Lubricant Additives

Sulfur Carriers 263

Step 1. Addition of disulfur dichloride to double bonds.

In case of fatty oil being used as olefi n source, the resulting product is a sulfurchlorinated

fatty oil useful as chlorine and sulfur-containing EP additives in metalworking. From a

technical point of view, their biggest problem is the split-off of chlorine and subsequent

severe corrosion problems that are diffi cult to control. From today’s point of view, the

presence of chlorine is not favorable anymore because of environmental concerns.

Step 2. Subsequent treatment of the sulfurchlorinated products with sodium sulfi de (NaS 2 )

solution in water. It is a substitution reaction of sulfur versus chlorine (Figure 9.9). Inter-

molecular linkage as well as ring closure may occur. The water-soluble sodium chloride

is washed out.

9.3.3.2 Alkylhalogenide/NaSx

This process is closely related to the fi rst step reaction discussed in Section 9.3.3.1. Starting materi-
als may be alkyl- or arylhalogenides. As shown in Figure 9.10, it is possible to substitute halogens
with sulfur using alkali sulfi des. If Na 2 S is used, monosulfi des are generated. In case alkali polysul-
fi de is applied, alkyl- or arylpolysulfi des are the resulting derivatives.
This route has not found commercial interest as raw material costs are too high compared to
other synthetic methods.

2 +2Na 2 S −4 NaCl

Sulfurized isobutene

n

S

S

S

S

S S

S

S

S

Cl

Cl

FIGURE 9.9 Dechlorination reaction.

2 +S 2 Cl (^22) S S
Cl
Cl
FIGURE 9.8 Sulfurchlorination reaction.
(^2) +
Arylhalogenide
(or Alkylhalogenide)
Sodium polysulfide
in water
−2 NaCl
Diarylpolysulfide
(or dialkylpolysulfide)
S S
S
0 − 5
Na
S
S
S
Na
0 − 5
Cl
FIGURE 9.10 Dechlorination of arylhalogenides.