Lubricating oil composition and ethylene-cyclic olefin copolymer

Abstract

To provide a lubricant composition that has particularly excellent viscosity properties, specifically at a low temperature of -35°C, in other words, the lubricant composition that maintains required viscosity at a high temperatures, mitigates viscosity increase at low temperatures, and demonstrates outstanding solubility with a base oil in cold environments.SOLUTION: A lubricant composition of the present invention comprises a copolymer (A) and a base oil (B), wherein the copolymer (A) satisfies the following requirements (a-1), (a-2), and regarding a content ratio of the copolymer (A) and the base oil (B), the polymer (A) is in a range of 0.1 to 50 parts by mass when a total of the copolymer (A) and the base oil (B) is 100 parts by mass. The requirement (a-1): the copolymer is a copolymer of ethylene and cyclic olefin, which contains structural units derived from ethylene in a range of 80 mol % or more to 95 mol % or less based on all structural units. The requirement (a-2): the cyclic olefin has a specific structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil composition containing a specific copolymer and having excellent viscosity characteristics at low temperatures, and to an ethylene-cyclic olefin copolymer suitable for use in a lubricating oil composition. [Background technology]

[0002] Environmental issues such as the dwindling use of petroleum resources and global warming have led to calls for improved fuel efficiency in lubricated machinery, with the aim of reducing exhaust pollutants and CO2 emissions. Because fuel efficiency through lubrication is more cost-effective than physical improvements to lubricated machinery, it is expected to be an important fuel-saving technology, and demand for improved fuel efficiency through lubricants is growing. Power loss in lubricated machinery can be divided into friction loss at sliding parts and agitation loss due to the viscosity of the lubricant, and one method of fuel efficiency is to reduce the viscosity of the lubricant. Low-temperature viscosity, in particular, contributes to improved fuel efficiency from engine start-up to warm-up under low-temperature conditions, so there remains a great need for it.

[0003] As one method for improving the low-temperature storage stability and low-temperature properties of a lubricating oil composition, a lubricating oil composition containing a copolymer containing 30 to 90 mol% of structural units derived from 4-methyl-1-pentene and a base oil has been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 124070 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional lubricating oil compositions are still insufficient in terms of the balance between base oil solubility at low temperatures and low-temperature properties. The object of the present invention is to provide a lubricating oil composition that exhibits particularly excellent viscosity characteristics at a low temperature of −35°C, i.e., that maintains the necessary viscosity at high temperatures while suppressing an increase in low-temperature viscosity and exhibits excellent base oil solubility in low-temperature environments, and to provide an ethylene-cyclic olefin copolymer that is suitable for obtaining such a lubricating oil composition. [Means for solving the problem]

[0006] The present invention relates to a lubricating oil composition comprising a copolymer (A) and a base oil (B), wherein the copolymer (A) satisfies the following requirements (a-1) and (a-2), and the content ratio of the copolymer (A) to the base oil (B) is in the range of 0.1 to 50 parts by mass when the total of the copolymer (A) and the base oil (B) is 100 parts by mass. (a-1) A copolymer (A) is a copolymer of ethylene and a cyclic olefin, and contains 80 mol % or more and 95 mol % or less of structural units derived from ethylene based on all structural units. (a-2) The cyclic olefin has a structure represented by general formula (I).

[0007] [ka] [In the formula, R1 to R6 may be the same or different, and may each represent a hydrogen atom, a halogen atom, a methyl group, an ethyl group, or R1 and R2, R3 and R4, or R5 and R6 together may form an alkylidene group having 1 or 2 carbon atoms.] [Effects of the Invention]

[0008] The lubricating oil composition of the present invention maintains its viscosity index (VI) while improving its low-temperature viscosity characteristics (CCS) at -35°C (reducing its viscosity), thereby reducing loss from start-up to warm-up and achieving a high fuel economy. Furthermore, its excellent base oil solubility prevents the precipitation of insoluble matter or the formation of gel, and it also has excellent storage stability in low-temperature environments. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be specifically described below. In the following description, the symbol "to" indicating a range of values ​​means from above to below unless otherwise specified.

[0010] <Lubricating oil composition> The lubricating oil composition of the present invention contains an ethylene-cyclic olefin copolymer (A) (hereinafter sometimes referred to as "copolymer (A)") and a base oil (B). Each of the constituent components is described in detail below.

[0011] Ethylene-cyclic olefin copolymer (A) The ethylene-cyclic olefin copolymer (A), which is one of the components contained in the lubricating oil composition of the present invention, is a copolymer that satisfies the following requirements (a-1) and (a-2).

[0012] <Requirement (a-1)> The copolymer (A) is a copolymer of ethylene and a cyclic olefin, and contains 80 mol % or more and 95 mol % or less, and preferably 85 mol % or more and 90 mol % or less, of structural units derived from ethylene relative to all structural units.

[0013] <Requirement (a-2)> The cyclic olefin constituting the copolymer (A) has a structure represented by general formula (I).

[0014] [ka] [In the formula, R1 to R6 may be the same or different, and may each represent a hydrogen atom, a halogen atom, a methyl group, an ethyl group, or R1 and R2, R3 and R4, or R5 and R6 together may form an alkylidene group having 1 or 2 carbon atoms.]

