Rubber composition, and studless tire using the same

Abstract

To solve problems that a friction coefficient reduces on an icy and snowy road surface compared to a normal road surface and the road becomes easily slippery although a large number of methods have conventionally been proposed in order to improve on-ice performance (braking performance on ice) of a studless tire, and to provide a rubber composition with an increased on-ice performance.SOLUTION: A rubber composition in which 30 to 100 pts.mass of carbon black and / or white filler and 0.1 to 20 pts.mass of polymer of cashew nut shell liquid are blended into 100 pts.mass of diene-based rubber containing 30 pts.mass or more of butadiene rubber.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition and a studless tire using the same, and more particularly to a rubber composition having excellent ice performance and a studless tire using the same.

Background Art

[0002] On icy and snowy roads, the friction coefficient is lower than that on ordinary roads, making it easier to slip. Therefore, conventionally, many methods have been proposed to improve the ice performance (braking performance on ice) of studless tires. For example, Patent Document 1 below discloses a tread rubber composition containing 2 to 40 parts by mass of liquefied wood and 10 to 150 parts by mass of a filler with respect to 100 parts by mass of a rubber component.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a rubber composition having even higher ice performance than the prior art and a studless tire using the same.

Means for Solving the Problems

[0005] As a result of intensive research, the present inventors have found that a rubber composition obtained by blending carbon black and / or a white filler with a diene rubber containing butadiene rubber and further blending a specific amount of a polymer of cashew nut shell liquid can solve the above problems, and thus have completed the present invention.

[0006] That is, the present invention provides a rubber composition characterized in that 30 to 100 parts by mass of carbon black and / or white filler and 0.1 to 20 parts by mass of a polymer of cashew nut shell liquid are compounded per 100 parts by mass of a diene rubber containing 30 parts by mass or more of butadiene rubber. The present invention also provides a studless tire using the above rubber composition.

Effects of the Invention

[0007] Since the rubber composition of the present invention is characterized in that 30 to 100 parts by mass of carbon black and / or white filler and 0.1 to 20 parts by mass of a polymer of cashew nut shell liquid are compounded per 100 parts by mass of a diene rubber containing 30 parts by mass or more of butadiene rubber, it is possible to provide a rubber composition having improved ice performance compared to the prior art due to the scratching effect of the polymer on the road surface, and a studless tire using the same.

Modes for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described in more detail.

[0009] (Diene Rubber) As the diene rubber used in the present invention, any diene rubber that can be compounded into the rubber composition can be used. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), etc. can be mentioned. These may be used alone or in combination of two or more. Further, the molecular weight and microstructure are not particularly limited, and they may be end-modified with an 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 from the reason that the effects of the present invention are more excellent, it is preferably from 100,000 to 5,000,000, more preferably from 200,000 to 3,000,000, and even more preferably from 300,000 to 2,000,000. In addition, in this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement. Further, from the viewpoint of improving the performance on ice, it is preferable that the butadiene rubber occupies 30 parts by mass or more, preferably 40 parts by mass or more, in 100 parts by mass of the diene rubber. In addition, the diene rubber preferably has a glass transition temperature (Tg) of -50°C or lower. By defining Tg in this way, the performance on ice is improved. When a plurality of types of diene rubbers are included, the Tg referred to in this specification is a value calculated based on the sum of the products of the glass transition temperature of each rubber multiplied by the weight fraction of each rubber, that is, the weighted average. In the calculation, the sum of the weight fractions of each component is set to 1.0. The glass transition temperature (Tg) referred to in the present invention is the temperature at the midpoint of the transition region measured by a thermogram under the condition of a heating rate of 20°C / min by differential scanning calorimetry (DSC). The more preferable average Tg is -60°C or lower.

[0010] (Carbon black and / or white filler) Specific examples of the carbon black used in the present invention include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. In addition, from the viewpoint of improving the performance on ice, the carbon black preferably has a nitrogen adsorption specific surface area (N2SA) of 10 to 300 m 2 / g, and more preferably 50 to 150 m 2 / g. The nitrogen adsorption specific surface area (N2SA) is a value measured in accordance with JIS K 6217-2:2001, "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single-point method".

[0011] Specific examples of the white filler used in the present invention include, for example, silica, calcium carbonate, magnesium carbonate, talc, clay, alumina, aluminum hydroxide, titanium oxide, calcium sulfate, etc. These may be used alone or in combination of two or more. Among these, silica is preferred because of better performance on ice.

