Rubber composition and tire

Abstract

To provide a rubber composition which has excellent extrusion processability and gives a cured product excellent in durability and mechanical strength, and to provide a tire.SOLUTION: The rubber composition contains, as rubber components: a polybutadiene rubber having a 1,4-cis bond content of 80 mass% or more; a natural rubber and / or a synthetic polyisoprene rubber having a 1,4-cis bond content of 80 mass% or more; and a block copolymer of butadiene and isoprene. In the block copolymer, the total 1,4-cis bond content derived from the butadiene and the isoprene is 90 mol% or more in the total amount of repeating units derived from the butadiene and the isoprene. The vinyl bond content derived from the butadiene is less than 5 mol% in the total amount of the repeating unit derived from the butadiene. The block copolymer has a weight average molecular weight of 500,000-1,500,000. The content of the block copolymer is 0.5-30 pts.mass in 100 pts.mass of the rubber components. The tire is produced using the rubber composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and a tire. [Background technology]

[0002] 2. Description of the Related Art Known rubber compositions used for tires and the like include rubber compositions containing polyisoprene-based rubber, polybutadiene-based rubber, and block copolymers (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-12702 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have studied the rubber composition disclosed in Patent Document 1 and have found that the rubber composition may have poor durability, mechanical strength, or extrusion processability.

[0005] Therefore, an object of the present invention is to provide a rubber composition which has excellent extrusion processability and which gives a cured product having excellent durability and mechanical strength. Another object of the present invention is to provide a tire. [Means for solving the problem]

[0006] As a result of intensive research into solving the above problems, the present inventors have found that the problems can be solved by the following configuration.

[0007] [1] As a rubber component, a polybutadiene rubber having a 1,4-cis bond content of 80 mass% or more; Natural rubber and / or synthetic polyisoprene rubber having a 1,4-cis bond content of 80% by mass or more, and Contains a block copolymer of butadiene and isoprene, In the block copolymer, a total 1,4-cis bond content derived from the butadiene and the isoprene is 90 mol % or more of the total amount of repeating units derived from the butadiene and the isoprene, the content of vinyl bonds derived from the butadiene is less than 5 mol % in the total amount of repeating units derived from the butadiene, The weight average molecular weight of the block copolymer is 500,000 to 1,500,000; The rubber composition has a content of the block polymer of 0.5 to 30 parts by mass in 100 parts by mass of the rubber component. [2] The rubber composition according to [1], wherein the block copolymer has a molecular weight distribution of 2 to 4. [3] the content of the polybutadiene rubber is 49.5 parts by mass or less based on 100 parts by mass of the rubber component, The rubber composition according to [1] or [2], wherein the content of the natural rubber and / or the synthetic polyisoprene rubber is 50 parts by mass or more per 100 parts by mass of the rubber component. [4] Further, it contains carbon black and / or silica, The rubber composition according to any one of [1] to [3], wherein the content of the carbon black and / or the silica is 30 to 90 parts by mass per 100 parts by mass of the rubber component. [5] The rubber composition according to [3] or [4], which is used to form a tread of a heavy-duty tire. [6] the content of the polybutadiene rubber is 50.0 parts by mass or more based on 100 parts by mass of the rubber component, The rubber composition according to [1] or [2], wherein the content of the natural rubber and / or the synthetic polyisoprene rubber is 49.5 parts by mass or less per 100 parts by mass of the rubber component. [7] The rubber composition according to [4] or [6], which is used to form a side tread of a tire. [8] A tire manufactured using the rubber composition according to any one of [1] to [7]. Effect of the Invention

[0008] According to the present invention, it is possible to provide a rubber composition which has excellent extrusion processability, and which gives a cured product which has excellent durability and mechanical strength. The present invention also provides a tire. [Brief description of the drawings]

[0009] [Figure 1] 1 is a partial cross-sectional schematic view showing an example of an embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. The following description of the configuration may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present specification, each component may be used alone or in combination of two or more kinds. In this specification, when two or more kinds of each component are used in combination, the amount of that component means the total amount of those two or more kinds, unless otherwise specified. In this specification, the method for producing each component is not particularly limited unless otherwise specified. For example, a conventionally known method can be used. For each component or a raw material used in producing each component, for example, a commercially available product can be used unless otherwise specified. In this specification, when the rubber composition of the present invention is superior in at least any one of extrusion processability, durability, and mechanical strength, it is also referred to as "having superior effects of the present invention."

[0011] [Rubber composition] The rubber composition of the present invention comprises: As a rubber component, a polybutadiene rubber having a 1,4-cis bond content of 80 mass% or more; Natural rubber and / or synthetic polyisoprene rubber having a 1,4-cis bond content of 80% by mass or more, and Contains a block copolymer of butadiene and isoprene, In the block copolymer, a total 1,4-cis bond content derived from the butadiene and the isoprene is 90 mol % or more of the total amount of repeating units derived from the butadiene and the isoprene, the content of vinyl bonds derived from the butadiene is less than 5 mol % in the total amount of repeating units derived from the butadiene, The weight average molecular weight of the block copolymer is 500,000 to 1,500,000; The rubber composition has a content of the block polymer of 0.5 to 30 parts by mass in 100 parts by mass of the rubber component. In this specification, the above block copolymer may be simply referred to as a "copolymer" or a "block copolymer".

