JP2017122171A - Rubber composition for crawler and rubber crawler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a crawler that has excellent wear resistance and cut resistance while maintaining driving stability, and even when rubber powder occurs, can prevent the rubber powder from adhering to a drive part and therearound, and provide a crawler having a crawler member composed of the rubber composition.SOLUTION: A rubber composition for a crawler comprises a rubber component that comprises 70 mass% or more of a diene rubber obtained by polymerization of only a diene monomer and has a content of a 1,2-bond butadiene unit of 15-50 mass%. A crawler has a crawler member composed of the rubber composition.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for a crawler and a rubber crawler having a crawler member made of the rubber composition for a crawler.

  One important industrial application for rubber products is rubber crawlers. Rubber crawlers are mainly used in traveling parts of agricultural machines, construction machines, civil engineering machines, etc. The performance required for rubber compositions (rubber compositions for crawlers) used for rubber crawlers is wear resistance and cut resistance. It has crack growth resistance, ozone degradation resistance, running stability, etc., and having these properties in a good balance leads to a long life of the rubber crawler.

  Patent Document 1 describes a technique for improving cut resistance by using a crawler rubber composition containing styrene butadiene rubber (SBR) and natural rubber (NR) or high styrene polymer (HSR). However, there is a problem that crack growth resistance is reduced by containing SBR.

  Further, it has been studied to improve the cut resistance by lowering the hardness of the rubber composition for crawlers, but there is a problem that the running stability is lowered.

  Patent Document 2 describes a technique for improving the bending resistance and wear resistance of a rubber composition for crawlers by using cis 1,4-polybutadiene rubber. However, when BR is contained, there is a problem that cut resistance is lowered.

  Patent Document 3 uses an ultra-high cis BR having a cis 1,4-bond content of 98% or more and a vinyl bond content of 0.3% or less to achieve both cut resistance and crack growth resistance, and other rubber for crawlers. A rubber composition having excellent performance required for the composition is described.

JP 08-208890 A JP 2001-26671 A JP 2009-298905 A Japanese Patent No. 3560890

  However, the drive unit (wheel unit) of the crawler type vehicle is often a sprocket type having a relatively acute-angled substantially triangular projection (tooth) on the outer surface as described in Patent Document 4, for example. Even a rubber crawler composed of a rubber composition with improved performance required for such a crawler rubber composition, the contact part with the drive part is worn by repeated contact with the teeth of the drive part, There is a problem that rubber powder is generated when a part is cut, and the rubber powder adheres to the drive unit and causes malfunction of the drive unit, or adheres to the periphery of the drive unit and deteriorates appearance. .

  The present invention is for crawlers that are excellent in wear resistance and cut resistance while maintaining running stability, and can prevent rubber powder from adhering to the drive unit and the periphery of the drive unit even when rubber powder is generated. It is an object to obtain a crawler having a rubber composition and a crawler member composed of the rubber composition.

  As a result of intensive studies, the present inventors include a rubber component containing 70% by mass or more of a diene rubber obtained by polymerizing only a diene monomer and having a 1,2-bonded butadiene unit amount of 15 to 50% by mass. The present inventors have found that the above-mentioned problems can be solved by using a rubber composition for crawlers, and have further completed the present invention through further studies.

  That is, the present invention provides a rubber composition for a crawler containing a rubber component containing 70% by mass or more of a diene rubber obtained by polymerizing only a diene monomer and having a 1,2-bonded butadiene unit amount of 15 to 50% by mass. Related to things.

  The rubber composition for crawlers preferably has a JIS-A hardness of 70 or more at 25 ° C.

  The rubber component is preferably a rubber component containing 15% by mass or more of butadiene rubber having a 1,2-bond butadiene unit amount of 80% by mass or more.

  It is preferable that the rubber component is a rubber component containing 40% by mass or more of natural rubber.

  It is preferable to contain 40 to 80 parts by mass of carbon black with respect to 100 parts by mass of the rubber component.

0 to 40 parts by mass of carbon black A having a nitrogen adsorption specific surface area of 70 to 90 m ² / g and 0 to 30% of carbon black B having a nitrogen adsorption specific surface area of 30 to 50 m ² / g with respect to 100 parts by mass of the rubber component It is preferable to contain 40 parts by mass.

