Thermoplastic resins can have excellent processability and mechanical properties and accordingly are used in the production of a variety of molded products. However, the thermoplastic resins can be easily burned by ignition sources and can spread fire. Therefore, thermoplastic resins used in housings of electronic heat-emitting products such as computers, facsimiles, and the like, should be treated to impart flame retardancy thereto.
Conventionally, a halogen-containing compound and an antimony-containing compound had been added to thermoplastic resins to impart flame retardancy. Examples of halogen-containing compounds include polybromodiphenyl ether, tetrabromobisphenol-A, epoxy compounds substituted with bromine, chlorinated polyethylene, and the like. Examples of the antimony-containing compounds include antimony trioxide and antimony pentoxide.
A halogen-containing compound and antimony-containing compound can impart flame retardancy to a thermoplastic resin with minimal deterioration of the physical properties thereof. Halogen-containing compounds such as polybromodiphenyl ether, however, can generate toxic hydrogen halide gases during molding processes. Therefore, there is an increased need for improving flame retardancy of thermoplastic resins without using halogen-containing compounds.
Phosphoric ester compounds can be used as a flame retardant for thermoplastic resins instead of a halogen-containing flame retardant. However, typically the phosphoric ester flame retardant must be used in such a large amount to provide adequate flame retardancy, which can negatively impact other physical properties of the thermoplastic resin.