JP2023028919A - Polymer composition and tire - Google Patents

Abstract

To provide a rubber composition that achieves improved overall performances including dry grip performance and wet grip performance, and a tire including the same.SOLUTION: A polymer composition contains a polymer component containing a modified polymer having hydrophilicity and modified with an acid or a base, at least one selected from the group consisting of metal oxide and surface-modified silica having a basic molecule on its surface, and a hydrophilic polymer, wherein the water contact angle at 25° is 90° or less, the action of water causes a reversible change in complex elastic modulus (E*) and loss tangent (tanδ), and the following formula (1) and/or the following formula (2) are satisfied. E* under water-wet condition/E* under dry condition≤0.90 (1) and tanδ under water-wet condition/tanδ under dry condition≥1.10 (2) (where E* and tanδ each denote a complex elastic modulus and a loss tangent at a temperature of 30°C, an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and a stretched mode).SELECTED DRAWING: None

Description

The present disclosure relates to polymer compositions and tires.

The grip performance of tires is important in that it is directly linked to safety, and various studies have been conducted to improve grip performance (dry grip performance, wet grip performance), and improvements are required (for example, See Patent Document 1).

JP 2008-285524 A

An object of the present disclosure is to solve the above problems and to provide a polymer composition that improves overall dry grip performance and wet grip performance, and a tire using the same.

The present disclosure provides a hydrophilic polymer component containing a modified polymer that has been modified with an acid or base;
at least one selected from the group consisting of metal oxides and surface-modified silica having basic molecules on the surface;
and a hydrophilic polymer,
The contact angle with water at 25° is 90° or less,
It relates to a polymer composition whose complex elastic modulus (E*) and loss tangent (tan δ) reversibly change with water and which satisfies the following formula (1) and/or the following formula (2).
E* when wet with water / E* when dry ≤ 0.90 (1)
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(Wherein, E* and tan δ are the complex elastic modulus and loss tangent measured under the conditions of a temperature of 30° C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an extensional mode.)

According to the present disclosure, a polymer component having hydrophilicity and containing a modified polymer modified with an acid or base, a metal oxide, and a surface-modified silica having basic molecules on its surface are selected from the group consisting of and a hydrophilic polymer, the contact angle with water at 25 ° C. is 90 ° or less, and the polymer composition satisfies the formula (1) and / or the formula (2). , the overall performance of dry grip performance and wet grip performance can be improved.

1 is a cross-sectional view showing a portion of a pneumatic tire; FIG. 2 is an enlarged cross-sectional view showing the vicinity of a tread 4 of the tire 2 of FIG. 1; FIG.

<Polymer composition>
The present disclosure is at least selected from the group consisting of a hydrophilic polymer component containing a modified polymer modified with an acid or base, a metal oxide, and a surface-modified silica having a basic molecule on its surface. 1 and a hydrophilic polymer, the contact angle with water at 25° C. is 90° or less, and the polymer composition satisfies the above formula (1) and/or the above formula (2). The polymer composition improves overall dry grip performance and wet grip performance.

Although the reason why the above effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
These days, it is not uncommon for drivers to drive on a mixture of dry and wet roads due to the effects of localized rain. Therefore, it is desired to exhibit stable grip performance regardless of whether the road surface is dry or wet.
The polymer composition includes a hydrophilic modified polymer modified with an acid or base, and surface-modified silica having metal oxides and/or basic molecules on the surface. As a result, ionic bonds are generated between these materials, and they are bonded in a dry state, so it is thought that a good elastic modulus can be exhibited and excellent grip performance on a dry road surface can be maintained. On the other hand, on a wet road surface, the modified polymer is hydrophilic, and the contact angle of the polymer composition with water is hydrophilic such that it is 90° or less. Water can easily be taken in. In addition, since the polymer composition further contains a hydrophilic polymer, the composition becomes more hydrophilic, and the speed of water uptake into the composition increases, so that water can be absorbed more effectively. It is possible to take in. Therefore, when water is efficiently incorporated into the composition, the ionic bond is dissociated on a wet road surface, and the complex elastic modulus is reduced by 10% or more (formula (1)), and / or the loss tangent is 10 % or more (formula (2)), it is thought that the following property and heat generation can be instantaneously obtained on a wet road surface, and therefore excellent grip performance on a wet road surface is exhibited. As described above, even when driving on a dry road surface and a wet road surface mixedly, the state of the composition changes instantly and the grip performance is stably exhibited, so the polymer composition has dry grip performance and It is speculated that the overall performance of wet grip performance will improve.

(polymer component)
The polymer composition contains a modified polymer that has hydrophilicity and has been modified with an acid or base.
In the polymer composition, the content of the modified polymer in 100% by mass of the polymer component is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and particularly 70% by mass or more. preferable. Although the upper limit is not particularly limited, it is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. Within the above range, the effect can be suitably obtained.

The modified polymer is hydrophilic, and the term "hydrophilic" as used herein means having greater affinity for water than for organic solvents. For example, the hydrophilicity of a polymer is quantified by measuring the partition coefficient between water (or a buffered aqueous solution) and a water-immiscible organic solvent such as octanol, ethyl acetate, methylene chloride, or methyl tert-butyl ether. can be A polymer is considered hydrophilic if, after equilibration, there is a higher concentration of the polymer in water than in the organic solvent. The "hydrophilicity" of the modified polymer can be imparted by various methods capable of imparting hydrophilicity. For example, hydrophilicity can be imparted by introducing an acidic functional group or a basic functional group to the polymer, which will be described later.

Examples of the acidic functional group (acidic group) in the acid-modified modified polymer (hereinafter also referred to as "acid-modified polymer") include a carboxylic acid group (carboxy group), a sulfonic acid group, a phosphoric acid group, a phenolic hydroxyl group, and the like. mentioned. A hydrogen atom in the acidic functional group may be substituted with a metal atom or the like, or may be dissociated. Among them, carboxylic acid group (-COOH), sulfonic acid group (-SO ₃ H), salts thereof (carboxylic acid ion (-COO ^- ) and/or sulfonic acid ion (-SO ₃ ^- ), and counters thereof cations) are preferred. The counter cation is not particularly limited as long as it can form a salt, and examples thereof include Na + and K + .

The basic functional group (basic group) in the base-modified modified polymer (hereinafter also referred to as "base-modified polymer") includes an amino group, an imino group (=NH), an ammonium base, and a basic nitrogen atom. A heterocyclic group and the like are exemplified.

The amino group may be a primary amino group (--NH ₂ ), a secondary amino group (--NHR) or a tertiary amino group (--NRR').

Examples of R and R' include substituted or unsubstituted monovalent hydrocarbon groups, which may be linear, branched or cyclic. The above R and R' may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group, and may have a heteroatom such as oxygen.

The number of carbon atoms in the substituted or unsubstituted monovalent hydrocarbon group of R and R' is preferably 1 to 10, more preferably 1 to 8, and even more preferably 1 to 6.

Examples of the substituted or unsubstituted monovalent hydrocarbon groups for R and R′ include substituted or unsubstituted aliphatic, alicyclic, and aromatic hydrocarbon groups that may contain a heteroatom, specifically includes substituted or unsubstituted linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups and the like which may contain heteroatoms.

When R and R' are substituted or unsubstituted linear or branched alkyl groups which may contain heteroatoms, the number of carbon atoms is preferably 1 to 8, more preferably 1 to 4, even more preferably 1 to 2. . When the above R and R' are substituted or unsubstituted cyclic alkyl groups which may contain heteroatoms, they preferably have 3 to 12 carbon atoms. When the above R and R' are substituted or unsubstituted aryl groups which may contain heteroatoms, they preferably have 6 to 10 carbon atoms. When R and R' are substituted or unsubstituted aralkyl groups which may contain heteroatoms, the number of carbon atoms is preferably 7-10.

Examples of the substituted or unsubstituted linear or branched alkyl group which may contain a hetero atom include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group and sec-butyl group. group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, and groups containing these heteroatoms. Examples of the substituted or unsubstituted cyclic alkyl group which may contain a hetero atom include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantyl group, a 1-ethylcyclopentyl group, a 1- An ethylcyclohexyl group and the like can be mentioned. Examples of the substituted or unsubstituted aryl group which may contain a heteroatom include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and groups containing these heteroatoms. . Examples of the substituted or unsubstituted aralkyl group which may contain a heteroatom include a benzyl group, a phenethyl group, and groups containing these heteroatoms.

Examples of the ammonium base include tertiary ammonium bases and quaternary ammonium bases.

Examples of the heterocyclic group having a basic nitrogen atom include nitrogen-containing heterocyclic groups such as a pyridine group, a pyrimidine group, a pyrazine group, an imidazole group, an imidazole group containing a thiol, a triazole group, and a thiazole group. In the case of a heterocyclic group, having a double bond facilitates dispersion in rubber.

Among the basic functional groups, a pyridine group, an imidazole group, a thiazole group and an amino group (primary amino group, secondary amino group and tertiary amino group) are preferable, and an amino group is more preferable.

Examples of the polymer constituting the skeleton of the modified polymer include polymers having carbon-carbon double bonds. Polymers having carbon-carbon double bonds include, for example, diene rubbers; thermoplastic resins such as polycarbonate resins and polyester resins; thermosetting resins such as epoxy resins and polyamideimide resins; . Among them, the diene rubber is preferable from the viewpoint that more effects can be obtained.

Diene rubbers include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR). ) and the like. In addition, butyl-based rubber, fluororubber, and the like can also be used. Among them, SBR, BR, and isoprene-based rubber are preferred, and SBR and BR are more preferred, from the viewpoint of obtaining more effects. These may be used alone or in combination of two or more.

The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. can be used. These may be used alone or in combination of two or more.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. Also, the styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above range, the effect tends to be obtained more favorably.
In this specification, the styrene content of SBR is calculated by ¹ H-NMR measurement.

The vinyl content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass or more. The vinyl content is preferably 75% by mass or less, more preferably 70% by mass or less. Within the above range, the effect tends to be obtained more favorably.
The vinyl content (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectrometry.

As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

When the polymer composition contains modified SBR modified with an acid or base as the modified polymer, the content of the modified SBR in 100% by mass of the polymer component is preferably 30% by mass or more, and 50% by mass or more. It is more preferably 60% by mass or more, and particularly preferably 70% by mass or more. Although the upper limit is not particularly limited, it is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. Within the above range, the effect can be suitably obtained.

BR is not particularly limited, and for example, high cis BR having a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), and the like can be used. These may be used alone or in combination of two or more. Among them, high-cis BR having a cis content of 90% by mass or more is preferable because it improves wear resistance.

