RUBBER COMPOSITION FOR TIRE INNER LINER AND PNEUMATIC TIRE

Abstract

A rubber composition for a tire inner liner according to an embodiment contains a rubber component containing halogenated butyl rubber, a carbon black, a pulverized bituminous coal, and an aliphatic/aromatic copolymer petroleum, resin. A pneumatic tire according to the embodiment includes an inner liner formed of the rubber composition for a tire inner liner.

Claims

1. A rubber composition for a tire inner liner, comprising a rubber component containing halogenated butyl rubber, a carbon black, a pulverized bituminous coal, and an aliphatic/aromatic copolymer petroleum resin.

2. The rubber composition for a tire inner liner according to claim 1, containing 5 to 30 parts by mass of the pulverized bituminous coal, and 0.1 to 20 parts by mass of the aliphatic/aromatic copolymer petroleum resin, with respect to 100 parts by mass of the rubber component.

3. The rubber composition for a tire inner liner according to claim 1, wherein a ratio of the halogenated butyl rubber to the rubber component is 70% by mass or more.

4. The rubber composition for a tire inner liner according to claim 1, wherein the carbon black has a nitrogen adsorption specific surface area of 20 to 70 m.sup.2/g.

5. The rubber composition for a tire inner liner according to claim 2, containing 10 to 70 parts by mass of the carbon black with respect to 100 parts by mass of the rubber component.

6. The rubber composition for a tire inner liner according to claim 1, wherein the aliphatic/aromatic copolymer petroleum resin has a softening point of 90 to 110° C.

7. A pneumatic tire comprising an inner liner containing the rubber composition for a tire inner liner according to claim 1.

8. A pneumatic tire comprising an inner liner containing the rubber composition for a tire inner liner according to claim 2.

9. A pneumatic tire comprising an inner liner containing the rubber composition for a tire inner liner according to claim 3.

10. A pneumatic tire comprising an inner liner containing the rubber composition for a tire inner liner according to claim 4.

11. A pneumatic tire comprising an inner liner containing the rubber composition for a tire inner liner according to claim 5.

12. A pneumatic tire comprising an inner liner containing the rubber composition for a tire inner liner according to claim 6.

Description

EXAMPLES

[0031] Hereinafter, certain embodiments are described below, but the present disclosure is not construed as being limited to these examples.

[0032] First, using a Bunbury mixer, according to the composition (part by mass) shown in Table 1 below, in the first mixing step, the compounding agents excluding sulfur and the vulcanization accelerator were added to the rubber component and kneaded (discharge temperature=160° C.). Next, in the final mixing step, sulfur and the vulcanization accelerator were added to the obtained kneaded product and kneaded (discharge temperature=90° C.). As a result, a rubber composition for a tire inner liner was prepared.

[0033] The details of each components in Table 1 are as follows. [0034] Brominated butyl rubber: “Bromobutyl 2222” manufactured by ExxonMobil Chemical Company. [0035] Carbon black: “SEAST V” manufactured by Tokai Carbon Co., Ltd. (N.sub.2SA: 27 m.sup.2/g) [0036] Pulverized bituminous coal: “Austin Black 325” manufactured by Coal Fillers, Inc. (average particle size: 5.5 μm) [0037] Petroleum resin 1: Aliphatic petroleum resin, “Escorez 1102” manufactured by ExxonMobil Chemical Company. [0038] Petroleum resin 2: Aliphatic/aromatic copolymer petroleum resin, “Petrotack 90” manufactured by Tosoh Co., Ltd. (containing a constituent unit derived from indene, styrene and vinyltoluene, and a constituent unit derived from piperylene. Softening point: 95° C.) [0039] Oil: “NC-140” manufactured by JXTG Energy Corporation. [0040] Zinc oxide: “Zinc Oxide 3 Species” manufactured by Mitsui Mining & Smelting Co., Ltd. [0041] Stearic acid: “BEADS STEARIC ACID” manufactured by NOF Corp. [0042] Vulcanization accelerator: “NOCCELER-DM-P” manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. [0043] Sulfur: “5%-Oil Filled Powdered Sulfur” manufactured by Tsurumi Chemical Industry Co., Ltd.

[0044] Each of the obtained rubber compositions was evaluated for air permeability resistance and low temperature flexural fatigue resistance using a sample vulcanized at 160° C. for 30 minutes. The opening property of the joint portion at the time of producing a green tire was evaluated for each rubber composition. Each measurement and evaluation method is as follows. [0045] Air permeability resistance: The air permeability was measured by a gas permeability tester (“BT-3” manufactured by Toyo Seiki Seisaku-sho Co., Ltd.) using a vulcanized rubber sheet having a thickness of 1 mm as a sample, and the reciprocal of the measured value was indicated by an index with the value of Comparative Example 1 as being 100. It is demonstrated that as the numerical value is larger, the air permeability resistance is better. [0046] Low temperature flexural fatigue resistance: According to JIS K6260, a crack growth test was conducted in an environment of −35° C. using a De Mattia flex test device, and the number of times of flexing until the crack length reached 10 mm was measured. An index was represented relative to the number of flexing in Comparative Example 1 as being 100, and it is demonstrated that, as the numerical value is greater, the low temperature flexural fatigue resistance is better. [0047] Joint opening property: 1000 green tires (tire size: 11R22.5) were produced using each rubber composition as an inner liner, and the presence of opening in the joint portion of the inner liner was examined. Regarding the number of green tires with opening, based on the number of occurrences in Comparative Example 1, it was evaluated as “A” for a decrease of 20% or more, “B” for a decrease of 10% or more and less than 20%, “C” for a decrease of 1% or more and less than 10%, and “D” for no decrease or increase.

TABLE-US-00001 TABLE 1 Com.1 Ex.. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Composition (parts by mass) Brominated 100 100 100 100 100 100 100 butyl rubber Carbon black 50 50 50 50 50 50 30 Pulverized 10 10 10 10 10 10 30 bituminous coal Petroleum 3 — — — — — — resin 1 Petroleum — 1 3 5 10 15 5 resin 2 Oil 5 5 5 5 5 5 5 Zinc oxide 3 3 3 3 3 1 3 Stearic acid 1 1 1 1 1 1 1 Vulcanization 2 2 2 2 2 2 2 accelerator Sulfur 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Evaluation Air 100 115 121 127 138 145 140 permeability resistance Low 100 120 126 130 140 130 120 temperature flexural fatigue resistance Joint — A A A B C C opening property

[0048] The results are shown in Table 1. Compared to Comparative Example 1 in which the pulverized bituminous coal and the aliphatic petroleum resin were combined, in Examples 1 to 6 in which the pulverized bituminous coal and the aliphatic/aromatic copolymer petroleum resin are combined, air permeability resistance and flexural fatigue resistance at low temperatures were greatly improved, and opening at the joint portion was also prevented.

[0049] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, these embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures These embodiments, omissions, replacements, changes, and the like thereof are included in the scope and gist of the disclosure, as well as in the scope of the disclosure described in the claims and the equivalent scope thereof.