BR112014030171B1 - lubricating oil composition, and, use of a lubricating oil composition - Google Patents

Abstract

“LUBRICATION OIL COMPOSITION, AND, USE OF A LUBRICATION OIL COMPOSITION” The purpose of this invention is to offer a lubricating oil composition that has superior extreme pressure properties (ability to avoid welding), which generates a small amount of mud and which also has a high viscosity index. The invention provides a lubricating oil composition that has been added to a copolymer of specified olefins and alkyl methacrylates.

Description

Technical Field of the Invention

[001] The present invention relates to a lubricating oil composition, and specifically refers to a lubricating oil composition which has superior extreme pressure properties, which generates a small amount of sludge and which also has a high index of viscosity.

Fundamentals of the Invention

[002] Attention has been paid to the generation of electricity by wind energy as a renewable energy source. In a device for generating wind energy from electricity, the slow rotation of the blades is accelerated by means of reinforced gears, so that an electricity generator can be rotated by means of its energy. But there are many gear wheels in the reinforced gearbox and a gear oil is needed to lubricate these wheels (Gekkan Tribology, No. 273, pages 50 to 51, May 2010).

[003] In particular, the scale of the apparatus for generating wind energy from electricity has increased in recent years, and as it is necessary to convert large slow forces to high speed by means of reinforced gear, the burden on the gear wheels within the gear has been increased, with the result that there is a demand for greater capacity in gear oils that lubricate them to resist welding (extreme pressure properties). However, extreme pressure agents that are able to withstand welding when mixed with gear oils are likely to turn into sludge through aging and oxidation, and the sludge thus produced can cause wear and welding by hitting the wheels. as foreign matter, and can also end up causing problems through clogging filters and blocking oil tubes. Maintenance such as making oil changes well before large amounts of sludge are generated in the oil is therefore important.

[004] At the same time, the apparatus for generating wind energy from electricity is usually located in remote areas such as mountainous regions or sea coasts, so frequent maintenance is difficult. In addition, higher costs are required for maintenance in areas out of the way, so that to reduce operating costs, there is a demand to extend maintenance intervals and oil change intervals. Therefore, in order to reduce costs for the protection and operation of gear wheels, there has been a demand to improve the oxidative stability performance of gear oils and to minimize the amount of sludge created.

[005] In addition, the apparatus for generating wind energy from electricity is run continuously under a wide range of temperature conditions in response to fluctuations between day and night and weather conditions, and so there is little demand for the gear oil used for have small fluctuations in viscosity due to temperature changes, which is to have a high viscosity index.

[006] Given the above, there has been a demand for an industrial-grade lubricating oil that has superior extreme pressure properties (ability to prevent welding), which generates a small amount of sludge and which also has a high index of viscosity.

[007] The problem to be addressed by the present invention is to offer a lubricating oil composition that has superior extreme pressure properties (ability to prevent welding), which generates a small amount of mud and which also has a high viscosity index .

Summary of the Invention

[008] By virtue of several and repeated investigations and research to reduce the amount of sludge generated in an industrial-grade lubrication oil, the inventors arrive at this invention after discovering that when a copolymer of a specified olefin and an alkyl methacrylate is added in a given fixed range of molecular weights, the amount of sludge generated is reduced, and in addition the viscosity index improves.

[009] In general, olefin and alkyl methacrylate copolymers are used in the composition of lubricating oils as viscosity index enhancers, but nothing has been known about reducing the amount of sludge generated. This invention is an attempt to reduce the amount of sludge by adding an olefin copolymer and an alkyl methacrylate as an effective constituent for a lubricating oil base oil that contains an extreme pressure agent.

[0010] Suitably the present invention provides a lubricating oil composition comprising (A) 50 to 90% by weight of at least one type of lubricating oil base oil selected from mineral oils and synthetic oils and ( B) 10 to 50% by weight of a copolymer, which is 1200 to 50,000 molecular weight, of an olefin and an alkyl methacrylate.

[0011] According to this invention, a lubricating oil composition that has superior extreme pressure properties (ability to prevent welding), that generates a small amount of mud and that also has a high viscosity index is obtained. Reducing the amount of sludge generated by oxidative aging, wear and welding due to foreign matter that becomes incorporated are inhibited, and the service life of the machinery (for example, gears) is extended. Also, the fact that the viscosity index is higher means that the flow characteristics at low temperature are superior and an oil film can be maintained at higher temperatures.

Brief Description of Drawings

[0012] Figure 1 shows the molecular weight distribution curves for Additive A1 and Additive A2.

Detailed Description of the Invention

[0013] This invention relates to a lubricating oil composition characterized by comprising (A) at least one type of lubricating oil base oil selected from mineral oils and synthetic oils and (B) a copolymer of an olefin and an alkyl methacrylate of molecular weight within a specified range. The lubricating oil comprises components (A) and (B), but in particular embodiments the lubricating oil may contain components (A) and (B) or may consist essentially of components (A) and (B).

[0014] For the base oil in the present lubricating oil composition, it is possible to use mineral oils and synthetic oils known as highly refined base oils, and in particular it is possible to use, solely or as mixtures, base oils which belong to Group II, Group III and Group IV of the API (American Petroleum Institute) base oil categories. For the base oils used here, the sulfur content is not more than 300 ppm, but preferably not more than 200 ppm, more preferably not more than 100 ppm, and even more preferably not more than 50 ppm. In addition, the density is 0.8 to 0.9 g / cm 3, but preferably 0.8 to 0.865 g / cm 3, and more preferably 0.81 to 0.83 g / cm 3. The aromatic content (aromatic content in this invention is determined by analysis of n-d-M according to ASTM D3238) is less than 3%, but preferably less than 2% and more preferably less than 0.1%.

