JP7020018B2 - Rubber composition - Google Patents

Description

The present invention relates to a rubber composition.

Various technologies have been developed as phenolic resins to be blended in rubber.
For example, Patent Document 1 describes a phenol resin having a high softening point and an excellent reinforcing effect of rubber. According to Patent Document 1, the phenol resin has a structure derived from a specific plant-derived phenol, a structure derived from other phenols, a structure derived from aldehydes, and a structure derived from sugars. It is described that the softening point is high and the reinforcing effect of rubber is excellent.

Japanese Unexamined Patent Publication No. 2017-11976

The present inventors have studied to reinforce rubber by blending the phenol resin described in Patent Document 1 with rubber. As a result, it was found that the rubber composition reinforced with the phenol resin has room for further improvement in terms of hardness and mechanical properties such as tensile strength and elongation at break.
Therefore, it is an object of the present invention to provide an ester compound capable of improving hardness and mechanical properties when blended with rubber to form a rubber composition.

The present inventors have investigated a compound that can improve the hardness and mechanical properties of a rubber composition when blended with rubber to form a rubber composition. As a result, an ester compound obtained by reacting a structural unit derived from unsaturated carboxylic acid anhydride of a copolymer having a structural unit derived from unsaturated carboxylic acid anhydride with a phenolic hydroxyl group of a phenolic resin is blended in rubber. By doing so, it has been found that the hardness of the rubber composition and the mechanical properties of the rubber composition can be improved.
From the above, the present inventors have found that it is effective to blend an ester compound having a specific structure into rubber in order to improve hardness and mechanical properties, and have completed the present invention.

According to the present invention
With the phenolic hydroxyl group of the phenolic resin having a phenolic hydroxyl group,
An ester compound formed by reacting a copolymer represented by the following general formula (1) with a structural unit represented by the following general formula (B1) .
With rubber
A rubber composition comprising the above is provided.

（上記一般式（１）において、
ｌおよびｍは共重合体中におけるモル含有率を示し、
ｌ＋ｍ＝１であり、
Ａは、炭素数１以上３０以下のアルキレン基、及び、下記一般式（Ａ１）、下記一般式（Ａ２）、下記一般式（Ａ３）、ならびに、下記一般式（Ａ４）により示される構造単位からなる群より選択される１種以上を含み、
Ｂは、下記一般式（Ｂ１）により示される構造単位を含む。）

(In the above general formula (1)
l and m indicate the molar content in the copolymer.
l + m = 1,
A is an alkylene group having 1 or more and 30 or less carbon atoms, and a structural unit represented by the following general formula (A1), the following general formula (A2), the following general formula (A3), and the following general formula (A4). Including one or more species selected from the group
B includes a structural unit represented by the following general formula (B1). )

（上記一般式（Ａ１）中、Ｒ^１からＲ^４は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。ａ_１は０、１または２である。）

(In the above general formula (A1), R ¹ to R ⁴ are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms. A ₁ is 0, 1 or 2.)

（上記一般式（Ａ２）中、Ｒ^５からＲ^９は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。）

( ^In the above general formula ⁽ A2), R5 to R9 are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

（上記一般式（Ａ３）中、Ｒ^１０からＲ^１６は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。）

(In the above general formula (A3), R ¹⁰ to R ¹⁶ are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

（上記一般式（Ａ４）中、Ｒ^１７は、水素または炭素数１以上３０以下の有機基である。）

(In the above general formula (A4), R ¹⁷ is hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

（上記一般式（Ｂ１）中、Ｒ^Ｘ、Ｒ^Ｙは、それぞれ独立して、水素または炭素数１以上３以下の有機基である。）

(In the above general formula (B1), ^{RX and RY are} each independently hydrogen or an organic group having 1 or more and 3 or less carbon atoms.)

According to the present invention, there is provided an ester compound capable of improving hardness and mechanical properties when blended with rubber to form a rubber composition.

6 is an infrared absorption spectrum obtained by measuring the ester compound of Example 2 by infrared spectroscopy.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

According to the present embodiment, an ester compound formed by reacting the phenolic hydroxyl group of a phenolic resin having a phenolic hydroxyl group with a structural unit derived from an unsaturated carboxylic acid anhydride of a copolymer having a specific structure is formed. Provided.

The present inventors have investigated a compound that can improve the hardness and mechanical properties of a rubber composition when blended with rubber to form a rubber composition.
The present inventors have considered using an ester compound obtained by reacting a copolymer having a rigid skeleton with a phenolic resin as the above compound. Here, the present inventors have considered using a copolymer having a structural unit derived from an unsaturated carboxylic acid anhydride as a copolymer having a rigid skeleton. The ester compound is formed by reacting a structural unit derived from an unsaturated carboxylic acid anhydride of a copolymer with a phenolic hydroxyl group of a phenolic resin. This makes it possible to introduce a molecular chain of a phenol-based resin into a copolymer having a rigid skeleton, for example, like a graft chain, to form a linked structure.
It has been found that such an ester compound can improve the hardness and mechanical properties of a rubber composition obtained by blending with rubber, as compared with the case of using a phenolic resin conventionally used for reinforcing rubber. Although the detailed mechanism that can improve the mechanical properties is not clear, it is speculated that the linked structure of the ester compound can limit the mobility of the rubber molecules and improve the hardness and mechanical properties.
From the above, the ester compound according to the present embodiment can improve hardness and mechanical properties when blended with rubber to form a rubber composition.

Hereinafter, the ester compound will be described.

<Ingredient components of ester compounds>
First, the raw material components of the ester compound will be described.
The ester compound is formed by reacting a phenolic resin having a phenolic hydroxyl group with a copolymer represented by the general formula (1) described later. Specifically, this reaction is carried out by a phenolic hydroxyl group of a phenolic resin and a structural unit represented by the general formula (B1) described later of the copolymer, that is, an acid anhydride ring derived from an unsaturated carboxylic acid anhydride. It is a reaction with.
In order to explain the ester compound, first, the phenolic resin and the copolymer used in the reaction will be described.