[0012] Herein, the microstructure of each rubber component was analyzed using solution NMR techniques. Regarding the microstructure of the repeating units derived from butadiene in the above block copolymer 1 H-NMR analysis was carried out. 1 The 1 H-NMR analysis was carried out using a Bruker NMR device, with a deuterated chloroform solution of the sample being measured at room temperature. 1 The assignment of the repeating units derived from butadiene in the H-NMR chemical shifts is as follows. The same applies to polybutadiene rubber. cis (1,4-cis bond): 5.3 ppm trans (1,4-trans bond): 5.35 ppm vinyl (1,2-vinyl bond): 4.9 ppm The proportion of each microstructure of the repeating unit derived from butadiene in the block copolymer is as follows: 1 It was calculated from the integral ratio of H-NMR. The 1,4-cis bond content A of the butadiene units constituting the block copolymer can be obtained by the following formula (I). A = integral of the above cis / (total of the above cis, trans, and vinyl integrals) (I)

[0013] Regarding the microstructure of the repeating units derived from isoprene in the above block copolymers 13 C-NMR analysis was performed. 13 C-NMR analysis was performed using a Bruker NMR device, with a deuterated chloroform solution of the sample being measured at room temperature. 13 The chemical shifts of the repeating units derived from isoprene in C-NMR are as follows. The same applies to natural rubber and synthetic polyisoprene rubber. cis (1,4-cis bond): 23.3 ppm trans (1,4-trans bond): 15.9 ppm 1,2-vinyl (1,2-vinyl bond): 13.1 ppm 3,4-vinyl (3,4-vinyl bond): 18.6 ppm The ratio of each microstructure of the repeating unit derived from isoprene in the block copolymer is as follows: 13 It was calculated from the integral ratio of C-NMR. The 1,4-cis bond content B of the isoprene units constituting the block copolymer can be obtained by the following formula (II). B = integral of the above cis / (total of the above cis, trans, 1,2-vinyl, and 3,4-vinyl integrals) (II)

[0014] In this specification, the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of each rubber component are standard polystyrene-equivalent values ​​obtained by gel permeation chromatography (GPC) measurement under the following conditions. Solvent: Tetrahydrofuran Detector: RI detector

[0015] Since the rubber composition of the present invention has the above-mentioned structure, it is believed that the above-mentioned problems of the present invention can be solved. Although the reason for this is not clear, the present inventors speculate as follows. That is, while polybutadiene rubber and natural rubber or synthetic polyisoprene rubber are generally incompatible, in the rubber composition of the present invention, the butadiene-derived repeating units and isoprene-derived repeating units contained in the copolymer interact with the polybutadiene rubber, and the natural rubber and / or synthetic polyisoprene rubber in the rubber composition, respectively, to make them compatible, and it is believed that the compatibility leads to improved extrusion processability, durability, and mechanical strength. The mechanism by which the effects are obtained is not limited by the following speculation. In other words, even if the effects are obtained by a mechanism other than the following, it is included in the scope of the present invention.

[0016] [Rubber component] The rubber composition of the present invention comprises, as a rubber component: A polybutadiene rubber having a 1,4-cis bond content of 80% by mass or more; Natural rubber and / or synthetic polyisoprene rubber having a 1,4-cis bond content of 80% by mass or more, and It contains a block copolymer of butadiene and isoprene.

[0017] [Polybutadiene rubber] In the present invention, the polybutadiene rubber contained as the rubber component has a 1,4-cis bond content of 80 mass % or more based on the total amount of butadiene units constituting the polybutadiene rubber.

[0018] In one preferred embodiment, the polybutadiene rubber is a homopolymer of butadiene.

[0019] (Microstructure of polybutadiene rubber) 1,4-cis bond content From the viewpoint of obtaining superior effects of the present invention, the 1,4-cis bond content (1,4-cis content) of the polybutadiene rubber is preferably 85 to 98 mass % and more preferably 90 to 98 mass % of the total amount of butadiene units constituting the polybutadiene rubber. 1,4-trans bond content, vinyl bond content In the above-mentioned polybutadiene rubber, the total amount of the 1,4-trans bond content and the vinyl bond content is 20 mass% or less of the total amount of butadiene units constituting the polybutadiene rubber, and is preferably in a numerical range obtained by excluding the above-mentioned preferred range of the 1,4-cis bond content from the total amount of butadiene units constituting the polybutadiene rubber. The 1,4-trans bond content and vinyl bond content of the polybutadiene rubber are each preferably independently 1 to 8 mass %.

[0020] ·Weight average molecular weight The weight average molecular weight (Mw) of the polybutadiene rubber is preferably from 100,000 to 2,000,000, and more preferably from 200,000 to 1,500,000, because the effects of the present invention are more excellent.

[0021] [Natural rubber and / or synthetic polyisoprene rubber] In the present invention, the rubber component contains natural rubber and / or synthetic polyisoprene rubber having a 1,4-cis bond content of 80 mass % or more. From the viewpoint of obtaining superior effects of the present invention, the rubber component preferably contains natural rubber.

[0022] [Natural rubber] The natural rubber that can be contained in the rubber composition of the present invention is not particularly limited, and examples thereof include conventionally known natural rubbers.

[0023] [Synthetic polyisoprene rubber] The synthetic polyisoprene rubber that can be contained in the rubber composition of the present invention has a 1,4-cis bond content of 80 mass % or more based on the total amount of isoprene units constituting the synthetic polyisoprene rubber.

[0024] In one preferred embodiment, the synthetic polyisoprene rubber is a homopolymer of isoprene.

[0025] (Microstructure of synthetic polyisoprene rubber) 1,4-cis bond content From the viewpoint of obtaining superior effects of the present invention, the 1,4-cis bond content (1,4-cis content) of the synthetic polyisoprene rubber is preferably 85 to 98 mass% and more preferably 90 to 96 mass% of the total amount of isoprene units constituting the synthetic polyisoprene rubber. 1,4-trans bond content, 1,2-vinyl bond content, 3,4-vinyl bond content In the above synthetic polyisoprene rubber, the total amount of the 1,4-trans bond content, the 1,2-vinyl bond content, and the 3,4-vinyl bond content is 20 mass% or less of the total amount of isoprene units constituting the synthetic polyisoprene rubber, and is preferably in a numerical range excluding the above-mentioned preferred range of the 1,4-cis bond content from the total amount of isoprene units constituting the synthetic polyisoprene. The 1,4-trans bond content and the 1,2-vinyl bond content of the synthetic polyisoprene rubber are each preferably independently 1 to 5 mass %. The synthetic polyisoprene rubber preferably has a 3,4-vinyl bond content of 0 to 5% by mass.

[0026] ·Weight average molecular weight The weight average molecular weight (Mw) of the synthetic polyisoprene rubber is preferably 100,000 to 2,000,000, and more preferably 200,000 to 1,500,000, because the effects of the present invention are more excellent.

