Extreme pressure additive with improved copper corrosion

Abstract

A sulfurized extreme pressure additive that provides good copper corrosion and seal compatibility and a lubricant comprising the additive.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202311228123.6 (filing date: September 22, 2023; invention title: Extreme Pressure Additive with Improved Copper Corrosion). Technical Field

[0002] The present disclosure relates to extreme pressure additives having improved extreme pressure, friction, and / or copper corrosion characteristics and lubricating compositions comprising such additives suitable for use in gear oils, drive train applications, axle fluids, and / or power transmission fluids. Background Art

[0003] Gears, transmissions, and / or axles typically require lubricants that provide specific friction characteristics suitable for the desired application. Generally, such applications require the fluid to have appropriate extreme pressure performance, appropriate friction characteristics, appropriate copper corrosion performance, and other performance requirements. A variety of additives may be included in the lubricant to achieve the desired performance. For example, such lubricants may typically include sulfurized additives to protect gears and other components from wear and scuffing, and sulfurized isobutene oligomers or polymers are an exemplary extreme pressure additive for such applications. However, although sulfurized isobutene oligomers or polymers can provide good extreme pressure and / or wear performance, such sulfurized additives tend to be harmful to copper and copper alloys, resulting in unacceptable copper corrosion. Additionally, in some cases, some sulfurized isobutene oligomers or polymers also have the undesirable drawback of being insoluble in API Group IV base oils such as polyalphaolefin (PAO) base oils, which may limit the use of such additives in some applications. Summary of the Invention

[0004] In one method or embodiment, sulfurized polyolefin oligomers prepared by a three-step process are described herein. In the method, the product is prepared by a process comprising the steps of: (a) reacting a C2 to C18 olefin with sulfur halide to form an intermediate sulfurized olefin reaction product; (b) reacting the intermediate sulfurized olefin reaction product with an alkali metal hydrosulfide, an alkali metal hydroxide, and sulfur in an aqueous solution to form a sulfurized polyolefin reaction product; and (c) treating the sulfurized polyolefin reaction product with an aqueous alkaline solution at a time and temperature effective to form an improved sulfurized polyolefin oligomer.

[0005] In other methods or embodiments, the product described in the previous paragraph may include optional features or embodiments in any combination. These optional features or embodiments may include one or more of the following: wherein a copper strip immersed in the sulfurized polyolefin oligomer at about 121 °C for about 180 minutes according to ASTM D130 exhibits a copper weight loss of about 15 mg or less, and wherein about 2 wt% to about 5 wt% of the sulfurized polyolefin oligomer is soluble in both API Group III base oil and API Group IV base oil; and / or wherein the sulfurized polyolefin oligomer has a structure of Formula I: R-S x -R-[S x -R-S x n ​-R (Formula I), where each R is independently a C2 to C6 straight-chain or branched carbon chain, x is an integer from 1 to 5, and n is an integer such that the sulfurized polyolefin oligomer has a weight-average molecular weight of about 300 to about 800; and / or where the sulfurized polyolefin oligomer has about 30 wt% to about 50 wt% sulfur; and / or where the olefin is selected from the group consisting of ethylene, propylene, isopropylene, butene, isobutene, n-pentene, isopentene, neopentene, hexane, octane, styrene, αω-diene, 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, branched α-olefin, methyl-pentene, methyl-heptene, or a mixture thereof; and / or where the sulfur halide is selected from sulfur monochloride, sulfur dichloride, disulfur dibromide, sulfur dibromide, or a mixture thereof; and / or where the aqueous alkaline solution contains an alkali metal hydroxide selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, or a combination thereof; and / or where the treatment is carried out at a temperature of about 100 °C to about 150 °C for about 1 hour to about 5 hours; and / or where the treatment comprises about 10 wt% to about 50 wt% of the aqueous alkaline solution; and / or where the aqueous alkaline solution contains about 40 wt% to about 60 wt% of the alkali metal hydroxide and does not contain alcohol or ketone; and / or where the intermediate sulfurized olefin reaction product of step (a) is obtained by reacting about 0.4 mol to about 2 mol of the C2 to C18 olefin / about 0.3 mol to about 0.8 mol of the sulfur halide; and / or where the sulfurized polyolefin reaction product of step (b) is obtained by reacting about 0.2 mol to about 0.5 mol of sulfur / mol of the intermediate sulfurized olefin reaction product, about 0.7 mol to about 1.1 mol of the alkali metal hydroxide / mol of the intermediate sulfurized olefin reaction product, and the weight ratio of sulfur to sodium hydrosulfide is 0.01:1 to about 0.25:1; and / or where the sulfurized polyolefin oligomer of step (c) is obtained by treating the sulfurized polyolefin reaction product with about 10 wt% to about 50 wt% of the aqueous alkaline solution having about 40 wt% to about 60 wt% of the alkali metal hydroxide; and / or where the intermediate sulfurized olefin reaction product is obtained by reacting sulfur monochloride, sulfur dichloride, or a combination thereof with a C2 to C4 olefin, where the sulfurized polyolefin reaction product is obtained by reacting the intermediate sulfurized olefin reaction product with sodium hydrosulfide, sodium hydroxide, and elemental sulfur, and where the sulfurized polyolefin reaction product is treated with an aqueous sodium hydroxide solution of about 12 wt% to about 40 wt% to form the sulfurized polyolefin oligomer.

[0006] In other methods or embodiments, lubricating compositions are described herein that include a major amount of a base oil selected from API Group I to API Group V base oils and a minor amount of a sulfurized polyolefin oligomer. In one aspect, the sulfurized polyolefin oligomer is prepared by a three-step process that includes: (a) reacting a C2 to C18 olefin with sulfur halide to form an intermediate sulfurized olefin reaction product; (b) reacting the intermediate sulfurized olefin reaction product with an alkali metal hydrosulfide, an alkali metal hydroxide, and sulfur in an aqueous solution to form a sulfurized polyolefin reaction product; and (c) treating the sulfurized polyolefin reaction product with an aqueous alkaline solution at a time and temperature effective to form the sulfurized polyolefin oligomer.

[0007] The lubricating compositions described in the previous paragraph can be combined with one or more optional features or embodiments in any combination. Such embodiments or features can include one or more of the following: wherein a copper strip immersed in the sulfurized polyolefin oligomer at about 121 °C for about 180 minutes according to ASTM D130 exhibits a copper weight loss of less than about 15 mg, and wherein about 2 wt% to about 5 wt% of the sulfurized polyolefin oligomer is soluble in both API Group III base oil and API Group IV base oil; and / or wherein the sulfurized polyolefin oligomer has a structure of Formula I: R-S x -R-[S x -R-S x n ​-R (Formula I), where each R is independently a C2 to C6 straight-chain or branched-chain carbon chain, x is an integer from 1 to 5, and n is an integer such that the sulfurized polyolefin oligomer has a weight-average molecular weight of about 300 to about 800; and / or where the sulfurized polyolefin oligomer has about 30 wt% to about 50 wt% sulfur; and / or where the olefin is selected from the group consisting of: ethylene, propylene, isopropylene, butene, isobutene, n-pentene, isopentene, neopentene, hexane, octane, styrene, αω-diene, 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, branched α-olefin, methyl-pentene, methyl-heptene, or a mixture thereof; and / or where the sulfur halide is selected from sulfur monochloride, sulfur dichloride, disulfur dibromide, sulfur dibromide, or a mixture thereof; and / or where the aqueous alkaline solution contains an alkali metal hydroxide selected from sodium hydroxide, potassium hydroxide, or a combination thereof; and / or where the treatment is carried out at a temperature of about 100 °C to about 150 °C for about 1 hour to about 5 hours; and / or where the treatment comprises about 10 wt% to about 50 wt% of the aqueous alkaline solution; where the aqueous alkaline solution contains about 40 wt% to about 60 wt% of the alkali metal hydroxide and does not contain alcohol, ketone, or other alkanol; and / or where the intermediate sulfurized olefin reaction product of step (a) is obtained by reacting about 0.4 mol to about 2 mol of the C2 to C18 olefin / about 0.3 mol to about 0.8 mol of the sulfur halide; and / or where the sulfurized polyolefin reaction product of step (b) is obtained by reacting about 0.2 mol to about 0.5 mol of sulfur / mol of the intermediate sulfurized olefin reaction product, about 0.7 mol to about 1.1 mol of the alkali metal hydroxide / mol of the intermediate sulfurized olefin reaction product, and the weight ratio of sulfur to sodium hydrogen sulfide is 0.01:1 to about 0.25:1; and / or where the sulfurized polyolefin oligomer of step (c) is obtained by treating the sulfurized polyolefin reaction product with about 10 wt% to about 50 wt% of the aqueous alkaline solution having about 40 wt% to about 60 wt% of the alkali metal hydroxide; and / or where the intermediate sulfurized olefin reaction product is obtained by reacting sulfur monochloride, sulfur dichloride, or a combination thereof with a C2 to C4 olefin, where the sulfurized polyolefin reaction product is obtained by reacting the intermediate sulfurized olefin reaction product with sodium hydrogen sulfide, sodium hydroxide, and elemental sulfur, and where the sulfurized polyolefin reaction product is treated with an aqueous sodium hydroxide solution of about 12 wt% to about 40 wt% to form the sulfurized polyolefin oligomer.

