JP7550004B2 - Conjugated diene graft polymer and method for producing same - Google Patents

Description

The present invention relates to a conjugated diene graft polymer that has a high tan δ peak intensity derived from dangling chains and has excellent shear stability.

The loss tangent (tan δ) obtained by dynamic viscoelasticity measurement of polymeric materials is an index of the ability to dissipate mechanical energy into heat and other energy to attenuate energy, and materials with high tan δ are required to have excellent vibration-damping and gripping performance. In particular, materials that show high tan δ over a wider temperature and frequency range are more preferable because they can be applied to a variety of usage environments. It is possible to widen the temperature range of tan δ by blending multiple materials that have tan δ peaks in different temperature ranges, but the intensity of each tan δ peak decreases depending on the blend ratio. Therefore, there was a demand for technology that can widen the temperature range of tan δ without reducing the intensity of the main peak derived from glass transition.

In order to solve the above problems, it has been proposed to utilize the relaxation of dangling chains, which are polymer chains that are bonded to structures with poor fluidity contained in polymer materials (for example, three-dimensional network structure parts contained in polymer crosslinked products, crystal structure parts contained in crystalline polymers, and phase separation structure parts derived from polymer blocks that do not merge at room temperature contained in block copolymers) at one end, but are not bonded to the structure part at the other end. For example, it is known that crosslinked products of acrylic polymers having dangling chains exhibit a tan δ peak derived from the dangling chains on the high temperature side of the main peak without reducing the intensity of the main peak derived from the glass transition (see Non-Patent Document 1). However, in the method described in Non-Patent Document 1, in order to form dangling chains, it is necessary to mix and UV-cure polymers having monofunctional and bifunctional UV-curable functional groups synthesized in advance, making the process very complicated and limiting the scope of application.

As a method for more easily expressing the relaxation caused by the dangling chains contained in the polymer material, a method is considered in which a material containing dangling chains and a structure with poor fluidity is prepared from a material containing a graft polymer having a main chain and a side chain, and the material is used. Examples of a method for synthesizing a graft polymer include a method in which a polymer constituting a main chain previously synthesized in the presence of tetramethylethylenediamine is reacted with an organic alkali metal compound to lithiate the main chain, and then a monomer that becomes a structural unit of the side chain is polymerized (see Patent Document 1). However, the graft polymer described in Patent Document 1 has a low side chain density, and a material containing dangling chains and a structure with poor fluidity (typically a crosslinked body having dangling chains) prepared from a material containing the graft polymer has a problem in that the peak intensity of tan δ resulting from the relaxation of the dangling chains is low.

Other methods for synthesizing graft polymers include a method of modifying a polymer that will be a component of the main chain, which has already been synthesized, with a functional group, and reacting the functional group-modified polymer with the active end of a polymer obtained by polymerizing a monomer that will be a component unit of the side chain (see Non-Patent Document 2), and a method of polymerizing a macromonomer (a macromonomer obtained by reacting a compound having a polymerizable functional group with the active end of a polymer obtained by polymerizing a monomer that will be a component unit of the side chain) with a monomer that will be a component unit of the main chain (see Non-Patent Document 3). These graft polymers have a higher side chain density than the graft polymer described in Patent Document 1, but the graft polymer described in Non-Patent Document 2 has problems with shear stability because it contains silicon at the branch point connecting the main chain/side chain, and the graft polymer described in Non-Patent Document 3 has problems with shear stability because it contains a styrene-like unit derived from the macromonomer at the branch point connecting the main chain/side chain.

U.S. Patent No. 8,623,980

Macromolecules, 2011, 44, 8829 Macromolecules, 1997, 30, 5602 Journal of Polymer Science: Part A: Polymer Chemistry, 2007, 45, 3513

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a conjugated diene graft polymer that has a high tan δ peak intensity derived from dangling chains and has excellent shear stability.

As a result of intensive research, the present inventors have found that a conjugated diene-based graft polymer in which a main chain (a) made of a polymer containing conjugated diene units is bonded to a side chain (b) made of a polymer containing at least one monomer unit selected from the group consisting of conjugated diene units and aromatic vinyl compound units, and further, the bonding method between the main chain (a) and the side chain (b) satisfies specific conditions, can provide a graft polymer that has a high peak intensity of tan δ derived from dangling chains and excellent shear stability, and have completed the present invention.

That is, the present invention provides the following [1] to [7].
[1] A conjugated diene-based graft polymer in which a main chain (a) made of a polymer containing a conjugated diene unit is bonded to a side chain (b) made of a polymer containing at least one monomer unit selected from the group consisting of a conjugated diene unit and an aromatic vinyl compound unit, and a monomer unit that becomes a branching portion contained in the main chain (a),
the side chain density of the side chain (b) of the conjugated diene graft polymer is 2.0 mol % or more;
The monomer unit that becomes the branched portion does not contain a heteroatom,
the linking moiety bonded to the side chain (b) contained in the monomer unit that becomes the branched moiety is not an aromatic group derived from an aromatic vinyl compound;
Conjugated diene graft polymer.

[2] (A-1) A step of reacting a polymer (M) containing a conjugated diene unit with an organolithium compound in the presence of a polar compound to lithiate an anion active site contained in the polymer (M);
(B) a step of adding at least one monomer selected from the group consisting of conjugated dienes and aromatic vinyl compounds, polymerizing the lithiated portion of the polymer (M) to form a side chain on the main chain of the polymer (M) to prepare a conjugated diene graft polymer; and (C) a step of recovering the obtained conjugated diene graft polymer.
The method for producing a conjugated diene graft polymer, in which the side chain density of the side chain (b) is 2.0 mol % or more, comprises:
[3] Furthermore, after the step (A-1),
(A-2) a step of adding a Lewis acid;
The method for producing the conjugated diene graft polymer according to [2],
[4] The method for producing a conjugated diene graft polymer according to [2] or [3], wherein in ^1H -NMR measurement of the polymer (M) after the lithiation in the step (A-1), the peak area in the range of 5.7 to 6.4 ppm is in the range of 0.1 to 10, where the peak area in the range of 4.0 to 5.7 ppm is taken as 100.

[5] A polymer composition comprising the conjugated diene graft polymer according to [1].
[6] A molded article obtained by molding the polymer composition according to [5].
[7] A crosslinked product obtained by crosslinking the polymer composition according to [5].

The present invention provides a conjugated diene graft polymer that has a high tan δ peak intensity derived from dangling chains and has excellent shear stability.

The present invention will be described in detail below.
The conjugated diene graft polymer of the present invention is
a conjugated diene-based graft polymer in which a main chain (a) made of a polymer containing a conjugated diene unit is bonded to a side chain (b) made of a polymer containing at least one monomer unit selected from the group consisting of a conjugated diene unit and an aromatic vinyl compound unit, and a monomer unit that becomes a branching portion contained in the main chain (a);
the side chain density of the side chain (b) of the conjugated diene graft polymer is 2.0 mol % or more;
The monomer unit that becomes the branched portion does not contain a heteroatom,
The linking moiety which is bonded to the side chain (b) contained in the monomer unit which becomes the branched moiety is not an aromatic group derived from an aromatic vinyl compound.
In the present invention, a graft polymer refers to a polymer having a main chain made of a polymer chain as a trunk and side chains made of a polymer chain as branches, and the monomer units constituting the main polymer chain and the monomer units constituting the side polymer chains may be the same or different.

<Main Chain (a)>
The conjugated diene graft polymer of the present invention has a main chain (a) made of a polymer containing a conjugated diene unit. The main chain contained in the conjugated diene graft polymer of the present invention refers to the entire portion derived from all monomer units including the conjugated diene unit constituting the main chain. It refers to the entire portion derived from a conjugated diene polymer (M) synthesized in advance, which will be described later. For example, when a conjugated diene graft polymer is produced by the production method of the present invention, if the previously synthesized conjugated diene polymer (M) contains a vinyl-bonded 1,3-butadiene unit, the main chain includes up to the -CH= _CH2 portion bonded to a carbon atom in the polymer backbone (-(C-C) _n- ).

The main chain (a) contains a conjugated diene unit as a monomer unit constituting the polymer. Examples of conjugated dienes include 1,3-butadiene, isoprene, farnesene, and myrcene; 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, and chloroprene, and other conjugated dienes. Among these conjugated dienes, 1,3-butadiene, isoprene, farnesene, and myrcene are preferred, 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is even more preferred. The conjugated diene units may be used alone or in combination of two or more types.

In one embodiment, the main chain (a) preferably has conjugated diene units that account for 40% by mass or more of all monomer units constituting the polymer. The total content of conjugated diene units is preferably 50 to 100% by mass, and more preferably 60 to 100% by mass, of all monomer units in the main chain (a).

In one embodiment, the main chain (a) is such that 40% by mass or more of all monomer units constituting the polymer are at least one monomer unit selected from the group consisting of 1,3-butadiene and isoprene. The total content of 1,3-butadiene units and isoprene units is preferably 50 to 100% by mass, and more preferably 60 to 100% by mass, of the total monomer units in the main chain (a).

Examples of monomer units other than 1,3-butadiene units and isoprene units that may be contained in the main chain (a) include the above-mentioned conjugated diene units other than 1,3-butadiene and isoprene, and aromatic vinyl compound units.

Examples of aromatic vinyl compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-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 and α-methylstyrene are preferred. The aromatic vinyl compounds that form the aromatic vinyl compound units may be used alone or in combination of two or more.

The content of other monomer units than 1,3-butadiene units and isoprene units in the main chain (a) is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. For example, when the aromatic vinyl compound units are within the above range, the processability of the resulting conjugated diene graft polymer tends to be improved.

In one embodiment, the weight average molecular weight (Mw) of the main chain (a) is preferably 1,000 to 1,000,000, more preferably 2,000 to 500,000, and even more preferably 3,000 to 100,000. In the present invention, the Mw of the main chain (a) is the Mw of the conjugated diene polymer (M) previously synthesized as described below. When the Mw of the main chain (a) is within the above range, when a conjugated diene graft polymer is produced by the production method of the present invention, the process passability during production tends to be excellent and the economic efficiency is good. In the present invention, unless otherwise specified, Mw is the weight average molecular weight calculated in terms of standard polystyrene by gel permeation chromatography (GPC).

