JP4577490B2 - Rubber composition for belt and belt - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a rubber composition for a belt and a belt, and more particularly to a rubber composition for a belt and a belt that achieve both high hardness and energy saving (low energy loss).

In particular, in industrial fields such as steel, coal, and cement, it is necessary to transport a transported object over a long distance with a conveyor belt. Conveyor belts used for transporting goods are often composed of rubber belts reinforced with canvas or steel cords. Natural rubber (NR), natural rubber and polybutadiene rubber (BR) are used as materials for such rubber belts. In general, blended rubber and the like are used.
Here, when long-distance conveyance of a transported object is carried out by a conveyor belt, the belt inevitably comes into contact with a large number of rollers, and the energy loss generated at that time is the power consumption for driving the conveyor belt. Cause an increase. For this reason, from the viewpoint of reducing power consumption for conveyance, development of an energy-saving belt with a small energy loss when contacting with a roller has been conventionally demanded.

As a rubber material for the purpose of reducing energy loss, a technology for blending a specific butadiene rubber (see Patent Document 1: Japanese Patent Laid-Open No. 2001-026670), a technology for blending a specific carbon black (Patent Document 2: Special) No. 2002-069241), a technology for blending a specific amount of butadiene rubber having a specific molecular weight distribution (Patent Document 3: Japanese Patent Laid-Open No. 2003-048609), a technology for blending silica and a silane coupling agent (patent) Reference 4: Japanese Patent Laid-Open No. 2004-010215), technology for blending specific carbon black (Patent Reference 5: Japanese Patent Laid-Open No. 2004-018752), composition of styrene-butadiene copolymer having a specific structure and natural rubber Technology of blending carbon black and silica into a product (Patent Document 6: Japanese Patent Application Laid-Open No. 2004-143244) Broadcast reference), and the like are known.
However, development of a rubber composition capable of further reducing energy loss, desirably development of a rubber composition excellent in hardness (durability), and development of a belt that achieves both energy saving and high hardness is desired. It was.

JP 2001-026670 A Japanese Patent Application Laid-Open No. 2002-069241 Japanese Patent Laid-Open No. 2003-048609 JP 2004-010215 A JP 2004-018752 A JP 2004-143244 A

  This invention is made | formed in view of the said situation, and it aims at providing the rubber composition used as the raw material of the belt which compatible high hardness and energy saving property (reduction of energy loss), and the said belt.

  As a result of intensive studies to achieve the above object, the present inventors have found that a rubber composition for a belt containing specific amounts of a specific rubber component, a specific hydrazide compound, silica, and a silane coupling agent has high hardness and energy saving properties. As a result, it was found that the rubber composition can realize a belt that achieves both the above and the present invention.

（式中、Ａは単結合、ヘテロ元素を含んでいてもよい炭素数４〜１８の２価の芳香族基（置換基を有していてもよい）、置換又は非置換のヒダントイン環、あるいは炭素数１〜１８の飽和又は不飽和直鎖状炭化水素、Ｂはヘテロ元素を含んでいてもよい炭素数４〜１８の２価の芳香族基（置換基を有していてもよい）、置換又は非置換のヒダントイン環、あるいは炭素数１〜１８の飽和又は不飽和直鎖状炭化水素を示す。また、Ｘはヒドロキシル基またはアミノ基、Ｙはピリジル基またはヒドラジノ基を示し、Ｒ¹〜Ｒ⁴は水素原子または炭素原子数１〜１８のアルキル基またはアリール基のいずれかを示す。Ｒ¹〜Ｒ⁴は同一でも異なっても良い。）
（Ｃ）シリカ、及び、
（Ｄ）シランカップリング剤、
（Ｅ）カーボンブラック、
を含み、
前記（Ａ）成分１００質量部に対し前記（Ｂ）成分が０．３〜１０質量部、前記（Ｃ）成分が５〜５０質量部、前記（Ｄ）成分が０．１〜５質量部、前記（Ｅ）成分が３０〜７５質量部配合されたことを特徴とするベルト用ゴム組成物。
請求項２：
前記（Ａ）成分が液状ゴムを３〜１５質量％含む請求項１記載のベルト用ゴム組成物。
請求項３：
前記（Ａ）成分における天然ゴムと末端変性ポリブタジエンゴムとの配合比が、天然ゴム／末端変性ポリブタジエンゴム＝１０／９０〜３５／６５（質量比）である請求項１又は２記載のベルト用ゴム組成物。
請求項４：
前記（Ｂ）成分が、イソフタル酸ジヒドラジド及び／又は２−ナフタレン酸−３−ヒドロキシ（１，３−ジメチルブチリデン）ヒドラジドである請求項１，２又は３記載のベルト用ゴム組成物。
請求項５：
請求項１乃至４のいずれかに記載のベルト用ゴム組成物を用いてなるベルト。 That is, the present invention provides the following rubber composition for belt and belt.
Claim 1:
Each component of the following (A)-(E),
(A) A rubber component containing natural rubber and terminal-modified polybutadiene rubber, wherein the blending ratio of natural rubber and terminal-modified polybutadiene rubber is natural rubber / terminal-modified polybutadiene rubber = 10/90 to 90/10 (mass ratio). ) Rubber component,
(B) one or more selected from the group consisting of hydrazide compounds represented by the following general formulas (I) to (VI),

