LUBRICATING COMPOSITION
A lubricating composition for use in the crankcase of an engine comprising a base oil and one or more additives, wherein the lubricating composition comprises from 0.01 wt % to 5 wt %, by weight of the lubricating composition, of one or more liquid crystal compounds, wherein the one or more liquid crystal compounds is a terphenyl compound. The lubricating composition provides improvements in terms of reduced friction and wear, in addition to improved fuel economy performance.
This non-provisional application claims priority from U.S. Provisional Application Ser. No. 61/815,011 filed Apr. 23, 2013, which is hereby incorporated by reference in its entirety.
The present invention relates to a lubricating oil composition, in particular to a lubricating oil composition which is suitable for lubricating internal combustion engines and which has improved friction and wear reduction and improved fuel economy.
Increasingly severe automobile regulations in respect of emissions and fuel efficiency are placing increasing demands on both engine manufacturers and lubricant formulators to provide effective solutions to improve fuel economy.
Optimising lubricants through the use of high performance basestocks and novel additives represents a flexible solution to a growing challenge.
Friction-reducing additives (which are also known as friction modifiers) are important lubricant components in reducing fuel consumption and various such additives are already known in the art.
Friction modifiers can be conveniently divided into two categories, that is to say, metal-containing friction modifiers and ashless (organic) friction modifiers.
Organo-molybdenum compounds are amongst the most common metal-containing friction modifiers. Typical organo-molybdenum compounds include molybdenum dithiocarbamates (MoDTC), molybdenum dithiophosphates (MoDTP), molybdenum amines, molybdenum alcoholates, and molybdenum alcohol-amides. WO-A-98/26030, WO-A-99/31113, WO-A-99/47629 and WO-A-99/66013 describe tri-nuclear molybdenum compounds for use in lubricating oil compositions.
However, the trend towards low-ash lubricating oil compositions has resulted in an increased drive to achieve low friction and improved fuel economy using ashless friction modifiers.
Ashless (organic) friction modifiers which have been used in the past typically comprise esters of fatty acids and polyhydric alcohols, fatty acid amides, amines derived from fatty acids and organic dithiocarbamate or dithiophosphate compounds.
However, current strategies with regard to friction reduction for fuel economy oils are not sufficient to meet ever increasing fuel economy targets set by Original Equipment Manufacturers (OEMs).
For example, molybdenum friction modifiers typically outperform ashless friction modifiers in the boundary regime and there is a challenge to approach similar levels of friction modification using solely ashless friction modifiers.
Thus, given the increasing fuel economy demands placed on engines, there remains a need to further improve the friction reduction and fuel economy of internal combustion engines utilising low ash lubricating oil compositions.
Liquid crystalline components have not attracted as much attention within the field of lubrication as have more conventional chemical additives.
WO99/24533 discloses a friction reducing lubricant composition comprising a liquid crystal and a surfactant.
EP-A-567 649 discloses an electroviscous fluid containing an antioxidant and/or a metal corrosion inhibitor or solid particles as a dispersoid in an electrically insulating fluid as a dispersion medium consisting principally of a liquid crystal substance. Example 3 contains a mixtures of four liquid crystal substances namely: 4-cyano-4′-pentyl-biphenyl, 4-cyano-4′-septyl-biphenyl, 4-cyano-4′-octyloxy-biphenyl, and 4-cyano-4′-pentyl-terphenyl.
There has now been surprisingly found in the present invention a lubricating oil composition comprising ashless friction modifiers which has good friction and wear reduction and improved fuel economy.
Accordingly, the present invention provides a lubricating composition for use in the crankcase of an engine comprising a base oil and one or more additives, wherein the lubricating composition comprises from 0.01 wt % to 5 wt %, by weight of the lubricating composition, of one or more liquid crystal compounds, wherein the one or more liquid crystal compounds is a terphenyl compound.
By “liquid crystal” it is meant highly anisotropic fluids that exist between the boundaries of the solid and conventional isotropic liquid phase. The phase is a result of long-range orientational ordering among constituent molecules that occurs within certain ranges or temperature in melts and solutions of many organic compounds.
The one or more liquid crystal compounds is present in the lubricating composition at a level of from 0.01 wt % to 5 wt o, preferably from 0.01 wt % to 4 wt %, more preferably from 0.1 wt % to 2 wt %, and especially from 0.2 wt % to 1 wt %, by weight of the lubricating composition.
Preferred terphenyl compounds for use herein include cyanoterphenyl compounds such as alkylterphenylnitriles and alkyletherterphenylnitriles and mixtures thereof.
