Method Of Viscosity Control

Abstract

This invention relates to a method of lubricating an internal combustion engine comprising at least one of a crankcase, a gear and a wet-clutch, said method comprising supplying to said crankcase, gear and wet-clutch a lubricating composition comprising: (a) an oil of lubricating viscosity; and (b) a viscosity modifier with a number average molecular weight from 1000 to 75,000, wherein the lubricating composition has a SAE viscosity grade from XW—Y, wherein X is from 0 to 20 and Y is from 20 to 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less.

Description

FIELD OF INVENTION

The present invention relates to a method of viscosity control by lubricating an internal combustion engine comprising at least one of a crankcase, a gear, and a wet-clutch with a lubricating composition.

BACKGROUND OF THE INVENTION

It is well known for lubricating oils to contain a number of additives used to protect the engine from wear and provide viscosity control. Common additives for engine lubricating oils include zinc dialkyldithiophosphate (ZDDP) an antiwear additive. It is believed that ZDDP antiwear additives protect the engine by forming a protective film on metal surfaces. Viscosity modifiers with a number average molecular weight above 100,000 are known in crankcase applications as viscosity modifiers because they help control high temperature viscometrics in multi-grade lubricants. Viscosity modifiers in various applications are known from, e.g., U.S. Pat. No. 5,112,509.

Current and future government legislation regulating exhaust emissions from internal combustion engines that contain exhaust treatment devices are requiring a reduction in the phosphorus and metal content of engine oils used in these engines. This reduction in the phosphorus and metal content of engine oils is being implemented because it is thought that they can adversely affect the performance of exhaust treatment devices.

However, any reduction in the performance of catalytic converters caused by phosphorus poisoning tends to result in increased amounts of greenhouse gases such as nitric oxide and/or ash formation. Furthermore, reducing the amount of ZDDP will increase the amount of wear in an engine crankcase.

In an internal combustion engine with a wet-clutch (e.g. a 4-stroke motorcycle engine) legislation regulating exhaust emissions affects/restricts the amount of emissions. However, as the internal combustion engine has a common oil reservoir, the oil must be suitable for a crankcase application and a gear, a transmission system or a clutch mechanism which all have higher operating conditions resulting in a severe wear environment. Therefore removing antiwear chemistry, such as, a phosphorus containing compound will tend to increase the viscosity modifier (with a number average molecular weight of 100,000 or more) is employed in combination with reduced amounts of antiwear chemistry, it is believed that surface film break down due to the viscosity modifier shear will give rise to increased wear. The surface film break down is believed to be due to reduction in high temperature viscosity of a lubricating oil proportional to the rate of shear of the viscosity modifier.

It would be advantageous to have a method of viscosity control for an internal combustion engine with a wet-clutch capable of imparting at least one of wear control, acceptable fuel economy, acceptable high temperature viscometrics and increased lubricant oil service drains. The present invention provides a method of viscosity control for said internal combustion engine and capable of imparting at least one of wear control, acceptable fuel economy, acceptable high temperature viscometrics and increased lubricant oil service drains.

SUMMARY OF THE INVENTION

This invention provides a method of lubricating an internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch, said method comprising supplying to said crankcase and to at least one of the gear and wet-clutch a lubricating composition comprising: (a) an oil of lubricating viscosity; and (b) a viscosity modifier with a number average molecular weight from 1000 to 75,000, wherein the lubricating composition has a SAE viscosity grade from XW—Y, wherein X is from 0 to 20 and Y is from 20 to 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a method of lubricating an internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch, said method comprising supplying to said crankcase and to at least one of the gear and wet-clutch a lubricating composition comprising: (a) an oil of lubricating viscosity; and (b) a viscosity modifier with a number average molecular weight from 1000 to 75,000, wherein the lubricating composition has a SAE viscosity grade from XW—Y, wherein X is from 0 to 20 and Y is from 20 to 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less.

The internal combustion engine of the invention typically comprises a crankcase, a gear and a wet-clutch. Optionally the internal combustion engine further comprises a manual or automatic transmission. In one embodiment the gear is from a gearbox.

As used herein the term “wet-clutch” is known to a person skilled in the art as meaning one that contains a clutch plate(s) that is bathed or sprayed by a lubricant, e.g., that of the transmission, and the lubricating oil gets between the plate(s).

