JP2019157047A - Method for producing (meth) acrylate polymer and viscosity index improver - Google Patents

Abstract

To provide a method for producing a polymer that can improve polymerizability when polymerizing a monomer component containing a (meth) acrylate monomer having an aliphatic hydrocarbon group including a large number of carbon atoms.SOLUTION: A method for producing a (meth) acrylate polymer includes the step of polymerizing a monomer component containing a (meth) acrylate monomer (a) having an aliphatic hydrocarbon group including 6 or more carbon atoms, in the presence of metalalkoxide.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a (meth) acrylate polymer, and more particularly to a (meth) acrylate polymer useful as a viscosity index improver and a method for producing a lubricating oil composition containing the polymer.

  In recent years, lubricating oils for internal combustion engines have been strongly required to improve fuel saving characteristics, and one means is to reduce friction loss by reducing the viscosity of the lubricating oil. However, simply reducing the viscosity causes problems such as liquid leakage and seizure, so it is effective to use a lubricating oil additive that has a viscosity index improving effect that keeps the viscosity at low temperature while keeping the viscosity at high temperature low, Such lubricating oil additives are known as viscosity index improvers.

  As the viscosity index improver, those containing a polymer are known, and among them, the viscosity index improver composed of an alkyl (meth) acrylate polymer is said to exhibit a high viscosity index improving effect. On the other hand, since the viscosity index improver made of an alkyl (meth) acrylate polymer has poor shear stability, there has been a problem that fuel-saving properties are deteriorated (long life property is poor) during long-term use. In view of this, a method using a polymer using a macromonomer as a monomer component has been proposed as a means for achieving both a viscosity index improvement effect and shear stability. Patent Documents 1 and 2 disclose that a (meth) acrylate having a long-chain aliphatic hydrocarbon group in the structure is used as such a macromonomer.

JP2013-133460A Special table 2012-520358 gazette

  A monomer having an aliphatic hydrocarbon group usually has a tendency that the higher the carbon number, the lower the polymerizability and the lower the polymerization rate. As a result, the composition of the resulting polymer tends to deviate from the composition of the monomer component used for the polymerization, making it difficult to impart the desired properties to the polymer. The decrease in the polymerization rate also causes an increase in the amount of unreacted monomer remaining in the produced polymer. However, since such a monomer having an aliphatic hydrocarbon group having a large number of carbon atoms has a high boiling point and is difficult to separate from the polymer, in order to reduce the amount of unreacted monomer, It is desired to increase the polymerizability during the reaction.

  The present invention has been made in view of the above circumstances, and its purpose is to polymerize a monomer component containing a (meth) acrylate monomer having an aliphatic hydrocarbon group having a large number of carbon atoms. An object of the present invention is to provide a method for producing a polymer capable of increasing the viscosity.

The present invention includes the following inventions.
[1] It comprises a step of polymerizing a monomer component containing a (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms in the presence of a metal alkoxide ( A method for producing a (meth) acrylate polymer.
[2] The (meth) acrylate polymer according to [1], wherein the monomer component further includes a (meth) acrylate monomer (b) having an aliphatic hydrocarbon group having 1 to 5 carbon atoms. Production method.
[3] The method for producing a (meth) acrylate polymer according to [1] or [2], wherein the aliphatic hydrocarbon group of the monomer (a) has 12 or more carbon atoms.
[4] The monomer (a) according to any one of [1] to [3], wherein at least a (meth) acrylate monomer (a1) having an aliphatic hydrocarbon group having 50 or more carbon atoms is used. A method for producing a (meth) acrylate polymer.
[5] As the metal alkoxide, use is made of at least one transition metal alkoxide selected from Group 4 elements, Group 5 elements, Group 12 elements, Group 14 elements and Group 15 elements [1] to [4] ] The manufacturing method of the (meth) acrylate type polymer in any one of.
[6] The method for producing a (meth) acrylate polymer according to any one of [1] to [5], wherein the monomer component is polymerized in a solvent containing a high boiling point solvent having a boiling point of 200 ° C. or higher.
[7] A method for producing a viscosity index improver, wherein a viscosity index improver is obtained by the production method of any one of [1] to [6].
[8] A step of obtaining a (meth) acrylate polymer by the production method according to any one of [1] to [6], and a lubricating oil composition is obtained by blending the (meth) acrylate polymer with a lubricating oil. A process for producing a lubricating oil composition comprising the steps of:
[9] A viscosity index improver containing a (meth) acrylate polymer having a unit derived from a (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms, wherein the viscosity The content of the monomer (a) in the index improver is X, and the content of the unit derived from the monomer (a) contained in the (meth) acrylate polymer in the viscosity index improver is Y. In this case, the viscosity index improver is characterized in that X / (X + Y) is 0.18 or less.
[10] A lubricating oil composition comprising the viscosity index improver according to [9] and a lubricating oil.

  According to the production method of the present invention, when the monomer component containing the (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms is polymerized, the polymerizability is increased and the efficiency is increased. In particular, the polymerization reaction can be advanced. The (meth) acrylate polymer thus obtained can be suitably applied to lubricating oil additives such as viscosity index improvers.

  The present invention relates to a method for producing a (meth) acrylate polymer, and in particular, a method for efficiently polymerizing a monomer component containing a (meth) acrylate monomer having a long-chain aliphatic hydrocarbon group. It is about. The production method of the present invention can be suitably applied to the production of oil-soluble (meth) acrylate polymers such as lubricating oil additives.

  The method for producing a (meth) acrylate polymer of the present invention includes a step of polymerizing a monomer component containing a (meth) acrylate monomer (a) in the presence of a metal alkoxide, and a polymerization reaction. The (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms is essentially used as the monomer component to be provided for. When the (meth) acrylate monomer (a) having such an aliphatic hydrocarbon group is polymerized, usually, as the carbon number of the aliphatic hydrocarbon group increases, the polymerizability tends to decrease. Therefore, the polymerization rate in the polymerization reaction is lowered, the time required for the polymerization reaction is increased, and the production efficiency of the polymer is lowered. In the production method of the present invention, a metal alkoxide is allowed to coexist in the polymerization reaction in order to suppress such a decrease in polymerizability. Thereby, even if a monomer component contains the (meth) acrylate monomer which has an aliphatic hydrocarbon group with many carbon atoms, a polymerization reaction can be advanced efficiently.

As the monomer (a), (meth) acrylate having an aliphatic hydrocarbon group having 6 or more carbon atoms is used. The (meth) acrylate used as the monomer (a) is represented by the following formula (1), in which R ¹ represents a hydrogen atom or a methyl group, and R ² is a fatty acid having 6 or more carbon atoms. Represents a group having an aromatic hydrocarbon group.

  The aliphatic hydrocarbon group possessed by the (meth) acrylate monomer (a) may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Saturated aliphatic hydrocarbon group is preferable from the viewpoint of suppressing the increase in viscosity. The aliphatic hydrocarbon group of the (meth) acrylate monomer (a) may be linear, branched or cyclic, but is preferably linear or branched.

The aliphatic hydrocarbon group of the (meth) acrylate monomer (a) may be directly bonded to the ester bond (—CO—O—) of the formula (1) or indirectly bonded. There may be. In the latter case, the aliphatic hydrocarbon group includes a urethane bond (—NH—CO—O—), a urea bond (—NH—CO—NH—), an ester bond (—CO—O—), an amide bond (—NH The ester bond of the formula (1) via a linking group containing at least one selected from —CO—), a sulfonate bond (—SO ₂ —O—), and a sulfonamide bond (—SO ₂ —NH—) It is preferable that it is couple | bonded with. In addition, the direction of each bond of a urea bond, an ester bond, an amide bond, a sulfonic acid ester bond, or a sulfonamide bond is not particularly limited. Taking a urethane bond as an example, the nitrogen atom of the urethane bond may be located on the ester bond side of the formula (1), and the oxygen atom may be located on the ester bond side of the formula (1). In addition to these bonds, the linking group may include, for example, an alkylene group having 1 to 4 carbon atoms.

  From the viewpoint of further exerting the effect of improving the polymerizability due to the metal alkoxide that is present during the polymerization reaction, it is preferable that the aliphatic hydrocarbon group of the monomer (a) has more than 6 carbon atoms. For example, the number of carbon atoms of the aliphatic hydrocarbon group of the monomer (a) is preferably 8 or more, more preferably 10 or more, and still more preferably 12 or more. The upper limit of the carbon number of the aliphatic hydrocarbon group of the monomer (a) is not particularly limited, but is preferably 3500 or less, more preferably 1500 or less, from the viewpoint of securing the polymerizability of the monomer (a) to some extent. 700 or less is more preferable.

  Monomer (a) may use only 1 type and may use 2 or more types together. What is necessary is just to set the usage-amount of a monomer (a) suitably according to the physical property which the (meth) acrylate type polymer obtained by a polymerization reaction desires. For example, as described later, when the (meth) acrylate polymer is applied to the viscosity index improver, the amount of the monomer (a) used is 100 parts by mass in total of all monomer components. 10 parts by mass or more is preferable, 15 parts by mass or more is more preferable, 20 parts by mass or more is more preferable, 70 parts by mass or less is preferable, 60 parts by mass or less is more preferable, 50 parts by mass or less is further preferable, 45 parts by mass The following are even more preferred: Thereby, it becomes easy to obtain a viscosity index improver excellent in shear stability and solubility in lubricating base oil. In the present specification, the lubricating base oil may be simply referred to as “base oil”.

  In the polymerization step, the monomer component containing the (meth) acrylate monomer (a) described above is polymerized in the presence of a metal alkoxide. Thereby, the polymerizability of the monomer component containing the (meth) acrylate monomer (a) is increased, the polymerization rate can be increased, and the reaction rate of the polymerization reaction can be increased. As a result, the yield of the (meth) acrylate polymer can be increased, the time required for the polymerization reaction can be shortened, and the production efficiency of the (meth) acrylate polymer can be increased. Although the mechanism by which the metal alkoxide increases the polymerizability of the monomer component containing the (meth) acrylate monomer (a) is unclear, metal alkoxide has been used as a catalyst for the polymerization reaction of (meth) acrylate so far. It is not known to act, and the polymerizability of the (meth) acrylate monomer (a) may be increased by an action other than the catalyst, for example, a metal alkoxide acts on an inhibitor of the polymerization reaction. There is also sex.

  The metal alkoxide is not particularly limited as long as it is a compound in which an alkoxy group is bonded to a metal element. It is sufficient that at least one alkoxy group is bonded to the metal element of the metal alkoxide, and a group other than the alkoxy group (for example, alkyl group, aryl group, aralkyl group, acyloxy group, acylate group, aryloxy group, etc.) is bonded. You may do it. Note that it is preferable that two or more alkoxy groups are bonded to the metal element of the metal alkoxide. In this case, the plurality of alkoxy groups bonded to the metal element may be the same as or different from each other.

  The alkyl group of the alkoxy group bonded to the metal element is preferably linear or branched. Moreover, 1-10 are preferable and, as for the carbon number, 1-8 are more preferable.

  The metal element of the metal alkoxide is not particularly limited as long as it can increase the polymerizability of the monomer component containing the (meth) acrylate monomer (a). It is preferably a transition metal element selected from the group elements, group 12 elements, group 14 elements and group 15 elements. That is, as the metal alkoxide, it is preferable to use at least one transition metal alkoxide selected from Group 4 elements, Group 5 elements, Group 12 elements, Group 14 elements and Group 15 elements. Examples of Group 4 transition metal elements include titanium, zirconium, hafnium, and the like. Examples of Group 5 transition metal elements include vanadium, niobium, and tantalum. Examples of Group 12 transition metal elements include zinc, cadmium, mercury, and the like. Examples of the Group 13 metal element include gallium, indium, and thallium. Examples of the Group 14 metal element include germanium, tin, lead, and the like. Examples of Group 15 metal elements include antimony and bismuth. Among these, as the metal alkoxide, it is preferable to use an alkoxide of at least one metal element selected from titanium, zirconium, zinc, tin, and bismuth.

