A lubricating oil composition with improved oxidation performance, containing an alkylated diphenylamine antioxidant and a carboxylic acid cleaning agent.

Abstract

A lubricating oil composition is provided that includes several components, including a base oil, a primary antioxidant including an alkylated diphenylamine having an alkyl group derived from propylene tetramer, and a carboxylic acid detergent.

Description

[Technical Field]

[0001] Cross-reference of related applications This application relates to a U.S. provisional application filed on March 11, 2020, entitled "IMPROVED OXIDATIVE PERFORMANCE WITH SULFONATE DETERGENTS" (Agent Reference Number: T-11174), the contents of which are incorporated herein by reference.

[0002] This disclosure relates to lubricant additives that inhibit oxidation and extend the effective life of lubricants. More specifically, this disclosure relates to lubricant compositions comprising alkylated diphenylamine antioxidants and carboxylic acid cleaning agents. [Background technology]

[0003] Oxidation is a concern for lubricants in use because it can cause oil viscosity increase, sludge formation, varnish formation, increased acid value, and corrosion. These consequences generally detriment the proper functioning of automotive engines and limit the lifespan of the lubricant. With constantly evolving engine designs, operating conditions, and expectations for oil performance, oxidation remains a significant ongoing technical challenge.

[0004] One way to slow down engine oxidation is to introduce antioxidants into the lubricating oil. Furthermore, antioxidants can extend the discharge interval, maintain viscosity, reduce deposits, reduce foam formation, protect against corrosion, and protect the lubricating oil from high temperatures.

[0005] There are many antioxidants with varying degrees of effectiveness. Commercial lubricants are usually formulated with one or more antioxidants to protect the fluid under various conditions (e.g., temperature, time, air mixture, pressure, etc.).

[0006] In particular, alkylated diphenylamines are used as antioxidants. Widely used alkylated diphenylamine antioxidants include nonylated (C9) diphenylamine, which can be added to organic fluids such as engine oil, gear oil, hydraulic oil, compressor oil, turbine oil, and grease.

SUMMARY OF THE INVENTION

[0007] The present disclosure relates to a lubricant additive that inhibits oxidation and extends the useful life of lubricating oil. More specifically, the present disclosure relates to a composition comprising an alkylated diphenylamine and a carboxylic acid detergent.

[0008] In one aspect, a lubricating oil composition is provided that includes: a base oil, a primary antioxidant comprising an alkylated diphenylamine having an alkyl group derived from propylene tetramer, and a carboxylic acid detergent.

[0009] In a further aspect, a method of improving the oxidation stability of a lubricating oil is provided, the method comprising supplying to an engine a lubricating oil composition comprising a large amount of base oil, a primary antioxidant comprising an alkylated diphenylamine having an alkyl group derived from propylene tetramer, and a carboxylic acid detergent. Furthermore, [1] to

[20] below all represent one embodiment or aspect of the present invention. [1] A lubricating oil composition, base oil, A primary antioxidant containing alkylated diphenylamine having an alkyl group derived from propylene tetramer, and Carboxylic acid cleaning agent, The lubricating oil composition comprising the above. [2] [1] The lubricating oil composition described above, further The lubricating oil composition comprising a secondary antioxidant including dithiocarbamate, hindered phenol, or molybdenum succinimide. [3] The lubricating oil composition according to [1], wherein at least 50% of the alkyl group of the alkylated diphenylamine has a number of carbon atoms between 10 and 15. [4] The lubricating oil composition according to [1], wherein the carboxylic acid cleaning agent is an aromatic carboxylate or an aliphatic carboxylate. [5] The lubricating oil composition according to [1], wherein the carboxylic acid cleaning agent is a salicylate, naphthenate, or stearate. [6] The lubricating oil composition according to [1], wherein the primary antioxidant is present in an amount of 0.4% to 20% by weight of the lubricating oil composition. [7] The lubricating oil composition according to [1], wherein the carboxylic acid cleaning agent is low-overbasic, moderately-overbasic, highly-overbasic, or highly-overbasic. [8] The lubricating oil composition according to [1], wherein the secondary antioxidant is present in an amount of 0.01% to 20% by weight of the lubricating oil composition. [9] The lubricating oil composition according to [1], wherein the carboxylic acid cleaning agent is present in an amount of 0.01% to 10% by weight of the lubricating oil composition.

