WO2024116768A1 - Polymer, rubber composition, and crosslinked rubber composition - Google Patents

Abstract

A polymer which is at least one polymer selected from the group consisting of specific polymers (A) having a side chain containing a specific hydrogen-bond-forming crosslinking moiety and specific polymers (B) containing a hydrogen-bond-forming crosslinking moiety, etc. in a side chain, wherein each of the polymers (A) and (B) has a main chain in which 2.0-60 mol% of all the monomer units constituting the main chain are specific double-bond-containing monomer units.

Description

Polymer, rubber composition and crosslinked rubber composition

The present invention relates to a polymer, a rubber composition, and a crosslinked rubber composition.

Conventionally, the use of various polymers has been considered for modifying rubber compositions. For example, in International Publication No. 2021/261406 (Patent Document 1), a specific polymer (A) having a side chain (a) containing a hydrogen-bond crosslinking moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle and having a glass transition point of 25°C or less is disclosed as a polymer, and a specific polymer (B) having a hydrogen-bond crosslinking moiety and a covalent crosslinking moiety in the side chain and having a glass transition point of 25°C or less is disclosed as a rubber composition. Furthermore, a composition containing such a polymer and an uncrosslinked rubber that does not have a hydrogen-bond crosslinking moiety is disclosed as a rubber composition. However, even with such a rubber composition described in Patent Document 1, there was room for improvement in terms of the self-repairing property of the composition after crosslinking. In addition, such a polymer described in Patent Document 1 itself also had room for improvement in terms of self-repairing property and mechanical properties based on 100% modulus and breaking strength.

International Publication No. 2021/261406

The present invention has been made in consideration of the problems with the prior art, and aims to provide a polymer that has excellent mechanical properties based on 100% modulus and breaking strength, as well as excellent self-repairing properties, and that, when contained in a rubber composition, makes it possible to obtain a cross-linked rubber composition with excellent self-repairing properties. Furthermore, the present invention aims to provide a rubber composition that makes it possible to obtain a cross-linked rubber composition with excellent self-repairing properties, as well as a cross-linked rubber composition with excellent self-repairing properties.

The inventors have conducted intensive research to achieve the above object, and have found that in at least one polymer selected from the group consisting of polymer (A) having a side chain (a) containing a hydrogen-bond cross-linking moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle and having a glass transition point of 25°C or less, and polymer (B) having a side chain containing a hydrogen-bond cross-linking moiety and a covalent cross-linking moiety and having a glass transition point of 25°C or less, by making both of the polymer (A) and the polymer (B) polymers having 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, the polymer can be made to have excellent mechanical properties based on 100% modulus and breaking strength, as well as excellent self-repairing properties. They also found that when such a polymer is contained in a rubber composition and the rubber is cross-linked, the self-repairing properties of the cross-linked reaction product of the rubber composition (cross-linked rubber composition) can be made excellent, and have completed the present invention.

In other words, the present invention provides the following aspects:

[1] At least one polymer selected from the group consisting of polymer (A) having a side chain (a) containing a hydrogen-bond crosslinking moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle and having a glass transition point of 25°C or less, and polymer (B) having a side chain containing a hydrogen-bond crosslinking moiety and a covalent crosslinking moiety and having a glass transition point of 25°C or less, wherein 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.

[2] The polymer according to [1], in which the type of polymer constituting the main chain of both the polymer (A) and the polymer (B) is 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, and butyl-based polymer.

[3] The polymer according to [1] or [2], in which the type of polymer constituting the main chain of both the polymer (A) and the polymer (B) is at least one selected from the group consisting of hydrogenated styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, and hydrogenated butadiene-acrylonitrile copolymer.

[4] The polymer according to any one of [1] to [3], wherein both the polymer (A) and the polymer (B) are reaction products of a maleic anhydride-modified polymer having 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, and a crosslinking compound.

[5] A polymer according to any one of [1] to [4],
an uncrosslinked rubber having no hydrogen-bond crosslinkable site;
A rubber composition comprising:

[6] The rubber composition according to [5], wherein the uncrosslinked rubber having no hydrogen-bond crosslinking sites is at least one selected from the group consisting of diene rubber having no hydrogen-bond crosslinking sites, hydrogenated diene rubber having no hydrogen-bond crosslinking sites, and olefin rubber having no hydrogen-bond crosslinking sites.

[7] The rubber composition according to [5] or [6], wherein the uncrosslinked rubber having no hydrogen-bond crosslinking sites is a hydrogenated styrene-butadiene rubber having no hydrogen-bond crosslinking sites.

[8] A crosslinked rubber composition which is a crosslinking reaction product of the rubber composition described in any one of [5] to [7].

[9] The crosslinked rubber composition described in [8], which is a composition for industrial rubber parts.

According to the present invention, it is possible to provide a polymer that has excellent mechanical properties based on 100% modulus and breaking strength, as well as excellent self-repairing properties, and that, when contained in a rubber composition, makes it possible to obtain a cross-linked rubber composition with excellent self-repairing properties. Furthermore, according to the present invention, it is possible to provide a rubber composition that makes it possible to obtain a cross-linked rubber composition with excellent self-repairing properties, as well as a cross-linked rubber composition with excellent self-repairing properties.

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 expressions, when a unit is assigned only to numerical value Y, the unit is also applied to numerical value X.

[polymer]
First, the polymer of the present invention will be described. The polymer of the present invention is at least one polymer 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,
Both of 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 site forming the main chain skeleton.

In such polymers (A) and (B), "side chain" refers to the side chain and terminal of the polymer. Also, "side chain (a) containing a hydrogen-bond cross-linkable moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle" means that a carbonyl-containing group and/or a nitrogen-containing heterocycle (more preferably a carbonyl-containing group and a nitrogen-containing heterocycle) serving as a 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. In addition, the phrase "the side chain contains a hydrogen-bond cross-linking moiety and a covalent-bond cross-linking moiety" refers to a case where the side chain of the polymer contains both a side chain having a hydrogen-bond cross-linking 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)"), and thus both a hydrogen-bond cross-linking moiety and a covalent-bond cross-linking moiety are contained in the side chain of the polymer, as well as a case where the side chain of the polymer contains both a hydrogen-bond cross-linking moiety and a covalent-bond cross-linking moiety (a side chain containing both a hydrogen-bond cross-linking moiety and a covalent-bond cross-linking moiety in one side chain: hereinafter, such a side chain is referred to as "side chain (c)" for convenience, as the case may be).

The polymers (A) to (B) all have a main chain that satisfies the condition that 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. That is, the main chain of such polymers (A) to (B) is a double bond-containing monomer unit containing a double bond at a site forming the main chain skeleton, of which 2.0 mol % to 60 mol % of the total amount of monomer units constituting the main chain. The "double bond-containing monomer unit" referred to here refers to a monomer unit containing a double bond not in a side chain portion but in a portion forming the main chain skeleton (a portion other than the side chain), and examples thereof include a monomer unit represented by the formula: -CH ₂ -CH=CH-CH ₂ - among monomer units derived from butadiene, and a monomer unit represented by the formula: -CH ₂ -C(CH ₃ )=CH-CH ₂ - among monomer units derived from isoprene. Hereinafter, the content ratio of double bond-containing monomer units to the total amount of monomer units constituting the main chain may be simply referred to as the "content ratio of double bond-containing monomer units" in some cases. When the content of such double bond-containing monomer units is 2.0 mol% or more, the maleinization rate can be increased when maleinization is performed during the production of the polymer, compared to when it is less than 2.0 mol%, and the introduction rate of hydrogen bond crosslinking sites in the final polymer can be increased more efficiently, so that a high effect can be obtained, particularly in terms of self-repairability. 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 than when it 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, and the handling after production can be improved, and the decrease in self-repairability due to gelation can be sufficiently suppressed. Furthermore, from the viewpoint of making it possible to make the mechanical properties based on the 100% modulus and breaking strength and the self-repairability more advanced, it is more preferable that the content of the double bond-containing monomer units in the main chain of the polymers (A) to (B) is 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 the double bond-containing monomer unit is more preferably 2.5 mol %, and even more preferably 3.0 mol %.

In the present invention, the content ratio of the double bond-containing monomer unit can be calculated by measuring a 1 H NMR spectrum using a known nuclear magnetic resonance (NMR) measurement device (e.g., Avance 600, product name, manufactured by Bruker) under the following measurement conditions: measurement temperature: 25° C., solvent: CDCl ₃ , sample concentration: ^1.0 mass %, sample amount: 1.5 cm ³ , and number of accumulations: 64, to analyze the monomer units constituting the main chain. Thus, the "content ratio (mol %) of the double bond-containing monomer unit" described in this specification is a value determined by NMR measurement. In addition, when the polymer to be measured for the content ratio of double bond-containing monomer units is a reaction product between a maleic anhydride-modified polymer and a crosslinking compound, the content ratio of double bond-containing monomer units in the main chain of the maleic anhydride-modified polymer before the reaction and the content ratio of double bond-containing monomer units in the main chain of the reactant (the polymer to be measured) after the reaction are the same value, and the content ratio of double bond-containing monomer units in the main chain of the maleic anhydride-modified polymer before and after the reaction does not change. Therefore, when the polymer to be measured for the content ratio of double bond-containing monomer units is the reaction product, the content ratio of double bond-containing monomer units in the main chain of the maleic anhydride-modified polymer before the reaction may be adopted as the content ratio of double bond-containing monomer units in the polymer (polymer (A) or (B)) obtained after the reaction.

In the present invention, both the polymer (A) and the polymer (B) contain double bonds in the main chain, and from the viewpoint of easier satisfaction of the condition of the content ratio of the double bond-containing monomer unit as described above and further improvement of 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 product), and butyl-based polymer (including butyl rubber and hydrogenated product), 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 manufacturing method (method of adding hydrogen) of the hydrogenated product (hydrogenated styrene-butadiene copolymer, hydrogenated butadiene-acrylonitrile copolymer, etc.) referred to here is not particularly limited, and a known method can be appropriately adopted. In this case, the hydrogenation conditions can be appropriately changed so that the content ratio of the double bond-containing monomer unit falls within the desired range to form the desired hydrogenated product. In addition, commercially available products may be appropriately used as the raw polymer for the polymer that constitutes such a main chain.

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

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 side chain (b) containing a covalent cross-linkable moiety; and a side chain (c) containing a hydrogen-bond cross-linkable moiety and a covalent cross-linking moiety. In the present invention, the side chain (c) can be said to be a side chain that functions both as the side chain (a') and as the side chain (b). Each side chain will be described below.