  Specific examples of the metal alkoxide include, for example, tetraisopropoxy titanium, tetra n-butoxy titanium, tetra tert-butoxy titanium, tetraoctyl titanate, titanium diisopropoxy bisethyl acetoacetate, tri n-butoxy titanium monostearate. , Di n-butoxy titanium distearate, tetra n-butoxy zirconium, tetra tert-butoxy zirconium, bis tert-butoxy zinc, tetra n-butoxy tin, tetra tert-butoxy tin, tri-n-butoxy bismuth, pentaethoxy tantalum, pentaethoxy Niobium, tetra tert-butoxy hafnium, tetraethoxy germanium and the like can be mentioned.

  The amount of metal alkoxide used is, for example, preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, with respect to 100 parts by mass of the monomer component, from the viewpoint of reliably exhibiting the effect of improving the polymerizability. 0.01 parts by weight or more is more preferable. On the other hand, even if the amount of metal alkoxide used is too large, further significant improvement in polymerizability cannot be expected. Therefore, the amount of metal alkoxide used is preferably 3 parts by mass or less with respect to 100 parts by mass of the monomer component. 1 part by mass or less is more preferable, and 0.5 part by mass or less is more preferable.

  The metal alkoxide may be supplied to the polymerization reaction system (reactor) together with the monomer component during the polymerization reaction, or may be supplied to the polymerization reaction system in the middle of the polymerization reaction of the monomer component. Alternatively, a metal alkoxide may be present in the polymerization reaction system in advance, and then the monomer component may be supplied to carry out the polymerization reaction. For example, the metal alkoxide is charged in the step before the polymerization step and an arbitrary operation is performed, and then the polymerization step can be performed.

  In the polymerization step, the monomer (a) has, for example, a (meth) acrylate monomer having an aliphatic hydrocarbon group having 50 or more carbon atoms so that the effect of improving the polymerizability by the metal alkoxide can be achieved. It is preferable to use the body (a1). When the monomer component containing such a (meth) acrylate monomer (a1) having a long-chain aliphatic hydrocarbon group is polymerized, the metal alkoxide is usually reduced in the polymerization reaction when the polymerization property is lowered. By coexisting, the effect of improving the polymerizability becomes noticeable.

  When the (meth) acrylate polymer obtained by the production method of the present invention is applied to a viscosity index improver, a (meth) acrylate monomer (a1) having an aliphatic hydrocarbon group having 50 or more carbon atoms is simply used. By using it as a monomer component, the viscosity index improving effect of the viscosity index improver can be enhanced. Moreover, it becomes easy to increase the shear stability of the polymer while increasing the weight average molecular weight of the (meth) acrylate polymer. From such a viewpoint, the number of carbon atoms of the aliphatic hydrocarbon group of the monomer (a1) is more preferably 70 or more, further preferably 100 or more, and even more preferably 150 or more. On the other hand, the upper limit of the carbon number of the aliphatic hydrocarbon group of the monomer (a1) is not particularly limited, but is preferably 3500 or less, more preferably 1500 or less, and even more preferably 700 or less.

  It is convenient to use a so-called macromonomer as the monomer (a1). Therefore, from the viewpoint of ease of production of the monomer (a1) as a macromonomer, the aliphatic hydrocarbon group of the monomer (a1) includes a repeating structure derived from a hydrocarbon monomer or a hydride thereof. Is preferred. Examples of the hydrocarbon monomer include ethylene, propylene, 1-butene, isobutene, 1-tetradecene, 1-octadecene and other monoolefins; 1,3-butadiene, 2-methyl-1,3-butadiene, 1, Examples include alkadienes such as 3-pentadiene, 1,4-pentadiene, 1,5-hexadiene, and 2,5-dimethyl-1,5-hexadiene (also called diisobutene). In the case where the hydrocarbon monomer is an alkadiene, the repeating structure derived from the alkadiene may contain an unsaturated bond. In this case, the unsaturated bond may be hydrogenated (hydrogenated). . These monoolefins and alkadienes preferably have 2 or more carbon atoms, more preferably 3 or more, more preferably 20 or less, still more preferably 10 or less, and still more preferably 6 or less.

  The aliphatic hydrocarbon group of the monomer (a1) is preferably linear or branched, and is branched from the viewpoint of inhibiting crystallization of the (meth) acrylate polymer at low temperature and preventing thickening. It is more preferable that In this case, the aliphatic hydrocarbon group preferably includes a branched alkylene group as a repeating unit, and preferably includes both a branched alkylene group and a linear alkylene group as a repeating unit. Examples of the branched alkylene group include 1,2-propylene group, 1,2-butylene group, 1,3-butylene group, 2,3-butylene group, 1,2-hexylene group and the like. Examples of the linear alkylene group include ethylene, 1,3-propylene group, 1,4-butylene group, 1,5-pentylene group, 1,6-hexylene group and the like. Further, the aliphatic hydrocarbon group of the monomer (a1) preferably does not contain an unsaturated bond, and therefore is particularly preferably an aliphatic saturated hydrocarbon group.

  In the monomer (a1), from the viewpoint of ease of production of the monomer (a1), the aliphatic hydrocarbon group is bonded to the ester bond of the above formula (1) via the linking group described above. It is preferable. As such a monomer (a1), a (meth) acrylate macromonomer represented by the following formula (2) is preferably shown.

In the above formula (2), R ³ represents a hydrogen atom or a methyl group, R ⁴ represents an aliphatic hydrocarbon group having 50 or more carbon atoms, X represents a urethane bond, a urea bond, an ester bond, an amide bond, a sulfonic acid Represents a linking group containing an ester bond or a sulfonamide bond. For the details of the aliphatic hydrocarbon group of R ⁴ and the linking group of X, the above description is referred to. The linking group X is more preferably one containing a urethane bond, a urea bond or an amide bond from the viewpoint of ease of production of the (meth) acrylate macromonomer.

  The number average molecular weight of the aliphatic hydrocarbon group of the monomer (a1) is preferably 750 or more, more preferably 1000 or more, and further preferably 1500 or more, from the viewpoints of base oil solubility, viscosity index, and shear stability. 2000 or more is still more preferable, 50000 or less is preferable, 20000 or less is more preferable, and 10,000 or less is more preferable.

  As the monomer (a1), only one type may be used, or two or more types may be used in combination. What is necessary is just to set the usage-amount of a monomer (a1) suitably according to the physical property which the (meth) acrylate type polymer obtained by a polymerization reaction desires. When the (meth) acrylate polymer is applied to the viscosity index improver, the amount of the monomer (a1) used is preferably 6 parts by mass or more with respect to a total of 100 parts by mass of all monomer components. 7 parts by mass or more is more preferable, 8 parts by mass or more is further preferable, 25 parts by mass or less is preferable, 20 parts by mass or less is more preferable, 18 parts by mass or less is further preferable, and 16 parts by mass or less is even more preferable. Thereby, it becomes easy to increase the effect of improving the viscosity index of the (meth) acrylate polymer (viscosity index improver) or to increase the shear stability.

  As the monomer (a), (meth) acrylate having an aliphatic hydrocarbon group having a smaller number of carbon atoms than that of the monomer (a1) can also be used. For example, as the monomer (a), a (meth) acrylate monomer (a2) having an aliphatic hydrocarbon group having 6 to 49 carbon atoms can be used. When the (meth) acrylate polymer is applied to a viscosity index improver, the solubility of the viscosity index improver in the base oil can be increased by using the monomer (a2). The number of carbon atoms of the aliphatic hydrocarbon group of the monomer (a2) is preferably 8 or more, more preferably 10 or more, further preferably 12 or more, more preferably 40 or less, more preferably 35 or less, and further preferably 30 or less. preferable.

As the monomer (a2), it is convenient to use C _6-49 alkyl (meth) acrylate. Such an alkyl (meth) acrylate can be easily obtained by an ester reaction of (meth) acrylic acid with an alcohol having 6 to 49 carbon atoms. In addition, _C6-49 alkyl (meth) acrylate is alkyl (meth) acrylate, Comprising: The carbon number of the said alkyl group means 6-49. Examples of the alkyl group having 6 to 49 carbon atoms include hexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, Linear or branched alkyl groups such as icosyl group, tetracosyl group, 2-decyltetradecyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group, dicyclopentanyl group, adamantyl And cyclic alkyl groups such as groups. Among these, a linear or branched alkyl group is preferable, and a linear alkyl group is more preferable.

  As the monomer (a2), only one type may be used, or two or more types may be used in combination. When applying the (meth) acrylate polymer to the viscosity index improver, it is preferable to use the monomer (a1) and the monomer (a2) in combination as the monomer component. As usage-amount of the monomer (a2) in this case, 5 mass parts or more are preferable with respect to a total of 100 mass parts of all monomer components, for example, 8 mass parts or more are more preferable, 12 mass parts or more are preferable. Furthermore, 50 mass parts or less are preferable, 40 mass parts or less are more preferable, and 35 mass parts or less are more preferable. Thereby, when applied to a viscosity index improver, it becomes easy to improve the base oil solubility of the (meth) acrylate polymer, and it becomes easy to ensure the fluidity of the base oil solution of the (meth) acrylate polymer. .

  In the polymerization step, a (meth) acrylate monomer (b) having an aliphatic hydrocarbon group having 1 to 5 carbon atoms is used as a monomer component in addition to the monomer (a) described above. It is also preferable. Thereby, the polymerizability of the monomer (a) is enhanced, and the heat resistance of the resulting (meth) acrylate polymer is easily enhanced. When the (meth) acrylate polymer is applied to the viscosity index improver, it is easy to increase the viscosity index.

As the monomer (b), it is convenient to use C _1-5 alkyl (meth) acrylate. Such an alkyl (meth) acrylate can be easily obtained by an ester reaction of (meth) acrylic acid and an alcohol having 1 to 5 carbon atoms. The alkyl group having 1 to 5 carbon atoms is linear or branched such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, and isopentyl group. A chain alkyl group is exemplified. Among these, a linear alkyl group is preferable. As C _1-5 alkyl (meth) acrylate, it is preferable to use at least C _2-5 alkyl (meth) acrylate, and methyl (meth) acrylate may be used in combination therewith.

  Monomer (b) may use only 1 type and may use 2 or more types together. What is necessary is just to set the usage-amount of a monomer (b) suitably according to the desired physical property of the (meth) acrylate type polymer obtained by a polymerization reaction. In addition, when applying a (meth) acrylate type polymer to a viscosity index improver, it is preferable to use the monomer (b) in addition to the monomer (a). In this case, the monomer (b) Is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, still more preferably 45 parts by mass or more, and even more preferably 50 parts by mass or more with respect to 100 parts by mass in total of all monomer components. Moreover, 75 mass parts or less are preferable, 72 mass parts or less are more preferable, 70 mass parts or less are more preferable, 68 mass parts or less are still more preferable.

  In the polymerization step, a maleimide monomer (c) may be used as a monomer component. When applying a (meth) acrylate polymer to a viscosity index improver, by using a maleimide monomer as a monomer component, a succinimide ring structure is introduced into the main chain of the polymer, thereby causing a viscosity index. While ensuring the solubility of the improver in the base oil, shear stability and heat resistance can be improved. Furthermore, when added to lubricating oil, effects such as improvement in clean dispersibility of sludge and the like and suppression of wear on the metal surface are expected.

