CERISE - Cellulose pre-treatment for in situ fibrillation by extrusion

With the recent development of bio-based products and materials in different industries, microfibrillated cellulose (MFC) has become one of the most promising additive made from renewable resources, and an always increasing number of research results keeps confirming its high potential for several applications in biocomposites, barrier coatings, high added value flexible substrates or biomedical devices. Since mid of 2000’s, new fibre pretreatments have been proposed to limit energy consumption during MFC production and in 2011, the way of thinking for such bio-based nanomaterials has completely changed with the announcement of their industrialisation. However, their production remains costly; the toxicity of some chemicals used in the pre-treatments has been evidenced, and in most of the cases, MFC are produced under the form of highly diluted suspension, rendering transport more expensive and formulation more difficult. One of the obstacles to the large-scale exploitation of MFC therefore lies in the development of cost-effective processes enabling the production of high solid content suspensions of MFC.

In 2015, a research group at the LGP2 has validated the concept of using the twin screw extrusion as a nanofibrillation method for the direct production of MFC at high solid content. Extrusion is a thermal-mechanical process, widely used in different industries (e.g. food , composites or paper pulps) for transforming low-moisture ingredients into intermediate or finished products. During twin screw extrusion, the raw material is conveyed in a channel through two rotating screws. The control of the shear stress, of the mixing efficiency and of the temperature inside the extruder screw channel renders this method very flexible and allows the operation to be designed specifically. Moreover, twin screw extruder is an energy-efficient process.

The aim of the CERISE project is to further adapt this original technology for the in situ nanofibrillation of cellulosic materials, and to confirm its potential for the production of high solid content MFC suspensions using less energy.

The principle is to directly feed the extruder with high solid content cellulosic fibres, in order to increase the density of the MFC suspension obtained after extrusion. In parallel of the mechanical defibrillation of the cellulosic fibres, several reaction media are tested directly into the extruder to validate the feasibility of an in-situ chemical modification of the MFC and to develop a single-step process for the production of chemically modified MFC suspensions at high solid content.