A method to obtain polycarbonate-grade bisphenol A

Polycarbonate-grade bisphenol A is obtained by condensing phenol with acetone in the presence of a cation exchanger either in two or in four steps that are effected either in one or in two reactors which are divided into reaction zones by means of sets of filtration-injection nozzles that are located at not less than three heights. Two reaction steps are effected in a single reactor, Step I being effected in the upper zone of the first reactor while the reaction mixture is made to flow downwards, whereas Step II is effected in the lower zone of the first reactor while the reaction mixture is made to flow upwards in the reactor. The four reaction steps are effected in two reactors with filtration slot nozzles, Steps I and II being effected in the first reactor as described above whereas Steps III and IV are effected in the second reactor while the reaction mixture is made to flow either upwards or downwards in the reactor. Bisphenol A from the post-reaction mixture is purified and separated by way of distillation and by falling-film melt fractional crystallization or by suspension crystallization.