Semibatch emulsion polymerization of butyl acrylate. I. Effect of monomer distribution

Abstract

ABSTRACT:The effects of initial monomer charge on the particle formation and on the rate of polymerization were investigated for semibatch emulsion polymerization of butyl acrylate using sodium lauryl sulfate (SLS) as a surfactant and potassium persulfate (KPS) as an initiator. For the semibatch process with monomer (M) feed, it was found that by varying the monomer distribution ratio between the initial reactor charge and the feed it is possible to alter the contribution of monomer-flooded and monomerstarved nucleation mechanisms to the whole nucleation process. The number of particles increases as the initial monomer charge decreases, if the monomer concentration is below a critical value for any fixed system. The increase in number of particles is associated with a broad particle-size distribution which might depict an emerging second peak on the particle-size distribution curve. For low emulsifier concentration systems, a larger number of particles was obtained for a lower amount of monomer charge. Particle coagulation and emulsifier adsorption on the monomer droplets were counted as the main reasons for such behavior. For a semibatch process with monomer emulsion (ME) feed, the larger number of particles was formed at a lower initial monomer charge, similar to an M-add semibatch process. However, the application of monomer charge to an ME-add process was found to increase the possibility of secondary nucleation and led to the occurrence of a bimodal particle-size distribution.

Some comparative aspects of particle formation and rate of reaction in emulsion polymerization of vinyl acetate and butyl acrylate

“…In many occasions, the reactor content could be a small fraction of the total reactor volume. The variations in reaction volume are particularly important in semibatch emulsion polymerization reactors where a significant part of the monomer and other ingredients are added to the reactor over the time 23…”

Exploring the limits of particle size for nanolatexes produced via monomer-starved semicontinuous emulsion polymerization

“…where a s is the area occupied by the surfactant molecule on the surface of the polymer particles, which is 0.43 nm 2 for SDS [18], and N A is Avogadro's constant. D ps is the average diameter of the monomer-swollen particles, which can be calculated by…”

“…Sajjadi [10] showed that in a typical semicontinuous monomer-starved emulsion polymerization, the size of particles and the number of particles can be manipulated by the rate of monomer addition (R a ), surfactant concentration ([S]), and initiator concentration ([I]) or the rate of initiator decomposition (R I ) [17][18][19]. He derived an analytical equation for the formation and growth of nanoparticles in monomer-starved semicontinuous emulsion polymerization of styrene-like monomers, which showed that the number of particles (N p ) and their volume-average diameter (D v ) at the end of nucleation vary according to the following equations [18,20]:…”

“…He derived an analytical equation for the formation and growth of nanoparticles in monomer-starved semicontinuous emulsion polymerization of styrene-like monomers, which showed that the number of particles (N p ) and their volume-average diameter (D v ) at the end of nucleation vary according to the following equations [18,20]:…”

Emulsion Polymerization: Effects of Polymerization Variables on the Properties of Vinyl Acetate Based Emulsion Polymers

“…The monomer accumulates in the system as monomer droplets and the polymer particles are saturated with the monomer, as in Interval II of a batch process. In the monomer-starved type, the rate of addition is lower than the rate of polymerization and the polymerization reaction occurs in Interval III where particles are not swollen to their maximum size, leading to the production of small sized, high solid content latexes [56][57][58][59][60][61][62][63][64][65][66].…”