JP2015143310A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for improving grip performance and rolling resistivity of a tire, and a pneumatic tire having a tread using the same.SOLUTION: There is provided the rubber composition composed of 100 pts.mass of a rubber component (A) and 0 to 50 pts.mass of an isobutylene-based copolymer (B) with respect to the rubber component (A). The rubber component (A) is composed of : 60 to 80 mass% of styrene-butadiene rubber having a styrene content of 20 to 40 mass%, a carbon-carbon double bond content of 50 to 60 mass%, a glass transition temperature of -40 to -20°C and a weight average molecular weight of 500,000 to 1,000,000; and 20 to 40 mass% of styrene-butadiene rubber having a styrene content of 20 to 35 mass%, a carbon-carbon double bond content of 50 to 65 mass%, a glass transition temperature of -30 to -20°C and a weight average molecular weight of 200,000 to less than 500,000. The isobutylene-based copolymer (B) has an isobutylene structure unit and a norbornenyl-based alicyclic group-containing vinyl ether structural unit.

Description

  The present invention relates to a rubber composition that is a raw material for rubber having excellent grip properties, and a pneumatic tire that is excellent in grip properties comprising a crosslinked product of the rubber composition.

  Diene rubber cross-linked products of styrene-butadiene copolymer rubber (hereinafter abbreviated as SBR) are excellent in grip properties and are used in the tread portion that contacts the road surface of the tire, but two or more different glass transition temperatures. A rubber composition containing SBR having a weight average molecular weight or a styrene / butadiene blend ratio may be used. However, it is not yet clear what blends of SBRs having different chemical structures (such as the molar ratio of styrene and butadiene, the chemical structure of the butadiene part, etc.) and different molecular weights are optimal (Patent Documents 1 and 2).

  In addition, in the presence of an α-olefin-nonconjugated diene copolymer crosslinking system (Patent Document 3) or a rubber component (SBR, butyl rubber, norbornene polymer, etc.) containing an olefinic double bond in the copolymer system. Co-crosslinking systems are also being studied (Patent Documents 4 and 5). However, in recent years, when the molecular structure of diene rubbers is precisely controlled and rubbers with various chemical structures are provided, it is confirmed that the individual rubber additivity cannot be easily established in blend rubber properties. It has been done. This is thought to be due to the morphology that appears based on the compatibility between the two rubbers and the difference in the crosslinking rate between the two rubbers. The latter may lead to a decrease in productivity in some cases. Although the proposal of the isobutylene-type copolymer used for the rubber composition which concerns on this invention, and the rubber composition using the same is also performed in the said patent documents 3 and 4, two or more types of different glass transition temperatures and weight averages are carried out. The grip resistance effect exhibited by the blend rubber system containing a plurality of types of SBR having a molecular weight and a styrene / butadiene blend ratio has not yet been clarified.

JP 2007-321046 A JP2013-221032A International Publication No. WO2010 / 137655 International Publication WO2011 / 021437 JP 2014-9300 A

  The present inventors have investigated a rubber composition excellent in grip resistance, and a combination of a specific styrene-butadiene copolymer rubber or a combination of an α-olefin-nonconjugated diene copolymer having a specific structure is suitable. As a result, the present invention has been completed.

［式（２）中、Ｘは２価の基を示し、Ｙは環内に不飽和結合を有する置換又は未置換の脂環基を示し、ｎは０又は１を示す。］ In the first aspect of the present invention, the styrene content is 20 to 40% by mass, the carbon-carbon double bond content is 50 to 60% by mass, the glass transition temperature is −40 to −20 ° C., and the weight average molecular weight is 500,000. ~ 1 million styrene-butadiene rubber (hereinafter referred to as "SBR1") 60-80 mass%; styrene content 20-35 mass%, carbon-carbon double bond content 50-65 mass%, glass Styrene-butadiene rubber (hereinafter referred to as “SBR2”) having a transition temperature of −30 to −20 ° C. and a weight average molecular weight of 200,000 to less than 500,000; 20 to 40% by mass; (“SBR1”, “SBR2”) 100 parts by mass of a rubber component (A) comprising an isobutylene polymer (B) having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2): ) (A) Go To provide a rubber composition consisting of 0-50 parts by mass relative to 100 parts by weight of component.

