阅读说明：本技术 橡胶组合物和制造橡胶组合物的方法 (Rubber composition and method for producing rubber composition ) 是由 杉野由隆 滨久胜 金坂将 于 2020-03-27 设计创作，主要内容包括：本发明提供了一种橡胶组合物,其包含橡胶成分、添加剂及填充剂,添加剂含有如下化合物,该化合物包含选自硅原子、氮原子及氧原子中的至少一种原子以及碳原子,构成化合物的硅原子、氮原子及氧原子的总数相对于碳原子数为0.27以上且0.80以下,化合物的汉森溶解度参数满足下式(2)所表示的关系,化合物的分子量为200以上且15000以下。6≤{4(δD-(1)-δD-(2))～(2)+(δP-(1)-δP-(2))～(2)+(δH-(1)-δH-(2))～(2)}～(0.5) (2)。(The present invention provides a rubber composition comprising a rubber component, an additive and a filler, wherein the additive comprises a compound containing at least one atom selected from the group consisting of a silicon atom, a nitrogen atom and an oxygen atom, and a carbon atom, and the total number of the silicon atom, the nitrogen atom and the oxygen atom constituting the compound is 0.27 or more and 0 or more relative to the number of carbon atoms80 or less, the compound has a hansen solubility parameter satisfying the relationship represented by the following formula (2), and a molecular weight of 200 or more and 15000 or less. 6 is less than or equal to {4 (delta D) 1 ‑δD 2 ) 2 +(δP 1 ‑δP 2 ) 2 +(δH 1 ‑δH 2 ) 2 } 0.5 (2)。)

1. A rubber composition comprising a rubber component, an additive and a filler,

the additive contains a compound containing at least one atom selected from a silicon atom, a nitrogen atom and an oxygen atom, and a carbon atom,

the total number of silicon atoms, nitrogen atoms and oxygen atoms constituting the compound is 0.27 or more and 0.80 or less relative to the number of carbon atoms, the Hansen solubility parameter of the compound satisfies the relationship represented by the following formula (2), the molecular weight of the compound is 200 or more and 15000 or less,

6≤{4(δD₁-δD₂)²+(δP₁-δP₂)²+(δH₁-δH₂)²}^0.5 (2)，

(in the formula, δ D represents a dispersion term, δ P represents a polarity term, and δ H represents a hydrogen bond term).

2. The rubber composition according to claim 1, wherein the compound has a structure based on at least one selected from the group consisting of an amino group, a siloxy group, an imino group, an ether bond, an ester bond, and an amide bond.

3. The rubber composition according to claim 1 or 2, wherein the compound has a tertiary amino group.

4. The rubber composition according to any one of claims 1 to 3, wherein the rubber component contains a diene rubber.

5. The rubber composition according to claim 4, wherein the diene rubber is a modified diene rubber.

6. A rubber composition comprising a rubber component, an additive and a filler,

the additive contains a polymer of a monomer represented by the following formula (I),

(in the formula, R¹Represents a hydrogen atom or a methyl group, R²And R³Each independently represents an alkyl group, L¹Represents an amide bond or an ester bond, L²Represents an alkanediyl group which may have a substituent).

7. The rubber composition according to claim 6, wherein the rubber component contains a diene rubber.

8. The rubber composition according to claim 7, wherein the diene rubber is a modified diene rubber.

9. A method for producing the rubber composition according to any one of claims 1 to 8, comprising a step of mixing the rubber component and the additive.

10. A method for producing the rubber composition according to any one of claims 6 to 8,

the method comprises the following steps:

a step of obtaining a polymerization liquid containing a diene rubber by a solution polymerization method in a polymerization reactor;

and (b) adding a monomer represented by the formula (I) to a polymerization reactor containing the polymerization solution, and polymerizing the monomer to produce the additive.

Technical Field

The present invention relates to a rubber composition and a method for producing the rubber composition.

Background

In recent years, due to increasing concerns about environmental problems, there has been an increasing demand for fuel economy in automobiles, and rubber compositions used for automobile tires are also required to have excellent fuel economy. As the rubber composition for automobile tires, a rubber composition containing a conjugated diene polymer and a filler such as silica can be used.

On the other hand, the processability of a rubber composition containing a filler such as silica tends to be poor. Therefore, it has been proposed to improve the processability of a rubber composition for a tire by blending a rubber component with silica having a specific fine particle diameter and a specific monoalkanolamide (for example, refer to patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013 and 245639.

Disclosure of Invention

Problems to be solved by the invention

Rubber compositions for automobile tires are required to have both processability and fuel economy, but it is difficult to achieve both of these properties. Under such circumstances, an object of the present invention is to provide a rubber composition having excellent processability and good fuel economy, and a method for producing the rubber composition.

Means for solving the problems

The rubber composition according to one embodiment of the present invention includes a rubber component, an additive and a filler, the additive contains a compound containing at least one atom selected from a silicon atom, a nitrogen atom and an oxygen atom and a carbon atom, the total number of the silicon atom, the nitrogen atom and the oxygen atom constituting the compound is 0.27 or more and 0.80 or less relative to the number of the carbon atoms, a Hansen solubility parameter (Hansen solubility parameter) of the compound satisfies a relationship represented by the following formula (2), and a molecular weight of the compound is 200 or more and 15000 or less.

6≤{4(δD₁-δD₂)²+(δP₁-δP₂)²+(δH₁-δH₂)²}^0.5 (2)

(wherein δ D represents a dispersion term, δ P represents a polarity term, and δ H represents a hydrogen bond term.)

The rubber composition according to one embodiment of the present invention contains a rubber component, an additive and a filler, and the additive contains a polymer of a monomer represented by the following formula (I).

[ chemical formula 1]

In the formula, R¹Represents a hydrogen atom or a methyl group, R²And R³Each independently represents an alkyl group, L¹Represents an amide bond or an ester bond, L²Represents alkanediyl groups which may have a substituent.

Further, the method for producing a rubber composition according to one embodiment of the present invention includes a step of mixing the rubber component and the additive.

Effects of the invention

According to the present invention, a rubber composition having excellent processability and good fuel economy and a method for producing the rubber composition can be provided.

