Lubricating oil compositions containing dispersants for two-cycle engines

Abstract: Lubricating oil compositions for two-cycle (two-stroke) engines are described, of three types, comprising by weight (viscosity being kinetic at 100°C) : 1. (a) 30 to 70% of a polyol ester having a viscosity of 9 to 15 cSt, (b) 30 to 70% of a diester having a viscosity of 2 to 5 cSt, (c) 1 to 5% of a polybutene having a molecular weight of 500 to 2,500 and/or 1 to 5% of a polymethacrylate having a molecular weight of 5,000 to 40,000, and (d) 5 to 25% of a dispersant. 2. (a) 30 to 70% of a polyol ester having a viscosity of 4 to 15 cSt, (b) 0 to 35% of a complex ester having a viscosity of 10 to 14 cSt, (c) 10 to 70% of a diester having a viscosity of 2 to 5 cSt, and (d) 5 to 25% of a dispersant. The dispersant (d) is preferably a polyamide; it prevents formation of deposits on the engine. 3. A lubricating base oil contains 5 to 25% of a polyamide type of dispersant and also a neutral calcium sulfonate and a neutral calcium salicylate which together amount to 0.1 to 5% by weight of the composition. The base oil can be a mixture of components (a) to (c) of composition 1 or 2, a mineral oil or a poly-α-olefin. The compositions can have other additives, and can be used as a low-oil, e.g. 100:1, mixture with gasoline, and they have good biodegradibility.

Description: The present invention relates to a lubricating oil composition for two-cycle engines, which is excellent in biodegradability, miscibility with gasoline, anti-seizure performance, and detergency at high temperature, and can have reduced viscosity at low temperature. Engine oil - in which an inexpensive mineral oil type of lubricating oil is used as the base oil and which may optionally contain cleaners and anti-wear agents - has been widely used. Lubricating oil used with two-cycle engines (called two-stroke engines in Britain) e.g. for motorcycles or outboard motors, on the other hand, is now increasingly required to have miscibility with gasoline (petroleum spirit) and anti-seizure performance, especially biodegradability. Unburned lubricating oil discharged from two-cycle engines is now known to pollute the sea, and lakes and marshes, posing grave environmental problems. Thus, there is a strong need for lubricating oil which has a high engine oil function so as to ensure that the required properties are achievable in small quantities, and also is biodegradable, so that, when discharged into water, it can be easily degraded by aquatic microorganisms. Therefore, there has recently been developed a biodegradable type of lubricating oil which is mainly made of an easily-biodegradable polyol ester and in which an oil diluent such as kerosene or hydrogenated mineral oil is incorporated so as to assure miscibility with gasoline (see JP-A-4-120195). However, oil products containing a hydrocarbon type base oil as the oil diluent are still less than satisfactory, due to their low biodegradability. A so-called separated lubrication mode - in which fuel is mixed with lubricating oil in a two-cycle engine - has also been proposed. However, problems associated with this mode are that the lubricating oil has low fluidity at low temperature, so that it cannot be well mixed with gasoline, and it becomes poor in detergency at high temperature, making the amount of deposits on the engine larger. Compositions having an ester as base oil and used in two-cycle engines have been previously described (FR-A-2187894) however, the properties of such compositions mostly relate to improved anti-seizure properties. Lubricating oil compositions containing polyol ester and petroleum type solvent have also been described in (JP-A-4120195). However, none of the disclosures appear to provide the advantages of the present invention. The first object of the invention is to provide a lubricating oil composition for two-cycle engines, which can be used as engine oil that is excellent not only in biodegradability but also in miscibility with gasoline, anti-seizure performance and detergency. The second object of the invention is to provide a lubricating oil composition for two-cycle engines, which has application in a wide range of temperatures; that is, which is excellent in