JP6584925B2 - Rubber composition and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  Rubber products such as tires are deteriorated in the presence of ozone, and the rubber surface is cracked, which causes deterioration in durability. Therefore, in order to suppress the occurrence and progression of such cracks, it is known to add an amine-based anti-aging agent to the rubber composition. However, although the amine-based anti-aging agent is excellent in ozone resistance, it excessively migrates (blooms) to the rubber surface and causes deterioration in appearance such as discoloration.

  In order to suppress discoloration due to an amine-based anti-aging agent, Patent Document 1 discloses that a polyoxyalkylene alkyl ether-based nonionic surfactant is added to a diene rubber. Patent Document 2 discloses that an ester having a tetrahydropyran ring or a tetrahydrofuran ring in its molecule and a polyether type nonionic surfactant are blended in a diene rubber. Patent Document 3 discloses that an ester-type nonionic surfactant is blended in a rubber component. However, in these documents, the nonionic surfactant improves the appearance by smoothing the concavo-convex surface of the amine-based anti-aging agent and the like deposited on the rubber surface. The use of polyoxyalkylene naphthyl ether as a surfactant is not disclosed.

JP 2012-057153 A JP 2006-045279 A Japanese Patent Laying-Open No. 2015-000973

  An object of this invention is to provide the rubber composition which can suppress the deterioration of the external appearance by mix | blending an amine type anti-aging agent, and a pneumatic tire using the same.

  The rubber composition according to the present invention contains a diene rubber, carbon black, an amine antioxidant, and a polyoxyalkylene naphthyl ether.

  The pneumatic tire according to the present invention is produced using the rubber composition.

  According to the present invention, in the case where the amine-based antioxidant is blended with the diene rubber, the polyoxyalkylene naphthyl ether is blended together with the carbon black, thereby suppressing the migration of the amine-based antioxidant to the rubber surface. Deterioration of appearance can be suppressed. Moreover, the dispersibility of carbon black is improved by polyoxyethylene naphthyl ether, so that processability and low heat build-up can be improved.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition according to this embodiment contains a diene rubber as a rubber component, carbon black, an amine anti-aging agent, and a polyoxyalkylene naphthyl ether.

  The diene rubber as the rubber component is not particularly limited. Examples of usable diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene-isoprene rubber, butadiene-isoprene rubber, and styrene-butadiene-. Examples include isoprene rubber, nitrile rubber (NBR), and chloroprene rubber (CR). These can be used alone or in combination of two or more. More preferably, it is at least one selected from the group consisting of NR, SBR, and BR.

  In one embodiment, the diene rubber may be natural rubber alone or a blend of natural rubber and another diene rubber (eg, butadiene rubber). In the case of blending, it is preferable to contain 40 parts by mass or more of NR in 100 parts by mass of the diene rubber. For example, 100 parts by mass of the diene rubber may be composed of 40 to 80 parts by mass of NR and 20 to 60 parts by mass of BR.

  The carbon black is not particularly limited, and various known varieties can be used. For example, SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF class (N500 series), GPF class (N600 series) (both ASTM grade) are preferably used. Any one or a combination of two or more of these grades of carbon black can be used.

  The compounding quantity of carbon black is not specifically limited, For example, 10-150 mass parts with respect to 100 mass parts of diene rubbers, 20-100 mass parts may be sufficient, and 30-80 mass parts may be sufficient.

  Examples of the amine-based antiaging agent include N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine (6PPD), N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD). ), N, N′-diphenyl-p-phenylenediamine (DPPD), N, N′-di-2-naphthyl-p-phenylenediamine (DNPD), N- (3-methacryloyloxy-2-hydroxypropyl)- P-Phenylenediamine aging such as N′-phenyl-p-phenylenediamine, N-cyclohexyl-N′-phenyl-p-phenylenediamine, N- (1-methylheptyl) -N′-phenyl-p-phenylenediamine Inhibitor; p- (p-toluenesulfonylamide) diphenylamine, 4,4′-bis (α, α-dimethyl) Benzyl) diphenylamine (CD), octylated diphenylamine (ODPA), styrenated diphenylamine and other diphenylamine antioxidants; naphthylamines such as N-phenyl-1-naphthylamine (PAN) and N-phenyl-2-naphthylamine (PBN) Anti-aging agent; 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydro-quinoline (ETMDQ), diphenylamine and acetone And an amine-ketone-based anti-aging agent such as a reaction product (ADPAL). These can be used alone or in combination of two or more.

  Among these, the amine-based antioxidant is at least one aromatic secondary selected from the group consisting of p-phenylenediamine-based antioxidants, diphenylamine-based antioxidants, and naphthylamine-based antioxidants. Amine-based antioxidants are preferred. More preferred is a p-phenylenediamine-based antioxidant, and still more preferred is N-alkyl-N′-phenyl-p-phenylenediamine (wherein alkyl is an alkyl group having 3 to 8 carbon atoms).