Detailed Description

This embodiment will be described in detail. The present invention is not limited to the following embodiments.

[ rubber composition ]

The rubber composition of the present embodiment includes a rubber component, an additive, and a filler. The respective components contained in the rubber composition will be described below.

(additives)

The rubber composition of the 1 st aspect of the present embodiment contains, as an additive, a compound containing at least 1 atom selected from a silicon atom, a nitrogen atom, and an oxygen atom, and a carbon atom. The total number of silicon atoms, nitrogen atoms and oxygen atoms constituting the compound is 0.27 to 0.80 relative to the number of carbon atoms, the hansen solubility parameter of the compound satisfies the relationship represented by the following formula (2), and the molecular weight of the compound is 200 to 15000. In the formula, δ D represents a dispersion term, δ P represents a polarity term, and δ H represents a hydrogen bond term.

6≤{4(δD₁-δD₂)²+(δP₁-δP₂)²+(δH₁-δH₂)²}^0.5 (2)

The present inventors have considered that by using a specific compound as an additive together with a rubber component and a filler, the interaction between the filler and the rubber component is enhanced by the compound existing at the boundary between the filler and the rubber component in the rubber composition, and thereby the fuel economy performance can be enhanced without deteriorating the processability of the rubber composition.

The value of the total number of silicon atoms, nitrogen atoms, and oxygen atoms constituting the compound with respect to the number of carbon atoms is defined as parameter a. The parameter A is defined as formula (1).

A＝(Si+N+O)/C (1)

In the formula (1), Si represents the number of silicon atoms, N represents the number of nitrogen atoms, O represents the number of oxygen atoms, and C represents the number of carbon atoms. For example, in the case where the compound does not contain silicon, Si is 0. The compound of this embodiment may contain atoms other than silicon, nitrogen, oxygen, and carbon, but the parameter a does not take this number of atoms into account.

From the viewpoint of enhancing the interaction by the compound contained in the rubber composition being present at the boundary between the filler and the rubber component, the compound is preferably composed of at least 1 atom selected from the group consisting of a silicon atom, a nitrogen atom, and an oxygen atom, and a carbon atom and a hydrogen atom, and more preferably composed of an oxygen atom, a nitrogen atom, a carbon atom, and a hydrogen atom.

Si, N, O, and C in formula (1) can be calculated by measuring the element content using an element analysis method such as X-ray photoelectron spectroscopy (XPS), an element analyzer, a carbon-sulfur analyzer, an oxygen-nitrogen-hydrogen analyzer, and an X-ray fluorescence analyzer, or ion chromatography. Further, Si, N, O, and C can also be calculated from the structure of the compound. These methods may be used alone or in combination of plural kinds. The method using a carbon-sulfur analyzer, an oxygen-nitrogen-hydrogen analyzer, a method of measuring the element content by ion chromatography, or a method of calculating the element content from the structure of the compound is preferably used, and more preferably, the method is determined from the structure of the compound.

In order to determine the structure of a compound, a common method such as nuclear magnetic resonance spectroscopy (NMR), liquid chromatography, gas chromatography, ultraviolet-visible spectroscopy, or infrared spectroscopy can be used.

The compound of the present embodiment is a component that enhances fuel economy performance by being present at the boundary between the filler and the rubber component and enhancing the interaction between the filler and the rubber component. The parameter A reflects the compatibility of the compound with the rubber component and the strength of the interaction of the compound with the filler. The compound having the parameter a of 0.27 or more is likely to be present in the vicinity of the filler because of its high affinity with the filler, and can enhance the interaction between the filler and the rubber component. The compound having the parameter A of less than 0.27 is biased to exist in the rubber component region, and when too much, biased to exist in the filler region, and therefore it is difficult to effectively improve the interaction between the rubber component and the filler.

When the parameter a is 0.27 or more and 0.80 or less, the compound contained in the composition exists at the boundary between the filler and the rubber component, and the interaction thereof can be improved, resulting in improvement of fuel economy performance. The parameter a is preferably 0.27 or more and 0.70 or less, more preferably 0.27 or more and 0.60 or less, and further preferably 0.27 or more and 0.40 or less.

The parameter B calculated from the Hansen solubility parameter of the compound is defined as formula (2).

B＝{4(δD₁-δD₂)²+(δP₁-δP₂)²+(δH₁-δH₂)²}^0.5 (2)

In the calculation of the Hansen solubility parameter, for δ D₁、δP₁And δ H₁Using a model compound represented by the following formula (H) for δ D₂、δP₂And δ H₂The compounds contained in the rubber composition are used.

[ chemical formula 2]

δ D, δ P, and δ H in the present embodiment are calculated using commonly available commercially available software, namely (HSPiP) developed by Charles Hansen et al.

The parameter B can be adjusted by using the contents described in HANSEN solvaty PARAMETERS A User's handbook (Charles m. For example, each component of the model compound's Hansen solubility parameter is (δ D)₁，δP₁，δH₁) (16.92, 0.27, 4.03). Each component of the hansen solubility parameter for each individual radical can be calculated using HSPiP. When each component of the hansen solubility parameter calculated using each atomic group and the hansen solubility parameter calculated using the model compound are substituted for formula (2) to calculate the parameter B, for example, in CH₃In the case of (3), the parameter B is 9.0. In CH₂In the case of (2), the parameter B is 3.5, which is expected to include more CH₂The compound (2) gives a parameter B which is higher than the parameter B containing more CH₃The parameter B of the compound (2) is small. In CH, SH (S is a sulfur atom), CF₃In the case where F is a fluorine atom, the parameters B are 9.5 and 11, respectively.3. 13.2 from CH₃The resulting parameter B is slightly increased compared to. At OH, NH₂NHCO, NCO, the parameters B are 36.6, 16.5, 16.3, 27.9, 28.3, and from CH₃The resulting parameter B is increased compared to the one obtained. The parameter B can be adjusted to a preferable value by appropriately combining atomic groups based on these values or the respective components of the hansen solubility parameter described in the Handbook.

