WO2011036919A1 - Lubricant composition - Google Patents

Abstract

Disclosed is a lubricant composition which exhibits excellently low friction and excellent low-temperature storage stability, while having high flash point. Specifically disclosed is a lubricant composition for a sliding guide surface having excellent positioning performance, which is characterized by containing, in a lubricant base oil, (A) an acidic phosphate ester represented by the general formula (1) below in an amount of 0.02-0.1% by mass based on the total amount of the composition and (B) an aliphatic monoamine represented by the general formula (2) below in an amount of 0.005-0.1% by mass based on the total amount of the composition. (R1O)mP(=O)(OH)3-m (1) (In the formula (1), R1 represents a linear alkyl group having 4-8 carbon atoms, and m represents 1 or 2. When m is 2, the R1s may be the same as or different from each other.) R2 nNH3-n (2) (In the formula (2), R2 represents a linear alkyl group or linear alkenyl group having 12-18 carbon atoms, and n represents an integer of 1-3. When n is 2 or 3, the R2s may be the same as or different from each other.)

Description

Lubricating oil composition

The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition used for a machine tool, and preferably used for a sliding guide surface of a machine tool.

Lubricating oils for sliding guide surfaces such as processing tables of machine tools are required to have low friction performance, prevention of stick-slip, storage stability, corrosion resistance, and the like in order to improve processing accuracy. In addition, in a place where machine tools are installed, the lubricating oil is preferably flame retardant from the viewpoint of fire safety, and a flash point of 250 ° C. which is not subject to the regulation of the fourth oil of the Fire Service Law from the viewpoint of management. The above lubricating oil is preferred.
Various extreme pressure agents and oil-based agents have been used as friction reducing agents. In recent machine tools, there is an increasing demand for machine accuracy, and in order to reduce friction in low-speed areas that have an important influence on machine accuracy, phosphate esters, acid phosphate esters, phosphite esters, carvone esters Acids, sulfur compounds, amines and the like are used (see, for example, Patent Document 1). In addition, attempts have been made to improve stability by neutralizing acidic phosphate esters with alkylamines (see, for example, Patent Document 2).
In addition, as one of the oily agents, it is described in many patent documents (for example, Patent Document 2) that amines such as monoamine, polyamine and alkanolamine may be blended. As for alkanolamine, a method of using it as a compound forming a salt such as an amine salt with an acidic phosphate ester or an amide with a carboxylic acid is described (for example, Patent Document 3).
In this way, various lubricity improvers have been studied, and long-term performance improvements such as friction performance and stain resistance have been improved and maintained, but sliding guide surface oil requires further improvements such as positioning accuracy. ing. In addition, the safety against fire is still not sufficient, and many products with a flash point of less than 250 ° C. are seen.

JP-A-8-134488 JP 2007-238764 A JP 2008-013688 A

However, although additives such as phosphate ester compounds and amine compounds in these prior art lubricating oil compositions have improved initial frictional performance and positioning performance of machine tools, acidic components such as phosphoric acid use iron. This causes deterioration of the machining accuracy in the machine tool, such as the occurrence of corrosion on the sliding surface, and the positioning accuracy tends to deteriorate as the use of the apparatus proceeds.

Up to now, attempts have been made to improve corrosion resistance and storage stability by neutralizing acidic phosphate esters with amines. It was difficult to keep up. Therefore, there is a need for an oil that has excellent friction performance over a long period of time, maintains positioning performance, and can suppress the occurrence of corrosion. On the other hand, due to management problems, a lubricating oil composition having a flash point of 250 ° C. or higher that is not subject to the regulation of the fourth petroleum of the Fire Service Act is desired.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a lubricating oil composition that is excellent in low friction properties, positioning properties, low temperature storage stability, and has a high flash point. Another object of the present invention is to provide a lubricating oil composition having excellent corrosion resistance.

As a result of intensive studies to achieve the above object, the present inventors have found that the above problem is caused by a lubricating oil composition containing a specific acidic phosphate compound and a specific aliphatic monoamine compound in the lubricating base oil. As a result, the present invention has been completed.
That is, the present invention is as follows.

