Development of starch-based barrier coatings against mineral oil for recycled paper

Dr. Doris Rengstl EFPRO – CEPI 3rd Early Stage Researchers Workshop

25th November 2014

Problem of mineral oil components in recycled paper used as food packaging Announcement from European Food Safety Authority (EFSA), Federal Institute for Risk Assessment (BfR) and Cantonal Laboratory of Zurich

mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) from recycled paper are present in the food chain and are a potential human health hazard: MOSH/MOAH migrate through gaseous phase or direct food contact into food

no specific harmonised measures presently exist at EU level

German draft law

limits by the BMEL Mineral Oil Regulation, third draft dated 24th July 2014

mineral oil content in board (used for all foods) max. 24 mg/kg MOSH C16-35 max. 6 mg/kg MOAH C16-35 alternative migration into food max. 2 mg/kg C20-C35 MOSH max. 0.5 mg/kg C16-C35 MOAH

one possible solution to hinder MOSH/MOAH migration: BARRIER COATING

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3 Permeation of volatile substances

Requirements for aqueous barrier coating: • can be applied using standard coating equipment • least possible change in barrier properties after creasing and folding processes • no blocking, no invisible set-off • no negative effects on the recyclability of paper and board • suitable for food contact (recommendation XXXVI, FDA)

C 1

p 1 p

2

C 2

board barrier coating food side

Transfer rate P according to Dissolution-Diffusion Model

P = S • D

solubility coefficient S

•high polarity (e.g. starch)

diffusion coefficient D

•high density •high connectivity •high crystallinity

Starch – the most important reserve material in plant cells

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SUNLIGHT

WATER

CO2

O2

STARCH

Amylose (helix): α (14) linked D-glucose

Amylopectin (branched): α (14) and α (16) linked D-glucose

Polysaccharide: chemical formula (C6H10O5)n; composed of α-D-glucose units

Native starches and modified starches as barrier coating

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Modified starch: Variation in degree of degradation and modification

Modified starch

high degree of degradation (hD)

low degree of degradation (lD)

carboxylated potato starch, anionic (cK)

hD

lD

amylopectin-rich, carboxylated potato starch, anionic (acK)

hD

lD

hydroxypropylated, hot water soluble potato starch ether (hhK)

hD

lD

thermochemically degraded maize starch (taM)

hD

lD

cold water soluble, chemically degraded potato starch ester (kcaK)

maize (27/73) waxy maize (1/99)

wheat (28/72)

pea (68/32)

potato (21/79) amylopectin starch (5/95)

Source: www.asv.nienborg.de www.klopfermuehle.de www.tomatengruen.at www.menshealth.de

Native starch: Variation in crop, degree of degradation (α-amylase), amylose/amylopectin ratio (%/%)

Determination of mineral oil migration with Tenax ®

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stainless steel board

5 days/ 60°C

Release of adsorbed components

Analysis

Tenax ® : porous polymer material chemical: poly(2,6-diphenylenoxide) - very strong adsorber - low affinity to water - simulant for dry food

Stainless steel migration cell

Tenax ® (food simulant), 4g/dm2 (DIN 14388) barrier coating

Native starch - determination of mineral oil migration with Tenax®

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high degree of degradation

low degree of degradation

Potato and pea starch show potential as a good barrier to the migration of mineral oil components.

Coating condition: 12 g/m2 on smooth board front side using a handsheet rod coater

high degree of degradation

low degree of degradation

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Modified starch - determination of mineral oil migration with Tenax®

Coating condition: 12 g/m2 on smooth carton board front side using a handsheet rod coater

cK (hD), hhK (lD), kcaK show potential as a good barrier to the migration of mineral oil components.

