JP2002161139A - Block copolymer and method of producing the same and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a block copolymer having high hysteresis (loss tangent coefficient) and excellent in abrasion resistance and also excellent in road surface gripping force while running (gripping property) when used in a tread of a tire. SOLUTION: The block copolymer has as a block unit a diene-based polymer and a polymer incompatible therewith. The preferable features include that the block copolymer has a micro phase separation structure and 50% or less of the polymer incompatible with the diene-based polymer and that the polymer incompatible with the diene-based polymer is a cyclohexane-based polymer, the cyclohexane-based polymer being polydimethylsiloxane, and that a terminal has a structure except Si-OH structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a block having a large hysteresis loss (tangent loss coefficient), excellent abrasion resistance, and excellent grip (gripability) on a road surface during running when used for a tire tread. The present invention relates to a polymer and an efficient production method thereof, and a rubber composition using the block copolymer, which is particularly suitable as a tread rubber for racing tires and the like.

[0002]

2. Description of the Related Art In general, tread rubbers for highly competitive vehicle tires, such as racing tires, are required to have high grip properties. Conventionally, to obtain high grip,
Use a styrene-butadiene copolymer rubber (SBR) with a high styrene component content, use an equivalent substitution blend of a high softening point resin and process oil, or use a highly filled softener or carbon black. Or relying on small particle carbon black, or relying on a combination thereof. However, styrene having a high styrene content
When a butadiene copolymer rubber is used, there is a problem that the temperature dependence is increased due to a high glass transition temperature, and the performance change with temperature change is increased. In addition, when a high softening point resin and a process oil are replaced by the same amount, if the replacement amount is large, there is a problem that the temperature dependency becomes large due to the influence of the high softening point resin. Furthermore, when carbon black having a small particle size or a large amount of a softening agent is used, there is a problem that the dispersibility of the carbon black is poor and abrasion resistance is reduced.

On the other hand, various block copolymers have been proposed for a long time as rubber compositions satisfying grip properties in a wide temperature range. For example, Japanese Patent Application Laid-Open No. 57-9201
No. 4, JP-B-63-60768, JP-B-63-607
No. 69, JP-B-63-39015, JP-A-57-20
No. 0413, JP-B-3-80165, JP-A-61-5
5135, JP-A-61-141742, JP-A-61-141742
JP-A-231016, JP-A-62-240347, JP-A-63-112648, JP-A-63-137945
JP-A-63-90522, JP-A-1-29741
No. 2 etc. include a block copolymer of a styrene-butadiene copolymer having a high styrene content and a styrene-butadiene copolymer having a low styrene content, and a styrene-butadiene copolymer having a high vinyl content and a low vinyl content. A rubber composition using a block polymer of a high Tg polymer and a low Tg polymer, such as a block (co) polymer with a (styrene) butadiene (co) polymer, is disclosed. These rubber compositions increase the Tg width of the polymer,
It is intended to improve wet skid properties, ice skid properties, and fuel efficiency. However, in the case of these rubber compositions, there is a problem that the dry grip property, which greatly affects running stability at high speed, is still insufficient.

On the other hand, JP-B-49-37415, JP-A-62-143959 and the like disclose a high Tg polymer and a low Tg polymer.
And a rubber composition obtained by adding a process oil to a block polymer of a polymer having a high Tg and a block polymer of a polymer having a low Tg are added thereto. Have been. However, in the case of these rubber compositions, the ride comfort when used as an automobile tire, is intended to improve vibration damping when used as an industrial product,
There is a problem that the abrasion resistance, destructibility, wet skid property, ice skid property, etc. of the automobile tire are not sufficiently satisfactory.

Also, Japanese Patent Publication No. 59-52664, Japanese Patent Application Laid-Open No. 58-147442, Japanese Patent Application Laid-Open No. 58-147443,
JP-A-60-240746, JP-A-61-20314
5, JP-A-62-135506, JP-A-64-16
No. 845 and the like disclose a rubber composition intended to improve processability, low fuel consumption, breakage characteristics, and grip properties by blending a high molecular weight substance and a low molecular weight substance. But,
In the case of these rubber compositions, there is a problem that wet skid properties, ice skid properties, dry grip properties, and abrasion resistance are not sufficiently satisfactory.

