JP2018024768A - Rubber composition and tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition capable of obtaining excellent durability (tensile stress at break, elongation at break and tensile strength) when polyrotaxane is blended with the rubber composition without using a special polymer, and to provide a tire using the rubber composition.SOLUTION: A rubber composition contains polyrotaxane having straight-chain molecules, cyclic molecules including the straight-chain molecules in a skewered state, and blocking groups which are arranged at both terminals of the straight-chain molecules and prevent detachment of the cyclic molecules, and a diene rubber, where the cyclic molecules have mercapto groups.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition and a tire.

In general, rubber products (tires, conveyor belts, anti-vibration rubber, seismic isolation rubber, etc.) are required to have high durability, and various rubber components and rubber compositions have been developed to satisfy such demands. .
For example, Patent Document 1 aims to obtain a rubber composition for a tire rim cushion or gum finishing capable of improving heat resistance and breaking strength and improving steering stability and durability, and includes 40 to 60 parts by mass of natural rubber and A cyclic molecule having a blocked isocyanate group and a straight chain that includes the cyclic molecule in a skewered manner with respect to 100 parts by mass of a rubber component comprising 60 to 40 parts by mass of a diene rubber having a modifying group capable of reacting with an isocyanate group. 1 to 30 parts by mass of a polyrotaxane compound having blocking groups arranged at both ends of the linear molecule so that the cyclic molecule is not detached from the molecule and the linear molecule, and a nitrogen adsorption specific surface area (N ₂ SA) of 90 Tire rim cushion or gum finish characterized by blending 70 to 90 parts by mass of carbon black of ˜130 m ² / g A rubber composition for sealing is disclosed.

JP 2014-34623 A

In Patent Document 1, in order to chemically bond the polyrotaxane and the rubber component, it is necessary to use a diene rubber having a modified group capable of reacting with an isocyanate group (also referred to as an isocyanato group).
The object of the present invention is to have excellent durability (tensile stress at break, elongation at break, and tensile strength) when a polyrotaxane is blended with a rubber composition without using such a special polymer. Is to provide a rubber composition. Furthermore, an object of the present invention is to provide a tire using the rubber composition.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by using a rubber composition containing a polyrotaxane having a cyclic molecule having a mercapto group and a diene rubber.

That is, the present invention relates to the following <1> to <8>.
<1> A linear molecule, a cyclic molecule that includes the linear molecule in a skewered manner, and a blocking group that is disposed at both ends of the linear molecule and prevents the cyclic molecule from being detached. A rubber composition comprising a polyrotaxane having a diene rubber and a cyclic molecule having a mercapto group.
<2> The rubber composition according to <1>, wherein an average number of mercapto groups included in one cyclic molecule is 2 or less.
<3> The rubber composition according to <1> or <2>, wherein the polyrotaxane has a mercapto group concentration of 0.001 to 0.7 mmol / g.
<4> The rubber composition according to any one of <1> to <3>, wherein the diene rubber is unmodified.
<5> The rubber composition according to any one of <1> to <4>, wherein the cyclic molecule is a cyclodextrin.
<6> The rubber composition according to any one of <1> to <5>, wherein the sealing group is an adamantyl group.
<7> The rubber composition according to any one of <1> to <6>, wherein the content of the polyrotaxane is 0.1 to 30% by mass with respect to the total mass of the diene rubber.
<8> A tire using the rubber composition according to any one of <1> to <7>.

  According to the present invention, excellent durability (tensile stress at break, elongation at break, and tensile strength) can be obtained when a polyrotaxane is blended in a rubber composition without using a special polymer. A rubber composition can be provided. Furthermore, according to the present invention, a tire using the rubber composition can be provided.

Hereinafter, the present invention will be described in detail based on the embodiments. In the following description, the description of “A to B” indicating a numerical range represents a numerical range including A and B as end points, and “A or more and B or less” (when A <B), or “ “A or less and B or more” (when A> B).
Moreover, a mass part and mass% are synonymous with a weight part and weight%, respectively.

