JP5525478B2 - Viscosity index improver and lubricating oil composition - Google Patents

Description

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

  For lubricating oils used in various temperature ranges, the polymer is dissolved in the base oil, and the increase in viscosity is suppressed by utilizing the low solubility of the polymer at low temperatures. Conversely, the polymer is dissolved at high temperatures. The device has been devised to improve the operating temperature range by suppressing the decrease in viscosity by utilizing the fact that the property is improved. This polymer is called a viscosity index improver (see, for example, Non-Patent Document 1).

  Various compounds are used as viscosity index improvers. Among them, the polyacrylate viscosity index improver tends to exhibit a higher viscosity index improving effect than other viscosity index improvers. 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 viscosity index improver is added to the lubricating oil (see, for example, Patent Documents 1 to 3).

  In the machine sliding portion to which the lubricating oil is supplied, since a shearing force is applied to the lubricating oil, a phenomenon occurs in which the polymer contained in the lubricating oil is broken and the molecular weight becomes relatively small. As a result, the initial viscosity cannot be maintained, resulting in poor control due to a decrease in hydraulic pressure, an increase in oil consumption, and the like, resulting in poor lubrication due to lack of oil.

  In order to prevent the occurrence of these phenomena, generally, measures are taken to reduce the molecular weight of the polymer and suppress the decrease in viscosity even when sheared as much as possible. However, this method not only increases the amount of polymer used and increases the economic burden, but also lowers the original purpose of suppressing the increase in viscosity at low temperatures and maintaining the viscosity at high temperatures.

  On the other hand, in the case of oil to which a polymer has been added, it is known that the effective viscosity decreases due to the polymer being oriented in the shear direction under conditions of a high shear rate. The degree of decrease in the effective viscosity increases as the polymer molecule increases. This phenomenon leads to a reduction in viscous resistance at high speeds, and hence a reduction in energy loss, that is, a fuel saving effect. For this reason, this phenomenon tends to be actively used in automotive lubricating oil.

JP 2010-053252 A Special table 2008-518052 gazette JP 2007-031666 A

"Petroleum product additive", supervised by Toshio Sakurai, pp. 342-359, Kobo Shobo (1986)

  As described above, since the polyacrylate viscosity index improver is a polymer, it is unavoidable that the polyacrylate viscosity index improver is sheared at the sliding portion to lower the molecular weight and the viscosity. In order to avoid such a phenomenon, a polymer having a relatively low molecular weight may be used in advance. However, this method is economically disadvantageous because it involves an increase in the amount of polymer added. Further, since the polymer has a low molecular weight, the fuel saving effect described above is also reduced.

  Here, the expression “shear stability” is used as an index representing the degree of decrease in molecular weight due to shearing. For example, “good shear stability” means that the molecular weight of the polymer does not decrease, and as a result, the viscosity is kept high. In general, the smaller the molecular weight of the polymer, the better the shear stability.

  In other words, if there is a polymer that has high shear stability while being a polymer, it can be said to be a preferred viscosity index improver. An example of such a viscosity index improver is a star polymer. This has a core part, the molecular chain extends radially from this part, and even if a part of the molecule is broken by shear, there is little effect on the structure of the whole molecule, so the decrease in the molecular weight of the polymer is small and good High shear stability is maintained. Further, as another polymer structure effective for improving shear stability, a three-dimensional structure in which a molecular chain is bonded to another molecular chain in the middle of the molecule can be considered.

  However, when the molecular structure of the polymer is three-dimensional as described above, the solubility of the polymer in the base oil becomes insufficient. For this reason, as a polyacrylate viscosity index improver having a three-dimensional structure, there is no actual development that can be put to practical use.

  The present invention has been made in view of such circumstances, and has an improved three-dimensional polyacrylate viscosity index that exhibits good shear stability and sufficient solubility in a lubricating base oil. It is an object of the present invention to provide a lubricating oil composition using an agent and the polyacrylate viscosity index improver.

Further, the present invention has a structure represented by the above general formula (1), and wherein R ¹ in the formula is a hydrogen atom or a methyl group, R ² is an alkyl group having 1 to 4 carbon atoms A first 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 20 or more carbon atoms. A monomer mixture comprising a monomer of 2 and a third monomer that is an acrylate monomer having two or more vinyl groups, the monomer mixture having the structure represented by the general formula (1), A monomer mixture in which the content ratio of the fourth monomer, wherein R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 6 to 15 carbon atoms, relative to the second monomer is 0 to 200% by weight , Polyacrylate viscosity index improver obtained by copolymerization To provide.

  The present invention also includes a lubricating base oil, the polyacrylate viscosity index improver of the present invention, an antiwear agent, a metallic detergent, an ashless dispersant, an antioxidant, a corrosion inhibitor, a defoamer, and Provided is a lubricating oil composition containing at least one additive selected from friction modifiers.

  As described above, according to the present invention, a polyacrylate viscosity index improver having a three-dimensional structure that exhibits good shear stability and sufficient solubility in a lubricating base oil, and the polyacrylate Lubricating oil compositions using viscosity index improvers are provided.

