JP7683200B2 - Rubber composition for tires and tires - Google Patents

Description

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

Various methods have been studied to improve the fracture properties of rubber compositions for tires (for example, Patent Document 1).

JP 2012-116909 A

However, as a result of the investigations conducted by the present inventors, it has become clear that there is room for improvement in the conventional techniques in terms of improving the overall performance of fracture properties, crack and flex resistance, and fracture properties after thermal degradation.
An object of the present invention is to provide a rubber composition for tires and a tire which can solve the above problems and improve the overall performance of fracture properties, crack and flex resistance, and fracture properties after heat degradation.

The present invention relates to a rubber composition for tires that contains a rubber component containing at least an isoprene-based rubber, a styrene-butadiene rubber and/or a butadiene rubber, and a filler, and that contains a resin having, as monomers, compound A having a structure in which an aromatic ring is modified with a hydroxymethyl group and compound B having a structure in which an aromatic ring is modified with a hydroxy group, and that contains 35 mass% or more of isoprene-based rubber in 100 mass% of the rubber component.

It is preferable that the carbon black content in 100% by mass of the above filler is 80% by mass or more.

It is preferable that the content of the above resin (parts by mass) / the content of isoprene-based rubber (parts by mass) is ≦ 0.5.

The rubber component preferably contains butadiene rubber, and the ratio of butadiene rubber or styrene butadiene rubber content (parts by mass)/isoprene rubber content (parts by mass) is preferably 0.15 or more.

It is preferable that the content of isoprene-based rubber in 100% by mass of the above rubber component is 80% by mass or less.

The present invention also relates to a tire having tire components using the above rubber composition.

The present invention is a rubber composition for tires that contains a rubber component containing at least an isoprene-based rubber, a styrene-butadiene rubber and/or a butadiene rubber, and a filler, and contains a resin whose monomers are compound A having a structure in which an aromatic ring is modified with a hydroxymethyl group and compound B having a structure in which an aromatic ring is modified with a hydroxy group, and the content of isoprene-based rubber in 100% by mass of the rubber component is 35% by mass or more, and therefore the overall performance of the fracture properties, crack resistance and flexural resistance, and fracture properties after thermal degradation can be improved.

The rubber composition for tires of the present invention is a rubber composition for tires that contains a rubber component containing at least an isoprene-based rubber, a styrene butadiene rubber (SBR) and/or a butadiene rubber (BR), and a filler, and contains a resin whose monomers are compound A having a structure in which an aromatic ring is modified with a hydroxymethyl group and compound B having a structure in which an aromatic ring is modified with a hydroxy group, and the content of the isoprene-based rubber in 100% by mass of the rubber component is 35% by mass or more.

The reason why the above-mentioned effects are obtained with the above-mentioned rubber composition is presumed to be as follows.
(1) The above resin has good compatibility with isoprene-based rubber, and therefore can enhance the strength and rigidity of the isoprene-based rubber phase, improving fracture properties and crack and flex resistance.
(2) By including SBR and/or BR together with the isoprene-based rubber, the resin forms a domain in the isoprene-based rubber phase, which improves the fracture properties and crack-flex resistance as well as the fracture properties after thermal degradation.
(3) By making the content of the isoprene-based rubber equal to or greater than a specific amount, it becomes easier to form a co-continuous structure of SBR/BR/isoprene-based rubber.
As a result, the strength and rigidity of the entire rubber composition can be improved, thereby improving the fracture properties and crack-resistance-flexibility as well as the fracture properties after thermal degradation, thereby improving the overall performance of the fracture properties, crack-resistance-flexibility, and fracture properties after thermal degradation.

<Rubber component>
The rubber composition contains a rubber component.
Here, the rubber component is a component that contributes to crosslinking, and generally has a weight average molecular weight (Mw) of 10,000 or more.

The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within the above range, the effect tends to be better.

In this specification, the weight average molecular weight (Mw) can be calculated based on the measured value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) and converted into standard polystyrene.

The rubber composition contains at least styrene butadiene rubber (SBR) and/or butadiene rubber (BR) and isoprene-based rubber as rubber components.

Isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. NR can be, for example, SIR20, RSS#3, TSR20, etc., which are common in the tire industry. IR is not particularly limited, and can be, for example, IR2200, etc., which are common in the tire industry. Modified NR can be, for example, deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR can be, for example, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Modified IR can be, for example, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. These can be used alone or in combination of two or more. Of these, NR is preferred.

The content of isoprene-based rubber in 100% by mass of the rubber component is 35% by mass or more, preferably 40% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less. Within the above range, the effect tends to be better obtained.

The BR is not particularly limited, and BR with a high cis content, BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. can be used. Commercially available products include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. These may be used alone or in combination of two or more types.

The cis amount (cis content) of BR is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, most preferably 90% by mass or more, and most preferably 95% by mass or more, with no particular upper limit. When it is within the above range, the effect tends to be better.
The cis amount of BR can be measured by infrared absorption spectroscopy.

The BR content in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more, and is preferably 65% by mass or less, more preferably 60% by mass or less. Within the above range, the effect tends to be better obtained.

The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. These may be used alone or in combination of two or more types.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 40% by mass or less, and particularly preferably 30% by mass or less. When it is within the above range, the effect tends to be better obtained.
In this specification, the styrene content of SBR is calculated by ¹ H-NMR measurement.

The amount of SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more, and is preferably 65% by mass or less, more preferably 60% by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition contains BR as a rubber component, and further, it is preferable that the BR or SBR content (parts by mass) / isoprene-based rubber content (parts by mass) is ≥ 0.15. This makes it easier for the resin to form domains in the isoprene-based rubber phase, which improves fracture properties and crack-flex resistance, and also tends to improve fracture properties after thermal degradation.