(Rubber composition)
The rubber composition of the present invention is disposed at both ends of a linear molecule, a cyclic molecule that includes the linear molecule in a skewered manner, and prevents the elimination of the cyclic molecule. It contains a polyrotaxane having a sealing group and a diene rubber, and the cyclic molecule has a mercapto group.

In Patent Document 1, it is necessary to blend a special polymer called diene rubber having a modifying group capable of reacting with an isocyanato group.
As a result of intensive studies, the present inventors can achieve a chemical bond with the main chain of the diene rubber by introducing a mercapto group into the cyclic molecule of the polyrotaxane, even if a general-purpose diene rubber is used. It has been found that versatility is dramatically improved, and the present invention has been completed.
The mechanism by which the above effect is obtained is unknown, but a part is estimated as follows.
The mercapto group introduced into the polyrotaxane cyclic molecule reacts with the ethylenically unsaturated bond of the diene rubber, thereby chemically bonding the polyrotaxane and the diene rubber, thereby stably bonding the polyrotaxane to the diene rubber. It is thought that. In the vulcanized rubber composition obtained from such a rubber composition, the cyclic molecule of the polyrotaxane is mobile, and when stress is applied to the vulcanized rubber composition, the stress concentration is reduced, and as a result, It is presumed that durability, particularly destruction physical properties, has been improved.
In particular, in the present invention, the polyrotaxane and the diene rubber form a chemical bond by an ene-thiol reaction, so that the hydrolysis resistance is higher than when the polyrotaxane and the diene rubber are chemically bonded by a conventional urethane bond or the like. It is presumed that a rubber composition excellent in weather resistance and weather resistance was obtained.

<Polyrotaxane>
The rubber composition of the present invention has a polyrotaxane, and the polyrotaxane is disposed at both ends of the linear molecule, a cyclic molecule that includes the linear molecule in a skewered manner, A sealing group that prevents the elimination of the cyclic molecule, and the cyclic molecule has a mercapto group.

(Cyclic molecule)
The cyclic molecule is not particularly limited as long as it is a molecule in which a linear molecule is included in a skewered manner in the opening and has a mercapto group (—SH).
Examples of cyclic molecules include cyclodextrins such as α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, crown ethers, benzocrowns, dibenzocrowns, dicyclohexanocrowns, cyclophanes, calixarenes And cucurbiturils, pillar arenes, cyclic amides and the like.
Among these, cyclodextrins are preferable.
The cyclic molecule may be modified. It is preferable that a part or all of the hydroxyl group of the cyclic molecule is modified. When the cyclic molecule is a cyclodextrin, the hydroxyl group bonded to the carbon atom at the 6-position is preferably modified.
The cyclic molecule may be modified with a nonionic group, and a nonionic group for modifying a cyclic molecule and a method for modifying the nonionic group are described in International Publication No. 2005-080469. Further, the cyclic molecule may be a polymer derived from a lactone monomer and / or a cyclic carbonate monomer, and for example, see JP-A-2014-224270.
A cyclic molecule may be used individually by 1 type and may use 2 or more types together.

The average number of mercapto groups contained in one cyclic molecule (one cyclic molecule) is preferably 3 or less, more preferably 2.5 or less, still more preferably 2 or less, and 1.5 More preferably, it is as follows. Moreover, it is preferable that the average number of mercapto groups which one cyclic molecule has is 0.5 or more.
When the average number of mercapto groups in the cyclic molecule is within the above range, the formation of crosslinks with the diene rubber is controlled within an appropriate range, and the performance of the polyrotaxane is sufficiently exhibited, resulting in high durability. Therefore, it is preferable.
Here, for example, when the cyclic molecule is α-cyclodextrin and a mercapto group is introduced into this, the hydroxyl group bonded to the 6-position of α-cyclodextrin or the terminal of the substituent is substituted with a mercapto group, or A mercapto group is introduced into the hydroxyl group of the cyclic molecule via a linking group. In the present invention, the number of mercapto groups introduced into one hydroxyl group is preferably one.
That is, when a mercapto group is introduced via a linking group, it is preferable that there is one mercapto group bonded to the linking group.

