Lubricating Compositions for Industrial Gear Fluids

Abstract

To provide a gear fluid composition for lubricating a driveline, which minimizes sulfur loss and maintains high extreme pressure performance.SOLUTION: A lubricant composition comprising: a) a first polysulfide which is a first polysulfide extreme pressure agent comprising a mixture of C2 to C6 polysulfides that are predominantly trisulfides, and b) a second polysulfide which is a second polysulfide extreme pressure agent comprising a mixture of C10 to C14 polysulfides that are predominantly trisulfides, wherein the first polysulfide has a structure represented by the formula R1-Sx-R2, where R1 and R2 are, independently, C2 to C6 hydrocarbyl groups, x is an integer of at least 2, and x is predominantly 3, the second polysulfide has a structure represented by the formula R3-Sy-R4, where R3 and R4 are, independently, C10 to C14 hydrocarbyl groups, y is an integer of at least 2, and y is predominantly 3, and the weight ratio of sulfur provided by the first and second polysulfides is about 0.3 to about 0.8.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to lubricating compositions for driveline applications, including, for example, gear, axle, and / or power transmission fluids, having improved properties for extreme pressure, friction, and / or sulfur retention. [Background technology]

[0002] Gears, transmissions, and / or axles for heavy-duty or industrial applications generally require lubricants that provide specific frictional characteristics suited to the desired application. For example, axles, transfer cases, differentials, and transmissions are often found in many heavy-duty or industrial vehicles, each requiring their own lubricant composition. In reality, gears and axles in such applications may be operated at full load capacity and / or with frequent stop-and-go operation that places additional stresses and strains on the hardware. Thus, lubricants for heavy-duty or industrial gear and axle applications require additive chemistry to reliably protect the gears and axles under both full load and stop-and-go operating conditions.

[0003] Typically, lubricants for such applications require fluids that meet one or more performance characteristics, such as extreme pressure, antiwear, friction, and / or copper corrosion, to suggest only some of the general requirements of axle or gear fluids. To achieve such performance, many additives may be included in the lubricant. For example, such lubricants often contain sulfurized additives to protect gears and other components from wear and scoring. However, the sulfur additives commonly used in such gear oils tend to be volatile, resulting in a certain amount of sulfur being lost over time. Sulfur loss is undesirable for many reasons, including deteriorated extreme pressure performance as well as potential environmental concerns. Summary of the Invention

[0004] In one approach or embodiment, described herein is a lubricant composition for drivelines that provides good extreme pressure and low sulfur loss. In one aspect, the lubricating composition includes (a) a first polysulfide extreme pressure agent comprising a mixture of C2-C6 polysulfides that are mostly trisulfides, and (b) a second polysulfide extreme pressure agent comprising a mixture of C10-C14 polysulfides that are mostly trisulfides, wherein the weight ratio of sulfur provided by the first polysulfide and the second polysulfide is from about 0.3 to about 0.8.

[0005] In other approaches or embodiments, the lubricant composition of the preceding paragraph may be combined with one or more optional features, approaches, or embodiments. These optional features or embodiments may include one or more of the following: the first and second polysulfides provide the lubricant composition with about 0.2 to about 0.5 weight percent sulfur, and / or the first polysulfide has about 40 to about 50 weight percent sulfur and the second polysulfide has about 18 to about 30 weight percent sulfur, and / or the first polysulfide has about 1 to about 10 mole percent disulfides and about 51 to about 95 mole percent trisulfides, and / or the second polysulfide has about 1 to about 10 mole percent disulfides and about 51 to about 95 mole percent trisulfides, and / or the first polysulfide has a molar ratio of about 1 to about 10 mole percent disulfides and about 51 to about 95 mole percent trisulfides, and / or the first polysulfide has a molar ratio of about 1 to about 10 mole percent disulfides and about 51 to about 95 mole percent trisulfides, x and / or R1 and R2 are each a C4 hydrocarbyl group; and / or the first polysulfide comprises di-tert-butyl polysulfide; and / or the second polysulfide has the structure R3-S yand / or the second polysulfide comprises di-tert-dodecyl polysulfide, and / or the lubricant composition has a sulfur loss of less than about 30 weight percent as measured in accordance with ASTM D2893 and greater than about 200 kgf in accordance with the 4-ball test of ASTM D2596, and / or further comprises from about 0.2 to about 0.4 weight percent of the first polysulfide and from about 0.8 to about 1.2 weight percent of the second polysulfide, and further comprises a weight percent ratio of the first polysulfide to the second polysulfide of from about 0.2 to about 0.38.

[0006] In another approach or embodiment of the present disclosure, described herein is a method of lubricating a driveline to provide good extreme pressure performance and maintain low sulfur losses. In one aspect of this embodiment, the method includes lubricating a driveline component with a lubricating composition including a first polysulfide extreme pressure agent including a mixture of C2-C6 polysulfides that are mostly trisulfides and a second polysulfide extreme pressure agent including a mixture of C10-C14 polysulfides that are mostly trisulfides, wherein the weight ratio of sulfur contributed by the first polysulfide and the second polysulfide is about 0.3 to about 0.8.

[0007] In other approaches or embodiments, the method of the preceding paragraph may be combined with one or more optional steps, features, or embodiments in any combination. These optional features or embodiments of the method may include one or more of the following: the first and second polysulfides provide about 0.2 to about 0.5 weight percent sulfur to the lubricating composition, and / or the first polysulfide has a formula R1-S x -R2, where R1 and R2 are independently a C4 to C6 hydrocarbyl group, x is an integer of at least 2 and a majority of x is 3, and / or the second polysulfide has the structure R3-S y-R4, wherein R3 and R4 are independently a C10 to C14 hydrocarbyl group, y is an integer of at least 2 and a majority of y is 3, and / or the first polysulfide comprises di-tert-butyl polysulfide, and / or the second polysulfide comprises di-tert-dodecyl polysulfide, and / or the lubricant composition has a sulfur loss of less than about 30 weight percent as measured in accordance with ASTM D2893 and greater than about 200 kgf in accordance with the 4-ball test of ASTM D2596.

[0008] In further embodiments or approaches, a use of any embodiment of the lubricants described herein is provided to form a lubricant composition and / or to lubricate a driveline composition and to have a sulfur loss of less than about 30 weight percent as measured in accordance with ASTM D2893 and / or greater than about 200 kgf in accordance with the 4-ball test of ASTM D2596.

[0009] Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The following definitions are provided to clarify the meaning of certain terms used herein.

[0010] The terms "gear oil," "gear fluid," "gear lubricant," "base gear lubricant," "lubricant," "lubricant composition," "lubricating composition," "lubricant," and "lubricating fluid" refer to a finished lubricant product comprising a major amount of a base oil and a minor amount of an additive composition as discussed herein. Such gear fluids are intended for use in extreme pressure conditions, such as in transmissions and gear driven components having metal-to-metal contact, for example, in transmissions, turbines, and / or limited slip differentials.

[0011] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary sense and is known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having a predominantly hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents, the substituted hydrocarbon substituents containing one or more of halo, hydroxyl, alkoxy, mercapto, nitro, nitroso, amino, pyridyl, furyl, imidazolyl, oxygen, and nitrogen, and no more than two non-hydrocarbon substituents are present for every 10 carbon atoms in the hydrocarbyl group.

[0012] As used herein, the term "weight percent" or "wt. %" means the percentage of the listed component expressed by weight of the entire composition, unless otherwise specified. All percentages herein are weight percent unless otherwise specified.

[0013] The terms "soluble", "oil-soluble" or "dispersible" used herein may, but do not necessarily, indicate that a compound or additive is soluble, dissolvable, miscible, or can be suspended in oil in any proportion. However, the terms mean that they are, for example, soluble, suspendable, soluble, or stably dispersible in oil to a sufficient degree to exert their intended effect in the environment in which the oil is used. Furthermore, if desired, the incorporation of other additives may also allow the incorporation of higher levels of the specific additive.

[0014] As used herein, the term "alkyl" refers to straight, branched, cyclic, and / or substituted saturated chain moieties of about 1 to about 200 carbon atoms. As used herein, the term "alkenyl" refers to straight, branched, cyclic, and / or substituted saturated chain moieties of about 3 to about 30 carbon atoms. As used herein, the term "aryl" refers to monocyclic and polycyclic aromatic compounds that may contain alkyl, alkenyl, alkylaryl, amino, hydroxyl, alkoxy, halo substituents, and / or heteroatoms such as, but not limited to, nitrogen and oxygen.