<Side Chain (a'): Side Chain Containing a Hydrogen-Bond Cross-Linking Moiety>
The side chain (a') containing such a hydrogen-bond cross-linking moiety has a group capable of forming a cross-link by hydrogen bonding (for example, a hydroxyl group, a hydrogen-bond cross-linking moiety contained in the side chain (a) described later, etc.), and may be a side chain that forms a hydrogen bond based on the group, and its structure is not particularly limited. Here, the hydrogen-bond cross-linking moiety is a moiety that cross-links the molecules of the polymer by hydrogen bonding. Note that a cross-link by hydrogen bonding is formed only when there is a hydrogen acceptor (a group containing an atom containing a lone electron pair, etc.) and a hydrogen donor (a group having a hydrogen atom covalently bonded to an atom with a large electronegativity, etc.). Therefore, a cross-link by hydrogen bonding is not formed in the side chains of the polymer molecules when there is neither a hydrogen acceptor nor a hydrogen donor. Therefore, a hydrogen-bond cross-linking moiety is present in the system only when there is both a hydrogen acceptor and a hydrogen donor between the side chains of the polymer molecules. In the present invention, when a moiety capable of functioning as a hydrogen acceptor (e.g., a carbonyl group) and a moiety capable of functioning as a hydrogen donor (e.g., a hydroxyl group) are both 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 a hydrogen-bond cross-linkable site.

As such a side chain (a'), from the viewpoint of forming stronger hydrogen bonds, the side chain (a) described below is more preferable. From the same viewpoint, the hydrogen-bond cross-linking moiety in the side chain (a') is more preferably a hydrogen-bond cross-linking moiety having a carbonyl-containing group and a nitrogen-containing heterocycle.

<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 preferable.

Such carbonyl-containing groups are not particularly limited as long as they contain a carbonyl group, and specific examples include amide, ester, imide, carboxy group, carbonyl group, thioester group, acid anhydride group, etc.

In addition, when the side chain (a) has a nitrogen-containing heterocycle, the nitrogen-containing heterocycle may be introduced directly or via an organic group into the side chain (a), and the structure thereof is not particularly limited. As long as the nitrogen-containing heterocycle contains a nitrogen atom in the heterocycle, it may also contain a heteroatom other than the nitrogen atom, such as a sulfur atom, an oxygen atom, or a phosphorus atom. Such a nitrogen-containing heterocycle may have a substituent. Here, when a nitrogen-containing heterocycle is used in the side chain (a), the hydrogen bonds that form the crosslink due to the heterocycle structure become stronger, and the durability and impact resistance of the composition are further improved, which is preferable. In addition, 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 further improving the resistance to compression set and mechanical strength. In addition, such a nitrogen-containing heterocycle may be a nitrogen-containing heterocycle condensed with a benzene ring, or a nitrogen-containing heterocycle condensed with another nitrogen-containing heterocycle. As such a nitrogen-containing heterocycle, known ones (for example, those described in paragraphs [0054] to [0067] of Japanese Patent No. 5918878, those described in paragraphs [0035] to [0048] of Japanese Patent Publication No. 2017-206604, etc.) can be appropriately used. In addition, such a nitrogen-containing heterocycle may have a substituent.

From the viewpoint of 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.

Examples of the substituents that may be possessed by such nitrogen-containing heterocycles 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 consisting of 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; thioether groups; and the like. There are no particular limitations on the substitution positions of these substituents, and there are no limitations on the number of substituents.

In addition, 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 preferable that the carbonyl-containing group and the nitrogen-containing heterocycle are introduced into the main chain as one 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.

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. As a crosslinking compound used when forming such a side chain (a), a compound capable of reacting with a maleic anhydride group to form a hydrogen-bond crosslinking site (hereinafter, sometimes simply referred to as a "compound that forms a hydrogen-bond crosslinking site") can be suitably used. As a "compound that forms a hydrogen-bond crosslinking site" that can be used as such a crosslinking compound, a compound that can introduce a nitrogen-containing heterocycle can be suitably used. In this way, as the crosslinking compound, a "compound that forms a hydrogen-bond crosslinking site (more preferably, a compound that can introduce a nitrogen-containing heterocycle)" can be suitably used. As such a "compound that forms a hydrogen-bond crosslinking site (more preferably, a compound that can introduce a nitrogen-containing heterocycle)", 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.) is preferred, a compound having at least one of a hydroxyl group, an amino group, an imino group, and a thiol group is more preferred, and as such a compound, a compound having a nitrogen-containing heterocycle is particularly preferred.

<Side Chain (b): Side Chain Containing a Covalent Cross-Linking Moiety>
In this specification, “side chain (b) containing a covalent cross-linking moiety” means a side chain containing a moiety that cross-links polymer molecules forming the main chain together by a covalent bond (covalent cross-linking moiety: for example, when polymer (A) or (B) is formed by a reaction between a maleic anhydride-modified polymer and a cross-linking compound, a moiety that cross-links polymers together by a chemically stable bond (covalent bond) such as at least one bond selected from the group consisting of amide, ester, and thioester that can be formed by reacting a maleic anhydride group with a cross-linking compound).

Side chain (b) is a side chain containing a covalent cross-linking moiety, but in cases where it has a covalent cross-linking moiety and further has a group capable of hydrogen bonding, forming a cross-link between side chains by hydrogen bonding, it will be used as side chain (c) described below. (Note that if the side chains of the polymer molecules do not contain both a hydrogen donor and a hydrogen acceptor capable of forming hydrogen bonds between them, for example, if there are only side chains containing ester groups (-COO-) in the system, hydrogen bonds are not formed between the ester groups (-COO-), and such groups do not function as hydrogen-bond cross-linking moieties. On the other hand, in cases where the side chains of the polymer molecules do not contain both a hydrogen donor and a hydrogen acceptor capable of forming hydrogen bonds between them, for example, if there are only side chains containing ester groups (-COO-), such groups do not function as hydrogen-bond cross-linking moieties. On the other hand, When the side chains of the polymer molecules each contain a structure having both a hydrogen donor site and a hydrogen acceptor site, such as a triazole ring, hydrogen bonds are formed between the side chains of the polymer molecules, and thus a hydrogen bond crosslinking site is contained. In addition, 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 site that forms the hydrogen bond becomes a hydrogen bond crosslinking site. Therefore, depending on the structure of the side chain (b) itself, the structure of the side chain (b) and the type of substituents of the other side chains, it may be used as the side chain (c). In addition, the "covalent crosslinking site" referred to here is a site that crosslinks the polymer molecules by a covalent bond.

Such a side chain (b) containing a covalent cross-linking moiety is not particularly limited, but is preferably a side chain containing a covalent cross-linking moiety formed by reacting a maleic anhydride modified polymer with a cross-linking compound consisting of a compound capable of forming a covalent cross-linking moiety by reacting 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 a side chain (b) is preferably formed by at least one bond selected from the group consisting of amide, ester, and thioester.

As a "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 (e.g., 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.

Furthermore, examples of "compounds that form covalent cross-linking sites" 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 forming a covalent cross-linking moiety" can be a compound capable of introducing both the hydrogen-bond cross-linking moiety and the covalent cross-linking moiety depending on the type of substituent possessed by such a compound, the degree of progress of the reaction when such a compound is used for reaction, and the like (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, and the remaining one hydroxyl group may remain as a hydroxyl group, in which case a moiety forming a hydrogen-bond cross-linking may also be introduced.). Therefore, the "compound forming a covalent cross-linking moiety" exemplified here may also include a "compound forming both a hydrogen-bond cross-linking moiety and a covalent cross-linking moiety". From this viewpoint, when forming a side chain (b), a compound may be appropriately selected from the "compound forming a covalent cross-linking moiety" according to the intended design, or the degree of progress of the reaction may be appropriately controlled, etc., to form the side chain (b). In addition, when the compound forming the covalent cross-linking moiety has a heterocycle, it is possible to more efficiently produce a hydrogen-bond cross-linking moiety at the same time, and it is possible to efficiently form a side chain having the covalent cross-linking moiety as the side chain (c) described below. Therefore, specific examples of compounds having 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 be said to be a suitable form of the side chain such as the side chain (a) or the side chain (b) based on its structure.

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 (such as those described in paragraphs [0094] to [0106] of Japanese Patent No. 5918878) can be used as appropriate.

<Side Chain (c): Side Chain Containing Both Hydrogen-Bond Cross-Linking Moiety and Covalent-Bond Cross-Linking Moiety>
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-linkable 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 preferred cross-links can also be similar).

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

As a "compound that forms both hydrogen-bond cross-linking sites and covalent cross-linking sites (a compound that introduces both hydrogen-bond cross-linking sites and covalent cross-linking sites)" 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. In addition, as a compound that forms both hydrogen-bond cross-linking sites and covalent cross-linking sites (a compound that introduces both hydrogen-bond cross-linking sites and covalent cross-linking sites), a compound that has a heterocycle (particularly preferably a nitrogen-containing heterocycle) and is capable of forming a covalent cross-linking site (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. In addition, the polyol, polyamine, and polythiol containing such a heterocycle may be the same as the polyol compound, polyamine compound, and polythiol compound described in the above section "Compound capable of forming a covalent cross-linking moiety (compound that forms a covalent bond)" except that the heterocycle (particularly preferably a nitrogen-containing heterocycle) is present. In addition, known polyols, polyamines, and polythiols containing a heterocycle (for example, those described in paragraph [0113] of Japanese Patent No. 5918878) may be used as appropriate.

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

The covalent 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 a covalent cross-linking moiety containing the tertiary amino bond and/or the ester bond.

Preferred examples of compounds capable of forming a covalent cross-linking site containing the tertiary amino bond and/or the ester bond (compounds capable of forming both a hydrogen bond cross-linking site and a covalent cross-linking site: one of the cross-linking compounds) 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).

The crosslinking at the covalent crosslinking site of the side chain (b) and/or the side chain (c) may be similar to, for example, 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.

　The above describes side chain (a'), side chain (a), side chain (b), and side chain (c), but the groups (structures) of the side chains in such polymers can be confirmed by commonly used analytical means such as NMR and IR spectroscopy.

The polymer (A) is a polymer having the side chain (a) and a glass transition point of 25°C or less, and the polymer (B) is a polymer containing a hydrogen bond crosslinking moiety and a covalent bond crosslinking moiety in the side chain and having a glass transition point of 25°C or less (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). It is preferable that all of the polymers (A) to (B) according to the present invention are thermoplastic elastomers. As the polymer of the present invention, one of the polymers (A) to (B) may be used alone, or two or more of them may be used in combination.

The polymer (B) may be a polymer having both side chain (a') and side chain (b), or may be a polymer having side chain (c). However, the hydrogen-bond cross-linking moiety contained in the side chain of the polymer (B) is preferably a hydrogen-bond cross-linking moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle (more preferably a hydrogen-bond cross-linking moiety having a carbonyl-containing group and a nitrogen-containing heterocycle) from the viewpoint of forming stronger hydrogen bonds. In addition, the cross-linking at the covalent 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 being able to cause intermolecular interactions such as hydrogen bonds between side chains containing the cross-linking moiety.

Furthermore, each of the polymers (A) to (B) according to the present invention is preferably a reaction product 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%, even more preferably 2.0 to 50 mol%) and a crosslinking compound. The content of double bond-containing monomer units in the maleic anhydride-modified polymer does not change 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 the polymers (A) and (B) are reaction products of a maleic anhydride-modified polymer and a crosslinking compound, the side chains have groups derived from the "maleic anhydride group" in the maleic anhydride-modified polymer (for example, ester groups, carbonyl groups, amide groups, imide groups, carboxy groups, etc., depending on the type of crosslinking compound reacted). In addition, the remaining unreacted "maleic anhydride group" can function as a hydrogen acceptor, and therefore can also function as a group that forms a hydrogen bond crosslinking site.