The mercapto group concentration of the polyrotaxane is preferably 0.001 to 0.7 mmol / g, more preferably 0.002 to 0.4 mmol / g, and 0.005 to 0.2 mmol / g. Is more preferable.
When the concentration of the mercapto group in the polyrotaxane is within the above range, the reactivity with the diene rubber is controlled to an appropriate range, the performance of the polyrotaxane is sufficiently exhibited, and as a result, high mechanical properties are obtained.

The method for introducing a mercapto group into the cyclic molecule of polyrotaxane is not particularly limited, and may be appropriately selected from known methods.
When cyclodextrins are used as the cyclic molecule, for example, the bromine atom is replaced with a mercapto group by replacing the hydroxyl group of the cyclodextrin with a bromine atom by hydrogen bromide and reacting it with sodium hydrogen sulfide. A mercapto group can be introduced into cyclodextrins by substitution.
In the case of using cyclodextrins as the cyclic molecule, a compound having at least one mercapto group and having at least one group having reactivity with the alcoholic hydroxyl group of the cyclodextrins is added to the cyclodextrin. A cyclic molecule having a mercapto group can be obtained by reacting with an alcoholic hydroxyl group of dextrins.
As such a compound, a silane coupling agent having a mercapto group is preferable, and specific examples thereof include compounds represented by the following formula (I) or formula (II).

(In Formula (I) and Formula (II), R ¹ , R ² , and R ³ each independently represent —O—C _j H _{2j + 1} , — (OC _k H _2k −) _a —OC _m H _{2m + 1} and — A group selected from the group consisting of C _n H _{2n + 1} , j, m, and k each independently represent an integer of 0-30, k and a are each independently an integer of 1-12, At least one selected from the group consisting of R ¹ , R ² and R ³ represents —O—C _j H _{2j + 1} , or — (OC _k H _2k −) _a —OC _m H _{2m + 1} , and R ⁴ represents C1-C12 linear, branched or cyclic, saturated or unsaturated, alkylene, cycloalkylene, cycloalkylalkylene, cycloalkenylalkylene, alkenylene, cycloalkenylene, cycloalkyl Rukeniren group, a group selected from cycloalkenyl alkenylene group, an arylene group and an aralkylene group, W is ^-NR 8 -, - O-and ^-CR 9 ^{R 10} - (wherein, ^{R 8} and ^{R 9} is -C _p H _{2p + 1} , R ¹⁰ is —C _q H _{2q + 1} , p and q are each independently 0 to 20, and R ⁵ and R ⁶ are each independently _{-M-C r H 2r} - (wherein, M is -O- or -CH ₂ -, r is 1 to 20.) is represented by, ^{R 7} is _{-O-C j H 2j + 1} , - (O—C _k H _2k −) _a —O—C _m H _{2m + 1} and —C _n H _{2n + 1} are groups selected, j, m and n are each independently 0 to 12, k and a Are each independently 1-12.

In formula (I), at least one of R ¹ , R ² and R ³ is preferably — (O—C _k H _2k —) _a —O—C _m H _{2m + 1} .
Examples of the compound represented by the formula (I) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, (mercaptomethyl) dimethylethoxysilane, and (mercaptomethyl). Examples thereof include dimethylethoxysilane and mercaptomethyltrimethoxysilane.
Examples of the compound represented by the above formula (II) include 3-mercaptopropyl (ethoxy) -1,3-dioxa-6-methylaza-2-silacyclooctane, 3-mercaptopropyl (ethoxy) -1, Examples include 3-dioxa-6-butylaza-2-silacyclooctane and 3-mercaptopropyl (ethoxy) -1,3-dioxa-6-dodecylaza-2-silacyclooctane.
In addition, you may use individually by 1 type and may use 2 or more types together.
Among these, 3-mercaptopropylmethyldimethoxysilane, (mercaptomethyl) dimethylethoxysilane, 3-mercaptopropyl (ethoxy) -1,3-dioxa-6-methylaza-2-silacyclooctane are preferable, and (mercaptomethyl) Dimethylethoxysilane and 3-mercaptopropylmethyldimethoxysilane are more preferable.

