JP6708783B2 - Rubber composition for tires for ice and snow roads and studless tires - Google Patents

Description

The present invention relates to a rubber composition for tires for ice and snow roads and a studless tire.

From the viewpoint of improving vehicle safety, it is required to improve tire performance not only on a dry road surface but also on various road surfaces such as a wet road surface and an ice and snow road surface.

For example, the rubber compositions described in Patent Documents 1 to 3 have been proposed in order to improve the steering stability (snow performance) on a snowy and snowy road surface. Patent Document 1 contains a specific amount of a diene rubber mainly composed of natural rubber and/or butadiene rubber, carbon black and silica having a nitrogen adsorption specific surface area of 90 m ² /g or more, and ultra-high molecular weight polyethylene. A rubber composition is described. Patent Document 2 discloses a rubber composition containing specific amounts of a rubber component containing 50% by mass or more of natural rubber, a thermoplastic resin, a filler containing silica, a vulcanization accelerator, a silane coupling agent, and a vulcanizing agent. Have been described. In Patent Document 3, a specific amount of myrcene resin, silica having a nitrogen adsorption specific surface area of 40 to 400 m ² /g or more, and a silica coupling agent are kneaded, and the obtained masterbatch is kneaded with a rubber component. The rubber composition thus obtained is described.

According to the inventions described in these Patent Documents 1 to 3, the snow performance of the rubber composition can be improved, and as a result, a tire having excellent snow performance can be obtained.

However, these rubber compositions of Patent Documents 1 to 5 have not been sufficiently effective in reducing the heat buildup of the tire.

Japanese Patent Laid-Open No. 2006-241338 Japanese Patent Publication No. 2016-222871 Japanese Patent Laid-Open No. 2016-3266

An object of the present invention is to provide a rubber composition for tires for ice and snow roads, which can exhibit excellent low heat buildup while maintaining snow performance.

Another object of the present invention is to provide a studless tire that maintains snow performance and is excellent in low heat buildup.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by mixing a diene rubber and a specific tetrazine compound. The present inventors have completed the present invention as a result of further studies based on such findings.

The present invention provides the following rubber composition for tires for ice and snow roads and a studless tire.
Item 1.
Diene rubber and the following general formula (1):

[In the formula, X ¹ and X ² represent a heterocyclic group which may have a substituent. ]
A rubber composition for a snowy road tire containing a tetrazine compound or a salt thereof represented by:
A rubber composition containing 0.1 to 10 parts by mass of the tetrazine compound or a salt thereof with respect to 100 parts by mass of a diene rubber.
Item 2.
Item 2. The rubber composition according to Item 1, further containing an inorganic filler and/or carbon black.
Item 3.
Item 3. The rubber composition according to Item 2, wherein the total amount of the inorganic filler and/or carbon black is 30 to 130 parts by mass with respect to 100 parts by mass of the diene rubber.
Item 4.
Item 4. The rubber composition according to Item 2 or 3, wherein the inorganic filler is silica.
Item 5.
Item 5. The rubber composition according to any one of Items 1 to 4, which is used in the tread portion.
Item 6.
Item 12. A tread for tires for ice and snow roads, which is produced using the rubber composition according to any one of items 1 to 4.
Item 7.
Item 10. A studless tire produced using the tread for tires for ice and snow roads according to Item 6.

According to the present invention, by combining a diene rubber and a tetrazine compound represented by the general formula (1) or a salt thereof, a rubber composition capable of exhibiting excellent low heat buildup while maintaining snow performance. Can be provided.

Further, by producing a studless tire using the rubber composition of the present invention, it is possible to maintain the snow performance of the tire and further reduce the heat generation property of the tire, and thus a studless suitable for running on ice and snow roads. Tires can be provided.

The present invention will be described in detail below.

1. Ice and snow for the rubber composition for a tire invention, diene rubber, and the following general formula (1):

[In the formula, X ¹ and X ² represent a heterocyclic group which may have a substituent. ]
A rubber composition for a tire for ice and snow roads, comprising a tetrazine compound represented by or a salt thereof (hereinafter, also referred to as “tetrazine compound (1)”),
A rubber composition containing 0.1 to 10 parts by mass of the tetrazine compound or a salt thereof with respect to 100 parts by mass of a diene rubber.

Diene rubber The rubber component blended in the rubber composition of the present invention is a diene rubber. Examples of the diene rubber include natural rubber (NR), synthetic diene rubber, and a mixture of natural rubber and synthetic diene rubber. When the rubber component is a diene rubber, it is possible to obtain a rubber composition excellent in low heat buildup. The rubber composition of the present invention contains only a diene rubber as a rubber component, but it is inevitable that a rubber other than the diene rubber, for example, a non-diene rubber is unavoidably contained as an impurity.

Examples of natural rubber include natural rubber latex, technically graded rubber (TSR), smoked sheet (RSS), gutta percha, natural rubber derived from Tochu, natural rubber derived from guayule, natural rubber derived from dandelion, fermented rubber derived from plant components, and the like. In addition, modified natural rubber such as epoxidized natural rubber, methacrylic acid modified natural rubber, and styrene modified natural rubber can be used.

Examples of the synthetic diene rubber include styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene-propylene-diene ternary copolymer. Examples thereof include polymer rubber (EPDM), styrene-isoprene-styrene ternary block copolymer (SIS), styrene-butadiene-styrene ternary block copolymer (SBS), and modified synthetic diene rubbers thereof. Examples of the modified synthetic diene rubber include a diene rubber obtained by a modification method such as main chain modification, one-end modification, and both-end modification. Here, the modified functional group of the modified synthetic diene rubber includes at least one kind of functional group containing a hetero atom such as epoxy group, amino group, alkoxy group, hydroxyl group, alkoxysilyl group, polyether group, and carboxyl group. There are things. Further, the ratio of cis/trans/vinyl in the diene moiety is not particularly limited, and any ratio can be preferably used. The average molecular weight and the molecular weight distribution of the diene rubber are not particularly limited, and the average molecular weight of 5 to 3,000,000 and the molecular weight distribution of 1.5 to 15 are preferable. Also, the method for producing the synthetic diene rubber is not particularly limited, and examples thereof include those synthesized by emulsion polymerization, solution polymerization, radical polymerization, anion polymerization, cation polymerization and the like.

The butyl rubber is a copolymer of isobutylene and a small amount of isoprene rubber and contains 3 mol% or less of double bonds, but is not included in the diene rubber in the present specification.

