JPH11227644A - Rubber composition for elastic crawler of tire drive type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire drive type elastic crawler which is light in weight and has excellent durability and low in friction property by forming a side guide part of the crawler from a rubber composition equipped both with a high hardness and a low friction property. SOLUTION: A rubber composition mainly contains natural rubber, butadiene rubber, isoprene rubber, and diene series rubber of styrene-butadiene rubber, etc. Besides the rubber component of 100 pts.wt., it contains 40-150 pts.wt. supper-highpolymer polyolefin powder, 30-80 pts.wt. carbon black, one or more pts.wt. sulfur, and one or more pts.wt. vulcanization accelerating agent, wherein the hardness is over 70 deg. according to JIS A-hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire-driven elastic crawler, and more particularly to a composition used for a garter portion forming side guides on both sides in the width direction of the inner peripheral surface of an elastic crawler body. .

[0002]

2. Description of the Related Art As shown in FIGS. 1 and 5, an endless shape of a crawler body 2 formed of an elastic material and having a running lug 1 on an outer circumferential surface is provided on both sides in the width direction of the inner circumferential surface.
A large number of garters 4, 4,... Forming the side guide portion 3 are integrally protruded toward the inner periphery of the crawler body 2, are made of an elastic material between the side guide portions 3, and at least the outer periphery of the shoulder portion. Tire T provided with friction reducing member 6 on its surface
The elastic crawler belt C driven by
177 publication.

On the other hand, the publication discloses that the friction reducing member 6 may be provided on the garter 4 side, or the friction reducing member 6 may be provided on the tire T side and the garter 4 side. Further, in the publication, as the friction reducing member 6, for example, rubber kneaded with Teflon (trade name), rubber containing a cotton chip filler,
A Teflon (trade name) sheet, wax, silicone oil, or the like is used. By adopting such a structure, when a side force is applied at the time of turning or the like, or when a gap such as a curb is passed, a gap between the tire T and the garter 4 is provided. With the provided friction reducing member 6, the coefficient of friction between the two members can be reduced to make it easier to slip, so that the tire T can be effectively prevented from coming off the crawler belt C. In FIG. 5, reference numeral 7 denotes a metal core embedded at regular intervals in the longitudinal direction of the crawler belt C, and reference numeral 8 denotes a tensile material embedded on the lug 1 side of the core metal 7 extending over the entire longitudinal direction of the crawler belt C. Wire. On the other hand, in the figure, the crawler belt C is made of a normal rubber such as diene.

[0004]

In the above-mentioned prior art, an arbitrary material is used as a friction reducing member on the tire side, and a rubber containing kneaded rubber such as Teflon (trade name) or a cotton chip filler is provided on the crawler belt garter side. Even when a friction reducing member such as a Teflon (trade name) sheet, wax, silicone oil, or the like is used, the portion of the garter that comes into contact with the tire side wears quickly or the adhesion between the Teflon (trade name) sheet and rubber is difficult. Therefore, there has been a problem that they are peeled off. If the garter portion is made of metal, low abrasion and durability are no problem, but an increase in the weight of the crawler is inevitable. The present invention improves the rubber hardness by using a special compounding amount in the rubber composition on the garter side of the rubber crawler to improve the rigidity and enables low frictional properties in order to improve the above disadvantages. Aim.

[0005]

The present invention employs the following technical means to achieve the above object. That is, a large number of garters forming side guides are formed on the both sides in the width direction of the inner peripheral surface of the crawler main body formed of an elastic material in an endless shape and having a lug for running on the outer peripheral surface toward the inner periphery of the crawler main body. In an elastic crawler belt protruded integrally and driven by a tire made of an elastic material between the side guide portions, the rubber composition of at least a portion of the garter corresponding to the tire is superposed with respect to 100 parts by weight of a diene rubber component. 40 to 15 high molecular weight polyolefin powder
0 parts by weight, 30 to 80 parts by weight of carbon black, and 1 part by weight or more of each of sulfur and a vulcanization accelerator,
A rubber composition for a tire-driven elastic crawler, wherein the rubber composition has a hardness of 70 ° or more in JIS-A hardness (Claim 1). At this time, in the present invention, the ultrapolymer has a molecular weight of 1,000,000 to 6,000,000 and an average particle size of 200 μm.
The following are preferably used (claim 2), and the carbon preferably has an iodine adsorption amount of 70 mg / g or more and a DBP oil absorption of 80 ml / 100 gm or more (claim 3).

