JP7354293B2 - Viscosity index improver comprising conjugated diene graft polymer and oil composition - Google Patents

Description

The present invention relates to a viscosity index improver made of a conjugated diene-based graft polymer, and an oil composition containing a base oil and the viscosity index improver.

Lubricating oils used as engine oils and automatic transmission fluids commonly contain additives called viscosity index improvers to improve their viscosity properties. Examples of these viscosity index improvers include olefin copolymers, polymethacrylates, styrene/hydrogenated diene block polymers, and the like. Viscosity index improvers are subjected to high shear in the environment in which they are used, so long-term use causes a decrease in viscosity due to a decrease in molecular weight, resulting in a decrease in the necessary lubricating performance. Due to increased environmental awareness in recent years, viscosity index improvers with higher shear stability are required.

It is known that a viscosity index improver made of a star-shaped polymer has better shear stability than a linear polymer due to its molecular structure. For example, Patent Document 1 describes that a viscosity index improver made of star-shaped hydrogenated polyisoprene obtained by coupling living polyisoprene synthesized by anionic polymerization with divinylbenzene has excellent shear stability. Further, Patent Document 2 describes that the performance as a viscosity index improver can be further improved by optimizing the structure of the arm chains of a star-shaped polymer.

U.S. Patent No. 4,116,917 Japanese Patent Application Publication No. 2005-23320

However, due to stricter environmental regulations in recent years, viscosity index improvers with higher shear stability are required. It has been found that the star-shaped polymer described in the above-mentioned patent document has a limit in improving shear stability due to the polyvinyl aromatic compound forming the core. Although the above-mentioned patent documents describe the appropriate structure of the arm chains, there is no study at all about the relationship between the core structure of the star-shaped polymer and shear stability.

The present invention has been made in view of the above circumstances, and aims to provide a new viscosity index improver having higher shear stability and an oil composition containing the viscosity index improver.

As a result of intensive studies by the present inventors, at least one compound selected from the group consisting of a conjugated diene and an aromatic vinyl compound is added to the main chain of a polymer containing a structural unit derived from a conjugated diene through a branch point. It was discovered that a viscosity index improver made of a specific conjugated diene-based graft polymer to which a side chain made of a polymer containing a structural unit derived from a monomer is bonded has high shear stability, and the present invention was completed. reached.

That is, the present invention provides the following [1] to [9].
[1] A viscosity index improver comprising a conjugated diene graft polymer,
The conjugated diene-based graft polymer has conjugated diene and A side chain (b) made of a polymer containing a structural unit derived from at least one monomer selected from the group consisting of aromatic vinyl compounds is bonded,
The main chain (a) is connected to a branch point directly or through a connecting chain,
The side chain (b) is directly bonded to the branch point,
A viscosity index improver, wherein the heteroatom is at least one selected from the group consisting of Si, Sn, Ge, Pb, P, B, and Al.
[2] The viscosity index improver according to [1], wherein the heteroatom is Si.
[3] The average number W of side chains (b) directly bonded to the branch point per molecule of the conjugated diene graft polymer and the average number Y of branch points per molecule of the conjugated diene graft polymer are expressed by the following formula: (5);
0.5≦(W/Y) (5)
The viscosity index improver according to [1] or [2], which satisfies the following relationship.
[4] The viscosity index improver according to any one of [1] to [3], wherein 50 mol% or more of the carbon-carbon double bonds in the conjugated diene graft polymer are hydrogenated.
[5] At least one functional group (c) selected from the group consisting of an alkoxy group and a hydroxyl group is directly bonded to at least one of the branch points,
The average number X of functional groups (c) directly bonded to the branch points per molecule of the conjugated diene graft polymer and the average number Y of branch points per molecule of the conjugated diene graft polymer are expressed by the following formula (3- 2);
0<(X/Y)<1 (3-2)
The viscosity index improver according to any one of [1] to [4], which satisfies the following relationship.
[6] The average number X of functional groups (c) directly bonded to the branch point per molecule of the conjugated diene graft polymer is expressed by the following formula (4-2);
0<X≦10 (4-2)
The viscosity index improver according to any one of [1] to [5], which satisfies the following relationship.
[7] The viscosity index improver according to any one of [1] to [6], which has a halogen content of 1000 ppm or less.
[8] An oil composition comprising a base oil and the viscosity index improver according to any one of [1] to [7].
[9] An oil composition comprising a base oil and the conjugated diene graft polymer according to [1].

According to the present invention, there are provided a viscosity index improver made of a conjugated diene graft polymer having high shear stability, and an oil composition containing the viscosity index improver.

The present invention will be explained in detail below.
The viscosity index improver of the present invention comprises a conjugated diene graft polymer.
The conjugated diene-based graft polymer has conjugated diene and A side chain (b) made of a polymer containing a structural unit derived from at least one monomer selected from the group consisting of aromatic vinyl compounds is bonded,
The main chain (a) is connected to a branch point directly or through a connecting chain,
The side chain (b) is directly bonded to the branch point,
A conjugated diene-based graft polymer in which the heteroatom is at least one selected from the group consisting of Si, Sn, Ge, Pb, P, B, and Al.
In addition, in the present invention, the graft polymer refers to a polymer having a main chain consisting of a polymer chain as a trunk and a side chain consisting of a polymer chain as a branch, and the monomer constituting the polymer chain serving as the main chain. The structural unit derived from the polymer chain and the structural unit derived from the monomer constituting the polymer chain serving as the side chain may be the same or different.

<Main chain (a)>
The conjugated diene graft polymer used in the present invention has a main chain (a) made of a polymer containing a structural unit derived from a conjugated diene. Note that the main chain contained in the conjugated diene-based graft polymer used in the present invention refers to the entire structural unit portion derived from all monomers containing the conjugated diene that constitute the main chain. For example, when producing a conjugated diene-based graft polymer by the production method described below, an unmodified conjugated diene-based polymer ( Refers to the entire portion derived from F'). For example, if the unmodified conjugated diene polymer (F') contains a structural unit derived from butadiene with a vinyl bond, the bond is attached to a carbon atom in the polymer skeleton (-(C-C) _n -). The main chain includes the -CH═CH ₂ part (the part that becomes -CH-CH ₂ - when a modifying compound is added).

The main chain (a) contains units other than structural units derived from vinyl monomers such as conjugated dienes and aromatic vinyl compounds (for example, Si atoms derived from coupling agent residues, It is preferable not to contain a unit having an N atom. If a unit other than the structural unit derived from the vinyl monomer is included in the main chain skeleton, the bond between the heteroatom and carbon, which is a branching point, will be broken under conditions such as shearing or heat, as described below. Because the main chain skeleton is cleaved, physical properties tend to deteriorate. Note that the polymer chain terminal serving as the main chain may have a group other than the structural unit derived from the monomer.

The main chain (a) includes a structural unit derived from a conjugated diene as a structural unit derived from a monomer constituting the polymer. Examples of the conjugated diene include butadiene (1,3-butadiene), isoprene; 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3 - Conjugated dienes other than butadiene and isoprene such as hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene, farnesene, and chloroprene can be mentioned. Among these conjugated dienes, butadiene and isoprene are preferred, and butadiene is more preferred. The conjugated diene serving as the structural unit derived from the above-mentioned conjugated diene may be used alone or in combination of two or more.

Main chain (a) is a structural unit in which 50% by mass or more of the structural units derived from all monomers constituting the polymer is derived from at least one monomer selected from the group consisting of butadiene and isoprene. In one preferred embodiment, The total content of structural units derived from butadiene and isoprene is preferably 60 to 100% by mass, and preferably 70 to 100% by mass, based on the structural units derived from all monomers of the main chain (a). It is more preferable.

Structural units derived from monomers other than butadiene and isoprene that may be included in the main chain (a) include structural units derived from conjugated dienes other than butadiene and isoprene, aromatic vinyl Examples include structural units derived from compounds.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, -Dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 1-vinylnaphthalene, 2 -vinylnaphthalene, vinylanthracene, N,N-diethyl-4-aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, and divinylbenzene. Among these aromatic vinyl compounds, styrene, α-methylstyrene, and 4-methylstyrene are preferred. The aromatic vinyl compound serving as the structural unit derived from the above-mentioned aromatic vinyl compound may be used alone or in combination of two or more.

The content of structural units derived from monomers other than those derived from butadiene and isoprene in the main chain (a) is preferably 50% by mass or less, more preferably 40% by mass or less, More preferably, it is 30% by mass or less. For example, if the structural unit derived from the aromatic vinyl compound is below the above range, the shear stability of the resulting viscosity index improver made of the conjugated diene graft polymer tends to improve. Furthermore, the processability of the resulting conjugated diene graft polymer tends to be improved. Furthermore, when a conjugated diene graft polymer is produced by the production method described below, the reactivity tends to improve when the unmodified conjugated diene polymer (F') is modified with a functional group.

In one embodiment, the weight average molecular weight (Mw) of the main chain (a) is preferably 1,000 or more and 500,000 or less, more preferably 2,000 or more and 300,000 or less, and 2,000 or more and 100,000 or less. The following are more preferred. In the present invention, Mw of the main chain (a) is, for example, when producing a conjugated diene-based graft polymer by the production method described below, a functional group-modified conjugated diene-based polymer (F) or an unmodified conjugated diene-based polymer. This is the Mw of the polymer (F'). When the Mw of the main chain (a) is within the above range, process passability during production tends to be excellent, economical efficiency tends to be good, and the viscosity index of the resulting conjugated diene graft polymer is improved. The agent tends to have a good balance between thickening effect and shear stability. In the present invention, unless otherwise specified, Mw is a weight average molecular weight in terms of standard polystyrene determined from gel permeation chromatography (GPC) measurements. The conjugated diene-based graft polymer used in the present invention may be a polymer that has been hydrogenated, for example, by a method such as a hydrogenation step described below. In the case of a hydrogenated hydrogenated conjugated diene graft polymer, the Mw of the main chain (a) means the Mw in the state before hydrogenation.

The vinyl content of the main chain (a) is not particularly limited, but is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less. The vinyl content of the main chain (a) is preferably 0.5 mol% or more, more preferably 1 mol% or more. In the present invention, "vinyl content" refers to 1,2-bonds, 3,4-bonds (in cases other than farnesene), and Structural units derived from conjugated dienes that are bonded with 3,13-bonds (in the case of farnesene) (bonds with other than 1,4-bonds (in cases other than farnesene) and 1,13-bonds (in the case of farnesene)) conjugated diene (structural units derived from conjugated dienes). In the present invention, also in the case of hydrogenated hydrogenated conjugated diene-based graft polymers, the vinyl content determined from the bonding form of the structural units derived from the conjugated diene contained in the polymer before hydrogenation is Defined as the vinyl content of The vinyl content is derived from conjugated dienes that are bonded through 1,2-bonds, 3,4-bonds (for cases other than farnesene), and 3,13-bonds (for farnesene) using ¹ H-NMR. From the area ratio of the peak derived from the structural unit derived from the structural unit and the peak derived from the structural unit derived from the conjugated diene bonded by 1,4-bond (in the case of other than farnesene) and 1,13-bond (in the case of farnesene). calculate.

The vinyl content of the main chain (a) can be designed depending on the purpose. For example, if the vinyl content is less than 50 mol%, the glass transition temperature (Tg) of the main chain (a) described below will be low. Therefore, the resulting conjugated diene graft polymer tends to have excellent fluidity and low-temperature properties. Moreover, when the content is 50 mol% or more, the resulting conjugated diene graft polymer tends to have excellent reactivity. Further, when the main chain (a) is composed only of structural units derived from butadiene, the conjugated diene graft polymer is a hydrogenated hydrogenated conjugated diene graft polymer, and its Mw is relatively large (e.g. When Mw is about 10,000 or more), the vinyl content is preferably 25 mol % or more in order to prevent performance deterioration due to crystallization after hydrogenation.

In addition, when producing a conjugated diene-based graft polymer by the production method described below, the vinyl content of the main chain (a) is, for example, the vinyl content of the unmodified conjugated diene-based polymer ( A desired value can be obtained by controlling the type of solvent used in producing F'), the polar compound used as necessary, the polymerization temperature, etc.

The glass transition temperature (Tg) of the main chain (a) is derived from the vinyl content of structural units derived from conjugated dienes such as butadiene, isoprene, and other conjugated dienes, the type of conjugated diene, and monomers other than conjugated dienes. Although it may vary depending on the content of structural units, etc., it is preferably -150 to 50°C, more preferably -130 to 50°C, and even more preferably -130 to 30°C. When Tg is within the above range, for example, increase in viscosity can be suppressed and handling becomes easy. In the present invention, Tg is the value of the peak top of DDSC determined by differential scanning calorimetry (DSC) measurement.

<Side chain (b)>
The conjugated diene-based graft polymer used in the present invention has a side chain (b) made of a polymer containing a structural unit derived from at least one monomer selected from the group consisting of a conjugated diene and an aromatic vinyl compound.

The side chain (b) contains a structural unit derived from at least one monomer selected from the group consisting of a conjugated diene and an aromatic vinyl compound as a structural unit derived from a monomer constituting the polymer.

Specific examples of the conjugated diene that can constitute the structural unit derived from the monomer of the side chain (b) are the same as the specific examples of the conjugated diene that can constitute the structural unit derived from the monomer of the main chain (a). be. Among the conjugated dienes that are structural units derived from the conjugated diene contained in the side chain (b), butadiene and isoprene are preferred. The conjugated diene serving as the structural unit derived from the above-mentioned conjugated diene may be used alone or in combination of two or more.

Specific examples of aromatic vinyl compounds that can constitute a structural unit derived from the monomer of the side chain (b) include aromatic vinyl compounds that can constitute a structural unit derived from the monomer of the main chain (a). Same as the specific example. Among these aromatic vinyl compounds, styrene, α-methylstyrene, and 4-methylstyrene are preferred. The aromatic vinyl compound serving as the structural unit derived from the above-mentioned aromatic vinyl compound may be used alone or in combination of two or more.

The side chain (b) is selected from the group consisting of a homopolymer, a conjugated diene, and an aromatic vinyl compound, in which the skeleton of the polymer chain is composed only of structural units derived from one type of conjugated diene or one type of aromatic vinyl compound. A copolymer consisting of structural units derived from two or more monomers, or one or more monomers selected from the group consisting of conjugated dienes and aromatic vinyl compounds, and other than conjugated dienes and aromatic vinyl compounds. It may also be a copolymer consisting of a structural unit derived from a vinyl monomer. Further, the polymer constituting the side chain (b) may be one type alone, or two or more types having different structures.

The ratio of structural units derived from a conjugated diene that can constitute the side chain (b) is not particularly limited, but is preferably 50% by mass or more, more preferably 70% by mass or more, and 80% by mass or more. It is particularly preferable that the amount is 100% by mass. When the ratio of structural units derived from conjugated diene is 50% by mass or more, the shear stability of the resulting viscosity index improver made of the conjugated diene graft polymer tends to improve.

Among the conjugated dienes that can constitute the side chain (b), butadiene and isoprene are preferably included. The structural unit derived from butadiene and isoprene that can constitute the side chain (b) is preferably 50% by mass or more, more preferably 70% by mass or more, particularly preferably 80% by mass or more. , 100% by mass. The mass ratio of butadiene and isoprene (butadiene/isoprene) that can constitute the side chain (b) is preferably in the range of 0/100 to 50/50, more preferably in the range of 0/100 to 30/70, and A range of /100 to 20/80 is particularly preferred. When the ratio of structural units derived from butadiene and isoprene and the mass ratio of butadiene and isoprene are within the above ranges, the obtained viscosity index improver made of the conjugated diene graft polymer has an excellent balance between the thickening effect and low-temperature properties. There is a tendency.

The ratio of structural units derived from aromatic vinyl compounds that can constitute the side chain (b) is not particularly limited, but is preferably 50% by mass or less, more preferably 30% by mass or less, and 20% by mass. It is particularly preferable that the amount is below, and may be 0% by mass. When the ratio of the structural units derived from the aromatic vinyl compound is 50% by mass or less, the shear stability of the resulting viscosity index improver made of the conjugated diene graft polymer tends to improve.

The side chain (b) includes units other than structural units derived from vinyl monomers such as conjugated dienes and aromatic vinyl compounds (for example, Si atoms derived from coupling agent residues, etc.) in the polymer chain skeleton. It is preferable not to contain a unit having an N atom. Conditions such that when a unit other than the structural unit derived from the vinyl monomer is included in the polymer chain skeleton of the side chain (b), the bond between the heteroatom and carbon, which is a branching point described below, is broken; Alternatively, the polymer chain skeleton of the side chain (b) is cleaved by shearing or heat, so that the physical properties tend to deteriorate. Note that the end of the polymer chain, which becomes a side chain, may have a group other than the structural unit derived from the monomer.

In one embodiment, the weight average molecular weight (Mw) of the side chain (b) is preferably 1,000 or more and 300,000 or less, more preferably 10,000 or more and 200,000 or less, and 30,000 or more and 150,000 or less. The following are more preferred. In the present invention, the Mw of the side chain (b) is, for example, the Mw of the active terminal polymer (I) when a conjugated diene graft polymer is produced by the production method described below. When the Mw of the side chain (b) is within the above range, process passability during production tends to be excellent, economical efficiency tends to be good, and the viscosity index of the resulting conjugated diene graft polymer is improved. The agent tends to have a good balance between thickening effect and shear stability. The conjugated diene-based graft polymer used in the present invention may be a polymer that has been hydrogenated, for example, by a method such as a hydrogenation step described below. In the case of a hydrogenated conjugated diene graft polymer, the Mw of the side chain (b) is the Mw before hydrogenation.

