JP5756280B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition excellent in improving fluidity at low temperatures, which is obtained by adding a predetermined amount of a specific pour point depressant to a base oil having specific properties.

Lubricating oil is used in various temperature ranges. In particular, if the fluidity is low at low temperatures, the engine cannot be started, which can be extremely dangerous in extremely cold regions. For this reason, it is necessary to maintain the fluidity of engine oil even at the lowest possible temperature.
There are various indicators of fluidity of oil at low temperatures, one of which is the pour point. The pour point is a value defined by JIS K 2269, but simply speaking, it is the highest temperature at which the flow does not start for more than 5 seconds when the oil is tilted. The higher the pour point, the worse the fluidity at low temperatures.

As an index of low-temperature fluidity of lubricating oil, there is one specified by ASTM D 4684 (Standard Test Method for Determination of Yield Stress and Apparent Viscosity of Engine Oils at Low Temperature). This is evaluated based on the viscosity at a low temperature measured by an MRV viscometer (Mini Rotary Viscometer) and the presence or absence of yield stress (Yield Stress) generated at the start of the measurement. This method is employed in SAE J300, which is a standard for engine oil viscosity.
The fluidity of lubricating oil at low temperatures is greatly influenced by the structure and composition of the base oil used. Generally, when the amount of linear paraffin in the base oil increases, the pour point showing low temperature fluidity increases. This is because the linear paraffin contained in the base oil crystallizes in the oil, so that the fluidity is lowered and finally solidifies.

In order to improve this low temperature fluidity | liquidity, a pour point depressant is used normally (for example, refer nonpatent literature 1). Various compounds are used as pour point depressants. Among them, the polyacrylate pour point depressant tends to exhibit a high pour point depressing action as compared with other compounds. Therefore, in the field of automotive lubricants used in environments where the temperature changes greatly, such as engine oils and drive system oils (automatic transmission lubricants, manual transmission lubricants, etc.), polyacrylates are usually used. A pour point depressant is added to the lubricating oil.
This polyacrylate pour point depressant, when paraffin in the oil crystallizes, the side chain part of polyacrylate is taken into the crystal, the crystallization is inhibited, and the pour point is increased by not making the crystal huge It is said to suppress.
Therefore, there is a structural relationship between the pour point depressant and the base oil in which it is used, and a pour point depressant suitable for the base oil structure is required (for example, see Patent Documents 1 to 3).

JP 7-48421 A JP-A-8-53686 Japanese Patent Laid-Open No. 10-310758

Toshio Sakurai, “Petroleum Product Additives”, Koshobo, 1986, p. 352-369

As described above, the polyacrylate pour point depressant is compatible with the base oil used. Therefore, in order to find a pour point depressant that matches the base oil to be used, it is necessary to repeat trial and error, select the optimum one, and determine the optimum amount. Since this requires a lot of man-hours and time, development of a simple selection method is strongly desired.
In particular, among the base oils, API classification groups II to III, which have become mainstream in engine oils, can reduce the pour point relatively easily although they contain a large amount of paraffin. However, although base oils classified as Group I have been used for a long time, it is still difficult to improve this low temperature fluidity.

  The present invention has been made in view of such circumstances, and in particular, for the purpose of improving the low temperature fluidity of base oils classified as Group I among base oils, a specific polyacrylate pour point depressant is used. It aims at providing the used lubricating oil composition.

The present inventor has completed the present invention as a result of intensive studies to solve the above problems.
That is, according to the present invention, a base oil having a paraffin content of 90% by mass or less and a sulfur content of 0.03% by mass or more is added to acrylic monomers (A) 1 to 5 % by mass (B A polyacrylate pour point depressant obtained by copolymerizing a monomer mixture consisting of 50 to 60 % by mass, (C) 30 to 45 % by mass, and (D) 0 to 20 % by mass is based on the total amount of the composition. The present invention relates to a lubricating oil composition to which 02% by mass or more and 5% by mass or less are added.
(A) An acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 4 carbon atoms (B An acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 5 to 12 carbon atoms (C) An acrylic monomer having a structure represented by the general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 13 to 16 carbon atoms (D) An acrylic monomer having a structure represented by (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 17 or more carbon atoms.

