- 期刊
對苯二甲酸二甲酯與乙二醇酯交換反應之研究
Exter Exchange of Dimethyl Terephthalate with Ethylene Glycol
摘要
在不同醋酸鹽及氫氧化物觸媒之存在下，改變反應物莫耳比及反應溫度，研討對苯二甲酸二甲酯(dimethyl terephthalate, DMT)與乙二醇(ethylene glycol)之酯交換反應。由實驗結果得知，不同觸媒各顯示不同之催化教果，其活性依醋酸鋅＞醋酸鉛＞醋酸鎘＞醋酸鈣＞醋酸鋇＞醋酸鈉＞氫氧化鋰＞醋酸汞、醋酸銅、醋酸鐵之次序而遞減。觸媒用量之增加可促進酯化速率，惟用量達1 X 10^(-3) mole/DMT mole 以上，則有接近一定值之趨勢。在所用反應物莫耳比(M = 2~5)之範圍內，酯交換反應對於甲基酯與乙二醇各屬於一級之反應;由反應速率常數與溫度之關係估計活化能，各為醋酸鋅26.8 kcal/mole，醋酸鉛30 kcal/mole，及醋酸鎘33.7 kcal/mole。酯交換反應所用觸媒對於後段聚縮合反應生成物之物理化學性質之影響亦加以研討。聚對苯二甲酸二乙酯(Polyethylene terephthalate, PET)屬於多元酯，為現今主要合成織雄之一。其名雖有Tetoron、Terylene、Dacron等，因生產國家而異，但其製造方法不外分為酯化(單體bis-β-hydroxyethyl terephthalate, BHET之製造)與聚縮合之兩個過程。1960年由於亨克法等製造高純度對苯二甲酸(terephthalic acid, TPA)之成功，PET之製造有逐漸採用TPA與EG之直接酯化法之趨勢。然而直接酯化法需要較苛刻之反應條件，所用溫度、壓力均較酯交換法為高，且其酯化速率不及酯交換反應速率之快，所以在可預見之將來酯交換法仍不失其重要性。基於此，對於酯交換反應速率之探討及前段酯交換所用觸媒是否嚴重影響到聚合物之物理與化學性質，乃為化學纖維研究者所注意之問題。由於酯交換若不添加觸媒，反應則無從進行，選擇適當之觸煤，可提高其反應速率。本文使用各種不同之醋酸鹽類觸媒，研討此等關係。
關鍵字
無資料並列摘要
The ester exchange of dimethyl terephthalate with ethylene glycol is investigated in the presence of nine different acetates as catalysts. It was found from the experimental results that the catalytic activity of the acetates decreases in the orders: zinc acetate＞lead acetate＞cadmium acetate＞ calcium acetate＞ barium acetate＞ sodium acetate＞ mecurric acetate, ferrous acetate, cupric acetate. The increase in amount of catalyst used increases the rate of ester exchange, but up to 1 x 10^(-3)mole/DMT mole, the rate constants would remain to a constant value. Under the reactant mole ratio M=EG/DMT 2~5, the ester exchange obeys the second order kinetic law, first order with respect to both methyl ester group and E. G. The active energies are estimated to be 26.8 kcal/mole for zinc acetate catalyst, 30 kcal/mole for lead acetate and 33.7 kcal/mole for cadmium acetate. The effects of catalyst on the physical and chemical properities of polycondensation products are also studied.