Flame retardant phosphonate

Halogenated All l Phosphates and Phosphonates. In this important class of additives, the halogen contributes somewhat to flame retardancy although this contribution is offset by the lower phosphoms content. The halogens reduce vapor pressure and water solubHity, thus aiding retention of these additives. Efficient manufacturing processes lead to favorable economics. 

Antlblaze 19. Antiblaze 19 (Mobil), a flame retardant for polyester fibers (134), is a nontoxic mixture of cycHc phosphonate esters. Antiblaze 19 is 100% active, whereas Antiblaze 19T is a 93% active, low viscosity formulation for textile use. Both are miscible with water and are compatible with wetting agents, thickeners, buffers, and most disperse dye formulations. Antiblaze 19 or 19T can be diffused into 100% polyester fabrics by the Thermosol process for disperse dyeing and printing. This requires heating at 170—220°C for 30—60 s. 

Phosphonium Salt—Urea Precondensate. A combination approach for producing flame-retardant cotton-synthetic blends has been developed based on the use of a phosphonium salt—urea precondensate (145). The precondensate is appUed to the blend fabric from aqueous solution. The fabric is dried, cured with ammonia gas, and then oxidized. This forms a flame-resistant polymer on and in the cotton fibers of the component. The synthetic component is then treated with either a cycUc phosphonate ester such as Antiblaze 19/ 19T, or hexabromocyclododecane. The result is a blended textile with good flame resistance. Another patent has appeared in which various modifications of the original process have been claimed (146). Although a few finishers have begun to use this process on blended textiles, it is too early to judge its impact on the industry. 

MixedPhosphona.te Esters. Unsaturated, mixed phosphonate esters have been prepared from monoesters of 1,4-cyclohexanedimethanol and unsaturated dicarboxyhc acids. Eor example, maleic anhydride reacts with this diol to form the maleate, which is treated with benzenephosphonic acid to yield an unsaturated product. These esters have been used as flame-retardant additives for thermoplastic and thermosetting resias (97). 

The remaining 15% of the elemental P is used in P -dependent apphcations which require the element as a direct reactant. The principal products include P2S5, PCl and POCl, 2 5 hypophosphite, with much smaller amounts leading to PH, red P, phosphonates, and various other phosphoms derivatives. Pinal apphcations include flame retardants (qv), lubricant additives, insecticides, herbicides, water treatment, cleaning compounds, plastici2ers, and semiconductors (14). 

This reaction is catalyzed by hydrogen chloride and yields can be essentially quantitative when using either free phosphonic acid or its diesters. The flame retardant, Eyrol 6, produced by Akzo Chemicals, Inc. and used for rigid urethane foams, is synthesized as follows (24). 

The phosphonate esters, HP(=0(OR)2, of alkylated phenols are used extensively as lubricating-oil additives to control bearing corrosion and oxidation, and to impart antimst properties as stabilizers, as antioxidants (qv) and flame retardants in plastics, as specialty solvents, and as intermediates (see Corrosion AND corrosion control Heat stabilizers). 

Phosphoms compounds are effective flame retardants for oxygenated synthetic polymers such as polyurethanes and polyesters. Aryl phosphates and chloroalkyl phosphates are commonly used, although other compounds such as phosphonates are also effective. The phosphoms compounds can promote char formation, thereby inhibiting further ignition and providing an efficient thermal insulation to the underlying polymer. 

Trialkyl esters of phosphonic acid exist ia two structurally isomeric forms. The trialkylphosphites, P(OR)2, are isomers of the more stable phosphonates, 0=PR(0R)2, and the former may be rearranged to resemble the latter with catalytic quantities of alkylating agent. The dialkyl alkylphosphonates are used as flame retardants, plasticizers, and iatermediates. The MichaeUs-Arbusov reaction may be used for a variety of compound types, including mono- and diphosphites having aryl as weU as alkyl substituents (22). Triaryl phosphites do not readily undergo the MichaeUs-Arbusov reaction, although there are a few special cases. 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

The mechanism of the action of the phosphonate as a flame retardant is generally believed to be decomposition into acid fragments which contribute to char formation. These acidic species catalyze decomposition of the polyester, and give rise to species which on reaction with the phosphorus moiety cause char formation. TGA curves of the copolymers confirm that the incorporation of phosphorus into the polymer increases the char residue (Figure 4). These curves, however, show little evidence that the presence of phosphorus has any effect upon the temperature or rate of decomposition of the polyester. The curves are all fairly similar up to about 450°C. After that point, the amount of residue is proportional to the amount of phosphorus in the terpolymer. 

Antiblaze 19, a phosphonate ester and flame retardant used in textiles and polyurethane foam manufactured from trimethyl phosphite, dimethyl methylphosphonate, and trimethyl phosphate. 

Polymer mixtures of aromatic PC, ABS graft polymer and styrene-containing copolymers and monophosphates are described as flameproofing additives (20). It has been claimed that phosphonate amines are superior flame retardants for PC/ABS molding compositions (21). 

