JP2024076305A - tire - Google Patents

Abstract

[Problem] The present invention aims to provide a tire that achieves a high level of balance between wet grip performance, low fuel consumption performance, and wear resistance. [Solution] A mass ratio of resin component/isoprene skeleton rubber is ≥ 0.5, the thickness of the tread rubber is 9.5 mm or less, or the groove depth of the circumferential main groove is 7.5 mm or less, and the mass of the sidewall portion in a tire radial direction region between positions spaced apart by 15% of the tire cross-sectional height on the inner and outer sides in the tire radial direction from the tire maximum width position in a standard state is 1.5% to 5% of the total mass of the tire, or the thickness of the sidewall portion in a tire radial direction region between positions spaced apart by 15% of the tire cross-sectional height on the inner and outer sides in the tire radial direction from the tire maximum width position in a standard state is 1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion. [Selected Figure] Figure 1

Description

The present invention relates to tires.

Conventionally, from the viewpoint of improving vehicle safety, various studies have been made to improve the braking performance on wet road surfaces (hereinafter, abbreviated as "wet grip performance"). For example, the following Patent Document 1 discloses that the braking performance of a tire on both dry and wet road surfaces is improved by applying a rubber composition obtained by compounding a rubber component containing 70% by mass or more of natural rubber with a thermoplastic resin and a filler containing silica to the tread rubber of the tire.
On the other hand, in response to the recent trend toward global carbon dioxide emission regulations in response to growing interest in environmental issues, there is a growing demand for improved fuel efficiency in automobiles. In order to meet such demands, there is also a demand for improved fuel efficiency in tires (reduced rolling resistance).
From the viewpoint of tire economics, in the development of rubber compositions for tires, it is also required to improve abrasion resistance in addition to wet grip performance and fuel economy.

International Publication No. 2015/079703

However, the inventors' investigations revealed that while the technology described in Patent Document 1 can improve the wet grip performance of tires, there is still room for improvement in fuel economy and wear resistance.

Therefore, the objective of the present invention is to provide a tire that achieves a high level of balance between wet grip performance, fuel efficiency, and wear resistance.

The gist of the present invention to solve the above problems is as follows.
(1) A tire having a tread rubber made of a rubber composition for tires containing a rubber component, a resin component, and a filler,
The rubber component includes an isoprene skeleton rubber and a styrene-butadiene rubber,
The styrene-butadiene rubber has a glass transition temperature of less than −40° C.
an amount of the resin component per 100 parts by mass of the rubber component is 1 part by mass or more and less than 50 parts by mass;
the resin component is at least partially hydrogenated, and the difference in SP value between the resin component and the isoprene skeleton rubber is 1.40 (cal/cm ³ ) ^1/2 or less;
The formula:
The mass ratio of the resin component to the isoprene skeleton rubber is ≧0.5
The filling,
The thickness of the tread rubber is 9.5 mm or less, or the tread rubber is provided with a circumferential main groove extending in the tire circumferential direction, and the groove depth of the circumferential main groove is 7.5 mm or less,
The standard condition is when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and unloaded.
A tire characterized in that a mass of a sidewall portion in a tire radial region between positions spaced 15% of the tire cross-sectional height on the inner and outer sides in the tire radial direction from a maximum width position of the tire in the reference state is 1.5% to 5% of an entire mass of the tire.

Here, the glass transition temperature of the styrene-butadiene rubber is measured in accordance with ISO 22768: 2006 by recording a DSC curve while increasing the temperature within a predetermined temperature range, and the peak top (inflection point) of the DSC differential curve is taken as the glass transition temperature. Specifically, the glass transition temperature is measured by the method described in the examples below.
In this specification, the SP values (solubility parameters) of the isoprene skeleton rubber, the styrene-butadiene rubber and the resin component are calculated according to the Fedors method.

(2) A tire having a tread rubber made of a rubber composition for tires containing a rubber component, a resin component, and a filler,
The rubber component includes an isoprene skeleton rubber and a styrene-butadiene rubber,
The styrene-butadiene rubber has a glass transition temperature of less than −40° C.
an amount of the resin component per 100 parts by mass of the rubber component is 1 part by mass or more and less than 50 parts by mass;
the resin component is at least partially hydrogenated, and the difference in SP value between the resin component and the isoprene skeleton rubber is 1.40 (cal/cm ³ ) ^1/2 or less;
The formula:
The mass ratio of the resin component to the isoprene skeleton rubber is ≧0.5
The filling,
The thickness of the tread rubber is 9.5 mm or less, or the tread rubber is provided with a circumferential main groove extending in the tire circumferential direction, and the groove depth of the circumferential main groove is 7.5 mm or less,
The tire aspect ratio is 10 to 65.
The standard condition is when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and unloaded.
a thickness of a sidewall portion in a tire radial region between positions spaced 15% of the tire cross-sectional height on the inner and outer sides in the tire radial direction from a maximum width position of the tire in the reference state is 1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion.
Here, the "thickness of the sidewall portion" means the thickness measured in a direction perpendicular to the carcass line in a cross section in the tire width direction.
Furthermore, the thickness of the sidewall portion in the tire radial region being "1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion" means that the average thickness of the sidewall portion in the tire radial region is "1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion." Note that, if a protrusion is formed in the tire radial region, the thickness includes the height of the protrusion.
In this specification, the term "applicable rim" refers to a standard rim for an applicable size that is an industrial standard effective in the region where the tire is manufactured and used, and is described or will be described in the future in the JATMA YEAR BOOK of the Japan Automobile Tire Manufacturers Association (JATMA), the STANDARDS MANUAL of the European Tire and Rim Technical Organization (ETRTO), the YEAR BOOK of the Tire and Rim Association, Inc. (TRA), and the like. The term "rim" refers to the width of the rim that corresponds to the bead width of the tire (i.e., the above "rim" includes not only the current sizes but also sizes that may be included in the above industrial standard in the future. An example of "sizes to be described in the future" is the size described in "FUTURE DEVELOPMENTS" in the 2013 edition of ETRTO). However, in the case of a size not described in the above industrial standard, the term refers to a rim with a width corresponding to the bead width of the tire. Furthermore, "prescribed internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size/ply rating described in the above JATMA etc., and in the case of a size not described in the above industrial standard, the "prescribed internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, "maximum load" refers to the load corresponding to the above maximum load capacity.

(3) The tire according to the above-mentioned (1) or (2), wherein the resin component has an SP value difference from the isoprene skeleton rubber of 0.50 (cal/cm ³ ) ^1/2 or less.

(4) The tire according to any one of (1) to (3) above, wherein the difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is 0.3 (cal/cm ³ ) ^1/2 or more.

(5) A tire according to any one of (1) to (4) above, in which the content of the isoprene skeleton rubber is 1 to 80 parts by mass per 100 parts by mass of the rubber component.

(6) The tire described in (5) above, in which the content of the isoprene skeleton rubber is 1 to 40 parts by mass per 100 parts by mass of the rubber component.

(7) A tire according to any one of (1) to (6) above, in which the styrene-butadiene rubber is modified with a modifying agent having a functional group containing a nitrogen atom and an alkoxy group.

(8) The tire according to any one of (1) to (7) above, wherein the resin component has a softening point higher than 110° C. and a weight average molecular weight in terms of polystyrene of 200 to 1600 g/mol.
The softening point of the resin component is measured in accordance with JIS-K2207-1996 (ring and ball method).
The weight average molecular weight of the resin component is measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

(9) A tire according to any one of (1) to (8) above, in which the resin component is at least one selected from the group consisting of hydrogenated C5 resins, hydrogenated C5-C9 resins, hydrogenated dicyclopentadiene resins, and hydrogenated terpene resins.

The present invention provides a tire that achieves a high level of balance between wet grip performance, fuel efficiency, and wear resistance.

1 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to one embodiment of the present invention. 1 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to a first modified example. FIG. FIG. 11 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to a second modified example. FIG. 1 is a diagram showing evaluation results of Example 1. FIG. 1 is a diagram showing the evaluation results of Example 2 (Reference Example 4 and Comparative Examples 2 and 3). FIG. 1 is a diagram showing the evaluation results of Example 2 (Reference Example 4 and Comparative Example 4). FIG. 1 is a diagram showing an example of an arrangement of RFIDs.

The following describes in detail an embodiment of the present invention with reference to the drawings.

The tire according to one embodiment of the present invention has a tread rubber made of a rubber composition for tires that contains a rubber component, a resin component, and a filler, so we will first explain the rubber composition for tires.

<Rubber composition for tires>
The rubber composition for tires includes a rubber component, a resin component, and a filler, and the rubber component includes an isoprene skeleton rubber and a styrene-butadiene rubber, the styrene-butadiene rubber has a glass transition temperature of less than -40°C, the content of the resin component is 1 part by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, the resin component is at least partially hydrogenated, and the difference in SP value with the isoprene skeleton rubber is 1.40 (cal/cm ³ ) ^1/2 or less, and the following formula:
The mass ratio of the resin component to the isoprene skeleton rubber is ≧0.5
Meet the following.

In a rubber composition for tires, by blending a resin component that is at least partially hydrogenated and has an SP value difference from an isoprene skeleton rubber of 1.40 (cal/cm ³ ) ^1/2 or less in an amount of 1 part by mass or more per 100 parts by mass of the rubber component, the wet grip performance of a tire to which the rubber composition is applied can be improved.
However, simply blending the resin component reduces the fuel economy and wear resistance of a tire to which the rubber composition is applied, and if the content of the resin component is 50 parts by mass or more per 100 parts by mass of the rubber component, the fuel economy and wear resistance of a tire to which the rubber composition is applied deteriorates. In contrast, in the rubber composition for tires of the present invention, the content of the resin component is less than 50 parts by mass per 100 parts by mass of the rubber component, and a styrene-butadiene rubber having a glass transition temperature of less than -40°C is further blended, thereby improving the dispersibility of the filler and complementing the fuel economy and wear resistance of a tire to which the rubber composition is applied.
Furthermore, by setting the mass ratio of the resin component to the isoprene skeleton rubber to be 0.5 or more, the wet grip performance of a tire to which the rubber composition is applied can be further improved.
Therefore, by applying the rubber composition for tires to tires, it is possible to achieve a high level of balance between wet grip performance, fuel efficiency, and wear resistance of the tire.

(Rubber component)
The rubber composition for tires contains a rubber component, which contains an isoprene skeleton rubber and a styrene-butadiene rubber, and may further contain other rubber components.

-Isoprene-based rubber-
The isoprene skeleton rubber is a rubber having an isoprene unit as a main skeleton, and specific examples thereof include natural rubber (NR) and synthetic isoprene rubber (IR).
The rubber component contains an isoprene skeleton rubber, which can increase the breaking strength of the rubber composition, thereby reducing the rolling resistance of a tire using the rubber composition, improving fuel economy, and improving the wear resistance of the tire.

The content of the isoprene skeleton rubber is preferably 1 to 80 parts by mass, and more preferably 1 to 40 parts by mass, per 100 parts by mass of the rubber component. When the content of the isoprene skeleton rubber is 1 to 80 parts by mass per 100 parts by mass of the rubber component, the fuel efficiency and wet grip performance of a tire to which the rubber composition is applied can be further improved. When the content of the isoprene skeleton rubber is 1 to 40 parts by mass per 100 parts by mass of the rubber component, the fuel efficiency and wet grip performance of a tire to which the rubber composition is applied can be further improved. From the viewpoint of further increasing the compounding effect of the isoprene skeleton rubber, the content of the isoprene skeleton rubber is more preferably 10 parts by mass or more per 100 parts by mass of the rubber component.

-Styrene-butadiene rubber-
The styrene-butadiene rubber (SBR) has a glass transition temperature of less than -40°C, preferably less than -45°C, more preferably less than -50°C, and preferably higher than -90°C. When the glass transition temperature of the styrene-butadiene rubber is less than -40°C, the fuel economy and wear resistance of a tire to which the rubber composition is applied can be sufficiently improved. In addition, a styrene-butadiene rubber having a glass transition temperature higher than -90°C is easy to synthesize.

The content of the styrene-butadiene rubber is preferably 20 to 99 parts by mass, more preferably 30 to 99 parts by mass, more preferably 40 to 99 parts by mass, more preferably 50 to 99 parts by mass, and even more preferably 60 to 99 parts by mass, per 100 parts by mass of the rubber component. When the content of the styrene-butadiene rubber is 60 to 99 parts by mass per 100 parts by mass of the rubber component, the fuel economy and wet grip performance of a tire to which the rubber composition for tires is applied can be further improved.

The difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is preferably 0.3 (cal/cm ³ ) ^1/2 or more, and more preferably 0.35 (cal/cm ³ ) ^1/2 or more. When the difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is 0.3 (cal/cm ³ ) ^1/2 or more, the isoprene skeleton rubber and the styrene-butadiene rubber tend to be incompatible.

The styrene-butadiene rubber preferably has a bound styrene content of less than 15% by mass. The bound styrene content of the styrene-butadiene rubber means the ratio of styrene units contained in the styrene-butadiene rubber. When the bound styrene content of the styrene-butadiene rubber is less than 15% by mass, the glass transition temperature is likely to be low. The bound styrene content of the styrene-butadiene rubber is more preferably 14% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less. In addition, the bound styrene content of the styrene-butadiene rubber is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more, from the viewpoint of the wear resistance performance of a tire to which the rubber composition is applied.
The amount of bound styrene in the styrene-butadiene rubber can be adjusted by the amount of monomer used in polymerization of the styrene-butadiene rubber, the degree of polymerization, and the like.

The styrene-butadiene rubber is preferably modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group. When the styrene-butadiene rubber is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group, the balance of wet grip performance, fuel economy, and wear resistance of a tire to which the rubber composition is applied is further improved, and in particular, the fuel economy and wear resistance can be further improved.
The modifying agent having a functional group containing a nitrogen atom and an alkoxy group is a general term for modifying agents having at least one functional group containing a nitrogen atom and at least one alkoxy group.
The functional group containing a nitrogen atom is preferably selected from the following:
The functional group is selected from the group consisting of a primary amino group, a primary amino group protected with a hydrolyzable protecting group, an onium salt residue of a primary amine, an isocyanate group, a thioisocyanate group, an imine group, an imine residue, an amide group, a secondary amino group protected with a hydrolyzable protecting group, a cyclic secondary amino group, an onium salt residue of a cyclic secondary amine, a non-cyclic secondary amino group, an onium salt residue of a non-cyclic secondary amine, an isocyanuric acid triester residue, a cyclic tertiary amino group, a non-cyclic tertiary amino group, a nitrile group, a pyridine residue, an onium salt residue of a cyclic tertiary amine, and an onium salt residue of a non-cyclic tertiary amine, and is a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, or a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, which may contain at least one heteroatom selected from an oxygen atom, a sulfur atom, and a phosphorus atom.

