Rubber compositions and pneumatic tires

Abstract

To provide a rubber composition with excellent processability and a pneumatic tire comprising vulcanized rubber of the rubber composition. [Solution] A rubber composition containing diene rubber and graphene, wherein the graphene has a specific surface area of ​​200 m² 2 A rubber composition comprising graphene having a particle size of 10 μm or less, an average particle thickness of 10 nm or less, and an oxygen content of 1% by mass or less. Preferably, the graphene content is 1.5 to 10 parts by mass when the total amount of diene rubber is 100 parts by mass. Furthermore, it is preferable that the rubber composition does not contain N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

Description

[Technical Field]

[0001] This invention relates to a rubber composition and a pneumatic tire. [Background technology]

[0002] Pneumatic tires consist of a rubber section formed by vulcanizing a rubber composition. These rubber compositions typically contain fillers such as carbon black and silica to enhance their reinforcing properties. Recently, tires incorporating graphene as a filler have also been reported.

[0003] Patent Document 1 below describes a rubber composition containing diene rubber, graphene oxide, and carbon black, wherein the content of graphene oxide is 0.1 to 10 parts by mass, the content of carbon black is 30 to 80 parts by mass, and the oxygen content of graphene oxide is 45 to 60 atom% per 100 parts by mass of diene rubber.

[0004] The following Patent Document 2 describes a base rubber composition comprising 0.1 to 20% by weight of graphene carbon particles having a bendable 3D shape and an oxygen content of 2 atomic percent or less, and 1 to 50% by weight of filler particles containing silica, which hardens to 10 10 A curable rubber compound having a surface resistivity of less than Ω / sq is described.

[0005] Patent Document 3 below describes at least one elastomer resistant to heating at 100°C for 70 hours, exhibiting at least one of the following properties: (a) a change in durometer hardness of 15 points or less, (b) a change in tensile strength of 40% or less, and (c) a change in ultimate elongation of 40% or less; and at least one graphene-based material present in the amount of the at least one elastomer in the range of 0.01 to 30 phr, selected from reduced graphene oxide, and with a range of 40 to 1600 m 2The document describes an elastomer compound comprising at least one graphene-based material having a BET surface area in the range of / g, and at least one carbon black present in an amount in the range of 15 to 150 phr relative to the at least one elastomer.

[0006] Patent Document 4 below describes a composition comprising a graphene sheet, at least one reinforcing material containing silicon, and at least one type of rubber.

[0007] Patent Document 5 below describes a composition comprising a graphene sheet, at least one reinforcing material containing silicon, and at least one type of rubber, wherein the composition includes 2 to 4 parts by weight of the graphene sheet per 100 parts by weight of the rubber. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 7385429 [Patent Document 2] Patent No. 6087424 [Patent Document 3] Patent No. 6802281 [Patent Document 4] Japanese Patent Publication No. 2018-15054 [Patent Document 5] Patent No. 6404121 [Overview of the project] [Problems that the invention aims to solve]

[0009] As a result of diligent research by the inventors, it was found that in rubber compositions containing graphene as a filler, the processability deteriorates due to the aggregation of graphene within the rubber. Further diligent research to improve processability revealed that by using graphene with specific physical properties, the processability of the rubber composition is significantly improved.

[0010] The present invention has been made in view of the above circumstances, and its object is to provide a rubber composition with excellent processability and a pneumatic tire comprising vulcanized rubber of the rubber composition. [Means for solving the problem]

[0011] The above problems can be solved by the following configuration. That is, the present invention is a rubber composition containing diene rubber and graphene, wherein the graphene has a specific surface area of ​​200 m². 2 The present invention relates to a rubber composition (1) characterized by being graphene having a particle size of 10 μm or less, an average particle thickness of 10 nm or less, and an oxygen content of 1% by mass or less.

[0012] In the above rubber composition (1), a rubber composition (2) is preferred in which the graphene content is 0.5 to 30 parts by mass when the total amount of the diene-based rubber is 100 parts by mass.

[0013] Of the above rubber compositions (1) or (2), rubber composition (3) that does not contain N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine is preferred.