[0027] [Butadiene and isoprene block copolymer] In the present invention, the rubber component contains a block copolymer (copolymer) of butadiene and isoprene.

[0028] [Skeleton] The skeleton (main chain structure) of the copolymer contained in the rubber composition of the present invention is a block copolymer of butadiene and isoprene, and is composed of a homopolymer of butadiene (butadiene block polymer) and a homopolymer of isoprene (isoprene block polymer). The fact that the copolymer is a block copolymer can be confirmed by the fact that it has two glass transition temperatures (butadiene block polymer, isoprene block polymer).

[0029] (form) Examples of the form of the block copolymer include multiblock copolymers such as a diblock copolymer (a diblock copolymer consisting of one butadiene block polymer and one isoprene block polymer), a triblock copolymer (a triblock copolymer consisting of two butadiene block polymers and one isoprene block polymer, or a triblock copolymer consisting of one butadiene block polymer and two isoprene block polymers).

[0030] (Butadiene unit content) In the block copolymer, the proportion of repeating units derived from butadiene (hereinafter, "repeating units derived from butadiene" will also be referred to as "butadiene units") among all repeating units constituting the block copolymer (hereinafter, also referred to as "butadiene unit content") is not particularly limited, but for reasons of superior effects of the present invention, it is preferably 10 to 90 mol%, more preferably 15 to 60 mol%, and even more preferably 18 to 40 mol%.

[0031] (Isoprene unit content) In the above block copolymer, the proportion of repeating units derived from isoprene (hereinafter, "repeating units derived from isoprene" will also be referred to as "isoprene units") among all repeating units constituting the block copolymer (hereinafter, also referred to as "isoprene unit content") is not particularly limited, but for reasons of superior effects of the present invention, it is preferably 10 to 90 mol%, more preferably 40 to 85 mol%, and even more preferably 60 to 82 mol%.

[0032] [Total 1,4-cis bond content] In the block copolymer, the total 1,4-cis bond content (total 1,4-cis content) derived from the butadiene and the isoprene is 90 mol % or more in the total amount of repeating units derived from the butadiene and the isoprene. In the present invention, the total 1,4-cis bond content can be calculated by the following formula (III). Total 1,4-cis bond content (mol%) = [A + B] / [C + D] × 100 (III) A to D in the above formula (III) are as follows: A: The 1,4-cis bond content of the butadiene units constituting the block copolymer. The value of A obtained in the above formula (I) is substituted for A in the above formula (III). B: The 1,4-cis bond content in the isoprene units constituting the above block copolymer. The value of B obtained in the above formula (I) is substituted for B in the above formula (III). C: A butadiene unit constituting the block copolymer. C in the above formula (III) is substituted with the molar equivalent of butadiene used in producing the above block copolymer. D: isoprene unit constituting the block copolymer D in the above formula (III) is substituted with the molar equivalent of isoprene used in producing the above block copolymer. In this specification, the total amount of butadiene used in producing the block copolymer can be considered to have been converted into butadiene units constituting the block copolymer, and the same applies to the isoprene used in producing the block copolymer. From the viewpoint of obtaining superior effects of the present invention, the total 1,4-cis bond content is preferably 90 to 98 mol % based on the total amount of repeating units derived from butadiene and isoprene.

[0033] (1,4-cis bond content derived from butadiene) In the block copolymer, the 1,4-cis bond content (1,4-cis content) derived from the butadiene is preferably 10 mol % or more, and more preferably 15 to 30 mol %, of the total amount of repeating units derived from the butadiene and the isoprene, from the viewpoint of achieving superior effects of the present invention.

[0034] (1,4-cis bond content derived from isoprene) In the block copolymer, the 1,4-cis bond content (1,4-cis content) derived from the isoprene is preferably 80 mol % or less, and more preferably 60 to 80 mol %, of the total amount of repeating units derived from the butadiene and the isoprene, from the viewpoint of achieving superior effects of the present invention.

[0035] [Vinyl bond content derived from butadiene] In the block copolymer, the vinyl bond content (1,2-vinyl content) derived from the butadiene is less than 5 mol % in the total amount of repeating units derived from the butadiene. That is, in the present invention, the vinyl bond content (1,2-vinyl content) derived from the butadiene constituting the block copolymer is less than 5 mol % of the total amount of repeating units derived from the butadiene constituting the block copolymer. From the viewpoint of obtaining superior effects of the present invention, the vinyl bond content is preferably 1 to 4 mol % based on the total amount of repeating units derived from butadiene.

[0036] [Weight average molecular weight of copolymer] In the present invention, the weight average molecular weight of the block copolymer is 500,000 to 1,500,000. From the viewpoint of obtaining superior effects of the present invention, the weight average molecular weight of the block copolymer is preferably from 600,000 to 1,200,000, and more preferably from 750,000 to 1,000,000.

[0037] [Molecular weight distribution of copolymer] The molecular weight distribution (Mw / Mn) of the block copolymer is preferably 2 to 4, from the viewpoint of achieving better effects of the present invention and excellent cold flow resistance (the excellent cold flow property of the block copolymer in the state of raw rubber has the advantage of making the block copolymer easy to handle, easy to measure, and leads to obtaining good physical properties).

[0038] (end) The copolymer may be a block copolymer having no functional group at its terminal (unmodified block copolymer), or a block copolymer having a functional group at its terminal (modified block copolymer). The modified block copolymer may be, for example, a block copolymer having at least one functional group A (hereinafter, simply referred to as "functional group A") selected from the group consisting of a hydroxyl group (-OH), a carboxyl group (-COOH), and an alkoxysilyl group at its terminal. The functional group A may be bonded to the skeleton (main chain structure) via a divalent linking group.

[0039] (glass transition temperature) As mentioned above, the copolymer can have two glass transition temperatures (Tg). At least one of the two Tgs is preferably −60° C. or lower, more preferably −70° C. or lower, because the effects of the present invention are more excellent. In particular, both of the two Tgs are preferably −60° C. or lower, because the effects of the present invention are more excellent. The lower limit of the two Tgs is not particularly limited, but is preferably −120° C. or higher, because the effects of the present invention are more excellent.