(Phenol resin)
Examples of the phenol-based resin include novolak-type phenol-based resins, resol-type phenol-based resins, and arylalkylene-type phenol-based resins. As the phenolic resin, one of the above specific examples may be used alone, or two or more different types may be used in combination. As the phenol-based resin, it is preferable to use a novolak-type phenol-based resin among the above specific examples. This allows the graft chain, i.e., the linkage structure introduced to the copolymer to be rigid. Therefore, the hardness and mechanical properties of the rubber composition can be improved.

The novolak-type phenol-based resin may be any resin obtained by reacting phenols and aldehydes under a non-catalyst, an acidic catalyst, and a transition metal catalyst.
As the novolak-type phenol-based resin, for example, a random novolak-type phenol-based resin or a high-ortho-novolak-type phenol-based resin can be used.
The novolak-type phenol-based resin can usually be obtained by controlling the molar ratio of aldehydes to phenols (aldehydes / phenols) to 0.1 or more and 1.0 or less, and then reacting them.

Specific examples of the acid catalyst described above include organic acids such as acetic acid and oxalic acid; mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid; diethyl sulfate; paratoluene sulfonic acid, paraphenol sulfonic acid, benzene sulfonic acid and methane. Organic sulfonic acid such as sulfonic acid; organic phosphonic acid such as 1-hydroxyethylidene-1,1'-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid can be used. As the acidic catalyst, one or a combination of two or more of the above specific examples can be used.

Specific examples of the transition metal catalyst described above include salts of iron, cobalt, nickel, chromium, manganese, zinc, copper, calcium, magnesium, barium and the like. Examples of this salt include organic salts such as acetate, halides and oxides. Specific examples of the salt include zinc chloride, zinc acetate, manganese acetate, magnesium acetate, magnesium oxide and the like. As the salt, one or a combination of two or more of the above specific examples can be used.

The resol-type phenol-based resin may be any resin obtained by reacting phenols and aldehydes in the presence of a basic catalyst.
The resol-type phenol-based resin can usually be obtained by reacting after controlling the molar ratio of aldehydes to phenols (aldehydes / phenols) to be 0.9 or more and 4.0 or less. can.

Specific examples of the above-mentioned basic catalyst include hydroxides of alkali metals such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; oxides of alkaline earth metals such as calcium, magnesium, and barium, and hydroxides. Substances; Amines such as sodium carbonate, aqueous ammonia, triethylamine, hexamethylenetetramine and the like can be used. As the basic catalyst, one or a combination of two or more of the above specific examples can be used.

The phenols used in the synthesis of the novolak-type phenol-based resin and the resol-type phenol-based resin are not limited as long as they are derived from a monomer having a phenolic hydroxyl group.
Specific examples of such phenols include phenol; dihydroxybenzene such as o-dihydroxybenzene, m-dihydroxybenzene, and p-dihydroxybenzene; cresol such as o-cresol, m-cresol, and p-cresol; ethyl. Alkylphenol such as phenol, butylphenol, octylphenol, nonylphenol; xylenol; components of cashew oil such as 3-pentadecylphenol, 3-pentadecylphenol monoene, 3-pentadecylphenoldiene, 3-pentadecylphenol triene; 1,3 -Dihydroxy-5-pentadecylbenzene, 1,3-dihydroxy-5-pentadecylbenzene monoene, 1,3-dihydroxy-5-pentadecylbenzenediene, 1,3-dihydroxy-5-pentadecylbenzenetriene, etc. Ingredients; 2-methyl-1,3-dihydroxy-5-pentadecylbenzene, 2-methyl-1,3-dihydroxy-5-pentadecylbenzene monoene, 2-methyl-1,3-dihydroxy-5-pentadecyl Examples thereof include components containing methyl cardol such as benzenediene and 2-methyl-1,3-dihydroxy-5-pentadecylbenzenetriene; ursiol; bisphenol A; bisphenol F; bisphenol S and the like. As the phenols, one or a combination of two or more of the above specific examples can be used. As the phenols, among the above specific examples, for example, it is preferable to use components containing phenol, o-cresol, m-cresol, p-cresol, m-dihydroxybenzene, butylphenol, octylphenol, and cashew oil. As a result, it is considered that the copolymer and the phenolic resin can appropriately form a linked structure by making the position of the phenolic hydroxyl group appropriate. Therefore, the hardness and mechanical properties of the rubber composition can be improved.
The above-mentioned cardol and 2-methyl cardol do not have pure substances.

The aldehydes used in the synthesis of the novolak-type phenol-based resin and the resol-type phenol-based resin are not limited as long as they are conventionally known.
Specific examples of aldehydes include aldehyde compounds such as formaldehyde, paraformaldehyde, acetaldehyde, paraaldehyde, butylaldehyde, crotonaldehyde, benzaldehyde, and salicylaldehyde; and substances that are sources of aldehyde compounds such as hexamethylenetetramine. Can be used. As the aldehydes, one or a combination of two or more of the above specific examples can be used.

Specific examples of the skeleton structure of the phenolic resin include unmodified phenolic resin, cresol resin, resorcinol resin, xylenol resin, cresol / xylenol resin, cresol-modified phenolic resin, resorcinol-modified phenolic resin, and xylenol-modified phenolic resin. Examples thereof include resins, alkylphenol-based resins, alkylphenol-modified phenolic resins, bisphenol-modified phenolic resins, cashew oil-modified phenolic resins, tall oil-modified phenolic resins, rosin-modified phenolic resins, and terpene oil-modified phenolic resins. As the skeleton structure of the phenol-based resin, one or a combination of two or more of the above-mentioned specific examples may be used.

The phenolic resin preferably contains, for example, a structural unit represented by the following general formula (2). Thereby, an appropriate linking structure can be formed with the copolymer, and the rubber composition can be appropriately reinforced.

