Lubricant Composition

The present invention relates to a lubricant oil composition excellent in biodegradability, lubricating property (extreme pressure property), stability against oxidation and demulsibility, low in toxicity to and bioaccumulation property in an aquatic life, and excellent in stability against shearing even in the presence of water. The lubricating oil composition may preferably be applied for a bearing oil, hydraulic oil, gear oil or the like, and may appropriately applied particularly for a stern tube bearing oil, thruster oil or the like used in ocean areas.

Recently, it is demanded new trials for environmental preservation as important mission worldwide, and in the field of a lubricant oil, it is further demanded a lubricant oil capable of reducing environmental load more than ever. As a lubricant oil capable of reducing the environmental load, a biodegradable lubricant oil draws attention, as the lubricant oil is susceptible to decomposition in natural world to reduce its effects on ecosystem even in the case that the lubricant oil is leaked out.

Various kinds of researches have been made about the biodegradable lubricant oil until now. For example, according to patent document 1, it is disclosed a biodegradable gear oil produced by blending an acidic phosphate ester amine salt into a base oil composed of a complex ester of a polyvalent alcohol and a straight-chain saturated fatty acid and straight-chain divalent fatty carboxylic acid. Further, according to patent document 2, it is disclosed a biodegradable hydraulic oil produced by blending an oxidization preventing agent and load bearing additive into a complex ester of a polyvalent alcohol and a straight-chain fatty acid and straight-chain saturated polycarboxylic acid.

Many of biodegradable lubricant oils have been applied as a countermeasure in the case of leakage into livers and oceans, and its use is mandatory in some regions and applications. For example, in European countries, the use of the biodegradable lubricant oil is mandated in 2-cycle engine oil in an outboard motor for use in lake regions, hydraulic oil for construction machinery used near a liver for taking drinking water, or the like. As such lubricant oil applied in the vicinity of water, for example, according to patent document 3, it is disclosed a biodegradable lubricant oil including a base of (poly)alkylene glycol and which is soluble in water.

Further, recently in the United States, in a lubricant oil for ships applied for ships moving in water region of the United States, it is mandated a lubricant oil having biodegradability and low toxicity and bioaccumulation property in an aquatic life, and it is demanded a lubricant oil having lower environmental load. Among the above applications, in the stern tube bearing oil, thruster oil or the like, it is difficult to terminate the operation of an equipment directly at the time of contamination of water content, and the equipment may be used for a specific time period while the water content is contaminated therein. Thus, the demulsibility and stability against mechanical shearing force are required even in the state that the water content is incorporated therein.

However, according to the prior techniques described above, the objects described above have not been sufficiently studied, and it is demanded a biodegradable lubricant oil having low toxicity and bio accumulative property in an aquatic life, having demulsibility and excellent in the stability against shearing even in the presence of water.

An object of the present invention is to provide a lubricant oil composition excellent in biodegradability, lubricating property (extreme pressure property), stability against oxidation and demulsibility, having low toxicity and bioaccumulation property in an aquatic life, and excellent in stability against shearing even in the presence of water.

As the present inventors have extensively researched for solving the objects described above, a specific ester compound (A), of pentaerythritol and a specific straight-chain fatty acid and adipic acid, and a specific acidic phosphoric acid ester amine salt (B) are blended in a specific ratio. It is thus found that it is possible to provide a composition excellent in biodegradability, lubricant property (extreme pressure property), stability against oxidation and demulsibility, having low toxicity and bioaccumulation property in an aquatic life and having excellent stability against shearing even in the presence of water.

That is, the present invention is as follows.

A lubricant oil composition comprising 100 mass parts of the following ester compound (A), 0.1 to 1.5 mass parts of the following amine salt of an acidic phosphoric acid ester (B), 0.3 to 2.0 mass parts of an amine-based oxidation preventing agent (C), and 0.3 to 2.0 mass parts of a phenol-based oxidation preventing agent (D),

As the lubricant oil composition of the present invention is excellent in biodegradability, lubricating property (extreme pressure property), stability against oxidation and demulsibility, has low toxicity and bioaccumulation property and has excellent stability against shearing even in the presence of water, it can be appropriately applied for a bearing oil, hydraulic oil, gear oil or the like, and may appropriately applied particularly for a stern tube bearing oil, thruster oil or the like used in ocean areas.

The lubricant oil composition of the present invention will be described below. Further, a numerical range defined by the symbol “-” in the specification includes numerals at both ends (upper limit and lower limit). For example, “2 to 5” means 2 or more and 5 or less.

The ester compound (A) of the present invention is an ester compound of (a) pentaerythritol, (b) straight-chain fatty acid having a carbon number of 14 to 22 and (c) adipic acid.

As a raw material of the ester compound (A), pentaerythritol is applied due to its excellent stability against oxidation and heat resistance.

