Flame retardants phosphorus type

Organophosphorus Derivatives. Neopentyl glycol treated with pyridine and phosphorus trichloride in anhydrous dioxane yields the cycHc hydrogen phosphite, 5,5-dimethyl-l,3-dioxaphosphorinane 2-oxide (2) (32,33). Compounds of this type maybe useful as flameproofing plasticizers, stabilizers, synthetic lubricants, oil additives, pesticides, or intermediates for the preparation of other organophosphoms compounds (see Flame retardants Phosphorus compounds). 

Reduction in flammability is achieved by the incorporation of flame retardants into the polymer. Two possible approaches to this are available either the use of additives blended into the polymer at processing stage (additive type) or the use of alternative monomers which confer reduced flammability on the final product (reactive type). A number of elements have been found to assist with conferring flame retardancy on polymers, the main ones being bromine, chlorine, nitrogen, and phosphorus. 

The mode of action of phosphorus-based flame retardants is believed to take place in either the condensed or the vapor phase (refs. 1,2) depending on the type of phosphorus compound and the chemical composition of the polymer. Phosphorus has been reported to be 3 to 8 times more effective than bromine depending on the polymer type (ref. 3). 

The term brominated flame retardant (BFR) incorporates more than 175 different types of substances, which form the largest class of flame retardants other classes are phosphorus-containing, nitrogen-containing, and inorganic flame retardants (Bimbaum and Sttaskal 2004). The major BFR substances in use today (depicted in Fig. 4.6) are tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), and mixtures of polybrominated diphenyl ethers (PBDEs) (namely, deca-bromodiphenyl ether (DBDE), octabromodiphenyl ether (OBDE), and pentabro-modiphenyl ether (pentaBDE)). 

Monomers such as Structures 5.16 and 5.17 copolymerize, free radically, as readily with styrene as they do with MMA and give rise to products that are also significantly flame retarded. Flame retardance here too involves both the vapor- and condensed-phase action, with the condensed-phase activity leading to a significant char. In this case, char production is probably initiated by the Friedel-Crafts type condensation of phenyl groups, catalyzed by phosphorus acids liberated during combustion.43 48 49... 

Reactive polyols which contain halogen groups, phosphorus, or both, are offered by a number of suppliers for flame-netardant urethane-foam applications. These materials can be used alone, or with other flame retardants as synergists. Although reactive flame retardants may appear to be more costly initially, in the long run they may be found to be less expensive than the additive types (31). 

Phosphine is used as an insecticide for the fumigation of grains, animal feed, and leaf-stored tobacco, and as a rodenticide. Phosphine is also used as an intermediate in the synthesis of flame retardants for cotton fabrics, as a doping agent for -type semiconductors, as a polymerization initiator, and as a condensation catalyst. Phosphine is used in the semiconductor industry to introduce phosphorus into silicon crystals. 

Our original goal of making thermoplastic phosphorus containing polymers was considered a technical success. However, we weren t able to commercialize any of them. So this technical success was a commercial failure for us. About twenty some years later, the Japanese chemists from Toyobo Ltd. (6) prepared a polymer using phenylphosphonic dichloride and sulfonyl bisphenol as the dihydroxy reactant. That polymer called Heim Additive (equation 11) was considered seriously for use as an additive type of flame retardant for polyester fibers. 

The additive type of flame retardants are compounds containing chlorine, bromine or phosphorus without reactive groups to get involved in PU chemistry (without -OH, -NH2 or -NCO groups). These compounds are physically added to PU and are not part of the PU structure. 

Thermoplastics. Many flame-retardant chemicals have been developed for use in thermoplastics. Most of these flame retardants are of the additive type, usually halogen- and/or phosphorus-based compounds. 

Inorganic phosphorus compounds are also used as flame-retardants. Elemental red phosphorus itself is applied, for example, in polyurethane foams and more recently in polyamides. Some marketed types of red phosphorus-based flame-retardants are collected in Table 5.6. 

Kou and co-workers [64] have reported on the use of non-halogenated phosphorus type flame retardants in the formulation of alkylphosphate-type polyols and their corresponding PU. 

Various types of flame retardant additives have been used in polyamides including magnesium hydroxide - red phosphorus in glass fibre reinforced polyamide [76], chemically modified montmorillonite organoclays [77], surface modified nanosilica [77], carbon nanofibres in polyamides 11 and 12 [78], and dodecyl sulfate anion-modified MgAl (H-DS) interlayers in polyamide 6 [79]. 

The formation of unsaturated polyphosphoesters via acyclic diene metathesis pol5nnerization has been described (90). The ADMET copol5m erization of a phosphorus based a,(u-diene with different amounts of a castor oil derived diene has been exemplified. These pol3nner types show a good flame retardancy. The synthesis of a di-lO-undecenoylglycerol mixture is shown in Figure 4.16. 

A large number of organic phosphorus compounds are available to provide flame retardancy. However, it is known that such additives do not generally provide sufficient protection in epoxy resins. They are not resistant to migration and affect the mechanical properties. As a consequence epoxies are often proteeted by bromine containing types. 

For flame-retardant polyester fibres the copolymerisation of phosphorus retardants is the most common method. However, a serious difficulty is that the phosphorus-containing polymer is easily hydrolysed. Work by the Toyobo Company Limited in Japan has shown that two identical PET fibres can offer differing properties depending on where the phosphorus compound is situated within the pol5mier chains. One has the addition as a side chain and the other an identical phosphorus compound in the polymer backbone. Both fibres had almost the same physical and flame retardant properties, yet the main-chain type hydrolysed around twice as fast as the side-chain type, and led to an immediate drop in toughness. 

Other, US firms, including Merrill Lynch arrived at a similar value total, but gave a slightly differing breakdown of types. The market for flame retardants in 2000 globally was estimated as 2.16 billion. This was broken into bromine 34%, phosphorus 22%, antimony oxide at 17%, ATH 14%, chlorine-based at 7% and others on 5%. 

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