JPH0737623B2 - Lubricating oil composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is excellent in oxidation stability, cryogenic temperature, high temperature cleanability, and friction characteristics of a wet clutch, and is used in internal combustion engine oil, automatic transmission oil (ATF), The present invention relates to a lubricating oil composition that can be widely used as a lubricating oil for a wet clutch, a compressor oil, a gear oil, a bearing oil, etc. in an agricultural tractor or the like.

[Problems to be Solved by Prior Art and Invention]

Poly-α-olefin, which is a synthetic lubricating oil, has oxidative stability,
It is used as a high-grade lubricating base oil due to its excellent low-temperature fluidity.

However, this poly α-olefin is expensive and has a problem in economy, and when it is actually used as an internal combustion engine oil or a lubricating oil for a wet clutch, it has poor high-temperature detergency and has sufficient friction characteristics with the wet clutch. It turns out that there is a technical problem such as not.

On the other hand, due to economic problems, it has been proposed to mix this poly α-olefin with mineral oil. However,
This method deteriorates the cryogenicity and oxidative stability, which are the characteristics of poly α-olefin, and is not a true technical solution.

The present inventor has conducted extensive studies in order to solve the above conventional problems. As a result, by blending the poly α-olefin having the specific property with the mineral oil having the specific property, the economical stability of the poly α-olefin is eliminated, and the oxidation stability and the cryogenic property thereof are utilized, and the high temperature detergency is high. It was found that a lubricating oil composition having improved friction characteristics with a wet clutch and a wet clutch was obtained, and the present invention was completed based on this finding.

[Means for solving problems]

That is, the present invention has a kinematic viscosity of 1.5 to 150 centistokes (cSt) (100 ° C.) of poly-α-olefin of 15 to 85% by weight and a kinematic viscosity of 2 to 50 cSt (100 ° C.), pour point of −35 ° C. or less, aromatic carbonization. It is intended to provide a lubricating oil composition comprising a mixture of 15% by weight of mineral oil having a hydrogen content (% C _A ) of 10% or less as a base oil.

Poly α-used as one component of the base oil in the present invention
The olefin is a synthetic lubricating oil also called an α-olefin oligomer and has the following general formula [I]: (In the formula, R represents an alkyl group having 4 to 12 carbon atoms, and m is 0.
Indicates ~ 30. ) Is represented by. Here, as the poly α-olefin, one having a kinematic viscosity at 100 ° C. of 1.5 to 150 cSt, preferably 2 to 50 cSt is used. Specifically, it is a 2- to 10-mer of 1-octene, 1-decene, 1-dodecene, preferably 1
It is desirable to use a low degree of polymerization poly alpha-olefin such as a decene dimer to tetramer.

Such poly α-olefin can be produced by a known method including a polymerization step, a catalytic decomposition step, a distillation step and a hydrogenation step. The degree of polymerization may be adjusted by changing the residence time of the reactor in the polymerization process.

Next, in the present invention, as the other component of the base oil, a mineral oil having a kinematic viscosity at 100 ° C. of 2 to 50 cSt, preferably 5 to 35 cSt and a pour point of −35 ° C. or lower, preferably −40 ° C. or lower is used. Moreover, in the present invention, it is necessary to use a mineral oil having an aromatic hydrocarbon content (% C _A ) of 10% or less. The sulfur content is 50 ppm or less, preferably 5 ppm or less. Here, if the sulfur content exceeds 50 ppm, the oxidation stability will decrease, which is not preferable.

Such mineral oil is a distillate obtained by distilling paraffinic crude oil or intermediate base crude oil (boiling point 250 to 450 ° C at atmospheric pressure).
Is purified by a conventional method and then subjected to deep dewaxing treatment.

The distillate means a crude oil obtained by atmospheric distillation or a residual oil obtained by atmospheric distillation under reduced pressure. The purification method is not particularly limited, but it can be obtained by carrying out any of the following treatments 1 to.

The distillate oil is hydrotreated, or after hydrotreated, alkali distillation or washing with sulfuric acid is performed. The distillate oil is subjected to solvent refining treatment, or after solvent refining treatment, alkali distillation or sulfuric acid washing is performed. After the distillate oil is hydrotreated, the second stage hydrotreatment is subsequently performed. After hydrotreating the distillate oil, the second-stage hydrotreatment and the third-stage hydrotreatment are performed. After the distillate oil is hydrotreated, the second stage hydrotreatment is carried out, and further alkaline distillation or sulfuric acid washing is carried out. An example of the processing method is shown below.

