In recent years, as the environmental protection and the safety protection consciousness continuously increase, the flame retardant problem of the polymeric materials gets more and more attention. It is the most effective manner to add flame retardants into polymeric bulk to improve the flame retardant property of the polymeric materials. Ideal flame retardants not only have the high-effective flame retardant feature, but also have the characteristics such as the environment friendliness, etc. At present, for the selection of the flame retardants, the following five aspects generally need to be sufficiently considered: (1) the flame retardant efficiency of the flame retardants on the polymeric materials; (2) the influence of the flame retardants on the processing technology of the polymeric materials; (3) the compatibility of the flame retardants with the matrix and the influence of the flame retardants on the physical property of the matrix; (4) the balance of the performance-price ratio of the flame retardants; and (5) the environmental compatibility of the flame retardants and the like. The conventional polymeric materials use flame retardants, such as halogen and antimony flame retardants, and although they have good flame retardant efficacy, use thereof is increasingly restricted due to their bad environmental compatibility. In contrast, the research and use of the phosphorus, nitrogen, silicon and inorganic hydrate flame retardants have been rapidly developed in recent years (Wilkie C A, Morgan A B. Fire retardency of polymeric materials, CRC Press, 2010, pp 1˜14).
During the research and development of the new type of flame retardants, another development trend is to pay increasing attention to the function of “synergistic effect” in a flame retardant system. In the flame retardant design of the polymeric materials, people increasingly realize that use of single flame retardant system tends to have defects, such as low efficiency, large addition amount, great influence on the property of the polymeric bulk, and the like. However, use of the synergistic effect among the different kinds of the flame retardants can largely improve the flame retardant efficiency. “Synergistic effect” means that, when the addition amounts are the same, the performance improvement of the system consisting of two or more components is superior to the sum of performance improvements when two components solely work respectively. For the flame retardants, the “halogen-antimony” and “phosphorus-nitrogen” flame retardant systems are the two most common synergistic systems. Because of the implementation of European Environmental Law, mainly WEEE and ROHS ACTs, the use of the “halogen-antimony” synergistic system is gradually forbidden. Therefore, the current synergistic flame retardant system is mainly the “phosphorus-nitrogen” system. For example, FUSHIMI Pharmaceutical Co., Ltd., Japan, develops the highly-efficient “phosphorus-nitrogen” synergistic flame retardant polyphosphazene (trade name: Rabitle® FP-100). This flame retardant has excellent flame retardant characteristic to epoxy molding compound and engineering plastic (polycarbonate, ABS resin, high impact polystyrene etc.) system.
In recent years, another kind of synergistic flame retardant system, “phosphorus-silicon” flame retardants, gets more attention. Research indicates that the coexistence of phosphorus and silicon elements has the effect of synergistic flame retardance. Research by Li et al. has found that the phosphorus-nitrogen-silicon type flame retardants have a good synergistic flame retardant effect on polypropylene materials (Li Q, et al. Synergistic effect of phosphorus, nitrogen, and silicon on flame-retardant properties and char yield in polypropylene. J. Appl. Polym. Sci., 2005, 96: 854-860). Patent ZL 200710178086.7 reports an organosilicon compound containing phosphorus. This compound is prepared by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with silicone compounds containing carbon-carbon double bonds under the action of a catalyst such as platinic chloride, rhodium chloride and the like. The research indicates that such compounds all have good flame retardant effects on the polymeric materials such as phenolic resin, polycarbonate, polymethyl methacrylate, etc. However, there is an easily hydrolyzable phosphonate ester bond in the molecular structure of such compounds, thus their use is limited. In addition, because the preparation reaction uses the expensive heavy metal catalyst, the cost is high, and it is difficult to achieve the mass production.
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