Rubber composition for rim cushioning

Abstract

This invention provides a rubber composition for wheel rim cushioning that achieves a good balance of high performance while maintaining good hardness, elongation at break, and abrasion resistance, while also improving low heat generation. The composition comprises a CTAB adsorption specific surface area of ​​60 m², blended with a diene rubber containing 35%–65% isoprene rubber and 35%–65% butadiene rubber. 2 / g~100m 2 The adsorption specific surface area of ​​ / g silica and CTAB is 60m². 2 / g~160m 2 / g of carbon black and sulfur-containing silane coupling agent, using at least one type of silica-terminated butadiene rubber as butadiene rubber, such that the amount of silica mixed is 10 parts by mass or more relative to 100 parts by mass of diene rubber, and the total amount of silica and carbon black mixed is more than 50 parts by mass relative to 100 parts by mass of diene rubber, and the product of stress M100 at 100% elongation and hardness is set to 150 or more.

Description

Technical Field

[0001] This invention relates to a rim cushioning rubber composition intended primarily for use in tire rim cushioning rubber layers. Background Technology

[0002] In pneumatic tires, improving fuel efficiency during driving is required to reduce environmental impact. Therefore, efforts are made to suppress heat generation in the rubber compositions that make up the various parts of the pneumatic tire. In recent years, to further improve fuel efficiency, for example, there has been a demand for suppressing heat generation in the rubber compositions that make up the rim cushioning rubber layer of the pneumatic tire.

[0003] As an indicator of the heat generation properties of a rubber composition, tanδ at 60°C (hereinafter referred to as "tanδ(60°C)"), obtained by dynamic viscoelasticity measurement, is generally used. The smaller the tanδ(60°C) of the rubber composition, the lower the heat generation properties. Furthermore, as a method to reduce the tanδ(60°C) of the rubber composition, examples include reducing the amount of filler materials such as carbon black, or increasing the particle size of the carbon black. Alternatively, it has been proposed to mix in silica with a large particle size (for example, Patent Document 1 teaches the use of silica with a large particle size in rubber compositions for tire sidewalls to achieve low heat generation). However, these methods may not adequately achieve rubber hardness, and there are further concerns about their impact on the elongation at break and abrasion resistance required for rubber compositions used as rim cushioning. Therefore, in rubber compositions used for rim cushioning, further measures are needed to improve the low heat generation properties (tanδ(60°C)) while maintaining good elongation at break and abrasion resistance.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-001889 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The purpose of this invention is to provide a rubber composition for rim cushioning that can improve low heat generation while maintaining good elongation at break and abrasion resistance, and to achieve a good balance of these properties.

[0009] Methods for solving problems

[0010] The rim cushioning rubber composition of the present invention, which achieves the above-mentioned objective, is characterized in that it contains a CTAB adsorption specific surface area of ​​60 m² mixed in a diene rubber comprising 35% to 65% by mass of isoprene rubber and 35% to 65% by mass of butadiene rubber. 2 / g~100m 2The adsorption specific surface area of ​​ / g silica and CTAB is 60m². 2 / g~160m 2 The butadiene rubber comprises at least one silica-terminated butadiene rubber, wherein the amount of silica in the mixture is 10 parts by mass or more relative to 100 parts by mass of the butadiene rubber, and the total amount of silica and carbon black in the mixture is more than 50 parts by mass relative to 100 parts by mass of the butadiene rubber. The product of the stress M100 (unit: MPa) at 100% elongation at room temperature and the hardness at room temperature of the rubber composition is 150 or more.

[0011] The effects of the invention

[0012] The rim cushioning rubber composition of the present invention, by being formulated as described above, and wherein the stress M100 at 100% elongation and hardness satisfy the aforementioned relationship, can effectively maintain elongation at break and wear resistance while improving low heat generation, thus achieving a good balance of these properties. In particular, by using CTAB with an adsorption specific surface area of ​​60 m²... 2 / g~100m 2 The large particle size of silica ( / g) improves elongation at break, allowing for good maintenance of elongation at break while using silica-terminated butadiene rubber, and also resulting in excellent low heat generation. Through their synergy, low heat generation (tanδ at 60°C) can be improved while maintaining good elongation at break and abrasion resistance. Furthermore, with the product of stress M100 and hardness at 100% elongation exceeding 150, the required physical properties for rim cushioning rubber, such as abrasion resistance, are well achieved.