The parameter B reflects the compatibility with the rubber component. When the parameter B is small, the compound is biased to exist around the rubber component. When the parameter B is 6 or more, the compound can be present in the vicinity of the filler, and therefore the interaction with the rubber component can be improved, resulting in an improvement in fuel economy performance. The parameter B is preferably 7 or more. When the parameter B is large, the compound is biased to exist around the filler. From the viewpoint of improving the interaction between the rubber component and the filler without causing the compound to be unevenly present around the filler, the parameter B is preferably 22 or less, more preferably 17 or less, and further preferably 12 or less.

The molecular weight of a compound can be calculated using a method calculated from the structural formula of the compound, a method using a mass spectrometer, or gel permeation chromatography. The method of calculating the molecular weight is preferably a method of calculating from the structural formula of the compound or a method using a mass spectrometer, and more preferably a method of calculating from the structural formula of the compound.

When the molecular weight of the compound is high, the interaction between the filler and the rubber component can be stabilized to improve fuel economy, and therefore, when a compound having a molecular weight of 200 or more is used as an additive, a stabilizing effect is easily obtained. The molecular weight of the compound is preferably 300 or more, more preferably 340 or more.

The molecular weight of the compound, parameter a and parameter B can be measured using an extract from the rubber composition as a sample. As a method for extracting a compound, a general method such as a soxhlet extraction method or a dissolution reprecipitation method can be used.

When the molecular weight of the compound is low, the molecular mobility becomes high, so that the compound is easily moved during mixing, and therefore, the mobility of the compound having a molecular weight of 15000 or less is high, and the compound can be easily moved to the boundary between the filler and the rubber component during mixing. The molecular weight of the compound is preferably 10000 or less, more preferably 5000 or less, and further preferably 2000 or less.

When the compound has a structure based on at least 1 selected from the group consisting of an amino group, a siloxy group, an imino group, an ether bond, an ester bond, and an amide bond, the interaction between the filler and the rubber component can be further enhanced. The compound has more preferably an amide bond or amino group-based structure, and still more preferably an amino group-based structure. The amino group is particularly preferably a tertiary amino group. The compound of the present embodiment can be used alone or in combination of 2 or more.

The rubber composition of embodiment 2 contains a polymer of a monomer represented by the following formula (I) as an additive.

[ chemical formula 3]

In the formula (I), R¹Represents a hydrogen atom or a methyl group, R²And R³Each independently represents an alkyl group, L¹Represents an amide bond or an ester bond, L²Represents an alkanediyl group which may have a substituent.

The present inventors have considered that, by using an oligomer obtained by polymerizing a specific monomer as an additive together with a rubber component and a filler, the oligomer is present at the boundary between the filler and the rubber component in a rubber composition, and the interaction thereof is improved, whereby the fuel economy performance can be improved without lowering the processability of the rubber composition.

From the viewpoint of further enhancing the interaction between the filler and the rubber component, the polymer of the present embodiment is preferably an oligomer in which the polymerization degree of the monomer represented by formula (I) is 2 or more. The polymerization degree of the oligomer is more preferably 2 or more and 100 or less, still more preferably 2 or more and 20 or less, and particularly preferably 2 or more and 10 or less.

Examples of the monomer represented by the formula (I) include: n- (2-dimethylaminoethyl) acrylamide, N- (2-diethylaminoethyl) acrylamide, N- (3-dimethylaminopropyl) acrylamide, N- (3-diethylaminopropyl) acrylamide, N- (4-dimethylaminobutyl) acrylamide, N- (4-diethylaminobutyl) acrylamide, N-methyl-N- (2-dimethylaminoethyl) acrylamide, N-methyl-N- (2-diethylaminoethyl) acrylamide, N-methyl-N- (3-dimethylaminopropyl) acrylamide, N-methyl-N- (3-diethylaminopropyl) acrylamide, N-methyl-N- (4-dimethylaminobutyl) acrylamide, N-methyl-N- (2-dimethylaminoethyl) acrylamide, N-methyl-N- (3-diethylaminobutyl) acrylamide, N-methyl-N- (4-dimethylaminobutyl) acrylamide, N-methyl-N- (3-diethylaminobutyl) acrylamide, N-methyl-N- (3-dimethylaminopropyl) acrylamide, N-methyl-N- (2-methylaminobutyl) acrylamide, N-methyl-N-butylacrylamide, N- (4-dimethylaminopropyl) acrylamide, N-butylacrylamide, and N-isopropylacrylamide, Acrylamide compounds such as N-methyl-N- (4-diethylaminobutyl) acrylamide; n- (2-dimethylaminoethyl) methacrylamide, N- (2-diethylaminoethyl) methacrylamide, N- (3-dimethylaminopropyl) methacrylamide, N- (3-diethylaminopropyl) methacrylamide, N- (4-dimethylaminobutyl) methacrylamide, N- (4-diethylaminobutyl) methacrylamide, N-methyl-N- (2-dimethylaminoethyl) methacrylamide, N-methyl-N- (2-diethylaminoethyl) methacrylamide, N-methyl-N- (3-dimethylaminopropyl) methacrylamide, N-methyl-N- (3-diethylaminopropyl) methacrylamide, Methacrylamide compounds such as N-methyl-N- (4-dimethylaminobutyl) methacrylamide and N-methyl-N- (4-diethylaminobutyl) methacrylamide; methacrylate compounds such as 2-diethylaminoethyl acrylate, 3-dimethylaminopropyl acrylate, 3-diethylaminopropyl acrylate, 4-dimethylaminobutyl acrylate and 4-diethylaminobutyl acrylate; acrylate compounds such as 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, 3-dimethylaminopropyl methacrylate, 3-diethylaminopropyl methacrylate, 4-dimethylaminobutyl methacrylate, 4-diethylaminobutyl methacrylate and 2-dimethylaminoethyl methacrylate. These may be used alone or in combination of 2 or more.

The content of the additive in the rubber composition may be 0.001 to 30 parts by mass, 0.01 to 15 parts by mass, or 0.1 to 5 parts by mass per 100 parts by mass of the rubber component, from the viewpoint of achieving both processability and fuel economy.

