JPH06184580A - Lubricating oil composition - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a lubricating oil composition exhibiting shear stability and fuel economy. (I) A poly (polyalkenyl-aromatic) having 4 to 25 hydrogenated polymer chains of one or more C _{4 to} C ₁₂ conjugated dienes and optionally a monoalkenyl aromatic compound extending outward. Coupling agent) containing a core, having a weight average molecular weight of 10,000 to 400,000, and 50%
0.15 to 30% by weight of hydrogenated star polymer having less than 10 primitive olefinic unsaturated bonds, (ii) polyacrylic acid alkyl ester or alkyl polymethacrylate having a weight average molecular weight of 10,000 to 400,000 A lubricating oil composition comprising 1 to 30% by weight of ester and (iii) the balance of the base oil.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel lubricating oil composition.

[0002]

2. Description of the Related Art As a performance required for engine oil, it is practically desirable that the viscosity does not change as much as possible over a wide temperature range from low temperature to high temperature. When the engine oil is usually formulated with only mineral oil, the viscosity becomes too low at high temperature and causes wear of engine parts, and the viscosity becomes too high at low temperature, which may cause deterioration of engine startability. A viscosity index improver is used as a solution to such a phenomenon, and an oil-soluble polymer compound having a molecular weight of 10,000 or more is usually used. Conventionally, as the viscosity index improver used only for the above purpose, it is usual to use one type of viscosity index improver. Further, it is already known that engine oil added with a viscosity index improver has better fuel economy than engine oil formulated only with mineral oil (see FIG. 1). However, in order to improve fuel economy, the addition of an extreme viscosity index improver or the addition of a high-molecular-weight type viscosity index improver deteriorates shear stability, and there is a concern that viscosity may be insufficient during use. Not preferable for use.

[0003]

[Object] An object of the present invention is to provide a lubricating oil composition exhibiting shear stability and fuel economy.

[0004]

[Structure] The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, have already known a viscosity index improver comprising a star polymer described in JP-B-61-50120 as a pour point depressant. Surprisingly, it has been found that the combined use of the known polymethacrylic acid alkyl ester can achieve fuel economy without deteriorating the shear stability, and thus completed the present invention.

The present invention provides (i) one or more C ₄
-C ₁₂ conjugated dienes and, optionally, poly hydrogenated polymer chains 4 to 25 monoalkenyl aromatic compound extends outwardly - include (polyalkenyl aromatic coupling agent) nucleus, weight average molecular weight of 10, 000 to 400,000
And 0.15 to 30% by weight of hydrogenated star polymer having less than 50% of primitive olefinic unsaturated bonds, (i
The present invention relates to a lubricating oil composition comprising 1 to 30% by weight of a polyacrylic acid alkyl ester or a polymethacrylic acid alkyl ester having a weight average molecular weight of 10,000 to 400,000, and (iii) the balance of the base oil.

The hydrogenated star polymer (i) used in the present invention can be produced by the following method. That is, forming a living polymer by polymerizing in the presence of (i) one or more C ₄ -C ₁₂ conjugated diene and optionally one or more monoalkenyl aromatic compound solution seven-week mourning period ionic initiator (B) reacting the living polymer with a polyalkenyl-aromatic coupling agent to form a star polymer, and (c) hydrogenating the star polymer to form a hydrogenated star polymer. It can be produced by a method comprising a reaction step.
For details, refer to the invention of the affiliated company of the applicant described in JP-B-61-50120.

The alkyl group in the poly (meth) acrylic acid alkyl ester used in the present invention is usually methyl, ethyl, propyl or butyl, with methyl being particularly preferred. Among the poly (meth) acrylic acid alkyl esters, polymethacrylic acid methyl ester is particularly preferable. (Below margin)

[0008]

【Example】

 (1) Composition

[Table 1] * ¹ : Mineral oil 100N is the oil obtained by solvent removal of the lubricating oil fraction obtained by vacuum distillation or the distillation residue, and the aromatic oil contained in the oil as an unsuitable aromatic oil. Is an oil refined by a clay treatment or a hydrofinishing after the wax component is separated and removed by another solvent. * ² : Hydrogenated star polymer is a weight average molecular weight of 216,000 obtained by hydrogenating 95% or more of the star polymer obtained by using 250 g of living polyisoprene polymer and 75 g of divinylbenzene. belongs to. * ³ : SG package (API SG
In order to obtain the performance, a commercial product in which various additives are put together is used. The viscosity according to SEA viscosity classification No. 30 at 100 ° C. was adjusted to 10.5 ± 0.3 cSt by the above formulation. (Below margin)

(2) General properties of the composition shown in Table 1

[Table 2]

(3) Experimental method (a) Shear stability CEC (Coordinating European)
Bosch Injector Rig Test (Test No. CEC-L36-A78) prescribed by Council) (b) Fuel economy characteristics ASTM Research Report: D02: 1
Seq VI fuel economy test specified in 204.

(4) Experimental Results (a) Shear Stability As shown in Table 3 below, Sample A has a weight average molecular weight of 2
The shear stability was superior to that of the sample C in which the viscosity was adjusted only with 94,000 polymethacrylate.
Sample B has a weight average molecular weight of 29
The shear stability was superior to that of Sample D whose viscosity was adjusted only with 4,000 polymethacrylate.

[Table 3] (Note) Samples A to E were adjusted to the same viscosity grade using the same base oil and the same additives except for the components (i) and (ii).

(B) Fuel economy characteristics ASTM Research Report: D02: 1
The Seq VI fuel economy test specified in 204 was conducted.

[Table 4] * An oil prepared to a 5W-20 grade using an ethylene-propylene copolymer with a molecular weight of 64500. As is clear from Table 4, two kinds of components (i) and (ii)
By using, it showed higher fuel economy than using alone. Furthermore, it showed higher fuel economy than 5W-20 oil having a lower viscosity than 5W-30 formulated with a different type of viscosity index improver.

[0013]

[Effect] According to the present invention, a lubricating oil composition having high shear stability and fuel economy can be provided.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a viscosity (shear stability) and a fuel consumption rate according to a conventional concept.

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Claims (2)

[Claims] 1. A poly (polyalkenyl-) having (i) 4 to 25 hydrogenated polymer chains of one or more C _{4 to} C ₁₂ conjugated dienes and optionally monoalkenyl aromatic compounds extending outward. Aromatic coupling agent), having a weight average molecular weight of 10,000 to 400,000, and 50
0.15 to 30% by weight of hydrogenated star polymer having less than 10% of primitive olefinic unsaturated bond, (ii) weight average molecular weight 10,000 to 400,000
1-30% by weight of polyacrylic acid alkyl ester or polymethacrylic acid alkyl ester, and (iii) the balance of the base oil. 2. The lubricating oil composition according to claim 1, wherein the (ii) is polymethylmethacrylate.