JP7620643B2 - Lubricating oil composition comprising comb polymethacrylate and ethylene-based olefin copolymer viscosity modifier - Patents.com - Google Patents

Description

The technology disclosed relates to lubricating oils for internal combustion engines, and in particular, lubricating oils for spark ignition engines.

Engine oils are blended with a variety of additives to meet performance requirements. The challenge in engine oil formulation is to simultaneously achieve wear, deposit and gloss control while also improving fuel economy.

One known method to improve the fuel economy of a lubricating oil composition is to reduce the viscosity (i.e., high temperature high shear (HTHS) viscosity). HTHS is a measure of the viscosity of a lubricating oil composition under severe engine conditions. However, this approach is reaching the limits of current equipment capabilities and specifications. The addition of organic or organometallic friction modifiers at a given viscosity reduces the surface friction of the lubricating oil composition, allowing for better fuel economy. However, these additives often result in adverse effects such as increased deposit formation and seal impact, or they outcompete anti-wear components at finite surface sites, thereby preventing the formation of an anti-wear film and causing increased wear.

Viscosity modifiers are also widely used to improve the viscosity index (VI) of lubricating oil compositions, making the oil thicker with increasing temperature. However, at high temperatures and under high stress conditions, degradation of viscosity modifiers can occur. When this occurs, the viscosity of the lubricating oil composition decreases, which can lead to increased engine wear.

Therefore, despite advances in lubricant formulation technology, there continues to be a need for engine lubricants that provide adequate fuel economy while also providing excellent antiwear performance, particularly lubricants having a viscosity rating of SAE 0W-20 or lower.

In one aspect, the present disclosure provides a lubricating oil composition having a kinematic viscosity at 100° C. of less than 9.3 mm ² /s,
a) a major amount of an oil of lubricating viscosity;
b) a non-dispersant comb polymethacrylate (PMA); and c) a non-dispersant ethylene-based olefin copolymer.

Another aspect of the present disclosure is a method of reducing wear in an internal combustion engine comprising lubricating the engine with a lubricating oil composition having a kinematic viscosity at 100° C. of less than 9.3 mm ² /s, the lubricating oil composition comprising:
a) a major amount of oil of lubricating viscosity;
b) a non-dispersed comb polymethacrylate (PMA); and c) a non-dispersed ethylene-based olefin copolymer.

Yet another aspect of the present disclosure is a lubricating oil composition comprising:
a) a major amount of an oil of lubricating viscosity;
b) a non-dispersant comb polymethacrylate (PMA) in an amount from 0.4 wt. % to 1.9 wt. %, based on the total weight of the lubricating oil composition; and c) a non-dispersant ethylene-based olefin copolymer in an amount from 0.01 wt. % to 0.36 wt. %, based on the total weight of the lubricating oil composition.

Another aspect of the present disclosure is a method of reducing wear in an internal combustion engine comprising lubricating the engine with a lubricating oil composition comprising:
a) a major amount of oil of lubricating viscosity;
b) a non-dispersant comb polymethacrylate (PMA) in an amount from 0.4 wt. % to 1.9 wt. %, based on the total weight of the lubricating oil composition; and c) a non-dispersant ethylene-based olefin copolymer in an amount from 0.01 wt. % to 0.36 wt. %, based on the total weight of the lubricating oil composition.
Note that the following [1] to [23] are all one embodiment or one aspect of the present invention.
[1]
1. A lubricating oil composition comprising:
a) a major amount of oil of lubricating viscosity;
b) non-dispersed comb polymethacrylate (PMA); and
c) Non-dispersed ethylene-based olefin copolymer
wherein the lubricating oil composition has a kinematic viscosity at 100° C. of less than 9.3 mm ² /s.
[2]
The lubricating oil composition according to [1], wherein the non-dispersed comb-type PMA has a weight average molecular weight (Mw) of 390,000 g/mol to 460,000 g/mol.
[3]
The lubricating oil composition according to [1], wherein the non-dispersing comb-type PMA has a shear stability index (SSI) of 0.3 to 0.8.
[4]
The lubricating oil composition of claim 1, wherein the non-dispersed comb PMA is present in an amount of 0.4 wt % to 2.0 wt %, based on the total weight of the lubricating oil composition.
[5]
The lubricating oil composition according to [1], wherein the non-dispersant ethylene-based olefin copolymer has a weight average molecular weight (Mw) of 90,000 g/mol to 160,000 g/mol.
[6]
The lubricating oil composition according to [1], wherein the non-dispersant ethylene-based olefin copolymer has a shear stability index (SSI) of 10 to 70.
[7]
2. The lubricating oil composition of claim 1, wherein the non-dispersant ethylene-based olefin copolymer is present in an amount of 0.08 wt % to 0.4 wt %, based on the total weight of the lubricating oil composition.
[8]
2. The lubricating oil composition of claim 1, wherein the non-dispersant ethylene-based olefin copolymer has a total ethylene content of 45 to 60 weight percent, based on the total weight of the non-dispersant ethylene-based olefin copolymer.
[9]
The lubricating oil composition according to [1], wherein the non-dispersant ethylene-based olefin copolymer is an ethylene propylene copolymer.
[10]
2. The lubricating oil composition of claim 1, wherein the non-dispersant comb PMA is present in an amount of 0.76 wt % to 1.33 wt % and the non-dispersant ethylene-based olefin copolymer is present in an amount of 0.08 to 0.4 wt %, based on a total weight of the lubricating oil composition.
[11]
The lubricating oil composition of claim 1, wherein the non-dispersant comb PMA and the non-dispersant ethylene-based olefin copolymer are present in a total amount of 0.4 wt % to 4 wt %, based on the total weight of the lubricating oil composition.
[12]
The lubricating oil composition according to claim 1, wherein the oil of lubricating viscosity is an API Group III base oil.
[13]
The lubricating oil composition according to claim 1, further comprising a molybdenum compound.
[14]
The lubricating oil composition according to [13], wherein the molybdenum compound is molybdenum dithiocarbamate (MoDTC).
[15]
The lubricating oil composition of claim 13, wherein the molybdenum compound provides the lubricating oil composition with an amount of molybdenum in the range of 50 ppm to 1200 ppm.
[16]
The lubricating oil composition of claim 1, wherein the lubricating oil composition has an SAE 0W-20, 0W-16, or 0W-12 viscosity grade.
[17]
The lubricating oil composition according to [1], wherein the lubricating oil composition has a 150° C. high temperature high shear (HTHS) viscosity of 2.55 cP to less than 2.9 cP.
[18]
The lubricating oil composition according to [1], wherein the lubricating oil composition has a viscosity index of 200 to 240.
[19]
1. A method for reducing wear in an internal combustion engine, comprising:
Lubricating said engine with a lubricating oil composition having a kinematic viscosity at 100° C. of less than 9.3 mm ² /s.
and the lubricating oil composition comprises
a) a major amount of oil of lubricating viscosity;
b) non-dispersed comb polymethacrylate (PMA); and
c) Non-dispersed ethylene-based olefin copolymer
The method comprising:
[20]
20. The method of claim 19, wherein the engine comprises a roller follower rocker arm.
[21]
1. A lubricating oil composition comprising:
a) a major amount of oil of lubricating viscosity;
b) a non-dispersant comb polymethacrylate (PMA) in an amount of 0.4 wt. % to 1.9 wt. %, based on the total weight of the lubricating oil composition; and
c) a non-dispersant ethylene-based olefin copolymer in an amount of 0.01 wt. % to 0.36 wt. %, based on the total weight of the lubricating oil composition.
The lubricating oil composition comprising:
[22]
1. A method for reducing wear in an internal combustion engine, comprising:
lubricating said engine with the lubricating oil composition.
and the lubricating oil composition comprises
a) a major amount of oil of lubricating viscosity;
b) a non-dispersant comb polymethacrylate (PMA) in an amount of 0.4 wt. % to 1.9 wt. %, based on the total weight of the lubricating oil composition; and
c) a non-dispersant ethylene-based olefin copolymer in an amount of 0.01 wt. % to 0.36 wt. %, based on the total weight of the lubricating oil composition.
The method comprising:
[23]
23. The method of claim 22, wherein the engine comprises a roller follower rocker arm.