[0015] The cyclic olefin having the structure represented by the above general formula (I) according to the present invention is specifically a bicyclo[2.2.1]hept-2-ene derivative, a tetracyclo[4.4.0.1]hept-2-ene derivative, a ... 2,5 .1 7,10 ]-3-dodecene derivatives, hexacyclo[6.6.1.1 3,6 .110,13 .0 2,7 .0 9,14 ]-4-heptadecene derivatives, octacyclo[8.8.0.1 2,9 .1 4,7 .1 11,18 .1 13,16 .0 3,8 .0 12,17 ]-5-docosene derivatives, pentacyclo[6.6.1.1 3,6 .0 2,7 .0 9,14 ]-4-hexadecene derivatives, heptacyclo-5-eicosene derivatives, heptacyclo-5-heneicosene derivatives, tricyclo[4.3.0.1 2,5 ]-3-decene derivatives, tricyclo[4.4.0.1 2,5 ]-3-undecene derivatives, pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]-4-pentadecene derivatives, pentacyclopentadecadiene derivatives, pentacyclo[7.4.0.1 2,5 .1 9,12 .0 8,13 ]-3-pentadecene derivatives, heptacyclo[8.7.0.1 3,6 .1 10,17 .1 12,15 .0 2,7 .0 11,16 ]-4-eicosene derivatives, nonacyclo[10.9.1.1 4,7 .1 13,20 .1 15,18 .0 3,8 .0 2,10 .0 12,21 .0 14,19 ]-5-pentacosene derivatives, pentacyclo[8.4.0.1 2,5 .1 9,12 .0 8,13 ]-3-hexadecene derivatives, heptacyclo[8.8.0.1 4,7 .1 11,18 .1 13,16 .0 3,8 .0 12,17 ]-5-heneicosene derivatives, nonacyclo[10.10.1.1 5,8 .1 14,21 .1 16,19 .0 2,11 .04,9 .0 13,22 .0 15,20 ]-5-hexacosene derivatives, 1,4-methano-1,4,4a,9a-tetrahydrofluorene derivatives, 1,4-methano-1,4,4a,5,10,10a-hexahydroanthracene derivatives, and cyclopentadiene-acenaphthylene adducts.

[0016] Among these cyclic olefins, tetracyclododecene is particularly preferred because it has a rigid skeleton which has the effect of reducing compatibility with the base oil, and it can be copolymerized with ethylene to give an oil-soluble copolymer.

[0017] The copolymer (A) according to the present invention preferably satisfies the following requirement (a-3) in addition to the above requirements (a-1) and (a-2), and also satisfies at least one of requirements (a-4) and (a-5):

[0018] <Requirement (a-3)> The intrinsic viscosity [η] measured in decalin at 135°C is in the range of 0.01 to 5.0 dl / g, preferably 0.05 to 4.0 dl / g, more preferably 0.1 to 2.5 dl / g, and even more preferably 0.3 to 2.0 dl / g.

[0019] The intrinsic viscosity [η] can be adjusted within the above range by controlling the polymerization temperature during polymerization of the copolymer (A), the use of a molecular weight modifier such as hydrogen, etc. The higher the intrinsic viscosity [η], the higher the viscosity of the copolymer (A) and the resulting lubricating oil composition. When obtaining a lubricating oil composition, the amount of lubricating oil viscosity modifier added is usually adjusted appropriately to adjust the required physical properties of the lubricating oil composition, for example, to a specific kinematic viscosity at 100°C. However, it is preferable that the intrinsic viscosity [η] of the copolymer (A) be within the above range, since it can be appropriately proportioned to the base oil.

[0020] <Requirement (a-4)> In differential scanning calorimetry (DSC), no melting point (Tm) is detected in the range of 70° C. to 160° C. In other words, the copolymer (A) is amorphous or has low crystallinity, and therefore it can be said that it has excellent storage stability at low temperatures.

[0021] <Requirement (a-5)> The glass transition temperature (Tg) measured by differential scanning calorimetry (DSC) is 70° C. or lower, preferably 50° C. or lower. When the glass transition temperature (Tg) is within the above range, the copolymer (A) is vitrified in the temperature range below the glass transition temperature (Tg), and the cohesive force of the molecules is increased, which is expected to reduce the volume occupied by the polymer molecules in the lubricating oil composition.

[0022] It is believed that by adjusting the glass transition temperature (Tg) of copolymer (A) to a temperature below the above temperature, it is possible to increase the molecular cohesion at low temperatures without crystallinity, thereby reducing the low-temperature viscosity of the resulting lubricating oil composition. In other words, it is believed that the lubricating oil composition maintains its excellent storage stability in low-temperature environments due to its amorphous or low-crystalline nature, while having a higher glass transition temperature than conventionally used amorphous polymers, ensuring excellent fluidity at low temperatures.

