SULFURIZED OLEFINS AS ANTIWEAR ADDITIVES AND COMPOSITIONS THEREOF

Abstract: Direct reaction products of (1) elemental sulfur and olefins and (2) resultant sulfurized olefins and amine-containing polymers are effective multifunctional lubricant additives providing antiwear, friction-modifying and thermal and oxidative stability to compositions thereof.

Description: This invention relates to sulfurized products prepared by the reaction of a sulfurized olefinic compound and a nitrogen-containing polymeric compound having at least one reactable amine group, e.g., polyisobutenyl succinimide, which are useful as additives to lubricant compositions, various greases and normally liquid hyrocarbyl or hyrocarbyloxy fuels. This invention is particularly directed to a process of preparing these sulfurized products, the products so prepared; their use; and lubricating and fuel compositions containing them. The reaction products prepared in accordance with the invention are highly effective multifunctional antiwear additives which also provide surprisingly improved thermal and oxidative stability coupled with good frictional modifying characteristics. The use of amine-containing polymeric succinimides has found widespread use in both fuels and lubricants as dispersants and detergent additives. U.S. Patent 3,600,327 teaches reacting sulfur with olefin polymers and subsequently reacting the product thereof with primary, secondary or tertiary amines; and discloses mixtures of sulfurized additive products and soluble amines. This invention provides a multifunctional additive product having antiwear, friction modifying, thermal and oxidative stability characteristics, suitable for use in an oil of lubricating viscosity or a grease prepared therefrom or in a liquid hydrocarbyl or hydrocarbyloxy fuel, preparable by (1) reacting an olefinic hydrocarbyl compound having at least one olefinic double bond with elemental sulfur in a molar ratio of sulfur to olefinic hydrocarbyl compound from 1.7:1 to 2.3:1 at a pressure from 2070 to 6200 kPa (300 to 900 psi) and a temperature from 140 to l80°C, the reaction product containing at least 40 wt % sulfur, preferably up to 55 wt. % sulfur, and (2) reacting at a temperature from 30° to l50°C the product of (1) with a nitrogen-containing polymeric compound having at least one reactable amine group wherein the weight ratio of the nitrogen-containing compound to the sulfurized olefin is from 1:40 to 1:1. Compositions containing small concentrations of these reaction products possess excellent antiwear properties and have significantly improved thermal and oxidative stability. Moreover, the sulfurized olefinic amine-containing polymers unexpectedly demonstrate significantly enhanced frictional properties. This frictional property is especially noted as a reduction in drag of the roller bearings in key lubricant performance tests. This invention further provides a process for the preparation of a multifunctional additive product as aforesaid, which process comprises: (1) reacting an olefinic hydrocarbyl compound having at least one olefinic double bond with elemental sulfur in a molar ratio of sulfur to olefinic hydrocarbyl compound from 1 7:1 to 2.3:1 at a pressure from 2070 to 6200 kPa (300 to 900 psi) and a temperature from 140 to l80°C to produce a reaction product containing at least 40 wt % of sulfur, preferably up to 55 wt % of sulfur; and (2) reacting at a temperature from 30° to l50°C the product of (1) with a nitrogen-containing polymeric compound having at least one reactable amine group wherein the weight ratio of the nitrogen-containing compound to the sulfurised olefin is from 1:40 to 1:1. It is believed that this concept can be extended to the reaction of sulfurized olefins with polymeric esters, polymeric ester/amides, and/or borated polymeric esters and/or amide dispersants to form other improved and novel products. In accordance with a preferred aspect of this invention, step (1) is carried out in the presence of a rate accelerating catalyst, selected from n-butylamine, di-n-butylamine, n-octylamine, triethylamine, diisopropylamine, cyclohexylamine, dicyclohexylamine, quinoline and attapulgite acid clay or a mixture thereof. The invention also provides a composition comprising a major proportion of an oil of lubricating viscosity or a grease prepared therefrom or a liquid hydrocarbyl or hydrocarbyloxy fuel and a minor proportion of an additive of the invention as herein defined. This invention further provides the use of an additive of the invention as herein defined to modify the friction properties of an oil of lubricating viscosity or a grease prepared therefrom or a liquid