Oil-based graphite lubricant composition

Abstract

A lubricant composition includes graphite, oil, and a dispersant selected from the group consisting of sulfosuccinate salts, polyalkylene glycols comprising propylene oxide and butylene oxide, and combinations thereof. The combination of sulfosuccinate and polyalkylene glycol dispersant comprises 80% by weight or less of the polyalkylene glycol, based on the total weight of the combined sulfosuccinate and polyalkylene glycol dispersant.

Description

BACKGROUND OF THE INVENTION Technical Field

[0001] The present disclosure relates to lubricant compositions, and more particularly to lubricant compositions comprising an oil-based graphite lubricant composition.

[0002] Introduction

[0003] Graphite is utilized as a lubricant in a variety of applications. For example, automotive applications, household applications, and industrial applications can all utilize graphite as a lubricant. An example of an industrial application is hot forging. Hot forging is an industrial process in which a metal workpiece is placed in a die and deformed under pressure. The energy applied to the metal workpiece to cause plastic deformation is converted into heat. The repeated forging of the workpiece and the generation of heat increase the temperature of the die. A lubricant is used at the interface between the workpiece and the die during forging to reduce friction and ensure that the workpiece can be removed from the die. Good lubrication can improve workpiece deformation, facilitate precise filling of the die cavity, reduce tool wear at those points with free-flowing movement and high specific pressure, and reduce the forging force. Such characteristics will reduce the stress induced in the forging tool and prevent direct contact between the tool and the workpiece, which contributes to longer tool life and better quality control.

[0004] One available option for hot forging lubricants is oil-based lubricants. Oil-based lubricants typically include an oil as a carrier and lubricating particles such as graphite. The oil-based lubricant adheres the graphite to the die to form a coating. Oil-based lubricants are disadvantageous relative to water-based lubricants because oil-based lubricants tend to flow out of the die surface and be extruded from the workpiece / die interface under pressure. There are also additional problems. For example, the graphite dispersion in the oil is unstable and requires continuous agitation, otherwise gelling and caking will occur in the graphite-rich portion of the dispersion. Caking that occurs in the lubricant storage tank can result in an incorrect amount of graphite being applied to the die, thereby reducing the die's service life. Flocculation and sedimentation can also cause blockages in the pipes and nozzles used to apply the lubricant to the forging die. Gelling is particularly disadvantageous because it renders the precipitated graphite non-dispersible. Ideally, the oil-based graphite dispersion should not gel and remain dispersible within 31 days (i.e., one month) ("gelling test").

[0005] The gelling test is difficult to pass because there are multiple competing theories to explain the dispersion of graphite. For example, one hypothesis speculates that the dispersant acts as a spacer that accumulates on the surface area of the graphite particles and prevents their spatial proximity, but it is not known which parts affect such properties. In contrast, Chinese Patent Application Publication No. CN111925697A ("the '697 publication") provides a graphene and polymer dispersant composite. The '697 publication explains that an enhanced graphene dispersion can be obtained by including a water-soluble polymer dispersant containing an aromatic ring structure and a hydrophilic group because the dispersant improves the compatibility between the surface-inert graphene and the water-soluble polymer due to the interaction between the dispersant and graphene. The '697 publication does not mention how the position or amount of the aromatic structure affects the dispersion.

[0006] Given the competing theories behind the efficacy of graphite dispersants, the unclear effects of different molecular moieties on the dispersion performance, and the complexity of the intermolecular forces present in oil-based graphite dispersions, it has surprisingly been found that a dispersant capable of passing the gelling test exists. Summary of the Invention

[0007] The inventors of the present application have discovered a lubricant composition comprising an oil-based graphite dispersion capable of passing the gelling test.

[0008] The present disclosure is the result of discovering that dispersants selected from the group consisting of sulfosuccinates, polyalkylene glycols comprising propylene oxide and butylene oxide, and combinations thereof enable a lubricant composition to pass the gelling test. Without being bound by theory, it is believed that the above-mentioned dispersants not only interact with the graphite surface to enhance the dispersion of graphite in oil but also remain adhered to the graphite after precipitation. It is believed that the persistence of the dispersant on the graphite surface prevents gelling from occurring even when precipitated from the oil, thus keeping the graphite in a redispersible state upon agitation and thereby passing the gelling test.

[0009] The present disclosure can be particularly used to form lubricants utilizing graphite.