To facilitate understanding of the subject matter disclosed herein, several terms, abbreviations or other shorthand expressions used herein are defined below. Any term, abbreviation or shorthand expression not defined will be understood to have the ordinary meaning used by those of ordinary skill in the art contemporaneous with the filing of this application.

DEFINITIONS As used herein, the following words and expressions, if and when used, have the meanings set forth below.

"Major amount" means greater than 50% by weight of the composition.

"Minor amount" means less than 50% by weight of the composition, expressed with respect to the indicated additive and with respect to the total mass of all additives present in the composition, counted as the active ingredient of the additive or additives.

"Active ingredient" or "active substance" refers to an additive substance that is not a diluent or solvent.

All percentages reported are weight percent (wt%) on an active ingredient basis (i.e., without regard to carrier or diluent oil) unless otherwise specified.

The abbreviation "ppm" means parts per million by weight based on the total weight of the lubricating oil composition.

Kinematic Viscosity (KV) at 100° C. is measured in mm ² /s and is determined in accordance with ASTM D445.

150°C high temperature high shear (HTHS) viscosity is determined in accordance with ASTM D4683.

Apparent viscosity at temperatures between -35°C and -5°C is measured using a cold cranking simulator in accordance with ASTM D5293.

Metal - The term "metal" refers to an alkali metal, an alkaline earth metal, or a mixture thereof.

By oil soluble or dispersible material, it is meant that the amount of material needed to provide the desired level of activity or performance can be incorporated by dissolving, dispersing, or suspending in an oil of lubricating viscosity. Typically, this means that at least about 0.001 wt. % of the material can be incorporated in the lubricating oil composition. For further discussion of oil solubility or dispersibility, and particularly the term "stably dispersible," see U.S. Pat. No. 4,320,019, the teachings of which are expressly incorporated herein by reference.

As used herein, the term "sulfated ash" refers to non-combustible residues resulting from detergents and metallic additives in a lubricating oil. Sulfated ash may be determined in accordance with ASTM D874.

As used herein, the term "Total Base Number" or "TBN" refers to the amount of base equivalent to milligrams of KOH in one gram of sample. Thus, a higher TBN number reflects more alkaline product and therefore more alkalinity. TBN is determined in accordance with ASTM D2896.

The boron, calcium, magnesium, molybdenum, phosphorus, sulfur and zinc contents are determined in accordance with ASTM D5185.

The weight average molecular weight (Mw) and number average molecular weight (Mw) are measured by GPC (gel permeation chromatography) using polystyrene as the standard.

Shear Stability Index (SSI) is measured in accordance with ASTM D7109.

All ASTM standards referenced herein are current as of the filing date of this application.

Olefins - The term "olefins" refers to a class of unsaturated aliphatic hydrocarbons with one or more carbon-carbon double bonds, obtained by several processes. Those containing one double bond are called monoalkenes, those with two double bonds are called dienes, alkyldienes or diolefins. Alpha olefins are particularly reactive because the double bond is between the first and second carbon. Examples are 1-octene and 1-octadecene, which are used as starting points for surfactants with moderate biodegradability. Linear and branched olefins are also included in the definition of olefins.

While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are described in detail herein. It should be understood, however, that the description of specific embodiments herein is not intended to limit the disclosure to the particular forms disclosed, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

Please note that not all of the activities described in the general description or in the examples are required, that some of the specific activities may not be required, and that one or more additional activities may be performed in addition to those described. Moreover, the order in which the activities are listed is not necessarily the order in which they are performed.

Benefits, other advantages, and solutions to problems are described herein with respect to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature or features that may give rise to or make more pronounced any benefit, advantage, or solution to a problem should not be construed as essential, required, or essential features of any or all of the claims.

The specifications and illustrations of the embodiments described herein are intended to provide a comprehensive understanding of the structure of the various embodiments.

As used herein, the terms "comprises," "comprising," "includes," "including," "having," "having," or any other variation thereof, are intended to include non-exclusive inclusions. For example, a process, method, article, or apparatus that includes recited features is not necessarily limited to only those features, but may include other features not expressly recited or that are inherent to such process, method, article, or apparatus. Furthermore, "or" means inclusive or, not exclusive or, unless expressly indicated otherwise. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and A and B are both true (or present).

The use of "a" or "an" is employed to describe elements and components described herein. This is done merely for convenience and to give a general understanding of the scope of the embodiments of the present disclosure. This description should be interpreted to include one, or at least one, and the singular also includes the plural and vice versa, unless it is clear that something else is meant.

The term "on average" when referring to values is intended to mean the mean, geometric mean, or median. Group numbers corresponding to columns in the Periodic Table of the Elements use the "modern notation" convention as found in the CRC Handbook of Chemistry and Physics, 81st Edition (2000-2001).

Unless otherwise defined, all scientific and technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The materials, methods, and examples are illustrative only and are not intended to be limiting. Unless otherwise described herein, many details regarding specific materials and processing operations are conventional and can be found in textbooks and other sources within the scope of the lubricants and oil and gas industries.

The specification and illustrations are not intended to serve as an exhaustive and comprehensive description of all elements and features of the formulations, compositions, devices and systems that use the structures or methods described herein. Separate embodiments may be provided in combination as one embodiment, and conversely, various features that are described for brevity in the context of a single embodiment may be provided separately or in any subcombination. Furthermore, references to values given in ranges include any and all values within that range. Many other embodiments may become apparent to those skilled in the art upon reading this specification. Other embodiments may be used and derived from this disclosure, such that structural substitutions, logical substitutions or other changes may be made without departing from the scope of this disclosure. The present disclosure should therefore be considered illustrative and not limiting.

Oil of lubricating viscosity/base oil component An oil of lubricating viscosity (sometimes referred to as a "base stock" or "base oil") is the primary liquid component of a lubricating oil composition into which additives and possibly other oils are blended to produce, for example, the final lubricating oil composition. Base oils serve to make concentrates and lubricating oil compositions therefrom, and may be selected from natural and synthetic oils, and combinations thereof.

Natural oils include animal and vegetable oils, liquid petroleum-based oils, and hydrorefined and solvent-treated paraffinic, naphthenic, and mixed paraffinic-naphthenic mineral lubricating oils. Oils of lubricating viscosity derived from coal or shale are also useful base oils.

Synthetic oils include hydrocarbon oils such as polymerized and copolymerized olefins (e.g., polybutylene, polypropylene, propylene-isobutylene copolymers, chlorinated polybutylene, poly(1-hexene), poly(1-octene), and poly(1-decene); alkylbenzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, and di(2-ethylhexyl)benzene); polyphenols (e.g., biphenyl, terphenyl, and alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulfides, and their derivatives, analogs, and homologs).

Another suitable class of synthetic oils includes esters of dicarboxylic acids (e.g., malonic acid, alkylmalonic acids, alkenylmalonic acids, succinic acid, alkylsuccinic acids and alkenylsuccinic acids, maleic acid, fumaric acid, azelaic acid, suberic acid, sebacic acid, adipic acid, linoleic acid dimer, and phthalic acid) with various alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, and propylene glycol). Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting 1 mole of sebacic acid with 2 moles of tetraethylene glycol and 2 moles of 2-ethylhexanoic acid.

