JP7291525B2 - Viscosity modifier for lubricating oil and lubricating oil composition - Google Patents

Description

The present invention relates to a lubricating oil viscosity modifier and a lubricating oil composition.

Petroleum products generally have so-called temperature dependence of viscosity, in which the viscosity changes greatly when the temperature changes. For example, lubricating oils used in automobiles preferably have low temperature dependence of viscosity (that is, have a high viscosity index). Therefore, in lubricating oils, certain polymers soluble in lubricating base oils are used as viscosity modifiers (also referred to as viscosity index improvers) for the purpose of reducing the temperature dependence of viscosity.

Ethylene/α-olefin copolymers are widely used as viscosity modifiers for lubricating oils, and various improvements have been made to further improve the performance balance of lubricating oils (see, for example, Patent Document 1).

2. Description of the Related Art In recent years, as demand for reducing the environmental load of automobiles has increased, there has been a strong demand for improving the fuel efficiency of automobiles. In particular, reduction of viscous resistance in a wide temperature range from low to high is mentioned as one of measures to save fuel consumption by using engine oil.

To reduce the viscous drag of engine oil, it is effective to lower the viscosity. Especially at low temperatures, it is effective in reducing both friction loss and agitation loss. On the other hand, at high temperatures, wear occurs in sliding parts, so simple reduction in viscosity must be avoided. Therefore, there is a demand for a lubricating oil viscosity modifier that has a high viscosity index and excellent thickening properties.

WO2006/101206

An object of the present invention is to provide a lubricating oil viscosity modifier having a high viscosity index and excellent thickening properties, and a lubricating oil composition containing the lubricating oil viscosity modifier.

In order to achieve a high viscosity index of the lubricating oil composition, the present inventors use a polymer having a structure in which the molecular chain expands at high temperatures (e.g. 100 ° C.) and shrinks at low temperatures (e.g. 40 ° C.). was considered desirable, and intensive studies were conducted in order to solve the above problems. As a result, the present inventors have found that the above problems can be solved by using a specific polymer having high crystallinity, which increases the cohesion of the polymer at low temperature due to crystallization, thereby completing the present invention. The present invention relates to, for example, the following [1] to [4].

[1] A lubricating oil viscosity modifier comprising an ethylene/α-olefin copolymer (X) having the following properties (x-1) to (x-4):
(x-1) the content of ethylene-derived structural units is in the range of 50 to 99 mol%;
(x-2) the α-olefin is an olefin having 3 to 20 carbon atoms;
(x-3) a melting point (Tm: °C) of 65°C to 80°C as measured by a differential scanning calorimeter;
(x-4) The intrinsic viscosity [η] measured in decalin at 135°C is 0.01 to 5.0 dl/g.

[2] The lubricating oil viscosity modifier according to item [1], which contains the ethylene/α-olefin copolymer (X) in an amount of 1 to 100% by mass.
[3] The viscosity modifier for lubricating oil according to item [1] or [2], wherein the α-olefin of the ethylene/α-olefin copolymer (X) is propylene.

[4] The ethylene/α-olefin copolymer containing the lubricating oil viscosity modifier according to any one of items [1] to [3] and a lubricating base oil (Y) A lubricating oil composition containing (X) in the range of 0.01 to 20% by mass.

According to the present invention, it is possible to provide a lubricating oil viscosity modifier having a high viscosity index and excellent thickening properties, and a lubricating oil composition containing the lubricating oil viscosity modifier.

The present invention will be described in detail below.
[Viscosity modifier for lubricating oil]
The lubricating oil viscosity modifier of the present invention is an ethylene/α-olefin copolymer (X) having the following properties (x-1) to (x-4) (hereinafter simply referred to as "copolymer (X)" Also called.) is characterized by including.
(x-1) The content of ethylene-derived structural units is in the range of 50 to 99 mol %.
(x-2) α-olefin is an olefin having 3 to 20 carbon atoms.
(x-3) The melting point (Tm:°C) measured by a differential scanning calorimeter is 65°C to 80°C.
(x-4) The intrinsic viscosity [η] measured in decalin at 135°C is 0.01 to 5.0 dl/g.

The copolymer (X) can be used alone or in combination of two or more. The content of the copolymer (X) in the lubricating oil viscosity modifier of the present invention is usually 1 to 100% by mass, preferably 10 to 100% by mass, more preferably 50 to 100% by mass.

The lubricating oil viscosity modifier of the present invention further contains at least one selected from lubricating base oil (Y) and additives described later, as long as the content of the copolymer (X) is within the above range. be able to.

