悬浮聚合法色粉制备条件及树脂性能控制

Preparation Process and Resin Properties Control of the Toner in Suspension Polymerization

研究了超声波及颜料颗粒铁黑和碳黑对苯乙烯聚合过程的影响。结果表明,超声波对苯乙烯聚合过程的影响可分为三个阶段,在聚合反应前期,超声波引发聚合作用显著,对苯乙烯聚合有加速作用;在聚合反应中期,超声波降解作用加强,使聚合反应速率降低;在聚合反应后期,由于聚合体系的粘度增大,超声波引发聚合作用显著而加速反应过程。铁黑颗粒加入聚合体系,会阻碍链自由基的扩散,因而加快聚合反应;碳黑颗粒对聚合过程的影响与加入量有关,碳黑加入量低于1%(wt)时,碳黑颗粒造成的空间效应会阻碍链自由基的扩散,使反应加速;碳黑加入量高于5%(wt)时,由于碳黑表面活性基团对自由基的捕捉作用而使反应减速。实验研究了悬浮聚合法色粉制备过程中温度、引发剂浓度和颜料颗粒对聚合树脂分子量分布、熔融特性的影响。结果表明,聚合温度升高或引发剂用量增加,聚合树脂的分子量减小,软化点降低,熔融指数增大;加入碳黑可降低聚合树脂分子量,加入铁黑可显著提高树脂分子量,且均能显著增大分子量的多分散系数; 加入铁黑颗粒,色粉的软化点升高,熔融指数减小。通过参数调节,可有效控制树脂的熔融特性。

Toner preparation process and the resin composition control in suspension polymerization were researched for improving the application properties of the toner. Bulk polymerization process of styrene was studied in the presence of carbon black, iron black pigments and ultrasonic action, respectively. Experimental results showed that the ultrasonic effect on the bulk polymerization of styrene can be divided into three stages. In the earlier stage, the polymerization was accelerated due to the remarkable effect of ultrasonic polymerization. In the middle stage, the polymerization was retarded due to the decomposition effect of ultrasonic on polymerized resin. In the later stage, the ultrasonic polymerization was accelerated remarkably again due to the high viscosity of reactant slurry. Non-reactive surface of the iron black particles speeded polymerization for its hindering termination of chain radicals, and with the increase of adding amount of iron black, the accelerating function was more remarkable. Adding low amount of carbon black accelerated the polymerization, while adding large amount resulted in hindering the polymerization of styrene. Because the resin characteristics in toner affect the fixation quality crucially in printing process, the effect of reaction temperature, the amount of initiator and pigments of carbon black and iron black on the average molecular weight and its distribution, softening point and melt index were studied in this research. The average molecular weight and the polydispersity (ratio of weight average molecular weight to number average), softening point and melt index were employed as characterization parameters. Research results showed that increasing the reaction temperature or the initiator amount, the resin molecular weight decreases, the softening point decreases and the melt index increases. Adding carbon black results in the decrease of molecular weight, which results from that the active functional groups on the surface of carbon black can trap the chain radical. Adding iron black retards coupling termination, and polymer resin with higher molecular weight and wider distribution forms, which leads to that the softening point increases and the melt index decreases. Therefore, the resin properties can be controlled through the adjustment of parameters in the suspension polymerization process.