The strait-chain fatty acid having a carbon number of 14 to 22 and applied in the ester compound (A) is a straight-chain saturated fatty acid having a carbon number of 14 to 22, a straight-chain unsaturated fatty acid having a carbon number of 14 to 22 or the mixed fatty acids thereof. The straight-chain saturated fatty acid having a carbon number of 14 to 22 may be, for example, myristic acid, palmitic acid, stearic acid, arachidic acid or behenic acid. The straight-chain unsaturated fatty acid having a carbon number of 14 to 22 may be, for example, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid or erucic acid. The straight-chain saturated fatty acid and straight-chain unsaturated fatty acid as described above may preferably be palmitoleic acid, oleic acid, linoleic acid, linolenic acid or erucic acid, more preferably oleic acid, linoleic acid or linolenic acid, and most preferably oleic acid.

In the case that the carbon number of the straight-chain fatty acid is less than 14, the lubricating property (extreme pressure property) may possibly be deteriorated. On the other hand, in the case that the carbon number of the straight-chain fatty acid is more than 22, the fuel efficiency may possibly be deteriorated due to the energy loss caused by the internal resistance of the lubricating oil itself accompanied with a high viscosity, and the generated ester compound becomes solid so that it cannot be possibly applied as a lubricating oil. On such viewpoint, the carbon number of the straight-chain fatty acid may preferably be 16 or more or more preferably be 20 or less. In the mixed fatty acids of the straight-chain saturated fatty acid and straight-chain unsaturated fatty acid each having a carbon number of 14 to 22 (the total content is defined as 100 mass %), the content of the straight-chain unsaturated fatty acid may preferably be 60 mass % or higher, more preferably be 65 mass % or higher and most preferably be 70 mass % or higher.

As the raw material of the ester compound (A), adipic acid is applied as a dibasic acid. In the case that succinic acid or the like with a carbon number less than that of adipic acid is applied, effects may not be exhibited upon the addition of various kinds of additives, so that it may not be suitable as a lubricating base oil. On the other hand, in the case that sebacic acid or the like with a carbon number more than that of adipic acid is applied or that maleic acid or the like including an unsaturated bond is applied, the stability against oxidation or heat resistance may possibly be deteriorated. Thus, adipic acid is preferred as the dibasic acid applied in the present invention.

According to the ester compound (A), the molar percentage of the constituent component (a) derived from pentaerythritol is 20 to 30 mol %, the molar percentage of the constituent component (b) derived from the straight-chain fatty acid having a carbon number of 14 to 22 is 55 to 79 mol %, the molar percentage of the constituent component (c) derived from adipic acid is 1 to 15 mol %, and the ratio [(c) mol %/(b) mol %] of the molar percentage of the constituent component (b) derived from the straight-chain fatty acid having a carbon number of 14 to 22 with respect to the molar percentage of the constituent component (c) derived from adipic acid is 0.02 to 0.25.

The molar percentages of the respective constituent components (a), (b) and (c) derived from the respective raw materials are defined as (a) mol %, (b) mol % and (c) mol %.

(a) mol %, (b) mol %, (c) mol % and [(c) mol %/(b) mol %] are values calculated after the ester compound is analyzed by 1H NMR and the molar ratios of the constituent components derived from the respective raw materials are obtained.

The measurement condition of 1H NMR are shown below.

TheH NMR chart of the thus obtained ester by the measurement condition described above is analyzed to calculate the molar ratios.

Specifically, the following four peaks are applied.

The integral values of the four peaks described above are calculated as follows to obtain the molar ratios (a) mol, (b) mol and (c) mol of the respective constituent components derived from the respective raw materials.

(a) mol %, (b) mol % and (c) mol % are calculated as follows, based on (a) mol, (b) mol and (c) mol obtained as described above.

Further, the molar ratios of the constituent components can be calculated as follows based on (a) mol %, (b) mol % and (c) mol % described above.

According to the ester compound (A), (a) mol %:(b) mol %:(c) mol %=20 to 30 mol %: 55 to 79 mol %: 1 to 15 mol %. Further, (a) mol %+ (b) mol %+ (c) mol % is defined as 100 mol %.

In the case that the ranges are out of the ranges described above, there are possibilities that the rust resistance may be deteriorated, the fuel efficiency may be deteriorated due to energy loss caused by internal resistance of the lubricant oil itself accompanied with a high viscosity, the biodegradability maybe deteriorated and lubricant property (extreme pressure property) may be deteriorated. On such viewpoints, (a) mol % may preferably be 21 to 27 mol % and more preferably be 22 to 25 mol %. Further, (b) mol % may preferably be 60 to 79 mol % and more preferably be 70 to 75 mol %. Further, (c) mol % may preferably be 2 to 10 mol % and more preferably be 3 to 6 mol %.

Further, according to the ester compound (A), (c) mol %/(b) mol % is 0.02 to 0.25. In the case that (c) mol %/(b) mol % is less than 0.02, the rust prevention property may possible be deteriorated. On the other hand, in the case that (c) mol %/(b) mol % exceeds 0.25, the energy loss due to internal resistance of the lubricant oil itself accompanied with a high viscosity may be larger, so that the fuel efficiency may be deteriorated or biodegradability may be deteriorated. (c) mol %/(b) mol % may preferably be 0.03 to 0.20 and more preferably be 0.05 to 0.10.

