Nip flow and tack of printing inks

Abstract

The squeezing flow of a printing ink in the nip between rotating rollers is investigated. A numerical analysis is used which takes into account the viscoelastic nonlinear behavior of the deformable roller. Contributions from the central creeping flow zone to tack reading are calculated and compared with experiments for three different rubbers on the measuring roller. The said zone only contributes a minor fraction to the tack force. Nevertheless the effect of roller characteristics on performance can be understood on the basis of the creeping flow theory. Slip is found to be an important element in quality considerations of tackmeters. Its effect on tack is investigated theoretically and experimentally. The flow pattern is so complicated that no simple scaling-up procedure can be formulated.Systematic experiments show a vehicle-related effect which might be associated with fluid elasticity.