JPH06200277A - Lubricating oil composition - Google Patents

Abstract

(57) [Summary] [Objective] To provide a lubricating oil which has improved antioxidant property especially at high temperature and is suitable for a lubricating system such as a compressor oil, a turbine oil, a hydraulic oil having a large working load. [Structure] A lubricating base oil containing alkyldiphenyl and / or alkyldiphenyl ether, and an alkylated phenyl-α-alkylated naphthylamine as an antioxidant,
Lubricating oil composition containing a three-component antioxidant comprising alkylated diphenylamine and phosphite, or a four-component antioxidant containing a hindered phenol having an average molecular weight of 400 to 700 added thereto To prepare.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lubricating oil composition having excellent oxidation resistance. More specifically, the present invention shows that long-term oxidative stability and insoluble sludge formed by blending a specific antioxidant (radical scavenger and peroxide decomposer) with a lubricating base oil. The present invention relates to a lubricating oil composition that has an excellent balance of lubricating oil characteristics, such as extremely low occurrence.

[0002]

2. Description of the Related Art As is well known, when a synthetic base lubricating base oil is oxidized, a radical reaction proceeds due to autoxidation, and alcohols and ketones are generated by a reaction with oxygen.
Then, these oxides of alcohols and ketones are polycondensed to produce sludge insoluble in the base oil, which causes a great obstacle to the lubricating system.

That is, the sludge produced by the oxidation of the lubricating oil causes the clogging of the oil tank and the reduction of the efficiency of the cooler. On the other hand, the properties of the lubricating oil rapidly deteriorate as the oxidation reaction progresses. To explain this point more concretely, for example, in a screw type compressor, the lubricating oil cools the rotor and the casing that have become high in temperature during the compression process, and the heat itself gets high temperature and releases this heat to the outside of the system. However, at this time, since the oxidation reaction is accelerated by the oxidation catalyst reaction of the oil cooler made of copper, the demand for the oxidation stability is extremely high.

Conventionally, an antioxidant is generally blended in order to improve the oxidative stability of the lubricating oil. Radical scavengers, peroxide decomposers and the like are known as antioxidants of this kind due to their actions, and these are used alone or in combination. In addition to these antioxidants, other additives such as metal deactivators have been used to deactivate metal compounds eluted in lubricating oils.
However, the present situation is that no stabilizer has been developed for enhancing the oxidation resistance of lubricating oil and for exhibiting stable lubricating characteristics for a long period of time.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, a specific component having excellent additive solubility is selected as a lubricating base oil, and a specific amino antioxidant as a radical scavenger,
And by combining a specific phosphite as a peroxide decomposing agent, by further mixing a specific phenolic antioxidant, the long-term oxidation resistance is excellent and the amount of sludge generated is extremely small. It is intended to provide a lubricating oil composition having an excellent balance of lubricating oil properties.

[0006]

The present invention uses at least one of alkyl diphenyl and alkyl diphenyl ether as a lubricating base oil, and (1) (i) alkylated phenylamine-α-alkylated naphthylamine, (ii) ) A lubricant composition comprising an antioxidant composed of three types of alkylated diphenylamine and (iii) phosphite.

Alternatively, (2) (i) alkylated phenylamine-α-alkylated naphthylamine, (ii) alkylated diphenylamine, (iii) phosphite, and (iv) four hindered phenols having an average molecular weight of 400 to 700. It is a lubricating oil composition prepared by blending various types of antioxidants.

The present invention exhibits high oxidative stability and is used in comparison with mineral oils and other synthetic lubricating oils based on the fact that the base oil is at least one of alkyl diphenyl and alkyl diphenyl ether. It is highly soluble in additives such as antioxidants, and exhibits various properties as a lubricating oil.

The structure of the present invention will be described in detail below.

First, the base oil component constituting the lubricating oil composition of the present invention will be described.

[0011] any if a lubricating oil to enter the alkyl diphenyl such categories may be used, typically represented by the following formula.