detergency at high temperature, can have a reduced viscosity at low temperature, and is improved in its miscibility with gasoline. According to one aspect of the invention, there is provided a lubricating oil composition for two-cycle engines, which comprises by weight; (a) 30 to 70% of a polyol ester having a kinetic viscosity of 9 to 15 cSt at 100°C, (b) 30 to 70% of a diester having a kinetic viscosity of 2 to 5 cSt at 100°C, (c) 1 to 5% of a polybutene having a molecular weight of 500 to 2,500 and/or 1 to 5% of a polymethacrylate having a molecular weight of 5,000 to 40,000, and (d) 5 to 25% of a dispersant. This first composition is obtained by incorporating the diester in the polyol ester so as to achieve miscibility with gasoline, with the addition to it of the polybutene and/or the polymethacrylate to provide anti-seizure performance, and of the ashless dispersant to provide detergency. Since both the polyol ester and diester are excellent in biodegradability, this composition is well suitable as a lubricating oil composition for two-cycle engines that are used with outboard motors, chainsaw motors, etc., and so must be improved in terms of the properties needed, such as biodegradability, anti-seizure performance, miscibility with gasoline and detergency. According to a further aspect of the invention, there is provided a lubricating oil composition for two-cycle engines, which is obtained by the incorporation in a lubricating base oil of 5 to 25% by weight of a polyamide type dispersant and a neutral calcium sulfonate and a neutral calcium salicylate which together amount to 0.1% by weight to 5% by weight. The second composition of the invention, because the lubricating base oil contains the polyamide type dispersant as a dispersant and further includes the neutral calcium sulfonate and calcium salicylate, can be used in a wide range of temperatures; that is, it can achieve detergency at high temperature, can have reduced viscosity at low temperature, and can have excellent miscibility with gasoline. Thus, this composition is well suitable as a lubricating oil composition for two-cycle engines which are used e.g. with outboard motors or chain-saw motors, and is particularly best suited for use in the so-called separate lubrication mode in which, as already mentioned, fuel is mixed with lubricating oil in a two-cycle engine. The components of the first composition according to the invention will now be explained in detail. The polyol ester is a polyester of an aliphatic polyhydric alcohol with a linear or branched fatty acid. Examples of the aliphatic polyhydric alcohol forming the polyester are neopentyl gylcol, trimethylolpropane, ditrimethylolpropane, trimethylolethane, ditrimethylolethane, pentaerythritol, dipentaerythritol and tripentaerythritol; the fatty acid used preferably has 16 to 24 carbon atoms, such as heptadecylic acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid or lignoceric acid. Also, partial esters of the aliphatic polyhydric alcohol with the linear or branched fatty acid may be used. These partial esters may be obtained by the reaction of the aliphatic polyhydric alcohol with the fatty acid while their molar reacting ratio is controlled. The polyol ester used has a kinetic viscosity of 9 to 15 cSt, preferably 11 to 14 cSt, as measured at 100°C, and is excellent in biodegradability, and is used as the base for lubricating oil. This polyol ester becomes poor in anti-seizure performance at less than 9 cSt and has reduced biodegradability at higher than 15 cSt. The polyol ester comprises 30 to 70%, preferably 40 to 60% by weight of the composition. At less than 30% the composition tends to have a reduced anti-seizure performance, and at higher than 70% its miscibility with gasoline is lowered. We now describe the diester used in the invention. The carboxylic acid component of the diester may be a linear or branched aliphatic dibasic acid having 6 to 10 carbon atoms, such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and other acids having like properties. The alcoholic component may be an aliphatic alcohol having 6 to 10 carbon atoms, such as hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol and decyl alcohol as well as their isomers. The