According to the ester compound (A), (c) mol %/(a) mol % may preferably be 0.05 to 0.55. (c) mol %/(a) mol % is made 0.05 or higher, so that the rust preventing property can be further improved. Further, (c) mol %/(a) mol % is made 0.55 or lower, so that the energy loss due to the internal resistance of the lubricant oil itself accompanied with a high viscosity can be prevented to suppress the deterioration of the fuel efficiency and deterioration of biodegradation. On such viewpoint, (c) mol %/(a) mol % may preferably be 0.10 to 0.40 and more preferably be 0.15 to 0.30.

According to the ester compound (A), (b) mol %/(a) mol % may preferably be 2.0 to 4.0. (b) mol/(a) mol is made 2.0 or higher, so that the energy loss due to the internal resistance of the lubricant oil itself accompanied with a high viscosity can be suppressed and the deterioration of fuel efficiency due to the internal resistance and deterioration of biodegradability can be suppressed. (b) mol %/(a) mol % may be made 4.0 or higher, so that the rust preventing property can be further improved. On such viewpoints, (b) mol %/(a) mol % may preferably be 2.3 to 3.8 and more preferably be 2.5 to 3.5.

The ester compound (A) has a hydroxyl value of 10 to 100 mgKOH/g. In the case that the hydroxyl value of the ester is lower than 10 mgKOH/g, the rust preventing property may possibly be deteriorated. On the other hand, in the case that the hydroxyl value of the ester exceeds 100 mgKOH/g, the lubricating property (extreme pressure property) or demulsibility may possibly be deteriorated. On such viewpoints, the hydroxyl value of the ester compound (A) may preferably be 15 to 75 mgKOH/g and more preferably be 20 to 60 mgKOH/g.

According to the ester compound (A), the kinetic viscosity at 40° C. may preferably be 60 to 300. The kinetic viscosity of the ester at 40° C. is made 60 or higher, so that the lubricating property (extreme pressure property) can be further improved. Further, the kinetic viscosity of the ester at 40° C. is made 300 or lower, so that the energy loss due to the internal resistance of the lubricating oil itself accompanied with a high viscosity can be reduced and the deterioration of the fuel efficiency can be suppressed. On such viewpoints, the kinetic viscosity of the ester compound (A) at 40° C. may preferably be 70 to 200 and more preferably be 75 to 150.

The acid value of the ester compound (A) may preferably be 10.0 mgKOH/g or lower. The acid value of the ester can be made 10.0 mgKOH/g or lower, so that the reduction of lubricating property (extreme pressure property) or stability against oxidation can be suppressed. On such viewpoints, the acid value of the ester compound (A) may preferably be 5.0 mgKOH/g or lower, more preferably be 3.0 mgKOH/g or lower and most preferably be 1.0 mgKOH/g or lower.

Further, the lubricating oil composition of the present invention contains the amine salt of an acidic phosphoric acid ester represented by the following formula.

Here, R″ represents hydrogen or a straight-chain or branched-chain alkyl group having a carbon number of 11 to 14. The carbon number of R″ may more preferably be 12 or more and more preferably be 13 or less. At least one of the three R″ may preferably be the straight-chain alkyl group or branched-chain alkyl group having a carbon number of 11 to 14.

According to the amine salt (B) of an acidic phosphoric acid ester, as n represents an integer of 1 or 2, one or two hydroxide groups may be contained. In the case that one hydroxide group is contained, the number of —OR′— group is two, and in the case that two hydroxide groups are contained, the number of —OR′— is one. These may be mixture.

R′ represents a straight-chain alkyl group having a carbon number of 4 to 6. In the case that the carbon number of R′ is less than 4, sufficient extreme pressure property may not possibly be obtained. Further, in the case that carbon number of R′ exceeds 6, sufficient extreme pressure property may not possibly be obtained. According to the present invention, on the viewpoint that excellent lubricating property (extreme pressure property) and stability against oxidation can be obtained, monohexyl or dihexyl phosphate having a carbon number of 6 is most preferred.

R″ represents hydrogen or a straight-chain or branched-chain alkyl group having a carbon number of 11 to 14. In the case that the carbon number of R″ is 10 or less, as the solubility in the lubricating oil is lowered, so that precipitation or the like may possibly occur at a low temperature upon blending, which is not preferred. On the other hand, in the case that the carbon number of R″ is 15 or more, sufficient extreme pressure property may not be obtained. According to the present invention, it is preferred to contain the salt, in which the carbon number of R″ is 12 to 14, as a main component.

According to the present invention, 0.1 to 1.5 mass parts of the amine salt (B) of an acidic phosphoric acid ester is contained, with respect to 100 mass parts of the ester compound (A). In the case that the content of amine salt (B) of an acidic phosphoric acid ester is less than 0.1 mass parts, sufficient lubricating property (extreme pressure property) may not possibly be obtained. Further, in the case that the content of the amine salt (B) of an acidic phosphoric acid ester exceeds 1.5 mass parts, the demulsibility may be deteriorated and toxicity in an aquatic life may possibly be increased. On such viewpoints, the content of the amine salt (B) of an acidic phosphoric acid ester may preferably be 0.15 mass parts or higher, more preferably be 1.25 mass parts or higher and most preferably be 1.00 mass parts or lower.