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-C8 alkylene 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-C8 alkylene groups and having a total of 8 to 30 carbon atoms, and aryl,
• comprising the steps of:
• a) carbodiimidization of isocyanates in the presence of a catalyst to give a reaction mixture comprising carbodiimide and monomeric isocyanate,
• b) at least partial separation of the catalyst and/or monomeric isocyanate from the reaction mixture comprising carbodiimide and monomeric isocyanate by distillation or extraction to obtain a crude carbodiimide comprising monomeric isocyanate, and
• c) addition of one or more alcohols to the crude carbodiimide comprising monomeric isocyanate and partial or complete reaction of the alcohol with the monomeric isocyanate of the crude carbodiimide.