The vinyl content of the side chain (b) is not particularly limited, but is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 20 mol% or less. The vinyl content of the side chain (b) is preferably 0.5 mol% or more, more preferably 1 mol% or more. For example, when producing a conjugated diene-based graft polymer by the production method described below, the vinyl content of the side chain (b) can be determined by determining the vinyl content of the main chain (a) by the ¹ H-NMR spectrum of the active terminal polymer (I). Calculate in the same way as in the case of . When the vinyl content of the side chain (b) is within the above range, the resulting viscosity index improver made of the conjugated diene graft polymer tends to have an excellent balance between the thickening effect and low-temperature properties. Further, when the side chain (b) is composed only of structural units derived from butadiene, the conjugated diene graft polymer is a hydrogenated conjugated diene graft polymer, and its Mw is relatively large (e.g. When Mw is about 10,000 or more), the vinyl content is preferably 25 mol % or more in order to prevent performance deterioration due to crystallization after hydrogenation.

In addition, when producing a conjugated diene-based graft polymer by the production method described below, the vinyl content of the side chain (b) can be determined by, for example, A desired value can be obtained by controlling the type of solvent used during production, the polar compound used if necessary, the polymerization temperature, etc.

The glass transition temperature (Tg) of the side chain (b) can vary depending on the vinyl content of the structural unit derived from the conjugated diene, the type of conjugated diene, the content of the structural unit derived from a monomer other than the conjugated diene, etc. However, the temperature is preferably -150 to 50°C, more preferably -130 to 50°C, and even more preferably -130 to 30°C. When Tg is within the above range, for example, increase in viscosity can be suppressed and handling becomes easy.

The chain (b) is a block copolymer chain containing a polymer block (b1) containing a structural unit derived from an aromatic vinyl compound and a polymer block (b2) containing a structural unit derived from a conjugated diene compound. It may be.

The polymer block (b1) contains a structural unit derived from an aromatic vinyl compound (hereinafter sometimes abbreviated as "aromatic vinyl compound unit"). In the polymer block (b1), the content of aromatic vinyl compound units is preferably more than 70 mol%, more preferably more than 70 mol%, from the viewpoint of improving the physical properties of the oil composition containing the obtained conjugated diene graft polymer. The content is 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably substantially 100 mol%.

Examples of the aromatic vinyl compounds include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, β-methylstyrene, 2,6-dimethylstyrene, and 2,4-dimethylstyrene. , α-methyl-o-methylstyrene, α-methyl-m-methylstyrene, α-methyl-p-methylstyrene, β-methyl-o-methylstyrene, β-methyl-m-methylstyrene, β-methyl- p-methylstyrene, 2,4,6-trimethylstyrene, α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, β-methyl-2,6-dimethylstyrene, β-methyl -2,4-dimethylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, α-chloro-o-chlorostyrene, α-chloro- m-chlorostyrene, α-chloro-p-chlorostyrene, β-chloro-o-chlorostyrene, β-chloro-m-chlorostyrene, β-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, α-chloro-2,6-dichlorostyrene, α-chloro-2,4-dichlorostyrene, β-chloro-2,6-dichlorostyrene, β-chloro-2,4-dichlorostyrene, ot-butylstyrene , m-t-butylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, o- Examples include bromomethylstyrene, m-bromomethylstyrene, p-bromomethylstyrene, styrene derivatives substituted with a silyl group, indene, vinylnaphthalene, and N-vinylcarbazole. These aromatic vinyl compounds may be used alone or in combination of two or more.

Among these, from the viewpoint of manufacturing cost and physical property balance, styrene, α-methylstyrene, p-methylstyrene, and mixtures thereof are preferred, and styrene is more preferred.

Unless it interferes with the purpose and effects of the present invention, the polymer block (b1) may be a structural unit derived from an unsaturated monomer other than the aromatic vinyl compound (hereinafter referred to as "other unsaturated monomer unit"). ) may be contained in the polymer block (b1) in a proportion of 30 mol% or less, preferably less than 20 mol%, more preferably less than 15 mol%, even more preferably It is less than 10 mol%, even more preferably less than 5 mol%, particularly preferably 0 mol%.

Examples of the other unsaturated monomers include butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadiene, myrcene, farnesene, isobutylene, methyl methacrylate, methyl vinyl ether, β- At least one member selected from the group consisting of pinene, 8,9-p-menthene, dipentene, methylenenorbornene, 2-methylenetetrahydrofuran, etc., can be mentioned. When the polymer block (b1) contains the other unsaturated monomer units, the bonding form is not particularly limited and may be either random or tapered.

When the chain (b) is the block copolymer chain, the Mw of the polymer block (b1) is not particularly limited, but the Mw of the polymer block (b1) is preferably 1,000 to 100,000. , more preferably 2,000 to 70,000, still more preferably 3,000 to 30,000. By having the chain (b) of the conjugated diene graft polymer having the polymer block (b1) having Mw within the above range, properties such as shear stability of the oil composition containing the conjugated diene graft polymer can be improved. It tends to improve further.

The content of the polymer block (b1) in the conjugated diene graft polymer is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, It is particularly preferably 40% by mass or less. When the content of the polymer block (b1) is below the upper limit value, the properties such as shear stability of the resulting oil composition containing the conjugated diene graft polymer tend to be further improved. Further, the content of the polymer block (b1) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. When the content of the polymer block (b1) is at least the lower limit, the conjugated diene graft polymer tends to be easily produced. The content of the polymer block (b1) in the conjugated diene graft polymer can be determined by ¹ H-NMR measurement.

When the chain (b) is the block copolymer chain, it is sufficient that it contains at least one of the polymer blocks (b1). When the block copolymer chain contains two or more polymer blocks (b1), these polymer blocks (b1) may be the same or different. Further, when the different chains (b) are also the block copolymer chains, the polymer blocks (b1) contained in these two or more copolymer chains may be the same or different. . In addition, in the present invention, "the polymer blocks are different" refers to the monomer units constituting the polymer blocks, Mw, stereoregularity, and when there are multiple monomer units, the ratio of each monomer unit and the form of copolymerization. It means that at least one of (random, gradient, block) is different.

When the chain (b) is the block copolymer chain, the contained polymer block (b2) is a structural unit derived from a conjugated diene compound (hereinafter sometimes abbreviated as "conjugated diene compound unit") ). In the polymer block (b2), the content of conjugated diene compound units is preferably 50 mol% or more, more preferably 70 mol%, from the viewpoint of improving the properties of the resulting oil composition containing the conjugated diene graft polymer. Above, it is more preferably 90 mol% or more, and particularly preferably substantially 100 mol%.

Examples of the conjugated diene compound include butadiene, isoprene, hexadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, myrcene, farnesene, and the like. These conjugated diene compounds may be used alone or in combination of two or more.

Among these, butadiene, isoprene, and farnesene are preferred. In addition, one preferable embodiment includes isoprene as the conjugated diene compound. For example, as the conjugated diene compound, it is preferable to use isoprene alone, a combination of isoprene and butadiene, a combination of isoprene and farnesene, and the like.

For example, when isoprene and butadiene are used together, the mixing ratio [isoprene/butadiene] (mass ratio) is not particularly limited, but is preferably 5/95 to 95/5, more preferably 10/90 to 90/10. , more preferably 40/60 to 70/30, particularly preferably 45/55 to 65/35. In addition, when the mixing ratio [isoprene/butadiene] is expressed as a molar ratio, it is preferably 5/95 to 95/5, more preferably 10/90 to 90/10, still more preferably 40/60 to 70/30, especially Preferably it is 45/55 to 55/45.

When the chain (b) is the block copolymer chain described above and contains two or more polymer blocks (b2), the polymer blocks (b2) may be the same or different. It's okay. Furthermore, when the different chains (b) are also block copolymer chains, the polymer blocks (b2) contained in these two or more copolymer chains may be the same or different. Good too.

The vinyl content of the conjugated diene compound unit of the polymer block (b2) is not particularly limited, but the vinyl content is preferably 1 to 60 mol%, more preferably 2 to 40 mol%, and even more preferably 3 to 30 mol%. %, particularly preferably 4 to 20 mol %. In addition, when producing a conjugated diene graft polymer by anionic polymerization described below, the vinyl content of the polymer block or polymer chain depends on the type of solvent used, the polar compound used as necessary, A desired value can be obtained by controlling the polymerization temperature and the like.

The polymer block (b2) may contain a structural unit derived from a polymerizable monomer other than the conjugated diene compound, as long as it does not interfere with the purpose and effects of the present invention. In this case, in the polymer block (b2), the content of structural units derived from polymerizable monomers other than the conjugated diene compound is preferably less than 50 mol%, more preferably less than 30 mol%, and Preferably it is less than 20 mol%, even more preferably less than 10 mol%, particularly preferably 0 mol%.

Examples of the other polymerizable monomers include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, 2,4-dimethylstyrene, N - Aromatic vinyl compounds such as vinylcarbazole, vinylnaphthalene and vinylanthracene, as well as methyl methacrylate, methyl vinyl ether, β-pinene, 8,9-p-menthene, dipentene, methylenenorbornene, 2-methylenetetrahydrofuran, 1,3- Preferred examples include at least one compound selected from the group consisting of cyclopentadiene, 1,3-cyclohexadiene, 1,3-cycloheptadiene, 1,3-cyclooctadiene, and the like.

When the chain (b) is the block copolymer chain, the Mw of the polymer block (b2) is not particularly limited, but from the viewpoint of improving the physical properties of the oil composition containing the resulting conjugated diene graft polymer. Therefore, the Mw of the polymer block (b2) is preferably 5,000 to 250,000, more preferably 10,000 to 200,000, still more preferably 20,000 to 150,000, particularly preferably is between 25,000 and 120,000, most preferably between 30,000 and 100,000.

When the chain (b) is the block copolymer chain, it is sufficient that it has at least one of the polymer blocks (b2). When the block copolymer chain has two or more polymer blocks (b2), these polymer blocks (b2) may be the same or different. Further, when the different chains (b) are also the block copolymer chains, the polymer blocks (b2) contained in these two or more copolymer chains may be the same or different. .

When the chain (b) is the block copolymer chain described above, the block copolymer chain may include polymer blocks other than the polymer blocks (b1) and (b2) as long as it does not interfere with the purpose and effect of the present invention. It may also contain polymer blocks composed of other monomers. When the chain (b) contains the block copolymer chain, the total content of the polymer block (b1) and the polymer block (b2) with respect to the entire chain (b) is 90% by mass or more. It is preferably at least 95% by mass, more preferably at least 95% by mass, particularly preferably substantially 100% by mass. When the content is 90% by mass or more, the physical properties of the resulting oil composition containing the conjugated diene graft polymer tend to improve.

When the chain (b) is the block copolymer chain, the bonding format is not limited as long as the block copolymer chain contains the polymer block (b1) and the polymer block (b2). The bonding mode may be linear, branched, radial, or a combination of two or more of these. Further, these polymer blocks may be directly bonded to each other or may be indirectly bonded to each other via another polymer block. Among these, it is preferable that the polymer block (b1) and the polymer block (b2) are bonded together directly and in a linear form. As an example of such a bonding format, if the polymer block (b1) is represented by b1 and the polymer block (b2) is represented by b2, and each polymer block is represented in order from the closest to the branching point, b2-b1 Diblock copolymer chain shown, triblock copolymer chain shown b2-b1-b2 or b1-b2-b1, tetrablock shown b2-b1-b2-b1 or b1-b2-b1-b2 Examples include copolymer chains, pentablock copolymer chains represented by b2-b1-b2-b1-b2 or b1-b2-b1-b2-b1.

Among these, when the polymer blocks are expressed in order from the closest to the branching point, the physical properties of the resulting oil composition containing the conjugated diene graft polymer are more easily improved and the production is easier. Diblock copolymer chains represented by b2-b1 are preferred.

<Conjugated diene graft polymer>
In the conjugated diene graft polymer used in the present invention, the side chain (b) is bonded to the main chain (a) via one heteroatom having a valence of 3 or more, which is a branch point.

The main chain (a) is bonded to the branch point directly or through a connecting chain, and the side chain (b) is bonded directly to the branch point. Here, the expression "directly bonded to a branch point" means that a heteroatom serving as a branch point is directly bonded to a structural unit portion derived from a monomer constituting the main chain. A branch point and a bond through a connecting chain is one where one end of the connecting chain is bonded to a structural unit derived from a monomer that makes up the main chain, and the other end of the connecting chain is a branch point. It means that the heteroatoms are directly bonded. For example, when a branch point is bonded to a structural unit derived from 1,2-bonded butadiene, the case represented by the following formula (III-1) is a case where the main chain is directly bonded to the branch point. , the case represented by the following formula (III-2) is the case where the main chain is bonded to the branch point through a connecting chain.

In the above formulas (III-1) and (III-2), Z ⁰ is a heteroatom serving as a branching point, and R ^2a is a connecting chain. Although R ^2a is a divalent organic group, an alkylene group which may have a hetero atom is preferable.

When the branching portion from the main chain including the bonding form between the main chain (a) and the branch point is shown by a chemical formula, a form in which the branch point is directly bonded to the main chain (a) as shown in the following formula (III-3) There are branched moieties including a form in which the branch point is bonded to a branch point through a linking chain as shown in the following formula (III-4). Among these branched moieties, a branched structure including a form bonded to a branch point through a linking chain as shown in formula (III-4) is desirable.

In the above formulas (III-3) and (III-4), the wavy line portion is the main chain (a), Z ¹ is the branch point, P is the side chain (b), and R ^2b is the connecting chain.

In formulas (III-3) and (III-4), Z ¹ is Si, Sn, Ge, Pb, P, B, or Al, and R ^2b has 1 to 1 carbon atoms, which may have a hetero atom. 12 alkylene group, R ³ is an aryl group having 6 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or a hydrogen atom, and P is at least one selected from the group consisting of conjugated dienes and aromatic vinyl compounds. It represents a polymer chain containing a structural unit derived from one monomer, and V represents an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. N represents the valence of Z, and m and n are each independently integers that satisfy the following formula (1);
0≦m≦N-1, 0≦n≦N-1 (1)
When m is 2 or more, P may be the same or different; when n is 2 or more, V may be the same or different; when N-1-m-n is 2 or more, R ³ is They may be the same or different, and when a plurality of side chains are included in the main chain, Z ¹ may be the same or different. However, P (side chain (b)) must be bonded to at least one branch point (Z ¹ ) contained in the conjugated diene graft polymer used in the present invention. In this case, the conjugated diene-based graft polymer satisfies the relationship of formula (5) described below. In addition, in the conjugated diene-based graft polymer used in the present invention, it is sufficient that there is ^one or more side chains for one main chain ^. ) may be included, but in that case Z ¹ is also defined as a branch point.

The above-mentioned branch point consists of one heteroatom, and the heteroatom has a valence of 3 or more. The heteroatom having a valence of 3 or more and serving as a branching point is at least one selected from the group consisting of Si, Sn, Ge, Pb, P, B, and Al. Among these heteroatoms, Si, Sn, and B are preferred, and Si is more preferred.

R ³ in the above formulas (III-3) and (III-4) represents an aryl group having 6 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or a hydrogen atom. Among these, alkyl groups having 1 to 6 carbon atoms are preferred, and n-butyl, sec-butyl, n-propyl, isopropyl, ethyl, and methyl groups are more preferred. R ³ may be used alone or in combination of two or more selected from the above group. R ³ may be a single group or two or more groups.

The alkylene group having 1 to 12 carbon atoms and having a hetero atom that can serve as R ^2b is preferably an alkylene group having 1 to 12 carbon atoms, and SR ^2b' (R ^2b' is an alkylene group having 1 to 12 carbon atoms). ) is more preferable.

In the conjugated diene-based graft polymer used in the present invention, at least one branch point has at least one group selected from the group consisting of an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. c) may be combined. Therefore, the above formulas (III-3) and (III-4) may contain a group V (functional group (c)). Examples of the alkoxy group include methoxy group, ethoxy group, and propoxy group. Among the functional groups (c), from the viewpoint of affinity with polar materials and stability of the conjugated diene polymer, at least one group selected from the group consisting of an alkoxy group and a hydroxyl group is preferable, and a methoxy group, At least one group selected from the group consisting of an ethoxy group and a hydroxyl group is more preferred. The functional group (c) may be a single type of group, or may be a plurality of groups of two or more types.

In the conjugated diene graft polymer used in the present invention, when focusing on the heteroatom that is a branch point contained in the graft polymer, the valence of the hetero atom is N, and it is directly bonded to one branch point. When the average number of side chains (b) is defined as B, the following formula (2) is satisfied. By satisfying this condition, the branch point is bonded to the main chain (a) directly or through a connecting chain, and the conjugated diene graft polymer used in the present invention contains at least the side chain (b). Become.
N-1≧B, B>0 (2)

As mentioned above, the conjugated diene graft polymer used in the present invention has at least one functional group (c ) may be combined. In that case, when the average number of the functional groups (c) bonded to one branch point is C, the valence number N of the heteroatoms and the average number B of the side chains (b) are expressed by the following formula: It is preferable that the relationship (2') is satisfied.
N-1≧B+C, B>0, C>0 (2')

The conjugated diene graft polymer used in the present invention is determined by the average number X of functional groups (c) directly bonded to the above branch points per molecule of the conjugated diene graft polymer and the number of branches per molecule of the conjugated diene graft polymer. It is preferable that the average number Y of points satisfies the relationship of formula (3-1) below. When (X/Y) is less than 1, the conjugated diene graft polymer tends to have excellent stability.
0≦(X/Y)<1 (3-1)
When (X/Y) is larger than 0, it tends to have excellent affinity with polar materials. When the following formula (3-2) is satisfied, there is a tendency for an excellent balance between affinity with polar materials and stability of the conjugated diene graft polymer. In particular, when at least one functional group (c) selected from the group consisting of an alkoxy group and a hydroxyl group is directly bonded to the branch point, the above-mentioned tendency is remarkable.
0<(X/Y)<1 (3-2)

Further, (X/Y) may be 0, and when the relationship of the following formula (3-3) is satisfied, the stability of the conjugated diene graft polymer tends to be excellent. In addition, when a polymer satisfying the relationship of the following formula (3-3) is produced by the production method described below, the functional group contained in the functional group-modified conjugated diene polymer (F) used for the production is a fluorine atom, When at least one functional group (c) is selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom, a conjugated diene-based graft polymer with (X/Y)=0 is easily obtained. The conjugated diene graft polymer with (X/Y)=0 thus obtained has excellent stability.
(X/Y)=0 (3-3)

From the viewpoint of a better balance of stability and affinity with polar materials such as detergents, antioxidants, and friction modifiers contained in lubricating oil, the above (X/Y) is 0.01 or more and 0.99 or less. The range is preferably 0.01 or more and 0.9 or less, more preferably 0.01 or more and 0.5 or less, and particularly preferably 0.01 or more and 0.5 or less. In the present invention, (X/Y) (the average number of functional groups (c) per branch point contained in the conjugated diene graft polymer) is, for example, when Z is Si, the conjugated diene graft polymer It is determined from the results of ²⁹ Si-NMR measurement of the polymer. Specifically, the integral values of Si to which one functional group (c) is bonded, Si to which two functional groups (c) are bonded, etc. are multiplied by the number of functional groups, and then the integrals are calculated. Calculated by comparing with the simple sum of values. (X/Y) can be similarly determined when Z is a heteroatom other than Si.