The vinyl content of the main chain (a) is not particularly limited, but in one embodiment, it is preferably 90 mol% or less, more preferably 70 mol% or less, and even more preferably 50 mol% or less. The vinyl content of the main chain (a) is preferably 0.5 mol% or more, and more preferably 1 mol% or more. In the present invention, the "vinyl content" refers to the total mol% of conjugated diene units bonded via 1,2-bonds, 3,4-bonds (in the case of other than farnesene), and 3,13-bonds (in the case of farnesene) (conjugated diene units bonded via bonds other than 1,4-bonds (in the case of other than farnesene) and 1,13-bonds (in the case of farnesene)) out of a total of 100 mol% of conjugated diene units contained in a polymer. The vinyl content is calculated from the area ratio of ^the peaks derived from conjugated diene units having 1,2-bonds, 3,4-bonds (in the case of other than farnesene), and 3,13-bonds (in the case of farnesene) to the peaks derived from conjugated diene units having 1,4-bonds (in the case of other than farnesene) and 1,13-bonds (in the case of farnesene) using 1H-NMR.

The vinyl content of the main chain (a) can be designed according to 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, and the resulting conjugated diene graft polymer will tend to have excellent fluidity and low-temperature properties. Also, if the vinyl content is 50 mol% or more, the resulting conjugated diene graft polymer will tend to have excellent reactivity.

When producing a conjugated diene graft polymer by the production method of the present invention, the vinyl content of the main chain (a) can be adjusted to a desired value by controlling the type of solvent used in producing the previously synthesized conjugated diene polymer (M) described below, the polar compound used as necessary, the polymerization temperature, etc.

The glass transition temperature (Tg) of the main chain (a) may vary depending on the vinyl content of 1,3-butadiene units, isoprene units and 1,3-butadiene units, conjugated diene units other than isoprene units, the type of conjugated diene units, the content of units derived from monomers other than conjugated dienes, etc., but is preferably -150 to 50°C, more preferably -130 to 50°C, and even more preferably -130 to 30°C. If the Tg is in the above range, for example, an increase in viscosity can be suppressed, making handling easier. In the present invention, Tg is the value of the peak top of differential scanning calorimetry (DSC) measured by DSC.

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

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

Specific examples of conjugated dienes that can form the monomer units of the side chain (b) are the same as the specific examples of conjugated dienes that form the monomer units of the main chain (a). Among the conjugated dienes that form the conjugated diene units contained in the side chain (b), 1,3-butadiene, isoprene, farnesene, and myrcene are preferred, 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is even more preferred. The conjugated dienes that form the conjugated diene units may be used alone or in combination of two or more types.

Specific examples of aromatic vinyl compounds that can form the monomer units of the side chain (b) are the same as the specific examples of aromatic vinyl compounds that can form the monomer units of the main chain (a). Among these aromatic vinyl compounds, styrene, α-methylstyrene, and 4-methylstyrene are preferred. The aromatic vinyl compounds that form the aromatic vinyl compound units may be used alone or in combination of two or more.

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

The ratio of the conjugated diene units that can constitute the side chain (b) is not particularly limited and can be designed according to the purpose, but is preferably 40% by mass or more, more preferably 50% by mass or more, particularly preferably 60% by mass or more, and may be 100% by mass. When the ratio of the conjugated diene units is 50% by mass or more, the processability of the resulting conjugated diene graft polymer tends to be improved.

The ratio of aromatic vinyl compound units that can constitute the side chain (b) is not particularly limited and can be designed according to the purpose, but is preferably 10% by mass or more, more preferably 20% by mass or more, particularly preferably 30% by mass or more, and may be 100% by mass. If the ratio of aromatic vinyl compound units is 50% by mass or more, the mechanical properties of the resulting conjugated diene graft polymer tend to be improved.

When the side chain (b) contains conjugated diene units and aromatic vinyl compound units, the weight ratio of the content of the conjugated diene units to the content of the aromatic vinyl compound units (conjugated diene units)/(aromatic vinyl compound units) is preferably 30/70 to 99/1, more preferably 40/60 to 95/5, and particularly preferably 50/50 to 90/10. When the weight ratio of the content of the conjugated diene units to the content of the aromatic vinyl compound units is within the above range, the processability of the resulting conjugated diene graft polymer tends to be improved.

In one embodiment, the number average molecular weight (Mn) of the side chain (b) is preferably 500 or more, more preferably 1,000 or more, even more preferably 2,000 or more, and particularly preferably 3,000 or more. In another embodiment, the number average molecular weight (Mn) is preferably 1,00,000 or less, more preferably 50,000 or less, even more preferably 20,000 or less, and particularly preferably 15,000 or less. In the present invention, the Mn of the side chain (b) is calculated from the charge ratio of the organic alkali metal compound used in the lithiation reaction in step (A) described later and the monomer that becomes the structural unit of the side chain in step (B), for example, when a conjugated diene graft polymer is produced by the production method of the present invention. When the Mn of the side chain (b) is within the above range, the peak intensity of tan δ derived from the relaxation of the dangling chain tends to be excellent. In addition, the process passability during production tends to be excellent, and the economic efficiency tends to be good.

The preferred number average molecular weight (Mn) of the side chain (b) is expressed by the ratio to the molecular weight between the entanglement points of the polymer constituting the side chain (b). That is, the number average molecular weight (Mn) of the side chain (b) is preferably 5 times or less of the molecular weight between the entanglement points of the polymer constituting the side chain (b), more preferably 3 times or less, even more preferably 2 times or less, even more preferably 1.5 times or less, and particularly preferably 1 time or less. Also, 0.01 times or more is preferable, 0.05 times or more is more preferable, 0.1 times or more is more preferable, and 0.2 times or more is particularly preferable. When the Mn of the side chain (b) is within the above range, the peak intensity of tan δ derived from the relaxation of the dangling chain described later tends to be excellent. In addition, when a conjugated diene-based graft polymer is produced by the production method of the present invention, the process passability during production tends to be excellent and the economic efficiency tends to be good. In this specification, the molecular weight between entanglement points is a value calculated from the theoretical formula described in POLYMER ENGINEERING AND SCIENCE, 1992, 32, 823.

The vinyl content of the side chain (b) is not particularly limited, but in one embodiment, it is 99 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less. The vinyl content of the side chain (b) is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, and particularly preferably 30 mol% or more. When a conjugated diene graft polymer is produced by the production method of the present invention, the vinyl content of the side chain (b) can be calculated from the vinyl content of the conjugated diene graft polymer calculated by ¹ H-NMR spectrum, the vinyl content of the main chain (a) described above, and the charge ratio of the monomer units constituting the main chain and the side chain.

The vinyl content of the side chain (b) can be designed according to the purpose. For example, if the vinyl content is less than 50 mol%, the glass transition temperature (Tg) of the side chain (b) described below will be low, and the resulting conjugated diene graft polymer will tend to have excellent fluidity and low-temperature properties. Also, if the vinyl content is 50 mol% or more, the resulting conjugated diene graft polymer will tend to have excellent reactivity.

When a conjugated diene graft polymer is produced by the production method of the present invention, the vinyl content of the side chain (b) can be adjusted to a desired value by controlling the type of solvent used in polymerizing the side chain (b) in step (B) described below, the polar compound or Lewis acid used as necessary, the polymerization temperature, etc.

The glass transition temperature (Tg) of the side chain (b) may vary depending on the vinyl content of the conjugated diene units, the type of conjugated diene units, the content of units derived from monomers other than conjugated dienes, etc., but is preferably -150 to 50°C, more preferably -130 to 50°C, and even more preferably -130 to 30°C. When the Tg is in the above range, for example, an increase in viscosity can be suppressed, making handling easier.

<Conjugated diene graft polymer>
The conjugated diene graft polymer of the present invention is a conjugated diene graft polymer in which a main chain (a) made of a polymer containing a conjugated diene unit is bonded to a side chain (b) made of a polymer containing at least one monomer unit selected from the group consisting of a conjugated diene unit and an aromatic vinyl compound unit, and a monomer unit which becomes a branching portion contained in the main chain (a),
the side chain density of the side chain (b) of the conjugated diene graft polymer is 2.0 mol % or more;
The monomer unit that becomes the branched portion does not contain a heteroatom,
The linking moiety which is bonded to the side chain (b) contained in the monomer unit which becomes the branched moiety is not an aromatic group derived from an aromatic vinyl compound.

The main chain (a) of the conjugated diene graft polymer of the present invention contains a monomer unit that becomes a branched portion. The main chain (a) is bonded to the side chain (b) at this branched portion. The monomer unit that becomes the branched portion does not contain a heteroatom. If the branched portion contains a heteroatom, it is not preferable because the shear stability and thermal stability tend to deteriorate.
The branched portion is bonded to the side chain (b) means that one of the atoms (typically carbon atoms) constituting the monomer unit that becomes the branched portion in the main chain is bonded to an atom constituting the side chain. A method for bonding the branched portion to the side chain (b) will be described in detail below as an example of a method for producing a conjugated diene-based graft polymer, and for example, a method of lithiating a site containing a carbon atom having an anionic activity contained in the monomer unit that becomes the branched portion of the polymer that becomes the main chain (a), and then addition-polymerizing a monomer with the lithiated site as a starting point to form the side chain (b) can be mentioned.

In the conjugated diene graft polymer of the present invention, the monomer units that become the branching portions do not contain heteroatoms. If the conjugated diene graft copolymer contains heteroatoms at the branching points of the branching portions, etc., this is not preferred because it tends to deteriorate the shear stability and thermal stability.

For example, the graft polymer described in the above-mentioned non-patent document 2 is synthesized by modifying a polymer that is a component of the main chain, which has been synthesized in advance, with a compound containing a silicon atom to form a functional group modified polymer, and reacting the functional group modified polymer with the active end of a polymer obtained by polymerizing a monomer that is a component unit of the side chain. A heteroatom such as a silicon atom derived from this functional group modified polymer is included at the branch point connecting the main chain and the side chain. In addition, the graft polymer described in Japanese Patent No. 5089007 is synthesized by preparing a mixture of a polymer having two active ends that are components of the main chain and a polymer having one active end that is a component of the side chain, and adding a coupling agent containing a silicon atom having three or more reactive sites to this mixture and reacting them. A heteroatom such as a silicon atom derived from this coupling agent is included at the branch point connecting the main chain and the side chain. In the conjugated diene-based graft polymer of the present invention described later, the branch portion contained in the main chain (a) does not contain a heteroatom, and is directly bonded to the side chain (b). Therefore, unlike the polymers described in the above-mentioned conventional documents, the conjugated diene graft polymer of the present invention does not contain a heteroatom at the portion (connection point) where the main chain and the side chain are bonded.