(rubber component)

The rubber component of the present embodiment is not particularly limited. The rubber component may contain a diene rubber. The diene rubber is a rubber obtained by using a diene monomer having a conjugated double bond as a raw material. Examples of the diene rubber include: natural rubber, polyisoprene rubber, chloroprene rubber, polybutadiene rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber, and nitrile rubber. The rubber component may be used in combination of 2 or more.

The diene rubber may be a modified diene rubber having units based on various modifiers in the molecular chain or the terminal. The modified diene rubber can be produced by reacting a monomer containing a conjugated diene compound with a modifier during solution polymerization.

The modifier is not particularly limited as long as it is a compound that can be used when a modified diene rubber is produced by solution polymerization. By using the diene rubber modified with a compound having a hetero atom, the filler can be easily dispersed in the rubber composition. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom and a silicon atom. Examples of the compound having a hetero atom include an amine compound, an acrylamide compound, a vinyl silane compound, an alkoxysilane compound, a polysiloxane compound, a sulfidosilane compound, a sulfosilane compound, a cyanate ester compound, and a polyimine compound. The diene rubber may be modified with a secondary amine compound, an acrylamide compound having an amino group, or a vinylsilane compound having an amino group.

As the modifier of the present embodiment, compounds specifically disclosed in Japanese patent laid-open Nos. 2012-214711, 2008-239966, 2010-77413, 2014-189720, 2015-120785, 2017-106029, 2017-110230, international publication No. 2014/133096, international publication No. 2014/014052, international publication No. 2015/199226, international publication No. 2016/133154, U.S. Pat. No. 9718911, U.S. Pat. No. 9249276, and the like can be used.

In the production of the rubber component, a coupling agent may be added to the polymerization solution from the initiation of polymerization of the monomer to the termination of polymerization.

Examples of the coupling agent include: silicon tetrachloride, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, tin tetrachloride, methyltrichlorotin, dimethyldichlorotin, trimethylchlorotin, tetramethoxysilane, methyltrimethoxysilane, dimethoxydimethylsilane, methyltriethoxysilane, ethyltrimethoxysilane, dimethoxydiethylsilane, diethoxydimethylsilane, tetraethoxysilane, ethyltriethoxysilane, and diethoxydiethylsilane.

The rubber component preferably contains a diene rubber, and more preferably contains a modified diene rubber, from the viewpoint of optimizing the compatibility and interaction between the rubber component and the filler and further improving the processability and fuel economy of the rubber composition. From the viewpoint of precisely introducing a modifying group into a polymer and further improving fuel economy performance, the modified diene rubber is preferably a diene rubber synthesized by a solution polymerization method, and more preferably a modified styrene-butadiene rubber. From the viewpoint of further improving the compatibility with the additives, a diene rubber modified with the monomer represented by the above formula (I) can be used as the rubber component.

(Filler)

Examples of the filler in the present embodiment include silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. These may be used alone or in combination of 2 or more.

Examples of the silica include dry silica (anhydrous silicic acid), wet silica (hydrous silicic acid), colloidal silica, precipitated silica, calcium silicate, and aluminum silicate. These may be used alone or in combination of 2 or more.

The BET specific surface area of the silica is usually 50 to 250m²(ii) in terms of/g. The BET specific surface area can be measured in accordance with ASTM D1993-03. As a commercial product of Silica, trade name "Ultrasil VN 3" manufactured by Evonik Industries, and trade name "NIPSIL" manufactured by Tosoh Silica CorporationVN3, NIPSIL AQ, NIPSIL ER, NIPSIL RS-150, and trade names "Zeosil 1115 MP" and "Zeosil 1165 MP" available from Rhodia.

Examples of the carbon black include furnace black, acetylene black, thermal black, channel black, and graphite. Examples of the channel black include EPC, MPC and CC. Examples of the furnace black include SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF. Examples of the thermal black include FT and MT. The carbon black may be used alone or in combination of 2 or more.

Nitrogen adsorption specific surface area (N) of carbon black₂SA) is usually 5 to 200m²The dibutyl phthalate (DBP) absorption of the carbon black is usually 5 to 300mL/100 g. The nitrogen adsorption specific surface area can be measured according to ASTM D4820-93, and the DBP absorption can be measured according to ASTM D2414-93. Commercially available products of CARBON Black include, for example, the product name "DIABLACK N339", the product name "SEAST 6", the product name "SEAST 7 HM", the product name "SEAST KH", the product name "CK 3", and the product name "Special Black 4A", which are manufactured by Mitsubishi Chemical Corporation, TOKAI CARBON CO., and LTD.

The content of the filler in the rubber composition may be 10 to 150 parts by mass, 20 to 120 parts by mass, or 30 to 100 parts by mass per 100 parts by mass of the rubber component, from the viewpoint of improving wear resistance and strength.

(other Components)

The rubber composition of the present embodiment may further contain a vulcanizing agent, a vulcanization accelerator, a vulcanization activator, an organic peroxide, a silane coupling agent, a filling oil (extender oil), a processing aid, an age resistor, a lubricant, and the like.

As the vulcanizing agent, sulfur can be used. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The amount of sulfur is preferably 0.1 to 15 parts by mass, more preferably 0.3 to 10 parts by mass, and still more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

Examples of the vulcanization accelerator include: thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, benzothiazole disulfide and N-cyclohexyl-2-benzothiazylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, N-tert-butyl-2-benzothiazolesulfenamide, N-oxymethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N, N' -diisopropyl-2-benzothiazolesulfenamide; guanidine-based vulcanization accelerators such as diphenylguanidine, diorthotolylguanidine and orthotolylbiguanide. The compounding amount of the vulcanization accelerator is preferably 0.1 to 5 parts by mass, and more preferably 0.2 to 3 parts by mass, per 100 parts by mass of the rubber component.

Examples of the vulcanization activator include stearic acid and zinc oxide. Examples of the organic peroxide include dicumyl peroxide and di-t-butyl peroxide.

