阅读说明：本技术 橡胶组合物和轮胎 (Rubber composition and tire ) 是由 鹫头健介 于 2020-05-15 设计创作，主要内容包括：本公开旨在提供橡胶组合物和轮胎,所述橡胶组合物和轮胎提供就湿抓地性能和干抓地性能而言的改进的整体性能。本公开涉及橡胶组合物,所述橡胶组合物的硬度随水可逆地变化且满足以下关系式(1)和(2)：干燥时的硬度-水润湿时的硬度≥1 (1)式中,各硬度表示橡胶组合物在25℃下的JIS-A硬度；以及干燥时在70℃下的tanδ≥0.18 (2)式中,70℃下的tanδ表示在70℃、10％的初始应变、2％的动态应变和10Hz的频率下测量的损耗角正切。(The present disclosure aims to provide rubber compositions and tires that provide improved overall performance in terms of wet and dry grip performance. The present disclosure relates to a rubber composition whose hardness reversibly changes with water and satisfies the following relational formulae (1) and (2): hardness at drying-hardness at wetting ≥ 1(1) where each hardness represents JIS-A hardness of the rubber composition at 25 ℃; and tan delta at 70 ℃ when dried is not less than 0.18(2), wherein tan delta at 70 ℃ represents a loss tangent measured at 70 ℃, 10% initial strain, 2% dynamic strain and 10Hz frequency.)

1. A rubber composition comprising a rubber component and a rubber component,

wherein the hardness of the rubber composition reversibly changes with water and satisfies the following relational formulae (1) and (2):

hardness at drying-hardness at wetting ≥ 1(1)

Wherein each hardness represents JIS-A hardness of the rubber composition at 25 ℃; and

tan delta at 70 ℃ is not less than 0.18(2) when dried

In the formula, tan. delta. at 70 ℃ represents the loss tangent measured at 70 ℃, 10% initial strain, 2% dynamic strain and 10Hz frequency.

2. The rubber composition according to claim 1,

wherein the value of "hardness at drying-hardness at wetting with water" in the relational expression (1) is 4 or more.

3. The rubber composition according to claim 1 or 2,

wherein the value of "tan. delta. at 70 ℃ in the relational expression (2)" is 0.21 or more.

4. The rubber composition according to any one of claims 1 to 3,

wherein the rubber composition comprises at least one hydrophilic material.

5. The rubber composition according to any one of claims 1 to 4,

wherein the rubber composition comprises at least one isoprene-based rubber.

6. The rubber composition according to any one of claims 1 to 5,

wherein the rubber composition comprises at least one polybutadiene rubber.

7. The rubber composition according to any one of claims 1 to 6,

wherein the styrene-butadiene rubber content of the rubber composition is 95% by mass or less based on 100% by mass of at least one rubber component in the rubber composition.

8. The rubber composition according to any one of claims 1 to 7,

wherein the rubber composition satisfies the following relationship:

a styrene-butadiene rubber content >50 mass% based on 100 mass% of the rubber component > a polybutadiene rubber content based on 100 mass% of the rubber component > an isoprene-based rubber content based on 100 mass% of the rubber component.

9. The rubber composition according to any one of claims 1 to 8,

wherein the content of silica and carbon black in the rubber composition is each 20 parts by mass or more per 100 parts by mass of at least one rubber component in the rubber composition.

10. The rubber composition according to any one of claims 1 to 9,

wherein the rubber composition comprises at least one petroleum resin.

11. The rubber composition according to any one of claims 1 to 10,

wherein the rubber composition is used for a tread.

12. A tire having a tire component at least partially comprising the rubber composition of any one of claims 1 to 11.

13. The tire as set forth in claim 12,

wherein the tire component is a tread, and the thickness of the tread is more than 4 mm.

14. Tire according to claim 12 or 13,

wherein the tire member is a tread, and a ground contact ratio of the tread is 30% or more.

15. Tire according to any one of claims 12 to 14,

wherein the tire component is a tread having at least one of a groove that is continuous in the tire circumferential direction or a groove that is discontinuous in the tire circumferential direction.

Technical Field

The present disclosure relates to a rubber composition and a tire.

Background

In recent years, safety has become an increasingly important issue for all automobiles. This creates a need for further improvement in wet grip performance. Various studies have been made to improve wet grip performance, and many inventions relating to silica-containing rubber compositions have been reported (for example, patent document 1). In particular, the characteristics of the rubber composition in the tread portion in contact with the road surface greatly affect the wet grip performance. Therefore, various technical improvements of rubber compositions for tire applications (e.g., treads) have been proposed and put to practical use.

Disclosure of Invention

List of references:

patent document 1: JP2008-285524A

Technical problem

The present inventors have extensively studied and found that, although the wet grip performance of a tire is greatly improved with the technical improvement of a silica-containing rubber composition for a tread, a major technical problem such as a change in road conditions (from a dry road to a wet road or from a wet road to a dry road) resulting in a change in grip performance still remains, and thus there is room for improvement.

The inventors have made extensive studies on this problem and found that: when conventional rubber compounds change from a dry state, in which they are not wetted with water, to a so-called wet state, in which they are wetted with water, their hardness does not change or become harder as a result of cooling with water. Therefore, the road surface contact area may be reduced; therefore, wet grip performance tends to be reduced as compared with dry grip performance.

Accordingly, it has been found that the conventional techniques leave room for improvement in overall performance improvement in terms of wet grip performance and dry grip performance.

The present disclosure aims to solve this problem and to provide a rubber composition and a tire that provide improved overall performance in terms of wet grip performance and dry grip performance.

Means for solving the problems

The present disclosure relates to a rubber composition whose hardness reversibly changes with water and satisfies the following relational formulae (1) and (2):

hardness at drying-hardness at wetting ≥ 1(1)

Wherein each hardness represents JIS-A hardness of the rubber composition at 25 ℃; and

tan delta at 70 ℃ is not less than 0.18(2) when dried

In the formula, tan. delta. at 70 ℃ represents the loss tangent measured at 70 ℃, 10% initial strain, 2% dynamic strain and 10Hz frequency.

The value of "hardness at drying-hardness at wetting with water" in the relational expression (1) is preferably 2 or more, more preferably 3 or more, and still more preferably 4 or more.

The value of "tan δ at 70 ℃ during drying" in the relational expression (2) is preferably 0.19 or more, more preferably 0.20 or more, and still more preferably 0.21 or more.

Preferably, the rubber composition comprises at least one hydrophilic material.

Preferably, the rubber composition comprises at least one diene rubber and at least one polymer having carbon-carbon double bonds and heteroatoms.

Preferably, the heteroatom is at least one atom selected from the group consisting of: oxygen atom, nitrogen atom, silicon atom, sulfur atom, phosphorus atom and halogen atom.

When suspended in an amount of 1g/10mL of water, the polymer preferably contains at least 5 mass% of insolubles.

When suspended in an amount of 1g/10mL of tetrahydrofuran, the polymer preferably contains at least 5 mass% of insolubles.

The rubber composition preferably contains at least 5 parts by mass of the polymer relative to 100 parts by mass of at least one rubber component in the rubber composition.

Preferably, the rubber composition comprises at least one isoprene-based rubber.

Preferably, the rubber composition comprises at least one polybutadiene rubber.

The styrene-butadiene rubber content of the rubber composition is preferably 95% by mass or less based on 100% by mass of at least one rubber component in the rubber composition.

Preferably, the rubber composition satisfies the following relationship:

based on 100 mass% of the rubber component, the styrene-butadiene rubber content is more than 50 mass% > the polybutadiene rubber content is more than the isoprene rubber content.