[0014] The present invention also relates to a pneumatic tire comprising at least one vulcanized rubber from rubber compositions (1) to (3). [Effects of the Invention]

[0015] Generally, graphene tends to aggregate and disperse easily when mixed in diene-based rubber. However, the graphene used in this invention is designed with a specific specific surface area, particle size, average particle thickness, and oxygen content, making it less prone to aggregation and easier to disperse in diene-based rubber. As a result, the processability of the rubber composition is significantly improved. [Modes for carrying out the invention]

[0016] The rubber composition according to the present invention contains diene rubber and graphene.

[0017] The rubber composition according to the present invention contains a diene rubber. The diene rubber is not particularly limited, and examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and the like. These can be used alone or in combination of two or more. In the present invention, it is particularly preferable to use natural rubber (NR) and / or butadiene rubber (BR).

[0018] The graphene used in the present invention is designed to have a specific specific surface area, particle size, average thickness of particles, and oxygen content. Graphene is a two-dimensional sheet-like substance classified as a nanocarbon material and has a structure covered with six-membered rings of carbon. By having such a structure, anti-aging performance can be imparted to the finally obtained vulcanized rubber. This point will be described later. 2 It has a structure covered with six-membered rings of carbon. By having such a structure, anti-aging performance can be imparted to the finally obtained vulcanized rubber. This point will be described later.

[0019] The BET specific surface area of the graphene used in the present invention is designed to be 200 m 2 / g or less. From the viewpoint of improving the dispersibility in the diene rubber, it is preferable to use graphene having a BET specific surface area of 80 m 2 / g or less. In the present invention, the BET specific surface area of graphene is measured according to the BET method described in JIS K6430.

[0020] The particle size of the graphene used in the present invention is designed to be 10 μm or less. From the viewpoint of improving the dispersibility in the diene rubber, it is preferable to use graphene having a particle size of 7 μm or less. In the present invention, the particle size of graphene is defined as the particle diameter (D50) at 50% of the integrated value in the particle size distribution (volume basis) measured by the laser diffraction / scattering method.

[0021] The average thickness of the graphene particles used in this invention is designed to be 10 nm or less. From the viewpoint of improving dispersibility in diene-based rubber, it is preferable to use graphene with an average particle thickness of 3 nm or less. In this invention, the average thickness of the graphene particles is calculated from the thickness measured by transmission electron microscopy (TEM) observation. The average thickness of 100 graphene particles is measured, and the arithmetic mean is taken as the average thickness of the graphene particles.

[0022] The oxygen content of the graphene used in this invention is designed to be 1% by mass or less. From the viewpoint of improving dispersibility in diene-based rubber, it is preferable to use graphene with an oxygen content of 1% by mass or less. In this invention, the oxygen content of graphene is determined using X-ray photoelectron spectroscopy (for example, the method described in DRDreyer et al., Chem. Soc. Rev. 39, 228-240 (2010)).

[0023] Graphene is a two-dimensional sheet-like material classified as a nanocarbon material, and it readily forms a layered structure by aggregating or bonding with other elements through van der Waals forces. However, it is preferable to use graphene with a layered structure of 20 layers or less in this invention.

[0024] From the viewpoint of improving the processability of the rubber composition, when the total amount of diene rubber is 100 parts by mass, the graphene content is preferably 0.5 to 30 parts by mass, and more preferably 1.5 to 10 parts by mass.

[0025] The rubber composition according to the present invention may contain fillers other than graphene. Examples of fillers include carbon black and silica.

[0026] As carbon black, in addition to carbon black commonly used in the rubber industry, such as SAF, ISAF, HAF, FEF, and GPF, conductive carbon blacks such as acetylene black and Ketjen black can be used. In the rubber composition according to the present invention, when the total amount of diene rubber is 100 parts by mass, the carbon black content may be 20 to 150 parts by mass, 30 to 100 parts by mass, or 40 to 80 parts by mass. Preferably, it is 40 to 80 parts by mass.