  That is, according to the polyacrylate viscosity index improver of the present invention, good shear stability can be obtained without lowering the molecular weight, and the shear stability and lubricating base oil that have been difficult to achieve in the past have been obtained. It is possible to achieve a high level of compatibility with the solubility of sucrose. Furthermore, the polyacrylate viscosity index improver of the present invention is economically advantageous because it can reduce the amount added to the lubricating oil as compared with other viscosity index improvers. A fuel-saving effect can be expected. Furthermore, because of sufficient durability, or by maintaining a three-dimensional structure even in an ultra-thin lubricating state, an oil film can be secured, and an effect of suppressing wear and fatigue life reduction can be expected.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

[First embodiment: polyacrylate viscosity index improver]
The polyacrylate viscosity index improver according to the first embodiment of the present invention includes the following monomers (A), (B) and (C):
(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 16 or more carbon atoms; And (C) a copolymer obtained by copolymerizing a monomer mixture containing an acrylate monomer having two or more vinyl groups. Such polyacrylate viscosity index improvers usually have a three-dimensional structure, and bind to other molecules at a plurality of positions in the molecule to form a giant polymer as a whole.

The monomer (A) may be a single monomer for each of R ¹ and R ^2, or may be a mixture of two or more monomers having different R ¹ and / or R ² . From the viewpoint of reactivity, R ¹ is preferably a hydrogen atom or a methyl group. From the viewpoint of viscosity index improvers, R ² is preferably an alkyl group having 1 to 4 carbon atoms.

Further, when R ² of the monomer (A) is an alkyl group having 3 or 4 carbon atoms, the alkyl group may be either a linear alkyl group or a branched alkyl group, but the polyacrylate viscosity index From the viewpoint of the viscosity index which is an intrinsic characteristic of the improver, it is preferable that R ² is linear.

From the viewpoint of the viscosity index of the resulting polyacrylate viscosity index improver, the amount of monomer (A) used is preferably as large as possible. On the other hand, as the amount of the monomer (A) used increases, the solubility of the resulting polyacrylate viscosity index improver in the lubricating base oil tends to decrease. It is desirable to consider these points. Further, the usable amount of the monomer (A) varies depending on the type of the lubricating base oil to which the polyacrylate viscosity index improver is added. For example, in the case of a naphthenic base oil or a base oil rich in aromatics, solubility tends to be ensured even if the amount of the monomer (A) used is increased.
Further, the solubility varies depending on the molecular weight of the polyacrylate viscosity index improver, the size of the carbon number of R ² of the monomer (A), and the like. As the molecular weight of the polyacrylate viscosity index improver is smaller and the carbon number of R ² is larger, the amount of the monomer (A) used can be increased.
For example, the lubricating base oil is a paraffin base oil, and the amount of the monomer (A) used is preferably 85% by weight or less from the viewpoint of solubility, based on the total weight of the monomer mixture. On the other hand, the lower limit of the amount of the monomer (A) used is preferably 10% by weight or more based on the total weight of the monomer mixture in order to ensure the viscosity index of the resulting polyacrylate viscosity index improver. However, the amount used varies depending on the structure. For example, when R ² of the monomer (A) is an alkyl group having 4 carbon atoms, the amount of the monomer (A) used is the total weight of the monomer mixture from the viewpoint of solubility. As a reference, it is preferably 85% by weight or less, more preferably 75% by weight or less. On the other hand, the lower limit of the amount of the monomer (A) used is preferably 30% by weight or more, more preferably, based on the total weight of the monomer mixture, in order to ensure the viscosity index of the polyacrylate viscosity index improver obtained. It is 40% by weight or more, more preferably 50% by weight or more.
Further, when the lubricating base oil is a paraffinic base oil and R ² of the monomer (A) is an alkyl group having 1 carbon atom (that is, a methyl group), the amount of the monomer (A) used is determined based on its solubility. From the viewpoint, it is preferably 70% by weight or less, more preferably 60% by weight or less, and still more preferably 50% by weight or less, based on the total weight of the monomer mixture. On the other hand, the lower limit of the amount of the monomer (A) used is preferably 10% by weight or more, more preferably 20% by weight or more, and further preferably 30% or more in order to ensure the viscosity index.
A preferable range of the amount of the monomer (A) used when the lubricating base oil is a paraffinic base oil and R ² of the monomer (A) is a C 2 or C 3 alkyl group is R of the monomer (A). ² is located in the middle between the amount of the intermediate when R ² is an alkyl group having 1 carbon atom when the monomer (a) is an alkyl group having 4 carbon atoms.

  The monomer (B) is an important element for imparting solubility to the lubricating base oil to the polyacrylate viscosity index improver according to this embodiment. Usually, the greater the amount of monomer (B) contained in the monomer mixture, the higher the solubility of the resulting polyacrylate viscosity index improver in lubricating oil. However, since a predetermined amount of the monomer (A) and the monomer (C) is used from the viewpoint of securing the viscosity index, the relative amount of the monomer (B) with respect to the monomers (A) and (C) is substantially It is a determinant of the solubility of the polyacrylate viscosity index improver in the lubricating base oil.