As the maleimide monomer (c), those represented by the following formula (3) are preferably used. In formula (3), R ⁵ and R ⁶ each independently represent a hydrogen atom or an alkyl group, and R ⁷ represents a hydrogen atom or an organic group having 1 to 40 carbon atoms.

The alkyl group of R ⁵ and R ⁶ in Formula (3) preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 to 3 carbon atoms. R ⁵ and R ⁶ are more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom or a methyl group.

Examples of the organic group represented by R ^{7 in} the formula (3) include an alkyl group, an aryl group, an aralkyl group, a group in which a part of —CH ₂ — contained in the alkyl group is replaced by —O—, and the like. A substituent such as a hydroxyl group, a halogen group, a nitro group, an alkyl group (in the case of an aryl group or an aralkyl group), an alkoxy group, or a carboxy group may be bonded to the group. The organic group of R ⁷ preferably has 1 to 24 carbon atoms, more preferably 1 to 18 carbon atoms, and still more preferably 1 to 12 carbon atoms, from the viewpoint of increasing the solubility of the (meth) acrylate polymer in the base oil.

Examples of the alkyl group for R ⁷ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-pentyl group, isopentyl group, n-hexyl group, and isohexyl group. Linear or branched alkyl groups such as xyl group, n-heptyl group, isoheptyl group, n-octyl group, 2-ethylhexyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclononyl group, Examples thereof include cyclic alkyl groups such as a cyclodecyl group, a dicyclopentanyl group, and an adamantyl group. Examples of the aryl group for R ⁷ include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. Examples of the aralkyl group for R ⁷ include a benzyl group and a naphthylmethyl group. Examples of the group in which a part of —CH ₂ — contained in the alkyl group of R ⁷ is replaced by —O— include polyoxyalkylene groups such as a polyoxyethylene group and a polyoxypropylene group.

  Specific examples of the maleimide monomer (c) include, for example, maleimide, N-methylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, Nt-butylmaleimide, N-cyclohexylmaleimide, N-octylmaleimide, N-2-ethylhexylmaleimide, N-decylmaleimide, N-laurylmaleimide, N-tetradecylmaleimide, N-stearylmaleimide, N-2-decyltetradecylmaleimide, N-phenylmaleimide, N-benzyl Maleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide, N-naphthylmaleimide, N-hydroxylethylmaleimide, N-hydroxylphenylmaleimide, N-methoxyphenylmaleimide, N-carboxypheny Maleimide, N- nitro-phenyl maleimide, N- tribromophenyl maleimide and the like. Among these, from the viewpoint of availability and base oil solubility, as the maleimide monomer (c), N-phenylmaleimide, N-cyclohexylmaleimide, N-isopropylmaleimide, N-benzylmaleimide, N-lauryl Maleimide and N-stearylmaleimide are preferably used.

  As the maleimide monomer (c), only one type may be used, or two or more types may be used in combination. When the maleimide monomer (c) is used as the monomer component, the amount used is preferably 1 part by mass or more and more preferably 2 parts by mass or more with respect to a total of 100 parts by mass of all monomer components. 3 parts by mass or more is more preferable, 20 parts by mass or less is preferable, 15 parts by mass or less is more preferable, and 10 parts by mass or less is more preferable.

  In the polymerization step, monomers other than those described above (hereinafter may be referred to as “other monomers (d)”) may be used as the monomer component. The other monomer (d) is not particularly limited as long as it is a radical polymerizable monomer, and a monofunctional monomer having one radical polymerizable group in the molecule and a radical polymerizable group in the molecule. It can be classified as a polyfunctional monomer having two or more.

  Examples of monofunctional monomers include (meth) acrylates other than alkyl (meth) acrylates, unsaturated mono- or dicarboxylic esters, unsaturated carboxylic acids, vinyl aromatic compounds, vinyl esters, vinyl ethers, olefins, cyanides Examples include vinyl and N-vinyl compounds. These monofunctional monomers may be used alone or in combination of two or more and may not be used as a monomer component.

  Examples of (meth) acrylates other than alkyl (meth) acrylate include phenyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-methoxyethyl. (Meth) acrylate, tetrahydrofurfuryl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, morpholinoalkylene (meth) acrylate, methyl α-hydroxymethyl acrylate, polyethylene glycol mono (meth) acrylate, etc. Can be mentioned.

Examples of the unsaturated mono- or dicarboxylic acid ester include butyl crotonate, octyl crotonate, dibutyl maleate, dilauryl maleate, dioctyl fumarate, distearyl fumarate and the like.
Examples of the unsaturated carboxylic acids include (meth) acrylic acid, maleic acid, fumaric acid, maleic anhydride and the like.
Examples of the vinyl aromatic compound include styrene monomers such as styrene, α-methylstyrene, vinyltoluene, and methoxystyrene, 2-vinylpyridine, 4-vinylpyridine, and the like.
Examples of the vinyl ester include vinyl acetate, vinyl propionate, vinyl octylate and the like.
Examples of the vinyl ether include methyl vinyl ether, butyl vinyl ether, octyl vinyl ether, dodecyl vinyl ether and the like.
Examples of olefins include ethylene, propylene, 1-butene, isobutene, 1-tetradecene, 1-octadecene, diisobutene and the like.
Examples of vinyl cyanide include acrylonitrile and methacrylonitrile.
Examples of the N-vinyl compound include N-vinyl pyrrolidone, N-vinyl caprolactam, N-vinyl imidazole, N-vinyl morpholine, N-vinyl acetamide and the like.

  Of these monofunctional monomers, (meth) acrylates other than alkyl (meth) acrylate and N-vinyl compounds are preferred, such as 2-hydroxyethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, Particularly preferred are methyl α-hydroxymethyl acrylate and N-vinylpyrrolidone.

  Among other monomers (d), examples of polyfunctional monomers include polyfunctional (meth) acrylate, vinyl ether group-containing (meth) acrylate, allyl group-containing (meth) acrylate, polyfunctional (meth) acryloyl. Examples thereof include polyfunctional (meth) acrylic compounds such as group-containing isocyanurates and polyfunctional urethane (meth) acrylates, polyfunctional maleimide compounds, polyfunctional vinyl ethers, polyfunctional allyl compounds, and polyfunctional aromatic vinyls. These polyfunctional monomers may be used alone or in combination of two or more and may not be used as a monomer component.

  Examples of the polyfunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, and bisphenol A alkylene oxide di (meth). Acrylate, trimethylolpropane tri (meth) acrylate, 2,2 ′-[oxybis (methylene)] bisacrylic acid, dialkyl-2,2 ′-[oxybis (methylene)] bis-2-propenoate, and the like.

Examples of the vinyl ether group-containing (meth) acrylate include 2-vinyloxyethyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 2- (vinyloxyethoxy) ethyl (meth) acrylate, and the like.
Examples of the allyl group-containing (meth) acrylate include, for example, allyl (meth) acrylate, methyl α-allyloxymethyl acrylate, stearyl α-allyloxymethyl acrylate, α-allyloxymethyl acrylate 2-decyltetradecyl etc. Is mentioned.
Examples of the polyfunctional (meth) acryloyl group-containing isocyanurate include tri (acryloyloxyethyl) isocyanurate, tri (methacryloyloxyethyl) isocyanurate, and the like.
Examples of the polyfunctional urethane (meth) acrylate include polyfunctional isocyanates such as tolylene diisocyanate, isophorone diisocyanate, and xylylene diisocyanate, and hydroxyl groups such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. The polyfunctional urethane (meth) acrylate obtained by reaction with containing (meth) acrylic acid ester, etc. are mentioned.

Examples of the polyfunctional maleimide compound include 4,4′-diphenylmethane bismaleimide, m-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 1,6-bismaleimide- (2,2,4-trimethyl) hexane, and the like. Can be mentioned.
Examples of the polyfunctional vinyl ether include ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, trimethylolpropane trivinyl ether, and the like.
Examples of polyfunctional allyl compounds include ethylene glycol diallyl ether, diethylene glycol diallyl ether, polyethylene glycol diallyl ether, hexanediol diallyl ether, bisphenol A alkylene oxide diallyl ether, trimethylolpropane triallyl ether, ditrimethylolpropane tetraallyl ether, and the like. Polyfunctional allyl ethers; polyfunctional allyl group-containing isocyanurates such as triallyl isocyanurate; polyfunctional allyl esters such as diallyl phthalate and diallyl diphenate; bisallyl nadiimide compounds; bisallyl nadiimide compounds and the like .
Examples of the polyfunctional aromatic vinyl include divinylbenzene.

  When other monomer (d) is used, the amount used is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, with respect to 100 parts by mass in total of all monomer components. Part or more is more preferable, 40 parts by mass or less is preferable, 30 parts by mass or less is more preferable, 20 parts by mass or less is further preferable, and 10 parts by mass or less is particularly preferable.

  In the case of applying the (meth) acrylate polymer to the viscosity index improver, other monomers (d) from the viewpoint of increasing the base oil solubility of the (meth) acrylate polymer or enhancing the effect of improving the viscosity index. ) Is preferably suppressed as much as possible. Therefore, when using a styrenic monomer, the amount used is preferably less than 3 parts by weight, more preferably 2 parts by weight or less, with respect to a total of 100 parts by weight of all monomer components. 1 part by mass or less is more preferable. Styrene monomers include not only styrene but also those having a substituent bonded to the benzene ring or vinyl group of styrene, such as styrene, α-methylstyrene, vinyltoluene, and methoxystyrene. In addition, since radical copolymerization may decrease if the amount of vinyl ether or olefin used is large, from the viewpoint of ease of production of the polymer, when these monomer components are used, the total amount used is The total monomer component is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass in total.

  When a polyfunctional monomer is used as the monomer (d), the amount used is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, based on a total of 100 parts by mass of all monomer components. Preferably, 2 parts by mass or less is more preferable. If the amount of the polyfunctional monomer used is too large, gelation may proceed during polymerization, or the base oil solubility of the polymer may decrease. However, 2,2 ′-[oxybis (methylene)] bisacrylic acid, dialkyl-2,2 ′-[oxybis (methylene)] bis-2-propenoate, methyl α-allyloxymethyl acrylate, α-allyloxymethyl When using a polyfunctional monomer in which polymerization proceeds while cyclization, such as stearyl acrylate and α-allyloxymethyl acrylate 2-decyltetradecyl, the amount used is the sum of all monomer components. It may be 30 parts by mass or less, 100 parts by mass or less, or 15 parts by mass or less with respect to 100 parts by mass. In this case, due to the effect of the ring structure introduced into the main chain, the heat resistance of the polymer is improved and the shear stability can be improved.

  In the polymerization step, the monomer component essentially containing the monomer (a) is radically polymerized. The polymerization method of the monomer component in the polymerization step may be any of, for example, solution polymerization, suspension polymerization, emulsion polymerization, and the like, when a (meth) acrylate polymer obtained by polymerization is applied to the viscosity index improver, etc. In view of its handleability, it is preferable to perform polymerization by solution polymerization. In addition, when using a dispersion medium, an emulsifier, a dispersing agent, etc., a well-known thing can be used without a restriction | limiting in particular.