  The compounding amount of the amine-based anti-aging agent can be appropriately set according to the required ozone resistance performance and the like, and is not particularly limited. For example, 0.5 to 10 parts per 100 parts by mass of the diene rubber. A mass part may be sufficient, 1-8 mass parts may be sufficient, and 2-6 mass parts may be sufficient.

  In the rubber composition according to the present embodiment, polyoxyalkylene naphthyl ether is blended together with the carbon black and the amine-based antioxidant. By blending polyoxyalkylene naphthyl ether, it is possible to suppress the deterioration of appearance by suppressing the migration of amine-based anti-aging agent to the rubber surface, and to improve the dispersibility of carbon black, And low heat build-up can be improved. The reason is presumed as follows, but is not intended to be limited thereby. That is, the naphthyl group of polyoxyalkylene naphthyl ether acts with carbon black, and the polyoxyalkylene part acts with an amine-based anti-aging agent, so that the amine-based anti-aging agent becomes carbon black with polyoxyalkylene naphthyl ether. Therefore, it is considered that the migration (bloom) of the amine-based anti-aging agent can be stopped by the carbon black, or the migration can be delayed. Also, since the naphthyl group acts with carbon black to prevent aggregation between carbon blacks and improve dispersibility, it is considered that this reduces the viscosity of unvulcanized rubber and improves low heat buildup. . In addition, since the polyoxyalkylene naphthyl ether is held in a dispersed state together with the carbon black, it is considered that the migration of the amine-based anti-aging agent acting on the rubber to the rubber surface is more effectively suppressed.

  Examples of the polyoxyalkylene naphthyl ether include compounds represented by the following general formula (1). Such a compound itself is known as a nonionic surfactant.

式中、Ｒは、水素原子又は炭素数が１〜２５のアルキル基を示す。好ましくは、Ｒは水素原子である。Ａ及びＢは、オキシエチレン基又はオキシプロピレン基を示し、オキシエチレン基とオキシプロピレン基の配列はブロックでもランダムでもよい。ｍ及びｎはそれぞれＡ及びＢの平均付加モル数であって０〜４０の数であり、但し、ｍ＋ｎは２〜４０の範囲内である。ポリオキシアルキレン基のナフチル基に対する置換位置は、α位でもβ位でもよい。ポリオキシアルキレン基は、好ましくは、ポリオキシエチレン基、又はオキシエチレン基とオキシプロピレン基の双方を含むポリ（オキシエチレン・オキシプロピレン）基である。ｍ及びｎは、より好ましくは、それぞれ０〜２０の数であり、ｍ＋ｎは２〜２０の範囲内である。

In the formula, R represents a hydrogen atom or an alkyl group having 1 to 25 carbon atoms. Preferably, R is a hydrogen atom. A and B represent an oxyethylene group or an oxypropylene group, and the arrangement of the oxyethylene group and the oxypropylene group may be block or random. m and n are the average added mole numbers of A and B, respectively, and are 0 to 40, provided that m + n is in the range of 2 to 40. The substitution position of the polyoxyalkylene group with respect to the naphthyl group may be α-position or β-position. The polyoxyalkylene group is preferably a polyoxyethylene group or a poly (oxyethylene / oxypropylene) group containing both an oxyethylene group and an oxypropylene group. More preferably, m and n are each a number of 0 to 20, and m + n is in the range of 2 to 20.

  As the polyoxyalkylene naphthyl ether, polyoxyethylene naphthyl ether represented by the following general formula (2) can be used as a more preferred example.

式中、ｐはオキシエチレン基の平均付加モル数であって２〜４０の数であり、より好ましくは２〜２０の数である。

In the formula, p is the average number of added moles of oxyethylene groups and is a number of 2 to 40, more preferably a number of 2 to 20.

  The content of the polyoxyalkylene naphthyl ether is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the diene rubber. The addition effect can be exhibited by being 0.1 parts by mass or more, and the deterioration of low heat generation can be suppressed by being 10 parts by mass or less. The content of the polyoxyalkylene naphthyl ether is more preferably 0.5 to 10 parts by mass, and further preferably 2 to 8 parts by mass with respect to 100 parts by mass of the diene rubber.

  In the rubber composition according to this embodiment, in addition to the above-described components, other fillers such as silica, other anti-aging agents such as phenolic anti-aging agents, silane coupling agents, process oil, zinc white, Various additives usually used in the rubber industry, such as stearic acid, wax, softener, plasticizer, anti-aging agent, vulcanizing agent, and vulcanization accelerator can be blended.

  Examples of the vulcanizing agent include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount is 100 parts by mass of diene rubber. It is preferable that it is 0.1-10 mass parts, More preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 0.5-5 mass parts.

  The rubber composition according to the present embodiment can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. That is, in the first mixing stage, carbon black, amine antioxidant and polyoxyalkylene naphthyl ether are added to and mixed with the diene rubber and other additives except for the vulcanizing agent and the vulcanization accelerator, The rubber composition can be prepared by adding and mixing the vulcanizing agent and the vulcanization accelerator to the obtained mixture in the final mixing stage.