The base oil may be a renewable or bio-derived engine oil. Examples of such engine oils are disclosed in WO2016061050, which is incorporated herein by reference. According to some embodiments, the renewable or bio-derived base oil comprises isoparaffinic hydrocarbons derived from biohydrocarbons, e.g., hydrocarbon terpenes such as myrcene, ocimene, and farnesene.

Esters useful as synthetic oils also include those made from C ₅ to C ₁₂ monocarboxylic acids and polyols, and polyol ethers, such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tripentaerythritol.

Base oils may be derived from Fischer-Tropsch synthesized hydrocarbons. Fischer-Tropsch synthesized hydrocarbons are made from synthesis gas containing _H2 and CO using a Fischer-Tropsch catalyst. Such hydrocarbons typically require further processing to be useful as base oils. For example, the hydrocarbons may be subjected to hydroisomerization; hydrocracking and hydroisomerization; dewaxing; or hydroisomerization and dewaxing using processes known to those skilled in the art.

Unrefined, refined and re-refined oils may be used as the base oil of the lubricating oil composition of the present invention. Unrefined oils are oils obtained directly from natural or synthetic sources without further refining treatment. For example, shale oil obtained directly from a retorting operation, petroleum-based oil obtained directly from distillation, or ester oil obtained directly from an esterification process and used without further treatment would be unrefined oils. Refined oils are similar to unrefined oils except that they have been further processed in one or more purification steps to improve one or more properties. Many such refining techniques, such as distillation, solvent extraction, acid or base extraction, filtration and percolation, are known to those skilled in the art.

Thus, the base oils that may be used to make the lubricating oil compositions of the present invention may be selected from any of the base oils of Groups I to V as defined in the American Petroleum Institute (API) Base Oil Interchangeability Specification (API Publication 1509). Such base oil groups are summarized in Table 1 below:

Suitable base oils for use herein are any of the grades corresponding to API Group II, Group III, Group IV and Group V oils, and combinations thereof, preferably Group III to Group V oils due to their exceptional volatility, stability, viscosity and cleanliness characteristics.

The base oil constitutes the major component of the lubricating oil composition and is present in an amount ranging from greater than 50% to 99% by weight (e.g., 70-95% by weight, or 85-95% by weight).

The base oil may be selected from any of the synthetic or natural oils typically used as crankcase lubricants for spark ignition internal combustion engines. The base oil typically has a 100°C kinematic viscosity in the range of 1.5 to 6 ^mm2 /s. If the 100°C kinematic viscosity of the lubricating base oil exceeds 6 ^mm2 /s, the low temperature viscometric properties may be reduced and sufficient fuel efficiency may not be obtained. At a kinematic viscosity of ^{1.5 mm2} /s or less, the formation of oil films at lubrication points may be insufficient, which may result in poor lubricity and increased evaporation losses of the lubricating oil composition.

However, in some embodiments, a base oil having a kinematic viscosity above 6 ^mm2 /s is required. For example, the base oil as a whole could also include a minor proportion of a heavier base oil, e.g., a 10 cSt polyalphaolefin.

Preferably, the base oil has a viscosity index of at least 90 (e.g., at least 95, at least 105, at least 110, at least 115, or at least 120). If the viscosity index is less than 90, not only will the viscosity-temperature characteristics, thermal and oxidative stability, and volatility resistance decrease, but the coefficient of friction will tend to increase and resistance to wear will tend to decrease.

The lubricating oil composition may be a multigrade oil having a viscosity rating of SAE 0W-XX, where XX is any one of 8, 10, 12, 16, and 20. According to one preferred embodiment, the lubricating oil composition has a viscosity rating of SAE 0W-20.

The lubricating oil composition has a 150°C high temperature high shear (HTHS) viscosity of 3.0 cP or less (e.g., 1.0 cP to 3.0 cP, or 1.3 cP to 3.0 cP), 2.8 cP or less (e.g., 1.0 cP to 2.8 cP, or 1.3 cP to 2.8 cP), 2.7 cP or less (e.g., 1.0 cP to 2.7 cP, or 1.3 cP to 2.7 cP), 2.6 cP or less (e.g., 1.0 cP to 2.6 cP, or 1.3 cP to 2.6 cP), for example, 2.5 cP or less (e.g., 1.0 cP to 2.5 cP, or 1.3 cP to 2.5 cP), or 2.0 cP or less (e.g., 1.0 cP to 2.0 cP, or 1.3 cP to 2.0 cP). According to exemplary embodiments, the lubricating oil composition has a 150°C HTHS viscosity of 2.5 cP to 2.6 cP, 2.55 cP to less than 2.9 cP, or 2.55 cP to 2.58 cP.

The lubricating oil composition has a viscosity index of at least 135 (e.g., 135-400, or 135-250), at least 150 (e.g., 150-400, or 150-250), at least 165 (e.g., 165-400, or 165-250), at least 190 (e.g., 190-400, or 190-250), or at least 200 (e.g., 200-400, or 200-250). If the viscosity index of the lubricating oil composition is less than 135, it may be difficult to maintain the desired 150°C HTHS viscosity while improving fuel efficiency. If the viscosity index of the lubricating oil composition is greater than 400, evaporation characteristics may be reduced and defects due to insufficient additive solubility and matching characteristics with sealing materials may occur. According to exemplary embodiments, the lubricating oil composition has a viscosity index of 200 to 240, 203 to 235, 200 to 210, 220 to 225, or 230 to 240.

The lubricating oil composition has a 100° C. kinematic viscosity in the range of 3 mm ² /s to 12 mm ² /s (eg, 3 mm ² /s to 11 mm ² /s, 5 mm ² /s to 9 mm ² /s, or 6 mm ² /s to 8 mm ² /s). According to exemplary embodiments, the lubricating oil composition has a 100° C. kinematic viscosity in the range of from 6.9 ^{mm 2} /s to less than 9.3 mm ² /s, from 7.4 mm ^{2 /s to 7.8 mm 2 /s, from 7.45 mm 2 / s} to 7.76 mm ² /s, from 7.4 mm ² / ^s to 7.5 mm ^{2 /s, from 7.5 mm 2 / s} to 7.6 mm ² /s, from 7.6 mm 2 /s to 7.7 mm 2 /s, or from 7.7 mm ² /s to 7.8 mm ² /s.

The lubricating oil composition has an apparent viscosity of 3600 mPa·s to 3900 mPa·s at temperatures ranging from 35° C. to −5° C. as measured by a cold cranking simulator (CCS). According to exemplary embodiments, the lubricating oil composition has an apparent viscosity of 3600 mPa·s to 3700 mPa·s, 3700 mPa·s to 3800 mPa·s, or 3800 mPa·s to 3900 mPa·s.

Generally, the level of sulfur in the lubricating oil composition is about 0.7 wt.% or less, based on the total weight of the lubricating oil composition. For example, the lubricating oil composition may have a sulfur level of about 0.01 wt.% to 0.5 wt.%, 0.01 wt.% to 0.4 wt.%, 0.01 wt.% to 0.3 wt.%, 0.01 wt.% to 0.2 wt.%, or 0.01 wt.% to 0.10 wt.%. In one embodiment, the level of sulfur in the lubricating oil composition is about 0.60 wt.% or less, about 0.50 wt.% or less, about 0.40 wt.% or less, about 0.30 wt.% or less, about 0.20 wt.% or less, or about 0.10 wt.% or less, based on the total weight of the lubricating oil composition.

