Rubber composition for tire, crosslinked rubber composition for tire and pneumatic tire

Abstract

To provide a rubber composition for a tire particularly useful for a tire for heavy load, which is capable of obtaining a crosslinked rubber composition for a tire having excellent wet grip performance, low rolling resistance and wear resistance.SOLUTION: There is provided a rubber composition for a tire which comprises at least one rubber component selected from the group consisting of a conjugated diene-based rubber and its hydrogenated product, silica and at least one polymer component selected from the group consisting of a polymer (A) having a side chain (a) containing a hydrogen-bonding cross-linking site having a carbonyl-containing group and / or a nitrogen-containing heterocycle and a glass transition point of 25°C or less and a polymer (B) containing a hydrogen-bonding cross-linking site and a covalent bonding cross-linking site on the side chain and having a glass transition point of 25°C or less, wherein the rubber component contains 50 mass% more of an isoprene-based rubber, the average glass transition temperature of the rubber component is -90°C or more and -50°C or less, the content of the polymer component is 1 to 100 pts.mass based on 100 pts.mass of the rubber component and the type A rubber hardness after curing the rubber composition for a tire at 0°C as specified in ISO is 55 to 70.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for tires, a crosslinked rubber composition for tires, and a pneumatic tire using them. [Background technology]

[0002] Conventionally, the use of various polymers for modifying rubber compositions has been investigated. For example, International Publication No. 2021 / 261406 (Patent Document 1) discloses a specific polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle and having a glass transition temperature of 25°C or lower, and a specific polymer (B) having a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linkable moiety in the side chain and having a glass transition temperature of 25°C or lower. Furthermore, the document also discloses a rubber composition comprising such a polymer and uncross-linked rubber. However, even with the rubber composition described in Patent Document 1, there is still room for improvement in terms of wet grip performance, low rolling resistance, and abrasion resistance of the resulting cross-linked rubber composition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 261406 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the problems associated with the prior art, and an object of the present invention is to provide a rubber composition for tires that is particularly useful for heavy-duty tires, making it possible to obtain a crosslinked rubber composition for tires and a pneumatic tire that are superior in wet grip performance, low rolling resistance, and abrasion resistance. [Means for solving the problem]

[0005] The present inventors have conducted extensive research to achieve the above-mentioned object, and have found that by using at least one polymer component selected from the group consisting of a polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle and having a glass transition point of 25°C or lower, and a polymer (B) containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety in a side chain and having a glass transition point of 25°C or lower, and by incorporating a specific rubber component, silica, and the polymer component so as to obtain a specific composition, and further by preparing a rubber composition for tires having a Type A rubber hardness after curing within a specific range, the wet grip performance, low rolling resistance, and abrasion resistance of the obtained cross-linked rubber composition and pneumatic tire can be improved in a well-balanced manner, and the rubber composition is particularly useful for heavy load tires, and have completed the present invention.

[0006] That is, the present invention provides the following aspects.

[0007] [1] At least one rubber component selected from the group consisting of conjugated diene rubbers and hydrogenated products thereof; Silica and at least one polymer component selected from the group consisting of a polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle and having a glass transition point of 25°C or lower, and a polymer (B) having a side chain containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety and having a glass transition point of 25°C or lower; A rubber composition for a tire comprising: The rubber component contains 50% by mass or more of an isoprene-based rubber, The rubber component has an average glass transition temperature of −90° C. or higher and −50° C. or lower, the content of the polymer component is 1 to 100 parts by mass relative to 100 parts by mass of the rubber component, The rubber composition for tires has an ISO Type A rubber hardness of 55 to 70 at a temperature of 0°C after curing.

[0008] [2] The rubber composition for a tire according to [1], wherein both the polymer (A) and the polymer (B) have a main chain in which 2.0 mol % to 60 mol % of the total amount of monomer units constituting the main chain are double-bond-containing monomer units containing a double bond at a position forming the main chain skeleton.

[0009] [3] The rubber composition for tires according to [1] or [2], wherein the rubber component is an uncrosslinked rubber component that does not have a hydrogen-bond crosslinkable site.

[0010] [4] The rubber composition for a tire according to any one of [1] to [3], wherein the isoprene-based rubber is a natural rubber.

[0011] [5] The CTAB adsorption specific surface area of ​​the silica is 150 to 300 m 2 / g, and the content of the silica is 5 to 80 parts by mass per 100 parts by mass of the rubber component.

[0012] [6] A crosslinked rubber composition for a tire, which is a crosslinking reaction product of the rubber composition for a tire according to any one of [1] to [5].

[0013] [7] A pneumatic tire in which the crosslinked rubber composition for tires according to [6] is used in the tire tread.

[0014] [8] A pneumatic tire according to [7], which is used as a heavy-duty tire. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a crosslinked rubber composition for tires and a pneumatic tire that are excellent in wet grip performance, low rolling resistance, and abrasion resistance, and a rubber composition for tires that is particularly useful for heavy-duty tires. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below with reference to preferred embodiments. In this specification, unless otherwise specified, the expression "X to Y" for numerical values ​​X and Y means "X or more and Y or less." In such an expression, when a unit is assigned only to the numerical value Y, the unit is also applied to the numerical value X.

[0017] [Rubber composition for tires] First, the rubber composition for tires of the present invention will be described. The rubber composition for tires of the present invention includes at least one rubber component selected from the group consisting of conjugated diene rubbers and hydrogenated products thereof, silica, and at least one polymer component selected from the group consisting of a polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle and having a glass transition temperature of 25°C or lower, and a polymer (B) having a side chain containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linkable moiety and having a glass transition temperature of 25°C or lower, wherein the rubber component contains 50% by mass or more of an isoprene-based rubber, the average glass transition temperature of the rubber component is -90°C or higher and -50°C or lower, the content of the polymer component is 1 to 100 parts by mass per 100 parts by mass of the rubber component, and the rubber composition for tires has an ISO Type A rubber hardness of 55 to 70 at a temperature of 0°C after curing. Each element will be described in detail below.

[0018] (rubber component) The rubber component contained in the rubber composition for tires of the present invention is at least one selected from the group consisting of conjugated diene rubbers and their hydrogenated products, and must contain at least one isoprene rubber. Isoprene rubbers have high mechanical strength and are also excellent in viscoelasticity and abrasion resistance, and the use of isoprene rubber makes it possible to improve the wet grip performance, low rolling resistance, and abrasion resistance of the resulting crosslinked rubber composition in a well-balanced manner.

[0019] Examples of isoprene-based rubbers include natural rubber, isoprene rubber, isoprene-butadiene rubber, and halogenated isoprene rubber, with natural rubber being preferred. Examples of natural rubber include natural rubber latex, technically graded rubber (TSR), smoked sheet (RSS), gutta-percha, Eucommia-derived natural rubber, guayule-derived natural rubber, Russian dandelion-derived natural rubber, and plant-fermented rubber. Modified versions of these natural rubbers, such as epoxidized natural rubber, methacrylic acid-modified natural rubber, styrene-modified natural rubber, sulfonic acid-modified natural rubber, and zinc sulfonate-modified natural rubber, are also included in the natural rubber category.

[0020] The content of the isoprene-based rubber in the rubber component (conjugated diene-based rubber and / or its hydrogenated product) used in the present invention must be 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. If the content of the isoprene-based rubber is within the above numerical range, it is easy to adjust the average glass transition temperature to within the numerical range described below, and a rubber composition for tires can be obtained that can improve the wet grip performance, low rolling resistance, and abrasion resistance of the resulting crosslinked rubber composition in a well-balanced manner.

[0021] In the present invention, the rubber component may consist solely of the isoprene-based rubber, but the rubber component may also be a combination of at least one selected from the group consisting of conjugated diene-based rubbers other than the isoprene-based rubbers and hydrogenated products thereof.

[0022] Examples of conjugated diene rubbers other than the isoprene rubber include aromatic vinyl-conjugated diene copolymer rubbers such as styrene-butadiene rubber, styrene-isoprene-butadiene rubber, styrene-isoprene rubber, and styrene-α-methylstyrene-butadiene rubber; and conjugated diene (co)polymer rubbers such as butadiene rubber, butyl rubber, halogenated butyl rubber, and ethylene-propylene-diene rubber. Of these, butadiene rubber is preferred. Because butadiene rubber has a low glass transition temperature, the use of butadiene rubber makes it easier to adjust the average glass transition temperature of the rubber component to within the numerical range described below, which tends to enable the resulting crosslinked rubber composition to have better balanced improvements in wet grip performance, low rolling resistance, and abrasion resistance.

[0023] The hydrogenated products of conjugated diene rubbers other than the isoprene rubber are not particularly limited in hydrogenation rate, and include hydrogenated products of the aromatic vinyl-conjugated diene copolymer rubber and hydrogenated products of the conjugated diene (co)polymer rubber, and examples thereof include hydrogenated styrene-butadiene rubber and partially hydrogenated styrene-butadiene rubber.

[0024] The conjugated diene rubber also includes modified conjugated diene rubbers. Modified conjugated diene rubbers include conjugated diene rubbers modified by main chain modification, one-end modification, both-end modification, etc. Here, examples of the modified functional group of the modified conjugated diene rubber include various functional groups such as epoxy groups, amino groups, alkoxysilyl groups, and hydroxyl groups, and one or more of these functional groups may be contained in the modified conjugated diene rubber.

[0025] The cis / trans / vinyl ratio of double bonds in the rubber component used in the present invention is not particularly limited, and any ratio can be suitably used. The number average molecular weight and molecular weight distribution of the rubber component are not particularly limited, but a number average molecular weight of 500 to 3,000,000 and a molecular weight distribution of 1.5 to 15 are preferred. The method for producing the rubber component is not particularly limited, and examples include emulsion polymerization, solution polymerization, radical polymerization, anionic polymerization, and cationic polymerization.