[10] [1] The lubricating oil composition described above, further: The lubricating oil composition further comprises an antioxidant, an ashless dispersant, an anti-wear agent, a cleaning agent, a rust inhibitor, a dehazing agent, a deemulsifier, a friction modifier, a metal deactivator, a pour point depressant, a viscosity modifier, an antifoaming agent, a co-solvent, a package compatibility agent, a corrosion inhibitor, a pigment, or an extreme pressure additive.

[11] A method for improving the oxidation stability of lubricating oil, A large amount of base oil, A primary antioxidant comprising an alkylated diphenylamine having an alkyl group containing a propylene tetramer, The method comprising providing an engine with a lubricating oil composition comprising a carboxylic acid cleaning agent.

[12] The method described in

[11] , wherein the lubricating oil composition further comprises: The lubricating oil composition comprising a secondary antioxidant including dithiocarbamate, hindered phenol, or molybdenum succinimide.

[13] The method according to

[11] , wherein at least 50% of the alkyl group of the alkylated diphenylamine has 10 to 15 carbon atoms.

[14] The method according to

[11] , wherein the carboxylic acid cleaning agent is an aromatic carboxylate or an aliphatic carboxylate.

[15] The method according to

[11] , wherein the carboxylic acid cleaning agent is a salicylate, naphthenate, or stearate.

[16] The method according to

[11] , wherein the primary antioxidant is present in an amount of 0.4% to 20% by weight of the lubricating oil composition.

[17] The method according to

[11] , wherein the carboxylic acid cleaning agent is low-overbasic, moderately-overbasic, highly-overbasic, or highly-overbasic.

[18] The method according to

[11] , wherein the secondary antioxidant is present in an amount of 0.01% to 20% by weight of the lubricating oil composition.

[19] The method according to

[11] , wherein the carboxylic acid cleaning agent is present in an amount of 0.01% to 10% by weight of the lubricating oil composition.

[20] The method described in

[11] , wherein the lubricating oil composition further comprises The method comprising an antioxidant, an ashless dispersant, an anti-wear agent, a cleaning agent, a rust inhibitor, a de-haze agent, a de-emulsifier, a friction modifier, a metal deactivator, a pour point depressant, a viscosity modifier, an anti-foaming agent, a co-solvent, a package compatibility agent, a corrosion inhibitor, a dye, or an extreme pressure additive. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows a comparison of the oxidation induction times of the blended oil samples described in the examples. [Modes for carrying out the invention]

[0011] In this specification, the following words and expressions, when used and when used, have the meanings assigned to them below.

[0012] The term "antioxidant" or equivalent terms (e.g., "oxidation stabilizer" or "oxidation inhibitor") refer to compositions and their ability to resist harmful attacks in oxidative environments. Antioxidants are often used in organic fluids (e.g., lubricants, gear oils, compressor oils, mineral oils, hydraulic oils) to improve the oxidation stability of these fluids.

[0013] The term "alkyl" or related terms refer to a saturated hydrocarbon group, which may be linear, branched, cyclic, or a combination of cyclic, linear, and / or branched.

[0014] The term "olefin" refers to hydrocarbons having at least one carbon-carbon double bond that is not part of an aromatic ring or ring system. Olefins may include aliphatic and aromatic, cyclic and acyclic, and / or linear and branched compounds that, unless otherwise specified, have at least one carbon-carbon double bond that is not part of an aromatic ring or ring system. Olefins having one, two, three, or more carbon-carbon double bonds may be identified by using terms such as "mono," "di," or "tri" in the name of the olefin. Olefins may be further identified by the position of the carbon-carbon double bond(s). Depending on the context, the term "olefin" may refer to an "olefin oligomer," an "olefin monomer," or both.

[0015] An "olefin oligomer" is an oligomer obtained by oligomerizing an "olefin monomer." For example, a "propylene oligomer" is produced by oligomerizing a propylene monomer. Examples of propylene oligomers include propylene tetramers and propylene pentamers. A "propylene tetramer" is an olefin oligomer product resulting from the oligomerization of nominally four propylene monomers. These terms can also be commonly used to describe homooligomers, cooligomers, oligomer salts, oligomer derivatives, and so on.

