Microfibrillated cellulose and method for preparing a microfibrillated cellulose

A process for the preparation of microfibrillated cellulose from primary wall plant pulp containing cellulose, pectins, hemicelluloses, proteins and mineral materials, the process comprising the following steps:

• (a) hydrolyzing the pulp with acid or base at a temperature between about 60.degree. C. and 100.degree. C. partially to extract the pectins and hemicelluloses to form a suspension;
• (b) recovering a solid residue from the suspension from step (a);
• (c) carrying out, under alkaline conditions, a second extraction of the residue of cellulosic material from step (b), when step (a) is an acidic hydrolysis and
• recovering the cellulosic material residue by separating the suspension;
• (d) washing the residue from step (b) or step (c);
• (e) diluting the cellulosic material from step (d) in water to obtain between 2% and 10% dry matter;
• (f) homogenizing the cell suspension from step (e) wherein
• at least one alkaline extraction step is carried out on the cellulosic material, said alkaline extraction being carried out with a base at a concentration less than about 9% by weight, and
• the homogenizing step (f) is carried out by a high mechanical shear operation to provide a cell suspension, passing the cell suspension through a small diameter orifice, subjecting the suspension to a pressure drop of at least 20 MPa and to a high velocity shearing action followed by a high velocity decelerating impact.