Composition Control of Copolymer in Semibatch Emulsion CopolymerizationI. Methyl Methacrylate/Styrene Two-Component System

Abstract

ABSTRACT:This research studies the Methyl methacrylate/Styrene two-component system through either soapless semi-batch emulsion copolymerization or soapless batch emulsion copolymerization. The optimal monomer feed flow rate was determined from experiments and theory through semi-batch emulsion copolymerization. The instantaneous composition of polymers was effectively controlled to get the desired final products. We used the monomer feed flow rate as a function of conversion, derived by Canu et al. from the monomer reactivity ratios and the interphase partition laws, along with the correspondence between conversion and time, to obtain the monomer feed flow rate as a function of time. The optimal monomer feed flow rate was obtained from iterative experiments, and through this we could effectively control the polymer composition.KEY WORDS Two-Component/ Semi-Batch/ Emulsion Copolymerization / Polymer latex is used widely for the applications in paint, textile coating, adhesives, and paper coating. Polymer latex of diverse properties is in great demand for different applications. It is critical to know how to get the desired copolymer latex by controlling polymer composition in a polymerization reaction.Traditionally, polymer composition is controlled through semi-batch emulsion polymerization under a starved condition. 1 -5 In a reaction system like this, the composition of the monomer mixture is equal to the desired copolymer composition, with the monomer feed rate much lower than the polymerization rate. Since the monomers are added at slow rate, the composition of the copolymer obtained would be identical to that of the monomer mixture added to the reactor. Although the heat generated during reaction is easier to handle due to the slow reaction rate, it takes much longer time to complete the whole reaction. The low concentration of monomers throughout the entire reaction process changes the distribution of molecular weight, 4 which would have further impact on the properties of the final product.Therefore, researchers work hard to produce a copolymer with a given composition while keeping the polymerization rate maximum. To maintain the desired copolymer composition, we need to keep the corresponding monomer composition in the reaction under control by adding the monomers at an appropriate rate. To calculate the optimal monomer addition policy, we know what the time evolutions of both the number of polymer particles (Np) and average number of free radicals per polymer particle (n) are. Variation of the number of polymer particles during polymerization can be minimized in semi-batch seeded emulsion polymerization by adjusting the amount of surfactant. Average numbers of free radicals per polymer particle were determined by the rates of adsorption and desorption of the polymer particles tTo whom correspondence should be addressed. and bimolecular termination in the polymer particles. These values could not be accurately predicted and are usually unknown.To solve this problem, Dimitratos et al. 6 • 7 proposed a...

Further insight into the mechanism of poly(styrene-co-methyl methacrylate) microsphere formation

“…Based on monomer material properties and previous studies of SFEP kinetics for each monomer, it was expected that, under mixed monomer conditions, the MMA species would participate in considerably more reactions shortly after initiation, relative to styrene. Therefore, an approximation will be taken that the reaction kinetics of this system at times shortly after initiator addition can be described using results derived from MMA studies …”