The ratio of the content (parts by mass) of BR or SBR to the content (parts by mass) of isoprene-based rubber is preferably 0.15 or more, more preferably 0.30 or more, even more preferably 0.50 or more, particularly preferably 0.70 or more, most preferably 0.90 or more, even more preferably 1.10 or more, even more preferably 1.20 or more, especially most preferably 1.40 or more, and is preferably 2.50 or less, more preferably 2.25 or less, even more preferably 2.00 or less, particularly preferably 1.90 or less, most preferably 1.80 or less, and even more preferably 1.70 or less. Within the above ranges, the effect tends to be better obtained.
In this relationship, the BR content, the SBR content, and the isoprene-based rubber content are amounts per 100 parts by mass of the rubber component (unit: parts by mass).

In 100% by mass of the rubber component, the total content of isoprene-based rubber and BR is preferably 40% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may be 100% by mass. If it is within the above range, the effect tends to be better.

In 100% by mass of the rubber component, the total content of isoprene-based rubber and SBR is preferably 40% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may be 100% by mass. If it is within the above range, the effect tends to be better obtained.

Other rubber components that can be used besides isoprene-based rubber, BR, and SBR include diene-based rubbers such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more types.

The rubber component may be modified to introduce a functional group that interacts with a filler such as silica.
Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among them, an amino group (preferably an amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

Specific examples of compounds (modifiers) having the above functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc.

<Resin>
The rubber composition contains a resin having, as monomers, a compound A having a structure in which an aromatic ring is modified with a hydroxymethyl group and a compound B having a structure in which an aromatic ring is modified with a hydroxy group. The resins may be used alone or in combination of two or more kinds.

（式中、Ａｒは、芳香環を示し、Ａは、ＣＨＯ（アルデヒド基）又はＣＨ_２ＯＨ（ヒドロキシメチル基）を示す）。 <<Compound A>>
First, compound A will be described.
Compound A is a compound having a structure in which an aromatic ring is modified with a hydroxymethyl group. Compound A may be used alone or in combination of two or more kinds.
Compound A is preferably an aromatic compound containing at least one aromatic ring having at least two functional groups, one of which is a hydroxymethyl group and the other of which is an aldehyde group or a hydroxymethyl group, and is more preferably a compound represented by the following general formula (A):
In this specification, compound A may also be referred to as an aromatic compound.

(wherein Ar represents an aromatic ring, and A represents CHO (aldehyde group) or CH ₂ OH (hydroxymethyl group).

The aromatic ring is preferably a 5- or 6-membered ring, and more preferably a 5-membered ring. The aromatic ring may contain a carbon atom as a membered ring, and may contain one or more heteroatoms, particularly nitrogen, oxygen, or sulfur atoms, which may be oxidized in the form of an N-oxide or S-oxide. In particular, the aromatic ring preferably contains a carbon atom as a membered ring and one heteroatom, particularly nitrogen, oxygen, or sulfur atom, and more preferably contains a carbon atom as a membered ring and one oxygen atom.

The aromatic ring contains 0, 1 or 2 heteroatoms. The remainder of the aromatic ring may be substituted or unsubstituted.
The aromatic ring may have 0, 1 or 2 aldehyde groups, preferably 0 or 1 aldehyde group.
The aromatic ring may have 1, 2 or 3 hydroxymethyl groups, preferably 1 or 2 hydroxymethyl groups.
Additionally, the aromatic ring may also contain 0, 1 or 2 other functional groups, particularly hydroxy groups.

In embodiments in which the aromatic ring is a 6-membered ring, the A and hydroxymethyl groups are preferably in the meta or para positions relative to each other. In embodiments in which the aromatic ring is a 5-membered ring, the ring may contain one or more heteroatoms, in particular nitrogen, oxygen or sulfur atoms, which may be oxidized in the form of an N-oxide or S-oxide. The aromatic ring preferably contains one or two heteroatoms, preferably one heteroatom.

When the aromatic ring is a five-membered ring, it is preferable that at least one of the following three conditions is satisfied, it is more preferable that at least two of the following three conditions are satisfied, and it is even more preferable that all of the following three conditions are satisfied:
the aromatic ring contains zero or one aldehyde group;
the aromatic ring contains 1 or 2 hydroxymethyl groups;
Apart from the aldehyde and hydroxymethyl groups, the remainder of the aromatic ring does not bear any substituents.

（式中、Ａは、ＣＨＯ又はＣＨ_２ＯＨを示し、Ｘは、Ｏ、ＮＲ_１、ＮＯ、Ｓ、ＳＯ、ＳＯ_２又はＳＲ_２Ｒ_３を示し、Ｒ_１は、水素、アルキル基、アリール基、アリールアルキル基、アルキルアリール基又はシクロアルキル基を示し、Ｒ_２及びＲ_３は、同一又は異なって、水素、アルキル基、アリール基、アリールアルキル基、アルキルアリール基又はシクロアルキル基を示す）。

（式中、Ｘ及びＡは、式（Ａ１）の場合と同様である）。 Compound A is preferably a compound represented by the following formula (A1), and more preferably a compound represented by the following formula (A1-1).

_{(In the formula, A represents CHO or CH2OH, X represents O, NR1, NO, S, SO, SO2 or SR2R3, R1 represents hydrogen , an alkyl} group, an aryl group, an arylalkyl group, an alkylaryl group or a cycloalkyl group, and _R2 and _R3 may be the same or different and represent hydrogen, an alkyl group, an aryl group, an arylalkyl group, an alkylaryl group or a cycloalkyl group).

(In the formula, X and A are the same as in formula (A1)).

In the above general formula (A1) and general formula (A1-1), A is preferably CHO, and X is preferably O.

Compound A is preferably a compound represented by the following formula (A1-1a) or a compound represented by the following formula (A1-1b), and more preferably a compound represented by the following formula (A1-1a) (5-(hydroxymethyl)-furfural).