  The present invention further comprises at least one additive selected from an antiwear agent, a metallic detergent, an ashless dispersant, an antioxidant, a corrosion inhibitor, an antifoaming agent, and a friction modifier. The above-mentioned lubricating oil composition.

According to the present invention, in the case of using a base oil having a specific molecular structure, the low temperature fluidity of which has not been easily reduced by the conventional technology, a specific polyacrylate pour point depressant is used to reduce the temperature. A lubricating oil composition having good fluidity can be obtained.
That is, by using the polyacrylate pour point depressant according to the present invention, the low-temperature fluidity can be improved even for base oils classified into Group I with low purity. Moreover, since it is a polyacrylate pour point depressant having a specific structure, not only the selection thereof is easy, but also the effect of reducing the development cost can be expected.

  Hereinafter, the present invention will be described in detail.

As the lubricating base oil in the lubricating oil composition of the present invention, at least a mineral base oil is used.
As the mineral base oil used in the present invention, specifically, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil, solvent removal, solvent purification , Hydrocracking, solvent dewaxing, hydrorefining and the like, and mineral oil base oil refined by combining one or more, preferably two or more. However, the purification process is various and is not limited to the above example.

  The paraffin (saturated hydrocarbon) content of the mineral base oil used in the present invention is required to be 90% by mass or less based on the total base oil used in the lubricating oil composition of the present invention, preferably 80%. It is at most 70% by mass, particularly preferably at most 70% by mass. On the other hand, when the paraffin content of the base oil is less than 50% by mass, the oxidation stability is inferior.

  Further, the aromatic content of the mineral oil base oil used in the present invention is not particularly limited, but is preferably 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 2.5% by mass. % Or more, particularly preferably 3% by mass or more, and most preferably 5% by mass or more. On the other hand, when the aromatic content of the base oil exceeds 50% by mass, the oxidation stability is inferior, so that it is preferably 50% by mass or less.

The paraffin content and aromatic content are% C _P and% C _A measured according to ASTM D3238 ring analysis method.

  The sulfur content in the mineral base oil must be 0.03% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and further preferably 0.3% by mass. % Or more, most preferably 0.5% by mass or more. On the other hand, since oxidation stability is inferior when the sulfur content exceeds 1.0% by mass, it is preferably 1.0% by mass or less.

The kinematic viscosity at 100 ° C. of the mineral oil base oil is not particularly limited, but is preferably 1 to 35 mm ² / s.

  In the lubricating oil composition of the present invention, the mineral oil base oil may be used alone, or may be used in combination with one or more of the mineral oil base oil and other base oils. it can. When used in combination with other base oils, the proportion of the mineral oil base oil in the mixed base oil is preferably 30% by mass or more, more preferably 50% by mass or more, and 70% by mass. % Or more is more preferable, and 100% by mass is most preferable.

Examples of other base oils that can be mixed into the mineral base oil include the following base oils (1) to (6) as raw materials, and this base oil and / or lubrication recovered from this raw oil The base oil obtained by refine | purifying an oil fraction by a conventionally well-known refinement | purification method and collect | recovering lubricating oil fractions can be mentioned.
(1) Distilled oil (WVGO) by distillation under reduced pressure of paraffin base crude oil and / or mixed base crude oil at atmospheric distillation residue
(2) Wax (such as slack wax) obtained by the lubricant dewaxing process and / or synthetic wax (Fischer-Tropsch wax, GTL wax, etc.) obtained by the gas-liquid (GTL) process, etc.
(3) One or two or more mixed oils selected from base oils (1) to (2) and / or mild hydrocracked oils of the mixed oils (4) Paraffin-based crude oil and / or mixed-base crude oil Degassed oil (DAO) of vacuum distillation residue oil of atmospheric distillation residue oil
(5) Hydrocracking mild hydrocracking oil (MHC) of base oil (4), solvent dewaxing or catalytic dewaxing of the product or lubricating oil fraction recovered from the product by distillation, etc. The hydrocracked mineral oil obtained by performing the dewaxing treatment or distillation after the dewaxing treatment (6) recovered from the base oil selected from the above base oils (1) to (5) or the base oil The obtained oil fraction is hydroisomerized, and the product or the oil fraction recovered from the product by distillation or the like is subjected to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or the dewaxing is performed. Hydroisomerized mineral oil obtained by distillation after treatment