When the polymer composition contains a modified BR modified with an acid or a base as the modified polymer, the content of the modified BR in 100% by mass of the polymer component is preferably 30% by mass or more, and is preferably 50% by mass or more. It is more preferably 60% by mass or more, and particularly preferably 70% by mass or more. Although the upper limit is not particularly limited, it is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less. Within the above range, the effect can be suitably obtained.

The isoprene rubber includes natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, and the like. As NR, those commonly used in the rubber industry, such as SIR20, RSS#3, and TSR20, can be used. The IR is not particularly limited, and for example IR2200 or the like commonly used in the rubber industry can be used. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, and the like. These may be used alone or in combination of two or more.

When the polymer composition contains a modified isoprene-based rubber modified with an acid or base as the modified polymer, the content of the modified isoprene-based rubber in 100% by mass of the polymer component is preferably 5% by mass or more. It is more preferably at least 15% by mass, particularly preferably at least 20% by mass. Although the upper limit is not particularly limited, it is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less. Within the above range, the effect can be suitably obtained.

Among the modified polymers described above, acid-modified SBR and acid-modified BR are preferred from the viewpoint of obtaining more effects, and carboxylic acid-modified SBR, sulfonic acid-modified SBR, carboxylic acid-modified BR, sulfonic acid-modified BR, and salts thereof are preferred. More preferred are carboxylic acid-modified SBR, carboxylic acid-modified BR, and salts thereof.

The polymer composition may contain polymer components other than the modified polymer. Other polymer components include, for example, the modified SBR, the modified BR, and diene rubbers other than the modified isoprene rubber (unmodified SBR, BR, isoprene rubber). Also, the polymer composition may contain a modified polymer other than the modified polymer. Among them, unmodified isoprene rubber and unmodified BR are preferable.

When the polymer composition contains a polymer component other than the modified polymer, the content of the other polymer component in 100% by mass of the polymer component is preferably 5% by mass or more, more preferably 10% by mass or more. 15% by mass or more is more preferable, and 20% by mass or more is particularly preferable. Although the upper limit is not particularly limited, it is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less. Within the above range, the effect can be suitably obtained. When unmodified isoprene rubber or unmodified BR is used as the other polymer component, the content of unmodified isoprene rubber and the content of unmodified BR are preferably within the same range.

(metal oxide)
The polymer composition preferably contains a metal oxide from the viewpoint of obtaining better effects.

Metal oxides include metal single oxides, composite oxides, and the like, for example, MxOy (M represents a metal atom. x and y each independently represents an integer of 1 to 6.) and the like compounds shown. These may be used individually by 1 type, and may use 2 or more types together. It should be noted that the metal oxide is preferably other than zinc oxide.

Specific metal oxides include alkali metal oxides such as lithium oxide, sodium oxide, potassium oxide, rubidium oxide and cesium oxide; alkaline earth metal oxides such as calcium oxide, strontium oxide and barium oxide; scandium, titanium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, nickel oxide, copper oxide, yttrium oxide, zirconium oxide, niobium oxide, molybdenum oxide, technetium oxide, ruthenium oxide, rhodium oxide, palladium oxide, Transition metal oxides such as silver oxide, hafnium oxide, tantalum oxide, tungsten oxide, osmium oxide, iridium oxide, platinum oxide, gold oxide; beryllium oxide, magnesium oxide, aluminum oxide, gallium oxide, cadmium oxide, indium oxide, oxide oxides of base metals such as tin, thallium oxide, lead oxide, bismuth oxide, and polonium oxide; A metal oxide can also be used individually or as a mixture of 2 or more types.

Among them, at least selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, from the viewpoint of suitably obtaining the effect. It preferably contains one, more preferably at least one selected from the group consisting of beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, and still more preferably magnesium oxide.

In the polymer composition, the content of the metal oxides (total amount of the metal oxides) is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the polymer component. , More preferably 2.0 parts by mass or more, particularly preferably 2.2 parts by mass or more, and preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 4.0 parts by mass It is not more than 3.0 parts by mass, particularly preferably not more than 3.0 parts by mass. Within the above range, the effect tends to be obtained more favorably. The total amount of at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide, beryllium oxide, and magnesium oxide , the total amount of at least one selected from the group consisting of calcium oxide, strontium oxide, and barium oxide, and the content of magnesium oxide, the same range is preferable.

The apparent specific gravity of the metal oxide is preferably less than 0.4 g/ml, more preferably 0.3 g/ml or less, still more preferably 0.25 g/ml or less, and preferably 0.05 g/ml. 0.15 g/ml or more, more preferably 0.15 g/ml or more. Within the above range, the effect tends to be obtained more favorably. Moreover, it is preferable that the apparent specific gravity of magnesium oxide is also within the same range.
The apparent specific gravity of the metal oxide is a value obtained by weighing 30 ml in apparent volume into a 50 ml graduated cylinder and calculating from the mass.

The d50 of the metal oxide is preferably less than 10 μm, more preferably 4.5 μm or less, even more preferably 1.5 μm or less, particularly preferably less than 0.75 μm, and more preferably 0.05 μm or more, more preferably is 0.45 μm or more. Within the above range, the effect tends to be obtained more favorably. Also, the d50 of magnesium oxide is preferably within the same range.
The d50 of the metal oxide is the particle diameter at 50% of the integrated value in the mass-based particle size distribution curve obtained by the laser diffraction scattering method.

The nitrogen adsorption specific surface area (N ₂ SA) of the metal oxide is preferably 100 m ² /g or more, more preferably 115 m ² /g or more, and is preferably 250 m ² /g or less, more preferably 225 m ^{2 .} /g or less, more preferably 200 m ² /g or less. Within the above range, the effect tends to be obtained more favorably. Also, N ₂ SA of magnesium oxide is preferably within the same range.
The N ₂ SA of the metal oxide is a value measured by the BET method according to JIS Z8830:2013.

Commercially available metal oxides include Kyowa Chemical Industry Co., Ltd., Fujifilm Wako Pure Chemical Industries, Ltd., Kishida Chemical Co., Ltd., Kyowa Chemical Industry Co., Ltd., Tateho Chemical Industry Co., Ltd., JHE Co., Ltd., Products such as Nippon Kagaku Kogyo Co., Ltd. and Ako Kasei Co., Ltd. can be used.

(Surface-modified silica having basic molecules on its surface)
The polymer composition preferably contains surface-modified silica having basic molecules on its surface, from the viewpoint of obtaining better effects.

Silica constituting the surface-modified silica is not particularly limited, and examples thereof include dry silica (anhydrous silica) and wet silica (hydrous silica). Among them, wet-process silica is preferable because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 30 m ² /g or more, more preferably 100 m ² /g or more, still more preferably 125 m ² /g or more. The N ₂ SA of silica is preferably 300 m ² /g or less, more preferably 250 m ² /g or less, and even more preferably 200 m ² /g or less. Within the above range, the effect can be suitably obtained.
The N ₂ SA of silica is a value measured by the BET method according to ASTM D3037-93.

As silica, for example, products of Degussa, Rhodia, Tosoh Silica, Solvay Japan, Tokuyama, etc. can be used.

Basic molecules constituting the surface-modified silica can be used as long as they are basic molecules, and for example, compounds having basic functional groups can be preferably used. Examples of the basic functional group include the basic functional groups described above. Among basic functional groups, pyridine group, imidazole group, thiazole group and amino group (primary amino group, secondary amino group and tertiary amino group) are preferable, and amino group is more preferable.

The compound having an amino group as a basic compound is not particularly limited, but for example, a compound having a primary to tertiary amino group and an alkoxysilyl group in one molecule can be preferably used. As the compound having an amino group, specifically, compounds represented by the following formulas (I) and (II) are suitable.

(R ¹¹ O) _n R ¹² _3-n —Si—R ¹³ —NR ¹⁴ R ¹⁵ (I)
(wherein R ¹¹ , R ¹² , R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ¹³ is a substituted or unsubstituted divalent hydrocarbon represents a hydrogen group, n represents 1 to 3.)

(R ²¹ O) _p R ²² _3-p —Si—R ²³ —NR ²⁴ —R ²⁵ —Si—(R ²⁶ O) _q R ²⁷ _3-q (II)
(wherein R ²¹ , R ²² , R ²⁴ , R ²⁶ and R ²⁷ each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group; R ²³ and R ²⁵ each independently represents a substituted or unsubstituted divalent hydrocarbon group, p and q each independently represents 1 to 3.)

The substituted or unsubstituted monovalent and divalent hydrocarbon groups of R ¹¹ to R ¹⁵ and R ²¹ to R ²⁷ in formulas (I) and (II) may be linear, branched or cyclic. The substituted or unsubstituted monovalent and divalent hydrocarbon groups of R ¹¹ to R ¹⁵ may be either saturated hydrocarbon groups or unsaturated hydrocarbon groups, and may have a heteroatom such as oxygen.

The number of carbon atoms in the substituted or unsubstituted monovalent hydrocarbon groups of R ¹¹ , R ¹² , R ¹⁴ and R ¹⁵ in formula (I) and R ²¹ , R ²² , R ²⁴ , R ²⁶ and R ²⁷ in formula (II) is , 1 to 10 are preferred, 1 to 8 are more preferred, and 1 to 6 are even more preferred. The substituted or unsubstituted divalent hydrocarbon group of R ¹³ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 6 carbon atoms.

Specific examples of substituted or unsubstituted monovalent hydrocarbon groups for R ¹¹ , R ¹² , R ¹⁴ and R ¹⁵ in formula (I) and R ²¹ , R ²² , R ²⁴ , R ²⁶ and R ²⁷ in formula (II) includes the same substituted or unsubstituted monovalent hydrocarbon groups for R and R′ described above.

Specifically, the substituted or unsubstituted divalent hydrocarbon group of R ¹³ of formula (I), R ²³ and R ²⁵ of formula (II) is a substituted or unsubstituted C 1 group optionally containing a heteroatom. to 18 alkylene groups, cycloalkylene groups having 5 to 18 carbon atoms, and the like. Specific examples include methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octylene, nonylene, decylene and 1,2-propylene groups.

Specific examples of the compound having an amino group represented by formula (I) include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]- 1-butanamine, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminobutyl)-3-aminobutyltrimethoxysilane, N-2-(aminoethyl)-3-amino Examples include propylmethyltrimethoxysilane.

Specific examples of the compound having an amino group represented by formula (II) include bis(3-trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)amine, bis(4-trimethoxy silylbutyl)amine, bis(triethoxysilylmethyl)amine, bis(6-trimethoxysilylhexyl)amine and the like.

