Nitrogen-based flame retardants

Horacek, H. Grabner, W. Nitrogen based flame retardants for nitrogen-containing polymers. Makromol. Chem. Macromol. Symp. 1993, 74, 271-276. 

Phosphorus and Phosphorus/Nitrogen-Based Flame Retardants... 

Nitrogen-containing FRs (without any phosphorus compounds) hold only a small share of the global FR market at present, although their popularity is growing. The main active ingredients are usually melamine cyanurate and melamine hydrobromide, although melamine phosphate is used in intumescent FR systems in combination with pentaerythritol. Melamine based flame retardants employ several modes of flame retardant action. 

Several approaches have been used to make polymers fire-retardant. Phosphorus-based flame retardants have been effectively used in a wide variety of polymeric materials. The efficiency of phosphorus compounds is often dramatically increased in the presence of certain nitrogen compounds. Thus, the improved flame resistance of polyesters in the presence of triphenylphosphine oxide and Nylon-6 has been attributed to the synergistic effect of phosphorus and nitrogen atoms. However, the fire-retardant additives (1) frequently influence the decomposition reaction in... 

Degradation products from both antimony-halogen based and nitrogen-phosphorus based flame retardants were studied using X-ray diffraction and atomic emission analysis. Evidence of the retardation mechanisms in use against combustion was obtained for each system and in each case emission of volatile combustion inhibitors at the degradation temperature of the polymer matrix was the critical factor. 11 refs BELARUS BELORUSSIA... 

A series of compounded flame retardants, based on finely divided insoluble ammonium polyphosphate together with char-forming nitrogenous resins, has been developed for thermoplastics (52—58). These compounds are particularly useful as iatumescent flame-retardant additives for polyolefins, ethylene—vinyl acetate, and urethane elastomers (qv). The char-forming resin can be, for example, an ethyleneurea—formaldehyde condensation polymer, a hydroxyethylisocyanurate, or a piperazine—triazine resin. 

Phosphoric Acid-Based Systems for Cellulosics. Semidurable flame-retardant treatments for cotton (qv) or wood (qv) can be attained by phosphorylation of cellulose, preferably in the presence of a nitrogenous compound. Commercial leach-resistant flame-retardant treatments for wood have been developed based on a reaction product of phosphoric acid with urea—formaldehyde and dicyandiamide resins (59,60). 

In the 1990s, two types of flame retardants are preferred for outdoor fabrics, ie, a system based on phosphoms and nitrogen such as the precondensate—NH finish and an antimony—bromine system based on decabromodiphenyl oxide [1163-19-5] and antimony(III) oxide (20,40—42). 

In tile 1990s. two lypes lit flame retardants are preferred lor outdoor fabrics, i.e.. a system based on phosphorus and nitrogen such as the precondensuie-NHi finish and an antimony-bromine system based on decahromodiphetiyl oxide and antimony)III) oxide. 

It has been reported that the effectiveness of copolymerized DOPO-type monomers can be further improved if the alcohol-amine derivatives of DOPO, for example, Structure 5.11, are used rather than similar structures not containing nitrogen.30 Of the FR fibers based on P-containing comonomers, it has been found that those based on Structure 5.10 are more hydrolytically stable, presumably because the P-containing group is in a cyclic structure and also should the hydrolysis of the P-0 bond occur, it will not lead automatically to a marked reduction in molecular weight.31 All the P-modified PETs appear to be subject to both the vapor-and condensed-phase mechanisms of flame retardance, with the former predominating.32 33... 

Also phosphorus- and nitrogen-containing polyols are shown to be effective in flame retardancy of PU foams24 such as polyols based on phosphonic acid ester or obtained by partial or full substitution of methylol groups of tetrakis(hydroxymethyl)phosphonium chloride with amine several examples of such polyols were reported by Levchik and Weil.15 Rigid PU foam modified with these polyols showed improved oxygen index values moreover better results were achieved with higher functionality polyols. 

Although inorganic salts can provide excellent flame-retardant properties for cellulose, reasonable laundering durability must be incorporated into any finish destined for apparel use. The most successful durable flame retardants for cellulose are based on phosphorous- and nitrogen-containing chemical systems that can react with the fibre or form crosslinked structures on the fibre. The key ingredient of one of these finishes is tetrakis(hydroxymethyl)phosphonium chloride (THPC), made from phosphine, formaldehyde and hydrochloric acid (Fig. 8.11). THPC reacts with urea to form an insoluble structure on cellulose in a pad-dry-cure process (Fig. 8.12). 

The incorporation of DOPO derivatives in DGEBA has been found to increase not only flame retardancy but also thermal stability. The DOPO-based diamine shown in Fig. 9, having a reactivity toward DGEBA intermediate between DDS and DDM, has also proved to be an effective FR. It displays a char yield (in a DEGBA/DOPO-amine) polymer of 32% at TOO C under nitrogen, compared with 13-15% for a phosphorus-free... 

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