FRACTIONAL PULPING USING RECOVERED PAPER MIXTURES OF FLEXOGRAPHIC AND OFFSET PRINTED NEWSPAPERS WITH MAGAZINES, 2012 TAPPI PEERS Conference

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The extent of deinking pulping is normally controlled so that complete defibering is achieved. Recent results have, however, shown that the ink redeposition begins at the very early phase of pulping and some amount of printing ink is redeposited irreversibly onto the fibers before the complete defibering is obtained. Furthermore, it has been shown that the redeposition of printing ink can be prevented by performing fractionation after a very short pulping, where the pulping is continued for the incompletely defibered fiber fraction. This paper aims to find out the suitability of a true neutral fractional pulping process for recovered paper mixtures containing magazines along with flexographic and offset printed newspapers. Fractional pulping was compared to reference pulping, which was performed with and without deinking chemicals, in terms of dirt specks, ERIC700, and brightness. The results showed that the dirt specks fragmented efficiently during the pulping of the fiber fraction after fractionation. Furthermore, because the fractional pulping process prevents ink redeposition onto the fibers, a similar or higher brightness was obtained for true neutral fractional pulping process in comparison with alkaline reference pulping with peroxide.