In compounds A, the aromatic ring is six-membered and may contain zero, one or more heteroatoms, especially nitrogen, which may be oxidized in the N-oxide form.
The A and the hydroxymethyl group are preferably located at the meta or para position relative to each other.
The aromatic ring may have 0, 1 or 2 aldehyde groups, preferably 0 or 1 aldehyde group.
The aromatic ring may have 1, 2 or 3 hydroxymethyl groups, preferably 1 or 2 hydroxymethyl groups.
Additionally, the aromatic ring may also contain 0, 1 or 2 other functional groups, particularly hydroxy groups.

（式中、Ｘは、Ｃ又はＮＲ_１を示し、ｎは、０、１又は２の数値であり、ｍは、０又は１の数値であり、ｐは、１、２又は３の数値である。Ｒ_１は、水素、アルキル基、アリール基、アリールアルキル基、アルキルアリール基又はシクロアルキル基を示す。ここで、ｐ＋ｎ＞１、ｐ＞０である）。 Compound A is also preferably a compound represented by the following general formula (A2).

(wherein, X represents C or _NR1 , n is a value of 0, 1 or 2, m is a value of 0 or 1, and p is a value of 1, 2 or 3. _R1 represents hydrogen, an alkyl group, an aryl group, an arylalkyl group, an alkylaryl group or a cycloalkyl group, where p+n>1 and p>0.)

_R1 preferably denotes hydrogen or a _C1 - _C6 alkyl group.

The aromatic ring of the compound represented by the above general formula (A2) is preferably a benzene ring. The compound represented by the above general formula (A2) is more preferably 2-(hydroxymethyl)benzene-1-carboxaldehyde, 3-(hydroxymethyl)benzene-1-carboxaldehyde, 4-(hydroxymethyl)benzene-1-carboxaldehyde, 3-hydroxymethyl-6-hydroxybenzene-1-carboxaldehyde, 3-hydroxymethyl-4-hydroxybenzene-1-carboxaldehyde, 3-hydroxymethyl-2-hydroxybenzene-1-carboxaldehyde, 3-hydroxymethyl-2-hydroxybenzene-1,5-dicarboxaldehyde, 5-hydroxymethyl-2-hydroxybenzene-1,3-dicarboxaldehyde, 3,5-dihydroxymethyl-4-hydroxybenzene It is selected from the group consisting of 1,2-dihydroxymethylbenzene, 1,3-dihydroxymethylbenzene, 1,4-dihydroxymethylbenzene, 1,3-dihydroxymethyl-6-hydroxybenzene, 1,3-dihydroxymethyl-4-hydroxybenzene, 1,3-dihydroxymethyl-2-hydroxybenzene, 1,3,5-trihydroxymethyl-2-hydroxybenzene, 1,3-dihydroxymethyl-6-hydroxybenzene, 1,3,5-trihydroxymethyl-4-hydroxybenzene, 1,3,2-trihydroxymethyl-2-hydroxybenzene, and mixtures of these compounds.

It is also preferred that compound A is 1-(hydroxymethyl)benzene-4-carboxaldehyde of formula (A2a) or 1,4-dihydroxymethylbenzene of formula (A2b).

In addition, in this specification, compound A is a compound having a structure in which an aromatic ring is modified with a hydroxymethyl group, but compounds having a structure in which an aromatic ring is modified with a hydroxymethyl group include not only compounds having a structure in which an aromatic ring is modified with a hydroxymethyl group, but also compounds derived from a structure in which an aromatic ring is modified with a hydroxymethyl group.

（式中、Ｒ_１、Ｒ_２は、同一又は異なって、炭化水素基を示す。） Examples of the compound derived from a structure in which an aromatic ring is modified with a hydroxymethyl group include compounds obtained by reacting a compound represented by the above general formula (A) with a compound represented by the following general formula (α) and/or a compound represented by the following general formula (β).

(In the formula, R ₁ and R ₂ are the same or different and each represents a hydrocarbon group.)

（式中、Ｘは、式（Ａ１）の場合と同様であり、Ｒ_１、Ｒ_２は、式（α）、式（β）の場合と同様である。） Examples of the compound obtained by reacting a compound represented by the above general formula (A) (preferably a compound represented by the above general formula (A1), more preferably a compound represented by the above general formula (A1-1)) with a compound represented by the above general formula (α) and/or a compound represented by the above general formula (β) include compounds having the following structures.

(In the formula, X is the same as in formula (A1), and R ₁ and R ₂ are the same as in formulas (α) and (β).)

Compound A is preferably a compound represented by the above general formula (A), more preferably a compound represented by the above general formula (A1), even more preferably a compound represented by the above general formula (A1-1), and particularly preferably a compound represented by the above formula (A1-1a) (5-(hydroxymethyl)-furfural).

<<Compound B>>
Next, compound B will be described.
Compound B is a compound having a structure in which an aromatic ring is modified with a hydroxy group. Compound B may be used alone or in combination of two or more kinds.
Compound B is preferably a phenol compound, more preferably an aromatic polyphenol or an aromatic monophenol, and even more preferably an aromatic polyphenol.
As used herein, aromatic polyphenol refers to an aromatic compound that contains at least one aromatic ring, preferably a benzene ring, having more than one hydroxy group.
In the present specification, the term "aromatic monophenol" refers to an aromatic compound containing at least one aromatic ring (preferably a benzene ring) having one hydroxy group.
In this specification, compound B may also be referred to as a phenol compound or phenol.

The aromatic polyphenol preferably comprises at least one aromatic ring having at least two hydroxy groups meta to one another and the two ortho positions to at least one of the hydroxy groups being unsubstituted.
Preferably, the aromatic monophenol comprises at least one six-membered aromatic ring having a single hydroxy group, and more preferably, the two ortho positions to the hydroxy group are unsubstituted, or at least one of the ortho and para positions to the hydroxy group are unsubstituted.