--First Preferred Embodiment of Modified Styrene-Butadiene Rubber--
The styrene-butadiene rubber (SBR) is preferably modified with an aminoalkoxysilane compound, and from the viewpoint of having a high affinity for the filler, it is more preferable that the terminal is modified with an aminoalkoxysilane compound. When the terminal of the styrene-butadiene rubber is modified with an aminoalkoxysilane compound, the interaction between the modified styrene-butadiene rubber and the filler (particularly silica) becomes particularly large.

The modified site of the styrene-butadiene rubber may be the molecular terminal as described above, but may also be the main chain.
Styrene-butadiene rubber having modified molecular terminals can be produced by reacting various modifiers with the terminals of a styrene-butadiene copolymer having active terminals, for example, according to the methods described in WO 2003/046020 and JP 2007-217562 A.
In a preferred embodiment, the styrene-butadiene rubber having modified molecular terminals can be produced by reacting an aminoalkoxysilane compound with the terminals of a styrene-butadiene copolymer having an active terminal with a cis-1,4 bond content of 75% or more, and then reacting the resulting mixture with a carboxylic acid partial ester of a polyhydric alcohol for stabilization, according to the methods described in WO 2003/046020 and JP 2007-217562 A.

The carboxylic acid partial ester of a polyhydric alcohol means an ester of a polyhydric alcohol and a carboxylic acid, which has one or more hydroxyl groups. Specifically, an ester of a sugar or modified sugar having 4 or more carbon atoms and a fatty acid is preferably used. More preferred examples of this ester include (1) a fatty acid partial ester of a polyhydric alcohol, in particular a partial ester (which may be a monoester, diester, or triester) of a saturated higher fatty acid or an unsaturated higher fatty acid having 10 to 20 carbon atoms and a polyhydric alcohol, and (2) an ester compound in which 1 to 3 partial esters of a polycarboxylic acid and a higher alcohol are bonded to a polyhydric alcohol.
The polyhydric alcohol used as a raw material for the partial ester is preferably a saccharide having 5 or 6 carbon atoms and at least three hydroxyl groups (which may or may not be hydrogenated), glycol, polyhydroxy compound, etc. The raw material fatty acid is preferably a saturated or unsaturated fatty acid having 10 to 20 carbon atoms, such as stearic acid, lauric acid, or palmitic acid.
Among the fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferred, and specific examples thereof include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate.

The aminoalkoxysilane compound is not particularly limited, but is preferably an aminoalkoxysilane compound represented by the following general formula (i).
R ¹¹ _a —Si—(OR ¹² ) _4-a ... (i)

In general formula (i), R ¹¹ and R ¹² each independently represent a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, at least one of R ¹¹ and R ¹² is substituted with an amino group, a is an integer of 0 to 2, and when there are multiple OR ¹² , each OR ¹² may be the same or different, and no active proton is contained in the molecule.

As the aminoalkoxysilane compound, an aminoalkoxysilane compound represented by the following general formula (ii) is also preferred.

In general formula (ii), n1+n2+n3+n4=4 (wherein n2 is an integer from 1 to 4, and n1, n3 and n4 are integers from 0 to 3).
A ¹ is at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group, an isocyanuric acid trihydrocarbyl ester group, a nitrile group, a pyridine group, a (thio)ketone group, an amide group, and a primary or secondary amino group having a hydrolyzable group. When n4 is 2 or more, A ¹ may be the same or different, and A ¹ may be a divalent group that bonds with Si to form a cyclic structure.
R ^{21 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n1 is 2 or more, R 21} may be the same or different.
R ²² is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, either of which may contain a nitrogen atom and/or a silicon atom. When n2 is 2 or greater, R ²² may be the same or different from each other, or may be joined together to form a ring.
R ²³ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom, and when n3 is 2 or greater, may be the same or different.
R ²⁴ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n4 is 2 or greater, R 24 may be the same or different.
As the hydrolyzable group in the hydrolyzable group-containing primary or secondary amino group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii).

In general formula (iii), p1+p2+p3=2 (wherein p2 is an integer of 1 or 2, and p1 and p3 are integers of 0 or 1).
^A2 is NRa (Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group).
R ²⁵ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ²⁶ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, any of which may contain a nitrogen atom and/or a silicon atom. When p2 is 2, R ²⁶ may be the same or different from each other, or may be joined together to form a ring.
R ²⁷ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom.
R ²⁸ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
As the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (iv) or (v).

In the general formula (iv), q1+q2=3 (wherein q1 is an integer of 0 to 2, and q2 is an integer of 1 to 3).
R ³¹ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ³² and R ³³ each independently represent a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ³⁴ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q1 is 2, may be the same or different.
R ³⁵ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q2 is 2 or greater, R 35 may be the same or different.

In general formula (v), r1+r2=3 (wherein r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2).
R ³⁶ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ³⁷ is a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a dimethylsilylaminoethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r1 is 2 or more, they may be the same or different.
R ³⁸ is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r2 is 2, they may be the same or different.
A specific example of the aminoalkoxysilane compound represented by the general formula (v) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propaneamine.

The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (vi) or (vii).

In general formula (vi), R ⁴⁰ is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ⁴¹ is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ⁴² is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
Here, TMS represents a trimethylsilyl group (hereinafter the same).

In general formula (vii), R ⁴³ and R ⁴⁴ each independently represent a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ⁴⁵ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R ⁴⁵ may be the same or different.

The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (viii) or the following general formula (ix).

In general formula (viii), s1+s2 is 3 (wherein s1 is an integer of 0 to 2, and s2 is an integer of 1 to 3).
R ⁴⁶ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ⁴⁷ and R ⁴⁸ are each independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. Multiple R ^47s or R ^48s may be the same or different.

In general formula (ix), X is a halogen atom.
R ⁴⁹ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ⁵⁰ and R ⁵¹ are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R ⁵⁰ and R ⁵¹ combine together to form a divalent organic group.
R ⁵² and R ⁵³ each independently represent a halogen atom, a hydrocarbyloxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ⁵⁰ and R ⁵¹ are preferably a hydrolyzable group, and the hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, and particularly preferably a trimethylsilyl group.

The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (x), the following general formula (xi), the following general formula (xii), or the following general formula (xiii).

In the general formulas (x) to (xiii), the symbols U and V each represent an integer of 0 to 2 and satisfy U+V=2.
R ⁵⁴ to R ⁹² in general formulas (x) to (xiii) may be the same or different and are a monovalent or divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent or divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
In general formula (xiii), α and β are integers of 0 to 5.

Among the compounds satisfying general formula (x), general formula (xi), and general formula (xii), N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine, 2-((hexyl-dimethoxysilyl)methyl)-N1,N1,N3,N3-2-pentamethylpropane-1,3-diamine, N1-(3-(dimethylamino)propyl)-N3,N3-dimethyl-N1-(3-(trimethoxysilyl)propyl)propane-1,3-diamine, and 4-(3-(dimethylamino)propyl)-N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine are particularly preferred.
Among the compounds satisfying general formula (xiii), N,N-dimethyl-2-(3-(dimethoxymethylsilyl)propoxy)ethanamine, N,N-bis(trimethylsilyl)-2-(3-(trimethoxysilyl)propoxy)ethanamine, N,N-dimethyl-2-(3-(trimethoxysilyl)propoxy)ethanamine, and N,N-dimethyl-3-(3-(trimethoxysilyl)propoxy)propan-1-amine are particularly preferred.

--Second Preferred Modified Styrene-Butadiene Rubber--
It is also preferable that the styrene-butadiene rubber (SBR) is modified with a coupling agent represented by the following general formula (I), in which case the fuel economy and wear resistance of a tire to which the rubber composition is applied can be further improved.

In the above general formula (I), R ¹ , R ² and R ³ each independently represent a single bond or an alkylene group having 1 to 20 carbon atoms.
R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁹ each independently represent an alkyl group having 1 to 20 carbon atoms.
R ⁸ and R ¹¹ each independently represent an alkylene group having 1 to 20 carbon atoms.
R ¹⁰ represents an alkyl group or a trialkylsilyl group having 1 to 20 carbon atoms.
m represents an integer of 1 to 3; p represents 1 or 2.
When a plurality of R ¹ to R ¹¹ , m and p are present, they are each independent.
i, j, and k each independently represent an integer of 0 to 6, provided that (i+j+k) is an integer of 3 to 10.
A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom and a phosphorus atom and having no active hydrogen.
In the general formula (I), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic and aromatic hydrocarbon groups. Examples of the organic group not having active hydrogen include organic groups not having a functional group having active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH ₂ ) or a sulfhydryl group (-SH).

The styrene-butadiene rubber modified with the coupling agent represented by the above general formula (I) has a weight average molecular weight (Mw) of 20×10 ⁴ to 300×10 ⁴ , contains 0.25 to 30 mass% of modified styrene-butadiene rubber having a molecular weight of 200×10 ⁴ to 500×10 ⁴ based on the total amount of the modified styrene-butadiene rubber, and preferably has a shrinkage factor (g') of less than 0.64.

In general, a polymer having branches tends to have a smaller molecular size compared to a linear polymer having the same absolute molecular weight, and the contraction factor (g') is an index of the ratio of the molecular size to that of a linear polymer having the same absolute molecular weight. That is, the contraction factor (g') tends to be smaller as the branching degree of the polymer increases. In this embodiment, the intrinsic viscosity is used as an index of the molecular size, and the linear polymer is used as being in accordance with the relational expression of intrinsic viscosity [η] = -3.883 M ^0.771 . The contraction factor (g') at each absolute molecular weight of the modified styrene-butadiene rubber is calculated, and the average value of the contraction factor (g') at the absolute molecular weight of 100 x 10 ⁴ to 200 x 10 ⁴ is taken as the contraction factor (g') of the modified styrene-butadiene rubber. Here, "branch" is formed by directly or indirectly bonding one polymer to another polymer. Also, "branching degree" is the number of polymers that are directly or indirectly bonded to one branch. For example, when five styrene-butadiene copolymer chains described below are indirectly bonded to each other via coupling residues described below, the degree of branching is 5. The coupling residue is a structural unit of a modified styrene-butadiene rubber bonded to the styrene-butadiene copolymer chain, and is, for example, a structural unit derived from a coupling agent produced by reacting a styrene-butadiene copolymer described below with a coupling agent. The styrene-butadiene copolymer chain is a structural unit of a modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer produced by reacting a styrene-butadiene copolymer described below with a coupling agent.
The shrinkage factor (g') is preferably less than 0.64, more preferably 0.63 or less, more preferably 0.60 or less, even more preferably 0.59 or less, and even more preferably 0.57 or less. The lower limit of the shrinkage factor (g') is not particularly limited and may be equal to or less than the detection limit, but is preferably 0.30 or more, more preferably 0.33 or more, even more preferably 0.35 or more, and even more preferably 0.45 or more. By using a modified styrene-butadiene rubber having a shrinkage factor (g') in this range, the processability of the rubber composition is improved.
Since the shrinkage factor (g') tends to depend on the degree of branching, for example, the shrinkage factor (g') can be controlled using the degree of branching as an index. Specifically, in the case of a modified styrene-butadiene rubber having a degree of branching of 6, the shrinkage factor (g') tends to be 0.59 or more and 0.63 or less, and in the case of a modified styrene-butadiene rubber having a degree of branching of 8, the shrinkage factor (g') tends to be 0.45 or more and 0.59 or less.

The styrene-butadiene rubber modified by the coupling agent represented by the general formula (I) preferably has a branch and a degree of branching of 5 or more. The modified styrene-butadiene rubber has one or more coupling residues and a styrene-butadiene copolymer chain bonded to the coupling residue, and more preferably, the branch includes a branch in which 5 or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 5 or more and the branch includes a branch in which 5 or more styrene-butadiene copolymer chains are bonded to one coupling residue, the contraction factor (g') can be more reliably made less than 0.64. The number of styrene-butadiene copolymer chains bonded to one coupling residue can be confirmed from the value of the contraction factor (g').
Moreover, it is more preferable that the modified styrene-butadiene rubber has branches, and the degree of branching is 6 or more. Moreover, it is more preferable that the modified styrene-butadiene rubber has one or more coupling residues and a styrene-butadiene copolymer chain bonded to the coupling residue, and further, the above-mentioned branches include branches in which 6 or more of the styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 6 or more and the branches include branches in which 6 or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.63 or less.
Furthermore, the modified styrene-butadiene rubber has branches, and the degree of branching is more preferably 7 or more, and even more preferably 8 or more. The upper limit of the degree of branching is not particularly limited, but is preferably 18 or less. The modified styrene-butadiene rubber has one or more coupling residues and a styrene-butadiene copolymer chain bonded to the coupling residue, and further, it is more preferable that the above-mentioned branches include a branch in which 7 or more styrene-butadiene copolymer chains are bonded to one coupling residue, and it is particularly preferable that the above-mentioned branches include a branch in which 8 or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 8 or more and the branch includes a branch in which 8 or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.59 or less.

It is preferable that at least one end of the styrene-butadiene copolymer chain is bonded to a silicon atom of the coupling residue. In this case, the ends of a plurality of styrene-butadiene copolymer chains may be bonded to one silicon atom. In addition, an end of the styrene-butadiene copolymer chain and an alkoxy group or hydroxyl group having 1 to 20 carbon atoms may be bonded to one silicon atom, and as a result, that one silicon atom may constitute an alkoxysilyl group or silanol group having 1 to 20 carbon atoms.

The modified styrene-butadiene rubber can be an oil-extended rubber to which an extender oil has been added. The modified styrene-butadiene rubber may be either non-oil-extended or oil-extended, but from the viewpoint of wear resistance, the Mooney viscosity measured at 100°C is preferably 20 or more and 100 or less, and more preferably 30 or more and 80 or less.

The weight average molecular weight (Mw) of the modified styrene-butadiene rubber is preferably 20×10 ⁴ or more and 300×10 ⁴ or less, more preferably 50×10 ⁴ or more, more preferably 64×10 ⁴ or more, and even more preferably 80×10 ⁴ or more. The weight average molecular weight is preferably 250×10 ⁴ or less, more preferably 180×10 ⁴ or less, and more preferably 150×10 ⁴ or less. When the weight average molecular weight is 20×10 ⁴ or more, the low loss property and abrasion resistance of the rubber composition can be sufficiently improved. When the weight average molecular weight is 300×10 ⁴ or less, the processability of the rubber composition is improved.