Examples of other base oils that can be mixed with the mineral oil base oil include synthetic base oils.
Such synthetic oil base oils include poly α-olefins or their hydrides, isobutene oligomers or their hydrides, alkyl aromatics such as isoparaffin, alkylbenzene, alkylnaphthalene, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate). , Diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol esters (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.), etc. And ethers such as polyoxyalkylene glycol, dialkyldiphenyl ether, and polyphenyl ether. Among them, poly α-olefin is preferred. That's right. As the poly α-olefin, typically, an oligomer or co-oligomer (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and those. Of the hydrides. The kinematic viscosity at 100 ° C. of the synthetic oil base oil is preferably 1 to ²⁰ mm ² / s.

The polyacrylate pour point depressant according to the present invention is a copolymer obtained by copolymerizing a monomer mixture containing the following acrylic monomers (A) to (D) in a predetermined ratio.
(A): an acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 4 carbon atoms. B): an acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 5 to 12 carbon atoms (C ): An acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 13 to 16 carbon atoms (D) : Acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 17 or more carbon atoms.

The polyacrylate pour point depressant according to the present invention is obtained by copolymerizing a monomer mixture containing at least 50 % by mass of the monomer (B) . Hand, since the mixing amount of the monomers in the monomer mixture (B) is lowered solubility exceeds 60 wt%, the mixing amount of the monomer (B) is 6 0 wt% or less.
Moreover, it is preferable that the mixing amount of a monomer (B) is larger than the mixing amount of the monomer (C) mentioned later. Thereby, in combination with the base oil prescribed | regulated by this invention, higher pour point depressing performance is exhibited.

In the present invention, the mixing amount of the monomer (A) in the monomer mixture is 1 to 5% by mass.

In the present invention, the mixing amount of the monomer (C) in the monomer mixture is 45% by mass or less. On the other hand, it is the solubility of the surface or et 3 0 wt% or more.

In the present invention, the mixing amount of the monomer (D) in the monomer mixture is 0 to 20 % by mass.

  The method for producing the polyacrylate pour point depressant according to the present invention by copolymerizing a mixture of the monomers (A) to (D) is not particularly limited and can be produced by any method. Usually, it can be easily obtained by radical solution polymerization in the presence of a polymerization initiator.

  The solvent used in the copolymerization is not particularly limited, and a mineral base oil or a synthetic base oil that can be used for so-called lubricating oils can be suitably used.

  As a preferable example of the base oil (solvent base oil) used as a solvent, the following base oils (1) to (7) are used as raw materials, and this raw oil and / or a lubricating oil fraction recovered from this raw oil is used. The base oil obtained by refine | purifying a part by the conventionally well-known arbitrary refining methods, and collect | recovering lubricating oil fractions can be mentioned. Moreover, the following base oil (8) obtained by performing a predetermined | prescribed process about the base oil selected from (7) or the lubricating oil fraction collect | recovered from the said base oil is especially preferable.

