阅读说明：本技术 轮胎和评估轮胎抓地性能的方法 (Tire and method for evaluating grip performance of tire ) 是由 松永贵信 小森佳彦 宫崎达也 于 2019-09-05 设计创作，主要内容包括：本发明旨在提供在磨合前后均显示出令人满意的抓地性能的轮胎。本发明涉及包含胎面橡胶的轮胎,所述胎面橡胶满足以下关系式(I)：(a)/(b)≥0.75(I)式中,符号(a)和符号(b)分别表示在距轮胎表面的轮胎径向深度为10μm至200μm的区域中测得的轮胎胎面接触部分的最小马氏硬度和最大马氏硬度。(The present invention aims to provide a tire exhibiting satisfactory gripping performance before and after running-in. The present invention relates to a tire comprising a tread rubber satisfying the following relational formula (I): (a) in the formula,/(b) ≧ 0.75(I), the symbol (a) and the symbol (b) respectively represent the minimum and maximum March's hardness of the tire tread contact portion measured in a region of a tire radial depth of 10 μm to 200 μm from the tire surface.)

1. A tire, the tire comprising a tread rubber,

the tread rubber satisfies the following relational formula (I):

(a)/(b)≥0.75(I)

in the formula, the symbol (a) and the symbol (b) represent the minimum and maximum mahalanobis hardness, respectively, of the tire tread contact portion measured in a region having a depth of 10 to 200 μm in the tire radial direction from the tire surface.

2. The tire as set forth in claim 1,

wherein the minimum Martensitic hardness (a) is 0.35 mgf/. mu.m²The following.

3. Tire according to claim 1 or 2,

wherein the maximum Martensitic hardness (b) is 0.05 mgf/. mu.m²The above.

4. Tire according to any one of claims 1 to 3,

wherein the tread rubber is formed from a rubber composition containing 2.1 parts by mass or more of at least one phenylenediamine-based antioxidant per 100 parts by mass of a rubber component in the rubber composition.

5. Tire according to any one of claims 1 to 4,

wherein the tread rubber is formed of a rubber composition containing 20 parts by mass or more of at least one liquid plasticizer with respect to 100 parts by mass of a rubber component in the rubber composition.

6. Tire according to any one of claims 1 to 5,

wherein the tread rubber is formed from a rubber composition containing 0.1 part by mass or more of at least one amide compound or at least one nonionic surfactant having an SP value of 9.0 or more per 100 parts by mass of the rubber component in the rubber composition.

7. A method of evaluating tire grip performance, wherein the method comprises:

preparing a test piece cut from a tire tread rubber, the test piece having a ground contact surface forming a tire tread contact portion and a measurement surface extending perpendicular to the ground contact surface and in a tire radial direction; and

the mohs hardness of the measurement face of the specimen prepared in the specimen preparation step is measured in the tire radial direction using a microhardness meter or a film hardness meter.

8. The method of evaluating the grip performance of a tire according to claim 7,

wherein, the measuring step comprises: the mohs hardness of the measurement plane corresponding to a region having a tire radial depth of 10 to 200 μm from the tire surface was measured.

9. The method of evaluating tire grip performance according to claim 7 or 8,

wherein the method comprises the following steps: removing the surface of the measurement surface of the sample prepared in the sample preparation step to a depth of 20 μm or more before measuring the mahalanobis hardness, to form a new measurement surface; and measuring the mahalanobis hardness of the new measuring surface.

Technical Field

The present invention relates to a tire and a method of evaluating the grip performance of a tire.

Background

Good wet grip performance is an important property of a desired tire. It is generally known to improve wet grip performance by increasing hysteresis loss of tire tread rubber. For this reason, it is known to increase the tan δ peak temperature (Tg) of the temperature dependence curve of the rubber (for example, see patent document 1). It is also known to incorporate resins to improve wet grip performance.

Reference list

Patent document

Patent document 1: JP 2006 + 056979A

Disclosure of Invention

Technical problem

However, the present inventors' studies have shown that even with techniques of increasing the tan δ peak temperature or incorporating a resin, the resulting new tire may exhibit insufficient grip performance before running-in (break-in period).

The present invention aims to solve the problem and provide a tire exhibiting satisfactory gripping performance both before and after running-in (running-in period).

Means for solving the problems

The present inventors have conducted extensive studies on the new problems found by the present inventors, and have found that satisfactory grip performance can be exhibited before and after running-in by adjusting the martensitic hardness (Martens hardnes) of a specific portion of the tread rubber to satisfy a specific relationship, thereby completing the present invention.

Specifically, the present invention relates to a tire comprising a tread rubber satisfying the following relational formula (I):

(a)/(b)＞0.75 (I)

in the formula, the symbol (a) and the symbol (b) represent the minimum and maximum mahalanobis hardness, respectively, of the tire tread contact portion measured in a region having a depth of 10 to 200 μm in the tire radial direction from the tire surface.

Preferably, the minimum Martensitic hardness (a) is 0.35 mgf/. mu.m²The following.

Preferably, the maximum Martensitic hardness (b) is 0.05 mgf/. mu.m²The above.

Preferably, the tread rubber is formed of a rubber composition containing 2.1 parts by mass or more of at least one phenylenediamine-based antioxidant per 100 parts by mass of the rubber component in the rubber composition.

Preferably, the tread rubber is formed of a rubber composition containing 20 parts by mass or more of at least one liquid plasticizer per 100 parts by mass of the rubber component in the rubber composition.

Preferably, the tread rubber is formed of a rubber composition containing 0.1 parts by mass or more of at least one amide compound or at least one nonionic surfactant having an SP value of 9.0 or more, relative to 100 parts by mass of the rubber component in the rubber composition.

The invention also relates to a method for evaluating the grip performance of a tyre, said method comprising:

preparing a test piece cut from a tire tread rubber, the test piece having a ground contact surface forming a tire tread contact portion and a measurement surface extending perpendicular to the ground contact surface and in a tire radial direction; and

the mohs hardness of the measurement face of the specimen prepared in the specimen preparation step is measured in the tire radial direction using a microhardness meter or a film hardness meter.

Preferably, the measuring step comprises: the measurement plane corresponds to the mahalanobis hardness of a region having a tire radial depth of 10 to 200 μm from the tire surface.

Preferably, the method comprises: removing the surface of the measurement surface of the sample prepared in the sample preparation step to a depth of 20 μm or more before measuring the mahalanobis hardness, to form a new measurement surface; and measuring the mahalanobis hardness of the new measuring surface.

Advantageous effects of the invention

The tire of the first aspect of the present invention comprises a tread rubber satisfying the relation (I). Such tires exhibit satisfactory grip performance before and after break-in.

The method of evaluating the grip performance of a tire of the second aspect of the present invention includes: preparing a test piece cut from a tire tread rubber, wherein the test piece has a ground contact surface forming a tire tread contact portion and a measurement surface extending perpendicular to the ground contact surface and in a tire radial direction; and measuring the mohs hardness of the measurement face of the specimen prepared in the specimen preparation step in the tire radial direction using a microhardness meter or a film hardness meter. Tire grip performance can be evaluated by this method.

Drawings

FIG. 1 shows an exemplary Mahalanobis hardness distribution for tread rubber.

FIG. 2 shows a cross-sectional view of a portion of a tire according to an embodiment of the present invention.

FIG. 3 shows a cross-sectional view of a portion of a tire according to an embodiment of the present invention.

Fig. 4(a), (b) and (c) each show a schematic view of a sample.

Detailed Description

(first aspect of the invention)

The tire of the first aspect of the present invention comprises a tread rubber satisfying the following relational formula (I):

(a)/(b)≥0.75 (I)

in the formula, the symbol (a) and the symbol (b) represent the minimum and maximum mahalanobis hardness, respectively, of the tire tread contact portion measured in a region having a depth of 10 to 200 μm in the tire radial direction from the tire surface. Therefore, the tire can exhibit satisfactory gripping performance before and after running-in.

Hereinafter, the minimum mahalanobis hardness (a) is also simply referred to as "mahalanobis hardness (a)", the maximum mahalanobis hardness (b) is also simply referred to as "mahalanobis hardness (b)", and both hardnesses are also collectively referred to as "mahalanobis hardness (a) and mahalanobis hardness (b)".

The tire provides the above effects. The reason why such advantageous effects are produced is not completely understood, but can be explained as follows.