[0023] That is, an ethylene-cyclic olefin copolymer that satisfies the requirements (a-1) to (a-3) and further satisfies at least one of (a-4) and (a-5) is an example of an ethylene-cyclic olefin copolymer suitable for obtaining a lubricating oil composition. (a-1) A copolymer (A) is a copolymer of ethylene and a cyclic olefin, and contains 80 mol % or more and 95 mol % or less of structural units derived from ethylene based on all structural units. (a-2) The cyclic olefin has a structure represented by general formula (I). (a-3) The intrinsic viscosity [η] measured in decalin at 135°C is in the range of 0.01 to 5.0 dl / g. (a-4) No melting point (Tm) is detected in the range of 70°C to 160°C in differential scanning calorimetry (DSC). (a-5) The glass transition temperature (Tg) is 70°C or lower in differential scanning calorimetry (DSC).

[0024] [ka] [In the formula, R1 to R6 may be the same or different, and may each represent a hydrogen atom, a halogen atom, a methyl group, an ethyl group, or R1 and R2, R3 and R4, or R5 and R6 together may form an alkylidene group having 1 or 2 carbon atoms.]

[0025] <Method for producing copolymer (A)> The method for producing the copolymer (A) according to the present invention is not particularly limited as long as it can produce a copolymer that satisfies the above-mentioned predetermined requirements, and the copolymer (A) can be obtained by polymerizing ethylene and a cyclic olefin in the presence of a suitable polymerization catalyst.

[0026] As a polymerization catalyst suitable for obtaining the copolymer (A) according to the present invention, a conventionally known catalyst, for example, a magnesium-supported titanium catalyst, or a method using a metallocene catalyst described in WO 01 / 53369, WO 01 / 27124, JP-A 3-193796, JP-A 02-41303, or WO 14 / 050817, can be used.

[0027] Base oil (B) The base oil (B), which is one of the components contained in the lubricating oil composition of the present invention, preferably satisfies the following requirement (b-1).

[0028] <Requirement (b-1)> 100℃ kinematic viscosity 1~50mm 2 / s range. The base oil (B) according to the present invention includes mineral oils; and synthetic oils such as poly-α-olefins, diesters, and polyalkylene glycols.

[0029] The base oil (B) according to the present invention may be a mineral oil or a blend of a mineral oil and a synthetic oil. Examples of diesters include polyol esters, dioctyl phthalate, and dioctyl sebacate.

[0030] Mineral oils are generally used after a refining process such as dewaxing, and there are several grades depending on the refining method. Mineral oils containing 0.5 to 10% wax are generally used. For example, highly refined oils with a low pour point, high viscosity index, and a composition mainly consisting of isoparaffins, produced by hydrocracking refining, can also be used. Kinematic viscosity at 40°C is 10 to 200 mm 2 / s mineral oil is commonly used.

[0031] As mentioned above, mineral oils are generally used after undergoing refining processes such as dewaxing, and there are several grades depending on the refining method, which are specified by the API (American Petroleum Institute) classification. Table 1 shows the characteristics of lubricating oil base stocks classified into each group.

[0032] [Table 1]

[0033] The polyα-olefins in Table 1 are hydrocarbon polymers obtained by polymerizing an α-olefin having at least 10 carbon atoms as one of the raw material monomers, and examples include poly-1-decene obtained by polymerizing 1-decene.

[0034] As the base oil (B), mineral oils belonging to group (ii) or group (iii) or poly-α-olefins belonging to group (iv) are preferred. Groups (ii) and (iii) tend to have lower wax concentrations than group (i). Among the mineral oils belonging to group (ii) or group (iii), those having a kinematic viscosity at 100°C of 1 to 50 mm are preferred. 2 / s is preferred.

[0035] <<Ratio of copolymer (A) and base oil (B)>> In the lubricating oil composition of the present invention, the content ratio of copolymer (A) to base oil (B) is in the range of 0.1 to 50 parts by mass of copolymer (A) when the total of copolymer (A) and base oil (B) is 100 parts by mass.

[0036] When the lubricating oil composition of the present invention is used for engine applications, it preferably contains 0.1 to 5 parts by mass of copolymer (A) and 95 to 99.9 parts by mass of base oil (B) (where the total of copolymer (A) and base oil (B) is 100 parts by mass). The copolymer (A) is preferably contained in an amount of 0.2 to 4 parts by mass, more preferably 0.4 to 3 parts by mass, and even more preferably 0.6 to 2 parts by mass, and the base oil (B) is preferably contained in an amount of 96 to 99.8 parts by mass, more preferably 97 to 99.6 parts by mass, and even more preferably 98 to 99.4 parts by mass. One type of copolymer (A) may be used alone, or multiple types may be used in combination.

[0037] On the other hand, when the lubricating oil composition of the present invention is used as a lubricating oil additive composition (so-called concentrate), it preferably contains 1 to 50 parts by mass of copolymer (A) and 50 to 99 parts by mass of base oil (B) (where the total of copolymer (A) and base oil (B) is 100 parts by mass). More preferably, it contains 2 to 40 parts by mass of copolymer (A) and 60 to 98 parts by mass of base oil (B), and even more preferably, it contains 3 to 30 parts by mass of copolymer (A) and 70 to 97 parts by mass of base oil (B).

