羟基聚硅氧烷平衡聚合脱挥及反应器研究
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摘要
目前国内的液体硅橡胶的基础胶α，ω—二羟基聚二甲基硅氧烷(简称羟基聚硅氧烷)的聚合主要采取先聚合再加水降解的间歇聚合工艺，不仅生产效率很低，而且聚合所得的羟基聚硅氧烷粘度难以控制，分子量分布很宽，最终导致产品质量不高。本文在自清洁反应器中进行了羟基聚硅氧烷的平衡聚合研究；并对羟基聚硅氧烷在单螺杆中的脱挥进行了实验研究；为寻找实现工业化、连续化生产羟基聚硅氧烷的途径，本文还对卧式双轴自清洁反应器进行了停留时间分布(RTD)的研究，并提出中试方案。
羟基聚硅氧烷的聚合方面：以八甲基环四硅氧烷(D_4)为单体原料，分别以氢氧化钾(KOH)和四甲基氢氧化铵[(CH_3)_4NOH]作为催化剂，采用卧式双轴自清洁反应器研究了催化剂用量、反应时间等因素对聚合结果的影响。得到了在平衡聚合实验中加入水量的计算方法。结果发现：使用四甲基氢氧化铵作为催化剂催化效率更高，反应温度110℃。反应时间为1.5h即可达到平衡，实验中加入水的损失率与反应最终转化率基本一致，据此，我们认为可以通过调节反应温度、反应时间等来控制最终转化率，从而，当确定所需要的聚合物分子量时候，可以计算出所需加入的水量，为实现连续化、工业化的羟基聚硅氧烷生产奠定了基础。
羟基聚硅氧烷的脱挥方面：以单螺杆挤出机为脱挥实验装置，以D_4和羟基聚硅氧烷配制实验物料，研究了温度、真空度、螺杆转速、进料流量、初始挥发分含量等因素对脱挥结果的影响。在实验范围内，对最终挥发分含量与螺杆转速、进料流量的关系进行了拟合，得到了关联式。
论文的最后部分以水、糖浆为实验介质对卧式双轴自清洁反应器的停留时间分布(RTD)特性进行了实验。研究了搅拌桨转速、物料流量、物料粘度以及同轴相邻搅拌桨之间夹角等因素对RTD的影响。利用返混模型编程计算出各实验状态下的返混系数及模拟曲线，通过对比发现，所有的模拟曲线与实验曲线都吻合较好。以水和糖浆为物料，分别在固定搅拌雷诺数的情况下，拟合出返混系数与混合雷诺数的关系，并分别得到表达式。讨论了搅拌雷诺数、物料粘度、搅拌桨叶安装角度等因素对返混系数的影响。
At present, hydroxyl-terminated polydimethylsiloxane (PDMS) was generally synthesized with batch process in China, that is, hydroxyl-terminated PDMS was synthesized firstly, then water was put into it for degradation. The viscosity of the product was hard to control and the molecular weight distribution (MWD) of the products was wide, so the quality of the product was not so high. In this article, hydroxyl-terminated PDMS was synthesized and was studied in self-cleaning reactor, then, the devolatilization of hydroxyl terminated PDMS was studied in single-screw extruder. The residence time distribution (RTD) of the self-cleaning reactor was studied. Finally one pilot experimental scheme was proposed.
The hydroxyl-terminated PDMS was balanced synthesized by ring-opening of Octamethylcyclotetrasiloxane (D4) in self-cleaning reactor, with potassium hydroxide (KOH) or tetramethyl ammonium hydroxide [(CH3)4NOH]] as the catalyst. The study focused on the efficiency of the two catalysts, and the amount of catalyst and reaction time on the conversion of the balanced reaction. It was found that the efficiency of [(CH3)4NOH]] was higher than that of KOH, and the reaction could be equilibrated at temperature 110 for 1.5 hours, and the loss ratio of the water that put into the reactor was almost equal to conversion of the reaction. So we can control the conversion of the reaction by controlling the condition of the reaction, then we can calculate the quantity of water we should put into the reactor.
About the devolatilization of hydroxyl-terminated PDMS in a single-screw extruder, the factors that affect final mass fraction of the volatile were analyzed. It was found that both temperature and vacuum were the key parameters. Then the formulas between the final mass fraction of volatile with the rotational speed of the screw and with the feed rate were proposed respectively.
