JP2019001864A - tire - Google Patents

Abstract

To provide a tire that contains a crosslinked rubber composition having excellent cracking resistance and low heat build-up properties, the tire having excellent durability.SOLUTION: A tire contains a crosslinked rubber composition obtained by cross-linking a rubber composition containing a rubber component, silica, a hydrazide compound, a guanidine vulcanization accelerator, and a sulfenamide-based vulcanization accelerator, and has a crown center gage thickness of 70 mm or more.SELECTED DRAWING: None

Description

  The present invention relates to a tire.

In recent years, there has been a demand for tires that are excellent in low heat buildup and have improved fracture properties even in heavy-duty tires.
Patent Document 1 discloses a rubber composition for tire treads that improves chipping resistance, has high strength and elongation, and can maintain its performance over a long period of time without deteriorating heat generation in a rubber composition for heavy-duty tire treads. For the purpose of providing a product, it is disclosed that a specific resin and a cyclic sulfide compound are used in combination with a vulcanizable rubber mainly composed of natural rubber / synthetic polyisoprene rubber.
Patent Document 2 discloses a rubber composition for treads of heavy-duty tires for icy and snowy roads, which can improve the adhesion to snow on the surface of the tire tread without deteriorating the heat generation and fatigue resistance, thereby improving the performance on ice. For the purpose of providing, a total amount of carbon black and silica having a specific nitrogen adsorption specific surface area of 30 to 70 parts by mass with respect to 100 parts by mass of a diene rubber mainly composed of natural rubber and / or butadiene rubber, and ultra-high A rubber composition for treads of heavy-duty tires for icy and snowy roads containing less than 3 parts by weight of molecular weight polyethylene is disclosed.

JP 2005-225909 A JP 2006-241338 A

  An object of the present invention is to provide a tire having excellent durability by having a crosslinked rubber composition having excellent crack resistance and low heat build-up.

  As a result of intensive studies, the present inventor has found that the use of a specific rubber composition can solve the above problems even for a tire having a crown center gauge thickness of 70 mm or more.

That is, the present invention relates to the following <1> to <8>.
<1> It has a crosslinked rubber composition obtained by crosslinking a rubber composition containing a rubber component, silica, a hydrazide compound, a guanidine vulcanization accelerator, and a sulfenamide vulcanization accelerator, and has a crown center gauge thickness. Is a tire characterized by being 70 mm or more.
<2> The total content of the guanidine vulcanization accelerator and the sulfenamide vulcanization accelerator in the rubber composition is 2 parts by mass or less with respect to 100 parts by mass of the rubber component, according to <1>. tire.
<3> The tire according to <1> or <2>, wherein the content of the guanidine vulcanization accelerator in the rubber composition is 0.3 parts by mass or less with respect to 100 parts by mass of the rubber component.
<4> The tire according to any one of <1> to <3>, wherein the rubber composition contains natural rubber and synthetic polyisoprene rubber in an amount of 50% by mass or more of the rubber component.
<5> The tire according to any one of <1> to <4>, wherein the content of silica in the rubber composition is 20 parts by mass or less with respect to 100 parts by mass of the rubber component.
<6> The tire according to any one of <1> to <5>, wherein the content of the hydrazide compound in the rubber composition is 0.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the rubber component. .
<7> The tire according to any one of <1> to <6>, wherein the crosslinked rubber composition is used as an internal member.
<8> The tire according to <7>, wherein the internal member is an internal member adjacent to a rubber member.

  According to the present invention, a tire having excellent durability can be provided by having a crosslinked rubber composition having excellent crack resistance and low heat build-up.

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 "B or more" (when A> B).
Moreover, a mass part and mass% are synonymous with a weight part and weight%, respectively.

