搅拌转速对悬浮PVC树脂平均粒径的影响

在5L小釜中分别采用恒转速和变转速工艺进行氯乙烯(VC)悬浮聚合,考察粒径随转化率的变化规律,发现两者规律相似,即在低转化率时粒径随转化率的增加而逐渐增大,当转化率约为15%以后粒径几乎不再变化.同时发现搅拌转速、分散剂用量和聚合温度等对上述转化率～粒径变化规律几无影响,只是粒径大小的不同.将变转速工艺应用于大型釜生产中,考察变速时间、前转速及后转速对最终树脂粒径及其分布的影响,计算两工艺的生产能耗,发现变转速聚合除了有利于树脂颗粒的形成外,还可以降低搅拌功率的消耗,节约能源.

Effects of Agitation Speed on the Average Diameter of PVC Suspension Resin

The law of polymerized PVC particle size varying with the conversion rate of vinyl chloride suspension polymerization was studied in a 5 L autoclave by respectively using two different agitation schemes, such as agitation with constant-speed and agitation with variable-speed. The results show that the above law for using these two agitation schemes are similar, i.e. when the conversion rate is low, the polymerized particle size increases gradually with the increase of conversion rate, while when the conversion rate reaches 15%, then the diameter of the polymerized particles will no longer change with the further increase of the conversion rate. Moreover, the polymerization parameters, such as the agitation speed, the dispersant amount used and the polymerization temperature only affect the final obtained PVC grain diameter and have little effect on the variation law of the obtained particle diameter with the conversion rate. In our study, the variable agitation scheme was adopted for the PVC suspension polymerization in a large-scale autoclave, and the effects of the time after which the agitation speed is changed, the former agitation speed and the later agitation speed on the polymerized PVC grain diameter and its distribution were studied. After calculating respectively the energy consumptions of the PVC suspension polymerization with above two agitation schemes, it was found that scheme of agitation with variable-speed not only benefits the formation of grains, but can also reduce the agitation power and save the energy consumption.