STRUCTURE-PROPERTY RELATIONSHIPS IN INTUMESCENT FIRE-RETARDANT DERIVATIVES OF 2,6,7-TRIOXA-1-PHOSPHABICYCLO[2,2,2]OCTANE-1-OXIDE

A series of ester derivatives of the bicyclic phosphate 2,6,7-trioxa-1 -phosphabicyclo[2,2,2]octane-1-oxide has been prepared via its reactio ns with acid anhydrides, or, in the case of the methacrylate ester, vi a reaction with methacryloyl chloride. With an excess of diketene, the bicyclic phosphate is converted into the related acetoacetate ester, which forms an aluminium salt on reaction with aluminium isopropoxide. Only those derivatives having a free, ionisable hydrogen undergo intu mescent decomposition on heating. The effects of variation in the stru cture of the melamine base component of a series of salts of a dialkyl phosphoric acid derived from the bicyclic phosphate on thermal stabili ty and intumescent behaviour have also been studied. With trimethylolm elamine, a highly insoluble, thermally stable salt has been obtained w hich exhibits marked intumescence on thermal decomposition and which i mparts fire-retardance on incorporation into polyester, polypropylene and polyurethane systems. The structure of the intumescent foam derive d from this salt has been compared with that generated under identical conditions from the related melamine salt, the former leading to the formation of a denser foam with smaller cells.