hydrocarbyl or hydrocarbyloxy fuel. Olefinic hydrocarbyl compounds useful in the present invention may suitably contain from 2 to 36 carbon atoms and may be stright, branched chain or cyclic compounds with terminal or internal double bonds. Desirably, the olefinic hydrocarbyl compound comprises from 2 to 8 or more carbon atoms; for example, ethylene, propylene, 1-butene, cis - or trans -2-butene, isobutylene, diisobutylene, triisobutylene, pentene, cyclopentene, hexene, cyclohexene, octene,1-decene, butadiene, isoprene, divinylbenzene, pinene, p-menthene, limonene, or a mixture thereof. In general, a C 3 to C 6 olefin or a mixture thereof, is preferred and, more preferably, butylenes are desirable for preparing the sulfurized products embodied herein because the combined sulfur content of the product decreases with increasing carbon content and the miscibility of the product with oil is lower in the case of propylene and ethylene derivatives. In some embodiments of the invention isobutylene is particularly preferred as the predominant olefinic reactant, but it may be employed, desirably in major proportions, in mixtures containing one or more other olefins; moreover substantial proportions of saturated aliphatic hydrocarbons, as exemplified by methane, ethane, propane, butane, pentane, may be contained in the olefinic feed. Such alkanes are preferably present in minor proportions in most instances to avoid unnecessary dilution of the reaction since they neither react nor remain in the product, but are expelled in the off-gases or by subsequent distillation. Such mixed feed can substantially improve the economics of the process since such streams are of lower value than a stream of, for example, relatively pure isobutylene. Volatile olefins are often readily available in liquid form, and it is usually desirable to utilize olefinic liquids which are vaporized by the heat of reaction, since such evaporation provides a substantial cooling effect that permits the flow of water for cooling the reactor to be reduced considerably for greater economy. Also there are indications that the use of a volatile liquid olefin reactant may have the unexpected and desirable effect of lowering the viscosity of the final product. The molar ratio of sulfur to olefin is from 1.7:1 to 2.3:1. Notably in the case of butylene, the optimum ratio preferably is from 1.9:1 to 2.1:1 and, under some circumstances, ratios from 1.95:1 to 2.05:1 are used. The reaction temperature is from 140 to 180°C, preferably from 158 to 165 or 170°C and most preferably is l60°C (e.g., 159-161°C). The reaction pressure is from 2070 to 6200 kPa (300 to 900 psi), the preferred pressures are from 5170 to 5320 kPa (750 to 850 psi). The reaction may be carried out in the absence of added hydrogen sulfide (H 2 S). Any suitable nitrogen-containing polymeric substance may be used herein as long as it has at least one free amine group. The polymeric substance may have a molecular weight of from 300 to 30,000. Especially preferred are the reaction products of alkenyl succinic anhydrides or alkenyl succinic acids with polyalkylene amines. Particularly preferred is polyisobutenyl succinic anhydride with tetraethylene pentamine. The polyalkyleneamines include those of the general formula: wherein n is preferably 2 or 3 and m is 0 to 10. Examples of such polyalkyleneamines include ethylenediamine, diethylene triamine, tetraethylene pentamine, octaethylene nonamine, tetrapropylene pentamine. The sulfurized olefin and the nitrogen-containing polymeric material are usually reacted in less than molar or stoichiometric amounts. However, molar amounts may be used if desired. The pressures and temperatures of reaction between the nitrogen-containing compound and the sulfurized olefinic material may be any under which the reaction may be carried out conveniently, such as from 40 to 150°C or more, preferably from 65 to l20°C. However, elevated temperatures and pressures may be used if desired. A slow nitrogen purge can also be used to aid in the elimination of any volatile sulfur-containing byproducts. The weight ratio of the nitrogen containing compound, e.g., succinimide, to sulfurized olefin is from 1:40 to 1:1. However, weight ratios of 1:20 to 1:5 can be effectively used with 1:10 to 1:14 often being preferred. The reaction product can be optionally filtered before use. A mixture of products is believed to form during the reaction in accordance with the invention leading to a surprising multifunctional product with antiwear properties, improved thermal and oxidative stability and improved friction properties especially under severe service. If instead of prereacting the sulfurized