JP2005335611A - Rubber crawler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber crawler excellent in a braking/driving property on an iced road surface and a snowed road surface in an extremely cold area and in crack-prevention property, etc. <P>SOLUTION: This rubber crawler constitutes its characteristic feature of using a rubber composite a value of a complex elastic modulus (E*) of which is less than 30 MPa at -35°C and its temperature at which a value of tanδ measured by a viscoelastic testing machine shows the maximum value is equal to or less than -35°C. It is preferable that the value of the complex elastic modulus (E*) at -35°C is adjusted to be not less than 20 MPa and not more than 30MPa. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber crawler, and more particularly to a rubber crawler excellent in performance such as braking / driving performance and anti-cracking on an icy road surface and a snowy road surface in an extremely cold region.

  Conventionally, rubber crawlers are used for traveling drive wheels of construction machines and agricultural machines. The performance required for the rubber crawler includes cut resistance, wear resistance, and braking / driving performance. With regard to these characteristics, technological development has been advanced on the premise of normal operating temperatures and traveling conditions of construction machinery and agricultural machinery.

  Recently, rubber crawlers are suitable for mounting high-speed vehicle bodies, and there is an increasing demand for weight reduction. On the other hand, a use of the rubber crawler that can withstand severe use conditions in a cold region has been demanded. In other words, it can be applied to a drive shaft of a general high-speed vehicle body, and excellent running characteristics on a snowy road surface or an icy road surface in a cold region in winter have been required.

  However, conventional rubber crawlers are mounted on the driving wheels of construction machinery and agricultural machinery and are used under normal temperature and driving conditions. Driving and braking on snowy and icy road surfaces in cold regions. Furthermore, there are few things that consider wear resistance.

In Patent Document 1, in order to improve performance on ice in a cold region, the rubber material at least on the ground contact surface side of the rubber track mounted on the drive shaft of the traveling machine body has a dynamic elastic modulus of rubber at 0 ° C .: E ′ Is used at 180 kgf / cm ² or less.

In Patent Document 2, as a low-temperature embrittlement rubber composition for tires, dynamic viscoelasticity measured at −40 ° C., 20 Hz, initial strain 10% and dynamic strain ± 0.5% has a predetermined relational expression. It is disclosed whether it meets. However, none of these techniques sufficiently improve the running characteristics and the basic physical properties in extremely cold regions.
JP 11-139359 A JP 2003-20365 A

  The present invention solves the above problems and provides a rubber crawler in which performances such as icing road surfaces in extremely cold regions, braking / driving performance on snowy road surfaces, and crack resistance are sufficiently improved.

  The present invention relates to a rubber composition in which the temperature at which the value of tan δ measured with a viscoelasticity testing machine is maximum is −35 ° C. or lower, and the value of complex elastic modulus (E *) at −35 ° C. is 30 MPa or lower. It is a rubber crawler characterized by using. Here, in the present invention, it is more preferable to use a rubber composition having a complex elastic modulus (E *) at −35 ° C. of 20 MPa to 30 MPa.

  The rubber composition of the present invention contains at least one of natural rubber or polybutadiene rubber as a rubber component in an amount of 30 parts by mass or more and 25 to 70 parts by mass of styrene-butadiene rubber, and relative to 100 parts by mass of the rubber component. 1.0 to 2.0 parts by mass of sulfur, 0.5 to 1.5 parts by mass of a sulfenamide-based vulcanization accelerator, and the ratio of vulcanization accelerator to sulfur (vulcanization accelerator / sulfur) However, it is preferable to set it as 0.25-1.5.

  In the rubber composition of the present invention, the temperature at which the value of tan δ measured with a viscoelasticity testing machine shows a maximum value is −35 ° C. or less, and the value of complex elastic modulus (E *) at −35 ° C. is 30 MPa or less. Therefore, there is a rubber crawler that maintains flexible rubber characteristics even when used in extremely cold regions of -35 ° C or less, and sufficiently maintains the performance of braking / driving, crack resistance, etc. on icing road surfaces and snowy road surfaces. can get.

  The present invention relates to a rubber composition in which the temperature at which the value of tan δ measured with a viscoelasticity testing machine is maximum is −35 ° C. or lower, and the value of complex elastic modulus (E *) at −35 ° C. is 30 MPa or lower. It is a rubber crawler using.