Regarding the glass transition point of the diene rubber, a glass transition point in the range of -120°C to -15°C is effective from the viewpoint of achieving both low heat buildup and snow performance. In the rubber composition of the present invention, 50% by mass or more of the diene rubber is preferably a diene rubber having a glass transition point in the range of -70°C to -20°C.

The diene rubbers can be used alone or as a mixture (blend) of two or more. Among them, preferable diene rubber is natural rubber, IR, SBR, BR, or a mixture of two or more selected from these. The blending ratio of these is not particularly limited, and it is preferable that 100 parts by mass of the diene rubber be blended with natural rubber, SBR, BR or a mixture thereof at a ratio of 70 to 100 parts by mass, and 75 to 100 parts by mass. It is more preferable to blend in parts by mass. When blending a mixture of natural rubber, SBR and BR, the total amount of natural rubber, SBR and BR is preferably within the above range.

Tetrazine compound (1)
The rubber composition of the present invention contains a compound represented by the following general formula (1) or a salt thereof.
General formula 1:

[In the formula, X ¹ and X ² represent a heterocyclic group which may have a substituent. ]

In the present specification, the "heterocyclic group" is not particularly limited, and includes, for example, 2-pyridyl group, 3-pyridyl group, 4-pyridyl group, 2-pyrazinyl group, 2-pyrimidyl group, 4-pyrimidyl group, 5-pyrimidyl group, 3-pyridazyl group, 4-pyridazyl group, 4-(1,2,3-triazyl) group, 5-(1,2,3-triazyl) group, 2-(1,3,5- Triazyl) group, 3-(1,2,4-triazyl) group, 5-(1,2,4-triazyl) group, 6-(1,2,4-triazyl) group, 2-quinolyl group, 3- Quinolyl group, 4-quinolyl group, 5-quinolyl group, 6-quinolyl group, 7-quinolyl group, 8-quinolyl group, 1-isoquinolyl group, 3-isoquinolyl group, 4-isoquinolyl group, 5-isoquinolyl group, 6- Isoquinolyl group, 7-isoquinolyl group, 8-isoquinolyl group, 2-quinoxalyl group, 3-quinoxalyl group, 5-quinoxalyl group, 6-quinoxalyl group, 7-quinoxalyl group, 8-quinoxalyl group, 3-cinnolyl group, 4- Cinnolyl group, 5-cinnolyl group, 6-cinnolyl group, 7-cinnolyl group, 8-cinnolyl group, 2-quinazolyl group, 4-quinazolyl group, 5-quinazolyl group, 6-quinazolyl group, 7-quinazolyl group, 8- Quinazolyl group, 1-phthalazyl group, 4-phthalazyl group, 5-phthalazyl group, 6-phthalazyl group, 7-phthalazyl group, 8-phthalazyl group, 1-tetrahydroquinolyl group, 2-tetrahydroquinolyl group, 3-tetrahydro Quinolyl group, 4-tetrahydroquinolyl group, 5-tetrahydroquinolyl group, 6-tetrahydroquinolyl group, 7-tetrahydroquinolyl group, 8-tetrahydroquinolyl group, 1-pyrrolyl group, 2-pyrrolyl group, 3 -Pyrrolyl group, 2-furyl group, 3-furyl group, 2-thienyl group, 3-thienyl group, 1-imidazolyl group, 2-imidazolyl group, 4-imidazolyl group, 5-imidazolyl group, 1-pyrazolyl group, 3 -Pyrazolyl group, 4-pyrazolyl group, 5-pyrazolyl group, 2-oxazolyl group, 4-oxazolyl group, 5-oxazolyl group, 2-thiazolyl group, 4-thiazolyl group, 5-thiazolyl group, 3-isoxazolyl group, 4 -Isoxazolyl group, 5-isoxazolyl group, 3-isothiazolyl group, 4-isothiazolyl group, 5-isothiazolyl group, 4-(1,2,3-thiadiazolyl) group, 5-(1,2,3-thiadiazolyl) group, 3-(1,2,5-thiadiazolyl) group, 2-(1,3,4-thiadiazolyl) Group), 4-(1,2,3-oxadiazolyl) group, 5-(1,2,3-oxadiazolyl) group, 3-(1,2,4-oxadiazolyl) group, 5-(1,2,2) 4-oxadiazolyl) group, 3-(1,2,5-oxadiazolyl) group, 2-(1,3,4-oxadiazolyl) group, 1-(1,2,3-triazolyl) group, 4-(1, 2,3-triazolyl) group, 5-(1,2,3-triazolyl) group, 1-(1,2,4-triazolyl) group, 3-(1,2,4-triazolyl) group, 5-( 1,2,4-triazolyl) group, 1-tetrazolyl group, 5-tetrazolyl group, 1-indolyl, 2-indolyl group, 3-indolyl group, 4-indolyl group, 5-indolyl group, 6-indolyl group, 7 -Indolyl group, 1-isoindolyl group, 2-isoindolyl group, 3-isoindolyl group, 4-isoindolyl group, 5-isoindolyl group, 6-isoindolyl group, 7-isoindolyl group, 1-benzimidazolyl group, 2-benzimidazolyl group, 4 -Benzimidazolyl group, 5-benzimidazolyl group, 6-benzimidazolyl group, 7-benzimidazolyl group, 2-benzofuranyl group, 3-benzofuranyl group, 4-benzofuranyl group, 5-benzofuranyl group, 6-benzofuranyl group, 7-benzofuranyl group, 1 -Isobenzofuranyl group, 3-isobenzofuranyl group, 4-isobenzofuranyl group, 5-isobenzofuranyl group, 6-isobenzofuranyl group, 7-isobenzofurnyl group, 2-benzothienyl group, 3-benzothienyl group, 4-benzothienyl group, 5-benzothienyl group, 6-benzothienyl group, 7-benzothienyl group, 2-benzoxazolyl group, 4-benzoxazolyl group, 5-benzoxa Zolyl group, 6-benzoxazolyl group, 7-benzoxazolyl group, 2-benzothiazolyl group, 4-benzothiazolyl group, 5-benzothiazolyl group, 6-benzothiazolyl group, 7-benzothiazolyl group, 1-indazolyl group, 3-indazolyl group, 4-indazolyl group, 5-indazolyl group, 6-indazolyl group, 7-indazolyl group, 2-morpholyl group, 3-morpholyl group, 4-morpholyl group, 1-piperazyl group, 2-piperazyl group, 1-piperidyl group, 2-piperidyl group, 3-piperidyl group, 4-piperidyl group, 2-tetrahydropyranyl group, 3-tetrahydropyranyl group, 4-tetrahydropyranyl group, 2-tetrahydrothiopyranyl group Group, 3-tetrahydrothiopyranyl group, 4-tetrahydrothiopyranyl group, 1-pyrrolidyl group, 2-pyrrolidyl group, 3-pyrrolidyl group, 2-tetrahydrofuranyl group, 3-tetrahydrofuranyl group, 2-tetrahydrothienyl group , 3-tetrahydrothienyl group and the like. Among them, a preferable heterocyclic group is a pyridyl group, a furanyl group, a thienyl group, a pyrimidyl group or a pyrazyl group, and a pyridyl group is more preferable.