[0015] As used herein, molecular weight is measured by gel permeation chromatography (GPC) using commercially available polystyrene standards (with Mn of about 180 to about 18,000 as calibration standards). The molecular weight (Mn) of any embodiment herein may be determined using a gel permeation chromatography (GPC) instrument obtained from Waters or similar instrument, and data processed with Waters Empower Software or similar software. The GPC instrument may be provided with a Waters separation module and a Waters refractive index detector (or similar optional instrument). The operating conditions for the GPC may include a guard column, four Agilent PLgel columns (length 300 x 7.5 mm, particle size 5μ, and pore size range 100-10000 Å), and a column temperature of about 40°C. Non-stabilized HPLC grade tetrahydrofuran (THF) may be used as the solvent at a flow rate of 1.0 mL / min. GPC instruments can be calibrated with commercially available polystyrene (PS) standards with narrow molecular weight distributions ranging from 500 to 380,000 g / mol. The calibration curve can be extrapolated for samples with masses less than 500 g / mol. Samples and PS standards can be dissolved in THF and prepared at concentrations of 0.1 to 0.5 weight percent and can be used without filtration. GPC measurements are also described in U.S. Pat. No. 5,266,223, which is incorporated herein by reference. The GPC method further provides molecular weight distribution information. See, for example, W.W. Yau, J.J. Kirkland and D.D. Ly, "Modern Size Exclusion Liquid Chromatography", John Wiley and Sons, New York, 1979, which is incorporated herein by reference.

[0016] As used herein, any sulfur fraction distribution or ratio is measured using a Bruker Avance-3 HD 500 MHz instrument equipped with a 5 mm BBO Prodigy probe (or equivalent). 13The NMR spectroscopy was performed using 1C NMR. The sample was dissolved in chloroform-d and 1 Approximately 3% (wt / wt) for H NMR one-dimensional (1D) and two-dimensional (2D) homonuclear experiments; 13 For C 1D and 2D heteronuclear experiments, the concentration was approximately 30% (wt / wt). Chloroform-d was used as the chemical shift standard, and d H = 7.27 and d C =77.0 ppm. The experiment was performed at ambient temperature. Direct Observation 1D 1 H and 13 C- 1 The H decoupling experiment was performed with a 90 degree pulse width, 5×T1 delay, and 13 Gating for C NMR experiments 1 H decoupling was used and run under quantitative conditions. In addition, distortion-free enhancement by polarization transfer (DEPT) experiments using the 135° pulse option were also obtained. 2D experiments used to aid in structure assignment were homonuclear correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC) and heteronuclear multibond correlation spectroscopy (HMBC). All NMR data were acquired using Bruker Topspin 3.62 software from Bruker Inc (Billerica MA) and processed using ACD / Spectrus Processor 2021.1.3 software from Advanced Chemistry Development, Inc. using standard parameters (or equivalent equipment / software).

[0017] Throughout this disclosure, the terms "comprises," "includes," "contains," and the like are considered to be open ended and should be understood to include any element, step, or ingredient not expressly recited. The phrase "consisting essentially of" is meant to include any explicitly recited element, step, or ingredient, as well as any additional elements, steps, or ingredients that do not materially affect the basic and novel aspects of the invention. This disclosure also contemplates that any composition described using the terms "comprises," "includes," "contains" should be construed as including a disclosure of the same composition "consisting essentially of" or "consisting of" that specifically recited ingredient. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In one approach or embodiment, disclosed herein are lubricating compositions suitable for gear fluid, power transmission fluid, and / or axle applications having up to about 1.0 weight percent sulfur provided by a mixture of polysulfide extreme pressure agents (in other approaches, the lubricant can have from about 0.2 weight percent to about 1.0 weight percent sulfur, from about 0.2 to about 0.75 weight percent sulfur, or from about 0.2 weight percent to about 0.5 weight percent sulfur from the mixture of polysulfide extreme pressure agents). The sulfur provided by the polysulfide extreme pressure agents has a particular profile of sulfur moieties, and each polysulfide of the mixture has a particular profile of organic moieties thereon. In one aspect, the lubricating compositions herein have a combination of at least two or more polysulfide extreme pressure agents, each having selected sulfur moieties and selected organic moiety structures configured to minimize sulfur volatility and maintain high extreme pressure performance in the lubricating composition.

[0019] In one approach or embodiment, the lubricant compositions herein include a first polysulfide extreme pressure agent comprising a mixture of short chain polysulfides, such as C2-C6 polysulfides, where a majority of the first polysulfides are trisulfides, and a second polysulfide extreme pressure agent comprising a mixture of long chain polysulfides, such as C10-C14 polysulfides, where a majority of the second polysulfides are also trisulfides. In one aspect of the embodiments herein, the lubricant compositions also have a weight ratio of sulfur contributed by the first polysulfide and the second polysulfide of about 0.3 to about 0.8. Lubricant compositions including such a mixture of polysulfide extreme pressure agents have a sulfur loss (measured according to the S200 oxidation test of ASTM D2893, as shown in the examples below) of less than about 30% by weight and a sulfur loss of greater than about 200 kgf according to the 4-ball test of ASTM D2596.

[0020] In some approaches and embodiments, the first polysulfide extreme pressure agent has the formula R1-S x -R2, where R1 and R2 are independently short chain hydrocarbyl groups, such as C4 to C6 hydrocarbyl groups, and x is an integer of at least 2 (i.e., at least disulfides) and a majority of the integers of x are 3 (i.e., a majority of trisulfides). In another approach or embodiment, the second polysulfide extreme pressure agent has the structure R3-S y -R4 structure, where R3 and R4 are independently long chain hydrocarbyl groups, such as C10-C14 hydrocarbyl groups, and y is an integer of at least 2 (i.e., at least disulfides) and a majority of the integers of y are 3 (i.e., primarily trisulfides). Thus, each polysulfide extreme pressure agent is a compound having at least -S2- moieties and a majority of the polysulfides having -S3- moieties. In some approaches, each of the polysulfide extreme pressure agents herein may also have less than about 1 weight percent -S4- and higher moieties. As described in more detail below, the selected sulfur content aids in extreme pressure performance, and the selected organic groups, particularly the ratio of short chain organic groups to long chain organic groups, aid in sulfur retention.

[0021] The first polysulfide extreme pressure agent The first polysulfide extreme pressure agent (also referred to herein as EP agent A) is represented by the formula R1-S x -R2, where R1 and R2 are independently short chain hydrocarbyl groups, preferably C2-C6 hydrocarbyl groups (in other approaches, C3-C6 hydrocarbyl groups or C4-C6 hydrocarbyl groups), and x is an integer of at least 2, preferably the majority of integers of x is 3. That is, each hydrocarbyl group of the first polysulfide extreme pressure agent has 2-6 carbon atoms, preferably 4-6 carbon atoms, or more preferably 4 carbon atoms. In several approaches, each hydrocarbyl group of the organosulfide compound may be aromatic or aliphatic, preferably the hydrocarbyl group may be an aliphatic group such as alkyl, alkenyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, cycloalkenyl, and most preferably the hydrocarbyl group is an alkyl group having the recited amount of carbon atoms. Suitable alkyl groups may be linear or branched ethyl, propyl, butyl, pentyl, and / or hexyl groups. As described in more detail below, the hydrocarbyl group may be derived from a suitable olefin and may have from 2 to 6 carbon atoms or other ranges as described above. Preferably, the first polysulfide extreme pressure agent has a C4 hydrocarbyl group, most preferably di-tert-butyl polysulfide.

[0022] Suitable olefins for preparing the first polysulfide extreme pressure agent herein may be mono- or di-substituted mono-olefins having 2 to 6 carbon atoms. Di-substituted mono-olefins are olefins having at least one double bond carbon atom with two alkyl substituents. Examples of suitable olefins for deriving the first polysulfide extreme pressure agent include ethylene, propylene, butylene, isobutylene, 2-methyl-2-pentene, 2-methyl-2-butene, 2-methyl-1-butene, diisobutylene, triisobutylene, and mixtures thereof, as well as dimers, trimers, tetramers, and mixtures thereof, such that the polysulfide formed has C2 to C6 organic groups thereon.

[0023] In an approach or embodiment, the first polysulfide extreme pressure agent can be prepared by reacting a predetermined amount of molten sulfur with a desired olefin in the presence of aqueous sodium hydrosulfide under high pressure conditions. Preferably, the sulfur source for forming the first polysulfide is substantially free of sulfur chlorides, hydrogen sulfide, and combinations thereof, and in this context, the reaction herein has about 0.1 weight percent or less, about 0.05 weight percent or less, about 0.01 weight percent or less, or no sulfur chlorides, hydrogen sulfide, etc. The first polysulfide extreme pressure agent can be obtained at a temperature of about 75°C to about 300°C, preferably about 120°C to about 220°C, more preferably about 120°C to about 150°C. A suitable molar ratio of sulfur to hydrosulfide can range from about 20:1 to about 0.25:1. The molar ratio of sulfur + hydrosulfide to olefin can range from about 5:1 to about 0.5:1. The high pressure can vary from about 100 psig to over 2000 psig. The reaction time can vary and can range from about 2 to about 24 hours, preferably less than about 8 hours, and can be from 1 to 4 hours. Any suitable olefin can be used, but the selection of the olefin is necessary to achieve the short chain hydrocarbyl groups as described above. For example, olefins containing 2 to about 6 carbons are useful feedstocks required to achieve the desired short chain hydrocarbyl groups in the final product, and preferably isotubylene is used in the first polysulfide extreme pressure agent. The selected olefin or mixture of olefins may optionally be reacted with a preformed mixture of sulfurized aqueous hydrosulfide prepared by direct sulfidation of aqueous sodium sulfide. The reaction can suitably be carried out by sequential addition of the reactants. An aqueous solution of any suitable alkali metal or alkaline earth metal salt of hydrosulfide can be used. An aqueous solution of sodium hydrosulfide is preferred, with concentrated solutions of sodium hydrosulfide being preferred over dilute solutions.