[0006]

Embodiments of the present invention will be described below. FIG. 2A is one embodiment of the present invention, and is a cross-sectional view taken along line II of FIG. Reference numeral 2 denotes a crawler body formed of an elastic material such as a diene rubber or the like in an endless shape and having a running lug 1 on an outer peripheral surface. The crawler main body 2 has a large number of garters 4, 4,. Reference numeral 7 denotes a metal core buried in the width direction of the garter 4 in the longitudinal direction of the crawler body 2, and 8 is buried below the metal core 7, that is, on the lug 1 side of the crawler body 2 in the longitudinal direction of the crawler body 2. It is a tensile wire rod that has been made. Reference numeral 9 denotes a friction reducing member provided from the inner peripheral surface of the garter 4 to the top 4 'of the side guide portion 3 of the crawler body 2 described later.

The present invention is a rubber composition used for the friction reducing member 9. The rubber composition is obtained by mixing 40 to 150 parts by weight of ultrahigh molecular weight polyolefin powder having a small particle diameter of 1 to 6 million in molecular weight and 200 μm or less in average with 100 parts by weight of a diene rubber component.
In particular, the present invention has obtained a rubber composition for a crawler having high hardness and low friction by using the specific ultrahigh molecular weight polyolefin powder. The type of the diene rubber component is not particularly limited, but natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene rubber (SBR), and the like are used. In addition to the above components, the rubber composition of the present invention contains 30 to 8 carbon blacks having an iodine adsorption amount of 70 mg / g or more and a DBP oil absorption of 80 ml / 100 g or more.
0 parts by weight, 1 part by weight or more of sulfur and vulcanization accelerator,
One or more of the diene rubber components NR, BR, IR, and SBR are added to 100 parts by weight of the polymer. In addition to the above components, various additives such as an antioxidant, wax, and silicone oil may be added. Next, the reasons for limiting the numerical values of the composition of the present invention will be described. <About ultra-high molecular weight polyolefin powder> Generally, polyolefin powder has an average particle size of 150 to 20.
0 μm and a molecular weight of 20,000 to 300,000, whereas in the present invention, the average particle size is 200 μm or less, preferably 2 μm or less.
0-200 μm, and the molecular weight is 1,000,000-600.
Ultra-high molecular weight polyolefin powder with a small particle size of 10,000. Here, when the average particle size exceeds 200 μm, there is a disadvantage that the hardness of the composition is reduced. For this reason, when the polyolefin powder of the specific numerical value is added to and blended with the diene rubber component, high hardness and low friction properties are exhibited. Here, the present invention relates to the use of the ultra-high molecular weight polyolefin powder as the rubber 1
When the amount is less than 40 parts by weight, sufficient low friction and high hardness cannot be obtained. On the other hand, when the amount is more than 150 parts by weight, workability (poor kneading of powder) is required. ) Has a problem. <Regarding Carbon Black> In the present invention, 30 to 80 parts by weight (preferably 40 to 60 parts by weight) of carbon black having an iodine adsorption amount of 70 mg / g or more and a DBP oil absorption of 80 ml / 100 g or more with respect to 100 parts by weight of diene rubber. If the carbon black content, iodine adsorption, and DBP oil absorption are less than the specified values, sufficient hardness (i.e., a rubber hardness of 70 ° or more) cannot be obtained. It becomes larger and causes problems in workability. <Sulfur and Vulcanization Accelerator> In the present invention, 1 part by weight or more, preferably 1 to 5 parts by weight of sulfur and vulcanization accelerator are added to 100 parts by weight of the diene rubber component. If the amount is less than 1 part by weight, the hardness is not sufficient. As described above, in the present invention, since the rubber composition of the specific component is used as the friction reducing member 9 on the inner surface of the garter 4 shown in FIG. 2 (A), the hardness is 70 ° or more in JIS-A hardness. In addition, the coefficient of friction with the friction reducing member 6 on the tire T side, for example, a woven fabric made of nylon, was 0.6 or less.