In addition, the average number Y of branch points per molecule of the conjugated diene graft polymer is determined by the specific heteroatoms (Si, Sn, , Ge, Pb, P, B, and Al) (mass %) and the number average molecular weight (Mn) in terms of standard polystyrene.
(Average number of branch points Y per molecule of conjugated diene graft polymer) = [(Hetero atom content (mass%))/100] x [(Number average molecular weight Mn)/(Structural unit derived from styrene) ) × (average molecular weight of the structural unit derived from the conjugated diene and other monomers other than the conjugated diene included as necessary)] / (atomic weight of the heteroatom) (8)

The conjugated diene graft polymer used in the present invention has an average number X of functional groups (c) directly bonded to the branch point per molecule of the conjugated diene graft polymer that satisfies the relationship expressed by the following formula (4-1). It is preferable to meet the requirements. The average number X of functional groups (c) is calculated by the method described below. When X is 10 or less, the conjugated diene graft polymer tends to have excellent stability.
0≦X≦10 (4-1)
When X is larger than 0, there is a tendency for excellent affinity with polar materials. When the following formula (4-2) is satisfied, there is a tendency for an excellent balance between affinity with polar materials and stability of the conjugated diene graft polymer.
0<X≦10 (4-2)
Further, X may be 0, and when the following formula (4-3) is satisfied, the stability of the conjugated diene graft polymer tends to be excellent.
X=0 (4-3)

From the viewpoint of a better balance of stability and affinity with polar materials such as detergents, antioxidants, and friction modifiers contained in lubricating oil, X should be in the range of 0.01 to 9.9. is preferably in the range of 0.02 or more and 9 or less, and particularly preferably in the range of 0.05 or more and 5 or less. In the present invention, the average number X of functional groups (c) directly bonded to the branch point per molecule of the conjugated diene graft polymer is the number of functional groups per branch point contained in the conjugated diene graft polymer. It is determined using the average number (X/Y) of (c) and the average number Y of branch points per molecule of the conjugated diene graft polymer.

In addition, the number of side chains (b) and the number of functional groups (c) directly bonded to the above-mentioned branch point can be determined, for example, in the step ( From the types of functional groups and the molar ratio of the charged amount of the active terminal polymer (I) and the functional group-modified conjugated diene polymer (F) in A-1), the alkoxy group and hydroxyl group in the step (A-2) described below The amount and reaction time of the reagent used to inactivate a portion of at least one remaining functional group (unreacted functional group V) selected from the group consisting of: It can be adjusted to a desired range depending on the type and amount of the polar compound added.

The stability of a conjugated diene-based graft polymer can be evaluated, for example, by the change in appearance or the formation of insoluble matter (gelled material) when stored for a long period of time at room temperature and pressure. It is also possible to evaluate the conjugated diene graft polymer under conditions that promote the condensation reaction of alkoxysilyl groups or silanol groups by heating and reducing pressure.

Affinity with polar materials can be determined, for example, by applying a conjugated diene-based graft polymer or a polymer composition containing a conjugated diene-based graft polymer onto a glass substrate and curing it by heating for a certain period of time. It can be evaluated by measuring peel strength or conducting a grid test. Furthermore, the reactivity and affinity with polar materials such as glass and silica can be evaluated based on the condensation reactivity of the alkoxysilyl group or silanol group. When a solution containing a conjugated diene-based graft polymer is shaken under acidic or basic conditions, if the condensation reactivity is high, insoluble matter (gelled material) will be produced. Reactivity with materials can be evaluated.

In the conjugated diene graft polymer used in the present invention, the average number of side chains (b) directly bonded to the above branch points per molecule of the conjugated diene graft polymer is W, and the average number of side chains (b) per molecule of the conjugated diene graft polymer is When the average number of branch points is Y, it is preferable that (W/Y) satisfies the following equation (5).
0.5≦(W/Y) (5)

The above (W/Y) is more preferably 0.6 or more (0.6≦(W/Y)), and even more preferably 0.8 or more (0.8≦(W/Y)). In the present invention, the average number W of side chains (b) directly bonded to the branch point per molecule of the conjugated diene graft polymer is as follows: In the following step (A-1), the charged amount (number of moles) per active end of the active end polymer (I) that becomes the side chain (b) of the conjugated diene graft polymer and the functional group-modified conjugated diene polymer It is determined by the following formula (9) using the charged amount (number of moles) of (F).
(Average number W of side chains (b) directly bonded to the above branch points per conjugated diene graft polymer molecule) = (Preparation per active end of the active end polymer (I) that becomes the side chain (b) Amount (number of moles))/(Amount of charged functional group-modified conjugated diene polymer (F) (number of moles)) (9)

Further, the average number Y of branch points per molecule of the conjugated diene graft polymer is calculated by the method described above. If the above (W/Y) is less than 0.5, the shear stability of the obtained viscosity index improver made of the conjugated diene graft polymer tends to decrease, and the flow rate of the conjugated diene graft polymer tends to decrease. The balance between processability and mechanical properties tends to be poor.

The degree of branching of a conjugated diene graft polymer is determined by the slope (α _s ) when the radius of gyration (R) is plotted log-logarithmically against the absolute weight average molecular weight (Mw) of the conjugated diene graft polymer. Alternatively, it can be determined from the slope (αη) when the intrinsic viscosity (η) is plotted log-logarithmically against the weight average molecular weight (Mw) of the conjugated diene graft polymer by absolute method. A random coil chain of a normal linear polymer exhibits a value of about 0.6 to 0.8 for both α _s and αη, and a value of less than 0.6 suggests the presence of a branched chain. The value of α _s or αη of the conjugated diene graft polymer used in the present invention is preferably less than 0.6, more preferably 0.55 or less, and even more preferably 0.50 or less. . Note that a log-logarithmic plot of the absolute weight average molecular weight (Mw) and the radius of gyration (R) or intrinsic viscosity (η) of the conjugated diene-based graft polymer can be obtained, for example, by the SEC-MALS-VISCO method. The SEC-MALS-VISCO method is a type of liquid chromatography (SEC) that separates polymer chains based on differences in molecular size (hydrodynamic volume), and uses a differential refractometer (RI) and a multi-angle light scattering detector. (MALS) and a viscosity detector (VISCO), it is possible to calculate the radius of gyration and intrinsic viscosity for each molecular weight of a polymer solution size-sorted by SEC. When the value of α _s or αη of the conjugated diene graft polymer used in the present invention is within the above range, the shear stability of the resulting viscosity index improver made of the conjugated diene graft polymer tends to improve, Conjugated diene graft polymers tend to have improved fluidity and a good balance between processability and mechanical properties.

The conjugated diene graft polymer used in the present invention preferably has an average number W of side chains (b) directly bonded to the branch point per molecule of the conjugated diene graft polymer of 1 or more, and 3 or more. It is more preferable that the number is 5 or more, and even more preferably 5 or more. The average number W of the side chains (b) is calculated by the method described above. If the average number W of the side chains (b) is less than 1, the shear stability of the resulting viscosity index improver made of the conjugated diene graft polymer tends to decrease; The fluidity of these materials decreases, and the balance between processability and mechanical properties tends to be poor.

In addition, when producing a conjugated diene-based graft polymer by the production method described below, the average number W of the side chains (b) is determined by, for example, the active terminal polymer (I) in the step (A-1) described below. It can be adjusted to a desired range by adjusting the ratio of the charged amounts of the functional group-modified conjugated diene polymer (F) and the functional group-modified conjugated diene polymer (F). For example, in the case of (charged amount (number of moles) of active end polymer (I))/(charged amount (number of moles) of functional group-modified conjugated diene polymer (F)) = 4/1, the side chain (b ), the average number W is 4. However, the upper limit of W is the number of functional groups V that one molecule of the functional group-modified conjugated diene polymer (F) has.

The combination of the polymer serving as the main chain (a) and the polymer serving as the side chain (b) contained in the conjugated diene graft polymer is not particularly limited, and may be the same or different, and may be designed according to the purpose. Is possible. The expression that the polymer serving as the main chain (a) and the polymer serving as the side chain (b) are different means that at least one selected from the group consisting of (i) to (iv) below is different.
(i) The molecular weight of the polymer forming the main chain (a) is different from the molecular weight of the polymer forming the side chain (b).
(ii) The type or combination of types of structural units derived from the monomer of the polymer forming the main chain (a) is the type or combination of structural units derived from the monomer of the polymer forming the side chain (b). Different combinations of types.
(iii) When the main chain (a) and the side chain (b) each contain structural units derived from multiple monomers of the same type, the monomer of the polymer forming the main chain (a) The derived structural unit composition ratio is different from the structural unit composition ratio derived from the monomer of the polymer serving as the side chain (b).
(iv) When the main chain (a) and the side chain (b) each contain a structural unit derived from a conjugated diene, the vinyl content of the structural unit derived from the conjugated diene in the polymer that becomes the main chain (a) is different from the vinyl content of the structural unit derived from the conjugated diene of the polymer serving as the side chain (b).

In the conjugated diene graft polymer used in the present invention, 50% by mass or more of the structural units derived from all the monomers constituting the polymer contains at least one monomer selected from the group consisting of butadiene and isoprene. In one preferred embodiment, the structural unit is derived from. The total content of structural units derived from butadiene and isoprene is more preferably 60 to 100% by mass, and more preferably 70 to 100% by mass, based on the structural units derived from all monomers of the conjugated diene graft polymer. It is more preferable that

The content of structural units derived from monomers other than butadiene and isoprene in the conjugated diene graft polymer used in the present invention is preferably 50% by mass or less, more preferably 40% by mass or less, More preferably, it is 30% by mass or less. For example, if the structural unit derived from the aromatic vinyl compound is below the above range, the shear stability of the resulting viscosity index improver made of the conjugated diene graft polymer tends to improve; The processability of polymers tends to improve.

The conjugated diene graft polymer used in the present invention is a hydrogenated conjugated diene graft polymer in which at least a portion of the carbon-carbon double bonds contained in the structural unit derived from the conjugated diene contained in the polymer are hydrogenated. It may be a polymer or an unhydrogenated conjugated diene-based graft copolymer in a non-hydrogenated state. The conjugated diene graft polymer used in the present invention is preferably a hydrogenated conjugated diene graft polymer from the viewpoint of heat resistance and weather resistance. It is preferable that 50 mol% or more of the carbon-carbon double bonds contained in the structural units derived from the conjugated diene in the hydrogenated conjugated diene-based graft polymer are hydrogenated, and 80 mol% or more of the carbon-carbon double bonds are hydrogenated. It is more preferable that 90 mol% or more is hydrogenated. Further, the hydrogenation rate is usually 100 mol% or less. Furthermore, the hydrogenation rate (hydrogenation rate) may be substantially 100 mol% (that is, substantially complete hydrogenation). When the hydrogenation rate is 50 mol% or more, the thermal stability and shear stability of the viscosity index improver made of the hydrogenated conjugated diene graft polymer tend to improve. The hydrogenation rate is determined by calculating the content of carbon-carbon double bonds contained in structural units derived from conjugated diene in the polymer before and after hydrogenation using ¹ H-NMR, and This is the value determined from the content.

The weight average molecular weight (Mw) of the conjugated diene graft polymer used in the present invention is preferably 10,000 or more and 2,000,000 or less, and preferably 100,000 or more and 1,500,000 or less. , more preferably 300,000 or more and 1,000,000 or less. When the Mw of the conjugated diene-based graft polymer is within the above range, the viscosity index improver made of the conjugated diene-based graft polymer tends to have an excellent balance between the thickening effect and shear stability. It has excellent permeability and tends to be economical.

The molecular weight distribution (Mw/Mn) of the conjugated diene graft polymer used in the present invention is preferably from 1.0 to 20.0, more preferably from 1.0 to 10.0, even more preferably from 1.0 to 5.0. , 1.0 to 2.0 are particularly preferred. When Mw/Mn is within the above range, the variation in viscosity of the conjugated diene graft polymer is small, which is more preferable. In the present invention, Mn means a number average molecular weight, and Mn is a standard polystyrene equivalent number average molecular weight determined from GPC measurement. Moreover, the molecular weight distribution (Mw/Mn) means the ratio (Mw/Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of standard polystyrene determined by GPC measurement.

The vinyl content of the conjugated diene-based graft polymer used in the present invention is not particularly limited, but is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 20 mol% or less. The vinyl content of the conjugated diene graft polymer is preferably 0.5 mol% or more, more preferably 1 mol% or more. When the vinyl content of the conjugated diene graft polymer is within the above range, the resulting viscosity index improver made of the conjugated diene graft polymer tends to have an excellent balance between thickening effect and low temperature properties. In addition, when the conjugated diene graft polymer is composed only of structural units derived from butadiene, the conjugated diene graft copolymer is a hydrogenated conjugated diene graft polymer, and its Mw is relatively large. (For example, when the Mw of at least one of the main chain (a) or the side chain (b) is about 10,000 or more), in order to prevent performance deterioration due to crystallization after hydrogenation, the vinyl content should be set to 25 mol% or more. It is preferable to

The glass transition temperature (Tg) of a conjugated diene-based graft polymer is determined by the vinyl content of the structural unit derived from conjugated dienes such as butadiene, isoprene, and other conjugated dienes, the type of conjugated diene, and the monomer other than the conjugated diene. Although it may vary depending on the content of structural units, etc., it is preferably -150 to 50°C, more preferably -130 to 50°C, and even more preferably -130 to 30°C. When Tg is within the above range, for example, increase in viscosity can be suppressed and handling becomes easy.

The mass ratio of the main chain to the side chain in the conjugated diene graft polymer used in the present invention is preferably in the range of 0.05/99.95 to 70/30, and preferably in the range of 0.1/99.9 to 60/40. is more preferable, and the range of 0.5/99.5 to 50/50 is even more preferable. When the mass ratio of the main chain to the side chain is within the above range, process passability during production tends to be excellent and economical efficiency tends to be good.

The conjugated diene graft polymer used in the present invention preferably has a total amount of catalyst residue derived from the polymerization catalyst, hydrogenation catalyst (hydrogenation catalyst), etc. used in its production, in the range of 0 to 500 ppm in terms of metal. . For example, when an organic alkali metal such as an organic lithium compound as described below is used as a polymerization catalyst for producing a conjugated diene-based graft polymer, an alkali metal such as lithium may be included. Further, when a hydrogenated conjugated diene graft polymer is used as the conjugated diene graft polymer, nickel and aluminum may be contained when a Ziegler catalyst, which will be described later, is used as a catalyst in the hydrogenation reaction. When the amount of catalyst residue is within the above range, the tack does not decrease during processing, and the heat resistance of the conjugated diene graft polymer used in the present invention is improved. The total amount of catalyst residue of the conjugated diene graft polymer is more preferably 0 to 300 ppm in total, more preferably 0 to 200 ppm in terms of metal. The amount of catalyst residue can be measured using, for example, an inductively coupled plasma mass spectrometer (ICP-MS) or a polarized Zeeman atomic absorption spectrophotometer.

Examples of a method for adjusting the amount of catalyst residue in the conjugated diene graft polymer to such a specific amount include a method in which the conjugated diene graft polymer is purified to sufficiently remove the catalyst residue. Preferred methods for purification include washing with water or warm water, acidic aqueous solutions, organic solvents such as methanol and acetone, or washing with supercritical fluid carbon dioxide. The cleaning efficiency can be further improved by using an acidic aqueous solution for cleaning. Examples of acids used include strong monovalent or polyvalent acids such as hydrochloric acid, nitric acid, and sulfuric acid; monovalent or polyvalent carboxylic acids such as acetic acid, propionic acid, succinic acid, and citric acid; and monovalent acids such as carbonic acid and phosphoric acid. Or a polyvalent weak acid is preferred. The number of washings is preferably 1 to 20 times, more preferably 1 to 10 times, from an economical point of view. Further, the washing temperature is preferably 20 to 100°C, more preferably 40 to 90°C. In addition, the amount of polymerization catalyst required can be reduced by removing impurities that may inhibit polymerization using distillation or adsorbents to increase the purity of the monomer before the polymerization reaction. The amount of catalyst residue can be reduced.

One embodiment of the conjugated diene graft polymer used in the present invention preferably has a halogen content of 0 to 1,000 ppm. For example, when a silyl chloride-modified conjugated diene polymer is used as the functional group-modified conjugated diene polymer (F) for producing a conjugated diene graft polymer, the reference halogen is chlorine. When the halogen content is within the above range, transparency, heat resistance, and weather resistance tend to be good. The halogen content of the conjugated diene graft polymer is more preferably 0 to 500 ppm, and even more preferably 0 to 100 ppm. Note that the halogen content can be measured, for example, by using combustion ion chromatography.

As a method for adjusting the halogen content of the conjugated diene graft polymer to such a specific amount, as a functional group-modified conjugated diene polymer (F), which is a raw material for producing the conjugated diene graft polymer, A method using an alkoxysilane-modified conjugated diene polymer that does not produce a halide as a by-product may be mentioned.