（上記一般式（２）において、
Ｒ^１８、Ｒ^１９は、それぞれ独立して、水素原子、ヒドロキシル基、アミノ基、または、炭素数１以上２０以下の有機基であり、
Ｒ^２０は、水素原子、または、炭素数１以上２０以下の有機基である。）

(In the above general formula (2)
R ¹⁸ and R ¹⁹ are independently hydrogen atoms, hydroxyl groups, amino groups, or organic groups having 1 or more and 20 or less carbon atoms.
R ²⁰ is a hydrogen atom or an organic group having 1 or more and 20 or less carbon atoms. )

In the above general formula (2), R ¹⁸ is a hydrogen atom, a hydroxyl group, an amino group or an organic group having 1 or more and 20 or less carbon atoms, and is, for example, a hydrogen atom, a hydroxyl group, an amino group, a hydroxymethyl group and a carbon number of carbon atoms. It must be a hydrocarbon group of 1 or more and 20 or less or a carbon number of 1 or more and 20 or less-CH ₂ -Ar ¹ -OH, -C (CH ₃ ) ₂ -Ar ¹ -OH, -SO ₂ -Ar ¹ -OH. Is preferable, hydrogen atom, hydroxyl group, methyl group, butyl group, octyl group, n-1,4,7-pentadecyltriene group, n-4,7-pentadecyldiene group, n-7-pentadecylmonoene group. Alternatively, an n-pentadecyl group is more preferable, a hydrogen atom, a hydroxyl group, a methyl group, an n-1,4,7-pentadecyltriene group, an n-4,7-pentadecyldiene group and an n-7-pentadecylmonoene group. Alternatively, an n-pentadecyl group is more preferred. Thereby, an appropriate connecting structure can be formed, and the hardness and mechanical properties of the rubber composition can be improved.
Specifically, Ar ¹ indicates an arylene group such as a phenylene group.

In the above general formula (2), R ¹⁹ is a hydrogen atom, a hydroxyl group, an amino group or an organic group having 1 or more and 20 or less carbon atoms, and is, for example, a hydrogen atom, a hydroxyl group, a hydroxymethyl group or a methyl group. Is preferable. As a result, an appropriate linking structure can be formed with the copolymer, and the hardness and mechanical properties of the rubber composition can be improved.

In the above general formula (2), R ²⁰ is a hydrogen atom or an organic group having 1 or more and 20 or less carbon atoms, and is, for example, a hydrogen atom, a hydrocarbon group having 1 or more and 20 or less carbon atoms, a trill group, or a xylyl group. , Aryl group having 1 or more and 20 or less carbon atoms such as phenyl group, naphthyl group and anthracenyl group, or -Ar ² -OH having 1 or more and 20 or less carbon atoms, preferably hydrogen, methyl group or 1 to 20 carbon atoms. It is more preferable that it is −Ar ² -OH as follows. Thereby, an appropriate connecting structure can be formed, and the hardness and mechanical properties of the rubber composition can be improved.
In addition, Ar ² of the above-Ar ² -OH specifically indicates an arylene group such as a phenylene group.

The lower limit of the weight average molecular weight Mw of the phenolic resin is, for example, preferably 300 or more, more preferably 1000 or more, and further preferably 2000 or more. Thereby, the connecting structure can be formed more appropriately, and the hardness and the mechanical strength of the rubber composition can be improved.
The upper limit of the weight average molecular weight Mw of the phenol-based resin is, for example, preferably 200,000 or less, more preferably 100,000 or less, and further preferably 50,000 or less. Thereby, the handleability of the ester compound can be appropriately controlled. Therefore, when blended with rubber to form a rubber composition, the ester compound can be uniformly dispersed in the rubber composition, and the hardness and mechanical strength of the rubber composition can be improved.

The upper limit of the dispersion degree (weight average molecular weight Mw / number average molecular weight Mn) of the phenolic resin is, for example, preferably 50 or less, more preferably 40 or less, still more preferably 30 or less. , 20 or less is more preferable, and 10 or less is particularly preferable. As a result, the length of the connecting structure can be made uniform, and the hardness and mechanical strength of the rubber composition can be suppressed from becoming locally non-uniform. Therefore, the hardness and mechanical strength of the rubber composition can be improved.
The lower limit of the dispersity of the phenolic resin may be, for example, 1 or more, or 3 or more.

In this embodiment, the above-mentioned weight average molecular weight Mw and number average molecular weight Mn can be calculated by gel permeation chromatography (GPC) measurement based on a calibration curve prepared using a polystyrene standard material. ..

The upper limit of the content of unreacted phenols in the phenol-based resin is, for example, preferably 5% or less, more preferably 3% or less, still more preferably 1% or less. This makes it possible to suppress the opening of the structural unit derived from the unsaturated carboxylic acid anhydride in the copolymer without forming a linked structure. Therefore, the hardness and mechanical strength of the rubber composition can be improved.
Further, the lower limit of the content of unreacted phenols in the phenol-based resin may be, for example, 0% or more, or 0.1% or more.
The content of unreacted phenols in the phenol-based resin can be calculated by using, for example, gas chromatography.

(Copolymer)
The copolymer according to this embodiment is represented by the following general formula (1). The following formula (1) does not limit the arrangement of the copolymer. As the copolymer arrangement, for example, a random copolymer, an alternating copolymer, a block copolymer, a periodic copolymer, or the like can be selected.
Here, A is represented by an alkylene group having 1 or more and 30 or less carbon atoms, the following general formula (A1), the following general formula (A2), the following general formula (A3), and the following general formula (A4). It contains one or more selected from the group consisting of structural units, and for example, it preferably contains an alkylene group having 1 or more and 30 or less carbon atoms, and more preferably an alkylene group having 1 or more and 30 or less carbon atoms. As a result, the steric hindrance of the molecular chain of the copolymer derived from the structure of A can be alleviated, and the copolymer can appropriately form a linked structure. Therefore, the hardness and mechanical strength of the rubber composition can be improved.
Further, B contains a structural unit derived from an unsaturated carboxylic acid anhydride represented by the following general formula (B1). When the copolymer contains a structural unit represented by the following general formula (B1), a linked structure can be formed with the above-mentioned phenolic resin.

