Rubber composition for tires and tires

Abstract

To improve on-ice performance, wear resistance, low heat build-up properties, and wet grip performance in a well-balanced manner.SOLUTION: A rubber composition for tires according to an embodiment contains 0.1-20 pts.mass of a terpene-based resin containing an α-pinene unit and a β-pinene unit and 1-30 pts.mass of plant-based granules having an average particle diameter of 0.1-500 μm with respect to 100 pts.mass of a rubber component.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] It is known to incorporate terpene resins in rubber compositions for tires (see Patent Documents 1 to 3). For example, Patent Document 1 describes that, in order to improve grip performance on snow or ice, an adhesion promoter such as a terpene resin is incorporated into a diene rubber together with a softening agent-containing norbornene polymer.

[0003] Patent Document 2 describes that, in order to improve the overall performance of ice performance and wear performance, a terpene resin having an α-pinene unit content of 65 to 100% by mass and a β-pinene unit content of 0 to 35% by mass is incorporated into isoprene rubber and butadiene rubber.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The performances required for tires include grip performance on frozen road surfaces (i.e., ice performance) and grip performance on wet road surfaces (wet grip performance). Also, from the perspective of tire life, abrasion resistance is required, and from the perspective of fuel efficiency, low heat generation is required. However, it is difficult to improve these performances in a well-balanced manner, that is, to satisfy them simultaneously without deteriorating any of the performances, and further improvement is required.

[0006] The embodiments of the present invention aim to provide a rubber composition for tires that can improve ice performance, wear resistance, low heat generation, and wet grip performance in a well-balanced manner, and a tire using the same. [Means for solving the problem]

[0007] The present invention includes embodiments shown below. [1] A rubber composition for tires comprising 0.1 to 20 parts by mass of a terpene resin containing α-pinene units and β-pinene units, and 1 to 30 parts by mass of plant-derived granular material with an average particle size of 0.1 to 500 μm, per 100 parts by mass of rubber component. [2] The tire rubber composition according to [1], further comprising 0.1 to 20 parts by mass of a rosin resin and / or a petroleum resin. [3] The tire rubber composition according to [1] or [2], wherein the plant-derived granules are surface-treated plant-derived granules that have been surface-treated with a resin liquid of a rubber adhesion improver, and untreated plant-derived granules that have not been surface-treated. [4] A tire rubber composition according to any one of the items [1] to [3], which is for heavy-duty tires. [5] A tire made using any one of the tire rubber compositions described in [1] to [4]. [Effects of the Invention]

[0008] According to embodiments of the present invention, ice performance, wear resistance, low heat generation, and wet grip performance can be improved in a well-balanced manner. [Modes for carrying out the invention]

[0009] The rubber composition for tires according to this embodiment (hereinafter also referred to as the rubber composition) comprises (A) a rubber component, (B) a terpene resin, and (C) plant-derived granular material. In one embodiment, it is preferable that the rubber composition further comprises (D) a rosin resin and / or (E) a petroleum resin.

[0010] [(A) Rubber component] Diene rubber is used as the rubber component. Diene rubber refers to rubber that has repeating units corresponding to diene monomers with conjugated double bonds, and has double bonds in the polymer main chain. Specific examples of diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, and various other diene rubbers commonly used in rubber compositions. These can be used individually or in combination of two or more. Furthermore, the above-mentioned diene rubbers also include those with modified ends or main chains as needed (e.g., end-modified SBR) or those modified to impart desired properties (e.g., modified NR), as well as those modified to impart desired properties.

[0011] In one embodiment, the rubber component preferably includes at least one selected from the group consisting of natural rubber, styrene-butadiene rubber, and butadiene rubber. More preferably, the rubber component includes natural rubber and butadiene rubber. 100 parts by mass of the rubber component preferably contains 40 to 90 parts by mass of natural rubber and 10 to 60 parts by mass of butadiene rubber, more preferably 50 to 80 parts by mass of natural rubber and 20 to 50 parts by mass of butadiene rubber, and even more preferably 55 to 70 parts by mass of natural rubber and 30 to 45 parts by mass of butadiene rubber.

[0012] [(B) Terpene resins] Terpene resins are resins having units derived from terpene compounds, and in this embodiment, those containing α-pinene units and β-pinene units are used. Preferably, a terpene resin consisting of a copolymer containing α-pinene units and β-pinene units is used as the terpene resin. Terpene resins containing α-pinene units and β-pinene units have high compatibility with rubber components and excellent dispersibility in rubber components. Therefore, when combined with plant-derived granular material, it is believed that ice performance, abrasion resistance, low heat generation, and wet grip performance can be improved in a well-balanced manner.

