| 摘要 |
In an improvement of the process of U.S. patent No. 3,941,752, according to which flame retarding linear polyesters are manufactured by reaction of dicarboxylic acids capable of forming high molecular weight linear polyesters or the esters thereof with lower aliphatic alcohols, with diols, and phosphorous compounds of the formula <IMAGE> or the esters thereof with lower aliphatic alcohols or also the cyclic anhydrides thereof, the cyclic anhydrides are used after having been dissolved previously at elevated temperature in a diol suitable for the polyester manufacture, preferably in the diol used as main component. The symbols of the formula have the following meanings: R = saturated open-chain or cyclic alkylene, arylene or aralkylene, R1= alkyl having up to 6 carbon atoms, aryl or aralkyl; R as well as R1 optionally containing 1 or more hetero atoms, preferably F, Cl, Br, O or S. By dissolving the cyclic carboxyphosphinic acid anhydrides in a diol before adding them to the polyester manufacturing batch the formerly necessary comminution of the hydroscopic cyclic anhydrides with absolute exclusion of moisture may be omitted, and furthermore it is possible to expose the anhydrides to the elevated polycondensation temperatures for a short time only.
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