<Ethylene/α-olefin copolymer (X)>
The copolymer (X) has the following properties (x-1) to (x-4).
(x-1) The content of structural units derived from ethylene (hereinafter also referred to as "ethylene content") is in the range of 50 to 99 mol%.

The ethylene content in the copolymer (X) is usually 50 to 99 mol%, preferably 60 to 98 mol, when the total amount of structural units derived from the monomers constituting the copolymer (X) is 100 mol%. %, more preferably 70 to 95 mol %, particularly preferably 80 to 90 mol %. By keeping the ethylene content within the above range, a lubricating oil composition having good viscosity-temperature characteristics can be obtained.

(x-2) α-olefin is an olefin having 3 to 20 carbon atoms.
Examples of the α-olefins having 3 to 20 carbon atoms include propylene, butene-1, pentene-1, hexene-1, 4-methyl-pentene-1, heptene-1, octene-1, decene-1, and undecene. -1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, eicosene-1, etc., having 3 to 20 carbon atoms, preferably carbon atoms 3 to 12 α-olefins are included. Also, the α-olefin may be linear or branched. Among the α-olefins, propylene, butene-1, octene-1, and 4-methyl-pentene-1 are preferable in terms of imparting good low-temperature viscosity properties, shear stability, and heat resistance to the lubricating oil composition. , and propylene are particularly preferred. The copolymer (X) may contain one or more α-olefin-derived structural units.

The copolymer (X) may contain constitutional units derived from monomers other than ethylene and α-olefin within a range that does not impair the effects of the present invention. Other monomers include, for example, cyclic olefins, aromatic vinyl compounds, conjugated dienes, non-conjugated polyenes, functional vinyl compounds, hydroxyl group-containing olefins, and halogenated olefins. Cyclic olefins, aromatic vinyl compounds, conjugated dienes, non-conjugated polyenes, functional vinyl compounds, hydroxyl group-containing olefins and halogenated olefins include, for example, paragraphs [0035] to [0041] of JP-A-2013-169685. compound.

(x-3) The melting point (Tm:°C) measured by a differential scanning calorimeter (DSC) is 65°C to 80°C.
The melting point (Tm) of the copolymer (X) is 65 to 80°C, preferably 66 to 78°C. By setting the melting point of the copolymer (X) within the above range, it is possible to obtain a lubricating oil viscosity modifier having a high viscosity index and excellent thickening properties.

(x-4) The intrinsic viscosity [η] measured in decalin at 135°C is 0.01 to 5.0 dl/g.
The intrinsic viscosity [η] of the copolymer (X) is usually 0.01 to 5.0 dl/g, preferably 0.05 to 4.0 dl/g, more preferably 0.1 to 3.5 dl. /g, more preferably 0.3 to 3.0 dl/g, particularly preferably 0.5 to 2.5 dl/g. When the intrinsic viscosity [η] is within the above range, it is possible to obtain a lubricating oil composition having an excellent balance between shear stability and low-temperature properties.
Details of the measurement conditions for the physical properties described above are described in Examples.

<Method for producing copolymer (X)>
The copolymer (X) includes, for example, a compound containing a transition metal such as vanadium, zirconium, titanium, and hafnium, and at least one selected from organoaluminum compounds, organoaluminumoxy compounds, and ionized ionic compounds. It can be produced by copolymerizing at least ethylene and an α-olefin having 3 to 20 carbon atoms using a catalyst. The olefin polymerization catalyst used at this time includes, for example, the catalyst described in International Publication No. 00/34420.

[Lubricating oil composition]
The lubricating oil composition of the present invention contains the lubricating oil viscosity modifier of the present invention and a lubricating base oil (Y).

The content of the copolymer (X) in the lubricating oil composition of the present invention is generally 0.01 to 20% by mass, preferably 0.05 to 10% by mass, more preferably 0.05% to 10% by mass, based on the total amount of the composition. It is 1 to 5% by mass. In the present invention, the effect of adjusting the viscosity of the composition due to the copolymer (X) is high, and a sufficient effect can be obtained by using only a small amount of the copolymer (X), which is therefore preferable from the viewpoint of cost.

<Lubricating base oil (Y)>
As the lubricating base oil (Y) (hereinafter also referred to as "base oil (Y)") contained in the lubricating oil composition of the present invention, those usually used as lubricating base oils can be used without limitation. , mineral oil and synthetic oil. As the base oil (Y), a blend of mineral oil and synthetic oil may be used.

