Lubricant viscosity index improver and lubricant composition containing the same

Abstract

To provide a lubricant viscosity index improver and a lubricant composition containing the same.SOLUTION: A lubricant viscosity index improver of the present invention comprises a liquid α-olefin copolymer obtained by copolymerization of ethylene and an α-olefin monomer having 3 or more carbon atoms, wherein the liquid α-olefin copolymer has a weight average molecular weight of 10,000 to 120,000 g / mol, the lubricant viscosity index improver has a permanent shear stability index (PSSI) of more than 1 and less than 25, and the lubricant viscosity index improver has a thickening power at 100°C of more than 2.5 and less than 3.6 cSt. A lubricant composition comprises the lubricant viscosity index improver.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a lubricating oil viscosity index improver having excellent shear stability and high-temperature high-shear viscosity characteristics, and a lubricating oil composition containing the same.

Background Art

[0002] The lubricating oil used in internal combustion engines not only serves to reduce the friction of mechanical driving parts of the engine such as piston rings, cylinder liners, bearings of crankshafts and connecting rods, and valve trains, but also cools the engine, suspends combustion products to keep the engine clean, and prevents corrosion. Therefore, the lubricating oil used in internal combustion engines must have various performances. These performances include, for example, anti-wear property, thermal stability, dispersibility, low evaporability, and good fuel consumption characteristics.

[0003] On the other hand, engine manufacturers and automobile manufacturers are not only meeting the increasing demands of users day by day, but also entering the era of energy conversion, and are trying to improve performance such as increasing the engine output and adding many functions to meet such requirements. According to a survey by the US Environmental Protection Agency, as the output per unit displacement of passenger cars increases and the engine becomes more precise, the lubricating oil used for this also requires better performance.

[0004] Moreover, recently, in order to prevent global warming, there is a very high demand to improve the fuel consumption of automobiles and suppress the emission of carbon dioxide (CO2). To improve the fuel consumption of such automobiles, it is important to improve the efficiency of the engine. In gasoline engines, lean burn and direct injection technologies are adopted. In the case of diesel engines, many studies are being conducted to improve the fuel consumption while reducing the amount of soot (PM, Particulate Matters) in the exhaust gas. Generally, it is known that reducing the cold cranking viscosity of engine oil or reducing the friction of the engine can contribute to improving the fuel consumption, and for this purpose, many studies are being advanced.

[0005] Generally, lubricating oils contain additives that help the lubricating oil to have a certain viscosity at a predetermined temperature. The viscosity of the lubricating oil is inversely proportional to the temperature. When the temperature of the lubricating oil rises, the viscosity of the lubricating oil decreases, and when the temperature of the lubricating oil drops, the viscosity of the lubricating oil increases. It is preferable to have a lower viscosity at a lower temperature for easy starting of the engine in cold weather and a higher viscosity at a higher ambient temperature when the lubricating characteristics usually decrease. Lubricating oil viscosity index improvers have been manufactured as such additives for lubrication.

[0006] In the current industry, as lubricating oil viscosity index improvers, olefin copolymers (Olefin Copolymer (OCP)), hydrogenated styrene-isoprene block polymers (Hydrogenated Styrene-isoprene Block Polymer (HSP)), polymethylacrylates (Polymethylacrylate (PMA)), styrene-polyesters (Styrene-Polyester (SPE)), styrene-polybutylenes (Styrene-Polybutylene (SPB)), etc. are mainly used. Such viscosity index improvers give the lubricating oil a high viscosity index and reduce the viscosity change of the lubricating oil due to temperature changes.

[0007] Usually, when the molecular weight of the lubricating oil viscosity index improver is high, the shear stability decreases under high shear conditions. In recent years, the lubricating oil grade-up speed has been increasing, and the molecular weight of the lubricating oil viscosity index improver tends to be high. Therefore, in this field, the requirements for lubricating oil viscosity index improvers and lubricating oil compositions having excellent shear stability are increasing. On the other hand, as a similar prior art document for this, Korean Patent Publication No. 10-2018-0080820 has been presented.

Prior Art Document

Patent Document

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a lubricating oil viscosity index improver having excellent shear stability and high-temperature high-shear viscosity characteristics, and a lubricating oil composition containing the same. However, the above object is exemplary, and the technical idea of the present invention is not limited thereto.

Means for Solving the Problems

[0010] One aspect of the present invention is a lubricating oil viscosity index improver containing a liquid α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin monomer having 3 or more carbon atoms, wherein the liquid α-olefin copolymer has a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) of more than 1 and less than 25, and a thickening power at 100 °C of more than 2.5 and less than 3.6 cSt. In the above aspect, the liquid α-olefin copolymer may be one obtained by copolymerizing ethylene and an α-olefin monomer having 3 to 6 carbon atoms.

