Polyurethane Laminating Adhesives and Food Safety ... - · PDF filePolyurethane Laminating...

November 2009 Dr. Claudia Meckel-Jonas TAPPI conference India1

Polyurethane Laminating Adhesivesand Food Safety: A Smart Alliance

Dr. Claudia Meckel-JonasHenkel Company China Ldt.

Flexible Packaging Symposium India 2009


Flexible packaging


Sustainable packaging system

Source:

EnvironmentResources

EconomyCost for production

distribution, merchandizing of goods

SocialMeet customer expectations

•Product protection•Safety

•Handling•Information

Packagingwith adhesives


PAA in food!

So called “Danish food scandal”


Laminating adhesivesPolyurethane (PUR) chemistry

• Advantages

• Performance

• Price

• Availability

• Established equipment

• Disadvantages

• Interaction with films/inks/additives

R-NCO + HO-R‘ R-NH-CO-O-R‘Urethane

• Curing needs time


Production stage

Days0

1st lamination

slitting

heat sealing

boiling resistance

retort resistance

Physical Curing

Curing time

high performance

medium performance

standard performance

safe for food contact ?


We have to get the

chemical curing the physicalof the adhesives requirements

balanced for a sustainable and safe packaging.

&


Curing mechanism of2-c polyurethane adhesives• First curing step: Reaction of NCO with OH

Polyurethane prepolymer after first curing step

NH

NCO N C ONH

O OC

O

C

O

IsocyanateIsocyanate AlcoholAlcohol

UrethaneUrethane

N C ONCO HO OH+

N C ONCO N C ONCO N C ONCO

N C ONCO


• Final curing (1): Reaction of NCO with H2O

IsocyanateIsocyanate WaterWater

H2O+NH

NCO N C ONH

O OC

O

C

O

Curing mechanism of2-c polyurethane adhesives

UrethaneUrethaneUreaUrea

NH

NH

NH

NH

O OC

O

C

O

CNH

O

CNH

O

Completely cured polyurethane adhesive

N C ONCO


Flexible packaging in contact with food

Adhesive in indirect food contactOuter Layer Adh. Sealing Layer

Monomeric MDIE.g.:

NCO + Water ⇒

Aromatic Amines

“PAA”

Food

ONLY present in not fully cured PUR-adhesives !

Suspected to be carcinogenic


Migration of aromatic amines in screening test – cited in BfR XXVIII

141,4 mm

141,

4 m

m

Sample from reel Make pouch (200cm²) + 100ml acetic acid

Store in oven2h@70°C

Derivatisation of filling UV-Detection

Chemistry!Chemistry!


1,120 ppb 600 ppb 120 ppb 76 ppb 28 ppb 12 ppb < 2 ppb

PAA-Migration: Photometric Test (BfR)

• Colour intensity corresponds to level of migration of non-reacted NCO-monomer!

• Detection limit: 2ppb!


PAA Migration Level

Days0

1st lamination

slitting

heat sealing

Oiling resistance

retort resistance

Chemical Curing - Conventional

0

1st lamination

Conventional System

Curing time

high performance

medium performance

standard performance


Cure mechanism of a modified2-component PUR with smart chemistry

Cure mechanism

----urea------urethane------urea------fully cured PUR

NCO/OH>1based on mix ratio

with free MDI-monomerOCN-----------NCO + HO------OH

step 1: fast

step 2: slow+ water- carbon dioxide

OCN-------urethane-------NCOno retain NCO-monomer safe for indirect food contact


PAA Migration Level

Days0

1st lamination

slitting

heat sealing

Oiling resistance

retort resistance

Chemical Curing - Smart

0

1st lamination

Conventional System

Smart System

Curing time


EC Regulations for safe food packaging

EC 1935/2004framework

2002/72/ECPlastic directive

(90/128 + amendm.)

82/711+amendments

time/temp. 85/572food simulants

amendments2004/1/EC2004/19/EC2005/79/EC2007/19/EC

5th amendment2008/39/EC


Flexible packaging in food contact Legal requirements

• framework regulation 1935/2004/EC

• directive plastics2002/72/EC and amendments (actual change: 2007/19/EC)

• FDA § 175.300direct food contact

• FDA § 175.105indirect food contact

• FDA § 177.139540°C – 120°C

• FDA § 177.1390> 120°C

• LFGB

• BedGgstV

• BfR Recommen-dation XXVIII for cured poly-urethanes as adhesive layers for food packaging

• GB 9685-2008


Framework Regulation 1935/2004/EC

EC 1935/2004 (replaced 89/109), Article 3:

Packaging materials have to be manufactured in a way that

under the conditions of use no components will be transferred into the food, which

• are a potential hazard to the human health

• change the food composition or

• influence the organoleptic properties


EC migration limit for aromaticamines & BfR-method - Conclusion

We recommend to use the BfR-method for compliance testing using a limit of 2ppb

Otherwise there will be the risk of non-conformity with EU-legislatives!

2


Limitations of „BfR-test“

• SUMMARIZING method• All PAA are measured at once

• Known to give false positive results!!!• No distinction between PAA and others substances

possible.

• Problematic in presence of additives (films/ink)

• Results for retort applications & higher temperatures are doubtfull and have to be cross-checked

A specific method is required for cross-check!


Summary: Compliance testing forPAA

4th amendment of 2002/72/EC: 2007/19/ECDL=0,01 mg/kg (aniline, without analytical tolerance)

compliance testing

Screening methodBfR photometric test

threshold of action limit0,002 mg/kg

considers lower responsefactors of real PAA vs aniline

Specific methodHPLC-UV

if >0,002 mg/kg DL = sum PAA <0,01mg/kg

2 10


Factors Influencing Migration Time

• Adhesive system• free monomeric isocyanate content• Curing mechanism (most important)• coating weight• Mix ratio

• Laminating AND storing conditions• Temperature• Humidity• Thickness of rolls• Width of rolls

• Film• Type• Thickness• Additives (e.g. copolymers (EVA), pigments..)• Type of film for outer layer


Conclusion

• Laminates should not be used for food packages until physical AND chemical curing is completed!

• Packages, that do not comply with legislatives endanger human health.

• The answer is....


…responsible care…training and information of converters…the choice of the smart & appropriate adhesive!

Henkel CAC India and

will help to meet the demands of safe food packaging!!

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