The monomer (B) may be a single monomer for each of R ¹ and R ^2, or may be a mixture of two or more monomers having different R ¹ and / or R ² . From the viewpoint of further increasing the solubility of the resulting polyacrylate viscosity index improver in the lubricating base oil, it is preferable to use two or more monomers having different R ¹ and / or R ² as the monomer (B). Further, R ² of the monomer (B) may be either a linear alkyl group or a branched alkyl group. From the viewpoint of the viscosity index, which is an inherent characteristic of the polyacrylate viscosity index improver, it is preferable that R ² is linear. On the other hand, from the viewpoint of fluidity at low temperatures, the R ² is preferably a branched alkyl group. From the viewpoint of reactivity, R ¹ is preferably a hydrogen atom or a methyl group. From the viewpoint of solubility, R ² preferably has 16 or more carbon atoms, more preferably 18 or more, and even more preferably 20 or more. In terms of reactivity, the carbon number of R ² is preferably 500 or less, and more preferably 300 or less.
In particular, as the R ² of the monomer (B), it is preferable to use a β-branched alcohol obtained by dimerizing a straight-chain alcohol having 8 to 18 carbon atoms by the Gerbe reaction, because both the effect of improving the viscosity index and the low temperature fluidity are highly compatible. .
A preferable range of the content of these monomers (B) is 5% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more, most preferably 30% by mass or more and 80% by mass or less, preferably 70% by mass. Hereinafter, it is more preferably 60% by mass or less, and most preferably 50% by mass or less.
Furthermore, when using beta branched alcohol, it is preferable to use other B component and / or D component together. A preferable range of the total of the monomer (B) and the monomer (D) other than the β-branched alcohol is 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and most preferably 40% by mass or more, 80% by mass. % Or less, preferably 70% by mass or less, more preferably 65% by mass or less.

  The monomer (C) contributes to increase the molecular weight and the shear stability of the resulting polyacrylate viscosity index improver. That is, under the same reaction conditions, the greater the amount of monomer (C) contained in the monomer mixture, the higher the molecular weight of the resulting polyacrylate viscosity index improver. Moreover, when the molecular weights of the polyacrylate viscosity index improvers obtained are similar, the greater the amount of monomer (C), the better the shear stability. However, on the other hand, since the solubility tends to decrease as the molecular weight increases, it is desirable to take this point into consideration when determining the amount of monomer (C) used. Specifically, the amount of the monomer (C) used is preferably 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 0.2% by weight or more, based on the total weight of the monomer mixture. Further, it is 5% by weight or less, more preferably 3.5% by weight or less, and further preferably 2.5% by weight or less. If it is less than this, there is no effect in three dimensions, and if it is too much, it will not dissolve.

  The monomer (C) is not particularly limited as long as it is an acrylate monomer having two or more vinyl groups. Examples of acrylate monomers having two vinyl groups include dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, tricyclodecane dimethanol diacrylate, neopentyl glycol diacrylate, bisphenol diacrylate, and tricyclodecane dimethanol. Examples include diacrylate. Examples of the acrylate monomer having three vinyl groups include pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxytriacrylate, glycerin propoxytriacrylate, and the like. Examples of the acrylate monomer having four or more vinyl groups include dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxytetraacrylate, and ditrimethylolpropane tetraacrylate.

  The polyacrylate viscosity index improver according to this embodiment may be obtained by copolymerizing a monomer mixture composed of the monomers (A), (B) and (C), or In addition to the monomers (A), (B) and (C), it may be obtained by copolymerizing a monomer mixture further containing other monomers.

As a preferable example of the monomer used in combination with the monomers (A), (B) and (C), the following monomer (D):
(D) 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 6 to 15 carbon atoms. Is mentioned.

Monomer (D) may be a single monomer for each of R ¹ and R ^2, or may be a mixture of two or more monomers having different R ¹ and / or R ² . From the viewpoint of further improving the solubility of the resulting polyacrylate viscosity index improver in the lubricating base oil, it is preferable to use two or more monomers having different R ¹ and / or R ² as the monomer (D). Further, R ² of the monomer (D) may be either a linear alkyl group or a branched alkyl group. From the viewpoint of fluidity at low temperatures, which is an inherent characteristic of the polyacrylate viscosity index improver, it is preferable that R ² is linear. From the viewpoint of reactivity, R ¹ is preferably a hydrogen atom or a methyl group. Further, from the viewpoint of improving the fluidity at low temperatures of the lubricating oil composition, the carbon number of R ² is more preferably 8 or more, and for the same reason, the carbon number of R ² is 14 or less. Is preferred.