The heterocyclic group may have one or more substituents at substitutable positions. The substituent is not particularly limited, and examples thereof include a halogen atom, amino group, aminoalkyl group, alkoxycarbonyl group, acyl group, acyloxy group, amide group, carboxyl group, carboxyalkyl group, formyl group, nitrile group, nitro group. Examples thereof include a group, an alkyl group, a hydroxyalkyl group, a hydroxyl group, an alkoxy group, an aryl group, an aryloxy group, a heterocyclic group, a thiol group, an alkylthio group and an arylthio group. The substituent may have preferably 1 to 5, more preferably 1 to 3.

In the present specification, examples of the “halogen atom” include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, preferably a chlorine atom, a bromine atom and an iodine atom.

In the present specification, the “amino group” includes not only an amino group represented by —NH ₂ but also, for example, a methylamino group, an ethylamino group, an n-propylamino group, an isopropylamino group, an n-butylamino group. , Isobutylamino group, s-butylamino group, t-butylamino group, 1-ethylpropylamino group, n-pentylamino group, neopentylamino group, n-hexylamino group, isohexylamino group, 3-methylpentyl group A linear or branched monoalkylamino group having 1 to 6 carbon atoms (particularly 1 to 4 carbon atoms) such as amino group; 1 to 6 carbon atoms (particularly, dimethylamino group, ethylmethylamino group, diethylamino group) Substituted amino groups such as dialkylamino groups having two linear or branched alkyl groups having 1 to 4 carbon atoms are also included.

In the present specification, the "aminoalkyl group" is not particularly limited, and examples thereof include aminoalkyl groups such as aminomethyl group, 2-aminoethyl group, 3-aminopropyl group (preferably having an amino group having 1 carbon atom). ~6 straight-chain or branched alkyl groups).

In the present specification, the "alkoxycarbonyl group" is not particularly limited, and examples thereof include a methoxycarbonyl group and an ethoxycarbonyl group.

In the present specification, the “acyl group” is not particularly limited and includes, for example, a linear or branched alkylcarbonyl group having 1 to 4 carbon atoms such as acetyl group, propionyl group, pivaloyl group and the like.

In the present specification, the “acyloxy group” is not particularly limited, and examples thereof include an acetyloxy group, a propionyloxy group, an n-butyryloxy group and the like.

In the present specification, the "amide group" is not particularly limited, and examples thereof include carboxylic acid amide groups such as acetamide group and benzamide group; thioamide groups such as thioacetamide group and thiobenzamide group; N-methylacetamide group, N -N-substituted amide group such as benzylacetamide group; and the like.

In the present specification, the "carboxyalkyl group" is not particularly limited, and includes, for example, carboxymethyl group, carboxyethyl group, carboxy-n-propyl group, carboxy-n-butyl group, carboxy-n-pentyl group, carboxy. Examples thereof include a carboxy-alkyl group such as an -n-hexyl group (preferably an alkyl group having a carboxy group and having 1 to 6 carbon atoms).

In the present specification, the “alkyl group” is not particularly limited and includes, for example, a linear, branched or cyclic alkyl group, and specifically, for example, methyl group, ethyl group, n-propyl group. Group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, 1-ethylpropyl group, n-pentyl group, neopentyl group, n-hexyl group, isohexyl group, 3-methylpentyl group A linear or branched alkyl group having 1 to 6 carbon atoms (especially 1 to 4 carbon atoms); a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and the like having a carbon number of 3 to Examples thereof include cyclic alkyl groups having 8 (particularly 3 to 6 carbon atoms).

In the present specification, the “hydroxyalkyl group” is not particularly limited, and examples thereof include hydroxymethyl groups, hydroxyethyl groups, hydroxy-n-propyl groups, hydroxy-n-butyl groups, and other hydroxy-alkyl groups (preferably And an alkyl group having 1 to 6 carbon atoms having a hydroxy group).

In the present specification, the “alkoxy group” is not particularly limited and includes, for example, a linear, branched or cyclic alkoxy group, and specifically, for example, methoxy, ethoxy group, n-propoxy group. , Isopropoxy group, n-butoxy group, t-butoxy group, n-pentyloxy group, neopentyloxy group, n-hexyloxy group having 1 to 6 carbon atoms (especially 1 to 4 carbon atoms), or A branched alkoxy group; a cyclopropyloxy group, a cyclobutyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, and the like, having 3 to 8 carbon atoms (in particular, 3 to 6 carbon atoms) An alkoxy group etc. are mentioned.

In the present specification, the "aryl group" is not particularly limited, and examples thereof include a phenyl group, a biphenyl group, a naphthyl group, a dihydroindenyl group, a 9H-fluorenyl group and the like.

In the present specification, the “aryloxy group” is not particularly limited, and examples thereof include a phenoxy group, a biphenyloxy group and a naphthoxy group.

In the present specification, the “alkylthio group” is not particularly limited and includes, for example, a linear, branched or cyclic alkylthio group, and specifically, for example, methylthio group, ethylthio group, n-propylthio group. Group, isopropylthio group, n-butylthio group, isobutylthio group, s-butylthio group, t-butylthio group, 1-ethylpropylthio group, n-pentylthio group, neopentylthio group, n-hexylthio group, isohexylthio group Group, a linear or branched alkylthio group having 1 to 6 carbon atoms (in particular, 1 to 4 carbon atoms) such as 3-methylpentylthio group; cyclopropylthio group, cyclobutylthio group, cyclopentylthio group, cyclohexylthio group And a cyclic alkylthio group having 3 to 8 carbon atoms (in particular, 3 to 6 carbon atoms) such as a group, a cycloheptylthio group and a cyclooctylthio group.

In the present specification, the “arylthio group” is not particularly limited, and examples thereof include a phenylthio group, a biphenylthio group, a naphthylthio group and the like.

The “salt” of the tetrazine compound represented by the general formula (1) is not particularly limited and includes all kinds of salts. Examples of such salts include inorganic acid salts such as hydrochloride, sulfate and nitrate; organic acid salts such as acetate and methanesulfonate; alkali metal salts such as sodium salt and potassium salt; magnesium salt, calcium Examples thereof include alkaline earth metal salts such as salts; ammonium salts such as dimethylammonium and triethylammonium.

