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The challenge in making lithium complex greases lies in the fact that the term complex in lubricating greases is misnomer, and refers to co-crystallization of two salts. The challenge lies in making two salts appropriately and then co-crystallizing them to get the desired quality of product, which also depends on type of complexing agent used. Calcium greases, in general, fall in three categories: hydrated calcium, anhydrous calcium and calcium complex greases. For hydrated calcium greases also known as cup greases, the trick of making them lies in simultaneously controlling the heat and keeping the grease hydrated, whereas in the case of anhydrous calcium grease controlling the temperature around its dropping point is critical. Sodium base greases appear simple to make, but need careful control of temperature and mixing, avoiding overflowing the kettle due to the presence of water.
Other complex greases such as aluminium complex greases, are made by reaction of aluminium isopropoxide, benzoic acid and stearic acid where reaction evolves low flash isopropanol. If the reaction is not controlled properly and isopropanol is not driven off/ collected suitably, one can not only end up with a fire risk but also poor quality of grease. That’s why trimer of aluminium isopropoxide which either releases minimal amount of isopropanol or completely eliminates, are safer and a more efficient way of making this type of grease. Calcium sulfonate greases are becoming more popular these days and can be made in a variety of ways. The trick lies in maximizing the calcite formation and minimizing Vaterite form of isomers. If the reaction is not controlled appropriately the finished grease could possibly have hardening tendency and be of poor quality. Polyurea greases in general are made using isocyanates (MDI / TDI) and handling toxic isocyanate is not only a challenge to any plant but also controlling polymerization may play crucial role on quality of finished grease.
In last few decades, grease manufacturing techniques and processes have advanced remarkably and have become pretty much standardized. However, it’s practically difficult to erect a fully automated plant due to nature of reaction and ingredients
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used and therefore some kind of manual operations are still involved in grease manufacturing. As there are so many variables like time, temperature, mixing method, the type of vessel and milling / homogenizing in grease making and are not mutually exclusive, therefore there is always a chance that one operator can make grease slight different to another, leading to differences in their end use properties. During my 25 years of experience of working on products and processes of lubricating greases in-lab as well as in-plant, there could be significant difference in the overall properties of a particular grease made in two different kettles and by different operators. Although the lubricating grease composition could typically be a time-tested recipe, lubricating grease manufacturing is still vulnerable, to an extent, to the personal touch.
About the Author: Anoop Kumar, Ph.D. in Chemistry from Indian Institute of Technology, Roorkee, India, is Director of R&D and Business Development at Royal Mfg Co LP. He has over 25 years of experience in formulation, manufacturing and market development of lubricating greases and industrial oils. Dr Kumar has published / presented over 80 technical papers on lubricants and has authored over 25 patents worldwide. Over the years, he has several awards to his credit and currently representing serval technical societies and committees. He played a crucial role in formation of NLGI India Chapter and currently serves in Executive Committee as Treasurer of NLGI.
LINK
www.royalmfg.com
LUBE MAGAZINE NO.138 APRIL 2017
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