[0038] When the lubricating oil composition of the present invention is used as a lubricating oil additive composition (so-called concentrate), it generally does not contain the pour point depressant (C) and other components (additives) described below, or contains the antioxidant described below in an amount of 0.01 to 1 mass %, preferably 0.05 to 0.5 mass %, as needed. The lubricating oil additive composition can be used for various applications as a lubricating oil composition by blending the base oil (B) with the pour point depressant (C) and other components (additives) described below.

[0039] <Pour point depressant (C)> The lubricating oil composition of the present invention may further contain a pour point depressant (C). The content of the pour point depressant (C) is not particularly limited as long as the effects of the present invention are achieved, but it is usually contained in an amount of 0.05 to 5 mass%, preferably 0.05 to 3 mass%, more preferably 0.05 to 2 mass%, and even more preferably 0.05 to 1 mass%, per 100 mass% of the lubricating oil composition.

[0040] Examples of the pour point depressant (C) that may be contained in the lubricating oil composition of the present invention include alkylated naphthalene, alkyl methacrylate (co)polymers, alkyl acrylate (co)polymers, copolymers of alkyl fumarate and vinyl acetate, α-olefin polymers, copolymers of α-olefin and styrene, etc. In particular, alkyl methacrylate (co)polymers and alkyl acrylate (co)polymers may be used.

[0041] <Other ingredients (additives)> The lubricating oil composition of the present invention may also contain other components (additives) in addition to the copolymer (A) and base oil (B). Examples of other components include any one or more of the materials described below.

[0042] When the lubricating oil composition of the present invention contains additives, the content of the additives is not particularly limited, but when the total of the base oil (B) and the additives is taken as 100 mass%, the content of the additives is usually more than 0 mass%, preferably 1 mass% or more, more preferably 3 mass% or more, and even more preferably 5 mass% or more. Also, the content of the additives is usually 40 mass% or less, preferably 30 mass% or less, more preferably 20 mass% or less, and even more preferably 15 mass% or less.

[0043] One such additive is a detergent. Many conventional detergents used in engine lubrication impart basicity or TBN to lubricating oils through the presence of basic metal compounds (typically metal hydroxides, oxides, or carbonates based on metals such as calcium, magnesium, or sodium). Such metallic overbased detergents (also known as overbased or superbased salts) are single-phase homogeneous Newtonian systems characterized by a metal content in excess of that which would be present for neutralization according to the stoichiometry of the metal and the particular acidic organic compound with which it reacts. Overbased materials are typically prepared by reacting an acidic material (typically an inorganic acid such as carbon dioxide or a lower carboxylic acid) with a mixture of an acidic organic compound (also known as a substrate) and a stoichiometric excess of a metal salt, typically in an organic solvent inert to the acidic organic substrate (e.g., mineral oil, naphtha, toluene, xylene, etc.). A small amount of a promoter, such as a phenol or alcohol, is optionally present. The acidic organic substrate will usually have a sufficient number of carbon atoms to impart some degree of solubility in oil.

[0044] Such conventional overbased materials and their preparation methods are well known to those skilled in the art.Patents that describe the technology of making basic metal salts of sulfonic acid, carboxylic acid, phenol, phosphoric acid, and mixtures of two or more thereof include U.S. Patent Nos. 2,501,731; 2,616,905; 2,616,911; 2,616,925; 2,777,874; 3,256,186; 3,384,585; 3,365,396; 3,320,162; 3,318,809; 3,488,284; and 3,629,109.Salixarate detergents are described in U.S. Patent No. 6,200,936 and WO 01 / 56968. Saligenin detergents are described in US Pat. No. 6,310,009.

[0045] The amount of detergent in the lubricating oil composition is not particularly limited as long as it achieves the effects of the present invention, but is generally 1 to 10 mass %, preferably 1.5 to 9.0 mass %, and more preferably 2.0 to 8.0 mass %, all of which are based on an oil-free state (i.e., without the diluent oil conventionally provided therewith).

[0046] Another type of additive is dispersants. Dispersants are well known in the lubricating oil field and primarily include those known as ashless dispersants, also known as polymeric dispersants. Ashless dispersants are characterized by a polar group attached to a relatively high molecular weight hydrocarbon chain. Typical ashless dispersants include nitrogen-containing dispersants such as N-substituted long-chain alkenyl succinimides, also known as succinimide dispersants. Succinimide dispersants are more fully described in U.S. Pat. Nos. 4,234,435 and 3,172,892. Another class of ashless dispersants is high molecular weight esters prepared by the reaction of polyhydric aliphatic alcohols, such as glycerol, pentaerythritol, or sorbitol, with hydrocarbyl acylating agents. Such materials are described in more detail in U.S. Pat. No. 3,381,022. Another class of ashless dispersants is Mannich bases. These are materials formed by the condensation of high molecular weight alkyl-substituted phenols, alkylene polyamines, and aldehydes such as formaldehyde, and are described in more detail in U.S. Patent No. 3,634,515. Other dispersants include polyhydric dispersant additives, which are generally hydrocarbon-based polymers containing polar functionality that imparts dispersant properties to the polymer.