The inventors' studies have shown that, in order to obtain good gripping performance, it is desirable that the inner portion of the tread rubber is rigid and the outer portion of the tread rubber is soft.

Specifically, the inner portion of the tread is preferably hard in view of preventing deformation of the rubber to allow the rubber to maintain a large actual road surface contact area and ensuring a cornering force for steering stability.

On the other hand, the surface portion of the tread is preferably soft in view of allowing the rubber to conform to minute unevenness (80 μm to 0.1mm) of stone aggregate (pitch 8mm) on a road surface. This compliance will increase the actual contact area between the rubber and the road surface, resulting in higher hysteresis losses and thus good grip.

Based on the above considerations, the inventors investigated why new tires may show insufficient grip performance before running-in.

The results show that at a depth of 0 to 100 μm from the tread surface, where the plasticizer-rich polymer layer is formed, the tread is soft immediately after vulcanization (i.e. immediately after tire manufacture); however, due to oxygen permeation, particularly when the crosslink density is low or the antioxidant content is low, the tread is easily hardened during storage of the tire. In other words, it was found that during the period from the manufacture of the tire to the use of the tire, the surface layer of the tread becomes hard, resulting in a decrease in grip performance before running-in.

Through extensive studies on this phenomenon, the present inventors found that, although a tire is generally used after several months to about 1 year of manufacture, storage in a warehouse or the like for several months to about 1 year hardens a surface layer, while additives (such as an antioxidant, a plasticizer, and a wax) migrate to the surface layer to soften the surface layer or inhibit the surface layer from hardening. Specifically, the phenylenediamine-based antioxidant can migrate and bleed out to the surface layer to suppress hardening of the surface layer by oxygen, ozone, or ultraviolet rays. Further, the liquid plasticizer, the amide compound, and the nonionic surfactant may migrate and bleed out to the surface layer to soften the surface layer and uniformly distribute the phenylenediamine-based antioxidant in the surface layer, so that the surface layer hardening may be more suitably suppressed. In addition, liquid plasticizers may be used as carriers for the antioxidant to promote migration of the antioxidant to the surface layer. In addition, the amide compound and the nonionic surfactant can also be used to soften the bleeding layer on the outermost surface. It should be noted that additives having SP values that differ more from the rubber component are more likely to bleed out.

In addition, the liquid plasticizer and the nonionic surfactant do not provide grip by themselves, but function to improve dispersibility of the resin in rubber and plasticize resin exudation or a film.

Then, for the tread rubber of the tire stored in a warehouse for several months to about 1 year, migration of the compounding additive to the surface layer and hardening of the surface layer have proceeded, and thus hardening caused by oxygen, ozone, or UV deterioration may be significant at a position having a tire radial depth of 10 μm to 200 μm from the tire surface (as shown in fig. 1). Therefore, significant differences may occur between tires.

With respect to the minimum mahalanobis hardness and the maximum mahalanobis hardness occurring at any position between 10 μm and 200 μm, satisfying the relation (I) means that: in a region having a tire radial depth of 10 μm to 200 μm from the tire surface, the difference between the minimum mahalanobis hardness and the maximum mahalanobis hardness is small. In other words, satisfying the relation (I) means: in a region having a tire radial depth of 10 μm to 200 μm from the tire surface, local hardening is suppressed. Therefore, it has been found that by satisfying the relation (I) so that local hardening in the region of 10 μm to 200 μm can be suppressed, minute irregularities on the road surface can be conformed to increase the actual contact area, so that the grip performance before running-in is brought closer to the grip performance after running-in, so that satisfactory grip performance can be exhibited both before and after running-in.

It is considered that this is because satisfying the relation (I) makes it possible to conform to minute irregularities on the road surface to increase the actual contact area, thereby bringing the grip performance before running-in closer to the grip performance after running-in, and thus showing good grip performance before running-in; furthermore, the deformation of the rubber block can be reduced to reduce the lifting of the edge of the rubber block, so that good grip performance can be shown after running-in. Therefore, satisfactory gripping performance can be exhibited both before and after running-in.

For the above reasons, the tire including the tread rubber satisfying the relation (I) can exhibit satisfactory grip performance before and after running-in. Therefore, the present invention solves the problem (object) of providing satisfactory grip performance both before and after running-in by a tire structure containing a tread rubber satisfying the parameters of the relation (I). In other words, the parameters do not specify the problem (purpose) to be solved by the present application to provide satisfactory grip performance both before and after running-in. In order to provide a solution to this problem, a tread rubber structure satisfying the parameters of the relational expression (1) is designed. Therefore, the key feature is the parameter satisfying the relation (I).

The tire of the first aspect of the present invention comprises a tread rubber that satisfies the following relational formula (I):

(a)/(b)＞0.75 (I)

in the formula, the symbol (a) and the symbol (b) represent the minimum and maximum mahalanobis hardness, respectively, of the tire tread contact portion measured in a region having a depth of 10 to 200 μm in the tire radial direction from the tire surface.

As used herein, the term "tire tread contacting portion" refers to the portion of the tread that will contact the road surface. In the tire 2 shown in fig. 2, the tire tread contact portion refers to the tread surface 20 of the tread 4 and does not correspond to the groove 22 that is not in contact with the road surface.

The tire of the first aspect of the invention contains a tread rubber satisfying the relation (I), wherein the symbol (a) and the symbol (b) respectively represent the minimum mahalanobis hardness and the maximum mahalanobis hardness of the tire tread contact portion measured in a region (i.e., the position a to the position b in fig. 3) having a tire radial depth of 10 μm (the position "a" in fig. 3) to 200 μm (the position "b" in fig. 3) from the tire surface.

The lower limit of the relation (I) is preferably 0.75, more preferably 0.76, further more preferably 0.78, particularly preferably 0.79, most preferably 0.80, further preferably 0.83, further preferably 0.85, further preferably 0.90, further preferably 0.92, further preferably 0.93, further preferably 0.94. The upper limit of the relation (I) is not limited, but is preferably 1.00. When the value is within the above range, the advantageous effects can be more suitably obtained.

The minimum mahalanobis hardness (a) is not limited as long as it satisfies the relation (I).

Minimum hardness in Mahalanobis: (a) The lower limit of (A) is not particularly limited, but the minimum Martensitic hardness (a) is preferably 0.05 mgf/. mu.m²More preferably 0.10 mgf/. mu.m or more²More preferably 0.12 mgf/. mu.m²While the minimum Martensitic hardness (a) is preferably 0.35mgf/m²Less than, more preferably 0.30mgf/m²Less than, more preferably 0.25 mgf/. mu.m²The following. When the value is within the above range, the advantageous effects can be more suitably obtained.

The maximum mahalanobis hardness (b) is not limited as long as it satisfies the relation (I).

The minimum mahalanobis hardness (a) and the maximum mahalanobis hardness (b) are roughly related to shore (a) Hs (shore a hardness) used in the tire technology field, which is a macroscopic hardness measured at an indentation depth of several millimeters. Typically, Hs of 60 to 75 corresponds to a maximum mahalanobis hardness (b) of 0.10 to 0.30. The maximum Mad hardness (b) is preferably 0.05 mgf/. mu.m²More preferably 0.10 mgf/. mu.m or more²More preferably 0.13 mgf/. mu.m or more²The above. The upper limit is not limited, but is preferably 0.50 mgf/. mu.m²Less than, more preferably 0.45mgf/m²Less than, more preferably 0.40 mgf/. mu.m²The content of the metal oxide is preferably at most, particularly preferably 0.35 mgf/. mu.m²Less than, most preferably 0.30 mgf/. mu.m²The lower, more preferably 0.25 mgf/. mu.m²The following. When the value is within the above range, the advantageous effects can be more suitably obtained.

Herein, the mahalanobis hardness (a) and the mahalanobis hardness (b) are measured by the measurement methods described in the examples below.

Specifically, as shown in table 1, the mahalanobis hardness (a) and the mahalanobis hardness (b) can be controlled by changing the type or amount of chemicals (particularly, phenylenediamine-based antioxidants, liquid plasticizers, amide compounds, or nonionic surfactants having an SP value of 9.0 or more) incorporated in a rubber composition for forming a tread rubber (hereinafter also referred to as "tread rubber composition").