In one embodiment, the level of phosphorus in the lubricating oil composition is about 0.08 wt. % or less, e.g., about 0.01 wt. % to about 0.08 wt. % based on the total weight of the lubricating oil composition. In one embodiment, the level of phosphorus in the lubricating oil composition is about 0.07 wt. % or less, e.g., about 0.01 wt. % to about 0.07 wt. % based on the total weight of the lubricating oil composition. In one embodiment, the level of phosphorus in the lubricating oil composition is about 0.05 wt. % or less, e.g., about 0.01 wt. % to about 0.05 wt. % based on the total weight of the lubricating oil composition.

In one embodiment, the lubricating oil composition produces a sulfated ash level of about 1.00 wt. % or less as determined by ASTM D874, e.g., about 0.10 wt. % to about 1.00 wt. % sulfated ash as determined by ASTM D874. In one embodiment, the lubricating oil composition produces a sulfated ash level of about 0.80 wt. % or less as determined by ASTM D874, e.g., about 0.10 wt. % to about 0.80 wt. % sulfated ash as determined by ASTM D874. In one embodiment, the lubricating oil composition produces a sulfated ash level of about 0.60 wt. % or less as determined by ASTM D874, e.g., about 0.10 wt. % to about 0.60 wt. % sulfated ash as determined by ASTM D874.

Suitably, the lubricating oil composition of the present invention may have a total base number (TBN) of 4 to 15 mg KOH/g (e.g., 5 mg KOH/g to 12 mg KOH/g, 6 mg KOH/g to 12 mg KOH/g, or 8 mg KOH/g to 12 mg KOH/g).

Viscosity Modifiers Viscosity modifiers (VM), sometimes referred to as viscosity index improvers (VII), are present in lubricating oil compositions to impart high and low temperature operability. Viscosity modifiers increase the viscosity of the lubricating oil composition at elevated temperatures, thereby increasing film thickness, while having limited effect on viscosity at low temperatures.

Viscosity modifiers may be used to provide their sole function or may be multifunctional. Multifunctional viscosity modifiers may also function as dispersants.

Examples of suitable viscosity modifiers are polymers and copolymers of methacrylates, butadienes, olefins or alkylated styrenes. Other suitable viscosity modifiers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (e.g., copolymers of acrylates of various chain lengths).

The viscosity modifier may be present in the lubricating oil composition in a total amount of 0.001 wt % to 10 wt %, based on the total weight of the lubricating oil composition. In other embodiments, the viscosity modifier may be present in a total amount of 0.01 wt % to 8 wt %, 0.1 wt % to 5 wt %, 0.4 wt % to 4 wt %, 0.6 wt % to 3 wt %, 0.7 wt % to 2 wt %, 1 wt % to 1.5 wt %, or 1.05 wt % to 1.44 wt %, based on the total weight of the lubricating oil composition. In some exemplary embodiments, the viscosity modifier is present in a total amount of 1.0 wt % to 1.2 wt %, 1.3 wt % to 1.4 wt %, or 1.4 wt % to 1.5 wt %, based on the total weight of the lubricating oil composition.

Particularly useful in lubricating oil compositions is the combination of a non-dispersant comb polymethacrylate (comb PMA) with at least one non-dispersant ethylene-based olefin copolymer (OCP).

Non-dispersed Comb Polymethacrylates Non-dispersed comb polymethacrylates (comb PMA) are comb-shaped polymers and therefore macromolecules whose main chains have one long branch per repeat unit.

In one embodiment, the non-dispersed comb PMA has a weight average molecular weight (Mw) of 300,000 g/mol to 600,000 g/mol, 350,000 g/mol to 550,000 g/mol, 375,000 g/mol to 500,000 g/mol, or 390,000 g/mol to 460,000 g/mol.

In one embodiment, the non-dispersed comb PMA has a number average molecular weight (Mn) of 35,000 g/mol to 105,000 g/mol, 45,000 g/mol to 95,000 g/mol, 55,000 g/mol to 85,000 g/mol, or 65,000 g/mol to 75,000 g/mol. In another embodiment, the non-dispersed comb PMA has a number average molecular weight (Mn) of 150,000 g/mol to 250,000 g/mol, or 200,000 g/mol to 215,000 g/mol.

In one embodiment, the non-dispersed comb PMA has a shear stability index (SSI) of 0.1 to 1.0, 0.2 to 0.9, or 0.3 to 0.8.

The non-dispersant comb PMA of the lubricating oil composition may be described as set forth in US 2017/0298287 A1 and JP 2019014802, the disclosures of which are incorporated herein by reference. The non-dispersant comb PMA may be provided by Viscoplex® viscosity index improvers 3-201 and/or 3-162, which are available from Evonik.

According to one embodiment, the non-dispersed comb PMA is provided by a compound designated Viscoplex® 3-201, which includes comb PMA as the major resin component. The non-dispersed comb PMA has a weight average molecular weight (Mw) of 420,000 g/mol, a number average molecular weight (Mn) of 70,946 g/mol, and an Mw/Mn of 5.92. The compound has at least building blocks derived from macromonomers having an Mn of 500 or greater. The non-dispersed comb PMA is present in an amount of 19% by weight, based on the total weight of the compound.

According to another embodiment, the non-dispersed comb PMA is provided by a compound designated Viscoplex® 3-162, which also contains comb PMA as the major resin component. The non-dispersed comb PMA has a weight average molecular weight (Mw) of 399,292 g/mol, a number average molecular weight (Mn) of 205,952 g/mol, an Mw/Mn of 1.94, and a shear stability index (SSI) of 0.6.

According to another embodiment, the non-dispersed comb PMA is provided by a combination of compounds, for example, Viscoplex® 3-201 and Viscoplex® 3-162.

The non-dispersed comb PMA is typically present in an amount of 0.4 wt % to 2.0 wt %, 0.5 wt % to 1.9 wt %, 0.6 wt % to 1.8 wt %, 0.77 wt % to 1.5 wt %, or 0.76 wt % to 1.33 wt %, based on the total weight of the lubricating oil composition. According to one embodiment, the non-dispersed comb PMA is present in an amount of 0.4 wt % to 1.9 wt %, based on the total weight of the lubricating oil composition.

Non-dispersant ethylene-based olefin copolymer The lubricant composition also includes a non-dispersant ethylene-based olefin copolymer (OCP) as a viscosity modifier. In one embodiment, the non-dispersant ethylene-based olefin copolymer has a weight average molecular weight (Mw) of 50,000 g/mol to 200,000 g/mol, 70,000 g/mol to 180,000 g/mol, or 90,000 g/mol to 160,000 g/mol. For example, the non-dispersant ethylene-based olefin copolymer could have a weight average molecular weight of 95,000 g/mol to 105,000 g/mol, 110,000 g/mol to 115,000 g/mol, or 145,000 g/mol to 150,000 g/mol.

In one embodiment, the non-dispersed ethylene-based olefin copolymer has a number average molecular weight (Mn) of 20,000 g/mol to 100,000 g/mol, 30,000 g/mol to 90,000 g/mol, or 35,000 g/mol to 85,000 g/mol.

In one embodiment, the non-dispersed ethylene-based olefin copolymer has a shear stability index (SSI) of 10 to 70, 15 to 65, or 20 to 60.

The non-dispersed ethylene-based olefin copolymers may be described as follows and as set forth in US 2013/0203640, the disclosure of which is incorporated herein by reference.

In one embodiment, the non-dispersed ethylene-based olefin copolymer is an ethylene propylene copolymer.

