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JP-7855857-B2 - Rubber composition for crawler and rubber crawler

JP7855857B2JP 7855857 B2JP7855857 B2JP 7855857B2JP-7855857-B2

Inventors

  • 長井 遥
  • 河合 郭葵
  • 遠矢 昴

Assignees

  • 住友ゴム工業株式会社

Dates

Publication Date
20260511
Application Date
20211221

Claims (8)

  1. It contains rubber components including isoprene-based rubber and styrene-butadiene rubber, and carbon black. The content of the styrene-butadiene rubber in the rubber component is 30% by mass or more. The carbon black content / styrene-butadiene rubber content > 2.0, The amount of polymer × the amount of styrene-butadiene rubber in the rubber component > the amount extracted with acetone. The amount of acetone extracted from the rubber composition was measured according to the method for measuring the amount of acetone extracted in accordance with JIS K 6229:2015 (unit: mass %) of the rubber composition. The amount of polymer is calculated from the amount of organic matter lost (by mass) when the sample remaining after acetone extraction is thermally decomposed and vaporized by heating in nitrogen (raising the temperature from room temperature to 750°C) in accordance with JIS K6226-1:2003 (unit: mass %) of the rubber composition for crawlers.
  2. It contains zinc oxide, The rubber composition for crawlers according to claim 1, wherein the carbon black content / zinc oxide content < 30.
  3. The crawler rubber composition according to claim 1 or 2 , wherein the total amount of styrene in the rubber component is less than 8% by mass.
  4. The crawler rubber composition according to any one of claims 1 to 3 , wherein the cetyltrimethylammonium bromide specific surface area of the carbon black is 130 m² /g or more.
  5. The rubber composition for crawlers according to any one of claims 1 to 4 , wherein the rubber component comprises butadiene rubber.
  6. A rubber composition for crawlers according to any one of claims 1 to 5 , containing silica.
  7. A rubber composition for crawlers according to any one of claims 1 to 6 , containing vulcanized rubber particles.
  8. A rubber crawler using the rubber composition described in any one of claims 1 to 7 .

Description

This disclosure relates to a rubber composition for crawler tracks and a rubber crawler. Various methods have been considered to improve the durability of rubber tracks (see, for example, Patent Document 1). However, in recent years, there has been a demand for further improvements in durability. Japanese Patent Publication No. 2019-119431 The crawler rubber composition of this disclosure contains a rubber component comprising isoprene-based rubber and styrene-butadiene rubber, and carbon black, wherein the carbon black content / styrene-butadiene rubber content > 2.0, and the polymer amount × styrene-butadiene rubber content in the rubber component > acetone extraction amount. The reason why the above rubber composition produces the aforementioned effects is presumed to be as follows. The presence of isoprene-based rubber and styrene-butadiene rubber in the rubber components is thought to create an interface between these rubber phases, as well as micro-domains formed by the styrene portion of the styrene-butadiene rubber. Since each molecular chain, including the styrene portion, exhibits high mobility at high temperatures, it is thought that it absorbs external inputs within the molecule and also facilitates input absorption at the interface. Furthermore, by ensuring a sufficiently large amount of carbon black compared to the styrene-butadiene rubber, it is thought that the interfaces between each rubber phase will be more easily reinforced by the carbon black. On the other hand, by using a higher proportion of styrene-butadiene rubber than acetone-extracted components such as plasticizers, excessive softening of each rubber phase can be suppressed, allowing each rubber phase and interface to absorb external inputs while providing sufficient reinforcement at the interface. The above effects are thought to result in improved crack resistance under high-temperature conditions. In the above rubber composition, the acetone extract amount (AE) is preferably 4% by mass or more, more preferably 6% by mass or more, even more preferably 8% by mass or more, and also preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. Within this range, a better effect tends to be obtained. In the above rubber composition, the polymer content (PC) is preferably 35% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, and also preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. Within this range, a better effect tends to be obtained. In the above rubber composition, the amount of carbon black (BC) is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and also preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. Within this range, a better effect tends to be obtained. In the above rubber composition, the ash content is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 1.5% by mass or more, and also preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less. Within this range, a better effect tends to be obtained. The acetone extract amount (AE), polymer amount (PC), carbon black amount (BC), and ash amount (Ash) are measured by the following methods. First, the amount of acetone extracted (AE) is measured for the above rubber composition (sample) using the method for measuring the amount of acetone extracted in accordance with JIS K 6229:2015 (unit: mass %) of the above rubber composition (sample). The polymer content (PC) is calculated from the amount of weight lost (by mass) when the organic matter in the sample remaining after the acetone extraction is thermally decomposed and vaporized by heating in nitrogen (raising the temperature from room temperature to 750°C), in accordance with JIS K6226-1:2003 (unit: mass %) of the above rubber composition (sample). The amount of carbon black (BC) is calculated from the amount of weight (mass) lost when the sample, after the above-mentioned thermal decomposition and vaporization, is oxidized and burned by heating in air (unit: mass %) of the above-mentioned rubber composition (sample). The ash content is calculated from the mass of components (ash) that do not burn in the above-mentioned oxidative combustion (unit: mass %) of the above-mentioned rubber composition (sample). Based on the above definitions, the sum of AE, PC, BC, and Ash is 100% by mass. Methods known to those skilled in the art can be used to adjust AE, PC, BC, and Ash. For example, AE tends to increase as the amount of plasticizers such as oil in the rubber composition increases. PC tends to increase as the amount of rubber components in the rubber composition increases. BC tends to increase as the amount of carbon black in the rubber compositi