<Method for producing conjugated diene graft polymer>
The method for producing the conjugated diene graft polymer used in the present invention is not particularly limited.
For example, (i) a macromonomer containing a structural unit derived from at least one monomer selected from the group consisting of a conjugated diene and an aromatic vinyl compound (a macromonomer containing a structural unit derived from at least one monomer selected from the group consisting of a conjugated diene and an aromatic vinyl compound); Conjugated diene grafting is achieved by polymerizing a monomer containing a conjugated diene with a macromonomer (obtained by reacting a compound having a polymerizable functional group with the active terminal of a polymer containing a structural unit derived from a monomer). A method (macro The polymerizable functional group contained in the monomer and the part derived from the polymer chain obtained from the monomer reacted with the macromonomer are polymers other than the main chain / the part derived from the compound containing the polymerizable functional group contained in the macromonomer. The part derived from the combined chain is the side chain);
(ii) In the presence of tetramethylethylene diamine, a polymer containing a structural unit derived from a conjugated diene is reacted with an organic alkali metal compound to convert the polymer into a polymer having a metal active moiety, and then the metal A conjugated diene-based graft polymer is produced by polymerizing a monomer containing at least one monomer selected from the group consisting of a conjugated diene and an aromatic vinyl compound from the active moiety, and the conjugated diene obtained as necessary. A method for producing a conjugated diene graft polymer (unhydrogenated or hydrogenated conjugated diene graft polymer) by hydrogenating a conjugated diene graft polymer (derived from a polymer chain contained in a polymer reacted with an organic alkali metal compound) The part derived from the polymer chain obtained by polymerization from the main chain/metal active part is the side chain);
(iii) A polymer containing a structural unit derived from a conjugated diene and having two active terminals, and a structural unit derived from at least one monomer selected from the group consisting of a conjugated diene and an aromatic vinyl compound. A mixture of a polymer having , and one active end is prepared, and a coupling agent having three or more reactive sites is added to this mixture and reacted to produce a conjugated diene-based graft polymer, and as necessary. A method of hydrogenating the obtained conjugated diene graft polymer to produce a conjugated diene graft polymer (unhydrogenated or hydrogenated conjugated diene graft polymer) (contained in a polymer having two active terminals) The part derived from the polymer chain is the main chain/the part derived from the polymer chain contained in the polymer having one active end is the side chain);
(iv) A polymer containing a structural unit derived from a conjugated diene synthesized in advance is modified with a functional group to prepare a functional group-modified polymer, and the functional group contained in the functional group-modified polymer and the conjugated diene and aromatic A conjugated diene graft polymer is produced by reacting a monomer containing at least one monomer selected from the group consisting of vinyl compounds with the active end of a polymerized polymer, and if necessary, a conjugated diene-based graft polymer is produced. A method of hydrogenating a diene-based graft polymer to produce a conjugated diene-based graft polymer (unhydrogenated or hydrogenated conjugated diene-based graft polymer) (a portion derived from a polymer chain contained in a functional group-modified polymer) A side chain is a portion derived from a polymer chain contained in a polymer having a main chain/an active end.

As a method for producing the conjugated diene graft polymer used in the present invention, a method including the following step (A-1) and step (C) is preferred.

(A-1) An active terminal polymer (I) represented by the following formula (I) and a functional group-modified conjugated diene polymer ( F) A step of producing a conjugated diene graft polymer by reacting with

P-X (I)
(In formula (I), P represents a polymer chain containing a structural unit derived from at least one monomer selected from the group consisting of a conjugated diene and an aromatic vinyl compound, and X represents an active terminal for anionic polymerization. .)

（式（ＩＩ）中、Ｖは、アルコキシ基、水酸基、フッ素原子、塩素原子、臭素原子、又はヨウ素原子を示し、ＺはＳｉ、Ｓｎ、Ｇｅ、Ｐｂ、Ｐ、Ｂ、又はＡｌであり、Ｒ^１は炭素数６～１２のアリール基、炭素数１～１２のアルキル基、又は水素原子を示し、Ｎは前記Ｚの価数を示し、ｎは下記式（６）を満たす整数であり；
１≦ｎ≦Ｎ－１ （６）
ｎが２以上の場合、Ｖは同一でも異なっていてもよく、Ｎ－ｎ－１が２以上の場合、Ｒ^１は同一でも異なっていてもよく、分岐鎖が主鎖に対し、複数含まれる場合には、Ｚは同一でも異なっていてもよい。）；及び
（Ｃ）得られた共役ジエン系グラフト重合体を回収する工程。

(In formula (II), V represents an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; Z is Si, Sn, Ge, Pb, P, B, or Al; R ¹ represents an aryl group having 6 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or a hydrogen atom, N represents the valence of Z, and n is an integer satisfying the following formula (6);
1≦n≦N-1 (6)
When n is 2 or more, V may be the same or different, and when N-n-1 is 2 or more, R ¹ may be the same or different, and multiple branches are included in the main chain. In some cases, Z may be the same or different . ); and (C) a step of recovering the obtained conjugated diene-based graft polymer.

The branched chain of the functional group-modified conjugated diene polymer (F) means a portion other than the main chain of the functional group-modified conjugated diene polymer (F), and this main chain refers to the conjugated diene graft Similar to the main chain (a) in a polymer, it refers to the entire structural unit portion derived from all the monomers containing the conjugated diene that constitute the main chain.

[Step (A-1)]
The active terminal polymer (I) used in the above step (A-1) can be produced using a known polymerization method. For example, monomers are anionically polymerized in an inert solvent, using an anionically polymerizable active metal or active metal compound as an initiator, optionally in the presence of a polar compound, to polymerize the active end. Combined (I) can be obtained. P of this active terminal polymer (I) or its hydrogenated product becomes the side chain (b) of the graft polymer.

Specific examples of monomers serving as structural units derived from the monomers constituting the active terminal polymer (I), explanations of preferred embodiments, etc., and descriptions of monomers derived from the monomers contained in the active terminal polymer (I) The specific examples and preferred embodiments of the structural unit are the same as the explanation regarding the side chain (b) of the conjugated diene graft polymer.

As the anionically polymerizable active metal or active metal compound, organic alkali metal compounds are preferred, and organic lithium compounds are more preferred. Examples of the organic lithium compounds include methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, and pentyllithium.

Examples of the solvent include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; benzene; , aromatic hydrocarbons such as toluene and xylene.

A polar compound may be added during the anionic polymerization. Polar compounds are generally used in anionic polymerization to adjust the microstructure (vinyl content) of the conjugated diene moiety without deactivating the reaction. Examples of the polar compound include ether compounds such as dibutyl ether, tetrahydrofuran, and ethylene glycol diethyl ether; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides and phosphine compounds. The polar compound is usually used in an amount of 0.01 to 1000 mol based on the organic alkali metal compound.

The temperature of the anionic polymerization is usually in the range of -80 to 150°C, preferably in the range of 0 to 100°C, more preferably in the range of 10 to 90°C. The polymerization mode may be either batchwise or continuous.

P of the above active terminal polymer (I) or a product obtained by hydrogenating it ultimately becomes the side chain (b) of the conjugated diene graft polymer used in the present invention. The description of the preferred embodiments of the weight average molecular weight (Mw), vinyl content, Tg, etc. of P in the active terminal polymer (I) is the same as that regarding the side chain (b) of the conjugated diene graft polymer.

In the above step (A-1), the functional group-modified conjugated diene polymer (F) is obtained by, for example, modifying the unmodified conjugated diene polymer (F') with a functional group in the modification step described below. . The method for producing the unmodified conjugated diene polymer (F') is not particularly limited, but for example, an emulsion polymerization method and a solution polymerization method are preferred, and a solution polymerization method is more preferred from the viewpoint of the molecular weight distribution of the resulting polymer. . The portion of the functional group-modified conjugated diene polymer (F) other than the functional group-modified portion or the hydrogenated portion thereof becomes the main chain (a) of the conjugated diene graft polymer used in the present invention.

Specific examples, preferred examples, and preferred contents of conjugated dienes, which are structural units derived from monomers constituting the unmodified conjugated diene polymer (F'), and other monomers other than conjugated dienes Descriptions of specific examples, preferred examples, preferred content, etc. of the (aromatic vinyl compound) are the same as those regarding the main chain (a) of the conjugated diene graft polymer. Further, the explanation of the weight average molecular weight (Mw), vinyl content, preferred embodiments of Tg, etc. of the unmodified conjugated diene polymer (F') is the same as the explanation regarding the main chain (a) of the conjugated diene graft polymer. be.

As the emulsion polymerization method, which is an example of the method for producing the unmodified conjugated diene polymer (F'), any known or similar method can be applied. For example, a monomer containing a predetermined amount of conjugated diene is emulsified and dispersed in a dispersion medium in the presence of an emulsifier, and emulsion polymerization is performed using a radical polymerization initiator.

Examples of emulsifiers include long-chain fatty acid salts having 10 or more carbon atoms, rosinate salts, and the like. Examples of long-chain fatty acid salts include potassium salts or sodium salts of fatty acids such as capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and stearic acid.

Water is usually used as the dispersion medium. The dispersion medium may contain a water-soluble organic solvent such as methanol or ethanol as long as the stability during polymerization is not impaired.

Examples of the radical polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate, organic peroxides, and hydrogen peroxide.

A chain transfer agent may be used to adjust the molecular weight of the resulting unmodified conjugated diene polymer (F'). Examples of the chain transfer agent include mercaptans such as t-dodecylmercaptan and n-dodecylmercaptan; carbon tetrachloride, thioglycolic acid, diterpene, terpinolene, γ-terpinene, and α-methylstyrene dimer.

The emulsion polymerization temperature can be appropriately set depending on the type of radical polymerization initiator used, but it is usually in the range of 0 to 100°C, preferably in the range of 0 to 60°C. The polymerization mode may be continuous polymerization or batch polymerization.

The polymerization reaction can be stopped by adding a polymerization terminator. Examples of the polymerization terminator include amine compounds such as isopropylhydroxylamine, diethylhydroxylamine, and hydroxylamine, quinone compounds such as hydroquinone and benzoquinone, and sodium nitrite.

After termination of the polymerization reaction, an anti-aging agent may be added if necessary. After the polymerization reaction has been terminated, unreacted monomers are removed from the obtained latex as necessary, and then salts such as sodium chloride, calcium chloride, potassium chloride, etc. are used as coagulants, and as necessary, nitric acid, sulfuric acid, etc. After the unmodified conjugated diene polymer (F') is coagulated while adjusting the pH of the coagulation system to a predetermined value by adding an acid, the polymer is recovered by separating the dispersion medium. Next, the unmodified conjugated diene polymer (F') is obtained by washing with water, dehydrating, and drying. In addition, at the time of coagulation, if necessary, the latex and an extension oil made into an emulsified dispersion may be mixed in advance and recovered as an oil-extended unmodified conjugated diene polymer (F').

As the above-mentioned solution polymerization method, which is an example of a method for producing the unmodified conjugated diene polymer (F'), a known method or a method similar to a known method can be applied. For example, monomers containing conjugated dienes can be prepared in a solvent using Ziegler-based catalysts, metallocene-based catalysts, or anionically polymerizable active metals or active metal compounds as initiators, optionally in the presence of polar compounds. Polymerize the body.

Examples of the solvent include aliphatic hydrocarbons such as n-butane, n-pentane, isopentane, n-hexane, n-heptane, and isooctane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; benzene; Examples include aromatic hydrocarbons such as toluene and xylene.

The initiator is preferably an anionically polymerizable active metal or an active metal compound, more preferably an anionically polymerizable active metal compound.

Examples of active metals capable of anionic polymerization include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium; and lanthanoid rare earth metals such as lanthanum and neodymium. . Among these, alkali metals and alkaline earth metals are preferred, and alkali metals are more preferred.

The active metal compound capable of anionic polymerization is preferably an organic alkali metal compound. Examples of organic alkali metal compounds include organic monolithium compounds such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; dilithiomethane, dilithionaphthalene; , 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and other polyfunctional organolithium compounds; sodium naphthalene, potassium naphthalene, and the like. Among these organic alkali metal compounds, organic lithium compounds are preferred, and organic monolithium compounds are more preferred.

The amount of the above-mentioned initiator to be used can be set appropriately depending on the melt viscosity, molecular weight, etc. of the unmodified conjugated diene polymer (F') and the functional group-modified conjugated diene polymer (F). It is usually used in an amount of 0.01 to 3 parts by weight per 100 parts by weight of the monomer.

When an organic alkali metal compound is used as an initiator, the organic alkali metal compound can be reacted with a secondary amine such as dibutylamine, dihexylamine, dibenzylamine, etc., and used as an organic alkali metal amide. .

Polar compounds are generally used in anionic polymerization to adjust the microstructure (vinyl content) of the conjugated diene moiety without deactivating the reaction. Examples of the polar compound include ether compounds such as dibutyl ether, tetrahydrofuran, and ethylene glycol diethyl ether; tertiary amines such as tetramethylethylenediamine and trimethylamine; alkali metal alkoxides and phosphine compounds. The polar compound is usually used in an amount of 0.01 to 1000 mol based on the organic alkali metal compound.

The temperature of solution polymerization is usually in the range of -80 to 150°C, preferably in the range of 0 to 100°C, more preferably in the range of 10 to 90°C. The polymerization mode may be either batchwise or continuous.

The polymerization reaction of the solution polymerization described above can be stopped by adding a polymerization terminator. Examples of the polymerization terminator include alcohols such as methanol and isopropanol. The resulting polymerization reaction solution may be poured into a poor solvent such as methanol to precipitate the unmodified conjugated diene polymer (F'), or the polymerization reaction solution may be washed with water, separated, and then dried to remove the above-mentioned residues. The modified conjugated diene polymer (F') can be isolated.

The unmodified conjugated diene polymer (F') obtained in this way may be directly modified with a functional group, but the unmodified conjugated diene polymer (F') contained in the structural unit derived from the conjugated diene in the conjugated diene polymer may be modified with a functional group. Modification may be performed after hydrogenating at least a portion of the carbon-carbon double bonds in the carbon-carbon double bond by the hydrogenation method described below.

By modifying the above-mentioned unmodified conjugated diene-based polymer (F') with a functional group, a functional group-modified conjugated diene-based polymer (F') having a moiety containing a functional group represented by the above formula (II) as a branched chain can be obtained. Although there are no particular restrictions on the method for producing , from the viewpoint of introducing a functional group with a preferable structure, for example, a mercapto group (-SH ) A method of introducing a functional group derived from an alkoxysilane compound or a silyl halide compound by radical addition reaction of a compound having a carbon-carbon double bond contained in an unmodified conjugated diene polymer (F') Examples include a method of introducing a functional group derived from an alkoxysilane compound or a silyl halide compound by hydrosilylating it in the presence of a platinum compound-containing catalyst and a co-catalyst used as necessary. Among these production methods, from the viewpoint of availability of modifying reagents and catalysts and production costs, the method of radical addition reaction of a compound having a mercapto group (-SH) is preferable, and the resulting functional group-modified conjugated diene polymer From the viewpoint of stability of the composite (F), a method of introducing a functional group derived from an alkoxysilane compound by hydrosilylation is preferred.

By subjecting a compound having a mercapto group (-SH) to a carbon-carbon double bond contained in the unmodified conjugated diene polymer (F') to a radical addition reaction, a compound derived from an alkoxysilane compound or a silyl halide compound is produced. As a method for introducing a functional group, there is a method in which a silane compound (IV) represented by the following formula (IV) is subjected to a radical addition reaction to a carbon-carbon double bond contained in an unmodified conjugated diene polymer (F'). preferable.

（式（ＩＶ）中、Ｖはアルコキシ基、水酸基、フッ素原子、塩素原子、臭素原子、又はヨウ素原子を示し、Ｒ⁴は炭素数１～６の２価のアルキレン基を示し、Ｒ⁵は炭素数６～１２のアリール基、炭素数１～１２のアルキル基、又は水素原子を示し、ｎは１～３の整数であり、ｎが２以上の場合、Ｖは同一でも異なっていてもよく、３－ｎが２以上の場合、Ｒ⁵は同一でも異なっていてもよい。）

(In formula (IV), V represents an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, R ⁴ represents a divalent alkylene group having 1 to 6 carbon atoms, and R ⁵ represents a carbon represents an aryl group having 6 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or a hydrogen atom, n is an integer of 1 to 3, and when n is 2 or more, V may be the same or different, When 3-n is 2 or more, R ⁵ may be the same or different.)

Examples of the silane compound (IV) include mercaptomethylenemethyldiethoxysilane, mercaptomethylenetriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 2-mercaptoethylmethoxydimethylsilane, 2-mercaptoethyltriethoxysilane, and 2-mercaptoethyltriethoxysilane. Mercaptoethyl ethoxydimethylsilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyldiethoxymethylsilane, 3-mercaptopropyldimethoxyethylsilane, 3-mercapto Silane compounds containing alkoxysilyl groups such as propyldiethoxyethylsilane, 3-mercaptopropylmethoxydimethylsilane, 3-mercaptopropylethoxydimethylsilane; mercaptomethylenemethyldichloridesilane, mercaptomethylenetrichloridesilane, 2-mercaptoethyltrichloridesilane , 2-mercaptoethyldimethylchloridesilane, 3-mercaptopropyltrichloridesilane, 3-mercaptopropyldichloridemethylsilane, 3-mercaptopropyldichlorideethylsilane, 3-mercaptopropylchloridedimethylsilane, mercaptomethylenemethyldibromosilane, mercaptomethylenetrisilane Bromosilane, 2-mercaptoethyltribromosilane, 2-mercaptoethyldimethylbromosilane, 3-mercaptopropyltribromosilane, 3-mercaptopropyldibromomethylsilane, 3-mercaptopropyldibromoethylsilane, 3-mercaptopropylbromodimethylsilane Examples include silane compounds containing a silyl halide group such as.
These silane compounds may be used alone or in combination of two or more.

