Method of producing finely divided fibrous cellulose particles

A method of producing finely divided fibrous cellulose particles, comprising the steps of:

• suspending cellulose particles in a liquid not chemically reactive to the cellulose particles to provide a cellulose particle slurry;
• treating the cellulose particle slurry in a solid medium-agitation type grinder in which the cellulose particles are agitated and ground with solid medium particles to an extent such that the cellulose particles are finely divided into fine fibrous cellulose particles having a water-retaining power of at least 150%, determined by centrifugally hydroextracting a sample of a slurry of the resultant finely divided fibrous cellulose particles in water at an acceleration of 3,000 G for 15 minutes, measuring the weight of the hydroextracted sample, drying the hydroextracted sample at a temperature of 105.degree. C. for at least 5 hours, measuring the weight of the dried sample, and calculating the water-retaining power of the finely divided fibrous cellulose particles in accordance with the equation ):
• WRP(%)=(A-B)/B.times.100 (I)
• wherein WRP represents the water-retaining power of the finely divided fibrous cellulose particles, A represents the weight of the hydroextracted sample, and B represents the weight of the dried sample.