[0012]

[Chemical 1]

[M is 1 to 3, n is 0 to 3, R is carbon number 1
0-20 alkyl groups (they may be the same or different when there are a plurality of R's)] Specifically, n-decyldiphenyl, n-undecyldiphenyl, n-dodecyldiphenyl, n-tridecyldiphenyl, n -Tetradecyldiphenyl, n-heptadecyldiphenyl, n-hexadecyldiphenyl, n-nonadecyldiphenyl, n-octadecyldiphenyl, n
-Eicosyldiphenyl, 2-decyldiphenyl, 2-
Hexadecyldiphenyl, 2-octadecyldiphenyl, 3-decyldiphenyl, 4-decyldiphenyl, di (n-decyl) diphenyl, di (n-dodecyl) diphenyl, di (2-decyl) diphenyl, di (2-dodecyl) diphenyl , Penta (2-tetradecyl) diphenyl, tri (2-dodecyl) di (2-tetradecyl) diphenyl, hexa (2-dodecyl) diphenyl, and the like. Preferable ones are R having 12 to 18 carbon atoms and m being 1
And n is 0 to 1, and particularly preferable is that R has 12 carbon atoms.
~ 14 alkyl groups, m is 1, n is 1, R
Is an alkyl group having 16 to 18 carbon atoms, m is 1 and n is 0.
belongs to. When the alkyl group has less than 10 carbon atoms, the lubricity is poor, and when it exceeds 20 carbon, the viscosity becomes high and the thermal stability and the oxidation stability become poor.

The kinematic viscosity at 100 ° C. is 2.0 to
Those having a thickness of 30.0 mm ² / s can be used.

Even if it is out of the above range,
From the viewpoint of average molecular weight, any compound can be used as long as it falls within the above range by mixing.

Alkyl diphenyl ethers Any lubricating oil that falls within this category may be used, but is typically represented by the formula:

[0017]

[Chemical 2]

[M is 1 to 3, n is 0 to 3, R is a carbon number 1
0 to 20 alkyl groups (when R is plural, they may be the same or different)] Specifically, monodecyl diphenyl ether, monododecyl diphenyl ether, monotetradecyl diphenyl ether, monohexadecyl diphenyl ether, monooctadecyl diphenyl ether, mono Eicosyl diphenyl ether, ditetradecyl diphenyl ether,
Didodecyl diphenyl ether, didecyl diphenyl ether, dihexadecyl diphenyl ether, dioctadecyl diphenyl ether, dieicosyl diphenyl ether, tetradecyl dodecyl diphenyl ether, tetradecyl hexadecyl diphenyl ether, didodecyl tetradecyl diphenyl ether, ditetradecyl dodecyl diphenyl ether, didodecyl ditetradecyl Diphenyl ether, tridecyl tetradecyl diphenyl ether, tridecyl diphenyl ether, tridecyl diphenyl ether, tritetradecyl diphenyl ether, tetradecyl diphenyl ether, tetradodecyl diphenyl ether, pentadecyl diphenyl ether, pentadodecyl diphenyl ether, pentatetradecyl diphenyl ether Ether, hexa dodecyl diphenyl ether, hexa-tetradecyl ether (including alkyl group different diphenyl ether) and the like.

Preferably, m = 1, n = 0, R is an alkyl group having 16 to 20 carbon atoms, and m = 1, 2 is n = 1 to 3 and R is 10 to 14 carbon atoms. The alkyl group of is mentioned.

The kinematic viscosity at 100 ° C. is 2.0 to
Those having a thickness of 30.0 mm ² / s can be used.

Even if it is out of the above range,
From the viewpoint of average molecular weight, any compound can be used as long as it falls within the above range by mixing.

Next, the antioxidant system which is a major feature of the present invention will be described.

The antioxidant used in the present invention is
It is defined in relation to the required characteristics or target characteristics of the lubricating oil as follows.

(1) RBOT (min) characteristics One of the methods for evaluating the antioxidant performance of a lubricating oil is JI
Evaluation is carried out by the rotary cylinder type oxidation stability established by SK2514.