Further, Japanese Patent Application Laid-Open No. 1-197541 discloses a rubber composition intended to improve dry grip characteristics and high abrasion resistance by increasing the Tg width of a high molecular weight compound and adding a low molecular weight compound. Is disclosed. However, in the case of this rubber composition, since it contains a styrene-butadiene copolymer obtained by emulsion polymerization, there is a problem that the improvement of ice skid characteristics is insufficient.

[0007] Conventional use of block copolymers is as follows.
It is intended to obtain a wide glass transition region and does not exceed the use of hysteresis loss accompanying the glass transition, so that no significant improvement in hysteresis loss has been obtained at present. There is a limit in securing grip force only by using hysteresis loss associated with the glass transition phenomenon, and hysteresis loss by another mechanism is necessary to secure dramatic grip force.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention has a large hysteresis loss (tangent loss coefficient), is excellent in abrasion resistance, and has a gripping force (grip property) on a running road surface when used for a tread of a tire.
Excellent block copolymer and its efficient production method,
Another object of the present invention is to provide a rubber composition using the block copolymer, which is particularly suitable as a tread rubber for racing tires and the like.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies and as a result have obtained the following findings.
That is, a strongly incompatible block copolymer exhibits self-aggregation properties, and the microdomains of the block copolymer upon aggregation have an ordered structure. The ordered structure resulting from the self-aggregation shows a certain liquid-like solid structure even when each block unit of the block copolymer is in a rubbery region. It is a finding that hysteresis loss occurs due to a mechanism that causes temporary collapse, reaggregation, and ordering when such a liquid solid structure is deformed.

The present invention is based on such knowledge of the present inventor, and means for solving the above problems are as follows. That is, <1> a block copolymer comprising a diene-based polymer and a polymer incompatible with the diene-based polymer as block units. <2> The block copolymer according to <1>, which has a microphase-separated structure. <3> The block copolymer according to <1> or <2>, wherein the block copolymer has 50% by weight or less of a polymer incompatible with the diene-based polymer. <4> The above <1> to <3>, wherein the polymer incompatible with the diene-based polymer is a siloxane-based polymer.
The block copolymer according to any one of the above. <5> The block copolymer according to <4>, wherein the siloxane-based polymer is polydimethylsiloxane. <6> The above-mentioned <whose terminal is a structure other than the Si-OH structure
It is a block copolymer as described in any one of <1> to <5>. <7> The method for producing a block copolymer according to any one of claims 1 to 6, wherein a diene monomer and an aromatic vinyl monomer are polymerized in a hydrocarbon solvent using an alkali metal polymerization initiator. After obtaining a polymer, an oxolanyl alkane derivative oligomer (O
A method for producing a block copolymer, which comprises reacting a siloxane-based monomer in the presence of OPS to bond the monomers. <8> The method for producing a block copolymer according to <7>, wherein the reaction of binding the siloxane-based monomer to the active terminal of the polymer is stopped using a trialkylsilyl halide. <9> A rubber composition containing the block copolymer according to any one of <1> to <6>. <10> The rubber composition according to <9>, containing the block copolymer in an amount of 10% by weight or more. <11> The diene-based polymer in the block copolymer is compatible with the matrix polymer.
It is a rubber composition as described in 9> or <10>. <12> From the above <9> used for competition tires <
11>.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Block Copolymer) The block copolymer of the present invention has a diene polymer and a polymer incompatible with the diene polymer as block units.

It is preferable that both the diene-based polymer and the polymer incompatible with the diene-based polymer have a glass transition temperature of room temperature or lower. When the diene-based polymer and the polymer that is incompatible with the diene-based polymer do not have a glass transition temperature below room temperature, the modulus of elasticity is significantly increased, and the above-mentioned liquid state When the solid structure is deformed, a mechanism that causes temporary collapse, re-agglomeration, and regularization hardly occurs, which is not preferable because hysteresis loss hardly occurs.

The conditions for having the microphase-separated structure include, for example, Bates, FS; Fredrickson, GH Annu.
Rev. Phys. Chem. 1990, 41, 525. These are described in detail and can be referred to in the present invention. The micro phase separation structure is, for example, a small angle X
It can be confirmed by analysis using line scattering (SAXS) or observation using a transmission electron microscope (TEM).