Suitable terphenyl compounds for use herein have the following general formula I:
wherein X is CN, and R is a C1-C22 alkyl or C1-C22 alkylether group. Preferably the R group is a C1-C22 alkyl group, more preferably a C4-C16 alkyl group and even more preferably a C5-C10 alkyl group.
A particular preferred liquid crystal compound for use herein is 4-cyano-4′-pentyl-terphenyl. This compound is commercially available from Alfa-Aesar under the designation “T15”.
The total amount of base oil incorporated in the lubricating oil composition of the present invention is preferably present in an amount in the range of from 60 to 92 wt. %, more preferably in an amount in the range of from 75 to 90 wt. % and most preferably in an amount in the range of from 75 to 88 wt. %, with respect to the total weight of the lubricating oil composition.
There are no particular limitations regarding the base oil used in the present invention, and various conventional known mineral oils and synthetic oils may be conveniently used.
The base oil used in the present invention may conveniently comprise mixtures of one or more mineral oils and/or one or more synthetic oils.
Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic, or mixed paraffinic/naphthenic type which may be further refined by hydrofinishing processes and/or dewaxing.
Naphthenic base oils have low viscosity index (VI) (generally 40-80) and a low pour point. Such base oils are produced from feedstocks rich in naphthenes and low in wax content and are used mainly for lubricants in which colour and colour stability are important, and VI and oxidation stability are of secondary importance.
Paraffinic base oils have higher VI (generally >95) and a high pour point. Said base oils are produced from feedstocks rich in paraffins, and are used for lubricants in which VI and oxidation stability are important.
Fischer-Tropsch derived base oils may be conveniently used as the base oil in the lubricating oil composition of the present invention, for example, the Fischer-Tropsch derived base oils disclosed in EP-A-776959, EP-A-668342, WO-A-97/21788, WO-00/15736, WO-00/14188, WO-00/14187, WO-00/14183, WO-00/14179, WO-00/08115, WO-99/41332, EP-1029029, WO-01/18156 and WO-01/57166.
Synthetic processes enable molecules to be built from simpler substances or to have their structures modified to give the precise properties required.
Synthetic oils include hydrocarbon oils such as olefin oligomers (PAOs), dibasic acids esters, polyol esters, and dewaxed waxy raffinate. Synthetic hydrocarbon base oils sold by the Royal Dutch/Shell Group of Companies under the designation “XHVI” (trade mark) may be conveniently used.
Preferably, the base oil comprises mineral oils and/or synthetic oils which contain more than 80% wt of saturates, preferably more than 90% wt., as measured according to ASTM D2007.
It is further preferred that the base oil contains less than 1.0 wt. %, preferably less than 0.1 wt. % of sulphur, calculated as elemental sulphur and measured according to ASTM D2622, ASTM D4294, ASTM D4927 or ASTM D3120.
Preferably, the viscosity index of the base fluid is more than 80, more preferably more than 120, as measured according to ASTM D2270.
Preferably, the lubricating oil composition has a kinematic viscosity in the range of from 2 to 80 mm2/s at 100 ° C., more preferably of from 3 to 70 mm2/s, most preferably of from 4 to 50 mm2/s.
The total amount of phosphorus in the lubricating oil composition of the present invention is preferably in the range of from 0.04 to 0.12 wt. %, more preferably in the range of from 0.04 to 0.09 wt. % and most preferably in the range of from 0.045 to 0.08 wt. %, based on total weight of the lubricating oil composition.
The lubricating oil composition of the present invention preferably has a sulphated ash content of not greater than 2.0 wt. %, more preferably not greater than 1.0 wt. % and most preferably not greater than 0.8 wt. %, based on the total weight of the lubricating oil composition.
The lubricating oil composition of the present invention preferably has a sulphur content of not greater than 1.2 wt. %, more preferably not greater than 0.8 wt. % and most preferably not greater than 0.2 wt. %, based on the total weight of the lubricating oil composition.
The lubricating oil composition of the present invention may further comprise additional additives such as anti-oxidants, anti-wear additives, detergents, dispersants, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors, defoaming agents and seal fix or seal compatibility agents.
Antioxidants that may be conveniently used include those selected from the group of aminic antioxidants and/or phenolic antioxidants.
In a preferred embodiment, said antioxidants are present in an amount in the range of from 0.1 to 5.0 wt. %, more preferably in an amount in the range of from 0.3 to 3.0 wt. %, and most preferably in an amount in the range of from 0.5 to 1.5 wt. %, based on the total weight of the lubricating oil composition.
