Method for Preparing Isocyanurate-Group-Containing Polyisocyanates

A process for preparing isocyanurate group-containing polyisocyanates P′ by trimerizing

• A′) at least one organic di- or polyisocyanate having independently aliphatically, cycloaliphatically and/or araliphatically bonded isocyanate groups, in the presence of
• B′) at least one trimerization catalyst selected from the group consisting of quaternary tetraalkylammonium hydroxides, quaternary trialkylarylammonium hydroxides and hydroxyalkyl-substituted quaternary ammonium hydroxides of choline type
• and
• C′) at least one alcohol as solvent,
• comprising or consisting of the following steps
• I′) initially charging component A′ into a reactor,
• II′) feeding a first partial amount of catalyst component B′ (B′T1), and a first partial amount of component C′ (C′T1),
• where catalyst component B′T is used in amounts of ≥0.6% to ≤8% by weight based on the first partial amount of component C′ (C′T1) used in step II′,
• and trimerizing component A′ until a degree of trimerization Tg′ in the range of ≥0.5% to ≤25% is obtained, where
• T
• g
• ′
• =
• (
• NCO
• 0
• -
• NCO
• t
• )
• /
• NCO
• 0
• ,
• where
• NCO0 corresponds to the amount of free NCO groups originally present in the initially charged component A′ and
• NCOt corresponds to the amount of free NCO groups in the reaction solution at time t,
• in each case determined by NCO titration in accordance with M105-ISO 11909,
• III′) feeding a second partial amount of catalyst component B′ (B′T2), and a second partial amount of component C′ (C′T2),
• where catalyst component B′T2 is used in amounts of >0% to ≤0.5% by weight based on the second partial amount of component C′ (C′T2) used in step III′,
• continuing the trimerization of component A′.