In the conjugated diene graft polymer of the present invention, the linking portion of the main chain (a) that is bonded to the side chain (b) contained in the monomer unit that becomes the branching portion is not an aromatic group derived from an aromatic vinyl compound. The aromatic group here means a group that contains an aromatic ring other than _CH2 =CR (R is hydrogen, an optionally substituted alkyl group, or an optionally substituted aryl group) that an aromatic vinyl compound has.
Here, the term "the linking moiety is not an aromatic group derived from an aromatic vinyl compound" means that
This means that the monomer unit which becomes the branched portion contained in the main chain is itself a monomer unit derived from a monomer (e.g., a conjugated diene) other than an aromatic vinyl compound, or that even if the monomer unit which becomes the branched portion contained in the main chain is itself a monomer unit derived from an aromatic vinyl compound, the aromatic group possessed by the aromatic vinyl compound does not have a side chain (b) bonded to it.
Hereinafter, a specific example will be described. For example, in the case of 4-methylstyrene, an aromatic vinyl compound having a substituent in the aromatic group that has high anionic activity (high reactivity with an organolithium compound), the reactivity of the methyl group portion derived from 4-methylstyrene is high, and the side chain (b) bonds to this methyl group portion.
On the other hand, in the case of an aromatic vinyl compound that does not have a substituent with high anionic activity in the aromatic group, such as styrene, the side chain (b) is bonded to the _CH2 adjacent to the _CH2 to which the benzene ring is bonded, which is contained in the ( _-CH2 - _CH2- ) portion of the monomer unit derived from styrene, which is the skeleton of the main chain (a). In this case, the side chain (b) is not bonded to the benzene ring derived from styrene, and the linking portion in the branched portion contained in the main chain (a) is not an aromatic group derived from an aromatic vinyl compound.

As described above, in the conjugated diene graft polymer of the present invention, the linking portion that is bonded to the side chain (b) contained in the monomer unit that becomes the branching portion contained in the main chain (a) is not an aromatic group derived from an aromatic vinyl compound. If the linking portion is an aromatic group, the shear stability and thermal stability are deteriorated.

For example, the graft polymer described in the above-mentioned Non-Patent Document 3 or Japanese Patent No. 5,508,066 is synthesized by a method of polymerizing a macromonomer (a macromonomer obtained by directly reacting an aromatic vinyl compound having a polymerizable functional group other than CH ₂ ═C- bonded to an aromatic group with the active end of a polymer obtained by polymerizing a monomer that becomes a structural unit of the side chain) with a monomer that becomes a structural unit of the main chain. The linking portion that is derived from this macromonomer and that is bonded to the side chain (b) contained in the branched portion of the main chain (a) is an aromatic group. In the graft polymer of the present invention, the linking portion that is bonded to the side chain (b) contained in the branched portion of the main chain (a) is not an aromatic group, as is clear from, for example, an example of a method for producing the graft polymer described in detail below.

The average number of side chains (b) per molecule of the conjugated diene graft polymer is preferably 2 or more, more preferably 5 or more, even more preferably 10 or more, and particularly preferably 15 or more. When the graft polymer of the present invention is produced by the production method described below, for example, the average number of side chains (b) per molecule of the conjugated diene graft polymer is calculated from the charge ratio of the organic alkali metal compound used in the lithiation reaction in step (A) and the conjugated diene polymer serving as a structural unit of the main chain. When the average number of side chains (b) per molecule of the conjugated diene graft polymer is within the above range, the product containing the conjugated diene graft polymer of the present invention tends to have excellent tan δ peak intensity due to relaxation of the dangling chains in the product containing the dangling chains.

The conjugated diene graft polymer of the present invention has a side chain density of the side chain (b) of 2.0 mol% or more, more preferably 3.0 mol% or more, even more preferably 4.5 mol% or more, and particularly preferably 6.0 mol% or more. When the side chain density of the conjugated diene graft polymer is within the above range, the product containing the conjugated diene graft polymer of the present invention tends to have excellent tan δ peak intensity due to relaxation of dangling chains, including dangling chains.

In the present invention, the side chain density of the side chain (b) is calculated from the average number of the side chains (b) per molecule of the conjugated diene graft polymer and the number average molecular weight (Mn) of the main chain (a) in terms of standard polystyrene according to the following formula (2).
(Side chain density)=(average number of side chains (b) per molecule of conjugated diene graft polymer)/[(number average molecular weight Mn of main chain (a))/(molecular weight of styrene unit)]×100 (2)
The Mn of the main chain (a) is the standard polystyrene-equivalent Mn of a previously synthesized conjugated diene polymer (M) which is a component of the main chain, described below.

The combination of the polymer that forms the main chain (a) and the polymer that forms the side chain (b) contained in the conjugated diene graft polymer is not particularly limited, and may be the same or different, and can be designed according to the purpose. The fact that the polymer that forms the main chain (a) and the polymer that forms the side chain (b) are different means that they are different in at least one of the following (i) to (iv):
(i) The molecular weight of the polymer that becomes the main chain (a) is different from the molecular weight of the polymer that becomes the side chain (b).
(ii) The type or combination of types of monomer units of the polymer that forms the main chain (a) is different from the type or combination of types of monomer units of the polymer that forms the side chain (b).
(iii) When the main chain (a) and the side chain (b) each contain a plurality of monomer units of the same type, the monomer unit composition ratio of the polymer that becomes the main chain (a) is different from the monomer unit composition ratio of the polymer that becomes the side chain (b).
(iv) When the main chain (a) and the side chain (b) each contain a conjugated diene unit, the vinyl content of the conjugated diene unit of the polymer that becomes the main chain (a) is different from the vinyl content of the conjugated diene unit of the polymer that becomes the side chain (b).

In one embodiment of the conjugated diene graft polymer of the present invention, at least 40% by mass of all monomer units constituting the polymer are at least one monomer unit selected from the group consisting of 1,3-butadiene and isoprene. The total content of 1,3-butadiene units and isoprene units is more preferably 50 to 100% by mass, and even more preferably 60 to 100% by mass, of the total monomer units of the conjugated diene graft polymer.

In the conjugated diene graft polymer of the present invention, the content of other monomer units than 1,3-butadiene units and isoprene units is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. For example, when the aromatic vinyl compound units are within the above range, the processability of the conjugated diene graft polymer of the present invention tends to be improved.

In one embodiment, the weight average molecular weight (Mw) of the conjugated diene graft polymer of the present invention is preferably 5,000 or more and 2,000,000 or less, more preferably 30,000 or more and 1,500,000 or less, and more preferably more than 100,000 and 1,000,000 or less. When the Mw of the conjugated diene graft polymer is within the above range, the processability during production tends to be excellent and the economic efficiency tends to be good. In addition, the processability of the polymer composition containing the conjugated diene graft polymer tends to be improved.

The molecular weight distribution (Mw/Mn) of the conjugated diene graft polymer of the present invention is preferably 1.0 to 20.0, more preferably 1.0 to 10.0, even more preferably 1.0 to 5.0, and particularly preferably 1.0 to 2.0. When Mw/Mn is within the above range, the viscosity of the conjugated diene graft polymer varies less, which is more preferable. In the present invention, Mn means number average molecular weight, and Mn is the number average molecular weight calculated based on standard polystyrene obtained by GPC measurement. Furthermore, the molecular weight distribution (Mw/Mn) means the ratio (Mw/Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) calculated based on standard polystyrene obtained by GPC measurement.

The melt viscosity of the conjugated diene graft polymer of the present invention measured at 38°C is preferably 0.1 to 3,000 Pa·s, more preferably 0.1 to 2,000 Pa·s, and even more preferably 0.1 to 1,500 Pa·s. When the melt viscosity of the conjugated diene graft polymer is within the above range, the processability during production tends to be excellent and the cost efficiency is good. In the present invention, the melt viscosity of the conjugated diene graft polymer is a value measured at 38°C using a Brookfield viscometer.

The vinyl content of the conjugated diene graft polymer of the present invention is not particularly limited, but in one embodiment, it is preferably 99 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less. The vinyl content of the conjugated diene graft polymer is preferably 1 mol% or more, and more preferably 5 mol% or more.

The vinyl content of the conjugated diene graft polymer can be designed according to the purpose. For example, if the vinyl content is less than 50 mol%, the glass transition temperature (Tg) of the conjugated diene graft polymer described below will be low, and the conjugated diene graft polymer will tend to have excellent fluidity and low-temperature properties. Also, if the vinyl content is 50 mol% or more, the conjugated diene graft polymer will tend to have excellent reactivity.

The glass transition temperature (Tg) of the conjugated diene graft polymer may vary depending on the vinyl content of 1,3-butadiene units, isoprene units and 1,3-butadiene units, conjugated diene units other than isoprene units, the type of conjugated diene units, the content of units derived from monomers other than conjugated dienes, etc., but is preferably -150 to 50°C, more preferably -130 to 50°C, and even more preferably -130 to 30°C. When the Tg is in the above range, for example, it is possible to prevent the viscosity from increasing, making it easier to handle.

The mass ratio of the main chain to the side chain in the conjugated diene graft polymer of the present invention is preferably in the range of 1/99 to 90/10, more preferably in the range of 3/97 to 80/20, and even more preferably in the range of 5/95 to 70/30. When the mass ratio of the main chain to the side chain is in the above range, the processability of the polymer composition containing the conjugated diene graft polymer tends to be improved.

