JP2010120460A - Rubber composition for rubber crawler and rubber crawler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a rubber crawler that has both hardness and great deformation followability, and is superior in durability, and to provide the rubber crawler manufactured by using the rubber composition. <P>SOLUTION: A protruding rubber composition for the rubber crawler forms a protrusion which is provided on an inner circumferential surface of the rubber crawler so as to protrude therefrom. The rubber composition for the rubber crawler contains 5 to 40 wt.% of 1,2-polybutadiene in the rubber component and has a JIS-A hardness after vulcanization of 75 to 100. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a rubber composition mainly used for a rubber crawler mounted on an undercarriage such as an agricultural machine or a civil engineering construction machine, and a rubber crawler manufactured using the rubber composition.

  A rubber crawler is usually composed of a rubber crawler body that is reinforced by embedding a core metal and a steel cord in an endless rubber elastic body, and a large number of protrusions called lugs are formed on the outer surface (tread surface) of the rubber crawler body. Attached to the undercarriage of various agricultural and civil engineering machinery such as combines, tractors, mini excavators, etc. that are required to run on soft ground, which is difficult to drive with ordinary tires such as wet fields, fields, and muddy areas. Has been.

  However, in the above machine equipped with the rubber crawler in which the above-described core metal is embedded, the rubber crawler is driven by hooking the driving wheel (sprocket) to the core metal. There is a problem that vibration and noise are increased particularly when traveling at high speed. For this reason, recently, an increasing number of machines employ a crawler that does not embed a core metal (no core metal).

  In the core bar-less crawler, instead of the core bar, protrusions (protrusion rubber) that mesh with the sprocket are continuously formed over the entire inner peripheral surface of the crawler. This protrusion meshes with the wheel of the traveling device of the machine to efficiently transmit the driving force and prevent the wheel from being removed. For this reason, when this coreless crawler is used, there is no metal part that contacts the sprocket on the rubber crawler. It is possible to reduce the fatigue of the workers. Furthermore, since there is no contact between the metal parts, it is effective for improving the durability of the undercarriage of the machine.

  The coreless rubber crawler is classified into a positive drive type and a friction drive type according to the main purpose of forming the protrusion. The former is mainly engaged with the sprocket (drive wheel) and the driving force from the machine is transmitted to the rubber crawler by this engagement, and the latter is arranged mainly for the purpose of preventing the wheel from being removed. Is transmitted by the frictional force between the inner peripheral surface of the crawler and the drive wheel.

  In any case, the above-described protrusion is required to have very high durability due to its role. Various attempts have been made so far in order to improve the durability of the protrusions. The applicant has disclosed in JP-A-10-53171 (Patent Document 1) other members in the protrusions protruding on the inner peripheral surface of the rubber crawler. A technique has been proposed in which the protrusion is reinforced by exposing a high-hardness resin member having low friction performance to the contact surface with (a sprocket, idler or wheel). Japanese Patent Application Laid-Open No. 2002-21455 (Patent Document 2) discloses a technique for reinforcing a protrusion by providing a reinforcing member made of sheet metal along the protrusion shape of the driving protrusion.

  Further, in order to make the rubber crawler more reliable in terms of driving force transmission performance and wheel slip prevention performance, in addition to the above-described reinforcement of the protrusion, it is required to improve the hardness of the rubber forming the protrusion and reduce the friction coefficient. ing. In order to meet this requirement, conventionally, in order to increase the hardness of rubber, the amount of carbon and sulfur is increased to increase the hardness of rubber, but this method causes a significant decrease in workability. Even if the hardness is increased, the followability to large deformation may be impaired, and as a result, the effect of improving the durability is often reduced.

  On the other hand, the applicant reduced the friction coefficient of the protruding rubber by blending a predetermined amount of fatty acid amide and ultrahigh molecular weight polyethylene into the raw rubber in Japanese Patent Application Laid-Open No. 9-164980 (Patent Document 3). Proposal of a rubber composition for rubber crawlers that can improve the wear resistance and anti-derailing performance of the crawler.