In addition, when it is desired that the conjugated diene graft polymer used in the present invention has at least one functional group (c) selected from the group consisting of an alkoxy group and a hydroxyl group bonded to the branch point, the conjugated diene graft polymer used in the present invention can be used as a silane compound (IV). Step (A-1) may be carried out using a functional group-modified conjugated diene polymer (F) obtained by adding a silane compound containing an alkoxysilyl group to an unmodified conjugated diene polymer (F').
Further, when the conjugated diene graft polymer used in the present invention is desired to have at least one functional group (c) selected from the group consisting of fluorine atom, chlorine atom, bromine atom, and iodine atom bonded to the branch point. , or when it is desired to obtain a polymer satisfying the above formula (3-3), a functional group-modified conjugate obtained by adding a silane compound containing a silyl halide group to an unmodified conjugated diene polymer (F') as the silane compound (IV). Step (A-1) may be performed using the diene polymer (F).

The mercapto group (-SH) of the above silane compound (IV) is derived from the silane compound (IV) through a radical addition reaction with the carbon-carbon double bond contained in the unmodified conjugated diene polymer (F'). A functional group-modified conjugated diene polymer (F) having a functional group, specifically a partial structure represented by the following formula (V), as a functional group is obtained.

（式（Ｖ）中、Ｒ⁴、Ｒ⁵、Ｖ、及びｎの定義は式（ＩＶ）と同一である。）

(In formula (V), the definitions of R ⁴ , R ⁵ , V, and n are the same as in formula (IV).)

The method of adding the silane compound (IV) to the unmodified conjugated diene polymer (F') is not particularly limited, and for example, adding the silane compound (IV) to the unmodified conjugated diene polymer (F'), Furthermore, a method of adding a radical generator as necessary and heating in the presence or absence of an organic solvent can be adopted. The radical generator to be used is not particularly limited, and commonly available commercially available organic peroxides, azo compounds, hydrogen peroxide, etc. can be used.

Examples of the organic peroxides include methyl ethyl ketone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, acetylacetone peroxide, 1,1-bis(t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, 2,2-bis(t-butylperoxy) Butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, para-menthane hydroperoxide, 2,5-dimethylhexane 2,5-dihydroperoxide, 1,1,3,3-tetra Methyl butyl hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t- butylperoxy)hexane, 2,5-hexanoyl peroxide, lauroyl peroxide, succinic peroxide, benzoyl peroxide and its substituted products, 2,4-dichlorobenzoyl peroxide, metatoluoyl peroxide, diisopropyl peroxide Dicarbonate, t-butyl-2-ethylhexanoate, di-2-ethylhexyl peroxydicarbonate, dimethoxyisopropyl peroxycarbonate, di(3-methyl-3-methoxybutyl) peroxydicarbonate, t-butyl peroxydicarbonate Oxyacetate, t-butyl peroxy pivalate, t-butyl peroxy neodecanoate, t-butyl peroxy octanoate, t-butyl peroxy 3,3,5-trimethylhexanoate, t-butyl peroxy Examples include oxylaurate, t-butyl peroxycarbonate, t-butyl peroxybenzoate, t-butyl peroxyisobutyrate, and the like.

Examples of the azo compounds include 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(2-methylbutyronitrile). , 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis(2-(2-imidazoline) -2-yl)propane), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), 2,2'-azobis(2-hydroxymethylpropion) nitrile), 4,4'-azobis(4-cyanovaleric acid), dimethyl 2,2'-azobis(2-methylpropionate), 2-cyano-2-propylazoformamide, 2-phenylazo-4- Examples include methoxy-2,4-dimethylvaleronitrile.
The above radical generators may be used alone or in combination of two or more.

The organic solvent used in the above method generally includes hydrocarbon solvents and halogenated hydrocarbon solvents. Among these organic solvents, hydrocarbon solvents such as n-butane, n-hexane, n-heptane, cyclohexane, benzene, toluene, and xylene are preferred.
The above organic solvents may be used alone or in combination of two or more.

Furthermore, when carrying out the reaction of adding a modified compound by the above method, an anti-aging agent may be added from the viewpoint of suppressing side reactions.
Preferred anti-aging agents used at this time include, for example, 2,6-di-t-butyl-4-methylphenol (BHT), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4 '-Thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol) (AO-40), 3,9-bis[1,1-dimethyl- 2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (AO-80), 2,4-bis[(octylthio)methyl]-6-methylphenol (Irganox1520L), 2,4-bis[(dodecylthio)methyl]-6-methylphenol (Irganox1726), 2-[1-(2-hydroxy- 3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate (SumilizerGS), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate (SumilizerGM), 6-t-butyl-4-[3-(2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxa phosphepin-6-yloxy)propyl]-2-methylphenol (SumilizerGP), tris(2,4-di-t-butylphenyl) phosphite (Irgafos168), dioctadecyl 3,3'-dithiobispropionate , hydroquinone, p-methoxyphenol, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (Nocrac 6C), bis(2,2,6,6-tetramethyl-4-piperidyl) Sebacate (LA-77Y), N,N-dioctadecylhydroxylamine (IrgastabFS042), bis(4-t-octylphenyl)amine (Irganox5057), and the like.
The above anti-aging agents may be used alone or in combination of two or more.

The amount of the antiaging agent added is preferably 0 to 10 parts by weight, more preferably 0 to 5 parts by weight, per 100 parts by weight of the unmodified conjugated diene polymer (F').

The temperature in the reaction of adding the silane compound (IV) to the unmodified conjugated diene polymer (F') is preferably 10 to 200°C, more preferably 50 to 180°C. The reaction time is preferably 1 to 200 hours, more preferably 1 to 100 hours, and even more preferably 1 to 50 hours.

By hydrosilylating the carbon-carbon double bonds contained in the unmodified conjugated diene polymer (F') in the presence of a platinum compound-containing catalyst and a co-catalyst used as necessary, an alkoxysilane compound or silyl As a method for introducing a functional group derived from a halide compound, a carbon-carbon double bond contained in the unmodified conjugated diene polymer (F') is introduced into the unmodified conjugated diene polymer (F') in the presence of a platinum compound-containing catalyst, preferably a platinum compound-containing catalyst. A preferred method is hydrosilylation using a silane compound (VI) represented by the following formula (VI) in the presence of a cocatalyst.

（式（ＶＩ）中、Ｖはアルコキシ基、水酸基、フッ素原子、塩素原子、臭素原子、又はヨウ素原子を示し、Ｒ⁶は炭素数６～１２のアリール基、又は炭素数１～１２のアルキル基を示し、ｎは１～３の整数であり、ｎが２以上の場合、Ｖは同一でも異なっていてもよく、３－ｎが２以上の場合、Ｒ⁶は同一でも異なっていてもよい。）

(In formula (VI), V represents an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and R ⁶ is an aryl group having 6 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms. and n is an integer from 1 to 3; when n is 2 or more, V may be the same or different; when 3-n is 2 or more, R ⁶ may be the same or different. )

Examples of the silane compound (VI) include silane compounds containing an alkoxysilyl group such as trimethoxysilane, methyldimethoxysilane, dimethylmethoxysilane, triethoxysilane, methyldiethoxysilane, and dimethylethoxysilane; trichloridosilane, methyl Examples include silane compounds containing a silyl halide group such as dichloridosilane, dimethylchloridesilane, tribromosilane, methyldibromosilane, and dimethylbromosilane. These silane compounds may be used alone or in combination of two or more.

In addition, when it is desired that the conjugated diene-based graft polymer used in the present invention has at least one functional group (c) selected from the group consisting of an alkoxy group and a hydroxyl group bonded to the branch point, it can be used as a silane compound (VI). Step (A-1) may be carried out using a functional group-modified conjugated diene polymer (F) obtained by hydrosilylating an unmodified conjugated diene polymer (F') with a silane compound containing an alkoxysilyl group.
Further, when the conjugated diene graft polymer used in the present invention is desired to have at least one functional group (c) selected from the group consisting of fluorine atom, chlorine atom, bromine atom, and iodine atom bonded to the branch point. , or when it is desired to obtain a polymer satisfying the above formula (3-3), the unmodified conjugated diene polymer (F') is hydrosilylated with a silane compound containing a silyl halide group as the silane compound (VI). Step (A-1) may be carried out using the functional group-modified conjugated diene polymer (F).

The above-mentioned silane compound (VI) causes the carbon-carbon double bonds contained in the unmodified conjugated diene polymer (F') to undergo a hydrosilylation reaction, whereby the functional groups derived from the silane compound (VI), specific A functional group-modified conjugated diene polymer (F) having a partial structure represented by the following formula (VII) as a functional group is obtained.

（式（ＶＩＩ）中、Ｒ⁶、Ｖ及びｎの定義は式（ＶＩ）と同一である。）

(In formula (VII), the definitions of R ⁶ , V and n are the same as in formula (VI).)

The platinum compound-containing catalyst used in the hydrosilylation reaction is not particularly limited, but examples include chloroplatinic acid, alcoholic solution of chloroplatinic acid, platinum-1,3-divinyl-1,1,3,3-tetramethyl Toluene or xylene solutions of disiloxane complexes, tetrakistriphenylphosphine platinum, dichlorobistriphenylphosphine platinum, dichlorobisacetonitrile platinum, dichlorobisbenzonitrile platinum, dichlorocyclooctadiene platinum, etc., platinum-carbon, platinum-alumina, platinum- Examples include supported catalysts such as silica.
From the viewpoint of selectivity during hydrosilylation, a zero-valent platinum complex is preferred, and a toluene or xylene solution of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex is more preferred.

The amount of the platinum compound-containing catalyst to be used is not particularly limited, but from the viewpoint of reactivity and productivity, the amount of platinum atoms contained is 1 x 10 ^-7 per mol of the silane compound (VI). The amount is preferably from 1 x 10 ^-2 mol, more preferably from 1 x 10 ^-7 to 1 x 10 ^-3 mol.

As the cocatalyst in the above reaction, it is preferable to use one or more selected from ammonium salts of inorganic acids, acid amide compounds, and carboxylic acids.

Examples of ammonium salts of inorganic acids include ammonium chloride, ammonium sulfate, ammonium amidosulfate, ammonium nitrate, monoammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium diphosphite, ammonium carbonate, and ammonium hydrogen carbonate. , ammonium sulfide, ammonium borate, ammonium borofluoride, and the like. Among these, ammonium salts of inorganic acids having a pKa of 2 or more are preferred, and ammonium carbonate and ammonium hydrogen carbonate are more preferred.

Examples of acid amide compounds include formamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, acrylamide, malonamide, succinamide, maleamide, fumaramide, benzamide, phthalamide, palmitic acid amide, stearic acid amide, and the like. Can be mentioned.

Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, methoxyacetic acid, pentanoic acid, caproic acid, heptanoic acid, octanoic acid, lactic acid, and glycolic acid. Among these, formic acid, acetic acid, and lactic acid are preferred, and acetic acid is more preferred.

The amount of co-catalyst to be used is not particularly limited, but from the viewpoint of reactivity, selectivity, cost, etc., it is 1 x 10 ^-5 to 1 x 10 ^-1 mol per 1 mol of the silane compound (VI). Preferably, 1×10 ⁻⁴ to 0.5×10 ⁻¹ mol is more preferable.

Although the above hydrosilylation reaction proceeds without a solvent, a solvent can also be used. Usable solvents include, for example, hydrocarbon solvents such as pentane, hexane, cyclohexane, heptane, isooctane, benzene, toluene, and xylene; ether solvents such as diethyl ether, tetrahydrofuran, and dioxane; and ethyl acetate, butyl acetate, etc. Examples include ester solvents; aprotic polar solvents such as N,N-dimethylformamide; and chlorinated hydrocarbon solvents such as dichloromethane and chloroform. These solvents may be used alone or in a mixture of two or more.

The reaction temperature in the above-mentioned hydrosilylation reaction is not particularly limited, and it can be carried out usually at a temperature of 0°C or higher, and if necessary, under heating conditions, but 0 to 200°C is preferable. In order to obtain an appropriate reaction rate, it is preferable to carry out the reaction under heating, and from this point of view, the reaction temperature is more preferably 40 to 110°C, and even more preferably 40 to 90°C. Further, the reaction time is not particularly limited, and is usually about 1 to 60 hours, preferably 1 to 30 hours, and more preferably 1 to 20 hours.

In the above functional group-modified conjugated diene polymer (F), the functional group having the partial structure represented by the above formula (V) or formula (VII) may be contained singly, or two or more types may be contained. It's okay. Therefore, the functional group-modified conjugated diene polymer (F) may be a diene polymer modified with one type of compound selected from the group consisting of the above-mentioned silane compound (IV) and silane compound (VI). , or a diene polymer modified with two or more kinds of compounds.

From the viewpoint of affinity and stability with the polar material of the resulting conjugated diene-based graft polymer, Z in the above formula (II) is preferably Si, Sn, or B, and more preferably Si. .

From the viewpoint of affinity with polar materials, stability, and transparency of the resulting conjugated diene-based graft polymer, V in the above formula (II) is preferably an alkoxy group, and an alkoxy group having 1 to 5 carbon atoms. are more preferred, and methoxy and ethoxy groups are particularly preferred. Furthermore, from the viewpoint of reactivity in the coupling step described below, V in the above formula (II) is preferably a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, and more preferably a chlorine atom.

n in the above formula (II) is an integer that satisfies the above formula (6). From the viewpoint of control, it is preferably 2 or more, more preferably 3 or more, and particularly preferably the same as "the valence of Z - 1".

The average number of moieties represented by the above formula (II) per molecule of the functional group-modified conjugated diene polymer (F) is preferably 1 to 50, more preferably 2 to 30, and further preferably 3 to 20. preferable.

The average number of functional groups V in the above formula (II) per molecule of the functional group-modified conjugated diene polymer (F) is preferably 2 to 150, more preferably 4 to 90, and 6 to 60. More preferred.

The average number of functional groups V in the above formula (II) per molecule of the functional group-modified conjugated diene polymer (F) is equal to the average number X of the functional groups (c) contained in the conjugated diene graft polymer. It can be calculated using a similar method.

The mixing ratio of the unmodified conjugated diene polymer (F') and the silane compound (IV) or the silane compound (VI) is, for example, the formula (II) per molecule of the functional group-modified conjugated diene polymer (F). ) may be set appropriately so that the average number of functional groups V contained in ) may be mixed so that the mass ratio with 0.3 to 100 is achieved.

The preferred ranges of Mw and vinyl content of the functional group-modified conjugated diene polymer (F) are the same as those for the unmodified conjugated diene polymer (F').

The melt viscosity of the functional group-modified conjugated diene polymer (F) measured at 38°C is preferably 0.1 to 2,000 Pa·s, more preferably 0.1 to 1,500 Pa·s, and 0.1 to 2,000 Pa·s, more preferably 0.1 to 1,500 Pa·s. 1 to 1,000 Pa·s is more preferable. When the melt viscosity of the functional group-modified conjugated diene polymer (F) is within the above range, it tends to have excellent process passability during production and good economic efficiency.

In step (A-1), by reacting the active terminal polymer (I) with the functional group-modified conjugated diene polymer (F), the functional group V in the moiety represented by the formula (II) and the above-mentioned A substitution reaction of the active end polymer (I) occurs, and a conjugated diene-based graft polymer is formed in which the active end polymer (I), which becomes a side chain, is bonded to the heteroatom Z, which is a branch point (hereinafter referred to as the present invention). (The reaction is called a coupling reaction). At least one remaining functional group V selected from the group consisting of an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom remains unreacted in the coupling reaction and the inactivation step described below. from the group consisting of an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom bonded to the branch point of the conjugated diene-based graft polymer when the functional group (functional group) remains as it is or is hydrolyzed. At least one selected functional group (c) is formed.

The average number W of the side chains (b) directly bonded to the branch point per molecule of the conjugated diene graft polymer is determined by the number W of the side chains (b) directly bonded to the branch point in the coupling reaction between the active end polymer (I) and the functional group-modified conjugated diene polymer ( It can be adjusted to a desired range by adjusting the ratio of the amounts of F). For example, in the case of (charged amount (number of moles) of active end polymer (I))/(charged amount (number of moles) of functional group-modified conjugated diene polymer (F)) = 4/1, the side chain (b ), the average number W is 4. However, the upper limit of W is the number of functional groups V that one molecule of the functional group-modified conjugated diene polymer (F) has.

The molar ratio of (amount of active end polymer (I) charged)/(amount of functional group-modified conjugated diene polymer (F) charged) is determined by direct bonding to the above branch point per molecule of conjugated diene graft polymer. The average number W of side chains (b) may be set as desired, for example, preferably from 1 to 200, more preferably from 2 to 100, and from 3 to 50. It is even more preferable that there be. If the molar ratio of (charged amount of active end polymer (I))/(charged amount of functional group-modified conjugated diene polymer (F)) is smaller than 1, the number of side chains that can be introduced will be smaller than 200. If it is large, the coupling rate, which will be described later, tends to decrease.

The above coupling reaction is usually carried out at a temperature range of 0 to 100°C for 0.5 to 50 hours. The functional group-modified conjugated diene polymer (F) may be used after being diluted, and the diluting solvent is not particularly limited as long as it is inert to the active end and does not adversely affect the reaction, such as hexane, cyclohexane, etc. , heptane, octane, decane, toluene, benzene, xylene, and other saturated aliphatic hydrocarbons or aromatic hydrocarbons.
Furthermore, a Lewis base may be added as an additive during the coupling reaction. Examples of Lewis bases include ethers such as dimethyl ether, diethyl ether, and tetrahydrofuran; glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; triethylamine, N,N,N',N'-tetramethylethylenediamine, and N-methylmorpholine. Examples include amines such as. These Lewis bases may be used alone or in combination of two or more.

In the coupling reaction, the functional group-modified conjugated diene polymer (F) may be added to the reaction vessel in which the active terminal polymer (I) has been synthesized, or conversely, the functional group-modified conjugated diene polymer (F) may be added to the reaction vessel in which the active terminal polymer (I) has been synthesized. The active terminal polymer (I) may be added to the polymer (F). Furthermore, as described above, either the active terminal polymer (I) or the functional group-modified conjugated diene polymer (F) may be used after being diluted with a solvent, if necessary. Further, the active terminal polymer (I) may be used alone or in combination of two or more, and the functional group-modified conjugated diene polymer (F) may also be used alone. Also, two or more types may be used in combination.