[tire]
The tire of the present invention has a crosslinked rubber composition obtained by crosslinking a rubber composition containing a rubber component, silica, a hydrazide compound, a guanidine vulcanization accelerator, and a sulfenamide vulcanization accelerator, The center gauge thickness is 70 mm or more. In the following description, a rubber component, silica, a hydrazide compound, a guanidine vulcanization accelerator, and a sulfenamide vulcanization accelerator are used, and an uncrosslinked rubber composition is simply referred to as “rubber composition” or The rubber composition of the present invention is referred to. On the other hand, the crosslinked rubber composition obtained by crosslinking the uncrosslinked rubber composition is also referred to as “crosslinked rubber composition” or “crosslinked rubber composition of the present invention”.
Conventionally, there has been a demand for a tire having a crosslinked rubber composition having excellent crack resistance and low heat build-up.
The present inventor has intensively studied that a crosslinked rubber composition obtained by crosslinking a rubber composition having a specific component with respect to a tire having a crown center gauge thickness of 70 mm or more is excellent in crack resistance and low heat build-up. As a result, the present invention has been completed.
In general, a tire is crosslinked (vulcanized) by heating an uncrosslinked rubber composition called raw rubber to obtain a crosslinked rubber composition. Tires with a large thickness (for example, large industrial tires) having a crown center gauge thickness of 70 mm or more are excessively vulcanized compared to ordinary passenger car tires and the like in order to advance vulcanization to the inside of the tire. In other words, vulcanization is performed under conditions that increase the degree of vulcanization. The inventor has found that when vulcanization is performed under such conditions, the characteristics of low heat generation and crack resistance are different from those of general passenger car tires and the like.
As a result of intensive studies on such a rubber composition that is vulcanized under excessively vulcanized conditions with a crown center gauge thickness of 70 mm or more, the rubber component, silica, hydrazide compound, and specific vulcanization It has been found that a crosslinked rubber composition excellent in low heat buildup and crack resistance can be obtained by vulcanizing a rubber composition containing an accelerator.
The detailed mechanism of action for obtaining such an effect is unknown, and an effect that is difficult to predict is obtained by a specific combination thereof.
Hereinafter, after describing the various components contained in the rubber composition of the present invention, the crosslinked rubber composition and the tire will be described.

<Rubber composition>
[Rubber component]
The rubber composition of the present invention contains a rubber component.
As the rubber component, either natural rubber or synthetic rubber may be used, natural rubber may be used alone, synthetic rubber may be used alone, or natural rubber and synthetic rubber may be used. You may use together.
Although it does not specifically limit as a synthetic rubber, A synthetic diene type rubber is illustrated preferably. Synthetic diene rubbers include polybutadiene rubber (BR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), ethylene-propylene-diene terpolymer rubber, chloroprene rubber, butyl rubber, halogenated Examples include butyl rubber and acrylonitrile-butadiene rubber. These synthetic rubbers may be used alone or in combination of two or more.

  In the present invention, the rubber component preferably contains at least one selected from the group consisting of natural rubber and synthetic polyisoprene rubber. From the viewpoint of further improving the crack resistance and low heat build-up of the crosslinked rubber composition, the total content of natural rubber and synthetic polyisoprene rubber in the rubber component is preferably 50% by mass or more, more preferably 70% by mass or more. More preferably, it is 80% by mass or more, more preferably 90% by mass or more, and most preferably consists of only natural rubber and synthetic polyisoprene rubber. That is, the total amount of natural rubber and synthetic polyisoprene rubber is particularly preferably 100% by mass of the rubber component.

〔silica〕
The rubber composition of the present invention contains silica. By containing silica, a crosslinked rubber composition excellent in crack resistance and low heat build-up can be obtained.
There is no restriction | limiting in particular as a silica used in this invention, What is necessary is just to use the silica currently used for the rubber composition, wet silica (hydrous silicic acid), dry-type silica (anhydrous silicic acid), colloidal silica, calcium silicate. And aluminum silicate. Among these, it is preferable to use wet silica.

Silica may be used alone or in combination of two or more.
The compounding amount of silica in the rubber composition is preferably 0.5 parts by mass or more, more preferably 100 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of obtaining a crosslinked rubber composition excellent in crack resistance and low heat build-up. Is 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less.

