Rubber composition and tires

Abstract

The present invention provides a tire rubber composition containing plant-derived raw materials that can replace some or all of the mineral oil. [Solution] The rubber composition according to the embodiment contains diene rubber, silica, plant-derived oleic acid glyceride, and an optional mineral oil. The oleic acid glyceride contains monooleic acid glyceride as part of it. The mineral oil (including the spreading oil) is included such that the mass ratio of the mineral oil to the oleic acid glyceride is 0 or more and 5.0 or less.

Description

Technical Field

[0001] The present invention relates to a rubber composition and a tire using the same.

Background Art

[0002] Generally, as a plasticizer blended during the production of a rubber composition, mineral oils such as aromatic oil, naphthene oil, and paraffin oil are used.

[0003] On the other hand, it is known to blend a surfactant such as glycerin monofatty acid ester as an additive in a rubber composition. For example, in Patent Document 1, a diene rubber having a heteroatom-containing functional group in the main chain and / or at the terminal is blended with silica, a silane coupling agent, and a glycerin monofatty acid ester derived from a fatty acid having 8 to 24 carbon atoms, and a rubber composition excellent in dispersibility of silica and low fuel consumption without reducing processability and hardness is disclosed.

[0004] In Patent Document 2, a rubber composition excellent in dispersibility, processability, and rolling resistance of silica is disclosed by blending a diene rubber, silica having a BET specific surface area of 200 to 400 m 2 / g, a silane coupling agent, and a glycerin monofatty acid ester derived from a fatty acid having 8 to 24 carbon atoms.

[0005] In Patent Document 3, a rubber component composed of natural rubber and / or diene rubber, a glycerin fatty acid ester composition containing glycerin fatty acid monoester, and silica having a BET specific surface area of 100 to 130 m 2 / g is disclosed, which achieves both grip performance and WET performance and abrasion resistance, and has processability for a tire rubber composition.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] From the perspective of resource conservation and environmental considerations, there is a need to develop rubber compositions in which some or all of the mineral oil used as a plasticizer is replaced with new raw materials. When considering raw materials that can replace mineral oil (hereinafter sometimes referred to as "alternative raw materials"), it is desirable that the rubber composition containing the alternative raw material has at least equivalent physical properties to conventional rubber compositions. Furthermore, if plant-derived raw materials can be used as alternative raw materials, a reduction in the use of petroleum-derived resources can also be expected. However, for example, if mineral oil is replaced with vegetable oil, the physical properties of the vulcanized rubber may be inferior.

[0008] In view of the above, embodiments of the present invention aim to provide a tire rubber composition containing plant-derived raw materials that can replace part or all of mineral oil. [Means for solving the problem]

[0009] The present invention includes embodiments shown below. [1] A tire rubber composition comprising diene rubber, silica, plant-derived oleic acid glyceride, and an optional mineral oil, wherein the oleic acid glyceride includes monooleic acid glyceride, and the mass ratio of the mineral oil to the oleic acid glyceride is 0 or more and 5.0 or less. [2] The tire rubber composition according to [1], wherein the mass ratio of the mineral oil to the oleic acid glyceride is 0 or more and 1.5 or less. [3] A tire having a rubber portion made using the rubber composition described in [1] or [2]. [Effects of the Invention]

[0010] According to embodiments of the present invention, it is possible to provide a tire rubber composition containing plant-derived raw materials that can replace part or all of mineral oil. [Modes for carrying out the invention]

[0011] The inventors diligently investigated raw materials that could function as a substitute for mineral oil without degrading the properties of vulcanized rubber. As a result, they found that oleic acid glycerides derived from plants, specifically those containing monooleic acid glycerides, can replace part or all of the mineral oil, thereby reducing the use of petroleum-derived resources while improving the 300% modulus of vulcanized rubber. Oleic acid glycerides containing monooleic acid glycerides are thought to function as a substitute for mineral oil and improve the physical properties of vulcanized rubber because the unsaturated bond portion of oleic acid has high compatibility with rubber, and the hydroxyl groups of the glycerin skeleton increase its affinity with silica.

[0012] The rubber composition according to this embodiment comprises a diene rubber as a rubber component, silica as a reinforcing filler, oleic acid glyceride including monooleic acid glyceride, and mineral oil as plasticizers. Here, the mineral oil is an optional component, and therefore the rubber composition according to this embodiment may or may not contain mineral oil.

[0013] In this embodiment, diene rubber refers to rubber having repeating units corresponding to a diene monomer with a conjugated double bond, and the polymer's main chain contains a carbon-carbon double bond. Specific examples of diene rubber include natural rubber (NR), synthetic isoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber, among other diene rubbers commonly used in rubber compositions. These diene rubbers also include those with modified ends or main chains, or those modified to impart desired properties, as needed. These diene rubbers may be used individually or in combination of two or more types.

