Absorption behavior of vinyl chloride/calcium carbonate and pressure/temperature/conversion relationship for vinyl chloride suspension polymerization in the presence of calcium carbonate

The absorption of vinyl chloride (VC) on surface-treated light-grade and nano-scale calcium carbonate (CaCO3), and VC suspension polymerization in the presence of CaCO3 were carried out in a 5 L autoclave. It showed that the absorption of VC on CaCO3 increased with the partial pressure of VC up to a critical point. Nano-scale CaCO3 was more effective in absorbing VC than light-grade CaCO3 at the same temperature and partial pressure of VC due to its greater surface area. The absorption behavior of VC/CaCO3 follows Langmuir isothermal equation. In view of the absorption of VC on CaCO3, Xie’s model [J. Appl. Polym. Sci. 34 (1987) 1749] was modified to relate pressure, temperature, the amount of CaCO3 and conversion for VC suspension polymerization in the presence of CaCO3. The model simulation showed that VC conversions at the pressure drop point and at a certain pressure drop decreased with the increase of the amount of added CaCO3, and the influence of nano-scale CaCO3 was greater than that of light-grade CaCO3. The simulated VC conversions fitted well with that obtained from VC suspension polymerizations in the presence of different amounts of light-grade or nano-scale CaCO3.