If the number of carbon atoms in R ² of the monomer (B) is less than 20, it is preferable that the content ratio of the monomer (B) Monomer (D) for the 50 wt% or less. Further, it is preferably 30% by weight or less, and most preferably 15% by weight or less. When the content ratio of the monomer (D) with respect to the monomer (B) exceeds 50% by weight, the solubility of the polymethacrylate viscosity index improver obtained by copolymerization is lowered.
The monomer mixture preferably used when the number of carbon atoms of R ² of the monomer (B) is less than 20 is 10 to 50% by weight of the monomer (A) and 40% of the monomer (B) based on the total weight of the monomer mixture. A monomer mixture containing ˜90 wt%, monomer (C) 0.01 to 5 wt%, and monomer (D) 0 to 45 wt% can be mentioned.

Also, if the number of carbon atoms in ^{R 2} of the monomer (B) is 20 or more, and a content ratio of the monomer monomer to (B) (D) is 200 wt% or less. Further, it is preferably 150% or less, and most preferably 120% or less. When the amount of the monomer (D) used is too large, the solubility of the polymethacrylate of the present invention tends to decrease. On the other hand, the greater the amount of monomer (D), the better the fluidity of the resulting polyacrylate viscosity index improver at low temperatures. From this point, the one proportion of monomer (D) to monomer (B) is preferably 10% or more, more preferably 20% by weight or more, and more preferably 50% or more.
The monomer mixture that is preferably used when the carbon number of R ² of the monomer (B) is 20 or more is 10 to 50% by weight of the monomer (A) and 10% of the monomer (B) based on the total weight of the monomer mixture. Mention may be made of a monomer mixture containing -80% by weight, monomer (C) 0.01-5% by weight and monomer (D) 0-60% by weight.

［一般式（２）中、Ｒ^３は水素原子又はメチル基を示し、Ｒ^４は炭素数１〜１８のアルキレン基を示し、Ｅ^１は窒素原子を１〜２個、酸素原子を０〜２個含有するアミン残基又は複素環残基を示し、ａは０又は１を示す。］

［一般式（３）中、Ｒ^５は水素原子又はメチル基を示し、Ｅ^２は窒素原子を１〜２個、酸素原子を０〜２個含有するアミン残基又は複素環残基を示す。］ Further, the polyacrylate viscosity index improver according to this embodiment includes the following general formula (2) in addition to the monomers (A), (B) and (C) and the monomer (D) used as necessary. ) Represented by a monomer (hereinafter also referred to as “monomer (E)”) and a monomer represented by the following general formula (3) (hereinafter also referred to as “monomer (F)”). It may be obtained by copolymerizing a monomer mixture further containing a monomer having a basic nitrogen atom. When the monomer (E) and / or the monomer (F) is used, the dispersion performance of the lubricating oil composition with the resulting polyacrylate viscosity index improver is enhanced.

[In General Formula (2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an alkylene group having 1 to 18 carbon atoms, E ¹ represents ¹ to 2 nitrogen atoms, and 0 to 2 oxygen atoms. Each represents an amine residue or a heterocyclic residue, and a represents 0 or 1. ]

[In General Formula (3), R ⁵ represents a hydrogen atom or a methyl group, and E ² represents an amine residue or a heterocyclic residue containing 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms. ]

Specific examples of the group represented by E ¹ and E ² include a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, an anilino group, a toluidino group, a xylidino group, an acetylamino group, and a benzoylamino group. Morpholino group, pyrrolyl group, pyrrolino group, pyridyl group, methylpyridyl group, pyrrolidinyl group, piperidinyl group, quinonyl group, pyrrolidonyl group, pyrrolidono group, imidazolino group, pyrazino group and the like.

  As preferable examples of the monomer (E) and the monomer (F), specifically, dimethylaminomethyl methacrylate, diethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-methyl-5-vinylpyridine, morpholinomethyl methacrylate , Morpholinoethyl methacrylate, N-vinylpyrrolidone, and mixtures thereof.

  When using monomer (E) and / or monomer (F), monomers (E) and (F) with respect to the total molar amount M-1 of monomers (A), (B), (C) and (D) The total molar amount M-2 ratio (molar ratio) is preferably in the range of (M-1) / (M-2) = 99.5 / 0.5 to 80/20, 99/1 More preferably, it is in the range of ˜90 / 10, and further preferably in the range of 98/2 to 95/5.

  In addition, the polyacrylate viscosity index improver according to this embodiment is a monomer (A) for controlling the rigidity of the polymer for controlling the viscosity under high shear conditions and the solubility in the base oil. In addition to (C) and monomers (D) to (F) used as necessary, a monomer mixture further containing styrene may be copolymerized. The amount of styrene used in this case is preferably 20% by weight or less, more preferably 10% by weight or less, still more preferably 5% by weight or less, based on the total weight of the monomer mixture.