In the study of self-cleaning reactor, water and syrup were adopted as the experimental media and the researches were focused on the characterization of the RTD. The residence time distributions were tested, and the relations between the backflow coefficient and rotational speed, viscosity, feed rate and the angle between two adjacent blades were studied, and the formulas between backflow coefficient and the mixing Reynolds were proposed. It was found that the experimental curves were in consist with the theoretical ones well.
羟基聚硅氧烷的聚合方面：以八甲基环四硅氧烷(D_4)为单体原料，分别以氢氧化钾(KOH)和四甲基氢氧化铵[(CH_3)_4NOH]作为催化剂，采用卧式双轴自清洁反应器研究了催化剂用量、反应时间等因素对聚合结果的影响。得到了在平衡聚合实验中加入水量的计算方法。结果发现：使用四甲基氢氧化铵作为催化剂催化效率更高，反应温度110℃。反应时间为1.5h即可达到平衡，实验中加入水的损失率与反应最终转化率基本一致，据此，我们认为可以通过调节反应温度、反应时间等来控制最终转化率，从而，当确定所需要的聚合物分子量时候，可以计算出所需加入的水量，为实现连续化、工业化的羟基聚硅氧烷生产奠定了基础。
羟基聚硅氧烷的脱挥方面：以单螺杆挤出机为脱挥实验装置，以D_4和羟基聚硅氧烷配制实验物料，研究了温度、真空度、螺杆转速、进料流量、初始挥发分含量等因素对脱挥结果的影响。在实验范围内，对最终挥发分含量与螺杆转速、进料流量的关系进行了拟合，得到了关联式。
论文的最后部分以水、糖浆为实验介质对卧式双轴自清洁反应器的停留时间分布(RTD)特性进行了实验。研究了搅拌桨转速、物料流量、物料粘度以及同轴相邻搅拌桨之间夹角等因素对RTD的影响。利用返混模型编程计算出各实验状态下的返混系数及模拟曲线，通过对比发现，所有的模拟曲线与实验曲线都吻合较好。以水和糖浆为物料，分别在固定搅拌雷诺数的情况下，拟合出返混系数与混合雷诺数的关系，并分别得到表达式。讨论了搅拌雷诺数、物料粘度、搅拌桨叶安装角度等因素对返混系数的影响。
At present, hydroxyl-terminated polydimethylsiloxane (PDMS) was generally synthesized with batch process in China, that is, hydroxyl-terminated PDMS was synthesized firstly, then water was put into it for degradation. The viscosity of the product was hard to control and the molecular weight distribution (MWD) of the products was wide, so the quality of the product was not so high. In this article, hydroxyl-terminated PDMS was synthesized and was studied in self-cleaning reactor, then, the devolatilization of hydroxyl terminated PDMS was studied in single-screw extruder. The residence time distribution (RTD) of the self-cleaning reactor was studied. Finally one pilot experimental scheme was proposed.
The hydroxyl-terminated PDMS was balanced synthesized by ring-opening of Octamethylcyclotetrasiloxane (D4) in self-cleaning reactor, with potassium hydroxide (KOH) or tetramethyl ammonium hydroxide [(CH3)4NOH]] as the catalyst. The study focused on the efficiency of the two catalysts, and the amount of catalyst and reaction time on the conversion of the balanced reaction. It was found that the efficiency of [(CH3)4NOH]] was higher than that of KOH, and the reaction could be equilibrated at temperature 110 for 1.5 hours, and the loss ratio of the water that put into the reactor was almost equal to conversion of the reaction. So we can control the conversion of the reaction by controlling the condition of the reaction, then we can calculate the quantity of water we should put into the reactor.
About the devolatilization of hydroxyl-terminated PDMS in a single-screw extruder, the factors that affect final mass fraction of the volatile were analyzed. It was found that both temperature and vacuum were the key parameters. Then the formulas between the final mass fraction of volatile with the rotational speed of the screw and with the feed rate were proposed respectively.
In the study of self-cleaning reactor, water and syrup were adopted as the experimental media and the researches were focused on the characterization of the RTD. The residence time distributions were tested, and the relations between the backflow coefficient and rotational speed, viscosity, feed rate and the angle between two adjacent blades were studied, and the formulas between backflow coefficient and the mixing Reynolds were proposed. It was found that the experimental curves were in consist with the theoretical ones well.
