Preparation of urethane prepolymers having low levels of residual toluene diisocyanate
AssigneeAir Products and Chemicals, Inc.
InventorsWilliam E. Starner, Bernard A. Toseland, Reinaldo M. Machado
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Abstract
A wiped film evaporation process for reducing the amount of residual organic polyisocyanate, especially toluene diisocyanate, in a polyurethane prepolymer reaction product mixture. An inert sweeping gas is added to the evaporation process, preferably after first passing through a holdup volume of the prepolymer which has passed through the evaporation zone.
Claims15
In a process for reducing the amount of residual organic diisocyanate ("di-NCO") in a polyurethane prepolymer reaction product mixture which comprises passing the prepolymer reaction product mixture through a wiped film evaporation zone, the improvement which consists essentially of passing an inert gas through a quantity of the prepolymer which has passed through the evaporation zone and passing the inert gas in a countercurrent flow through the evaporation zone such that ##EQU3## to provide a resulting prepolymer product which contains less than about 0.1 wt % residual organic diisocyanate.
In a process for reducing the amount of residual organic diisocyanate ("di-NCO") in a polyurethane prepolymer reaction product mixture, the organic diisocyanate being selected from the group consisting of toluene diisocyanate, methylene-bis[(4-cyclohexyl)isocyanate] and isophorone diisocyanate, which comprises passing the prepolymer reaction product mixture through a wiped film evaporation zone, the improvement which consists essentially of passing an inert gas selected from the group consisting of nitrogen, dry air and helium through a quantity of the prepolymer which has passed through the evaporation zone and passing the inert gas in a countercurrent flow through the evaporation zone such that ##EQU4## to provide a resulting prepolymer product which contains less than about 0.1 wt % residual organic diisocyanate.
In a process for reducing the amount of residual organic diisocyanate ("di-NCO") in a polyurethane prepolymer reaction product mixture which comprises passing the prepolymer reaction product mixture through a wiped film evaporation zone, the improvement which consists essentially of passing an inert gas through the evaporation zone and passing the inert gas in a countercurrent flow through the evaporation zone such that ##EQU5## to provide a resulting prepolymer product which contains less than about 0.1 wt % residual organic diisocyanate.
Dependencies are inferred from the claim text.