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ANTIWEAR DISPERSANT TECHNOLOGY

2 U.S.Patents issued, both assigned to R. T. Vanderbilt.

By Thomas J. Karol, Ph.D. and Steven G. Donnelly (Manager of Technical Services)

Dispersants have been around since the early 1960s when motor oils went from "non-detergent" to formulated oils. Dispersants are used in lubricant formulations to prevent deposits such as sludge and varnish which otherwise might accumulate on metal surfaces and interfere with the performance of the machinery. Oil passages can become "plugged" and cause catastrophic damage to the equipment. Dispersants function by coordinating with either deposit or deposit precursors, and holding them in the oil. This allows deposit precursors to be removed when the oil is changed.

Dispersants are typically a polyisobutenylsuccinic acid derivative. The most widely used group is the succinimide, which can be further divided into mono-succinimide and bis-succinimide dispersants.

During the 1980s, the literature showed that antioxidants could be linked to the dispersant and provide effective antioxidant performance. One example was the polyisobutenylsuccinimide linked to a simple t-butylphenol antioxidant. Only bis-(t-butylphenols) are typically used in motor oil because the simple phenol is too volatile for high engine temperatures and is lost due to evaporation. When the more cost effective simple t-butylphenol is linked to the dispersant, the volatility is eliminated.

The R.T. Vanderbilt Company has patented the technology to modify the dispersant to "carry" antiwear performance. Thiadiazoles have been demonstrated as effective antiwear performers in engine evaluation (VANLUBE 871, motor oil antiwear additive). Thiadiazoles do not form a sacrificial coating as do the phosphorus additives (e.g. zinc dithiophosphate). It is known that they coordinate with the metal surface directly rather than decompose to form the protective layer (as do the phosphate type antiwear additives). It is believed that they might be called "lubricity additives" since in their coordination with the metal surface, they maintain an oil film with their alkyl substitution. This is similar to water on a car surface with and without soap. With soap, the water forms a film; with no soap, the water beads up. The thiadiazole is a very stable additive and resists oxidation. This allows the stressed or oxidized oil the ability to maintain good wear performance.

ANTIWEAR DISPERSANT TECHNOLOGY


2 U.S. patents issued, both to R.T. Vanderbilt.

Our wear evaluations (shown below) were performed in an SAE 30 grade base oil with no additives except a zinc dialkyldithiophosphate (ZnDTP). We reduced the amount of ZnDTP from 0.08% P to 0.015% P and ran a 500 pound load Falex Pin and Vee Block 3.5 hour (210 minute) Wear Test.

Mass Percent

	1	2	3	4	5	6	7
Mono-Succinimide Dispersant1	5.0	5.0	5.0	5.0	5.0	5.0	0
ZnDTP2	0.84	0.53	0.32	0.16	0.16	0.16	0.16
Antiwear Dispersant3	0	0	0	0	0	0	5.0
% Phosphorus in blend:	0.08	0.05	0.03	0.015	0.015	0.015	0.015
Falex Pin & Vee Block
(500lb.; 210 minutes)
wt. loss: Pin, mg	90.4	72.4	78.1	1,325	76.5	60.0	51.7
Blocks, mg	1.1	6.0	1.3	166	1.9	2.2	1.9
Total, mg	91.5	78.4	79.4	1,491	78.4	62.2	53.6
Actual Test Time, min	210	210	210	210	210	~150*	210

*Pin broke.

1. OLOA 370 available from the Oronite Division of Chevron Chemical
2. Lubrizol 1395 available from the Lubrizol Corporation
3. Antiwear Dispersant using OLOA 370 and OCD-075, 1:1 molar ratio

It is clear from the above data that the antiwear-dispersant (formulation/column 7) in the low phosphorus oil (0.015% P) surpasses the level of wear performance in the higher phosphorus oil (0.08%P, formulation/column 1).

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