Heat Seal Characteristics of COC/PE Blends

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  • 1. Heat Seal Characteristics of Cyclic Olefin Copolymer / Polyethylene Blends Randy D. Jester TAPPI 2002 PLACE Conference Boston, Massachusetts1
  • 2. Topas® COC Manufacturing Plant • Oberhausen, Germany • Start-up October 2000 • COC Capacity: 66 MM lbs. • Backward integrated in Norbornene • Cost efficient continuous process using metallocene technologyLargest COC and Norbornene Plant in the World
  • 3. What is COC? catalyst + CH2 CH2 CH2 CH2 n mFeedstocks Catalyst : Metallocenes Norbornene High activity, low residues Ethylene Narrow MW distribution Microstructure controlCOC properties can be tailored by adjusting the Norbornene content
  • 4. Abstract• Cyclic Olefin Copolymers (COC) use is growing in flexible packaging films• Attributes include easy processing, stiffness, heat resistance, moisture barrier and clarity• Can be used to modify the heat sealing characteristics of polyethylenes: – improvements in seal strength – improvement of hot-tack strength – high temperature seal through capability with high Tg grades.
  • 5. Experimental• Materials: MI Density Tg°C – Dow 2045 LLDPE 4 0.920 -127 – Equistar NA 952 LDPE 2 0.918 -127 – Equistar NA 204 LDPE 3 0.931 -127 – Borealis 7230 LDPE 4.5 0.923 -127 – Exxon Mobil 3125 Plastomer 1.2 0.91 -121 – Dow 1140 Plastomer 1.2 0.902 -121 – Ticona 8007 COC 1.8 1.02 80 (low) – Ticona 5013 COC < 1.0 1.02 136 (high)• Extrusion: – 25 mm Killion (DS), DSB I barrier type screw, 30: 1 L/D, Maddock Mixing head • T range: 160 - 260°C, Cast rolls: 35°C,film: 51 microns
  • 6. Experimental (cont.)• Testing Equipment: – Tensiles MTS 8016 Tensile testing machine,, 23°C, 50% r.h. (ASTM D 882) – Microscopy Optical (phase contrast) – DMA TA Instruments Dynamic Mechanical Analyzer (DMA), model 2980, tension mode on MD film, 3°C/min. temperature sweeps, at 10HZ – Heat Seal Davinor Inc., J&B Hot Tack Tester • Seal Strength Test - Seal Pressure = 0.3034 N/mm (44psi), Seal Time = 1 sec., Cool Time = 30 sec., Peel speed = 200 mm/sec, sample size = 25.4 mm (1 inch ) wide. • Hot-Tack Test - Seal Pressure = 0.3034 N/mm (44psi), Seal Time = 1 sec., Cool Time = 0.1 sec., Peel speed = 200 mm/sec, sample size = 25.4 mm (1 inch ) wide. • Seal Initiation Temperature - defined as seal temperature where a 8.8 Newton seal strength is achieved.
  • 7. COC allows downgauging of films 1.E+05 1.00 Blend Modulus Thickness @ Constant Initial Stiffness(mils) Film Stiffness @Constant Thickness Blend Layer Thickness (mils) Blend Modulus (psi) 1.E+04 Initial Construction: Plastomer - 0.6 mils Dowlex 2032 - 0.8 mils Plastomer - 0.6 mils 1.E+03 0.10 0.0% 2.5% 5.0% 7.5% 10.0% 12.5% 15.0% 17.5% 20.0%Reference 2 Wt % 80C Tg COCCOC blends offer potential cost savings
  • 8. Improved Ultimate Seal Strength with 80ºC Tg COC blended with LLDPE 40 0 % COC 35 15 % COCSeal Strength (Newtons) 25 % COC 30 25 20 15 Dwell Time = 250 ms 10 Seal Pressure = 63 psi 5 cast film 0 70 80 90 100 110 120 130 140 150 160 170 Reference 2 Sealing Temperature (°C) COC blends produce a wider sealing window
  • 9. Effect of Blending 80ºC Tg COC with LLDPE on Hot Tack Force 5 0 % COC 15 % COCHot Tack Force (Newtons) 4 25 % COC 3 2 Dwell Time = 250 ms 1 Seal Pressure = 63 psi 0 70 80 90 100 110 120 130 140 150 160 170 Reference 2 Sealing Temperature (°C) COC blends produce a wider sealing window