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. From the viewpoint of the length and ease of movement of the crosslinked sites, however, it is more preferable that the polymer is 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%.

The method for producing such maleic anhydride-modified polymers is not particularly limited, but for example, a method can be employed in which a raw material polymer (a polymer before being modified with maleic anhydride) having a content ratio of double bond-containing monomer units 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. In addition, such raw material polymers are 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%, even more preferably 2.0 to 50 mol%), but are more preferably at least one selected from the group consisting of styrene-butadiene copolymers, hydrogenated styrene-butadiene copolymers, butadiene-acrylonitrile copolymers, hydrogenated butadiene-acrylonitrile copolymers, hydrogenated butadiene polymers, isoprene-based polymers (including natural rubber, epoxidized isoprene polymers, and hydrogenated products), and butyl-based polymers (including butyl rubber and hydrogenated products), and even more preferably at least one selected from the group consisting of hydrogenated styrene-butadiene copolymers, butadiene-acrylonitrile copolymers, and hydrogenated butadiene-acrylonitrile copolymers.

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

In this specification, the value of "maleic acid ratio" (unit: mass %) is a value determined by the following [Method of measuring maleic acid ratio].
[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. Next, the THF solution for measurement is titrated with a 0.1 mol/L ethanol solution of potassium hydroxide for which a factor of three or more decimal places is required (a standard solution for volumetric analysis: a 0.1 mol/L ethanol solution of potassium hydroxide with correction: a commercially available solution for which a factor (characteristic value: correction value) of three or more decimal places is described may be used). Here, the end point (neutralization point) is determined by potentiometric titration using an instrument. The factor (characteristic value: correction value) of the 0.1 mol/L ethanol solution of potassium hydroxide may be determined by titration with an oxalic acid standard solution, or when a commercially available product for which a factor is required is used, the factor described in the commercially available reagent (for example, the factor described in the test report of the reagent) 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 to determine the amount of 0.1 mol/L potassium hydroxide ethanol solution dropped into 80 mL of THF (blank value). Next, the acid value is calculated based on the "acid value calculation formula" below using the determined titration value (drop amount), and the maleinization ratio is calculated based on the "maleinization ratio calculation formula" below using the obtained acid value, thereby determining the maleinization ratio (unit: mass%).
<Acid value calculation formula>
[Acid value] = (A - B) x M ₁ x C x f/S
(In the formula, A represents the amount of 0.1 mol/L potassium hydroxide ethanol solution dropped (titration value: mL) required to neutralize the solution for measurement, B represents the amount of 0.1 mol/L potassium hydroxide ethanol solution dropped in a blank (blank test) (titration 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 concentration of potassium hydroxide 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 described in a commercially available reagent (for example, the factor described in the inspection report of the reagent) may be used as it is), and S represents the mass of the maleic anhydride-modified polymer used in the measurement. The unit of the "acid value" obtained by such calculation is "mgKOH/g".)
<Formula for calculating maleic acid ratio>
[Maleinization rate] = [Acid value] ÷ _M1 × _M2 ÷ 1000 × 100 ÷ 2
(In the formula, the acid value is the value calculated by the above "acid value calculation formula" (unit: mgKOH/g), _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 "maleic acid ratio" calculated by this calculation is "mass %.")

The cross-linking compound is not particularly limited as long as it is capable of reacting with the maleic anhydride groups in the maleic anhydride-modified polymer to form either of the polymers (A) and (B). Depending on the intended design, a compound capable of reacting with the maleic anhydride groups to form various cross-linking sites (a compound capable of forming the intended side chain) may be appropriately selected and used.

As such a crosslinking compound, the above-mentioned "compounds that form hydrogen bond crosslinking sites (more preferably, compounds that can introduce a nitrogen-containing heterocycle)" and "compounds that form covalent crosslinking sites" can be suitably used. In addition, 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, and among them, those having a nitrogen-containing heterocycle (such a nitrogen-containing heterocycle is more 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 preferable (note that the "nitrogen-containing heterocycle" here is the same as the above, including preferred ones). As such a compound, for example, those described in paragraph [0049] of WO 2020/027109 can be appropriately used. Such compounds may be used alone or in a mixture of two or more types.

Furthermore, from the viewpoint of high reactivity and industrial availability, such crosslinking compounds are preferably at least one compound selected from the group consisting of nitrogen-containing compounds that may have at least one substituent selected from the group consisting of hydroxyl groups, thiol groups, amino groups, and imino groups (such a substituent may be simply referred to as "substituent (A)" below in some cases), oxygen-containing compounds that may have the substituent (A), and sulfur-containing compounds that may have the substituent (A). Note that such "compounds that form hydrogen-bond crosslinking sites (more preferably compounds that can introduce a nitrogen-containing heterocycle)" and "compounds that form covalent crosslinking sites (compounds that form covalent bonds)" can be appropriately selected 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.

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.

From the viewpoint of the strength of crosslinking by 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.

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 is possible to form the polymers (A) and (B) by reacting the maleic anhydride groups in the maleic anhydride modified polymer with the functional groups in the crosslinking compound (any method can form the crosslinked sites described in 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 adopted in which the maleic anhydride modified polymer is mixed (kneaded) with a kneading machine such as a kneader at a temperature (e.g., about 100 to 250°C) that can plasticize the maleic anhydride modified polymer and can react with the added crosslinking compound and the crosslinking compound is added to cause the reaction.

The polymer of the present invention may be at least one polymer selected from the group consisting of the polymers (A) and (B), and may be composed of only the polymer (A) or (B), or may be a mixture of the polymers (A) and (B). Such a polymer of the present invention is excellent in mechanical properties based on 100% modulus and breaking strength, self-repairing properties, and handleability, and can be used appropriately for various applications. Furthermore, such a polymer of the present invention is particularly preferable for use as a rubber modifier, since it can improve the self-repairing properties of the rubber composition after crosslinking, particularly when used to modify rubber.

[Rubber composition]
Next, the rubber composition of the present invention will be described. The rubber composition of the present invention contains the above-mentioned polymer of the present invention and an uncrosslinked rubber having no hydrogen-bond crosslinkable site.

The uncrosslinked rubber of the present invention is a rubber that does not have a hydrogen bond crosslinking site and is in an uncrosslinked (unvulcanized) state. In this case, "not having a hydrogen bond crosslinking site" means that it does not have a site that crosslinks with other rubbers (for example, when the rubber is a diene rubber, between diene rubbers) or other components by hydrogen bonding, and does not have a structural portion that can form a crosslink by hydrogen bonding (for example, groups such as hydroxyl groups and carbonyl groups that can form a crosslink by hydrogen bonding). In addition, "uncrosslinked" in this case refers to a state before crosslinking (vulcanization) by reacting with a rubber crosslinking agent (vulcanizing agent) described later. From this perspective, "uncrosslinked rubber" refers to a rubber that has not reacted with a rubber crosslinking agent (rubber that has not yet formed a crosslink by a rubber crosslinking agent: unvulcanized rubber). The "rubber cross-linking agent" referred to here may be any agent capable of cross-linking (vulcanizing) the uncross-linked rubber, and includes sulfur-based agents (sulfur-based cross-linking agents) as well as non-sulfur-based agents (non-sulfur-based cross-linking agents, such as peroxide-based cross-linking agents). Agents that can be used as such "rubber cross-linking agents" will be described later.

Such uncrosslinked rubbers that do not have hydrogen-bond crosslinking sites include, for example, diene rubbers that do not have hydrogen-bond crosslinking sites, hydrogenated diene rubbers that do not have hydrogen-bond crosslinking sites (hydrogenated diene rubbers), silicone rubbers that do not have hydrogen-bond crosslinking sites, chlorosulfonated polyethylene rubbers that do not have hydrogen-bond crosslinking sites, epichlorohydrin rubbers that do not have hydrogen-bond crosslinking sites, polysulfide rubbers that do not have hydrogen-bond crosslinking sites, fluororubbers that do not have hydrogen-bond crosslinking sites, vinyl chloride rubbers that do not have hydrogen-bond crosslinking sites, and olefin rubbers that do not have hydrogen-bond crosslinking sites. As such rubbers that do not have hydrogen-bond crosslinking sites, one type may be used alone, or two or more types may be used in combination.

The uncrosslinked rubber is not particularly limited, and any known rubber may be used as appropriate. For example, the rubber described in International Publication No. 2019/027022 may be used as appropriate.

As such an uncrosslinked rubber that does not have a hydrogen-bond crosslinking site, a polymer that is uncrosslinked and has a glass transition point of 25°C or less can be suitably used. From the viewpoint of moldability (fluidity) and mechanical properties (tensile properties), it is more preferable to use at least one selected from the group consisting of diene rubber that does not have a hydrogen-bond crosslinking site, hydrogenated diene rubber that does not have a hydrogen-bond crosslinking site, and olefin rubber that does not have a hydrogen-bond crosslinking site, and it is particularly preferable to use diene rubber that does not have a hydrogen-bond crosslinking site and/or hydrogenated diene rubber that does not have a hydrogen-bond crosslinking site. The "diene rubber" that is suitably used as the uncrosslinked rubber referred to here may be any rubber that contains a double bond in its molecular structure. Therefore, the "diene rubber" that is suitably used as the uncrosslinked rubber described in this specification is a concept that includes ethylene-propylene-diene copolymer (EPDM) and butyl rubber (IIR), as exemplified below. In addition, in this specification, the "silicone rubber" may be any rubber that contains a siloxane structure.

The diene rubber or hydrogenated diene rubber that can be suitably used as the uncrosslinked rubber that does not have such hydrogen-bond crosslinking sites may be any that does not have hydrogen-bond crosslinking sites, and known diene rubbers that can be used in the manufacture of industrial rubber parts (preferably tires) (for example, known diene rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-butadiene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), IIR, brominated IIR, chlorinated IIR, and EPDM, including hydrogenated products) can be appropriately used.

Among such diene rubbers, from the viewpoint that when the composition is used as a material for manufacturing industrial rubber parts (preferably tires, belts, hoses), industrial rubber parts (preferably tires, belts, hoses) having superior performance can be obtained, NR, SBR, EPDM, IR, BR, NBR, CR, IIR, brominated IIR, and chlorinated IIR are preferred, NR, SBR, EPDM, IR, BR, NBR, CR, and IIR are more preferred, NR, SBR, and EPDM are even more preferred, and SBR is particularly preferred. Such diene rubbers may be used alone or in combination of two or more types.

Furthermore, from the viewpoint of versatility and performance, as the uncrosslinked rubber that does not have such hydrogen-bond crosslinking sites, SBR, CR, IIR, EPDM, millable type silicone rubber, NR, IR, BR, NBR, hydrogenated NBR, brominated IIR, and chlorinated IIR are more preferable, and SBR, IIR, EPDM, NR, hydrogenated NBR, brominated IIR, and chlorinated IIR are even more preferable. Note that such rubbers that do not have hydrogen-bond crosslinking sites may be used alone or in the form of a mixture of two or more types.

