Effects of oligomer-to-monomer ratio on ink film properties of white UV-curable gravure ink for printing on biaxially oriented polypropylene (BOPP).

摘要

The high shear rate environment of gravure requires very low viscosity, fluid inks. The problems associated with low viscosity such as spilling, crawling, scumming and crazing, have hindered the development of UV-curable gravure inks. This led the researcher to study UV-curable gravure ink formulation. The effects of oligomer-to-monomer ratio and pigment dispersion loading on white ultraviolet (UV)-curable gravure ink film properties (surface cure efficiency, abrasion resistance, substrate adhesion, and ink film flexibility) were investigated. In this study, molecules normally used as monomers, in UV-curable systems, were selected as oligomers relative to the selected monomer, Glycerol Propoxylate Triacrylate (GPTA). The selected oligomers were, Trimethylolpropane Triacrylate (TMPTA), Trimethylolpropane Ethoxylate Triacrylate (ETMPTA), and a commercially available oligomer, Commerical Product A, used in flexographic ink applications. The outcome of this research created a starting point for white UV-curable gravure ink formulation, which will be used in the researcher's family printing business.;The results of the experiment showed that oligomer-to-monomer ratio did not have significant effects on surface cure efficiency, substrate adhesion, and ink film flexibility in the range from 70 to 90% oligomer concentration. Abrasion resistance was dependent on the type of oligomer. Using oligomer Commercial Product A, a soft oligomer, in combination with monomer Glycerol Propoxylate Triacrylate (GPTA), exhibited a decrease in abrasion resistance from 70:30 to 90:10 ratio. However, when using oligomers Trimethylolpropane Triacrylate (TMPTA) and Trimethylolpropane Ethoxylate Triacrylate (ETMPTA), oligomer-to-monomer ratio had no effect on abrasion resistance within the same range. Titanium dioxide pigment dispersion loading on 70:30 ratio (TMPTA:GPTA) did not have significant effects on substrate adhesion and ink film flexibility. Surface curing efficiency increased to 100% (from 99.5% with no pigment present) with pigment loadings equal to about 20%, but would begin to slightly decrease from complete curing at concentrations exceeding 40%. A significant decrease in abrasion resistance, caused by increased friction, was observed at 20 percent loading. There was, however, an increase in ink film strength from 30 to 50 percent pigment loading.;Developments in UV ink components and persistent research will most likely solve the issues of UV-curable gravure inks. This research opened up a wide array of research opportunities in UV-curable gravure ink formulation and taken a step towards creating an effective white UV-curable gravure ink.