[0040] In this specification, the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a temperature rise rate of 20° C. / min and calculated by the midpoint method.

[0041] (Method of Producing Copolymer) As a method for producing the copolymer, for example, when the copolymer is an unmodified diblock copolymer, the following production method 1 or 2 is preferable because the effect of the present invention is more excellent for the obtained copolymer. Also, when the copolymer is a modified diblock copolymer, for example, the following production method 3 is used. Since Production Methods 1 to 3 all use a rare earth element-based catalyst and aluminoxane for polymerization, it is believed that copolymers having the above-mentioned predetermined microstructure and the like can be obtained. In the following description, when the effect of the present invention is excellent with respect to the obtained copolymer, it will be simply referred to as "the effect of the present invention is excellent."

[0042] (Manufacturing method 1) The production method 1 is a production method including the following (1-1) and (2-1). (1-1) First polymerization step Polymerization of butadiene using rare earth catalyst and aluminoxane (2-1) Second polymerization step Then, a step of obtaining the above-mentioned copolymer (unmodified diblock copolymer) by reacting with isoprene.

[0043] Each step will be described below.

[0044] [First polymerization step] The first polymerization step is a step of polymerizing butadiene using a rare earth catalyst and an aluminoxane, and a butadiene block polymer is obtained by the first polymerization step.

[0045] <Rare earth element catalyst> The rare earth element catalyst includes, for example, a rare earth element or a compound containing a rare earth element. Rare earth elements include scandium; yttrium; and the lanthanides (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium lanthanides). Examples of compounds containing rare earth elements include halides of rare earth elements, complexes of rare earth elements, and alloys of rare earth elements and metals.

[0046] The rare earth element catalyst is preferably Sc (scandium), Gd (gadolinium) or Nd (neodymium), and more preferably Nd, because the effects of the present invention are superior.

[0047] (Amount used) The amount of the rare earth element catalyst used is not particularly limited, but in order to obtain a better effect of the present invention, the amount is preferably 0.00001 to 10 mol %, and more preferably 0.0001 to 1 mol %, based on the amount of all monomers (butadiene and isoprene) used.

[0048] <Aluminoxane> Aluminoxanes are products of the reaction of trialkylaluminum with water, and are believed to act as co-catalysts. Examples of aluminoxanes include methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, isobutylaluminoxane, methylethylaluminoxane, methylbutylaluminoxane, and methylisobutylaluminoxane. Among them, modified methylaluminoxanes (MMAOs) such as methylethylaluminoxane, methylbutylaluminoxane, and methylisobutylaluminoxane are preferred. These aluminoxanes can be used alone or in combination of two or more.

[0049] (Amount used) The amount of the aluminoxane used is not particularly limited, but in order to obtain better effects of the present invention, the molar equivalent ratio of aluminum atoms in the aluminoxane to the rare earth element-based catalyst is preferably 20 to 10,000, more preferably 50 to 2,000, and even more preferably 100 to 1,000.

[0050] [Second polymerization step] The second polymerization step is a step of obtaining the above-mentioned copolymer (unmodified diblock copolymer) by reacting isoprene after the first polymerization step. By polymerizing isoprene subsequently to the butadiene block polymer obtained in the first polymerization step, a diblock copolymer of butadiene and isoprene (a diblock copolymer consisting of a butadiene block polymer and an isoprene block polymer) is obtained.

[0051] [Stopping process] The production method 1 may further include a terminating step of terminating the polymerization with an alcohol (eg, methanol) or the like.

[0052] [Proportion of each monomer] The ratio of the amount of butadiene used to the amount of all monomers used is not particularly limited, but the preferred range and the reasons therefor are the same as those for the butadiene unit content described above. The ratio of the amount of isoprene used to the amount of all monomers used is not particularly limited, but the preferred range and the reasons for it are the same as those for the isoprene unit content described above.

[0053] (Manufacturing method 2) The production method 2 includes the following (1-2) and (2-2). (1-1) First polymerization step Polymerizing isoprene using rare earth catalysts and aluminoxanes (2-1) Second polymerization step Then, a step of obtaining the above-mentioned copolymer (unmodified diblock copolymer) by reacting with butadiene.

[0054] Production method 2 is the same as production method 1, except that isoprene is used instead of butadiene in the first polymerization step and butadiene is used instead of isoprene in the second polymerization step. The definitions, amounts used, and preferred embodiments of each component are the same as those of production method 1.

[0055] (Manufacturing method 3) Production method 3 is a production method which includes production method 1 or 2 and further includes the following (3): (3) Terminal modification step Further, a step of obtaining the above-mentioned copolymer (modified butadiblock copolymer) by terminating the polymerization using a modifying agent.

[0056] [Terminal modification step] The terminal modification step is a step of obtaining the copolymer (modified butadiene copolymer) by terminating the polymerization using a modifier after Production method 1 or Production method 2. By terminating the polymerization using a modifier, the modifier is bonded to the growing end of the diblock copolymer obtained in the second polymerization step. When a terminal modification step is provided after Production method 1, the modifier is bonded to the end on the isoprene block polymer side, and when a terminal modification step is provided after Production method 2, the modifier is bonded to the end on the butadiene block polymer side. From the viewpoint of completely terminating the polymerization, an alcohol (eg, methanol) or the like may be added in addition to the denaturant.

[0057] (Modifier) The modifier is not particularly limited, but because the effects of the present invention are more excellent, it is preferable that the modifier reacts with the growing end of the diblock copolymer obtained in the second polymerization step to form the above-mentioned functional group A.

[0058] The modifying agent is preferably at least one selected from the group consisting of epoxides, lactones having a carboxy group or an alkoxysilyl group, and epoxides having a carboxy group or an alkoxysilyl group, because this provides better effects for the present invention.

[0059] (Amount used) The amount of the modifier used is not particularly limited, but is preferably 0.1 to 10, and more preferably 1 to 5, in terms of molar equivalent ratio to the rare earth catalyst, because this provides better effects for the present invention.