In one embodiment, the non-dispersed ethylene-based olefin copolymer has a total ethylene content of 35% to 70% by weight, or 40% to 65% by weight, based on the total weight of the non-dispersed ethylene-based olefin copolymer. In another embodiment, the non-dispersed ethylene-based olefin copolymer has a total ethylene content of 45% to 60% by weight, based on the total weight of the non-dispersed ethylene-based olefin copolymer.

The lubricating oil composition may include more than one non-dispersant ethylene-based olefin copolymer. In one embodiment, the lubricating oil composition includes a combination of a first ethylene-α-olefin copolymer (a) and a second ethylene-α-olefin copolymer (b). In this case, the lubricating oil composition typically contains from about 30 wt % to about 70 wt % of the first ethylene-α-olefin copolymer (a) and from about 70 wt % to about 30 wt % of the second ethylene-α-olefin copolymer (b), based on the total amount of (a) and (b) in the lubricating oil composition. In another embodiment, the lubricating oil composition contains from about 40 wt % to about 60 wt % of the first ethylene-α-olefin copolymer (a) and from about 60 wt % to about 40 wt % of the second ethylene-α-olefin copolymer (b), based on the total amount of (a) and (b) in the composition. In certain embodiments, the lubricating oil composition contains about 50% to about 54% by weight of the first ethylene-α-olefin copolymer (a) and about 46% to about 50% by weight of the second ethylene-α-olefin copolymer (b), based on the total amount of (a) and (b) in the composition.

In one embodiment, the weight average molecular weight of the first ethylene-α-olefin copolymer is typically about 60,000 g/mol to about 120,000 g/mol. In another embodiment, the weight average molecular weight of the first ethylene-α-olefin copolymer is typically about 70,000 g/mol to about 110,000 g/mol. In one embodiment, the weight average molecular weight of the second ethylene-α-olefin copolymer is typically about 60,000 g/mol to about 120,000 g/mol. In another embodiment, the weight average molecular weight of the second ethylene-α-olefin copolymer is typically about 70,000 g/mol to about 110,000 g/mol. In one embodiment, the weight average molecular weight of the composition of the first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer is typically about 60,000 g/mol to about 120,000 g/mol. In another embodiment, the weight average molecular weight of the composition of the first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer is typically from about 70,000 g/mol to about 110,000 g/mol. In a further embodiment, the weight average molecular weight of the composition of the first ethylene-α-olefin copolymer and the second ethylene-α-olefin copolymer is typically from about 80,000 g/mol to about 100,000 g/mol. The molecular weight distribution of each ethylene-α-olefin copolymer is typically less than about 2.5, more typically from about 2.1 to about 2.4. The polymer distribution as determined by GPC is typically unimodal.

The at least one non-dispersant ethylene-based olefin copolymer is typically present in an amount of 0.01 wt.% to 1.5 wt.%, 0.05 wt.% to 1.0 wt.%, 0.08 wt.% to 0.4 wt.%, 0.1 wt.% to 0.5 wt.%, or 0.15 wt.% to 0.4 wt.%, based on the total weight of the lubricating oil composition. According to one embodiment, the at least one non-dispersant ethylene-based olefin copolymer is present in an amount of 0.01 wt.% to 0.36 wt.%, based on the total weight of the lubricating oil composition.

Additional Additives In addition to the non-dispersant comb PMA and non-dispersant ethylene-based olefin copolymer viscosity modifiers described above, the lubricating oil composition of the present disclosure may contain one or more additional performance additives that may impart or improve any desired property of the lubricating oil composition. Any additive known to those skilled in the art may be used in the lubricating oil composition disclosed herein. Some suitable additives are described in R. M. Mortier et al. "Chemistry and Technology of Lubricants," 3rd Edition, Springer (2010), and L. R. Rudnik "Lubricant Additives: Chemistry and Applications," Second Edition, CRC Press (2009).

For example, the lubricating oil composition may contain antioxidants, antiwear agents, metal detergents, dispersants, additional friction modifiers, corrosion inhibitors, demulsifiers, additional viscosity modifiers, pour point depressants, foam inhibitors, etc.

Typically, the concentration of each additive in the lubricating oil composition, when used, may range from 0.001 wt % to 10 wt % (e.g., 0.01 wt % to 5 wt %, or 0.05 wt % to 2.5 wt %) based on the total weight of the lubricating oil composition. Furthermore, the total amount of additives in the lubricating oil composition may range from 0.001 wt % to 20 wt % (e.g., 0.01 wt % to 15 wt %, or 0.1 wt % to 10 wt %) based on the total weight of the lubricating oil composition.

Antioxidants Antioxidants retard the oxidative deterioration of base oils during use. Such deterioration can cause deposits on metal surfaces, the presence of sludge, or viscosity increase in lubricating oil compositions. Useful antioxidants include hindered phenols, aromatic amines, and sulfurized alkylphenols, as well as the alkali and alkaline earth metal salts thereof.

The hindered phenol antioxidant may contain secondary butyl and/or tertiary butyl groups as sterically hindering groups. The phenol group may be further substituted with hydrocarbyl groups and/or bridging groups linking to a second aromatic group. Examples of suitable hindered phenol antioxidants include 2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 4,4'-bis(2,6-di-tert-butylphenol), and 4,4'-methylenebis(2,6-di-tert-butylphenol). The hindered phenol antioxidant may be an ester or an addition product derived from 2,6-di-tert-butylphenol and an alkyl acrylate, where the alkyl group may contain 1 to 18 carbon atoms.

Suitable aromatic amine antioxidants include diarylamines, such as alkylated diphenylamines (e.g., dioctyldiphenylamine, dinonyldiphenylamine), phenyl-alpha-naphthalene, and alkylated phenyl-alpha-naphthalene.

According to an exemplary embodiment, the lubricating oil composition includes an amine-based antioxidant.

Antiwear agents Antiwear agents help reduce the wear of metal parts lubricated with the lubricating oil composition. Examples of antiwear agents include phosphorus-containing antiwear/extreme pressure agents, such as metal thiophosphates, phosphoric acid esters and their salts; phosphorus-containing carboxylic acids, esters, ethers and amides; and phosphites. Antiwear agents may be zinc dialkyldithiophosphates (ZnDTP). Non-phosphorus-containing antiwear agents include borate esters (including borated epoxides), dithiocarbamate compounds, molybdenum-containing compounds, and sulfurized olefins.

According to one exemplary embodiment, the lubricating oil composition includes ZnDTP as an antiwear agent.

Metal Detergents Typical detergents are anionic materials containing a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically an organic acid, such as a sulfur acid, a carboxylic acid, a phosphoric acid, a phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal.

In some embodiments, the lubricating oil compositions provided herein include at least a neutral or overbased metal detergent as an additive or additive component. In some embodiments, the metal detergent in the lubricating oil composition acts as a neutralizer of acidic products in the lubricating oil composition. In some embodiments, the metal detergent prevents the formation of deposits on the engine surfaces. Depending on the nature of the acid used, the detergent may have additional functions, such as antioxidant properties. In some aspects, the lubricating oil composition contains a metal detergent, including either an overbased detergent or a mixture of neutral and overbased detergents. The term "overbased" is intended to define an additive that contains a metal in an amount above that required by the stoichiometry of the particular metal and the particular organic acid used. The excess metal is present in the form of particles of an inorganic base (e.g., hydroxide or carbonate) surrounded by a coating of a metal salt. The coating serves to keep the particles dispersed in the liquid oily vehicle. The amount of excess metal is generally expressed as a ratio of the total equivalents of excess metal to the equivalents of organic acid, and typically ranges from 0.1 to 30.

