Environment friendly method for synthesizing polyurethane

This invention publishes an environmentally friendly synthesis method for polyurethanes, of which the technique is specific that: a) a green chemical productí¬dialkyl carbonate (especially dimethyl carbonate and diethyl carbonate) which is adopted as raw materials reacts with organic diamine to produce bifunctional dicarbamate; b) transesterification between dicarbamates and polyols or some other hydroxyl-containing orgainic compounds takes place to directly produce carbamate prepolymers; c) polymerization or direct condensation polymerization chain-extending between carbamate prepolymers and polyols takes places to produce polyurethanes. This method is free of carbamates thermolysis into isocyanates and thus avoids the employments of ultra-toxic phosgene and isocyanates. It is a moderate and environmentally friendly method for polyurethane synthesis.