[0060] (Method of Producing Multiblock Copolymer) In the above-mentioned production methods 1 and 2, a step (third polymerization step) of reacting a monomer different from that in the second polymerization step (butadiene when the second polymerization step is a step of reacting isoprene, and isoprene when the second polymerization step is a step of reacting butadiene) can be further provided after the second polymerization step, thereby producing a triblock copolymer. In this way, a multiblock copolymer can be produced by providing a step of reacting different monomers alternately. In addition, in the above-mentioned production method 3, a modified triblock copolymer can be produced by further providing the above-mentioned third polymerization step after the second polymerization step and before the terminal modification step. Similarly, a modified multiblock copolymer can be produced by providing a step of alternately reacting different monomers.

[0061] [Copolymer content] In the present invention, the content of the block polymer is 0.5 to 30 parts by mass in 100 parts by mass of the rubber component. The content of the block copolymer is preferably 10 to 30 parts by mass, and more preferably 15 to 25 parts by mass, in 100 parts by mass of the rubber component, from the viewpoint of obtaining superior effects of the present invention.

[0062] (Polybutadiene rubber, natural rubber, synthetic polyisoprene rubber content) The remainder (70 to 99.5 parts by mass) obtained by subtracting the content of the copolymer from 100 parts by mass of the rubber component can be the total content of the polybutadiene rubber, natural rubber and synthetic polyisoprene rubber. Regarding the respective contents of polybutadiene rubber, natural rubber and synthetic polyisoprene rubber, for example, the following modes 1, 2 and 3 may be mentioned.

[0063] (Aspect 1 regarding content of polybutadiene rubber, etc.) Regarding the contents of the polybutadiene rubber, the natural rubber, and the synthetic polyisoprene rubber, from the viewpoint of achieving superior effects of the present invention, it is preferable that the content of the polybutadiene rubber is 49.5 parts by mass or less in 100 parts by mass of the rubber component, and the content of the natural rubber and / or the synthetic polyisoprene rubber is 50 parts by mass or more in 100 parts by mass of the rubber component (Aspect 1), When the content of the block copolymer is 15 to 25 parts by mass per 100 parts by mass of the rubber component, it is more preferable that the content of the polybutadiene rubber is 15 to 35 parts by mass per 100 parts by mass of the rubber component, and the content of the natural rubber and / or the synthetic polyisoprene rubber is 50 to 70 parts by mass per 100 parts by mass of the rubber component. When the first embodiment contains the natural rubber and the synthetic polyisoprene rubber, the total content of the natural rubber and the synthetic polyisoprene rubber may be 50 parts by mass or more per 100 parts by mass of the rubber component. The above-mentioned content of polybutadiene rubber etc. (embodiment 1) is suitable when the rubber composition of the present invention is used to form the tread of a heavy duty tire.

[0064] (Aspect 2 regarding content of polybutadiene rubber, etc.) Regarding the contents of the polybutadiene rubber, natural rubber, and synthetic polyisoprene rubber, from the viewpoint of obtaining superior effects of the present invention, an example of embodiment 2 is where the content of the polybutadiene rubber is 30.0 to 79.5 parts by mass based on 100 parts by mass of the rubber component, and the content of the natural rubber and / or the synthetic polyisoprene rubber is 20.0 to 69.5 parts by mass based on 100 parts by mass of the rubber component. In the second embodiment, when the content of the block copolymer is 15 to 25 parts by mass per 100 parts by mass of the rubber component, it is more preferable that the content of the polybutadiene rubber is 45.0 to 55.0 parts by mass per 100 parts by mass of the rubber component and the content of the natural rubber and / or the synthetic polyisoprene rubber is 30.0 to 40.0 parts by mass per 100 parts by mass of the rubber component.

[0065] (Aspect 3 regarding content of polybutadiene rubber, etc.) Regarding the contents of polybutadiene rubber, natural rubber, and synthetic polyisoprene rubber, a preferred embodiment (embodiment 3) is when the content of the polybutadiene rubber is 50.0 parts by mass or more per 100 parts by mass of the rubber component, and the content of the natural rubber and / or the synthetic polyisoprene rubber is 49.5 parts by mass or less per 100 parts by mass of the rubber component. The above-mentioned contents of polybutadiene rubber and the like (embodiments 2 and 3) are suitable when the rubber composition of the present invention is used to form a side tread of a tire.

[0066] (Carbon black and / or silica) The rubber composition of the present invention preferably further contains carbon black and / or silica. The carbon black is not particularly limited, and any conventionally known carbon black can be used. Examples of the carbon black include SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, SRF, and T-NS carbon black. The silica is not particularly limited, and any conventionally known silica can be used. Examples of the silica include wet silica, dry silica, fumed silica, and diatomaceous earth.

[0067] From the viewpoint of obtaining superior effects of the present invention, the content of the carbon black and / or the silica is preferably 30 to 90 parts by mass per 100 parts by mass of the rubber component. When the rubber composition of the present invention contains carbon black and silica, the total content of the carbon black and the silica may be within the above range per 100 parts by mass of the rubber component.

[0068] (optional ingredient) The rubber composition of the present invention may further contain components (optional components) other than the above-mentioned components, as necessary. Examples of such components include various additives commonly used in rubber compositions, such as silane coupling agents, terpene resins (preferably aromatic modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, oils, waxes, processing aids, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), vulcanization accelerators (accelerators), and vulcanization activators.

[0069] (Method of manufacturing rubber composition) The method for producing the rubber composition of the present invention is not particularly limited, and specific examples thereof include a method of mixing the above-mentioned components using a known method or device (e.g., a Banbury mixer, a kneader, a roll, etc.) When the rubber composition of the present invention contains sulfur or a vulcanization accelerator, it is preferable to first mix the components other than the sulfur and the vulcanization accelerator at a high temperature (preferably 100 to 160°C), cool the mixture, and then mix the sulfur or the vulcanization accelerator. The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0070] (Application) The rubber composition of the present invention is suitably used for, for example, tires, conveyor belts, hoses, vibration-proof materials, rubber rolls, outer covers of railway cars, etc. In particular, it is suitably used for tires (particularly cap treads and side treads).

[0071] [tire] The tire of the present invention is a tire manufactured using the rubber composition of the present invention described above. The tire of the present invention is preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, or other gases.