[0026] The average glass transition temperature of the rubber component (conjugated diene rubber and / or its hydrogenated product) used in the present invention (the average glass transition temperature of the mixture when two or more rubber components are included) must be −90°C or higher and −50°C or lower, more preferably −85°C or higher and −55°C or lower, and particularly preferably −80°C or higher and −60°C or lower. When the average glass transition temperature of the rubber component is within the above-mentioned range, a rubber composition for a tire can be obtained that can improve the wet grip performance, low rolling resistance, and abrasion resistance of the resulting crosslinked rubber composition in a well-balanced manner. In the present invention, the average glass transition temperature is a glass transition point measured by differential scanning calorimetry (DSC). The heating rate is preferably 10°C / min. When two or more rubber components are included and are incompatible, two glass transition temperatures are determined. In this case, the average glass transition temperature is determined by multiplying each glass transition temperature by the mass ratio of each rubber component.

[0027] The rubber component (conjugated diene rubber and / or its hydrogenated product) used in the present invention preferably does not have a hydrogen-bond cross-linkable moiety and is in an uncross-linked (unvulcanized) state. The phrase "does not have a hydrogen-bond cross-linkable moiety" means that the rubber does not have a moiety that cross-links with itself or with other components through hydrogen bonding, and does not have a structural moiety that can form a cross-link by hydrogen bonding (for example, a group such as a hydroxyl group or a carbonyl group that can form a cross-link by hydrogen bonding). The phrase "uncross-linked" means that the rubber is in a state prior to cross-linking (vulcanization) by reaction with a rubber cross-linking agent (vulcanizing agent) or the like.

[0028] The content of the rubber component in the rubber composition for tires of the present invention is preferably 20 to 80 mass %, more preferably 25 to 75 mass %, and particularly preferably 30 to 70 mass %, based on the total mass of the solid content of the rubber composition. When the content of the rubber component is within the above range, there is a tendency to obtain a rubber composition for tires that can further improve the wet grip performance, low rolling resistance, and abrasion resistance of the resulting crosslinked rubber composition in a well-balanced manner.

[0029] (silica) The silica contained in the rubber composition for tires of the present invention is not particularly limited, and conventionally known silicas can be used. Examples of such silica include dry process silica, wet process silica, colloidal silica, and precipitated silica. Among these, wet process silica containing hydrous silicic acid as the main component is preferred. These silicas can be used alone or in combination of two or more.

[0030] The specific surface area of ​​the silica is not particularly limited, but from the viewpoint of processability during mixing of the rubber composition for tires and reinforcement of pneumatic tires, the specific surface area measured by the CTAB adsorption method (CTAB adsorption specific surface area) is preferably 150 to 300 m 2 / g, more preferably 150 to 250m 2 / g, and particularly preferably 150 to 200m 2 / g, where the specific surface area (m 2 / g) is a value measured in accordance with JIS K6430.

[0031] The content of the silica in the rubber composition for tires of the present invention is preferably 5 to 80 parts by mass, more preferably 10 to 60 parts by mass, and particularly preferably 20 to 40 parts by mass, relative to 100 parts by mass of the rubber component. When the content of the silica is within the above range, the Shore A hardness at 0°C after curing can be easily adjusted to fall within the range described below, and a rubber composition for tires tends to be obtained that can further improve the wet grip performance, low rolling resistance, and abrasion resistance of the resulting crosslinked rubber composition in a well-balanced manner.

[0032] (polymer component) The polymer component contained in the rubber composition for a tire of the present invention is at least one polymer component selected from the group consisting of a polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle and having a glass transition point of 25° C. or lower, and a polymer (B) having a side chain containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety and having a glass transition point of 25° C. or lower. It is preferable that both of the polymers (A) and (B) have a main chain in which 2.0 mol % to 60 mol % of the total amount of monomer units constituting the main chain are double-bond-containing monomer units containing a double bond at a site forming the main chain skeleton.

[0033] In the rubber composition for tires of the present invention, the inclusion of the polymer component together with the silica enables the resulting crosslinked rubber composition to achieve a balanced improvement in wet grip performance, low rolling resistance, and abrasion resistance. While the reason for this is not entirely clear, the inventors speculate as follows: The interaction between the silica and the hydrogen-bond crosslinkable moieties in the side chains of the polymer enhances the dispersibility of the silica. This results in a sharper rise in the temperature distribution near the glass transition temperature (Tg) in the temperature dispersion DMA (dynamic viscoelasticity measurement) of the resulting crosslinked rubber composition, improving tan δ (0°C), an indicator of wet grip performance, and decreasing tan δ (60°C), an indicator of low rolling resistance (fuel economy). Furthermore, the increased energy loss due to the dissociation and recombination of hydrogen-bond crosslinks, along with the increase in mechanical strength due to energy dissipation, also contributes to the increase in tan δ (0°C). Furthermore, the interaction between the silica and the hydrogen-bond crosslinkable moieties in the side chains of the polymer improves the reinforcing properties of the silica (filler), resulting in increased mechanical strength. Therefore, in a crosslinked rubber composition obtained using the rubber composition for tires of the present invention, wet grip performance is improved, and low rolling resistance (fuel economy) and abrasion resistance are improved in a well-balanced manner.

[0034] In the polymers (A) and (B), the term "side chain" refers to the side chain and terminal of the polymer. Also, the term "side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle" means that the carbonyl-containing group and / or the nitrogen-containing heterocycle (more preferably the carbonyl-containing group and the nitrogen-containing heterocycle) serving as the hydrogen-bond cross-linkable moiety is chemically stablely bonded (covalently bonded) to an atom (usually a carbon atom) forming the main chain of the polymer. Furthermore, the phrase "the side chain contains a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety" refers to a concept including a case where both a side chain having a hydrogen-bond cross-linkable moiety (hereinafter, for convenience, sometimes referred to as "side chain (a')") and a side chain having a covalent-bond cross-linking moiety (hereinafter, for convenience, sometimes referred to as "side chain (b)") are contained, thereby causing the side chain of the polymer to contain both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety, as well as a case where both a side chain having both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety (a side chain containing both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety in one side chain: hereinafter, such a side chain is occasionally referred to as "side chain (c)" for convenience), thereby causing the side chain of the polymer to contain both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety.

[0035] The main chain of the polymers (A) and (B) preferably comprises 2.0 mol % to 60 mol % of double-bond-containing monomer units, which contain a double bond at a site forming the main chain skeleton, of the total amount of monomer units constituting the main chain. The term "double-bond-containing monomer units" as used herein refers to monomer units containing a double bond not in a side chain but in a site forming the main chain skeleton (a site other than the side chain). Examples include butadiene-derived monomer units represented by the formula -CH2-CH=CH-CH2- and isoprene-derived monomer units represented by the formula -CH2-C(CH3)=CH-CH2-. Hereinafter, the proportion of double-bond-containing monomer units relative to the total amount of monomer units constituting the main chain may be referred to simply as the "double-bond-containing monomer unit proportion." When the content of such double bond-containing monomer units is 2.0 mol% or more, the maleation rate can be increased when maleating during polymer production compared to when the content is less than 2.0 mol%, and the introduction rate of hydrogen-bond cross-linkable moieties in the final polymer can be more efficiently increased, resulting in particularly high self-repairing properties. Furthermore, when the content of the double bond-containing monomer units is 60 mol% or less, the 100% modulus and breaking strength are particularly higher compared to when the content exceeds 60 mol%. Furthermore, when the content of the double bond-containing monomer units is 60 mol% or less, gelation during production can be more easily suppressed, improving handleability after production and sufficiently suppressing a decrease in self-repairing properties due to gelation. Furthermore, from the viewpoint of enabling the mechanical properties based on 100% modulus and breaking strength and the self-repairing property to be improved, the content of double bond-containing monomer units in the main chains of polymers (A) and (B) is more preferably 2.0 to 60 mol % (more preferably 2.0 to 55 mol %, particularly preferably 2.0 to 50 mol %). From the same viewpoint, the lower limit of the content of double bond-containing monomer units is more preferably 2.5 mol %, and even more preferably 3.0 mol %.

[0036] In the present invention, the content ratio of the double bond-containing monomer unit is measured using a known nuclear magnetic resonance (NMR) measurement device (for example, "Avance 600" manufactured by Bruker), at a measurement temperature of 25°C, a solvent of CDCl3, a sample concentration of 1.0 mass%, and a sample amount of 1.5 cm 3 , Accumulation count: 64 times 1 The double bond-containing monomer unit content can be calculated by measuring H NMR spectra and analyzing the monomer units constituting the main chain. Thus, the "content (mol %) of double bond-containing monomer units" described herein is a value determined by NMR measurement. When the polymer to be measured for the content of double bond-containing monomer units is a reaction product of a maleic anhydride-modified polymer and a crosslinking compound, the content of double bond-containing monomer units in the main chain of the maleic anhydride-modified polymer before the reaction is the same as the content of double bond-containing monomer units in the main chain of the reaction product (the polymer to be measured) after the reaction, and the content of double bond-containing monomer units in the main chain of the maleic anhydride-modified polymer before the reaction does not change. Therefore, when the polymer to be measured for the content of double bond-containing monomer units is the reaction product, the content of double bond-containing monomer units in the main chain of the maleic anhydride-modified polymer before the reaction may be used as the content of double bond-containing monomer units in the polymer (polymer (A) or (B)) obtained after the reaction.

[0037] In the present invention, both the polymer (A) and the polymer (B) contain a double bond in the main chain. From the viewpoint of making it easier to satisfy the condition for the content ratio of the double bond-containing monomer unit as described above and from the viewpoint of further improving mechanical properties, the type of polymer constituting the main chain is more preferably at least one selected from the group consisting of styrene-butadiene copolymer, hydrogenated styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, hydrogenated butadiene-acrylonitrile copolymer, hydrogenated butadiene polymer, isoprene-based polymer (including natural rubber, epoxidized isoprene polymer, and hydrogenated products), and butyl-based polymer (including butyl rubber and hydrogenated products), and even more preferably at least one selected from the group consisting of hydrogenated styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, and hydrogenated butadiene-acrylonitrile copolymer. The method for producing the hydrogenated product (hydrogenated styrene-butadiene copolymer, hydrogenated butadiene-acrylonitrile copolymer, etc.) referred to herein (method for adding hydrogen) is not particularly limited, and known methods can be appropriately adopted. In this case, the desired hydrogenated product can be formed by appropriately changing the hydrogenation conditions so that the content ratio of the double bond-containing monomer unit falls within the desired range. Furthermore, commercially available products may be appropriately used as the raw material polymer for the polymer constituting such a main chain.

