RUBBER COMPOSITION AND A PNEUMATIC TIRE

Abstract

The present invention provides a rubber composition having reduced its odor, which can show a durability improvement effect, as well as to provide a pneumatic tire including the rubber for coating steel cords which is superior in its durability. The objectives above can be solved by providing a rubber composition, including a rubber component a filler, a vulcanization agent, a vulcanization accelerator, and a resorcinol resin, in which the resorcinol resin includes a cresol residue at a content of 0.2 mass % or less, as well as providing a pneumatic tire which has been obtained by vulcanizing the rubber composition, and in particular providing a pneumatic tire in which the rubber is a rubber for coating steel cords.

Claims

1: A rubber composition, comprising: a rubber component; a filler; a vulcanization agent; a vulcanization accelerator; and a resorcinol resin, wherein the resorcinol resin includes a cresol residue at a content of 0.2 mass % or less.

2: The rubber composition according to claim 1, wherein the vulcanization accelerator is a sulfenamide vulcanization accelerator.

3: A pneumatic tire comprising a rubber which has been obtained by vulcanizing the rubber composition according to claim 1.

4: The pneumatic tire according to claim 3, wherein the rubber is a rubber for coating steel cords.

Description

EXAMPLES

[0031] Hereinafter, the examples of the present invention are explained.

Preparation of Rubber Composition

[0032] In accordance with the blending prescription shown in Table 1, each of the rubber compositions of Examples 1 to 4 and Comparative Example 1 was blended, which was kneaded by using a Banbury Mixer to obtain a rubber composition. The agents in Table 1 are explained below. In Table 1, the blending amount of each agent is based on parts by mass with respect to 100 parts by mass of the rubber component.

a) The “natural rubber” (NR) is RSS #3.
b) The “carbon black” is a commercial name, “SEAST 300,” manufactured by Tokai Carbon Co., Ltd.
c) The “silica” is a commercial name “ULTRASIL VN3” manufactured by Evonik Industries AG.
d) The “zinc oxide” is the third type of zinc oxide manufactured by Mitsui Mining And Smelting Company.
e) The “stearic acid” is stearic acid in beads manufactured by NOF Corp.
f) The “antioxidant” is NOCRAC 6C manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.
g) The “resorcinol resin (1)” a commercial name “SUMIKANOL 620” manufactured by Sumitomo Chemical Co., Ltd., which includes a cresol residue at an amount of 4.0 mass %.
h) The “resorcinol resin (2)” is a resorcinol resin having a structural unit derived from a styrenated resorcinol represented by formula (1) as explained above, which includes a cresol residue at an amount of 0.03 mas %, whose commercial name is “B20S” manufactured by Techno Waxchem Pvt. Ltd.
i) The “hexamethoxymethyl melamine” is a commercial name “CYLETS 963L” manufactured by Allnex Japan Corporation.
j) The “stearic acid cobalt” is a commercial name “COREBOND CS-9.5” manufactured by Taekwang Fine Chemical Co. Ltd.
k) The “sulfur” is a commercial name “MUCRON OT-20” manufactured by Shikoku Chemicals Corporation.
l) The vulcanization accelerator, “DCBS” is N, N-dicyclohexyl-2-benzothiazolyl sulfenamide, whose commercial name is “NOCCELER DZ-G” manufactured by Ouchi Shinko Chemical Industry Corporation.
m) The vulcanization accelerator “TBBS” is N-tert-butyl-2-benzothiazole sulfenamide, whose commercial name is “SUNCELER NS-G”, manufactured by Sanshin Chemical Industry Co., Ltd.

[0033] The amount of the cresol residue included the resorcinol resin of the agent was measured by collecting 10 mg of a resorcinol resin sample, followed by dissolving it in 10 mL of a solvent, to measure it by means of a gas chromatography (GC). The measurement conditions are explained below.

The solvent: Acetone including DBP (DBP 0.1 mg/ml);
The column: HP-5;
The GC Apparatus: GC-2010 manufactured by Shimadzu Corporation; and
The Calibration curve: m-cresol at three points (0.01 mg, 1 mg and 5 mg).