Examples of aminic antioxidants which may be conveniently used include alkylated diphenylamines, phenyl-α-naphthylamines, phenyl-β-naphthylamines and alkylated α-naphthylamines.
Preferred aminic antioxidants include dialkyldiphenylamines such as p,p′-dioctyl-diphenylamine, p,p′-di-α-methylbenzyl-diphenylamine and N-p-butylphenyl-N-p′-octylphenylamine, monoalkyldiphenylamines such as mono-t-butyldiphenylamine and mono-octyldiphenylamine, bis(dialkylphenyl)amines such as di-(2,4-diethylphenyl)amine and di(2-ethyl-4-nonylphenyl)amine, alkylphenyl-1-naphthylamines such as octylphenyl-1-naphthylamine and n-t-dodecylphenyl-1-naphthylamine, 1-naphthylamine, arylnaphthylamines such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine and N-octylphenyl-2-naphthylamine, phenylenediamines such as N,N′-diisopropyl-p-phenylenediamine and N,N′-diphenyl-p-phenylenediamine, and phenothiazines such as phenothiazine and 3,7-dioctylphenothiazine.
Preferred aminic antioxidants include those available under the following trade designations: “Sonoflex OD-3” (ex. Seiko Kagaku Co.), “Irganox L-57” (ex. Ciba Specialty Chemicals Co.) and phenothiazine (ex. Hodogaya Kagaku Co.).
Examples of phenolic antioxidants which may be conveniently used include C7-C9 branched alkyl esters of 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-benzenepropanoic acid, 2-t-butylphenol, 2-t-butyl-4-methylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-4-alkylphenols such as 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol and 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-alkoxyphenols such as 2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol, 3,5-di-t-butyl-4-hydroxybenzylmercaptooctylacetate, alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionates such as n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, n-butyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and 2′-ethylhexyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,6-d-t-butyl-α-dimethylamino-p-cresol, 2,2′-methylene-bis(4-alkyl-6-t-butylphenol) such as 2,2′-methylenebis(4-methyl-6-t-butylphenol, and 2,2-methylenebis(4-ethyl-6-t-butylphenol), bisphenols such as 4,4′-butylidenebis(3-methyl-6-t-butylphenol, 4,4′-methylenebis(2,6-di-t-butylphenol), 4,4′-bis(2,6-di-t-butylphenol), 2,2-(di-p-hydroxyphenyl)propane, 2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane, 4,4′-cyclohexylidenebis(2,6-t-butylphenol), hexamethyleneglycol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethyleneglycolbis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], 2,2′-thio-[diethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3,9-bis{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methyl-phenyl)propionyloxy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane, 4,4′-thiobis(3-methyl-6-t-butylphenol) and 2,2′-thiobis(4,6-di-t-butylresorcinol), polyphenols such as tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis-[3,3′-bis(4′-hydroxy-3′-t-butylphenyl)butyric acid]glycol ester, 2-(3′,5′-di-t-butyl-4-hydroxyphenyl)methyl-4-(2″,4″-di-t-butyl-3″-hydroxyphenyl)methyl-6-t-butylphenol and 2,6-bis(2′-hydroxy-3′-t-butyl-5′-methylbenzyl)-4-methylphenol, and p-t-butylphenol-formaldehyde condensates and p-t-butylphenol-acetaldehyde condensates.
Preferred phenolic antioxidants include those available under the following trade designations: “Irganox L-135” (ex. Ciba Specialty Chemicals Co.), “Yoshinox SS” (ex. Yoshitomi Seiyaku Co.), “Antage W-400” (ex. Kawaguchi Kagaku Co.), “Antage W-500” (ex. Kawaguchi Kagaku Co.), “Antage W-300” (ex. Kawaguchi Kagaku Co.), “Irganox L109” (ex. Ciba Speciality Chemicals Co.), “Tominox 917” (ex. Yoshitomi Seiyaku Co.), “Irganox L115” (ex. Ciba Speciality Chemicals Co.), “Sumilizer GA80” (ex. Sumitomo Kagaku), “Antage RC” (ex. Kawaguchi Kagaku Co.), “Irganox L101” (ex. Ciba Speciality Chemicals Co.), “Yoshinox 930” (ex. Yoshitomi Seiyaku Co.).
The lubricating oil composition of the present invention may comprise mixtures of one or more phenolic antioxidants with one or more aminic antioxidants.