Modified starch

carboxylated potato starch, anionic, high degree of

degradation cK (hD)

hydroxypropylated, hot water soluble potato starch ether, low degree of degradation

hhK (lD)

cold water soluble, chemically degraded potato starch ester kcaK

Plasticizer – increasing the flexibility of starch films

Effective formulation (% related to dry starch):

•pkcaK: cold water soluble, chemically degraded potato starch ester (kcaK) with 10% PVOH 98 and 10% glycerin

•pcK (hD): carboxylated potato starch, (anionic; cK (hD)) with 10% PVOH 98 and 10% glycerin

•phhK(lD): hydroxypropylated, hot water soluble potato starch ether (hhK (lD)) with 10% PVOH 98 and 10% glycerin

•pK: potato (0.005% amylase) with 10% PVOH 98 and 30% glycerin

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Starch forms optical defect-free coatings on board (SEM), but coatings are brittle and mechanical processing needs to be improved! plasticizer: glycerin and polyvinyl alcohol (98% degree of hydrolysis; PVOH98)

optical, defect-free, flexible coatings (pinhole test, SEM)

Pigments - cost reduction of barrier coating Using the following pigments:

•Standard kaolin (92 % by wgt. < 2 µm; 74 % by wgt. < 1 µm): approx. 275 €/t of dry pigment

•Standard calcium carbonate (GCC; 90 % by wgt. < 2 µm): approx. 120 €/t of dry pigment

Cost balance: Calculated for 1 tonne of barrier coating (costs for materials only) kcaK with 10% PVOH 98, 10% glycerin 75 % by wgt. kcaK with 10% PVOH 98, 10% glycerin and 25 % by wgt. standard calcium carbonate

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kcaK 1000 Euro PVOH 98 192 Euro glycerin 767 Euro total 1959 Euro

kcaK 749 Euro PVOH 98 144 Euro glycerin 574 Euro GCC 30 Euro total 1497 Euro

In comparison: Cost of synthetic polymer coatings approx. 2000-4000 €/t

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Starch-plasticizer-pigment - determination of mineral oil migration with Tenax® Coating condition: 12 g/m2 on smooth carton board front side using a handsheet rod coater

Mineral oil barrier effect is not influenced by introducing pigments into starch coating.

Reverse side coating - board and testliner 12

Coating condition: 20 g/m2 pre-coating + 20 g/m2 barrier formulation with handsheet rod coater Pre-coating: 100 parts kaolin (aspect ratio 100) with 100 parts barrier formulation (used as binder) Barrier formulation: pkcaK or 75 % by wgt. pkcaK + 25 % by wgt. GGC

Characterization Testliner Board grammage in g/m² 160 400

mineral oil content MOSH/MOAH in µg/dm2 1812 1874

roughness according to Bendtsen in ml/min 1900 ±320.8 (reverse side) 1281 ± 150.6

surface tension in mN/m 44.87 (reverse side) 51.12

effective coating against mineral oil component migration for testliner and board

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Food regulatory compliance

Acceptance

Limits by the BMEL Mineral Oil Regulation, third draft dated 24th July 2014

•Migration into food max. 2 mg/kg C20-C35 MOSH max. 0.5 mg/kg C16-C35 MOAH

Calculation basis

• board / food = 6 dm2/kg (EU cube)

Testliner: 20 g/m2 pre-coating + 20 g/m2 pkcaK Tenax, MOSH C14-C35 43 µg/dm2, MOAH C14-C35 86 µg/dm2

→0.3 mg/kg MOSH C14-C35 ok ; 0.5 mg/kg MOAH C14-C35 ok

https://static.allyouneed.com/productpictures/05/large/14046/2028/1/Lambertz-Coco-Fleur-Kekse-125-g.jpg

1 dm

1 dm

Summary

• potato starch (0.005% amylase); hydroxypropylated, hot water soluble potato starch ether (hhK (lD)); carboxylated potato starch, anionic (cK (hD)) and cold water soluble, chemically degraded potato starch ester (kcaK) form a good barrier coating on board and testliner to the migration of mineral oil components

• PVOH 98 in combination with glycerin increase the flexibility of the starch coating

• pigments such as standard kaolin and standard calcium carbonate reduce coating costs without lowering the efficiency of the barrier effect of the starch coating

• a starch-plasticizer formulation is a more effective binder for the pre-coating than a synthetic binder

• the coated testliner and board are recyclable

• all coatings form defect-free films on testliner and board without blocking

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Contact

Food packaging Dr. Doris Rengstl Phone: 089/12146-459 doris.rengstl@ptspaper.de PTS Hess Str. 134 80797 Munich http://www.ptspaper.de

This research was conducted within the framework of IGF project 17676N

Thank you for your kind attention!!!

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