Enhancement of poly(vinyl chloride) productivity by continuous initiator injection

Abstract

Polymerization of vinyl chloride monomer with continuous initiator dosage at constant temperature was modeled. Initiators with a half-life shorter than 0.4 hour at the reaction temperature are suitable for continuous injection. Using a suitable initiator dosage regime, it is possible to keep the reaction rate at its maximum permissible value until critical conversion. It is found that a suitable dosage regime allows the total polymerization time to be reduced by as much as 38.6%, while the final conversion remains unchanged from standard isothermal polymerization. Also, addition of initiators with a half-life greater than 0.47 hour, preferably from 0.47 hour to the time needed to reach the critical conversion, at the polymerization temperature at the beginning of the reaction are required to achieve a high conversion. The injection of initiators during polymerization into the reactor causes the weight-averaged molecular weight and corresponding K value of the product to decrease. The drop in K value can be compensated by a decrease in reaction temperature. Initiator dosage shows no significant effect on the structural chemical defects in the PVC chains. Dispersibility and persistent gels (fisheyes) were not measured. J. VINYL ADDIT. TECHNOL., 23:248-258, 2017.

S-PVC Grain Morphology: A Review

“…This mechanism determinedly causes the primary particles to aggregate earlier, thereby, as mentioned, resulting in a more porous internal structure. When the internal structure of a regular PVC grain is compared with the interior of those grains produced through continuous dosing of very fast initiators during polymerization reactions, similar results can be observed . From a mechanistic point of view, the method of addition of initiator also can influence on the morphology of the final PVC grains .…”

“…When the internal structure of a regular PVC grain is compared with the interior of those grains produced through continuous dosing of very fast initiators during polymerization reactions, similar results can be observed. 65 From a mechanistic point of view, the method of addition of initiator also can influence on the morphology of the final PVC grains. 66 When initiator is first predispersed in the aqueous continuous phase, subsequent mass transfer of initiator to the monomer droplets can be incomplete before an appreciable amount of monomer is polymerized, thereby decreasing the effective initiator concentration.…”

Mechanistic investigation of nonisothermal suspension polymerization of vinyl chloride

“…Several process variables, such as polymerization temperature, agitation rate, type, concentration of stabilizers, and so on, involved in the development of the morphology of suspension-PVC (S-PVC) have been found to have a significant influence on the internal structures in S-PVC [1,[8][9][10][11][12][13][14][15][16][17][18][19]. Although a significant amount of research has been done, the mechanism by which morphology arises in S-PVC is not completely understood.…”