The kinematic viscosity of base oil (Y) at 100° C. is usually 1 to 50 mm ² /s, preferably 1.5 to 40 mm ² /s, more preferably 2 to 30 mm ² /s.
Mineral oil is generally used through a refining process such as dewaxing, and there are several grades depending on the method of refining, and this grade is defined by the API (American Petroleum Institute) classification. Mineral oils with a wax content of 0.5 to 10% by weight are generally used. For example, a highly refined oil having a low pour point, a high viscosity index, and a composition mainly composed of isoparaffins produced by a hydrocracking refining method can be used. Mineral oils with kinematic viscosities at 40° C. of 5 to 200 mm ² /s are commonly used.

Synthetic oils include, for example, poly-α-olefins; diesters such as polyol esters, dioctyl phthalate and dioctyl sebacate; and polyalkylene glycols.

Table 1 shows the properties of the lubricating base oils classified into each group.

The poly-α-olefin in Table 1 is a hydrocarbon polymer obtained by polymerizing at least an α-olefin having 10 or more carbon atoms as a raw material monomer, and includes, for example, polydecene obtained by polymerizing decene-1. .

As the base oil (Y), 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 mineral oils belonging to group (II) or group (III), those having a kinematic viscosity at 100° C. of 1 to 50 mm ² /s are preferred.

One or two or more base oils (Y) can be used.
The content of the base oil (Y) in the lubricating oil composition of the present invention is usually 50% by mass or more, preferably 70% by mass or more, particularly preferably 80% by mass or more, relative to the total amount of the composition. The upper limit of the content of (Y) is determined by the amounts of copolymer (X) and additives.

<Other components (additives)>
The lubricating oil composition of the present invention may, if necessary, contain components (additives) other than the viscosity modifier for lubricating oil and the base oil (Y) of the present invention described above. Other ingredients include, for example, other viscosity modifiers, pour point depressants, detergents and dispersants, antiwear agents, defoamers, antioxidants, friction modifiers, color stabilizers, rust inhibitors, corrosion inhibitors and Metal deactivators are included.

Other viscosity modifiers include, for example, polyisobutenes, polymethacrylates, diene polymers, polyalkylstyrenes, esterified styrene-maleic anhydride copolymers, alkenylarene conjugated diene copolymers. and polymers such as polyolefins, hydrogenated SBR (styrene-butadiene rubber), and SEBS (styrene-ethylene-butylene-styrene block copolymer). Multifunctional viscosity modifiers that also have dispersant and/or antioxidant properties are known and may optionally be used.

Pour point depressants include, for example, alkylated naphthalenes, (co)polymers of alkyl (meth)acrylates, copolymers of alkyl fumarate and vinyl acetate, α-olefin polymers, and α-olefins and styrene. A copolymer is mentioned. (Co)polymers of alkyl (meth)acrylates are particularly preferred.

Detergents and dispersants include, for example, sulfonates such as calcium sulfonate and magnesium sulfonate; finates; salicylates; succinimide; and benzylamine. The amount of a typical detergent-dispersant in a lubricating oil composition is not particularly limited as long as the effect of the present invention is exhibited, but is usually 1 to 10% by mass, preferably 1.5 to 9.0% by mass, more preferably is 2.0 to 8.0% by mass. It should be noted that all such amounts are based on oil-free conditions in the detergent-dispersant (ie, no diluent oil conventionally supplied to them).

Antiwear agents include metal thiophosphates, phosphate esters and their salts, phosphorus-containing carboxylic acids, esters, ethers, amides; and phosphorus-containing antiwear agents such as phosphites/ Examples include extreme pressure agents. Often the antiwear agent is a zinc dialkyldithiophosphate (ZDP). A typical ZDP may contain 11 wt% P (calculated on an oil-free basis), and a suitable amount may include 0.09-0.82 wt%. Phosphorus-free antiwear agents include borate esters (including borate epoxides), dithiocarbamate compounds, molybdenum-containing compounds, and sulfurized olefins. Also, the phosphorus-containing antiwear agent is not particularly limited as long as the effect of the present invention is exhibited, but is usually 0.01 to 0.2% by mass, preferably 0.015 to 0.15% by mass, more preferably 0.01% to 0.15% by mass. It may be present in an amount to provide 02 to 0.1 wt%, more preferably 0.025 to 0.08 wt% phosphorous.

