scale
610203040 30 20 10
d Spacing (Å)
Inte
nsity
(Cou
nts)
15
Analysis of Nanocomposites: XRD
Nanocomposites with Higher Clay Loadings
Sample # 4 - File: E-REQ09-4163-Sapmle4-EXFO-9-4-2009.raw - Type: Locked Coupled - Start: 2.250 ° - End: 15.00
Inte
nsity
0
20
40
60
80
100
120
140
160
180
200
d - Scale
610203040
d=26
.466
51Sample # 1 - File: E-REQ09-4163-Sapmle1-EXFO-9-4-2009.raw - Type: Locked Coupled - Start: 2.250 ° - End: 15.00
Inte
nsity
0
20
40
60
80
100
120
140
160
180
200
d - Scale
610203040
35 Å
26 Å
30 10 20 30 10 20
d Spacing (Å) d Spacing (Å)
Nanocomposite;
c.25% (w/w) Clay
Nanocomposite;
c.40% (w/w) Clay
Intercalated composites or highly ordered exfoliated composites?
16
Analysis of Nanocomposites; Electron Microscopy
TEM: Nanocomposite Coating
Cast of Dilute Coating on Cu Grid (Sun Chemical)
SEM: Agglomerated Clay
17
TEM of Cross Sectioned Coating on PET Film
Clay Particles
18
The Effect of Exfoliation on the Visual Appearance of NanoComposites
19
05
101520253035404550
Unfilled Polymer 'MicroComposite'
Nanocomposite AnnealedNanocomposite
The Effect of Clay Exfoliation on the Oxygen Barrier O
xyge
n Ta
nsm
issi
on R
ate
(cm
3 /m2 /d
ay)
Oxygen Transmission Rates were measured with an Oxtran 2/21 at 23oC&75%RH.
20
Nanocomposite Coatings- Influence of Aspect Ratio
0
5
10
15
20
25
30
35
40
0 10 20 30 40
AR=1AR=25AR=100AR=200
Oxygen barrier vs Aspect Ratio
Oxy
gen
Tran
smis
sion
Rat
e at
23o C
& 5
0%R
H (c
m3 /m
2 /24h
)
Concentration of Mineral in the Coating (% (w/w)
0
0.5
1
1.5
2
2.5
25 100 200 500>1000
l
d Aspect Ratio = l/d
Lamination Bond Strengths vs Aspect Ratio
N/ 1
5mm
Aspect Ratio
21
Understanding the Role of Clay on Oxygen Barrier Performance; a Mechanistic Study
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0.00331 0.00336 0.00341 0.00346 0.00351 0.00356 0.00361
0% Clay15% Clay30% Clay45% Clay
Log
(OTR
)
1/T(K)
Arrhenius Plots used to determine the effect of changing clay concentration
on Oxygen Permeability
• Slope α – Ea (Activation Energy)
Therefore; no change in Ea
Polymer Matrix character does not change
Increase in diffusion path length the likely mechanism
O2
(% Clay = wt. % in the dry coating applied to PET)
22
Using Arrhenius Plots; Log OTR v. 1/T to Extrapolate Performance
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0.00331 0.00336 0.00341 0.00346 0.00351 0.00356 0.00361
Expt 1Expt 2Expt 3Expt 4
1.8-2.0
1.4-1.6
0.8-0.9
0.4-0.5
OTR Prediction at 4-5oC
Mocon Oxtran 2/21 Min Temp =11°C
23
Performance Clay Composite Coatings in Packaging Applications
24
Comparison of Functional Barriers on PET
Untreated polyester film OTR 100-110 cm3 / cm2
PVDC major disadvantage – contains chlorine & higher OTR AlOx / SiOx major disadvantage – brittle & higher OTR EVOH deteriorates over time in humid storage conditions
Oxygen transmission rate measured using a MOCON OX-TRAN® 221 within 24 hours of coating
0
1
2
3
4
5
6
7
8
9
PVdC Al PET AlOx SiOx PET EVOH ClayCompoiste
23ºC & 50% RH
Varies with grade and cost
PET: 50µ PE:EVOH:PE Extrusion
0.3µ dry coating weight
25
Influence of Coatings Thickness on Barrier performance
The clay composite coatings provide excellent barrier performance on both PET and OPP with dry film weights as
low as 0.2 g/sm (dry).