[0013] An α-pinene unit is a unit derived from α-pinene. A β-pinene unit is a unit derived from β-pinene. A terpene resin containing α-pinene units and β-pinene units can be obtained by polymerizing a mixture containing α-pinene and β-pinene. The mass ratio of α-pinene units to β-pinene units is not particularly limited, but is preferably 35:65 to 4:96, more preferably 20:80 to 4:96, and even more preferably 10:90 to 4:96. In one embodiment, the content of α-pinene units in the terpene resin is preferably 4 to 35% by mass, more preferably 4 to 20% by mass, and even more preferably 4 to 10% by mass. The content of β-pinene units in the terpene resin is preferably 65 to 96% by mass, more preferably 80 to 96% by mass, and even more preferably 90 to 96% by mass.

[0014] The terpene resin may use only α-pinene and β-pinene as its constituent monomers, but it may also contain other terpene compounds, and even monomers other than terpene compounds, as long as the effect is not impaired. In one embodiment, the terpene resin may be a polyterpene resin obtained by polymerizing only terpene compounds (terpene monomers), that is, a polyterpene resin containing α-pinene units and β-pinene units.

[0015] In one embodiment, the terpene resin preferably contains substantially no limonene units, which are units derived from limonene. For example, the limonene unit content in the terpene resin may be less than 10% by mass, less than 5% by mass, less than 2% by mass, less than 1% by mass, or 0% by mass.

[0016] The method for synthesizing the terpene resin is not particularly limited. For example, the terpene resin can be synthesized by cationically polymerizing a monomer mixture containing α-pinene and β-pinene using a Lewis acid catalyst. Specific examples of the Lewis acid catalyst are not particularly limited, and include metal halides (for example, BF3, BBr3, AlF3, AlBr3, TiCl4, TiBr4, FeCl3, FeCl2, SnCl4, WCl6, MoCl5, ZrCl4, SbCl3, SbCl5, TeCl2, and ZnCl2), metal alkyl compounds (for example, Et3Al, Et2AlCl, EtAlCl2, Et3Al2Cl3, (iBu)3Al, (iBu)2AlCl, (iBu)AlCl2, Me4Sn, Et4Sn, Bu4Sn, and Bu3SnCl), and metal alkoxy compounds (for example, Al(OR) 3-x Cl x and Ti(OR) 4-y Cl y (wherein, R represents an alkyl group or an aryl group, x represents an integer of 1 or 2, and y represents an integer of 1 to 3)). Here, Et represents an ethyl group, iBu represents an isobutyl group, Me represents a methyl group, and Bu represents a butyl group, respectively).

[0017] In one embodiment, the terpene resin preferably has a softening point of 60 to 150°C, more preferably 70 to 140°C, and still more preferably 80 to 130°C. The softening point is measured in accordance with ASTM D6090 (publication date: 1997).

[0018] In one embodiment, the terpene resin preferably has a glass transition temperature (Tg) of 38 to 81°C. Tg is measured in accordance with ASTM D6604 (publication date: 2013) using a differential scanning calorimeter SC Q2000 of TA Instruments.

[0019] The content of the terpene resin is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, still more preferably 0.8 to 7 parts by mass, and particularly preferably 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

[0020] [(C) Vegetable granules] Examples of the vegetable granules include pulverized products such as seed husks, fruit cores, grains, and their core materials, and at least one of these can be blended. For example, pulverized products of fruit cores and seed husks such as walnuts, apricots, camellias, peaches, plums, ginkgoes, peanuts, chestnuts, etc., pulverized products of grains such as rice, wheat, millet, barnyard millet, corn, etc., and pulverized products of grain core materials such as corn cob cores. These have a Mohs hardness of about 2 to 5 and are harder than ice, so they can exert a scratching effect on the ice and snow road surface. Also, among such anti-slip materials with a scratching effect, if they are vegetable granules, when used in combination with terpene resins, the ice performance, low heat generation property, and wet grip performance can be improved without impairing the abrasion resistance.

[0021] As the vegetable granules, those having an average particle size of 0.1 to 500 μm are preferably used. The average particle size of the vegetable granules is preferably 10 to 500 μm, more preferably 100 to 400 μm, and still more preferably 150 to 300 μm. Here, the average particle size of the vegetable granules is the 90% volume particle size (D90), which means the particle size at 90% of the integrated value in the particle size distribution (volume basis) measured by the laser diffraction / scattering method. For example, the average particle size is determined by a laser diffraction type particle size distribution measuring device "SALD-2200" manufactured by Shimadzu Corporation using a red semiconductor laser (wavelength 680 nm) as the light source.

