Plasticizers in Food ContactMaterials and Adhesives
Dr. Monika Tönnießen, Hartmut Büsching I October 2016
Europe- specific content
02/11 | Plasticizers in Food Contact Materials and Adhesives
Why are plasticizers used andwhere do we find them?
Plasticizers are additives that increase the plasticity or fluidity of a material. The use of plasticizers allows improved compound processing characteristics. At the same time it provides flexibility in the final product.
Some technical effects of plasticizers are:
• Brittle materials become flexible, soft, stretchable or sticky• Improved workability and elasticity• Decrease of the elastic modulus and the glass transition temperature• Swelling or dissolving of the polymer
Plasticizers can be found in many products we use frequently in our daily life. This includes toys, gaskets, floor coverings, window profiles, varnishes and lacquers, cigarettes, chewing gum and tablet coatings. Plasticizers are also used in adhesives. As adhesives play an important role when it comes to food packaging they should be chosen with particular focus on the risk of migration of plasticizers into the foodstuff.
03/11 | Plasticizers in Food Contact Materials and Adhesives
Definition of plasticizers
Plasticizer
Effect of plasticizers
Figure 1
Rigid PVC
• Strong dipole-dipole interaction � Crystalline structure
Externally plasticized PVC
• Incorporation of plasticizer � physical interaction � Breaking-up of the polymer chains � Amorphous structure
Internally plasticized PVC
• Incorporation of co-monomers (e.g. vinyl acetate) with large side groups � chemical bonding � Reduction of the intermolecular attractive force � Amorphous structure
Typically we differentiate two types of plasticization that are characterized by the use of either internal plasticizers or external plasticizers.
Internal plasticizers Internal plasticizers cause a chemical modification of a rigid polymer (copolymerization). The molecular weight is > 1000 Da. As a result of the (internal) chemical reaction of the plasticizer with the polymer chain, the intermolecular attractive force is reduced. The polymer beeing of crystalline structure before now shows an amorphous structure. An internal plasticizer is chemically bonded. Therefore it cannot move outside of the adhesive film. On these grounds the common understanding in the adhesive world is that internally plasticized products are considered plasticizer-free.
External plasticizers External plasticizers are added to a polymer. There is no chemical reaction with the polymer chain. The molecular weight of an external plasticizer is < 1000 Da. This relatively low molecular weight leads to a relatively high molecular mobility. External plasticizers are liquid or solid organic substances with a low vapor pressure and a high boiling point (> 250 °C). They are indifferent substances that show no chemical reaction but a physical interaction. External plasticizers break up the interaction of the polymer chains and widen their separation from each other and thus raising the polymer chain mobility. Even though the external plasticizers are not chemically bonded, they are supposed to remain in the final product and therefore also in the adhesive film after drying.
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04/11 | Plasticizers in Food Contact Materials and Adhesives
Difference between plasticizers and solvents
Plasticizers based on esters
Figure 2
Both plasticizers and solvents are used in adhesives but with different characteristics and functions.
Solvents• Influence the production process of the final product.• Low boiling point.• Should not remain in the final product (e.g. the adhesive film).
Plasticizers• Influence the properties of the final product.• High boiling point.• Are supposed to remain in the final product and (therefore) also in the adhesive film after drying.• Internal plasticizers remain in the final product because they are chemically bonded.• External plasticizers are critical to migration as there is no chemical bonding which leads to a high tendency of migration.
Types of external plasticizers
Today there are more than 300 known external plasticizers. Approximately 100 of them are commercially important.
Plasticizers based on esterIn this documentation we focus on external plasticizers that are based on ester. Plasticizers based on ester qualify for the use in water-based adhesives because of their dipole character.
Examples of ester-based external plasticizers are: Phthalates, Adipates, Phosphates, Benzoates, Citrates and Acetates.
The most commonly added ester-based plasticizers for the use in water-based adhesives are either a mixture of benzoates or Triacetin. Especially Triacetin has been much used recently due to its good performance and very low impact on human health.