In addition, for example, a compound having an isocyanato group and an ethylenically unsaturated group is reacted with a hydroxyl group of a cyclic molecule to introduce an ethylenically unsaturated group into the cyclic molecule, and then reacted with a dithiol compound to form a cyclic compound. A method for introducing a mercapto group into the molecule is also exemplified. Examples of the compound having an isocyanato group and an ethylenically unsaturated group include 2-isocyanatoethyl (meth) acrylate, and examples of the dithiol compound include benzenedithiol, 4,4′-biphenyldithiol, ethanedithiol, and propane. Examples include dithiol, butanedithiol, pentanedithiol, hexanedithiol, heptanedithiol, octanedithiol, nonanedithiol, decanedithiol, and the like.
Moreover, for example, a method of introducing a mercapto group into a cyclic molecule by reacting dihydrolipoic acid with a hydroxyl group of the cyclic molecule is also exemplified.
Further, after introducing a carboxylic acid into a cyclic molecule to produce a carboxy-modified polyrotaxane, a mercapto group is introduced by reacting a carbodiimide compound with a compound having a mercapto group such as cysteamine and an amino group as a dehydrating condensing agent. Are also illustrated.

(Linear molecule)
The linear molecule of the polyrotaxane is not particularly limited as long as it can be included in a skewered manner in the opening of the cyclic molecule.
As linear molecules, polyvinyl alcohol; polyvinyl pyrrolidone; poly (meth) acrylic acid; cellulose resin (carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc.); polyacrylamide; polyethylene oxide; polyethylene glycol; polypropylene glycol; Polyethylene; Polyethyleneimine; Casein, gelatin, starch, etc. and / or copolymers thereof; Polyolefin resins such as copolymers of polyethylene, polypropylene, and other olefinic monomers; Polyester resin; Polyvinyl chloride resin; Polystyrene resins such as polystyrene and acrylonitrile-styrene copolymer resin; Polymethyl methacrylate (Meth) acrylic acid ester copolymers such as carbonates, acrylic resins such as acrylonitrile-methyl acrylate copolymer resins; polycarbonate resins; polyurethane resins; vinyl chloride-vinyl acetate copolymer resins; polyvinyl butyral resins; Modified body: polyisobutylene; polytetrahydrofuran; polyaniline; acrylonitrile-butadiene-styrene copolymer (ABS resin), polyamides such as nylon; polydienes such as polyimides, polyisoprene and polyisobutadiene; poly such as polydimethylsiloxane Siloxanes, polysulfones, polyimines; polyacetic anhydrides, polyureas, polysulfides; polyphosphazenes, polyketones, polyphenylenes, polyhaloolefins, and these Derivatives are exemplified.
Among these, it is preferable to be selected from the group consisting of polyethylene glycol, polyisoprene, polyisobutylene, polybutadiene, polypropylene glycol, polytetrahydrofuran, polydimethylsiloxane, polyethylene, polypropylene, polyvinyl alcohol, and polyvinyl methyl ether. More preferably.

The weight average molecular weight of the linear molecule is preferably 3,000 or more, more preferably 5,000 to 100,000, and still more preferably 10,000 to 50,000. It is preferable that the weight average molecular weight of the linear molecule is within the above range because the molecular weight is sufficient to allow the cyclic molecule to move.
In the present invention, the weight average molecular weight is a value measured by GPC (gel permeation chromatography) and calculated using polystyrene as a calibration curve.

(Sealing group)
The sealing group is not particularly limited as long as it is a group that is arranged at both ends of the linear molecule and acts so that the cyclic molecule is not detached.
Examples of the sealing group include dinitrophenyl groups, cyclodextrins, adamantyl groups, trityl groups, fluoresceins, silsesquioxanes, pyrenes, substituted benzenes (alkyl groups, alkyloxys as substituents). Group, hydroxy group, halogen atom, cyano group, sulfonyl group, carboxyl group, amino group, phenyl group, etc., but not limited to them, one or more substituents may be present). Polynuclear aromatics that may be substituted (substituents include, but are not limited to, the same as those described above. One or more substituents may be present), and steroids Preferably it is selected from the group. Among these, it is more preferably selected from the group consisting of dinitrophenyl groups, cyclodextrins, adamantyl groups, trityl groups, fluoresceins, silsesquioxanes, and pyrenes, adamantyl groups or trityl More preferred are groups, and particularly preferred are adamantyl groups. In addition, as for said sealing group, one or several hydrogen atoms may be substituted, and the substituent mentioned above is illustrated as a substituent.