[In formula (2), X represents a divalent group, Y represents a substituted or unsubstituted alicyclic group having an unsaturated bond in the ring, and n represents 0 or 1. ]

［式（３）中、ｎは０又は１を示す。］

［式（４）中、ｎは０又は１を示す。］ A second aspect of the present invention is the rubber composition according to the first aspect of the present invention, wherein the isobutylene polymer has structural units represented by the following formula (3) and the following formula (4). provide.

[In the formula (3), n represents 0 or 1. ]

[In Formula (4), n shows 0 or 1. ]

  A third aspect of the present invention provides a pneumatic tire having a tread using the rubber composition according to the first or second aspect of the present invention.

ADVANTAGE OF THE INVENTION According to this invention, the crosslinked rubber excellent in the grip property useful as a tire structure material etc. can be obtained, without impairing the characteristic which SBR has. It is well known to those skilled in the art that the grip performance of the crosslinked rubber can be determined by the value of tan δ in various characteristics measured using a viscoelastic spectrometer. The rubber composition of the present invention is a rubber composition having a large tan δ value at 0 ° C.
For tan δ and tire characteristics at low and high temperatures, see Patent Document 4 [0049] and Patent Document 5 [0073]. In the rubber composition according to the present invention, tan δ at 60 ° C. is small, and it has been confirmed that it has excellent rolling resistance characteristics.

  The rubber composition of the present invention comprises, as a rubber component, two types of SBR having different glass transition temperatures and weight average molecular weights, and an α-olefin-nonconjugated diene copolymer having a specific structure added as necessary. Containing the mixture.

The first SBR (hereinafter referred to as “SBR1”) has a styrene content measured in accordance with JISK6239 in the range of 20 to 40% by mass, preferably 20 to 30% by mass, and is measured in accordance with JISK6239. The amount of carbon-carbon double bonds is in the range of 50 to 60% by mass, preferably 50 to 55% by mass.
Moreover, the glass transition temperature measured by DSC method (temperature rising rate 5 degree-C / min, based on JISK7121) is -40--20 degreeC, Preferably it is -40--30 degreeC, The weight average molecular weight measured by GPC method is. It is 500,000 to 1,000,000, preferably 500,000 to 700,000.

  The second SBR (hereinafter referred to as “SBR2”) has a styrene content measured in accordance with JISK6239 in the range of 20 to 35% by mass and a carbon-carbon double bond content in the range of 50 to 65% by mass. It is in. The glass transition temperature measured by DSC method is −30 to −20 ° C., preferably −27 to −22 ° C., and the weight average molecular weight measured by GPC method is 200,000 to less than 500,000, preferably 220,000 to 480,000.

  In the present invention, the rubber composition is SBR1 in the range of 60 to 80% by mass and SBR2 in the range of 40 to 20% by mass. The rubber composition refers to a uniformly dispersed state after the kneading step. In the rubber composition of the present invention, when observed with a transmission microscope (TEM), a clear dispersed phase having a particle diameter of 1 μm or more is not substantially detected. The production method of SBR1 and SBR2 is not particularly limited, and examples thereof include emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR) and the like. Among these, solution-polymerized styrene butadiene rubber (S-SBR) is preferable because the effects of the present invention can be suitably obtained.

  In the present invention, it is considered that SBR2, which is a relatively small component and a low viscosity component, is well dispersed in the continuous phase of SBR1, which is a relatively large component and a high viscosity component. The former is a relatively low glass transition temperature component, and the latter is a relatively high glass transition temperature component. When the content of SBR1 is less than 60% by mass, the characteristics of SBR1 mainly responsible for the basic characteristics of the tire characteristics may not be sufficiently exhibited. When the content of SRR2 is less than 20% by mass, the high glass An increase in tan δ at 0 ° C. (improvement of grip characteristics), which is considered to depend on the transition temperature, may not be obtained.