[0038] As described above, the glass transition points of the polymers (A) and (B) are both 25°C or lower. In the present invention, the "glass transition point" refers to a glass transition point measured by differential scanning calorimetry (DSC). The measurement is performed at a temperature rise rate of 10°C / min. By setting the glass transition point of such a polymer to 25°C or lower, it becomes possible to impart flexibility in the normal temperature range for use (room temperature (25°C) or higher).

[0039] As described above, the polymers (A) and (B) have at least one of the following side chains: a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle; a side chain (a') containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety; and a side chain (c) containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety. In the present invention, the side chain (c) can also be said to function as both the side chain (a') and the side chain (b). Each side chain is described below.

[0040] <Side Chain (a'): Side Chain Containing a Hydrogen-Bond Cross-Linking Moiety> The side chain (a') containing such a hydrogen-bond cross-linkable moiety has a group capable of forming a cross-link via a hydrogen bond (e.g., a hydroxyl group, a hydrogen-bond cross-linkable moiety contained in the side chain (a) described below, etc.), and the side chain may be one that forms a hydrogen bond based on the group, and its structure is not particularly limited. Here, the hydrogen-bond cross-linkable moiety is a moiety that cross-links polymer molecules together by hydrogen bonding. Note that a cross-link via a hydrogen bond can only be formed in the presence of a hydrogen acceptor (e.g., a group containing an atom containing a lone electron pair) and a hydrogen donor (e.g., a group having a hydrogen atom covalently bonded to an atom with high electronegativity). Therefore, a cross-link via a hydrogen bond cannot be formed between the side chains of polymer molecules unless both a hydrogen acceptor and a hydrogen donor are present between the side chains of polymer molecules. Therefore, a hydrogen-bond cross-linkable moiety can only be present in a system when both a hydrogen acceptor and a hydrogen donor are present between the side chains of polymer molecules. In the present invention, when both a moiety capable of functioning as a hydrogen acceptor (for example, a carbonyl group) and a moiety capable of functioning as a hydrogen donor (for example, a hydroxyl group) are present between side chains of polymer molecules, the moiety capable of functioning as a hydrogen acceptor and the moiety capable of functioning as a hydrogen donor in the side chain can be determined to be hydrogen-bond cross-linkable moieties.

[0041] From the viewpoint of forming stronger hydrogen bonds, the side chain (a') is more preferably the side chain (a) described below. From the same viewpoint, the hydrogen-bond cross-linkable moiety in the side chain (a') is more preferably a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and a nitrogen-containing heterocycle.

[0042] <Side Chain (a): Side Chain Containing a Hydrogen-Bond Cross-Linkable Moiety Having a Carbonyl-Containing Group and / or a Nitrogen-Containing Heterocycle> The side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle is not particularly limited as long as it has a carbonyl-containing group and / or a nitrogen-containing heterocycle. As such a hydrogen-bond cross-linkable moiety, one having a carbonyl-containing group and a nitrogen-containing heterocycle is more preferred.

[0043] Such a carbonyl-containing group is not particularly limited as long as it contains a carbonyl group, and specific examples thereof include amide, ester, imide, carboxy group, carbonyl group, thioester group, and acid anhydride group.

[0044] Furthermore, when the side chain (a) has a nitrogen-containing heterocycle, the nitrogen-containing heterocycle may be introduced into the side chain (a) directly or via an organic group, and its structure is not particularly limited. Such a nitrogen-containing heterocycle may contain a heteroatom other than the nitrogen atom, such as a sulfur atom, an oxygen atom, or a phosphorus atom, as long as it contains a nitrogen atom in the heterocycle. Such a nitrogen-containing heterocycle may have a substituent. The use of a nitrogen-containing heterocycle in the side chain (a) is preferred because the heterocyclic structure strengthens the hydrogen bonds that form crosslinks, thereby improving the durability and impact resistance of the composition. Furthermore, such a nitrogen-containing heterocycle is preferably a 5-membered ring and / or a 6-membered ring, from the viewpoint of strengthening the hydrogen bonds and improving the resistance to compression set and mechanical strength. Furthermore, such a nitrogen-containing heterocycle may be a nitrogen-containing heterocycle fused with a benzene ring or a nitrogen-containing heterocycle fused with another nitrogen-containing heterocycle. As such a nitrogen-containing heterocycle, known compounds (for example, those described in paragraphs

[0054] to

[0067] of Japanese Patent No. 5918878, those described in paragraphs

[0035] to

[0048] of Japanese Patent Laid-Open No. 2017-206604, etc.) can be used as appropriate. Note that such a nitrogen-containing heterocycle may have a substituent.

[0045] From the viewpoint of achieving excellent recyclability, compression set, hardness, and mechanical strength (particularly tensile strength), such a nitrogen-containing heterocycle is preferably at least one selected from a triazole ring, an isocyanurate ring, a thiadiazole ring, a pyridine ring, an imidazole ring, a triazine ring, and a hydantoin ring, each of which may have a substituent, and more preferably at least one selected from a triazole ring, an isocyanurate ring, a thiadiazole ring, a pyridine ring, an imidazole ring, and a hydantoin ring, each of which may have a substituent.

[0046] Examples of substituents that such nitrogen-containing heterocycles may have include hydroxyl groups, amino groups, imino groups, carboxy groups, isocyanate groups, epoxy groups, alkoxysilyl groups, and thiol groups (mercapto groups). Examples of such substituents include alkyl groups such as methyl groups, ethyl groups, (iso)propyl groups, and hexyl groups; alkoxy groups such as methoxy groups, ethoxy groups, and (iso)propoxy groups; groups containing halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; cyano groups; amino groups; imino groups; aromatic hydrocarbon groups; ester groups; ether groups; acyl groups; and thioether groups. The substitution positions of these substituents are not particularly limited, and the number of substituents is also not limited.

[0047] Furthermore, when the side chain (a) contains both the carbonyl-containing group and the nitrogen-containing heterocycle, the carbonyl-containing group and the nitrogen-containing heterocycle may be introduced into the main chain as independent side chains, but it is preferred that the carbonyl-containing group and the nitrogen-containing heterocycle are introduced into the main chain as a single side chain in which they are bonded via different groups. The structure of such side chain (a) may be, for example, a structure such as that described in paragraphs

[0068] to

[0081] of Japanese Patent No. 5918878.

[0048] Furthermore, such a side chain (a) can be efficiently formed, for example, by a reaction between a maleic anhydride-modified polymer and a crosslinking compound. A compound capable of forming a hydrogen-bond crosslinkable moiety upon reaction with a maleic anhydride group (hereinafter, sometimes simply referred to as a "compound that forms a hydrogen-bond crosslinkable moiety") can be suitably used as a crosslinking compound used to form such a side chain (a). A compound that can introduce a nitrogen-containing heterocycle can be suitably used as a "compound that forms a hydrogen-bond crosslinkable moiety" that can be used as such a crosslinking compound. Thus, a "compound that forms a hydrogen-bond crosslinkable moiety (more preferably, a compound that can introduce a nitrogen-containing heterocycle)" can be suitably used as the crosslinking compound. Such a "compound that forms a hydrogen-bond cross-linkable moiety (more preferably, a compound that can introduce a nitrogen-containing heterocycle)" is preferably, for example, a compound having a substituent that reacts with a maleic anhydride group (e.g., a hydroxyl group, a thiol group, an amino group, an imino group, etc.), more preferably a compound having at least one of a hydroxyl group, an amino group, an imino group, and a thiol group, and particularly preferably such a compound having a nitrogen-containing heterocycle.

[0049] <Side chain (b): Side chain containing a covalent cross-linking moiety> In this specification, the term "side chain (b) containing a covalent cross-linking moiety" refers to a side chain containing a moiety that cross-links polymer molecules forming the main chain together via a covalent bond (covalent cross-linking moiety: for example, when polymer (A) or (B) is formed by reacting a maleic anhydride-modified polymer with a cross-linking compound, the covalent cross-linking moiety is a moiety that cross-links polymer molecules together via a chemically stable bond (covalent bond) such as at least one bond selected from the group consisting of amide, ester, and thioester, which can be formed by reacting a maleic anhydride group with the cross-linking compound).

[0050] The side chain (b) is a side chain containing a covalent-bond cross-linking moiety, but when it has a covalent-bonding moiety and also has a group capable of hydrogen bonding, and cross-linking by hydrogen bonding is formed between side chains, it will be used as side chain (c) described below. (Note that when both a hydrogen donor and a hydrogen acceptor capable of forming a hydrogen bond between side chains of the polymer molecules are not contained, for example, when only side chains containing an ester group (-COO-) are present in the system, no particular hydrogen bond is formed between the ester groups (-COO-), and therefore such a group does not function as a hydrogen-bond cross-linking moiety. On the other hand, when, for example, a carboxyl group or a carboxyl group is present in the system, a hydrogen bond is not formed between the ester groups (-COO-), and therefore such a group does not function as a hydrogen-bond cross-linking moiety. When the side chains of the polymer molecules each contain a structure having both a hydrogen donor moiety and a hydrogen acceptor moiety, such as a triazole ring, hydrogen bonds are formed between the side chains of the polymer molecules, resulting in the inclusion of a hydrogen-bond cross-linkable moiety. Furthermore, for example, when an ester group and a hydroxyl group coexist between the side chains of the polymer molecules and hydrogen bonds are formed between the side chains by these groups, the moiety forming the hydrogen bond is a hydrogen-bond cross-linkable moiety. Therefore, side chain (b) may be used as side chain (c) depending on the structure of side chain (b) itself, the type of substituents of the structure of side chain (b) and other side chains, etc.). The term "covalent cross-linkable moiety" as used herein refers to a moiety that cross-links polymer molecules by a covalent bond.