The diene polymer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a copolymer of a diene monomer and a vinyl aromatic monomer is preferably used. Examples of the copolymer of the diene monomer and the vinyl aromatic monomer include a styrene-butadiene copolymer, a styrene-isoprene copolymer, and an α-methylstyrene-butadiene copolymer. Among these, a styrene-butadiene copolymer is preferred. These may be used alone or in combination of two or more,
In addition, commercially available products can be used.

As the diene monomer, for example,
Those having 4 to 12 carbon atoms per molecule are preferable, and those having 4 to 8 carbon atoms per molecule are more preferable. Specifically, 1,3-butadiene, isoprene, piperylene, Examples thereof include 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and octadiene. Among these, in terms of versatility and cost, 1,3-
Butadiene is preferred. These may be used alone or in combination of two or more.

The vinyl aromatic monomer includes, for example, styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, p-butylstyrene, vinylnaphthalene, and derivatives thereof. Styrene is preferred from the viewpoint of versatility and cost. These may be used alone or in combination of two or more.

The proportion of the vinyl aromatic monomer in the copolymer is preferably 20 to 60% by weight, more preferably 30 to 50% by weight. When the rubber composition containing the block copolymer is used for racing tires, if the proportion is less than 20% by weight, hysteresis loss may be reduced, and if the proportion is more than 60% by weight,
It becomes glassy at room temperature and may cause cracking problems.

The polymer incompatible with the diene polymer is not particularly limited and may be appropriately selected depending on the intended purpose.
Examples thereof include polyolefin-based polymers, polyamide-based polymers, and polyester-based polymers. These are 1
The species may be used alone, or two or more species may be used.
Among these, a siloxane-based polymer is preferable because it can be highly controlled by anionic polymerization.

Whether or not the diene polymer is compatible with the diene polymer can be determined, for example, by performing light scattering measurement.

Examples of the siloxane-based polymer include polydimethylsiloxane, diglycidoxypolydimethylsiloxane, and dichloropolydimethylsiloxane. Among them, polydimethylsiloxane is preferable because a monomer that can be easily anion-polymerized can be used.

The content (weight ratio) of the polymer incompatible with the diene polymer in the block copolymer is preferably 50% by weight or less, more preferably 30% by weight or less. If the content exceeds 50% by weight, the compatibility with the diene-based polymer is significantly reduced, and the strength of the rubber composition obtained by precipitation from the mixture and vulcanization may be significantly reduced.

The terminal of the block copolymer is preferably a structure other than the Si-OH structure (there is no Si-OH structure).
The existence ratio of the OH structure is preferably 30% or less, and 10%
The following is more preferred. The terminal of the block copolymer is S
If it has an i-OH structure, that is, if it has a strong polar functional group such as Si-OH, a strong bonding force such as a hydrogen bond acts, and the property of adsorbing and bonding to a filler or the like which is usually added becomes stronger. It is not preferable in respect of the point. The presence or absence of the Si-OH structure at the terminal of the block copolymer, and the abundance thereof can be confirmed by, for example, measuring a nuclear magnetic resonance spectrum.

The method for producing the block copolymer of the present invention is not particularly limited, but it can be suitably produced by the following method for producing a block copolymer of the present invention. Although the block copolymer of the present invention can be suitably used in various fields, it can be suitably used for the following rubber composition of the present invention.

(Method for Producing Block Copolymer) In the method for producing a block copolymer of the present invention, a diene monomer and an aromatic vinyl monomer are polymerized in a hydrocarbon solvent using an alkali metal polymerization initiator. Then, a siloxane-based monomer is reacted and bonded to the active terminal of the polymer in the presence of an oxolanylalkane derivative oligomer (OOPS).

The diene-based monomer and the aromatic vinyl monomer include those described above.

The addition amount of the diene monomer is as follows:
The amount is preferably 5 to 50 parts by weight, more preferably 10 to 35 parts by weight, based on 100 parts by weight of the hydrocarbon solvent. If the amount exceeds 50 parts by weight, the viscosity during the polymerization may be too high, and if it is less than 5 parts by weight, the productivity may be low.

The amount of the aromatic vinyl monomer to be added is preferably 5 to 50 parts by weight, more preferably 10 to 35 parts by weight, based on 100 parts by weight of the hydrocarbon solvent. If the amount exceeds 50 parts by weight, the viscosity during the polymerization may be too high, and if it is less than 5 parts by weight, the productivity may be low.