[0008] In other embodiments, the use of an alkaline wash or treatment as described in any of the embodiments of the present disclosure for treating a sulfurized polyolefin reaction product to form a sulfurized polyolefin oligomer is disclosed, wherein a copper strip immersed in the sulfurized polyolefin oligomer at about 121 °C for about 180 minutes according to ASTM D130 exhibits a copper weight loss of less than about 15 mg, and wherein about 2 wt% to about 5 wt% of the sulfurized polyolefin oligomer is soluble in both API Group III base oil and API Group IV base oil.

[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 term definitions are provided to clarify the meaning of certain terms as used herein.

[0010] The terms "gear oil", "gear fluid", "gear lubricant", "base gear lubricant", "lubricating oil", "lubricant composition", "lubricating composition", "lubricant" and "lubricating fluid" refer to finished lubricating products containing a major amount of a base oil as discussed herein and a minor amount of an additive composition as discussed herein. Such gear fluids are used in extreme pressure situations, such as for transmission and gear drive components having metal-to-metal contact situations, such as in transmissions and / or limited slip differentials.

[0011] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary meaning, which is well 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 predominantly having a hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents and substituted hydrocarbon substituents containing one or more halogen groups, hydroxy groups, alkoxy groups, mercapto groups, nitro groups, nitroso groups, amino groups, pyridyl groups, furyl groups, imidazolyl groups, oxygen and nitrogen, and wherein there are no more than two non-hydrocarbon substituents for every ten carbon atoms in the hydrocarbyl group.

[0012] As used herein, unless otherwise expressly stated, the term "weight percent" or "wt%" means the percentage by weight of the component in the entire composition. Unless otherwise indicated, all percentages herein are weight percentages.

[0013] The terms "soluble", "oil-soluble" or "dispersible" as used herein may but do not necessarily mean that the compound or additive is soluble, dissolvable, miscible or capable of being suspended in oil in all proportions. However, the foregoing terms do mean that they are, for example, soluble, suspendable, dissolvable or stably dispersible in oil to an extent sufficient to perform their intended function in the environment in which the oil is used. Additionally, the incorporation of other additives, if desired, may also permit the incorporation of higher levels of a particular additive.

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

[0015] As used herein, the molecular weight is determined by gel permeation chromatography (GPC) using commercially available polystyrene standards (having an Mn of about 180 to about 18,000 as the calibration reference). The molecular weight (Mn) of any embodiment herein can be measured using an instrument such as a gel permeation chromatography (GPC) instrument obtained from Waters, and the data is processed using software such as Waters Empower software. The GPC instrument can be equipped with a Waters separation module and a Waters refractive index detector (or similar optional equipment). The GPC operating conditions can include a guard column, 4 Agilent PLgel columns (length 300×7.5 mm; particle size 5 μm, and pore size range of )), the column temperature is about 40 °C. Unstabilized HPLC grade tetrahydrofuran (THF) can be used as the solvent, and the flow rate is 1.0 mL / min. The GPC instrument can be calibrated with commercially available polystyrene (PS) standards having a narrow molecular weight distribution in the range of 500 g / mol to 380,000 g / mol. For samples with a mass less than 500 g / mol, the calibration curve can be extrapolated. The samples and PS standards can be dissolved in THF and prepared at a concentration of 0.1 wt% to 0.5 wt% and used without filtration. The GPC measurement is also described in US 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. Bly, "Modern Size Exclusion Liquid Chromatography", John Wiley and Sons, New York, 1979, which is also incorporated herein by reference.

[0016] As used herein, any reported sulfur moiety distribution or ratio (i.e., -S x -) is determined using 13C NMR via a Bruker Avance-3 HD 500 MHz instrument equipped with a 5 mm BBO Prodigy probe (or equivalent). The sample is dissolved in chloroform-d, for 11H NMR one-dimensional (1D) and two-dimensional (2D) homonuclear experiments were about 3% weight / wt, and for 13 13C 1D and 2D heteronuclear experiments were about 30% weight / wt. Chloroform-d was used as the chemical shift reference, at δ H = 7.27 and δ C = 77.0 ppm, respectively. The experiments were carried out at ambient temperature. For 13 13C NMR experiments, a ninety-degree pulse width, 5x T1 delay, and gated 1 1H decoupling were used, and direct observation 1D 1 1H and 13 13C- 1 1H decoupling experiments were carried out under quantitative conditions. In addition, distortionless enhancement by polarization transfer (DEPT) experiments using the 135-degree pulse option were also obtained. The 2D experiments for assisting structure assignment were homonuclear correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), and heteronuclear multiple bond correlation (HMBC). All NMR data were obtained using Bruker Topspin 3.62 software from Bruker Inc of 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] It should be understood that throughout this disclosure, the terms "comprising", "including", "containing", etc. are considered open-ended and include any element, step, or ingredient not explicitly listed. The phrase "consisting essentially of" means including any explicitly listed element, step, or ingredient and any additional element, step, or ingredient that does not materially affect the basic and novel aspects of the invention. This disclosure also contemplates that any composition described using the terms "comprising", "including", "containing" is also interpreted as including the disclosure of the same composition "consisting essentially of its specifically listed components" or "consisting of its specifically listed components". BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is an image of three lubricant additives (including a comparative isobutene sulfide oligomer of the present disclosure and two isobutene sulfide oligomers of the present invention) in a Group III base oil, showing that all oligomers are soluble in Group III oil considering the clear solutions in each container; and

[0019] Figure 2Images of three lubricant additives in Group IV base oils, including a comparative sulfurized isobutene oligomer and two sulfurized isobutene oligomers of the present invention, showing that the comparative sulfurized isobutene oligomer is insoluble in Group IV oil (left container), and considering the clear solution, the two sulfurized isobutene oligomers of the present invention are soluble in Group IV oil (middle container and right container). Detailed Description

[0020] In the methods or embodiments of the present disclosure, there are provided sulfurized polyolefin oligomers or polymer extreme pressure agents and lubricating compositions comprising such extreme pressure agents suitable for use in drive train systems, gear fluids, power transmission fluids, and / or axle applications. The sulfurized polyolefin oligomers or polymer extreme pressure additives herein provide good extreme pressure performance and one or more of low levels of copper corrosion, solubility in API Group III and Group IV base oils, and / or combinations thereof.

[0021] In one aspect, the sulfurized polyolefin oligomers or polymer extreme pressure agents of the present disclosure are prepared by a three-step process that at least includes the following steps: (a) reacting an olefin (such as a C2 to C18 olefin) with sulfur halide to form an adduct or intermediate sulfurized olefin reaction product; (b) reacting the adduct or intermediate sulfurized olefin reaction product with an alkali metal hydrosulfide, an alkali metal hydroxide, and a sulfur source in an aqueous solution to form a sulfurized polyolefin reaction product; and (c) washing or treating the sulfurized polyolefin reaction product with an aqueous alkaline solution at a time and temperature effective to form the sulfurized polyolefin oligomer extreme pressure agents of the present disclosure. The resulting sulfurized polyolefin oligomers or polymers can be used as extreme pressure additives and, in the methods or embodiments, provide improved copper corrosion and / or improved solubility in both API Group III and API Group IV base oils. For example, a copper strip immersed in a sulfurized polyolefin oligomer (prepared by the three-step process of this application) at about 121 °C for about 180 minutes according to ASTM D130 exhibits a copper weight loss of about 15 mg or less (preferably about 10 mg or less or about 5 mg or less of copper weight loss) and about 2 wt% to about 5 wt% (preferably 2 wt% to 4 wt%) of the sulfurized polyolefin oligomer is soluble in both API Group III base oil and API Group IV base oil.

[0022] In other methods or embodiments, when prepared by the above three-step process, the sulfurized polyolefin oligomers or polymers are different from discrete polysulfide molecules and are polymers or oligomers having a structure of Formula I:

[0023] R-S x -R-[S x -R-S x n -R (Formula I) ​

[0024] Each R is independently derived from an olefin (preferably a C2 to C6 straight or branched carbon chain or hydrocarbon group or other olefins as described below), x is an integer of at least 1, and preferably an integer from 1 to 5 (or an integer from 2 to 4 or an integer from 2 to 3), and n is an integer such that the entire sulfurized polyolefin oligomer or polymer has a weight average molecular weight of about 300 to about 800, preferably about 500 to about 750, or more preferably about 600 to about 750. In the process, the sulfurized polyolefin oligomer has a total sulfur content of about 30 wt% to about 50 wt%, preferably about 40 wt% to about 50 wt%, and more preferably about 40 wt% to about 45 wt%. As discussed in more detail below, the sulfurized polyolefin oligomers herein are prepared by a three-step process.

