Process for purification of phosphate esters
A crude phosphate ester product can be purified by first washing it with chelating agent composition (such as a dilute acidic solution) and then, preferably, water, drying the resulting product, and then treating the resulting product with an acid scavenger, as exemplified by an epoxy-containing compound, such as 3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl carboxylate.
1. A process for purifying crude bisphenol A bis(diphenyl phosphate), said process consisting essentially of washing said crude bisphenol A bis(diphenyl phosphate) with an aqueous acidic chelating agent composition and then, optionally, with water, to provide a washed bisphenol A bis(diphenyl phosphate), drying the resulting washed bisphenol A bis(diphenyl phosphate), to provide a dried bisphenol A bis(diphenyl phosphate) and treating the dried bisphenol A bis(diphenyl phosphate) with an epoxy group containing acid scavenger.
2. A process according to claim 1 in which the epoxy group containing acid scavenger is 3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl carboxylate.
3. A process according to claim 1 in which washing with the chelating agent composition takes place at a temperature of from about 40° C. to about 90° C.
4. A process according to claim 1 in which treatment with acid scavenger takes place at a temperature of from about 25° C. to about 200° C.
5. A process according to claim 1 in which the number of equivalents of epoxy group containing acid scavenger is equal to or greater than the number of equivalents of acid present in the crude bisphenol A bis(diphenyl phosphate) based on the acid number of the crude bisphenol A bis(diphenyl phosphate).
6. A process according to claim 1 in which the dried bisphenol A bis(diphenyl phosphate) is treated with the epoxy group containing compound at a temperature ranging from about 40° C. to about 200° C.