Examples of the silane coupling agent include: vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (beta-methoxyethoxy) silane, beta- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane, N- (beta-aminoethyl) -gamma-aminopropylmethyldimethoxysilane, N-phenyl-gamma-aminopropyltrimethoxysilane, gamma-chloropropyltrimethoxysilane, gamma-mercaptopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, bis (3- (triethoxysilyl) propyl) disulfide, beta-glycidyloxy-propyltrimethoxysilane, gamma-glycidyloxy-propyltrimethoxysilane, beta-glycidyloxy-ethyltrimethoxysilane, gamma-ethylpropyltrimethoxysilane, tert-butyltrimethoxysilane, or a-butyltrimethoxysilane, a-butylor a-a, Bis (3- (triethoxysilyl) propyl) tetrasulfide, gamma-trimethoxysilylpropyl dimethylthiocarbamoyl tetrasulfide, gamma-trimethoxysilylpropyl benzothiazole tetrasulfide, 3-octanoylthio-1-propyltriethoxysilane, and mercapto-thiocarboxylate oligomers.

The amount of the silane coupling agent is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and still more preferably 5 to 10 parts by mass, per 100 parts by mass of the reinforcing material.

Examples of the extender oil include aromatic mineral oils (having a viscosity-specific gravity constant (v.g.c. value) of 0.900 to 1.049), naphthenic mineral oils (having a v.g.c. value of 0.850 to 0.899), and paraffinic mineral oils (having a v.g.c. value of 0.790 to 0.849). The polycyclic aromatic content of the extender oil is preferably less than 3 mass%, more preferably less than 1 mass%. The polycyclic aromatic content was measured according to the british petroleum institute 346/92 standard. The aromatic compound Content (CA) of the extender oil is preferably 20 mass% or more.

[ method for producing rubber composition ]

The method for producing the rubber composition of the present embodiment has a step of mixing the rubber component and the additive. The method of mixing the rubber component and the additive is not particularly limited, and may be, for example, the following method (a) or method (B).

The method (A) is a method of mixing after preparing the rubber component and the additive separately. In the method (a), a composition containing a rubber component and an additive can be obtained by mixing an additive prepared separately into a solution of a diene rubber produced by a solution polymerization method.

The method (B) is a method of obtaining a composition comprising a rubber component and an additive by in-situ polymerization. In the method (B), a composition containing a rubber component and an additive can be obtained by a step of obtaining a polymerization liquid containing a diene rubber by a solution polymerization method and a step of adding a monomer represented by the above formula (I) to a polymerization reactor containing the polymerization liquid and polymerizing the monomer to prepare the additive.

The rubber composition of the present embodiment can be prepared by mixing a filler and other components added as needed in a composition containing a rubber component and an additive. For the preparation of the rubber composition, for example, a method of kneading the respective components with a known mixer such as a roll or a banbury mixer can be used.

When components other than the vulcanizing agent and the vulcanization accelerator are blended as the kneading conditions, the kneading temperature is usually 50 to 200 ℃, preferably 80 to 190 ℃, and the kneading time is usually 30 seconds to 30 minutes, preferably 1 minute to 30 minutes. When a vulcanizing agent or a vulcanization accelerator is blended, the kneading temperature is usually 100 ℃ or lower, and preferably from room temperature to 80 ℃. In addition, a composition containing a vulcanizing agent and a vulcanization accelerator is generally used after vulcanization such as press vulcanization. The vulcanization temperature is usually 120 to 200 ℃ and preferably 140 to 180 ℃.

The rubber composition of the present embodiment has excellent processability and good fuel economy, and therefore can be preferably used for tires.

Examples

The present invention will be described in further detail with reference to examples below, but the present invention is not limited to these examples.

The physical properties were evaluated in the following manner.

1. Parameter A, molecular weight and degree of polymerization

The structure of the additive was determined by NMR method and the resulting chemical structure was used to calculate the parameter a, molecular weight and degree of polymerization of the additive.

2. Parameter B

For the calculation of the Parameter B of the additive, the software developed by Charles Hansen et al (Hansen Solubility Parameter in Practice (HSPiP)) was used. The structure determined by NMR method was used in the calculation.

3. Mooney viscosity (ML1+4 or MS1+4)

The Mooney viscosity of the rubber composition was measured at 100 ℃ in accordance with JIS K6300 (1994). The smaller the value of the Mooney viscosity, the more excellent the processability.

Tan delta (60 ℃ C.) and tan delta (0 ℃ C.)

A long test piece having a width of 1mm and a length of 40mm was punched out of the vulcanized sheet and used for the test. The measurement was performed by measuring the loss tangent (tan δ (60 ℃)) of the test piece at a temperature of 60 ℃ and the loss tangent (tan δ (0 ℃)) of the test piece at a temperature of 0 ℃ under the conditions of a strain of 1% and a frequency of 10Hz with an viscoelasticity measuring apparatus (Ueshima Seisakusho co., ltd.). the smaller the tan δ (60 ℃ C.), the better the fuel economy, and the larger the tan δ (0 ℃ C.), the better the grip performance.

< preparation of additive solution A >

55.23mmol of N- (3-dimethylaminopropyl) acrylamide and 184.1mL of cyclohexane were charged into a reactor under nitrogen atmosphereAnd an n-hexane solution containing 55.23mmol of n-butyllithium (n-BuLi), the temperature in the reactor was raised to 65 ℃ with stirring, and the mixture was stirred at the same temperature for 15 minutes. Subsequently, 3.36mL of methanol was added to the reactor, and the temperature in the reactor was cooled to room temperature, thereby obtaining 173.1g of additive solution A containing an oligomer of N- (3-dimethylaminopropyl) acrylamide. According to¹As a result of H-NMR spectrum analysis, it was confirmed that the compound represented by the following formula (A) was contained. The average degree of polymerization of the oligomer of N- (3-dimethylaminopropyl) acrylamide was 2, and the average molecular weight of the additive was 370.6 in terms of the degree of polymerization.

[ chemical formula 4]

[ production of rubber composition and vulcanized sheet ]

(example 1)

A30L capacity stainless polymerization reactor was purged and dried, and then replaced with dry nitrogen, and 15.3kg of industrial hexane (density: 680 kg/m) was charged into the polymerization reactor³) 912g of 1, 3-butadiene, 288g of styrene, 9.1mL of tetrahydrofuran and 6.54mL of ethylene glycol diethyl ether. Subsequently, a small amount of n-BuLi in hexane solution was charged into the polymerization reactor as a scavenger, and then 18.41mmol of piperidine and 18.14mmol of n-BuLi in n-hexane solution were charged to initiate polymerization at 30 ℃.