  The solvent (reaction solvent) used for the polymerization is not particularly limited as long as it is inert to the polymerization reaction. The polymerization mechanism, the type and amount of the monomer used, the polymerization initiator and the polymerization catalyst are not limited. What is necessary is just to set suitably according to superposition | polymerization conditions, such as a kind and quantity. For example, when the solubility of the (meth) acrylate polymer is ensured and the solvent is removed after the polymerization, the solvent used for the polymerization is an aromatic hydrocarbon such as toluene or xylene; Aliphatic hydrocarbons; ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers such as tetrahydrofuran, dioxane, diethyl ether and dibutyl ether are preferably used. These solvents may be used alone or in combination of two or more.

  When a (meth) acrylate polymer is applied to a viscosity index improver, it can be used as a viscosity index improver without completely replacing the polymerization reaction solution with a solvent. In this case, the polymerization reaction is preferably performed in a solvent containing a high-boiling solvent having a boiling point of 200 ° C. or higher, or in a solvent containing a lubricating base oil. These high-boiling solvents and lubricating base oils do not affect the quality of the lubricating oil, or do not significantly impair the quality of the lubricating oil, even if added to the lubricating oil. Can be used. Therefore, a viscosity index improver can be easily produced.

  The high boiling point solvent is not particularly limited as long as it has a boiling point of 200 ° C. or higher at 1 atm. In consideration of handling of the high boiling point solvent as a reaction solvent, the high boiling point solvent is preferably liquid at room temperature, and the melting point of the high boiling point solvent at 1 atm is, for example, preferably 25 ° C. or less, preferably 10 ° C. or less. More preferred is 0 ° C. or lower.

  Examples of the high boiling point solvent include alkanes having 12 or more carbon atoms (for example, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, and nonadecane), and one or more carbon-carbon bonds of the alkane are double bonds or Chain aliphatic hydrocarbons such as alkenes, alkadienes, alkynes, etc. substituted by triple bonds; cycloalkanes having 10 or more carbon atoms (for example, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, cyclotetradecane, cyclopentadecane, cyclo Hexadecane, cycloheptadecane, cyclooctadecane, cyclononadecane), and cycloalkenes, cycloalkadienes, cycloathenes in which one or more of the carbon-carbon bonds of the cycloalkane are replaced by double bonds or triple bonds Cycloaliphatic hydrocarbons such as quinine; aromatic hydrocarbons such as naphthalene, biphenyl, anthracene, tetracene, phenanthrene, cyclotetradecaheptaene, azulene; diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol Glycol diethers such as ethylene glycol butyl methyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether (glycols having both ends etherified); glycol ethers such as diethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate Esters (both ends are etherified and Glycol diesters such as triethylene glycol diacetate (glycols esterified at both ends); benzoic acid esters such as ethyl benzoate, propyl benzoate, butyl benzoate, and benzyl benzoate; And phenyl ethers such as butyl phenyl ether and diphenyl ether; and phenyl ketones such as acetophenone, propiophenone and benzophenone. As the high boiling point solvent, only one kind may be used, or two or more kinds may be mixed and used.

  As the lubricating base oil, known lubricating base oils can be used, and mineral base oils and synthetic base oils are preferred. Examples of the mineral oil base oil include paraffinic and naphthenic base oils. Mineral base oils include those obtained by subjecting raw material base oils to solvent refining, hydrocracking or hydroisomerization. Examples of synthetic base oils include hydrocarbon, ester, ether, silicone, and fluorine base oils.

  As specific examples of the mineral oil base oil, the following oils (1) to (7) are used as raw materials, and the raw oil and / or lubricating oil fraction recovered from the raw oil is refined by a predetermined refining method. And a base oil obtained by recovering the lubricating oil fraction. Considering that it is easy to improve the quality of the obtained lubricating oil additive, the lubricating base oil may be a base oil selected from (1) to (7) or a lubricating oil fraction recovered from the base oil. The following base oil (8) or (9) obtained by performing a predetermined treatment on is preferably used.

(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) 2 or more kinds of mixed oils (5) Base oils (1) to (4)
(6) Mild hydrocracking treatment oil (MHC) of base oil (5)
(7) Two or more mixed oils selected from base oils (1) to (6) (8) A base oil selected from the above base oils (1) to (7) or a lubricating oil fraction recovered from the base oil Hydrocrack the fraction, and perform dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the product or lubricating oil fraction recovered from the product by distillation or the like, or distill after the dewaxing treatment Hydrocracked mineral oil obtained by
(9) A base oil selected from the base oils (1) to (7) or a lubricating oil fraction recovered from the base oil is hydroisomerized and recovered from the product or the product by distillation or the like. Hydroisomerized mineral oil obtained by subjecting the lubricating oil fraction to dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or distillation after the dewaxing treatment.

  Specific examples of 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, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate, etc.), dialkyldiphenyl ether, Examples thereof include polyphenyl ether, and among them, poly α-olefin is preferable. As the poly α-olefin, typically, an α-olefin oligomer or co-oligomer having 1 to 32 carbon atoms, preferably 6 to 16 (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.) and the like. Of the hydrides.

The high boiling point solvent and the lubricating base oil must have a viscosity index of 100 or more from the viewpoint that it is easy to ensure the required quality as a viscosity index improver when the polymerization reaction solution is applied to the viscosity index improver. Is preferable, 120 or more is more preferable, and 160 or less is preferable. For example, when the viscosity index is less than 100, the viscosity-temperature characteristics, thermal / oxidative stability, and volatilization prevention properties are likely to deteriorate, the friction coefficient increases, and the wear prevention properties tend to decrease. On the other hand, when the viscosity index exceeds 160, the low-temperature viscosity characteristic tends to be lowered. The viscosity index is measured based on JIS K 2283. The kinematic viscosity at 100 ° C. of the high boiling point solvent and the lubricating base oil is preferably 1 to ²⁰ mm ² / s.

  The content of the high-boiling solvent in the reaction solvent, that is, the content of a fraction having a boiling point of 200 ° C. or higher is, for example, preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. The reaction solvent may consist of only a fraction having a boiling point of 200 ° C. or higher, but may contain a fraction having a lower boiling point. When a lubricating base oil is used as the reaction solvent, the content of the lubricating base oil in the reaction solvent is, for example, preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. The reaction solvent may be composed only of a lubricating base oil.

  Although the usage-amount of the reaction solvent in a superposition | polymerization process is not specifically limited, The grade from which the total density | concentration of a monomer component, a polymerization initiator, and another component will be 20 to 80 mass% of the whole is preferable.

  In the polymerization, it is preferable to use a polymerization initiator. A known polymerization initiator may be used as the polymerization initiator. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, dimethyl-2, Azo compounds such as 2′-azobis (2-methylpropionate) and 4,4′-azobis (4-cyanopentanoic acid); persulfates such as potassium persulfate; cumene hydroperoxide, diisopropylbenzene hydroperoxide , Di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, t-amyl peroxy-2-ethyl hexanoate, t-amyl peroxy octoate, t-amyl per Peroxides such as oxyisononanoate can be used. Moreover, a polyfunctional initiator can also be used so that it may demonstrate below. These may use only 1 type and may use 2 or more types together. It is preferable that the usage-amount of a polymerization initiator shall be 0.01-3 mass parts with respect to 100 mass parts of monomer components, for example.

  In the polymerization step, the polymerization reaction may be performed in the presence of an acidic substance. Thereby, the initial polymerization rate can be increased. As the acidic substance, an organic phosphorus compound or an organic acid is preferably used. Examples of the organic phosphorus compound include alkyl (aryl) phosphonous acid and its monoester, dialkyl (aryl) phosphinic acid, alkyl (aryl) phosphonic acid and its monoester, alkylphosphinic acid, phosphorous acid di or monoester And phosphoric acid di or monoester. Examples of the organic acid include saturated or unsaturated fatty acids, aromatic carboxylic acids, hydroxy acids and the like. Fatty acids and aromatic carboxylic acids may be anhydrides. Among these, it is preferable to use a fatty acid having 6 or more carbon atoms as the acidic substance. Thereby, an acidic substance becomes easy to be compatible with the monomer component containing a monomer (a) and a (meth) acrylate type polymer. Moreover, the hydrolysis resistance of a metal alkoxide can be improved. Furthermore, when applying a (meth) acrylate type polymer to a viscosity index improver, the solubility to a base oil can also be improved. The number of carbon atoms of the fatty acid is preferably 8 or more, more preferably 10 or more, 35 or less is preferable, 25 or less is more preferable, and 20 or less is more preferable. The amount of the acidic substance used is, for example, preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, further preferably 0.02 parts by mass or more with respect to 100 parts by mass of the monomer component. It is preferably no greater than 0.5 parts by mass, more preferably no greater than 0.5 parts by mass, and even more preferably no greater than 0.3 parts by mass.

  In the polymerization step, a chain transfer agent or the like may be used. By using a chain transfer agent, it becomes easy to obtain a polymer having a small molecular weight distribution. In addition, thermal decomposition due to depolymerization is easily suppressed. Chain transfer agents include butanethiol, octanethiol, octadecanethiol, dodecanethiol, cyclohexyl mercaptan, thiophenol, octyl thioglycolate, octyl 2-mercaptopropionate, octyl 3-mercaptopropionate, 2-ethylhexyl mercaptopropionate , Mercaptans such as 2-mercaptoethyl ester of octanoic acid, 1,8-dimercapto-3,6-dioxaoctane, dodecyl mercaptan, ethylene glycol bisthioglycolate; carbon tetrachloride, carbon tetrabromide, methylene chloride, bromoform, Halogen compounds such as bromotrichloroethane; α-methylstyrene dimer and the like. Moreover, a polyfunctional chain transfer agent can also be used so that it may demonstrate below. The amount of the chain transfer agent used is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the monomer component, for example.

  The temperature of the polymerization reaction may be appropriately adjusted according to the type of reaction solvent and the degree of progress of the polymerization reaction. For example, 0 ° C or higher is preferable, 25 ° C or higher is more preferable, and 180 ° C or lower is preferable, and 155 ° C is preferable. The following is more preferable. The polymerization reaction time may be appropriately adjusted according to the degree of progress of the polymerization reaction. For example, the polymerization reaction time may be 1 to 48 hours (preferably 3 to 24 hours).

  In the polymerization step, a polyfunctional chain transfer agent or a polyfunctional polymerization initiator may be used. That is, the monomer component may be polymerized in the presence of a polyfunctional chain transfer agent and / or a polyfunctional polymerization initiator. By carrying out the polymerization reaction in this way, a branched unit derived from a polyfunctional chain transfer agent or a polyfunctional polymerization initiator is introduced into the (meth) acrylate polymer, and is obtained when applied to a viscosity index improver. Shear stability can be improved without significantly impairing the solubility of the polymer in the base oil.

  The polyfunctional chain transfer agent is preferably a trifunctional or higher polyvalent mercaptan. For example, trimethylolpropane trimercaptoacetate, trimethylolpropane tri (3-mercaptopropionate), pentaerythritol tetrakismercaptoacetate, pentaerythritol. Tetrakis (3-mercaptopropionate), dipentaerythritol hexakis mercaptoacetate, dipentaerythritol hexakis (3-mercaptopropionate) and other compounds having three or more hydroxyl groups and carboxy group-containing mercaptans polyester compounds, Triazine polyvalent thiols, compounds obtained by adding three or more mercapto groups per molecule by adding hydrogen sulfide to a plurality of epoxy groups of a polyvalent epoxy compound, polyvalent carboxylic Compounds having a plurality of carboxyl groups and mercaptoethanol esterified three or more mercapto groups per molecule comprising the like. These polyfunctional chain transfer agents may use only 1 type and may use 2 or more types together.