  • 10. Effect of COC Addition on Seal Strength 60 LDPE, Den.=0.923, MI = 4.5 LLDPE Den.=0.920, MI=4 Plastomer Den.=0.91, MI=3Seal Strength @ 120C (Newtons) 50 40 30 20 10 0 0 20 40 60 80 100 0 20 40 60 80 100 0 10 15 20 40 60 80 100 LDPE LLDPE Plastomer % 80ºC Tg COC in Blend
  • 11. Effect of COC Addition on Hot-Tack 16 LDPE, Den.=0.923, MI = 4.5 LLDPE Den.=0.920, MI=4 Plastomer Den.=0.91, MI=3 14Hot Tack Strength @ 120 Co 12 10 8 6 4 2 0 0 20 40 60 80 100 0 20 40 60 80 100 0 10 15 20 40 60 80 100 LDPE LLDPE Plastomer % 80ºC Tg COC in Blend
  • 12. Effect of 80º C Tg COC Addition on SIT 140 LDPE, Den.=0.923, MI = 4.5 LLDPE Den.=0.920, MI=4 Plastomer Den.=0.91, MI=3 130 Seal Initiation Temperature (SIT) = Temp. where 8.8 Newton seal strength achievedSeal initiation Temperature (ºC) 120 110 100 90 Seal < 8.8 N 80 0 20 40 60 80 100 0 20 40 60 80 100 0 10 15 20 40 60 80 100 LDPE LLDPE Plastomer % COC
  • 13. Seal Strength at 120ºC of LDPE vs. LLDPE 35 30 LLDPE to COC - no distortion of COC, LLDPE tore during pullUltimate Seal Strength (Newtons) LDPE to COC - no distortion of COC, LDPE peeled off cleanly 25 20 15 10 5 0 LLDPE 60% LLDPE/ LDPE 60% LDPE/ LLDPE to LDPE to 40% COC 40% COC COC COC 60% LLDPE/40% 60% LDPE / COC @ 2X seal 40%COC @ 2X pressure seal pressure
  • 14. Phase Contrast Optical Microscopy:80% 12 MI LDPE + 20% 80°C Tg COC, 51 µm cross section, 625X 160C 180C 200C Reference 3
  • 15. Seal Through Test Results 200 180Seal BarTemperature (Celsius) 160 140 120 100 80 Initial Seal Bar Sticking 60 Seal Bar contamination 40 LLDPE - density=0.920, MI=4 20 Plastomer, density=0.902, MI=1.2 0 90% 130 Tg 5% 130 Tg 10% 130 Tg 15% 130 Tg 20% 130 Tg 30% 130 Tg 40% 130 Tg COC / 10% COC / 95% COC / 90% COC / 85% COC / 80% COC / 70% COC / 60% Plastomer LLDPE LLDPE LLDPE LLDPE LLDPE LLDPE High Tg COC as an outer layer blend component can provide seal through capability
  • 16. Conclusions• COC/polyethylene blends can exhibit both improved modulus and heat seal performance• COC is more compatible with LLDPE and Plastomers than LDPE• COC level and matrix polymer affect heat seal performance – 80º Tg COC generally improves hot tack strength at all blend levels for the polyethylene systems studied. – 80º Tg COC reduced the seal strength of LDPE at concentrations of 20% and up while maintaining or improving the seal strength of LLDPE and Plastomer• 130º Tg COC blended at levels above 20% can provide “seal through” capability to polyethylenes
  • 17. Acknowledgements I would like to thank the following people for their contributions to this paper: • Dr. Rong Chen • Dr. Angel Romo-Uribe • David Constant • Robert Roschen • Rick Vliet • Betsy Kelly • Kathy Fitzgibbon • Betty Fernekess1
  • 18. References1. ASTM, Designation: F 1921-98, Standard Test Methods for Hot Seal Strength (Hot Tack) of Thermoplastic Polymers and Blends Comprising the Sealing Surfaces of Flexible Webs, ASTM Standards 19992. R.R. Lamonte, “Stiffer, Thinner, Packaging Films with Improved Sealing Using Cyclic Olefin Copolymers”, Flexpac Conference, Amsterdam, Holland, November 20003. D.R. Constant, “Cyclic-Olefinic Copolymers as Non-Migrating Polymeric Slip Additives in LDPE Cast Films”, ANTEC 2002 Conference, San Franscico, CA
  • 19. Backup Slides
  • 20. Regulatory Status FDA Food Contact Notification (FCN No. 75) became effective August 22, 2000 Norbornene is listed by the EU as an approved monomer for use in polymers in contact with food. USP Class VI FDA Drug Master File, DMF# 12132 and Device Master File, MAF # 1043 established COC meets all major regulatory requirements