The use of silicones to render PC/ABS blends flame retardant, at least by any economically viable means, is not possible (77). However, by the phosphonation of silanes, flame retardants can be synthesized. The reaction is shown in Figure 8.5. The products of the first step can further undergo oligomerization. 

Five-membered cyclic phosphate and phosphonate esters have rates of hydrolysis orders of magnitude greater than those of the corresponding acyclic esters (6), therefore such five-membered cyclic esters are undesirable components if the oligomers are used as flame retardants. 

A related methylphosphate/phosphonate oligomer has primary alcohol end groups, and can coreact with amino resins to form a water-resistant flame retardant resin finish on paper or on textile substrates. The application of this oligomer with a coreactant methylolmelamine on cotton upholstery fabric can enable furniture covered with this fabric to pass the Consumer Product Safety Commission s proposed cigarette ignition test. 

D. Price, L.K. Cunliffe, K.J. Bullett (formerly Pyrah), T.R. Huh, G.J. Milnes, J.R. Ebdon, B.J. Hunl, and P. Joseph, Thermal behavior of covalently bonded phosphonate flame retarded poly(methyl methacrylate) systems. Polym. Adv. Technol., 19 (6), 710-723 (2008) and previous references therein. 

ORGANOPHOSPHORUS ADDITIVE FLAME RETARDANTS 5.4.1 Phosphates and Phosphonates... 

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)... 

Amino and functional aromatic phosphates, phosphonates, and phosphine oxides have also been used as reactive components to impart flame retardancy to cured epoxy resins. Phosphine oxides are particularly hydrolytically stable and several studies have been reported, for example, of the curing of epoxy resins with bis(aminophenyl) alkyl and aryl phosphine oxides65-67 (Structure 5.19). The relative performances of epoxies cured with aromatic diamine hardeners containing phosphine oxide, phosphinate, phosphonate, or phosphate units have recently been assessed.68 Aromatic phosphine oxides have been functionalized also with maleimide and hydroxyl groups for use as epoxy resin hardeners.69,70... 

A common approach with segmented PUs has been to incorporate a P-containing group (phosphate, phosphonate, phosphine oxide, or phosphazene) into a diol which is then chain-extended with a diisocyanate (e.g., Structures, 5.20 and 5.21).73,74 In one such study,75 phosphonate was found to be a more effective flame retardant than phosphate at the same phosphorus concentration, and in... 

Ebdon, J. R Hunt, B. J., Joseph, P Konkel, C. S Price,D Pyrah, K Hull,T. R Milnes, G. J., Hill, S.B Lindsay, C. I., McCluskey, J., and Robinson, I., Thermal degradation and flame retardance in copolymers of methyl methacrylate with diethyl(methacryloyloxymethyl)phosphonate, Polym. Degrad. Stab., 2000, 70, 425 136. 

Price, D., Pyrah, K., Hull, T. R., Milnes, G. J., Wooley, W. D., Ebdon, J. R., Hunt, B. J., and Konkel, C. S., Ignition temperatures and pyrolysis of a flame-retardant methyl methacrylate copolymer containing diethyl(methacryloyloxymethyl)-phosphonate units, Polym. Int., 2000, 49, 1164-1168. 

Banks, M., Ebdon, J. R., and Johnson, M., The flame-retardant effect of diethylvinyl phosphonate in copolymers with styrene, methyl methacrylate, acrylonitrile and acrylamide, Polymer, 1994, 35, 3470-3473. 

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 ... 

The CPSC staff performed quantitative risk assessments on various flame-retardants for both upholstered residential furniture fabrics and foam.89 CPSC addresses chemical hazards under the Federal Hazardous Substances Act (FHSA), which is risk based. For fabrics, five flame-retardants were evaluated, that include antimony trioxide, deca-BDE, HBCD, phosphonic acid, (3- [hydroxymethyl]amino)-3-oxopropyl)-, dimethyl ester (PA), and tetrakis (hydroxymethyl) phosphonium chloride (THPC). These flame-retardants were selected for study because they are used to comply with the U.K. upholstered furniture flammability standard (except THPC) and fabric samples were available for testing. The staff concluded in 2006 that deca-BDE, HBCD, and PA would not present a hazard to consumers and that additional data would be needed to assess antimony trioxide and THPC. 

At Bolton, we also have attempted to introduce volatile and possible vapor phase-active, phosphorus-based FR components in back-coating formulations.60 62 The selected FRs included tributyl phosphate (TBP), a monomeric cyclic phosphate Antiblaze CU (Rhodia Specialties) and the oligomeric phosphate-phosphonate Fyrol 51 (Akzo). When combined with an intumescent char-forming pentaerythritol (PER) derivative (NH1197, Chemtura) and applied as a back-coating on to cotton and polypropylene substrates, significant improvements in overall flame retardancy were observed. 

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. 

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