[0010] According to a first feature of the present disclosure, the lubricant composition comprises graphite, oil, and a dispersant selected from the group consisting of sulfosuccinates, polyalkylene glycols comprising propylene oxide and butylene oxide, and combinations thereof, provided that based on the total weight of the combined sulfosuccinate and polyalkylene glycol dispersants, the combination of sulfosuccinate and polyalkylene glycol dispersants comprises 80 wt% or less of polyalkylene glycol.

[0011] According to a second feature of the present disclosure, based on the total weight of the lubricant composition, the lubricant composition comprises 1 wt% to 60 wt% of graphite.

[0012] According to a third feature of the present disclosure, the graphite has a D90 particle diameter of 0.5 μm to 5.0 μm.

[0013] According to a fourth feature of the present disclosure, based on the total weight of the lubricant composition, the lubricant composition comprises 50 wt% to 98 wt% of an oil.

[0014] According to a fifth feature of the present disclosure, based on the total weight of the lubricant composition, the lubricant composition comprises 0.01 wt% to 5.0 wt% of a dispersant.

[0015] According to a sixth feature of the present disclosure, the dispersant comprises a sulfosuccinate.

[0016] According to a seventh feature of the present disclosure, the sulfosuccinate dispersant comprises sodium di-2-ethylhexyl sulfosuccinate.

[0017] According to an eighth feature of the present disclosure, the dispersant comprises a polyalkylene glycol, and based on the combined weight of propylene oxide and butylene oxide in the polyalkylene glycol, the polyalkylene glycol comprises 30 wt% to 70 wt% of propylene oxide.

[0018] According to a ninth feature of the present disclosure, based on the combined weight of propylene oxide and butylene oxide in the polyalkylene glycol, the polyalkylene glycol comprises 40 wt% to 60 wt% of propylene oxide.

[0019] According to a tenth feature of the present disclosure, the dispersant comprises sodium di-2-ethylhexyl sulfosuccinate and a polyalkylene glycol initiated with dodecanol, and based on the combined weight of propylene oxide and butylene oxide in the polyalkylene glycol, the polyalkylene glycol initiated with dodecanol comprises 50 wt% of propylene oxide. Detailed Description

[0020] As used herein, the term "and / or" when used in a list of two or more items means that any one of the listed items can be used alone or any combination of two or more of the listed items can be used. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; contain B alone; contain C alone; contain A and B in combination; contain A and C in combination; contain B and C in combination; or contain A, B, and C in combination.

[0021] Unless otherwise specified, all ranges include the endpoints.

[0022] As used herein, unless otherwise specified, the term weight percentage ("wt%") represents the weight percentage of a component based on the total weight of the lubricant composition.

[0023] As used herein, the Chemical Abstracts Service Registry Number ("CAS#") refers to the unique numerical identifier most recently assigned by the Chemical Abstracts Service to a chemical compound since the priority date of this document.

[0024] Lubricant Composition

[0025] The present disclosure relates to a lubricant composition. The lubricant composition comprises graphite, oil, and a dispersant. The lubricant composition may comprise one or more other additives designed to modify the properties or characteristics of the lubricant composition.

[0026] Graphite

[0027] The lubricant composition comprises graphite. The graphite may have a spherical shape, a plate-like shape, a rectangular shape, and / or an irregular shape. The particles of the graphite may have a D90 of 0.5 micrometers (“μm”) to 10 μm. As used herein, the term “D90” means that 90% of the graphite particles have a diameter or longest length dimension less than the indicated value, and 10% of the particles have a diameter or longest length dimension greater than the indicated value. The graphite has a D90 particle size of: 0.5 μm or greater, or 1.0 μm or greater, or 1.5 μm or greater, or 2.0 μm or greater, or 2.5 μm or greater, or 3.0 μm or greater, or 3.5 μm or greater, or 4.0 μm or greater, or 4.5 μm or greater, or 5.0 μm or greater, or 5.5 μm or greater, or 6.0 μm or greater, or 6.5 μm or greater, or 7.0 μm or greater, or 7.5 μm or greater, or 8.0 μm or greater, or 8.5 μm or greater, or 9.0 μm or greater, or 9.5 μm or greater, while at the same time 10 μm or less, or 9.5 μm or less, or 9.0 μm or less, or 8.5 μm or less, or 8.0 μm or less, or 7.5 μm or less, or 7.0 μm or less, or 6.5 μm or less, or 6.0 μm or less, or 5.5 μm or less, or 5.0 μm or less, or 4.5 μm or less, or 4.0 μm or less, or 3.5 μm or less, or 3.0 μm or less, or 2.5 μm or less, or 2.0 μm or less, or 1.5 μm or less, or 1.0 μm or less. The D90 particle size of the graphite is measured using a Malvern Mastersizer TM laser diffraction particle size analyzer.

