JP2021195494A - Rubber composition, rubber composition for tire, cross-linked rubber for tire, tire and additive for rubber - Google Patents

Abstract

To provide a rubber composition and an additive for a rubber, capable of producing a cross-linked rubber having a high dynamic storage modulus, to provide a cross-linked rubber for a tire, and a tire having a high dynamic storage modulus, and to provide a rubber composition for a tire capable of producing them.SOLUTION: A rubber composition contains diene rubber-containing rubber components, a cross-linking agent, and a compound represented by formula (1). In the formula (1), Z represents a single bond or divalent 1-5C hydrocarbon group, A represents independently a 1-6C alkoxy group or hydroxy group, and n represents an integral number of 2-5, provided that when Z is a single bond and n is 2, adjacent As do not simultaneously become a methoxy group.SELECTED DRAWING: None

Description

The present invention relates to rubber compositions, tire rubber compositions, tire crosslinked rubbers, tires and rubber additives.

In recent years, under the social demand for energy saving, tires with low rolling resistance have been required in order to promote fuel efficiency for automobiles, and a rubber composition having lower heat generation (lower loss) than before has been desired. There is.
On the other hand, it is desired to improve the wear resistance of automobile tires, and a rubber composition having a large storage elastic modulus, particularly a dynamic storage elastic modulus (G'), is desired.

In Patent Document 1, a specific resin composition and a thermoplastic resin are specified with respect to natural rubber and synthetic isoprene rubber for the purpose of providing a rubber composition having low heat generation and high elasticity. The rubber compositions blended in proportion are described.

Japanese Unexamined Patent Publication No. 2012-92179

In Patent Document 1, a rubber composition having low heat generation and high elasticity with respect to a specific rubber component was obtained, but the rubber component used was limited. In addition, the amount of the resin composition and the thermoplastic resin to be added was large, and the selectivity of the formulation of the rubber composition was limited.

An object of the present invention is a rubber composition and an additive for rubber capable of producing a crosslinked rubber having a high dynamic storage elastic modulus; and a crosslinked rubber and a tire for a tire having a high dynamic storage elastic modulus, and these can be produced. It is an object of the present invention to provide a rubber composition for a tire, and to solve the problem.

As a result of diligent studies, the present inventor has found that the above-mentioned problems can be solved by blending a compound having a specific structure.
That is, the present invention relates to the following <1> to <10>.
<1> A rubber composition containing a rubber component containing a diene-based rubber, a cross-linking agent, and a compound represented by the formula (1).

In the formula (1), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms, and A independently represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms, and n Represents an integer of 2-5. However, when Z is a single bond and n is 2, the adjacent A does not become a methoxy group at the same time.

<2> The rubber composition according to <1>, wherein the compound represented by the formula (1) is represented by the formula (2).

In the formula (2), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms. A ² represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms, and A ¹ and A ³ independently represent an alkoxy group, a hydroxy group or a hydrogen atom having 1 to 6 carbon atoms. However, A ¹ and A ³ do not become hydrogen atoms at the same time, ^{and when Z is a single bond, A 2} and A ³ and A ¹ and A ² do not become methoxy groups at the same time.

<3> The rubber composition according to <2>, wherein Z is a single bond in the above formula (2).

<4> Described in any one of <1> to <3>, wherein the content of the compound represented by the formula (1) is 0.05 to 10 parts by mass with respect to 100 parts by mass of the rubber component. Rubber composition.
<5> The rubber composition according to any one of <1> to <4>, further containing 20 to 120 parts by mass of a filler with respect to 100 parts by mass of the rubber component.
<6> The cross-linking agent contains a vulcanizing agent, further contains a vulcanization accelerator, and the content of the vulcanization accelerator with respect to the content (b) of the compound represented by the formula (1) (a). The rubber composition for a tire according to any one of <1> to <5>, wherein the mass ratio (a / b) of) is 0.2 to 5.0.

