Rubber composition for tires, and pneumatic tire

Abstract

To provide a rubber composition for tires which serves as a raw material of a vulcanized rubber for tires improved in WET performance, rolling resistance and wear resistance in a well-balanced manner, and to provide a pneumatic tire comprising a vulcanized rubber of the rubber composition.SOLUTION: The rubber composition for tires contains a rubber component, carbon black, and a vegetable oil. The nitrogen adsorption specific surface area of the carbon black is 120-250 (m2 / g). The nitrogen adsorption specific surface area of the carbon black is preferably 160-250 (m2 / g).SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Pneumatic tires are expected to be driven in a variety of environments, and improving tire performance on wet road surfaces (hereinafter also referred to as "wet performance") is essential.

[0003] In the following Patent Document 1, a crosslinkable or crosslinked rubber composition that can be used to constitute a tire tread is described, which comprises at least 50 phr to 100 phr of a major component diene elastomer selected from the group consisting of a styrene-butadiene copolymer prepared in a solution, a styrene-butadiene copolymer prepared in an emulsion, natural polyisoprene, a synthetic polyisoprene having a cis-1,4 bond content of more than 95%, and a mixture of these elastomers, and 0 phr to 50 phr of a minor component diene elastomer which is a polybutadiene having a cis-1,4 bond content of more than 90%. and a plasticizer containing a vegetable oil containing at least one glycerol oleate triester, the vegetable oil being sunflower oil, in which oleic acid accounts for 70% or more by mass of the total fatty acids, at a mass fraction of 45% to 100%, and one or more paraffinic, aromatic or naphthenic plasticizing oils extracted from petroleum at a mass fraction of 55% to 0%, the amount of sunflower oil being in the range of 10 to 40 phr, and the amount of the optionally contained plasticizing oil extracted from petroleum being in the range of 0 to 30 phr.

[0004] Patent Document 2 listed below describes a rubber composition for tire treads, which contains raw rubber including 20 to 50 parts by weight of a first styrene-butadiene rubber, 20 to 50 parts by weight of a second styrene-butadiene rubber, and 10 to 40 parts by weight of a butadiene rubber (BR), and further contains, relative to 100 parts by weight of the raw rubber, 80 to 180 parts by weight of a reinforcing filler, 2 to 50 parts by weight of a natural oil, and 2 to 30 parts by weight of a hydrocarbon resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4209200 [Patent Document 2] JP2019-172957A Summary of the Invention [Problem to be solved by the invention]

[0006] The techniques described in Patent Documents 1 and 2 both address the issue of improving the wet performance of pneumatic tires. As a result of extensive research, the present inventors have found that there is a trade-off between wet performance and rolling resistance, and that there is room for further improvement when the wear resistance of pneumatic tires is also taken into consideration.

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a rubber composition for tires, which is a raw material for vulcanized rubber for tires having improved and balanced wet performance, rolling resistance, and abrasion resistance, and a pneumatic tire including vulcanized rubber of the rubber composition. [Means for solving the problem]

[0008] The above-mentioned problems can be solved by the following constitution. That is, the present invention is a rubber composition for tires containing a rubber component, carbon black, and vegetable oil, wherein the nitrogen adsorption specific surface area of ​​the carbon black is 120 to 250 (m 2 / g).

[0009] In the rubber composition for tires (1), the nitrogen adsorption specific surface area of ​​the carbon black is 160 to 250 (m 2 / g) is preferred.

[0010] In the above rubber composition for tires (1) or (2), the vegetable oil is preferably a rubber composition for tires (3) having an iodine value of 95 or less.

[0011] In any one of the rubber compositions for tires (1) to (3), a rubber composition for tires (4) in which the vegetable oil is sunflower oil is preferred.

[0012] In any of the rubber compositions for tires (1) to (4), a rubber composition for tires (5) is preferred in which the amount of the carbon black is 70 to 150 parts by mass when the total amount of the rubber components is taken as 100 parts by mass.