[0027] As silica, wet silica, dry silica, sol-gel silica, and surface-treated silica, which are commonly used for rubber reinforcement, can be used. Among these, wet silica is preferred. In the rubber composition according to the present invention, when the total amount of diene-based rubber is 100 parts by mass, the silica content may be 5 to 130 parts by mass, 10 to 80 parts by mass, or 20 to 50 parts by mass.

[0028] When silica is included as a filler, it is also preferable to include a silane coupling agent. The silane coupling agent is not particularly limited as long as it contains sulfur in its molecule, and various silane coupling agents that are compounded together with silica in rubber compositions can be used. Examples include sulfidosilanes such as bis(3-triethoxysilylpropyl)tetrasulfide (e.g., "Si69" manufactured by Evonik Japan), bis(3-triethoxysilylpropyl) disulfide (e.g., "Si75" manufactured by Evonik Japan), bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triecethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, and bis(2-trimethoxysilylethyl) disulfide; mercaptosilanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, mercaptopropylmethyldimethoxysilane, mercaptopropyldimethylmethoxysilane, and mercaptoethyltriethoxysilane; and protected mercaptosilanes such as 3-octanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane. The amount of silane coupling agent is preferably 2 to 20% by mass, when the total amount of silica is considered to be 100% by mass.

[0029] The rubber composition according to the present invention contains diene rubber and graphene. In addition to these, the rubber composition according to the present invention may also contain fillers such as carbon black and silica, vulcanizing agents, antioxidants, zinc oxide, stearic acid, softeners such as waxes and oils, processing aids, and the like.

[0030] Preferably, sulfur and a vulcanization accelerator can be used as vulcanizing agents.

[0031] Any ordinary sulfur for rubber can be used, such as powdered sulfur, precipitated sulfur, insoluble sulfur, or highly dispersible sulfur. The rubber composition according to the present invention preferably contains 0.1 to 5 parts by mass of sulfur, and more preferably 0.5 to 3 parts by mass, when the total amount of diene rubber is 100 parts by mass.

[0032] As the vulcanization accelerator, vulcanization accelerators commonly used for rubber vulcanization, such as sulfenamide-based vulcanization accelerators, thiram-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiourea-based vulcanization accelerators, guanidine-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators, may be used individually or in appropriate mixtures. The rubber composition according to the present invention preferably contains 0.1 to 5 parts by mass of vulcanization accelerator, and more preferably 0.5 to 3 parts by mass, when the total amount of diene rubber is 100 parts by mass.

[0033] Examples of anti-aging agents commonly used for rubber include aromatic amine-based anti-aging agents, amine-ketone-based anti-aging agents, monophenol-based anti-aging agents, bisphenol-based anti-aging agents, polyphenol-based anti-aging agents, dithiocarbamate-based anti-aging agents, and thiourea-based anti-aging agents. However, in recent years, from the perspective of developing environmentally friendly products, there has been a focus on reducing the use of materials derived from fossil fuels or replacing them with other materials. The graphene used in this invention is sp 2 Because it has a structure that is tiled with six-membered rings of carbon, sp 2 The remaining electrons in the hybrid orbitals can capture radicals that cause aging of vulcanized rubber. For this reason, the rubber composition according to the present invention preferably contains diene rubber and graphene, with reduced amount or no N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), taking the environment into consideration. The rubber composition according to the present invention preferably contains 1 to 10 parts by mass of the antioxidant, and more preferably 2 to 5 parts by mass, when the total amount of diene rubber is 100 parts by mass.

[0034] The rubber composition according to the present invention is obtained by mixing diene rubber with fillers such as graphene, carbon black, and silica, vulcanizing agents, antioxidants, zinc oxide, stearic acid, waxes, oils, and other softening agents and processing aids using a kneader commonly used in the rubber industry, such as a Banbury mixer, kneader, and rolls.

[0035] Also, the blending method of each of the above components is not particularly limited, and methods such as pre-kneading blending components other than vulcanization system blending agents such as sulfur and vulcanization accelerators to form a masterbatch, adding the remaining components and further kneading, adding each component in an arbitrary order and kneading, or adding all components simultaneously and kneading may be used.