Specific examples of compounds having an amino group other than the above include amino group-containing aromatic compounds such as N-phenyl-3-aminopropyltrimethoxysilane; 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxy Amino group-containing dialkoxysilane compounds such as silane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, bis(3-methyldimethoxysilylpropyl)amine; N,N'-bis[3-( ethylenediamine compounds such as trimethoxysilyl)propyl]ethylenediamine, N-(2-aminoethyl)-N'-(3-(trimethoxysilyl)propyl)ethylenediamine; and the like.

As the method for producing the surface-modified silica having basic molecules on the surface (method for treating (coating) the silica surface with basic molecules), a method capable of bringing the basic molecules into contact with silica can be used. For example, it can be prepared by mixing a basic compound and silica by a known method. Specifically, a basic molecule and silica are kneaded with other components such as a polymer component using a kneading apparatus such as an open roll mixer or a Banbury mixer, so that the basic molecules are added to the surface of the kneaded product. It can be produced by generating surface-modified silica having. Alternatively, it can be produced by mixing only the basic compound and silica by a known method.

In the polymer composition, the content of the surface-modified silica is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, and particularly preferably It is 50 parts by mass or more. Although the upper limit of the content is not particularly limited, it is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 parts by mass or less. Within the above range, the effect can be suitably obtained. The content of the surface-modified silica is the total amount of the silica and the basic molecule with respect to 100 parts by mass of the polymer component in the polymer composition, and includes the basic molecule not attached to the silica surface. . In addition, when the basic molecule is a compound having an amino group, the content of the silica having the compound having the amino group on its surface is preferably within the same range.

In the polymer composition, the content of the basic molecule is preferably 2.0 parts by mass or more, more preferably 4.0 parts by mass or more, relative to 100 parts by mass of all silica contained in the polymer composition. , more preferably 6.0 parts by mass or more. The content is preferably 30.0 parts by mass or less, more preferably 20.0 parts by mass or less, and even more preferably 15.0 parts by mass or less. Within the above range, the effect can be suitably obtained.

The polymer composition may further contain a silane coupling agent in addition to the basic molecule.
The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, Bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis ( 3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) ) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3- sulfides such as triethoxysilylpropyl methacrylate monosulfide; mercaptos such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyls such as vinyltriethoxysilane and vinyltrimethoxysilane; Amino compounds such as propyltriethoxysilane and 3-aminopropyltrimethoxysilane, glycidoxy compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane, 3-nitropropyltrimethoxysilane, Nitro-based agents such as 3-nitropropyltriethoxysilane and chloro-based agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane can be mentioned. Commercially available products such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., and the like can be used. These may be used alone or in combination of two or more.

When a silane coupling agent is contained, the content of the silane coupling agent is appropriately selected in consideration of the silica amount of the surface-modified silica having basic molecules on the surface, the basic molecular weight, the amount of silica to be added separately, and the like. Just do it.

(other fillers)
The polymer composition may contain a filler other than the metal oxide and the surface-modified silica as a filler (filler). Other fillers include inorganic fillers such as untreated silica (silica having no basic molecules on the surface), carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, mica; difficult-to-disperse fillers. Materials known in the field of rubber such as rubber can be used. Among them, carbon black is preferred.

Usable carbon blacks include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762 and the like. These may be used alone or in combination of two or more. Commercially available products include Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin Nikka Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² /g or more, more preferably 80 m ² /g or more, and even more preferably 100 m ² /g or more. The N ₂ SA is preferably 200 m ² /g or less, more preferably 150 m ² /g or less, and even more preferably 130 m ² /g or less. Within the above range, the effect tends to be obtained more favorably.
The nitrogen adsorption specific surface area of carbon black is determined according to JIS K6217-2:2001.

In the polymer composition, the content of carbon black is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the polymer component. The upper limit is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

(Hydrophilic polymer)
The polymer composition contains a hydrophilic polymer. In the present specification, the hydrophilic polymer does not correspond to the above-mentioned polymer component, and the above-mentioned modified polymer having hydrophilicity and modified with an acid or base corresponds to a hydrophilic polymer. shall not. In other words, the hydrophilic polymer is a hydrophilic polymer other than the modified polymer modified with an acid or a base. The “hydrophilicity” of the hydrophilic polymer has the same meaning as the hydrophilicity of the modified polymer described above.

In the polymer composition, the content of the hydrophilic polymer is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, and particularly preferably 100 parts by mass of the polymer component. is 30 parts by mass or more, preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The hydrophilic polymer is selected from the group consisting of an isoprene-based rubber modified with a hydrophilic functional group, a hydrophilic thermoplastic elastomer, an acrylic acid-based polymer, and a sulfonic acid-based polymer, from the viewpoint of obtaining more effects. It is desirable to include at least one

In the isoprene-based rubber modified with hydrophilic functional groups, the hydrophilic functional groups include, for example, one or more functional groups selected from the group consisting of hydroxyl groups, amino groups, and ether groups. Among them, from the viewpoint of obtaining more effects, a hydrophilic modifying compound having a hydroxyl group, an amino group, an ether group, etc. is added to the epoxy group of epoxidized natural rubber (ENR) or epoxidized isoprene rubber. Furthermore, modified ENR and modified epoxidized isoprene rubber are preferred, and modified ENR is more preferred.

The modified ENR is preferably an ENR modified with one or more functional groups selected from the group consisting of a hydroxyl group, an amino group, and an ether group, and more preferably a modified ENR having a polyethylene glycol monoalkyl ether residue on the side chain of the ENR. preferable. The modified epoxidized isoprene rubber is preferably an epoxidized isoprene rubber modified with one or more functional groups selected from the group consisting of a hydroxyl group, an amino group, and an ether group. Modified poxylated isoprene rubber with ether residues is more preferred.

The epoxidation rate of ENR and epoxidized isoprene rubber is preferably 1 to 80 mol%, more preferably 5 to 65 mol%, still more preferably 25 to 50 mol%, and particularly preferably 30 to 50 mol%. Here, the epoxidation ratio means the ratio of the number of epoxidized carbon-carbon double bonds to the total number of carbon-carbon double bonds in the natural rubber and isoprene rubber before epoxidation. NMR) analysis or the like. As ENR, for example, those commercially available from Kumpuran Guthrie can be used.

ENR, modified ENR having a polyethylene glycol monoalkyl ether residue on the side chain of epoxidized isoprene rubber, and modified epoxidized isoprene rubber are obtained by reacting ENR or epoxidized isoprene rubber with polyethylene glycol monoalkyl ether, for example , RSC Adv. , 2016, 6, 107021-107028, Advanced Materials Research, 2013, 795, 251-255 and the like. Specifically, for example, it can be synthesized by the following reactions.

The epoxy groups of ENR, epoxidized isoprene rubber, are partially or wholly ring-opened by the addition of polyethylene glycol monoalkyl ether. The rate of modification (ring opening) of the epoxy group can be adjusted by adjusting the charge ratio of ENR, epoxidized isoprene rubber, and polyethylene glycol monoalkyl ether, but is preferably 50% or more, more preferably 70% or more. Preferably, 90% or more is more preferable, and 100% is particularly preferable.

In the polymer composition, the content of the isoprene-based rubber modified with the hydrophilic functional group is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 100 parts by mass of the polymer component. It is 25 parts by mass or more, particularly preferably 30 parts by mass or more, preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

As the hydrophilic thermoplastic elastomer, a hydrophilic polyurethane-based elastomer (hereinafter also referred to as "hydrophilic polyurethane-based elastomer") can be preferably used from the viewpoint of obtaining more effects.

The hydrophilic polyurethane-based elastomer is produced, for example, by subjecting a high-molecular-weight polyol compound and an organic polyisocyanate compound, optionally together with a chain extender, to a urethanization reaction in a solvent that is inert to the reaction and has a high affinity for water. to form a prepolymer, neutralize the prepolymer, and then disperse it in an aqueous solvent containing a chain extender to increase the molecular weight. Specifically, for example, it can be synthesized by the production methods described in Japanese Patent No. 3588375, Japanese Patent Application Laid-Open No. 8-34897, Japanese Patent Application Laid-Open No. 11-92653, Japanese Patent Application Laid-Open No. 11-92655.

Among the hydrophilic polyurethane-based elastomers, a copolymer having a styrene-based elastomer portion and a hydrophilic polyurethane-based elastomer portion is desirable from the viewpoint of obtaining more effects. The copolymer is a diblock copolymer having one styrene-based elastomer block and one hydrophilic polyurethane-based elastomer block, a total of three styrene-based elastomer blocks and hydrophilic polyurethane-based elastomer blocks, or Any polyblock copolymer having 4 or more bonds may be used, but the diblock copolymer is particularly preferred.

In the copolymer having the styrene-based elastomer portion and the hydrophilic polyurethane-based elastomer portion, the styrene-based elastomer portion (styrene-based elastomer) is, for example, a portion formed of an elastomer having units based on styrene. and can be produced by a known method.

The styrene-based elastomer part (styrene-based elastomer) includes, for example, styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), styrene-based thermoplastic elastomer, styrene-isobutylene-styrene block copolymer (SIBS), styrene- isoprene-styrene block copolymer (SIS), styrene-isobutylene block copolymer (SIB), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butene-styrene block copolymer (SEBS), Styrene-ethylene/propylene-styrene block copolymer (SEPS), styrene-ethylene/ethylene/propylene-styrene block copolymer (SEEPS), styrene-butadiene/butylene-styrene block copolymer (SBBS), etc. . These may be used alone or in combination of two or more. Among them, SBR is preferable because the effect can be obtained more preferably.

In the copolymer having the styrene-based elastomer portion and the hydrophilic polyurethane-based elastomer portion, the hydrophilic polyurethane-based elastomer portion (thermoplastic polyurethane elastomer) includes, for example, isocyanate, polyol, and chain extension if necessary. Examples include sites formed by agents, and the like, and can be produced by known methods.

The isocyanate constituting the thermoplastic polyurethane elastomer is not particularly limited as long as it is an isocyanate compound having two or more isocyanate groups. Mixture of 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3'-bitrylene-4,4'-diisocyanate (TODI) , xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisocyanate (PPDI), 4,4′-methylene-bis(phenyl isocyanate) and other aromatic isocyanates; 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI), hydrogenated xylylene diisocyanate (H ₆ XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and other alicyclic or aliphatic isocyanates. 1 type may be used for these and they may use 2 or more types together.