[0015] As examples of Group II base oils, mention can be made of paraffinic mineral oils obtained through the appropriate use of an appropriate combination of refining processes such as hydrorefine and dewaxing with respect to the lubricating oil fractions obtained by distillation atmospheric crude oil. Group II base oils refined by hydrorefine methods such as the Gulf Company method have a total sulfur content of less than 10 ppm and an aromatic content of no more than 5% and are therefore suitable for this invention . The viscosity of these base oils is not particularly limited, but the viscosity index (viscosity indices in this invention are determined according to ASTM D2270 and JIS K2283) must be 80 to 120 and preferably 100 to 120. The kinematic viscosity at 40 ° C (kinematic viscosities in this invention are determined according to ASTM D445 and JIS K2283) should preferably be 2 to 680 mm2 / s and even more preferably 8 to 220 mm2 / s. In addition, the total sulfur content should be less than 300 ppm, preferably less than 200 ppm and even more preferably less than 10 ppm. The total nitrogen content should be less than 10 ppm and preferably less than 1 ppm. In addition, oils with an aniline point (aniline points in this invention are determined according to ASTM D611 and JIS K2256) from 80 to 150 ° C and preferably 100 to 135 ° C should be used.

[0016] Suitable Group III and Group II + base oils include paraffinic mineral oils manufactured by a high degree of hydrorefine with respect to lubricating oil fractions obtained by atmospheric distillation of crude oil, base oils refined by the isodesparafination process which dewaxes and replaces the wax produced by the dewaxing process with isoparaffins, and refined base oils by the Mobil wax isomerization process. The viscosity of these base oils is not particularly limited, but the viscosity index should be 95 to 145 and preferably 100 to 140. The kinematic viscosity at 40 ° C should preferably be 2 to 680 mm2 / s and even more preferably 8 to 220 mm2 / s. In addition, the total sulfur content should be 0 to 100 ppm and preferably less than 10 ppm. The total nitrogen content should be less than 10 ppm and preferably less than 1 ppm. In addition, oils with an aniline point of 80 to 150 ° C and preferably 110 to 135 ° C should be used.

[0017] GTLs (gas to liquid) synthesized by the Fischer-Tropsch method to convert fuel from natural gas to liquid have a very low sulfur content and aromatic content compared to refined mineral oil base oils from crude oil and have a very high paraffin constituent ratio, and thus have excellent oxidative stability, and since they also have extremely small evaporation losses, they are suitable as base oils for this invention. The viscosity characteristics of GTL base oils are not particularly limited, but normally the viscosity index should be 130 to 180 and preferably 140 to 175. In addition, the kinematic viscosity at 40 ° C should be 2 to 680 mm2 / s and preferably 5 at 120 mm2 / s.

[0018] Normally the total sulfur content should also be less than 10 ppm and the total nitrogen content should be less than 1 ppm. A commercial example of such a GTL base oil is Shell XHVI (registered trademark).

[0019] As the examples of synthetic oils mention can be made of polyolefins, alkylbenzenes, alkylnaphthalenes, esters, polyoxyalkylene glycols, polyphenyl ethers, dialkyl diphenyl ethers, fluorine-containing compounds (perfluoropolyesters, fluorinated polyolefins) and mixtures of the same silicone oils, or mixtures of the same .

[0020] The polyolefins mentioned above include polymers of various olefins or hydrides thereof. Any olefin can be used, and as examples mention may be made of ethylene, propylene, butene g-olefins with five or more carbons. In the manufacture of polyolefins, one type of the olefins mentioned above can be used alone or two or more types can be used in combination.

[0021] Particularly suitable are polyolefins called polyalphaolefins (PAO). These are Group IV base oils. Polyalphaolefins can also be mixtures of two or more types of synthetic oil.

[0022] The viscosity of these synthetic oils is not particularly limited, but the kinematic viscosity at 40 ° C should be 2 to 680 mm2 / s, but preferably 20 to 500 mm2 / s and more preferably 30 to 450 mm2 / s. The kinematic viscosity at 100 ° C of said synthetic base oils should be 2 to 100 mm2 / s, but preferably 4 to 70 mm2 / s and more preferably 6 to 50 mm2 / s. The viscosity index of said synthetic base oils should be 110 to 170, but preferably 120 to 160 and more preferably 130 to 155. The density at 15 ° C of said synthetic base oils should be 0.8000 to 0.8600 g / cm3, but preferably 0.8100 to 0.8550 g / cm3 and more preferably 0.8250 to 0.8550 g / cm3. The aniline point of said synthetic base oils should be 110 to 180 ° C, but preferably 120 to 170 ° C and more preferably 130 to 165 ° C.

[0023] The amount of base oil mentioned above to be incorporated into the lubricating oil composition of this invention is not particularly limited, but taking as a base the total amount of the lubricating oil composition, a typical range can be given as 50 to 90% by weight, but preferably 50 to 80% by weight and more preferably 50 to 70% by weight. The lower limit of the amount incorporated in the base oil, based on the total amount of the lubricating oil composition, must be selected from any one of not less than 50, 51, 52, 53.54, 55, 56, 57, 58 or 59% by weight, and the upper limit of the amount incorporated in the base oil, based on the total amount of the lubricating oil composition, must be selected from any one of no more than 67, 68, 69 or 70% by weight.

[0024] In addition to what is stated above, said base oils can also include carboxylic acid ester compounds. These are discussed below.

[0025] As examples of the olefin and alkyl methacrylate copolymers of the present lubricating oil composition, mention can be made of copolymers in which the essential constituent monomers are at least one type of olefin having 2 to 20 carbons and at least one type of alkyl methacrylate having alkyl groups of 1 to 20 carbons.

[0026] The olefins mentioned above include various types of olefin polymers or hydrides thereof. Any olefin can be used, but as examples mention may be made of ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, tridecene, tetradecene, pentadecene, hexadecene, heptadecene, octadecene, nonadecene and eicosene. It is also possible to use a single type of olefins mentioned above or combinations of two or more types for the olefins comprised in the constituent monomers.