diester has a kinetic viscosity of 2 to 5 cSt, preferably 2 to 4 cSt, as measured at 100°C, and is used so as to achieve an improvement in miscibility with gasoline. At higher than 5 cSt the miscibility becomes poor. The diester comprises 30 to 70%, preferably 40 to 50% by weight of the composition. At less than 30% by weight the composition becomes poor in miscibility with gasoline, and at higher than 70% by weight the composition has poorer anti-seizure performance. The polybutene is added to the composition as a heavy base oil so as to impart anti-seizure performance thereto, and so needs to have a molecular weight of 500 to 2,500, preferably 500 to 1,500, more preferably 700 to 1,000. If the molecular weight exceeds 2,500 the composition has poor detergency. The polybutene comprises 1 to 5%, preferably 1.5 to 3.5% by weight of the composition. If more than 5% of the polybutene is present, the anti-seizure performance of the composition drops, because the amount of the diester used must be increased so as to regulate the viscosity of the composition. The polymethacrylate may be used in place of the polybutene. The polymethacrylate has a molecular weight of 5,000 to 40,000, preferably 10,000 to 20,000, and is added to the composition as a heavy base oil so as to impart anti-seizure performance thereteo. If the molecular weight exceeds 40,000 the composition has poor detergency. The polymethyacrylate used may be of either (i) a dispersion type or (ii) a non-dispersion type, and has the following structures: wherein, R stands for a hydrocarbon group having 1 to 18 carbon atoms, R' a hydrogen atom or a methyl group, X a polar group, and n an integer of 10 to 1,000. The polymethacrylate comprises 1 to 5% by weight, preferably 2 to 5% by weight of the composition. If the composition contains more than 5% by weight of the polymethacrylate, there is the problem that its detergency drops. In this connection, the polymethacrylate may be used in combination with the polybutene. The dispersant is added to the composition for the purpose of achieving detergency, and is preferably of the ashless type. Preferably, polyamides, amide succinates (which may be denatured by boron) and benzylamines (which may be denatured by boron) are used, but the most preference is given to polyamides. Examples of the polyamide dispersant are Lubrizol 390™, Lubrizol 397™ and Lubrizol 398™, as well as Oronite 340R™ and Oronite RB™. These are added to the composition so as to prevent formation of deposits or varnish on piston/cylidner sites, and used in an amount of 5 to 25% by weight, preferably 10 to 20% by weight. The components of the second composition of the invention will now be explained. The base oil of the second lubricating oil composition according to the invention may comprise, a mixture of, by weight, (a) 30 to 70% of a polyol ester having a kinetic viscosity of 9 to 15 cSt at 100°C, (b) 30 to 70% of a diester having a kinetic viscosity of 2 to 5 cSt at 100°C, and (c) 1 to 5% of a polybutene having a molecular weight of 500 to 2,500 and/or 1 to 5% of a polymethacrylate having a molecular weight of 5,000 to 40,000 - as used in the first composition mentioned above. Those comprising the components (a), (b) and (c) of the first composition of the invention are preferable in view of biodegradability, anti-seizure performance and high-temperature detergency. The second composition according to the invention is characterized by containing as dispersants a polyamide type dispersant in an amount of 5 to 25%, preferably 10 to 20% by weight, and a neutral calcium sulfonate and a neutral calcium salicylate which together amount to 0.1 to 5.0%, preferably 0.5 to 3% by weight of the composition. The polyamide type dispersant is generally excellent in detergency, but is inferior in heat resistance, e.g., high-temperature detergency, to an imide succinate type dispersant. According to the invention, however, it is found that a composition which is excellent in detergency at high temperature, can have a low viscosity at low temperature and is improved in its miscibility with gasoline is achievable by the incorporation therein, with the polyamide type of dispersant, of the neutral calcium sulfonate and calcium salicylate