In the table, symbol ↓indicates "decrease", symbol ↓ > indicates "increase", and symbol → indicates "not affected". Here, a change of 0.1 or less is also regarded as "not affected".

[ Table 1]

If the hardness (Shore (A) hardness) changes by more than 2 with increasing chemical content, it may be necessary to control the amount of oil or the like incorporated.

More specifically, for example, the prescribed ratio (a)/(b) and the mohs hardness (a) and the mohs hardness (b) of the rubber composition for forming the tread rubber can be imparted by appropriately selecting chemicals (particularly, a phenylenediamine-based antioxidant, a liquid plasticizer, an amide compound, or a nonionic surfactant having an SP value of 9.0 or more) to be incorporated into the rubber composition or appropriately controlling the amounts of the chemicals. Specifically, the prescribed ratio (a)/(b) and the mohs hardness (a) and the mohs hardness (b) can be given by: (1) the amount of the phenylenediamine-based antioxidant is adjusted to 2.1 parts by mass or more per 100 parts by mass of the rubber component; (2) the amount of the liquid plasticizer is adjusted to 20 parts by mass or more with respect to 100 parts by mass of the rubber component; and/or (3) the amount of the amide compound or the nonionic surfactant having an SP value of 9.0 or more is adjusted to 0.1 part by mass or more per 100 parts by mass of the rubber component. In particular, the techniques (1) and (2), especially (2), are important. In addition, the technique (3) is also important because the amount of the additive has a great influence.

Further, a combination of the techniques (1) and (2), a combination of the techniques (1) and (3), and a combination of the techniques (1), (2), and (3) are also suitable.

Although the hardnesses (a) and (b) tend to vary in the same direction, other techniques for controlling the ratio (a)/(b) and the mohs hardness (a) and (b) include appropriately controlling silica, carbon black, high molecular weight polymers (SBR, BR), rare earth-catalyzed BR (high-cis BR), or vulcanizing agents.

A tire including a tread rubber satisfying a prescribed ratio (a)/(b) and a mohs hardness (a) and a mohs hardness (b) can be manufactured by the following method: preparing a tread rubber composition according to the above-described technique; and preparing a tire having a tread formed of the rubber composition.

More specifically, a tire including a tread rubber satisfying a prescribed ratio (a)/(b) and a mohs hardness (a) and a mohs hardness (b) can be manufactured by the following method: preparing a tread rubber composition according to the above-described technique; preparing a tire having a tread formed of a rubber composition; and storing the tire in a warehouse or the like until use, during which migration of the compounding additive to the surface layer and hardening of the surface layer are performed within the tread rubber.

The following describes chemicals that can be used in a rubber composition (a rubber composition for forming a tread rubber).

Examples of the rubber component that can be used in the rubber composition include diene-based rubbers such as isoprene-based rubber, polybutadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), acrylonitrile-butadiene rubber (NBR), Chloroprene Rubber (CR), and butyl rubber (IIR). The rubber component may be composed of a single rubber or a combination of two or more rubbers. Among these, SBR, BR and isoprene-based rubbers are preferable, and SBR and/or BR are more preferable.

Any SBR may be used, examples including those commonly used in the tire industry, such as emulsion polymerized SBR (E-SBR) and solution polymerized SBR (S-SBR). These may be used alone or in combination of two or more.

The weight average molecular weight (Mw) of the rubber component is preferably 150,000 or more, more preferably 350,000 or more. The upper limit of the Mw is not limited, but is preferably 4,000,000 or less, more preferably 3,000,000 or less.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more, but is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less. When the styrene content is within the above range, the advantageous effects tend to be more suitably obtained.

The vinyl content of SBR is preferably 10 mass% or more, more preferably 15 mass% or more, but preferably 50 mass% or less, more preferably 40 mass% or less. When the vinyl content is within the above range, the advantageous effects tend to be more suitably obtained.

The SBR may be an unmodified SBR or a modified SBR.

The modified SBR may be any SBR having functional groups that interact with the filler (e.g., silica). For example, it may be: chain-end-modified SBR obtained by modifying at least one chain end of SBR with a compound having a functional group (modifier) (i.e., chain-end-modified SBR terminated with a functional group); a main chain-modified SBR having a functional group on the main chain; a main chain and chain end-modified SBR having a functional group at both a main chain and a chain end (for example, a main chain and chain end-modified SBR in which a main chain has a functional group and at least one chain end is modified with a modifier); alternatively, chain-end modified SBR having been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule to introduce a hydroxyl group or an epoxy group. These may be used alone or in combination of two or more.

Examples of functional groups include: amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazolyl, ureido, ether, carbonyl, oxycarbonyl, mercapto, thioether, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imide, hydrazono, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, and epoxy groups. These functional groups may be substituted. Of these, preferred are amino groups (preferably amino groups in which a hydrogen atom is substituted with a C1-C6 alkyl group), alkoxy groups (preferably C1-C6 alkoxy groups), alkoxysilyl groups (preferably C1-C6 alkoxysilyl groups), and amide groups.

SBR products manufactured or sold by Sumitomo chemical Co., Ltd., JSR company, Asahi Kasei corporation, Riweng Kasei corporation and the like can be used as SBR.

The amount of SBR is preferably 40% by mass or more, more preferably 50% by mass or more, and further more preferably 70% by mass or more, but is preferably 95% by mass or less, more preferably 90% by mass or less, based on 100% by mass of the rubber component. When the amount of SBR is within the above range, the advantageous effects tend to be better obtained.

Any BR may be used, including those commonly used in the tire industry. Examples include those commonly used in the tire industry, such as high cis BR, BR containing 1, 2-syndiotactic polybutadiene crystals (BR containing SPB), polybutadiene rubber synthesized using a rare earth catalyst (rare earth-catalyzed BR), and tin-modified polybutadiene rubber obtained by modification with a tin compound (tin-modified BR). These may be used alone or in combination of two or more. Among these, rare earth catalyzed BR is preferred.

Rare earth catalyzed BR refers to polybutadiene rubber synthesized using rare earth catalysts, characterized by a high cis content and a low vinyl content. The rare earth catalyzed BR may be one commonly used in tire manufacture.

Known rare earth catalysts can be used. Examples include catalysts comprising lanthanide rare earth compounds, organoaluminum compounds, aluminoxanes, or halogen-containing compounds, which optionally contain lewis bases. Among these, a neodymium (Nd) catalyst using a Nd-containing compound as a lanthanoid rare earth compound is particularly preferable.

The cis content of BR is preferably 90 mass% or more, more preferably 93 mass% or more, and further more preferably 95 mass% or more. When the cis content is not less than the lower limit, the advantageous effect can be more suitably obtained.

The BR has a vinyl group content of preferably 1.8% by mass or less, more preferably 1.0% by mass or less, further more preferably 0.5% by mass or less, and particularly preferably 0.3% by mass or less. When the vinyl content is not higher than the upper limit, the advantageous effect can be more suitably obtained.

The BR can be unmodified BR or modified BR.

Examples of the modified BR include modified BR into which the above-mentioned functional group is introduced. Preferred embodiments are as described for modified SBR.

BR can be purchased from Utsuki Kagaku K.K., JSR Kabushiki Kaisha, Asahi Kabushiki Kaisha, Rui Weng K.K.

The amount of BR is preferably 5% by mass or more, more preferably 10% by mass or more, but preferably 60% by mass or less, more preferably 50% by mass or less, and further more preferably 30% by mass or less, based on 100% by mass of the rubber component. When the amount of BR is within the above range, the advantageous effects tend to be more suitably obtained.

Examples of the isoprene-based rubber include Natural Rubber (NR), polyisoprene rubber (IR), refined NR, modified NR, and modified IR. The NR may be one commonly used in the tire industry, such as SIR20, RSS #3, or TSR 20. Any IR may be used, examples including those commonly used in the tire industry, such as IR 2200. Examples of the refined NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of the modified NR include Epoxidized Natural Rubber (ENR), Hydrogenated Natural Rubber (HNR), and grafted natural rubber. Examples of the modified IR include epoxidized polyisoprene rubber, hydrogenated polyisoprene rubber and grafted polyisoprene rubber. These may be used alone or in combination of two or more. Among these, natural rubber is preferable.

The total amount of SBR and BR is preferably 30% by mass or more, more preferably 50% by mass or more, further more preferably 70% by mass or more, particularly preferably 90% by mass or more, and most preferably 100% by mass, based on 100% by mass of the rubber component. When the total amount of SBR and BR is within the above range, the advantageous effects tend to be more suitably obtained.