  However, when a large impact or skewing force is applied to the rubber crawler during traveling, sudden meshing abnormality or the like may occur, resulting in large deformation.In such a case, the conventional reinforcement described above, Protrusions that have been improved by blending rubber, etc., have high rubber modulus (tensile stress) and low elongation, so the protrusions are likely to break and have a negative impact on durability after large deformations. Is concerned.

  Thus, in order to improve the durability of the protrusions, it is important to reconcile the rubber composition that forms the protrusions so that both the hardness of the rubber and the large deformation followability are compatible. It is desired to solve the contradictory problem of increasing the hardness and following large deformation.

JP-A-10-53171 Japanese Patent Laid-Open No. 2002-212455 Japanese Patent Laid-Open No. 9-164980

  Accordingly, an object of the present invention is to provide a rubber composition for a rubber crawler that has both hardness and large deformation followability and is excellent in durability, and a rubber crawler in which protrusions are formed on the inner peripheral surface using the rubber composition. To do.

  As a result of intensive studies to solve the above problems, the present inventors have added 1,2-polybutadiene as a part of the rubber component to the rubber component of the rubber composition for rubber crawlers. It is possible to achieve high hardness and good large deformation followability, and to realize a reduction in the coefficient of friction with higher sophistication. By using this rubber composition, a rubber crawler It has been found that the durability of the protrusions formed on the inner peripheral surface can be improved.

  Therefore, as a result of further investigations, the present inventors have determined that the content of the 1,2-polybutadiene is 5 to 40% by mass in the total rubber component contained in the composition, thereby reducing the tensile stress in the low strain region. (Modulus) is greatly increased, and the modulus in the high strain region is reduced or maintained, and a rubber having good large deformation followability is obtained, thereby increasing the amount of filler and increasing the crosslinking density. In addition, it is possible to achieve a good hardness of 75 to 100 in JIS-A hardness while achieving good large deformation followability, and by blending the above 1,2-polybutadiene as a thermoplastic polymer, a rubber composition It has been found that the processability of is also improved. And, by forming a protrusion on the inner peripheral surface of the rubber crawler using the rubber composition for a rubber crawler containing this 1,2-polybutadiene, both good hardness and large deformation followability can be achieved, and a good friction coefficient The rubber crawler can be formed with good workability, and is resistant to breakage and excellent durability even when a large amount of impact or skew is applied to the rubber crawler during traveling, causing a wheel to be removed or large deformation. And the present invention has been completed.

  Accordingly, the present invention provides a rubber composition for a rubber crawler that forms a protrusion protruding from the inner peripheral surface of a rubber crawler, the rubber component containing 5 to 40% by mass of 1,2-polybutadiene, and an additive. A rubber composition for a rubber crawler having a JIS-A hardness of 75 to 100 after vulcanization, and a protrusion formed on the inner peripheral surface of the rubber crawler using the rubber composition A rubber crawler is provided.

  Since the rubber composition for a rubber crawler of the present invention can be a rubber having both high hardness and large deformation followability after vulcanization, the protrusion on the inner peripheral surface of the rubber crawler is formed using the rubber composition. By providing a rubber crawler that is less likely to break and has excellent durability even when sudden meshing abnormalities or large deformations occur due to the addition of large impacts or skewing forces due to low vibration and noise during traveling Can do. Also, by adding a predetermined amount of fatty acid amide and / or ultrahigh molecular weight polyethylene as a low friction agent to the rubber composition, the friction coefficient of the vulcanized rubber can be reduced, and the durability can be further improved. it can.

The present invention will be described in further detail below.
As described above, the rubber composition for a rubber crawler of the present invention is obtained by adding 1,2-polybutadiene as a part of the rubber component to the rubber component.

  As the rubber component, natural rubber or synthetic rubber known in this field can be used. Specific examples include natural rubber, butadiene rubber, styrene / butadiene rubber, isoprene rubber, ethylene / propylene / diene rubber, butyl rubber, halogenated butyl rubber, chloroprene rubber, isobutylene / isoprene rubber, acrylonitrile / butadiene rubber, silicone rubber, acrylic rubber. Examples thereof include synthetic rubbers such as rubber, epoxidized natural rubber, and acrylate butadiene rubber, and those in which the molecular chain ends of these natural rubber or synthetic rubber are modified, and one or more of these are appropriately selected. do it. In the present invention, natural rubber, butadiene rubber, styrene / butadiene rubber and isoprene rubber can be suitably used.