Some examples of suitable metal detergents include sulfurized or non-sulfurized alkyl or alkenyl phenates, alkyl or alkenyl aromatic sulfonates, borated sulfonates, sulfurized or non-sulfurized metal salts of polyhydroxyalkyl or alkenyl aromatic compounds, alkyl or alkenyl hydroxyaromatic sulfonates, sulfurized or non-sulfurized alkyl or alkenyl naphthenates, metal salts of alkanoic acids, metal salts of alkyl or alkenyl multiple acids, and chemical and physical mixtures thereof. Other examples of suitable metal detergents include metal sulfonates, phenates, salicylates, phosphonates, thiophosphonates, and combinations thereof. The metal can be any metal suitable for making sulfonate, phenate, salicylate, or phosphonate detergents. Non-limiting examples of suitable metals include alkali metals, alkaline metals, and transition metals. In some embodiments, the metal is Ca, Mg, Ba, K, Na, Li, etc.

The metal detergent may be an overbased detergent, for example a low overbased (LOB), medium overbased (MOB) or high overbased (HOB) detergent.

The low overbased detergent may be an overbased salt having a base number (BN) of less than 100. In one embodiment, the BN of the low overbased salt may be from about 5 to about 50. In another embodiment, the BN of the low overbased salt may be from about 10 to about 30. In yet another embodiment, the BN of the low overbased salt may be from about 15 to about 20. The base number of the overbased detergent is measured in the presence of diluent oil and not on an oil-free basis.

The medium overbased detergent may be an overbased salt having a BN of about 100 to about 250. In one embodiment, the BN of the medium overbased salt may be about 100 to about 200. In another embodiment, the BN of the medium overbased salt may be about 125 to about 175. The base number of the overbased detergent is measured in the presence of diluent oil and not on an oil-free basis.

The high overbased detergent may be an overbased salt having a BN greater than 250. In one embodiment, the BN of the high overbased salt may be from about 250 to about 550. The base number of the overbased detergent is measured in the presence of diluent oil and not on an oil-free basis.

Exemplary metal detergents that may be employed in the lubricating oil composition include overbased calcium phenates. According to another exemplary embodiment, the lubricating oil composition includes LOB Ca sulfonate, HOB Ca salicylate, and MOB Ca salicylate as detergents.

Ashless Dispersants Dispersants are additives whose primary function is to keep solid and liquid contaminants in suspension, thereby passivating them and reducing sludge precipitation while at the same time reducing engine deposits. For example, dispersants maintain in suspension oil-insoluble materials formed by oxidation during use of the lubricating oil composition, thus preventing flocculation and deposition or precipitation of sludge on metal parts of the engine. Typically, dispersants are "ashless", non-metallic organic materials that do not substantially form ash on combustion, unlike materials that contain metals and therefore form ash. They comprise long hydrocarbon chains with a polar head, the polarity being derived from the inclusion of at least one nitrogen, oxygen or phosphorus atom. The hydrocarbon is an oleophilic group that confers oil solubility, for example having 40 to 500 carbon atoms. Thus, ashless dispersants may comprise an oil-soluble polymer backbone.

A preferred class of olefin polymers consists of polybutylenes, specifically polyisobutylene (PIB) or poly-n-butylenes, e.g., those that can be prepared by polymerization of C4 refinery streams.

Dispersants include, for example, derivatives of long chain hydrocarbon-substituted carboxylic acids, such as derivatives of high molecular weight hydrocarbyl-substituted succinic acids. A notable group of dispersants consists of the hydrocarbon-substituted succinimides, made, for example, by reacting the above acids (or derivatives) with nitrogen-containing compounds, conveniently polyalkylene polyamines, such as polyethylene polyamines. A typical commercially available polyisobutylene-based succinimide dispersant contains a polyisobutylene polymer having a number average molecular weight in the range of 900 to 2500, functionalized with maleic anhydride and derivatized with a polyamine having a molecular weight of 100 to 350.

Other suitable dispersants include succinic acid esters and ester amides, Mannich bases, polyisobutylene succinic acid (PIBSA), and other related components.

Succinic acid esters are formed by the condensation reaction between hydrocarbyl-substituted succinic anhydrides and alcohols or polyols. For example, the condensation product of hydrocarbyl-substituted succinic anhydrides with pentaerythritol is a useful dispersant.

Succinic acid ester-amides are formed by the condensation reaction between a hydrocarbyl-substituted succinic anhydride and an alkanolamine. For example, suitable alkanolamines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines, and polyalkenylpolyamines, such as polyethylenepolyamines. One example is propoxylated hexamethylenediamine.

Mannich bases are made from the reaction of alkylphenols, formaldehyde, and polyalkylenepolyamines. The molecular weight of the alkylphenols can range from 800 to 2500.

Nitrogen-containing dispersants may be post-treated in conventional manner to improve their properties by reaction with any of a variety of agents. Among these are boron compounds (e.g., boronic acids) and cyclic carbonates (e.g., ethylene carbonate).

According to one exemplary embodiment, the lubricating oil composition includes borated succinimide and ethylene carbonate (EC) treated succinimide as ashless dispersants.

Friction Modifiers The lubricating oil composition may contain a friction modifier. A friction modifier is any material or materials that can change the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers include alkoxylated fatty amines, borated fatty epoxides, fatty phosphates, fatty epoxides, fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, fatty acid amides, glycerol esters, borated glycerol esters, and fatty imidazolines. As used herein, the term "aliphatic" refers to a hydrocarbon chain having from 10 to 22 carbon atoms, typically a straight hydrocarbon chain.

According to an exemplary embodiment, the lubricating oil composition includes an organomolybdenum compound, also referred to as a molybdenum-containing compound. The organomolybdenum compound contains at least molybdenum, carbon and hydrogen atoms, but may also contain sulfur, phosphorus, nitrogen and/or oxygen atoms. Suitable organomolybdenum compounds include molybdenum dithiocarbamates, molybdenum dithiophosphates, and various organomolybdenum complexes, such as molybdenum carboxylates, molybdenum esters, molybdenum amines, molybdenum amides, which can be obtained by reacting molybdenum oxide or ammonium molybdate with fats, glycerides, or fatty acids or fatty acid derivatives (e.g., esters, amines and amides). The term "aliphatic" means a carbon chain having 10 to 22 carbon atoms, typically a linear carbon chain.

Molybdate esters may be prepared by the methods disclosed in U.S. Pat. Nos. 4,889,647 and 6,806,241 B2. A commercial example is MOLYVAN® 855 additive, which is manufactured by R. T. Vanderbilt Company, Inc.

〔式中、Ｒ^１、Ｒ^２、Ｒ^３、及びＲ^４は互いに独立して、４～１８個の炭素原子（例えば、８～１３個の炭素原子）を有する直鎖または分岐アルキル基である〕
によって表される有機モリブデン化合物である。 According to an exemplary embodiment, the lubricating oil composition includes a molybdenum dithiocarbamate (MoDTC), which has the following structure (I):

wherein R ¹ , R ² , R ³ , and R ⁴ are each independently a straight or branched alkyl group having 4 to 18 carbon atoms (e.g., 8 to 13 carbon atoms).
It is an organomolybdenum compound represented by the formula:

The preparation of these compounds is well known in the literature and in U.S. Pat. Nos. 3,356,702 and 4,098,705, which are incorporated herein by reference. Commercially available examples include MOLYVAN® 807, MOLYVAN® 822, and MOLYVAN® 2000 manufactured by R. T. Vanderbilt Company Inc., SAKURA-LUBE® 165 and SAKURA-LUBE® 515 manufactured by ADEKA CORPORATION, and Naugalube® Moly FM manufactured by Chemtura Corporation.

