Rubber composition and tire using the same

Abstract

To further reduce road noise since an electric vehicle which travels using a motor as a power source has a significantly reduced noise derived from a vehicle compared to a vehicle which travels using an internal combustion engine as a power source and also to give tire physical properties such as tensile strength (TB) and elongation at break (EB) at a certain level or higher.SOLUTION: There is provided a rubber composition which comprises 1 to 10 pts.mass of a foaming agent and 1 to 100 pts.mass of iron oxide based on 100 pts.mass of a diene-based rubber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and a tire using the same, and more particularly, to a rubber composition capable of reducing road noise without impairing tensile strength (TB) or elongation at break (EB), and a tire using the same. [Background technology]

[0002] Electric vehicles that run on a motor as their power source have significantly reduced vehicle-induced noise compared to vehicles that run on an internal combustion engine as their power source. As a result, tire-induced noise (road noise) has been highlighted as a noise source during vehicle operation, and there is a demand for further reduction in road noise. On the other hand, tires are also required to have physical properties such as tensile strength (TB) and elongation at break (EB) at a certain level or higher.

[0003] The following Patent Document 1 discloses a halogen-containing rubber composition characterized in that a vulcanizing agent containing iron oxide as a main component is blended with a halogen-containing rubber. Patent Document 2 listed below discloses an NBR composition containing 100 parts by weight of NBR, 1 to 150 parts by weight of white carbon, and 0.5 to 50 parts by weight of an inorganic compound having an average particle size of 2 μm or less and a Mohs hardness of 6 or more. Patent Document 3 listed below discloses a tire in which a rubber composition containing 40 to 80 parts by mass of a magnetic filler per 100 parts by mass of a rubber component that is at least one type selected from the group consisting of natural rubber, butadiene rubber, and styrene-butadiene rubber is used in the base tread portion. However, none of Patent Documents 1 to 3 discloses any technical idea of ​​blending specific amounts of a foaming agent and iron oxide with the rubber component to reduce road noise without compromising tensile strength (TB) or elongation at break (EB). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-181451 A [Patent Document 2] JP 2006-37044 A [Patent Document 3] JP 2010-150324 A Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to provide a rubber composition capable of reducing road noise without impairing the tensile strength (TB) or elongation at break (EB), and a tire using the same. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have discovered that the above-mentioned problems can be solved by compounding specific amounts of a foaming agent and iron oxide with a diene rubber, and have thus completed the present invention. That is, the present invention provides a rubber composition characterized by containing 1 to 10 parts by mass of a foaming agent and 1 to 100 parts by mass of iron oxide per 100 parts by mass of diene rubber. Effect of the Invention

[0007] The rubber composition of the present invention is characterized by containing 1 to 10 parts by mass of a foaming agent and 1 to 100 parts by mass of iron oxide per 100 parts by mass of diene rubber, and therefore it is possible to provide a rubber composition capable of reducing road noise without impairing tensile strength (TB) or elongation at break (EB), and a tire using the same.

[0008] The foaming agent forms a hollow space in the rubber by foaming after heating, for example. When road noise passes through this hollow space, it is reflected many times, and the energy is attenuated. In addition, iron oxide can exhibit a good sound absorbing effect according to the weight law. In addition, since the compounding amounts of the foaming agent and the iron oxide are appropriately determined in the present invention, there is no adverse effect on the tensile strength (TB) or the elongation at break (EB). As a result, according to the present invention, a rubber composition and a tire that can reduce road noise without impairing the tensile strength (TB) or the elongation at break (EB) can be provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will now be described in further detail.

[0010] (Diene rubber) Examples of the diene rubber used in the present invention include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), etc. The diene rubber used in the present invention is not particularly limited in its molecular weight or microstructure, and may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized. The weight average molecular weight (Mw) of the diene rubber is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated using standard polystyrene as determined by gel permeation chromatography (GPC).