(In the formula, A is a single bond, a divalent aromatic group having 4 to 18 carbon atoms that may contain a hetero element (which may have a substituent), a substituted or unsubstituted hydantoin ring, or C1-C18 saturated or unsaturated linear hydrocarbon, B is a C4-C18 bivalent aromatic group which may contain a hetero element (may have a substituent), A substituted or unsubstituted hydantoin ring, or a saturated or unsaturated linear hydrocarbon having 1 to 18 carbon atoms, X represents a hydroxyl group or an amino group, Y represents a pyridyl group or a hydrazino group, R ¹ to R ⁴ represents either a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an aryl group, and R ^{1 to} R ⁴ may be the same or different.
(C) silica and
(D) a silane coupling agent,
(E) Carbon black,
Including
The component (B) is 0.3 to 10 parts by mass, the component (C) is 5 to 50 parts by mass, and the component (D) is 0.1 to 5 parts by mass with respect to 100 parts by mass of the component (A). A rubber composition for belts comprising 30 to 75 parts by mass of the component (E).
Claim 2:
The rubber composition for a belt according to claim 1, wherein the component (A) contains 3 to 15% by mass of a liquid rubber.
Claim 3:
The rubber for a belt according to claim 1 or 2, wherein a blending ratio of the natural rubber and the terminal-modified polybutadiene rubber in the component (A) is natural rubber / terminal-modified polybutadiene rubber = 10/90 to 35/65 (mass ratio). Composition.
Claim 4:
The rubber composition for a belt according to claim 1, 2 or 3, wherein the component (B) is isophthalic acid dihydrazide and / or 2-naphthalenic acid-3-hydroxy (1,3-dimethylbutylidene) hydrazide.
Claim 5:
A belt comprising the rubber composition for a belt according to any one of claims 1 to 4.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for belts suitable for the belt for long-distance conveyance in which energy saving property (energy loss is small at the time of a contact with a roller) is calculated | required and its material is provided.

（式中、Ａは単結合、ヘテロ元素を含んでいてもよい炭素数４〜１８の２価の芳香族基（置換基を有していてもよい）、置換又は非置換のヒダントイン環、あるいは炭素数１〜１８の飽和又は不飽和直鎖状炭化水素、Ｂはヘテロ元素を含んでいてもよい炭素数４〜１８の２価の芳香族基（置換基を有していてもよい）、置換又は非置換のヒダントイン環、あるいは炭素数１〜１８の飽和又は不飽和直鎖状炭化水素を示す。また、Ｘはヒドロキシル基またはアミノ基、Ｙはピリジル基またはヒドラジノ基を示し、Ｒ¹〜Ｒ⁴は水素原子または炭素原子数１〜１８のアルキル基またはアリール基のいずれかを示す。Ｒ¹〜Ｒ⁴は同一でも異なっても良い。）
（Ｃ）シリカ、及び、
（Ｄ）シランカップリング剤、
（Ｅ）カーボンブラック、
を含むベルト用ゴム組成物である。 Hereinafter, the present invention will be described in more detail.
The rubber composition for a belt of the present invention includes the following components (A) to (E):
(A) A rubber component containing natural rubber and terminal-modified polybutadiene rubber, wherein the blending ratio of natural rubber and terminal-modified polybutadiene rubber is natural rubber / terminal-modified polybutadiene rubber = 10/90 to 90/10 (mass ratio). ) Rubber component,
(B) one or more selected from the group consisting of hydrazide compounds represented by the following general formulas (I) to (VI),