[I] In the lubricating base oil, the acid phosphate ester represented by the following general formula (1) as the component (A) is 0.02 to 0.1% by mass based on the total amount of the composition, and the component (B) A lubricating oil composition comprising an aliphatic monoamine represented by the following general formula (2) in an amount of 0.005 to 0.1% by mass based on the total amount of the composition.
(R ¹ O) _m P (═O) (OH) _3-m (1)
(In Formula (1), R ¹ represents a linear alkyl group having 4 to 8 carbon atoms, and m is 1 or 2. When m is 2, R ¹ may be the same or different. )
R ² _n NH _3-n (2)
(In the formula (2), R ² represents a linear alkyl group or linear alkenyl group having 12 to 18 carbon atoms, and n is an integer of 1 to 3. When n is 2 or 3, R ² represents They may be the same or different.)

[II] The lubricating oil composition according to [I], further including a reaction product of the component (A) and the component (B).

[III] The lubricating oil composition as described in [I] or [II] above, which is used for a sliding guide surface of a machine tool.

[IV] The lubricating oil composition according to any one of [I] to [III] above, having a flash point of 250 ° C. or higher.

The lubricating oil composition of the present invention has high positioning properties, excellent storage stability, and high flash point. Therefore, the lubricating oil composition of the present invention is very useful in terms of stabilizing the operation of the machine tool, extending its life, and safety.

Hereinafter, the present invention will be described.

The lubricating base oil used in the present invention is not particularly limited, and examples thereof include mineral oils, fats and oils, and synthetic oils.
There are no particular limitations on the production method of the mineral oil base oil. For example, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and vacuum distillation is subjected to solvent removal, solvent extraction, hydrocracking, solvent Mention may be made of paraffinic or naphthenic mineral oils obtained by applying one or more refining means such as dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment as appropriate.

Examples of fats and oils include beef tallow, pork tallow, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and hydrogenated products thereof. Moreover, the said fats and oils which raised the oleic acid content using the gene recombination technique can also be used conveniently.

Synthetic oils include, for example, poly-α-olefins (ethylene-propylene copolymers, polybutenes, 1-octene oligomers, 1-decene oligomers, hydrides thereof), alkylbenzenes, alkylnaphthalenes, monoesters (butyl stearate). , Octyl laurate, etc.), diester (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sepacate, etc.), polyester (trimellitic acid ester, etc.), polyol ester ( Trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene Recall, polyphenyl ether, dialkyl diphenyl ether, phosphate ester (tricresyl phosphate, etc.), fluorine-containing compound (perfluoropolyether, such as fluorinated polyolefins), such as silicone oil can be exemplified.

As the lubricating base oil, one kind selected from mineral oil, fats and oils and synthetic oils can be used alone or in combination of two or more kinds.

The viscosity of the lubricating base oil used in the present invention is not particularly limited, but the kinematic viscosity at 40 ° C. is preferably in the range of 10 to 700 mm ² / s, and is preferably in the range of 15 to 500 mm ² / s Is more preferable. Further, the content of the lubricating base oil in the lubricating oil composition of the present invention is not particularly limited, but is preferably in the range of 50 to 99.98% by mass based on the total amount of the composition.

Specific examples of the phosphorus compound of component (A) in the lubricating oil composition of the present invention include monoalkyl acidic phosphate esters, dialkyl acidic phosphate esters, and mixtures thereof. The alkyl group of these alkyl acidic phosphates is a linear alkyl group, and is an alkyl group having 4 to 8, preferably 6 to 8 carbon atoms. Moreover, the carbon number of the two alkyl groups of the dialkyl acidic phosphate ester may be the same or different.
When the carbon number is less than 4 and the carbon number exceeds 8, the positioning performance is inferior, which is not preferable.

Specific examples of the linear alkyl group having 4 to 8 carbon atoms include a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group.

Specific examples of preferable compounds as the component (A) include mono n-butyl acid phosphate, mono n-pentyl acid phosphate, mono n-hexyl acid phosphate, mono n-heptyl acid phosphate, and mono n-octyl acid phosphate. , Di-n-butyl acid phosphate, di-n-pentyl acid phosphate, di-n-hexyl acid phosphate, di-n-heptyl acid phosphate, di-n-octyl acid phosphate, and the like.