[0013] In this invention, the proportion of the silica-modified butadiene rubber contained in the butadiene rubber can be from 15% to 100% by mass. Preferably, the total amount of silica and carbon black is 80 parts by mass or less relative to 100 parts by mass of the diene rubber. Furthermore, it is preferable to blend sulfur and a vulcanization accelerator into the diene rubber, and the total amount of sulfur and the vulcanization accelerator is 3.5 parts by mass or more relative to 100 parts by mass of the diene rubber.

[0014] The rubber composition for rim cushioning rubber of the present invention is suitable for use in the rim cushioning rubber layer of tires. Tires equipped with the rim cushioning rubber layer formed by the rim cushioning rubber composition of the present invention, through the excellent physical properties of the rim cushioning rubber composition of the present invention, can achieve good performance in terms of elongation at break and wear resistance required for rim cushioning rubber, while reducing rolling resistance and improving fuel efficiency. Attached Figure Description

[0015] Figure 1 A radial cross-sectional view showing an example of a pneumatic tire using the rim cushioning rubber composition of the present invention. Detailed Implementation

[0016] The structure of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] like Figure 1 As shown, the pneumatic tire using the rim cushioning rubber composition of the present invention includes a tread portion 1, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed radially inside the sidewall portions 2. Figure 1 In the symbol CL, the tire equator is represented. Figure 1 Because this is a radial cross-sectional view, although not depicted, the tread portion 1, sidewall portion 2, and bead portion 3 extend circumferentially along the tire to form a ring, thus constituting the basic ring-shaped structure of a pneumatic tire. Hereinafter, we will use... Figure 1 The description is basically based on the meridian cross-sectional shape shown in the figure, but each tire component extends along the tire circumference to form a ring.

[0018] A carcass layer 4 is installed between a pair of left and right bead portions 3. This carcass layer 4 includes multiple reinforcing cords extending radially along the tire, which are folded back from the inside of the vehicle to the outside around the bead core 5 disposed in each bead portion 3. Furthermore, a bead filler 6 is disposed on the outer periphery of the bead core 5, and this bead filler 6 is enclosed by the main body and folded-back portion of the carcass layer 4. On the other hand, multiple layers (in...) are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. Figure 1 The belt layer 7 consists of two layers. Each belt layer 7 contains multiple reinforcing cords inclined relative to the tire circumference, and the reinforcing cords are arranged in a crisscrossing manner between the layers. In these belt layers 7, the inclination angle of the reinforcing cords relative to the tire circumference is set to, for example, a range of 10° to 40°. Further, a belt reinforcement layer 8 (two layers: a full-coverage layer 8a covering the total width of the belt layer 7 and an edge-coverage layer 8b partially covering the ends of the belt layer 7) is provided on the outer periphery of the belt layer 7. The belt reinforcement layer 8 contains organic fiber cords oriented along the tire circumference. In the belt reinforcement layer 8, the angle of the organic fiber cords relative to the tire circumference is set to, for example, 0° to 5°.

[0019] A tread rubber layer 10 is provided on the outer periphery of the carcass layer 4 in the tread portion 1, a sidewall rubber layer 20 is provided on the outer periphery of the carcass layer 4 (outer side in the tire width direction) in the sidewall portion 2, and a rim buffer rubber layer 30 is provided on the outer periphery of the carcass layer 4 (outer side in the tire width direction) in the bead portion 3. The rim buffer rubber composition of the present invention is used in the rim buffer rubber layer 30 of such a tire. Therefore, the basic structure of other parts is not limited to the above structure. In addition, the rim buffer rubber layer 30 is a layer adjacent to the sidewall rubber layer 20, but since it forms the sidewall portion 2, which has the greatest bending during driving, it is different from the sidewall rubber layer 20, which requires, for example, resistance to bending fatigue, etc. It is a component that is in contact with the rim (not shown) and is prone to wear caused by friction with the rim. Therefore, it is a layer that requires high hardness and excellent wear resistance.

[0020] Tires using the rim cushioning rubber composition of the present invention are preferably pneumatic tires as described above (tires filled with inactive gases such as air, nitrogen, or other gases), but non-pneumatic tires are also possible. In the case of non-pneumatic tires, the portion of the rim cushioning rubber composition of the present invention that abuts against the rim when installed on the rim (corresponds to the portion of the rim cushioning rubber layer 30 in a pneumatic tire).