Next, FIGS. 2 (B), 3 (A) and 3 (B) and FIGS. 4 (A) and 4 (B) show examples of applying the rubber composition of the present invention to an elastic crawler C. FIG. 2B is different from FIG. 2A in the structure of the metal core 7, and both ends of the metal core 7 extend to the inside of the garter 4, 4. FIG.
(A) corresponds to FIG. 2 (A), and FIG. 3 (B) corresponds to FIG. 2 (B), in which the rubber composition of the present invention is applied to the outer part of the garter 4 respectively. is there. FIG. 4
Is a garter 4 formed entirely of the rubber composition of the present invention. Hereinafter, Examples of the rubber composition of the present invention are shown in Table 1 together with Comparative Examples.

[0009]

[Table 1]

[0010] In addition to the components listed in Table 1, the rubber composition for a tire driven elastic crawler of the present invention contains 3 parts by weight of zinc oxide, 2 parts by weight of stearic acid and 100 parts by weight of a diene rubber component. 2 parts by weight of agent, 2 parts by weight of wax,
Although 5 parts by weight of aroma oil is blended, it goes without saying that each blending amount can be appropriately increased or decreased depending on the case.
The carbon black used in the present invention is carbon N
339, the vulcanization accelerator is BBS, and the anti-aging agent is N- (1,
3-dimethylbutyl) -N'-phenyl-P-phenylenediamine, but need not be limited thereto.

The prepared rubber composition was evaluated for hardness, coefficient of friction, kneading processability of polyolefin powder, and adhesion according to the following methods. [Evaluation Method] 1) Hardness: JIS-A hardness was measured according to JIS K6301. 2) Friction coefficient: Portable skid resistance tester (AS
Using TM E303), the rubber composition was measured by sliding it on a nylon woven fabric. The measured value of the rubber composition not containing the ultrahigh molecular weight polyolefin powder is μ = 0.7 to
0.8. If the measured values of the ten types of rubber compositions shown in Table 1 were lower than the measured values, it was determined that the rubber composition had low friction. In addition, at least μ = 0.6 (for nylon woven fabric) is necessary in order for the tire not to come off the crawler, and thus μ = 0.6 was determined to be one partition having low friction. 3) Processability of kneading polyolefin powder: Dropout was performed at a mixer temperature of 110 ° C. using a closed mixer, and the amount of excess powder that was not mixed with the rubber was measured. If the surplus powder amount is 10% or less of the charged amount, the powder loss is reduced, and the surplus powder amount is 1% of the charged amount.
When it was 0% or more, the powder loss was determined to be large. When there was no powder loss, it was determined that the polyolefin powder was uniformly kneaded. 4) Adhesion: The rubber composition of the present invention and the rubber composition of the above-mentioned composition not containing wax, silicone oil and the ultra-high molecular weight polyolefin powder were formed into a sheet having a width of 25 mm, a length of 125 mm and a thickness of 3 mm, respectively. . The two types of rubber sheets are bonded together, and adhesive vulcanization is performed at 150 ° for 30 minutes, and then peeled at 180 ° (peeling speed 50 mm
/ Min) was evaluated. At this time, it was determined that peeling of the interface between the two rubber sheets (the surface was smooth) resulted in interface delamination, and that the surface was torn into a jagged state, resulting in rubber destruction.

Comparative Examples 1 and 2 in Table 1 are rubber compositions not containing the ultrahigh molecular weight polyolefin powder. By blending wax and silicone oil, low friction properties can be obtained without using the ultrahigh molecular weight polyolefin powder. However, since the JIS-A hardness is 70 ° or less, the rigidity required for a tire driven elastic rubber crawler cannot be obtained, and there is a problem in rubber adhesion.