The conjugated diene graft polymer of the present invention preferably has a catalyst residue amount derived from the polymerization catalyst used in its production in the range of 0 to 200 ppm in terms of metal. For example, when an organic alkali metal such as an organolithium compound as described below is used as the polymerization catalyst for producing the conjugated diene graft polymer, the metal that is the standard for the catalyst residue amount is an alkali metal such as lithium. By having the catalyst residue amount in the above range, the tack does not decrease during processing, and the heat resistance of the conjugated diene graft polymer of the present invention is improved. The catalyst residue amount derived from the polymerization catalyst used in the production of the conjugated diene graft polymer is more preferably 0 to 150 ppm, and even more preferably 0 to 100 ppm in terms of metal. The catalyst residue amount can be measured, for example, by using an inductively coupled plasma mass spectrometer (ICP-MS) or a polarized Zeeman atomic absorption spectrophotometer.

As a method for making the amount of catalyst residue in the conjugated diene graft polymer into such a specific amount, a method of purifying the conjugated diene graft polymer and thoroughly removing the catalyst residue can be mentioned. As a purification method, washing with water or hot water, or an organic solvent such as methanol or acetone, or supercritical fluid carbon dioxide is preferable. From an economical point of view, the number of washings is preferably 1 to 20 times, more preferably 1 to 10 times. In addition, the washing temperature is preferably 20 to 100°C, more preferably 40 to 90°C. In addition, by removing impurities that inhibit polymerization by distillation or an adsorbent before the polymerization reaction and increasing the purity of the monomer before carrying out the polymerization, the amount of polymerization catalyst required can be reduced, and the amount of catalyst residue can be reduced.

<Method for producing conjugated diene graft polymer>
The method for producing a conjugated diene graft polymer of the present invention includes the following steps (A-1), (B), and (C).
(A-1) a step of reacting a polymer (M) containing a conjugated diene unit with an organolithium compound in the presence of a polar compound to lithiate an anion active site contained in the polymer (M); and (B) a step of adding at least one monomer selected from the group consisting of conjugated dienes and aromatic vinyl compounds to polymerize from the lithiated portion in the polymer (M) to form a side chain on the main chain of the polymer (M) to prepare a conjugated diene graft polymer; and (C) a step of recovering the obtained conjugated diene graft polymer.

[Step (A-1)]
The method for producing the polymer (M) containing the conjugated diene unit, which is a constituent element of the main chain in the above step (A-1), is not particularly limited, but for example, an emulsion polymerization method or a solution polymerization method is preferable, and from the viewpoint of the molecular weight distribution of the obtained polymer, a solution polymerization method is more preferable. The polymer (M) containing the conjugated diene unit becomes the main chain (a) of the conjugated diene graft polymer of the present invention.

The explanations of specific examples, preferred examples, and preferred contents of conjugated dienes that are monomer units constituting the polymer (M) containing conjugated diene units, as well as specific examples, preferred examples, and preferred contents of other monomers (aromatic vinyl compounds) other than conjugated dienes, are the same as those for the main chain (a) of the conjugated diene graft polymer. The explanations of preferred aspects of the weight average molecular weight (Mw), vinyl content, and Tg of the polymer (M) containing conjugated diene units are the same as those for the main chain (a) of the conjugated diene graft polymer.

As the emulsion polymerization method, which is an example of a method for producing a polymer (M) containing a conjugated diene unit, a method known in the art or a method similar to a known 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 polymerized with a radical polymerization initiator.

Examples of emulsifiers include salts of long-chain fatty acids having 10 or more carbon atoms and rosin acid salts. Examples of salts of long-chain fatty acids 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 water-soluble organic solvents such as methanol and ethanol, as long as the stability during polymerization is not impaired.

Radical polymerization initiators include, for example, persulfates such as ammonium persulfate and potassium persulfate, organic peroxides, hydrogen peroxide, etc.

A chain transfer agent may be used to adjust the molecular weight of the resulting polymer (M) containing conjugated diene units. Examples of chain transfer agents include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan; carbon tetrachloride, thioglycolic acid, diterpenes, terpinolene, γ-terpinene, and α-methylstyrene dimer.

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

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

After the polymerization reaction is stopped, an antioxidant may be added as necessary. After the polymerization reaction is stopped, unreacted monomers are removed from the obtained latex as necessary, and then the polymer (M) containing the conjugated diene units is coagulated using salts such as sodium chloride, calcium chloride, and potassium chloride as a coagulant, and an acid such as nitric acid or sulfuric acid is added as necessary to adjust the pH of the coagulation system to a predetermined value, and the polymer is recovered by separating the dispersion medium. The polymer is then washed with water, dehydrated, and dried to obtain the polymer (M) containing the conjugated diene units. Note that, during coagulation, the latex and an extender oil that has been previously made into an emulsified dispersion may be mixed as necessary, and the polymer (M) containing oil-extended conjugated diene units may be recovered.

As an example of the solution polymerization method for producing the polymer (M) containing a conjugated diene unit, a known method or a method equivalent to a known method can be applied. For example, a monomer containing a conjugated diene is polymerized in a solvent using a Ziegler catalyst, a metallocene catalyst, or an anionically polymerizable active metal or active metal compound as an initiator, and if necessary, in the presence of a polar compound.

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

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

Examples of active metals capable of anion 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.

As an anionically polymerizable active metal compound, an organic alkali metal compound is preferred. Examples of the organic alkali metal compound include organic monolithium compounds such as methyl lithium, ethyl lithium, n-butyl lithium, sec-butyl lithium, t-butyl lithium, hexyl lithium, phenyl lithium, and stilbene lithium; polyfunctional organic lithium compounds such as dilithiomethane, dilithionaphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene; 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 initiator used can be set appropriately depending on the melt viscosity, molecular weight, etc. of the polymer (M) containing conjugated diene units, but it is usually used in an amount of 0.01 to 3 parts by mass per 100 parts by mass of all monomers including conjugated dienes.

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, or dibenzylamine to be used as an organic alkali metal amide.

In anionic polymerization, polar compounds are usually used to adjust the microstructure (vinyl content) of the conjugated diene moiety without deactivating the reaction. Examples of polar compounds 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. Polar compounds are usually used in an amount of 0.01 to 1,000 moles per mole of the organic alkali metal compound.

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

The polymerization reaction of the above solution polymerization can be terminated by adding a polymerization terminator. Examples of the polymerization terminator include alcohols such as methanol and isopropanol. The obtained polymerization reaction liquid is poured into a poor solvent such as methanol to precipitate the polymer (M) containing conjugated diene units, or the polymerization reaction liquid is washed with water, separated, and then dried to isolate the polymer (M) containing conjugated diene units. Note that the polymerization reaction liquid after polymerization termination may be used as is for the lithiation reaction, as long as it does not affect the lithiation reaction. If necessary, the solvent may be partially removed or a solvent may be added to dilute the polymerization reaction liquid.

In the step (A-1), the anion active site contained in the polymer (M) obtained as described above is reacted with an organolithium compound in the presence of a polar compound to be lithiated.
Lithiation under such conditions results in lithiation of anion active sites, particularly carbon-carbon double bond moieties contained in vinyl bond type conjugated diene units contained in polymer (M). In addition, particularly, the CH2 moiety adjacent to the CH bonded to the benzene ring contained in the (-CH2-CH2-) moiety forming the backbone of the main chain (a) of a monomer unit derived from an aromatic vinyl compound not having in its aromatic group a substituent highly reactive to anions contained in polymer ( _M ), such as _{a monomer} unit derived from styrene, is lithiated.
In the graft polymer obtained by this manufacturing method, therefore, the linking portion bonded to the side chain (b) contained in the monomer unit that becomes the branching portion is not an aromatic group derived from an aromatic vinyl compound. In order to more reliably lithiate the conjugated diene unit, when the polymer (M) contains an aromatic vinyl compound unit, it is desirable that the aromatic vinyl compound unit does not contain a functional group having high anionic activity (a functional group highly reactive with an organolithium compound) in the aromatic group. Examples of styrenes having an aromatic group containing such a functional group include 4-methylstyrene and 4-propylstyrene.

Examples of organolithium compounds used in the lithiation of polymer (M) in step (A-1) above include organomonolithium compounds such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; and polyfunctional organolithium compounds such as dilithiomethane, dilithonaphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene. Among these organolithium compounds, organomonolithium compounds are preferred, with n-butyllithium and sec-butyllithium being more preferred, and sec-butyllithium being particularly preferred.

The amount of the organolithium compound used can be appropriately set according to the average number of side chains (b) of the above-mentioned conjugated diene graft polymer. For example, when (amount of organolithium compound charged (number of moles))/(amount of polymer (M) containing conjugated diene units charged (number of moles))=4/1, the average number of side chains (b) is 4.

As described above, the side chain density is calculated by the following formula (2).
(Side chain density)=(average number of side chains (b) per molecule of conjugated diene graft polymer)/[(number average molecular weight Mn of main chain (a))/(molecular weight of styrene unit)]×100 (2)
That is, the amount of the organolithium compound used can be naturally determined by designing the number average molecular weight Mn of the main chain (a) and the average number of side chains (b) per molecule of the conjugated diene graft polymer so as to obtain a desired side chain density.

The polar compound used in the lithiation of the polymer (M) in the above step (A-1) is used to promote the lithiation reaction. Examples of polar compounds 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. Among these polar compounds, tertiary amines are preferred, and tetramethylethylenediamine is particularly preferred. The amount of polar compound used is preferably 0.01 mol or more, more preferably 0.05 mol or more, and particularly preferably 0.1 mol or more, per mol of the organic alkali metal compound. Also, it is preferably 100 mol or less, more preferably 50 mol or less, and particularly preferably 10 mol or less. If it is less than 0.01 mol, the reaction rate tends to be poor, and if it exceeds 100 mol, the economy tends to be poor.

The lithiation in the above step (A-1) is usually carried out in a state where the polymer (M) is dissolved in a solvent. 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; and aromatic hydrocarbons such as benzene, toluene, and xylene.

The reaction temperature for the lithiation in step (A-1) above is preferably 0°C or higher, more preferably 10°C or higher, and particularly preferably 20°C or higher. Also, it is preferably 100°C or lower, more preferably 80°C or lower, and particularly preferably 60°C or lower. If the temperature is lower than 0°C, the reaction rate tends to be poor, and if the temperature is higher than 100°C, side reactions such as decomposition tend to increase.

The reaction time for the lithiation in step (A-1) above can be set appropriately depending on the progress of the reaction, but is preferably 0.01 to 100 hours, more preferably 0.1 to 50 hours, and particularly preferably 0.2 to 20 hours.

