Rubber composition, rubber composition for tires, and tire

Abstract

To provide a rubber composition having improved dispersibility of a filler while having high strength, and a rubber composition for tires.SOLUTION: A rubber composition contains a rubber component containing diene rubber, and a composite filler, wherein the composite filler contains a carbon-based filler, an inorganic filler, and a cationic polymer compound.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition, a rubber composition for a tire, and a tire. [Background technology]

[0002] In recent years, there has been a strong demand for low fuel consumption of automobiles, and tires with low rolling resistance are in demand. For this reason, rubber compositions for use in tire treads and the like that have low tan δ and excellent low heat build-up properties are desired.

[0003] In conventional pneumatic tires, measures such as increasing the particle size of the carbon black in the rubber composition or reducing the amount of carbon black mixed in can be considered in order to achieve low heat generation. However, at the same time, there are problems in that the abrasion resistance of the tread rubber is reduced and the fracture resistance of the rubber, such as cut resistance and chipping resistance, is reduced. Therefore, there has been a demand for the development of a technology that can improve low heat generation without deteriorating other physical properties such as strength.

[0004] As one of the techniques for improving low heat build-up properties, for example, Patent Document 1 discloses a rubber composition in which carbon black and a specific hydrazide compound are blended with an elastomer containing natural rubber in order to improve the dispersibility of carbon black in the rubber composition.

[0005] As a technique for improving the dispersibility of a filler contained in a rubber composition, for example, Patent Document 2 discloses a technique in which surface-treated silica-impregnated carbon black, which has silica adhering or depositing on its surface, is treated by reacting a silane coupling agent with the surface-treated silica-impregnated carbon black, and the surface is compounded with a rubber composition. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-27315 [Patent Document 2] JP 2009-185115 A Summary of the Invention [Problem to be solved by the invention]

[0007] The techniques disclosed in Patent Documents 1 and 2 both increase the dispersibility of the filler in the rubber composition, making it possible to improve low heat build-up properties. However, from the viewpoint of further reducing fuel consumption and improving durability, there has been a demand for the development of a rubber composition having excellent breaking strength and further improved filler dispersibility.

[0008] Therefore, an object of the present invention is to provide a rubber composition and a rubber composition for tires, which have excellent strength and improved filler dispersibility, and another object of the present invention is to provide a tire having low heat buildup and excellent durability. [Means for solving the problem]

[0009] As a result of investigations to solve the above problems, the present inventors have found that by using a rubber composition containing a rubber component containing a diene rubber and a composite filler, it is possible to improve the dispersibility of the filler to a certain degree while maintaining good strength. As a result of further intensive research, it has been found that by making the composite filler contain a carbon-based filler, an inorganic filler, and a cationic polymer compound, it is possible to significantly improve the dispersibility of the filler compared to a normal compounding, and it is also possible to improve the strength of the rubber composition.

[0010] That is, the rubber composition of the present invention is a rubber composition comprising a rubber component containing a diene-based rubber and a composite filler, and is characterized in that the composite filler contains a carbon-based filler, an inorganic filler, and a cationic polymer compound. By having the above-mentioned configuration, it is possible to improve the dispersibility of the filler while maintaining excellent strength.

[0011] In addition, in the rubber composition of the present invention, the content of the composite filler is preferably 10 to 100 parts by mass per 100 parts by mass of the rubber component, because this allows for achieving superior strength without reducing the dispersibility of the filler.

[0012] Furthermore, in the rubber composition of the present invention, it is preferable that the carbon-based filler contains at least carbon black, since this makes it possible to realize better strength and dispersibility of the filler.

[0013] Furthermore, in the rubber composition of the present invention, it is preferable that the inorganic filler contains at least silica, since this makes it possible to realize better strength and dispersibility of the filler.

[0014] In addition, in the rubber composition of the present invention, the weight average molecular weight of the cationic polymer compound is preferably 5,000 to 100,000. This is because better dispersibility of the filler can be achieved.