Polyols (high molecular weight polyols) constituting thermoplastic polyurethane elastomers include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), polyoxytetramethylene glycol (PTMG); polyethylene adipate (PEA); ), polybutylene adipate (PBA), polyhexamethylene adipate (PHMA) and other condensed polyester polyols; poly-ε-caprolactone (PCL) and other lactone polyester polyols; polyhexamethylene carbonate and other polycarbonate polyols; is mentioned. Among them, polyether polyols and polycarbonate polyols are preferable from the viewpoint of riding comfort performance after long-term storage. 1 type may be used for these and they may use 2 or more types together.

Examples of chain extenders include low-molecular-weight polyols, polyamines, aminoalcohols, and the like.

Commercially available copolymers having a styrene-based elastomer portion and a hydrophilic polyurethane-based elastomer portion include Kuramilon TU Polymer manufactured by Kuraray Co., Ltd., and the like.

In the polymer composition, the content of the hydrophilic thermoplastic elastomer is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 25 parts by mass or more with respect to 100 parts by mass of the polymer component. is particularly preferably 30 parts by mass or more, preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

Examples of acrylic acid-based polymers include polyacrylic acid, sodium polyacrylate, potassium polyacrylate, acrylic acid/alkyl methacrylate copolymer, polyacrylamide, (Na acrylate/Na acryloyldimethyltaurate) copolymer, (acrylic acid hydroxyethyl/acryloyldimethyltaurate Na) copolymer, (acrylamide/ammonium acrylate) copolymer, and the like.

In the polymer composition, the content of the acrylic acid-based polymer is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, and particularly preferably 100 parts by mass of the polymer component. is 30 parts by mass or more, preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

Examples of sulfonic acid-based polymers include polysulfonic acid, sodium polysulfonate, potassium polysulfonate, and sulfonic acid/acrylic acid copolymers.

In the polymer composition, the content of the sulfonic acid-based polymer is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 25 parts by mass or more, and particularly preferably 100 parts by mass of the polymer component. is 30 parts by mass or more, preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

(Plasticizer)
The polymer composition preferably contains a plasticizer. Here, the plasticizer is a material that imparts plasticity to the polymer component. ) and the like.

In the polymer composition, the content of the plasticizer (total amount of plasticizer) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the polymer component. be. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

Liquid plasticizers (plasticizers in liquid state at room temperature (25° C.)) that can be used in the polymer composition are not particularly limited, and include oils, liquid polymers (liquid resins, liquid diene-based polymers, liquid farnesene-based polymers, etc.). is mentioned. These may be used alone or in combination of two or more.

In the polymer composition, the content of the liquid plasticizer is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the polymer component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, the effect tends to be obtained more favorably. The content of the liquid plasticizer also includes the amount of oil contained in the oil-extended rubber and the amount of oil contained in the sulfur. Also, the same range is suitable for the oil content.

Oils include, for example, process oils, vegetable oils, or mixtures thereof. As the process oil, for example, paraffinic process oil, aromatic process oil, naphthenic process oil, etc. can be used. 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, and olive oil. , sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil and the like. Commercially available products include Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Oil Co., Ltd., Fuji Kosan Co., Ltd., Products such as Nisshin OilliO Group Co., Ltd. can be used. Among them, process oils (paraffinic process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred.

Liquid resins include terpene resins (including terpene phenolic resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5/C9 resins, and dicyclopentadiene (DCPD) resins. , coumarone-indene resins (including coumarone and indene simple substance resins), phenol resins, olefin resins, polyurethane resins, acrylic resins, and the like. Hydrogenated products of these can also be used.

Examples of the liquid diene polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene 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, liquid farnesene butadiene copolymer, and the like. . These may be modified with a polar group at the terminal or main chain. Hydrogenated products of these can also be used.

Examples of the resins (resins in a solid state at room temperature (25°C)) that can be used in the polymer composition include aromatic vinyl polymers in a solid state at room temperature (25°C), coumarone-indene resins, coumarone resins, and indene. Resins, phenol resins, rosin resins, petroleum resins, terpene resins, acrylic resins, and the like. Also, the resin may be hydrogenated. These may be used alone or in combination of two or more. Among them, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred.

In the polymer composition, the content of the resin is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more with respect to 100 parts by mass of the polymer component. The upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, the effect tends to be obtained more favorably.

The softening point of the resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. Within the above range, the effect tends to be obtained more favorably. The softening point of the resin is the temperature at which the ball descends when the softening point specified in JIS K6220-1:2001 is measured with a ring and ball type softening point measuring device.

The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a structural unit. Examples thereof include α-methylstyrene and/or resins obtained by polymerizing styrene. Specifically, styrene homopolymers (styrene resins), α-methylstyrene homopolymers (α-methylstyrene resins ), copolymers of α-methylstyrene and styrene, and copolymers of styrene and other monomers.

The coumarone-indene resin is a resin containing coumarone and indene as main monomer components constituting the skeleton (main chain) of the resin. Examples of monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

The coumarone resin is a resin containing coumarone as a main monomer component that constitutes the skeleton (main chain) of the resin.

The indene resin is a resin containing indene as a main monomer component that constitutes the skeleton (main chain) of the resin.

As the phenolic resin, for example, known polymers obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde and furfural with an acid or alkali catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolac phenolic resins) are preferable.

Examples of the rosin resin include natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and rosin-based resins represented by hydrogenated products thereof.

Examples of the petroleum resins include C5-based resins, C9-based resins, C5/C9-based resins, dicyclopentadiene (DCPD) resins, and hydrogenated products thereof. Among them, DCPD resin and hydrogenated DCPD resin are preferable.

The terpene-based resin is a polymer containing terpene as a structural unit. Examples thereof include polyterpene resins obtained by polymerizing terpene compounds, and aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Aromatic modified terpene resins include terpene phenol resins made from terpene compounds and phenol compounds, terpene styrene resins made from terpene compounds and styrene compounds, and terpene compounds, phenol compounds and styrene compounds as raw materials. Terpene phenol styrene resins can also be used. The terpene compounds include α-pinene and β-pinene, the phenolic compounds include phenol and bisphenol A, and the aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

The acrylic resin is a polymer containing an acrylic monomer as a structural unit. Examples thereof include styrene-acrylic resins such as styrene-acrylic resins, which have a carboxyl group and are obtained by copolymerizing an aromatic vinyl monomer component and an acrylic monomer component. Among them, solvent-free carboxyl group-containing styrene-acrylic resins can be preferably used.

Examples of plasticizers include Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, Nichinuri Chemical Co., Ltd. Products of Nippon Shokubai, ENEOS Co., Ltd., Arakawa Chemical Co., Ltd., Taoka Chemical Co., Ltd., etc. can be used.

(other ingredients)
From the viewpoint of crack resistance, ozone resistance, etc., the polymer composition preferably contains an anti-aging agent.

Antiaging agents are not particularly limited, but naphthylamine antiaging agents such as phenyl-α-naphthylamine; diphenylamine antiaging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine. ; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylene p-phenylenediamine antioxidants such as diamines; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; 2,6-di-t-butyl-4-methyl monophenol antioxidants such as phenol and styrenated phenol; bis, tris and polyphenols such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane anti-aging agent, etc. Among them, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferable, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 2,2,4-trimethyl-1 , 2-dihydroquinoline polymers are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Kagaku Kogyo Co., Ltd., Flexis, etc. can be used.

In the polymer composition, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polymer component. The content is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less.

The polymer composition may contain stearic acid. In the polymer composition, the stearic acid content is preferably 0.5 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the polymer component.

As the stearic acid, conventionally known ones can be used, for example, products of NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acids Co., Ltd., etc. can be used.

The polymer composition may contain zinc oxide. In the polymer composition, the content of zinc oxide is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the polymer component.

As the zinc oxide, conventionally known ones can be used. products can be used.

Wax may be blended in the polymer composition. In the polymer composition, the wax content is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the polymer component.

The wax is not particularly limited, and examples thereof include petroleum waxes and natural waxes. Synthetic waxes obtained by refining or chemically treating a plurality of waxes can also be used. These waxes may be used alone or in combination of two or more.

Examples of petroleum wax include paraffin wax and microcrystalline wax. The natural wax is not particularly limited as long as it is derived from a resource other than petroleum. Examples include plant waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; beeswax, lanolin, spermaceti, and the like. animal waxes; mineral waxes such as ozokerite, ceresin and petrolactam; and refined products thereof. As commercially available products, for example, products of Ouchi Shinko Kagaku Kogyo Co., Ltd., Nippon Seiro Co., Ltd., Seiko Kagaku Co., Ltd., etc. can be used.

Sulfur may be added to the polymer composition from the viewpoint of forming appropriate crosslinked chains in the polymer chains and imparting a good balance of performance.

In the polymer composition, the sulfur content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and still more preferably 0.7 parts by mass or more with respect to 100 parts by mass of the polymer component. be. The content is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

Sulfur includes powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur and the like commonly used in the rubber industry. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Io Co., Ltd., Shikoku Kasei Kogyo Co., Ltd., Flexis Co., Ltd., Nippon Kantan Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These may be used alone or in combination of two or more.

The polymer composition may contain a vulcanization accelerator.
In the polymer composition, the content of the vulcanization accelerator is usually 0.3-10 parts by mass, preferably 0.5-7 parts by mass, per 100 parts by mass of the polymer component.

The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram disulfide (TMTD ), tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N) and other thiuram vulcanization accelerators; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl- Sulfenamide-based vulcanization accelerators such as 2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N,N'-diisopropyl-2-benzothiazolesulfenamide; diphenylguanidine, Guanidine-based vulcanization accelerators such as dioltolylguanidine and orthotolylbiguanidine can be mentioned. These may be used alone or in combination of two or more. Among them, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred.

Among vulcanization accelerators, sulfenamide-based vulcanization accelerators and guanidine-based vulcanization accelerators are preferred. Although the content of the sulfenamide-based vulcanization accelerator is not particularly limited, it is preferably 0.3 to 4.0 parts by mass, preferably 0.5 to 2.5 parts by mass, based on 100 parts by mass of the polymer component. More preferably, it is 0.7 to 1.6 parts by mass. The content of the guanidine-based vulcanization accelerator is not particularly limited, but is preferably 0.5 to 5.0 parts by mass, preferably 0.8 to 3.0 parts by mass, more preferably 0.8 to 3.0 parts by mass, relative to 100 parts by mass of the polymer component. is 1.0 to 2.3 parts by mass.

In addition to the components described above, the polymer composition may also contain additives such as release agents and pigments, which are commonly used for their use, as appropriate according to the field of application.

The polymer composition is desirably a rubber composition containing a rubber component such as a diene rubber as a polymer component from the viewpoint of obtaining more effects.