[0028] Based on the total weight of the lubricant composition, the lubricant composition may comprise from 1 wt% to 60 wt% of graphite. For example, based on the total weight of the lubricant composition, the lubricant composition may comprise 1 wt% or more, or 5 wt% or more, or 10 wt% or more, or 15 wt% or more, or 20 wt% or more, or 25 wt% or more, or 30 wt% or more, or 35 wt% or more, or 40 wt% or more, or 45 wt% or more, or 50 wt% or more, or 55 wt% or more of graphite, while simultaneously 60 wt% or less, or 55 wt% or less, or 50 wt% or less, or 45 wt% or less, or 40 wt% or less, or 35 wt% or less, or 30 wt% or less, or 25 wt% or less, or 20 wt% or less, or 15 wt% or less, or 10 wt% or less, or 5 wt% or less of graphite.

[0029] Oil

[0030] The medium for dissolving the graphite and the dispersant is oil. The oil can be a Group (I) oil, a Group (II) oil, or a Group (III) oil as defined by the American Petroleum Institute. As used herein, a Group (I) oil is an oil that meets one of the following two criteria: (i) the oil consists of less than 90 wt% saturates and / or greater than 0.03 wt% sulfur. As used herein, a Group (II) oil is an oil with more than 90 wt% saturates and less than 0.03 wt% sulfur. As used herein, a Group (III) oil meets the same criteria as a Group (II) oil but also has a viscosity index greater than 120 as measured according to ASTM D2270. The oil can be derived from petroleum and / or can be derived from biological sources (e.g., plants, beans, seeds, nuts, fruits, etc.). In a specific example, the oil used can be a mineral oil distilled from crude oil (i.e., a colorless and odorless mixture of alkanes and cycloalkanes). The oil can have a density of from 0.70 grams per cubic centimeter ("g / cc") to 0.95 g / cc. Any oil can be used in the lubricant composition.

[0031] Based on the total weight of the lubricant composition, the lubricant composition may comprise from 50 wt% to 98 wt% of oil. For example, based on the total weight of the lubricant composition, the lubricant composition may comprise 50 wt% or more, or 55 wt% or more, or 60 wt% or more, or 65 wt% or more, or 70 wt% or more, or 75 wt% or more, or 80 wt% or more, or 85 wt% or more, or 90 wt% or more, or 95 wt% or more of oil, while simultaneously 98 wt% or less, or 95 wt% or less, or 90 wt% or less, or 85 wt% or less, or 80 wt% or less, or 75 wt% or less, or 70 wt% or less, or 65 wt% or less, or 60 wt% or less, or 55 wt% or less of oil.

[0032] Dispersant

[0033] The lubricant composition contains a dispersant. As explained above, the dispersant is used to disperse graphite and prevent gelling after prolonged non-mixing. The dispersant is selected from the group consisting of sulfosuccinates, polyalkylene glycols containing propylene oxide (“PO”) and butylene oxide (“BO”), and combinations thereof.

[0034] The sulfosuccinate may have the general formula provided in Structure (I)

[0035]

[0036] wherein R1 and R2 are each independently a C4-C 16 alkyl group, and M + is a cation. Each of R1 and R2 may independently be straight-chain or branched-chain. Each of R1 and R2 may independently be a C4 alkyl group, or a C5 alkyl group, or a C6 alkyl group, or a C7 alkyl group, or a C8 alkyl group, or a C9 alkyl group, or a C 10 alkyl group, or a C 11 alkyl group, or a C 12 alkyl group, or a C 13 alkyl group, or a C 14 alkyl group, or a C 15 alkyl group, or a C 16 alkyl group. M + may be selected from the group consisting of Li, Na, K, Rb, and other cations. In a specific example, the sulfosuccinate may be sodium di-2-ethylhexyl sulfosuccinate, dioctyl sulfosuccinate, or other succinates.