[0072] Fig. 1 shows a partial cross-sectional schematic view of a tire showing one example of an embodiment of a tire according to the present invention. However, the tire according to the present invention is not limited to the embodiment shown in the attached drawings.

[0073] In FIG. 1, reference numeral 1 denotes a bead portion, reference numeral 2 denotes a side tread (sidewall portion), and reference numeral 3 denotes a tread (cap tread). Between the pair of left and right bead portions 1, a carcass layer 4 having fiber cords embedded therein is installed, and the ends of the carcass layer 4 are folded back and wrapped around the bead cores 5 and bead fillers 6 from the inside to the outside of the tire. In the tread 3, a belt layer 7 is disposed on the outer side of the carcass layer 4 over one circumference of the tire. In addition, a rim cushion 8 is disposed in the bead portion 1 at a portion that comes into contact with the rim. There is no particular limitation as to which part of the tire of the present invention the rubber composition of the present invention is applied to, but a preferred embodiment is to form the tread (e.g., tread 3 in FIG. 1) and / or side tread (e.g., side tread 2 in FIG. 1) from the rubber composition of the present invention.

[0074] The tire of the present invention can be manufactured, for example, according to a conventionally known method. The gas to be filled in the tire can be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. The tire of the present invention can be used, for example, as a tire for ordinary automobiles; or a tire for heavy loads (heavy load vehicles) such as trucks and buses. EXAMPLES

[0075] The present invention will be described in further detail below with reference to examples. The materials, amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0076] (Production of block copolymers) Each copolymer was produced as follows. Copolymers 1 and 2 correspond to the copolymers contained in the rubber composition of the present invention.

[0077] [Copolymer 1]

[0078] <First polymerization step> Nd (4.0 g), MMAO (modified methylaluminoxane) methylisobutylaluminoxane (trade name MMAO-3A, ​​Tosoh Finechem Co., Ltd.) (30 mL), and butadiene (15% by mass toluene solution) (50 g) were added to a two-neck flask (500 mL) and stirred (room temperature, 1.5 hours) to polymerize butadiene. In this way, a butadiene block polymer was obtained. In this example, it is assumed that the entire amount of butadiene used in producing the block copolymer in the first polymerization step reacts to become a butadiene block polymer.

[0079] <Second polymerization step> Thereafter, isoprene (37.9 g) was added and stirred (room temperature, 1.5 hours) to polymerize isoprene successively to the butadiene block polymer. In this example, it is assumed that the entire amount of isoprene used in producing the block copolymer in the second polymerization step reacts to form an isoprene block polymer linked to a butadiene block polymer.

[0080] <Stopping process> Then, a hydrochloric acid / methanol solution (30 mL) was added and stirred (room temperature, 1.0 hour). Next, the mixture was purified twice using toluene as a good solvent and methanol as a poor solvent. Then, the mixture was vacuum dried (60°C, 5.0 hours). Thus, a copolymer was obtained. The obtained copolymer is designated as Copolymer 1.

[0081] Copolymer 1 was a diblock copolymer of butadiene and isoprene (butadiene unit content: 20 mol %, isoprene unit content: 80 mol %), in which the vinyl bond content in the total amount of butadiene units was 3 mol %, the total 1,4-cis bond content in the total amount of butadiene units and isoprene units was 92 mol %, the weight average molecular weight was 800,000, and the molecular weight distribution was 3.0. Furthermore, the Tg of Copolymer 1 was -104°C and -67°C.

[0082] [Copolymer 2]

[0083] <First polymerization step> Nd (1.0 g), MMAO (modified methylaluminoxane) methylisobutylaluminoxane (trade name MMAO-3A, ​​Tosoh Finechem Co., Ltd.) (15 mL), and butadiene (15% by mass toluene solution) (50 g) were added to a two-neck flask (500 mL) and stirred (room temperature, 1.5 hours) to polymerize butadiene. In this way, a butadiene block polymer was obtained.

[0084] <Second polymerization step> Thereafter, isoprene (9.5 g) was added and stirred (room temperature, 1.5 hours) to polymerize isoprene successively to the butadiene block polymer.

[0085] <Stopping process> Then, a hydrochloric acid / methanol solution (15 mL) was added and stirred (room temperature, 1.0 hour). Next, the mixture was purified twice using toluene as a good solvent and methanol as a poor solvent. Then, the mixture was vacuum dried (60°C, 5.0 hours). Thus, a copolymer was obtained. The obtained copolymer is referred to as Copolymer 2.

[0086] Copolymer 2 was a diblock copolymer of butadiene and isoprene (butadiene unit content: 50 mol %, isoprene unit content: 50 mol %), in which the vinyl bond content in the total amount of butadiene units was 3 mol %, the total 1,4-cis bond content in the total amount of butadiene units and isoprene units was 91 mol %, the weight average molecular weight was 700,000, and the molecular weight distribution was 2.8. Furthermore, the Tg of Copolymer 2 was -106°C and -68°C.

[0087] [Copolymer 3 (comparison)] A copolymer was obtained according to Example 1 described in JP-A-2002-12702. The copolymer obtained is designated as Copolymer 3.

[0088] Copolymer 3 is a diblock copolymer of butadiene and isoprene (butadiene unit content: 48 mass%, isoprene unit content: 52 mass%), in which the vinyl bond content in the total amount of butadiene units is 7 mol%, the total 1,4-cis bond content in the total amount of butadiene units and isoprene units is 89 mol%, the weight average molecular weight is 310,000, and the molecular weight distribution is 1.25. Copolymer 3 does not correspond to the copolymer contained in the rubber composition of the present invention since the vinyl bond content in the total amount of butadiene units, the total 1,4-cis bond content in the total amount of butadiene units and isoprene units, and the weight average molecular weight are all outside the specified ranges.

[0089] [Summary of the structure and properties of each copolymer]

[0090] The structures and physical properties of each copolymer are summarized in the following Table 1. In Table 1, for Copolymer 3, the butadiene unit content and isoprene unit content in the copolymer are expressed in units of "mass %."

