272 Lubricant Additives: Chemistry and Applications
9.5.3.1 Industrial Gear Oils
Typical sulfur carriers for this application are short-chain sulfurized olefi ns. Sulfurized Isobutene
(SIB) or Sulfurized Diisobutene are widely used as EP additive in industrial gear oils. SIB is used
for some decades as the EP additive of almost all industrial gear oil packages. The high sulfur
content, combined with a relative low active sulfur level, is ideally suited to match the require-
ments. Unfortunately, these products have a very distinct odor and, depending on the manufactur-
ing process, can contain chlorine compounds. Newer developments are based on sulfurized olefi ns
with a longer chain length. Specialty products with additional demands on lubricity are based on
sulfurized triglycerides or mixtures of sulfurized olefi ns and triglycerides.
9.5.3.2 Slideway Oils
Slideway oils are a special type of gear oils with very good anti-stick–slip properties. Besides the
austere requirements on coeffi cient of friction, there are also demands on compatibility and demulsi-
bility with metalworking emulsions. Inactive sulfurized triglycerides are suitable to reduce the coef-
fi cient of friction. Unfortunately, most of these products are easy to emulsify and will, therefore, not
meet the requirements on demulsibility without extensive formulation work. Modern slideway oils
are based on demulsifying sulfurized olefi n/triglyceride-based products that have the advantages of
low coeffi cient of friction, good demulsibility, and high EP loads.
9.5.3.3 Hydraulic Fluids
It is possible to use inactive sulfur car riers in hydraulic systems with only moderate requirements on
thermal stability. Typical products are sulfurized olefi ns and triglycerides or mixtures thereof.
9.5.3.4 Multifunctional Lubricants
Multifunctional lubricants cover more than just one lubrication application. There are increasing
demands for this lubricant type, especially in metalworking shops. As one lubricant will be used for
different applications with sometimes very different requirements, it is important that multifunc-
tional additives are used. Depending on the overall performance requirements, sulfur carriers are
used as EP, AW, or lubricity additive (see Tables 9.1 and 9.2). Multifunctional lubricants are almost
always a compromise in their formulation. For example, metalworking machines with combined
gear oil/process oil sump require a fi ne-tuned additive, especially on the EP side. Sulfur carriers
with a medium activity, additionally passivated with sulfur scavengers, are widely used for this
application.
9.5.3.5 Agricultural Applications
Lubricants in agricultural applications can be spilled on soil because of either the machine design
or leaks in hydraulic and gear systems. Therefore, there are increasing requirements on environ-
mentally compatible or less harmless lubricants. Sulfurized products are ideally suited for this
type of applications. They can be designed to meet performance and ecological requirements
(e.g., biodegradability). A wide range of lubricants exists for outdoor equipment based on veg-
etable oils (e.g., soybean, canola, rapeseed, and sunfl ower oil).
Sulfur carriers for these applications are mainly based on vegetable oils and synthesized in strictly
controlled manufacturing processes.
Typical sulfur carriers for agricultural applications are shown in Table 9.4.
9.5.3.6 Automotive Applications
It is disclosed in U.S. Patent Nos. 4,394,276 and 4,394,277 that various sulfur-containing alkane
diols may be formulated with lubricating oils to effectively reduce fuel consumption in an inter-
nal combustion engine. Sulfurized products in general and inactive sulfurized, oxidatively stable