Properties of an ideal external plasticizerIf we wanted to list the properties of an ideal external plasticizer, it would look like this:
• Odorless• Colorless• Resistant against light, cold and heat• Low volatile• Not harmful• Relatively large size (i. e. extended separation of the polymer chains for a good plasticizing effect)• With polar and non-polar groups (to enable interaction with both polymer parts)• Very effective at low amount• No migration (which is impossible to realize)
Phthalates Adipates
Phosphates Benzoates
Citrates Acetates
• Triacetin
• Diisobutyl phthalate (DIBP)• Dibutyl phthalate (DBP)• Dioctyl phthalate (= Di(2-ethylhexyl)– phthalate, DOP, DEHP)
• Dioctyl adipate (DOA)• Diisononyl adipate (DINA)
§
05/11 | Plasticizers in Food Contact Materials and Adhesives
External plasticizers and migration
In many chemicals different external plasticizers are used. According to their toxicological assessment they may or may not be used for adhesives for food contact materials.
Plasticizers like Phthalates have been commonly used for many years until critical health concerns have been raised. Today, Phthalates should not be used. They are marked as SVHC (Substances of very high concern), i. e. their use must be authorized in the EU. For us at Henkel the SVHC classification is reason enough to ban Phthalates as plasticizers!
Other types of plasticizers are under evaluation by the European Chemicals Agency (ECHA) under the Community Rolling Action Plan (CoRAP). As there is still no sufficient data available for a severe evaluation and complete assessment, the use of these alternative plasticizers is currently restricted to certain application.
Finally there are two external plasticizers that can be declared as suitable for the use with food contact material.
• Acetyltributylcitrate is not classified according to CLP classification. Anyway its use for FCM can be justified due to the toxicological assessment. However, citrates are not likely to be used in adhesives.• Triacetin represents no risk according to its toxicological assessment. It is permitted as an additive for food in the EU under the E-Number E 1518 (explicitly for chewing gum; EU No 1129/2011).
Migration of plasticizers from adhesives
Figure 3
Impact of external plasticizers on human health
In a typical packaging profile for a food packaging two materials are bonded by an adhesive to protect the foodstuff inside the packaging.
Migration is the transfer of molecules from the adhesive layer into the foodstuff causing a contamination. At the same time there is also the tendency that substances from the foodstuff migrate into the packaging. This leads to a loss of the foodstuffs' composition, i. e. to a possible quality degration.
All parts of the packaging materials contribute to the migration of the whole packaging, not only the adhesive layer!
In case the adhesive contains an external plasticizer, the small plasticizer molecules quickly migrate (definately in both directions) causing a massive contamination of the foodstuff with the plasticizer.
Possible effects of the migration of plasticizers:• Incipient dissolution of contact materials• Corrosion of contact materials• Swelling of contact materials• Adhering/sticky on the surface• Contribution to windscreen fogging• Contamination of foodstuff
Packaging
material 1 AdhesivePackaging
material 2 Food
Plasticizer
Migration
06/11 | Plasticizers in Food Contact Materials and Adhesives
PlasticizerCAS No
HarmonizedC&L
Toxicological assessment
Phthalates
Diisobutyl phthalate (DIBP) 84-69-5 H360DfShould not be used, SVHC-substance: use must be authorized in the EU
Dibutyl phthalate (DBP) 84-74-2 H360DfShould not be used, SVHC-substance: use must be authorized in the EU
Dioctyl phthalate (= Di (2-ethylhexyl) phthalate, DOP, DEHP)
117-81-7 H400Should not be used, SVHC-substance: use must be authorized in the EU
Adipates
Dioctyl adipate (= Di(2-ethylhexyl)adipate, DOA, DEHA)
103-23-1 H360FDSome uncertainty due to lack of data, under further evaluation by ECHA (CORAP), current use might be justified for some applications
Diisononyl adipate (DINA) 33703-08-1no harmonized classification
Some uncertainty due to lack of data, use might be justified for some applications
Phosphates
Tri-2-ethylhexyl phosphate (TOP, TEHP)
78-42-2no harmonized classification
Some uncertainty due to lack of data, use might be justified for some applications
2-Ethylhexyl diphenyl phosphate 1241-94-7no harmonized classification
Some uncertainty due to lack of data, use might be justified for some applications