Antifoaming agents include, for example, silicone antifoaming agents such as dimethylsiloxane and silica gel dispersion; alcohol and ester antifoaming agents.
Antioxidants include, for example, phenol antioxidants such as 2,6-di-t-butyl-4-methylphenol; and amine antioxidants such as dioctyldiphenylamine. Typical amounts of antioxidants will of course depend on the particular antioxidant and its individual effectiveness, but an exemplary total amount is 0.01 to 5% by weight, preferably 0.15%. It can be up to 4.5% by weight, more preferably 0.2-4% by weight. Additionally, one or more antioxidants may be present, and certain combinations of these may be synergistic to their combined overall effect.

Rust inhibitors include, for example, carboxylic acids, carboxylates, esters, and phosphoric acids. Examples of corrosion inhibitors include benzotriazole, thiadiazole, and imidazole compounds.

When the lubricating oil composition of the present invention contains additives, the content ratio is not particularly limited, but the total content ratio of the additives is , usually more than 0% by mass, preferably 1% by mass or more, more preferably 3% by mass or more; usually 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less.

<Method for producing lubricating oil composition>
The lubricating oil composition of the present invention can be prepared by a conventionally known method, for example, by mixing the copolymer (X), optionally the base oil (Y) and additives. Copolymer (X) may optionally be supplied as a concentrate in base oil (Y) for ease of handling.

<Application>
The lubricating oil composition of the present invention includes, for example, engine oils for automobiles, lubricating oils for heavy-duty diesel engines, lubricating oils for marine diesel engines, lubricating oils for two-stroke engines, automatic transmissions and manual transmissions. It can be used to lubricate any of a variety of known mechanical devices such as machine lubricants, gear lubricants and greases.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.
[Physical properties of copolymer]
Various physical properties of the copolymers used in Examples and Comparative Examples were measured as follows.

<Ethylene content (C2 content)>
The content ratio (mol %) of the ethylene-derived structural unit in the ethylene/α-olefin copolymer was determined by analysis of ¹ H-NMR spectrum.

(measuring device)
JEOL ECX400P type nuclear magnetic resonance apparatus (measurement conditions)
Measurement nucleus: ¹ H (400 MHz), measurement mode: single pulse, pulse width: 45° (5.25 μs), number of points: 32 k, measurement range: 20 ppm (-4 to 16 ppm), repetition time: 7.0 seconds , accumulation number: 64 times, measurement solvent: ortho-dichlorobenzene-d ₄ , sample concentration: ca. 20 mg/0.6 mL, measurement temperature: 120° C., window function: exponential (BF: 0.12 Hz), chemical shift standard: ortho-dichlorobenzene (7.1 ppm).

<Melting point (Tm)>
The melting point (Tm) of the ethylene/α-olefin copolymer was measured as follows using a differential scanning calorimeter "X-DSC7000" manufactured by SII, calibrated with an indium standard.

About 10 mg of a measurement sample (ethylene/α-olefin copolymer) was weighed onto an aluminum DSC pan. A sample pan was obtained by crimping a lid onto the pan to create a closed atmosphere. A sample pan was placed in the DSC cell and an empty aluminum pan was placed as a reference. The temperature of the DSC cell was raised from 30° C. (room temperature) to 200° C. at a rate of 10° C./min in a nitrogen atmosphere (first temperature raising process). After holding the temperature at 200° C. for 5 minutes, the temperature was lowered at 10° C./min to cool the DSC cell to −40° C. (temperature lowering process). After holding at -40°C for 5 minutes, the temperature of the DSC cell was raised to 200°C at a rate of 10°C/min (second temperature raising process).

The melting peak top temperature of the enthalpy curve obtained in the second heating process was defined as the melting point (Tm). When two or more melting peaks were present, the maximum peak temperature was defined as Tm. The fact that no melting point is observed means that the material is amorphous, and is indicated as "None".

<Intrinsic viscosity [η] (dl/g)>
The intrinsic viscosity [η] of the copolymer was measured at 135°C using decalin solvent. Specifically, about 20 mg of copolymer powder, pellets or resin mass was dissolved in 15 ml of decalin, and the specific viscosity ηsp was measured in an oil bath at 135°C. 5 ml of the decalin solvent was added to the decalin solution to dilute it, and then the specific viscosity ηsp was measured in the same manner. This dilution operation was repeated twice, and the value of ηsp/C when the concentration (C) was extrapolated to 0 was determined as the intrinsic viscosity (see the following formula).
[η]=lim(ηsp/C) (C→0)

[Physical properties of lubricating oil composition]
Various physical properties of the lubricating oil compositions obtained in Examples and Comparative Examples were measured as follows.

