Phosphonate Polyols

The best known phosphorus polyol of significant commercial importance is diethyl-N,N-bis (2-hydroxyethyl) aminomethyl phosphonate, which is obtained by a Mannich reaction between diethylphosphite, formaldehyde and diethanolamine (reaction 18.11) [5, 34]  

The same structure is easy to obtain by reacting diethylphosphite with an oxazolidine [16, 35] (reaction 18.12)  

This phosphonate polyol is very resistant to hydrolysis and has in its structure both phosphorus and nitrogen. A synergism between phosphorus - nitrogen has previously been mentioned in this chapter [1, 4, 5, 11]. 

Phosphorus acid is used to generate, by direct alkoxylation with PO, a bis (hydroxypropyl) phosphite. The resulting bis (hydroxypropyl) phosphite is reacted with oxazolidine, under similar conditions to reaction 18.12 and a tetrafunctional phosphonate polyol is obtained (reaction 18.13) [16]  

Unfortunately, the phosphorus content of phosphonate polyol in reaction 18.13 is lower (around 7-7.5%), but being a tetrafunctional polyol gives rigid PU foams with excellent physico-mechanical properties. 

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The phosphonate polyols are characterised by the presence of -P-C- bonds which are very resistant to hydrolysis. The phosphonate polyols are one of the most important groups of reactive flame retardants - they are produced industrially and are used in many formulations, especially for rigid PU foams. The phosphonate polyols are esters of phosphonic acids (Figure 18.5) [1, 4-6, 11, 30, 34]. 

A variant of the Mannich reaction using an equilibration between phosphorus acid and a trialkyl phosphite was developed [36]. The trialkyl phosphite was synthesised in situ by the reaction of phosphorus trichloride with PO, with the formation of tris (2-chloropropyl) phosphite (reaction 18.14). By equilibration of phosphorus acid with tris (2-chloropropyl) phosphite, bis (2-chloropropyl) phosphite (reaction 18.15) is formed which, by reaction with oxazolidine, gives an interesting phosphonate polyol containing phosphorus, chlorine and nitrogen (reaction 18.16) ... 

The scientific literature mentions some variants of the phosphonate polyols synthesis by Mannich reaction. For example, by reacting of dimethylphosphite with acetone and monoethanolamine a higher phosphorus content (15%) phosphonate polyol is formed (reaction 18.17) [37] ... 

The resulting phosphonate polyol (18.17) is a bifunctional polyol having one hydroxyl group and one secondary amino group. 

Phosphonate polyols are obtained by the direct alkoxylation of phosphonic acids with PO, at moderate temperatures (70-90 °C) [5, 16] (reactions 18.19 and 18.20). 

A representative phosphonate polyol is obtained by the propoxylation of phenylphosphonic acid (reaction 18.21) [16] ... 

If the group R is a hydroxyalkyl group - phosphonate polyols are obtained. One example is the transformation of tris (dipropylene glycol) phosphite in phosphonate polyol, at 160-180 °C, by the following reactions with butyl bromide [5] (reaction 18.25 with a catalytic quantity of butylbromide). 

There are several possibilities for phosphonate polyol synthesis by Mannich reactions, Arbuzov reactions and by alkoxylation of phosphonic acids. Phosphonate polyols proved to be very efbcient flame retardants in practice. An important quality of these phosphorus polyols is the stability over time of formulated polyols containing phosphonate and water as reactive blowing agent, without a significant loss of their reactivity. 

Fyrol 35 Stauffer Phosphonate polyol 18.5% P 1.16 18 Rigid polyurethane foam... 

A variety of non-cyanoacrylate-based modifiers have also been proposed over the last two decades. Some of the earliest of these were the dialkenyl phthalates. Addition of 1-25% concentrations of the phthalate ester to the cyanoacrylate was claimed to improve wet heat resistance. A similar type of heat durability promoter consists of acrylate or methacrylate esters of phosphonates, polyols, or cyanuric acid. Here too, the improvement in heat resistance depends upon curing at elevated temperature, presumably to form a network of the additive, which may also coreact radically with the cyanoacrylate. The use of such additives results in improved heat resistance at 1-20% concentrations. 

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. 