[Hydrazide compound]
The rubber composition of the present invention contains a hydrazide compound. By containing a hydrazide compound, a crosslinked rubber composition excellent in low heat build-up can be obtained.
As the hydrazide compound, compounds represented by the following formulas (I) to (III) are preferable.

(In Formula (I) to Formula (III), R ^{1 to} R ⁴ each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and R ¹ and R ² , R ³ and R ⁴ may be bonded to each other to form a ring structure, and A is a substituted or unsubstituted aromatic ring, a substituted or unsubstituted hydantoin ring, or a saturated or unsaturated chain carbonization having 1 to 18 carbon atoms. Represents a hydrogen group, X represents an aryl group substituted by W, W represents a hydroxy group or an amino group, n represents an integer of 1 or more, and Y represents a pyridyl group or a hydrazide group.

In formulas (I) to (III), R ^{1 to} R ⁴ represent a hydrogen atom, a monovalent hydrocarbon group having 1 to 18 carbon atoms, a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and a carbon number. A cycloalkyl group having 3 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 18 carbon atoms is preferable. The hydrocarbon group may further have a substituent, and is substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group, or an alkyl group having 1 to 6 carbon atoms. You may have substituents, such as an amino group and a hydroxy group.

In formula (I), A represents a substituted or unsubstituted aromatic ring, a substituted or unsubstituted hydantoin ring, or a saturated or unsaturated chain hydrocarbon group having 1 to 18 carbon atoms, and is substituted or unsubstituted. The aromatic ring is substituted with —C (═O) —NH—N═CR ¹ R ² and —C (═O) —NH—N═CR ³ R ⁴ at any position of the ortho, meta, and para positions. There is no particular limitation. As the saturated or unsaturated chain hydrocarbon group having 1 to 18 carbon atoms, a saturated or unsaturated linear hydrocarbon group is preferable. Specifically, an ethylene group, a tetramethylene group, a heptamethylene group, octamethylene Group, octadecamethylene group, octadecane-7,11-diyl group.

  Specific compounds represented by the formula (I) include isophthalic acid dihydrazide, isophthalic acid di (1-methylethylidene) hydrazide, adipic acid di (1-methylethylidene) hydrazide, isophthalic acid di (1-methylpropylidene). ) Hydrazide, adipic acid di (1-methylpropylidene) hydrazide, isophthalic acid di (1,3-dimethylpropylidene) hydrazide, adipic acid di (1,3-dimethylpropylidene) hydrazide, isophthalic acid di (1-phenyl) Examples thereof include derivatives of isophthalic acid dihydrazide and adipic acid dihydrazide such as ethylidene) hydrazide and adipic acid di (1-phenylethylidene) hydrazide. In addition to these isophthalic acid dihydrazide and adipic acid dihydrazide derivatives, the following effects can be obtained with the following dihydrazide compound derivatives. For example, terephthalic acid dihydrazide, azelaic acid dihydrazide, succinic acid dihydrazide, eicosanedioic acid dihydrazide and the like. Among these, a derivative of isophthalic acid dihydrazide is preferable from the viewpoint of obtaining a high exothermic effect.

In formula (II), X represents an aryl group substituted by W, and the aryl group preferably has 6 to 20, more preferably 6 to 14, and still more preferably 6 to 10, The aryl group is preferably a group obtained by removing n hydrogen atoms from a phenyl group or a naphthyl group.
W represents a hydroxy group or an amino group, and is preferably a hydroxy group. X is substituted with n Ws, and n is an integer of 1 or more, preferably 1 to 3, more preferably 1 or 2, and still more preferably 1.

