JP2022167317A - Rubber composition for truck tires or bus tires, and truck tire and bus tire - Google Patents

Abstract

To provide a rubber composition for truck tires or bus tires having an excellent expansion ratio, and a truck tire or a bus tire.SOLUTION: A rubber composition for truck tires or bus tires contains the following components (a), (b), (c), and (d). (a) A rubber component containing natural rubber, (b) a chemical foamer, (c) at least one compound selected from a specific pyrazolone compound and a salt of the compound and (d) carbon black.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a rubber composition for truck tires or bus tires, and truck tires and bus tires.

Truck tires and bus tires are required to have improved braking performance when traveling on ice or snow. As a solution to these problems, there is a method using a foamed rubber composition (Patent Document 1).

Generally, a foamed rubber composition can be produced by adding a foaming agent to a rubber component. However, such a method cannot obtain a sufficient expansion ratio. Therefore, it is not preferable from the viewpoint of manufacturing efficiency or final physical properties of the tire such as braking performance.

JP 2008-149934 A

In view of the circumstances as described above, an object of the present invention is to provide a rubber composition for truck tires or bus tires having an excellent foaming ratio, and truck tires and bus tires.

The inventors of the present invention have made intensive studies to solve the above problems, and found that a truck tire having an excellent expansion ratio by adding a pyrazolone-based compound to a rubber component containing natural rubber containing a chemical foaming agent. Or it discovered that the rubber composition for bus tires could be obtained. The inventors of the present invention conducted further studies based on such knowledge, and completed the present invention.

〔式中、Ｒ^１は水素原子、アルキル基、又はアラルキル基を示し、Ｒ^２、Ｒ^３及びＲ^４は、同一又は異なって、水素原子、アルキル基、アラルキル基、又はアリール基を示し、これら各基は、それぞれ１個以上の置換基をさらに有していてもよい。〕
項２．
成分（ａ）として、更にブタジエンゴム（ＢＲ）及びスチレン－ブタジエン共重合体ゴム（ＳＢＲ）からなる群より選択されるゴム成分の少なくとも一種を含む、項１に記載のトラック又はバスタイヤ用ゴム組成物。
項３．
前記式（１）において、Ｒ^１、Ｒ^３及びＲ^４が水素原子であり、Ｒ^２がメチル基である、項１又は２に記載のゴム組成物。
項４．
更に成分（ｅ）発泡助剤を含む、項１～３のいずれかに記載のゴム組成物。
項５．
項１～４の何れかに記載のゴム組成物を用いて作製されたトラックタイヤ又はバスタイヤ。 That is, the present invention provides the following rubber composition for truck tires or bus tires, and truck tires or bus tires.
Section 1.
A rubber composition for truck tires or bus tires, comprising the following components (a), (b), (c) and (d).
(a) a rubber component containing natural rubber (b) a chemical foaming agent (c) at least one compound selected from compounds represented by the following formula (1) and salts of said compounds (d) carbon black

[In the formula, R ¹ represents a hydrogen atom, an alkyl group, or an aralkyl group; R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group; Each group may further have one or more substituents. ]
Section 2.
Item 2. The rubber composition for truck or bus tires according to item 1, further comprising at least one rubber component selected from the group consisting of butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR) as component (a). thing.
Item 3.
Item 3. The rubber composition according to item 1 or 2, wherein in the formula (1), R ¹ , R ³ and R ⁴ are hydrogen atoms, and R ² is a methyl group.
Section 4.
Item 4. The rubber composition according to any one of items 1 to 3, further comprising component (e) a foaming aid.
Item 5.
A truck tire or a bus tire produced using the rubber composition according to any one of Items 1 to 4.

The rubber composition for truck tires or bus tires according to the present invention as described above has an excellent foaming ratio.

(1. Rubber composition for truck tires or bus tires)
The rubber composition for truck tires or bus tires of the present invention contains the following components (a), (b), (c) and (d).
(a) a rubber component containing natural rubber (b) a chemical foaming agent (c) at least one compound selected from compounds represented by formula (1) and salts of said compounds (d) carbon black

〔式中、Ｒ^１は水素原子、アルキル基、又はアラルキル基を示し、Ｒ^２、Ｒ^３及びＲ^４は、同一又は異なって、水素原子、アルキル基、アラルキル基、又はアリール基を示し、これら各基は、それぞれ１個以上の置換基をさらに有していてもよい。〕

[In the formula, R ¹ represents a hydrogen atom, an alkyl group, or an aralkyl group; R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group; Each group may further have one or more substituents. ]

The rubber composition for truck tires or bus tires of the present invention may be a mixture of components (a), (b), (c) and (d), or may be a mixture of components (a), (b), (c) and (d). and (b), (c) and (d) may be mixed and then component (b) may be foamed. In other words, it includes an embodiment in which components (a), (b), (c) and (d) are mixed in any order.

(1.1. Component (a): Rubber component containing natural rubber)
Component (a) is a rubber component including natural rubber. Component (a) of the rubber composition for truck tires or bus tires of the present invention may be natural rubber alone, or may contain other rubber components in addition to natural rubber. The amount of natural rubber used is preferably 1 to 100% by mass, more preferably 40 to 100% by mass, based on 100% by mass of component (a).

Examples of natural rubber include natural rubber latex, technical grade rubber (TSR), smoked sheet (RSS), gutta-percha, Eucommia-derived natural rubber, guayule-derived natural rubber, Russian dandelion-derived natural rubber, etc. Further, these natural rubbers are modified. Modified natural rubbers such as epoxidized natural rubber, methacrylic acid-modified natural rubber, halogen-modified natural rubber, deproteinized natural rubber, maleic acid-modified natural rubber, sulfonic acid-modified natural rubber, and styrene-modified natural rubber can also be used. preferable.

The ratio of cis/trans/vinyl in the double bond of natural rubber is not particularly limited, and any ratio can be suitably used.

Further, the rubber composition for truck tires or bus tires of the present invention, in addition to natural rubber as component (a), further comprises butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR). It may contain at least one selected rubber component. Component (a) includes natural rubber and butadiene rubber (BR), natural rubber and styrene-butadiene copolymer rubber (SBR), natural rubber, butadiene rubber (BR), and styrene-butadiene copolymer rubber ( SBR) can be exemplified. These rubbers also include modified rubbers by modification techniques such as main chain modification, single end modification, or both end modification.

When component (a) contains natural rubber and butadiene rubber (BR), or consists only of natural rubber and butadiene rubber (BR), the mixing ratio of natural rubber and butadiene rubber (BR) is natural rubber:butadiene rubber (BR)=99:1 to 1:99 is preferred, 80:20 to 20:80 is more preferred, and 60:40 to 40:60 is particularly preferred.

