ExxonMobil Chemical Company
Synesstic™ Alkylated Napthalene Basestocks for Incidental Food Contact
By Sandra Mazzo-Skalski, Performance Product Specialist, ExxonMobil Chemical | TLT CMF Plus November 2010
Formulations of food contact-grade lubricants operate in an environment of escalating challenges, from new and more-stringent food health and safety laws to restrictions on additive selections and treat rates. Exxon Mobil Chemical is helping them adapt to these new market realities, announcing that its Synesstic™ Alkylated Naphthalene (AN) base stocks are now available for applications with incidental food contact.
Synesstic™ AN base stocks are proven API Group V fluids that extend the performance of automotive and industrial lubricants in extreme operating environments. For lubricants used in food-processing equipment, formulators can achieve optimal performance with a synthetic product and know that it won’t compromise food quality or safety in the event of incidental contact.
Making the Grade
The U.S. Food and Drug Administration accepted Food Contact Notification filings for both grades of Synesstic™ AN base stocks, 5 cSt and 12 cSt. Synesstic™ AN base stocks are also registered as HX-1 ingredients with the National Sanitation Foundation, enabling their use in H1 lubricants for food-processing environments where there is the possibility of incidental food contact.
Synesstic™ AN base stocks are certified for use in Kosher food-processing applications, and approval is being sought for Halal certification.
Performance Requirements
Food-grade lubricants must provide the same performance as any lubricant – such as protection against friction, wear and deposits – in an environment where the risk of dust, water and other contamination is high. Added complexity comes from the fact that food-related applications are often in high-temperature and moist environments, making thermal and hydrolytic stability essential performance requirements.
Synesstic™ AN base stocks are high-quality synthetic lubricants that can provide the high-level performance needed in food processing. That’s because Synesstic™ AN basestocks are pure hydrocarbon materials that do not have any ester linkages and contain an aromatic group, offering the potential stability of a PAO and the solubility effects of an ester.
These characteristics make Synesstic™ AN base stocks particularly well-suited for use as a blend stock in synthetic lubricant applications that require high stability under extreme operating conditions.
Proven Advantages
Across a broad spectrum of tests, Synesstic™ AN basestocks demonstrate their performance capabilities and versatility either as an automotive or industrial lubricant. They can be used as a 100-percent base oil or blended with other fluids as a performance enhancer.
The solubility of Synesstic™ AN basestocks can be demonstrated in aniline testing, where two equal volumes of aniline and a sample are stirred and heated at a controlled rate. After the materials become miscible, the mixture is cooled to find the temperature at which they separate – the aniline point. The aniline points for Synesstic™ AN base stocks are similar to esters, and they can therefore be used to improve additive solvency in PAO blends (
Figure 1).
Figure 1.
In typical applications, some degree of seal swell is desirable to ensure a good fit for seals and prevent lube leakage. Since some seal shrinkage can be seen with the use of PAO, esters are often used with PAO to counteract the shrinkage. Synesstic™ AN-5 demonstrates seal swelling similar to that of esters. Overall, alkylated naphthalenes are good alternatives to esters to control seal swell (
Figure 2).
Figure 2.
The Rotary Pressure Vessel Oxidation Test (RPVOT), used to measure the oxidation resistance of oils for industrial applications, showed that Synesstic™ AN base stocks can actually improve the oxidative performance of AN/PAO blends. The test oxidizes oils in the presence of pressurized oxygen and copper wire catalyst at 150ºC. The time taken for the pressure to drop from 90 psi to 65 psi is a measure of the test fluid’s resistance to oxidation.
The observed convex curve shows that Synesstic™ AN base stocks have a synergistic effect on co-basestocks – improving the oxidation performance of the blend to a greater extent than would be expected (
Figure 3).
Figure 3.
Many lubricant additives, in order to be effective, need to attach to the metal surface of the equipment being lubricated. When esters are used in a formulation, they are also attracted to the surface due to their polarity and compete with the additives. Synesstic™ AN base stocks are less polar and not as attracted to the metal surface, enabling greater effectiveness of additives in lubricant formulations (
Figure 4).
Figure 4.
Focus on Food Grade
In food grade-specific testing, the addition of Synesstic™ AN base stocks to PAO increases overall blend solubility, cleanliness and oxidation performance in formulated industrial oils.
Three oils formulated with a general food grade additive package were measured for thermal stability in the Cincinnati Milacron Test. Clean, polished, pre-weighed copper and steel rods are placed in a 250 milliliter (ml) beaker, which contains 200 ml of the oil sample. The rods are completely below the surface of the oil and in contact with each other.
The samples are placed in an electric oven at 135°C (275ºF) for 168 hours. The results show that while the all-PAO formulation delivers good sludge performance, the addition of Synesstic™ AN 5 and Synesstic™ AN 12 base stocks improve the overall sludge performance (
Figure 5).
Figure 5.
The Rotary Pressure Vessel Oxidation Test (RPVOT) for fully formulated food-grade lubricants blended with PAO and Synesstic™ AN base stocks showed that adding 20 percent Synesstic™ AN 5 or Synesstic™ AN 12 improves the oxidative stability of these food-grade fluids (
Figure 6).
Figure 6.
Grease Performance
In grease testing, Synesstic™ AN base stocks offer significant manufacturing and performance benefits compared with PAO grease.
To demonstrate improved high-temperature life in grease, a test was run using five ball bearings packed with two cubic centimeters of grease and placed in high temperature and load environments. The test ends when the drive power to turn the bearings increases to twice the original value due to lubricant starvation. A grease blended with all Synesstic™ AN 12 showed a six-fold improvement in high-temperature life over an all-PAO grease, at both 140°C and 160°C (
Figure 7).
Figure 7.
Synesstic™ AN base stocks in greases also provide improved thickening efficiency. A test batch using 15 percent Synesstic™ AN 5 in PAO required 13 percent less thickener than an all-PAO grease; while an all-Synesstic™ AN 12 grease needed 30 percent less thickener than a similar all-PAO grease (
Figure 8).
Figure 8.
Summary
For food-grade lubricant formulations, Synesstic™ AN base stocks provide:
•
good thermal and oxidative stability for improved oil life and deposit control
•
good hydrolytic stability for use in high-moisture environments
•
solvency for additives and oxidation products
•
seal compatibility enhancement
•
improved additive effectiveness (when replacing esters)
Visit
www.synesstic.com for more information, as well as to download a brochure and presentation about Synesstic™ AN base stocks for incidental food contact.
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