The modified styrene-butadiene rubber preferably contains 0.25% by mass or more and 30% by mass or less of a modified styrene-butadiene rubber having a molecular weight of 200 × 10 ⁴ or more and 500 × 10 ⁴ or less (hereinafter also referred to as "specific high molecular weight component") relative to the total amount (100% by mass) of the modified styrene-butadiene rubber. When the content of the specific high molecular weight component is 0.25% by mass or more and 30% by mass or less, the low loss property and wear resistance of the rubber composition can be sufficiently improved. The modified styrene-butadiene rubber preferably contains 1.0% by mass or more of the specific high molecular weight component, more preferably contains 1.4% by mass or more, even more preferably contains 1.75% by mass or more, even more preferably contains 2.0% by mass or more, particularly preferably contains 2.15% by mass or more, and extremely preferably contains 2.5% by mass or more. The modified styrene-butadiene rubber contains the specific high molecular weight component in an amount of preferably 28% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and still more preferably 18% by mass or less.
In this specification, the "molecular weight" of the rubber component is the standard polystyrene equivalent molecular weight obtained by GPC (gel permeation chromatography). In order to obtain a modified styrene-butadiene rubber having a content of a specific high molecular weight component in such a range, it is preferable to control the reaction conditions in the polymerization step and the reaction step described later. For example, in the polymerization step, the amount of an organic monolithium compound used as a polymerization initiator described later may be adjusted. In addition, in the polymerization step, in both the continuous and batch polymerization modes, a method having a residence time distribution is used, that is, the time distribution of the propagation reaction is expanded.

In the modified styrene-butadiene rubber, the molecular weight distribution (Mw/Mn), which is expressed as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.6 or more and 3.0 or less. If the molecular weight distribution of the modified styrene-butadiene rubber is in this range, the rubber composition will have good processability.

The manufacturing method of the modified styrene-butadiene rubber is not particularly limited, but it is preferable that the method has a polymerization step of copolymerizing butadiene and styrene using an organic monolithium compound as a polymerization initiator to obtain a styrene-butadiene copolymer, and a reaction step of reacting an active terminal of the styrene-butadiene copolymer with a pentafunctional or higher reactive compound (hereinafter also referred to as a "coupling agent").

The polymerization step is preferably a polymerization by a propagation reaction due to a living anionic polymerization reaction, which makes it possible to obtain a styrene-butadiene copolymer having an active terminal, and thus to obtain a modified styrene-butadiene rubber with a high modification rate.
The styrene-butadiene copolymer is obtained by copolymerizing 1,3-butadiene and styrene.

The amount of the organic monolithium compound used as a polymerization initiator is preferably determined depending on the molecular weight of the target styrene-butadiene copolymer or modified styrene-butadiene rubber. The amount of monomers such as 1,3-butadiene and styrene used relative to the amount of polymerization initiator used is related to the degree of polymerization, that is, the number average molecular weight and/or the weight average molecular weight. Therefore, in order to increase the molecular weight, it is preferable to adjust the amount of polymerization initiator to a smaller amount, and in order to decrease the molecular weight, it is preferable to adjust the amount of polymerization initiator to a larger amount.
The organic monolithium compound is preferably an alkyllithium compound from the viewpoint of industrial availability and ease of control of the polymerization reaction. In this case, a styrene-butadiene copolymer having an alkyl group at the polymerization initiation terminal is obtained. Examples of the alkyllithium compound include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. As the alkyllithium compound, n-butyllithium and sec-butyllithium are preferred from the viewpoint of industrial availability and ease of control of the polymerization reaction. These organic monolithium compounds may be used alone or in combination of two or more.

In the polymerization step, examples of the polymerization reaction mode include a batch polymerization mode and a continuous polymerization mode. In the continuous mode, one or more connected reactors can be used. For the continuous mode, for example, a tank type or a tube type reactor equipped with an agitator is used. In the continuous mode, preferably, the monomer, the inert solvent, and the polymerization initiator are continuously fed into the reactor, a polymer solution containing the polymer is obtained in the reactor, and the polymer solution is continuously discharged. For the batch mode, for example, a tank type reactor equipped with an agitator is used. In the batch mode, preferably, the monomer, the inert solvent, and the polymerization initiator are fed, and if necessary, the monomer is continuously or intermittently added during the polymerization, a polymer solution containing the polymer is obtained in the reactor, and the polymer solution is discharged after the polymerization is completed. In this embodiment, in order to obtain a styrene-butadiene copolymer having a high proportion of active ends, a continuous mode is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short time.

The polymerization step is preferably carried out in an inert solvent. Examples of the solvent include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific examples of the hydrocarbon solvent include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene, and hydrocarbons consisting of mixtures thereof. By treating the impurities of allenes and acetylenes with an organometallic compound before subjecting the mixture to the polymerization reaction, a styrene-butadiene copolymer having a high concentration of active ends tends to be obtained, and a modified styrene-butadiene rubber with a high modification rate tends to be obtained, which is preferable.

In the polymerization step, a polar compound may be added. By adding a polar compound, styrene can be randomly copolymerized with 1,3-butadiene, and the polar compound tends to be usable as a vinylating agent for controlling the microstructure of the 1,3-butadiene portion.
Examples of the polar compound that can be used include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium tert-amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

In the polymerization step, from the viewpoint of productivity, the polymerization temperature is preferably 0°C or higher, more preferably 120°C or lower, and particularly preferably 50°C or higher and 100°C or lower. By keeping the temperature in this range, it tends to be possible to ensure a sufficient amount of reaction of the coupling agent with the active terminals after the polymerization is completed.

The amount of bound butadiene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably from 40% by mass to 100% by mass, and more preferably from 55% by mass to 80% by mass.
The amount of bound styrene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably more than 0 mass% and not more than 60 mass%, and more preferably 20 mass% or more and not more than 45 mass%.
When the bound butadiene amount and the bound styrene amount are within the above ranges, the low loss property and the wear resistance of the rubber composition can be further improved.
The amount of bound styrene can be measured by ultraviolet absorption of the phenyl group, from which the amount of bound butadiene can also be calculated.

In the styrene-butadiene copolymer or modified styrene-butadiene rubber, the amount of vinyl bonds in the butadiene bond units is not particularly limited, but is preferably 10 mol% to 75 mol%, more preferably 20 mol% to 65 mol%. When the amount of vinyl bonds is within the above range, the low loss property and wear resistance of the rubber composition can be further improved.
For modified styrene-butadiene rubber, the amount of vinyl bonds (1,2-bonds) in the butadiene bond units can be determined by the Hampton method [R. R. Hampton, Analytical Chemistry, 21, 923 (1949)].

The alkoxysilyl group of the coupling agent represented by the above general formula (I) tends to react with, for example, the active terminal of the styrene-butadiene copolymer, dissociating the alkoxylithium and forming a bond between the terminal of the styrene-butadiene copolymer chain and the silicon of the coupling residue. The number of alkoxysilyl groups in the coupling residue is the total number of SiOR in one molecule of the coupling agent minus the number of SiORs reduced by the reaction. The azasilacycle group in the coupling agent forms an >N-Li bond and a bond between the terminal of the styrene-butadiene copolymer and the silicon of the coupling residue. The >N-Li bond tends to easily become >NH and LiOH due to water, etc. during finishing. The alkoxysilyl group remaining unreacted in the coupling agent tends to easily become a silanol (Si-OH group) due to water, etc. during finishing.

The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the styrene-butadiene copolymer, more preferably from 0° C. to 120° C., and even more preferably from 50° C. to 100° C. The temperature change from the end of the polymerization step to the addition of the coupling agent is preferably 10° C. or less, more preferably 5° C. or less.
The reaction time in the reaction step is preferably 10 seconds or more, more preferably 30 seconds or more. From the viewpoint of the coupling rate, the time from the end of the polymerization step to the start of the reaction step is preferably shorter, and more preferably within 5 minutes.
The mixing in the reaction step may be performed by mechanical stirring, stirring with a static mixer, or the like. When the polymerization step is a continuous process, it is preferable that the reaction step is also a continuous process. The reactor used in the reaction step may be, for example, a tank type or a tube type equipped with a stirrer. The coupling agent may be diluted with an inert solvent and continuously fed to the reactor. When the polymerization step is a batch process, the coupling agent may be added to the polymerization reactor, or may be transferred to another reactor to carry out the reaction step.

In the general formula (I), A is preferably represented by any one of the following general formulas (II) to (V). When A is represented by any one of the general formulas (II) to (V), a modified styrene-butadiene rubber with superior performance can be obtained.

In the general formula (II), B ¹ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 1s are present, each B ¹ is independent.

In the general formula (III), ^B2 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, ^B3 represents an alkyl group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When there are a plurality of each of ^B2 and ^B3 , they are independent of each other.

In the general formula (IV), ^B4 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B4s are present, each ^B4 is independent.

In the general formula (V), ^B5 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B5s are present, each ^B5 is independent.

With regard to B ¹ , B ² , B ⁴ and B ⁵ in the general formulae (II) to (V), examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms.

Preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k is 0.
More preferably, in the general formula (I), A is represented by the general formula (II) or (III), k represents 0, and in the general formula (II) or (III), a represents an integer of 2 to 10.
More preferably, in said general formula (I), A is represented by said general formula (II), k represents 0, and in said general formula (II), a represents an integer of 2 to 10.
Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl). bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, and the like. Among these, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine and tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane are particularly preferred.

The amount of the compound represented by general formula (I) added as the coupling agent can be adjusted so that the moles of the styrene-butadiene copolymer to the moles of the coupling agent react in the desired stoichiometric ratio, which tends to achieve the desired degree of branching. The specific number of moles of the polymerization initiator is preferably 5.0 times or more, more preferably 6.0 times or more, relative to the moles of the coupling agent. In this case, in general formula (I), the number of functional groups of the coupling agent ((m-1) x i + p x j + k) is preferably an integer of 5 to 10, and more preferably an integer of 6 to 10.

In order to obtain a modified styrene-butadiene rubber having the specific polymer component, the molecular weight distribution (Mw/Mn) of the styrene-butadiene copolymer is preferably 1.5 or more and 2.5 or less, more preferably 1.8 or more and 2.2 or less. In addition, it is preferable that the obtained modified styrene-butadiene rubber has a single peak in the molecular weight curve by GPC.
When the peak molecular weight of the modified styrene-butadiene rubber as measured by GPC is Mp ₁ and the peak molecular weight of the styrene-butadiene copolymer is Mp ₂ , it is preferable that the following formula is satisfied.
( _Mp1 / _Mp2 ) < 1.8 x 10-12 x ( _Mp2-120 x ¹⁰⁴ ) ² + 2
_Mp2 is more preferably 20×10 ⁴ or more and 80×10 ⁴ or less, and _Mp1 is more preferably 30×10 ⁴ or more and 150×10 ⁴ or less. _Mp1 and _Mp2 are determined by the method described in the examples below.

The modification rate of the modified styrene-butadiene rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. A modification rate of 30% by mass or more can further improve the low loss properties and wear resistance of the rubber composition.

After the reaction step, a deactivator, neutralizing agent, etc. may be added to the copolymer solution as necessary. Examples of deactivators include, but are not limited to, water; alcohols such as methanol, ethanol, isopropanol, etc. Examples of neutralizing agents include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, with the main carbon atom being 10); aqueous solutions of inorganic acids, and carbon dioxide gas.
In addition, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add an antioxidant such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, or 2-methyl-4,6-bis[(octylthio)methyl]phenol to the modified styrene-butadiene rubber.

The modified styrene-butadiene rubber can be obtained from the polymer solution by known methods. Examples of such methods include a method in which the solvent is separated by steam stripping or the like, the polymer is filtered, and then dehydrated and dried to obtain the polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly devolatilized using a drum dryer or the like.

The modified styrene-butadiene rubber obtained by reacting the coupling agent represented by the above general formula (I) with a styrene-butadiene copolymer is represented, for example, by the following general formula (VI).

In general formula (VI), D represents a styrene-butadiene copolymer chain, and the weight average molecular weight of the styrene-butadiene copolymer chain is preferably 10 × 10 ⁴ to 100 × 10 ^4. The styrene-butadiene copolymer chain is a structural unit of a modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer produced by reacting a styrene-butadiene copolymer with a coupling agent.
R ¹² , R ¹³ and R ¹⁴ each independently represent a single bond or an alkylene group having 1 to 20 carbon atoms.
R ¹⁵ and R ¹⁸ each independently represent an alkyl group having 1 to 20 carbon atoms.
R ¹⁶ , R ¹⁹ , and R ²⁰ each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.
R ¹⁷ and R ²¹ each independently represent an alkylene group having 1 to 20 carbon atoms.
R ²² represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.
m and x are integers of 1 to 3, with x≦m; p is 1 or 2; y is an integer of 1 to 3, with y≦(p+1); and z is an integer of 1 or 2.
When there are multiple D, R ¹² to R ²² , m, p, x, y, and z, they are each independent and may be the same or different.
In addition, i represents an integer from 0 to 6, j represents an integer from 0 to 6, k represents an integer from 0 to 6, (i+j+k) is an integer from 3 to 10, and ((x×i)+(y×j)+(z×k)) is an integer from 5 to 30.
A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen. The hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include organic groups having no functional groups having active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH ₂ ), or a sulfhydryl group (-SH).

In the above general formula (VI), A is preferably represented by any one of the above general formulas (II) to (V). By having A represented by any one of general formulas (II) to (V), the low loss properties and wear resistance of the rubber composition can be further improved.

--Third preferred embodiment of modified styrene-butadiene rubber--
It is also preferable that at least one end of the styrene-butadiene rubber (SBR) is modified with a modifying agent containing a compound (alkoxysilane) represented by the following general formula (1).

By using, as the rubber component, a styrene-butadiene rubber modified with a modifier containing a compound represented by the above general formula (1) containing an oligosiloxane and a tertiary amino group, which are filler affinity functional groups, the dispersibility of fillers such as silica can be improved. As a result, the rubber composition of the present invention has improved filler dispersibility, and therefore the low loss properties are greatly improved, and the rolling resistance of tires to which the rubber composition is applied can be reduced, thereby improving fuel efficiency.

In the above general formula (1), R ¹ to R ⁸ are each independently an alkyl group having 1 to 20 carbon atoms; L ¹ and L ² are each independently an alkylene group having 1 to 20 carbon atoms; and n is an integer of 2 to 4.

