Thiobisphenol esters of pentavalent phosphorus acids

A process for the preparation of polymeric phosphorus acid esters comprising:

• reacting an aryl ester of a pentavalent phosphorus acid of the formula:
• ##STR53## with a sulfur compound of the formula S.sub.n Y.sub.2, in a ratio of less than or equal to about 1.5:1 wherein A.sub.1 and A.sub.2 are independently selected from the group consisting of alkyl, alkoxy, aryl, alkaryl, haloaryl, arylalkyl, alkoxyaryl, alkaryloxy, aryloxy, hydroxy, chlorine, bromine and ##STR54## each of said alkyl, alkoxy, aryl, alkaryl, haloaryl, arylalkyl, alkoxyaryl, alkaryloxy, and aryloxy groups having from 1 to 20 carbon atoms;
• R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, and R.sub.8 are independently selected from the group consisting of hydrogen, alkyl, alkoxy, aryl, alkaryl, haloaryl, arylalkyl, aryloxy, and halogen;
• each of said alkyl, alkoxy, aryl, alkaryl, haloaryl, arylalkyl, and aryloxy groups having from 1 to 20 carbon atoms, Y is a halogen of atomic weight between 33 and about 84 and n is an integer having a value of from 1 to about 6 inclusive;
• said reaction being conducted in the presence of a Friedel-Crafts catalyst.