JPH04292694A - High-viscosity heat-resistant lubricant composition - Google Patents

Abstract

PURPOSE:To obtain a compound having excellent heat and oxidation stability, high kinematic viscosity and viscosity index by blending a base oil composed of an mu-olefin-dibasic acid copolymer ester (mixture) with a specific amount of an aromatic amine-based antioxidant. CONSTITUTION:(A) A base oil which comprises an mu-olefin-dibasic acid copolymer ester alone or a mixture prepared by blending a polymu-alpha-olefin with >=20wt.% of ester and has >=100 cst kinematic viscosity at 40 deg.C, >=10O viscosity index and >=-20 deg.C pour point is blended with (B) 0.1-4.0 pts.wt. (preferably 0.6-1.5 pt.wt.) aromatic amine-based antioxidant alone or mixture of the aromatic amine-based antioxidant and an alkylphenol-based antioxidant to give the objective composition.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to high viscosity heat resistant lubricating oil compositions. More specifically, the present invention relates to a high-viscosity, heat-resistant lubricating oil composition for various industrial machines that has excellent thermal and oxidative stability, high kinematic viscosity, high viscosity index, and low pour point.

0002

[Prior Art] Mineral oil-based lubricating oils are widely used in bearings, gears, etc. of various industrial machines, machine tools, turbines, etc., and the viscosity range of lubricating oils ranges from ISO viscosity grade VG2 to 1500 depending on load and rotation speed. are used. In particular, high viscosity mineral oil-based lubricants with a VG of 100 or higher are suitable for use in areas where sliding bearings rotate at low speeds even under light to medium loads or areas where high loads are applied, and in rolling bearings where operating temperature conditions are relatively high. DN where high or high impact load is applied
This applies to conditions where the value is 15,000 or less.

On the other hand, among synthetic lubricating oils, neopentyl polyol esters, which have many advantages in terms of thermal and oxidative stability, lubricity, and volatile loss, are widely used in automobile engine oils, jet engine oils, etc. but,
In order to improve thermal and oxidative stability, medium- and short-chain fatty acid esters are used, so the kinematic viscosity at 40°C is 20.
~40 centistokes small, various industrial machines mentioned above,
It is difficult to apply it under severe conditions such as machine tools, bearings for turbines, gears, etc.

0004

[Problems to be Solved by the Invention] In recent years, as machines have become larger, faster, and more sophisticated, lubricating oils are used in high-temperature environments, and on the other hand, there is a demand for longer lifespans of lubricating oils from the viewpoint of maintenance-free operation. Therefore, there is a need for a lubricating oil with excellent thermal and oxidative stability and low evaporation loss.

[0005] Lubricating oil is oxidized by oxygen in the air, and the oxidation progresses at an accelerated pace due to an increase in temperature and the presence of metals and water. As oxidation progresses, the viscosity may significantly thicken or solidify, and a large amount of insoluble substances will be generated, which will clog the filter and make it difficult to lubricate lubricated parts such as bearings and gears, resulting in seizure and abnormalities. This causes wear and corrosion of the bearings, which in turn adversely affects the safety and durability of the equipment. The operating temperature limit for mineral oil-based lubricating oils is generally around 100°C for long-term use; at temperatures higher than that, it is necessary to use synthetic lubricating oils with excellent heat resistance, especially at oil temperatures of 150°C or higher. Synthetic lubricants are essential. As ester-based high-viscosity synthetic oils, there are examples of using long-chain fatty acids of neopentyl polyol type esters, but these have high pour points, and when branched fatty acids are used, the pour points are lowered but the viscosity index is lowered. On the other hand, long-chain unsaturated fatty acids can provide base oils with relatively high viscosity, but they have the drawback of causing problems such as a marked decrease in thermal and oxidative stability.

An object of the present invention is to solve the above-mentioned problems and to provide a high viscosity, heat-resistant lubricating oil composition particularly excellent in thermal and oxidative stability.

