Hydrolysis of aromatic polyurethane in water under high pressure of CO2

We have demonstrated a hydrolysis reaction of polyurethane (PU) under high pressure of carbon dioxide (CO2) in water. We employed the PU sample, poly(methylene bis-(1,4-phenylene)hexamethylene dicarbamate), denoted as M-PU, which was synthesized from 4,4′-diphenyl methane diisocyanate and 1,4-butane diol (BD). The optimum hydrolysis reaction condition was 190 °C under CO2 pressures over 4.1 MPa in water medium, and 93% hydrolysis of M-PU was achieved. After the reaction, the water-soluble parts were obtained, and isolated by column chromatography. The isolated products were 4,4′-methylenedianiline (MDA) and 1,4-butane diol (BD), which were components of repeating unit of M-PU. In addition, the hydrolysis reaction gave no byproduct. This hydrolysis under high pressure of CO2 with water is a reaction by which M-PU is selectively hydrolyzed into MDA and BD by cleaving urethane linkage. Moreover, the resulting hydrolyzed products were easily obtained by evaporation of aqueous layer after the reaction, indicating an efficient chemical recycling of PU was achieved