[0011] In the above aspect, the liquid α-olefin copolymer may contain 40 to 60 mol% of ethylene units and 60 to 40 mol% of α-olefin units having 3 to 20 carbon atoms. In the above aspect, the liquid α-olefin copolymer may have a specific gravity at 20 °C of 0.8 to 0.95. In the above aspect, the liquid α-olefin copolymer may have a viscosity index of 130 to 150 when diluted in a base oil at a concentration of 5% by weight.

[0012] In the above aspect, more preferably, the liquid α-olefin copolymer may have a weight average molecular weight of 20,000 to 80,000 g / mol, and at this time, the permanent shear stability index (PSSI) may be 1.5 to 3.5. Another aspect of the present invention relates to a lubricating oil composition characterized by including a base oil and the lubricating oil viscosity index improver. In the above another aspect, the lubricating oil composition may include 0.1 to 15% by weight of the lubricating oil viscosity index improver and the balance of the base oil.

[0013] In the above another aspect, the lubricating oil composition may be for gasoline engine oil. At this time, the lubricating oil composition may have a mini rotary viscometer (MRV) viscosity of 15,000 to 19,000 cP at -35°C, a cold cranking simulator (CCS) viscosity of 7,000 cP or less at -30°C, a viscosity loss rate of 2% or less at 100°C after 30 cycles of shearing by a Bosch pump, and a viscosity loss rate of 3% or less at 40°C after 30 cycles of shearing by a Bosch pump.

[0014] In the above another aspect, the lubricating oil composition may be for large diesel engine oil. At this time, the lubricating oil composition may have a mini rotary viscometer (MRV) viscosity of 19,000 to 30,000 cP at -30°C, a cold cranking simulator (CCS) viscosity of 9,000 cP or less at -25°C, a viscosity loss rate of 6% or less at 100°C after 90 cycles of shearing by a Bosch pump, and a viscosity loss rate of 5% or less at 40°C after 90 cycles of shearing by a Bosch pump.

Advantages of the Invention

[0015] The viscosity index improver for lubricating oil according to the present invention contains a liquid α-olefin copolymer having a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) of more than 1 and less than 25, and a thickening power at 100 °C of more than 2.5 and less than 3.6 cSt, and thus can have more excellent shear stability and high-temperature high-shear viscosity characteristics. Thereby, the lubricating oil composition containing this can stably maintain the viscosity even in a high-temperature and high-shear environment, reduce metal wear between engine parts, improve the durability of the engine, and has the advantage of improving fuel efficiency by reducing fuel consumption due to reduced friction within the engine parts.

Embodiments for Carrying Out the Invention

[0016] Advantages, features, and methods for achieving them for the embodiments of the present invention will become clear by referring to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and can be realized in various different forms. However, this embodiment is provided to make the disclosure of the present invention complete and to fully inform those with ordinary knowledge in the technical field to which the present invention pertains of the scope of the invention. The present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals indicate the same components.

[0017] When explaining the embodiments of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. And the terms described below are terms defined in consideration of the functions in the embodiments of the present invention, and these can vary depending on the intention or convention of the user or operator. Therefore, the definition should be given based on the content throughout this specification.

[0018] One aspect of the present invention is a lubricating oil viscosity index improver containing a liquid α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin monomer having 3 or more carbon atoms, wherein the liquid α-olefin copolymer has a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) exceeding 1 and less than 25, and a thickening power at 100 °C exceeding 2.5 and less than 3.6 cSt. The present invention relates to a lubricating oil viscosity index improver characterized by the above.

[0019] Such a lubricating oil viscosity index improver according to the present invention contains a liquid α-olefin copolymer having a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) exceeding 1 and less than 25, and a thickening power at 100 °C exceeding 2.5 and less than 3.6 cSt, whereby it can have more excellent shear stability and high-temperature high-shear viscosity characteristics. As a result, a lubricating oil composition containing this can stably maintain its viscosity even in a high-temperature and high-shear environment, reduce metal wear between engine parts, improve the durability of the engine, and reduce fuel consumption by reducing friction within the engine parts, thereby improving fuel efficiency.

[0020] In an example of the present invention, the liquid α-olefin copolymer is for improving the viscosity of lubricating oil. As described above, the liquid α-olefin copolymer according to the present invention has a weight average molecular weight (Mw) of 10,000 to 120,000 g / mol, preferably 15,000 to 100,000 g / mol, and more preferably 20,000 to 80,000 g / mol. Excellent shear stability and high-temperature high-shear viscosity characteristics can be ensured within such a range.