[0047] Dispersants may be post-treated by reaction with any of a variety of materials, including urea, thiourea, dimercaptothiadiazole, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitriles, epoxides, boron compounds, and phosphorus compounds. A reference detailing such treatments is found in U.S. Pat. No. 4,654,403. The amount of dispersant in the compositions of the present invention is not particularly limited as long as it achieves the effects of the present invention, but typically ranges from 1 to 10% by weight, preferably 1.5 to 9.0% by weight, and more preferably 2.0 to 8.0% by weight (all based on an oil-free basis).

[0048] Another component is an antioxidant. Antioxidants include phenolic antioxidants, which may include butyl-substituted phenols having two or three t-butyl groups. The para position may be occupied by a hydrocarbyl group or a group linking two aromatic rings. The latter antioxidants are described in more detail in U.S. Pat. No. 6,559,105. Antioxidants also include aromatic amines, such as nonylated diphenylamine. Other antioxidants include sulfurized olefins, titanium compounds, and molybdenum compounds. For example, U.S. Pat. No. 4,285,822 discloses lubricating oil compositions containing molybdenum and sulfur. Typical amounts of antioxidants will, of course, depend on the specific antioxidant and its individual effectiveness, but exemplary total amounts can be 0.01 to 5 mass %, preferably 0.15 to 4.5 mass %, and more preferably 0.2 to 4 mass %. Additionally, more than one antioxidant may be present, and certain combinations of these may be synergistic in their combined overall effectiveness.

[0049] Thickeners (sometimes called viscosity index improvers or viscosity modifiers) may be included in lubricating oil additive compositions. Thickeners are typically polymers, including polyisobutenes, polymethacrylates, diene polymers, polyalkylstyrenes, esterified styrene-maleic anhydride copolymers, alkenylarene-conjugated diene copolymers, and polyolefins, hydrogenated SBR (styrene butadiene rubber), SEBS (styrene ethylene butylene styrene block copolymer), and the like. Multifunctional thickeners, which also have dispersant and / or antioxidant properties, are known and may optionally be used.

[0050] Another type of additive is an antiwear agent. Examples of antiwear agents include phosphorus-containing antiwear agents / extreme pressure agents such as metal thiophosphates, phosphate esters and their salts, phosphorus-containing carboxylic acids, esters, ethers, and amides, and phosphites. In certain embodiments, the phosphorus antiwear agent is not particularly limited as long as it achieves the effects of the present invention, but may be present in an amount that provides a phosphorus content of typically 0.01 to 0.2 mass %, preferably 0.015 to 0.15 mass %, more preferably 0.02 to 0.1 mass %, and even more preferably 0.025 to 0.08 mass %.

[0051] In many cases, the antiwear agent is zinc dialkyldithiophosphate (ZDP). A typical ZDP may contain 11 wt. % P (calculated on an oil-free basis), with a preferred amount being 0.09 to 0.82 wt. %. Phosphorus-free antiwear agents include borate esters (including borate epoxides), dithiocarbamate compounds, molybdenum-containing compounds, and sulfurized olefins.

[0052] Other additives that may be optionally used in the lubricating oil composition include the extreme pressure agents and antiwear agents described above, as well as friction modifiers, color stabilizers, rust inhibitors, metal deactivators and antifoaming agents, each of which may be used in a conventionally known amount.

[0053] <Method of manufacturing lubricating oil composition> The lubricating oil compositions of the present invention can be prepared by blending copolymer (A) and base oil (B), optionally together with other desired components, in a manner known in the art. Copolymer (A) may optionally be supplied as a concentrate in base oil (B) for ease of handling.

[0054] The lubricating oil composition of the present invention has excellent low-temperature storage properties and low-temperature viscosity. Therefore, the lubricating oil composition of the present invention can be used to lubricate a variety of known mechanical devices, for example, as a lubricating oil for gasoline engines, diesel engines, marine engines, two-stroke engines, automatic transmissions, manual transmissions, gear lubricants, and greases. [Example]

[0055] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples. The copolymers used in the examples and comparative examples were produced by the following production method.

[0056] [Polymerization Example 1] A 1.5-liter stainless steel autoclave equipped with a stirrer and thoroughly purged with nitrogen was charged with 570 ml of cyclohexane / Mitsui Light Hexane (v / v = 9 / 1) and 30 ml of tetracyclododecene (TD) at 23 °C. 1.36 ml of a 0.55 mmol / ml hexane solution of triisobutylaluminum (TIBAl) was then added to the autoclave, and the stirrer was turned on. The autoclave was then heated to an internal temperature of 50 °C, 17.8 ml of hydrogen was added, and ethylene was added until the internal pressure of the autoclave reached 0.75 MPaG. The autoclave was then pressurized with nitrogen until the total pressure reached 0.80 MPaG. Next, 4.0 ml of a previously prepared heptane solution containing 3.0 mmol of methylaluminoxane (calculated as Al) and 0.010 mmol of diphenylmethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride (catalyst A) was added to initiate the polymerization. Twenty minutes after the start of polymerization, 5 ml of methanol was injected into the autoclave with nitrogen to terminate the polymerization, and the autoclave was depressurized to atmospheric pressure. A methanol / acetone mixed solution was poured into the reaction solution with stirring. The resulting solvent-containing copolymer (A-1) was dried at 80°C under reduced pressure for 12 hours.