[0021] In the rim cushioning rubber composition of the present invention, the rubber component is a diene-based rubber, which necessarily includes isoprene-based rubber and butadiene rubber. Furthermore, the butadiene rubber includes at least one type of silica-terminated butadiene rubber. Thus, by using isoprene-based rubber and butadiene rubber (silica-terminated butadiene rubber), it is advantageous to improve low heat generation while maintaining good elongation at break and abrasion resistance.

[0022] Examples of isoprene-based rubbers include various natural rubbers, epoxidized natural rubbers, and various synthetic polyisoprene rubbers. Among these isoprene-based rubbers, natural rubber is particularly suitable. The blending amount of isoprene-based rubber is 35% to 65% by mass, preferably 40% to 60% by mass, in 100% by mass of the isoprene-based rubber. By blending such an amount of isoprene-based rubber, the elongation at break, low heat generation, and abrasion resistance can be improved in a balanced manner. If the blending amount of isoprene-based rubber is less than 35% by mass, the elongation at break decreases. If the blending amount of isoprene-based rubber exceeds 65% by mass, the abrasion resistance and low heat generation deteriorate.

[0023] The term "silica-terminated butadiene rubber" refers to a butadiene rubber obtained by modifying one or both of its molecular ends with a functional group that reacts with the silanol group on the surface of silica. Examples of functional groups that react with the silanol group include, for example, at least one selected from polyorganosiloxane, polyorganosiloxane structures containing hydroxyl groups, alkoxysilyl groups, hydroxyl groups, aldehyde groups, carboxyl groups, amino groups, imino groups, epoxy groups, amide groups, thiol groups, and ether groups. Among these, polyorganosiloxane, polyorganosiloxane structures containing hydroxyl groups, alkoxysilyl, hydroxyl, and amino groups are preferred. Furthermore, a combination of multiple functional groups (e.g., amino and alkoxysilyl groups) can be used. By including at least one type of silica-terminated butadiene rubber as the butadiene rubber, the affinity with the large-particle-size silica described later becomes good, which is beneficial for improving low heat generation while maintaining good elongation at break and abrasion resistance. In addition, there are no particular limitations on the types of butadiene rubber except for end-modified butadiene rubber for silica, and any rubber that can generally be used in tire rubber compositions can be used.

[0024] From the perspective of improving wear resistance, silica-terminated butadiene rubber can preferably be a material with a glass transition temperature (Tg) of -110°C to -70°C. This low glass transition temperature improves wear resistance. Furthermore, the glass transition temperature can be determined using differential scanning calorimetry (DSC).

[0025] The butadiene rubber content in the blend is 35% to 65% by mass, preferably 40% to 60% by mass, within 100% by mass of butadiene rubber. By blending an appropriate amount of butadiene rubber in this way, it is beneficial to achieve a balanced improvement in elongation at break, low heat generation, and abrasion resistance. If the butadiene rubber content is less than 35% by mass, abrasion resistance and low heat generation deteriorate. If the butadiene rubber content exceeds 65% by mass, the elongation at break decreases.

[0026] As described above, the butadiene rubber must contain at least one type of silica-terminated butadiene rubber. When the total amount of butadiene rubber contained in the rim cushioning rubber composition of the present invention is set to 100% by mass, the proportion of silica-terminated butadiene rubber is preferably 15% to 100% by mass, more preferably 40% to 70% by mass. By including such a sufficient amount of silica-terminated butadiene rubber, the affinity with the large-particle-size silica described later becomes good, which is beneficial for improving low heat generation while maintaining good elongation at break and wear resistance.

[0027] In addition to the isoprene and butadiene rubbers described above, the rim cushioning rubber composition of the present invention may also contain other diene rubbers. As other diene rubbers, rubbers generally applicable to tire rubber compositions can be used. Examples include styrene-butadiene rubber (SBR). These other diene rubbers can be used alone or as any blend.

[0028] In this invention, silica and carbon black are always blended into the aforementioned diene rubber as fillers. When blending these fillers, the amount of silica is 10 parts by mass or more relative to 100 parts by mass of the diene rubber, preferably 20 to 70 parts by mass. Furthermore, the total amount of silica and carbon black is more than 50 parts by mass relative to 100 parts by mass of the diene rubber, preferably 80 parts by mass or less, more preferably 55 to 70 parts by mass. By blending silica and carbon black in such appropriate amounts, the elongation at break, low heat generation, and abrasion resistance can be improved in a balanced manner. If the amount of silica is less than 10 parts by mass, the elongation at break decreases. If the total amount of silica and carbon black is less than 50 parts by mass, the abrasion resistance decreases. The amount of carbon black alone is not particularly limited, but is preferably 0 to 60 parts by mass, more preferably 5 to 50 parts by mass.

