Modified polymeric aromatic isocyanates having allophanate linkages

摘要

The invention relates to modified polymeric aromatic isocyanates having allophanate linkages prepared by (a) reacting a polymeric aromatic isocyanate with a monofunctional aliphatic alcohol to form an intermediate modified polymeric isocyanate; and (b) reacting the intermediate modified polymeric isocyanate at an elevated temperature in the presence of a divalent metal catalyst. The invention also relates to foundry binder systems which use these modified polyisocyanates. These modified polyisocyanates, along with a phenolic resole resin, are added to a foundry aggregate to form a foundry mix which is shaped and cured with a gaseous amine curing catalyst by the cold-box process.