LUBRICATING COMPOSITION WITH ENHANCED FILTERABILITY
A lubricating oil composition that includes a highly paraffinic base oil, a controlled release friction modifier (CRFM) and an effective amount of detergent. The CRFM includes an ionic tetrahedral borate compound comprising a cation and a tetrahedral borate anion which includes a boron atom, the boron atom having two bidentate di-oxo ligands of C18 tartrimide. The CRFM is a high stabilizer CRFM. The detergent includes a mixed magnesium and calcium detergent system having a calcium to magnesium ratio of less than 2:1.
Latest ExxonMobil Research and Engineering Company Patents:
- High manganese steel pipe with step-out weld zone erosion-corrosion resistance and method of making the same
- Fuel cell module assembly and systems using same
- HYDROCARBON COMPOSITIONS USEFUL AS LUBRICANTS FOR IMPROVED OXIDATION STABILITY
- Glycol ether ester compounds of neo-alcohols useful in lubricating oil compositions and methods of making the same
- DIVIDING WALL COLUMN SEPARATOR WITH INTENSIFIED SEPARATIONS
This nonprovisional application claims priority to U.S. Provisional Application No. 62/535,547, which was filed on Jul. 21, 2017, and is herein incorporated by reference.
BACKGROUND OF THE INVENTION Field of the InventionThe present invention relates to lubricating compositions, in particular to a lubricating composition having a highly paraffinic basestock with improved filterability performance.
Description of the Background ArtLubricant compositions must provide crucial lubrication to engines, but these compositions must also provide additional benefits to the engines in which they are used. Such additional benefits include fuel economy, oxidation stability of the composition over time, control of deposit formation on internal engine surfaces and maintenance of the filterability of the composition. In addition, lubricant compositions must be formulated to meet stringent government testing standards before it may be used as a motor oil. Because of all of these requirements, formulating a lubricant composition that meets these requirements is a challenging endeavor.
Various additives are included in a lubricant composition to achieve the above benefits. Improving any of these benefits while maintaining the others is challenging because a particular additive that may improve one benefit will often negatively affect at least one of the other required benefits of a lubricant composition. In view of the chemical interactions both among the additives and between the additives and the base stock used, developing a formulation for a lubricant composition that provides the above benefits is a difficult and complex task.
Friction modifiers, which are among the additives used in lubricant compositions, are used to improve the composition's ability to reduce friction. Among the friction modifiers that can be used in a lubricant composition are borated friction modifiers. Documents disclosing conventional borated friction modifiers include U.S. Pat. No. 4,522,734A disclosing borated long-chain (C10-20) epoxides, EP 0036708A1 disclosing borated fatty acid esters of glycerol, U.S. Pat. No. 5,759,965A disclosing borated alkoxylated fatty amines, US 2009/0005276A1 disclosing borated polyalkene succinimides, WO 2007005423A2 disclosing a reaction product of C8-20 fatty acids with dialkanolamines and boric acid, CA 1336830C disclosing borated hydroxyl ether amines and U.S. Pat. No. 4,522,629A disclosing borated phosphonates. While these documents disclose borated friction modifiers, there still exists a need for lubricant compositions including borated friction modifiers, which better facilitate improvements in the necessary benefits described above.
Known lubricant compositions for use as motor oils are described in documents such as U.S. Pat. No. 9,193,934B2, U.S. Pat. No. 9,163,196B2, US 2014/0045734A1, U.S. Pat. No. 9,175,241B2, US 2012/0283158A1 and US 2014/0107000A1. These documents describe compositions that have been formulated for clarity and stability; however, they do not describe compositions that have been formulated to provide enhanced filterability.
Further, in the case of some lubricant compositions, the additives used in lubricant compositions may participate in the formation of needle crystals which may cause clogging of oil filters. The influences of various conditions and combinations of lubricant additives have been studied. It has been shown that needle crystals form when the lubricant composition includes a magnesium-based detergent. When a magnesium-based detergent comes into contact with water and carbonic acid gas the needle crystals form.
Furthermore, a major source of energy loss within internal combustion engines is the friction that occurs between lubricated parts that are in sliding contact with each-other during the combustion cycle. Critical engine parts that often contribute to these losses include the piston ring on liner contact, cam lobe contacts and journal bearings. Friction modifiers are capable of changing the surface properties of the materials commonly used in engines. Although both inorganic (metal ash-containing) and organic (ash-free) friction modifiers exist, organic friction modifiers are preferred as they do not contribute to ash in the exhaust stream. It is well known that friction modifiers (especially organic friction modifiers) are quickly destroyed in high temperatures and oxidative environments such as those that are present in a combustion engine.
It is therefore advantageous to develop formulations with controlled release friction modifiers (CRFM) that allow for low friction benefits to be retained hours, days, weeks and even months after the lubricant has been added to the engine. The use of a CRFM can enable a vehicle to have better aged-oil fuel economy than fresh oil fuel economy. This is important for minimizing the carbon intensity of the lubricant over the entire lubricant drain interval.
However, CRFM often are accompanied by solubility limitations of the friction modifier, poor deposit performance and poor filterability of the finished lubricant. Until now, this has prohibited the development of high-performing controlled release friction modified formulations
Moreover, the highest performance lubricants usually entail the use of base oils that are highly paraffinic. Such base oils would include API Group IV polyalphaolefins (PAO), API Group III's such as gas-to-liquids (GTL) base oils and potentially even highly saturated Group II base oils. Such oils are highly non-polar and as a result have a limited amount of solubility for polar additives.
Most of the fuel economy additives are highly polar and as such are challenged to remain soluble in the lube oil. With limited solubility and availability of the additives, improvements in fuel economy are similarly limited.
Accordingly, there exists a need for improved lubricant compositions capable of providing enhanced filterability while meeting all of the requirements for the use of a lubricant composition in an engine.
SUMMARY OF THE INVENTIONIn view of the forgoing of other exemplary problems, drawbacks and disadvantages of the conventional methods and compositions, an exemplary feature of the present invention is to provide a lubricating composition containing a CRFM in a highly paraffinic basestock while maintaining strong filterability performance.