[0037] The polyalkylene glycol is a copolymer of PO and BO (“PO / BO copolymer”) and is an oil-soluble polyalkylene glycol (OSP). The PO / BO copolymer can be a block copolymer or a random copolymer. Based on the combined weight of PO and BO in the polyalkylene glycol, the polyalkylene glycol on average contains 10 wt% to 90 wt% of PO. For example, based on the combined weight of PO and BO in the polyalkylene glycol, the polyalkylene glycol contains 10 wt% or more, or 20 wt% or more, or 30 wt% or more, or 40 wt% or more, or 50 wt% or more, or 60 wt% or more, or 70 wt% or more, or 80 wt% or more, while 90 wt% or less, or 80 wt% or less, or 70 wt% or less, or 60 wt% or less, or 50 wt% or less, or 40 wt% or less, or 30 wt% or less, or 20 wt% or less of PO. Based on the combined weight of PO and BO in the polyalkylene glycol, the polyalkylene glycol on average contains 10 wt% to 90 wt% of BO. For example, based on the combined weight of PO and BO in the polyalkylene glycol, the polyalkylene glycol contains 10 wt% or more, or 20 wt% or more, or 30 wt% or more, or 40 wt% or more, or 50 wt% or more, or 60 wt% or more, or 70 wt% or more, or 80 wt% or more, while 90 wt% or less, or 80 wt% or less, or 70 wt% or less, or 60 wt% or less, or 50 wt% or less, or 40 wt% or less, or 30 wt% or less, or 20 wt% or less of BO.

[0038] The polyalkylene glycol can be alcohol-initiated. The alcohol initiator can be a primary alcohol or a secondary alcohol. The alcohol can have 8 or more carbons, 9 or more carbons, or 10 or more carbons, or 11 or more carbons, or 12 or more carbons, or 13 or more carbons, or 14 or more carbons, or 15 or more carbons, or 16 or more carbons, or 17 or more carbons, or 18 or more carbons, or 19 or more carbons, while 20 or fewer carbons, or 19 or fewer carbons, or 18 or fewer carbons, or 17 or fewer carbons, or 16 or fewer carbons, or 15 or fewer carbons, or 14 or fewer carbons, or 13 or fewer carbons, or 12 or fewer carbons, or 11 or fewer carbons, or 10 or fewer carbons, or 9 or fewer carbons. The number of carbons in the alcohol initiator is evident from the number of carbons in the end groups of the polyalkylene glycol. In a specific example, the alcohol initiator can be dodecanol (i.e., a 12-carbon alcohol).

[0039] The polyalkylene glycol may have a number average molecular weight (“Mn”) of from 500 grams per mole (“g / mol”) to 2500 g / mol. For example, as measured by gel permeation chromatography, the Mn of the polyalkylene glycol may be 500 g / mol or greater, or 600 g / mol or greater, or 700 g / mol or greater, or 800 g / mol or greater, or 900 g / mol or greater, or 1000 g / mol or greater, or 1100 g / mol or greater, or 1200 g / mol or greater, or 1300 g / mol or greater, or 1400 g / mol or greater, or 1500 g / mol or greater, or 1600 g / mol or greater, or 1700 g / mol or greater, or 1800 g / mol or greater, or 1900 g / mol or greater, or 2000 g / mol or greater, or 2100 g / mol or greater, or 2200 g / mol or greater, or 2300 g / mol or greater, or 2400 g / mol or greater, while being 2500 g / mol or less, or 2400 g / mol or less, or 2300 g / mol or less, or 2200 g / mol or less, or 2100 g / mol or less, or 2000 g / mol or less, or 1900 g / mol or less, or 1800 g / mol or less, or 1700 g / mol or less, or 1600 g / mol or less, or 1500 g / mol or less, or 1400 g / mol or less, or 1300 g / mol or less, or 1200 g / mol or less, or 1100 g / mol or less, or 1000 g / mol or less, or 900 g / mol or less, or 800 g / mol or less, or 700 g / mol or less, or 600 g / mol or less.

[0040] The polyalkylene glycol for use in the lubricant composition may comprise a dodecanol-initiated random copolymer which, based on the total weight of PO and BO in the dispersant, comprises 50 wt% PO and 50 wt% BO. Such copolymers are commercially available under the trade names UCON TM OSP-18, UCON TM OSP-32, UCON TM OSP-46, UCON TM OSP-68, UCON TM OSP-150 and UCON TM OSP-220 and are commercially available (UCON TMis a trademark of Union Carbide Corporation and is commercially available from The Dow Chemical Company, Midland, Michigan.