  Specific compounds represented by the above formula (II) include 2-hydroxy-N ′-(1-methylethylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N ′-(1-methylpropylidene)- 3-naphthoic acid hydrazide, 2-hydroxy-N ′-(1,3-dimethylpropylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N ′-(1,3-dimethylbutylidene) -3-naphthoic acid In addition to derivatives of 2-hydroxy-3-naphthoic acid hydrazide such as hydrazide, 2-hydroxy-N ′-(1-phenylethylidene) -3-naphthoic acid hydrazide, salicylic acid hydrazide, 4-hydroxybenzoic acid hydrazide, anthranilic acid Examples thereof include hydrazide and 1-hydroxy-2-naphthoic acid hydrazide derivatives. Among these, derivatives of 2-hydroxy-3-naphthoic acid hydrazide are particularly preferable in that high low heat buildup can be obtained.

In formula (III), Y represents a pyridyl group or a hydrazide group, and is preferably a pyridyl group.
Specific compounds represented by the above formula (III) include isonicotinic acid (1-methylethylidene) hydrazide, isonicotinic acid (1-methylpropylidene) hydrazide, isonicotinic acid (1,3-dimethylpropylidene). In addition to derivatives of isonicotinic acid hydrazide such as hydrazide and isonicotinic acid (1-phenylethylidene) hydrazide, derivatives of carbonic acid dihydrazide can be mentioned. Among these, a derivative of isonicotinic acid hydrazide is particularly preferable from the viewpoint of obtaining high low exothermic properties.
In addition, the synthesis | combining method of the hydrazide compound represented by said formula (I)-(III) is Pant, UC; Ramchandran, Reena; Joshi, BC Rev. Roum.Chim. (1979), 24 (3), 471-82. In the literature.

  In the present invention, the hydrazide compound is preferably a compound represented by the above formula (II), more preferably a compound represented by the following formula (II-1) or the following formula (II-2). preferable.

(In Formula (II-1) and Formula (II-2), R ⁵ and R ⁶ each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and R ⁵ and R ⁶ are They may be bonded to each other to form a ring structure.)

In Formula (II-1) and Formula (II-2), R ⁵ and R ⁶ represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and a hydrogen atom or an alkyl having 1 to 18 carbon atoms. A cycloalkyl group having 3 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 7 to 18 carbon atoms. The cycloalkyl group, aryl group or aralkyl group may further have a substituent on the ring, and the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, the amino group, and the carbon number 1 You may have substituents, such as an amino group substituted by the alkyl group of -6, and a hydroxy group. Among these, R ⁵ and R ⁶ are preferably alkyl groups having 1 to 6 carbon atoms. The alkyl group may be linear or branched.

Specific examples of the compound represented by formula (II-1) or formula (II-2) include 2-hydroxy-N ′-(1-methylethylidene) -3-naphthoic acid hydrazide, 2-hydroxy- N ′-(1-methylpropylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N ′-(1-methylbutylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N ′-(1,3- Dimethylbutylidene) -3-naphthoic acid hydrazide, 2-hydroxy-N ′-(2,6-dimethyl-4-heptylidene) -3-naphthoic acid hydrazide, N ′-(1-methylethylidene) -salicylic acid hydrazide, N '-(1-methylpropylidene) -salicylic acid hydrazide, N'-(1-methylbutylidene) -salicylic acid hydrazide, N '-(1,3-dimethylbutylidene) -salicylic acid hydrazide N '-(2,6-dimethyl-4-heptylidene) -salicylic acid hydrazide.
Among these, 2-hydroxy-N ′-(1,3-dimethylbutylidene) -3-naphthoic acid hydrazide is particularly preferable.

A hydrazide compound may be used individually by 1 type, and may use 2 or more types together.
The content of the hydrazide compound in the rubber composition of the present invention is preferably 0.05 parts by mass or more, more preferably 100 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of obtaining a crosslinked rubber composition having excellent low heat build-up. 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, still more preferably 0.5 parts by mass or more, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1. 5 parts by mass or less, more preferably 1 part by mass or less.