[0027] As specific examples of the aforementioned alkyl methacrylates having 1 to 20 carbon alkyl groups, mention may be made of: (1) alkyl methacrylates having 1 to 4 carbon alkyl groups: for example, methyl methacrylate, ethyl methacrylate, N - or isopropyl methacrylate, N-butyl, iso-butyl or sec-butyl methacrylate; (2) alkyl methacrylates having 8 to 20 carbon alkyl groups: for example, N-octyl methacrylate, 2-ethylhexyl methacrylate, N-decyl methacrylate, N-isodecyl methacrylate, N-undecyl methacrylate, N-dodecyl methacrylate, 2 -methylundecyl methacrylate, N-tridecyl methacrylate, 2-methyldodecyl methacrylate, N-tetradecyl methacrylate, 2-methyltridecyl methacrylate, N-pentadecyl methacrylate, 2-methyltetradecyl methacrylate, N-hexadyl and methacrylate, methacrylate, methacrylate and methacrylate N- docosyl methacrylate, Dobanol methacrylate 23 [mixture of C-12 / C-13 oxoalcohols made by Mitsubishi Chemical (Ltd.)] and Dobanol methacrylate 45 [mixture of C-13 / C-14 oxoalcoholes made by Mitsubishi Chemical Company Ltd.]; (3) alkyl methacrylates having 5 to 7 carbon alkyl groups: for example, N-pentyl methacrylate and n-hexyl methacrylate.

[0028] Of the monomers mentioned above (1) to (3), those belonging to (1) and (2) are preferred, and the monomers of (2) are additionally preferred. In addition, the preferred monomers of those mentioned above (1), from the point of view of the viscosity index, are those with 1 to 2 carbons in the alkyl groups. The preferred monomers of those mentioned above (2), from the point of view of solubility in the base oil and low temperature characteristics, are those with 10 to 20 carbons in the alkyl groups, and those with 12 to 14 carbons are additionally preferred.

[0029] The molecular weight of the aforementioned olefin and alkyl methacrylate copolymers is 1,200 to 80,000, but preferably 1,200 to 50,000 and more preferably 2,000 to 50,000. The mass average molecular weight is 5,000 to 30,000, but preferably 7,000 to 20,000 and more preferably 9,000 to 16,000. The numerical average molecular weight is 2,000 to 12,000, but preferably 4,000 to 10,000 and more preferably 5,000 to 9,000. In the case of these molecular weights, the mass average molecular weight (Mw) and the numerical average molecular weight (Mn) are those determined by means of gel permeation chromatography (GPC), and are those obtained by conversion, taking polystyrene as the pattern.

[0030] The mass average molecular weight mentioned above can be regulated by means of the temperature during polymerization, the monomer concentration (solvent concentration), the amount of catalyst or the amount of chain transfer agent.

[0031] The dispersion (Mw / Mn) of the aforementioned olefin and alkyl methacrylate copolymers is 1 to 2.5, but preferably 1.3 to 2.2 and especially 1.7 to 1.9.

[0032] The viscosity of the aforementioned olefin and alkyl methacrylate copolymers is not particularly limited, but the viscosity index should be 100 to 250, but preferably 130 to 220 and more preferably 160 to 200. The kinematic viscosity at 40 ° C of the said copolymers should be 1,000 to 12,000 mm2 / s, but preferably 2,000 to 10,000 mm2 / s and more preferably 2,500 to 9,000 mm2 / s. The kinematic viscosity at 100 ° C of said copolymers should be 50 to 600 mm2 / s, but preferably 100 to 500 mm2 / s and more preferably 150 to 450 mm2 / s. The density at 15 ° C of said copolymers should be 0.900 to 0.950 g / cm3, but preferably 0.910 to 0.940 g / cm3 and more preferably 0.925 to 0.935 g / cm3.

[0033] The copolymers of this invention can be readily obtained by any of the usual methods, and the method of manufacture is not limited. For example, they can be obtained by radical polymerization using a diluent, olefins and alkyl methacrylates of selected types and amounts, a copolymerization initiator and a chain transfer agent. They can also be obtained by thermal polymerization of the olefins and alkyl methacrylates of the types and quantities selected with a diluent. The use of a diluent is optional, but the use of a diluent makes it easier to control the molecular weight of the copolymer. Thus it is also generally possible to solve problems with handling, since copolymers have viscous properties. Any diluent can be used as long as it is an inert hydrocarbon, but it must have solubility properties for the copolymer and the lubricating oil. As examples of suitable copolymerization initiators, mention can be made of initiators that break through application of heat and produce free radicals, for example peroxide compounds such as benzoyl peroxide, t-butyl peroctoate and cumene hydroperoxide, and azo compounds such as azobisisobutyronitrile and 2,2O-azobis (2-methylbutanonitrile). As examples of suitable chain transfer agents, mention may be made of those commonly used in the art, for example, styrene, dodecylmercaptan and ethylmercaptan dimers. The use of a chain transfer agent is optional, but the use of a chain transfer agent makes it easier to control the molecular weight of the copolymer.

[0034] The amount of olefin mentioned above and alkyl methacrylate copolymer in the lubricating oil composition of this invention (the amount of olefin mentioned above and alkyl methacrylate copolymer within the aforementioned molecular weight range) is not particularly limited, but, taking as a base the total amount of the lubricating oil composition, a typical range can be given as 10 to 50% by weight, but preferably 10 to 45% by weight and more preferably 15 to 40% by weight. The lower limit of the amount of alkyl methacrylate and olefin copolymer, based on the total amount of the lubricating oil composition, must be selected from any one of not less than 10, 11, 12, 13, 14 or 15% by weight, and the upper limit of the amount incorporated in the base oil, based on the total amount of the lubricating oil composition, should be selected from any one of no more than 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50% by weight. The method for determining the amount of said copolymer within a certain molecular weight range in this case is not particularly limited, and can be a value theoretically converted from the molecular weight distribution curves. For example, when using additives containing said copolymers as a raw material {containing alkyl methacrylate and olefin copolymers within a specified range mentioned above (a suitable range or especially suitable range that belongs to it), diverging alkyl methacrylate and olefin copolymers of said specified range and diluents}, molecular weight distribution curves can be produced by analyzing said additives (see, for example, Figure 1). The molecular weight component of a specified range (say, 1200 to 50000) in said molecular weight distribution curves is inferred to be an "alkyl methacrylate and olefin copolymer within said specified range" and the amount of the component within said range specified in the total additive is calculated based on said molecular weight distribution curves.