  It is preferable to use a trifunctional or higher functional peroxide as the polyfunctional polymerization initiator. For example, 2,2-bis (4,4-t-butylperoxycyclohexyl) propane, tris (t-butylperoxy) triazine , 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone and other organic peroxides having 3 or more functional groups. These polyfunctional polymerization initiators may be used alone or in combination of two or more.

  Each use amount of the polyfunctional chain transfer agent and the polyfunctional polymerization initiator may be 0 parts by mass or more, preferably 0.01 parts by mass or more, and 0.02 parts by mass with respect to 100 parts by mass of the monomer component. The above is more preferable, 0.05 parts by mass or more is further preferable, 3 parts by mass or less is preferable, 2 parts by mass or less is more preferable, and 1 part by mass or less is more preferable.

  According to the production method of the present invention, in the polymerization step, the monomer component containing the monomer (a) which is a (meth) acrylate having an aliphatic hydrocarbon group having 6 or more carbon atoms is added in the presence of a metal alkoxide. Polymerization of the monomer (a) can be enhanced by polymerization. As a result, the reaction rate of the polymerization reaction can be increased or the polymerization rate can be increased. For example, the polymerization rate of the monomer (a) can be 82% or more, or 85% or more. In addition, the said polymerization rate means the average polymerization rate, when using 2 or more types of monomers (a). With respect to the monomer (a2) which is a (meth) acrylate having an aliphatic hydrocarbon group having 6 to 49 carbon atoms, the polymerization rate can be further increased and is 86% or more, 88% or more, or 90% or more. can do. Regarding the monomer (a1) which is a (meth) acrylate having an aliphatic hydrocarbon group having 50 or more carbon atoms, the polymerization rate can be 70% or more, or 72% or more, depending on conditions, 82% Or 84% or more.

  The (meth) acrylate polymer obtained in the polymerization step preferably has the following physical properties, assuming application to a viscosity index improver. In addition, even when not applying a (meth) acrylate type polymer to a viscosity index improver, it can be set as the (meth) acrylate type polymer provided with the following physical property.

  The weight average molecular weight (Mw) of the (meth) acrylate polymer is preferably 100,000 or more, more preferably 250,000 or more, further preferably 310,000 or more, preferably 700,000 or less, more preferably 650,000 or less. Preferably, 600,000 or less is more preferable. In order to adjust to a desired viscosity when the weight average molecular weight of the polymer is small, the viscosity index improving effect of the polymer is reduced, or the thickening effect when the polymer is added to the base oil is likely to be reduced. The amount of the viscosity index improver used is increased, which is disadvantageous in terms of cost. When the weight average molecular weight of the polymer is excessively large, the base oil solubility of the polymer is lowered, and the shear stability of the polymer is liable to be lowered.

  The number average molecular weight (Mn) of the (meth) acrylate polymer is preferably 90,000 or more, more preferably 110,000 or more, preferably 300,000 or less, more preferably 250,000 or less.

  The molecular weight distribution (Mw / Mn) calculated from Mw and Mn of the (meth) acrylate polymer is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.1 or less. When the molecular weight distribution exceeds 4.0, the solubility of the polymer in the base oil is insufficient, and the shear stability of the polymer tends to be lowered. On the other hand, the lower limit of the molecular weight distribution is preferably 1.0, but the molecular weight distribution (Mw / Mn) is preferably 1.5 or more and more preferably 1.8 or more from the viewpoint of easy synthesis of the polymer. In addition, the weight average molecular weight (Mw) and number average molecular weight (Mn) of a polymer are calculated | required by the method as described in an Example.

  The glass transition temperature (Tg) of the (meth) acrylate polymer is preferably −50 ° C. or higher, more preferably −40 ° C. or higher, further preferably −30 ° C. or higher, and preferably 0 ° C. or lower, and −10 ° C. or lower. Is more preferable, and −20 ° C. or lower is more preferable. When the Tg of the polymer is in such a range, the solubility of the polymer in the base oil is ensured, and the fluidity near room temperature is easily improved while maintaining a high viscosity index.

  The SP value (solubility parameter) of the (meth) acrylate polymer is preferably 8.8 or more, more preferably 8.9 or more, further preferably 9.0 or more, and more preferably 9.6 or less, 9.5 The following is more preferable, and 9.4 or less is more preferable. The SP value of the lubricating base oil generally shows a value of about 8.0 to 8.5. If the SP value of the polymer is 8.8 or higher, the viscosity index is increased when this is added to the lubricating oil. It becomes easy. On the other hand, if the SP value of the polymer is 9.6 or less, it becomes easy to ensure the solubility of the polymer in the base oil.

  When the (meth) acrylate polymer is applied to a viscosity index improver, it is preferable that the viscosity index improving effect and shear stability can be achieved at a high level. As specific numerical values of the shear stability, SSI and decomposition start temperature obtained by the following method are used as indexes.

The SSI of the (meth) acrylate polymer is preferably 38 or less, more preferably 36 or less, and even more preferably 34 or less, thereby improving the shear stability and storage stability of the polymer. The lower limit of the SSI of the polymer is not particularly limited, but is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 2 or more, and even more preferably 5 or more. When SSI is less than 0.1, the effect of improving the viscosity index of the polymer tends to decrease. The SSI of the polymer is obtained by diluting the polymer in the base oil so that the kinematic viscosity at 100 ° C. is 7.0 mm ² / sec, and the kinematic viscosity before and after the shear treatment by the ultrasonic homogenizer and the kinematic viscosity at 100 ° C. of the base oil. Is obtained by the following formula: SSI = {1- (kinematic viscosity after shearing process−dynamic viscosity of base oil) / (kinematic viscosity before shearing process−dynamic viscosity of base oil)} × 100.

  The decomposition start temperature of the (meth) acrylate polymer is preferably 290 ° C or higher, more preferably 295 ° C or higher, further preferably 300 ° C or higher, particularly preferably 310 ° C or higher, and preferably 500 ° C or lower, 450 ° C. or lower is more preferable, 400 ° C. or lower is further preferable, and 380 ° C. or lower is particularly preferable. By increasing the decomposition start temperature of the polymer, heat resistance is improved, and thermal decomposition stability and shear stability are improved. On the other hand, when the heat resistance is excessively improved, the solubility tends to be insufficient or the viscosity index tends to decrease when the polymer is added to the lubricating oil.

  The polymerization reaction liquid obtained in the polymerization step can be made into a viscosity index improver by diluting with a lubricating base oil or replacing the solvent as necessary. In particular, when the polymerization reaction is carried out in a solvent containing a high boiling point solvent having a boiling point of 200 ° C. or higher, or in a solvent containing a lubricating base oil, the lubricating base oil can be used as needed without solvent replacement. The viscosity index improver can be easily obtained by diluting with. The concentration of the (meth) acrylate polymer in the viscosity index improver is, for example, preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 70% by mass or less. Less than 50% by weight is more preferable, and less than 50% by weight is more preferable.

  The viscosity index improver may include a polymer other than the (meth) acrylate polymer described above. Examples of such a polymer include polymethacrylate, polyisobutylene, ethylene-propylene copolymer. Examples thereof include a polymer, a styrene-diene hydrogenated copolymer, a graft polymer, a comb polymer, and a star polymer. When a polymer other than the (meth) acrylate polymer is included in the viscosity index improver, the total concentration in the viscosity index improver combining the polymer and the (meth) acrylate polymer is 5% by mass. It is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 70% by mass or less, more preferably 60% by mass or less, and further preferably less than 50% by mass.

  In the production method of the present invention, a macromonomer synthesis step may be provided before the polymerization step. For example, a step of synthesizing a (meth) acrylate macromonomer represented by the above formula (2) may be provided. In this case, in the macromonomer synthesis step, a compound having a functional group and an aliphatic hydrocarbon group having 50 or more carbon atoms and a (meth) acrylate having a reactive group with the functional group are reacted to form a macromonomer. It is preferable to synthesize. Hereinafter, a compound having a functional group and an aliphatic hydrocarbon group having 50 or more carbon atoms is referred to as a “macro compound”, and a (meth) acrylate having a reactive group with a functional group of the macro compound is referred to as a “counter compound”. .

  For the aliphatic hydrocarbon group having 50 or more carbon atoms of the macro compound, the description of the aliphatic hydrocarbon group of the monomer (a1) is referred to. The functional group possessed by the macro compound is preferably a group that undergoes an addition reaction or a condensation reaction with the reactive group of the counter compound, and examples thereof include a hydroxyl group, an amino group, a carboxy group and an esterified product thereof, an isocyanate group, and a sulfo group. . Among these, a hydroxyl group, a carboxy group, and an esterified product thereof are preferable from the viewpoint of ease of production and availability. The macro compound preferably has only one such functional group, and more preferably has such a functional group at the end of the macro compound.

  The (meth) acrylate serving as the counter compound has a reactive group with the functional group of the macro compound, and the group having the reactive group is bonded to the ester group of (meth) acrylate. By reacting the macro compound with the counter compound, the (meth) acrylate macromonomer represented by the above formula (2) can be obtained. Examples of the reactive group possessed by the counter compound include a hydroxyl group, an amino group, a carboxy group and an esterified product thereof, an isocyanate group, a sulfo group, and an oxazoline group. Among these, a hydroxyl group, an isocyanate group, and a sulfo group are preferable. The counter compound preferably has only one reactive group. Examples of the counter compound include 2-isocyanatoethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and 3-sulfopropyl (meth) acrylate.

  The reaction between the macro compound and the counter compound includes urethanation reaction in which an isocyanate group and a hydroxyl group react, urea formation reaction in which an isocyanate group and an amino group react, esterification reaction in which a carboxy group and a hydroxyl group react, a carboxy group and an amino group Amidation reaction in which a group reacts, sulfonic acid esterification reaction in which a sulfo group and a hydroxyl group react, sulfonamidation reaction in which a sulfo group and an amino group react, transesterification reaction in which an esterified product of a hydroxyl group and a carboxy group reacts Amide esterification reaction in which an oxazoline group and a carboxy group react. Among these, from the viewpoint of excellent reactivity, a urethanization reaction, a urealation reaction, an esterification reaction, a transesterification reaction, or an amidation reaction is preferable, and a urethanization reaction is particularly preferable. As the macro compound, it is particularly preferable to use a macro compound having a hydroxyl group from the viewpoint of ease of production and availability. As the counter compound, it is particularly preferable to use a counter compound having an isocyanate group because of its reactivity with a macro compound having a hydroxyl group.

  The amount of the macro compound and the counter compound used is preferably 0.7 to 1.5 mol, more preferably 0.8 to 1.3 mol, with respect to 1 mol of the macro compound. .

  The solvent used in the reaction between the macro compound and the counter compound is not particularly limited as long as it is inert to the reaction. For example, aromatic hydrocarbons such as toluene and xylene; fats such as hexane and cyclohexane Group hydrocarbons; ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran, dioxane, diethyl ether, and dibutyl ether can be used.

  The reaction between the macro compound and the counter compound can also be carried out in a solvent containing a high boiling point solvent having a boiling point of 200 ° C. or higher, or in a solvent containing a lubricating base oil. In this case, the reaction solution obtained by the reaction can be used in the next polymerization step, thereby simplifying the process. When shifting from the macromonomer synthesis step to the polymerization step, the high boiling point solvent or lubricating base oil used in the macromonomer synthesis step need not be actively separated from the reaction solution. In the polymerization step, the polymerization reaction may be carried out by adding the above-described high boiling point solvent or lubricating base oil to the reaction solution obtained in the macromonomer synthesis step. In addition, when using the (meth) acrylate type polymer obtained at a superposition | polymerization process as a viscosity index improver, it is preferable to use a lubricating base oil as a solvent (when adding a solvent) added at a superposition | polymerization process.