1, 3-butadiene was continuously supplied to the polymerization reactor at a stirring speed of 130rpm and a polymerization reactor internal temperature of 65 ℃ over 2.5 hours at 547 g/hr, and styrene was continuously supplied to the polymerization reactor at 216 g/hr over 2 hours, and polymerization was carried out for 3 hours in total. The total amount of 1, 3-butadiene supplied was 1368g and the total amount of styrene supplied was 432 g. 25 minutes after initiation of the polymerization, 30mL of a hexane solution containing 2.75g of bis (diethylamino) methylvinylsilane was charged into the polymerization reactor.

Subsequently, the polymerization reaction solution was stirred at a stirring speed of 130rpm, 18.41mmol of N- (3-dimethylaminopropyl) acrylamide was added thereto at 65 ℃ and stirred for 15 minutes, and then 30mL of a hexane solution containing 1.12mL of methanol was added thereto and stirred for 5 minutes.

Then, 173.1g of the additive solution A was added to the polymerization reaction solution, followed by addition of 12.0g of 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate (product name: SUMILIZER GM, manufactured by Sumitomo chemical Co., Ltd.) and 6.0g of pentaerythritol tetrakis (3-laurylthiopropionate) (product name: SUMILIZER TP-D, manufactured by Sumitomo chemical Co., Ltd.) as an antioxidant, and stirring was carried out for 10 minutes to obtain a polymer solution.

The polymer solution was allowed to stand at normal temperature for 24 hours, the solvent was evaporated, and the polymer solution was dried under reduced pressure at 55 ℃ for 12 hours to obtain a composition a1 containing a copolymer of styrene and 1, 3-butadiene (styrene-butadiene rubber) and an oligomer of N- (3-dimethylaminopropyl) acrylamide.

Labo Plastomill was used to knead 80 parts by mass of composition a1, 20 parts by mass of high-cis BR (manufactured by Nippon Corporation, trade name: BR1220), 80 parts by mass of silica (manufactured by EVONIK INDUSTRIES, trade name: ULTRASIL 7000GR), 6.4 parts by mass of a silane coupling agent (manufactured by EVONIK INDUSTRIES, trade name: Si75), 5 parts by mass of carbon black (manufactured by Mitsubishi Chemical Corporation, trade name: DIABLACK N339), 30 parts by mass of a filling oil (manufactured by JXTDUG, trade name: TDAE aromatic), 2 parts by mass of an anti-aging agent (manufactured by CHIOUCHIOUSHINKO INDUSTRIAL CO., LTD., trade name: NOCA 6C), 2 parts by mass of stearic acid, 3 parts by mass of zinc oxide, 2 parts by mass of a vulcanization accelerator (manufactured by CHIOUSHINKO KO CO., trade name: 5 parts by SULFURAL, CROSE.1. COR.5. and COR. RTM. by Labo. RTM. A rubber composition is prepared. The rubber composition was molded into a sheet by a 6-inch roll, and the sheet was vulcanized by heating at 160 ℃ for 55 minutes to prepare a vulcanized sheet.

(example 2)

A polymerization reactor having an internal volume of 30L and made of stainless steel was washed, dried, and then replaced with dry nitrogen to carry out polymerization15.3kg of industrial hexane (density: 680 kg/m) was charged into the reactor³) 912g of 1, 3-butadiene, 288g of styrene, 9.1mL of tetrahydrofuran and 6.54mL of ethylene glycol diethyl ether. Subsequently, a small amount of n-BuLi in hexane solution was charged into the polymerization reactor as a scavenger, and then 18.41mmol of piperidine and 18.14mmol of n-BuLi in n-hexane solution were charged to initiate polymerization at 30 ℃.

1, 3-butadiene was continuously supplied to the polymerization reactor at a stirring speed of 130rpm and a polymerization reactor internal temperature of 65 ℃ over 2.5 hours at 547 g/hr, and styrene was continuously supplied to the polymerization reactor at 216 g/hr over 2 hours, and polymerization was carried out for 3 hours in total. The total amount of 1, 3-butadiene supplied was 1368g and the total amount of styrene supplied was 432 g. 25 minutes after initiation of the polymerization, 30mL of a hexane solution containing 2.75g of bis (diethylamino) methylvinylsilane was charged into the polymerization reactor.

Subsequently, the polymerization reaction solution was stirred at a stirring speed of 130rpm, 18.41mmol of N- (3-dimethylaminopropyl) acrylamide was added thereto at 65 ℃ and stirred for 15 minutes, and then an N-hexane solution containing 55.23mmol of N-BuLi was poured in. After N-BuLi in hexane solution was poured for 10 seconds, 55.23mmol of N- (3-dimethylaminopropyl) acrylamide was added, and after stirring for 15 minutes, 30mL of a hexane solution containing 4.47mL of methanol was added at 65 ℃ and further stirring was carried out for 5 minutes.

Next, 12.0g of "SUMILIZER GM" and 6.0g of "SUMILIZER TP-D" were added to the polymerization reaction solution, and stirred for 10 minutes to obtain a polymer solution.

The polymer solution was allowed to stand at ordinary temperature for 24 hours, the solvent was evaporated, and further dried under reduced pressure at 55 ℃ for 12 hours to obtain composition a2 containing an oligomer of styrene-butadiene rubber and N- (3-dimethylaminopropyl) acrylamide. Of composition a2¹As a result of H-NMR spectrum analysis, a compound represented by the formula (A) was observed. The oligomer of N- (3-dimethylaminopropyl) acrylamide had an average degree of polymerization of 3, and the average molecular weight of the additive was 526.8 in terms of the degree of polymerization.

A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition a2 was used.

Comparative example 1

A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the additive solution a was not added.

Comparative example 2

A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that an additive solution B prepared by mixing 55.23mmol of N- (3-dimethylaminopropyl) acrylamide and 184.1mL of cyclohexane was used instead of the additive solution A.

