True-neutral fractional deinking for flexographic and offset newsprints

摘要

One of the main purposes of deinking is to detach ink particles from collected papers and remove it from the pulp suspension. The importance of pulping lies in the fact that only the free ink particles can be removed without sacrificing yield. In the traditional approach pulping is continued until complete defibering is achieved. However, recently it has been shown that offset newsprint ink fragmentation and redeposition could be avoided by using a very short pulping time, while the pulping is continued after the removal of free ink. It is expected that this procedure would be even more beneficial for flexographic prints for which the ink fragmentation behaviour is known to be higher, but no information on this exists in the literature. This paper aims to study whether the excessive fragmentation and redeposition of flexographic ink can be avoided by using very short pulping with fractionation and secondary pulping of the long fibre fraction. The results showed that lower ink fragmentation and redeposition resulting in a reduced amount of attached ink could be achieved for flexographic and offset newsprints using the proposed process concept.