This is the addition of 5 ml of water to 50 g of lubricating oil,
Oxygen is pressed into a closed system containing a copper catalyst to 6.3 kg / cm ² and oxidized at 150 ° C. Then, a pressure drop occurs due to oxidative inhalation, and this is evaluated by measuring the time (induction time; minutes) until a prescribed amount of pressure drop is reached.

Generally, a lubricating oil having a high RBOT value is used as a compressor oil under severe environmental conditions, but commercially available compressor oils including a mineral oil type or a synthetic oil type have an RBOT value of about 2000 minutes. And
We have to develop something better than this.

(2) Thermal stability This is carried out by the test method specified in JIS K2520, and the tendency of sludge generation due to heat and oxidation of the lubricating oil is evaluated under the condition of the oil temperature of 160 ° C. It is a thing. Lubricating oil with long sludge generation time must be developed.

(3) 250 ml of modified ISOT oil was poured into a glass beaker, immersed in oil using a steel plate and a copper plate as catalysts, and air was blown at a rate of 10 liters / h through an air blowing pipe to promote oxidation. To Then, the oil is heated to 165.5 ° C., stirred in the presence of iron and copper catalysts while blowing air, and heated for 96 hours to oxidize at high temperature.

As an evaluation, changes in the viscosity and total acid value of the oil before and after the test and the amount of sludge (captured amount with a 0.8 μm filter mg / ml) are measured.

In connection with the above-mentioned various properties, the antioxidant system of the present invention is defined in the above-mentioned composite system, that is, (1) (i) to (iii) or (2) (i) to (iv). Composed of things.
Hereinafter, the composite-type oxidation stabilizer of the present invention will be described more specifically.

(1) (i) Alkylated phenyl-α-alkylated naphthylamine component: The alkylated phenyl-α-alkylated naphthylamine used in the present invention is represented by the following chemical formula 3.

[0032]

[Chemical 3]

(However, R ₁ represents an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 4 to 8 carbon atoms. R ₂
~ R ₈ may be present or absent, and when present, represents an alkyl group having 1 to 10 carbon atoms. ) A typical compound of this type is octylphenyl-α-naphthylamine.

(1) (ii) Alkylated diphenylamine component: The alkylated diphenylamine used in the present invention is represented by the following chemical formula 4.

[0035]

[Chemical 4]

(However, R ₁ and R ₂ each represent H, or an alkyl group having 1 to 18 carbon atoms, preferably an alkyl group having 4 to 8 carbon atoms.) A typical compound of this type is Octyldiphenylamine.

(1) (iii) Phosphite component: The phosphite used in the present invention is represented by the following chemical formulas 5 to 7.

[0038]

[Chemical 5]

(However, R ₁ and R ₂ are H or C _{4 to} C
₁₂ alkyl groups. Preferred is a t-butyl group. )

[0040]

[Chemical 6]

(However, R represents an alkyl group having 12 to 18 carbon atoms, a di-t-butylphenyl group or a nonylphenyl group, preferably a di-t-butylphenyl group.)

[0042]

[Chemical 7]

(However, R ₁ is an alkyl group having 4 to 30 carbon atoms, and R ₂ , R ₃ and R ₄ are alkyl groups having 1 to 4 carbon atoms, preferably an alkyl group having 4 carbon atoms.) A typical compound of this type is tris-di-t-butylphenylphosphite.

(2) (iv) Hindered phenol component having an average molecular weight of 400 to 700: In the present invention, among various hindered phenol compounds, the average (weight) molecular weight is 400 as shown in Examples described later. Those of ˜700 are preferable. Particularly preferably, the molecular weight is 550.
700. This kind of hindered phenol is a single compound represented by the following chemical formula (8).

[0045]

[Chemical 8]

(Wherein R ₁ and R ₂ are H or a t-Bu group, at least one of t ₁ and R ₂ is t-Bu, and R ₃ is a methylene group having 1 to 5 carbon atoms. In addition, in the present invention, the average molecular weight is 400 to 700.
If it is, for example, a mixture of a plurality of hindered phenols represented by Chemical Formulas 9 to 11 below may be used.