  It is preferable to contain 0.5 to 10 parts by mass of a resin having a softening point of 50 ° C. or higher with respect to 100 parts by mass of the rubber component.

  Moreover, this invention relates to the rubber crawler which has the crawler member comprised with the said rubber composition for crawlers.

  According to the rubber composition for a crawler of the present invention and the rubber crawler having a crawler member composed of the rubber composition for a crawler, the rubber composition is excellent in wear resistance and cut resistance while maintaining running stability, and further rubber. Even when powder is generated, it is possible to provide a rubber composition for a crawler that can be prevented from adhering to the drive section and the periphery of the drive section, and a rubber crawler having a crawler member that is constituted by the rubber composition for a crawler.

  The rubber composition for a crawler of the present invention is a rubber containing a predetermined amount of a diene rubber obtained by polymerizing only a diene monomer, and the amount of 1,2-bonded butadiene units in the total amount of rubber components is within a predetermined range. A rubber composition for a crawler containing a component.

  The rubber component according to the present invention includes a diene rubber obtained by polymerizing only a diene monomer. Examples of the diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene and the like.

  Examples of the diene rubber obtained by polymerizing only the diene monomer include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), butadiene isoprene copolymer rubber, and the like. It may be used alone or in combination of two or more. From the viewpoint of cut resistance and running stability, it is preferable to contain NR, and from the viewpoint of rubber strength and rubber powder adhesion preventing effect, it is preferable to contain BR, and the effect of the present invention can be suitably obtained. Therefore, it is more preferable to use NR and BR together.

  The NR is not particularly limited, and those commonly used in the rubber industry can be used, and examples thereof include SIR20, RSS # 3, TSR20, and the like.

  In the case of containing NR, the content in the rubber component is preferably 40% by mass or more, more preferably 50% by mass or more, and more preferably 55% by mass or more from the viewpoints of cut resistance and running stability. In addition, the content of NR is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of balance between low fuel consumption, wet grip properties, and BR content. 65 mass% or less is the most preferable.

  Examples of the BR include BR having a large amount of cis 1,4-butadiene units (high cis BR), BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), and BR having a large amount of 1,2-bonded butadiene units. (High vinyl BR), modified BR and the like. Among these, the fuel economy and wet grip properties are excellent, the amount of 1,2-bonded butadiene units in the total amount of rubber components can be within the range described below, and the crystallinity of BR can be improved. BR with a large amount of 2-bonded butadiene units is preferred.

  The BR having a large amount of 1,2-bonded butadiene units (high vinyl BR) is a BR having 80% by mass or more of 1,2-bonded butadiene units having a vinyl group. It can be manufactured by a manufacturing method described in JP-A-2014-80619.

The amount of 1,2-bonded butadiene units in BR having a large amount of 1,2-bonded butadiene units is 80% by mass or more, and from the viewpoint of low fuel consumption, wet grip properties and crystallinity of BR, 85% by mass or more is present. Preferably, 90 mass% or more is more preferable. Although the upper limit of the said unit amount is not specifically limited, Usually, it is 98 mass% or less. In addition, the 1,2-bond butadiene unit amount of BR in the present specification is a value calculated by ¹ H-NMR measurement.

  The content in the rubber component in the case of containing BR having a large amount of 1,2-bonded butadiene units is preferably 15% by mass or more, more preferably 20% by mass or more from the viewpoint of rubber strength and the effect of preventing adhesion of rubber powder. Preferably, 30% by mass or more is more preferable, and 35% by mass or more is most preferable. Further, the content of BR having a large amount of 1,2-bonded butadiene units is preferably 60% by mass or less, more preferably 50% by mass or less, and more preferably 45% by mass from the viewpoint of the balance between fracture characteristics and NR content. The following is more preferable.

  The content of the diene rubber obtained by polymerizing only the diene monomer in the rubber component is 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass. Most preferred. When it is less than 70% by mass, there is a possibility that excellent cut resistance and running stability cannot be obtained.

  The rubber composition for a crawler of the present invention may contain a rubber component (other rubber component) other than the diene rubber obtained by polymerizing only the diene monomer, but from the viewpoint of cut resistance and running stability. Therefore, it is preferable that only the diene rubber obtained by polymerizing only the diene monomer without containing other rubber components is used as the rubber component.