In one embodiment the internal combustion engine has a common oil reservoir supplying the same lubricating composition to the crankcase and at least one of a gear and a wet-clutch. In certain embodiments the lubricating composition is supplied to the crankcase and to the gear (or multiplicity of gears), or to the crankcase and the wet clutch, or to the crankcase and both the gear (or gears) and the wet clutch.

In one embodiment the internal combustion engine is a 4-stroke engine. In one embodiment the internal combustion engine is also referred to generically as a small engine.

The small engine in one embodiment has a power output of 2.24 to 18.64 kW (3 to 25 horsepower (hp)), in another embodiment 2.98 to 4.53 kW (4 to 6 hp) and in another embodiment exhibits 100 or 200 cm³ displacement. Examples of small engines include those in home/garden tools such as lawnmowers, hedge trimmers, chainsaws, snow blowers or roto-tillers.

In one embodiment the internal combustion engine has a capacity of up to 3500 cm³ displacement, in another embodiment up to 2500 cm³ displacement and in another embodiment up to 2000 cm³ displacement. Examples of suitable internal combustion engines with a capacity up to 2500 cm³ displacement include motorcycles, snowmobiles, jet-skis, quad-bikes, or all-terrain vehicles. In one embodiment the internal combustion engine is a tractor or other agricultural vehicle such as a combined harvester.

In one embodiment the internal combustion engine is not a tractor or other agricultural vehicle. In another embodiment the internal combustion engine does not contain a dry-clutch i.e. a system that separates the engine from the transmission such as a transmission on an automotive vehicle. In another fuel.

In one embodiment the internal combustion engine is suitable for motorcycles for example motorcycles with a 4-stroke internal combustion engine.

Oil of Lubricating Viscosity

The lubricating composition includes natural or synthetic oils of lubricating viscosity; oil derived from hydrocracking, hydrogenation or hydrofinishing; and unrefined, refined and re-refined oils, and mixtures thereof.

Natural oils include animal oils, vegetable oils, mineral oils and mixtures thereof. Synthetic oils include hydrocarbon oils, silicon-based oils, and liquid esters of phosphorus-containing acids. Synthetic oils may be produced by Fischer-Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils. In one embodiment the polymer composition of the present invention is useful when employed in a gas-to-liquid oil. Often Fischer-Tropsch hydrocarbons or waxes may be hydroisomerised.

In one embodiment the base oil is a polyalphaolefin (PAO) including a PAO-2, PAO-4, PAO-5, PAO-6, PAO-7 or PAO-8 (the numerical value relating to Kinematic Viscosity at 100° C.). The polyalphaolefin in one embodiment is prepared from dodecene and in another embodiment from decene. Generally, the polyalphaolefin suitable as an oil of lubricating viscosity has a less than that of a PAO-20 or PAO-30 oil, the reason being that a polyalphaolefin with a viscosity higher than a PAO-30 is typically too viscous for effective lubrication of an internal combustion engine.

Oils of lubricating viscosity may also be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. In one embodiment the oil of lubricating viscosity comprises an API Group I, II, III, IV, V, VI oil or mixtures thereof, and in another embodiment API Group II, III, IV oil or mixtures thereof. In another embodiment the oil of lubricating viscosity is a Group III or IV base oil and in another embodiment a Group IV base oil. If the oil of lubricating viscosity is an API Group II, III, IV, V or VI oil there may be up to 40 wt % and in another embodiment up to a maximum of 5 wt % of the lubricating oil an API Group I oil present.

grade from XW—Y, wherein X is from 0 to 20 and Y is from 20 to 50.

In one embodiment X is chosen from 0, 5, 10, 15 or 20.

In one embodiment Y is chosen from 20, 25, 30, 35, 40, 45 or 50.

The oil of lubricating viscosity in one embodiment is present from 2 wt % to 99.5 wt % of the lubricating composition, in another embodiment from 29 wt % to 98.25 wt % of the lubricating composition and in another embodiment from 40 wt % to 97 wt % of the lubricating composition. Examples of suitable amounts of an oil of lubricating viscosity include 55 wt %, 60 wt %, 65 wt %, 70 wt %, 75 wt % or 80 wt %.

Viscosity Modifier

The viscosity modifier of the invention includes at least one of the following polymers such as:

• • (a) polyalkenes or derivative thereof (such as polyisobutene, olefin copolymers such as ethylene-alpha-olefin copolymers or ethylene-propylene polymers);
  • (b) polyalphaolefins (which can be a type of polyalkene (a));
  • (c) alpha-olefin-unsaturated carboxylic reagent copolymers;
  • (d) poly(meth)acrylates;
  • (e) interpolymers derived from the polymerisation of a vinyl aromatic monomer and an unsaturated carboxylic acid or derivatives thereof; and
  • (f) mixtures thereof.