Specifically, in formula (1), R ¹ to R ⁴ may each independently be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. When R ¹ to R ⁴ are substituted, they may each independently be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkoxy group having 4 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an alkanoyloxy group having 2 to 12 carbon atoms (Ra-COO-, where Ra is an alkyl group having 1 to 9 carbon atoms), an aralkyloxy group having 7 to 13 carbon atoms, an arylalkyl group having 7 to 13 carbon atoms, and an alkylaryl group having 7 to 13 carbon atoms.
More specifically, R ¹ to R ⁴ may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and even more specifically, R ¹ to R ⁴ may be each independently a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

In addition, in formula (1), R ⁵ to R ⁸ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, specifically, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, more specifically, a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and when substituted, may be substituted with the substituents described above for R ¹ to R ⁴ .
When R ⁵ to R ⁸ are not alkyl groups but hydrolyzable substituents, the bonds N-R ⁵ R ⁶ and N-R ⁷ R ⁸ may be hydrolyzed to N-H in the presence of moisture, which may adversely affect the processability of the polymer.

More specifically, in the compound represented by the formula (1), R ¹ to R ⁴ can be a methyl group or an ethyl group, and R ⁵ to R ⁸ can be an alkyl group having 1 to 10 carbon atoms.

The amino groups in the compound represented by formula (1), i.e., N-R ⁵ R ⁶ and N-R ⁷ R ⁸ , are preferably tertiary amino groups. The tertiary amino groups provide the compound represented by formula (1) with better processability when used as a modifying agent.
In addition, when a protecting group for protecting an amino group is bonded to R ⁵ to R ^{8 or when hydrogen is bonded to R 5 to R 8} , it may be difficult to realize the effect of the compound represented by formula (1). When hydrogen is bonded, the anion reacts with hydrogen during the modification process and loses reactivity, making the modification reaction itself impossible, and when a protecting group is bonded, the modification reaction takes place, but in the state bonded to the polymer end, it is deprotected by hydrolysis during post-processing to become a primary or secondary amino group, and the deprotected primary or secondary amino group may cause an increase in the viscosity of the compound during subsequent blending, which may cause a decrease in processability.

In addition, L ¹ and L ² in the compound represented by the formula (1) are each independently a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms.
More specifically, L ¹ and L ² can each independently be an alkylene group having 1 to 10 carbon atoms, and even more specifically, an alkylene group having 1 to 6 carbon atoms, such as a methylene group, an ethylene group, or a propylene group.

Regarding L ¹ and L ² in the compound represented by the formula (1), the closer the distance between the Si atom and the N atom in the molecule, the better the effect. However, when Si is directly bonded to N, there is a risk that the bond between Si and N may be broken during the subsequent treatment process, and the secondary amino group generated at this time is likely to be washed away by water during the post-treatment, and in the modified styrene-butadiene rubber produced, it is difficult to bond with the filler by the amino group that promotes the bond with the filler such as silica, and as a result, the effect of improving the dispersibility of the filler may be reduced. In this way, considering the improvement effect due to the length of the bond between Si and N, it is more preferable that the L ¹ and L ² are each independently an alkylene group having 1 to 3 carbon atoms such as a methylene group, an ethylene group, or a propylene group, and more specifically, a propylene group. In addition, L ¹ and L ² may be substituted with the substituents described above for R ¹ to R ⁴ .

The compound represented by the formula (1) is preferably, for example, any one of the compounds represented by the following structural formulas (1-1) to (1-5), because this allows for the realization of more excellent low loss properties.

The compound represented by the formula (1) has an alkoxysilane structure that bonds with the active end of the styrene-butadiene copolymer, while the Si-O-Si structure and three or more amino groups bonded to the end show affinity for fillers such as silica, and can therefore promote the bonding between the filler and the modified styrene-butadiene rubber compared to conventional modifiers containing one amino group in the molecule. In addition, the degree of bonding of the active end of the styrene-butadiene copolymer is uniform, and when the change in molecular weight distribution is observed before and after coupling, the molecular weight distribution is not increased after coupling and remains constant. Therefore, there is no deterioration in the physical properties of the modified styrene-butadiene rubber itself, and the aggregation of the filler in the rubber composition can be prevented, and the dispersibility of the filler can be increased, thereby improving the processability of the rubber composition. These effects make it possible to improve fuel efficiency and wet grip performance in a well-balanced manner, particularly when the rubber composition is applied to tires.

The compound represented by the formula (1) can be produced through a condensation reaction represented by the following reaction scheme.

In the reaction scheme, R ¹ to R ⁸ , L ¹ and L ² , and n are the same as those defined in the above formula (1), and R′ and R″ are any substituents that do not affect the condensation reaction. For example, R′ and R″ can each independently be the same as any one of R ¹ to R ⁴ .

The reaction in the above reaction scheme proceeds in the presence of an acid, and the acid can be any acid that is generally used in condensation reactions without limitation. Those skilled in the art can select the most suitable acid for various process variables such as the type of reactor in which the reaction is carried out, the starting materials, and the reaction temperature.

The styrene-butadiene rubber modified with the modifier containing the compound represented by formula (1) can have a narrow molecular weight distribution (Mw/Mn, also called "polydispersity index (PDI)") of 1.1 to 3.0. If the molecular weight distribution of the modified styrene-butadiene rubber exceeds 3.0 or is less than 1.1, the tensile properties and viscoelasticity may be reduced when applied to a rubber composition. Considering the remarkable effect of improving the tensile properties and viscoelasticity by controlling the molecular weight distribution of the modified styrene-butadiene rubber, the molecular weight distribution of the modified styrene-butadiene rubber is preferably in the range of 1.3 to 2.0. By using the modifier, the modified styrene-butadiene rubber has a molecular weight distribution similar to that of the styrene-butadiene copolymer before modification.

The molecular weight distribution of the modified styrene-butadiene rubber can be calculated from the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). Here, the number average molecular weight (Mn) is the common average of the molecular weights of individual polymers calculated by measuring the molecular weights of n polymer molecules, calculating the sum of the molecular weights, and dividing the sum by n, and the weight average molecular weight (Mw) represents the molecular weight distribution of a polymer composition. The average of the total molecular weight can be expressed in grams per mole (g/mol).
The weight average molecular weight and number average molecular weight are each a polystyrene-equivalent molecular weight analyzed by gel permeation chromatography (GPC).

The modified styrene-butadiene rubber satisfies the above-mentioned molecular weight distribution conditions, and at the same time, the number average molecular weight (Mn) can be 50,000 g/mol to 2,000,000 g/mol, more specifically, 200,000 g/mol to 800,000 g/mol, and the weight average molecular weight (Mw) can be 100,000 g/mol to 4,000,000 g/mol, more specifically, 300,000 g/mol to 1,500,000 g/mol.
When the weight average molecular weight (Mw) of the modified styrene-butadiene rubber is less than 100,000 g/mol or the number average molecular weight (Mn) is less than 50,000 g/mol, the tensile properties may be deteriorated when applied to a rubber composition. When the weight average molecular weight (Mw) is more than 4,000,000 g/mol or the number average molecular weight (Mn) is more than 2,000,000 g/mol, the processability of the modified styrene-butadiene rubber is deteriorated, the workability of the rubber composition is deteriorated, kneading becomes difficult, and it may be difficult to sufficiently improve the physical properties of the rubber composition.
More specifically, when the modified styrene-butadiene rubber satisfies the conditions of weight average molecular weight (Mw) and number average molecular weight (Mn) together with the molecular weight distribution, when the modified styrene-butadiene rubber is applied to a rubber composition, the rubber composition can have a well-balanced improvement in viscoelasticity and processability.

The modified styrene-butadiene rubber preferably has a vinyl bond content in the butadiene portion of 5% or more, more preferably 10% or more, and more preferably 60% or less. By setting the vinyl bond content in the butadiene portion within the above range, the glass transition temperature can be adjusted to an appropriate range.

The modified styrene-butadiene rubber may have a Mooney viscosity (MV) at 100° C. of 40 to 140, specifically 60 to 100. When the modified styrene-butadiene rubber has a Mooney viscosity in the above range, it can exhibit better processability.
The Mooney viscosity can be measured using a Mooney viscometer, for example, MV2000E manufactured by Monsanto, at 100° C., rotor speed 2±0.02 rpm, and a large rotor. The sample used here is left at room temperature (23±3° C.) for 30 minutes or more, and then 27±3 g of the sample is taken and filled into the die cavity, and the platen is operated to measure.

As described above, the modified styrene-butadiene rubber is preferably modified at one end with a modifier containing a compound represented by the above general formula (1), and is preferably further modified at the other end with a modifier containing a compound represented by the following general formula (2). By modifying both ends of the modified styrene-butadiene rubber, the dispersibility of the filler in the rubber composition is further improved, and a tire to which the rubber composition is applied can achieve both low fuel consumption performance and wet grip performance at a higher level.

In the above general formula (2), R ⁹ to R ¹¹ are each independently hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms.
In addition, in formula (2), R ¹² is a single bond; an alkylene group having 1 to 20 carbon atoms which is substituted or unsubstituted with a substituent; a cycloalkylene group having 5 to 20 carbon atoms which is substituted or unsubstituted with a substituent; or an arylene group having 5 to 20 carbon atoms which is substituted or unsubstituted with a substituent, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
In addition, in formula (2), R ¹³ is an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 3 to 30 carbon atoms; or a functional group represented by the following general formula (2a) or general formula (2b), where m is an integer of 1 to 5, and at least one of R ¹³ is a functional group represented by the following general formula (2a) or general formula (2b), and when m is an integer of 2 to 5, the multiple R ¹³ may be the same as or different from each other.

In the above general formula (2a), R ¹⁴ is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
In addition, in formula (2a), R ¹⁵ and R ¹⁶ are each independently an alkylene group having 1 to 20 carbon atoms which is substituted or unsubstituted with an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
In addition, in formula (2a), R ¹⁷ is hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms; and X is an N, O, or S atom, with the proviso that when X is O or S, R ¹⁷ does not exist.

In the above general formula (2b), R ¹⁸ is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
In addition, in formula (2b), R ¹⁹ and R ²⁰ are each independently an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms.

In the compound represented by the above general formula (2), R ⁹ to R ¹¹ are each independently hydrogen; an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; or an alkynyl group having 2 to 10 carbon atoms; R ¹² is a single bond; or an unsubstituted alkylene group having 1 to 10 carbon atoms; R ¹³ is an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; an alkynyl group having 2 to 10 carbon atoms; or a functional group represented by the above general formula (2a) or general formula (2b); in the above general formula (2a), R ¹⁴ is an unsubstituted alkylene group having 1 to 10 carbon atoms; R ¹⁵ and R ¹⁶ are each independently an unsubstituted alkylene group having 1 to 10 carbon atoms; R In the above general formula (2b), ^{R 18} is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R ¹⁹ and R ²⁰ may each independently be an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to ²⁰ carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms.

More specifically, the compound represented by the above general formula (2) can be a compound represented by the following structural formulas (2-1) to (2-3).

In addition, when the styrene-butadiene copolymer is modified with a modifying agent containing the compound represented by the above general formula (2), the modifying agent containing the compound represented by formula (2) is used as a modification initiator.
Specifically, for example, a butadiene monomer and a styrene monomer are polymerized in a hydrocarbon solvent in the presence of a modifying agent containing the compound represented by formula (2), whereby a modifying group derived from the compound represented by formula (2) can be imparted to the styrene-butadiene copolymer.

-Other rubber-
The rubber component may further contain other rubbers, and the content of the other rubbers in 100 parts by mass of the rubber component is preferably 35 parts by mass or less. Examples of such other rubbers include styrene-butadiene rubber, butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber (EPR, EPDM), fluororubber, silicone rubber, and urethane rubber, each of which has a glass transition temperature of −40° C. or higher. Among these, diene rubbers such as butadiene rubber (BR) and chloroprene rubber (CR) are preferred, and butadiene rubber (BR) is more preferred.
As the butadiene rubber (BR), high-cis polybutadiene is preferable, and the high-cis polybutadiene preferably has a cis-1,4 bond content of 90% by mass or more. When the rubber component contains butadiene rubber, the content of the butadiene rubber is preferably in the range of 1 to 35 parts by mass per 100 parts by mass of the rubber component.

(Resin Component)
The rubber composition for tires includes a resin component, which is at least partially hydrogenated and has an SP value difference between the resin component and the isoprene skeleton rubber of 1.40 (cal/cm ³ ) ^1/2 or less,
The formula:
The mass ratio of the resin component to the isoprene skeleton rubber is ≧0.5
Meet the following.

When the resin component is at least partially hydrogenated and the difference in SP value with the isoprene skeleton rubber is 1.40 (cal/cm ³ ) ^1/2 or less, compatibility with the isoprene skeleton rubber is increased, the mobility of the rubber component is controlled, and the hysteresis loss (tan δ) in the low temperature region can be improved, thereby improving the wet grip performance of a tire to which the rubber composition is applied. From the viewpoint of further improving compatibility, the difference in SP value between the resin component and the isoprene skeleton rubber is preferably 1.35 (cal/cm ³ ) ^1/2 or less, more preferably 0.50 (cal/cm ³ ) ^1/2 or less, more preferably 0.45 (cal/cm ³ ) ^1/2 or less, more preferably 0.3 (cal/cm ³ ) ^1/2 or less, and even more preferably 0.25 (cal/cm ³ ) ^1/2 or less. When the difference in SP value between the resin component and the isoprene skeleton rubber is 0.50 (cal/cm ³ ) ^1/2 or less, the compatibility between the resin component and the isoprene skeleton rubber is further improved, and the wet grip performance of a tire to which the rubber composition is applied is further improved.

In addition, when the mass ratio of the resin component to the isoprene skeleton rubber [mass ratio of resin component/isoprene skeleton rubber] is 0.5 or more, the wet grip performance of the tire to which the rubber composition is applied can be further improved. The mass ratio of the resin component to the isoprene skeleton rubber [mass ratio of resin component/isoprene skeleton rubber] is preferably 0.65 or more, more preferably 0.7 or more, and more preferably 0.8 or more, and is preferably 2.0 or less, more preferably 1.9 or less, and even more preferably 1.8 or less.