<7> A rubber composition for a tire comprising the rubber composition according to any one of <1> to <6>.
<8> A cross-linked rubber for a tire obtained by cross-linking the rubber composition for a tire according to <7>.
<9> A tire containing the crosslinked rubber for the tire according to <8>.

<10> An additive for rubber containing a compound represented by the formula (1).

In the formula (1), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms, and A independently represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms, and n Represents an integer of 2-5. However, when Z is a single bond and n is 2, the adjacent A does not become a methoxy group at the same time.

According to the present invention, a rubber composition and an additive for rubber capable of producing a crosslinked rubber having a high dynamic storage elastic modulus; and a crosslinked rubber and a tire for a tire having a high dynamic storage elastic modulus, and these can be produced. A rubber composition for a tire can be provided.

Hereinafter, the present invention will be illustrated in detail based on the embodiments thereof. In the following description, the description of "A to B" indicating the numerical range represents the numerical range including the end points A and B, and is "A or more and B or less" (in the case of A <B) or ". It represents "A or less and B or more" (when A> B).

<Rubber composition>
The rubber composition of the present invention contains a rubber component containing a diene-based rubber, a cross-linking agent, and a compound represented by the formula (1).
As a result of diligent studies, the present inventors have found that the crosslinked rubber obtained by crosslinking the rubber composition containing the compound represented by the formula (1) has a high dynamic storage elastic modulus (G'). .. The detailed mechanism by which such an effect is obtained is unknown, but some are presumed as follows.
In the process of crosslinking, it is considered that the compound represented by the formula (1) and the rubber component form a pseudo-crosslink, and it is presumed that a high dynamic storage elastic modulus (G') was achieved.
Hereinafter, the present invention will be described in detail.

[Rubber component]
The rubber composition of the present invention contains a rubber component containing a diene-based rubber.
The rubber component can be appropriately selected from rubber components including diene-based rubber used in the rubber industry. The diene-based rubber may be a natural rubber or a synthetic rubber, and these may be used alone or in combination.
Examples of the diene synthetic rubber include styrene-butadiene copolymer (SBR), polybutadiene (BR), polyisoprene (IR), styrene-isoprene copolymer (SIR), butadiene-isoprene copolymer, and butadiene-styrene-. Examples thereof include isoprene copolymer, acrylonitrile-butadiene copolymer, chloroprene rubber, butyl rubber (IIR), halogenated butyl rubber and the like. Further, a part thereof may have a branched structure by using a polyfunctional modifier, for example, a modifier such as tin tetrachloride.
The rubber component preferably contains a styrene-butadiene copolymer or natural rubber. The rubber component may be used alone or in combination of two or more.

[Compound represented by the formula (1)]
The rubber composition of the present invention contains a compound represented by the formula (1).
In the formula (1), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms, A independently represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms, and n represents an alkoxy group or a hydroxy group. , Represents an integer of 2-5. However, when Z is a single bond and n is 2, the adjacent A does not become a methoxy group at the same time. That is, 2,3-dimethoxybenzoic acid and 3,4-dimethoxybenzoic acid are not included in the compound represented by the formula (1).

When the rubber composition of the present invention contains the compound represented by the formula (1), the compounds represented by the formula (1) bonded to the rubber molecule interact with each other by a hydrogen bond, thereby pseudo. It is possible to improve the storage elasticity G'of the crosslinked rubber by performing cross-linking. Further, when the rubber composition contains a filler, the compound represented by the formula (1) can be bonded to the filler to aggregate the filler and suppress heat generation.

Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms.
When Z is a single bond, the carboxy group is directly bonded to the benzene ring, and the compound represented by the formula (1) is a benzoic acid derivative.
Examples of the divalent hydrocarbon group include alkylene and alkenylene, which may be linear, branched or cyclic. Specific low examples include a methylene group, an ethylene group, a butylene group, a vinylene group, a propenylene group and the like. The divalent hydrocarbon group may further have a substituent such as a halogen atom and a monovalent hydrocarbon group. The carbon number of Z is preferably 1 to 5 including the carbon number of the substituent.
Among the above, Z is preferably a single bond or an alkenylene having 2 to 4 carbon atoms, more preferably a single bond or an alkenylene having 2 to 3 carbon atoms, and further preferably a single bond.