In ^1H -NMR measurement of the polymer (M) after the lithiation in step (A-1), when the peak area in the range of 4.0 to 5.7 ppm is taken as 100, the peak area in the range of 5.7 to 6.4 ppm is preferably in the range of 0.1 to 10, more preferably in the range of 0.3 to 5, and particularly preferably in the range of 0.5 to 4. When the peak area is in this range, it can be said that the lithiation reaction has proceeded properly, and the average number of side chains (b) of the obtained conjugated diene graft polymer is in a proper range.

[Step (A-2)]
In the method for producing a conjugated diene graft polymer of the present invention, in order to adjust the vinyl content of the side chain (b) to a desired range, after the step (A-1),
(A-2) a step of adding a Lewis acid;
In one embodiment, the compound is preferably

The Lewis acid is added to reduce the action of the polar compound added to promote the lithiation reaction and to adjust the vinyl content of the side chain to a desired range in step (B) described below. As the Lewis acid, an alkyl metal compound that does not deactivate the lithiation point generated in step (A-1) is preferred, and examples thereof include alkyl aluminum compounds such as trimethyl aluminum, tri-n-propyl aluminum, tri-n-butyl aluminum, triisobutyl aluminum, tri-n-hexyl aluminum, and trioctyl aluminum; alkyl magnesium compounds such as butylethyl magnesium, di-n-butyl magnesium, and di-n-hexyl magnesium; and alkyl zinc compounds such as dimethyl zinc, diethyl zinc, di-n-propyl zinc, diisobutyl zinc, and di-n-butyl zinc. Among these alkyl metal compounds, alkyl aluminum compounds or alkyl zinc compounds are preferred, alkyl aluminum compounds are more preferred, and triisobutyl aluminum is particularly preferred.

The amount of the Lewis acid used can be adjusted appropriately depending on the vinyl content of the desired side chain (b). For example, it is preferably 0.01 mol or more, more preferably 0.05 mol or more, and particularly preferably 0.1 mol or more, relative to 1 mol of the organic alkali metal compound used in the above step (A-1). It is also preferably 10 mol or less, more preferably 5 mol or less, and particularly preferably 1 mol or less. If it is less than 0.01 mol, the effect of adding the Lewis acid is poor and it is difficult to adjust to the desired vinylization degree, and if it exceeds 10 mol, the polymerization rate of the side chain polymerization tends to decrease and the economy tends to be poor. It is also preferably 0.02 mol or more, more preferably 0.1 mol or more, and particularly preferably 0.2 mol or more, relative to 1 mol of the polar compound used in the above step (A-1). It is also preferably 20 mol or less, more preferably 10 mol or less, and particularly preferably 2 mol or less. If the amount is less than 0.02 moles, the effect of adding the Lewis acid is poor and it is difficult to adjust the vinylization degree to the desired level, and if the amount is more than 20 moles, the polymerization rate of the side chain polymerization tends to decrease and the cost efficiency tends to be poor.

The timing of adding the Lewis acid may be any time after step (A-1), before step (B) described below, or any time during step (B), and can be selected arbitrarily depending on the vinyl content of the desired side chain (b).

[Step (B)]
The method for producing a conjugated diene graft polymer of the present invention comprises the steps of:
(B) a step of adding at least one monomer selected from the group consisting of conjugated dienes and aromatic vinyl compounds to polymerize the lithiated portion of the polymer (M) to form a side chain on the main chain of the polymer (M), thereby preparing a conjugated diene-based graft polymer;
The monomer polymerized in the above step (B) becomes the side chain (b) of the conjugated diene graft polymer of the present invention. The specific examples, preferred examples, and preferred contents of the conjugated diene that becomes the monomer unit constituting the polymer polymerized in step (B), as well as the specific examples, preferred examples, and preferred contents of other monomers (aromatic vinyl compounds) other than the conjugated diene, are the same as those described for the side chain (b) of the conjugated diene graft polymer. The preferred aspects of the weight average molecular weight (Mw), vinyl content, and Tg of the polymer polymerized in step (B) are the same as those described for the side chain (b) of the conjugated diene graft polymer.

In the above step (B), a polar compound may be further added to adjust the vinyl content of the side chain (b) to a desired range. Also, a Lewis acid may be added as described above to adjust the vinyl content to a desired range.

The solvents that can be used in the above step (B) are the same as the preferred examples of the solvents in the above step (A-1). If necessary, a solvent may be further added at any time after step (A-1).

The polymerization temperature in step (B) is preferably 0°C or higher, more preferably 10°C or higher, and particularly preferably 20°C or higher. Also, it is preferably 100°C or lower, more preferably 80°C or lower, and particularly preferably 60°C or lower. If the temperature is lower than 0°C, the polymerization rate tends to be poor, and if the temperature is higher than 100°C, side reactions such as decomposition tend to increase.

The polymerization time in step (B) can be set appropriately depending on the progress of the reaction, but is preferably 0.01 to 100 hours, more preferably 0.1 to 50 hours, and particularly preferably 0.2 to 20 hours.

The polymerization reaction in step (B) can be terminated by adding a polymerization terminator. Examples of polymerization terminators include alcohols such as methanol and isopropanol.

[Step (C)]
The method for producing a conjugated diene graft polymer of the present invention comprises the steps of:
(C) a step of recovering the obtained conjugated diene graft polymer;
Includes.

In step (C), the obtained conjugated diene graft polymer of the present invention is recovered. There are no particular limitations on the method for recovering the conjugated diene graft polymer, but when a solution containing the conjugated diene graft polymer is obtained in step (B), the conjugated diene graft polymer can be recovered, for example, by pouring the obtained solution into a poor solvent such as methanol to precipitate the conjugated diene graft polymer, or by washing the polymerization reaction solution with water, separating it, and then drying to isolate the conjugated diene graft polymer.

[Polymer composition]
The polymer composition of the present invention contains the conjugated diene graft polymer of the present invention (hereinafter also referred to as conjugated diene graft polymer (α)). The polymer composition may further contain another polymer (β) other than the conjugated diene graft polymer (α). The other polymer (β) may be a thermoplastic polymer (β1) or a curable polymer (β2).

Examples of the thermoplastic polymer (β1) include acrylic resins such as polymethyl methacrylate and (meth)acrylic acid ester polymers or copolymers; olefin resins such as polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; ethylene ionomers; styrene resins such as polystyrene, styrene-maleic anhydride copolymer, high-impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, and MBS resin; styrene-methyl methacrylate copolymer; styrene-methyl methacrylate-maleic anhydride copolymer; Polymers; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid; polyamides such as nylon 6, nylon 66, polyamide elastomers; polycarbonate; polyvinyl chloride; polyvinylidene chloride; polyvinyl alcohol; ethylene-vinyl alcohol copolymers; polyacetal; polyvinylidene fluoride; polyurethane; modified polyphenylene ether; polyphenylene sulfide; silicone rubber modified resins; acrylic rubber; silicone rubber; styrene-based thermoplastic elastomers such as SEPS, SEBS, SIS; olefin-based rubbers such as IR, EPR, EPDM, etc.

Examples of the curable polymer (β2) include epoxy resins, unsaturated polyester resins, epoxy (meth)acrylate resins, ester (meth)acrylate resins, phenolic resins, urea resins, melamine resins, thermosetting urethane resins, silicon resins, imide resins, furan resins, alkyd resins, allyl resins, and diallyl phthalate resins. Among these, epoxy resins, unsaturated polyester resins, and epoxy (meth)acrylate resins are preferred from the viewpoints of availability and basic physical properties of the cured product, and also from the viewpoints of obtaining a polymer composition that is more excellent in terms of bubble removal and toughness of the resulting cured product, and among these, epoxy resins and unsaturated polyester resins are more preferred, and epoxy resins are even more preferred. The curable polymer (β2) may be used alone or in combination of two or more types.

When the above polymer composition contains a conjugated diene graft polymer (α) and another polymer (β), the mass ratio (α)/(β) of the conjugated diene graft polymer (α) to the other polymer (β) is preferably 1/99 to 99/1.

In addition, various additives may be added to the polymer composition of the present invention to the extent that the effect of the present invention is not impaired. For example, when the other polymer (β) is a thermoplastic polymer (β1), such additives may be, for example, calcium carbonate, silica, carbon black, glass fiber, clay, or other reinforcing or filler, or process oil, polyethylene glycol, glycerin, phthalic acid ester, or other plasticizer. In addition, other additives may be, for example, heat stabilizers, antioxidants, ultraviolet absorbers, colorants, pigments, lubricants, surfactants, and the like. Furthermore, foaming agents may be included as the additives, and foams can be produced from the polymer composition containing the foaming agent and the thermoplastic polymer (β1).
For example, when the other polymer (β) is a curable polymer (β2), such additives include a curing agent, a curing accelerator, known rubbers, thermoplastic elastomers, impact modifiers such as core-shell particles, fillers (inorganic particles such as silica, talc, calcium carbonate, and aluminum hydroxide), flame retardants, defoamers, pigments, dyes, antioxidants, weather resistance agents, lubricants, and mold release agents.

The polymer composition of the present invention can be prepared by a conventional method for mixing polymeric substances according to the composition ratio of each component, such as the conjugated diene graft polymer (α) and the other polymer (β).

When the other polymer (β) is a thermoplastic polymer (β1), the polymer composition can be produced using a mixing device such as an extruder, mixing roll, Banbury mixer, or kneader. In particular, in the present invention, a method of melt kneading using such a mixing device is a preferred embodiment.

When the other polymer (β) is a curable polymer (β2), the polymer composition can be produced, for example, by thoroughly mixing them in a mixer, melt-kneading them using a mixing roll or extruder, and then cooling and pulverizing them.