The manufacturing method of the polyacrylate viscosity index improver according to this embodiment is arbitrary. The type and concentration of the catalyst (initiator) vary depending on the target molecular weight and molecular weight distribution. For example, in the presence of benzoyl peroxide peroxide or an azo polymerization initiator such as 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile) Or monomers containing monomers (A) to (C) and monomers (D) to (F) and styrene used as necessary in the presence of a sulfur compound such as 1-dodecanethiol to control the molecular weight distribution It can be easily obtained by radical solution polymerization of the mixture.
Further, a redox initiator system using a combination of a peroxide initiator and an appropriate reducing agent can be used.
In addition to 1-dodecanethiol, sulfur compounds for controlling the molecular weight distribution, that is, chain transfer agents include thiophenol, 2-mercaptoethanol, carbon tetrachloride, carbon tetrabromide and the like. The preferred amount of chain transfer agent is 0.1 to 3% by weight, more preferably 0.2 to 2% by weight. By setting it in this range, the molecular weight distribution is narrowed and the shear stability is improved.

Since narrowing the molecular weight distribution is very advantageous from the viewpoint of improving the viscosity index and improving the shear stability, the polymerization method includes Living Radical Polymerization. Specific examples of such methods include Reversible Addition Fragmentation Chain Transfer Polymerization (RAFT method), Nitroxide-Mediated Polymerization (NMP method), and Atom-Transfer Random Polymerization (RP). These details are not described here because there are many books, but are outlined in Aldrich Material Matters Volume 5, Number 1-2010 mentioned above. Moreover, there is a special table 2008-518052 as an example of its use.
There are various specific examples of the catalyst, and they are not listed here because they are described in the cited documents, patents and the like. In the examples of the present invention, the RAFT method was used and 2-phenylpropan-2-yl dithiobenzoate was used as a catalyst, but the present invention is not limited thereto.

  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 preferred example of the base oil, the following base oils (1) to (7) are used as raw materials, and the raw oil and / or the lubricating oil fraction recovered from the raw oil is purified by a predetermined refining method. And a base oil obtained by recovering the lubricating oil fraction. 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) Two or more mixed oils selected from base oils (1) to (6).
The product or the lubricating 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 treatment is performed and then distilled. Hydrocracked mineral oil obtained by the above (8) Hydroisomerization of a base oil selected from the above base oils (1) to (7) or a lubricating oil fraction recovered from the base oil, and its product or its production Hydroisomerized mineral oil obtained by performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the lubricating oil fraction recovered from the product by distillation or the like, or by distilling after the dewaxing treatment.

Synthetic base oils include poly α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridec Decyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycol, dialkyl Examples thereof include diphenyl ether and polyphenyl ether, and among them, poly α-olefin is preferable. 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 base oil is preferably 1 to ²⁰ mm ² / s.

The capacity of the reaction vessel is preferably appropriately selected according to the molecular weight of the target polyacrylate viscosity index improver. For example, when the weight average molecular weight is 50,000 or less, the amount of the monomer used is 1.5 times or more, preferably 2 times or more, more preferably 3 times or more, and 7 times or less, preferably 6 times or less, More preferably, it is 5 times or less. When the target molecular weight exceeds 50,000, the amount of monomer used is 3 times or more, preferably 4 times or more, more preferably 5 times or more, and 10 times or less, preferably 8 times or less, more preferably 7 times. The following is preferable. This is because the amount of the solvent is adjusted so that the viscosity of the manufactured polymer becomes a viscosity that allows handling.
However, this is not the case when the amount of solvent is limited for molecular weight control.

  Moreover, the kind of stirring apparatus and stirring speed should just be a speed | rate in which a monomer mixture and a solvent are stirred vigorously and uniformly.

  The copolymerization reaction is preferably carried out in an inert gas atmosphere such as nitrogen, and it is preferable to completely replace the inside of the reaction vessel with nitrogen before starting the reaction.

  Further, in the copolymerization reaction, it is preferable to use a cooling device for allowing the monomer not to evaporate from the container but to reflux into the container.

  The method and rate of introduction of the monomer into the reaction vessel can be appropriately selected depending on the amount of monomer and the type of the desired polyacrylate viscosity index improver. For example, when the target polyacrylate viscosity index improver is a random copolymer, a completely mixed monomer may be introduced into the reaction vessel at a predetermined rate. On the other hand, when the target polyacrylate viscosity index improver is a block copolymer, one monomer is introduced into the reaction vessel at a time and sufficiently reacted to obtain a homopolymer, and then another monomer. Similarly, it is possible to react sequentially.

  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 viscosity index improver. 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.

  PSSI (Permanent Cystability Index: ASTM D 6022) is used as a specific numerical value of the shear stability described above. The PSSI of the polyacrylate viscosity index improver according to this embodiment is preferably 40 or less, more preferably 35 or less, still more preferably 30 or less, and particularly preferably 25 or less. The PSSI is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 2 or more, and particularly preferably 5 or more. When PSSI is less than 0.1, the effect of improving the viscosity index is small and the cost may increase. When PSSI exceeds 40, shear stability and storage stability may be deteriorated.