Herein, the weight average molecular weight (Mw) and the number average molecular weight (Mn) can be measured by Gel Permeation Chromatography (GPC) (GPC-8000 series available from Tosoh Co., Ltd., detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M available from Tosoh Co., Ltd.), which has been calibrated with polystyrene standards.

The cis content (cis-1, 4-butadiene unit content) and the vinyl content (1, 2-butadiene unit content) can be measured by infrared absorption spectroscopy. The styrene content can be determined by¹H-NMR analysis.

Preferably, the rubber composition comprises at least one wax.

Any wax may be used. Examples include: petroleum-based waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable waxes and animal waxes; synthetic waxes, such as polymers of ethylene, propylene, or other similar monomers. These may be used alone or in combination of two or more. Among these, petroleum-based waxes are preferable, and paraffin waxes or microcrystalline waxes are more preferable. Further preferred is a microcrystalline wax containing 50 mass% or more of a branched paraffin (based on 100 mass% of the microcrystalline wax).

Waxes are available from Dai-Neisson chemical industries, Japan wax Seiko, Seiko chemical Co.

The amount of the paraffin wax is preferably 2.3 parts by mass or less, more preferably 2.0 parts by mass or less, further more preferably 1.5 parts by mass or less, and particularly preferably 1.3 parts by mass or less, relative to 100 parts by mass of the rubber component. The amount of the paraffin is preferably 0.3 part by mass or more, more preferably 0.5 part by mass or more, further more preferably 0.8 part by mass or more, and particularly preferably 1.0 part by mass or more for improving the static ozone resistance.

The amount of the microcrystalline wax is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and further more preferably 0.8 parts by mass or more, relative to 100 parts by mass of the rubber component, in order to improve grip performance before running-in; meanwhile, the amount of the microcrystalline wax is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and further preferably 1.5 parts by mass or less, in order to improve grip performance after running-in.

Preferably, the rubber composition comprises at least one antioxidant.

Examples of antioxidants include: naphthylamine-based antioxidants, such as phenyl- α -naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4, 4 '-bis (α, α' -dimethylbenzyl) diphenylamine; phenylenediamine-based antioxidants (p-phenylenediamine-based antioxidants), such as N-isopropyl-N '-phenyl-p-phenylenediamine, N- (1, 3-dimethylbutyl) -N' -phenyl-p-phenylenediamine, N '-di-2-naphthyl-p-phenylenediamine, and N, N' -bis (1, 4-dimethylpentyl) -p-phenylenediamine; quinoline-based antioxidants, such as 2, 2, 4-trimethyl-1, 2-dihydroquinoline polymers; monophenol-based antioxidants such as 2, 6-di-t-butyl-4-methylphenol and styrenated phenol; and bisphenol-based antioxidants, triphenol-based antioxidants or polyphenol-based antioxidants, such as tetrakis [ methylene-3- (3 ', 5 ' -di-tert-butyl-4 ' -hydroxyphenyl) propionate ] methane. These may be used alone or in combination of two or more. Among these, phenylenediamine antioxidants are preferred, and N- (1, 3-dimethylbutyl) -N '-phenyl-p-phenylenediamine or N, N' -bis (1, 4-dimethylpentyl) -p-phenylenediamine is more preferred.

Although the quinoline-based antioxidant can be used together with the phenylenediamine-based antioxidant, the quinoline-based antioxidant has a slower migration rate than the phenylenediamine-based antioxidant and thus has less softening effect on the surface layer.

Antioxidants are available from Seiko chemical Co., Ltd, Sumitomo chemical Co., Ltd, Innova chemical industry Co., Ltd, Furex, etc.

The amount of the phenylenediamine-based antioxidant is preferably 2.1 parts by mass or more, more preferably 2.4 parts by mass or more, further more preferably 3 parts by mass or more, particularly preferably 3.4 parts by mass or more, most preferably 4 parts by mass or more, and further most preferably 5 parts by mass or more, but is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 7 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the phenylenediamine-based antioxidant is within the above range, the ratio (a)/(b) and the mohs hardness (a) and the mohs hardness (b) can be adjusted within predetermined ranges, and the advantageous effects can be more suitably obtained.

The amount (total amount) of the antioxidant is preferably 3 parts by mass or more, more preferably 4 parts by mass or more, and further more preferably 6 parts by mass or more, but is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 8 parts by mass or less, with respect to 100 parts by mass of the rubber component. When the amount of the antioxidant is within the above range, the advantageous effects tend to be better obtained.

Preferably, the rubber composition comprises at least one liquid plasticizer.

Any liquid plasticizer that is liquid at 20 ℃ may be used, examples include oils, liquid resins, and liquid polymers. These may be used alone or in combination of two or more. Among these, oil or liquid resin is preferable.

The amount of the liquid plasticizer is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, further more preferably 25 parts by mass or more, particularly preferably 30 parts by mass or more, and most preferably 35 parts by mass or more, with respect to 100 parts by mass of the rubber component, but is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, further more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less. When the amount of the liquid plasticizer is within the above range, the ratio (a)/(b) and the mohs hardness (a) and the mohs hardness (b) may be adjusted within predetermined ranges, and advantageous effects may be more suitably obtained. In this context, the amount of liquid plasticizer includes the amount of oil contained in the oil extended rubber (if used).

Examples of oils include process oils, vegetable oils, and mixtures thereof. Examples of process oils include paraffinic, aromatic, naphthenic, Mild Extraction Solvates (MES), and Treated Distillate Aromatic Extracts (TDAE). Examples of vegetable oils include: castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and oleic oil. These may be used alone or in combination of two or more. Among these, the process oil is preferable in order to better obtain the advantageous effects of the present invention; among them, aromatic process oils or oleic acid-containing oils are preferred.

The oil can be purchased from Shih oil Co., Ltd, Sanko oil chemical industries, Japan energy Co., Ltd, Olisoy, H & R Co., Ltd, Toyobo oil Co., Ltd, Fuji oil Co., Ltd, etc.

Examples of the liquid resin include resins which are liquid at 20 ℃, such as terpene resins (including terpene phenol resins and aromatic-modified terpene resins), styrene resins, C5 resins, C9 resins, C5/C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone-based resins only or indene-based resins only), phenol resins, olefin resins, polyurethane resins and acrylic resins. These may be used alone or in combination of two or more. Among these, coumarone-indene resins are preferred.

Examples of the liquid polymer (liquid diene polymer) include liquid polymers that are liquid at 20 ℃, such as liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene polymer (liquid BR), liquid polyisoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid farnesene polymer, and liquid farnesene-butadiene copolymer. The chain ends or the main chain of these polymers may be modified with polar groups. These liquid polymers may be used alone or in combination of two or more.

Preferably, the rubber composition contains at least one resin (solid resin: a resin that is solid at room temperature (25 ℃). In this case, better grip performance tends to be obtained.

The softening point of the resin is preferably 60 ℃ or higher, more preferably 65 ℃ or higher, and still more preferably 80 ℃ or higher. The upper limit of the softening point is not limited, but is preferably 160 ℃ or less, more preferably 135 ℃ or less. When the softening point is within the above range, the advantageous effects tend to be more appropriately obtained.

Softening point of resin according to JIS K6220-1: 2001 were measured using a ring and ball softening point measuring device and are defined as the temperature at which the ball dropped.

Any resin (solid resin) may be used, and examples include aromatic vinyl polymers, coumarone-indene resins, terpene resins, dicyclopentadiene resins (DCPD resins), C5 petroleum resins, C9 petroleum resins, C5/C9 petroleum resins, p-tert-butylphenol acetylene resins, and acrylic resins. These may be used alone or in combination of two or more.

In addition, these resins may be hydrogenated. Among these, aromatic vinyl polymers or terpene resins are preferable.

The aromatic vinyl polymer refers to a resin prepared by polymerizing alpha-methylstyrene and/or styrene. Examples include styrene homopolymers (styrene resins), alpha-methylstyrene homopolymers (alpha-methylstyrene resins), copolymers of alpha-methylstyrene with styrene, and copolymers of styrene with other monomers.