The aromatic polyphenol may be a simple molecule containing one or more aromatic rings, at least one of these aromatic rings, or even each aromatic ring, having at least two hydroxy groups in the meta position relative to one another, with the two ortho positions to at least one of said hydroxy groups being unsubstituted.
Similarly, the aromatic monophenol may be a simple molecule containing one or more, at least one of, or even each of the six-membered aromatic rings bearing a single hydroxy group, and preferably the two ortho positions to the hydroxy group are unsubstituted, or at least one of the ortho and para positions to the hydroxy group are unsubstituted.
Such simple molecules do not contain repeating units.

The aromatic polyphenol may be a pre-condensed resin based on the following components:
at least one aromatic polyphenol comprising at least one aromatic ring having at least two hydroxy groups in meta position relative to one another, the two ortho positions to at least one of said hydroxy groups being unsubstituted; and at least one compound capable of reacting with said polyphenol comprising at least one aldehyde group and/or at least one compound capable of reacting with said polyphenol comprising at least two hydroxymethyl groups carried by the aromatic ring.

Such pre-condensed resins based on aromatic polyphenols, unlike the simple molecules described above, contain repeating units, which in this case contain at least one aromatic ring having at least two hydroxy groups in meta position relative to each other.

Similarly, the aromatic monophenol may be a pre-condensed resin based on the following components:
at least one aromatic monophenol containing at least one six-membered aromatic ring carrying a single hydroxy group:
- the two ortho positions to said hydroxy group are unsubstituted, or - at least one of the ortho and para positions to said hydroxy group are unsubstituted;
at least one compound capable of reacting with said monophenols containing at least one aldehyde group and/or at least one compound capable of reacting with said monophenols containing at least two hydroxymethyl groups carried by an aromatic ring.

Such pre-condensed resins based on aromatic monophenols, unlike the simple molecules described above, contain repeating units, where the repeating units contain at least one six-membered aromatic ring bearing a single hydroxyl group.

In the following, the aromatic polyphenols and/or aromatic monophenols are described in their simple molecular form. These aromatic polyphenols and/or aromatic monophenols may then be condensed to form, in part, the above repeat units.

<<<<Aromatic polyphenols>>>
Next, the aromatic polyphenols will be described.
The aromatic ring of the aromatic polyphenol preferably has three hydroxy groups in meta positions relative to one another.
Preferably, the two ortho positions to each hydroxy group are unsubstituted.
More preferably, it has three hydroxy groups meta to each other, with the two ortho positions to each hydroxy group being unsubstituted, meaning that the two carbon atoms on either side (ortho positions) of the hydroxylated carbon atom (i.e. bearing said hydroxy group) have simple hydrogen atoms.
Preferably, the remainder of the aromatic ring of the aromatic polyphenol is unsubstituted, meaning that the other carbon atoms of the remainder of the aromatic ring (other than the carbon atom bearing the hydroxy group) bear simple hydrogen atoms.
It is also preferred that the aromatic polyphenol comprises a plurality of aromatic rings, at least two of which have at least two hydroxy groups each in the meta position relative to one another, with at least one aromatic ring being unsubstituted in the ortho position relative to at least one of the hydroxy groups.

At least one of the aromatic rings of the aromatic polyphenol preferably has three hydroxy groups in the meta position relative to one another.
Preferably, the two ortho positions to each hydroxy group of at least one aromatic ring are unsubstituted.
Preferably, the two ortho positions to each hydroxy group on each aromatic ring are unsubstituted.
Preferably, the remainder of each aromatic ring is unsubstituted, which is taken to mean that the other carbon atoms of the remainder of each aromatic ring (other than the carbon atom bearing the hydroxy group or the group linking the aromatic rings together) bear simple hydrogen atoms.
Preferably, said aromatic ring having at least two hydroxy groups meta to each other and at least one of the two ortho positions to said hydroxy group being unsubstituted is a benzene ring.
Each aromatic ring of the aromatic polyphenol is preferably a benzene ring.

Examples of aromatic polyphenols containing only one aromatic ring include the compound represented by the following formula (B1) (resorcinol), the compound represented by the following formula (B2) (phloroglucinol), etc. Among these, the compound represented by the following formula (B2) (phloroglucinol) is preferred.

（式中、Ｚ_１及びＺ_２は、同一又は異なるものであって、同じ芳香環上に複数個のＺ_１及びＺ_２が存在する場合、上記芳香族ポリフェノールの残余部に少なくともこれら２個の芳香環を結合させる原子（例えば、炭素、イオウ又は酸素）又は、少なくとも２価の結合基を示す）。 When the aromatic polyphenol contains a plurality of aromatic rings, it is preferred that at least two of these aromatic rings, which may be the same or different, are selected from aromatic rings of the following general formula:

(wherein _Z1 and _Z2 are the same or different, and when a plurality of _Z1 and _Z2 are present on the same aromatic ring, they represent an atom (e.g., carbon, sulfur or oxygen) or an at least divalent linking group linking at least these two aromatic rings to the remainder of the aromatic polyphenol).

The aromatic polyphenol may be 2,2',4,4'-tetrahydroxydiphenyl sulfide of the following structural formula (B4):

The aromatic polyphenol may be a derivative of 2,2',4,4'-tetrahydroxydiphenylbenzophenone of the following structural formula (B5):

Each of compounds (B4) and (B5) is an aromatic polyphenol (having formula B3-c) containing two aromatic rings, each of which has at least two (in this case two) hydroxy groups in the meta position relative to each other.
For aromatic polyphenols containing at least one aromatic ring according to formula B3-b, the two ortho positions to each hydroxy group of at least one aromatic ring are unsubstituted. For aromatic polyphenols containing multiple aromatic rings according to formula B3-b, the two ortho positions to each hydroxy group of each aromatic ring are unsubstituted.