In the lubricating oil composition of the present invention, the content of the acidic phosphate ester as the component (A) is 0.005 to 0.1% by mass based on the total amount of the composition, and is further excellent in low friction performance and positioning performance. Therefore, it is preferably 0.01% by mass or more based on the total amount of the composition. Moreover, from the point which is further excellent in the corrosion resistance of the obtained lubricating oil composition for sliding guide surfaces, and since it does not have a bad influence on a flash point, content of the acidic phosphate ester of (A) component is the composition whole quantity. On the basis, it is 0.1% by mass or less, preferably 0.08% by mass or less.

The aliphatic monoamine of component (B) in the lubricating oil composition of the present invention is a monoamine having 1 to 3 linear alkyl groups and / or linear alkenyl groups having 12 to 18 carbon atoms. Any of secondary amines and tertiary amines may be used, but primary amines or secondary amines are preferred, and primary amines are most preferred.
When the carbon number is less than 12 and the carbon number exceeds 18, the positioning performance is inferior, which is not preferable.

Specific examples of the linear alkyl group or linear alkenyl group having 12 to 18 carbon atoms include dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group; dodecenyl group, tridecenyl group Group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, alkenyl group of octadecenyl group (the position of the double bond of these alkenyl groups is arbitrary), and the like.

In the lubricating oil composition of the present invention, the content of the aliphatic monoamine as the component (B) is 0.005 to 0.1% by mass based on the total amount of the composition, and the corrosion resistance performance to the metal material is further improved. Therefore, it is preferably 0.008% by mass or more based on the total amount of the composition. Moreover, from the point which does not have a bad influence on low odor property, solubility, and flash point, content of the aliphatic monoamine of the component (B) is preferably 0.08% by mass or less based on the total amount of the composition. Preferably it is 0.05 mass% or less.

The lubricating oil composition of the present invention may further contain a reaction product of the components (A) and (B) in order to impart performance such as positioning performance.
The content of the reaction product of component (A) and component (B) is preferably 0.005 to 0.1% by mass, more preferably 0.008 to 0.08% by mass, based on the total amount of the composition. .

The lubricating oil composition of the present invention is known in the lubricating oil field in order to further enhance its performance, or to impart performance required as a lubricating oil composition, particularly a lubricating oil composition for sliding surfaces of machine tools. Additives can be blended.

Examples of such additives include monohydric alcohols or polyhydric alcohols, monobasic acids or polybasic acids, esters of the alcohol and the acid, amines other than the aliphatic monoamine represented by the general formula (2); Antioxidants such as phenol compounds such as tert-butyl-p-cresol and bisphenol A, and amine compounds such as phenyl-α-naphthylamine and N, N′-di (2-naphthyl) -p-phenylenediamine; Metal deactivators such as triazole and alkylthiadiazole; Antifoaming agents such as silicone oil and fluorosilicone oil; Phosphate ester compounds containing sulfur; Rust prevention additives such as alkenyl succinic acid and sorbitan monooleate; Polymethacrylate, etc. Pour point depressants; polymethacrylate, polybutene, polyalkylstyrene, o Fin copolymer, styrene - diene copolymers, styrene - such as viscosity index improvers, such as maleic anhydride copolymers.

The lubricating oil composition of the present invention has high positioning properties, excellent storage stability, and high flash point. Therefore, the lubricating oil composition of the present invention is very useful in terms of stabilizing the operation of the machine tool, extending its life, and safety.
Therefore, the lubricating oil composition of the present invention is suitably used in various applications that require low friction and stain resistance. In particular, the effect of the present invention is further exhibited when used as a lubricant for a sliding guide surface (sliding surface) of a machine tool or the like.

Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to these examples.

[Examples 1 to 9, Comparative Examples 1 to 17]
Various lubricating oil compositions according to the present invention having compositions as shown in Table 1 and Table 2 and lubricating oil compositions for comparative examples were prepared. The components used for the preparation of each composition are as follows. The flash point was measured according to JIS K 2265 “Crude oil and petroleum products—Flash point test method (Cleveland open type)”.