A lubricating oil crude material is prepared from a paraffinic crude oil or an intermediate base crude oil by a conventional method and subjected to severe hydrotreating. By this treatment, a reaction such as removal of an undesirable component such as an aromatic component in the lubricating oil fraction or conversion into an effective component is carried out. At this time, most of the sulfur and nitrogen components are removed.

Then, fractional distillation is carried out by vacuum distillation so as to obtain the required viscosity. After that, known solvent dewaxing was performed, and the pour point of ordinary paraffin base oil, that is, −
Dewax to about 15 to -10 ℃.

After the dewaxing treatment, if necessary, further hydrogenation treatment is carried out to hydrogenate most of the aromatic component to a saturated component, thereby improving the thermal and chemical stability of the base oil. However, its pour point is still high, so it is not suitable as a lubricating oil.
For that purpose, deep dewaxing treatment is continuously performed. This treatment uses a solvent dewaxing method under severe conditions and a zeolite catalyst to selectively decompose paraffin (mainly normal paraffin) adsorbed in the pores of the catalyst under a hydrogen atmosphere to form a wax component. The catalytic hydrodewaxing method to remove is applied.

Although the hydrogenation treatment varies depending on the properties of the feedstock, the reaction temperature is usually 200 to 480 ° C, preferably 250 to 480 ° C, and the hydrogen pressure is 5
~ 300 kg / cm ² , preferably 30 to 250 kg / cm ² , hydrogen introduction amount (per 1 kl of supplied distillate) 30 to 3000 Nm ³ , preferably 100
It is performed under the condition of ~ 2000Nm ³ . The catalyst used in this case is alumina, silica, silica-alumina, zeolite, activated carbon, bauxite, etc. as a carrier.
Metals such as Group VI and Group VIII of the Periodic Table, preferably catalyst components such as cobalt, nickel, molybdenum and tungsten supported by a known method are used. The catalyst is preferably pre-sulphurized in advance.

As described above, the distillate oil is subjected to various kinds of treatment after being hydrotreated, but when performing the second or third stage hydrotreatment, the hydrotreatment conditions should be set within the above range. The conditions of the first to third stages may be the same or different. However, usually, the conditions for the second stage rather than the first stage and the conditions for the third stage rather than the second stage are made stricter.

Next, alkaline distillation is performed as a step of removing a trace amount of acidic substances to improve the stability of the distillate, and is performed by adding an alkali such as NaOH or KOH and performing vacuum distillation.

Sulfuric acid washing is generally performed as a finishing process for petroleum products, and removes aromatic hydrocarbons, especially polycyclic aromatic hydrocarbons, olefins, sulfur compounds, etc. Applied to improve. In the present invention, 0.5 to 5% by weight of concentrated sulfuric acid is added to the treated oil at room temperature to 60%.
The treatment is carried out at a temperature of ℃, and then neutralized with NaOH or the like.

As for the treatment of the distillate oil, there are the specific methods 1 to 3 as described above depending on the combination of the above operations. Among these methods, the methods 1 and 2 are particularly preferable.

The properties of the distillate oil obtained by the treatment as described above are such that the kinematic viscosity is 2 to 50 cSt (100 ° C.) and the pour point is −35 ° C. or less.
Further, the aromatic hydrocarbon content (% C _A) is of 10% or less.

The base oil in the lubricating oil composition of the present invention is the above-mentioned poly α-
Consists of olefin and mineral oil, the mixing ratio of which is the former
The latter 85 to 15 to 85% by weight, preferably 20 to 80% by weight
-15% by weight, preferably 80-20% by weight. If the mixing ratio is out of the above range, the high temperature detergency will be poor and the friction with the wet clutch will be insufficiently specified, which is not preferable.

The lubricating oil composition of the present invention basically comprises the above-mentioned two components, but various additives can be further compounded if necessary. For example, as the antioxidant, zinc thiophosphate, phenolic antioxidant such as di-tert-butylparacresol (DBPC), amine antioxidant such as diphenylamine can be used. In addition, sulfonate-based, finate-based, phosphonate-based, imide-based, amide-based cleaning dispersants and molybdenum dithiophosphate,
In addition to extreme pressure and oiliness agents such as molybdenum dithiocarbamate, phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, friction modifiers, etc., various additives such as corrosion inhibitors, antifoaming agents, and rust inhibitors should be used as appropriate. it can.

