Ultraviolet (UV) cured coatings show excellent appearance, durability, and little or no volatile organic compound (VOC) emissions, while enabling increased productivity and lower overall costs. An UV-curable coating is one of the best finishing methods in the paper and packaging industries for protecting ink layers from physical and mechanical defects [1]. Liquid UV-curing printing inks cure within a few seconds by irradiation with UV light.
The majority of commercial light cure resins are based on free radical curing acrylic compounds (acrylates).
In addition to photoinitiators, which start this polymerization, the formulations of printing inks contains monofunctional acrylic esters for viscosity adjustment and as a crosslinker to ensure rapid polymerization. Upon curing, it is possible and likely that this reaction will not be complete and the diluents and crosslinkers used will be unbound in the polymer. The UV-curing printing inks and coatings are widely used, even in the printing of food contact materials.
For the photoinitiator isopropylthioxanthone (ITX) a mass transition from the printed packaging material in the foodstuff was shown [2]. A migration of uncomplete cured acrylate monomers is likely. At least for trimethylolpropane triacrylate (TMPTA), a carcinogenic effect was shown [3].
Target screening of acrylates from radiation-curing inks
A sensitive LC-ESI-MS/MS method was developed and validated for the target screening of different acrylate monomers in food simulants used for migration tests.
[1] Soltani, M. et al. (2013) UV-curable coating process on CMYK-printed duplex paperboard, Part 1: Mechanical and optical properties, BioRes. 9(1), 86-92.
[2] T. Jung , T.J. Simat & W. Altkofer (2010) Mass transfer ways of ultraviolet printing ink ingredients into foodstuffs, Food Additives & Contaminants: Part A, 27:7, 1040-1049, DOI: 10.1080/19440041003596543
[3] Kromhout, H. et al. (2018) Carcinogenicity of isobutyl nitrite, β-picoline, and some acrylates. The Lancet Oncology. 19. 10.1016/S1470-2045(18)30491-1.