[0025] The first step of the process is the reaction of an olefin with sulfur halide to form an adduct or intermediate sulfurized olefin reaction product. The olefin used in this first reaction step can be any unsaturated aliphatic hydrocarbon, and in some processes is an olefin having 2 to 18 carbon atoms, in other processes is an olefin having 2 to 12 carbon atoms, or in yet other processes is an olefin having 2 to 6 carbon atoms. Examples of suitable olefins include, but are not limited to, ethylene, propylene, isopropylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 1-hexene, 2-hexene, 3-hexene, 2-methyl-1-pentene, 2-methyl-2-pentene, 2-ethyl-2-butene, neopentene, hexane, octane, styrene, αω-dienes, 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, branched α-olefins, methyl-pentene, methyl-heptene and other olefins and mixtures thereof. Suitable olefins can also include branched olefins such as isobutene, 2-methyl-1-butene, 1-methyl-2-butene, 2-methyl-2-pentene and mixtures thereof. Preferably, the olefin is isobutene.

[0026] Suitable sulfur halide reactants for preparing the adduct or intermediate sulfurized olefin reaction product of the first reaction step can be selected from sulfur monochloride, sulfur dichloride, disulfur dibromide, sulfur dibromide or mixtures thereof. Preferably, the sulfur halide is sulfur monochloride, which is understood by those skilled in the art to be S 2 Cl 2 .

[0027] In the method, the selected olefin can be added to the sulfur halide as a gas or a liquid to form an adduct or an intermediate sulfurized olefin reaction product, as the first step in forming the extreme pressure additives of the present invention. Preferably, the olefin is added as a gas below the surface of the sulfur halide. In practice, the selected olefin is added until the reaction with the sulfur halide stops as indicated, e.g., by the loss of exotherm. In the method, about 0.4 moles to about 2 moles of olefin per 0.3 moles to 0.8 moles of sulfur halide (e.g., sulfur monochloride) are suitable for the first reaction step of the method of the present invention.

[0028] In the method, in the first process step, an adduct (i.e., an intermediate sulfurized olefin reaction product) of an olefin and a sulfur halide is formed in the absence or without the use of an alkanol promoter, a ketone, or other alcohol medium. Preferably, the reaction is carried out in an aqueous medium that allows a higher reaction temperature. As used herein, an alkanol promoter is any lower alcohol having 1 to 4 carbon atoms, such as methanol, ethanol, n-propanol, isopropanol, isobutanol, tert-butanol, etc. As used herein, the absence or non-presence of an alcohol, a ketone, or an alkanol promoter means that such a process step has about 1% or less, about 0.5 wt% or less, about 0.25 wt% or less, about 0.1 wt% or less of an alcohol, a ketone, or an alkanol promoter, or is free of an alcohol, a ketone, or an alkanol promoter.

[0029] The adduct formation step can be carried out at any elevated temperature sufficient to cause the reaction to proceed. In the method or embodiment, the adduct or intermediate sulfurized olefin reaction product is carried out at a temperature of about 0 °C to about 100 °C, in other methods, about 0 °C to about 75 °C, in further methods, about 0 °C to about 40 °C, and in further methods, about 5 °C to about 40 °C or about 20 °C to about 40 °C.

[0030] The adduct formation step should be carried out for a time sufficient to complete the reaction between the sulfur halide and the olefin. This is usually limited by heat removal, and in the method, the olefin feed rate can be controlled to maintain the reaction temperature within the desired range. When the sulfur halide is consumed, the temperature will drop. If desired, external heat can be added to continue the reaction for an additional period of time.

[0031] Next, in a second step, the adduct formed or the intermediate sulfurized olefin reaction product formed is treated in an alkaline aqueous medium or reacted with an additional sulfur source to form a sulfurized polyolefin reaction product. The additional sulfur source can be selected from elemental sulfur and / or metal sulfides such as sodium hydrosulfide, sodium sulfide, bismuth sulfide, copper sulfide, hydrogen sulfide, manganese sulfide, tin sulfide and other sulfur sources, or any combination thereof. Preferably, the sulfur source is provided by elemental sulfur or an alkali metal sulfide or hydrogen sulfide, and most preferably by a combination of elemental sulfur and sodium hydrosulfide. In the process, the alkaline aqueous medium for this partial reaction step includes alkali metal hydroxides (such as an aqueous solution of 40 wt% to 60 wt%), such as sodium hydroxide, potassium hydroxide, lithium hydroxide, etc., or a combination thereof. Preferably, the alkaline aqueous medium for this second reaction step includes sodium hydroxide, and more preferably, a 50% aqueous sodium hydroxide solution. An optional alkanol, such as propanol, can be used during the second reaction step.

[0032] In the process, the alkaline aqueous medium for this second reaction step can include a molar ratio of sulfur atoms fed during this second step to the adduct from the first step of about 0.2:1 to about 0.5:1, in other processes about 0.22:1 to about 0.4:1, or in additional processes about 0.25:1 to about 0.3:1. In some embodiments, the second reaction step of the process herein can also have a weight ratio of elemental sulfur to metal sulfide (such as NaSH) of about 0.01:1 to about 0.25:1, in some processes about 0.04:1 to about 0.2:1 and in other processes about 0.08:1 to about 0.1:1.

[0033] When a metal sulfide and elemental sulfur are used as additional sulfur sources in the second reaction step, the aqueous medium also includes an alkaline solution, typically an aqueous solution of a metal hydroxide or an alkali metal hydroxide as described above. In one process, the alkaline aqueous medium preferably includes sodium hydroxide and can include greater than about 0.7 moles of sodium hydroxide / mole of adduct, preferably greater than about 0.8 moles of sodium hydroxide / mole of adduct, and most preferably in the range of about 0.8 moles to about 1.1 moles of sodium hydroxide / mole of adduct.

[0034] In one process of the second reaction step, the alkaline aqueous solution is first heated before adding the adduct or the intermediate sulfurized olefin reaction product. In one embodiment, the alkaline solution is heated to about 50 °C or higher, about 60 °C or higher, or about 70 °C or higher, and preferably about 45 °C to about 65 °C or about 50 °C to about 65 °C. Then the adduct or intermediate is added with stirring for about 10 hours, preferably about 2 hours to about 4 hours. Then the mixture is held at an elevated temperature for a period of time sufficient to form an organic phase containing the sulfurized polyolefin reaction product.

[0035] The sulfurized polyolefin reaction product formed by the above two reaction steps can be used as an extreme pressure additive, but often has the disadvantage of being more corrosive to copper and, in some cases, is insoluble in API Group IV base oils such as those exemplified in the following examples. Thus, the method herein uses a washing or treatment step with a caustic solution or an aqueous alkaline solution in a third method step at the time and temperature effective to form the sulfurized polyolefin oligomers of the present disclosure with improved copper corrosion and Group IV base oil solubility to further treat or wash the formed sulfurized polyolefin reaction product.

[0036] In one method, the third method step of the present disclosure washes or treats the sulfurized polyolefin reaction product formed by the second process step with a caustic solution or an aqueous alkaline solution containing an alkali metal hydroxide. In one method or embodiment, the caustic or aqueous alkaline solution comprises sodium hydroxide, potassium hydroxide, lithium hydroxide, or a combination thereof. Preferably, the final treatment or washing step uses a caustic solution of sodium hydroxide. The washing or treatment step can be carried out at a temperature of about 100 °C or higher, such as a temperature of about 100 °C to about 150 °C (in other methods, about 100 °C to about 130 °C, or in other methods, about 105 °C to about 115 °C) for about 1 hour to about 5 hours (in other methods, about 2 hours to about 4 hours, or in other methods, about 2 hours to about 3 hours).

[0037] In some methods, based on the total amount of the sulfurized polyolefin reaction product and the caustic solution in the washing step, the washing or treatment step comprises about 10 wt% to about 50 wt% of the caustic / aqueous alkaline solution, or in other methods, about 10 wt% to about 20 wt%, or about 30 wt% to about 50 wt% of the caustic / aqueous alkaline solution. Preferably, the aqueous alkaline solution used in the washing step is an aqueous solution containing about 40 wt% to about 60 wt% of an alkali metal hydroxide (preferably, a 50% caustic or sodium hydroxide solution) and free of alcohols, ketones, and / or alkanol promoters as described above. For example, the washing or final treatment step is free of alcohols, ketones, or alkanol promoters, and in such cases, has about 1% or less, about 0.5 wt% or less, about 0.25 wt% or less, about 0.1 wt% or less of alcohols, ketones, or alkanol promoters in the final washing or treatment step, or is free of alcohols, ketones, or alkanol promoters.

[0038] In a preferred method, an adduct or intermediate sulfurized olefin reaction product is obtained by reacting sulfur monochloride, sulfur dichloride, or a combination thereof (and preferably sulfur monochloride) with a C2 to C4 olefin (and preferably isobutene) in the first step of the method. Subsequently, in the second step of the method, a sulfurized polyolefin reaction product is obtained by reacting the adduct or intermediate sulfurized olefin reaction product with sodium hydrosulfide, sodium hydroxide, and elemental sulfur. Finally, in the third or final step of the method, the sulfurized polyolefin reaction product is treated or washed with an aqueous solution of about 15 wt% to about 40 wt% caustic or sodium hydroxide at a certain temperature for a period of time to form the final sulfurized polyolefin oligomer or polymer of the present disclosure having improved copper corrosion and improved solubility in API Group IV base oils.