[0024] In some approaches or embodiments, the polysulfide product formed from the above reaction may then be treated with caustic (i.e., sodium hydroxide) and / or an alkali metal sulfide such as sodium sulfide or potassium sulfide, optionally an aqueous solution of sodium sulfide, which may be prepared, for example, by mixing sodium hydrosulfide and a caustic solution (such as an aqueous sodium hydroxide solution) in amounts effective to produce a desired sulfide profile / ratio in the final product. The caustic may be a 40-60 percent solution of a metal hydroxide such as sodium hydroxide. The solution may contain a co-solvent such as methanol. The caustic and / or sodium sulfide solution and the polysulfide formed above may be mixed in a stirred reactor and heated under an inert atmosphere such as nitrogen at a temperature up to about 100°C, such as about 50°C to about 100°C (preferably about 90°C to about 100°C), for about 30 minutes to about 4 hours, optionally about 1 to about 2 hours. The reaction mixture may then be cooled and the separated organic product on top of the aqueous layer may be collected. The amount of caustic can be varied as needed to shape each of the reaction products and their sulfur profiles / ratios. Alternatively, the polysulfide product formed above can be distilled using a suitable distillation apparatus to collect appropriate fractions containing trisulfide and disulfide content as described herein.

[0025] The first polysulfide extreme pressure agent formed may be predominantly trisulfide, having about 1 to about 10 mole percent disulfide, about 51 to about 99 mole percent trisulfide, and up to about 1 mole percent tetrasulfide or higher sulfides. In other approaches or embodiments, the first polysulfide extreme pressure agent has about 51 to about 95 mole percent trisulfide, about 65 to about 95 mole percent trisulfide, about 75 to about 95 mole percent trisulfide, or about 85 to about 95 mole percent trisulfide. In other approaches or embodiments, the first polysulfide extreme pressure agent may also have, on a weight basis, about 40 to about 50 weight percent sulfur, in other approaches about 42 to about 48 weight percent sulfur, or in yet another approach about 42 to about 46 weight percent sulfur. As noted above, any embodiment herein of the first polysulfide extreme pressure agent has a short chain organic group as described above which is preferably a C2 to C6 hydrocarbyl group, more preferably a C3 to C6 hydrocarbyl group, even more preferably a C4 hydrocarbyl group, and most preferably a tert-butyl group.

[0026] Secondary polysulfide extreme pressure agent The second polysulfide extreme pressure agent (also referred to herein as EP agent B) is also a dihydrocarbyl sulfide compound and has the formula R y-R4, where R3 and R4 are independently long chain hydrocarbyl groups, preferably C10-C14 hydrocarbyl groups, and y is an integer of at least 2 (preferably the majority of integers for y are 3). That is, each hydrocarbyl group of the second polysulfide extreme pressure agent has 10-14 carbon atoms, preferably 12-14 carbon atoms, or more preferably 12 carbon atoms. In several approaches, each hydrocarbyl group of the second organosulfide compound may be aromatic or aliphatic, preferably the hydrocarbyl group may be an aliphatic group such as alkyl, alkenyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, cycloalkenyl, and most preferably the hydrocarbyl group is an alkyl group having the recited amount of carbon atoms. Suitable alkyl groups for the second polysulfide extreme pressure agent may be linear or branched decyl, undecyl, dodecyl, tridecyl, and / or tetradecyl groups. In such an approach, the hydrocarbyl groups may be derived from suitable olefins and / or hydrocarbyl mercaptans which may have from 10 to 14 carbon atoms, or other ranges as described above. Preferably, the second polysulfide extreme pressure agent has a C12 hydrocarbyl group, most preferably di-tert-dodecyl polysulfide.

[0027] In one embodiment, the second polysulfide extreme pressure agent may be prepared from elemental sulfur and a suitable hydrocarbyl mercaptan. Mercaptans suitable for preparing the second polysulfide extreme pressure agent herein may be mercaptans containing 10 to 14 carbon atoms. Examples of suitable mercaptans include those having linear or branched decene, undecene, dodecene, tridecene, tetradecene hydrocarbyl groups, as well as dimers, trimers, tetramers, and mixtures thereof, such that the polysulfides formed have C10 to C14 organic groups thereon.

[0028] In an approach or embodiment, the second polysulfide extreme pressure agent herein may be prepared by reacting one or more of the above hydrocarbyl mercaptans with a sulfur source (preferably elemental sulfur or molten sulfur) with or without a catalyst, such as an optional alkylamine catalyst, optionally under superatmospheric pressure, followed by removal of low boiling materials. Preferably, the sulfur source for the second polysulfide is also substantially free of sulfur chlorides, hydrogen sulfide, and combinations thereof, and in this context, the reactions herein have about 0.1 wt. % or less, about 0.05 wt. % or less, about 0.01 wt. % or less, or no sulfur chlorides, hydrogen sulfide, etc.

[0029] In some embodiments, the second polysulfide extreme pressure agent herein can be obtained by combining or reacting a hydrocarbyl mercaptan with elemental sulfur in a ratio including, but not limited to, about 2:1 to about 1:2 moles of hydrocarbyl mercaptan to grams of sulfur in, for example, an autoclave or other reaction vessel suitable for conducting superatmospheric pressure and high temperature reactions. In several approaches, the reaction can be carried out at a temperature of about 80° C. to about 200° C., a pressure of about 250 to about 1,000 psi, and a reaction time of about 2 to about 30 hours (or as appropriate) until the elemental sulfur is consumed and the desired sulfur level of the polysulfide is achieved.

[0030] The reaction can be carried out with or without a catalyst. If used, suitable catalysts can include amines and sulfur compounds such as dithiocarbamate salts and mercaptans, including but not limited to n-butylamine, n-octylamine, triethylamine, tetramethylthiuram disulfide, and mercaptobenzothiazole. Catalysts can be used, if desired, in amounts of about 0.01 to about 5.0% by weight of the reaction mixture, or other amounts appropriate for the particular application and sulfur level. The reaction can be carried out in the absence of oxygen. In some approaches, the reaction can include a non-reactive solvent, such as heptane, dichloromethane, or the like, or a combination thereof.

[0031] In some approaches or embodiments, the sulfurized product may then be treated with caustic (sodium hydroxide) and / or an alkali metal sulfide such as sodium or potassium sulfide, optionally an aqueous solution of sodium sulfide, which may be prepared, for example, by mixing sodium hydrosulfide and a caustic solution (such as an aqueous sodium hydroxide solution) in amounts effective to produce a desired sulfide profile / ratio. The solution may contain a co-solvent, such as methanol. The caustic and / or sodium sulfide solution and the sulfurized intermediate may be mixed in a stirred reactor and heated under an inert atmosphere, such as nitrogen, at a temperature up to about 100°C, such as about 50°C to about 100°C, for about 30 minutes to about 4 hours, optionally about 1 to about 2 hours. The reaction mixture may then be cooled and the organic product separated on top of the aqueous layer may be collected. In some approaches, the caustic solution may be about 40 to about 60 wt.% alkali metal hydroxide (i.e., sodium hydroxide). The amount of caustic may also be varied as needed to produce each of the reaction products and sulfur profiles / ratios herein. Alternatively, the sulfurized polysulfides formed above may also be distilled using a suitable distillation apparatus to collect appropriate fractions containing trisulfide and disulfide content as described herein.

[0032] The second polysulfide extreme pressure agent formed is predominantly trisulfide groups and may have about 1 to about 10 mole percent disulfides, about 51 to about 99 mole percent trisulfides, and up to about 1 mole percent tetrasulfides or higher sulfides. In other approaches or embodiments, the second polysulfide extreme pressure agent may have about 51 to about 95 mole percent trisulfides, about 65 to about 95 mole percent trisulfides, about 75 to about 95 mole percent trisulfides, or about 85 to about 95 mole percent trisulfides. In some approaches or embodiments, the second polysulfide extreme pressure agent has, on a weight basis, about 18 to about 30 weight percent sulfur, in other approaches about 18 to about 28 weight percent sulfur, or in still further approaches about 20 to about 26 weight percent sulfur. As noted above, any embodiment herein of the second polysulfide extreme pressure agent has a long chain organic group as described above which is preferably a C10 to C14 hydrocarbyl group, more preferably a C12 hydrocarbyl group, and most preferably a tert-dodecyl group.