[0011] (foaming agent) The foaming agent used in the present invention is not particularly limited, and examples thereof include thermally expandable microcapsules, chemical foaming agents, physical foaming agents, supercritical fluids, etc. Among these, thermally expandable microcapsules and / or chemical foaming agents are preferred because they provide superior effects of the present invention. Specific examples of chemical foaming agents include azodicarbonamide (ADCA), dinitrosopentamethylenetetraamine (DPT), dinitrosopentastyrenetetramine, oxybisbenzenesulfonylhydrazide (OBSH), benzenesulfonylhydrazide derivatives, ammonium bicarbonate that generates carbon dioxide, ammonium carbonate, sodium bicarbonate, toluenesulfonylhydrazide that generates nitrogen, P-toluenesulfonylsemicarbazide, nitrososulfonyl azo compounds, N,N'-dimethyl-N,N'-dinitrosophthalamide, P,P'-oxybis(benzenesulfonylsemicarbazide), and the like. These may be used alone or in combination of two or more. The thermally expandable microcapsules are configured by encapsulating a thermally expandable substance in a shell material made of a thermoplastic resin. The shell material of the thermally expandable microcapsules can be made of a nitrile polymer. The thermally expansive substance contained in the shell material of the microcapsule has a property of vaporizing or expanding by heat, and is exemplified by at least one selected from the group consisting of hydrocarbons such as isoalkanes and normal alkanes. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane, and examples of normal alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used alone or in combination. A preferred form of the thermally expansive substance is one in which a hydrocarbon that is gaseous at room temperature is dissolved in a hydrocarbon that is liquid at room temperature. By using such a mixture of hydrocarbons, sufficient expansive force can be obtained from the low temperature region to the high temperature region in the vulcanization molding temperature range (150°C to 190°C) of an unvulcanized tire. Examples of such thermally expandable microcapsules include those manufactured by Expancel AB of Sweden under the trade names "EXPANCEL 091DU-80" or "EXPANCEL 092DU-120" and those manufactured by Matsumoto Yushi Seiyaku Co., Ltd. under the trade names "Matsumoto Microsphere F-85D", "Matsumoto Microsphere F-100D", and "FN-105".

[0012] From the viewpoint of reducing road noise, the foaming agent used in the present invention is preferably a hollow microcapsule with a particle size of 1 μm to 5 mm after foaming. Such hollow microcapsules may be appropriately selected from the above-mentioned thermally expandable microcapsules that satisfy the above conditions. The particle size after foaming is more preferably 50 μm to 400 μm.

[0013] (Iron oxide) The iron oxide used in the present invention is not particularly limited, and its composition does not matter, but the average particle size of the iron oxide is preferably 1 μm to 200 μm, more preferably 1 μm to 150 μm, from the viewpoint of the road noise reduction effect. The average particle size of the iron oxide is determined by measuring the lengths of two sides (vertical and horizontal) in a planar image of the iron oxide particles by observation under an electron microscope and calculating the average value.

[0014] (Rubber composition blend ratio) The rubber composition of the present invention is characterized by containing 1 to 10 parts by mass of a foaming agent and 1 to 100 parts by mass of iron oxide per 100 parts by mass of diene rubber. If the amount of the foaming agent is less than 1 part by mass, the amount is too small to achieve the effects of the present invention, whereas if it exceeds 10 parts by mass, the tensile strength (TB) and elongation at break (EB) decrease. If the amount of iron oxide is less than 1 part by mass, the amount is too small to achieve the effects of the present invention, whereas if it exceeds 100 parts by mass, the tensile strength (TB) and elongation at break (EB) decrease. From the viewpoint of improving the effects of the present invention, the compounding amount of the foaming agent is preferably 1 to 10 parts by mass based on 100 parts by mass of the diene rubber. From the viewpoint of improving the effects of the present invention, the compounding amount of the iron oxide is preferably 1 to 100 parts by mass, and more preferably 1 to 50 parts by mass, per 100 parts by mass of the diene rubber. From the viewpoint of improving the effects of the present invention and from the viewpoint of lowering the specific gravity and improving fuel efficiency, the ratio of the foaming agent to the iron oxide (mass ratio) is preferably 1:1 to 1:5.

[0015] (Other ingredients) In addition to the above-mentioned components, the rubber composition of the present invention may contain various additives that are generally compounded in rubber compositions, such as vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, various fillers such as zinc oxide, carbon black, silica, clay, talc, and calcium carbonate, antioxidants, plasticizers, and reinforcing materials, and these additives can be kneaded by a general method to form a composition and used for vulcanization or crosslinking. The amounts of these additives may be conventional amounts as long as they do not go against the object of the present invention.

[0016] The tire of the present invention is preferably a pneumatic tire, which can be filled with air, an inert gas such as nitrogen, or other gases. Furthermore, the rubber composition of the present invention is suitable for manufacturing pneumatic tires according to conventional manufacturing methods for pneumatic tires, and can reduce road noise without impairing the tensile strength (TB) or elongation at break (EB). Therefore, it is preferable to apply the rubber composition to treads, particularly cap treads, to make studless tires. EXAMPLES

[0017] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0018] Examples 1 to 6 and Comparative Examples 1 to 6 In the formulation (parts by mass) shown in Table 1, the components other than the vulcanization accelerator and sulfur were mixed in a 1.7-liter internal Banbury mixer for 5 minutes, and then the vulcanization accelerator and sulfur were added and further mixed to obtain a rubber composition. The unvulcanized rubber composition obtained was then press-vulcanized in a specified mold at 160°C for 20 minutes to obtain a vulcanized rubber test piece, and the physical properties of the vulcanized rubber test piece were measured by the test methods shown below.

[0019] Specific gravity: Measured in accordance with JIS K6250 and JIS K6268.