  In the rubber composition of the present invention, 1,2-polybutadiene is added to the rubber component as a part of the rubber component. In this case, known 1,2-polybutadiene can be used, but syndiotactic 1,2-polybutadiene having a high degree of crystallinity is preferably used from the viewpoint of high rigidity (high hardness). Specifically, JSR RB manufactured by JSR Corporation can be used as a commercially available product. The blending ratio of the 1,2-polybutadiene in the rubber component is 5 to 40% by mass, preferably 10 to 30% by mass. If the ratio of 1,2-polybutadiene in the rubber component is too high, the elongation at break and the strength at break may be reduced. If it is too low, the hardness and followability during large deformation may not be obtained.

  In the present invention, a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerating agent, a plasticizer, which are usually used in the rubber industry, as necessary, within a range that does not impair the effects of the present invention with respect to the rubber component. Additives such as carbon, waxes, low friction agents, lubricants, anti-aging agents, antioxidants, fillers, foaming agents, tackifiers, petroleum resins, ultraviolet absorbers, dispersants, etc. it can.

  As the low friction agent, a known low friction agent can be used, and is not particularly limited. For example, fatty acid amide or ultrahigh molecular weight polyethylene can be used.

  As the fatty acid amide, an amide of an aliphatic carboxylic acid can be used, and in particular, an amide of an aliphatic monocarboxylic acid having 12 to 22 carbon atoms can be suitably used. Specific examples thereof include stearic acid amide, oleic acid amide, erucic acid amide, lauric acid amide and the like, and one of these may be used alone or in combination of two or more. In the present invention, stearic acid amide, oleic acid amide, and erucic acid amide can be preferably used. By blending these fatty acid amides, the coefficient of friction on the surface of the cured product of the rubber composition can be reduced. The amount of the fatty acid amide is 1 to 15 parts by mass, preferably 2 to 10 parts by mass with respect to 100 parts by mass of the rubber component. If it exceeds 15 parts by mass, the adhesion to other members may be reduced, and if it is less than 1 part by mass, the effect of reducing the friction coefficient may not be exhibited.

  Further, as the ultra-high molecular weight polyethylene, polyethylene having an average molecular weight of 1 million or more can be used. In the present invention, polyethylene having an average molecular weight in the range of 1,200,000 to 3,000,000, preferably 1,500,000 to 2,500,000 is used. It can be used suitably. In addition, the average molecular weight here means a viscosity average molecular weight. Further, although not particularly limited in the present invention, the ultra high molecular weight polyethylene used is one having an average particle diameter of usually 100 μm or less, preferably 50 μm or less, particularly preferably 30 μm or less, and a lower limit of 25 μm or more. It is preferable to do. The blending amount of the ultra high molecular weight polyethylene is 2 to 40 parts by mass, preferably 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. If it exceeds 40 parts by mass, the elongation at break, strength reduction and workability may be reduced, and if it is less than 2 parts by mass, the effects of reducing the friction coefficient and increasing the hardness may not be obtained. In addition, the said fatty acid amide and ultra high molecular weight polyethylene may be mix | blended independently with the rubber composition of this invention, and may be used combining both as needed.

As carbon black, those usually used in the rubber industry can be used, and are not particularly limited. For example, carbon such as SRF, GPF, FEF, HAF, ISAF, SAF, FT, MT, etc. Black can be mentioned. In the present invention, it is desirable to use high-grade carbon from the viewpoint of wear resistance and the like, and FEF, HAF, ISAF, and SAF can be suitably used. The carbon black preferably has a nitrogen adsorption specific surface area of 10 to 150 m ² / g and a DBP absorption amount (Method A) of 50 to 200 ml / 100 g. Moreover, these carbon blacks may be used individually by 1 type, and may use 2 or more types together. The compounding amount of the carbon black is 10 to 80 parts by mass with respect to 100 parts by mass of the rubber component.

  The vulcanizing agent is not particularly limited as long as it is usually used in this field, but sulfur can be suitably used in the present invention. The blending amount is 0.5 to 4 parts by mass with respect to 100 parts by mass of the rubber component.