A is 2 to 5 groups, each independently representing an alkoxy group or a hydroxy group having 1 to 6 carbon atoms.
The alkyl moiety of the alkoxy group may be linear, branched or cyclic. For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n-hexyl group, a cyclohexyl group and the like can be mentioned. The alkyl moiety of the alkoxy group preferably has 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 to 2 carbon atoms.
The plurality of A's may be the same or different.
n represents the number of A and is an integer of 2 to 5. n is preferably 2 to 4, more preferably 2 to 3.

The compound represented by the formula (1) is preferably represented by the formula (2).

In formula (2), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms. A ² represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms, and A ¹ and A ³ independently represent an alkoxy group, a hydroxy group or a hydrogen atom having 1 to 6 carbon atoms. However, A ¹ and A ³ do not become hydrogen atoms at the same time, ^{and when Z is a single bond, A 2} and A ³ and A ¹ and A ² do not become methoxy groups at the same time.
That is, the compound represented by the formula (1) has two alkoxy groups or hydroxy groups having 1 to 6 carbon atoms at the para position with respect to the group having a carboxy group (-Z-COOH). It is preferable that the compound has an alkoxy group or a hydroxy group having 1 to 6 carbon atoms in one or both of the meta positions.

In the formula (2), Z is synonymous with Z in the formula (1), and the preferred embodiment is also the same.
In the formula (2), ^{the embodiment of the alkoxy group having 1 to 6 carbon atoms represented by A 1 to} A ³ is the same as that of A in the formula (1), and the preferred embodiment is also the same.
Examples of the compound represented by the formula (2) include 3,4,5-trimethoxybenzoic acid (TMGA), 3,4,5-trimethoxybenzoic acid (TMCA), and 3-hydroxy-4-methoxybenzoic acid ( (Also also referred to as isovaniphosphate) (VA) and the like, and have the following structure.

The rubber composition of the present invention may contain only one kind of the compound represented by the formula (1), or may contain two or more kinds.
Among the above, the compound represented by the formula (1) is preferably represented by the formula (2), preferably a compound in which Z is a single bond or an alkenylene having 2 to 4 carbon atoms, and is represented by the formula (2). A compound in which Z is a single bond is more preferable.
The compound represented by the formula (1) may be obtained as a commercially available product or may be synthesized.

The content of the compound represented by the formula (1) in the rubber composition is preferably 0.05 to 10 parts by mass with respect to 100 parts by mass of the rubber component. Within such a range, the storage elastic modulus (G') of the crosslinked rubber can be further improved, and the tan δ at 50 ° C. can be lowered. From the same viewpoint, the content of the compound represented by the formula (1) in the rubber composition is more preferably 0.1 part by mass or more, further preferably 0.3 part by mass or more. It is more preferably 0.5 parts by mass or more, further preferably 5 parts by mass or less, further preferably 3 parts by mass or less, and more preferably 2.5 parts by mass or less. Even more preferable.

[Crosslinking agent]
The rubber composition of the present invention contains a cross-linking agent.
The cross-linking agent is not particularly limited as long as it is a component capable of cross-linking rubber molecules. Examples thereof include vulcanizing agents that crosslink sulfur, organic peroxides that crosslink peroxides, oxymu compounds that crosslink quinoids, and diamine compounds that crosslink amines. Usually, a vulcanizing agent is used.
Sulfur is usually used as the vulcanizing agent, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

In the rubber composition, the content of the cross-linking agent is preferably 0.1 part by mass or more, more preferably 0.3 part by mass with respect to 100 parts by mass of the rubber component from the viewpoint of sufficiently advancing the cross-linking between the rubber molecules. More than parts, more preferably 0.5 parts by mass or more, still more preferably 1 part by mass or more, and from the viewpoint of improving anti-aging resistance, preferably 10 parts by mass or less, more preferably 5 parts by mass or less. It is more preferably 3 parts by mass or less.