[0016] "Small amounts" or related terms are expressed with respect to the listed additives and the total weight of the composition, meaning less than 50% by weight of the composition as the active ingredient of the additive.

[0017] "Major amount" or related terms mean an amount exceeding 50% by weight based on the total weight of the composition.

[0018] Antioxidant composition This invention relates to antioxidant compositions that inhibit oxidation and extend the effective life of lubricating oils. More specifically, this invention describes antioxidant compositions comprising a plurality of lubricating oil additives. The lubricating oil additives comprise at least two antioxidants and at least one cleaning agent, which work together to improve oxidation performance. The improved performance is the result of previously unknown synergistic effects arising from the lubricating oil additive components of this invention in the lubricating oil composition. Antioxidants and cleaning agents conforming to this invention are described herein.

[0019] Primary antioxidant The antioxidant composition comprises a primary antioxidant and one or more secondary antioxidants. The primary antioxidant of the present invention is an alkylated diphenylamine having one or more relatively long alkyl groups. Conventional alkylated diphenylamine antioxidants usually utilize relatively short alkyl groups. Examples of these include nonylated diphenylamines ("propylene trimers") which nominally have nine carbon atoms and can be formed from the oligomerization of propylene.

[0020] The alkylated diphenylamines of the present invention are alkylated by a propylene tetramer (nominally having 12 carbon atoms) or by a mixture containing a propylene tetramer, the propylene tetramer being the primary olefin oligomer alkylating agent. The propylene tetramer can be obtained by oligomerizing four propylene monomers. The propylene tetramer has several potential advantages over the propylene trimer, including, but not limited to, improved oil solubility, lower cost, and superior stability against oxidation.

[0021] The alkylated diphenylamine of the present invention may be present in the lubricating oil composition in an amount of about 0.4% to about 20% by weight, for example, about 0.5% to about 15% by weight, 0.1% to about 10% by weight, 0.5% to about 8% by weight, or 1% to about 5% by weight.

[0022] Propylene oligomer The propylene oligomers (i.e., propylene tetramers) of the present invention can be prepared by any interchangeable method known in the art. As an example, the process for preparing the propylene oligomers uses a liquid phosphate oligomerization catalyst. A description of this liquid phosphate catalyzed propylene oligomerization process can be found in U.S. Patents 2,592,428, 2,814,655 and 3,887,634, the relevant portions of which are incorporated herein by reference.

[0023] Unpurified products of oligomerization processes typically contain a mixture of branched olefins with a distribution of carbon atoms. In commercial settings, olefin oligomers are subjected to extreme conditions during the oligomerization process, resulting in cracking, recombination, isomerization, etc. Purified or processed oligomerized products usually have a higher concentration of the desired product. Therefore, the term "propylene tetramer" does not necessarily refer to a pure propylene tetramer product, but may also refer to a mixture of olefin or olefin oligomer products. Thus, alkylation products containing diphenylamine and propylene tetramers may have a distribution of carbon atoms within the alkylated alkyl group.

[0024] Propylene tetramers may also be obtained from the oligomerization of four propylene monomers. Propylene tetramers are cost-effective for producing olefins. The oligomerization product is characterized by a highly branched chain consisting of 10 to 15 carbon atoms and high methyl branching, which imparts excellent oil solubility and compatibility with other oil-soluble lubricant additive components. In some embodiments, the average number of carbon atoms may be in the range of about 10 to about 15.

[0025] The oligomerization products can have different degrees of branching. For example, a propylene tetramer may exhibit total branching (i.e., the sum of olefinic and aliphatic branching) ranging from 1 to 15. In some embodiments, the average total branching may range from about 1 to about 15.