  In the above case, the production method of the present invention includes a compound having a functional group and an aliphatic hydrocarbon group having 50 or more carbon atoms in a solvent containing a high boiling point solvent having a boiling point of 200 ° C. or higher or a lubricating base oil, and the functional group. And a macromonomer synthesis step for producing a (meth) acrylate macromonomer by reacting with a (meth) acrylate having a reactive group, and a high boiling point solvent having a boiling point of 200 ° C. or higher used in the macromonomer synthesis step or It is preferable to have a polymerization step of polymerizing a monomer component containing the (meth) acrylate macromonomer in a solvent containing a lubricating base oil. For details of the solvent containing a high boiling point solvent having a boiling point of 200 ° C. or higher or a lubricating base oil, reference is made to the description of these solvents in the polymerization step.

  The temperature at which the macro compound and the counter compound are reacted may be appropriately adjusted according to the type of reaction solvent and the progress of the reaction, but is preferably 0 ° C. or higher, more preferably 25 ° C. or higher, and 180 ° C or lower is preferable, and 155 ° C or lower is more preferable. The reaction time may be appropriately adjusted according to the degree of progress of the reaction. For example, the reaction time may be 20 minutes to 16 hours (preferably 30 minutes to 12 hours).

  The reaction between the macro compound and the counter compound can be performed in the presence of the metal alkoxide described above. In this case, the metal alkoxide can function as a reaction catalyst between the macro compound and the counter compound, which is efficient. In addition, when shifting from the macromonomer synthesis step to the polymerization step, it is not necessary to actively separate the metal alkoxide used in the macromonomer synthesis step, so that the process can be simplified. Since the metal alkoxide functions as a catalyst in the macromonomer synthesis process, when the metal alkoxide used in the macromonomer synthesis process is brought into the polymerization process, the function described above while maintaining the form of the metal alkoxide in the polymerization process Can be demonstrated.

  In the above case, the production method of the present invention includes a compound having a functional group and an aliphatic hydrocarbon group having 50 or more carbon atoms in the presence of a metal alkoxide, and a (meth) acrylate having a reactive group with the functional group; The presence of the metal alkoxide used in the macromonomer synthesis step, a macromonomer synthesis step for producing a (meth) acrylate macromonomer, and a monomer component containing the (meth) acrylate macromonomer It is preferred to have a polymerization step that polymerizes under. At this time, if the macromonomer synthesis step is performed in a high boiling point solvent having a boiling point of 200 ° C. or higher or a solvent containing a lubricating base oil, and the reaction solution obtained here is used in the next polymerization step, Since the metal alkoxide can be brought into the next polymerization step together with the solvent used, the process can be further simplified.

When bringing the metal alkoxide used in the macromonomer synthesis process into the polymerization process, for example, the content ratio (mass basis) of the macromonomer (MM) and the metal (Me) derived from the metal alkoxide in the reaction solution obtained in the macromonomer synthesis process ) Is Me ₁ / MM ₁ , the content ratio Me ₂ / MM _{2 of the} macromonomer (MM) and the metal (Me) derived from the metal alkoxide in the reaction solution used for the polymerization reaction in the polymerization step is 0.5 × Me. ₁ / MM ₁ or more and 2.0 × Me ₁ / MM ₁ or less is preferable, 0.7 × Me ₁ / MM ₁ or more and 1.5 × Me ₁ / MM ₁ or less is more preferable, and 0.8 × Me ₁ / MM ₁ or more and 1.2 × Me ₁ / MM ₁ or less are more preferable.

  The (meth) acrylate polymer obtained by the production method of the present invention can be suitably applied to a viscosity index improver. Therefore, the method for producing a (meth) acrylate polymer of the present invention can be a method for producing a viscosity index improver. In this case, the method for producing a viscosity index improver has the polymerization step described above, and may further include a macromonomer synthesis step and the like.

  According to the present invention, a viscosity index improver containing a (meth) acrylate polymer having a unit derived from a (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms is obtained. Can do. The (meth) acrylate polymer may have a unit derived from the monomer (a1) described above as a unit derived from the monomer (a), and a unit derived from the monomer (a2). You may have. Moreover, you may have a unit derived from a monomer (b), and you may have a unit derived from a monomer (c) and a unit derived from a monomer (d). When a polyfunctional chain transfer agent or a polyfunctional polymerization initiator is used in the polymerization reaction, the (meth) acrylate polymer may have a branch unit derived therefrom. The present invention also includes a viscosity index improver containing such a (meth) acrylate polymer.

  According to the present invention, it is possible to increase the polymerization rate of the (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms, which is usually difficult to achieve a high polymerization rate. In addition, the (meth) acrylate monomer having such an aliphatic hydrocarbon group has a higher boiling point as the number of carbons of the aliphatic hydrocarbon group increases, and the (meth) acrylate polymer obtained by the polymerization reaction Separation becomes difficult. Therefore, when the polymerization reaction liquid obtained in the polymerization step is applied to a viscosity index improver, it can be a viscosity index improver with a small content of unpolymerized monomer components.

  The viscosity index improver of the present invention is derived from the monomer (a) contained in the (meth) acrylate polymer in the viscosity index improver, where X is the content of the monomer (a) in the viscosity index improver. When the content of the unit is Y, X / (X + Y) (mass ratio) can be 0.18 or less. X / (X + Y) is preferably 0.16 or less, more preferably 0.15 or less. In addition, when there are two or more units derived from the monomer (a) contained in the (meth) acrylate polymer, the value of X / (X + Y) of each monomer is obtained, and the content of each monomer Obtained by weighted average based on percentage (mass basis). X / (X + Y) is substantially equal to the (average) polymerization rate of the monomer (a) in the polymerization step.

  The viscosity index improver of the present invention is defined as follows from the viewpoint of the content of the (meth) acrylate monomer (a1) having an aliphatic hydrocarbon group having 50 or more carbon atoms and having more carbon atoms. It is also preferable. That is, the viscosity index improver of the present invention has a monomer (a1) content in the viscosity index improver of X1, and the monomer (a1) contained in the (meth) acrylate polymer in the viscosity index improver. ) When the content of the derived unit is Y1, X1 / (X1 + Y1) (mass ratio) may be 0.30 or less. X1 / (X1 + Y1) is preferably 0.25 or less, more preferably 0.20 or less, and still more preferably 0.18 or less.

  When the polymerization reaction liquid obtained in the polymerization step is applied to a viscosity index improver, the viscosity index improver contains a metal derived from a metal alkoxide together with a (meth) acrylate polymer. From such a viewpoint, the viscosity index improver obtained by the present invention contains 0.001 part by mass or more of a metal derived from a metal alkoxide with respect to 100 parts by mass of the (meth) acrylate polymer in the viscosity index improver. It can also be considered to be. In the viscosity index improver, the metal content derived from the metal alkoxide is preferably 0.005 parts by mass or more, more preferably 0 with respect to 100 parts by mass of the (meth) acrylate polymer in the viscosity index improver. 0.01 parts by mass or more, preferably 3 parts by mass or less, more preferably 1 part by mass or less, and further preferably 0.5 parts by mass or less. As described above, the metal derived from the metal alkoxide is preferably a transition metal element selected from Group 4 elements, Group 5 elements, Group 12 elements, Group 14 elements and Group 15 elements.

  The (meth) acrylate polymer obtained by the production method of the present invention can be used by blending with a lubricating oil, whereby a lubricating oil composition containing the (meth) acrylate polymer is obtained. In this case, the (meth) acrylate polymer can function as a viscosity index improver in the lubricating oil composition. From such a viewpoint, the present invention can also provide a method for producing a lubricating oil composition. In this case, in addition to the polymerization step described above, the (meth) acrylate polymer obtained in the polymerization step is lubricated. It has a blending step of blending with oil to obtain a lubricating oil composition. The lubricating oil composition contains lubricating oil and the (meth) acrylate polymer or viscosity index improver.

  In the blending step, the concentration of the (meth) acrylate polymer in the lubricating oil composition is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 15% in the lubricating oil composition. It is preferable to blend the (meth) acrylate-based polymer so as to be not more than mass%, more preferably not less than 0.5 mass% and not more than 10 mass%.

  The lubricating oil contains at least a lubricating base oil and may contain any additive. For example, pour point depressants, antiwear agents, metallic detergents, ashless detergents, antioxidants, corrosion inhibitors, defoamers, friction modifiers, rust inhibitors, demulsifiers, and metal inertness It is preferable that at least one additive selected from the group consisting of an agent is blended in the lubricating oil or lubricating oil composition.

  As the pour point depressant, any pour point depressant used for lubricating oil can be used. Examples of pour point depressants include polymethacrylates, naphthalene-chlorinated paraffin condensation products, phenol-chlorinated paraffin condensation products, and the like. Of these, polymethacrylates are preferred.

  As the antiwear agent (or extreme pressure agent), any antiwear agent / extreme pressure agent used in lubricating oils can be used. As the antiwear agent (or extreme pressure agent), for example, sulfur-based, phosphorus-based, sulfur-phosphorus-based extreme pressure agents and the like can be used. Specifically, zinc dialkyldithiophosphate (ZnDTP), phosphite, etc. Thiophosphites, dithiophosphites, trithiophosphites, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, these Examples thereof include metal salts, derivatives thereof, dithiocarbamate, zinc dithiocarbamate, MoDTC, disulfides, polysulfides, sulfurized olefins, and sulfurized fats and oils. Of these, sulfur-based extreme pressure agents are preferred, and sulfurized fats and oils are particularly preferred.

  Examples of the metal detergent / dispersant 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 particularly preferable.

  As the ashless detergent / dispersant, any ashless detergent / dispersant used for lubricating oil can be used. Examples of the ashless detergent dispersant include mono- or bissuccinimides having at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, and alkyl groups having 40 to 400 carbon atoms. Alternatively, a benzylamine having at least one alkenyl group in the molecule, a polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a modification thereof with a boron compound, carboxylic acid, phosphoric acid, or the like. Examples include products. 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. Specific examples of the antioxidant include, for example, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2, 6-di-tert-butylphenol) and the like, and amine-based ashless antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, dialkyldiphenylamine and the like.

  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.

  As friction modifiers, in addition to organic molybdenum compounds such as succinimide molybdenum complexes such as molybdenum dithiocarbamate and molybdenum dithiophosphate, and amine salts of organic molybdic acid, linear alkyl and metal having 8 to 30 carbon atoms as a 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 alkoxy alcohol having an amine and a hydroxyl group in the same molecule.

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

  Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and 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 dialkyl dithiocarbamate, 2- (alkyldithio) benzimidazole, β- (o-carboxybenzylthio) propiononitrile.

  Lubricating oil compositions include pour point depressants, antiwear agents, metal detergents, ashless detergents, antioxidants, corrosion inhibitors, foam inhibitors, friction modifiers, rust inhibitors, demulsifiers, And one or more selected from the group consisting of metal deactivators, for example, each content is 0.01 parts by mass or more and 10 parts by mass or less in 100 parts by mass of the lubricating oil composition. If it is.

  When the lubricating oil composition contains a metallic detergent / dispersant, the content thereof is preferably 0.01 parts by mass or more and less than 30 parts by mass in 100 parts by mass of the lubricating oil composition. If the content is less than 0.01 parts by mass, the fuel saving effect may last only for a short period of time, and if it is 30 parts by mass or more, it is difficult to obtain an effect commensurate with the content.

  When the lubricating oil composition contains an antifoaming agent, the content is preferably 0.0001 parts by mass or more and 0.01 parts by mass or less in 100 parts by mass of the lubricating oil composition.