(In the formula, A is a single bond, a divalent aromatic group having 4 to 18 carbon atoms that may contain a hetero element (which may have a substituent), a substituted or unsubstituted hydantoin ring, or C1-C18 saturated or unsaturated linear hydrocarbon, B is a C4-C18 bivalent aromatic group which may contain a hetero element (may have a substituent), A substituted or unsubstituted hydantoin ring, or a saturated or unsaturated linear hydrocarbon having 1 to 18 carbon atoms, X represents a hydroxyl group or an amino group, Y represents a pyridyl group or a hydrazino group, R ¹ to R ⁴ represents either a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an aryl group, and R ^{1 to} R ⁴ may be the same or different.
(C) silica and
(D) a silane coupling agent,
(E) Carbon black,
A rubber composition for a belt comprising

The terminal-modified polybutadiene rubber in the component (A) is not particularly limited as long as the terminal is modified polybutadiene rubber. As a terminal modification method of the polybutadiene rubber, for example, a method of modifying the terminal (active terminal) of the polybutadiene rubber using a modifier can be used.
Examples of such modifiers include tin halides such as tin tetrachloride and tin tetrabromide, halogenated organotin compounds such as tributyltin chloride, silicon compounds such as silicon tetrachloride and chlorotriethylsilane, and isocyanates such as phenyl isocyanate. Examples thereof include group-containing compounds, amide compounds, lactam compounds, urea compounds, and isocyanuric acid derivatives.

The component (A) in the present invention is a rubber component containing natural rubber and terminal-modified polybutadiene rubber, and the blend ratio of natural rubber and terminal-modified polybutadiene rubber is natural rubber / terminal-modified polybutadiene rubber = 10/90. ~ 90/10 (mass ratio), preferably 10/90 to 85/15, more preferably 10/90 to 35/65, and still more preferably 20/80 to 30/70. . If the blending ratio of natural rubber is too large, the effect of energy saving will be reduced. On the other hand, if it is too small, normal physical properties (elongation, strength, etc.) as a rubber composition for belts will not reach the required level. Even in this case, the object of the present invention cannot be achieved.
In addition, it is suitable for the point that especially the balance of an energy-saving effect and a normal state physical property is excellent as said compounding ratio is 10 / 90-35 / 65 (mass ratio).

As said (A) component, it is suitable that liquid rubber is further included from a viewpoint of improving the workability in a roll, without impairing an energy-saving effect and normal state physical property.
Here, in the present invention, “liquid rubber” refers to Non-Patent Document 1: “Chemical product of 14102”, published by Chemical Industry Daily, January 29, 2002, page 1077 or page 1156 thereof. It means liquid rubber as used in the eye, and usually refers to a polymer having a molecular weight of about several thousand to several tens of thousands, fluidity at room temperature, and capable of crosslinking with other polymers by chemical reaction. In addition, when the terminal modified polybutadiene rubber in this invention corresponds to the said liquid rubber, it is suitable in order to expect the said workability improvement effect, without mix | blending liquid rubber separately.

As such a liquid rubber, for example, any of the liquid rubbers described on pages 1076 to 1080 of Non-Patent Document 1 can be used. More specifically, for example, liquid polyisoprene rubber, Examples thereof include liquid polybutadiene rubbers or those obtained by modifying their ends. These may be used alone or in combination of two or more. As commercially available products, for example, “LIR-50 (manufactured by Kuraray Co., Ltd.)” as liquid polyisoprene, “Nisseki polybutadiene B-2000 (Shin Nippon Petrochemical)” as liquid polybutadiene can be used.
In addition, as a content rate (mass%) which occupies in the said (A) component of such a liquid rubber, it is 3-15 mass% normally, Preferably it is 3-10 mass%.

