On semicontinuous polymerization of vinyl acetate

Abstract

SynopsisA semicontinuous emulsion process was used to polymerize vinyl acetate. The parameters studied were the rate of addition of the various ingredients. The polymerization evolution was followed as samples were taken a t regular intervals. These emulsion samples were analyzed for monomer conversion, rate of polymerization as well as for the size and the size distribution of the particles. The molecular weight and molecular weight distribution were obtained by gel permeation chromatography (GPC). Our study showed that the total surface of the particles is an important factor, that the reaction mechanism follows Krackeler's and Wessling's theory, and that the Smith-Ewart ideal case does not apply here.

Unseeded semibatch emulsion polymerization of butyl acrylate: Bimodal particle size distribution

“…Such a policy, called a noncoagulating system by Snuparek, has been used by some other researchers. 5,6 It was shown elsewhere 7 that by using no or little emulsifier in the initial charge, secondary particle nucleation occurs and a bimodal PSD is obtained. However, it was also demonstrated that if polymerization starts with emulsifier in the initial charge, the possibility of secondary nucleation increases with increasing monomer concentration in the initial charge.…”

Semibatch Surfactant-Free Emulsion Polymerization of Butyl Acrylate

“…At a lower total solids content (e.g., 8.7% at t=0.5h), the colloidal system is less crowded and, therefore, the latex should be more stable. As a result, the reproducibility of the dP data is quite poor because it is extremely difficult to control the particle size without using surfactants.…”

Semi-Batch Emulsion Copolymerization of Vinyl Acetate and Butyl Acrylate Using Oligomeric Nonionic Surfactants

“…[1,8] Kinetic studies on the semi-continuous emulsion polymerization of VAc/BuA have shown that the number of radicals per particle is large and, thus, the polymerization does not follow the classical Smith-Ewart kinetics. [9] The number of radicals per particle was determined to be between 1 and 7 for BuA compositions between 20 and 100%. [1] On the other hand, in batch copolymerizations the number of radicals per particle was initially large but decreased below 0.5 at higher monomer conversions after the consumption of BuA.…”

“…However, Vandezande and Rudin observed a reduction in the polymerization rate in the presence of a nonionic surfactant, which was attributed to the inhibition of oligomer radical entry rate by the viscous surfactant layer. In a similar study, Bataille et al [9] employed polyoxyethylene-b-polypropylene nonionic surfactants with limited success.…”