  The vulcanization accelerator is not particularly limited as long as it is usually used in this field. For example, CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (Nt Sulfenamide-based vulcanization accelerators such as -butyl-2-benzothiazylsulfenamide) and TBSI (Nt-butyl-2-benzothiazylsulfenimide), and guanidines such as DPG (diphenylguanidine) And vulcanization accelerators such as tetrauric vulcanization accelerators, thiuram vulcanization accelerators such as tetraoctyl thiuram disulfide and tetrabenzyl thiuram disulfide, and zinc dialkyldithiophosphates. The compounding quantity of the said vulcanization accelerator is 0.3-4 mass parts with respect to 100 mass parts of said rubber components.

  The vulcanization acceleration aid is blended from the viewpoint of promoting vulcanization, and known zinc white (ZnO), fatty acids, and the like can be blended. The fatty acid may be a saturated, unsaturated, linear or branched fatty acid, and is not particularly limited as the carbon number of the fatty acid. For example, the fatty acid has 1 to 30 carbon atoms, preferably 15 carbon atoms. ~ 30 fatty acids, more specifically, cyclohexane acid (cyclohexanecarboxylic acid), naphthenic acid such as alkylcyclopentane having a side chain, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acid such as neodecanoic acid) , Saturated fatty acids such as dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid, linolenic acid, and resin acids such as rosin, tall oil acid, and abietic acid Etc. These may be used alone or in combination of two or more. In the present invention, zinc white and stearic acid can be preferably used. The compounding amount of these vulcanization accelerators is 0 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

  Examples of waxes include waxes such as known paraffin wax and microcrystalline wax, and amide compounds such as stearic acid amide, oleic acid amide, and erucic acid amide, and the like can be used alone or in combination of two or more. Can be used. In particular, in the present invention, paraffin wax and microcrystalline wax can be preferably used. By these blending, molding workability can be improved. The compounding amount of the wax is 0 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

  As the plasticizer, known ones can be used, and are not particularly limited. Specific examples thereof include process oils such as aromatic oils, naphthenic oils and paraffin oils, vegetable oils such as palm oil, and alkylbenzenes. Synthetic oils such as oil can be used, and one or more of them may be appropriately selected and used from these. The amount of the plasticizer is 0 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

  As the anti-aging agent, known ones can be used, and are not particularly limited, and examples thereof include a phenol type anti-aging agent, an imidazole type anti-aging agent and an amine type anti-aging agent. The amount of the anti-aging agent is 0 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

  By setting the rubber composition of the present invention as described above, a rubber having a JIS-A hardness of 75 to 100, particularly 80 to 95 can be obtained after vulcanization. If the hardness is less than 75, there is a risk of impeding driving force transmission. If the hardness exceeds 100, the modulus in the high strain region becomes high, and the followability during large deformation may be insufficient. . In addition, normal conditions can be employ | adopted for vulcanization | cure conditions, Although it does not restrict | limit in particular, It can be set as the conditions of 100-180 degreeC and 1 minute-5 hours.

  When obtaining the rubber composition of the present invention, there is no particular limitation on the blending method of each of the above components, and all the component raw materials may be blended and kneaded at once, and each component may be divided into two or three stages. You may mix | blend and knead | mix. In the kneading, a kneader such as a roll, an internal mixer, a Banbury rotor or the like can be used.

  The rubber composition for a rubber crawler of the present invention can be applied to any rubber crawler, and can be suitably used particularly for a protrusion on the inner peripheral surface of a cored bar-less crawler. And when manufacturing a rubber crawler by forming the processus | protrusion using the rubber composition of this invention in an internal peripheral surface, a conventionally well-known manufacturing method can be employ | adopted.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not restrict | limited to the following Example.

[Examples 1 to 12, Comparative Examples 1 to 10]
A rubber composition having the composition shown in Tables 1 to 3 was kneaded according to a conventional method, formed into a sheet of length 150 mm × width 150 mm × thickness 2 mm, and vulcanized and cured at 155 ° C. for 30 minutes. Was evaluated. The characteristics of the obtained evaluation body were evaluated by the following methods, and the results are shown in Tables 1 to 3.