In the hydrazide compounds represented by the general formulas (I) to (VI) of the component (B), A is a divalent aromatic group having 4 to 18 carbon atoms, which may contain a simple bond or a hetero element. (Which may have a substituent), a substituted or unsubstituted hydantoin ring, or a saturated or unsaturated linear hydrocarbon having 1 to 18 carbon atoms, B may contain a hetero element, 4 carbon atoms -18 divalent aromatic groups (which may have a substituent), a substituted or unsubstituted hydantoin ring, or a saturated or unsaturated linear hydrocarbon having 1 to 18 carbon atoms. Among these, A and B are preferably a C 4-18 divalent aromatic group (which may have a substituent) which may contain a hetero element.
Examples of the divalent aromatic group having 4 to 18 carbon atoms that may contain a hetero element (which may have a substituent) include, for example, an o-phenylene group, an m-phenylene group, a p-phenylene group, Naphthalene-1,4-diyl group, naphthalene-1,5-diyl group, naphthalene-2,6-diyl group, naphthalene-2,3-diyl group, biphenyl-4,4′-diyl group, biphenyl-3, 3'-diyl group, p-terphenyl-4,4 "-diyl group, 2,2-diphenylpropane-4 ', 4" -diyl group, fluorene-2,2'-diyl group, fluorene-3,3 Divalent hydrocarbon group such as' -diyl group, carbazole-2,7-diyl group, carbazole-3,6-diyl group, thiophene-2,5-diyl group, dibenzothiophene-2,5-diyl Group, furan-2,5-diyl A divalent group containing a hetero atom such as dibenzofuran-2,7-diyl group, dibenzofuran-3,6-diyl group, diphenylamine-4,4′-diyl group, diphenylether-4,4′-diyl group, etc. Among them, o-phenylene group, m-phenylene group and p-phenylene group are preferable, and m-phenylene group is particularly preferable.
Examples of the substituted or unsubstituted hydantoin ring include 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin.
Examples of the saturated or unsaturated linear hydrocarbon having 1 to 18 carbon atoms include methylene group, ethylene group, propylene group, tetramethylene group, heptamethylene group, octamethylene group, octadecamethylene group, 7,11-octa A decadienylene group etc. are mentioned.

Moreover, R < ¹ > -R < ⁴ > in the said general formula shows either hydrogen, a C1-C18 alkyl group, or an aryl group. Examples of the alkyl group having 1 to 18 carbon atoms include a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a tert-butyl group, and a hexyl group, a cyclopentyl group, a cyclohexyl group, and a cyclo group. Examples thereof include cyclic alkyl groups such as a heptyl group, among which a methyl group and an ethyl group are preferable. On the other hand, examples of the aryl group include a phenyl group and a naphthyl group (which may have a substituent).

Specific compounds represented by the above general formula (I) or (IV) are not particularly limited, and examples thereof include isophthalic acid dihydrazide, adipic acid dihydrazide, isophthalic acid di (1-methylethylidene) hydrazide, and adipine. Di (1-methylethylidene) hydrazide, di (1-methylpropylidene) hydrazide, isophthalic acid di (1-methylpropylidene) hydrazide, di (1,3-dimethylpropylidene) hydrazide, adipic acid Examples thereof include di (1,3-dimethylpropylidene) hydrazide, di (1-phenylethylidene) hydrazide, isophthalic acid, and di (1-phenylethylidene) hydrazide. In addition to these isophthalic acid dihydrazide and adipic acid dihydrazide derivatives, derivatives such as terephthalic acid dihydrazide, azelaic acid dihydrazide, succinic acid dihydrazide, icosanoic dicarboxylic acid dihydrazide, and the like can also be used. These can be used alone or in combination of two or more.
Among the compounds represented by the general formula (I) or (IV), isophthalic acid dihydrazide, adipic acid dihydrazide, and isophthalic acid di (1,3-dimethylpropylidene) hydrazide are particularly preferable from the viewpoint of energy saving effect and low cost. Preferably used.

The specific compound represented by the general formula (II) or (V) is not particularly limited, and examples thereof include salicylic acid hydrazide, 2-naphthalenic acid-3-hydroxyhydrazide, and salicylic acid (1-methylethylidene). Hydrazide, 2-naphthalenic acid-3-hydroxy (1-methylethylidene) hydrazide, salicylic acid (1-methylpropylidene) hydrazide, 2-naphthalenic acid-3-hydroxy (1-methylpropylidene) hydrazide, salicylic acid (1,3 -Dimethylpropylidene) hydrazide, 2-naphthalenic acid-3-hydroxy (1,3-dimethylpropylidene) hydrazide, 2-naphthalenic acid-3-hydroxy (1,3-dimethylbutylidene) hydrazide, salicylic acid (1-phenyl) Ethylidene) hydrazide, 2-naphthalene acid And 3-hydroxy (1-phenyl ethylidene) hydrazide. In addition to these salicylic acid hydrazide and 2-naphthalenic acid-3-hydroxyhydrazide derivatives, derivatives such as anthranilic acid hydrazide and 1-hydroxy-2-naphthalic acid hydrazide can also be used. These can be used alone or in combination of two or more.
Among the compounds represented by the general formula (II) or (V), 2-naphthalenoic acid-3-hydroxy (1,3-dimethylpropylidene) hydrazide, 2-naphthalene acid from the viewpoint of energy saving effect and low cost -3-Hydroxy (1,3-dimethylbutylidene) hydrazide and salicylic acid (1,3-dimethylpropylidene) hydrazide are particularly preferably used.