Examples of the aromatic polyphenols include resorcinol (B1), phloroglucinol (B2), 2,2',4,4'-tetrahydroxydiphenyl sulfide (B4), 2,2',4,4'-tetrahydroxybenzophenone (B5), and pre-condensed resins made from at least one of these phenols. Among these, phloroglucinol is preferred.

Aromatic polyphenols include pre-condensed resins based on the aromatic polyphenols listed above.
This precondensed resin is preferably based on the following components:
at least one aromatic polyphenol selected from the group consisting of resorcinol (B1), phloroglucinol (B2), 2,2',4,4'-tetrahydroxydiphenyl sulfide (B4), 2,2',4,4'-tetrahydroxybenzophenone (B5) and mixtures thereof; and at least one compound capable of reacting with said polyphenols containing at least one aldehyde group and/or at least one compound capable of reacting with said polyphenols containing at least two hydroxymethyl groups carried by the aromatic ring.

The compound capable of reacting with the polyphenol containing at least one aldehyde group and/or the compound capable of reacting with the polyphenol containing at least two hydroxymethyl groups on the aromatic ring may be compound A or any other aldehyde. Preferably, the compound capable of reacting with the polyphenol containing at least one aldehyde group and/or the compound capable of reacting with the polyphenol containing at least two hydroxymethyl groups on the aromatic ring is selected from the group consisting of aromatic compounds containing aromatic rings having at least two functional groups, one of which is a hydroxymethyl group and the other is an aldehyde group or a hydroxymethyl group, formaldehyde, benzaldehyde, furfuraldehyde, 2,5-furan dicarboxyaldehyde, 1,4-benzenedicarboxaldehyde, 1,3-benzenedicarboxaldehyde, 1,2-benzenedicarboxaldehyde and mixtures thereof. More preferably, when the compound is an aromatic compound containing an aromatic ring having at least two functional groups, one of which is a hydroxymethyl group and the other of which is an aldehyde group or a hydroxymethyl group, the compound is selected from the group consisting of 5-(hydroxymethyl)furfural, 2,5-di(hydroxymethyl)furan, and mixtures of these compounds.

Thus, in the pre-condensed resin based on an aromatic polyphenol, the repeating units satisfy the properties of the aromatic polyphenol, except that at least one of the carbon atoms of the aromatic ring that was not substituted is bonded to another unit.

The aromatic polyphenols may also include a mixture of free molecular aromatic polyphenols and pre-condensed resins based on aromatic polyphenols, as described above. In particular, the aromatic polyphenols may also include a mixture of phloroglucinol and pre-condensed resins based on phloroglucinol.

<<<Aromatic monophenols>>>
Next, the aromatic monophenol will be described.
The aromatic monophenol may be of two types: in one embodiment, the two ortho positions relative to the hydroxy group are unsubstituted, and in another embodiment, at least one of the ortho and para positions relative to the hydroxy group are unsubstituted.
In variations in which at least one of the ortho and para positions to the hydroxy group is unsubstituted, it is preferred that a single ortho position is unsubstituted and that the para position to the hydroxy group is unsubstituted.
Regardless of the embodiment, it is preferred that the two ortho positions of the hydroxy group are unsubstituted, meaning that the two carbon atoms located on either side (ortho positions) of the hydroxylated carbon atom (i.e. bearing the hydroxy group) have simple hydrogen atoms.
Preferably, the remainder of the aromatic ring is unsubstituted, meaning that the other carbon atoms of the remainder of the aromatic ring (other than the carbon atom bearing the hydroxy group) bear simple hydrogen atoms.
The aromatic monophenol comprises a plurality of six-membered aromatic rings, at least two of which each bear a single hydroxy group, and preferably at least one of the hydroxy groups is unsubstituted at both ortho positions relative to the hydroxy group, or at least one of the ortho and para positions relative to the hydroxy group is unsubstituted.

Preferably, the two ortho positions to each hydroxy group of at least one of the six-membered aromatic rings are unsubstituted.Preferably, the two ortho positions to each hydroxy group of each of the six-membered aromatic rings are unsubstituted.
Preferably, the remainder of each aromatic ring is unsubstituted, meaning that the other carbon atoms of the remainder of each aromatic ring (other than the carbon atom bearing the hydroxy group or the group linking the aromatic rings together) bear simple hydrogen atoms.
Preferably, one or each aromatic ring of the aromatic monophenol is a benzene ring.

Examples of the aromatic monophenols include phenol, ortho-cresol, meta-cresol, para-cresol, ortho-chlorophenol, meta-chlorophenol, para-chlorophenol, 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 4-vinylphenol, 4-ethylphenol, 4-isopropylphenol, 4-isobutylphenol, and paracoumaric acid.

The aromatic monophenol may be a pre-condensed resin based on the aromatic monophenol.
This precondensed resin is preferably based on the following components:
at least one aromatic monophenol selected from the group consisting of phenol, ortho-cresol, meta-cresol, para-cresol, ortho-chlorophenol, meta-chlorophenol, para-chlorophenol, 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 4-vinylphenol, 4-ethylphenol, 4-isopropylphenol, 4-isobutylphenol, para-coumaric acid and mixtures of these compounds; and at least one compound capable of reacting with said monophenol containing at least one aldehyde group and/or at least one compound capable of reacting with said monophenol containing at least two hydroxymethyl groups on the aromatic ring.