(1) Distilled oil (WVGO) by distillation under reduced pressure of paraffin base crude oil and / or mixed base crude oil at atmospheric distillation residue
(2) Wax (such as slack wax) obtained by the lubricant dewaxing process and / or synthetic wax (Fischer-Tropsch wax, GTL wax, etc.) obtained by the gas-liquid (GTL) process, etc.
(3) One or two or more mixed oils selected from base oils (1) to (2) and / or mild hydrocracked oils of the mixed oils (4) selected from base oils (1) to (3) Two or more kinds of mixed oils (5) Paraffin-based crude oil and / or degassed oil (DAO) of vacuum-distilled residue oil of atmospheric distillation residue oil of mixed-base crude oil
(6) Mild hydrocracking treatment oil (MHC) of base oil (5)
(7) Hydrocracking two or more mixed oils selected from base oils (1) to (6), and solvent dewaxing of the product or lubricating oil fraction recovered from the product by distillation or the like Hydrocracked mineral oil obtained by performing dewaxing treatment such as catalytic dewaxing or distillation after the dewaxing treatment (8) Base oil selected from the above base oils (1) to (7) or the base Hydroisomerizing the lubricating oil fraction recovered from the oil, and performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the product or the lubricating oil fraction recovered from the product by distillation, or Hydroisomerized mineral oil obtained by distillation after the dewaxing treatment.

Synthetic oil base oils that can be used as solvent base oils include poly-α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkyl aromatics such as alkylbenzenes and alkylnaphthalenes, diesters (ditriols). Decyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc., polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexa) Esters such as noate and pentaerythritol pelargonate) and ethers such as polyoxyalkylene glycol, dialkyldiphenyl ether and polyphenyl ether. Among them, poly α- olefins are preferred. As the poly α-olefin, typically, an oligomer or co-oligomer (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) having 2 to 32 carbon atoms, preferably 6 to 16 carbon atoms, and those. Of the hydrides. The kinematic viscosity at 100 ° C. of the synthetic oil base oil is preferably 1 to ²⁰ mm ² / s.

  The type and concentration of the catalyst (initiator) used for the copolymerization vary depending on the molecular weight and molecular weight distribution of the target polyacrylate pour point depressant. When it is desired to obtain a polymer product, it is preferable to lower the reaction temperature (for example, about 70 ° C.) and reduce the amount of catalyst. However, the amount of the catalyst is preferably adjusted in consideration of the amount of oxygen remaining in the container, the amount of the polymerization inhibitor remaining in the monomer, and the like. On the other hand, when it is desired to obtain a low-molecular product, it is preferable to increase the reaction temperature (for example, 85 to 90 ° C.) and increase the catalyst. Examples of the catalyst include 1-dodecanethiol, 2,2′-azobis (2,4-dimethylvaleronitrile) (2,2′-Azobis (2,4-dimethylvaleronitrile)), 2-phenylpropane- 2-yl dithiobenzoate (2-phenylpropan-2-yl dithiobenzoate) etc. are mentioned.

The weight average molecular weight (Mw) of the polyacrylate pour point depressant according to the present invention is preferably 0.5 × 10 ⁴ or more, more preferably 1 × 10 ⁴ or more, and further preferably 2 × 10 ^4. As described above, it is particularly preferably 4 × 10 ⁴ or more. When Mw is less than 0.5 × 10 ⁴ , the effect as a pour point depressant is not recognized. On the other hand, Mw is preferably 50 × 10 ⁴ or less, more preferably 20 × 10 ⁴ or less, further preferably 15 × 10 ⁴ or less, and particularly preferably 10 × 10 ⁴ or less. When Mw exceeds 50 × 10 ⁴ , the viscosity increases, and conversely, the low temperature viscosity temperature characteristic may be deteriorated.

  Narrowing the molecular weight distribution is very advantageous from the viewpoint of improving the viscosity index and improving the shear stability. An example of the polymerization method for narrowing the molecular weight distribution is Living Radical Polymerization. Specific examples of such methods include Reversible Addition Fragmentation Chain Transfer Polymerization, Nitroxide-Mediated Polymerization, and Atom-Transfer Radial Polymerization.