[0026] The propylene tetramer of the present invention generally contains at least 50% by weight of C 10 ~C 15 It contains carbon atoms. In one embodiment, the propylene tetramer contains at least 60% by weight of C 10 ~C 15 Includes a distribution of carbon atoms, including carbon atoms. In one embodiment, the propylene tetramer contains at least 70% by weight of C 10 ~C 15 Includes a distribution of carbon atoms, including carbon atoms. In one embodiment, the propylene oligomer contains at least 80% by weight of C 10 ~C15 It includes the distribution of carbon atoms containing carbon atoms. In one embodiment, the propylene oligomer is at least 90% by weight of C 10 ~C 15 It includes the distribution of carbon atoms containing carbon atoms.

[0027] As will be apparent to those skilled in the art, the propylene oligomers used herein may also contain small amounts of lower molecular weight propylene oligomers, e.g., propylene trimers, and higher molecular weight propylene oligomers, e.g., propylene pentamers. For example, the propylene tetramer of the present invention may contain 0 to 1% by weight of C9H 18 , 0 to 5% by weight of C 10 H 20 , 0 to 10% by weight of C 11 H 22 , 50 to 90% by weight of C 12 H 24 , 10 to 20% by weight of C 13 H 26 , 5 to 15% by weight of C 14 H 28 , and / or 1 to 10% by weight of C 15 H 30 and may be a mixture of olefin hydrocarbons.

[0028] Alkylation The alkylated diphenylamine of the present invention may be obtained by any alkylation process compatible with the present invention. For example, U.S. Patent No. 6,355,839, which is incorporated herein by reference, describes the preparation of alkylated diphenylamine in which diphenylamine is alkylated with polyisobutylene.

[0029] Any suitable catalyst may be used. For example, the alkylation of diphenylamine can proceed in the presence of a clay catalyst. The reaction temperature may be in the range of 140°C to 200°C, more typically 150°C to 190°C. In some embodiments, the reaction temperature is in the range of 160°C to 180°C. The reaction may be carried out at a single temperature or sequentially at different temperatures. The propylene oligomer is packed in relation to the diphenylamine charge at a charge mole ratio (CMR) of 2:1 to 8:1. In some embodiments, the CMR is 3:1 to 7:1 or 4:1 to 6:1. The reaction product may be filtered to remove the catalyst, and then distilled to remove unreacted olefin oligomer and diphenylamine. The use of clay as a catalyst is disclosed in U.S. Patent No. 3,452,056, which is incorporated herein by reference.

[0030] As those skilled in the art would expect, reaction conditions can vary considerably depending on the catalyst used. For example, reactions involving homogeneous acid catalysts may only require temperatures in the range of 75°C to 100°C.

[0031] Depending on the reaction conditions, the alkylated diphenylamine product may have various relative amounts of monoalkylated, dialkylated, and / or trialkylated diphenylamine products. For a given dialkylated diphenylamine molecule or trialkylated diphenylamine molecule, it should be clear that two or more alkylating alkyl groups may be the same or different according to this disclosure.

[0032] Secondary antioxidants The present invention uses one or more secondary antioxidants in combination with a primary antioxidant. The secondary antioxidants may be present in about 0.01% to about 20% by weight of the lubricating oil composition, for example, about 0.05% to about 15% by weight, 0.1% to about 10% by weight, 0.5% to about 8% by weight, or 1% to about 5% by weight.

[0033] Many secondary antioxidants are suitable for the present invention. Examples of secondary antioxidants include molybdenum succinimide, dithiocarbamate, and hindered phenol. These oil-soluble components are generally known.

[0034] For example, mono and polysuccinimides that can be used to prepare the molybdenum complexes described herein are disclosed in numerous references and are well known in the art. Specific basic types of succinimides and related substances included in the technical term “succinimide” are taught in U.S. Patents 3,219,666, 3,172,892, and 3,272,746, the disclosures of which are incorporated herein by reference. The term “succinimide” is understood in the art to include many of the amides, imides, and amidine species that can be formed. However, the main product is succinimide, and the term has generally been accepted to mean the reaction product of an alkenyl-substituted succinic acid or anhydride with a nitrogen-containing compound.

[0035] Preferred succinimides are those prepared from a hydrocarbyl succinic anhydride containing about 24 to about 350 carbon atoms in a hydrocarbyl group, which is commercially available, and an ethyleneamine, the ethyleneamine being particularly characterized by ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. Particularly preferred are succinimides prepared from a polyisobutenyl succinic anhydride with 70 to 128 carbon atoms and tetraethylenepentamine or triethylenetetramine or a mixture thereof.

