Rubber composition for tire and tire therewith

Abstract

To provide a rubber composition in order to solve a problem that when trying to improve, as the most important performance of heavy weight tires used as tires for trucks and buses, as contrary performance, decrease of breaking elongation and wear resistance are caused.SOLUTION: The above problem was solved by a rubber composition for tires characterized by containing 10-150 pts.mass of a filler consisting of carbon black and / or silica, and 0.5-50 pts.mass of a citric acid ester which may have a substituent, in relation to 100 pts.mass of a diene rubber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition for tires and a tire using the same, and more particularly, to a rubber composition for tires having excellent durability without impairing breaking elongation and abrasion resistance, and a tire using the same. [Background technology]

[0002] For heavy-duty tires used as truck and bus tires, durability is one of the most important performance characteristics. However, when attempting to improve durability by increasing modulus, there is a problem that the breaking elongation and abrasion resistance are reduced as trade-off performances.

[0003] The following Patent Document 1 discloses a rubber composition for tires that contains at least one compound selected from ascorbic acid and its derivatives. Patent Document 2 below discloses a tire including a tread, the tread including a heat expandable rubber composition in an unvulcanized state, the heat expandable rubber composition including a diene elastomer, 70 phr or more and 120 phr or less of silica and 1 phr or more and 10 phr or less of carbon black, a plasticizer that is liquid at 20°C, the plasticizer being included in an amount such that the mass ratio of the sum of the silica and the carbon black to the plasticizer is greater than 2.0, between 8 and 20 phr of a carbonate or bicarbonate, the carbonate or bicarbonate including sodium or potassium, and between 2 and 20 phr of a carboxylic acid having a melting point between 60°C and 220°C, the carboxylic acid being selected from the group of acids consisting of malic acid, α-ketoglutaric acid, citric acid, stearic acid, and mixtures thereof, and the total amount of the carboxylic acid and the carbonate or bicarbonate is greater than 15 phr. However, neither Patent Documents 1 nor 2 discloses any technical idea of ​​providing a rubber composition for tires having excellent durability without impairing elongation at break or abrasion resistance by blending a filler consisting of carbon black and / or silica, and a citric acid ester which may have a substituent, in specific amounts with a rubber component. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3735432 [Patent Document 2] Patent No. 6027097 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 for tires which is excellent in durability without impairing breaking elongation and abrasion resistance, 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 blending a filler consisting of carbon black and / or silica, and a citric acid ester which may have a substituent, in specific amounts with a diene-based rubber, and have thus completed the present invention. That is, the present invention provides a rubber composition for tires, characterized by containing, per 100 parts by mass of diene rubber, 10 to 150 parts by mass of a filler consisting of carbon black and / or silica, and 0.5 to 50 parts by mass of a citric acid ester which may have a substituent. Effect of the Invention

[0007] The rubber composition of the present invention is characterized by containing, per 100 parts by mass of diene rubber, 10 to 150 parts by mass of a filler consisting of carbon black and / or silica, and 0.5 to 50 parts by mass of a citric acid ester which may have a substituent (hereinafter, may be simply referred to as a citric acid ester), and therefore it is possible to provide a rubber composition for tires and a tire using the same, which are excellent in durability without impairing breaking elongation or abrasion resistance.

[0008] The carbon portion contained in the citrate ester acts as a plasticizer for diene rubber and disperses well in the diene rubber. The ester groups contained in the citrate ester interact with each other to attract each other, improving the modulus of the rubber composition for tires. In this case, the citrate ester does not adversely affect the elongation at break or the abrasion resistance. 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 as standard polystyrene by gel permeation chromatography (GPC).

[0011] (B) Filler The rubber composition of the present invention contains a filler made of carbon black and / or silica. From the viewpoint of improving the effect of the present invention, the carbon black is preferably carbon black having a nitrogen adsorption specific surface area (N2SA) of 60 to 150 m 2 The nitrogen adsorption specific surface area (N2SA) is a value determined in accordance with JIS K6217-2. On the other hand, from the viewpoint of improving the effect of the present invention, silica having a nitrogen adsorption specific surface area (N2SA) of 150 to 220 m 2 It is preferred that the molecular weight is / g. The rubber composition of the present invention may contain only carbon black or only silica as the filler, or may contain a combination of carbon black and silica.

