LATEX BINDER MODIFICATION TO REDUCE COATING PICK ON 6-COLOR OFFSET PRESSES

The fast-setting inks used on multicolor offset presses can cause coat ing pick, especially on coatings containing a linear carboxylated styr ene-butadiene polymer, which is added to improve blister resistance. I f ink tack builds too quickly, coating pick can occur at downstream co lor stations. The rate of build is affected by the interaction between the latex polymer and the solvents in the ink. Polymer solubility is known to be dependent on the polymer's physical state (linear vs. cros slinked) and its chemical structure (surface energy/polarity). Modifyi ng the latex polymers to a higher level of surface energy/polarity red uced the interaction between ink and polymer, thus slowing the rate of ink-tack build. The surface-energy/polarity modification of linear po lymers resulted in excellent blister-resistant coatings that ran on a commercial six-color press without showing coating pick.