  As described above, the present inventors have found that SBR2 having a relatively low glass transition temperature is well dispersed in SBR1 having a relatively high glass transition temperature and causes an inherent interaction. It is presumed that an increase in tan δ (improvement of grip characteristics) of the

  In the present invention, the molecular weight range of both SBR1 and SBR2 is set to a predetermined range in order to balance such good interaction appearance, rubber kneading process, ease of handling of crosslinking, and pneumatic tire characteristics.

In the present invention, as the α-olefin-nonconjugated diene compound copolymer rubber, an isobutylene polymer containing the following formula (1) and the following formula (2) as structural units is used.

Preferably, an isobutylene polymer containing the following formula (3) and the following formula (4) as structural units is used.

  The present inventors consider that these isobutylene polymers are excellent in compatibility with SBR and co-crosslinking properties, as judged from the results of Examples described later. The present inventors have carried out a crosslinking reaction between the olefin structure in SBR and the cyclic olefin arranged in the side chain of the isobutylene polymer without being greatly affected by steric hindrance, and two different types are obtained by this co-crosslinking effect. It is presumed that the interaction between SBRs (denoted as SBR1 and SBR2) is enhanced and the effect of the present invention is enhanced.

［式（２）中、Ｘは２価の基を示し、Ｙは環内に不飽和結合を有する置換または未置換の脂環基を示し、ｎは０または１を示す。］
で表されるビニルエーテルを含有するカチオン重合性モノマーを共重合させて得ることができる。
上記共重合に関する詳細は、特許文献３の段落［００３５］〜［００６０］に開示されているが、概略以下の通りである。 The isobutylene-based polymer used in the present invention is isobutylene and formula (2):

[In the formula (2), X represents a divalent group, Y represents a substituted or unsubstituted alicyclic group having an unsaturated bond in the ring, and n represents 0 or 1. ]
It can obtain by copolymerizing the cation polymerizable monomer containing vinyl ether represented by these.
Details regarding the copolymerization are disclosed in paragraphs [0035] to [0060] of Patent Document 3, which are outlined below.

  The vinyl ether represented by the above formula (5) does not contain a polar group, that is, has a norbornenyl alicyclic group having only unsaturated atoms in the ring as a substituent Y. Monomers are preferred.

Specific examples of norbornenyl alicyclic groups that do not contain a polar group include:
Dicyclopentadienyl alicyclic groups such as dicyclopentadienyl; tetracyclododecenyl alicyclic groups; norbornenyl alicyclic groups such as 2-norbornenyl; And so on.

In the isobutylene polymer of the present invention, the copolymerization ratio of the structural unit represented by the above formula (1) and the structural unit represented by the above formula (2) is not particularly limited, but based on the total amount of both. The structural unit represented by the formula (2) is preferably 1 mol% to 60 mol%, more preferably 1 mol% to 40 mol%, and more preferably 1 mol% to 20 mol%. More preferably. The copolymerization ratio here is an average value of the copolymerization ratio per molecule, and the intensity of the resonance signal of carbon belonging to each structure is measured and compared by the ¹³ C-NMR (500 MHz) method. It can ask for. Both polymerization forms may be block copolymerization or random copolymerization. When deviating from these ranges, the co-crosslinking resulting from the above formula (2) becomes excessive or insufficient, and sufficient effects such as high grip properties when applied to tires may not be obtained.

  In the copolymerization reaction according to the present invention, a Lewis acid is used as a polymerization catalyst. As a Lewis acid, it can use widely from well-known things which can be used for cationic polymerization. For example, boron halide compounds such as boron trichloride and boron trifluoride; titanium halide compounds such as titanium tetrachloride; tin halide compounds such as tin tetrachloride; aluminum halide compounds such as aluminum trichloride; antimony pentachloride Antimony halide compounds such as antimony pentafluoride; tungsten halide compounds such as tungsten pentachloride; molybdenum halide compounds such as molybdenum pentachloride; tantalum halide compounds such as tantalum pentachloride; It is not limited. Of these Lewis acids, boron trifluoride, aluminum trichloride, ethyldichloroaluminum, tin tetrachloride, titanium tetrachloride and the like are preferable. Of these Lewis acids, boron trifluoride is preferred from the viewpoint that the molecular weight can be easily controlled by changing the reaction temperature.