[Vulcanization accelerator]
When the cross-linking agent contains a vulcanizing agent, the rubber composition of the present invention preferably further contains a vulcanization accelerator.
The vulcanization accelerator is not particularly limited and may be appropriately selected depending on the intended purpose. Specifically, CBS (N-cyclohexyl-2-benzothiazolesulfenamide), TBBS (N-t-butyl-2-benzothiazolesulfenamide), TBSI (N-t-butyl-2-benzothiazolesulfenamide) Sulfenamide-based vulcanization accelerator such as fenimide); guanidine-based vulcanization accelerator such as DPG (diphenylguanidine); thiuram-based vulcanization accelerator such as tetraoctylthiuram disulfide and tetrabenzylthiuram disulfide; MBT ( 2-mercaptobenzothiazole), a thiazole-based vulcanization accelerator such as MBTS (di-2-benzothiazolyl disulfide); a vulcanization accelerator such as zinc dialkyldithiophosphate; and the like. These may be used alone or in combination of two or more.
Among these, from the viewpoint of advancing appropriate vulcanization in the presence of the compound represented by the formula (1), it is preferable to contain at least a sulfenamide-based vulcanization accelerator as the vulcanization accelerator. , At least one or both of CBS and TBBS are more preferable.

The content of the vulcanization accelerator in the rubber composition is preferably 0.1 part by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of advancing appropriate vulcanization at an appropriate vulcanization rate. It is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, still more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 7.5 parts by mass or less, further. It is preferably 5 parts by mass or less.

Further, the mass ratio (a / b) of the content (a) of the vulcanization accelerator to the content (b) of the compound represented by the formula (1) in the rubber composition is represented by the formula (1). From the viewpoint of suppressing the vulcanization inhibitory action of the compound, advancing appropriate vulcanization, and obtaining a crosslinked rubber composition having low heat buildup, it is preferably 0.2 or more, more preferably 0.3 or more, still more preferable. Is 1.0 or more, and is preferably 5.0 or less, more preferably 3.0 or less, still more preferably 2.5 or less.

[Filler]
The rubber composition of the present invention preferably contains a filler, if necessary.
As the filler, an organic filler such as carbon black, an inorganic filler such as silica, or a blend of these two types of filler may be used. Among these, one or more fillers selected from carbon black and silica are preferably used.
The carbon black is not particularly limited, and any carbon black that has been conventionally used as a filler for rubber can be appropriately selected and used. For example, SRF, GPF, FEF, HAF, ISAF, SAF and the like are used, and FEF, HAF, ISAF, SAF and the like, which are particularly excellent in bending resistance and fracture resistance, are preferably mentioned.
From the viewpoint of reinforcing property, carbon black has a nitrogen adsorption specific surface area N ₂ SA (based on JIS K 6217-2: 2001), preferably 30 m ² / g or more, and more preferably 35 m ² / g or more. , And ^{more preferably 150 m 2} / g or less, more preferably 130 m ² / g or less.
One type of carbon black may be used alone, or two or more types may be used in combination.

On the other hand, examples of silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like, with wet silica being preferred.
The BET specific surface area (measured based on ISO 5794/1) of this wet silica is preferably 40 m ² / g or more, more preferably 80 m ² / g or more, and preferably 350 m from the viewpoint of reinforcing property. ^{It is 2} / g or less, more preferably 300 m ² / g or less. As such silica, commercially available products such as "Nipsil AQ" and "Nipsil KQ" manufactured by Tosoh Silica Co., Ltd. and "Ultrazil VN3" manufactured by Degussa Co., Ltd. can be used.
One type of silica may be used alone, or two or more types may be used in combination.
Examples of the inorganic filler other than silica include aluminum hydroxide, clay, talc, calcium carbonate, zeolite and the like.