The compound capable of reacting with a monophenol containing at least one aldehyde group and/or a compound capable of reacting with a monophenol containing at least two hydroxymethyl groups on an aromatic ring and capable of reacting with said aromatic monophenol may be compound A or any other aldehyde. Preferably, said compound capable of reacting with a monophenol containing at least one aldehyde group and/or a monophenol containing at least two hydroxymethyl groups on an aromatic ring is selected from the group consisting of aromatic compounds containing an aromatic ring having at least two functional groups, one of which is a hydroxymethyl group and the other is an aldehyde group or a hydroxymethyl group, formaldehyde, benzaldehyde, furfuraldehyde, 2,5-furan dicarboxyaldehyde, 1,4-benzenedicarboxaldehyde, 1,3-benzenedicarboxaldehyde, 1,2-benzenedicarboxaldehyde and mixtures thereof. More preferably, when the compound is an aromatic compound containing an aromatic ring having at least two functional groups, one of the functional groups is a hydroxymethyl group and the other is an aldehyde group or a hydroxymethyl group, and the compound is selected from the group consisting of 5-(hydroxymethyl)furfural, 2,5-di(hydroxymethyl)furan, and mixtures of these compounds.

Thus, in the pre-condensed resin based on an aromatic monophenol, the repeating units meet the characteristics of the aromatic monophenol, except that at least one of the carbon atoms of the six-membered aromatic ring that was not substituted is bonded to another unit.

The aromatic monophenols may also include mixtures of free molecules of aromatic monophenols and precondensed resins based on aromatic monophenols, as described above. In particular, the aromatic monophenols may also include mixtures of phenols and precondensed resins based on phenols.

In addition, in this specification, compound B is a compound having a structure in which an aromatic ring is modified with a hydroxy group, but compounds having a structure in which an aromatic ring is modified with a hydroxy group include not only compounds having a structure in which an aromatic ring is modified with a hydroxy group, but also compounds derived from a structure in which an aromatic ring is modified with a hydroxy group.

Examples of compounds derived from a structure in which an aromatic ring is modified with a hydroxy group include compounds in which a hydroxy group on an aromatic ring has reacted with another compound. Examples of compounds derived from a structure in which an aromatic ring is modified with a hydroxy group include compounds having the following structure:

Compound B is preferably a phenol compound, more preferably an aromatic polyphenol or an aromatic monophenol, and even more preferably an aromatic polyphenol.
The aromatic ring of the aromatic polyphenol preferably has three hydroxyl groups at meta positions relative to each other. Also, it is preferable that the two ortho positions relative to each hydroxyl group are not substituted. That is, it is more preferable that the three hydroxyl groups are at meta positions relative to each other, and the two ortho positions relative to each hydroxyl group are not substituted. Here, it is preferable that the aromatic polyphenol has one aromatic ring, and it is more preferable that the aromatic ring is a benzene ring.
It is also preferred that the aromatic polyphenol is a simple molecule having no repeating units.
That is, as compound B, the compound represented by the above formula (B2) (phloroglucinol) is most preferable.

The resin having as monomers a compound A having a structure in which an aromatic ring is modified with a hydroxymethyl group and a compound B having a structure in which an aromatic ring is modified with a hydroxy group may be any resin having compound A and compound B as monomers, and such a resin can be polymerized by reacting compound A with compound B according to a known method.
The resin may be polymerized before being blended into the rubber composition, that is, the resin may be first synthesized according to a known method, and the synthesized resin may be blended into the rubber composition.
The resin may be polymerized after being blended into the rubber composition. That is, the resin may be synthesized during kneading and vulcanization of the rubber composition. Specifically, compound A and compound B may be added to the rubber composition, and the resin may be generated during kneading and vulcanization of the rubber composition, to prepare a rubber composition blended with the resin.

The content of units derived from compound A in 100% by mass of the resin is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 40% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, particularly preferably 60% by mass or less. Within the above range, the effect tends to be better obtained.

The content of units derived from compound B in 100% by mass of the resin is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 40% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, particularly preferably 60% by mass or less. Within the above range, the effect tends to be better obtained.

The total content of the units derived from compound A and the units derived from compound B in 100% by mass of the resin is preferably 20% by mass or more, more preferably 40% by mass or more, even more preferably 60% by mass or more, particularly preferably 80% by mass or more, most preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more, and may be 100% by mass. When it is within the above range, the effect tends to be better obtained.
In this specification, the contents of units derived from compound A and units derived from compound B are values measured by NMR.

The content of the above resin (the total amount of compound A and compound B when compounded as compound A and compound B) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 8 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less. Within the above range, the effect tends to be better obtained.

It is preferable that the resin content (parts by mass)/isoprene-based rubber content (parts by mass) be ≦0.5.
The ratio of the resin content (parts by mass) to the isoprene-based rubber content (parts by mass) is preferably 0.4 or less, more preferably 0.3 or less, and even more preferably 0.26 or less, and is preferably 0.05 or more, more preferably 0.1 or more, and even more preferably 0.15 or more.
When the amount is within the above range, the effect tends to be better. This is presumably because when the amount of the resin relative to the isoprene-based rubber is too large, the hardness difference between the sea and islands tends to become large.
In this relationship, the content of the resin and the content of the isoprene-based rubber are the contents (unit: parts by mass) per 100 parts by mass of the rubber component. When the resin is compounded as compound A and compound B, the content of the resin means the total compounding amount of compound A and compound B.

The rubber composition may contain a resin other than the above-mentioned resins.
Examples of the resin include cyclopentadiene resins, terpene resins, rosin resins, coumarone-indene resins (including resins of simple coumarone and indene), olefin resins, polyurethane resins, and acrylic resins. These may be used alone or in combination of two or more. They may also be hydrogenated (hydrogenated resins).

Commercially available examples of the above-mentioned resins include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries Co., Ltd., and Taoka Chemical Co., Ltd.

<Filler>
The rubber composition contains a filler (reinforcing filler). Examples of the filler include carbon black, silica, talc, clay, aluminum hydroxide, and titanium oxide. These may be used alone or in combination of two or more. Among these, carbon black and silica are preferred, and carbon black is more preferred.

The amount of the filler is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less. Within the above range, the effect tends to be better.

The carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone or in combination of two or more types.