The polymer composition has a contact angle with water of 90° or less at 25°C. The contact angle with water is preferably 80° or less, more preferably 75° or less, even more preferably 70° or less, and particularly preferably 65° or less. The lower limit is not particularly limited, and a smaller value is more desirable. Within the above range, the effect can be suitably obtained. Here, the contact angle with water is the angle formed by the tangent line of the water droplet and the surface of the polymer composition when water is dropped on the surface of the polymer composition. method can be measured.

It should be noted that the "contact angle with water at 25 ° is 90 ° or less" of the polymer composition is, for example, the use of a hydrophilic substance such as a modified polymer that has hydrophilicity and has been modified with an acid or base. It can be realized by using a flexible polymer, or the like.

The polymer composition reversibly changes its complex elastic modulus (E*) and loss tangent (tan δ) with water, and satisfies the above formula (1) and/or the above formula (2).

Thus, the present disclosure provides dry grip performance and wet grip performance by configuring a polymer composition that has a contact angle with water of 90 ° or more and satisfies the parameters of the above formulas (1) and / or (2). It solves the problem (objective) of improving the overall performance of That is, the parameter does not define a problem (objective), but the problem of the present application is to improve the overall performance of dry grip performance, wet grip performance, and fuel economy. An angle of 90° or more satisfies the parameters of the above formulas (1) and/or (2).

In the present specification, E* and tan δ of the polymer composition refer to E* and tan δ of the polymer composition after cross-linking when the polymer composition is cross-linkable. In the case of a crosslinkable rubber composition containing, it means E* and tan δ of the rubber composition after vulcanization (after crosslinking). E* and tan δ are values obtained by conducting a viscoelasticity test on the polymer composition (in the case of the polymer composition after cross-linking, the polymer composition after cross-linking).

As used herein, the reversible change in complex elastic modulus (E*) and loss tangent (tan δ) by water means that the presence of water reversibly changes E* and tan δ of the polymer composition (after vulcanization). It means to get bigger or smaller. It should be noted that, for example, E* and tan δ may reversibly change when dry→wet with water→dry. or may have the same E* and tan δ in the previous drying and the subsequent drying.

In the present specification, E* and tan δ at the time of drying mean the E* and tan δ of the polymer composition in a dried state, specifically, the polymer composition dried by the method described in Examples. of E*, tan δ.
As used herein, E* and tan δ when wet with water mean the E* and tan δ of the polymer composition in a state of being wet with water. means E*, tan δ of the polymer composition wetted by .

In the present specification, E* and tan δ of the polymer composition are E* and tan δ measured under the conditions of temperature of 30° C., initial strain of 10%, dynamic strain of 1%, frequency of 10 Hz, and elongation mode.

The polymer composition desirably satisfies the following formula (1).
E* when wet with water / E* when dry ≤ 0.90 (1)
(In the formula, E* is the complex elastic modulus measured under the conditions of a temperature of 30° C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an extensional mode.)
E* when wet with water/E* when dry is preferably 0.80 or less, more preferably 0.70 or less, still more preferably 0.65 or less, and particularly preferably 0.60 or less. The lower limit of E* when wet with water/E* when dry is not particularly limited, but is preferably 0.10 or more, more preferably 0.20 or more, still more preferably 0.30 or more, and particularly preferably 0.35 or more. is. Within the above range, the effect can be suitably obtained.

The polymer composition preferably has a dry E* of 4.0 MPa or more, more preferably 4.5 MPa or more, still more preferably 5.0 MPa or more, particularly preferably 5.5 MPa or more, and most preferably 8.0 MPa or more. is. Although the upper limit of E* during drying is not particularly limited, it is preferably 20.0 MPa or less, more preferably 15.0 MPa or less, even more preferably 13.0 MPa or less, and particularly preferably 11.0 MPa or less. Within the above range, the effect can be suitably obtained.

The polymer composition desirably satisfies the following formula (2).
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(In the formula, tan δ is the loss tangent measured under the conditions of a temperature of 30° C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an extensional mode.)
The tan δ when wet with water/tan δ when dry is preferably 1.25 or more, more preferably 1.30 or more, still more preferably 1.35 or more, and particularly preferably 1.40 or more. The upper limit of tan δ when wet with water/tan δ when dry is not particularly limited, but is preferably 1.80 or less, more preferably 1.70 or less, still more preferably 1.65 or less, and particularly preferably 1.60 or less. . Within the above range, the effect can be suitably obtained.

The dry tan δ of the polymer composition is preferably 2.2 or more, more preferably 2.7 or more, still more preferably 3.0 or more, and particularly preferably 3.3 or more. Although the upper limit of tan δ during drying is not particularly limited, it is preferably 6.0 or less, more preferably 5.5 or less, still more preferably 5.2 or less, and particularly preferably 5.0 or less. Within the above range, the effect can be suitably obtained.

In addition, the reversible E* change and tan δ change due to water represented by the above formulas (1) and / or (2) of the polymer composition are, for example, hydrophilic and modified with an acid or base It can be achieved by blending a modified polymer, surface-modified silica having a metal oxide and/or basic molecule on its surface, and optionally a hydrophilic polymer. Specifically, for example, when a modified polymer such as carboxylic acid-modified SBR is used in combination with a surface-modified silica having a metal oxide and/or a basic molecule on its surface, an anion derived from a carboxylic acid and a metal oxide or base With cations derived from organic molecules, an ionic bond is formed between the modified polymer and the metal oxide and/or surface-modified silica, and between them, the ionic bond is cleaved by the addition of water and the As a result of recombination of ionic bonds, it is believed that E* decrease and/or tan δ increase occurs when wet with water, and E* increase and/or tan δ decrease occurs when dry. Furthermore, by blending a hydrophilic polymer, water is effectively taken in, and as a result, the speed of the cleavage and recombination is accelerated, resulting in a decrease in E* and/or an increase in tan δ when wet with water, and an increase in E* when dry. and/or tan δ reduction occurs effectively.

E* at the time of drying can be adjusted by the type and amount of chemicals (in particular, polymer components, fillers, and softening agents such as oils) blended in the polymer composition. By decreasing the amount or increasing the amount of the filler, the dry E* tends to increase.

The dry tan δ can be adjusted by adjusting the type and amount of chemicals (particularly polymer components, fillers, softeners, resins, sulfur, vulcanization accelerators, and silane coupling agents) blended in the polymer composition. For example, using a softening agent (e.g., resin) that has low compatibility with the polymer component, using an unmodified polymer, increasing the amount of filler, increasing the amount of oil as a plasticizer, sulfur , the vulcanization accelerator, or the silane coupling agent, the tan δ at the time of drying tends to increase.

In addition, regarding E* and tan δ at the time of drying, for example, the amount of acidic functional groups and basic functional groups of the modified polymer, the amount of metal oxide, the basic molecule coating amount of the surface-modified silica (in other words, the amount of basic functional groups) It is possible to adjust E* and tan δ at the time of drying by adjusting the base coating amount. Specifically, when the amount of acidic functional groups and the amount of basic functional groups of the modified polymer, the amount of the metal oxide, and the amount of basic molecule coating of the silica are increased, E* tends to increase during drying, and when drying tan δ tends to be small.

E* and tan δ when wet with water are, for example, a polymer composition crosslinked by ionic bonds partially or entirely between the modified polymer and the metal oxide and/or surface-modified silica. By doing so, it is possible to reduce E* and/or increase tan δ when wet with water compared to when dry, and it is possible to adjust E* and tan δ when dry and when wet with water. Specifically, by using the modified polymer together with the metal oxide and/or the surface-modified silica, a polymer composition crosslinked by ionic bonds is obtained, and the E* when wet with water is lower than that when dry. can be reduced and/or tan δ increased. Furthermore, by blending the hydrophilic polymer, water is effectively taken in, and the rate of decrease in E* and/or increase in tan δ when wet with water is increased, and effectively, when wet with water compared to when dry. E* can be lowered and/or tan delta increased. In addition, the E* and tan δ when wet with water can be adjusted by the type and amount of the chemical compounded in the polymer composition. Similar tendencies can be obtained for E* and tan δ when wet with water by using the same method as in .

Specifically, after adjusting the E* and tan δ at the time of drying within the desired range, a modified polymer having hydrophilicity and modified with an acid or base, a metal oxide and / or a basic By using a surface-modified silica having a molecule on the surface and a hydrophilic polymer in combination, the polymer composition has a contact angle with water of 90° or less, represented by the above formulas (1) and / or (2). reversible E* change and/or tan δ change with water can be achieved.

A known method can be used as a method for producing the polymer composition. For example, each component can be kneaded using a rubber kneading device such as an open roll mixer or a Banbury mixer, and crosslinked as necessary. As for kneading conditions, the kneading temperature is usually 50 to 200° C., preferably 80 to 190° C., and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes.

Although the tire member using the above polymer composition is not particularly limited, it can be suitably used for a tread (cap tread).

Hereinafter, the present disclosure will be described in detail based on an example of a preferred embodiment with reference to the drawings as appropriate, but the present disclosure is not limited to this example.

A pneumatic tire 2 is shown in FIG. In FIG. 1 , the vertical direction is the radial direction of the tire 2 , the horizontal direction is the axial direction of the tire 2 , and the direction perpendicular to the paper surface is the circumferential direction of the tire 2 . In FIG. 1 , the dashed-dotted line CL represents the equatorial plane of the tire 2 . The shape of this tire 2 is symmetrical with respect to the equatorial plane, except for the tread pattern.

This tire 2 comprises a tread 4, a pair of sidewalls 6, a pair of wings 8, a pair of clinches 10, a pair of beads 12, a carcass 14, a belt 16, a band 18, an inner liner 20 and a pair of chafers 22. there is This tire 2 is of the tubeless type. This tire 2 is mounted on a passenger car.

The tread 4 has a shape that is convex radially outward. The tread 4 forms a tread surface 24 that contacts the road surface. Grooves 26 are cut in the tread 4 . The grooves 26 form a tread pattern. The tread 4 has a base layer 28 and a cap layer 30 . The cap layer 30 is positioned radially outwardly of the base layer 28 . Cap layer 30 is laminated to base layer 28 .

Although FIG. 1 shows an example of a two-layer tread 4 consisting of a cap layer 30 and a base layer 28, a single-layer tread 4 or a tread 4 having three or more layers may also be used.