[0033] lubricating composition The lubricating compositions herein comprise a mixture of first and second polysulfide extreme pressure agents as described above in amounts configured to minimize any sulfur loss and maintain high extreme pressure performance. In several approaches or embodiments, for example, the lubricating compositions comprise (a) a first polysulfide extreme pressure agent comprising a mixture of C2-C6 polysulfides, mostly trisulfides, as described above, and (b) a second polysulfide extreme pressure agent comprising a mixture of C10-C14 polysulfides, mostly trisulfides, also as described above.

[0034] The combined first and second polysulfide extreme pressure agents may provide up to about 1 wt. % sulfur to the lubricating composition, preferably about 0.2 to about 0.5 wt. % sulfur (in other approaches, about 0.3 to about 0.4 wt. %). In some approaches or embodiments, the sulfur is provided by each polysulfide in a specific sulfur ratio configured to achieve low sulfur losses and maintain extreme pressure performance. In some embodiments, the weight ratio of sulfur provided by the first polysulfide and the second polysulfide is about 0.3 to about 0.8, in other embodiments, about 0.4 to about 0.8, and in further embodiments, about 0.45 to about 0.75.

[0035] In yet another approach or embodiment, the treat rate or weight percent of the polysulfide extreme pressure agents in the lubricant compositions herein may include (a) from about 0.2 to about 0.4 weight percent of a first polysulfide (EP agent A) and (b) from about 0.8 to about 1.2 weight percent of a second polysulfide (EP agent B). In another approach, the weight percent ratio of the first polysulfide to the second polysulfide may be from about 0.2 to about 0.38.

[0036] Such combinations of first and second polysulfide extreme pressure agents enable the lubricant compositions herein to have high extreme pressure performance of greater than about 200 kgf according to the 4-ball test of ASTM D2596 with less than about 30 weight percent sulfur loss (measured according to the S200 oxidation test of ASTM D2893, as shown in the examples below).In other approaches, the lubricants herein have only about 20 to about 30 weight percent sulfur loss (or about 21 to 28 weight percent) and have strong 4-ball performance of about 200 kgf to about 225 kgf.

[0037] Base oil In one approach, suitable base oils for use in the lubricating compositions or gear fluids herein include mineral oils, synthetic oils, including all common mineral oil base stocks. Mineral oils can be naphthenic or paraffinic. Mineral oils can be refined by conventional methods using acids, alkalis, and other agents such as clay or aluminum chloride, or can be extracted oils produced by solvent extraction using solvents such as phenol, sulfur dioxide, furfural, or dichlorodiethyl ether. Mineral oils can be hydrotreated or hydrofined, dewaxed by cooling or catalytic dewaxing processes, or hydrocracked (such as the Yubase® family of hydrocracked base oils from SK Innovation Co., Ltd., Seoul, Korea). Mineral oils can be produced from natural crude oil sources or can be composed of isomerized wax materials or residues of other refining processes.

[0038] The base oil, or base oil of lubricating viscosity used in the compositions herein, may be selected from any base oil suitable for driveline or gear oil applications. Examples include base oils in Groups I-V as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. These three base oil groups are as follows:

[0039] [Table 1]

[0040] Groups I, II, and III are mineral oil process stocks and may be preferred for driveline or gear fluids of the present application. It should be noted that although Group III base oils are derived from mineral oils, the rigorous processing these fluids undergo makes their physical properties very similar to some true synthetic oils, such as PAO. Thus, oils derived from Group III base oils may be referred to as synthetic fluids in the industry. Suitable oils may be derived from hydrocracked, hydrogenated, hydrofinished, unrefined, refined, and rerefined oils, and mixtures thereof. In some approaches, the base oil may be a blend of Group I and Group II oils, which may be about 0% to about 100% Group I oil, about 0% to about 100% Group II oil, about 0% to about 100% Group III oil, or various blends of blends of Group I and II, Group I and III, or Group II and III oils.

[0041] Unrefined oils are derived from natural, mineral, or synthetic sources with little or no further purification treatment. Refined oils are similar to unrefined oils, except that they have been treated with one or more purification steps that may result in the improvement of one or more properties. Examples of suitable purification techniques are solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Oils refined to edible quality may or may not be useful. Edible oils may also be called white oils. In some embodiments, the lubricating oil composition does not include edible oils or white oils.

[0042] Rerefined oils are also known as reclaimed or reprocessed oils. These oils are obtained similarly to refined oils using the same or similar processes. Often these oils are further processed by techniques directed to the removal of spent additives and oil breakdown products.

[0043] Mineral oils may include oils obtained by drilling or from plants and animals, or any mixture thereof. For example, such oils may include, but are not limited to, castor oil, lard oil, olive oil, peanut oil, corn oil, soybean oil, and linseed oil, as well as mineral lubricating oils, such as liquid petroleum oils, and solvent- or acid-treated mineral lubricating oils of the paraffinic, naphthenic, or mixed paraffinic-naphthenic types. Such oils may be partially or fully hydrogenated, if desired. Oils derived from coal or shale may also be useful.

[0044] The major amount of base oil included in the gear fluids herein may be selected from the group consisting of Group I, Group II, Group III, and combinations of two or more of the foregoing, the major amount of base oil being other than the base oil resulting from the provision of an additive component or viscosity index improver in the composition. In another embodiment, the major amount of base oil included in the lubricating composition may be selected from the group consisting of Group I, Group II, and combinations of two or more of the foregoing, the major amount of base oil being other than the base oil resulting from the provision of an additive component or viscosity index improver in the composition.

[0045] The base oil can also be any of the synthetic base oils. Useful synthetic lubricating oils can include hydrocarbon oils such as polymerized, oligomerized, or interpolymerized olefins (e.g., polybutylene, polypropylene, propylene isobutylene copolymers); poly(1-hexene), poly(1-octene), trimers or oligomers of 1-decene, such as poly(1-decene) (such materials are often referred to as alpha-olefins), and mixtures thereof; alkyl-benzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di-(2-ethylhexyl)-benzene); polyphenyls (e.g., biphenyl, terphenyl, alkylated polyphenyls); diphenylalkanes, alkylated diphenylalkanes, alkylated diphenyl ethers, and alkylated diphenyl sulfides, as well as their derivatives, analogs, and homologs, or mixtures thereof. Polyalphaolefins are typically hydrogenated materials.

[0046] Other synthetic lubricating oils include polyol esters, diesters, liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, and diethyl ester of decane phosphonic acid), or polymeric tetrahydrofurans. Synthetic oils may be produced by the Fischer-Tropsch reaction and typically may be hydroisomerized Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oils may be prepared by the Fischer-Tropsch gas-liquid synthesis procedure, as well as other gas-liquid oils.

[0047] The amount of base oil of lubricating viscosity in the compositions herein may be the balance remaining after the sum of the amounts of performance additives is subtracted from 100% by weight. For example, the oil of lubricating viscosity may be present in the final fluid in a "major amount", such as greater than about 50% by weight, greater than about 60% by weight, greater than about 70% by weight, greater than about 80% by weight, greater than about 85% by weight, greater than about 90% by weight, or greater than 95% by weight.

[0048] In some approaches, the preferred base oil or base oil of lubricating viscosity has less than about 25 ppm sulfur, a viscosity index greater than about 120 ppm, and a kinematic viscosity at about 100° C. of about 2 to about 8 cSt. In other approaches, the base oil of lubricating viscosity has less than about 25 ppm sulfur, a viscosity index greater than 120, and a kinematic viscosity at 100° C. of about 4 cSt. The base oil may have a CP (paraffinic carbon content) of greater than 40%, greater than 45%, greater than 50%, greater than 55%, or greater than 90%. The base oil may have a CA (aromatic carbon content) of less than 5%, less than 3%, or less than 1%. The base oil may have a CN (naphthenic carbon content) of less than 60%, less than 55%, less than 50%, or less than 50%, and greater than 30%. The base oil may have a ratio of 1-ring naphthenes to 2-ring naphthenes to 6-ring naphthenes of less than 2, or less than 1.5, or less than 1.

[0049] Suitable driveline, axle, or gear lubricant compositions herein may contain additive components in the ranges listed in Table 2 below.

[0050] [Table 2]

[0051] The percentages of each component above represent the weight percent of each component based on the total weight of the final additive or lubricant composition. The remainder of the lubricant composition consists of one or more base oils or solvents. The additives used in formulating the compositions described herein can be blended into the base oil or solvent individually or in various subcombinations. However, it may be preferred to use an additive concentrate (i.e., additives plus a diluent such as a hydrocarbon solvent) to blend all of the components at the same time.