In the preferable tetrazine compound (1), X ¹ and X ² are the same or different and each have a pyridyl group which may have a substituent, a furanyl group which may have a substituent, and a substituent. The compound is a thienyl group which may be substituted, a pyrazolyl group which may be substituted, a pyrimidyl group which may be substituted, or a pyrazyl group which may be substituted.

In a more preferred tetrazine compound (1), X ¹ and X ² are the same or different and may have a 2-pyridyl group which may have a substituent, a 3-pyridyl group which may have a substituent, or a substituent. 4-pyridyl group which may have a group, 2-furanyl group which may have a substituent, 2-thienyl group which may have a substituent, and which may have a substituent A compound which is a 1-pyrazolyl group, a 2-pyrimidyl group which may have a substituent, or a 2-pyrazyl group which may have a substituent, and specifically has a substituent. A compound that is an optionally substituted 2-pyridyl group, an optionally substituted 3-pyridyl group, or an optionally substituted 2-furanyl group is particularly preferable.

Specific examples of the tetrazine compound (1) include:
3,6-bis(2-pyridyl)-1,2,4,5-tetrazine,
3,6-bis(3-pyridyl)-1,2,4,5-tetrazine,
3,6-bis(4-pyridyl)-1,2,4,5-tetrazine,
3,6-bis(2-furanyl)-1,2,4,5-tetrazine,
3,6-bis(3,5-dimethyl-1-pyrazolyl)-1,2,4,5-tetrazine,
3,6-bis(2-thienyl)-1,2,4,5-tetrazine,
3-methyl-6-(2-pyridyl)-1,2,4,5-tetrazine,
3,6-bis(2-pyrimidinyl)-1,2,4,5-tetrazine,
3,6-bis(2-pyrazyl)-1,2,4,5-tetrazine and the like can be mentioned.

Among them, preferred tetrazine compounds (1) are 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine and 3,6-bis(3-pyridyl)-1,2,4,5-tetrazine. Tetrazine, 3,6-bis(2-furanyl)-1,2,4,5-tetrazine, and 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine, and more preferable tetrazine. The compound (1) includes 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, 3,6-bis(3-pyridyl)-1,2,4,5-tetrazine, and 3 , 6-bis(4-pyridyl)-1,2,4,5-tetrazine.

The amount of the tetrazine compound (1) is usually 0.1 to 10 parts by mass, preferably 0.25 to 5 parts by mass, and more preferably 100 parts by mass of the diene rubber in the rubber composition. Is 0.5 to 2 parts by mass.

When the tetrazine compound (1) is a powder, its volume average diameter is not particularly limited. From the viewpoint of low heat buildup, the volume average diameter is preferably 300 μm or less, more preferably 150 μm or less, and particularly preferably 75 μm or less.

The volume average diameter can be obtained as a particle diameter corresponding to 50% of the cumulative distribution curve from the volume standard particle size distribution by using a particle size distribution measuring device such as a laser beam diffraction method.

Further, from the viewpoint of handling property during handling and risk of ignitability or explosiveness reduction, powder may be surface-treated with oil, resin, stearic acid or the like, or powder may be used such as calcium carbonate or silica. You may use it, mixing with the filler etc. of.

The rubber composition of the present invention preferably further contains an inorganic filler and/or carbon black in addition to the diene rubber and the tetrazine compound (1).

The compounding amount of the inorganic filler is usually 20 to 150 parts by mass, preferably 30 to 120 parts by mass, and more preferably 40 to 90 parts by mass with respect to 100 parts by mass of the diene rubber.

The blending amount of carbon black is usually 2 to 150 parts by mass, preferably 4 to 120 parts by mass, and more preferably 6 to 100 parts by mass with respect to 100 parts by mass of the diene rubber.

In the rubber composition of the present invention, the inorganic filler and/or carbon black is a total amount of both components, for example, usually 30 to 130 parts by mass, preferably 40 to 100 parts by mass with respect to 100 parts by mass of the diene rubber. It may be appropriately adjusted within the range of the above-mentioned compounding amount of each component so as to be 130 parts by mass, more preferably 45 to 100 parts by mass.

If the total amount of the inorganic filler and/or carbon black is 30 parts by mass or more, it is preferable from the viewpoint of improving the snow performance of the rubber composition, and if it is 130 parts by mass or less, it is preferable from the viewpoint of reducing rolling resistance. .. When blending the inorganic filler and/or carbon black, a masterbatch polymer preliminarily mixed with the polymer in a wet or dry manner may be used.

Inorganic Filler The inorganic filler is not particularly limited as long as it is an inorganic compound that is usually used in the rubber industry. Examples of inorganic compounds that can be used include alumina (Al ₂ O ₃ ) such as silica, γ-alumina, and α-alumina; alumina monohydrate (Al ₂ O ₃ .H ₂ O) such as boehmite and diaspore; gibbsite. , Aluminum hydroxide [Al(OH) ₃ ] such as bayerite; aluminum carbonate [Al ₂ (CO ₃ ) ₃ ], magnesium hydroxide [Mg(OH) ₂ ], magnesium oxide (MgO), magnesium carbonate (MgCO ₃ ). ), talc _{(3MgO · 4SiO 2 · H 2} O), attapulgite _{(5MgO · 8SiO 2 · 9H 2} O), titanium white _(TiO 2), titanium black _{(TiO 2n-1),} calcium oxide (CaO), hydroxide Calcium [Ca(OH) ₂ ], aluminum magnesium oxide (MgO·Al ₂ O ₃ ), clay (Al ₂ O ₃ ·2SiO ₂ ), kaolin (Al ₂ O ₃ ·2SiO ₂ ·2H ₂ O), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite _{(Al 2 O 3 · 4SiO 2} · 2H 2 O), aluminum silicate _{(Al 2 SiO 5, Al 4} · 3SiO 4 · 5H 2 O , etc.), Magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ ·SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ ·CaO·2SiO ₂ etc.), magnesium calcium silicate (CaMgSiO _{4 ).} ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO(OH) ₂ ·nH ₂ O], zirconium carbonate [Zr(CO ₃ ) ₂ ], and various zeolites to correct the charge. And a crystalline aluminosilicate containing an alkali metal or an alkaline earth metal. In these inorganic fillers, the surface of the inorganic filler may be organically treated in order to improve the affinity with the rubber component.

Silica is preferably added because it can impart rubber strength. Any commercially available silica can be used. Among them, preferable silica is wet silica, dry silica, or colloidal silica, more preferably wet silica. The surface of the inorganic filler of these silicas may be organically treated in order to improve the affinity with the rubber component.