Furthermore, as a "hydrogenated diene rubber having no hydrogen-bond cross-linking sites" suitable as an uncross-linked rubber having no hydrogen-bond cross-linking sites, hydrogenated styrene-butadiene rubber (hydrogenated SBR) having no hydrogen-bond cross-linking sites is more preferable from the viewpoint of excellent durability due to the small number of double bonds in the main chain. In this way, hydrogenated styrene-butadiene rubber having no hydrogen-bond cross-linking sites (hydrogenated SBR) can be suitably used as an uncross-linked rubber having no hydrogen-bond cross-linking sites.

The rubber composition of the present invention may contain the above-mentioned polymer of the present invention and the uncrosslinked rubber that does not have a hydrogen-bond crosslinking site. The content (content ratio) of the polymer is not particularly limited, but is preferably 1 to 200 parts by mass (more preferably 3 to 150 parts by mass, even more preferably 5 to 100 parts by mass, particularly preferably 5 to 75 parts by mass, and most preferably 5 to 50 parts by mass) per 100 parts by mass of the uncrosslinked rubber. When the content of such a polymer is equal to or greater than the lower limit, the self-repairing property tends to be improved, whereas when the content is equal to or less than the upper limit, the mechanical properties (tensile properties) tend to be improved while maintaining moldability (fluidity).

The rubber composition of the present invention preferably further contains at least one selected from the group consisting of silica and carbon black. By including such silica and/or carbon black, it is possible to further increase the hardness and improve the modulus and breaking strength. When silica and/or carbon black are included in the rubber composition of the present invention, they interact with the hydrogen bond crosslinking sites of the side chains in the polymer, making it possible to improve the dispersibility of the silica and/or carbon black (more preferably silica). When such a rubber composition is used in, for example, a tire, tan δ (0°C), which is an index of wet grip performance, tends to improve.

When the rubber composition of the present invention contains at least one selected from the group consisting of silica and carbon black, the total amount of silica and carbon black is preferably 10 to 150 parts by mass (more preferably 15 to 120 parts by mass, and even more preferably 30 to 100 parts by mass) per 100 parts by mass of the uncrosslinked rubber. If the total amount of such silica and/or carbon black is less than the lower limit, the effect (reinforcing effect) obtained by including them tends to be insufficient, while if it exceeds the upper limit, the breaking strength tends to decrease.

Moreover, as such silica, those having a BET specific surface area (based on ASTM D1993-03) of 40 to 250 m ² /g (more preferably 70 to 200 m ² /g) are preferred. Examples of such silica include dry-process silica (e.g., fumed silica, etc.) produced by thermal decomposition of silicon halide or organosilicon compound, and wet-process silica produced by decomposition of sodium silicate with acid. From the viewpoints of cost and performance, wet-process silica is more preferred. Furthermore, as such silica, commercially available silica for the rubber industry (commercially available products) can be used as is. Such silica may be used alone or in combination with carbon black.

When the rubber composition of the present invention contains silica, it is preferable to further contain a silane coupling agent from the viewpoint of further improving the properties required of silica and further improving dispersibility in rubber that does not have the hydrogen bond crosslinking site (silica has poor affinity with rubber polymers, and has the property that silica forms hydrogen bonds with itself in rubber through silanol groups, reducing the dispersibility of silica in rubber). When such a silane coupling agent is contained, the content is preferably about 0.5 to 15 parts by weight per 100 parts by weight of silica. Furthermore, as such a silane coupling agent, a polysulfide-based silane coupling agent having an alkoxysilyl group that reacts with the silanol group on the silica surface and a sulfur chain that reacts with a polymer, such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, etc., can be suitably used. Commercially available products can be used as silane coupling agents, such as those sold under the trade names "Si-69" and "Si-75" by Evonik Industries AG (formerly Evonik Degussa).

The carbon black is not particularly limited, and any known carbon black that can be used in a rubber composition can be used as appropriate. Among these carbon blacks, furnace blacks such as SAF, ISAF, HAF, FEF, GPF, and SRF are preferred from the viewpoint of reinforcing properties and dispersibility. As such carbon black, commercially available products may be used as they are. Such carbon black is an effective component when forming the tread portion of a tire, particularly the cap tread portion. Such carbon black may be used alone or in combination with silica.

In addition, such a rubber composition preferably further contains a crosslinking agent for rubber (vulcanizing agent) in order to crosslink (vulcanize) the uncrosslinked rubber for use. Such a crosslinking agent for rubber is not particularly limited as long as it is capable of crosslinking (vulcanizing, etc.) the uncrosslinked rubber that does not have the hydrogen bond crosslinking site (e.g., the diene rubber), and any known crosslinking agent for rubber can be used as appropriate. Note that such a crosslinking agent for rubber may be a so-called sulfur-based one (sulfur-based crosslinking agent) or a non-sulfur-based one (non-sulfur-based crosslinking agent: e.g., peroxide-based crosslinking agent, etc.).

In addition, as such a crosslinking agent for rubber, a peroxide-based crosslinking agent, a phenolic resin-based crosslinking agent, a sulfur-based crosslinking agent, and a silane-based crosslinking agent can be suitably used. There are no particular limitations on the peroxide-based crosslinking agent, the phenolic resin-based crosslinking agent, the sulfur-based crosslinking agent, and the silane-based crosslinking agent that can be used as such a crosslinking agent for rubber, and known crosslinking agents can be used as appropriate. For example, the peroxide-based crosslinking agent, the phenolic resin-based crosslinking agent, the sulfur-based crosslinking agent, and the silane-based crosslinking agent described in International Publication No. 2019/027022 may be used as appropriate.

Among such crosslinking agents for rubber, sulfur-based crosslinking agents and peroxide-based crosslinking agents are preferred from the viewpoint of further improving physical properties, with sulfur-based crosslinking agents being more preferred. As such sulfur-based crosslinking agents, powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, inert sulfur, and oil-treated sulfur are preferred from the viewpoint of reactivity, with powdered sulfur and oil-treated sulfur being more preferred, and oil-treated sulfur being even more preferred. Furthermore, as the peroxide-based crosslinking agents, benzoyl peroxide, di-t-butyl peroxide, and dicumyl peroxide are preferred from the viewpoint of crosslinking ability, with dicumyl peroxide being more preferred.

When such a cross-linking agent for rubber is contained, it is preferable to further contain a cross-linking aid (vulcanization aid). As such a cross-linking aid, for example, known ones (compounds described in paragraph [0088] of WO 2018/235961, zinc dimethacrylate, zinc diacrylate, etc.) can be appropriately used.

When the rubber crosslinking agent is added, it is preferable to further add a crosslinking accelerator (vulcanization accelerator). As such crosslinking accelerators, it is preferable to use thiazole-based (MBT, MBTS, ZnMBT, etc.), sulfenamide-based (CBS, DCBS, BBS, etc.), guanidine-based (DPG, DOTG, OTBG, etc.), thiuram-based (TMTD, TMTM, TBzTD, TETD, TBTD, TOTN (tetrakis(2-ethylhexyl)thiuram disulfide), etc.), dithiocarbamate-based (ZTC, NaBDC, etc.), thiourea-based (ETU, etc.), xanthate-based (ZnBX, etc.) crosslinking accelerators, etc.

When using such a rubber crosslinking agent, it is preferable to use a crosslinking promoter (vulcanization promoter) in combination. As such a crosslinking promoter, it is also preferable to include zinc oxide (e.g., three types of zinc oxide); fatty acids such as stearic acid, propionic acid, butanoic acid, acrylic acid, and maleic acid; and zinc fatty acids such as zinc stearate, zinc propionate, zinc butanoate, zinc acrylate, and zinc maleate together with the sulfur-based crosslinking agent.

When a silane-based crosslinking agent is used as the rubber crosslinking agent, a silane compound may be graft-copolymerized onto the rubber in order to silane-crosslink the uncrosslinked rubber. As such a silane compound, one having an alkoxy group that forms a crosslink by silanol condensation with a group that can react with the uncrosslinked rubber is preferable. As such a silane compound, a known compound (for example, one described in International Publication No. 2019/027022) can be appropriately used. In addition, when graft-copolymerizing a silane compound onto the uncrosslinked rubber, a known method (for example, a method of mixing a predetermined amount of a silane compound and a free radical generator with the uncrosslinked rubber and melt-kneading at a temperature of 80 to 200°C) can be appropriately used. As such a silane-based crosslinking agent, polysilane is more preferable from the viewpoint of crosslinking property.

The content of such a cross-linking agent for rubber is preferably 0.1 to 10 parts by mass (more preferably 0.1 to 5 parts by mass) per 100 parts by mass of the uncross-linked rubber. If the content of such a cross-linking agent for rubber is less than the lower limit, the cross-linking density tends to be too low when cross-linked, resulting in poor physical properties, whereas if the content exceeds the upper limit, the cross-linking density tends to be too high, resulting in poor physical properties.

Moreover, it is more preferable that the rubber composition of the present invention further contains a process oil. Examples of such process oils include paraffin-based oils, naphthenic oils, and aromatic oils. With regard to such oils, when the uncrosslinked rubber is a diene-based rubber, it is particularly preferable to use aromatic oils, and when the uncrosslinked rubber is a chloroprene rubber or butyl rubber, it is particularly preferable to use naphthenic oils in combination. There are no particular limitations on such process oils, and known process oils can be used as appropriate, and commercially available ones can be used as appropriate.

The content (content ratio) of such process oil (more preferably paraffin-based oil) is not particularly limited, but is preferably 5 to 1000 parts by mass (more preferably 5 to 800 parts by mass) per 100 parts by mass of the uncrosslinked rubber. When the content of such process oil is equal to or higher than the lower limit, there is a tendency for fluidity and processability to be improved, whereas when the content is equal to or lower than the upper limit, there is a tendency for oil bleeding to be less induced.

In addition, since the rubber composition of the present invention can improve thermal aging properties, an anti-aging agent may be further used. Any known anti-aging agent that can be used in rubber compositions can be used as appropriate. Examples of such anti-aging agents include hindered phenol-based, aliphatic and aromatic hindered amine-based, and quinoline-based compounds. The content of such an anti-aging agent is preferably 0.1 to 10 parts by mass (more preferably 1 to 5 parts by mass) per 100 parts by mass of the uncrosslinked rubber.

