EVALUATION OF BORON ESTERS IN LITHIUM COMPLEX GREASES PREPARED WITH HYDROGENATED CASTOR OIL Vijay Deshmukh, Bhupendra K. Rajput Standard Greases & Specialities Pvt. Ltd.
Abstract:
Traditionally, lithium complex greases are prepared using complexing agents such as boric acid, sebacic acid, azelaic acid etc. to boost the dropping point of lithium base greases. These complexing agents are added in the initial stage of soap making. The process of lithium complex grease preparation using these complexing agents is tedious, time consuming and not very flexible. The advent of Boron Esters as dropping point boosters has made the Lithium Complex grease making process very simple, less time consuming, flexible and economical. The commercial boron esters are recommended in lithium greases prepared using 12 hydroxy stearic acid (12 HSA) and these boron esters are added at the final stage of the process before homogenization and at temperatures below 90°C, like other performance additives. The boron ester additive suppliers recommend their additives to be used in Lithium Grease prepared with 12 HSA as the same are not very effective in boosting the dropping point in lithium grease prepared with Hydrogenated Castor Oil (HCO). Lithium complex greases using boron esters with Hydrogenated Castor Oil (HCO) have been prepared with a modified process to get higher dropping point. This paper describes the evaluation of some commercially available boron esters as dropping point boosters in lithium greases prepared using Hydrogenated Castor Oil (HCO) in place of 12 hydroxy stearic acid (12 HSA). The resulting boost in dropping point is almost same as in lithium complex grease with 12 HSA. Lithium complex greases have been prepared with HCO in different base oils using the modified process and different boron esters. The results are discussed. Lithium complex grease prepared with HCO & one of the boron esters has been tested fully & its properties are compared with lithium complex grease prepared with 12 HSA with the same boron ester. The comparative test data indicates that the developed process gives superior lithium
complex grease. The various advantages of the process have been discussed. Introduction: NLGI Annual Production Survey of 2013 indicates that over 77 % of the total grease produced in the world is based on lithium soap. Out of this, around 19% is lithium complex grease. As per the survey, Lithium Greases having dropping point above 210°C are considered as complex greases in the NLGI Production Survey. In India, around 90% of the total grease produced is lithium base and out of this, around 5-‐7% is Lithium complex grease.₁ Lithium Complex Greases are popular for high temperature applications especially in Steel Plants where the operating conditions are most severe. These greases are also used as long life wheel bearing greases in automotive industry. For wide temperature applications, lithium complex greases are also prepared using synthetic oils such as PAO, OSP etc. Traditionally, lithium complex greases are prepared using complexing agents such as boric acid, salicylic acid, dibasic acids etc. Among the dibasic acids, sebacic acids and azelaic acids are the most popular. Lithium complex greases prepared using sebacic acid and azelaic acid in synthetic hydrocarbon have similar physical properties.₂ Cost of these acids keep on varying and plays a role in the final selection of these acids for use as a complexing agent. In lithium complex grease, the boric acid & dibasic acids as complexing agents are introduced in the initial stage of saponification. The use of these complexing agents increases the percentage of lithium hydroxide and there by increases the cost of the product. The manufacturing process for these greases is generally an open kettle process and is tedious, long and not very flexible. It is known that lithium complex greases having high dropping points, good extreme pressure properties and very satisfactory water resistance properties can be
- 42 VOLUME 80, NUMBER 4
