Influence of coating structure on ink tack dynamics

The coating pore structure, the binder chemistry and the ink composition co ntrol the ink tack dynamics. However a good understanding of the relationsh ips between these parameters is lacking. A series of characterized model co atings with two latexes differing in solubility parameter; three spherical polystyrene pigments with different sizes, and six latex levels are compare d. Ink rack is characterized by bringing an inked probe into contact with t he surface and measuring the force to pull the probe off the surface as a f unction of time. The latex type has a significant influence on tack develop ment for binder levels larger than 16 pph. However at low levels of binder; little difference in tack development is found between two types of latex. Ink setting rate increases with decreasing pigment size, even at the same level of pore volume. A mathematical model is proposed to quantify ink sett ing and tack dynamics. The model qualitatively agrees with experiments in t hat the ink sets faster oil coating layers with small pores compared to lar ge pores.