  The weight average molecular weight of the polyrotaxane is preferably 20,000 to 10,000,000, more preferably 50,000 to 3,000,000, from the viewpoint of obtaining a rubber composition having good durability. Preferably, it is 100,000-2,000,000.

In the present invention, the inclusion rate of the polyrotaxane is preferably 0.01 to 0.5, more preferably 0.05 to 0.3, and still more preferably from the viewpoint of improving the durability of the rubber composition. Is 0.1-0.25.
In the present invention, the inclusion rate refers to the number of cyclic molecules included in the linear molecule when the cyclic molecule is skewered into the linear molecule. This is a value relative to the reference value when the maximum number of inclusions (calculated value) is 1 (reference value). The number of cyclic molecules in the polyrotaxane can be measured by NMR or the like. Further, the maximum inclusion amount of the cyclic molecule can be determined by the length of the linear molecule and the thickness of the cyclic molecule. Reference is made to Macromolecules 1993, 26, 5698-5703.

A polyrotaxane may be used individually by 1 type and may use 2 or more types together.
In the present invention, a polyrotaxane in which the cyclic molecule has a mercapto group may be used together with the polyrotaxane in which the cyclic molecule has a mercapto group, but the content of the polyrotaxane in which the cyclic molecule has a mercapto group is 50% of the total polyrotaxane. It is preferably at least 70% by mass, more preferably at least 70% by mass, even more preferably at least 80% by mass, particularly preferably at least 90% by mass, and substantially the total amount of polyrotaxane is Most preferably, the cyclic molecule is a polyrotaxane having a mercapto group. Note that substantially all of the polyrotaxane is a polyrotaxane in which the cyclic molecule has a mercapto group. The polyrotaxane in which the cyclic molecule does not have a mercapto group is intentionally added and the polyrotaxane in which the cyclic molecule has a mercapto group is contained. It means that the amount is 98% by mass or more, preferably 99% by mass or more of the whole polyrotaxane.

  The content of the polyrotaxane in the rubber composition of the present invention is preferably 0.1 to 30% by mass with respect to the total mass of the diene rubber described later from the viewpoint of obtaining a rubber composition having excellent durability. More preferably, it is 0.2-20 mass%, More preferably, it is 0.5-15 mass%.

<Diene rubber>
The rubber composition of the present invention contains a diene rubber. As the diene rubber, either natural rubber or synthetic diene rubber may be used.
Synthetic diene rubbers include styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR), ethylene-propylene-diene terpolymer rubber (EPDM). Examples thereof include acrylonitrile-butadiene copolymer rubber (NBR), ethylene-butadiene copolymer rubber, propylene-butadiene copolymer rubber, and halogenated butyl rubber.
Among these, as the diene rubber, styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), and acrylonitrile-butadiene copolymer rubber (NBR) are preferable. More preferred are copolymer rubber (SBR), polybutadiene rubber (BR), and acrylonitrile-butadiene copolymer rubber (NBR), and styrene-butadiene copolymer rubber (SBR) and acrylonitrile-butadiene copolymer rubber (NBR). Further preferred.
A diene rubber may be used individually by 1 type, and may use 2 or more types together.

  In the present invention, the diene rubber may be modified, but is preferably an unmodified diene rubber. Unmodified diene rubber is preferred because of its high versatility and availability at low cost.

<Other ingredients>
In the present invention, the rubber composition may contain other components in addition to the above components. Other ingredients include fillers, vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, vulcanization retarders, anti-aging agents, process oils, silane coupling agents, zinc white (zinc oxide), and antioxidants. Additives usually used in the rubber industry such as an agent, an ozone degradation inhibitor, and a foaming agent may be appropriately selected and blended within a range not inhibiting the effect of the present invention.

(Filler)
The rubber composition of the present invention preferably contains a filler. Examples of the filler include silica, carbon black, white carbon, activated calcium carbonate, and ultrafine magnesium silicate. Among these, silica or carbon black is preferable.
A filler may be used individually by 1 type and may use 2 or more types together.
The content of the filler in the rubber composition of the present invention is preferably 5 to 200 parts by mass and more preferably 10 to 100 parts by mass with respect to 100 parts by mass of the diene rubber.

