直接法制备聚脲润滑脂工艺研究及分析

RESEARCH AND ANALYSIS ON DIRECT PREPARATION PROCESS OF POLYUREA LUBRICATING GREASE

考察了直接法制备工艺条件(加料顺序、炼制温度、炼制时间)对聚脲润滑脂性能的影响,重点分析了加料方式对聚脲稠化剂化学组成与平均分子结构的影响,及其与聚脲润滑脂性能的关联性;采用红外光谱、热重分析仪、扫描电镜对直接法聚脲润滑脂进行表征,深入探讨了其构效关系,并与预制法制备的润滑脂产品进行了比较。优化的直接法制备方案为:将有机二胺溶于基础油中,升温至80~90℃后同时加入异氰酸酯和有机单胺,反应60 min,然后在170~180℃下炼制1.5 h。结构和性能表征结果表明:在基础油和稠化剂种类与配比相同、制备条件相同情况下,由直接法与预制法得到的聚脲稠化剂中脲基基团数量及比例存在差异,从而导致聚脲润滑脂产品的性能出现差异;当稠化剂质量分数均为20%时,预制法所制备的四聚脲润滑脂的滴点比直接法高20℃,钢网分油量仅为直接法的21.8%,水淋流失量仅为直接法的41.3%,铜片腐蚀比直接法高一个等级,最大无卡咬负荷比直接法高24.5%。总之,直接法得到的聚脲润滑脂的胶体安定性、氧化安定性及极压抗磨性能略逊于预制法,但其机械安定性优于预制法。

The effects of direct preparation conditions(feeding sequence,refining temperature,and refining time)on the properties of polyurea grease were investigated,and the influence of feeding method on the chemical composition and average molecular structure of polyurea thickeners and its relationship with the properties of polyurea grease were analyzed.The prepared polyurea lubricating grease by direct method was characterized by infrared spectroscopy,thermogravimetric analysis and scanning electron microscopy,the structure-activity relationship of the grease was thoroughly explored,and the products were compared with those obtained by the prefabricated method.The basic optimized experimental scheme was to dissolve organic diamine in the base oil,raise the temperature to 80-90℃,add isocyanate and organic monoamine at the same time,react for 60 min,then react for 1.5 h at temperature of 170-180℃.The results of structural and performance characterization indicated that the number and proportion of urea group in polyurea thickener prepared by the direct and prefabrication methods were different under the same types and ratios of base oil and thickener,as well as the same preparation conditions.There were differences in the number and proportion of urea groups in the polyurea thickeners obtained by the direct method and prefabricated method,which led to differences in the performance of polyurea lubricating grease products.When the mass fraction of thickening agent was 20%,the dropping point tetrapolyurea grease prepared by the prefabrication method was 20℃higher than that by the direct method,the oil content of a steel mesh was only 21.8%of that by the direct method,the leaching loss was only 41.3%of that of direct method,the corrosion rate of copper strip was one grade higher than that of the direct method,and the last non-seizure load for the prefabricated method was 24.5%higher than that of the direct method.In a word,the colloidal stability,oxidation stability,and extreme pressure plus anti-wear performance of polyurea lubricating grease prepared by the direct method were slightly inferior to those of the prefabricated method,but its mechanical stability was superior to that by the prefabricated method.