Grease types calcium-soap greases

Since 1977 several new thickener types have become widely used, including complex (sodium, lithium, calcium or aluminium), polyurea, modified clays, and other non-soap thickeners. To bring the picture up-to-date, Risdon carried out an evaluation in 1986 of three of the newer grease types not inciuded in the previous programme. They were lithium complex, aluminium complex and polyurea. They included one EP (extreme pressure) and one non-EP grease for each type of thickener, and all were of the same consistency grade, NLGI No 2. 

To make grease the soap is dispersed in the oil as fibers of such a size that it may only be possible to detect them by microscopy. The fibers form a matrix for the oil, and the type, amount, size, shape, and distribution of the soap fibers dictate the consistency, texture, and bleeding characteristics, as well as the other properties of grease. Grease may contain from 50% to 30% soap, and although the fatty acid influences the properties of grease, the metal in the soap has the most important effect. For example, calcium soaps form smooth, buttery grease that is resistant to water but is limited in use to temperatures under about 95°C (200°F). 

Nevertheless, calcium greases of this type are still in use today for less demanding applications and their manufacture is very similar to the processes used over 100 years ago. Calcium soap is produced with a small residual water content which acts as a stabiliser for the soap matrix and thus provides the required structure of the thickener. In some operating conditions, when the temperature is constantly above 50°C, water evaporation may result in the complete breakdown of consistency in the grease and it will revert to a fluid state. 

Heavy-metal soaps (loosely called metallic soaps) are those formed by metals heavier than sodium (aluminum, calcium, cobalt, lead, and zinc). These soaps are not water soluble specific types are used in lubricating greases, gel thickeners, and in paints as driers and flatting agents. Napalm is an aluminum soap. See saponification detergent. 

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