CARATTERIZZAZIONI DI LABORATORIO' ENVIRONMENTALLY FRIENDLY LACQUERS FOR TINPLATE CANS INTENDED FOR PRESERVED VEGETABLE PRODUCTS. PART 1; SELECTION BY LABORATORY CHARACTERISATION

摘要

Some environmentally friendly wafer-based and UV-cured lacquers for metal cans intended for packing vegetable products were selected. Comparisons were made with different types of coatings applied to both the inner and the outer sides of the can surfaces (body/ends and welded side seam). The UV-cured lacquer was applied only to the outer side of the body/end surface, whereas the water-based lacquer was used for the other three surfaces. The UV lacquer (solvenf-freej caused no VOC (volatile organic components] emission, whereas VOC ranged befween 0.525 and 2.166 g of solvent/g of dry maffer in the case of water-based lacquers. This implies a considerable potential reduction in the emission of organic compounds with estimates of about 900t/year (datarelating to Italian factories). The results are reported of the preliminary laboratory-scale selection tests performed by means of adhesion, resistance to chemical agents and flexibility measurements; a comparison was made between the best performing coating and a high-VOC epoxyphenolic lacquer in the production phase. The metal base was not reported to strongly affect lacquer performances, apart from a higher degree of adhesion to the chromium plate (ECCS). The behaviour of the selected lacquers was experimentally validated by using as prototypes different batches of lacquered cans filled with different types of vegetable products whose shelf-life was monitored under different storage conditions.