The weight average molecular weight and PSSI ratio of polyacrylate based viscosity index improver according to the present embodiment _(M W / PSSI) is preferably 1.0 × 10 ⁴ or more, preferably 1.5 × 10 ⁴ or more, more preferably 2.0 × 10 ⁴ or more, further preferably 2.5 × 10 ⁴ or more, and particularly preferably 3.0 × 10 ⁴ or more. If M _W / PSSI is below 1.0 × 10 ^4, there is a possibility that the viscosity-temperature characteristic is deteriorated i.e. deteriorates fuel efficiency.
In addition, the weight average molecular weight used here is two columns of Tosoh GMHHR-M (7.8 mm ID × 30 cm) in a 150-CALC / GPC apparatus manufactured by Waters, and the solvent is tetrahydrofuran, temperature. 23 ° C., flow rate of 1 mL / min, sample concentration of 1% by mass, sample injection amount of 75 μL, and weight average molecular weight in terms of polystyrene measured with a detector differential refractometer (RI).

The weight average molecular weight (M _W ) of the polyacrylate viscosity index improver according to the present embodiment is desirably selected as appropriate according to the type and application of the lubricating oil to be applied.
For example, if the power transmission device such as a transmission, is large shearing force, _{M W} is preferably 2,500 or more, more preferably 5,000 or more, more preferably 10,000 or more, particularly preferably 15 1,000 or more. Further, _MW is preferably 200,000 or less, more preferably 100,000 or less, further preferably 70,000 or less, and particularly preferably 50,000 or less.
Also, as in the engine oil, when the shear force is not so large, _{M W} is preferably 50,000 or more, more preferably 100,000 or more, more preferably 150,000 or more, particularly preferably 200,000 That's it. Further, _MW is preferably 1,000,000 or less, more preferably 800,000 or less, further preferably 600,000 or less, and particularly preferably 500,000 or less. When the weight average molecular weight is less than 2,500, the effect of the viscosity index improver may not be obtained. When the weight average molecular weight exceeds 1,000,000, shear stability and solubility in base oil , Storage stability may be deteriorated.

[Second Embodiment: Lubricating Oil Composition]
The lubricating oil composition according to the second embodiment of the present invention includes a lubricating base oil, the polyacrylate viscosity index improver according to the first embodiment, an antiwear agent, a metallic detergent, and an ashless dispersant. And at least one additive selected from an antioxidant, a corrosion inhibitor, a defoaming agent, and a friction modifier. In addition, the overlapping description about the polyacrylate viscosity index improver according to the first embodiment is omitted here.

As the lubricating base oil according to the present embodiment, a base oil selected from the base oils (1) to (7) described as the solvent of the first embodiment or a lubricating oil fraction recovered from the base oil is predetermined. The following base oil (8) obtained by performing the treatment is particularly preferred.
(8) Hydrocracking a base oil selected from the base oils (1) to (7) or a lubricating oil fraction recovered from the base oil, and recovering the product or the product by distillation or the like Hydrocracked mineral oil obtained by performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the lubricating oil fraction, or by distillation after the dewaxing treatment

  Moreover, when obtaining the lubricating base oil of (8) above, a solvent refining treatment and / or a hydrofinishing treatment step may be further provided as necessary at an advantageous step.

A synthetic base oil may be used as the lubricating base oil according to the present embodiment. Synthetic base oils include poly α-olefins or hydrides thereof, isobutene oligomers or hydrides thereof, isoparaffins, alkylbenzenes, alkylnaphthalenes, diesters (ditridecylglutarate) having a kinematic viscosity at 100 ° C of 1 to 20 mm ² / s. Rate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol esters (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, Pentaerythritol pelargonate), polyoxyalkylene glycols, dialkyldiphenyl ethers, polyphenyl ethers, etc., among which 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 viscosity index of the lubricating base oil according to the present embodiment is preferably 120 or more, more preferably 120 to 160. When the viscosity index is less than the lower limit, not only the viscosity-temperature characteristics, thermal / oxidative stability, and volatilization prevention properties deteriorate, but also the friction coefficient tends to increase, and the wear prevention properties tend to decrease. It is in. On the other hand, when the viscosity index exceeds the upper limit, the low-temperature viscosity characteristics tend to decrease.

  In addition, the viscosity index as used in the field of this invention means the viscosity index measured based on JISK2283-1993.

  In the lubricating oil composition according to the present embodiment, the lubricating base oil according to the present embodiment may be used alone, and the lubricating base oil according to the present embodiment may be one of other base oils or You may use together with 2 or more types. In addition, when using together the lubricating base oil which concerns on this embodiment, and another base oil, the ratio of the lubricating base oil which concerns on this embodiment in those mixed base oils is 30 weight% or more Is more preferable, 50% by weight or more is more preferable, and 70% by weight or more is further preferable.

  In the lubricating oil composition according to the present embodiment, the content of the polyacrylate viscosity index improver according to the first embodiment is preferably 0.01 to 20% by weight, based on the total weight of the lubricating oil composition, More preferably, it is 0.1 to 15 weight%, More preferably, it is 0.5 to 10 weight%.