The components (including components that can be suitably used) used in the rubber composition of the present invention have been described above, but the components that can be used in the rubber composition of the present invention are not limited to the above-mentioned components, and known additives that can be used in rubber compositions in addition to the above-mentioned components can be used as appropriate depending on the application. Such additives are not particularly limited, and examples thereof include polymers other than the uncrosslinked rubber and the polymer of the present invention; reinforcing agents other than the silica and carbon black described above (for example, hydrogen-bonding fillers, fillers having an amino group introduced therein (amino group-introduced fillers), etc.); amino group-containing compounds other than the amino group-introduced fillers; compounds containing metal elements (metal salts); maleic anhydride-modified polymers; antioxidants; pigments (dyes); plasticizers (softeners); thixotropy-imparting agents; ultraviolet absorbers; flame retardants; solvents; surfactants (including leveling agents); oils other than the process oils described above; dispersants; dehydrating agents; rust inhibitors; adhesion-imparting agents; antistatic agents; fillers; lubricants; processing aids; slip agents; ultraviolet absorbers; light stabilizers; conductivity-imparting agents; antistatic agents; dispersants; flame retardants; antibacterial agents; neutralizing agents; softening agents; fillers; colorants; thermally conductive fillers; and various other components. In addition, such additives are not particularly limited, and generally used ones (known ones: for example, those described in paragraphs [0169] to [0174] of Japanese Patent No. 5918878, those exemplified in JP-A-2006-131663 and WO 2021/261406, etc.) can be used as appropriate.

The method for producing the rubber composition of the present invention is not particularly limited, and for example, a method of producing the rubber composition by mixing (kneading) the uncrosslinked rubber not having the hydrogen-bond crosslinking site with the polymer of the present invention may be adopted. In such mixing, a known kneading machine (for example, a kneader, a pressure kneader, a Banbury mixer, a single-screw extruder, a twin-screw extruder, etc.) can be appropriately used. In such mixing, the order of adding each component and the mixing method are not particularly limited. Even when various components other than the uncrosslinked rubber not having the hydrogen-bond crosslinking site and the polymer of the present invention are contained, the order of adding each component and the mixing method are not particularly limited, and the components may be mixed while appropriately changing the mixing order, etc. by appropriately adopting a method adopted in a known method for producing a rubber composition.

In addition, when the above-mentioned cross-linking agent for rubber is further contained, from the viewpoint of obtaining a composition in an uncross-linked state, it is preferable to mix the above-mentioned polymer of the present invention with the uncross-linked rubber not having the hydrogen-bond cross-linking moiety to obtain a mixture, and then add and mix the cross-linking agent for rubber to the obtained mixture under a temperature condition of 20 to 150°C (the optimum temperature condition may be appropriately selected from the above temperature range depending on the type of the cross-linking agent for rubber and the uncross-linked rubber not having the hydrogen-bond cross-linking moiety so that the cross-linking reaction (vulcanization reaction) does not proceed).

The use of such a rubber composition is not particularly limited, and it can be appropriately used in known uses in which the rubber composition can be used (for example, uses of the rubber composition described in paragraphs [0151] to [0152] of WO 2019/027022). Examples of uses of such a rubber composition include rubber parts for daily necessities, automobile parts (for example, rubber parts such as hoses, belts, bushes, and mounts in the engine room), electrical appliances, industrial parts, etc., rubber for building materials, soundproofing rubber, rubber for automobile interior materials (instrument panels, etc.), and materials for manufacturing tires, etc. In addition, such a rubber composition can be suitably used as rubber for building materials, soundproofing rubber, rubber for automobile interior materials (instrument panels, etc.), and materials for forming tires, among others.

[Crosslinked Rubber Composition]
The crosslinked rubber composition of the present invention is a crosslinked reaction product of the above-mentioned rubber composition of the present invention.

The method for producing such a crosslinked reaction product of the rubber composition is not particularly limited. For example, when the rubber composition before crosslinking contains a rubber crosslinking agent, the rubber composition before crosslinking can be appropriately heated to a temperature at which the crosslinking reaction between the uncrosslinked rubber not having the hydrogen bond crosslinking site in the composition and the rubber crosslinking agent proceeds depending on the type and compounding ratio, and the rubbers are crosslinked by reacting at least the uncrosslinked rubber not having the hydrogen bond crosslinking site with the rubber crosslinking agent in the composition. In this way, the crosslinked rubber composition of the present invention is obtained by crosslinking the rubber composition of the present invention, and is a composition containing a crosslinked body of the uncrosslinked rubber (crosslinked rubber: vulcanized rubber), which is a reaction product of the uncrosslinked rubber not having the hydrogen bond crosslinking site and the rubber crosslinking agent.

The conditions of the crosslinking reaction for obtaining the crosslinked reaction product of the rubber composition are not particularly limited, and known conditions can be appropriately adopted, and may be appropriately set depending on the type of the uncrosslinked rubber not having the hydrogen bond crosslinking site in the rubber composition of the present invention, the crosslinking agent for rubber, etc., and may be, for example, a condition of heating at a temperature of 20 to 230°C for 1 to 60 minutes (regarding the temperature, an optimal temperature may be appropriately selected depending on the type of the rubber crosslinking agent or the uncrosslinked rubber not having the hydrogen bond crosslinking site so that the crosslinking reaction proceeds sufficiently). The crosslinked reaction product of such a rubber composition may be prepared by allowing the crosslinking reaction to proceed while appropriately molding according to the application. The method of such molding is also not particularly limited, and known molding methods (for example, known methods such as press molding using a press machine or cutting molding using a cutting machine) may be appropriately adopted depending on the application and purpose design. The crosslink formed in the crosslinked reaction product of such a rubber composition is preferably a crosslink formed using a sulfur-based crosslinking agent from the viewpoint of further improving physical properties (particularly breaking elongation).

The crosslinked rubber composition of the present invention can be suitably used for so-called industrial rubber parts (for example, rubber parts in various automobile-related products, rubber parts used in industrial machines, etc., as described in paragraph [0157] of WO 2019/027022). Thus, the crosslinked rubber composition of the present invention is preferably a composition for industrial rubber parts. Examples of such industrial rubber parts include daily necessities, automobile parts (for example, rubber parts such as hoses, belts, bushes, and mounts in the engine room), electrical appliances, industrial parts, rubber parts for building materials, soundproofing rubber, automobile interior materials (instrument panels, etc.), tires, etc. In addition, the crosslinked rubber composition of the present invention is more preferably used for the manufacture of tires, from the viewpoints of abrasion resistance and viscoelasticity.

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

[Polymers Having Hydrogen-Bond Cross-Linkable Moieties in Side Chains]
<Types of raw polymers>
First, in each Example, the type of "raw polymer" used in the synthesis of the polymer having a hydrogen-bond cross-linkable moiety in the side chain (the polymer corresponding to the polymer (A) or (B) and the comparative polymer) is shown in Table 1. In addition, as for the abbreviations in Table 1, SBR indicates styrene-butadiene rubber, IR indicates isoprene rubber, NBR indicates butadiene-acrylonitrile rubber, and EPDM indicates ethylene-propylene-diene rubber. In addition, the double bond amount shown in Table 1 indicates the content ratio (unit: mol%) of the double bond-containing monomer unit. In addition, as the content ratio of the double bond-containing monomer unit, a value obtained by analyzing the monomer unit constituting the main chain by measuring the ¹ H NMR spectrum using "Avance 600" manufactured by Bruker under the measurement conditions of measurement temperature: 25°C, solvent: CDCl ₃ , sample concentration: 1.0 mass %, sample amount: 1.5 cm ³ , and number of accumulations: 64 was adopted.

For reference, the method for calculating the content of the double bond-containing monomer unit in the hydrogenated SBR, which is the raw material polymer, will be briefly described below. First, the "formula for calculating the molar fraction ratio of each unit in hydrogenated SBR" used to calculate the content of the double bond-containing monomer unit is shown below.
<Calculation formula for mole fraction ratio of each unit of hydrogenated SBR>
A: B: C = _S1 ÷ 5: _S2 ÷ 2: ( _S3 - _S2 ÷ 2 x 4 - _S1 ÷ 5 x 3) ÷ 8
(In the formula, A represents the molar ratio of styrene units, B represents the molar ratio of butadiene units, and C represents the molar ratio of hydrogenated butadiene units. _S1 is the integral value of the aromatic region obtained by integrating the range of 6.5-7.5 ppm, _S2 is the integral value of the olefin region obtained by integrating the range of 4.7-5.7 ppm, and _S3 is the integral value of the aliphatic region obtained by integrating the range of 0.5-2.7 ppm. The number of protons in each unit of the hydrogenated SBR is as follows: the aromatic proton in the styrene unit is 5H, the aliphatic proton is 3H, the olefin proton in the butadiene unit is 2H, the aliphatic proton is 4H, and the aliphatic proton in the hydrogenated butadiene unit is 8H.)
Next, the procedure adopted for calculating the content ratio of the double bond-containing monomer unit in the hydrogenated SBR will be described. That is, first, ^1H NMR spectrum was measured under the above conditions, and then the molar fraction ratio (A:B:C) of each unit in the hydrogenated SBR was calculated from the measurement data using the above-mentioned calculation formula. Next, the content ratio of the double bond-containing monomer unit was calculated from the molar fraction ratio of each unit obtained by the above-mentioned calculation formula using the calculation formula described below.
<Calculation formula for the content ratio of double bond-containing monomer units in hydrogenated SBR>
Content ratio of double bond-containing monomer unit=B/(A+B+C)
(In the formula, A represents the molar ratio of styrene units, B represents the molar ratio of butadiene units, and C represents the molar ratio of hydrogenated butadiene units.)
The content of double bond-containing monomer units in the hydrogenated SBR (NT120) calculated by this method was 5.3 mol %.

<Types of crosslinking compounds>
In each of the Examples, the types and abbreviations of crosslinking compounds used in the synthesis of polymers having a hydrogen-bond crosslinkable moiety in the side chain (polymers corresponding to the above polymer (A) or (B) and comparative polymers) are shown in Table 2. In the following Examples, compounds are sometimes simply represented by abbreviations.

Example 1
<Preparation process of maleic anhydride modified polymer>
First, 65.6 g of hydrogenated SBR (ENEOS Materials (sometimes referred to as "ENS"), product name: NT120) as a raw material polymer was charged into a pressure kneader (Toyo Seiki Seisakusho, product name: Labo Plastomill (using an R100 mixer)) and kneaded for 30 seconds under conditions of temperature: 90°C and rotation speed: 50 rpm. Next, 9.84 g of maleic anhydride (Tokyo Chemical Industry Co., Ltd.) and 6.56 g of aromatic oil (ENEOS: T-DAE) were charged into the pressure kneader and kneaded for a further 10 minutes under conditions of temperature: 90°C and rotation speed: 50 rpm, and then the mixture was discharged. The mixture thus discharged was again charged into a pressure kneader (manufactured by Toyo Seiki Seisakusho, trade name: Labo Plastomill (using an R100 mixer)) and kneaded for 30 minutes under conditions of a temperature of 250° C. and a rotation speed of 50 rpm, and then discharged (note that such kneading conditions may be simply referred to as "kneading conditions for maleinization modification" in some cases). The mixture thus discharged was dried under reduced pressure at 160° C. for 3 hours, and unreacted maleic anhydride was distilled off to obtain a hydrogenated SBR modified with maleic anhydride (hereinafter simply referred to as "maleinized, hydrogenated SBR").