  In the present invention, the carbon black used as the filler is not particularly limited, and those of FEF, SRF, HAF, ISAF, SAF grade and the like can be used. By blending carbon black, various physical properties of the rubber composition can be improved, but those of HAF, ISAF, and SAF grades are preferable from the viewpoint of improving wear resistance.

  The silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. Among these, a rubber composition having excellent durability is obtained. Therefore, wet silica is preferable.

(Silane coupling agent)
When silica is used as the filler, it is preferable to add a silane coupling agent from the viewpoint of further improving the reinforcement.
The silane coupling agent may have both a functional group that gives a silanol group when hydrolyzed and a functional group that can achieve chemical bonding by sulfur crosslinking with the main chain of the diene elastomer during the vulcanization reaction. Bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2- Mercaptoethyltrie Xisilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl Tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-di Ethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthioca Vamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazole tetrasulfide, and the like. Among these, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3- Triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and mixtures thereof are preferred. These silane coupling agents may be used alone or in combination of two or more.

(Vulcanizing agent)
The rubber composition of the present invention may contain a vulcanizing agent. Examples of the vulcanizing agent include sulfur. In addition, a vulcanizing agent means vulcanizing agents other than the polyrotaxane in which the above-mentioned cyclic molecule has a mercapto group.
In the present invention, since the polyrotaxane has a mercapto group and reacts with a diene rubber to form a crosslink, the content of sulfur atoms is compared with that of a conventional rubber composition in which sulfur is added as a vulcanizing agent. Can be reduced.
When sulfur is added as a vulcanizing agent, re-crosslinking occurs due to thermal degradation, and there is a problem that the modulus of elasticity (modulus) increases. However, in the present invention, crosslinking is performed without using sulfur as a vulcanizing agent. Can be obtained, and a rubber composition and a crosslinked rubber composition with little change with time can be obtained.

  The content of the vulcanizing agent (sulfur) is preferably less than 2.0 parts by mass and more preferably less than 1.8 parts by mass with respect to 100 parts by mass of the diene rubber.

(Vulcanization accelerator)
The rubber composition of the present invention preferably contains a vulcanization accelerator.
The vulcanization accelerator is not particularly limited, but 2-mercaptobenzothiazole (M), dibenzothiazyl disulfide (DM), N-cyclohexyl-2-benzothiazylsulfenamide (CZ), N Examples include thiazole vulcanization accelerators such as -t-butyl-2-benzothiazolylsulfenamide (NS), and guanidine vulcanization accelerators such as diphenylguanidine (DPG). The amount of the vulcanization accelerator used is preferably from 0.1 to 5 parts by weight, more preferably from 0.2 to 3 parts by weight, based on 100 parts by weight of the diene rubber. These vulcanization accelerators may be used alone or in combination of two or more.

(Vulcanization accelerator)
The rubber composition of the present invention may contain a vulcanization acceleration aid.
Specific examples of the vulcanization accelerator include stearic acid, palmitic acid, myristic acid, lauric acid, arachidic acid, behenic acid, lignoceric acid, capric acid, pelargonic acid, caprylic acid, enanthic acid, caproic acid, oleic acid, Organic acids including saturated fatty acids such as vaccenic acid, linoleic acid, linolenic acid, nervonic acid and unsaturated fatty acids, resin acids such as rosin acid and modified rosin acid, and esters of saturated fatty acids, unsaturated fatty acids and resin acids, etc. Can be mentioned.
Here, when a styrene-butadiene copolymer or natural rubber obtained by emulsion polymerization is used as the diene rubber, rosin acid (including modified rosin acid) and fatty acid contained in these raw materials are vulcanized. Accelerating aid). Since the emulsifier usually contains rosin acid and the like, the styrene-butadiene copolymer obtained by emulsion polymerization also contains rosin acid and the natural rubber usually contains a small amount of fatty acid.