[0057] [Polymerization Example 2] A 1.5-liter stainless steel autoclave equipped with a stirrer and thoroughly purged with nitrogen was charged with 590 ml of cyclohexane / Mitsui Light Hexane (v / v = 9 / 1) and 10 ml of tetracyclododecene (TD) at 23°C. 1.36 ml of a 0.55 mmol / ml hexane solution of triisobutylaluminum (TIBAl) was then added to the autoclave, and the stirrer was turned on. The autoclave was then heated to an internal temperature of 50°C, 35.6 ml of hydrogen was added, and ethylene was added until the internal pressure of the autoclave reached 0.20 MPaG. The autoclave was then pressurized with nitrogen until the total pressure reached 0.60 MPaG. Next, 4.0 ml of a previously prepared heptane solution containing 3.0 mmol of methylaluminoxane (calculated as Al) and 0.010 mmol of diphenylmethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride (catalyst A) was added to initiate the polymerization. Twenty minutes after the start of polymerization, 5 ml of methanol was injected into the autoclave with nitrogen to terminate the polymerization, and the autoclave was depressurized to atmospheric pressure. A methanol / acetone mixed solution was poured into the reaction solution with stirring. The resulting solvent-containing copolymer (A-2) was dried at 80°C under reduced pressure for 12 hours.

[0058] [Polymerization Example 3] A 1.5-liter stainless steel autoclave equipped with a stirrer and thoroughly purged with nitrogen was charged with 562.5 ml of cyclohexane / Mitsui Light Hexane (v / v = 9 / 1) and 37.5 ml of tetracyclododecene (TD) at 23°C. 1.36 ml of a 0.55 mmol / ml hexane solution of triisobutylaluminum (TIBAl) was then added, and the stirrer was turned on. The autoclave was then heated to an internal temperature of 50°C, 35.6 ml of hydrogen was added, and ethylene was added until the internal pressure of the autoclave reached 0.75 MPaG. The autoclave was then pressurized with nitrogen until the total pressure reached 0.80 MPaG. Next, 4.0 ml of a previously prepared heptane solution containing 3.0 mmol of methylaluminoxane (calculated as Al) and 0.005 mmol of diphenylmethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride (catalyst A) was added to initiate the polymerization. Ten minutes after the start of polymerization, 5 ml of methanol was injected into the autoclave with nitrogen to terminate the polymerization, and the autoclave was depressurized to atmospheric pressure. A methanol / acetone mixed solution was poured into the reaction solution with stirring. The resulting solvent-containing copolymer (A-3) was dried at 80°C under reduced pressure for 12 hours.

[0059] [Polymerization Example 4] A 1.5-liter stainless steel autoclave equipped with a stirrer and thoroughly purged with nitrogen was charged with 490 ml of cyclohexane / Mitsui Light Hexane (v / v = 9 / 1) and 30 ml of tetracyclododecene (TD) at 23 °C. 1.36 ml of a 0.55 mmol / ml hexane solution of triisobutylaluminum (TIBAl) was then added and the stirrer was turned on. The autoclave was then heated to an internal temperature of 50 °C, and ethylene was added until the internal pressure reached 0.40 MPaG. The autoclave was then pressurized with nitrogen until the total pressure reached 0.60 MPaG. Subsequently, 2.0 ml of a previously prepared heptane solution containing 3.0 mmol of methylaluminoxane (calculated as Al) and 0.005 mmol of dimethylmethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride (catalyst B) was added to initiate the polymerization. Ten minutes after the start of polymerization, 5 ml of methanol was injected into the autoclave with nitrogen to terminate the polymerization, and the autoclave was depressurized to atmospheric pressure. A methanol / acetone mixed solution was poured into the reaction solution while stirring. The resulting solvent-containing copolymer (F-1) was dried at 80°C under reduced pressure for 12 hours.

[0060] [Polymerization Example 5] A 1.5-liter stainless steel autoclave equipped with a stirrer and thoroughly purged with nitrogen was charged with 590 ml of cyclohexane / Mitsui Light Hexane (v / v = 9 / 1) and 10 ml of tetracyclododecene (TD) at 23°C. 1.36 ml of a 0.55 mmol / ml hexane solution of triisobutylaluminum (TIBAl) was then added to the autoclave, and the stirrer was turned on. The autoclave was then heated to an internal temperature of 50°C, 35.6 ml of hydrogen was added, and ethylene was added until the internal pressure of the autoclave reached 0.40 MPaG. The autoclave was then pressurized with nitrogen until the total pressure reached 0.60 MPaG. Next, 4.0 ml of a previously prepared heptane solution containing 3.0 mmol of methylaluminoxane (calculated as Al) and 0.010 mmol of diphenylmethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride (catalyst A) was added to initiate the polymerization. Ten minutes after the start of polymerization, 5 ml of methanol was injected into the autoclave with nitrogen to terminate the polymerization, and the autoclave was depressurized to atmospheric pressure. A methanol / acetone mixed solution was poured into the reaction solution while stirring. The resulting solvent-containing copolymer (F-2) was dried at 80°C under reduced pressure for 12 hours.