The hydrocarbon solvent is not particularly limited as long as it is stable with respect to the alkali metal polymerization initiator, and can be appropriately selected from known ones according to the purpose. Aromatic hydrocarbon solvents such as benzene, toluene, and xylene; aliphatic hydrocarbon solvents such as n-pentane, n-hexane and n-heptane; alicyclic hydrocarbon solvents such as cyclohexane; and mixtures thereof are preferable. No.

The alkali metal polymerization initiator includes:
There is no particular limitation, and it can be appropriately selected according to the purpose. For example, an organic lithium compound is preferably used. Examples of the organic lithium compound include ethyl lithium, propyl lithium, n-butyl lithium, s
ec-butyllithium, alkyllithium such as tert-butyllithium, phenyllithium, allyllithium such as tolyllithium, for example, vinyllithium, alkenyllithium such as propenyllithium, tetramethylenedilithium, pentamethylenedilithium, hexamethylenedilithium, And alkylenedilithium such as decamethylenedilithium. Among these, n-butyllithium and tert-butyllithium are preferred. They are,
One type may be used alone, or two or more types may be used in combination. The amount of the alkali metal polymerization initiator used,
It is preferably about 0.2 to 30 mmol per 100 g in total of the diene monomer and the vinyl aromatic monomer.

As the oxolanyl alkane derivative oligomer (OOPS), for example, 2,2-di (2-tetrahydrofuryl) propane is preferably exemplified. The amount of the oxolanyl alkane derivative oligomer (OOPS) to be added is preferably less than 1.5 mole equivalent as a hetero atom, and more than 0.1 mole equivalent to 1.5 mole equivalent to 1 mole equivalent of the alkali metal polymerization initiator. Less than a molar equivalent is more preferable, and 0.3 to 1.0 molar equivalent is further preferable. The amount of the oxolanyl alkane derivative oligomer (OOPS) added can be adjusted to increase or decrease the vinyl (1,2-bond) content in the block copolymer, and the amount added is 1.5 molar equivalents or more. In this case, the vinyl content becomes 50% by weight or more, and the glass transition temperature of the block copolymer becomes high, so that desirable physical properties may not be obtained. In some cases, the glass transition temperature of the polymer is lowered and the heat resistance is poor.

The siloxane-based monomer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, hexamethylcyclotrisiloxane (D
3), octamethylcyclotetrasiloxane (D4) and the like are preferred. These may be used alone or in combination of two or more. Among these, hexamethylcyclotrisiloxane (D3) is preferable in terms of high reactivity in anionic polymerization.

The amount of the siloxane monomer to be added is preferably 3 to 50 parts by weight, more preferably 5 to 45 parts by weight, based on 100 parts by weight of the hydrocarbon solvent. If the amount exceeds 50 parts by weight, the viscosity may be too high. If the amount is less than 3 parts by weight, the influence of impurities may increase.

In the present invention, the reaction for binding the siloxane monomer to the active terminal of the polymer is preferably stopped by using a trialkylsilyl halide. Examples of the trialkylsilyl halide include trialkylsilyl chloride and trialkylsilyl bromide.

The amount of the trialkylsilyl halide to be added is preferably 0.8 to 1.2 equivalents to the active terminal. When the addition amount is less than 0.8 equivalent, Si—O
The amount of H may increase, and if it exceeds 1.2 equivalents, unreacted trialkylsilyl halide may remain in the reaction system.

The polymerization temperature is usually from 0 to 15
It is about 0 ° C, preferably 30 to 100 ° C. The concentration of the diene-based monomer and the vinyl aromatic monomer (hereinafter sometimes referred to as “monomer component”) in the hydrocarbon solvent during the polymerization is usually 5 to 5
It is about 0% by weight, preferably 10 to 35% by weight. The content of the vinyl aromatic monomer in the charged monomer mixture is about 3 to 50% by weight, and preferably 5 to 45% by weight.

The polymerization reaction is carried out by bringing the monomer components into contact with a catalyst in a liquid phase, and the pressure is usually operated at a pressure sufficient to essentially maintain the liquid phase. preferable. Further, it is preferable that all the substances added to the reaction system exclude substances that hinder the catalytic action.