[0015] Furthermore, the rubber composition of the present invention preferably further contains a silane coupling agent, because this can increase the elastic modulus of the rubber composition.

[0016] The rubber composition for a tire of the present invention is characterized by comprising the above-mentioned rubber composition of the present invention. By having the above-mentioned configuration, it is possible to improve the dispersibility of the filler while maintaining excellent strength.

[0017] The tire of the present invention is characterized by using the above-mentioned rubber composition of the present invention. By providing the above configuration, excellent low heat generation properties and durability can be achieved. Effect of the Invention

[0018] According to the present invention, it is possible to provide a rubber composition and a rubber composition for a tire, which have excellent strength and improved filler dispersibility, and also to provide a tire having low heat buildup and excellent durability. [Brief description of the drawings]

[0019] [Figure 1] 3 is a photograph showing an enlarged view of the state of the structure of each of the samples of the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, the embodiments of the present invention will be specifically illustrated and described. <Rubber composition> The rubber composition of the present invention includes a rubber component containing a diene rubber and a composite filler. The rubber composition of the present invention is characterized in that the composite filler contains a carbon-based filler, an inorganic filler, and a cationic polymer compound.

[0021] The carbon-based filler constituting the composite filler has a positive charge, and the inorganic filler constituting the composite filler has a negative charge. Therefore, by using these fillers as the composite filler, the carbon-based filler and the inorganic filler are blended in a rubber composition in an adsorbed state, so that the carbon-based filler and the inorganic filler are prevented from individually agglomerating, and the dispersion of the filler can be prevented from being hindered. Furthermore, in the present invention, by incorporating a cationic polymer compound as a filler to be blended in the rubber composition, the adsorption between the above-mentioned carbon-based filler and the inorganic filler can be promoted, so that the aggregation of each of the above-mentioned fillers can be further suppressed, and the dispersibility of the filler in the rubber composition blended with the composite filler can be greatly improved.

[0022] Each component constituting the rubber composition of the present invention will be described below. (Rubber component) The rubber component contained in the rubber composition of the present invention contains a diene rubber. By containing the diene rubber, the strength of the rubber can be increased. Examples of the diene rubber include natural rubber, polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), etc., and among these, it is preferable to use at least one of natural rubber and styrene-butadiene copolymer rubber (SBR), because this allows for better strength and low heat buildup. The diene rubber may be contained alone or in the form of a blend of two or more kinds.

[0023] The content of the diene rubber in the rubber component is not particularly limited, but from the viewpoint of maintaining excellent strength, it is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0024] (Composite filler) The rubber composition of the present invention contains a composite filler in addition to the above-mentioned rubber component. The composite filler is a filler that is not mixed individually when mixed into a rubber composition, but is previously combined into a single filler (composite filler). By mixing various fillers into a rubber composition as a composite filler, aggregation of each filler can be suppressed, and dispersibility can be improved compared to when each filler is mixed individually.

[0025] Here, the composite filler contains a carbon-based filler, an inorganic filler, and a cationic polymer compound. A carbon-based filler such as carbon black having a positive charge is adsorbed (bonded) to an inorganic filler such as silica having a negative charge. The cationic polymer compound amplifies the charge of the carbon-based filler and promotes the bonding force between the carbon-based filler and the inorganic filler in the composite filler. As a result, in the rubber composition of the present invention, the dispersibility of each filler contained therein is increased, and thereby the reinforcing property of the rubber composition can also be improved.

[0026] The content of the composite filler is not particularly limited, but is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass, and even more preferably 30 to 70 parts by mass, relative to 100 parts by mass of the rubber component. By making the content of the composite filler 10 parts by mass or more relative to 100 parts by mass of the rubber component, the effect of improving the reinforcing property by containing the filler can be sufficiently obtained, and by making the content of the composite filler 100 parts by mass or less relative to 100 parts by mass of the rubber component, the deterioration of the dispersibility of the filler can be more reliably suppressed.

