Engineering the paper production by combined fiber fractionation and reinforcement with microfibrillated cellulose

Extending the use of mechanical pulp into non-traditional paper markets that requires moving towards producing high-bulk, porous paper grades with sufficient strength has gained intensive interest. This paper explores the potential of incorporating fiber fractionation with microfibril production to create high-bulk, porous, and strong enough material appropriate for a wide range of non-traditional mechanical pulp applications. Two different pressure-screen fractionation trials were conducted to fractionate a primary pulp into a long and coarse fiber stream (reject) and a fine and short fiber stream (accept). High-bulk, low-tensile sheets were obtained using the long and coarse reject fibers. The accept fibers were low-consistency refined at high specific energy to produce a microfibrilated cellulose (MFC) material and used to strengthen the high-bulk reject pulp sheets. The results illuminated that incorporating highly refined accept fibers having MFC-mimetic network into the paper structure could be a promising route to engineer the paper properties and extend the property range in comparison to low consistency refined whole pulp. Different series of handsheets were made and systematically studied by means of fiber length, fine percentage, bulk, tensile index, tensile energy absorption, Tear and burst indices, and freeness. Moreover, SEM micrographs were used to interpret the variations of paper properties. We believe that our results shed light on future mechanical pulp materials suitable for packaging and absorbency grades of paper that are high-bulk with sufficient strength for the specific application.