  The Lewis acid can be used in an amount of 0.01 to 1000 mmol equivalent, preferably 0.05 to 500 mmol equivalent, per 1 mol of the raw material monomer.

  The above Lewis acid can also be used as a complex in which a polar compound such as alcohol is coordinated (hereinafter referred to as “Lewis acid complex”). A compound that coordinates to a Lewis acid to form a complex is also referred to as a complexing agent.

  As the Lewis acid complex, a boron trifluoride complex obtained by coordinating the above complexing agent to boron trifluoride is preferable. Further, an alcohol complex of boron trifluoride is more preferable. According to such a Lewis acid complex, the molecular weight can be easily controlled by changing the reaction temperature.

  In the copolymerization reaction, a reaction solvent can be used. Examples of the reaction solvent include a single solvent selected from the group consisting of halogenated hydrocarbons, aliphatic hydrocarbons, and aromatic hydrocarbons, or a mixed solvent thereof.

  When using a reaction solvent as an embodiment of the present invention, considering the solubility of the resulting polymer, the viscosity of the solution, and the ease of heat removal, the polymer concentration is 0.1 to 80% by mass. It is preferable to use a solvent, and it is more preferable to use it so that it may become 1-50 mass% from a viewpoint of production efficiency and operativity. Further, the monomer concentration at the time of polymerization is preferably about 0.1 to 8 mol / liter, more preferably about 0.5 to 5 mol / liter. In addition, the amount of the organic solvent used during the polymerization is preferably 0.5 to 100 times the mass of the monomer used from the viewpoint of controlling appropriate viscosity and heat generation.

  Since the polymerization temperature affects the average molecular weight of the resulting isobutylene polymer, the polymerization temperature to be employed may be appropriately selected according to the target average molecular weight, but the polymerization temperature is about −80 ° C. to 20 ° C. More preferably, it is good to set it as about -70-0 degreeC, and superposition | polymerization time is about 0.5 to 180 minutes normally, Preferably it is about 20 to 150 minutes.

  In the present invention, SBR and diene rubber other than SBR1 and SBR2 may be included. For example, a styrene butadiene copolymer having a cis-1,4 bond content of the butadiene unit of less than 35%, natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), nitrile butadiene rubber (NBR), Chloroprene rubber (CR) and the like. These may use only 1 type and can also use 2 or more types together.

  In the present invention, an α-olefin-nonconjugated diene compound copolymer rubber other than the α-olefin-nonconjugated diene compound copolymer rubber according to the present invention may be included. For example, EPDM using 1,6-hexadiene, dicyclopentadiene, ethylidene norbornene, or the like. These may use only 1 type and can also use 2 or more types together. The rubber compounding material having excellent compatibility with the α-olefin-nonconjugated diene compound copolymer rubber according to the present invention may contain a polymer other than the isobutylene copolymer. Examples thereof include polyisobutylene, polyisobutylene-styrene copolymer, butyl rubber and the like. These may use only 1 type and can also use 2 or more types together.

  In this invention, 0-50 mass parts of said isobutylene copolymers are included with respect to 100 mass parts combining SBR1 and SBR2. If it exceeds 50 parts by mass, the properties of the crosslinked rubber composition comprising SBR1 and SBR2 when processed into a tire together with other components and additives may be impaired. Preferably, it is 5-30 mass parts, More preferably, it is 10-20 mass parts. If it is less than 5 parts by mass, the effect of uniformly co-crosslinking in the rubber composition comprising SBR1 and SBR2 may be insufficient.

