Pilot Chemical
Cleaner Fluids with DPOS from Pilot Chemical
By Dr. Robert Golden | TLT CMF Plus November 2010
Sulfonates are still the most efficient and economical emulsifiers for metal working fluids. These fluids have a several general issues to contend with, and choosing the sulfonates in combination with other co-emulsifiers can provide fluids that have the desired characteristics of performance. Some of the more important issues deal with the changes that occur during the lifetime of the fluid. As water is evaporated, the water hardness increases. Metal scraps, extraneous oils and other debris get incorporated into the fluid. As oxidation occurs, the contaminant content increases and the performance of the fluid decreases. The incorporation of DPOS (di-phenyl oxide di-sulfonates) can make the metal working fluids more hard water tolerant, and keep sumps cleaner, while not decreasing the corrosion protection, or increasing the foam. The combination of Aristonate® S-4600 and Calfax® 16L35 has yielded superb results for emulsifier packages.
Hard Water Tolerance
Table 1 lists the emulsion stability in hardened waters. While increasing the water hardness by 100 ppm, the last stable water hardness of the Calfax® 16L35/S-4600-containing fluid, Fluid #1, was 900 ppm. When this was exceeded at 1000 ppm, some oil separated. This mode of instability was similar to a commercial emulsifier package, Fluid #2, but the commercial package tolerated only 600 ppm water hardness, and separated the oil at 700 ppm. A comparable emulsifier blend using a competitive sulfonate, Fluid #3, had hard water stability similar to the Calfax® 16L35/S-4600-containing fluid; but the mode of failure was the precipitation of lime soap. In the field, dealing with oil separation should be easier than dealing with lime soap deposits. Furthermore, as was shown in the foam data, Fluid #3 at 900 ppm generated scum that precipitated on the blender blade. The Blender of Fluid #1 was clean with respect to anything sticking to the blender components. Lime soap dispersion is a characteristic of the DPOS additions, and the combination of Aristonate® S-4600 and Calfax® 16L35 does a superb job at keeping the lime soaps from depositing in the sumps, on the parts, or on the machines.
Table 1.
Cleaner Sumps
As a fluid ages, it picks up tramp oils and the metal fines that dirty the fluid. Pilot is experimenting with an artificial aging procedure that contacts the fluid with metal fines, in an oxidizing environment. There have been some interesting observations, which seem to have some association with anecdotal stories from the field.
After the aging procedure, these soluble oils definitely had different performances when allowed to further settle after filtration. In the photos shown, we can see that the DPOS-containing Fluid #1 had some particulates float, but not much sink. Compare this to Fluid #2 that is based on the commercial emulsifier package that dropped out more sludge to the bottom, while having a similar layer of oil float to the surface. Fluid #3 did not separate oil (but did separate some cream), but had a great deal of material drop to the bottom. In a sump that gets skimmed, Fluid #1 would maintain the cleanest sump. More important is that the fluids were filtered, so the material at the bottom was suspended in the fluid that was re-circulating, and coalesced when it was allowed to settle. This dark precipitate is probably not going to enhance the fluid performance properties. The implication is that Fluid #1 did not hold as much of this dark material as the other two fluids, and therefore the fluid itself was cleaner. A cleaner fluid is expected to perform better.
Fluid #1
Fluid #2
Fluid #3
Corrosion Protection
The Fluid #1 which contained the Aristonate® S-4600 and Calfax® 16L35 had excellent corrosion inhibition properties, passing the cast iron chip test at 4%. The Fluid #2 failed at a 5% concentration, while the Fluid #3 passed at 5%, but failed at 4%. Obviously, the presence of the DPOS does not adversely impact the corrosion, and due to the Aristonate® S-4600’s ability to incorporate more amine, can even do better. These are shown in
Table 2.
Table 2.
Foam Stability
Table 3 shows the results of the blender foam test for the three fluids in distilled water, tap water, 600 ppm and 900 ppm water, and after the aging process. Note that the Fluid #1, containing the DPOS, had a foam that broke after four minutes in tap water, while the other fluids had foam remaining after completion at 5 minutes. The Fluid #3 had a stable emulsion in 900 ppm water, but when put to the blender test, the product generated some scum, which is most likely the lime soap deposit. Similarly, Fluid #2 was stable at 600 ppm, but generated scum in the blender test, while Fluid #1 did not generate either foam or any deposits at 900 ppm water hardness. When the fluids were artificially aged, Fluid #1 did not generate any foam, such that there were no bubbles when the blender stopped. Fluid #3, was capable of having the foam break within one minute, but Fluid #2 left some foam after 5 minutes.
Table 3.
Summary
The Aristonate® S-4600 has been shown to have excellent properties when formulated into soluble oil emulsifier packages, and these can be further enhanced with the addition of Calfax® 16L35. The data shown demonstrates the increased hard water tolerance and greater fluid cleanliness of the S-4600-based system, and its further enhancement with the addition of Calfax® 16L35. This fluid cleanliness did not come at the expense of corrosion inhibition or foam performance.
Dr. Robert Golden obtained his doctorate from the University of California, Irvine, and his bachelor’s degree from the California Institute of Technology. The last seventeen years have been with Pilot Chemical Company where he developed his expertise in the sulfonation process, and surfactants in general. Having been influenced by pre-graduate opportunities at Chevron and UNOCAL, his applications side of the surfactant chemistry has focused on the oil soluble sulfonates, both for corrosion inhibition and emulsification.