Crosslinked phenoxyphosphazene compounds, process for the preparation thereof, flame retardants, flame-retardant resin compositions, and moldings of flame-retardant resins

A crosslinked phenoxyphosphazene compound characterized in that:

• at least one phosphazene compound selected from the group consisting of a cyclic phosphazene compound represented by the formula (1)
• wherein m is an integer of 3 to 25 and Ph is phenyl group, and a straight- or branched-chain phosphazene compound represented by the formula (2)
• wherein X1 represents a group —N═P(OPh)3 or a group —N═P(O)OPh, Y1 represents a group —P(OPh)4 or a group —P(O)(OPh)2, and n is an integer of 3 to 10000 and Ph is as defined above,
• is crosslinked with at least one crosslinking group selected from the group consisting of o-phenylene group, m-phenylene group, p-phenylene group and bisphenylene group represented by the formula (3)
• wherein A is —C(CH3)2—, —SO2—, —S— or —O— and z is 0 or 1;
• (a) each of the crosslinking groups is interposed between the two oxygen atoms left after the elimination of phenyl groups from the phosphazene compound;
• (b) the amount of the phenyl groups in the crosslinked compound is 50 to 99.9% based on the total amount of the phenyl groups in said phosphazene compound represented by the formula (1) and/or said phosphazene compound represented by the formula (2);
• and
• (c) the crosslinked phenoxyphosphazene compound has no free hydroxyl groups in the molecule.