When component (a) contains natural rubber and styrene-butadiene copolymer rubber (SBR), or consists only of natural rubber and styrene-butadiene copolymer rubber (SBR), natural rubber and styrene-butadiene copolymer rubber The compounding ratio of coalesced rubber (SBR) is preferably natural rubber: styrene-butadiene copolymer rubber (SBR) = 99:1 to 1:99, more preferably 80:20 to 20:80, and 60:40 to 40. :60 is particularly preferred.

Component (a) contains natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR), or only natural rubber, butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR) When it consists of, the mixing ratio of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR) is natural rubber: butadiene rubber (BR): styrene-butadiene copolymer rubber (SBR) = 98: 1:1 to 1:50:49 is preferred, 95:3:2 to 10:45:45 is more preferred, and 90:5:5 to 50:30:20 is particularly preferred.

The content of component (a) in the total 100% by mass of components (a), (b), (c), and (d) in the rubber composition is preferably 0.01 to 95% by mass. , more preferably 0.1 to 70% by mass. By containing 0.01% by mass or more of component (a), elasticity can be imparted to the rubber composition. On the other hand, by making the component (a) contained in the rubber composition 95% by mass or less, the cost of the rubber composition can be reduced, and as a result, the economic efficiency can be improved. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

The rubber composition for truck tires or bus tires of the present invention may contain rubber components other than the natural rubber, butadiene rubber (BR), and styrene-butadiene copolymer rubber (SBR) of component (a). .

Such rubber components are not particularly limited, and examples thereof include diene rubbers, non-diene rubbers, and mixtures of diene rubbers and non-diene rubbers.

Diene rubbers include isoprene rubber (IR), styrene-isoprene-butadiene rubber (SIBR), nitrile rubber (NBR), chloroprene rubber (CR), styrene-isoprene-styrene triblock copolymer (SIS), styrene -butadiene-styrene triblock copolymer (SBS), etc., and modified diene rubbers thereof.

The modified diene-based rubber includes diene-based rubbers obtained by modification techniques such as main chain modification, single-end modification, and both-end modification. Here, the modified functional group of the modified diene rubber includes various functional groups such as an epoxy group, an amino group, an alkoxysilyl group, and a hydroxyl group. may be included.

The method for producing the diene rubber is not particularly limited, and examples thereof include emulsion polymerization, solution polymerization, radical polymerization, anionic polymerization, and cationic polymerization. Also, the glass transition point of the synthetic diene rubber is not particularly limited.

Non-diene rubbers include butyl rubber, ethylene-propylene rubber (EPM), ethylene-propylene-diene terpolymer rubber (EPDM), urethane rubber (U), propylene hexafluoride-vinylidene fluoride copolymer ( FKM), tetrafluoroethylene-propylene copolymer (FEPM), tetrafluoroethylene-perfluorovinyl ether copolymer (FFKM), methyl silicone rubber (MQ), vinyl-methyl silicone rubber (VMQ), phenyl-methyl silicone rubber (PMQ), acrylic rubber (ACM), polysulfide rubber (T), epichlorohydrin rubber (CO, ECO), and modified non-diene rubbers thereof. Among them, butyl rubber and ethylene-propylene-diene terpolymer rubber (EPDM) are preferred.

Modified non-diene rubbers include non-diene rubbers obtained by modification techniques such as main chain modification, single end modification, and both end modification. Here, the modified functional group of the modified non-diene rubber includes various functional groups such as epoxy group, amino group, alkoxysilyl group, and hydroxyl group. may be contained in the system rubber.

The method for producing the non-diene rubber is not particularly limited, and examples thereof include emulsion polymerization, solution polymerization, radical polymerization, anionic polymerization, and cationic polymerization. Also, there is no particular limitation on the glass transition point of the synthetic non-diene rubber.

Moreover, the ratio of cis/trans/vinyl in the double bond portion of the diene rubber is not particularly limited, and any ratio can be suitably used. There are no particular restrictions on the number average molecular weight and molecular weight distribution of the diene rubber, and a number average molecular weight of 500 to 3,000,000 and a molecular weight distribution of 1.5 to 15 are preferred. A wide range of known rubbers can be used as the non-diene rubber.

(1.2. Component (b); chemical blowing agent)
The chemical foaming agent is not particularly limited, and a wide range of known chemical foaming agents can be used. For example, azodicarbonamide, N,N'-dinitrosopentane methylenetetramine, p,p'-oxybisbenzenesulfonyl hydrazide, paratoluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, diazoaminobenzene, hydrazodicarbonamide, barium azo Dicarboxylate, azobisisobutyronitrile, organic acids such as monosodium citrate and organic chemical foaming agents such as their metal salts, and sodium bicarbonate, ammonium hydrogen carbonate, sodium carbonate, ammonium carbonate, aluminum acetate, ammonium nitrite, Inorganic chemical blowing agents such as sodium borohydride are included.

The above chemical foaming agents may be used singly or in combination of two or more.

Among the above chemical foaming agents, azodicarbonamide, p,p'-oxybisbenzenesulfonyl hydrazide, or sodium bicarbonate are preferred.

The amount of component (b) compounded is preferably 0.1 to 100 parts by mass, more preferably 0.1 to 80 parts by mass, per 100 parts by mass of component (a) in the rubber composition. It is more preferably 0.5 to 60 parts by mass, and particularly preferably 1 to 50 parts by mass. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

The content of component (b) in the total 100% by mass of components (a), (b), (c), and (d) in the rubber composition is preferably 0.01 to 95% by mass. , more preferably 0.05 to 90% by mass, even more preferably 0.1 to 50% by mass, and particularly preferably 0.5 to 30% by mass. By containing 0.01% by mass or more of component (b), the expansion ratio of component (a) is improved. On the other hand, by making the component (b) contained in the rubber composition 95% by mass or less, the cost of the rubber composition is suppressed and the economic efficiency is improved. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

(1.3. Component (c): Compound Represented by Formula (1), or Salt of the Compound)
Component (c) is a compound represented by the following formula (1) or a salt thereof (hereinafter, the compound and a salt thereof may be collectively referred to simply as "compound (1)").

〔式（１）中、Ｒ^１は水素原子、アルキル基、又はアラルキル基を示し、Ｒ^２、Ｒ^３及びＲ^４は同一又は異なって、水素原子、アルキル基、アラルキル基、又はアリール基を示す。これら各基は、それぞれ１個以上の置換基を有していてもよい。〕

[In formula (1), R ¹ represents a hydrogen atom, an alkyl group, or an aralkyl group, and R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group. . Each of these groups may have one or more substituents. ]

The "alkyl group" in compound (1) is not particularly limited, and examples thereof include linear, branched or cyclic alkyl groups, and specific examples include methyl, ethyl, n-propyl, Linear or branched alkyl groups having 1 to 4 carbon atoms such as isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, further 1-ethylpropyl, n-pentyl, isopentyl, neopentyl, n -hexyl, isohexyl, 3-methylpentyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, 5-propylnonyl, n-tridecyl, n-tetradecyl, n-pentadecyl , hexadecyl, heptadecyl, octadecyl, etc., linear or branched C5-18 alkyl groups; C3-8 cyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and the like.