The content of silica and carbon black in the rubber composition is each preferably 20 parts by mass or more with respect to 100 parts by mass of at least one rubber component in the rubber composition.

Preferably, the rubber composition comprises at least one petroleum resin.

Preferably, the rubber composition is used for a tread.

The present disclosure also relates to a tire having a tire component at least partially comprising the rubber composition.

Preferably, the tyre component is a tread.

Preferably, the tire component is a tread, the tread having a thickness of 4mm or more.

Preferably, the tire component is a tread, and the tread has a ground contact ratio (land ratio) of 30% or more.

Preferably, the tire member is a tread having at least one of a groove continuous in the tire circumferential direction or a groove discontinuous in the tire circumferential direction.

Advantageous effects of the invention

The hardness of the rubber composition of the present disclosure reversibly changes with water and satisfies the relational expressions (1) and (2). Such rubber compositions provide improved overall performance in terms of wet and dry grip performance.

Detailed Description

The hardness of the rubber composition of the present disclosure reversibly changes with water, and satisfies the following relational expressions (1) and (2). Thus, the rubber composition provides improved overall performance in terms of wet grip performance and dry grip performance.

Hardness at drying-hardness at wetting ≥ 1(1)

In this relational expression, each hardness represents JIS-A hardness of the rubber composition at 25 ℃.

Tan delta at 70 ℃ is not less than 0.18(2) when dried

In this relation, tan δ at 70 ℃ represents the loss tangent measured at 70 ℃, 10% initial strain, 2% dynamic strain and 10Hz frequency.

The rubber composition provides the above effects. The reason for this beneficial effect is not completely clear, but can be explained as follows.

The hardness of the rubber composition of the present disclosure reversibly changes with water and satisfies the relational expression (1). The relation (1) shows that the hardness is lower when wet than when dry. In other words, "the hardness of the rubber composition of the present disclosure reversibly changes with water and satisfies the relational expression (1)" means that the hardness of the rubber composition when wetted with water is lower than that when dried, and the hardness can reversibly change in the presence of water.

Therefore, when the road condition changes from dry to wet, the rubber composition is wetted with water, and the hardness is reduced, which makes it possible to reduce the reduction in grip performance (wet grip performance), thereby obtaining good grip performance (wet grip performance). This is considered to be because: if the hardness is kept suitable for dry road surfaces, sufficient gripping performance cannot be obtained on wet road surfaces that are more prone to slip; in contrast, the decrease in hardness leads to an increase in road surface contact area, which makes it possible to reduce the decrease in grip performance (wet grip performance), thereby obtaining good grip performance (wet grip performance).

On the other hand, when the road condition changes from wet to dry, the water-wet rubber composition dries and the hardness increases, which makes it possible to reduce the decrease in grip performance (dry grip performance) and thereby obtain good performance (dry grip performance). This is considered to be because: if the hardness is maintained to be suitable for a wet road surface, sufficient grip performance cannot be obtained on a dry road surface that is not liable to slip; in contrast, an increase in hardness (suitable for dry roads) makes it possible to reduce a decrease in grip performance (dry grip performance), thereby obtaining good grip performance (dry grip performance).

Therefore, the hardness of the rubber composition reversibly changes with water and further satisfies the relation (1), the rubber composition can provide an appropriate hardness according to the water condition on a road surface (wet road surface or dry road surface), thereby providing improved overall performance in terms of wet grip performance and dry grip performance.

Further, the rubber composition of the present disclosure can provide better wet grip performance and dry grip performance by satisfying the relation (2).

Thus, the hardness of the rubber composition of the present disclosure reversibly changes with water and satisfies the relations (1) and (2), which can provide improved overall properties in terms of wet grip performance and dry grip performance.

As described above, the present disclosure addresses the problem (object) of improving overall performance in terms of wet and dry grip performance by formulating a rubber composition that satisfies the parameters of the relationships (1) and (2). In other words, the parameters do not define the problem (objective) herein of improving the overall performance in terms of wet and dry grip performance. In order to solve this problem, a rubber composition satisfying the parameters of the relational expressions (1) and (2) is formulated. Therefore, parameters satisfying the relations (1) and (2) are basic features.

Herein, the hardness and tan δ of the rubber composition refer to the hardness and tan δ of the vulcanized rubber composition, respectively. Further, tan δ was determined by subjecting the vulcanized rubber composition to a viscoelasticity test.

Herein, the phrase "hardness reversibly changes with water" means that the hardness of the (vulcanized) rubber composition reversibly increases or decreases depending on the presence of water. Here, it is sufficient that the hardness can be reversibly changed when the state of the rubber composition is changed (for example, as follows: drying → water wetting → drying). The rubber composition in the former dry state may or may not have the same hardness as the latter dry state.

Herein, the term "hardness at the time of drying" refers to the hardness of the (vulcanized) rubber composition in a dry state, specifically refers to the hardness of the (vulcanized) rubber composition after having been dried by the method described in the examples.

Herein, the term "hardness when wetted with water" refers to the hardness of the (vulcanized) rubber composition in a water-wet state, specifically to the hardness of the (vulcanized) rubber composition that has been wetted with water by the method described in the examples.

Herein, "vulcanized or thermoplastic rubber-determination of hardness-part 3 according to JIS K6253-3 (2012): durometer method ", the hardness (JIS-A hardness) of the rubber composition is measured (vulcanized) at 25 ℃ using A type A durometer.

Herein, the term "tan δ at 70 ℃ when dried" refers to tan δ at 70 ℃ of a (vulcanized) rubber composition in a dried state, specifically to tan δ at 70 ℃ of the (vulcanized) rubber composition after having been dried by the method described in the examples.

Herein, tan δ at 70 ℃ of the (vulcanized) rubber composition means the loss tangent measured at 70 ℃, 10% initial strain, 2% dynamic strain and a frequency of 10 Hz.

As shown in the relational expression (1), "hardness at drying-hardness at water wetting" [ ((vulcanized) rubber composition hardness in a dry state) - ((vulcanized) rubber composition hardness in a water wetting state) ] has a value of 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, particularly preferably 5 or more, most preferably 6 or more, further preferably 8 or more, further preferably 9 or more, further preferably 10 or more, further preferably 11 or more, further preferably 13 or more, further preferably 15 or more, further preferably 18 or more, further preferably 21 or more, further preferably 24 or more. The upper limit is not limited, but is preferably 50 or less, more preferably 40 or less, further preferably 30 or less, particularly preferably 28 or less, and most preferably 26 or less. When the value is within the above range, the advantageous effects can be more suitably achieved.

The "hardness at drying" ((vulcanized) rubber composition hardness in a dry state) can be suitably controlled within a range satisfying the relation (1). It is preferably 20 or more, more preferably 25 or more, further preferably 30 or more, particularly preferably 40 or more, most preferably 50 or more, further preferably 55 or more, further preferably 58 or more, further preferably 62 or more, further preferably 64 or more, but preferably 95 or less, more preferably 90 or less, further preferably 85 or less, particularly preferably 75 or less, most preferably 70 or less, further preferably 66 or less, further preferably 65 or less. When the hardness is within the above range, the advantageous effects can be more suitably achieved.