[0052] The lubricating compositions described herein can be formulated to provide lubrication, improved friction performance characteristics, and improved copper corrosion for various applications. The driveline lubricating compositions herein can be used to lubricate machine parts such as gears. The lubricating fluids according to the present disclosure can be used in gear applications such as industrial gear applications, automotive gear applications, axles, and fixed gearboxes. Gear types can include, but are not limited to, spur, spiral, worm, rack and pinion, involute, bevel, helical, planetary, and hypoid gears, as well as limited slip applications and differentials. The driveline lubricating compositions disclosed herein are also suitable for automatic or manual transmissions, including step automatic transmissions, continuously variable transmissions, semi-automatic transmissions, automated manual transmissions, toroidal transmissions, and dual clutch transmissions. The driveline lubricating compositions herein are particularly suitable for use in axles, transfer cases, differentials, such as linear differentials, rotary differentials, limited slip differentials, clutch-type differentials, and locking differentials.

[0053] Optional Additives In another approach, lubricants containing such additives as described above may also contain one or more optional ingredients, so long as such ingredients and their amounts do not affect the performance characteristics as described in the paragraphs above. These optional ingredients are described in the following paragraphs.

[0054] phosphorus-containing compounds The lubricant compositions herein may include one or more phosphorus-containing compounds that may impart antiwear benefits to the fluid. The one or more phosphorus-containing compounds may be present in the lubricant composition in an amount ranging from about 0% to about 15%, or from about 0.01% to about 10%, or from about 0.05% to about 5%, or from about 0.1% to about 3% by weight of the lubricant composition. The phosphorus-containing compounds may provide the lubricant composition with up to 5000 ppm phosphorus, or from about 50 to about 5000 ppm phosphorus, or from about 300 to about 1500 ppm phosphorus, or up to 600 ppm phosphorus, or up to 900 ppm phosphorus.

[0055] The one or more phosphorus-containing compounds may include ashless phosphorus-containing compounds.Suitable examples of phosphorus-containing compounds include, but are not limited to, thiophosphates, dithiophosphates, phosphates, phosphoric acid esters, phosphate esters, phosphites, phosphonates, phosphorus-containing carboxylic acid esters, ethers, or amide salts thereof, and mixtures thereof.Phosphorus-containing antiwear agents are more fully described in EP 0612839.

[0056] It should be noted that the terms phosphonate and phosphite are often used interchangeably in the lubricant industry. For example, dibutyl hydrogen phosphonate is sometimes referred to as dibutyl hydrogen phosphite. It is within the scope of the present invention that the lubricant compositions of the present invention include phosphorus-containing compounds that may be referred to as either phosphites or phosphonates.

[0057] In any of the above phosphorus-containing compounds, the compound can have from about 5 weight percent to about 20 weight percent phosphorus, or from about 5 weight percent to about 15 weight percent phosphorus, or from about 8 weight percent to about 16 weight percent phosphorus, or from about 6 weight percent to about 9 weight percent phosphorus.

[0058] When the phosphorus-containing compound is included in the lubricant composition in combination with the dispersant described above, it unexpectedly imparts positive friction properties, such as a low coefficient of friction, to the lubricant composition. The effect of the present invention is even more pronounced in some cases where the phosphorus-containing compound alone imparts negative friction properties to the fluid. When these relatively poorly friction-reducing phosphorus-containing compounds are combined with the olefin copolymer dispersants described herein, the lubricant composition has an improved, i.e., lower, coefficient of friction. That is, the dispersants herein tend to convert fluids containing phosphorus-containing compounds with relatively poor coefficients of friction into fluids with improved friction properties.

[0059] This improvement in the frictional properties of lubricating compositions comprising a phosphorus-containing compound and an olefin copolymer dispersant described herein is surprising because the frictional properties of the fluid are improved over combinations of a phosphorus-containing compound and other types of dispersants, including polyisobutylene succinimide dispersants and olefin copolymer succinimide dispersants, which do not have the specified properties of the copolymers described above.

[0060] Another type of phosphorus-containing compound that imparts improved frictional properties to lubricating compositions when combined with the olefin copolymer dispersants herein is the ashless (metal-free) phosphorus-containing compounds.

[0061] In some embodiments, the ashless phosphorus-containing compound can be a dialkyldithiophosphate ester, amyl acid phosphate, diamyl acid phosphate, dibutyl hydrogen phosphate, dimethyloctadecyl phosphate, salts thereof, and mixtures thereof.

[0062] The ashless phosphorus-containing compound has the formula:

[0063] [ka] It may have where R1 is S or O, R2 is -OR, -OH, or -R'', R3 is -OR'', -OH, or SR'''C(O)OH, R4 is -OR'', R''' is a C1-C3 branched or straight alkyl chain, and R'' is a C1-C18 hydrocarbyl chain. When the phosphorus-containing compound has the structure shown in formula XIV, the compound can have from about 8 weight percent to about 16 weight percent phosphorus.

[0064] In some embodiments, the lubricant composition comprises a phosphorus-containing compound of Formula XIV, where R1 is S, R2 is -OR'', R3 is SR'''COOH, R4 is -OR'', R''' is a C3 branched alkyl chain, and R'' is C4, and the phosphorus-containing compound is present in an amount to provide 80 to 900 ppm of phosphorus to the lubricant composition.

[0065] In another embodiment, the lubricant composition comprises a phosphorus-containing compound of Formula XIV, where R1 is O, R2 is -OH, R3 is -OR" or -OH, R4 is -OR", and R" is C5, and the phosphorus-containing compound is present in an amount to provide 80 to 1500 ppm phosphorus to the lubricant composition.

[0066] In yet another embodiment, the lubricant composition comprises phosphorus-containing compounds of Formula XIV, where R1 is O, R2 is OR'', R3 is H, R4 is -OR'', and R'' is C4, and the one or more phosphorus-containing compounds are present in an amount providing 80-1550 ppm phosphorus to the lubricant composition.

[0067] In another embodiment, the lubricant composition comprises a phosphorus-containing compound of Formula XIV, where R1 is O, R2 is -R'', R3 is -OCH3 or -OH, R4 is -OCH3, and R'' is C18, and the one or more phosphorus-containing compounds are present in an amount to provide 80-850 ppm phosphorus to the lubricant composition.

[0068] In some embodiments, the phosphorus-containing compound has the structure shown in Formula XIV and provides from about 80 to about 4500 ppm of phosphorus to the lubricant composition. In other embodiments, the phosphorus-containing compound is present in an amount to provide from about 150 to about 1500 ppm of phosphorus, or from about 300 to about 900 ppm of phosphorus, or from about 800 to 1600 ppm of phosphorus, or from about 900 to about 1800 ppm of phosphorus to the lubricant composition.

[0069] Anti-wear Agent The lubricant composition may also contain other antiwear agents that are phosphorus-free compounds. Examples of such antiwear agents include borate esters, borate epoxides, thiocarbamate compounds (e.g., thiocarbamate esters, alkylene-linked thiocarbamates, and bis(S-alkyldithiocarbamyl) disulfides, thiocarbamate amides, thiocarbamic acid ethers, alkylene-linked thiocarbamates, and bis(S-alkyldithiocarbamyl) disulfides, and mixtures thereof), sulfurized olefins, tridecyl adipate, titanium compounds, and long-chain derivatives of hydroxyl carboxylic acids, such as tartrate derivatives, tartramides, tartrimides, citrates, and mixtures thereof. A suitable thiocarbamate compound is molybdenum dithiocarbamate. A suitable tartrate derivative or tartrimides may contain an alkyl-ester group, where the total number of carbon atoms on the alkyl group may be at least 8. The tartrate derivatives or tartrimides may contain alkyl-ester groups, where the total number of carbon atoms on the alkyl group may be at least 8. The antiwear agent may include citrate in one embodiment. The additional antiwear agent may be present in a range including from about 0% to about 15%, or from about 0.01% to about 10%, or from about 0.05% to about 5%, or from about 0.1% to about 3% by weight of the lubricating oil composition.

[0070] Extreme Pressure Agent The lubricant compositions of this disclosure may also contain other extreme pressure agents, so long as the lubricant compositions herein contain the recited amounts and profiles described herein. The optional extreme pressure agent may contain sulfur and may contain at least 12 weight percent sulfur.