引文
[1] 幸松民，王一璐．有机硅合成工艺及产品应用．北京：化学工业出版社，2000
[2] 冯连芳，曹松峰等．高粘搅拌聚合反应装置.合成橡胶工业，2001,24(5)：257～261
[3] 赵望前．混炼技术的革命．有机硅材料,2000,14(2)：26～27
[4] Schickmann H, et al. DD250935. 1988
[5] Kennan JJ, et al. EP497530. 1992
[6] 晨光化研院有机硅编写组．有机硅单体及聚合物.北京：化学工业出版社，1986
[7] 章基凯．有机硅材料．北京：物资出版社，1999
[8] 吕伟，杨峰，α，ω—二羟基聚二甲基硅氧烷制备新工艺研究．吉化科技，1997，5(4)：30～35
[9] 谢建军，潘勤敏等．聚合物系脱挥研究进展．合成橡胶工业，1998，21(3)：135～141
[10] 王凯，孙建中．工业聚合反应装置．北京：中国石化出版社 1997
[11] Latinen G A. Adv. Chem. Ser, 1959,34:235
[12] Biesenberger J A, Lee S T. A fundamental study of polymer melts devolatilization:Ⅳ.some theories and models for foam-enhanced devolatilization. Polym Eng Sci, 1989,29(12):782～790
[13] Secor R M. A mass transfer modeling for a twin-screw extruder. Polym Eng Sci,1986.26(9):647～652
[14] Foster R W, Lindt J T. Twin-screw extrusion devolatilization :from foam to bubble free mass transfer. Poly Eng Sci, 1990,30(11):621～633
[15] 黄志恭．聚酯生产技术剖析.合成纤维工业，1992，15(2)：58～62
[16] 发明专利说明书．卧式双轴搅拌机．1995，6，7，CN：1028723C，西见晴行等人
[17] ZbioinskiⅠ.Chem. Eng .J, 1995, 58: 123～133.
[18] Riccardo P, Nicoletta C, Synthesis of syndiotactic polystyrene :reaction mechanics an catalysis. Prog Polym Sci,1996,21 : 47.
[19] EP. 0584646. Process for producing styrenic polymer.
[20] EP. 0389939 Coordination polymerization process.
[21] EP. 0390000 Process for producing styrene-based polymers.
[22] EP. 0328915 Process for producing styrene-based polymers and apparatus.
[23] EP. 0420134 Process for producing styrene polymers.
[24] EP. 0379128 Process for producing styrene-based polymers.
[25] Schebesta, U S,US 5 669 710. 1997
[26] Schebesta, U S.US 5 876 115 1999
[27] Schuchardt, U S.US 5 399 012 1995
[28] Schuchardt, U S. US 5 505 536 1996
[29] Wen C Y, Fan L T. Models for flow systems and chemical reactors. New York:Marcel Dekker,1975
[30] Nauman E B,Buffham B A. Mixing in continuous flow system. New York:Wiley ,1983
[31] 李绍芬．反应工程.北京：高等教育出版社，1992
[32] Cassagnau P, Mijangos C, Michel A. An ultraviolet method for the determination of the RTD in a twin-screw extruder. Polym Eng Sci,1991, 31(11)
[33] 天田次雄、小森悟、村上泰弘．固气卧式双轴搅拌槽的动力特性.化学工学协会第53年会(仙台，1988年4月)发表．
[34] 小田亲生、中元英和、木下高年、丸子盛久．双轴格子形卧式高粘度搅拌机的流动特性．化学工学协会第52年(名古屋，1987年4月)发表
[35] Todd D B，Lrving H F．Axial Mixing in a Self-Wiping Reactor.Chemical Engineering Progress，65(9):84～89
[36] 娓本彦久寿、屿田隆文、德男雅宽．高粘物质搅拌装置的开发和研究.三菱重工技报，30(3)
[37] Cozewith C, Squire K R. Effect of reactor residence time distribution on polymer functionalization Reactions. Chem Eng Sci, 2000,55:2019～2029
[38] Iedema P D ,Claudia W, et al. Using molecular weight distribution to determine the kinetics of peroxide-induced degradation of polypropylene.Chem Eng Sci , 2001,56:3659～3669
[39] 彭忠利，伍青等．羟基封端聚二甲基硅氧烷低聚物阴离子乳液聚合研究、中山大学学报(自然科学版)，2003,42(5)：47～50
[40] 许德成，刘秦玉.高效凝胶色谱测定硅油分子量及其分布．烟台大学学报(自然科学与工程版)，1994,3
[41] 周安安．有水条件下环硅氧烷开环聚合机理及动力学研究．浙江大学博士学位论文，2003：87～90
[42] Roberts G W. A surface renewal model for the drying of polymers during screw extrusion. AIChe, 1970,16(5):879～882