(Process oil)
In the rubber composition of the invention, a process oil or the like can be used as a softening agent, and examples of the process oil include paraffinic oil, naphthenic oil, and aromatic oil. Among these, aromatic oils are preferable from the viewpoint of tensile strength and wear resistance, and naphthenic oils and paraffinic oils are preferable from the viewpoint of hysteresis loss and low-temperature characteristics. The amount of these process oils used is preferably 100 parts by mass or less and more preferably 30 parts by mass or less with respect to 100 parts by mass of the diene rubber. When the amount of the process oil used is 100 parts by mass or less with respect to 100 parts by mass of the diene rubber, the durability of the vulcanized rubber is favorable and preferable.

[Crosslinked rubber composition]
A crosslinked rubber composition can be obtained by crosslinking the rubber composition of the present invention. The crosslinking conditions are not particularly limited and may be appropriately selected depending on the intended purpose. However, the temperature is preferably 120 to 200 ° C. and the heating time is 1 minute to 900 minutes.

[tire]
The tire of the present invention is not particularly limited as long as the rubber composition of the present invention is used, and can be appropriately selected according to the purpose. Such a tire is excellent in durability since the rubber composition of the present invention is used. The application site of the rubber composition of the present invention in a tire is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include tread, base tread, sidewall, side reinforcing rubber, and bead filler. . Among these, it is advantageous from the viewpoint of durability to use the rubber composition of the present invention for a tread.
As a method for manufacturing the tire, a conventional method can be used. For example, on a tire molding drum, members usually used for manufacturing a tire such as a carcass layer, a belt layer, a tread layer, and the like made of at least one selected from the group consisting of an unvulcanized rubber composition and a cord are sequentially laminated. Pull out the drum to make a green tire. Then, a desired tire (for example, a pneumatic tire) can be manufactured by heating and vulcanizing the green tire according to a conventional method.

[Applications other than tires]
The rubber composition of the present invention can be used for a vibration-proof rubber, a seismic isolation rubber, a belt such as a conveyor belt, a rubber crawler, various hoses, etc. in addition to a tire application.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

[Production Example 1 of polyrotaxane having a mercapto group]
10 ml of a toluene solution of 2.0 mg (0.011 mmol) of 3-mercaptopropylmethyldimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to a polyrotaxane (SH3400P, manufactured by Advanced Soft Materials, Inc., molecular weight of linear molecule: 3 50,000, total molecular weight: 700,000, hydroxyl value: 72 mg KOH / g) In addition to 5.0 ml of toluene solution, the reaction was carried out at 100 ° C. for 1 hour under basic conditions, and a polyrotaxane having a mercapto group (hereinafter, polyrotaxane- 1) was obtained.

[Production Example 2 of polyrotaxane having a mercapto group]
A mercapto group-containing polyrotaxane into which a mercapto group was introduced (hereinafter referred to as polyrotaxane-2) was obtained in the same manner as in Production Example 1 except that the addition amount was changed to 11.5 mg (0.064 mmol) in Production Example 1. It was.

[Production Example 3 of polyrotaxane having a mercapto group]
In the above Production Example 1, a mercapto group-containing polyrotaxane having a mercapto group introduced (hereinafter, polyrotaxane-3) was produced in the same manner as in Production Example 1 except that the addition amount was changed to the following 38.5 mg (0.21 mmol). Got.

[Production Example 4 of polyrotaxane having a mercapto group]
A polyrotaxane having 5.00 g of 1,4-polybutadiene having a number average molecular weight of 3,000 as a skeleton, α-cyclodextrin as a cyclic component, and an inclusion rate of 5%, and 0.09 g / mL of lithium chloride Dispersed in 30 mL of dehydrated N, N-dimethylformamide. 100 mg of 4-dimethylaminopyridine and 2.0 mL of dehydrated pyridine were added to the resulting suspension, and finally 2.5 g of succinic anhydride was added. The reaction mixture was stirred at room temperature overnight, 120 mL of ion exchange water was added, and dialysis was performed with a dialysis membrane having a molecular weight cutoff of 3,500 for 2 days. The obtained solution was freeze-dried to obtain 3.65 g of a carboxyl-modified polyrotaxane.
Next, 2.00 g of the obtained carboxyl-modified polyrotaxane was dispersed in 20 mL of dehydrated N, N-dimethylformamide containing 0.09 g / mL of lithium chloride to give 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide. 1.50 g, 1.00 g of N-hydroxysuccinimide and 2.50 g of cysteamine were added and stirred overnight at room temperature. Thereafter, 80 mL of ion-exchanged water was added, and dialysis was performed for 2 days with a dialysis membrane having a fractional molecular weight of 3,500. The obtained solution was freeze-dried to obtain 1.70 g of a mercapto group-containing polyrotaxane (hereinafter, polyrotaxane-4).