Boutevin, B., Hervaud, Y., Mouledous, G., and Vera, R., Synthesis of polyols bearing phosphonate groups. Part 2. Epoxides used as starting materials. Phosphorus, Sulfur Silicon Relat. Elem., 161, 9,... 

The preparation of potential polyene macrolide mimics by cyclodimerization of symmetrical segments was reported by Floyd and Fritz [148] in 1982 using a phosphonate-aldehyde coupling as a key ring closure reaction. Diphosphonate 245 was obtained from diphosphonate 243 by reaction with aldehyde 244, deprotection to a triene diol, and esterification with dimethyl phosphonoacetyl chloride (Scheme 34). Condensation with dialdehyde 246 provided the desired macrocycle 248. A closer mimic bearing a 1,3-polyol chain 249 was also prepared by reacting the all-syn triacetate 247 obtained in a three-step process from endoperoxide 250 [149] with diphosphonate 245. 

Phosphorus-containing reactive flame-retardants are mainly phosphonates or phosphates with hydrogen atoms which can be substituted by hydrocarbon groups, so that they are capable of bonding to molecules of the matrix polymer. A notable example is the series of phosphorus-containing polyols. Their alcoholic hydroxyl groups are involved in a polyaddition reaction of the polyurethane foam production. 

Copper catalysts for the formation of biaryl ethers have also been developed that contain diketonate ligands. Researchers at Merck Laboratories reported the coupling of aryl halides with phenols catalyzed by the combination of CuCl and 2,2,6,6-tetramethylhep-tane-3,5-dione (TMHD), which generates a copper diketonate catalyst (Equation 19.111). Catalysts containing related O-donor ligands have also been used. Two examples of reactions conducted with a polyol and with a phosphonic acid as ligand are shown in Equation 19.112 and Equation 19.113. ... 

Bayer markets a dimethylpropane phosphonate-based FR called Levagard VP SP 51009 to enable rigid PU foam to meet fire regulations. Clariant offers liquid phosphorus polyols for the protection of polyether flexible and slabstock moulded automotive foams. Flexible PU is also commonly flame retarded in Europe with chlorinated phosphate esters. Borates have not shown... 

A number of sugar-based polyols (e.g. derived from sucrose, a-methyl glucoside, dextrose, sorbitol, etc.) containing phosphorus in the form of phosphate, phosphite or phosphonate linkages have been reported for use in flame-retardant, rigid urethane foams (52-59). Recent reviews on flame-retardant urethanes incTu3e those of Papa ( 2) and Frisch and Reegen ( 3). 

Having access to protected sucroses 10, 11, 12, and 14 we proposed an efficient method of the preparation of various derivatives such as amines (15), uronic acids (16), or higher sucroses i.e. compounds homologated at the desired terminal position by functionalized carbon unit e.g. 17) examples are shown in Fig. 2. The most complex derivative representing higher sucroses was prepared from phosphonate 18 and di-acetonogalactose aldehyde 19 which - under mild phase transfer conditions - provided enone 20 converted further into polyol 21. ... 

Due to the bulky size of the TBDPS group, TBDPS-Cl has been studied under a number of different circumstances for the selective protection of a single hydroxyl group in various polyols. For example, t-butyldiphenylsilylation of threo-a,p-dihy(iioxy-phosphonate afforded the sUyl ether at the position with good regioselectivity (eq 7). ... 

Flame Retardant n (1947) A material that reduces the tendency of plastics to burn. Flame retardants are usually incorporated as additives during compounding, but sometimes applied to surfaces of finished articles. Some plasticizers, particularly the phosphate esters and chlorinated paraffins, also serve as flame retardants. Inorganic flame retardants include antimony trioxide, hydrated alumina, monoammonium phosphate, dicyandiamide, zinc borate, boric acid, and ammonium sulfamate. Another group, called reactive-type flame retardants, includes bromine-containing polyols, Chlorendic acid and anhydride, tetrabromo- and tetrachlorophthalic anhydride, tetrabromo bisphenol A, diallyl chlorendate, and unsaturated phosphonated chlorophenols. A few neat resins, such as PVC and the fluoro- and chlorofluo-rocarbons, are flame-retardant (Elias, H (2003) An introduction to plastics. Wiley, New York Modem plastics encyclopedia. McGraw-Hill/Modem Plastics, New York, 1986 1990, 1992, 1993 editions). See Flammability. 

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