Synthesis of Polyamides and Polycarbonates using Supercritical CO_2

摘要

Among the advantages of traditional melt phase polymerization processes is the potential to produce a high molecular weight polymer without the use of solvent. While solvent-free melt phase polymerization methods avoid the use of environmentally detrimental solvent mixtures, it would be convenient to mediate the high viscosity of the polymer melt associated with the attainment'of high.molecular weight polymer near the end of the polymerization. Additionally, for step-growth polymerizations the enhancement of condensate removal may be accomplished by swelling or plasticizing the polymer melt in some manner, thus increasing both chain mobility and free volume in the melt phase. Swelling agents can improve polymerization rate by increasing the surface area available for condensate removal,1 but such a technique is not an advantage from a processing standpoint if it introduces to the reaction a swelling agent that is toxic, costly, or difficult to separate from the end product. Since a high volume use of many step growth polymers such as polyesters or polycarbonates is . for food and .beverage packaging, absolute safety of any additive to the melt phase is imperative.