Sulfurized vegetable oil products as lubricant additives

Sulfurized products based on hog fat and its derivatives have extensive commercial use as additives for metalworking and industrial oils, but only relatively small quantities of vegetable oils find such application in North America. Products were made by sulfurization of soybean, sunflower, cottonseed, high erucic rapeseed, canola, Limnanthes (meadowfoam) and prime lard oils. Unlike products from the wax ester jojoba oil, the sulfurized vegetable triglycerides alone had physical properties generally undesirable for lubricant additives. When the oils were sulfurized in the presence of methyl lardate, however, the products had potential practical application. High‐sulfur (active) products were made using a 50:50 ratio of triglyceride to methyl lardate, and low‐sulfur (inactive) products were made using a 70:30 ratio. Compared to the other sulfurized vegetable triglyceride products, Limnanthes products showed the best solubility in high viscosity‐index paraffinic oil. For solutions, measurements of extreme pressure, friction and wear were compared. Whereas products from jojoba were best, of the triglyceride group the Limnanthes ‐containing products generally gave the best performance. Although this oil had much promise, it is only in its early stage of commercial development. The other vegetable oils also have potential depending on cost and applications. However, overall competition with the well‐established, usually lower‐cost products from hog fat or greases would appear to be difficult.