In order to investigate the influence of the physical state of the catalyst on polymerization of poly(ethylene terephthalate) (PET), liquid-phase catalysts of Sb₂O₃ solutions such as Sb₂O₃ dissolved in EG-based glycol [ethylene glycol (EG), neopenthyl glycol (NPG), ethylene glycol-neopenthyl glycol (EG-NPG)] was utilized In Polycondensation reaction using bis(2-hydroxyethyl)terephthalate (BHET). Reaction using Sb₂O₃ Powder as catalysts was also carried out for comparison with the liquid-phase catalyst, the rate of polycondensation reaction markedly increased in the early state compared to that of Sb₂O₃ powder-catalyzed case. The liquid-phase catalyst accelarated more effectively both the condensation and the decomposition during polycondensation than Sb₂O₃ powder catalyst. PET with intrinsic viscosity of up to 0.65 dL/g could be obtained by the polycondensation using liquid-phase catalyst in shorter time than by that using powder solid catalyst. The properties of the resultant PET were measured. The DSC thermogram showed melting point of PET at 254℃, and cooling crystallization temperature, at 196℃. PET prepared using catalysts with NPG showed that NPG decreased T_m by 3℃ and T_c by 5℃.

Sb₂O₃ 분말을 glycol[ethylene glycol (EG), neopenthyl glycol(NPG), ethylene glycol-neopenthyl glycol (EG-NPG(5:1)), ethylene glycol- eopenthyl glycol (EG-NPG(1:5))]에 용해시킨 Sb계 액상촉매를 bis(2-hydroxyethyl) erephthalate (BHET)에 투입하여 poly (ethylene terephthalate) (PET)를 중합하고, 중합과정에서 일어나는 반응성과 중합된 PET의 특성을 조사하였다. 반응속도에 있어서는 Sb계 액상촉매를 사용한 경우가 Sb₂O₃ 분말촉매를 사용한 경우보다 초기반응 속도가 증가하였고 액상촉매중에서도 용액을 안정화시킨 용액계가 보다 효과적으로 초기반응 속도를 증가시켰다. 또한 액상촉매를 사용한 경우는 2시간 이내에 중합속도와 분해속도가 평형을 이루고, 고유점도가 0.65dL/g정도의 PET를 얻기 위해서는 액상촉매를 사용하는 것이 중합시간을 단축시키는데 유리하였다. DSC 열곡선에서 PET시료의 용융점 (T_m) 및 냉각시 결정화온도(T_c)가 중합도의 증가와 함께 감소하는 경향을 보이고 있었으며, NPG를 함유한 액상촉매를 사용한 경우에는 NPG의 영향으로 T_m에서 약 3℃정도 감소하였으며, T_c에서는 5℃ 정도 감소함을 알 수 있었다.

Keywords: Liquid-phase catalyst; PET polycondensation; degree of reaction; thermal analysis