The polymerization method may be a batch polymerization method, a continuous polymerization method, or any of isothermal polymerization, elevated temperature polymerization, and adiabatic polymerization.

In the block copolymer, the amount of bound styrene is preferably 20 to 60% by weight, and
The content is more preferably from 0 to 50% by weight, and the vinyl content is preferably from 30 to 80% by weight, more preferably from 40 to 70% by weight, based on the butadiene portion. When the amount of the bound styrene exceeds 60% by weight, or when the vinyl content exceeds 80% by weight, the glass transition temperature becomes high, and the abrasion resistance and the gripping property may be insufficient. If it is less than 20% by weight, or if the vinyl content is less than 30% by weight, the glass transition point may be too low and the grip may not be sufficient. The amount of bound styrene can be calculated, for example, from the absorption intensity of aromatic protons in a nuclear magnetic resonance (NMR) spectrum. The vinyl content can be calculated, for example, by ozonolysis and GPC.

The block copolymer preferably has a weight average molecular weight of 5,000 to 500,000,
It is more preferably from 000 to 200,000. If the weight average molecular weight is less than 5,000, a microphase separation structure may not be obtained, and if it exceeds 500,000, the microphase separation structure becomes too strong and gripping properties do not sufficiently occur. Sometimes.

In the present invention, after the completion of the polymerization reaction, if necessary, a softening agent, for example, an aromatic oil or a liquid polymer may be added, and the solvent may be dried by a direct drying method or a steam strip method. it can.

(Rubber Composition) The rubber composition of the present invention contains at least the above-mentioned block copolymer of the present invention and, if necessary, other components.

The block copolymer may be added as a matrix polymer in the rubber composition, but is preferably added as a low molecular weight liquid component from the viewpoint of increasing hysteresis loss. For example,
In the block copolymer of styrene-butadiene copolymer (SBR) and polydimethylsiloxane (PDMS), the glass transition temperature of both can be set to room temperature or lower, and the incompatibility is very strong, so that the low molecular weight block copolymer is used. Polymers are also preferred because they have a microphase-separated structure. In this case, the block copolymer whose apparent molecular weight has increased due to the association is advantageous in that the melt viscosity does not increase and the processability of the rubber composition does not significantly decrease. On the other hand, in the case of a block copolymer consisting only of a styrene-butadiene copolymer (SBR), a butadiene rubber (BR), an isoprene rubber (IR), etc., it is not highly incompatible, so that when the molecular weight is low, it is completely disordered. It becomes a state and the action by the mechanism does not occur, so that it is necessary to have a certain molecular weight.

When the block copolymer is added to the matrix polymer, the diene polymer in the block copolymer is preferably compatible with the matrix polymer. This case is advantageous in that the degree of freedom in compounding is increased.

Examples of the matrix polymer include natural rubber and synthetic rubber. Examples of the synthetic rubber include polyisoprene, solution-polymerized butadiene-styrene copolymer, emulsion butadiene-styrene copolymer, polybutadiene, ethylene-propylene-diene copolymer, chloroprene, halogenated butyl rubber, acrylonitrile-butadiene rubber ( NBR) and the like. These may be used alone or in combination of two or more.

The content of the block copolymer in the rubber composition is preferably at least 10% by weight,
0% by weight or more is more preferable. If the content of the block copolymer is less than 10% by weight, the effect may not be clearly exhibited.

The rubber composition further includes, as other components, for example, carbon black, an inorganic filler, a softener,
Vulcanizing agents such as sulfur, vulcanization accelerators such as dibenzothiazyl disulfide, vulcanization aids, N-cyclohexyl-2-benzothiazyl-sulfenamide, N-oxydiethylene-
Antioxidants such as benzothiazyl-sulfenamide, zinc oxide, stearic acid, antiozonants, coloring agents, antistatic agents, lubricants, antioxidants, softeners, coupling agents, foaming agents, foaming assistants, etc. In addition to additives and the like, various compounding agents usually used in the rubber industry can be mentioned. These can use a commercial item suitably.

After the above components are mixed with the rubber composition, kneading, heating, extrusion, vulcanization and the like can be appropriately performed. In addition, at the time of the mixing, it is preferable to mix the matrix polymer and the block copolymer of the present invention in a solution state, since uniform dispersion can be obtained.