In a preferred embodiment, the lubricating oil composition may comprise a single zinc dithiophosphate or a combination of two or more zinc dithiophosphates as anti-wear additives, the or each zinc dithiophosphate being selected from zinc dialkyl-, diaryl- or alkylaryl-dithiophosphates.
Zinc dithiophosphate is a well known additive in the art and may be conveniently represented by general formula II;
wherein R2 to R5 may be the same or different and are each a primary alkyl group containing from 1 to 20 carbon atoms preferably from 3 to 12 carbon atoms, a secondary alkyl group containing from 3 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, an aryl group or an aryl group substituted with an alkyl group, said alkyl substituent containing from 1 to 20 carbon atoms preferably 3 to 18 carbon atoms.
Zinc dithiophosphate compounds in which R2 to R5 are all different from each other can be used alone or in admixture with zinc dithiophosphate compounds in which R2 to R5 are all the same.
Preferably, the or each zinc dithiophosphate used in the present invention is a zinc dialkyl dithiophosphate.
Examples of suitable zinc dithiophosphates which are commercially available include those available ex. Lubrizol Corporation under the trade designations “Lz 1097” and “Lz 1395”, those available ex. Chevron Oronite under the trade designations “OLOA 267” and “OLOA 269R”, and that available ex. Afton Chemical under the trade designation “HITEC 7197”; zinc dithiophosphates such as those available ex. Lubrizol Corporation under the trade designations “Lz 677A”, “Lz 1095” and “Lz 1371”, that available ex. Chevron Oronite under the trade designation “OLOA 262” and that available ex. Afton Chemical under the trade designation “HITEC 7169”; and zinc dithiophosphates such as those available ex. Lubrizol Corporation under the trade designations “Lz 1370” and
“Lz 1373” and that available ex. Chevron Oronite under the trade designation “OLOA 260”.
The lubricating oil composition according to the present invention may generally comprise in the range of from 0.4 to 1.2 wt. % of zinc dithiophosphate, based on total weight of the lubricating oil composition.
Additional or alternative anti-wear additives may be conveniently used in the composition of the present invention.
Typical detergents that may be used in the lubricating oil of the present invention include one or more salicylate and/or phenate and/or sulphonate detergents.
However, as metal organic and inorganic base salts which are used as detergents can contribute to the sulphated ash content of a lubricating oil composition, in a preferred embodiment of the present invention, the amounts of such additives are minimised.
Furthermore, in order to maintain a low sulphur level, salicylate detergents are preferred.
Thus, in a preferred embodiment, the lubricating oil composition of the present invention may comprise one or more salicylate detergents.
In order to maintain the total sulphated ash content of the lubricating oil composition of the present invention at a level of preferably not greater than 2.0 wt. %, more preferably at a level of not greater than 1.0 wt. % and most preferably at a level of not greater than 0.8 wt. %, based on the total weight of the lubricating oil composition, said detergents are preferably used in amounts in the range of 0.05 to 20.0 wt. %, more preferably from 1.0 to 10.0 wt. % and most preferably in the range of from 2.0 to 5.0 wt. %, based on the total weight of the lubricating oil composition.
Furthermore, it is preferred that said detergents, independently, have a TBN (total base number) value in the range of from 10 to 500 mg.KOH/g, more preferably in the range of from 30 to 350 mg.KOH/g and most preferably in the range of from 50 to 300 mg.KOH/g, as measured by ISO 3771.
The lubricating oil compositions of the present invention may additionally contain an ash-free dispersant which is preferably admixed in an amount in the range of from 5 to 15 wt. %, based on the total weight of the lubricating oil composition.
Examples of ash-free dispersants which may be used include the polyalkenyl succinimides and polyalkenyl succininic acid esters disclosed in Japanese Patent Nos. 1367796, 1667140, 1302811 and 1743435. Preferred dispersants include borated succinimides.
Examples of viscosity index improvers which may be conveniently used in the lubricating oil composition of the present invention include the styrene-butadiene copolymers, styrene-isoprene stellate copolymers and the polymethacrylate copolymer and ethylene-propylene copolymers. Such viscosity index improvers may be conveniently employed in an amount in the range of from 1 to 20 wt. %, based on the total weight of the lubricating oil composition.
Polymethacrylates may be conveniently employed in the lubricating oil compositions of the present invention as effective pour point depressants.
Furthermore, compounds such as alkenyl succinic acid or ester moieties thereof, benzotriazole-based compounds and thiodiazole-based compounds may be conveniently used in the lubricating oil composition of the present invention as corrosion inhibitors.
Compounds such as polysiloxanes, dimethyl polycyclohexane and polyacrylates may be conveniently used in the lubricating oil composition of the present invention as defoaming agents.
