Copolyme Rization Of Ethylene And Norbornene At Model Scale

Cyclic olefin copolymer (COC) is a promising engineering materials with excellent transparency, high heat resistance, low dielectric loss, low moisture. It has a broad range of applications in optical, electric, medical fields and etc. Ethylene-norbornene copolymers (ENC) is a typical kind of COC. Preparation of ENC by addition copolymerization has been studied by many groups. These studies are mainly focused on the development of copolymerization catalysts, with the objects to improve the catalyst activity, norbornene content in copolymer and molecular weight. A few studies are aimed at controling the macromolecular chain structure and sequence distribution. There are also a few studies about the influence of reaction conditions on the polymerization process and the copolymer properties, including our group. However, these studies are mostly carried out in little scale devices. Besides, prepareing ENC at elevated pressure with fixed initial monomer molar ratio has not been studied intentionally. The kinetic model of ethylene-norbornene copolymerization is also developed for predicating the polymerization rate and copolymer composition by several groups including our group, while the effect of mass transfer process has never been taken into account in these models.A series of ENC were prepared with rac-[Et(Ind)2]ZrCl2/MAO catalysts at elevated pressure. The influences of different monomer feed ratio, catalyst concentration and reaction pressure on the ethylene/norbornene copolymerization process and copolymer composition have been studied respectively. A remarkable difference between ethylene/norbornene copolymerization process in bench reactor scale and model scale is observed. That is, in scaled-up reactor, the influence of mass transfer process can not be neglected. In model scale reactor, both the dissolving process between the gas-liquid phase and the diffution process in the liquid phase have remarkable influences on the polymerization process. Besides, the molecular structure of copolymers generated at different reaction pressure was analysed. The optical properties, moisture absorption and mechanical properties of the copolymers with different composition and molecular weight were compared in this paper.Based on our group’s former works, terminal and penultimate models taking mass transfer process into account are developed in this thesis. Besides, a new relationship between the catalyst active site concentration and norbornene concentration is developed. The models are validated with batch polymerization experimental data. The terminal model gives better correlation with the composition data while both of these two models fit the polymerization rate data well. The terminal model was then used to calculate the viscosity variation in the polymerization process, which affect the mass transfer rate directly. As the mass transfer process is different for ethylene and norbornene, an interesting inflection point was found for the monomer ratio curve at reaction pressure between 2bar and 3bar. That is, monomer ratio is decreased with the reaction proceeding below 2bar, while it is increased progressively above 3bar. Besides, the monomer ratio variation range was calculated and used to relate the copolymer composition distribution.The models developed in this paper are able to predict the ethylene/norbornene copolymerization process with norbornene concentration from 0.2 mol/L to 5.7 mol/L under reaction pressure from 1.2 bar to 5 bar.