[0014] As the diene rubber, oil-applied diene rubber may be used. Examples of spreading oils used for oil-applied diene rubber include mineral oils such as aromatic oils, naphthenic oils, and paraffin oils.

[0015] In one embodiment, the diene rubber may include styrene-butadiene rubber (SBR). The SBR may be solution-polymerized styrene-butadiene rubber (SSBR) or emulsion-polymerized styrene-butadiene rubber (ESBR). Furthermore, the SBR may be modified styrene-butadiene rubber (modified SBR) or unmodified styrene-butadiene rubber (unmodified SBR), and these may be used in combination.

[0016] Preferably, in one embodiment, the diene rubber includes modified styrene-butadiene rubber (modified SBR). As the modified SBR, one is used that has been modified by introducing a functional group to the terminals and / or main chain. The functional group preferably contains an oxygen atom and / or a nitrogen atom, and examples include at least one selected from the group consisting of an amino group, a hydroxyl group, an alkoxy group, an alkoxysilyl group, an epoxy group, and a carboxyl group.

[0017] As the modified styrene-butadiene rubber (modified SBR), modified solution polymerization styrene-butadiene rubber (modified SSBR) may be used, modified emulsion polymerization styrene-butadiene rubber (modified ESBR) may be used, or a combination of these may be used. The amount of modified SBR in 100 parts by mass of the diene rubber is not particularly limited. For example, it may be 30 parts by mass or more, 40 parts by mass or more, or 50 parts by mass or more.

[0018] In one embodiment, the diene rubber may be used in combination with unmodified SBR and modified SBR, and preferably, unmodified ESBR and modified SSBR are used. For example, 100 parts by mass of the diene rubber may include 20 to 60 parts by mass, more preferably 30 to 50 parts by mass, of unmodified SBR (preferably unmodified ESBR), and 40 to 80 parts by mass, more preferably 50 to 70 parts by mass, of modified SBR (preferably modified SSBR).

[0019] In this embodiment, examples of the silica include wet silica and dry silica. Preferably, wet silica such as precipitated silica or gelled silica is used.

[0020] The BET specific surface area of the silica is not particularly limited. For example, it may be 100 to 300 m 2 / g, more preferably 150 to 250 m 2 / g. Here, the BET specific surface area of the silica is measured according to the BET method described in JIS K6430:2008.

[0021] The amount of silica is preferably 30 to 150 parts by mass, more preferably 50 to 120 parts by mass, more preferably 60 to 110 parts by mass, and still more preferably 70 to 100 parts by mass with respect to 100 parts by mass of the diene rubber.

[0022] The rubber composition according to this embodiment contains a plant-derived oleic acid glyceride, which includes monooleic acid glyceride as a part. Oleic acid glyceride is an ester of oleic acid and glycerin (glycerin fatty acid ester), and refers to a compound that includes monooleic acid glyceride, dioleic acid glyceride, and trioleic acid glyceride. The plant-derived oleic acid glyceride may be synthesized from plant-derived oleic acid and plant-derived glycerin.

[0023] The components of plant-derived oleic acid glycerides may include monooleic acid glycerides, dioleic acid glycerides, and / or trioleic acid glycerides, or they may contain only monooleic acid glycerides. The content of monooleic acid glycerides in the oleic acid glycerides is not particularly limited and may be, for example, 30-80%, 40-70%, or 50-60%. The content (%) of each component in the oleic acid glycerides is determined by measuring high-performance liquid chromatography (GPC). Specifically, for example, the content (%) of monooleic acid glycerides is calculated as an area percentage from the peak area value of the monooleic acid glyceride component within the total peak area obtained by GPC measurement.

[0024] The rubber composition according to this embodiment may contain propylene glycol along with plant-derived oleic acid glyceride. The amount of propylene glycol is not particularly limited; for example, it may be 20 parts by mass or less, or 5 to 15 parts by mass, per 100 parts by mass of oleic acid glyceride.

[0025] The rubber composition according to this embodiment may optionally contain mineral oil. Examples of mineral oil include aroma oil, naphthenic oil, and paraffin oil. These may be used individually or in combination of two or more.

[0026] In this embodiment, the mineral oil is included such that the mass ratio of mineral oil to oleic acid glyceride (mineral oil / oleic acid glyceride) is between 0 and 5.0. When oil-spreadable rubber is used as the diene rubber, the mass of the mineral oil also includes the mass of the mineral oil (spreading oil) contained in the oil-spreadable rubber. The mass ratio (mineral oil / oleic acid glyceride) is preferably between 0 and 3.0, more preferably between 0 and 1.5, more preferably between 0 and less than 1.0, and even more preferably between 0 and 0.8.