（上記一般式（１）において、
ｌおよびｍは共重合体中におけるモル含有率を示し、
ｌ＋ｍ＝１であり、
Ａは、炭素数１以上３０以下のアルキレン基、及び、下記一般式（Ａ１）、下記一般式（Ａ２）、下記一般式（Ａ３）、ならびに、下記一般式（Ａ４）により示される構造単位からなる群より選択される１種以上を含み、
Ｂは、下記一般式（Ｂ１）により示される構造単位を含む。）

(In the above general formula (1)
l and m indicate the molar content in the copolymer.
l + m = 1,
A is an alkylene group having 1 or more and 30 or less carbon atoms, and a structural unit represented by the following general formula (A1), the following general formula (A2), the following general formula (A3), and the following general formula (A4). Including one or more species selected from the group
B includes a structural unit represented by the following general formula (B1). )

（上記一般式（Ａ１）中、Ｒ^１からＲ^４は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。ａ_１は０、１または２である。）

（上記一般式（Ａ２）中、Ｒ^５からＲ^９は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。）

（上記一般式（Ａ３）中、Ｒ^１０からＲ^１６は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。）

（上記一般式（Ａ４）中、Ｒ^１７は、水素または炭素数１以上３０以下の有機基である。）

（上記一般式（Ｂ１）において、Ｒ^Ｘ、Ｒ^Ｙは、それぞれ独立して、水素または炭素数１以上３以下の有機基である。）

(In the above general formula (A1), R ¹ to R ⁴ are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms. A ₁ is 0, 1 or 2.)

( ^In the above general formula ⁽ A2), R5 to R9 are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

( ^In the above general formula (A3), R10 to ^R16 are each independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

(In the above general formula (A4), R ¹⁷ is hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

(In the above general formula (B1), ^{RX and RY are} each independently hydrogen or an organic group having 1 or more and 3 or less carbon atoms.)

The composition ratio of the structural unit of A and the structural unit of B in the copolymer will be described. When the molar content (mol%) of the structural unit of A is l and the molar content (mol%) of the structural unit of B is m in the copolymer, the numerical range of l is l + m = 1. For example, 0.1 ≦ l ≦ 0.9 is preferable. Further, the numerical range of m is preferably, for example, 0.1 ≦ m ≦ 0.9.

The alkylene group having 1 or more and 30 or less carbon atoms in A of the general formula (1) may be, for example, a linear alkylene group or a branched chain alkylene group. Specific examples of the linear alkylene group include methylene group, ethylene group, propylene group, butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decanylene group, trimethylene group and tetramethylene group. , Pentamethylene group, hexamethylene group and the like. Specific examples of the branched alkylene group include -C (CH ₃ ) _2- , -CH (CH ₃ )-, -CH (CH ₂ CH ₃ )-, and -C (CH ₃ ) (CH ₂ ). Alkylmethylene groups such as CH ₃ )-, -C (CH ₃ ) (CH ₂ CH ₂ CH ₃ )-, -C (CH ₂ CH ₃ ) _2- ; -CH (CH ₃ ) CH _2- , -CH ( Alkylethylene such as CH ₃ ) CH (CH ₃ )-, -C (CH ₃ ) ₂ CH _2- , -CH (CH ₂ CH ₃ ) CH _2- , -C (CH ₂ CH ₃ ) ₂ -CH _2- The group etc. can be mentioned. As the alkylene group, among the above specific examples, only one kind may be contained, or two or more kinds may be contained.
As the alkylene group, among the above specific examples, for example, those having 1 or more and 10 or less carbon atoms are preferable, those having 1 or more and 7 or less are more preferable, those having 1 or more and 5 or less are further preferable, and those having 1 or more and 3 or less. Is more preferable. This makes it possible to form a linked structure while suppressing a decrease in the rigidity of the copolymer. Therefore, the hardness and mechanical strength of the rubber composition can be improved.

The organic groups having 1 to 30 carbon atoms constituting R ¹ to R ¹⁷ in the above general formulas (A1) to (A4) are independently composed of O, N, S, P and Si in their structures. It may contain one or more atoms of choice.

In the above general formulas (A1) to (A4), ^R1 to ^R17 are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms, and for example, hydrogen or an organic group having 1 or more and 15 or less carbon atoms. It is preferably a group, more preferably hydrogen or an organic group having 1 or more and 10 or less carbon atoms, and further preferably hydrogen or an organic group having 1 or more and 3 or less carbon atoms.

Examples of the organic group constituting R ¹ to R ¹⁷ in the above general formulas (A1) to (A4) include an alkyl group, an alkenyl group, an alkynyl group, an alkylidene group, an aryl group, an aralkyl group, an alkalinel group and a cycloalkyl group. Examples include groups, alkoxy groups and heterocyclic groups.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group and a heptyl group. Examples include octyl group, nonyl group, and decyl group. Examples of the alkenyl group include an allyl group, a pentaenyl group, and a vinyl group. Examples of the alkynyl group include an ethynyl group. Examples of the alkylidene group include a methylidene group and an ethylidene group. Examples of the aryl group include a tolyl group, a xylyl group, a phenyl group, a naphthyl group, and an anthrasenyl group. Examples of the aralkyl group include a benzyl group and a phenethyl group. Examples of the alkaline group include a tolyl group and a xylyl group. Examples of the cycloalkyl group include an adamantyl group, a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an s-butoxy group, an isobutoxy group and a t-butoxy group, an n-pentyloxy group and a neopentyloxy group. , N-hexyloxy group. Examples of the heterocyclic group include an epoxy group and an oxetanyl group.

In the above general formula (A1), a1 is 0, ₁ or 2, and may be 0 or 1, or may be 0.

In the above general formula (B1), ^{RX and RY are} independently hydrogen or an organic group having 1 or more and 3 or less carbon atoms, and are, for example, hydrogen or an organic group having 1 or more and 2 or less carbon atoms. Is preferable, and hydrogen is more preferable.

In the above general formula (B1), the organic group having 1 or more and 3 or less carbon atoms constituting ^{RX and RY is} specifically an alkyl group such as a methyl group, an ethyl group or an n-propyl group; an allyl group. , Alkenyl group such as vinyl group; Alkinyl group such as ethynyl group; Alkylidene group such as methylidene group and ethylidene group; Cycloalkyl group such as cyclopropyl group; Heterocyclic group such as epoxy group oxetanyl group and the like.