"Evaluation methods"
-Mooney viscosity Measured according to JIS K6300-1.
・ Hardness (JIS-A hardness)
Based on JIS K6253, it measured with durometer A.
-Modulus (tensile stress) and elongation Based on JIS K6251, the tensile stress at the time of elongation 50%, 100% and 300%, and elongation at the time of cutting were measured using a dumbbell-shaped No. 3 test piece.
・ Fatigue resistance (200% fatigue)
Using a DIN S3A type dumbbell test piece, measurement was performed at room temperature under conditions of 0 to 200% and 5 Hz.
In Table 1, the measurement result of Comparative Example 1 is set to 100, the measurement results of Examples 1 to 4 and Comparative Examples 2 and 3 are expressed as indices relative to Comparative Example 1, and in Table 2, the measurement result of Comparative Example 4 is set to 100. The measurement results of Examples 5 to 8 and Comparative Examples 5 to 7 were expressed as indices relative to Comparative Example 4. In Table 3, the measurement result of Comparative Example 8 was set to 100, and the measurement results of Examples 9 to 12 and Comparative Examples 9 and 10 were expressed as indices relative to Comparative Example 8.
・ Abrasion resistance (coefficient of friction)
Based on DIN 53516, DIN abrasion was measured at room temperature using a DIN abrasion tester. In Table 1, the measurement result of Comparative Example 1 is set to 100, the measurement results of Examples 1 to 4 and Comparative Examples 2 and 3 are expressed as indices relative to Comparative Example 1, and in Table 2, the measurement result of Comparative Example 4 is set to 100. The measurement results of Examples 5 to 8 and Comparative Examples 5 to 7 were expressed as indices relative to Comparative Example 4. In Table 3, the measurement result of Comparative Example 8 was set to 100, and the measurement results of Examples 9 to 12 and Comparative Examples 9 and 10 were expressed as indices relative to Comparative Example 8.

NR: Natural rubber, “RSS # 4”
SBR: Styrene-butadiene rubber, “Taipol 1500E” manufactured by TSRC
BR: High cis 1,4-polybutadiene rubber, “BR01” manufactured by JSR
RB: Syndiotactic 1,2-polybutadiene, “RB820” manufactured by JSR
Carbon black: HAF grade carbon black, "Asahi # 70" manufactured by Asahi Carbon Co.
Oil: Aroma oil, “Nippon Oil Co., Ltd.” “Komolex NH-60T”
Stearic acid: “PALMAC1600” manufactured by ACIDCHEM
Zinc flower: "Ginza SR" manufactured by Toho Zinc Co., Ltd.
Wax: “OZOAGE-0017” manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent: “ANTIGENE6C” manufactured by Sumitomo Chemical Co., Ltd.
Ultra high molecular weight polyethylene: "Miperon" manufactured by Mitsui Chemicals
Fatty acid amide: Oleic acid amide, “Diamid M309” manufactured by Nippon Kasei Co., Ltd.
Sulfur: “Sulfax 5” manufactured by Tsurumi Chemical Co., Ltd.
Vulcanization accelerator: “Noxeller CZ-G” manufactured by Ouchi Shinsei Chemical Co., Ltd.

Table 1 shows an example using NR and SBR as rubber components.
In Table 1, Comparative Example 1 is a conventional formulation in which 1,2-polybutadiene is not blended, and the blending amount of the vulcanizing agent and carbon is also a standard amount. The rubber composition obtained by the prescription has a low Mooney viscosity, good processability, large elongation, low 300% modulus, and excellent deformation resistance, but low hardness and 50% modulus. Therefore, it is easily deformed and inferior in the ability to prevent the wheel from being removed.

  Comparative Example 2 is a prescription in which the amount of the vulcanizing agent is increased with respect to Comparative Example 1 described above. The rubber composition obtained by the prescription increased in JIS-A hardness and 50% modulus, and improved anti-wheel-release performance. However, the elongation decreased to 60% of Comparative Example 1, and the modulus (especially 300% modulus) in the high strain region significantly increased (not measurable due to breakage), so the large deformation followability was significantly impaired. . Further, the fatigue resistance was reduced to 24% of Comparative Example 1. Therefore, the improvement by increasing the amount of the vulcanizing agent can increase the hardness by increasing the crosslinking density and improve the anti-derailing performance, but it becomes too hard and greatly impairs the large deformation followability and fatigue resistance. It became. In addition, Mooney viscosity is equivalent to the comparative example 1, and workability is maintained.