  The rubber composition thus obtained can be used for various rubber products such as tires, anti-vibration rubbers and conveyor belts. It is preferably used for tires, and can be used for various uses such as passenger cars, heavy loads of trucks and buses, and pneumatic tires of various sizes. A pneumatic tire according to an embodiment includes a rubber portion made of the rubber composition. Examples of the application site of the tire include sidewall rubber, rim strip rubber, and the like. The rubber composition is formed into a predetermined shape by, for example, extrusion processing according to a conventional method, and after combining with other parts to produce a green tire (unvulcanized tire), the green tire is heated at 140 to 180 ° C., for example. By performing sulfur molding, a pneumatic tire can be manufactured. Preferably, it is used as a compound for a sidewall, and the pneumatic tire according to one embodiment includes a sidewall rubber made of the rubber composition.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. The raw materials used in the examples and comparative examples are as follows.

・ NR: RSS3 ・ BR: “BR150B” manufactured by Ube Industries, Ltd.
・ Carbon black: HAF, “Seast 3” manufactured by Tokai Carbon Co., Ltd.
・ Oil: “Process NC140” manufactured by JX Nippon Oil & Energy
・ Zinc flower: "Zinc flower 3" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
Anti-aging agent 1: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine (6PPD), “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Anti-aging agent 2: 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), “NOCRACK 224” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Anti-aging agent 3: 2,2′-methylenebis (4-methyl-6-tert-butylphenol) (MBMBP), “NOCRACK NS-6” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Wax: Nippon Seiki Co., Ltd. “OZOACE0355”
Polyoxyethylene naphthyl ether: nonionic surfactant represented by the above formula (2), “Neugen EN” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
・ Polyoxyethylene alkyl ether: “Emulgen 1118” manufactured by Kao Corporation
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator: “Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd.

  The evaluation methods of rubber compositions in the following examples and comparative examples are as follows.

  Low exothermic property: In accordance with JIS K6394, a vulcanized test piece was measured for a loss factor tan δ under conditions of a temperature of 50 ° C., a static strain of 5%, a dynamic strain of 1%, and a frequency of 50 Hz. Expressed with an index of 100. The smaller the index, the smaller the tan δ and the better the low heat buildup (low fuel consumption).

  -Unvulcanized rubber viscosity: In accordance with JIS K6300, using a rotorless Mooney measuring machine manufactured by Toyo Seiki Seisakusho Co., Ltd., preheated the unvulcanized rubber at 100 ° C for 1 minute, and then measured the torque value after 4 minutes. It is a value measured in the unit ML (1 + 4), and is represented by an index with the value of Comparative Example 1 being 100. The smaller the index, the lower the viscosity and the better the workability.

Appearance: The vulcanized rubber pieces were placed in a gear oven whose temperature was adjusted to 40 ° C. and left for 3 weeks. Thereafter, the surface of the vulcanized rubber pieces was visually observed to evaluate the appearance according to the following criteria.
A: The surface is black and hardly discolored. B: Slightly brown or white. B: Slightly brown, yellow, or white. X: Brown or white.

[Preparation of rubber composition]
Using a Banbury mixer, according to the blending (parts by mass) shown in Table 1 below, first, in the first step, other blending agents excluding sulfur and vulcanization accelerator are added and kneaded (discharge Then, in the second step, sulfur and a vulcanization accelerator were added and kneaded (discharge temperature = 90 ° C.) to the kneaded product obtained to prepare a rubber composition. About the obtained rubber composition, while measuring the unvulcanized rubber viscosity, low exothermic property and appearance were evaluated using a test piece having a predetermined shape vulcanized at 160 ° C. for 30 minutes.

  The results are as shown in Table 1. In Comparative Example 2 in which polyoxyethylene alkyl ether was blended with respect to Comparative Example 1 as a control, although the viscosity reduction effect was obtained, the low exothermic property was deteriorated and the effect of suppressing deterioration in appearance was insufficient. Met. Moreover, although the polyoxyethylene naphthyl ether was mix | blended, in the comparative example 3 which mix | blended the phenolic anti-aging agent instead of the amine type anti-aging agent, the effect which suppresses the deterioration of an external appearance property was inadequate. On the other hand, when it is Examples 1-3 which mix | blended polyoxyethylene naphthyl ether with carbon black and amine type anti-aging agent, while low exothermic property is improved, vulcanized rubber viscosity falls and processability In addition, it was also excellent in the effect of suppressing deterioration in appearance.

Claims (4)

A rubber composition comprising a diene rubber, carbon black, an amine antioxidant including a p-phenylenediamine antioxidant and a polyoxyalkylene naphthyl ether.   The rubber composition according to claim 1, wherein a content of the polyoxyalkylene naphthyl ether is 0.1 to 10 parts by mass with respect to 100 parts by mass of the diene rubber.   The rubber composition according to claim 1 or 2, which is a rubber composition for a tire sidewall.   The pneumatic tire produced using the rubber composition of any one of Claims 1-3.