The viscosity modifier in one embodiment is present from 0.5 wt % to 95 wt %, in another embodiment 0.75 wt % to 70 wt % and in another embodiment 1 wt % to 40 wt % of the lubricating composition. Examples of a suitable amount of viscosity modifier include 8 wt %, 10 wt %, 12 wt %, 14 wt %, 16 wt %, 18 wt %, 20 wt %, 22 wt %, 24 wt %, 30 wt %, 35 wt %, or 55 wt %.

The viscosity modifiers (which may also be dispersant viscosity modifiers, as further described below) are known in the art and commercially available from a number of corporations, including The Lubrizol Corporation, Degussa AG and Rohmax GmbH.

(SSI) as determined by CEC L-45-A-99 of 22 or less, 20 or less or 18 or less. In one embodiment the viscosity SSI is 2 or more or 4 or more. Examples of suitable ranges of SSI include 2 to 22 or 4 to 18.

In one embodiment the viscosity modifier has a number average molecular weight from 1000 to 75,000, in another embodiment 2000 to 60,000, in another embodiment 6000 to 50,000 and in another embodiment 8000 to 40,000. In one embodiment the viscosity modifier has a number average molecular weight from 1000 to 20,000 and in another embodiment from 25,000 to 40,000. In one embodiment the dispersant viscosity modifier has a number average molecular weight that is the same as the ranges given for the viscosity modifier.

In one embodiment the viscosity modifier is a dispersant viscosity modifier. The polymeric dispersant viscosity modifier may be derived from a functionalised polyolefin, an esterified polymer derived from: (i) a vinyl aromatic monomer; and (ii) an unsaturated carboxylic acid or derivatives thereof; or mixtures thereof.

Poly(Meth)Acrylates

In one embodiment the viscosity modifier can be a poly(meth)acrylate with a number average molecular weight of 10,000 to 35,000, 12,000 to 20,000 or 25,000 to 35,000.

In one embodiment the poly(meth)acrylate viscosity modifier includes copolymers of (i) a methacrylic acid ester containing 9 to 30 carbons in the ester group, (ii) a methacrylic acid ester containing 7 to 12 carbons in the ester group wherein the ester group contains a 2-(C_1-4 alkyl)-substituents and optionally (iii) at least one monomer selected from the group consisting of a methacrylic acid ester containing from 2 to 8 carbon atoms in the ester group and which are different from methacrylic acid esters used in (i) and (ii) above. A more detailed description of polymethacrylate viscosity modifiers can be found in U.S. Pat. No. 6,124,249.

In one embodiment the viscosity modifier is a functionalized poly(meth)acrylate. The poly(meth)acrylate is functionalized with a nitrogen containing monomer thus forming a dispersant viscosity modifier. In one embodiment the nitrogen containing monomer is incorporated into the poly(meth)acrylate through standard copolymerization techniques. The nitrogen a dialkylaminoalkyl(meth)acrylate monomer, a dialkylaminoalkyl (meth)acrylamide monomer, a tertiary-(meth)acrylamide monomer and mixtures thereof. The alkyl groups can contain 1 to 8, or from 1 to 3 carbon atoms. In one embodiment, the dispersant viscosity modifier is a poly(meth)acrylate.

Useful nitrogen containing monomers include vinyl pyridine, N-vinyl imidazole, N-vinyl pyrrolidinone, and N-vinyl caprolactam, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminobutylacrylamide dimethylamine propyl methacrylate, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, dimethylaminoethylacrylamide, tertiary butyl acrylamide or mixtures thereof.

The poly(meth)acrylate polymeric dispersant viscosity modifier includes a copolymer derived from a (meth)acrylate monomer containing an alkyl group with 1 to 30 carbon atoms, in another embodiment 1 to 26 carbon atoms and in another embodiment 1 to 20 carbon atoms. The alkyl group includes mixtures derived from an alcohol containing 1 to 4 carbon atoms, 8 to 10 carbon atoms, 12 to 14 carbon atoms, 12 to 15 carbon atoms, 16 to 18 carbon atoms or 16 to 20 carbon atoms. Examples of commercially available alcohol mixtures include the following products sold under the brand names of Dobanol™ 25, Neodol™ 25, Lial™ 125, and Alchem™ 125. In one embodiment the alcohol is a single alcohol, i.e., not a mixture.