The "aralkyl group" in compound (1) is not particularly limited, and examples thereof include benzyl, phenethyl, trityl, 1-naphthylmethyl, 2-(1-naphthyl)ethyl, 2-(2-naphthyl)ethyl groups and the like. mentioned.

The "aryl group" in compound (1) is not particularly limited, and examples thereof include phenyl, biphenyl, naphthyl, dihydroindenyl, 9H-fluorenyl groups and the like.

Each of these alkyl groups, aralkyl groups and aryl groups may have one or more substituents at any substitutable position. The "substituent" is not particularly limited, and examples thereof include halogen atoms, amino groups, aminoalkyl groups, alkoxycarbonyl groups, acyl groups, acyloxy groups, amide groups, carboxyl groups, carboxyalkyl groups, formyl groups, and nitrile groups. , nitro group, alkyl group, hydroxyalkyl group, hydroxyl group, alkoxy group, aryl group, aryloxy group, thiol group, alkylthio group, arylthio group and the like. The substituent may preferably have 1 to 5, more preferably 1 to 3.

The "halogen atom" in compound (1) includes fluorine, chlorine, bromine, iodine and astatine atoms, preferably fluorine, chlorine, bromine and iodine atoms.

The “amino group” in compound (1) includes not only the amino group represented by —NH ₂ but also, for example, methylamino, ethylamino, n-propylamino, isopropylamino, n-butylamino, isobutylamino, s -linear or branched carbon such as butylamino, t-butylamino, 1-ethylpropylamino, n-pentylamino, neopentylamino, n-hexylamino, isohexylamino, 3-methylpentylamino groups monoalkylamino group having a number of about 1 to 6; substituted amino such as a dialkylamino group having two linear or branched alkyl groups having about 1 to 2 carbon atoms such as dimethylamino, ethylmethylamino and diethylamino groups A group is also included.

The "aminoalkyl group" in compound (1) is not particularly limited, and examples include aminomethyl, methylaminomethyl, ethylaminomethyl, dimethylaminomethyl, ethylmethylaminomethyl, diethylaminomethyl, 2-aminoethyl, 2- (methylamino) ethyl, 2-(ethylamino) ethyl, 2-(dimethylamino) ethyl, 2-(ethylmethylamino) ethyl, 2-(diethylamino) ethyl, 3-aminopropyl, 3-(methylamino) propyl , 3-(ethylamino) propyl, 3-(dimethylamino) propyl, 3-(ethylmethylamino) propyl, 3-(diethylamino) propyl groups and other aminoalkyl groups having about 1 to 7 carbon atoms, monoalkyl-substituted amino Examples include an alkyl group or a dialkyl-substituted aminoalkyl group.

The "alkoxycarbonyl group" in compound (1) is not particularly limited, and examples thereof include straight-chain or branched-chain alkoxycarbonyl groups having 1 to 4 carbon atoms such as methoxycarbonyl and ethoxycarbonyl groups.

The "acyl group" in compound (1) is not particularly limited, and examples thereof include linear or branched alkylcarbonyl groups having 1 to 4 carbon atoms such as acetyl, propionyl and pivaloyl groups.

The "acyloxy group" in compound (1) is not particularly limited, and examples thereof include linear or branched acyloxy groups having 1 to 4 carbon atoms such as acetyloxy, propionyloxy, n-butyryloxy groups, and the like. .

The "amide group" in compound (1) is not particularly limited, and examples thereof include carboxylic acid amide groups such as acetamide and benzamide groups; thioamide groups such as thioacetamide and thiobenzamide groups; N-methylacetamide and N-benzylacetamide. N-substituted amide groups such as groups;

The "carboxyalkyl group" in compound (1) is not particularly limited, and examples thereof include carboxymethyl, carboxyethyl, carboxy-n-propyl, carboxy-n-butyl, carboxy-n-pentyl, and carboxy-n-hexyl groups. and other carboxyalkyl groups.

The "hydroxyalkyl group" in compound (1) is not particularly limited, and examples thereof include hydroxyalkyl groups such as hydroxymethyl, hydroxyethyl, hydroxy-n-propyl and hydroxy-n-butyl groups.

The "alkoxy group" in compound (1) is not particularly limited, and examples thereof include linear, branched or cyclic alkoxy groups, and specific examples include methoxy, ethoxy, n-propoxy, Linear or branched alkoxy groups of isopropoxy, n-butoxy, t-butoxy, n-pentyloxy, neopentyloxy and n-hexyloxy groups; cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy , cycloheptyloxy, and cyclic alkoxy groups such as cyclooctyloxy groups.

The "aryloxy group" in compound (1) is not particularly limited, and examples thereof include phenoxy, biphenyloxy, naphthoxy and the like.

The "alkylthio group" in compound (1) is not particularly limited, and examples thereof include methylthio group, ethylthio group, n-propylthio group and the like.

The "arylthio group" in compound (1) is not particularly limited and includes, for example, a phenylthio group, a naphthylthio group, a biphenylthio group and the like.

Among the compounds represented by formula (1), compounds in which R ¹ is a hydrogen atom are preferred.

Among the compounds represented by formula (1), R ² is preferably a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an aralkyl group, and a hydrogen atom or a carbon number A compound having 1 to 4 linear or branched alkyl groups is more preferred, and a compound having a methyl group is even more preferred.

Among the compounds represented by formula (1), compounds in which at least one of R ³ and R ⁴ is a hydrogen atom are preferred, and compounds in which both R ³ and R ⁴ are hydrogen atoms are more preferred.

Among the compounds represented by formula (1), R ¹ is a hydrogen atom, R ² is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or an aralkyl group, and R ³ and R ⁴ are both hydrogen atoms, R ¹ is a hydrogen atom, R ² is a hydrogen atom, or a linear or branched alkyl group having 1 to 4 carbon atoms, and R ³ and R Compounds in which both ⁴ are hydrogen atoms are more preferred, and compounds in which R ¹ is a hydrogen atom, R ² is a methyl group, and both R ³ and R ⁴ are hydrogen atoms are particularly preferred.

Examples of compounds represented by formula (1) include 5-pyrazolone, 3-methyl-5-pyrazolone, 3-(naphthalen-2-yl)-1H-pyrazol-5(4H)-one, 3-phenyl -1H-pyrazol-5(4H)-one, 3-propyl-1H-pyrazol-5(4H)-one, 3-undecyl-1H-pyrazol-5(4H)-one, 4-(2-hydroxyethyl) -3-methyl-1H-pyrazol-5(4H)-one, 4-benzyl-3-methyl-1H-pyrazol-5(4H)one, and 5-methyl-2-(4-nitrophenyl)-1H -pyrazol-3(2H)-one, and the like.