[Guanidine vulcanization accelerator]
The rubber composition of the present invention contains a guanidine vulcanization accelerator.
Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, dicatechol borate di-o-tolylguanidine salt, 1,3- Examples include di-o-cumenyl guanidine, 1,3-di-o-biphenyl guanidine, 1,3-di-o-cumenyl-2-propionyl guanidine, and the like. Among these, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine and 1-o-tolylbiguanide are preferable from the viewpoint of reactivity.

  The content of the guanidine vulcanization accelerator in the rubber composition is preferably 1.2 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of obtaining a crosslinked rubber composition excellent in crack resistance and low heat build-up. Part or less, more preferably 0.5 part by weight or less, still more preferably 0.3 part by weight or less, still more preferably 0.25 part by weight or less, preferably 0.05 part by weight or more, more preferably 0.00 part by weight. 1 part by mass or more, more preferably 0.15 part by mass or more.

[Sulfenamide vulcanization accelerator]
The rubber composition of the present invention contains a sulfenamide vulcanization accelerator. By using the guanidine vulcanization accelerator and the sulfenamide vulcanization accelerator described above together with the hydrazide compound, the vulcanization characteristics of the rubber composition containing silica are improved, and as a result, crack resistance is improved. In addition, it is presumed that a crosslinked rubber composition excellent in low heat buildup can be obtained.
Examples of the sulfenamide-based vulcanization accelerator include N-cyclohexyl-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolyl. Rusulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2- Benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-heptyl- 2-benzothiazolylsulfenamide, N-octyl-2-benzothia Rylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl- 2-benzothiazolylsulfenamide, N, N-dimethyl-2-benzothiazolylsulfenamide, N, N-diethyl-2-benzothiazolylsulfenamide, N, N-dipropyl-2-benzothiazol Rusulfenamide, N, N-dibutyl-2-benzothiazolylsulfenamide, N, N-dipentyl-2-benzothiazolylsulfenamide, N, N-dihexyl-2-benzothiazolylsulfenamide, N , N-diheptyl-2-benzothiazolylsulfenamide, N, N-dioctyl-2- Nzothiazolylsulfenamide, N, N-di-2-ethylhexylbenzothiazolylsulfenamide, N, N-didecyl-2-benzothiazolylsulfenamide, N, N-didodecyl-2-benzothiazoli Examples include rusulfenamide and N, N-distearyl-2-benzothiazolylsulfenamide. Among these, N-cyclohexyl-2-benzothiazolylsulfenamide and N-tert-butyl-2-benzothiazolylsulfenamide are preferable from the viewpoint of reactivity.

  The content of the sulfenamide vulcanization accelerator in the rubber composition is preferably 1. with respect to 100 parts by mass of the rubber component from the viewpoint of obtaining a crosslinked rubber composition excellent in crack resistance and low heat build-up. Less than 8 parts by weight, more preferably less than 1.5 parts by weight, still more preferably less than 1.2 parts by weight, and preferably 0.1 parts by weight or more, more preferably 0.3 parts by weight or more, even more preferably. Is 0.5 parts by mass or more, more preferably 0.8 parts by mass or more.

  The content of the guanidine vulcanization accelerator and the sulfenamide vulcanization accelerator in the rubber composition is 100 parts by mass of the rubber component from the viewpoint of obtaining a crosslinked rubber composition excellent in crack resistance and low heat build-up. On the other hand, it is preferably 2.5 parts by mass or less, more preferably 2 parts by mass or less, still more preferably 1.5 parts by mass or less, preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more. More preferably, it is 1.0 part by mass or more.

[Other ingredients]
The rubber composition of the present invention may contain other components in addition to the components described above. Other components are not particularly limited, and additives usually used in the rubber industry, for example, fillers excluding silica such as carbon black and aluminum hydroxide, softeners, anti-aging agents, guanidines and sulfenes. Vulcanization accelerators other than amides, vulcanizers (eg, sulfur), vulcanization accelerators (eg, fatty acids such as zinc oxide and stearic acid), vulcanization retarders, silane coupling agents, resins, waxes Oils and the like may be appropriately selected and blended within a range that does not impair the object of the present invention.
In the present invention, it is preferable to contain carbon black as the other component. By containing carbon black, a crosslinked rubber composition having more excellent crack resistance can be obtained. The total content of carbon black and silica described above in the rubber composition of the present invention is preferably 30 to 70 parts by mass, more preferably 35 to 60 parts by mass, and still more preferably 100 parts by mass of the rubber component. 35-50 parts by mass.