[0071] A wide variety of sulfur-containing extreme pressure agents are suitable, including sulfurized animal or vegetable fats or oils, sulfurized animal or vegetable fatty acid esters, fully or partially esterified esters of trivalent or pentavalent acids of phosphorus, sulfurized olefins (e.g., those described in U.S. Pat. Nos. 2,995,569, 3,673,090, 3,703,504, 3,703,505, 3,796,661, 3,873,454, 4,119,549, 4,119,550, 4,147,640, 4,191,659, 4,240,958, 4,344,854, 4,472,306, and 4, No. 711,736), dihydrocarbyl polysulfides (see, for example, U.S. Pat. Nos. 2,237,625; 2,237,627; 2,527,948; 2,695,316; 3,022,351; 3,308,166; 3,392,201; 4,564,709; and British Patent No. 1,162,334), functionally substituted dihydrocarbyl polysulfides (see, for example, U.S. Pat. No. 4,218,332), and polysulfide olefin products (see, for example, U.S. Pat. No. 4,795,576). Other suitable examples include sulfurized olefins, sulfur-containing aminoheterocyclic compounds, 5-dimercapto-1,3,4-thiadiazoles, polysulfides having a majority of S3 and S4 sulfides, sulfurized fatty acids, sulfurized branched chain olefins, organic polysulfides, and mixtures thereof.

[0072] In some embodiments, the extreme pressure agent is present in the lubricant composition in an amount of up to about 3.0 wt.% or up to about 5.0 wt.%. In other embodiments, the extreme pressure agent is present in an amount of from about 0.05 wt.% to about 0.5 wt.%, based on the total weight of the lubricant composition. In other embodiments, the extreme pressure agent is present in an amount of from about 0.1 wt.% to about 3.0 wt.%, based on the total weight of the lubricant composition. In other embodiments, the extreme pressure agent is present in an amount of from about 0.6 wt.% to about 1 wt.%, based on the total weight of the lubricant composition. In yet other embodiments, the detergent is present in an amount of about 1.0 wt.%, based on the total weight of the lubricant composition.

[0073] One suitable class of extreme pressure agents are polysulfides composed of one or more compounds represented by the formula: Ra-Sx-Rb, where Ra and Rb are hydrocarbyl groups, each of which may contain 1 to 18, and in other approaches 3 to 18, carbon atoms, and x may range from 2 to 8, typically 2 to 5, and especially 3. In some approaches, x is an integer from 3 to 5, with about 30 to about 60 percent of the x's being integers 3 or 4. The hydrocarbyl groups may be of a wide variety of types, such as alkyl, cycloalkyl, alkenyl, aryl, or aralkyl. Tertiary alkyl polysulfides, such as di-tert-butyl trisulfide, and mixtures including di-tert-butyl trisulfide (e.g., mixtures composed primarily or entirely of tri-, tetra-, and pentasulfides) may be used. Examples of other useful dihydrocarbyl polysulfides include diamyl polysulfide, dinonyl polysulfide, didodecyl polysulfide, and dibenzyl polysulfide.

[0074] Another suitable class of extreme pressure agents is sulfurized isobutene, made by reacting an olefin such as isobutene with sulfur. Sulfurized isobutene (SIB), particularly sulfurized polyisobutylene, typically has a sulfur content of about 10 to about 55% by weight, desirably about 30 to about 50% by weight. A wide variety of other olefins or unsaturated hydrocarbons, such as isobutene dimers or trimers, can be used to form sulfurized olefin extreme pressure agents. Various methods for preparing sulfurized olefins have been disclosed in the prior art. See, for example, U.S. Pat. No. 3,471,404 to Myers, U.S. Pat. No. 4,204,969 to Papay et al., U.S. Pat. No. 4,954,274 to Zaweski et al., U.S. Pat. No. 4,966,720 to DeGonia et al., and U.S. Pat. No. 3,703,504 to Horodysky et al., each of which is incorporated herein by reference.

[0075] Methods for preparing sulfurized olefins, including those disclosed in the aforementioned patents, involve the formation of a material typically referred to as an "adduct," in which an olefin is reacted with a sulfur halide, such as sulfur monochloride. The adduct is then reacted with a sulfur source to provide the sulfurized olefin. The quality of the sulfurized olefin is generally measured by various physical properties, such as viscosity, sulfur content, halogen content, copper corrosion test weight loss, etc. U.S. Patent No. 4,966,720 relates to sulfurized olefins useful as extreme pressure additives in lubricating oils, and a two-step reaction for their preparation.

[0076] Antioxidants The lubricating oil composition herein may also optionally contain one or more antioxidants. Antioxidant compounds are known and include, for example, phenates, phenate sulfides, sulfurized olefins, phosphosulfurized terpenes, sulfurized esters, aromatic amines, alkylated diphenylamines (e.g., nonyldiphenylamine, di-nonyldiphenylamine, octyldiphenylamine, di-octyldiphenylamine), phenyl-alpha-naphthylamines, alkylated phenyl-alpha-naphthylamines, hindered non-aromatic amines, phenols, hindered phenols, oil-soluble molybdenum compounds, polymeric antioxidants, or mixtures thereof. The antioxidant compounds may be used alone or in combination.

[0077] The hindered phenol antioxidant may contain secondary butyl and / or tertiary butyl groups as steric hindrance groups. The phenol group may be further substituted with a hydrocarbyl group and / or a bridging group that connects to a second aromatic group. Examples of suitable hindered phenol antioxidants include 2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, or 4-dodecyl-2,6-di-tert-butylphenol. In one embodiment, the hindered phenol antioxidant may be an ester and may include, for example, Irganox® L-135 available from BASF or an addition product derived from 2,6-di-tert-butylphenol and an alkyl acrylate, where the alkyl group may contain from about 1 to about 18, or from about 2 to about 12, or from about 2 to about 8, or from about 2 to about 6, or about 4 carbon atoms. Another commercially available hindered phenol antioxidant may be an ester and may include Ethanox® 4716 available from Albemarle Corporation.

[0078] Useful antioxidants may include diarylamines and phenols. In one embodiment, the lubricating oil composition may contain a mixture of diarylamines and phenols, with each antioxidant being present in an amount sufficient to provide up to about 5% by weight, based on the weight of the lubricating oil composition. In one embodiment, the antioxidant may be a mixture of about 0.3% to about 1.5% by weight of diarylamines and about 0.4% to about 2.5% by weight of phenols, based on the weight of the lubricating oil composition.

[0079] Examples of suitable olefins that can be sulfurized to form sulfurized olefins include propylene, butylene, isobutylene, polyisobutylene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, tridecene, tetradecene, pentadecene, hexadecene, heptadecene, octadecene, nonadecene, eicosene, or mixtures thereof. In one embodiment, hexadecene, heptadecene, octadecene, nonadecene, eicosene, or mixtures thereof, as well as their dimers, trimers, and tetramers, are particularly useful olefins. Alternatively, the olefins can be Diels-Alder adducts of dienes such as 1,3-butadiene and unsaturated esters such as butyl acrylate.

[0080] Another class of sulfurized olefins includes sulfurized fatty acids and their esters. The fatty acids are often derived from vegetable or animal oils and typically contain from about 4 to about 22 carbon atoms. Examples of suitable fatty acids and their esters include triglycerides, oleic acid, linoleic acid, palmitoleic acid, or mixtures thereof. Often, the fatty acids are derived from lard oil, tall oil, peanut oil, soybean oil, cottonseed oil, sunflower seed oil, or mixtures thereof. The fatty acids and / or esters may be mixed with olefins, such as α-olefins.

[0081] The one or more antioxidants may be present in the range of from about 0% to about 20%, or from about 0.1% to about 10%, or from about 1% to about 5% by weight of the lubricating oil composition.

[0082] Dispersants Dispersants contained in the lubricant composition may include, but are not limited to, an oil-soluble polymeric hydrocarbon backbone having functional groups capable of associating with particles to be dispersed. Typically, dispersants contain amine, alcohol, amide, or ester polar moieties attached to the polymer backbone, often through a bridging group. Dispersants may be selected from Mannich dispersants such as those described in U.S. Pat. Nos. 3,634,515, 3,697,574, and 3,736,357, ashless succinimide dispersants such as those described in U.S. Pat. Nos. 4,234,435 and 4,636,322, amine dispersants such as those described in U.S. Pat. Nos. 3,219,666, 3,565,804, and 5,633,326, Koch dispersants such as those described in U.S. Pat. Nos. 5,936,041, 5,643,859, and 5,627,259, and polyalkylene succinimide dispersants such as those described in U.S. Pat. Nos. 5,851,965, 5,853,434, and 5,792,729.

[0083] In some embodiments, the additional dispersant may be derived from polyalphaolefin (PAO) succinic anhydride, olefin maleic anhydride copolymer. As an example, the additional dispersant may be described as poly-PIBSA. In another embodiment, the additional dispersant may be derived from anhydrides grafted to ethylene-propylene copolymers. Another additional dispersant may be a high molecular weight ester or half ester amide.

[0084] When present, the additional dispersant can be used in an amount sufficient to provide up to about 10% by weight, based on the final weight of the lubricating oil composition. Alternative amounts of dispersant that can be used can be from about 0.1% to about 10% by weight, or from about 0.1% to about 10% by weight, or from about 3% to about 8% by weight, or from about 1% to about 6% by weight, based on the final weight of the lubricating oil composition.