  When the lubricating oil composition contains a friction modifier, the content thereof is preferably 0.01 parts by mass or more and 3 parts by mass or less in 100 parts by mass of the lubricating oil composition. If the content of the friction modifier is less than 0.01 parts by mass, the effect of reducing friction due to the addition tends to be insufficient, and if it exceeds 3 parts by mass, the effects of other additives are likely to be hindered. Or the solubility of the additive tends to decrease.

  The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

(1) Analysis and evaluation method (1-1) Weight average molecular weight and number average molecular weight The weight average molecular weight and the number average molecular weight were determined using gel permeation chromatography (manufactured by Tosoh Corporation, HLC-8320GPC ECOSEC). The measurement conditions are as follows.
-Column: manufactured by Tosoh Corporation, two TSKgel GMHXL-developing solvent: tetrahydrofuran-flow rate of developing solvent: 1.0 mL / min-standard sample: TSK standard polystyrene (PS-oligomer kit manufactured by Tosoh Corporation)
-Column temperature: 40 ° C
-Sample concentration: 0.5%
-Injection volume: 200 μL

(1-2) Macromonomer polymerization rate The macromonomer polymerization rate was determined using gel permeation chromatography (HLC-8320GPC ECOSEC, manufactured by Tosoh Corporation). Specifically, a calibration curve solution in which the macromonomer was dissolved in tetrahydrofuran was prepared, measured by gel permeation chromatography, and a calibration curve was created from the peak area. Next, a sample solution in which the polymerization solution was dissolved in tetrahydrofuran was prepared, and similarly measured by gel permeation chromatography. From the peak area of the obtained macromonomer, the content of the macromonomer in the polymerization solution was determined, and the macromonomer polymerization rate was calculated by dividing by the macromonomer amount charged in the polymerization system. The measurement conditions of gel permeation chromatography are as follows.
-Column: manufactured by Tosoh Corporation, two TSKgel GMHXL-developing solvent: tetrahydrofuran-flow rate of developing solvent: 1.0 mL / min-standard sample: TSK standard polystyrene (PS-oligomer kit manufactured by Tosoh Corporation)
-Column temperature: 40 ° C
-Sample concentration: 0.5%
-Injection volume: 200 μL

(1-3) Polymerization rate of monomer components other than macromonomer The polymerization rate of each monomer component excluding the macromonomer was determined using gas chromatography (manufactured by Shimadzu Corporation, GC-2010plus). Specifically, a calibration curve solution in which each monomer and tridecane were dissolved in ethyl acetate was prepared, measured by gas chromatography, and a calibration curve was created from the peak area. Next, a sample solution in which the polymerization solution and tridecane were dissolved in ethyl acetate was prepared, and similarly measured by gas chromatography. The polymerization rate of each monomer component was determined by an internal standard method. The measurement conditions for gas chromatography are as follows.
Column: Inert Cap1 (liquid phase film thickness: 0.25 μm, length: 30 m, inner diameter: 0.25 mm) manufactured by GL Science
-Temperature: 40 ° C (5 min hold) + 40 ° C to 170 ° C (10 ° C / min) + 170 ° C to 210 ° C (5 ° C / min) + 210 ° C to 330 ° C (15 ° C / min) + 330 ° C (20 min hold)
-Vaporization chamber temperature: 200 ° C
-Detector temperature: 350 ° C (FID)
-Carrier gas: helium (column flow rate 1.33 mL / min)
Injection volume: 0.5 μL (split method, split ratio: 30.0)
-Internal standard: Tridecane-Diluting solvent: Ethyl acetate

(1-4) Average polymerization rate The polymerization rate of each monomer was multiplied by the mass ratio of each monomer added to the polymerization system, and the average polymerization rate was determined from the sum of them. For example, there are three types of monomers used for the polymerization, the blending ratio (mass%) of each monomer with respect to the total amount of monomers is A, B, and C, and the polymerization rate (mass%) of each monomer. ) Is a, b, c, the average polymerization rate is calculated as (Aa + Bb + Cc) / 100 (mass%).

(1-5) Base oil solubility A polymer base oil solution was prepared by blending 4 parts by mass of a polymer and 96 parts by mass of a base oil (manufactured by SK, YUBASE4), and stirred at room temperature for 1 hour. The presence or absence of precipitates was visually confirmed, and the case where no precipitates or insoluble matters were confirmed was defined as solubility ○. When precipitates and insolubles were confirmed, the solution was heated at 80 ° C. for 30 minutes while stirring. Thereafter, the base oil solution of the polymer was cooled to room temperature, and the presence or absence of precipitates was confirmed visually. The case where the precipitate was confirmed was evaluated as solubility x, and the case where the precipitate was not confirmed was evaluated as solubility Δ. YUBASE4 manufactured by SK is a Group III base oil (viscosity index 122, 40 ° C. kinematic viscosity 19.6 mm ² / s) in the American Petroleum Institute (API) classification.

(1-6) Viscosity Index Base oil (manufactured by SK, YUBASE4: Group III base oil in the American Petroleum Institute (API) classification (viscosity index 122, 40) so that the kinematic viscosity at 100 ° C. is 7.0 mm ² / s. The polymer was diluted to 1 ° C. and kinematic viscosity 19.6 mm ² / s)), and measured by the method of JIS K 2283.

(1-7) Shear stability (SSI)
The base oil (SKBASE, YUBASE4) was diluted so that the kinematic viscosity at 100 ° C. was 7.0 mm ² / s to prepare a base oil solution of the polymer, and this was maintained at 100 ° C. Then, using an ultrasonic homogenizer (manufactured by Ultrasonics, Hielscher UP400S), ultrasonic treatment was applied for 10 minutes under the conditions of Amplitude = 70% and Cycle = 1, and shear treatment was performed. The kinematic viscosity at 100 ° C. of the base oil solution and base oil of the polymer before and after the shearing treatment was measured, and the shear stability (SSI) was determined by the following formula: SSI = [1− (kinematic viscosity after shearing treatment− Base oil kinematic viscosity) / (kinematic viscosity before shearing-base oil kinematic viscosity)] × 100.

(2) Production example of base oil solution of (meth) acrylate polymer (2-1) Example 1
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, a one-terminal hydroxyl group-containing polymer of hydrogenated polybutadiene (manufactured by TOTAL, Krasol (registered trademark) HLBH-5000M, number average molecular weight 8200). ) 48.6 parts by mass, 2-isocyanatoethyl acrylate (Showa Denko, Karenz AOI (registered trademark)) 1.38 parts by mass, base oil (SK Corporation, YUBASE4) 50 parts by mass, tetraoctyl titanate (Matsumoto Fine Chemical) 0.1 parts by mass) were charged, and the mixture was stirred for 1 hour while being heated to 70 ° C. in an oil bath while introducing nitrogen gas, to obtain a base oil solution of macromonomer 1 shown in Table 1. 24 parts by mass of base oil solution of the obtained macromonomer 1, 40 parts by mass of n-butyl methacrylate (BMA), 18 parts by mass of stearyl methacrylate (SMA), 3 parts by mass of N-phenylmaleimide (PMI), base oil (SK YUBASE4) 143.1 parts by mass and pentaerythritol tetrakis (mercaptoacetate) 0.05 parts by mass were charged into a reaction vessel, and the contents were heated to 105 ° C. while stirring while introducing nitrogen gas into the reaction vessel. Allowed to warm. Thereto, 0.049 parts by mass of t-amylperoxoisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) as a polymerization initiator was dissolved in 4.76 parts by mass of base oil (manufactured by SK, YUBASE4). 19.3 parts by weight of base oil (manufactured by SK, YUBASE4) 0.193 parts by mass of t-amyl peroxoisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) was added as a polymerization initiator. The solution polymerization was allowed to proceed while dripping the solution dissolved in the part and the solution obtained by dissolving 2 parts by mass of PMI in 25 parts by mass of BMA over 4 hours, followed by aging for 4 hours. The base oil solution (polymer concentration 25 mass%) of the polymer 1 was obtained by adding and diluting 130.5 mass parts of base oil (the SKBASE make, YUBASE4) there.

(2-2) Example 2
In Example 1, except that the amount of tetraoctyl titanate used was changed from 0.1 parts by mass to 0.2 parts by mass, the same operation as in Example 1 was carried out, whereby a base oil solution (heavy A coalescence concentration of 25% by mass was obtained.

(2-3) Example 3
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, a one-terminal hydroxyl group-containing polymer of hydrogenated polybutadiene (manufactured by TOTAL, Krasol (registered trademark) HLBH-5000M, number average molecular weight 8200). ) 48.6 parts by mass, 1.38 parts by mass of 2-isocyanatoethyl methacrylate (Showa Denko, Karenz MOI (registered trademark)), 307.1 parts by mass of base oil (manufactured by SK, YUBASE4), tetraoctyl titanate ( (Matsumoto Fine Chemical Co., Ltd.) 0.1 parts by mass was charged, and this was stirred for 1 hour while heating to 70 ° C. in an oil bath while introducing nitrogen gas, to obtain a base oil solution of macromonomer 2 shown in Table 1 It was. 85.7 parts by mass of the obtained base oil solution of Macromonomer 2, 65 parts by mass of BMA, 18 parts by mass of SMA, 5 parts by mass of PMI, 138.5 parts by mass of base oil (manufactured by SK, YUBASE4), pentaerythritol tetrakis (mercaptoacetate) ) 0.05 part by mass was charged into a reaction vessel, and the contents were heated to 105 ° C. with stirring while introducing nitrogen gas into the reaction vessel. Thereto, 0.049 parts by mass of t-amylperoxoisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) as a polymerization initiator was dissolved in 4.76 parts by mass of base oil (manufactured by SK, YUBASE4). 19.3 parts by weight of base oil (manufactured by SK, YUBASE4) 0.193 parts by mass of t-amyl peroxoisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) was added as a polymerization initiator. Solution polymerization was allowed to proceed while dripping the solution dissolved in the portion over 4 hours, and then aging was performed for 2 hours. The base oil solution (polymer concentration 25 mass%) of the polymer 3 was obtained by adding and diluting 71.2 mass parts of base oil (the SKBASE make, YUBASE4) there.

(2-4) Example 4
85.7 parts by mass of the base oil solution of macromonomer 2 obtained in Example 3 was charged into a reaction vessel, 0.038 parts by mass of lauric acid was added thereto, and the mixture was heated and stirred at 75 ° C for 10 minutes. After cooling the obtained solution to room temperature, 57 parts by mass of BMA, 23 parts by mass of lauryl methacrylate / tridecyl methacrylate mixture (mass ratio = 54/46) (SLMA), 5 parts by mass of PMI, base oil (manufactured by SK, YUBASE4) 153.6 parts by mass was added, and the contents were heated to 105 ° C. with stirring while introducing nitrogen gas into the reaction vessel. Thereto was added 0.025 parts by mass of pentaerythritol tetrakis (mercaptoacetate), and 1,1′-azobis (cyclohexane-1-carbonitrile) (V-40, manufactured by Wako Pure Chemical Industries, Ltd.) 0.146 as a polymerization initiator. Mass parts, 5.8 parts by mass of base oil (manufactured by SK, YUBASE4) and 3 parts by mass of BMA were added, and solution polymerization was performed at 105 ° C. for 6 hours. The base oil solution (polymer concentration 25 mass%) of the polymer 4 was obtained by adding and diluting 66.6 mass parts of base oil (the SKBASE make, YUBASE4) there.

