JP2922666B2 - High viscosity heat resistant lubricating oil composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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, which has excellent thermal / oxidative stability, high kinematic viscosity, high viscosity index, and low pour point.

[0002]

2. Description of the Related Art Mineral oil-based lubricating oils are widely used for bearings, gears, etc. of various industrial machines, machine tools, turbines, etc., and the viscosity range of the lubricating oils is ISO viscosity grades VG2 to 1500 according to the load and rotation speed. Are used. In particular, a high-viscosity mineral lubricating oil of VG 100 or more is light in the case of a sliding bearing, in a region where it rotates at a low speed even under a medium load or in a region where a high load is applied, and in the case of a rolling bearing, the operating temperature condition is relatively high. High or high impact load d
It is applied to the condition where the n value is 15,000 or less.

On the other hand, among synthetic lubricating oils, neopentyl type polyol esters, which have many advantages in heat / oxidation stability, lubricity, volatilization loss, etc., are widely used in automobile engine oils, jet engine oils and the like. But,
In order to improve the thermal and oxidative stability, medium- and short-chain fatty acid esters are used.
~ 40 centistokes and small, the above various industrial machines,
It is difficult to apply under severe conditions such as in bearings for machine tools, turbines, gears, and the like.

[0004]

In recent years, with the increase in size, speed, and performance of machines, lubricating oils have been used in high-temperature environments. On the other hand, long life of lubricating oils has been demanded from the viewpoint of maintenance-free. Therefore, lubricating oils having excellent heat and oxidation stability and low evaporation loss are required.

[0005] Lubricating oil is oxidized by oxygen in the air, and the oxidation proceeds at an accelerated rate due to a rise in temperature, the presence of metal and water. If oxidation progresses, the viscosity may increase significantly or solidify, and the filter may be blocked due to the generation of a large amount of insoluble substances, making it difficult to lubricate lubricating points such as bearings and gears. Wear and corrosion of bearings occur, which adversely affects the safety and durability of the equipment. The service limit temperature of mineral oil-based lubricating oil is generally around 100 ° C for long-term use. At higher temperatures, synthetic lubricating oil with excellent heat resistance is required, especially at oil temperature of 150 ° C or more. Synthetic lubricants are essential. As an ester-based high-viscosity synthetic oil, there is an example using a long-chain fatty acid of a neopentyl polyol type ester, but the pour point is high, and when a branched fatty acid is used, the pour point decreases but the viscosity index decreases. On the other hand, long-chain unsaturated fatty acids can provide a base oil having a relatively high viscosity, but have the drawback of causing problems such as a remarkable decrease in heat and oxidation 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 having particularly excellent heat and oxidation stability.

[0007]

According to the present invention, there is provided (A) an α-olefin / dibasic acid copolymer ester alone or a poly-α-olefin / α-olefin / dibasic acid copolymer ester in an amount of 20% by weight. % Or more, and 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. 0.1 to 4.0 parts by weight of the sum total of one kind and at least one of the alkylphenol-based antioxidants, or 0.1 to 4.0 parts by weight of at least one of the aromatic amine-based antioxidants It is characterized by including.

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

[0009]

Embedded image (R is a C6-C28, preferably C8-C18 alkyl group) α-olefin represented by the formula 2 C _2X H _4X-2 (COOH) ₂ (X is an integer of 1-4, preferably X is 1 or The copolymer synthesized from the dibasic acid represented by 2) was esterified with a monohydric alcohol represented by the formula 3 C _Y H _{2Y + 1} OH (Y is 1 to 6, preferably Y is 2 to 4). Formula 1

[0010]

Embedded image (N is 1 to 8, preferably 2 to 6).

The base oil used in the present invention can be prepared by adjusting the viscosity of the α-olefin / dibasic acid copolymer ester represented by the above general formula or by adjusting the viscosity by mixing with the poly-α-olefin. Good, especially suitable as high viscosity base oils of ISO viscosity grades VG100 to 680.

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

The high-viscosity heat-resistant lubricating oil composition of the present invention means that the viscosity-adjusted base oil contains at least one of aromatic amine-based antioxidants and at least one of alkylphenol-based antioxidants, At least one of the aromatic amine-based antioxidants is contained, but as the aromatic amine-based compound, R ₁ —NH—R ₂ (R ₁ and R ₂ may be the same or different;
Represents an aryl group or an alkaryl group) and the general formula 3

[0014]

Embedded image (R _{1 to} R ₄ may be the same or different, and a C1 to C4 alkyl group, and n represents 1 to 4);

[0015]

Embedded image (R _{1 to} R ₄ may be the same or different, and a C1 to C4 alkyl group, and n represents 1 to 4). Examples are p, p'-dioctyldiphenylamine,
Examples thereof include phenyl-α-naphthylamine, phenyl-β-naphthylamine, phenyl-p-octylphenylamine, and tetramethyldiaminodiphenylmethane.

