Gas Barrier Coatings For Flexible Packaging

Transcription

1 Gas Barrier Coatings For Flexible Packaging Mike Leonard Manager Functional Coatings Research working for you. AIMCAL EUROPE WEB COATING CONFERENCE th June Prague

2 Outline 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 2

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 CO 2 Barrier UV Barrier Aroma Barrier 3

4 History/Evolution Of Gas Barriers in Packaging 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 Excellent moisture vapour and O2 barriers, transparent but brittle Organic polymer structures and nanocomposites Glass & Tin Al Foil Plastics First coatings on plastics Extrusion Lamination SiOx & AlOx Ceramics Emerging Technologies All of these materials are in present use today There is no one barrier technology that meets all requirements 4

5 Oxygen Transmission Rates of Typical Flexible Packaging Materials 20 c. 100 > OTR (cm 3 /m 2 23 o C&50%RH) Printable Oxygen Barrier Coatings will offer an alternative to existing High Barrier Options 2 0 Al Foil PET-Al PET- SiOx/AlOx PET-PVDC PET-EVOH Nylon PET PP/PE (Sun Chemical Measurements) 5

6 Gas Barrier Coatings: Market information 6

7 Market Overview - Barrier Materials for Food Packaging Global Addressable (Printable) Market for Barrier Coatings potential 2,074,000tonnes 2008 Market Segmentation by Application MET-Films (205) EVOH Resins (55) Glass Oxides (34) Snack Foods, 17% Confectionery, 2% Dry Mixes, 2% Coffee, 4% Prepared Food, 2% Cheese & Dairy, 9% PVDC Resins (164) Aluminum Foil (535) Processed Meat, 7% Fresh Meat, 59% Conversion from current barrier technology/ film is a multi $ million coating opportunity Source: ADC/Kline 7

8 Coating Applications Packaging market overview (barriers) Market / Applications Chilled Food Dry Food Liquid Packaging Barrier technology PVdC EVOH Nylon Speciality Oxides Metallised Co-extrusions Package structure Bags Lidding Stand Up Pouches Forming Webs Wraps Temperature & Relative Humidity are Important Considerations 8

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. 9

10 Nanocomposite Gas Barrier Coatings Description, Preparation, Function & Analysis 10

11 Emerging Technologies Nanocomposites Highly dispersed/exfoliated silicates/clays Sol-Gel Coatings Inorganic/Organic composites formed in-situ Condensation e.g. Si(EtOH) 4 Si(OH) 4 SiOx Organically modified ceramic lacquers. vapor and barrier layer strategy Epoxy Based Coatings Hydrolysis PAA & PGA-based coatings 11

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 cm 3 /m 2 /24h at 23 o C & 75%RH 12

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. O 2 O 2 + Mineral Dispersion d 1 d 2 Polymer Matrix Layered Silicate Exfoliated Nanocomposite d 2 > d 1 13

14 Analysis of Nanocomposites: XRD X-Ray Diffraction shows the increase in d-spacing (001) when the clay is successfully exfoliated Clay Nanocomposite; <10% (w/w) Clay Intensity Intensity (Counts) d 001 =12.1 Å Intensity d - Scale Cloisite Na+ - File: E-REQ Cloisite-Na-EXFO raw - Type: Locked Coupled - Start: End d Spacing (Å) d - Scale Sample # 3 - File: E-REQ Sapmle3-EXFO raw - Type: Locked Coupled - Start: End: d Spacing (Å) 6 14

15 Analysis of Nanocomposites: XRD Nanocomposites with Higher Clay Loadings Nanocomposite; Nanocomposite; c.25% (w/w) Clay Å d= c.40% (w/w) Clay Å Intensity 100 Intensity d - Scale d - Scale Sample # 1 - File: E-REQ Sapmle1-EXFO raw - Type: Locked Coupled - Start: End: Sample # 4 - File: E-REQ Sapmle4-EXFO raw - Type: Locked Coupled - Start: End: d Spacing (Å) 0 d Spacing (Å) Intercalated composites or highly ordered exfoliated composites? 6 15

16 Analysis of Nanocomposites; Electron Microscopy SEM: Agglomerated Clay TEM: Nanocomposite Coating Cast of Dilute Coating on Cu Grid (Sun Chemical) 16