[0035] In the case of the present lubricating oil composition, the aforementioned base lubricating oil may contain carboxylic acid ester compounds.

[0036] As examples of carboxylic acid ester compounds, mention can be made of polyol esters. As examples of polyol esters mention can be made of trihydroxymethylpropyl trioleate (CAS No. 11138-60-6), TMP esters (trimethylolpropane) and carboxylic acids, PE esters (pentaerythritol) and carboxylic acids, esters of dicarboxylic acid and trimellitic acid esters. The number of carbons in the residual carboxylic acid groups of the ester molecules should also preferably be from 4 to 20 but more preferably from 6 to 18.

[0037] The amount of the aforementioned carboxylic acid ester incorporated in the lubricating oil composition of this invention is not particularly limited, but, taking as a base the total amount of the lubricating oil composition, a typical range can be given as 5 to 15% by weight, but preferably 7 to 13% by weight and more preferably 8 to 12% by weight. The amount of carboxylic acid ester incorporated, based on the total amount of the lubricating oil composition, should be selected from any of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15% by weight.

[0038] In order to further improve performance, it is possible where necessary to make appropriate use of various types of additives other than the constituents mentioned above. As examples of these, mention may be made of antioxidants, metal deactivators, extreme pressure agents, oil enhancers, defoaming agents, viscosity index enhancers, pour point depressants, detergent dispersants, rust preventives, demulsifying agents, and other lubricating oil additives of the known art.

[0039] For the antioxidants used in this invention, those used in lubricating oils are preferred for practical use, and mention can be made of amine-based antioxidants, sulfur-based antioxidants, phenol-based antioxidants and phosphorus-based antioxidants. These antioxidants can be used alone or in various combinations within the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of the base oil.

[0040] As examples of the amine-based antioxidants mentioned above, mention may be made of dialkyl-diphenylamines such as p, pÓ-dioctyl-diphenylamine (Nonflex OD-3, made by eiko Chemical Ltd), p, pÓ-di-g -methylbenzyl-diphenylamine and Np-butylphenyl-N-pÓ-octylphenylamine, monoalkyl diphenylamines such as mono-t-butyldiphenylamine and monooctyldiphenylamine, bis (dialkylphenyl) amines such as di (2,4-diethylphenyl) amine and di (2 -nonylphenyl) amine, alkylphenyl-1-naphthylamine such as octyl-phenyl-1-naphthylamine and Nt-dodecylphenyl-1-naphthylamine, 1-naphthylamine, aryl-naphthylamine such as phenyl-1-naphthylamine, phenyl-2-naphthylamine, N -hexylphenyl-2-naphthylamine and N-octylphenyl-2-naphthylamine, phenylenediamines such as NK-di-isopwpil-p-phenylenediamine and N, NÓ-diphenyl-p-phenylenediamine, and phenothiazines such as Phenothiazine Ltd. (made by Hodogenzia Ltd. ) and 3,7-dioctylphenothiazine.

[0041] As examples of sulfur-based antioxidants, mention may be made of dialkyl sulfides such as didodecyl sulfide and dioctadecyl sulfide, thiodipropionate esters such as didodecyl thiodipropionate, dioctadecyl tiodipropionate, dimiristyl tiodipropionate and dodecyl dihydrocyanate.

[0042] Phenol-based antioxidants include 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 (Antage DBH, made by Kawaguchi Chemical Industry Co. Ltd. ), 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-alkylphenols such as 2,6-di-t-butyl-4-methylphenol and 2,6-di-t-butyl -4-ethylphenol, and 2,6-di-t-butyl-4-alkoxyphenols such as 2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol.

[0043] In addition, there are 3,5-di-t-butyl-4-hydroxybenzylmercapto-octylacetate, alkyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionates such as n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Yoshinox SS, made by Yoshitomi Fine Chemicals Ltd.), n-dodecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and 2-ethyl-hexyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, and benzene propanoic acid 3,5-bis (1,1-dimethyl-ethyl) -4-hydroxy- C7 ~ C9 alkyl esters on the side chain (Irganox L135, made by Ciba Specialty Chemicals Ltd.), 2,6-di-t-butyl-g-dimethylamino-p-cresol, and 2,2-methylenebis (4-alkyl- 6-t-butylphenol) are such as 2,2-methylenebis (4-methyl-6-t-butylphenol) (Antage W-400, made by Kawaguchi Chemical Industry Ltd.) and 2,2-methylenobis (4-ethyl- 6-t-butylphenol) (Antage W-500, made by Kawaguchi Chemical Industry Ltd).

[0044] Additionally, there are bisphenols such as 4,4O-butylidenobis (3-methyl-6-t-butylphenol) (Antage W-300, made by Kawaguchi Chemical Industry Ltd.), 4,4Ó-methylenebis (2,6- di-t-butylphenol) (Ionox 220AH, made by Shell Japan Ltd.), 4,4O-bis (2,6-di-t-butylphenol), 2,2- (di-p-hydroxyphenyl) propane (Bisphenol A , made by Shell Japan Ltd.), 2,2-bis (3,5-di-t-butyl-4-hydroxyphenyl) propane, 4,4O-cyclohexylidenobis (2,6-t-butylphenol), hexamethylene glycol bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (Irganox L109, made by Ciba Specialty Chemicals Ltd.), triethylene glycol bis [3- (3-t-butyl-4-hydroxy -5-methylphenyl) propionate] (Tominox 917, made by Yoshitomi Fine Chemicals Ltd.), 2,2O-thio- [diethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Irganox L115 , made by Ciba Specialty Chemicals Ltd.), 3,9-bis {1,1-dimethyl-2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl} 2,4, 8,10-tetraoxaspiro [5.5] undecane (Sumilizer GA80, made by Sumitomo Chemicals), 4,4O-thiobis (3-methyl- 6-t-butylphenol) (Antage RC, made by Kawaguchi Chemical Industry Ltd.) and 2,2-thiobis (4,6-di-t-butyl-resorcinol).