As the alkylphenol, a compound represented by the general formula 5

[0017]

Embedded image (R _{1 to} R ₃ may be the same or different and each represents a C1 to C4 alkyl group);

[0018]

Embedded image (R _{1 to} R ₄ may be the same or different; C _{1 to} C ₄ alkyl groups; Z is (CH ₂ ) _n (n is 0 to 4);
—, —S—S—, —CH ₂ —S—CH ₂ — and the like;

[0019]

Embedded image (R _{1 to} R ₄ may be the same or different; C _{1 to} C ₄ alkyl groups; Z is (CH ₂ ) _n (n is 0 to 4);
-, - S-S -, - CH 2 -S-CH 2 - represents a divalent group, etc.) and the general formula 8

[0020]

Embedded image (R _{1 to} R ₃ may be the same or different, and C _{1 to} C 20
Represents an alkyl group. n includes the compounds represented by 1 to 4). Examples are 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 Can be mentioned.

In the antioxidant of the present invention, at least one of aromatic amines and alkylphenols is preferably used in combination. It is particularly preferable to use p, p'-dioctyldiphenylamine and phenyl-α-naphthylamine in combination as aromatic amines, and 4,4′-methylenebis (2,6-di-t-butylphenol) as alkylphenols.

The compounding amount of the antioxidant is 0.1 to 4.0 parts by weight, preferably 0.1 part by weight, per 100 parts by weight of the base oil.
If the amount is less than this range, the effect as an antioxidant is not sufficient. On the other hand, if it exceeds this range, the effect corresponding to the increase in weight cannot be obtained.

In the high-viscosity heat-resistant lubricating oil composition of the present invention, in addition to the above-mentioned antioxidant, various additives such as an oiling agent, an extreme pressure agent, an antifoaming agent, and a rust preventive may be added in an appropriate amount, if necessary. You can do it.

[0024]

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

Samples were prepared by adding an antioxidant to a base oil whose viscosity was adjusted with various ester-based synthetic oils and poly-α-olefin-based synthetic oils, and an oxidation stability test was performed.
Further, an antioxidant was added to the above-mentioned synthetic base oil, other typical ester-based synthetic base oils and mineral oils, and viscosity, viscosity index, pour point measurement and oxidation stability tests were carried out.

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

[0027]

[Table 1]

[0028]

[Table 2] The examples of the present invention are superior in heat and oxidation stability to the comparative examples and have properties of 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 heat and oxidation stability, and is only about １ ／ of Examples 1 to 3. Comparative Example 3 below
As shown in Tables (1) to (5), when a synthetic oil other than the α-olefin / dibasic acid copolymer or a base oil obtained by mixing a synthetic oil with another poly-α-olefin is used, heat / oxidation stability Properties are significantly reduced.

In Examples 1-4, 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 replaced. However, the effects of the present invention were observed.

Description of Test Method <RBOT> JIS K2514 Rotating Bomb Type 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 into the container. 3k
gf / cm ² {620 KPa} and put into a 150 ° C. thermostat. The cylinder is rotated at a speed of 100 revolutions per minute while maintaining the cylinder at an angle of 30 °, and the time (min) until the sample reacts with a certain amount of oxygen is determined by a specified pressure drop. <ISOT> Based on JIS K2514 Lubricating Oil Oxidation Stability Test Method for Internal Combustion Engine Stir and oxidize a sample and a sample container containing copper and iron catalysts with a stirrer at a certain temperature for a certain time, then kinematic viscosity of oxidized oil and total acid The value is measured and compared with those of the unoxidized oil.
The weight of the sludge is measured as pentane-insoluble matter.

[0031]

The high-viscosity heat-resistant lubricating oil composition according to the present invention has a high viscosity and a high viscosity by selecting a synthetic oil as a base oil and adding an effective amount of the selected antioxidant to the base oil. Excellent heat resistance was obtained while maintaining the viscosity index and the low pour point.

Therefore, when used as a high-viscosity heat-resistant lubricating oil for various industrial machines at high temperatures, remarkable thickening and solidification due to oxidation can be prevented, and troubles such as clogging of filters due to insoluble substances, so-called sludge, can be solved. Insufficient lubrication can be prevented, resulting in prevention of seizure and abnormal wear of bearings, gears, etc., as well as extending the life of lubricating oil, improving safety, streamlining lubrication work, and improving productivity. It is also a great place to contribute.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 133: 14 129: 10) C10N 20:02 30:08 30:10 40:02 40:04 (56) References 2-110194 (JP, A) JP-A-62-84186 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C10M 169/04 C10M 107/02-107/22 C10M 129 / 10 C10M 133/12-133/14 C10N 30:08-30:10 C10N 40:02-40:04 WPI / L (QUESTEL)

Claims (1)

(57) [Claims] (A) an α-olefin / dibasic acid copolymer ester alone or a mixture of a poly-α-olefin and 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 is obtained by adding at least one of (B) an aromatic amine antioxidant and an alkylphenol antioxidant. A high viscosity comprising 0.1 to 4.0 parts by weight of the total of at least one of the above, or 0.1 to 4.0 parts by weight of at least one of the aromatic amine antioxidants. Heat resistant lubricating oil composition.