[0051] The side chain (b) containing such a covalent cross-linking moiety is not particularly limited, but is preferably a side chain containing a covalent cross-linking moiety formed by, for example, reacting a maleic anhydride-modified polymer with a cross-linking compound comprising a compound capable of forming a covalent cross-linking moiety upon reaction with a maleic anhydride group (functional group) (hereinafter sometimes referred to as a "compound forming a covalent cross-linking moiety"). The cross-link at the covalent cross-linking moiety of such side chain (b) is preferably formed by at least one bond selected from the group consisting of amide, ester, and thioester.

[0052] As the "compound that forms a covalent cross-linking moiety" that can be used as such a cross-linking compound, a compound having a substituent that reacts with a maleic anhydride group (for example, a hydroxyl group, a thiol group, an amino group, an imino group, etc.) is preferred, a compound having at least one of a hydroxyl group, an amino group, and an imino group is more preferred, and as such a compound, a compound having a nitrogen-containing heterocycle is particularly preferred.

[0053] Furthermore, examples of "compounds that form covalent cross-linking moieties" that can be used as such cross-linking compounds include polyamine compounds having two or more amino groups and / or imino groups in one molecule (when both amino groups and imino groups are present, the total number of these groups is two or more); polyol compounds having two or more hydroxyl groups in one molecule; polyisocyanate compounds having two or more isocyanate (NCO) groups in one molecule; polythiol compounds having two or more thiol groups (mercapto groups) in one molecule; and the like. Here, the "compound that forms a covalent cross-linking moiety" can be a compound that can introduce both the hydrogen-bond cross-linkable moiety and the covalent cross-linking moiety, depending on the type of substituents possessed by the compound, the degree of progress of the reaction when the compound is used for reaction, and other factors. (For example, when a compound having three or more hydroxyl groups is used as a cross-linking compound to form a cross-linking moiety by a covalent bond, depending on the degree of progress of the reaction, two hydroxyl groups may react with the functional group (maleic anhydride group) of the maleic anhydride-modified polymer, leaving the remaining hydroxyl group as a hydroxyl group. In such cases, a moiety that forms a hydrogen-bond cross-link can also be introduced.) Therefore, the "compound that forms a covalent cross-linking moiety" exemplified here can also include a "compound that forms both a hydrogen-bond cross-linkable moiety and a covalent cross-linking moiety." From this perspective, when forming side chain (b), side chain (b) can be formed by appropriately selecting a compound from "compounds that form a covalent cross-linking moiety" according to the intended design, or by appropriately controlling the degree of progress of the reaction, for example. In addition, when the compound that forms the covalent-bond cross-linking moiety has a heterocycle, it becomes possible to simultaneously produce a hydrogen-bond cross-linkable moiety more efficiently, and it becomes possible to efficiently form a side chain having the covalent-bond cross-linking moiety as the side chain (c) described below. Therefore, specific examples of compounds that have such a heterocycle will be described as suitable compounds for producing the side chain (c), particularly together with the side chain (c). In addition, the side chain (c) can also be said to be a suitable form of side chains such as the side chain (a) and the side chain (b) based on its structure.

[0054] As the polyamine compound, the polyol compound, the polyisocyanate compound, and the polythiol compound that can be used as such a "compound that forms a covalent cross-linking moiety," known compounds (for example, those described in paragraphs

[0094] to

[0106] of Japanese Patent No. 5918878) can be used appropriately.

[0055] <Side Chain (c): Side Chain Containing Both Hydrogen-Bond Cross-Linking Moieties and Covalent-Bond Cross-Linking Moieties> Such a side chain (c) is a side chain containing both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety in one side chain. The hydrogen-bond cross-linkable moiety contained in such a side chain (c) is the same as the hydrogen-bond cross-linkable moiety described in the side chain (a'), and is preferably the same as the hydrogen-bond cross-linking moiety in the side chain (a). In addition, as the covalent-bond cross-linking moiety contained in the side chain (c), the same as the covalent-bond cross-linking moiety in the side chain (b) can be used (the same preferred cross-links can also be used).

[0056] Such a side chain (c) is preferably a side chain formed by reacting a maleic anhydride-modified polymer with a cross-linking compound comprising a compound that reacts with a functional group (maleic anhydride group) of the maleic anhydride-modified polymer to form both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety (a compound that introduces both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety).

[0057] As a "compound that forms both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linkable moiety (a compound that introduces both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linkable moiety)" that can be used as such a cross-linking compound, a compound having a substituent that reacts with a maleic anhydride group (e.g., a hydroxyl group, a thiol group, an amino group, an imino group, etc.) is preferred, and a compound having at least one of a hydroxyl group, an amino group, an imino group, and a thiol group is more preferred. Furthermore, as such a compound that forms both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linkable moiety (a compound that introduces both a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linkable moiety), a compound that has a heterocycle (particularly preferably a nitrogen-containing heterocycle) and is capable of forming a covalent-bond cross-linkable moiety (a compound that forms a covalent bond) is preferred, and among these, a heterocycle-containing polyol, a heterocycle-containing polyamine, a heterocycle-containing polythiol, etc. are more preferred. The heterocyclic polyols, polyamines, and polythiols may be the same as those described in the above section "Compounds capable of forming covalent cross-linking moieties (compounds that form covalent bonds)," except that they have a heterocyclic ring (particularly preferably a nitrogen-containing heterocyclic ring). Known heterocyclic polyols, polyamines, and polythiols may be used as appropriate (for example, those described in paragraph

[0113] of Japanese Patent Publication No. 5918878).

[0058] <Structures suitable for covalent cross-linking sites in side chains (b) and (c)> With regard to the side chains (b) and / or (c), when the crosslink at the covalent-bond cross-linking moiety contains a tertiary amino bond (-N=) or an ester bond (-COO-), and when these bond moieties also function as hydrogen-bond cross-linking moieties, this is preferable from the viewpoint that the crosslink becomes stronger by forming a hydrogen bond with other hydrogen-bond cross-linking moieties. In this way, when the tertiary amino bond (-N=) or ester bond (-COO-) in the side chain having a covalent-bond cross-linking moiety forms a hydrogen bond with other side chains, the covalent-bond cross-linking moiety containing such a tertiary amino bond (-N=) or ester bond (-COO-) also has a hydrogen-bond cross-linking moiety and can function as the side chain (c).

[0059] The covalent-bond cross-linking moiety containing the tertiary amino bond and / or the ester bond is preferably formed by reacting a maleic anhydride-modified polymer with a compound capable of reacting with a functional group (maleic anhydride group) of the maleic anhydride-modified polymer to form the covalent-bond cross-linking moiety containing the tertiary amino bond and / or the ester bond.

[0060] Preferred examples of the compound capable of forming a covalent-bond cross-linking moiety containing the tertiary amino bond and / or the ester bond (a compound capable of forming both a hydrogen-bond cross-linking moiety and a covalent-bond cross-linking moiety: one type of cross-linking compound) include polyethylene glycol laurylamine (e.g., N,N-bis(2-hydroxyethyl)laurylamine), polypropylene glycol laurylamine (e.g., N,N-bis(2-methyl-2-hydroxyethyl)laurylamine), polyethylene glycol octylamine (e.g., N,N-bis(2-hydroxyethyl)octylamine), polypropylene glycol octylamine (e.g., N,N-bis(2-methyl-2-hydroxyethyl)octylamine), polyethylene glycol stearylamine (e.g., N,N-bis(2-hydroxyethyl)stearylamine), and polypropylene glycol stearylamine (e.g., N,N-bis(2-methyl-2-hydroxyethyl)stearylamine).

[0061] The crosslink at the covalent crosslinking site of the side chain (b) and / or the side chain (c) may be, for example, the same as the structure described in paragraphs

[0100] to

[0109] of JP 2017-206604 A or the structure described in paragraphs

[0055] to

[0061] of WO 2019 / 027022 A.

[0062] The side chain (a'), the side chain (a), the side chain (b), and the side chain (c) have been described above, but each group (structure) of the side chain in such a polymer can be confirmed by commonly used analytical means such as NMR or IR spectroscopy.

[0063] The polymer (A) is a polymer having the side chain (a) and a glass transition point of 25°C or lower, and the polymer (B) is a polymer containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety in the side chain and having a glass transition point of 25°C or lower (such as a polymer having both side chain (a') and side chain (b) as side chains, or a polymer containing side chain (c) in the side chain). Both of the polymers (A) and (B) according to the present invention are preferably thermoplastic elastomers. As the polymer of the present invention, one of the polymers (A) and (B) may be used alone, or two or more of them may be used in combination.

[0064] The polymer (B) may be a polymer having both the side chain (a') and the side chain (b), or may be a polymer having the side chain (c). However, the hydrogen-bond cross-linkable moiety contained in the side chain of such polymer (B) is preferably a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle (more preferably a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and a nitrogen-containing heterocycle) from the viewpoint of forming stronger hydrogen bonds. Furthermore, the crosslink at the covalent-bond cross-linking moiety contained in the side chain of the polymer (B) is preferably formed by at least one bond selected from the group consisting of amide, ester, and thioester, from the viewpoint of enabling intermolecular interactions such as hydrogen bonds to be induced between side chains containing the cross-linking moiety.

[0065] Furthermore, both polymers (A) and (B) according to the present invention are preferably reaction products of a maleic anhydride-modified polymer having a double-bond-containing monomer unit content of 2.0 mol % to 60 mol % (more preferably 2.0 to 55 mol %, and even more preferably 2.0 to 50 mol %) with a crosslinking compound. The content of double-bond-containing monomer units in the maleic anhydride-modified polymer remains unchanged before and after the reaction with the crosslinking compound, so the content of double-bond-containing monomer units in the main chain of the polymer (polymer (A) or (B)) obtained as the reaction product is the same as the content of double-bond-containing monomer units in the main chain of the maleic anhydride-modified polymer. In the present invention, when polymers (A) and (B) are reaction products of a maleic anhydride-modified polymer with a crosslinking compound, their side chains will have groups derived from the "maleic anhydride groups" in the maleic anhydride-modified polymer (e.g., ester groups, carbonyl groups, amide groups, imide groups, carboxy groups, etc., depending on the type of crosslinking compound reacted). Furthermore, the remaining unreacted "maleic anhydride group" is a moiety that can function as a hydrogen acceptor, and therefore can also function as a group that forms a hydrogen-bond crosslinking site.