[0036] The term "succinimide" also includes co-oligomers of hydrocarbyl succinic acid or anhydride with a polysecondary amine containing two or more secondary amino groups in addition to at least one tertiary amino nitrogen. Typically, the average molecular weight of this composition is between 1,500 and 50,000. Typical compounds would be prepared by reacting polyisobutenyl succinic anhydride with ethylenedipiperazine.

[0037] Succinimides having an average molecular weight of 1000, 1300, or 2300, and mixtures thereof, are most preferred. Such succinimides may be post-treated with boron or ethylene carbonate, as is well known in the art.

[0038] Suitable dithiocarbamates include, but are not limited to, dithiocarbamates, ashless thiocarbamates, or dithiocarbamates (i.e., essentially metal-free) where the metal is zinc, copper, or molybdenum, such as methylenebis(dialkyldithiocarbamate), ethylenebis(dialkyldithiocarbamate), and isobutyldisulfide-2,2'-bis(dialkyldithiocarbamate), where the alkyl group of alkyldithiocarbamate may preferably have 1 to 6 carbon atoms. Preferred examples of ashless dithiocarbamates are methylenebis(dibutyldithiocarbamate), ethylenebis(dibutylthiocarbamate), and isobutyldisulfide-2,2'-bis(dibutyldithiocarbamate).

[0039] The secondary antioxidant used in the lubricating oil of the present invention may be a sterically hindered phenol. Hindered phenol antioxidants often contain secondary butyl and / or tertiary butyl groups as sterically hindered groups. The phenol group is often further substituted with a hydrocarbyl group and / or a crosslinking group (bonding to a second aromatic group). Suitable hindered phenols include, but are not limited to, 2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol, or 4-butyl-2,6-di-tert-butylphenol, or 4-dodecyl-2,6-di-tert-butylphenol.

[0040] Cleaning agent The antioxidant composition of the present invention comprises one or more detergents. The detergents may be present in about 0.01% to about 10% by weight of the lubricating oil composition, for example, about 0.05% to about 8% by weight, 0.1% to about 5% by weight, 0.5% to about 4% by weight, or 1% to about 3% by weight.

[0041] Detergents are typically salts (e.g., overbasic salts) and are single-phase, homogeneous Newtonian systems characterized by an excess metal content, which may be present depending on the stoichiometry of the metal and the specific acidic organic compound that reacts with the metal.

[0042] Examples of cleaning agents of the present invention include carboxylic acid cleaning agents, such as aromatic carboxylic acid salts (e.g., salicylates, naphthenates) and aliphatic carboxylic acid salts (e.g., stearates). In particular, salicylates can be prepared by reacting aromatic carboxylic acids with suitable metal compounds such as oxides or hydroxides.

[0043] The cleaning agent may be overbasic. Overbasic cleaning agents may have a range of overbasicity (measured by ASTM D2896). Suitable carboxylates include, for example, low-overbasic (TBN 15-30), moderately overbasic (TBN 31-170), highly overbasic (TBN 171-400), and highly overbasic (TBN > 400) carboxylic acid cleaning agents. One or more overbasic carboxylic acid cleaning agents (e.g., low-overbasic and moderately overbasic) may be used. The carboxylic acid cleaning agent may be present in about 0.05% to 5% by weight of the lubricating oil composition.

[0044] Metals in carboxylates also include alkali or alkaline earth metals, such as barium, sodium, potassium, lithium, calcium, and magnesium. The most commonly used metals are calcium and magnesium, both of which can be found in cleaning agents used as lubricants, as well as in mixtures of calcium and / or magnesium with sodium.

[0045] In some embodiments, additional detergents may be used. Examples of additional detergents include phenates, salicylates, phenolates, phosphonates, thiophosphonates, and ionic surfactants. In some embodiments, additional detergents may include hybrid and / or composite detergents.

[0046] lubricating oil composition The antioxidant compositions of this disclosure may be used in lubricating oils to impart oxidation stability to the lubricating oil. Primary antioxidants, secondary antioxidants, and one or more detergents may be present in any ratio, as long as their concentrations fall within the guidelines provided herein.