[0013] In any of the rubber compositions for tires (1) to (5), a rubber composition for tires (6) is preferred in which the amount of the vegetable oil is 20 to 100 parts by mass when the total amount of the rubber components is taken as 100 parts by mass.

[0014] The present invention also relates to a pneumatic tire (7) having a rubber member formed by vulcanization molding of any of the above rubber compositions for tires (1) to (6). Effect of the Invention

[0015] The nitrogen adsorption specific surface area of ​​carbon black is inversely proportional to the particle size, and the particle size of carbon black with a large nitrogen adsorption specific surface area is small. Here, when carbon black with a small particle size, for example SAF or carbon black with a particle size smaller than SAF, is blended into rubber, the viscosity of the rubber compound during mixing becomes very high, making it difficult to mix uniformly, and so dispersibility in the rubber tends to deteriorate. This tendency becomes even more pronounced as the blending amount of carbon black increases. With regard to this tendency, the present inventors have found that carbon black with a nitrogen adsorption specific surface area of ​​120 to 250 (m 2 It has been found that when carbon black having a particle size of 10 ...

[0016] The vulcanized rubber of the rubber composition for tires according to the present invention has a well-balanced improvement in wet performance, rolling resistance and abrasion resistance, and is therefore particularly useful for use in the tread of pneumatic tires. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The rubber composition for a tire according to the present invention contains a rubber component, carbon black and vegetable oil.

[0018] The rubber composition for tires according to the present invention contains a rubber component. As the rubber component, for example, a diene rubber is preferable. 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, and styrene-isoprene-butadiene copolymer rubber. These may be used alone or in combination of two or more.

[0019] The rubber composition for tires according to the present invention is made of small particle size carbon black, specifically carbon black having a nitrogen adsorption specific surface area of ​​120 to 250 (m 2 / g). When such small particle size carbon black is blended into rubber, the viscosity of the rubber compound during mixing generally becomes very high, making it difficult to mix uniformly. However, in the present invention, blending it together with vegetable oil enhances the plasticizing performance of the rubber compound during mixing, resulting in a significant increase in the dispersibility of the carbon black in the rubber. In the present invention, the effect of improving dispersibility by the vegetable oil, and therefore the effect of improving WET performance, rolling resistance, and abrasion resistance in a balanced manner, are particularly enhanced in the range where the particle size of the carbon black is smaller or the blending amount of carbon black is greater. Specifically, the lower limit of the nitrogen adsorption specific surface area of ​​the carbon black used in the present invention is 130 (m 2 / g), and 160 (m 2 On the other hand, the upper limit of the nitrogen adsorption specific surface area of ​​the carbon black used in the present invention is 250 (m 2 / g), and 225 (m 2 / g). The lower limit of the amount of carbon black used in the present invention is preferably 60 parts by mass, more preferably 70 parts by mass, and particularly preferably 80 parts by mass, when the total amount of the rubber components is 100 parts by mass. On the other hand, the upper limit of the amount of carbon black used in the present invention is preferably 150 parts by mass, more preferably 140 parts by mass, and particularly preferably 130 parts by mass, when the total amount of the rubber components is 100 parts by mass.

[0020] The rubber composition according to the present invention is characterized in that vegetable oil is blended together with carbon black having a specific particle size. From the viewpoint of improving the dispersibility of carbon black, and thus from the viewpoint of improving the WET performance, rolling resistance, and abrasion resistance in a well-balanced manner when the rubber is vulcanized, it is preferable to use a vegetable oil having an oleic acid content of 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 70% by mass or more. The iodine value of the vegetable oil used in the present invention is preferably 95 or less, more preferably 90 or less. Since such vegetable oil has a relatively small amount of double bonds, it is possible to suppress the deterioration of scorch property when the rubber is vulcanized. As the vegetable oil used in the present invention, sunflower oil and palm oil are preferable, and sunflower oil is particularly preferable. The lower limit of the blending amount of the vegetable oil used in the present invention is preferably 10 parts by mass, more preferably 20 parts by mass, and particularly preferably 30 parts by mass, when the total amount of the rubber component is 100 parts by mass. On the other hand, the upper limit of the amount of the vegetable oil used in the present invention is preferably 100 parts by mass, more preferably 80 parts by mass, and particularly preferably 70 parts by mass, when the total amount of the rubber component is 100 parts by mass.