At least one of the rubber layers constituting the tread 4 (the layer of the polymer composition after cross-linking) includes a hydrophilic modified polymer modified with an acid or base, a metal oxide and/or a basic molecule. on the surface, the contact angle with water at 25° C. is 90° or less, and the polymer composition satisfies the above formula (1) and/or the above formula (2). In the case of a single-layer structure tread, the polymer composition is a single-layer structure tread, in the case of a two-layer structure tread, the cap layer of the two-layer structure tread, and in the case of a tread having a structure of three or more layers, the cap layer (outermost layer) is the polymer composition. It is desirable to consist of

FIG. 2 is an enlarged sectional view showing the vicinity of the tread 4 of the tire 2 of FIG. In FIG. 2 , the vertical direction is the radial direction of the tire 2 , the horizontal direction is the axial direction of the tire 2 , and the direction perpendicular to the paper surface is the circumferential direction of the tire 2 .

In FIG. 2 , reference P is a point on the tread surface 24 . The point P is positioned outside the groove 26 that is positioned furthest inward in the axial direction. A double-headed arrow T is the thickness of the tread 4 at the point P. Thickness T is the sum of the thicknesses of cap layer 30 and base layer 28 at point P; This thickness T is measured along the normal to the tread surface 24 at point P. 1 and 2 show an example of the two-layer structure tread 4 consisting of the cap layer 30 and the base layer 28, but in the case of the single-layer structure tread 4, the thickness T of the tread is the single layer thickness at the point P. Structural tread thickness, in the case of a tread having a construction of three or more layers, the tread thickness T is the sum of the thicknesses of the three or more layers at that point P, in which case the thickness T at that point P is also Measured along the normal to the tread surface 24 .

The maximum thickness T of the tread 4 is preferably 10.0 mm, more preferably 9.0 mm or less, even more preferably 8.0 mm or less, particularly preferably 7.5 mm or less. The lower limit is preferably 5.5 mm or more, more preferably 6.0 mm or more. Within the above range, the effect tends to be obtained more favorably. Here, the maximum thickness T of the tread 4 is the maximum dimension among the thicknesses of each tread at each point on the tread surface 24 (the sum of the thicknesses of the cap layer 30 and the base layer 28 in FIG. 2).

In the tire 2 of FIG. 1, from the viewpoint of obtaining a better effect, the maximum thickness T (mm) of the tread 4 and the above-mentioned E* when wet with water/E* when dry should satisfy the following expression. is desirable.
T/(E* when wet with water/E* when dry)>8.5
T/(E* when wet with water/E* when dry) is preferably 10.0 or more, more preferably 11.0 or more, still more preferably 11.5 or more, and particularly preferably 12.0 or more. . The upper limit is preferably 22.0 or less, more preferably 20.0 or less, still more preferably 18.0 or less, and particularly preferably 17.0 or less. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
The smaller the maximum thickness T of the tread 4, the higher the rigidity of the tread portion, which makes it easier to generate a reaction force on dry road surfaces. It is thought that Therefore, as T is decreased, E* when wet/E* when dry is decreased, and by increasing the tracking performance when wet, it is good on both dry and wet road surfaces. It is thought that good grip performance can be easily obtained. Therefore, it is presumed that the overall performance of dry grip performance and wet grip performance is further improved.

In the tire 2 of FIG. 1, from the viewpoint of obtaining a better effect, it is desirable that the maximum thickness T (mm) of the tread 4 and the above-mentioned tan δ when wet with water/tan δ when dry satisfy the following expression. .
T × (tan δ when wet with water/tan δ when dry) > 8.5
Tx (tan δ when wet with water/tan δ when dry) is preferably 9.5 or more, more preferably 10.5 or more, still more preferably 11.0 or more, and particularly preferably 11.5 or more. The upper limit is preferably 21.0 or less, more preferably 19.0 or less, still more preferably 17.0 or less, and particularly preferably 16.0 or less. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
The smaller the maximum thickness T of the tread 4, the higher the rigidity of the tread portion, which makes it easier to generate a reaction force on dry road surfaces. It is thought that Therefore, as T is decreased, tan δ when wet/tan δ when dry is increased, and by improving the followability when wet, good grip is obtained on both dry and wet road surfaces. It is considered that the performance can be easily obtained. Therefore, it is presumed that the overall performance of dry grip performance and wet grip performance is further improved.

In the tire 2 of FIG. 1, each sidewall 6 extends generally radially inward from the edge of the tread 4 . A radially outer portion of this sidewall 6 is joined to the tread 4 . A radially inner portion of this sidewall 6 is joined with a clinch 10 .

Each wing 8 is located between the tread 4 and sidewall 6 . A wing 8 joins with each of the tread 4 and the sidewall 6 .

Each clinch 10 is positioned substantially radially inside the sidewall 6 . The clinch 10 is located outside the bead 12 and the carcass 14 in the axial direction.

Each bead 12 is located axially inside the clinch 10 . The bead 12 has a core 32 and an apex 34 extending radially outward from the core 32 . The core 32 is ring-shaped and includes a wound non-elastic wire or the like. Apex 34 tapers radially outward.

The carcass 14 includes carcass plies 36 . In this tire 2, the carcass 14 is composed of one carcass ply 36, but may be composed of two or more plies.

In this tire 2 , the carcass ply 36 is spanned between the beads 12 on both sides and along the tread 4 and the sidewalls 6 . The carcass ply 36 is folded back around each core 32 from the axial inner side to the outer side. By this folding, the carcass ply 36 is formed with a main portion 36a and a pair of folded portions 36b. That is, the carcass ply 36 includes a main portion 36a and a pair of folded portions 36b.

Although not shown, the carcass ply 36 may be composed of a large number of parallel cords and a topping rubber. This carcass 14 preferably has a radial structure.

The belt 16 is positioned radially inside the tread 4 . The belt 16 is laminated with the carcass 14 . Belt 16 consists of an inner layer 38 and an outer layer 40 .

Although not shown, each of the inner layer 38 and the outer layer 40 may be composed of a number of parallel cords and a topping rubber. Each code is, for example, slanted with respect to the equatorial plane. The direction of inclination of the cords of the inner layer 38 with respect to the equatorial plane is opposite to the direction of inclination of the cords of the outer layer 40 with respect to the equatorial plane.

The band 18 is located radially outside the belt 16 . In the axial direction, band 18 has a width equal to the width of belt 16 . This band 18 may have a width greater than the width of this belt 16 .

Although not shown, the band 18 may be composed of a cord and a topping rubber. The cord is, for example, spirally wound.

Belt 16 and band 18 constitute a reinforcing layer. The reinforcing layer may be composed only of the belt 16 .

The inner liner 20 is positioned inside the carcass 14 . An inner liner 20 is joined to the inner surface of the carcass 14 .

Each chafer 22 is positioned near the bead 12 . In this embodiment, the chafer 22 may be made of cloth and rubber impregnated in the cloth. This chafer 22 may be integrated with the clinch 10 .

In this tire 2 , the tread 4 has main grooves 42 as the grooves 26 . As shown in FIG. 1, the tread 4 is provided with a plurality of, more specifically, three main grooves 42 . These main grooves 42 are spaced apart in the axial direction. The tread 4 is formed with four ribs 44 extending in the circumferential direction by cutting three main grooves 42 . That is, the main groove 42 is between the ribs 44 .

Each main groove 42 extends in the circumferential direction. The main groove 42 is continuous in the circumferential direction.

The tire 2 having the tread 4 made of the polymer composition preferably has a negative rate (S) of 50% or less.
The negative rate (S) of the tread 4 is preferably 40% or less, more preferably 35% or less, even more preferably 30% or less. The negative rate is preferably 5% or more, more preferably 10% or more, still more preferably 15% or more. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
As described above, by satisfying the above formulas (1) and/or (2), the friction (μ) on wet road surfaces is improved due to an increase in the contact area with the road surface and/or an increase in energy loss when wet. However, wet grip performance improves, and when dry, ionic bonding occurs again, and the complex elastic modulus E* returns, so it is presumed that good friction (μ) and fuel efficiency can be maintained when driving on dry roads. However, it is thought that the low negative rate of the tread further improves the friction (μ) on wet road surfaces and further improves the wet grip performance. Therefore, it is presumed that a tire having a tread composed of the polymer composition has improved overall dry grip performance and wet grip performance.

In the tire 2 having the tread 4 composed of the polymer composition, the E* of the polymer composition when wet with water and the E* of the dry time, and the negative rate S (%) of the tread 4 satisfy the following formula. is preferred.
(E* when wet with water/E* when dry) x S ≤ 28.0
(E* when wet with water/E* when dry)×S is preferably 25.0 (%) or less, more preferably 22.0 (%) or less, still more preferably 20.0 (%) or less, Especially preferably, it is 19.0 (%) or less. Although the lower limit is not particularly limited, it is preferably 5.0 (%) or more, more preferably 10.0 (%) or more, and still more preferably 12.0 (%) or more. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
As described above, by satisfying the above formula (1), the friction (μ) on the wet road surface is improved due to the increase in the contact area with the road surface when wet, and the wet grip performance is improved. , It is presumed that good friction (μ) and low fuel consumption can be maintained when driving on dry roads by ionic bonding occurring again and E* returning. Friction (μ) is further improved, and wet grip performance is considered to be further improved. Therefore, it is presumed that the overall performance of dry grip performance and wet grip performance is further improved.

In the tire 2 having the tread 4 composed of the polymer composition, the tan δ of the polymer composition when wet with water and the tan δ when dry, and the negative rate S (%) of the tread 4 preferably satisfy the following formula. .
(tan δ when wet with water/tan δ when dry)/S≧0.035
(tan δ when wet with water/tan δ when dry)/S is preferably 0.040 (1/%) or more, more preferably 0.043 (1/%) or more, and still more preferably 0.045 (1/ %) or more, particularly preferably 0.047 (1/%) or more. Although the upper limit is not particularly limited, it is preferably 0.100 (1/%) or less, more preferably 0.080 (1/%) or less, and still more preferably 0.070 (1/%) or less. Within the above range, the effect tends to be obtained more favorably.

Although the reason why such an effect is obtained is not necessarily clear, it is presumed to be due to the following mechanism.
As described above, by satisfying the above formula (2), the friction (μ) on the wet road surface is improved due to the increase in energy loss when wet with water, and the wet grip performance is improved. It is speculated that good friction (μ) and fuel efficiency can be maintained when driving on dry road surfaces by returning tan δ, but the low negative rate of the tread reduces friction (μ) on wet road surfaces. It is thought that the wet grip performance will further improve. Therefore, it is presumed that the overall performance of dry grip performance, wet grip performance, and low fuel consumption is further improved.