In the rubber composition according to the present invention, additives such as the above-mentioned SBR1, SBR2 and α-olefin-nonconjugated diene copolymer rubber, softener / plasticizer, antioxidant, ultraviolet absorber, anti-aging agent, etc. Crosslinking is carried out by blending chemicals used in normal rubber processing, such as reinforcing materials such as carbon black and silica, and coupling agents. There is no particular limitation on the crosslinking method.
The Mooney viscosity of the rubber composition before crosslinking is not limited, but the Mooney viscosity (ML1 + 4, 100 ° C.) is preferably 30-50. Outside these ranges, the torque during kneading becomes excessive and insufficient, and the dispersion / diffusion of various additives becomes insufficient, and the effects of the present invention may not be sufficiently obtained.

  Examples of the reinforcing agent include carbon black and silica.

  Carbon black is suitably used as a reinforcing agent from the viewpoints of improving wear resistance, improving rolling resistance characteristics, preventing cracks and cracks caused by ultraviolet rays (preventing ultraviolet degradation), and the like. The type of carbon black is not particularly limited, and conventionally known carbon blacks such as furnace black, acetylene black, thermal black, channel black, and graphite can be used. Further, the physical characteristics such as particle size, pore volume and specific surface area of carbon black are not particularly limited, and various carbon blacks conventionally used in the rubber industry, for example, SAF, ISAF, HAF, FEF, GPF, SRF (all are abbreviations of carbon black classified according to the US ASTM standard D-1765-82a) and the like can be used as appropriate. When carbon black is used, the blending amount is preferably 5 to 80 parts by mass, more preferably 10 to 60 parts by mass with respect to 100 parts by mass of the rubber component (A). Moreover, it can also be set as 30-80 mass parts, and can also be set as 40-60 mass parts. In such a blending amount, the effect as a reinforcing agent can be favorably obtained in the rubber composition and the crosslinked rubber composition according to the present embodiment.

  As silica, those conventionally used as rubber reinforcing agents can be used without particular limitation, such as dry method white carbon, wet method white carbon, synthetic silicate white carbon, colloidal silica, precipitated silica and the like. It is done. The specific surface area of silica is not particularly limited, but a silica having a surface area of 40 to 600 m2 / g, preferably 70 to 300 m2 / g, and a primary particle diameter of 10 to 1000 nm can be used. . These may be used alone or in combination of two or more. The amount of silica used is preferably 0.1 to 150 parts by mass, more preferably 10 to 100 parts by mass, and 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component (A). Is more preferable.

  Moreover, you may mix | blend a silane coupling agent with a rubber composition in order to mix | blend a silica. Examples of the silane coupling agent include vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, and 3-chloropropyltrimethoxy. Silane, 3-chloropropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis (3- (triethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) propyl ) Disulfide and the like. These may be used alone or in combination of two or more. Although the addition amount of a silane coupling agent can be suitably changed with the compounding quantity of the desired silica, it is preferable that it is 0.1-20 mass parts with respect to 100 mass parts of rubber components (A).

  As fillers, mineral powders such as clay and talc, carbonates such as magnesium carbonate and calcium carbonate, and alumina hydrates such as aluminum hydroxide are mainly used to improve strength, workability and economic efficiency. be able to.

  As softeners and plasticizers, plant oil softeners such as tall oil, mainly linoleic acid, oleic acid, and abithienic acid, pineapple, rapeseed oil, cottonseed oil, peanut oil, castor oil, palm oil, fuacitis, paraffinic oil, Examples thereof include naphthenic oils, aromatic oils, and phthalic acid derivatives such as dibutyl phthalate. It is preferable that the compounding quantity of a softener is 0-50 mass parts with respect to 100 mass parts of rubber components (A).

  The rubber composition according to this embodiment also includes various additives used in the field of the rubber industry, such as anti-aging agents, sulfur, crosslinking agents, vulcanization accelerators, vulcanization retarders, peptizers, processes. You may contain 1 type, or 2 or more types, such as oil and a plasticizer, as needed. It is preferable that the compounding quantity of these additives is 0.1-10 mass parts with respect to 100 mass parts of rubber components (A).