  In addition to the polyacrylate viscosity index improver according to the first embodiment, the lubricating oil composition according to the present embodiment includes an antiwear agent, a metallic detergent, an ashless dispersant, an antioxidant, a corrosion inhibitor, a foam. It further contains at least one additive selected from a quencher and a friction modifier.

  As the antiwear agent (or extreme pressure agent), any antiwear agent / 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. Among these, addition of a sulfur-based extreme pressure agent is preferable, and sulfurized fats and oils are particularly 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 capable of adsorbing 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 according to this embodiment contains one or more of an antiwear agent, a metal-based detergent, an ashless dispersant, an antioxidant, a rust inhibitor, a defoamer, and a friction modifier, Each content is preferably 0.01 to 10% by weight based on the total weight of the lubricating oil composition. Moreover, when the lubricating oil composition which concerns on this embodiment contains an antifoamer, the content becomes like this. Preferably it is 0.0001 to 0.01 weight%.

  In addition to the above components, the additive composition according to this embodiment includes a viscosity index improver other than the polyacrylate viscosity index improver according to the first embodiment, a rust inhibitor, a demulsifier, and a metal inertness. An agent or the like can be further contained.

  The viscosity index improver other than the polyacrylate viscosity index improver according to the first embodiment is specifically a non-dispersed or dispersed ester group-containing viscosity index improver, such as a non-dispersed or dispersed poly (Meth) acrylate viscosity index improver, non-dispersed or dispersed olefin- (meth) acrylate copolymer viscosity index improver, styrene-maleic anhydride copolymer viscosity index improver, and mixtures thereof Among these, non-dispersed or dispersed poly (meth) acrylate viscosity index improvers are preferable. A non-dispersed or dispersed polymethacrylate viscosity index improver is particularly preferable. In addition, a non-dispersed or dispersed ethylene-α-olefin copolymer or a hydrogenated product thereof, polyisobutylene or a hydrogenated product thereof, a styrene-diene hydrogenated copolymer, a polyalkylstyrene, and the like can be given.

  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.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[ Reference Example 1: Synthesis of polyacrylate viscosity index improver-1]

Using a four-necked flask equipped with a stirrer, a nitrogen blowing tube, a cooling device, and a monomer introduction device, 40 parts by weight of methyl methacrylate, 60 parts by weight of stearyl methacrylate, and tri Random copolymerization of 0.5 parts by weight of trimethylolpropane methacrylate (Trimethylolpropane Trimethylacrylate) was performed to obtain a polyacrylate viscosity index improver-1.
As the solvent, 100 parts by weight of wax isomerized base oil (GT 70 Pale, kinematic viscosity at 100 ° C .: 2.7 mm ² / s, viscosity index: 125, pour point: −27.5 ° C.) was used. The catalyst was 1.5 parts by weight of 1-dodecanethiol at the start of the reaction and 2,2′-azobis (2,4-dimethylvaleronitrile) (2,2′-Azobis (2,4-dimethylvaleronitrile). ) Using 0.5 parts by weight, 0.3 hours by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) was added after 6 hours from the start of the reaction, and the reaction was further carried out for 3 hours. The reaction temperature was 85 ° C.
Further, the inside of the reaction vessel was completely replaced with nitrogen before starting the reaction, and 3 ml / min of nitrogen was blown in during the synthesis. Further, the inside of the reaction vessel was cooled by a cooling device so that the monomer did not evaporate from the vessel and refluxed in the reaction vessel.
The monomer introduction rate was set so that the total amount of monomers could enter the reaction vessel in 4 hours.
After completion of the reaction, the temperature of the container was raised to 130 ° C., and the pressure was reduced to about 3 mmHg to remove unreacted monomers.

