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Evaluation of Alternatives for Compounds under Risk Assessment in the EU, Bisphenol A

7 Printing inks

Printing inks are applied in thin films on many substrates such as paper, paper board, metal sheets and metallic foil, plastic films and molded plastic articles, textiles and glass (Kirk-Othmer, 1996).

Printing inks can be coloured or non-coloured and are used on e.g. labels and ice lollies, which are in contact with food (The Danish Veterinary and Food Administration, 2003).

Printing inks typically contain three main components: Pigments (the coloured or solid ingredient), vehicles (the fluid ingredients) and additives (such as driers and extenders). Printing ink is thus a mixture of colouring matter dispersed or dissolved in a vehicle or carrier, forming a fluid or paste, which can be printed on a substrate and dried (Kirk-Othmer, 1996).

The vehicles consist of a combination of resin, oil and solvent. The solvent is absorbed by the paper, leaving a thin ink film of resin and oil that binds the pigment to the paper. This film hardens by oxidation (Kirk-Othmer, 1996).

Printing inks are produced by e.g. Resino Trykfarver A/S (Resino, 2003), BASF (2003B), Akzo Nobel (2003) and Sun Chemical (2003B).

The bisphenol A resin is used as e.g. an ingredient in rosin-modified phenolics for printing inks, where rosin-modified phenolics possess good oil solubility, which may be used for water-washable inks and adhesives (Shanghai Nanda, 2003). Another phenolic resin is used in printing ink products from the Japanese Arakawa Chemical Industries (2003) in Japan. Raw materials, e.g. bisphenol A, are supplied for the printing ink industry by e.g. the Eastern Chemical Corporation (2003).

7.1 Alternatives to BPA in printing inks

Printing inks produced by BASF have no content of bisphenol A (BASF, 2003B).

According to Akzo Nobel Inks, binders based on bisphenol A have only very limited use in traditional printing inks whereas UV-printing ink types more often use binders based on bisphenol A (Akzo Nobel, 2003).

Resino Trykfarver mainly uses nitrocellulose, polyvinyl butyral, polyamide, blocked polyurethane as binder and ketones, maleinate, polyester, etc. as auxillary binders. The main binder in their cationic UV-printing inks is, however, based on bisphenol A containing epoxy (Resino Trykfarver, 2003).

Also urethane resins are used in food packaging gravure inks. They are used as binders for gravure inks for printing on polyolefin films for food packaging, e.g. polypropylene, polyester and nylon, which has good adhesion and flexibility properties (Arakawa Chemical Industries, 2003). The urethane acrylates are among the popular monomers and prepolymers acrylate resins used as drier (UV-curing inks) in the UV printing inks (HDM, 2003).

Furthermore, one company offers polymerised rosin in hectograph ink to replace bisphenol resin, for the printing ink industry (Pinechem, 2003).

7.1.1 Environmental and health screening of alternatives to bisphenol A in printing inks

Urethane acrylates and polymerised rosin were considered as possible alternatives to bisphenol A in UV-printing inks. Comparing this with the information available from the DPR (Tables 3.6 and 3.7), one polymerised rosin substance can be identified, but none of the polyacrylates were identified as an urethane acrylate.

Urethane acrylates

Urethane acrylates are acrylates, which contain diisocyanates (Figure 7.1).

Where R is CH3,; Y is H and R' is an isocyanate. The isocates can be:

• TDI, toluene diisocyanate (CAS No. 584-84-9)
• HMDI, dicyclohexane diisocyanate
• IPDI, isophorone diisocyanate
• MDI, diphenylmethane 4,4'-diisocyanate (CAS No. 101-68-8).

Figure 7.1 Urethane acrylates (HDM, 2003)

Urethane acrylates are various substances such as urethane diacrylate, urethane dimethacrylate or diurethane dimethacrylate (CAS No. 103597-45-1), which is a 4-tert-octylphenol compound (Chemfinder, 2003).

The environmental and health properties of a urethane acrylate will depend on the specific substance. Octylphenols, for instance, is included on the list of substances considered having endocrine disrupting properties. However, in general, some acrylate monomers are classified with N; R51/53, i.e. toxic to aquatic organisms and may cause long-term effects in the aquatic environment (Danish EPA, 2002).