<Kinematic viscosity (KV)>
The kinematic viscosities (KV) of the lubricating oil compositions at 40°C and 100°C were measured according to ASTM D445, and these results were used to calculate the viscosity index (VI) according to ASTM D2270.

[Polymerization example of ethylene/α-olefin]
Polymerization examples of ethylene/α-olefin copolymers are described below. In some cases, multiple polymerizations are performed to ensure the amount required for analysis and lubricating oil modifier evaluation.

A compound (1) represented by the following formula used as a catalyst was synthesized by a known method.

<Polymerization Example 1>
After introducing 500 ml of xylene into a glass reactor having an internal volume of 1.0 L which was sufficiently purged with nitrogen, the temperature was raised to 90° C., and while stirring the inside of the polymerization reactor at 600 rpm, ethylene and propylene were added at 99 liters/hour and 99 liters/hour, respectively. Feed continuously at 36.0 l/hr to saturate the liquid and gas phases. Subsequently, while ethylene and propylene were continuously supplied, 6.0 mL (6.0 mmol) of a toluene solution (1.0 mol/L) of triisobutylaluminum (also referred to as iBu ₃ Al) was added, and the compound (1) was added to toluene. 3.0 mL (0.030 mmol) of the solution (0.010 mol/L), and then a toluene solution (0.030 mmol) of triphenylcarbenium tetrakis(pentafluorophenyl)borate (Ph ₃ CB(C ₆ F ₅ ) ₄ ). 010 mol/L) was added, and polymerization was carried out at 90° C. for 40 minutes under normal pressure. Polymerization was terminated by adding a small amount of isobutanol. The obtained polymerization reaction solution was washed with dilute hydrochloric acid, and the organic layer obtained by liquid separation was put into a large amount of methanol to precipitate an ethylene/propylene copolymer. The ethylene/propylene copolymer obtained by filtration was dried under reduced pressure at 130° C. for 10 hours. Table 2 shows the analysis results of the ethylene/propylene copolymer.

<Polymerization Examples 2 to 11>
Polymerization Example 1 was repeated except that the polymerization conditions were changed as shown in Table 2.

[Examples and Comparative Examples]
A lubricating oil composition was prepared using the ethylene/α-olefin copolymer obtained in the above polymerization example as a viscosity modifier for a lubricating oil. The amount of the ethylene/α-olefin copolymer added was adjusted so that the kinematic viscosity at 100° C. of the lubricating oil composition was about 8.0 mm ² /s.

The formulation composition is as follows.
API group (III) base oil (“Yubase-4”, manufactured by SK Lubricants, kinematic viscosity at 100° C.: 4.21 mm ² /s, viscosity index: 123)
Additive ^* : 8.64% by mass
Pour point depressant: 0.3% by mass
(Polymethacrylate “Leblanc 165”, manufactured by Toho Chemical Industry Co., Ltd.)
Ethylene/α-olefin copolymer: Total 100.0 (mass%) as shown in Table 3
Note (*) Additives = Ca and Na overbased detergents, N-containing dispersants, aminic and phenolic antioxidants, zinc dialkyldithiophosphates, friction modifiers, and defoamers. Conventional engine oil additive package for GF-5 containing.

Table 3 shows the evaluation results.

As shown in Table 3, when the examples and the comparative examples are compared, the examples have a low 40° C. kinematic viscosity and a high viscosity index.

Claims (4)

A lubricating oil viscosity modifier comprising an ethylene/α-olefin copolymer (X) having the following properties (x-1) to (x-4):
(x-1) the content of ethylene-derived structural units is in the range of 80 to 99 mol%;
(x-2) the α-olefin is an olefin having 3 to 20 carbon atoms;
(x-3) a melting point (Tm: °C) of 66 °C to 80°C as measured by a differential scanning calorimeter;
(x-4) The intrinsic viscosity [η] measured in decalin at 135°C is 0.01 to 5.0 dl/g. 2. The lubricating oil viscosity modifier according to claim 1, wherein the ethylene/α-olefin copolymer (X) is contained in an amount of 1 to 100% by mass. 3. The lubricating oil viscosity modifier according to claim 1, wherein the α-olefin of the ethylene/α-olefin copolymer (X) is propylene. It contains the lubricating oil viscosity modifier according to any one of claims 1 to 3 and a lubricating base oil (Y), and the ethylene/α-olefin copolymer (X) is 0.00. A lubricating oil composition characterized by containing in the range of 01 to 20% by mass.