[0066] Such maleic anhydride-modified polymers are not particularly limited as long as they are polymers having a double bond-containing monomer unit content of 2.0 mol % to 60 mol % (more preferably 2.0 to 55 mol %, and even more preferably 2.0 to 50 mol %) and are modified with maleic anhydride, but from the viewpoint of the length and ease of movement of the crosslinked moiety, they are more preferably polymers graft-modified with maleic anhydride. From the same viewpoint, the lower limit of the double bond-containing monomer unit content of the maleic anhydride-modified polymer is more preferably 2.5 mol %, and even more preferably 3.0 mol %.

[0067] The method for producing such a maleic anhydride-modified polymer is not particularly limited, and for example, a method can be employed in which a raw material polymer (a polymer before modification with maleic anhydride) having a double bond-containing monomer unit content of 2.0 mol % to 60 mol % (more preferably 2.0 to 55 mol %, and even more preferably 2.0 to 50 mol %) is modified with maleic anhydride. The method for modification with maleic anhydride is not particularly limited, and any known method capable of modifying a polymer with maleic anhydride can be appropriately employed. Furthermore, such raw material polymer is not particularly limited as long as the content of double bond-containing monomer units is 2.0 mol % to 60 mol % (more preferably 2.0 to 55 mol %, and even more preferably 2.0 to 50 mol %), but is more preferably at least one selected from the group consisting of styrene-butadiene copolymer, hydrogenated styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, hydrogenated butadiene-acrylonitrile copolymer, hydrogenated butadiene polymer, isoprene-based polymer (including natural rubber, epoxidized isoprene polymer, and hydrogenated products), and butyl-based polymer (including butyl rubber and hydrogenated products), and even more preferably at least one selected from the group consisting of hydrogenated styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, and hydrogenated butadiene-acrylonitrile copolymer.

[0068] The maleic anhydride-modified polymer more preferably has a maleic acid content of 0.5 to 10% by mass. The upper limit of the numerical range of the maleic acid content is more preferably 8% by mass, and even more preferably 5% by mass. The lower limit of the numerical range of the maleic acid content is more preferably 1.0% by mass, and even more preferably 1.5% by mass. When the maleic acid content is equal to or greater than the lower limit, the crosslink density of the polymer can be increased during the crosslinking reaction, tending to improve the mechanical properties (tensile properties) of the composition. On the other hand, when the maleic acid content is equal to or less than the upper limit, the crosslink density of the resulting polymer does not become too high, and compatibility between the polymer and rubber tends to be maintained.

[0069] In this specification, the value of "maleic acid ratio" (unit: mass %) is a value determined by the following [method for measuring maleic acid ratio].

[0070] [Method for measuring maleic acid ratio] First, 400 mg of the maleic anhydride-modified polymer to be measured is dissolved in 80 mL of tetrahydrofuran (hereinafter, for convenience, sometimes abbreviated as "THF") to obtain a THF solution for measurement. The THF solution for measurement is then titrated with a 0.1 mol / L ethanol solution of potassium hydroxide for which a factor is calculated to three or more decimal places (volumetric standard solution: a 0.1 mol / L ethanol solution of potassium hydroxide with correction; a commercially available solution with a factor (characteristic value: corrected value) calculated to three or more decimal places may be used). The endpoint (neutralization point) is determined by potentiometric titration using an instrument. The factor (characteristic value: corrected value) of the 0.1 mol / L ethanol solution of potassium hydroxide may be determined by titration with an oxalic acid standard solution. When using a commercially available product with a calculated factor, the factor listed on the commercially available reagent (e.g., the factor listed on the reagent's test report) may be used as is. Next, a similar measurement (blank test) is performed except that the maleic anhydride-modified polymer is not used, and titration is performed, and the amount of 0.1 mol / L potassium hydroxide ethanol solution added to 80 mL of THF (blank value) is also determined. Next, the acid value is calculated using the determined titration value (addition amount) based on the "Acid Value Calculation Formula" below, and the maleinization ratio is then calculated using the obtained acid value based on the "Maleinization Ratio Calculation Formula" below, thereby determining the maleinization ratio (unit: mass%). <Calculation formula for acid value> [Acid value]=(AB)×M1×C×f / S (In the formula, A represents the amount of 0.1 mol / L potassium hydroxide ethanol solution added (titer value: mL) required to neutralize the measurement solution, B represents the amount of 0.1 mol / L potassium hydroxide ethanol solution added in a blank (blank test) (the titer value (blank value: mL) obtained by performing the same measurement except that no maleic anhydride-modified polymer is used), M1 represents the molecular weight of potassium hydroxide (56.1 (constant)), C represents the potassium hydroxide concentration in the potassium hydroxide ethanol solution (0.1 mol / L (constant)), f represents the factor of the potassium hydroxide ethanol solution (correction value: the factor listed in a commercially available reagent (for example, the factor listed in the test report for the reagent) may be used as is), and S represents the mass of the maleic anhydride-modified polymer used in the measurement. The unit of the "acid value" determined by this calculation is "mgKOH / g.") <Maleate ratio calculation formula> [Maleication rate] = [Acid value] ÷ M1 × M2 ÷ 1000 × 100 ÷ 2 (In the formula, the acid value is the value (unit: mgKOH / g) calculated using the above-mentioned "acid value calculation formula," M1 is the molecular weight of potassium hydroxide (56.1 (constant)), and M2 is the molecular weight of maleic anhydride (98.1 (constant)). The unit of the "maleication ratio" calculated by this calculation is "mass %.")

[0071] The crosslinking compound is not particularly limited as long as it can react with the maleic anhydride groups in the maleic anhydride-modified polymer to form either the polymer (A) or (B). Depending on the intended design, a compound capable of reacting with the maleic anhydride groups to form various crosslinked moieties (a compound capable of forming the intended side chain) can be appropriately selected and used.

[0072] As such a crosslinking compound, the aforementioned "compounds that form hydrogen-bond crosslinkable moieties (more preferably, compounds that can introduce a nitrogen-containing heterocycle)" and "compounds that form covalent crosslinking moieties" can be suitably used. Furthermore, from the viewpoint of efficient reaction progression, such crosslinking compounds are preferably compounds having at least one of a hydroxyl group, an amino group, an imino group, and a thiol group. Among these, compounds having a nitrogen-containing heterocycle (such nitrogen-containing heterocycles are preferably at least one selected from a triazole ring, an isocyanurate ring, a thiadiazole ring, a pyridine ring, an imidazole ring, a triazine ring, and a hydantoin ring) are more preferred (note that the "nitrogen-containing heterocycle" referred to here is the same as the above, including preferred examples). Examples of such compounds include those described in paragraph

[0049] of International Publication No. 2020 / 027109. Such compounds may be used alone or in combination of two or more.

[0073] Furthermore, from the viewpoints of high reactivity and industrial availability, such crosslinking compounds are preferably at least one compound selected from the group consisting of nitrogen-containing compounds optionally having at least one substituent selected from the group consisting of hydroxyl, thiol, amino, and imino groups (such substituents are sometimes referred to as "substituent (A)"), oxygen-containing compounds optionally having the substituent (A), and sulfur-containing compounds optionally having the substituent (A). Such "compounds that form hydrogen-bond crosslinkable moieties (more preferably, compounds that can introduce a nitrogen-containing heterocycle)" and "compounds that form covalent crosslinkable moieties (compounds that form covalent bonds)" can be appropriately selected and used from known compounds (compounds described in JP 2017-57322 A and JP 5918878 A) as long as they are capable of reacting with maleic anhydride groups.

[0074] Furthermore, such a crosslinking compound is preferably at least one selected from the group consisting of triazole which may have the substituent (A); pyridine which may have the substituent (A); thiadiazole which may have the substituent (A); imidazole which may have the substituent (A); isocyanurate which may have the substituent (A); triazine which may have the substituent (A); hydantoin which may have the substituent (A); pentaerythritol; sulfamide; methanol; and polyether polyol.

[0075] From the viewpoint of the strength of crosslinking through hydrogen bonds, such crosslinking compounds are preferably 3-amino-1,2,4-triazole (abbreviation: ATA), tris(2-hydroxyethyl)isocyanurate (abbreviation: THI), 2,4-diamino-6-phenyl-1,3,5-triazine (benzoguanamine), 2,4-diamino-6-methyl-1,3,5-triazine (acetoguanamine), pentaerythritol, sulfamide, methanol, and polyether polyol, with ATA, THI, and methanol being more preferred.

[0076] The method for obtaining the reaction product of the maleic anhydride-modified polymer and the crosslinking compound is not particularly limited, and any method can be used as long as it can react the maleic anhydride groups in the maleic anhydride-modified polymer with the functional groups in the crosslinking compound to form the polymers (A) and (B) (as long as it can form the crosslinked moieties described for the polymers (A) and (B)), and the reaction can be carried out appropriately depending on the type of the crosslinking compound, etc. For example, a method can be employed in which the maleic anhydride-modified polymer is plasticized using a kneader or other kneading machine at a temperature (e.g., about 100 to 250°C) that allows the crosslinking compound to react with the maleic anhydride groups while mixing (kneading) the maleic anhydride-modified polymer, and the crosslinking compound is added to cause the reaction.

[0077] The polymer component used in the present invention may be at least one polymer selected from the group consisting of the polymers (A) and (B), and may consist of only the polymer (A) or (B), or may be a mixture of the polymers (A) and (B). The polymer component has excellent mechanical properties based on 100% modulus and breaking strength, self-repairing properties, and handleability. The polymer component can improve the self-repairing properties of the rubber composition after crosslinking, and therefore also functions as a rubber modifier.