The (meth)acrylate monomer includes those derived from natural or synthetic sources. When derived by synthetic sources the (meth)acrylate monomer may be prepared using known direct esterification and/or transesterification processes.

In one embodiment the poly(meth)acrylate polymeric dispersant viscosity modifier is derived from a methyl(meth)acrylate monomer and at least one other (meth)acrylate monomer including an alkyl group with 8 to 20 carbon atoms, in another embodiment 10 to 18 carbon atoms and in another embodiment 12 to 15 carbon atoms. The methyl(meth)acrylate monomer is in the range from 1 wt % or more of the poly(meth)acrylate, in another embodiment in the range from 8 wt % or more of the poly(meth)acrylate and in another embodiment in the range from 10 wt % or more of the poly(meth)acrylate. Upper limits on the amount of methyl(meth)acrylate include 40 wt % of the poly(meth)acrylate, in embodiment 20 wt % of the poly(meth)acrylate.

Polyalphaolefins

In one embodiment the viscosity modifier can be one or more polyalphaolefins having a kinematic viscosity at 100° C. from 40 mm/s (cSt) to 100 mm/s (cSt). In one embodiment a polyalphaolefin viscosity modifier is PAO-40, PAO-50, PAO-60 or PAO-80. In one embodiment the polyalphaolefin's number average molecular weight is from 1400 to 2000. Generally the polyalphaolefin viscosity modifier is too viscous to be considered as an oil of lubricating viscosity.

In one embodiment the olefin copolymers have a number average molecular weight of 14,500 to 70,000.

Interpolymers

In one embodiment the viscosity modifier can be a polymeric dispersant viscosity modifier such as an esterified polymer derived from monomers comprising: (i) a vinyl aromatic monomer; and (ii) an unsaturated carboxylic acid or derivatives thereof. The polymer prior to esterification is generally referred to as an interpolymer. In one embodiment the esterified polymer is substantially free of to free of a (meth)acrylate ester. In one embodiment the interpolymer is a styrene-maleic anhydride copolymer. In one embodiment the esterified polymer contains a nitrogen derived from a nitrogen containing compound capable of reacting with a functionalised polymer backbone to form an amidated polymer.

The molecular weight of the interpolymer may also be expressed in terms of the “reduced specific viscosity” of the polymer which is a recognized means of expressing the molecular size of a polymeric substance. As used herein, the reduced specific viscosity (abbreviated as RSV) is the value obtained in accordance with the formula RSV=(Relative Viscosity−1)/Concentration, wherein the relative viscosity is determined by measuring, by means of a dilution viscometer, the viscosity of a solution of 1 g of the polymer in 10 cm³ of acetone and the viscosity of acetone at 30° C. For purpose of computation by the above formula, the concentration is adjusted to 0.4 g of the interpolymer per 10 cm³ of acetone. A more detailed discussion of the reduced specific viscosity, also known as the specific viscosity, as well as its relationship to the average molecular weight of an interpolymer, appears in Paul J. Flory, Principles of interpolymer polymer of the invention has a RSV in the range of 0.05 to 2 in another embodiment 0.06 to 1, in another embodiment 0.06 to 0.8 and in another embodiment 0.07 to 0.2. In another embodiment the RSV is 0.12. In one embodiment the interpolymer number average molecular weight is 10,000 to 40,000.

Examples of a vinyl aromatic monomer include styrene (often referred to as ethenylbenzene), substituted styrene or mixtures thereof. Substituted styrene monomers include functional groups such as a hydrocarbyl group, halo-, amino-, alkoxy-, carboxy-, hydroxy-, sulphonyl- or mixtures thereof. The functional groups include those located at the ortho, meta or para positions relative to the vinyl group on the aromatic monomer, the functional groups are located at the ortho or para position being especially useful. In one embodiment the functional groups are located at the para position. Halo-functional groups include chlorine, bromine, iodine or mixtures thereof. In one embodiment the halo functional group is chlorine or mixtures thereof. Alkoxy functional groups may contain 1 to 10 carbon atoms, in another embodiment 1 to 8 carbon atoms, in another embodiment 1 to 6 carbon atoms and in yet another embodiment 1 to 4 carbon atoms. Alkoxy functional groups containing 1 to 4 carbon atoms is referred to as lower alkoxy styrene.

