Ammonium polyphosphate flame retardant

Water-based ammonium polyphosphate flame retardant. 

Enrlit . [HoechstCelanese/Spec.Chem.] Ammonium polyphosphate flame retardant for polyurethanes, epoxy, PE, PP, EVA, adhesives, paints, elastomers. 

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. 

Related esters of this alcohol are disclosed by Ak2o as useflil flame retardants for polypropylene, particularly in combination with ammonium polyphosphate (90). 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

The aim was to assess the feasibility of substitution with less hazardous flame retardants. They selected red phosphorus, ammonium polyphosphate and aluminium trihydroxide as the least environmentally problematic alternatives. Red phosphorus can technically be used in a variety of polymers to meet even the toughest fire safety standards, although it may network forall applications. ... 

Significant changes in the distribution of the products of pyrolysis were observed with the flame retardants mentioned above. This indicates that the polyphosphoric residue of ammonium polyphosphate modifies the mechanisms of the thermal decomposition of these polymers. 

Many thousands of phosphorus compounds have been described as having flame-retardant utility. The compounds demonstrating commercial utility arc much more limited in number. They include inorganic phosphorus compounds [red phosphorus, ammonium phosphates. insoluble ammonium polyphosphate, phosphoric acid-bascd systems for cellulosics). additive organic phosphorus flstme retardants... 

J. Zhang, A.R. Horrocks, and M.E. Hall, Flammability of polyacrylonitrile and its copolymers. III. The flame retardant mechanism of ammonium polyphosphate. Fire Mater., 18, 307-312 (1994). 

Ammonium polyphosphates, on the other hand, are relatively water insoluble, nonmelting solids with very high phosphorus contents (up to about 30%). There are several crystalline forms and the commercial products differ in molecular weights, particle sizes, solubilities, and so on. They are also widely used as components of intumescent paints and mastics where they function as the acid catalyst (i.e., by producing phosphoric acid upon decomposition). They are used in paints with pentaerythritol (or with a derivative of pentaerythritol) as the carbonific component and melamine as the spumific compound.22 In addition, the intumescent formulations typically contain resinous binders, pigments, and other fillers. These systems are highly efficient in flame-retarding hydroxy-lated polymers. 

Pentaerythritol phosphate has an excellent char-forming ability owing to the presence of the pentaerythritol structure. The bis-melamine salt of the bis acid phosphate of pentaerythritol is also available commercially. This is a high melting solid that acts as an intumescent flame-retardant additive for polyolefins. Synergistic combinations with ammonium polyphosphates have also been developed primarily for urethane elastomers. Self-condensation of tris(2-chloroethyl) phosphate produces oligomeric 2-chloroethylphosphate. It has a low volatility, and is useful in resin-impregnated air filters, in flexible urethane foams and in other structural foams.11... 

Cyclic oligomeric phosphonates with the varying degrees of structural complexity (Structure 5.4) are also available in the market.25 They are widely used as flame-retardant finishes for polyester fabrics. After the phosphonate is applied from an aqueous solution, the fabric is heated to swell and soften the fibers, thus allowing the phosphonate to be absorbed and strongly held. It is also a useful retardant in polyester resins, polyurethanes, polycarbonates, polyamide-6, and in textile back coatings. A bicyclic pentaerythritol phosphate has been more recently introduced into the market for use in thermosets as well as for polyolefins (preferably, in combination with melamine or ammonium polyphosphate)... 

Montaudo, G., Scamporrino, E., and Vitalini, D. 1983. Intumescent flame retardants for polymers. II. The polypropylene-ammonium polyphosphate-polyurea system. J. Polym. Sci., Polym. Chem. Ed. 21 3361-3371. 

Davies, P.J., Horrocks, A.R., and Alderson, A. 2005. The sensitisation of thermal decomposition of ammonium polyphosphate by selected metal ions and their potential for improved cotton fabric flame retardancy. Polym. Deg. Stab. 88 114-122. 

Levchik, S.V., Camino, G., Costa, L., and Levchik, G.F. 1995. Mechanism of action of phosphorus-based flame retardants in nylon 6.1. Ammonium polyphosphate. Fire Mater. 19 1-10. 