[0078] The content of the polymer component in the rubber composition for tires of the present invention must be 1 to 100 parts by mass, more preferably 1 to 80 parts by mass, even more preferably 1.5 to 70 parts by mass, and particularly preferably 2 to 60 parts by mass, per 100 parts by mass of the rubber component. When the content of the polymer component is within the above range, it becomes possible to improve the wet grip performance, low rolling resistance, and abrasion resistance of the obtained crosslinked rubber composition in a well-balanced manner, and the self-repairing property of the obtained crosslinked rubber composition is also improved.

[0079] (Shore A hardness at 0°C after curing) The rubber composition for tires of the present invention must have an ISO Type A rubber hardness (Shore A hardness (0°C)) of 55 to 70, and more preferably 55 to 65, after curing at a temperature of 0°C. By using a rubber composition having a Shore A hardness (0°C) within the above range, it is possible to improve wet grip performance, low rolling resistance, and abrasion resistance in a well-balanced manner, making the composition suitable for tire treads of pneumatic tires, and particularly suitable for tire treads of heavy-duty tires. Here, the Shore A hardness (0°C) is a value measured in accordance with JIS K6253.

[0080] (Other processing aids) The rubber composition for a tire of the present invention may contain processing aids such as a silane coupling agent, carbon black, a crosslinking agent (vulcanizing agent), a crosslinking accelerator (vulcanization accelerator), a crosslinking acceleration aid (vulcanization acceleration aid), a softener, an antioxidant, an antioxidant, and a colorant, within a range that does not impair its functions.

[0081] The rubber composition for tires of the present invention preferably contains a silane coupling agent from the viewpoint of further improving the dispersibility of the silica. The silane coupling agent is not particularly limited, and conventionally known agents can be used. Examples of such silane coupling agents include polysulfide-based silane coupling agents having an alkoxysilyl group that reacts with the silanol group on the silica surface and a sulfur chain that reacts with the polymer, such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, and bis(3-triethoxysilylpropyl)disulfide. Commercially available products, such as those sold under the trade names "Si69" and "Si75" by Evonik Industries AG, may also be used. When a silane coupling agent is used, the amount is preferably 0.5 to 15 parts by weight per 100 parts by weight of the silica.

[0082] The rubber composition for tires of the present invention may further contain carbon black in addition to the silica. The carbon black is not particularly limited, and conventionally known carbon blacks can be used. Examples of such carbon black include furnace blacks such as SAF, ISAF, HAF, FEF, GPF, and SRF. These carbon blacks can be used alone or in combination of two or more. The specific surface area of ​​the carbon black is not particularly limited, but from the viewpoints of processability during mixing of the rubber composition for tires and reinforcement of pneumatic tires, the specific surface area measured by a nitrogen adsorption method (nitrogen adsorption specific surface area, N2SA) is preferably 10 to 300 m 2 / g, more preferably 20 to 200m 2 / g. Here, N2SA is the amount of nitrogen adsorption on the surface of carbon black measured in accordance with JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method." When carbon black is blended, the blending amount is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and particularly preferably 30 to 60 parts by mass, per 100 parts by weight of the rubber component. When the content of carbon black is within the above numerical range, it tends to be possible to improve the wet grip performance, low rolling resistance, and abrasion resistance of the obtained crosslinked rubber composition in a well-balanced manner.

[0083] The rubber composition for a tire of the present invention preferably contains a crosslinking agent (vulcanizing agent) to crosslink (vulcanize) the rubber component for use. The crosslinking agent is not particularly limited, and conventionally known crosslinking agents for rubber can be used. Such rubber crosslinking agents may be sulfur-based (sulfur-based crosslinking agents) or non-sulfur-based (non-sulfur-based crosslinking agents: for example, peroxide-based crosslinking agents). From the viewpoint of reactivity, preferred sulfur-based crosslinking agents include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, inactive sulfur, oil-treated sulfur, dimorpholine disulfide, and alkylphenol disulfide. Furthermore, from the viewpoint of crosslinking ability, preferred peroxide-based crosslinking agents include benzoyl peroxide, di-t-butyl peroxide, and dicumyl peroxide. Furthermore, other non-sulfur crosslinking agents include magnesium oxide, litharge, p-quinone dioxime, p-dibenzoylquinone dioxime, tetrachloro-p-benzoquinone, poly-p-dinitrobenzene, methylenedianiline, phenol resin, brominated alkylphenol resin, chlorinated alkylphenol resin, etc. When a crosslinking agent is compounded, the compounding amount is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0084] The rubber composition for tires of the present invention preferably further contains a crosslinking accelerator (vulcanization accelerator) in addition to the crosslinking agent. The crosslinking accelerator is not particularly limited, and conventionally known accelerators can be used. Examples of such crosslinking accelerators include thiazole-based accelerators (MBT (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide), MBTS, ZnMBT, etc.), sulfenamide-based accelerators (CBS (N-cyclohexyl-2-benzothiazyl sulfenamide), BBS (Nt-butyl-2-benzothiazyl sulfenamide), DCBS, etc.), guanidine-based accelerators (DPG (diphenylguanidine), DOTG, OTBG, etc.), thiuram-based accelerators (TMTD (tetramethylthiuracil)), and the like). Preferred examples of crosslinking accelerators include tetrakis(2-ethylhexyl)thiuram disulfide (TBzTD), TMTM (tetramethylthiuram monosulfide), TETD (tetraethylthiuram disulfide), TOT-N (tetrakis(2-ethylhexyl)thiuram disulfide), TBzTD, TBTD, etc.), dithiocarbamate-based accelerators (zinc dimethyldithiocarbamate (ZnPDC), ZTC, NaBDC, etc.), aldehyde-ammonia-based accelerators (hexamethylenetetramine, etc.), thiourea-based accelerators (ETU, etc.), and xanthogenate-based accelerators (ZnBX, etc.). Commercially available accelerators include those manufactured by Ouchi Shinko Chemical Co., Ltd. under the trade names "Noccela CZ" and "Noccela D." When a crosslinking accelerator is used, the amount thereof is preferably 0.1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0085] In the rubber composition for tires of the present invention, it is preferable to use a crosslinking accelerator (vulcanization accelerator) in addition to the crosslinking agent and crosslinking accelerator. The crosslinking accelerator is not particularly limited, and conventionally known ones can be used. Preferred examples of such crosslinking accelerators include zinc oxide (e.g., three types of zinc oxide); fatty acids such as stearic acid, propionic acid, butanoic acid, acrylic acid, maleic acid, and acetyl acid; and zinc fatty acids such as zinc stearate, zinc propionate, zinc butanoate, zinc acrylate, zinc maleate, and zinc acetylate. When a crosslinking accelerator is added, the amount added is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0086] The rubber composition for tires of the present invention preferably contains a softener from the viewpoint of improving processability and facilitating adjustment of the hardness of the resulting crosslinked rubber composition to a desired range. The softener is not particularly limited, and conventionally known softeners can be used. Examples of such softeners include petroleum-based softeners (process oils) such as aromatic oils, paraffinic oils, and naphthenic oils, and plant-based softeners such as palm oil, castor oil, cottonseed oil, and soybean oil. The softeners may be used alone or in combination of two or more. When a softener is contained, from the viewpoint of ease of handling, those that are liquid at room temperature such as 25°C, for example, petroleum-based softeners, are preferred, and aromatic oils are particularly preferred. The aromatic oil preferably used is T-DAE (Treated-Distillate Aromatic Extracts: a petroleum-derived rubber softener that can be obtained as an extract fraction obtained by solvent extraction of crude vacuum diesel fuel. To reduce highly carcinogenic polycyclic aromatics, the solvent extraction is performed twice, etc.). Other preferred aromatic oils include A / O (Asphalt / Oil) mix and NC-RAE (Residual Aromatic Extracts). When a softener is used, the amount is preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and particularly preferably 3 to 9 parts by mass, per 100 parts by mass of the rubber component. When the amount of softener is within the above-mentioned range, the processability is improved, and the Shore A hardness at 0°C after curing of the resulting crosslinked rubber composition tends to be easily adjusted to the above-mentioned range.

[0087] The rubber composition for a tire of the present invention preferably contains an antioxidant from the viewpoint of improving heat aging resistance. The antioxidant is not particularly limited, and conventionally known antioxidants can be used. Examples of such antioxidants include hindered phenol compounds, aliphatic and aromatic hindered amine compounds, and quinoline compounds. When an antioxidant is added, the amount added is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0088] The rubber composition for tires of the present invention may further contain an antioxidant. Examples of antioxidants include butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA). When an antioxidant is added, the amount added is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0089] The rubber composition for tires of the present invention may further contain a colorant. Examples of colorants include inorganic pigments such as titanium dioxide, zinc oxide, ultramarine, red iron oxide, lithopone, lead, cadmium, iron, cobalt, aluminum, hydrochlorides, and sulfates, as well as azo pigments and copper phthalocyanine pigments. When a colorant is added, the amount of the colorant added is preferably 0.1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0090] The components that can be used in the rubber composition for a tire of the present invention have been described above, but the components that can be used in the rubber composition for a tire of the present invention are not limited to the above components, and known additives that can be used in rubber compositions (petroleum resins, thixotropy-imparting agents, ultraviolet absorbers, flame retardants, leveling agents, rust inhibitors, antistatic agents, etc.) other than the above components can be used as appropriate depending on the application.

[0091] The method for producing the rubber composition for tires of the present invention is not particularly limited, and for example, a method of mixing (kneading) the rubber component, the silica, and the polymer component, further including the other processing aids as needed, may be employed. For such mixing, a known kneading machine (e.g., a roll, a Banbury mixer, a kneader, a pressure kneader, a single-screw extruder, a twin-screw extruder, etc.) may be appropriately used. For such mixing, the order in which the components are added and the mixing method are not particularly limited, and any method employed in a known method for producing a rubber composition may be appropriately employed to mix the components while appropriately changing the mixing order, etc.

[0092] Alternatively, a method can be appropriately adopted in which the polymer component is formed during the production process of the rubber composition for tires by mixing the rubber component, the silica, the maleic anhydride-modified polymer, and the crosslinking compound, further together with the other processing aids as required.