The obtained maleated, hydrogenated SBR was subjected to 1 H NMR measurement using an NMR measurement device (trade name "Avance ⁶⁰⁰ " manufactured by Bruker) under the following measurement conditions: measurement temperature: 25° C., solvent: CDCl ₃ , sample concentration: 1.0 mass %, sample amount: 1.5 cm ³ , and number of integrations: 64. 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 ratio of the double bond-containing monomer unit was calculated, and it was confirmed that the value was 5.3 mol %. The maleation ratio of the obtained maleated, hydrogenated SBR was measured using the method described in the above-mentioned [Method for measuring maleation ratio], and the maleation ratio was 4.0 mass %. The properties thus obtained, the components used in the production, the production conditions, etc. are shown in Table 3. The amounts of the raw material components of the maleic anhydride-modified polymer shown in Table 3 are converted values (unit: parts by mass) when the amount of the raw material polymer used is converted to 100 parts by mass.

<Preparation process 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 put into a pressure kneader (manufactured by Toyo Seiki Seisakusho, product name: Labo Plastomill (using R100 mixer)) and kneaded for 30 seconds under conditions of temperature: 180°C and rotation speed: 20 rpm, and then 1.70 g of ATA (manufactured by Tokyo Chemical Industry Co., Ltd.) as a crosslinking compound was put in and further kneaded for 8 minutes under conditions of temperature: 180°C and rotation speed: 50 rpm, and then released to obtain a polymer (thermoplastic elastomer) having a hydrogen bond crosslinkable moiety in the side chain. The ratio of the amount of the crosslinking compound used (molar equivalent relative to the molar amount of the maleic anhydride moiety in the maleic anhydride modified polymer) is shown in Table 3.

It was confirmed by IR spectrum that an addition reaction of ATA to acid anhydride occurred during production, forming hydrogen-bond cross-linking moieties. Furthermore, the double bond amount of the polymer having hydrogen-bond cross-linking moieties in its side chains obtained by such a production method is the same as the double bond amount of the maleated hydrogenated SBR, and therefore the double bond amount of the maleated hydrogenated SBR (calculated value obtained by NMR measurement) was used as the double bond amount of the polymer having hydrogen-bond cross-linking moieties in its side chains obtained in this example. The steps employed in Example 1 have been described above, and the reactions that take place when each of the above steps is carried out are outlined below.

(Examples 2 to 5)
Except for changing the type of raw polymer, the type of crosslinking compound, the amount of each component (raw polymer, maleic anhydride, crosslinking compound, aromatic oil), and the kneading conditions during maleinization modification as shown in Table 3, the same method as in Example 1 was adopted to prepare maleic anhydride-modified polymers, and then polymers having hydrogen-bond crosslinkable moieties in their side chains were produced. It was confirmed by IR spectrum that hydrogen-bond crosslinkable moieties were formed in all of the obtained polymers. The double bond amount and maleinization rate of the maleic anhydride-modified polymers were measured in the same manner as in Example 1. It was found that the polymers having hydrogen-bond crosslinkable moieties in their side chains obtained in Examples 1 to 5 have glass transition points of 25° C. or lower based on the type of resin constituting the main chain.

(Comparative Examples 1 to 3)
The same method as in Example 1 was employed to prepare maleic anhydride-modified polymers, and then polymers having hydrogen-bond crosslinkable moieties in their side chains for comparison were produced, except that the type of raw polymer, the type of crosslinking compound, the amount of each component (raw polymer, maleic anhydride, crosslinking compound, aromatic oil) used, and the kneading conditions during maleinization modification were changed as shown in Table 3. The double bond amount and maleinization rate of the maleic anhydride-modified polymers were measured in the same manner as in Example 1.

(Comparative Example 4)
A polymer having a hydrogen-bond cross-linkable moiety in a side chain for comparison was obtained in the same manner as in Example 1, except that the preparation step of a maleic anhydride modified polymer was not performed, maleated EPDM (manufactured by Dow, product name: N416) was used instead of maleated hydrogenated SBR, and the amount of the cross-linking compound used was changed as shown in Table 3.

<Evaluation of properties of polymers obtained in Examples 1 to 5 and Comparative Examples 1 to 4>
[Gelling resistance]
The gelation resistance of the maleic anhydride modified polymer was evaluated using 50 mg of each of the maleic anhydride modified polymers obtained in the "maleic anhydride modified polymer preparation step" of Examples 1 to 5 and Comparative Examples 1 to 3. In this evaluation, 2 mL of toluene was added to 50 mg of the maleic anhydride modified polymer, and the solubility of the polymer after 24 hours had elapsed was visually confirmed and evaluated for gelation resistance based on the following evaluation criteria. The obtained results are shown in Table 3.
<Evaluation Criteria for Gelation Resistance>
A: The polymer is completely dissolved and has high gelation resistance.
B: A portion is swollen and becomes insoluble, and sufficient gelation resistance is not obtained.
C: The entire polymer is swollen and has poor gelation resistance.

[Self-repairing test (heating temperature: 120°C, heating time: 1 hour)]
The self-repairing property was evaluated as follows using the polymers (polymers having hydrogen-bond cross-linking sites in the side chains) finally obtained in Examples 1 to 5 and Comparative Examples 1 to 4. That is, first, 25 g of the obtained polymer was hot-pressed at 200 ° C for 10 minutes to produce a sheet having a thickness of 1 mm (length: 15 mm, width: 15 mm). Then, the surface of the obtained sheet was scratched with a diamond pen (D pen manufactured by Ogura Jewelry Precision Machinery Co., Ltd.). The sheet thus scratched was heated in an oven set at 120 ° C, and removed after 1 hour from the start of heating, and the change in the scratches before and after heating was observed with an optical microscope, and the self-repairing property (120 ° C, 1 h) was evaluated based on the following evaluation criteria. The obtained results are shown in Table 3.
<Evaluation criteria for self-repairability>
A: After heating, the scratches completely disappeared, and the material had a very high degree of self-repairing ability.
B: The damage has partially disappeared, indicating that the material has self-repairing properties.
C: No change was observed in the scratch, and self-repairing properties were not confirmed.

[Self-repairing test (room temperature (25°C), 24 hours)]
Instead of heating the scratched sheet in an oven set at 120°C and removing it one hour after the start of heating to observe the change in the scratches before and after heating with an optical microscope, the scratched sheet was left at room temperature (25°C) for 24 hours and the change in the scratches before and after 24 hours was observed with an optical microscope. The self-repairability (25°C, 24h) was evaluated using the same method (the evaluation criteria were the same) as in the above <Self-repairability test (120°C)>. The results are shown in Table 3.

[Recyclability (repeated molding test)]
First, 25 g of the polymer was hot-pressed at 200° C. for 10 minutes to produce a sheet having a thickness of 1 mm (length: 15 mm, width: 15 mm) using each of the polymers finally obtained in Examples 1 to 5 and Comparative Examples 1 to 4. The resulting sheet was then cut into small pieces and press-molded by hot-pressing again at 200° C. for 10 minutes to produce a sheet as a recycled product. This recycling process (a manufacturing process of recycled products including cutting the sheet and press molding again) was repeated until a seam was confirmed in the resulting recycled product sheet (while the recycled product sheet was seamless and integrated), and was terminated at the stage where a seam was confirmed in the sheet. The recyclability was evaluated based on the number of times the recycling process could be repeated according to the following criteria. The evaluation results are shown in Table 3.
<Recyclability evaluation criteria>
A: Even if the recycling process is repeated 10 times or more, a seamless sheet can be produced, and the sheet has a high degree of recyclability.
B: When the recycling process is repeated 2 or more and less than 10 times, a seamless sheet can be produced and the sheet has sufficient recyclability.
C: A seamless sheet was produced only in the first recycling step, or a seamless sheet could not be produced from the first step, and recyclability was low.

[Tensile test]
First, 25 g of the polymer finally obtained in each of Examples 1 to 5 and Comparative Examples 1 to 4 was hot-pressed at 200° C. for 10 minutes to produce a sheet having a thickness of 1 mm (length: 15 mm, width: 15 mm). Next, a No. 3 dumbbell-shaped test piece was punched out from the obtained sheet, and a tensile test was performed at a tensile speed of 500 mm/min in accordance with JIS K 6251, and the 100% modulus (M100), breaking strength, and breaking elongation were measured at room temperature (25° C.). The obtained results are shown in Table 3.

As is clear from the results shown in Table 3, all of the polymers having hydrogen-bond cross-linking moieties in the side chains obtained in Examples 1 to 5 were confirmed to have excellent self-repairing properties when heated to 120°C, as well as to exhibit self-repairing properties even at room temperature (25°C). In contrast, none of the polymers having hydrogen-bond cross-linking moieties in the side chains for comparison obtained in Comparative Examples 1 to 4 were confirmed to have self-repairing properties at room temperature (25°C). Regarding Comparative Examples 1 to 4, the polymer obtained in Comparative Example 2 exhibited a certain degree of self-repairing properties (rating B) when heated to 120°C, but none of the other polymers exhibited self-repairing properties even at 120°C. From these results, it was found that the polymers of the present invention have excellent self-repairing properties.

In addition, from the results shown in Table 3, it was found that all of the polymers having hydrogen-bond cross-linking moieties in the side chains obtained in Examples 1 to 5 had 100% modulus of 1.8 MPa or more and breaking strength of 8.6 MPa or more, and had higher mechanical properties than the polymers obtained in Comparative Examples 1 to 4. It was also found that all of the polymers having hydrogen-bond cross-linking moieties in the side chains obtained in Examples 1 to 5 had elastic bodies with breaking elongations of 421% or more, and were fully usable as thermoplastic elastomers. From these results, it was found that the polymers of the present invention not only have excellent self-repairing properties, but also have excellent mechanical properties based on 100% modulus and breaking strength. It was also confirmed that all of the polymers having hydrogen-bond cross-linking moieties in the side chains obtained in Examples 1 to 5 also have excellent recyclability.

When the polymers having hydrogen-bond cross-linking moieties in the side chains produced in each Example and Comparative Example were checked for gelation during production, none of the polymers having hydrogen-bond cross-linking moieties in the side chains obtained in Examples 1 to 5 gelled (swelled) at any stage during production, but in Comparative Examples 1 to 3, gelation occurred during production of the maleic anhydride-modified polymer, and the final polymer was at least partially swollen. From these results, it was found that when modifying the raw material polymers used in Comparative Examples 1 to 3, gelation or swelling cannot be suppressed by the methods adopted in Examples 1 to 5, and maleic anhydride-modified polymers with high efficiency and ease of handling cannot be obtained. In Example 1, despite the use of high-temperature conditions of 250°C during production, gelation did not occur, and the polymer had excellent handleability after production. In this way, it was also found that the polymers having hydrogen-bond cross-linking moieties in the side chains obtained in Examples 1 to 5 did not gel during production and had high handleability. In addition, in the preparation process of the maleic anhydride modified polymer used in Examples 1 to 5 and Comparative Examples 1 to 3, it is believed that the diene rubber was maleated at a relatively high modification rate, but taking into account the results described above, it is presumed that the raw material polymer used in Comparative Examples 1 to 3 had a large amount of double bonds in the main chain (70.5 mol% or more), which caused gelation during production and did not increase the strength of the final ATA crosslinked polymer. In contrast, in Examples 1 to 5, the raw material polymer had a double bond amount in the range of 2.0 to 60 mol%, so gelation did not occur during production and mechanical properties (breaking strength, etc.) were improved.