[0022] In order to improve the compatibility with the rubber component and prevent shedding, it is preferable to use vegetable granules surface-treated with a resin solution of a rubber adhesion improver. Examples of the rubber adhesion improver include a mixture of a resorcinol-formalin resin initial condensate described in JP-A-10-7841 and natural rubber latex or diene-based synthetic rubber latex.

[0023] In one embodiment, the plant-derived granules preferably include surface-treated plant-derived granules that have been surface-treated with a resin liquid of a rubber adhesion improver, and untreated plant-derived granules that have not undergone such surface treatment. By using surface-treated plant-derived granules and untreated plant-derived granules in combination, ice performance can be further improved. When using them in combination in this way, the mass ratio of surface-treated plant-derived granules to untreated plant-derived granules is not particularly limited, but is preferably 20:80 to 60:40, more preferably 30:70 to 50:50, and particularly preferably 30:70 to 45:55, with a preference for a larger proportion of untreated plant-derived granules than surface-treated plant-derived granules. Furthermore, when using them in combination, the relationship between the average particle sizes of the two is not particularly limited, but it is preferable that the average particle size of the surface-treated plant-derived granules is larger than the average particle size of the untreated plant-derived granules.

[0024] The content of plant-derived granular material is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, even more preferably 3 to 10 parts by mass, and particularly preferably 3 to 8 parts by mass, per 100 parts by mass of rubber component.

[0025] [(D) Rosin-based resin] The rubber composition according to this embodiment may contain a rosin-based resin. By adding a rosin-based resin, wear resistance can be significantly improved without impairing the ice performance, low heat generation, and wet grip performance achieved by using a combination of terpene-based resin and plant-derived granules.

[0026] Rosin-based resins are resins whose main component is rosin acid, and various known types can be used, such as raw material rosins like gum rosin, wood rosin, and tall oil rosin; disproportionates of raw material rosins; stabilized rosins obtained by hydrogenating raw material rosins; polymerized rosins; esterified rosins (rosin ester resins); phenol-modified rosins; unsaturated acid (maleic acid, etc.)-modified rosins; and formylated rosins obtained by reducing rosins.

[0027] The content of the rosin-based resin is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.8 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0028] [(E) Petroleum resin] The rubber composition according to this embodiment may contain petroleum resin. By adding petroleum resin, wear resistance and wet grip performance can be improved without impairing the ice performance and low heat generation properties achieved by using terpene resin and plant-derived granules in combination.

[0029] Examples of petroleum resins include aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins. Aliphatic petroleum resins are resins obtained by cationic polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions with 4 to 5 carbon atoms (C5 fractions) (also called C5 petroleum resins), and may be hydrogenated. Aromatic petroleum resins are resins obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions with 8 to 10 carbon atoms (C9 fractions) (also called C9 petroleum resins), and may be hydrogenated. Aliphatic / aromatic copolymer petroleum resins are resins obtained by copolymerizing the above C5 fraction and C9 fraction (also called C5 / C9 petroleum resins), and may be hydrogenated.

[0030] The petroleum resin content is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.8 to 5 parts by mass, per 100 parts by mass of rubber component. When rosin-based resin and petroleum resin are used in combination, the total amount of rosin-based resin and petroleum resin is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.8 to 5 parts by mass, per 100 parts by mass of rubber component.

[0031] [Other ingredients] In addition to the above-mentioned components, the rubber composition according to this embodiment may contain various additives commonly used in rubber compositions, such as fillers, zinc oxide, stearic acid, antioxidants, oils, waxes, vulcanizing agents, and vulcanization accelerators.

[0032] As a filler, carbon black and / or silica are preferably used, and it is more preferable to include carbon black. Carbon black and silica may also be used in combination. When silica is included, a silane coupling agent may also be used in combination.

[0033] The carbon black is not particularly limited, and various known varieties can be used. Specifically, examples include SAF grade (N100 series), ISAF grade (N200 series), HAF grade (N300 series), and FEF grade (N500 series) (all ASTM grades). One or more of these grades of carbon black can be used. The silica is not particularly limited, and examples include wet silica and dry silica. Preferably, wet silica such as wet sedimentation silica and wet gelation silica is used.

[0034] The content of the filler is not particularly limited; for example, it may be 20 to 100 parts by mass or 30 to 80 parts by mass per 100 parts by mass of rubber component. The filler may mainly consist of carbon black. That is, the amount of carbon black relative to the total mass of the filler may be more than 50% by mass, 70% or more by mass, or 100% by mass.