Exemplary embodiments of the invention are directed to a lubricating oil composition that includes a highly paraffinic base oil. In an embodiment of the invention, the base oil is a blend of a Group III base oil and a polyalphaolefin base oil.
The composition further includes a CRFM and an effective amount of at least one additive. According to an embodiment of the invention, the CRFM is an ashless CRFM including a dispersant-stabilized, borated CRFM comprising an ionic tetrahedral borate compound including a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C18-tartrimide, a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, a second dispersant comprising an ammonium substituted polyisobutenyl succinimide compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500, wherein one or more of the first dispersant and the second dispersant are in cationic form (referred to herein as a “dispersant-stabilized borated CRFM”)
Further, the lubricating oil composition includes an effective amount of a detergent that provides for improved levels of filterability as compared to the levels achieved when the lubricating oil composition does not include the CRFM. Specifically, in accordance with certain exemplary aspects of the invention, the detergent is a mixed calcium and magnesium detergent system, preferably with a ratio of calcium to magnesium of less than 2.
DETAILED DESCRIPTIONAspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the scope of the invention. Additionally, well-known elements of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiments of the invention” does not require that all embodiments of the invention include the discussed feature, advantage or mode of operation.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The present invention is directed to a lubricating oil composition that includes a base oil. The composition further includes a CRFM and an effective amount of at least one additive. The effective amount of an additive is the sufficient amount to provide for improved levels of filterability as compares to the levels achieved when the lubricating oil composition does not include the CRFM. The additive may be selected from the group of inorganic friction modifiers, dispersants, detergents, viscosity modifiers and cleanliness boosters.
CRFMs are highly advantageous due to their ability to reduce friction over long oil drain intervals. Friction reduction is important in improving fuel economy. However, it is well known that CRFMs often pose filterability issues. In order to be efficacious, friction modifiers generally have limited oil solubility in order to provide a high affinity for metallic surfaces in the engine. This low solubility poses filtration problems, particularly when an oil is at low temperatures or mixed with water and other contaminants. In controlled release friction modifiers, friction modifier molecules are used above their solubility limit, creating even greater potential for filterability issues.
Acceptable filterability is particularly challenging to achieve in highly paraffinic basestocks such as those used here. The present disclosure shows a surprising improvement of the compatibility of CRFMs by using a combination of high dispersant stabilizer and magnesium based detergents. This is particularly surprising as it is well known in the industry that magnesium based detergents are detrimental to filterability, and therefore would not be anticipated as a solution to a filterability issue.
In order to measure filterability of a composition the standardized ASTM D6795 is generally used. ASTM D6795 standard method measures the effects on filterability of engine oils after treatment with water and dry ice and a short (30 min) heating time. This standardized test is part of ILSAC (International Lubricants Specification Advisory Committee) and the American Petroleum Institute (API) S engine oil specifications.
The key rating of the ASTM D6795 involves the change in flow rate of a lubricating oil as it is passed through a filter. A lubricant that does not flow through the filter is reported as “clogged.” This is a failing result.
Controlled Release Friction Modifier (CRFM)
In accordance with certain exemplary aspects of the present invention, the lubricating composition includes a CRFM. The CRFM is a dispersant-stabilized, borated CRFM comprising an ionic tetrahedral borate compound including a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C18-tartrimide, a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, a second dispersant comprising an ammonium substituted polyisobutenyl succinimide compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500, wherein one or more of the first dispersant and the second dispersant are in cationic form. As used herein, the term “conventional ammonium substituted polyisobutenyl succinimide,” refers to an ammonium substituted polyisobutenyl succinimide made by the chorine-assisted process. Such a process is well known in the art. One such process includes grafting maleic anhydride to polyisobutenyl in the presence of chorine followed by reaction with a poly(amine) to form the imide.
In accordance with another aspect of the exemplary embodiment, the CRFM includes a reaction product of a trivalent boron compound, such as boric acid, with a tartaric acid and a linear C18 amine under conditions suitable to form an ionic tetrahedral borate compound. The ionic tetrahedral borate compound is combined with a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500, wherein one or more of the first dispersant and the second dispersant are converted to a cationic form.
The above described ionic tetrahedral borate compound can serve as a friction modifier, in a lubricating composition.
In one embodiment, the structure of the tetrahedral borate ion of the tetrahedral borate compound may be represented by the structure shown in Formula I:
where R3, R4 form a 5 membered nitrogen-containing heterocyclic ring substituted with a linear C18 group.
The cations in Formula I include one or more of a first ammonium cation including a conventional polyisobutylene succinimide with number average molecular weight of the polyisobutylene substituent of at least 750, and can be up to 2500, and a second ammonium cation is including a polyisobutylene succinimide with number average molecular weight of the polyisobutylene substituent of at least 750, and can be up to 2,500, having an N:CO ratio of 1.8. Such succinimides can be formed, for example, from high vinylidene polyisobutylene and maleic anhydride.
Total base number (TBN) is the quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide (meq KOH), that is required to neutralize all basic constituents present in 1 gram of a sample of the lubricating oil. The TBN may be determined according to ASTM Standard D2896-11, “Standard Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration” (2011), ASTM International, West Conshohocken, Pa., 2003 DOI: 10.1520/D2896-11 (hereinafter, “D2896”).
Specific examples of such amine and ammonium compounds include polyisobutylene derived succinimide dispersants wherein the polyisobutylene may be 1000 Mn and the succinimide amine is a polyethylenepolyamine (Mn 1700 g/mol).
A useful molar ratio of the tartaric acid, the trivalent boron compound, and counter ion charge used in forming the combination and/or reaction product is 2:1:1.