Trinuclear molybdenum dialkyldithiocarbamates are also known in the art, as taught by U.S. Patent Nos. 5,888,945 and 6,010,987, which are incorporated herein by reference. The trinuclear molybdenum compounds preferably have the formula _Mo3S4 ( _dtc ) ₄ , _Mo3S7 (dtc) ₄ , and mixtures thereof, where dtc represents an independently selected _{diorganodithiocarbamate} ligand containing an independently selected organic group, the ligand having a sufficient number of carbon atoms among the organic groups of the ligand of the compound to render the compound soluble or dispersible in the lubricating oil composition.

〔式中、Ｒ^５、Ｒ^６、Ｒ^７及びＲ^８は互いに独立して、４～１８個の炭素原子（例えば、８～１３個の炭素原子）を有する直鎖または分岐アルキル基である〕
によって表される有機モリブデン化合物である。 According to another embodiment, the lubricating oil composition comprises molybdenum dithiophosphate (MoDTP), which has the following structure (2):

wherein R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a straight or branched alkyl group having 4 to 18 carbon atoms (e.g., 8 to 13 carbon atoms).
It is an organomolybdenum compound represented by the formula:

Molybdenum carboxylates are described in U.S. Patent RE38,929 and U.S. Patent 6,174,842, which are incorporated herein by reference. Molybdenum carboxylates may be derived from any oil-soluble carboxylic acid. Exemplary carboxylic acids include naphthenic acid, 2-ethylhexanoic acid, and linoleic acid. Commercial sources of carboxylates produced from these particular acids are MOLYBDENUM NAP-ALL, MOLYBDENUM HEX-CEM, and MOLYBDENUM LIN-ALL, respectively. The manufacturer of these products is OMG OM Group.

Ammonium molybdate is prepared by the reaction of an acidic molybdenum source, such as molybdenum trioxide, molybdic acid, ammonium molybdate, and ammonium thiomolybdate, with an oil-soluble amine, optionally in the presence of a sulfur source, such as sulfur, inorganic sulfides, polysulfides, and carbon disulfide. Preferred amine-based compounds are polyamine dispersants commonly used in engine oil compositions. Examples of such dispersants are succinimide and Mannich-type dispersants. References to these dispersants are provided in U.S. Pat. Nos. 4,259,194, 4,259,195, 4,265,773, 4,265,843, 4,727,387, 4,283,295, and 4,285,822.

In one embodiment, the molybdenum amine is a molybdenum-succinimide complex. Suitable molybdenum-succinimide complexes are described, for example, in U.S. Patent No. 8,076,275. These complexes are prepared by reacting an acidic molybdenum compound with an alkyl or alkenyl succinimide of a polyamine of structure (3) or (4):

wherein R is a C ₂₄ -C ₃₅₀ (e.g., C ₇₀ -C ₁₂₈ ) alkyl or alkenyl group, R′ is a straight or branched chain alkylene group having 2 to 3 carbon atoms, x is 1 to 11, and y is 1 to 10.
or a mixture thereof.

The molybdenum compounds used to prepare the molybdenum-succinimide complexes are acidic molybdenum compounds or salts of acidic molybdenum compounds. By "acidic" it is meant that the molybdenum compound is one that reacts with basic nitrogen compounds as measured by ASTM D664 or D2896. Generally, acidic molybdenum compounds are hexavalent. Representative examples of suitable molybdenum compounds include molybdenum trioxide, molybdic acid, ammonium molybdate, sodium molybdate, potassium molybdate _and other alkali metal molybdates, as well as other molybdenum salts such as hydrogen salts (e.g., sodium hydrogen molybdate), _MoOCl4 , _{MoO2Br2 , Mo2O3Cl6 ,} and the like.

Succinimides that can be used to prepare molybdenum-succinimide complexes are disclosed in many references and are well known in the art. Some basic succinimides and related materials encompassed by the term "succinimide" are taught in U.S. Pat. Nos. 3,172,892, 3,219,666, and 3,272,746. The term "succinimide" is understood in the art to include many of the amide, imide, and amidine species that can be further formed. However, the primary product is succinimide, and the term is generally accepted to mean the product of the reaction of an alkyl or alkenyl substituted succinic acid or anhydride with a nitrogen-containing compound. A preferred succinimide is one prepared by reacting a polyisobutenyl succinic anhydride having about 70 to 128 carbon atoms with a polyalkylene polyamine selected from triethylenetetramine, tetraethylenepentamine, and mixtures thereof.

In one embodiment, the molybdenum-containing compound is sulfur-free.

The molybdenum-succinimide complex may be post-treated with a sulfur source at a suitable pressure and a temperature not to exceed 120° C. to provide a sulfurized molybdenum-succinimide complex. The sulfurization step may be carried out for a period of about 0.5 to 5 hours (e.g., 0.5 to ₂ hours). Suitable sulfur sources include elemental sulfur, hydrogen sulfide, phosphorus pentasulfide, organic polysulfides of the formula R ₂ S _x , where R is hydrocarbyl (e.g., C ₁ -C 10 alkyl) and x is at least 3, C ₁ -C ₁₀ mercaptans, inorganic sulfides and polysulfides, thioacetamide, and thiourea.

The molybdenum-containing compound is used in an amount to provide the lubricating oil composition with 50 ppm to 1200 ppm, 50 ppm to 1000 ppm, 50 ppm to 800 ppm, 50 ppm to 600 ppm, 50 ppm to 400 ppm, or 50 ppm to 200 ppm of molybdenum.

In some embodiments, the lubricating oil composition is substantially free of molybdenum-containing compounds.

During use of the lubricating oil composition in an engine, the molybdenum-containing compound may promote the formation of a molybdenum-containing lubricating film on metal surfaces of the engine.

According to an exemplary embodiment, the lubricating oil composition comprises MoDTC in an amount of 0.6 wt % to 0.8 wt %, based on the total weight of the lubricating composition.

Corrosion Inhibitors Corrosion inhibitors protect lubricated metal surfaces from chemical attack by water or other contaminants. Suitable corrosion inhibitors include polyoxyalkylene polyols and their esters, polyoxyalkylene phenols, thiadiazoles, and anionic alkylsulfonic acids.

Pour Point Depressants Pour point depressants lower the minimum temperature at which a fluid will flow or can be poured. Suitable pour point depressants include C8-C18 dialkyl fumarate/vinyl acetate copolymers, polyalkyl methacrylates, and the like.

Foam Suppressors Foam suppressors retard the formation of stable foam. Examples of suitable foam suppressors include polysiloxanes, polyacrylates, and the like.

Process for Preparing the Lubricating Oil Composition The lubricating oil compositions disclosed herein may be prepared by any method known to one skilled in the art for making lubricants. The viscosity modifier and other additives may be added to the base oil individually or simultaneously. In some embodiments, the additives are added to the base oil individually in one or more additions, and the addition may be in any order. In other embodiments, the additives are added to the base oil simultaneously, optionally in the form of an additive concentrate. According to another embodiment, some of the additives are added individually and some are added in the form of an additive concentrate. In some embodiments, solubilization of the additives in the base oil may be aided by heating the mixture to a temperature of about 25°C to about 200°C, about 50°C to about 150°C, or about 75°C to about 125°C.

Any mixing or dispersing equipment known to those skilled in the art may be used to blend, mix or solubilize the raw materials used to form the lubricating oil composition. Blending, mixing or solubilization may be performed using a compounder, agitator, disperser, mixer (e.g., planetary mixer and double planetary mixer), homogenizer (e.g., Gaulin homogenizer and Rannie homogenizer), grinder (e.g., colloid mill, ball mill and sand mill), or any other mixing or dispersing equipment known in the art.