[0039] As shown in the following examples, a three-step process for forming sulfurized polyolefin oligomers or polymers herein forms extreme pressure additives that also exhibit low copper corrosion and solubility in API Group IV base oils such as polyalphaolefins. Additionally, high levels of sulfur are generally detrimental to copper corrosion, but when the lubricating compositions herein contain sulfurized polyolefin oligomers or polymers prepared by the methods herein, the compositions can surprisingly contain comparable and / or higher levels of total sulfur but still achieve better copper corrosion performance than comparative fluids containing existing sulfurized oligomers or polyolefins.

[0040] In one method, a sulfurized polyolefin oligomer or polymer as described above can be used as an extreme pressure additive in a suitable base oil and optionally combined with one or more other additives required for drivetrain, transmission, gear oil, or axle lubricant applications, having a KV100 (ASTM 445) of, for example, about 6 cSt to about 18 cSt, or in some methods about 12 cSt to about 18 cSt, or in other methods about 6 cSt to about 12 cSt.

[0041] Base oil

[0042] Suitable base oils for the lubricating compositions or gear fluids herein include mineral oils, synthetic oils, and include all common mineral oil base stocks. Mineral oils can be naphthenic oils or paraffinic oils. Mineral oils can be refined by conventional methods using acids, bases, and clays or other reagents such as aluminum chloride, or can be extracted oils, such as produced by solvent extraction with solvents such as phenol, sulfur dioxide, furfural, or dichlorodiethyl ether. Mineral oils can be hydrotreated or hydrorefined, dewaxed by a chilling or catalytic dewaxing process, or hydrocracked, such as the series of hydrocracked base oils from SK Innovation Co., Ltd. (Seoul, Korea). Mineral oils can be produced from natural crude oil sources or consist of isomerized wax materials or residues from other refining processes.

[0043] The base oil for the lubricating oil composition or the base oil having lubricating viscosity herein may be selected from any suitable base oil. Examples include base oils in Groups I - V as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. These three groups of base oils are as follows:

[0044] Table 1: Base oil types

[0045]

[0046] Groups I, II, and III are mineral oil processing stocks and can be preferably used for the 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 results in their physical properties being very similar to some true synthetic oils, such as PAO. Thus, oils derived from Group III base oils can be referred to as synthetic fluids in the industry. Suitable oils can be derived from hydrocracked, hydrogenated, hydrorefined, unrefined, refined, and re-refined oils and mixtures thereof. In some methods, the base oil can be a blend of Group I oil and Group II oil, and the blend can 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 Group I and Group II, Group I and Group III, or Group II and Group III oils.

[0047] Unrefined oils are those oils derived from natural, mineral, or synthetic sources without or with little further purification treatment. Refined oils are similar to unrefined oils, except that they have been treated with one or more purification steps, which 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 can also be referred to as white oils. In some embodiments, the lubricating oil composition does not contain edible oil or white oil.

[0048] Re-refined oils are also referred to as recycled oils or reprocessed oils. Similar to refined oils, these oils are obtained using the same or similar processing. Typically, these oils are further processed by techniques directed at removing waste additives and oil decomposition products.

[0049] Mineral oils can include oils obtained by drilling or oils from plants and animals or any mixtures thereof. For example, such oils can include, but are not limited to, castor oil, lard, olive oil, peanut oil, corn oil, soybean oil, and linseed oil, as well as mineral lubricating oils such as liquid petroleum and solvent-treated or acid-treated paraffinic, naphthenic, or mixed paraffinic-naphthenic type mineral lubricating oils. If desired, such oils can be partially or fully hydrogenated. Oils derived from coal or shale can also be suitable.

[0050] The major amount of base oil included in the gear fluids herein can be selected from the group consisting of Group I, Group II, Group III, and combinations of two or more of the foregoing, and wherein the major amount of base oil is not the base oil resulting from providing additive components or viscosity index improvers in the composition. In another embodiment, the major amount of base oil included in the lubricating composition can be selected from the group consisting of Group I, Group II, and combinations of two or more of the foregoing, and wherein the major amount of base oil is not the base oil resulting from providing additive components or viscosity index improvers in the composition.

[0051] The base oil can also be any synthetic base oil. Useful synthetic lubricating oils can include hydrocarbon oils such as polymerized, oligomerized, or copolymerized olefins (e.g., polybutene, polypropylene, propylene-isobutylene copolymer); poly(1-hexene), poly(1-octene), trimers or oligomers of 1-decene such as poly(1-decene), such materials are commonly referred to as α-olefins, and mixtures thereof; alkyl-benzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di-(2-ethylhexyl)-benzene); polyphenyls (e.g., biphenyl, terphenyl, alkylated polyphenyl); diphenylalkanes, alkylated diphenylalkanes, alkylated diphenyl ethers, and alkylated diphenyl sulfides and their derivatives, analogs, and homologs or mixtures thereof. Poly-α-olefins are typically hydrogenated materials.

[0052] Other synthetic lubricating oils include polyol esters containing phosphoric acid, diesters, liquid esters (e.g., tolyl phosphate, trioctyl phosphate, and diethyl decane phosphonate), or polytetrahydrofuran. Synthetic oils can be produced by the Fischer-Tropsch reaction and can typically be hydroisomerized Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oil can be prepared by a Fischer-Tropsch gas-liquid synthesis procedure as well as other gas-liquid oils.

[0053] In the compositions of the present disclosure, the amount of the base oil having lubricating viscosity can be the balance remaining after subtracting the sum of the amounts of the performance additives from 100 weight %. For example, the oil having lubricating viscosity that can be present in the finished fluid can be a "major amount", such as greater than about 50 weight %, greater than about 60 weight %, greater than about 70 weight %, greater than about 80 weight %, greater than about 85 weight %, greater than about 90 weight % or greater than about 95 weight %.

[0054] In some embodiments, the preferred base oil or base oil having lubricating viscosity has less than about 25 ppm of sulfur, a viscosity index greater than about 120, and a kinematic viscosity of from about 2 cSt to about 8 cSt at about 100 °C. In other embodiments, the base oil having lubricating viscosity has less than about 25 ppm of sulfur, a viscosity index greater than 120, and a kinematic viscosity of about 4 cSt at 100 °C. The base oil can have a CP (chain paraffinic carbon content) of greater than 40%, greater than 45%, greater than 50%, greater than 55% or greater than 90%. The base oil can have a CA (aromatic carbon content) of less than 5%, less than 3% or less than 1%. The base oil can 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 ratio of monocyclic naphthenes to 2-6 ring naphthenes that the base oil can have is less than 2 or less than 1.5 or less than 1.

[0055] Suitable drive train or gear lubricant compositions of the present disclosure can include additive components in the ranges listed in Table 2 below.

[0056] Table 2: Suitable and preferred transmission system or gear fluid compositions

[0057]

[0058] The percentages of each of the above components represent weight percentages of each component based on the weight of the total final additive or lubricating oil composition. The remainder of the lubricating oil composition consists of one or more base oils or solvents. The additives used to formulate the compositions described herein can be blended into the base oil or solvent individually or in various sub-combinations. However, it can be suitable to blend all components simultaneously using an additive concentrate (i.e., an additive plus a diluent, such as a hydrocarbon solvent).

[0059] The lubricating compositions described herein can be formulated to provide lubrication, enhanced friction properties, and improved copper corrosion for various applications. The drive train lubricating compositions herein can be used to lubricate machine components 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 gears, helical gears, worm gears, rack gears, involute gears, bevel gears, helical gears, planetary gears, and hypoid gears, as well as limited slip applications and differentials. The drive train lubricating compositions disclosed herein are also suitable for automatic or manual transmissions, including stepped automatic transmissions, continuously variable transmissions, semi-automatic transmissions, automated manual transmissions, toroidal transmissions, and dual clutch transmissions. The drive train lubricating compositions herein are particularly suitable for axles, transfer cases, differentials such as straight differentials, steering differentials, limited slip differentials, clutch type differentials, and locked differentials, etc.

[0060] Optional additive

[0061] In other methods, lubricants containing such additives as described above may also contain one or more optional components, provided that such components and their amounts do not affect the performance characteristics as described in the above paragraphs. These optional components are described in the following paragraphs.

[0062] Phosphorus-containing compound

[0063] The lubricant compositions herein can contain one or more phosphorus-containing compounds that can confer antiwear benefits to the fluid. The one or more phosphorus-containing compounds are present in the lubricating oil composition in an amount in the range of about 0 wt% to about 15 wt%, or about 0.01 wt% to about 10 wt%, or about 0.05 wt% to about 5 wt%, or about 0.1 wt% to about 3 wt% of the lubricating oil composition. The phosphorus-containing compound can provide up to 5000 ppm of phosphorus to the lubricant composition, or about 50 to about 5000 ppm of phosphorus, or about 300 to about 1500 ppm of phosphorus, or up to 600 ppm of phosphorus, or up to 900 ppm of phosphorus.