  In the lubricating oil composition according to the present invention, the content of the polyacrylate pour point depressant must be 0.02% by mass or more based on the total weight of the lubricating oil composition, preferably 0. 0.1% by mass or more, more preferably 0.2% by mass or more, and most preferably 0.3% by mass or more. If the amount added is less than 0.02% by mass, sufficient effects cannot be exhibited. On the other hand, the upper limit is 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. If the amount added is more than 5% by mass, the viscosity is increased, which is not preferable.

  In addition to the polyacrylate pour point depressant according to the present invention, the lubricating oil composition of the present invention includes a viscosity index improver, an antiwear agent, a metallic detergent, an ashless dispersant, an antioxidant, a corrosion inhibitor, It is preferable to further contain at least one additive selected from a foam quencher and a friction modifier.

  As the viscosity index improver, specifically, a so-called non-dispersion type viscosity index improver such as a polymer or copolymer of one or more monomers selected from various methacrylic esters or a hydrogenated product thereof. Or a so-called dispersion-type viscosity index improver obtained by copolymerizing various methacrylic acid esters containing a nitrogen compound, and an ethylene-α-olefin copolymer (propylene, 1-butene, 1-pentene and the like are exemplified as the α-olefin) Non-dispersion type, or dispersion type obtained by copolymerization of a monomer containing a nitrogen compound or a hydride thereof, polyisobutylene or a hydrogenation product thereof, a hydride of a styrene-diene copolymer, styrene-maleic anhydride Examples include ester copolymers and polyalkylstyrene.

  The molecular weight of these viscosity index improvers needs to be selected in consideration of shear stability. Specifically, the number average molecular weight of the viscosity index improver is usually 5,000 to 1,000,000, preferably 10,000 to 900,000 in the case of dispersed and non-dispersed polymethacrylates, for example. In the case of polyisobutylene or a hydride thereof, usually 800 to 5,000, preferably 1,000 to 4,000, and in the case of an ethylene-α-olefin copolymer or a hydride thereof, usually 800 to 500. 3,000, preferably 3,000 to 200,000 are used.

Further, among these viscosity index improvers, when an ethylene-α-olefin copolymer or a hydride thereof is used, a lubricating oil composition particularly excellent in shear stability can be obtained. One or two or more compounds arbitrarily selected from the above viscosity index improvers can be contained.
The content when the viscosity index improver is contained is preferably 0.1 to 20% by mass based on the lubricating oil composition.

  As the antiwear agent (or extreme pressure agent), any antiwear agent or extreme pressure agent used for lubricating oil can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, zinc dialkyldithiophosphate (ZnDTP), phosphites, thiophosphites, dithiophosphites Acid esters, trithiophosphites, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamate, zinc dithio Carbamate, MoDTC, disulfides, polysulfides, sulfurized olefins, sulfurized fats and oils, and the like can be given. In these, addition of a sulfur type extreme pressure agent is preferable.

  Examples of the metal detergent include normal salts or basic salts such as alkali metal / alkaline earth metal sulfonate, alkali metal / alkaline earth metal phenate, and alkali metal / alkaline earth metal salicylate. Examples of the alkali metal include sodium and potassium, and examples of the alkaline earth metal include magnesium, calcium and barium. Magnesium or calcium is preferable, and calcium is more preferable.

  As the ashless dispersant, any ashless dispersant used in lubricating oils can be used. For example, a mono- or mono-chain having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule or Bisuccinimide, benzylamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or these And modified products of boron compounds, carboxylic acids, phosphoric acids, and the like. In use, one kind or two or more kinds arbitrarily selected from these can be blended.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants such as copper and molybdenum. Specifically, for example, as a phenol-based ashless antioxidant, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert- Butylphenol) and the like are amine-based ashless antioxidants such as phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, or imidazole compounds.

Examples of the defoaming agent include silicone oil having a kinematic viscosity at 25 ° C. of 1000 to 100,000 mm ² / s, fluorosilicone oil, alkenyl succinic acid derivative, ester of polyhydroxy aliphatic alcohol and long chain fatty acid, methyl salicy Rate and o-hydroxybenzyl alcohol.