[0047] Generally, antioxidant compositions are oil-soluble, meaning they are, for example, soluble or stably dispersible in oil to a degree sufficient to exert the intended effect in the environment in which the oil is used. Furthermore, higher levels of specific additives can be incorporated by incorporating other additives as needed. The term oil-soluble does not necessarily indicate that the compound or additive is soluble, dissolvable, miscible, or suspendable in oil at all proportions. If other antioxidants are present in the lubricating oil composition, a smaller amount of the antioxidant of the present invention may be used.

[0048] The oil used as the base oil is selected or blended according to the desired end use and additives in the finished oil to obtain a lubricating oil composition having the desired grade of engine oil, for example, an engine oil with a Society of Automotive Engineers (SAE) viscosity grade of 0W, 0W-8, 0W-16, 0W-20, 0W-30, 0W-40, 0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40, 10W-50, 15W, 15W-20, 15W-30, or 15W-40. Straight grade base oils such as SAE 30, 40, 50, and 60 may also be used.

[0049] Lubricating viscosity oils (sometimes called "base stocks" or "base oils") are the primary liquid component of lubricants, and are blended with additives and, optionally, other oils to produce, for example, the final lubricant (or lubricant composition). Base oils useful for producing concentrates and from which lubricant compositions may be selected from natural (vegetable, animal, or mineral) lubricants, synthetic lubricants, and mixtures thereof.

[0050] The definitions of base stock and base oil in this disclosure are the same as those found in American Petroleum Institute (API) Publication 1509 Annex E ("API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils," December 2016). Group I base stocks contain less than 90% saturated sulfur and / or more than 0.03% sulfur, and have a viscosity index of 80 or more and less than 120, using the test method specified in Table E-1. Group II base stocks contain 90% or more saturated sulfur and 0.03% or less sulfur, and have a viscosity index of 80 or more and less than 120, using the test method specified in Table E-1. Group III base stocks contain 90% or more saturated sulfur and 0.03% or less sulfur, and have a viscosity index of 120 or more, using the test method specified in Table E-1. Group IV base stocks are polyalphaolefins (PAOs). Group V base stocks include all other base stocks not included in Groups I, II, III, or IV.

[0051] Examples of natural oils include animal oils, vegetable oils (e.g., castor oil and lard), and mineral oils. Animal and vegetable oils with desirable thermal oxidative stability may be used. Of the natural oils, mineral oils are preferred. Mineral oils differ considerably in terms of their crude oil source, for example, whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils also differ in the methods used for their production and refining, for example, their distillation range, and whether they are straight-run, cracked, hydrogen-refined, or extracted solvents.

[0052] Examples of synthetic oils include hydrocarbon oils. Examples of hydrocarbon oils include oils of polymerized and crosspolymerized olefins (e.g., polybutylene, polypropylene, propylene-isobutylene copolymer, ethylene-olefin copolymer, and ethylene-alphaolefin copolymer). Polyalphaolefin (PAO) oil base stocks are commonly used for synthetic hydrocarbon oils. Examples include C8-C 14 Olefins, for example, C8, C 10 , C 12 , C 14 PAO derived from olefins or mixtures thereof may be used.

[0053] Other useful fluids for use as base oils include unconventional or non-conventional base stocks, which are preferably catalytically treated or synthesized to provide high-performance properties.

[0054] Non-conventional or non-conventional base stocks / base oils include mixtures of base stocks derived from one or more gas-to-liquid (GTL) materials, as well as isomerized / iso-dewaxed base stocks derived from natural waxes or waxy feedstocks, mineral oil and / or non-mineral oil waxy feedstock stocks, e.g., slack wax, natural waxes and wax stocks, e.g., gas oil, waxy fuel hydrocracker bottom, waxy raffinate, hydrocracker, thermal cracker, or other mineral, mineral oil, and even non-petroleum-derived waxy materials, e.g., waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks.

[0055] The base oils for use in the lubricating oil compositions of this disclosure are API Group I, Group II, Group III, Group IV, and Group V oils, and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils, and mixtures thereof, more preferably any of the various oils corresponding to Group III to Group V base oils (due to their outstanding volatility, stability, viscosity measurement, and cleanliness characteristics).