Benzoates
Diethylene glycol dibenzoate (DEGB) 120-55-8no harmonized classification
Some uncertainty due to lack of data, under further evaluation by ECHA (CORAP), current use might be justified for some applications
Triethylene glycol dibenzoate 120-56-9no harmonized classification
Some uncertainty due to lack of data, use might be justified for some applications
Dipropylene glycol dibenzoate 27138-31-4no harmonized classification
Some uncertainty due to lack of data, under further evaluation by ECHA (CORAP), use might be justified for some applications
Citrates Acetyltributylcitrate (ATBC) 77-90-7no harmonized classification
Use in FCM justified
Acetates Triacetin (E 1518) 102-76-1no harmonized classification
Food additive (permitted in chewing gum according to regulation (EU) No 1129/2011)
Toxicological assessment of external plasticizers
Toxicological assessment of external plasticizers
Figure 4
07/11 | Plasticizers in Food Contact Materials and Adhesives
Plasticizer CAS No
Legislation / Restriction
(EU) No 10/2011BfR XIV
BfR XXI BfR XXXVI FDA
Phthalates
Diisobutyl phthalate (DIBP) 84-69-5 no no nomax. 0.3 mg/kg foodstuff sum of DBP and DIBP max. 0.3 mg/kg foodstuff
175.105
Dibutyl phthalate (DBP) 84-74-2
FCM: 157 SML = 0.3 mg/kg plasticizer in repeated use materials and articles con-tacting non-fatty foods
no nomax. 0.3 mg/kg foodstuff sum of DBP and DIBP max. 0.3 mg/kg foodstuff
175.105
Dioctyl phthalate (= Di (2-ethylhexyl) phthalate, DOP, DEHP)
117-81-7 no nomax. 10 %
max. 1.5 mg/kg foodstuff 175.105
Adipates
Dioctyl adipate (= Di(2-ethylhexyl)adipate, DOA, DEHA)
103-23-1FCM: 207 SML = 18 mg/kg SML (T) = 60 mg/kg
nomax. 10 %
no 175.105
Diisononyl adipate (DINA) 33703-08-1 no no no no 178.3740
Phosphates
Tri-2-ethylhexyl phosphate (TOP, TEHP)
78-42-2 no no no no 175.105
2-Ethylhexyl diphenyl phosphate 1241-94-7FCM: 392 SML = 2.4 mg/kg
no no no 175.105
Benzoates
Diethylene glycol dibenzoate (DEGB) 120-55-8 no no no no 175.105
Triethylene glycol dibenzoate 120-56-9 no no no no 175.105
Dipropylene glycol dibenzoate 27138-31-4 no no no no 175.105
Citrates Acetyltributylcitrate (ATBC) 77-90-7FCM: 138 SML (T) = 60 mg/kg
no no no 175.105
Acetates Triacetin (E 1518) 102-76-1FCM: 40 SML = OML
no no no 175.105
Plasticizers in food contact legislation
Looking at external plasticizers in food contact legislation we focus on the following legislations / restrictions:
• (EU) No 10/2011 (on plastic materials and articles intended to come into contact with food)• BfR XIV, XXI or XXXVI (recommendations of the German Federal Institute for Risk Assessment)• FDA (legislation of the U.S. Food and Drug Administration)
None of the below listed plasticizers is in compliance with the BfR XIV recommendation due to the fact that BfR XIV deals only with plasticizer-free dispersions.
Plasticizers in food contact legislation
Figure 5
Recycling – You always meet plasticizers twice!Plasticizers are not eliminated during the paper recycling process. Looking at recycled cardboard, plasticizers rather enrich during the manifold recycling steps leading to a high risk for food contact contamination when using the recycled cardboard in food packaging. You always meet plasticizers twice – first in the original packaging and again in the recycled material.
Acetyltributylcitrate and Triacetin as the most recommended substances under the toxicological point of view are listed in (EU) No 10/2011. For Triacetin the specific migration limit (SML) equals the overall migration limit (OML) meaning that this acetate is allowed to migrate up to the maximum permitted amount of non-volatile substances released into the food, the OML value of 60 mg/kg.
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History of improvements for food packaging adhesives
History of improvements for food packaging adhesives containing plasticizers
1950 1990 2007 2010 2012 2016
Figure 6
Looking at the common use of external plasticizers there has been a number of improvements during the last decades. Henkel reacted whenever a substance became evaluated and/or considered as critical with respect to consumer health.
Already in 2007 important associations in Germany committed themselves to stop using the Phthalate DIBP. As a result of the aligned actions of the involved industries, DIBP in recycled cardboard dropped significantly.
Henkel does not use DBP, DIBP or other Phthalates in its products. The very high concern these plasticizers cause has made Henkel looking for alternatives from the very beginning.