[0021] Also, as described above, the liquid α-olefin copolymer according to the present invention has a permanent shear stability index (PSSI) exceeding 1 and less than 25, preferably 1.3 to 15, more preferably 1.5 to 10, even more preferably 1.5 to 5, and most preferably 1.5 to 3.5. Further, the thickening power at 100 °C may be more than 2.5 and less than 3.6 cSt, preferably 2.6 to 3.5, more preferably 2.7 to 3.4, and most preferably 2.8 to 3.3. Excellent shear stability and high-temperature high-shear viscosity characteristics can be ensured within such ranges.

[0022] Also, the liquid α-olefin copolymer according to the present invention has a specific gravity at 20 °C of 0.8 to 0.95, preferably 0.82 to 0.92, more preferably 0.85 to 0.90, and most preferably 0.86 to 0.87. Within such a range, it can be more readily mixed with the base oil when mixed with the lubricating oil composition.

[0023] Further, the liquid α-olefin copolymer has a viscosity index of 130 to 150, preferably 130 to 140, more preferably 131 to 138, and most preferably 133 to 137 when diluted to a concentration of 5% by weight in the base oil. Within such a range, it is less sensitive to temperature changes, the viscosity does not become too low at high temperatures, and the viscosity does not become too high during cold cranking.

[0024] On the one hand, the liquid α-olefin copolymer according to an example of the present invention may be produced by copolymerizing an ethylene monomer and an α-olefin monomer excluding ethylene, and the α-olefin monomer is an aliphatic olefin having 3 to 20 carbon atoms. Specifically, it may be one or more selected from propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, and 1-tetradecene. Preferably, the liquid α-olefin copolymer may be one in which ethylene and an α-olefin monomer having 3 to 6 carbon atoms are copolymerized, and the α-olefin monomer is at least one selected from propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, and 3-methyl-1-pentene, and most preferably propylene.

[0025] Preferably, the liquid α-olefin copolymer suitable for the present invention may contain 40 to 60 mol% of ethylene units and 60 to 40 mol% of α-olefin units having 3 to 20 carbon atoms, and preferably 45 to 55 mol% of ethylene units and 55 to 45 mol% of α-olefin units having 3 to 20 carbon atoms. Using a liquid α-olefin copolymer having such a range is preferable for improving the friction reduction characteristics.

[0026] On the other hand, the liquid α-olefin copolymer is polymerized through a metallocene catalyst composition. Specifically, for example, the metallocene catalyst composition may contain (A) a bridged metallocene compound and (B) at least one compound selected from the following (b-1) to (b-3). (b-1) an organoaluminum oxy compound, (b-2) a compound that reacts with the bridged metallocene compound (A) to form an ion pair, (b-3) an organoaluminum compound that activates a compound that reacts with the bridged metallocene compound (A) to form an ion pair.

[0027] As a result, it is possible to obtain a polymer with high polymerization activity and high molecular weight that could not be achieved conventionally, and to produce a liquid α-olefin copolymer that has a narrow molecular weight distribution and a low double bond distribution while having a high comonomer content, and is excellent in thermal stability and durability. In an example of the present invention, the crosslinked metallocene compound (A) may be represented by the following Chemical Formula 1. [Chemical Formula] (In the formula, M is one or more transition metals selected from the group consisting of titanium, zirconium, and hafnium,

[0028] B is an alkylene group having 1 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, a dialkyl silicon having 1 to 20 carbon atoms, a dialkyl germanium having 1 to 20 carbon atoms, an alkyl phosphine group having 1 to 20 carbon atoms, or an alkyl amine group having 1 to 20 carbon atoms, or is in a form without a linking group,

[0029] X1 and X2 are each independently a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 40 carbon atoms, an arylalkyl group having 7 to 40 carbon atoms, an alkylamide group having 1 to 20 carbon atoms, an arylamide group having 6 to 20 carbon atoms, an alkylidene group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms,

[0030] R1 to R 14 may each independently be hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkenyl having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, an arylalkyl group having 7 to 20 carbon atoms, a cycloalkyl group having 5 to 60 carbon atoms, a heterocyclic group having 4 to 20 carbon atoms, an alkynyl group having 1 to 20 carbon atoms, a hetero group containing an aryl group having 6 to 20 carbon atoms, or a silyl group.) In an example of the present invention, the (b-1) organoaluminum oxy compound may be one or more selected from the group consisting of the following Chemical Formulas 2 to 5. [Chemical Formula] [Chemical Formula] (In the formula, R is a hydrocarbon group having 1 to 10 carbon atoms, and n is an integer of 2 or more.)

