PROCESS FOR THE PREPARATION OF NAPHTHALENESULFONIC ACID/FORMALDEHYDE CONDENSATES HAVING A LOW FREE FORMALDEHYDE CONTENT

摘要

Process for the preparation of naphthalenesulfonic acid/formaldehyde condensates having a low content of free formaldehyde, in which the condensation products of naphthalenesulfonic acid and formaldehyde obtained after the condensation are brought to a pH of greater than 11.5 at a temperature of not less than 80 DEG C. immediately after the condensation, and are kept under these conditions until the desired formaldehyde content is reached. The resins are preferably used as plasticizers for building materials, for example as concrete plasticizers.