The conditions for the kneading are not particularly limited, and various conditions such as the volume to be charged into the kneading apparatus, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading apparatus, etc. Can be appropriately selected according to the purpose. Examples of the kneading apparatus include a Banbury mixer, an intermix, and a kneader that are usually used for kneading a rubber composition.

The heating conditions are not particularly limited, and various conditions such as a heating temperature, a heating time, and a heating device can be appropriately selected according to the purpose. As the warming device, for example, a roll machine usually used for warming a rubber composition can be used.

The conditions of the extrusion are not particularly limited, and various conditions such as an extrusion time, an extrusion speed, an extrusion apparatus, and an extrusion temperature can be appropriately selected depending on the purpose. As the extruder, for example, an extruder or the like usually used for extruding a rubber composition for a tire can be used. The extrusion temperature can be appropriately determined.

At the time of the extrusion, a plasticizer such as an aroma oil, a naphthene oil, a paraffin oil, an ester oil, a liquid polyisoprene rubber, a liquid polybutadiene rubber or the like is used for the purpose of controlling the fluidity of the rubber composition. A processability improver such as a liquid polymer can be appropriately added to the rubber composition. In this case, the viscosity of the rubber composition before vulcanization can be reduced, the fluidity thereof can be increased, and extrusion can be performed very well.

There are no particular restrictions on the apparatus, system, conditions and the like for performing the vulcanization, and they can be appropriately selected according to the purpose. As an apparatus for performing the vulcanization, for example, a molding vulcanizer using a mold usually used for vulcanizing a rubber composition for a tire may be mentioned. As the vulcanization conditions, the temperature is usually about 100 to 190 ° C.

The rubber composition can be suitably used in various fields, but can be particularly preferably used in treads of competition tires and the like.

[0054]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1 to 4 and Comparative Examples 1 to 4) In a 5 l reactor equipped with a stirrer, 1500 g of cyclohexane was added.
240 g of 1,3-butadiene, 60 g of styrene, and 2,2-di (2-tetrahydrofuryl) propane (OO
(PS) 0.080 g, and the temperature in the reaction vessel was set to 60 ° C.
Then, 0.100 g of n-butyllithium was added to initiate polymerization. The obtained styrene-butadiene copolymer (SBR) was used as the matrix polymer.

Next, the low molecular weight styrene-butadiene copolymer added to the matrix polymer is 5
1,500 g of cyclohexane in a reactor equipped with 1 stirrer,
168 g of 1,3-butadiene, 42 g of styrene, and 2,2-di (2-tetrahydrofuryl) propane (OO
PS) 5.60 g, and the temperature in the reaction vessel was adjusted to 60 ° C., and then n-butyllithium was added to 1.00 to 7.00.
The polymerization was started by adding a variable amount within the range of g. SB
One hour after the polymerization of the R portion was sufficiently completed, 5 equivalents of a hexamethylcyclotrisiloxane (D3) monomer was added to n-butyllithium, and the mixture was allowed to stand at 70 ° C. for 1 hour.
Reacted. Thereafter, the remaining hexamethylcyclotrisiloxane (D3) was added so that the total amount of hexamethylcyclotrisiloxane (D3) became 90 g, 100 g of diglyme was added, and the mixture was further reacted for 3 hours.
The reaction was stopped with trimethylsilyl chloride. Thus, the block copolymer of the present invention (Examples 1-4: SBR
-PDMS 1 to 4) were obtained.

For comparison, SBRs having the same designed molecular weight and the same initiator / total monomer ratio were synthesized. That is,
In a 5 l reactor equipped with a stirrer, cyclohexane 1500 was added.
g, 240 g of 1,3-butadiene, 60 g of styrene, and 2,2-di (2-tetrahydrofuryl) propane (O
(OPS) 0.080 g, and the temperature in the reaction vessel is 60
After adjusting to ℃, n-butyl lithium was added to 1.00-7.
00 g was added to initiate polymerization. Thus, comparative copolymers (Comparative Examples 1-4: SBR1-4) were obtained.

S as the obtained matrix polymer
BR, block copolymer (SBR-PDMS), and
Comparative copolymers (Comparative Examples 1 to 4: SBR1 to 4) were mixed in a solution state and dried in Examples and Comparative Examples, respectively.