[0085] Viscosity Index Improver The lubricant compositions herein may also optionally contain one or more viscosity index improvers. Suitable viscosity index improvers may include polyolefins, olefin copolymers, ethylene / propylene copolymers, polyisobutene, hydrogenated styrene-isoprene polymers, styrene / maleic acid ester copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, alpha-olefin maleic anhydride copolymers, polymethacrylates, polyacrylates, polyalkylstyrenes, hydrogenated alkenylaryl conjugated diene copolymers, or mixtures thereof. Viscosity index improvers may include star polymers, suitable examples of which are described in U.S. Patent Application Publication No. 2012 / 0101017(A1), which is incorporated herein by reference.

[0086] The lubricating oil compositions herein may also optionally contain one or more dispersant viscosity index improvers in addition to or instead of the viscosity index improver. Suitable viscosity index improvers may include functionalized polyolefins, such as ethylene-propylene copolymers functionalized with the reaction product of an acylating agent (such as maleic anhydride) with an amine, amine-functionalized polymethacrylates, or esterified maleic anhydride-styrene copolymers reacted with amines.

[0087] The total amount of viscosity index improver and / or dispersant viscosity index improver can be from about 0% to about 20%, from about 0.1% to about 15%, from about 0.1% to about 12%, or from about 0.5% to about 10%, from about 3% to about 20%, from about 3% to about 15%, from about 5% to about 15%, or from about 5% to about 10% by weight of the lubricating oil composition.

[0088] In some embodiments, the viscosity index improver is a polyolefin or olefin copolymer having a number average molecular weight of about 10,000 to about 500,000, about 50,000 to about 200,000, or about 50,000 to about 150,000. In some embodiments, the viscosity index improver is a hydrogenated styrene / butadiene copolymer having a number average molecular weight of about 40,000 to about 500,000, about 50,000 to about 200,000, or about 50,000 to about 150,000. In some embodiments, the viscosity index improver is a polymethacrylate having a number average molecular weight of about 10,000 to about 500,000, about 50,000 to about 200,000, or about 50,000 to about 150,000.

[0089] Other optional additives The other additives may be selected to perform one or more functions required for the lubricant composition. Furthermore, one or more of the aforementioned additives may be multifunctional and may provide functions in addition to or other than those described herein. The other additives may be in addition to the additives specified in this disclosure and / or may include one or more of metal deactivators, viscosity index improvers, ashless TBN boosters, antiwear agents, corrosion inhibitors, rust inhibitors, dispersants, dispersant viscosity index improvers, extreme pressure agents, antioxidants, foam suppressants, demulsifiers, emulsifiers, pour point depressants, seal swell agents, and mixtures thereof. Typically, fully formulated lubricating oils contain one or more of these performance additives.

[0090] Suitable metal deactivators may include derivatives of benzotriazole (typically tolyltriazole), dimercaptothiadiazole derivatives, 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole, or 2-alkyldithiobenzothiazole; foam suppressors including copolymers of ethyl acrylate and 2-ethylhexyl acrylate and optionally vinyl acetate; demulsifiers including trialkyl phosphates, polyethylene glycol, polyethylene oxide, polypropylene oxide, and (ethylene oxide-propylene oxide) polymers; pour point depressants including esters of maleic anhydride-styrene, polymethacrylates, polyacrylates, or polyacrylamides.

[0091] Suitable suds suppressors include silicon-based compounds such as siloxanes.

[0092] Suitable pour point depressants may include polymethyl methacrylate or mixtures thereof. The pour point depressant may be present in an amount sufficient to provide from about 0 wt. % to about 1 wt. %, from about 0.01 wt. % to about 0.5 wt. %, or from about 0.02 wt. % to about 0.04 wt. %, based on the final weight of the lubricating oil composition.

[0093] A suitable rust inhibitor can be a single compound or a mixture of compounds that have the property of inhibiting corrosion of ferrous metal surfaces. Non-limiting examples of rust inhibitors useful herein include oil-soluble high molecular weight organic acids such as 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, and cerotic acid, as well as oil-soluble polycarboxylic acids including dimer and trimer acids such as those produced from tall oil fatty acids, oleic acid, and linoleic acid. Other suitable corrosion inhibitors include long chain alpha, omega-dicarboxylic acids in the molecular weight range of about 600 to about 3000, and alkenyl succinic acids in which the alkenyl group contains about 10 or more carbon atoms, such as tetrapropenyl succinic acid, tetradecenyl succinic acid, and hexadecenyl succinic acid. Another useful type of acidic corrosion inhibitor is the half ester of an alkenyl succinic acid having about 8 to about 24 carbon atoms in the alkenyl group with an alcohol, such as a polyglycol. The corresponding half amides of such alkenyl succinic acids are also useful. Useful rust inhibitors are high molecular weight organic acids. In some embodiments, the engine oil does not contain a rust inhibitor.

[0094] Rust inhibitors, when present, may be used in any amount sufficient to provide from about 0 wt. % to about 5 wt. %, from about 0.01 wt. % to about 3 wt. %, from about 0.1 wt. % to about 2 wt. %, based on the final weight of the lubricating oil composition.

[0095] The lubricant composition may also include a corrosion inhibitor (it should be noted that some of the other mentioned components may also have copper corrosion inhibiting properties). Suitable copper corrosion inhibitors include ether amines, polyethoxylated compounds such as ethoxylated amines and ethoxylated alcohols, imidazolines, mono-alkyl, and di-alkyl thiadiazoles, and the like.

[0096] Thiazoles, triazoles, and thiadiazoles may also be used in the lubricant. Examples include benzotriazole, tolyltriazole, octyltriazole, decyltriazole, dodecyltriazole, 2-mercaptobenzothiazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazole, and 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazole. In one embodiment, the lubricant composition includes a 1,3,4-thiadiazole, such as 2-hydrocarbyldithio-5-mercapto-1,3,4-dithiadiazole.

[0097] Antifoaming agents / surfactants may also be included in the fluid according to the invention. Various agents are known for such applications. Copolymers of ethyl acrylate and hexyl ethyl acrylate, such as PC-1244 available from Solutia, may be used. In other embodiments, silicone fluids such as 4% DCF may be included. Mixtures of antifoaming agents may also be present in the lubricant composition. EXAMPLES

[0098] The following examples illustrate exemplary embodiments of the present disclosure. In these examples, as well as elsewhere in this application, all ratios, parts, and percentages are by weight unless otherwise indicated. It is intended that these examples are presented for illustrative purposes only and are not intended to limit the scope of the invention disclosed herein. EXAMPLES

[0099] EP Agent A: Di-tert-butyl polysulfide suitable for the short chain polysulfide or first polysulfide extreme pressure agent herein may be prepared as follows: A high pressure reactor may be charged with aqueous sodium hydrosulfide solution and molten sulfur at a temperature of about 130°C. Isobutylene may then be added to the stirred mixture via a high pressure pump while maintaining the reaction temperature at about 130°C to about 170°C. Following the charge of isobutylene, the reaction may be heated to about 150°C to about 170°C for about 120 minutes. Heating may then be stopped and excess isobutylene may be vented while the reactor is cooled to about 90°C to about 100°C. The aqueous phase may be separated and the organic phase may be placed under vacuum to remove residual water. The organic product may be filtered through diatomaceous earth if necessary. The aqueous by-product may be extracted with portions of hexane, the extracts combined, and additional organic product recovered by evaporating the hexane.

[0100] The crude organic product may be mixed with 50% aqueous sodium hydroxide in a suitable flask equipped with a mechanical stirrer. The mixture may be stirred and heated to at least about 90° C. (or from about 90° C. to about 110° C.) for 1 hour (or up to about 3 hours), cooled, and then transferred to a separatory funnel. The aqueous phase may be removed, and the organic product may be optionally washed twice with water. The organic product may be transferred to another flask, sparged with nitrogen, and optionally heated again to at least about 100° C. for up to about 1.5 hours. The organic product may be cooled to room temperature under a nitrogen sparge, and then optionally filtered through diatomaceous earth. Alternatively, the crude organic product may be distilled to recover the appropriate fractions containing the desired trisulfide and disulfide content.

[0101] An exemplary short chain di-tert-butyl polysulfide suitable for the first polysulfide extreme pressure agent can be made by the process described above and can include a majority trisulfide having about 43 to about 47 weight percent sulfur. The sulfide profile can be determined as described above. 13 It can be determined by CNMR.