[0041] Based on the total weight of the lubricant composition, the lubricant composition comprises from 0.01 wt% to 5.0 wt% of a dispersant. For example, based on the total weight of the lubricant composition, the lubricant composition may comprise 0.01 wt% or more, or 0.05 wt% or more, or 0.1 wt% or more, or 0.5 wt% or more, or 1.0 wt% or more, or 1.5 wt% or more, or 2.0 wt% or more, or 2.5 wt% or more, or 3.0 wt% or more, or 3.5 wt% or more, or 4.0 wt% or more, or 4.5 wt% or more, while at the same time 5.0 wt% or less, or 4.5 wt% or less, or 4.0 wt% or less, or 3.5 wt% or less, or 3.0 wt% or less, or 2.5 wt% or less, or 2.0 wt% or less, or 1.5 wt% or less, or 1.0 wt% or less, or 0.5 wt% or less, or 0.1 wt% or less, or 0.05 wt% or less of the dispersant.

[0042] The dispersant may comprise both succinates and polyalkylene glycols. In such examples, based on the total weight of the combined sulfosuccinate and polyalkylene glycol dispersants, the dispersant combination comprises 80 wt% or less of the polyalkylene glycol. For example, based on the combined weight of the combined sulfosuccinate and polyalkylene glycol dispersants, the combined dispersant may comprise 80 wt% or less, or 75 wt% or less, or 70 wt% or less, or 65 wt% or less, or 60 wt% or less, or 55 wt% or less, 50 wt% or less, or 45 wt% or less, 40 wt% or less, or 35 wt% or less, 30 wt% or less, or 25 wt% or less, 20 wt% or less, or 15 wt% or less, 10 wt% or less, or 5 wt% or less, 1 wt% or less of the polyalkylene glycol dispersant.

[0043] Examples

[0044] Materials

[0045] The following materials were used in the examples.

[0046] Graphite is graphite particle powder having a D90 of 5.0 μm and is commercially available from Molygraph Lubricants, Mumbai, India.

[0047] PIBSA is polyisobutylene succinic anhydride with CAS# 67762 - 77 - 0 and is commercially available from Transasia Petrochem Pvt Ltd., Mumbai, India.

[0048] The oil is a Group (II) oil obtained from the refining of the vacuum distillate of a specific crude oil fraction by dewaxing and hydrotreating. The oil has a minimum viscosity index of 85 as measured according to ASTM D 227 and a density of 0.875 g / cc to 0.89 g / cc as measured according to ASTM D 4052 - 18. Examples of the oil are available from Sigma Aldrich, St. Louis, Missouri.

[0049] DISP1 is 95 wt% or more of Structure (II).

[0050]

[0051] Where x is 31 and R is C4H9OH. DISP1 is commercially available from The Dow Chemical Company, Midland, Michigan.

[0052] DISP2 is a mixture of 65.5 wt% or less of di - 2 - ethylhexyl sodium C and other components and is available as TRITON TM GR - 7M from The Dow Chemical Company, Midland, Michigan.

[0053] DISP3 is a mixture of 56 wt% to 60 wt% of sodium di - 2 - ethylhexyl sulfosuccinate, 20 wt% of isopropanol and 20 wt% of water and is available as TRITON TM GR - 5M from The Dow Chemical Company, Midland, Michigan.

[0054] DISP4 is a random copolymer (PO / BO, 50 / 50 by weight) initiated by dodecanol with a typical kinematic viscosity of 18 mm 2 / s (cSt) at 40 °C. Its average Mn is 500 g / mol. DISP5 is available as UCON TM OSP - 18 from The Dow Chemical Company, Midland, Michigan.

[0055] DISP5 is a random copolymer (PO / BO, 50 / 50 by weight) initiated by dodecanol with a typical kinematic viscosity of 32 mm 2 / s (cSt). Its average Mn is 760 g / mol. DISP5 can be obtained commercially from The Dow Chemical Company, Midland, Michigan under the trade name UCON TM OSP-32 was obtained commercially from The Dow Chemical Company, Midland, Michigan.

[0056] DISP6 is a random copolymer initiated by dodecanol (PO / BO, 50 / 50 by weight), with a typical kinematic viscosity at 40 °C of 150 mm / s (cSt). Its average molecular weight (Mn) is 1900 g / mol. DISP6 can be obtained commercially from The Dow Chemical Company, Midland, Michigan under the trade name UCON TM OSP-150 was obtained commercially from The Dow Chemical Company, Midland, Michigan.

