The invention discloses a preparation method of thermal degradation-resistant PBT
polyester with the high
viscosity. The preparation method comprises the technology process that the thermal degradation-resistant PBT
polyester with the specific
viscosity of 1.25-1.35 L / g is finally prepared through
slurry preparing, negative-pressure esterification reacting, pre-polycondensation reacting, low-
viscosity final polycondensation reacting, chain-extension liquid-phase tackifying reacting and discharging and grain-sized dicing in sequence. According to the preparation method, by adopting lower negative pressure and longer esterification
retention time in the esterification stage, the esterification rate of the esterification stage is effectively increased and reaches 99.5% or above, and the terminal
carbonyl group content in melt of a consequent reaction is decreased; by controlling the reacting time and the
melt viscosity in final polycondensation and adding a carboxyl-terminated chain
extender in the liquid-phase tackifying stage, the terminal
carbonyl group content in the melt is further decreased, the chain extending and tackifying effects are achieved, the effect of quickly achieving tackifying in short time is achieved, and the production efficiency is improved; the chain
extender is stable in property, does not influence the product
hue, is high in
boiling point and cannot be taken away from a
reaction system along with liquid-phase tackifying vacuumizing.