Among them, silica is preferable as the inorganic filler from the viewpoint of snow performance, and the BET specific surface area of silica is not particularly limited, and examples thereof include a range of 40 to 350 m ² /g. Silica having a BET specific surface area within this range has an advantage that snow performance and dispersibility in a rubber component can both be achieved. The BET specific surface area is measured according to ISO 5794/1.

From this viewpoint, preferred silica is silica having a BET specific surface area of 50 to 250 m ² /g, more preferably silica having a BET specific surface area of 80 to 230 m ² /g, and particularly preferably. , BET specific surface area in the range of 100 to 210 m ² /g. Further, these silicas having different BET specific surface areas may be used in combination.

As commercial products of such silica, trade names “HD165MP” (BET specific surface area =165 m ² /g), “HD115MP” (BET specific surface area =115 m ² /g) manufactured by Quechen Silicon Chemical Co., Ltd., "HD200MP" (BET specific surface area = 200 m ² /g), "HD250MP" (BET specific surface area = 250 m ² /g), trade name "Nipseal AQ" manufactured by Tosoh Silica Corporation (BET specific surface area = 205 m ² /g) ), "Nipseal KQ" (BET specific surface area = 240 m ² /g), trade name "Ultrasil VN3" manufactured by Degussa (BET specific surface area = 175 m ² /g), trade name "Z1085Gr" manufactured by Solvay (BET). Specific surface area=90 m ² /g), “Z Premium 200MP” (BET specific surface area=215 m ² /g), “Z HRS 1200 MP” (BET specific surface area=200 m ² /g) and the like.

The amount of silica added is usually 20 to 120 parts by mass, preferably 30 to 100 parts by mass, and more preferably 40 to 90 parts by mass with respect to 100 parts by mass of the diene rubber.

Carbon black Carbon black is not particularly limited, and examples thereof include commercially available carbon black and Carbon-Silica Dual phase filler.

Specifically, examples of the carbon black include high, medium or low structure SAF, ISAF, IISAF, N110, N134, N220, N234, N330, N339, N375, N550, HAF, FEF, GPF, and SRF grade carbon. Examples include black. Among them, preferable carbon black is SAF, ISAF, IISAF, N134, N234, N330, N339, N375, HAF, or FEF grade carbon black.

The DBP absorption amount of carbon black is not particularly limited and is preferably 60 to 200 cm ³ /100 g, more preferably 70 to 180 cm ³ /100 g or more, and particularly preferably 80 to 160 cm ³ /100 g.

The nitrogen adsorption specific surface area of carbon black (N2SA, measured according to JIS K 6217-2:2001) is preferably 30 to 200 m ² /g, more preferably 40 to 180 m ² /g, and particularly preferably. It is 50 to 160 m ² /g.

By blending the tetrazine compound (1) in the rubber composition containing carbon black, the dispersibility of the carbon black is significantly improved, and the low heat buildup of the rubber composition can be significantly improved.

Other compounding agents In addition to the above tetrazine compound (1) and the inorganic filler and/or carbon black, other compounding agents commonly used in the rubber industry, such as sulfur, are added to the rubber composition of the present invention. A sulfurizing agent can be added. The rubber composition of the present invention may further contain other compounding agents such as antiaging agent, antiozonant, softening agent, processing aid, wax, resin, foaming agent, oil, stearic acid, zinc white (ZnO). A vulcanization accelerator, a vulcanization retarder or the like may be added. These compounding agents can be appropriately selected and compounded within a range not impairing the object of the present invention. Commercially available products can be preferably used as these compounding agents.

Further, in a rubber composition containing an inorganic filler such as silica, a silane coupling agent is used for the purpose of enhancing the reinforcing property of the rubber composition by silica, or for enhancing the abrasion resistance as well as the low heat generation property of the rubber composition. You may mix an agent.

The silane coupling agent that can be used in combination with the inorganic filler is not particularly limited, and commercially available products can be preferably used. Examples of such silane coupling agents include sulfide-based, polysulfide-based, thioester-based, thiol-based, olefin-based, epoxy-based, amino-based, and alkyl-based silane coupling agents.

Examples of the sulfide-based silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-methyldimethoxysilylpropyl)tetrasulfide, bis( 2-triethoxysilylethyl) tetrasulfide, bis(3-triethoxysilylpropyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(3-methyldimethoxysilylpropyl) disulfide, bis(2-triethoxysilyl) Ethyl) disulfide, bis(3-triethoxysilylpropyl) trisulfide, bis(3-trimethoxysilylpropyl) trisulfide, bis(3-methyldimethoxysilylpropyl) trisulfide, bis(2-triethoxysilylethyl)tri Sulfide, bis(3-monoethoxydimethylsilylpropyl) tetrasulfide, bis(3-monoethoxydimethylsilylpropyl) trisulfide, bis(3-monoethoxydimethylsilylpropyl) disulfide, bis(3-monomethoxydimethylsilylpropyl) Tetrasulfide, bis(3-monomethoxydimethylsilylpropyl) trisulfide, bis(3-monomethoxydimethylsilylpropyl) disulfide, bis(2-monoethoxydimethylsilylethyl) tetrasulfide, bis(2-monoethoxydimethylsilylethyl) ) Trisulfide, bis(2-monoethoxydimethylsilylethyl) disulfide and the like. Of these, bis(3-triethoxysilylpropyl) tetrasulfide is particularly preferable.

Examples of the thioester-based silane coupling agent include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, and 3-lauroylthiopropyltriethoxysilane. , 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2 -Decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane and the like can be mentioned.

Examples of the thiol-based silane coupling agent include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-[ethoxybis(3,6,9,12,15). -Pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol and the like.

Examples of the olefin-based silane coupling agent include dimethoxymethylvinylsilane, vinyltrimethoxysilane, dimethylethoxyvinylsilane, diethoxymethylvinylsilane, triethoxyvinylsilane, vinyltris(2-methoxyethoxy)silane, allyltrimethoxysilane, allyltrisilane. Ethoxysilane, p-styryltrimethoxysilane, 3-(dimethoxymethylsilyl)propyl acrylate, 3-(trimethoxysilyl)propyl acrylate, 3-[dimethoxy(methyl)silyl]propyl methacrylate, 3-(trimethoxysilyl)propyl Methacrylate, 3-[dimethoxy(methyl)silyl]propyl methacrylate, 3-(triethoxysilyl)propyl methacrylate, 3-[tris(trimethylsiloxy)silyl]propyl methacrylate and the like can be mentioned.