[0012] (Citrate ester) From the viewpoint of improving the effects of the present invention, the citrate ester used in the present invention is preferably one represented by the following formula (I).

[0013] [ka]

[0014] (In formula (I), R1 and R2 are each independently hydrogen or a carbon-containing group having 1 to 18 carbon atoms which may have a substituent. However, all of R1 and R2 cannot be hydrogen.) Among these, from the viewpoint of improving the effects of the present invention, it is preferable that either R1 or R2 in the formula (I) is a carbon-containing group having 1 to 5 carbon atoms (e.g., an alkyl group or an acyl group), and it is particularly preferable that R1 is all ethyl groups and R2 is hydrogen, i.e., triethyl citrate, and / or R1 is all butyl groups and R2 is acetyl groups, i.e., tributyl acetyl citrate, in the formula (I) where R1 is all butyl groups and R2 is acetyl groups.

[0015] (Compounding ratio of rubber composition for tires) The rubber composition for tires of the present invention is characterized by containing 10 to 150 parts by mass of a filler made of carbon black and / or silica, and 0.5 to 50 parts by mass of a citric acid ester, relative to 100 parts by mass of diene rubber. If the amount of the filler is less than 10 parts by mass, the modulus and abrasion resistance decrease, whereas if it exceeds 150 parts by mass, the elongation at break deteriorates. If the amount of the citric acid ester is less than 0.5 parts by mass, the amount is too small to achieve the effects of the present invention, whereas if it exceeds 50 parts by mass, the modulus, elongation at break, and abrasion resistance decrease.

[0016] In the filler, the blending amount of carbon black is preferably 10 to 100 parts by mass relative to 100 parts by mass of the diene rubber, and the blending amount of silica is preferably 10 to 100 parts by mass, more preferably 10 to 80 parts by mass, relative to 100 parts by mass of the diene rubber.

[0017] (Other ingredients) In addition to the above-mentioned components, the rubber composition for tires of the present invention may contain various additives that are generally incorporated in rubber compositions, such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various fillers such as zinc oxide, clay, talc, and calcium carbonate, antioxidants, and plasticizers, and these additives can be kneaded by a general method to form a composition, which can be used for vulcanization or crosslinking. The amounts of these additives may be conventional amounts, so long as they do not go against the object of the present invention.

[0018] 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. In addition, the rubber composition for tires of the present invention is suitable for producing pneumatic tires according to conventional methods for producing pneumatic tires, and has excellent durability without impairing breaking elongation or abrasion resistance, and is therefore suitable for use in the treads of passenger car tires and heavy load tires. EXAMPLES

[0019] 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.

[0020] Examples 1 to 8 and Comparative Examples 1 to 5 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.

[0021] 100% modulus (M100), 300% modulus (M300): Measured according to JIS K6251. The results are expressed as an index, with the value of Comparative Example 1 being 100. A larger index indicates better durability.

[0022] Breaking elongation (EB): Tested at room temperature according to JIS K 6251. The results are expressed as an index, with the value of Comparative Example 1 being 100. A larger index indicates a higher breaking elongation (EB).

[0023] Abrasion resistance: A Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd. was used to measure and determine the abrasion loss under conditions of a load of 5 kg (49 N), a slip rate of 25%, a time of 4 minutes, and room temperature. The results were calculated by calculating the reciprocal of the measured value, and expressed as an index with the value of Comparative Example 1 set at 100. A larger index indicates better abrasion resistance.

[0024] The results are shown in Table 1.