(1) Lubricating oil base oil Base oil 1: solvent dewaxing, hydrorefined paraffinic mineral oil (viscosity index 98, sulfur content 0.62 mass%, kinematic viscosity at 40 ° C. 68.8 mm ² / s, flash point 256 ℃)

(2) Phosphorus compound A1: Mixture of mono n-hexyl acid phosphate and di n-hexyl acid phosphate (phosphorus content: 14.5% by mass)
A2: Mixture of mono n-octyl acid phosphate and di n-octyl acid phosphate (phosphorus content: 11.6% by mass)
A3: Mixture of mono-n-lauryl acid phosphate and di-n-lauryl acid phosphate (phosphorus content: 8.6% by mass)
A4: Mixture of mono-n-oleyl acid phosphate and di-n-olyl acid phosphate (phosphorus content: 6.6% by mass)
A5: Mixture of dimethyl acid phosphate, diethyl acid phosphate, di-n-propyl acid phosphate.
A6: Mixture of mono-2-ethylhexyl acid phosphate and di-2-ethylhexyl acid phosphate (phosphorus content: 12.0% by mass)

(3) Aliphatic monoamine B1: Laurylamine B2: Oleylamine B3: Hexylamine B4: Icosylamine B5: Di-2-ethylhexylamine B6: Di-isotridecylamine

Next, the following tests were performed on the lubricating oil compositions of Examples 1 to 9 and Comparative Examples 1 to 17.

<Positioning accuracy test>
Instructed by numerical control to perform minute feed at a rapid feed rate (24 m / min) 20 times in total, 1 μm in the positive direction every 10 seconds from an arbitrary coordinate on the NC precision lathe, followed by And commanded the same minute feed in the minus direction. The actual displacement was measured with a capacitance displacement meter, and the response accuracy of the lathe guide surface to the numerical control command was measured for each lubricant.
The evaluation of the positioning accuracy was made by evaluating the number of commands required until the movement actually started with respect to the command to be reversed in the minus direction after being sent in the plus direction.
The test was performed at 25 ° C., and after sufficiently running in with the test oil, each test oil was measured three times and the average value was obtained.

<Additive solubility test>
80 mL of the composition described in Tables 1 and 2 was collected in a transparent glass bottle (capacity 100 mL), stoppered, and left in a thermostatic bath at 0 ° C. for 30 days in a light-shielded state. Thereafter, the appearance was visually confirmed, and a product having no turbidity or precipitation was regarded as acceptable.

 

 

As is clear from the results shown in Tables 1 and 2, the lubricating oil compositions of Examples 1 to 9 have higher positioning accuracy and better solubility of the additives than Comparative Examples 1 to 17, Further, it can be seen that the reduction in flash point due to the addition of additives is small.

The lubricating oil composition of the present invention has a high positioning accuracy and is particularly suitable for a sliding guide surface of a machine tool.

Claims (4)

In lubricating base oil,
The acidic phosphoric acid ester represented by the following general formula (1) as the component (A) is represented by 0.02 to 0.1% by mass based on the total amount of the composition, and the general formula (2) as the component (B). The aliphatic monoamine is 0.005 to 0.1% by mass based on the total amount of the composition,
A lubricating oil composition comprising:
(R ¹ O) _m P (═O) (OH) _3-m (1)
(In Formula (1), R ¹ represents a linear alkyl group having 4 to 8 carbon atoms, and m is 1 or 2. When m is 2, R ¹ may be the same or different. )
R ² _n NH _3-n (2)
(In the formula (2), R ² represents a linear alkyl group or linear alkenyl group having 12 to 18 carbon atoms, and n is an integer of 1 to 3. When n is 2 or 3, R ² represents They may be the same or different.) The lubricating oil composition according to claim 1, further comprising a reaction product of the component (A) and the component (B). The lubricating oil composition according to claim 1 or 2, wherein the lubricating oil composition is used for a sliding guide surface of a machine tool. The lubricating oil composition according to any one of claims 1 to 3, having a flash point of 250 ° C or higher.