[0047]

[Chemical 9]

[0048]

[Chemical 10]

[0049]

[Chemical 11]

(However, in Chemical formulas 9 to 11, n is 1 to 4
, R ₁ and R ₂ are H or a t-Bu group, R ₁
And at least one of R ₂ represents t-Bu. ) In the present invention, alkylated phenyl-α-alkylated naphthylamine and alkylated diphenylamine as the amine-based antioxidant, hindered phenol having an average molecular weight of 400 to 700 as the phenol-based antioxidant, and further peroxide decomposition The compounding ratio of phosphite as a base agent to the base oil is 0.1 to 2.0% by weight, 0.1 to 2.0% by weight, 0.1 to 0.5% by weight, and
It is 0.1 to 0.5% by weight, and a sufficient effect can be obtained under this usage ratio. That is, a well-balanced RBOT (minute) characteristic, thermal stability and the like are secured under the above-mentioned usage ratio.

In the present invention, the above (1) (i) to (i)
ii), (2) The oxidation stabilizer comprising the components (i) to (iv) is essential, but if desired, other known oxidation stabilizers or other additives can be added.

As the above-mentioned additives, (a) pour point depressant: PMA (polymethacrylate), PIB (polyisobutylene), EPC (ethylene-propylene copolymer), SBC (styrene-butadiene water-added copolymer) Union) etc.

(B) Defoaming agent: dimethyl polysiloxane, polyacrylate, etc.

(C) Metal deactivators: triazole-based and thiadiazole-based metal deactivators.

(D) Demulsifier: a polyoxypropylene copolymer having 10 to 80% by weight of ethylene oxide with respect to propylene oxide and an average molecular weight of 1,000 to 15,000.

(E) Anticorrosion agent: alkenyl succinic acid or its partial ester.

Etc., and these may be used in an appropriate combination.

As described above, since the lubricating oil composition of the present invention is excellent in antioxidation property at high temperature, it is useful for lubricating a lubricating system such as compressor oil, turbine oil, hydraulic oil, etc., which has a large operating load. Suitable for oil.

[0059]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

(Examples 1 to 3 / Comparative Example 1) Example 1
Nos. 2 and 3 were base oils such as didodecyl biphenyl (viscosity: 23 mm ² / s at 40 ° C), didodecyl biphenyl ether (viscosity: 58 mm ² / s), monododecyl monotetradecyl biphenyl ether (viscosity). Of 13 mm ² / s at 40 ° C. was used, and the antioxidant and the additives shown in Table 1 below were added to the base oil to prepare a lubricating oil composition.

Next, various performance evaluations were performed. The results are also shown in Table 1. As a comparative example, the performance of commercial compressor oil (mineral oil) was also evaluated. The results are also shown in Table 2.

In Table 1 below, the alkylated PAN represents R = C ₈ H ₁₇ in Chemical formula 3, that is, octylphenyl-α-naphthylamine.

Alkylated DPA represents R ₁ , R ₂ ═C ₈ H _{17 in} the formula 4, ie octyldiphenylamine.

The additive pour point depressant (a) is polymethacrylate, the metal deactivator (b) is a methylbenzotriazole derivative, the rust inhibitor (c) is an alkenyl succinic acid ester, and a demulsifier (d). Represents a polyoxyethylene polyoxypropylene copolymer.

It can be seen from Table 1 that Examples 1 to 3 of the present invention show remarkable effects as compared with the commercially available compressor oil (mineral oil).

[0066]

[Table 1]

[0067]

The lubricating oil composition of the present invention is based on alkyldiphenyl and / or alkyldiphenyl ether as a base oil component, and has a specific amine antioxidant and phosphite, or a specific average molecular weight. It is prepared by blending a hindered phenol, and is particularly excellent in oxidative stability. Moreover, the compatibility of the base oil and the antioxidant is particularly excellent, and a wide range of lubricating oil properties can be maintained for a long period of time.

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Claims (1)

[Claims] 1. As a lubricating base oil, at least one of alkyl diphenyl and alkyl diphenyl ether is used, and (i) alkylated phenylamine-α-alkylated naphthylamine, (ii) alkylated diphenylamine, and (iii) phosphite A lubricating oil composition containing three kinds of antioxidants.