Investigation of the effects of silicone oil coating and hot air drying on the optical and physical properties of heat-set web offset printing papers

Web offset printing machines use an irrevocable printing method with high production speed (Kulachenko, Gradin, & Westerlind, 2005) and offset printing quality, especially for companies which have a high production capacity. Heat-set web offset printing is a versatile printing technique in terms of paper and production. The products produced with heat-set printing are usually high circulation products such as magazines, catalogs, mails, newspapers, flyers, animation books and user guides. Generally, paper types from 35 g/m2 to 150 g/m2 WFC (Wood free Coated), MWC (Medium weight Coated), LWC (Lightweight Coated), MFC (Machine finished Coated), SC (Super calendared), UWF (Wood free uncoated)) and newsprint papers are preferred for heat-set printing. Heat-set printing has a market worth of 80 billion Euros worldwide. In particular, when coated papers are used in high quality jobs such as magazines and catalogs, ink cannot be absorbed by the paper therefore a heat-set process should be applied to dry it quickly (Weboffsetprint, 2018). In heat-set printing, the ink is applied to the paper surface by the printing units, and then the printed paper is passed through an oven to provide the drying of the ink by means of hot air. During this passing, the drying takes place by evaporation of the binding agents (mineral oils) in the ink. However, surface characterization of the paper is of utmost importance during the settlement and absorption of the fluid ink on the paper surface (Akgul, Aydemir & Tutak 2017). However, despite all this process even after the printed papers have been out of the oven, it is still not possible to achieve 100% drying, thus protecting the ink by silicone coating on it (Kozak, 2018).