[0061] [Polymerization Example 6] A 1.0 L glass reactor was thoroughly purged with nitrogen and charged with 500 mL of xylene. The temperature was raised to 90°C, and while stirring the inside of the reactor at 600 rpm, ethylene and propylene were continuously fed at 99 L / h and 36.0 L / h, respectively, to saturate the liquid and gas phases. While ethylene and propylene were continuously fed, 6.0 mL (6.0 mmol) of a 1.0 mol / L toluene solution of triisobutylaluminum (also referred to as iBuAl), 3.0 mL (0.030 mmol) of a 0.010 mol / L toluene solution of catalyst (B), and then 12.0 mL (0.120 mmol) of a 0.010 mol / L toluene solution of triphenylcarbenium tetrakis(pentafluorophenyl)borate (also referred to as PhCB(CF)) were added, and polymerization was carried out at 90°C for 40 minutes under atmospheric pressure. The polymerization was terminated by adding a small amount of isobutanol. The resulting polymerization reaction solution was washed with dilute hydrochloric acid, and the resulting organic layer was poured into a large amount of methanol to precipitate an ethylene-propylene copolymer. The ethylene-propylene copolymer (R-1) obtained by filtration was dried under reduced pressure at 130°C for 10 hours. The physical properties of the copolymers obtained in Polymerization Examples 1 to 6 were measured by the following methods.

[0062] [Content of constituent units] The content of the structural units derived from ethylene and the structural units derived from tetracyclododecene in the copolymer is 13 It was determined by analyzing the C-NMR spectrum. In Table 2, C2 represents a structural unit derived from ethylene, and TD represents a structural unit derived from tetracyclododecene.

[0063] (Measuring equipment) Bruker BioSpin AVANCE III 500 CryoProbe Prodigy nuclear magnetic resonance spectrometer

[0064] (Measurement conditions) Measurement nuclei: 13C (125 MHz), measurement mode: single pulse proton broadband decoupling, pulse width: 45° (5.00 μsec), number of points: 64k, measurement range: 250 ppm (-55 to 195 ppm), repetition time: 5.5 sec, number of accumulations: 512, measurement solvent: orthodichlorobenzene / benzene-d6 (4 / 1 v / v), sample concentration: ca. 60 mg / 0.6 mL, measurement temperature: 120 °C, window function: exponential (BF: 1.0 Hz), chemical shift reference: benzene-d6 (128.0 ppm).

[0065] [Glass transition temperature (Tg)] The copolymer is subjected to DSC measurement using a differential scanning calorimeter (X-DSC7000) manufactured by SII Co., Ltd., calibrated with an indium standard. The above measurement sample is weighed out so that it weighs about 10 mg on an aluminum DSC pan. A lid is crimped onto the pan to create a sealed atmosphere, and a sample pan is obtained. The sample pan is placed in the DSC cell, and an empty aluminum pan is placed as a reference. The DSC cell is heated from 30°C (room temperature) to 150°C at a rate of 10°C / min under a nitrogen atmosphere (first heating step).

[0066] Next, after holding at 150°C for 5 minutes, the temperature is decreased at 10°C / min to cool the DSC cell to -100°C (cooling-down process). After holding at -100°C for 5 minutes, the DSC cell is heated to 150°C at 10°C / min (second heating process). The glass transition temperature (Tg) was determined as the intersection of the straight line just before the first inclination of the enthalpy curve obtained in the second heating process toward the endothermic side and the straight line just after that.

[0067] [Intrinsic viscosity [η]] The intrinsic viscosity [η] of the copolymer was measured at 135°C using decalin as a solvent. Specifically, approximately 20 mg of copolymer powder, pellets, or copolymer chunks was dissolved in 15 ml of decalin, and the specific viscosity [η] was measured in an oil bath at 135°C. sp After diluting this decalin solution by adding 5 ml of decalin solvent, the specific viscosity η spThis dilution procedure was repeated two more times, and the η when the concentration (C) was extrapolated to 0 was measured. sp The value of / C was calculated as the intrinsic viscosity (see the formula below). [η]=lim(η sp / C) (C→0) The physical properties of the copolymer are shown in Tables 2 and 3.

[0068] [Table 2]

[0069] [Table 3]

[0070] Example 1 The copolymer (A-1) obtained in Polymerization Example 1 was used, and a kinematic viscosity at 100°C of 8.0 mm 2 The blending amounts were adjusted to give a lubricating oil composition of about 1 / s. The lubricating oil composition had the following formulation:

[0071] API Group (III) base oil ("Yubase-4", manufactured by SK Lubricants, kinematic viscosity at 100°C: 4.21 mm 2 / s, viscosity index: 123) Additives*: 8.64% by mass Pour point depressant: 0.3% by mass (Polymethacrylate "Product name Leblanc 165", manufactured by Toho Chemical Industry Co., Ltd.) Copolymer: as shown in Table 4. Total: 100.0 (mass%) Note (*) Additives = Conventional GF-5 engine oil additive package including calcium and sodium overbased detergents, nitrogen-containing dispersants, aminic and phenolic antioxidants, zinc dialkyldithiophosphates, friction modifiers, and antifoam agents. The physical properties of the obtained lubricating oil compositions were measured by the following methods.