[0045] Mention may also be made of polyphenols such as tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (Irganox L101, made by Ciba Specialty Chemicals Ltd.), 1 , 1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane (Yoshinox 930, made by Yoshitomi Fine Chemicals Ltd.), 1, 3,5-trimethyl-2, 4, 6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (Ionox 330, made by Shell Japan Ltd.), bis- [3,3O-bis- (6Ó-hydroxy-3Ó-t-butylphenyl) butyric acid ] glycol ester, 2- (3Ó, 5Ó-di-t-butyl-4-hydroxyphenyl) methyl-4- (2ÓÓ, 4ÓÓ-di-t-butyl-3ÓÓ-hydroxyphenyl) methyl-6-t-butylphenol and 2, 6, -bis (2O-hydroxy-3O-t-butyl-5O-methyl-benzyl) -4-methylphenol, and phenol aldehyde condensates such as pt-butylphenol and formaldehyde condensates and pt-butylphenol and acetaldehyde condensates.

[0046] As examples of phosphorus-based antioxidants mention may be made of triarylphosphites such as triphenylphosphite and tricresylphosphite, trialkylphosphites such as trioctadecylphosphite and tridecylphosphite, and tridodecyltrithiophosphite.

[0047] Metal deactivators that can be used in conjunction with the composition of this invention include benzotriazole and benzotriazole derivatives which are 4-alkyl-benzotriazoles such as 4-methyl-benzotriazole and 4-ethyl-benzotriazole, 5-alkyl-benzotriazols such as 5-methyl-benzotriazole and 5-ethyl-benzotriazole, 1-alkyl-benzotriazols such as -dioctylaminomethyl-2, 3-benzotriazole and -alkyl-tolutriazols such as 1-dioctylaminomethyl-2,3-tolutriazole, and benzoimidazole and benzoimidazole derivatives which are 2- (alkyldithio) -benzoimidazoles such as 2- (octyltidium) -benzoimidazole, 2- (decildithio) -benzoimidazole and 2- (dodecildithio) -benzoimidazole and 2- (alkylldithio) toluimidazols such as 2- (octyltid) -toluimidazole , 2- (decyldithio) -toluimidazole and 2- (dodecyldithium) toluimidazole.

[0048] Also, mention can be made of indazole, indazole derivatives which are toluindazols such as 4-alkyl-indazols and 5-alkyl-indazols, benzothiazole, and benzothiazole derivatives which are derived from 2-mercaptobenzothiazole (Thiolite B-3100 , made by Chiyoda Chemical Industries Ltd.), 2- (alkyldithio) benzothiazoles such as 2- (hexyldithio) benzothiazole and 2- (octyldithium) benzothiazole, 2- (alkyldithio) tolutiazols such as 2- (hexildithio) tolutiazole and 2- ( octilditio) tolutiazole, 2- (N, N-dialkylidithiocarbamyl) -benzothiazoles such as 2- (N, N-diethyldithiocarbamyl) - benzothiazole, 2- (N, N-dibutyldiocarbamyl) -benzothiazole and 2- (N, N-di- hexilditiocarbamil) -benzothiazole, and 2- (N, N-dialkylidithiocarbamyl) - benzothiazoles such as 2- (N, N-diethyldithiocarbamyl) -tolutiazole, 2- (N, N-dibutilditiocarbamil) -tolutiazole and 2- (N, N- dihexyldithiocarbamyl) -tolutiazole.

[0049] Additionally, mention may be made of benzooxazole derivatives that are 2- (alkylldithio) benzooxazols such as 2- (octyltid) benzooxazole, 2- (decildithio) benzooxazole and 2- (dodecildithio) benzooxazole or that are 2- (alkyldithio) ) toluoxazols such as 2- (octyldithium) toluoxazole, 2- (decildithio) toluoxazole and 2- (dodecildithio) toluoxazole, thiadiazole derivatives which are 2,5-bis (alkyldithium) -1,3,4-thiadiazols such as 2, 5-bis (heptyltidium) -1,3,4-thiadiazole, 2,5-bis (nonildithio) -1,3,4-thiadiazole, 2,5-bis (dodecildithio) -1,3,4-thiadiazole and 2 , 5-bis (octadecilditio) -1,3, 4-thiadiazole, 2,5-bis (N, N-dialkilditiocarbamil) -1,3,4-thiadiazols such as 2,5-bis (N, - dietilditiocarbamil) - 1,3,4-thiadiazole, 2,5-bis (N, -dibutyldithiocarbamyl) -1,3,4-thiadiazole and 2,5-bis (N, -dioctilditiocarbamyl) -1,3,4-thiadiazole and 2- N, - dialkilditiocarbamil-5-mercapto-1, 3,4-thiadiazole such as 2-N, N-dibutilditiocarbamil-5-mercapto-1, 3,4-thiadiazole and 2-N, N-dioctyditiocarbamyl-5-mercapto- 1,3,4-thiadiazole, and derivatives and triazole which are, for example, 1-alkyl-2,4-triazoles such as 1-dioctylaminomethyl-2,4-triazole. These metal deactivators can be used alone or in various combinations within the range of 0.01 to 0.5 part by weight with respect to 100 parts by weight of the base oil.