[0027] The total content of plasticizers (total of oleic acid glyceride and mineral oil) in the rubber composition is not particularly limited. For example, per 100 parts by mass of diene rubber, it may be 10 to 100 parts by mass, 15 to 50 parts by mass, 20 to 40 parts by mass, or 20 to 30 parts by mass. The content of oleic acid glyceride is not particularly limited. For example, per 100 parts by mass of diene rubber, it may be 3 to 50 parts by mass, 5 to 45 parts by mass, 7 to 40 parts by mass, or 10 to 30 parts by mass. The content of mineral oil is not particularly limited. For example, per 100 parts by mass of diene rubber, it may be 0 to 50 parts by mass, 1 to 40 parts by mass, 3 to 30 parts by mass, or 5 to 20 parts by mass.

[0028] In addition to the components mentioned above, the rubber composition according to this embodiment may contain various additives commonly used in rubber compositions, such as carbon black, silane coupling agents, stearic acid, zinc oxide, wax, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0029] The amount of carbon black added is not particularly limited, but is preferably 0 to 30 parts by mass per 100 parts by mass of diene rubber, more preferably 0 to 20 parts by mass, even more preferably 3 to 15 parts by mass, and may also be 3 to 10 parts by mass.

[0030] Examples of silane coupling agents include sulfide silane coupling agents, mercaptosilane coupling agents, and thioester group-containing silane coupling agents. The content of the silane coupling agent is not particularly limited and may be 5 to 20 parts by mass or 5 to 15 parts by mass per 100 parts by mass of silica.

[0031] The stearic acid content is not particularly limited; for example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass per 100 parts by mass of diene rubber.

[0032] The zinc oxide content is not particularly limited; for example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass per 100 parts by mass of diene rubber.

[0033] The wax content is not particularly limited; for example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass per 100 parts by mass of diene rubber.

[0034] Examples of antioxidants include amine-ketone, aromatic secondary amine, monophenol, bisphenol, and benzimidazole types, and these can be used individually or in combination of two or more. The amount of antioxidant is not particularly limited and may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass per 100 parts by mass of diene rubber.

[0035] Sulfur is preferably used as the vulcanizing agent. The amount of vulcanizing agent is not particularly limited; for example, it may be 0.1 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass per 100 parts by mass of diene rubber.

[0036] Examples of vulcanization accelerators include sulfenamide-based, guanidine-based, thiuram-based, and thiazole-based accelerators, which can be used individually or in combination of two or more. The content of the vulcanization accelerator is not particularly limited; for example, it may be 0.1 to 10 parts by mass, 1 to 7 parts by mass, or 2 to 5 parts by mass per 100 parts by mass of diene rubber.

[0037] The rubber composition according to this embodiment can be prepared by kneading in a conventional manner using a commonly used mixer such as a Banbury mixer, kneader, or roll. That is, for example, in the first mixing stage, other additives excluding the vulcanizing agent and vulcanization accelerator can be added to the diene rubber and mixed, and then, in the final mixing stage, the vulcanizing agent and vulcanization accelerator can be added to the resulting mixture and mixed to prepare the rubber composition. Before the final mixing stage, the mixture obtained in the first mixing stage may be kneaded again.

[0038] The rubber composition according to this embodiment can be used in various parts of tires, such as the tread, sidewall, and bead portion, of pneumatic tires of various uses and sizes, including passenger car tires and large tires for trucks and buses. Preferably, it is used in the tread and sidewall of the tire. That is, a tire according to one embodiment has a rubber portion made using the above rubber composition.

[0039] In one embodiment, the method for manufacturing a tire including a rubber portion made using the above-mentioned rubber composition is not particularly limited. For example, the rubber composition may be molded into a predetermined shape by extrusion according to a conventional method to obtain an unvulcanized rubber component (e.g., tread rubber, sidewall rubber, etc.). By combining this rubber component with other tire components, an unvulcanized tire (green tire) can be produced. Subsequently, the tire can be manufactured by vulcanization molding at, for example, 140 to 180°C. [Examples]

[0040] The following are examples of the present invention, but the present invention is not limited to these examples.

