Self-polycondensation reaction of polyurethane isocyanate

——Carbodiimide

Under organic phosphine catalyst and heating conditions, isocyanate can undergo self-condensation polymerization reaction. Compounds containing carbodiimino groups (—NCN—) are generated. This reaction is another important autopolymerization reaction besides isocyanate trimerization and dimerization. Organophosphine catalysts include 1-phenyl-3-methylphosphine-1-oxide (structural formula as follows), triethyl phosphate, triphenylphosphine oxide, etc. The pentacyclic phosphine oxygen type catalyst has good effect and is a high-efficiency catalyst with very small dosage and low reaction temperature.

With phenyl Taking isocyanate as an example, in the presence of pentacyclic phosphine oxygen catalyst, the yield can reach about 90% when the reaction is performed above 40℃. ——Carbodiimide Under organic phosphine catalyst and heating conditions, isocyanate can undergo self-condensation polymerization reaction to generate compounds containing carbodiimide (—NCN—). This reaction is another reaction besides isocyanate trimerization and dimerization. Important autopolymerization reaction. Organophosphine catalysts include 1-phenyl-3-methylphosphine-1-oxide (structural formula as follows), triethyl phosphate, triphenylphosphine oxide, etc. The pentacyclic phosphine oxygen type catalyst has good effect and is a high-efficiency catalyst with very small dosage and low reaction temperature.

With phenyl Taking isocyanate as an example, in the presence of pentacyclic phosphine oxygen catalyst, the yield can reach about 90% when the reaction is performed above 40℃.

Due to carbon dioxide The imine will react with isocyanate to form a four-membered cyclic substance called uretonimine. A steric hindrance group can be added to the adjacent carbon atom of NCO to inhibit side reactions.

There are two types of carbodiimides used in the polyurethane industry Method: One is carbodiimide additives, including monocarbodiimide and poly or polycarbodiimide, which are used as hydrolysis stabilizers for polyester typepolyurethaneelastomers and other systems. ; The other is carbodiimide-modified diphenylmethane diisocyanate, which is the main variety of liquefied MDI.