Cationic microfibrillated plant fibre and manufacturing method for same

A method for manufacturing a microfibrillated cellulose fiber cationically modified with a quaternary-ammonium-group-containing compound, the microfibrillated cellulose fiber cationically modified with a quaternary-ammonium-group-containing compound having a degree of substitution of quaternary ammonium groups of not less than 0.03 to less than 0.4 per anhydrous glucose unit and an average diameter of 4 to 200 nm, the method comprising the steps of:

• (1) reacting hydroxyl groups in a material containing a cellulose fiber with a quaternary-ammonium-group-containing cationization agent to cationically modify the material containing a cellulose fiber to form a cationically modified cellulose-fiber-containing material, and
• (2) defibrating the cationically modified cellulose-fiber-containing material from step (1), in a mixture with water to an extent that a fiber average diameter becomes 4 to 200 nm by using a twin-screw kneader,
• wherein the lower limit of the screw circumferential speed of the twin-screw kneader is 45 m/min, and
• and wherein the proportion of the cationically modified cellulose-fiber-containing material from step (1) in the mixture subjected to defibration is 10%-70% by weight,
• and the method not comprising, between step (1) and step (2), a step of drying the cationically modified cellulose-fiber-containing material.