[0056] Typically, the base oil is 2.5-20 mm 2 / s (for example, 3-12mm) 2 / s, 4-10mm 2 / s, or 4.5-8mm 2 It has a kinetic viscosity (ASTM D445) at 100°C in the range of / s).

[0057] The lubricating oil composition may also contain conventional lubricant additives to impart auxiliary functions, resulting in a finished lubricating oil composition in which these additives are dispersed or dissolved. For example, the lubricating oil composition may be blended with antioxidants, ashless dispersants, anti-wear agents, cleaning agents such as metal cleaners, rust inhibitors, dehazing agents, deemulsifiers, friction modifiers, metal deactivators, pour point depressants, viscosity modifiers, antifoaming agents, cosolvents, package conforming agents, corrosion inhibitors, dyes, extreme pressure additives, and mixtures thereof. Various additives are known and commercially available. These additives, or compounds similar thereto, may be used in the preparation of the lubricating oil composition of the present invention by conventional blending procedures.

[0058] Each of the aforementioned additives, when used, is used in a functionally effective amount to impart the desired properties to the lubricant. Therefore, for example, if the additive is an ashless dispersant, the functionally effective amount of this ashless dispersant is sufficient to impart the desired dispersion characteristics to the lubricant. Generally, the concentration of each of these additives when used may range from about 0.001 to about 20% by weight, for example, from about 0.01 to about 10% by weight, unless otherwise specified.

[0059] The following exemplary embodiments are intended to be non-limiting. [Examples]

[0060] As shown in Figure 1, the oxidation induction time of fully formulated engine oil was tested. Fully formulated engine oil contains one or more antioxidants and salicylic acid-based detergents, as well as common lubricant additives such as dispersants and corrosion inhibitors.

[0061] The first engine oil sample ("DPA only") contains salicylate detergents and alkylated diphenylamine. Alkylated diphenylamine is either nonylated diphenylamine or diphenylamine (alkylated with a propylene tetramer). The gas chromatography analysis of propylene tetramer-alkylated diphenylamine is summarized in Table 1 below. This analysis shows that approximately half of the sample is monoalkylated diphenylamine. The other half of the sample is dialkylated diphenylamine. A very small amount of diphenylamine with a C3-C8 alkyl group is present. [Table 1]

[0062] The test engine oil samples contain one or more secondary antioxidants (i.e., molybdenum succinimide, hindered phenol, dithiocarbamate). In mixed engine oil samples containing multiple antioxidants, each antioxidant is present at an equivalent treatment level / weight percentage.

[0063] Other engine oil samples featuring two antioxidants include alkylated diphenylamine and molybdenum succinimide ("DPA / Mo succinimide"), hindered phenol ("DPA / hindered phenol"), or dithiocarbamate ("DPA / dithiocarbamate"). Test engine oil samples featuring three antioxidants include alkylated diphenylamine and molybdenum succinimide and hindered phenol ("DPA / Mo succinimide / hindered phenol"), molybdenum succinimide and dithiocarbamate ("DPA / Mo succinimide / dithiocarbamate"), or hindered phenol and dithiocarbamate ("DPA / hindered phenol / dithiocarbamate"). The test engine oil sample, characterized by four types of antioxidants, contains alkylated diphenylamine, molybdenum succinimide, hindered phenol, and dithiocarbamate ("DPA / Mo succinimide / hindered phenol / dithiocarbamate").

[0064] For each test sample, the salicylate detergent is present at 65.2 mM, while the total concentration of antioxidants (multiple antioxidants are possible) is 1.5% by weight.

[0065] This data demonstrates that the oxidation induction time for samples containing diphenylamine alkylated with a propylene tetramer is consistently higher compared to samples containing nonylated diphenylamine.

[0066] Oxidation induction time was evaluated using pressurized differential scanning calorimetry (PDSC) according to the ASTM D 6186 test protocol. Longer oxidation induction times indicated improved oxidation stability.