[0031] In Chemical Formula 2 or 3, the organoaluminum oxy compound in which R is a methyl group may also be referred to as methylaluminoxane, and those in which n is 3 or more, preferably 10 or more, are used.

[0032] Methylaluminoxane is an organoaluminum oxy compound that has been widely used in the polyolefin industry in terms of its easy availability and high polymerization activity. However, since it is difficult to dissolve in saturated hydrocarbons, it has sometimes been used as an aromatic hydrocarbon solution such as toluene or benzene, which has a large environmental burden. Under such circumstances, methylaluminoxane analogs that dissolve in saturated hydrocarbons have been developed. Examples of such analogs include modified methylaluminoxane represented by the following General Formula [IX]. The (b-1) organoaluminum oxy compound related to the high-temperature solution polymerization method of the present invention also includes such modified methylaluminoxane. [Chemical Formula] (In the formula, R represents a hydrocarbon group having 2 to 20 carbon atoms, and m and n represent integers of 2 or more.)

[0033] The modified methylaluminoxane represented by Chemical Formula 4 is prepared using trimethylaluminum and an alkylaluminum other than trimethylaluminum. Those in which R is isobutyl, prepared using trimethylaluminum and triisobutylaluminum by manufacturers such as Tosoh Finechem Corporation, are commercially produced under trade names such as MMAO and TMAO.

[0034] In addition, examples of the organoaluminum oxy compound used in the present invention include an organoaluminum oxy compound containing boron represented by the following Chemical Formula 5.

Chemical Formula

[0035] (In the formula, R c represents a hydrocarbon group having 1 to 10 carbon atoms, and R d may be the same or different from each other and represents a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 10 carbon atoms.) In the above-mentioned (b-1) organoaluminum oxy compound, a small amount of an organoaluminum compound may be mixed.

[0036] In an example of the present invention, the compound that reacts with the (b-2)(A) bridged metallocene compound to form an ion pair is also referred to as an ionic compound, and examples thereof include a Lewis acid, an ionic compound, a borane compound, and a carborane compound. In addition, heteropoly compounds and isopoly compounds can also be mentioned.

[0037] In the present invention, the preferably employed ionic compound is a compound represented by the following Chemical Formula 6. Since the amount of such an ionic compound used is smaller than that of the organoaluminum oxy compound, the generation of sludge is reduced, resulting in an economic advantage.

Chemical Formula

[0038] (In the formula, R e+ includes H + , a carbenium cation, an oxonium cation, an ammonium cation, a phosphonium cation, a cycloheptyltrienyl cation, a ferrocenium cation having a transition metal, and the like. R f to R imay be the same as or different from each other and is an organic group, preferably an aryl group.) Specific examples of the carbocation include dimethylanilinium cation and the like.)

[0039] In an example of the present invention, the organoaluminum compound (b-3) can include, for example, an organoaluminum represented by the following chemical formula 7, a complex alkyl compound of a Group 1 metal and aluminum represented by the following chemical formula 8, and the like.) [Chemical formula]

[0040] (In the formula, R a and R b may be the same as or different from each other and represent a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms. X represents a halogen atom, m is a number where 0 < m ≤ 3, n is a number where 0 ≤ n < 3, p is a number where 0 < p ≤ 3, q is a number where 0 ≤ q < 3, and m + n + p + q = 3.) [Chemical formula] (In the formula, M2 represents Li, Na or K, and R a represents a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms.)

[0041] The compound represented by Chemical formula 8 is a complex alkylated product of a Group 1 metal in the periodic table and aluminum. Examples of such a compound include LiAl(C2H5)4, LiAl(C7H 15 )4, etc.)

[0042] Also, compounds similar to the compound represented by Chemical formula 8 can be used. For example, an organoaluminum compound in which two or more aluminum compounds are bonded via a nitrogen atom can be mentioned. Specific examples of such a compound include (C2H5)2AlN(C2H5)Al(C2H5)2, etc.) From the viewpoint of ease of handling, as the organoaluminum compound (b-3), trimethylaluminum and triisobutylaluminum are preferably used.

[0043] Another aspect of the present invention relates to a lubricating oil composition containing the lubricating oil viscosity index improver described above. Specifically, it relates to a lubricating oil composition characterized by containing a base oil and the lubricating oil viscosity index improver.

[0044] As described above, the lubricating oil composition according to the present invention contains a lubricating oil viscosity index improver containing a liquid α-olefin copolymer having a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) of more than 1 and less than 25, and a thickening power at 100 °C of more than 2.5 and less than 3.6 cSt. By stably maintaining the viscosity even in high-temperature and high-shear environments and reducing metal wear between engine parts, the durability of the engine can be improved. At the same time, there is an advantage that fuel consumption can be improved by reducing fuel consumption due to reduced friction within the engine parts.