  Antiaging agents include primary amines such as p, p′-diaminodiphenylmethane; secondary amines such as phenyl-α-naphthylamine and N, N′-diphenyl-p-phenylenediamine; 2,6-di Alkylphenols such as -tert-butyl-p-cresol, 2,5-di-tert-butyl-hydroquinone, hydroquinone monobenzyl ether; and imidazoles such as 2-mercaptobenzimidazole. It is preferable that a compounding quantity is 0.1-10 mass parts with respect to 100 mass parts of rubber components (A).

  Examples of the vulcanization accelerator include thiuram accelerators such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetraethylthiuram disulfide; thiazole accelerators such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide; N-cyclohexyl Sulfenamide accelerators such as 2-benzothiazylsulfenamide and N-oxydiethylene-2-benzothiazolylsulfenamide; guanidine accelerators such as diphenylguanidine and diortolylguanidine; n-butyraldehyde -Aldehyde-amine accelerators such as aniline condensates and butyraldehyde-monobutylamine condensates; aldehyde-ammonia accelerators such as hexamethylenetetramine; thiourea accelerators such as thiocarbanilide Agents, and the like. When blending these vulcanization accelerators, one type may be used alone, or two or more types may be used in combination. It is preferable that content of a vulcanization accelerator is 0.1-10 mass parts with respect to 100 mass parts of rubber components (A).

  Vulcanization aids include metal oxides such as zinc oxide (zinc white) and magnesium oxide; metal hydroxides such as calcium hydroxide; metal carbonates such as zinc carbonate and basic zinc carbonate; stearic acid and oleic acid Aliphatic acid salts such as zinc stearate and magnesium stearate; amines such as di-n-butylamine and dicyclohexylamine; ethylene dimethacrylate, diallyl phthalate, N, Nm-phenylene dimaleimide, triallyl isocyanurate And trimethylolpropane trimethacrylate. When blending these vulcanization aids, one type may be used alone, or two or more types may be used in combination. The content of the vulcanization aid is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component (A).

  The rubber composition according to the present embodiment can be produced by applying a method generally used as a method for producing a rubber composition. For example, it can manufacture by mixing each component mentioned above using kneading machines, such as a Brabender, a Banbury mixer, and a roll mixer.

  The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples.

[Example 1]
<Kneading of rubber composition>
As SBR, 80 parts by mass of SL-563 manufactured by JSR Corporation and 20 parts by mass of NS116R manufactured by Nippon Zeon Co., Ltd. were used.
A filler, a plasticizer, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid and an anti-aging agent are blended in the amounts shown in Table 2 in 100 parts by weight of the SBR, and a roll mixer (6 inches φ × 16 inches) is added. ) And kneaded under the conditions of a rotation speed of 30 rpm and a front / rear roll rotation ratio of 1: 1.22 to obtain a rubber composition.
Silica AQ (manufactured by Tosoh Silica) is used as the filler, process oil “NS-100” (manufactured by Idemitsu Kosan Co., Ltd.) as the plasticizer, and sulfur (Kawagoe Chemical Co., Ltd.) as the vulcanizing agent. Made of Zinc Oxide No. 3 (Hakusui Tech Co., Ltd.) and stearic acid (made by Nippon Seika Co., Ltd.) as vulcanization aids, and sulfenamide accelerators as vulcanization accelerators. “Noxeller CZ (N-cyclohexyl-2-benzothiazylsulfenamide)” (manufactured by Ouchi Shinsei Chemical Co., Ltd.) and the guanidine accelerator “Noxeller D (1,3-diphenylguanidine)” (Emerging Ouchi) Chemical Co., Ltd.) and “Aging Prevention Agent 224” (manufactured by Ouchi Shinsei Chemical Co., Ltd.) were used as anti-aging agents.
The rubber composition after kneading was compression molded under a vulcanization condition of 160 ° C. × 20 minutes to produce a sheet. The dynamic viscoelasticity (that is, an index of grip resistance) at the time of producing the sheet was evaluated. These results are shown in Table 2.
Hereinafter, rubber compositions were kneaded according to Examples 2 to 6 and Comparative Example 1 according to Table-2, and Comparative Examples 2 to 10 according to Table 3 and vulcanized to prepare measurement sheets. The dynamic viscoelasticity (that is, an index of grip resistance) at the time of producing the sheet was evaluated. These results are shown in Table 3.