[0036] The vulcanized rubber of the rubber composition according to the present invention has excellent dispersibility of graphene in the diene rubber, so that the reinforcing effect of graphene is effectively exerted. Therefore, the vulcanized rubber of the rubber composition according to the present invention is particularly useful for the rubber part applications of pneumatic tires.

Examples

[0037] Hereinafter, examples of the present invention will be described for more specific explanation.

[0038] (Preparation of Rubber Composition) Based on 100 parts by mass of the rubber component, rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 2 were blended according to the formulation shown in Table 1, and kneaded using an ordinary Banbury mixer to prepare the rubber compositions. Each compounding agent described in Table 1 is shown below.

[0039] (Diene Rubber) · Butadiene rubber: manufactured by UBE, trade name "UBEPOL BR150B" · Natural rubber: RSS#3 (Graphene) · Graphene 1: manufactured by avanzare, trade name "av-PLAT-7", specific surface area 70m 2 / g, particle size (Lateral size (LD50)) 7.2 μm, average thickness of particles 3 nm, oxygen content (XPS) <1% by mass, 5 - 10-layer layered structure · Graphene 2: manufactured by avanzare, trade name "av-PLAT-2", specific surface area >200m 2 / g, particle size (Lateral size (LD50)) 2 μm, average thickness of particles <10 nm, oxygen content (XPS) <1% by mass, 20-layer or less layered structure • Graphene 3: Manufactured by Tokyo Chemical Industry Co., Ltd., product name "Graphene Nanoplatelets Aggregates (sub-micron particles, surface area 500m²)" 2 / g)", specific surface area 500m 2 / g, particle size 2μm, average particle thickness 10nm or less, oxygen content 0.5% by mass or less • Graphene 4: Manufactured by Tokyo Chemical Industry Co., Ltd., product name "Graphene Nanoplatelets Aggregates (sub-micron particles, surface area 750m2 / g)", specific surface area 750m 2 / g, particle size 2μm, average particle thickness 10nm or less, oxygen content 0.5% by mass or less (Filler) • Carbon Black: Manufactured by Tokai Carbon Co., Ltd., product name "Seast KH" (Other combination drugs) • Zinc oxide: "Zinc Oxide No. 3" manufactured by Mitsui Mining & Smelting Co., Ltd. • Stearic acid: Kao Corporation's "Lunaq S-20" (Vulcanizing agent) • Sulfur: Manufactured by Tsurumi Chemical Industry Co., Ltd., product name "Powdered Sulfur" • Sulfurization accelerator (sulfenamide-based sulfurization accelerator): Manufactured by Sumitomo Chemical Co., Ltd., product name "Soxinol CZ"

[0040] After preparing unvulcanized samples of the rubber compositions obtained in Examples 1-4 and Comparative Examples 1-2 above, the t5 (processability) was evaluated by the following method.

[0041] (t5 (processability) of rubber composition) Using a Mooney scorch tester (L-type rotor) conforming to JIS K6300-1, the t5 value was determined after preheating for 1 minute and at a temperature of 125°C. The value was then expressed as an index with the value of Comparative Example 1 set to 100. A higher value indicates less burning and superior scorching (machinability).

[0042] [Table 1]

[0043] The results in Table 1 show that the rubber compositions in Examples 1-3 exhibit high scorch resistance and excellent processability. The rubber composition in Example 4 also exhibits high scorch resistance and excellent processability, but its effectiveness is inferior to that of Examples 1-3.

Claims

1. A rubber composition containing diene rubber and graphene, The graphene has a specific surface area of ​​200 m². ２ A rubber composition characterized by being graphene having a particle size of 10 μm or less per gram, an average particle thickness of 10 nm or less, and an oxygen content of 1% by mass or less.

2. The rubber composition according to claim 1, wherein the graphene content is 0.5 to 30 parts by mass when the total amount of the diene rubber is 100 parts by mass.

3. The rubber composition according to claim 1, which does not contain N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.

4. A pneumatic tire comprising at least vulcanized rubber of the rubber composition described in claim 1.

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