[0091] [Table 1]

[0092] [Production of rubber composition] The components in the following Tables 2 to 4 were mixed in the compositions (parts by mass) shown in the tables. Specifically, first, the components other than sulfur and the vulcanization accelerator in Tables 2 to 4 were mixed in a 1.8 L internal mixer at 160°C or less for 5 minutes, and a master batch was discharged. Then, sulfur and the vulcanization accelerator were added to the master batch, and the mixture was mixed at 100°C or less using an open roll to produce each rubber composition. In each table, examples in which synthetic polyisoprene rubber was replaced with natural rubber (natural rubber, TSR20) are also shown. Examples containing natural rubber (NR) instead of synthetic polyisoprene rubber are Example 27 (based on Example 7) in Table 2, Example 28 (based on Example 15) in Table 3, and Example 29 (based on Example 24) in Table 4. In addition, Examples 1 to 8 and 27 in Table 2 correspond to the case where the content of polybutadiene rubber is 49.5 parts by mass or less in 100 parts by mass of the rubber component, and the content of natural rubber and / or synthetic polyisoprene rubber is 50 parts by mass or more in 100 parts by mass of the rubber component (above-mentioned embodiment 1). In Examples 1 to 8 and 27 in Table 2, the content of polyisoprene components in the entire rubber component (i.e., the total amount of synthetic polyisoprene rubber or natural rubber and polyisoprene block polymers in each copolymer) is set to be approximately 80% by mass in the entire rubber component. In addition, the content of polybutadiene components in the entire rubber component (i.e., the total amount of polybutadiene rubber and polybutadiene block polymers in each copolymer) is set to be approximately 20% by mass. The same applies to Examples 9 to 16 and 28 in Table 3. Examples 17 to 26 and 28 in Table 4 correspond to the case where the content of polybutadiene rubber is 30.0 to 79.5 parts by mass in 100 parts by mass of the rubber component, and the content of the natural rubber and / or the synthetic polyisoprene rubber is 20.0 to 69.5 parts by mass in 100 parts by mass of the rubber component (above-mentioned embodiment 2). In Examples 17 to 20, 22 to 24, 26 and 28 in Table 4, the content of polyisoprene component in the entire rubber component (i.e., the total amount of synthetic polyisoprene rubber or natural rubber and polyisoprene block polymer in each copolymer) is set to be approximately 50% by mass in the entire rubber component. In addition, the content of polybutadiene component in the entire rubber component (i.e., the total amount of polybutadiene rubber and polybutadiene block polymer in each copolymer) is set to be approximately 50% by mass. Examples 21 and 25 in Table 4 correspond to the case where the content of polybutadiene rubber is 50.0 parts by mass or more per 100 parts by mass of the rubber component, and the content of natural rubber and / or synthetic polyisoprene rubber is 49.5 parts by mass or less per 100 parts by mass of the rubber component (above-mentioned embodiment 3).

[0093] Details of each component in Tables 2 to 4 are as follows. (Rubber component) Synthetic polyisoprene rubber: NIPOL IR2200 manufactured by Nippon Zeon. A homopolymer of isoprene. The microstructure of the synthetic polyisoprene rubber contains 97% by mass of 1,4-cis bonds. Polybutadiene rubber: NIPOL BR1220 manufactured by Nippon Zeon. Homopolymer of butadiene. The 1,4-cis bond content of the microstructure of the polybutadiene rubber is 98% by mass. Weight average molecular weight: 450,000. Copolymers 1 to 3: Copolymers 1 to 3 prepared as above

[0094] Carbon black: SHOU BLACK N330T CABOT Japan made

[0095] ·Silica: Solvay ZEOSIL 1165MP (CTAB adsorption specific surface area: 160m 2 / g) Silane coupling agent: Evonik Si69

[0096] Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. Stearic acid: Lunac S-25 (Kao) · Anti-aging agent (6PPD): Flexis Santoflex 6PPD Oil: Aromatherapy oil. Extract No. 4 S manufactured by Showa Shell Sekiyu Co., Ltd.

[0097] Vulcanization accelerator (NS): Noccela NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator (CZ): Noccela CZ-G (CZ) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: Akzo Nobel Krystex HS OT 20

[0098] [evaluation] The rubber compositions thus obtained were subjected to the following evaluations, and the results are shown in Tables 2 to 4.

[0099] [Durability] In the present invention, durability was evaluated by abrasion resistance or crack extension resistance. In the present invention, when abrasion resistance or crack extension resistance is excellent, durability is considered to be excellent. Abrasion resistance and crack extension resistance are evaluation items generally considered for tires in general, but abrasion resistance is an evaluation item particularly related to the tread of heavy load tires, and crack extension resistance is an evaluation item particularly related to the side tread of tires.

[0100] [Wear resistance] Each of the rubber compositions obtained in Tables 2 to 3 was press-vulcanized in a mold (15 cm x 15 cm x 0.2 cm) at 160°C for 30 minutes to produce each vulcanized rubber sheet. Then, for the obtained vulcanized rubber sheet, the amount of wear was measured under the conditions of a load of 15.0 kg (147.1 N) and a slip ratio of 25% using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) in accordance with JIS K6264-2:2005. The results were expressed as an index with the reciprocal of the wear amount of the standard example being set to 100. In Table 2, the standard example was designated as Experimental Example 2. In Table 3, the standard example was designated as Experimental Example 4. In the present invention, when durability is evaluated by abrasion resistance, the durability (abrasion resistance) is deemed to be excellent if the abrasion index is 102 or more. The higher the index, the more excellent the durability. On the other hand, when the index was less than 102, the durability was evaluated as poor.

[0101] [Crack extension resistance] Each rubber composition obtained in Table 4 was press-vulcanized at 160°C for 30 minutes to produce a vulcanized rubber sheet with a thickness of 2 mm, length of 10 cm, and width of 1 cm. A 1 mm notch was made horizontally in the center of the vulcanized rubber sheet, and the rubber was gripped by 2 cm above and below. Then, a crack extension test was performed in which the vulcanized rubber sheet was subjected to repeated deformation at 10 Hz and 40% strain. The crack length was measured every 5,000 repeated strains, and the crack growth rate up to a crack length of 3 mm was calculated. The results are expressed as an index with the reciprocal of the crack propagation rate in Experimental Example 6 in Table 4 set to 100. In the present invention, when durability is evaluated by crack extension resistance, the durability is considered to be excellent (low crack growth rate and excellent crack extension resistance) if the index of the crack extension rate is 102 or more. The larger the index, the more excellent the durability. On the other hand, when the index was less than 102, the durability was evaluated as poor.

