Studies on the melt transesterification of DPC and BPA for synthesis of polycarbonate

本論文研究二苯基碳酸酯與丙二酚的熔融酯交換反應及其對聚碳酸酯合成的影響。文中提出羰基親核性取代的反應機構理論，說明熔融酯交換的反應行為，並導出簡潔的分子物質動力模式。這個模式的計算結果與文獻上報導的實驗數據都相當吻合，可驗證此模式具有顯著的實用性。這個熔融酯交換反應為可逆反應，正反應的反應速率為正比於二苯基碳酸酯濃度和觸媒濃度的二次式，逆反應則為正比於酚濃度、寡聚物濃度和觸媒濃度的三次式。接著，使用4-dimethylaminopyridine (DMAP)作為酯交換觸媒探討合成聚碳酸酯的影響因素。發現單體比例明顯影響合成的聚合物的內在黏度(intrinsic viscosity)，單體比例在1.03-1.05之間可得到較高內在黏度的聚碳酸酯，所合成聚碳酸酯的分子量分佈呈最可能分佈(the most probable distribution)。實驗結果也顯示觸媒的濃度對聚碳酸酯樹脂的顏色影響極鉅，當DMAP作為觸媒時，我們建議不要超過50 ppm。同時，我們也建立一個機械攪拌式反應器的數學模式來模擬熔融酯交換合成聚碳酸酯的過程。由簡化反應器的流動模式和應用滲透理論來處理揮發性成分質量傳送的操作。此反應器模式的適用性由揮發性組成分冷凝液、聚合物的末端基比例和聚合物的重量分率分佈等的預測值與實驗資料進行比較檢驗，結果顯示模式的預測值與實驗資料是相當貼近。由核磁共振測量的末端基比例充分支持模式對聚合物的預測結果，同時，預測的分子量分佈與由膠凝體滲透色譜法測量的結果也相當吻合。The catalytic reaction of the melt transesterification of diphenyl carbonate (DPC) and bisphenol-A (BPA) is investigated theoretically. A reaction mechanism based on the nucleophilic substitution on the carbonyl group of reactants is proposed for the description of the kinetic behavior of the reaction under consideration. The applicability of the present model is justified by fitting it to the available experimental data reported in the literature, and its performance is found to be satisfactory for a wide range of operating conditions. The transesterification of DPC and BPA is of reversible nature; the forward reaction is second order in the concentrations of DPC and catalyst, and the reverse reaction is third order in the concentrations of phenol, oligomer, and catalyst. The synthesis of polycarbonate (PC) by the melt transesterification using 4-dimethylamino pyridine (DMAP) as the catalyst was studied experimentally. The monomer ratio markedly influenced the intrinsic viscosity of the resulting polymer. A ratio in the range 1.03-1.05 was found to yield polymer with a high intrinsic viscosity. The molecular weight distribution of the PC was with the most probable distribution. The concentration of the catalyst reasonably affected the hue of the PC resin, and we suggest that it should not to exceed 50 ppm when DMAP is used as the catalyst. Also, a mathematical model was of the melt transesterification of polycarbonate in a mechanically agitated reactor system, was proposed. The ideal penetration theory was applied to the mass-transfer operation of volatile components in both a transesterification reactor and a polymerization reactor by simplifying the flow pattern. The applicability of the proposed model was examined by comparing its predictions with experimental data. NMR measurements support the predicted end-group ratio of the resulting polymer. The predicted distribution of weight fractions is well matched to the profiles measured by GPC.目錄 頁次 中文摘要 I 英文摘要 II 目錄 Ⅲ 圖表目錄 VI CHAPTER 1. INTRODUCTION AND BACKGROUND 1 1.1 PREPARATION OF POLYCARBONATE 2 1.2 CHEMISTRY OF POLYCARBONATE BY TRANSESTERIFICATION 7 1.3 KINETIC AND PROCESS MODELING OF TRANSESTERIFICATION 10 1.4 APPROACHES OF THIS STUDY 13 1.5 REFERENCES 16 CHAPTER 2. KINETIC MODELING OF MELT TRANSESTERIFICATION OF DIPHENYL CARBONATE AND BISPHENOL-A 19 2.1 INTRODUCTION 20 2.2 REACTION MECHANISM 21 2.3 KINETIC MODEL 27 2.4 JUSTIFICATION OF KINETIC MODEL AND DISCUSSION 34 2.5 CONCLUSIONS 37 2.6 REFERENCES 38 2.7 NOMENCLATURES 40 2.8 APPENDIX: Abbreviations for Molecular Formulas 41 CHAPTER 3. MELT TRANSESTERIFICATION OF POLYCARBONATE CATALYZED BY DMAP 49 3.1 INTRODUCTION 50 3.2 EXPERIMENTAL 53 3.3 RESULTS AND DISCUSSION 56 3.4 CONCLUSION 60 3.5 REFERENCES 63 CHAPTER 4. MODELING THE MELT TRANSESTERIFICATION OF POLYCARBONATE 73 4.1 INTRODUCTION 74 4.2 EXPERIMENT 76 4.3 REACTOR MODEL 78 4.4 RESULTS AND DISCUSSION 91 4.5 CONCLUSION 95 4.6 REFERENCES 96 4.7 NOMENCLATURES 98 CHAPTER 5. CONCLUSIONS 110 APPENDIX： COMPUTER PROGRAM OF REACTOR MODELING 11