The hydrocarbyl group includes ranges from 1 to 30 carbon atoms, in another embodiment 1 to 20 carbon atoms, in another embodiment 1 to 15 carbon atoms and in yet another embodiment 1 to 10 carbon atoms. Examples of a suitable hydrocarbyl group on styrene monomers include alpha-methylstyrene, para-methylstyrene (often referred to as vinyl toluene), para-tert-butylstyrene, alpha-ethylstyrene, para-lower alkoxy styrene or mixtures thereof.

In one embodiment the alpha-olefin-unsaturated carboxylic reagent copolymer has a number average molecular weight of 15,000 to 40,000.

Polyalkene or Derivatives Thereof

In one embodiment, the viscosity modifier is a polyalkene or derivatives thereof. In one embodiment the polyalkene or derivative thereof can have a number average molecular weight of 2300 to 25,000. The polyalkene includes homopolymers and interpolymers of olefins having from 2 to 40, or from 3 to 24, or from 4 to 12 carbon atoms. The olefins may be monoolefins, monomers, including diolefinic monomers such 1,3-butadiene and isoprene. The alpha-olefins generally have from 4 to 30, or from 8 to 18 carbon atoms. These olefins are sometimes referred to as mono-1-olefins or terminal olefins. The alpha-olefins and isomerized alpha-olefins include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-heneicosene, 1-docosene, and 1-tetracosene. Commercially available alpha-olefin fractions that can be used include the C15-18 alpha-olefins, C12-16 alpha-olefins, C14-16 alpha-olefins, C14-18 alpha-olefins, C16-18 alpha-olefins, C16-20 alpha-olefins, C18-24 alpha-olefins, and C22-28 alpha-olefins. The polyalkenes may be prepared by conventional procedures. The polyalkenes are described in U.S. Pat. Nos. 3,219,666 and 4,234,435. Examples of polyalkenes include polypropylenes, polybutylenes, polyisoprene and polybutadienes. In one embodiment, the polyalkene is a homopolymer, such as a polyisobutene. One example of a useful polybutene is a polymer where 50% of the polymer is derived from isobutylene.

In another embodiment, the viscosity modifier is an ethylene-alpha-olefin copolymer. Typically, the copolymer is a random copolymer. The copolymer generally has from 30% to 80%, or from 50% to 75% by mole of ethylene. The alpha-olefins include butene, pentene, hexene or one more of the above-described alpha-olefins. In one embodiment, the alpha-olefin contains from 3 to 20, or from 4 to 12 carbon atoms. In one embodiment, the ethylene-alpha-olefin copolymers have a number average molecular weight from 800 to 6000, or from 1500 to 5000, or from 2000 to 4500. Examples of ethylene alpha-olefins copolymers include ethylene-butene copolymers and ethylene-octene copolymers. Examples of commercially available copolymers include Lucant™ HC 600 and Lucant™ HC 2000 (Mw=25,000), available from Mitsui Petrochemical Co. Ltd.

In another embodiment, the viscosity modifier is an ethylene propylene polymer. These polymers include ethylene propylene copolymers and ethylene propylene terpolymers. When the ethylene propylene polymer is an ethylene propylene copolymer (EPM, also called EPR polymers), it may be formed by copolymerization of ethylene and propylene under known conditions propylene copolymer contains units derived from ethylene in an amount from 40 mol % to 70 mol %, or from 50 mol % to 60 mol %, or 55 mol %, the remainder being derived from propylene.

In another embodiment, the ethylene propylene polymer is a terpolymer of ethylene, propylene and a diene monomer. In one embodiment, the diene is a conjugated diene. The dienes are disclosed above. The terpolymers are produced under similar conditions as those of the ethylene propylene copolymers. The preferred terpolymers contain units derived form ethylene in amount from 10% to 80%, or from 25% to 85%, or 35% to 60% by mole, and units derived from propylene in amount from 15% to 70%, or from 30% to 60% by mole, and units derived from diene third monomer in amount from 0.5% to 20%, or from 1% to 10%, or 2% to 8% by mole.

In one embodiment the polyalkene or derivatives thereof is a dispersant viscosity modifier. Typically a dispersant viscosity modifier from polyalkene or derivatives thereof is prepared by the reaction of (a) a polyalklene; (b) an acylating agent such as maleic anhydride; and (c) an amine.