  Friction modifiers include succinimide molybdenum complexes such as molybdenum dithiocarbamate and molybdenum dithiophosphate, organic molybdenum compounds such as amine salts of organic molybdic acid, and linear alkyl and metal having 8 to 30 carbon atoms as the basic structure. And having a polar group that can be adsorbed on the same molecule in the same molecule. Examples of polar groups include amines, polyamines, amides, urea compounds and alkenyls such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, aliphatic ethers, urea compounds, hydrazide compounds having these simultaneously in the molecule. Examples thereof include succinimide type, ester, alcohol and diol, or monoalkyl glycerol ester having ester and hydroxyl group at the same time. In addition, there are various types such as an alkylamine afucosyl alcohol having an amine and a hydroxyl group in the same molecule.

  When the lubricating oil composition of the present invention contains one or more of an antiwear agent, a metal detergent, an ashless dispersant, an antioxidant, a rust inhibitor and a friction modifier, each content is The amount is preferably 0.01 to 10% by mass based on the total weight of the lubricating oil composition. Further, the content when the lubricating oil composition of the present invention contains an antifoaming agent is preferably 0.0001 to 0.01% by mass.

  The lubricating oil composition of the present invention can further contain a rust inhibitor, a demulsifier, a metal deactivator, and the like in addition to the above components.

  Examples of the rust inhibitor include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.

  Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, or polyoxyethylene alkyl naphthyl ether.

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

  The contents of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

  Table 1 shows the properties of the base oils used in the examples and comparative examples. Base oil 1 and base oil 2 are base oils compatible with the base oil according to the present invention, and the other base oils (base oils 3 to 6) were used for reference.

Table 2 shows the composition of the pour point depressant used in Examples and Comparative Examples. PPD1 and PPD2 are compatible with the present invention, and other pour point depressants (PPD 3-6) were used for comparison. Incidentally, PPD of ^{R 1} described in Table 2 are all methyl groups.

(Examples 1-5, Comparative Examples 1-10)
Table 3 shows the results of preparing the lubricating oil compositions of the present invention (Examples 1 to 5) and comparative lubricating oil compositions (Comparative Examples 1 to 10) and measuring the MRV viscosity and the yield stress.
In Examples 1 to 5, as compared with Comparative Examples 1 to 10, not only the MRV viscosity is low at −30 ° C., but also no yield stress is observed.

(Reference Examples 1-8)
Table 4 shows the results obtained by preparing respective lubricating oil compositions for reference (Reference Examples 1 to 8) and measuring MRV viscosity and yield stress.
When a base oil that does not conform to the scope of the present invention, that is, a base oil that does not have the properties defined in the present invention (base oils 3 to 6) is used, the pour point depressant according to the present invention and other There is no difference in the performance of pour point depressants. That is, it turns out that the pour point depressant according to the present invention is an effective pour point depressant only in combination with the base oil defined in the present invention.

  According to the present invention, even base oils classified into Group I with low refining degree can be easily improved in low-temperature fluidity, which is extremely useful in the industry.

Claims (2)

In the base oil having a paraffin content of 90% by mass or less and a sulfur content of 0.03% by mass or more, acrylic monomers (A) 1 to 5 % by mass and (B) 50 to 60 % by mass shown below. , (C) 30 to 45 % by mass and (D) 0 to 20 % by mass of a polyacrylate pour point depressant obtained by copolymerizing 0.02% by mass or more and 5% by mass based on the total amount of the composition. % Lubricating oil composition.
(A) An acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 4 carbon atoms (B An acrylic monomer having a structure represented by the following general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 5 to 12 carbon atoms (C) An acrylic monomer having a structure represented by the general formula (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 13 to 16 carbon atoms (D) An acrylic monomer having a structure represented by (1), wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 17 or more carbon atoms.

  The anti-wear agent, the metal-based detergent, the ashless dispersant, the antioxidant, the corrosion inhibitor, the antifoaming agent, and the friction modifier, further comprising at least one additive. The lubricating oil composition described.