17 TEM of Cross Sectioned Coating on PET Film Clay Particles 17

18 The Effect of Exfoliation on the Visual Appearance of NanoComposites 18

19 The Effect of Clay Exfoliation on the Oxygen Barrier Oxygen Tansmission Rate (cm 3 /m 2 /day) Unfilled Polymer 'Micro Composite' Nanocomposite Annealed Nanocomposite Oxygen Transmission Rates were measured with an Oxtran 2/21 at 23 o C&75%RH. 19

20 Nanocomposite Coatings- Influence of Aspect Ratio Oxygen barrier vs Aspect Ratio Oxygen Transmission Rate at 23 o C & 50%RH (cm 3 /m 2 /24h) Concentration of Mineral in the Coating (% (w/w) AR=1 AR=25 AR=100 AR=200 Aspect Ratio = l/d d l Lamination Bond Strengths vs Aspect Ratio N/ 15mm Aspect Ratio 500 >

21 Understanding the Role of Clay on Oxygen Barrier Performance; a Mechanistic Study Arrhenius Plots used to determine the effect of changing clay concentration on Oxygen Permeability Log (OTR) % Clay 15% Clay 30% Clay 45% Clay Slope α E a (Activation Energy) Therefore; no change in E a Polymer Matrix character does not change Increase in diffusion path length the likely mechanism O /T(K) (% Clay = wt. % in the dry coating applied to PET) 21

22 Using Arrhenius Plots; Log OTR v. 1/T to Extrapolate Performance Expt 1 Expt 2 Expt 3 Expt 4 OTR Prediction at 4-5 o C Mocon Oxtran 2/21 Min Temp =11 C

23 Performance Clay Composite Coatings in Packaging Applications 23

24 Comparison of Functional Barriers on PET Untreated polyester film OTR cm 3 / cm ºC & 50% RH Oxygen transmission rate measured using a MOCON OX-TRAN 221 within 24 hours of coating Varies with grade and cost PET: 50µ PE:EVOH:PE Extrusion 0.3µ dry coating weight 0 PVdC Al PET AlOx SiOx PET EVOH Clay Compoiste PVDC major disadvantage contains chlorine & higher OTR AlOx / SiOx major disadvantage brittle & higher OTR EVOH deteriorates over time in humid storage conditions 24

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). 25

26 Influence of Relative Humidity & Coat Weight Clay Composite coating 12μm PET, tested at 50%RH and 75% RH, at 23ºC Higher Coat Weights are Generally needed at Elevated %RH 26

27 Performance Benchmark Effect of Humidity 30 Oxygen Transmission Rate (cm 3 / m 2 / 23C) Clay-Composite PET-PE/EVOH/PE PET-PVDC Relative Humidity 27

28 Performance Benchmark Effect of Temperature at 75% RH Oxygen Transmission Rate (cm 3 / m 2 /24 hrs) [5.6 gsm wet] Temperature ºC PVdC-PET Clay Composite PE/EVOH/PE-PET Clay-composite coating improved performance at elevated temperature 28

29 Flexibility of Barrier Coatings 23 o C & 50%RH (cm 3 /m 2 /24h) PET-AlOx PET-SiOx PET-PVDC PET-EVOH PET-Clay- Composite No. of Gelbo Flexes Oxide-coated films have poor flex resistance ( Performance improves when laminated and coated) 29

30 Chilled Foods-Real Time Packaging Performance % Oxygen Ingress Time (weeks) 2-4 ºC Temperature External Humidity 43%RH Internal Humidity 100% RH Non Invasive measurement Clay Composite 1 Clay Composite 2 PET PVdC PET SiOx PET PE EVOH PE Clay composite coatings perform as well as EVOH Structures 30

31 Coating Applications Key Packaging Trends 1. Rigid to flexible 2. Visible product contents 3. Light weighting 4. Single piece packs 31

32 Coating Applications Trend #2: Visible product contents Longer shelf life. Visible content packs with high oxygen barrier 32

33 Coating Applications Trend #4: Single piece packs Excellent oxygen and aroma / odor barrier for base substrates. 33

34 Coating Applications Light weighting Commercial 3-Ply Laminate Polymer Film Ink Adhesive MET Polymer Film Adhesive Polymer Film 2-Ply Laminate plus printable barrier coating Polymer Film Barrier Coating Ink Adhesive Polymer Film Removal of barrier film or foil and one layer of adhesive Lighter weight packaging (up to 30% reduction) Improved laminate integrity (post flexing O 2 barrier improvement) Lower material and / or operational costs Improved recycling Improved shelf life 34

35 Conclusions SunBar TM 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 ). 35

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) Fax: +44 (0) Mobile: +44 (0) mike.leonard@sunchemical.com Web: 36