[0064] The one or more phosphorus-containing compounds can include ashless phosphorus-containing compounds. Examples of suitable phosphorus-containing compounds include, but are not limited to, thiophosphates, dithiophosphates, phosphates, phosphoric esters, phosphate esters, phosphites, phosphonates, phosphorus-containing carboxylic esters, ethers, or their amide salts and mixtures thereof. Phosphorus-containing antiwear agents are more fully described in European Patent 0612839.

[0065] It should be noted that the terms phosphonate and phosphite are often used interchangeably in the lubricant industry. For example, dibutyl hydrogen phosphonate is commonly referred to as dibutyl hydrogen phosphite. The lubricant compositions of the present invention containing phosphorus-containing compounds that can be referred to as phosphites or phosphonates are within the scope of the present invention.

[0066] In any of the above phosphorus-containing compounds, the compound may have from about 5 wt% to about 20 wt% phosphorus, or from about 5 wt% to about 15 wt% phosphorus, or from about 8 wt% to about 16 wt% phosphorus, or from about 6 wt% to about 9 wt% phosphorus.

[0067] Combining the phosphorus-containing compound with the above dispersant and adding it to the lubricant composition unexpectedly imparts positive friction characteristics to the lubricant composition, such as a low coefficient of friction. In some cases, the effect of the present invention is even more significant when the phosphorus-containing compound itself imparts negative friction characteristics to the fluid. When these relatively poor friction-reducing phosphorus-containing compounds are combined with the olefin copolymer dispersants described herein, the lubricant composition has improved, i.e., lower, coefficients of friction. That is, the dispersants herein tend to transform a fluid containing a phosphorus-containing compound having a relatively poor coefficient of friction into a fluid having improved friction performance.

[0068] This improvement in the friction performance of the lubricating composition comprising the phosphorus-containing compound and the olefin copolymer dispersant described herein is surprising because the friction performance of the fluid is superior to the combination of the phosphorus-containing compound with other types of dispersants, including polyisobutylene succinimide dispersants and olefin copolymer succinimide dispersants that do not have the specified characteristics of the above copolymers.

[0069] Another type of phosphorus-containing compound that imparts improved friction characteristics to the lubricant composition when combined with the olefin copolymer dispersants herein is an ashless (metal-free) phosphorus-containing compound.

[0070] In some embodiments, the ashless phosphorus-containing compound can be dialkyl dithiophosphates, amyl phosphates, dipentyl phosphates, dibutyl hydrogen phosphonate, dimethyl octadecyl phosphonate, their salts, and mixtures thereof.

[0071] The ashless phosphorus-containing compound can have the following formula:

[0072]

[0073] wherein R1 is S or O; R2 is -OR, -OH or -R"; R3 is -OR", -OH or SR'"(O)OH; R4 is -OR"; R'" is a C1-C3 branched or straight-chain alkyl chain; and R" is a C1 to C18 hydrocarbon chain. When the phosphorus-containing compound has the structure shown in Formula XIV, the compound may have from about 8 to about 16 wt% phosphorus.

[0074] In some embodiments, the lubricant composition comprises a phosphorus-containing compound of Formula XIV, wherein R1 is S; R2 is -OR"; R3 is SR'"COOH; R4 is -OR"; R'" is a C3 branched alkyl chain; R" is C4; and wherein the phosphorus-containing compound is present in an amount to deliver 80 ppm to 900 ppm of phosphorus to the lubricant composition.

[0075] In another embodiment, the lubricant composition comprises a phosphorus-containing compound of Formula XIV, wherein R1 is O; R2 is -OH; R3 is -OR" or -OH; R4 is -OR"; R" is C5; and wherein the phosphorus-containing compound is present in an amount to deliver 80 ppm to 1500 ppm of phosphorus to the lubricant composition.

[0076] In a further embodiment, the lubricant composition comprises a phosphorus-containing compound of Formula XIV, wherein R1 is O; R2 is OR"; R3 is H; R4 is -OR"; R" is C4; and wherein one or more phosphorus-containing compounds are present in an amount to deliver 80 ppm to 1550 ppm of phosphorus to the lubricant composition.

[0077] In other embodiments, the lubricant composition comprises a phosphorus-containing compound of Formula XIV, wherein R1 is O; R2 is -R"; R3 is -OCH3 or -OH; R4 is -OCH3; R" is C18; and wherein one or more phosphorus-containing compounds are present in an amount to deliver 80 ppm to 850 ppm of phosphorus to the lubricant composition.

[0078] In some embodiments, the phosphorus-containing compound has the structure shown in Formula XIV and delivers from about 80 ppm to about 4500 ppm of phosphorus to the lubricant composition. In other embodiments, the phosphorus-containing compound is present in an amount to deliver from about 150 ppm to about 1500 ppm of phosphorus, or from about 300 ppm to about 900 ppm of phosphorus, or from about 800 ppm to 1600 ppm of phosphorus, or from about 900 ppm to about 1800 ppm of phosphorus to the lubricant composition.

[0079] Antiwear agent

[0080] The lubricant composition may further comprise other antiwear agents that are phosphorus-free compounds. Examples of such antiwear agents include borate esters, borate ester epoxides, thiocarbamate compounds (including thiocarbamates, alkylene-coupled thiocarbamates, and bis(S-alkyl dithiocarbamoyl) disulfides, thiocarbamate amides, thiocarbamate ethers, alkylene-coupled thiocarbamates, and bis(S-alkyl dithiocarbamoyl) disulfides and mixtures thereof), sulfurized olefins, tridecyl adipate, titanium compounds, and long-chain derivatives of hydroxycarboxylic acids such as tartrate esters, tartramides, tartrimides, citrates, and mixtures thereof. A suitable thiocarbamate compound is molybdenum dithiocarbamate. Suitable tartrate esters or tartrimides may contain alkyl ester groups, where the total number of carbon atoms on the alkyl group can be at least 8. The tartrate ester derivative or tartrimide may contain alkyl ester groups, where the total number of carbon atoms on the alkyl group can be at least 8. In one embodiment, the antiwear agent may include citrate esters. The additional antiwear agent may be present in the range of about 0 wt% to about 15 wt%, or about 0.01 wt% to about 10 wt%, or about 0.05 wt% to about 5 wt%, or about 0.1 wt% to about 3 wt% of the lubricating oil composition.

[0081] Other extreme pressure agents

[0082] The lubricant compositions of the present disclosure may further comprise other extreme pressure agents, provided that the lubricating compositions herein include the noted amounts and distributions described herein. The optional extreme pressure agent may contain sulfur and may contain at least 12 wt% sulfur. In some embodiments, the extreme pressure agent added to the lubricating oil is sufficient to provide at least 350 ppm sulfur, 500 ppm sulfur, 760 ppm sulfur, from about 350 ppm to about 2,000 ppm sulfur, from about 2,000 ppm to about 30,000 ppm sulfur, or from about 2,000 ppm to about 4,800 ppm sulfur, or from about 4,000 ppm to about 25,000 ppm sulfur to the lubricant composition.

[0083] A variety of sulfur-containing extreme pressure agents are suitable and include sulfided animal or vegetable fats or oils, sulfided animal or vegetable fatty acid esters, fully or partially esterified esters of trivalent or pentavalent acids of phosphorus, sulfided olefins (see, for example, 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 4,711,736), 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 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 organic sulfur compounds selected from sulfided olefins, sulfur-containing amino heterocyclic compounds, 5-dimercapto-1,3,4-thiadiazole, polysulfides having mostly S3 and S4 sulfides, sulfided fatty acids, sulfided branched olefins, organic polysulfides, and mixtures thereof.

[0084] In some embodiments, the extreme pressure agent is present in the lubricating composition in an amount of up to about 3.0 wt% or up to about 5.0 wt%. In other embodiments, based on the total lubricant composition, the extreme pressure agent is present in an amount of about 0.05 wt% to about 0.5 wt%. In other embodiments, based on the total lubricant composition, the extreme pressure agent is present in an amount of about 0.1 wt% to about 3.0 wt%. In other embodiments, based on the total lubricant composition, the extreme pressure agent is present in an amount of about 0.6 wt% to about 1 wt%. In additional embodiments, based on the total lubricant composition, the detergent is present in an amount of about 1.0 wt%.

[0085] One class of suitable extreme pressure agents is a polysulfide composed of one or more discrete compounds represented by the formula: Ra-Sx-Rb, where Ra and Rb are hydrocarbon groups, each hydrocarbon group may contain from 1 to 18 and in other methods from 3 to 18 carbon atoms, and x may range from 2 to 8 and typically ranges from 2 to 5, especially 3. In certain methods, x is an integer from 3 to 5, where 30% to 60% of x is an integer of 3 or 4. The hydrocarbon groups can have a wide variety of types, such as alkyl, cycloalkyl, alkenyl, aryl, or aralkyl. Tertiary alkyl polysulfides can be used, such as di-tert-butyl trisulfide, and mixtures containing di-tert-butyl trisulfide (e.g., mixtures consisting mainly or entirely of trisulfide, tetrasulfide, and pentasulfide). Examples of other useful dihydrocarbon polysulfides include dipentyl polysulfide, dinonyl polysulfide, dodecyl polysulfide, and dibenzyl polysulfide.