The amine includes a monoamine, a polyamine or mixtures thereof. The amine includes primary functionality, secondary functionality or mixtures thereof. The amine includes cyclic, linear or branched structures, and examples include an alkylenemonoamine, a heterocyclic monoamine, an alkylenepolyamine, a heterocyclic polyamine or mixtures thereof. In one embodiment the amine contains not more than one primary or secondary amino group, for example N,N-dimethylaminopropylamine.

In one embodiment the amine may be a hydroxy-substituted hydrocarbyl amine such as a hydroxyalkyl amine. Examples of a suitable hydroxy-substituted hydrocarbyl amine include aminoethyl ethanolamine, aminopropyl ethanolamine, aminobutyl ethanolamine or mixtures thereof.

In one embodiment the amine includes compounds that are represented by the formula:

w is the number of R¹ atoms, including ranges from 4 to 16 atoms, in another embodiment 5 to 12 atoms, and in another embodiment 5 to 8 atoms;

y is the number of carbon atoms associated with R², including ranges from 1 to 8, in another embodiment 1 to 6, and in another embodiment 2 to 5 carbon atoms;

R¹ is independently an atom including carbon, oxygen, nitrogen, phosphorus or mixtures thereof;

R² is an alkyl or an alkenyl group with containing y carbon atoms, especially useful examples of R² including ethyl, propyl or mixtures thereof; and

R³ and R⁴ are independently hydrogen or a hydrocarbyl group; in another embodiment at least one is hydrogen, and in another embodiment both are hydrogen.

When R³ or R⁴ is a hydrocarbyl group, the number of carbon atoms present therein is in the range from 1 to 8, in another embodiment in the range from 1 to 5 and in another embodiment in the range from 1 to 3. Examples of a hydrocarbyl group include methyl, ethyl, propyl, butyl, pentyl or mixtures thereof.

Formula (I) represents a compound that includes a mononuclear cyclic structure, a polynuclear cyclic structure or mixtures thereof. When formula (I) represents a mononuclear structure, w in one embodiment ranges from 5 to 8 and in another embodiment 6 to 7. When formula (I) represents a polynuclear cyclic structure w in one embodiment ranges from 8 to 16 and in another embodiment 10 to 12. The cyclic ring includes aromatic, non-aromatic or mixtures thereof, although a non-aromatic ring is especially useful.

Suitable cyclic amines include 4-aminodiphenylamine, 4-(3-aminopropyl)morpholine, 4-(2-aminoethyl)morpholine or mixtures thereof. In one embodiment the cyclic amine is 4-(3-aminopropyl)morpholine or mixtures thereof.

Metal Hydrocarbyl Dithiophosphate

In one embodiment of the invention the composition further contains a metal hydrocarbyl dithiophosphate. The amount of the metal hydrocarbyl dithiophosphate present is enough to provide a phosphorus content in the % or less.

In one embodiment the phosphorus content in the lubricating composition from a metal hydrocarbyl dithiophosphate is below 0.1 wt %, in another embodiment below 0.085 wt %, in another embodiment below 0.06 wt % or lower. In one embodiment the lower limit of the phosphorus content in the lubricating composition from a metal hydrocarbyl dithiophosphate is 0 ppm or higher, in another embodiment 50 ppm or higher, in another embodiment 125 ppm or higher and in another embodiment 200 ppm or higher. Examples of suitable ranges include 50 ppm to 0.1 wt % or 125 ppm to 0.085 wt %.

Examples of a metal hydrocarbyl dithiophosphate include zinc dihydrocarbyl dithiophosphates (often referred to as ZDDP, ZDP or ZDTP). In one embodiment the number of carbon atoms of each hydrocarbyl group is 2 to 30, 3 to 14 or 4 to 10.

Examples of suitable zinc hydrocarbyl dithiophosphates compounds may include those with a hydrocarbyl group of octyl, 2-ethylhexyl, methylpentyl-isopropyl. 2-ethylhexyl-isopropyl, pentyl-isobutyl or mixtures thereof.

Additional Performance Additives

In one embodiment of the invention the composition optionally includes at least one additional performance additive. The additional performance additive includes at least one of metal deactivators, detergents, dispersants, extreme pressure agents, antiwear agents, antioxidants, corrosion inhibitors, foam inhibitors, demulsifiers, pour point depressants, friction modifiers, seal swelling agents and mixtures thereof. In one embodiment the additional performance additives may be used alone or in combination.