[0027] The carbon-based filler constituting the composite filler is a filler mainly composed of carbon, and examples thereof include carbon black, carbon nanotubes, carbon nanofibers, graphite, graphene, etc. Among these, it is preferable to contain at least carbon black, which is easy to obtain and can further increase the strength of the rubber composition. Examples of the carbon black include carbon black of GPF, FEF, SRF, HAF, ISAF, IISAF, SAF grade, etc. Note that only one type of these carbon-based fillers can be contained, or multiple types can be contained. Here, the content (mass%) of the carbon black in the composite filler is not particularly limited, but from the viewpoint of improving the dispersibility of the filler and increasing the strength of the rubber composition, it is preferably 5 to 50 mass%, and more preferably 10 to 40 mass%.

[0028] Examples of the inorganic filler constituting the composite filler include silica, and oxides or hydrates of metals such as aluminum, magnesium, titanium, calcium, and zirconium. Among these, the inorganic filler preferably contains at least silica, from the viewpoint of increasing the strength of the rubber composition and contributing to improving the dispersibility of the filler. As the silica, wet silica, dry silica, colloidal silica, and the like can be used. Note that only one type of these inorganic fillers can be contained, or multiple types can be contained. Here, the content (mass%) of the silica in the composite filler is not particularly limited, but from the viewpoint of improving the dispersibility of the filler and increasing the strength of the rubber composition, it is preferably 50 to 95 mass%, and more preferably 60 to 90 mass%.

[0029] The cationic polymer compound that constitutes the composite filler is a cationic polymer electrolyte, and when contained in the composite filler, it adheres to the carbon-based filler and exerts the effect of amplifying the charge of the carbon-based filler.

[0030] The cationic polymer compound is not particularly limited as long as it can increase the positive charge, but from the viewpoint of more reliably increasing the dispersibility of the filler, the weight average molecular weight is preferably 5000 to 100000, and more preferably 10000 to 100000. The weight average molecular weight of the cationic polymer compound is determined as a polystyrene equivalent value by gel permeation chromatography (GPC). Examples of cationic polymer compounds having such a weight average molecular weight include polyethyleneimine, polydiallyldimethylammonium chloride, dimethylamine-epichlorohydrin polycondensates, dialkylamine-ammonia-epichlorohydrin polycondensates, diallylamine hydrochloride-acrylamide copolymers, and dicyandiamide-polyalkylenepolyamine polycondensates.

[0031] Here, the content (mass%) of the cationic polymer compound in the composite filler is not particularly limited, but from the viewpoint of improving the dispersibility of the filler, it is preferably 0.05 to 4%, and more preferably 0.1 to 2%.

[0032] The method for obtaining the composite filler is not particularly limited, and the carbon-based filler, the inorganic filler, and the cationic polymer compound can be mixed by a known method to form the composite filler. For example, a composite filler can be obtained by preparing a slurry solution containing the carbon-based filler, the inorganic filler, and the cationic polymer compound, stirring and mixing the mixture, and then drying the mixture.

[0033] (Other Ingredients) In addition to the rubber component and the composite filler, the rubber composition of the present invention may contain compounding agents commonly used in the rubber industry, such as silane coupling agents, crosslinking agents, vulcanization accelerators, antioxidants, softeners, stearic acid, zinc oxide, etc. (hereinafter collectively referred to as "other components"), which are appropriately selected within a range that does not impair the object of the present invention. As these other components, commercially available products can be suitably used.

[0034] Among the other components, a silane coupling agent is preferably contained since it can increase the elastic modulus of the rubber composition. The silane coupling agent may be any known silane coupling agent. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxy ... Examples of the silane coupling agent include bamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, 3-octanoylthiopropyltriethoxysilane, etc. These silane coupling agents may be used alone or in combination of two or more.