[0050] It is also possible to add phosphorus compounds to the lubricating oil composition of this invention in order to impart anti-wear properties and extreme pressure properties. As examples of suitable phosphorus compounds for this invention, mention may be made of phosphate esters, acid phosphate esters, amine salts of acid phosphate esters, basic phosphate esters, phosphite esters, phosphothionates, zinc dithiophosphates, esters of dithiophosphoric acid and alkanols or alcohols of the polyether type, and derivatives thereof, phosphorus-containing carboxylic acids and phosphorus-containing carboxylic acid esters. These phosphorus compounds can be used alone or in various combinations within the range of 0.01 to 2 parts by weight with respect to 100 parts by weight of the base oil.

[0051] As examples of phosphate esters mentioned above, mention may be made of tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tridecyl , tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, triphenyl phosphate, tris (iso-propylphenyl) phosphate, trialyl phosphate, tricresyl phosphenyl phosphate, trisylphenyl phosphate, trixyl

[0052] As specific examples of the acid phosphate esters mentioned above, mention may be made of monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate , monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, monooleyl acid phosphate, monooleyl acid phosphate , diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, di-hexadecyl phosphate , dioctadecyl acid phosphate and dioleyl acid phosphate.

[0053] As examples of the aforementioned amine salts of acid phosphate esters, mention may be made of salts of methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine and trioctylamine of the acid phosphate esters mentioned above.

[0054] As examples of the phosphite esters mentioned above, mention may be made of dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite and triphenyl phosphite.

[0055] As examples of phosphothionates mentioned above, mention may be made specifically of tributyl phosphothionate, tripentyl phosphothionate, trihexyl phosphothionate, triheptyl phosphothionate, trioctyl phosphothionate, trinonyl phosphothionate, tridecyl phosphothionate, triundecyl phosphothionate, tridodecyl phosphorylate, tridodecyl phosphate tritetradecyl phosphothionate, tripentadecyl phosphothionate, trihexadecyl phosphothionate, triheptadecyl phosphothionate, trioctadecyl phosphothionate, trioleyl phosphothionate, triphenyl phosphothionate, tricresyl phosphothionate, triphenyl phosphorylate (trisylphenylphenyl) , tris (n-butylphenyl) phosphothionate, tris (isobutylphenyl) phosphothionate, tris (s-butylphenyl) phosphothionate and tris (t-butylphenyl) phosphothionate. Mixtures of these can also be used.

[0056] As examples of the zinc dithiophosphates mentioned above, mention may be made in general of dialkyl zinc dithiophosphates, diaryl zinc dithiophosphates and arylalkyl zinc dithiophosphates. For example, dialkyl zinc dithiophosphates where the alkyl groups of the dialkyl zinc dithiophosphates have primary or secondary alkyl groups of 3 to 22 carbons or alkyl groups substituted with alkyl groups of 3 to 18 carbons. As specific examples of zinc dialkyl dithiophosphates, mention can be made of zinc dipropyl dithiophosphate, zinc dibutyl dithiophosphate, zinc dipentyl dithiophosphate, zinc dihexyl dithiophosphate, zinc diiso isopentyl dithiophosphate, diethylhexyl phosphate dioctyl zinc dithiophosphate, zinc dithiophosphate dinonyl, zinc dithiophosphate didecyl, didodecyl zinc dithiophosphate, zinc dithiophosphate dipropilfenil, zinc dithiophosphate dipentilfenil, zinc dithiophosphate dipropilmetilfenil, dinonilfenil zinc dithiophosphate didodecilfenil zinc dithiophosphate and didodecilfenil zinc dithiophosphate.

[0057] It is possible to incorporate fatty acid esters of polyhydric alcohols in the lubricating oil composition of this invention with a view to improving oiliness. For example, it is possible to use partial or complete esters of saturated or unsaturated fatty acids having 1 to 24 carbons of polyhydric alcohols such as glycerol, sorbitol, alkylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol and xylidol, and additionally it is also possible to incorporate those made with different types from the aforementioned carboxylic acid ester compounds.

[0058] Examples of glycerol esters include glycerol monolaurylate, glycerol monostearate, glycerol monopalmitate, glycerol mono-oleate, glycerol dilaurylate, glycerol distearate, glycerol dipalmitate and glycerol dioleate. For sorbitol esters mention can be made of sorbitol monolaurylate, sorbitol monopalmitate, sorbitol monostearate, sorbitol mono-oleate, sorbitol dilaurylate, sorbitol dipalmitate, sorbitol distearate, sorbitol dioleate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate, sorbitol tristrate.

[0059] Alkylene glycol esters include ethylene glycol monolaurylate, ethylene glycol monostearate, ethylene glycol monooleate, ethylene glycol dilaurylate, ethylene glycol distearate, ethylene glycol dioleate, propylene glycol monolaurylate, propylene glycol monostearate, propylene glycol monoleate, propylene glycol monoleate , propylene glycol distearate and propylene glycol dioleate. For mentioning neopentyl glycol esters can be made of neopentyl glycol monolaurylate, neopentyl glycol monostearate, neopentyl glycol monooleate, neopentyl glycol dilaurylate, neopentyl glycol distearate and neopentyl glycol dioleate.

[0060] Trimethylolpropane esters include trimethylolpropane monolaurylate, trimethylolpropane monostearate, trimethylolpropane monooleate, trimethylolpropane dilaurylate, trimethylolpropane distearate, and trimethylolpropane dioleate. Pentaerythritol esters include pentaerythritol monostearate, pentaerythritol mono-oleate, pentaerythritol dilaurylate, pentaerythritol distearate, pentaerythritol dioleate and dipentaerythritol monooleate. For such fatty acid esters of polyhydric alcohols it is preferable to use esters of partial polyhydric alcohols and unsaturated fatty acids.

