Lubricating Composition and Method of Lubricating an Internal Combustion Engine

The disclosed technology relates to lubricants for internal combustion engines.

Lubrication of internal combustion engines has been a practice for many decades, yet continual improvement in lubricant technology is ongoing as new engines and new standards have been developed. Formulations directed to spark ignition engines and compression ignition engines, for instance, must address limits placed on sulfated ash, phosphorus, and sulfur content (“SAPS”), and restrictions in these components often lead to upper limits on the amount of metal-containing additives that can be included in the lubricant. Reduction in metal containing additives is necessary to reduce the impact of metal ash on exhaust aftertreatment devices and to reduce the emission of particulate matter.

Chief among these metal-containing additives are zinc dialkyldithiophosphates (ZDDP) for wear and oxidation protection and overbased metal detergents for cleanliness and acid control. ZDDP has been the industry standard for reducing valve train wear, protecting against liner wear, and reducing oxidation leading to corrosive wear. However, the zinc contributes to an increase in sulfated ash in the lubricating oil and the phosphorus causes inactivation of oxidation catalysts used in exhaust after-treatment devices.

The disclosed technology provides a lubricating composition containing an alternative additive to ZDDP or suitable for use in low zinc lubricant compositions where the composition provides deposit and/or oxidation control during the operation of internal combustion engines.

The present invention provides a composition for lubricating an internal combustion engine comprising an oil of lubricating viscosity, and a 2,5-dimercapto-1,3,4-thiadiazole (“DMTD”) derivative additive, which is the reaction product of DMTD and an α, β-unsaturated carbonyl compound.

In one embodiment, the present invention provides a composition for lubricating an internal combustion engine comprising an oil of lubricating viscosity, and a DMTD derivative additive, which is the reaction product of DMTD and an α, β-unsaturatedcarbonyl compound, such as an ester, amide, or imide. In another embodiment, the present invention provides a composition for lubricating an internal combustion engine comprising an oil of lubricating viscosity, and a DMTD derivative additive, which is the reaction product of DMTD and an α, β-unsaturated ester. In another embodiment, the present invention provides a composition for lubricating an internal combustion engine comprising an oil of lubricating viscosity, and a DMTD derivative additive, which is the reaction product of DMTD and an α, β-unsaturated ester, wherein the α, β-unsaturated ester is selected from the group consisting of maleates, acrylates, methacrylates, fumarates, crotonates, itaconates, and mixtures thereof. In some embodiments, the DMTD derivative additive is a metal or amine salt of the reaction product of DMTD and an α, β-unsaturated carbonyl compound.

The invention further provides a method of lubricating an internal combustion engine comprising supplying to the engine a lubricating composition comprising an oil of lubricating viscosity, and a DMTD derivative additive, which is the reaction product of DMTD and an α, β-unsaturated carbonyl compound or a salt thereof.

The invention further provides a method of decomposing peroxide in a lubricating composition when used to lubricate an internal combustion engine by operating the engine with a lubricant composition comprising an oil of lubricating viscosity, and a DMTD derivative additive, which is the reaction product of DMTD and an α, β-unsaturated carbonyl compound or a salt thereof.

The invention also provides for the use of a lubricating composition comprising an oil of lubricating viscosity, and a DMTD derivative additive, which is the reaction product of DMTD and an α, β-unsaturated carbonyl compound or a salt thereof for oxidation and deposit control in an internal combustion engine.

Various preferred features and embodiments will be described below by way of non-limiting illustration.

The lubricating composition comprises an oil of lubricating viscosity. Such oils include natural and synthetic oils, oil derived from hydrocracking, hydrogenation, and hydrofinishing, unrefined, refined, re-refined oils or mixtures thereof. A more detailed description of unrefined, refined and re-refined oils is provided in International Publication WO2008/147704, paragraphs [0054] to [0056](a similar disclosure is provided in US Patent Application 2010/197536, see [0072] to [0073]). A more detailed description of natural and synthetic lubricating oils is described in paragraphs [0058] to [0059] respectively of WO2008/147704 (a similar disclosure is provided in US Patent Application 2010/197536, see [0075] to [0076]). Synthetic oils may also be produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one embodiment, oils may be prepared by a Fischer-Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in the April 2008 version of “Appendix E—API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils”, section 1.3 Sub-heading 1.3. “Base Stock Categories”. The API Guidelines are also summarized in U.S. Pat. No. 7,285,516 (see column 11, line 64 to column 12, line 10). In one embodiment, the oil of lubricating viscosity may be an API Group II, Group III, or Group IV oil, or mixtures thereof. The five base oil groups are as follows:

The amount of the oil of lubricating viscosity present is typically the balance remaining after subtracting from 100 weight % (wt %) the sum of the amount of the compound of the invention and the other performance additives.