The rubber composition of the present invention preferably contains 20 to 120 parts by mass of a filler with respect to 100 parts by mass of the rubber component as a total content.
When the rubber composition contains the filler in the above range, the reinforcing property of the crosslinked rubber can be improved and the tan δ at 50 ° C. can be further lowered.
Generally, when the rubber composition contains a large amount of filler, the crosslinked rubber tends to generate heat due to rubbing between the fillers. However, when the rubber composition contains the compound represented by the formula (1), the filler is aggregated. Can be increased and heat generation can be suppressed. That is, it is easy to lower the tan δ at 50 ° C.
From the viewpoint of further improving the reinforcing property of the crosslinked rubber and further lowering the tan δ at 50 ° C., the total content of the filler in the rubber composition is more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. It is more preferably 40 parts by mass or more, more preferably 90 parts by mass or less, still more preferably 80 parts by mass or less.

In the present invention, it is preferable to use carbon black and silica together as a filler. In this case, the content of carbon black in the rubber composition of the present invention is a rubber component from the viewpoint of reinforcing property and low heat generation. With respect to 100 parts by mass, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, and preferably 60 parts by mass or less, more preferably 55 parts by mass or less, further. It is preferably 50 parts by mass or less.
When carbon black and silica are used in combination, the content of silica in the rubber composition of the present invention is preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of reinforcing property and low heat generation. , More preferably 3 parts by mass or more, further preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 35 parts by mass. It is less than a part.

(Silane coupling agent)
When silica is used as a filler in the rubber composition of the present invention, it is preferable to add a silane coupling agent for the purpose of further improving the reinforcing property thereof.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxysilyl). Ethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltri Methoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilyl Ethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzolyltetrasulfide, 3-triethoxysilylpropylmethacrylate monosulfide, 3-trimethoxy Cyrilpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyl dimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazolyl Examples thereof include tetrasulfide, and among these, bis (3-triethoxysilylpropyl) polysulfide and 3-trimethoxysilylpropylbenzothiaziltetrasulfide are preferable from the viewpoint of improving the reinforcing property.
These silane coupling agents may be used alone or in combination of two or more.

In the rubber composition of the present invention, the preferable blending amount of the silane coupling agent varies depending on the type of the silane coupling agent and the like, but from the viewpoint of improving the dispersibility of silica and suppressing the gelation of the rubber component, from the viewpoint of improving the dispersibility of silica. It is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 2 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass with respect to 100 parts by mass of silica. Hereinafter, it is more preferably 10 parts by mass or less.

[Other ingredients]
The rubber composition of the present invention may contain other additives in addition to the above-mentioned components as long as the object of the present invention is not impaired. Other additives may be appropriately selected from various additives usually used in the rubber industry, and specifically, vulcanization accelerators, antistatic agents, softeners, colorants, flame retardants, lubricants, etc. Examples thereof include foaming agents, plasticizers, processing aids, antioxidants, ultraviolet inhibitors, antistatic agents, anticoloring agents, and other compounding agents.

(Vulcanization acceleration aid)
From the viewpoint of promoting vulcanization, the rubber composition of the present invention may contain a vulcanization promoting aid such as zinc oxide and fatty acid. The fatty acid may be saturated or unsaturated, and may be linear or branched. Further, the number of carbon atoms is not particularly limited, and for example, one having 1 to 30 carbon atoms, preferably 15 to 30 carbon atoms can be used.
Specific examples of the fatty acid include cyclohexaneic acid (cyclohexanecarboxylic acid), naphthenic acid such as alkylcyclopentane having a side chain, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acids such as neodecanoic acid), and dodecanoic acid. , Saturated fatty acids such as tetradecanoic acid, hexadecanoic acid and octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid and linolenic acid, resin acids such as rosin, tall oil acid and avietic acid. And stearic acid is preferred. These may be used alone or in combination of two or more. In the present invention, stearic acid and zinc oxide can be preferably used, and it is particularly preferable to use zinc oxide and stearic acid in combination.
The total content of these vulcanization accelerating aids in the rubber composition is not particularly limited, but from the viewpoint of kneading workability and vulcanization promotion, it is preferably 0. It is 5 parts by mass or more, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, and preferably 15 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 7 parts by mass or less.