(Method for producing copolymer)
A method for producing a copolymer according to the present embodiment will be described.
In the method for producing a copolymer according to the present embodiment, for example, the monomer from which A is derived in the above general formula (1) and the unsaturated carboxylic acid anhydride from which B is derived are copolymerized to form a copolymer. The polymerization step (S1) for obtaining the above is included.
Further, after the polymerization step (S1), a low molecular weight component removing step (S2) may be performed. The low molecular weight component is removed from the copolymer by the low molecular weight component removing step (S2).
Hereinafter, details of each step will be described.

(Polymerization step (S1))
In the polymerization step, the monomer from which A is derived in the general formula (1) and the unsaturated carboxylic acid anhydride from which B is derived are copolymerized to obtain a copolymer.
First, as a monomer used for polymerization, a monomer from which A is derived and an unsaturated carboxylic acid anhydride are prepared.
In the following description, when an alkene monomer derived from an alkylene group having 1 to 30 carbon atoms is used as the monomer from which A is derived, and maleic anhydride is used as the unsaturated carboxylic acid anhydride. Will be described as an example.
Instead of the alkene monomer, another monomer may be used. Specific examples of such a monomer include a norbornene-type monomer from which the general formula (A1) is derived, a styrene-type monomer from which the general formula (A2) is derived, and the general formula (A3). The use of an inden-type monomer and a maleimide-type monomer from which the above general formula (A4) is derived is not limited. Further, these monomers may be used alone or in combination of two or more.

Specific examples of the alkene monomer include chain alkene monomers such as ethene, propene, cyclopropene, 1-butene, 2-butene, and isobutene; and cyclic alkene monomers such as cyclopropene, cyclobutene, cyclopentene, and cyclohexene. Can be mentioned.

Specific examples of the norbornene-type monomer include norbornene, norbornene, bicyclo [2.2.1] -hept-2-ene (common name: 2-norbornene), 5-methyl-2-norbornene, and 5-ethyl. -2-Norbornene, 5-Butyl-2-Norbornene, 5-Hexil-2-Norbornene, 5-Decil-2-Norbornene, 5-Allyl-2-Norbornene, 5- (2-Propenyl) -2-Norbornene, 5 -(1-Methyl-4-pentenyl) -2-norbornene, 5-ethynyl-2-norbornene, 5-benzyl-2-norbornene, 5-phenethyl-2-norbornene, 2-acetyl-5-norbornene, 5-norbornene Examples thereof include methyl-2-carboxylate, 5-norbornene-2,3-dicarboxylic acid anhydride and the like. As the norbornene-type monomer, one or a combination of two or more of the above specific examples can be used.

Specific examples of the styrene-type monomer include styrene, vinyltoluene, α-methylstyrene and the like. As the styrene type monomer, one or a combination of two or more of the above specific examples can be used.

Specific examples of the indene-type monomer include indene, 2-methylindene, and 3-methylindene. As the indene-type monomer, one or a combination of two or more of the above specific examples can be used.

Specific examples of the maleimide-type monomer include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-isobutylmaleimide, N-t-butylmaleimide and the like. N-Cycloalkylmaleimide, N-phenylmaleimide, N-chlorophenyl such as N-alkylmaleimide, N-cyclohexylmaleimide, N-cyclopentylmaleimide, N-norbornylmaleimide, N-cyclohexylmethylmaleimide, N-cyclopentylmethylmaleimide. N-arylmaleimide such as maleimide, N-methylphenylmaleimide, N-naphthylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide, N-alkylmaleimide, N- Cycloalkylmaleimide, N-arylmaleimide, N-hydroxymaleimide and the like can be mentioned.

In addition, in addition polymerization, a monomer that can be copolymerized may be further added in addition to the above-mentioned alkene monomer, norbornene type monomer, styrene type monomer, indene type monomer, maleimide type monomer, and maleic anhydride. Examples of such a monomer include a monomer containing a group having an ethylenic double bond other than the above-mentioned alkene monomer. Specific examples of the group having such an ethylenic double bond include an allyl group, an acrylic group, a methacrylic group, and a maleimide group.

Then, the alkene monomer and maleic anhydride are addition-polymerized.
The method of addition polymerization is not limited, but in the present embodiment, a copolymer is synthesized by radical polymerization using a radical polymerization initiator.

The molar ratio of propylene to maleic anhydride is preferably, for example, 0.5: 1 to 1: 0.5. The above 0.5: 1 to 1: 0.5 include 0.5: 1 and 1: 0.5.

As a polymerization method, for example, a method of polymerizing using a radical polymerization initiator and, if necessary, a molecular weight adjusting agent is preferable. In this case, methods such as suspension polymerization, solution polymerization, dispersion polymerization, and emulsion polymerization can be used. Above all, solution polymerization is preferable. At the time of solution polymerization, all the monomers may be charged in a batch, or a part thereof may be charged in a reaction vessel and the rest may be dropped.
For example, the alkene monomer, maleic anhydride, and the polymerization initiator are dissolved in a solvent and then heated for a predetermined time to promote the polymerization of the alkene monomer and maleic anhydride. At the time of polymerization, the heating temperature is, for example, a temperature of 50 ° C. or higher and 80 ° C. or lower. The heating time is, for example, 10 hours or more and 20 hours or less. As a result, the copolymer represented by the above-mentioned general formula (1) can be obtained.

Specific examples of the solvent used for the polymerization include diethyl ether, tetrahydrofuran, toluene, methyl ethyl ketone, ethyl acetate and the like. As the solvent used for the polymerization, one or a combination of two or more of the above specific examples can be used.

As the radical polymerization initiator, any one or more of an azo compound and an organic peroxide can be used.
Examples of the azo compound include azobisisobutyronitrile (AIBN), dimethyl 2,2'-azobis (2-methylpropionate), and 1,1'-azobis (cyclohexanecarbonitrile) (ABCN). Of these, any one or more can be used.
Examples of the organic peroxide include hydrogen peroxide, ditert-butyl peroxide (DTBP), benzoyl peroxide (benzoyl peroxide, BPO), and methyl ethyl ketone peroxide (MEKP). , Any one or more can be used.