The "hardness upon water wetting" ((hardness of the vulcanized rubber composition in a water-wet state)) can be suitably controlled within a range satisfying the relation (1). It is preferably 20 or more, more preferably 25 or more, further preferably 30 or more, particularly preferably 35 or more, most preferably 40 or more, further preferably 43 or more, further preferably 45 or more, further preferably 46 or more, further preferably 49 or more, further preferably 50 or more, further preferably 51 or more, further preferably 53 or more, further preferably 55 or more, but preferably 80 or less, more preferably 70 or less, even more preferably 65 or less, even more preferably 62 or less, particularly preferably 61 or less, most preferably 60 or less, further preferably 59 or less, further preferably 56 or less. When the hardness is within the above range, the advantageous effects can be more suitably achieved.

As shown in the relational expression (2), "tan δ at 70 ℃ when dried" (tan δ at 70 ℃ of a (vulcanized) rubber composition in a dry state) is 0.18 or more, preferably 0.19 or more, more preferably 0.20 or more, even more preferably 0.21 or more, particularly preferably 0.22 or more, and most preferably 0.23 or more. The upper limit is not limited, but is preferably 0.60 or less, more preferably 0.40 or less, further preferably 0.30 or less, and particularly preferably 0.25 or less. When the tan δ is within the above range, the advantageous effects can be more suitably achieved.

By adding a hydrophilic material, particularly a compound capable of forming a reversible molecular bond (e.g., a hydrogen bond or an ionic bond) with water, a rubber composition can be obtained, the hardness of which changes as shown in relation (1) and can reversibly change with water.

The hydrophilic material can be any compound capable of forming a reversible molecular bond (e.g., hydrogen or ionic bond) with water, including, for example, heteroatom-containing compounds.

The production guidelines satisfying the above parameters will be described in more detail below. When the rubber composition contains at least one rubber component (including diene rubber) in combination with a polymer (having a carbon-carbon double bond and a hetero atom), hardness that varies as shown in relation (1) and reversibly varies with water can be achieved.

This is because: the heteroatoms in the rubber composition may form reversible molecular bonds (e.g., hydrogen or ionic bonds) with water, resulting in a decrease in hardness of the rubber composition in a water-wet state.

Furthermore, due to this combination, the polymer is crosslinked, fixed to the rubber component through its carbon-carbon double bond during vulcanization. This can suppress the polymer from being released from the rubber component, thereby suppressing the polymer from being precipitated on the rubber surface. Therefore, the deterioration of the grip performance (wet grip performance, dry grip performance) can also be reduced.

Further, tan δ at 70 ℃ upon drying can be controlled by the type and amount of chemicals (particularly, rubber component, filler, softener, resin, sulfur, vulcanization accelerator, silane coupling agent) added to the rubber composition. For example, tan δ at 70 ℃ tends to be reduced by using a softening agent (e.g., resin) having low compatibility with rubber components, or by using an unmodified rubber, or by increasing the amount of filler, or by increasing the amount of oil as a plasticizer, or by reducing the amount of sulfur, or by reducing the amount of vulcanization accelerator, or by reducing the amount of silane coupling agent.

Further, the hardness at the time of drying can be controlled by the type and amount of chemicals (particularly, rubber component, filler, softener such as oil and resin) added to the rubber composition. For example, by increasing the amount of the softening agent, the hardness at the time of drying tends to decrease; by increasing the amount of filler, the hardness upon drying tends to increase; by reducing the amount of sulfur, the hardness upon drying tends to decrease. The hardness on drying can also be controlled by varying the amounts of sulfur and vulcanization accelerators. More specifically, increasing the amount of sulfur tends to increase the hardness upon drying; increasing the amount of vulcanization accelerator tends to increase the hardness upon drying.

More specifically, when the hardness at the time of drying is controlled within a desired range and a hydrophilic material, preferably at least one rubber component (including a diene rubber) is further incorporated in combination with a polymer (having a carbon-carbon double bond and a hetero atom), the rubber composition achieves a hardness that varies as shown in relation (1) and reversibly varies with water, while tan δ at 70 ℃ at the time of drying can be adjusted within a desired range. Further, the amount of filler may be increased to increase tan δ at 70 ℃ when dried.

As another method for allowing the rubber composition to achieve hardness that changes as shown in relation (1) and reversibly changes with water, when the rubber composition contains a combination of at least one rubber component (including diene rubber) and a polymer (having a carbon-carbon double bond and a hetero atom), the polymer is crosslinked through its carbon-carbon double bond during vulcanization, being fixed to the rubber component. This can suppress the polymer from being detached from the rubber component, thereby allowing the rubber composition to achieve a hardness that changes as shown in relation (1) and reversibly changes with water.

If the polymer does not have carbon-carbon double bonds, it may be released into water when the rubber composition is contacted with water, and thus a reversible change in hardness does not occur.

Further, another method for allowing the rubber composition to achieve hardness that changes as shown in relation (1) and reversibly changes with water is to reversibly break or reform ionic bonds between rubber molecules, for example, by adding water or drying. More specifically, when the rubber composition contains a combination of a rubber (containing halogen or oxygen) and a compound (containing metal, metalloid or nitrogen), the rubber composition realizes a hardness that changes as shown in relation (1) and reversibly changes with water. This is because; due to this combination, cations derived from metal, metalloid or nitrogen and anions derived from halogen or oxygen form ionic bonds between rubber molecules, and then the ionic bonds are broken by addition of water and reformed by drying water, resulting in a decrease in hardness when wetted with water and an increase in hardness when dried.

The chemicals that can be used are described below.

Examples of the rubber component include diene rubbers such as isoprene-based rubbers, polybutadiene rubbers (BR), styrene-butadiene rubbers (SBR), styrene-isoprene-butadiene rubbers (SIBR), acrylonitrile-butadiene rubbers (NBR), Chloroprene Rubbers (CR), and butyl rubbers (IIR). The rubber component may be used alone or in combination of two or more. Among these, diene rubbers are preferable, isoprene rubbers, BR and SBR are more preferable, and SBR is even more preferable. It is also preferable that: a combination of isoprene-based rubber and SBR, a combination of BR and SBR, or a combination of isoprene-based rubber, BR and SBR.

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 amount of the diene rubber is preferably 20% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, most preferably 90% by mass or more, and may be 100% by mass based on 100% by mass of the rubber component. When the amount of the diene rubber is within the above range, the advantageous effects tend to be more preferably achieved.

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

The styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and further more preferably 20% by mass or more, but is preferably 50% by mass or less, more preferably 40% by mass or less, and more preferably 30% by mass or less. When the styrene content is within the above range, the advantageous effects tend to be more suitably achieved.

The vinyl content of SBR is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 40% by mass or more, and most preferably 50% by mass or more, but preferably 75% by mass or less, and more preferably 65% by mass or less. SBR having a vinyl content within the above range tends to have good compatibility with BR, and thus tends to more suitably achieve advantageous effects.

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). Examples include: 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 in the main chain; a main chain and chain end-modified SBR in which both the main chain and the chain end have a functional group (for example, a main chain and chain end-modified SBR in which the main chain has a functional group and at least one chain end is modified with a modifier); and chain-end modified SBR in which a hydroxyl group or an epoxy group is introduced by modification (coupling) with a polyfunctional compound having two or more epoxy groups in the molecule. 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. Among these, preferred is an amino group (preferably a hydrogen atom is replaced by C)₁-C₆Alkyl-substituted amino), alkoxy (preferably C)₁-C₆Alkoxy), alkoxysilyl (preferably C)₁-C₆Alkoxysilyl) 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 20% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more, but is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on 100% by mass of the rubber component. When the amount is within the above range, the advantageous effects tend to be more achieved.

Any BR may be used. Examples include those commonly used in the tire industry. These may be used alone or in combination of two or more.

