Abstract: Disclosed is a red phosphorus flame retardant comprising a fine red phosphorus powder subjected to a surface modification treatment, said fine red phosphorus powder consisting of spherical red phosphorus particles and/or agglomerates thereof directly obtained by the thermal conversion of white phosphorus in the presence of a dispersant and has an average particle size of 10 .mu.m or smaller and of which at least 80% by weight is accounted for by particles having particle sizes of 20 .mu.m or smaller, said flame retardant having an average particle size of 15 .mu.m or smaller, with the particles having particle sizes of 35 .mu.m or smaller accounting for at least 80% by weight of the flame retardant; and a nonflammable resinous composition composed of a synthetic resin and the red phosphorus flame retardant.

Abstract: A process for the production of a red phosphorus powder, which comprises heating a yellow phosphorus at the boiling point therof in the presence of a dispersant selected from the group of a surfactant, a sparingly in water, finely powdered inorganic compound, an inorganic ammonium salt or an organic compound containing an amino group, thereby to partly convert the yellow phosphorus to red phosphorus, removing most of the unconverted yellow phosphorus by distillation at the boiling point of yellow phosphorus, and further removing the slight amount of the still remaining yellow phosphorus by heating a temperature not lower than the boiling point of yellow phosphorus to obtain a red phosphorus fine powder which is less apt to undergo a disproportionation reaction.