In an embodiment the linear C18 tartrimide compound is derived from tartaric acid. The tartaric acid used for preparing the tartrates of the invention can be commercially available, and it is likely to exist in one or more isomeric forms such as d-tartaric acid, I-tartaric acid, d,l-tartaric acid, or mesotartaric acid, often depending on the source (natural) or method of synthesis (from maleic acid). For example a racemic mixture of d-tartaric acid and I-tartaric acid is obtained from a catalyzed oxidation of maleic acid with hydrogen peroxide (with tungstic acid catalyst). These derivatives can also be prepared from functional equivalents to the diacid readily apparent to those skilled in the art, such as esters, acid chlorides, or anhydrides. The suitable amines will have the formula RNH2 wherein R represents a hydrocarbyl group, typically of 6 to 26. Exemplary primary amines include n-hexylamine, n-octylamine (caprylylamine), n-decylamine, n-dodecylamine (laurylamine), n-tetradecylamine (myristylamine), n-pentadecylamine, n-hexadecylamine (palmitylamine), n-octadecylamine (stearylamine), and oleylamine.
Suitable trivalent boron compounds include borate esters of the general form B(OR)3 where each R is 2-propylheptyl. In an embodiment, the counter ion is a basic component, such as a dispersant. The source of the counter ion may be an aminic dispersant. For solubilization in mineral oil, particular examples include polyisobutenyl succinimide and polyamine dispersants with a N:CO ratio of 1.8 and with a TBN of at least 50.
In an embodiment, the ionic borate compound is the reaction product of a tartrimide, a borate ester, and at least one basic component, such as two dispersants, to form a “boro-tartrimide” friction modifier. The ionic boron compound described herein is used to improve friction.
A problem with conventional friction modifiers, as noted above, is that the friction modifier is not sufficiently soluble, which leads to an insufficient amount of friction modifier being available during consumption of the lubricating oil and sludge (i.e., deposits) may form. The CRFM in accordance with certain exemplary embodiments of the present invention maintains sufficient friction modifier at the surface to provide lower friction lubricating oils while improving overall fuel economy. That is, the CRFM described herein raises the amount of friction modifier by using a tetra-valent boron chemistry to complex the friction modifier. This results in a much larger amount of friction modifier in the lubricating oil with resulting improvements to fuel economy. Also, it is know that ash can damage the particulate filter of an engine. High ash compositions (i.e., compositions with high amounts of detergent) are not desirable. The present CRFM is preferably a low ash CRFM.
In accordance with certain exemplary embodiments of the present invention, the CRFM is an ashless, dispersant-stabilized, borated friction modifier. Additionally, the lubricating oil composition may include an amount of CRFM in a range of 2 wt % to 8 wt %, and more preferably in a range of 3 wt % to 5 wt %, of the total lubricating oil composition. In certain specific preferred embodiments, the CRFM is provided in an amount of 3.96 wt %.
Further, in an embodiment, the CRFM comprises an amount of nitrogen contributed from the tartrimide from about 35 to about 55 weight percent, based on the total weight percent of the CRFM. Nitrogen from the tartrimide is preferably present in the CRFM in amount from about 40 to about 50 weight percent, based on the total weight percent of the CRFM. Even more preferably, nitrogen from the tartrimide is present in the CRFM in an amount from about 43 to about 47 weight percent, based on the total weight percent of the CRFM.
Base Oil Stocks
A wide range of lubricating base oils is known in the art. Lubricating base oils are both natural oils and synthetic oils. Natural and synthetic oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as feed stock.
Groups I, II, III, IV and V are broad categories of base oil stocks developed and defined by the American Petroleum Institute (API Publication 1509) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between about 80 to 120 and contain greater than about 0.03% sulfur and less than about 90% saturates. Group II base stocks have a viscosity index of between about 80 to 120, and contain less than or equal to about 0.03% sulfur and greater than or equal to about 90% saturates. Group III stocks have a viscosity index greater than or equal to 120 and contain less than or equal to 0.03% sulfur and greater than 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.
Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source; for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification; for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.
Group II and/or Group III hydroprocessed or hydrocracked base stocks, as well as synthetic oils such as polyalphaolefins, alkyl aromatics and synthetic esters, i.e. Group IV and Group V oils are also well known base stock oils.
Synthetic oils include hydrocarbon oil such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks, the Group IV API base stocks, are a commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C8, C10, C12, C14 olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073, which are incorporated herein by reference in their entirety. Group IV oils, that is, the PAO base stocks have viscosity indices preferably greater than 130, more preferably greater than 135, still more preferably greater than 140.
The hydrocarbyl aromatics can be used as base oil or base oil component and can be any hydrocarbyl molecule that contains at least about 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and the like. The aromatics can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from about C6 up to about C60 with a range of about C8 to about C40 often being preferred. A mixture of hydrocarbyl groups is often preferred. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least about 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 3 cSt to about 50 cSt are preferred, with viscosities of approximately 3.4 cSt to about 20 cSt often being more preferred for the hydrocarbyl aromatic component. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be about 2% to about 25%, preferably about 4% to about 20%, and more preferably about 4% to about 15%, depending on the application.
Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.
Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols such as the neopentyl polyols; e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol with alkanoic acids containing at least about 4 carbon atoms, preferably C5 to C30 acids such as saturated straight chain fatty acids including caprylic acid, capric acids, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.
Non-conventional or unconventional base stocks and/or base oils include one or a mixture of base stock(s) and/or base oil(s) derived from: (1) one or more Gas-to-Liquids (GTL) materials, as well as (2) hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oils derived from synthetic wax, natural wax or waxy feeds, mineral and/or non-mineral oil waxy feed stocks such as gas oils, slack waxes (derived from the solvent dewaxing of natural oils, mineral oils or synthetic oils; e.g., Fischer-Tropsch feed stocks), natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, foots oil or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials recovered from coal liquefaction or shale oil, linear or branched hydrocarbyl compounds with carbon number of about 20 or greater, preferably about 30 or greater and mixtures of such base stocks and/or base oils.
GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.
GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from about 2 mm2/s to about 50 mm2/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to about −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of about 80 to about 140 or greater (ASTM D2270).
In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than about 10 ppm, and more typically less than about 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this materially especially suitable for the formulation of low SAP products.
The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.
The GTL material, from which the GTL base stock and/or base oil is/are derived, is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).
Base oils for use in the formulated lubricating oils useful in the present invention are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, Group V and Group VI oils and mixtures thereof, preferably API Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group VI base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluent/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.
