Recycled paper – the influence of digital prints

The process of paper recycling changes the properties of cellulose fibres. The fibres become harder, more brittle, less flexible and more fragile. Their swelling ability is also reduced. These changes reduce the contact surface and weaken the hydrogen bonds between the fibres in recycled paper. Paper recycling takes place in several phases, the most important of which is the process of de-inking. This is particularly important in the production of recycled printing paper. De-inking is a process by which the particles of printing ink are removed from the pulp, i.e. from de-fibrated prints. Due to the fact that in every printing technique the ink adheres in a specific way to the substrate, the de-inking process for various types of prints can have a different outcome. Chemical de-inking flotation, along with particles of ink, extracts a certain amount of fibres and fillers from the pulp. With respect to the optical properties of recycled paper, the efficiency of de-inking directly affects quality. The aim of the study is to determine to what extent the extraction of certain quantities of fillers from the pulp influences the mechanical properties of recycled paper. To test evaluate access this effect, we expect that tests of tensile strength, tearing and bursting resistance of handsheets made of recycled fibers from offset and digital prints, will provide some answers. The addition of digital prints during recycling will decrease the mechanical properties of handsheets despite the presence of primary cellulose fibers. This is due to the influence of the fillers, as well as the residual ElectroInk particles in the recycled paper.