Any terpene resin having units derived from terpene compounds may be used. Examples include polyterpenes (resins prepared by polymerizing terpene compounds), terpene aromatic resins (resins prepared by copolymerizing terpene compounds and aromatic compounds), and aromatic modified terpene resins (resins obtained by modifying terpene resins with aromatic compounds). These may be used alone or in combination of two or more. Among these, terpene aromatic resins or aromatic modified terpene resins are preferable, and aromatic modified terpene resins are more preferable.

The terpene compound is a compound having the formula (C)₅H₈) A hydrocarbon or oxygenated derivative thereof of composition represented by n, having a terpene backbone and classified as: monoterpene (C)₁₀H₁₆) Sesquiterpenes (C)₁₅H₂₄) Diterpene (C)₂₀H₃₂) And other terpenes. Examples include: alpha-pinene, beta-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, alpha-phellandrene, alpha-terpinene, gamma-terpinene, terpinolene, 1, 8-cineol, 1, 4-cineol, alpha-terpineol, beta-terpineol, and gamma-terpineol. Other examples of terpene compounds include resin acids (abietic acid), such as abietic acid (abietic acid), neoabietic acid, palustric acid (palustric acid), levopimaric acid (levopimaric acid), pimaric acid, and isopimaric acid. Thus, terpene resins include rosin resins, which contain primarily rosin acids obtained by processing pine resins. Examples of rosin resins include: natural rosin resins (polymerized rosins) such as gum rosin (gum rosin), wood rosin, and tall oil rosin; modified rosin resins such as maleic acid-modified rosin resins and rosin-modified phenol resins; rosin esters, such as rosin glycerol esters; and disproportionated rosin resins obtained by disproportionating rosin resins.

The aromatic compound may be any compound having an aromatic ring, and examples include: phenolic compounds such as phenol, alkylphenol, alkoxyphenol and phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol and naphthol containing unsaturated hydrocarbon group; styrene and styrene derivatives, such as alkylstyrene, alkoxystyrene and styrene containing unsaturated hydrocarbon groups. Among these, styrene is preferable.

The resin and the liquid resin are commercially available from Maruzhitian Kaisha, Sumitomo Bakko, Anyuan chemical Co., Tosoh Kaisha, Rogue chemical Co., BASF, Arizona chemical Co., Nissan chemical Co., Ltd, Japanese catalyst Co., Ltd, JXTG energy Co., Ltd, Mikan chemical industry Co., Ltd, Takan chemical industry Co., Ltd, and the like.

The amount of the resin is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, further more preferably 10 parts by mass or more, and particularly preferably 20 parts by mass or more, but more preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 40 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the resin is within the above range, the advantageous effects tend to be better obtained.

Preferably, the rubber composition contains at least one amide compound and/or at least one nonionic surfactant having an SP value of 9.0 or more.

Any amide compound may be used, examples including fatty acid amides and fatty acid amide esters. These may be used alone or in combination of two or more. Among these, fatty acid amides are preferred, and mixtures of fatty acid amides and fatty acid amide esters are more preferred.

Mixtures of amide compounds and fatty acid metal salts may also be used. In order to more suitably obtain the beneficial effect, a mixture of the amide compound and the fatty acid metal salt is preferable.

Examples of the metal of the fatty acid metal salt include potassium, sodium, magnesium, calcium, barium, zinc, nickel and molybdenum. These may be used alone or in combination of two or more. Among these, alkaline earth metals such as calcium and zinc are preferred, and calcium is more preferred.

The fatty acid of the fatty acid metal salt may be a saturated fatty acid or an unsaturated fatty acid. Examples of saturated fatty acids include capric acid, lauric acid and stearic acid. Examples of unsaturated fatty acids include oleic acid and elaidic acid. These may be used alone or in combination of two or more. Saturated fatty acids are preferred, stearic acid being more preferred. Among the unsaturated fatty acids, oleic acid is preferred.

The fatty acid amide may be a saturated fatty acid amide or an unsaturated fatty acid amide. Examples of saturated fatty acid amides include stearic acid amide and behenamide (behenamide). Examples of unsaturated fatty acid amides include oleamide and erucamide. These may be used alone or in combination of two or more. Among these, unsaturated fatty acid amides are preferable, and oleic acid amide is more preferable.

The fatty acid amide ester may be a saturated fatty acid amide ester or an unsaturated fatty acid amide ester. Examples of saturated fatty acid amide esters include stearic acid amide ester and behenic acid amide ester. Examples of unsaturated fatty acid amide esters include oleamide ester and erucamide ester. These may be used alone or in combination of two or more. Among these, unsaturated fatty acid amide esters are preferable, and oleic acid amide esters are more preferable.

Amide compounds are available from Nichigan oil Co., Ltd, Jiatoto (Struktol), Lansheng (Lanxess), etc.

The amount of the amide compound is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and further more preferably 0.8 part by mass or more, but is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, further preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the amide compound is within the above range, the ratio (a)/(b) and the mohs hardness (a) and the mohs hardness (b) can be adjusted within predetermined ranges, and the advantageous effects can be more suitably obtained. Herein, when the amide compound is present in the form of a mixture with the fatty acid metal salt, the amount of the amide compound includes the amount of the fatty acid metal salt contained in the amide compound.

Any nonionic surfactant having an SP value of 9.0 or more may be used, and examples include: a nonionic surfactant represented by the following formula (1) and/or the following formula (2); a Pluronic type nonionic surfactant; sorbitan fatty acid esters such as polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate and polyoxyethylene sorbitan tripalmitate; and polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene oleyl ether, ethylene glycol dibutyl ether, ethylene glycol dilauryl ether, ethylene glycol di-2-ethylhexyl ether, and ethylene glycol oleyl ether. These nonionic surfactants may be used alone or in combination of two or more. Among these, the Pluronic type nonionic surfactant is more preferable in order to more suitably obtain the advantageous effects.

In the formula (1), R¹Represents a C6-C26 hydrocarbon group, and d represents an integer.

In the formula (2), R²And R³The same or different and each represents a C6-C26 hydrocarbon group, and e represents an integer.

Examples of the nonionic surfactant of formula (1) include: ethylene glycol monooleate, ethylene glycol monopalmitate (palmeate), ethylene glycol monopalmitate (palmitate), ethylene glycol monooleate (vaccenate), ethylene glycol monooleate, ethylene glycol monolinolate, ethylene glycol monooleate tetraacrylate, ethylene glycol monostearate, ethylene glycol monopalmitate (cethylate), and ethylene glycol monolaurate.

Examples of the nonionic surfactant of formula (2) include: ethylene glycol dioleate, ethylene glycol dipalmitate, ethylene glycol diisooleate, ethylene glycol dilinoleate, ethylene glycol dillenate, ethylene glycol arachidonate, ethylene glycol distearate, ethylene glycol dipalmitate, and ethylene glycol dilaurate.

The Pluronic type nonionic surfactant, also called polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxypropylene block polymer or polypropylene glycol ethylene oxide adduct, is generally represented by the following formula (I). As shown in formula (I), the Pluronic type nonionic surfactant has hydrophilic groups (having an ethylene oxide structure) on both sides thereof, and also has a hydrophobic group having a propylene oxide structure between the hydrophilic groups.

In formula (I), a, b and c represent integers.

The polymerization degree of the polypropylene oxide block of the Pluronic type nonionic surfactant (b in formula (I)) and the number of polyethylene oxide units added (a + c in formula (I)) are not limited and may be appropriately selected depending on the use conditions, the purpose, or other factors. Surfactants with higher polypropylene oxide block ratios tend to have higher affinities for rubber and therefore migrate to the rubber surface at a slower rate. In particular, in order to suitably control blooming of the nonionic surfactant to more suitably obtain the beneficial effect, the polymerization degree (b in the formula (I)) of the polypropylene oxide block is preferably 100 or less, more preferably 10 to 70, further more preferably 10 to 60, particularly preferably 20 to 60, most preferably 20 to 45. For the same reason, the number of polyethylene oxide units added (a + c in formula (I)) is preferably 100 or less, more preferably 3 to 65, further more preferably 5 to 55, particularly preferably 5 to 40, most preferably 10 to 40. When the polymerization degree of the polypropylene oxide block and the number of added polyethylene oxide units are within the above ranges, blooming of the nonionic surfactant can be suitably controlled, and the advantageous effects can be more suitably obtained.