The content of the resin component is 1 part by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component. When the content of the resin component in the rubber composition is 1 part by mass or more per 100 parts by mass of the rubber component, the effect of the resin component is fully expressed, and when it is less than 50 parts by mass, the resin component is less likely to precipitate from the tire, and the effect of the resin component can be fully expressed. On the other hand, when the content of the resin component is 50 parts by mass or more per 100 parts by mass of the rubber component, the fuel efficiency performance and wear resistance performance of the tire to which the rubber composition is applied deteriorates. From the viewpoint of further enhancing the effect of the resin component, the content of the resin component in the rubber composition is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, more preferably 9 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 17 parts by mass or more per 100 parts by mass of the rubber component. In addition, from the viewpoint of suppressing precipitation of the resin component from the tire and suppressing deterioration of the tire appearance, the content of the resin component in the rubber composition is more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less, per 100 parts by mass of the rubber component.

The resin component preferably has a softening point higher than 110° C. and a weight average molecular weight in terms of polystyrene of 200 to 1600 g/mol. By applying a rubber composition containing such a resin component to a tire, the wear resistance of the tire can be further improved.
The softening point of the resin component is measured in accordance with JIS-K2207-1996 (ring and ball method).
The weight average molecular weight of the resin component is measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

When the softening point of the resin component is higher than 110°C, the tire to which the rubber composition is applied can be sufficiently reinforced, and the wear resistance can be further improved. From the viewpoint of the wear resistance of the tire, the softening point of the resin component is preferably 116°C or higher, more preferably 120°C or higher, more preferably 123°C or higher, and even more preferably 127°C or higher. From the viewpoint of processability, the softening point of the resin component is preferably 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, more preferably 141°C or lower, and even more preferably 136°C or lower.

When the weight average molecular weight of the resin component in terms of polystyrene is 200 g/mol or more, the resin component is less likely to precipitate from the tire and the effects of the resin component can be fully exhibited, and when it is 1600 g/mol or less, the resin component is easily compatible with the rubber component.
From the viewpoint of suppressing precipitation of the resin component from the tire and suppressing deterioration in the tire appearance, the polystyrene-equivalent weight average molecular weight of the resin component is preferably 500 g/mol or more, more preferably 550 g/mol or more, even more preferably 600 g/mol or more, still more preferably 650 g/mol or more, and even more preferably 700 g/mol or more. In addition, from the viewpoint of improving the compatibility of the resin component with the rubber component and further enhancing the effect of the resin component, the polystyrene-equivalent weight average molecular weight of the resin component is more preferably 1570 g/mol or less, more preferably 1530 g/mol or less, more preferably 1500 g/mol or less, more preferably 1470 g/mol or less, more preferably 1430 g/mol or less, more preferably 1400 g/mol or less, more preferably 1370 g/mol or less, more preferably 1330 g/mol or less, more preferably 1300 g/mol or less, more preferably 1200 g/mol or less, more preferably 1100 g/mol or less, more preferably 1000 g/mol or less, and even more preferably 950 g/mol or less.

The ratio (Ts _HR /Mw _HR ) of the softening point (Ts _HR ) (unit: ° C.) of the resin component to the polystyrene-equivalent weight average molecular weight (Mw _HR ) (unit: g/mol) of the resin component is preferably 0.07 or more, more preferably 0.083 or more, more preferably 0.095 or more, more preferably 0.104 or more, more preferably 0.125 or more, more preferably 0.135 or more, more preferably 0.14 or more, and even more preferably 0.141 or more. The ratio (Ts _HR /Mw _HR ) is preferably 0.25 or less, preferably 0.24 or less, preferably 0.23 or less, preferably 0.19 or less, more preferably 0.18 or less, and even more preferably 0.17 or less.
The softening point and polystyrene-equivalent weight average molecular weight of the resin component can be determined by the method described in the examples below.

The above-mentioned at least partially hydrogenated resin component means a resin obtained by reducing and hydrogenating a resin.
Examples of resins that can be used as raw materials for the hydrogenated resin component include _C5 resins, _C5 - _C9 resins, _C9 resins, terpene resins, dicyclopentadiene resins, and terpene-aromatic compound resins. These resins may be used alone or in combination of two or more.

The _C5 resin may be an aliphatic petroleum resin obtained by (co)polymerizing a _C5 fraction obtained by thermal cracking of naphtha in the petrochemical industry.
The _C5 fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene, etc. Note that, as the _C5 resin, commercially available products can be used.

The _C5 - _C9 resin refers to a _C5 - _C9 synthetic petroleum resin. Examples of the _C5 -C9 resin include solid polymers obtained by polymerizing a petroleum-derived _C5 - _C11 fraction using a Friedel-Crafts catalyst such as _AlCl3 or _BF3 . More specific examples of the C5- _C9 resin include copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, etc.
As the _C5 - _C9 resin, a resin having a small amount of _C9 or more components is preferred from the viewpoint of compatibility with the rubber component. Here, "having a small amount of _C9 or more components" means that the amount of _C9 or more components in the total amount of the resin is less than 50 mass%, preferably 40 mass% or less. Commercially available _C5 - _C9 resins can be used.

The _C9 resin refers to a _C9 synthetic petroleum resin, for example, a solid polymer obtained by polymerizing a _C9 fraction using a Friedel-Crafts type catalyst such as _AlCl3 or _BF3 .
Examples of _C9 resins include copolymers containing indene, α-methylstyrene, vinyltoluene, or the like as main components.

The terpene resin is a solid resin obtained by blending turpentine, which is obtained at the same time as rosin is obtained from pine trees, or a polymerization component separated from the turpentine, and polymerizing it using a Friedel-Crafts catalyst, and examples of the terpene resin include β-pinene resin and α-pinene resin. A representative example of a terpene-aromatic compound resin is terpene-phenol resin. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing with formalin. There are no particular restrictions on the terpenes used as raw materials, and monoterpene hydrocarbons such as α-pinene and limonene are preferred, and those containing α-pinene are more preferred, with α-pinene being particularly preferred. Styrene, etc. may also be included in the skeleton.

The dicyclopentadiene-based resin refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts type catalyst such as _AlCl3 or _BF3 .

Furthermore, the resin that is the raw material for the hydrogenated resin component may contain, for example, a resin obtained by copolymerizing a _C5 fraction with dicyclopentadiene (DCPD) ( _C5 -DCPD resin).
Here, when the dicyclopentadiene-derived component is 50% by mass or more in the total amount of the resin, the _C5 -DCPD-based resin is considered to be included in the dicyclopentadiene-based resin. When the dicyclopentadiene-derived component is less than 50% by mass in the total amount of the resin, the _C5 -DCPD-based resin is considered to be included in the _C5 -based resin. The same applies to the case where a small amount of a third component or the like is further contained.

From the viewpoints of increasing the compatibility between the rubber component and the resin component, further improving the wet grip performance of a tire to which the rubber composition is applied, and further reducing the rolling resistance, the resin component is preferably at least one selected from the group consisting of hydrogenated _C5 resins, hydrogenated _C5 - _C9 resins, hydrogenated dicyclopentadiene resins (hydrogenated DCPD resins), and hydrogenated terpene resins, more preferably at least one selected from the group consisting of hydrogenated _C5 resins and hydrogenated _C5 - _C9 resins, and even more preferably hydrogenated _C5 resins. Also, it is preferable that the resin has a hydrogenated DCPD structure or a hydrogenated cyclic structure in at least a monomer.

(filler)
The rubber composition for tires contains a filler. By containing the filler, the reinforcing property of the rubber composition is improved.
The content of the filler in the rubber composition is preferably in the range of 40 to 125 parts by mass per 100 parts by mass of the rubber component. When the content of the filler in the rubber composition is 40 parts by mass or more per 100 parts by mass of the rubber component, the reinforcement of the tire to which the rubber composition is applied is sufficient, and the wear resistance performance can be further improved, and when the content is 125 parts by mass or less, the elastic modulus of the rubber composition does not become too high, and the wet grip performance of the tire to which the rubber composition is applied is further improved. From the viewpoint of lowering the rolling resistance of the tire (from the viewpoint of improving fuel efficiency performance), the content of the filler in the rubber composition is more preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more per 100 parts by mass of the rubber component. In addition, from the viewpoint of improving the wet grip performance of the tire, the content of the filler in the rubber composition is more preferably 105 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 95 parts by mass or less per 100 parts by mass of the rubber component.

-silica-
The filler preferably contains silica, and more preferably contains silica having a nitrogen adsorption specific surface area (BET method) of 80 m ² /g or more and less than 330 m ² /g. When the nitrogen adsorption specific surface area (BET method) of silica is 80 m ² /g or more, the tire to which the rubber composition is applied can be sufficiently reinforced, and the rolling resistance of the tire can be further reduced. When the nitrogen adsorption specific surface area (BET method) of silica is less than 330 m ² /g, the elastic modulus of the rubber composition does not become too high, and the wet grip performance of the tire to which the rubber composition is applied is further improved. From the viewpoint of further reducing the rolling resistance and further improving the wear resistance of the tire, the nitrogen adsorption specific surface area (BET method) of silica is preferably 110 m ² /g or more, preferably 130 m ² /g or more, preferably 150 m ² /g or more, and more preferably 180 m ² /g or more. From the viewpoint of further improving the wet grip performance of the tire, the nitrogen adsorption specific surface area (BET method) of silica is preferably 300 m ² /g or less, more preferably 280 m ² /g or less, and even more preferably 270 m ² /g or less.

Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., and among these, wet silica is preferred. These silicas may be used alone or in combination of two or more types.

From the viewpoint of improving the mechanical strength of the tire and further improving the abrasion resistance, the content of silica in the rubber composition is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more, per 100 parts by mass of the rubber component. From the viewpoint of further improving the wet grip performance of the tire, the content of silica in the rubber composition is preferably 125 parts by mass or less, more preferably 105 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 95 parts by mass or less, per 100 parts by mass of the rubber component.

-Carbon black-
The filler preferably contains carbon black, which reinforces the rubber composition and improves the abrasion resistance of the rubber composition.
The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination of two or more.

From the viewpoint of improving the wear resistance of the rubber composition and a tire to which the rubber composition is applied, the content of carbon black in the rubber composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. Also, from the viewpoint of workability of the rubber composition, the content of carbon black in the rubber composition is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, per 100 parts by mass of the rubber component.
When the filler contains silica and carbon black, the proportion of silica in the total amount of silica and carbon black is preferably 80% by mass or more and less than 100% by mass, and more preferably 90% by mass or more and less than 100% by mass. When the proportion of silica is 80% by mass or more, the mechanical strength of a tire to which the rubber composition is applied is improved, and the rolling resistance can be further reduced.

-Other fillers-
The filler may include inorganic fillers such as clay, talc, calcium carbonate, and aluminum hydroxide, in addition to silica and carbon black.
The above-mentioned other fillers are preferably contained in such a range that the ratio of silica in the filler is 70% by mass or more. By the ratio of silica in the filler being 70% by mass or more, the mechanical strength of the tire to which the rubber composition is applied is improved, and the rolling resistance can be further reduced. The ratio of silica in the filler is more preferably 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more and less than 100% by mass.

(styrene-based thermoplastic elastomer)
The rubber composition for tires may contain a styrene-based thermoplastic elastomer (TPS). The styrene-based thermoplastic elastomer (TPS) has a styrene-based polymer block (hard segment) and a conjugated diene-based polymer block (soft segment), in which the styrene-based polymer portion forms a physical crosslink and serves as a crosslinking point, while the conjugated diene-based polymer block imparts rubber elasticity. The double bonds of the conjugated diene-based polymer block (soft segment) may be partially or completely hydrogenated.
In addition, the styrene-based thermoplastic elastomer (TPS) is thermoplastic, whereas the rubber component (preferably, diene-based rubber) is not thermoplastic. Therefore, in this specification, the styrene-based thermoplastic elastomer (TPS) is not included in the rubber component. The content of the styrene-based thermoplastic elastomer (TPS) is preferably in the range of 1 to 30 parts by mass per 100 parts by mass of the rubber component.

Examples of the styrene-based thermoplastic elastomer (TPS) include styrene/butadiene/styrene (SBS) block copolymer, styrene/isoprene/styrene (SIS) block copolymer, styrene/butadiene/isoprene/styrene (SBIS) block copolymer, styrene/butadiene (SB) block copolymer, styrene/isoprene (SI) block copolymer, styrene/butadiene/isoprene (SBI) block copolymer, styrene/ethylene/butylene/styrene (SEBS) block copolymer, styrene/ethylene/propylene/styrene (SEPS) block copolymer, styrene/ethylene/ethylene/propylene/styrene (SEEPS) block copolymer, styrene/ethylene/butylene (SEB) block copolymer, styrene/ethylene/propylene (SEP) block copolymer, and styrene/ethylene/ethylene/propylene (SEEP) block copolymer.

(others)
The rubber composition for tires may contain the above-mentioned rubber component, resin component, filler, and styrene-based thermoplastic elastomer, as well as various components commonly used in the rubber industry, such as silane coupling agents, antioxidants, waxes, softeners, processing aids, stearic acid, zinc oxide (zinc oxide), vulcanization accelerators, vulcanizing agents, etc., which are appropriately selected within the range not impairing the object of the present invention. Commercially available products can be suitably used as these compounding agents.

When the rubber composition for tires contains silica, it is preferable to contain a silane coupling agent in order to improve the effect of the silica. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, Examples of the silane coupling agent include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide. The content of the silane coupling agent is preferably in the range of 2 to 20 parts by mass, more preferably in the range of 5 to 15 parts by mass, relative to 100 parts by mass of the silica.

Examples of the anti-aging agent include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6C), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), N,N'-diphenyl-p-phenylenediamine (DPPD), etc. The content of the anti-aging agent is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

Examples of the wax include paraffin wax and microcrystalline wax. There are no particular limitations on the amount of the wax, but it is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

The amount of zinc oxide (zinc white) is not particularly limited, but is preferably in the range of 0.1 to 10 parts by mass, and more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component.

Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. There are no particular restrictions on the content of the vulcanization accelerator, and it is preferably in the range of 0.1 to 5 parts by mass, and more preferably in the range of 0.2 to 4 parts by mass, per 100 parts by mass of the rubber component.

The vulcanizing agent may be sulfur. The content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by mass, more preferably 1 to 4 parts by mass, in terms of sulfur content per 100 parts by mass of the rubber component.

(Method for producing rubber composition)
The method for producing the rubber composition is not particularly limited, but for example, the rubber composition can be produced by blending various components appropriately selected as necessary with the above-mentioned rubber component, resin component, and filler, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

There are no particular limitations on the conditions for the kneading, and the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, and other conditions can be appropriately selected according to the purpose. Examples of kneading devices include Banbury mixers, intermixes, kneaders, rolls, and the like that are typically used for kneading rubber compositions.