The lubricating composition may be in the form of a concentrate and/or a fully formulated lubricant. If the lubricating composition of the invention (comprising the additives disclosed herein) is in the form of a concentrate which may be combined with additional oil to form, in whole or in part, a finished lubricant), the ratio of the of these additives to the oil of lubricating viscosity and/or to diluent oil include the ranges of 1:99 to 99:1 by weight, or 80:20 to 10:90 by weight.

In one embodiment, the base oil has a kinematic viscosity at 100° C. from 2 mm/s (centiStokes−cSt) to 16 mm/s, from 3 mm/s to 10 mm/s, or even from 4 mm/s to 8 mm/s.

In one embodiment, the base oil comprises at least 30 wt % of Group II or Group III base oil. In another embodiment, the base oil comprises at least 60 weight % of Group II or Group III base oil, or at least 80 wt % of Group II or Group III base oil. In one embodiment, the lubricant composition comprises less than 20 wt % of Group IV (i.e. polyalphaolefin) base oil. In another embodiment, the base oil comprises less than 10 wt % of Group IV base oil. In one embodiment, the lubricating composition is substantially free of (i.e. contains less than 0.5 wt %) of Group IV base oil.

Ester base fluids, which are characterized as Group V oils, have high levels of solvency as a result of their polar nature. Addition of low levels (typically less than 10 wt %) of ester to a lubricating composition may significantly increase the resulting solvency of the base oil mixture. Esters may be broadly grouped into two categories: synthetic and natural. An ester base fluid would have a kinematic viscosity at 100° C. suitable for use in an engine oil lubricant, such as between 2 cSt and 30 cSt, or from 3 cSt to 20 cSt, or even from 4 cSt to 12 cSt.

Synthetic esters may comprise esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acids, and alkenyl malonic acids) with any of variety of monohydric alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, and propylene glycol). Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid. Other synthetic esters include those made from C5 to C12 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tripentaerythritol. Esters can also be monoesters of mono-carboxylic acids and monohydric alcohols.

Natural (or bio-derived) esters refer to materials derived from a renewable biological resource, organism, or entity, distinct from materials derived from petroleum or equivalent raw materials. Natural esters include fatty acid triglycerides, hydrolyzed or partially hydrolyzed triglycerides, or transesterified triglyceride esters, such as fatty acid methyl ester (or FAME). Suitable triglycerides include, but are not limited to, palm oil, soybean oil, sunflower oil, rapeseed oil, olive oil, linseed oil, and related materials. Other sources of triglycerides include, but are not limited to, algae, animal tallow, and zooplankton. Methods for producing biolubricants from natural triglycerides is described in, e.g., United States patent application 2011/0009300A1.

In one embodiment, the lubricating composition comprises at least 2 wt % of an ester base fluid. In one embodiment the lubricating composition of the invention comprises at least 4 wt % of an ester base fluid, or at least 7 wt % of an ester base fluid, or even at least 10 wt % of an ester base fluid.

Dimercaptodithiadiazole, referred to herein as DMTD, can be derivatized by the reaction product resulting from the Michael addition of α,β-unsaturated carbonyl compounds and DMTD, that is, a 1,4 addition between DMTD and acarbonyl compound, such as ester, amide, or imide groups capable of 1,4 addition.

While the reaction products to prepare the derivatives often result in a mixture of products, the products can be provided as pure compounds as well. In general, the DMTD derivatives can be represented in the pure form by formula I:

Metals can include transition metals such as zinc, titanium, cobalt, zirconium, manganese, or molybdenum, for example, post-transition metals and even some metalloids, such as, for example, aluminum, antimony or boron. Where a salt is desired, it can be obtained by 1,4 addition to the ester monomer followed by reaction with a metal oxide or hydroxide. In some embodiments, the DMTD can be substantially free of or free of antimony.