Examples of the Pluronic type nonionic surfactants include Pluronic series available from BASF (japan), Newpol PE series available from sanyo chemical corporation, Adeka Pluronic L or F series available from asahi electric and chemical industries, Epan series available from japanese first industrial pharmaceutical company, and Unilub or Pronon series available from japanese oil company. These may be used alone or in combination of two or more.

The SP value of the nonionic surfactant is 9.0 or more, preferably 9.1 or more, more preferably 9.2 or more, but preferably 12 or less, more preferably 11 or less, and still more preferably 10.5 or less. When the SP value is within the above range, advantageous effects can be more suitably obtained.

As used herein, the term "SP value" refers to a Solubility parameter calculated using the structure of a compound by the Hoy method described, for example, in K.L. Hoy, "Table of Solubility Parameters," Solvent and Coatings Materials Research and Development Department, Union Carbits Corp. (1985).

The amount of the nonionic surfactant having an SP value of 9.0 or more is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and further more preferably 0.8 part by mass or more, but is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and further preferably 2 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount is within the above range, the ratio (a)/(b) and the mohs hardness (a) and the mohs hardness (b) can be adjusted within predetermined ranges, and more suitable overall grip performance can be obtained without impairing adhesion.

The rubber composition may comprise at least one silica.

Examples of the silica include dry silica (anhydrous silica) and wet silica (hydrous silica). Among these, wet-process silica is preferable because it has a large amount of silanol groups. These may be used alone or in combination of two or more.

Nitrogen adsorption specific surface area (N) of silica₂SA) is preferably 80m²A value of 110m or more, more preferably 110m²A total of 300m or more²(ii) less than g, more preferably 280m²(ii) less than g, more preferably 200m²The ratio of the carbon atoms to the carbon atoms is less than g. When N2SA is within the above range, the advantageous effects tend to be better obtained.

N of silicon dioxide₂SA is measured by the BET method according to ASTM D3037-81.

Silica is available from degussa, luodia, dongtoa siliconization co, japan solvi, german corporation, etc.

The amount of silica is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, further more preferably 70 parts by mass or more, and particularly preferably 90 parts by mass or more, but is preferably 200 parts by mass or less, more preferably 160 parts by mass or less, further more preferably 150 parts by mass or less, and particularly preferably 130 parts by mass or less, with respect to 100 parts by mass of the rubber component. When the amount of silica is within the above range, the advantageous effects tend to be better obtained.

In the rubber composition, the amount of silica is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the filler (reinforcing filler). The upper limit is not limited and may be 100 mass%.

Preferably, the rubber composition comprising silica further comprises at least one silane coupling agent.

Any silane coupling agent may be used, examples including: sulfide-based silane coupling agents, for example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (, Bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silane coupling agents such as gamma-glycidoxypropyltriethoxysilane and gamma-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chlorine-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercial products available from degussa, magie, shin-yue silicone, tokyo chemical industry co, Azmax co, dow corning dongli co. These may be used alone or in combination of two or more. Among these, sulfide-based silane coupling agents are preferable because they tend to obtain advantageous effects better.

The amount of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, but preferably 20 parts by mass or less, more preferably 15 parts by mass or less, relative to 100 parts by mass of silica. When the amount of the silane coupling agent is within the above range, the advantageous effects tend to be better obtained.

The rubber composition may comprise at least one carbon black as reinforcing filler.

Any carbon black may be used, examples include: n134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. These may be used alone or in combination of two or more.

Nitrogen adsorption specific surface area (N) of carbon black₂SA) is preferably 80m²A value of 100m or more, more preferably²A ratio of one to more than g, preferably 400m²A ratio of the total amount of the components to the total amount of the components is 300m or less²A ratio of not more than g, more preferably 150m²A ratio of 130m or less in particular²The ratio of the carbon atoms to the carbon atoms is less than g. When N is present₂When SA is within the above range, the advantageous effects tend to be obtained better.

Herein, N of carbon black₂SA according to JIS K6217-2: 2001, and then measured.

Carbon black is available from Asahi carbon Co., Ltd, Kabet (Japan), east China carbon Co., Ltd, Mitsubishi chemical corporation, Shiwang Kabushiki Kaisha, Columbia carbon, etc.

The amount of carbon black is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, but is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, more preferably 40 parts by mass or less, particularly preferably 20 parts by mass or less, and most preferably 10 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of carbon black is within the above range, the advantageous effects can be more suitably obtained.

The rubber composition may comprise at least one of aluminium hydroxide, magnesium sulphate, alumina, magnesium oxide, talc or diatomaceous earth as reinforcing filler. In this case, better grip performance tends to be obtained.

Nitrogen adsorption specific surface area (N) of aluminum hydroxide₂SA) is preferably 3m²G to 60m²/g。N₂The lower limit of SA is preferably 6m²A value of at least g, more preferably 12m²A ratio of the total amount of the components is 50m or more²A ratio of 40m or less per gram²A ratio of 20m or less per gram²The ratio of the carbon atoms to the carbon atoms is less than g. When N is present₂When SA is within the above range, the advantageous effects tend to be obtained better. N of aluminum hydroxide₂SA is measured by the BET method according to ASTM D3037-81.

The amount of the aluminum hydroxide is preferably 3 parts by mass or more, more preferably 4 parts by mass or more, but preferably 60 parts by mass or less, more preferably 50 parts by mass or less, further more preferably 40 parts by mass or less, particularly preferably 20 parts by mass or less, and most preferably 15 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of aluminum hydroxide is within the above range, the advantageous effects tend to be more suitably obtained.

The rubber composition may comprise at least one stearic acid.

The stearic acid may be a conventional stearic acid, and is available, for example, from Nichigan oil Co., Ltd, Kao, Fuji film and Wako pure chemical industries, Ltd.

The amount of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, but preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of stearic acid is within the above range, the beneficial effect tends to be better obtained.

The rubber composition may comprise at least one zinc oxide.

The zinc oxide may be a conventional zinc oxide, and is available, for example, from Mitsui Metal mining, Toho Zinc, white Water science, Kangsui chemical industries, or Kanghua chemical industries.

The amount of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, but preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of zinc oxide is within the above range, the advantageous effects tend to be better obtained.

The rubber composition may comprise at least one sulfur.

Examples of sulfur include those commonly used in the rubber industry, such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. These may be used alone or in combination of two or more.

Sulfur is available from Hello chemical industries, light Jingze sulfur, four kingdom chemical industries, Flexsys, Japan Dry industries, Fine Jing chemical industries, etc.

The amount of sulfur is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, but is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and further more preferably 3 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of sulfur is within the above range, the advantageous effects tend to be better obtained.

The rubber composition may comprise at least one vulcanization accelerator.

Examples of the vulcanization accelerator include: thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazyl disulfide and N-cyclohexyl-2-benzothiazylsulfenamide; thiuram based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD) and tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, N-tert-butyl-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide and N, N' -diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine and orthotolylbiguanide. These may be used alone or in combination of two or more. Among these, sulfenamide-based vulcanization accelerators and/or guanidine-based vulcanization accelerators are preferable, and a combination of sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators is more preferable for more suitably obtaining the advantageous effects.

The vulcanization accelerator is commercially available from Kayokou chemical industries, Dainixing chemical industries, and the like.

The amount of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, but preferably 10 parts by mass or less, more preferably 7 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the vulcanization accelerator is within the above range, the advantageous effects tend to be more obtained.

In addition to the above components, the rubber composition may contain additives commonly used in the tire industry, including, for example, organic peroxides and fillers such as calcium carbonate, clay, and mica. The amount of each additive is preferably 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

For example, the rubber composition can be prepared as follows: the components are kneaded in a rubber kneading machine (e.g., an open roll mill or a Banbury mixer), and the kneaded mixture is vulcanized as necessary.

The kneading conditions were as follows: in the basic kneading step of kneading the additives other than the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 100 to 180 ℃, preferably 120 to 170 ℃; in the final kneading step of kneading the vulcanizing agent and the vulcanization accelerator, the kneading temperature is usually 120 ℃ or less, preferably 80 ℃ to 110 ℃. Then, the composition obtained by kneading the vulcanizing agent and the vulcanization accelerator is usually vulcanized by, for example, press vulcanization. For passenger vehicle tires, the vulcanization temperature is generally from 140 ℃ to 190 ℃, preferably from 150 to 185 ℃; for truck and passenger vehicle tires, the curing temperature is generally from 130 to 160 ℃ and preferably from 135 to 155 ℃. For passenger car tires, the cure time is typically 5 to 15 minutes; for truck and passenger tire curing times are typically 25 to 60 minutes.