The cis content of BR is preferably 90 mass% or more, more preferably 95 mass% or more, and further preferably 97 mass% or more. The upper limit is not limited and may be 100 mass%. When the cis content is within the above range, the advantageous effects tend to be more suitably achieved.

The BR can be unmodified BR or modified BR. Examples of the modified BR include those into which the above-mentioned functional groups are 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 70% by mass or less, more preferably 40% by mass or less, even 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 achieved.

Examples of the isoprene-based rubber include Natural Rubber (NR), polyisoprene rubber (IR), refined NR, modified NR and modified IR. NR may be those commonly used in the tire industry, such as SIR20, RSS #3, and 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, NR is preferable.

The amount of the isoprene-based rubber is preferably 3% by mass or more, more preferably 5% by mass or more, but preferably 60% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, based on 100% by mass of the rubber component. When the amount of the isoprene-based rubber is within the above range, the advantageous effects tend to be more suitably achieved.

The rubber composition preferably satisfies the following relationship:

based on 100 mass% of the rubber component, the styrene-butadiene rubber content is more than 50 mass% > the polybutadiene rubber content is more than the isoprene rubber content. In this case, the advantageous effects tend to be more appropriately achieved.

Herein, the weight average molecular weight (Mw) and the number average molecular weight (Mn) can be determined by Gel Permeation Chromatography (GPC) (GPC-8000 series, available from Tosoh Corp., detector: differential refractometer; column: TSKGEL SUPERMULTIPORE HZ-M, available from Tosoh Corp.) 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 more than one hydrophilic material.

As previously mentioned, the hydrophilic material may be any compound capable of forming a reversible molecular bond (e.g., hydrogen bond or ionic bond) with water, including, for example, a heteroatom-containing compound. Among these, compounds having a carbon-carbon double bond and a heteroatom are preferable, and polymers having a carbon-carbon double bond and a heteroatom are more preferable.

Carbon-carbon double bonds are necessary for crosslinking with diene rubbers. The number of such bonds is not limited.

The term "heteroatom" refers to an atom other than carbon and hydrogen atoms. It may be any heteroatom capable of forming a reversible molecular bond (e.g. hydrogen or ionic) with water. The hetero atom is preferably at least one atom selected from an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, a phosphorus atom and a halogen atom, more preferably an oxygen atom, a nitrogen atom and/or a silicon atom, and further preferably an oxygen atom. Furthermore, the hetero atom is preferably present in the main chain (skeleton) of the polymer, more preferably in the repeating unit of the polymer.

Examples of the structure or group having an oxygen atom include an ether group, an ester group, a carboxyl group, a carbonyl group, an alkoxy group, and a hydroxyl group. Among these, ether groups are preferable, and oxyalkylene groups are more preferable.

Examples of the structure or group having a nitrogen atom include amino groups (primary, secondary and tertiary), amide groups, nitrile groups and nitro groups. Among these, an amino group is preferable, and a tertiary amino group is more preferable.

Examples of the structure or group having a silicon atom include a silyl group, an alkoxysilyl group and a silanol group. Among these, a silyl group is preferable, and an alkoxysilyl group is more preferable.

Examples of the structure or group having a sulfur atom include a sulfide group, a sulfate group and a sulfo group, and a sulfate ester.

Examples of the structure or group having a phosphorus atom include a phosphate group and a phosphate ester.

Examples of the structure or group having a halogen atom include a halogeno group such as a fluoro group, a chloro group, a bromo group and an iodo group.

The term "oxyalkylene" refers to a group represented by- (AO) -, preferably by- (AO)_n-a group represented by (a), wherein n represents the number of repeating units.

The alkylene group a of the oxyalkylene group AO has preferably 1 or more, more preferably 2 or more, but preferably 10 or less, more preferably 8 or less, and further preferably 6 or less carbon atoms. When the carbon number of the alkylene group a of the oxyalkylene group AO is within the above range, the advantageous effect tends to be more suitably achieved.

The alkylene group a of the oxyalkylene group AO may be linear or branched, but is preferably branched to form a structure larger in volume so that the advantageous effects can be more suitably achieved.

To more suitably achieve the beneficial effect, AO is preferably C₂-C₃Oxyalkylene (oxyethylene (EO), oxypropylene (PO)) or linked to a branch R⁴C of (A)₂-C₃Oxyalkylene group (R4 represents a hydrocarbon group optionally having hetero atom), more preferably C₂-C₃Oxyalkylene radical and linking to a branch R⁴C of (A)₂-C₃A combination of oxyalkylene groups. Branched chain R⁴Preferably to a carbon atom adjacent to the oxygen atom.

As R⁴The optional hydrocarbon group having a hetero atom of (1) is not limited. The number of carbon atoms of the hydrocarbon group is preferably 1 or more, more preferably 2 or more, but preferably 10 or less, more preferably 6 or less, and still more preferably 4 or less. When the carbon number of the hydrocarbon group is within the above range, the advantageous effects tend to be more suitably achieved.

As R⁴Preferred examples of the optional hydrocarbon group having a hetero atom of (b) are groups represented by the following formula.

-CH₂-O-CH₂-CH＝CH₂

Even more preferably, the group represented by- (AO) -includes a group represented by the following formula (B), particularly preferably groups represented by the following formulae (a) and (B), optionally in combination with a group represented by the following formula (C).

When the polymer has at least two types of oxyalkylene groups, the oxyalkylene groups may be arranged in blocks or in random.

Among the polymers, preferred are polymers having a group (structural unit) of the formula (B), and more preferred are polymers having groups (structural units) of the formulae (a) and (B).

The amount of the group (structural unit) of the formula (B) is preferably 2 mol% or more, more preferably 5 mol% or more, but preferably 50 mol% or less, more preferably 40 mol% or less, further preferably 30 mol% or less, and particularly preferably 20 mol% or less, based on 100 mol% of the polymer.

The weight average molecular weight (Mw) of the polymer is preferably 10,000 or more, more preferably 50,000 or more, further preferably 100,000 or more, and particularly preferably 500,000 or more, but is preferably 3,000,000 or less, more preferably 2,500,000 or less, further preferably 2,000,000 or less, particularly preferably 1,500,000 or less, and most preferably 1,000,000 or less.

When suspended in an amount of 1g/10mL of water, the polymer preferably contains at least 5% by mass, more preferably at least 10% by mass, further preferably at least 30% by mass, particularly preferably at least 50% by mass, most preferably at least 70% by mass, further most preferably at least 80% by mass, and further most preferably at least 90% by mass of insoluble matter (water-insoluble matter). The upper limit of the amount of such insoluble matter is not limited.

The amount of such insolubles can be measured as described in the examples.

A larger amount of such insolubles indicates that when the rubber compound is wetted with water, the polymer is less soluble in water and therefore a reversible change in hardness can be more suitably achieved.

When suspended in an amount of 1g/10mL of tetrahydrofuran, the polymer preferably contains at least 5 mass%, more preferably at least 10 mass%, even more preferably at least 30 mass%, particularly preferably at least 50 mass%, most preferably at least 70 mass%, and even most preferably at least 90 mass% of insolubles (THF insolubles). The upper limit of the amount of such insoluble matter is not limited.

The amount of such insolubles can be measured as described in the examples.

Since the diene rubber is soluble in tetrahydrofuran, a polymer having a relatively large amount of tetrahydrofuran-insoluble matter is poor in compatibility with the diene rubber, and thus the effect of lowering the hardness upon water wetting tends to be sufficiently achieved.

The polymer may be a commercial product. Alternatively, they may be prepared by polymerizing heteroatom-containing monomers.