In one embodiment, the carbonyl compound is a carboxylate group capable of 1,4 addition. Such carboxylate groups capable of 1,4 addition (i.e., α,β-unsaturated carbonyl compounds) can be readily envisaged by those of skill in the art, and include, both mono-carboxylates and di-carboxylates as well as higher carboxylates, e.g., tricarboxylates, tetracarboxylates, etc. In general, the carboxylate may be a C4 to C24 carboxylate, or a C5 to C22 carboxylate, or C6 to C20 carboxylate, or even a C6 to C18 carboxylate. In some circumstances C6 to C12 carboxylate or even C6 to C10 carboxylate and even a C8 to C12 carboxylate are often sufficient. Example carboxylates can include, but not be limited to itaconates, citraconates, maleates, fumarates, mesaconates, as well as (meth)acrylates (where the parentheses “( )” around (meth) indicate the methyl group may or may not be present). In the present invention, the carboxylates are in the form of an ester.

In another embodiment, the carbonyl compound may be in the form of an amide or imide.

As used herein, the term “group,” for example as in a (meth)acrylate group, depending on the context, refers to the structure of the stated group on its own or as the structure in which the group would form after reaction with another compound. For example, a methyl group, or, as a further example, methyl acrylate, could refer to CH═CHC(O)OCH, as in its lone state, or —CHCHC(O)OCH, as in its bonded form.

An example of the DMTD derivative can include the DMTD derivative resulting from the 1,4 addition between DMTD and a methacrylate, for example wherein the substituent Y of the DMTD derivatives of Formula I can be, for example, a methyl methacrylate group, for example, as represented by Formula IL

In the foregoing example, the DMTD derivative could also be salted, for example, by reacting Formula II with a half a molar equivalent of a metal oxide or hydroxide, such as a zinc oxide to form a compound represented, for example, by Formula IIa:

A further example can include the DMTD derivative resulting from the 1,4 addition between DMTD and an acrylate, wherein the substituent Y of the DMTD derivatives of Formula I can be, for example, a 2-ethylhexyl acrylate group, for example, as represented by Formula III:

A salt of the foregoing formula can be prepared by the reaction with a metal hydroxide, such as, for example, a titanium alkoxide to obtain the salt of Formula IIIa below.

A still further example can include the DMTD derivative resulting from the 1,4 addition between DMTD and a maleate, wherein the substituent Y of the DMTD derivatives of Formula I can be, for example, a diethylhexyl maleate group, for example, as represented by Formula IV:

A salt of the foregoing formula can be prepared by the reaction with a metal oxide, such as, for example, an antimony oxide to obtain the salt of Formula IVa below.

Further examples could include DMTD derivatives resulting from the 1,4 addition between DMTD and a dialkyl itaconate, such as dimethyl itaconate, dimethyl citraconate, dimethyl fumarate, and dimethyl mesaconate and the like.

Other embodiments may include DMTD derivatives resulting from the Michael addition of an α,β-unsaturated carbonyl compounds and DMTD, salted with an amine compound. The amines which may be suitable for use as the amine salt include mono-, di-, or tri-substituted amine with secondary and tertiary amines preferred. Specific examples include primary alkylamines, such as methylamine, ethylamine, n-propylamine, n-butylamine, n-hexylamine, n-octylamine, 2-ethylhexylamine, benzylamine, 2-phenylethylamine, cocoamine, oleylamine, and tridecylamine (CAS #86089-17-0); secondary and tertiary alkylamines such as isopropylamine, sec-butylamine, t-butylamine, tert-hexylamine, 1-methyl-1-amino-cyclohexane, tert-octylamine, tert-decylamine, tert-dodecylamine, tert-tetradecylamine, tert-hexadecylamine, tertoctadecylamine, tert-tetracosanylamine, and tertoctacosanylamine, cyclopentylamine, cyclohexylamine, and 1-phenylethylamine; dialkylamines, such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, dicyclohexylamine, di-(2-ethylhexyl)amine, dihexylamine, ethylbutylamine, N-ethylcyclohexylamine, and N-methylcyclohexylamine; cycloalkylamines, such as piperidine, N-ethylpiperidine, N,N″-dimethylpiperazine, morpholine, N-methylmorpholine, N-ethylmorpholine, N-methylpiperidine, pyrrolidine, N-methylpyrrolidine, and N-ethylpyrrolidine; and trialkylamines, such as tetramethylethylenediamine, trimethylamine, triethylamine, tripropylamine, triisopropylamine, tri-butylamine, trihexylamine, N, N-dimethylbenzylamine, dimethylethylamine, dimethylisopropylamine, dimethylbutylamine, and N, N-dimethylcyclohexylamine.