[0102] EP Agent B: Di-tert-dodecyl polysulfide suitable for the long chain polysulfide or second polysulfide extreme pressure agents herein can be prepared as follows: A stainless steel autoclave can be charged with sulfur and tert-dodecyl sulfide. Optionally, an amine or other suitable catalyst can be simultaneously charged with a non-reactive solvent (e.g., heptane or dichloromethane). The reactants can be heated to a temperature of from ambient temperature (i.e., about 25° C.) to about 100° C. until all elemental sulfur is consumed. Volatile organics can be removed by vacuum stripping, and the organic product containing di-tert-dodecyl polysulfide can then be treated with 50% caustic or fractionally distilled as described in Example 1 to obtain primarily trisulfide products.

[0103] An exemplary long chain di-tert-dodecyl polysulfide suitable for the second polysulfide extreme pressure agent can be made by the process described above and can contain a majority of trisulfides having about 20 to about 23 weight percent sulfur. The sulfide profile can be determined as described above. 13 It can be determined by CNMR.

[0104] The first and second polysulfide extreme pressure agents resulting from the above methods for EP agents A and B, respectively, were evaluated in the lubricating compositions of Table 3 and tested for extreme pressure (ASTM D2596) and percent sulfur loss (ASTM D2893). The lubricating compositions of Table 3 also contained, in addition to the polysulfide extreme pressure agents described above, the same amounts of additive packages along with the same detergents, friction modifiers, viscosity modifiers, antioxidants, rust inhibitors, corrosion inhibitors, seal swell agents, and antifoam agents. The comparative and inventive compositions also contained the balance of base oil and / or process oil required to achieve a target KV100 of about 10 cSt to 14 cSt.

[0105] [Table 3] * The treat rate ratio is the weight percent of EP agent A to the weight percent of EP agent B. ** The sulfur ratio is the weight percent of sulfur from EP agent A to the weight percent of sulfur from EP agent B. *** Sulfur loss is measured by ICP before and after performing the S200 oxidation test (ASTM D2893). The %S loss is calculated as (SOT%S-EOT%S) / SOT%S*100, where SOT is the start of the test and EOT is the end of the test. **** ASTM D2596 (fresh lubricant before aging / oxidation testing, preferably above 200kgf).

[0106] As shown in Table 3 above, only lubricating compositions of fluids 1 and 2 of the present invention having sulfur ratios selected from a blend of short and long chain polysulfide extreme pressure agents passed both extreme pressure tests and maintained low sulfur loss below 30 percent. All comparative fluids had high levels of sulfur loss. It is preferable to have a 4-ball extreme pressure of at least about 200 kgf, and more importantly, to control and minimize sulfur loss over time, which can lead to reduced extreme pressure performance and / or tends to be undesirable for various environmental drawbacks.

[0107] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless expressly and unambiguously limited to one referent. Thus, for example, a reference to an "antioxidant" includes two or more different antioxidants. As used herein, the term "comprises" and grammatical variations thereof are intended to be open-ended, such that the recitation of items in a list does not exclude other similar items that may be substituted for or added to the items in the list.

[0108] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values ​​used in the specification and claims should be understood in all instances to be modified by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending on the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0109] It is understood that each component, compound, substituent, or parameter disclosed herein should be construed as disclosed for use alone or in combination with one or more of any and all other components, compounds, substituents, or parameters disclosed herein.

[0110] It is further to be understood that each range disclosed herein should be construed as a disclosure of each specific value within the disclosed range having the same number of significant digits. Thus, for example, a range of 1 to 4 should be construed as an explicit disclosure of not only the values ​​1, 2, 3, and 4, but any range of such values.

[0111] It is further understood that each lower limit of each range disclosed herein should be interpreted as being disclosed in combination with each upper limit of each range and each specific value within each range disclosed herein for the same component, compound, substituent, or parameter. Thus, the present disclosure should be interpreted as a disclosure of all ranges derived by combining each lower limit of each range with each upper limit of each range or each specific value within each range, or by combining each upper limit of each range with each specific value within each range. That is, it is further understood that any range between the endpoint values ​​within the broad range is also contemplated herein. Thus, a range of 1 to 4 also means a range of 1 to 3, 1 to 2, 2 to 4, 2 to 3, etc.

[0112] Furthermore, a specific amount / value of a component, compound, substituent, or parameter disclosed in the description or examples should be construed as a disclosure of either a lower or upper limit of a range and therefore can be combined with any other lower or upper limit of a range or specific amount / value for the same component, compound, substituent, or parameter disclosed elsewhere in this application to form a range for that component, compound, substituent, or parameter.

[0113] While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents may occur that are not presently anticipated or that cannot be currently anticipated by the applicants or others skilled in the art. It is therefore intended that the appended claims as filed, and the appended claims as they may be amended, cover all such alternatives, modifications, variations, improvements, and substantial equivalents.

Claims

1. 1. A lubricant composition comprising: a) a first polysulfide extreme pressure agent comprising a mixture of C2 to C6 polysulfides having 51 to 99 mole % trisulfides, said first polysulfide having the formula R 1 -Sx-R 2 wherein R 1 and R 2 is independently a C2 to C6 linear or branched alkyl group, and x is an integer of at least 2; b) a second polysulfide extreme pressure agent comprising a mixture of C10 to C14 polysulfides having 51 to 99 mole % trisulfides, said second polysulfide extreme pressure agent being represented by the formula R 3 -Sy-R 4 wherein R 3 and R 4 is independently a C10 to C14 linear or branched alkyl group and y is an integer of at least 2; and the ratio of weight percent of sulfur from the first polysulfide to weight percent of sulfur from the second polysulfide is 0.3 to 0.8; The lubricant composition, wherein the first and second polysulfides provide 0.2 to 0.5 wt. % sulfur to the lubricant composition.

2. 2. The lubricant composition of claim 1, wherein the first polysulfide has 40-50 wt. % sulfur and the second polysulfide has 18-30 wt. % sulfur.

3. 2. The lubricant composition of claim 1, wherein the first polysulfide has 1 to 10 mole percent disulfides and 51 to 95 mole percent trisulfides and / or the second polysulfide has 1 to 10 mole percent disulfides and 51 to 95 mole percent trisulfides.

4. R 1 and R 2 are independently a C4 to C6 linear or branched alkyl group, and / or R 1 and R 2 2. The lubricant composition of claim 1, wherein each of the alkyl groups is a C4 straight or branched alkyl group.

5. 2. The lubricant composition of claim 1, wherein the first polysulfide comprises di-tert-butyl polysulfide and / or the second polysulfide comprises di-tert-dodecyl polysulfide.

6. R 3 and R 4 2. The lubricant composition of claim 1, wherein each of the alkyl groups is a C12 straight or branched alkyl group.

7. 2. The lubricant composition of claim 1, wherein the lubricant composition has a sulfur loss of less than 30 weight percent calculated based on the amount of sulfur measured before and after oxidation testing according to ASTM D2893, and an extreme pressure of greater than 200 kgf measured according to the four-ball test of ASTM D2596.

8. 2. The lubricant composition of claim 1, further comprising 0.2 to 0.4 weight percent of the first polysulfide and 0.8 to 1.2 weight percent of the second polysulfide, and / or a weight percent ratio of the first polysulfide to the second polysulfide of 0.2 to 0.

38.

9. A first polysulfide extreme pressure agent comprising a mixture of C2 to C6 polysulfides having 51 to 99 mole % trisulfides, said first polysulfide having the formula R 1 -Sx-R 2 wherein R 1 and R 2 is independently a C2 to C6 linear or branched alkyl group, and x is an integer of at least 2; A second polysulfide extreme pressure agent comprising a mixture of C10 to C14 polysulfides having 51 to 99 mole % trisulfides, said second polysulfide having the formula R 3 -Sy-R 4 wherein R 3 and R 4 is independently a C10 to C14 straight or branched chain alkyl group and y is an integer of at least 2; and a second polysulfide extreme pressure agent, the ratio of weight percent of sulfur from the first polysulfide to weight percent of sulfur from the second polysulfide is 0.3 to 0.8; said first and second polysulfides providing 0.2 to 0.5 wt. % sulfur to said lubricant composition. A method of lubricating a driveline comprising lubricating a driveline component.

10. R 1 and R 2 The method of claim 9, wherein each is independently a C4 to C6 straight or branched chain alkyl group.

11. 10. The method of claim 9, wherein the first polysulfide comprises di-tert-butyl polysulfide and / or the second polysulfide comprises di-tert-dodecyl polysulfide.

12. 10. The method of claim 9, wherein the lubricant composition has a sulfur loss of less than 30 wt. %, calculated based on the amount of sulfur measured before and after oxidation testing according to ASTM D2893, and an extreme pressure of greater than 200 kgf, measured according to the 4-ball test of ASTM D2596.

13. 12. The method of claim 11, wherein the lubricant composition has a sulfur loss of less than 30 wt. %, calculated based on the amount of sulfur measured before and after oxidation testing according to ASTM D2893, and an extreme pressure of greater than 200 kgf, measured according to the four-ball test of ASTM D2596.

Images