26
Influence of Relative Humidity & Coat Weight
Higher Coat Weights are Generally needed at Elevated %RH
Clay Composite coating 12μm PET, tested at 50%RH and 75% RH, at 23ºC
27
Oxy
gen
Tran
smis
sion
Rat
e (c
m3 /
m2 /
day
@ 2
3C)
0
5
10
15
20
25
30
45 50 55 60 65 70 75 80 85
Clay-CompositePET-PE/EVOH/PEPET-PVDC
Relative Humidity
Performance Benchmark – Effect of Humidity
28
0
5
10
15
20
25
30
35
40
10 15 20 25 30 35 40
PVdC-PETClay CompositePE/EVOH/PE-PET
Clay-composite coating improved performance at elevated temperature
Temperature ºC
[5.6 gsm wet]
Oxy
gen
Tran
smis
sion
Rat
e (c
m3 /
m2 /
24 h
rs)
Performance Benchmark – Effect of Temperature at 75% RH
29
Flexibility of Barrier Coatings
0
1
2
3
4
5
6
7
8
9
0 5 10 20 50
No. of Gelbo Flexes
PET-AlOx
PET-Clay-Composite
PET-SiOx
OTR
@ 2
3oC
& 5
0%R
H (c
m3 /m
2 /24h
)
PET-EVOH
PET-PVDC
Oxide-coated films have poor flex resistance ( Performance improves when laminated and coated)
30
0
1
2
3
4
5
6
7
1 2 4 6 8 10
Clay Composite 1Clay Composite 2PET PVdCPET SiOxPET PE EVOH PE
Chilled Foods-Real Time Packaging Performance
2-4 ºC Temperature External Humidity 43%RH Internal Humidity 100% RH Non Invasive measurement
Time (weeks)
% O
xyge
n In
gres
s
Clay composite coatings perform as well as EVOH Structures
31
Key Packaging Trends
Coating Applications
2. Visible product contents
1. Rigid to flexible
3. Light weighting
4. Single piece packs
32
Trend #2: Visible product contents
Coating Applications
Longer shelf life. Visible content packs with high oxygen barrier
33
Trend #4: Single piece packs
Coating Applications
Excellent oxygen and aroma / odor barrier for base substrates.
34
Light weighting
Coating Applications
Commercial 3-Ply Laminate
Removal of barrier film or foil and one layer of adhesive Lighter weight packaging (up to 30% reduction) Improved laminate integrity (post flexing O2 barrier improvement) Lower material and / or operational costs Improved recycling Improved shelf life
Polymer Film Ink Adhesive MET Polymer Film Adhesive
Polymer Film
Polymer Film Barrier Coating Ink Adhesive Polymer Film
2-Ply Laminate plus printable barrier coating
35
Conclusions SunBarTM Clay composite oxygen barrier coatings enable (transparent) barrier packaging having exceptional barrier
properties.
Oxygen Barrier Performance equivalent/superior to existing technologies
Can be applied by conventional printing methods
can reduce the environmental impact of plastic packaging.(lightweighting, improved recycling, Cl free, replace metal, more flexible)
Increasing the mineral aspect ratio provides improved barrier performance.
Improvements in oxygen barrier shown to result from an increase in diffusional path length (‘Tortuousity’).
36
Acknowledgements
Thank you for your attention
The Functional Coatings Research team at St. Mary Cray (UK) – Derek Illsley, Asad Khan, Robert Lines, Safraz Khan, Farid Azizian,Peter
Brownrigg
Analytical Departments at St. Mary Cray and Colours Group (USA) – Jayne Barnes, Hetal Patel, Lisa Clapp, Costas Nicolaou
Mike Leonard Manager - Functional Coatings Research
Sun Chemical Ltd
Cray Avenue St Mary Cray
Orpington, Kent BR5 3PP
Tel: +44 (0) 1689 894 173 Fax: +44 (0) 1689 894 020
Mobile: +44 (0) 7976 969873 Email: [email protected]
Web: www.sunchemical.com