Claims

1. A lubricating oil composition, base oil, A primary antioxidant containing alkylated diphenylamine having an alkyl group derived from a propylene tetramer, in an amount of 0.4% to 20% by weight. and Aromatic or aliphatic carboxylic acid detergent containing salicylates, naphthenates, or stearates, having low overbasity (TBN 15-30), moderate overbasity (TBN 31-170), high overbasity (TBN 171-400), or high overbasity (TBN > 400), in an amount of 0.01% to 10% by weight. The lubricating oil composition comprising the above.

2. The lubricating oil composition according to claim 1, further The lubricating oil composition comprising a secondary antioxidant including dithiocarbamate, hindered phenol, or molybdenum succinimide.

3. The lubricating oil composition according to claim 1, wherein at least 50% of the alkyl group of the alkylated diphenylamine has a number of carbon atoms between 10 and 15.

4. The lubricating oil composition according to claim 1, wherein the carboxylic acid cleaning agent is an aromatic carboxylic acid salt.

5. The lubricating oil composition according to claim 1, wherein the carboxylic acid cleaning agent is a salicylate.

6. The lubricating oil composition according to claim 1, wherein the primary antioxidant is present in an amount of 0.1% to 10% by weight of the lubricating oil composition.

7. The lubricating oil composition according to claim 1, wherein the carboxylic acid cleaning agent is low-overbasic with a TBN of 15 to 30, or moderately overbasic with a TBN of 31 to 170.

8. The lubricating oil composition according to claim 2, wherein the secondary antioxidant is present in an amount of 0.01% to 20% by weight of the lubricating oil composition.

9. The lubricating oil composition according to claim 1, wherein the carboxylic acid cleaning agent is present in an amount of 0.05% to 5% by weight of the lubricating oil composition.

10. The lubricating oil composition according to claim 1, further comprising: The lubricating oil composition further comprises an antioxidant, an ashless dispersant, an anti-wear agent, a cleaning agent, a rust inhibitor, a dehazing agent, a deemulsifier, a friction modifier, a metal deactivator, a pour point depressant, a viscosity modifier, an antifoaming agent, a co-solvent, a package compatibility agent, a corrosion inhibitor, a pigment, or an extreme pressure additive.

11. A method for improving the oxidation stability of lubricating oil, A large amount of base oil, A primary antioxidant comprising 0.4% to 20% by weight of alkylated diphenylamine having an alkyl group containing a propylene tetramer, The method comprising providing an engine with a lubricating oil composition comprising 0.01% to 10% by weight of an aromatic or aliphatic carboxylic acid cleaning agent containing a salicylate, naphthenate, or stearate, which has low overbasicity of TBN 15 to 30, medium overbasicity of TBN 31 to 170, high overbasicity of TBN 171 to 400, or high overbasicity of TBN > 400.

12. The method according to claim 11, wherein the lubricating oil composition further comprises: The lubricating oil composition comprising a secondary antioxidant including dithiocarbamate, hindered phenol, or molybdenum succinimide.

13. The method according to claim 11, wherein at least 50% of the alkyl group of the alkylated diphenylamine has 10 to 15 carbon atoms.

14. The method according to claim 11, wherein the carboxylic acid cleaning agent is an aromatic carboxylic acid salt.

15. The method according to claim 11, wherein the carboxylic acid cleaning agent is a salicylate.

16. The method according to claim 11, wherein the primary antioxidant is present in an amount of 0.1% to 10% by weight of the lubricating oil composition.

17. The method according to claim 11, wherein the carboxylic acid cleaning agent is low-overbasic with a TBN of 15 to 30, or moderately overbasic with a TBN of 31 to 170.

18. The method according to claim 12, wherein the secondary antioxidant is present in an amount of 0.01% to 20% by weight of the lubricating oil composition.

19. The method according to claim 11, wherein the carboxylic acid cleaning agent is present in an amount of 0.05% to 5% by weight of the lubricating oil composition.

20. The method according to claim 11, wherein the lubricating oil composition further comprises The method comprising an antioxidant, an ashless dispersant, an anti-wear agent, a cleaning agent, a rust inhibitor, a de-haze agent, a de-emulsifier, a friction modifier, a metal deactivator, a pour point depressant, a viscosity modifier, an anti-foaming agent, a co-solvent, a package compatibility agent, a corrosion inhibitor, a dye, or an extreme pressure additive.

Images