[0057] DISP7 is a homopolymer of epoxybutane, with a typical kinematic viscosity at 40 °C of 680 mm 2 / s (cSt) and a number average molecular weight of 5100 g / mol. DISP6 can be obtained commercially from The Dow Chemical Company, Midland, Michigan under the trade name UCON TM OSP-680 was obtained commercially from The Dow Chemical Company, Midland, Michigan.

[0058] Sample Preparation

[0059] Samples were prepared by adding the indicated dispersant to the oil and stirring the mixture for 15 minutes at 700 revolutions per minute ("RPM") using an overhead stirrer. Next, graphite was slowly added to the mixture while stirring was continued. Next, the mixture was stirred for an additional 15 minutes at 700 RPM using the same overhead stirrer. Finally, the mixture was transferred to a clear graduated cylinder and capped to observe the stability of the mixture. The mixture was allowed to stand at approximately 23 °C for 31 days and then observed.

[0060] Results

[0061] Table 1 presents the results for Comparative Examples ("CE") and Examples of the Invention ("IE").

[0062] Table 1

[0063]

[0064]

[0065] Referring now to Table 1, it can be seen that a lubricant composition comprising graphite, oil, and a dispersant selected from the group consisting of sulfosuccinates and polyalkylene glycols comprising propylene oxide and butylene oxide is capable of passing the gelling test. CE1 demonstrates that the absence of a dispersant results in the gelling of graphite. Similarly, the addition of PIBSA and other dispersants in CE2 - CE5 fails to prevent the gelling of graphite in oil. CE6 shows that an 80:20 weight ratio of DISP5 and DISP2 (i.e., approximately 86 wt% of the active substance of polyalkylene glycol DISP5) also fails to prevent the gelling of graphite. In contrast to CE6, IE5 with equal weights of DISP5 and DISP2 (i.e., approximately 61 wt% of the active substance of polyalkylene glycol DISP5) is able to successfully prevent the gelling of graphite. Similarly, the use of succinates and polyalkylene glycols alone in IE1 - IE4 is able to prevent the gelling of graphite and keep the graphite in a dispersible form.

Claims

1. A lubricant composition comprising: graphite; an oil; and a dispersant selected from the group consisting of sulfosuccinates, polyalkylene glycols comprising propylene oxide and butylene oxide, and combinations thereof, provided that based on the total weight of the combined sulfosuccinate and polyalkylene glycol dispersants, the combination of sulfosuccinate and polyalkylene glycol dispersants comprises 80 wt% or less of the polyalkylene glycol.

2. The lubricant composition according to claim 1, wherein based on the total weight of the lubricant composition, the lubricant composition comprises 1 wt% to 60 wt% of graphite.

3. The lubricant composition according to any one of claims 1 and 2, wherein the graphite has a D90 particle diameter of 0.5 μm to 5.0 μm.

4. The lubricant composition according to any one of claims 1 to 3, wherein based on the total weight of the lubricant composition, the lubricant composition comprises 50 wt% to 98 wt% of the oil.

5. The lubricant composition according to any one of claims 1 to 4, wherein based on the total weight of the lubricant composition, the lubricant composition comprises 0.01 wt% to 5.0 wt% of the dispersant.

6. The lubricant composition according to any one of claims 1 to 5, wherein the dispersant comprises a sulfosuccinate.

7. The lubricant composition according to claim 6, wherein the sulfosuccinate dispersant comprises sodium di-2-ethylhexyl sulfosuccinate.

8. The lubricant composition according to any one of claims 1 to 5, wherein the dispersant comprises the polyalkylene glycol, and based on the combined weight of propylene oxide and butylene oxide in the polyalkylene glycol, the polyalkylene glycol comprises 30 wt% to 70 wt% of propylene oxide.

9. The lubricant composition according to claim 8, based on the combined weight of propylene oxide and butylene oxide in the polyalkylene glycol, the polyalkylene glycol comprises 40 wt% to 60 wt% of propylene oxide.

10. The lubricant composition according to any one of claims 1 to 5, wherein the dispersant comprises sodium di-2-ethylhexyl sulfosuccinate and a dodecanol-initiated polyalkylene glycol, and based on the combined weight of propylene oxide and butylene oxide in the polyalkylene glycol, the dodecanol-initiated polyalkylene glycol comprises 50 wt% of propylene oxide.

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