[0061] In order to improve the low temperature flow characteristics and viscosity characteristics, pour point depressants and viscosity index enhancers can also be added to the lubricating oil composition of this invention. As examples of viscosity index enhancers, mention can be made of non-dispersing viscosity index enhancers such as polymethacrylates and olefin polymers such as ethylene - propylene copolymers, styrene - diene copolymers, polyisobutylene and polystyrene, and viscosity index dispersant enhancers where nitrogen-containing monomers were copolymerized with these, and they can be made with different types from the aforementioned copolymers of olefins and alkyl methacrylates. With respect to the amount to be added, they can be added within the range of 0.05 to 20 parts by weight with respect to 100 parts by weight of the base oil.

[0062] As examples of pour point depressants, mention can be made of polymers based on polymethacrylate. With respect to the amount to be added, they can be used within the range of approximately 0.01 to 5 parts by weight with respect to 100 parts by weight of the base oil.

[0063] Defoaming agents can also be added in order to impart defoaming characteristics to the lubricating oil composition of this invention. As examples of such defoaming agents suitable for this invention, mention may be made of organosilicates such as dimethylpolysiloxane, diethyl silicate and fluorosilicone, and defoaming agents of the silicone-free type such as polyalkylacrylates. With respect to the amount to be added, they can be used alone or in various combinations within the range of 0.0001 to 0.1 part by weight with respect to 100 parts by weight of the base oil.

[0064] As examples of suitable demulsifiers for this invention, mention can be made of those known in the art normally used as additives for lubricating oils. With respect to the amount to be added, they can be used within the range of 0.0005 to 0.5 part by weight with respect to 100 parts by weight of the base oil.

[0065] The viscosity of the lubricating oil composition of this invention is not particularly limited, but the viscosity index should be not less than 130, preferably not less than 140 and more preferably not less than 150. The kinematic viscosity at 40Â ° C of said lubricating oil composition should be 140 to 320 mm2 / s, but preferably 140 to 200 mm2 / s and more preferably 140 to 160 mm2 / s. The amount of sludge in a dry TOST test of said lubricating oil composition should be not more than 1500 mg / kg, but preferably not more than 1300 mg / kg and more preferably not more than 1200 mg / kg. The remaining rate of RPVOT in RPVOT tests in a fresh oil of said lubricating oil composition and the test oil after a dry TOST test should be not less than 40% but preferably not less than 50% and more preferably not less than 60%.

[0066] The lubricating oil composition of this invention is used as a machine oil, hydraulic oil, turbine oil, compressor oil, toothed gear oil, oil for sliding surfaces, bearing oil or a calibration oil. The lubricating oil composition of this invention is ideally used as a long draining gear oil. What is meant by "long draining gear oil" in this invention is an industrial-grade gear oil with long intervals between changes in the lubricating oil. The intervals between lubricating oil changes are not particularly limited, but typical examples can be not less than one year and preferably not less than 2 years or more preferably not less than 3 years. In particular, the lubricating oil composition of this invention is ideally used for the reinforced gear wheels in the apparatus for generating wind energy from electricity.

Examples

[0067] A more specific explanation of the lubricating oil composition of this invention which has superior extreme pressure properties (ability to prevent welding), which generates a small amount of sludge and which also has a high viscosity index is given below using Examples of the Modality and comparative examples, but the invention is not limited in any way by them.

[0068] The following constituent materials were used for the preparation of the Examples of the Modality and the comparative examples.

1. Base oils

[0069] Polyalphaolefin (PAO) synthetic oils classified as Group IV according to API base oil categories (American Petroleum Institute). (1-1) Base oil 1: Polyalphaolefin (common name: PA06, characteristics being kinematic viscosity at 40 ° C: 35.4 mm2 / s; kinematic viscosity at 100 ° C: 6.44 mm2 / s; viscosity index 136; density at 15 ° C: 0.8291 g / cm3; aniline point: 130 ° C) (1-2) Base oil 2: Polyalphaolefin (common name: PAO40, characteristics being kinematic viscosity at 40 ° C: 401 mm2 / s; kinematic viscosity at 100 ° C: 40.3 mm2 / s; viscosity index 151; density at 15 ° C: 0.8491 g / cm3; aniline point: 161 ° C) 2. Additives (2- 1) Additive A1: Olefin and alkyl methacrylate copolymer (common name: Viscobase 11-570, made by Evonik Ltd.) • Molecular weight: 1200 to 25,000 (Figure 1) • Numerical average molecular weight: 5400 • "Mass average molecular weight : 9400 • FkuVtkdwk> «q fg molecular res: 1.7 • Xkuequkfcfg ekpgoávkec c 40 ° C: 2500 mm2 / s • Xkuequkfcfg ekpgoávkec c 100 ° C: 150 mm2 / s • Viscosity index: 160 • Fgpukfcfg 37 0.926 g / cm3 (2-2) Additive A2: Olefin and alkyl methacryl copolymer ilato (common name: Viscobase 11-574, made by Evonik Ltd.) • Molecular weight: 1200 to 50,000 (Figure 1) • Numerical average molecular weight: 8000 • Mass average molecular weight: 15000 • FkuVtkdwk> «q fg rguq oqngewnct: 1.9 • Xkuequkfcfg ekpgmatic at 40 ° C: 9,000 mm2 / s • Xkuequkfcfg ekpgoávkec c 100 ° C: 450 mm2 / s • Viscosity index: 200 • Density at 15 ° C: 0.934 g / cm3 (2-3) Additive A3: Olefin copolymer (common name: Lucant HC-1100, made by Mitsui Chemicals Ltd.) • Numerical average molecular weight: 6,000 • Xkuequkfcfg ekpgoávkec c 40 ° C: 18,900 mm2 / s • Xkuequkfcfg ekpgoávkec c 100 ° C: 1,100 mm2 / s • Viscosity index: 270 • Density at 15 ° C: 0.850 g / cm3 (2-4) Additive A4: Polyisoolefin (common name: Nisseki Polybutene HV300, made by JX Nippon Oil & Energy Corp.) • Weight numerical average molecular: 1,400 • Kinematic viscosity at 40 ° C: 26,000 mm2 / s • Kinematic viscosity at 100 ° C: 590 mm2 / s • Viscosity index: 155 • 15 ° C density: 0.898 g / cm3 (2-5 ) Additive B: Package of gear oil additives (common name: Anglamo 199, made by Lubrizol Corp.) • Kinematic viscosity at 40 ° C: 68 mm2 / s • Kinematic viscosity at 100 ° C: 8.2 mm2 / s • Fensity at 15 ° C : 1.07 g / cm3 • Sulfur content: 29.8 to 33.8% by weight • Phosphorus EqpVg: 1.55 to 1.89% by weight • EqpVgúfq fg pkVtqiêpkq: 0.85 to 1.03% by weight Additive B: Anglamo is a gear oil additive package and it is stated in the Lubrizol catalog that if 3.25 to 3.9% of this package is mixed for the lubricating oil, it will satisfy the API GL-4 standard .

