Preparation Of High Solid Polystyrene Emulsion By One Step Method

This paper focused on the emulsion polymerization system consisting essentially of styrene (St), sodium dodecyl sulfate (SDS) and persulfate. The high solid content and low viscosity latexes of polymer styrene emulsion was prepared by a one-step batch emulsion polymerization. Firstly, a series of seed emulsion with certain solid content, particle size (PS), particle size distribution (PSD), polydispersity index (PDI) and the number of latex particle per unit volume of water (Np) was prepared by means of seed semi-continuous emulsion polymerization; and then this seed emulsion based, adding a quantity of emulsifier (SDS) caused by secondary nuclear system with a certain particle size distribution of solid content reached more than 60% of polystyrene latex. The effect of emulsifier coverage rate, monomer feeding acceleration rate, particle size and distribution of seed emulsion on the solid content, viscosity and stability of polystyrene latex, optimal process conditions for preparation of stable emulsion with high solid content and low viscosity stabilized emulsion prepared by one-step method. The main results of this work are as follows:1. The effect of emulsifier coverage on the preparation of high solid content emulsion is very large. Firstly, when the emulsifier coverage rate of less than 80%, the latex particles will aggregate and the emulsion demulsification in advance, in the emulsion polymerization process; when the emulsifier coverage rate is 82%～167%, the emulsion viscosity increases slightly with the increase of the emulsifier coverage rate, but the rate of the emulsion is decreased, and the stability is enhanced.2. The monomer feeding rate is another important parameter. When the monomer feeding rate is too fast, which makes the emulsion polymerization rate to accelerate and the heat radiation of the reaction system is difficult, that lead to implosion and demulsification; on the other hand, the residual St in aqueous phase will form new particles by precipitate nucleation or micelle nucleation, which will reduce the emulsifier of the system coverage, leads to the increase of the viscosity of the emulsion, latex particles decreased stability, is not conducive to the stability’of the emulsion system. In this research system, in order to improve the efficiency of polymerization, we can improve the monomer feeding rate, but the rate is not more than1.38ml/min.3. High solid content emulsion was prepared by seed emulsion with a larger particle size distribution (PDI> 0.1), the overall solid content of emulsion is higher than that of particle size distribution, and the emulsion viscosity is slightly higher, but the emulsion storage stability time is longer. In this research system, the seed size distribution is wide, which is beneficial to increase the spatial volume of latex particles.4. In this paper, the high solid content, low viscosity and stabilized polystyrene emulsion was prepared by a one-step batch emulsion polymerization. The results of the study show that the suitable condition were as follows:the emulsifier coverage rate in 123%～167%, monomer feeding rate was less than 1.38ml/min, seed size about 134.9nm, seed particle size distribution was wide (PDI> 0.1), the solid content can achieve to 63.4% and viscosity less than 600mpa.s of polymer emulsion under these conditions.