The 1,2-bond butadiene unit amount in the total amount of the rubber component according to the present invention is 15% by mass or more, preferably 18% by mass or more, more preferably 25% by mass or more, and further preferably 30% by mass or more. If it is less than 15% by mass, the effect of preventing the adhesion of rubber powder tends to be reduced. The amount of 1,2-bonded butadiene units in the total amount of the rubber component is 50% by mass or less, preferably 40% by mass or less, and more preferably 35% by mass or less. When it exceeds 50 mass%, there exists a tendency for cut resistance, rubber strength, and running stability to fall. In addition, the 1,2-bond butadiene unit amount of the rubber component in the present specification is a value calculated by ¹ H-NMR measurement.

  The rubber composition for crawlers of the present invention includes, in addition to the rubber component, compounding agents generally used in the production of rubber compositions for crawlers, for example, reinforcing agents such as carbon black and silica, anti-aging agents, Resins, anti-scorch agents, softeners, zinc oxide, stearic acid, vulcanizing agents, vulcanization accelerators, vulcanization acceleration aids, and the like can be appropriately blended.

  Examples of the carbon black include SAF, ISAF, HAF, FF, FEF, and GPF that are generally used in the rubber industry. These carbon blacks can be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 10 m ² / g or more, more preferably 20 m ² / g or more, from the viewpoint of wear resistance. Further, N ₂ SA of carbon black is preferably 280 m ² / g or less, more preferably 150 m ² / g or less, from the viewpoints of dispersibility and wear resistance. In addition, N ₂ SA of carbon black is a value measured according to A method of JIS K6217.

  In the case of containing carbon black, the content with respect to 100 parts by mass of the rubber component is preferably 40 to 80 parts by mass, and more preferably 50 to 60 parts by mass from the viewpoints of rubber strength, running stability, and ozone degradation resistance.

Further, from the viewpoint of running stability and rubber strength, relative to 100 parts by mass of the rubber component, carbon black A0~40 weight of N ₂ SA is 70~90m ² / g, and N ₂ SA is 30 to 50 m ² It is preferable to contain carbon black containing 0 to 40 parts by mass of carbon black B / g. The content of carbon black A is more preferably 25 to 35 parts by mass, and the content of carbon black B is more preferably 25 to 35 parts by mass.

  The rubber composition for a crawler according to the present invention preferably further contains a resin because a good hardness can be obtained.

  The softening point of the resin is preferably 50 ° C. or higher, and more preferably 80 ° C. or higher. Further, the softening point of the resin is preferably 150 ° C. or lower, and more preferably 110 ° C. or lower. By setting the softening point of the resin within the above range, rubber strength, running stability, and processability can be improved in a balanced manner. In addition, in this specification, the softening point of resin is the temperature at which the softening point specified by JIS K6220-1: 2001 was measured with a ring and ball softening point measuring device and the ball descended.

  Examples of the resin include C5 and C9 petroleum resins, aromatic vinyl polymers, coumarone indene resins, indene resins, polyterpene resins, and phenolic resins. Among these, C5 petroleum resin, coumarone indene resin, and phenolic resin are preferable, and phenolic resin is particularly preferable because rubber strength, running stability, and processability can be obtained in a well-balanced manner.

  Examples of phenolic resins include phenol resins, modified phenolic resins, and those obtained by reacting alkylphenols such as butylphenol with alkynes such as acetylene (condensates). Phenol resins are obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, furfural, etc. with acid or alkali catalysts. Modified phenol resins are cashew oil, tall oil, linseed oil, various animal and vegetable oils. Phenol resin modified with compounds such as unsaturated fatty acid, rosin, alkylbenzene resin, aniline and melamine. As the phenolic resin, a modified phenol resin is preferable because good hardness can be obtained by a curing reaction, and among them, a cashew oil-modified phenol resin and a rosin-modified phenol resin are more preferable.

（化学式（１）中、ｎは１〜９の整数を表す。） As a cashew oil modified phenol resin, what is shown by following Chemical formula (1) can be used conveniently.

(In the chemical formula (1), n represents an integer of 1 to 9.)

  In the cashew oil-modified phenol resin represented by the chemical formula (1), n is an integer of 1 to 9, and 5 or 6 is preferable from the viewpoint of reactivity and dispersibility.