[0007]

[Means for Solving the Problems] The present invention provides (A) α-olefin/dibasic acid copolymer ester alone or poly-α-olefin with 20% α-olefin/dibasic acid copolymer ester by weight. % or more, and has a kinematic viscosity of 100 centistokes or more at 40°C, a viscosity index of 100 or more, and a pour point of -20°C or less, (B) at least one of the aromatic amine antioxidants. 0.1 to 4.0 parts by weight of both one type and at least one alkylphenol antioxidant, or 0.1 to 4.0 parts by weight of at least one aromatic amine antioxidant. It is characterized by containing.

The α-olefin/dibasic acid copolymer ester used in the present invention is represented by the formula 1

[0009]

[Formula 1] (R is a C6-C28, preferably C8-C18 alkyl group) and an α-olefin of the formula 2C2XH4X-
2(COOH)2 (X is an integer of 1 to 4, preferably X is 1 or 2) A copolymer synthesized from a dibasic acid represented by the formula 3CY H2
Esterified with a monohydric alcohol represented by Y+1OH (Y is 1 to 6, preferably Y is 2 to 4), and has the general formula 1

0010
]

[Chemical 2] (n is 1-8, preferably 2-6).

The base oil used in the present invention can be prepared either by adjusting the viscosity by using α-olefin/dibasic acid copolymer esters shown in the above general formula, or by adjusting the viscosity by mixing with poly-α-olefin. It is especially suitable as a high viscosity base oil with an ISO viscosity grade of VG 100 to 680.

When adjusting the viscosity by mixing with poly-α-olefin, the amount of α-olefin/dibasic acid copolymer ester blended is preferably 20% by weight or more from the viewpoint of heat resistance and oxidation stability. If it is less than 20% by weight, α-olefin
The blending effect of the dibasic acid copolymer ester is not achieved and the heat resistance and oxidation stability are reduced.

The high viscosity heat-resistant lubricating oil composition of the present invention is characterized in that the viscosity-adjusted base oil is combined with at least one aromatic amine antioxidant and at least one alkylphenol antioxidant, or an aromatic The aromatic amine type antioxidant has the general formula 2 R1 -NH-R2 (R1 and R2 may be the same or different, and C6 to C
18 aryl group or alkaryl group) and general formula 3

[0014]

[Chemical formula 3] (R1 to R4 may be the same or different, and C1 to C
4 alkyl group, n represents 1 to 4) and general formula 4

[
0015

[Formula 4] (R1 to R4 may be the same or different, and C1 to C
4 alkyl group, n represents 1 to 4). Examples include p,p'-dioctyldiphenylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, phenyl-p-octylphenylamine, and tetramethyldiaminodiphenylmethane.

As the alkylphenol type, general formula 5 is used.

[0017]

[Formula 5] (R1 to R3 may be the same or different, and C1 to C
4) and general formula 6

[0018]

[Formula 6] (R1 to R4 may be the same or different, and C1 to C
4 alkyl group, Z is (CH2)n (n is 0 to 4)
, -S-, -S-S-, -CH2 -S-CH2 -, etc.) and general formula 7

[0019]

[Formula 7] (R1 to R4 may be the same or different, and C1 to C
4 alkyl group, Z is (CH2)n (n is 0 to 4)
, -S-, -S-S-, -CH2 -S-CH2 -, etc.) and general formula 8

[0020]

[Chemical formula 8] (R1 to R3 may be the same or different, and C1 to C
Represents 20 alkyl groups. n includes compounds represented by 1 to 4). Examples include 2,6-di-t-butyl-p-cresol, 4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-thiobis(2,6-di-
t-butylphenol), bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide, 2,2'
-methylenebis(4-methyl-6-t-butylphenol), n-octadecyl-3-(3'5'-di-t-butyl-4'-hydroxyphenyl), and the like.

[0021] Among the antioxidants used in the present invention, it is preferable to use a combination of at least one of aromatic amine type antioxidants and at least one type of alkylphenol type antioxidants. Particularly preferably, as the aromatic amine type, p,p'-dioctyl diphenylamine and phenyl-α-naphthylamine are used in combination, and as the alkylphenol type, 4,4'-methylenebis(2,6-di-t-butylphenol) is preferably used.

The amount of antioxidants to be blended is 0.1 to 4.0 parts by weight, preferably 0.1 to 4.0 parts by weight, based on 100 parts by weight of the base oil.
The amount is preferably 6 to 1.5 parts by weight; if it is less than this range, the effect as an antioxidant will not be sufficient, while if it exceeds this range, the effect commensurate with the increased amount will not be obtained.