The evaluation results of the parameter A, the parameter B and the molecular weight of the additive, the Mooney viscosity of the rubber composition, and the tan. delta. of the vulcanized sheet are shown in Table 1. Here, the mooney viscosity and tan δ in table 1 are relative values when comparative example 1 is taken as 100.

[ Table 1]

(example 3)

A30L capacity stainless polymerization reactor was purged and dried, and then replaced with dry nitrogen, and 15.3kg of industrial hexane (density: 680 kg/m) was charged into the polymerization reactor³) 968g of 1, 3-butadiene, 334g of styrene, 12.0mL of tetrahydrofuran and 4.15mL of ethylene glycol diethyl ether. Subsequently, a small amount of n-BuLi in hexane solution was charged into the polymerization reactor as a scavenger, and then 13.89mmol of piperidine and 18.52mmol of n-BuLi in n-hexane solution were charged to initiate polymerization at 30 ℃.

1, 3-butadiene was continuously fed into the polymerization reactor at a stirring speed of 130rpm and a polymerization reactor internal temperature of 65 ℃ for 2.5 hours at 513 g/hour and styrene was continuously fed into the polymerization reactor for 2 hours at 208 g/hour, and polymerization was carried out for 3 hours in total. The total amount of 1, 3-butadiene supplied was 1282g and the total amount of styrene supplied was 416 g. 25 minutes after initiation of the polymerization, 30mL of a hexane solution containing 12.5g of bis (diethylamino) methylvinylsilane was charged into the polymerization reactor.

Subsequently, the polymerization reaction solution was stirred at a stirring speed of 130rpm, 1.95mmol of tin tetrachloride was added at 65 ℃ and stirred for 15 minutes, 10.72mmol of N- (3-dimethylaminopropyl) acrylamide was added thereto and stirred for 15 minutes, and then an N-hexane solution containing 31.35mmol of N-BuLi was poured in. After charging N-BuLi in hexane for 15 minutes, 15.68mmol of N- (3-dimethylaminopropyl) acrylamide was added, and after stirring for 15 minutes, 30mL of a hexane solution containing 2.02mL of methanol was added at 65 ℃ and further stirring was carried out for 5 minutes.

Then, 16.8g of 4, 6-bis (octylthiomethyl) -o-cresol (product name: Irganox1520L, manufactured by BASF corporation) as an antioxidant was added to the polymerization reaction solution and stirred for 10 minutes to obtain a polymer solution.

The polymer solution was allowed to stand at normal temperature for 24 hours, the solvent was evaporated, and further dried under reduced pressure at 55 ℃ for 12 hours to obtain composition b1 containing an oligomer of styrene-butadiene rubber and N- (3-dimethylaminopropyl) acrylamide.

A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition b1 was used.

(example 4)

A polymerization reactor having an internal volume of 20L and made of stainless steel was washed, dried, and replaced with dry nitrogen, and 10.2kg of commercial hexane (density: 680 kg/m) was charged into the polymerization reactor³) 504g of 1, 3-butadiene, 546g of styrene, 6.07mL of tetrahydrofuran and 1.27mL of ethylene glycol diethyl ether. Subsequently, a small amount of n-BuLi in hexane solution was charged into the polymerization reactor as a scavenger, and then 3.16mmol of piperidine and 6.31mmol of n-BuLi in n-hexane solution were charged to initiate polymerization at 30 ℃.

1, 3-butadiene was continuously fed into the polymerization reactor at a stirring speed of 130rpm and a polymerization reactor internal temperature of 65 ℃ for 2 hours at 394 g/hr, styrene was continuously fed into the polymerization reactor for 2 hours at 101 g/hr, and 1, 3-butadiene was continuously fed into the polymerization reactor for 20 minutes at 180 g/hr, and polymerization was carried out for 170 minutes in total. The total amount of 1, 3-butadiene supplied was 1352g, and the total amount of styrene supplied was 748 g. 20 minutes after initiation of the polymerization, 30mL of a hexane solution containing 0.182g of bis (diethylamino) methylvinylsilane was charged into the polymerization reactor.

Subsequently, the polymerization reaction solution was stirred at a stirring speed of 130rpm, 0.474mmol of silicon tetrachloride was added at 65 ℃ and stirred for 10 minutes, 4.42mmol of N- (3-dimethylaminopropyl) acrylamide was added thereto and stirred for 10 minutes, and then an N-hexane solution containing 13.9mmol of N-BuLi was poured in. After a 5-minute charge of N-BuLi in hexane, 13.9mmol of N- (3-dimethylaminopropyl) acrylamide was added, and after stirring for 15 minutes, 20mL of a hexane solution containing 1.23mL of methanol was added at 65 ℃ and further stirring was carried out for 15 minutes.

Next, 8.40g of "Irganox 1520L" as an antioxidant and 788g of extender oil (product name: Process NC-140, manufactured by JXTG Energy Co., Ltd.) were added to the polymerization reaction solution, and the mixture was stirred for 10 minutes to obtain a polymer solution.

The polymer solution was allowed to stand at normal temperature for 24 hours, the solvent was evaporated, and further dried under reduced pressure at 55 ℃ for 12 hours to obtain composition b2 containing an oligomer of styrene-butadiene rubber and N- (3-dimethylaminopropyl) acrylamide.

A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition b2 was used.

Comparative example 3

A30L capacity stainless polymerization reactor was purged and dried, and then replaced with dry nitrogen, and 15.3kg of industrial hexane (density: 680 kg/m) was charged into the polymerization reactor³) 968g of 1, 3-butadiene, 334g of styrene, 12.0mL of tetrahydrofuran and 4.15mL of ethylene glycol diethyl ether. Subsequently, a small amount of n-BuLi in hexane solution was charged into the polymerization reactor as a scavenger, and then 13.89mmol of piperidine and 18.52mmol of n-BuLi in n-hexane solution were charged to initiate polymerization at 30 ℃.

