Effect of Catalyst on the Polycondensation of Poly(ethylene terephthalate)

Abstract

PET의 중축합(polycondensation) 단계의 중합 속도를 증가시킨다고 알려진 titanium alkoxide 촉매들의 효과를 공업적으로 주로 사용되고 있는 Sb2O3 촉매와 비교하였다. 즉 중축합 단계에서 촉매비를 titanium alkoxide/Sb2O3=40/60으로 하고 titanium(IV) alkoxlde의 alkoxide ligand를 ethoxide, butoxide, 2-ethylhexoxide로 바꾸었을 때 ligand의 carbon수가 적을수록 반응시간이 현저히 단축되나 부반응도 동시에 일어나 생성된 중합체에 색상이 나타나는 등 ligand의 크기에 따라 정반응과 부반응이 영향을 받는 steric effect 효과가 나타남을 알았다. 따라서 균일 촉매인 titanium alkoxide 대신에 열안정제로의 역할을 할 수 있는 phosphate compound를 TiCl4와 반응시켜 새로운 Ti-P계 촉매(PETCA)를 합성하였다. PETCA 촉매는 Sb2O3 촉매보다 중축합 시간을 단축시켰으며, titanium alkoxide 촉매를 단독으로 사용할 때 보다 중합물의 백색도를 향상시켰다.

In this study several titanium alkoxide catalysts were tested first in combination with Sb2O3 catalyst in the polycondensation stage of PET, poly(ethylene terephthalate). With titanium alkoxide/Sb2O3=40/60 it was found that titanium alkoxide catalysts shortened the polycondensation reaction time considerably, as the carbon number of alkoxide ligand decreased from 2-ethylhexoxide, butoxide to ethoxide in the titanium alkoxide catalyst. However, Side reactions which form the yellowish byproduct in PET also increased by the same order. From these results it was noted that steric control occurred at active strate in Ti(IV) catalyst in the polycondensation stage of PET synthesis. New Ti-P type catalyst (PETCA) was synthesized from TiC14 and phosphate compounds which are known to be effective as thermal stabilizer in the polycondensation reaction of PET. The new PETCA catalyst was found to be effective in shortening reaction time and improving color of PET.