[0045] More specifically, the lubricating oil composition according to an example of the present invention can be used as a vehicle engine oil. Specifically, for example, it can be utilized for gasoline engine oil or large diesel engine oil.

[0046] When the lubricating oil composition is utilized for gasoline engine oil, the lubricating oil composition may have a mini-rotary viscometer (MRV) viscosity of 15,000 to 19,000 cP at -35°C, preferably 15,500 to 18,800 cP, more preferably 16,000 to 18,500 cP, even more preferably 16,500 to 18,300 cP, and most preferably 17,000 to 18,000 cP. On the other hand, when the MRV viscosity is less than 15,000 cP, although the pumping property and starting performance during cold cranking are excellent, the engine protection performance under high-temperature and high-load conditions may decrease. When it exceeds 19,000 cP, since the lubricating oil composition does not flow sufficiently during cold cranking, there may be problems with the operation of the pump, and the lubricating effect may decrease, which is not good. Also, the lubricating oil composition may have a cold cranking simulator (CCS) viscosity of 7,000 cP or less at -30°C, preferably 4,000 to 7,000 cP, more preferably 4,600 to 6,500 cP, even more preferably 5,000 to 6,800 cP, and most preferably 5,200 to 6,500 cP. On the other hand, when the CCS viscosity exceeds 7,000 cP, there may be a risk that the lubricating oil composition is too viscous during cold cranking and it is difficult to start the engine. When the CCS viscosity is less than 4,000 cP, there may be a risk that the oil is too thin to form a lubricating film of sufficient thickness during cold cranking, and problems with durability may occur because the engine parts cannot be sufficiently protected under high-temperature and high-load conditions. Also, the lubricating oil composition may have a viscosity loss rate of 2% or less at 100°C after 30 cycles of shearing by a Bosch pump, and the lubricating oil composition may have a viscosity loss rate of 3% or less at 40°C after 30 cycles of shearing by a Bosch pump. Because it has such excellent shear stability, the viscosity of the lubricating oil composition does not easily change due to the shearing force generated during engine operation, and the lubricating performance can be stably maintained for a long time. At this time, the lower limit of the viscosity loss rate is not particularly limited, but the lower limit of the viscosity loss rate at 100°C or 40°C after 30 cycles of shearing by a Bosch pump can be 0.1% respectively.

[0047] Also, when the lubricating oil composition is utilized for large diesel engine oil, the lubricating oil composition may have a mini-rotary viscometer (MRV) viscosity at -30°C of 19,000 to 30,000 cP, preferably 20,000 to 28,000 cP, more preferably 24,000 to 26,000 cP. On the other hand, when the MRV viscosity is less than 19,000 cP, there may be a problem of insufficient lubricating film formation and a decrease in engine protection performance. When it exceeds 30,000 cP, the cold cranking startability and pumping property may decrease, and problems may occur during engine starting. Further, the lubricating oil composition may have a cold cranking simulator (CCS) viscosity at -25°C of 9,000 cP or less, preferably 5,000 to 9,000 cP, more preferably 5,500 to 8,500 cP, even more preferably 6,000 to 8,000 cP, and most preferably 6,300 to 7,500 cP. On the other hand, when the CCS viscosity exceeds 9,000 cP, there may be a risk that the lubricating oil composition becomes too viscous during cold cranking and it is difficult to start the engine. When the CCS viscosity is less than 5,000 cP, the oil may be too thin to form a lubricating film of sufficient thickness during cold cranking, and it may not be able to sufficiently protect engine parts under high temperature and high load conditions, and there may be a problem with durability. Also, the lubricating oil composition may have a viscosity loss rate at 100°C after shearing by 90 cycles of a Bosch pump of 6% or less, and the lubricating oil composition may have a viscosity loss rate at 40°C after 90 cycles of shearing of a Bosch pump of 5% or less. Since it has such excellent shear stability, the viscosity of the lubricating oil composition does not easily change due to the shear force generated during engine operation, and the lubricating performance can be stably maintained for a long time. At this time, the lower limit of the viscosity loss rate is not particularly limited, but the lower limit of the viscosity loss rate at 100°C or 40°C after 90 cycles of shearing of a Bosch pump may be 0.1% respectively.