Uses of the Lubricating Oil Compositions The lubricating oil compositions disclosed herein may be suitable for use as motor oils (engine oils or crankcase oils) in spark-ignition internal combustion engines. The lubricating oil compositions are preferably used in engines or crankcases that require an SAE 0W-20, 0W-16, or 0W-12 viscosity grade. For example, the lubricating oil compositions may be used to lubricate engines that include valve train systems equipped with roller follower rocker arms.

The following examples of the present invention are provided to illustrate embodiments of the present invention and are not intended to limit the invention to the specific embodiments presented. All parts and percentages are by weight, unless indicated to the contrary. All numerical values are approximate. When numerical ranges are given, it should be understood that embodiments outside the specified ranges may still fall within the scope of the invention. Specific details provided in each example should not be construed as necessary features of the invention.

A baseline formulation for all of the inventive and comparative examples was prepared by blending the following ingredients, provided in weight percent, based on the total weight of the lubricating oil composition:
(a) 1% by weight of borated succinimide;
(b) 3% by weight ethylene carbonate (EC) treated succinimide;
(c) 0.34 wt. % of a second ZnDTP;
(d) 0.72 wt. % of a first ZnDTP;
(e) 0.5 wt. % LOB Ca sulfonate;
(f) 0.77 wt. % HOB Ca Salicylate;
(g) 0.5 wt. % MOB Ca Salicylate;
(h) 2 wt. % of an amine antioxidant;
(i) 0.004 wt. % of a foam suppressor; and (h) a diluent oil.

The weight percentages of ingredients (a)-(h) include any diluents and/or solvents that may be present and therefore are not on an active basis.

All inventive and comparative examples were made by first treating a baseline formulation in Group III base oil, Yubase 4+, with 0.7 wt. % molybdenum dithiocarbamate (MoDTC) to provide 700 ppm molybdenum, and then treating with the viscosity modifier(s) (comb PMA and/or OCP) from Tables 2 and 3 to obtain a lubricating oil composition having a viscosity rating of SAE 0W-20. The compositions of the inventive examples are shown in Table 2, and the comparative examples are shown in Table 3.

Fuel Economy Test in Toyota 2ZR-FE Motor Engine The lubricating oil compositions of Examples 1-9 of the present invention and Comparative Examples 1-4 were tested for their fuel economy performance in a gasoline motor engine test. The engine was a Toyota 2ZR-FE 1.8L with an in-line 4-cylinder configuration. A torque meter was positioned between the motor and crankshaft of the engine and the percent torque change was measured between the reference and candidate lubricating oil compositions. The percent torque change (%) was measured at oil temperatures of 60°C, 80°C and 100°C and engine speeds of 400 rpm, 550 rpm, 750 rpm, 1000 rpm, 1500 rpm and 2000 rpm. A lower (i.e., more negative) percent torque change reflects better fuel economy. The motor engine friction torque test configuration and its test conditions are further described in SAE Paper 2013-01-2606. Table 4 shows the average % torque change at oil temperatures of 60°C, 80°C and 100°C for the example compositions of the present invention, and Table 5 shows the average % torque change at oil temperatures of 60°C, 80°C and 100°C for the comparative compositions.

Claims (17)

1. A lubricating oil composition comprising:
a) a major amount of an oil of lubricating viscosity;
b) 0.4 wt % to 2.0 wt %, based on the total weight of the lubricating oil composition, of a non-dispersant comb polymethacrylate (PMA) having a weight average molecular weight (Mw) of 390,000 g/mol to 460,000 g/mol ; and c) an amount of 0.08 wt % to 0.4 wt %, based on the total weight of the lubricating oil composition, of a non-dispersant ethylene-based olefin copolymer having a weight average molecular weight (Mw) of 90,000 g/mol to 160,000 g/mol, wherein the lubricating oil composition has a kinematic viscosity at 100° C. of less than 9.3 mm ² /s. 2. The lubricating oil composition of claim 1, wherein the non-dispersant comb PMA has a Shear Stability Index (SSI) , measured according to ASTM D7109, of 0.3 to 0.8. 2. The lubricating oil composition of claim 1, wherein the non-dispersant ethylene-based olefin copolymer has a Shear Stability Index (SSI) , as measured in accordance with ASTM D7109, of 10 to 70. The non-dispersed ethylene-based olefin copolymer is
(i) having a total ethylene content of 45% to 60% by weight, based on the total weight of the non-dispersed ethylene-based olefin copolymer ; or
(ii) is an ethylene propylene copolymer;
The lubricating oil composition of claim 1. The lubricating oil composition of claim 1, wherein the non-dispersed comb PMA is present in an amount of 0.76 wt% to 1.33 wt% and the non-dispersed ethylene-based olefin copolymer is present in an amount of 0.08 to 0.4 wt%, based on the total weight of the lubricating oil composition. The lubricating oil composition of claim 1, wherein the non-dispersed comb PMA and the non-dispersed ethylene-based olefin copolymer are present in a total amount of 0.4 wt.% to 4 wt.%, based on the total weight of the lubricating oil composition. The lubricating oil composition of claim 1, wherein the oil of lubricating viscosity is an API Group III base oil. The lubricating oil composition of claim 1, wherein the composition further comprises a molybdenum compound. 9. The lubricating oil composition of claim 8 , wherein the molybdenum compound is molybdenum dithiocarbamate (MoDTC). The lubricating oil composition of claim 8 , wherein the molybdenum compound provides the lubricating oil composition with an amount of molybdenum in the range of 50 ppm to 1200 ppm. The lubricating oil composition of claim 1, wherein the lubricating oil composition has a viscosity grade of SAE 0W-20, 0W-16, or 0W-12. The lubricating oil composition of claim 1, wherein the lubricating oil composition has a 150°C high temperature high shear (HTHS) viscosity of 2.55 cP to less than 2.9 cP. The lubricating oil composition of claim 1, wherein the lubricating oil composition has a viscosity index of 200 to 240. 1. A method for reducing wear in an internal combustion engine, comprising:
lubricating said engine with a lubricating oil composition having a kinematic viscosity at 100° C. of less than 9.3 mm ² /s, said lubricating oil composition comprising:
a) a major amount of oil of lubricating viscosity;
b) 0.4 wt.% to 2.0 wt.%, based on the total weight of the lubricating oil composition, of a non-dispersant comb polymethacrylate (PMA) having a weight average molecular weight (Mw) of 390,000 g/mol to 460,000 g/mol ; and c) a non-dispersant ethylene-based olefin copolymer having a weight average molecular weight (Mw) of 90,000 g/mol to 160,000 g/mol in an amount of 0.08 wt.% to 0.4 wt.%, based on the total weight of the lubricating oil composition. 2. The lubricating oil composition of claim 1 ,
the non-dispersed comb polymethacrylate (PMA) is present in an amount of 0.4 wt. % to 1.9 wt. %, based on the total weight of the lubricating oil composition; and
The lubricating oil composition , wherein the non-dispersant ethylene-based olefin copolymer is present in an amount from 0.08 to 0.36 weight percent, based on the total weight of the lubricating oil composition. 15. A method of reducing wear in an internal combustion engine as claimed in claim 14 , comprising the steps of:
the non-dispersed comb polymethacrylate (PMA) is present in an amount of 0.4 wt. % to 1.9 wt. %, based on the total weight of the lubricating oil composition; and
The method wherein the non-dispersant ethylene-based olefin copolymer is present in an amount of from 0.08 to 0.36 weight percent, based on the total weight of the lubricating oil composition. 17. The method of claim 14 or 16 , wherein the engine comprises a roller follower rocker arm.