[0035] Furthermore, the content of the silane coupling agent varies depending on the type of silane coupling agent, but is more preferably 0.5 to 20 parts by mass relative to 100 parts by mass of the composite filler. By making the content of the silane coupling agent 0.5 parts by mass or more relative to 100 parts by mass of the composite filler, the effect of improving the elastic modulus can be more reliably obtained, and by making the content of the silane coupling agent 20 parts by mass or less relative to 100 parts by mass of the composite filler, the decrease in cut resistance of the rubber composition can be suppressed.

[0036] The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose. For example, sulfur-based crosslinking agents, organic peroxide-based crosslinking agents, inorganic crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, sulfur compound-based crosslinking agents, oxime-nitrosamine-based crosslinking agents, etc. are listed. Among these crosslinking agents, sulfur-based crosslinking agents (vulcanizing agents) are more preferable for rubber compositions for tires. The content of the crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose, but it is preferably 0.1 to 20 parts by mass per 100 parts by mass of the rubber component.

[0037] In addition, when sulfur is used as the crosslinking agent, it is preferable to include a vulcanization accelerator. As the vulcanization accelerator, a conventionally known one can be used, and there is no particular limitation. For example, sulfenamide-based vulcanization accelerators such as CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (Nt-butyl-2-benzothiazylsulfenamide), and TBSI (Nt-butyl-2-benzothiazylsulfenimide) can be mentioned; guanidine-based vulcanization accelerators such as DPG (diphenylguanidine); thiuram-based vulcanization accelerators such as tetraoctylthiuram disulfide and tetrabenzylthiuram disulfide; and zinc dialkyldithiophosphate. The content is preferably less than the content of the sulfur, and more preferably about 1 to 10 parts by mass per 100 parts by mass of the rubber component.

[0038] The method for preparing the rubber composition before vulcanization is not particularly limited, and any known method can be used. For example, the rubber composition can be obtained by adding each compounding component simultaneously or in any order and kneading the components using a kneading machine such as a Banbury mixer, a roll, or an internal mixer.

[0039] <Rubber composition for tires> The rubber composition for a tire of the present invention is characterized by comprising the above-mentioned rubber composition of the present invention. The rubber composition of the present invention has excellent strength and improved filler dispersibility, and is therefore suitable as a rubber composition for use in tires. Other matters regarding the rubber composition for tires of the present invention are the same as those explained above in connection with the rubber composition of the present invention.

[0040] <Tires> The tire of the present invention is characterized by being made using the tire rubber composition of the present invention described above. The tire of the present invention uses, as a material, the tire rubber composition of the present invention, which has excellent strength and improved filler dispersibility, and therefore can achieve excellent low heat generation properties and durability. The portion to which the rubber composition is applied is not particularly limited, and may be used in at least one of the tread portion, shoulder portion, sidewall portion, bead portion, belt layer (belt coating rubber), and carcass (ply coating rubber). Among these portions, the rubber composition is preferably used in the tread portion. By applying the rubber composition to the tire tread portion, it is possible to improve performance such as low rolling resistance and abrasion resistance. The tire of the present invention can be manufactured according to a conventional method without any particular limitation other than using the above-mentioned rubber composition of the present invention for any of the tire components. The gas to be filled in the tire can be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. EXAMPLES

[0041] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0042] <Samples 1-6> According to the compounding recipe shown in Table 1, samples of the rubber composition were prepared. Each sample of the prepared rubber composition was evaluated by the following methods.

[0043] (1) Tensile strength The rubber composition of each sample was vulcanized at 145°C for 33 minutes to obtain a vulcanized rubber. In accordance with JIS K 6251 (2017), the test piece was pulled at a specified speed (300±25mm / min) at 25°C until it broke, and the maximum tensile force (unit: MPa) required to break the test piece was measured. The measurement results of the tensile strength are shown in Table 1. A larger value indicates better strength.