The negative rate (negative rate within the contact surface of the tread portion) is the ratio of the total groove area within the contact surface to the total area of the contact surface, and is measured by the following method.
In this specification, when the tire is a pneumatic tire, the negative rate is calculated from the contact shape under normal rim, normal internal pressure, and normal load conditions. Non-pneumatic tires can be similarly measured without the need for regular internal pressure.
A "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. If there is, it means "Measuring Rim".
The "regular internal pressure" is the air pressure specified for each tire by the above-mentioned standards. For JATMA, it is the maximum air pressure. If there is, it means "INFLATION PRESSURE", which is 180 kPa in the case of a passenger car tire.
"Normal load" is the load defined for each tire by the above standards, maximum load capacity for JATMA, maximum value described in table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, ETRTO If so, it means the load obtained by multiplying "LOAD CAPACITY" by 0.88.
As for the shape of the ground contact, the tire tread surface was painted with ink after being assembled on a regular rim, applying regular internal pressure, and allowed to stand at 25°C for 24 hours. obtained by transferring to
The tire is rotated by 72° in the circumferential direction and transferred at five locations. That is, the ground shape is obtained five times.
Let L be the average value of the maximum length in the axial direction of the tire, and W be the average value of the length in the direction perpendicular to the axial direction of the five ground contact shapes.
The negative rate (%) is calculated by [1−{Average area of 5 transferred ground shapes (black parts) of cardboard/(L×W)}]×100 (%).
Here, the average value of length and area is a simple average of five values.

In manufacturing the tire 2, a plurality of rubber members are assembled to obtain a raw cover (unvulcanized tire 2). This raw cover is put into the mold. The outer surface of the raw cover abuts the cavity surface of the mold. The inner surface of the raw cover abuts the bladder or core. The raw cover is pressurized and heated within the mold. The pressure and heat cause the polymer composition of the raw cover to flow. Heating causes the rubber to undergo a cross-linking reaction, and the tire 2 is obtained. An uneven pattern is formed on the tire 2 by using a mold having an uneven pattern on the cavity surface.

Examples of the tire 2 include a pneumatic tire and a non-pneumatic tire. Among them, pneumatic tires are preferred. For example, it can be suitably used as summer tires (summer tires) and winter tires (studless tires, snow tires, stud tires, etc.). Tires can be used as tires for passenger cars, tires for large passenger cars, tires for large SUVs, tires for heavy loads such as trucks and buses, tires for light trucks, tires for two-wheeled vehicles, tires for racing (high performance tires), and the like.

The present disclosure will be specifically described based on Examples, but the present disclosure is not limited thereto.

Various chemicals used in Examples and Comparative Examples will be collectively described.
Carboxylic acid-modified SBR: Synthesized according to Production Example 1 below (Carboxylic acid group content: 5% by mass, styrene content: 23% by mass, butadiene content: 72% by mass)
SBR: Nipol 1502 (E-SBR) manufactured by ZEON Co., Ltd.
Carboxylic acid-modified BR: Synthesized according to Production Example 2 below (Carboxylic acid group content: 5% by mass, butadiene content: 95% by mass)
BR: BR730 (high-cis polybutadiene (cis content 96% by mass) manufactured by JSR)
NR: TSR20
Carbon black: Diablack I manufactured by Mitsubishi Chemical Corporation (N220, N ₂ SA114m ² /g, DBP 114ml/100g)
Silica: Ultrasil VN3 from Evonik Degussa (N ₂ SA 175 m ² /g)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by EVONIK
Magnesium oxide 1: Kyowamag 150 manufactured by Kyowa Chemical Industry Co., Ltd. (apparent specific gravity 0.36 g/ml, d50: 4.46 μm, N ₂ SA: 145 m ² /g)
Magnesium oxide 2: Kyowamag 150MF manufactured by Kyowa Chemical Industry Co., Ltd. (apparent specific gravity 0.23 g/ml, d50: 0.72 μm, N ₂ SA: 119 m ² /g)
Calcium oxide: Calcium oxide manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Basic molecule 1: KBE-903 (3-aminopropyltriethoxysilane) manufactured by Shin-Etsu Chemical
Basic molecule 2: Shin-Etsu Chemical KBM-903 (3-aminopropyltrimethoxysilane)
Basic molecule 3: Shin-Etsu Chemical KBM-603 (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane)
Hydrophilic polymer 1: Production example 3 below
Hydrophilic polymer 2: Production example 4 below
Hydrophilic polymer 3: Kuramilon TU polymer manufactured by Kuraray Co., Ltd. (diblock copolymer having one styrene-based elastomer block and one hydrophilic polyurethane-based elastomer block)
Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd.
and styrene copolymer, softening point: 85 ° C.)
Resin: PR120 manufactured by Exxon Mobil (hydrogenated DCPD resin, softening point 120°C)
Zinc oxide: zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: stearic acid "Tsubaki" manufactured by NOF Corporation
Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd.
Antiaging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Antiaging agent 2: Nocrac RD (poly (2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Sulfur: powdered sulfur (containing 5% oil) manufactured by Tsurumi Chemical Industry Co., Ltd.
Vulcanization accelerator DPG: Noccellar D (diphenylguanidine) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
Vulcanization accelerator NS: Noxcellar NS (N-tert-butyl-2-benzothiazylsulfenamide (TBBS)) manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.

<Production Example 1: Synthesis of carboxylic acid-modified SBR>
(Preparation of latex)
A pressure-resistant reactor equipped with a stirrer was charged with 2000 g of distilled water, 45 g of emulsifier (1), 1.5 g of emulsifier (2), 8 g of electrolyte, 250 g of styrene, 50 g of methacrylic acid, 700 g of butadiene and 2 g of molecular weight modifier. The reactor temperature was set to 5° C., and an aqueous solution in which 1 g of a radical initiator and 1.5 g of SFS were dissolved and an aqueous solution in which 0.7 g of EDTA and 0.5 g of a catalyst were dissolved were added to the reactor to initiate polymerization. After 5 hours from the initiation of polymerization, 2 g of a polymerization terminator was added to terminate the reaction to obtain a latex.
(Preparation of rubber)
Unreacted monomers were removed from the resulting latex by steam distillation. Thereafter, the latex was added to alcohol and coagulated while adjusting the pH to 3 to 5 with a saturated sodium chloride aqueous solution or formic acid to obtain a crumb-like polymer. The polymer was dried in a vacuum dryer at 40° C. to obtain a solid rubber (emulsion polymerized rubber).

<Production Example 2: Synthesis of carboxylic acid-modified BR>
(Preparation of latex)
A pressure-resistant reactor equipped with a stirrer was charged with 2000 g of distilled water, 45 g of emulsifier (1), 1.5 g of emulsifier (2), 8 g of electrolyte, 50 g of methacrylic acid, 950 g of butadiene and 2 g of molecular weight modifier. The reactor temperature was set to 5° C., and an aqueous solution in which 1 g of a radical initiator and 1.5 g of SFS were dissolved and an aqueous solution in which 0.7 g of EDTA and 0.5 g of a catalyst were dissolved were added to the reactor to initiate polymerization. After 5 hours from the initiation of polymerization, 2 g of a polymerization terminator was added to terminate the reaction to obtain a latex.
(Preparation of rubber)
Unreacted monomers were removed from the resulting latex by steam distillation. Thereafter, the latex was added to alcohol and coagulated while adjusting the pH to 3 to 5 with a saturated sodium chloride aqueous solution or formic acid to obtain a crumb-like polymer. The polymer was dried in a vacuum dryer at 40° C. to obtain a solid rubber (emulsion polymerized rubber).

The materials used in Production Examples 1 and 2 are as follows.
Emulsifier (1): rosin acid soap manufactured by Harima Chemicals Co., Ltd. Emulsifier (2): fatty acid soap manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd. Electrolyte: sodium phosphate styrene manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.: Fuji Styrene methacrylic acid manufactured by Film Wako Pure Chemical Industries, Ltd.: Butadiene methacrylate manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.: 1,3-butadiene manufactured by Takachiho Chemical Industry Co., Ltd. Molecular weight modifier: Fuji Film Wako Pure Chemical Industries, Ltd. ( Co., Ltd. tert-dodecyl mercaptan radical initiator: NOF Corporation paramenthan hydroperoxide SFS: FUJIFILM Wako Pure Chemical Co., Ltd. sodium formaldehyde sulfoxylate EDTA: FUJIFILM Wako Pure Chemical ( Co., Ltd. Sodium ethylenediaminetetraacetate Catalyst: FUJIFILM Wako Pure Chemical Co., Ltd. ferric sulfate Polymerization terminator: FUJIFILM Wako Pure Chemical Co., Ltd. N,N'-dimethyldithiocarbamate Alcohol: Kanto Chemical Co., Ltd. methanol, ethanol Formic acid: Kanto Kagaku Co., Ltd. Sodium formate chloride: Fujifilm Wako Pure Chemical Co., Ltd. sodium chloride

<Production Example 3: Synthesis of hydrophilized ENR50>
A tetrahydrofuran solution of ENR50 (manufactured by Kumpuran Guthrie, epoxidation rate: 50 mol %) was poured into methanol, washed with alcohol, and then dried. The purified ENR50 was dissolved in dimethylformamide, polyethylene glycol monomethyl ether (Mw: 400) was added, and the mixture was heated in an oil bath at 140°C and stirred under a nitrogen atmosphere for 8 hours. After that, the solvent was removed with an evaporator, and vacuum drying was performed at 80° C. for 12 hours. Further, this was subjected to Soxhlet extraction using methanol for 24 hours, and the purified product was vacuum-dried in an oven at 25°C for 3 days to obtain a hydrophilized ENR50. Polyethylene glycol monomethyl ether was added to all the epoxy groups in the obtained hydrophilized ENR50 to open the ring (ring-opening rate: 100%).

<Production Example 4: Synthesis of Hydrophilized ENR25>
Hydrophilized ENR25 was obtained in the same manner as in Production Example 2, except that ENR25 (manufactured by Kumpuran Guthrie, epoxidation rate: 25 mol%) was used. Polyethylene glycol monomethyl ether was added to all of the epoxy groups in the resulting hydrophilic ENR25 to open the ring (ring opening rate: 100%).

(Examples and Comparative Examples)
Chemicals other than sulfur and a vulcanization accelerator were kneaded at 160°C for 4 minutes using a 16L Banbury mixer manufactured by Kobe Steel, Ltd. according to the compounding recipe shown in each table to obtain a kneaded product. rice field. Next, sulfur and a vulcanization accelerator were added to the resulting kneaded product, and the mixture was kneaded at 80° C. for 4 minutes using an open roll to obtain an unvulcanized polymer composition. The resulting unvulcanized polymer composition was molded into a tread shape, laminated together with other tire members on a tire building machine to form an unvulcanized tire, and then vulcanized at 170° C. for 12 minutes. A tire (size: 195/65R15) was produced.