In an embodiment, the lubricating oil composition includes the base oil comprising the Group III oil from about 10 to about 90 weight percent, based on the total weight percent of the composition. The Group III oil is preferably present in the base oil in an amount from about 30 to about 70 weight percent, based on the total weight percent of the composition. Even more preferably, the Group III oil is present in an amount from about 40 to 64.21 weight percent, based on the total weight percent of the composition.
Additionally, the base oil also may contain polyalphaolefin oil basestocks (the Group IV oil) up to about 60 weight percent, based on the total weight percent of the composition. The Group IV oil is preferably present in an amount from about 5 to about 50 weight percent, based on the total weight percent of the composition. Even more preferably, the Group IV oil is present in an amount from about 10 to about 31.99 weight percent, based on the total weight percent of the composition.
Even further, the base oil may also comprise a Group V oil chosen from ester and alkylated naphthalene in an amount up to about 15 weight percent, based on the total weight percent of the composition. The Group V oil is preferably present in an amount up to about 10 weight percent, based on the total weight percent of the composition. Even more preferably, the Group V oil is present in an amount about 5 weight percent, based on the total weight percent of the composition.
Additives
The lubricating oil composition according to the present disclosure additionally contains one or more of commonly used lubricating oil performance additives including but not limited to detergents, antiwear additives, dispersants, viscosity modifiers, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N J (1973); see also U.S. Pat. No. 7,704,930, the disclosure of which is incorporated herein in its entirety. These additives are commonly delivered with varying amounts of diluent oil that may range from 5 weight percent to 50 weight percent.
The types and quantities of performance additives used in combination with the instant disclosure in the lubricating oil composition are not limited by the examples shown herein as illustrations.
Detergents
Illustrative detergents useful in this disclosure include, for example, alkali metal detergents, alkaline earth metal detergents, or mixtures of one or more alkali metal detergents and one or more alkaline earth metal detergents. A typical detergent is an anionic material that contains 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 derived from an organic acid such as a sulfur acid, carboxylic acid (e.g., salicylic acid), phosphorous acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal. The detergent can be overbased as described herein.
The detergent is preferably a metal salt of an organic or inorganic acid, a metal salt of a phenol, or mixtures thereof. The metal is preferably selected from an alkali metal, an alkaline earth metal, and mixtures thereof. The organic or inorganic acid is selected from an aliphatic organic or inorganic acid, a cycloaliphatic organic or inorganic acid, an aromatic organic or inorganic acid, and mixtures thereof.
The metal is selected from, for example, an alkali metal, an alkaline earth metal, and mixtures thereof. More preferably, the metal is selected from calcium (Ca), magnesium (Mg), and mixtures thereof.
The organic acid or inorganic acid is preferably selected from a sulfur acid, a carboxylic acid, a phosphorus acid, and mixtures thereof.
Preferably, the metal salt of an organic or inorganic acid or the metal salt of a phenol comprises calcium phenate, calcium sulfonate, calcium salicylate, magnesium phenate, magnesium sulfonate, magnesium salicylate, an overbased detergent, and mixtures thereof.
Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Useful detergents can be neutral, mildly overbased, or highly overbased. These detergents can be used in mixtures of neutral, overbased, highly overbased calcium salicylate, sulfonates, phenates and/or magnesium salicylate, sulfonates, phenates. The TBN ranges can vary from low, medium to high TBN products, including as low as 0 to as high as 600. Mixtures of low, medium, high TBN can be used, along with mixtures of calcium and magnesium metal based detergents, and including sulfonates, phenates, salicylates, and carboxylates. A detergent mixture with a metal ratio of 1, in conjunction of a detergent with a metal ratio of 2, and as high as a detergent with a metal ratio of 5, can be used. Borated detergents can also be used.
Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)2, BaO, Ba(OH)2, MgO, Mg(OH)2, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C1-C30 alkyl groups, preferably, C4-C20 or mixtures thereof. Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched and can be used from 0.5 to 6 weight percent. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.
Metal salts of carboxylic acids are preferred detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula
where R is an alkyl group having 1 to about 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C11, preferably C13 or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, or barium. More preferably, M is calcium.
Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.
Alkaline earth metal phosphates can also be used as detergents.
Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See U.S. Pat. No. 6,034,039.
Preferred detergents include calcium sulfonates, magnesium sulfonates, calcium salicylates, magnesium salicylates, calcium phenates, magnesium phenates, and other related components (including borated detergents), and mixtures thereof. Preferred mixtures of detergents include magnesium sulfonate and calcium salicylate, magnesium sulfonate and calcium sulfonate, magnesium sulfonate and calcium phenate, calcium phenate and calcium salicylate, calcium phenate and calcium sulfonate, calcium phenate and magnesium salicylate, calcium phenate and magnesium phenate. Overbased detergents are also preferred.
Even more preferred detergents include overbased calcium salicylate detergent, low base calcium salicylate detergent, neutral calcium sulfonate detergent, overbased calcium sulfonate detergent and overbased magnesium sulfonate detergent.
The detergent concentration in the lubricating oil composition of this disclosure can range from about 1 to about 10 weight percent, preferably about 1 to 5 weight percent, and more preferably from about 2.03 weight percent to about 3.83 weight percent, based on the total weight of the lubricating oil composition.
More specifically, the lubricating oil composition of this disclosure preferably contains about 3.0 weight percent of calcium salicylate detergent and about 0.83 percent of magnesium sulfonate detergent, based on the total weight of the composition.
Alternatively, the lubricating oil composition of this disclosure may contain 1.15 weight percent of calcium sulfonate detergent and about 0.88 weight percent of magnesium sulfonate detergent.
Further, the detergent of the lubricating oil composition of this disclosure can have calcium (Ca) to magnesium (Mg) ration from about 0.25 to about 10, preferably about 0.5 to 3, and more preferably from about 1.2-1.58.
As used herein, the detergent concentrations are given on an “as delivered” basis. Typically, the active detergent is delivered with a process oil. The “as delivered” detergent typically contains from about 20 weight percent to about 100 weight percent, or from about 40 weight percent to about 60 weight percent, of active detergent in the “as delivered” detergent product.
Dispersants
During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants used in the formulation of the lubricating oil may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.
Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.
A particularly useful class of dispersants are the (poly)alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,2145,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.
Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.
Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from about 1:1 to about 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and U.S. Pat. Nos. 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.
Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful dispersant.
Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.
The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500 or more. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated dispersants, to form borated dispersants generally having from about 0.1 to about 5 moles of boron per mole of dispersant reaction product.
Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.
Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HNR2 group-containing reactants.
Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.
Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from about 500 to about 5000, or from about 1000 to about 3000, or about 1000 to about 2000, or a mixture of such hydrocarbylene groups, often with high terminal vinylic groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components.
Polymethacrylate or polyacrylate derivatives are another class of dispersants. These dispersants are typically prepared by reacting a nitrogen containing monomer and a methacrylic or acrylic acid esters containing 5-25 carbon atoms in the ester group. Representative examples are shown in U.S. Pat. Nos. 2,100,993, and 6,323,164. Polymethacrylate and polyacrylate dispersants are normally used as multifunctional viscosity modifiers. The lower molecular weight versions can be used as lubricant dispersants or fuel detergents.
Illustrative preferred dispersants useful in this disclosure include those derived from polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester, which dispersant has a polyalkenyl moiety with a number average molecular weight of at least 900 and from greater than 1.3 to 1.7, preferably from greater than 1.3 to 1.6, most preferably from greater than 1.3 to 1.5, functional groups (mono- or dicarboxylic acid producing moieties) per polyalkenyl moiety (a medium functionality dispersant). Functionality (F) can be determined according to the following formula:
F=(SAP×Mn)/((112,200×A.I.)−(SAP×98))
wherein SAP is the saponification number (i.e., the number of milligrams of KOH consumed in the complete neutralization of the acid groups in one gram of the succinic-containing reaction product, as determined according to ASTM D94); Mn is the number average molecular weight of the starting olefin polymer; and A.I. is the percent active ingredient of the succinic-containing reaction product (the remainder being unreacted olefin polymer, succinic anhydride and diluent).
The polyalkenyl moiety of the dispersant may have a number average molecular weight of at least 900, suitably at least 1500, preferably between 1800 and 3000, such as between 2000 and 2800, more preferably from about 2100 to 2500, and most preferably from about 2200 to about 2400. The molecular weight of a dispersant is generally expressed in terms of the molecular weight of the polyalkenyl moiety. This is because the precise molecular weight range of the dispersant depends on numerous parameters including the type of polymer used to derive the dispersant, the number of functional groups, and the type of nucleophilic group employed.
Polymer molecular weight, specifically Mn, can be determined by various known techniques. One convenient method is gel permeation chromatography (GPC), which additionally provides molecular weight distribution information (see W. W. Yau, J. J. Kirkland and D. D. Bly, “Modern Size Exclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979). Another useful method for determining molecular weight, particularly for lower molecular weight polymers, is vapor pressure osmometry (e.g., ASTM D3592).
The polyalkenyl moiety in a dispersant preferably has a narrow molecular weight distribution (MWD), also referred to as polydispersity, as determined by the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn). Polymers having a Mw/Mn of less than 2.2, preferably less than 2.0, are most desirable. Suitable polymers have a polydispersity of from about 1.5 to 2.1, preferably from about 1.6 to about 1.8.
Suitable polyalkenes employed in the formation of the dispersants include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at least one C3 to C2 alpha-olefin having the formula H2C═CHR1 wherein R1 is a straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and wherein the polymer contains carbon-to-carbon unsaturation, and a high degree of terminal ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of ethylene and at least one alpha-olefin of the above formula, wherein R1 is alkyl of from 1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8 carbon atoms, and more preferably still of from 1 to 2 carbon atoms.
Another useful class of polymers is polymers prepared by cationic polymerization of monomers such as isobutene and styrene. Common polymers from this class include polyisobutenes obtained by polymerization of a C4 refinery stream having a butene content of 35 to 75% by wt., and an isobutene content of 30 to 60% by wt. A preferred source of monomer for making poly-n-butenes is petroleum feedstreams such as Raffinate II. These feedstocks are disclosed in the art such as in U.S. Pat. No. 4,952,739. A preferred embodiment utilizes polyisobutylene prepared from a pure isobutylene stream or a Raffinate I stream to prepare reactive isobutylene polymers with terminal vinylidene olefins. Polyisobutene polymers that may be employed are generally based on a polymer chain of from 1500 to 3000.
The dispersant(s) are preferably non-polymeric (e.g., mono- or bis-succinimides). Such dispersants can be prepared by conventional processes such as disclosed in U.S. Patent Application Publication No. 2008/0020950, the disclosure of which is incorporated herein by reference.
The dispersant(s) can be borated by conventional means, as generally disclosed in U.S. Pat. Nos. 3,087,936, 3,254,025 and 5,430,105.
Such dispersants may be used in accordance with the present disclosure in an amount of about 1 to 15 weight percent, preferably about 2 to 12 weight percent, or more preferably 5.4 to 9.8 weight percent, based on the total weight of the composition. These dispersants may contain both neutral and basic nitrogen, and mixtures of both. Dispersants can be end-capped by borates and/or cyclic carbonates.
More specifically, in accordance with the present disclosure, Borated Succinimide Dispersant B may be used in an amount about 0.74 weight percent, in combination with Succinimide Dispersant B in an amount about 3.7 weight percent, based on the total weight of the composition.
Ethylene Capped Succinimide Dispersant may be present in an amount about 7.35 weight percent, based on the total weight of the composition.
Succinimide Dispersant B may be present in an amount about 5.4 weight percent, based on the total weight of the composition.
Borated polyaolefin amide alkeneamine dispersant may be present in an amount about 8.75 weight percent, based on the total weight of the composition.
Succinimide Dispersant A may be present in an amount about 6.13 weight percent, based on the total weight of the composition.
Viscosity Modifiers
Viscosity modifiers (also known as viscosity index improvers (VI improvers), and viscosity improvers) can be included in the lubricant compositions of this disclosure.
Viscosity modifiers provide lubricants with high and low temperature operability. These additives impart shear stability at elevated temperatures and acceptable viscosity at low temperatures.