In one embodiment the total combined amount of the other performance additive compounds present ranges from 0 wt % to 30 wt %, in another embodiment from 1 wt % to 25 wt % and in another embodiment 2 wt % to 20 wt % or from 3 wt % to 10 wt % of the lubricating composition. Although one or more of the other performance additives may be present, it is common for the other additional performance additives to be present in different amounts relative to each other.

combined with additional oil to form, in whole or in part, a finished lubricant), the ratio of the various additives to the oil of lubricating viscosity and/or to diluent oil include the ranges of 80:20 to 10:90 by weight.

Friction modifiers include fatty amines, esters such as borated glycerol esters, fatty phosphites, fatty acid amides, fatty epoxides, borated fatty epoxides, alkoxylated fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, fatty imidazolines, condensation products of carboxylic acids and polyalkylene-polyamines, amine salts of alkylphosphoric acids, molybdenum dithiocarbamate or mixtures thereof. Antioxidants include sulphurised olefins, hindered phenols, diphenylamines. Detergents include neutral or overbased, Newtonian or non-Newtonian, basic salts of alkali, alkaline earth and transition metals with one or more of a phenate, a sulphurised phenate, a sulphonate, a carboxylic acid, a phosphorus acid, a mono- and/or a di-thiophosphoric acid, a saligenin, an alkylsalicylate, a salixarate or mixtures thereof. Dispersants include N-substituted long chain alkenyl succinimide as well as post-treated versions thereof. Post-treated dispersants include those further treated by reaction with materials such as urea, boron, thiourea, dimercaptothiadiazoles, carbon disulphide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitriles, epoxides and phosphorus compounds.

Antiwear agents include compounds such as metal thiophosphates, especially zinc dialkyldithiophosphates; phosphoric acid esters or salt thereof; phosphites; and phosphorus-containing carboxylic esters, ethers, and amides; antiscuffing agents including organic sulphides and polysulphides, such as benzyldisulphide, bis-(chlorobenzyl)disulphide, dibutyl tetrasulphide, di-tertiary butyl polysulphide, di-tert-butylsulphide, sulphurised Diels-Alder adducts or alkyl sulphenyl N′N-dialkyl dithiocarbamates. Extreme pressure (EP) agents including chlorinated wax, organic sulphides and polysulphides, such as benzyldisulphide, bis-(chlorobenzyl)disulphide, dibutyl tetrasulphide, sulphurised methyl ester of oleic acid, sulphurised alkylphenol, sulphurised dipentene, sulphurised terpene, and sulphurised Diels-Alder adducts; phosphosulphurised hydrocarbons, metal thiocarbamates, such as zinc dioctyldithiocarbamate and barium heptylphenol diacid; may also be used in the composition of the invention.

octylamine octanoate, condensation products of dodecenyl succinic acid or anhydride and a fatty acid such as oleic acid with a polyamine; metal deactivators including derivatives of benzotriazoles, thiadiazoles such as dimercaptohtiadiazole and its derivatives, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles or 2-alkyldithiobenzothiazoles; foam inhibitors including copolymers of ethyl acrylate and 2-ethylhexylacrylate and optionally vinyl acetate; demulsifiers including polyethylene glycols, polyethylene oxides, polypropylene oxides and (ethylene oxide-propylene oxide) polymers; pour point depressants including esters of maleic anhydride-styrene, polymethacrylates, polyacrylates or polyacrylamides; and seal swell agents including Exxon Necton-37™ (FN 1380) and Exxon Mineral Seal Oil (FN 3200); may also be used in the composition of the invention.

The following examples provide an illustration of the invention. These examples are non exhaustive and are not intended to limit the scope of the invention.

EXAMPLES

Example 1 and Reference Examples 1-2

Lubricating compositions are prepared by blending additives as shown in Table I into a 10W-40 lubricant. The lubricating compositions have a phosphorus content in the lubricating composition from a metal hydrocarbyl dithiophosphate of less than 0.12 wt %. The compositions prepared are:

	TABLE 1
			Number Average
	Example	Polymer Type	Molecular Weight
	REF1	Commercially available	Over 100,000
		Olefin copolymer
	REF2	Commercially available	84,000
		Olefin copolymer
	EX1	Polymethacrylate	15,000

A viscosity test to determine Shear Stable Index (SSI) is carried out employing (i) a KRL Rig at 80° C. for 20 hours and the methodology of CEC L-45-A-99; and (ii) separately an Orbahn™ Rig and the methodology of CEC-14-A-93_—30. Generally, better results are obtained for examples with lower percentage reductions in viscosity. Further acceptable results are obtained when the percentage loss in viscosity is 12% or less. The results obtained are shown in Table 2.