The amount of the radical polymerization initiator added is preferably 1 mol% to 10 mol% with respect to the total of the alkene monomer and maleic anhydride. By appropriately setting the amount of the polymerization initiator within the above range and appropriately setting the reaction temperature and the reaction time, the weight average molecular weight Mw of the obtained polymer can be controlled within an appropriate range.

(Low molecular weight component removing step (treatment S2))
After the polymerization step (S1), a low molecular weight component removing step (S2) may be performed. The low molecular weight component is removed from the copolymer by the low molecular weight component removing step (S2). The specific method is shown below.
The copolymer is coagulated and precipitated by adding a large amount of a poor solvent such as hexane or methanol to the organic layer containing the copolymer and the low molecular weight component. The low molecular weight component includes a residual monomer, an oligomer, a polymerization initiator and the like. Then, filtration is performed and the obtained coagulated product is dried. This makes it possible to remove the low molecular weight component from the copolymer.

<Manufacturing method of ester compound>
The ester compound is a structural unit derived from the phenolic hydroxyl group of the above-mentioned phenolic resin and the unsaturated carboxylic acid anhydride represented by the following general formula (B1) of the copolymer represented by the above general formula (1). Is reacted to form an ester bond.
The reaction method is obtained by dissolving and mixing the phenolic resin and the copolymer represented by the above general formula (1) in a solvent and heat-treating at a temperature of 40 ° C. or higher and 120 ° C. or lower.
The reactivity between the copolymer and the phenolic resin changes depending on factors such as the monomer from which A of the copolymer represented by the above general formula (1) is derived. The heat treatment time can be appropriately set according to the monomer from which A of the copolymer represented by the above general formula (1) is derived. For example, when an alkene monomer is used as the monomer from which A of the copolymer represented by the above general formula (1) is derived, it can be 1 minute or more and 200 hours or less.
Further, when the monomer from which A of the copolymer represented by the above general formula (1) is derived is a norbornene-type monomer or the like, the reactivity between the copolymer and the phenol-based resin is low. If the reactivity is low, for example, amine catalysts such as triethylamine, pyridine, dimethylaminopyridine; acid catalysts such as methanesulfonic acid, p-toluenesulfonic acid, hydrochloric acid, sulfuric acid; pyridinesulfonic acid such as betahistin methanesulphonate. Reactivity may be improved by using a catalyst such as a neutralizing salt catalyst. Further, as the catalyst, for example, a known catalyst that promotes esterification may be used.
Even when the monomer from which A of the copolymer represented by the above general formula (1) is derived has good reactivity such as an alkene monomer or an indene type monomer, the use of a catalyst is not limited.

In the ester compound, all of the structural units represented by the above general formula (B1) in the copolymer may react with the phenolic hydroxyl group of the phenolic resin, and some of them may react with the phenolic hydroxyl group of the phenolic resin. You may. For the ester compound, for example, it is preferable that a part of the structural unit represented by the above general formula (B1) in the copolymer reacts with the phenolic hydroxyl group of the phenolic resin. This makes it possible to form an appropriate connecting structure.

In the present embodiment, the mode of reacting the phenolic resin with the copolymer represented by the above general formula (1) in a solvent has been described. For example, the phenolic resin and the above general formula (1) have been described. ) May be added to the reinforced rubber together with other components described below, and then heat-treated to obtain an ester compound in the rubber.

In the preparation of the ester compound, the lower limit of the addition amount of the phenolic resin is, for example, 5 parts by mass or more with respect to 100 parts by mass in total of the phenolic resin and the copolymer represented by the above general formula (1). It is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 40 parts by mass or more. This makes it possible to sufficiently form a linking structure of the phenol-based resin with respect to the copolymer. Therefore, the hardness and mechanical properties of the rubber composition can be improved.
Further, in the production of the ester compound, the upper limit of the addition amount of the phenolic resin is, for example, 95 parts by mass or less with respect to 100 parts by mass in total of the phenolic resin and the copolymer represented by the above general formula (1). It is more preferably 90 parts by mass or less, further preferably 80 parts by mass or less, and further preferably 70 parts by mass or less. This makes it possible to form a linked structure of the phenol-based resin at an appropriate density with respect to the rigid copolymer. Therefore, the ester compound can be uniformly dispersed in the rubber. Therefore, the hardness and mechanical strength of the rubber composition can be improved.

(Use)
The ester compound according to the present embodiment is added to rubber to form a rubber composition, which is suitably used for reinforcing rubber. That is, the rubber composition according to the present embodiment contains an esterified product and rubber.

The rubber composition according to this embodiment is used, for example, for a tire member. Specific examples of the tire member include an inner liner, a tread, a sidewall, a bead, a carcass, and a belt.
In the conventional rubber composition, the characteristics of hardness and elongation at break have a trade-off relationship. That is, when the hardness was improved, the breaking elongation tended to decrease, and when the breaking elongation was improved, the hardness tended to decrease. On the other hand, the rubber composition according to the present embodiment can improve both hardness and elongation at break due to the above-mentioned linked structure of the ester compound. A rubber composition capable of improving both hardness and elongation at break is convenient in that it can be suitably used for applications of tire members that are required to have the characteristics of being thinner and more resistant to external forces.

The rubber to which the ester compound according to the present embodiment is added is not limited, and specifically, natural rubber, isoprene rubber, butadiene rubber, styrene / butadiene rubber, isoprene / butadiene rubber, butyl rubber, acrylonitrile / butadiene rubber, and chloroprene. Examples include rubber. As the rubber, one or a combination of two or more of the above specific examples can be reinforced.
As the rubber, among the above specific examples, for example, when a diene-based rubber such as butadiene rubber, styrene-butadiene rubber, isoprene rubber, isoprene-butadiene rubber, or butyl rubber is used, the ester compound according to the present embodiment is suitable. It exerts a reinforcing effect and can improve hardness and mechanical properties.