[0034] The calibration curve was prepared based on the area ratio of DBP to m-cresol.

[0035] The rubber compositions thus obtained above was then vulcanized, followed by evaluating them in accordance with the following conditions.

(1) Evaluation of Odor

[0036] The evaluation of odor was carried out in accordance with JIS Z9080. An odor bag of a 5 L polyethylene terephthalate was charged with 100 g of a molded sheet and an air having passed through an activated carbon, followed by leaving it at a room temperature of 60 degrees Celsius for two hours. Then, five panelists evaluated the air in the odor bag to classify it into one of six categories (i.e., to 6). The average of the results by the five panelists was calculated. As the number becomes higher, it means it had a stronger odor.

1: No feeling of the odor at all.
2: Very slight feeling of the odor.
3: Weak feeling of the odor.
4: Clear feeling of the odor.
5: Strong feeling of the odor.
6: Very strong feeling of the odor.

(2) Vulcanized Rubber Reinforcement Property

[0037] In accordance with JIS K6251, a tensile test (a dumbbell shape No. 3) was carried out to measure a break strength (TS) and a break elongation (EB), and a product of these values (TS×EB) was assumed to be a tension product. It was shown by an index, assuming that a value of Comparative Example 1 was 100. As the numerical value becomes larger, it means that the reinforcement property becomes more superior.

(3) Peeling Resistance in a Humid, Heated and Aging Condition

[0038] The rubber composition was made sheeting to provide a rubber sheet having a thickness of 1.0 mm. Twelve steel cords, each having a brass plating (structure: 3×0.20 mm+6×0.35 mm), were aligned as a layer with an intervention of 25 mm with each other, which was sandwiched by two sheets of the rubber sheets, two of which were laminated, thereby obtaining an unvulcanized complex including two layers of the steel cords.

[0039] The unvulcanized complex thus obtained was vulcanized at 150 degrees Celsius for 30 minutes to obtain a test piece The test piece was left in a saturated steam condition at 105 degrees Celsius for 96 hours, followed by carrying out a peeling test between the two layers of the steel cords by using an autograph (DCS500 manufactured by Shimadzu Corporation) to evaluate a peeling resistance. It was shown by an index, assuming that a value of Comparative Example 1 was 100. As the numerical value becomes larger, it means that the peeling resistance becomes more superior.

TABLE-US-00001 TABLE 1 Comp. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 natural rubber 100 100 100 100 100 carbon black 60 60 60 60 60 silica — — — 5 — zinc oxide 8 8 8 8 8 stearic acid 1 1 1 1 1 antioxidant 2 2 2 2 2 resorcinol resin 2 — — — — (1) resorcinol resin — 2 2 2 2.5 (2) hexamethoxymethyl 2 2 2 2 2 melamin stearic acid 2 2 2 2 2 cobalt sulfur 6 6 6 6 6 DCBS 1 1 — 1 1 TBBS — — 1 — — Evaluation Of 5 2 2 2 2 Odor Vulcanized Rubber 100 116 114 114 110 Reinforcement Property (tension product) Peeling 100 110 108 109 110 Resistance In A Humid, Heated And Aging Condition

[0040] As shown in Table 1, the vulcanized rubber reinforcement property of the Examples of the present invention was in a range of 110 to 116 and superior to that of Comparative Example 1. The vulcanized rubber reinforcement property of the present invention is preferably higher than that of Comparative Example 1 (the vulcanized rubber reinforcement property=100), and more preferably in a range of 105 to 170, and yet more preferably in a range of 108 to 150.

[0041] As shown in Table 1, the peeling resistance in a humid, heated and aging condition of the Examples of the present invention was in a range of 108 to 110 and superior to that of Comparative Example 1. The peeling resistance in a humid, heated and aging condition of the rubber of the present invention is preferably higher than that of Comparative Example 1 (the peeling resistance in a humid, heated and aging condition=100), and more preferably in a range of 105 to 150, and yet more preferably in a range of 106 to 130.