(Anti-aging agent)
Examples of the antioxidant that can be used in the rubber composition of the present invention include 3C (N-isopropyl-N'-phenyl-p-phenylenediamine) and 6C [N- (1,3-dimethylbutyl) -N'-phenyl. -P-Phenylenediamine], TMDQ (2,2,4-trimethyl-1,2-dihydroquinoline polymer), AW (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), diphenylamine And high temperature condensates of acetone and the like.
The anti-aging agent may be used alone or in combination of two or more.
The blending amount of the antiaging agent in the rubber composition is preferably with respect to 100 parts by mass of the rubber component from the viewpoint of imparting sufficient weather resistance and ozone resistance and suppressing discoloration and deterioration of crack resistance. 0.1 part by mass or more, more preferably 0.3 part by mass or more, further preferably 1 part by mass or more, and preferably 6 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3 parts by mass. It is as follows.

<Preparation of rubber composition>
The method for producing the rubber composition of the present invention is not particularly limited.
The rubber composition contains a rubber component, a cross-linking agent, a compound represented by the formula (1), and various compounding agents, and is kneaded by a Banbury mixer, a roll, an intensive mixer, a twin-screw extruder, or the like, and heat. It can be manufactured by putting it in, extruding it, or the like.
From the viewpoint of suppressing the occurrence of vulcanization during the production of the rubber composition and improving the handleability during the production, the components contained in the rubber composition, excluding the cross-linking agent and the vulcanization accelerator, are pre-blended. It is preferable to prepare a rubber composition by mixing and mixing (first kneading step), and then blending and mixing a cross-linking agent and a vulcanization accelerator (second kneading step).

By preparing the rubber composition by the above method, vulcanization is unlikely to occur even if the first kneading step is performed under high temperature conditions, so that the rubber composition can be produced with high productivity.
The maximum temperature of the kneading temperature in the first kneading step is preferably 250 ° C. or lower, more preferably 200 ° C. or lower, still more preferably 180 ° C. or lower, from the viewpoint of suppressing thermal decomposition of each component. From the viewpoint of productivity, the kneading temperature in the first kneading step is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 140 ° C. or higher.
The maximum temperature of the kneading temperature in the second kneading step is preferably 150 ° C. or lower, more preferably 130 ° C. or lower, from the viewpoint of suppressing the occurrence of vulcanization during kneading. Further, from the viewpoint of productivity, the kneading temperature in the second kneading step is preferably 80 ° C. or higher, more preferably 100 ° C. or higher.

<Rubber composition for tires>
The rubber composition for a tire of the present invention comprises the rubber composition of the present invention.
Since the rubber composition of the present invention can produce a crosslinked rubber having a high elastic modulus, it is suitable for producing a tire, and the rubber composition is particularly preferable to be used as a rubber composition for a tire.
Further, when the rubber composition for a tire contains a filler, a tire having an excellent balance between a high elastic modulus and a low tan δ can be manufactured.

<Cross-linked rubber for tires>
The cross-linked rubber for a tire of the present invention is obtained by cross-linking the rubber composition for a tire of the present invention.
In the cross-linked rubber for tires, cross-linking is formed between the rubber molecules by a cross-linking agent, and in addition, pseudo-cross-linking by a compound represented by the formula (1) may be formed.
The conditions for the cross-linking are not particularly limited and may be appropriately selected depending on the intended purpose, but the cross-linking temperature is preferably 120 to 200 ° C. and the cross-linking time is preferably 1 minute to 900 minutes.

<Tire>
The crosslinked rubber for a tire of the present invention is suitably used for manufacturing a tire. The tire of the present invention includes a crosslinked rubber for a tire.
The application site of the crosslinked rubber for a tire of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. For example, it can be suitably used for at least one member of a tread portion, a sidewall portion, a bead portion, an inner liner, and other reinforcing rubber portions.

Further, the tire of the present invention is not particularly limited except that the rubber composition for a tire of the present invention is used, and can be produced according to a conventional method. For example, the rubber composition for a tire of the present invention is extruded into a tread member at an unvulcanized stage, and is affixed and molded on a tire molding machine by a usual method to form a raw tire. The raw tire is manufactured by heating and pressurizing the raw tire in a vulcanizer. Further, as the gas to be filled in the tire, an inert gas such as nitrogen, argon or helium can be used in addition to normal air or air having an adjusted oxygen partial pressure.