The DMTD derivatives can be employed in an automotive or industrial lubricant at 0.05 wt. % to 2 wt. %, or from 0.08 wt. % to 1.8 wt. %, or even from 0.1 wt. % to 1.6 wt. % or 0.12 wt. % to 1.4 wt. % or even 0.15 wt. % to 1.2 or even 0.4 to 1 wt. %. In another embodiment, the DMTD derivative is present in an amount to deliver at least 0.05% to 0.35% by weight or 0.07% to 0.3% by weight or 0.08% to 0.26% by weight sulfur to the lubricating composition.

Likewise, the DMTD derivatives can be employed in an automotive or industrial lubricant sufficient to provide from 100 to 5000 ppm sulfur, or even from 250 to 4000 ppm sulfur or 500 to 3000 ppm sulfur, or even from 750 to 2500 ppm sulfur or 1050 to 2000 ppm sulfur.

The compositions of the invention may optionally comprise one or more other additional performance additives. These additional performance additives may include, but are not limited to, one or more dispersants, including borated dispersants, anti-wear additives, detergents, metal deactivators, viscosity modifiers, detergents, friction modifiers, antiwear agents, corrosion inhibitors, dispersant viscosity modifiers, extreme pressure agents, antioxidants, foam inhibitors, demulsifiers, pour point depressants, seal swelling agents, and any combination or mixture thereof. Typically, fully-formulated lubricating oil will contain one or more of these performance additives, and often a package of multiple performance additives.

In one embodiment, the lubricating compositions of the present invention may contain a borated dispersant. The borated dispersant may be a succinimide dispersant, a Mannich dispersant, a polyolefin succinic acid ester, amide, or ester-amide, or mixtures thereof, borated using one or more of a variety of agents selected from the group consisting of the various forms of boric acid (including metaboric acid, HBO, orthoboric acid, HBO, and tetraboric acid, HBO), boric oxide, boron trioxide, and alkyl borates. In one embodiment the borating agent is boric acid which may be used alone or in combination with other borating agents. Methods of preparing borated dispersants are known in the art. The borated dispersant may be prepared in such a way that they contain 0.1 wt % to 2.5 wt % boron, or 0.1 wt % to 2.0 wt % boron or 0.2 to 1.5 wt % boron or 0.3 to 1.0 wt % boron.

In one embodiment, the borated dispersant may be a borated succinimide dispersant. The succinimide dispersant may be a derivative of an aliphatic polyamine, or mixtures thereof. The aliphatic polyamine may be aliphatic polyamine such as an ethylenepolyamine, a propylenepolyamine, a butylenepolyamine, or mixtures thereof. In one embodiment, the aliphatic polyamine may be ethylenepolyamine. In one embodiment the aliphatic polyamine may be selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyamine still bottoms, and mixtures thereof.

The succinimide dispersant may be a derivative of an aromatic amine, an aromatic polyamine, or mixtures thereof. The aromatic amine may be 4-aminodiphenylamine (ADPA) (also known as N-phenylphenylenediamine), derivatives of ADPA (as described in United States Patent Publications 2011/0306528 and 2010/0298185), a nitroaniline, an aminocarbazole, an amino-indazolinone, an aminopyrimidine, 4-(4-nitrophenylazo)aniline, or combinations thereof. In one embodiment, the dispersant is derivative of an aromatic amine wherein the aromatic amine has at least three non-continuous aromatic rings.

The succinimide dispersant may be a derivative of a polyether amine or polyether polyamine. Typical polyether amine compounds contain at least one ether unit and will be chain terminated with at least one amine moiety. The polyether polyamines can be based on polymers derived from C-Cepoxides such as ethylene oxide, propylene oxide, and butylene oxide. Examples of polyether polyamines are sold under the Jeffamine® brand and are commercially available from Huntsman Corporation located in Houston, Texas.

The borated dispersant may be based upon a borated polyisobutylene succinimide dispersant, wherein the polyisobutylene of the borated polyisobutylene succinimide has a number average molecular weight of 350 to 5000, or 550 to 3000 or 750 to 2500 or 350 to 2200, or 350 to 1350, or 350 to 1150 or 350 to 750 or 550 to 2200 or 550 to 1350 or 750 to 2200.