Study On Preparation Process Of Cycloolefin Copolymer

Cycloolefin and α-olefin copolymers (COC) boast glass-like transparency, low moisture absorption, low dielectric loss, excellent dimensional stability and high heat resistance etc. It will be used in optical,electric,medical apparatus fields.Three different catalysts Cp₂ZrCl₂, [Ph₂C(Flu)(Cp) ]ZrCl₂ Et₂OLiCl, rac-[Et(Ind)₂]ZrCl₂, which have C_2v,C_s,C₂ symmetric structure respectively, have been evaluated. It has been found that rac-[Et(Ind)₂]ZrCl₂ had the highest activity while the highest cycololefin incorporation ratio was achieved by [Ph₂C(Flu)(Cp) ]ZrCl₂ Et₂OLiC. Catalyst Cp₂ZrCl₂ performed poorly with respect to both polymerization activity and cycololefin poincorporation.The norbornene and ethylene copolymerization processes using rac-[Et(Ind)₂]ZrCl₂ as catalyst have been extensively studied. It has been found that:(1) When molar ratio of NB to ethylene was between 10 and 30, NB molecular fraction in copolymer could exceed 50%. The glass transfer temperature of the obtained COC would be above 120°C, and reaction activity remained high. Other optimization conditions are: temperature is 60°C;catalyst concentration is 6×10^-5 mol/L and Al/Zr is 1000—2000.(2) The ethylene polymerization activity is very high when rac-Et(Ind)₂ZrCl₂ is used as the copolymerization catalyst, and the reaction rate of ethylene could exceed the its mass transfer rate between gas phase and liquid phase. Therefore, ethylene concentration in polymerization system is unsaturated. Copolymerization process was affected by the ethylene flow rate to a significant extent. Copolymerization activity increased two times but copolymer composition changed very little as ethylene flow rate was increased. This phenomenon has been explained through a simple model simulation.The influences of COC concentration on polymerization process have been investigated. The copolymerization rate was decreased as diffusion coefficient of ethylene was decreased due to the increase in viscosity of polymerization system. A kinetics model base on reptation theory has been developed to describe the relationbetween reaction rate and the viscosity of polymerization system.Parameters of Mark-Houwink equation also be estimated in this thesis using GPC and intrinsic viscosity data. For COC with 50mol% fraction of NB, a is 0.664 and K is 1.742*10⁴ with 1,2,4-trichlorobenzene as the solvent at 150"C.