Any heteroatom containing monomer may be used. Examples of such a monomer having an oxygen atom include: ethers such as vinyl ether, alkoxystyrene, allyl glycidyl ether, ethylene oxide, propylene oxide, tetrahydrofuran; (meth) acrylic acid and esters or anhydrides thereof. Examples of such monomers having a nitrogen atom include: acrylonitrile, N-vinylcarbazole, carbamic acid, and caprolactam. Examples of such a monomer having a silicon atom include: alkoxysilylstyrenes and alkoxysilylvinyls.

When the heteroatom-containing monomer has no unsaturated bond, the heteroatom-containing monomer may be polymerized together with a monomer having a carbon-carbon double bond (for example, a conjugated diene monomer such as butadiene or isoprene; or a vinyl polymer such as styrene).

The polymerization may be carried out by any method, including known methods.

The amount of the polymer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, most preferably 40 parts by mass or more, further most preferably 50 parts by mass or more, further most preferably 60 parts by mass or more, particularly most preferably 70 parts by mass or more, further preferably 80 parts by mass or more, further preferably 90 parts by mass or more, further preferably 100 parts by mass or more, but preferably 150 parts by mass or less, more preferably 120 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the polymer is within the above range, the advantageous effects tend to be more preferably achieved.

The rubber composition may comprise more than one type of silica.

Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrous silicic acid). Wet silica is preferred because it contains 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) of 40m²A ratio of 60m or more, preferably 60m²A ratio of 80m or more, more preferably 80m²A value of 160m or more, more preferably 160m²More than g. N is a radical of₂SA is preferably 600m²A ratio of the total amount of the components to the total amount of the components is 300m or less²(ii) less than g, more preferably 250m²A specific ratio of 200m 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, SA tends to be more suitably realizedHas the beneficial effects.

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

Silica is available from degussa, luodia, dongtoa, sowell, german corporation, etc.

The amount of silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, particularly preferably 20 parts by mass or more, most preferably 30 parts by mass or more, further preferably 50 parts by mass or more, further preferably 60 parts by mass or more, further preferably 70 parts by mass or more, but is preferably 150 parts by mass or less, more preferably 140 parts by mass or less, further more preferably 120 parts by mass or less, particularly preferably 100 parts by mass or less, most preferably 90 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 more achieved.

The amount of silica in the rubber composition is preferably 10% by mass or more, more preferably 20% by mass or more, and further more preferably 30% by mass or more, based on 100% by mass of the filler (reinforcing filler). The upper limit is not limited, but is preferably 90% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. When the amount of the filler is within the above range, the advantageous effects tend to be more suitably achieved.

The silica-containing rubber composition preferably further contains 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 (trimethoxysilylethyl) sulfide, and the like, Bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide and 3-triethoxysilylpropyl methacrylic acid 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. For example, commercial products available from degussa, mezzanine, shin-to-go silicone, tokyo chemical industry co, AZmax, dow corning dongli corporation, and the like can be used. These may be used alone or in combination of two or more. Among these, sulfide-based silane coupling agents and mercapto-based silane coupling agents are preferable, and disulfide-based silane coupling agents having a disulfide bond such as bis (3-triethoxysilylpropyl) disulfide are more preferable, because the advantageous effects tend to be more achieved.

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 more preferably achieved.

The rubber composition may comprise more than one type of carbon black.

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 total of 150m or more²A ratio of 130m or less per gram²The ratio of the carbon atoms to the carbon atoms is less than g. When N is present₂With SA in the above range, the beneficial effects tend to be better achieved.

Herein, N of carbon black₂SA according to JIS K6217-2: 2001, measurement was performed.

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 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more, with respect to 100 parts by mass of the rubber component, but is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, further preferably 80 parts by mass or less, particularly preferably 60 parts by mass or less, and most preferably 50 parts by mass or less. When the amount of carbon black is within the above range, the advantageous effects tend to be more achieved.

The content of silica and carbon black in the rubber composition is each preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. The content of silica and carbon black in the rubber composition is each more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. When the amounts of silica and carbon black are within the above ranges, the advantageous effects tend to be more achieved.

The rubber composition may comprise more than one oil.

Examples of oils include: process oil, vegetable oil and mixtures thereof. Examples of the process oil include: paraffinic process oils, aromatic process oils, and naphthenic process oils. 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 seed oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Among these, process oils are preferred, and aromatic process oils are more preferred, because the advantageous effects can be well achieved.

The oil can be purchased from shinning corporation, Sanko Industrial Co., Ltd, Japan energy Co., Ltd, Oulisong, H & R, Fengkou Petroleum Co., Ltd, Japan Showa Shell oil Co., Ltd, Fuji K.K., and the like.

The amount of the oil is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further more preferably 20 parts by mass or more, but preferably 50 parts by mass or less, and more preferably 35 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the oil is within the above range, the advantageous effects tend to be more achieved. The amount of oil, if used, includes the amount of oil contained in the rubber (oil-extended rubber).

The rubber composition may comprise more than one resin.

Any resin commonly used in the tire industry may be used, examples include: rosin resins, coumarone-indene resins, α -methylstyrene resins, terpene resins, p-tert-butylphenol acetylene resins, acrylic resins, C5 resins and C9 resins. Commercial products available from Maruzhitian Kaisha, Sumitomo Bakelite Co.Ltd, Anyuan chemical Co.Ltd, Tosoh Kaisha, Rogue chemical, Pasfu, Arizona chemical, Ridongton chemical Co.Ltd, Japanese catalyst Kaisha, JXTG energy Co.Ltd, Mitsukawa chemical industry Co.Ltd, Taoka chemical Co.Ltd, Toyata synthetic Co.Ltd and the like can be used. These may be used alone or in combination of two or more. Among these, petroleum resins such as coumarone-indene resin, α -methylstyrene resin, p-tert-butylphenol acetylene resin, C5 resin, and C9 resin are preferable, and coumarone-indene resin is more preferable.

The softening point of the resin is preferably 30 ℃ or higher, more preferably 60 ℃ or higher, and still more preferably 80 ℃ or higher, but is preferably 200 ℃ or lower, more preferably 160 ℃ or lower, still more preferably 140 ℃ or lower, and particularly preferably 120 ℃ or lower. When the softening point is within the above range, the advantageous effects tend to be more suitably achieved.

Herein, the softening point of the resin is in accordance with JIS K6220-1: 2001 was measured using a ball and ring softening point measuring device, and was defined as the temperature at which the ball fell.

The amount of the resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, further more preferably 10 parts by mass or more, particularly preferably 20 parts by mass or more, most preferably 30 parts by mass or more, and even most preferably 40 parts by mass or more, but preferably 80 parts by mass or less, more preferably 60 parts by mass or less, with respect 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 more preferably achieved.

The rubber composition may comprise more than one wax.

Any wax may be used. Examples include petroleum waxes, such as paraffin wax and microcrystalline wax; naturally occurring waxes, such as vegetable waxes and animal waxes; and 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 waxes are preferred, and paraffin waxes are more preferred.

The wax can be purchased from Dainixin photochemical industry Co., Ltd, Japan wax Co., Ltd, Seiko chemical Co., Ltd, etc.

The amount of the wax is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, but preferably 20 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of the rubber component. When the amount of the wax is within the above range, the advantageous effects tend to be more preferably achieved.

The rubber composition may comprise more than 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; p-phenylenediamine antioxidants, such as N-isopropyl-N ' -phenyl-p-phenylenediamine, N- (1, 3-dimethylbutyl) -N ' -phenyl-p-phenylenediamine, and N, N ' -di-2-naphthyl-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, a p-phenylenediamine-based antioxidant or a quinoline-based antioxidant is preferable.