[0041] The raw materials used in the examples and comparative examples are as follows: • SBR-1: Unmodified ESBR, manufactured by ENEOS Material Co., Ltd. as "SBR1502" • SBR-2: Alkoxysilyl and amino-terminated SSBR, manufactured by ENEOS Material Co., Ltd., "HPR350" • Carbon Black: HAF, manufactured by Tokai Carbon Co., Ltd. "N339 Seast KH" • Silica: Tosoh Silica Co., Ltd. "Nip Seal AQ" (BET specific surface area = 205 m²) 2 / g) • Silane coupling agent: Evonik "Si69" • Aroma oil: ENEOS Corporation's "Process NC140" • Oleic acid glyceride: Kao Corporation's "Leodol MO-60", plant-derived oleic acid glyceride (monoleic acid glyceride content in oleic acid glyceride = 48-58%), oleic acid glyceride / propylene glycol = 89 / 11 (mass%) • Stearic acid: "Lunaq S-20" manufactured by Kao Corporation • Zinc oxide: "Zinc Oxide Type 2" manufactured by Mitsui Mining & Smelting Co., Ltd. • Wax: "OZOACE0355" manufactured by Nippon Seiro Co., Ltd. • Anti-aging agent - 1: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Nocrac 6C" • Anti-aging agent-2: Poly(2,2,4-trimethyl-1,2-dihydroquinoline), manufactured by Kawaguchi Chemical Industry Co., Ltd., "Antage RD" • Vulcanization accelerator-1: "Soxinol CZ" manufactured by Sumitomo Chemical Co., Ltd. • Vulcanization accelerator-2: Diphenylguanidine, Ouchi Shinko Chemical Industry Co., Ltd. "Noxellar D" • Vulcanizing agent: Powdered sulfur manufactured by Tsurumi Chemical Industries, Ltd.

[0042] The evaluation method for the 300% modulus in the examples and comparative examples is as follows. Tensile tests (dumbbell-shaped, type 3) were conducted in accordance with JIS K6251:2017, and the 300% modulus (stress at 300% elongation) was measured. In Table 1, the value for Comparative Example 1 is set to 100, and the values ​​for each comparative example and example are shown as indices. A larger index indicates a larger 300% modulus. A larger 300% modulus indicates higher tire rigidity, resulting in superior handling stability.

[0043] Rubber compositions were prepared using a Banbury mixer according to the formulations (parts by mass) listed in Table 1 below. Specifically, in the first mixing stage, silica, oleic acid glyceride, and an optional mineral oil were added to the diene rubber, along with all compounding agents except the vulcanizing agent and vulcanization accelerator, and the mixture was kneaded (discharge temperature = 160°C). The discharged rubber composition was put into the Banbury mixer, kneaded again, and then discharged (discharge temperature = 160°C). Next, in the final mixing stage, the vulcanizing agent and vulcanization accelerator were added to the resulting mixture and kneaded (discharge temperature = 100°C) to prepare the rubber composition.

[0044] For each rubber composition obtained, a rubber sample was prepared by vulcanizing at 160°C for 20 minutes, and the 300% modulus was evaluated.

[0045] The results are shown in Table 1 below. In the table, the number in parentheses in the oleic acid glyceride column represents the mass parts of oleic acid glyceride contained in "Leodol MO-60," excluding the mass of propylene glycol. Also, the mass ratio of plasticizer components in the table refers to the mass ratio of aroma oil to oleic acid glyceride (hereinafter sometimes simply referred to as the mass ratio of plasticizer components). In Table 1, the rubber compositions obtained were evaluated by changing only the mass ratio of plasticizer components.

[0046] Comparative Example 1 is an example in which only aroma oil was used as a plasticizer, while Comparative Example 2 is an example in which the mass ratio of the plasticizer component was 10.1. Although Comparative Example 2 showed a 300% improvement in modulus compared to Comparative Example 1, the improvement was slight.

[0047] Examples 1-5 show cases where the mass ratios of the plasticizer components were 4.5, 2.6, 1.1, 0.55, and 0, respectively. In all examples, the 300% modulus was clearly improved compared to Comparative Example 1. Furthermore, a significant improvement in the 300% modulus was observed as the mass ratio of the plasticizer components approached 0, that is, as the proportion of oleic acid glyceride increased.

[0048] [Table 1]

[0049] Furthermore, the various numerical ranges described in this specification can be any combination of their upper and lower limits, and all such combinations are described herein as preferred numerical ranges. Also, the description of a numerical range as "X~Y" means X or greater and Y or less.

[0050] Although several embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their omissions, substitutions, and modifications are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

Claims

1. A tire rubber composition comprising diene rubber, silica, plant-derived oleic acid glyceride, and an optional mineral oil, The aforementioned oleic acid glyceride includes monooleic acid glyceride. A rubber composition for tires, wherein the mass ratio of the mineral oil to the oleic acid glyceride is 0 or more and 5.0 or less.

2. The tire rubber composition according to claim 1, wherein the mass ratio of the mineral oil to the oleic acid glyceride is 0 or more and 1.5 or less.

3. A tire having a rubber portion made using the rubber composition described in claim 1 or 2.

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