<Preparation of rubber composition>
The rubber composition of the present invention can be produced by blending the above-described components and kneading them using a kneader such as a Banbury mixer, a roll, or an internal mixer.
Here, the compounding amounts of the rubber component, silica, hydrazide compound, guanidine vulcanization accelerator, sulfenamide vulcanization accelerator and the like are the same as those already described as the content in the rubber composition.
The kneading of each component may be carried out in one step or in two or more steps. For example, in the first step, the rubber component, silica, hydrazide compound, vulcanizing agent and vulcanization accelerator are used. A method of kneading other ingredients other than (including a guanidine vulcanization accelerator and a sulfenamide vulcanization accelerator) and kneading the vulcanizing agent and the vulcanization accelerator in the second stage can be mentioned.
The maximum temperature of the first stage of kneading is preferably 130 to 160 ° C, and the maximum temperature of the second stage is preferably 90 to 120 ° C.

<Crosslinked rubber composition>
The crosslinked rubber composition of the present invention is formed by crosslinking the above-described rubber composition of the present invention. In the present invention, crosslinking is preferably performed by vulcanization.
The crosslinking method of the rubber composition is not particularly limited, and a known crosslinking method can be applied. The uncrosslinked rubber composition may be cross-linked after molding. After a pre-crosslinking step or the like, after obtaining a semi-crosslinked rubber from the uncrosslinked rubber composition, after molding using this, the It may be obtained by crosslinking.
In the present invention, the crosslinking conditions are not particularly limited, but it is necessary to select conditions under which crosslinking proceeds to the inside of a tire having a crown center gauge thickness of 70 mm or more as described later.

<Tire>
The tire of the present invention has a crown center gauge thickness of 70 mm or more. Here, the crown center gauge thickness means the gauge thickness of the land portion on the tread equator of the tire tread.
The upper limit of the crown center gauge thickness is not particularly limited.
As in the present invention, in a tire having a large tire size with a crown center gauge thickness of 70 mm or more, the vulcanization time must be lengthened, and therefore, a portion having a high vulcanization heat history occurs. The effect of the present invention is more remarkable when the vulcanization heat history is high.

The tire of the present invention is not limited as long as it has the crosslinked rubber composition of the present invention, and any member may have the crosslinked rubber composition, and the crosslinked rubber composition of the present invention is not particularly limited. It is preferable to have as an internal member.
Here, the internal member means that an external member that is in contact with the outside air such as a tread rubber or a side rubber is excluded.
The crosslinked rubber composition of the present invention is preferably an internal member adjacent to the rubber member among the internal members. Here, the internal member adjacent to the rubber member means an internal member in contact with a member other than rubber such as a cord covering member, and examples thereof include pad rubber (bead pad rubber, shoulder pad rubber, etc.).

  In addition, the rubber composition and the crosslinked rubber composition of the present invention are not limited to the tire use described above, and can be used for various rubber products. Other than tire applications, anti-vibration rubber, seismic isolation rubber, belts (conveyor belts), rubber crawlers, various hoses, Moran and the like can be mentioned.

  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.

[Compounding ingredients of rubber composition]
The components blended in the rubber compositions of the examples and comparative examples are as follows.
<Rubber component>
・ NR: Natural rubber, TSR20
<Silica>
・ Silica: NIPSEAL AQ manufactured by Tosoh Silica Co., Ltd.
<Hydrazide compound>
Hydrazide compound: naphthoic acid hydrazide (2-hydroxy-N ′-(1,3-dimethylbutylidene) -3-naphthoic acid hydrazide)
<Guanidine vulcanization accelerator>
・ Vulcanization accelerator DPG: Diphenylguanidine, Noxeller D (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
<Sulfenamide vulcanization accelerator>
・ Vulcanization accelerator NS: N-tert-butyl-2-benzothiazolylsulfenamide, Sunseller NS-G (manufactured by Sanshin Chemical Industry Co., Ltd.)