  When a phenolic resin is contained as the resin, it is preferable to further contain a curing agent having a curing action of the phenolic resin. The curing agent is not particularly limited as long as it has a curing action. For example, hexamethylenetetramine (HMT), hexamethoxymethylol melamine (HMMM), hexamethoxymethylol pentamethyl ether (HMMPME), melamine, methylol melamine and the like. Is mentioned. Among them, HMT, HMMM, and HMMPME are preferable because they are excellent in the action of increasing the hardness of the phenolic resin, and HMT is particularly preferable because methylene groups can be effectively released in a small amount and is inexpensive. .

  The content with respect to 100 parts by mass of the phenolic resin in the case of containing a curing agent is preferably 1 part by mass or more, and more preferably 5 parts by mass or more, because it can be sufficiently cured. Further, the content of the curing agent is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, because it can be uniformly cured and can prevent the occurrence of scorch during extrusion.

  In the case of containing a resin, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1.5 parts by mass or more from the viewpoints of low fuel consumption, running stability, and processability. The resin content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and still more preferably 4 parts by mass or less because sufficient rubber strength can be obtained.

  Examples of the vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N-dicyclohexyl-2- Sulfenamide vulcanization accelerators such as benzothiazolylsulfenamide (DZ), thiazole accelerators, thiuram accelerators, dithiocarbamic acid accelerators, aldehyde-amine or aldehyde-ammonia vulcanization accelerators Etc. Of these, sulfenamide-based vulcanization accelerators are preferred because of their excellent vulcanization characteristics, low heat build-up after vulcanization, and good rubber scorch (scorch properties).

  In the case of containing a vulcanization accelerator, the content with respect to 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 0.6 parts by mass or more from the viewpoint of running stability. Further, the content of the vulcanization accelerator is preferably 2.2 parts by mass or less, more preferably 1.8 parts by mass or less, and further preferably 1.4 parts by mass or less from the viewpoint of cut resistance.

  Since the rubber composition for crawlers of the present invention has a high NR content ratio, the vulcanization speed is high, and there is a possibility that rubber burn (discoloration) may occur in the kneading process. Therefore, it is preferable to further contain a vulcanization acceleration aid (vulcanization retarder).

  As the vulcanization accelerator, N-cyclohexylthiophthalimide (retarder CTP manufactured by Ouchi Shinsei Chemical Co., Ltd., retarder PVI manufactured by Monsanto Co., Ltd.), which can slow down the vulcanization and prevent rubber burning, is used. It is preferable. In the case where N-cyclohexylthiophthalimide is contained, the content with respect to 100 parts by mass of the rubber component is preferably 0.3 parts by mass or less from the reason of suppressing bloom. Moreover, 0.1 mass part or more is preferable and, as for content of N-cyclohexyl thiophthalimide, 0.2 mass part or more is more preferable.

  It does not specifically limit as a manufacturing method of the rubber composition for crawlers of this invention, A well-known method can be used. For example, it can be produced by a method in which each of the above components is kneaded using a rubber kneader such as an open roll, a Banbury mixer, a kneader, and then vulcanized.

  The JIS-A hardness at 25 ° C. of the rubber composition for crawlers of the present invention is preferably 70 or more, more preferably 72 or more, and further preferably 75 or more, from the viewpoint of running stability. The JIS-A hardness at 25 ° C. of the rubber composition for crawlers of the present invention is preferably 105 or less, more preferably 100 or less, from the viewpoint of cut resistance.

  The rubber crawler of this invention is manufactured by a normal method using the rubber composition for crawlers of this invention. That is, the rubber composition for a crawler of the present invention is extruded in accordance with the shape of the crawler member at an unvulcanized stage, and bonded to another crawler member to form an unvulcanized rubber crawler on a rubber crawler molding machine. To do. The rubber crawler of the present invention can be manufactured by heating and pressing the unvulcanized rubber crawler in a vulcanizer.

  The rubber crawler of the present invention is used in a crawler type vehicle for construction, agriculture, etc., and in particular, a crawler type in which a rubber crawler having a sprocket type drive portion having a substantially triangular tooth having an acute angle on the outer surface is severely worn. It can be suitably used for a vehicle.

  The present invention will be described based on examples, but the present invention is not limited to the examples.

