| abstract |
The invention is concerned with a thermostable flameproofing agent for copolyester compositions, which comprises the reaction product of 1 mole of a dialkyl diester of an alkali dicarboxyaryl-sulphonate having the general formula: wherein R' represents an alkyl radical containing from 1 to 3 carbon atoms and M represents an alkali metal atom, with 1 to 2 moles of at least one tetrabrominated diol having the general formula: wherein a and b represent, independently one of the other, a whole number from 1 to 3 inclusive; the reaction is effected in the presence of a transesterification catalyst selected from the group consisting of compounds of Zn, Co, Ca, Sn, Ti and Mn. The flame-proofing agent of the invention imparts to polyester materials, besides improved self-extinguishing properties, a considerable thermostability with a substantial improvement of the resistance to the propagation of flame. |