Suitable viscosity modifiers include high molecular weight hydrocarbons, polyesters and viscosity modifier dispersants that function as both a viscosity modifier and a dispersant. Typical molecular weights of these polymers are between about 10,000 to 1,500,000, more typically about 20,000 to 1,200,000, and even more typically between about 50,000 and 1,000,000.
Examples of suitable viscosity modifiers are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity modifier. Another suitable viscosity modifier is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity modifiers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.
Olefin copolymers are commercially available from Chevron Oronite Company LLC under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”); from Afton Chemical Corporation under the trade designation “HiTEC®” (such as “HiTEC® 58506”; and from The Lubrizol Corporation under the trade designation “Lubrizol® 7067C”. Hydrogenated polyisoprene star polymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV200” and “SV600”. Hydrogenated diene-styrene block copolymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV 150”.
The polymethacrylate or polyacrylate polymers can be linear polymers which are available from Evnoik Industries under the trade designation “Viscoplex®” (e.g., Viscoplex 6-954) or star polymers which are available from Lubrizol Corporation under the trade designation Asteric™ (e.g., Lubrizol 87708 and Lubrizol 87725).
Illustrative vinyl aromatic-containing polymers useful in this disclosure may be derived predominantly from vinyl aromatic hydrocarbon monomer. Illustrative vinyl aromatic-containing copolymers useful in this disclosure may be represented by the following general formula:
A-B
wherein A is a polymeric block derived predominantly from vinyl aromatic hydrocarbon monomer, and B is a polymeric block derived predominantly from conjugated diene monomer.
In certain preferred embodiments of the present invention, the viscosity modifier is a hydrogenated star polymer. In an embodiment of this disclosure, the viscosity modifiers may be used in an amount from about 1 to about 15 weight percent, preferably in an amount from about 1 to about 8 weight percent weight percent, and more preferably in an amount from about 1.8 to about 6.4 weight percent, based on the total weight of the composition. Viscosity modifiers are typically added as concentrates, in large amounts of diluent oil.
Antioxidants
Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197, for example.
Useful antioxidants include hindered phenols. These phenolic antioxidants may be ashless (metal-free) phenolic compounds or neutral or basic metal salts of certain phenolic compounds. Typical phenolic antioxidant compounds are the hindered phenolics which are the ones which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic antioxidants include the hindered phenols substituted with C6+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful hindered mono-phenolic antioxidants may include for example hindered 2,6-di-alkyl-phenolic proprionic ester derivatives. Bis-phenolic antioxidants may also be advantageously used in combination with the instant disclosure. Examples of ortho-coupled phenols include: 2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol); and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols include for example 4,4′-bis(2,6-di-t-butyl phenol) and 4,4′-methylene-bis(2,6-di-t-butyl phenol).
Effective amounts of one or more catalytic antioxidants may also be used. The catalytic antioxidants comprise an effective amount of a) one or more oil soluble polymetal organic compounds; and, effective amounts of b) one or more substituted N,N′-diaryl-o-phenylenediamine compounds or c) one or more hindered phenol compounds; or a combination of both b) and c). Catalytic antioxidants are more fully described in U.S. Pat. No. 8,048,833, herein incorporated by reference in its entirety.
Non-phenolic oxidation inhibitors which may be used include aromatic amine antioxidants and these may be used either as such or in combination with phenolics. Typical examples of non-phenolic antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R8R9R10N where R8 is an aliphatic, aromatic or substituted aromatic group, R9 is an aromatic or a substituted aromatic group, and R10 is H, alkyl, aryl or R11S(O)XR12 where R11 is an alkylene, alkenylene, or aralkylene group, R12 is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R8 may contain from 1 to about 20 carbon atoms, and preferably contains from about 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R8 and R9 are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R8 and R9 may be joined together with other groups such as S.
Typical aromatic amines antioxidants have alkyl substituent groups of at least about 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than about 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Polymeric amine antioxidants can also be used. Particular examples of aromatic amine antioxidants useful in the present disclosure include: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.
Sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof also are useful antioxidants.
Preferred antioxidants include hindered phenols, arylamines. These antioxidants may be used individually by type or in combination with one another.
Pour Point Depressants (PPDs)
Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present disclosure if desired. These pour point depressant may be added to lubricating compositions of the present disclosure to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pour point depressants and/or the preparation thereof.
Antifoam Agents
Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers.
Additional Friction Modifiers
A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure.
Illustrative additional friction modifiers may include, for example, organometallic compounds or materials, or mixtures thereof. Illustrative organometallic friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, molybdenum amine, molybdenum diamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates, and the like, and mixtures thereof. Similar tungsten based compounds may be preferable.
Other illustrative friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, alkoxylated fatty acid esters, alkanolamides, polyol fatty acid esters, borated glycerol fatty acid esters, fatty alcohol ethers, and mixtures thereof.
Illustrative alkoxylated fatty acid esters include, for example, polyoxyethylene stearate, fatty acid polyglycol ester, and the like. These can include polyoxypropylene stearate, polyoxybutylene stearate, polyoxyethylene isosterate, polyoxypropylene isostearate, polyoxyethylene palmitate, and the like.
Illustrative alkanolamides include, for example, lauric acid diethylalkanolamide, palmic acid diethylalkanolamide, and the like. These can include oleic acid diethyalkanolamide, stearic acid diethylalkanolamide, oleic acid diethylalkanolamide, polyethoxylated hydrocarbylamides, polypropoxylated hydrocarbylamides, and the like.
Illustrative polyol fatty acid esters include, for example, glycerol mono-oleate, saturated mono-, di-, and tri-glyceride esters, glycerol mono-stearate, and the like. These can include polyol esters, hydroxyl-containing polyol esters, and the like.