The specific compound represented by the general formula (III) or (VI) is not particularly limited, but for example, isonicotinic acid hydrazide, isonicotinic acid (1-methylethylidene) hydrazide, isonicotinic acid ( 1-methylpropylidene) hydrazide, isonicotinic acid (1,3-dimethylpropylidene) hydrazide, isonicotinic acid (1-phenylethylidene) hydrazide and the like. In addition to these isonicotinic acid hydrazide derivatives, for example, derivatives of carbonic acid dihydrazide can also be used. These can be used alone or in combination of two or more.
Among the compounds represented by the general formula (III) or (VI), isonicotinic acid hydrazide and isonicotinic acid (1,3-dimethylpropylidene) hydrazide are particularly preferably used from the viewpoint of energy saving effect and low cost. It is done.
As a method for synthesizing the hydrazide compounds represented by the above general formulas (I) to (VI), for example, see Pant, U., et al. C. Ramchandran, Reena; Joshi, B .; C. Rev. Room. Chim. (1979) 24 (3), 471-82.

  The blending amount of the component (B) with respect to the component (A) (the total amount when two or more hydrazide compounds represented by the general formulas (I) to (VI) are used in combination) is (A) It is 0.3-10 mass parts with respect to 100 mass parts of components, Preferably it is 0.5-5 mass parts, More preferably, it is 1-3 mass parts. If the blending amount of the component (B) is too large, the physical properties of the rubber are lowered, and if it is too little, the energy saving effect is lowered, so that the object of the present invention cannot be achieved in any case.

Examples of the component (C) include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Is preferred.
As a compounding quantity with respect to the said (A) component of such (C) component, it is 5-50 mass parts with respect to 100 mass parts of (A) component, Preferably it is 10-30 mass parts, More preferably, it is 15-30 mass parts. It is. If the amount of the component (C) is too large, the physical properties of the rubber deteriorate, and if it is too small, the required rubber hardness and energy saving effect cannot be obtained, so that in either case, the object of the present invention cannot be achieved.

The component (C) preferably has a nitrogen adsorption specific surface area (N ₂ SA) in the range of 30 to 240 m ² / g. If this N ₂ SA is less than 30 m ² / g, the required rubber properties may not be obtained, whereas if it exceeds 240 m ² / g, processability and energy saving may not be obtained. Here, the N ₂ SA is a value measured according to ASTM D1765-01 after drying at 300 ° C. for 1 hour.

As the component (D), any silane coupling agent used in the field of rubber can be used, but from the viewpoint of affinity with the component (A), a silane coupling agent containing sulfur is preferable. . Examples of such component (D) include polysulfide silane coupling agents such as bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide.
As a compounding quantity with respect to the said (A) component of such (D) component, 0.1-5 mass parts with respect to 100 mass parts of (A) component, Preferably it is 0.5-3 mass parts, More preferably, it is 0. .5 to 2 parts by mass. If the blending amount of the component (D) is too large, the physical properties are lowered and the cost is high, and if it is too small, the required energy saving property cannot be obtained, and in any case, the object of the present invention cannot be achieved.

In the present invention, from the viewpoint of reinforcing rubber strength, the following component (E):
(E) Carbon black,
Is blended.
The component (E) is not particularly limited, and examples thereof include SRF, GPF, FEF, HAF, ISAF, SAF, FT, and MT. These carbon blacks may be used alone or in combination of two or more.
As a compounding quantity with respect to the said (A) component of such (E) component, it is 30-75 mass parts with respect to 100 mass parts of (A) component, Preferably it is 30-50 mass parts, More preferably, it is 30-40 mass parts. It is. When the amount of the component (E) is too large, the required energy saving property may not be obtained, and when it is too small, the normal physical properties of the rubber may be inferior.

  In addition to the above components, the rubber composition for belts in the present invention includes a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, zinc white (ZnO), waxes, and antioxidants that are usually used in the rubber industry. Additives such as fillers, softeners, foaming agents, plasticizers, lubricants, tackifiers, and UV absorbers can be appropriately blended.