The flammability properties of an intumescent fire retardant PP formulation with added MH has been investigated.65 The results show that the intumescent flame-retardant ammonium polyphosphate-filled PP has superior flammability properties but gives higher CO and smoke evolution. The addition of MH was found to reduce smoke density and CO emissions, in addition to giving superior fire resistance. PP filled with ammonium polyphosphate, pentaerythritol, and melamine has given improved flammability performance, without reducing its mechanical properties. 

At an optimum addition level of only 1.5 w t %, nano-size magnesium-aluminum LDHs have been shown to enhance char formation and fire-resisting properties in flame-retarding coatings, based on an intumescent formulation of ammonium polyphosphate, pentaerythritol, and melamine.89 The coating material comprised a mixture of acrylate resin, melamine formaldehyde resin, and silicone resin with titanium dioxide and solvent. It was reported that the nano-LDH could catalyze the esterification reaction between ammonium polyphosphate and pentaerythritol greatly increasing carbon content and char cross-link density. 

Chiu, S.H. and Wang, W.K., Dynamic flame retardancy of polypropylene filled with ammonium polyphosphate, pentaerythritol and melamine additives, Polymer, 39, 1951-1955, 1998. 

Recently, some reports have explored the potential of synergistic effect between silica and other flame retardants.53-55 For example, silica showed synergistic effect with alumina in polypropylene (PP)/ammonium polyphosphate (APP)—pentaerythritol (PER) intumescent-based system. The data indicate that the HRR values improved by incorporating silica into the intumescent-based formulation and the improvement was much more pronounced by combining both silica and alumina in the formulation. 

C.X. Zhao, Y. Liu, D.Y. Wang, D.L. Wang, and Y.Z. Wang, Synergistic effect of ammonium polyphosphate and layered double hydroxide on flame retardant properties of poly(vinyl alcohol), Polym. Degrad. Stabil., 2008, 93 1323-1331. 

Schartel B, WeiB A, Mohr F, Kleemeier M, Hartwig A, Braun U. Flame retarded epoxy resins by adding layered silicate in combination with the conventional protection layer building flame retardants melamine borate and ammonium polyphosphate. J. Appl. Polym. Sci., 2009, submitted. 

Quantitative risk assessments have been performed on a variety of flame-retardants used both in upholstered furniture fabric and foam. The National Research Council performed a quantitative risk assessment on 16 chemicals (or chemical classes) identified by the U.S. Consumer Product Safety Commission (CPSC). The results were published in 2000.88 The 16 flame-retardants included in this NRC study were HBCD, deca-BDE, alumina trihydrate, magnesium hydroxide, zinc borate, calcium and zinc molybdates, antimony trioxide, antimony pentoxide and sodium antimonate, ammonium polyphosphates, phosphonic acid, (3- [hydroxymethyl]amino -3-oxopropyl)-dimethylester, organic phosphonates, tris (monochloropropyl) phosphate, tris (l,3-dichloropropyl-2) phosphate, aromatic phosphate plasticisers, tetrakis (hydroxymethyl) hydronium salts, and chlorinated paraffins. The conclusions of the assessment was that the following flame-retardants can be used on residential furniture with minimal risk, even under worst-case assumptions ... 

Wool Wool, though not as flammable as cotton, still needs flame retardation for specific applications, e.g., carpets, upholstered furniture in transport, etc. Ammonium phosphates and polyphosphate, boric acid-borax, and ammonium bromide can be successfully used in nondurable FR finishes for wool. Various commercial products have been reviewed by Horrocks.3 The most successful durable treatment for wool is Zirpro, developed by Benisek, which involves exhaustion of negatively charged complexes of zirconium or titanium onto positively charged wool fibers under acidic conditions at 60°C. The treatment can be applied to wool at any processing stage from loose fiber to fabric using exhaustion techniques. 

A munber of nitrogen derivatives of phosphoric and polyphosphoric acid (ammonium polyphosphate, melamine pyrophosphate) are used for improving the flame retardance of polyurethanes and other polymers. In thermal decomposition these compounds produce ammonia and the corresponding phosphoric acids which catalyze dehydration and other reactions, causing polymer dehydration during combustion. The coke produced in this process is more or less foamed. Ammonium polyphosphate and melamine pyrophosphate are added to compositions of intumes-cent coatings used for fire protection of various structural elements in construction... 