[Example 5]
<Synthesis of isobutylene polymer>
As disclosed in Example 1 of Patent Document 3, a septum cap, a reflux tube connected to a vacuum line, and a temperature tube were attached to a 300 mL three-necked flask, a stirrer chip was placed, and a vacuum line (with a Schlenk tube) was used. Then, deaeration-nitrogen replacement in the system was repeated twice to obtain a normal pressure nitrogen atmosphere. Into the flask, 34.8 g of toluene solvent dried and distilled with calcium hydride was injected from the septum cap using a syringe.
Next, 5.68 mmol of tricyclodecene vinyl ether (manufactured by Maruzen Petrochemical Co., Ltd.) was injected using a syringe. The flask was immersed in a low temperature bath at a predetermined temperature, and after confirming that the liquid temperature in the system reached a predetermined temperature, 51.2 mmol of isobutylene was transferred to the reaction system. When the temperature of the liquid in the system sufficiently reaches a predetermined temperature (about 10 ° C.), a 1.06 mol / L ethylaluminum dichloride (EADC) / n-hexane solution is used as purified hexane in a glove box under a nitrogen atmosphere. The adjusted catalyst solution (1.14 mmol as ethylaluminum dichloride) diluted 10 times was weighed with a syringe and injected into the reactor. Two hours after the injection of the catalyst solution, the flask was taken out of the low temperature bath and allowed to stand at room temperature. The reaction mixture was extracted with a 1N aqueous sodium hydroxide solution (twice), and the resulting oil phase was extracted with pure water. After confirming that the pH of the aqueous phase became neutral, the solvent was distilled off from the oil phase with an evaporator, and the residue was dried with a vacuum dryer at 1 mmHg for 12 hours at 60 ° C. 2.41 g of isobutylene polymer (copolymer of isobutylene and tricyclodecene vinyl ether) was obtained.
In addition, it was confirmed by ¹³ C-NMR measurement that the obtained substance was the target isobutylene polymer (copolymer of isobutylene and tricyclodecene vinyl ether). Content of the said Formula (2) was 1.1 mol%.
<Kneading of rubber composition>
A rubber composition was obtained in the same manner as described in Example 1 except that 10 parts by mass of the isobutylene polymer obtained above was additionally used, and a vulcanized sheet was prepared and subjected to measurement.

[Example 6]
In Example 5, a rubber composition was obtained in the same manner as described in Example 1 except that 20 parts by mass of an isobutylene polymer was used, and a vulcanized sheet was produced and subjected to measurement.

［Ｍｗ３５，０００、Ｍｗ／Ｍｎ１．１、ｍ＝７］
に示す構造を有する重合体 The types of raw materials used in Tables 2 to 3 other than those described above are shown below (shown in Table 1).
SBR3: rubber manufacturer SBR sample, styrene 24% by weight, carbon-carbon double bond 57% by weight, Tg-23 ° C, Mw 480,000, non-oil-extended product SBR4: JSR SL-552, styrene 23% by weight, carbon -Carbon double bond 31 wt%, Tg-53 ° C, Mw 230,000, non-oil-extended product, SBR5: Asahi Kasei Chemicals Toughden 2003, styrene 26 wt%, carbon-carbon double bond 9 wt%, Tg-87 ° C, Mw 240,000, non-oil-extended product / isobutylene polymer: Formula (5) below:

[Mw 35,000, Mw / Mn 1.1, m = 7]
Polymer having the structure shown in

[Measurement of dynamic viscoelasticity]
The measurement of dynamic viscoelasticity was performed according to JIS K 7244-4: 1999 “Plastics—Testing method of dynamic mechanical properties—Part 4: Tensile vibration—Non-resonance method”. Specifically, from 16 types of rubber sheets for tire treads, test pieces each having a thickness of 1 mm, a width of 5 mm, and a length of 40 mm were cut out and used one by one under the conditions of a frequency of 10 Hz and a dynamic strain of 0.1%. The temperature was measured in the tensile mode while raising the temperature in the range of -50 to 100 ° C. at 2 ° C./min. The apparatus used is a dynamic viscoelasticity measuring apparatus RSA-3 (manufactured by TA INSTRUMENTS). The obtained results are shown in the columns of “tan δ (0 ° C.)” and “tan δ (60 ° C.)” in Tables 2 and 3 as indexes with the value of Comparative Example 1 as 100. The larger the index of tan δ (0 ° C.), the better the grip performance, and the smaller the index of tan δ (60 ° C.), the better the rolling resistance performance.
(Reference: “Development of high-performance tires by building a nanoparticle network structure model in rubber”, p. 36, line 22, Marine Research and Development Organization Earth Simulator Project 2011.3.31, “Silica dispersibility by terminal-modified S-SBR” Improvement and reduction of rolling resistance ”JSR Technical Review No. 117/2010, p-18, 3.1)

From Table 2, it is confirmed that the rubber compositions of Examples 1 to 4 improve the grip performance (0 ° C. tan δ is 105 or more) while maintaining rolling resistance (60 ° C. tan δ is 105 or less).
Further, the rubber compositions of Examples 5 to 6 further improved grip performance (0 ° C. tan δ) compared to the rubber composition described in Example 1 by containing the isobutylene polymer according to the present invention. Is 120 or more).
From Table 3, the rubber composition of Comparative Examples 2 and 4 has too little compounding amount of SBR2 or SBR3 and the effect of increasing 0 ° C. tan δ does not appear, and the rubber composition of Comparative Examples 3 and 5 has the compounding amount of SBR2 or SBR3. However, the grip performance is improved (0 ° C. tan δ increase), but the rolling resistance performance is deteriorated (60 ° C. tan δ decrease). Since Comparative Examples 6 to 9 had a carbon-carbon double bond amount of SBR4 and SBR5 of less than 50 wt%, a glass transition temperature of less than -40 ° C, and a weight average molecular weight of less than 500,000, The rolling resistance performance is significantly deteriorated in Comparative Examples 7 and 9.
In the rubber composition of Comparative Example 10, since the isobutylene polymer was added to SBR1 alone, the grip performance was improved, but the rolling resistance performance was deteriorated.

  According to the present invention, it is possible to obtain a crosslinked rubber having excellent grip properties and rolling resistance useful as a tire structure material and the like without impairing the characteristics of the SBR, and applying it to a pneumatic tire using the tread. Is done.

Claims (3)

Styrene having a styrene content of 20 to 40% by mass, a carbon-carbon double bond content of 50 to 60% by mass, a glass transition temperature of −40 to −20 ° C., and a weight average molecular weight of 500,000 or more and 1,000,000 or less. -60-80 mass% butadiene rubber (hereinafter referred to as “SBR1”),
Styrene having a styrene content of 20 to 35 mass%, a carbon-carbon double bond content of 50 to 65 mass%, a glass transition temperature of -30 to -20 ° C, a weight average molecular weight of 200,000 or more and less than 500,000 -Butadiene rubber (hereinafter referred to as "SBR2") 20-40% by mass,
("SBR1" and "SBR2" are combined to 100% by mass)
100 parts by mass of a rubber component (A) comprising:
From 0 to 50 parts by mass of the isobutylene polymer (B) having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2) with respect to 100 parts by mass of the (A) rubber component: A rubber composition.

[In formula (2), X represents a divalent group, Y represents a substituted or unsubstituted alicyclic group having an unsaturated bond in the ring, and n represents 0 or 1. ] The rubber composition according to claim 1, wherein the isobutylene polymer has a structural unit represented by the following formula (3) and the following formula (4).

[In the formula (3), n represents 0 or 1. ]

[In Formula (4), n shows 0 or 1. ]   A pneumatic tire having a tread using the rubber composition according to claim 1.