Preparation of Lubrication Grease for Spindle Motor

Abstract

Grease for bearing used in a spindle motor of a computer was prepared by three steps: (i) preparation of lithium stearate by a saponification reaction of stearic acid and lithium hydroxide, (ii) mixing lithium stearate and base oil, such as paraffin or trimethylol propane (TMP) ester oil, at temperature 220°C to form lithium-base grease, and (iii) adding additives into the lithium-base grease and rolling the mixture by a three-roll mill to obtain finished grease. The lithium-base grease formulated from 82% TMP-ester oil and 18% lithium stearate or from 85% paraffin oil and 15% lithium stearate were found to give good properties and performance with a penetration value in a range of 220-250 as specified in JIS K 2220-1993. An addition of additives such as zinc dialkyldithiophosphate (ZDDP), molybdenum dithiocarbamate (MDTC) or diphenyl amine (DPA) into the grease was found to improve oxidation and corrosion resistance properties of both types of greases.