The coupling rate in the above coupling reaction is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. If the coupling rate is less than 50%, the mechanical properties of the resulting conjugated diene graft polymer will deteriorate, which is not preferable. The coupling rate is determined by the following formula (10) using the peak area of the component derived from the unreacted active end polymer (I) obtained by GPC measurement and the sum of all peak areas.
(Coupling rate (%)) = [{(sum of all peak areas) - (peak area of component derived from active end polymer (I))}/(sum of all peak areas)] x 100 ( 10)

The coupling rate can be increased by increasing the amount of the functional group-modified conjugated diene polymer (F), increasing the amount of Lewis base, increasing the reaction temperature, or increasing the reaction time. be able to. The coupling reaction can be carried out until the coupling rate is within the desired range. Thereafter, the coupling reaction can be stopped by adding a polymerization terminator such as methanol or isopropanol.

The number of functional groups (c) directly bonded to the branch point can be determined by the molar ratio of the charged amounts of the active end polymer (I) and the functional group-modified conjugated diene polymer (F) in the coupling reaction, or as described below. A reagent in the step of inactivating a part of at least one remaining functional group (unreacted functional group V) selected from the group consisting of an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. It can be adjusted to a desired range by adjusting the amount used, the reaction time, and the type and amount of the polar compound used if necessary.
As a method for adjusting the number of functional groups (c) directly bonded to the branch point to a desired range, for example, the amount of the active end polymer (I) and the functional group-modified conjugated diene polymer (F) to be charged is as follows. A coupling reaction is performed at a molar ratio such that the average number (X/Y) of functional groups (c) per branch point contained in the conjugated diene graft polymer is 1 or more, and then (X/Y) An example of this method is to inactivate a portion of the remaining functional groups (unreacted functional groups V) so that V is less than 1.

[Step (A-2)]
In the method for producing a conjugated diene-based graft polymer used in the present invention, in order to adjust the number of functional groups (c) directly bonded to the branch point to a desired range, after step (A-1),
(A-2) At least one remaining functional group (existing unreacted) selected from the group consisting of an alkoxy group, a hydroxyl group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom in the conjugated diene-based graft polymer. A step of inactivating a part of the functional group V) (hereinafter referred to as an inactivation step);
In one aspect, it is preferable to include the following.
When the remaining functional groups contained in the resulting conjugated diene graft polymer react with the water and acid added in the recovery step (C) to produce hydroxyl groups, and a relatively large number of hydroxyl groups are contained, these Since it is thought that a large amount of hydroxyl groups are likely to cause a condensation reaction, the inactivation step (A-2) is preferably performed before the recovery step (C). Furthermore, when the method for producing a conjugated diene-based graft polymer includes the hydrogenation step (B) described below, the inactivation step (A-2) may be performed either before or after the hydrogenation step (B). However, from the viewpoints of ease of adjusting the number of functional groups (c) and reactivity in the hydrogenation step (B), it is preferable to carry out this step before the hydrogenation step (B).

Examples of reagents used to inactivate alkoxy groups, hydroxyl groups, fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms (hereinafter sometimes referred to as inactivating reagents) include methyllithium, ethyllithium, Alkyllithiums such as n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, t-butyllithium; methyl sodium, ethyl sodium, n-propyl sodium, isopropyl sodium, n-butyl sodium, sec-butyl Alkyl sodiums such as sodium and t-butyl sodium; alkyl potassiums such as methylpotassium, ethylpotassium, n-propylpotassium, isopropylpotassium, n-butylpotassium, sec-butylpotassium, t-butylpotassium; methylmagnesium bromide, Alkylmagnesium halides such as ethylmagnesium bromide, t-butylmagnesium bromide, t-butylmagnesium chloride, sec-butylmagnesium iodide; dimethylcopperlithium, diethylcopperlithium, methylethylcopperlithium, methyl n-propylcopperlithium , dialkyl copper lithiums such as ethyl n-butyl copper lithium; lithium amides such as lithium diisopropylamide, lithium diisoethylamide, lithium di-t-butylamide; and the like. Among these, n-butyllithium, sec-butyllithium, methyllithium, methylmagnesium bromide, and dimethylcopperlithium are preferred, since it is desirable that steric hindrance be small in order for the inactivation reaction to proceed rapidly.

Amount of inactivating reagent used in step (A-2)/alkoxy group, hydroxyl group, fluorine atom, chlorine derived from functional group V contained in the conjugated diene graft polymer obtained in step (A-1) The molar ratio of the total amount of atoms, bromine atoms, and iodine atoms is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 2.0 or more. Further, it is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less. If the amount of the inactivating reagent is small, the number of functional groups (c) directly bonded to the branch point cannot be adjusted to the desired range, and if the amount of the inactivating reagent is large, it may not be economical. tends to get worse.

The inactivation reaction in step (A-2) above is usually carried out at a temperature range of 0 to 100°C for 0.1 to 50 hours. The inactivating reagent may be used diluted, and the diluting solvent is not particularly limited as long as it is inert to the inactivating reagent and does not adversely affect the reaction, such as hexane, cyclohexane, heptane, octane, Examples include saturated aliphatic hydrocarbons or aromatic hydrocarbons such as decane, toluene, benzene, and xylene. Furthermore, a Lewis base may be added as an additive during the above inactivation reaction. Examples of Lewis bases include ethers such as dimethyl ether, diethyl ether, and tetrahydrofuran; glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; ; Examples include amines such as triethylamine, N,N,N',N'-tetramethylethylenediamine, and N-methylmorpholine. These Lewis bases may be used alone or in combination of two or more.

The above-mentioned inactivation reaction can be carried out until the number of functional groups (c) directly bonded to the above-mentioned branch point reaches a desired range. Thereafter, the deactivation reagent can be deactivated by adding a polymerization terminator such as methanol or isopropanol.

Note that the conjugated diene-based graft polymer obtained by the production method including step (A-1) and step (C) without including step (B) described in detail below is an unhydrogenated conjugated diene-based graft polymer. .

[Process (B)]
The method for producing the conjugated diene graft polymer used in the present invention includes, before step (C),
(B) a step of hydrogenating the unhydrogenated conjugated diene graft polymer to form a hydrogenated conjugated diene graft polymer;
In one aspect, it is preferable to include the following.

By subjecting the unhydrogenated conjugated diene graft polymer obtained by the above method to a step of hydrogenating it, a hydrogenated conjugated diene graft polymer can be obtained. There are no particular limitations on the hydrogenation method, and for example, known methods can be used. The above step (A-1) (or step (A-2)) and hydrogenation may be performed successively, or the unhydrogenated conjugated diene graft polymer may be isolated and then hydrogenated. The method for isolating the unhydrogenated conjugated diene graft polymer is the same as the recovery step (C) described below.

As the catalyst used in the hydrogenation reaction in step (B), a catalyst capable of hydrogenating a carbon-carbon double bond contained in an olefin compound or the like can be used. Such catalysts usually include heterogeneous catalysts, homogeneous catalysts, and the like.

The above-mentioned heterogeneous catalyst is not particularly limited, but specific examples include sponge metal catalysts such as sponge nickel, sponge cobalt, and sponge copper; nickel silica, nickel alumina, nickel zeolite, nickel diatomaceous earth, palladium silica, palladium alumina, and palladium zeolite. , palladium diatomaceous earth, palladium carbon, palladium calcium carbonate, platinum silica, platinum alumina, platinum zeolite, platinum diatomaceous earth, platinum carbon, platinum calcium carbonate, ruthenium silica, ruthenium alumina, ruthenium zeolite, ruthenium diatomaceous earth, ruthenium carbon, ruthenium calcium carbonate, iridium Supported metal catalysts include silica, iridium alumina, iridium zeolite, iridium diatomaceous earth, iridium carbon, iridium calcium carbonate, cobalt silica, cobalt alumina, cobalt zeolite, cobalt diatomaceous earth, cobalt carbon, and cobalt calcium carbonate.
These heterogeneous catalysts may be modified with iron, molybdenum, magnesium, etc. for the purpose of improving activity, selectivity, and stability. Further, these heterogeneous catalysts may be used alone or in a mixture of two or more.

The above-mentioned homogeneous catalyst is not particularly limited, but specific examples include Ziegler-based catalysts and metallocene-based catalysts consisting of a transition metal compound and alkyl aluminum or alkyl lithium.
Specific examples of transition metal compounds used in Ziegler catalysts include nickel salts such as nickel acetate, nickel octylate, and nickel acetylacetonate; cobalt salts such as cobalt acetate, cobalt octylate, and cobalt acetylacetonate; titanocene dichloride, and zirconocene. Dichloride is mentioned.
Specific examples of aluminum alkyl used in the Ziegler catalyst include trimethylaluminum, triethylaluminum, triisobutylaluminum, and trioctylaluminum.
Specific examples of the alkyllithium used in the Ziegler catalyst include methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, and t-butyllithium.
These homogeneous catalysts may be used alone or in combination of two or more. Furthermore, the homogeneous catalyst may be used in combination with a heterogeneous catalyst.

In the hydrogenation reaction of step (B), since the polymer is hydrogenated, the reaction activity toward low-molecular compounds is generally low. Therefore, relatively high temperature and high pressure conditions are often preferable as reaction conditions, and it is preferable to use a heterogeneous catalyst with high thermal stability. From the viewpoint of hydrogenation activity, it is preferable to use nickel or palladium as the metal having hydrogenation activity. Further, in order to suppress undesirable side reactions during the hydrogenation reaction, it is preferable to use calcium carbonate or a carbon carrier as the carrier, and it is more preferable to use a carbon carrier.

The hydrogenation reaction is usually performed in an organic solvent. Such an organic solvent is not particularly limited, and for example, the solvent used in the anionic polymerization exemplified in the above step (A-1) can be used.

The above hydrogenation reaction is carried out, for example, while the unhydrogenated conjugated diene-based graft polymer is present in the solvent used in the above step (A-1), without any particular treatment of the organic solvent. Alternatively, the reaction may be carried out in the remaining solvent after a portion of the solvent is removed by a method such as distillation, or the reaction may be carried out in the solvent after being separately diluted with an organic solvent. Further, after the above step (A-1) (or step (A-2)) is completed, the unhydrogenated conjugated diene graft polymer is once taken out, and the unhydrogenated conjugated diene graft polymer is put into an organic solvent. However, the hydrogenation reaction may be carried out in the solvent.

When the hydrogenation reaction is carried out in an organic solvent, the amount of organic solvent used should be such that the concentration of the unhydrogenated conjugated diene graft polymer in the reaction solution is 1% by mass or more and 30% by mass or less. is preferred. If the amount is less than 1% by mass, productivity may drop significantly, and if it exceeds 30% by mass, the viscosity may increase significantly and the mixing efficiency may decrease.

The reaction pressure of the hydrogenation reaction may be set appropriately depending on the catalyst used, but the total pressure is usually 0.1 MPa to 20 MPa, preferably 0.5 MPa to 15 MPa, more preferably 0.5 MPa to 5 MPa. be.

The hydrogenation reaction is carried out in the presence of hydrogen gas, but may be carried out in the presence of a gas mixed with a gas other than hydrogen gas that is inert to the hydrogenation reaction. Specific examples of gases inert to the hydrogenation reaction include nitrogen, helium, argon, and carbon dioxide. Further, depending on the reaction conditions, the solvent used in the reaction may have a significant partial pressure as a gas component, but such a situation usually poses no problem as long as the hydrogenation reaction proceeds.

The reaction temperature of the hydrogenation reaction may be appropriately set depending on the catalyst used, but is usually 20°C to 250°C, preferably 50°C to 180°C, more preferably 70°C to 180°C. In general, it may be desirable for heterogeneous catalysts to react at higher temperatures than for homogeneous catalysts.
The reaction time of the hydrogenation reaction may be appropriately set depending on the type of catalyst used, the amount of catalyst, and the reaction temperature, but is usually 0.1 to 100 hours, preferably 1 to 50 hours. If the reaction time is too short, it may not be possible to obtain the desired hydrogenation rate. Furthermore, if the reaction time is too long, undesired side reactions will proceed significantly, and a hydrogenated conjugated diene-based graft polymer with desired physical properties may not be obtained.

The reaction format of the hydrogenation reaction is not particularly limited and may be appropriately set depending on the type of catalyst used in the reaction. Examples of the reaction format include a batch reaction format, a semi-continuous reaction format (semi-batch reaction format), and a continuous reaction format. Suitable continuous reaction formats include plug flow format (PFR), continuous flow stirring format (CSTR), and the like.
When using a heterogeneous catalyst, a fixed bed reactor can be used for the hydrogenation reaction.
When the hydrogenation reaction is carried out under active mixing conditions, examples of the mixing method include a mixing method using stirring and a mixing method where the reaction solution is circulated in a loop format.
When a heterogeneous catalyst is used under mixed conditions, the reaction takes place in a suspended bed, creating a gas-liquid-solid reaction field. Furthermore, when a homogeneous catalyst is used under mixed conditions, it becomes a gas-liquid two-phase reaction field.
Hydrogen is produced in a reaction format in which the hydrogenation reaction in the reactor is once completed, the reaction liquid is extracted, and at least a portion of the extracted reaction liquid is charged into the same or different reactor to further carry out the hydrogenation reaction. An addition reaction may also be performed. By carrying out the hydrogenation reaction in such a reaction format, if it becomes possible to avoid localized heat generation accompanying the hydrogenation reaction, the hydrogenation rate may be improved.
The hydrogenation reaction may be performed in a single reaction format, or in combination of two or more of the same or different reaction formats.
When aiming for a higher hydrogenation rate, it may be desirable to use a fixed bed reaction tank and use a hydrogenation reaction process that includes a step of reacting in a plug flow format.

The amount of catalyst used in the hydrogenation reaction may be determined as appropriate depending on the type of catalyst used, the concentration of the unhydrogenated conjugated diene graft polymer, the reaction format, etc. When carrying out a hydrogenation reaction, the amount of catalyst used per 100 parts by mass of the reaction solution containing the unhydrogenated conjugated diene graft polymer is usually 0.01 to 20 parts by mass, preferably 0.05 to 15 parts by mass, More preferably, it is 0.1 to 10 parts by mass. If the amount of catalyst used is too small, a long time may be required for the hydrogenation reaction, and if the amount of catalyst used is too large, more power may be required to mix the heterogeneous catalyst. In addition, when carrying out a hydrogenation reaction in a fixed bed, it is difficult to specify the amount of catalyst to be used per reaction solution containing an unhydrogenated conjugated diene-based graft polymer. Just set it.
Ziegler-based catalyst as a homogeneous catalyst; When using a metallocene-based catalyst, the concentration in the reaction solution containing the unhydrogenated conjugated diene-based graft polymer of the transition metal compound is usually 0.001 mmol/liter to 100 mmol/liter. , preferably from 0.01 mmol/liter to 10 mmol/liter.

The catalyst used in the hydrogenation reaction may be separated from the liquid containing the hydrogenated conjugated diene graft polymer, if necessary, after the hydrogenation reaction is completed. The separation method is not particularly limited as long as the catalyst can be separated. If a heterogeneous catalyst is used, it can be separated, for example, by continuous or batch filtration, centrifugation, settling by standing, and decantation. When a homogeneous catalyst is used, the catalyst can be separated by, for example, coagulation precipitation, adsorption, washing, and aqueous phase extraction.
Even if the used catalyst is separated by these separation methods, trace amounts of metal components derived from the catalyst may remain in the liquid containing the hydrogenated conjugated diene graft polymer. In this case as well, since metal components remain in the liquid, the remaining metal components can be separated by separation methods such as coagulation and precipitation, adsorption, washing, and aqueous phase extraction, as described above.
The catalyst recovered by separation can be used again in the hydrogenation reaction after removing a portion of it or adding a new catalyst as necessary.

[Step (C)]
The method for producing the conjugated diene graft polymer used in the present invention is as follows:
(C) recovering the obtained conjugated diene graft polymer;

In step (C), the obtained conjugated diene graft polymer used in the present invention is recovered. There is no particular restriction on the method for recovering the conjugated diene graft polymer, but for example, before performing step (C), the conjugated diene graft polymer is made into a solution containing the polymer, and the conjugated diene graft polymer is recovered. The conjugated diene-based graft polymer was precipitated by pouring the solution containing it into a poor solvent such as methanol, or the polymerization reaction solution was poured into hot water with steam to remove the solvent by azeotropy (steam stripping). After that, the conjugated diene graft polymer can be isolated and recovered by drying or by washing the polymerization reaction solution with water, separating and drying. In addition, if the conjugated diene graft polymer has already been obtained as a solution containing the conjugated diene graft polymer before performing step (C), it can be used as is or after concentrating or diluting the solution. , the step (C) may be performed by the method described above.

[Oil composition]
The oil composition of the present invention comprises a base oil and the viscosity index improver of the present invention.

[Base oil]
There are no particular limitations on the base oil, and for example, known base oils can be used. Base oils include, for example, fuel oils such as middle distillate fuels, synthetic and natural lubricating oils, unrefined oils, and industrial oils. Furthermore, the base oil may be at least one of paraffinic base oil, naphthenic base oil, and aromatic base oil, and may be at least one of natural oil and synthetically prepared oil. . Furthermore, the base oil may be any base oil from Groups I to V in the classification of API (American Petroleum Institute), but from the economic point of view, base oils from Groups I to III are preferred as base oils. Preferably, Group I base oils are more preferred. Examples of Group I base oils include "AP/E CORE 150" and "AP/E CORE 600" manufactured by ExxonMobil. Furthermore, examples of base oils that can be used in the oil composition of the present invention include those described in Japanese Patent No. 5933263 and Japanese Patent Application Laid-open No. 2005-23320.

[Content of viscosity index improver]
The oil composition of the present invention contains a viscosity index improver comprising the conjugated diene graft polymer of the present invention. The content of the viscosity index improver in the oil composition can be adjusted as appropriate so that the viscosity and viscosity index of the lubricating oil fall within a desired range, but it is preferably 0.1 to 20% by mass, and 0.1 to 20% by mass. It is more preferably 5 to 15% by weight, and particularly preferably 0.5 to 10% by weight. When the content of the viscosity index improver is within the above range, the lubricating oil tends to have an excellent balance between performance and economic efficiency.

