PURPOSE: To efficiently obtain titled prepolymer with low diisocyanate monomer content, for use in curing agent, etc., by carrying out a treatment, using an improved thin-film evaporator of a crude isocyanate group-terminated prepolymer containing diisocyanate monomer(s).
CONSTITUTION: The objective prepolymer can be obtained by carrying out a treatment under reduced pressure (pref. at 0.5W100mmHg) at 40W200°C, of a crude isocyanate group-terminated prepolymer containing diisocyanate monomer(s) (e.g., tolylene diisocyanate, xylylene diisocyanate), using a thin-film evaporator eqquipped, at its resin removal section, with a rotor-type pump 12 having a screw 11 capable of continuously conveying downward through its revolving motion the prepolymer treated by the movable blades 9.
IIZUKA TADAHISA
TAKAHASHI NOBUO
NOMURA SEIJI
INOUE YUKIO
HITACHI LTD