[0048] In order to achieve such excellent properties, the addition amounts of the respective components of the lubricating oil composition are important. As described above, the lubricating oil composition according to an example of the present invention may contain 0.1 to 15% by weight of a lubricating oil viscosity index improver and the balance of base oil. Preferably, it contains 1 to 12% by weight of a lubricating oil viscosity index improver, more preferably 3 to 11% by weight of a lubricating oil viscosity index improver, still more preferably 5 to 10% by weight of a lubricating oil viscosity index improver, and particularly preferably 6.5 to 8% by weight of a lubricating oil viscosity index improver, and the balance may be base oil. It is preferable that the target levels of shear stability and high-temperature high-shear viscosity characteristics can be satisfied within such a range.

[0049] Hereinafter, the lubricating oil composition according to an example of the present invention will be described in more detail. First, in an example of the present invention, the base oil has different performances such as viscosity characteristics, heat resistance, and oxidation stability depending on the production method, purification method, etc., but can be used without particular limitation as long as it is commonly used in the art. Generally, API (American Petroleum Institute) classifies base oils into five types: Group I, II, III, IV, and V. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002, as shown in Table 1 below.

Table 1

[0050] The base oil may be any of Groups I to V of the API category. The base oils suitable for the present invention belong to I to III of the above-mentioned API category. "Saturated hydrocarbons" can mean paraffinic and naphthenic compounds. The paraffinic compounds may be branched or linear, and the naphthenic compounds may be cyclic saturated hydrocarbons, i.e., cycloparaffins. Saturated hydrocarbons having a cyclic structure are typically derivatives of cyclopentane or cyclohexane. Naphthenic compounds include monocyclic structures (mononaphthenes), or two isolated ring structures (isolated dinaphthenes), or two fused ring structures (fused dinaphthenes), or three or more fused ring structures (polycyclic naphthenes or polynaphthenes).

[0051] In addition, the lubricating oil composition according to an example of the present invention may further contain additives commonly added in the art. Specifically, for example, it can further contain one or more selected from the group consisting of pour point depressants, antioxidants, corrosion inhibitors, friction modifiers, foam suppressants, antiwear agents, and dispersants. The addition amounts of these can be added at 0.001 to 10% by weight respectively, and are not necessarily limited thereto.

[0052] Hereinafter, the present invention will be specifically described by way of examples and comparative examples. These examples are only for helping the understanding of the present invention, and the scope of the present invention is not limited by the following examples. % not specifically specified in the present invention can mean % by weight.

[0053] [Property Evaluation Method] The properties of the liquid α-olefin copolymer and the lubricating oil composition were tested by the following methods.

[0054] 1) Liquid α-olefin copolymer: a) Weight average molecular weight (Mw, g / mol): The weight average molecular weight was measured based on ASTM D5296. b) Viscosity (at 100 °C, cSt): The viscosity at 100 °C was measured based on ASTM D445. c) Specific gravity: The specific gravity at 20 °C was measured based on ASTM D1480. d) Permanent Shear Stability Index (PSSI) and Viscosity Loss Rate: The Permanent Shear Stability Index and Viscosity Loss Rate were measured based on ASTM D6278. e) Viscosity Index (at 100 °C, cSt): The viscosity index at 100 °C was measured based on ASTM D445. f) Viscosity Index: The base oil was diluted with a liquid α-olefin copolymer at a concentration of 5 wt%, and the viscosity index was measured based on ASTM D2270.

[0055] 2) Lubricating oil composition: a) Kinematic viscosity (cSt): Based on ASTM D445, the kinematic viscosity at 40 °C (V 40 ) and the kinematic viscosity at 100 °C (V 100 ) were measured respectively. b) Viscosity Index: The viscosity index was measured based on ASTM D2270. c) Cold Cranking Simulator viscosity (cP): Based on ASTM D5293, the CCS viscosity at -25 °C or -30 °C was measured using a Cold Cranking Simulator Viscometer. d) MRV viscosity (Mini Rotary Viscometer viscosity, cP): Based on ASTM D4684, the MRV viscosity at -30 °C or -35 °C was measured. e) High Temperature High Shear viscosity (cP): Based on ASTM D5481, the HTHS viscosity at 150 °C was measured using a High Temperature High Shear Viscometer. f) Cold Cranking Pour Point (°C): Based on ASTM D97, the Cold Cranking Pour Point was measured using a Pour Point Apparatus. g) Noack Volatility (wt%): The Noack volatility at 250 °C was measured using a Noack Volatility Tester based on ASTM D5800. h) Permanent Shear Stability Index (PSSI) and Viscosity Loss Rate: The Permanent Shear Stability Index and Viscosity Loss Rate were measured based on ASTM D6278.