The ester compound according to the present embodiment is not limited to being added to rubber after making a rubber compounding composition mixed with other substances before compounding with rubber.
Specific examples of such other components include hexamethylenetetramine, paraformaldehyde, a polycondensate of melamine and formaldehyde, and a methylene donor such as a methyl etherified product thereof.

（上記一般式（１）において、
ｌおよびｍは共重合体中におけるモル含有率を示し、
ｌ＋ｍ＝１であり、
Ａは、炭素数１以上３０以下のアルキレン基、及び、下記一般式（Ａ１）、下記一般式（Ａ２）、下記一般式（Ａ３）、ならびに、下記一般式（Ａ４）により示される構造単位からなる群より選択される１種以上を含み、
Ｂは、下記一般式（Ｂ１）により示される構造単位を含む。）

（上記一般式（Ａ１）中、Ｒ ^１ からＲ ^４ は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。ａ _１ は０、１または２である。）

（上記一般式（Ａ２）中、Ｒ ^５ からＲ ^９ は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。）

（上記一般式（Ａ３）中、Ｒ ^１０ からＲ ^１６ は、それぞれ独立して、水素または炭素数１以上３０以下の有機基である。）

（上記一般式（Ａ４）中、Ｒ ^１７ は、水素または炭素数１以上３０以下の有機基である。）

（上記一般式（Ｂ１）中、Ｒ ^Ｘ 、Ｒ ^Ｙ は、それぞれ独立して、水素または炭素数１以上３以下の有機基である。）
［２］
［１］に記載のエステル化合物であって、
当該エステル化合物は、ジエン系ゴムに配合するために用いられる、エステル化合物。
［３］
［１］または［２］に記載のエステル化合物であって、
上記エステル化合物は、上記一般式（Ｂ１）により示される構造単位を含む、エステル化合物。
［４］
［１］から［３］のいずれか１つに記載のエステル化合物と、
ゴムと、を含む、ゴム組成物。
［５］
［４］に記載のゴム組成物であって、
上記ゴム組成物は、タイヤ部材として用いられる、ゴム組成物。 The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like to the extent that the object of the present invention can be achieved are included in the present invention.
Hereinafter, an example of the reference form will be added.
[1]
With the above-mentioned phenolic hydroxyl group of the phenolic resin having a phenolic hydroxyl group,
An ester compound obtained by reacting with the structural unit represented by the above general formula (B1) of the copolymer represented by the following general formula (1).

(In the above general formula (1)
l and m indicate the molar content in the copolymer.
l + m = 1,
A is an alkylene group having 1 or more and 30 or less carbon atoms, and a structural unit represented by the following general formula (A1), the following general formula (A2), the following general formula (A3), and the following general formula (A4). Including one or more species selected from the group
B includes a structural unit represented by the following general formula (B1). )

(In the above general formula (A1), R ¹ to R ⁴ are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms . A ₁ is 0, 1 or 2.)

( ^In the above general formula (A2), R5 to R9 are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms. ⁾

(In the above general formula (A3), R ¹⁰ to R ¹⁶ are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

(In the above general formula (A4), R ¹⁷ is hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

(In the above general formula (B1), RX ^{and RY} are ^each independently hydrogen or an organic group having 1 or more and 3 or less carbon atoms.)
[2]
The ester compound according to [1].
The ester compound is an ester compound used for blending with a diene rubber.
[3]
The ester compound according to [1] or [2].
The ester compound is an ester compound containing a structural unit represented by the general formula (B1).
[4]
The ester compound according to any one of [1] to [3] and
A rubber composition comprising, with rubber.
[5]
The rubber composition according to [4].
The rubber composition is a rubber composition used as a tire member.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the description of these examples.
First, each material used in the examples was prepared as shown below.

<Copolymer>
-Copolymer 1: Propylene / maleic anhydride copolymer (manufactured by Mitsubishi Chemical Corporation, Diacarna 30)

<Phenol resin>
As the phenol-based resin, the following phenol-based resins 1 to 3 were used. The details will be described below.

As the phenol-based resin 1, the following novolak-type phenol-based resin was synthesized. The details will be described below.
First, m-cresol and p-cresol were mixed in a 3 L 4-port flask equipped with a stirrer, a thermometer, and a heat exchanger at a ratio of m-cresol: p-cresol in a molar ratio of 5: 5. 1000 parts of phenols, 526 parts of a 37% formalin aqueous solution (formole / phenol molar ratio = 0.70) and 10 parts of oxalic acid were charged, and the reaction was carried out under reflux for 6 hours. Then, the temperature was raised to an internal temperature of 170 ° C., and dehydration was performed under normal pressure. Then, the temperature was raised to 230 ° C. under a reduced pressure of 8.0 kPa, and dehydration was performed under reduced pressure. As a result, 1050 parts of a novolak-type phenolic resin having a weight average molecular weight of Mw = 11000, a dispersity of Mw / Mn = 9.0, and a content of unreacted phenols of 0.5 wt% was obtained.

-Phenol-based resin 2: An unmodified phenol resin obtained by reacting phenol with formaldehyde (manufactured by Sumitomo Bakelite, PR-50731).
-Phenol-based resin 3: Cashew-modified phenol resin obtained by reacting phenol, cashew oil, and formaldehyde (manufactured by Sumitomo Bakelite Co., Ltd., PR-12686E).

(Example 1)
25 parts by mass of copolymer 1 (propylene / maleic anhydride copolymer) and 75 parts by mass of phenolic resin 1 (novolak type phenol resin) are dissolved in 95 parts by weight of methyl ethyl ketone, and then 5 parts by weight of methyl ethyl ketone. The ester compound 1 is obtained by adjusting the content of the resin component to 50% by weight by adding pyridine, heating at 70 ° C. for 2 days, removing the solvent and pyridine, and filtering the ester compound 1. Obtained.
Infrared spectroscopy (IR) measurement was performed on the ester compound 1, and the infrared absorption spectrum was confirmed. As a result, peaks derived from the anhydrous ring of 1850 cm ^-1 and 2000 cm ^-1 were hardly confirmed, and 1780 cm ^-1 . A peak derived from the ester bond was confirmed in the vicinity. As a result, it was confirmed that the ester compound 1 formed by the reaction of the copolymer 1 and the phenolic resin 1 was formed.