The antioxidant can be purchased from Seiko chemical Co., Ltd., Sumitomo chemical Co., Ltd., Innova chemical industry Co., Ltd., Furex, etc.

The amount of the antioxidant 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 the antioxidant is within the above range, the beneficial effects tend to be more achieved.

The rubber composition may comprise more than one type of stearic acid.

The stearic acid may be a conventional stearic acid, for example, a stearic acid available from Nichigan oil Co., Ltd, Kao corporation, Fuji film and Wako pure chemical industries, Ltd or Kara fatty acid Co., 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 effects tend to be more achieved.

The rubber composition may comprise more than one type of zinc oxide. The zinc oxide may be a conventional zinc oxide, and is available from Mitsui metal mining, Toho zinc corporation, white water science and technology, Kansai chemical industry co.

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 more achieved.

The rubber composition may contain more than 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 Kabushiki Kaisha, Furex, Japan Dry and technology industries, Mitsui chemical industry.

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, 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 more achieved.

The rubber composition may contain one or more vulcanization accelerators.

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 because the advantageous effects can be more suitably achieved.

The vulcanization accelerator is commercially available from Kakko chemical industries, Dai New photo chemical industries, etc.

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 achieved.

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 (e.g., calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica). The amount of such additives is preferably 0.1 to 200 parts by mass each relative to 100 parts by mass of the rubber component.

For example, the rubber composition can be prepared by kneading the components in a rubber kneader (e.g., open roll, Banbury mixer) and vulcanizing the kneaded mixture.

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 ℃, and 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 ℃. The composition obtained by kneading the vulcanizing agent and the vulcanization accelerator is usually vulcanized by, for example, press vulcanization. The vulcanization temperature is generally from 140 to 190 ℃ and preferably from 150 to 185 ℃. The vulcanization time is generally from 5 to 15 minutes.

The rubber composition can be used for tire components (i.e., as a rubber composition for a tire), such as a tread (cap tread), a sidewall, a base tread, an undertread, a shoulder, a clinch, a bead apex, a breaker cushion rubber, a carcass cord topping rubber, a barrier layer, a chafer, and an inner liner, and a side reinforcing layer of a run-flat tire. The rubber composition is particularly suitable for tire components (tread, sidewall, shoulder) which may come into contact with water, and more particularly for treads. In the case where the tread is composed of a cap tread and a base tread, the rubber composition can be suitably used for the cap tread.

Examples of tire components that may come into contact with water when the tire is new or during driving with worn tire include components located at the outermost surface of the tire (tread, sidewall, shoulders).

The tire (e.g., pneumatic tire) of the present disclosure can be made from the rubber composition by conventional methods. Specifically, the unvulcanized rubber composition containing the additive may be extruded into the shape of a tire member, particularly a tread (tread cap), as required, and then molded in a conventional manner in a tire molding machine and assembled with other tire members to obtain an unvulcanized tire, which may then be heated and pressurized in a vulcanizer to produce a tire.

It is sufficient that the tire component (e.g., tread) of the tire at least partially comprises the rubber composition. The rubber composition may be contained throughout the tire component.

The tire may be suitable for use as, for example, a tire for passenger cars, large SUVs, trucks, and buses or two-wheeled vehicles, or as a racing tire, winter tire (studless winter tire, snow tire, or studded tire), all season tire, run flat tire, airplane tire, or mining tire.

The thickness of the tread in the tire is preferably 4mm or more, more preferably 6mm or more, further preferably 8mm or more, and particularly preferably 11mm or more. When the thickness is within the above range, the advantageous effects tend to be better achieved. The upper limit is not limited, but is preferably 35mm or less, more preferably 25mm or less, further preferably 20mm or less, and particularly preferably 15mm or less.

The groove depth (the distance from the tire radial direction to the deepest portion of the groove) of the tread of a tire is typically about 70% of the tread thickness and is related to the tread thickness.

The tire preferably has a tread comprising a rubber composition and having a thickness of 4mm or more, the hardness of the rubber composition reversibly changing with water and satisfying the relations (1) and (2). Such tires provide more suitable improved overall performance in terms of wet and dry grip performance.

The tire provides the above effects. The reason for this beneficial effect is not completely clear, but can be explained as follows.

As described previously, the rubber composition which reversibly changes in hardness with water and further satisfies the relation (1) provides an appropriate hardness depending on the condition of water on a road surface (wet road surface or dry road surface), thus providing improved overall performance in terms of wet grip performance and dry grip performance. Further, the rubber composition of the present disclosure provides better wet grip performance and dry grip performance by satisfying the relation (2).

The thickness of the tread is related to the groove depth. Treads of greater thickness tend to have greater groove depths. Accordingly, wet grip performance may be improved by increasing the groove depth of the tread (i.e., increasing the thickness of the tread) for tread thickness considerations.

Therefore, increasing the tread thickness can improve wet grip performance. The tire (tread formed of a rubber composition having a thickness within a predetermined range) provides more suitable improved overall performance in terms of dry grip performance and wet grip performance.

Accordingly, the tire has a tread comprising a rubber composition whose hardness reversibly changes with water and satisfies the relations (1) and (2) and has a thickness within a predetermined range, and thus, provides more suitable improved overall performance in terms of dry grip performance and wet grip performance.

Further, by using a rubber compound whose hardness reversibly changes with water, it is possible to provide appropriate grip performance according to road conditions. Further, as the range of rubber hardness available for the tread becomes wider, the flexibility of tread design can be improved.

Herein, when the tread consists of a single layer, the thickness of the tread refers to: the length of the portion of the tire having the largest width of the layers in the radial direction of the tire. In the case of a multilayer tread, for example, the tread has two layers: tread cap and tread base, the thickness of the tread being: the length of the portion of the tread surface (located on the outer surface layer) having the largest width in the tire radial direction is in the tire radial direction.

The ground contact ratio of the tread in the tire is preferably 30% or more, more preferably 40% or more, further more preferably 50% or more, further preferably 75% or more, from the viewpoint of dry grip performance. From the viewpoint of wet grip performance, the upper limit is preferably 95% or less, more preferably 90% or less, and further preferably 85% or less.

Preferably, the tire has a tread comprising a rubber composition having a hardness reversibly changing with water and satisfying relational expressions (1) and (2) and a ground contact ratio of 30% or more. Such tires provide more suitable improved overall performance in terms of wet and dry grip performance.

The tire provides the above-described effects. The reason for this beneficial effect is not completely clear, but can be explained as follows.

As described previously, the rubber composition which reversibly changes in hardness with water and further satisfies the relation (1) provides an appropriate hardness depending on the water condition on a road surface (wet road surface or dry road surface), thus providing improved overall performance in terms of wet grip performance and dry grip performance. Further, the rubber composition of the present disclosure provides better wet grip performance and dry grip performance by satisfying the relation (2).

Further, treads having a higher ground contact ratio have improved dry grip performance, while treads having a lower ground contact ratio have improved wet grip performance. The tire (tread formed of a rubber composition and having a ground contact ratio within a predetermined range) provides more suitable improved overall performance in terms of dry grip performance and wet grip performance.

Therefore, the tire has a tread comprising a rubber composition whose hardness reversibly changes with water and satisfies the relations (1) and (2) and a ground contact ratio within a predetermined range, and thus provides more suitable improved overall performance in terms of dry grip performance and wet grip performance.

Further, by using a rubber compound whose hardness reversibly changes with water, it is possible to provide appropriate grip performance according to road conditions. Further, as the range of rubber hardness available for the tread becomes wider, the flexibility of tread design can be improved.