in the total amount of 0.1 to 5.0% by weight. An amount thereof of more than 5% is undesirable because these dispersants then deposit out. The polyamide type dispersant is of the ashless type, and examples thereof are the Lubrizol™ and Oronite™ products described above. Examples of the neutral calcium sulfonate used with the polyamide type dispersant are Lubrizol 65™, PARANOX-24™, Ca-Petrona™ , OLOA 246B™ and TLA 256™. An example of the neutral calcium salicylate is SAP 002™. Any of the compositions of the invention may if desired contain rust inhibitors, anti-foamants, metal detergents, anti-wear agents, antioxidants, pour point dispersants or other conventional additives. Each of the three types of compositions, may be used in the form of a low-oil mixture, e.g., a 100-to-1 gasoline mixture. EXAMPLES The first composition of the invention will now be illustrated by the samples shown in the following examples. "M.W" = molecular wt. Example 1 Sample Oil 1 of the invention was prepared according to the composition given below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 43.5% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100°C 39.5% by weight (3) Polybutene with an M.W. of 1,500 and 750 cSt at 100°C 2.0% by weight (4) Polyamide type ashless dispersant (Lubrizol 397™) 15.0% by weight Sample Oil 2 of the invention was prepared according to the composition given below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 43.5% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100° 39.5% by weight (3) Polybutene with an M.W. of 800 and 120 cSt at 100°C 2.0% by weight (4) Polyamide type ashless dispersant (Lubrizol 297™) 15.0% by weight Sample Oil 3 of the invention was prepared according to the composition given below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 34.0% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol with a viscosity of 2.5 cSt at 100°C 49.0% by weight (3) Polymethyl methacrylate with an M.W. of 20,000 2.0% by weight (4) Polyamide type ashless dispersant (Lubrizol 397™) 15.0% by weight Sample Oil 4 of the invention was prepared according to the composition given below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 34.0% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol with a viscosity of 2.5 cSt at 100°C 49.0% by weight (3) Polymethyl methacrylate with an M.W. of 10,000 2.0% by weight (4) Polyamide type ashless dispersant (Lubrizol 397™) 15.0% by weight Samples Oils 1-4 were tested together with Comparative Oils 1-3 (with the compositions given below) in terms of (1) biodegradability, (2) anti-seizure performance, (3) detergency, and (4) miscibility with gasoline and low-temperature fluidity. Comparative Oil 1 (1) Mineral oil 1 with a viscosity of 13 cSt at 100°C 58.0% by weight (2) Mineral oil 2 with a viscosity of 31 cSt at 100°C 8.0% by weight (3) Kerosene having a boiling point of 155°C to 270°C 19.0% by weight (4) Polyamide type dispersant 15.0% by weight Comparative Oil 2 (1) Polybutene 1 with a viscosity of 90 cSt at 100°C 5.0% by weight (2) Polybutene 2 with a viscosity of 240 cSt at 100°C 15.0% by weight (3) Kerosene having a boiling point of 155°C to 270°C 20.0% by weight (4) Mineral oil with a viscosity of 13 cSt at 100°C 55.0% by weight (5) Ca sulfonate 1.0% by weight (6) Imide succinate 4.0% by weight Comparative Oil 3 (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 15 cSt at 100°C 72.0% by weight (2) Kerosene having a boiling point of 155°C to 270°C 18.0% by weight (3) Polyamide type of ashless dispersant - Lubrizol 397™ 10.0% by weight (A) Biodegradability According to the amended MITI method, a basic culture solution (300 cc) and cultured cells (obtained by acclimatizing waste water discharged from a municipal sewage disposal plant with artificial sewage) were added to each of the sample and comparative oils (30 mg), followed by a 28-day stirring at 25°C. Then, the biodegradability of each oil was estimated by the ratio of the amount of oxygen consumed by the microorganisms so as to decompose the oil to the theoretical oxygen amount. The results of the sample oils according to the invention are set out in Table 1, and the results of the comparative oils are shown in Table 2. (B) Anti-Seizing Property Under the