How To Build A Coextruded Film

Transcription

1 Coextruded Film Structures of PLA and EVOH Presented by: Pablo J. Garcia Research Engineer Kuraray America Inc. EVAL Business Unit

2 Outline Background and objectives PLA and EVOH Method & materials Results & discussion Conclusions

3 Background Customer objectives Drive for environmental sustainability Increase use of bio-based renewable sourced materials Maintain gas barrier and food shelflife PLA alone inadequate for prolonged food packaging requirements

4 Addressing Customer Needs 1. High O 2 barrier 2. Packaging with high bio-based polymer content Experiment objectives Coextrude PLA/EVOH multi-layer films Thermoform films into flexible food packages Assess compatibility and O 2 barrier performance

5 Polylactic Acid (PLA) Aliphatic polyester Thermoplastic biopolymer Derived from renewable resources Corn starch or sugarcanes Biodegradable Application examples Disposable beverage cups Food containers Trash bags (Wikipedia)

6 Ethylene Vinyl Alcohol (EVOH) Common in food applications Excellent functional gas barrier Impermeable to oxygen and odor Lengthens shelf life Locks in aromas Maintains flavor and quality Protects vitamins EVOH Multi-layer film crosssection 50

7 EVOH Chemical Structure Ethylene mol % Greater flexibility and ease of processing High barrier, density and melt point Random co-polymer Ethylene Vinyl ALcohol (CH 2 -CH 2 ) m (CH 2 -CH) n OH

8 Oxygen Barrier of Polymers Polymer Polymer 20 C, 65%RH (cm 3.20μm/m 2.day.atm) EVOH 32 mol% Et. (EVAL J171) 0.6 EVOH 38 mol% Et. (EVAL H171) 0.7 EVOH 48 mol% Et. (EVAL G176) 3.2 Oriented Nylon X Oriented PET 54.0 PLA 700 HDPE 2300 PP 3000 LDPE EVA X

9 Past Challenges PLA processability Complexities in film extrusion PLA / tie adhesion Lack of physical affinity Poor adhesion tie layers

10 Method and Materials Five structures PLA/tie/EVOH/tie/LLDPE EVOH grades: 32, 38 and 48 mol% Et. Blown film coextrusion Target film thickness: 125 and 150 µm Thermoforming 5 preheat-times / film temperatures: C Microscope structure analysis Inter-layer adhesion testing Tensile tests Oxygen transmission rate (OTR) testing

11 Resins and Multi-Layer Structure Film Cross-Section and Schematic 21 25% 9 10% μm (Inside) PLA (Ingeo 4042D) Tie (Admer SF600) EVOH (EVAL J, H & G) Tie (Admer NF489A) LLDPE (Nova Sclair FP120A) (Outside)

12 Multi-Layer Structures Experiment Variables and Measured Layer Thicknesses

13 Blown Film Coextrusion 7-Layer/Extruder Pilot Line Brampton Engineering 152 mm die diameter 4.8 Blow-up ratio 6.55 m/min line speed

14 Blown film line procedure Started with 48 mol% EVOH and minimal PLA Ramped-up PLA layer and total thickness Transitioned between different EVOH grades Temperature zone settings 210 C die for PLA 221 C die for EVOH

15 Blown Film Trial Observations Limited temperature window for PLA PLA was soupy fluid with little melt strength Increased BUR and line-speed Increase cooling and tension Keep bubble inflated and prevent sagging Original experiment plan: 40% PLA thickness Adjusted plan to reduce to 20% PLA thickness

16 Inter-Layer Adhesion T-peel type test Initiation of delamination Tensile peel strength Relatively weak strength No delaminations during forming or handling

17 Adhesion Strength Results EVOH/tie/HIPS bond 363 Adhesion (g/25 mm) G-5mil H-5mil H-6mil J-5mil J-6mil

18 Adhesion Microscope Analysis Delaminations at PLA/tie interface No performance impact No delaminations Acceptable adhesion EVOH 100 µm Delamination at PLA/tie PLA

19 Thermoforming Table-top vacuum thermoformer Pre-heating times 4 to 12 s 150 to 177 C

20 Thermoforming Oblong tub 290 ml volume 190 cm 2 surface area 2.2 areal draw ratio Visually clear with little haze No delaminations

21 Thermoforming Evaluation Thickness gauge variations Three sidewall locations vs. forming temperature (pre-heat time)

22 Thickness Gauge vs. Location and Temperature Thickness reduction ratio 100% 50% 0% G-5mil J-5mil T M H-5mil J-6mil C T H-6mil M C 100% 50% 0% T M C Side wall location (Top, Middle, Corner) ( C)

23 Side Wall Cross-Sections EVOH 100 µm PLA Top Flange Mid Wall Corner Polarized microscopy; Structure H-6-mil at 12 s preheat time

24 Forming Films Oxygen Barrier Analysis PLA contributes less than 0.3% of barrier PLA is 37 to 559 times more permeable Measured O 2 permeation rate for PLA 951 cm 3.20μm/m 2.day.atm at 20 C, 65%RH (c.f cm 3.20μm/m 2.day.atm for EVOH)

25 Package OTR measurements Vacuum Port Perforation Failures Mold vacuum ports Designed for thick sheet, not thin flexible Minimum preheat structures were unaffected

26 Package OTR results Thermoformed Structure OTR (cm 3 /pkg.day) G-5mil (48 mol% Et. EVOH) H-5mil (38 mol% Et. EVOH) H-6mil (38 mol% Et. EVOH) - J-5mil (32 mol% Et. EVOH) J-6mil (32 mol% Et. EVOH) PLA monolayer C thermoformed samples Calculated PLA value: (951.3 cm 3.20μm/m 2.day.atm; 190 cm 2 ; 67 μm thick)

27 Calculated Oxygen Ingress Package Oxygen Content (cm³) cm³/yr 12.7 cm³/yr 3.7 cm³/yr 3.4 cm³/yr Time (days) Grade EVOH 32mol% EVOH 38mol% EVOH 48mol% PLA monolayer 150 C thermoforming m² (pkg+lid); L; 21% O 2

28 Application Examples Subject to food product specifics: 48, 32 or 38 mol% Et. EVOH for Oils, salad dressings and peanut butter 32 or 38 mol% Et. EVOH for Fruit, vegetables and dried foods

29 Conclusions 1. Testing validated the technical feasibility of high barrier PLA/EVOH forming films 2. Weak but acceptable layer adhesion strengths 3. Well thermoformed structures; least gauge reduction for 48 mol% Et. EVOH 4. Capability of less than 3.7 cm 3 /year O 2 ingress with 32 or 38 mol% Et. EVOH Improved thermoforming using 32 mol% Et. EVOH could yield packages exceeding 1-year shelf-life, while utilizing at least a 20% bio-based polymer content

30 Acknowledgements Shige Yasui Technical Manager - Admer Division Mitsui Chemicals America, Inc. Norman Aubee Technical Service Specialist NOVA Chemicals Technical Centre Tim Vanyo Principal Applications Engineer NatureWorks LLC

31 Thank you PRESENTED BY Pablo Garcia Research Engineer Kuraray America Inc. EVAL Business Unit Please remember to turn in your evaluation sheet...