In addition, the gelation resistance results shown in Table 3 also confirm that all of the polymers having hydrogen-bond cross-linking sites in the side chains obtained in Examples 1 to 5 were completely dissolved in toluene (2 mL) and had excellent gelation resistance.

In addition, considering that the polymers having hydrogen-bond cross-linkable moieties in their side chains obtained in Examples 1-2 and 5 and the comparative polymers obtained in Comparative Examples 1-4 share the cross-linking compound ATA in common, it was found from the comparison that a polymer having hydrogen-bond cross-linkable moieties in its side chains with a double bond amount in the main chain in the range of 2.0-60 mol % can be obtained to obtain a polymer (thermoplastic elastomer) with excellent self-repairing properties and mechanical properties.

[Regarding rubber composition and crosslinked rubber composition]
<Raw material components of rubber composition>
<Uncrosslinked rubber>
As the uncrosslinked rubber having no hydrogen-bond crosslinkable sites, SBR (manufactured by Nippon Zeon Co., Ltd., product name "Nipol 1502") was used.

Polymer (rubber modifier)
In the examples and comparative examples described later (except for Comparative Example 5), various polymers were used to modify the properties of the rubber composition containing the uncrosslinked rubber. The types of polymers used as rubber modifiers are shown in Tables 5 and 6. In the examples and comparative examples (except Comparative Example 5) described later, any of the following was used: the raw material polymer used in Example 1 (the polymer used is described in Table 5 with the abbreviations shown in Table 1), the maleic anhydride modified polymer obtained in Example 1 (the polymer used is described in Table 5 with the abbreviations shown in Table 3); the polymer having a hydrogen bond crosslinkable moiety in a side chain obtained in Example 1, Examples 3 to 5, and Comparative Examples 1 to 3 (the polymer used is described in Tables 5 and 6 with the abbreviations shown in Table 3); "styrene-ethylene-butylene-styrene block copolymer (abbreviation: SEBS, manufactured by Asahi Kasei Corporation, product name: H1052)";"maleated SEBS (manufactured by Asahi Kasei Corporation, product name: M1943), maleation rate: 0.9 mass%"; and "ATA crosslinked SEBS" obtained by crosslinking the maleated SEBS (manufactured by Asahi Kasei Corporation, product name: M1943) with ATA. Here, the ATA cross-linked SEBS used was produced in the same manner as in Comparative Example 4, except that maleated SEBS (manufactured by Asahi Kasei Corporation, product name: M1943) was used instead of maleated EPDM (manufactured by Dow Corporation, product name: N416).

<Other Ingredients>
The other components used were those listed in Table 4 below.

(Examples 6 to 9)
In Examples 6 to 9, a rubber composition (uncrosslinked, unvulcanized) containing a crosslinking agent for rubber and a crosslinked rubber composition (rubber sheet made of a crosslinked reaction product of the rubber composition) were produced by adopting the "rubber composition production process" and the "crosslinked rubber composition production process" described below while adjusting the amount of each component used to obtain the composition shown in Table 5 below. The numerical values of the composition in Table 5 below are values (parts by mass) converted based on the amount of the uncrosslinked rubber [SBR (manufactured by Nippon Zeon Co., Ltd., product name "Nipol 1502") used shown in Table 5 as 100 parts by mass, and the amount of the uncrosslinked rubber used in each Example was 110 g.

<Production process of rubber composition>
First, a powder material was prepared consisting of a mixed powder of silica (manufactured by Tosoh Corporation, product name "Nipsil AQ"), zinc oxide (zinc oxide No. 3, manufactured by Toho Zinc Co., Ltd., product name: Ginrei R), stearic acid (manufactured by New Japan Chemical Co., Ltd., product name: Stearic Acid 300), and an antioxidant (manufactured by Ouchi Shinko Chemical Co., Ltd., product name "Nocrac 6C").

Next, uncrosslinked rubber (SBR, Zeon Corporation's product name: Nipol 1502) and the type of polymer (rubber modifier) listed in Table 5 were added to a pressure kneader (Toyo Seiki Co., Ltd., product name: Labo Plastomill, capacity 250 mL) heated to 160°C, and plasticized by kneading at a temperature of 160°C and a rotation speed of 30 rpm for 1 minute. After that, half (1/2) of the powder material, the entire amount of aroma oil (ENEOS Corporation, product name: T-DAE), and the entire amount of silane coupling agent (Evonik Corporation, product name: Si75) were further added to the pressure kneader, while changing the rotation speed from 30 rpm to 50 rpm, and kneading was performed at a temperature of 160°C and a rotation speed of 50 rpm for 1.5 minutes. Next, the remaining half (1/2 amount) of the powder material was further added to the pressure kneader and kneaded for 1.5 minutes at a rotation speed of 50 rpm. Next, the ram (floating weight) was moved up and down so that the powder material attached 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 not containing a rubber crosslinking agent was obtained.

Next, using an open roll machine (roll size: diameter 6 inches x length 18 inches, number of rolls: 2), the rubber composition obtained as described above that does not contain a crosslinking agent for rubber was kneaded with sulfur (manufactured by Hosoi Chemical Co., Ltd., product name: oil-treated sulfur) as a crosslinking agent for rubber, vulcanization accelerator (A) (manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Noccela CZ), and vulcanization accelerator (B) (manufactured by Ouchi Shinko Chemical Co., Ltd., product name: Noccela D) to obtain a rubber composition that contains a crosslinking agent for rubber.

<Production process of crosslinked rubber composition>
50 g of the rubber composition containing the rubber crosslinking agent obtained as described above was used in a press molding machine (manufactured by Dumbbell) to perform press crosslinking (crosslinking (vulcanization) while press molding) at 160°C for 30 minutes, thereby obtaining a crosslinked rubber composition in the form of a sheet having a thickness of 1 mm (length: 15 mm, width: 15 mm).

(Comparative Example 5)
A rubber composition and a crosslinked rubber composition each containing a rubber crosslinking agent were produced in the same manner as in Example 6, except that no polymer (rubber modifier) was used.

(Comparative Examples 6 to 12)
Except for changing the type of polymer (rubber modifier) to that shown in Table 5, rubber compositions and crosslinked rubber compositions each containing a rubber crosslinking agent were produced in the same manner as in Example 6.

<Evaluation of characteristics of rubber compositions obtained in Examples 6 to 9 and Comparative Examples 5 to 12>
[Self-repairing test (heating temperature: 120°C, 150°C, 180°C, heating time: 1 hour)]
In Examples 6 to 9 and Comparative Examples 5 to 12, the "rubber composition containing a crosslinking agent for rubber" obtained before the "production process of a crosslinked rubber composition" was used to evaluate the self-repairing property as follows. That is, first, 25 g of the rubber composition was hot-pressed at 200°C for 10 minutes to perform press crosslinking, thereby producing a 1 mm thick sheet (length: 15 mm, width: 15 mm) made of the crosslinked rubber composition. Thereafter, the surface of the obtained sheet was scratched with a diamond pen (D pen, manufactured by Ogura Jewel Precision Machinery Co., Ltd.). The sheet thus scratched was heated in an oven set to a predetermined temperature (heating temperature), and removed after 1 hour from the start of heating, and the change in the scratches before and after heating was observed with an optical microscope, and the self-repairing property at that heating temperature was evaluated based on the following evaluation criteria. In such an evaluation, the heating temperature was set to 120°C, 150°C, or 180°C, and the self-repairing property was determined for each rubber composition at each heating temperature. The results are shown in Table 5 as self-repairing property (120° C., 1 h), self-repairing property (150° C., 1 h), and self-repairing property (180° C., 1 h).
<Evaluation criteria for self-repairability>
A: After heating, the scratches completely disappeared, and the material had a very high degree of self-repairing ability.
B: The damage has partially disappeared, indicating that the material has self-repairing properties.
C: No change was observed in the scratch, and self-repairing properties were not confirmed.

[Self-repairing test (room temperature (25°C), 24 hours)]
Instead of heating the scratched sheet in an oven set at a predetermined temperature and removing it one hour after the start of heating to observe the change in the scratches before and after heating with an optical microscope, the scratched sheet was left at room temperature (25 ° C) for 24 hours and the change in the scratches before and after 24 hours was observed with an optical microscope. The same method (the evaluation criteria were the same) as in the above <Self-repairing property test (heating temperature: 120 ° C, 150 ° C, 180 ° C, heating time: 1 hour)> was used to evaluate the self-repairing property (25 ° C, 24 h). The results are shown in Table 5.

[Tensile test]
Using the 1 mm thick sheets (rubber sheets made of a crosslinked reaction product of a rubber composition) obtained in Examples 6 to 9 and Comparative Examples 5 to 12, respectively, a No. 3 dumbbell-shaped test piece was prepared by punching out from each sheet, and a tensile test was performed at a tensile speed of 500 mm/min in accordance with JIS K 6251, and the 100% modulus (M100) and 300% modulus (M300) were measured at room temperature (25 ° C.). The value of "M300/M100" was obtained from the values of M100 and M300 measured for each test piece, and the "relative value of M300/M100" was calculated for each sheet obtained in each Example and Comparative Example, where the measured value (M300/M100) of the rubber sheet of Comparative Example 5 was set to 100. The obtained results are shown in Table 5. It can be judged that the larger the relative value, the more the reinforcement is improved with respect to the crosslinked reaction product of the rubber composition of Comparative Example 5, which does not use a polymer as a rubber modifier.

[Wear test (measurement of wear resistance)]
In Examples 6 to 9 and Comparative Examples 5 to 12, the "rubber composition containing a crosslinking agent for rubber" obtained before the "production process of a crosslinked rubber composition" was used to evaluate the abrasion resistance as follows. That is, first, 25 g of the rubber composition was hot-pressed at 160°C for 30 minutes to perform press crosslinking, thereby obtaining a disk-shaped test piece having a thickness of 8 mm and a diameter of 16 mm made of the crosslinked rubber composition. Next, a DIN abrasion tester (manufactured by Yasuda Seisakusho, product name: No. 151 DIN abrasion tester) was used for each test piece in accordance with JIS K6264-2 to determine the amount of abrasion from the mass of the test piece before and after abrasion, and the specific abrasion volume was calculated for each test piece from the amount of abrasion and the calculated specific gravity. Then, for the test pieces of each Example and Comparative Example, the "relative value of the specific abrasion volume" was calculated for each test piece when the specific abrasion volume of the test piece of Comparative Example 5 was set to 100. The obtained results are shown in Table 5. In addition, it can be determined that the smaller the relative value, the more improved the abrasion resistance is compared to the crosslinked reaction product of the rubber composition of Comparative Example 5, which does not use a polymer as a rubber modifier.