[ Reference Examples 2 to 9, Examples 10 to 18, Comparative Examples 1 to 4: Synthesis of polyacrylate viscosity index improvers -2 to 22]
Polyacrylate viscosity index improvers-2 to 22 were synthesized in the same manner as in Reference Example 1 except that the reaction conditions shown in Tables 1 to 4 were changed. Details of the solvents, catalysts (initiators) and monomers shown in Tables 1 to 4 are as follows.
However, in Reference Example 2 and Example 18, when 2-phenylprop-2-yl dithiobenzoate was used as a catalyst, the monomer was basic alumina and the polymerization inhibitor was removed. Used. Further, in the reaction, the entire amount of the monomer in which the catalyst was dissolved was charged into the reaction vessel from the beginning.
<Solvent>
Solvent 1: Wax isomerized base oil (kinematic viscosity at 100 ° C. 2.7 mm ² / s, viscosity index: 125, pour point: −27.5 ° C.)
Solvent 2: hydrocracking base oil (kinematic viscosity at 100 ° C .: 4.3 mm ² / s, viscosity index 123, pour point—17.5 ° C., hydrocracking base oil)
<Catalyst (polymerization initiator)>
DM: 1-Dodecanethiol
CDTBA: 2-phenylpropan-2-yl dithiobenzoate (prepared according to the method described in 2-phenylpropan-2-yl dithiobenzoate, US Pat. No. 7,666,962)
ADVN: 2,2′-azobis (thymethylvaleronitrile) (2,2′-Azobis (2,4-dimethylvaleronitile))
AIBN: 2,2′-azobis (isobutyronitrile) (2,2′-Azobis (isobutyronitrile))
AMBN: 2,2′-azobis (methylbutyronitrile) (2,2′-Azobis (2-methylbutyronitrile))
<Monomer>
C1: Methyl methacrylate (Methyl Methacrylate)
C12: n-Dodecyl Methacrylate
C18: Stearyl Methacrylate
C12-C12: 1-dodecanol (1-Dodecanol) is subjected to a gel reaction to form an alcohol having 24 carbon atoms, and a residue obtained by removing a hydroxyl group from the alcohol as R ² in formula (1) C8-C18: n-Octyl alcohol and stearyl alcohol (Stearyl alcohol, 1-octadecanol) are subjected to a gel reaction to form an alcohol having 26 carbon atoms, and a residue obtained by removing the hydroxyl group from the alcohol is represented by R in formula (1). methacrylate was introduced as ² C18-C18: stearyl alcohol stearyl alcohol by Guerbet reaction and alcohols having 36 carbon atoms, methacrylate were introduced residue obtained by removing hydroxyl groups from the alcohol as ^{R 2} in the formula (1) TM MA: trimethylol propane trimethacrylate (Trimethylolpropane Trimethacrylate)
EGDMA: Ethylene glycol dimethacrylate (Ethylene Glycol Dimethacrylate)
BDDMA: 1,3-butanediol dimethacrylate (1,3-butanediol dimethacrylate)

Table 1 shows the number average molecular weight Mn, weight average molecular weight Mw and Mw / Mn of the polyacrylate viscosity index improvers-1 to 21 obtained in Reference Examples 1 to 9, Examples 10 to 18 and Comparative Examples 1 to 3. Show. In Comparative Example 4, the polyacrylate viscosity index improver itself was cloudy and the molecular weight was not measured.

[ Reference Examples 19 to 27 , Examples 28 to 36 : Preparation of lubricating oil compositions]
In Reference Examples 19 to 27 and Examples 28 to 36, the polyacrylate viscosity index improvers- 1 to 18 obtained in Reference Examples 1 to 9 and Examples 10 to 18, respectively, and the base oils and additives shown below. Were used to prepare lubricating oil compositions having the compositions shown in Tables 5-7.
<Lubricant base oil>
Base oil 3: hydrocracked base oil (kinematic viscosity at 100 ° C .: 4.1 mm ² / s, viscosity index: 120, pour point: −22.5 ° C.)
<Additives>
Additive PK: Lubricant additive package for automatic transmission, 12% by mass (antiwear agent: alkyl phosphite ester, lubricant composition standard phosphorus content 300 ppm, metallic detergent: calcium sulfonate (base number 300) , Lubricating oil composition standard calcium content 100 ppm, Ashless dispersant: Boronated succinimide, Lubricating oil composition standard 3% by mass, Non-boronated succinimide, Lubricating oil composition standard 2% by mass, Antioxidant: Alkyldiphenylamine, 0.5% by mass based on lubricating oil composition, corrosion inhibitor: thiadiazole, 150-200 ppm sulfur content based on lubricating oil composition, defoaming agent: silicone oil, 50 ppm based on lubricating oil composition, friction modifier: Alkyl succinimide, 2.5 mass% based on lubricating oil composition, others)

Tables 5 to 7 show the kinematic viscosity at 40 ° C. or 100 ° C. of the lubricating oil compositions of Reference Examples 19 to 27 and Examples 28 to 36 and the results of the shear stability test (JASO M 347, ultrasonic irradiation time 1 h). Show.

[Comparative Examples 5 to 8: Preparation of lubricating oil composition]
In Comparative Examples 5 to 8, the lubricating oils having the compositions shown in Table 8 using the polyacrylate viscosity index improvers -19 to 22 obtained in Comparative Examples 1 to 4 and the above base oils and additives, respectively. An attempt was made to prepare the composition. However, in Comparative Example 5, when the polyacrylate viscosity index improver-19 was dissolved in the base oil 3, turbidity occurred. Further, in Comparative Examples 6 to 8, the polyacrylate viscosity index improvers 20 to 22 could not be dissolved in the base oil 3.

Claims (2)

A first 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;
A second 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 20 or more carbon atoms;
A third monomer that is an acrylate monomer having two or more vinyl groups;
A monomer mixture having the 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 6 to 15 carbon atoms. A polyacrylate viscosity index improver obtained by copolymerizing a monomer mixture in which the content ratio of the fourth monomer is 0 to 200% by weight with respect to the second monomer.

Lubricating base oil,
A polyacrylate viscosity index improver according to claim 1 ;
At least one additive selected from an antiwear agent, a metallic detergent, an ashless dispersant, an antioxidant, a corrosion inhibitor, a defoamer and a friction modifier;
A lubricating oil composition containing