Illustrative borated glycerol fatty acid esters include, for example, borated glycerol mono-oleate, borated saturated mono-, di-, and tri-glyceride esters, borated glycerol mono-sterate, and the like. In addition to glycerol polyols, these can include trimethylolpropane, pentaerythritol, sorbitan, and the like. These esters can be polyol monocarboxylate esters, polyol dicarboxylate esters, and on occasion polyoltricarboxylate esters. Preferred can be the glycerol mono-oleates, glycerol dioleates, glycerol trioleates, glycerol monostearates, glycerol distearates, and glycerol tristearates and the corresponding glycerol monopalmitates, glycerol dipalmitates, and glycerol tripalmitates, and the respective isostearates, linoleates, and the like. On occasion the glycerol esters can be preferred as well as mixtures containing any of these. Ethoxylated, propoxylated, butoxylated fatty acid esters of polyols, especially using glycerol as underlying polyol can be preferred.
Illustrative fatty alcohol ethers include, for example, stearyl ether, myristyl ether, and the like. Alcohols, including those that have carbon numbers from C3 to C50, can be ethoxylated, propoxylated, or butoxylated to form the corresponding fatty alkyl ethers. The underlying alcohol portion can preferably be stearyl, myristyl, C11-C13 hydrocarbon, oleyl, isosteryl, and the like.
The lubricating oils of this disclosure exhibit desired properties, e.g., wear control, in the presence or absence of a friction modifier.
Antiwear Additives
Illustrative antiwear additives useful in this disclosure include, for example, metal salts of a carboxylic acid. The metal is selected from a transition metal and mixtures thereof. The carboxylic acid is selected from an aliphatic carboxylic acid, a cycloaliphatic carboxylic acid, an aromatic carboxylic acid, and mixtures thereof.
The metal is preferably selected from a Group 10, 11 and 12 metal, and mixtures thereof. The carboxylic acid is preferably an aliphatic, saturated, unbranched carboxylic acid having from about 8 to about 26 carbon atoms, and mixtures thereof.
The metal is preferably selected from nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadium (Cd), mercury (Hg), and mixtures thereof.
The carboxylic acid is preferably selected from caprylic acid (C8), pelargonic acid (C9), capric acid (C10), undecylic acid (C11), lauric acid (C12), tridecylic acid (C13), myristic acid (C14), pentadecylic acid (C15), palmitic acid (C16), margaric acid (C17), stearic acid (C18), nonadecylic acid (C19), arachidic acid (C20), heneicosylic acid (C21), behenic acid (C22), tricosylic acid (C23), lignoceric acid (C24), pentacosylic acid (C25), cerotic acid (C26), and mixtures thereof.
Preferably, the metal salt of a carboxylic acid comprises zinc stearate, silver stearate, palladium stearate, zinc palmitate, silver palmitate, palladium palmitate, and mixtures thereof.
The metal salt of a carboxylic acid is present in the engine oil formulations of this disclosure in an amount of from about 0.01 weight percent to about 5 weight percent, based on the total weight of the formulated oil.
Low phosphorus engine oil formulations are included in this disclosure. For such formulations, the phosphorus content is typically less than about 0.12 weight percent preferably less than about 0.10 weight percent and most preferably less than about 0.085 weight percent.
A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) can be a useful component of the lubricating oils of this disclosure. ZDDP can be derived from primary alcohols, secondary alcohols or mixtures thereof. ZDDP compounds generally are of the formula:
Zn[SP(S)(OR1)(OR2)]2
where R1 and R2 are C1-C18 alkyl groups, preferably C2-C12 alkyl groups. These alkyl groups may be straight chain or branched. Alcohols used in the ZDDP can be 2-propanol, butanol, secondary butanol, pentanols, hexanols such as 4-methyl-2-pentanol, n-hexanol, n-octanol, 2-ethyl hexanol, alkylated phenols, and the like. Mixtures of secondary alcohols or of primary and secondary alcohol can be preferred. Alkyl aryl groups may also be used.
Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, The Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from for example Afton Chemical under the trade designation “HITEC 7169”.
Cleanliness Booster
Cleanliness Boosters refer to a broad class of commercially available components used to reduce hard carbonaceous deposits that form on the piston land and groove surfaces of diesel and gasoline engines due to degradation of the base oil and oil additives under extremely high temperatures. Keeping an engine free of deposits is highly desirable as the deposits in an engine reduce effective heat transfer, contribute to friction, and change the highly engineered clearances of a modern engine which can result is wear.
Cleanliness is difficult to achieve in a modern engine oil formulation due to limits placed on ash containing componentry (e.g., overbased detergents) which are used to prevent formation of deposits. These ash limits are in place to reduce blockage of diesel particulate filters and limit the amount of an overbased detergent that may be used in a given engine oil formulation.
One method of overcoming this limit is through the use of ashless cleanliness boosters. Some of these materials which are commercially available include alkyl phenol ether polymers, polyisobutylene polymers and ashless detergent chemistries. These materials are typically used in a formulation in a range from 0.5-2.0 wt % and provide a modest but consistent improvement in cleanliness, in particular in the VW PV1452 TDi-2 Deposit Test (CEC L-078-99) which is used in multiple ACEA and OEM specifications. This cleanliness boost can range from 1-5 piston deposit merits in the VW PV1452 test depending on depending on specific chemistry selected, formulation, and treat rate.
When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present disclosure are shown in Table 1 below.
It is noted that many of the additives are shipped from the additive manufacturer as a concentrate, containing one or more additives together, with a certain amount of base oil diluents. The weight percent (wt %) indicated below is based on the total weight of the lubricating oil composition.
Examples and Comparative ExamplesThe following examples are non-limiting in nature and are provided to more particularly illustrate the disclosure.
ASTM D6795 Test
An ASTM D6795 test was performed. ASTM D6795 is a standard method for measuring the effect on filterability of engine oils after treatment with water and dry ice and a short (30 min) heating time. Specifically, the test oil is treated with 0.6% deionized water and dry ice. The sample is heated to 70° C. for 30 min, followed by storage at room temperature for 48 hours. The sample is filtered and the flow rate is calculated and compared to the flow rate of a sample of the engine oil that was not treated with water and dry ice. The change in flow rate provides a measure of the engine oil filterability characteristics. This standard is part of the ILSAC GF-x (x=1, 2, 3, 4, or 5) and API S engine oil specifications.