[0056] [Production Examples 1 - 2 and Comparative Production Examples 1 - 2] Synthesis of Liquid α - Olefin Copolymer 1) Preparation of Catalyst Solution 0.15 mmol of diphenylmethylene{η5-(3 - n - butylcyclopentadienyl)}{η5-(2,7 - di - tert - butylfluorenyl)}zirconium dichloride, 0.2 mmol of dimethylanilinium tetra(pentafluorophenyl)borate, 8 mmol of triisobutylaluminum, and toluene were mixed in a glass flask sufficiently purged with nitrogen to produce 120 ml of catalyst solution. 2) Polymerization 375 mL of hexane was injected into a 1.1 L stainless - steel autoclave with sufficient nitrogen substitution, and after raising the temperature of the system to 70 °C, 15 mL of the prepared catalyst solution was added. Then, 260 g / hr of ethylene, 12.40 mL / min of liquid propylene, 1.95 g / hr of hydrogen, 30 mL / min of hexane, and 0.25 mL / min of catalyst solution were continuously fed, and copolymerization was carried out while maintaining the stirring speed at 1630 rpm. Then, by reducing the catalyst feed rate and finally continuously feeding 0.07 mL / min, polymerization was carried out while maintaining a temperature of 100 °C and a pressure of 16 Bar. This copolymer solution was continuously discharged through a back - pressure regulator and mixed with a 1 M aqueous solution of sodium hydroxide to deactivate it. 3) Post - treatment after Polymerization After removing the aqueous sodium hydroxide solution from the mixture of the generated polymer solution and the aqueous sodium hydroxide solution, the impurities on the polymer solution were extracted with distilled water. Then, the polymer solution was concentrated under reduced pressure at 100 °C for 30 minutes and dried under reduced pressure at 230 °C for 30 minutes. As a result, 435 g of an ethylene-propylene copolymer was obtained. A resultant was obtained by mixing base oil with the generated polymer and diluting it to a kinematic viscosity of 1250 cSt at 100 °C.

[0057] [Characterization of Liquid α-Olefin Copolymer] The main physical properties of the liquid α-olefin copolymer produced above were measured and shown in Table 2 below. The permanent shear stability index (PSSI at 100 °C) and viscosity loss (at 100 °C) of the liquid α-olefin copolymer according to ASTM D6278 were measured and shown in Table 3 and Table 4 below, respectively. At this time, Comparative Production Example 3 described in Table 3 and Table 4 below used a commercial product (trade name Infineum SV261L, hydrogenated styrene-diene copolymer, Mw 650,000).

Table 2

Table 3

[0058] Referring to Table 3 above, in Production Example 1, the PSSI value did not increase significantly to 5.3 even after shearing by 150 cycles of a Bosch pump. In contrast, in Comparative Production Example 2, the PSSI value increased rapidly to 21.9 after shearing by 30 cycles of a Bosch pump. In Comparative Production Example 3 as well, the PSSI value increased slightly to 22.8 after shearing by 30 cycles of a Bosch pump and showed a tendency to increase rapidly to 49.3 after shearing by 150 cycles of a Bosch pump.

Table 4

[0059] Referring to Table 4 above, in Production Example 1, the viscosity loss after shearing by 150 cycles of the Bosch pump was as low as 1.9%. In contrast, in Comparative Production Example 2, the viscosity loss increased significantly to 7.1% after shearing by 30 cycles of the Bosch pump. In Comparative Production Example 3 as well, the viscosity loss became slightly higher at 8.1% after 30 engine operations, and showed a sharp increase to 17.4% after shearing by 150 cycles of the Bosch pump.

[0060] [Examples 1 - 2 and Comparative Examples 1 - 2] Production of Lubricating Oil Compositions According to the addition amounts (by mass) shown in Table 5 below, DI PKG (Detergent - Inhibitor Package), pour point depressant (PPD), the liquid α - olefin copolymers produced respectively above, Group II mineral oil (150N, kinematic viscosity at 100°C of 5.2 cSt), and Group III mineral oil (kinematic viscosity at 100°C of 4 cSt) were mixed to prepare a lubricating oil composition for gasoline engines (5W30). The physical properties of the lubricating oil composition were measured and shown in Table 7 below.

Table 5

[0061] [Example 3 and Comparative Example 3] According to the addition amounts (by mass) shown in Table 6 below, DI PKG (Detergent - Inhibitor Package), pour point depressant (PPD), the liquid α - olefin copolymers produced respectively above, Group II mineral oil (150N, kinematic viscosity at 100°C of 5.2 cSt), and Group III mineral oil (kinematic viscosity at 100°C of 6 cSt) were mixed to prepare a lubricating oil composition for large diesel engines (10W40). The physical properties of the lubricating oil composition were measured and shown in Table 8 below.

