One of the most important developments in cellulose technology in the last decade is the emergence of a class of cellulosic materials; microfibrillated celluloses (MFC). MFC, or its finer scale counterpart, nanofibrillated celluloses (NFC) may be an important raw material for a range of new fiber products. However, many of the processes that are used to produce MFC or NFC are not robust enough, nor cost efficient enough, for industrial application. In the present work, we explore a high consistency enzymatic hydrolysis process that appears to be highly scalable and has a potentially attractive cost structure. In this research, the effect of hydrolysis time at optimal pH and temperature and at 20% pulp solids is examined. A commercial endoglucanase enzyme is used. A previously dried, bleached Kraft Birch was used in all experiments. Thus, we examine how the virgin pulp fibers are broken down from the in-tact fibers to a fully defibrillated state. The MFC properties are considered in some detail. This includes, crystallinity, swelling, dimensions, DP and rheological parameters. Films were formed from the MFC and various physical properties were examined. The film properties were compared to films produced from the same pulp, but mechanically refined. In some experiments, the swelling of the MFC is modified to improve its bonding characteristics. The high consistency process is an extremely efficient way to break down macroscopic fibers to, small fibrillated fragments. The disintegration continued over the range of the experiment – up to 300 minutes. However, by some metrics the pulp was fully broken down by about 120-180 minutes. The high consistency conditions allowed for an increased enzyme concentration at the fiber internal surfaces, while the mixing at high consistency caused the fibers to flex and facilitated both diffusion of the enzyme throughout the cell wall and the attrition of the fibers. The swelling of the enzymatic MFC was quite low compared to other grades of MFC. This, together with low DP of the cellulose, resulted in low film strength properties. There are several viable options for increasing the swelling and improving the bonding potential of the MFC. The MFC is shear thinning and its viscosity decreases monotonically with hydrolysis time. This allows the enzymatic MFC to be pumped and processed at fairly high solids contents. Likewise, the dewatering properties of the enzymatic MFC are quite good due to its low swelling.

Microfibrillated cellulose produced with a high consistency enzymatic process

253rd National Meeting (2017)

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