Pigment is the "HEART" of any ink formulation as this is the key raw material that imparts color to the printed image in any packaging material; and thereby initiates the visual communication with the consumers. However, unfortunately, pigment is one of the major sources of unwanted migrants those have to be purified by carefully optimizing the pigment manufacturing process and their formulations.
The scope of the article is to discuss the potential migrants other than heavy metals (heavy metals are separately covered in one of the other articles by this author) present in the organic pigments particularly focusing solvent-borne flexible packaging ink formulations for food packaging application.
It is very important note here that most of the local and global regulations are very particular about these pigment related migrants and have already adopted principles with regular amendments to safeguard the health of the consumers in their respective regional domains.
EuPIA guideline on printing inks recommends following the Article 3 of the Regulation (EC) No 1935/2004 which states that the constituents of the inks should not endanger the human health or bring about an unacceptable change in the composition of the food; or bring about deterioration in the organoleptic characteristics of the food. It suggests that all colorants used in the manufacture of packaging inks have to comply with the specifications of the Council of Europe Resolution AP (89)1.
The EuPIA exclusion policy for printing inks and related products (current edition) explicitly excluded Dye/colorants Auramine (Basic Yellow 2 CI 41000), Chrysoidine (Basic Orange 2 CI 11270), Fuchsine (Basic Violet 14 CI 42510), Induline (Solvent Blue 7 CI 50400), Cresylene Brown (Basic Brown 4 CI 21010) and Other soluble azo dyes which can decompose in the body to bio-available carcinogenic aromatic amines of Category 1A and 1B according to the CLP Regulation (EC) No.1272/2008 for intentional use. The pigment and ink formulators should also go through the other clauses of this exclusion list for detailed understanding on heavy metals and other hazard classes.
A list of carcinogenic primary aromatic amines provided in the REACH Regulation (EC) No 1907/2006, which are produced by reductive cleavage of one or more azo groups present in the azo dyes. These should not be used in the ink formulations. The list of these amines along with their CAS No’s are 4-Aminodiphenyl (CAS 92-67-1), Benzidine (CAS 92-87-5), 4-Chlor-o-toluidine (CAS 95-69-2), 2-Naphthylamine (CAS. 91-59-8), o-Aminoazotoluene (CAS 97-56-3), 2-Amino-4-nitrotoluene (CAS 99-55-8), p-Chloraniline (CAS 106-47-8), 2,4-Diaminoanisol (4-Methoxy-m-phenylendiamine) (CAS 615-05-4), 4,4’-Diaminodiphenylmethane (CAS 101-77-9), 3,3’-Dichlorobenzidine (CAS 91-94-1), 3,3’-Dimethoxybenzidine (CAS 119-90-4), 3,3’-Dimethylbenzidine (CAS 119-93-7), 3,3’-Dimethyl-4,4’-diaminodiphenylmethane(4,4'-methylene di-o-toluidine) (CAS 838-88-0), p-Cresidine (CAS 120-71-8), 4,4’-Methylene bis(2-chloraniline) (CAS 101-14-4), 4,4’-Oxydianiline (CAS 101-80-4) and 4,4’-Thiodianiline (CAS 139-65-1). The readers are requested to visit the REACH website to get regular updates of any further amendments.
The exclusion list present in Annex A (section A-2) of Indian Standard IS 15495:2004 (Reaffirmed 2015) for Printing Ink for food packaging – code of practice excludes the use of particular dyes/colorants such as Auramine (Basic Yellow 2 — Cl 41000), Chrysoidine (Basic Orange 2 — CI 11270), Cresylene Brown (Basic Brown 4 — CI 21010), Fuschine (Basic Violet 14—CI42510) (NOTE — Formerly listed as ‘magenta’), and Induline (Solvent Blue 7 — CI 50400). In addition, it also excludes the use of azo dyes which can decompose in the body to aromatic amines that are category 1 or 2 carcinogens. Also in section A-5 of Annex-A, related compounds such as Dioxins, Polychlorinated bi- or terphenyls, Polychlorinated dibenzofuranes etc. are listed.
It is also very important to study the brand owners’ requirement pertaining to pigments. One such example is Nestlé Guidance Note on Packaging Inks, which provides a specific exclusion list. It excludes Rhodamine-based ("Fanal") pigments which may contain residual rhodamine, which is a suspected carcinogenic substance. These pigments are generally less stable (visual aspect changes, migrations). The prohibited pigments are Pigment Red 81, Pigment Red 81:1, Pigment Red 81:2, Pigment Red 81:3, Pigment Red 81:5, Pigment Red 169, Pigment Green 1, Pigment Blue 1, Pigment Blue 62, Pigment Violet 1, Pigment Violet 2, Pigment Violet 3, Pigment Violet 27, Pigment Violet 39. All of these pigments are listed in Swiss Ordinance Part-B. Pigments that generate small amounts of polychlorobiphenyls (PCBs) or are manufactured from 3,3’-dichlorobenzidine with different couplers must be minimized or phased-out where suitable alternatives exist.
Colorants are exempted from being listed in the Union list of the Regulation (EU) No. 10/2011. However, for formulating printing ink with respect to Swiss Ordinance and/or European plastics regulation (EU 10/2011 and its subsequent amendments), readers are requested to go through the respective positive lists and search the CAS number of the impurities and CI numbers for getting more clarity on the migration limits.
The Food and Drug Administration in United States (US FDA) regulates color in cosmetics, medical devices, drugs, and food (including food additives in food packaging and articles). However, the USFDA does not approve printing inks or any other specific products for direct or indirect food contact. In the event of migration, any component of printing ink or coating e.g. colorants etc. may potentially become an indirect food additive and would be regulated under 21 CFR 170-190. Detailed regulatory information for colorants for polymers will be found in § 178.3297.
In Japan, the use of printing inks for food packaging is restricted by a negative list, which is produced by the Japan Printing Ink Makers Association (JPIMA). In China, there is a positive list available such GB9685-2008. The Australian regulation practically requires that the colorant product should fulfill the purity criteria of the CoE Resolution AP (89)1 and the additives should be listed in Regulation (EU) No. 10/2011.
For pigment manufacturers’, the most important point is to meet the purity criteria of CoE Resolution AP (89)1 for the pigments, so that it would be easier towards getting compliance with regards to global printing ink and packaging regulations for food packaging applications. For flexible packaging inks, apart from heavy metals, the pigment impurities that are critical as per CoE Resolution AP (89)1 is as follows (which is not an exhaustive list, but sufficient enough to initiate discussion with analytical laboratories):
Unsulfonated primary aromatic amines (unsulfonated PAA’s) are particularly be evaluated for Pigment Yellows, pigment reds and pigment oranges. For sulfonated primary aromatic amines (sulfonated PAA’s) will be of particular interest for pigment Reds such as PR48:1, PR48:2, PR 49:1, PR 49:2, PR 53:1 & PR 57:1; and pigment orange such as PO46. Polychlorinated biphenyls (PCB’s) can be evaluated in most of the pigment variants for flexible packaging inks. Hexachlorobenzene (HCB’s), Dioxins, and furans can be determined for Pigment pthalo Blues, green and violets. 4-Nitro biphenyls are of prime importance for pthalocyanines.
The information present in this article is to provide a general understanding of various regulations related to organic pigment based printing inks for food packaging application. However, the formulator should go through these regulations in detail to further deep understanding of the techno-legal aspects as well as the complete scope of these significant regulations.