Compounds which may be conveniently used in the lubricating oil composition of the present invention as seal fix or seal compatibility agents include, for example, commercially available aromatic esters.
The lubricating compositions of the present invention may be conveniently prepared using conventional formulation techniques by admixing base oil with the liquid crystal compound and one or more additives at a temperature of 60° C.
In another embodiment of the present invention, there is provided a method of lubricating an internal combustion engine comprising applying a lubricating oil composition as hereinbefore described thereto.
The present invention further provides the use of a lubricating composition as described herein for reducing friction.
The present invention further provides the use of a lubricating composition as described herein for reducing wear.
The present invention further provides the use of a lubricating composition as described herein for improving fuel economy.
The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way.
EXAMPLESTable 1 indicates the formulations that were tested. Said formulations were manufactured by blending together the components using conventional mixing techniques.
The Examples and Comparative Examples contained “America Core 600” as base oil, commercially available from Exxon Mobil. The Comparative Examples contained base oil only. The Examples according to the present invention contained 99 wt % base oil and 1 wt % T15 (4-cyano-4′-pentyl-terphenyl commercially available from Alfa-Aesar).
Boundary friction coefficient measurements for the Examples and Comparative Examples were obtained using a Plint TE-77 High Frequency Friction Machine (commercially available from Phoenix Tribology). A pin on plate geometry was used. The test plate was annealed ground gage cold worked tool steel plate (AISI-01; maximum hardness of 20 on the Rockwell C scale) surface ground in the direction of pin motion to a Ra roughness of 0.35-0.45 μm. A 16×6 mm pin (polished high carbon steel, 60-63 Rockwell C,) and was held in position on a moving arm against the stationary plate. Load was applied to the top of the reciprocating head.
A new test plate was placed in the specimen holder on the TE-77 with a new dowel pin placed in the movable arm. A few ml of lubricant was placed on the plate for each test (thin film lubrication). The test sequence was started. The TE-77 Friction Screener test conditions are summarised in Table 1. Wear measurements on the cylinder were conducted by stylus profilometry. After profilometry data collection was completed, the “curved” surface of the pin was “flattened”, so that the cylinder wear appeared as an apparent wear volume (obtained by multiplying the wear area times the wear length, μm3) and a maximum wear depth (nm).
The friction coefficient and wear measurements are shown in Table 2.
Table 2 shows that addition of 1 wt % of a liquid crystal terphenyl compound (T15) to a lubricating composition leads to a reduction in friction coefficient and wear.
Claims
1. A lubricating composition for use in the crankcase of an engine comprising a base oil and one or more additives, wherein the lubricating composition comprises from 0.01 wt % to 5 wt %, by weight of the lubricating composition, of one or more liquid crystal compounds, wherein the one or more liquid crystal compounds is a terphenyl compound.
2. A lubricating composition according to claim 1 wherein the one or more liquid crystal compounds is present at a level of from 0.01 wt % to 4 wt %, by weight of the lubricating composition.
3. Lubricating composition according to claim 1 or 2 wherein the one or more liquid crystal compounds is present at a level of from 0.1 wt % to 2 wt %, by weight of the lubricating composition.
4. Lubricating composition according to any of claims 1 to 3 wherein the one or more liquid crystal compounds is present at a level of from 0.2 wt % to 1 wt %, by weight of the lubricating composition.
5. Lubricating composition according to any of claims 1 to 4 wherein the one or more terphenyl compounds is a cyano-substituted terphenyl compound.
6. Lubricating composition according to claim 5 wherein the cyano-substituted terphenyl compound is selected from alkylterphenylnitriles and alkyletherterphenylnitriles and mixtures thereof.
7. Lubricating composition according to any of claims 1 to 6 wherein the one or more terphenyl compounds is 4-cyano-4′-pentylterphenyl.
8. Use of a lubricating composition according to any of claims 1 to 7 in the crankcase of an engine, in order to reduce friction.
9. Use of a lubricating composition according to any one of claims 1 to 7 in the crankcase of an engine, in order to reduce wear.
10. Use of a lubricating composition according to any one of claims 1 to 7 in the crankcase of an engine, in order to improve fuel economy properties.
Type: Application
Filed: Apr 23, 2014
Publication Date: Oct 23, 2014
Inventors: Brian Lee PAPKE (Sugar Land, TX), Arjun PRAKASH (Houston, TX), Mark Clift SOUTHBY (Cheshire)
Application Number: 14/259,239
International Classification: C10M 133/24 (20060101);