[0012] Specific examples of silica include, for example, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. These may be used alone or in combination of two or more.

[0013] From the viewpoint of improving performance on ice, silica preferably has a CTAB adsorption specific surface area of 50 to 300 m 2 / g, more preferably 90 to 200 m 2 / g. The CTAB adsorption specific surface area is a value obtained by measuring the adsorption amount of n-hexadecyltrimethylammonium bromide on the silica surface in accordance with JIS K6217-3:2001, "Part 3: Method for determining specific surface area - CTAB adsorption method".

[0014] (Polymer of cashew nut shell liquid) Cashew nut shell liquid (CNSL) is a liquid extracted from cashew nut shells, and industrially produced cashew nut shell liquid (CNSL) mainly contains cardanol. Therefore, the polymer of cashew nut shell liquid used in the present invention contains a polymer of a monomer containing a cardanol structure, and the polymer can include a homopolymer of cardanol, a condensate with formaldehyde, a copolymer with other comonomers, etc. Cardanol has the following structure.

[0015] [Chemical formula]

[0016] In the above formula, R is -(CH2) 14 CH3, -(CH2)6CH=CH(CH2)6CH3, -(CH2)6CH=CHCH2CH=CH(CH2)3CH3, -(CH2)6CH=CHCH2CH=CH(CH2)2CH=CH2, etc. can be mentioned.

[0017] Also, from the viewpoint of improving the effects of the present invention, the polymer of cashew nut shell liquid is preferably the polymer of the residue (distillation residue polymer) generated when cashew nut shell liquid (CNSL) is purified and distilled. From the viewpoint of improving the effects of the present invention, the polymer of cashew nut shell liquid preferably has a particle size of 50 mesh or more, more preferably 60 mesh or more and 1000 mesh or less. Note that the particle size of 50 mesh or more means powder passing through a sieve having a mesh opening of 297 μm of 50 mesh or finer. In the present invention, commercially available polymers of cashew nut shell liquid can be used. For example, as distillation residue polymers, products such as Cardolite Japan Co., Ltd.'s trade names NX-1500 (particle size passing 60 mesh) and NX-5208 (particle size passing 100 mesh) can be mentioned.

[0018] (Blending ratio of rubber composition) The rubber composition of the present invention is characterized in that 30 to 100 parts by mass of carbon black and / or white filler and 0.1 to 20 parts by mass of the polymer of cashew nut shell liquid are blended with respect to 100 parts by mass of diene rubber. When the blending amount of carbon black and / or white filler is less than 30 parts by mass with respect to 100 parts by mass of diene rubber, the mechanical properties and abrasion resistance of the rubber composition deteriorate. Conversely, when it exceeds 100 parts by mass, the low-temperature flexibility of the rubber composition decreases and the ice performance deteriorates. When the compounding amount of the polymer of cashew nut shell liquid is less than 0.1 part by mass with respect to 100 parts by mass of the diene rubber, the addition amount is too small to exhibit the effects of the present invention. Conversely, when it exceeds 20 parts by mass, the mechanical properties deteriorate.

[0019] The compounding amount of the carbon black is preferably 5 to 80 parts by mass with respect to 100 parts by mass of the diene rubber. The compounding amount of the white filler is preferably 15 to 80 parts by mass with respect to 100 parts by mass of the diene rubber. The compounding amount of the polymer of cashew nut shell liquid is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the diene rubber.

[0020] (Other components) In the rubber composition of the present invention, in addition to the above-mentioned components, vulcanizing or crosslinking agents; vulcanization or crosslinking accelerators; zinc oxide; anti-aging agents; plasticizers; silane coupling agents; heat-expandable microcapsules and other various additives generally compounded in rubber compositions can be compounded. Such additives can be kneaded by a general method to form a composition and can be used for vulcanization or crosslinking. The compounding amounts of these additives can also be set to conventional general compounding amounts as long as they do not conflict with the object of the present invention.

[0021] Further, the tire of the present invention can be prepared using the rubber composition of the present invention, and is preferably a pneumatic tire, and can be filled with an inert gas such as air, nitrogen, and other gases. Further, the tire of the present invention is preferably applied to a tread, particularly a cap tread, to form a studless tire.

