Lubricant Additives

264 Lubricant Additives: Chemistry and Applications

9.3.4 RAW MATERIALS

In principle, any single- or multi-double-bond-containing molecule may be sulfurized. Therefore, the
list of olefi nic raw materials is long. The list of sulfur-containing materials is rather short. It is mainly
sulfur fl ower (S 8 ), hydrogen sulfi de gas, some S 2 Cl 2 , and some alkali polysulfi de (e.g., NaSx).
On the olefi n side, patent literature reports of the following:

Vegetable oils (soybean, canola, rapeseed, cottonseed, rice peel, sunfl ower, palm, tall oil,

terpenes, etc.)

Animal fats and oils (fi sh oils, lard oil, tallow oil, sperm oil, etc.)

Fatty acids

Synthetic esters

Olefi ns (isobutene, diisobutene, triisobutene, tripropylene, tertapropylene, α-olefi ns, n-ole-

fi ns, cyclohexene, styrene, polyisobutene, etc.)

Acrylates, methacrylates

Succinic acid derivatives, and more

The choice of commercially applied raw material is certainly limited to those compounds that have
a reasonable price level and give certain performance benefi ts. Sulfur carriers based on low-boiling
olefi ns (e.g., C4-types) are limited to closed lubricating systems due to the volatility of the decom-
position products and associated offensive smell. For water-based lubricant oil systems, sulfurized
fatty acids that can be easily emulsifi ed and active types of olefi ns that cannot be hydrolyzed are
preferred. In oil applications, one can fi nd the full range of products.

9.4 PROPERTIES AND PERFORMANCE CHARACTERISTICS

9.4.1 CHEMICAL PROPERTIES

9.4.1.1 Effect of Additive Structure on Performance

9.4.1.1.1 Raw Materials
The additive structure is mainly infl uenced by the choice of the raw materials and the sulfurization
method. A general overview of the performance properties of sulfurized products based on differ-
ent raw materials is shown in Table 9.1.

9.4.1.1.2 Infl uence of Raw Materials on Extreme Pressure and Antiwear
The raw material determines the polarity and, therefore, the affi nity of the product to a metal surface
[33]. With increasing polarity, an increasing EP performance can be observed. Straight sulfurized

• • • • • • •

TABLE 9.1

Performance Properties of Sulfurized Products

Ester Triglyceride Olefi ns

Inactive Active Inactive Active Inactive Active

Extreme pressure Fair Good Good Very good Low Fair

Antiwear Good Low Very good Low Good Poor

Reactivity Low High Low High Low Very high

Cu corrosion Low High Low High Low High

Antioxidant Good Low Good Poor Good Poor

Lubricity Fair Fair Very high Very high Poor Poor