[Other additives]
The oil composition of the present invention contains additives such as rust inhibitors, antioxidants, surfactants, pour point depressants, detergent dispersants, metal deactivators, antifoaming agents, friction modifiers, and extreme pressure agents. May contain. These additives may be used alone or in combination of two or more.

[Method for producing oil composition]
The method for producing the oil composition of the present invention is not particularly limited as long as the oil composition can be produced; for example, it can be produced by mixing the base oil and the viscosity index improver. Mixing can be performed using, for example, a known mixing device. Preferably, the mixing is performed while heating. The heating temperature is preferably 80 to 180°C.

When the oil composition of the present invention is used as an engine oil, automatic transmission fluid, gear lubricating oil, hydraulic oil, etc., the kinematic viscosity at 40°C is preferably in the range of 40 to 300 mm 2 /sec, and in the range of 50 to 300 mm ² /sec. A range of 150 mm ² /sec is preferred. Further, from the same viewpoint, the kinematic viscosity at 100° C. is preferably in the range of 3 to 30 mm ² /sec, more preferably in the range of 4 to 20 mm ² /sec. Within this range, when used for the above purpose, the fuel consumption of the vehicle can be reduced. In the present invention, the kinematic viscosity is a value measured in accordance with JIS K2283:2000.

When the oil composition of the present invention is used as an engine oil, automatic transmission fluid, gear lubricating oil, hydraulic oil, etc., its shear stability is preferably in the range of 0 to 20%, and preferably in the range of 0 to 10%. is more preferable, and a range of 0 to 4% is particularly preferable. In the present invention, the shear stability is measured using an oil composition adjusted to have a kinematic viscosity of 15 to 16 mm ² /sec at 100°C in accordance with JPI-5S-29-2006. This is a value obtained by measuring the rate of decrease in viscosity.

The conjugated diene graft polymer obtained in the present invention can be mixed with the base oil and used as an oil composition.
The oil composition containing this conjugated diene graft polymer and base oil can be used, for example, in a cosmetic composition constituting a cosmetic product. Cosmetic products include, for example, hair make-up products such as shampoos, hair-setting gels or lotions, blow-drying lotions, fixing and styling agents; skin make-up products such as foundations, eye shadows, blushers, concealers, compact powders, and make-up bases. lip makeup products such as lipstick, liquid lipstick, and lip gloss; cleansing products such as facial foam and makeup remover; cream products such as vaseline cream, hand cream, and cream for ultrasound diagnosis. Can be mentioned.
In addition, the above oil compositions can be used as asphalt modifiers, adhesives, adhesives, resin modifiers, compatibilizers, sealants, coating materials, molded products, fibers/nonwoven fabrics, drilling fluids, optical fiber cables and electric cables. It can be used as an internal buffer for cables, etc.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, in the following Examples and Comparative Examples, the physical properties of the conjugated diene graft polymer were evaluated by the following method.

(1) Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw/Mn)
By gel permeation chromatography (GPC), the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw/Mn) of the conjugated diene-based graft polymer and the polymer at each stage of its production are determined. Calculated in terms of standard polystyrene.
Equipment: Tosoh Corporation GPC equipment “HLC-8220”
Separation column: “TSKgel SuperMultiporeHZ-M (column diameter = 4.6 mm, column length = 15 cm)” manufactured by Tosoh Corporation (used by connecting two columns in series)
Eluent: Tetrahydrofuran Eluent flow rate: 0.35 mL/min Column temperature: 40°C
Detection method: Differential refractive index (RI)
Injection volume: 10μl
Concentration: 1mg/1cc (conjugated diene graft polymer/THF)

(2) Vinyl content, structural unit content derived from styrene, hydrogenation rate
By ¹ H-NMR, the vinyl content of the conjugated diene-based graft polymer and the polymer at each stage of its production, the content of structural units derived from styrene, and the hydrogenation rate were calculated. From the area ratio of the double bond peak derived from the structural unit derived from the vinylated conjugated diene and the double bond peak derived from the structural unit derived from the non-vinylated conjugated diene in the obtained spectrum, the vinyl The content was calculated, and the content of structural units derived from styrene was calculated from the area ratio of the peak of the aromatic ring derived from the structural unit derived from styrene and the peak of the double bond derived from the structural unit derived from the conjugated diene. . The vinyl content and the content of structural units derived from styrene were determined using ¹ H-NMR of the conjugated diene graft polymer before hydrogenation. In addition, the hydrogenation rate is calculated from the ratio of the peaks of double bonds derived from structural units derived from conjugated dienes in the conjugated diene graft polymer before hydrogenation and the hydrogenated conjugated diene graft polymer after hydrogenation. did.
Equipment: Nuclear magnetic resonance apparatus “JNM-ECX400” manufactured by JEOL Ltd.
Solvent: Deuterated chloroform Measurement temperature: 50°C
Accumulated number of times: 1024 times

(3) Average number Y of Si atoms (branch points) per polymer molecule
The average number Y of Si atoms (branch points) per molecule of the conjugated diene-based graft polymer and the functional group-modified conjugated diene-based polymer (F) is determined by the It is determined by the following formula using the Si content (mass %) of the union and the number average molecular weight (Mn) in terms of standard polystyrene.
(Number of Si atoms per molecule of polymer) = [(Si content (mass%)) / 100] × [(number average molecular weight Mn) / (molecular weight of structural unit derived from styrene) × (conjugated diene and Average molecular weight of structural units derived from monomers other than the conjugated diene included as necessary)]/Atomic weight of Si For Synthesis Example 6, the B atom per polymer molecule (branch point ) was calculated.

(4) Average number of functional groups (c) per Si atom (branch point) contained in the conjugated diene graft polymer (X/Y)
The average number (X/Y) of functional groups (c) (at least one selected from the group consisting of alkoxy groups and hydroxyl groups) per Si atom (branch point) contained in the conjugated diene graft polymer is It was determined from the results of ²⁹ Si-NMR measurement of the graft polymer. Specifically, the integral values of Si to which one functional group (c) is bonded, Si to which two functional groups (c) are bonded, etc. are multiplied by the number of functional groups, and then the integral is calculated. Calculated by comparing with the simple sum of the values.
Regarding Synthesis Example 6, by measuring ¹¹ B-NMR, the average number (X/Y) of functional groups (c) per B atom (branch point) contained in the conjugated diene graft polymer was determined by the same method. I asked for

(5) Average number of functional groups (c) per molecule of conjugated diene graft polymer
The average number of functional groups (c) per molecule of the conjugated diene graft polymer, X, is the average number of functional groups (c) per Si atom (branch point) contained in the conjugated diene graft polymer (X/Y ) and the average number Y of Si atoms per molecule of the above-mentioned conjugated diene graft polymer.
(Average number of functional groups (c) per molecule of conjugated diene graft polymer /Y))×(Average number of Si atoms per conjugated diene graft polymer molecule Y)
Regarding Synthesis Example 6, the average number of functional groups (c) per B atom (branch point) contained in the conjugated diene graft polymer and the average number of B atoms per molecule of the conjugated diene graft polymer were used. Then, the average number X of functional groups (c) per molecule of the conjugated diene graft polymer was determined.

(6) Average number W of side chains (b) per molecule of conjugated diene graft polymer
The average number W of side chains (b) per molecule of the conjugated diene graft polymer is determined by the number of active terminal polymers ( It was determined from the following formula using the charged amount (number of moles) per active terminal of I) and the charged amount (number of moles) of the functional group-modified conjugated diene polymer (F).
(Average number W of side chains (b) per molecule of conjugated diene graft polymer) = (Amount charged per active end of active end polymer (I) that becomes a component of side chain (b) (number of moles) ))/(Amount of functional group-modified conjugated diene polymer (F) (number of moles))

(7) Average number of side chains (b) per Si atom (branch point) contained in the conjugated diene graft polymer (W/Y)
The average number (W/Y) of side chains (b) per Si atom (branch point) contained in the conjugated diene graft polymer is the average number of side chains (b) per molecule of the conjugated diene graft polymer. It was determined from the following formula using the number W and the average number Y of Si atoms per molecule of the conjugated diene graft polymer.
(Average number of side chains (b) per Si atom contained in the conjugated diene graft polymer (W/Y)) = (Average number W of side chains (b) per molecule of the conjugated diene graft polymer) /(average number of Si atoms per conjugated diene graft polymer molecule Y)
Regarding Synthesis Example 6, using the average number W of side chains (b) per molecule of the conjugated diene graft polymer and the average number Y of B atoms per molecule of the conjugated diene graft polymer, The average number (W/Y) of side chains (b) per B atom (branch point) contained in the graft polymer was determined.

(8) Coupling rate The coupling rate of the conjugated diene graft polymer was calculated from the following formula using the peak area of the unreacted polymer component obtained in the above GPC measurement and the sum of all peak areas. .
(Coupling rate (%)) = [{((sum of all peak areas) - (peak area of component derived from active end polymer (I))}/(sum of all peak areas)] x 100

(9) Content of chlorine The content of chlorine contained in the conjugated diene graft polymer was calculated by automatic combustion ion chromatography.
<Combustion device>
・Device: Automatic sample combustion device “AQF-2100H” manufactured by Mitsubishi Chemical Analytech Co., Ltd.
・Combustion temperature: 1000℃
・Absorption liquid: Ion exchange water <Ion chromatography>
・Device: Ion chromatograph “ICS-2100” manufactured by Thermo Fisher Scientific
・Separation column: “IonPac AS20” manufactured by Thermo Fisher Scientific
・Eluent: KOH aqueous solution ・Column temperature: 40°C

(10) Kinematic viscosity Kinematic viscosity at 40°C and 100°C was measured in accordance with JIS K2283:2000.

(11) Viscosity index The viscosity index was measured in accordance with JIS K2283:2000.

(12) Shear stability degree Shear stability degree (rate of decrease in kinematic viscosity at 100° C.) was measured in accordance with JPI-5S-29-2006.

[Synthesis example 1]
(Step (1))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 1370 g of cyclohexane and 240 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then brought to a polymerization temperature of 50°C under stirring conditions. While controlling as follows, 1250 g of butadiene was successively added and polymerized for 1 hour. Thereafter, 14 g of methanol was added to stop the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After finishing the stirring and confirming that the polymer solution phase and the aqueous phase were separated, water was separated. After the washing, the polymer solution was vacuum-dried at 70° C. for 24 hours to obtain an unmodified conjugated diene polymer (F'-1).

(Step (2))
Subsequently, 460 g of the unmodified conjugated diene polymer (F'-1) obtained in step (1) was charged into an autoclave having a capacity of 1 L, and the autoclave was degassed with nitrogen while stirring at 60° C. for 3 hours. 0.6 g of t-butylperoxypivalate and 290 g of 3-mercaptopropyltriethoxysilane were added and reacted at 80° C. for 8 hours to obtain a functional group-modified conjugated diene polymer (F-1). Analysis of the obtained functional group-modified conjugated diene polymer (F-1) revealed the weight average molecular weight, vinyl content, and styrene origin of the main chain (a) of the conjugated diene graft polymer (G-1), which will be described later. The structural unit content can be determined. The weight average molecular weight of the obtained functional group-modified conjugated diene polymer (F-1) was 6,000, the vinyl content was 10 mol%, the content of structural units derived from styrene was 0% by mass, and the content was per molecule of the polymer. The average number of Si atoms was 8. 1750 g of cyclohexane was added to the obtained functional group-modified conjugated diene polymer (F-1) to dilute it to a concentration of 30% by mass, and the resulting functional group-modified conjugated diene polymer (F-1) was diluted to a concentration of 30% by mass. ) was obtained.

(Step (3))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 2270 g of cyclohexane and 8.7 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then set the polymerization temperature to 50°C under stirring conditions. 570 g of isoprene was successively added while controlling the polymerization so that the polymerization was carried out for 1 hour to obtain an active terminal polymer (I-1). By sampling and analyzing the polymer solution in step (3), the weight average molecular weight, vinyl content, and structural unit derived from styrene of the side chain (b) of the conjugated diene graft polymer (G-1), which will be described later, can be determined. The content can be determined. The weight average molecular weight of the obtained active terminal polymer (I-1) was 60,000, the vinyl content was 10 mol%, and the content of structural units derived from styrene was 0% by mass.

(Step (4))
Subsequently, 0.7 g of tetrahydrofuran and the functional group-modified conjugated diene polymer (F-1) obtained in step (2) were added to the solution containing the active terminal polymer (I-1) obtained in step (3). 20 g of the diluted solution was added and a coupling reaction was carried out at 50° C. for 2 hours. Thereafter, 26 g of sec-butyllithium (10.5% by mass cyclohexane solution) was added and reacted for 6 hours to seal off a portion of the remaining alkoxy groups. Thereafter, 1.0 g of methanol was added to stop the polymerization reaction to obtain a solution containing the (unhydrogenated) conjugated diene graft polymer (G'-1) before hydrogenation.

(Step (5))
To the obtained polymer solution, 100 mL of a Ziegler hydrogenation catalyst (0.095 mmol/L cyclohexane solution) formed from nickel octylate and trimethylaluminum was added, and the mixture was reacted for 5 hours at a hydrogen pressure of 1 MPa and a temperature of 80°C. A solution containing a conjugated diene graft polymer (hydrogenated conjugated diene graft polymer) (G-1) was obtained.

(Step (6))
The obtained solution containing the hydrogenated conjugated diene-based graft polymer (G-1) was washed with water to remove the catalyst, and the polymer solution after washing was vacuum-dried at 70°C for 24 hours to perform hydrogenation. A conjugated diene graft polymer (G-1) was obtained. The weight average molecular weight of the obtained hydrogenated conjugated diene graft polymer (G-1) was 486,000, Mw/Mn was 1.5, the content of structural units derived from styrene was 0% by mass, and the coupling rate was 95%, the hydrogenation rate is 99 mol%, the average number of Si atoms (branch points) per polymer molecule is 8, the average number of functional groups (c) per polymer molecule is 0.8, The average number of functional groups (c) per Si atom (branch point) is 0.1, the average number of side chains (b) per polymer molecule is 8, side chains per Si atom (branch point) The average number of pieces in (b) was one. The types and amounts of each reagent used in Example 1 are shown in Table 1, and the molecular specifications and physical properties of the obtained hydrogenated conjugated diene graft polymer (G-1) are shown in Tables 2 and 3.

[Synthesis Examples 2 to 4]
(Step (1))
Conjugated diene graft polymer (G-2 ) to (G-4) were obtained. The molecular specifications and physical properties of the obtained conjugated diene graft polymers (G-2) to (G-4) are shown in Tables 2 and 3.

[Synthesis example 5]
(Step (1))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 1370 g of cyclohexane and 240 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then brought to a polymerization temperature of 50°C under stirring conditions. While controlling as follows, 1250 g of butadiene was successively added and polymerized for 1 hour. Thereafter, 14 g of methanol was added to stop the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After finishing the stirring and confirming that the polymer solution phase and the aqueous phase were separated, water was separated. After the washing, the polymer solution was vacuum-dried at 70° C. for 24 hours to obtain an unmodified conjugated diene polymer (F'-5).

(Step (2))
Subsequently, 530 g of the unmodified conjugated diene polymer (F'-5) obtained in step (1), 1400 g of toluene, A toluene solution of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (1.8×10 ^-4 mol as platinum atoms) and 1.1 g of acetic acid were charged. 220 g of triethoxysilane was added dropwise into the mixture over 2 hours at an internal temperature of 75 to 85°C, followed by stirring at 80°C for 1 hour. After stirring, the mixture was concentrated under reduced pressure and filtered to obtain a functional group-modified conjugated diene polymer (F-5). Analysis of the obtained functional group-modified conjugated diene polymer (F-5) revealed the weight average molecular weight, vinyl content, and styrene origin of the main chain (a) of the conjugated diene graft polymer (G-5), which will be described later. The structural unit content can be determined. The weight average molecular weight of the obtained functional group-modified conjugated diene polymer (F-5) was 6,000, the vinyl content was 10 mol%, the content of structural units derived from styrene was 0% by mass, per molecule of the polymer. The average number of Si atoms was 8. Add 1750 g of cyclohexane to the obtained functional group-modified conjugated diene polymer (F-5) to dilute it to a concentration of 30% by mass, and prepare the functional group-modified conjugated diene polymer (F-5) to be used in the coupling reaction described below. ) was obtained.

(Step (3))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 2270 g of cyclohexane and 8.7 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then set the polymerization temperature to 50°C under stirring conditions. 570 g of isoprene was successively added while controlling the polymerization to be as follows, and polymerization was carried out for 1 hour to obtain an active terminal polymer (I-5). By sampling and analyzing the polymer solution in step (3), the weight average molecular weight, vinyl content, and structural unit derived from styrene of the side chain (b) of the conjugated diene graft polymer (G-5), which will be described later, can be determined. The content can be determined. The weight average molecular weight of the obtained active terminal polymer (I-5) was 60,000, the vinyl content was 10 mol%, and the content of structural units derived from styrene was 0% by mass.

(Step (4))
Subsequently, 0.7 g of tetrahydrofuran and the functional group-modified conjugated diene polymer (F-5) obtained in step (2) were added to the solution containing the active terminal polymer (I-5) obtained in step (3). 20 g of the diluted solution was added and a coupling reaction was carried out at 50° C. for 2 hours. Thereafter, 26 g of sec-butyllithium (10.5% by mass cyclohexane solution) was added and reacted for 6 hours to seal off a portion of the remaining alkoxy groups. Thereafter, 1.0 g of methanol was added to stop the polymerization reaction, and a solution containing an unhydrogenated conjugated diene graft polymer (G'-5) was obtained.

(Step (5))
Add 100 mL of Ziegler hydrogenation catalyst (0.095 mmol/L cyclohexane solution) formed from nickel octylate and trimethylaluminum to the obtained solution containing the unhydrogenated conjugated diene graft polymer (G'-5). The mixture was reacted for 5 hours at a hydrogen pressure of 1 MPa and at 80° C. to obtain a solution containing a conjugated diene graft polymer (hydrogenated conjugated diene graft polymer) (G-5).