[0044] (2) 200% elastic modulus The rubber composition of each sample was vulcanized for 33 minutes at 145° C. The elastic modulus at 200% elongation (200% modulus) of the obtained vulcanized rubber was measured in accordance with JIS K 6251 (2010). The measurement results of the 200% elastic modulus are shown in Table 1. The larger the value, the better the elastic modulus. The results of observing the cross section of the vulcanized rubber of each sample are shown in Figure 1.

[0045] (3) Filler dispersion (white area) Each rubber composition was vulcanized at 145° C. for 33 minutes to obtain a vulcanized rubber. The white area (%) of the obtained vulcanized rubber was measured using a disperser (manufactured by Tech Pro, USA) to evaluate the dispersibility of carbon. The larger the white area, the larger the filler aggregates are, and the smaller the value, the better the dispersibility.

[0046] [Table 1]

[0047] *1: Styrene butadiene rubber, JSR Corporation "SBR♯1500" *2: "HS-100" manufactured by Denka Co., Ltd. *3: Silica synthesized by Toyama Prefectural University (dried version of "Snowtex (registered trademark) YL" manufactured by Nissan Chemical Industries, Ltd.) *4: A composite filler containing carbon black and silica, made by mixing approximately 2% by mass of carbon black (Denka Black (registered trademark) HS-100 manufactured by Denka Co., Ltd.) and approximately 12.5% ​​by mass of silica (Nissan Chemical Industries, Ltd.'s Snowtex (registered trademark) YL) in a water slurry solution, stirring and mixing, and then drying. *5: A composite filler containing carbon black, silica, and a cationic polymer compound. Approximately 2% by mass of carbon black (Denka Black® HS-100 manufactured by Denka Co., Ltd.), approximately 12.5% ​​by mass of silica (Snowtex® YL manufactured by Nissan Chemical Industries, Ltd.), and approximately 0.05% by mass of a cationic polymer compound (polydiallyldimethylammonium chloride, Unisense FPA100L manufactured by Senka Co., Ltd.) are stirred and mixed in a water slurry solution and then dried. *6: Bis(3-triethoxysilylpropyl)tetrasulfide, Evonik "Si69" *7: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, "Knocklac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. *8: Diphenylguanidine, "Noccela D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. *9: Benzothiazyl disulfide, "Noccela DM-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. *10: Nt-butyl-2-benzothiazylsulfenamide, "Noccela NS-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0048] From the results in Table 1, it was found that the rubber compositions of each Example exhibited strength and elongation. On the other hand, the rubber compositions of each Comparative Example showed results inferior to those of the Examples in either strength or elongation. Furthermore, from the results in Table 1 and FIG. 1, it was found that the rubber compositions of each Example were excellent in filler dispersibility. On the other hand, it was found that the rubber compositions of the Comparative Examples did not achieve sufficient filler dispersibility. [Industrial Applicability]

[0049] According to the present invention, it is possible to provide a rubber composition and a rubber composition for a tire, which have excellent strength and improved filler dispersibility, and also to provide a tire having low heat buildup and excellent durability.

Claims

1. A rubber composition comprising a rubber component containing a diene rubber and a composite filler, The composite filler contains a carbon-based filler, an inorganic filler containing at least silica, and a cationic polymer compound, The rubber composition has a composite filler content of 10 to 100 parts by mass per 100 parts by mass of the rubber component.

2. The rubber composition according to claim 1 , wherein the carbon-based filler comprises at least carbon black.

3. 3. The rubber composition according to claim 1, wherein the cationic polymer compound has a weight average molecular weight of 5,000 to 100,000.

4. The rubber composition according to any one of claims 1 to 3, further comprising a silane coupling agent.

5. A rubber composition for tires, comprising the rubber composition according to any one of claims 1 to 4.

6. A tire comprising the rubber composition for tires according to claim 5.

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