(Example 2)
50 parts by mass of copolymer 1 (propylene / maleic anhydride copolymer) and 50 parts by mass of phenolic resin 1 (novolak type phenol resin) are dissolved in 95 parts by weight of methyl ethyl ketone, and then 5 parts by weight of methyl ethyl ketone. The ester compound 2 is obtained by adjusting the content of the resin component to 50% by weight by adding pyridine, heating at 70 ° C. for 2 days, removing the solvent and pyridine, and filtering the ester compound 2. Obtained.
Infrared spectroscopy (IR) measurement was performed on the ester compound 2, and the infrared absorption spectrum was confirmed. As in Example 1, most of the peaks derived from the anhydrous ring of 1850 cm ^-1 and 2000 cm ^-1 were observed. No peak was confirmed near 1780 cm ^-1 due to the ester bond. As a result, it was confirmed that the ester compound 2 formed by the reaction of the copolymer 1 and the phenolic resin 1 was formed. The IR spectrum of the ester compound of Example 2 is shown in FIG. 1 below.

(Comparative Example 1)
In Comparative Example 1, the above-mentioned phenolic resin 2 (unmodified phenolic resin) was used as it was as a substitute for the ester compound of Examples.

(Comparative Example 2)
In Comparative Example 2, the above-mentioned phenolic resin 3 (cashew-modified phenolic resin) was used as it was as a substitute for the ester compound of Examples.

(Preparation of rubber composition)
A rubber composition was prepared using the ester compound of each example and the phenolic resin of each comparative example. Details will be described below.
First, 137 parts by mass of styrene / butadiene rubber (JSR, JSR1723), 5 parts by mass of carbon black (Tokai Carbon, Seast 6), 50 parts by mass of silica (NippilAQ, Toso Silica), and silane. Coupling agent (EVONIK INDUSTRIES AG, Si75) 5 parts by mass, stearic acid (Tokyo Kasei Kogyo) 1 part by mass, zinc oxide (Tokyo Kasei Kogyo) 2 parts by mass, vulcanization accelerator (manufactured by Tokyo Kasei Kogyo) Wako Pure Chemical Industries, Ltd., N- (tert-butyl) -2-benzothiazolesulfenamide) 1 part by mass, sulfur (Tokyo Kasei Kogyo Co., Ltd.) 1.5 parts by mass, hexamethylenetetramine (Wako Pure Chemical Industries, Ltd.) 1 part by mass (manufactured by Kogyo Co., Ltd.) was prepared as a raw material component of the rubber composition. Next, 250 cc of the ester compound of each example, 10 parts by mass of the phenolic resin of each comparative example, styrene-butadiene rubber, carbon black, silica, a silane coupling agent, stearic acid, and zinc oxide. The mixture was kneaded for 5 minutes using a closed Banbury mixer. After kneading, the mixture was discharged to the outside of the mixer and cooled to room temperature. Subsequently, the kneaded product was put into the same Banbury mixer again, a vulcanization accelerator, sulfur, and hexamethylenetetramine were further added and kneaded for 5 minutes to obtain a rubber composition.

(Preparation of rubber composition of reference example)
As the rubber composition of the reference example, a rubber composition containing no ester compound or phenolic resin was prepared. Specifically, the rubber composition of Reference Example 1 was produced by the same formulation and method as the method for producing the rubber compositions of the above-mentioned Examples and Comparative Examples without blending the ester compound and the phenolic resin. Got

<Evaluation>
The rubber compositions of each example, each comparative example, and each reference example were press-vulcanized to a thickness of 2 mm by heating at a temperature of 160 ° C. for 30 minutes. The growth was evaluated.

(hardness)
Shore A hardness was evaluated using a durometer (manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS K 6253. The evaluation results are shown in Table 1 below. The unit is dimensionless.

(Tensile strength, elongation at break)
The test piece was punched into the shape of a JIS No. 3 dumbbell according to JIS K 6251, and a tensile test was performed to evaluate the tensile strength and the elongation at break. The evaluation results are shown in Table 1 below.
The unit of tensile strength is MPa. The unit of elongation at break is%.

As shown in Table 1 above, it was confirmed that the rubber composition containing the ester compound of each example can improve mechanical properties such as hardness, tensile strength, and elongation at break as compared with the rubber composition of each comparative example. Was done.

Claims (4)

With the phenolic hydroxyl group of the phenolic resin having a phenolic hydroxyl group,
An ester compound formed by reacting with a structural unit represented by the following general formula (B1) of a copolymer represented by the following general formula (1) .
With rubber
A rubber composition comprising.

(In the above general formula (1)
l and m indicate the molar content in the copolymer.
l + m = 1,
A is an alkylene group having 1 or more and 30 or less carbon atoms, and a structural unit represented by the following general formula (A1), the following general formula (A2), the following general formula (A3), and the following general formula (A4). Including one or more species selected from the group
B includes a structural unit represented by the following general formula (B1). )

(In the above general formula (A1), R ¹ to R ⁴ are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms. A ₁ is 0, 1 or 2.)

( ^In the above general formula ⁽ A2), R5 to R9 are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

(In the above general formula (A3), R ¹⁰ to R ¹⁶ are independently hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

(In the above general formula (A4), R ¹⁷ is hydrogen or an organic group having 1 or more and 30 or less carbon atoms.)

(In the above general formula (B1), ^{RX and RY are} each independently hydrogen or an organic group having 1 or more and 3 or less carbon atoms.) The rubber composition according to claim 1.
The ester compound is a rubber composition used for blending with a diene-based rubber. The rubber composition according to claim 1 or 2.
The ester compound is a rubber composition containing a structural unit represented by the general formula (B1). The rubber composition according to any one of claims 1 to 3 .
The rubber composition is a rubber composition used as a tire member.

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