Ion exchange modified with mercapto amines

A process for the preparation of anhydrous ion exchangers modified with mercapto amines having improved stability in the production of bisphenols using acid ion exchanger resins having total capacities of acid functions of from 0.7 to 2.1 mval/ml of ion exchanger in the water-moist form with a water content of about 75 to 85% by weight or total capacities of acid functions of from 3.5 to 5 mval or higher when based on 1 g of dry substance of ion exchanger, said process being characterized in that the resin is dried and thereafter rinsed with the phenol required for preparation of the bisphenol and thereafter neutralized with at least 0.3 mol of mercapto amines corresponding to formula (I) per mol of acid function of the ion exchanger at a temperature above the melting point of bisphenol ##STR4## in which formula (I), R.sup.1 stands for C.sub.1 -C.sub.6 -alkylene, C.sub.5 -C.sub.10 -cycloalkylene or C.sub.6 -C.sub.14 -arylene and R.sup.2 and R.sup.3 denote, independently of one another, C.sub.1 -C.sub.6 -alkyl groups or hydrogen.