Among them, preferable compounds as the compound represented by formula (1) are 5-pyrazolone, 3-methyl-5-pyrazolone, 3-(naphthalen-2-yl)-1H-pyrazol-5(4H)-one, 3 -Phenyl-1H-pyrazol-5(4H)-one and 3-propyl-1H-pyrazol-5(4H)-one are more preferred, and 3-methyl-5-pyrazolone is particularly preferred.

The component (c) in the rubber composition for truck tires or bus tires of the present invention may contain one of the above compounds alone, or may contain two or more of them in combination.

Some compounds (1) give rise to tautomers. A chemical equilibrium of tautomers can be reached when tautomerization is allowed (eg, in solution). Compound (1) can exist as tautomers, such as those represented by formulas (2) to (7).

In the above formula (1), the compound in which R ¹ and R ³ are hydrogen atoms (compound (1)-A) has tautomers represented by the following formulas (2) to (4). .

〔式中、Ｒ^２及びＲ^４は前記に同じである。〕

[In the formula, R ² and R ⁴ are the same as above. ]

In the above formula (1), the compound in which R ³ is a hydrogen atom (compound (1)-B) has tautomers represented by the following formulas (5) and (6).

〔式中、Ｒ^１、Ｒ^２及びＲ^４は前記に同じである。〕

[In the formula, R ¹ , R ² and R ⁴ are the same as above. ]

In the above formula (1), the compound in which R ¹ is a hydrogen atom (compound (1)-C) has a tautomer represented by the following formula (7).

〔式中、Ｒ^２、Ｒ^３及びＲ^４は前記に同じである。〕

[In the formula, R ² , R ³ and R ⁴ are the same as above. ]

The tautomers represented by the above formulas (2) to (7) and compound (1) have reached an equilibrium state in which all isomers coexist. Thus, unless otherwise stated, all tautomeric forms of compound (1) are within the scope of the invention herein.

Moreover, the salt of the compound represented by formula (1) is not particularly limited and includes all kinds of salts. Examples of such salts include inorganic acid salts such as hydrochlorides, sulfates and nitrates; organic acid salts such as acetates and methanesulfonates; alkali metal salts such as sodium salts and potassium salts; magnesium salts and calcium salts; alkaline earth metal salts such as salts; ammonium salts such as dimethylammonium and triethylammonium;

Component (c) in the rubber composition for truck/bus tires of the present invention may include a mixture containing compound (1) in any proportion.

The amount of component (c) compounded is preferably 0.01 to 50 parts by mass, more preferably 0.05 to 40 parts by mass, with respect to 100 parts by mass of component (a) in the rubber composition. is more preferable, 0.1 to 30 parts by mass is more preferable, and 0.5 to 10 parts by mass is particularly preferable.

The content of component (c) in the total 100% by mass of components (a), (b), (c), and (d) in the rubber composition is preferably 0.01 to 50% by mass. , more preferably 0.05 to 30% by mass, still more preferably 0.1 to 20% by mass, and particularly preferably 0.2 to 5% by mass. By containing 0.01% by mass or more of component (c), the expansion ratio of component (a) can be improved. On the other hand, when the component (c) contained in the rubber composition is 50% by mass or less, the cost of the rubber composition can be reduced and the economic efficiency can be improved. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

The mixing ratio of the components (b) and (c) is 1 to 80 parts by mass of the component (c) when the total mass of the components (b) and (c) is 100 parts by mass. It is preferably 5 to 75 parts by mass, more preferably 10 to 70 parts by mass, and particularly preferably 15 to 65 parts by mass.

(1.4. Component (d): carbon black)
Component (d) is carbon black. In this specification, the inorganic filler is defined as not including carbon black.

Carbon black is not particularly limited, and examples thereof include commercially available carbon black, Carbon-Silica Dual phase filler, and the like. By including carbon black in the rubber component, it is possible to obtain the effect of reducing the electrical resistance of the rubber to suppress electrification and the effect of improving the strength of the rubber.

Specifically, carbon black includes, for example, high-, medium-, or low-structure SAF, ISAF, IISAF, N110, N134, N220, N234, N330, N339, N375, N550, HAF, FEF, GPF, and SRF grade carbon. black and the like. Among the preferred carbon blacks are SAF, ISAF, IISAF, N134, N234, N330, N339, N375, HAF, or FEF grade carbon blacks.

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

In addition, the nitrogen adsorption specific surface area of carbon black (N2SA, measured according to JISK6217-2:2001) is preferably 30 to 200 m ² /g, more preferably 40 to 180 m ² /g, particularly preferably 50 to 200 m 2 /g. 160 m ² /g.

The amount of component (d) compounded is preferably 0.1 to 95 parts by mass, more preferably 0.5 to 90 parts by mass, relative to 100 parts by mass of component (a) in the rubber composition. is more preferable, 1 to 85 parts by mass is more preferable, and 2 to 80 parts by mass is particularly preferable. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

The content of component (d) in the total 100% by mass of components (a), (b), (c), and (d) in the rubber composition is preferably 0.01 to 95% by mass. , more preferably 0.05 to 90% by mass, still more preferably 0.1 to 85% by mass, and particularly preferably 0.5 to 80% by mass. By containing 0.01% by mass or more of component (d), mechanical properties can be imparted to the rubber composition. On the other hand, when the component (d) contained in the rubber composition is 95% by mass or less, the cost of the rubber composition can be reduced and the economic efficiency can be improved. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

In addition, in the rubber composition of the present invention, a silane coupling agent and a titanate coupling agent are added for the purpose of increasing the toughness of the rubber composition by the component (d), or for the purpose of increasing the abrasion resistance as well as the tear strength of the rubber composition. agent, an aluminate coupling agent, and a zirconate coupling agent.

The silane coupling agent is not particularly limited, and commercially available products can be suitably used. Examples of such silane coupling agents include sulfide, polysulfide, thioester, thiol, olefin, epoxy, amino and alkyl silane coupling agents.

Examples of sulfide-based silane coupling agents 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)trisulfide 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 preferred.

Thioester-based silane coupling agents include, for example, 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.

Thiol-based silane coupling agents include, for example, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-[ethoxybis(3,6,9,12,15 -Pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol and the like.

Examples of olefinic silane coupling agents include dimethoxymethylvinylsilane, vinyltrimethoxysilane, dimethylethoxyvinylsilane, diethoxymethylvinylsilane, triethoxyvinylsilane, vinyltris(2-methoxyethoxy)silane, allyltrimethoxysilane, allyltri Ethoxysilane, p-styryltrimethoxysilane, 3-(methoxydimethoxydimethylsilyl)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 epoxy-based silane coupling agents 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 preferred.

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

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

Among these silane coupling agents, bis(3-triethoxysilylpropyl)tetrasulfide can be particularly preferably used.

The titanate coupling agent is not particularly limited, and commercially available products can be suitably used. Examples of such titanate coupling agents include alkoxide, chelate and acylate titanate coupling agents.

Examples of alkoxide-based titanate coupling agents include tetraisopropyl titanate, tetra-normal butyl titanate, butyl titanate dimer, tetraoctyl titanate, tetra-tert-butyl titanate, tetra-stearyl titanate, and the like. Of these, tetraisopropyl titanate is preferred.

