Clear Re-Tort Packaging Via Extrusion Lamination

TAPPI: Flexible Packaging SymposiumIndia – Mumbai and Delhi

November 2009Author: Jessica Bodine, Mica Corporation

Outline

IntroductionMaleic Anhydride tie-layersMaleic Anhydride concentrates

ObjectiveExperimentalResults

Dry bonds, water soaks and retort testingConclusions

Introduction -

The starting point of the structure: Nylon extrusion coated with polypropylene

Why Polypropylene?Many other resins can not with-stand the high temperatures required for retort processingTough and grease resistant

Problems with polypropylene:No inherent reactive sitesHomogenous chemistry does not allow for chain cleavage and production of reactive sites in extrusion processes

Introduction – Maleic Anhydride Tie Layers

Tie layers increase adhesion when used in co-extrusion Primers increase adhesion of many extruded polyolefinsTie-layers and primers together have better adhesion than either alonePolyamide/Primer/Tie-layer/PP seal layer structure proven to be effective in clear retort conditions (reference 1)

Introduction – Maleic Anhydride Concentrates

WHY CONENTRATES?Using tie-layers in conjunction with primers may be cost prohibitive Non-availability of co-extrusion equipment Blending MAH resin “concentrates” in conjunction with primers without co-extrusion allows for same improved adhesion performance at lower-cost

Reference 2

Maleic Anhydride Concentrate Considerations

Backbone (concentrate base resin) needs to be compatible with resin to be extrudedNeeds 1-2% maleic anhydride (or equivalent) in order to be diluted to 0.2% total anhydride content in final blendBlending 10 – 20% of material must not interfere with extrusion properties (melt strength, neck-in etc.)

Reference 3

Previous Work (TAPPI, Place division - Europe 2003 and 2005)

(2003) 100% Tie-layer (not concentrate) – was found to be effective for clear re-tort on polyamide

(2005) One adhesive concentrate blend exhibited adhesion to primed PET, paper and aluminum foil using polypropylene base resins (reference 2)Polyamide was not testedDry bonds and water soaks were tested but not retort

Retort Testing on Nylon (Feb. 2009)

Three adhesive concentratesMaleic Anhydride adhesive resin concentrates:

Resin 1: DuPont Bynel 50E803 Resin 2: Chemtura Polybond 3000Resin 3: Arkema Orevac CA 100

Nylon and PETOnly 1 primer – Mica A-131-XOnly 1 polypropylene carrier resin – Chevron MarlexResults – produced one structure which may be able to survive retort conditions in limited applications

AC1

AC2

AC3

Retort

Dry after retort

0

50

100

150

200

250

300

350

400

Adhesive Concentrate Resins

Gra

ms/

15

mm

Results from Retort Bond Strength Testing - February 2009

RetortDry after retort

Objectives – Try to Improve on Previous Results by:

Evaluating an additional primerEvaluating effect of carrier polypropylene resin on post retort bond strengthEvaluating effect of corona treatmentEvaluating effect of new adhesive concentrate

Extrusion Conditions

Randcastle Pilot line1 inch vertical screw – three heating zones,

limited mixingExtrudate temperature - 305°C (580° F)Extrudate thickness - 50 micron (60 rpm screw

speed at 6.1 meters per minute)3.8 cm air gap

MaterialsResinsPolypropylene base resins (homopolymer):

Polypropylene Resin 1 (PP1): Dow DX5E66Polypropylene Resin 2 (PP2): Sabic 520P

Maleic Anhydride adhesive resin concentrates:Adhesive Concentrate Resin 1 (C1): Chemtura Polybond 3000Adhesive Concentrate Resin 2 (C2): Arkema Orevac 811

Concentrates were blended into polypropylene so that the final MAH concentration was 0.20%

Materials:

PrimerP1 = Mica A-131-X P2 = Mica M-2420

FilmPolyamide

Corona Treatment As suppliedRe-treated with a hand-held treater

Testing

Dry bond strength – 24 hours RT aging, 1 -inch strips on Twing-Albert tensile tester (g/15 mm)Retort –

1 inch strips in steam sterilizer at 19 p.s.i, 130°C for 30 minutes tested while still wet and after drying for 30 minutes at room temperatureAllowed retort sample to dry and re-tested bond

Results!

PP1 C1 P1 PP1 C1 P2PP1C2P1

PP1C2P2PP2C1P1

PP2C1P2PP2C2P1

PP2C2P2

no retreat

treated

0

50

100

150

200

250

300

350

400

Samples

gram

s/15

mm

Dry Bond Strengths of All Samples After Retort

no retreattreated

PP1 C1 P1PP1 C1 P2 PP1C2P1

PP1C2P2PP2C1P1

PP2C1P2PP2C2P1

PP2C2P2

no retreat

treated

0

50

100

150

200

250

300

350

400

Samples

gram

s/1

5mm

Wet Bonds of All Samples After Retort

no retreattreated

PP1 (no)PP1 (yes)

PP2 (no)PP2 (yes)

Concntrate 1

Concentrate 20

50

100

150

200

250

300

350

400

Polypropylene Carrier Resins with and without corona

gram

s/15

m

mMAH Concentrate 1 vs. MAH Concentrate 2

Concntrate 1Concentrate 2

C1 (no)C2 (no)

C1 (yes) C2 (yes)

Polypropyelne 1

Polypropylene 20

50

100

150

200

250

300

350

400

Adhesive Concentrate (with and without corona treatment)

gram

s/15

m

mPolypropylene Carrier Resin 1 vs. Carrier Resin 2

Polypropyelne 1Polypropylene 2

PP1 C1PP1 C2

PP2 C1PP2 C2

Non-treated

Treated0

50

100

150

200

250

300

350

Polyproylene Carrier Resin and Tie-Layers

gram

s/ 1

5 m

mNon-Treated PA Film Vs. Treated Film

Non-treatedTreated

Discussion

Without co-extrusion – lamination of a seal layer will be necessary – this added layer will be protection against moisture ingress Edge exposure from strip samples may be more severe than pouch stockPoor mixing of resins may contribute to lower bonding

Discussion

Dramatic improvement of bonds was not achievedTrends were discovered which may lead to further optimizationTrends:

Alternate primer did not improve bondsCorona treatment had minimal effectTie-layer 1 resulted in higher bondsPolypropylene carrier resin 1 resulted in higher bonds

Conclusions

Dry bonds – all samples needed both primer and MAH to have any bond at all to extruded PPReal world extrusion and pouch structures may yield higher bonds100% tie-layer may still be best way to make clear retort structuresNEW WORK on non-maleic containing tie layers may benefit from these results.

References1. Foster, Bruce W. and Trouilhet, Yves, “New Approach for

Clear, Retortable Packaging Films”, Proceedings of the TAPPI, Place Conference, Rome, Italy 2003

2. Allen, Richard “Using Primers in Combination with Adhesive Tie-Layer Resins or Their Blends to Make Structures with Unique Performance”, TAPPI, Place Conference, Vienna, Austria 2005

3. Bodine, Jessica C. and Tanny, Stephen R. “Improved Bonding Performance of Low Temperature Extrudate on Primed Substrates”, SPE, Flexible Packaging Conference, Orlando, Florida, 2006

4. Pascal, J. “Adhesive Properties of Ethylene-Acrylic Ester-Maleic Anhydride Terpolymers in Extrusion Coating/Lamination” TAPPI PLACE Europe, Rome, Italy 2003

Thank you!

Questions?

Contact: Jbodine@mica-corp.com203-922-8888