[0025] [Table 1]

[0026] *1: SBR (Nipol 1502 manufactured by Zeon Corporation) *2: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *3: Stearic acid (NOF Corporation Stearic Acid YR) *4: Carbon black (Cabot Japan Co., Ltd., Show Black N339) *5: Silica (EVONIK WELLINK ULTRASIL VN3GR) *6: Silane coupling agent (Si69, bis(3-triethoxysilylpropyl)tetrasulfide, manufactured by Evonik Degussa *7: Vulcanization accelerator (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *8: Sulfur (Kinka-jirushi oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.) *9: Process oil (Diana Process NH-60 manufactured by Idemitsu Kosan Co., Ltd.) *10: Citric acid (Kanto Chemical Co., Ltd.) *11: Triethyl citrate (manufactured by Jungbunzlauer) *12: Acetyl tributyl citrate (manufactured by Jungbunzlauer) *13: Butyl propionate (Kanto Chemical Co., Ltd.)

[0027] The results in Table 1 show that the rubber composition of each Example contains 10 to 150 parts by mass of a filler consisting of carbon black and / or silica, and 0.5 to 50 parts by mass of a citric acid ester per 100 parts by mass of diene rubber, and therefore has excellent durability without compromising breaking elongation or abrasion resistance compared to Comparative Example 1. In contrast, in Comparative Example 2, the breaking elongation was lower than that of Comparative Example 1 because no citric acid ester was blended. In Comparative Example 3, citric acid was added, and therefore no improvement in various physical properties was observed compared to Comparative Example 1. In Comparative Example 4, the amount of the citric acid ester blended exceeded the upper limit specified in the present invention, so that compared with Comparative Example 1, the modulus, elongation at break, and abrasion resistance were decreased. Comparative Example 5 is an example in which butyl propionate was blended, and therefore, compared with Comparative Example 1, no improvement in modulus and abrasion resistance was observed.

[0028] The present invention includes the following embodiments. Embodiment 1: A rubber composition for tires, comprising 100 parts by mass of diene rubber, 10 to 150 parts by mass of a filler consisting of carbon black and / or silica, and 0.5 to 50 parts by mass of a citric acid ester which may have a substituent. Embodiment 2: The rubber composition for tires according to embodiment 1, wherein the rubber composition contains the silica, and the content of the silica is 10 to 150 parts by mass per 100 parts by mass of the diene rubber. Embodiment 3: The rubber composition according to embodiment 1 or 2, wherein the optionally substituted citric acid ester is represented by the following formula (I):

[0029] [ka]

[0030] (In formula (I), R1 and R2 are each independently hydrogen or a carbon-containing group having 1 to 18 carbon atoms. However, all of R1 and R2 cannot be hydrogen.) Embodiment 4: The rubber composition according to embodiment 3, wherein in formula (I), either R1 or R2 is a carbon-containing group having 1 to 5 carbon atoms. Embodiment 5: The rubber composition according to any one of embodiments 1 to 4, wherein the citric acid ester which may have a substituent is triethyl citrate and / or tributyl acetyl citrate. Embodiment 6: A tire formed using the rubber composition according to any one of the first to fifth embodiments.

Claims

1. A rubber composition for tires, comprising, per 100 parts by mass of diene rubber, 10 to 150 parts by mass of a filler made of carbon black and / or silica, and 0.5 to 50 parts by mass of a citric acid ester which may have a substituent.

2. The rubber composition for tires according to claim 1, characterized in that the rubber composition for tires contains the silica, and the content of the silica is 10 to 150 parts by mass per 100 parts by mass of the diene rubber.

3. 2. The rubber composition for a tire according to claim 1, wherein the citric acid ester which may have a substituent is represented by the following formula (I): 【Chemistry 1】 (In formula (I), R1 and R2 are each independently hydrogen or a carbon-containing group having 1 to 18 carbon atoms which may have a substituent. However, all of R1 and R2 cannot be hydrogen.)

4. 2. The rubber composition for tires according to claim 1, wherein in formula (I), either R1 or R2 is a carbon-containing group having 1 to 5 carbon atoms.

5. 2. The rubber composition for tires according to claim 1, wherein the citric acid ester which may have a substituent is triethyl citrate and / or tributyl acetylcitrate.

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

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