[0029] As the silica used in this invention, silica commonly used in tire rubber compositions, such as wet silica, dry silica, or surface-treated silica, can be used. However, CTAB with an adsorption specific surface area of ​​60 m² is required. 2 / g~100m 2 / g, preferably 65m 2 / g~95m 2 / g of silica. By using silica with a large particle size in this way, the low-heat-generating properties can be improved. If the CTAB adsorption specific surface area of ​​silica is less than 60m² 2 If the surface area of ​​silica with CTAB adsorption exceeds 100 m² / g, then the elongation at break and wear resistance will decrease. 2 If the concentration of silica is less than 1 / g, its low-heating properties decrease. If silica that meets the above conditions is required, it can be selected appropriately from commercially available products, or silica obtained by conventional manufacturing methods can be used.

[0030] As the carbon black used in this invention, carbon black commonly used in tire rubber compositions can be used. However, it is essential to use CTAB with an adsorption specific surface area of ​​60 m². 2 / g~160m 2 / g, preferably 80m 2 / g~135m 2 / g of carbon black. Using such carbon black facilitates a balanced improvement in elongation at break, low heat generation, and abrasion resistance. If the CTAB adsorption specific surface area of ​​the carbon black is less than 60m²... 2 / g, then the elongation at break and abrasion resistance decrease. If the CTAB adsorption specific surface area of ​​carbon black exceeds 160m², the elongation at break and abrasion resistance will decrease. 2 / g, then the low-grade fever worsens.

[0031] The rubber composition of the present invention can be blended with fillers other than silica and carbon black. Examples of other fillers include materials commonly used in tire rubber compositions, such as clay, talc, calcium carbonate, mica, and aluminum hydroxide.

[0032] For the rim cushioning rubber composition of the present invention, a sulfur-containing silane coupling agent must be mixed in when compounding the aforementioned silica. By mixing in the silane coupling agent, the dispersibility of silica relative to diene rubber can be improved. Examples of sulfur-containing silane coupling agents include bis-(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane. Among these, substances having tetrasulfide bonds in their molecules are particularly suitable. The amount of silane coupling agent mixed in relative to the amount of silica is preferably less than 10% by mass, more preferably 3% to 9% by mass. If the amount of silane coupling agent in the mixture is more than 10% by mass of the amount of silica in the mixture, the silane coupling agents will condense with each other and will not achieve the desired hardness and strength in the rubber composition.

[0033] It is preferable to further incorporate sulfur and a vulcanization accelerator into the rim cushioning rubber composition of the present invention. When sulfur and a vulcanization accelerator are incorporated, the total amount of these two components relative to 100 parts by weight of the diene rubber is preferably 3.5 parts by weight or more, more preferably 4 to 7.5 parts by weight. By incorporating sufficient amounts of sulfur and vulcanization accelerator in this way, the balance of hardness, stress M100 at 100% elongation at room temperature, and low heat generation can be effectively improved. If the total amount of sulfur and vulcanization accelerator is less than 3.5 parts by weight, the balance of hardness, stress M100 at 100% elongation at room temperature, and low heat generation is reduced. Furthermore, the individual amounts of sulfur and vulcanization accelerator are not particularly limited, but regarding sulfur, it is preferable to incorporate 1.5 to 5 parts by weight, more preferably 2 to 4 parts by weight; regarding the vulcanization accelerator, it is preferable to incorporate 1.5 to 4 parts by weight, more preferably 2 to 3.5 parts by weight.

[0034] As vulcanization accelerators, substances commonly used in tire rubber compositions can be used, such as sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, and thiuram-based vulcanization accelerators. Examples of sulfenamide-based vulcanization accelerators include N,N-dicyclohexyl-1,3-benzothiazole-2-sulfenamide (DZ), N-cyclohexyl-2-benzothiazole sulfenamide (CZ), N-oxodiethylene-2-benzothiazole sulfenamide (OBS), and N-(tert-butyl)benzothiazole-2-sulfenamide (NS). Examples of guanidine-based vulcanization accelerators include diphenylguanidine (DPG) and di-o-tolylguanidine. Examples of thiuram-based vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetrabenzylthiuram disulfide. Among these, N-cyclohexyl-2-benzothiazole sulfenamide (CZ), N-(tert-butyl)benzothiazole-2-sulfenamide (NS), and diphenylguanidine (DPG) are particularly suitable. Furthermore, a mixture of sulfenamide systems is preferred, with optional use of either guanidine or thiuram systems. In particular, a combination of both sulfenamide and guanidine systems is preferred.