<Additives for rubber>
The rubber additive of the present invention contains a compound represented by the formula (1).

In the formula (1), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms, A independently represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms, and n represents an alkoxy group or a hydroxy group. , Represents an integer of 2-5. However, when Z is a single bond and n is 2, the adjacent A does not become a methoxy group at the same time.
The compound represented by the formula (1) contained in the rubber additive is the same as the compound represented by the formula (1) contained in the rubber composition of the present invention, and the preferred embodiment is also the same. That is, the compound represented by the formula (1) is represented by the formula (2), preferably a compound in which Z is a single bond or an alkenylene having 2 to 4 carbon atoms, and is represented by the formula (2). It is more preferable that Z is a single bond compound.
The additive for rubber of the present invention may contain only one kind of the compound represented by the formula (1), or may contain two or more kinds.

The rubber additive of the present invention may be mixed with other components and used as a rubber additive composition.
The rubber additive composition contains at least the rubber additive of the present invention, and further comprises additives commonly used in the rubber industry, such as antiaging agents, softeners, silane coupling agents, stearic acid and the like. It may contain fatty acid, zinc oxide (zinc white), vulcanizing agent, vulcanization accelerator and the like.

The rubber additive and rubber additive composition of the present invention are not limited to the rubber composition for tires, and may be widely added to other rubber compositions, and the rubber additive or rubber additive of the present invention may be added. The rubber composition to which the agent composition is added or the crosslinked rubber composition obtained by cross-linking the rubber composition can be used for various rubber products.
Examples of rubber products include vibration-proof rubber, seismic isolation rubber, belts such as conveyor belts, rubber crawlers, and various hoses, in addition to the above-mentioned tires.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

<Examples 1 to 3 and Comparative Examples 1 to 3>
[Adjustment and cross-linking of rubber composition]
The components of the blending ratio shown in Table 1 are kneaded using a Banbury mixer to prepare a rubber composition, and further heated at 145 ° C. for 33 minutes at 145 ° C. for cross-linking (vulcanization) using a pressure-type vulcanizer to cross-link (vulcanize) the cross-linked rubber. (Vulcanized rubber) was obtained. The components shown in Table 1 are as follows.
・ NR: Natural rubber, RSS # 1
-Carbon black: Made by Tokai Carbon Co., Ltd., trade name "Seast 3", HAF, N ₂ SA = 79m ² / g
-Silica: Made by Tosoh Silica, trade name "Nipsil AQ", BET specific surface area = 205 m ² / g
・ Sulfen coupling agent: Ebonic, trade name “Si69”, bis [(3-triethoxysilyl) propyl] tetrasulfide ・ Anti-aging agent: Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name “Nocrack 6C”, N-phenyl-N'-(1,3-dimethylbutyl) -p-phenylenediamine / vulcanization accelerator: manufactured by Sanshin Chemical Industry Co., Ltd., trade name "Sunceller NS-G", N- (t-butyl)- 2-Benzothiazole sulfenamide stearic acid: manufactured by Kao, trade name "Lunac S-70V",
・ Zinc oxide: manufactured by Wako Pure Chemical Industries, Ltd. ・ Sulfur: manufactured by Wako Pure Chemical Industries, Ltd.