Examples of the epoxy-based silane coupling agent include 3-glycidyloxypropyl(dimethoxy)methylsilane, 3-glycidyloxypropyltrimethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and triethoxy(3-glycidyloxypropyl)silane. , 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and the like. Of these, 3-glycidyloxypropyltrimethoxysilane is preferable.

Examples of amino-based silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-aminopropyl. Trimethoxysilane, 3-aminopropyltriethoxysilane, 3-ethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)- 2-aminoethyl-3-aminopropyl trimethoxysilane etc. can be mentioned. Of these, 3-aminopropyltriethoxysilane is preferable.

Examples of the alkyl silane coupling agent include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, and isobutyltriethoxy. Examples thereof include silane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, and n-decyltrimethoxysilane. Of these, methyltriethoxysilane is preferred.

Among these silane coupling agents, bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, and 3-[ethoxybis(3,6,9,12,15-pentaoxaoctaoctane Cosan-1-yloxy)silyl]-1-propanethiol can be used particularly preferably.

In the present invention, the silane coupling agent may be used alone or in combination of two or more.

The compounding amount of the silane coupling agent of the rubber composition of the present invention is preferably 0.1 to 20 parts by mass, and particularly preferably 3 to 15 parts by mass with respect to 100 parts by mass of the inorganic filler. If it is 0.1 parts by mass or more, the effect of low heat build-up of the rubber composition can be exhibited more suitably, and if it is 20 parts by mass or less, the cost of the rubber composition is reduced and the economical efficiency is improved. Because it does.

Further, in a case where the braking characteristic is particularly emphasized, a resin or the like may be added. Specific examples thereof include natural resins such as rosin-based resins and terpene-based resins, petroleum-based resins, phenol-based resins, coal-based resins, and xylene-based resins. Examples of the rosin-based resin include gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, or modified rosin glycerin and pentaerythritol ester. Examples of the terpene-based resin include α-pinene-based, β-pinene-based, dipentene-based terpene resins, aromatic-modified terpene resins, terpene phenol resins, hydrogenated terpene resins, and the like.

Further, in the case where importance is attached to processability, as a processing aid, mineral oil, petrolatum, paraffin wax, petroleum resin, fatty acid, fatty acid ester, fatty alcohol, metal soap, fatty acid amide, phenol resin, polyethylene, polybutene, peptizer, Regenerating agents, organosiloxanes, etc. can be added.

Use of rubber composition The use of the rubber composition of the present invention is a tread for tires for ice and snow roads.

Production Method of Rubber Composition The production method of the rubber composition of the present invention is not particularly limited. The method for producing a rubber composition of the present invention includes, for example, a step (I) of mixing a diene rubber, a tetrazine compound (1), and optionally a raw material component containing an inorganic filler and/or carbon black, and a step The step (II) of mixing the mixture obtained in (I) and the vulcanizing agent is included. In the present specification, "mixing" includes "kneading".

Process (I)
The step (I) is a step of mixing the diene rubber, the tetrazine compound (1), and optionally raw material components including an inorganic filler and/or carbon black, and is a step before the vulcanizing agent is added. It means that there is. In this step (I), the tetrazine compound (1) reacts with the double bond of the diene rubber.

In the step (I), the above-mentioned other compounding agents and the like can be further compounded, if necessary.

Examples of the mixing method in step (I) include a method of mixing a composition containing a diene rubber, a tetrazine compound (1), an inorganic filler and/or carbon black. In this mixing method, the entire amount of each component may be kneaded at once, or each component may be dividedly added and kneaded depending on the purpose such as viscosity adjustment. In addition, after the diene rubber and the inorganic filler and/or carbon black are kneaded, the tetrazine compound (1) is added and mixed, or the diene rubber and the tetrazine compound (1) are mixed and then the inorganic filler is added. Materials and/or carbon black may be added and mixed. Step (I) may be repeatedly mixed multiple times.

The temperature at the time of mixing the rubber composition in the step (I) may be such that the tetrazine compound (1) reacts with the diene rubber, and the upper limit of the temperature of the rubber composition is 120 to 120° C., for example. The temperature is preferably 190°C, more preferably 130 to 175°C, further preferably 140 to 170°C.

The mixing time in step (I) is not particularly limited and is, for example, preferably 10 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, further preferably 2 minutes to 7 minutes. preferable.

In the step (I), the compounding amount of the tetrazine compound (1) is not particularly limited, and is, for example, 0.1 to 10 parts by mass, preferably 0.25 to 100 parts by mass of the diene rubber. 5 parts by mass, more preferably 0.5 to 2 parts by mass.

The amount of the inorganic filler compounded in the step (I) is usually 20 to 150 parts by mass, preferably 30 to 120 parts by mass, and more preferably 40 to 90 parts by mass with respect to 100 parts by mass of the diene rubber. It is a department.

The compounding amount of carbon black in the step (I) is usually 2 to 150 parts by mass, preferably 4 to 120 parts by mass, and more preferably 6 to 100 parts by mass with respect to 100 parts by mass of the diene rubber. Is.

In addition, in the step (I), the inorganic filler and/or carbon black is a total amount of both components, for example, 30 to 130 parts by mass is usually added to 100 parts by mass of the diene rubber. It may be appropriately adjusted within the range of the compounding amount.

As another mixing method in the step (I), a step (I-1) of mixing the rubber component and the tetrazine compound (1), and the mixture and the inorganic filler obtained in the step (I-1), And/or a two-step mixing method including a step (I-2) of mixing with carbon black.

As a method of mixing the diene rubber and the tetrazine compound (1) in the step (I-1), when the diene rubber is a solid, a method of kneading the diene rubber and the tetrazine compound (1) ( Solid mixing method); when the diene rubber is liquid (liquid), a method of mixing the solution or emulsion (suspension) of the diene rubber and the tetrazine compound (1) (liquid mixing method), etc. Can be mentioned.

As the mixing temperature, the amount of heat for the tetrazine compound (1) to react with the diene rubber may be given. For example, in the case of the solid mixing method, the upper limit of the temperature of the rubber composition is 80 to 190°C. It is preferably from 90 to 160° C., more preferably from 100 to 150° C. In the case of the liquid mixing method, the upper limit of the temperature of the liquid rubber composition is preferably 80 to 170°C, more preferably 90 to 160°C, and further preferably 100 to 150°C.

The mixing time is, for example, preferably 10 seconds to 20 minutes in the case of the solid mixing method, more preferably 30 seconds to 10 minutes, and further preferably 60 seconds to 7 minutes. In the case of a liquid mixing method, it is preferably 10 seconds to 60 minutes, more preferably 30 seconds to 40 minutes, and further preferably 60 seconds to 30 minutes. After the mixing reaction by the liquid mixing method, the solvent in the mixture can be removed (removed) under reduced pressure to recover the solid rubber composition.

