Lubricant Additives

258 Lubricant Additives: Chemistry and Applications

Depending on the temperature, inter- or intramolecular bonding of sulfur occurs preferably.

The catalyst directs the addition of sulfur in a certain way (Markovnikov, etc.).

It is a fact that sulfur carriers are technical products based on technical raw materials. In the follow-
ing, the most typical structures of sulfur carriers based on different, contemporary raw materials
are shown. Taking the rather complex reaction pathways of a sulfurization reaction into account,
they necessarily are simplifi ed model structures.

9.3.1.1 Sulfurized Isobutene

This is the standard EP additive for gear oils with typical sulfur contents in the range of 40–50%
(Figure 9.1).

9.3.1.2 Active-Type Sulfurized Olefi ns

These are the polysulfi de types of sulfur carriers that have been introduced as substitute for sulfu-
rization of base oil and are widely used today in metalworking applications (Figure 9.2).

9.3.1.3 Inactive Sulfurized α-Olefi ns

These are used in noncorrosive lubricant applications ranging from metalworking, greases to even
engine oil applications (Figure 9.3).

9.3.1.4 Sulfurized Synthetic Esters (Light Color)

These are widely used in metalworking and grease applications. Depending on the type of synthetic
ester chosen, special properties such as low temperature stability/fl uidity and low viscosity may be
achieved (Figure 9.4).

S

S S

S

n

FIGURE 9.1 Sulfurized isobutene.

0 − 4

S S

S

S

S

S

0 − 4

FIGURE 9.2 Sulfurized diisobutene, sulfurized tetrapropylene.

S

S

S

FIGURE 9.3 Inactive sulfurized α-olefi ns.