DBP
DIBP
Benzoates
Triacetin
Low Migration (LM)
Plasticizer Migration potential EU BfR XIV FDA
DBPDIBPBenzoatesTriacetininternal plasticizer
highhighhighhighlow
SVHCSVHC
x
PP
x
x x
P P
P P P P P
09/11 | Plasticizers in Food Contact Materials and Adhesives
Plasticizer-free with Henkel
Since many years Henkel has developed and promoted a low migration product range without external plasticizers. Henkel's development focuses on internally plasticized products as these are commonly considered plasticizer-free, and therefore also these Henkel products are free of plasticizers.
Adhesives play a key role in the manufacturing of food packaging.
Adhesives of Henkel’s AQUENCE LM line provide the full range of low migration water-based adhesives. All AQUENCE LM adhesives use a plasticizer-free formulation with a minimum content of critical substances compared to traditional adhesives and a significantly higher efficiency through lower adhesive consumption.
Plasticizer-free and low migration by HenkelLM (Low Migration) shows the highest advantage for food contact with the best criteria.
Safe Food Packaging with AQUENCE LM adhesivesAQUENCE LM offers a complete water-based product range for the use with packaging from bags and sacks to folding boxes.
AQUENCE LM adhesives• Full range of low migration water-based adhesives• Plasticizer-free formulation with minimum content of critical substances• Easy and clean processing• Equal or better adhesive strength compared to traditional adhesives• Significantly higher efficiency through lower adhesive consumption
AQUENCE® LM for the Packaging Industry
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Key take aways
Adhesives could contain internal or external plasticizers.
Internal plasticizers are chemically bonded. They cannot migrate into the foodstuff.
Adhesives with such plasticizers are considered ‘plasticizer-free’.
External plasticizers are small molecules with a high migration potential. They show
different toxicological behavior, some species are classified as SVHC, Triacetin is allowed
as a food additive.
Water-based adhesives containing external plasticizers cannot comply with the XIV.
BfR recommendation.
Henkel can offer plasticizer-free adhesives as low migration products. These products
are in compliance with the relevant food contact legislation (FDA, (EU) No 10/2011 and
BfR recommendation).
Literature and useful links
D. F. Cadogan, Ch. J. Howick, Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag, Vol. 27, p. 599-617, 2012
Römpp Online Lexikon Chemie, Thieme-Verlag, 2014 https://roempp.thieme.de/roempp4.0/do/data/RD-23-00480
Datenbank BfR-Empfehlungen zu Materialien für den Lebensmittelkontakthttps://bfr.ble.de/kse/faces/DBEmpfehlung.jsp
Database BfR Recommendations on Food Contact Materialshttps://bfr.ble.de/kse/faces/DBEmpfehlung_en.jsp?filter=clear
Plastics Regulation (EU) No 10/2011http://eur-lex.europa.eu/legal-content/EN/TXT/?qid=1476646824639&uri=CELEX:32011R0010
Hartmut Büsching works in the product development for water-based paper converting adhesives with more than 35 years of experience. His main application fields are adhesives for packaging and consumer goods. A major part of his product development projects are adhesives for food packaging.
The information provided herein, especially recommendations for the usage and the application of our products, is based upon our knowledge and experience. Due to different materials used as well as to varying working conditions beyond our control we strictly recommend to carry out intensive trials to test the suitability of our products with regard to the required processes and applications. We do not accept any liability with regard to the above information or with regard to any verbal recommendation, except for cases where we are liable of gross negligence or false intention. The information is protected by copyright. In particular, any reproductions, adaptations, translations, storage and processing in other media, including storage or processing by electronic means, enjoy copyright protection. Any exploitation in whole or in part thereof shall require the prior written consent of Henkel AG & Co. KGaA. Except as otherwise noted, all marks used in this document are trademarks and/or registered trademarks of Henkel and/or its affiliates in the US, Germany, and elsewhere. © Henkel AG & Co. KGaA, 10/2016
Further information Visit the Food Safe Packaging Premium Area offering webinars, white papers, FAQs, videos and more: www.henkel-premium-area.com
Webinars Our webinars allow you to directly communicate with our Henkel food safety experts. Check our website for the dates of upcoming webinars.
Dr. Monika Tönnießen is a chemist by profession and works in the Product Safety Department of the Henkel Adhesive Technologies division. Since 2006 she deals with customer inquiries and is an expert on all food contact related questions. She is member of the paper & packaging group of the European Adhesive Association FEICA.
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