[0093] In the case where the crosslinking agent is contained, from the viewpoint of obtaining a rubber composition in an uncrosslinked state, it is preferable to obtain a mixture by appropriately mixing the polymer component, the rubber component, the silica, and an appropriate processing aid other than the crosslinking agent, and then to add and mix the crosslinking agent and the remaining processing aid to the obtained mixture under a temperature condition of 20 to 150°C (optimal temperature conditions may be appropriately selected from the above temperature range depending on the type of crosslinking agent and rubber component so that the crosslinking reaction (vulcanization reaction) does not proceed).

[0094] [Crosslinked rubber composition for tires and pneumatic tire using the same] The crosslinked rubber composition for a tire of the present invention is a crosslinked reaction product of the rubber composition for a tire of the present invention. The pneumatic tire of the present invention is characterized in that the crosslinked rubber composition for a tire of the present invention is used in a tire tread.

[0095] The method for producing the crosslinked reaction product of the rubber composition for a tire of the present invention is not particularly limited. For example, when the rubber composition before crosslinking contains a crosslinking agent, a method can be employed in which the rubber is heated appropriately to a temperature at which the crosslinking reaction between the rubber component and the crosslinking agent proceeds, depending on the type and compounding ratio of the crosslinking agent, and at least the rubber component is reacted with the crosslinking agent to crosslink the rubbers together.

[0096] The conditions for the crosslinking reaction are not particularly limited, and known conditions can be appropriately adopted, and can be set appropriately depending on the types of rubber component, crosslinking agent, etc. used. For example, heating at a temperature of 20 to 230°C for 1 to 60 minutes may be used. The crosslinking reaction may also be allowed to proceed while molding is performed as appropriate. The molding method is also not particularly limited, and known molding methods (such as press molding using a press or cutting molding using a cutting machine) may be appropriately adopted.

[0097] As a method for producing a pneumatic tire, for example, the rubber composition for a tire of the present invention is extruded, and then molded using a tire building machine, and then heated and pressurized using a vulcanizer to form crosslinks, thereby producing a pneumatic tire.

[0098] The crosslinked rubber composition for a tire of the present invention obtained using the rubber composition for a tire of the present invention has excellent wet grip performance, low rolling resistance, and abrasion resistance, as described above, and therefore, by using the crosslinked rubber composition for a tire as a material for a tire tread, etc., the pneumatic tire of the present invention having excellent wet grip performance, low rolling resistance, and abrasion resistance can be obtained. Such a pneumatic tire of the present invention is particularly suitable for heavy-duty tires for trucks, buses, etc. [Example]

[0099] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0100] (Synthesis Example 1: Synthesis of ATA crosslinked hydrogenated SBR) <Preparation process of maleic anhydride modified polymer> First, 65.6 g (100 parts by mass) of hydrogenated styrene-butadiene rubber (hydrogenated SBR, manufactured by ENEOS Materials Corporation, trade name: NT120), which is the raw polymer, was placed in a pressure kneader (manufactured by Toyo Seiki Seisakusho Co., Ltd., trade name: Labo Plastomill (using an R100 mixer)) and kneaded for 30 seconds at a temperature of 90 ° C and a rotation speed of 50 rpm. Next, 9.84 g (15 parts by mass) of maleic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) and 6.56 g (10 parts by mass) of aromatic oil (manufactured by ENEOS Corporation: T-DAE) were placed in the pressure kneader and kneaded for another 10 minutes at a temperature of 90 ° C and a rotation speed of 50 rpm, after which the mixture was discharged. The mixture thus discharged was again placed in the pressure kneader and kneaded for 30 minutes at a temperature of 250 ° C and a rotation speed of 50 rpm, after which it was discharged. The released mixture was dried under reduced pressure at 160°C for 3 hours, and then unreacted maleic anhydride was distilled off to obtain hydrogenated SBR modified with maleic anhydride (hereinafter referred to as "maleated, hydrogenated SBR"). Note that the amounts of the raw material components used for the maleic anhydride-modified polymer in parentheses are converted values ​​(unit: parts by mass) when the amount of raw material polymer used is converted to 100 parts by mass.

[0101] The obtained maleated, hydrogenated SBR was analyzed using an NMR measurement device (trade name "Avance 600" manufactured by Bruker) at a measurement temperature of 25°C, solvent of CDCl3, sample concentration of 1.0 mass%, and sample amount of 1.5 cm 3 , Accumulation count: 64 times 1 H NMR measurement was carried out. The structure of the monomer units constituting the main chain of the maleated, hydrogenated SBR was confirmed from the obtained NMR spectrum, and the content of double bond-containing monomer units was calculated, which was confirmed to be 5.3 mol%. Furthermore, the maleation ratio of the obtained maleated, hydrogenated SBR was measured using the method described above in [Method for measuring maleation ratio], and the maleation ratio was found to be 4.0 mass%.

[0102] <Preparation step of polymer having hydrogen-bond cross-linkable moiety in side chain> 65.0 g of the maleated, hydrogenated SBR obtained as the maleic anhydride-modified polymer was placed in the pressure kneader and kneaded for 30 seconds at 180°C and 20 rpm. Then, 1.70 g of 3-amino-1,2,4-triazole (ATA, manufactured by Tokyo Chemical Industry Co., Ltd.) (corresponding to 1.0 molar equivalent of the molar amount of maleic anhydride in the maleic anhydride-modified polymer) was added. The mixture was further kneaded for 8 minutes at 180°C and 50 rpm, and then released to obtain a polymer (thermoplastic elastomer) having hydrogen-bond crosslinkable moieties in its side chains. The polymer thus obtained having hydrogen-bond crosslinkable moieties in its side chains is referred to as "ATA-crosslinked, hydrogenated SBR."

[0103] It was confirmed by IR spectroscopy that an addition reaction of ATA to acid anhydride occurred during production, resulting in the formation of hydrogen-bond cross-linkable moieties. Furthermore, the double bond content of the polymer having hydrogen-bond cross-linkable moieties in its side chains obtained by this production method remains unchanged from the double bond content of maleated, hydrogenated SBR, and therefore the double bond content of the polymer having hydrogen-bond cross-linkable moieties in its side chains obtained in this synthesis example is 5.3 mol %. Furthermore, the glass transition point of the obtained polymer having hydrogen-bond cross-linkable moieties in its side chains was found to be 25°C or lower based on the type of resin constituting the main chain, and it corresponds to polymer (A). The reactions that occur when the above-mentioned steps are carried out are outlined below.

[0104] [ka]

[0105] (Synthesis Example 2: Synthesis of THI crosslinked hydrogenated SBR) A polymer (thermoplastic elastomer) having hydrogen-bond cross-linkable moieties in its side chains was obtained in the same manner as in Synthesis Example 1, except that tris(2-hydroxyethyl)isocyanurate (THI, manufactured by Nissei Corporation) was used as the cross-linking compound instead of ATA in an amount corresponding to 0.33 molar equivalents relative to the molar amount of maleic anhydride moieties in the maleic anhydride-modified polymer. The polymer having hydrogen-bond cross-linkable moieties in its side chains obtained in this manner is referred to as "THI cross-linked, hydrogenated SBR."

[0106] The formation of hydrogen-bond cross-linkable moieties in the obtained polymer was confirmed by IR spectroscopy. The amount of double bonds in the obtained polymer having hydrogen-bond cross-linkable moieties in its side chains was 5.3 mol %. Furthermore, the glass transition point of the obtained polymer having hydrogen-bond cross-linkable moieties in its side chains was found to be 25°C or lower based on the type of resin constituting the main chain, and it corresponds to polymer (B).

[0107] (Synthesis Example 3: Synthesis of MeOH cross-linked hydrogenated SBR) A polymer (thermoplastic elastomer) having hydrogen-bond cross-linkable moieties in its side chains was obtained in the same manner as in Synthesis Example 1, except that methanol (MeOH, manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the cross-linking compound instead of ATA in an amount corresponding to 1.0 molar equivalent relative to the molar amount of maleic anhydride moieties in the maleic anhydride-modified polymer. The polymer having hydrogen-bond cross-linkable moieties in its side chains obtained in this manner is referred to as "MeOH-cross-linked hydrogenated SBR."

[0108] The formation of hydrogen-bond cross-linkable moieties in the obtained polymer was confirmed by IR spectroscopy. The amount of double bonds in the obtained polymer having hydrogen-bond cross-linkable moieties in its side chains was 5.3 mol %. Furthermore, the glass transition point of the obtained polymer having hydrogen-bond cross-linkable moieties in its side chains was found to be 25°C or lower based on the type of resin constituting the main chain, and it corresponded to polymer (A).

[0109] Examples 1 to 5 In Examples 1 to 5, a rubber composition (uncrosslinked) containing a rubber crosslinking agent and a crosslinked rubber composition (vulcanized rubber sheet made of the crosslinked reaction product of the rubber composition) were produced by employing the "rubber component," "polymer component," and "other components" described below, adjusting the amounts of each component to obtain the compositions shown in Table 2 below. The numerical values ​​of the compositions in Table 2 below are values ​​(parts by mass) converted based on 100 parts by mass of the rubber component used, and the amount of rubber component used in each Example was 110 g.

[0110] <Rubber component> The rubber components used were natural rubber (product name "RSS#3"), butadiene rubber (manufactured by UBE, product name "UBEPOL BR150"), and solution-polymerized styrene-butadiene rubber (manufactured by ZS Elastomers, product name "Nipol NS522", oil-extended SBR, amount of oil extension per 100 parts by mass of rubber: 37.5 parts by mass).

[0111] <Polymer component> The ATA crosslinked hydrogenated SBR, THI crosslinked hydrogenated SBR, and MeOH crosslinked hydrogenated SBR synthesized in Synthesis Examples 1 to 3 were used.

[0112] <Other ingredients> Other components used were those listed in Table 1 below.

