Research of rheological properties of newspaper black inks for offset printing method

The choice of printing inks, which would provide consistently high printing results in specific production conditions, is a very difficult task, the solution of which depends on many factors. The research of printing and technological characteristics of offset black inks with different methods of fixing Cold Set and Heat Set, which are used in publishing conditions, is an important component of optimizing the technological process of offset printing method. The determination of the ink resistance to ethyl alcohol, alkali and acid showed that both inks show very good resistance. The density determination showed slightly higher values in Cold Set inks. The study of the flow limit of offset printing ink was performed at a settling time of 2 minutes and 15 minutes The best stabilization of the colloidal system at a settling time of 15 minutes was established. It was found that the value of the structural viscosity of Heat Set ink does not change over time. The viscosity of Cold Set ink increases during aging, but over time, the processes of structure formation slow down. Rheological curves of the dependence of the structural viscosity of inks on the time of their maturation are constructed. Each section of such rheological curves has its own separate flow mechanism. The main processes of physicochemical interaction, which determine the formation of structural bonds between the components of the studied inks and their stabilization, occur within 15-20 minutes after mixing. The different nature of the approval of Cold Set and Heat Set determine the choice of the optimal technological process of their use.

Keywords: offset printing method, newsprint, performance, thixotropy, structural viscosity, yield strength.

doi: 10.32403/1998-6912-2021-1-62-80-86