[0086] Another class of suitable extreme pressure agents is sulfurized isobutene prepared by reacting an olefin such as isobutene with sulfur. Sulfurized isobutene (SIB), especially sulfurized polyisobutene, typically has a sulfur content of about 10% to about 55% by weight, desirably about 30% to about 50% by weight. A 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. Patent 3,471,404 to Myers; U.S. Patent 4,204,969 to Papay et al.; U.S. Patent 4,954,274 to Zaweski et al.; U.S. Patent 4,966,720 to DeGonia et al.; and U.S. Patent 3,703,504 to Horodysky et al., each of which is incorporated herein by reference.

[0087] Methods for preparing sulfurized olefins, including those disclosed in the above patents, generally involve forming a material commonly referred to as an "adduct", where the olefin reacts 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 typically measured by various physical properties, including, for example, viscosity, sulfur content, halogen content, and weight loss in a copper corrosion test. U.S. Patent 4,966,720 relates to sulfurized olefins used as extreme pressure additives in lubricating oils and to a two-step reaction for their preparation.

[0088] Antioxidant

[0089] 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, phosphorus-sulfurized terpenes, sulfurized esters, aromatic amines, alkylated diphenylamines (e.g., nonyl diphenylamine, dinonyl diphenylamine, octyl diphenylamine, dioctyl diphenylamine), phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, hindered non-aromatic amines, phenols, hindered phenols, oil-soluble molybdenum compounds, macromolecular antioxidants, or mixtures thereof. The antioxidant compounds may be used alone or in combination.

[0090] The hindered phenol antioxidant may contain secondary butyl and / or tertiary butyl as the sterically hindered group. The phenolic group may be further substituted with a hydrocarbon group and / or a bridging group attached 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, L-135 available from BASF or an adduct derived from 2,6-di-tert-butylphenol and an alkyl acrylate, wherein the alkyl 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 4716 available from Albemarle Corporation. L-135 or an adduct derived from 2,6-di-tert-butylphenol and an alkyl acrylate, wherein the alkyl 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 4716 available from Albemarle Corporation. 4716.

[0091] Useful antioxidants may include diarylamines and phenols. In one embodiment, the lubricating oil composition may contain a mixture of a diarylamine and a phenol such that each antioxidant is present in an amount sufficient to provide up to about 5 wt% based on the weight of the lubricant composition. In one embodiment, based on the lubricant composition, the antioxidant may be a mixture of about 0.3 wt% to about 1.5 wt% of a diarylamine and about 0.4 wt% to about 2.5 wt% of a phenol.

[0092] Examples of suitable olefins that can be sulfided to form sulfided olefins include propylene, butene, isobutene, polyisobutene, 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, and their dimers, trimers, and tetramers are particularly suitable olefins. Alternatively, the olefin can be a Diels - Alder adduct of a diene (such as 1,3 - butadiene) and an unsaturated ester (such as butyl acrylate).

[0093] Another class of sulfided olefins includes sulfided fatty acids and their esters. Fatty acids are typically obtained from vegetable oils 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. Generally, the fatty acids are obtained from lard, pine oil, peanut oil, soybean oil, cottonseed oil, sunflower oil, or mixtures thereof. The fatty acids and / or esters can be mixed with olefins (such as alpha - olefins).

[0094] The one or more antioxidants can be present in the lubricating oil composition in the range of about 0 wt% to about 20 wt%, or about 0.1 wt% to about 10 wt%, or about 1 wt% to about 5 wt%.

[0095] Dispersant

[0096] The dispersants contained in the lubricant composition can include, but are not limited to, oil - soluble polymeric hydrocarbon backbones having functional groups capable of associating with the particles to be dispersed. Generally, the dispersant contains amine, alcohol, amide, or ester polar moieties that are typically attached to the polymer backbone via a bridging group. Dispersants can be, for example, Mannich dispersants as described in U.S. Patents 3,634,515, 3,697,574, and 3,736,357; ashless succinimide dispersants as described in U.S. Patents 4,234,435 and 4,636,322; amine dispersants as described in U.S. Patents 3,219,666, 3,565,804, and 5,633,326; Koch dispersants as described in U.S. Patents 5,936,041, 5,643,859, and 5,627,259; and polyalkylene succinimide dispersants as described in U.S. Patents 5,851,965; 5,853,434; and 5,792,729.

[0097] 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 an anhydride grafted to an ethylene-propylene copolymer. Another additional dispersant may be a high molecular weight ester or half-ester amide.

[0098] If present, the additional dispersant may be used in an amount sufficient to provide up to about 10 wt% based on the final weight of the lubricating oil composition. Another amount of the dispersant that may be used may be from about 0.1 wt% to about 10 wt%, or from about 0.1 wt% to about 10 wt%, or from about 3 wt% to about 8 wt%, or from about 1 wt% to about 6 wt% based on the final weight of the lubricating oil composition.

[0099] Viscosity index improver

[0100] The lubricating oil compositions herein may also optionally contain one or more viscosity index improvers. Suitable viscosity index improvers may include polyolefins, olefin copolymers, ethylene / propylene copolymers, polyisobutylene, hydrogenated styrene-isoprene polymers, styrene / maleate copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, alpha-olefin maleic anhydride copolymers, polymethacrylates, polyacrylates, polyalkylstyrenes, hydrogenated vinyl aromatic conjugated diene copolymers, or mixtures thereof. Other viscosity index improvers may include star polymers, and suitable examples are described in U.S. Publication No. 20120101017A1, which is incorporated herein by reference.

[0101] The lubricating oil compositions herein may also optionally contain one or more dispersant viscosity index improvers in addition to or in place of the viscosity index improver. Suitable viscosity index improvers may include functionalized polyolefins, such as ethylene-propylene copolymers that have been functionalized with the reaction product of an acylating agent (such as maleic anhydride) and an amine; polymethacrylates functionalized with an amine, or esterified maleic anhydride-styrene copolymers reacted with an amine.

[0102] The total amount of the viscosity index improver and / or the dispersant viscosity index improver may be from about 0 wt% to about 20 wt%, from about 0.1 wt% to about 15 wt%, from about 0.1 wt% to about 12 wt%, or from about 0.5 wt% to about 10 wt%, from about 3 wt% to about 20 wt%, from about 3 wt% to about 15 wt%, from about 5 wt% to about 15 wt%, or from about 5 wt% to about 10 wt% of the lubricating oil composition.

[0103] In some embodiments, the viscosity index improver is a polyolefin or olefin copolymer having a number average molecular weight of from about 10,000 to about 500,000, from about 50,000 to about 200,000, or from 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 from about 40,000 to about 500,000, from about 50,000 to about 200,000, or from about 50,000 to about 150,000. In some embodiments, the viscosity index improver is a polymethacrylate having a number average molecular weight of from about 10,000 to about 500,000, from about 50,000 to about 200,000, or from about 50,000 to about 150,000.

[0104] Other optional additives

[0105] Other additives can be selected to perform one or more functions required of the lubricating composition. Additionally, one or more of the additives mentioned can be multifunctional and provide functions other than or different from the functions specified herein. The other additives can be additives other than the specified additives of the present disclosure and / or can comprise one or more of the following: metal deactivators, viscosity index improvers, ashless TBN boosters, antiwear agents, corrosion inhibitors, rust inhibitors, dispersants, dispersant viscosity index improvers, extreme pressure agents, antioxidants, foam inhibitors, demulsifiers, emulsifiers, pour point depressants, seal swell agents, and mixtures thereof. Generally, a fully formulated lubricating oil will contain one or more of these additives.

[0106] Suitable metal deactivators can include derivatives of benzotriazole (usually tolyltriazole), dimercaptothiadiazole derivatives, 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole, or 2-alkyldithiobenzothiazole; foam inhibitors, including copolymers of ethyl acrylate and 2-ethylhexyl acrylate and optionally vinyl acetate; demulsifiers, including trialkyl phosphates, polyethylene glycols, polyethylene oxides, polypropylene oxides, and (ethylene oxide - propylene oxide) polymers; pour point depressants, including esters of maleic anhydride - styrene, polymethacrylates, polyacrylates, or polyacrylamides.

[0107] Suitable foam inhibitors include silicon-based compounds such as siloxanes.

[0108] Suitable pour point depressants can include polymethyl methacrylate or mixtures thereof. The pour point depressant can 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.

[0109] Suitable rust inhibitors can be a single compound or a mixture of compounds having the property of inhibiting corrosion on the surface of ferrous metals. 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; and oil-soluble polycarboxylic acids including dimer acids and trimer acids such as those produced from tall oil fatty acids, oleic acid, and linoleic acid. Other suitable corrosion inhibitors include long-chain α,ω-dicarboxylic acids having a molecular weight in the 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 type of acidic corrosion inhibitor that can be used is a half-ester of an alkenyl succinic acid having about 8 to about 24 carbon atoms in the alkenyl group with an alcohol such as polyethylene glycol. 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.