[0035] In the rim cushioning rubber composition of the present invention, other compounding agents besides those described above may be added. Examples of other compounding agents include vulcanizing or crosslinking agents other than sulfur, antioxidants, liquid polymers, and various other compounding agents commonly used in tire rubber compositions. The mixing amounts of these compounding agents can be conventional amounts as long as they do not deviate from the purpose of the present invention. Furthermore, conventional rubber mixing machinery can be used as the mixing machine, such as a Banbury mixer, kneader, rollers, etc.

[0036] In addition to the above-described compounding, the product of the stress M100 (unit: MPa) at 100% elongation at room temperature and the hardness at room temperature in the rim cushioning rubber composition of the present invention is set to be 150 or more, preferably 200 to 400. By having this characteristic, suitable rubber properties (e.g., hardness, elongation at break, abrasion resistance) for use as rim cushioning rubber can be obtained. If the product is less than 150, the abrasion resistance decreases. This product can be adjusted, for example, by adjusting the amount of filler and the combined amount of sulfur and vulcanization accelerator. Furthermore, the stress M100 at 100% elongation at room temperature is a value measured according to JIS K6251 using a No. 3 dumbbell test piece at a tensile speed of 500 mm / min and at room temperature (20°C). Moreover, the hardness at room temperature is measured according to JIS K6253 using a type A hardness tester at room temperature (20°C). If the product of stress M100 and hardness satisfies the above relationship, then their respective values ​​are not particularly limited. However, the stress M100 at 100% elongation at room temperature can be set to, for example, 1.0 MPa to 10.0 MPa, and the hardness at room temperature can be set to, for example, 50 to 80, preferably 60 to 75.

[0037] The present invention will be further illustrated below by way of examples, but the scope of the present invention is not limited to these examples.

[0038] Example

[0039] In preparing 22 rubber compositions for rim cushioning (Standard Example 1, Comparative Examples 1-10, and Examples 1-11) composed of the blends shown in Tables 1-2, the blending components, excluding the vulcanization accelerator and sulfur, were weighed and mixed in a 1.8L closed Banbury mixer for 5 minutes. The masterbatch was then released and cooled to room temperature. The masterbatch was then fed into a 1.8L closed Banbury mixer, and the vulcanization accelerator and sulfur were added and mixed for 2 minutes to obtain the various rubber compositions for rim cushioning.

[0040] Using the obtained rim cushioning rubber composition, vulcanized rubber test pieces were prepared by vulcanizing at 170°C for 10 minutes using a mold of a specified shape. The hardness of the vulcanized rubber test pieces was measured using a type A hardness tester at 20°C according to JIS K6253. Furthermore, JIS No. 3 dumbbell-shaped test pieces were cut from the obtained vulcanized rubber test pieces according to JIS K6251, and the stress M100 at 100% elongation at room temperature was measured at a tensile speed of 500 mm / min and room temperature (20°C). Using these hardness and M100 values, the product of the stress M100 at 100% elongation at room temperature (unit: MPa) and the hardness at room temperature was calculated and recorded in the "M100 × Hardness" column of Tables 1-2. In addition, the total amount of carbon black and silica mixed in Tables 1-2 is also recorded ("Total of CB + Silica" in the tables).

[0041] Using the above-mentioned rim cushioning rubber compositions (vulcanized rubber test pieces), the elongation at break (EB), tanδ at 60°C, and abrasion resistance were evaluated by the methods shown below.

[0042] Elongation at break (EB)

[0043] Using various rim cushioning rubber compositions (vulcanized rubber test pieces), JIS No. 3 dumbbell-shaped test pieces were cut according to JIS K6251. Tensile tests were conducted at room temperature (20°C) at a tensile speed of 500 mm / min, and the elongation at break was measured. The results are expressed as an index with the value of Standard Example 1 set to 100. A higher index value indicates a higher elongation at break. Furthermore, an index value of "95" or higher indicates maintaining a good elongation at break comparable to Standard Example 1.