Diammonium phosphate and ammonium sulfamate are used at 15 % solids addon and function as condensed phase flame retardants, not only by crosslinking but also by dehydrating cellulose to polymeric char with reduced formation of flammable by-products (Fig. 8.6). The water insoluble ammonium polyphosphate is an effective flame retardant and is added to coatings and binder systems, for example for pigment printing. Ammonium bromide is applied at 10 % solids add-on and is effective in the gas phase. 

Organophosphorus and polyphosphate compounds also have been used as fire retardants. In one study, ammonium polyphosphate was used at loading levels of 96 kg/m to achieve a flame-spread index of 15 according to ASTM E 84 (J2). This treatment produced low smoke yields however, this treatment was corrosive to aluminum, slightly corrosive to mild steel, but not corrosive to brass (77). In a patent by Clermont (78), phosphorus pentoxide, dimethylformamide, and urea were used to produce fire-retardant paper or veneer. Other patents (79, 80) describe the reaction of ammonia with partial esters of polyphosphoric acid. All patents demonstrated some leach resistance of the phosphorus. 

Combinations of inorganic and organic flame retardants are discussed hcrc. " Figure 13.6 shows than the addition of regular fillers, such as talc and CaCOs, to ammonium polyphosphate increased the fire resistance of PA-6. The function of filler in these combinations is to increase char yield and increase insulation properties of char. On the other hand, ammonium polyphosphate protects char Ifom oxidation and hinders diffusion of combustible gases to the flame. 

Less than 10% of the polyamide produced is made in a flame retardant version. The best system is composed of a combination of red phosphorus and zinc borate (see table above). The only drawback of this system is its color which is restricted to brick red or black. If other colors are required, ammonium polyphosphate is used either in combination with organic flame retardants or with antimony trioxide. It is possible to manufacture a very wide range of colors in the halogen free system. Some systems make use of the addition of novolac or melamine resins. For intumescent applications, ammonium polyphosphate, in combination with other components, is the most frequently used additive. Figure 13.6 shows that fillers such as calcium carbonate and talc (at certain range of concentrations) improve the effectiveness of ammonium polyphosphate. This is both unusual and important. It is unusual because, in most polymers, the addition of fillers has an opposite influence on the efficiency of ammonium polyphosphate and it is important because ammonium polyphosphate must be used in large concentrations (minimum 20%, typical 30%) in order to perform as a flame retardant. 

In fire retardant applications, a combination of zinc borate with ammonium polyphosphate gives V-0 rating. The use of zinc borate permits a reduction in the amount of ammonium polyphosphate. Red phosphorus alone or in combination with ammonium polyphosphate or melamine phosphate also produced a V-0 rating. The heat release rate can be effectively improved by small additions (1-2 wt%) of silicone powder in combination with other flame retarding additives or at higher concentration (15 wt%) when used by itself. 

Flame retardant polyurethanes are mostly manufactured with compounds of phosphorus, such as ammonium phosphate or polyphosphate. Aluminum hydroxide alone or in combination with melamine is an alternate approach. In intumescent applications, graphite is frequently used. Calcium carbonate is useful as a flame retarding additive, in combination with other flame retarding materials, because of its large endothennic peak found in DTA curves. ... 

Fire resistant PU are obtained by the addition or by introduction into the PU structure of special compounds, called flame retardants. The flame retardants are organic compounds containing halogens (chlorine, bromine) and phosphorus. Compounds of antimony (Sb) or boron [1-13] are rarely used. Sometimes inorganic compounds are used as flame retardants for PU, such as, hydrated alumina (Al203 nH20), Sb203 or ammonium polyphosphate [1-3, 14]. 

By acting as char formers, as phosphorous flame retardants do. They are also subdivided into nonhalogenated organophosphate esters, ammonium polyphosphate, and others. When heated, they produce a solid form of phosphoric acid that in turn chars the material and shields it from releasing of flammable gases feeding flames. Phosphorous flame retardants account for about 20% of flame retardants in the industry (mainly not with polyolefins). Boron compounds also work as char formers [2]. 

Red phosphorus itself can be used as an efficient flame retardant, as well as organic phosphorus compounds, for example, ammonium polyphosphate, bisphenol-A-diphenylphosphate, or resorcinol diphenylphosphate, or phosphorus-containing salts, for example, the aluminum salt of diethylphosphinate (Fig. 11.19). Phosphorus-containing... 

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