PROCESS FOR THE PRODUCTION OF BLOCK POLYMERS CONTAINING AT LEAST THREE POLYOXYALKYLENE BLOCKS

1. Process for the preparation of polyalkylene oxide block polymers having at least three polyalkylene oxide blocks, with at least two polyalkylene oxide blocks having the same structure but being able to differ in structure from the other polyalkylene oxide block or the other polyalkylene oxide blocks, by addition reaction of alkylene oxides or mixtures thereof with an at least trihydric alcohol, characterised in that a) alkylene oxides or their mixtures are caused to undergo addition reaction with the free hydroxyl group of a trihydric or polyhydric alcohol of which at least two hydroxyl groups are in the form of an acetal or ketal and at least one of these two hydroxyl groups is a primary hydroxyl group, b) the acetal or ketal group is cleaved by the action of acid and c) alkylene oxides or their mixtures are caused to undergo addition reaction with the compound obtained according to b).