The nitrogen adsorption specific surface area ( _N2SA ) of carbon black is preferably 50 ^m2 /g or more, more preferably 70 ^m2 /g or more, and even more preferably 90 ^m2 /g or more. The _N2SA is preferably 200 ^m2 /g or less, more preferably 150 ^m2 /g or less, and even more preferably 130 ^m2 /g or less. When the N2SA is within the above range, the effect tends to be better.
The nitrogen adsorption specific surface area of carbon black is determined in accordance with JIS K6217-2:2001.

The carbon black content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and most preferably 35 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less. Within the above range, the effect tends to be better obtained.

The carbon black content in 100% by mass of the filler is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more, and may be 100% by mass. Within the above range, the effect tends to be better. It is presumed that a higher carbon ratio reduces the hardness difference in the sea-island phase, making stress less likely to concentrate.

Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Among these, wet process silica is preferred because it has a large number of silanol groups. Commercially available products include those from Degussa, Rhodia, Tosoh Silica, Solvay Japan, and Tokuyama. These may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area ( _N2SA ) of silica is preferably ^50m2 /g or more, more preferably ^100m2 /g or more, and even more preferably ^150m2 /g or more. The upper limit of the _N2SA of silica is not particularly limited, but is preferably ^350m2 /g or less, more preferably ^250m2 /g or less, and even more preferably ^200m2 /g or less. Within the above range, the effect tends to be better obtained.
The N ₂ SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

The content of silica is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, particularly preferably 25 parts by mass or less, and most preferably 15 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be better obtained.

<Compound ingredients other than rubber components, resins, and fillers>
When silica is contained, it is preferable to use the silica in combination with a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. As commercially available products, for example, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, relative to 100 parts by mass of silica, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition preferably contains a liquid plasticizer (a plasticizer that is in a liquid state at room temperature (25° C.)).
The liquid plasticizer (a plasticizer in a liquid state at room temperature (25° C.)) is not particularly limited, and examples thereof include oil and liquid polymer (such as liquid diene-based polymer). These may be used alone or in combination of two or more kinds. Among them, oil is preferred.

The content of the liquid plasticizer is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 25 parts by mass or less. Within the above range, the effect tends to be better obtained.

Examples of the oil include process oil, vegetable oil, or a mixture thereof. Examples of the process oil include paraffin-based process oil, aromatic process oil, and naphthenic process oil. Examples of the vegetable oil include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Examples of commercially available products include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Seiyu Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Co., Ltd. These may be used alone or in combination of two or more. Among these, process oils (paraffin-based process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred, with aromatic process oils being more preferred.

The content of the oil is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. The upper limit of the content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 25 parts by mass or less. Within the above range, the effect tends to be better obtained.
The oil content includes the oil contained in the extender oil.

Liquid diene polymers include liquid styrene butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene isoprene copolymers (liquid SIR), liquid styrene butadiene styrene block copolymers (liquid SBS block polymers), liquid styrene isoprene styrene block copolymers (liquid SIS block polymers), liquid farnesene polymers, liquid farnesene butadiene copolymers, etc. that are liquid at 25°C. The ends or main chains of these may be modified with polar groups. Hydrogenated products of these may also be used. These may be used alone or in combination of two or more.

The content of the liquid diene polymer is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 25 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition may contain an antioxidant.
Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine;N-isopropyl-N'-phenyl-p-phenylenediamine,N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of the antioxidant include p-phenylenediamine antioxidants such as quinolinone; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Commercially available products include those of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. These antioxidants may be used alone or in combination of two or more. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, and p-phenylenediamine antioxidants are more preferred.

The content of the anti-aging agent is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less. Within the above range, the effect tends to be better.

The rubber composition may contain a wax.
The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. Commercially available products include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. These may be used alone or in combination of two or more kinds.

The wax content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be better.

The rubber composition may contain zinc oxide.
As the zinc oxide, a conventionally known one can be used, and as a commercially available product, there can be used products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more kinds.

The amount of zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be better.

The rubber composition may contain stearic acid.
As the stearic acid, a conventionally known one can be used, and as a commercially available product, a product from NOF Corp., Kao Corp., Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used. These may be used alone or in combination of two or more kinds.

The content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. If it is within the above range, the effect tends to be better.

The rubber composition contains sulfur. In the rubber composition after vulcanization, most of the sulfur is bonded to the rubber component.
Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are generally used as crosslinking agents in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more kinds.

The sulfur content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 3.5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2.5 parts by mass or less. Within the above range, the effect tends to be better obtained.

The rubber composition may contain a vulcanization accelerator.
Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD) and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. Commercially available products include products from Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Co., Ltd. These may be used alone or in combination of two or more. Of these, sulfenamide vulcanization accelerators are preferred.

The content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the rubber component. If it is within the above range, the effect tends to be better.

The rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides, in addition to the above components. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

The rubber composition can be produced, for example, by kneading the above components using a rubber kneading device such as an open roll or a Banbury mixer, and then vulcanizing the mixture.

As for kneading conditions, in the base kneading process where additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading process where the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 80 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

The rubber composition can be used (as a rubber composition for tires) for tire components such as treads (cap treads), sidewalls, base treads, undertreads, shoulders, clinches, bead apexes, breaker cushion rubbers, carcass cord covering rubbers, insulations, chafers, inner liners, and the like, as well as side reinforcing rubbers and bead reinforcing rubbers of run-flat tires. In particular, it is preferably used for sidewalls, clinches, side reinforcing rubbers, and bead reinforcing rubbers, and more preferably for sidewalls.

The tire (pneumatic tire, etc.) of the present invention is manufactured by a conventional method using the above rubber composition. That is, the rubber composition, which contains various additives as necessary, is extruded to match the shape of each tire component (particularly the sidewall) while still unvulcanized, molded by a conventional method on a tire building machine, and laminated together with other tire components to form an unvulcanized tire, which is then heated and pressurized in a vulcanizer to manufacture the tire.

The tire components of the tire may be at least partially made of the rubber composition, or may be entirely made of the rubber composition.