Compound · TMGA: 3,4,5-trimethoxy benzoic acid (Tokyo Kasei Kogyo Co., Ltd., in the formula (2), Z is a single ^bond, any compound is A 1 to A ³ is methoxy group)
· TMCA: 3,4,5-trimethoxy cinnamic acid (Tokyo Kasei Kogyo Co., Ltd., in the formula (2), Z is a compound of ^alkenylene, both the A 1 to A ³ is a methoxy group having 2 carbon atoms)
VA: 3-Hydroxy-4-methoxybenzoic acid (manufactured by Tokyo Kasei Kogyo Co., Ltd., in formula (2), Z is a single bond, A ¹ is a hydroxy group, A ² is a methoxy group, and A ³ is a hydrogen atom compound).
・ BA: Benzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., structure below)
-PCBA: p-carboxybenzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., structure below)

〔evaluation〕
The storage elastic modulus (G'(50 ° C., 5%)) and loss tangent (tan δ (50 ° C., 5%)) were measured for the obtained crosslinked rubber.
Specifically, the obtained crosslinked rubber was subjected to a viscoelasticity measuring device "ARES-G2" (manufactured by TA Instruments) under the condition of a frequency of 10 Hz and a strain of 5% at 50 ° C. Dynamic storage elastic modulus (tensile dynamic storage elastic modulus, G'(50 ° C., 5%)) and loss tangent (tan δ (50 ° C., 5%)) were measured.
The dynamic storage elastic modulus (G') was expressed exponentially with the dynamic storage elastic modulus (G') of Comparative Example 1 as 100. The larger the value of G', the better the steering stability and wear resistance of the vehicle.
Further, regarding the loss tangent (tan δ), the loss tangent (tan δ) of Comparative Example 1 was set as 100 and displayed as an exponential notation. The smaller the value of tan δ, the lower the heat generation and the lower the rolling resistance when used in a tire.

From the results in Table 1, it was shown that a crosslinked rubber having a high dynamic storage elastic modulus (G') can be obtained by adding a compound having a specific structure.

INDUSTRIAL APPLICABILITY According to the present invention, a tire rubber composition for obtaining a crosslinked rubber for a tire having a high dynamic storage elastic modulus is provided, and a rubber additive to be added to the tire rubber composition is provided. The rubber composition and crosslinked rubber are applicable to rubber products and are particularly useful for tire applications. Tires using the rubber composition or the crosslinked rubber composition are expected to be excellent in wear resistance, low heat generation, and excellent energy saving.

Claims (10)

Rubber components including diene rubber and
With a cross-linking agent,
A rubber composition containing the compound represented by the formula (1).

[In the above formula (1), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms, and A independently represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms. n represents an integer of 2 to 5. However, when Z is a single bond and n is 2, the adjacent A does not become a methoxy group at the same time. ] The rubber composition according to claim 1, wherein the compound represented by the formula (1) is represented by the formula (2).

[In the above formula (2), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms. A ² represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms, and A ¹ and A ³ independently represent an alkoxy group, a hydroxy group or a hydrogen atom having 1 to 6 carbon atoms. However, A ¹ and A ³ do not become hydrogen atoms at the same time, ^{and when Z is a single bond, A 2} and A ³ and A ¹ and A ² do not become methoxy groups at the same time. ] The rubber composition according to claim 2, wherein Z is a single bond in the formula (2). The rubber composition according to any one of claims 1 to 3, wherein the content of the compound represented by the formula (1) is 0.05 to 10 parts by mass with respect to 100 parts by mass of the rubber component. The rubber composition according to any one of claims 1 to 4, further comprising a filler of 20 to 120 parts by mass with respect to 100 parts by mass of the rubber component. The cross-linking agent contains a vulcanizing agent, further contains a vulcanization accelerator, and the mass of the vulcanization accelerator content (a) with respect to the content (b) of the compound represented by the formula (1). The rubber composition according to any one of claims 1 to 5, wherein the ratio (a / b) is 0.2 to 5.0. A rubber composition for a tire comprising the rubber composition according to any one of claims 1 to 6. A cross-linked rubber for a tire obtained by cross-linking the rubber composition for a tire according to claim 7. A tire containing the crosslinked rubber for the tire according to claim 8. An additive for rubber containing a compound represented by the formula (1).

[In the above formula (1), Z represents a single bond or a divalent hydrocarbon group having 1 to 5 carbon atoms, and A independently represents an alkoxy group or a hydroxy group having 1 to 6 carbon atoms. n represents an integer of 2 to 5. However, when Z is a single bond and n is 2, the adjacent A does not become a methoxy group at the same time. ]