Preparation Of Poly(Methyl Methacrylate) With Narrow Molecular Weight Distribution By Continuous Polymerization

Poly(methyl methacrylate) (PMMA) is widely used as plexiglass and fiber optics for its good transparency. And the transparency of PMMA is directly related to molec-ular weight distribution (MWD) as narrower MWD could decrease the transmission loss of the light passing through. Therefore study on how to continuously produce nar-row-MWD PMMA is significant to polymer industry.The research on Narrow-MWD PMMA was divided into two parts:I. study on kinetic parameters. II. Study on continuous polymerization process. In part I we ob-tained kinetic data of MMA free radical polymerization through experiments, and es-tablished a gel effect model to describe the gel effect process. The model was also ap-plied to the simulation of multi PFR process. And in part II we studied the polymeriza-tion processes of AIBN and DTBP initiators. The results are summarized as followed:1. We established a new gel effect model based on three-stage diffusion theory, the new model is suitable for CTA system while exponent model and Soong diffusion model do not. Model described as followed:2. The MMA polymerization in tubular reactor with AIBN initiator was studied and the highest conversion is around 35%. At low conversion stage, changing the flow rate has little influence on the molecular weight. To obtain PMMA particles, we de-signed a tubular reactor-twin screw extruder device which could continuously produce narrow-MWD PMMA particles (Mw/Mn=1.79). Then we designed a multi plug flow reactors(PFR) process, conversion of each plug and the amount of CTA were optimized based on the gel effect model to produce targeting PMMA(Mw=82000, Mw/Mn=2.00). The results show either higher or lower conversion of R-1 will cause the increase of MWD.3. In high temperature free radical polymerization with DTBP initiator, the molec-ular weight is much more sensitive to CTA amount than the reaction temperature. The reaction conditions for targeting PMMA (Mw=82000, Mw/Mn=2.00) were simulated with the gel effect model and show only 1/5 initiator is needed comparing to AIBN initiation system. The conditions were applied to practical operation and the quality of the product is close to targeting PMMA.