  It is necessary to increase the frictional force of the rubber composition at extremely low temperatures in order to improve the braking performance and drivability on frozen road surfaces and snowy road surfaces in extremely cold regions. Therefore, the rubber composition of the present invention can maintain rubber properties even at extremely low temperatures by adjusting the temperature at which the value of tan δ exhibits a maximum value to −35 ° C. or less. Furthermore, the value of the complex elastic modulus (E *) at −35 ° C. is set to 30 MPa or less, the flexibility is maintained at an extremely low temperature, and the frictional force is further improved. If the complex elastic modulus (E *) exceeds 30 MPa, the rubber becomes hard and the adhesion to the ice surface decreases, so the friction coefficient (μ) decreases significantly, ensuring the required drivability and braking performance. It becomes impossible and also crack resistance falls. Therefore, as a preferable range, the complex elastic modulus (E *) at −35 ° C. is 30 MPa or less, preferably 27 MPa or less.

  On the other hand, when the value of the complex elastic modulus (E *) is less than 20 MPa, the rubber elasticity is not sufficient, the wear resistance is lowered, and the braking performance and the driving performance tend to be lowered. Therefore, the value of the complex elastic modulus (E *) at −35 ° C. is more preferably in the range of 20 MPa to 30 MPa.

<Rubber component>
In the rubber composition of the present invention, a rubber component composed of a diene synthetic rubber or a mixture of a diene synthetic rubber and natural rubber is used as the rubber component. Here, examples of the diene-based synthetic rubber include polyisoprene synthetic rubber (IR), polybutadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and the like. Is mentioned. These rubbers may be used alone or in combination of two or more.

  In the present invention, it is preferable to mix 30 parts by mass of natural rubber and / or polybutadiene rubber with respect to 100 parts by mass of the rubber component. Further, styrene-butadiene rubber can be mixed with 25 to 70 parts by mass and further other rubber components with respect to 100 parts by mass of the rubber component. In the case of a rubber component in which the amount of styrene-butadiene rubber mixed is less than 25 parts by mass, workability is significantly reduced. A more preferable mixing amount of the styrene-butadiene rubber in the rubber component is 40 to 70 parts by mass. Here, the styrene-butadiene rubber can be produced by an emulsion polymerization method, a solution polymerization method or the like.

  In order to adjust the value of the complex elastic modulus (E *) at a low temperature to a low value, blending of polybutadiene rubber is desirable. However, from the viewpoint of maintaining crack resistance and wear resistance required as rubber rubber lug rubber, mixing with styrene-butadiene rubber is preferred.

<Carbon black>
In the rubber composition of the present invention, it is preferable to blend carbon black in order to improve the reinforcing property and wear resistance. Here, as the carbon black, any of channel black, furnace black, acetylene black, thermal black and the like can be used. Carbon black having a nitrogen adsorption specific surface area (BET value) of 80 m ² / g or more and a dibutyl phthalate oil absorption (DBP value) of 45 ml / 100 g or more is suitable for exhibiting the low temperature characteristics of the rubber composition. is there. When this BET value is less than 80 m ² / g, or when the DBP value is less than 45 ml / 100 g, sufficient reinforcement and wear resistance are difficult to obtain. It's hard to be done. In order to improve the wear resistance, reinforcement and crack resistance in a comprehensive manner, the BET value is 90 to 250 m ² / g, and the DBP value is 100 to 180 ml / 100 g. The BET value is measured according to ASTM D3037-88, and the DBP value is measured according to JIS K6221-1982.

  In the present invention, carbon black may be used singly or in combination of two or more. Moreover, the compounding quantity is 10 mass parts or more with respect to 100 mass parts of rubber components, Preferably it is 20-100 masses, Especially 40-70 mass parts.

  In the rubber composition of the present invention, silica and / or aluminum hydroxide can be blended together with carbon black or in place of carbon black. In that case, it is preferable to add a coupling agent, particularly a silane coupling agent, in order to improve dispersibility in the rubber composition of silica and aluminum hydroxide and improve the reinforcement.

<Vulcanizing agent, vulcanization accelerator>
A predetermined amount of a vulcanizing agent and a vulcanization accelerator is blended in the rubber composition of the present invention. In addition to sulfur, sulfur-containing organic compounds such as tetramethylthiuram / disulfide, tetraethylthiuram / disulfide, tetrabutylthiuram / disulfide, alkyl / phenol / disulfide, dithioate, etc. Can be used. The compounding quantity is 0.5-3.0 mass parts with respect to 100 mass parts of rubber components, Preferably it is the range of 1.0-2.0 mass parts.

  The vulcanization accelerator is not particularly limited, but a thiazole vulcanization accelerator, particularly preferably a sulfenamide vulcanization accelerator is preferably used. For example, 2-mercaptobenzothiazole (M), dibenzothiazyl disulfide (DM), 2-mercaptobenzothiazole hydrochloride (MZ), and cyclohexylamine of 2-mercaptobenzothiazole as thiazole vulcanization accelerators Salt (MH), sodium salt of 2-mercaptobenzothiazole (M-Na), 2- (2,4-dinitrophenyl) mercaptobenzothiazole (DBM), and the like.

