Study on Isocyanurate-Modified MDI. 1 — Preparation

Isocyanurate-modification of MDI was investigated. Certain modified MDIs which were stable liquids with lower viscosity were obtained. Direct trimerization of pure MDI resulted in crystallization at room temperature. After modification by diol with lower molecular weight, for instance tripropyleneglycol or tetrapropyleneglycol, at a molar ratio to isocyanate of more than 7·5/100, trimerization then produced a stable isocyanurate-modified isocyanate having an NCO content of about 25%. The trimerization of polymeric MDI by a tertiary amine catalyst, such as 2, 4, 6–tris(dimethylaminoethyl) phenol or N, N’, N”-tris(dimethylaminopropyl) hexahydro-s-triazine, followed by adding reaction-stopper and heating, also resulted in stable modified isocyanate with a 25 % NCO content.