olefin and polymeric amine prior to formulation of a lubricant, the sulfurized olefin is blended first, followed by other nitrogen and/or phosphorus components, followed by the polymeric amine undesirable results are obtained. It is critical to prereact the above two components. Merely adding the components at different times to a lubricant or under non-reaction conditions does not lead to the desirable results demonstrated by this invention. The compositions hereof may comprise any oleaginous materials where protection against excessive wear under operating conditions is required, but which normally exhibit insufficient anti-corrosion or antiwear properties. Especially suitable for use with the additives of this invention are liquid hydrocarbon oils of lubricating viscosity. Lubricant oils, improved in accordance with the present invention, may be of any suitable lubricating viscosity. In general, the lubricant compositions may comprise any mineral or synthetic oil of lubricating viscosity or mixtures thereof. The additives of this invention are especially useful in greases and in automotive fluids such as brake fluids and power brake fluids, transmission fluids, Power steering fluids, engine oils, various hydraulic fluids and gear oils and in liquid hydrocarbyl fuels and hydrocarbyloxy fuels. In instances where synthetic oils are desired in preference to refined petroleum or mineral oil they may be employed alone or in combination with a mineral oil. They may also be used as the vehicle or base of grease compositions. Typical synthetic lubricants include polyisobutylene, polybutenes, hydrogenated polydecenes, polypropylene glycol, polyethylene glycol, trimethylol propane esters, neopentyl and pentaerythritol esters of carboxylic acids, di(2-ethylhexyl) sebacate, di(2-ethylhexyl) adipate, dibutyl phthalate, fluorocarbons, silicate esters, silanes, esters of phosphorus-containing acids, liquid ureas, ferrocene derivatives, hydrogenated mineral oils, chain-type polyphenols, siloxanes and silicones (polysiloxanes), alkyl-substituted diphenyl ethers typified by a butyl-substituted bis(p-phenoxy phenyl) ether, phenoxy phenylethers, dialkylbenzenes, etc. As hereinbefore indicated, the aforementioned additives can be incorporated as additives in grease compositions. When high temperature stability is not a requirement of the finished grease, mineral oils having a viscosity of at least 40 SSU at 66°C (150°F) are useful. Otherwise those falling within the range of from 60 SSU to 6,000 SSU at 38°C (100°F) may be employed. The lubricating compositions of the improved greases of the present invention, containing the above-described additives, are combined with a grease forming quantity of a thickening agent. For this purpose, a wide variety of materials can be dispersed in the lubricating oil in grease-forming qualities in such degree as to impart to the resulting grease composition the desired consistency. Exemplary of the thickening agents that may be employed in the grease formulation are metal soaps as well as non-soap thickeners, such as surface-modified clays and silicas, aryl ureas, calcium complexes and similar materials. In general, grease thickeners are employed which do not melt or dissolve when used at the required temperature within a particular environment; however, in all other respects, any material which is normally employed for thickening or gelling oleaginous fluids or forming greases may be used in the present invention. Generally the lubricants and fuels of the present invention contain an amount of the sulfurized product effective to improve antiwear properties and oxidation and friction modifying characteristics. Normally this amount is 0.01-20%, preferably 0.1-10%, of the total weight of the lubricant or fuel. The invention also contemplates the use of other additives in amounts up to 20 wt.% for their intended purpose in combination with the sulfurized olefin product. Such additives include, for example, detergents and dispersants of the ash-producing or ashless type, corrosion-inhibiting agents, auxiliary oxidation-inhibiting agents, pour point depression agents, auxiliary extreme pressure agents, color stabilizers and anti-foam agents. Other such additives include but are not limited to phosphorus, sulfur, nitrogen and/or oxygenated additives, including phosphorodithioates, phosphates, phosphites, imidazolines, oxazolines, esters, metallic phenates, metallic sulfonates, olefin copolymers and the like. The following examples further illustrate the present invention. Example 1 Sulfurized Olefin-Succinimide Reaction Product Three hundred grams of sulfurized olefin made by the sulfurization of isobutylene