Metal Soap Greases - Progress in Organic and Physical Chemistry: Structures and Mechanisms - page 60

type. The texture or structure of soda base greases is affected materially by details of
processing and manufacturing variations are numerous.
Lithium Soap Greases
Lithium soap grease handles extremes of temperature quite well, which makes them
highly suitable for both high and low temperature application. They have a dropping
point of approximately 176 o C, and can be used in continuous temperatures of 135 o C.
One reason for their successful low temperature performance is that they are made
with oil having a low pour point. In fact, lithium soap greases have been used suc-
cessfully at temperatures of -51ºC. Use of lithium soap grease at higher temperatures
requires a different formula however: the same grease cannot be used at both extremes
of high and low temperatures because the change would be in the viscosity of the oil
used in the grease.
Barium Soap Greases
Barium soap greases are general purpose types, valued for their ability to work over
a wide temperature range. Their dropping point is approximately 176 o C or higher, al-
though they are not intended to be used in continuous operation at temperatures above
135 o C.
Calcium Soaphydrate Greases
Calcium soaphydrate greases , also called lime soap greases, are probably the best
known and most often used of all greases. They are smooth and buttery in texture,
have excellent water resistance, a fair mechanical stability, are easy to apply and have
melting points just under the boiling point of water. Depending on the method of
manufacture they are usually relatively inexpensive. Uses include axle grease, water
pump grease, and general machinery applications.
The major advantage of calcium soap grease is that they do not dissolve in water.
However, it is not suited to use in lubricating high speed bearings. Ordinary general
purpose calcium soap greases have a dropping point of approximately 79 to 93 o C. Be-
cause its water content begins to dry out, and the soap and oil separate, calcium-soap
grease is not suited to applications where the temperature will get above 71°C while
they may survive 93°C for short periods of time.
Calcium soap is produced with a small residual water content which acts as stabi-
lizer for the matrix and thus provides the required structure of the thickener. They are
made by chemically reacting hydrated lime with tallow fatty acid in presence of min-
eral oil. Saponi¿ cation under pressure of 15-100 lbs/inch 2 is frequently used to insure
complete reaction in minimum time. After saponi¿ cation is complete, more mineral
oil is added, along with water as structure modi¿ er, to obtain the desired consistency.
Water in concentrations of from a fraction up to several percent in ¿ nished greases
since the calcium soap oil system is essentially an emulsion wherein the water acts as
a stabilizer or coupling agent.
Anhydrous Calcium Soap Greases
Anhydrous calcium greases offer advantages of traditional calcium soap greases, ex-
cellent adhesion, low temperature adhesion, and water resistance. Anhydrous calcium