slack wax

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May 11, 2004
can anyone give me a list of oils known to use slack wax? i know the american syntec line is one, shell's helix oils?
thanks for the detailed description. i know shell uses it in their oils and castrol in the usa syntecs, but aside from those I dont know any other brands, would like to find out a few more if anyone knows them [Smile]
Ray, good information, thanks!
can anyone give me a list of oils known to use slack wax?
Good question! I've wondered the same thing. Adding to this; are there more base oils from slack wax than just XHVI? What percentage does Castrol use in their US Syntec? FWIW I believe Rotella 5w-40 WAS about 90%, but NOW I'm not sure. I'm really curious to find out which other oils use it? [I dont know]
In general, the cheapest to manufacture and/or the "heavier" viscosity ranges. Refined heavy paraffin oil contains considerable amounts of like-molecular weight waxes. How the wax is dealt with determines whether "slack wax" is recovered for sale as a commodity. The older method (Group I base oils) use solvent refining in a chilled environment to crystalize a significant amount of the heavier waxes out so they can be filtered and recovered commercially. This solvent refined base stock can then be blended and additized to commercial motor oil. Though some wax inevitably remains in the base stock, pour point depressants can keep it under control in most climates in appropriate viscosity grades. The second means is hydrotreating -- and can be used on both solvent refined base stocks or stocks straight from the distillation tower. The feed stock is subjected to high heat and catalytic action in the presence of hydrogen gas under high pressure. The process culminates in the isomerization of waxes and aromatics into desirable heavy paraffin base stocks. (Note: contrary to popular misconception, "paraffin" does not equate to "wax".) Obviously no slack wax is recovered commercially in this process. The duration of the process progressibvely results in Group II, Group II+, Group III, and now, Group III+ base stocks. These Group III+ base stocks meet and, in some cases, surpass the entry level 140 VI of Group IV (PAO) base stocks, which implicitly also defines their resistance to oxidation reactions as a measure of the scarcity of undesirable waxes and aromatics. Though not completely wax and aromatic-free, Group III+ base stocks give Group IVs a run for their money. Group IVs are, by definition, completely wax and aromatic-free since they're designer synthesized (polymerized) to the desired molecular weight from simple monomers through progressive stages.
"Slack wax" is technically just a feedstock. The base oil produced from this feedstock is a "wax isomerate." Shell realized well over a decade ago that pure slack wax makes a better feedstock than the VGO from the distiller. The typical wax isomerate will have a VI of 140+. The catalyst technology behind the hydrocracking/isodewaxing approach to Group III is just now to the point where base oils with VIs of over 140 are feasible. As far as I know, the only two wax isomerate base oils on the market at this time are Shell's XHVI and ExxonMobil's ExxSyn. As for which oils you'll find these in, the only ones I know for sure are Shell's Rotella T Synthetic, as well as most of the Helix line of oils (in conjunction with PAO and esters). Castrol's domestic Syntec uses wax isomerates in conjunction with conventional Group III, PAO, and esters. I don't know what oils are produced with ExxSyn, but it could be that Castrol is using both XHVI and ExxSyn.
Hehe interesting, Castrol putting in every base oil they can [Wink]
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