US Patent 11124900 Method for preparing flame-retardant cellulosic fibers

A type of flame-retardant cellulosic fiber and a preparation method thereof are disclosed. The preparation method includes extruding the cellulosic solution through a spinneret, coagulating, stretching, and water-washing to obtain a water-washed filament, which is then treated with a flame-retardant solution, and then rinsed and dried to prepare the flame-retardant cellulosic fiber. The water-washing temperature is ≤90° C., the temperature of the flame-retardant solution during treatment is 60-90° C., and the rinsing temperature is 20-40° C. The flame retardant contains more than one of a group that forms a covalent bond with a hydroxy group of the cellulosic macromolecule, a group having the ability of self-crosslinking reaction, and a group that forms a hydrogen bond with a hydroxy group of the cellulosic macromolecule. The prepared flame-retardant cellulosic fiber is mainly composed of the cellulosic fiber matrix and the flame retardant dispersed in the matrix.