with elemental sulfur at super atmospheric pressure at 160°C using a sulfur to olefin mole ratio of approximately 2:1 and 0.1% butylamine catalyst and 30g of a 50% concentrate in diluent oil of a polyisobutenyl succinimide (made by reacting polyisobutenyl (M.W.900) succininic anhydride with tetraethylenepentamine) were charged to a reactor equipped with heater, agitator and provision for providing a nitrogen sparge. The reactants were heated to 140°C for four hours with nitrogen sparge and then cooled to 120°C for two additional hours under reduced pressure to remove any volatile materials. The product was cooled and filtered through diatomaceous earth to form a liquid possessing a typical sulfurized olefin odor. (1) Test oil is a fully formulated mineral oil containing additionally corrosion inhibiting, copper passivating and phosphorus-containing antiwear additives. (2) Basis used for rating frictional drag of roller bearing in L-37 test: 0 - Very loose turning bearing with no frictional drag. 2 - Loose turning bearing, but not as loose as rating of 0. 3 - Some frictional drag noted when turning bearing. 4 - Definite bearing drag noted. 5 - Bearing turns with significant drag, difficulty and roughness. NOTE:Category 4 and 5 exhibit significant stick-slip properties. As can be clearly seen from the test results, the novel reaction products significantly reduce the friction of the CRC L-37 test bearings when compared to the identical untreated sulfurized isobutylene prior to reaction with the polymeric amine. The CRC L-37 test is a laboratory performance test for automotive gear lubricants in axles at high-speed, low-torque and low-speed, high-torque conditions. The procedure uses a hypoid differential housing assembly, 5.86 ratio, standard differential with uncoated gear and drive pinion. However, a test run may be made using a coated gear and drive pinion. Prior to each test the entire axle assembly is cleaned, no disassembly is allowed. This test is a candidate test for ASTM Special Technical Publication 512-637. The following is a brief summary of test procedure: Sequence 1 - High-speed, low-torque operation: The test unit is charged with 2.84 liters (six pints) of test oil, then run for 100 minutes at 440 wheel rpm and 535 N-M (4730 in-lb) torque per wheel. During this time, the axle sump temperature is maintained at 147 ± 1.5°C (297 ± 3°F). For purposes of cooling, a water spray over the differential housing is used. At the end of the 100 minute break-in an optional visual inspection is permitted. Note 2 : For purposes of evaluating lower viscosity lubricants (i.e., 75W types), the test lubricant temperature is controlled at 105 ± 1.1°C (220 ± 3°F). Sequence 2 - Low-speed, high-torque operation: Run the test axle for 24 hours at 80 wheel rpm, 2.35 kN-M (20,900 in-lb) torque per wheel and an axle sump temperature of 135 ± 1/4°C (275 ± 3°F). Note 3 : For purposes of evaluating lower viscosity lubricants (i.e., 75W types), the sump temperature is controlled at 93 ± 1.0°C (200 ± 3°F). At the end of the low-speed, high-torque phase, the test is completed; the ring and pinion are removed and rated for various forms of gear distress. The high temperature stability test is performed by immersing a freshly polished steel coupon in the test fluid and raising the temperature to 135°C (275°F) for a period of 96 hours and then examining the steel rod and lubricating fluid visually for evidence of thermal oxidative decomposition. NOTE:Test oil of Table 2 is identical to fully formulated test oil described in Table 1. As can be clearly seen from severe oxidation and thermal stability test results of Table 2, the reaction product of Example 1 possesses significantly improved thermal and oxidative stability properties when compared to the unreacted sulfurized isobutylene.

Claims: A multifunctional additive product having antiwear, friction modifying, thermal and oxidative stability characteristics, suitable for use in an oil of lubricating viscosity or a grease prepared therefrom or in a liquid hydrocarbyl or hydrocarbyloxy fuel, preparable by (1) reacting an olefinic hydrocarbyl compound having at least one olefinic double bond with elemental sulphur in a molar ratio of sulphur to olefinic hydrocarbyl compound from 1.7:1 to 2.3:1 at a pressure from 2070 to 6200 KPa(300 to 900 psi) and a temperature from 140 to l80⁰C, the reaction product containing at least 40 wt.