  The belt of the present invention is formed using the above-described rubber composition for a belt. Since the belt of the present invention has high hardness and good energy saving performance, it is particularly suitable for steel conveyor belt applications and long-distance conveyor belt applications.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples 1-7, Comparative Examples 1-4]
The raw material components were mixed together in the formulation shown in Table 1 (the numerical values of the components all represent parts by mass) and kneaded using a Banbury mixer to obtain an unvulcanized rubber composition. These compounded rubbers were vulcanized and cured at 155 ° C. for 10 to 15 minutes to obtain molded bodies. Various physical properties of the molded body after vulcanization and curing were evaluated. The results are shown in Tables 1 and 2.

Natural rubber product name RSS4.
End-modified polybutadiene Nippon Zeon, trade name Nippol BR1250H. End-modified polybutadiene rubber obtained by using an amide compound as a modifier.
Product name LIR-50, manufactured by Liquid Polyisoprene Kuraray.
Liquid polybutadiene , manufactured by Nippon Petrochemical Co., Ltd., trade name Nisseki Polybutadiene B-2000.
Product name BR01, manufactured by Polybutadiene JSR.
Styrene-butadiene rubber , manufactured by JSR Corporation, trade name SBR1500.
CB1
Carbon black FEF.
CB2
Carbon black ISAF.
Silica Nippon Silica Industry Co., Ltd., trade name Nipsil AQ.
Silane coupling agent, Degussa, trade name Si-69.
Stearic acid , manufactured by Shin Nippon Science Co., Ltd.
Anti-aging agent Ouchi Shinsei Chemical Co., Ltd., trade name NOCRACK 6C.
Zinc oxide , manufactured by Toho Zinc Co., Ltd.
Sulfur manufactured by Sulfur Tsurumi Chemical Co., Ltd.
Vulcanization accelerator manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name Noxeller NS.
Hydrazide 1
2-Naphthalenic acid-3-hydroxy (1,3-dimethylbutylidene) hydrazide.
Hydrazide 2
Isophthalic acid dihydrazide.

tan δ / E ' ^0.32 (20 ° C)
The loss tangent tan δ and dynamic elastic modulus E ′ at 20 ° C. were measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho under the conditions of a distortion rate of 2% and a frequency of 10 Hz, and tan δ / E ′ ^0.32 (20 ° C.) was obtained. Asked.
Hardness JIS-A hardness measured according to JIS K6301: 1995.
Elongation (%), Tensile strength (MPa)
It measured by the tension test based on JISK6257: 1993.

Claims (5)

Each component of the following (A)-(E),
(A) A rubber component containing natural rubber and terminal-modified polybutadiene rubber, wherein the blending ratio of natural rubber and terminal-modified polybutadiene rubber is natural rubber / terminal-modified polybutadiene rubber = 10/90 to 90/10 (mass ratio). ) Rubber component,
(B) one or more selected from the group consisting of hydrazide compounds represented by the following general formulas (I) to (VI),

(In the formula, A is a single bond, a divalent aromatic group having 4 to 18 carbon atoms that may contain a hetero element (which may have a substituent), a substituted or unsubstituted hydantoin ring, or C1-C18 saturated or unsaturated linear hydrocarbon, B is a C4-C18 bivalent aromatic group which may contain a hetero element (may have a substituent), A substituted or unsubstituted hydantoin ring, or a saturated or unsaturated linear hydrocarbon having 1 to 18 carbon atoms, X represents a hydroxyl group or an amino group, Y represents a pyridyl group or a hydrazino group, R ¹ to R ⁴ represents either a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, or an aryl group, and R ^{1 to} R ⁴ may be the same or different.
(C) silica and
(D) a silane coupling agent,
(E) Carbon black,
Including
The component (B) is 0.3 to 10 parts by mass, the component (C) is 5 to 50 parts by mass, and the component (D) is 0.1 to 5 parts by mass with respect to 100 parts by mass of the component (A). A rubber composition for belts comprising 30 to 75 parts by mass of the component (E).   The rubber composition for a belt according to claim 1, wherein the component (A) contains 3 to 15% by mass of a liquid rubber.   The rubber for a belt according to claim 1 or 2, wherein a blending ratio of the natural rubber and the terminal-modified polybutadiene rubber in the component (A) is natural rubber / terminal-modified polybutadiene rubber = 10/90 to 35/65 (mass ratio). Composition.   The rubber composition for a belt according to claim 1, 2 or 3, wherein the component (B) is isophthalic acid dihydrazide and / or 2-naphthalenic acid-3-hydroxy (1,3-dimethylbutylidene) hydrazide.   A belt comprising the rubber composition for a belt according to any one of claims 1 to 4.