[0035] Sulfur is preferably used as the vulcanizing agent. The content of the vulcanizing agent is not particularly limited, but it is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and may also be 1 to 3 parts by mass, per 100 parts by mass of rubber component.

[0036] Examples of vulcanization accelerators include sulfenamide-based, thiuram-based, thiazole-based, and guanidine-based vulcanization accelerators, which can be used individually or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, but is preferably 0.1 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, and may also be 1 to 3 parts by mass, per 100 parts by mass of the rubber component.

[0037] The rubber composition according to this embodiment can be prepared by kneading in accordance with conventional methods using a commonly used mixer such as a Banbury mixer, kneader, or roll. That is, for example, in the first mixing stage (non-professional kneading stage), additives other than the vulcanizing agent and vulcanization accelerator are added and mixed with the rubber component along with a terpene resin and plant-based granules. Then, in the final mixing stage (professional kneading stage), the vulcanizing agent and vulcanization accelerator are added and mixed into the resulting mixture. This allows for the preparation of an unvulcanized rubber composition.

[0038] The rubber composition according to this embodiment can be used as a rubber composition for tires. Examples of tires include passenger car tires, heavy-duty tires for trucks and buses, and pneumatic tires of various sizes and applications. Preferably, the rubber composition is used as a rubber composition for heavy-duty tires.

[0039] A tire according to one embodiment is a tire manufactured using the above-mentioned rubber composition. That is, the tire is equipped with a rubber portion made of the above-mentioned rubber composition. Examples of application parts of the tire include tread rubber and sidewall rubber, and the tread rubber is preferred.

[0040] The tread rubber of a tire may have a two-layer structure consisting of a cap rubber and a base rubber, or a single-layer structure in which both are integrated. In the case of a single-layer structure, the tread rubber may be formed from the above-mentioned rubber composition. In the case of a two-layer structure, the outer cap rubber that contacts the road surface may be formed from the above-mentioned rubber composition, the base rubber placed inside the cap rubber may be formed from the above-mentioned rubber composition, or both the cap rubber and the base rubber may be formed from the above-mentioned rubber composition.

[0041] The method for manufacturing a tire is not particularly limited. For example, the above rubber composition may be molded into a predetermined shape by extrusion according to a conventional method and combined with other parts to produce an unvulcanized tire (green tire). For example, a tread rubber may be made using the above rubber composition, and the tread rubber may be combined with other tire components to produce an unvulcanized tire. Subsequently, the tire can be manufactured by vulcanization molding at, for example, 140 to 180°C. [Examples]

[0042] The following are examples, but the present invention is not limited to these examples.

[0043] Using a Banbury mixer, the rubber composition was prepared according to the formulation (parts by mass) shown in Table 1 below. First, in the first mixing stage, compounding agents excluding sulfur and vulcanization accelerator were added to the rubber components and kneaded (discharge temperature = 160°C). Then, in the final mixing stage, sulfur and vulcanization accelerator were added to the resulting mixture and kneaded (discharge temperature = 90°C). Details of each component in Table 1 are as follows.

[0044] • Natural rubber: RSS#3 • Butadiene rubber: "BR150B" manufactured by Ube Industries, Ltd. • Carbon Black: "Seast 6" manufactured by Tokai Carbon Co., Ltd. • Zinc oxide: "Zinc Oxide Type 2" manufactured by Mitsui Mining & Smelting Co., Ltd. • Stearic acid: "Bead Stearic Acid" manufactured by NOF Corporation • Untreated plant-based granular material: Crushed walnut shells (Soft Grit #46, manufactured by Nippon Walnut Co., Ltd., D90 = 400 μm) • Surface-treated plant-based granular material: Crushed walnut shells ("Soft Grit #46" manufactured by Nippon Walnut Co., Ltd.) were surface-treated with an RFL treatment solution (mainly composed of a mixture of resorcinol-formaldehyde resin initial condensate and latex) according to the method described in paragraph 0015 of Japanese Patent Publication No. 10-7841 (D90 = 300 μm). • Oil: Aromatic type, "Process NC-140" manufactured by JXTG Energy Corporation • Terpene resin: α-pinene / β-pinene mixed resin, Kraton Corporation "SYLVATRAXX4150" (α-pinene units: 5% by mass, β-pinene units: 95% by mass, softening point: 115°C, Tg: 61°C) • Rosin-based resin: Rosin, "TR-80" manufactured by IREC Co., Ltd. • Petroleum resin: C5 / C9 series petroleum resin, "Petrotac 90" manufactured by Tosoh Corporation • Anti-aging agent: "Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. • Sulfur: Tsurumi Chemical Industries Co., Ltd. "Powdered Sulfur" • Vulcanization accelerator: "Soxinol CZ" manufactured by Sumitomo Chemical Co., Ltd.