[Viscoelasticity]
First, the 1 mm thick sheets (rubber sheets made of the crosslinked reaction product of the rubber composition) obtained in Examples 6 to 9 and Comparative Examples 5 to 12 were used, and a viscoelasticity measuring device (UBM REOGEL E-4000) was used to measure the tan δ of each sheet at a measurement temperature of 0 ° C. under conditions of strain of 20 μm, about 0.1%, and frequency of 10 Hz in accordance with JIS K 6394. Then, for the sheets obtained in each Example and each Comparative Example, the "relative value of tan δ (0 ° C.)" was calculated when the tan δ (0 ° C.) of the sheet of Comparative Example 5 was set to 100. The results obtained are shown in Table 5. It should be noted that the larger the relative value, the more improved the viscoelasticity is with respect to the crosslinked reaction product of the rubber composition of Comparative Example 5, which does not use a polymer as a rubber modifier.

As is clear from the results shown in Table 5, when the rubber compositions obtained in Examples 6 to 9 were used, the self-repairing property was rated B or A at all test temperatures, whereas when the rubber compositions obtained in Comparative Examples 5 to 12 were used, the self-repairing property was rated C at all relatively low test temperatures such as room temperature (25°C) and 120°C, and self-repairing property at low temperatures could not be confirmed. In addition, when the compositions in Examples 6 to 9 and Comparative Examples 5 to 12 were compared, the types of polymers (rubber modifiers) used in the rubber compositions were different (no polymer was used in Comparative Example 5). From the comparison results and the self-repairing property test results, it was found that the self-repairing property can be improved when the polymer used as the rubber modifier is a polymer having a hydrogen bond crosslinking site in the side chain and a main chain having a double bond amount (the content ratio of double bond-containing monomer units to the total monomer units constituting the main chain) in the range of 2.0 to 60 mol%. From these results, it was found that the rubber composition of the present invention can provide excellent self-repairing property of the crosslinking reaction product obtained after crosslinking (vulcanization).

In addition, the results shown in Table 5 show that when the rubber compositions obtained in Examples 6 to 9 were used, the crosslinked reaction product had superior reinforcement, abrasion resistance, and viscoelasticity compared to when the rubber composition obtained in Comparative Example 5 was used. These results also show that the rubber compositions obtained in Examples 6 to 9 are capable of improving the reinforcement, abrasion resistance, and viscoelasticity of the crosslinked reaction product obtained after crosslinking (vulcanization) compared to the rubber composition obtained in Comparative Example 5, which does not contain a polymer as a rubber modifier.

The rubber compositions obtained in Comparative Examples 8 to 9 have improved reinforcement, abrasion resistance, and viscoelasticity after crosslinking compared to the crosslinked reaction product of the rubber composition obtained in Comparative Example 5. However, even the rubber compositions obtained in Comparative Examples 8 to 9 were unable to have excellent self-repairing properties as described above, and were not necessarily sufficient in terms of having excellent self-repairing properties.

These results confirm that the rubber composition of the present invention is capable of providing excellent self-repairing properties to the cross-linked reaction product. Furthermore, it was found that the rubber composition of the present invention is also capable of improving the reinforcement, abrasion resistance, and viscoelasticity of the cross-linked reaction product compared to the cross-linked reaction product of a rubber composition that does not use a polymer.

(Examples 10 to 11)
A rubber composition and a crosslinked rubber composition containing a rubber crosslinking agent were produced in the same manner as in Example 6, except that the amount of the polymer (rubber modifier) used was changed as shown in Table 6. The properties of the rubber composition thus obtained (self-repairing property, reinforcing property, abrasion resistance and viscoelasticity of the crosslinked reaction product) were evaluated in the same manner as in the above-mentioned "Evaluation of the properties of the rubber compositions obtained in Examples 6 to 9 and Comparative Examples 5 to 12". The obtained results are shown in Table 6. For reference, Table 6 also shows the results of Example 6 and Comparative Example 5.

As is clear from the results shown in Table 6, when the rubber compositions obtained in Examples 10 to 11 were used, the self-repairing property was evaluated as B or A at all test temperatures, indicating self-repairing property, and it was confirmed that the self-repairing property was exhibited even at relatively low temperatures such as 25°C and 120°C, even if the amount of polymer used increased or decreased. From these results, it was found that it is possible to improve the self-repairing property of the crosslinked rubber composition by using a polymer having a main chain with a double bond amount (the content ratio of double bond-containing monomer units to all monomer units constituting the main chain) in the range of 2.0 to 60 mol% and having a hydrogen bond crosslinking site in the side chain. In addition, from the results shown in Table 6, when the rubber compositions obtained in Examples 10 to 11 were used, the reinforcement, wear resistance, and viscoelasticity of the crosslinked reaction product were all superior to those obtained in Comparative Example 5. From these results, it was also found that the rubber compositions obtained in Examples 10 to 11 were able to improve the reinforcement, wear resistance, and viscoelasticity of the crosslinked reaction product obtained after crosslinking (vulcanization) compared to the rubber composition obtained in Comparative Example 5, which does not contain a polymer as a rubber modifier.

Example 12
A rubber composition and a crosslinked rubber composition each containing a crosslinking agent for rubber were produced in the same manner as in Example 6, except that the type of uncrosslinked rubber was changed from SBR (Nippon Zeon Corporation, product name: Nipol 1502) to hydrogenated SBR (ENEOS Materials Corporation, product name: NT120) and the compositions shown in Table 7 were used.

(Comparative Example 13)
A rubber composition and a crosslinked rubber composition each containing a rubber crosslinking agent were produced in the same manner as in Example 12, except that no polymer (rubber modifier) was used.

(Comparative Example 14)
A rubber composition and a crosslinked rubber composition each containing a rubber crosslinking agent were produced in the same manner as in Example 12, except that the type of polymer (rubber modifier) was changed to one shown in Table 7.

<Evaluation of characteristics of rubber compositions obtained in Example 12 and Comparative Examples 13 to 14>
The properties of the rubber compositions obtained in Example 12 and Comparative Examples 13-14 (self-repairing properties, reinforcing properties, abrasion resistance, and viscoelasticity of the crosslinked reaction product) were measured as follows. That is, in the tensile test, abrasion test (measurement of abrasion resistance), and measurement of viscoelasticity, instead of obtaining the relative value when the measured value of the rubber sheet (test piece) of Comparative Example 5 (measurement of M300/M100, measurement of DIN abrasion volume, measurement of tan δ (0 ° C.)) was set to 100, the measured value of the rubber sheet (test piece) of Comparative Example 13 was set to 100, and the relative value was obtained by changing each measurement method, except that the same method as the method adopted in the above-mentioned "Evaluation of the properties of the rubber compositions obtained in Examples 6-9 and Comparative Examples 5-12" was adopted to evaluate the properties of the rubber compositions obtained in Example 12 and Comparative Examples 13-14 (Note that the self-repairing properties were evaluated by the same method as the method adopted in the above-mentioned "Evaluation of the properties of the rubber compositions obtained in Examples 6-9 and Comparative Examples 5-12"). The obtained results are shown in Table 7.

As is clear from the results shown in Table 7, when the rubber composition obtained in Example 12 was used, the self-repairing property was evaluated as A at all test temperatures, and it was confirmed that the rubber composition exhibited self-repairing property. In contrast, when the rubber composition obtained in Comparative Examples 13 to 14 was used, the self-repairing property was evaluated as C at all test temperatures, and self-repairing property was not confirmed at any test temperature. When the compositions in Example 12 and Comparative Examples 13 to 14 were compared, the types of polymers (rubber modifiers) used in the rubber compositions were different (no polymer was used in Comparative Example 13). From the comparison results and the self-repairing property test results, it was found that the self-repairing property can be improved when the polymer used as the rubber modifier is a polymer having a hydrogen bond crosslinking site in the side chain and a main chain having a double bond amount (the content ratio of double bond-containing monomer units to the total monomer units constituting the main chain) in the range of 2.0 to 60 mol%. From these results, it was found that the rubber composition of the present invention can provide excellent self-repairing property of the crosslinking reaction product obtained after crosslinking (vulcanization).

In addition, the results shown in Table 7 show that when the rubber composition obtained in Example 12 was used, the crosslinked reaction product had superior reinforcement, abrasion resistance, and viscoelasticity compared to when the rubber composition obtained in Comparative Example 13 was used. These results also show that the rubber composition obtained in Example 12 is capable of improving the reinforcement, abrasion resistance, and viscoelasticity of the crosslinked reaction product obtained after crosslinking (vulcanization) compared to the rubber composition obtained in Comparative Example 13, which does not contain a polymer as a rubber modifier.

As explained above, according to the present invention, it is possible to provide a polymer that has excellent mechanical properties based on 100% modulus and breaking strength, as well as excellent self-repairing properties, and that, when incorporated into a rubber composition, makes it possible to obtain a crosslinked rubber composition with excellent self-repairing properties. Furthermore, according to the present invention, it is possible to provide a rubber composition that makes it possible to obtain a crosslinked rubber composition with excellent self-repairing properties, as well as a crosslinked rubber composition with excellent self-repairing properties. Therefore, the polymer of the present invention is particularly useful as a material for modifying rubber by being incorporated into a rubber composition for producing industrial rubber parts (e.g., rubber for tires, etc.).

Claims (9)

1. At least one polymer selected from the group consisting of polymer (A) having a side chain (a) containing a hydrogen-bond crosslinking moiety having a carbonyl-containing group and/or a nitrogen-containing heterocycle and having a glass transition point of 25°C or less, and polymer (B) having a side chain containing a hydrogen-bond crosslinking moiety and a covalent crosslinking moiety and having a glass transition point of 25°C or less, wherein 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.
2. The polymer according to claim 1, wherein the type of polymer constituting the main chain of both the polymer (A) and the polymer (B) is 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, and butyl-based polymer.
3. The polymer according to claim 1, wherein the type of polymer constituting the main chain of both the polymer (A) and the polymer (B) is at least one selected from the group consisting of hydrogenated styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, and hydrogenated butadiene-acrylonitrile copolymer.
4. The polymer according to claim 1, wherein both the polymer (A) and the polymer (B) are reaction products of a maleic anhydride-modified polymer having 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, and a crosslinking compound.
5. A polymer according to any one of claims 1 to 4,
   an uncrosslinked rubber having no hydrogen-bond crosslinkable site;
   A rubber composition comprising:
6. The rubber composition according to claim 5, wherein the uncrosslinked rubber having no hydrogen-bond crosslinking moieties is at least one selected from the group consisting of diene rubber having no hydrogen-bond crosslinking moieties, hydrogenated diene rubber having no hydrogen-bond crosslinking moieties, and olefin rubber having no hydrogen-bond crosslinking moieties.
7. The rubber composition according to claim 5, wherein the uncrosslinked rubber having no hydrogen-bond crosslinking sites is a hydrogenated styrene-butadiene rubber having no hydrogen-bond crosslinking sites.
8. A crosslinked rubber composition which is a crosslinking reaction product of the rubber composition according to claim 5.
9. The crosslinked rubber composition according to claim 7, which is a composition for industrial rubber parts.