[0021] The rubber composition for tires according to the present invention may contain, in addition to the rubber component, carbon black and vegetable oil, silica, a silane coupling agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, stearic acid, a softener such as wax or oil, a processing aid, etc.

[0022] As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica, etc., which are used for ordinary rubber reinforcement, are used. Among them, wet silica is preferable. However, in the rubber composition for tires according to the present invention, from the viewpoint of maintaining a high effect of improving the dispersibility of carbon black, it is preferable that the composition does not contain silica, and even if the composition contains silica, the compounding amount is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, when the total amount of the rubber component is 100 parts by mass.

[0023] When silica is contained as a filler, it is also preferable to contain a silane coupling agent together. The silane coupling agent is not particularly limited as long as it contains sulfur in the molecule, and various silane coupling agents that are compounded together with silica in rubber compositions can be used. Examples of the silanes include sulfide silanes such as bis(3-triethoxysilylpropyl)tetrasulfide (e.g., "Si69" manufactured by Degussa), bis(3-triethoxysilylpropyl)disulfide (e.g., "Si75" manufactured by Degussa), bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)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.

[0024] As the vulcanizing agent, sulfur can be suitably used. The sulfur may be any ordinary rubber sulfur, for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur, etc. In the rubber composition for tires according to the present invention, the content of the vulcanizing agent is preferably 0.5 to 3.5 parts by mass when the total amount of the rubber component is 100 parts by mass.

[0025] As the vulcanization accelerator, those vulcanization accelerators usually used for rubber vulcanization, such as sulfenamide-based vulcanization accelerators, thiuram-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiourea-based vulcanization accelerators, guanidine-based vulcanization accelerators, and dithiocarbamate-based vulcanization accelerators, may be used alone or in appropriate mixtures.

[0026] As the age resistor, age resistors generally used for rubber, such as aromatic amine-based age resistors, amine-ketone-based age resistors, monophenol-based age resistors, bisphenol-based age resistors, polyphenol-based age resistors, dithiocarbamate-based age resistors, and thiourea-based age resistors, may be used alone or in appropriate mixtures.

[0027] The rubber composition for tires according to the present invention can be obtained by kneading a rubber component, carbon black, vegetable oil, silica, a silane coupling agent, a vulcanizing agent, a vulcanization accelerator, zinc oxide, an antioxidant, stearic acid, a softener such as wax, a processing aid, and the like, using a kneading machine typically used in the rubber industry, such as a Banbury mixer, a kneader, or a roll.

[0028] The method for blending each of the above components is not particularly limited, and may be any of a method in which the components other than the vulcanization-based compounding agents such as the vulcanizing agent and vulcanization accelerator are previously blended to form a master batch, and the remaining components are then added and further kneaded; a method in which the components are added in any order and kneaded; and a method in which all of the components are added simultaneously and kneaded.

[0029] The vulcanized rubber of the rubber composition for tires according to the present invention has a well-balanced improvement in wet performance, rolling resistance and abrasion resistance, and is therefore particularly useful for use in the tread of pneumatic tires. EXAMPLES

[0030] The present invention will be explained more specifically below by describing examples thereof.

[0031] (Preparation of Rubber Composition for Tires) The rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 3 were compounded with 100 parts by mass of the rubber component according to the compounding recipes in Tables 1 and 2, and kneaded using a normal Banbury mixer to prepare rubber compositions for tires. Each compounding ingredient in Tables 1 and 2 is shown below.