[0072] [Kinematic viscosity] The kinematic viscosity at 100°C (kinematic viscosity @ 100°C) and the kinematic viscosity at 40°C (kinematic viscosity @ 40°C) of the lubricating oil compositions were measured in accordance with ASTM D446.

[0073] [Viscosity index (VI)] The viscosity index (VI) of the lubricating oil composition was calculated based on ASTM D2270 using the kinematic viscosity (KV) at 40°C and 100°C measured based on ASTM D445.

[0074] [Cold Cranking Simulator (CCS) viscosity@-35℃] CCS viscosity (-35°C) is measured according to ASTM D2602. CCS viscosity is used to evaluate the sliding properties (startability) of crankshafts at low temperatures. The smaller the value, the better the low-temperature viscosity (low-temperature properties) of the lubricating oil.

[0075] [Base oil solubility] 100 g of base oil and 1 g of copolymer were heated to 120°C with stirring to dissolve, and then allowed to stand for 3 hours to observe the appearance. ○: Dissolved (transparent). ×: Cloudy, gelling, precipitation. The measurement results are shown in Table 4.

[0076] Example 2 A lubricating oil composition was obtained in the same manner as in Example 1, except that the copolymer (A-1) used in Example 1 was replaced with the copolymer (A-2) obtained in Polymerization Example 2. The obtained lubricating oil composition was measured by the methods described above. The results are shown in Table 4.

[0077] Example 3 A lubricating oil composition was obtained in the same manner as in Example 1, except that the copolymer (A-1) used in Example 1 was replaced with the copolymer (A-3) obtained in Polymerization Example 3. The obtained lubricating oil composition was measured by the method described above. The results are shown in Table 4.

[0078] Comparative Example 1 A lubricating oil composition was obtained in the same manner as in Example 1, except that the copolymer (A-1) used in Example 1 was replaced with the copolymer (F-1) obtained in Polymerization Example 4. The obtained lubricating oil composition was measured by the methods described above. The results are shown in Table 4.

[0079] Comparative Example 2 A lubricating oil composition was obtained in the same manner as in Example 1, except that the copolymer (A-1) used in Example 1 was replaced with the copolymer (F-2) obtained in Polymerization Example 5. The obtained lubricating oil composition was measured by the methods described above. The results are shown in Table 4.

[0080] [Reference example 1] A lubricating oil composition was obtained in the same manner as in Example 1, except that the copolymer (A-1) used in Example 1 was replaced with the copolymer (R-1) obtained in Polymerization Example 6. The obtained lubricating oil composition was measured by the methods described above. The results are shown in Table 4.

[0081] [Table 4] [Industrial Applicability]

[0082] The ethylene-cyclic olefin copolymer of the present invention is a viscosity index improver for lubricating oils that has an excellent balance of viscosity characteristics at low temperatures and base oil solubility compared to conventional viscosity index improvers, and can be used as a lubricating oil additive that is suitable for fuel economy and long drain intervals.

Claims

1. A lubricating oil composition comprising a copolymer (A) and a base oil (B), wherein the copolymer (A) satisfies the following requirements (a-1) and (a-2), and the content ratio of the copolymer (A) to the base oil (B) is in the range of 0.1 to 50 parts by mass when the total of the copolymer (A) and the base oil (B) is 100 parts by mass. (a-1) A copolymer (A) is a copolymer of ethylene and a cyclic olefin, and contains 80 mol % or more and 95 mol % or less of structural units derived from ethylene based on all structural units. (a-2) The cyclic olefin is tetracyclododecene, hexacyclo[6.6.1.1 3,6 .1 10,13 .0 2,7 .0 9,14 ]-4-heptadecene, pentacyclo[6.6.1.1 3,6 .0 2,7 .0 9,14 ]-4-hexadecene, tricyclo[4.3.0.1 2,5 ]-3-decene, tricyclo[4.4.0.1 2,5 ]-3-undecene, pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]-4-pentadecene, pentacyclopentadecadiene, and pentacyclo[7.4.0.1 2,5 .1 9,12 .0 8,13 ]-3-pentadecene.

2. 2. The lubricating oil composition according to claim 1, wherein the cyclic olefin in said copolymer (A) is tetracyclododecene.

3. The lubricating oil composition according to claim 1 or 2, which satisfies the following requirements (1) to (3): (1) The copolymer (A) satisfies the following requirement (a-3) and also satisfies at least one of (a-4) and (a-5): (2) The base oil (B) satisfies the following requirement (b-1): (3) When the total of the copolymer (A) and the base oil (B) is 100 parts by mass, the amount of the copolymer (A) is in the range of 0.1 to 50 parts by mass. (a-3) The intrinsic viscosity [η] measured in decalin at 135°C is in the range of 0.01 to 5.0 dl / g. (a-4) No melting point (Tm) is detected in the range of 70 to 160°C by differential scanning calorimetry (DSC). (a-5) The glass transition temperature (Tg) is 70° C. or lower in differential scanning calorimetry (DSC). (b-1) 100 ° C. kinematic viscosity is 1 to 50 mm 2 / s range.

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