% sulphur and (2) reacting at a temperature from 30° to l50⁰C the product of (1) with a nitrogen-containing polymeric compound having at least one reactable amine group wherein the weight ratio of the nitrogen-containing compound to the sulphurised olefin is from 1:40 to 1:1. An additive product according to claim 1 wherein the pressure in step (1) is from 5140 to 5820 kPa (750 to 850 psi); the temperature is from 158 to 165⁰C; the molar ratio of sulphur to olefin varies from 1.9:1 to 2.1; resulting in a reaction product containing from 40 to 55 wt.% of sulphur and wherein the weight ratio of nitrogen-containing compound to sulphurised olefin in step (2) is from 1:20 to 1:5. An additive product according to claim 1 or 2 wherein step (1) is carried out in the presence of a rate accelerating catalyst which is n-butylamine, di-n-butylamine, n-octylamine, triethylamine, diisopropylamine, cyclohexylamine, dicyclohexylamine, quinoline, attapulgite acid clay or a mixture thereof. An additive product according to any of the preceding claims wherein the olefinic compound is ethylene, propylene, 1-butene, cis- or trans -2-butene, isobutylene, diisobutylene, triisobutylene, pentene, cyclopentene, hexene, cyclohexene, octene, 1-decene, butadiene, isoprene, divinyl benzene, pinene, p-menthene, limonene or a mixture thereof. An additive product according to any of the preceding claims wherein the nitrogen-containing polymeric compound is the reaction product of an alkenyl succinic anhydride or acid and a polyalkyleneamine of the formula: wherein n is 2 or 3 and m is 0 to 10. An additive product according to any of the preceding claims wherein the reaction product of step (1) is prepared in the absence of added H 2 S. A process for the preparation of a multifunctional additive product having antiwear, friction modifying, thermal and oxidative stability characteristics suitable for use in an oil of lubricating viscosity or a grease prepared therefrom or in a liquid hydrocarbyl or hydrocarbyloxy fuel, which process comprises: (1) reacting an olefinic hydrocarbyl compound having at least one olefinic double bond with elemental sulphur in a molar ratio of sulphur to olefinic hydrocarbyl compound from 1.7:1 to 2.3:1 at a pressure from 2070 to 6200 kPa (300 to 900 psi) and a temperature from 140 to l80°C to produce a reaction product containing at least 40 wt.% sulphur; and (2) reacting (at a temperature from 30 to 150°C the product of (1) with a nitrogen containing polymeric compound having at least one reactable amine group wherein the weight ratio of the nitrogen-containing compound to the sulphurised olefin is from 1:40 to 1:1. A process according to claim 7 wherein the pressure in step (1) is from 5170 to 5860 kPa ( 750 to 850 psi); the temperature is from 158 to 165°C; the molar ratio of sulphur to olefin varies from 1.9:1 to 2.1:1 resulting in a reaction product containing from 40 to 55.wt% of sulphur and wherein the weight ratio of nitrogen-containing compound to sulphurised olefin is from 1:20 to 1:5. A process according to claim 7 or 8 wherein step (1) is carried out in the presence of a rate accelerating catalyst which is n-butylamine, di-n-butylamine, n-octylamine, triethylamine, diisopropylamine, cyclohexylamine, dicyclohexylamine, quinoline, attapulgite acid clay or a mixture thereof. A process according to claim 7, 8 or 9 wherein the olefinic compound is ethylene, propylene, 1-butene, cis- or trans -2-butene, isobutylene, diisobutylene, triisobutylene, pentene, cyclopentene, hexene, cyclohexene, octene, 1-decene, butadiene, isoprene, divinyl benzene, pinene, p -menthene, limonene or a mixture thereof. A process according to claim 7, 8, 9 or 10 wherein the nitrogen-containing polymeric substance is the reaction product of an alkenyl succinic anhydride or acid and a polyalkyleneamine of the formula: wherein n is 2 or 3 and m is 0 to 10. A process according to any of claims 7 to 11 wherein the product of step (1) is prepared in the absence of added H 2 S. A composition comprising a major proportion of an oil of lubricating viscosity or a grease prepared therefrom or a liquid hydrocarbyl or hydrocarbyloxy fuel and a minor proportion of the additive of any of claims 1 to 6. A composition according to claim 13 wherein the oil is a mineral oil, synthetic oil or a mixture thereof. A composition according to claim 13 wherein the fuel is a liquid hydrocarbyl or hydrocarbyloxy fuel. A composition according to claim 13 wherein the additive is present in an amount from 0.01 to 20 wt%. The use of an additive according to any of claims 1 to 6 to modify the friction properties of an oil of lubricating viscosity or a grease prepared therefrom or a liquid hydrocarbyl or hydrocarbyloxy fuel.

Inventors: HORODYSKY, ANDREW GENE, LAW, DEREK ALWYN
Applicants: MOBIL OIL CORPORATION
Application year: 1986
Main classification: C10M135
IPC codes: C10L1, C10N30, C10L10, C08F8, C10M159, C10N50, C10M135