SBR as the matrix polymer
Had a weight average molecular weight of 1.5 million, a bound styrene content of 30% by weight, and a vinyl content of 60%. The comparative copolymer (SBR) had a weight average molecular weight of 20,000, a bound styrene content of 30% by weight, and a vinyl content of 60%. The block copolymer (SBR-PDMS) as the low molecular weight component has a weight average molecular weight of 19,000, a microphase-separated structure in the SBR portion, a bound styrene content of 30% by weight, and a vinyl content. Is 60% and the weight fraction of the PDMS portion is 2
5%.

These polymers were kneaded and compounded with a 250 cc Labo Plastomill and a 3-inch roll according to the compounding shown in Table 1, and then vulcanized at 160 ° C. for 20 minutes. Table 2 shows the viscoelastic properties of the vulcanized product.

[0061]

[Table 1]

In Table 1, "SAF carbon black" is Asahi # 90 manufactured by Asahi Carbon Co., Ltd. "Stearic acid" is manufactured by Kao Corporation and "antiaging agent"
Is manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
eler) 6C, "Zinc flower" is manufactured by Hakusui Chemical Industry Co., Ltd., and "diphenylguanidine" is manufactured by Ouchi Shinko Chemical Industry Co., Ltd .: Nocceler.
D, and “Dibenzothiazyl disulfide” is manufactured by Ouchi Shinko Chemical Co., Ltd .: Noccele
r) DM, and "sulfur" is from Karuizawa Refinery.

[0063]

[Table 2]

The micro phase separation structure is 1H-NMR
Was measured and confirmed. The weight average molecular weight (Mw) was determined by gel permeation chromatography (GPC; HLC-8020 manufactured by Tosoh Corporation, two columns of GMH-XL columns).
And the results are shown on the basis of polystyrene. The bound styrene content and vinyl content are determined by nuclear magnetic resonance (NMR).
It was calculated from the absorption intensity of the spectrum. The content (weight ratio) of the PDMS portion was calculated from the NMR spectrum. Note that the viscoelastic properties are measured by ARE
Hysteresis loss (tangent loss: tan δ (30%)) at 50 ° C. was measured using an S viscoelasticity measuring apparatus.

From the results in Table 2, it can be seen that the hysteresis loss (tangent loss) indicating the frictional strength of the rubber composition was improved by using the block copolymer (SBR-PDMS1 to 4) of the present invention. it is obvious. This effect was not lost even when other components such as carbon black were used in combination.

[0066]

According to the present invention, the above-mentioned problems in the prior art can be solved, the hysteresis loss (tangent loss coefficient) is large, the abrasion resistance is excellent, and the road surface during running when used for a tire tread is used. To provide a block copolymer having excellent gripping power (gripability) and an efficient production method thereof, and to provide a rubber composition which is particularly suitable as a tread rubber for racing tires and the like using the block copolymer. Can be.

Claims (12)

[Claims] 1. A block copolymer comprising, as a block unit, a diene-based polymer and a polymer incompatible with the diene-based polymer. 2. The block copolymer according to claim 1, which has a microphase-separated structure. 3. The block copolymer according to claim 1, which has 50% by weight or less of a polymer incompatible with the diene-based polymer. 4. The polymer according to claim 1, wherein the polymer incompatible with the diene polymer is a siloxane polymer.
The block copolymer according to any one of the above. 5. The block copolymer according to claim 4, wherein the siloxane-based polymer is polydimethylsiloxane. 6. The block copolymer according to claim 1, wherein the terminal has a structure other than the Si—OH structure. 7. The method for producing a block copolymer according to claim 1, wherein a diene monomer and an aromatic vinyl monomer are used in a hydrocarbon solvent using an alkali metal polymerization initiator. And obtaining a polymer by polymerization with a siloxane monomer in the presence of an oxolanyl alkane derivative oligomer (OOPS) at the active terminal of the polymer, thereby binding the siloxane monomer. Production method. 8. The method for producing a block copolymer according to claim 7, wherein the reaction of binding the siloxane monomer to the active terminal of the polymer is stopped by using a trialkylsilyl halide. 9. A rubber composition comprising the block copolymer according to claim 1. 10. The rubber composition according to claim 9, comprising at least 10% by weight of the block copolymer. 11. The rubber composition according to claim 9, wherein the diene-based polymer in the block copolymer is compatible with the matrix polymer. 12. The rubber composition according to claim 9, which is used for a racing tire.