[0045] The ice performance, abrasion resistance, low heat generation, and wet grip performance of each obtained rubber composition were evaluated. The evaluation method is as follows.

[0046] • Ice performance: Each rubber composition was used as the tread rubber, and heavy-duty pneumatic tires (tire size: 11.5R22.5 14PR) were manufactured by vulcanization molding according to conventional methods. The resulting tires were mounted on a 25-ton truck, and the braking distance (m) was measured by applying emergency brakes from a speed of 30 km / h on an ice-covered road at -3±3℃ (ABS not activated). The reciprocal of the braking distance (average value for n=10) was compared and expressed as an index with the value of Comparative Example 1 set to 100. A larger index indicates a shorter braking distance and superior ice performance.

[0047] • Abrasion resistance: Test specimens of each rubber composition were vulcanized at 160°C for 30 minutes. Abrasion was measured using a Lambourn abrasion tester in accordance with JIS K6264, under a load of 3 kg, a slip ratio of 20%, a temperature of 23°C, and a sand flow rate of 20 g / min. The reciprocals of the abrasion amounts were compared and expressed as an index with the value of Comparative Example 1 set to 100. A larger index indicates less abrasion and superior abrasion resistance.

[0048] • Low heat generation: Tires manufactured as described in the evaluation method for ice performance were used. Immediately after drum running under the high-speed durability test conditions specified in the US automotive safety standard FMVSS119, a thermistor was inserted at the belt end position where the tread thickness was maximum on the belt, and the temperature was measured. The results are shown as an index calculated using the following formula. A larger value indicates less heat generation and superior low heat generation performance. (Temperature of the tire in Comparative Example 1) × 100 / (Temperature of each prototype tire)

[0049] • Wet grip performance: Tires manufactured according to the evaluation method for ice performance were used. A vehicle equipped with 50% worn tires entered a road surface with a water depth of 5 mm at a speed of 40 km / h and performed emergency braking. The braking distance was measured, and its reciprocal was calculated as an index. The result of Comparative Example 1 was used as the index, with 100, and a higher index indicates a shorter braking distance and superior wet grip performance.

[0050] [Table 1]

[0051] The results are shown in Table 1. In Comparative Example 1, plant-derived granular material was included, but terpene resin was not. Compared to Comparative Example 1, Examples 1 to 3, which included terpene resin and plant-derived granular material, were able to improve ice performance, low heat generation, and wet grip performance while maintaining or improving abrasion resistance, and were particularly effective in improving ice performance and low heat generation. In Examples 4 to 6, in addition to terpene resin and plant-derived granular material, rosin resin was further included. Compared to Examples 1 to 3, Examples 4 to 6 were able to significantly improve abrasion resistance while maintaining ice performance, low heat generation, and wet grip performance. In Examples 7 to 9, in addition to terpene resin and plant-derived granular material, petroleum resin was further included. Compared to Examples 1 to 3, Examples 7 to 9 were able to improve wet grip performance and abrasion resistance while maintaining ice performance and low heat generation.

[0052] 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.

[0053] Although several embodiments of the present invention have been described above, these embodiments are presented as examples 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. The rubber component comprises 100 parts by mass of 40 to 90 parts by mass of natural rubber and 10 to 60 parts by mass of butadiene rubber, 0.1 to 20 parts by mass of terpene resin containing α-pinene units and β-pinene units, and 1 to 30 parts by mass of plant-derived granular material with an average particle size of 0.1 to 500 μm. The terpene resin has a content of 4 to 35% by mass of α-pinene units, and the terpene resin has a content of 65 to 96% by mass of β-pinene units. A tire rubber composition wherein the plant granules are at least one selected from the group consisting of crushed seed hulls, crushed fruit kernels, crushed grains, and crushed grain core materials.

2. The tire rubber composition according to claim 1, further comprising 0.1 to 20 parts by mass of a rosin-based resin and / or petroleum resin.

3. The tire rubber composition according to claim 1, wherein the plant-derived granular material comprises surface-treated plant-derived granular material that has been surface-treated with a resin liquid of a rubber adhesion improver, and untreated plant-derived granular material that has not been surface-treated.

4. A tire rubber composition according to any one of claims 1 to 3, which is for use with heavy-duty tires.

5. A tire manufactured using the tire rubber composition described in any one of claims 1 to 3.

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