Examples of chelate titanate coupling agents include titanium acetylacetonate, titanium tetraacetylacetonate, titanium ethylacetoacetate, titanium dodecylbenzenesulfonic acid compounds, titanium phosphate compounds, titanium octylene glycolate, and titanium ethylacetoacetate. , titanium lactate ammonium salt, titanium lactate, titanium ethanolamine, titanium octylene glycolate, titanium aminoethylaminoethanolate, and the like. Among these, titanium acetylacetonate is preferred.

Examples of the acylate titanate coupling agent include titanium isostearate.

The aluminate coupling agent is not particularly limited, and commercially available products can be suitably used. Examples of such aluminate coupling agents include 9-octadecenylacetoacetate aluminum diisopropylate, aluminum secondary butoxide, aluminum trisacetylacetonate, aluminum bisethylacetoacetate monoacetylacetonate, aluminum trisethylacetoacetate and the like. can be mentioned. Of these, 9-octadecenylacetoacetate aluminum diisopropylate is preferred.

The zirconate coupling agent is not particularly limited, and commercially available products can be suitably used. Examples of such zirconate coupling agents include alkoxide, chelate, and acylate zirconate coupling agents.

Examples of alkoxide-based zirconate coupling agents include normal propyl zirconate and normal butyl zirconate. Among these, normal butyl zirconate is preferred.

Chelate-based zirconate coupling agents include, for example, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethylacetoacetate, zirconium lactate ammonium salt, and the like. Among these, zirconium tetraacetylacetonate is preferred.

Examples of the acylate zirconate coupling agent include zirconium stearate and zirconium octylate. Among these, zirconium stearate is preferred.

In the present invention, the silane coupling agent, titanate coupling agent, aluminate coupling agent, and zirconate coupling agent may be used singly or in combination of two or more.

The amount of the coupling agent compounded in the rubber composition of the present invention is preferably 0.1 to 20 parts by mass, more preferably 3 to 15 parts by mass, with respect to 100 parts by mass of the component (d). preferable. If it is 0.1 parts by mass or more, the effect of improving the tear strength of the rubber composition can be more suitably exhibited, and if it is 20 parts by mass or less, the cost of the rubber composition is reduced and economic efficiency is improved. do.

(1.5. Component (e): foaming aid)
The rubber composition for truck tires or bus tires of the present invention preferably further contains a foaming aid as component (e). Such a foaming aid is not particularly limited, and those conventionally widely used as foaming aids can be used. For example, urea compounds, zinc compounds, lead compounds and the like can be mentioned, and among these, urea compounds are preferred.

Urea compounds include urea, mixtures of urea with fatty acids and fatty acid metal salts, thiourea, tetramethylurea, dimethylthiourea, semicarbazide, carbohydrazide, etc. Among them, urea and thiourea are preferred.

Examples of the zinc compound include zinc oxide, zinc stearate, zinc benzenesulfinate, zinc toluenesulfonate, zinc trifluoromethanesulfonate, and zinc carbonate. Among them, zinc oxide and zinc stearate are preferred.

Lead compounds include lead dioxide, tribasic lead, and the like.

The urea compound includes azodicarbonamide, N,N'-dinitrosopentanemethylenetetramine, p,p'-oxybisbenzenesulfonyl hydrazide, paratoluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, hydra It is preferably used in combination with zodicarbonamide, and among these, it is particularly preferable to be used in combination with azodicarbonamide.

Further, the rubber composition of the present invention preferably contains 1 to 1000 parts by mass of the component (b) with respect to 100 parts by mass of the urea compound.

The zinc compound includes azodicarbonamide, N,N'-dinitrosopentanemethylenetetramine, p,p'-oxybisbenzenesulfonyl hydrazide, paratoluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, hydra A combined use with zodicarbonamide is preferred.

Further, it is preferable to use 1 to 1000 parts by mass of the component (b) with respect to 100 parts by mass of the zinc compound.

The lead compound includes azodicarbonamide, N,N'-dinitrosopentanemethylenetetramine, p,p'-oxybisbenzenesulfonyl hydrazide, paratoluenesulfonyl hydrazide, p-toluenesulfonyl semicarbazide, hydrazo as the component (b). It is preferably used in combination with dicarbonamide.

Further, it is preferable to use 1 to 1000 parts by mass of the component (b) with respect to 100 parts by mass of the lead compound.

The amount of component (e) compounded is preferably 0.01 to 90 parts by mass, more preferably 0.05 to 85 parts by mass, per 100 parts by mass of component (a) in the rubber composition. It is more preferably 0.1 to 80 parts by mass, and particularly preferably 0.5 to 50 parts by mass. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

The content of component (e) in the total 100% by mass of components (a), (b), (c), (d), and (e) in the rubber composition is 0.01 to 95% by mass. preferably 0.05 to 90% by mass, even more preferably 0.1 to 50% by mass. By containing 0.01% by mass or more of component (e), the expansion ratio of component (a) can be improved. On the other hand, by making the component (e) contained in the rubber composition 95% by mass or less, the cost of the rubber composition can be reduced and the economic efficiency can be improved. Here, preferred component (a) is natural rubber alone or a rubber component selected from the group consisting of natural rubber, butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR).

(1.6. Other compounds)
In addition to the above components (a), (b), (c), (d) and (e), the rubber composition for truck and bus tires of the present invention contains compounding agents commonly used in the rubber industry, For example, inorganic fillers, antioxidants, antiozonants, softeners, processing aids, waxes, resins, oils, fatty acids with 8 to 30 carbon atoms such as stearic acid, zinc oxide (ZnO), vulcanization accelerators, A vulcanization retarder, a vulcanizing agent (sulfur) and the like can be appropriately selected and blended within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these compounding agents.

The inorganic filler is not particularly limited as long as it is an inorganic compound commonly used in the rubber industry. Examples of usable inorganic compounds include silica; alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina; alumina monohydrate (Al ₂ O ₃ ·H ₂ O) such as boehmite and diaspore; , bayerite and other aluminum hydroxide [Al(OH) ₃ ]; aluminum carbonate [Al2 _{( CO3} ) ₃ ], magnesium hydroxide [Mg(OH) ₂ ], magnesium oxide (MgO), magnesium carbonate ( _MgCO3 ), talc (3MgO.4SiO.sub.2.H.sub.2O), attapulgite ( _{5MgO.8SiO.sub.2.9H.sub.2O} ), titanium white _{( TiO.sub.2} ), titanium black ( _{TiO.sub.2n - 1} ), calcium oxide (CaO), hydroxide Calcium [Ca ₍ OH) ₂ ], magnesium aluminum oxide _{( MgO.Al2O3} ), clay _{( Al2O3.2SiO2} ) _, kaolin _{( Al2O3.2SiO2.2H2O} ), _{pyrophyllite ( Al2O3.4SiO2.H2O} ), _{bentonite ( Al2O3.4SiO2.2H2O} ), _{aluminum silicate ( Al2SiO5 , Al4.3SiO4.5H2O , etc.} ), magnesium silicate ( _Mg2SiO4 , _MgSiO3 , etc.), calcium silicate _{( Ca2.SiO4} , etc.), aluminum calcium silicate _{( Al2O3.CaO.2SiO2 ,} etc.), magnesium calcium silicate _{( CaMgSiO4} ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO(OH) 2.nH ₂ O], zirconium carbonate [Zr ₍ CO ₃ ) ₂ ], zinc acrylate, zinc methacrylate, Examples include crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals that correct charge such as various zeolites. The surface of these inorganic fillers may be organically treated in order to improve the affinity with the rubber component.