[0113] [Table 1]

[0114] <Production Process of Rubber Composition> First, a powder material consisting of a mixed powder of silica, carbon black, zinc oxide, stearic acid, and an antioxidant was prepared. Next, the rubber component and the polymer components listed in Table 2 were added to a pressure kneader (manufactured by Toyo Seiki Seisakusho, Ltd., trade name: Labo Plastomill, capacity: 250 mL) heated to 160°C and plasticized by kneading at 160°C and 30 rpm for 1 minute. Subsequently, half of the powder material, the entire amount of the aroma oil, and the entire amount of the silane coupling agent were added to the pressure kneader, and the rotation speed was changed from 30 rpm to 50 rpm. The mixture was kneaded at 160°C and 50 rpm for 1.5 minutes. Next, the remaining half of the powder material was added to the pressure kneader and kneaded at 50 rpm for 1.5 minutes. Next, the ram (floating weight) was moved up and down so that the powder material adhering to the wall surface between the material inlet of the pressure kneader and the kneading chamber of the kneader was introduced into the kneading chamber, and the mixture in the kneader was kneaded for another minute at a temperature of 160°C and a rotation speed of 50 rpm. Next, the ram (floating weight) was moved up and down again in the pressure kneader, and the mixture was kneaded for another 3 minutes at a temperature of 160°C and a rotation speed of 50 rpm, and then released to obtain a rubber composition. In this way, a rubber composition in a form that does not contain a rubber crosslinking agent was obtained.

[0115] Next, using an open roll machine (roll size: diameter 6 inches × length 18 inches, number of rolls: 2), the rubber composition not containing a rubber crosslinking agent obtained as described above, sulfur as a rubber crosslinking agent, vulcanization accelerator (A), and vulcanization accelerator (B) were kneaded to obtain a rubber composition containing a rubber crosslinking agent.

[0116] <Production Process of Crosslinked Rubber Composition> 50 g of the rubber composition containing the rubber crosslinking agent obtained as described above was press-crosslinked (crosslinked (vulcanized) while press-molding) for 30 minutes at 160°C using a press molding machine (manufactured by Dumbbell Co., Ltd.) to obtain a crosslinked rubber composition (vulcanized rubber sheet) in the form of a sheet with a thickness of 1 mm (length: 15 mm, width: 15 mm).

[0117] Example 6 A rubber composition containing a cross-linking agent for rubber and a cross-linked rubber composition (vulcanized rubber sheet) were obtained in the same manner as in Example 1, except that in the production process of the rubber composition, a cross-linking compound (ATA) was further added to the powder material and maleated hydrogenated SBR (equivalent to the "maleic anhydride modified polymer" in Synthesis Example 1) was used as the polymer component.

[0118] (Comparative Example 1) In the manufacturing process of the rubber composition, a rubber composition containing a cross-linking agent for rubber and a cross-linked rubber composition (vulcanized rubber sheet) were obtained in the same manner as in Example 1, except that no polymer component was used and only the rubber component was introduced into a pressure kneader heated to 160°C.

[0119] (Comparative Examples 2 to 3) A rubber composition containing a rubber cross-linking agent and a cross-linked rubber composition (vulcanized rubber sheet) were obtained in the same manner as in Example 1, except that the composition of the rubber composition was changed as shown in Table 2.

[0120] <Evaluation of Properties of Rubber Compositions Obtained in Examples 1 to 6 and Comparative Examples 1 to 3> (average glass transition temperature) The average glass transition temperatures of the rubber components (mixtures) used in Examples 1 to 6 and Comparative Examples 1 to 3 were measured using a differential scanning calorimeter (DSC, manufactured by Hitachi, model number: DSC7000X). Thermograms were measured at a heating rate of 10°C / min, and the temperature at the midpoint of the transition region was taken as the average glass transition temperature. When the rubber component contained an extended oil, the glass transition temperature was determined for the rubber component without the extended oil. When two or more rubber components were contained and incompatible, two glass transition temperatures were determined. In this case, the average value obtained by multiplying each glass transition temperature by the mass ratio of each rubber component was taken as the average glass transition temperature. The results are shown in Table 2.

[0121] (Rubber hardness after curing: Shore A hardness (0°C)) For the vulcanized rubber sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 3, the ISO Type A rubber hardness (Shore A hardness (0°C)) at a temperature of 0°C was measured in accordance with JIS K6253 using a durometer (manufactured by Toyo Seiki Seisaku-sho, model number: GS-610). The results are shown in Table 2. The larger the Shore A hardness (0°C) value, the harder the rubber.

[0122] (Wet grip: viscoelasticity (tanδ(0℃))) For the vulcanized rubber sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 3, tan δ (tan δ(0°C)) was measured in tensile mode in accordance with JIS K6394 using a viscoelasticity measuring device (manufactured by UBM, model number: REOGEL E-4000) under conditions of a strain of approximately 0.1% and a frequency of 10 Hz at a measurement temperature of 0°C. The results are shown in Table 2 as relative values ​​(%), with the value for Comparative Example 1 taken as 100%. A higher value indicates better wet grip properties.

[0123] (Low rolling resistance: Viscoelasticity (tanδ(60℃))) For the vulcanized rubber sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 3, tan δ (tan δ(60°C)) was measured in tension mode in accordance with JIS K6394 under conditions of a strain of approximately 0.1% and a frequency of 10 Hz at a measurement temperature of 60°C using the viscoelasticity measuring device. The results are shown in Table 2 as relative values ​​(%), with the value for Comparative Example 1 taken as 100%. A lower value indicates better low rolling resistance (fuel economy).

[0124] (wear resistance) For the vulcanized rubber sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 3, a DIN abrasion tester (manufactured by Yasuda Seiki Seisakusho, Model No. 151) was used in accordance with JIS K6264-2 to measure the abrasion mass and determine the specific abrasion volume under conditions of an applied force of 10.0 N, a drum rotation speed of 40 rpm, and a traverse speed of 4.20 mm per drum rotation, thereby evaluating abrasion resistance. The results are shown in Table 2 as relative values ​​(%), with the value for Comparative Example 1 taken as 100%. A lower value indicates better abrasion resistance.

[0125] [Table 2]

[0126] From the results shown in Table 2, it was confirmed that the crosslinked rubber compositions of the present invention obtained by crosslinking the rubber compositions of the present invention obtained in Examples 1 to 6 were excellent in wet grip properties, low rolling resistance, and abrasion resistance.

[0127] On the other hand, it was confirmed that the crosslinked rubber composition of Comparative Example 1, which was obtained by crosslinking a rubber composition that did not contain the polymer component, was inferior in wet grip performance, low rolling resistance, and abrasion resistance.

[0128] Furthermore, it was confirmed that the crosslinked rubber composition of Comparative Example 2, which was obtained by crosslinking a rubber composition containing the polymer component but having an average glass transition temperature outside the range specified in the present invention, was inferior in low rolling resistance and abrasion resistance, and in particular, its abrasion resistance was even inferior to that of the crosslinked rubber composition of Comparative Example 1.

[0129] Furthermore, the crosslinked rubber composition of Comparative Example 3, which was obtained by crosslinking a rubber composition containing the polymer component but having a Shore A hardness (0°C) after curing outside the range specified in the present invention, was found to be inferior in wet grip performance, low rolling resistance, and abrasion resistance, and in particular, was even inferior to the crosslinked rubber composition of Comparative Example 1 in low rolling resistance and abrasion resistance.

[0130] Therefore, from the results shown in Table 2, it was confirmed that by crosslinking the rubber composition of the present invention, a crosslinked rubber composition excellent in wet grip properties, low rolling resistance, and abrasion resistance can be obtained, and therefore the rubber composition of the present invention and the crosslinked rubber composition of the present invention obtained by crosslinking it are excellent as rubber compositions for tires and crosslinked rubber compositions for tires used in tire treads of pneumatic tires, etc., and are particularly useful as materials for producing heavy-duty tires. [Industrial Applicability]

[0131] As explained above, the rubber composition for tires of the present invention makes it possible to obtain a crosslinked rubber composition for tires that is excellent in wet grip performance, low rolling resistance, and abrasion resistance. Therefore, the rubber composition for tires of the present invention and the crosslinked rubber composition for tires using the same make it possible to obtain pneumatic tires that are excellent in wet grip performance, low rolling resistance, and abrasion resistance, and are particularly useful as rubber compositions for producing heavy-duty tires for trucks, buses, etc.

Claims

1. At least one rubber component selected from the group consisting of conjugated diene rubbers and hydrogenated products thereof; Silica and at least one polymer component selected from the group consisting of a polymer (A) having a side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and / or a nitrogen-containing heterocycle and having a glass transition point of 25°C or lower, and a polymer (B) having a side chain containing a hydrogen-bond cross-linkable moiety and a covalent-bond cross-linking moiety and having a glass transition point of 25°C or lower; A rubber composition for a tire comprising: The rubber component contains 50% by mass or more of an isoprene-based rubber, The average glass transition temperature of the rubber component is −90° C. or higher and −50° C. or lower, the content of the polymer component is 1 to 100 parts by mass per 100 parts by mass of the rubber component, The rubber composition for tires has an ISO Type A rubber hardness of 55 to 70 at a temperature of 0°C after curing. A rubber composition for tires.

2. 2. The rubber composition for a tire according to claim 1, wherein both the polymer (A) and the polymer (B) have a main chain in which 2.0 mol % to 60 mol % of the total amount of monomer units constituting the main chain are double-bond-containing monomer units containing a double bond at a position forming the main chain skeleton.

3. 2. The rubber composition for a tire according to claim 1, wherein the rubber component is an uncrosslinked rubber component having no hydrogen-bond crosslinkable moieties.

4. 2. The rubber composition for a tire according to claim 1, wherein the isoprene-based rubber is a natural rubber.

5. The CTAB adsorption specific surface area of ​​the silica is 150 to 300 m ２ / g, and the content of the silica is 5 to 80 parts by mass per 100 parts by mass of the rubber component.

6. A crosslinked rubber composition for a tire, which is a crosslinked reaction product of the rubber composition for a tire according to any one of claims 1 to 5.

7. A pneumatic tire, characterized in that the crosslinked rubber composition for tires according to claim 6 is used in the tire tread.

8. 8. The pneumatic tire according to claim 7, which is used as a heavy-duty tire.

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