There are no particular limitations on the conditions for the heat-in process, and the heat-in process temperature, heat-in process time, heat-in process equipment, and other conditions can be appropriately selected according to the purpose. Examples of the heat-in process equipment include a heat-in process roll machine that is typically used for heat-in process of rubber compositions.

There are no particular limitations on the extrusion conditions, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of extrusion devices include extruders that are typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

There are no particular limitations on the vulcanization device, method, conditions, etc., and they can be selected appropriately depending on the purpose. Examples of devices for vulcanization include molding vulcanizers using a mold used to vulcanize rubber compositions. As for vulcanization conditions, the temperature is, for example, about 100 to 190°C.

<Tread rubber>
The tread rubber is characterized in that it is made of the above-mentioned rubber composition for tires. Since the tread rubber is made of the above-mentioned rubber composition for tires, by applying the tread rubber to a tire, it is possible to achieve a high level of balance between the wet grip performance, fuel efficiency, and wear resistance of the tire.
The tread rubber may be applied to new tires or retread tires.

<Tires>
The tire of the present invention is characterized by including the above-mentioned tread rubber. Since the tire of the present invention includes the above-mentioned tread rubber, the tire has a high level of balance between wet grip performance, fuel efficiency, and wear resistance.

Depending on the type of tire to which it is applied, the tire of the present invention may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like, and then further vulcanizing it. The tire of the present invention is preferably a pneumatic tire, and the gas to be filled in the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

(Internal structure of the tire)
Fig. 1 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to an embodiment of the present invention. Fig. 1 shows only one half in the tire width direction bounded by the tire equatorial plane CL, but the other half has a similar configuration. Fig. 1 is also a partial cross-sectional view in the tire width direction in the reference state.

As shown in FIG. 1, this pneumatic tire (hereinafter also simply referred to as a tire) 1 has a pair of bead portions 2, a pair of sidewall portions 6 connected to the bead portions 2, and a tread portion 5 connected to the pair of sidewall portions 6.

In this example, the bead portion 2 has a bead core 2a and a bead filler 2b. In this example, the bead core 2a has a plurality of bead wires covered with rubber. In this example, the bead wires are formed of steel cords. The bead filler 2b is made of rubber or the like and is located on the tire radial outside of the bead core 2a. In this example, the bead filler 2b has a cross-sectional shape that is approximately triangular and the thickness decreases toward the tire radial outside. On the other hand, the bead core 2a and the bead filler 2b are not limited to the above example and can have various configurations, and can also be configured without the bead core 2a or the bead filler 2b.

As shown in FIG. 1, the tire 1 has a carcass 3 consisting of one or more carcass plies that span a pair of bead portions 2 in a toroidal shape. The carcass 3 has a carcass main body portion 3a arranged between the bead cores 2a, and a carcass folded-back portion 3b that is folded back around the bead cores 2a from the inner side in the tire width direction to the outer side in the tire width direction. In this example, the end of the carcass folded-back portion 3b is located radially inward of the maximum tire width position, but the extension length of the carcass folded-back portion 3b from the inner side in the tire width direction to the outer side in the tire width direction can be set appropriately. The carcass 3 can be structured without the carcass folded-back portion 3b, or can be structured with the carcass folded-back portion 3b wrapped around the bead cores 2a. The carcass ply can be formed by rubber-coating organic fibers.

The belt 4 and tread rubber constituting the tread portion 5 are provided on the tire radial outer side of the crown portion of the carcass 3. The belt 4 can be composed of, for example, multiple belt layers stacked in the tire radial direction. In this example, the belt 4 is an inclined belt consisting of two belt layers in which the belt cords cross each other between the layers. The belt cords can also be, for example, steel cords. Note that the number of belt layers, the inclination angle of the belt cords, the width of each belt layer in the tire width direction, etc. are not particularly limited and can be set appropriately.

The tire 1 has an inner liner (not shown) on the inner surface 8 of the tire.

As shown in FIG. 1, in the above-mentioned reference state, the tire radial region between positions spaced 15% of the tire cross-sectional height SH on the tire radial inner side and outer side from the tire maximum width position P is defined as R. In this case, in the first embodiment, the mass of the sidewall portion in the tire radial region R is 1.5% to 5% of the total mass of the pneumatic tire 1. In this example, in the tire radial region R (only in the tire radial region R), a rubber member (in this example, a rubber sheet) 7 is attached to the surface of the sidewall portion to ensure that the above-mentioned mass range is achieved. In the second embodiment, the thickness of the sidewall portion in the tire radial region R is 1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion. In this example, in the tire radial region R (only in the tire radial region R), a rubber member (in this example, a rubber sheet) 7 is attached to the surface of the sidewall portion to ensure that the above-mentioned thickness range is achieved. In the second embodiment, the aspect ratio of the tire is further 10 to 65.

In this embodiment, the tire has a tread rubber made of a rubber composition for tires including a rubber component, a resin component, and a filler, the rubber component includes an isoprene skeleton rubber and a styrene-butadiene rubber, the styrene-butadiene rubber has a glass transition temperature of less than −40° C., the content of the resin component is 1 part by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, the resin component is at least partially hydrogenated, and the difference in SP value with respect to the isoprene skeleton rubber is 1.40 (cal/cm ³ ) ^1/2 or less, and the following formula:
Mass ratio of resin component/isoprene skeleton rubber ≧0.5
It meets the following criteria.
Furthermore, the thickness of the tread rubber is 9.5 mm or less, and the groove depth of the circumferential main groove is 7.5 mm or less.
Such a tire can reduce rolling resistance. However, the inventors of the present invention have found through their investigations that there is a concern that noise reduction may be impaired if the thickness of the tread rubber or the depth of the circumferential main groove is as described above.
The tire maximum width position and its vicinity form antinodes (portions where the amount of displacement of the amplitude is large) at 800 Hz to 1000 Hz. By locally increasing the mass or locally increasing the thickness in tire radial direction regions R between positions spaced apart by 15% of the tire cross-sectional height SH (0.15×SH above and below in the drawing) on the inner and outer sides in the tire radial direction from the tire maximum width position P, it is possible to reduce the amplitude at 800 Hz to 1000 Hz and improve the quietness of the tire, and by making the increase in mass localized, it is possible to minimize the increase in tire weight.
In the first embodiment, the mass of the sidewall portion in the tire radial region R is 1.5% to 5% of the total mass of the pneumatic tire 1. If the position where the weight is increased is on the outer or inner side in the tire radial direction from the tire radial region R, the effect of reducing the amplitude of 800 Hz to 1000 Hz and improving the quietness of the tire cannot be sufficiently obtained. In addition, if the mass of the sidewall portion in the tire radial region R is less than 1.5% of the total mass of the pneumatic tire, the effect of suppressing the vibration described above cannot be sufficiently exhibited, and the quietness of the tire cannot be sufficiently improved. On the other hand, if the mass of the sidewall portion in the tire radial region R exceeds 5% of the total mass of the pneumatic tire, the weight in the vicinity of the tire maximum width position P becomes too large locally, causing a large weight bias, and there is a risk of the tire flowing or shifting when vulcanizing. For the same reason, it is more preferable that the mass of the sidewall portion in the tire radial region R is 1.8% to 4.5% of the total mass of the pneumatic tire.
In the second embodiment, the aspect ratio of the tire is 10 to 65, and the thickness of the sidewall portion in the tire radial direction region R is 1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion. If the position where the thickness is increased is on the outer or inner side in the tire radial direction of the tire than the tire radial direction region R, the effect of reducing the amplitude of the vibration mode cannot be sufficiently obtained, and the effect of improving the quietness of the tire cannot be sufficiently obtained. If the thickness of the sidewall portion in the tire radial direction region R is thicker than the thickness of the thinnest part of the sidewall portion by less than 1.0 mm, the effect of suppressing the vibration described above cannot be sufficiently improved, and the quietness of the tire cannot be improved. On the other hand, if it is thicker than 4 mm, the thickness in the vicinity of the tire maximum width position P becomes too large locally, causing a large weight bias, and there is a risk of the tire flowing or shifting when vulcanizing. In addition, in a tire having an aspect ratio in the above range, it is possible to make the sidewall relatively thin, and therefore the tire is particularly suitable for achieving both a reduction in rolling resistance due to the thinning of the sidewall and a reduction in vibration and therefore noise due to a local increase in weight in the tire radial region R. That is, if the aspect ratio of the tire is less than 10, the tire is likely to pick up road vibrations, and the sidewall portion where a weight portion can be provided locally becomes small, making it difficult to obtain a sufficient effect of the invention. On the other hand, if the aspect ratio of the tire is more than 65, the weight of the tire itself becomes large, making it impossible to reduce the rolling resistance.
As described above, according to the tires of the first and second embodiments, deterioration in quietness can also be suppressed.

In the first embodiment, for the same reasons as above, it is more preferable that the mass of the sidewall portion in the tire radial region R is 1.8% to 4.5% of the total mass of the pneumatic tire.

In the first embodiment, it is more preferable that the mass of the sidewall portion in the tire radial region R (10%) between positions spaced 10% of the tire cross-sectional height radially inward and outward from the tire maximum width position P in the reference state is 1.5% to 5% of the total mass of the pneumatic tire. This is because it is possible to more effectively reduce vibrations and further improve the quietness of the tire.
In this case, too, for the same reason, it is more preferable that the mass of the sidewall portion in the tire radial direction region R (10%) is 1.8% to 4.5% of the entire mass of the pneumatic tire.

FIG. 2 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to a first modified example. FIG. 3 is a partial cross-sectional view in the tire width direction of a pneumatic tire according to a second modified example. In the first and second embodiments, when locally increasing the mass in the tire radial region R (or R (10%)), as shown in FIG. 2, the rubber member (rubber sheet) 7 can be disposed in the sidewall portion 6, or as shown in FIG. 3, the rubber member (rubber sheet) 7 can be attached to the tire inner surface 8 (in the case of having an inner liner, it may be on the inside or outside of the inner liner). However, since attaching the rubber member (rubber sheet) 7 to the tire inner surface 8 increases the energy loss of the inner liner, it is more preferable to attach the rubber member (rubber sheet) 7 to the outer surface of the tire or to arrange it in the sidewall portion (inside the sidewall rubber).
1 to 3 show an example in which the rubber member is a rubber sheet, but the rubber member is not limited to a sheet-like rubber member, and may be of various other shapes, such as a protruding shape having a semicircular or rectangular cross section.

Here, in the first embodiment, it is preferable that the thickness of the sidewall portion in the tire radial region R (or R(10%)) is 1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion. By making it 1.0 mm or thicker, the effect of suppressing the vibrations described above can be further enhanced, and the quietness of the tire can be further improved, while by making it 4 mm or less, the thickness in the vicinity of the maximum tire width position P becomes locally too large, which increases the weight bias, and it is possible to suppress the tire from flowing or shifting when vulcanizing.
Here, the "thickness of the sidewall portion" means the thickness measured in a direction perpendicular to the carcass line in a cross section in the tire width direction.
Furthermore, the thickness of the sidewall portion in the tire radial region R (or R(10%)) being "1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion" means that the average thickness of the sidewall portion in the tire radial region is "1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion." Note that, if a protrusion is formed in the tire radial region, the thickness includes the height of the protrusion.

For the same reason, it is even more preferable that the thickness of the sidewall portion in the tire radial region R (or R(10%)) is 1.5 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion.

In the first embodiment, it is preferable to change the weight by changing the specific gravity of the material in the tire radial region R (or R (10%)). This is because creating a localized weight-added area by specific gravity alone can reduce unevenness and thereby reduce structural stress concentration areas, thereby improving tire durability.
Also, the thickness of the sidewall portion at the tire maximum width position P can be 120% to 200% of the thickness of the thinnest part of the sidewall portion. By making it 120% or more, the effect of suppressing the vibration described above can be further enhanced, and the quietness of the tire can be further improved, while by making it 200% or less, the weight at the tire maximum width position P can be locally too large, resulting in a large weight bias, and it can be prevented from flowing or shifting when the tire is vulcanized.

In the first embodiment, the thickness of the sidewall portion in the tire radial region R (or R(10%)) is preferably 5 mm to 15 mm. By making it 5 mm or more, the effect of suppressing vibration and improving noise reduction can be further enhanced, while by making it 15 mm or less, weight increase can be minimized.

In the first and second embodiments, the specific gravity of the rubber member (e.g., rubber sheet) 7 is preferably 1.05 times or more, more preferably 1.1 times or more, that of the sidewall rubber. This is because it is suitable for locally increasing the weight. On the other hand, in order to prevent the weight bias from becoming too large, the specific gravity of the rubber member (e.g., rubber sheet) 7 is preferably 1.3 times or less that of the sidewall rubber. The specific gravity can be adjusted, for example, by adjusting the amount of filler. The filler is not particularly limited, but examples that can be used include silica, aluminum hydroxide, calcium carbonate, basic magnesium carbonate, clay, diatomaceous earth, reclaimed rubber and powdered rubber, and carbon black.

In the first and second embodiments, in the above example, a rubber member is arranged to locally increase the weight of the radial region R, but various other methods are possible. For example, it is also preferable to have a weighting member made of metal or fiber (metal fiber or nonmetal fiber) in the tire radial region R. The metal and fiber may be made of steel (linear metal with iron as the main component (the mass of iron with respect to the total mass of the metal filaments exceeds 50 mass%)) or iron alone, or may contain metals other than iron, such as zinc, copper, aluminum, and tin. Examples include steel, copper, and alloys containing them. A plating process may be performed to strengthen adhesion to the rubber.
According to the above embodiment in which the rubber member is disposed in the tire radial direction region R, there is an advantage in that durability against repeated deformation is high.

In the first and second embodiments, the gauge of the tread rubber is preferably 2 to 30 mm, and more preferably 2 to 15 mm. By making it 2 mm or more, noise reduction can be further improved, while by making it 30 mm or less, rolling resistance can be reduced by weight reduction.
The "gauge of tread rubber" refers to the thickness in the tire radial direction from the tread surface to the tire radially outermost reinforcing member (for example, the tire radially outermost belt layer, in the case where a belt reinforcing layer is arranged on the tire radially outer side of the belt) at the tire equatorial plane in the above-mentioned reference state. However, in the case where a groove is arranged at the tire equatorial plane, it is assumed that there is no groove.