  Comparative Example 3 is a prescription in which the amount of carbon is increased with respect to Comparative Example 1 above. As in Comparative Example 2, the rubber composition obtained by the prescription increased in JIS-A hardness and 50% modulus, and improved anti-wheeling performance. However, as the elongation decreased to about 60% of Comparative Example 1 and the modulus in the high strain region (particularly the 300% modulus) increased remarkably (measurement was impossible due to fracture), the large deformation followability was significantly impaired. Yes. Further, the fatigue resistance was reduced to 31% of Comparative Example 1. Therefore, although the improvement by increasing the amount of carbon can increase the hardness and the like and improve the anti-derailing performance, it becomes too hard and greatly deteriorates the large deformation followability and fatigue resistance. Further, in this example in which the amount of carbon was increased, the Mooney viscosity increased by 30% or more compared to Comparative Example 1, resulting in a decrease in workability.

  Examples 1 to 4 are formulations in which 1,2-polybutadiene is added and blended as a part of the rubber component at a predetermined blending ratio. In these examples, with an increase in the blending ratio of the 1,2-polybutadiene, the modulus of the low strain region and the JIS-A hardness were significantly increased (up to about 190%) compared to the comparative example 1. Even when compared with Comparative Examples 2 and 3, the same or higher effects were obtained. In addition, the 300% modulus in the high strain region was significantly reduced compared to Comparative Examples 2 and 3, and was maintained equal to that of Comparative Example 1, and the amount of the vulcanizing agent and carbon described above was increased. Problem has been resolved. Therefore, it has been confirmed that by adding 1,2-polybutadiene as a part of the rubber component, a rubber having high hardness and excellent large deformation followability can be obtained. Further, it was confirmed that the addition of 1,2-polybutadiene decreased the Mooney viscosity and improved the processability of the rubber composition, decreased the friction coefficient, and improved the durability.

  Table 2 shows an example using NR and BR as rubber components. As a result, as in the results of Table 1, by adding 1,2-polybutadiene to a part of the rubber component, a rubber having high hardness, excellent large deformation followability, and excellent durability and workability is obtained. It was confirmed that

  Table 3 above shows examples in which NR and BR are used as rubber components and no low friction agent is contained. As a result, as in the results of Table 1, by adding 1,2-polybutadiene to a part of the rubber component, a rubber having high hardness, excellent large deformation followability, and excellent durability and workability is obtained. It was confirmed that

  Therefore, from the above examples, by forming the protrusion on the inner peripheral surface of the rubber crawler using the rubber composition for a rubber crawler of the present invention, both good hardness and large deformation followability can be achieved, and a good friction coefficient can be obtained. Protrusions can be formed with good workability, and rubber crawlers with excellent durability are resistant to breakage and large deformation when a large impact or skewing force is applied to the rubber crawler during traveling. It was confirmed that it was obtained.

Claims (4)

A rubber composition for a rubber crawler that forms a protrusion protruding from the inner peripheral surface of the rubber crawler,
A rubber composition for a rubber crawler, comprising 5 to 40% by mass of 1,2-polybutadiene in a rubber component and having a JIS-A hardness after vulcanization of 75 to 100.   2. The rubber composition for a rubber crawler according to claim 1, wherein the rubber component further contains one or more selected from natural rubber, butadiene rubber, styrene-butadiene rubber and isoprene rubber.   The fatty acid amide is blended in an amount of 1 to 15 parts by mass with respect to 100 parts by mass of the rubber component, and / or 2 to 40 parts by mass of ultrahigh molecular weight polyethylene with respect to 100 parts by mass of the rubber component. Rubber composition for rubber crawler.   A rubber crawler in which the protrusion on the inner peripheral surface of the rubber crawler is formed using the rubber composition according to any one of claims 1 to 3.