The rubber composition is used for a tread of a tire. For use in a tread (including a cap and a base), the rubber composition can be suitably used for the cap.

The tire (pneumatic tire, etc.) of the present invention can be produced from the above rubber composition by a conventional method. Specifically, the unvulcanized rubber composition may be extruded into the shape of a tire component (e.g., a tread), and then assembled with other tire components in a conventional manner in a tire building machine to produce an unvulcanized tire, which may then be heated and pressurized in a vulcanizing machine to produce a tire.

Here, the tread of the tire at least partially comprises a rubber composition. The entire tread may comprise the rubber composition. In other words, the tread rubber is at least partially formed of the rubber composition, and the entire tread rubber may be formed of the rubber composition.

For passenger vehicle tires, the tread rubber has a thickness in the tire radial direction of 5mm to12 mm; for truck and passenger tires, the tread rubber has a thickness in the tire radial direction of 7mm to 25 mm. The present application focuses on the physical properties of the surface layer to a depth of up to 1mm and is therefore applicable to any application.

The tire may be suitably used as a passenger car tire, a large SUV tire, a truck and bus tire, or a two-wheel tire, or a racing tire, a studless winter tire (winter tire), an all season tire, a run flat tire, an aircraft tire, a mining tire, or the like.

(second aspect of the invention)

Shore (a) Hs (shore a hardness), which is conventionally used in the tire art, is measured at a pin length of about 2mm, and is also related to rubber testing and tensile properties, and is therefore commonly used as an indicator of tire handling performance. However, studies by the present inventors have shown that Hs may not be correlated with grip performance (particularly initial grip performance). Therefore, there is no conventional technique for evaluating grip performance (especially initial grip performance).

This problem is solved by a second aspect of the present invention, which relates to a method for evaluating the grip performance of a tire based on the above findings.

Specifically, the method of evaluating the grip performance of a tire of the second aspect of the present invention includes:

preparing a test piece cut from a tire tread rubber, the test piece having a ground contact surface forming a tire tread contact portion and a measurement surface extending perpendicular to the ground contact surface and in a tire radial direction; and

the mohs hardness of the measurement face of the specimen prepared in the specimen preparation step is measured in the tire radial direction using a microhardness meter or a film hardness meter.

< sample preparation step >

In the sample preparation step, rubber blocks may be cut from the tire tread rubber, as shown in fig. 4. The cutting is performed so that the ground contact surface (tread surface 20 in fig. 4) forming the tire tread contact portion remains in the rubber block. The cut rubber block can then be used to prepare a test piece shaped to have a ground contact surface (tread surface 20 in fig. 4) forming a tire tread contact portion and a measurement plane extending perpendicular to the ground contact surface and in the tire radial direction (see fig. 4). With respect to the measurement surface of the sample, there are four possible surfaces in total, including two surfaces shown in fig. 4 (measurement surface 30 in fig. 4) and two surfaces not shown in the drawings (i.e., hidden back surfaces), and any one of these surfaces may be used as the measurement surface.

Here, the rubber block may be cut from any portion of the tire as long as the cut rubber block has the tread surface 20, as shown in fig. 4(a) to (c). The rubber blocks may be cut in the tire circumferential direction or at an angle different from the tire circumferential direction.

The measuring surface can be formed by cutting out a rubber piece or by further processing the cut-out rubber piece, as shown in fig. 4.

< measurement step >

In the measurement step, the mohs hardness of the measurement face of the specimen prepared in the specimen preparation step may be measured in the tire radial direction using a microhardness meter or a film hardness meter.

Here, the mahalanobis hardness can be measured at any interval. Measurements at intervals of 20 μm are preferred as this provides efficiency and accuracy.

Any microhardness meter may be used, examples include an indenter microhardness meter, TI-950Triboindenter from Hysitron, Picoderator HM500 from Fischer, DUH-W201S dynamic ultra microhardness meter from Shimadzu corporation, HM-2000 from Fischer Instruments, and Fischer scope H100 from Fischer Instruments.

Any film durometer may be used, examples include a Mayer durometer, an ENT-2100 nanoindenter from Elionix, and an MHA-400 film durometer from Japan electric company. Among these, a film durometer is preferable.

The mahalanobis hardness can be measured in any region, but is preferably measured in a region where the measurement plane corresponds to a tire radial depth of 10 μm to 200 μm from the tire surface. In this case, the grip performance can be effectively evaluated.

The surface roughness (μm) of the measurement surface is preferably 2 or less, more preferably 1 or less, and further more preferably 0.5 or less, with no limitation on the lower limit. In this case, the grip performance can be evaluated more appropriately.

Herein, the term "surface roughness" refers to the centerline surface roughness Ra defined in JIS B0601-2001.

The load applied to the indenter is preferably 30mgf or more, more preferably 50mgf or more, but preferably 200mgf or less, more preferably 100mgf or less. In this case, the grip performance can be evaluated more appropriately.

The depth of the indenter is preferably 10 μm or less, more preferably 8 μm or less, but preferably 2 μm or more, more preferably 5 μm or more, although it can be controlled as appropriate. In this case, the grip performance can be evaluated more appropriately.

Here, in order to reduce the oxidation of air on the measurement surface, it is preferable that before the mahalanobis hardness is measured, the surface of the measurement surface of the sample prepared in the sample preparation step is removed to a depth of 20 μm or more (preferably 200 μm or more, more preferably 500 μm or more, without limitation on the upper limit) to form a new measurement surface; the mahalanobis hardness of the new measurement face was measured. In this case, the grip performance can be evaluated more appropriately.

Further, in order to reduce the oxidation of air on the measurement surface, it is preferable to measure the mahalanobis hardness within 6 hours after the measurement surface to be actually measured is formed.

< evaluation step >

In the evaluation step, the grip performance may be evaluated based on the mahalanobis hardness distribution measured in the measurement step. Specifically, the grip performance (particularly, the grip performance before and after running-in) can be evaluated based on whether or not the minimum mahalanobis hardness (a) and the maximum mahalanobis hardness (b) in a region having a radial depth of the tire from the tire surface of 10 μm to 200 μm satisfy the relation (I).

As described above, the method of evaluating the grip performance of a tire of the second aspect of the present invention includes: preparing a test piece cut from a tire tread rubber, wherein the test piece has a ground contact surface forming a tire tread contact portion and a measurement surface extending perpendicular to the ground contact surface and in a tire radial direction; and measuring the mohs hardness of the measurement face of the specimen prepared in the specimen preparation step in the tire radial direction using a microhardness meter or a film hardness meter. Thus, the method can evaluate the grip performance of the tire (particularly the grip performance before and after break-in).

Examples

Aspects of the present invention will be described below with reference to examples, but the present invention is not limited to the examples.

The chemicals used in examples and comparative examples are listed below.

< SBR1 >: n9548 (styrene content: 35% by mass, vinyl content: 18% by mass, oil content: 37.5 parts by mass (per 100 parts by mass of rubber solids)) commercially available from Ruizui;

< SBR2 >: NS612 (styrene content: 15% by mass, vinyl content: 30% by mass) was purchased from REQUEST;

< BR >: BUNA-CB25 (rare earth-catalyzed BR synthesized using Nd catalyst, vinyl content: 0.7 mass%, cis content: 97 mass%, SP value: 8.2) purchased from Langsheng;

<carbon black>：SHOBLACKN220(N₂SA：114m²Per gram), from cabot (japan);

<silicon dioxide 1>：ULTRASIL VN3(N₂SA：175m²(g), purchase of the win-win Chuangdegassy;

<silicon dioxide 2>：Z115Gr(N₂SA：115m²Per gram) from luodiya;

<aluminum hydroxide>：Apyral 200(N₂SA：15m²Per gram) from Nabaltec;

< silane coupling agent >: si75 (bis (3-triethoxysilylpropyl disulfide)), purchased from won engorge gutosie;

< α -methylstyrene resin >: SYLVARES SA85 (copolymer of alpha-methylstyrene and styrene, softening point: 85 ℃), available from Arizona chemical;