(Step (6))
The obtained solution containing the hydrogenated conjugated diene-based graft polymer (G-5) was washed with water to remove the catalyst, and the polymer solution after washing was vacuum-dried at 70°C for 24 hours to perform hydrogenation. A conjugated diene graft polymer (G-5) was recovered. The weight average molecular weight of the obtained hydrogenated conjugated diene graft polymer (G-5) was 486,000, Mw/Mn was 1.5, the content of structural units derived from styrene was 0% by mass, and the coupling rate was 95%, hydrogenation rate is 99 mol%, average number of Si atoms (branch points) per polymer molecule is 8, average number of functional groups (c) per polymer molecule is 0.8, The average number of functional groups (c) per Si atom (branch point) is 0.1, the average number of side chains (b) per polymer molecule is 8, side chains per Si atom (branch point) The average number of pieces in (b) was one. Table 2 shows the molecular specifications of the obtained hydrogenated conjugated diene graft polymer (G-5).

[Synthesis example 6]
(Step (1))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 1370 g of cyclohexane and 240 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then brought to a polymerization temperature of 50°C under stirring conditions. While controlling as follows, 1250 g of butadiene was successively added and polymerized for 1 hour. Thereafter, 14 g of methanol was added to stop the polymerization reaction to obtain a polymer solution. Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After completing the stirring and confirming that the polymer solution phase and the aqueous phase were separated, water was separated. After the washing, the polymer solution was vacuum-dried at 70° C. for 24 hours to obtain an unmodified conjugated diene polymer (F'-6).

(Step (2))
Subsequently, 590 g of the unmodified conjugated diene polymer (F'-6) obtained in step (1) and 1400 g of cyclohexane were placed in a 5 L separable flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer. The mixture was charged and replaced with nitrogen. To this, 160 g of trimethyl borate and 1.8 g of triethylamine borane were added, and the reaction was carried out at 80° C. for 10 hours. After the reaction was completed, the mixture was concentrated under reduced pressure and filtered to obtain a functional group-modified conjugated diene polymer (F-6). Analysis of the obtained functional group-modified conjugated diene polymer (F-6) revealed the weight average molecular weight, vinyl content, and styrene origin of the main chain (a) of the conjugated diene graft polymer (G-6), which will be described later. The structural unit content can be determined. The weight average molecular weight of the obtained functional group-modified conjugated diene polymer (F-6) was 6,000, the vinyl content was 10 mol%, the content of structural units derived from styrene was 0% by mass, and the content was per molecule of the polymer. The average number of B atoms was 8. Add 1750 g of cyclohexane to the obtained functional group-modified conjugated diene polymer (F-6) to dilute it to a concentration of 30% by mass, and prepare the functional group-modified conjugated diene polymer (F-6) to be used in the coupling reaction described below. ) was obtained.

(Step (3))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 2270 g of cyclohexane and 8.7 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then the polymerization temperature was increased to 50°C under stirring conditions. 570 g of isoprene was successively added while controlling the mixture so that the following reaction occurred, and polymerization was conducted for 1 hour to obtain an active terminal polymer (I-6). By sampling and analyzing the polymer solution in step (3), the weight average molecular weight, vinyl content, and structural unit derived from styrene of the side chain (b) of the conjugated diene graft polymer (G-6), which will be described later, can be determined. The content can be determined. The weight average molecular weight of the obtained active terminal polymer (I-6) was 60,000, the vinyl content was 10 mol%, and the content of structural units derived from styrene was 0% by mass.

(Step (4))
Next, 0.7 g of tetrahydrofuran and the functional group-modified conjugated diene polymer (F-6) obtained in step (2) were added to the solution containing the active terminal polymer (I-6) obtained in step (3). 20 g of the diluted solution was added and a coupling reaction was carried out at 50° C. for 2 hours. Thereafter, 26 g of sec-butyllithium (10.5% by mass cyclohexane solution) was added and reacted for 6 hours to seal off a portion of the remaining alkoxy groups. Thereafter, 1.0 g of methanol was added to stop the polymerization reaction, and a solution containing an unhydrogenated conjugated diene graft polymer (G'-6) was obtained.

(Step (5))
Add 100 mL of Ziegler hydrogenation catalyst (0.095 mmol/L cyclohexane solution) formed from nickel octylate and trimethylaluminum to the solution containing the obtained unhydrogenated conjugated diene graft polymer (G'-6). The mixture was reacted for 5 hours at a hydrogen pressure of 1 MPa and at 80° C. to obtain a solution containing a conjugated diene graft polymer (hydrogenated conjugated diene graft polymer) (G-6).

(Step (6))
The obtained solution containing the hydrogenated conjugated diene-based graft polymer (G-6) was washed with water to remove the catalyst, and the polymer solution after washing was vacuum-dried at 70°C for 24 hours to perform hydrogenation. A conjugated diene graft polymer (G-6) was recovered. The weight average molecular weight of the obtained hydrogenated conjugated diene graft polymer (G-6) was 486,000, Mw/Mn was 1.5, the content of structural units derived from styrene was 0% by mass, and the coupling rate was 95%, the hydrogenation rate is 99 mol%, the average number of Si atoms (branch points) per polymer molecule is 8, the average number of functional groups (c) per polymer molecule is 0.8, The average number of functional groups (c) per Si atom (branch point) is 0.1, the average number of side chains (b) per polymer molecule is 8, side chains per Si atom (branch point) The average number of pieces in (b) was one. Table 2 shows the molecular specifications of the obtained hydrogenated conjugated diene graft polymer (G-6).

[Synthesis example 7]
(Step (1))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 1370 g of cyclohexane and 240 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then brought to a polymerization temperature of 50°C under stirring conditions. While controlling as follows, 1250 g of butadiene was successively added and polymerized for 1 hour. Thereafter, 14 g of methanol was added to stop the polymerization reaction to obtain a polymer solution. Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After completing the stirring and confirming that the polymer solution phase and the aqueous phase were separated, water was separated. After the washing, the polymer solution was vacuum-dried at 70° C. for 24 hours to obtain an unmodified conjugated diene polymer (F'-7).

(Step (2))
Subsequently, 600 g of the unmodified conjugated diene polymer (F'-7) obtained in step (1), 1400 g of cyclohexane, 5.6 mL of a 2% by mass xylene solution of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (“PC072” manufactured by Petrarch Systems) and 120 g of trimethylchlorosilane were charged, and these were mixed overnight. was stirred. Thereafter, 150 g of dimethylchlorosilane was added dropwise into the mixture, and the mixture was gradually heated until the internal temperature reached 70°C, and the mixture was stirred under reflux for 24 hours while maintaining the internal temperature at 70°C. After stirring, the mixture was concentrated under reduced pressure and filtered to obtain a functional group-modified conjugated diene polymer (F-7). Analysis of the obtained functional group-modified conjugated diene polymer (F-7) revealed the weight average molecular weight, vinyl content, and styrene origin of the main chain (a) of the conjugated diene graft polymer (G-7), which will be described later. The structural unit content can be determined. The weight average molecular weight of the obtained functional group-modified conjugated diene polymer (F-7) was 6,000, the vinyl content was 10 mol%, the content of structural units derived from styrene was 0% by mass, per molecule of the polymer. The average number of Si atoms was 8. Add 1750 g of cyclohexane to the obtained functional group-modified conjugated diene polymer (F-7) to dilute it to a concentration of 30% by mass, and prepare the functional group-modified conjugated diene polymer (F-7) to be used in the coupling reaction described below. ) was obtained.

(Step (3))
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 2270 g of cyclohexane and 8.7 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then the polymerization temperature was increased to 50°C under stirring conditions. 570 g of isoprene was successively added while controlling the reaction mixture to have the following properties, and polymerization was carried out for 1 hour to obtain an active terminal polymer (I-7). By sampling and analyzing the polymer solution in step (3), the weight average molecular weight, vinyl content, and structural unit derived from styrene of the side chain (b) of the conjugated diene graft polymer (G-7), which will be described later, can be determined. The content can be determined. The obtained active terminal polymer (I-7) had a weight average molecular weight of 60,000, a vinyl content of 10 mol%, and a content of structural units derived from styrene of 0% by mass.

(Step (4))
Subsequently, 0.7 g of tetrahydrofuran and the functional group-modified conjugated diene polymer (F-7) obtained in step (2) were added to the solution containing the active terminal polymer (I-7) obtained in step (3). 20 g of the diluted solution was added and a coupling reaction was carried out at 50° C. for 2 hours. Thereafter, 26 g of sec-butyllithium (10.5% by mass cyclohexane solution) was added and reacted for 6 hours to seal off a portion of the remaining alkoxy groups. Thereafter, 1.0 g of methanol was added to stop the polymerization reaction, and a solution containing an unhydrogenated conjugated diene graft polymer (G'-7) was obtained.

(Step (5))
Add 100 mL of Ziegler hydrogenation catalyst (0.095 mmol/L cyclohexane solution) formed from nickel octylate and trimethylaluminum to the solution containing the obtained unhydrogenated conjugated diene graft polymer (G'-7). The mixture was reacted for 5 hours at a hydrogen pressure of 1 MPa and at 80° C. to obtain a solution containing a conjugated diene graft polymer (hydrogenated conjugated diene graft polymer (G-7)).

(Step (6))
The obtained solution containing the hydrogenated conjugated diene-based graft polymer (G-7) was washed with water to remove the catalyst, and the polymer solution after washing was vacuum-dried at 70°C for 24 hours to perform hydrogenation. A conjugated diene graft polymer (G-7) was recovered. The weight average molecular weight of the obtained hydrogenated conjugated diene graft polymer (G-7) was 486,000, Mw/Mn was 1.5, the content of structural units derived from styrene was 0% by mass, and the coupling rate was 95%, hydrogenation rate is 99 mol%, average number of Si atoms (branch points) per polymer molecule is 8, average number of functional groups (c) per polymer molecule is 0, Si atoms The average number of functional groups (c) per (branch point) is 0, the average number of side chains (b) per polymer molecule is 8, and the average number of side chains (b) per Si atom (branch point) is 0. The average number was one. Table 2 shows the molecular specifications of the obtained hydrogenated conjugated diene graft polymer (G-7).

[Synthesis example 8]
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 2400 g of cyclohexane and 12 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then brought to a polymerization temperature of 50°C under stirring conditions. While controlling as follows, 600 g of isoprene was successively added and polymerized for 1 hour to obtain an active terminal polymer (I-8). By sampling and analyzing the polymer solution in this step, the weight average molecular weight, vinyl content, and content of structural units derived from styrene of the arm chains of the conjugated diene star polymer (S-1), which will be described later, are determined. be able to. The obtained active terminal polymer (I-8) had a weight average molecular weight of 60,000, a vinyl content of 10 mol%, and a content of structural units derived from styrene of 0% by mass.

Subsequently, 11 g of divinylbenzene was added to the solution containing the active terminal polymer (I-8) obtained in the previous step, and the mixture was reacted at 50° C. for 2 hours. Thereafter, 1.0 g of methanol was added to stop the polymerization reaction to obtain a solution containing the conjugated diene star polymer (S'-1) before hydrogenation.

100 mL of a Ziegler hydrogenation catalyst (0.095 mmol/L cyclohexane solution) formed from nickel octylate and trimethylaluminum was added to the solution containing the obtained conjugated diene star polymer (S'-1), The mixture was reacted for 5 hours at a hydrogen pressure of 1 MPa and at 80° C. to obtain a solution containing a hydrogenated conjugated diene star polymer (S-1).

The resulting solution containing the hydrogenated conjugated diene star polymer (S-1) was washed with water to remove the catalyst, and the polymer solution after washing was vacuum-dried at 70°C for 24 hours to remove water. A conjugated diene star polymer (S-1) was recovered. The weight average molecular weight of the obtained hydrogenated conjugated diene star polymer (S-1) was 490,000, Mw/Mn was 1.5, the content of structural units derived from styrene was 0% by mass, and the hydrogenation rate was 99 mol%. Table 2 shows the molecular specifications of the obtained hydrogenated conjugated diene star polymer (S-1).

[Synthesis example 9]
A sufficiently dried 5L autoclave was purged with nitrogen, charged with 2400 g of cyclohexane and 13 g of sec-butyllithium (10.5% by mass cyclohexane solution), heated to 50°C, and then brought to a polymerization temperature of 50°C under stirring conditions. While controlling as follows, 600 g of a mixture of butadiene/isoprene (weight ratio = 50/50) was successively added and polymerized for 1 hour to obtain an active terminal polymer (I-9). By sampling and analyzing the polymer solution in this step, the weight average molecular weight, vinyl content, and content of structural units derived from styrene of the arm chains of the conjugated diene star polymer (S-2), which will be described later, are determined. be able to. The obtained active terminal polymer (I-9) had a weight average molecular weight of 60,000, a vinyl content of 10 mol %, and a structural unit content derived from styrene of 0 mass %.

Subsequently, 13 g of divinylbenzene was added to the solution containing the active terminal polymer (I-9) obtained in the previous step, and the mixture was reacted at 50° C. for 2 hours. Thereafter, 1.0 g of methanol was added to stop the polymerization reaction to obtain a solution containing an unhydrogenated conjugated diene star polymer (S'-2).

100 mL of a Ziegler hydrogenation catalyst (0.095 mmol/L cyclohexane solution) formed from nickel octylate and trimethylaluminum was added to the solution containing the obtained unhydrogenated conjugated diene star polymer (S'-2). was added and reacted for 5 hours under the conditions of a hydrogen pressure of 1 MPa and 80° C. to obtain a solution containing a conjugated diene-based graft polymer (hydrogenated conjugated diene-based star polymer (S-2)).

The resulting solution containing the hydrogenated conjugated diene star polymer (S-2) was washed with water to remove the catalyst, and the polymer solution after washing was vacuum-dried at 70°C for 24 hours to remove water. A conjugated diene star polymer (S-2) was recovered. The weight average molecular weight of the obtained hydrogenated conjugated diene star polymer (S-2) was 510,000, Mw/Mn was 1.5, the content of structural units derived from styrene was 0% by mass, and the hydrogenation rate was was 99 mol%. Table 2 shows the molecular specifications of the obtained hydrogenated conjugated diene star polymer (S-2).

[Example 1]
The conjugated diene graft polymer (G-1) obtained in Synthesis Example 1 above was used as a viscosity index improver, and Group I base oil "AP/E CORE 150" manufactured by ExxonMobil was used as a base oil. An oil composition was obtained by mixing for 6 hours at a heating temperature of 120° C. and a rotation speed of 350 rpm in a pressure-resistant container purged with nitrogen. Table 3 shows the results of physical property evaluation of the obtained oil composition.

[Examples 2 to 7]
Oil was prepared in the same manner as in Example 1, except that the type of conjugated diene graft polymer used as the viscosity index improver and the ratio of the viscosity index improver to the base oil were changed as shown in Table 3. A composition was obtained. Table 3 shows the results of physical property evaluation of the obtained oil composition.

[Comparative Examples 1-2]
An oil composition was obtained in the same manner as in Example 1, except that the star polymer synthesized from divinylbenzene obtained in Synthesis Examples 8 and 9 above was used as the viscosity index improver. Table 3 shows the results of physical property evaluation of the obtained oil composition.

In Table 1, the abbreviations are as follows: SBL: sec-butyl lithium THF: tetrahydrofuran t-BPOP: t-butylperoxypivalate Bd: butadiene Ip: isoprene MPTES: (3-mercaptopropyl)triethoxysilane MPTMS: ( 3-Mercaptopropyl)trimethoxysilane

From Table 3, the viscosity index improvers made of the conjugated diene-based graft polymers of Examples 1 to 7 have the same thickening effect and viscosity index improvement as the viscosity index improvers made of the star-shaped polymers of Comparative Examples 1 to 2. It can be seen that while still being effective, it has better shear stability.

The viscosity index improver made of the conjugated diene graft polymer of the present invention has high shear stability and is therefore useful as a viscosity index improver for lubricating oils used as engine oils and automatic transmission fluids.

Claims (8)

A viscosity index improver comprising a conjugated diene graft polymer,
The conjugated diene-based graft polymer has conjugated diene and A side chain (b) made of a polymer containing a structural unit derived from at least one monomer selected from the group consisting of aromatic vinyl compounds is bonded,
The main chain (a) is connected to a branch point directly or through a connecting chain,
The side chain (b) is directly bonded to the branch point,
A viscosity index improver, wherein the heteroatom is at least one selected from the group consisting of Si, Sn, Ge, Pb, P, B, and Al ,
The average number W of side chains (b) directly bonded to the branch point per molecule of the conjugated diene graft polymer and the average number Y of branch points per molecule of the conjugated diene graft polymer are expressed by the following formula (5) ;
0.5≦(W/Y) (5)
A viscosity index improver that satisfies the following relationship . The viscosity index improver according to claim 1, wherein the heteroatom is Si. The viscosity index improver according to claim 1 or 2 , wherein 50 mol% or more of carbon-carbon double bonds in the conjugated diene graft polymer are hydrogenated. At least one functional group (c) selected from the group consisting of an alkoxy group and a hydroxyl group is directly bonded to at least one of the branch points,
The average number X of functional groups (c) directly bonded to the branch points per molecule of the conjugated diene graft polymer and the average number Y of branch points per molecule of the conjugated diene graft polymer are expressed by the following formula (3- 2);
0<(X/Y)<1 (3-2)
The viscosity index improver according to any one of claims 1 to 3 , which satisfies the following relationship. The average number X of functional groups (c) directly bonded to the branch point per molecule of the conjugated diene graft polymer is expressed by the following formula (4-2);
0<X≦10 (4-2)
The viscosity index improver according to any one of claims 1 to 4 , which satisfies the following relationship. The viscosity index improver according to any one of claims 1 to 5 , having a halogen content of 1000 ppm or less. An oil composition comprising a base oil and the viscosity index improver according to any one of claims 1 to 6 . An oil composition comprising a base oil and the conjugated diene graft polymer according to claim 1.