following conditions, each of the sample and comparative oils was tested in combination with an engine, while the temperature of the ignition plug was increased at an increment of 5°C from the test start temperature of 245°C. The anti-seizure performance of the oil was estimated by the plug temperature at which the engine seized up. Again, the results are shown in Tables 1 and 2. Engine under test: Robin engine EC-10D™ Fuel/Oil: 100:1 Test Cycle: Four cycles, each comprising a five-minute full load and a one-minute non-load Sample Oil 1 2 3 4 Biodegradability, % 68 68 68 67 Seizing-Up Plug Temperature, °C 270 275 275 270 Comparative Oil 1 2 3 Biodegradability, % 20 20 55 Seizing-Up Plug Temperature, °C 265 260 270 From Tables 1 and 2, it is found that the sample oils of the invention provide lubricating oil compositions that are higher than the comparative oils in terms of biodegradability and seizing-up plug seat temperature. (C) Detergency A Robin engine EC-10D™ was driven at a full load of 5000 rpm for 4 hours. Then, the detergency was estimated by what states the rings and pistons were in (with a plug seat temperature of 215 to 218°C and a fuel to oil ratio of 100 to 1). Sample Oil 1 2 3 4 Top ring state 0.8 0.8 0.7 0.7 Top land 0.96 0.97 0.95 0.95 Top ring group 0.93 0.93 0.93 0.93 Second land 0.99 1.00 0.98 0.98 Second ring group 0.99 1.00 0.99 0.99 Piston skirt 0.99 1.00 0.99 0.99 Under crown 0.95 0.99 0.90 0.89 Total 6.61 6.69 6.44 6.43 Comparative Oil 1 3 Top ring state 0.5 0.3 Top land 0.91 0.86 Top ring group 0.88 0.89 Second land 0.98 0.96 Second ring group 0.99 0.97 Piston skirt 0.99 0.99 Under crown 0.85 0.78 Total 6.10 5.75 The sample oils according to the invention are superior to the comparative oils in terms of the rings and pistons. (C) Miscibility with Gasoline, and Low-Temperature Fluidity The miscibility-with-gasoline and low-temperature fluidity of each oil were evaluated according to ASTM D4682. The results are set out in Table 5. SO1 SO2 SO3 SO4 CO1 Miscibility with gasoline, rpm 26 26 26 26 26 Pour point, °C -37.5 -37.5 -37.5 -37.5 -37.5 SO: sample oil, and CO: comparative oil It is found that the sample oils according to the invention are equivalent to the conventional oil product in terms of miscibility with gasoline and pour point. In the ensuing description, the second composition of the invention will be explained, more specifically but not exclusively, with reference to the following examples. Example 2 Sample Oil 5 of the invention was prepared with the composition mentioned below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 49% 42.2% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100°C 15% 38.5% by weight (3) Polybutene with a molecular weight of 1,500 and a viscosity of 750 cSt at 100°C 1.8% 1.8% by weight (4) Polyamide type of ashless dispersant, Lubrizol 397 made by Lubrizol Co., Ltd. 15.0% by weight (5) Neutral calcium sulfonate, Ca-Petrona made by Uitoko Chemical Co., Ltd. 1.5% by weight (6) Netural calcium salicylate, SAP 002 made by Shell Chemical Co., Ltd. 1.0% by weight Example 3 Prepared was Sample Oil 6 according to the invention, with the composition mentioned below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 42.0% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100°C 38.3% by weight (3) Polybutene with a molecular weight of 800 and a viscosity of 120 cSt at 100°C 1.8% by weight (4) Polyamide type of ashless dispersant, Lubrizol 397™ 15.0% by weight (5) Neutral calcium sulfonate, TLA 256™ 1.9% by weight (6) Neutral calcium salicylate, SAP 002™ 1.0% by weight Example 4 Prepared was Sample Oil 7 according to the invention, with the composition mentioned below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 32.5% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100°C 46.9% by weight (3) Polymethyl methacrylate with a molecular weight of 20,000 1.8% by weight (4) Polyamide type of ashless dispersant, Lubrizol 397™ 15.0% by weight (5) Neutral calcium sulfonate, Lubrizol 65 ™ 2.8% by weight (6) Neutral calcium salicylate, SAP 002™ 1.0% by weight Example 5 Prepared was Sample Oil 8 according to the invention, with the composition mentioned below. (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 