The polymer composition of the present invention may be a crosslinkable polymer composition containing the conjugated diene graft polymer (α). In the case of such a polymer composition, it further contains a crosslinking agent.
Examples of the crosslinking agent include sulfur, sulfur compounds, hydrogen peroxide, peroxides such as organic peroxides, phenol resins, amino resins, quinones and quinone dioxime derivatives, halogen compounds, aldehyde compounds, alcohol compounds, epoxy compounds, metal halides and organometallic halides, and silane compounds.
When sulfur or a sulfur compound is contained as a crosslinking agent, a vulcanization accelerator and a vulcanization aid may be further contained.
The crosslinkable polymer composition may further contain additives such as solid rubbers (excluding the conjugated diene graft polymer (α)) such as natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene copolymer rubber, carbon black, fillers such as silica, crosslinking aids, softeners such as oil, tackifier resins, antioxidants, antioxidants, light stabilizers, scorch inhibitors, functional group-containing compounds, waxes, lubricants, plasticizers, processing aids, pigments, dyes, other colorants, flame retardants, antistatic agents, matting agents, antiblocking agents, ultraviolet absorbing agents, release agents, foaming agents, antibacterial agents, antifungal agents, fragrances, dispersants, and solvents.

The polymer composition of the present invention can be molded into a molded article by various conventional molding methods.

When the other polymer (β) is a thermoplastic polymer (β1), the polymer composition can be molded, for example, by extrusion molding, injection molding, blow molding, compression molding, vacuum molding, calendar molding, etc. to produce a molded article. These methods can be used to obtain molded articles, sheets, films, etc. of various shapes. In addition, molded articles such as nonwoven fabrics and fibrous materials can also be produced by methods such as the melt-blowing method and the spunbonding method.

When the other polymer (β) is a curable polymer (β2), the polymer composition can be thermally cured to produce a molded product, for example, by transfer molding. Other molding methods when the polymer composition contains a curable polymer (β2) include, for example, injection molding and compression molding.

When the polymer composition of the present invention is a crosslinkable polymer composition, it can be used as a crosslinked product by crosslinking. The crosslinking conditions for the crosslinkable polymer composition can be set appropriately depending on the application and the crosslinking agent used. For example, when the crosslinking agent is a peroxide, a crosslinked product can be produced by carrying out a crosslinking reaction for 10 to 60 minutes at a temperature range of 130°C to 250°C. For example, when the crosslinking agent is sulfur or a sulfur compound, it can be carried out using a vulcanization mold under conditions of a vulcanization temperature of 120 to 200°C and a vulcanization pressure of 0.5 to 20 MPa.

When the other polymer (β) is a thermoplastic polymer (β1), examples of uses of molded articles obtained from the polymer composition include automobile interior and exterior parts such as bumpers and instrument panels, housing materials for home appliances such as televisions, stereos, and vacuum cleaners, electrical and electronic parts such as connectors, materials for electric wires and cables, food packaging materials or food containers such as trays for fresh meat and fish, fruit and vegetable packs, and frozen food containers, packaging materials such as industrial materials, sporting goods such as materials for sports shoes, fabric or leather products, daily necessities such as toys and sandals, various films, sheets, laminating materials for molded articles, adhesives and pressure-sensitive adhesives, elastic materials used in paper diapers, various rubber products such as hoses, tubes, and belts, and medical supplies.

When the other polymer (β) is a curable polymer (β2), the uses of the polymer composition, its cured product, or molded product include, for example, various adhesives such as adhesives for fiber-reinforced composite materials (adhesives for fiber-reinforced composite materials for concrete, adhesives for fiber-reinforced composite materials for transportation equipment such as automobiles, railway vehicles, and aircraft, adhesives for fiber-reinforced composite materials for various sporting goods, etc.), and assembly adhesives (adhesives for assembling parts in transportation equipment such as automobiles, railway vehicles, and aircraft, etc.); various paints such as anticorrosive and waterproof paints for water supply and sewerage, and anticorrosive paints for metals; various paint primers such as paint primers for construction and civil engineering, and paint primers for transportation equipment such as automobiles, railway vehicles, and aircraft; various lining materials such as metal lining materials, concrete lining materials, and tank lining materials; various repair materials such as crack repair materials for concrete; various electric and electronic parts such as printed wiring boards, insulating boards, semiconductor encapsulants, and packaging materials.

Applications in which the above-mentioned crosslinkable polymer composition and crosslinked products of the polymer composition can be used include tires, belts, anti-vibration rubber, wire-coating rubber, rolls, shoes, sealants, adhesives, greases, printing plate materials, OCR, OCA, paints, fenders, coatings, gaskets, hoses, brake pads, etc.

The above-mentioned crosslinkable polymer composition or a crosslinked product of the polymer composition is suitably used, for example, as a part of a tire.
Examples of tire parts in which the polymer composition and the crosslinked product of the polymer composition can be used include treads (cap treads and under treads), sidewalls, rubber reinforcing layers for run-flat tires (liners and the like), rim cushions, bead fillers, bead insulation, bead apex, clinch apex, belts, belt cushions, breakers, breaker cushions, chafers, chafer pads, and strip apex.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the physical properties of the conjugated diene graft polymers were evaluated by the following methods.

(1) Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw/Mn)
The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw/Mn) of the conjugated diene graft polymer and the polymer at each stage of its production were measured by gel permeation chromatography (GPC). The number average molecular weight (Mn) of the side chain (b) was calculated based on the ratio of the initiator used in the polymerization of the polymer that becomes the structural unit of the side chain to the monomer that becomes the structural unit of the side chain. The ratio was calculated from the feed ratio.
Apparatus: Tosoh Corporation GPC device "HLC-8220"
Separation column: "TSKgel SuperMultiporeHZ-M (column diameter = 4.6 mm, column length = 15 cm)" manufactured by Tosoh Corporation (two columns connected in series)
Eluent: Tetrahydrofuran Eluent flow rate: 0.35 mL/min Column temperature: 40° C.
Detection method: Differential refractive index (RI)
Injection volume: 10 μl
Concentration: 1 mg/1 cc (conjugated diene graft polymer/THF)

(2) Vinyl content, styrene unit content
The vinyl content and styrene unit content of the conjugated diene graft polymer and the polymer at each stage of its production were calculated by ¹ H-NMR. The vinyl content was calculated from the area ratio of the peak of the double bond derived from the vinylated conjugated diene unit to the peak of the double bond derived from the non-vinylated conjugated diene unit in the obtained spectrum, and the styrene unit content was calculated from the area ratio of the peak of the aromatic ring derived from the styrene unit to the peak of the double bond derived from the conjugated diene unit.
Apparatus: Nuclear magnetic resonance apparatus "JNM-ECX400" manufactured by JEOL Ltd.
Solvent: deuterated chloroform Measurement temperature: 50°C
Number of times of accumulation: 1024 times

(3) Molecular Weight Between Entanglement Points The molecular weight between entanglement points of the polymer constituting the side chain (b) was calculated from the theoretical formula described in POLYMER ENGINEERING AND SCIENCE, 1992, 32, 823.

(4) Average number of side chains (b) per molecule of conjugated diene graft polymer The average number of side chains (b) per molecule of conjugated diene graft polymer was calculated from the charge ratio of the organic alkali metal compound used in the lithiation reaction to the conjugated diene polymer serving as the main chain constituent unit, when the conjugated diene graft polymer was produced by reacting a previously synthesized conjugated diene polymer described later with an organic alkali metal compound in the presence of tetramethylethylenediamine to lithiate the main chain, and then polymerizing a monomer serving as a side chain constituent unit. Also, when the conjugated diene graft polymer was produced by modifying a previously synthesized polymer serving as a main chain constituent unit with a functional group, and reacting the functional group modified polymer with the active terminal of a polymer obtained by polymerizing a monomer serving as a side chain constituent unit, the average number of side chains (b) per molecule of conjugated diene graft polymer was calculated from the charge ratio of the active terminal polymer serving as a side chain constituent unit in the coupling reaction to the functional group modified conjugated diene polymer.

(5) Side Chain Density of Side Chain (b) The side chain density of the side chain (b) was calculated from the average number of side chains (b) per molecule of the conjugated diene graft polymer and the number average molecular weight (Mn) of the main chain (a) in terms of standard polystyrene according to the following formula (2).
(Side chain density)=(average number of side chains (b) per molecule of conjugated diene graft polymer)/[(number average molecular weight Mn of main chain (a))/(molecular weight of styrene unit)]×100 (2)

(6) tan δ strength due to relaxation of dangling chains The tan δ strength due to relaxation of dangling chains is calculated by analyzing the temperature dispersion curve of tan δ obtained by dynamic viscoelasticity measurement of a vulcanizate prepared under the following conditions.
- Preparation conditions of vulcanizate 3.5 parts by mass of zinc oxide, 2 parts by mass of stearic acid, 1.2 parts by mass of N-(tert-butyl)-2-benzothiazolesulfenamide, 1 part by mass of N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, and sulfur were added and mixed with 100 parts by mass of conjugated diene graft polymer. The unvulcanized product was press molded (thickness 2 mm, temperature: 150°C, pressure: 2 MPa, time: 60 minutes) to obtain a vulcanized product, and then a strip of 20 mm x 5 mm x 2 mm required for the dynamic viscoelasticity measurement described later was cut out. The amount of sulfur added was adjusted so that the value of tan δ at 80°C was 0.06 when normalized so that the maximum intensity of the temperature dispersion curve of tan δ obtained by the dynamic viscoelasticity measurement described later was 1.
Measurement conditions for dynamic viscoelasticity: Using a Rheogel-E4000 manufactured by UBM Corporation, measurements were performed in tension mode at a temperature range of -100°C to 150°C (heating rate of 3°C/min) and a frequency of 11 Hz.
- Method for calculating the strength of tan δ derived from relaxation of dangling chains The temperature dispersion curve of tan δ obtained by the dynamic viscoelasticity measurement was normalized so that the maximum strength was 1. Only data with strengths of 0.5 or more relative to the maximum strength were used for fitting to the Gaussian function by the least squares method. As the Gaussian function, a function expressed by Y = exp(-[(X-u) ² /w ² ]) was used. In the Gaussian function, Y is the strength value of the temperature dispersion curve of normalized tan δ, X is temperature, w and u are variables, and the temperature at which the maximum strength value was shown was used as the initial value of u. An arbitrary value was used as the initial value of w for calculation by the least squares method. In a curve consisting of the difference between the approximation curve obtained under the above fitting conditions and the normalized temperature dispersion curve, the maximum strength in a region higher than the temperature showing the maximum strength in the normalized temperature dispersion curve was taken as the strength of tan δ derived from relaxation of dangling chains.