In the first embodiment, the tire aspect ratio is preferably 20 to 80, more preferably 20 to 65, and even more preferably 35 to 55. In a tire having an aspect ratio in the above range, it is possible to make the sidewall relatively thin, and therefore it is particularly suitable for achieving both a reduction in rolling resistance due to the thinning of the sidewall and a reduction in vibration and noise due to a local increase in weight in the tire radial region R. That is, by having a tire aspect ratio of 20 (preferably 35) or more, it is possible to reduce radiated sound, while by having a tire aspect ratio of 80 (preferably 65, more preferably 55) or less, it is easy to reduce the weight and the rolling resistance can be reduced. It is preferable that the tire does not have side reinforcing rubber.

In the second embodiment, for the same reasons as above, it is further preferable that the thickness of the sidewall portion in the tire radial region R is 1.5 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion.
The width in the tire radial direction of the part where the thickness of the sidewall portion in the tire radial region R is 1.0 to 4 mm (preferably 1.5 to 4 mm) thicker than the thinnest part of the sidewall portion is preferably 7% or more, and more preferably 10% or more, of the tire cross-sectional height, because the above-mentioned effects can be sufficiently obtained.
In addition, it is most preferable that the weight portion (convex portion) is provided in a circular shape at the maximum width position of the sidewall portion in the tire radial region R, but it may be interrupted on the circumference, and it is preferable that the weight portion is arranged in a total of 50% or more of one circumference.

In the second embodiment, it is also preferable that the thickness of the sidewall portion at the tire's maximum width position P is 110% to 200% of the thickness of the thinnest part of the sidewall portion. By making it 110% or more, the effect of suppressing the vibrations described above can be further enhanced, and the tire's quietness can be further improved, while by making it 200% or less, the weight at the tire's maximum width position P can be locally too large, resulting in a large weight bias, and it is possible to suppress the tire from flowing or shifting when vulcanized.

In the second embodiment, in the above-mentioned reference state, it is preferable that the thickness of the sidewall portion in the tire radial region R (10%) between positions spaced 10% of the tire cross-sectional height radially inward and outward from the tire maximum width position P is 1.0 to 4 mm thicker than the thickness of the thinnest part of the sidewall portion. This is because it is possible to more effectively reduce vibrations and further improve the quietness of the tire. For the same reason, it is even more preferable that the thickness of the sidewall portion in the tire radial region R (10%) is 1.0 to 3 mm thicker than the thickness of the thinnest part of the sidewall portion.

In the second embodiment, the mass of the sidewall portion in the tire radial region R (or R(10%)) is preferably 0.5% to 5% of the total mass of the pneumatic tire 1, and more preferably 1.5% to 5%. By making it 0.5% or more (more preferably 1.5% or more), the effect of suppressing the vibration described above can be further enhanced, and the quietness of the tire can be further improved, while by making it 5% or less, the weight in the vicinity of the maximum tire width position P becomes too large locally, which causes a large weight bias, and it is possible to suppress the tire from flowing or shifting when vulcanizing the tire.
For the same reason, the mass of the sidewall portion in the tire radial region R (10%) is more preferably 1.5% to 4.5% of the entire mass of the pneumatic tire, and further preferably 1.8% or more.

In the second embodiment, the thickness of the sidewall portion in the tire radial region R (or R(10%)) is preferably 5 mm to 15 mm. By making it 5 mm or more, the effect of suppressing vibration and improving noise reduction can be further enhanced, while by making it 15 mm or less, weight increase can be minimized.

(Example of RFID placement)
FIG. 7 is a diagram showing an example of an arrangement of RFIDs.

The tire may include an RF tag as the communication device 100. The RF tag includes an IC chip and an antenna. The RF tag may be, for example, sandwiched between a plurality of the same or different members that constitute the tire. In this way, the RF tag can be easily attached during tire production, and the productivity of tires equipped with RF tags can be improved. In this example, the RF tag may be, for example, sandwiched between a bead filler and another member adjacent to the bead filler.
The RF tag may be embedded in any of the components constituting the tire. In this way, the load applied to the RF tag can be reduced compared to when the RF tag is sandwiched between multiple components constituting the tire. This can improve the durability of the RF tag. In this example, the RF tag may be embedded in a rubber component such as tread rubber or side rubber.
It is preferable that the RF tag is not disposed at a position that is a boundary between members having different rigidity in the periphery length direction, which is a direction along the tire outer surface in a cross-sectional view in the tire width direction. In this way, the RF tag is not disposed at a position where distortion is likely to concentrate due to a rigidity step. Therefore, the load applied to the RF tag can be reduced. This makes it possible to improve the durability of the RF tag. In this example, it is preferable that the RF tag is not disposed at a position that is a boundary between an end of the carcass and a member adjacent to the end of the carcass (e.g., a side rubber, etc.) in a cross-sectional view in the tire width direction.
The number of RF tags is not particularly limited. A tire may include only one RF tag, or may include two or more RF tags. Here, an RF tag is described as an example of a communication device, but a communication device other than an RF tag may be used.

The RF tag may be located, for example, in the tread of the tire, so that the RF tag will not be damaged by side cuts on the tire.
The RF tag may be disposed, for example, in the tread center in the tire width direction. The tread center is a position in the tread where deflection is unlikely to concentrate. In this way, the load applied to the RF tag can be reduced. This can improve the durability of the RF tag. In addition, it is possible to suppress the occurrence of differences in communication with the RF tag from both outer sides of the tire in the tire width direction. In this example, the RF tag may be disposed, for example, in the tire width direction within a range of 1/2 the tread width centered on the tire equatorial plane.
The RF tag may be disposed, for example, at a tread end in the tire width direction. If the position of a reader that communicates with the RF tag is predetermined, the RF tag may be disposed, for example, at a tread end on one side closer to the reader. In this example, the RF tag may be disposed, for example, within a range of 1/4 of the tread width in the tire width direction, with the tread end as the outer end.

The RF tag may be disposed, for example, on the tire cavity side of a carcass including one or more carcass plies that spans between bead portions. In this way, the RF tag is less likely to be damaged by impacts applied from the outside of the tire, or damage such as side cuts and nail penetration. As an example, the RF tag may be disposed in close contact with the surface of the carcass on the tire cavity side. As another example, when there is another member on the tire cavity side of the carcass, the RF tag may be disposed, for example, between the carcass and another member located on the tire cavity side of the carcass. An example of another member located on the tire cavity side of the carcass is an inner liner that forms the tire inner surface. As another example, the RF tag may be attached to the tire inner surface facing the tire cavity. By configuring the RF tag to be attached to the tire inner surface, it is easy to attach the RF tag to the tire and to inspect and replace the RF tag. In other words, it is possible to improve the attachability and maintainability of the RF tag. In addition, by attaching the RF tag to the tire inner surface, it is possible to prevent the RF tag from becoming the core of tire failure compared to a configuration in which the RF tag is embedded in the tire.
Furthermore, when the carcass includes a plurality of carcass plies and there is a position where the plurality of carcass plies are overlapped, the RF tag may be disposed between the overlapped carcass plies.

The RF tag may be arranged, for example, in the tread portion of the tire, on the outer side in the tire radial direction of the belt including one or more belt plies. As an example, the RF tag may be arranged on the outer side in the tire radial direction of the belt and in close contact with the belt. As another example, in the case where a reinforcing belt layer is provided, the RF tag may be arranged on the outer side in the tire radial direction of the reinforcing belt layer and in close contact with the reinforcing belt layer. As another example, the RF tag may be embedded in the tread rubber on the outer side in the tire radial direction of the belt. By arranging the RF tag on the outer side in the tire radial direction of the belt in the tread portion of the tire, communication with the RF tag from the outer side of the tire in the tire radial direction is less likely to be hindered by the belt. Therefore, it is possible to improve the communication with the RF tag from the outer side of the tire in the tire radial direction.
Also, the RF tag may be arranged, for example, in the tread portion of the tire, radially inward of the belt. In this way, the outer side of the RF tag in the tire radial direction is covered by the belt, so that the RF tag is less likely to be damaged by impact from the tread surface, nail penetration, etc. As an example of this, the RF tag may be arranged in the tread portion of the tire, between the belt and the carcass located radially inward of the belt.
In addition, when the belt has a plurality of belt plies, the RF tag may be disposed between any two belt plies in the tire tread portion, so that the RF tag is less susceptible to damage from impacts from the tread surface, nail penetration, etc., since the outer side of the RF tag in the tire radial direction is covered by one or more belt plies.

The RF tag may be disposed, for example, at a position of a sidewall portion or a bead portion of the tire. The RF tag may be disposed, for example, at one sidewall portion or one bead portion close to a reader capable of communicating with the RF tag. In this manner, it is possible to improve communication between the RF tag and the reader. As an example, the RF tag may be disposed between the carcass and the side rubber, or between the tread rubber and the side rubber.
The RF tag may be disposed, for example, between the tire maximum width position and the tread surface position in the tire radial direction. In this manner, it is possible to improve communication with the RF tag from the outside of the tire in the tire radial direction, compared to a configuration in which the RF tag is disposed on the inside in the tire radial direction from the tire maximum width position.
The RF tag may be positioned, for example, radially inward of the position where the tire is at its widest point. In this way, the RF tag is positioned near the bead portion, which has high rigidity. This reduces the load applied to the RF tag. This improves the durability of the RF tag. As an example, the RF tag may be positioned adjacent to the bead core in the tire radial direction or tire width direction. Distortion is less likely to concentrate near the bead core. This reduces the load applied to the RF tag. This improves the durability of the RF tag.
In particular, it is preferable to place the RF tag radially inward from the position where the tire is at its widest point and radially outward from the bead core of the bead portion. This can improve the durability of the RF tag, and also improve the communication performance of the RF tag by making communication between the RF tag and a reader less likely to be hindered by the bead core.
In addition, when the side rubber is composed of multiple rubber members of the same or different types adjacent to each other in the tire radial direction, the RF tag may be positioned by being sandwiched between the multiple rubber members that make up the side rubber.

The RF tag may be disposed between the bead filler and a member adjacent to the bead filler. In this way, the RF tag can be disposed in a position where distortion is less likely to be concentrated due to the placement of the bead filler. This reduces the load applied to the RF tag. This improves the durability of the RF tag.
The RF tag may be arranged, for example, sandwiched between the bead filler and the carcass. The portion of the carcass that sandwiches the RF tag together with the bead filler may be located on the outer side of the bead filler in the tire width direction, or on the inner side of the tire width direction. When the portion of the carcass that sandwiches the RF tag together with the bead filler is located on the outer side of the bead filler in the tire width direction, the load applied to the RF tag due to impact or damage from the outside of the tire in the tire width direction can be further reduced. This can further improve the durability of the RF tag.
The bead filler may have a portion disposed adjacent to the side rubber. In this case, the RF tag may be disposed in a sandwiched state between the bead filler and the side rubber.
Furthermore, the bead filler may have a portion disposed adjacent to the rubber chafer. In this case, the RF tag may be disposed sandwiched between the bead filler and the rubber chafer.

The RF tag may be arranged, for example, sandwiched between a rubber chafer and a side rubber. In this way, the RF tag can be arranged in a position where distortion is less likely to be concentrated due to the placement of the rubber chafer. Therefore, the load applied to the RF tag can be reduced. This can improve the durability of the RF tag.
The RF tag may be arranged, for example, sandwiched between the rubber chafer and the carcass. In this way, the load applied to the RF tag due to impact or damage from the rim can be reduced, and the durability of the RF tag can be improved.

The RF tag may be sandwiched between the wire chafer and another adjacent member on the inside or outside of the wire chafer in the tire width direction. This makes it difficult for the position of the RF tag to fluctuate when the tire deforms. This reduces the load applied to the RF tag when the tire deforms. This improves the durability of the RF tag. The other adjacent member to the wire chafer on the inside or outside of the tire width direction may be, for example, a rubber member such as a rubber chafer. The other adjacent member to the wire chafer on the inside or outside of the tire width direction may be, for example, a carcass.

A belt reinforcing layer may be further provided on the radially outer side of the belt. For example, the belt reinforcing layer may be formed by winding a cord made of polyethylene terephthalate continuously in a spiral shape in the tire circumferential direction. Here, the cord may be adhesive-treated under a tension of 6.9×10 ⁻² N/tex or more, and may have an elastic modulus of 2.5 mN/dtex·% or more at a load of 29.4 N measured at 160° C. Furthermore, the belt reinforcing layer may be arranged so as to cover the entire belt or only both ends of the belt. Furthermore, the winding density per unit width of the belt reinforcing layer may differ depending on the position in the width direction. In this way, road noise and flat spots can be reduced without reducing high-speed durability.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

<Analysis method of rubber components>
The glass transition temperature (Tg) and bound styrene content of the styrene-butadiene rubber were measured by the following method. The SP values (solubility parameters) of natural rubber (isoprene skeleton rubber) and styrene-butadiene rubber were calculated according to the Fedors method.

(1) Glass transition temperature (Tg)
The synthesized styrene-butadiene rubber was used as a sample, and a DSC curve was recorded using a TA Instruments DSC250 while heating from −100° C. at 20° C./min under a helium flow of 50 mL/min. The peak top (inflection point) of the DSC differential curve was determined as the glass transition temperature.

(2) Bound styrene content The synthesized styrene-butadiene rubber was used as a sample, and 100 mg of the sample was diluted with chloroform to 100 mL and dissolved to prepare a measurement sample. The bound styrene content (mass%) relative to 100 mass% of the sample was measured based on the amount of absorption of ultraviolet light by the phenyl group of styrene at a wavelength (near 254 nm). The measurement device used was a spectrophotometer "UV-2450" manufactured by Shimadzu Corporation.

<Method of analyzing resin components>
The softening point and weight average molecular weight of the resin component were measured by the following methods. The SP value (solubility parameter) of the resin component was calculated according to the Fedors method.

(3) Softening Point The softening point of the resin component was measured in accordance with JIS-K2207-1996 (ring and ball method).

(4) Weight Average Molecular Weight The average molecular weight of the hydrogenated resin was measured by gel permeation chromatography (GPC) under the following conditions, and the weight average molecular weight in terms of polystyrene was calculated.
Column temperature: 40°C
Injection volume: 50 μL
Carrier and flow rate: Tetrahydrofuran 0.6 mL/min
Sample preparation: Approximately 2.5 mg of resin component was dissolved in 10 mL of tetrahydrofuran.

<Preparation of Rubber Composition>
According to the compounding recipes shown in Tables 1 and 2, the components were compounded and kneaded to prepare rubber compositions of the examples and comparative examples.