Herein, when the tire is a pneumatic tire, the ground contact ratio may be calculated from the ground contact patch under the conditions of having a normal rim, a normal internal pressure, and a normal load. When the tire is an airless tire, the ground contact ratio can be calculated as described above without the need for a normal internal pressure.

The term "normal rim" refers to a rim specified for each tire by a standard in a standard system (including a standard by which the tire is provided), and may be, for example, a "standard rim" in JATMA, a "design rim" in TRA, or a "measurement rim" in ETRTO.

The term "normal internal pressure" refers to the air pressure specified by the above standard for each tire, and may be the "maximum air pressure" in JATMA, the maximum value shown in the table "tire load limits at various cold inflation pressures" in TRA, or the "inflation pressure" in ETRTO. For passenger tires, the normal internal pressure is 180 kPa.

The term "normal load" refers to a load specified by the above standard for each tire, and may be a load obtained by multiplying the "maximum load capacity" in JATMA, the maximum values shown in the table "tire load limits at various cold inflation pressures" in TRA, or the "load capacity" in ETRTO by 0.88.

The ground plane may be determined by: the tire was mounted on a normal rim, normal internal pressure was applied to the tire, the tire was allowed to stand at 25 ℃ for 24 hours, and then black ink was applied to the tread surface of the tire, which was pressed against a cardboard sheet with normal load (camber angle: 0 °) to be transferred to the cardboard sheet.

The transfer may be performed at five positions rotated by 72 degrees with respect to each other in the tire circumferential direction. In other words, the ground plane can be measured five times.

The average of the maximum lengths of the five contact surfaces in the tire axial direction is denoted by L, and the average of the lengths in the direction orthogonal to the tire axial direction is denoted by W.

The ground ratio is calculated by the following formula: [ average value of areas of five ground planes (portions with black ink) transferred onto the paper sheet ]/(L × W) × 100 (%).

Here, the average length and the average area are each a simple average of five values.

The tread of the tire may have grooves that are continuous in the circumferential direction of the tire and/or grooves that are discontinuous in the circumferential direction of the tire. Examples of such groove patterns include rib-type (rib) patterns, cross-groove (lug) patterns, rib-cross-groove (rib-lug) patterns, and block (block) patterns.

Examples

The present disclosure is specifically described with reference to examples, but the present disclosure is not limited by the examples.

Production example 1

To a nitrogen purged autoclave reactor was added hexane, 1, 3-butadiene, styrene, tetrahydrofuran and ethylene glycol diethyl ether. Subsequently, a solution of bis (diethylamino) methylvinylsilane and n-butyllithium in cyclohexane and n-hexane, respectively, was added to initiate polymerization.

1, 3-butadiene and styrene were copolymerized for three hours at a stirring rate of 130rpm and a reactor internal temperature of 65 ℃ while continuously feeding the monomers into the reactor. Subsequently, the polymer solution was stirred at a stirring speed of 130rpm, and N- (3-dimethylaminopropyl) acrylamide was added thereto to conduct a reaction for 15 minutes. After the polymerization reaction is completed, 2, 6-di-tert-butyl-p-cresol is added. Then, the solvent was removed by stripping, and the resultant was dried on a hot roll adjusted to 110 ℃ to obtain a modified styrene-butadiene rubber (SBR).

Production example 2 Synthesis of Polymer 1 (epoxide/allyl glycidyl ether copolymer)

500mL of diethyl ether was charged to a glass flask purged with nitrogen. After the internal temperature had dropped below 0 ℃ 10mL of a 0.55mol/L solution of triisobutylaluminum (in hexane) was added, and then 0.55mol/L ethanol/diethyl ether solution was added dropwise while ensuring that the internal temperature did not exceed 10 ℃. Next, a solution prepared by mixing ethylene oxide and allyl glycidyl ether at a molar ratio of 9: 1 (total 200g) was added dropwise while ensuring that the internal temperature did not exceed 10 ℃ and then stirred for 8 hours. Then, the solvent was evaporated under reduced pressure at an external temperature of 50 ℃ and an internal pressure of 1.0kPa or less, and the residue was suspended in water and filtered. The filtration residue was washed with THF, and then dried under reduced pressure at 50 ℃ under 1kPa to a constant weight, to obtain polymer 1 (infrared absorption spectrum showed that ether peak and carbon-carbon peak are derived from formula (A) and formula (B), respectively; weight average molecular weight (Mw) was 780,000; amount of the group (structural unit) of formula (B) was 8 mol% based on 100 mol% of the polymer), yield was 80%.

Production example 3 Synthesis of Polymer 2 (amine/allyl glycidyl ether copolymer)

Polymer 2 (amine absorption peak and carbon-carbon double bond peak, analyzed in the same manner as in production example 2; weight average molecular weight 980,000; amount of the group (structural unit) of formula (B) was 8 mol% based on 100 mol% of the polymer) was obtained in 80% yield by following the procedure of production example 2 but using triglycidyl amine instead of ethylene oxide to obtain a polymer of triglycidyl amine and allyl glycidyl ether.

Production example 4 Synthesis of Polymer 3 (silyl/allyl glycidyl ether copolymer)

Following the procedure of production example 2 except using triethoxysilylglycidyl ether in place of ethylene oxide, a polymer of triethoxysilylglycidyl ether and allyl glycidyl ether was obtained as polymer 3 (analyzed in the same manner as in production example 2, silanol absorption peak and carbon-carbon double bond peak; weight average molecular weight: 640,000; amount of the group (structural unit) of the formula (B) was 8 mol% based on 100 mol% of the polymer), yield: 80%.

Further, polymers 1 to 3 were evaluated as described below.

< measurement of Water-insoluble substance >

In a glass flask, 1g of each polymer was weighed, 10mL of water was added, and the mixture was stirred at an internal temperature of 66 ℃ for 10 minutes. Then, stirring was continued until the internal temperature reached 25 ℃ or lower. The resulting mixture was filtered through a filter paper made of cellulose with a mesh size of 5C. The residue remaining on the filter paper was dried at a temperature of 80 ℃ and an internal pressure of 0.1kPa or less for 8 hours, and then the weight of the residue after drying was measured. The amount of water-insoluble matter was determined using the following equation.

The amount of water-insoluble matter (% by mass) is the weight (g) of the dried residue/the initial weight (g) of the polymer x 100

< measurement of THF-insoluble matter >

In a glass flask, 1g of each polymer was weighed, 10mL of tetrahydrofuran was charged, and the mixture was stirred at an internal temperature of 66 ℃ for 10 minutes. Then, stirring was continued until the internal temperature reached 25 ℃ or lower. The resulting mixture was filtered through a filter paper made of cellulose with a mesh size of 5C. The residue remaining on the filter paper was dried at a temperature of 80 ℃ and an internal pressure of 0.1kPa or less for 8 hours, and then the weight of the residue after drying was measured. The amount of THF insolubles was determined using the following equation.