  As sulfenamides, cyclohexyl / benzothiazylsulfenamide (CZ), N-oxydiethylene / benzothiazyl-2-sulfenamide (NS), Nt-butyl-2-benzothiazolesulfenamide (BNS) ), 2- (thymolpolynyl dithio) benzothiazole (DS) and the like.

  In addition, thiuram, dithioic acid, thiourea and the like can be used as the vulcanization accelerator, and a mixture of these can also be used. The compounding quantity of a vulcanization accelerator is 0.2-2.0 mass parts with respect to 100 mass parts of rubber components, Preferably it is the range of 0.5-1.5 mass parts.

  Furthermore, the blending ratio R (vulcanization accelerator / sulfur) of the vulcanizing agent and the vulcanization accelerator is adjusted to a range of 0.25 to 1.5, preferably 0.5 to 1.0. When the value of the blending ratio R is less than 0.25, unreacted sulfur remains in the rubber composition, and the basic characteristics of the rubber composition may not be stabilized and may change over time. On the other hand, when the blending ratio R exceeds 1.5, the amount of crosslinking by monosulfide becomes relatively higher than the amount of polysulfide crosslinking, and the complex elastic modulus (E *) at low temperature (−35 ° C.) is adjusted to 30 MPa or less. It becomes difficult.

<Other ingredients>
The rubber composition of the present invention may optionally be used in various chemicals used in the tire industry, such as fillers, reinforcing agents, anti-aging agents, tackifiers, scorch inhibitors, softeners, plasticizers, zinc white, stearic acid, etc. Can be contained. The rubber composition of the present invention can be obtained by kneading the above components with an ordinary roll, a Banbury mixer, a kneader or the like.

  Hereinafter, the rubber crawler of the present invention will be described in detail based on examples. The rubber crawler of the present invention was produced by the composition shown in Table 1, and a rubber sample was produced in the same manner to evaluate the performance. The test results are also shown in Table 1. The dynamic viscoelastic characteristics and performance evaluation were performed by the following methods.

(Note 1) Natural rubber: JSR20
(Note 2) Polybutadiene: 1220 manufactured by Nippon Zeon
(Note 3) Styrene-butadiene rubber: 1502 manufactured by JSR Corporation
(Note 4) Carbon black HAF: BET value: 70 to 90 m ² / g, DBP value: 115 ml / 100 g
(Note 5) Vulcanization accelerator CZ: cyclohexyl benzothiazylsulfenamide (1) tan δ: complex elastic modulus (E *)
It is a value measured using a viscoelasticity tester (manufactured by Ueshima Seisakusho Co., Ltd.) under conditions of a frequency of 10 Hz, dynamic strain, both sides 2% (DSA), and a temperature of −60 ° C. to −10 ° C.
(2) Crack resistance Using a dematcher tester, the bent portion was observed after bending 100 times at an ambient temperature of -35 ° C. A sample having a width of 25 mm, a length of 150 mm, and a thickness of 10 mm was used. The evaluation criteria were as follows.

  X: Cracks were generated by 50% or more.

  Δ: Cracks of 10% or more occurred.

  ○: A crack of less than 10% occurred.

  A: No crack was generated.

<Evaluation results>
In Table 1, each of Examples 1 to 4 has a peak temperature of tan δ of −35 ° C. or lower and a complex elastic modulus (E *) adjusted to 20 MPa to 27 MPa, which improves crack resistance. It is recognized that

Since the present invention uses a rubber composition that can maintain rubber properties at extremely low temperatures, it can maintain a high coefficient of friction with respect to icing road surfaces and snowy road surfaces even when used at temperatures near -35 ° C. And the rubber crawler which reduced generation | occurrence | production of a crack can be obtained.

Claims (3)

  The rubber composition having a maximum temperature of tan δ measured with a viscoelasticity tester is −35 ° C. or less and a complex elastic modulus (E *) value at −35 ° C. is 30 MPa or less. Rubber crawler characterized by.   The rubber crawler according to claim 1, wherein a rubber composition having a complex elastic modulus (E *) at −35 ° C. of 20 MPa to 30 MPa is used.   The rubber component includes at least one of natural rubber or polybutadiene rubber in an amount of 30 parts by mass or more, and 25 to 70 parts by mass of styrene-butadiene rubber. 0 part by mass, 0.5 to 1.5 parts by mass of a sulfenamide-based vulcanization accelerator, and the ratio of vulcanization accelerator to sulfur (vulcanization accelerator / sulfur) is 0.25 to 1.5. The rubber crawler according to claim 1, wherein: