EXTREME PRESSURE ADDITIVE COMBINATION, AND LUBRICANTS CONTAINING IT

Abstract: The load-bearing and/or extreme pressure ("EP") performance of a lubricating composition is enhanced by the inclusion of the combination of a metal-containing EP additive and a high molecular weight hydrocarbon polymer. The metal-containing EP additive may be an organo-Mo compound, and the hydrocarbon polymer may be a polyisobutene, preferably of molecular weight of about one million.

Description: EXTREME PRESSURE ADDITIVE COMBINATION. AND LUBRICANTS CONTAINING IT The present invention relates to an additive combination for enhancing the extreme- pressure ("EP") performance of lubricants and or for improving the load-carrying performance of lubricants, and to lubricants containing the additive combination. The present invention provides an additive combination for enhancing the extreme- pressure ("EP") and/or load-carrying properties of a lubricating composition comprising a metal- containing friction-modifying and/or EP additive and a hydrocarbon polymer having a weight average molecular weight of at least 75,000. The said polymer may be or may comprise a polyalkene. The polymer may be or may comprise polyisoalkene. The polyisoalkene may be or may comprise polyisobutene. The polymer may have a weight average molecular weight of at least 100,000, preferably at least 500,000. The polymer may have a weight average molecular weight which is at least predominantly less than 10,000,000, preferably at least predominantly less than 5,000,000, more preferably at least predominantly less than 2,500,000. The metal of the metal-containing friction-modifying and/or EP additive may be molybdenum. The molybdenum may be provided as an organic compound containing molybdenum. The amount of the hydrocarbon polymer may be such as to provide a concentration thereof, when formulated into a lubricating composition, of at least 0.001 wt.%, preferably at least 0.005 wt.%, more preferably at least 0.025 weight percent, based on the total weight of the lubricating composition. The amount of the hydrocarbon polymer may be such as to provide a concentration thereof, when formulated into a lubricating composition, not exceeding 1.0 wt.%, preferably no greater than 0.75 wt.%, more preferably no greater than 0.50 wt.%, based on the total weight of the lubricating composition. The additive combination may additionally contain one or more components selected from : metal-free extreme-pressure agents, anti-wear agents, antioxidants, lubricity agents, metal deactivators, metal passivators, dispersants, detergents, anti-staining additives, detergent-inhibitors, rust inhibitors, filtration reagents, anti-foam agents, defoamers, viscosity index improvers, demulsifiers. emulsifiers, bitumen, organic fats, esters, alcohols, soaps, thickeners, pour-point depressants, flow improvers. The invention also provides a lubricating composition comprising a lubricating basestock and the combination as described herein. The lubricating basestock may comprise a liquid lubricating basestock. The liquid lubricating basestock may be a hydrocarbon mixture. The lubricating composition may comprise a grease-forming thickener. The present invention is based on the surprising discovery that the incorporation in a lubricating composition of relatively high molecular weight hydrocarbon polymers and a metal- containing friction modifier and/or EP additive greatly increases the extreme pressure and/or load-carrying properties of the lubricating composition. The discovery is all the more remarkable in that the said hydrocarbon polymer, which exhibits no significant propensity to increase the EP and/or load bearing capabilities of a lubricating composition, enhances these capabilities even at quite low concentrations when the composition also contains a metal- containing friction-modifier and/or EP additive. The invention is now further illustrated with reference to some non -limitative examples and comparative examples. EXAMPLE 1 Eight samples of lubricating composition for open gears were prepared. The components of the compositions were as follows : SUBSTITUTE SHEET (RULΕ 26) Base Oil Brightstock; Base Wax A crude petrolatum serving as part of the lubricating basestock, and obtainable from Witco under the tradename AMBERTECH 2; Thickener 1 A polyisobutene of weight average molecular weight about 5,700, melting temperature about 70°C, used as a viscosity modifier, and obtainable from BP Chemicals under the tradename HYVIS 2000; Thickener 2 An aliphatic hydrocarbon resin of weight average molecular weight about 1700, used as a viscosity modifier and obtainable from Exxon Chemical under the tradename ESCOREZ 1102; Anti-Rust Agent An anti-rust agent, or rust inhibitor booster. A suitable agent is obtainable from Ethyl Petroleum Additives Limited under the tradename HITECH 536 and is believed to be an amine salt of an organic dibasic acid (or an alkylene succinimide); EP Agent A molybdenum-containing EP agent. A suitable agent is obtainable from R.T. Vanderbilt Co. Inc. under the trade name MOLYVAN L, which is based on molybdenum di(2-ethylhexyl) phosphorodithioate: Hydrocarbon Polymer A high molecular weight polyisobutene polymer. A suitable polymer is available from Exxon Chemical under the trade name PARATAC, which is a 6 wt.% solution of polyisobutene in mineral oil wherein the polyisobutene has an average molecular weight of about 10^. The samples were tested for extreme pressure properties in a standard Shell 4-ball test machine. The results are summarised in Table 1, wherein all concentrations are expressed in parts by weight except for sample B which was prepared by adding 1 part by weight hydrocarbon polymer to 100 parts by weight of sample A A comparison of sample A with samples B and C shows that the inclusion of 1 weight percent of the 6 wt.% hydrocarbon polymer solution (i.e. 0.06 wt.% hydrocarbon polymer) in samples B and C increases the weld load by some 14.9% and 8.6% (respectively) relative to the weld load for sample A. The increased weld loads .are substantial and remarkable, given the fact that the improvement is due to the presence of the hydrocarbon polymer, and that (moreover) it is present in a very low concentration. Sample D is similar to sample A in that no hydrocarbon polymer is present. However, the concentration of thickener 1, a low molecular weight hydrocarbon polymer, approximately is doubled in sample D relative to that in sample A. The weld load with sample D was slightly lower than with sample A, thereby demonstrating that thickener 1, even in high concentrations, does not enhance the EP performance of the samples. Samples E, F, G and H are higher viscosity samples, useful for lubricating open gears, wire ropes, cables and other equipment for which an adherent lubricating composition is desirable. A comparison of samples E and F reveals that eliminating the hydrocarbon polymer solution and increasing the concentration of the EP agent from 0.75 wt.% to 1.00 wt.% actually decreases the weld load by some 11%. Sample G is similar to sample F except that the concentration of anti-rust agent is increased from 0.10 wt.% to 0.30 wt.%. In the presence of 1.0 wt.% EP agent but with zero hydrocarbon polymer (sample G), the weld load increased from 211 kg (sample F) to 225 kg (sample G). A further increase in the amount of anti-rust agent to 0.50 wt.% (the same concentration as in samples A to D) and the provision of 1.0 wt.% hydrocarbon polymer solution increased the weld load to 235 kg (sample U), a figure comparable with that attained with the similar, but liquid, lubricating composition C. The data in Table 1 show that very small concentrations of hydrocarbon polymer markedly improve the EP performance of lubricating compositions comprising a metal- containing EP agent. EXAMPLE 3 Reference is now made to Table 2 wherein the formulations of sample blends I - Q are given. The same components were used as in the blends or lubricating compositions of Table 1. except that blends L and Q contained a volatile white spirit thinner. A suitable volatile white spirit is available under the trade-name VARSOL 40 and supplied by Esso Petroleum Company. The volatile thinner enables the otherwise grease-like blends to be applied to the surfaces to be lubricated either by brush (or similar applicator) or in the form of an aerosol spray. After application, the volatile white spirit thinner evaporates leaving behind the non-volatile lubricating composition. The white spirit-thinned blends are useful for applying to machine parts which are not easily accessible. The blends (-after evaporation of any white spirit) were sufficiently thick (semi-solid) to be useful for lubricating open gears, cables, wire ropes, chains, etc. Blends I, J, K and L are virtually the same as blends M, N, P and respectively, except that the former include 1.0 wt.% hydrocarbon polymer-solution (of which 6% is polyisobutene of weight average molecular weight of about 1,000,000). The blends I to Q were submitted to 4-ball weld and wear tests. The results are summarised in Table 3. TABLE 3 SAMPLE BLEND WELD LOAD (kg) WEAR SCAR (mm) I 165 0.30 M 185 0.63 J 230 0.29 N 240 0.41 K 240 0.45 P 260 0.68 L 190 044 Q 210 0.43 In each instance, it is observed that the addition of 0.06 wt.% hydrocarbon polymer (polyisobutene of weight average molecular weight 1 million, approx.) to a blend increased the weld load by from 10 to 20 kg, and also significantly reduced the size of the weld scar. The data demonstrate the enhanced load-carrying and EP-performance of a lubricating -composition comprising a metal-containing friction modifier when a high moleculaur weight hydrocarbon polymer is incorporated therewith even in relatively minute concentrations. EXAMPLE 3 Some blends of liquid lubricating compositions were made up using components of the s.ample blends of Examples 1, 2 and 3, but also, in addition, an organic sulfur-containing EP additive. The organic EP additive used for the following samples blends was available under the tradename ANGLAMOL 33, supplied by Lubrizol, .and is believed to be an organic sulfide containing chemically-active sulfur moieties, poossibly of the alkyl sulfide type. The compositions of the sample blends (R, S, T. U) are given in Table 4. TABLE 4 SAMPLE BLEND COMPONENT (grams) R S T U Base Oil 980.00 980.00 980.00 980.00 EP Agent 10.00 - 10.00 - Organic EP Additive - 10.00 • 10.00 Hydrocarbon - - 10.00 10.00 Polymer (6% Solution) The blends of Table 4 are liquid lubricating compositions and are suitable for the lubrication of industrial machinery and gears in general wherein high loadings prevail between relatively-moving parts during operation thereof. Blends T and U were similar to blends R and S respectively, except that the latter contain no hydrocarbon polymer solution while the former each contained 10 g hydrocarbon polymer solution, corresponding to 0.06 wt.% hydrocarbon polymer content. The blends of Table 4 were submitted to standard 4-ball weld and wear tests. The results are given in Table 5. TABLE 5 SAMPLE BLEND WELD LOAD (kg) WEAR SCAR (mm) R 260 0.39 S 295 0.36 T 370 0.60 U 365 0.60 The data in Table 5 demonstrate that the addition of minute amounts of hydrocarbon polymer enhances the EP-performance when the blend contains a metal-containing EP additive (blends R and T), but that this type of enhancement is not realised in the absence of the metal- containing EP additive even when a corresponding amount of organic EP additive is included in the composition (e.g., as evidenced by the performance of samples S and U). The foregoing examples demonstrate that small amounts of high molecular weight hydrocarbon polymer potentiates the EP-performance of metal-containing EP additives in liquid and semi-solid lubricating compositions. The potentiating effect is, however, not observed with organo-sulfide EP agents. The reason for the synergistic interaction of the hydrocarbon polymer with the metal-containing EP additive is not known, but clearly the effect can be utilised to maintain and extend the useful working life of relatively moving loaded parts and/or to enable them to resist increased loadings.

Claims: C MMS: 1. An additive combination for enhancing the extreme-pressure ("EP") and/or load-carrying properties of a lubricating composition comprising a metal-containing friction- modifying and/or EP additive and a hydrocarbon polymer having a weight average molecular weight of at least 75,000. 2. The combination of claim 1 wherein the said polymer is or comprises a polyalkene, preferably a polyisoalkene. 3. The combination of claim 2 wherein the polyisoalkene is or comprises polyisobutene. 4. The combination of any one of claims 1 to 3 wherein the polymer has a weight average molecular weight of at least 100,000, preferably at least 500,000. 5. The combination of any one of the preceding claims wherein the polymer has a weight average molecular weight which is at least predominantly less than 10,000,000, preferably at least predominantly less than 5,000,000. more preferably at least predominantly less than 2,500,000. 6. The combination of any one of the preceding claims wherein the metal of the metal-containing friction-modifying andor EP additive is molybdenum. 7. The combination as in any one of the preceding claims wherein the amount of the hydrocarbon polymer is such as to provide a concentration thereof, when formulated into a lubricating composition, of at least 0.001 wt.%, preferably at least 0.005 wt.%, more preferably at least 0.025 weight percent, based on the total weight of the lubricating composition. 8. The combination of any one of the preceding claims wherein the amount of the hydrocarbon polymer is such as to provide a concentration thereof, when formulated into a lubricating composition, not exceeding 1.0 wt.%, preferably no greater than 0.75 wt.%, more preferably no greater than 0.50 wt.%, based on the total weight of the lubricating composition. 9. A lubricating composition comprising a lubricating basestock and the combination of any one of the preceding claims. 10. The lubricating composition of claim 9 additionally comprising a grease- forming thickener.

Inventors: AIKEN ALISON JANE, GRAHAM JOHN KENNETH, AIKEN, ALISON, JANE, GRAHAM, JOHN, KENNETH
Applicants: AIKEN ALISON JANE, EXXON RESEARCH ENGINEERING CO, GRAHAM JOHN KENNETH, AIKEN, ALISON, JANE, EXXON RESEARCH AND ENGINEERING COMPANY, GRAHAM, JOHN, KENNETH
Application year: 1996
Main classification: C10M161
IPC codes: C10M161, C10M169