(7) Shear Stability The shear stability of the conjugated diene graft polymer was evaluated by carrying out a shear test in accordance with JPI-5S-29-2006 using an oil composition prepared under the following conditions. The shear stability was evaluated using the following index based on the visual change in viscosity before and after the shear test.
A: No visible change in viscosity B: Viscosity change visible Method for preparing oil composition ExxonMobil Group I base oil "AP/E CORE 150" was used as the base oil. The base oil was charged into a nitrogen-purged pressure vessel so that the weight ratio of base oil/conjugated diene graft polymer was 95/5, and mixed for 6 hours under conditions of a heating temperature of 120°C and a rotation speed of 350 rpm, to obtain an oil composition.

[Example 1]
(Step (1))
A 5L autoclave that was thoroughly dried was purged with nitrogen, and 1590 g of cyclohexane and 60 g of sec-butyllithium (10.5% by mass cyclohexane solution) were charged, and the temperature was raised to 50° C., and then 1350 g of 1,3-butadiene was successively added while controlling the polymerization temperature to 50° C. under stirring conditions, and polymerization was carried out for 1 hour. Thereafter, 3.5 g of methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution, and the mixture was stirred, and the polymer solution was washed with water. After the stirring was terminated, it was confirmed that the polymer solution phase and the aqueous phase were separated, and then the water was separated. The polymer solution after washing was vacuum dried at 70° C. for 24 hours to obtain a conjugated diene polymer (M-1). The weight average molecular weight and vinyl content of the main chain (a) of the conjugated diene graft polymer (G-1) described later can be obtained by analyzing the obtained conjugated diene polymer (M-1). The resulting conjugated diene polymer (M-1) had a weight average molecular weight of 28,000 and a vinyl content of 10 mol %.

(Step (2))
Next, 131 g of the conjugated diene polymer (M-1) obtained in step (1) was charged into a thoroughly dried 5 L autoclave, and the polymer was degassed with nitrogen and the autoclave was replaced with nitrogen while stirring at 60 ° C. for 3 hours. 1460 g of cyclohexane was charged, and the temperature was raised to 40 ° C., and then 108 g of sec-butyl lithium (10.5 mass % cyclohexane solution) and 10.5 g of N,N,N',N'-tetramethylethylenediamine were added successively, and a lithiation reaction was carried out at 40 ° C. for 1 hour. After the lithiation reaction was completed, 820 g of cyclohexane was added to dilute the reaction solution, and the temperature was raised to 40 ° C. again. The reaction solution after the lithiation was sampled, and the peak area in the range of 5.7 to 6.4 ppm was calculated by ¹ H-NMR measurement, where the peak area in the range of 4.0 to 5.7 ppm was taken as 100, and it was 1.52.

(Step (3))
While controlling the polymerization temperature to 40° C., 470 g of 1,3-butadiene was gradually added and polymerization was carried out for 2 hours. Thereafter, 29 g of methanol was added to terminate the polymerization reaction, and a polymer solution was obtained.
The number average molecular weight, vinyl content, and styrene unit content of the side chain (b) of the conjugated diene graft polymer (G-1) described below can be determined by analyzing the amounts of reagents charged in step (3) and the polymer solution in step (3). The number average molecular weight of the side chain (b) of the conjugated diene graft polymer (G-1) was 5,000, the vinyl content was 75 mol%, and the styrene unit content was 0 mass%.

(Step (4))
Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After the stirring was terminated and it was confirmed that the polymer solution phase and the aqueous phase were separated, the water was separated. The polymer solution after washing was vacuum dried at 70°C for 24 hours to obtain a conjugated diene graft polymer (G-1). The weight average molecular weight of the obtained conjugated diene graft polymer (G-1) was 128,000, Mw/Mn was 1.5, the average number of side chains (b) per molecule of the conjugated diene graft polymer was 20, and the side chain density was 7.4 mol%. In addition, the monomer unit that becomes the branching portion does not have a heteroatom, and the linking portion bonded to the side chain (b) is not an aromatic group derived from an aromatic vinyl compound. The molecular specifications and physical properties of the obtained conjugated diene graft polymer (G-1) are shown in Table 2.

[Examples 2 to 9]
Conjugated diene graft polymers (G-2) to (G-9) were obtained in the same manner as in Example 1, except that the types and amounts of the reagents used in steps (1) to (4) were changed as shown in Table 1. The molecular specifications and physical properties of the obtained conjugated diene graft polymers (G-2) to (G-9) are shown in Table 2. When triisobutylaluminum (TIBA) was used in step (2), the TIBA used was a 20.0 mass % n-hexane solution, and after completion of the lithiation reaction, cyclohexane was added to dilute the reaction solution, the temperature was raised again to 40° C., and this TIBA solution was then added.

[Comparative Example 1]
(Step (1))
A 5L autoclave that was thoroughly dried was purged with nitrogen, and 1590 g of cyclohexane and 60 g of sec-butyllithium (10.5% by mass cyclohexane solution) were charged. The temperature was raised to 50° C., and then 1350 g of 1,3-butadiene was successively added under stirring conditions while controlling the polymerization temperature to 50° C., and polymerization was carried out for 1 hour. Thereafter, 3.5 g of methanol was added to terminate 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 stopping the stirring and confirming that the polymer solution phase and the aqueous phase were separated, the water was separated. The polymer solution after washing was vacuum dried at 70° C. for 24 hours to obtain a conjugated diene-based linear polymer (L-1). The weight average molecular weight of the obtained conjugated diene-based polymer (L-1) was 28,000, and the vinyl content was 10 mol%. The molecular specifications and physical properties of the obtained conjugated diene-based graft polymer (L-1) are shown in Table 2.

[Comparative Example 2]
(Step (1))
A 5L autoclave that was thoroughly dried was purged with nitrogen, and 1570 g of cyclohexane and 78 g of sec-butyllithium (10.5% by mass cyclohexane solution) were charged, and the temperature was raised to 50° C., and then, under stirring conditions, 1350 g of 1,3-butadiene was successively added while controlling the polymerization temperature to 50° C., and polymerization was carried out for 1 hour. Thereafter, 4.6 g of methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution, and the mixture was stirred, and the polymer solution was washed with water. After the stirring was terminated, it was confirmed that the polymer solution phase and the aqueous phase were separated, and then the water was separated. The polymer solution after washing was vacuum dried at 70° C. for 24 hours to obtain an unmodified conjugated diene-based polymer (F'-1).

(Step (2))
Next, 700 g of the unmodified conjugated diene polymer (F'-1) obtained in step (1), 1400 g of cyclohexane, 5.6 mL of a 2% xylene solution of platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex ("PC072" manufactured by Petrarch System), and 120 g of trimethylchlorosilane were charged into a 5 L separable flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, and these were stirred overnight. Thereafter, 66 g of dimethylchlorosilane was dropped into the flask, and the mixture was gradually heated until the internal temperature reached 70 ° C., and stirred for 24 hours under reflux while maintaining the internal temperature at 70 ° C. After completion of the stirring, the mixture was concentrated under reduced pressure and filtered to obtain a functional group-modified conjugated diene polymer (F-1). By analyzing the obtained functional group-modified conjugated diene polymer (F-1), the weight average molecular weight and vinyl content of the main chain (a) of the conjugated diene graft polymer (G-10) described later can be obtained. The weight average molecular weight of the obtained functional group-modified conjugated diene polymer (F-1) was 20,000, and the vinyl content was 10 mol%. 1790 g of cyclohexane was added to the obtained functional group-modified conjugated diene polymer (F-1) to dilute it to a concentration of 30 mass%, and a diluted solution of the functional group-modified conjugated diene polymer (F-1) to be used in the coupling reaction described later was obtained.

(Step (3))
A 5L autoclave that was thoroughly dried was purged with nitrogen, and 1850 g of cyclohexane and 47 g of sec-butyllithium (10.5% by mass cyclohexane solution) were charged, and the temperature was raised to 50° C., and then 820 g of 1,3-butadiene was successively added under stirring conditions while controlling the polymerization temperature to 50° C., and 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 number average molecular weight, vinyl content, and styrene unit content of the side chain (b) of the conjugated diene graft polymer (G-10) described later can be obtained. The number average molecular weight of the obtained active terminal polymer (I-1) was 20,000, the vinyl content was 10 mol%, and the styrene unit content was 0% by mass.

(Step (4))
Next, 270 g of the diluted solution of the functional group-modified conjugated diene polymer (F-1) obtained in step (2) was added to the solution containing the active terminal polymer (I-1) obtained in step (3), and a coupling reaction was carried out at 50° C. for 2 hours. Then, 24 g of n-butyllithium (15% by mass hexane solution) was added and reacted for 6 hours to cap a portion of the remaining alkoxy groups. Then, 5.3 g of methanol was added to terminate the polymerization reaction, and a polymer solution was obtained.

(Step (5))
Water was added to the obtained polymer solution, and the mixture was stirred, and the polymer solution was washed with water. After the stirring was terminated and it was confirmed that the polymer solution phase and the aqueous phase were separated, the water was separated. The polymer solution after washing was vacuum dried at 70° C. for 24 hours to obtain a conjugated diene graft polymer (G-10). The weight average molecular weight of the obtained conjugated diene graft polymer (G-10) was 220,000, Mw/Mn was 1.5, the average number of side chains (b) per molecule of the conjugated diene graft polymer was 10, and the side chain density was 5.4 mol%. In addition, the monomer unit that becomes the branching portion contains a heteroatom, Si atom, derived from the functional group-modified conjugated diene polymer (F-1), and the linking portion bonded to the side chain (b) is not an aromatic group derived from an aromatic vinyl compound. The molecular specifications and physical properties of the obtained conjugated diene graft polymer (G-10) are shown in Table 2.

[Comparative Example 3]
(Step (1))
A 5L autoclave that was thoroughly dried was purged with nitrogen, and 2090 g of benzene and 31 g of sec-butyllithium (10.5% by mass solution in cyclohexane) were charged. The temperature was raised to 50° C., and then 540 g of 1,3-butadiene was successively added under stirring conditions while controlling the polymerization temperature to 50° C., and polymerization was carried out for 1 hour to obtain an active terminal polymer (I-2). By sampling and analyzing the polymer solution in step (1), the number average molecular weight, vinyl content, and styrene unit content of the side chain (b) of the conjugated diene graft polymer (G-11) described later can be obtained. The number average molecular weight of the obtained active terminal polymer (I-2) was 20,000, the vinyl content was 10 mol%, and the styrene unit content was 0% by mass.