[0110] The rust inhibitor, if present, can be used in an optional amount sufficient to provide about 0 wt% to about 5 wt%, about 0.01 wt% to about 3 wt%, about 0.1 wt% to about 2 wt% based on the final weight of the lubricating oil composition.

[0111] The lubricant composition may also include corrosion inhibitors (it should be noted that some of the other components mentioned may also have copper corrosion inhibition properties). Suitable copper corrosion inhibitors include ether amines, polyethoxylated compounds such as ethoxylated amines and ethoxylated alcohols, imidazolines, monoalkyl and dialkyl thiadiazoles, etc.

[0112] Thiazoles, triazoles, and thiadiazoles can also be used in lubricants. Examples include benzotriazole, tolyltriazole, octyltriazole, decyltriazole; dodecyltriazole, 2-mercaptobenzotriazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazole, and 2-mercapto-5-hydrocarbylthiono-1,3,4-thiadiazole. In one embodiment, the lubricant composition contains 1,3,4-thiadiazole such as 2-hydrocarbyldithio-5-mercapto-1,3,4-dithiadiazole.

[0113] An antifoaming agent / surfactant can also be included in the fluid according to the present invention. Various reagents are known for this use. A copolymer of ethyl acrylate and hexyl acrylate can be used, such as PC-1244 available from Solutia. In other embodiments, silicone fluids such as 4% DCF can be included. A mixture of antifoaming agents can also be present in the lubricant composition.

[0114] Example

[0115] The following examples are illustrative of the 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 be presented for illustrative purposes only and not for limiting the scope of the invention disclosed herein.

[0116] Comparative Example 1

[0117] The comparative sulfurized polyolefin oligomer was prepared as follows: In a first reaction step, liquid sulfur monochloride (about 73.6 g) was charged into a reactor equipped with a stirrer, thermometer, condenser, cooler system, and a subsurface gas distributor. While stirring, gaseous isobutene (about 57.5 g) was bubbled into the reactor below the surface of the liquid sulfur monochloride. The temperature was maintained at 25 °C or about 25 °C.

[0118] Next, about 4.7 g of elemental sulfur, about 1.8 g of n-propanol, about 29.0 g of 50% aqueous sodium hydroxide solution, about 42.3 g of 38 wt% aqueous sodium hydrosulfide solution, and about 0.007 g of an antifoaming agent were charged into the reactor. The mixture was stirred and heated to about 55 °C under nitrogen, at which time the isobutene-sulfur monochloride adduct from the above first reaction was added over 4 hours while maintaining the reaction mass at reflux (about 80 °C to about 94 °C). Heating was continued for two hours, and then the alcohol was stripped by heating to about 94 °C. After stripping at atmospheric pressure, the pressure was reduced to 150 mm Hg while cooling the flask to about 70 °C to complete the removal of the alcohol and most of the water. Washing water was added to the resulting product, and after stirring for about 10 minutes, it was allowed to settle for about 5 minutes. The lower brine layer was separated, and the organic layer was stripped under vacuum (<100 mm Hg) at about 100 °C. After filtering the stripped organic layer through a diatomaceous earth bed, a clear yellow oil containing sulfurized isobutene oligomer was obtained. The product formed had a viscosity in the range of about 7.0 cSt to about 9.0 cSt at 100 °C and a total sulfur content of about 45.5 wt% to about 48.5 wt%.

[0119] Example 1

[0120] The sulfurized isobutene oligomer of Comparative Example 1 was further treated with an aqueous alkaline solution as follows: About 1250 g of the sulfurized isobutene reaction product of Comparative Example 1 was added to a 2 L reactor equipped with a separatory funnel, a water-cooled condenser with a condensate receiver, and a vacuum pump. About 464 g of 50% sodium hydroxide solution was added at a stirring rate of 700 rpm. The mixture was reacted at about 110 °C for about 3 hours to form the caustic-treated sulfurized isobutene oligomer. The caustic-treated sulfurized isobutene oligomer formed had a specific gravity of 1.1076, about 0.1 wt% water, and about 43.0 wt% total sulfur.

[0121] Example 2

[0122] In another embodiment, the isobutene sulfide oligomer of Comparative Example 1 was further treated with an aqueous alkaline solution as follows: Approximately 1250 grams of the isobutene sulfide reaction product of Comparative Example 1 was added to a 2-liter reactor equipped with a separatory funnel, a water-cooled condenser with a condensate receiver, and a vacuum pump. Approximately 209 grams of a 50% sodium hydroxide solution was added at a stirring rate of 700 rpm. The mixture was reacted at approximately 110 °C for approximately 3 hours to form the caustic-treated isobutene sulfide oligomer. The caustic-treated isobutene sulfide oligomer thus formed had a specific gravity of approximately 1.1155, approximately 0.12 wt% water, and approximately 43.8 wt% total sulfur.

[0123] Example 3

[0124] The copper corrosion of the isobutene sulfide oligomer of Comparative Example 1 and the two caustic-treated isobutene sulfide oligomers of the present invention in Examples 1 and 2 was evaluated as follows: Annealed copper SAE CA 110 2.75" x 0.6" x 16 gauge polished specimens (available from Metaspec, San Antonio, Texas) were immersed in approximately 35 grams of each of the isobutene sulfide of the present invention and comparative isobutene sulfide (as a neat fluid) and subjected to the aging procedure of ASTM D130 at 121 °C for approximately 180 minutes. The mass of the copper test strips was measured before aging and after immersion in their respective neat solutions for 180 minutes. Before weighing the copper test strips after testing, they were washed with heptane and vigorously wiped with a towel wetted with heptane to remove any loose black scaly material. Before weighing, the copper test strips were given a final wash with acetone and completely dried. The copper corrosion weight loss (CCT) in the test was reported as follows: CCT = mass before test - mass after test, in mg. The results are provided in Table 3 below.

[0125] Table 3

[0126] Isobutene sulfide oligomer CCT, mg of copper Comparative Example 1 53.9 Example 1 of the present invention 11.7 Example 2 of the present invention 4.8

[0127] Example 4

[0128] The FZG Sprung test, as described in FVA information sheet #243 (specified as S-A-10 / 16.6R / 90 or 120), was used to evaluate the extreme pressure performance of the isobutene sulfide of Comparative Example 1 and the two caustic-treated isobutene sulfide oligomers of the present invention in Examples 1 and 2. The FZG Sprung test can be conducted in any number of test chambers, such as the FZG Institute, Southwest Research Institute, or other suitable test chambers. The extreme pressure performance is about 115 mm at a load stage of 10 or higher compared to a reference lubricant at 90 °C 2 or less of a wear scar.

[0129] For the extreme pressure evaluation, each of the isobutene sulfide oligomers of Comparative Example 1 and Examples 1 and 2 of the present invention was blended into the lubricant at a treatment rate of about 1.4 wt% sulfur provided by the oligomer. The lubricating composition also contained the same amount of an additive package that included the same pour point depressant, antiwear additive, and antifoaming agent. The composition also included a base oil and / or processing oil balanced as needed to achieve a target KV100 of about 6 cSt to about 18 cSt, preferably 13 cSt to 18 cSt.

[0130] (ASTM D445.)

[0131] Table 4

[0132] Lubricant Isobutene sulfide FZG, load stage 10, damaged mm2 Lubricant A (comparison) Comparative Example 1 110 Lubricant B (present invention) Example 1 115 Lubricant C (present invention) Example 2 40

[0133] Table 4 shows that the lubricants of the present invention provide comparable extreme pressure performance relative to the control, indicating that the isobutene sulfide oligomers of the present invention provide extreme pressure performance consistent with that of non-caustic-treated isobutene oligomers. Lubricant C of the present invention with the isobutene sulfide from Example 2 provides the best extreme pressure performance.

[0134] Example 4 :

[0135] The solubility of Lubricants A, B, and C of Example 3 was evaluated in API Group III base oil (Yubase4) and API Group IV PAO base oil (Spectrasyn). The lubricants evaluated had the same composition as described in Example 3, except that each fluid also contained the same amount of a thiadiazole additive. For this evaluation, about 3.25 wt% of each lubricant was blended into the base oil at room temperature (25 °C) and the solubility was observed. The results are provided in Table 5 below and shown in the Figure 1 and Figure 2 images.

[0136] Table 5

[0137]

[0138] Figure 2 Show that, considering the turbid mixture (left container), comparative lubricant A with non-caustic-treated sulfurized isobutene oligomers is insoluble in PAO, but inventive lubricants B and C with the caustic-treated sulfurized isobutene oligomers of the present invention are soluble in Group III ( Figure 1 ) and Group IV base oils ( Figure 2 ).