The inorganic filler is preferably silica from the viewpoint of imparting rubber strength, more preferably silica alone, or silica and one or more inorganic compounds commonly used in the rubber industry in combination. When silica and the inorganic compound other than silica are used together as the inorganic filler, the total amount of all components of the inorganic filler may be appropriately adjusted so as to fall within the above range.
Silica is preferably added because it can impart rubber strength.

Any commercially available silica can be used. Among them, preferred silica is wet silica, dry silica, or colloidal silica, and more preferred is wet silica. The surface of these silicas may be organically treated in order to improve the affinity with the rubber component.

The BET specific surface area of silica is not particularly limited, and is, for example, in the range of 40 to 350 m ² /g. Silica having a BET specific surface area within this range has the advantage of being able to achieve both rubber toughness and dispersibility in the rubber component. The BET specific surface area is measured according to ISO5794/1.

From this point of view, preferred silica is silica having a BET specific surface area of 80 to 300 m ² /g, more preferably silica having a BET specific surface area of 100 to 270 m ² /g, and particularly preferably Silica having a BET specific surface area in the range of 110 to 270 m ² /g.

Commercially available such silicas are available from Quechen Silicon Chemical Co.; , Ltd. product names "HD165MP" (BET specific surface area = 165 m ² /g), "HD115MP" (BET specific surface area = 115 m ² /g), "HD200MP" (BET specific surface area = 200 m ² /g), "HD250MP" ( BET specific surface area = 250 m ² /g), trade name “Nip Seal AQ” (BET specific surface area = 205 m ² /g) manufactured by Tosoh Silica Co., Ltd., “Nip Seal KQ” (BET specific surface area = 240 m ² /g), Degussa trade name "Ultrasil VN3" (BET specific surface area = 175 m ² /g) manufactured by Co., Ltd., and the like.

When an inorganic filler is added to the rubber composition for truck tires or bus tires of the present invention, the amount of the inorganic filler to be added is not particularly limited. 0.01 to 95 parts by mass, preferably 0.05 to 90 parts by mass, more preferably 0.1 to 80 parts by mass.

In addition, in the rubber composition containing an inorganic filler, a silane coupling agent or a titanate coupling agent may be added for the purpose of increasing the toughness of the rubber composition by silica, or for the purpose of increasing the abrasion resistance as well as the tear strength of the rubber composition. agent, an aluminate coupling agent, and a zirconate coupling agent. As these coupling agents, the same ones as described in the above item (1.4. Component (d): carbon black) can be used.

The amount of the silane coupling agent compounded in the rubber composition for truck tires or bus tires of the present invention is preferably 0.1 to 20 parts by mass, preferably 3 to 15 parts by mass, with respect to 100 parts by mass of the inorganic filler. is more preferable. If it is 0.1 parts by mass or more, the effect of improving the tear strength of the rubber composition can be more suitably exhibited, and if it is 20 parts by mass or less, the cost of the rubber composition is reduced and economic efficiency is improved. do.

(2. Truck tires and bus tires)
Furthermore, the present invention includes inventions relating to truck tires or bus tires produced from the rubber composition for truck tires or bus tires.

Since the truck tire and bus tire of the present invention are tires manufactured from a rubber composition having a high foaming ratio, they can be used in harsh environments such as crushing sites with durability performance (abrasion resistance, chipping resistance, Flex crack growth resistance, crack growth resistance, fracture resistance, uneven wear resistance, one-shot cut resistance, crack resistance, rubber chipping resistance (fin breakage), improved breaking strength, improved breaking elongation, tearing strength performance, etc.), excellent braking performance (dry braking performance, wet grip performance, braking performance on snow and ice, etc.), ride comfort, cornering performance, noise reduction during driving, tire appearance retention performance, tire weight reduction, etc. It can be effectively applied as a truck tire or a bus tire that requires

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

In the truck tire or bus tire of the present invention, the rubber composition is used for at least one member selected from the tread portion, sidewall portion, bead area portion, belt portion, carcass portion and shoulder portion.

Above all, it is preferable to form the tire tread portion of truck tires or bus tires from the rubber composition.

The tread part is the part that has a tread pattern and is in direct contact with the road surface, and is the outer skin part of the tire that protects the carcass and prevents wear and damage. Refers to the base tread on the inside.

The sidewall portion is, for example, the portion from the lower side of the shoulder portion to the bead portion in the pneumatic radial tire, which protects the carcass and is the portion that bends the most during running.

The bead area portion is a portion that has the role of fixing both ends of the carcass cord and fixing the tire to the rim at the same time. A bead is a bundled structure of high carbon steel.

The belt portion is a reinforcing band stretched in the circumferential direction between the radial structure tread and the carcass. The carcass is strongly tightened like a hoop on a bucket, increasing the rigidity of the tread.

The carcass portion is a portion of the cord layer that forms the skeleton of the tire, and plays a role in withstanding the load, impact, and filling air pressure that the tire receives.

The shoulder portion is the shoulder portion of the tire and serves to protect the carcass.

The truck tires or bus tires of the invention can be manufactured according to methods hitherto known in the field of tires. As the gas to be filled in the tire, normal air or air with adjusted oxygen partial pressure; inert gas such as nitrogen, argon, helium, etc. can be used.

(3. Method for producing a rubber composition for truck tires or bus tires)
As a method for producing the rubber composition for truck tires or bus tires of the present invention, the above components (a), (b), (c), and (d) may be mixed, and if necessary, a vulcanizing agent, and other ingredients may be mixed. The order of blending may be appropriately set. For example, a step (A) of mixing raw material components including the above components (a), (b), (c), and (d), and a step of mixing the mixture obtained in step (A) and a vulcanizing agent A method comprising (B), a step (A) of mixing the raw material components comprising the components (a), (b), and (c), and the mixture obtained in step (A), the component (d) and the addition A method comprising a step (B) of mixing a sulfur agent, a step (A) of mixing raw material components including the above components (a), (b), and (d), and the mixture obtained in the step (A), A method comprising step (B) of mixing component (c) and a vulcanizing agent, step (A) of mixing raw material components including components (a), (c), and (d) above, and step (A ), a method comprising a step (B) of mixing the mixture obtained in ), the component (b) and a vulcanizing agent, a step (A) of mixing the raw material components containing the components (a) and (b), and a step A method comprising a step (B) of mixing the mixture obtained in (A), components (c) and (d) and a vulcanizing agent, a step of mixing the raw material components containing the above components (a) and (c) ( A) and a process comprising step (B) of mixing the mixture obtained in step (A), components (b) and (d) and a vulcanizing agent, a raw material comprising components (a) and (d) above and a method comprising step (A) of mixing the components, and step (B) of mixing the mixture obtained in step (A), components (b) and (c), and a vulcanizing agent. Among them, a preferable production method includes the step (A) of kneading the raw material components including the components (a), (c) and (d), and the mixture obtained in the step (A), the component (b), and The method includes the step (B) of mixing a vulcanizing agent.

