Process for preparing carbodiimides

A process for preparing carbodiimides of formula (I)

• in which
• n is a number from 1 to 500,
• RI is C1-C24 alkylenes and/or C5-C12 cycloalkylenes, C1-C12-alkyl-substituted or C1-C24-oxyalkyl-substituted cycloalkylenes, C1-C12-alkyl-substituted arylenes, C1-C24-oxyalkyl-substituted arylenes, C7-C18-alkylaryl-substituted arylenes and optionally C1-C12-alkyl-substituted arylenes bridged via C1-C8alkylene groups and having a total of 8 to 30 carbon atoms, and arylene and
• RII, RIII identically or independently of one another are C1-C24-alkyl- and/or C5-C24-cyclo- or C1-C12-alkyl-substituted or C1-C24-oxyalkyl-substituted cycloalkyls, C1-C12-alkyl-substituted or C1-C24-oxyalkyl-substituted aryls, C7-C18-alkylaryl-substituted aryls and optionally C1-C12-alkyl-substituted aryls bridged via C1-C8alkylene groups and having a total of 8 to 30 carbon atoms, and aryl,
• comprising the steps of:
• a) carbodiimidizing isocyanates in the presence of a catalyst to give a reaction mixture comprising the carbodiimide of formula (I) and residual monomeric isocyanate,
• b) separating at least partially the catalyst and/or the residual monomeric isocyanate from the reaction mixture comprising the carbodiimide of formula (I) and the residual monomeric isocyanate by distillation or extraction to obtain a crude carbodiimide of the formula (I) comprising residual monomeric isocyanate, and
• c) adding one or more alcohols to the crude carbodiimide of the formula (I) to partially or completely react the one or more alcohols with the residual monomeric isocyanate of the crude carbodiimide.