Study on the application of DPU-B prefabricated biuret (preformed diurea) thickener Xu Hui and Tian Zhiyuan Shandong Honsing Chemcal Co., Ltd. Shandong, People’s Republic of China
Abstract In this paper, isocyanate and organic amines as raw materials were used to make prefabricated biuret (preformed diurea) thickener for grease. The DPU-B biuret (diurea) thickener was prepared by the reaction of isocyanate and mixed amines in different solvents. Laboratory and field data show that polyurea greases produced with this thickener have good thermal stability, colloidal stability, water resistance and especially outstanding mechanical stability and thickening ability. At the same time, the manufacturing temperature is only 120°C. This thickener can completely replace the traditional method to prepare polyurea grease. Keywords: Preformed thickener; Biuret; Diurea; Thickener; Polyurea grease; 1 Introduction With its high dropping point, polyurea grease has good oxidation stability because its thickener has no metal ions, as well as good thermal stability and long bearing life. It has been widely used in industrial fields such as electrical, metallurgy, food, papermaking, automobile and aircraft applications. It is noteworthy that the vigorous development of new electric vehicles in recent years led to a sharp rise in the price of lithium hydroxide, impacting the economics of lithium-based grease especially lithium complex soap grease. As a result, polyurea grease has attracted more and more attention from manufacturers and users. The main materials for preparing polyurea greases are base oil, isocyanate and organic amine. Different types of organic amines and isocyanates can be used to synthesize different polyurea greases. According to different chemical structures, polyurea greases can be divided into biuret (diurea) greases and tetraurea greases. The common production methods of biuret (diurea) grease include 1) one-step (or in situ) methods, and 2) methods that use preformed thickener. Onestep or in situ methods refer to the preparation of biuret (diurea) greases by the reaction of
isocyanates and amines in base oil. Preformed biuret (diurea) thickening agents are prepared in advance, and then the preformed thickener is diluted, blended and milled in the base oil to prepare grease of the desired consistency. Because of the strong toxicity, volatility and corrosiveness of isocyanates and some organic amines, there are very strict safety and protection requirements for the production of polyurea grease. The transport and storage of isocyanates and organic amines are also regulated by the relevant laws and regulations of various countries. Additionally, the polymerization of some isocyanates requires that they must be stored at low temperature. Therefore, if the production volume of polyurea grease is not up to a certain scale, the cost of environmental protection and safety precautions will be relatively very high. Meanwhile, the control of hazardous chemicals and the increasing demand for environmental protection in many countries restrict the production of polyurea grease in some enterprises. As an alternative, the use of preformed thickener to produce biuret (diurea) grease is not only convenient and fast, but also does not involve the use, transportation and storage of toxic chemicals and is safer and more environmentally friendly than one-step or in situ methods. At present, commercially available polyurea greases thickened by preformed biuret (diurea) thickeners present some problems such as high thickener dosage, poor mechanical stability, high swelling temperature and high selling prices. In this paper, formula-based adjustment, solvent screening and process improvement have been adopted to prepare a urea-based preformed biuret (diurea) thickener, named DPU-B preformed polyurea thickener (abbreviated as DPU-B ), with excellent performance and the ability to solve the existing problems. This paper also studies the effect of different base oils on the performance of DPU-B greases.
-4VOLUME 83, NUMBER 1