Hereinafter, various chemicals used in Examples and Comparative Examples are shown together.
NR: TSR20
BR1: BR manufactured in the following BR1 production example (1,2-bonded butadiene unit amount: 90% by mass, cis-1,4-bonded butadiene unit amount: 3% by mass, trans 1,4-bonded butadiene unit amount: 7 mass%)
BR2: BR150B manufactured by Ube Industries, Ltd. (high cis BR, 1,2-bonded butadiene unit amount: 1% by mass, cis 1,4-bonded butadiene unit amount: 97% by mass, trans 1,4-bonded butadiene unit amount : 2% by mass)
Carbon black 1: N330 manufactured by Tokai Carbon Co., Ltd. (N ₂ SA: 96 m ² / g)
Carbon black 2: N550 made by Tokai Carbon Co., Ltd. (N ₂ SA: 50 m ² / g)
Carbon black 3: N660 manufactured by Tokai Carbon Co., Ltd. (N ₂ SA: 40 m ² / g)
Resin 1: PR12686 manufactured by Sumitomo Bakelite Co., Ltd. (cashew oil-modified phenol resin represented by the above chemical formula (1), softening point: 100 ° C.)
Resin 2: Marukaretsu M890 manufactured by Maruzen Petrochemical Co., Ltd. (C5 petroleum resin, softening point: 105 ° C.)
HMT: Noxeller H manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator: Retarder PVI (N-cyclohexylthiophthalimide) manufactured by Monsanto
Sulfur: Seimisulfur manufactured by Nippon Kiboshi Kogyo Co., Ltd. (containing 10% oil, insoluble matter due to carbon disulfide: 60% or more)
Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<BR1 production example>
850 g of hexane, 1.74 mmol of bis [2- (N, N-dimethylamino) ethyl] ether (BDMAEE), 0.29 mmol of sodium 3, with stirring in a nitrogen-substituted 2 L autoclave 7-dimethyl-3-octanolate (Na-DMO), 150 g of 1,3-butadiene (as 50% strength solution in hexane), and 0.58 mmol n-butyllithium (BuLi) (23% strength solution in hexane) As) and stirred while heating to 80 ° C. for 60 minutes. The stirred rubber solution was then precipitated in ethanol and stabilized with 2,6-di-tert-butyl-4-cresol (BHT). The precipitated rubber was isolated from ethanol and dried in vacuo at 60 ° C. for 16 hours.

  The measurement methods of BR and the microstructure in the rubber component (1,2-bonded butadiene unit amount, cis 1,4-bonded butadiene unit amount, and trans 1,4-bonded butadiene unit amount) are shown below.

<Measurement of BR microstructure>
The measurement was performed using a JNM-ECA series NMR apparatus manufactured by JEOL Ltd. The measurement was carried out on 1 g of BR dissolved in 15 ml of toluene, slowly poured into 30 ml of methanol, purified and then dried and purified. In addition, the microstructure is the signal intensity ratio of 1,4-bond (5.30-5.50 ppm) and 1,2-bond (4.94-5.03 ppm) as determined by ¹ H-NMR, and ¹³ C- It calculated from the signal intensity ratio of the cis bond (25.5 ppm) and trans bond (32.8 ppm) by NMR measurement.

<Measurement of microstructure of rubber component>
The measurement was performed using a JNM-ECA series NMR apparatus manufactured by JEOL Ltd. The measurement was performed on 1 g of a rubber sample dissolved in 15 ml of toluene, slowly poured into 30 ml of methanol, purified, dried and purified. In addition, the microstructure is the signal intensity ratio of 1,4-bond (5.30-5.50 ppm) and 1,2-bond (4.94-5.03 ppm) as determined by ¹ H-NMR, and ¹³ C- It calculated from the signal intensity ratio of the cis bond (25.5 ppm) and trans bond (32.8 ppm) by NMR measurement.

Examples and Comparative Examples In accordance with the formulation shown in Table 1, various chemicals other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. in a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd. did. Thereafter, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded with an open roll at 80 ° C. for 5 minutes to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 0.5 mm thick mold at 170 ° C. for 20 minutes to obtain a vulcanized rubber sheet. The obtained unvulcanized rubber composition was molded into a crawler belt shape and vulcanized at 170 ° C. for 12 minutes to produce a test rubber crawler (size: 400-90 × 42 / WZ). The following evaluation was performed about the obtained vulcanized rubber sheet and the rubber crawler for a test. The results are shown in Table 1.