[0044] tanδ at 60℃

[0045] Regarding the rubber compositions (vulcanized rubber test pieces) used for rim cushioning, the tanδ at 60°C was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd., under conditions of initial strain of 10%, amplitude ±2%, frequency of 20Hz, and temperature of 60°C. The evaluation results are shown in the "tanδ (60°C)" column of Tables 1-2, with the value of Standard Example 1 set to 100. The smaller the value, the better the low-heat generation performance.

[0046] Wear resistance

[0047] For the rubber compositions (vulcanized rubber test pieces) used for rim cushioning, the abrasion resistance was determined using a Pick abrasion tester according to ASTM-D2228. Evaluation results were expressed as an index with the reciprocal of the measured value of Standard Example 1 set to 100. A higher index indicates better abrasion resistance. Furthermore, an index value of "98" or higher indicates that good abrasion resistance is adequately maintained at the current level.

[0048] [Table 1] Table 1

[0049]

[0050] [Table 2] Table 2

[0051]

[0052] The following shows the types of raw materials used in Tables 1-2.

[0053] NR: Natural rubber, STR20

[0054] •BR1: Butadiene rubber, Nipol BR1220 manufactured by Zion Corporation of Japan

[0055] •BR2: End-modified butadiene rubber for silica, JSR Corporation BR511

[0056] ·CB1: Carbon black (Grade: ISAF), キャボットジャパン Co., Ltd. ショウブラック N234 (CTAB adsorption specific surface area: 115m 2 / g)

[0057] ·CB2: Carbon black (Grade: FEF), Stereocarbon N550 manufactured by Kempinski Co., Ltd. (CTAB adsorption specific surface area: 40m 2 / g)

[0058] • Silica 1: Solvay 1085GR (CTAB adsorption specific surface area: 85m²) 2 / g)

[0059] • Silica 2: Solvay 115GR (CTAB adsorption specific surface area: 115m²) 2 / g)

[0060] ·Silane coupling agent: Si69 manufactured by Edotron Co., Ltd.

[0061] ·Fragrance oil: Showa Seiko Oil Co., Ltd.'s Esterol No. 4 S

[0062] Anti-aging agent 1: Santoflex 6PPD manufactured by Frekisys

[0063] Anti-aging agent 2: Nocrust 224 manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0064] • Wax: Paraffin wax produced by Ōuchi Shinshin Chemical Industry Co., Ltd.

[0065] Stearic acid: Nippon Oil Co., Ltd.'s stearic acid

[0066] • Zinc oxide: Three types of lead oxide produced by Zhengtong Chemical Industry Co., Ltd.

[0067] • Insoluble sulfur: Mukron OT-20 manufactured by Shikoku Chemical Industry Co., Ltd.

[0068] • Vulcanization accelerator 1: Sulphamide-based vulcanization accelerator, Noccellar NS-P manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0069] • Vulcanization accelerator 2: Guanidine-based vulcanization accelerator, Perkacit DPG manufactured by Flexsys

[0070] • Vulcanization accelerator 3: Thiuram-based vulcanization accelerator, tetrabenzylthiuram disulfide, PerformanceAdditives Perkacit TBzTD pdr-d

[0071] As shown in Tables 1-2, Examples 1-11, compared to Standard Example 1, maintain / improve hardness, elongation at break, and wear resistance while improving low heat generation (tanδ at 60°C), thus achieving a good balance of these properties.

[0072] On the other hand, in Comparative Example 1, due to the small CTAB adsorption surface area of ​​carbon black, the total amount of carbon black and silica mixed together was small, resulting in a small product of M100 × hardness, thus failing to maintain abrasion resistance. In Comparative Example 2, due to the small CTAB adsorption surface area of ​​carbon black, the small product of M100 × hardness, thus failing to maintain abrasion resistance. In Comparative Example 3, due to the small CTAB adsorption surface area of ​​carbon black, the small total amount of carbon black and silica mixed together, the small product of M100 × hardness, thus failing to maintain abrasion resistance. In Comparative Example 4, due to the small CTAB adsorption surface area of ​​carbon black, the small product of M100 × hardness, thus failing to maintain abrasion resistance. In Comparative Example 5, due to the small amount of natural rubber mixed together, and the large amount of butadiene rubber mixed together, with no carbon black mixed in, the total amount of carbon black and silica mixed together was small, resulting in a small product of M100 × hardness, thus failing to maintain abrasion resistance. Comparative Example 6: Due to the low amount of natural rubber and the high amount of butadiene rubber, the CTAB adsorption surface area of ​​carbon black was small, thus abrasion resistance could not be maintained. Comparative Example 7: Due to the low amount of natural rubber and the high amount of butadiene rubber, abrasion resistance could not be maintained, and the effect of improving low-heat generation was not achieved. Comparative Example 8: Because carbon black was not blended, the total amount of carbon black and silica was small, thus abrasion resistance could not be maintained. Comparative Example 9: Because silica has a large CTAB adsorption surface area, the elongation at break deteriorated, and the effect of improving low-heat generation was not achieved. Comparative Example 10: Because silica was not blended, the effect of improving low-heat generation was not achieved.