The physical properties of the materials used (carboxylic acid-modified SBR, carboxylic acid-modified BR, surface-modified silica) and the produced test tire were measured and evaluated as follows. The results are shown in the above various chemicals and in each table. The reference comparative example in Table 1 was Comparative Example 1-1, and the reference comparative example in Table 2 was Comparative Example 2-1.

<Reaction Rate of Basic Molecules>
Unreacted basic molecules of each surface-modified silica were eluted in water by the following method, and the reaction rate of the basic molecules was calculated by titration.
(1) Create a calibration curve for basic molecules.
(2) Disperse surface-modified silica in water, elute unreacted basic molecules, and perform titration.
(3) Calculate the amount of unreacted basic molecules from the titration constant and the calibration curve.
(4) Calculate the reaction rate from the amount of the basic molecule used in the synthesis.
From the above, it was found that each surface-modified silica of Examples has basic molecules on the silica surface.

<Carboxylic acid group content>
The carboxylic acid group contents of the carboxylic acid-modified SBR and the carboxylic acid-modified BR were calculated using ¹ H-NMR.

<Negative rate>
The resulting test tire was measured for negative rate by the following method (measured negative rates are shown in Tables 1 and 2).
The ground contact shape of the tread of the test tire is attached to the regular rim, the regular internal pressure is applied, and after standing at 25°C for 24 hours, the tire tread surface is painted with ink, a regular load is applied, and it is pressed against a cardboard (camber angle is 0°), obtained by transfer to paper. The tire was rotated by 72° in the circumferential direction and transferred at five locations to obtain five contact shapes. With respect to the five ground contact shapes, the negative rate (%) was measured by the following formula, where L is the average maximum length in the tire axial direction, and W is the average length in the direction orthogonal to the axial direction. The average value of length and area was a simple average of five values.
Negative rate (%) = [1-{average area of 5 ground shapes (black parts) transferred to cardboard/(L x W)}] x 100

<Contact angle with water>
A 2 mm-thick sheet (vulcanized polymer composition) was taken from the inside of the rubber layer of the tread of each test tire, and the contact angle with water at 25°C was measured.
Specifically, after wiping a sheet with a thickness of 2 mm with water, keeping it at a measurement temperature of 25 ° C. for 10 minutes, 20 μL of water droplets are dropped on the sheet surface, and the contact angle of the droplet after 15 seconds is measured by a contact angle measuring device. was measured using
The contact angles of carboxylic acid-modified SBR and carboxylic acid-modified BR with water were measured in the same manner, except that the 2 mm thick sheet (vulcanized polymer composition) was changed to carboxylic acid-modified SBR and carboxylic acid-modified BR. bottom.

<Viscoelasticity test>
A viscoelasticity measurement sample of length 40 mm x width 3 mm x thickness 0.5 mm was taken from the inside of the rubber layer of the tread of each test tire so that the tire circumferential direction was the long side, and tan δ and E* of the tread rubber were measured. , Using the RSA series manufactured by TA Instruments, temperature 30 ° C., initial strain 10%, dynamic strain 1%, frequency 10 Hz, extension mode, measurement time 30 minutes. Minutes later measurements were taken. In addition, the thickness direction of the sample was set to the tire radial direction.

<Drying E* and tan δ>
The viscoelasticity measurement sample (length 40 mm×width 3 mm×thickness 0.5 mm) was dried under the conditions of normal temperature and normal pressure until the weight became constant. The complex elastic modulus E* and the loss tangent tan δ of the vulcanized polymer composition (rubber piece) when dried were measured by the above-described methods, and were defined as E* and tan δ when dried.

<E* and tan δ when wet with water>
The viscoelasticity measurement sample (length 40 mm×width 3 mm×thickness 0.5 mm) was immersed in 100 ml of water at 23° C. for 2 hours to obtain a water-wet vulcanized polymer composition. The complex elastic modulus E* and the loss tangent tan δ of the resulting vulcanized polymer composition (rubber piece) when wet with water were measured using an RSA immersion measurement jig in water by the above method. , E* when wet with water, and tan δ. The water temperature was set at 30°C.

<Comprehensive performance of dry grip performance and wet grip performance>
Each test tire was installed on all wheels of a vehicle (made in Japan FF2000cc) and run 10 laps on a course with a mixture of dry and wet road surfaces. The test driver evaluated it on a scale of 1 to 5. A higher score indicates better performance. The total score of 20 people's evaluation was calculated, and the total score of the reference comparative example was set to 100, and indexed. A larger index indicates better overall dry grip performance and wet grip performance.

From each table, a polymer component containing a modified polymer having hydrophilicity and modified with an acid or base, a surface-modified silica having a metal oxide and / or a basic molecule on the surface, and a hydrophilic polymer and a contact angle with water at 25 ° C. of 90 ° or less, and the tire of the example provided with a tread made of a polymer composition that satisfies the above formula (1) and / or the above formula (2) is a dry grip The overall performance of performance and wet grip performance was remarkably superior.

The present disclosure (1) is selected from the group consisting of a polymer component containing a modified polymer that has hydrophilicity and is modified with an acid or base, a metal oxide, and a surface-modified silica having basic molecules on its surface. and a hydrophilic polymer,
The contact angle with water at 25° is 90° or less,
The polymer composition reversibly changes the complex elastic modulus (E*) and the loss tangent (tan δ) with water and satisfies the following formula (1) and/or the following formula (2).
E* when wet with water / E* when dry ≤ 0.90 (1)
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(Wherein, E* and tan δ are the complex elastic modulus and loss tangent measured under the conditions of a temperature of 30° C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an extensional mode.)

This disclosure (2) is a polymer composition according to this disclosure (1) that satisfies the following formula.
E* when wet with water / E* when dry ≤ 0.70

This disclosure (3) is a polymer composition according to this disclosure (1) or (2) that satisfies the following formula.
tan δ when wet with water/tan δ when dry ≥ 1.30

The present disclosure (4) is at least selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide. A polymer composition according to any one of the present disclosure (1) to (3) comprising one.

In the present disclosure (5), the hydrophilic polymer is selected from the group consisting of isoprene-based rubbers modified with hydrophilic functional groups, hydrophilic thermoplastic elastomers, acrylic acid-based polymers, and sulfonic acid-based polymers. A polymer composition according to any one of the present disclosure (1) to (4) comprising at least one.

Disclosure (6) is a tire having a tread composed of the polymer composition according to any one of Disclosures (1) to (5).

The present disclosure (7) is the tire according to the present disclosure (6), wherein the maximum thickness T of the tread and the wet E*/dry E* satisfy the following formula.
T/(E* when wet with water/E* when dry)>8.5

The present disclosure (8) is the tire according to the present disclosure (6) or (7), wherein the maximum thickness T of the tread and the wet tan δ/dry tan δ satisfy the following formula.
T × (tan δ when wet with water/tan δ when dry) > 8.5

(9) of the present disclosure is the tire according to any one of (6) to (8) of the present disclosure, wherein the negative ratio S of the tread is 40% or less.

The present disclosure (10) is the tire according to the present disclosure (9), wherein E* when wet with water and E* when dry of the polymer composition and the negative rate S (%) of the tread satisfy the following formulae.
(E* when wet with water/E* when dry) x S ≤ 28.0

The present disclosure (11) is the tire according to the present disclosure (9) or (10), wherein the tan δ of the polymer composition when wet with water and the tan δ of the dry state, and the negative ratio S (%) of the tread satisfy the following formulae. .
(tan δ when wet with water/tan δ when dry)/S≧0.035

2 pneumatic tire 4 tread 6 sidewall 8 wing 10 clinch 12 bead 14 carcass 16 belt 18 band 20 inner liner 22 chafer 24 tread surface 26 groove 28 base layer 30 cap layer 32 core 34 apex 36 carcass ply 36a main portion 36b Folded portion 38 Inner layer 40 Outer layer 42 Main groove 44 Rib CL Equatorial plane P of tire 2 Point T on tread surface 24 Thickness of tread 4

Claims (11)

a polymer component having hydrophilicity and containing a modified polymer modified with an acid or base;
at least one selected from the group consisting of metal oxides and surface-modified silica having basic molecules on the surface;
and a hydrophilic polymer,
The contact angle with water at 25° is 90° or less,
A polymer composition whose complex elastic modulus (E*) and loss tangent (tan δ) reversibly change with water and which satisfies the following formula (1) and/or the following formula (2).
E* when wet with water / E* when dry ≤ 0.90 (1)
tan δ when wet with water/tan δ when dry ≥ 1.10 (2)
(Wherein, E* and tan δ are the complex elastic modulus and loss tangent measured under the conditions of a temperature of 30° C., an initial strain of 10%, a dynamic strain of 1%, a frequency of 10 Hz, and an extensional mode.) 2. The polymer composition of claim 1, which satisfies the formula:
E* when wet with water / E* when dry ≤ 0.70 3. The polymer composition according to claim 1 or 2, which satisfies the following formula.
tan δ when wet with water/tan δ when dry ≥ 1.30 The metal oxide comprises at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide, and barium oxide. 4. The polymer composition according to any one of 1-3. The hydrophilic polymer includes at least one selected from the group consisting of isoprene-based rubber modified with a hydrophilic functional group, hydrophilic thermoplastic elastomer, acrylic acid-based polymer, and sulfonic acid-based polymer. Item 5. The polymer composition according to any one of items 1 to 4. A tire having a tread composed of the polymer composition according to any one of claims 1-5. 7. The tire according to claim 6, wherein the maximum thickness T of the tread and the wet E*/dry E* satisfy the following formula.
T/(E* when wet with water/E* when dry)>8.5 The tire according to claim 6 or 7, wherein the maximum thickness T of the tread and the wet tan δ/dry tan δ satisfy the following formula.
T × (tan δ when wet with water/tan δ when dry) > 8.5 The tire according to any one of claims 6 to 8, wherein the tread has a negative rate S of 40% or less. 10. The tire according to claim 9, wherein E* of the polymer composition when wet with water, E* of the polymer composition when dry, and negative rate S (%) of the tread satisfy the following formulae.
(E* when wet with water/E* when dry) x S ≤ 28.0 11. The tire according to claim 9 or 10, wherein tan δ of said polymer composition when wet with water, tan δ of said polymer composition when dry, and negative rate S (%) of said tread satisfy the following formulae.
(tan δ when wet with water/tan δ when dry)/S≧0.035

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