The compounding amount of the tetrazine compound (1) in the step (I-1) is not particularly limited and is, for example, usually 0.1 to 10 parts by mass, preferably 0.1 part by mass with respect to 100 parts by mass of the diene rubber. It is 25 to 5 parts by mass, more preferably 0.5 to 2 parts by mass.

In the step (I-1) of kneading the diene rubber and the tetrazine compound (1), the double bond of the diene rubber and the tetrazine compound (1) react with each other to form a modified polymer.

The temperature at the time of mixing the mixture (modified polymer) obtained in step (I-1) with the inorganic filler and/or carbon black in step (I-2) is not particularly limited, and for example, a mixture The upper limit of the temperature is preferably 120 to 190°C, more preferably 130 to 175°C, and further preferably 140 to 170°C.

The mixing time in the step (I-2) is not particularly limited and is, for example, preferably 10 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, and further preferably 2 minutes to 7 minutes. Is more preferable.

The compounding amount of the inorganic filler in the step (I-2) is usually 20 to 150 parts by mass, preferably 30 parts by mass with respect to 100 parts by mass of the mixture (modified polymer) obtained in the step (I-1). To 120 parts by mass, more preferably 40 to 90 parts by mass.

The compounding amount of carbon black in the step (I-2) is usually 2 to 150 parts by mass, preferably 4 to 100 parts by mass with respect to 100 parts by mass of the mixture (modified polymer) obtained in the step (I-1). It is 120 parts by mass, more preferably 6 to 100 parts by mass.

In the step (I-2), the inorganic filler and/or carbon black is the total amount of both components, for example, with respect to 100 parts by mass of the mixture (modified polymer) obtained in the step (I-1). Usually, it may be adjusted appropriately within the range of the above-mentioned blending amount of each component so as to be usually 20 to 150 parts by mass.

Process (II)
Step (II) is a step of mixing the mixture obtained in step (I) and the vulcanizing agent, and means the final stage of mixing.

In the step (II), a vulcanization accelerator and the like can be further compounded, if necessary.

The mixing temperature in step (II) is not particularly limited and is, for example, preferably 60 to 140°C, more preferably 80 to 120°C, and further preferably 90 to 120°C.

The mixing time is not particularly limited and is, for example, preferably 10 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, and further preferably 60 seconds to 5 minutes.

When proceeding from step (I) to step (II), it is preferable to lower the temperature by 30° C. or more from the temperature after the end of the previous step, and then proceed to the next step (II).

In the method for producing a rubber composition of the present invention, various compounding agents such as stearic acid, zinc white, a vulcanization accelerator, and an antioxidant, which are usually compounded in the rubber composition, are added in the step (I), if necessary. Alternatively, it can be added in step (II).

A rubber composition containing a modified polymer obtained by treating the diene rubber with the tetrazine compound (1), and an inorganic filler and/or carbon black is produced by the above steps (I) and (II). be able to.

The modified polymer formed in step (I) or (I-1) is produced by the progress of the reactions shown in the following reaction formulas-1 to 4.

[In the formula, X ¹ and X ² are the same as defined above. ]

In reaction formula-1, the double bond site of the diene rubber represented by the formula (A-1) and the tetrazine compound (1) are subjected to a reverse electron-requiring Aza-Diels-Alder reaction to give a formula (B-1). ) Form a bicyclo ring structure. The -N=N- moiety in this bicyclo ring structure facilitates denitrification and has a 6-membered ring structure represented by formula (C-1), (C-2) or (C-3). Although formed, it is further oxidized by oxygen in the air to produce a modified polymer having a 6-membered ring structure represented by the formula (2-1).

[In the formula, X ¹ and X ² are the same as defined above. ]

In Reaction formula-2, like the reaction formula-1, from the double bond site of the diene rubber represented by the formula (A-2) and the tetrazine compound (1), the formula (B-2) or ( B-2′) and then a 6-membered ring structure represented by formulas (C-4) to (C-9) are formed, and then the formula (2-2) or (2-3 A modified polymer having a six-membered ring structure represented by

[In the formula, X ¹ and X ² are the same as defined above. R represents an alkyl group or a halogen atom. ]

In reaction formula-3, a double bond site of the diene rubber represented by formula (A-3) and the tetrazine compound (1) are subjected to a reverse electron-requiring Aza-Diels-Alder reaction to give formula (B-3). Or a modified polymer having a 6-membered ring structure represented by formulas (2-4) to (2-7) by denitrification after forming a bicyclo ring structure represented by (B-3′). Manufactured. When R on the double bond site of the diene rubber represented by the formula (A-3) is a halogen atom, the elimination of the halogen atom may occur. A modified polymer having a 6-membered ring structure represented by (2-1) is produced.

[In the formula, X ¹ , X ² and R are the same as defined above. ]

In the reaction formula-4, similarly to the reaction of the reaction formula-3, the double bond site of the diene rubber represented by the formula (A-4) and the tetrazine compound (1) are reacted to give the formula (B- 4) or after forming a bicyclo ring structure represented by (B-4′), a modified polymer having a 6-membered ring structure represented by formulas (2-8) to (2-11) is produced. It

As described above, the produced modified polymer has a hetero atom such as a nitrogen atom, and since this hetero atom strongly interacts with the inorganic filler (particularly silica) and carbon black, the rubber composition It is possible to enhance the dispersibility in the inside and to impart high low heat buildup.

The rubber composition of the present invention is a modified polymer produced by reacting a double bond of a diene rubber with a tetrazine compound (1), preferably the following formulas (2-1) to (2-11). A rubber composition containing a modified polymer having at least one selected from the compound structures represented by:

[In the formula, X ¹ and X ² and R are the same as defined above. ]

2. Studless Tire The tire of the present invention is a tire produced by using the rubber composition of the present invention.

Examples of the tire of the present invention include pneumatic tires (radial tires, bias tires, etc.) and solid tires.

The use of the tire is not particularly limited, and examples thereof include passenger car tires, high-load tires, motorcycle (motorcycle) tires, studless tires, and the like, and among them, the studless tire can be preferably used.

The shape, structure, size and material of the tire of the present invention are not particularly limited and can be appropriately selected according to the purpose.

In the tire of the present invention, the rubber composition is used especially in the tread portion.

Among them, forming the tire tread portion of the pneumatic studless tire with the rubber composition is mentioned as one of the preferable embodiments.