(Step (2))
Next, 5.7 g of 2-(dichloromethylsilyl)ethylchloromethylsilyl-4-styrene was added to the solution containing the active terminal polymer (I-2) obtained in the step (2) and reacted at 50° C. for 5 hours to obtain a polymer solution containing a macromonomer.

(Step (3))
Subsequently, 8.7 g of sec-butyl lithium (10.5% by mass solution in cyclohexane) and 67 g of potassium 2,3-dimethyl-3-pentyl oxide were added to the polymer solution containing the macromonomer obtained in step (2), and then 360 g of 1,3-butadiene was successively added and polymerized for 5 hours under stirring conditions while controlling the polymerization temperature to 50°C. Thereafter, 2.3 g of methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. The weight average molecular weight and vinyl content of the main chain (a) of the conjugated diene graft polymer (G-11) described later can be obtained by analyzing the amount of reagent charged in step (3) and the polymer solution in step (3). The weight average molecular weight of the main chain (a) of the conjugated diene graft polymer (G-11) was 47,000 and the vinyl content was 10 mol%.

(Step (4))
Water was added to the obtained polymer solution, and the mixture was stirred, and the polymer solution was washed with water. After the stirring was terminated and it was confirmed that the polymer solution phase and the aqueous phase were separated, the water was separated. The polymer solution after washing was vacuum dried at 70° C. for 24 hours to obtain a conjugated diene graft polymer (G-11). The weight average molecular weight of the obtained conjugated diene graft polymer (G-11) was 127,000, Mw/Mn was 1.5, the average number of side chains (b) per molecule of the conjugated diene graft polymer was 4, and the side chain density was 0.9 mol%. In addition, the monomer unit that becomes the branching portion contains a Si atom, which is a heteroatom, derived from the macromonomer, and the linking portion that bonds to the side chain (b) is an aromatic group derived from the macromonomer. The molecular specifications and physical properties of the obtained conjugated diene graft polymer (G-11) are shown in Table 2.

[Comparative Example 4]
(Step (1))
A 5L autoclave that was thoroughly dried was purged with nitrogen, and 1570 g of cyclohexane and 78 g of sec-butyllithium (10.5% by mass cyclohexane solution) were charged, and the temperature was raised to 50° C., and then, under stirring conditions, 1350 g of 1,3-butadiene was successively added while controlling the polymerization temperature to 50° C., and polymerization was carried out for 1 hour. Thereafter, 4.6 g of methanol was added to terminate the polymerization reaction, and a polymer solution was obtained. Water was added to the obtained polymer solution, and the solution was stirred, and the polymer solution was washed with water. After the stirring was terminated, it was confirmed that the polymer solution phase and the aqueous phase were separated, and then the water was separated. The polymer solution after washing was vacuum dried at 70° C. for 24 hours to obtain a conjugated diene polymer (M-10). The weight average molecular weight and vinyl content of the main chain (a) of the conjugated diene graft polymer (G-12) described later can be obtained by analyzing the obtained conjugated diene polymer (M-10). The resulting conjugated diene polymer (M-10) had a weight average molecular weight of 20,000 and a vinyl content of 10 mol %.

(Step (2))
Next, 495 g of the conjugated diene polymer (M-10) obtained in step (1) was charged into a thoroughly dried 5 L autoclave, and the polymer was degassed with nitrogen and the autoclave was replaced with nitrogen while stirring at 60° C. for 3 hours. 1480 g of cyclohexane was charged and the temperature was raised to 40° C., after which 61 g of sec-butyllithium (10.5 mass% cyclohexane solution) and 5.9 g of N,N,N',N'-tetramethylethylenediamine were successively added, and a lithiation reaction was carried out at 40° C. for 1 hour. After completion of the lithiation reaction, 850 g of cyclohexane was added to dilute the reaction solution, and the temperature was raised again to 40° C.

(Step (3))
While controlling the polymerization temperature to 40° C., 110 g of 1,3-butadiene was gradually added and polymerization was carried out for 2 hours. Thereafter, 16 g of methanol was added to terminate the polymerization reaction, and a polymer solution was obtained.
The number average molecular weight, vinyl content, and styrene unit content of the side chain (b) of the conjugated diene graft polymer (G-12) described below can be determined by analyzing the amounts of reagents charged in step (3) and the polymer solution in step (3). The number average molecular weight of the side chain (b) was 2,000, the vinyl content was 75 mol%, and the styrene unit content was 0 mass%.

(Step (4))
Water was added to the obtained polymer solution and stirred, and the polymer solution was washed with water. After the stirring was terminated and it was confirmed that the polymer solution phase and the aqueous phase were separated, the water was separated. The polymer solution after washing was vacuum dried at 70°C for 24 hours to obtain a conjugated diene graft polymer (G-12). The weight average molecular weight of the obtained conjugated diene graft polymer (G-12) was 26,000, Mw/Mn was 1.5, the average number of side chains (b) per molecule of the conjugated diene graft polymer was 3, and the side chain density was 1.6 mol%. In addition, the monomer unit that becomes the branching portion does not have a heteroatom, and the linking portion bonded to the side chain (b) is not an aromatic group derived from an aromatic vinyl compound. The molecular specifications and physical properties of the obtained conjugated diene graft polymer (G-12) are shown in Table 2.

The types and amounts of each reagent used in steps (1) to (4) in Examples 1 to 9 are shown in Table 1 below, and the physical properties of the conjugated diene graft polymers and conjugated diene linear polymers obtained in Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 2.

In Table 1, the abbreviations indicate the following: SBL: sec-butyllithium (10.5% by mass solution in cyclohexane)
TMEDA: N,N,N',N'-tetramethylethylenediamine TIBA: triisobutylaluminum (20.0% by mass solution in n-hexane)
Bd: 1,3-butadiene Ip: isoprene St: styrene

From Table 2, it can be seen that the conjugated diene graft polymers of Examples 1 to 9, in which the side chain density is 2.0 mol% or more, the monomer unit that becomes the branched portion does not contain a heteroatom, and the linking portion that binds to the side chain (b) contained in the monomer unit that becomes the branched portion is not an aromatic group derived from an aromatic vinyl compound, have a high peak intensity of tan δ derived from a dangling chain and are excellent in shear stability.
On the other hand, the conjugated diene polymer of Comparative Example 1, which is a linear conjugated diene polymer, has a low peak intensity of tan δ derived from dangling chains. The conjugated diene graft polymer of Comparative Example 2, in which the monomer unit that becomes the branching portion contains a Si atom, has poor shear stability. The conjugated diene graft polymer of Comparative Example 3, in which the monomer unit that becomes the branching portion contains a Si atom and the linking portion that binds to the side chain (b) contained in the monomer unit that becomes the branching portion is an aromatic group derived from an aromatic vinyl compound, has poor shear stability. The conjugated diene graft polymer of Comparative Example 4, in which the side chain density is 1.6 mol%, has a low peak intensity of tan δ derived from dangling chains.

The conjugated diene graft polymer of the present invention has a high peak intensity of tan δ derived from dangling chains and excellent shear stability, and therefore can be effectively used in a wide range of fields, such as automotive interior and exterior parts, electrical and electronic parts, packaging materials, sporting goods, daily necessities, laminating materials, elastic materials, various rubber products, medical supplies, various adhesives, and various paint primers.

Claims (7)

a conjugated diene-based graft polymer in which a main chain (a) made of a polymer containing a conjugated diene unit is bonded to a side chain (b) made of a polymer containing at least one monomer unit selected from the group consisting of a conjugated diene unit and an aromatic vinyl compound unit at a monomer unit that becomes a branching portion contained in the main chain (a);
the side chain density of the side chain (b) of the conjugated diene graft polymer calculated by the following formula (2) is 2.0 mol % or more,
The monomer unit that becomes the branched portion does not contain a heteroatom,
the linking moiety bonded to the side chain (b) contained in the monomer unit that becomes the branched moiety is not an aromatic group derived from an aromatic vinyl compound;
Conjugated diene graft polymer.
(Side chain density)=(average number of side chains (b) per molecule of conjugated diene graft polymer)/[(number average molecular weight Mn of main chain (a))/(molecular weight of styrene unit)]×100 (2)
The Mn of the main chain (a) is the Mn calculated in terms of standard polystyrene obtained by GPC measurement of the conjugated diene polymer (M) which is a constituent element of the main chain. (A-1) a step of reacting a polymer (M) containing a conjugated diene unit with an organolithium compound in the presence of a polar compound to lithiate an anion active site contained in the polymer (M);
(B) a step of adding at least one monomer selected from the group consisting of conjugated dienes and aromatic vinyl compounds, polymerizing the lithiated portion of the polymer (M) to form a side chain on the main chain of the polymer (M), thereby preparing a conjugated diene graft polymer; and (C) a step of recovering the obtained conjugated diene graft polymer.
The side chain density of the side chain (b) calculated by the following formula (2) is 2.0 mol % or more,
(Side chain density)=(average number of side chains (b) per molecule of conjugated diene graft polymer)/[(number average molecular weight Mn of main chain (a))/(molecular weight of styrene unit)]×100 (2)
The Mn of the main chain (a) is the Mn calculated in terms of standard polystyrene obtained by GPC measurement of the conjugated diene polymer (M) which is a constituent element of the main chain. Furthermore, after the step (A-1),
(A-2) a step of adding a Lewis acid;
The method for producing the conjugated diene graft polymer according to claim 2, comprising: The method for producing a conjugated diene graft polymer according to claim 2 or 3, wherein in ^1H -NMR measurement of the polymer (M) after the lithiation in the step (A-1), the peak area in the range of 5.7 to 6.4 ppm is in the range of 0.1 to 10, where the peak area in the range of 4.0 to 5.7 ppm is taken as 100. A polymer composition containing the conjugated diene graft polymer according to claim 1. A molded article obtained by molding the polymer composition according to claim 5. A crosslinked product obtained by crosslinking the polymer composition according to claim 5.