(3.1. Step (A))
Step (A) is a step of mixing the raw material components including the components (a), (c) and (d).

In step (A), the above-mentioned other compounding agents and the like can be blended, if necessary. In this specification, "mixing" includes not only the mode of simply mixing, but also the mode of so-called "kneading".

In step (A), raw material components including components (a), (c) and (d) are mixed. In this mixing method, the total amount of each component may be mixed at once, or each component may be divided and mixed according to the purpose such as viscosity adjustment. The mixing operation may be repeated to evenly disperse the components. A filler masterbatch rubber in which a filler is previously added to the rubber by a wet method and/or a dry mixing method may also be used.

Further, as another mixing method in the step (A) in the case of adding and mixing the component (d) alone or the component (d) and the inorganic filler to the rubber composition for truck tires or bus tires of the present invention is a step (A-1) of mixing the components (a) and (c), and a raw material component containing the mixture obtained in the step (A-1), the component (d), and an inorganic filler. A two-stage mixing method including a mixing step (A-2) can be mentioned.

The temperature at which the rubber composition is mixed in step (A) is not particularly limited. For example, the upper limit of the temperature of the rubber composition is preferably 100 to 190°C, more preferably 110 to 175°C More preferably, it is 120 to 170°C.

The mixing time in step (A) is not particularly limited. For example, it is preferably 10 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, and further preferably 1 minute to 8 minutes. preferable.

The temperature at which the components (a) and (c) are mixed in step (A-1) is preferably 60 to 190°C, more preferably 70 to 160°C, and 80 to 150°C. is more preferable. This is because if the mixing temperature is lower than 60°C, the reaction does not proceed, and if the mixing temperature is higher than 190°C, the rubber deteriorates.

The mixing time in step (A-1) is desirably 10 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, even more preferably 60 seconds to 7 minutes. By setting the mixing time to 10 seconds or more, the reaction can be sufficiently advanced. On the other hand, by setting the mixing time within 20 minutes, it is excellent in terms of productivity.

The temperature at which the mixture obtained in step (A-1), the component (d), and the inorganic filler are mixed in step (A-2) is not particularly limited. is preferably 100 to 190°C, more preferably 110 to 175°C, even more preferably 130 to 170°C.

The mixing time in step (A-2) is not particularly limited. For example, it is preferably 10 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, and 1 minute to 8 minutes. is more preferred.

(3.2. Step (B))
Step (B) is a step of mixing the mixture obtained in step (A), the component (b), and a vulcanizing agent.

In the step (B), a vulcanization accelerator or the like can be blended as necessary.

Step (B) can be performed under heating conditions. The heating temperature in this step is not particularly limited, and is preferably 60 to 140°C, more preferably 80 to 120°C, and even more preferably 90 to 120°C.

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

When proceeding from step (A) to step (B), it is preferable to lower the temperature after completion of the previous step by 30° C. or more before proceeding to the next step (B).

In step (A), mixing is performed using a Banbury mixer, rolls, intensive mixer, kneader, single-screw extruder, twin-screw extruder, or the like. After that, it is extruded and processed in an extrusion process, and formed into, for example, a tread member or a sidewall member. Subsequently, it is pasted and molded by a normal method on a tire molding machine to mold a green tire. The raw tire is heated and pressurized in a vulcanizer to obtain a tire.

In the method for producing the rubber composition for truck and bus tires of the present invention, various compounding agents such as stearic acid, zinc oxide, anti-aging agents, etc., which are usually compounded in the rubber composition, are optionally added to the step (A) Or it can be added in step (B).

The compounding agents described above may be added in either step (A) or step (B), or may be added separately in step (A) and step (B).

(3.3. Molding method of rubber composition for truck/bus tires)
The rubber composition for truck and bus tires of the present invention is mixed using a Banbury mixer, rolls, intensive mixer, kneader, single-screw extruder, twin-screw extruder, or the like. After that, it is extruded and processed in an extrusion process, and formed into, for example, a tread member or a sidewall member. Subsequently, it is pasted and molded by a normal method on a tire molding machine to mold a green tire. A tire can be obtained by heating and pressurizing this raw tire in a vulcanizer.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to such examples, and can of course be embodied in various forms without departing from the gist of the present invention.

EXAMPLES Hereinafter, embodiments of the present invention will be described more specifically based on Examples, but the present invention is not limited to these.

Examples 1 to 6 and Comparative Examples 1 to 2: Production of rubber composition for truck tires or bus tires Each component described in step (A) in Table 1 below was mixed in its proportion (parts by mass) and mixed in a Banbury mixer. mixed with. After curing until the temperature of the mixture reaches 60 ° C. or lower, each component described in step (B) in Table 1 is added in the proportion (parts by mass), and the maximum temperature of the mixture is adjusted to 70 ° C. or lower. While mixing, a rubber composition for truck tires or bus tires was produced.

Examples 1 to 6 and Comparative Examples 1 to 2: Expansion ratio index The expansion ratio was calculated by measuring the specific gravity before and after foam molding using an electronic hydrometer (MDS-300 manufactured by ALFA MIRAGE). For comparison, rubber compositions (Comparative Examples 1 and 2) were prepared using the same compounding content and the same manufacturing method as in each example except that component (c) was not added, and the expansion ratio was set to 100. The expansion ratio index was calculated based on the following formula. The larger the value of the expansion ratio index, the higher the expansion ratio and the better the foam.