[0020] Road noise: A test tire with a tire size of 225 / 60R18 was prepared using a vulcanized rubber test piece as the tread. The test tire was mounted on a wheel with a rim size of 18×7J and installed as the front and rear wheels of a passenger car (front-wheel drive vehicle) with an engine displacement of 2.5L. The air pressure was set to 200 kPa, a sound-collecting microphone was installed on the backrest of the driver's seat, and the sound pressure (decibels) in the frequency range of 250 to 400 kHz was measured when the tire was driven on a test course consisting of an asphalt road surface at an average speed of 60 km / h. The evaluation results were calculated by calculating the reciprocal of the measured value, and expressed as an index with the value of Comparative Example 1 being 100. The larger the index, the more the road noise was reduced.

[0021] Tensile strength (TB): Based on JIS K6250 and JIS K6251 (JIS No. 3 dumbbell), tensile tests were conducted at room temperature. The higher the result, the better the tensile strength. If the TB is 11 MPa or more, it can be judged that the TB is sufficient for practical use.

[0022] Breaking elongation (EB): Breaking elongation was measured at room temperature according to JIS K6250 and JIS K6251. The higher the value, the better the breaking elongation. Note that an EB of 580% or more is considered to be sufficient for practical use.

[0023] The results are shown in Table 1.

[0024] [Table 1]

[0025] *1:NR (TSR20 manufactured by PT.NUSIRA (SAD)) *2: BR (Nipol BRX5000 manufactured by Zeon Corporation) *3: Carbon black (Cabot Japan Co., Ltd. Show Black N339) *4: Silica (EVONIK WELLINK ULTRASIL VN3GR) *5: Silane coupling agent (Si69 manufactured by EVONIK LANXING (RIZHAO)) *6: Foaming agent (Matsumoto Yushi Seiyaku Co., Ltd. FN-105, thermal expansion microcapsules, particle size after foaming = average 150 μm) *7: Iron oxide (Graphite Mill Scale #150, average particle size = 150 μm) *8: Vulcanization accelerator (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *9: Sulfur (Kinka-jirushi oil-containing fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0026] The results in Table 1 show that the rubber composition of each Example contains 1 to 10 parts by mass of a foaming agent and 1 to 100 parts by mass of iron oxide per 100 parts by mass of diene rubber, and therefore can reduce road noise without compromising tensile strength (TB) or elongation at break (EB) compared to Comparative Example 1. In contrast, Comparative Example 2 was poorer in reducing road noise than Comparative Example 1 because no foaming agent was blended. Comparative Example 3 did not contain iron oxide and was therefore less effective at reducing road noise than Comparative Example 1. In Comparative Examples 4 and 5, the amount of iron oxide blended exceeded the upper limit specified in the present invention, so that the specific gravity was higher than that of Comparative Example 1, raising concerns about deterioration of fuel efficiency, and the tensile strength (TB) and breaking elongation (EB) were also deteriorated. In Comparative Example 6, the blend amount of the foaming agent exceeded the upper limit specified in the present invention, so that the tensile strength (TB) and the elongation at break (EB) were deteriorated compared to Comparative Example 1.

[0027] The present invention includes the following embodiments. Embodiment 1: A rubber composition comprising 100 parts by mass of diene rubber, 1 to 10 parts by mass of a foaming agent, and 1 to 100 parts by mass of iron oxide. Embodiment 2: 2. The rubber composition according to embodiment 1, wherein a ratio of the foaming agent to the iron oxide is 1:1 to 1:5 in terms of mass ratio of the foaming agent:iron oxide. Embodiment 3: 3. The rubber composition according to embodiment 1 or 2, wherein the foaming agent is a hollow microcapsule having a particle size of 1 μm to 5 mm after foaming. Embodiment 4: 4. The rubber composition according to any one of embodiments 1 to 3, wherein the iron oxide has an average particle size of 1 μm to 200 μm. Embodiment 5: A tire formed using the rubber composition according to any one of embodiments 1 to 4. Embodiment 6: A studless tire using the rubber composition according to any one of the first to fourth embodiments.

Claims

1. A rubber composition comprising 1 to 10 parts by mass of a foaming agent and 1 to 100 parts by mass of iron oxide per 100 parts by mass of a diene rubber.

2. 2. The rubber composition according to claim 1, wherein a ratio of the foaming agent to the iron oxide is from 1:1 to 1:5 in terms of mass ratio of the foaming agent:the iron oxide.

3. 2. The rubber composition according to claim 1, wherein the foaming agent is a hollow microcapsule having a particle size of 1 μm to 5 mm after foaming.

4. 2. The rubber composition according to claim 1, wherein the iron oxide has an average particle size of 1 μm to 200 μm.

5. A tire made using the rubber composition according to claim 1.

6. The tire according to claim 5, which is a studless tire.

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