1, 3-butadiene was continuously fed into the polymerization reactor at a stirring speed of 130rpm and a polymerization reactor internal temperature of 65 ℃ for 2.5 hours at 513 g/hour and styrene was continuously fed into the polymerization reactor for 2 hours at 208 g/hour, and polymerization was carried out for 3 hours in total. The total amount of 1, 3-butadiene supplied was 1282g and the total amount of styrene supplied was 416 g. 25 minutes after initiation of the polymerization, 30mL of a hexane solution containing 12.5g of bis (diethylamino) methylvinylsilane was charged into the polymerization reactor.

Subsequently, the polymerization reaction solution was stirred at a stirring speed of 130rpm, 1.95mmol of tin tetrachloride was added at 65 ℃ and stirred for 15 minutes, 10.72mmol of N- (3-dimethylaminopropyl) acrylamide was added thereto and stirred for 15 minutes, and then 30mL of a hexane solution containing 2.02mL of methanol was added at 65 ℃ and stirred for 5 minutes.

To the polymerization reaction solution was added 16.8g of "Irganox 1520L" and stirred for 10 minutes to obtain a polymer solution. The polymer solution was allowed to stand at normal temperature for 24 hours, the solvent was evaporated, and further dried under reduced pressure at 55 ℃ for 12 hours to obtain composition b3 containing styrene-butadiene rubber.

A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition b3 was used.

Comparative example 4

A polymerization reactor having an internal volume of 20L and made of stainless steel was washed, dried, and replaced with dry nitrogen, and 10.2kg of commercial hexane (density: 680 kg/m) was charged into the polymerization reactor³) 504g of 1, 3-butadiene, 546g of styrene, 6.07mL of tetrahydrofuran and 1.27mL of ethylene glycol diethyl ether. Subsequently, a small amount of n-BuLi in hexane solution was charged into the polymerization reactor as a scavenger, and then 3.16mmol of piperidine and 6.31mmol of n-BuLi in n-hexane solution were charged to initiate polymerization at 30 ℃.

1, 3-butadiene was continuously fed into the polymerization reactor at a stirring speed of 130rpm and a polymerization reactor internal temperature of 65 ℃ for 2 hours at 394 g/hr, styrene was continuously fed into the polymerization reactor for 2 hours at 101 g/hr, and 1, 3-butadiene was continuously fed into the polymerization reactor for 20 minutes at 180 g/hr, and polymerization was carried out for 170 minutes in total. The total amount of 1, 3-butadiene supplied was 1352g, and the total amount of styrene supplied was 748 g. 20 minutes after initiation of the polymerization, 30mL of a hexane solution containing 0.182g of bis (diethylamino) methylvinylsilane was charged into the polymerization reactor.

Subsequently, the polymerization reaction solution was stirred at a stirring speed of 130rpm, 0.474mmol of silicon tetrachloride was added at 65 ℃ and stirred for 10 minutes, 4.42mmol of N- (3-dimethylaminopropyl) acrylamide was added thereto and stirred for 15 minutes, and then 20mL of a hexane solution containing 1.23mL of methanol was added at 65 ℃ and further stirred for 15 minutes.

Subsequently, 8.40g of "Irganox 1520L" and 788g of "Process NC-140" were added to the polymerization reaction solution, and stirred for 10 minutes to obtain a polymer solution. The polymer solution was allowed to stand at normal temperature for 24 hours, the solvent was evaporated, and further dried under reduced pressure at 55 ℃ for 12 hours to obtain composition b4 containing styrene-butadiene rubber.

A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition b4 was used.

The evaluation results of the parameter A, the parameter B and the molecular weight of the additive, the Mooney viscosity of the rubber composition, and the tan. delta. of the vulcanized sheet are shown in Table 2. Here, the mooney viscosity and tan δ in table 2 are relative values when comparative example 4 is taken as 100.

[ Table 2]

< preparation of additive solution C >

55.23mmol of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide and 184.1mL of tetrahydrofuran were charged into a reactor under nitrogen atmosphere, and the mixture was cooled to-78 ℃ with stirring. Subsequently, an n-hexane solution containing 27.62mmol of n-BuLi was charged into the reactor, the temperature in the reactor was raised to 25 ℃ with stirring, and the mixture was stirred at the same temperature for 1 hour. Subsequently, 1.12mL of methanol was added to the reactor, and the temperature in the reactor was cooled to room temperature, whereby 179.1g of additive solution C containing an oligomer of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide was obtained. According to¹As a result of H-NMR spectrum analysis, it was confirmed that the compound represented by the following formula (C) was contained. The oligomer of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide had an average degree of polymerization of 2 and an average molecular weight of 368.6 as calculated from the average degree of polymerization.

[ chemical formula 5]

(example 5)

A composition C1 was obtained in the same manner as in example 1, except that a polymerization reaction solution was prepared without adding piperidine, and 179.1g of an additive solution C was added to the polymerization reaction solution in place of the additive solution a. A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition c1 was used.

< preparation of additive solution D >

An additive solution D containing an oligomer of (3-isocyanatopropyl) trimethoxysilane was prepared in the same manner as the additive solution C except that (3-isocyanatopropyl) trimethoxysilane was used instead of 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide. According to¹As a result of H-NMR spectrum analysis, it was confirmed that the compound represented by the following formula (D) was contained. The oligomer of (3-isocyanatopropyl) trimethoxysilane had an average degree of polymerization of 2 and an average molecular weight of 468.7 calculated from the average degree of polymerization.

[ chemical formula 6]

(example 6)

A composition c2 was obtained in the same manner as in example 1, except that a polymerization reaction solution was prepared without adding piperidine, and 182.1g of an additive solution D was added to the polymerization reaction solution in place of the additive solution a. A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition c2 was used.

Comparative example 5

A composition c3 was obtained in the same manner as in example 1, except that a polymerization reaction solution was prepared without adding piperidine and that the additive solution a was not added to the polymerization reaction solution. A rubber composition was prepared and a vulcanized sheet was produced in the same manner as in example 1, except that the composition c3 was used.

The evaluation results of the parameter A, the parameter B and the molecular weight of the additive, the Mooney viscosity of the rubber composition, and the tan. delta. of the vulcanized sheet are shown in Table 3. Here, the mooney viscosity and tan δ in table 3 are relative values when comparative example 5 is taken as 100.

[ Table 3]