[0032] (Rubber component) SBR1 (ESBR (emulsion polymerized SBR)): Product name "SBR1502" (manufactured by ENEOS Materials Co., Ltd.) SBR2 (SSBR (solution polymerization SBR)): Product name "HPR355" (manufactured by ENEOS Materials Co., Ltd.) BR1: Product name "BR150B" (manufactured by UBE Elastomers) (Carbon Black) Carbon Black 1 (CB1) (SAF): Product name "Seast 9" (manufactured by Tokai Carbon Co., Ltd.) Nitrogen adsorption specific surface area 142 (m 2 / g) Carbon Black 2 (CB2) (SAF): Product name "Diablack UX10" (manufactured by Mitsubishi Chemical Corporation) Nitrogen adsorption specific surface area 190 (m 2 / g) (vegetable oil) Vegetable oil 1 (soybean white refined oil): (Nisshin Oillio Co., Ltd.) Iodine value: 128, Oleic acid: 23% by mass Vegetable oil 2 (sunflower oil): (Nisshin Oillio Co., Ltd.) Iodine value: 84, Oleic acid: 82% by mass Vegetable oil 3 (PL65 (palm olein)): (Nisshin Oillio Co., Ltd.) Iodine value: 65, Oleic acid: 48% by weight (Other Ingredients) Silica: Product name "Nipsil AQ" (manufactured by Tosoh Corporation) Silane coupling agent: Product name "Si69" (manufactured by Degussa) Naphthenic oil: Product name "Process NC140" (manufactured by JOMO) Stearic acid: Trade name "Lunac S-20" (manufactured by Kao Corporation) Zinc oxide: Product name "Zinc Oxide No. 1" (manufactured by Mitsui Mining & Smelting Co., Ltd.) Wax: Product name "OZOACE0355" (manufactured by Nippon Seiro Co., Ltd.) Anti-aging agent 1: Product name "Nocrac 6C" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Anti-aging agent 2: Product name "Antage RD" (manufactured by Kawaguchi Chemical Industry Co., Ltd.) Hydrocarbon resin: Product name "Petrotack 90" (manufactured by Tosoh Corporation) Vulcanization accelerator 1: Product name "Noccelaer D" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Vulcanization accelerator 2: Trade name "Sokushinol CZ" (manufactured by Sumitomo Chemical Co., Ltd.) Sulfur: Product name: Powdered sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0033] Unvulcanized samples of the rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 3 obtained above were prepared, and then the viscosity (processability) of the unvulcanized rubber compositions, the WET index (WET performance) of the vulcanized rubber, the heat generation index (rolling resistance) of the vulcanized rubber, and the LA index (abrasion resistance) of the vulcanized rubber were evaluated under the following conditions.

[0034] (Viscosity of Unvulcanized Rubber Composition (Processability)) In accordance with JIS K6300, the torque value after 4 minutes was measured in Mooney units using a rotorless Mooney measuring machine manufactured by Toyo Seiki Co., Ltd. after preheating the unvulcanized rubber at 100°C for 1 minute. For Examples 1 and 2, the value is expressed as an index with the value of Comparative Example 1 set to 100, and for Examples 3 to 6 and Comparative Example 3, the value is expressed as an index with the value of Comparative Example 2 set to 100. A smaller value indicates a lower viscosity of the unvulcanized rubber and better processability.

[0035] (WET index of vulcanized rubber (WET performance)) Using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd., the loss factor tan δ was measured at a frequency of 10 Hz, static strain of 10%, dynamic strain of 1%, and temperature of 0° C. For Examples 1 and 2, the value of Comparative Example 1 is expressed as an index of 100, and for Examples 3 to 6 and Comparative Example 3, the value of Comparative Example 2 is expressed as an index of 100. A larger value indicates better wet grip performance.