The amount of THF-insoluble matter (% by mass) was equivalent to the weight (g) of the dried residue/the initial weight (g) of the polymer x 100

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

SBR: the above-synthesized SBR (modified S-SBR having a styrene content of 25% by mass, a vinyl content of 59 mol%, and no oil extension);

BR: BR150B (cis content: 97 mass%) from Utsu Kaisha;

NR：TSR20；

polymer 1: polymer 1 synthesized above (water-insoluble: 96% by mass, THF-insoluble: 96% by mass);

polymer 2: polymer 2 synthesized above (water-insoluble: 82 mass%, THF-insoluble: 96 mass%);

polymer 3: polymer 3 synthesized above (water-insoluble: 92% by mass, THF-insoluble: 92% by mass);

silicon dioxide: ZEOSIL 1165MP (N)₂SA：160m²Per gram) from luodiya;

carbon black: seast 9H (DBP oil absorption: 115mL/100g, N₂SA：110m²(g) from east China sea carbon corporation;

silane coupling agent: si75 (bis (3-triethoxysilyl-propyl) disulfide), purchased from won indonesia;

oil: process X-140 (aromatic Process oil) available from Japan energy Co., Ltd;

resin: g90 (coumarone-indene resin, softening point: 90 ℃ C.), available from Nidong chemical Co., Ltd;

wax: ozoace 0355, available from japan ceresin;

antioxidant: santoflex 13(N- (1, 3-dimethylbutyl) -N' -phenyl-p-phenylenediamine, 6PPD), available from fulex;

stearic acid: stearic acid "TSUBAKI" from sun oil co;

zinc oxide: zinc oxide #2, purchased from mitsui metal mining, inc;

sulfur: powdered sulfur, purchased from crane, chemical industries co;

vulcanization accelerator 1: NOCCELER NS (N-tert-butyl-2-benzothiazolesulfenamide), available from DANEW PHOTOCHEMICAL INDUSTRIAL CO., LTD;

vulcanization accelerator 2: NOCCELER D (1, 3-diphenylguanidine), available from DAINXIN photochemistry Co.

(examples and comparative examples)

According to each formulation shown in Table 1, chemicals other than sulfur and a vulcanization accelerator were kneaded at 160 ℃ for four 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 four minutes to obtain an unvulcanized rubber composition.

The unvulcanized rubber composition was press-vulcanized at 170 ℃ for 12 minutes to obtain a vulcanized rubber composition.

The vulcanized rubber compositions prepared as above were evaluated as follows. The results are shown in Table 1.

(hardness (Hs) of vulcanized rubber)

"vulcanized rubber or thermoplastic rubber-determination of hardness-part 3" according to JIS K6253-3 (2012): durometer method ", the shore hardness (Hs, JIS-A hardness) of the vulcanized rubber composition (sample) was measured using A type A durometer. The measurement was carried out at 25 ℃.

(hardness in Water wetting)

The vulcanized rubber composition (having a rectangular parallelepiped shape of 30 mm. times.30 mm. times.4 mm) was immersed in 20mL of water at 25 ℃ for 6 hours to obtain a water-wet vulcanized rubber composition. The hardness of the water-wet vulcanized rubber composition was measured as described above and reported as the hardness upon water wetting.

(hardness in drying)

The water-wet vulcanized rubber composition was dried under reduced pressure at 80 ℃ and 1kPa or less to a constant weight to obtain a dried vulcanized rubber composition. After the temperature of the dried vulcanized rubber composition was returned to 25 ℃, the hardness of the dried vulcanized rubber composition was measured as described above and reported as the hardness at the time of drying.

(hardness upon rewetting with water)

The dried vulcanized rubber composition (having a rectangular parallelepiped shape of 30 mm. times.30 mm. times.4 mm) was immersed in 20mL of water at 25 ℃ for 6 hours to obtain a vulcanized rubber composition rewetted with water. The hardness of the vulcanized rubber composition rewetted with water was determined as described above and reported as the hardness upon rewetting with water.

(tan. delta. when dried)

The tan δ of the dried vulcanized rubber composition was measured at 70 ℃ using a viscoelasticity spectrometer VES (manufactured by shiba). The measurement conditions were as follows: the measurement temperature was 70 ℃, the initial strain was 10%, the dynamic strain was 2%, and the frequency was 10 Hz.

(Wet grip Performance index)

Each of the unvulcanized rubber composition sheets was made into a tread shape, assembled with other tire components, and then press-vulcanized at 150 ℃ for 15 minutes to prepare a kart tire (tire size: 11X 1.10-5). Each set of kart tires is mounted on the karts. The test driver driven a go-kart over a 2 km/circle test course (road surface previously sprayed with water) for 8 revolutions. Then, the driver scores the grip performance in the range of 1 to 200 (optimal), where the grip performance of comparative example 1 is set to 100.

(Dry grip Performance index)

Each of the unvulcanized rubber composition sheets was made into a tread shape, assembled with other tire components, and then press-vulcanized at 150 ℃ for 15 minutes to prepare a kart tire (tire size: 11X 1.10-5). Each set of kart tires is mounted on the karts. Under dry road conditions, test drivers driven 8 revolutions of a go-kart over a 2 km/revolution test course. Then, the driver scores the grip performance in the range of 1 to 200 (optimal), where the grip performance of comparative example 1 is set to 100.

[ Table 1]

The results in table 1 show that the examples in which the hardness reversibly changes with water and which satisfy the relations (1) and (2) show improved overall performance in terms of wet grip performance and dry grip performance (expressed as the sum of the indices of wet grip performance and dry grip performance).

(production of tires)

The unvulcanized rubber compositions prepared as above were molded into a tread shape (having a tread thickness shown in Table 2), then assembled with other tire components, and then press-vulcanized at 170 ℃ for 12 minutes to prepare test tires (size: 195/65R 15).

(Wet grip Performance index)

Each set of test tires was mounted on a car. The test driver drives the car for 8 runs on a test course (previously sprayed with water) of 2 km/turn. Then, the driver scores the grip performance in the range of 1 to 200 (optimal), where the grip performance of example 2-1 is set to 100. The results are shown in Table 2.

(Dry grip Performance index)

Each set of test tires was mounted on a car. Under dry road conditions, test drivers traveled 8 revolutions on a test course of 2 km/revolution. Then, the driver scores the grip performance in the range of 1 to 200 (optimal), where the grip performance of example 2-1 is set to 100. The results are shown in Table 2.

[ Table 2]

The results in table 2 show that a tire having a tread comprising a rubber composition whose hardness reversibly changes with water and satisfies the relations (1) and (2) and having a thickness of 4mm or more exhibits more suitable improved overall performance in terms of wet grip performance and dry grip performance (expressed as the sum of the indices of wet grip performance and dry grip performance).

(production of tires)

The unvulcanized rubber compositions prepared as above were molded into a tread shape (having a ground contact ratio shown in Table 3), and then assembled with other tire components, followed by press-vulcanization at 170 ℃ for 12 minutes to prepare test tires (size: 195/65R 15).

(measurement of ground ratio)

The grounding ratio (%) was measured using JATMA standard according to the grounding ratio measuring method described herein. The results are shown in Table 3.

(Wet grip Performance index)

Each set of test tires was mounted on a car. The test driver drives the car for 8 runs on a test course (previously sprayed with water) of 2 km/turn. Then, the driver scores the grip performance in the range of 1 to 200 (optimal), where the grip performance of example 3-1 is set to 100. The results are shown in Table 3.

(Dry grip Performance index)

Each set of test tires was mounted on a car. Under dry road conditions, test drivers traveled 8 revolutions on a test course of 2 km/revolution. Then, the driver scores the grip performance in the range of 1 to 200 (optimal), where the grip performance of example 3-1 is set to 100. The results are shown in Table 3.

[ Table 3]

The results of table 3 show that a tire having a tread comprising a rubber composition whose hardness reversibly changes with water and satisfies the relations (1) and (2) and a ground contact ratio of 30% or more shows a more suitable overall performance improvement in terms of wet grip performance and dry grip performance (as indicated by the sum of two indices of wet grip performance and dry grip performance).