[0102] [Mechanical strength] Each of the obtained rubber compositions was press-vulcanized in a mold (15 cm × 15 cm × 0.2 cm) at 160°C for 20 minutes, and a dumbbell JIS No. 3 test piece was prepared from the vulcanized rubber sheet in accordance with JIS K6251. Using the obtained test piece, a tensile test was performed at room temperature (20°C) at a tensile speed of 500 mm / min to measure the breaking elongation. The results are expressed as an index with the standard example being 100. In Table 2, the standard example is Experimental Example 2. In Table 3, the standard example is Experimental Example 4. In Table 4, the standard example is Experimental Example 6. In the present invention, the mechanical strength is considered to be excellent when the breaking elongation index exceeds 100. The larger the index, the more excellent the mechanical strength. On the other hand, when the index was 100 or less, the mechanical strength was evaluated as being poor.

[0103] [hardness] Each of the obtained rubber compositions was used in a mold of a predetermined shape and vulcanized at 160°C for 20 minutes to prepare a vulcanized rubber sheet. The hardness of the vulcanized rubber sheet was measured at a temperature of 20°C using a durometer type A in accordance with JIS K6253-3:2012. The results are expressed as an index with the standard example being 100. In Table 2, the standard example is Experimental Example 2. In Table 3, the standard example is Experimental Example 4. In Table 4, the standard example is Experimental Example 6. In the present invention, a hardness index of more than 100 and 120 or less is considered to be excellent in hardness (tire running performance), and a hardness index of 102 to 110 is considered to be even more excellent in hardness (tire running performance), which is more preferable. On the other hand, when the index was 100 or less, the hardness was evaluated as being low.

[0104] [Extrusion processability] Each of the obtained rubber compositions was extruded at 100° C. using a small rubber extruder, and the surface of the extruded rubber composition was visually observed. When the surface of the extruded rubber composition was smooth, the extrusion processability was evaluated as being very excellent, and this was indicated by "A". When the surface of the extruded rubber composition was almost smooth, the extrusion processability was evaluated as being somewhat excellent, and this was indicated by "◯". In the present invention, when the surface of the extruded rubber composition is marked with "A" or "B", it is deemed that the extrusion processability is excellent. On the other hand, when the surface of the extruded rubber composition had significant irregularities, the extrusion processability was evaluated as poor, and this was indicated by "X."

[0105] [Table 2]

[0106] [Table 3]

[0107] [Table 4]

[0108] It was confirmed from the results in Tables 2 to 4 that the rubber composition of the present invention exhibited the desired effects. Furthermore, the rubber composition of the present invention also gave a cured product with excellent hardness.

[0109] On the other hand, when neither polybutadiene rubber nor the specified copolymer was contained (Example 1 in Table 2, Example 3 in Table 3, and Example 5 in Table 4), the durability and extrusion processability were at least poor. Example 3 and Example 5 also had poor mechanical strength. When the specified copolymer was not contained (Experimental Example 2 in Table 2, Experimental Example 4 in Table 3, and Experimental Example 6 in Table 4), the durability, mechanical strength, and extrusion processability were poor. When the specified copolymer was not contained and instead copolymer 3 (comparison) was contained (Comparative Example 1 in Table 2, Comparative Example 4 in Table 4, and Comparative Example 7 in Table 5), the durability, mechanical strength, and extrusion processability were poor. When the copolymer content was outside the specified range (Comparative Examples 2 and 3 in Table 2, Comparative Examples 5 and 6 in Table 4, and Comparative Examples 8 and 9 in Table 5), any one of durability, mechanical strength, and extrusion processability was poor. Furthermore, in Experimental Examples 1 to 6 and Comparative Examples 1, 4 and 7, the hardness of the cured products obtained was low. [Explanation of symbols]

[0110] 1 Bead section 2 Side tread 3 Tread (cap tread) 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Rim cushion

Claims

1. As a rubber component, a polybutadiene rubber having a 1,4-cis bond content of 80 mass% or more; Natural rubber and / or synthetic polyisoprene rubber having a 1,4-cis bond content of 80% by mass or more, and Contains a block copolymer of butadiene and isoprene, In the block copolymer, a total 1,4-cis bond content derived from the butadiene and the isoprene is 90 mol % or more of a total amount of repeating units derived from the butadiene and the isoprene, the content of vinyl bonds derived from the butadiene is less than 5 mol% in the total amount of repeating units derived from the butadiene, The weight average molecular weight of the block copolymer is 500,000 to 1,500,000; The rubber composition has a block polymer content of 0.5 to 30 parts by mass based on 100 parts by mass of the rubber component.

2. The rubber composition according to claim 1, wherein the molecular weight distribution of the block copolymer is 2-4.

3. the content of the polybutadiene rubber is 49.5 parts by mass or less based on 100 parts by mass of the rubber component, The rubber composition according to claim 1, wherein a content of the natural rubber and / or the synthetic polyisoprene rubber is 50 parts by mass or more based on 100 parts by mass of the rubber component.

4. Further, it contains carbon black and / or silica, The rubber composition according to claim 1, wherein the content of the carbon black and / or the silica is 30 to 90 parts by mass based on 100 parts by mass of the rubber component.

5. The rubber composition according to claim 3 or 4, which is used to form a tread of a heavy duty tire.

6. The content of the polybutadiene rubber is 50.0 parts by mass or more based on 100 parts by mass of the rubber component, The rubber composition according to claim 1, wherein a content of the natural rubber and / or the synthetic polyisoprene rubber is 49.5 parts by mass or less based on 100 parts by mass of the rubber component.

7. The rubber composition according to claim 4 or 6, which is used to form a side tread of a tire.

8. A tire manufactured using the rubber composition according to claim 1 or 2.

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