Examples

[0022] Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

[0023] Standard Example, Examples 1 to 5, Comparative Example 1 In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization system (vulcanization accelerator, sulfur) were kneaded in a 1.7-liter sealed Banbury mixer for 5 minutes, then discharged outside the mixer and cooled to room temperature. Subsequently, the composition was put back into the same Banbury mixer, the vulcanization system was added and kneaded to obtain a rubber composition. The obtained rubber composition was press-vulcanized under the conditions of 170 °C for 10 minutes to obtain a vulcanized rubber test piece, and the physical properties were measured by the test methods shown below.

[0024] Ice performance: A sample was prepared by attaching the obtained vulcanized rubber test piece to a flat cylindrical base rubber. Using an ice friction tester, the ice friction coefficient was measured under the conditions of a measurement temperature of -1.5 °C, a load of 98 N, and a road surface speed of 20 km / h. The obtained ice friction coefficient was expressed as an index with the value of the standard example taken as 100. The larger the index, the greater the ice friction force and the better the ice performance. Elongation at break E B : In accordance with JIS K6251, a No. 3 dumbbell-shaped sample piece was punched out from the above vulcanized rubber test piece, and a tensile test was performed at a tensile speed of 500 mm / min to measure the elongation at break (%). The results were expressed as an index with the value of the standard example taken as 100. The larger this index, the better the breaking strength. If the index is 90 or more, it can be judged that it has a practically sufficient elongation at break.

[0025] The results are shown together in Table 1.

[0026]

Table 1

[0027] *1: NR (RSS#3) *2: BR (Nipol BR1220 manufactured by Zeon Corporation, Japan) *3: Carbon black (Seast KHA manufactured by Tokai Carbon Co., Ltd.) *4: Silica (Zeosil 1165MP manufactured by Rhodia, CTAB specific surface area = 159m 2 / g) *5: Silane coupling agent (Si69 manufactured by Evonik Degussa, bis(3-triethoxysilylpropyl)tetrasulfide) *6: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu KK) *7: Polymer 1 of cashew nut shell liquid (Product name NX-1500 (particle size passing 60 mesh) manufactured by Cardolite Japan Co., Ltd.) *8: Polymer 2 of cashew nut shell liquid (Product name NX-5208 (particle size passing 100 mesh) manufactured by Cardolite Japan Co., Ltd.) *9: Sulfur (Fine powder sulfur for Tsurumi Chemical Industry Co., Ltd.'s Kaneka stamp pad ink) *10: Vulcanization accelerator (Nocceler CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

[0028] From the results in Table 1, the rubber compositions of Examples 1 to 5 contain 30 to 100 parts by mass of carbon black and / or white filler and 0.1 to 20 parts by mass of a polymer of cashew nut shell liquid with respect to 100 parts by mass of a diene rubber containing 30 parts by mass or more of butadiene rubber. Therefore, the ice performance is improved compared to the standard example. In Comparative Example 1, since the polymer of cashew nut shell liquid exceeds the upper limit defined in the present invention, the elongation at break was less than 90.

[0029] The present invention includes the following forms. Embodiment 1: A rubber composition characterized in that 30 to 100 parts by mass of carbon black and / or white filler and 0.1 to 20 parts by mass of a polymer of cashew nut shell liquid are blended with respect to 100 parts by mass of a diene rubber containing 30 parts by mass or more of butadiene rubber. Embodiment 2: The rubber composition according to Embodiment 1, wherein the polymer of cashew nut shell liquid is a polymer containing a cardanol structure. Embodiment 3: The rubber composition according to Embodiment 1 or 2, wherein the particle size of the polymer of cashew nut shell liquid is 50 mesh or more. Embodiment 4: A studless tire using the rubber composition according to any one of Embodiments 1 to 3.

Claims

1. A rubber composition characterized by comprising 30 to 100 parts by mass of carbon black and / or white filler and 0.1 to 20 parts by mass of a polymer of cashew nut shell liquid with respect to 100 parts by mass of a diene rubber containing 30 parts by mass or more of butadiene rubber.

2. The rubber composition according to claim 1, wherein the polymer of cashew nut shell liquid is a distillation residue polymer of cashew nut shell liquid.

3. The rubber composition according to claim 1, wherein the polymer of cashew nut shell liquid is a polymer containing a cardanol structure.

4. The rubber composition according to claim 1, wherein the particle size of the polymer of cashew nut shell liquid is 50 mesh or more.

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

Images