(2-5) Example 5
In Example 3, the same operation as in Example 3 was performed except that 0.1 part by mass of tetraoctyl titanate was changed to 0.1 part by mass of titanium diisopropoxybisethyl acetoacetate (manufactured by Matsumoto Fine Chemical Co., Ltd.). A base oil solution of macromonomer 2 was obtained. The obtained base oil solution of Macromonomer 2 was 85.7 parts by mass, BMA 60 parts by mass, SLMA 23 parts by mass, PMI 5 parts by mass, base oil (manufactured by SK, YUBASE4) 191.2 parts by mass, pentaerythritol tetrakis (mercaptoacetate). ) 0.05 part by mass was charged into a reaction vessel, and the contents were heated to 105 ° C. with stirring while introducing nitrogen gas into the reaction vessel. Thereto, 0.049 parts by mass of t-amylperoxoisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) as a polymerization initiator was dissolved in 4.76 parts by mass of base oil (manufactured by SK, YUBASE4). The solution was added, and t-amyl peroxoisononanoate (manufactured by Arkema Yoshitomi Corp., Luperox (registered trademark) 570) 0.145 parts by mass of base oil (SK Corp., YUBASE4) 9.5 mass as a polymerization initiator The solution polymerization was allowed to proceed while dropping the solution dissolved in the part over 3 hours, followed by aging for 2 hours. Thereto, 22.7 parts by mass of base oil (manufactured by SK, YUBASE4) was added and diluted to obtain a base oil solution of polymer 5 (polymer concentration: 25% by mass).

(2-6) Example 6
In Example 3, 0.1 part by mass of tetraoctyl titanate was changed to 0.1 part by mass of tetrabutoxyzirconium (manufactured by Nippon Soda Co., Ltd.), and the heating temperature was changed from 70 ° C. to 85 ° C. Example 3 The base oil solution of macromonomer 2 was obtained by performing the same operation as in Example 1. Thereto was added 0.16 part by weight of lauric acid (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was stirred at 85 ° C. for 30 minutes. 85.7 parts by mass of the obtained macromonomer 2 containing solution, 57 parts by mass of BMA, 23 parts by mass of SLMA, 5 parts by mass of PMI, and 153.6 parts by mass of base oil (manufactured by SK, YUBASE4) were charged into the reaction vessel. The contents were heated to 105 ° C. with stirring while introducing nitrogen gas. Thereto was added 0.025 part by mass of pentaerythritol tetrakis (mercaptoacetate), and 1,1′-azobis (cyclohexane-1-carbonitrile) (manufactured by Wako Pure Chemical Industries, V-40) as a polymerization initiator. 146 parts by mass, 5.8 parts by mass of base oil (manufactured by SK, YUBASE4) and 3 parts by mass of BMA were added, and solution polymerization was performed at 105 ° C. for 6 hours. The base oil solution (polymer concentration 25 mass%) of the polymer 6 was obtained by adding and diluting 66.6 mass parts of base oil (the SKBASE make, YUBASE4) there.

(2-7) Example 7
In Example 3, 65 parts by mass of BMA was changed to 10 parts by mass of butyl acrylate (BA) and 50 parts by mass of BMA, 18 parts by mass of SMA was changed to 23 parts by mass of SLMA, and the amount of base oil charged into the reaction vessel at the time of polymerization was 138. The polymer 7 was obtained by performing the same operation as in Example 3, except that the amount was changed from 5 parts by mass to 86.8 parts by mass, and the base oil added after aging was changed from 71.2 parts by mass to 122.9 parts by mass. A base oil solution (polymer concentration 25% by mass) was obtained.

(2-8) Example 8
In Example 7, 10 parts by mass of BA was changed to 5 parts by mass, 50 parts by mass of BMA was changed to 55 parts by mass, and the amount of base oil charged into the reaction vessel during polymerization was changed from 86.8 parts by mass to 73.6 parts by mass. The base oil solution of polymer 8 (polymer concentration: 25 mass) was obtained by performing the same operation as in Example 7 except that the base oil added after aging was changed from 122.9 mass parts to 136.1 mass parts. %).

(2-9) Example 9
In Example 5, the base oil solution obtained in Example 3 was used as the base oil solution of macromonomer 2, and 60 parts by mass of BMA was changed to 60 parts by mass of isobutyl methacrylate (IBMA), and the base oil charged into the reaction vessel at the time of polymerization. Was changed from 191.2 parts by mass to 117.7 parts by mass, and the base oil added after aging was changed from 22.7 parts by mass to 92.0 parts by mass. Thus, a base oil solution of polymer 9 (polymer concentration: 25% by mass) was obtained.

(2-10) Comparative Example 1
A base oil solution of macromonomer 2 was obtained by performing the same operation as in Example 3 except that 0.1 part by mass of tetraoctyl titanate was changed to 0.05 part by mass of dibutyltin dilaurate in Example 3. Furthermore, the amount of base oil charged into the reaction vessel during polymerization was changed from 138.5 parts by mass to 133.6 parts by mass, and the base oil added after aging was changed from 71.2 parts by mass to 76.1 parts by mass. The base oil solution of polymer 10 (polymer concentration 25% by mass) was obtained by performing the same operations as in Example 3 except for the above.

(2-11) Comparative Example 2
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel, a one-terminal hydroxyl group-containing copolymer of hydrogenated polybutadiene (manufactured by TOTAL, Krasol (registered trademark) HLBH-5000M, number average) 50 parts by mass of molecular weight 8200), 1.6 parts by mass of 2-isocyanatoethyl methacrylate (manufactured by Showa Denko KK, Karenz MOI (registered trademark)), 20 parts by mass of toluene, 0.1 parts by mass of dibutyltin dilaurate were charged. The mixture was stirred for 6 hours while being heated to 65 ° C. in an oil bath while introducing nitrogen gas. After completion of the reaction, 50 parts by mass of water was added, and the supernatant was recovered with a separatory funnel. After raising the temperature to 65 ° C., toluene was removed under reduced pressure to obtain macromonomer 2 shown in Table 1. The obtained macromonomer 2 was charged in 12 parts by mass, 70 parts by mass of BMA, and 18 parts by mass of SMA in a reaction vessel, and further 138.7 parts by mass of base oil (manufactured by SK, YUBASE4) and 0.05 of pentaerythritol tetrakis (mercaptoacetate). A mass part was added, and the contents were heated to 105 ° C. while stirring while introducing nitrogen gas. Thereto, 0.052 parts by mass of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd., Luperox (registered trademark) 570) and 5.1 parts by mass of a base oil (manufactured by SK, YUBASE4) as a polymerization initiator. 12. While adding the mixed solution, 0.21 parts by mass of t-amyl peroxyisononanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 570) as a polymerization initiator is used as a base oil (manufactured by SK, YUBASE4). Solution polymerization was allowed to proceed while dripping the solution dissolved in 7 parts by mass over 4 hours, followed by further aging for 2 hours. The base oil solution (polymer concentration 25 mass%) of the polymer 11 was obtained by adding and diluting 140.0 mass parts of base oil (the SKBASE make, YUBASE4) there.

(2-12) Comparative Example 3
10 parts by mass of macromonomer 2 obtained in Comparative Example 2, 40 parts by mass of methyl methacrylate (MMA), 20 parts by mass of SMA, and 30 parts by mass of decyltetradecyl methacrylate (DTDMA) were charged into a reaction vessel, and further a base oil (SK Corporation). Manufactured, YUBASE4) 124.2 parts by mass and 0.05 parts by mass of pentaerythritol tetrakis (mercaptoacetate) were added, and the contents were heated to 105 ° C. while stirring while introducing nitrogen gas. Thereto, 0.12 parts by mass of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Co., Ltd., Luperox (registered trademark) 570) and 8.2 parts by mass of a base oil (manufactured by SK, YUBASE4) as a polymerization initiator. While adding the mixed solution, 0.051 parts by mass of t-amylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi, Luperox (registered trademark) 575) as a polymerization initiator was added to the base oil (manufactured by SK, YUBASE4) Solution polymerization was allowed to proceed while dropping a solution dissolved in 3.4 parts by mass over 2 hours, followed by further aging for 4 hours. The base oil solution (copolymer concentration 30 mass%) of the polymer 12 was obtained by adding and diluting 97.3 mass parts of base oil (the SKBASE make, YUBASE4) there.

(3) Results Tables 2 and 3 show the production conditions of each Example and Comparative Example, and the physical property evaluation results of the obtained polymers. Examples 1 to 9 represent examples in which a polymer component containing a macromonomer was polymerized in the presence of a metal alkoxide, and Comparative Examples 1 to 3 were polymerizations of a polymer component containing a macromonomer in the absence of a metal alkoxide. The example which performed is shown. In Examples 1 to 9, the average polymerization rate was higher than those of Comparative Examples 1 to 3, and the average polymerization rate was 90% or more in all by the polymerization reaction for 6 hours. The average polymerization rate of the (meth) acrylate monomer having an aliphatic hydrocarbon group having 6 or more carbon atoms (indicated as “C6 or more average” in Table 3) was also 86% or more in Examples 1 to 9. . On the other hand, in Comparative Examples 1 to 3, the average polymerization rate does not reach 90% even when the polymerization reaction is performed for 6 hours, and the average polymerization rate of the (meth) acrylate monomer having an aliphatic hydrocarbon group having 6 or more carbon atoms. Was also lower than Examples 1-9. As for the polymerization rate, Examples 1 to 9 were generally faster than Comparative Examples 1 to 3. In Examples 4 and 6 in which lauric acid was added as an acidic substance to the polymerization system, the initial average polymerization rate was high.

  The (meth) acrylate polymer obtained by the present invention can be used by adding to a lubricating oil as a viscosity index improver, for example. The lubricating oil thus obtained can be suitably used for drive system lubricating oil, hydraulic oil, engine oil and the like.

Claims (10)

  A (meth) acrylate comprising a step of polymerizing a monomer component containing a (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms in the presence of a metal alkoxide. A method for producing a polymer.   The method for producing a (meth) acrylate polymer according to claim 1, wherein the monomer component further comprises a (meth) acrylate monomer (b) having an aliphatic hydrocarbon group having 1 to 5 carbon atoms.   The method for producing a (meth) acrylate polymer according to claim 1 or 2, wherein the aliphatic hydrocarbon group of the monomer (a) has 12 or more carbon atoms.   The (meth) according to any one of claims 1 to 3, wherein at least a (meth) acrylate monomer (a1) having an aliphatic hydrocarbon group having 50 or more carbon atoms is used as the monomer (a). A method for producing an acrylate polymer.   The metal alkoxide is at least one transition metal alkoxide selected from Group 4 elements, Group 5 elements, Group 12 elements, Group 14 elements, and Group 15 elements. The manufacturing method of the (meth) acrylate type polymer as described in claim | item.   The method for producing a (meth) acrylate polymer according to any one of claims 1 to 5, wherein the monomer component is polymerized in a solvent containing a high boiling point solvent having a boiling point of 200 ° C or higher.   A method for producing a viscosity index improver, wherein a viscosity index improver is obtained by the production method according to claim 1. A step of obtaining a (meth) acrylate polymer by the production method according to claim 1;
And a step of blending the (meth) acrylate polymer with a lubricating oil to obtain a lubricating oil composition. A viscosity index improver containing a (meth) acrylate polymer having a unit derived from a (meth) acrylate monomer (a) having an aliphatic hydrocarbon group having 6 or more carbon atoms,
The content of the monomer (a) in the viscosity index improver is X, and the content of the unit derived from the monomer (a) contained in the (meth) acrylate polymer in the viscosity index improver is Y. Viscosity index improver, wherein X / (X + Y) is 0.18 or less.   A lubricating oil composition comprising the viscosity index improver according to claim 9 and a lubricating oil.