<Others>
Carbon black: SAF (ASAHI # 105, manufactured by Asahi Carbon Co., Ltd.)
・ Wax: Microcrystalline wax (Selected microcrystalline wax, manufactured by Seiko Chemical Co., Ltd.)
Anti-aging agent: NOCRACK 6C (Ouchi Shinsei Chemical Co., Ltd.)
・ Zinc flower: Zinc oxide (manufactured by Hakusuitec Co., Ltd.)

[Evaluation]
Evaluation in the following examples and comparative examples was performed as follows.
(1) Exothermic property Using a viscoelasticity measuring device (manufactured by Rheometrics), tan δ was measured at a temperature of 60 ° C., a dynamic strain of 5%, and a frequency of 15 Hz, and displayed as an index based on the result of Comparative Example 2. A smaller index value indicates a lower exothermic property and a smaller hysteresis loss.

(2) Crack resistance According to JIS K 6270: 2001 "Vulcanized rubber and thermoplastic rubber-Determination of tensile fatigue properties-Constant strain method", each rubber composition was subjected to repeated tensile tests at 23 ° C, and fatigue life ( The number of repeated tensions until breakage) was measured, and the index was displayed based on Comparative Example 2. The larger the index value, the better the crack resistance. A dumbbell-shaped No. 3 test piece was used, the test strain was 100%, and the test frequency was 3 Hz.

(Examples 1-7 and Comparative Examples 1-3)
The compounding composition shown in Table 1 was used to knead the compounding components of the rubber composition described above using a Banbury mixer to prepare a sample rubber composition. In the final stage of kneading, sulfur as a vulcanizing agent and a vulcanization accelerator were blended.
The obtained rubber composition was vulcanized at 145 ° C. for 90 minutes to produce a crosslinked (vulcanized) rubber composition, and the heat buildup and crack resistance were evaluated using the crosslinked rubber composition. The evaluation of Comparative Example 2 was evaluated as 100. The exothermic evaluation shows that the smaller the value, the lower the exothermic property. Moreover, evaluation of crack resistance shows that it is excellent in crack resistance, so that a numerical value is large.
The results are shown in Table 1 below.

  According to the present invention, a tire having excellent durability can be obtained by having a crosslinked rubber composition having low heat build-up and excellent crack resistance.

Claims (8)

A crosslinked rubber composition obtained by crosslinking a rubber composition containing a rubber component, silica, a hydrazide compound, a guanidine vulcanization accelerator, and a sulfenamide vulcanization accelerator;
A tire having a crown center gauge thickness of 70 mm or more.   The tire according to claim 1, wherein a total content of the guanidine vulcanization accelerator and the sulfenamide vulcanization accelerator in the rubber composition is 2 parts by mass or less with respect to 100 parts by mass of the rubber component.   The tire according to claim 1 or 2, wherein the content of the guanidine vulcanization accelerator in the rubber composition is 0.3 parts by mass or less with respect to 100 parts by mass of the rubber component.   The tire according to any one of claims 1 to 3, wherein the rubber composition contains natural rubber and synthetic polyisoprene rubber in an amount of 50% by mass or more of the rubber component.   The tire in any one of Claims 1-4 whose content of the silica in a rubber composition is 20 mass parts or less with respect to 100 mass parts of rubber components.   The tire according to any one of claims 1 to 5, wherein the content of the hydrazide compound in the rubber composition is 0.5 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the rubber component.   The tire according to any one of claims 1 to 6, wherein the crosslinked rubber composition is used as an internal member.   The tire according to claim 7, wherein the internal member is an internal member adjacent to a rubber member.