33.0% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100°C 47.5% by weight (3) Polymethyl methacrylate with a molecular weight of 10,000 1.8% by weight (4) Polyamide type of ashless dispersant, Lubrizol 397™ 15.0% by weight (5) Neutral calcium sulfonate, PARANOX 24™ 1.7% by weight (6) Neutral calcium salicylate, SAP 002™ 1.0% by weight Each of the thus obtained lubricating oil compositions was measured in terms of (1) high-temperature detergency, and (2) low-temperature viscosity. In the following description, the compositions of the reference oils used for the purpose of comparison are mentioned. Reference Oil 1 (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 39.6% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100°C 36.2% by weight (3) Polybutene with a molecular weight of 1,500 and a viscosity of 750 cSt at 100°C 1.7% by weight (4) Imide succinate 20.0% by weight (5) Neutral calcium sulfonate, Ca-Petrona™ 1.5% by weight (6) Neutral calcium salicylate, SAP 002™ 1.0% by weight Reference Oil 2 (1) Esterified product of trimethylolpropane (1 mole) with a C 18 monocarboxylic acid (3 moles), with a viscosity of 13 cSt at 100°C 40.9% by weight (2) Esterified product of adipic acid with a C 8 monoalcohol, with a viscosity of 2.5 cSt at 100°C 37.3% by weight (3) Polybutene with a molecular weight of 1,500 and a viscosity of 750 cSt at 100°C 1.8% by weight (4) Imide succinate 20.0% by weight How to measure high-temperature detergency and low-temperature high-temperature viscosity will now be described. The detergency was evaluated, using a hot tube test (HTT) made by Komatsu Ltd. According to HTT, each of the sample and comparative oils was passed through a glass tube of 2 mm in inner diameter and 300 mm in length at an air flow rate of 10±0.5 cc/min, an oil flow rate of 0.3±0.01 cc/h and a temperature of 280±1°C for 16 hours. Then, the glass tube was washed with hexane and fully dried to estimate the degree of contamination of the glass tube on the basis of 10 HTT color points. The higher the point, the higher detergency the oil has. The low-temperature viscosity of the oil was estimated by the Brookfield viscosity (cP) measured at -10°C according to TCW II provided on outboard motors. The lower the value, the better the low-temperature viscosity is. Also, these oils were measured for biodegradability and anti-seizure performance, as in Example 1. The results of these properties of the sample and reference oils measured are set out in Tables 6 and 7. High-Temp. Detergency (color points) Low-Temp. Viscosity, cP SO 5 9 880 SO 6 10 860 SO 7 10 880 SO 8 9 850 RO 1 9 1320 RO 2 4 760 Biodegradability, % Seizing-Up Plug Temperature, °C SO 5 68 270 SO 6 68 275 SO 7 68 275 SO 8 67 270 RO 1 65 275 RO 2 67 270 SO: sample oil, and RO: reference oil Tables 6 and 7 show that the two-cycle engine oils according to the third aspect of the invention are excellent in biodegradability, anti-seizure performance and high-temperature detergency, and are reduced in low-temperature viscosity as well.

Claims: A lubricating oil composition for two-cycle engines, which comprises by weight: (a) 30 to 70% of a polyol ester having a kinetic viscosity of 9 to 15 cSt at 100°C, (b) 30 to 70% of a diester having a kinetic viscosity of 2 to 5 cSt at 100°C, (c) 1 to 5% of a polybutene having a molecular weight of 500 to 2,500 and/or 1 to 5% of a polymethacrylate having a molecular weight of 5,000 to 40,000, and (d) 5 to 25% of a dispersant. A lubricating oil composition as claimed in Claim 1, wherein the dispersant (d) is a polyamide. A lubricating oil composition as claimed in Claim 2 which also includes: (e) a neutral calcium sulfonate and a neutral calcium salicylate which together amount to 0.1 to 5% by weight of the composition.

Inventors: KOGANEI KATSUYA, KURIBAYASHI TOSHIAKI, NOMURA TAKESHI, UMEMOTO NOBORU, KOGANEI, KATSUYA, KURIBAYASHI, TOSHIAKI, NOMURA, TAKESHI, UMEMOTO, NOBORU, Koganei, Katsuya, c/o Tonen Corporation Corp., Kuribayashi, Toshiaki, c/o Tonen Corporation Corp., Nomura, Takeshi, c/o Tonen Corporation Corp., UMEMOTO, NOBORU, C/O TONEN CORPORATION CORP.
Applicants: TONEN CORP, TONEN CORPORATION
Application year: 1993
Main classification: C10M169
IPC codes: C10N30, F02B75, C10M169, C10N20, C10N40