[0036] (Heat index of vulcanized rubber (rolling resistance)) A viscoelasticity tester manufactured by Toyo Seiki Co., Ltd. was used to measure the loss factor tan δ at a frequency of 10 Hz, static strain of 10%, dynamic strain of 1%, and temperature of 60° C. For Examples 1 and 2, the value of Comparative Example 1 is expressed as an index of 100, and for Examples 3 to 6 and Comparative Example 3, the value of Comparative Example 2 is expressed as an index of 100. A smaller value indicates less heat generation and better rolling resistance performance.

[0037] (LA index (abrasion resistance) of vulcanized rubber) The amount of wear was measured using a Lambourn abrasion tester in accordance with JIS K6264 under a load of 3 kg, a slip rate of 20%, and a temperature of 23° C. For Examples 1 and 2, the inverse of the value of Comparative Example 1 was expressed as an index value set to 100, and for Examples 3 to 6 and Comparative Example 3, the inverse of the value of Comparative Example 2 was expressed as an index value set to 100. A larger value indicates better abrasion resistance.

[0038] [Table 1]

[0039] The results in Table 1 show that, when the total amount of the rubber components is taken as 100 parts by mass, in a compounding system in which the carbon black content is high at around 90 parts by mass, the unvulcanized rubber compositions of Examples 1 and 2, which use sunflower oil, a vegetable oil, have a lower viscosity and are excellent in dispersibility of carbon black, compared to the unvulcanized rubber composition of Comparative Example 1, which uses naphthenic oil, a mineral oil. It is also seen that the vulcanized rubber of the unvulcanized rubber compositions of Examples 1 and 2 has a well-balanced improvement in WET performance, rolling resistance and abrasion resistance. In particular, the nitrogen adsorption specific surface area of ​​190 (m 2 It can be seen that in Example 2, which used carbon black 2 having a carbon black content of 1.0 g / g, the wet performance and abrasion resistance are significantly improved.

[0040] [Table 2]

[0041] From the results in Table 2, when the total amount of the rubber components is taken as 100 parts by mass, in a compounding system in which the carbon black content is particularly high at around 120 parts by mass, the unvulcanized rubber compositions of Examples 3 and 4, which use sunflower oil, a vegetable oil, and the unvulcanized rubber composition of Example 5, which uses palm oil, have lower viscosity and are excellent in dispersibility of carbon black, compared to the unvulcanized rubber compositions of Comparative Examples 2 and 3, which use naphthenic oil, a mineral oil. The unvulcanized rubber composition of Example 6, which uses soybean oil, showed a viscosity equivalent to that of Comparative Example 2, which used naphthenic oil, a mineral oil. It is also found that the vulcanized rubbers of the unvulcanized rubber compositions of Examples 3 to 5 have a well-balanced improvement in WET performance, rolling resistance, and abrasion resistance. In particular, the nitrogen adsorption specific surface area of ​​190 (m 2 It can be seen that in Examples 4 and 5, in which carbon black 2 having a molecular weight of 1.001g / g was used, the wet performance and abrasion resistance were further improved.

Claims

1. A rubber composition for tires containing a rubber component, carbon black, and vegetable oil, The carbon black has a nitrogen adsorption specific surface area of ​​120 to 250 (m ２ / g).

2. The carbon black has a nitrogen adsorption specific surface area of ​​160 to 250 (m ２ 2. The rubber composition for tires according to claim 1, wherein the molecular weight of the rubber component is 1 / g.

3. The rubber composition for a tire according to claim 1, wherein the vegetable oil has an iodine value of 95 or less.

4. 2. The rubber composition for tires according to claim 1, wherein said vegetable oil is sunflower oil.

5. 2. The rubber composition for tires according to claim 1, wherein the amount of the carbon black is 70 to 150 parts by mass when the total amount of the rubber components is 100 parts by mass.

6. 2. The rubber composition for tires according to claim 1, wherein the amount of the vegetable oil is 20 to 100 parts by mass when the total amount of the rubber components is 100 parts by mass.

7. A pneumatic tire comprising a rubber member formed by vulcanization molding the rubber composition for tires according to claim 1.

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