Example IA comparative lubricant composition labeled 1A is a typical all-calcium detergent package that shows no challenges in filterability but contains only a standard friction modifier, rather than the CRFM.
Compositions 1B, 1C and 1D contain additionally the low stabilizer CRFM consisting of about 43 percent weight of nitrogen from a dispersant and about 57 percent weight of nitrogen from the tartrimide. The filterability as measured by ASTM D6795 has failed in all three compositions.
The low stabilizer CRFM of the compositions 1B, 1C and 1D has been subsisted by high stabilizer CRFM in composition 1 E in order to improve the performance of this formulation. High stabilizer CRFM consists of about 55 percent weight of nitrogen from stabilizing dispersants and about 45 percent weight of nitrogen from the tartrimide as illustrated below in Table 2. While minor improvement through the use of a high stabilizer CRFM is evident, composition 1 E also failed the ASTM D6795 test as set forth below in Table 2. High stabilizer and low stabilizer CRFM are distinguished by the amount of nitrogen provided by the active friction modifier portion of the CRFM system and the amount of nitrogen contributed by e.g. the succinimide-derived conjugate. In a high stabilizer version of the CRFM the tartrimide provides lower nitrogen content than the nitrogen content provided by the friction modifier. In a low stabilizer CRFM the nitrogen content provided by the tartrimide is greater than the nitrogen provided by the e.g. succinimide-derived conjugate.
Surprisingly, in example compositions 1F, 1G, 1H, 1I and 1J by moving to a mixed magnesium and calcium detergent system with a ratio of calcium to magnesium of less than 2:1, these compositions have been shown to pass the ASTM D6795 test as evidenced by the results set forth in Table 3. This test has been shown to be insensitive to the dispersant as demonstrated. More specifically, the exemplary composition 1K provide both controlled release friction modification and exceptional filterability as shown in Table 3 set forth below. Specifically, in accordance with an exemplary preferred embodiment of the invention, example 1K is a formulation that contains a mixed magnesium and calcium detergent system with a calcium:magnesium ratio of 1.44:1 in addition to a high stabilizer CRFM. This formulation provides both controlled release friction modification and exceptional filterability.
While the foregoing disclosure shows illustrative embodiments of the invention, it should be noted that various changes and modifications could be made herein without departing from the scope of the invention as defined by the appended claims. The functions, steps and/or actions of the method claims in accordance with the embodiments of the invention described herein need not be performed in any particular order. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.
Claims
1. A lubricating oil composition, comprising:
- a base oil comprising a highly paraffinic base oil;
- a controlled release friction modifier (CRFM), including: a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C18-tartrimide, a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, and a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500; and
- an effective amount of a detergent.
2. The lubricating oil composition of claim 1, wherein the detergent comprises a mixed magnesium and calcium detergent system.
3. The lubricating oil composition of claim 2, wherein the mixed magnesium and calcium detergent system has a ratio of calcium to magnesium of less than 2:1.
4. The lubricating oil composition of claim 2, wherein the mixed magnesium and calcium detergent system has a calcium:magnesium ratio of 1.44:1.
5. The lubricating oil composition of claim 1, wherein the CRFM is a high stabilizer CRFM.
6. The lubricating oil composition of claim 2, wherein the CRFM is a high stabilizer CRFM.
7. The lubricating oil composition of claim 1, wherein the CRFM is present in a range of about 2 to 8 wt %, based on the total weight of the composition.
8. The lubricating oil composition of claim 1, wherein nitrogen in the CRFM derived from the tartrimide is present in the range of about 35% to 55 wt %, based on the total nitrogen content of the CRFM.
9. The lubricating oil composition of claim 1, wherein the detergent is selected from the group consisting of: overbased calcium salicylate detergent, low base calcium salicylate detergent, neutral calcium sulfonate detergent, overbased calcium sulfonate detergent and overbased magnesium sulfonate detergent.
10. The lubricating oil composition of claim 1, wherein the detergent is present in the range of about 1 to 10 wt %, based on the total weight of the composition.
11. The lubricating oil composition of claim 1, wherein the base oil comprises a Group III basestock and a polyalphaolefin (PAO) basestock.
12. The lubricating oil composition of claim 11, wherein the Group III basestock is present in a range of about 10 to about 90 wt % and the polyalphaolefin (PAO) basestock is present in a range of about 0 to about 60 wt %, based on the total weight of the composition.
13. A lubricating oil composition, comprising:
- a base oil comprising a highly paraffinic base oil;
- a high stabilizer controlled release friction modifier (CRFM), including: a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C18-tartrimide, a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, and a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500; and
- an effective amount of a mixed magnesium and calcium detergent system.
14. The lubricating oil composition of claim 13, wherein the mixed magnesium and calcium detergent system has a ratio of calcium to magnesium of less than 2:1.
15. The lubricating oil composition of claim 13, wherein the mixed magnesium and calcium detergent system has a calcium:magnesium ratio of 1.44:1.
16. A lubricating oil composition, comprising:
- a highly paraffinic base oil;
- a controlled release friction modifier (CRFM), including: a tetrahedral borate anion having a boron atom with two bidentate di-oxo ligands both being a linear C18-tartrimide, a first dispersant comprising a conventional ammonium substituted polyisobutenyl succinimide compound having a polyisobutenyl number average molecular weight of 750 to 2,500, and a second dispersant comprising an ammonium substituted polyisobutenyl succinimde compound having an N:CO ratio of 1.8 and a polyisobutylenyl number average molecular weight of 750 to 2,500; and
- an effective amount of a mixed magnesium and calcium detergent system having a calcium:magnesium ratio of less than 2:1.
Type: Application
Filed: Jul 20, 2018
Publication Date: Jan 24, 2019
Applicant: ExxonMobil Research and Engineering Company (Annandale, NJ)
Inventors: Michael L. BLUMENFELD (Haddonfield, NJ), Douglas E. DECKMAN (Mullica Hill, NJ), Smruti A. DANCE (Robbinsville, NJ), Charles L. BAKER, JR. (Thornton, PA), James David BURRINGTON (Gates Mills, OH), Ewan E DELBRIDGE (Concord, OH)
Application Number: 16/041,320