[0023] In addition to the above-mentioned antioxidant, the high viscosity heat-resistant lubricating oil composition of the present invention may further contain appropriate amounts of various additives such as an oily agent, an extreme pressure agent, an antifoaming agent, and a rust preventive agent, if necessary. There is no problem in doing so.

[0024]

EXAMPLES Examples and comparative examples of the present invention will be described below, but the present invention is not limited thereto.

[0025]Antioxidant was added to base oils whose viscosity had been adjusted using various ester-based synthetic oils and poly-α-olefin-based synthetic oils to prepare samples, and oxidation stability tests were conducted. Furthermore, an antioxidant was added to the above synthetic base oil, other typical ester-based synthetic base oils, and mineral oil, and viscosity, viscosity index, pour point measurements, and oxidation stability tests were conducted.

Table 1 shows the results of Examples and Comparative Examples. Table 2 shows the properties and oxidation stability results for each sample during the selection stage of compatible base oils.

[0027]

[Table 1]

[0028]

[Table 2] The examples of the present invention have excellent thermal and oxidative stability compared to the comparative examples, and have properties such as high viscosity, high viscosity index, and low pour point. As shown in Comparative Example 2, a composition using a base oil of poly-α-olefins has a high viscosity, but has low thermal and oxidative stability, and is only about 1/3 of that of Examples 1 to 3. Comparative example 3 below
As shown in ~5, when using a base oil made by mixing synthetic oils other than α-olefin/dibasic acid copolymer or a mixture of other synthetic oils and poly-α-olefin, thermal/oxidative stability is achieved. Sexuality is significantly reduced.

In Examples 1 to 4, the combination of an aromatic amine antioxidant represented by another general formula and an alkylphenol antioxidant, or the addition of an aromatic amine antioxidant alone was substituted. When only the differences were made, the effects of the present invention were observed in each case.

Description of test method <RBOT> JISK2514 rotating cylinder oxidation stability test method A sample container with a lid containing a sample, water and a copper catalyst coil is placed in a cylinder equipped with a pressure gauge, and oxygen is introduced in 6. 3kg
It is press-fitted to f/cm2 {620KPa} and placed in a constant temperature bath at 150°C. The cylinder is held at an angle of 30° and rotated at a speed of 100 revolutions per minute, and the time (min) until a certain amount of oxygen reacts with the sample is determined by a specified pressure drop. <ISOT> After oxidizing the sample in accordance with the JIS K2514 internal combustion engine lubricating oil oxidation stability test method and a sample container containing copper and iron catalysts with a stirring rod at a constant temperature for a certain period of time, the kinematic viscosity of the oxidized oil and the total acid The values are measured and compared with those of unoxidized oil. In addition, the weight of the sludge is measured as the pentane insoluble content.

[0031]

Effects of the Invention: The high viscosity, heat-resistant lubricating oil composition of the present invention has high viscosity and high Excellent heat resistance was obtained while maintaining a low viscosity index and pour point.

Therefore, when used at high temperatures as a high viscosity heat-resistant lubricant for various industrial machines, it can prevent significant thickening and solidification due to oxidation, and eliminate problems such as filter clogging due to insoluble substances, so-called sludge. This prevents insufficient oil supply, which in turn prevents seizure and abnormal wear of bearings, gears, etc., and extends the life of the lubricating oil, improving safety, streamlining, and productivity of lubrication work. It also greatly contributes to

Claims (1)

[Claims] Claim 1: (A) an α-olefin/dibasic acid copolymer ester alone or a poly-α-olefin mixed with 20% by weight or more of an α-olefin/dibasic acid copolymer ester; A base oil having a kinematic viscosity at 40°C of 100 centistokes or more, a viscosity index of 100 or more, and a pour point of -20°C or less, (B) at least one aromatic amine antioxidant and an alkylphenol antioxidant. 0.1 to 4.0 parts by weight of at least one of the above, or 0 parts of at least one of the aromatic amine antioxidants.
．． A high viscosity heat-resistant lubricating oil composition comprising 1 to 4.0 parts by weight.