Monoalkyl, monoaryl or monoalkylaryl esters of acrylic acid are included in the Annex 1 of the EU directive on classification and labelling of dangerous substances with a classification as irritating to eyes, skin and respiratory organs (HDM, 2003). The influence from these monomers should be considered as regards releases from the finished product and as regards the environment and working environment related to the production and manufacture.

The polyurethanes are as such relatively inert and harmless materials, having little specific toxicological activity. However, feedstock for polyurethanes, the isocyanates, are a group of very reactive substances, which may cause disabling respiratory diseases and skin sensitization by repeated exposure. In many countries, isocyanates are recognized as the most frequent cause of occupational asthma (Engelund & Pratt, 2001). Isocyanates (MDI, IPDI; HMDI and TDI) are included in the Annex 1 to the EU directive on classification and labelling of dangerous substances with classifications as very toxic, toxic or harmful by inhalation, irritating to eyes, skin and respiratory organs and sensitizing by inhalation and skin contact. Isocyanates may be formed in connection with heating of polyurethanes, e.g. during welding.

Polymerised rosin

Polymerised rosin is based on natural organic compounds such as gum and pine rosin. In printing inks, rosin is mainly used as a colour carrier of the ink and to increase its adhesion to the paper (Pinechem, 2003).

In EU the produced quantity of rosin (also named colophony), which is registered as CAS No. 8050-09-7, is 100,000 – 500,000 tonnes/year from e.g. Akzo Nobel, Helm AG and Henkel (Iuclid, 2003). This registered colophony is used as e.g. binder in printing inks (KemI, 2003).

The rosin specified in Table 3.7 as CAS No. 68333-69-7 (maleated polymer with pentaerythritol) is not included in the Iuclid database of High Production Volume Chemicals and it was not verified by the industry. The maleated rosin, which was indicated as a gum rosin in a datasheet, could not be identified as an ink ingredient in a search on the internet but was indicated as ingredient in pesticides.

The environmental and health essessments were thus based on available data for colophony, the registered polymerised rosins. Colophony is produced by fractionated distillation of raw tall oil, a by-product from the paper and pulp industry. The main components (approx. 90%) are diterpenenes of the abietic acid (CAS No. 514-10-3) and pimaric acid types (KemI, 2003).

Table 7.1 Properties of polymerised rosin

1. Iuclid (2003)
2. Danish EPA (2003)
3. N-Class (2003)
4. DermNet (2003)
5. Verschueren (1997)
6. GESTIS-Stoffdatenbank (2003).
7. RTECS (2003)
8. Reprotext (2003)

Colophony not pass the level for ready biodegradability (Iuclid, 2003). However, according to the N-Class database (KemI, 2003), colophony is considered to be readily degradable. Colophony is very toxic to fish. Based on the aquatic toxicity and the uncertainty of the biodegradability, colophony is presently considered to fulfil the criteria for the N;R50/53 classification.

Rosin may cause sensitisation at repeated skin contact. Thermal decomposition products of rosin may be irritating to eyes, nose and throat in acute exposure and can cause allergic reactions including asthma, contact dermatitis and eczema at repeated exposure.

7.2 Legislation on printing inks for food packaging materials

The description from the Danish Food Ministry regarding printing inks in food contact materials refers to the present work in the EU, in which it is stated that food contact materials shall be safe and not transfer their components into the foodstuff in unacceptable quantities (EU, 2003B). Therefore, printing inks are not covered by EU legislation other than the general Food Safety Framework Directive (89/109/EEC) and additional legislation which covers plastic packaging materials (90/128/EEC), (Coates Lorilleux International, 2003).

Bisphenol A is, however among the substances, that are not to be used in printing inks for food packaging materials in Japan as stated in the Voluntary Regulation concerning Printing Inks for Food Packaging Materials, 1999, from the Japan Printing Ink Makers Association (Sun Chemical , 2003A). Both bisphenol A type epoxy liquid resins and methylene bisphenol type epoxy liquid resins are included in this list.

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Version 1.0 March 2004, © Danish Environmental Protection Agency