[0139] It should be noted that, unless explicitly and affirmatively limited to one indicator, as used in this specification and the appended claims, the singular forms "a / an" and "the" include plural indicators. Thus, for example, reference to "an antioxidant" includes two or more different antioxidants. As used herein, the term "comprising" and its grammatical variants are intended to be non-limiting, such that the recitation of items in a list does not preclude other similar items that may be substituted or added to the listed items.

[0140] For this specification and the appended claims, unless otherwise indicated, all numbers and other numerical values representing quantities, percentages, or proportions used in the specification and claims should be understood to be modified in all instances by the term "about". Thus, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained by this 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 be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0141] It should be understood that each component, compound, substituent, or parameter disclosed herein should be construed as being disclosed for use alone or in combination with one or more of each of the other components, compounds, substituents, or parameters disclosed herein.

[0142] It should be further understood that each range disclosed herein should be construed as an express disclosure of every specific value within the disclosed range having the same numerical value of significant digits. Thus, for example, a range of 1 to 4 should be construed as an express disclosure of the values 1, 2, 3, and 4 and any range of such values.

[0143] It should be further understood that each lower limit of each range disclosed herein should be construed as being disclosed in combination with each upper limit of each range and each specific value within each range for the same component, compound, substituent, or parameter disclosed herein. Accordingly, the present disclosure should be construed as a disclosure of all ranges derived by combining each lower limit of each range with each upper limit of each range or with each specific value within each range, or by combining each upper limit of each range with each specific value within each range. That is to say, it should be further understood that any range between the endpoint values within a broad range is also discussed herein. Thus, a range of 1 to 4 also means ranges of 1 to 3, 1 to 2, 2 to 4, 2 to 3, etc.

[0144] In addition, a specific amount / value of a component, compound, substituent, or parameter disclosed in this specification or in an example should be construed as a disclosure of a lower limit or an upper limit of a certain range, and thus can be combined with any other lower limit or upper limit or specific amount / value of a range for the same component, compound, substituent, or parameter disclosed elsewhere in the present disclosure to form a range for that component, compound, substituent, or parameter.

[0145] Although specific embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently foreseen or that may not currently be foreseen by the applicant or other skilled artisans in the art may be contemplated. Accordingly, the appended claims, as filed and as they may be amended, are intended to cover all such alternatives, modifications, variations, improvements, and substantial equivalents.

Claims

1. A sulfurized polyolefin oligomer, the sulfurized polyolefin oligomer being prepared by a method comprising the following steps: (a) Reacting a C2 to C18 olefin with sulfur halide to form an intermediate sulfurized olefin reaction product; (b) Reacting the intermediate sulfurized olefin reaction product with an alkali metal hydrosulfide, an alkali metal hydroxide, and sulfur in an aqueous solution to form a sulfurized polyolefin reaction product; and (c) Treating the sulfurized polyolefin reaction product with an aqueous alkaline solution at a time and temperature effective to form the sulfurized polyolefin oligomer, wherein the aqueous alkaline solution contains 40 wt% to 60 wt% of the alkali metal hydroxide and does not contain alcohol or ketone.

2. The sulfurized polyolefin oligomer according to claim 1, wherein a copper strip immersed in the sulfurized polyolefin oligomer at 121 °C for 180 minutes exhibits a copper weight loss of 15 mg or less according to ASTM D130, and wherein 2 wt% to 5 wt% of the sulfurized polyolefin oligomer is soluble in both API Group III base oil and API Group IV base oil.

3. The sulfurized polyolefin oligomer according to claim 1, wherein the sulfurized polyolefin oligomer has a structure of Formula I: R-S x -R-[S x -R-S x n -R (Formula I)​ wherein each R is independently a C2 to C6 straight-chain or branched carbon chain, x is an integer from 1 to 5, and n is an integer such that the sulfurized polyolefin oligomer has a weight-average molecular weight of 300 to 800.

4. The sulfurized polyolefin oligomer according to claim 3, wherein the sulfurized polyolefin oligomer has 30 wt% to 50 wt% sulfur.

5. The sulfurized polyolefin oligomer according to claim 1, wherein the olefin is selected from the group consisting of: ethylene; propylene; isopropylene; butene; isobutene; n-pentene; isopentene; neopentene; hexene; octene; styrene; α,ω-diene; 1,5-hexadiene; 1,6-heptadiene; 1,7-octadiene; branched α-olefin; methyl-pentene; methyl-heptene; or a mixture thereof.

6. The sulfurized polyolefin oligomer according to claim 5, wherein the sulfur halide is selected from sulfur monochloride, sulfur dichloride, disulfur dibromide, sulfur dibromide, or a mixture thereof.

7. The sulfurized polyolefin oligomer according to claim 6, wherein the aqueous alkaline solution comprises an alkali metal hydroxide selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, or a combination thereof.

8. A lubricating composition, the lubricating composition comprising a major amount of a base oil selected from API Group I to API Group V base oils and a minor amount of a sulfurized polyolefin oligomer, wherein the sulfurized polyolefin oligomer is prepared by a method comprising the following steps: (a) Reacting a C2 to C18 olefin with sulfur halide to form an intermediate sulfurized olefin reaction product; (b) Reacting the intermediate sulfurized olefin reaction product with an alkali metal hydrosulfide, an alkali metal hydroxide, and sulfur in an aqueous solution to form a sulfurized polyolefin reaction product; and (c) Treat the sulfurized polyolefin reaction product with an aqueous alkaline solution at a time and temperature effective to form the sulfurized polyolefin oligomer, wherein the aqueous alkaline solution contains 40 wt% to 60 wt% of the alkali metal hydroxide and is free of alcohols, ketones or other alkanols.

9. The lubricating composition according to claim 8, wherein a copper strip immersed in the sulfurized polyolefin oligomer at 121 °C for 180 minutes according to ASTM D130 exhibits a copper weight loss of less than 15 mg, and wherein 2 wt% to 5 wt% of the sulfurized polyolefin oligomer is soluble in both API Group III base oil and API Group IV base oil.

10. The lubricating composition according to claim 8, wherein the sulfurized polyolefin oligomer has the structure of Formula I: R-S x -R-[S x -R-S x n -R (Formula I)​ wherein each R is independently a C2 to C6 straight or branched carbon chain, x is an integer from 1 to 5, and n is an integer such that the sulfurized polyolefin oligomer has a weight average molecular weight of 300 to 800.

11. The lubricating composition according to claim 10, wherein the sulfurized polyolefin oligomer has 30 wt% to 50 wt% sulfur.

12. The lubricating composition according to claim 11, wherein the olefin is selected from the group consisting of: ethylene; propylene; isopropylene; butene; isobutene; n-pentene; isopentene; neopentene; hexene; octene; styrene; α,ω-diene; 1,5-hexadiene; 1,6-heptadiene; 1,7-octadiene; branched α-olefins; methyl-pentene; methyl-heptene; or mixtures thereof.

13. The lubricating composition according to claim 12, wherein the sulfur halide is selected from sulfur monochloride, sulfur dichloride, disulfur dibromide, sulfur dibromide or mixtures thereof; and wherein preferably the aqueous alkaline solution comprises an alkali metal hydroxide selected from sodium hydroxide, potassium hydroxide or combinations thereof.

14. The sulfurized polyolefin oligomer according to claim 7 or the lubricating composition according to claim 13, wherein the treatment is carried out at a temperature of 100 °C to 150 °C for 1 hour to 5 hours, and the treatment preferably comprises 10 wt% to 50 wt% of the aqueous alkaline solution; and wherein in the lubricating composition, the aqueous alkaline solution comprises an alkali metal hydroxide selected from sodium hydroxide, potassium hydroxide or combinations thereof.

15. The sulfurized polyolefin oligomer according to claim 1 or the lubricating composition according to claim 8, wherein: (i) The intermediate sulfurized olefin reaction product of step (a) is obtained by reacting 0.4 mol to 2 mol of the C2 to C18 olefin / 0.3 mol to 0.8 mol of the sulfur halide; wherein the sulfurized polyolefin reaction product of step (b) is obtained by reacting 0.2 mol to 0.5 mol of sulfur / mol of the intermediate sulfurized olefin reaction product, 0.7 mol to 1.1 mol of the alkali metal hydroxide / mol of the intermediate sulfurized olefin reaction product, and the weight ratio of sulfur to sodium hydrosulfide is 0.01:1 to 0.25:1; and The sulfurized polyolefin oligomer in step (c) is obtained by treating the sulfurized polyolefin reaction product with 10 wt% to 50 wt% of the basic aqueous solution having 40 wt% to 60 wt% of alkali metal hydroxide; or (ii) The intermediate sulfurized olefin reaction product is obtained by reacting sulfur monochloride, sulfur dichloride, or a combination thereof with C2 to C4 olefins, wherein the sulfurized polyolefin reaction product is obtained by reacting the intermediate sulfurized olefin reaction product with sodium hydrosulfide, sodium hydroxide, and elemental sulfur, and wherein the sulfurized polyolefin reaction product is treated with 12 wt% to 40 wt% of an aqueous sodium hydroxide solution to form the sulfurized polyolefin oligomer.

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