Fire-retardant composition containing derivatives of polyphosphoric acid partial esters

#Numerous monophosphate derivatives are known to be effective fire-retarding agents. In general, however, polyphosphoric acid derivatives have not been used as fire-retarding agents. In particular partial esters of polyphosphoric acid have not been suitable because of the presence of residual acid functionality which is likely to adversely affect cellulosic materials with which it is brought into contact.

#Furthermore, monophosphate derivative fire-retarding agents are generally regarded as nonpermanent. Such fire-retarding agents are susceptible to leaching from the cellulosic material upon contact with water. Cellulosic materials so exposed are thereby rendered less resistant to fire. In U.S. Pat. No. 3,565,679 a list of non-permanent fire retardants includes the phosphates.

#According to the invention cellulosic materials that are resistant to fire are provided by incorporating therein fire-retarding amounts of a compound of the formula ##STR2## wherein, R is each occurrence the remnant of phenol, halophenol or a C.sub.1-20 aliphatic or halogenated aliphatic monohydroxyl compound formed by removal of the hydroxyl group;

#Phosphorous pentoxide (270 g, 1.9 moles) was slurried under nitrogen in a reaction flask containing 500 ml CH.sub.2 Cl.sub.2. Over approximately 2 hours 2-n-butoxyethanol (425 g, 3.6 moles reagent grade) was added from a dropping funnel causing a gentle reflux to occur. After complete addition only a small amount of unreacted P.sub.2 O.sub.5 remained. The flask contained a clear yellow colored solution. Reaction for an additional 24 hours resulted in complete conversion of P.sub.2 O.sub.5 and a darker colored solution. Analysis by .sup.31 P nuclear magnetic resonance specroscopy indicated the product comprised greater than 90 percent of the diphosphoric acid half ester with minor amounts of other partial esters of polyphosphoric acids, plus monophosphates and full ester contaminants.

#A portion of the product produced in Example 1 was neutralized by bubbling dry NH.sub.3 into the solution at a rate sufficient to cause a gentle reflux. After about 90 minutes no further exotherm occurred indicating the reaction was complete. The solution was further diluted with CH.sub.2 Cl.sub.2 to a concentration of 15 percent by weight and used to treat several small strips of fir plywood, 1/4".times.1/2".times.3" long. After immersion in the solution for between 2 and 8 hours, the strips were dried at 100.degree. C. for about 4 hours and then humidified at normal room conditions for 2 days. When clamped at a 45.degree. angle and ignited for 15 seconds with a bunsen flame, all the treated strips self-extinguished in an average of less than 20 seconds. By comparison untreated strips subjected to the same procedure are entirely consumed.

#A portion of the solution produced in Example 1 was combined with metallic aluminum so that the ratio of polyphosphoric acid partial ester to aluminum was 3:1. The mixture was gently heated taking care not to exceed 150.degree. C. to avoid decomposition of the diphosphoric acid partial ester. A trace of water or alcohol added to the mixture acted as a catalyst to initiate the dehydrogenation reaction.