[0073] This disclosure includes the following inventions.

[0074] [1] An invention provides a rubber composition for rim cushioning, characterized in that, relative to a diene rubber comprising 35% to 65% by mass of isoprene rubber and 35% to 65% by mass of butadiene rubber, it contains a CTAB adsorption specific surface area of ​​60 m². 2 / g~100m 2 The adsorption specific surface area of ​​ / g silica and CTAB is 60m². 2 / g~160m 2 The butadiene rubber comprises at least one silica-terminated butadiene rubber, wherein the amount of silica in the mixture is 10 parts by mass or more relative to 100 parts by mass of the butadiene rubber, and the total amount of silica and carbon black in the mixture is more than 50 parts by mass relative to 100 parts by mass of the butadiene rubber. The product of the stress M100 (unit: MPa) at 100% elongation at room temperature and the hardness at room temperature of the rubber composition is 150 or more.

[0075] [2] The rim cushioning rubber composition according to [1] is characterized in that the proportion of the silica-terminated butadiene rubber contained in the butadiene rubber is 15% to 100% by mass.

[0076] [3] The rim cushioning rubber composition according to [1] or [2] is characterized in that the total amount of the above-mentioned silica and carbon black is 80 parts by mass or less relative to 100 parts by mass of the diene rubber.

[0077] [4] The rim cushioning rubber composition according to any one of the inventions [1] to [3] is characterized in that sulfur and vulcanization accelerator are mixed with the diene rubber, and the total amount of the sulfur and the vulcanization accelerator is 3.5 parts by mass or more relative to 100 parts by mass of the diene rubber.

[0078] [5] A tire, characterized in that it comprises a rim buffer rubber layer formed of a rim buffer rubber composition according to any one of [1] to [4].

[0079] Explanation of symbols

[0080] 1. Fetal face

[0081] 2. Side of the tire

[0082] 3. Bead area

[0083] 4. Fetal body layers

[0084] 5. Bead core

[0085] 6. Bead filling

[0086] 7. Belt layer

[0087] 8. Belt Covering Layer

[0088] 10 Tread rubber layers

[0089] 20 Sidewall rubber layers

[0090] 30 Rim buffer rubber layer

[0091] CL stands for Tire Equator.

Claims

1. A rubber composition for rim cushioning, characterized in that, A CTAB adsorption specific surface area of ​​60 m² was mixed into a diene rubber comprising 35%–65% isoprene rubber and 35%–65% butadiene rubber. 2 / g~100m 2 The adsorption specific surface area of ​​ / g silica and CTAB is 80m². 2 / g~135m 2 The butadiene rubber comprises at least one silica-terminated butadiene rubber, wherein the amount of silica mixed is 10 parts by mass or more relative to 100 parts by mass of the butadiene rubber, and the total amount of silica and carbon black mixed is more than 50 parts by mass relative to 100 parts by mass of the butadiene rubber. The product of the stress M100 at 100% elongation at room temperature and the hardness at room temperature of the rubber composition is 150 or more, wherein the unit of stress M100 is MPa, and the proportion of silica-terminated butadiene rubber contained in the butadiene rubber is 40% by mass to 100% by mass.

2. The rubber composition for rim cushioning according to claim 1, characterized in that, The total amount of the silica and the carbon black is less than 80 parts by mass relative to 100 parts by mass of the diene rubber.

3. The rubber composition for rim cushioning according to claim 1 or 2, characterized in that, The diene rubber is mixed with sulfur and a vulcanization accelerator, wherein the total amount of sulfur and the vulcanization accelerator is 3.5 parts by mass or more relative to 100 parts by mass of the diene rubber.

4. A tire, characterized in that, It has a rim buffer rubber layer formed from the rim buffer rubber composition according to claim 1 or 2.

Images