The above tires are suitable for use as passenger car tires, large passenger car tires, large SUV tires, truck and bus tires, motorcycle tires, racing tires, winter tires (studless tires, snow tires, studded tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc.

The present invention will be specifically explained based on examples, but the present invention is not limited to these.

The various chemicals used in the examples and comparative examples will be described below.
NR: TSR20 (NR)
BR: BR150B (cis content: 97% by mass) manufactured by Ube Industries, Ltd.
SBR: Nipol 1502 (E-SBR, styrene content: 23.5% by mass) manufactured by Zeon Corporation
Carbon black: Diablack N220 ( _N2SA : 111 ^m2 /g) manufactured by Mitsubishi Chemical Corporation
Silica: Ultrasil VN3 ( _N2SA : ^175m2 /g) manufactured by Evonik Degussa
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Antioxidant: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Oil: Diana Process AH-24 (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd.
Resin: 5-(hydroxymethyl)furfural (manufactured by Aldrich, corresponding to compound A) and phloroglucinol (manufactured by Alfa Aesar, corresponding to compound B) mixed in a mass ratio of 1:1 Stearic acid: NOF Corporation's stearic acid "Tsubaki"
Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% by mass of oil) manufactured by Hosoi Chemical Industry Co., Ltd.
Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

Examples and Comparative Examples
According to the formulation shown in Tables 1 and 2, materials other than sulfur, vulcanization accelerator, and resin (compound A and compound B) were kneaded for 5 minutes under the condition of 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Next, sulfur, vulcanization accelerator, and resin (compound A and compound B) were added to the obtained kneaded product, and the mixture was kneaded for 5 minutes under the condition of 80°C using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized for 12 minutes under the condition of 150°C to obtain a vulcanized rubber composition. The obtained vulcanized rubber composition was used to perform the following evaluations, and the results are shown in Tables 1 and 2. The reference comparative example in Table 1 was Comparative Example 1-1, and the reference comparative example in Table 2 was Comparative Example 2-1.

(Breakdown characteristics)
According to JIS K 6251 "Vulcanized rubber and thermoplastic rubber -- Determination of tensile properties", the tensile strength and breaking elongation of a rubber slab sheet (2 mm x 130 mm x 130 mm) made of the vulcanized rubber composition were measured. Then, using the obtained measurement results, the breaking energy was calculated by tensile strength x breaking elongation / 2, and the breaking energy index (breaking property index) of the reference comparative example was set to 100, and the measurement results of each compound were expressed as an index according to the following calculation formula. The larger the index, the more excellent the breaking properties.
(Fracture energy index) = (Fracture energy of each formulation) / (Fracture energy of standard comparative example) x 100

(Crack resistance)
Using the vulcanized rubber composition, samples were prepared based on JIS-K-6260 "Vulcanized rubber and thermoplastic rubber - Dematcia flex crack test method", and a flex crack growth test was performed to bend the rubber sheet by repeating 70% elongation 1 million times, and the length of the crack that occurred was measured. The reciprocal of the measured value (length) of the reference comparative example was set to 100, and the result was expressed as an index. The larger the index, the more the crack growth was suppressed and the better the crack flex resistance.

(Breakdown characteristics after thermal degradation)
A vulcanized rubber composition (new sample) was thermally aged in an oven at 100° C. for 7 days to obtain a thermally aged vulcanized rubber composition (aged sample). The fracture energy was calculated using the obtained thermally aged vulcanized rubber composition according to the above-mentioned method, and expressed as an index, with the fracture energy index (fracture property index) of the reference comparative example being set at 100. A larger index indicates better fracture properties after thermal aging.

From Tables 1 and 2, it was found that the examples containing a rubber component containing at least an isoprene-based rubber, a styrene-butadiene rubber and/or a butadiene rubber, a filler, a resin containing, as monomers, compound A having a structure in which an aromatic ring is modified with a hydroxymethyl group and compound B having a structure in which an aromatic ring is modified with a hydroxy group, and in which the content of isoprene-based rubber in 100% by mass of the rubber component is 35% by mass or more, can improve the overall performance of fracture properties, crack resistance and bending resistance, and fracture properties after thermal degradation (represented by the sum of the three indexes of fracture properties, crack resistance and bending resistance, and fracture properties after thermal degradation).

Comparison between Example 1-1 and Comparative Examples 1-1 to 1-3, and comparison between Example 2-1 and Comparative Examples 2-1 to 2-3, reveals that the combined use of a specific rubber component and the above resin can synergistically improve the overall performance of fracture properties, crack resistance and flexural properties, and fracture properties after thermal degradation.

Claims (4)

A rubber composition for tires comprising a rubber component including at least an isoprene-based rubber, a styrene-butadiene rubber and/or a butadiene rubber, and a filler,
The resin contains, as monomers, a compound A having a structure in which an aromatic ring is modified with a hydroxymethyl group and a compound B having a structure in which an aromatic ring is modified with a hydroxy group,
said compound A is an aromatic compound containing at least one aromatic ring having at least two functional groups, one of which is a hydroxymethyl group and the other of which is an aldehyde group or a hydroxymethyl group;
The compound B is a phenol compound,
The content of the isoprene-based rubber in 100% by mass of the rubber component is 35% by mass or more and 80% by mass or less ,
The content (parts by mass) of butadiene rubber or styrene-butadiene rubber / the content (parts by mass) of isoprene-based rubber is 1.10 or more and 2.50 or less ,
A rubber composition for tires used in sidewalls . The rubber composition for tires according to claim 1, wherein the carbon black content in 100% by mass of the filler is 80% by mass or more. The rubber composition for tires according to claim 1 or 2, wherein the resin content (parts by mass)/isoprene-based rubber content (parts by mass) is ≦0.5. A tire having a sidewall using the rubber composition according to any one of claims 1 to 3 .