甲基丙烯酸甲酯聚合动力学和分子量及分布的开放控制

在甲基丙烯酸甲酯聚合过程中 ,凝胶效应会导致转化率在短时间内出现突变 ,这对工业反应器非常危险 ,同时也导致分子量剧增、分子量分布加宽 .为了使聚合反应速度、分子量及分布同时得到控制 ,提出 3个控制目标 ,即热荷分布指数、预定分子量及变化、分子量分布指数 .在甲基丙烯酸甲酯半间歇聚合动力学和分子量模型的基础上 ,通过单体、溶剂和链转移剂 3种物料的流量和加料方式的仿真计算 ,对动力学、分子量及分布进行开放控制 ,并进行优化 ,得到热荷分布指数和分子量分布指数分别小于 2 0和 2 2的控制策略 ,且分子量达到预定要求 .选择两种优化策略进行实验验证 ,结果与开放控制仿真结果一致

OPEN CONTROL OF KINETICS,MOLECULAR WEIGHT AND ITS DISTRIBUTION FOR METHYL METHACRYLATE POLYMERIZATION

The gel effects will bring a violent increase of conversion for methyl methacrylate polymerization.It will be very dangerous for the reactor and causes an increase of molecular weight and broadens the molecular weight distribution.In order to control the kinetics,molecular weight and its distribution of polymerization simultaneously,three characteristic parameters for polymerization of methyl methacrylate;the heat load distribution index,the change of molecular weight and molecular weight distribution index,were suggested for consideration.The effects of the flow rate and feeding mode of the monomer,solvent and chain transfer agent on the three parameters were investigated,respectively.The gel effect can not be eliminated by changing the flow rate of monomer.The change of monomer feed mode will result in a multiple violent increase of conversion,and the molecular weight will increase with the appearance of gel effect.So the method based on varying the flow rate and feed mode of monomer can not meet the demand of properly controlling the kinetics,molecular weight and molecular weight distribution of polymerization and its products.The molecular weight of polymers prepared by solution polymerization or by with the participation of chain transfer agent was always lower than that of bulk polymerization.However,by changing the flow rate and feed mode of solvent or chain transfer agent,not only the molecular weight can be equal to that of bulk polymerization,but also the gel effect can be eliminated,and the kinetics,molecular weight and molecular weight distribution of polymerization can be properly controlled simultaneously.The optimum heat load distribution index was even less than 2.0,the change of molecular weight was lower than 10%,and molecular weight distribution index was even in the range of 2.0～2 2,respectively.Two open control methods were selected and satisfied with the experimental data.