Abstract: The present invention aims to provide complex fibers of a cellulose fiber with inorganic particles exhibiting better drainage and retention when they are used as materials for forming sheets. In the complexes of the present invention, (1) the weight ratio B/A between the inorganic content (B) in the residue remaining on a 60-mesh sieve (having an opening of 250 ?m) after an aqueous suspension of a complex fiber having a solids content of 0.1% is filtered through the sieve and the inorganic content (A) in the complex fiber before treatment is 0.3 or more; or (2) the weight ratio C/A between the inorganic content (C) in fractions corresponding to an effluent volume (L) of 16.00 to 18.50 and an elution time (sec) of 10.6 to 37.3 and the inorganic content (A) in the complex fiber before treatment is 0.3 or more when an aqueous suspension of the complex fiber having a solids content of 0.3% is classified using a fiber classification analyzer under the conditions of a flow rate of 5.

Abstract: The present invention aims to provide complex fibers comprising a cellulose fiber strongly covered by a lot of inorganic particles on its surface. In the present invention, an excellent complex fiber of a cellulose fiber with inorganic particles can be prepared on the basis of the value of (D50?D10)/D50 calculated from the particle size distribution of (a) or (b) below: (a) the filtrate obtained by filtering an aqueous suspension of the complex fiber at a solids content of 0.1% through a 60-mesh sieve (having an opening of 250 ?m); or (b) the fraction corresponding to an effluent volume (L) of 18.51 to 19.50 and an efflux time (sec) of 37.4 to 48.0 when an aqueous suspension of the complex fiber at a solids content of 0.3% is classified using a fiber classification analyzer under the conditions of a flow rate of 5.7 L/min, a water temperature of 25±1° C., and a total effluent volume of 22 L.

Abstract: The present invention aims to provide a method for analyzing a fiber structure comprising a fiber and inorganic particles. An analysis method according to the present invention is a method for evaluating a structure comprising a fiber and inorganic particles, said method comprising the steps of: (A) capturing a two-dimensional image of the surface of the fiber structure using a scanning electron microscope; (B) denoising the captured image by adjusting each contrast value; and (C) calculating the standard deviation of the contrast value after denoising.

Abstract: The present invention aims to provide a technique for preparing a complex fiber covered by silica and/or alumina at a high coverage ratio. According to the present invention, complex fibers comprising silica and/or alumina deposited on the surface of a fiber at a high coverage ratio can be prepared by synthesizing silica and/or alumina on the fiber while maintaining the pH of the reaction solution containing the fiber at 4.6 or less.

Abstract: The present invention aims to provide complex fibers of inorganic particles and a fiber exhibiting high flame retardancy. According to the present invention, complex fibers of inorganic particles and a fiber treated with a flame retardant are provided. In the complex fibers of the present invention, 15% or more of the surface of the fiber is covered by the inorganic particles.

Abstract: The present invention aims to provide complex fibers of a cellulose fiber with inorganic particles exhibiting better drainage and retention when they are used as materials for forming sheets. In the complexes of the present invention, (1) the weight ratio B/A between the inorganic content (B) in the residue remaining on a 60-mesh sieve (having an opening of 250 ?m) after an aqueous suspension of a complex fiber having a solids content of 0.1% is filtered through the sieve and the inorganic content (A) in the complex fiber before treatment is 0.3 or more; or (2) the weight ratio C/A between the inorganic content (C) in fractions corresponding to an effluent volume (L) of 16.00 to 18.50 and an elution time (sec) of 10.6 to 37.3 and the inorganic content (A) in the complex fiber before treatment is 0.3 or more when an aqueous suspension of the complex fiber having a solids content of 0.3% is classified using a fiber classification analyzer under the conditions of a flow rate of 5.

Abstract: The present invention addresses the problem of providing products comprising a fiber composite of inorganic particles and fiber. The present invention provides products comprising a fiber composite of inorganic particles and fiber, said products being in the form of an aqueous suspension, pulp, sheet, powder, microsphere grains, granules, pellets, mold, yarn or foam.