Formula: expansion ratio = specific gravity before foam molding / specific gravity after foam molding × 100

Formula: Expansion ratio index = (Expansion ratio of Examples 1 to 4) x 100/(Expansion ratio of Comparative Example 1)

Formula: Expansion ratio index = (Expansion ratio of Examples 5-6) x 100/(Expansion ratio of Comparative Example 2)

尚、表１における各成分の詳細は、下記の通りである。
※１：成分（ａ）：天然ゴム；ＧＵＡＮＧＫＥＮ ＲＵＢＢＥＲ社製 、ＴＳＲ－２０
※２：成分（ａ）：ブタジエンゴム；宇部興産社製、ＵＢＥＰＯＬ １５０Ｂ
※３：成分（ｄ）：カーボンブラック；東海カーボン社製、シースト７ＨＭ（Ｎ２３４）
※４：老化防止剤；大内新興化学社製、ノクラック６Ｃ
※５：ワックス；大内新興化学社製、サンノック
※６：オイル；出光昭和シェル社製、ダイアナプロセスオイルＮＲ－２６
※７：ステアリン酸；新日本理化社製、ステアリン酸５０Ｓ
※８：酸化亜鉛；堺化学工業社製、「１種」
※９：成分（ｃ）：化合物Ａ；大塚化学社製、３－メチル－５－ピラゾロン
※１０：加硫促進剤Ａ；大内新興化学社製、ノクセラーＭ－Ｐ
※１１：加硫促進剤Ｂ；大内新興化学社製、ノクセラーＣＺ－Ｇ
※１２：硫黄；細井化学工業社製、ＨＫ２００－５
※１３：成分（ｅ）：発泡助剤；大塚化学社製、ユニフォームＡＺ ０１
※１４：成分（ｂ）：発泡剤Ａ；大塚化学社製、ユニフォームＡＺ ＶＩ－４０（アゾジカルボンアミド）

The details of each component in Table 1 are as follows.
*1: Component (a): Natural rubber; TSR-20 manufactured by GUANGKEN RUBBER
*2: Component (a): Butadiene rubber; UBEPOL 150B manufactured by Ube Industries, Ltd.
*3: Component (d): Carbon black; Seest 7HM (N234) manufactured by Tokai Carbon Co., Ltd.
*4: Anti-aging agent; Nocrac 6C manufactured by Ouchi Shinko Kagaku Co., Ltd.
*5: Wax: Sannok, manufactured by Ouchi Shinko Chemical Co., Ltd. *6: Oil: Diana Process Oil NR-26, manufactured by Idemitsu Showa Shell Co., Ltd.
* 7: Stearic acid; manufactured by Shin Nippon Chemical Co., Ltd., stearic acid 50S
*8: Zinc oxide; manufactured by Sakai Chemical Industry Co., Ltd., "Type 1"
*9: Component (c): Compound A; 3-methyl-5-pyrazolone, manufactured by Otsuka Chemical Co., Ltd. *10: Vulcanization accelerator A; Noxeller M-P, manufactured by Ouchi Shinko Chemical Co., Ltd.
*11: Vulcanization accelerator B; Noxcellar CZ-G manufactured by Ouchi Shinko Kagaku Co., Ltd.
*12: Sulfur; HK200-5 manufactured by Hosoi Chemical Industry Co., Ltd.
* 13: Component (e): Foaming aid; uniform AZ 01 manufactured by Otsuka Chemical Co., Ltd.
* 14: Component (b): Foaming agent A; uniform AZ VI-40 (azodicarbonamide) manufactured by Otsuka Chemical Co., Ltd.

Examples 7 to 15 and Comparative Examples 3 to 5: Manufacture of rubber composition for truck and bus tires Each component described in step (A) in Table 2 below was mixed in its ratio (parts by mass) and mixed in a Banbury mixer. Mixed. After curing until the temperature of the mixture reaches 60 ° C. or less, each component described in step (B) in Table 2 is added in the proportion (parts by mass), and the maximum temperature of the mixture is adjusted to 70 ° C. or less. While mixing, a rubber composition for truck tires or bus tires was produced.

Examples 7 to 15 and Comparative Examples 3 to 5: Expansion ratio index The expansion ratio was calculated by measuring the specific gravity before and after foam molding using an electronic hydrometer (MDS-300 manufactured by ALFA MIRAGE). For comparison, rubber compositions for truck tires or bus tires (Comparative Examples 3 to 5) were prepared using the same compounding content and the same production method as in each example except that component (c) was not added, and the foaming ratio was determined. Each index was set to 100, and the expansion ratio index was calculated based on the following formula. The larger the value of the expansion ratio index, the higher the expansion ratio and the better the foam.

Formula: expansion ratio = specific gravity before foam molding / specific gravity after foam molding × 100

Formula: Expansion ratio index = (expansion ratio of each of Examples 7 to 9) x 100/(expansion ratio of Comparative Example 3)

Formula: expansion ratio index = (expansion ratio of each of Examples 10 to 12) x 100/(expansion ratio of Comparative Example 4)

Formula: Expansion ratio index = (Expansion ratio of Examples 13 to 15) x 100/(Expansion ratio of Comparative Example 5)

尚、表２における各成分の詳細は、下記の通りである。
※１５：成分（ａ）：スチレン－ブタジエン共重合体ゴム；ＪＳＲ社製、ＪＳＲ１５０２
※１６：成分（ｂ）：発泡剤Ｂ；大塚化学社製、ユニフォームＡＺ Ｐ－５（重曹）

The details of each component in Table 2 are as follows.
*15: Component (a): Styrene-butadiene copolymer rubber; manufactured by JSR, JSR1502
* 16: Component (b): Foaming agent B; Uniform AZ P-5 (baking soda) manufactured by Otsuka Chemical Co., Ltd.

The rubber composition for truck tires or bus tires of the present invention is excellent because it contains a rubber component containing natural rubber, a chemical foaming agent, the compound represented by the above formula (1) or a salt thereof, and carbon black. A truck tire or bus tire can be provided with an expansion ratio.

Since the composition of the present invention is a rubber composition with a high foaming ratio, it has durability performance (wear resistance, chipping resistance, flex crack growth resistance, crack resistance) that can be used even in severe sites such as crushing sites. Progressiveness, fracture resistance, uneven wear resistance, one-shot cut resistance, crack resistance, rubber chipping resistance (fin breakage), improved breaking strength, improved breaking elongation, improved tearing strength, etc.), excellent braking Truck tires and bus tires that require performance (dry braking performance, wet grip performance, braking performance on snow and ice, etc.), ride comfort, cornering performance, noise reduction during driving, tire appearance retention performance, tire weight reduction, etc. can be effectively applied as

Claims (5)

A rubber composition for truck tires or bus tires, comprising the following components (a), (b), (c) and (d).
(a) a rubber component containing natural rubber (b) a chemical foaming agent (c) at least one compound selected from compounds represented by the following formula (1) and salts of said compounds (d) carbon black

[In the formula, R ¹ represents a hydrogen atom, an alkyl group, or an aralkyl group; R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group; Each group may further have one or more substituents. ] 2. The rubber composition according to claim 1, further comprising, as component (a), at least one rubber component selected from the group consisting of butadiene rubber (BR) and styrene-butadiene copolymer rubber (SBR). The rubber composition according to claim 1 or 2, wherein in formula (1), ^{R1 ,} R3 and ^R4 are hydrogen atoms, and ^R2 is a methyl group. The rubber composition according to any one of claims 1 to 3, further comprising component (e) a foaming aid. A truck tire or bus tire produced using the rubber composition according to any one of claims 1 to 4.