<Hardness>
The type A durometer hardness of each vulcanized rubber sheet is determined according to the measurement method described in JIS K6253-3 “Vulcanized rubber and thermoplastic rubber—How to obtain hardness—Part 3: Durometer hardness”. The measurement was performed in an atmosphere of ° C.

<Running stability>
Each test rubber crawler was mounted on a Powercro Zero Kingwell manufactured by Kubota Co., Ltd., and was run on an off-road test course. The test driver evaluated the stability of control during steering at that time, and the comparative example 1 was set to 100 and displayed as an index. The larger the value, the better the running stability. The running stability index is 95 or more as a performance target index.

<Cut resistance>
In accordance with JIS K6251, a tensile test was performed using No. 3 dumbbell-shaped test pieces made of each vulcanized rubber sheet, and the breaking strength (TB) (MPa) and elongation at break (EB) (%) were measured. Then, the numerical value of TB × EB / 2 was used as the breaking strength, and the breaking strength of each vulcanized rubber sheet was expressed as an index according to the following calculation formula with the breaking strength of Comparative Example 1 being 100. The larger the index, the better the cut resistance. The cut resistance index is 85 or more as the performance target index.
(Cut resistance index) = (TB of each formulation × EB / 2) / (TB of comparative example 1 × EB / 2) × 100

<Abrasion resistance>
The amount of lamborn wear of each vulcanized rubber sheet on the market road surface was measured using a lamborn wear tester manufactured by Iwamoto Seisakusho. A result is shown by the reciprocal number which made Comparative Example 1 100. It shows that it is excellent in abrasion resistance, so that an index | exponent is large. The wear resistance index is 90 or more as a performance target index.

<Adhesion of rubber powder>
After the running stability test, the adhesion of rubber powder to the drive unit and the periphery of the drive unit was observed and evaluated according to the following criteria. ○ The above is the performance target. A similar amount of rubber powder was generated from each test rubber crawler.
◎: There is no adhesion of rubber powder. ○: Rubber powder is attached slightly, but the appearance is not so bad. △: Rubber powder is attached slightly. ×: A lot of rubber powder is attached. The appearance is bad. Or, there is a problem with the drive unit due to a lot of rubber powder.

  From the results of Table 1, a rubber composition for crawlers containing a rubber component containing 70% by mass or more of a diene rubber obtained by polymerizing only a diene monomer and having a 1,2-bonded butadiene unit amount of 15 to 50% by mass. It can be seen that the object is excellent in wear resistance and cut resistance while maintaining running stability, and even when rubber powder is generated, the rubber powder can be prevented from adhering to the drive unit and the periphery of the drive unit.

Claims (8)

Containing 70% by mass or more of a diene rubber obtained by polymerizing only a diene monomer,
A rubber composition for a crawler comprising a rubber component having a 1,2-bonded butadiene unit amount of 15 to 50% by mass. The rubber composition for a crawler according to claim 1, wherein the JIS-A hardness at 25 ° C is 70 or more. The rubber composition for a crawler according to claim 1 or 2, wherein the rubber component is a rubber component containing 15% by mass or more of butadiene rubber having a 1,2-bond butadiene unit amount of 80% by mass or more. The rubber composition for a crawler according to any one of claims 1 to 3, wherein the rubber component is a rubber component containing 40% by mass or more of natural rubber. The rubber composition for a crawler according to any one of claims 1 to 4, comprising 40 to 80 parts by mass of carbon black with respect to 100 parts by mass of the rubber component. For 100 parts by mass of the rubber component,
0-40 parts by weight of carbon black A nitrogen adsorption specific surface area of 70~90m ² / g, and claim 1 of the nitrogen adsorption specific surface area contains 0 to 40 parts by weight of carbon black B of 30 to 50 m ² / g 5. The rubber composition for a crawler according to any one of 4 above. The rubber composition for a crawler according to any one of claims 1 to 6, comprising 0.5 to 10 parts by mass of a resin having a softening point of 50 ° C or higher with respect to 100 parts by mass of the rubber component. The rubber crawler which has the crawler member comprised with the rubber composition for crawlers of any one of Claims 1-7.