[0070] The API GL-4 standard is divided into six categories, and the proportion of additives is higher as the number increases, thereby increasing the extreme pressure properties. In the Modality Examples, the amount of this Additive B in the formulation was made 2.0% to satisfy the API GL-3 standard (having extreme pressure properties of at least a medium level), but the amount of Additive B in the formulation is not especially limited. (2-6) Additive C: Trihydroxymethylpropyl trioleate (common name: Unister H327R, made by NOF Corp.)

[0071] The composition of lubricating oils from Examples of Modality 1 to 4 and from Comparative Examples 1 to 4 were prepared using the constituent materials mentioned above and using the compositions shown in the Tables.

[0072] Dry TOST and RPVOT tests as shown below were performed on the composition of lubricating oils from Examples of Modality 1 to 4 and Comparative Examples 1 to 4 to observe their performance.

TOST a Seco

[0073] Following the test method for oxidative stability of turbine oils in JIS K2514, 360 ml of the test oil was poured into a container and, without adding any water or catalyst, was heated for 336 hours by blowing in 3 liters of oxygen every hour in a tank with a constant temperature of 120 ° C. 24 hours after the end of the test, the test oil was filtered through a 1 pm pore diameter membrane filter, and the amount of sludge produced was measured. RPVOT

[0074] According to the test method for the rotary pump oxidative stability test in JIS K2514, 50 g of the test oil was taken into a container, and in the combined presence of 5 ml of distilled water and a copper catalyst was positioned in a pump pressurized with oxygen at 6.3 kgf / cm2 at an ambient temperature of 25 ° C. The pump was spun 100 times per minute in a tank with a constant temperature of 150 ° C. The pressure inside the pump was recovered, and the time from the maximum pressure reached after introducing the pump to the tank with constant temperature until a pressure drop of 1.75 kgf / cm2 was observed and measured, and this value was taken as the value of RPVOT. The RPVOT was performed in fresh oil and in test oil (before filtration) after the end of TOST.

[0075] As shown in Table 1 below, Examples of Modality 1 and 2 in which an alkyl methacrylate and olefin copolymer was used as a viscosity index enhancer exhibits a high viscosity index of more than 150, and the amount of mud after the dry TOST test is less than 1,100 mg / kg. In contrast, Comparative Example 1, which uses an olefin copolymer, has a high viscosity index but a large amount of sludge. Comparative Example 2, which uses polyisobutylene, has little mud but a low value for the viscosity index.

[0076] Table 2 shows the results when trihydroxymethylpropyl trioleate (Additive C) was added to Examples of Mode 1 and 2 and Comparative Examples 1 and 2. Example of Mode 3 and Example of Mode 4, which used an alkyl copolymer methacrylate and olefin as a viscosity index enhancer showed greater improvement in viscosity index and greater reduction in the amount of sludge than Example of Mode 1 or Example of Mode 2 through the addition of trihydroxymethylpropyl trioleate. This effect due to the addition of trihydroxymethylpropyl trioleate is also clear from the difference in results between Comparative Example 3 and Comparative Example 1, and Comparative Example 4 and Comparative Example 2, but compared with Examples of Modality 3 and 4 , Comparative Example 3 still has a higher amount of sludge, and Comparative Example 4 can be observed to have a lower viscosity index.

[0077] For the remaining RPVOT rate, a value of not less than 40% is preferable, but a value of not less than 50% is more preferable.

Claims (6)

1. Composition of lubricating oil, characterized by the fact that it comprises: (A) 50 to 90% by mass of at least one type of lubricating oil base oil selected from mineral oils and synthetic oils; and (B) 10 to 50% by weight of a copolymer, which has a weight average molecular weight of 5000 to 20,000, of an olefin and an alkyl methacrylate; wherein the lubricating base oil comprises 5 to 14% by weight with respect to the total amount of the lubricating oil composition of (C) a carboxylic acid ester compound; and wherein the carboxylic acid ester (c) is a polyol ester. 2. Lubricating oil composition according to claim 1, characterized by the fact that the lubricating oil base oil is a polyalphaolefin or a GTL (gas to liquid) oil. Lubricating oil composition according to claim 1 or 2, characterized by the fact that the average molecular weight of the copolymer is 7000 to 20000. Lubricating oil composition according to any one of claims 1 to 3, characterized by the fact that the kinematic viscosity at 40 ° C of the lubricating oil composition is 140 to 320 mm2 / s, the viscosity index is not less than 150 and the amount of sludge in a dry TOST test is no more than 1200 mg / kg. 5. Use of a lubricating oil composition as defined in any of claims 1 to 4, characterized by the fact that it is like a machine oil, a hydraulic oil, a turbine oil, a compressor oil, a gear oil gear, sliding surface oil, bearing oil or calibration oil. 6. Use of a lubricating oil composition as defined in any one of claims 1 to 4, characterized by the fact that it is like a long draining gear oil.

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