[2] 冯连芳，曹松峰等．高粘搅拌聚合反应装置.合成橡胶工业，2001,24(5)：257～261
[3] 赵望前．混炼技术的革命．有机硅材料,2000,14(2)：26～27
[4] Schickmann H, et al. DD250935. 1988
[5] Kennan JJ, et al. EP497530. 1992
[6] 晨光化研院有机硅编写组．有机硅单体及聚合物.北京：化学工业出版社，1986
[7] 章基凯．有机硅材料．北京：物资出版社，1999
[8] 吕伟，杨峰，α，ω—二羟基聚二甲基硅氧烷制备新工艺研究．吉化科技，1997，5(4)：30～35
[9] 谢建军，潘勤敏等．聚合物系脱挥研究进展．合成橡胶工业，1998，21(3)：135～141
[10] 王凯，孙建中．工业聚合反应装置．北京：中国石化出版社 1997
[11] Latinen G A. Adv. Chem. Ser, 1959,34:235
[12] Biesenberger J A, Lee S T. A fundamental study of polymer melts devolatilization:Ⅳ.some theories and models for foam-enhanced devolatilization. Polym Eng Sci, 1989,29(12):782～790
[13] Secor R M. A mass transfer modeling for a twin-screw extruder. Polym Eng Sci,1986.26(9):647～652
[14] Foster R W, Lindt J T. Twin-screw extrusion devolatilization :from foam to bubble free mass transfer. Poly Eng Sci, 1990,30(11):621～633
[15] 黄志恭．聚酯生产技术剖析.合成纤维工业，1992，15(2)：58～62
[16] 发明专利说明书．卧式双轴搅拌机．1995，6，7，CN：1028723C，西见晴行等人
[17] ZbioinskiⅠ.Chem. Eng .J, 1995, 58: 123～133.
[18] Riccardo P, Nicoletta C, Synthesis of syndiotactic polystyrene :reaction mechanics an catalysis. Prog Polym Sci,1996,21 : 47.
[19] EP. 0584646. Process for producing styrenic polymer.
[20] EP. 0389939 Coordination polymerization process.
[21] EP. 0390000 Process for producing styrene-based polymers.
[22] EP. 0328915 Process for producing styrene-based polymers and apparatus.
[23] EP. 0420134 Process for producing styrene polymers.
[24] EP. 0379128 Process for producing styrene-based polymers.
[25] Schebesta, U S,US 5 669 710. 1997
[26] Schebesta, U S.US 5 876 115 1999
[27] Schuchardt, U S.US 5 399 012 1995
[28] Schuchardt, U S. US 5 505 536 1996
[29] Wen C Y, Fan L T. Models for flow systems and chemical reactors. New York:Marcel Dekker,1975
[30] Nauman E B,Buffham B A. Mixing in continuous flow system. New York:Wiley ,1983
[31] 李绍芬．反应工程.北京：高等教育出版社，1992
[32] Cassagnau P, Mijangos C, Michel A. An ultraviolet method for the determination of the RTD in a twin-screw extruder. Polym Eng Sci,1991, 31(11)
[33] 天田次雄、小森悟、村上泰弘．固气卧式双轴搅拌槽的动力特性.化学工学协会第53年会(仙台，1988年4月)发表．
[34] 小田亲生、中元英和、木下高年、丸子盛久．双轴格子形卧式高粘度搅拌机的流动特性．化学工学协会第52年(名古屋，1987年4月)发表
[35] Todd D B，Lrving H F．Axial Mixing in a Self-Wiping Reactor.Chemical Engineering Progress，65(9):84～89
[36] 娓本彦久寿、屿田隆文、德男雅宽．高粘物质搅拌装置的开发和研究.三菱重工技报，30(3)
[37] Cozewith C, Squire K R. Effect of reactor residence time distribution on polymer functionalization Reactions. Chem Eng Sci, 2000,55:2019～2029
[38] Iedema P D ,Claudia W, et al. Using molecular weight distribution to determine the kinetics of peroxide-induced degradation of polypropylene.Chem Eng Sci , 2001,56:3659～3669
[39] 彭忠利，伍青等．羟基封端聚二甲基硅氧烷低聚物阴离子乳液聚合研究、中山大学学报(自然科学版)，2003,42(5)：47～50
[40] 许德成，刘秦玉.高效凝胶色谱测定硅油分子量及其分布．烟台大学学报(自然科学与工程版)，1994,3
[41] 周安安．有水条件下环硅氧烷开环聚合机理及动力学研究．浙江大学博士学位论文，2003：87～90
[42] Roberts G W. A surface renewal model for the drying of polymers during screw extrusion. AIChe, 1970,16(5):879～882