Microcrystalline cellulose is produced by subjecting to a high shear
treatment, at elevated temperature and pressure, a reaction mixture of a
cellulose material, an active oxygen compound and water, for a time
effective to depolymerize the cellulose material. The mixture may be
further depolymerized after the high shear treatment by holding it
without cooling. A suitable active oxygen compound is hydrogen peroxide.
An extruder is a typical high shear device.