< terpene resin >: YS resin TO125 (aromatic modified terpene resin, softening point: 125 ℃ C.), available from Anyuan chemical Co., Ltd;

< aromatic oil >: AH-24 (aromatic process oil) available from Kyoto;

< liquid coumarone-indene resin >: NOVARES C10 (liquid coumarone-indene resin, softening point: 10 ℃ C.), available from Roots chemistry;

< surfactant >: NEWPOL PE-64(Pluronic type nonionic surfactant, PEG/PPG-25/30 copolymer, formula (I), wherein a + c is 25 and b is 30, SP value: 9.2) was purchased from sanyo chemical industries;

< WB16 >: WB16 (mixture of calcium fatty acid salt, fatty acid amide and fatty acid amide ester, ash: 4.5%) from Jiatuo;

< stearic acid >: stearic acid beads "TSUBAKI" from japan oil co;

< antioxidant 1 >: antigene 6C (6PPD, N- (1, 3-dimethylbutyl) N' -phenyl-p-phenylenediamine), available from Sumitomo chemical Co., Ltd;

< antioxidant 2 >: vulkanox 4030(77PD, N' -bis- (1, 4-dimethylpentyl) -p-phenylenediamine) available from langerhan;

< antioxidant 3 >: NORAC 224(TMQ, 2, 2, 4-trimethyl-1, 2-dihydroquinoline polymer), available from New chemical industries, Inc. in great interior;

< paraffin >: ozoace 0355, available from japan ceresin;

< microcrystalline wax >: Hi-Mic 1080 (branched paraffin content: 50.6% by mass based on 100% by mass of microcrystalline wax), available from Japan Fine wax Co., Ltd;

< Zinc oxide >: zinc oxide #2, available from white water science;

< Sulfur >: HK200-5 (powdered sulfur containing 5% oil), available from Mitsui chemical industries, Inc.;

< vulcanization accelerator 1 >: NOCCELER NS (N-tert-butyl-2-benzothiazolesulfenamide), available from New chemical industries, Inc.;

< vulcanization accelerator 2 >: NOCCELERD (diphenylguanidine), available from New chemical industries, Inc.

(examples and comparative examples)

According to each formulation shown in Table 2, chemicals other than sulfur and a vulcanization accelerator were kneaded at 150 ℃ for five minutes using a 1.7L Banbury mixer (Kobe Steel Co.) to obtain a kneaded mixture. Then, the kneaded mixture was kneaded with sulfur and a vulcanization accelerator in an open roll mill at 80 ℃ for 5 minutes to obtain an unvulcanized rubber composition.

The unvulcanized rubber composition is formed into the shape of a tread surface, and assembled with other tire components to obtain an unvulcanized tire. The unvulcanized tire was press-vulcanized at 170 ℃ for 10 minutes to obtain a tire (size: 225/50R17, thickness of tread rubber in the tire radial direction: 9 mm).

To simulate a new tire on the market, the tire was left in a warehouse with an air temperature of 20 to 40 ℃ for 3 months and then used as a test tire.

The test tires prepared as above were evaluated as follows. Table 2 shows the results.

(Ma hardness)

Rubber blocks were cut from the tread rubber of the test tires. The cutting is performed so that the ground contact surface forming the tire tread contact portion remains in the rubber block. Then, a test piece shaped to have a ground contact surface forming a tire tread contact portion and a measurement face extending perpendicular to the ground contact surface and in the tire radial direction was prepared using the cut rubber block (see fig. 4).

Further, in order to reduce the oxidation of air, the surface of the measurement face of the sample was removed to a depth of about 500 μm to form a new measurement face before the measurement (1 hour before the measurement). Then, in a region corresponding to a newly measured surface having a depth of 10 μm to 200 μm in the tire radial direction from the tire surface, the mahalanobis hardness is measured in the tire radial direction. Then, the minimum mahalanobis hardness (a) and the maximum mahalanobis hardness (b) in the region having a tire radial depth of 10 μm to 200 μm from the tire surface were measured.

The mahalanobis hardness is measured as follows.

The measurement was performed using an ENT-2100 nanoindenter (film hardness tester) available from eionix corporation.

The measurement conditions were as follows:

temperature: 23 deg.C

Specimen thickness (thickness in indentation direction of Berkovich indenter): 2mm

Surface roughness of the measurement face: 0.2

And F, loading: 50mgf

Angle α of Berkovich indenter: 65.03 degree

Material of Berkovich indenter: DLC (Diamond-like carbon) coated iron

Indentation depth h: 7 μm

Based on the indentation depth h and indenter angle α, the area as (h) (the surface area of the indenter at depth h (the projected contact area between the indenter and the test piece)) is calculated using the following formula:

As(h)＝3×3^1/2×tanα/cosα×h²。

based on the load F (maximum test load) applied to the indenter and the area as (h), the mahalanobis hardness is calculated using the following formula:

mahalanobis hardness F/as (h).

(grip performance before running-in (wet grip performance))

A set of test tires was mounted on each wheel of an automobile (2500cc, 4WD, manufactured in japan). The driver drives the car on the wet asphalt and subjectively evaluates the grip, the reactivity, the deceleration at the time of braking, and the loop traveling performance. The results are expressed as an index (grip performance index before running-in) with respect to comparative example 1(═ 100). The higher the index, the better the grip performance before running-in (wet grip performance).

(grip performance after running-in (wet grip performance))

After evaluating the grip performance before running-in (wet grip performance), the driver further drives the automobile on the loop for 0.5 hour for about 70km to wear the tread surface to a depth of about 10 μm. Then, as an evaluation of the grip performance before break-in (wet grip performance), the driver subjectively evaluated the grip performance (after break-in).

The results are expressed as an index (grip performance index after running-in) with respect to comparative example 1(═ 100). The higher the index, the better the grip performance after running-in (wet grip performance).

[ Table 2]

Table 2 shows that the tires of examples containing the tread rubber satisfying the relation (I) exhibited satisfactory grip performance before and after running-in.

Table 2 also shows the following results.

The incorporation of microcrystalline wax tends to lower the mahalanobis hardness (a) at higher phenylenediamine-based antioxidant contents or at lower paraffin contents.

At higher levels of liquid plasticizer and higher levels of surfactant, the phenylenediamine-based antioxidants tend to be more uniformly distributed on the surface, resulting in a further reduction in the mahalanobis hardness (a).

When the content of the liquid plasticizer is low, the influence of the incorporation of the phenylenediamine-based antioxidant is small, and the mahalanobis hardness increases (a).

The use of surfactants, microcrystalline waxes, or other additives tends to reduce the mahalanobis hardness (a) even when the liquid plasticizer content is low and the resin content is high.

Higher silica content tends to be accompanied by higher liquid plasticizer content, resulting in a decrease in the mahalanobis hardness (a).

Next, the surface of the measurement face of each sample prepared in comparative example 1, example 1 and example 01 was removed to a depth of 500 μm, and a new measurement face before measurement (before 1 hour) was formed. Then, the Mahalanobis hardness was measured in a region corresponding to a new measurement surface having a depth of 20 μm to 200 μm in the tire radial direction from the tire surface at an interval of 20 μm in the tire radial direction from the tire surface. Here, other conditions are as described above. The results are shown in FIG. 1.

As shown in fig. 1, at 20 μm from the tire surface, some embodiments show a significant hardening with a significant difference caused by oxygen, ozone or UV degradation. Such deterioration does not occur at 40 to 60 μm from the tire surface, and the hardness at 40 to 60 μm from the tire surface is lower than the hardness at 200 μm from the tire surface. Presumably because it may be a layer rich in plasticizer and resin components.

Although the tire is worn, since the actual contact area with the road surface is 1/10000, when the running temperature reaches 60 ℃ or more, the surface layer deteriorates and some components are deposited and exuded from the inside, presumably always reproducing the same phenomenon as a new tire.

The grip performance (particularly, grip performance before and after running-in) can be evaluated based on whether or not the minimum mahalanobis hardness (a) and the maximum mahalanobis hardness (b) in a region having a radial depth of the tire from the tire surface of 10 μm to 200 μm satisfy the relation (I).

List of reference numerals

2: tyre for vehicle wheels

4: tread

20: surface of tread

22: ditch (I)

30: measuring surface

Position a: a position having a tire radial depth of 10 μm from the tire surface

Position b: position of 200 μm in tire radial depth from the tire surface