The composition of Example 1 has an average particle size of 250 μm.
and a polyolefin powder having a molecular weight of 300,000. In Examples 2 to 4, ultrahigh molecular weight polyolefin powder having a predetermined average particle size and a predetermined molecular weight according to the present invention was blended within a predetermined range by weight. Example 1
Comparison between Nos. 1 and 2 reveals a difference in hardness, indicating that the increase in hardness of the rubber composition is affected by the average particle size and molecular weight of the polyrefin powder to be compounded. The ultra-high molecular weight polyolefin powder is mixed with the diene rubber 10
When 160 parts by weight is added to 0 parts by weight, a problem in processability starts to appear, so the compounding amount of the polyolefin powder is desirably 150 parts by weight or less.

As shown in Comparative Example 6, if the iodine adsorption amount of carbon black is 70 mg / g or less and the DBP oil absorption amount is 80 ml / 100 g or less, sufficient hardness cannot be obtained. Further, as shown in Comparative Example 4, the same result is obtained even when the amount of carbon black is less than 30 parts by weight based on 100 parts by weight of the diene rubber. Further, even if the amounts of sulfur and vulcanization accelerator (vulcanizing agent) are less than 1 part by weight based on 100 parts by weight of diene rubber, the hardness is not sufficient (Comparative Example 3).

[0015]

The rubber composition for crawlers of the present invention has high hardness and low friction due to the use of the above-mentioned predetermined ultra-high molecular weight polyolefin powder. Therefore, when the rubber composition of the present invention is used for the garter portion constituting the side guide portion of the crawler, a tire-driven elastic crawler that is lightweight and has excellent low friction and durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of an elastic crawler using the rubber composition of the present invention.

FIG. 2A is a sectional view taken along the line II of FIG. 1;
(B) shows two ends of the core metal 7 of FIG.
Extending to the inside of the surface.

FIG. 3 (A) shows a structure of a core metal 7 corresponding to FIG. 2 (A), in which the rubber composition of the present invention is applied to the outer part of the garter 4, and FIG. 3 (B). 2B shows the structure of the core 7 corresponding to FIG. 2B, in which the rubber composition of the present invention is coated on the outer part of the garter 4.

FIG. 4 is a view in which the entire garter 4 is formed of the rubber composition of the present invention.

FIG. 5 is a conventional example corresponding to the II section of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Running lug 2 Crawler main body 3 Side guide part 4 Garter 6 Friction reducing member 7 Core metal 8 Tensile wire 9 Friction reducing member provided on inner peripheral surface of garter 4

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 23/02 C08L 23/02

Claims (3)

[Claims] 1. A large number of garters forming side guides are formed on the inner periphery of the crawler body on both sides in the width direction of the inner periphery of the crawler body formed of an elastic material in an endless shape and having lugs for running on the outer peripheral surface. In an elastic crawler belt driven integrally by a tire made of an elastic material between the side portions, at least a portion of the garter corresponding to the tire has a rubber composition corresponding to 100 parts by weight of a diene rubber component. 40 ~ 1 ultra high molecular weight polyolefin powder
50 parts by weight, 30 to 80 parts by weight of carbon black, 1 part by weight or more of each of sulfur and a vulcanization accelerator, and the hardness of the rubber composition is JIS-A hardness 70 ° or more. A rubber composition for tire-driven elastic crawlers. 2. The rubber composition for a tire driven elastic crawler according to claim 1, wherein the ultrahigh molecular weight polyolefin powder has a molecular weight of 1,000,000 to 6,000,000 and an average particle size of 200 μm or less. 3. The carbon black has an iodine adsorption amount of 70.
The rubber composition for a tire driven elastic crawler according to any one of claims 1 and 2, wherein the rubber composition has a DBP oil absorption of 80 ml / 100 g or more.