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 Tm by 3℃ and Tc 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 (Tm) 및 냉각시 결정화온도(Tc)가 중합도의 증가와 함께 감소하는 경향을 보이고 있었으며, NPG를 함유한 액상촉매를 사용한 경우에는 NPG의 영향으로 Tm에서 약 3℃정도 감소하였으며, Tc에서는 5℃ 정도 감소함을 알 수 있었다.
Keywords: Liquid-phase catalyst; PET polycondensation; degree of reaction; thermal analysis