<Preparation and evaluation of vulcanized rubber>
The rubber compositions of the examples and comparative examples were vulcanized to obtain vulcanized rubber test pieces. The vulcanized rubber test pieces were evaluated for wet grip performance, fuel economy, and abrasion resistance by the following methods.

(5) Wet Grip Performance The coefficient of friction of the test specimen against a wet asphalt road surface was measured using a portable friction tester. The evaluation results are shown as an index in Table 1, with the coefficient of friction of Comparative Example 1 taken as 100, and in Table 2, with the coefficient of friction of Comparative Example 5 taken as 100. The larger the index value, the larger the coefficient of friction and the more excellent the wet grip performance.

(6) Fuel Economy Performance The loss tangent (tan δ) of the test specimen was measured using a viscoelasticity measuring device (manufactured by Rheometrics Corporation) under conditions of a temperature of 50° C., a strain of 1%, and a frequency of 52 Hz. The evaluation results are shown as an index in Table 1, with the reciprocal of tan δ of Comparative Example 1 set to 100, and in Table 2, with the reciprocal of tan δ of Comparative Example 5 set to 100. A larger index value indicates a smaller tan δ and better fuel economy performance.

(7) Abrasion resistance In accordance with JIS K 6264-2:2005, sandpaper was attached to the grinding wheel and the amount of abrasion was measured at room temperature with a slip rate of 15% using a Lambourn abrasion tester manufactured by Ueshima Seisakusho. The evaluation results are indexed in Table 1 with the reciprocal of the amount of abrasion in Comparative Example 1 set as 100, and in Table 2 with the reciprocal of the amount of abrasion in Comparative Example 5 set as 100. A larger index value indicates a smaller amount of abrasion and better abrasion resistance.

*1 Natural rubber: TSR#20, SP value = 8.20 (cal/cm ³ ) ^1/2
*2 Low Tg modified SBR: Hydrocarbyloxysilane compound modified styrene-butadiene rubber synthesized by the following method, Tg = -65°C, SP value = 8.65 (cal/cm ³ ) ^1/2
*3 High Tg modified SBR: Hydrocarbyloxysilane compound modified styrene-butadiene rubber synthesized by the following method, Tg = -25°C, SP value = 9.00 (cal/cm ³ ) ^1/2
*4 Silica: Tosoh Silica Corporation, product name "Nipsil AQ"
*5 Resin component: Hydrogenated C5 resin, manufactured by Eastman Co., trade name "Impera E1780", softening point = 130°C, weight average molecular weight (Mw) = 909 g/mol, SP value = 8.35 (cal/cm ³ ) ^1/2
*6 Silane coupling agent: Evonik Degussa, product name "Si75"
*7 Anti-aging agent: Product name "Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
*8 Wax: Product name "Ozoace 0701" manufactured by Nippon Seiro Co., Ltd.
*9 Vulcanization accelerator A: Product name "Noccela DM-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
*10 Vulcanization accelerator B: Sanshin Chemical Industry Co., Ltd., product name "Suncerer NS-G"
*11 Medium Tg modified SBR1: SBR obtained using butyl lithium as an initiator, having a Tg of -38°C, and a styrene-butadiene rubber modified at the end with N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine, Tg = -38°C, SP value = 8.95 (cal/cm ³ ) ^1/2
*12 Medium Tg modified SBR2: Hexamethyleneimine modified styrene-butadiene rubber produced using a blend of styrene and butadiene monomers with different ratios based on the method for producing Polymer K in JP 2007-70642 A, with a bound styrene content of 35% by mass and a vinyl bound content of 21% in the butadiene portion, Tg = -38°C, SP value = 8.95 (cal/cm ³ ) ^1/2
*13 Carbon black: Asahi Carbon Co., Ltd., product name "#80"

<Method for synthesizing low Tg modified SBR (*2)>
A cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to a dried, nitrogen-purged 800 mL pressure-resistant glass vessel so that the amounts of 1,3-butadiene and styrene were 67.5 g and 7.5 g, respectively, and 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium were added, followed by polymerization at 50° C. for 1.5 hours. To the polymerization reaction system in which the polymerization conversion rate reached nearly 100%, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and a modification reaction was carried out at 50° C. for 30 minutes. Thereafter, 2 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to terminate the reaction, and the mixture was dried in a conventional manner to obtain a modified SBR.
Measurement of the microstructure of the resulting modified SBR revealed that the bound styrene content was 10% by mass, and the glass transition temperature (Tg) was -65°C.

<Method of synthesizing high Tg modified SBR (*3)>
(i) Preparation of modified initiator Two vacuum-dried 4 L stainless steel pressure vessels are prepared. 944 g of cyclohexane, 161 g of a compound represented by the following structural formula (2-1), and 86 g of tetramethylethylenediamine are charged into the first pressure vessel to prepare a first reaction solution. At the same time, 318 g of liquid 20% by mass n-butyllithium and 874 g of cyclohexane are charged into the second pressure vessel to prepare a second reaction solution. At this time, the molar ratio of the compound represented by the following structural formula (2-1), n-butyllithium, and tetramethylethylenediamine is 1:1:1. With the pressure of each pressure vessel maintained at 7 bar, the first reaction solution is injected into the first continuous channel at a rate of 1.0 g/min, and the second reaction solution is injected into the second continuous channel at a rate of 1.0 g/min using a mass flow meter. At this time, the temperature of the continuous reactor is maintained at -10°C, the internal pressure is maintained at 3 bar using a back pressure regulator, and the residence time in the reactor is adjusted to within 10 minutes. The reaction is terminated to obtain a modified initiator.

(ii) Polymerization step In the first reactor of the continuous reactors in which three reactors are connected in series, 7.99 kg/h of a styrene solution in which styrene is dissolved at 60% by mass in n-hexane, 10.55 kg/h of a 1,3-butadiene solution in which 1,3-butadiene is dissolved at 60% by mass in n-hexane, 47.66 kg/h of n-hexane, 10 g/h of a 1,2-butadiene solution in which 1,2-butadiene is dissolved at 2.0% by mass in n-hexane, 10.0 g/h of a solution in which 2,2-di(2-tetrahydrofuryl)propane is dissolved at 10% by mass in n-hexane as a polar additive, and 292.50 g/h of the modified initiator prepared in the above Preparation Example are injected. At this time, the temperature of the first reactor is maintained at 50° C., and when the polymerization conversion rate reaches 43%, the polymer is transferred from the first reactor to the second reactor through the transfer pipe.
Subsequently, a 1,3-butadiene solution in which 1,3-butadiene is dissolved in n-hexane at a concentration of 60% by mass is injected into the second reactor at a rate of 0.95 kg/h. At this time, the temperature of the second reactor is maintained at 65° C., and when the polymerization conversion rate reaches 95% or more, the polymer is transferred from the second reactor to the third reactor through a transfer pipe.
The polymer is transferred from the second reactor to the third reactor, and a solution in which a compound represented by the following structural formula (1-1) is dissolved as a modifier is added to the third reactor (modifier:active Li=1:1 mol). The temperature of the third reactor is maintained at 65°C.
Thereafter, a solution of IR1520 (manufactured by BASF) dissolved at 30 mass % as an antioxidant is injected at a rate of 170 g/h into the polymerization solution discharged from the third reactor and stirred. The resulting polymer is put into hot water heated with steam and stirred to remove the solvent, thereby obtaining a modified SBR having modified both ends.
The resulting both-end-modified SBR had a glass transition temperature (Tg) of -25°C and a bound styrene content of 41 mass%.

It can be seen from Tables 1 and 2 that the rubber compositions of the examples have a high level of balance between wet grip performance, fuel economy and abrasion resistance.
On the other hand, it is seen that the rubber compositions of Comparative Examples 2 and 3, in which the resin component content is too high, have poor fuel economy and wear resistance. Also, it is seen that the rubber composition of Comparative Example 4, in which the resin component/isoprene skeleton rubber mass ratio is less than 0.5 and the glass transition temperature of the styrene-butadiene rubber used is too high, has poor fuel economy and wear resistance.

<Example of tire structure>
Example 1
In the tire radial direction region R of a tire having a tire size of 205/55R16, as shown in FIG. 1, three prototypes were made with different weights (thicknesses) in which mass (thickness) was added to the maximum width position (Reference Examples 1 to 3). A conventional tire without mass (thickness) added to the maximum width position was also prepared (Comparative Example 1). In Reference Example 1, a mass of 55 g was added, in Reference Example 2, a mass of 105 g was added, and in Reference Example 3, a mass of 165 g was added. As a result, in Reference Examples 1, 2, and 3, the mass of the sidewall portion in the tire radial direction region R was 0.5%, 1%, and 2% of the total mass of the pneumatic tire, respectively. In Reference Examples 1, 2, and 3, the thickness of the sidewall portion in the tire radial direction region R was 0.5 mm, 1 mm, and 2 mm thicker than the thickness of the thinnest part of the sidewall portion, respectively.

The vibration modes of these tires in the tire radial region R were measured using FEM simulation. The measurement results are shown in Figure 4.

As shown in Figure 4, it can be seen that the amplitude between 800 Hz and 1000 Hz is reduced in Reference Examples 1 to 3 compared to Comparative Example 1.

Example 2
Next, the effect of the present invention was confirmed by changing the position where the weight was increased. In Reference Example 4, a tire was prototyped in which a mass of 130 g was added to the maximum width position. In Reference Example 4, the mass of the sidewall portion in the tire radial region R was 1.1% of the total mass of the pneumatic tire. In Reference Example 4, the thickness of the sidewall portion in the tire radial region R was 1 mm thicker than the thickness of the thinnest part of the sidewall portion. In Comparative Example 2, a mass of 130 g was added to the surface of the sidewall portion in a region radially outward of the tire radial region R. In Comparative Example 3, a mass of 130 g was added to the surface of the sidewall portion in a region radially inward of the tire radial region R. In Comparative Example 4, a mass of 130 g was added to the entire sidewall portion.

The vibration modes of these tires at the rubber sheet attachment positions were measured by FEM simulation. The measurement results for Reference Example 4 and Comparative Examples 2 and 3 are shown in Figure 5. The measurement results for Reference Example 4 and Comparative Example 4 are shown in Figure 6.

As shown in FIG. 5, in Reference Example 4, the amplitude in the range of 800 Hz to 1000 Hz is reduced compared to Comparative Examples 2 and 3.
Moreover, as shown in FIG. 6, it is understood that in Reference Example 4, the amplitude in the range of 800 Hz to 1000 Hz is reduced compared to Comparative Example 4.

In addition, the weight increase in Reference Examples 1 to 3 was 0.5%, 1%, and 2%, respectively, which did not result in an excessive weight increase. Furthermore, when a rubber sheet corresponding to such a mass was attached, there was no rubber flow or shifting during vulcanization.

[Contribution to the United Nations-led Sustainable Development Goals (SDGs)]
The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 7 - Affordable and clean energy for all,""No. 12 - Responsible consumption and production," and "No. 13 - Take concrete measures against climate change."

1: pneumatic tire; 2: bead portion; 3: carcass;
4: belt, 5: tread portion, 6: sidewall portion,
7: Rubber member, 8: Tire inner surface

Claims (9)

A tire having a tread rubber made of a rubber composition for tires including a rubber component, a resin component, and a filler,
The rubber component includes an isoprene skeleton rubber and a styrene-butadiene rubber,
The styrene-butadiene rubber has a glass transition temperature of less than −40° C.
an amount of the resin component per 100 parts by mass of the rubber component is 1 part by mass or more and less than 50 parts by mass;
the resin component is at least partially hydrogenated, and the difference in SP value between the resin component and the isoprene skeleton rubber is 1.40 (cal/cm ³ ) ^1/2 or less;
The formula:
The mass ratio of the resin component to the isoprene skeleton rubber is ≧0.5
The filling,
The thickness of the tread rubber is 9.5 mm or less, or the tread rubber is provided with a circumferential main groove extending in the tire circumferential direction, and the groove depth of the circumferential main groove is 7.5 mm or less,
The standard condition is when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and unloaded.
A tire characterized in that a mass of a sidewall portion in a tire radial region between positions spaced 15% of the tire cross-sectional height on the inner and outer sides in the tire radial direction from a maximum width position of the tire in the reference state is 1.5% to 5% of an entire mass of the tire. A tire having a tread rubber made of a rubber composition for tires including a rubber component, a resin component, and a filler,
The rubber component contains an isoprene skeleton rubber and a styrene-butadiene rubber,
The styrene-butadiene rubber has a glass transition temperature of less than −40° C.
an amount of the resin component per 100 parts by mass of the rubber component is 1 part by mass or more and less than 50 parts by mass;
the resin component is at least partially hydrogenated, and the difference in SP value between the resin component and the isoprene skeleton rubber is 1.40 (cal/cm ³ ) ^1/2 or less;
The formula:
The mass ratio of the resin component to the isoprene skeleton rubber is ≧0.5
The filling,
The thickness of the tread rubber is 9.5 mm or less, or the tread rubber is provided with a circumferential main groove extending in the tire circumferential direction, and the groove depth of the circumferential main groove is 7.5 mm or less,
The tire aspect ratio is 10 to 65.
The standard condition is when the tire is mounted on an applicable rim, inflated to a specified internal pressure, and unloaded.
a thickness of a sidewall portion in a tire radial region between positions spaced 15% of the tire cross-sectional height on the inner and outer sides in the tire radial direction from a maximum width position of the tire in the reference state is 1.0 to 4 mm thicker than the thickness of the thinnest portion of the sidewall portion. The tire according to claim 1 or 2, wherein the resin component has an SP value that differs from that of the isoprene skeleton rubber by 0.50 (cal/cm ³ ) ^1/2 or less. 3. The tire according to claim 1, wherein a difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is 0.3 (cal/cm ³ ) ^1/2 or more. The tire according to claim 1 or 2, wherein the content of the isoprene skeleton rubber is 1 to 80 parts by mass per 100 parts by mass of the rubber component. The tire according to claim 5, wherein the content of the isoprene skeleton rubber is 1 to 40 parts by mass per 100 parts by mass of the rubber component. The tire according to claim 1 or 2, wherein the styrene-butadiene rubber is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group. The tire according to claim 1 or 2, wherein the resin component has a softening point higher than 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g/mol. 3. The tire according to claim 1, wherein the resin component is at least one selected from the group consisting of hydrogenated C5 resins, hydrogenated C5-C9 resins, hydrogenated dicyclopentadiene resins, and hydrogenated terpene resins.

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