Furthermore, polymethacrylate, olefin copolymer,
Viscosity index improvers such as polybutene and pour point depressants can also be added. In this case, in order to improve the low temperature viscosity, a small amount may be added as compared with the conventional case, so that the deterioration of the high temperature detergency due to these additives can be minimized.

〔The invention's effect〕

The above-described lubricating oil composition of the present invention has improved high temperature detergency and excellent friction characteristics with a wet clutch.

Further, the lubricating oil composition of the present invention sufficiently retains the excellent oxidative stability, cryogenicity and the like, which are advantages of poly α-olefins, and is more inexpensive.

Further, the lubricating oil composition of the present invention does not need to use a large amount of a pour point depressant or a viscosity index improver that may reduce high temperature detergency, and therefore exhibits excellent high temperature detergency.

Therefore, the present invention can be widely used as various lubricants.

〔Example〕

 Next, the present invention will be described with reference to examples.

Preparation Examples 1 to 7 (Preparation of Samples 1 to 7) Obtained by blending poly α-olefin (mixture of 1 to decene 2 to 4 mer) having properties shown in Table 1 and mineral oil in proportions shown in Table 2. Molecular weight of 6 to the base oil used (kinematic viscosity 5 cSt (100 ° C))
Adjusted to SAE viscosity grade 10W / 30 equivalent oil by adding 7% by weight of 15,000 ethylene-propylene copolymer, and further compounding 8% by weight of commercial engine oil additive package (main component calcium sulfonate). Samples 1 to 7 were prepared.

Preparation Example 8 (Preparation of Sample 8) From Preparation Example 6, a low-viscosity base oil (the ratio of poly α-olefin to mineral oil is the same as in Preparation Example 6) was used, and an ethylene-propylene copolymer having a molecular weight of 65,000 was used. Sample 8 was prepared by blending in a weight percentage.

Examples 1 to 4 and Comparative Examples 1 to 4 Samples 1 to 8 obtained in the above Preparation Examples 1 to 8 were subjected to a high temperature cleanability test by the method described below. The results are shown in Table 3 together with the measurement results of low temperature viscosity (ASTM D 2983).

High temperature cleanliness test Federal Test Method Standard No. 791a Method 3462T (Federal Test Method Std. No.
791a Method.3462T) and a panel caulking test was performed according to the weight increase (mg) of the panel after the test. The test was conducted under the conditions of a panel temperature of 320 ° C., an oil temperature of 100 ° C., and a test time of 3 hours.

Example 5 and Comparative Examples 5-6 Samples 2, 6, and 8 obtained in Preparation Examples 2, 6, and 8 were subjected to an oxidation stability test in accordance with JIS K 2514. The results are shown in Table 4.

Preparation Examples 9 to 11 (Preparation of Samples 9 to 11) A commercially available additive package for ATF was added to a base oil obtained by blending poly α-olefin having the properties shown in Table 1 and mineral oil in the ratio shown in Table 5. Samples 9 to 11 were prepared by mixing 10% by weight (the main component is an ashless dispersant) and 5% by weight of polymethacrylate (weight average molecular weight 80,000).

Example 6 and Comparative Examples 7 to 8 SAE No. 2 friction test was performed on the samples 9 to 11 obtained in the above Preparation Examples 9 to 11 by the following method. The results are shown in Table 6.

SAE No. 2 Friction Test The friction characteristics were evaluated under the following experimental conditions using a SAE No. 2 tester manufactured by Greening Company (USA).

[Experimental conditions]

Disc: Paper type disc for domestic automatic transmission (2
Plate: Plate: Steel plate for domestic automatic transmission (3) Motor rotation speed: 3000 rpm Piston pressing pressure: 10 kg / cm ² Oil temperature: 100 ° C, dynamic friction coefficient at rotation speed 1200 rpm under the above experimental conditions is μ _The coefficient of static friction when stopped was ₁₂₀₀ and μ ₀ was measured, and μ ₀ / μ ₁₂₀₀ was calculated.

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Claims (1)

[Claims] 1. A kinematic viscosity of 1.5 to 150 centistokes (100
15 to 85% by weight of poly α-olefin and kinematic viscosity 2
~ 50 centistokes (100 ℃), pour point −35 ℃ or less,
_A lubricating oil composition comprising a mixture of 85 to 15% by weight of a mineral oil having an aromatic hydrocarbon content (% CA) of 10% or less as a base oil.