	TABLE 2
	SOT	EOT	% Loss	SSI	SSI
Example	KRL Rig	(Orbahn)
REF1	KV100	14.96	7.94	46.93	76	25
	KV40	98.2	48.50	50.61	—	—
REF2	KV100	11.86	10.30	13.15	26	0
	KV40	77.39	65.52	15.34	—	—
EX1	KV100	12.72	11.68	8.18	14	0
	KV40	83.60	75.35	9.87	—	—
Footnote to Table 2, SOT is defined as Start of Test; and EOT is defined as End of Test and “—“ represents unmeasured values.

The results indicate that the presence of the viscosity modifier with a number average molecular weight from 1000 to 75,000 has acceptable shear stability and is suitable for viscosity control in an internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch. Further, the viscosity modifier is capable of imparting at least one of wear control, acceptable fuel economy, acceptable high temperature viscometrics and increased lubricant oil service drains. Furthermore, the results indicate that a polymer with a low Shear Stability Index of 26 and a number average molecular weight of above 75,000 provides poor a viscosity control performance.

In this specification the terms “hydrocarbyl substituent” or “hydrocarbyl group,” as used herein are used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group primarily composed of carbon and hydrogen atoms and attached to the remainder of the other atoms or groups in a proportion insufficient to detract from the molecule having a predominantly hydrocarbon character. In general, no more than two, in one aspect no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group. A more detailed definition of the terms “hydrocarbyl substituent” or “hydrocarbyl group,” is provided in U.S. Pat. No. 6,583,092.

As used herein the term poly(meth)acrylate and other generic stems with (meth)acryl means polymethacrylate, polyacrylate or other acryl or methacryl moieties.

Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention may be used together with ranges or amounts for any of the other elements.

Claims

1. A method of lubricating an internal combustion engine comprising a crankcase and at least one of a gear and a wet-clutch, said method comprising supplying to said crankcase and to at least one of said gear and wet-clutch a lubricating composition comprising:

(a) an oil of lubricating viscosity; and

(b) a viscosity modifier with a number average molecular weight from about 1000 to about 75,000,

wherein the lubricating composition has a SAE viscosity grade from XW—Y, wherein X is from 0 to about 20 and Y is from about 20 to about 50; and wherein the lubricating composition has a phosphorus content from a metal hydrocarbyl dithiophosphate of 0.12 wt % or less.

2. The method of claim 1, wherein the internal combustion engine has a common oil reservoir supplying the same lubricating composition to the crankcase and at least one of a gear and a wet-clutch.

3. The method of claim 1, wherein the lubricating composition is supplied to the crankcase and to the gear (or multiplicity of gears).

4. The method of claim 1, wherein the lubricating composition is supplied to the crankcase and the wet clutch.

5. The method of claim 1, wherein the lubricating composition is supplied to the crankcase and both the gear (or gears) and the wet clutch.

6. The method of claim 1, wherein the internal combustion engine is a 4-stroke engine.

7. The method of claim 6, wherein the 4-stroke engine is a motorcycle engine.

8. The method of claim 1, wherein the viscosity modifier includes at least one of:

(a) polyalkenes or a derivative thereof;

(b) polyalphaolefins;

(c) alpha-olefin-unsaturated carboxylic reagent copolymers;

(d) poly(meth)acrylates; aromatic monomer and an unsaturated carboxylic acid or derivatives thereof; or

(f) mixtures thereof.

9. The method of claim 1, wherein the viscosity modifier has a number average molecular weight 2000 to 60,000, or 8000 to 40,000.

10. The method of claim 1, wherein the viscosity modifier has a number average molecular weight from 1000 to 20,000, or from 25,000 to 40,000.

11. The method of claim 1, wherein the viscosity modifier is a poly(meth)acrylate.

12. The method of claim 11, wherein the viscosity modifier is a functionalized poly(meth)acrylate.

13. The method of claim 12, wherein the poly(meth)acrylate is functionalized with a nitrogen containing monomer.

14. The method of claim 1, wherein the viscosity modifier is present from 0.5 wt % to 95 wt %, or from 1 wt % to 40 wt % of the lubricating composition.

15. The method of claim 1, wherein the viscosity modifier has a Shear Stability Index (SSI) as determined by CEC L-45-A-99 of 22 or less.

16. The method of claim 1, wherein the viscosity modifier has a Shear Stability Index (SSI) as determined by CEC L-45-A-99 of 4 to 18.