Table 6

[0062] [Characteristic Evaluation of Lubricating Oil Compositions]

Table 7

[0063] Referring to Table 7 above, Examples 1 and 2 contain a liquid α-olefin copolymer according to the present invention having a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) of more than 1 and less than 25, and a thickening power at 100 °C of more than 2.5 and less than 3.6 cSt. As a result, they have excellent cold cranking performance because their CCS viscosity and MRV viscosity are lower than those of Comparative Example 1, and have excellent viscosity maintenance performance because their viscosity loss rate is significantly lower than that of Comparative Example 2.

Table 8

[0064] Referring to Table 8 above, Example 3 contains a liquid α-olefin copolymer according to the present invention having a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) of more than 1 and less than 25, and a thickening power at 100 °C of more than 2.5 and less than 3.6 cSt. As a result, it has excellent high-temperature shear stability because its HTHS viscosity value is higher than that of Comparative Example 3, and has excellent viscosity maintenance performance because its viscosity loss rate is significantly lower.

Claims

1. A lubricating oil viscosity index improver comprising a liquid α-olefin copolymer in which ethylene and an α-olefin monomer having 3 or more carbon atoms are copolymerized, The liquid α-olefin copolymer is a lubricating oil viscosity index improver characterized in that it has a weight average molecular weight of 10,000 to 120,000 g / mol, a permanent shear stability index (PSSI) of more than 1 and less than 25, and a thickening power at 100° C. of more than 2.5 and less than 3.6 cSt.

2. 2. The lubricating oil viscosity index improver according to claim 1, wherein the liquid α-olefin copolymer is a copolymer of ethylene and an α-olefin monomer having 3 to 6 carbon atoms.

3. 2. The lubricating oil viscosity index improver according to claim 1, wherein the liquid α-olefin copolymer comprises 40 to 60 mol % of ethylene units and 60 to 40 mol % of α-olefin units having 3 to 20 carbon atoms.

4. 2. The lubricating oil viscosity index improver according to claim 1, wherein the liquid α-olefin copolymer has a specific gravity at 20° C. of 0.8 to 0.

95.

5. 2. The lubricating oil viscosity index improver according to claim 1, wherein the liquid α-olefin copolymer has a viscosity index of 130 to 150 when diluted with a base oil at a concentration of 5% by weight.

6. 2. The lubricating oil viscosity index improver of claim 1, wherein the liquid alpha-olefin copolymer has a weight average molecular weight of 20,000 to 80,000 g / mol.

7. 7. The lubricating oil viscosity index improver of claim 6, wherein the liquid alpha-olefin copolymer has a permanent shear stability index (PSSI) of 1.5 to 3.

5.

8. A lubricating oil composition comprising a base oil and the lubricating oil viscosity index improver according to any one of claims 1 to 7.

9. 9. The lubricating oil composition of claim 8, wherein the lubricating oil composition comprises 0.1 to 15 wt. % of the lubricating oil viscosity index improver, the balance being base oil.

10. The lubricating oil composition of claim 8, wherein the lubricating oil composition is for use in a gasoline engine oil.

11. The lubricating oil composition according to claim 10, wherein the lubricating oil composition has a mini rotational viscometer (MRV) viscosity at -35°C of 15,000 to 19,000 cP.

12. The lubricating oil composition according to claim 10, wherein the lubricating oil composition has a cold cranking simulator (CCS) viscosity at -30°C of 7,000 cP or less.

13. 11. The lubricating oil composition of claim 10, wherein the lubricating oil composition has a viscosity loss of 2% or less at 100°C after 30 cycles of shear in a Bosch pump.

14. 11. The lubricating oil composition of claim 10, wherein the lubricating oil composition has a viscosity loss of 3% or less at 40°C after 30 cycles of shear in a Bosch pump.

15. The lubricating oil composition of claim 8, wherein the lubricating oil composition is for use in heavy duty diesel engine oil applications.

16. The lubricating oil composition according to claim 15, wherein the lubricating oil composition has a mini rotational viscometer (MRV) viscosity at -30°C of 19,000 to 30,000 cP.

17. The lubricating oil composition of claim 15, wherein the lubricating oil composition has a cold cranking simulator (CCS) viscosity at -25°C of 9,000 cP or less.

18. 16. The lubricating oil composition of claim 15, wherein the lubricating oil composition has a viscosity loss of 6% or less at 100°C after 90 cycles of shear in a Bosch pump.

19. 16. The lubricating oil composition of claim 15, wherein the lubricating oil composition has a viscosity loss of 5% or less at 40°C after 90 cycles of shear in a Bosch pump.

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