The tire tread portion has a tread pattern, is a portion that is in direct contact with the road surface, is a skin portion of the tire that protects the carcass and prevents abrasion and damage, and the cap tread and/or the cap tread that constitutes the ground contact portion of the tire. It is a base tread that is placed inside the.

The tire of the present invention can be manufactured according to a method known so far in the field of tires.

Further, as the gas to be filled in the tire, normal air or air whose oxygen partial pressure is adjusted; inert gas such as nitrogen, argon, helium or the like can be used.

Hereinafter, the present invention will be specifically described with reference to production examples and examples. However, the embodiments are merely examples, and the present invention is not limited to the embodiments.

Production Example 1: Production of 3,6-bis(3-pyridyl)-1,2,4,5-tetrazine (a) In a 200 mL four-necked flask, 24 g of 3-cyanopyridine , 15 g of hydrazine hydrate , and 48 mL of methanol was added and stirred at room temperature. Next, 3.6 g of sulfur was added to this mixture, a reflux tube was attached, and the mixture was heated and stirred overnight at an external temperature of 70°C. The reaction solution was ice-cooled, the crystals were filtered and washed with a small amount of cold methanol. The crude crystals were dried under reduced pressure to obtain 19 g of orange crude dihydrotetrazine crystals.

The obtained crude crystals (17.8 g) were dissolved in acetic acid (178 g), and sulfur was filtered off. A dihydrotetrazine acetic acid solution and 178 mL of distilled water were added to a 1 L four-necked eggplant flask, and the mixture was stirred under ice cooling. Sodium nitrite (15.5 g) was dissolved in distilled water (35 mL), added dropwise to the reaction solution over about 1 hour, and stirred overnight at room temperature. The precipitated crystals were filtered and the crystals were neutralized with 10% multi-layered water to give crude crystals. The crude crystals were purified by a silica gel column (ethyl acetate) to obtain 8.4 g of the title tetrazine compound (a) (reddish purple, needle crystals).
Melting point: 200°C,
¹ H-NMR (300 MHz, CDCl3, δppm):
7.59 (ddd, J = 0.9, 5.1, 7.8 Hz, 2H), 8.89-8.96 (m, 4H), 9.88 (dd, J = 0.9, 2) .4Hz, 2H)

Examples 1-6
The respective components described in the step (I) of the following Table 1 were mixed in the ratio (parts by mass) and kneaded for 5 minutes while adjusting the rotation speed so that the maximum temperature of the mixture was 160° C. with a Banbury mixer. After curing until the temperature of the mixture becomes 80° C. or lower, each component described in step (II) of Table 1 is added in the ratio (parts by mass) to adjust the maximum temperature of the mixture to 110° C. or lower. While kneading, each rubber composition was manufactured.

Low exothermicity (tan δ index) test With respect to the rubber compositions (test compositions) produced in Examples 1 to 6, a viscoelasticity measuring device (manufactured by Metravib) was used, and temperature 40°C, dynamic strain 5%, frequency 15Hz. Tan δ was measured.

In addition, except that the tetrazine compound (1) was not added, a rubber composition (reference) was prepared with the same formulation content and the same production method as in each example, and the low exothermic index was calculated based on the following formula.

The larger the value of the low heat buildup index, the lower the heat buildup and the smaller the hysteresis loss. The low heat buildup of each reference vulcanized rubber composition is 100.

The results are shown in Table 1.

Formula: Low exothermic index={(tan δ of reference)/(tan δ of test composition)}×100

For the rubber composition (test composition) and the reference prepared in the ice and snow performance test examples 1 to 6, a viscoelasticity measuring device (manufactured by Metravib) was used, and the temperature was stored at -20°C, dynamic strain 1%, and frequency 10 Hz. The elastic modulus was measured.

Formula: Ice and snow performance index={(storage elastic modulus of reference)/(storage elastic modulus of test composition)}×100

[Explanation of symbols in the table]
The raw materials used in Table 1 are shown below.
*1: Asahi Kasei Corporation, product name "Tuffden 2000R"
*2: Product name "BR150B" manufactured by Ube Industries, Ltd.
*3: Made by Chuka Kokusai Co., Ltd., product name "RSS#3"
*4: Tosoh Silica Co., Ltd. product name "Nipsil (brand AQ)"
*5: Product name "Si69" manufactured by Evonik Industries AG
*6: Tokai Carbon Co., Ltd., product name "Cast 3"
*7: Product name "Antilux 111" manufactured by Rhein Chemie Rheinau GmbH
*8: Product name "Antage 6C" manufactured by Kawaguchi Chemical Industry Co., Ltd.
*9: Zinc oxide brand "1 type" manufactured by Sakai Chemical Industry Co., Ltd.
*10: Manufactured by Sichuan Tianyu Grease Chemical Co., Ltd. *11: Manufactured by JX Nikko Nisseki Energy Co., Ltd., product name "X-140 (aroma oil)"
*12: 3,6-bis(3-pyridyl)-1,2,4,5-tetrazine (compound produced in Production Example 1)
*13: 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, manufactured by Tokyo Chemical Industry Co., Ltd. *14: 3,6-bis(4-pyridyl)-1,2,4. 5-Tetrazine, manufactured by Tokyo Kasei Kogyo Co., Ltd. *15: Hosoi Chemical Co., Ltd., trade name "HK200-5"
*16: Ouchi Shinko Chemical Industry Co., Ltd., product name "NOXCELLER D"
*17: Product name "NOXCELLER CZ-G" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Since the rubber composition for a tire for ice and snow roads of the present invention is more excellent in low heat generation property while maintaining the snow performance, the tread portion (tire tread) of a studless tire is produced by using the rubber composition. be able to.

Claims (7)

Diene rubber and the following general formula (1):

[In the formula, X ¹ and X ² represent a heterocyclic group which may have a substituent. ]
A rubber composition for a snowy road tire containing a tetrazine compound or a salt thereof represented by:
A rubber composition containing 0.1 to 10 parts by mass of the tetrazine compound or a salt thereof with respect to 100 parts by mass of a diene rubber. The rubber composition according to claim 1, further comprising an inorganic filler and/or carbon black. The rubber composition according to claim 2, wherein the total amount of the inorganic filler and/or carbon black is 30 to 130 parts by mass with respect to 100 parts by mass of the diene rubber. The rubber composition according to claim 2 or 3, wherein the inorganic filler is silica. The rubber composition according to claim 1, which is used in a tread portion. A tire tread for ice and snow roads, which is produced using the rubber composition according to any one of claims 1 to 4. A studless tire manufactured using the tread for tires for ice and snow roads according to claim 6.