In Table 1, the modifiers are as follows.
MPMDMS: 3-mercaptopropylmethyldimethoxysilane, manufactured by Tokyo Chemical Industry Co., Ltd.

[Preparation of rubber composition]
A rubber composition having a formulation shown in Table 2 was prepared by kneading with a plast mill. With respect to each prepared rubber composition, the tensile stress at break, the elongation at break, and the tensile strength were measured by the following methods. The results are shown in the table below.

Each component used in Table 2 is as follows.
(Diene rubber)
・ Tuffden 2000R: Solution polymerized styrene butadiene rubber (S-SBR), manufactured by Asahi Kasei Chemicals Corporation, trade name “Toughden 2000R”
(Polyrotaxane)
Polyrotaxane-1 to polyrotaxane-4: polyrotaxane having a mercapto group obtained by Production Examples 1 to 4 of a polyrotaxane having a mercapto group described above, unmodified polyrotaxane: polyrotaxane (molecular weight of linear molecule: 35,000 , Total molecular weight: 700,000, hydroxyl value: 72 mg KOH / g), manufactured by Advanced Soft Materials Co., Ltd., trade name “Celum Superpolymer SH3400P”
(Other)
Carbon black: manufactured by Tokai Carbon Co., Ltd., trade name 9H, DBP oil absorption = 130 ml / 100 g, N ₂ SA = 142 m ² / g
・ Oil: manufactured by Fuji Kosan Co., Ltd.
Anti-aging agent 6C: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (anti-aging agent), manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”
Accelerator CZ: N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ”
Accelerator TOT-N: Tetrakis (2-ethylhexyl) thiuram disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller TOT-N”

[Evaluation]
<Tensile stress at break, elongation at break, and tensile strength at 50% elongation>
For the vulcanized rubber obtained by vulcanizing each rubber composition at 145 ° C. for 33 minutes, using a dumbbell-shaped No. 3 test piece in accordance with JIS K 6251: 2010 (No. 3 type test piece), Measurement was performed at 25 ° C., and the tensile stress at break (Tb), the elongation at break (Eb), and the tensile strength at 50% elongation (hereinafter also simply referred to as “tensile strength”) were measured.
In Table 2, Tb, Eb, and tensile strength are shown as indexes when the value of Comparative Example 1 is set to 100, and the larger the value, the better the fracture characteristics.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition from which rubber products, such as a tire excellent in durability, can be obtained can be provided. Moreover, according to the present invention, it is possible to provide rubber products such as tires having excellent durability.

Claims (8)

A polyrotaxane having a linear molecule, a cyclic molecule that includes the linear molecule in a skewered manner, and a blocking group that is disposed at both ends of the linear molecule and prevents the cyclic molecule from being removed, And a diene rubber,
The cyclic molecule has a mercapto group,
Rubber composition.   The rubber composition according to claim 1, wherein the average number of mercapto groups contained in one cyclic molecule is 2 or less.   The rubber composition according to claim 1 or 2, wherein the polyrotaxane has a mercapto group concentration of 0.001 to 0.7 mmol / g.   The rubber composition according to any one of claims 1 to 3, wherein the diene rubber is unmodified.   The rubber composition according to any one of claims 1 to 4, wherein the cyclic molecule is a cyclodextrin.   The rubber composition according to any one of claims 1 to 5, wherein the sealing group is an adamantyl group.   The rubber composition according to any one of claims 1 to 6, wherein the content of the polyrotaxane is 0.1 to 30% by mass with respect to the total mass of the diene rubber.   A tire using the rubber composition according to claim 1.