METHOD FOR PRODUCING POLYMETHYL METHACRYLATE USING SUPERCRITICAL CARBON DIOXIDE TO INHIBIT DEGRADATION IN LIGHT TRANSMISSION AND DISCOLORATION

摘要

PURPOSE: Provided is a method for producing polymethyl methacrylate, which uses supercritical carbon dioxide as a plasticizer to decrease the melt viscosity of methacrylic resin during the extrusion process and to inhibit thermal decomposition of the resin, thereby reducing degradation in light transmission and discoloration. CONSTITUTION: The method for producing polymethyl methacrylate through an extrusion process comprises introducing 0.1-100 parts by weight of carbon dioxide into an extruder based on 100 parts by weight of a methacrylic resin. In the method, the temperature and pressure of carbon dioxide in the extruder are set to 31-300 deg.C and 1070-7000 psi, respectively. Additionally, one to three barriers formed by molten resin are present in each of the regions between a solid conveying zone and a melting zone of the extruder, and between a melt conveying zone and a vent zone. Further, the processing temperature between the barriers is set to 150-300 deg.C.